JP6686530B2 - Ultrahigh molecular weight polyethylene composition and stretched microporous membrane comprising the same - Google Patents

Description

  The present invention relates to an ultrahigh molecular weight polyethylene composition capable of providing a stretched microporous membrane, and more specifically, it has a high melting point and high strength and can be formed into a thin film, and has a low molecular weight component and is clean. TECHNICAL FIELD The present invention relates to an ultrahigh molecular weight polyethylene composition capable of providing a stretched microporous membrane having excellent properties and a stretched microporous membrane comprising the same.

  The ultrahigh 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 when melted, and it cannot be molded by kneading and extrusion like ordinary polyethylene having a molecular weight in the range of tens of thousands to 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 by a ram extruder for extrusion molding while intermittently compressing, a state of being dispersed in a solvent or the like. After extrusion molding, a method such as a method of removing a solvent is performed.

  Of these, it is known that in a molding method of extruding in a state of being dispersed in a solvent and the like, and then removing the solvent, uniaxially and biaxially stretching before and after removing the solvent, a porous membrane can be produced. ing. It is expected that the ultrahigh molecular weight polyethylene microporous membrane will have excellent physical properties such as heat resistance, strength and impact resistance due to the high molecular weight of the ultrahigh 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 a wide molecular weight distribution, The strength and heat resistance of the molded product cannot be said to have been sufficiently improved, and it cannot be said to exhibit expected performance.

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

  Further, as a method of imparting stretchability to ultrahigh molecular weight polyethylene, a method of mixing polyethylene having a low molecular weight has been proposed (see, for example, Patent Document 3).

Japanese Patent No. 4868853 JP, 2006-36988, A JP, 2003-105121, A

  However, in the case of producing a stretched microporous membrane using the ultrahigh molecular weight polyethylenes proposed in Patent Documents 1 and 2, the moldability is poor, so that stretching is difficult and the performance is not sufficiently satisfactory. .

  Further, in the method proposed in Patent Document 3, since the polyethylene to be mixed for imparting stretchability contains a large amount of low molecular weight components, the resulting composition has a large amount of low molecular weight components eluted, and thus has a problem of cleanliness. In addition to having the above-mentioned properties, it is extremely likely that the mechanical strength, which is a characteristic of ultra-high molecular weight polyethylene, is adversely affected.

  Therefore, the present invention is intended to provide an ultrahigh molecular weight polyethylene composition excellent in mechanical strength, heat resistance, stretchability, and also excellent in cleanliness, and an excellent stretched microporous membrane comprising the same. is there.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a composition containing ultra-high molecular weight polyethylene and a specific molecular weight, melt tension, and polyethylene having strain-hardening properties is mechanical strength, heat resistance, and stretching. It was found that the composition can be an ultra-high molecular weight polyethylene composition that can provide a stretched microporous membrane having excellent properties and cleanliness, and completed the present invention.

That is, the present invention has a weight average molecular weight (Mw) of 600,000 or less and a melt tension at 210 ° C. of 100 mN with respect to 100 parts by weight of an ultrahigh molecular weight polyethylene having an intrinsic viscosity ([η]) of 10 dl / g or more and 80 dl / g or less. As described above, an ultrahigh molecular weight polyethylene composition having strain hardening property and containing 5 parts by weight or more and 5000 parts by weight or less of polyethylene having a density according to JIS K6760 of 935 kg / m ³ or more and 960 kg / m ³ or less And a stretched microporous membrane comprising the same.

  The present invention will be described in detail below.

The ultrahigh molecular weight polyethylene composition of the present invention has a [w] of 600,000 or less and a melt tension at 210 ° C. of 100 mN or more with respect to 100 parts by weight of the ultrahigh molecular weight polyethylene having an [η] of 10 dl / g or more and 80 dl / g or less. A composition containing polyethylene having strain hardening properties and a density according to JIS K6760 of 935 kg / m ³ or more and 960 kg / m ³ or less.

  The ultrahigh molecular weight polyethylene composition is an ultrahigh molecular weight polyethylene in which [η] of the ultrahigh molecular weight polyethylene composition is 0.9 times or less, particularly 0.8 times or less of [η] of the ultrahigh molecular weight polyethylene. It is preferably a composition.

  The ultra high molecular weight polyethylene constituting the ultra high molecular weight polyethylene composition of the present invention may be any one belonging to the category called ultra high molecular weight polyethylene having [η] of 10 dl / g or more and 80 dl / g or less, and Ziegler It may be any ultra high molecular weight polyethylene prepared with a Natta catalyst, a metallocene catalyst or the like. Moreover, what is called ultrahigh molecular weight polyethylene includes, for example, ultrahigh molecular weight ethylene homopolymer; ultrahigh molecular weight ethylene-propylene copolymer, ultrahigh molecular weight ethylene-1-butene copolymer, ultrahigh molecular weight ethylene- Examples thereof include ultra-high molecular weight ethylene-α-olefin copolymers such as 1-hexene copolymer and ultra-high molecular weight ethylene-1-octene copolymer. Here, when [η] is less than 10 dl / g, the resulting composition has poor mechanical properties. On the other hand, when [η] exceeds 80 dl / g, the resulting composition has poor fluidity at the time of molding, and particularly has poor moldability when forming a stretched microporous membrane. In addition, [η] in the present invention is measured by a method of measuring at 135 ° C. in a solution having a polymer concentration of 0.0005 to 0.01% using decahydronaphthalene as a solvent, for example, using an Ubbelohde viscometer. Is possible.

