JP2000038481A - Silane-crosslinkable polyolefin resin composition and insulating cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silane-crosslinkable polyolefin resin composition that gives the molded products excellent smoothness on the surfaces of molded products and high heat resistance and provide insulation cables which can omit the step for moisture crosslinking. SOLUTION: In this silane-crosslinkable polyolefin resin composition that is prepared by melt-mixing a base polymer and a carrier polymer A containing a silanol condensation reaction catalyst and an antioxidant, the base polymer is composed of a mixture of a silane-modified polyethylene and a polyolefin resin the mixture has an average density of 0.926/cm3-0.935 g/cm3 and a heat distortion rate of <=40% according to JIS K 6723.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silane obtained by melting and mixing a mixture of a silane-modified polyolefin and a polyolefin as a base polymer and then a carrier polymer A containing a silanol condensation catalyst at a temperature not lower than the melting point of the base polymer. TECHNICAL FIELD The present invention relates to a crosslinked resin composition and an insulated cable which is coated with an electric wire and sheathed immediately after coating.

[0002]

2. Description of the Related Art As a simple method for crosslinking polyethylene, chemical crosslinking, electron beam irradiation crosslinking and hot water crosslinking (which proceed using an organic silane compound as a medium) are widely known, and one of them is hot water crosslinking. Has the advantages that the cost of a crosslinking apparatus is much lower than that of chemical crosslinking or electron beam irradiation crosslinking, and that crosslinking can be easily controlled. As a typical example of the hot water cross-linked polyethylene, the polyolefin is subjected to a graft reaction with an organic unsaturated silane in the presence of a free radical generator to perform silane grafting, and then the silane grafter is subjected to a silanol condensation catalyst in the presence of a silanol condensation catalyst. The so-called silane crosslinking method of crosslinking by contact with moisture is generally known. For example, JP-B-48-1711, JP-A-57-
No. 49109 discloses this.

[0003] However, the hot water cross-linking, in which the equipment cost is lower than other cross-linking methods, is missed in that much time and cost are required for the cross-linking treatment.
An electric wire coated with a water-crosslinkable resin composition undergoes a very slow cross-linking reaction at room temperature. Therefore, it is necessary to promote cross-linking in hot water of about 80 ° C. or a high-temperature and high-humidity tank. Even if it is promoted, it takes about one day, and the investment cost of the crosslinking treatment equipment is enormous. For this reason, even if the equipment cost is very low, the advantage will be diminished if a large cost is applied to the crosslinking treatment cost.

[0004] For this reason, various attempts have been made to reduce the time required for the cross-linking treatment of an electric wire extruded with a water-crosslinkable resin. For example, a method is known in which a catalyst or an auxiliary agent is added to a modified silane compound to promote cross-linking, which is disclosed in JP-A-57-208006 and JP-A-62-106.
No. 947. Also, a method of increasing the contact with moisture during the crosslinking of the water-crosslinked resin-coated electric wire and shortening the crosslinking time is known, which is disclosed in JP-A-60-254520 and JP-A-60-26510. .
Further, a method of shortening the time of the crosslinking treatment by promoting the diffusion of water into the inside of the water-crosslinking resin by performing the crosslinking treatment of the water-crosslinking resin-coated electric wire in an ultrasonic atmosphere is disclosed in JP-A-Hei.
It is disclosed by Japanese Patent Publication No. 31241. However, all of the above methods only shorten the time of the crosslinking treatment by hot water or steam treatment, and do not eliminate the water crosslinking step.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and provides a silane-crosslinked polyolefin resin composition which is particularly excellent in the smoothness and heat resistance of a molding surface. It is another object of the present invention to provide an insulated cable capable of sheathing an electric wire extrusion-coated with a silane-crosslinked polyolefin resin composition immediately after coating.

[0006]

SUMMARY OF THE INVENTION The present invention provides a silane-crosslinked polyolefin resin composition obtained by melt-mixing a base polymer and a carrier polymer A containing a silanol condensation catalyst and an antioxidant. And a polyolefin resin, and the mixture has an average density of 0.926 g / cm ^{3 to} 0.
It is a silane-crosslinked polyolefin resin composition having a heat deformation ratio after melting and mixing (JIS K 6723) of 935 g / cm ³ or less. Preferably, the silane-modified polyethylene is obtained by reacting a low-density polyethylene with an organic unsaturated silane and a free radical generator, and the polyolefin resin has a density of 0.915 g / cm ^{3 to} 0.955 g.
/ Cm ³ is a silane cross-linked polyolefin resin composition that is a high-density polyethylene. In a more preferred embodiment, the carrier polymer A is a polymer selected from the group consisting of polyethylene, polypropylene, and a copolymer of ethylene and an α-olefin.
Is a silane crosslinked polyolefin resin composition having an amount of 2 to 5% by weight. Further, an insulated cable is obtained by coating an electric wire with the silane-crosslinked polyolefin resin composition and immediately sheathing the coated electric wire.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The low-density polyethylene used as a raw material of the silane-modified polyethylene of the present invention is defined by a tubular method,
Or an ethylene polymer produced by high-pressure radical polymerization by an autoclave method. The high-density polyethylene used as the polyolefin of the present invention refers to various kinds of catalysts such as a gas phase method, a solution method, and a suspension polymerization method in medium-to-low pressure or high pressure using various catalysts such as Ziegler catalysts and chromium catalysts. It is an ethylene polymer obtained by a legal method and has a density of 0.915 to 0.955 g / cm ³ .

