WO2021101457A1 - Ultra-high molecular weight polyethylene - Google Patents

Abstract

Herein disclosed is a catalyst composition for preparation of an ultra-high molecular weight polyethylene (UHMWPE) from a reaction of an ethylene in the presence of the catalyst composition, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier: Formula(e) (A) The UHMWPE of the present disclosure has a characteristic of disentangled UHMWPE (dis-UHMWPE). A process for preparation of the ultra-high molecular weight polyethylene, and the ultra-high molecular weight polyethylene (UHMWPE) are also disclosed.

Description

ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Singapore Patent Application No. 10201910927U, filed 20 November 2019, the content of it being hereby incorporated by reference in its entirety for all purposes.

FIELD OF INVENTION

The present disclosure relates to an ultra-high molecular weight polyethylene (UHMWPE) and/or disentangled ultra-high molecular weight polyethylene (dis-UHMWPE), process for preparation and articles prepared thereof.

BACKGROUND

Ultra-high molecular weight polyethylene (UHMWPE) is a type of polyolefin bearing a viscometer molecular weight (Mv) greater than 1x106 g/mol. Such extremely high Mv of polyethylene may provide for extraordinary mechanical properties, such as higher tensile strength, modulus and abrasion resistance, and has been applicably used as an engineering material rather than a commodity plastic. However, due to its high molar mass, UHMWPE has a significant high number of entanglements between polyethylene chains. Such high degree of entanglements within this material, normally produced by Ziegler-Natta catalysts, tends to cause high melt-viscosity, which renders difficulty processing with conventional techniques used for other thermoplastics, thus limiting the applications of this material.

In 1980, the gel/solution-spinning process, pioneered by Smith and Lemstra, improved processability of UHMWPE by reducing the entanglement through dissolution of the polymer (less than 5 wt%) in a solvent, such as decalin or xylene. The UHMWPE with reduced entanglement achieved, so-called a disentangled ultra-high molecular weight polyethylene (dis-UHMWPE), is used for its ease in drawability to make high-modulus and high-strength tapes and fibers. However, this process may be deemed inefficient, uneconomical and environmentally unfriendly due to evaporating large amount of the solvents. Later, Smith et al, in Polym. Commun. 1985, 26, 258 - 260 and J. Mater. Sci. 1987, 22, 523 - 531, showed the possibility of synthesizing dis-UHMWPE in-situ in a polymerization reactor using supported vanadium catalyst under cryogenic conditions. The low polymerization temperature favoured crystallisation over the polymerization rate resulting in a “single chain forming single crystal”, thus avoiding the entanglement formation and producing the dis-UHMWPE in-situ. However, the polymer yield was undesirably low because of the low polymerization temperature, e.g. -20°C. In addition, though several conventional metallocenes and hemi-metallocene -based catalysts have been developed for synthesis of dis-UHMWPE, the targeted molecular weight (Mw > 2x106 g/mol) and the high degree of disentanglement was achieved only at very low temperature and pressure, but with low polymer yield.

For example, U.S. Pat. No. 7671159 describes the use of (C5Me5)*2Sm(THF)2 at -10 and 0°C polymerization temperatures for synthesizing dis-UHMWPE. In Macromol. Rapid. Commun. 2015, 36, 327 - 331, it was found that [l-(8-quinolyl)indenyl]chromium dichloride is capable of producing dis-UHMWPE at 10°C under trimethylaluminum (TMA) free condition.

Fujita et al, Mitsui chemical, U.S. Pat. No. 6875718, EP 0874005 and WO 2001/005231 disclose a highly active post-metallocene bis(phenoxyimine)titanium dichloride catalyst system (FI) capable of producing UHMWPE under milder conditions. In subsequent studies by Rastogi et al., Macromolecules, 2011, 44, 5558, Polym. Sci. Al, 2013, 51, 1630, Macromolecules, 2011, 44,

4922, EP 10308255 and U.S. 2010/0087929, the studies showed that this catalyst system may provide dis-UHMWPE using low catalyst concentration (solution-phase polymerization) at temperature above 10°C and 1 bar ethylene pressure.

Further development on post-metallocene catalyst systems for producing dis-UHMWPE were mainly focused on FI analogues, adjusting R-groups on imine or phenoxy moieties.

Some of the exemplified conventional means representing these post-metallocene catalyst systems are as followed: U.S. 2018/0171039 discloses an olefin polymerization catalyst that includes imine sulfonate or imine carboxylate ligands which can produce dis-UHMWPE; U.S. Pat. No. 9611345 discloses a substituted salicylaldehyde titanium dichloride catalyst system with improved reaction kinetic control; US. Pat. No. 9617362 discloses a Group 4 transition metal-based catalysts having iminonaphthol ligands. These disclosures describe that the more rigid aromatic naphthalene skeleton provides a precise control over the microstructure of polymer, in contrast to the phenoxyimine ligand of the FI catalyst system. However, even though homogeneous polymerization produces a higher degree of disentanglement, it is necessary to improve the morphology of the produced nascent dis-UHMWPE by supporting the catalyst on suitable material(s). This is to avoid fouling caused by crystallised dis- UHMWPE grown on the reactor wall from the solution-phase polymerization. Therefore, efforts on producing dis-UHMWPE with immobilized (post)-metallocene catalyst systems have been disclosed and discussed as follows: CN 106084101 discloses a procedure to synthesize dis- UHMWPE using modified porous support (Si02, Ti02 etc.) with Cp2ZrC12 and FI catalysts; WO 2018/004385 discloses a salicylaldehyde titanium catalyst which is supported on silica, MCM-41 or MCM-48; Polymer, 2012, 53, 2897 - 2907 discloses a FI catalyst immobilized on nanoparticles of inorganic supports, examples including Ti02, Zr02, hydroxyapatite and -OH functionalised single- wall carbon nanotubes.

