JP5082192B2 - Method for producing nanofiber synthetic paper - Google Patents

Description

  The present invention relates to a synthetic paper composed of nanofibers having a small pore area and a uniform pore diameter, and a method for producing the same.

  Various methods for producing synthetic paper from ultrafine fibers of synthetic polymers have been studied. The average single fiber average diameter of ordinary synthetic fibers is as thick as 10 μm or more, and it is difficult to fibrillate like natural pulp and cellulose, and there is little entanglement between fibers, and it is difficult to obtain a synthetic paper with good formation. It was. Therefore, for polyester fiber synthetic paper, when the fiber diameter is about 13 μm (see, for example, Patent Document 1), about 15 μm (for example, see Patent Documents 2 and 3), and about 11 μm (for example, Patent Document 4). However, the paper has been studied to make paper using a binder in combination with polyester fiber, but the paper is somewhat insufficient in flexibility. Also, if the paper thickness is reduced to improve flexibility or improve air permeability, the dispersibility is poor due to the thick fibers, and it is not possible to obtain a paper with a uniform thickness and good texture. It was. In addition, when the paper thickness is forcibly reduced, there are cases where it becomes impractical due to unevenness in the basis weight of the synthetic paper.

  For this reason, synthetic paper using ultrafine fibers having a diameter of 10 μm or less has recently been studied. In this method, sea components of sea-island composites and split composite fibers are dissolved or physically separated to produce ultrafine fibers, and synthetic paper is produced from the obtained ultrafine fibers. Such a basic method for producing ultrafine fibers has already been disclosed (for example, see Patent Document 5), and the ultrafine fibers themselves have also been disclosed (for example, see Patent Document 6). According to this, it is suggested that an ultrafine fiber can be obtained by removing the sea component of the sea-island composite fiber made of polyester fiber with an appropriate solvent, and that this ultrafine fiber can form a paper-like structure. In addition, the diameter of the ultrafine fibers was as large as 0.01 to 3 μm, and practical synthetic paper was not obtained.

  Thereafter, as a synthetic paper of ultrafine fibers, a method of treating sea-island composite fibers or split composite fibers of 10 μm or less with a high-pressure liquid flow has been proposed (see, for example, Patent Document 7), but uniform fiber fibrillation is proposed. Since it was difficult and a special high-pressure liquid fluid device was required, it was difficult to put it into practical use. Further, there is an example in which a synthetic fiber polyester fiber having a diameter of 1.5 to 4 μm is obtained by dispersing and beating a sea-island composite type polyester fiber in water (see, for example, Patent Document 8).

  Furthermore, although what has obtained synthetic paper (separator material) with the fiber which beaten the division | segmentation composite type | mold fiber of the polyolefin resin from which a component differs is disclosed (for example, refer patent document 9), the fiber diameter is about 5 micrometers. In addition, since the shape of the divided single fibers is non-uniform, the variation in the fiber diameter is large. Furthermore, although the sea-island composite-type and split-composite-type ultrafine fibers and synthetic paper using these short fibers are disclosed (for example, see Patent Document 10), the fiber diameter of this synthetic paper is 2 to 7 μm. It was a big one.

  In addition, a method has been proposed in which liquid crystalline fibers are made fine by fibrillation and paper is made to obtain a synthetic paper (see, for example, Patent Documents 11 and 12). However, in this method, although very thin fibers can be obtained by fibrillation, thick fibers that have not progressed much in fibrillation are also mixed, and only synthetic paper having a large variation in single fiber diameter can be obtained.

On the other hand, in the use of synthetic paper, especially in the fields of air cleaner filters, industrial dust removal filters, pure water production and chemical purification filters, pharmaceutical / medical filters, battery separators, etc. There has been a demand for synthetic paper that is thinner, has a uniform basis weight, and has high strength. This is highly accurate for removing very fine impurities out of the system and recovering the necessary trace components in the fields of electronics, mechatronics, water quality, pharmaceuticals, drugs and foods. This is because there is a demand for management. For this reason, examination of the synthetic paper by a nanofiber was calculated | required.
In the method using the conventional sea-island composite spinning technology, even though the diameter of the single fiber can be reduced to about 1 μm, there is a limit to manufacturing a fiber having a diameter smaller than that, and the needs for nanofibers can be sufficiently met. It was not a level. Moreover, although a method for obtaining ultrafine fibers from polymer blend fibers has been proposed (see, for example, Patent Documents 13 and 14), the ultrafine fibers obtained here have a diameter of about 0.4 μm at the smallest. Yes, it was not enough to meet the needs for nanofibers. In addition, the single fiber diameter of the ultrafine fibers obtained here is determined by the dispersion of the island component polymer in the polymer blend fiber. In such a normal polymer blend system, the polymer constituting the island component is used. The dispersion of the single fiber diameter of the obtained ultrafine fibers was large because of the insufficient dispersion.

By the way, as a simple technique for making ultrafine fibers down to the nano level, there is a technique called electrospinning which has recently attracted attention. The basic technique of this method has been known for a long time, and is a method proposed around 1935. The reason why this technology is in the spotlight is that the nanofiber nonwoven fabric (synthetic paper-like) produced by this method is suitable for cell culture, especially in the US biomedical field, and for research purposes. As a non-woven fabric of various polymers, it can be easily prepared. In this method, a polymer is dissolved in an electrolyte solution and extruded from a base. At that time, a high voltage of several thousand to 30,000 volts is applied to the polymer solution, and a high-speed jet of the polymer solution and a subsequent jet are applied. This is a technique for making the fiber extremely thin by bending and expanding, and is usually collected as a synthetic paper-like non-woven fabric by focusing the ultrafine fibers. When this technique is used, a fiber having a single fiber diameter of several tens of nanometers can be obtained, and the diameter may be reduced to 1/10 or less as compared with a conventional polymer blend technique. Furthermore, the target polymers are mostly biopolymers such as collagen and water-soluble polymers, but there are cases where electrospinning is performed by dissolving a thermoplastic polymer in an organic solvent. However, even in this method, the ultrafine fiber portions are often connected by a bead (diameter 0.5 μm) which is a large diameter fiber portion, and when viewed as a superfine fiber, the single fiber diameter varies greatly. (For example, refer nonpatent literature 1). For this reason, attempts have been made to make the fiber diameter uniform by suppressing the generation of the large-diameter fiber portion, but the variation is still large (for example, see Non-Patent Document 2). In addition, since the nonwoven fabric obtained by electrospinning is obtained by evaporation of the solvent during the fiberization process, the fiber aggregate is often not oriented and crystallized, and the strength is much weaker than that of a normal nonwoven fabric. It was not possible, and there was a big restriction on application development. Further, even when electrospinning is used as a manufacturing method, a solvent is generated when it is made into fibers, and thus there are problems in production such as countermeasures for working environment and solvent recovery. Further, the size of the nonwoven fabric that can be produced is also limited, the size is about 100 cm ² , the discharge rate is several g / hour at the maximum, the productivity is low, and a high voltage is required, which is harmful. Since organic solvents and ultrafine fibers float in the air, there are always dangers such as electric shock, explosion, and poisoning, and this is a practically difficult method.

  As described above, there has been a demand for a nanofiber synthetic paper having a small variation in single fiber diameter that can be widely applied and deployed without restriction on the polymer.

  Here, between the fineness (dtex) of the fibers usually used in the fibers described in the patent documents cited above and the number average diameter φ (μm) of the single fibers used in the synthetic paper of the present invention The following equation (1) is established.

φ = 10 × (4 × dtex / πρ) ^1/2 (1)
Here, dtex refers to the fiber thickness (JIS L 0101) (1978) that makes the fiber 1 g in weight of 10,000 m.

  For example, when the fineness is converted into the single fiber diameter referred to in the present invention, for example, when the polymer is nylon, the specific gravity is a value converted by 1.14 (corresponding to nylon 6), and is obtained by the following formula.

φ _n6 = 10.6 (dtex) ^1/2
Further, when the type of polymer is not nylon 6 but is different, the calculation may be performed by substituting the specific gravity (ρ) specific to the polymer in the above formula (1).
Japanese Patent Publication No.49-8809 Japanese Patent Laid-Open No. 55-110545 JP-A-60-34700 JP-A-1-118700 US Pat. No. 3,382,305 (1968) U.S. Pat. No. 354603 (1970) JP 56-169899 A JP-A-4-10992 JP 2003-59482 A JP 2003-253555 A Japanese Patent Laid-Open No. 8-209583 JP 2002-266281 A Japanese Patent Laid-Open No. 3-113082 JP-A-6-272114 Polymer, vol. 43,4403 (2002) Polymer, vol. 40, 4585 (1999)

  In recent industries, the accuracy required for raw materials and products has been improved in general industries such as electronics / information industry, pharmaceuticals, raw materials for industrial materials, foods, mechatronics, etc., and industries that dislike contamination such as dust, foreign matter, and bacteria have increased. In addition, various filter materials are required to be controlled at the nano level. In the biomedical field, there is a demand for materials that are controlled at the nano level according to the size of cells and proteins. In such an era, conventional paper technology depends on natural products such as wood pulp, and even when fibrillated, the fiber diameter and dispersion are random. It was difficult to control several μm, not nano level. Similarly, it has been difficult to uniformly control the fiber diameter in the electrospinning method that has become a hot topic, and there has been a variation of two or more digits from the nano level. In particular, when the above-mentioned bead phenomenon occurs, the variation in fiber diameter is large, and only a fiber having a nonuniform fiber diameter can be obtained. For this reason, the development to the above new fields was insufficient.

  In such a technical background, it is desired to provide a synthetic paper controlled at the nano level. In addition, because the fiber diameter is nano-level, the specific surface area of the fiber is not only enormously large, but in new applications such as medical, cells and proteins, fine particles in various filter fields, foreign substances, bacteria, There is a demand for nano-level interaction with pollen, drugs, and the like, and there is a demand for a synthetic paper having a new function not found in conventional synthetic paper.

  In addition, regarding the synthetic paper technology, there is a demand for improving the disadvantages of conventional synthetic paper using fibers having a large average fiber diameter of 1 μm or more and large fiber diameters and large variations. Due to the thick fiber diameter, the dispersibility of the fiber is poor and it is difficult to obtain a thin synthetic paper, but also the permeability of various substances such as gas, fluid, powder (dust), various proteins, bacteria due to unevenness in the basis weight. And cause non-uniform adhesion. Further, since the fiber diameter is large, the specific surface area is small, and the performance such as the adsorption performance of various substances is inferior. Until now, there has been no practical method for producing nanofibers necessary for improving the drawbacks of synthetic paper.

  An object of the present invention is to solve the above-mentioned problems of the prior art, which is made of synthetic polymer nanofibers, the number average diameter of single fibers is nano level, and the diameter variation is very small. It is an object of the present invention to provide a synthetic paper including a nanofiber having a small pore area and a uniform nanofiber, and a method for producing the same.

The above-described problems of the present invention are solved by the following means.
(1) A nanofiber synthetic paper containing a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 500 nm and a single fiber ratio Pa of 60% or more. A thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2. A nanofiber synthetic paper comprising: a nanofiber dispersion, wherein nanofiber short fibers are dispersed after beating, and paper is produced without using a binder.
(2) A nanofiber synthetic paper containing a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 200 nm and a single fiber ratio Pa of 60% or more. A thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2. A nanofiber synthetic paper comprising: a nanofiber dispersion, wherein nanofiber short fibers are dispersed after beating, and paper is produced without using a binder.
( 3 ) The nanofiber synthetic paper has a single fiber number average diameter as a median value, and a single fiber diameter concentration index Pb representing a ratio of fibers entering a width of 30 nm before and after that is 50% or more. A method for producing nanofiber synthetic paper.
( 4 ) A nanofiber synthetic paper comprising a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 500 nm and a single fiber ratio Pa of 60% or more. A thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2. A method of producing a nanofiber synthetic paper, comprising: a nanofiber synthetic paper comprising the nanofiber dispersion, wherein other fibers having a number average single fiber diameter of 1 μm or more are made using the nanofiber dispersion as a binder.
( 5 ) A nanofiber synthetic paper comprising a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 200 nm and a sum of single fibers Pa of 60% or more. A thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2. A method of producing a nanofiber synthetic paper, comprising: a nanofiber synthetic paper comprising the nanofiber dispersion, wherein other fibers having a number average single fiber diameter of 1 μm or more are made using the nanofiber dispersion as a binder.
(6) nanofiber synthetic paper, according to the number average single fiber diameter and median, the index Pb of extremal coefficient of single fiber diameters representing the percentage of fibers that appear in the front and rear 30nm width is 50% or more (4) A method for producing nanofiber synthetic paper.

  Recently, for example, filters (eg, air filters, chemical filters, water purification filters), mask filters, battery separators, synthetic paper laminates, synthetic paper-filled columns, blood filter materials in the medical field, base materials for extracorporeal circulation, cells Requirement for products such as culture substrate, electronic material insulation, electronic substrate, decorative paper, wiping paper, furniture decorative paper and wallpaper, high-quality printing paper, design paper, high-quality printing paper There are areas where the accuracy of being done is very high. In such fields, conventional ultrafine fibers and nanofibers by electrospinning have been insufficient in uniformity and shape stability such as fiber diameter, pore diameter, fabric weight, thickness, and density. In addition, the electrospinning apparatus at the present stage has a problem in practical use because it is difficult to produce a wide nonwoven fabric as well as a safety problem and a recovery problem due to generation of a solvent. The nanofiber synthetic paper of the present invention enables the design of a material having uniform accuracy, and a practical nanofiber synthetic paper can be provided. In addition, it uses nano-level interactions such as adsorptivity and absorbability, biocompatibility and compatibility of various substances (fine particles, chemical substances, proteins, etc.) that are difficult to handle with conventional ordinary synthetic fibers and ultrafine fibers. The nanofiber synthetic paper of the present invention can cope with the field, and can solve the conventional problems associated with ultrafine fibers and electrospun ultrafine fibers.

  In the present invention, examples of the thermoplastic polymer include polyester, polyamide, polyolefin, polyphenylene sulfide (PPS), and the like. Examples of the polyester include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polylactic acid (PLA). Examples of polyamide include nylon 6 (N6), nylon 66 (N66), nylon 11 (N11), and the like. Examples of the polyolefin include polyethylene (PE), polypropylene (PP), and polystyrene (PS). In addition to the thermoplastic polymers described above, it is of course possible to use phenol resins, polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polysulfone, fluorine-based polymers, and derivatives thereof. Among these polymers, a polymer having a melting point of 165 ° C. or higher is preferable from the viewpoint of heat resistance. More preferably, the polycondensation polymer represented by polyester or polyamide has a high melting point. The melting point of each polymer is, for example, 165 ° C for PP, 170 ° C for PLA, 220 ° C for N6, and 255 ° C for PET. These polymers may contain compounding agents such as fine particles, flame retardants and antistatic agents. Further, other components may be copolymerized as long as the properties of the polymer are not impaired. Furthermore, a polymer having a melting point of 300 ° C. or lower is preferable because of easy melt molding.

  In particular, PPS has excellent heat resistance and chemical resistance, and also has low moisture absorption, so it has excellent dimensional stability when made into synthetic paper, so it can be used for applications such as insulating paper and circuit boards in the field of electronic information. It can be used suitably.

  The nanofiber dispersion of the present invention refers to a single fiber having a diameter of 1 to 500 nm, and its form is a dispersion of single fibers. Moreover, what is necessary is just a fibrous form, and it does not stick to the length or cross-sectional shape. In the present invention, the average value and variation of the single fiber diameters of the nanofibers are important. Here, the average number of single fibers is evaluated by the measurement methods “H. SEM observation of synthetic paper” and “I. Average average number of single fibers of nanofibers” in Examples described later. , “H. SEM observation of synthetic paper” and “J. Evaluation of sum Pa of single fiber ratio of nanofiber single fiber diameter” and “M. Evaluation of concentration index Pb of single fiber diameter of nanofiber” The

  An example of the SEM photograph of the nanofiber dispersion on the surface of the synthetic paper of the present invention is shown in FIG. The average number of single fibers was measured by observing nanofibers on the surface of synthetic paper with an ultra-high resolution scanning electron microscope (FE-SEM) and measuring the diameters of 30 single fibers randomly extracted within the same surface. Are evaluated with 10 synthetic papers, and a total of 300 single fiber diameters are measured, and a simple average of them is obtained. In the present invention, this is referred to as “single fiber number average diameter (φm)”. In the present invention, it is important that the number average single fiber diameter is 1 to 500 nm. This is a fineness of 1/100 to 1 / 100,000 compared to the ultrafine fiber by the conventional sea-island composite spinning, etc., and in this invention, the formation is better than the synthetic paper using the conventional ultrafine fiber, and A high-performance synthetic paper having a large specific surface area can be obtained. The single fiber number average diameter is preferably 1 to 200 nm, more preferably 1 to 150 nm, and even more preferably 1 to 100 nm. Especially when the synthetic paper of the present invention is used as a filter, high performance and high efficiency collection is required as a required characteristic, and when it is used as a separator, a high liquid shielding property is required as a required characteristic. Therefore, the single fiber diameter of the nanofiber is desirably smaller. In this case, the single fiber number average diameter is preferably 1 to 150 nm, and more preferably 1 to 100 nm.

