JP6705467B2 - Ultra high molecular weight polyethylene compression molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a compression molded product formed by molding ultrahigh molecular weight polyethylene particles having a high melting point and high crystallinity, and more specifically, a bearing member having excellent strength, heat resistance and wear resistance. The present invention relates to an ultra-high molecular weight polyethylene compression molded product expected to be applied as an abrasive, a tape, a lining material, and the like.

The ultra high molecular weight ethylene polymer has an extremely high molecular weight equivalent to 1,000,000 or more in viscosity average molecular weight (Mv), and therefore has impact resistance, self-lubricating property, abrasion resistance, weather resistance and chemical resistance. It has excellent properties and dimensional stability, and has high physical properties comparable to engineering plastics. Therefore, various molding methods have been attempted to be applied to applications such as lining materials, food industry line parts, machine parts, artificial joints, sports equipment, and microporous membranes.

However, because of its high molecular weight, the ultra-high molecular weight ethylene polymer has extremely low fluidity at the time of melting and cannot be molded by kneading and extrusion like ordinary polyethylene having a molecular weight in the range of tens of thousands to about 500,000. Have difficulty. Therefore, ultra-high molecular weight polyethylene is a method of directly sintering a polymer powder obtained by polymerization, a method of compression molding, a molding method of a ram extruder for extrusion molding while intermittently compressing, a state of being dispersed in a solvent or the like. Attempts have been made to perform molding by a method such as a method of removing the solvent after extrusion molding.

Among them, the compression molded product of ultra-high molecular weight polyethylene is expected to improve various physical properties due to the high molecular weight which is a characteristic of ultra-high molecular weight polyethylene. However, the ultrahigh molecular weight polyethylene produced by the Ziegler catalyst currently on the market has a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (molecular weight distribution) of more than 4 and has a wide molecular weight distribution. The improvement in strength and heat resistance of the molded product cannot be said to be sufficiently improved as compared with polyethylene having a normal molecular weight, and it cannot be said that the expected performance is exhibited.

On the other hand, an ultrahigh molecular weight ethylene polymer having a narrow molecular weight distribution produced by using a metallocene catalyst or a postmetallocene catalyst has also been proposed (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 4868853 (for example, refer to the claims). JP, 2006-36988, A (for example, refer to a claim.)

However, when a compression molded product is produced using the ultrahigh molecular weight polyethylene proposed in Patent Documents 1 and 2, the performance as a molded product is improved, but in terms of strength, heat resistance and crystallinity, the performance is improved. Was not fully satisfied.

Further, in general ultrahigh molecular weight polyethylene, as the molecular weight becomes higher, the entanglement of the molecular chains becomes more difficult to unravel, and therefore the expected effect due to the increase in the molecular weight cannot be sufficiently expressed. Has a maximum at a molecular weight of about 3,000,000, and even if the molecular weight is increased more than that, the tensile rupture strength decreases.

Then, this invention is made|formed in view of the said subject, and an object of this invention is to provide the compression molding made from an ultrahigh molecular weight polyethylene excellent in strength, heat resistance, and abrasion resistance.

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, using a novel ultrahigh molecular weight polyethylene particle having a specific melting behavior, a compression molded article molded under specific conditions has a rigidity and a strength. The inventors have found that a compression molded article having excellent heat resistance and abrasion resistance can be obtained, and have completed the present invention.

That is, the present invention relates to an ultrahigh molecular weight polyethylene melt compression molded article characterized by satisfying at least the following characteristics (1) and (2).
(1) The intrinsic viscosity ([η]) is 15 dl/g or more and 60 dl/g or less,
(2) The content of titanium is 0.2 ppm or less or the measurement detection limit or less.

The present invention will be described in detail below.

The ultrahigh molecular weight polyethylene compression-molded product of the present invention has at least (1) an intrinsic viscosity ([η]) of 15 dl/g or more and 60 dl/g or less, and (2) a bulk density of 130 kg/m ³ or more and 700 kg/m ³ or less. (3) Melting point (Tm ₁ ) of 1st scan when the temperature was raised from 1° C. to 230° C. at a heating rate of 10° C./min with a differential scanning calorimeter (DSC), and then, After standing for 5 minutes, the temperature was lowered to −20° C. at a temperature lowering rate of 10° C./minute, and after standing for 5 minutes, the temperature was raised again from −20° C. to 230° C. at a temperature rising rate of 10° C./minute (2nd scan). The melting point (Tm ₂ ) of the 2nd scan at that time was measured, and the difference between the Tm ₁ and the Tm ₂ (ΔTm=Tm ₁ −Tm ₂ ) was 11° C. or higher and 30° C. or lower. It is obtained by compression-molding high-molecular-weight polyethylene particles at a molding temperature of 0°C to 300°C.

The ultra-high-molecular-weight polyethylene particles are particles of ultra-high-molecular-weight polyethylene, and the ultra-high-molecular-weight polyethylene belongs to the category called polyethylene. For example, ultra-high-molecular-weight ethylene homopolymer; Ultra high molecular weight ethylene-, such as molecular weight ethylene-propylene copolymer, ultra high molecular weight ethylene-1-butene copolymer, ultra high molecular weight ethylene-1-hexene copolymer, ultra high molecular weight ethylene-1-octene copolymer α-olefin copolymer; and the like.

The ultrahigh molecular weight polyethylene particles (1) have an intrinsic viscosity ([η]) of 15 dl/g or more and 60 dl/g or less, and particularly have excellent moldability and mechanical properties when formed into a compression molded product. Therefore, it is preferably 15 dl/g or more and 50 dl/g or less. Here, when the intrinsic viscosity is less than 15 dl/g, the obtained molded product has poor mechanical properties. On the other hand, when the intrinsic viscosity exceeds 60 dl/g, the fluidity at the time of molding is poor and the compression molding process becomes difficult. The intrinsic viscosity is measured at 135° C. in a solution having a polymer concentration of 0.0005 to 0.01% using ortho-dichlorobenzene, decahydranaphthalene, tetrahydronaphthalene, etc. as a solvent, using an Ubbelohde viscometer, for example. It can be measured by a method.