  The ultrahigh molecular weight polyethylene constituting the ultrahigh molecular weight polyethylene composition of the present invention may be any as long as it belongs to the above-mentioned category, and among them, mechanical strength and heat resistance when formed into a stretched microporous membrane. The metallocene-based ultra high molecular weight polyethylene is preferable, and the ultra high molecular weight polyethylene or particles thereof described below are particularly preferable because the metallocene-based ultra high molecular weight polyethylene has excellent properties, stretchability and cleanliness.

The ultrahigh molecular weight polyethylene has a particle shape because it has good fluidity of particles when it is formed into a stretched microporous membrane, and has excellent operability such as excellent filling rate in storage equipment, storage containers, and hoppers. It is preferable that (2) the bulk density at that time is 130 kg / m ³ or more and 700 kg / m ³ or less, and 200 kg because it is particularly excellent in processability when forming a stretched microporous membrane. / M ³ or more and 600 kg / m ³ or less is preferable. The bulk density can be measured, for example, by a method based on JIS K6760 (1995).

Since the ultrahigh molecular weight polyethylene has excellent heat resistance and strength when formed into a stretched microporous membrane, (3) a differential scanning calorimeter (hereinafter also referred to as DSC). Tm ₁ of 1st scan at the time of 1st scan, then left for 5 minutes, then cooled to −20 ° C. at a temperature decrease rate of 10 ° C./min, left for 5 minutes, and again Tm of 2nd scan at 2nd scan ₂ is measured, and ΔTm = Tm ₁ −Tm ₂ is preferably 9 ° C. or higher and 30 ° C. or lower, particularly preferably 11 ° C. or higher and 30 ° C. or lower, and further, heat resistance, mechanical strength and moldability It is preferable that ΔTm is 11 ° C. or higher and 15 ° C. or lower because the ultra high molecular weight polyethylene composition has excellent balance.

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 suitable for the ultrahigh molecular weight polyethylene composition of the present invention has an extremely high melting point (Tm) as compared with conventionally known polyethylene, and is, for example, an ethylene homopolymer. If any, it has a very high melting point above 140 ° C. as Tm ₁ . In the ultra-high molecular weight polyethylene, the molecular chain of polyethylene is highly oriented and crystallized, so that the difference ΔTm between Tm ₁ and Tm ₂ measured by DSC is 9 ° C. or higher and 30 ° C. or higher. I think that the difference is as follows:

  Further, the ultrahigh molecular weight polyethylene is capable of suppressing discoloration (yellowing) and oxidative deterioration caused by titanium, has a good color tone, and provides an ultrahigh molecular weight polyethylene composition having excellent weather resistance. Therefore, it is preferable that the content of titanium is small, and particularly, the content of titanium is 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.

Since the ultrahigh molecular weight polyethylene can provide a tougher stretched microporous membrane, (4) 2nd measured by the above (3) after being heated and compressed at a pressing temperature of 190 ° C. and a pressing pressure of 20 MPa. It is preferable that the tensile rupture strength (TS (MPa)) of the sheet formed by cooling at a mold temperature 10 ° C. to 30 ° C. lower than Tm _{2 of the} scan satisfies the following relational expression (a), and further more preferably: Since it is possible to provide a stretched microporous membrane that is tough, and has excellent mechanical strength and abrasion resistance, it is preferable that the following relational expression (c) is satisfied.
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 make full use of 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 by rolling and molding at a high draw ratio.

  However, since the polymer chains of the ultrahigh molecular weight polyethylene are appropriately entangled with each other, even in the ultrahigh molecular weight polyethylene region in which [η] exceeds 7 dl / g, preferably 15 dl / g, the molecular weight is further Even if it is increased, the tensile strength at break does not decrease, but rather tends to further improve. Since the ultrahigh molecular weight polyethylene becomes more excellent in strength when formed into a film, the tensile rupture strength measured by the above (4) is 40 MPa or more if it belongs to the area of high density polyethylene. It is preferable to have a value of 50 MPa or more, more preferably 50 MPa or more.

  The measuring conditions of the tensile breaking strength are not particularly limited, 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.

The ultra-high molecular weight polyethylene has a relatively low content of low-molecular weight components, allows appropriate entanglement of polymer chains, and is an ultra-high molecular weight polyethylene composition having particularly excellent heat resistance. It is preferable that the compression-molded sheet has a breaking stress (MTS (MPa)) of 1.5 MPa or more when melt-stretched at a temperature 20 ° C. higher than Tm _{2 of} 2nd scan measured in (3) above. Further, it is preferable that it further has 2 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), the molded body is deformed by its own weight, and melt stretching cannot be performed. Further, conventional ultra high 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 often found that the material was broken by a stress of about 1 MPa, resulting in poor heat resistance.

  The molding conditions for the heat-compression-molded sheet used for melt drawing are not particularly limited, and include, 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 (4) above. 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 pulling 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 becomes an ultra-high molecular weight polyethylene composition which is particularly excellent in heat resistance, (6) breaking stress (MTS (MPa)) and intrinsic viscosity (melt stress measured by the above (5) when melt-drawn. [Η]) preferably satisfies the following relational expression (b) and particularly satisfies the following relational expression (d) because it also has excellent melt stretchability and moldability. preferable.
MTS ≧ 0.079 × [η] (b)
0.079 × [η] ≦ MTS ≦ 0.23 × [η] (d)
Since the ultrahigh molecular weight polyethylene is an ultrahigh molecular weight polyethylene composition which is particularly excellent in fluidity as a powder, molding processability, and physical properties, (7) those having an average particle size of 1 μm or more and 1000 μm or less preferable. 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, any method may be used, and examples thereof include a method of homopolymerizing ethylene and a copolymerization of ethylene and another olefin using a catalyst for producing polyethylene. Examples of the α-olefin at that time include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like. 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, and among them, in particular, the production of ultra-high molecular weight polyethylene having a regulated particle shape is possible. In addition to having a high melting point and a high degree of crystallinity, it is possible to efficiently and stably produce ultrahigh molecular weight polyethylene capable of providing an ultrahigh molecular weight polyethylene composition having excellent mechanical strength, heat resistance, and abrasion resistance. The slurry polymerization method is preferable because it is possible. The solvent used in the slurry polymerization method may be any commonly used organic solvent, for example, benzene, toluene, xylene, pentane, hexane, heptane, etc., isobutane, liquefied gas such as propane, Olefins such as propylene, 1-butene, 1-octene and 1-hexene can also be used as a solvent.