  Moreover, the dispersion | variation in the single fiber diameter of nanofiber is evaluated as follows. In order to create a distribution table (histogram) from the single fiber diameter obtained above, the single fiber diameter φ is divided into arbitrary sections (n), and the average value at both ends of each section is defined as φi. The frequency fi for the diameter section φi (i = 1 to n) of each nanofiber of the section is counted, and a distribution table is created. As a method of dividing into arbitrary sections, for example, when the single fiber number average diameter φm is 500 nm or less, one section may be 1 to 10 nm and n may be 10 to 100 sections. (For comparison, in the case of other fibers having a single fiber number average diameter φm of more than 500 nm, one section should be 1/10 or less of the single fiber number average diameter φm, and n should be 10 to 100 sections. Can do).

  Next, “sum of single fiber ratio Pa” and “concentration index Pb” for evaluating the variation in single fiber diameter will be described.

  The frequency fi of nanofibers having a single fiber diameter φi that enters the same section is counted, and the result divided by N is the ratio Pi of the single fiber diameter. Pa can be obtained by simply adding Pi up to a section r in the range of 1 to 500 nm.

N = Σfi (i = 1 to n) (2)
Pa = Σ (fi / N) (i = 1 to r) (3)
Specifically, the individual fi / N up to the partition number r within the range of 1 to 500 nm may be added. In the present invention, it is important that the nanofiber has Pa of 60% or more, and more preferably 70% or more. As Pa is larger, the number ratio of nanofibers referred to in the present invention is larger, and the number of coarse single fiber diameters is smaller. Thereby, the function of the nanofiber can be sufficiently exhibited, and the quality stability of the product can be improved.

  Moreover, the concentration index Pb of the single fiber diameter indicates the concentration in the vicinity of the average diameter of the single fibers. Using the frequency fi of φi obtained as described above, a distribution table (histogram) of the frequency fj for the section of the square value χi of the single fiber diameter φi is prepared based on this data. A table of values Pj obtained by integrating the frequency numbers fj is created in advance.

Pj = Σ (fj / N) (j = 1 to n) (4)
Since the square value χ i of the single fiber diameter φ i is proportional to the weight of the fiber (cylindrical shape), it corresponds to the dtex, that is, the distribution with respect to the fineness, as can be seen from the equation (1). An approximate function Q (4 to 6th order function of χi) of “cumulative frequency Pj” for χi is created by Excel (trade name) manufactured by Microsoft Corporation. Then, assuming that the average number of single fibers φm is the median, the square value of 15 nm plus φm is χa, and the square of the value minus 15 nm of φm is χb, the single fiber diameter concentration index Pb is It is obtained from the following formula.

Pb = Q (χa) −Q (χb) (5)
In the present invention, the nanofiber dispersion in the synthetic paper has a single fiber diameter concentration index Pb representing a ratio of fibers entering the width of 30 nm before and after the average number of single fibers as a median value, and is 50% or more. Is preferably 60% or more, and more preferably 70% or more. This means the degree of concentration of the single fiber diameter variation around the single fiber number average diameter, and the higher the Pb, the smaller the single fiber diameter variation. The actual measurement methods of the actual single fiber number average diameter φm, the single fiber ratio sum Pa, and the single fiber diameter concentration index Pb are shown in the examples described later.

  The fiber diameter of the ultrafine fibers contained in the conventional synthetic paper is usually 1 μm or more, and even if fibers of 1 μm or less are contained, the fiber diameter varies greatly when viewed as a whole, and the fibers themselves are not entangled. For this reason, stable papermaking has been difficult. In addition, in order to enable papermaking, when a PVA fiber binder having a large fiber diameter or a pulp binder is used in combination, synthetic paper using 100% of the intended synthetic fiber cannot be obtained. Conventional ultrafine fibers have been difficult to deal with in fields that dislike other impurities, such as surgical separators, and fields that require thinness and accuracy, such as surgical anti-adhesion membranes in the medical field.

  By using the nanofiber dispersion in the synthetic paper of the present invention, it is possible to make paper with the nanofiber alone, and thus the above-mentioned problems can be solved.

  Moreover, since the number average single fiber diameter of the nanofiber dispersion in the synthetic paper of the present invention is 1/10 to 1/100 that of a conventional ultrafine fiber, the specific surface area is remarkably increased. For this reason, the characteristic property which cannot be seen with a normal extra fine fiber is shown, and the adsorption | suction characteristic can be improved significantly. That is, it easily adsorbs water vapor (that is, hygroscopicity), chemical vapor (odor), fine powder, and dust.

  For example, the moisture absorption of the conventional synthetic paper made of N6 ultrafine fibers is about 2.8% (Comparative Example 10 described later), whereas the moisture absorption of the N6 nanofiber synthetic paper of the present invention is 6.4% ( It became Example 1) described later.

In addition, by using nanofibers having a very small fiber diameter compared to conventional ultrafine fibers, pinholes can be formed even in synthetic paper with a very thin basis weight such as ² g / m ² as shown in Example 5 described later. There are few synthetic papers with uniform formation, and even if the thickness is very thin, it is possible to produce a synthetic paper with a very small air flow rate. This synthetic paper can be used for battery separator materials that are capable of ion migration, trace gas and trace drug migration, but dislikes large amounts of liquid migration. Also, in medical surgery, for example, leakage of bodily fluid or ascites from the affected area during or after surgery may become a fatal obstacle, or the leaked bodily fluid or ascites may cause contamination of other pathogenic bacteria Therefore, there has been a demand for a diaphragm material for surgery that has good compatibility with living bodies and prevents leakage of bodily fluids. An antithrombotic polymer film has been used as such a material, but such a polymer film is not flexible and difficult to handle during surgery. The synthetic paper of the present invention is also suitable for use in such a diaphragm material for surgery.

  In addition, the nanofiber synthetic paper of the present invention is characterized by a synthetic paper in which nanofibers are dispersed up to one single fiber as in Example 1 described later, and the basis weight, thickness, texture, etc. are uniform. It can be done. In addition, this nanofiber synthetic paper does not include fiber scraps that have been damaged when nanofibers are beaten, and when nanofibers are made to make synthetic paper. , A uniform sheet with few defects can be obtained.

  Nano-sized materials are becoming important for cell culture and protein adsorption / removal in the medical and bio fields, but with nanofibers using the “electrospinning” technology described in the background art, the fiber diameter of nanofibers is uniformly controlled. That was insufficient. The nanofibers present in the synthetic paper or on the surface of the present invention are compatible with the size and size of the adsorption sites of cells and proteins (proteins, enzymes, bacteria, viruses, etc. present in various blood). Since direct interaction between nanofibers and these cells and proteins is expected, it is also useful as an adsorbing material for medical and biotechnology.

The nanofiber synthetic paper used for such applications may use the surface of the synthetic paper, permeation or shielding as its function, or may be used by allowing fluid or fine particles to pass through. In the former case, battery separators and abrasives can be used as the application. However, it is preferable that the basis weight of the synthetic paper is relatively high, and the flexibility of the sheet when processing the synthetic paper into a target structure or nano Considering the packing property of the fiber in the synthetic paper, the basis weight of the synthetic paper is preferably 50 g / m ² or less, more preferably 30 g / m ² or less, and 10 g / m ² or less. Further preferred. Further, if the basis weight is too low, pinholes may be formed, so the lower limit of the basis weight is 1 g / m ² or more.

Furthermore, in the latter case, applications include medical products such as air filters, liquid filters, and blood filters, but there is a relationship with the density of synthetic paper. The thinner one is preferable, and the basis weight of the synthetic paper is preferably 10 g / m ² or less, more preferably 5 g / m ² or less.

Moreover, in the case of composite synthetic paper containing nanofibers in part, the basis weight of only the nanofibers present in the composite synthetic paper is preferably 5 g / m ² or less, and preferably 1 g / m ² or less. More preferably, it is preferably 0.0001 g / m ² or more.

  The synthetic paper of the present invention can be thickened or thinned according to the purpose, and can be freely controlled by the basis weight, but is not particularly limited. The thickness is preferably 10 μm or more, more preferably 100 μm or more, and more preferably 150 μm or more so that it can sufficiently withstand stress such as tension when processed into various products such as filters and separators. Is more preferable. The upper limit of the thickness is preferably 5000 μm (5 mm) or less.

The density of the nanofiber synthetic paper of the present invention is such that the synthetic paper does not easily wrinkle when used or processed according to each application, and the surface of the synthetic paper does not become uneven. Furthermore, it is preferably 0.3 g / cm ³ or less, more preferably 0.2 g / cm ³ or less, and further preferably 0.1 g / cm ³ or less. The lower limit of the density is preferably 0.001 g / cm ³ or more.

The synthetic paper of the present invention can be produced even if it is a thin synthetic paper having a basis weight of 8 g / m ² as in Example 1 described later, or even without a base material such as a binder, an aggregate, and a base material. Is possible. This is a strong cohesive force of nanofibers and its dispersion is difficult, but conversely, it is very convenient when making paper because of its strong cohesive force, and it has excellent entanglement and adhesion between nanofibers. It is thought that this is because. Moreover, in order to obtain such a papermaking good nanofiber, the freeness of the nanofiber is preferably 350 or less, more preferably 200 or less, further preferably 100 or less, The lower limit of the freeness is preferably 5 or more. Furthermore, by using such nanofibers, it was possible to make paper even if the basis weight was as low as ² g / m ² as in Example 5 described later. The nanofiber synthetic paper of Example 5, which will be described later, uses a screen wrinkle as a base substrate, but the nanofibers present in the opening portion of the screen wrinkle, that is, in the center of the lattice, are large pinholes even without a binder. There is no sheet.

Moreover, since the single fiber diameter of the nanofiber dispersion is uniform in the synthetic paper of the present invention, the size of the holes formed between the nanofibers in the synthetic paper is also uniform. The formation of pores is governed by the nanofiber's stiffness due to the type of nanofiber's polymer and the single fiber diameter. In addition, although formed by entanglement between nanofibers, an average pore diameter of about several to 10 times the single fiber diameter of the nanofiber is formed. For example, in order to efficiently collect fine particles and components to be removed in a fluid such as gas or liquid, the pore area of the nanofiber synthetic paper is 1.0 μm ² (pore diameter 1.1 μm) or less. Preferably, it is 0.5 μm ² (average pore diameter 0.75 μm) or less. The lower limit of the pore area is preferably 10 nm ² or more, and more preferably 50 nm ² or more. In addition, the nanofiber synthetic paper of the present invention is characterized not only by the pore size being nano-sized, but also by its small variation. Due to the small variation in pore size, various nano-level fine particles (generic name for dust, foreign matter, various proteins, bacteria, etc.) can be classified. Even if a filter with nano-sized pore size is simply made using nanofiber synthetic paper, clogging may occur immediately. Although there are cases where it is necessary to devise methods such as adopting a method, the uniform ultra-fine pores of the nanofiber synthetic paper are expected to exhibit functions utilizing the collection performance at the nano level.

In the nanofiber synthetic paper of the present invention, the air flow rate is preferably 30 cc / cm ² / sec or less. Since the air flow rate is small, that is, the gas shielding performance is high, it can be used for a partition wall such as a separator. The air flow rate is preferably 15 cc / cm ² / sec or less, more preferably 5 cc / cm ² / sec or less, and most preferably 1 cc / cm ² / sec or less. The lower limit of the air flow rate is preferably 0.25 cc / cm ² / sec or more.

The synthetic paper of the present invention is also characterized in that pinholes penetrating through the synthetic paper are suppressed because the voids in the synthetic paper are densely filled with the nanofiber dispersion. More specifically, it is preferable that the number of holes with a diameter of 50 μm or more penetrating from the front to the back of the paper is 0 to 1000 / cm ² . By setting the number of pinholes to 1000 / cm ² or less, gas permeability, liquid permeability, and the like can be suppressed. The number of pinholes is more preferably 100 / cm ² or less, further preferably 15 / cm ² or less, and most preferably 3 / cm ² or less.

  The synthetic paper of the present invention preferably has a surface smoothness of 300 seconds or more. The surface smoothness referred to here is Beck's surface smoothness (second display) defined in JIS P 8119-1976. Since the surface smoothness is high, the nanofiber synthetic paper of the present invention can be used for applications requiring smoothness such as a circuit board using insulating paper. The surface smoothness is preferably 1000 seconds or longer, more preferably 1500 seconds or longer, and still more preferably 3000 seconds or longer. The upper limit of the surface smoothness is preferably 20000 seconds or less.

  In the present invention, a mixed paper-making type comprising a nanofiber dispersion having a single fiber number average diameter of 500 nm or less and other fibers having a single fiber number average diameter of 1 μm or more, and further containing at least 5 wt% of the other fibers. Synthetic paper can also be produced. The nanofiber dispersion preferably has a single fiber number average diameter of 200 nm or less. Here, the weight mixing ratio of nanofibers can be evaluated by “P. Measuring method of weight mixing ratio of nanofibers” in Examples described later. Bulkiness can be imparted to the nanofiber synthetic paper by mixing paper making with the nanofiber dispersion and other fibers having a single fiber diameter of 1 μm or more.

  For example, by controlling the bulkiness of nanofiber synthetic paper, it becomes possible to control the movement of trace amounts of liquids such as circulating fluid and the passage of ions in battery separators and medical products. Improved functionality. The content of other fibers of 1 μm or more mixed with the nanofibers is preferably 5% or more by weight, more preferably 10% or more.

    Also, a composite papermaking type composition comprising a nanofiber dispersion having a single fiber number average diameter of 500 nm or less and other fibers having a single fiber number average diameter of 1 μm or more, and the nanofiber dispersion contains at most 3 wt% or less. Paper can also be made. The nanofiber dispersion preferably has a single fiber number average diameter of 200 nm or less. Further, the nanofiber content is more preferably 1 wt% or less. This is a mixed paper-making type nanofiber synthetic paper different from the previous synthetic paper. That is, the synthetic paper is characterized in that a small amount of the nanofiber dispersion is added to the synthetic paper mainly composed of other fibers of 1 μm or more. Synthetic paper composed of other fibers of 1 μm or more is bulky and has large gaps compared to synthetic paper composed of 100% nanofibers, and thus has excellent breathability, liquid permeability, and pressure resistance. Therefore, by mixing the nanofiber dispersion with other fibers of 1 μm or more to obtain a synthetic paper, the performance as a synthetic paper is sufficiently exhibited while taking advantage of the function of the nanofiber surface. In addition, since nanofiber dispersion easily aggregates, each nanofiber fiber is a space by dispersing a small amount of nanofiber in a spider web in a space in synthetic paper created by other fibers of 1 μm or more. It spreads and is held in the synthetic paper, and the original function of the nanofiber is easily exhibited. With this synthetic paper, it is expected that the surface area of the nanofibers can be used efficiently when used as a catalyst support for bio or chemical applications or battery applications.

  In the present invention, a nanofiber synthetic paper in which a nanofiber dispersion having a single fiber number average diameter of 500 nm or less is laminated on a support can also be produced. By laminating, not only can the strength of the synthetic paper of the present invention be improved by the reinforcing effect of the support, but also the permeability of gas and liquid can be controlled by laminating a small amount of nanofiber dispersion on the support. However, since the collection efficiency of various substances by nanofibers can be improved, such synthetic paper can be used for a filter or the like. As a laminating method, various methods such as a method of impregnating, dripping, spraying or coating with a dispersion liquid made of nanofibers can be adopted as well as papermaking. As the support, a woven fabric, a knitted fabric, a nonwoven fabric, a foam or the like can be appropriately selected depending on the application and purpose.

  In this invention, it can be set as the composite synthetic paper containing the above nanofiber synthetic paper, or a synthetic paper molded article. Also, by using nanofiber synthetic paper, it is possible to make a filter, separator, abrasive, medical product or circuit board.

  In the present invention, as shown in the text and examples, it is possible to make a nanofiber synthetic paper without using a binder. Although the nanofiber of the present invention is considered to have a form similar to natural pulp, the difference from this is that the nanofiber dispersion of the present invention has a uniform single fiber diameter compared to pulp, There is almost no fiber branching. Conventionally, various methods have been studied for making paper by fibrillating a thermoplastic polymer, but it has been very difficult to make paper without using a binder. Furthermore, it is difficult to make paper without using a binder even if the diameter of the conventional ultrafine fiber having a number average single fiber diameter of 0.5 μm or more is small.

  As described above, since the nanofiber dispersion of the present invention can be made in the same manner as natural pulp due to its cohesive strength and entanglement, synthetic paper can be produced without using a binder. Is possible. Furthermore, as shown in Example 3 to be described later, it is possible to use a nanofiber dispersion as a binder, and it is also possible to make a normal synthetic fiber or ultrafine fiber, using the nanofiber dispersion as a binder, and the average number of single fibers It is also possible to make a synthetic fiber made of a thermoplastic polymer having a thickness of 1 μm or more.