In addition, the ultra high molecular weight polyethylene particles (2) have a bulk density of 130 kg/m ³ or more and 700 kg/m ³ or less, and are excellent in workability during compression molding, and therefore 200 kg/m ³ or more and 600 kg/ It is preferably m ³ or less. Here, when the bulk density is less than 130 kg/m ³ , problems such as a decrease in fluidity of particles, a decrease in filling rate in a storage facility, a storage container, and a hopper, and a problem such as a significant decrease in operability occur. Easier to do. On the other hand, when the bulk density is more than 700 kg/m ³ , the workability during molding is poor and problems such as deterioration of physical properties of the obtained molded product are likely to occur. The bulk density can be measured, for example, by a method based on JIS K6760 (1995).

The ultra high molecular weight polyethylene particles are (3) melting point of 1st scan when the temperature is raised from 0°C to 230°C at a heating rate of 10°C/min (1st scan) by a differential scanning calorimeter (DSC). (Tm ₁ ), then, after being left for 5 minutes, the temperature is lowered to −20° C. at a temperature lowering rate of 10° C./min, and after being left for 5 minutes, again from −20° C. to 230° C. at a temperature raising rate of 10° C./min. The melting point (Tm ₂ ) of the 2nd scan when the temperature was raised (2nd scan) was measured, and the difference (ΔTm=Tm ₁ −Tm ₂ ) between Tm ₁ and Tm ₂ was 11° C. or higher and 30° C. or lower, In particular, it is preferable that ΔTm is 11° C. or more and 15° C. or less because it is a compression molded product made of ultra-high molecular weight polyethylene which is excellent in the balance of heat resistance, mechanical strength and moldability. Here, when ΔTm is less than 11° C., the obtained molded product is inferior in heat resistance and strength. On the other hand, when ΔTm exceeds 30° C., not only the moldability of the obtained ultrahigh molecular weight polyethylene particles when subjected to the molding process is deteriorated, but also the obtained molded product is deteriorated in physical properties.

In general polyethylene, an ethylene homopolymer belonging to high-density polyethylene is known as a polyethylene having a high melting point. However, the melting point of the high-density polyethylene is as low as about 130 to 135°C. On the other hand, the ultrahigh molecular weight polyethylene particles used in the compression molded article of the present invention have an extremely high melting point (Tm) as compared with conventionally known polyethylene, and for example, if it is an ethylene homopolymer. , Tm ₁ has an extremely high melting point exceeding 140° C. In the ultrahigh molecular weight polyethylene particles of the present invention, the molecular chains of polyethylene are oriented and so highly crystallized that Tm ₁ and Tm ₂ when measured with a differential scanning calorimeter (DSC). It is considered that the difference ΔTm will be an extremely large difference of 11° C. or more and 30° C. or less.

Further, the ultra-high molecular weight polyethylene particles can suppress discoloration (yellowing) and oxidative deterioration caused by titanium and have a good color tone, and also an ultra-high molecular weight polyethylene compression molded article excellent in weather resistance. Therefore, it is preferable that the titanium content is low, and (4) the titanium content is preferably 0.02 ppm or less or the detection limit or less. The content of titanium can be determined by a chemical titration method, a fluorescent X-ray analyzer, an ICP emission analyzer, or the like.

The ultra-high molecular weight polyethylene particles can provide a tougher ultra-high molecular weight polyethylene compression-molded article. Therefore, (5) the above-mentioned (3) after being heated and compressed at a press temperature of 190° C. and a press pressure of 20 MPa. The tensile breaking strength (TS (MPa)) of the sheet formed by cooling at a mold temperature 10° C. to 30° C. lower than the melting point (Tm ₂ ) of the 2nd scan measured according to () satisfies the following relational expression (a). And it is possible to provide an ultrahigh molecular weight polyethylene compression-molded product which is even tougher, and has excellent mechanical strength and wear resistance, and therefore, the following relational expression (c) is satisfied. preferable.
TS≧1.35×Tm ₂ −130 (a)
1.35×Tm ₂ −130≦TS≦2×Tm ₂ −175 (c)
Incidentally, the tensile breaking strength of general polyethylene is as low as about 45 MPa even for the highest high-density polyethylene. Further, the conventional ultra-high molecular weight polyethylene has not been able to fully utilize its high molecular weight, has a tensile breaking strength equivalent to that of general polyethylene and never exceeds 50 MPa. For this reason, a method has been adopted in which the strength is increased by orienting the material by rolling at a high draw ratio.

However, since the ultra-high molecular weight polyethylene particles used in the compression-molded article of the present invention have an appropriately entangled polymer chain, even if the intrinsic viscosity is in the ultra-high molecular weight polyethylene region of more than 15 dl/g, the molecular weight of Even if the value is increased, the tensile strength at break does not decrease, but rather it tends to be further improved. The ultrahigh molecular weight polyethylene particles used in the compression molded article of the present invention have excellent strength when formed into a molded article. The measured tensile breaking strength is preferably 40 MPa or more, more preferably 50 MPa or more.

There are no particular restrictions on the measurement conditions of the tensile breaking strength, and for example, a strip-shaped test piece having a thickness of 0.1 to 5 mm and a width of 1 to 50 mm, a dumbbell-shaped test piece, and the like, a pulling speed of 1 mm/min to 500 mm/min. A method of measuring the velocity can be exemplified.

Since the ultra-high molecular weight polyethylene particles have a relatively low content of low-molecular weight components, a suitable entanglement of polymer chains is possible, and an ultra-high-molecular-weight polyethylene compression molded product having particularly excellent heat resistance is obtained. 6) It has a breaking stress (MTS (MPa)) of 2 MPa or more when melt-stretched at a temperature 20° C. higher than the melting point (Tm ₂ ) of the 2nd scan measured in (3) above. It is preferable that it has a pressure of 3 MPa or more.

