JP6349843B2 - Ultra high molecular weight polyethylene rolled compact - Google Patents

Description

  The present invention relates to a rolled molded body obtained by molding ultra-high molecular weight polyethylene particles having a high melting point and high crystallinity, and more specifically, excellent in strength, heat resistance, impact resistance, and wear resistance. Thus, the present invention relates to an ultra-high molecular weight polyethylene rolled molded body which is expected to be applied as a tape, a sheet, a tube, a lining material and the like.

  The ultra high molecular weight ethylene polymer has an extremely high molecular weight corresponding to a viscosity average molecular weight (Mv) of 1 million or more, so that it has impact resistance, self-lubricity, abrasion resistance, weather resistance, chemical resistance It has excellent physical properties and dimensional stability, and has high physical properties comparable to engineering plastics. For this reason, application to applications such as lining materials, food industry line parts, machine parts, artificial joints, sporting goods, and microporous membranes has been attempted by various molding methods.

  However, ultra-high molecular weight ethylene polymer has extremely low fluidity when melted due to its high molecular weight, and it can be molded by kneading extrusion like ordinary polyethylene having a molecular weight in the range of tens of thousands to about 500,000. Have difficulty. Therefore, ultrahigh molecular weight polyethylene is a method of directly sintering polymer powder obtained by polymerization, a method of compression molding, a molding method by a ram extruder that extrudes while intermittently compressing, a state where it is dispersed in a solvent, etc. After extrusion molding, a method such as a method of removing the solvent is performed. Furthermore, a method of forming the obtained bulk molded body into a sheet or film by cutting called skive processing, compression molding, or molding by rolling the sheet or film obtained by cutting molding under heating is attempted. ing.

  Among these, the rolled molded body of ultra high molecular weight polyethylene is improved in molecular orientation by rolling, and therefore various physical properties expressed by the high molecular weight of ultra high molecular weight polyethylene are expected to be further improved than the molded body before rolling. Is done. However, the ultra-high 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) larger than 4, and the molecular weight distribution is wide. The improvement of the strength of the molded article cannot be said to be sufficiently improved as compared with the normal molecular weight polyethylene, and it cannot be said to exhibit the expected performance.

  On the other hand, an ultrahigh 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).

Japanese Patent No. 4868853 (see, for example, claims) Japanese Patent Laying-Open No. 2006-36988 (for example, refer to the claims)

  However, when a rolled molded body is produced using the ultrahigh molecular weight polyethylene proposed in Patent Documents 1 and 2, the performance as a molded product is improved, but the performance is sufficiently satisfactory in terms of strength. It was not a thing.

  In addition, general ultra-high molecular weight polyethylene, as the molecular weight increases, the entanglement between the molecular chains becomes difficult to unravel, so the expected effect due to the increase in molecular weight cannot be fully expressed, for example, tensile strength at break Has the maximum at a molecular weight of about 3 million, and even if the molecular weight is increased beyond that, there is a problem that the tensile strength at break decreases.

  Then, this invention is made | formed in view of the said subject, and it aims at providing the roll molded object made from ultra high molecular weight polyethylene which has high intensity | strength and is excellent in heat resistance and slipperiness.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have found that a rolled molded body having a specific draw ratio using a novel ultrahigh molecular weight polyethylene particle having a specific melting behavior has high strength. The present inventors have found that it becomes a rolled compact, and have completed the present invention.

That is, the present invention melts at a molding temperature of 150 ° C. to 250 ° C. using ultrahigh molecular weight polyethylene particles that satisfy at least any of the following properties (1), (2), (3), and (4). After compression molding to obtain a melt compression molded product made of ultra high molecular weight polyethylene, the melt compression molded product made of ultra high molecular weight polyethylene is rolled to a draw ratio of 2 times or more, and at least one of the characteristics shown in (1) and (4) The present invention also relates to a method for producing an ultra-high molecular weight polyethylene rolled compact characterized by satisfying the above.
(1) Intrinsic viscosity ([η]) is 15 dl / g or more and 60 dl / g or less,
(2) The bulk density is 130 kg / m ³ or more and 700 kg / m ³ or less,
(3) 1st scan melting point (Tm ₁ ) when the temperature was raised from 0 ° C. to 230 ° C. (1st scan) with a differential scanning calorimeter (DSC ), then 5 When the temperature is lowered to −20 ° C. at a temperature lowering rate of 10 ° C./min after standing for 5 minutes, and after standing for 5 minutes, the temperature is raised again from −20 ° C. to 230 ° C. at a temperature rising rate of 10 ° C./min (2nd scan). The 2nd scan melting point (Tm ₂ ) 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.
(4) The titanium content is 0.2 ppm or less or the measurement detection limit or less.