  Further, as the polyethylene production catalyst used for producing the ultra high molecular weight polyethylene, any catalyst can be used as long as it is possible to produce the ultra high molecular weight polyethylene, and for example, at least the transition metal compound (A) Examples thereof include metallocene catalysts obtained from an organically modified clay (B) modified with an aliphatic salt and an organic aluminum 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 is possible to efficiently produce polyethylene having a molecular weight, 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 It is preferably 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) zyl 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 (cyclopentadi) Nyl) (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) Enyl) (2,7-bis (dimethylamino) -9-fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl) (2,7-bis (diethylamino) -9-fluorenyl) zyl Diphenylmethylene (cyclopentadienyl) (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 (cyclopepylene) Tadienyl) (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-bis (diethylamino) -9-fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl) (2,5-bis (diisopropylamino) -9-fluorenyl) zirconium Zirconium compounds such as dichlorides; zirconium compounds obtained by converting these dichloro compounds into dimethyl compounds, diethyl compounds, dihydro compounds, diphenyl compounds and dibenzyl compounds, and hafnium compounds obtained by converting zirconium of these compounds 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-N-n-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-beh Nylamine 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-Nn-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 fluoride Hydrochloride, P, P-dimethyl-behenylphosphine hydrobromide, P, P-diethyl-behenylphosphine hydrobromide, P, P-dipropyl-behenylphosphine hydrobromide, P, P- Dimethyl-behenylphosphine hydroiodide, P, P-diethyl-behenylphosphine hydroiodide, P, P-dipropyl-behenylphosphine hydroiodide, P, P-dimethyl-behenylphosphine sulfate, P , P-diethyl-behenylphosphine sulfate, P, P-dipropyl-behenylphosphine sulfate, and other aliphatic phosphonium salts; and clays modified with an aliphatic salt such as.

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 of some silica tetrahedra is replaced with Al, Al of alumina octahedra is replaced with Mg, and Mg of magnesia octahedra is replaced with 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. And, as the clay compound, there are natural products or synthetic products such as kaolinite, talc, smectite, vermiculite, mica, brittle mica and curdstone, and it is possible to use these, and among 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. 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 an equivalent amount or more of the aliphatic salt to 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.

  Further, the particle size of the organically modified clay (B) constituting the catalyst for producing polyethylene is not limited, and among them, the efficiency at the time of catalyst preparation and the efficiency at the time of polyethylene production are excellent, so that it is 1 to 100 μm. preferable. 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 granulating May be combined. The particle size may be adjusted on the clay before the organic modification or on the organically 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)), the organically modified clay (B) (hereinafter sometimes referred to as the component (B)) that constitutes the catalyst for producing polyethylene, 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, in particular, Since it becomes a catalyst for producing polyethylene capable of producing ultrahigh molecular weight polyethylene with high production efficiency, the molar ratio of component (A) and component (C) per metal atom is (A) component: (C) component = It is preferably in the range of 100: 1 to 1: 100,000, and particularly preferably in the range of 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. It is preferable.

  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). Examples thereof include 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. 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 at the time of producing the ultrahigh molecular weight polyethylene can be arbitrarily selected, and among them, the polymerization temperature is 0 to 100 ° C. and the polymerization time is 10 seconds to 20. It is preferable to perform the polymerization at a polymerization pressure of atmospheric pressure to 100 MPa for a time. 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 ultrahigh molecular weight polyethylene 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.

  Next, the polyethylene constituting the ultrahigh molecular weight polyethylene composition of the present invention has an Mw of 600,000 or less, preferably 50,000 or more and 600,000 or less, and more preferably 100,000 or more and 600,000 or less. Here, when the Mw is more than 600,000, the viscosity of the obtained composition becomes high and molding becomes difficult.

  The polyethylene has a melt tension at 190 ° C. of 100 mN or more, preferably 150 mN or more. Further, the polyethylene exhibits a strain hardening property in which the (stretching) viscosity rapidly increases with strain in uniaxial stretching and the like. By configuring the polyethylene having such characteristics, the ultra-high molecular weight polyethylene composition of the present invention has a small variation in the film thickness when it is used as a microporous film, and has a uniform film thickness even when it is thinned. Will have.

The polyethylene has a density according to JIS K6760 of 935 kg / m ³ or more and 960 kg / m ³ or less. Here, when the density is less than 935 kg / m ³ , the obtained composition has low strength. On the other hand, when it exceeds 960 kg / m ³ , the obtained composition becomes brittle and inferior in handleability.

  When the obtained composition is formed into a stretched microporous membrane, the polyethylene becomes a stretched microporous membrane having excellent strength and surface appearance. Therefore, the weight average molecular weight and the number average molecular weight (hereinafter sometimes referred to as Mn). The ratio (Mw / Mn) of () is preferably 3.0 to 8.0.

  The polyethylene is produced, for example, by homopolymerizing ethylene or by copolymerizing ethylene with the α-olefin exemplified above in the presence of a catalyst in which a transition metal complex called a metallocene catalyst and a specific cocatalyst are combined. be able to. The polyethylene is disclosed in JP2004-346304A, JP2005-248013A, JP2006-2057A, JP2006-321991A, JP2007-169341A, and JP2010-43152A. It may be obtained by a method such as the publication, JP 2011-89019 A, JP 2011-89020 A or the like.