In addition, general polyethylene having a molecular weight of 500,000 or less has high fluidity at a temperature 20° C. higher than the melting point (Tm), and the molded body is deformed by its own weight, so that it cannot be melt-stretched. Further, conventional ultrahigh molecular weight polyethylene can be melt-stretched even at a temperature 20° C. higher than the melting point (Tm), but due to the influence of the low molecular weight component contained, strain hardening does not occur and the stress remains low. It was ruptured by a stress of about 1 MPa and was inferior in heat resistance.

The molding conditions of the heat-compression-molded sheet used for melt drawing are not particularly limited, and are, for example, a press temperature of 100 to 250° C. and a press pressure of 5 to 50 MPa, and among them, the heat compression described in (5) above is particularly preferable. A molding method can be exemplified. Further, as the melt drawing method, for example, a method of drawing a strip-shaped or dumbbell-shaped test piece having a thickness of 0.1 to 5 mm and a width of 1 to 50 mm at a drawing speed of 1 mm/min to 500 mm/min is exemplified. be able to. Further, as the rupture stress at the time of melt drawing, strain hardening occurs, and when the stress increases with drawing, the maximum value is taken as the breaking stress, strain hardening does not occur, and when the stress does not increase even after drawing, The stress in the flat region after yielding was taken as the breaking stress.

Since the ultra-high-molecular-weight polyethylene particles become a compression-molded article made of ultra-high-molecular-weight polyethylene which is particularly excellent in heat resistance, (7) stress at break (MTS (MPa)) at the time of melt drawing measured according to (6) above. And the intrinsic viscosity ([η]) satisfy the following relational expression (b), and in particular, they have excellent melt stretchability and moldability, and thus satisfy the following relational expression (d). It is preferably one.
MTS≧0.11×[η] (b)
0.11×[η]≦MTS≦0.32×[η] (d)
Since the ultrahigh molecular weight polyethylene particles are compression molded articles made of ultrahigh molecular weight polyethylene, which are particularly excellent in fluidity as powders, and are excellent in molding processability and physical properties, (8) the average particle diameter is 1 μm or more and 1000 μm or less. Some are preferred. The average particle diameter can be measured by a method such as a sieving test method using a standard sieve defined in JIS Z8801.

As a method for producing the ultrahigh molecular weight polyethylene particles used for the compression molded article of the ultrahigh molecular weight polyethylene of the present invention, any method may be used as long as the production of the ultrahigh molecular weight polyethylene particles is possible, for example, for producing polyethylene. Examples of the method include homopolymerization of ethylene using a catalyst and copolymerization of ethylene with another olefin. Examples of the α-olefin in this case include propylene, 1-butene, and 4-methyl-1-pentene. , 1-hexene, 1-octene and the like. Further, as the polymerization method, for example, a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, a slurry polymerization method, and the like can be mentioned. Among them, particularly, the production of ultra-high molecular weight polyethylene particles having a regulated particle shape is possible. It is possible to provide ultra high molecular weight polyethylene particles that have a high melting point, high crystallinity, and can provide compression molded products of ultra high molecular weight polyethylene that are excellent in mechanical strength, heat resistance, and wear resistance, efficiently and stably. The slurry polymerization method is preferred because it enables production. The solvent used in the slurry polymerization method may be any commonly used organic solvent, for example, benzene, toluene, xylene, pentane, hexane, heptane and the like, isobutane, liquefied gas such as propane, Olefins such as propylene, 1-butene, 1-octene and 1-hexene can also be used as a solvent.

As the polyethylene-producing catalyst used for producing the ultra-high molecular weight polyethylene particles, any catalyst can be used as long as it is possible to produce the ultra-high molecular weight polyethylene particles. For example, at least a transition metal compound Examples thereof include (A), an organically modified clay (B) modified with an aliphatic salt and an organoaluminum compound (C).

Examples of the transition metal compound (A) include a transition metal compound having a (substituted) cyclopentadienyl group and a (substituted) fluorenyl group, and a transition metal compound having a (substituted) cyclopentadienyl group and a (substituted) indenyl group. Examples thereof include a metal compound and a transition metal compound having a (substituted) indenyl group and a (substituted) fluorenyl group. Examples of the transition metal in this case include zirconium and hafnium. Since it becomes possible to efficiently produce molecular weight polyethylene particles, a zirconium compound having a (substituted) cyclopentadienyl group and an amino group-substituted fluorenyl group, and a (substituted) cyclopentadienyl group and an amino group-substituted fluorenyl group can be prepared. It is preferable that the compound has a hafnium compound.

And more specifically, for example, diphenylmethylene(1-indenyl)(9-fluorenyl)zirconium dichloride, diphenylmethylene(1-indenyl)(2,7-di-t-butyl-9-fluorenyl)zirconium dichloride, diphenyl. Methylene(4-phenyl-1-indenyl)(2,7-di-t-butyl-9-fluorenyl)zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(2-(dimethylamino)-9-fluorenyl)zirconium Dichloride, diphenylsilanediyl(cyclopentadienyl)(2-(diethylamino)-9-fluorenyl)zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(2-(dibenzylamino)-9-fluorenyl)zirconium dichloride, Diphenylsilanediyl(cyclopentadienyl)(2,7-bis(dimethylamino)-9-fluorenyl)zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(2,7-bis(diethylamino)-9-fluorenyl) Zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(2,7-bis(dibenzylamino)-9-fluorenyl)zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(4-(dimethylamino)-9- Fluorenyl)zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(4-(diethylamino)-9-fluorenyl)zirconium dichloride, diphenylsilanediyl(cyclopentadienyl)(4-(dibenzylamino)-9-fluorenyl) Zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2-(dimethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2-(diethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene (Cyclopentadienyl)(2-(dibenzylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-bis(dimethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene (Cyclopentadienyl)(2,7-bis(diethylamino)-9-fluorenyl)zirconium dichloride, diphenyl Methylene(cyclopentadienyl)(2,7-bis(dibenzylamino)-9-fluorenyl)zirconium dichloride Diphenylmethylene(cyclopentadienyl)(4-(dimethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene (Cyclopentadienyl)(4-(diethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(4-(dibenzylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl) Phenyl)(2,7-bis(dimethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-bis(diethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadiene) Dienyl)(2,7-bis(diisopropylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-bis(di-n-butyl-amino)-9-fluorenyl)zirconium Dichloride, diphenylmethylene(cyclopentadienyl)(2,7-bis(dibenzylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(3,6-bis(dimethylamino)-9- Fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(3,6-bis(diethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(3,6-bis(di-n-propyl) -Amino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,5-bis(dimethylamino)-9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,5- Zirconium compounds such as bis(diethylamino)-9-fluorenyl)zirconium dichloride and diphenylmethylene(cyclopentadienyl)(2,5-bis(diisopropylamino)-9-fluorenyl)zirconium dichloride; Zirconium compounds in which diethyl compounds, dihydro compounds, diphenyl compounds, and dibenzyl compounds are converted, and hafnium compounds in which zirconium of these compounds is converted to hafnium The thing etc. can be illustrated.