  The present invention is described in detail below.

The ultra-high molecular weight polyethylene rolled molded body 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) With a differential scanning calorimeter (DSC), the melting point (Tm ₁ ) of 1st scan when the temperature was raised from 0 ° C. to 230 ° C. at a rate of 10 ° C./min (1st scan), After standing for 5 minutes, the temperature was lowered to −20 ° C. at a temperature lowering rate of 10 ° C./min. After standing for 5 minutes, the temperature was raised again from −20 ° C. to 230 ° C. at a temperature rising rate of 10 ° C./min (2nd scan). Each of the 2nd scan melting points (Tm ₂ ) 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. Using high molecular weight polyethylene particles, It is formed by rolling to a draw ratio of 2 times or more.

  The ultra high molecular weight polyethylene particles are those in which ultra high molecular weight polyethylene has a particle shape, and ultra high molecular weight polyethylenes belong to a category called polyethylene, for example, ultra high molecular weight ethylene homopolymers; 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 an α-olefin copolymer; and the like.

  The ultra high 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 rolled compact. 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 article is inferior in mechanical properties. On the other hand, when the intrinsic viscosity exceeds 60 dl / g, the fluidity at the time of molding is inferior, so that the rolling forming process becomes difficult. The intrinsic viscosity is measured at 135 ° C. using a Ubbelohde viscometer, for example, in a solution having a polymer concentration of 0.0005 to 0.01% using orthodichlorobenzene, decahydronaphthalene, tetrahydronaphthalene or the like as a solvent. 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 at the time of roll forming, and therefore 200 kg / m ³ or more and 600 kg / m ^2. m ³ or less is preferable. Here, when the bulk density is less than 130 kg / m ³ , problems such as a significant decrease in operability such as a decrease in fluidity of particles, a decrease in the filling rate in storage equipment, storage containers, and hoppers occur. It becomes easy to do. On the other hand, when the bulk density exceeds 700 kg / m ³ , the processability at the time of molding is inferior, and problems such as a decrease in physical properties of the obtained molded body are likely to occur. The bulk density can be measured by a method based on, for example, 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. (1st scan) at a heating rate of 10 ° C./min with a differential scanning calorimeter (DSC). (Tm ₁ ) After that, after being left for 5 minutes, the temperature was lowered to −20 ° C. at a temperature lowering rate of 10 ° C./min. After being left for 5 minutes, again from −20 ° C. to 230 ° C. at a temperature rising 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 between the Tm ₁ and the Tm ₂ (ΔTm = Tm ₁ -Tm ₂ ) was 11 ° C. or higher and 30 ° C. or lower, In particular, ΔTm is preferably 11 ° C. or more and 15 ° C. or less because a rolled product made of ultrahigh molecular weight polyethylene having an excellent balance of heat resistance, mechanical strength, and moldability is obtained. Here, when ΔTm is less than 11 ° C., the obtained molded article is inferior in heat resistance, strength, and the like. On the other hand, when ΔTm exceeds 30 ° C., not only the obtained ultrahigh molecular weight polyethylene particles are inferior in molding processability, but also the obtained molded article is inferior 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 ultra high molecular weight polyethylene particles used in the rolled molded body of the present invention have an extremely high melting point (Tm) as compared with conventionally known polyethylene. For example, if it is an ethylene homopolymer , Tm ₁ has an extremely high melting point exceeding 140 ° C. The ultra high molecular weight polyethylene particles are highly crystallized due to the orientation of polyethylene molecular chains, etc., so the difference between Tm ₁ and Tm ₂ when measured with a differential scanning calorimeter (DSC). A certain ΔTm is considered to be an extremely large difference of 11 ° C. or more and 30 ° C. or less.

  Furthermore, the ultra high molecular weight polyethylene particles can suppress discoloration (yellowing) caused by titanium, oxidation deterioration, etc., have a good color tone, and are 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 titanium content can be determined by chemical titration, measurement using a fluorescent X-ray analyzer, ICP emission analyzer, or the like.