  The ultrahigh molecular weight polyethylene composition of the present invention contains 5 parts by weight or more and 5000 parts by weight or less, preferably 20 parts by weight or more and 2000 parts by weight or less of the polyethylene with respect to 100 parts by weight of the ultrahigh molecular weight polyethylene. . Here, when the amount of polyethylene is less than 5 parts by weight, the composition obtained has poor moldability. On the other hand, when it exceeds 5,000 parts by weight, the resulting composition is inferior in mechanical strength and heat resistance.

  The method for preparing the ultrahigh molecular weight polyethylene composition of the present invention may be any method as long as it is possible to obtain a composition of ultrahigh molecular weight polyethylene by mixing the ultrahigh molecular weight polyethylene and polyethylene. Well, for example, extrusion kneading in a molten state, roll kneading, or after being dissolved in a solvent and brought into a solution state, extrusion kneading, roll kneading, or after stirring mixing using a stirring blade, etc., solvent distillation, solvent Examples thereof include a method of removing the solvent by extraction and the like. Further, in the case of dissolving in an organic solvent, it is also possible to use the obtained mixture as it is, as well as the mixing reaction with the organic solvent described later. Examples of the solvent at this time include linear or branched saturated or unsaturated aliphatic compounds such as hexane, heptane, decane, dodecane, tetradecane, octadecane, eicosane, liquid paraffin, and isoparaffin; cyclohexane, cyclodecane, tetrahydronaphthalene. , Saturated or unsaturated alicyclic compounds such as decahydronaphthalene; aromatic compounds such as benzene, toluene, xylene, naphthalene, anthracene; methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, Examples thereof include halogenated hydrocarbon compounds such as dichlorobenzene; and the like.

  The ultra-high molecular weight polyethylene composition of the present invention is a heat stabilizer, a weather stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a slip agent, a lubricant, a nucleating agent, a pigment, unless it deviates from the object of the present invention. Etc .; 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, and further polypropylene-based resins , Poly-1-butene, poly-4-methyl-1-pentene, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, polystyrene, and maleic anhydride graft products thereof are blended with resins. As a method of adding such an additive, ultra high molecular weight polyethylene, a method of blending with polyethylene, ultra high molecular weight polyethylene, polyethylene, Method of blending in the form, a method of previously dry blending or melt-blending, and the like.

  The ultra-high molecular weight polyethylene composition of the present invention has excellent heat resistance and mechanical properties of the ultra-high molecular weight polyethylene, as well as excellent processability of polyethylene, and further has excellent stretchability and cleanliness. Therefore, it is particularly suitable for a stretched microporous membrane.

The stretched microporous membrane is a stretched microporous membrane having a porosity of 10% or more and 80% or less, particularly 25% or more and 65% or less, because it has an excellent balance between membrane strength and membrane resistance that affects permeability. Preferably there is. At that time, the film thickness is preferably 0.001 to 1 mm, and the average pore diameter is preferably 1 to 1000 nm. The porosity at that time is, for example, porosity (V%) = 100-10 × (weight of stretched microporous membrane of 10 cm × 10 cm) (W, g) / (true density of stretched microporous membrane (g / cm ³ ). It can be determined by the film thickness (d, mm) of the stretched microporous film. Further, the film thickness (mm) of the stretched microporous film can be obtained, for example, by measuring the film thickness with a contact-type film thickness meter at 30 points of the stretched microporous film and obtaining the average value thereof. The average pore size can also be determined by image analysis from an image obtained by observation with a scanning electron microscope, in addition to the nitrogen adsorption method and the mercury porosimetry method.

  Since the stretched microporous membrane is particularly excellent in strength and can be made into a thin film, the tensile breaking strength measured at 23 ° C. is preferably 150 MPa or more. Further, it is preferable that the heat shrinkage rate is 2% or less because it is particularly excellent in heat resistance, durability at high temperature, and stability. The tensile breaking strength in the present invention can be measured, for example, by a tensile tester or the like. The measurement conditions at that time can be measured by stretching a test piece having an initial length of 20 mm at a stretching speed of 10 to 100 mm / min. The heat shrinkage can be measured, for example, by heating a 5 cm square microporous membrane at 100 ° C. for 1 hour, allowing it to cool for 24 hours, and then measuring the shrinkage.

  There is no particular limitation on the production method when the ultrahigh molecular weight polyethylene composition of the present invention is used as a stretched microporous membrane, and for example, the ultrahigh molecular weight polyethylene composition and an organic solvent are mixed at a temperature of 50 ° C. or higher and 300 ° C. or lower. Examples of the method include a step of removing the organic solvent from the sheet-shaped material and a step of performing biaxial stretching after the sheet-shaped material.

  Examples of the organic solvent at that time include high-boiling aliphatic hydrocarbons or alicyclic hydrocarbons such as octane, decane, dodecane, octadencan, decahydronaphthalene, and tetrahydronaphthalene; aromatics such as benzene, toluene, xylene, and naphthalene. Hydrocarbons; halogenated hydrocarbons such as dichloroethane, trichloroethane, chlorobenzene, trichlorobenzene, etc .; linear or branched liquid paraffins; paraffin wax; higher alcohols having 5 or more carbon atoms; phthalates, or mixtures thereof. You can In addition, when the ultrahigh molecular weight polyethylene composition is mixed with an organic solvent, a stretched microporous membrane having excellent uniformity and smoothness can be obtained efficiently, so that the concentration of the ultrahigh molecular weight polyethylene composition is 0.5 wt%. It is preferably 60 wt% or less and more preferably 5 wt% or more and 40 wt% or less. Then, when mixing the ultra high molecular weight polyethylene composition and the organic solvent, for example, a method of mixing in a reaction tank equipped with a stirring blade, a method of extrusion kneading with a single-screw, twin-screw extruder or the like, in a reactor After mixing, the method such as extrusion kneading can be used. Then, the obtained mixture is molded as a sheet-like material containing an organic solvent by a method such as compression molding, extrusion from a T die or circular die, or inflation molding.