In the present invention, the organic unsaturated silane required for the production of the silane-modified polyolefin is grafted onto the base resin so as to be a cross-linking point between the base resins. The organic unsaturated silane used in the present invention is represented by the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R 'is an aliphatic unsaturated hydrocarbon group. Monovalent hydrocarbon groups other than hydrogen or
The same compound as used for Y) is used. It is desirable to use an organic unsaturated silane represented by the general formula RSiY _{3 in} which R ′ is the same as Y, for example, vinyltrimethoxysilane,
Vinyl triethoxy silane, vinyl tributoxy silane, allyl trimethoxy silane, allyl triethoxy silane and the like can be mentioned. The amount of these additives is from 0.1 to 5% by weight, preferably from 0.7 to 3% by weight, based on the total weight of the polymer. If the amount is less than 0.1% by weight, sufficient grafting does not occur, and if the amount exceeds 5% by weight, molding failure occurs and it is not economical.

[0009] The free radical generator of the present invention functions as an initiator in the production of a silane-modified polyolefin. The free radical generator used in the present invention includes various organic peroxides and peresters having a strong polymerization initiating action, such as dicumyl peroxide, α, α′-bis (t-butylperoxydiisopropyl) benzene, Di-t-butyl peroxide, t-butylcumyl peroxide, di-benzoyl peroxide, 2,5-dimethyl-2,
5-bis (t-butylperoxy) hexane, t-butylperoxypivalate, t-butylperoxy-2-
Ethyl hexanoate and the like can be mentioned. These additives may be added in an amount of 0.01 to 0.5 based on the total weight of the polymer.
It is 5% by weight, preferably 0.05 to 0.2% by weight.
If the amount is less than 0.01% by weight, a sufficient silane grafting reaction does not proceed. If the amount exceeds 0.5% by weight, the extrudability deteriorates and the molding surface deteriorates.

The carrier polymer A can be added by kneading and granulating a silanol condensation catalyst and an antioxidant with the carrier polymer A of the present invention. The carrier polymer A must also be in a particulate form and a solid compatible with the base polymer to be crosslinked. The carrier polymer A of the present invention is usually in the form of granules or granules in the form of pellets, and the preferred form is pellets. As the carrier polymer A used in the present invention, for example, polyethylene, polypropylene, a copolymer of ethylene and an α-olefin, and as the α-olefin, C3-C12 such as propylene, butene-1, pentene-1, octene-1 , 4-methylpentene-1, 4-methylhexene-1, 4,4-dimethylpentene-1, nonene-1, decene-1, undecene
1, dodecene-1 and the like, and mixtures thereof.

Examples of the silanol condensation catalyst of the present invention include dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, and stearic acid. Organic metal compounds such as lead, zinc stearate, cadmium stearate, barium stearate, calcium stearate and the like can be mentioned. These additives may be added in an amount of 0.01 to 0.2% by weight, preferably 0.02 to 0.1% by weight, based on the total weight of the polymer.
% By weight. If the amount is less than 0.01% by weight, a sufficient crosslinking reaction does not proceed. If the amount exceeds 0.2% by weight, crosslinking occurs locally in the extruder at the time of extrusion, and the appearance is significantly deteriorated.

The amount of the carrier polymer A is in the range of 2 to 5% by weight. If the amount is less than 2% by weight, a sufficient crosslinking reaction does not occur. If the amount exceeds 5% by weight, molding failure (scorch or unstable ejection) occurs, and it is not economical. As other additives, if desired, commonly used additives such as antioxidants, neutralizers, ultraviolet absorbers,
Antistatic agent, pigment, dispersant, thickener, metal deterioration inhibitor,
A fungicide, a flow regulator, other inorganic fillers, or the like, or other synthetic resins can be contained.

The crosslinked polyolefin resin composition of the present invention has extremely excellent heat deformation properties and can be used for various applications. If a post-crosslinking treatment step such as steam treatment or hot water treatment after extrusion is performed, the heat resistance is further improved, but this step can be omitted. Therefore, it is particularly suitable for the production of insulated cables that require heat resistance and flexibility, and can be covered with a sheath material without performing a water crosslinking step after covering the electric wires. For this purpose, it is necessary that the heating deformation ratio immediately after extrusion is 40% or less. As the sheath material, a vinyl chloride resin composition or the like is used.

[0014]

The following examples illustrate the invention, but are by way of example only and the invention is not limited thereto. << Production of Carrier Polymer A >> The carrier polymer A, a silanol condensation catalyst, an antioxidant and the like were kneaded and granulated according to the compounding ratio shown in Table 1 using a pressure kneader.

<< Production of Silane Graft Mer >> Next, a polyolefin base polymer, an unsaturated organic silane compound and a free radical generator were blended in the ratio shown in Table 2 to produce a silane graft mer.