Since the ultra-high molecular weight polyethylene particles can provide a tougher ultra-high molecular weight polyethylene rolled compact, (5) after being heated and compressed at a press temperature of 190 ° C. and a press pressure of 20 MPa, (3 ) Measured at a mold temperature lower by 10 ° C. to 30 ° C. than the melting point (Tm ₂ ) measured by 2nd scan, and the tensile strength at break (TS (MPa)) of the sheet satisfies the following relational expression (a) It is preferable that it is possible to provide an ultra-high molecular weight polyethylene rolled molded body that is further tough, excellent in mechanical strength, and wear resistance, and therefore satisfies the following relational expression (c). preferable.
TS ≧ 1.35 × Tm ₂ −130 (a)
1.35 × Tm ₂ −130 ≦ TS ≦ 2 × Tm ₂ −175 (c)
The tensile strength at break of general polyethylene is as low as about 45 MPa even with the highest density polyethylene. Further, conventional ultra-high molecular weight polyethylene has not been able to make full use of its high molecular weight, and the tensile strength at break was equivalent to that of general polyethylene, and did not exceed 50 MPa. For this reason, a method has been adopted in which the strength is increased by orientation by rolling at a high draw ratio.

  However, since the ultrahigh molecular weight polyethylene particles used in the rolled molded body of the present invention are moderately entangled with the polymer chains, even if the intrinsic viscosity exceeds 15 dl / g, the molecular weight is further increased. Even if it raises, tensile fracture strength does not fall, but rather shows the tendency to improve further. And, as the ultra-high molecular weight polyethylene particles used in the rolled molded body of the present invention, the strength becomes more excellent when formed into a molded body. Therefore, if it belongs to the region of high density polyethylene, the above (5) The measured tensile strength at break is preferably 40 MPa or more, more preferably 50 MPa or more.

  In addition, there is no restriction | limiting in particular as measurement conditions of tensile breaking strength, For example, test pieces, such as a strip shape and a dumbbell type | mold of thickness 0.1-5mm and width 1-50mm, are used for the tensile speed of 1 mm / min-500 mm / min. A method of measuring by speed can be exemplified.

Since the ultra-high molecular weight polyethylene particles have a relatively low content of low molecular weight components, can be appropriately entangled with polymer chains, and become an ultra-high molecular weight polyethylene rolled molded product that is particularly excellent in heat resistance. 6) When the heat-compressed sheet is melt-stretched at a temperature 20 ° C. higher than the melting point (Tm ₂ ) of the 2nd scan measured in (3) above, the breaking stress (MTS (MPa)) is 2 MPa or more. It is preferable that it has 3 MPa or more.

  Note that 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. In addition, the conventional ultrahigh molecular weight polyethylene can be melt-stretched even at a temperature 20 ° C. higher than the melting point (Tm), but strain hardening does not occur due to the low molecular weight component contained, and the stress remains low. It was ruptured by a stress of around 1 MPa and was inferior in heat resistance.

  And there is no restriction | limiting as a shaping | molding condition of the heat compression molding sheet | seat used for melt drawing, For example, it is the conditions of the press temperature of 100-250 degreeC, and the press pressure of 5-50 MPa, Among them, especially the heat compression described in said (5). A molding method can be exemplified. Examples of the melt stretching method include a method of stretching a test piece such as a strip shape having a thickness of 0.1 to 5 mm and a width of 1 to 50 mm and a dumbbell shape at a tensile speed of 1 mm / min to 500 mm / min. be able to. Furthermore, as the rupture stress at the time of melt stretching, strain hardening occurs, if the stress increases with stretching, the maximum value is the rupture stress, strain hardening does not occur, and if the stress does not increase even after stretching, The stress in the flat region after yielding was taken as the breaking stress.

Since the ultra-high molecular weight polyethylene particle is a rolled product made of ultra-high molecular weight polyethylene that is particularly excellent in heat resistance, (7) Stress at break (MTS (MPa) when melt stretched as measured in (6) above ) And the intrinsic viscosity ([η]) preferably satisfy the following relational expression (b), and in particular, satisfy the following relational expression (d) because the melt stretchability and moldability are excellent. It is preferable.
MTS ≧ 0.11 × [η] (b)
0.11 × [η] ≦ MTS ≦ 0.32 × [η] (d)
The ultra high molecular weight polyethylene particles are particularly excellent in fluidity as a powder, and become an ultra high molecular weight polyethylene rolled molded article having excellent 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 size can be measured by a method such as a sieving test method using a standard sieve defined in JIS Z8801, for example.