  Furthermore, as the step of removing the organic solvent from the sheet-like material, for example, a drying method by heating, a method of drying after solvent extraction with a low-melting aliphatic or alicyclic hydrocarbon, alcohol, halogenated hydrocarbon, etc. Is mentioned.

  In addition, examples of the step of performing biaxial stretching include a step of performing simultaneous biaxial stretching method, sequential biaxial stretching method of performing sequential biaxial stretching, and the like, and the stretching speed and stretching temperature at that time are constant. Alternatively, it may be multistage with changes. The stretching ratio is preferably 2 to 20 times in the machine direction and 2 to 20 times in the transverse direction. The stretching temperature is preferably 0 ° C or higher and 200 ° C or lower. The step of removing the organic solvent and the step of performing the biaxial stretching are arbitrary. For example, even if the biaxial stretching is performed after the removal of the organic solvent, or the organic solvent is removed after the biaxial stretching. However, these may be performed simultaneously. Also, annealing may be performed after stretching.

  Since the stretched microporous membrane has excellent strength and heat resistance, it can be used as a member such as a gas separation membrane, a gas permeable membrane, a tape, a tube, and a separator.

  The ultrahigh molecular weight polyethylene composition having a high melting point and high strength, capable of being formed into a thin film, having a low amount of low molecular weight components, and excellent in cleanliness can provide an excellent stretched microporous membrane.

  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 measuring device (manufactured by Nikkiso Co., Ltd., ( Ethanol was measured as a dispersant using a trade name) MT3000).

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

  Furthermore, various physical properties of ultra-high molecular weight polyethylene and polyethylene in the examples were measured by the following methods.

-Measurement of intrinsic viscosity ([η])-
Using an Ubbelohde viscometer, decahydronaphthalene was used as a solvent at 135 ° C., and 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 DSC (trade name: DSC6220 manufactured by SII Nano Technology Co., Ltd.), 1st scanning was performed at a temperature rising rate of 10 ° C./min, and a crystal melting peak (Tm ₁ ) of 1st scanning was measured. 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, 2nd scan was performed again and a crystal melting peak (Tm ₂ ) of 2nd scan was measured. The sample amount of ultra high molecular weight polyethylene at that time was 4 to 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) Optima 3000XL). It was measured.

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

-Preparation of evaluation sheet for ultra high molecular weight polyethylene particles-
The evaluation sheet for ultra-high molecular weight polyethylene particles was formed by the following method. That is, ultrahigh molecular weight polyethylene was sandwiched between polyethylene terephthalate films, preheated at 190 ° C. for 5 minutes, and then heated and rolled under the conditions of 190 ° C. and a pressing 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 sample (width of measurement part: 5 mm) cut out in a dumbbell shape from a stretched microporous membrane and a sheet for evaluation of ultra-high molecular weight polyethylene particles was allowed to stand at 23 ° C. for 48 hours, and then a tensile tester (A. Tensileon RTG-1210 manufactured by And D Co., Ltd.) was subjected to 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 measurement part: 10 mm) cut out in a dumbbell shape from the stretched microporous membrane and the ultrahigh molecular weight polyethylene particle evaluation sheet by the method described in the above-mentioned measurement of tensile breaking strength was allowed to stand at 23 ° C. for 48 hours. After that, a tensile tester (manufactured by A & D Co., Ltd., (trade name) Tensilon UMT2.5T) was used to conduct a tensile test at 150 ° C. at an initial length of the test piece of 10 mm and a pulling speed of 20 mm / min. Then, the breaking stress at the time of melt drawing was determined. 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. In addition, in the microporous membrane, a value obtained by dividing the load by the apparent initial cross-sectional area was used as the stress.

~ Weight average molecular weight (Mw), number average molecular weight (Mn), ratio of weight average molecular weight to number average molecular weight (Mw / Mn) ~
The weight average molecular weight (Mw), the number average molecular weight (Mn), and the ratio of the weight average molecular weight and the number average molecular weight (Mw / Mn) were measured by GPC. A column temperature was set to 140 ° C. using a GPC device (Tosoh Corp. (trade name) HLC-8121GPC / HT) and a column (Tosoh Corp. (trade name) TSKgel GMHhr-H (20) HT). , 1,2,4-trichlorobenzene was used as an eluent. A measurement sample was prepared at a concentration of 1.0 mg / ml, and 0.3 ml was injected for measurement. The calibration curve of the molecular weight was calibrated using a polystyrene sample of known molecular weight. Note that Mw and Mn were obtained as values in terms of linear polyethylene.

~ Measurement of melt tension ~
A capillograph (manufactured by Toyo Seiki Seisakusho) was used. At 210 ° C., the strand lowered at a piston lowering speed of 10 mm / min was taken at 10 m / min from a die having a length (L) of 8 mm and a diameter (D) of 2.095 mm, and the take-up load was the melt tension.