  Next, the manufacturing method of the nanofiber used for the synthetic paper of this invention is demonstrated.

  First, a method for producing a “polymer alloy fiber” that is a raw material for producing nanofibers will be described. As a method for producing the polymer alloy fiber, for example, the following method can be employed.

  That is, a polymer alloy chip made by alloying two or more kinds of polymers having different solubility in a solvent or a chemical solution is prepared, and this is introduced into a hopper 1 of a spinning device (see FIG. 1), and alloy melting is performed in a melting part 2. After being discharged and spun from the nozzle hole 5 disposed in the spinning pack 4 in the heat-insulating spin block 3, the chimney 6 is cooled and solidified to form the yarn 7, the converged oiling guide 8, the first take-up roller 9, The fiber is wound up by the winder 11 through the second take-up roller 10. And this is extended | stretched and heat-processed as needed and a polymer alloy fiber is obtained. Further, this is treated with a solvent or a chemical solution to remove sea components, and nanofibers used in the present invention are obtained. Here, in a polymer alloy fiber, a polymer that is hardly soluble in a solvent or chemical solution that later becomes a nanofiber is used as an island component, and an easily soluble polymer is used as a sea component, and by controlling the size of this island component, In addition, it is possible to design the number average diameter and variation of single fibers of nanofibers.

  Here, the size of the island component is obtained by observing the cross section of the polymer alloy fiber with a transmission electron microscope (TEM) or a scanning electron microscope (SEM), and evaluating it in terms of diameter. The evaluation method of the number average diameter of the single fiber of the island component in the polymer alloy fiber is shown in the items F and G of the measuring method in Examples described later. Since the diameter of the nanofiber is almost determined by the island component size in the polymer alloy fiber that is the nanofiber precursor, the distribution of the island size is designed according to the diameter distribution of the nanofiber. For this reason, kneading of the polymer to be alloyed is very important, and in the present invention, high kneading is preferably performed by a kneading extruder, a stationary kneader, or the like. It should be noted that simple chip blending (for example, Japanese Patent Application Laid-Open No. Hei 6-272114) is insufficient in kneading, and it is difficult to disperse island components with a size of several tens of nm.

  Specific guidelines for kneading depend on the polymer to be combined, but when using a kneading extruder, it is preferable to use a biaxial extrusion kneader, and when using a static kneader, the number of divisions Is preferably 1 million or more. In addition, a combination of polymers is also important for the ultrafine dispersion of island components with a size of several tens of nanometers.

In order to make the island domain (cross section of the nanofiber) close to a circle, the island polymer and the sea polymer are preferably incompatible. However, it is difficult for the island component polymer to be sufficiently finely dispersed by a simple combination of incompatible polymers. For this reason, it is preferable to optimize the compatibility of the polymer to be combined, but one index for this purpose is the solubility parameter (SP value). Here, the SP value is a parameter reflecting the cohesive strength of substances defined by (evaporation energy / molar volume) ^1/2 , and a polymer alloy having good compatibility can be obtained between those having close SP values. There is sex. The SP value is known for various polymers, and is described, for example, in “Plastic Data Book”, edited by Asahi Kasei Amidus Co., Ltd./Plastics Editorial Department, page 189.

It is preferable that the difference in SP value between the two polymers is 1 to 9 (MJ / m ³ ) ^{1/2 because} it is easy to achieve both circularization and ultrafine dispersion of island component domains due to incompatibility. For example, the difference in SP value between N6 and PET is about 6 (MJ / m ³ ) ^1/2, which is a preferable example. The difference between N6 and PE is about 11 (MJ / m ³ ) ^1/2. This is an undesirable example.

  Further, it is preferable that the difference in melting point between polymers is 20 ° C. or less because kneading using an extrusion kneader is easy to knead with high efficiency because the difference in melting state in the extrusion kneader hardly occurs. Here, in the case of an amorphous polymer, since there is no melting point, it is replaced by the Vicat softening temperature or the heat distortion temperature.

Furthermore, melt viscosity is also important, and if the polymer forming the island is set lower, the island polymer is likely to be deformed by shearing force. From the viewpoint of However, if the island polymer is excessively low in viscosity, it tends to be seamed and the blend ratio with respect to the whole fiber cannot be increased. Therefore, the viscosity of the island polymer is preferably 1/10 or more of the viscosity of the sea polymer. In addition, the melt viscosity of the sea polymer may greatly affect the spinnability, and it is preferable to use a low-viscosity polymer of 100 Pa · s or less as the sea polymer because the island polymer is easily dispersed. This can also significantly improve the spinnability. At this time, the melt viscosity is a value at a shear rate of 1216 sec ⁻¹ at the die temperature during spinning.

  In order to improve the spinnability and spinning stability, the die temperature is preferably 25 ° C. or more from the melting point of the sea polymer, and the distance from the die to the start of cooling is 1 to 15 cm to cool the yarn.

The spinning speed is preferably higher speed spinning from the viewpoint of increasing the draft in the spinning process, and a draft of 100 or more is preferred from the viewpoint of reducing the nanofiber diameter. The spun polymer alloy fibers are preferably subjected to drawing and heat treatment, but the preheating temperature during drawing is higher than the glass transition temperature (T _g ) of the island polymer in order to reduce the yarn unevenness. preferable.

  In this production method, by combining the above polymers and optimizing the spinning / drawing conditions, the island polymer is ultra-finely dispersed to several tens of nanometers, and a polymer alloy fiber with small thread spots is obtained. Thus, not only a certain cross section but also any cross section in the longitudinal direction can be used as a “polymer alloy fiber” having small island polymer diameter variation.

 “Polymer alloy fiber” spun by the above method usually has a single yarn fineness of 1 to 15 dtex (10 to 40 μm), and a bundled yarn (5,000 dtex or less) in which the fiber filaments are collected. it can. Depending on the single fiber diameter of the fiber, several thousand to several million island polymers (several wt% to 80 wt%) are precursors of nanofibers in the single yarn of “polymer alloy fiber”. It is dispersed in sea polymer (see Fig. 2).

  Next, a method for producing nanofiber synthetic paper will be described.

  To make nanofiber short fiber from “polymer alloy fiber” and make it into a synthetic paper, we can remove the nanofiber bundle from the “polymer alloy fiber” bundled yarn. , Then cut (first sea removal method), or cut the focused yarn of “polymer alloy fiber” and then sea water (post seawater method), or after obtaining nanofiber short fibers by either method Further, the obtained nanofiber short fibers are dispersed by a beater until the nanofibers are separated, and a paper can be made to obtain a synthetic paper.

  In the case of the pre-sea removal method, the sea component is first dissolved in the state of a “polymer alloy fiber” bundled yarn (5000 dtex or less) or a focused tow (over 5000 to several million dtex). Remove with a possible solvent (extract solution) or chemical solution, wash with water and dry, then cut to an appropriate fiber length with a guillotine cutter or slicing machine. In the case of the post-sea removal method, it is possible to dissolve the sea components after cutting to a suitable fiber length with a guillotine cutter or slicing machine in the state of the “polymer alloy fiber” bundling yarn and the state of the bundling tow. It is obtained after removing with a solvent or chemical, washing with water and drying.

  The appropriate fiber length of the nanofiber short fiber is preferably 0.1 to 20 mm, more preferably 0.1 to 5 mm, and more preferably 0.2 to 1 mm from the viewpoint of papermaking properties. More preferably.

  Solvents and chemicals used to remove sea components from “polymer alloy fibers” include alkalis such as caustic soda and caustic potash, acids such as formic acid, trichrene, limonene, xylene, etc. An organic solvent or the like can be used. When seaming a bundled yarn or tow of a “polymer alloy fiber”, it can be seamed in a crushed state or a state wrapped around a crushed frame. However, when the sea component of the “polymer alloy fiber” is seamed with a solvent or a chemical solution in the state of rags, the sea component of the sea component of the “polymer alloy fiber” is usually very high at 20 to 80 wt%. As the sea is removed, the volume shrinks in the direction of the diameter of the case, the “polymer alloy fibers” in the case come into close contact with each other, and solvents and chemicals cannot penetrate between the fibers. It becomes difficult to remove the polymer of the sea component gradually, because it is covered with the precipitated polymer, and in the worst case, it becomes a dumpling and it is very difficult to proceed with the sea removal of the “polymer alloy fiber” It may become. In order to improve this, it is possible to prevent the shrinkage of the casket by winding it around the casket frame rather than just a crushed state and suppress the adhesion between the “polymer alloy fibers”, so that the solvent always flows between the “polymer alloy fibers”. Since it becomes easy, it is preferable. By this method, sea removal can be performed not only in the bundle yarn of “polymer alloy fiber” but also in the tow state. In order to perform sea removal more efficiently, the total fineness of the tow is preferably 500,000 dtex or less, and more preferably 100,000 dtex or less. On the other hand, since the productivity of sea removal improves as the total fineness of the “polymer alloy fiber” increases, the “polymer alloy fiber” before sea removal preferably has a total fineness of 10,000 dtex or more.

  In addition, sea removal can also be achieved by decomposing a sea component polymer with a chemical solution such as alkali. In this case, sea components can be removed relatively easily even in a crushed state. This is because the sea component polymer can be easily dissolved and removed by becoming a low molecular weight substance or monomer by hydrolysis or the like. In addition, when sea components are removed by decomposition, gaps are created between fibers, and chemicals such as alkali penetrate into the interior of “polymer alloy fibers”, which are the precursors of nanofibers. The sea removal speed will be accelerated, and unlike sea components dissolved and removed by organic solvents, sea removal will be possible even in a casket state.

  As described above, a tow or casserole composed of “polymer alloy fibers” which are nanofiber-forming fibers, that is, a nanofiber bundle obtained by treating such a fiber bundle with a solvent or a chemical solution is a nanofiber for all the fibers. The area ratio of the fiber is preferably 95 to 100%. This means that in the nanofiber bundle after seawater removal, there is almost no part that has not been seawatered, which makes it possible to minimize the incorporation of coarse fibers, which can be made later by papermaking. High-quality nanofiber synthetic paper can be obtained.

In the present invention, a “polymer alloy fiber”, that is, a fiber bundle made of nanofiber-forming fibers, is subjected to sea removal treatment with a solvent or a chemical solution in a state where the fiber density of the fiber bundle is 0.01 to 0.5 g / cm ^3. It is preferable to do. When the fiber density of the fiber bundle is smaller than 0.01 g / cm ³ when performing sea removal treatment with a solvent or a chemical solution, the shape of the fiber bundle to be treated becomes unstable, and nanofiber formation cannot be performed uniformly. There is a case. On the other hand, when the fiber density of the fiber bundle exceeds 0.5 g / cm ³ , the penetration of the solvent or the chemical solution into the fiber bundle is deteriorated, the nanofiber formation becomes incomplete, and the nanofiber content in the nanofiber bundle is reduced. May decrease. The fiber density of the fiber bundle during the sea removal treatment with a solvent or a chemical solution is more preferably 0.01 to 0.4 g / cm ³ , and still more preferably 0.03 to 0.2 g / cm ³ .

  When the sea component is decomposed and removed with a chemical solution such as alkali, the sea component of the “polymer alloy fiber” is preferably a polymer that is easily decomposed by alkali, and the sea component is preferably a PLA-based or PVA-based polymer. preferable. As shown in Example 10 to be described later, the sea component was changed from the copolymerized PET of Example 1 to the PLA of Example 10, so that the concentration of sodium hydroxide was very low, from 10 wt% to 1 wt%. Can be Such sea removal work with alkali is very limited because it is extremely dangerous when treated with high-temperature and high-concentration alkali, and the work efficiency is poor, and countermeasures against leakage and corrosion are necessary for the equipment. Only the device could be used. In addition, when the alkali remaining in the treatment liquid after sea removal is waste-treated, the alkali is in a high concentration. There was a need to reconcile. By reducing the alkali concentration in the treatment liquid during alkaline seawater removal, this dangerous work can be avoided and seawater can be efficiently removed, reducing the burden on the waste liquid treatment process. be able to.

  Next, a specific method for the post-sea removal method will be described. The removal of short fibers obtained by cutting “polymer alloy fibers” can be achieved by placing the short fibers in an organic solvent or a chemical solution such as alkali or acid and dissolving or decomposing the sea components while stirring with a stirrer. To do. Such sea removal is usually performed by batch processing, and it is preferable to divide the processing steps into several stages. When the sea component is efficiently removed with a solvent such as trichlene, when the first-stage sea component is dissolved, the concentration of the sea component polymer dissolved in the solvent should be 6 wt% or less. Is preferable, and it is further more preferable to make it 3 wt% or less. At the time of sea removal after the second stage, the concentration of the polymer dissolved in the solvent is gradually decreased, and the concentration is preferably 0.1 wt% or less, and is preferably 0.01 wt%. More preferably. Further, when the sea component is efficiently decomposed and removed by hydrolysis with a chemical solution, the concentration of the sea component dissolved in the chemical solution in a low molecular weight or monomerized state is preferably 10 wt% or less. More preferably, it is 5 wt% or less. During sea removal after the second stage, gradually reduce the concentration of sea components dissolved in the chemical solution in a low molecular weight or monomerized state so that the concentration is 0.1 wt% or less. It is preferable that the content be 0.01 wt% or less. The short fiber obtained by cutting the “polymer alloy fiber” is treated with each solvent or chemical solution as described above, filtered through an appropriate stainless steel wire mesh filter, etc., and the nanofiber is recovered. Thoroughly wash away the solvent and chemicals adhering to the product, and then dry.

  Regardless of the method of seawater removal of bundled yarn, tow, and cut fiber of “polymer alloy fiber”, efficient seawater removal can be achieved by using a solvent such as an organic solvent, alkali or acid used for seawater removal in the second and subsequent stages. It is preferable to use a new chemical solution such as a high temperature of the desealing treatment as much as possible, and constantly circulate the solvent or the chemical solution with stirring. Moreover, it is preferable to make the fiber amount ratio with respect to the solvent or chemical used for sea removal as small as possible and to reduce the concentration of the sea component in the solvent or chemical after the sea removal treatment.

  It is preferable that the bundled yarn, tow, and cut fiber containing a solvent or a chemical solution are removed to some extent by a centrifuge between each step of the sea removal treatment after the first stage. When the amount is 200 wt% or less, the handleability in the next step is improved, which is preferable. Further, when the amount of the solvent or the chemical solution with respect to the fiber weight is 50 wt% or more, the solvent or the chemical solution between the fibers serves as a spacer, and the excessive adhesion of the fibers can be suppressed. It is preferable because sea removal efficiency is improved. Furthermore, in order to improve sea removal efficiency, when sea removal treatment is performed several times, washing is performed after the treatment in each stage, sea components adhering to the fibers are removed, and sea components mixed in the subsequent solvent or chemical solution It is preferable to reduce the amount. When sea removal with a solvent or chemical solution is completed, the residual sea component can be suppressed by washing until the sea component adhering to the fiber is preferably 0.1 wt%, more preferably 0.01 wt% or less. it can.

  In addition, when nanofiber bundles are obtained by the pre-sealing method, the nanofiber focusing yarn and tow obtained should be cut to an appropriate fiber length according to the purpose and purpose of the nanofiber using a guillotine cutter or slicing machine. However, such a bundled yarn or tow preferably has a moisture content of 20 to 100 wt% before being cut. The nanofiber converging yarn and tow after sea removal have better converging properties if they contain a certain amount of moisture, so that they are easier to handle and further improve the accuracy of cutting, so that the uniformity of the cut length is improved. Further, since the fusion of short fibers due to heat generation at the time of cutting is suppressed, the adhesion of the short fibers to the cutting blade is reduced, and the production efficiency at the time of cutting is improved. Furthermore, it is also preferable to apply 0.01 to 1 wt% (as pure oil agent of 100%) to the bundling yarn and tow.

  The nanofiber short fiber thus obtained is a fiber in which several thousand to several million nanofibers are aggregated depending on the diameter of the nanofiber.

  It is preferable that the ratio (L / D) of the fiber length L (mm) of the nanofiber short fiber obtained as described above and the single fiber number average diameter D (mm) of the nanofiber is in the range of 100 to 50,000. . Thereby, the entanglement property and adhesiveness of the nanofiber are improved, and the paper strength of the synthetic paper of the present invention can be improved. L / D is preferably 1000 to 35000, more preferably 3000 to 20000.

  Next, the nanofiber short fibers are beaten with a beater. By beating, nanofiber short fibers can be separated into nanofibers one by one. Examples of the beater include Niagara beaters and refiners at the production level, and experimentally include a home mixer and cutter, a laboratory grinder, a biomixer, a roll mill, a mortar, and a PFI beater. In the transmission electron microscope (TEM) or scanning electron microscope (SEM) photograph of the fiber cross section of the nanofiber short fiber, the nanofibers are observed one by one, and the nanofiber present on the surface is a small amount of nanofiber short fibers. Although it can be seen that it is liberated from the surface, most of the nanofibers in the short fibers exist as aggregates, so simply squeezing this aggregate or simply putting the nanofiber short fibers in water and stirring them It is difficult to separate nanofibers down to the single fiber level. This is because the fiber diameter of nanofibers is very thin and the specific surface area is significantly increased compared to conventional ultrafine fibers. This is thought to be due to the strong interaction and large cohesion.