  As a method for producing the ultra high molecular weight polyethylene particles used in the ultra high molecular weight polyethylene rolled molded product of the present invention, any method may be used as long as the ultra high molecular weight polyethylene particles can be produced. Examples thereof include a method for homopolymerization of ethylene and copolymerization of ethylene and other olefins using a catalyst. Examples of the α-olefin in this case include propylene, 1-butene and 4-methyl-1-pentene. , 1-hexene, 1-octene and the like. Examples of the polymerization method include a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, a slurry polymerization method, and the like. Among them, the production of ultra high molecular weight polyethylene particles having a particularly uniform particle shape is possible. Ultra-high-molecular-weight polyethylene particles that enable high-melting-point polyethylene rolled compacts that have high melting points and high crystallinity, and that are excellent in mechanical strength, heat resistance, and wear resistance The slurry polymerization method is preferable because it can be produced. Further, the solvent used in the slurry polymerization method may be any organic solvent that is generally used, such as benzene, toluene, xylene, pentane, hexane, heptane, etc., and liquefied gas such as isobutane and 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 particles, any catalyst can be used as long as the ultra high molecular weight polyethylene particles can be produced, for example, at least a transition metal compound. Examples thereof include (A), a metallocene catalyst obtained from 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 having a (substituted) cyclopentadienyl group and a (substituted) indenyl group. Metal compounds, transition metal compounds having a (substituted) indenyl group and a (substituted) fluorenyl group, etc. can be mentioned. Examples of the transition metal in this case include zirconium, hafnium, etc. Since it is possible to efficiently produce molecular weight polyethylene particles, a zirconium compound having a (substituted) cyclopentadienyl group and an amino group-substituted fluorenyl group, a (substituted) cyclopentadienyl group and an amino group-substituted fluorenyl group It is preferable that it is a hafnium compound.

  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 Nium 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 (cyclopentadiyl) 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 (cyclopentadi) Enyl) (2,7-bis (dimethylamino) -9-fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl) (2,7-bis (diethylamino) -9-fluorenyl) zyl Nium dichloride, 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 (cyclope 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 dichloride; zirconium compounds obtained by converting these dichloro compounds to dimethyl, diethyl, dihydro, diphenyl, and dibenzyl compounds, and hafnium compounds obtained by converting zirconium of these compounds to hafnium A thing etc. can be illustrated.

  Examples of the organically modified clay (B) modified with the aliphatic salt include N, N-dimethyl-behenylamine hydrochloride, N-methyl-N-ethyl-behenylamine hydrochloride, 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 hydrofluorate, 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-be Nylamine hydroiodide, N-methyl-N-ethyl-behenylamine hydroiodide, N-methyl-Nn-propyl-behenylamine hydroiodide, N, N-dioleyl-methylamine iodide Hydronate, N, N-dimethyl-behenylamine sulfate, N-methyl-N-ethyl-behenylamine sulfate, N-methyl-Nn-propyl-behenylamine sulfate, N, N-dioleoyl-methyl Aliphatic amine salts such as amine sulfates; 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 Hydronate, 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, and aliphatic phosphonium salts such as P, P-dipropyl-behenylphosphine sulfate;

Further, 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, and generally a tetrahedron in which a silica tetrahedron is two-dimensionally continuous. A layer called a silicate layer formed by combining a sheet and an octahedron sheet in which an alumina octahedron, a magnesia octahedron, etc. are two-dimensionally continuous in a 1: 1 or 2: 1 layer is formed to overlap. Some of the silica tetrahedrons are replaced with the same type of Si by Al, alumina octahedron Al by Mg, magnesia octahedron Mg by Li, etc. It is known that cations such as Na ⁺ and Ca ²⁺ exist between the layers in order to compensate for this negative charge. As the clay compound, kaolinite, talc, smectite, vermiculite, mica, brittle mica, curdstone and the like as natural products or synthetic products exist, and these can be used. Smectite is preferable from the viewpoint of easiness of modification and organic modification, and hectorite or montmorillonite is more preferable among smectites.

  The organically modified clay (B) can be obtained by introducing the aliphatic salt between layers of the clay compound to form an ionic complex. In preparing the organically modified clay (B), it is preferable to carry out the treatment by selecting conditions of a clay compound concentration of 0.1 to 30% by weight and a treatment temperature of 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 between the clay compound and the aliphatic salt, it is preferable to use an aliphatic salt having an equivalent amount or more with respect to exchangeable cations of the clay compound. Examples of the processing 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; Preferably, alcohols or water is used alone or as one component of a solvent.

  Moreover, there is no restriction | limiting in the particle size of the organic modified clay (B) which comprises the catalyst for polyethylene manufacture of this invention, and since it will become excellent in the efficiency at the time of catalyst preparation, and the efficiency at the time of polyethylene manufacture in 1-100 micrometers. Preferably there is. There is no limitation on the method of adjusting the particle size at that time, and large particles may be pulverized to an appropriate particle size, small particles may be granulated to an appropriate particle size, or pulverization and granulation May be combined. The particle size may be adjusted on the clay before organic modification or on the organic modified clay after modification.

