Ultra-high molecular weight polyethylene powder and molded article obtained by molding the ultra-high molecular weight polyethylene powder

Abstract

An ultra-high molecular weight polyethylene powder, wherein the viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 10×10 4 Above and 1000×10 4 Below, the difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder calculated by a specific method is greater than 3°C, and the liquid paraffin impregnation rate (weight increase rate) of the ultra-high molecular weight polyethylene powder calculated by a specific method is greater than 0.5% and less than 5.0%.

Description

Technical Field

[0001] The present invention relates to an ultra-high molecular weight polyethylene powder and a molded body obtained by molding the ultra-high molecular weight polyethylene powder. Background Art

[0002] Polyethylene is used in a variety of applications such as films, sheets, microporous films, fibers, foams, and tubes. Polyethylene is used because it is easy to melt-process and the resulting molded product has high mechanical strength, excellent chemical resistance, and excellent rigidity. Among them, ultra-high molecular weight polyethylene has higher mechanical strength due to its large molecular weight, excellent smoothness and wear resistance, and excellent chemical stability and long-term reliability.

[0003] However, ultra-high molecular weight polyethylene has low fluidity even when melted at a temperature above its melting point, and therefore the following methods are used: a compression molding method in which polyethylene powder is compressed and molded under heating and then cut; a molding method in which polyethylene powder is dissolved in a solvent such as liquid paraffin, then stretched and the solvent is removed to thereby mold it into a sheet or filament shape; etc.

[0004] Ultra-high molecular weight polyethylene is molded in a powder form, but the surface area of ​​the powder is larger than that of the pellets, and the powder has fine pores.

[0005] Regarding the pore state of polyethylene powder, for example, Patent Document 1 discloses a polyethylene powder that rapidly dissolves in a solvent and produces a molded body with little insoluble matter by adjusting the specific surface area determined by the BET method and the pore volume determined by the mercury intrusion method to appropriate ranges.

[0006] For example, Patent Document 2 discloses a polyethylene powder that can provide a molded body with less generation of undissolved matter by adjusting the ratio of the median diameter to the mode diameter of pores measured by mercury intrusion porosimetry within an appropriate range.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2017-88773

[0010] Patent Document 2: Japanese Patent Application Publication No. 2017-145306 Summary of the invention

[0011] Problems to be solved by the invention

[0012] As described above, the surface area of ​​ultra-high molecular weight polyethylene powder is larger than that of particles, and the powder has fine pores. Therefore, the shape, surface state, crystal state, pore state, etc. of the powder will change during heating, so when the ultra-high molecular weight polyethylene powder is molded, it is required to adjust to an appropriate temperature before dissolving, compressing, etc. In the case of compression molding of ultra-high molecular weight polyethylene powder, if the preheating temperature before compression is inappropriate, there is a tendency that bubbles remain in the molded body, or strain remains in the molded body, thereby causing deformation after cooling.

[0013] Regarding the polyethylene powder described in Patent Document 1, only the specific surface area and pore volume, which are the powder properties, are adjusted. In fact, the properties of the powder vary greatly at the temperature at which it is dissolved or melted, and there is room for improvement in molding processability.

[0014] In addition, regarding the polyethylene powder described in Patent Document 2, only the pore diameter of the powder is specified, and the pore diameter changes greatly during heating. Therefore, there is room for improvement in molding processability, and it is sometimes difficult to obtain a uniform molded body.

[0015] The present invention has been completed in view of the above situation, and its purpose is to provide an ultra-high molecular weight polyethylene powder with excellent processability, and a molded body (such as a microporous membrane, a high-strength fiber and a porous sintered body) with excellent dimensional accuracy (no wrinkles or unevenness) and high strength obtained by molding the ultra-high molecular weight polyethylene powder.

[0016] Means used to solve problems

[0017] The present inventors conducted intensive research to solve the above-mentioned problems and found that the above-mentioned problems can be solved by adjusting the difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder and adjusting the impregnation rate of liquid paraffin into the ultra-high molecular weight polyethylene powder, thereby completing the present invention.