-Measurement of strain hardening-
The measurement was performed using a Meissner type uniaxial elongational viscometer (manufactured by Toyo Seiki Seisakusho, trade name: Melten Rheometer) set at a temperature of 180 ° C. The nonlinear parameter (λ) was obtained as a value obtained by dividing the maximum value of extensional viscosity measured under the condition of strain rate of 0.07 to 0.1 s ⁻¹ by the extensional viscosity in the linear region of the time. The value of extensional viscosity in the linear region is described in Takeshi Fukuda, New Polymer Experiments 1, Fundamentals of Polymer Experiments, Molecular Property Analysis, “3-4. Molecular Shape and Morphology”, 295 (1994). It was calculated from the dynamic viscoelasticity using an approximate expression according to the method described in 1. When the obtained λ exceeded 1, it was judged to have strain hardening properties.

~density~
It was measured by the density gradient tube method according to JIS K6760 (1995).

-Measurement of thickness and porosity of stretched microporous membrane-
The film thickness (d, mm) of the microporous film was determined by measuring the film thickness at 30 points of the microporous film with a contact-type film thickness meter and taking the average value thereof. The porosity (V,%) was calculated by measuring the weight (W, g) of a 10 cm × 10 cm microporous membrane, and calculating the true density (0.950 g / cm ³ ) of the porous membrane and the following (e).

V = 100-W / 0.095d (e)
-Measurement of pore distribution of stretched microporous membrane-
After the gold vapor deposition, the surface of the microporous film was observed with a scanning electron microscope (manufactured by Keyence Corporation, (trade name) VE-9800) at a magnification of 10000, and finely obtained by image analysis of the obtained SEM photograph. The pore distribution was determined and approximated to the geometric logarithmic distribution function, and the median diameter was taken as the average pore diameter.

-Measurement of heat shrinkage-
Regarding the heat shrinkage rate, the rate of change in length and width after heating a 5 cm × 5 cm microporous membrane for 1 hour at 100 ° C. and allowing it to cool at room temperature for 24 hours was calculated as the average value.

Production example 1
(1) Preparation of organically modified clay In 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. and dispersing 100 g of synthetic hectorite (manufactured by 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 separated by filtration, 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. This 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 0.710 g of diphenylmethylene (cyclopentadienyl) (2- (diethylamino) -9-fluorenyl) hafnium dichloride and 142 ml of 20% triisobutylaluminum were added, and the mixture was stirred at 60 ° C. for 3 hours. 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 the catalyst for producing polyethylene (solid content: 11.5 wt%).

(3) Production of ultra-high molecular weight polyethylene 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum, and 95.2 mg of suspension of the catalyst for producing polyethylene obtained in (2) were placed in a 2 liter autoclave. After adding (corresponding to a solid content of 10.9 mg) and raising the temperature to 65 ° C., ethylene was continuously supplied so that the partial pressure became 1.3 MPa, and slurry polymerization of ethylene was performed. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 102 g of ultrahigh molecular weight polyethylene (1) (activity: 9360 g / g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene (1) are shown in Table 1.

Production example 2
(1) Preparation of Organic Modified Clay 300 ml of industrial alcohol (manufactured by Nippon Alcohol Sales Co., (trade name) Ekinen F-3) and 300 ml of distilled water were placed in a 1-liter flask, and 15.0 g of concentrated hydrochloric acid and dioleylmethylamine were added. (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. This 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 polyethylene catalyst suspension (solid weight: 11.3 wt%).

(3) Production of ultrahigh molecular weight polyethylene 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum were placed in a 2 liter autoclave, and 345 mg (solid) of the suspension of the catalyst for producing polyethylene obtained in (2). (Equivalent to 38.9 mg) was added and the temperature was raised to 45 ° C. Then, ethylene was continuously supplied so that the partial pressure became 1.6 MPa, and slurry polymerization of ethylene was performed. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 42.1 g of ultrahigh molecular weight polyethylene (2) (activity: 1080 g / g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene (2) 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 Polyethylene Production Catalyst Suspension 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 0.593 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 drawn off, 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 weight: 12.5 wt%).

(3) Production of ultra-high molecular weight polyethylene 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and 93.5 mg of suspension of the catalyst for producing polyethylene obtained in (2) were placed in a 2 liter autoclave. (Solid content equivalent to 11.7 mg) was added, the temperature was raised to 50 ° C., 1.0 g of 1-butene was added, and ethylene was continuously supplied so that the partial pressure was 1.1 MPa to carry out slurry polymerization. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 72.3 g of ultrahigh molecular weight polyethylene (3) (activity: 6180 g / g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene (3) are shown in Table 1.

Production Example 4
(1) Preparation of organically modified clay and (2) Preparation of suspension of catalyst for producing polyethylene were carried out in the same manner as in Production Example 3.

(3) Production of Ultra High Molecular Weight Polyethylene Particles 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum, and 102 mg of the suspension of the polyethylene production catalyst obtained in (2) were placed in a 2 liter autoclave. Solid content (corresponding to 12.8 mg) was added, the temperature was raised to 60 ° C., hydrogen / ethylene mixed gas containing 150 ppm of hydrogen was supplied so that the partial pressure became 1.2 MPa, and then the partial pressure became 1.3 MPa partial pressure. As a result, ethylene was continuously supplied to carry out slurry polymerization. After 210 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 75.0 g of ultrahigh molecular weight polyethylene (4) (activity: 6900 g / g catalyst). The physical properties of the obtained ultra high molecular weight polyethylene (4) are shown in Table 1.

製造例５
（１）固体触媒成分の調製は、製造例４と同様に実施した。

Production Example 5
(1) The solid catalyst component was prepared in the same manner as in Production Example 4.

(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 0.427 g of dimethylsilylene (cyclopentadienyl) (4,7-dimethyl-1-indenyl) zirconium dichloride and 142 ml of 20% triisobutylaluminum were added, and the mixture was stirred at 60 ° C. for 3 hours. 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 the catalyst for producing polyethylene (solid content: 11.5 wt%).