Notwithstanding the above, there is still a need to provide a solution that addresses one or more of the limitations mentioned above. The solution should at least provide for an ultra-high molecular weight polyethylene (UHMWPE) and a method of synthesizing the UHMWPE, wherein the UHMWPE can have a characteristic of disentangled UHMWPE (dis-UHMWPE). The solution should also provide a catalyst composition, wherein the catalyst composition can include a catalyst compound that can be applied in both mobilized and immobilized catalyst systems for synthesizing the UHMWPE and/or dis-UHMWPE.

SUMMARY OF THE INVENTION

The present disclosure provides an ultra-high molecular weight polyethylene (UHMWPE) that can be obtained in an ethylene polymerization process using a catalyst compound of the present disclosure, wherein the catalyst compound has a structure according to formula A defined herein. The UHMWPE of the present disclosure has a characteristic of disentangled UHMWPE (dis- UHMWPE). Said differently, the UHMWPE of the present disclosure can be a dis-UHMWPE, wherein the resultant polyethylene polymer chain or a substantial portion thereof has a high degree of disentanglements. Said differently, the dis-UHMWPE may be free/absent of any entanglements or substantially free/absent of any entanglements. The catalyst compound having the structure according to formula A can be applied in both mobilized and immobilized catalyst systems. In one aspect, the present disclosure provides a catalyst composition for preparation of ultra- high molecular weight polyethylene (UHMWPE) from a reaction of an ethylene in the presence of the catalyst composition, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl; Y is BR¹B²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which they (i.e. R¹ and R²) are attached, they (i.e. BR¹R²) form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl, and C_{1- 6}haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, or aryl.

In another aspect, the present disclosure provides a catalyst composition for preparation of disentangled ultra-high molecular weight polyethylene.

In another aspect, the present disclosure provides a process for preparation of an ultra-high molecular weight polyethylene (UHMWPE) including a reaction of an ethylene in the presence of the catalyst composition, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BP¹R ²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which they (i.e. R¹ and R²) are attached, they (i.e. BR¹ R²) form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl, and C_1-6haloalkyl;

Z is a polydentale ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, or aryl.

In another aspect, the present disclosure provides a process for preparation of a disentangled ultra-high molecular weight polyethylene (dis-UHMWPE) including a reaction of an ethylene in the presence of the catalyst composition, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

(A) wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BR¹R²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which they (i.e. R¹ and R²) are attached, they (i.e. BR¹R²) form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxyl, amino, nitro, C_1-6alkyl, and C_{1- 6}haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxyl, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, or aryl. In another aspect, the present disclosure further provides a catalyst composition that includes a catalyst compound having the structure according to formula A, a co-catalyst, and optionally a modifier.

The aforementioned catalyst composition can be used in mobilized or immobilized catalyst systems for polymerization of the ethylene to produce the ultra-high molecular weight polyethylene (UHMWPE) and/or disentangled UHMWPE (dis-UHMWPE).

The process further includes a solvent for polymerization, wherein the solvent can be selected from a saturated or unsaturated hydrocarbon, or combination thereof. The solvent for polymerization is preferably, for example, n-hexane.

The co-catalyst can be selected from aluminum based or boron based compounds, preferably methylaluminoxane or a modified methylaluminoxane as non-limiting examples.

Optionally, the modifier can be added as a co-catalyst modifier in polymerization of an ethylene, wherein the polymerization of the ethylene is based on an immobilized catalyst system. A support material for the immobilized catalyst system can be selected from silica, alumina, zeolite, layered double hydroxide, methylaluminoxane-activated silica, methylaluminoxane-activated layered double hydroxide, or solid methylaluminoxane.

The modifier can include or consist of a slerically hindered phenol. Preferably, the modifier is, for example, 2,6-di-tert-butyl-4-methylphenol (BHT).

The process of the present disclosure can be carried out in batch or continuous mode.

The process of the present disclosure provides an ultra-high molecular weight polyethylene having an intrinsic viscosity (IV) of at least 15 dl/g as measured according to ISO 1628-3. In various preferred aspects, the process of the present disclosure provides a disentangled ultra-high molecular weight polyethylene (dis-UHMWPE) having an intrinsic viscosity (IV) of at least 15 dl/g as measured according to ISO 1628-3.