Examples of the organic modified clay (B) modified with the aliphatic salt include N,N-dimethyl-behenylamine hydrochloride, N-methyl-N-ethyl-behenylamine hydrochloride and N-methyl-Nn-. Propyl-behenylamine hydrochloride, N,N-dioleyl-methylamine hydrochloride, N,N-dimethyl-behenylamine hydrofluoride, N-methyl-N-ethyl-behenylamine hydrofluoride, N- Methyl-Nn-propyl-behenylamine hydrofluoride, N,N-dioleyl-methylamine hydrofluoride, N,N-dimethyl-behenylamine hydrobromide, N-methyl-N- Ethyl-behenylamine hydrobromide, N-methyl-Nn-propyl-behenylamine hydrobromide, N,N-dioleyl-methylamine hydrobromide, N,N-dimethyl-behenylamine Hydroiodide, N-methyl-N-ethyl-behenylamine hydroiodide, N-methyl-Nn-propyl-behenylamine hydroiodide, N,N-dioleyl-methylamine iodide Hydrogen salt, N,N-dimethyl-behenylamine sulfate, N-methyl-N-ethyl-behenylamine sulfate, N-methyl-N-n-propyl-behenylamine sulfate, N,N-dioleyl-methyl Aliphatic amine salts such as amine sulfate; P,P-dimethyl-behenylphosphine hydrochloride, P,P-diethyl-behenylphosphine hydrochloride, P,P-dipropyl-behenylphosphine hydrochloride, P,P-dimethyl-behenyl Phosphine hydrofluoride, P,P-diethyl-behenylphosphine hydrofluoride, P,P-dipropyl-behenylphosphine hydrofluoride, P,P-dimethyl-behenylphosphine hydrobromide, P ,P-diethyl-behenylphosphine hydrobromide, P,P-dipropyl-behenylphosphine hydrobromide, P,P-dimethyl-behenylphosphine hydroiodide, P,P-diethyl-behenylphosphine hydrobromide Hydrochloride, P,P-dipropyl-behenylphosphine hydroiodide, P,P-dimethyl-behenylphosphine sulfate, P,P-diethyl-behenylphosphine sulfate, P,P-dipropyl-behenylphosphine sulfate Examples thereof include an aliphatic phosphonium salt such as a salt; and clay modified with an aliphatic salt such as a salt.

The clay compound constituting the organically modified clay (B) may be any clay compound as long as it belongs to the category of clay compounds. Generally, a tetrahedron in which silica tetrahedra are two-dimensionally continuous. A sheet called a silicate layer is formed by stacking a number of layers called a silicate layer, which is formed by combining a sheet and an octahedron sheet in which alumina octahedron, magnesia octahedron, etc. are two-dimensionally continuous in a 1:1 or 2:1 combination. , Si in some silica tetrahedra is Al, Al in alumina octahedra is Mg, and Mg in magnesia octahedra is replaced by Li and the like, so that the positive charge inside the layer is insufficient and the negative charge is generated in the entire layer. It is known that cations such as Na ⁺ and Ca ²⁺ exist between layers to compensate for this negative charge. As the clay compound, there are natural products or synthetic products such as kaolinite, talc, smectite, vermiculite, mica, brittle mica, curdstone, etc., and it is possible to use them. Smectites are preferred because of their ease of use and organic modification, and hectorite or montmorillonite is more preferred among the smectites.

The organically modified clay (B) can be obtained by introducing the aliphatic salt between the clay compound layers to form an ionic complex. When preparing the organically modified clay (B), it is preferable to perform the treatment by selecting conditions such that the concentration of the clay compound is 0.1 to 30% by weight and the treatment temperature is 0 to 150°C. Further, the aliphatic salt may be prepared as a solid and dissolved in a solvent for use, or a solution of the aliphatic salt may be prepared by a chemical reaction in the solvent and used as it is. Regarding the reaction amount ratio of the clay compound and the aliphatic salt, it is preferable to use the aliphatic salt in an amount equal to or more than the amount of the exchangeable cation of the clay compound. Examples of the treatment solvent include aliphatic hydrocarbons such as pentane, hexane and heptane; aromatic hydrocarbons such as benzene and toluene; alcohols such as ethyl alcohol and methyl alcohol; ethers such as ethyl ether and n-butyl ether. Halogenated hydrocarbons such as methylene chloride and chloroform; acetone; 1,4-dioxane; tetrahydrofuran; water and the like can be used. And, it is preferable to use alcohols or water alone or as one component of the solvent.

The particle size of the organically modified clay (B) that constitutes the catalyst for producing polyethylene of the present invention is not limited, and among them, the efficiency during catalyst preparation and the efficiency during polyethylene production are excellent, so 1-100 μm. Preferably. There is no limitation on the method of adjusting the particle size at that time, and large particles may be crushed to an appropriate particle size, small particles may be granulated to an appropriate particle size, or crushing and granulation may be performed. May be combined. The particle size may be adjusted on the clay before the organic modification or on the organic modified clay after the modification.