[0018] That is, the present invention is as follows. [1]

[0020] An ultra-high molecular weight polyethylene powder, wherein the viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 10×10 4 Above and 1000×10 4 the following,

[0021] The difference between the swelling onset temperature and the dissolution onset temperature of the ultra-high molecular weight polyethylene powder determined by the following method is 3°C or more, and

[0022] The liquid paraffin impregnation rate (weight increase rate) of the ultra-high molecular weight polyethylene powder determined by the following method is 0.5% or more and 5.0% or less.

[0023] [Method for measuring swelling onset temperature and dissolution onset temperature]

[0024] While confirming with an optical microscope, arbitrarily select a particle of ultra-high molecular weight polyethylene powder with a long diameter and a short diameter of 120 μm or more and 130 μm or less. Place the selected particle of ultra-high molecular weight polyethylene powder (hereinafter also referred to as "measurement particle") on a cover glass, use a 2mL dropper to drip 1 drop of liquid paraffin on the measurement particle, and then place the cover glass so that the measurement particle is sandwiched in the middle. Then, place the cover glass sandwiching the measurement particle on a heating table, and use an optical microscope with a camera to observe the process of heating the measurement particle from room temperature to 150°C under the following heating conditions. In the heating step, an observation image of the measurement particle is taken every 6 seconds. After the measurement, the image analysis software is used to calculate the equivalent circle diameter of the measurement particle based on each observation image, and the swelling start temperature and the dissolution start temperature are judged as follows.

[0025] (Temperature rising conditions)

[0026] Heating rate from room temperature to 35°C: 5°C / min

[0027] Heating rate within the range of 35℃~80℃: 8℃ / min

[0028] Heating rate within the range of 80℃~150℃: 5℃ / min

[0029] [Swelling start temperature]

[0030] The equivalent circle diameter of the measured particle was calculated from the observed image obtained by photographing the measured particle using image analysis software. Based on the equivalent circle diameter of the measured particle at 80°C, the lowest temperature at which the equivalent circle diameter of the measured particle increased by 1% or more in the temperature range of 80°C to 150°C was taken as the swelling start temperature. The average value of the three measurements was taken as the final swelling start temperature.

[0031] [Melting start temperature]

[0032] The equivalent circle diameter of the measured particle was calculated from the observed image obtained by photographing the measured particle using image analysis software, and the measured temperature when the equivalent circle diameter of the measured particle showed the maximum value was taken as the dissolution start temperature. The average value of the three measurements was taken as the final dissolution start temperature.

[0033] [Calculation method of liquid paraffin impregnation rate (weight increase rate)]

[0034] A sample was prepared by mixing 10g of ultra-high molecular weight polyethylene powder and 30g of liquid paraffin. The prepared sample was placed in a metal container, covered with aluminum foil, and left at 70°C for 3 hours. Next, the sample was dried under reduced pressure at 110°C / reduced pressure (-0.1MPaG) for 5 hours. Then, the sample was washed and filtered three times using 10g of hexane, and then air-dried for more than 24 hours, and the weight of the ultra-high molecular weight polyethylene powder was measured. The liquid paraffin (LP) impregnation rate (weight increase rate) was calculated based on the increase rate of the weight of the ultra-high molecular weight polyethylene powder after impregnation with liquid paraffin (weight after impregnation) relative to the original weight of the ultra-high molecular weight polyethylene powder (weight before impregnation), using the following formula:

[0035] Liquid paraffin impregnation rate (%) = (weight after impregnation - weight before impregnation) / weight before impregnation × 100. [2]

[0037] The ultra-high molecular weight polyethylene powder as described in [1], wherein the pore specific surface area is 0.10 m 2 / g or more and 1.50m 2 / g or less. [3]