In another aspect, the process of the present disclosure provides an ultra-high molecular weight polyethylene or a disentangled ultrahigh molecular weight polyethylene having a viscometer molecular weight (Mv) of at least 3xl0⁶ g/mol as calculated from intrinsic viscosity (IV) of the ultra-high molecular weight polyethylene or the disentangled ultrahigh molecular weight polyethylene. In a further aspect, the process of the present disclosure provides an ultra-high molecular weight polyethylene having a melting temperature (Tm) between 135-148 °C or a disentangled ultra-high molecular weight polyethylene having a melting temperature (Tm) equal to or above 140

°C,

Still in a further aspect, the process of the present disclosure provides (i) an ultra-high molecular weight polyethylene or (ii) a disentangled ultra-high molecular weight polyethylene, wherein (i) or (ii) has a difference between a first melting temperature (Tm1) and a second melting temperature (Tm2) as observed from differential scanning calorimetry (DSC) cycle, wherein the first melting temperature (Tm1) is obtained from a first heating to 160°C, and the second melting temperature (Tm2) is obtained from an isothermal heating at 160°C for 1440 mins, cooling to an isothermal temperature at 126°C for 180 mins, then cooling to 40-50°C, and a second heating (i.e. DSC heating) to 160°C. The second melting temperature (Tm2) can be less than the first melting temperature (Tm1). The difference between the first melting temperature (Tm1) and the second melting temperature (Tm2) can be less than 5°C. Preferably, the difference between the first melting temperature (Tm1) and the second melting temperature (Tm2) can be less than 4°C.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the present disclosure. In the following description, various embodiments of the present disclosure are described with reference to the following drawings, in which:

FIG. 1 depicts a differential scanning calorimetry (DSC) thermogram based on a sample demonstrated in a comparative example (CE1), As shown in FIG. 1, the thermal peaks denoting Tm1 (1st heating) and Tm2 (2nd heating) for the sample in CEl are not in the same temperature range (i.e, peaks do not coincide at a temperature range or are not proximal to each other).

FIG. 2 depicts a DSC thermogram based on a sample demonstrated in a present example (IE4) using the catalyst composition and process of the present disclosure. As shown in FIG. 2, the thermal peaks denoting Tm1 (1st heating) and Tm2 (2nd heating) for the sample in IE4 are within a similar temperature range (i.e. peaks coincide at the same temperature range or are proximal to each other). This indicates for the recurrence behavior that is observed for a disentangled UHMWPE. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

The various embodiments and advantages described for one aspect of the present disclosure can be analogously valid for other aspects and embodiments of the present disclosure described herein. For example, the present disclosure relates to a catalyst composition. Various embodiments and advantages described for the catalyst composition are analogously valid for other aspects and embodiments of the present disclosure, including a process for synthesizing the ultra-high molecular weight polyethylene and the disentangled ultra-high molecular weight polyethylene from the use of the catalyst composition. The various embodiments and advantages described for the catalyst composition are also analogously valid to the resultant polyethylene. Where the various embodiments and advantages have already been described in one aspect and its related embodiments and via the examples demonstrated herein, they shall not be iterated for brevity.

The present disclosure provides a catalyst composition for preparation of ultra-high molecular weight polyethylene (UHMWPE) from a reaction of an ethylene in the presence of the catalyst composition, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl; Y is BR¹R²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which they (i.e. R¹ and R²) are attached, they (i.e. BR^²) form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl, and C_{1- 6}haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, or aryl.

The present catalyst composition is operably usable in the synthesis of an ultra-high molecular weight polyethylene (UHMWPE) and/or synthesis of an ultra-high molecular weight polyethylene that has the characteristic of a disentangled ultra-high molecular weight polyethylene (dis-UHMWPE). Said differently, the present catalyst composition can be used to synthesize an ultra-high molecular weight polyethylene (UHMWPE), wherein the ultra-high molecular weight polyethylene includes or consists of the disentangled ultra-high molecular weight polyethylene. The ultra-high molecular weight polyethylene can be a disentangled ultra-high molecular weight polyethylene in various aspects and embodiments disclosed herein. The UHMWPE of the present disclosure can be a dis-UHMWPE, wherein the resultant polyethylene polymer chain or a substantial portion thereof has a high degree of disentanglements. Said differently, the dis- UHMWPE may be free/absent of any entanglements or substantially free/absent of any entanglements. The present catalyst composition advantageously addresses one or more of the limitations mentioned above. For example, the present catalyst composition aids in polymerization of an ethylene to form an ultra-high molecular weight polyethylene with high degree of disentanglement without compromising the polymerization yield (i.e. yield of the resultant polyethylene) compared to existing Ziegler-Natta catalyst and phenoxyimine catalyst. In various aspects and embodiments, the reaction of the ethylene may include or may be a polymerization of the ethylene.

The present disclosure also provides a process for preparation of an ultra-high molecular weight polyethylene (UHMWPE) including a reaction of an ethylene in the presence of the catalyst composition according to an aspect described above, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier.

wherein:

M is selected from a group coasisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BR¹R²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which they (i.e, R¹ and R²) are attached, they (i.e. BR¹R²) form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6 alkyl and C_1-6haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, or aryl.

The present disclosure further provides a process for the synthesis of disentangled ultra- high molecular weight polyethylene (dis-UHMWPE) including a reaction of an ethylene in the presence of the catalyst composition according to an aspect described above, wherein the catalyst composition includes a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium; X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BR¹R ’; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which they (i.e. R¹ and R²) are attached, they (i.e, BR¹R²) form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl, and C_1-6haloalkyl; Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, and aryl.