  Any organoaluminum compound (C) may be used as long as it belongs to the category called organoaluminum compound, and examples thereof include alkylaluminums such as trimethylaluminum, triethylaluminum, and triisobutylaluminum. Can do.

  The transition metal compound (A) (hereinafter also referred to as component (A)) constituting the catalyst for producing polyethylene, the organically modified clay (B) (hereinafter also referred to as component (B)), and The use ratio of the organoaluminum compound (C) (hereinafter sometimes referred to as component (C)) is not subject to any limitation as long as it can be used as a catalyst for polyethylene production. Since it becomes a catalyst for polyethylene production capable of producing ultra-high molecular weight polyethylene particles with high production efficiency, the molar ratio of the component (A) to the component (C) per metal atom is the component (A): component (C). = 100: 1 to 1: 100,000 is preferable, and 1: 1 to 1: 10000 is particularly preferable. The weight ratio of the component (A) to the component (B) is preferably (A) component: (B) component = 10: 1 to 1: 10000, particularly in the range of 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 the polyethylene production catalyst containing the component (A), the component (B) and the component (C). For example, there can be mentioned a method in which each of the components (A), (B) and (C) is mixed in an inert solvent or using a monomer for polymerization as a solvent. Moreover, there is no restriction | limiting also about the order which makes these components react, and the temperature and processing time which perform this process also have no restriction | limiting. It is also possible to prepare a catalyst for polyethylene production using two or more of each of the component (A), the component (B), and the component (C).

  The polymerization conditions such as polymerization temperature, polymerization time, polymerization pressure, and monomer concentration when producing ultra high molecular weight polyethylene particles used in the ultra high molecular weight polyethylene rolled molded product of the present invention can be arbitrarily selected. 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 adjust the molecular weight using hydrogen during polymerization. The polymerization can be carried out by any of batch, semi-continuous and continuous methods, and can be carried out 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.

  Next, the manufacturing method of the ultra high molecular weight polyethylene rolled molded product of the present invention will be described. The rolled molded body of the present invention may be formed by any method as long as it is a molded body using the ultra-high molecular weight polyethylene particles and rolled at a draw ratio of 2 times or more, for example, compression molding. A method of rolling a sheet, film, or pipe obtained by forming a molded body such as a sheet, film, or pipe by skive molding and the like. Examples of the compression molding method at that time include a compression molding with a compression molding machine or an extrusion molding with intermittent compression with a ram extruder. As the molding temperature for compression molding, the fusion property between ultrahigh molecular weight polyethylenes is good, and a dense molded body can be obtained, and oxidation deterioration, discoloration, physical property degradation, etc. can be suppressed. In particular, it is preferably 100 ° C. or higher and 250 ° C. or lower, and more preferably 150 ° C. or higher and 250 ° C. or lower.

  Moreover, when performing rolling forming, it becomes possible to perform rolling efficiently, and since it becomes a rolled molded object which is excellent in a physical property, the forming temperature in rolling forming is 0 degreeC or more and 200 degrees C or less, Especially 50. It is preferable that it is at least 160 ° C. The stretching speed at that time can be arbitrarily selected.

  The ultra high molecular weight polyethylene rolled molded article of the present invention has a draw ratio of 2 times or more, preferably 2 to 100 times. When the draw ratio is less than 2 times, the molecular orientation of the molecular chain of the ultrahigh molecular weight polyethylene constituting the rolled molded product is not sufficient, and the molded product is inferior in strength, impact resistance and the like.

  The atmosphere at the time of rolling forming may be air. Among these, in order to reduce oxidative degradation of ultrahigh molecular weight polyethylene, rolling can be performed in an inert gas atmosphere such as nitrogen or argon. Moreover, you may roll-form in a vacuum. Furthermore, the cooling conditions after the rolling forming at the time of heating are arbitrary, and annealing can also be performed.

  The ultra-high molecular weight polyethylene rolled molded product of the present invention is provided with a heat resistance stabilizer, a weather resistance stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a slip agent, a lubricant, and a nucleating agent as long as they do not depart from the object of the present invention. Inorganic fillers or reinforcing agents such as carbon black, talc, glass powder, glass fiber, and 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 Polymers, ethylene / vinyl alcohol copolymers, polystyrene, and these maleic anhydride grafts may be blended with such additives. The addition method, a method of blending the ultra high molecular weight polyethylene particles include ultra high molecular weight polyethylene particles, a method of blending at the time of molding, a method of preliminarily dry-blended or melt-blending, and the like.