The produced silane graft mer, polyolefin and carrier polymer A were mixed in the ratios shown in Tables 3 and 4, and the tape was extruded using an extruder. The heating deformation rate immediately after extrusion of this extruded tape was evaluated. In addition, the wire was extruded with the same composition as when the tape was extruded, and the smoothness of the molded surface was evaluated. The results are shown in Tables 3 and 4.

The raw materials used are as follows. (1) VTMOS: vinyltrimethoxysilane (2) DCP: dicumyl peroxide (3) LDPE (1): low-density polyethylene (density; 0.925 g / c
m ³ , MI; 1.5 g / 10 min) (4) PP: polypropylene (homopolymer, MI (230 ゜)
(5) DBTDL: dibutyltin dilaurate (6) Antioxidant: phenolic antioxidant / Irganox 1010 (manufactured by Ciba-Geigy) (7) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Chemical Industries, Ltd.) (8) LDPE (2): low-density polyethylene (density: 0.923
g / cm ³ ) (9) LDPE (3): low density polyethylene (density; 0.920
g / cm ³ ) (10) HDPE (1): high-density polyethylene (density; 0.95
0g / cm ³ ) (11) HDPE (2): high-density polyethylene (density; 0.93
1g / cm ³⁾

The evaluation method is as follows. (12) Appearance of tape extrusion (confirmation of presence or absence of bumps): Extruder of 50mmφ 130-160-180-190-180 ℃ L / D: 20 Compression ratio 3.5 Tape die: width 100mm Lip interval 1mmt Screw rotation speed 40rpm Tape appearance (Bugs) Evaluation: The order of △>△> × was given, and the level of ○ was judged to be acceptable. (13) Heat deformation ratio (%): JIS K 6723
by. (14) Coated wire extrusion appearance (evaluation of molding surface): Extruder with 50mmφ 130-160-180-190-180 ℃ L / D: 24 Compression ratio 4.0 Conductor diameter 0.8mmφ Coating thickness 1.00mmφ Screw speed 40 rpm Coating Appearance evaluation of the electric wire: ○>△> ×, in order, and the level of “O” was accepted.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

As is clear from the table, Examples 1 to 4 have good extrusion processability and smoothness of the molding surface, and show extremely excellent heat resistance. That is, the heat deformation ratio is 40% or less immediately after the extrusion, and the crosslinking treatment step can be omitted. On the other hand, all of the comparative examples have difficulty in smoothness, and the extrusion processability and heat resistance are not balanced.

[0024]

According to the present invention, it is possible to obtain a silane-crosslinked polyolefin having excellent molding surface smoothness and excellent heat resistance. Reduces the number of cross-linking processes,
Sheathing can be performed immediately. This not only significantly increases the productivity of the product, but also significantly reduces the manufacturing costs. The present invention greatly contributes to the manufacture of an insulated cable.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 83/10 C08L 83/10 H01B 3/44 H01B 3/44 D // C09D 123/04 C09D 123/04 123/08 123/08 123/10 123/10 123/26 123/26 151/06 151/06 183/04 183/04 F term (reference) 4J002 BB03X BB033 BB053 BB10W BB123 BQ00W EG036 EG046 EZ016 FD070 FD146 GQ01 4J038 CB021 CB022 CB041 CB042 CB081 CB082 CB101 CB102 CP021 JA23 JA46 JA47 JA50 JC40 KA04 LA06 LA07 MA02 NA12 NA13 NA14 NA27 PA15 PB09 PC02 5G305 AA02 AB24 AB40 BA13 CA01 CA40 CA51 CA54 CA55 DA23

Claims (7)

[Claims] 1. A silane-crosslinked polyolefin resin composition obtained by melt-mixing a base polymer and a carrier polymer A containing a silanol condensation catalyst and an antioxidant, wherein the base polymer comprises a mixture of a silane-modified polyethylene and a polyolefin resin, A silane-crosslinked polyolefin resin composition characterized in that the mixture has an average density of 0.926 g / cm ^{3 to} 0.935 g / cm ³ and a heat deformation ratio (JIS K 6723) of 40% or less after melt mixing. object. 2. The silane-crosslinked polyolefin resin composition according to claim 1, wherein the silane-modified polyethylene is obtained by reacting low-density polyethylene with an organic unsaturated silane and a free radical generator. 3. The polyolefin resin has a density of 0.91.
5g / cm ³ ~0.955g / cm ³ and a high density polyethylene according to claim 1 or 2 silane according crosslinked polyolefin resin composition. 4. The carrier polymer A is polyethylene,
The silane-crosslinked polyolefin resin composition according to claim 1, which is a polymer selected from the group consisting of polypropylene and a copolymer of ethylene and an α-olefin. 5. The silane-crosslinked polyolefin resin composition according to claim 1, wherein the amount of the carrier polymer A is 2 to 5% by weight. 6. An insulated cable obtained by coating an electric wire with the silane-crosslinked polyolefin resin composition according to claim 1. 7. An insulated cable, wherein an electric wire is coated with the silane-crosslinked polyolefin resin composition according to claim 1 and then coated with a sheath material.