In the present disclosure, the expression “optionally substituted” means that a compound, or a chemical group of the compound can be unsubstituted or substituted with one or more functional groups or substituents.

In the present disclosure, the term “halo” is an abbreviation of the term halogen. In the present disclosure, the term “hydroxyl” denotes -OH group. In the present disclosure, the term “alkyl” as a group or part of a group refers to a linear or branched aliphatic hydrocarbon group, such as Cl-6alkyl, Cl-5alkyl, Cl-4alkyl, Cl-3alkyl, Cl- 2alkyl, etc. Non-limiting examples of suitable straight and branched alkyl substituents include methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec -butyl, t-butyl, and hexyl.

In the present disclosure, the term “haloalkyl” refers to an alkyl defined herein in which one or more of the hydrogen atoms are replaced with a halogen atom selected from the group consisting of chlorine, bromine and iodine. Non-limiting examples of haloalkyl include bromomethyl, die hloro methyl and tri-iodo methyl.

In the present disclosure, the term “aryl” denotes an optionally substituted monocyclic, or fused polycyclic, carbocycle (ring structure having ring atoms that are all carbon) having from 5-20 carbon atoms, 6-20 carbon atoms, etc., in the ring structure. The ring structure can be an aromatic ring structure, for example, when there are 6 carbon atoms. Non-limiting examples of aryl groups include phenyl and naphthyl. The term “heteroaryl” herein refers to an aryl having one or more heteroatoms as a ring atom in the ring structure. The ring structure can be an aromatic ring structure, for example, when there are 6 carbon atoms. In other words, one or more heteroatoms may replace one or more carbons of the ring structure. Non-limiting examples of heteroaryl include thiophene, benzothiophene, benzimidazole, benzoxazole, benzothiazole, pyrrole, imidazole, pyrazole, pyridine, and pyrazine. The term “heteroatom” herein refers to an oxygen, sulfur, or nitrogen atom.

In the present disclosure, the term “carbocyclic ring” refers to a ring structure formed of carbon atoms. The “heterocyclic ring” herein refers to a ring structure formed of carbon atoms and at least one heteratom.

In the present disclosure, the term “amino” refers to NR¹⁰R¹¹, wherein R¹⁰and R¹¹ are individually selected from but not limited to hydrogen, an optionally substituted alkyl, etc.

In the present disclosure, the term “nitro” denotes for -NO2.

In the present disclosure, the “B” in the expression “BR1R2” herein denotes for boron.

The present disclosure further provides a catalyst composition having a structure according to formula A described above, a co-catalyst, and optionally a modifier. The aforementioned catalyst composition can be used in a mobilized or immobilized catalyst system for polymerization of the ethylene to produce an ultra-high molecular weight polyethylene (UHMWPE). In various instances, the reaction of an ethylene may refer to polymerization of the ethylene to produce an ultra-high molecular weight polyethylene. In various instances, the ultra-high molecular weight polyethylene can include or can be a disentangled ultra- high molecular weight polyethylene.

The process further includes a solvent for polymerization of the ethylene, wherein the solvent can be selected from a saturated or unsaturated hydrocarbon, or combination thereof. A non- limiting example of the solvent may be a hexane (i.e. n-hexane).

The co-catalyst can be selected from an aluminum based or a boron based compound, preferably methylaluminoxane, or modified methylaluminoxane as non-limiting examples. The cocatalyst helps to activate the catalyst compound so that the reaction (e.g. polymerization) of an ethylene can take place. The use of methylaluminoxane or modified methylaluminoxane may depend on the solvent and operating system (e.g. mobilized or immobilized catalyst system).

Optionally, the modifier can be added as co-catalyst modifier in polymerization of the ethylene, wherein the polymerization of the ethylene is based on an immobilized catalyst system. In other words, the modifier selectively modifies the co-catalyst and not the catalyst compound. The modifier helps to decrease the dormant sites and avoid chain termination in an ethylene undergoing polymerization in the presence of the catalyst composition, which in turn renders an increase of catalytic activity and promotes the polymerization of the ethylene. The modifier can comprise or consist of a sterically hindered phenol. Preferably, the modifier is, for example, 2,6-di-tert-butyl-4- methylphenol (BHT).

The immobilized catalyst system may include a support material. The support material for immobilized catalyst system can be selected from silica, alumina, zeolite, layered double hydroxide, methylaluminoxane-activated silica, methylaluminoxane -activated layered double hydroxide, or solid methylaluminoxane.

The process of this disclosure can be carried out in batch or continuous mode.

The process of this disclosure provides an ultra-high molecular weight polyethylene having an intrinsic viscosity (IV) of at least 15 dl/g as measured according to ISO 1628-3. For example, the intrinsic viscosity may range from 15-50 dl/g. In various instances, the ultra-high molecular weight polyethylene may include or may be a disentangled ultra-high molecular weight polyethylene.

In certain aspects, the process of this disclosure also provides an ultra-high molecular weight polyethylene or a disentangled ultra-high molecular weight polyethylene having a viscometer molecular weight (Mv) of at least 3x106 g/mol as calculated from intrinsic viscosity (IV) of the ultra-high molecular weight polyethylene. For example, the viscometer molecular weight may range from 3x106 to 18x106 g/mol. In various instances, the ultra-high molecular weight polyethylene may include or may be the disentangled ultra-high molecular weight polyethylene.