[0039] The ultra-high molecular weight polyethylene powder according to [1] or [2], wherein the pore volume is 0.30 mL / g or more and 1.70 mL / g or less when the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is measured by a mercury porosimeter. [4]

[0041] The ultra-high molecular weight polyethylene powder according to any one of [1] to [3], wherein the average pore diameter is 0.10 μm or more and 0.80 μm or less when the ultra-high molecular weight polyethylene powder having a particle diameter of less than 75 μm is measured by a mercury porosimeter. [5]

[0043] The ultra-high molecular weight polyethylene powder according to any one of [1] to [4], wherein the crystallinity of the ultra-high molecular weight polyethylene powder is greater than or equal to 70% and less than 82%. [6]

[0045] The ultrahigh molecular weight polyethylene powder according to any one of [1] to [5], wherein the proportion of the ultrahigh molecular weight polyethylene powder having a particle size of less than 75 μm is 35% by mass or less when the entire ultrahigh molecular weight polyethylene powder is taken as 100% by mass. [7]

[0047] The ultra-high molecular weight polyethylene powder according to any one of [1] to [6], wherein the ultra-high molecular weight polyethylene powder has an average particle size (D50) of 60 μm or more and 140 μm or less. [8]

[0049] The ultra-high molecular weight polyethylene powder according to any one of [1] to [7], wherein the titanium content in the ultra-high molecular weight polyethylene powder is 0.1 ppm or more and 5 ppm or less. [9]

[0051] The ultra-high molecular weight polyethylene powder according to any one of [1] to [8], wherein the aluminum content in the ultra-high molecular weight polyethylene powder is 0.1 ppm or more and 5 ppm or less.

[10]

[0053] A molded body obtained by molding the ultra-high molecular weight polyethylene powder according to any one of [1] to [9].

[11]

[0055] The molded body as described in

[10] , wherein the molded body is a microporous film, a high-strength fiber or a sintered body.

[0056] Effects of the Invention

[0057] According to the present invention, it is possible to obtain an ultra-high molecular weight polyethylene powder having excellent processability, and a molded body (e.g., a microporous film, a high-strength fiber, and a porous sintered body) having excellent dimensional accuracy (no wrinkles or unevenness) and high strength obtained by molding the ultra-high molecular weight polyethylene powder. DETAILED DESCRIPTION

[0058] Hereinafter, a mode for implementing the present invention (hereinafter also referred to as "this embodiment") will be described in detail. It should be noted that the present invention is not limited to this embodiment, and can be implemented in various modifications within the scope of the gist thereof.

[0059] [Ultra-high molecular weight polyethylene powder]

[0060] The viscosity average molecular weight of the ultra-high molecular weight polyethylene powder (hereinafter, also simply referred to as "powder") of this embodiment is 10×10 4 Above and 1000×10 4 the following.

[0061] In addition, from the viewpoint of moldability and final physical properties, the viscosity average molecular weight of the ultra-high molecular weight polyethylene powder of this embodiment is preferably within a range of 10×10 4 Above and 900×10 4 The following range is more preferably 10×10 4Above and 800×10 4 It should be noted that the viscosity average molecular weight in this embodiment refers to the value obtained by converting the intrinsic viscosity obtained from the specific viscosity of the polymer solution into the viscosity average molecular weight. Specifically, the viscosity average molecular weight can be obtained by the method described in the examples described below.

[0062] The ultrahigh molecular weight polyethylene powder of the present embodiment is preferably a powder containing an ethylene homopolymer and / or a copolymer of ethylene and an olefin copolymerizable with ethylene (hereinafter also referred to as a comonomer) (hereinafter also referred to as an ethylene-based polymer).

[0063] The olefin copolymerizable with ethylene is not particularly limited, and specifically, for example, alpha-olefins having 3 to 15 carbon atoms, cyclic olefins having 3 to 15 carbon atoms, and olefins of the formula CH2=CHR 1 (Here, R 1 is an aryl group having 6 to 12 carbon atoms), and at least one comonomer selected from the group consisting of a linear, branched or cyclic diene having 3 to 15 carbon atoms. Among these, α-olefins having 3 to 15 carbon atoms are preferred.