  For this reason, it is preferable that the nanofiber short fibers are separated by the above-described beater. However, among the beating machines, a device having a cutter or pulverized blades is liable to damage the fiber, and has the disadvantage of cutting the fiber and shortening the fiber length at the same time as the effect of separating the fiber. Although nanofibers have strong cohesive strength between fibers, the fibers are thin. Therefore, in a device having a cutter or a pulverized blade, the fiber is seriously damaged, and in severe cases, it may be pulverized into powder. For this reason, even if the fibers are beaten, it is preferable to loosen or break the agglomeration between the fibers by applying a shearing force rather than crushing or cutting force. In particular, since the PFI beating machine beats by the shearing force due to the difference in the peripheral speed between the inner blade and the outer container, the damage until the nanofibers are loosened one by one is very small and preferable. Even when other beating devices are used, in order to reduce the damage to the fibers by reducing the beating force against the nanofibers, it is possible to reduce the beating speed and pressure during beating and to process under soft conditions. preferable. Even if it is beaten for a long time under soft conditions such as a low rotation speed even in a mixer for home use or laboratory use, although it is inferior in efficiency, it can be beaten to one nanofiber in the same way as the above-described beating machine. it can.

  The beating is preferably performed separately for the primary beating and the secondary beating. In the primary beating, it is preferable that the nanofiber aggregate is lightly loosened with a shearing force to reduce the size of the nanofiber aggregate to some extent. The primary beating is preferably carried out until the freeness representing the degree of beating of the fibers is 500 or less, more preferably 350 or less, and more preferably 5 or more. The freeness herein refers to the Canadian standard freeness water described in JIS P 8121 “Pulp Freeness Test Method” shown in “Q. Nanofiber Freeness Test Method” in the Examples described later. It is a value measured according to the degree test method. When measuring the freeness of nanofibers, nanofibers that have been beaten and dispersed in water may clog the filter in the freeness tester container. Evaluate by water content. In the case of primary beating with a Niagara beater or refiner, nanofiber short fibers are generally dispersed in water. However, if the concentration of nanofibers in the entire dispersion is 5 wt% or less, beating is performed uniformly. ,preferable. Moreover, since 0.1-1 wt% improves the efficiency of beating, it is more preferable. In the primary beating, when the set clearance of a beating machine such as a Niagara beater or a refiner is set to a large value, for example, about 0.5 to 2 mm, the pressure load applied to the beating apparatus and the processing time of the beating process can be reduced. After beating the nanofiber short fiber, the nanofiber is filtered and collected with a wire mesh filter, etc., dehydrated with a dehydrator or the like so that the moisture content is 50 to 200%, and stored, the capacity of the nanofiber after beating This is preferable because it can be made small, and it is easy to secure a storage place and handle in the next process.

  Further, the secondary beating referred to in the present invention is a beating of nanofibers subjected to the primary beating more precisely. Niagara beaters, refiners, PFI beating machines, etc. can be used as the apparatus used at this time, but it is preferable to set the setting clearance of each beating machine to 0.1 to 1.0 mm, and to 0.1 to 0.5 mm. More preferably, it is preferable to reduce the pressure and process under soft conditions. When the refiner is used, the shape of the processing blade incorporated in the apparatus can be appropriately changed. However, it is preferable to select a shape having a scissor effect or shearing effect rather than cutting the fiber. In particular, it is optimal to use a PFI beating machine for experimentally performing secondary beating of nanofibers. Since the PFI beating machine beats by a shearing force due to the difference in peripheral speed between the inner blade and the outer container, the fiber damage until the nanofibers are beaten one by one is very small and more preferable. In addition, the fiber concentration of the nanofibers during beating can be increased to 5 to 20 wt%, and the inner wing part of the beating machine is always uniformly applied to the fibers, so that the nanofiber aggregate becomes thin according to the beating. Thus, even if the strength of the fiber is reduced, the fiber can be beaten uniformly without being further cut or powdered in the fiber length direction. Thus, the freeness of the nanofiber dispersion obtained by the secondary beating is preferably 350 or less, more preferably 200 or less, further preferably 100 or less, and 5 or more. Is preferred. When the freeness exceeds 350, the beating degree is small and fibers that are not sufficiently beaten remain, and the nanofibers are not sufficiently beaten. There is a case. When performing secondary beating with a Niagara beater or refiner, a household or laboratory mixer, or cutters, the nanofiber concentration in the water is processed at a low concentration. Since the rotating blade hits repeatedly locally, the effect of cutting and crushing the fiber is great, and it is easy to cut or powder in the fiber length direction, so beating with mild beating conditions such as blade shape, rotation speed, pressurizing condition etc. It is preferable to do. The nanofibers beaten in this way are preferably collected by filtration with a wire mesh filter or the like when beaten in water, and dehydrated and stored with a dehydrator or the like so that the moisture content is 50 to 200 wt%.

  Next, a method for adjusting the dispersion, which is a raw material for making the nanofiber synthetic paper, will be described.

  The beaten nanofiber and water, and if necessary, a dispersing agent and other additives are put into a stirrer and dispersed to a predetermined concentration. Depending on the single fiber diameter of the nanofiber and the basis weight of the synthetic paper to be produced, the nanofiber dispersion has a large specific surface area, and the hydrogen bonding force and intermolecular force acting between the nanofibers are large. In order to prevent this aggregation, it is preferable to adjust the dispersion at as low a concentration as possible. From the viewpoint of making the dispersibility of the nanofibers in the dispersion uniform, the concentration of the nanofibers in the dispersion is preferably 0.01 to 1.0 wt%. Furthermore, when the nanofiber dispersion liquid is made as it is, it may become a non-uniform synthetic paper, so it is preferable to add a dispersant to the slurry. Depending on the type and properties of the nanofiber polymer, an anionic, cationic, or nonionic dispersant is appropriately selected as the dispersant. Even with a dispersant having the same structure, its molecular weight, nanofiber concentration, and other compounding agents Therefore, it may be properly used depending on the type of nanofiber polymer and the intended application. In addition, as a principle of selecting an appropriate dispersant, for example, when dispersing by repulsion of electric charge between nanofibers, the type of the dispersant is selected according to the surface potential (zeta potential). In the case of nanofibers with a zeta potential in the range of −5 to +5 mV at pH = 7, it is preferable to add a nonionic dispersant, and when the zeta potential is −100 mV or more and less than −5 mV, an anionic dispersant Is preferably added, and when the zeta potential exceeds +5 mV and is 100 mV or less, it is preferable to add a cationic dispersant. For example, in N6 nanofibers, the zeta potential (pH = 7 vicinity) measured by laser Doppler electrophoresis is -14 mV, and the surface is negatively charged. To increase the absolute value of this potential, an anionic dispersion is used. When the agent is used, the zeta potential becomes −50 mV, so that dispersibility is improved. In addition, when dispersed by steric repulsion, if the molecular weight becomes too large, the effect as a flocculant rather than a dispersant increases, so it is preferable to control the molecular weight of the dispersant, and the molecular weight of the dispersant is 1000 It is preferably ˜50000, more preferably 5,000 to 15000.

Furthermore, the concentration of the dispersant to be added is preferably 0.01 to 1.0 wt%, and more preferably 0.05 to 0.5 wt%. Conventional paper making of ultrafine fibers of 1 μm or more is difficult because the fibers are not intertwined. However, in the case of nanofibers, it is possible to make paper with nanofibers alone. from the viewpoint of improving the paper strength, the basis weight of the nanofiber synthetic paper is preferably 50 g / ^{m 2} or less, more preferably 30 g / ^{m 2} or less, more preferably 0.05 g / ^{m 2} or more at 10 g / ^{m 2} or less. If the nanofiber has a relatively small single fiber diameter and good dispersibility, a basis weight of ² g / m ² or less is possible. In addition, when making paper with nanofibers alone, the fiber length is slightly longer, and the fiber length is preferably 1 to 6 mm, and more preferably 2 to 3 mm.

  Further, if necessary, a binder can be used when making the nanofiber synthetic paper. When fibers are used as binders, natural pulp (wood pulp, hemp pulp, straw, honey, etc.), preferably fusible fibers having a low melting point component or a low softening point component, PE, PP fibers, PLA fibers, PS-based fibers, copolymerized polyamides and copolymerized polyester-based fibers, and core-sheath composite fibers having an easily fusible component as a sheath component are preferable. Further, when the nanocomponent synthetic paper is obtained by removing the sea component after making the “polymer alloy fiber”, it is preferable to use a fiber for a binder having good resistance to chemicals and solvents. In general, since the number average single fiber diameter of commercially available binder fibers is as thick as 10 μm or more, a binder fiber made of ultrafine fibers having a single fiber diameter of 1 to 10 μm is required to obtain a dense sheet when paper is made. Is preferred. It is also preferable to use a resin binder. The resin is preferably a polyurethane, polyphenol, polyacrylic acid, polyacrylamide, epoxy, silicone, or vinylidene fluoride polymer. In the slurry in which nanofibers are dispersed, modifiers and additives are used in combination to improve performance such as strength, tear resistance, abrasion resistance, antistatic properties, surface gloss, smoothness, flexibility, and texture. be able to.

  As a method for making paper with such nanofibers, a dispersion (slurry) in which nanofibers are dispersed is put into a slurry box of a paper machine, and paper is made with a normal mechanical paper machine. As the paper machine, any of the long-mesh type paper machine, twin-wire type paper machine, and round net type paper machine can be used, and an appropriate paper machine may be used according to the purpose and purpose. When a paper having a relatively large basis weight is desired to be made, it is preferable to use a long net type paper machine. When a basis weight is relatively small and a thin matter is desired to be made, it is preferable to use a round net type paper machine. When making paper on a small scale such as in a lab, it is possible to make paper using a commercially available square sheet machine, etc., putting nanofiber slurry into a 25 cm square container, and suction filtering with a wire mesh filter. Nanofiber synthetic paper can be obtained by dehydration and drying.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, the measuring method in an Example used the following method. The measurement results in Examples and Comparative Examples are collectively shown in Tables 1 to 4.

A. Polymer melt viscosity The polymer melt viscosity was measured by Toyo Seiki Capillograph 1B. The polymer storage time from sample introduction to measurement start was 10 minutes.

B. Melting | fusing point The peak top temperature which shows melting | dissolving of a polymer by 2nd run was made into melting | fusing point of a polymer using Perkin Elmaer DSC-7. The temperature rising rate at this time was 16 ° C./min, and the sample amount was 10 mg.

C. Color tone (b ^* value):
The b ^* of the sample was measured using a color meter MINOLTA SPECTROPHOTOMETER CM-3700d. At this time, D ₆₅ (color temperature 6504K) was used as a light source, and measurement was performed in a 10 ° visual field.

D. Mechanical Properties of Polymer Alloy Fiber A sample fiber 10 m was sampled from the polymer alloy fiber, the weight was measured with n number = 5 times, and the fineness (dtex) was obtained from the average value. Then, at room temperature (25 ° C.), an initial sample length = 200 mm, a pulling rate = 200 mm / min, and a load-elongation curve was obtained under the conditions shown in JIS L1013. Next, the load value at the time of breaking was divided by the initial fineness, which was used as the strength, and the elongation at break was divided by the initial sample length to obtain a strength / elongation curve.

E. Worcester spots of polymer alloy fibers (U%)
Measurement was performed in the normal mode at a yarn feeding speed of 200 m / min using a USTER TESTER 4 manufactured by Zerbegger Worcester. F. Observation of cross section of fiber by TEM Ultra-thin sections were cut in the cross section direction of the fiber, and the cross section of the fiber was observed with a transmission electron microscope (TEM). Nylon was metal dyed with phosphotungstic acid.

TEM apparatus: H-7100FA type manufactured by Hitachi, Ltd. Single fiber number average diameter of island component (nanofiber precursor component) in “polymer alloy fiber” The number average value of single fiber diameter is determined as follows. In other words, we measured the diameter of 300 island components randomly extracted in the same cross-section using the image processing software (WINROOF) of the island component cross-section photograph by TEM, integrated the individual data, and divided by the total number. A simple average value was obtained. This was performed at five locations 10 m apart from each other as the length of the “polymer alloy fiber”, and the diameter of a total of 1500 island components was measured, and the average value was taken as the “island component number average diameter”.

H. SEM observation of synthetic paper Cut 10cm square synthetic paper from any place of nanofiber synthetic paper, take 5mm square sample at each arbitrary place of each synthetic paper, deposit platinum, Hitachi ( The surface of the synthetic paper was observed with an ultra-high resolution electrolytic emission scanning electron microscope (UHR-FE-SEM) manufactured by Co., Ltd.

I. Nanofiber single fiber average diameter φm
The average single fiber diameter φm is determined as follows. That is, the diameter of 30 single fibers randomly extracted from a sample of 5 mm square using the image processing software (WINROOF) from the nanofiber surface photograph taken in the above section H is measured, and the total number is obtained after integrating the individual data. The simple average value was obtained by dividing by. Sampling was performed a total of 10 times to obtain 30 single fiber diameter data, and a simple average obtained from the total 300 single fiber diameter data was defined as “single fiber number average diameter φm”.

J. et al. Evaluation of the sum Pa of the single fiber ratio of the nanofibers The sum Pa of the single fiber ratio is obtained from the formula (3) described in the column of [Best Mode for Carrying Out the Invention] using the data measured in the above section I. Ask.

K. Evaluation of Concentration Index Pb of Single Fiber Diameter of Nanofiber Evaluation of the concentration degree of single fiber diameter Pb is described in the column of [Best Mode for Carrying Out the Invention] using the data measured in the above section I. (5) It evaluates by Formula.

L. Thickness of synthetic paper Ten sheets of 10 cm square synthetic paper are cut from an arbitrary place of the nanofiber synthetic paper, and 10 points are measured for each sheet. The thickness was measured with a micrometer at 20 ° C. and 65% on a sample stage with a microphone meter, and all data were summed and simply averaged to obtain a thickness t (μm).

M.M. Synthetic paper weight and density Cut 10 sheets of 10cm square synthetic paper from any place on the nanofiber synthetic paper and measure the weight (g) of each piece at 20 ° C and 65%. the divided by 0.01 m ^2, was calculated basis weight M (g / ^{m 2).} Further, the density, the value of this weight per unit area M was divided by the value of the average thickness measured above in cm units, and calculate the average density (g / cm ^3).

N. Hole area of synthetic paper The average hole area of synthetic paper is determined as follows. Of the H term. In SEM observation of synthetic paper, the magnification of the SEM photograph used for evaluating the pore area is taken at a magnification K of the following formula (magnification within ± 30%) when the average number of single fibers is φm (nm).

K = 2500,000 / φm (6)
On the SEM photograph measured at the above magnification K, a square frame with a side length of 50 mm (constant at any magnification) is drawn at an arbitrary location. Further, the fiber image in the frame is taken into image processing software (WINROOF), and eight or more luminance distribution measurement lines are placed on the taken image at equal intervals, and the luminance distribution of each fiber on the image is displayed as an image. Measure to binarize. Ten fibers are selected from the higher surface luminance, and the luminance is averaged to obtain the average high luminance Lh. Using 50% of the average high luminance Lh as the threshold value Lu, fibers having the luminance Lu or less are erased by image processing (Threshold function) (the hole near the surface portion is selected by this processing). The total area Ai (nm ² ) surrounded by the selected fibers is measured by image processing (either manual operation or computer automatic method is possible). At this time, holes of 64% (nm ² ) or less of the square of the average number of single fibers φm in the total area data are excluded. The remaining area Ai after the exclusion is integrated and divided by the remaining number n to calculate the average pore area.

O. Method of measuring the weight mixing ratio of nanofibers The weight mixing ratio of nanofibers in composites and mixed synthetic paper containing nanofibers is evaluated by observing the cross section of the synthetic paper with an ultrahigh-electrolysis emission scanning electron microscope (SEM). . First, the synthetic paper is embedded in an embedding resin (such as an epoxy resin or a curable polyester resin), and the embedded sample is cut with a diamond cutter or a microtome so that the cross section of the synthetic paper is exposed. After polishing the cut surface of the sample with sandpaper or abrasive, wash well with water and dry at low temperature. Platinum is vapor-deposited on the sample, and a cross-sectional photograph of the synthetic paper is obtained with an ultra-high resolution field emission scanning electron microscope manufactured by Hitachi. First, the fibers in the photograph are divided into nanofibers having a diameter of 500 nm or less and other fibers having a number average single fiber diameter of 1 μm or more in synthetic paper. In this case, fibers having a single fiber diameter exceeding 0.5 μm are classified as being part of other fibers having a single fiber number average diameter of 1 μm or more.