In certain aspects, the process of the present disclosure also provides an ultra-high molecular weight polyethylene having a melting temperature (Tm) ranging from 130-150 °C, or 135-148 °C, etc. or a disentangled ultra- high molecular weight polyethylene having a melting temperature (Tm) equal to or above 140 °C, etc. In various instances, the ultra-high molecular weight polyethylene may include or may be the disentangled ultra-high molecular weight polyethylene.

Still in certain aspects, the process of this disclosure provides an ultra-high molecular weight polyethylene having a difference between a first melting temperature (Tm1) and a second melting temperature (Tm2) as observed from differential scanning calorimetry (DSC) cycle, wherein the first melting temperature (Tm1) is obtained from a first heating to 160°C, and the second melting temperature (Tm2) is obtained from an isothermal heating at 160°C for 1440 mins, cooling to an isothermal temperature at 126°C for 180 mins, then cooling to 40-50°C, and a second heating (i.e. DSC heating) to 160°C. The expression “DSC heating” herein refers to heating using differential scanning calorimetry. The first melting temperature (Tm1) refers to the melting temperature of the ethylene polymer during polymerization in its disentanglement state. Meanwhile, the second melting temperature refers to the melting temperature after the ethylene polymer reaches its equilibrium melting state. In various instances, the ultra-high molecular weight polyethylene in a disentanglement state from polymerization can have a Tm1 equal to or more than 140°C due to a perfectly folded chain crystal. For the case of Tm2, the disentanglement state may render a similar melting temperature compared to Tm1 due to a memory effect of crystal topology (e.g. the crystal topology or a part thereof from its state in Tm1 still exists). This memory effect may be understood to attribute to a recurrence behavior, wherein the polyethylene synthesized from the catalyst composition and process of the present disclosure is able to exhibit a similar melting temperature for Tm1 and Tm2 as observed via differential scanning calorimetry (DSC). For example, when heating the polyethylene at Tm1 via DSC, the polyethylene may have a disentangled state that demonstrates a melting temperature of 140 °C or more. When heating the polyethylene at Tm2 via DSC, the polyethylene may have an identical or substantially identical disentangled state that renders a melting temperature proximal to that of Tm1. Thus, the recurrence behaviour involves a polymer demonstrating such proximal melting temperatures at Tm1 and Tm2. In various aspects, the ultra-high molecular weight polyethylene has a second melting temperature (Tm2) less than the first melting temperature (Tm1). Further in certain aspects, the differences between the first melting temperature (Tm1) and the second melting temperature (Tm2) can be less than 5°C. Preferably, the difference between the first melting temperature (Tm1) and the second melting temperature (Tm2) can be less than 4°C. The difference in the melting temperature between Tm1 and Tm2 may indicate the disentanglement state, which means that the polymer at both Tm1 and Tm2 may have the same crystal topology, or an identical part thereof, that renders a recurrence behavior.

The word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the present disclosure.

In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance.

As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements. EXAMPLES

Hereinafter, the present disclosure is now described in details in connection with the various embodiments and various aspects thereof, which can be fully understood by way of non-limiting examples set forth below. Example 1: Characterization/Measurement Methods

Intrinsic viscosity ( IV)

Intrinsic Viscosity : The test method covers the determination of the dilute solution viscosity of

polyethylene at 135 °C or an ultra-high molecular weight polyethylene (UHMWPE) at 150°C. The polymeric solution was prepared by dissolving polymer in Decalin with 0.05-0.2% wt/vol stabilizer (Irganox 1010 or equivalent). The details are given for the determination of IV according to ISO 1628-3. Molecular weight by viscometer (Mv) can be calculated based on IV as shown in equation below:

Mv = 5.37 x 10⁴(IV)^1.49

Where Mv is viscometer molecular weight (g/mol), IV is intrinsic viscosity (dl/g). - Modulus built up (Rheology)

To indicate the disentangled chains, the sample preparation is performed under high pressure hot- press at 125°C. The initial value of G' and modulus built up are measured by oscillatory rheometer under 160°C where above melting temperature. The storage modulus at constant frequency 10 rad/s (Entangled response frequency) is recorded by time. The modulus increases with time due to entanglement formation. The initial value G' and the time spent to reach the plateau modulus value are observed.

The rheological measurements were performed using the protocol described in [Liu, K.; Ronca, S.; Andablo-Reyes, E.; Forte, G.; Rastogi, S., Unique rheological response of Ultrahigh Molecular Weight Polyethylene’s in the presence of reduced graphene oxide. Macromolecules 2015, 48 (1), 131-139], Such rheological measurements are already understood by a skilled person and therefore not described in detail for brevity.