[0064] The α-olefin is not particularly limited, and examples thereof include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, and 1-tetradecene.

[0065] When the ethylene polymer used in the present embodiment includes a comonomer, the content of the comonomer unit in the ethylene polymer is preferably 0.01 mol % or more and 5 mol % or less, more preferably 0.01 mol % or more and 2 mol % or less, further preferably 0.01 mol % or more and 1 mol % or less. It should be noted that, from the viewpoint of suppressing the decomposition rate, the amount of the comonomer is preferably 5 mol % or less.

[0066] [Viscosity average molecular weight]

[0067] The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder of this embodiment is 10×10 4 Above and 1000×10 4 Below, preferably 10×10 4 Above and 900×10 4 Below, more preferably 10×10 4 Above and 800×10 4 the following.

[0068] The ultra-high molecular weight polyethylene powder of this embodiment has a viscosity average molecular weight (Mv) of 10×10 4 The strength is further improved. In addition, the viscosity average molecular weight (Mv) is 1000×10 4 Thereafter, the moldability is further improved.

[0069] If the ultra-high molecular weight polyethylene powder of this embodiment is used for a molded product such as a microporous membrane, the viscosity average molecular weight (Mv) is preferably equal to or greater than 10×10 4 And less than 300×10 4 , more preferably 10×10 4 Above and 200×10 4 If the ultra-high molecular weight polyethylene powder of this embodiment is used for a molded product such as a high-strength fiber, the viscosity average molecular weight (Mv) is preferably 300×10 4 Above and 1000×10 4 Below, more preferably 300×10 4 Above and 800×10 4 the following.

[0070] There are no particular restrictions on the method for controlling the viscosity average molecular weight (Mv) within the above range, and for example, there can be cited a method of changing the polymerization temperature of the reactor when homopolymerizing ethylene or copolymerizing ethylene with an olefin copolymerizable with ethylene. The higher the polymerization temperature, the lower the viscosity average molecular weight (Mv) tends to be, and the lower the polymerization temperature, the higher the viscosity average molecular weight (Mv) tends to be. In addition, there are no particular restrictions on other methods for adjusting the viscosity average molecular weight (Mv) within the above range, and for example, there can be cited a method of changing the type of organic metal compound used as a co-catalyst when homopolymerizing ethylene or copolymerizing ethylene with an olefin copolymerizable with ethylene. In addition, there are no particular restrictions on other methods for adjusting the viscosity average molecular weight (Mv) within the above range, and for example, there can be cited a method of adding a chain transfer agent when homopolymerizing ethylene or copolymerizing ethylene with an olefin copolymerizable with ethylene. By adding a chain transfer agent, the viscosity average molecular weight of the generated ultra-high molecular weight polyethylene tends to decrease even at the same polymerization temperature.

[0071] [Swelling start temperature and dissolution start temperature of ultra-high molecular weight polyethylene powder]