(3) Production of polyethylene 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum were placed in a 2 liter autoclave, and 132 mg of the suspension of the polyethylene production catalyst obtained in (2) (solid content: 15. (Equivalent to 2 mg), and after heating to 70 ° C., 0.1 g of butene is added, and ethylene is further fed so that the partial pressure becomes 1.2 MPa, and then the partial pressure becomes 1.2 MPa partial pressure. Slurry polymerization was carried out by continuously supplying ethylene. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 71.7 g of polyethylene (6) (activity: 4720 g / g catalyst). The physical properties of the obtained polyethylene (6) are shown in Table 2. The weight average molecular weight of the obtained polyethylene was 15 × 10 ⁴ .

Production Example 6
(1) Preparation of solid catalyst component and (2) Preparation of suspension of polyethylene production catalyst were carried out in the same manner as in Production Example 5.

(2) Production of polyethylene 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum were placed in a 2 liter autoclave, and 250 mg of a suspension of the polyethylene production catalyst obtained in (2) (solid content 28. (Equivalent to 8 mg), and after heating to 55 ° C., 0.15 g of butene was added, and ethylene was further fed so that the partial pressure was 1.2 MPa, and then the partial pressure was adjusted to 1.2 MPa partial pressure. Slurry polymerization was carried out by continuously supplying ethylene. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 82.1 g of polyethylene (7) (activity: 2860 g / g catalyst). The physical properties of the obtained polyethylene (7) are shown in Table 2. The weight average molecular weight of the obtained polyethylene was 15 × 10 ⁴ .

Production Example 7
(1) The solid catalyst component was prepared in the same manner as in Production Example 4.

(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 Dimethylsilylene (cyclopentadienyl) (2,4,7-trimethyl-1-indenyl) zirconium dichloride 0.441 g and 20% triisobutylaluminum 142 ml were added, and the mixture was 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 polyethylene catalyst suspension (solid weight: 12.3 wt%).

(3) Production of polyethylene 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum were placed in a 2 liter autoclave, and 325 mg of a suspension of the polyethylene production catalyst obtained in (2) (solid content: 40. (Equivalent to 0 mg), and after heating to 50 ° C., 0.5 g of butene was added, ethylene was further fed so that the partial pressure was 1.2 MPa, 0.15 g of butene was added, and then the partial pressure was increased. Slurry polymerization was carried out by continuously supplying ethylene so as to have a partial pressure of 1.2 MPa. After 180 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 83.2 g of ultrahigh molecular weight polyethylene (8) (activity: 2080 g / g catalyst). The physical properties of the obtained polyethylene (8) are shown in Table 2. The weight average molecular weight of the obtained polyethylene was 41 × 10 ⁴ .

Production Example 8
(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. for 2 hours, and stirring was performed 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 of 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 the mixture was further stirred at 70 ° C for 1 hour to obtain a solid catalyst component. The residual unreacted material and by-products 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 polyethylene To a 2 liter autoclave, 1.2 liter of hexane, 1.0 ml of 20% triisobutylaluminum, and 8.3 mg of the solid catalyst component obtained in (1) were added, and the temperature was raised to 80 ° C. , Hydrogen was supplied at 0.08 MPa, and ethylene was continuously supplied at a partial pressure of 0.6 MPa. After 90 minutes, the pressure was released, the slurry was filtered off, and dried to obtain 195 g of an ethylene homopolymer (activity: 23500 g / g catalyst). The weight average molecular weight of the obtained polyethylene was 22 × 10 ⁴ .

実施例１
製造例１で製造した超高分子量ポリエチレン（１）２．１ｇ、製造例５で製造したポリエチレン（６）１１．９ｇ、及び、流動パラフィン（ＭＯＲＥＳＣＯ社製、（商品名）モレスコホワイトＰ−３５０Ｐ）５６ｇ、酸化防止剤として、（商品名）Ｉｒｇａｎｏｘ１０１０（ＢＡＳＦ製）０．１３ｇ、（商品名）Ｉｒｇａｆｏｓ１６８（ＢＡＳＦ製）０．１３ｇを、１００ｃｃのバッチ式混練機（（株）東洋精機製作所製、（商品名）ラボプラストミル４Ｃ１５０）で、混練温度１９０℃、回転数５０ｒｐｍにて、１０分間混練し、得られた混合物を圧縮成形し、厚さ０．６ｍｍのシート状物とした。

Example 1
2.1 g of ultra-high molecular weight polyethylene (1) produced in Production Example 1, 11.9 g of polyethylene (6) produced in Production Example 5, and liquid paraffin (manufactured by MORESCO, (trade name) Moresco White P-350P) ) 56 g, as a antioxidant, (trade name) Irganox 1010 (manufactured by BASF) 0.13 g, (trade name) Irgafos 168 (manufactured by BASF) 0.13 g, 100 cc batch type kneading machine (manufactured by Toyo Seiki Seisakusho Co., Ltd., (Trade name) Labo Plastomill 4C150) was kneaded at a kneading temperature of 190 ° C. and a rotation speed of 50 rpm for 10 minutes, and the obtained mixture was compression-molded to give a sheet having a thickness of 0.6 mm.

  Simultaneously biaxially stretch this sheet at 115 ° C. so that the set stretch ratio is 7 × 8 in the longitudinal direction × horizontal direction, wash with hexane, remove liquid paraffin, and dry. To produce a stretched microporous membrane.

  The resulting stretched microporous membrane had no holes and tears that could be visually confirmed, and micropores were observed by an electron microscope. Table 3 shows the film thickness, the standard deviation of the film thickness, the porosity, the tensile strength at break, and the heat shrinkage ratio of this stretched microporous film.