Entanglement density of sample has been done by measuring and identifying the normalized initial value of the storage modulus obtained on melting of the sample. Modulus recorded at 10 rad/s, 160 °C in the linear viscoelastic region. The change in the modulus is followed as a function of time and the plateau region is taken as a state observed or reached for a fully entangled material, as described e.g. by D. Lippits et al. in Macromolecules 2006, 39, 8882-8885 or by A. Pandey et. Al. in Macromolecules , 2011, 44, 4952-4960. As any skilled person can readily understand this characterization method, this characterization method is not described further in detail for brevity. - Differential Scanning Calorimetry (DSC)

The existence of disentangled structure in UHMWPE can be verified by DSC. The DSC can detect the crystalline structures due to entanglements of the polymer. Annealing of the nascent disentangled polymer powder at a certain temperature can track the disentanglement behavior of material. By adapting the method written in the literature review by Liu and co-workers, Macromolecules 2016, 49, 19, 7497-7509, DSC was used to demonstrate the disentanglement of material based on specific condition. The recurrence behavior is a characteristic that has to be considered for disentanglement. The specific conditions to verify recurrence behavior of material are listed below: a. The material was heating from 40 or 50 °C to 160 °C with rating of 10°C/min b . The material was isothermal at 160 °C for 1440 mins c. The material was cooling to temperature at 126 °C at a rate of 10°C/min and was isothermally maintained at this temperature for 180 mins d. The material was cooling to 40 °C or 50 °C at a rate of 10°C/min e. The material was heating to 160 °C again. The recurrence behavior was observed by comparing the melting temperature peak of the first heating in (a) and the second heating in (b) within the same range (140 °C-144 °C). This indicates that our material is disentanglement material. Accordingly, the term “disentanglement” and grammatical variants thereof, such as “disentangled”, herein means that the resultant polyethylene is essentially (e.g. substantially) free of or has a lower degree of knots and kinks in the polymeric chain, wherein the kinks is formed from entanglement (e.g. intertwining or interlocked) of two or more polymeric chains of a polyethylene of the present disclosure. Said differently, a part of the resultant polyethylene is essentially free of or has a lower degree of entanglement with another part thereof. Example 2: Catalyst Preparation

The present catalyst composition may include a borylimido catalyst. The borylimido catalyst may consist of a Ti=NB moiety and a neutral fac-N₃ tridentate ligand of the present disclosure for use in producing the dis-UHMWPE disclosed in the examples below. Ti{NB(NAr'CH)₂}Cl₂{HC(Me₂pz)₃} denoted as [A] for brevity. Ti denotes for titanium, N and B denote for nitrogen and boron, respectively. C, H and Me denote for carbon, hydrogen and methyl, respectively. Ar denotes aryl and pz denotes a pyrazolyl (5-membered ring with 2 nitrogen as depicted above for Z).

To a solution of Ti{NB(NAr'CH)₂}Cl₂(py)₃ (1.00 g, 1.295 mmol) in toluene (10 mL) at ambient temperature (e.g. 25-30 °C) was added BF₃-OEt₂ (495 mT, 3.885 mmol), which immediately resulted in a dark green solution. After stining the solution for 10 mins at ambient temperature, the solution was cannula transferred into another HC(Me₂pz)₃ (0.388 g, 1.295 mmol) charged Schlenk tube and stirred at ambient temperature for 1 hr, after which it became a yellow slurry. The volatiles were removed under reduced pressure, and the yellow solid washed with toluene (4 x 5 mL), then dried in vacuo, leaving [A] as a yellow powder. Yield: 0.900 g (85%). The ¹H NMR spectrum indicated one equivalent of by-product BF₂-py was remained.

Example 3: Polymerization of UHMWPE

Polymerization was carried out in a 2-litre reactor and the general procedure is described as follows:

All of the catalyst, co-catalyst and optional modifier are prepared and stored under inert atmosphere (e.g. nitrogen or argon) beforehand. The hexane diluent and triisobutylaluminum are introduced into the reactor as a scavenger. The reaction temperature is set and maintained at the desired conditions as described in Table 1. Ethylene monomer is introduced into the reactor and then the reaction started by feeding the catalyst and co-catalyst into the reactor. The polymerization conditions are summarised in Table 1 and polymer properties are summarised in Table 2. Table 1. Polymerization conditions and intrinsic viscosity (IV) of produced UHMWPE

IE : Present example

Catalyst system for Present Examples 1-3 (IE1, IE2 and IE3) were prepared based on borylimido ligand system [A], The catalyst was in solution form. MAO (methylaluminoxane) solution was used as co-catalyst. In IE3, BHT was used as a modifier for removing trace amount of TMA (trimethylaluminum) in MAO solution. Present Example 4 (IE4) was synthesised by the borylimido ligand based system [A] similar to the catalyst system in samples IE1 to IE3 but the catalyst was prepared in a solid supported form. Supported catalyst A* was prepared by mixing complex [A] (36 mg) and polyaluminoxane (1 g) in a toluene-charged round-bottomed flask for 1 h. Supported catalyst system A* was obtained as a yellow solid which was then dried in vacuo.

Table 2. Polymer properties of produced UHMWPE

CE: Comparative example n.m.: not measurable

Comparative Example, CE1, is based on a commercially available ultra-high molecular weight polyethylene.