[0072] The difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder of the present embodiment is 3°C or more, preferably 4°C or more, more preferably 5°C or more, and further preferably 7°C or more. The upper limit of the difference between the swelling start temperature and the dissolution start temperature is not particularly limited, and is, for example, 50°C or less, preferably 25°C or less, and more preferably 20°C or less. In addition, the difference between the swelling start temperature and the dissolution start temperature is preferably 3°C or more and 25°C or less, more preferably 4°C or more and 20°C or less, further preferably 5°C or more and 20°C or less, and particularly preferably 7°C or more and 20°C or less. By making the difference between the swelling start temperature and the dissolution start temperature 3°C or more, in the molding method of dissolving in liquid paraffin, sufficient time can be obtained until the liquid paraffin is impregnated into the ultra-high molecular weight polyethylene powder. During the molding process, sufficient liquid paraffin is impregnated into the center of the powder before the ultra-high molecular weight polyethylene powder is dissolved, so that a uniform gel without agglomerates (a substance obtained by melting and fusing the ultra-high molecular weight polyethylene powders) can be obtained. As a result, the ultra-high molecular weight polyethylene powder of the present embodiment can suppress defects (foreign matter in the molded body (lumps, substances remaining in an unmelted state, etc.)) and the amount of material scale during the molding process, and can obtain a molded body without uneven thickness. In addition, by making the difference between the swelling start temperature and the dissolution start temperature more than 3°C, when the ultra-high molecular weight polyethylene powder and liquid paraffin are mixed using a Labo Plastomill mixer, a uniform gel can be obtained even if the mixing time is shortened, thereby improving productivity. In addition, by sufficiently obtaining time until the liquid paraffin is impregnated into the ultra-high molecular weight polyethylene powder, the entanglement of the molecular chains can be untangled, and the obtained molded body can achieve high film strength. As can be seen from the above, the ultra-high molecular weight polyethylene powder of the present embodiment can produce a uniform gel, and by using the gel, a molded body with high film strength can be obtained.

[0073] It should be noted that the swelling onset temperature and the dissolution onset temperature were calculated according to the following method.

[0074] [Method for measuring swelling onset temperature and dissolution onset temperature]

[0075] While confirming with an optical microscope, arbitrarily select a particle of ultra-high molecular weight polyethylene powder with a long diameter and a short diameter of 120 μm or more and 130 μm or less. Place the selected particle of ultra-high molecular weight polyethylene powder (hereinafter also referred to as "measurement particle") on a cover glass, use a 2mL dropper to drip 1 drop of liquid paraffin on the measurement particle, and then place the cover glass so that the measurement particle is sandwiched in the middle. Then, place the cover glass sandwiching the measurement particle on a heating table, and use an optical microscope with a camera to observe the process of heating the measurement particle from room temperature to 150°C under the following heating conditions. In the heating step, an observation image of the measurement particle is taken every 6 seconds. After the measurement, the image analysis software is used to calculate the equivalent circle diameter of the measurement particle based on each observation image, and the swelling start temperature and the dissolution start temperature are judged as follows.

[0076] (Temperature rising conditions)

[0077] Heating rate from room temperature to 35°C: 5°C / min

[0078] Heating rate within the range of 35℃~80℃: 8℃ / min

[0079] Heating rate within the range of 80℃~150℃: 5℃ / min

[0080] [Swelling start temperature]

[0081] The equivalent circle diameter of the measured particle was calculated from the observed image obtained by photographing the measured particle using image analysis software. Based on the equivalent circle diameter of the measured particle at 80°C, the lowest temperature at which the equivalent circle diameter of the measured particle increased by 1% or more in the temperature range of 80°C to 150°C was taken as the swelling start temperature. The average value of the three measurements was taken as the final swelling start temperature.

[0082] [Melting start temperature]

[0083] The equivalent circle diameter of the measured particle was calculated from the observed image obtained by photographing the measured particle using image analysis software, and the measured temperature when the equivalent circle diameter of the measured particle showed the maximum value was taken as the dissolution start temperature. The average value of the three measurements was taken as the final dissolution start temperature.

[0084] It should be noted that, in the present embodiment, the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder can be accurately measured by using particles of ultra-high molecular weight polyethylene powder having a major diameter and a minor diameter of 120 μm or more and 130 μm or less as the measurement particles. However, in consideration of the fact that there are no particles of ultra-high molecular weight polyethylene powder having a major diameter and a minor diameter of 120 μm or more and 130 μm or less, particles of ultra-high molecular weight polyethylene powder within the range of an average particle size (D50) ±10 μm can also be used as the measurement particles of the above-mentioned swelling start temperature and the dissolution start temperature. If the particles of the ultra-high molecular weight polyethylene powder are within the range of an average particle size (D50) ±10 μm, there is a tendency to obtain the same swelling start temperature and the dissolution start temperature as the case of using particles of ultra-high molecular weight polyethylene powder having a major diameter and a minor diameter of 120 μm or more and 130 μm or less.