As the organoaluminum compound (C), any compound can be used as long as it belongs to the category called an organoaluminum compound, and examples thereof include alkylaluminum such as trimethylaluminum, triethylaluminum and triisobutylaluminum. You can

The transition metal compound (A) (hereinafter sometimes referred to as the component (A)) that constitutes the catalyst for producing polyethylene, the organically modified clay (B) (hereinafter sometimes referred to as the component (B)), and The use ratio of the organoaluminum compound (C) (hereinafter sometimes referred to as the component (C)) is not particularly limited as long as it can be used as a catalyst for producing polyethylene, and among them, particularly Since it becomes a catalyst for producing polyethylene capable of producing ultrahigh molecular weight polyethylene particles with high production efficiency, the molar ratio of component (A) and component (C) per metal atom is (component A):(component C). =100:1 to 1:100,000, and particularly preferably 1:1 to 1:10000. Further, the weight ratio of the component (A) and the component (B) is preferably (A component):(B component)=10:1 to 1:10000, and particularly 3:1 to 1:1000. Preferably.

Regarding the method for preparing the polyethylene production catalyst, any method may be used as long as it is possible to prepare a polyethylene production catalyst containing the component (A), the component (B) and the component (C). For example, a method of mixing in a solvent inert with respect to each of the components (A), (B) and (C) or using a monomer for polymerization as a solvent can be mentioned. Further, there is no limitation on the order in which these components are reacted, and there is no limitation on the temperature or treatment time for this treatment. It is also possible to prepare a polyethylene production catalyst by using two or more kinds of each of the component (A), the component (B) and the component (C).

Polymerization conditions, such as polymerization temperature, polymerization time, polymerization pressure, and monomer concentration during the production of the ultrahigh molecular weight polyethylene particles used for the compression molded article made of the ultrahigh molecular weight polyethylene of the present invention can be arbitrarily selected, among them. The polymerization temperature is preferably 0 to 100° C., the polymerization time is 10 seconds to 20 hours, and the polymerization pressure is normal pressure to 100 MPa. It is also possible to control the molecular weight by using hydrogen or the like during the polymerization. The polymerization can be carried out by any of batch method, semi-continuous method and continuous method, and it is also possible to carry out the polymerization in two or more stages by changing the polymerization conditions. The polyethylene particles obtained after the completion of the polymerization can be obtained by separating and recovering from the polymerization solvent by a conventionally known method and drying.

The ultra-high molecular weight polyethylene compression-molded product of the present invention can be produced by compression-molding the ultra-high-molecular-weight polyethylene particles with a compression molding machine or the like. Examples thereof include a method of extrusion molding while intermittently compressing with an extruder or the like. The molding temperature for compression molding is 0°C or more and 300°C or less, more preferably 100°C or more and 250°C or less, and further preferably 150°C or more and 250°C or less. When the compression molding temperature is lower than 0°C, the fusion bond between the ultra-high molecular weight polyethylenes is remarkably reduced, and a molded product cannot be obtained. On the other hand, when the temperature exceeds 300° C., the ultra-high molecular weight polyethylene particles are apt to be oxidized and deteriorated, so that the molded product is discolored and the physical properties are deteriorated.

In addition, there is no limitation on the resin pressure during compression molding, and above all, it is possible to obtain an ultrahigh molecular weight polyethylene compression molded article that is particularly excellent in strength, heat resistance, and wear resistance, so 0.2 MPa or more, In particular, it is preferably 0.5 MPa or more and 500 MPa or less. There is no particular limitation on the compression molding time, and it can be selected depending on the molecular weight and density of the ultra high molecular weight polyethylene, the properties of the ultra high molecular weight polyethylene particles, the compression molding conditions, etc. Among them, it is made of ultra high molecular weight polyethylene excellent in strength and heat resistance. It is preferably 0.1 minutes or more and 48 hours or less because a compression molded product is obtained. The compression molding conditions such as the compression molding temperature and the compression molding pressure may be constant, or the temperature, the pressure and the like may be continuously changed in multiple stages.

The atmosphere for the compression molding may be the air, but in order to reduce the oxidative deterioration of the ultrahigh molecular weight polyethylene, the compression molding can be performed in an atmosphere of an inert gas such as nitrogen or argon. Further, compression molding may be performed under vacuum.

After compression molding, especially after heating and compression molding, the cooling conditions are arbitrary, such as a cooling plate close to room temperature, a method of rapidly cooling by contact with a liquid, a method of gradually cooling at a temperature close to the crystallization temperature, and a heating of a compressor. Examples thereof include a method of stopping and allowing to cool, a method of cooling while changing the temperature and pressure in multiple stages or continuously. The cooling may be performed in a pressurized state or a non-pressurized state.

The ultra-high molecular weight polyethylene compression-molded product of the present invention is a heat-resistant stabilizer, a weather-resistant stabilizer, an antistatic agent, an antifogging agent, an anti-blocking agent, a slip agent, a lubricant, a nucleating agent, unless it deviates from the object of the present invention. , Pigments and the like; inorganic fillers or reinforcing agents such as carbon black, talc, glass powder, glass fibers, metal powders; organic fillers or reinforcing agents; flame retardants; known additives such as neutron shielding agents, Density polyethylene (HDPE), linear low density polyethylene (L-LDPE), low density polyethylene (LDPE), polypropylene resin, poly-1-butene, poly-4-methyl-1-pentene, ethylene/vinyl acetate A resin such as a polymer, an ethylene/vinyl alcohol copolymer, polystyrene, or a maleic anhydride graft product thereof may be blended. As a method of adding such an additive, it is blended in ultrahigh molecular weight polyethylene particles. Examples thereof include a method, a method of blending with ultra-high molecular weight polyethylene particles at the time of molding, a method of dry blending or melt blending in advance, and the like.

The ultra-high-molecular-weight polyethylene compression-molded product of the present invention has excellent strength, heat resistance, and wear resistance, so that it can be used as a bearing member for industrial machines, sliding members, abrasives, various tapes, sports such as skis. It can be used as a member for sheets, membranes, plates, rods, pipes, porous membranes, etc., for lining articles and the like.