  The ultra-high molecular weight polyethylene rolled molded body of the present invention has high strength and is excellent in heat resistance, slipperiness, etc., so that it is used for lining of sports equipment such as sliding members for industrial machines, various tapes, skis, etc. Etc., and can be used as a member such as a sheet, a membrane, and a tube.

  Since the ultra-high molecular weight polyethylene rolled molded body obtained by the present invention is excellent in strength and heat resistance, sliding members for industrial machines, various tapes, linings for sports equipment such as skis, sheets, membranes, tubes , Etc. are suitably used.

  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 noted, the reagents 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 pulverizing the organically modified clay, and the particle size after pulverization was measured using a microtrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., (Trade name) MT3000) was used to measure ethanol as a dispersant.

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

  Furthermore, various physical properties of the ultrahigh molecular weight polyethylene particles in the examples were measured by the following methods.

~ Measurement of intrinsic viscosity ([η]) ~
Using an Ubbelohde viscometer, ODCB (orthodichlorobenzene) was used as a solvent at 135 ° C. with an ultrahigh molecular weight polyethylene concentration of 0.005 wt%.

~ Measurement of bulk density ~
It measured by the method based on JISK6760 (1995).

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

-Measurement of titanium content-
The ultra high molecular weight polyethylene was incinerated, alkali melted, and the prepared solution was used to determine the titanium content in the ultra high molecular weight polyethylene using an ICP emission analyzer (manufactured by PerkinElmer Co., Ltd., (trade name) Optima 3000XL). It was measured.

~ Measurement of average particle diameter ~
Obtained when classifying 100 g of ultrahigh molecular weight polyethylene particles 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 diameter was determined by measuring the particle diameter at 50% weight on an integral curve obtained by integrating the weight of the particles remaining on each sieve from the side having a large opening.

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

~ Measurement of tensile strength at break ~
A sample cut into a dumbbell shape from a sheet for evaluation of ultrahigh molecular weight polyethylene particles used for forming a rolled compact (5 mm in width of the measurement part) was allowed to stand at 23 ° C. for 48 hours, and then a tensile tester ((stock) ) Tensile test was carried out at a measurement temperature of 23 ° C., an initial length of the test piece of 20 mm, and a tensile speed of 20 mm / min by A & D, (trade name) Tensilon RTG-1210) to determine the tensile breaking strength. .

-Measurement of breaking stress during melt drawing-
A sample cut into a dumbbell shape by the method described in the above measurement of tensile strength at break (10 mm in width of measurement part) 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. with an initial length of the test piece of 10 mm and a tensile speed of 20 mm / min, and the breaking stress at the time of melt drawing was determined. When strain hardening occurs and stress increases with stretching, the maximum value is the breaking stress, and when strain hardening does not occur and stress does not increase after stretching, the stress in the flat region after yielding is the breaking stress. did.

-Measurement of tear strength of rolled compact-
It cut out into the strip shape of width 100mm and length 200mm from the rolling-molded body sheet | seat, and cut | incised 70 mm in the length direction at the place of width 50mm, and was set as the test sample. Using a tensile tester (manufactured by A & D Co., Ltd., (trade name) Tensilon RTG-1210), the tear strength was determined at a measurement temperature of 23 ° C., a distance between grips of 50 mm, and a test speed of 200 mm / min.

Production Example 1
(1) Preparation of organically modified clay 300 ml of industrial alcohol (manufactured by Nippon Alcohol Sales Co., Ltd., (trade name) Echinen 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., (trade name) Armin M20) 64.2 g (120 mmol) was added and heated to 45 ° C. to disperse 100 g of synthetic hectorite (Rockwood Additives, (trade name) Laponite RDS). After that, the temperature was raised to 60 ° C. and stirred for 1 hour while maintaining the temperature. The slurry was separated by filtration, washed twice with 600 ml of water at 60 ° C., and dried in an oven 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 catalyst suspension 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. Add 0.795 g of diphenylmethylene (4-phenyl-1-indenyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride and 142 ml of 20% triisobutylaluminum and stir at 60 ° C. for 3 hours. did. 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 weight: 11.7 wt%).