  Measure cross-sectional images of individual fibers classified into nanofibers and other fibers using image processing software (WINROOF), and add up the cross-sectional areas. The total area of nanofibers is Sn, 0.5 μm. The total area of the above fibers is Sf. Further, when the specific gravity of nanofibers is ρn, the specific gravity of fibers exceeding 0.5 μm is ρf, the weight mixing ratio of nanofibers is α (%), and the weight mixing ratio of fibers of 1 μm or more is β (%), Calculate with

When A = Sn * ρn and B = Sf * ρf,
α = A / A + B * 100 (7)
β = B / A + B * 100 (8)
In addition, the sample for evaluation took five arbitrary places from synthetic paper, calculated | required each (alpha) or (beta) 5 times by said method, and made the average value the weight mixing rate of nanofiber or another fiber.

P. Nanofiber Freeness Test Method According to the Canadian standard freeness test method of JIS P 8121 “Pulp Freeness Test Method”, the freeness tester manufactured by Kumagaya Kikai Co., Ltd. was used. 1 liter of a 0.30 ± 5% concentration slurry of nanofibers was weighed in a room at 20 ° C. and placed in a Canadian freeness tester, which was measured three times to obtain an average value. In addition, using the above JIS correction table, the data was corrected by the concentration deviation from 0.30%, and the freeness was obtained.

Q. The air permeability of the synthetic paper was measured with a Frazier type constant pressure fabric air permeability tester manufactured by Daiei Kagaku Seiki Seisakusho according to JIS-1096 “Testing of constant pressure fabric air permeability”. An arbitrary place of the nanofiber synthetic paper was cut into 10 cm squares, and the air permeability Qa (cc / cm ² / sec) of each synthetic paper was measured at 20 ° C. and 65%, and it was simply averaged.

R. Mechanical Properties Five synthetic papers having a width of 2 cm and a length of 18 cm were cut from an arbitrary place of the nanofiber synthetic paper, and the tensile test was performed according to JIS L1013 with an initial sample length = 10 cm and a tensile speed = 20 cm / min. The value obtained by dividing the load value at the time of measurement break by the initial paper width is the strength (N / cm), and the value obtained by dividing the elongation at break by the initial sample length is the elongation (%). Was measured and simply averaged.

S. Hygroscopicity (ΔMR)
A synthetic paper sample is weighed in a weighing bottle, weighing about 1 to 2 g, kept at 110 ° C. for 2 hours, dried and weighed (W0). Measure (W65). And this is hold | maintained at 30 degreeC and relative humidity 90% for 24 hours, Then, a weight is measured (W90). And it calculated | required with the following formula | equation.

MR65 = [(W65−W0) / W0] × 100% (9)
MR90 = [(W90−W0) / W0] × 100% (10)
ΔMR = MR90−MR65 (11)
T.A. Weight loss rate of polymer Using TG / DTA6200 manufactured by Seiko Instruments Inc., the weight loss rate when the temperature was raised from room temperature to 300 ° C. at 10 ° C./min in a nitrogen atmosphere, and then held at 300 ° C. for 5 minutes. It was measured.

U. Measurement of the area ratio of the nanofibers The cross section of the nanofiber fiber bundle from which the sea component was removed from the polymer alloy fiber was observed with a TEM, and the cross-sectional area of the entire fiber bundle (Sa) was 1 to 500 nm present in the fiber bundle. The total area of the nanofibers was defined as (Sb), and the following formula was used.

Nanofiber area ratio (%) = (Sb / Sa) * 100 (12)
V. Surface smoothness It was measured by the surface smoothness (in seconds) of Beck prescribed in JIS P 8119-1976.

W. In SEM observation of the evaluation H section pinholes synthetic paper, observing the synthetic paper at a magnification of 500 times or less, counted the number of 50μm or more holes in a circle equivalent diameter which is present in the range of 100 [mu] m ² on the photograph, which Was performed in 10 fields of view, and this was simply averaged and then converted to 1 cm ² .

X. Zeta potential measurement 0.001M KCl was added in advance to the nanofiber blend solution or dispersion, and the pH was measured with an electrophoretic light scattering photometer ELS-800 (manufactured by Otsuka Electronics Co., Ltd.).

Example 1
Melt viscosity 53 Pa · s (262 ° C., shear rate 121.6 sec ⁻¹ ), melting point 220 ° C. N6 (20 wt%), melt viscosity 310 Pa · s (262 ° C., shear rate 121.6 sec ⁻¹ ), melting point 225 ° C. Polymer alloy chip of b ^* value = 4 by co-polymerizing PET (80% by weight) with a melting point of 225 ° C. obtained by copolymerization of 8 mol% of isophthalic acid and 4 mol% of bisphenol A and kneading at 260 ° C. with a biaxial extrusion kneader. Got. The copolymerized PET had a melt viscosity of 180 Pa · s at 262 ° C. and 1216 sec ⁻¹ . The kneading conditions at this time were as follows.

Screw type: Fully meshed in the same direction Double thread Screw: Diameter 37 mm, effective length 1670 mm, L / D = 45.1
The kneading part length is 28% of the effective screw length
The kneading part was located on the discharge side from 1/3 of the effective screw length.

There are three backflow parts in the middle. Polymer supply: N6 and copolymerized PET were weighed separately and separately fed to the kneader.

Temperature: 260 ° C
Vent: 2 places

A model diagram of a melt spinning apparatus used for melt spinning is shown in FIG. In the figure, 1 is a hopper, 2 is a melting section, 3 is a spin block, 4 is a spinning pack, 5 is a base, 6 is a chimney, 7 is a melted and discharged yarn, 8 is a converged oiling guide, and 9 is a first A take-up roller, 10 is a second take-up roller, and 11 is a take-up thread. This polymer alloy chip was melted in the melting part 2 at 275 ° C. and led to the spin block 3 at a spinning temperature of 280 ° C. The polymer alloy melt was filtered with a metal nonwoven fabric having a limit filtration diameter of 15 μm, and then melt-spun from the die 5 with a die surface temperature of 262 ° C. At this time, a base having a measuring portion having a diameter of 0.3 mm above the discharge hole, having a discharge hole diameter of 0.7 mm and a discharge hole length of 1.75 mm was used. And the discharge amount per single hole at this time was 2.9 g / min. Furthermore, the distance from the base lower surface to the cooling start point (the upper end of the chimney 6) was 9 cm. The discharged yarn is cooled and solidified over 1 m with cooling air of 20 ° C., and is supplied by an oil supply guide 8 installed 1.8 m below the base 5, and then the unheated first take-up roller 9 and second take-up roller 10 was wound up at 900 m / min. The spinnability at this time was good, and there was no yarn breakage during continuous spinning for 24 hours. This was subjected to a stretching heat treatment with the first hot roller at 98 ° C. and the second hot roller at 130 ° C. At this time, the draw ratio between the first hot roller and the second hot roller was 3.2 times.
The obtained polymer alloy fiber exhibited excellent properties of 120 dtex, 12 filaments, strength 4.0 cN / dtex, elongation 35%, U% = 1.7%. Moreover, when the cross section of the obtained polymer alloy fiber was observed with TEM, N6 is an island component (round portion), and copolymerized PET shows the sea island component structure of the sea (other portions) (see FIG. 2). The diameter of the island component N6 was 53 nm, and a polymer alloy fiber in which N6 was ultrafinely dispersed was obtained.
Hereinafter, 100% nanofiber synthetic paper will be described.

The obtained 120 dtex, 12 filament “polymer alloy fiber” was cut into 2 mm with a guillotine cutter. The cut “polymer alloy fiber” is treated with 98%, 10% sodium hydroxide for 1 hour to remove the polyester component of the sea component, filtered through a filter, and further centrifuged until the water content becomes about 100%. Short fibers were obtained by dehydration with a separator. The obtained short fiber was washed with water and dehydrated five times to remove sodium hydroxide to obtain a nanofiber short fiber. When the cross section of the obtained N6 nanofiber short fiber was observed by TEM, the number average diameter φm of single fibers was 57 nm, and the L / D of the N6 nanofiber short fiber at this time was about 35,000.
About 20 liters of water and 30 g of nanofiber short fibers were put into a Niagara beater, and the fibers were first beaten for 10 minutes. The freeness of the nanofiber subjected to the first beating was 362. Water was removed from this fiber with a centrifugal separator to obtain 250 g of primary beating fiber having a fiber concentration of 12 wt%. This primary beating fiber was subjected to secondary beating for 10 minutes with a PFI beating apparatus and then dehydrated to obtain nanofiber secondary beating fibers having a fiber concentration of 10 wt%. The freeness of the nanofibers subjected to secondary beating was 64.

  Further, 5.5 g of the secondary beating fiber and 0.5 g of the first industrial pharmaceutical anionic dispersant (Charol AN-103P: molecular weight 10,000) were placed in a disaggregator together with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator was put into a container of an experimental paper machine (rectangular sheet machine) manufactured by Rikuma Kumagai, and water was added to make a 20 liter adjustment solution. When the zeta potential of this adjusted solution was measured, it was -50 mV. Paper is prepared on the 25cm square filter paper # 2 (5μm) made by Advantech Co., Ltd., which is placed on a paper net for papermaking in advance. Then, it was further re-dried to obtain a synthetic paper consisting only of nanofibers.

The result of SEM observation of the surface of the obtained synthetic paper is shown in FIG. 3. Unlike the conventional synthetic fiber synthetic paper, a synthetic paper having nanofibers dispersed one by one was obtained. The resulting synthetic paper was very thin but had no pinholes and was a uniform synthetic paper. The distribution of the single fiber diameter of the synthetic paper is shown in Table 3. The single fiber average diameter φm of the nanofiber is 57 nm, the sum Pa of the single fiber ratio is 100%, and the single fiber diameter concentration index Pb Was 64%, and there was very little variation in fiber diameter, and it was uniform. In addition, a synthetic nanofiber paper having a very small basis weight of 8.4 g / m ² and a thickness of 30 μm was obtained. Moreover, although it was 100% of nanofibers, paper could be satisfactorily made even without a binder due to the cohesive strength and entanglement strength of the nanofibers. The obtained nanofiber synthetic paper had a very thin thickness, but a strength of 2.2 N / cm and an elongation of 12% were practically acceptable. Moreover, since the obtained synthetic paper was uniformly dispersed with nanofibers having a uniform single fiber diameter, the pore area was as small as 0.0033 μm ² and uniform. The pore area was measured by the measurement method described in the item O. As the image processing conditions for removing excess fibers that are not necessary for measuring the pore area, the maximum average luminance Lh is 91.6. Yes, the erase brightness level, which is 50%, is 45.8%, and the measured image at that time is shown in FIG. The synthetic paper of this example has such a fine pore area, and furthermore, since the dispersibility and uniformity of the nanofibers are good, there are no large pinholes, and pinholes of 50 μm or more are zero. Since it was uniform, the amount of ventilation was as small as 0.35 cc / cm ² / sec, and a synthetic paper with a high gas shielding power was obtained. Moreover, the surface smoothness was 1660 seconds, and it was a synthetic paper with high surface smoothness.

Further, while the density of commercial paper using ordinary pulp is about 0.5 g / cm ^3, the density of the nanofiber synthetic paper of this example 0.28 g / cm ³ and cohesion of nanofibers In spite of being large and difficult to disperse, a comparatively low density synthetic paper was obtained. This is thought to be because the nanofibers were well dispersed by the method for producing the nanofiber synthetic paper of the present invention. The nanofiber synthetic paper obtained this time was pressed and dried to remove moisture after papermaking, but simply pressurized to improve the density and strength commonly used in the synthetic paper field. Since there is no processing such as heat pressing, these characteristics may be adjusted according to the purpose and application. Further, when the moisture absorption rate (ΔMR) of the nanofiber synthetic paper of this example was measured, it was superior to 6.4% and 2.8% of the synthetic paper made of the conventional ultrafine fiber of Comparative Example 10, which was superior in moisture absorption. The characteristics are shown. Pinholes of 50 μm or more were zero. Moreover, the surface smoothness was 1660 seconds, and it was a synthetic paper with high surface smoothness.

Example 2
The example of the nanofiber synthetic paper in the case of using a screen basket as a base material is shown.

  Disperse 5.5 g of the secondary beating fiber obtained in Example 1 and 0.5 g of Daiichi Kogyo Anionic Dispersant (Charol AN-103P: molecular weight 10000) together with 1 liter of water in a disaggregator for 5 minutes. did. The dispersion in the disaggregator was placed in a container of a laboratory paper machine, and water was added to make a 20 liter adjustment solution. Paper this adjustment solution on a 25cm square “screen cage (PET, fiber diameter 70μm, hole diameter 80μm square)” placed on a wire net for papermaking in advance, dehydrated with a roller, and dried with a drum dryer An attempt was made to peel off the nanofiber and the screen wrinkle, but it was not possible to obtain a nanofiber synthetic paper using the screen wrinkle as a base substrate.

As a result of SEM observation of the surface of the obtained synthetic paper, nanofibers were dispersed one by one in the central part of the lattice of the screen basket as in Example 1. However, it was observed that the nanofibers were tightly entangled with the monofilaments near the monofilaments forming the screen lattice. The nanofibers in this synthetic paper had a single fiber number average diameter φm of 58 nm, the single fiber ratio sum Pa was 100%, and the single fiber diameter concentration index Pb was 66%. Even if no binder is used due to the nanofiber entangled with the screen filament monofilament, the cohesive strength between the nanofibers, and the strength of the entanglement, the nanofiber does not fall out of the screen cage, making paper well I was able to. In the nanofiber synthetic paper of this example, the nanofibers present in the center of the lattice portion of the screen ridge were evenly dispersed, and there were no large pinholes or tears in that portion, and sufficient strength was maintained. . The obtained synthetic paper was integrated with nanofibers based on a screen gutter. The synthetic paper had a total basis weight of 45.6 g / m ² , a thickness of 102 μm, and a density of 0.45 g / cm ³ . When the screen ridge part (37.4 g / m ² basis weight, thickness 70 μm, density 0.53 g / cm ³ ) is considered to be removed from this synthetic paper, the basis weight of the nanofiber alone is 8.2 g / m ² , thickness. Was 32 μm and the density was 0.26 g / cm ³ , and a synthetic paper of the same degree as that of the synthetic paper with 100% nanofibers of Example 1 was obtained for the part of the nanofiber alone of this example. That is, a nanofiber synthetic paper is formed on a screen basket and combined. Although a screen bottle is used as a base material, a nanofiber composite synthetic paper can be obtained without using a binder. In the obtained composite synthetic paper, the nanofibers and the screen wrinkles are integrated, but the density of the nanofibers present in the lattice portion of the screen wrinkles is about the same as that of the nanofiber synthetic paper of Example 1. Conceivable. Furthermore, this composite synthetic paper has a reinforcing effect by the screen wrinkle and has a strength of about 91.2 N / cm and an elongation of 34%. In practice, however, the nanofibers present in the lattice portion of the screen wrinkle are the same as in Example 1. Since the elongation is about 10% or more, it breaks when pulled with a strong force, but it is easier to handle than the synthetic paper of Example 1. Moreover, this composite synthetic paper has a uniform pore area due to the uniform single fiber diameter of the nanofibers, and its value is very small, 0.0045 μm ^2. There were no pinholes, and pinholes of 50 μm or more were 0, and since paper was uniformly processed, the air flow rate was very small at 0.27 (cc / cm ² / sec). Moreover, the surface smoothness was 830 seconds, and it was a synthetic paper with high surface smoothness. The nanofiber synthetic paper of this example was pressed and dried to remove moisture after papermaking, but because it was not processed such as simple pressing or hot pressing to improve density and strength, By performing such processing, there is a possibility that these characteristics can be adjusted according to the purpose and application. When the moisture absorption rate (ΔMR) of the nanofiber composite synthetic paper of this example was measured, it was superior to 5.7% and 2.8% of the synthetic paper made of the conventional ultrafine fiber of Comparative Example 10, and superior moisture absorption characteristics. showed that.

Example 3
In this example, a synthetic paper in which nanofibers and N6 ultrafine fibers having a diameter of 2 μm are mixed will be described.

16.6 g of the secondary beaten fibers obtained in Example 1 and 0.42 g of N6 ultrafine fibers with a mean diameter of 2 μm cut into 2 mm and a first industrial pharmaceutical anionic dispersant (Charol AN-103P: 0.5 g (molecular weight 10,000) was placed in a disaggregator together with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator was placed in a container of a laboratory paper machine (square sheet machine), and water was added to make a 20 liter adjustment solution. This adjustment solution is made directly on a paper net for paper making, dewatered with a roller, dried with a drum dryer, and a mixed paper type in which 80% of 32.3 g / m ² nanofibers and 20% N6 ultrafine fibers are mixed. Synthetic paper was obtained.