Comparative Example 1
An attempt was made to produce a microporous membrane in the same manner as in Example 1 except that 2.1 g of ultrahigh molecular weight polyethylene (1) was changed to 14 g without using polyethylene.

  The load at the time of stretching was high, and it was not possible to stretch to a predetermined ratio.

Example 2
Instead of the ultra high molecular weight polyethylene (1), 3.5 g of the ultra high molecular weight polyethylene (2) produced in Production Example 2 and 10.5 g of the polyethylene (7) produced in Production Example 6 were used in place of the polyethylene (6). An ultra high molecular weight polyethylene composition and a stretched microporous membrane were produced by the same method as in Example 1 except that the above was used.

  The resulting stretched microporous membrane had no holes and tears that could be visually confirmed, and micropores were observed by an electron microscope. Table 3 shows the film thickness, the standard deviation of the film thickness, the porosity, the tensile strength at break, and the heat shrinkage ratio of this stretched microporous film.

Comparative example 2
A microporous membrane was produced by the same method as in Example 2 except that ultrahigh molecular weight polyethylene was not used and polyethylene (7) was changed from 10.5 g to 14 g.

  The obtained film had no visible holes or tears, and micropores were observed under an electron microscope. Table 3 shows the film thickness, the standard deviation of the film thickness, the porosity, the tensile strength at break, and the heat shrinkage ratio. The tensile rupture strength was low, the heat shrinkage rate was high, and the eluted components were present.

Comparative Example 3
A microporous membrane was produced in the same manner as in Example 2 except that the polyethylene (9) produced in Production Example 8 was used instead of the polyethylene (7).

  The obtained film had no visible holes or tears, and micropores were observed under an electron microscope. Table 3 shows the film thickness, the standard deviation of the film thickness, the porosity, the tensile strength at break, and the heat shrinkage ratio. The tensile rupture strength was low, the heat shrinkage rate was high, and the eluted components were present.

Example 3
4.2 g of ultra-high molecular weight polyethylene (3) produced in Production Example 3 was used instead of ultra-high molecular weight polyethylene (1), and 9.8 g of polyethylene (8) produced in Production Example 7 was used instead of polyethylene (6). An ultrahigh molecular weight polyethylene composition was obtained in the same manner as in Example 1 except that the above was used to prepare a sheet of an ultrahigh molecular weight polyethylene mixture having a thickness of 0.9 mm. Further, a stretched microporous membrane was produced in the same manner as in Example 1, with the set stretch ratio being 6 × 6 in the machine direction × the transverse direction.

  The resulting stretched microporous membrane had no holes and tears that could be visually confirmed, and micropores were observed by an electron microscope. Table 3 shows the film thickness, the standard deviation of the film thickness, the porosity, the tensile strength at break, and the heat shrinkage ratio of this stretched microporous film.

Example 4
Example 3 was repeated except that 5.6 g of the ultrahigh molecular weight polyethylene (4) produced in Production Example 4 was used instead of the ultrahigh molecular weight polyethylene (3) and the polyethylene (8) was changed to polyethylene (7) 8.4 g. An ultra-high molecular weight polyethylene composition and a stretched microporous membrane were produced by the same method as described above.

  The stretched porous film thus obtained had no visible holes or tears and micropores were observed by an electron microscope. Table 3 shows the film thickness, the standard deviation of the film thickness, the porosity, the tensile strength at break, and the heat shrinkage ratio of this stretched microporous film.

  The ultra-high molecular weight polyethylene composition of the present invention is excellent in mechanical strength, heat resistance, and stretchability, and also excellent in cleanliness, and a stretched microporous membrane comprising the same has strength, heat resistance, and high temperature. Since it is excellent in durability and thinning, it can be applied as a member such as a gas separation membrane, a gas permeable membrane, a tape, a tube, and a separator.

Claims (5)

100 parts by weight of ultrahigh molecular weight polyethylene having an intrinsic viscosity ([η]) of 10 dl / g or more and 80 dl / g or less, weight average molecular weight (Mw) of 600,000 or less, melt tension at 210 ° C. of 100 mN or more, and strain hardening And 5 to 5,000 parts by weight of polyethylene having a density of 935 kg / m ³ or more and 960 kg / m ³ or less according to JIS K6760. The ultrahigh molecular weight polyethylene composition according to claim 1, wherein the intrinsic viscosity of the ultrahigh molecular weight polyethylene composition is 0.8 times or less the intrinsic viscosity of the ultrahigh molecular weight polyethylene. . The ultrahigh molecular weight polyethylene composition according to claim 1 or 2, wherein the tensile breaking strength measured at 23 ° C is 150 MPa or more and the thermal shrinkage is 2% or less. The melting point (Tm ₁ ) of the 1st scan when the ultra high molecular weight polyethylene was heated from 0 ° C. to 230 ° C. at a heating rate of 10 ° C./min (1st scan) by DSC, and then left for 5 minutes, After the temperature was decreased to −20 ° C. at a temperature decrease rate of 10 ° C./min, the temperature was left for 5 minutes, and then the temperature was increased from −20 ° C. to 230 ° C. at a temperature increase rate of 10 ° C./min (2nd scan). measuring the respective melting points (Tm _2), wherein the difference in the Tm ₁ and the _{Tm 2 (ΔTm = Tm 1 -Tm} 2) is an ultra high molecular weight polyethylene which is a 9 ° C. or higher 30 ° C. less claims Item 5. The ultrahigh molecular weight polyethylene composition according to any one of Items 1 to 3 . The stretched microporous membrane made of the ultrahigh molecular weight polyethylene composition according to any one of claims 1 to 4, which has a porosity of 10% or more and 80% or less.