As shown in Table 2, the produced polyethylene polymers from catalyst system involving [A] and A* of the present disclosure (IE1, IE2, and IE3) has an intrinsic viscosity (IV) of at least 29 dl/g while the intrinsic viscosity (IV) could not be measure in IE4. These intrinsic viscosity (IV) values translate to calculated viscometer molecular weight (Mv) of more than 8xl0⁶ g/mol. All samples of the present examples demonstrate the first melting temperature (Tm1, i.e, 1^st Tm in table 2) above 141 °C. The disentanglement UHMWPE behavior, specifically, GVGp and recurrence behavior are discussed further in details below. Example 4: Recurrence Behavior of Present Disentangled UHMWPE

Based on a report by Liu and co-workers, Macromolecules, 2016, 49, 19, 7497-7509, DSC was used to evaluate the disentanglement UHMWPE. The DSC was adapted by using the specific condition set out in one or more of the examples above. The melting temperature of the polymer was verified at 2 points (1st melting temperature (Tm1) and 2^nd melting temperature (Tm2)). The first melting temperature refers to the melting temperature of a fully crystallized polymer having a disentangled state during or from the polymerization (e.g. dis-UHMWPE) with Tm more than 140 °C. To confirm whether the UHMWPE demonstrates a disentanglement state or characteristic, the recurrence phenomena can be observed from the 2^nd melting temperature which can range from, for example, 140-145 °C, If the polymer is an entangled UHMWPE, the recurrence behavior cannot be observed as demonstrated through CE1. FIG. 1 and FIG. 2 depict the DSC thermograms of the samples from CEl and IE4, respectively. As shown in FIG. 1 for CE1, the Tm1 and Tm2 peaks are not in the similar range (not proximal to each other). However, in FIG. 2 for IE4, the Tm1 and Tm2 is in the similar range (proximal to each other), which indicates for the recurrence behavior characteristic of a disentangled UHMWPE.

Comparing the samples from (i) IE1, IE2, IE3, and IE4 to (ii) CEl, the 1st melting temperature of all samples from present examples are more than 140 °C and the 2^nd melting temperature are in the range of 140-145 °C. This apparently demonstrates that all samples of the present examples exhibited the recurrence behavior characteristic of a disentangled UHMWPE.

The difference in melting temperature herein refers to the difference between Tm1 and Tm2 as observed from DSC. Based on the recurrence behavior, the difference in melting temperature may be low (e.g. less than 4 °C). All samples of the present examples demonstrate a difference in Tm of less than 4 °C as compared to the sample from comparative example CEl which has the difference in melting temperature of about 21 °C.

Example 5: G’ Build-up of the Present Disentangled UHMWPE

The entanglement density was investigated via dynamic time sweep. The starting G’ is recorded as G’o while the ending G’ is recorded as G’p. The ratio of G’o/G’p characterizes the degree of entanglement. A lower value indicates higher degree of disentanglement.

The G’o/G’p of samples from the present examples IE1, IE2, IE3, and IE4 are lower than 90% of G’p compare to the sample from comparative example CEl wherein the initial G’o/G’p is close to 100%. This demonstrates for the existence of disentanglements in samples of the present examples using the catalyst composition and process of the present disclosure.

Example 6: Descriptive Example of Present Catalyst Composition

The catalyst composition of the present disclosure is advantageous as it can be used in producing disentangled ultra-high molecular weight polyethylene (dis-UHMWPE) from polymerization of ethylene. The catalyst composition can include (i) a borylimido catalyst, a co-catalyst, and optionally a modifier. The borylimido catalyst can be T i { NB(N Ar'CH)₂ }Cl₂ { HC(Me₂pz) ₃ } . The co- catalyst can be methylaluminoxane. The modifier can be butylated hydroxytoluene.

The disentangled ultra-high molecular weight polyethylene of the present disclosure, produced using the present catalyst composition, can have a characteristic recurrence behavior observed through DSC, i.e. having a second melting temperature (Tm2) less than a first melting temperature (Tm1). This characteristic is observed for the dis-UHMWPE of the present disclosure, wherein the difference between Tm2 and Tm1 is herein described as a difference in melting temperature. The difference in melting temperature can be less than 5°C. Preferably, the difference in melting temperature is less than 4°C.

The catalyst composition and processes disclosed herein are also applicable for synthesizing ultra- high molecular weight polyolefin. The ultra-high molecular weight polyolefin can be an ultra-high molecular weight polyethylene. The ultra-high molecular weight polyolefin can be essentially free of or has a lower degree of entanglement, i.e. disentangled ultra-high molecular weight polyolefin. The ultra-high molecular weight polyolefin or polyethylene of the present disclosure can have a viscometer molecular weight (Mv) of at least 3x10⁶ g/mol as calculated from intrinsic viscosity (IV). The ultra-high molecular weight polyolefin/polyethylene (UHMWPE) of the present disclosure can have an intrinsic viscosity (IV) of at least 15 dl/g according to ISO 1628-3.

While the present disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims. The scope of the present disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced

Claims

1 A catalyst composition for preparation of an ultra-high molecular weight polyethylene (UHMWPE) from a reaction of an ethylene in the presence of the catalyst composition, wherein the catalyst composition comprises a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BR¹R²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which R¹ and R² are attached, BR¹R² form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl and C_{1- 6}haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, C_1-6haloalkyl, or aryl

2. The catalyst composition according to claim 1, wherein the ultra-high molecular weight polyethylene comprises a disentangled ultra-high molecular weight polyethylene.