As a result of SEM observation of the surface of the obtained synthetic paper, the nanofiber single fiber number average diameter φm was 59 nm, the single fiber ratio sum Pa was 100%, and the single fiber diameter concentration index Pb was 65%. there were. The obtained nanofiber synthetic paper is nanofibers component was 80%, also papermaking properties were good, basis weight also there was a 32.3 g / m ² and microfine fibers and混抄synthetic paper, the thickness It was thin and 1.5N / cm in strength and 7.3% in elongation were obtained with no practical problems. In addition, when surface observation was performed by SEM, nanofibers in the ultrafine fibers also had some portions where the fibers were slightly intertwined, but most of them were dispersed up to one by one. A mixed paper with nanofibers uniformly dispersed was obtained. In addition, a space is secured by spreading the nanofibers like a spider's web, using ultrafine fibers thicker than the diameter as an aggregate. Compared to Example 2, the thickness becomes 154 μm and the density is 0. .21 g / cm ^{3, which} is slightly reduced, the air flow rate can be considerably increased to 11 cc / cm ² / sec as compared to Example 2, and the mixed synthetic paper of this example is in a field that requires air permeability. Is considered possible. Moreover, although the hole area also increased to 0.0113 μm ^2, there were no coarse holes or pinholes, and the pinholes of 50 μm or more were zero. Further, the surface smoothness was a synthetic paper having a high surface smoothness of 320 seconds.
The nanofiber-mixed synthetic paper obtained this time was pressed and dried to remove moisture after papermaking, but it was not processed by simple pressurization or heat press to improve density and strength. There is a possibility that these characteristics can be adjusted according to the purpose and application. In addition, when the moisture absorption rate (ΔMR) of the nanofiber mixed paper was measured, it was superior to 5.1% and 2.8% of the conventional synthetic fiber made of ultrafine fibers of Comparative Example 10. showed that.

Example 4
In this example, a case where 5% by weight or less of nanofiber is mixed is described.

  A nanofiber synthetic paper is prepared by mixing a small amount of nanofibers with a synthetic paper mainly composed of N6 ultrafine fibers having a single fiber number average diameter of 2 μm and pulp binder. Secondary beating fiber 0.50 g obtained in the same manner as in Example 1, 0.22 g of wood pulp having a freeness of 450, 1.80 g of N6 ultrafine fibers having a single fiber number average diameter of 2 μm, and Daiichi Kogyo Seiyaku An anionic dispersant (Charol AN-103P: molecular weight 10,000) and 1 liter of water were placed in a disaggregator and dispersed for 5 minutes. The dispersion in the disaggregator was placed in a container of a laboratory paper machine (square sheet machine), and water was added to make a 20 liter adjustment solution. This adjusted solution is directly made on a wire mesh net for paper making, dehydrated with a roller, and dried with a drum dryer, and mixed with a mixture ratio of 2.4% nanofibers, 87% extra fine fibers, and 10.6% wood pulp. Synthetic paper was obtained.

As a result of observing the surface of the obtained synthetic paper with SEM, the nanofiber single fiber number average diameter φm in this synthetic paper is 59 nm, the sum Pa of the single fiber ratio is 100%, and the concentration degree of the single fiber diameter The index Pb was 63%. Since wood pulp is present as a binder, paper can be satisfactorily produced even with a small amount of nanofibers. The basis weight is 31.6 g / m ² , the thickness is 243 μm, the strength is 3.1 N / cm, and the elongation is 15%. The mixed paper was obtained. In order to disperse the nanofibers in a state in which the nanofibers are spread in the space in the ultrafine fibers, the mixed paper obtained in this example was dried after reducing the pressure for removing the water after papermaking. Further, according to the surface observation by SEM, in this example, since the existence ratio of nanofibers is small in the mixed paper, compared with Example 3, there is less entanglement between the fibers, and each one is separated. It was a mixed paper with nanofibers uniformly dispersed. Furthermore, since the amount of nanofibers is very small compared to Example 3, the density is also as low as 0.13 g / cm ³ , the pore area is increased to 0.047 μm ² , and large pores or pins There were no holes, and pinholes of 50 μm or more were zero. The surface smoothness was 220 seconds.
This mixed paper has little permeation resistance to fluids such as gas and liquid, and is useful as a base material for separating and adsorbing useful components in these fluids and removing fine particles and foreign matters. The air permeability of the mixed paper of this example was 34 cc / cm ² / sec as compared with Example 3, and the air permeability could be considerably increased. This N6 nanofiber synthetic paper was suitable for an air filter because of its high air flow rate. Furthermore, since the surface of this N6 nanofiber paper contains many nano-level pores and the permeation resistance of the liquid is considered to be small, it is still suitable for liquid filters, secondary batteries, capacitor separators, etc. there were.

Example 5
In this example, a low-weight nanofiber synthetic paper will be described.

  Put 1.5 g of secondary beating fiber obtained in the same manner as in Example 1 and 0.5 g of an anionic dispersant (Charol AN-103P: molecular weight 10,000) manufactured by Daiichi Kogyo Seiyaku together with 1 liter of water in a disaggregator. Dispersed for 5 minutes. The dispersion in the disaggregator was placed in a container of a laboratory paper machine (square sheet machine), and water was added to make a 20 liter adjustment solution. Paper is made on a 25cm square screen basket (made of PET, fiber diameter 70μm, hole diameter 80μm square), which is placed on a wire mesh net for papermaking in advance, dehydrated with a roller, dried with a drum dryer, and nanofiber Attempts were made to peel off the screen wrinkles, but they could not be peeled off, and a nanofiber synthetic paper having a screen wrinkle as the base substrate was obtained.

As a result of SEM observation of the surface of the obtained synthetic paper, the nanofiber single fiber number average diameter φm of the synthetic paper is 57 nm, the sum Pa of the single fiber ratio is 99%, and the single fiber diameter concentration index Pb Was 73%. Since the entire composite synthetic paper is based on a screen wrinkle, the basis weight is 39.5 g / m ² , the thickness is 78 μm, the density is 0.51 g / cm ³ , the strength is 91.2 N / cm, and the elongation is 34. % Synthetic paper. The basis weight of only the nanofiber obtained by removing the screen wrinkles (37.4 g / m ² , thickness 70 μm, density 0.53 g / cm ³ ) from this synthetic paper is 2.1 g / m ² , thickness 8.0 μm, density Was 0.26 g / cm ³ , and the basis weight of only nanofibers was 2.1 g / m ^2, which was very thin. It is very difficult to produce a sheet of 10 g / m ² or less with a normal dry nonwoven fabric, but with nanofibers, the number of fibers is high and the coverage is high, so it is possible to produce unprecedented thin synthetic paper Met. In addition, nanofibers are entangled very thinly like a spider web uniformly over the entire lattice part of the screen ridge (fiber diameter 70 μm, hole diameter 80 μm square). Was 2 pieces / cm ² . As a result of measuring the air flow rate by sampling a portion having no pinhole and good formation, the air flow rate was slightly increased to 0.66 cc / cm ² / sec as compared with Example 1, but this slightly exists. This is probably due to the effect of pinholes. The pore area increased to 0.0042 μm ² compared to Example 1. Moreover, the surface smoothness was 430 seconds and was a synthetic paper with high surface smoothness.
Since the strength of the synthetic paper is reinforced by the screen as a whole, it is easy to handle without any problem of strength. In addition, the nanofibers existing between the lattice parts were not damaged at all.

Example 6
The nanofiber synthetic paper having a single fiber average diameter of 114 nm will be described.
N6 was changed to N6 (mixing ratio: 50% by weight) having a melt viscosity of 500 Pa · s (262 ° C., shear rate of 121.6 sec ⁻¹ ) and a melting point of 220 ° C., and melt spinning was performed in the same manner as in Example 1. The spinnability at this time was good, and there was one breakage during 24 hours of continuous spinning. This was also drawn and heat-treated in the same manner as in Example 1, and was a polymer alloy fiber having excellent characteristics of 128 dtex, 36 filaments, strength 4.3 cN / dtex, elongation 37%, U% = 2.5%. Got. When the cross section of the obtained polymer alloy fiber was observed with TEM, copolymerized PET was the sea, N6 was the island-island structure as in Example 1, and the diameter by the number average of the island N6 was 110 nm. A polymer alloy fiber in which N6 was ultrafinely dispersed was obtained.

The obtained 128 dtex, 36 filament “polymer alloy fiber” was cut into 2 mm with a guillotine cutter. The cut “polymer alloy fiber” is treated with 98%, 10% sodium hydroxide for 1 hour to remove the polyester component of the sea component, filtered through a filter, and further centrifuged to a moisture content of about 100%. It dehydrated with the separator and obtained the short fiber.
The obtained short fiber was washed with water and dehydrated 5 times, and then sodium hydroxide was removed to obtain a nanofiber short fiber. When the cross section of the obtained N6 nanofiber short fiber was observed with a TEM, the number average diameter φm of the single fiber was 114 nm, and the L / D of the N6 nanofiber short fiber at this time was about 17500.
About 20 liters of water and 30 g of the short fibers were put into a Niagara beater container, and the fibers were first beaten for 10 minutes. Water was removed from the obtained fiber with a centrifugal separator to obtain a primary beaten fiber having a fiber concentration of 10 wt%. This primary beating fiber was secondarily beaten with a PFI beating apparatus for 10 minutes and then dehydrated to obtain nanofiber secondary beating fibers having a fiber concentration of 10 wt%. Further, 5.5 g of this secondary beaten fiber and 0.5 g of an anionic dispersant (Charol AN-103P: molecular weight 10,000) manufactured by Daiichi Kogyo Seiyaku were placed in a disaggregator together with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator was put into a container of a laboratory paper machine (square sheet machine), and water was added to make a 20 liter prepared solution. Paper is made on a 25cm square screen basket (fiber diameter 70μm, hole diameter 80μm square), which is placed on a wire mesh net for papermaking in advance. Although it was going to peel off, it was not able to peel off, but the nanofiber synthetic paper which used the screen ridge as the base substrate was obtained.

As a result of SEM observation of the surface of the obtained synthetic paper, the single fiber number average diameter φm was 114 nm, the single fiber ratio sum Pa was 98%, and the single fiber diameter concentration index Pb was 58%. . The obtained nanofiber synthetic paper could be made on the screen without any problem. Further, as a result of SEM surface observation, the nanofibers were separated one by one as in Example 1, and a synthetic paper in which the nanofibers were uniformly dispersed was obtained. Since the entire synthetic paper obtained is based on a screen wrinkle, the basis weight is 46.9 g / m ² , the thickness is 111 μm, the density is 0.42 g / cm ³ , the strength is 91.2 N / cm, and the elongation is It was 34% synthetic paper. The basis weight of only the nanofiber obtained by removing the screen wrinkles (weight 37.4 g / m ² , thickness 70 μm, density 0.53 g / cm ³ ) from this synthetic paper is 8.7 g / m ² , thickness 41 μm, density 0 It was a nanofiber synthetic paper with a uniform texture of .21 g / cm ³ . Further, since the nanofibers were uniformly dispersed, there were no large holes or pinholes, and the pinholes of 50 μm or more were zero. Further, the surface smoothness was 1180 seconds, and the synthetic paper had high surface smoothness.
The amount of air flow was as small as 0.63 cc / cm ² / sec as in Example 1, and a synthetic paper having a high gas shielding power was obtained. However, the amount of air flow was slightly increased as compared with Example 1. This is because the hole area of the synthetic paper obtained in this example was increased to 0.0084 μm ² and the density was as low as 0.21 g / cm ³ compared to Example 1. In addition, since the number average single fiber diameter of the nanofiber is larger than that in Example 1, the dispersibility of the nanofiber is improved, and the portion where the fibers are in close contact with each other is less than in Example 1. .

Example 7
Below, the composite synthetic paper of the synthetic paper which consists of N6 extra fine fiber with a single fiber number average diameter of 2 micrometers and the synthetic paper which consists of nanofiber is demonstrated.

First, a synthetic paper made of ultrafine fibers is prepared from N6 ultrafine fibers having a single fiber diameter of 2 μm and a pulp binder. N6 ultrafine fibers cut to 2 mm and beaten until the freeness reaches 350, 1.85 g of N6 ultrafine fibers, 0.22 g of wood pulp having a freeness of 450, and Daiichi Kogyo Pharmaceutical's anionic dispersant (Charol) AN-103P: molecular weight 10,000) was placed in a disaggregator with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator was put into a container of a laboratory paper machine (square sheet machine), and water was added to make a 20 liter prepared solution. This prepared solution was directly made on a paper net for paper making, dehydrated with a roller, and dried with a drum dryer to obtain a synthetic paper composed of N6 ultrafine fibers and a wood pulp binder. The synthetic paper made of this ultrafine fiber had a basis weight of 33.4 g / m ² , a thickness of 242 μm, and a density of 0.14 g / cm ³ . The obtained synthetic paper made of ultrafine fibers was used as a filter instead of the screen gutter placed on the wire net of the experimental paper machine of Example 1. The nanofiber dispersion liquid dispersed in the disaggregator of Example 1 was put in a container of an experimental paper machine (square sheet machine), and water was added to make a 20 liter prepared solution. This prepared solution is made on a 25cm square N6 ultrafine fiber synthetic paper previously placed on a wire mesh net for papermaking, dehydrated with a roller, dried with a drum dryer, and nanofibers are laminated on the ultrafine fiber. Composite paper was obtained. Since the N6 ultrafine fibers made in advance are used as the base material, the nanofibers may be made so as to disperse the nanofibers on the surface or inside of the base material, and papermaking was possible.

As a result of SEM observation of the surface of the obtained synthetic paper, the nanofibers in the synthetic paper had a single fiber number average diameter φm of 57 nm, a single fiber ratio sum Pa of 99%, and a single fiber diameter concentration index Pb of 72. %Met. The obtained composite synthetic paper had a total basis weight of 42.2 g / m ² , a thickness of 285 μm, a strength of 3.2 N / cm, and an elongation of 16%. Assuming that the nanofibers are simply laminated on the ultrafine fiber synthetic paper, the difference between the composite synthetic paper and the N6 ultrafine fiber synthetic paper only becomes the nanofiber only part. The basis weight is 8.8 g / m ² , the thickness is 43 μm, and the density is 0.20 g / cm ³ . Actually, in the composite synthetic paper obtained in this example, the nanofibers spread in the space inside the N6 ultrafine fiber. In order to obtain the composite synthetic paper having such a configuration, the nanofibers can be more well dispersed among the ultrafine fibers by setting the density of the N6 ultrafine fiber synthetic paper to be small in advance. Further, the composite synthetic paper of this example was a synthetic paper having a high surface smoothness with a surface smoothness of 560 seconds with 0 pinholes of 50 μm or more.
Since the composite synthetic paper of this example has a density as low as 0.15 g / cm ³ and a pore area as large as 0.0174 μm ² , the ventilation rate is considerably 23 cc / cm ² / sec as compared with Example 3. The amount could be increased. This composite synthetic paper has low permeation resistance to fluids such as gas and liquid, and is useful as a base material for separating and adsorbing useful components from the fluid etc. and removing fine particles and foreign matters. Various filter media can be obtained by forming a synthetic paper molded product by processing or corrugating.

Example 8
The composite synthetic paper of melt blown nonwoven fabric and nanofiber synthetic paper will be described.

A PP meltblown nonwoven fabric (weight per unit area 30 g / m ² , thickness 130 μm, density 0.231 g / cm ³ ) produced by the meltblowing method and having a single fiber number average diameter of 3 μm was used as a papermaking filter. The nanofiber preparation solution was paper-made on top to obtain a composite synthetic paper of PP meltblown nonwoven fabric and nanofibers.

As a result of observing the surface of the obtained composite synthetic paper with SEM, the number average diameter φm of single fibers of the nanofiber was 57 nm, the sum Pa of the single fibers ratio was 99%, and the concentration index Pb of single fiber diameter was 63%. It was. The obtained composite synthetic paper had a total basis weight of 35.6 g / m ² , a thickness of 160 μm, a strength of 3.5 N / cm, and an elongation of 43%. If the nanofibers are simply laminated on the PP meltblown nonwoven fabric, the difference between the entire composite synthetic paper and the meltblown nonwoven fabric only becomes the nanofiber portion, so the basis weight of the nanofiber alone is 5.6 g / m ² , The thickness is 30 μm and the density is 0.19 g / cm ³ . Thus, using PP meltblown nonwoven fabric, nanofibers could be uniformly dispersed in the space of ultrafine fibers as in Example 7. For this reason, the density of this composite synthetic paper is as low as 0.23 g / cm ³ and the pore area is as large as 0.0153 μm ² , so that the air flow rate is as much as 15 cc / cm ² / sec compared to Example 3. The amount could be increased. The composite synthetic paper of this example is the pin hole of at least 50μm is one / cm ^2, surface smoothness was higher synthetic paper smoothness of 380 seconds and a surface.
Compared to Example 7, the fiber diameter of the PP meltblown nonwoven fabric is thick and the apparent density is high, but the number of ultrafine fibers in the PP meltblown nonwoven fabric is small, so the pores are not significantly different from Example 7. It was. The synthetic paper of this example has a small permeation resistance to fluids such as gas and liquid, and is useful as a base material used for separation and adsorption of useful components from the fluid and the like, and removal of fine particles and foreign matters. Various filter media can be obtained by forming paper into a synthetic paper molded product by pleating or corrugating.