[0085] [Permeation rate of liquid paraffin into ultra-high molecular weight polyethylene powder (weight increase rate)]

[0086] The liquid paraffin impregnation rate (weight increase rate, hereinafter also referred to as "liquid paraffin impregnation rate") of the ultra-high molecular weight polyethylene powder of the present embodiment obtained by the following method is 0.5% or more and 5.0% or less, preferably 1.0% or more and 4.5% or less, and more preferably 2.0% or more and 4.5% or less. For the ultra-high molecular weight polyethylene powder of the present embodiment, by adjusting the liquid paraffin impregnation rate to 0.5% or more, sufficient liquid paraffin is impregnated into the center of the ultra-high molecular weight polyethylene powder, so that a uniform gel without agglomerates (a substance obtained by melting and fusing the ultra-high molecular weight polyethylene powders with each other) can be obtained. As a result, the ultra-high molecular weight polyethylene powder of the present embodiment can suppress defects and material scale during molding processing, and can obtain a molded body without uneven thickness. In addition, for the ultra-high molecular weight polyethylene powder of the present embodiment, by adjusting the liquid paraffin impregnation rate to 5.0% or less, a molded body with high film strength and no wrinkles can be obtained. This is believed to be because, when the liquid paraffin impregnation rate into the ultra-high molecular weight polyethylene powder is 5.0% or less, the proportion of the amorphous part is reduced, and it is easy to make the film high-strength. In addition, it is speculated that when the proportion of the amorphous part is low, the entanglement of the molecular chains can be well untied by dispersing the liquid paraffin to form a uniform gel, thereby suppressing the difference in the degree of stretching during film stretching, resulting in less wrinkles and an increase in film strength.

[0087] That is, for the ultrahigh molecular weight polyethylene powder of this embodiment, by adjusting the impregnation rate of liquid paraffin impregnated into the powder to 5.0% or less, the ratio of the crystalline part to the amorphous part is optimized, resulting in a molded body with high film strength and few wrinkles.

[0088] The impregnation rate of the liquid paraffin into the ultra-high molecular weight polyethylene powder was determined by the following method.

[0089] [Calculation method of liquid paraffin impregnation rate (weight increase rate)]

[0090] 10g of ultra-high molecular weight polyethylene powder and 30g of liquid paraffin are mixed to make a sample. The prepared sample is placed in a metal container, covered with aluminum foil, and placed at 70°C for 3 hours. Next, the sample is dried under reduced pressure at 110°C / reduced pressure (-0.1MPaG) for 5 hours. Then, the sample is washed and filtered 3 times with 10g of hexane, then air-dried for more than 24 hours, and the weight of the ultra-high molecular weight polyethylene powder is measured. The liquid paraffin (LP) infiltration rate (weight increase rate) is calculated by the following formula based on the increase rate of the weight of the ultra-high molecular weight polyethylene powder after infiltration of liquid paraffin (weight after infiltration) relative to the original weight of the ultra-high molecular weight polyethylene powder (weight before infiltration).

[0091] Liquid paraffin impregnation rate (%) = (weight after impregnation - weight before impregnation) / weight before impregnation × 100

[0092] [Means of Implementation]

[0093] For the ultra-high molecular weight polyethylene powder of this embodiment, there is no particular limitation on the method of adjusting the difference between the swelling start temperature and the dissolution start temperature to 3°C or more and the liquid paraffin impregnation rate to 0.5% or more and 5.0% or less, and examples thereof include: a method of minimizing the difference in pore diameter between the center and the surface of the ultra-high molecular weight polyethylene powder and the difference in pore volume between the center and the surface, and a method of minimizing the difference in the ratio of the crystalline part to the amorphous part. There is no particular limitation on the method of producing such an ultra-high molecular weight polyethylene powder, and examples thereof include a method of increasing the catalyst activity at the end of polymerization and adjusting the drying temperature and drying time.