The ultra-high-molecular-weight polyethylene compression-molded product obtained by the present invention is excellent in strength, heat resistance, and wear resistance, so that it can be used as a bearing member for industrial machines, sliding members, abrasives, various tapes, sports such as skis. It is preferably used for lining products.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Unless otherwise specified, the reagents and the like used were commercially available products or those synthesized according to known methods.

A jet mill (manufactured by Seishin Enterprise Co., Ltd., (trade name) CO-JET SYSTEM α MARK III) was used for crushing the organically modified clay, and the particle size after crushing was measured by a Microtrac particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., ( Ethanol was measured as a dispersant using a trade name) MT3000).

Preparation of a catalyst for producing polyethylene, production of polyethylene and solvent purification were all carried out under an inert gas atmosphere. A hexane solution of triisobutylaluminum (20 wt%) manufactured by Tosoh Finechem Co., Ltd. was used.

Furthermore, various physical properties of the ultra high molecular weight polyethylene particles in the examples were measured by the methods described below.

-Measurement of intrinsic viscosity-
Using an Ubbelohde viscometer, ODCB (orthodichlorobenzene) was used as a solvent at 135° C., and the ultrahigh molecular weight polyethylene concentration was measured at 0.005 wt %.

-Measurement of bulk density-
It was measured by a method according to JIS K6760 (1995).

~Measurement of Tm ₁ and Tm ₂ ~
Using a differential scanning calorimeter (DSC) (SII Nanotechnology Co., Ltd. (trade name) DSC6220), the temperature was raised from 0° C. to 230° C. at a heating rate of 10° C./min (1st scan). The crystal melting peak (Tm ₁ ) of the 1st scan was measured. Then, after standing for 5 minutes, the temperature is lowered to −20° C. at a temperature lowering rate of 10° C./minute, and after standing for 5 minutes, the temperature is again raised from −20° C. to 230° C. at a temperature rising rate of 10° C./minute (2nd scan). ₂ ) The crystal melting peak (Tm ₂ ) of the 2nd scan was measured. The sample amount of ultra high molecular weight polyethylene at that time was 6 mg.

-Measurement of titanium content-
Ultrahigh molecular weight polyethylene was ashed, melted with alkali, and the prepared solution was used to determine the titanium content in the ultrahigh molecular weight polyethylene with an ICP emission spectrometer (manufactured by Perkin Elmer Co., Ltd. (trade name) Optima3000XL). It was measured.

~ Preparation of evaluation sheet for ultra high molecular weight polyethylene particles ~
The evaluation sheet for the ultrahigh molecular weight polyethylene particles used for molding the compression molded product was molded by the following method. That is, the ultra high molecular weight polyethylene particles were sandwiched between polyethylene terephthalate films, preheated at 190° C. for 5 minutes, and then heated and compressed under the conditions of 190° C. and a press pressure of 20 MPa. Then, the mold temperature was cooled to 110° C. for 10 minutes to prepare a press sheet having a thickness of 0.3 mm.

-Measurement of tensile breaking strength-
A dumbbell-shaped sample (width of the measurement part: 5 mm) cut out from the compression molded body and the evaluation sheet for ultra-high molecular weight polyethylene particles was allowed to stand at 23° C. for 48 hours, and then subjected to a tensile tester (A&And Co., Ltd.). Tensileon RTG-1210 manufactured by Dee) was used to perform a tensile test at a measurement temperature of 23° C., an initial length of the test piece of 20 mm, and a pulling speed of 20 mm/min to determine the tensile breaking strength.

-Measurement of breaking stress during melt drawing-
A sample (width of the measurement part: 10 mm) cut into a dumbbell shape by the method described in the measurement of the tensile breaking strength was allowed to stand at 23° C. for 48 hours, and then a tensile tester (manufactured by A&D Co., Ltd.). , (Trade name) Tensilon UMT2.5T), a tensile test was performed at 150° C. at an initial length of the test piece of 10 mm and a pulling speed of 20 mm/min to determine the breaking stress during melt drawing. When strain hardening occurs and the stress increases with stretching, the maximum value is taken as the breaking stress, and when strain hardening does not occur and the stress does not increase even after stretching, the stress in the flat area after yielding is called the breaking stress. did.

~Measurement of average particle size~
Obtained when 100 g of ultrahigh molecular weight polyethylene particles are classified using 9 types of sieves defined by JIS Z8801 (openings: 710 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 53 μm) The average particle size was determined by measuring the particle size at which the weight of the particles remaining on each sieve was 50% in the integral curve obtained by integrating the weight of the particles from the side with the larger openings.

-Evaluation of wear resistance-
A compression molded product made of ultra-high molecular weight polyethylene was cut by a planing machine to prepare a compression molded product of a round bar having a diameter of 5 mm and a height of 8 mm as a test sample, and a friction wear tester (Orientec Co., Ltd.) was used. , Model EFM-III-EN), the amount of wear was measured according to JIS K7218 under the conditions of a speed of 2.0 m/sec, a load of 25 MPa, a time of 360 minutes, and a mating material SS400. The smaller the amount of wear, the better the wear resistance.

Production example 1
(1) Preparation of organically modified clay Into a 1-liter flask, 300 ml of industrial alcohol (manufactured by Nippon Alcohol Sales Co., (trade name) Ekinen F-3) and 300 ml of distilled water were placed, and 15.0 g of concentrated hydrochloric acid and dioleylmethylamine. (Lion Co., Ltd., (brand name) Armin M20) 64.2 g (120 mmol) was added and heated to 45° C. to disperse 100 g of synthetic hectorite (Rockwood Additives, (brand name) Laponite RDS). After that, the temperature was raised to 60° C. and the mixture was stirred for 1 hour while maintaining the temperature. This slurry was filtered, washed twice with 600 ml of water at 60° C., and dried in a dryer at 85° C. for 12 hours to obtain 160 g of organically modified clay. The organically modified clay was pulverized by a jet mill to have a median diameter of 7 μm.