Example 9
A nanofiber synthetic paper that is cut after polymer alloy fibers have been desealed first will be described. Polymer alloy fibers were obtained in the same manner as in Example 1. The obtained 120 dtex, 12 filament polymer alloy fiber is made into a 130,000 dtex case, treated with 10% sodium hydroxide at 98 ° C. for 1 hour to remove the sea component polyester component, washed with water and dried. did. The nanofiber cassette obtained was cut into 2 mm with a guillotine cutter to obtain nanofiber short fibers. Further, the obtained short fiber was made into a preparation solution in the same manner as in Example 2 and then paper-made to obtain a nanofiber synthetic paper in which the nanofiber and the screen bottle were integrated.

As a result of SEM observation of the surface of the obtained synthetic paper, the single fiber number average diameter φm was 59 nm, the single fiber ratio sum Pa was 98%, and the single fiber diameter concentration index Pb was 71%. . Since this synthetic paper is based on screen wrinkles, the total weight is 46.5 g / m ² , the thickness is 108 μm, the density is 0.44 g / cm ³ , the strength is 91.2 N / cm, and the elongation is 34%. there were. When a screen wrinkle (weight 37.4 g / m ² , thickness 70 μm, density 0.53 g / cm ³ ) was removed from this synthetic paper, the nanofiber-only weight per unit area was 9.1 g / m ² and the thickness 38 μm. The nanofiber synthetic paper was the same as in Example 2. The hole area of this synthetic paper is as small as 0.0051 μm ² and the density is 0.24 g / cm ^3. As a result of measuring the air flow rate, it is as small as 0.33 cc / cm ² / sec. Nanofiber synthetic paper with high gas shielding power was obtained. In addition, the synthetic paper of this example was a synthetic paper having a high surface smoothness of 0 seconds with a pinhole of 50 μm or more and a surface smoothness of 900 seconds.

Example 10
The case where nanofiber synthetic paper is obtained from a polymer alloy fiber whose sea component is PLA will be described.

Using N6 used in Example 1, poly L lactic acid (optical purity of 99.5% or more) having a weight average molecular weight of 120,000, a melt viscosity of 30 Pa · s (240 ° C., 2432 sec ⁻¹ ), a melting point of 170 ° C., and containing N6 The rate was 20 wt%, the kneading temperature was 220 ° C., and melt kneading was performed in the same manner as in Example 1 to obtain a polymer alloy chip having a b ^* value = 3. In addition, the weight average molecular weight of poly L lactic acid was calculated | required as follows. The sample chloroform solution was mixed with THF (tetrahydrofuran) to obtain a measurement solution. This was measured at 25 ° C. using Waters 2690 gel permeation chromatography (GPC) Waters 2690, and the weight average molecular weight was calculated in terms of polystyrene. The melt viscosity of N6 used in Example 1 at 240 ° C. and 2432 sec ⁻¹ was 57 Pa · s. Moreover, the melt viscosity of this poly L lactic acid at 215 ° C. and 1216 sec ⁻¹ was 86 Pa · s.

  This was melt-spun in the same manner as in Example 1 at a melting temperature of 230 ° C., a spinning temperature of 230 ° C. (die surface temperature of 215 ° C.), and a spinning speed of 3500 m / min. At this time, a normal spinneret having a base diameter of 0.3 mm and a hole length of 0.55 mm was used as the base, but almost no ballast phenomenon was observed, and the spinnability was greatly improved as compared with Example 1. The yarn breakage during continuous spinning for 0 hours was zero. The single-hole discharge rate at this time was 0.94 g / min. As a result, a highly oriented undrawn yarn of 92 dtex and 36 filaments was obtained, and the strength thereof was 2.4 cN / dtex, the elongation was 90%, the boiling water shrinkage was 43%, and U% = 0.7%. It was extremely excellent as an undrawn yarn. In particular, as the ballast was significantly reduced as compared with Example 1, the yarn spots were greatly improved.

  This highly oriented undrawn yarn was drawn and heat treated in the same manner as in Example 1 at a drawing temperature of 90 ° C., a draw ratio of 1.39 times, and a heat setting temperature of 130 ° C. The obtained drawn yarn was 67 dtex, 36 filaments, and exhibited excellent properties of a strength of 3.6 cN / dtex, an elongation of 40%, a boiling water shrinkage of 9%, and U% = 0.7%. When the cross section of the obtained polymer alloy fiber was observed with a TEM, poly-L-lactic acid showed a sea-island structure where the sea (thin part) and N6 were islands (dense part), and the number average diameter of the island N6 was 55 nm. There was obtained a polymer alloy fiber in which N6 was nano-sized and uniformly dispersed.

The obtained 67 dtex, 36 filament “polymer alloy fiber” was focused to 2220 dtex and then cut into 2 mm with a guillotine cutter. The cut “polymer alloy fiber” is treated with 98 ° C. and 1% sodium hydroxide for 1 hour to remove the polyester component of the sea component, filtered through a filter, and further centrifuged until the water content becomes about 100%. Short fibers were obtained by dehydration with a separator. Thus, by changing the sea component from the copolymerized PET of Example 1 to the PLA of this example, the concentration of sodium hydroxide can be greatly reduced from 10% to 1%. . Thereafter, beating and papermaking were performed in the same manner as in Example 1 to obtain a synthetic paper with 100% nanofibers.
As a result of SEM observation of the surface of the obtained synthetic paper, as in Example 1, a synthetic paper in which nanofibers having a uniform diameter were dispersed one by one was obtained. Moreover, the single fiber average diameter φm of the nanofiber is 56 nm, the sum Pa of the single fiber ratio is 100%, the concentration index Pb of the single fiber diameter is 62%, and the fiber diameter is very uniform. Synthetic paper weight was 8.4 g / m ² and the nanofiber synthetic paper was as thin as 34 μm. Further, similarly to Example 1, paper could be satisfactorily produced without a binder. The obtained nanofiber synthetic paper was very thin with a basis weight of 8.4 g / m ² , but the strength was 2.0 N / cm and the elongation was 13%. Nothing was obtained. In addition, since the nanofibers having a uniform single fiber diameter were uniformly dispersed in the synthetic paper, the synthetic paper had a small pore area of 0.0037 μm ² . The pore area was measured by the measurement method of the example. As a condition of image processing for removing unnecessary fibers unnecessary for measuring the pore area, the maximum average luminance Lh is 88.4, The erase brightness level, which is 50%, was 44.2%. Further, the nanofiber synthetic paper had a small air permeability of 0.37 cc / cm ² / sec, a density of 0.26 g / cm ³ , and a synthetic paper having a high gas shielding and sealing force was obtained. The composite synthetic paper of this example was a synthetic paper having a high surface smoothness of 0680 for pinholes of 50 μm or more and a surface smoothness of 1680 seconds.

  When the moisture absorption rate (ΔMR) of the obtained nanofiber synthetic paper was measured, the moisture absorption characteristics were excellent compared to 6.1% and 2.8% of the synthetic paper made of the conventional ultrafine fiber of Comparative Example 10. Indicated.

Comparative Examples 1, 2, 3
PET having a melt viscosity of 180 Pa · s (290 ° C., shear rate of 121.6 sec ⁻¹ ) and a melting point of 255 ° C. as an island component, melt viscosity of 100 Pa · s (290 ° C., shear rate of 121.6 sec ⁻¹ ), Vicat softening temperature of 107 Sea-island composite fibers were obtained as described in Example 1 of JP-A-53-106872, using polystyrene (PS) at 0 ° C. as the sea component. Then, as described in Examples in JP-A-53-106872, PS was removed by 99% or more by trichlorethylene treatment to obtain ultrafine fibers. When the cross section of the fiber was observed with a TEM, the single fiber number average diameter of the ultrafine fiber was as large as 2.0 μm.

The obtained fiber was cut into 2 mm (Comparative Example 1), 3 mm (Comparative Example 2), and 5 mm (Comparative Example 3) to obtain ultrafine short fibers. 2 g of each short fiber (corresponding to 30 g / m ² when used as a synthetic paper) was collected and placed in a disaggregator with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator is placed in a container of a laboratory paper machine (rectangular sheet machine), water is added to prepare a 20-liter preparation solution, and a first industrial pharmaceutical anionic dispersant (Charol) AN-103P: molecular weight 10,000) was added to the prepared solution at 0.2%. This prepared solution was made on Advantech Co., Ltd. 5 μm specification filter paper # 2 placed on a wire mesh net for paper making with # 100 mesh. However, any ultrafine fiber of any fiber length was separated from the filter paper. Since the ultrafine fibers could not be peeled off, it was difficult to take out as a synthetic paper. Unlike nanofibers, such ultrafine fibers have a low cohesive force between the fibers. Therefore, when a binder is not used, it is considered difficult to make paper with ultrafine fibers alone.

Comparative Examples 4, 5, 6
As in Comparative Example 1, a PET ultrafine fiber having a single fiber diameter of 2.0 μm was obtained. The sea component of the obtained fiber was desealed in the same manner as in Comparative Example 1, and then cut into 3 mm to obtain ultrafine short fibers. 2 g of each short fiber (weighing 30 g / m ² when the synthetic paper was used) was collected and placed in a disaggregator with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator is put into a container of a laboratory paper machine (rectangular sheet machine), water is added to prepare a 20 liter preparation solution, and then a first industrial pharmaceutical anionic dispersant ( Charol AN-103P: molecular weight 10,000) was added to 0.2 wt% with respect to the prepared solution. This prepared solution was placed on a mesh # 100 paper wire mesh net (Comparative Example 4), on Advantech Co., Ltd. 5 μm specification filter paper # 2 (Comparative Example 5), and screen screen (fiber diameter 45 μm, pore diameter 80 μm square: comparison Paper was made on various filters such as Example 6), but could not be peeled off from each filter, the ultrafine fibers fell apart, and could not be taken out as a synthetic paper. Unlike the nanofiber, the ultrafine fiber has a small cohesive force between the fibers. Therefore, when a binder or the like is not used, it is difficult to make paper with the ultrafine fiber alone.

  Further, since the ultrafine fibers made on the screen ridges are not entangled with the lattice fibers of the screen ridge (Comparative Example 6), unlike Example 2, synthetic paper integrated with the screen ridges could not be obtained.

Comparative Examples 7, 8, 9
In the same manner as in Comparative Example 1, a 2.0 μm PET ultrafine fiber was obtained. The sea component of the obtained fiber was removed from the sea in the same manner as in Comparative Example 1, and cut into 3 mm to obtain PET ultrafine fiber short fibers. 4 g each of the obtained short fibers (corresponding to a weight of 60 g / m ^{2 when} compared to synthetic paper: Comparative Example 7), 6 g (corresponding to a weight of 90 g / m ² when compared to synthetic paper: Comparative Example 8), 8 g (The basis weight when synthetic paper was equivalent to 120 g / m ² : Comparative Example 9) was collected and placed in a disaggregator with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator is put into a container of a laboratory paper machine (rectangular sheet machine), water is added to prepare a 20 liter preparation solution, and then a first industrial pharmaceutical anionic dispersant ( Charol AN-103P: molecular weight 10,000) was added to 0.2 wt% with respect to the prepared solution. The dispersion was made on a mesh # 100 paper net for paper making or on a filter paper # 2 made by Advantech Co., Ltd. 5 μm specification filter paper # 2. Could not be removed. Thus, unlike the nanofiber, the ultrafine fiber has a small cohesive force between the fibers even when the basis weight is increased, and when the binder is not used, it is difficult to make paper with the ultrafine fiber alone.

Comparative Example 10
N6 with a melt viscosity of 50 Pa · s (280 ° C., 121.6 sec ⁻¹ ), a melting point of 220 ° C. and a PET with a melt viscosity of 210 Pa · s (280 ° C., 121.6 sec ⁻¹ ) and a melting point of 255 ° C. with an N6 blend ratio of 20 weight After blending at 290 ° C., the spinning temperature is 296 ° C., the die surface temperature is 280 ° C., the number of nozzle holes is 36, the discharge hole diameter is 0.30 mm, and the discharge hole length is 0.50 mm. Melt spinning was performed in the same manner as in Example 1, and the undrawn yarn was wound up at a spinning speed of 1000 m / min. However, it is a simple chip blend, and since the melting point difference between polymers is large, the blend spots of N6 and PET are large and not only a large ball is generated under the base, but also the spinnability is poor and stable. Although the yarn could not be wound up, a small amount of undrawn yarn was obtained, and the temperature of the first hot roller was 85 ° C. and the draw ratio was 3 times, and the drawing was performed in the same manner as in Example 1 to obtain 100 dtex, 36 filaments. A drawn yarn was obtained. When the fiber cross section was observed by TEM, it was confirmed that islands having a single fiber diameter of 550 to 1400 nm were generated. Moreover, the single fiber number average diameter of these island components was as large as 850 nm, and the sum Pa of the single fiber ratio was 0%.

The sea component of the obtained fiber was alkali-sealed and then cut into 2 mm in the same manner as the nanofiber of Example 1 to obtain N6 ultrafine fiber short fibers. 2 g of the obtained short fibers (corresponding to 30 g / m ² when used as a synthetic paper) was collected and placed in a disaggregator with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator is put into a container of a laboratory paper machine (rectangular sheet machine), water is added to prepare a 20 liter preparation solution, and then a first industrial pharmaceutical anionic dispersant ( Charol AN-103P: molecular weight 10,000) was added to 0.2 wt% with respect to the prepared solution. Although this prepared solution was made on a mesh net of mesh # 100, it was able to be taken out as a synthetic paper, but it was weak and could be partially broken or broken to obtain a uniform synthetic paper. There wasn't. This is thought to be because, unlike nanofibers, ultrafine fibers have low cohesive strength between the fibers, and particularly low strength when wet.

As a result of sampling a good portion of the obtained synthetic paper and observing with SEM, the single fiber number average diameter φm was 883 nm, and the sum of the single fiber ratios obtained from the distribution of single fiber diameters (see Table 4). Pa was 0%, the single fiber diameter concentration index Pb was 8.3%, the fiber diameter was large, and the variation was large. The synthetic paper had a total basis weight of 28.3 g / m ² , a thickness of 122 μm, a density of 0.23 g / cm ³ , and a pore area of 1.5 μm ² . When the hygroscopic property of the synthetic paper was measured, the hygroscopic property was 2.8% lower than that of the nanofiber of Example 1. On the other hand, since the strength of the synthetic paper was weak, the strength, elongation, and air flow could not be measured.

Example 11

Polystyrene (co-PS) copolymerized with 22% PBT and 2-ethylhexyl acrylate having a melt viscosity of 120 Pa · s (262 ° C., 121.6 sec ⁻¹ ) and a melting point of 225 ° C., the PBT content is 20% by weight, and the kneading temperature Was 240 ° C. and melt-kneaded in the same manner as in Example 1 to obtain a polymer alloy chip.

  This was melt-spun in the same manner as in Example 1 at a melting temperature of 260 ° C., a spinning temperature of 260 ° C. (die surface temperature of 245 ° C.), a single hole discharge rate of 1.0 g / min, and a spinning speed of 1200 m / min. The obtained undrawn yarn was drawn and heat-treated in the same manner as in Example 1 at a drawing temperature of 100 ° C., a draw ratio of 2.49 times, and a heat setting temperature of 115 ° C. The obtained drawn yarn was 161 dtex, 36 filaments, and the strength was 1.4 cN / dtex, the elongation was 33%, and U% = 2.0%. When the cross section of the obtained polymer alloy fiber was observed with a TEM, the sea-island structure in which co-PS was the sea and PBT was the island, the number average diameter of PBT was 100 nm, and the copolymerized PET was nano-sized. Uniformly dispersed polymer alloy fibers were obtained. By immersing this polymer alloy fiber in trichlene, 99% or more of the sea component co-PS was eluted and dried, and then cut into 2 mm with a guillotine cutter to obtain PBT nanofiber aggregate short fibers. . Secondary beating fibers were obtained from the cut fibers in the same manner as in Example 1. The fiber concentration of the PBT nanofiber after this secondary beating was 8 wt%, and the freeness was 96.

  6.9 g of the obtained PBT nanofiber after the secondary beating and 0.7 g of Daiichi Kogyo Seiyaku nonionic dispersant (Neugen EA-87: molecular weight 10,000) were put into a disaggregator together with 1 liter of water. Dispersed for minutes. The dispersion in the disaggregator was placed in a container of an experimental paper machine (square sheet machine) manufactured by Rikuma Kumagai, and water was added to make a 20 liter prepared solution. The prepared solution is made on a 25 cm square “screen basket (made of PET, fiber diameter 70 μm, hole diameter 80 μm square)” previously placed on a wire mesh net for paper making, dehydrated with a roller, dried with a drum dryer, A PBT nanofiber synthetic paper having a screen ridge as a base substrate was obtained.