(3) Production of ultra high molecular weight polyethylene particles 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum in a 2 liter autoclave, and 356 mg of a suspension of the catalyst for polyethylene production obtained in (2) ( (Equivalent to 41.7 mg of solid content) was added, and the temperature was set to 45 ° C., and then 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, and the slurry was filtered and dried to obtain 47.9 g of ultrahigh molecular weight polyethylene particles (1) (activity: 1150 g / g catalyst). The physical properties of the obtained ultrahigh molecular weight polyethylene particles (1) are shown in Table 1.

Production Example 2
(1) Preparation of organically modified clay The same procedure as in Production Example 1 was performed.

(2) Preparation of catalyst suspension 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. Diphenylmethylene (cyclopentadienyl) (2- (dimethylamino) -9-fluorenyl) zirconium dichloride (0.600 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 extracted, 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: 11.5 wt%).

(3) Production of ultrahigh molecular weight polyethylene particles 1.2 liters of hexane and 1.0 ml of 20% triisobutylaluminum in a 2 liter autoclave, and a suspension of the catalyst for polyethylene production obtained in (2) in 89. 9 mg (corresponding to a solid content of 10.3 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 became 1.1 MPa to perform slurry polymerization. After 180 minutes, the pressure was released, and the slurry was filtered and dried to obtain 65.0 g of ultrahigh molecular weight polyethylene particles (2) (activity: 6300 g / g catalyst). The physical properties of the obtained ultrahigh molecular weight polyethylene particles (2) are shown in Table 1.

Production Example 3
(1) Preparation of organically modified clay Into a 1 liter flask was placed 300 ml of industrial alcohol (manufactured by Nippon Alcohol Sales, (trade name) Echinen F-3) and 300 ml of distilled water, 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., 100 g of synthetic hectorite (Rockwood Additives, (trade name) Laponite RDS) was dispersed. The mixture was heated to 60 ° C. and stirred for 1 hour while maintaining the temperature. The slurry was separated by filtration, washed twice with 600 ml of 60 ° C. water, and dried in an oven at 85 ° C. for 12 hours to obtain 125 g of an organically modified clay. This organically modified clay was pulverized by a jet mill to have a median diameter of 7 μm.

(2) Preparation of catalyst suspension 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. 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 weight: 12.9 wt%).

(3) Production of ultra-high molecular weight polyethylene particles In a 2 liter autoclave, 1.2 liters of hexane and 1.0 ml of 20% triisobutylaluminum, and a suspension of the catalyst for producing polyethylene obtained in (2) is 108. 7 mg (corresponding to a solid content of 14.0 mg) was added, and after raising the temperature to 65 ° C., ethylene was continuously supplied so that the partial pressure became 1.3 MPa, and ethylene slurry polymerization was performed. After 180 minutes, the pressure was released, and the slurry was filtered and dried to obtain 130 g of ultrahigh molecular weight polyethylene particles (3) (activity: 9300 g / g catalyst). The physical properties of the obtained ultrahigh molecular weight polyethylene particles (3) are shown in Table 1.

Production Example 4
(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 metal magnesium powder and 210 g (0.62 mol) of titanium tetrabutoxide were added. Then, 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 further stirred at 140 ° C. for 2 hours under a nitrogen seal while excluding generated hydrogen gas to obtain a homogeneous solution. . Then 2100 ml of hexane was added.

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

(2) Production of ultra high molecular weight polyethylene 1.2 liters of hexane, 1.0 ml of 20% triisobutylaluminum, and 4.2 mg of the solid catalyst component obtained in (1) were added to a 2 liter autoclave and heated to 80 ° C. After the temperature increase, ethylene was continuously supplied so that the partial pressure became 0.6 MPa. After 90 minutes, the pressure was released, and the slurry was filtered and dried to obtain 170 g of ultrahigh molecular weight polyethylene (4) (activity: 51000 g / g catalyst). The physical properties of the obtained ultrahigh molecular weight polyethylene (4) are shown in Table 1.

実施例１
製造例１で製造した超高分子量ポリエチレン粒子（１）を、１９０℃で予備加熱した後、プレス圧力を２０ＭＰａにして２０分間、プレス成形した。その後、１１０℃、プレス圧力１０ＭＰａで１０分間冷却し、円柱状の圧縮成形体を作成した。この成形体からスカイブ加工にて厚さ３ｍｍのシートを作成した。このシートを１３５℃に予備加熱した後、ロール温度を１３５℃に調整した圧延ロール機にて、厚さ１ｍｍの超高分子量ポリエチレン製圧延成形体シート（延伸倍率；３．０倍）を作成した。得られたシートの引張破壊強度、引裂強度を表２に示す。

Example 1
The ultra high molecular weight polyethylene particles (1) produced in Production Example 1 were preheated at 190 ° C., and then press molded at a press pressure of 20 MPa for 20 minutes. Then, it cooled at 110 degreeC and the press pressure of 10 MPa for 10 minutes, and produced the cylindrical compression molding. A sheet having a thickness of 3 mm was prepared from the formed body by skiving. This sheet was preheated to 135 ° C., and then a roll molded body made of ultrahigh molecular weight polyethylene having a thickness of 1 mm (stretching ratio: 3.0 times) was prepared using a roll mill adjusted to 135 ° C. . Table 2 shows the tensile fracture strength and tear strength of the obtained sheet.