(2) Preparation of suspension of catalyst for polyethylene production After replacing a 300 ml flask equipped with a thermometer and a reflux tube with nitrogen, 25.0 g of the organically modified clay obtained in (1) and 108 ml of hexane were added, and then 0.795 g of diphenylmethylene(4-phenyl-1-indenyl)(2,7-di-t-butyl-9-fluorenyl)zirconium dichloride and 142 ml of 20% triisobutylaluminum were added and stirred at 60° C. for 3 hours. did. After cooling to 45° C., the supernatant was taken out and washed twice with 200 ml of hexane, and then 200 ml of hexane was added to obtain a suspension of a catalyst for producing polyethylene (solid content: 11.7 wt %).

(3) Production of Ultra High Molecular Weight Polyethylene Particles 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum, and 356 mg of suspension of the polyethylene production catalyst obtained in (2) in an autoclave of 2 liters. (Solid content: 41.7 mg) was added, and the mixture was heated to 40° C., and ethylene was continuously supplied so that the partial pressure became 1.6 MPa to carry out slurry polymerization of ethylene. After 180 minutes, the pressure was released, the slurry was filtered off, and then dried to obtain 37.1 g of ultrahigh molecular weight polyethylene particles (1) (activity: 890 g/g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene particles (1) are shown in Table 1.

Production example 2
(1) Preparation of Organically Modified Clay and (2) Preparation of Polyethylene Production Catalyst Suspension It was carried out in the same manner as in Production Example 1.

(3) Production of ultra-high molecular weight polyethylene particles In a 2 liter autoclave, 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and 326 mg of a suspension of the polyethylene production catalyst obtained in (2) ( Solid content (corresponding to 38.2 mg) was added, the mixture was heated to 30° C., 5 g of propylene was added, and ethylene was continuously supplied so that the partial pressure became 1.6 MPa to carry out slurry polymerization. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 35.1 g of ultrahigh molecular weight polyethylene particles (2) (activity: 920 g/g catalyst). The physical properties of the ultra high molecular weight polyethylene particles (2) thus obtained are shown in Table 1.

Production Example 3
(1) Preparation of organically modified clay It was carried out in the same manner as in Production Example 1.

(2) Preparation of suspension of catalyst for polyethylene production After replacing a 300 ml flask equipped with a thermometer and a reflux tube with nitrogen, 25.0 g of the organically modified clay obtained in (1) and 108 ml of hexane were added, and then 0.600 g of diphenylmethylene(cyclopentadienyl)(2-(dimethylamino)-9-fluorenyl)zirconium dichloride and 142 ml of 20% triisobutylaluminum were added and stirred at 60° C. for 3 hours. After cooling to 45° C., the supernatant was taken out, washed twice with 200 ml of hexane, and 200 ml of hexane was added to obtain a suspension of a catalyst for producing polyethylene (solid content: 11.5 wt %).

(3) Production of ultra-high molecular weight polyethylene particles In a 2 liter autoclave, 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and a suspension of the polyethylene production catalyst obtained in (2) of 89. After adding 9 mg (equivalent to a solid content of 10.3 mg) and raising the temperature to 50° C., 1.2 g of 1-butene was added, and ethylene was continuously supplied so that the partial pressure became 1.1 MPa to carry out slurry polymerization. After 180 minutes, the pressure was released, the slurry was filtered off, and then dried to obtain 70.2 g of ultrahigh molecular weight polyethylene particles (3) (activity: 6800 g/g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene particles (3) are shown in Table 1.

Production Example 4
(1) Preparation of organically modified clay Into a 1-liter flask, 300 ml of industrial alcohol (manufactured by Nippon Alcohol Co., Ltd. (trade name) Ekinen F-3) and 300 ml of distilled water were placed, and 15.0 g of concentrated hydrochloric acid and dimethylbehenylamine (lion After adding 42.4 g (120 mmol) of (trade name) Armin DM22D manufactured by Co., Ltd. and heating to 45° C. to disperse 100 g of synthetic hectorite (Rockwood Additives, trade name: Laponite RDS). The temperature was raised to 60° C. and the mixture was stirred for 1 hour while maintaining the temperature. This slurry was filtered, washed twice with 600 ml of water at 60° C., and dried in a dryer at 85° C. for 12 hours to obtain 125 g of organically modified clay. The organically modified clay was pulverized by a jet mill to have a median diameter of 7 μm.

(2) Preparation of suspension of catalyst for producing polyethylene After replacing a 300 ml flask equipped with a thermometer and a reflux tube with nitrogen, 25.0 g of the organically modified clay obtained in (1) and 108 ml of hexane were added, and then 0.715 g of diphenylmethylene(cyclopentadienyl)(2-(diethylamino)-9-fluorenyl)hafnium dichloride and 142 ml of 20% triisobutylaluminum were added and stirred at 60° C. for 3 hours. After cooling to 45° C., the supernatant was taken out, washed twice with 200 ml of hexane, and then 200 ml of hexane was added to obtain a suspension of a catalyst for producing polyethylene (solid content: 12.9 wt %).

(3) Production of ultra-high molecular weight polyethylene particles In a 2 liter autoclave, 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and 108. of the suspension of the polyethylene production catalyst obtained in (2). After adding 7 mg (corresponding to a solid content of 14.0 mg), the temperature was raised to 60° C., and ethylene was continuously supplied so that the partial pressure became 1.3 MPa to carry out slurry polymerization of ethylene. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 115 g of ultrahigh molecular weight polyethylene particles (4) (activity: 8200 g/g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene particles (4) are shown in Table 1.

Production Example 5
(1) Preparation of organically modified clay and (2) Preparation of suspension of catalyst for producing polyethylene The same procedure as in Production Example 4 was carried out.

(3) Production of ultra high molecular weight polyethylene particles In a 2 liter autoclave, 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and a suspension of the polyethylene production catalyst obtained in (2) of 87. After adding 7 mg (corresponding to 11.3 mg of solid content) and raising the temperature to 60° C., a hydrogen/ethylene mixed gas containing 40 ppm of hydrogen was supplied so that the partial pressure was 1.2 MPa, and then the partial pressure was 1.3 MPa. Ethylene was continuously fed so that ethylene was slurry-polymerized. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 86 g of ultrahigh molecular weight polyethylene particles (5) (activity: 7600 g/g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene particles (5) are shown in Table 1.