As a result of SEM observation of the surface of the obtained synthetic paper, synthetic paper in which up to one PBT nanofiber was dispersed was obtained. The resulting synthetic paper was very thin but had no pinholes and was a uniform synthetic paper. Further, the average number of single fibers was φm of 102 nm, the single fiber ratio sum Pa was 100%, and the single fiber diameter concentration index Pb was 69%. The synthetic paper had a total basis weight of 45.8 g / m ² , a thickness of 100 μm, a density of 0.46 g / cm ³ , a strength of 90.4 N / cm, and an elongation of 32%. When the screen wrinkle part (37.4 g / m ² basis weight, thickness 70 μm, density 0.53 g / cm ³ ) is considered to be removed from this synthetic paper, the basis weight of the nanofiber alone is 8.4 g / m ² , thickness. Was 30 μm and the density was 0.28 g / cm ³ . The synthetic paper had a pore area of 0.0040 μm ² . Further, the synthetic paper of this example was a synthetic paper having a high surface smoothness with a surface smoothness of 970 seconds with 0 pinholes of 50 μm or more.
The synthetic paper of this example has such a fine pore area, and furthermore, since the dispersibility and uniformity of the nanofiber are good, there is no large pinhole, and the air flow rate is 0.40 cc / cm ² / A synthetic paper having a gas shielding power as small as sec was obtained.

Example 12
Example ¹ with PP (20% by weight) having a melt viscosity of 300 Pa · s (220 ° C., 121.6 sec ⁻¹ ), a melting point of 162 ° C. and poly L lactic acid (80% by weight) of Example 10, and a kneading temperature of 220 ° C. In the same manner as above, melt kneading was performed to obtain a polymer alloy chip.

  This was melt-spun in the same manner as in Example 1 at a melting temperature of 220 ° C., a spinning temperature of 220 ° C. (die surface temperature of 205 ° C.), a single hole discharge rate of 2.0 g / min, and a spinning speed of 1200 m / min. The obtained undrawn yarn was drawn and heat treated in the same manner as in Example 1 at a drawing temperature of 90 ° C., a draw ratio of 2.0 times, and a heat setting temperature of 130 ° C. The obtained drawn yarn was 101 dtex, 12 filaments, and had a strength of 2.0 cN / dtex and an elongation of 47%.

  When a cross section of the obtained polymer alloy fiber was observed with a TEM, poly-L-lactic acid showed a sea-island structure with PP as an island, PP average diameter was 150 nm, PP was nano-sized and uniformly dispersed A polymer alloy fiber was obtained.

By immersing the obtained polymer alloy fiber in a 3% aqueous sodium hydroxide solution at 98 ° C. for 2 hours, 99% or more of the poly L-lactic acid component in the polymer alloy fiber is hydrolyzed and neutralized with acetic acid. Then, it washed with water, dried, and cut | disconnected to 2 mm length with the guillotine cutter, and obtained PP nanofiber short fiber. Secondary beating fibers were obtained from the cut fibers in the same manner as in Example 1. The fiber concentration of the PP nanofiber after this secondary beating was 6 wt%, and the freeness was 104.
9.2 g of the obtained secondary beating fiber and 0.9 g of Daiichi Kogyo Seiyaku nonionic dispersant (Neugen EA-87: molecular weight 10,000) were placed in a disaggregator together with 1 liter of water and dispersed for 5 minutes.
The dispersion in the disaggregator was placed in a container of an experimental paper machine (square sheet machine) manufactured by Rikuma Kumagai, and water was added to make a 20 liter prepared solution. This prepared solution is paper-made on a 25 cm square “screen cage (made of PET, fiber diameter 70 μm, hole diameter 80 μm square)” placed on a paper net for papermaking in advance, dehydrated with a roller, and dried with a drum dryer A PP nanofiber synthetic paper having a screen ridge as a base substrate was obtained. As a result of observing the surface of the obtained synthetic paper with SEM, synthetic paper in which up to one PP nanofiber was dispersed was obtained. The resulting synthetic paper was very thin but had no pinholes and was a uniform synthetic paper. Further, the number average single fiber diameter of the PP nanofibers was φm of 154 nm, the single fiber ratio sum Pa was 100%, and the single fiber diameter concentration index Pb was 69%. Further, this synthetic paper had a total basis weight of 45.7 g / m ² , a thickness of 102 μm, a density of 0.45 g / cm ³ , a strength of 91.2 N / cm, and an elongation of 33%. When the screen ridge portion (37.4 g / m ² basis weight, thickness 70 μm, density 0.53 g / cm ³ ) was removed from this synthetic paper, the basis weight of the nanofiber alone was 8.3 g / m ² , thickness. Was 32 μm and the density was 0.26 g / cm ³ . The synthetic paper had a hole area of 0.0062 μm ² . The synthetic paper of this example has such a fine pore area, and furthermore, since the dispersibility and uniformity of the nanofibers are good, there is no large pinhole and the air flow rate is 0.73 cc / cm ² / A synthetic paper having a gas shielding power as small as sec was obtained. Further, the composite synthetic paper of this example was a synthetic paper having a high surface smoothness of 0 for pinholes of 50 μm or more and a surface smoothness of 770 seconds.

Example 13
Melt viscosity 280Pa · s (300 ℃, 1216sec -1) 80 wt% of PET of melt viscosity 160Pa · s (300 ℃, 1216sec -1) as 20% by weight of PPS, a biaxial extrusion kneader under the following conditions Using this, melt kneading was performed to obtain a polymer alloy chip. Here, the PPS used was a linear type and the molecular chain terminal was replaced with calcium ions. The weight reduction rate when the PET used here was held at 300 ° C. for 5 minutes was 1%.

Screw L / D = 45
The kneading part length is 34% of the effective screw length
The kneading part was dispersed throughout the screw.

There are two backflow parts on the way. Polymer supply PPS and PET were weighed separately and supplied separately to the kneader.

Temperature 300 ° C
No vent The polymer alloy chip obtained here was guided to a spinning machine in the same manner as in Example 1 to perform spinning. At this time, the polymer alloy melt was filtered with a metal nonwoven fabric having a spinning temperature of 315 ° C. and a limit filtration diameter of 15 μm, and then melt-spun from a die having a die surface temperature of 292 ° C. At this time, as the base, a nozzle having a discharge hole diameter of 0.6 mm provided with a measuring portion having a diameter of 0.3 mm above the discharge hole was used. And the discharge amount per single hole at this time was 1.1 g / min. Furthermore, the distance from the base lower surface to the cooling start point was 7.5 cm. The discharged yarn is cooled and solidified over 1 m with a cooling air of 20 ° C., and after the process oil agent mainly composed of fatty acid ester is supplied, it is 1000 m / min through the non-heated first take-up roller and the second take-up roller. It was wound up. The spinnability at this time was good, and there was no yarn breakage during continuous spinning for 24 hours. This was subjected to a stretching heat treatment with the temperature of the first hot roller being 100 ° C. and the temperature of the second hot roller being 130 ° C. At this time, the draw ratio between the first hot roller and the second hot roller was 3.3 times. The obtained polymer alloy fiber exhibited excellent properties of 400 dtex, 240 filament, strength 4.4 cN / dtex, elongation 27%, U% = 1.3%. Moreover, when the cross section of the obtained polymer alloy fiber was observed by TEM, PPS was dispersed uniformly as an island with a diameter of less than 100 nm in PET, which is a marine polymer. Moreover, when the circle-equivalent diameter of the island was analyzed by the image analysis software WINROOF, the average diameter of the island was 65 nm, and a polymer alloy fiber in which PPS was ultrafinely dispersed was obtained.

The obtained polymer alloy fiber was scraped to form a casket-shaped tow having a fineness of 100,000 dtex. At this time, the toe was restrained from falling apart during sea removal treatment by tying the outer circumference of the tow with a cotton thread and fixing it every 30 cm. Then, the tension was adjusted so that the fiber density of the tow was 0.05 g / cm ³ and set in the sea removal device of FIG. Then, this tow was subjected to an alkali hydrolysis treatment using 98%, 10% by weight sodium hydroxide aqueous solution in combination with 5% owf of “Merseline PES” manufactured by Meisei Chemical Industry Co., Ltd. The sea polymer PET was removed from the sea to obtain a tow composed of PPS nanofibers having a tow fineness of 20,000 dtex. When the cross section of the PPS nanofiber tow obtained here was observed with a TEM, the single fiber number average diameter φm was 60 nm, and the sum Pa of the single fiber ratio was 100%.

  The tow composed of the PPS nanofiber was cut into a fiber length of 1 mm using a guillotine cutter to obtain a short fiber composed of PPS nanofiber. The L / D of the PPS nanofiber single fiber at this time was about 16700.

  Then, about 20 liters of water and 30 g of the short fibers composed of the PPS nanofibers were put into a Niagara beater container, and the fibers were first beaten for 10 minutes. Water was removed from the fiber with a centrifugal separator to obtain a primary beating fiber having a fiber concentration of 10 wt%. The primary beaten fibers were further beaten for 10 minutes with a PFI beater and then dehydrated. The fiber concentration of the PPS nanofiber of the obtained secondary beating fiber was 10 wt%.

  Then, 5.5 g of the above secondary beating fiber and 0.5 g of Daiichi Kogyo Seiyaku nonionic dispersant (Neugen EA-87: molecular weight 10,000) were placed in a disaggregator together with 1 liter of water and dispersed for 5 minutes. The dispersion in the disaggregator is put into a container of a laboratory paper machine (square sheet machine), water is added to make a 20 liter preparation solution, and this is placed in advance on a paper mesh net of 25 cm square “ Paper was made on a screen bottle (manufactured by PET, fiber diameter 70 μm, pore diameter 80 μm square), dehydrated with a roller, and dried with a drum dryer to obtain PPS nanofiber synthetic paper.

When the surface of the paper made of the obtained PPS nanofibers was observed by SEM, the PPS nanofibers were uniformly dispersed at the single fiber level, the single fiber number average diameter φm was 60 nm, and the sum Pa of the single fiber ratio was 100%. The single fiber diameter concentration index Pb was 63%. This synthetic paper had a total basis weight of 45.6 g / m ² , a thickness of 101 μm, a density of 0.45 g / cm ³ , a strength of 91.4 N / cm, and an elongation of 32%. When the screen ridge part (37.4 g / m ² basis weight, thickness 70 μm, density 0.53 g / cm ³ ) is considered to be removed from this synthetic paper, the basis weight of the nanofiber alone is 8.2 g / m ² , thickness. Was 31 μm and the density was 0.26 g / cm ³ . The synthetic paper had a hole area of 0.0044 μm ² . The synthetic paper of this example has such a fine pore area, and furthermore, since the dispersibility and uniformity of the nanofibers are good, there are no large pinholes, and pinholes of 50 μm or more are zero. The surface smoothness was 1710 seconds and was a synthetic paper having a high surface smoothness.
Further, a synthetic paper having a low gas permeability of 0.29 cc / cm ² / sec and high gas shielding power was obtained. Furthermore, the surface of the PPS paper contains a large number of nano-level pores, and this is suitable for liquid filters, secondary batteries, capacitor separators, and the like.

  The PPS nanofiber paper was further hot pressed at 180 ° C. to obtain a denser PPS paper. This was suitable for a circuit board having little dimensional change due to moisture absorption.

Example 14
The dispersion obtained in Example 1 was further diluted 10 times to obtain a dispersion having a fiber concentration of 0.0055%. This is sprayed 100 times from a spray nozzle onto a PP meltblown nonwoven fabric (Tremicron manufactured by Toray Industries, Inc.) having a fiber diameter of about 3 μm, dried with a drum dryer, and then N6 nanofibers with a thickness of 30 μm on the PP meltblown nonwoven fabric. A synthetic paper was formed into a composite synthetic paper.

As a result of SEM observation of the obtained composite synthetic paper, the average number of single fibers of the N6 nanofibers was φm of 57 nm, the single fiber ratio sum Pa was 100%, and the single fiber diameter concentration index Pb was 64. %Met. In this composite synthetic paper, N6 nanofibers are uniformly dispersed on a PP meltblown nonwoven fabric, there are no large holes or pinholes, pinholes of 50 μm or more are zero, and the surface smoothness is 650 seconds. It was a highly synthetic paper.
It contains many nano-level pores and is suitable for liquid filters and air filters.

Example 15
A composite synthetic paper was formed by spraying NPP nanofiber synthetic paper having a thickness of 30 μm on the foam by spraying in the same manner as in Example 14 except that the PP meltblown nonwoven fabric was made into a foam (Toraypef manufactured by Toray Industries, Inc.). It was. This composite synthetic paper is one in which N6 nanofibers are uniformly coated on a foam and is suitable as an abrasive.

Example 16
In Example 2, a nanofiber composite synthetic paper having a screen wrinkle as a base substrate was obtained in the same manner as in Example 2 except that the secondary beating fiber was changed to 0.55 g.

As a result of SEM observation of the surface of the obtained composite synthetic paper, the single fiber number average diameter φm of the nanofibers in the synthetic paper was 58 nm, the single fiber ratio sum Pa was 100%, and the single fiber diameter concentration index Pb Was 66%. Further, this synthetic paper had a total basis weight of 38.2 g / m ² , a thickness of 70 μm, and a density of 0.54 g / cm ³ . When the screen wrinkle portion (37.4 g / m ² basis weight, thickness 70 μm, density 0.53 g / cm ³ ) was removed from this synthetic paper, the basis weight of the nanofiber alone was 0.8 g / m ² , thickness. Was 3.2 μm and the density was 0.026 g / cm ³ . Further, when the air flow rate was measured, it was 28 cc / cm ² / sec, which was excellent as a gas permeability, and thus was suitable as an air filter. Further, the composite synthetic paper of this example was a synthetic paper having a high surface smoothness of 0 for pinholes of 50 μm or more and a surface smoothness of 390 seconds.

It is the schematic which shows an example of the spinning machine for "polymer alloy fiber" used as the raw yarn of nanofiber. 2 is a TEM photograph showing an example of the shape of a fiber in a cross section of the polymer alloy fiber of Example 1. FIG. 2 is an ultra-high resolution SEM photograph showing an example of the shape of a fiber of nylon nanofibers on the synthetic paper surface of Example 1. The synthetic paper surface photograph (FIG. 3) of Example 1 was image-processed to measure holes. FIG. It is a TEM photograph which shows an example of the shape of the fiber of the cross section of the PPS nanofiber of Example 13.

Explanation of symbols

1: Hopper 2: Melting part 3: Spin block 4: Spin pack 5: Base 6: Chimney 7: Yarn 8: Converging oiling guide 9: First take-up roller 10: Second take-up roller 11: Winder 12: Detachment Sea treatment tank 13: Sea removal treatment liquid piping 14: Pump 15: Upper bar 16: Lower bar 17: Treatment liquid discharge hole 18: Fassete tow 19: Sea removal treatment liquid

Claims (6)

A method for producing a nanofiber synthetic paper comprising a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 500 nm and a sum of single fibers Pa of 60% or more. A nanofiber of a thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2 A method of producing nanofiber synthetic paper, comprising nanofiber synthetic paper containing a dispersion, wherein nanofiber short fibers are dispersed after beating, and paper is produced without using a binder. A method for producing a nanofiber synthetic paper comprising a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 200 nm and a single fiber ratio Pa of 60% or more. A nanofiber of a thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2 A method of producing nanofiber synthetic paper, comprising nanofiber synthetic paper containing a dispersion, wherein nanofiber short fibers are dispersed after beating, and paper is produced without using a binder. 2. The nanofiber synthesis paper according to claim 1, wherein the nanofiber synthetic paper has a single fiber number average diameter as a median value, and a single fiber diameter concentration index Pb representing a ratio of fibers entering a width of 30 nm before and after that is 50% or more. Paper manufacturing method. A method for producing a nanofiber synthetic paper comprising a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 500 nm and a sum of single fibers Pa of 60% or more. A nanofiber of a thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2 A method for producing a nanofiber synthetic paper, which is a nanofiber synthetic paper containing a dispersion, and which uses the fiber dispersion as a binder to produce other fibers having a single fiber number average diameter of 1 µm or more. A method for producing a nanofiber synthetic paper comprising a nanofiber dispersion of a thermoplastic polymer obtained from a polymer alloy fiber having a single fiber number average diameter of 1 to 200 nm and a single fiber ratio Pa of 60% or more. A nanofiber of a thermoplastic polymer obtained by desealing a polymer alloy fiber in which the nanofiber dispersion has a polymer SP value difference of 1 to 9 (MJ / m ³ ) ^1/2 A method for producing a nanofiber synthetic paper, comprising a nanofiber synthetic paper containing a dispersion, and using the nanofiber dispersion as a binder and making other fibers having a number average single fiber diameter of 1 μm or more. Nanofiber synthetic paper, a number average single fiber diameter and median, nanofiber synthesis described in claim 4 index Pb of extremal coefficient of single fiber diameters representing the percentage of fibers that appear in the front and rear 30nm width is 50% or more Paper manufacturing method.