Comparative Example 1
Instead of the ultrahigh molecular weight polyethylene particles (1), a rolled molded sheet (stretching ratio: 3.0) was obtained in the same manner as in Example 1 except that the ultrahigh molecular weight polyethylene (4) produced in Production Example 4 was used. Times). Table 2 shows the tensile strength and tear strength of the obtained sheet. Both tensile strength at break and tear strength were inferior.

Comparative Example 2
Example 1 except that (trade name) Million 240M (manufactured by Mitsui Chemicals, Inc.) (hereinafter referred to as ultra high molecular weight polyethylene (5)) was used in place of the ultra high molecular weight polyethylene particles (1). A rolled compact sheet (stretching ratio: 3.0 times) was produced by the same method. Table 2 shows the tensile strength and tear strength of the obtained sheet. Both tensile strength at break and tear strength were inferior.

Example 2
Example except that the ultrahigh molecular weight polyethylene particles (2) produced in Production Example 2 were used in place of the ultrahigh molecular weight polyethylene particles (1), the rolling temperature was 130 ° C., and the thickness of the skive sheet was 3.6 mm. In the same manner as in No. 1, an ultrahigh molecular weight polyethylene rolled molded sheet (stretching ratio: 2.8 times) having a thickness of 1.3 mm was produced. Table 2 shows the tensile fracture strength and tear strength of the obtained sheet.

Example 3
Except that the rolling temperature was 135 ° C. and the thickness of the skive sheet was 4.7 mm, a rolled sheet of ultrahigh molecular weight polyethylene having a thickness of 0.9 mm (stretching ratio; 5.2) was obtained in the same manner as in Example 2. Times). Table 2 shows the tensile fracture strength and tear strength of the obtained sheet.

Example 4
Example except that the ultrahigh molecular weight polyethylene particles (3) produced in Production Example 3 were used instead of the ultrahigh molecular weight polyethylene particles (1), the rolling temperature was 145 ° C., and the thickness of the skive sheet was 3.3 mm. 1 was used to produce an ultra-high molecular weight polyethylene rolled molded sheet (stretching ratio: 3.0 times) having a thickness of 1.0 mm. Table 2 shows the tensile fracture strength and tear strength of the obtained sheet.

  The ultra-high molecular weight polyethylene rolled molded body obtained by the present invention is excellent in strength and heat resistance, so various tapes for industrial machines, linings for sports equipment such as skis, sheets, membranes, tubes, etc. Available for use.

Claims (1)

Using ultra-high molecular weight polyethylene particles satisfying at least any of the following properties (1), (2), (3), and (4), melt compression molding at a molding temperature of 150 ° C. to 250 ° C. and ultra high molecular weight After forming a polyethylene melt compression molded product, the ultra high molecular weight polyethylene melt compression molded product is rolled to a stretch ratio of 2 times or more, and at least satisfies the characteristics shown in (1) and (4). A method for producing an ultra-high-molecular-weight polyethylene rolled molded product characterized in that:
(1) Intrinsic viscosity ([η]) is 15 dl / g or more and 60 dl / g or less,
(2) Bulk density is 130kg / m ³ 700 kg / m or more ³ Less than,
(3) 1st scan melting point (Tm) when the temperature was raised from 0 ° C. to 230 ° C. (1st scan) with a differential scanning calorimeter (DSC). ₁ ) After that, after 5 minutes, the temperature was lowered to −20 ° C. at a rate of 10 ° C./min. After left for 5 minutes, the temperature was raised again from −20 ° C. to 230 ° C. at a rate of 10 ° C./min ( 2nd scan melting point (Tm) ₂ ) For each Tm ₁ And the Tm ₂ Difference (ΔTm = Tm ₁ -Tm ₂ ) Is 11 ° C. or higher and 30 ° C. or lower.
(4) The titanium content is 0.2 ppm or less or the measurement detection limit or less.