Production Example 6
(1) Preparation of solid catalyst component In a 1 liter glass flask equipped with a thermometer and a reflux tube, 50 g (2.1 mol) of magnesium metal powder and 210 g (0.62 mol) of titanium tetrabutoxide were placed, and iodine 2 was added. 320 g (4.3 mol) of n-butanol in which 0.5 g was dissolved was added at 90° C. over 2 hours, and the mixture was stirred at 140° C. for 2 hours under a nitrogen blanket while eliminating generated hydrogen gas to obtain a uniform solution. .. Then, 2100 ml of hexane was added.

90 g of this component (corresponding to 0.095 mol in magnesium) was placed in a separately prepared 500 ml glass flask and diluted with 59 ml of hexane. 106 ml of a hexane solution containing 0.29 mol of isobutylaluminum dichloride was added dropwise at 45°C over 2 hours, and further stirred at 70°C for 1 hour to obtain a solid catalyst component. The remaining unreacted materials and byproducts were removed by a gradient method using hexane, and the composition was analyzed. As a result, the titanium content was 8.6 wt %.

(2) Production of ultra high molecular weight polyethylene To a 2 liter autoclave, 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and 4.2 mg of the solid catalyst component obtained in (1) were added, and the mixture was heated to 85°C. After the temperature was raised, ethylene was continuously supplied so that the partial pressure became 0.6 MPa. After 90 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 180 g of ultrahigh molecular weight polyethylene (6) (activity: 54000 g/g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene (6) are shown in Table 1.

Example 1
The ultra-high molecular weight polyethylene particles (1) produced in Production Example 1 were filled in a 15 cm square die and preheated at 190° C., and then the press pressure was set to 20 MPa, and press molding was performed for 20 minutes. Then, it was cooled at 110° C. and a press pressure of 10 MPa for 10 minutes to prepare a compression molded body made of ultra-high molecular weight polyethylene, which is a flat sheet having a thickness of 10 mm. Table 2 shows the breaking stress, tensile strength, and abrasion resistance of the obtained sheet when melt-stretched.

Comparative Example 1
A compression molded article was produced in the same manner as in Example 1 except that the ultra high molecular weight polyethylene (6) produced in Production Example 6 was used in place of the ultra high molecular weight polyethylene particles (1). Table 2 shows the breaking stress, tensile strength, and abrasion resistance of the obtained sheet during melt drawing. The breaking stress, the tensile strength, and the abrasion resistance when melt-drawn were inferior.

Example 2
Ultrahigh molecular weight polyethylene particles (1) were used in place of the ultrahigh molecular weight polyethylene particles (1), preheated at 200° C., and then press-molded at a pressure of 15 MPa for 30 minutes. In the same manner as in Example 1, a compression molded body made of ultra-high molecular weight polyethylene, which is a flat sheet having a thickness of 15 mm, was manufactured. Table 2 shows the breaking stress, tensile strength, and abrasion resistance of the obtained sheet when melt-stretched.

Example 3
A flat sheet made of ultra high molecular weight polyethylene, which is a flat sheet, was prepared in the same manner as in Example 2 except that the ultra high molecular weight polyethylene particles (3) produced in Production Example 3 were used in place of the ultra high molecular weight polyethylene particles (2). A compression molded body was produced. Table 2 shows the breaking stress, tensile strength, and abrasion resistance of the obtained sheet when melt-stretched.

Comparative example 2
A compression molded product was produced by the same method as in Example 3 except that commercially available ultrahigh molecular weight polyethylene (trade name) HYZEX Million 240M (manufactured by Mitsui Chemicals) was used in place of the ultrahigh molecular weight polyethylene particles (3). did. Table 2 shows the breaking stress, the tensile strength and the elongation at the time of melt drawing of the obtained sheet. The breaking stress, the tensile strength, and the abrasion resistance when melt-drawn were inferior.

Example 4
The ultrahigh molecular weight polyethylene particles (5) were filled in a 15 cm square mold, compression-molded at 80° C. and a pressing pressure of 10 MPa for 10 minutes, and then press-molded at 210° C. and a pressing pressure of 30 MPa for 15 minutes. Then, it was cooled at 110° C. and a press pressure of 10 MPa for 20 minutes to prepare an ultrahigh molecular weight polyethylene compression-molded body which was a flat sheet having a thickness of 20 mm. Table 2 shows the breaking stress, tensile strength, and abrasion resistance of the obtained sheet when melt-stretched.

Example 5
Ultra-high molecular weight polyethylene particles (5) were filled in a 15 cm square mold, compression-molded at 100° C. and a press pressure of 10 MPa for 10 minutes, and then press-molded at 200° C. and a press pressure of 20 MPa for 30 minutes. Then, it was cooled at 80° C. and a press pressure of 10 MPa for 15 minutes to prepare an ultrahigh molecular weight polyethylene compression molded body which was a flat sheet having a thickness of 20 mm. Table 2 shows the breaking stress, tensile strength, and abrasion resistance of the obtained sheet when melt-stretched.

The ultra-high-molecular-weight polyethylene compression-molded product obtained by the present invention is excellent in strength, heat resistance, and wear resistance, so that it can be used as a bearing member for industrial machines, sliding members, abrasives, various tapes, sports such as skis. It can be used for various purposes such as lining of products.

Claims (3)

An ultrahigh molecular weight polyethylene melt compression molded article characterized by satisfying at least any of the following characteristics (1), (2) and (3) .
(1) The intrinsic viscosity ([η]) is 15 dl/g or more and 60 dl/g or less,
(2) The content of titanium is 0.2 ppm or less or the measurement detection limit or less.
(3) Tensile breaking strength (TS (MPa)) is 40 MPa or more. The ultrahigh molecular weight polyethylene melt compression molded article according to claim 1, which has a breaking stress (MTS (MPa)) of 2 MPa or more when melt-stretched at 150°C . The ultrahigh molecular weight polyethylene melt compression molded article according to claim 1 or 2, which is one selected from the group consisting of a sheet, a membrane, a plate, a rod, a pipe, and a tape .