3. The catalyst composition according to claim 1 or 2, wherein the catalyst composition is operable in a mobilized catalyst system or an immobilized catalyst system for polymerization of the ethylene to produce the ultra-high molecular weight polyethylene

(UHMWPE).

4. The catalyst composition according to any one of claims 1-3, wherein the co-catalyst is selected from an aluminum based or a boron based compound.

5. The catalyst composition according to any one of claims 1-4, wherein the co-catalyst is methylaluminoxane or modified methylaluminoxane.

6. The catalyst composition according to any one of claims 1-5, wherein the modifier comprises a sterically hindered phenol.

7. The catalyst composition according to any one of claims 1-6, wherein the modifier is 2,6-di- tert-butyl-4-methylphenol (BHT) .

8. A process for preparation of an ultra-high molecular weight polyethylene (UHMWPE) comprising a reaction of an ethylene in the presence of the catalyst composition according to any one of claims 1-7, wherein the catalyst composition comprises a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier:

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BR¹R²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which R¹ and R² are attached, BR¹R² form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl, and C_{1- 6}haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

- w herein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_{1 - 6} alkyl, C_1-6haloalkyl, or aryl.

9. A process for synthesis of a disentangled ultra-high molecular weight polyethylene (dis-

UHMWPE) comprising a reaction of an ethylene in the presence of the catalyst composition according to any one of claims 1-7, wherein the catalyst composition comprises a catalyst compound having a structure according to formula A shown below, a co-catalyst, and optionally a modifier.

wherein:

M is selected from a group consisting of titanium, zirconium, and hafnium;

X¹ and X² are independently selected from chlorine, bromine, iodine, or C_1-6alkyl;

Y is BR¹R²; wherein R¹ and R² are linked, such that when taken in combination with the boron atom to which R¹ and R² are attached, BR¹R² form a group:

wherein ring A is a carbocyclic or heterocyclic ring, optionally substituted with one or more substituents selected independently from a group consisting of aryl and heteroaryl, wherein said aryl and heteroaryl are optionally substituted with one or more substituents selected independently from a group consisting of halo, hydroxy, amino, nitro, C_1-6alkyl, and C_{1- 6}haloalkyl;

Z is a polydentate ligand coordinated to M by at least 2 donor atoms selected from one of the following ligands:

wherein R³ is C_1-20alkyl optionally substituted with one or more substituents selected from halo, hydroxy, amino, nitro, C_1-6alkyl, Ci d aloalkyl, or aryl; wherein the ultra-high molecular weight polyethylene has a difference between a first melting temperature (Tm1) and a second melting temperature (Tm2) which is less than 5°C as observed from differential scanning calorimetry (DSC) heating cycles, wherein the first melting temperature (Tm1) is obtained from a first heating to 160°C, and the second melting temperature (Tm2) is obtained from an isothermal heating at 160°C for 1440 mins, cooling to an isothermal temperature at 126°C for 180 mins, then cooling to 40-50°C, and a second heating to 160°C

10. The process according to claim 8 or 9, further comprising a solvent for polymerization of the ethylene, wherein the solvent is selected from a saturated or unsaturated hydrocarbon, or combination thereof.

11. The process according to any one of claims 8-10, wherein the modifier is added as a cocatalyst modifier in polymerization of the ethylene, wherein the polymerization of the ethylene is based on an immobilized catalyst system.

12. The process according to any one of claims 8-11, wherein the immobilized catalyst system comprises a support material.

13. The process according to claim 12, wherein the support material is selected from silica, alumina, zeolite, layered double hydroxide, methylaluminoxane-activated silica, methylaluminoxane -activated layered double hydroxide, or solid methylaluminoxane,

14. The process according to any one of claims 8-13, wherein the process is carried out in batch or continuous mode.

15. An ultra-high molecular weight polyethylene obtained from the process according to any one of claims 8-14, wherein the ultra-high molecular weight polyethylene has an intrinsic viscosity (IV) of at least 15 dl/g as measured according to ISO 1628-3.

16. An ultra-high molecular weight polyethylene obtained from the process according to any one of claims 8-14, wherein the ultra-high molecular weight polyethylene has a viscometer molecular weight (Mv) of at least 3x106 g/mol as calculated from intrinsic viscosity (IV) of the ultra-high molecular weight polyethylene.

17. An ultra-high molecular weight polyethylene obtained from the process according to any one of claims 8-14, wherein the ultra-high molecular weight polyethylene has a melting temperature (Tm) between 135-148 °C or the ultra-high molecular weight polyethylene is a disentangled ultra-high molecular weight polyethylene having a melting temperature (Tm) equal to or above 140 °C.

18. The ultra-high molecular weight polyethylene according to claim 17, wherein the ultra-high molecular weight polyethylene or the disentangled ultra-high molecular weight polyethylene has a second melting temperature (Tm2) less than a first melting temperature (Tm1).

19. The ultra-high molecular weight polyethylene according to claim 18, wherein the difference between the first melting temperature (Tm1) and the second melting temperature (Tm2) is less than 5°C.

20. The ultra-high molecular weight polyethylene according to claim 18 or 19, wherein the difference between the first melting temperature (Tm1) and the second melting temperature (Tm2) is less than 4°C.