[0094] The specific method for improving the catalyst activity at the end of the polymerization is not particularly limited, and examples thereof include a method of increasing the pressure in the reactor at the end of the polymerization and a method of extending the slurry residence time.

[0095] The mechanism by which the difference between the swelling start temperature and the dissolution start temperature and the liquid paraffin impregnation rate can be controlled by such a method is not clear, and it is speculated as follows. Generally, when the catalyst is introduced into the system, it reacts violently at the beginning of the reaction, and then the reaction activity gradually decreases. The polymer chains generated at the beginning of the reaction are squeezed outward from the center of the catalyst (the center of the powder). Therefore, there are polymer chains generated at the beginning of the reaction on the surface of the powder. The catalyst activity decreases at the end of the reaction, so the polymer is slowly generated. Therefore, the powder structure (the pores on the powder surface are large, and the pores in the center of the powder are small) and the polyethylene properties (the ratio of the crystalline part and the amorphous part) are different on the surface and center of the powder. Therefore, it is believed that by increasing the pressure in the reactor at the end of the polymerization, or extending the slurry residence time, it is possible to adjust the structure and physical properties to be uniform at the center and surface of the powder.

[0096] In addition, there is no particular limitation on the specific method for adjusting the drying temperature and drying time, and for example, the following three-stage drying can be cited. The following methods can be cited: the first stage is to spray a mixed solution of water: methanol = 20:80 into the dryer, and while it is impregnated into the ultra-high molecular weight polyethylene powder, dry it at a high temperature of the crystallization temperature ±5°C for a time equivalent to 1 / 4 of the total drying time; the second stage is to dry it at a temperature of 90°C or more and 105°C or less for a time equivalent to 2 / 4 of the total drying time; the third stage is to dry it at a low temperature of 60°C or more and less than 90°C for a time equivalent to 1 / 4 of the total drying time. It is believed that by setting such drying conditions, the pore size and pore volume of the center and surface of the polyethylene powder can be adjusted by volatilizing methanol and water in sequence, and the annealing of the polyethylene powder can be prevented by gradually lowering the temperature and drying at a low temperature for a certain time, and the ratio of the crystalline part and the amorphous part of the center and surface of the polyethylene powder can be adjusted.

[0097] [Pore specific surface area when BET (Kr) is measured for ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm]

[0098] When the ultra-high molecular weight polyethylene powder of the present embodiment is measured by the BET method based on krypton gas adsorption (hereinafter also referred to as "BET (Kr)"), the pore specific surface area is preferably 0.10 m 2 / g or more and 1.50m 2 / g or less, more preferably 0.10m 2 / g or more and 1.40m 2 / g or less, more preferably 0.20m 2 / g or more and 1.20m 2 / g or less. The pore specific surface area of ​​ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm is 0.10 m2 / g or more, during the molding process, before the ultra-high molecular weight polyethylene powder dissolves, sufficient liquid paraffin is impregnated into the center of the powder, so there is a tendency to obtain a uniform gel without agglomeration (a substance obtained by melting and fusing the ultra-high molecular weight polyethylene powders with each other). As a result, the ultra-high molecular weight polyethylene powder of this embodiment has a tendency to suppress defects and material scale during molding, and to obtain a molded body without uneven thickness. In addition, the ultra-high molecular weight polyethylene powder of this embodiment also has the following tendency: when mixing with liquid paraffin using a LaboPlastomill mixer, a uniform gel can be obtained even if the mixing time is shortened, and since the liquid paraffin is fully impregnated into the ultra-high molecular weight polyethylene powder, the entanglement of the molecular chains can be untied in a short time, and the obtained molded body can achieve high strength of the film.

[0099] In addition, regarding the ultra-high molecular weight polyethylene powder of the present embodiment, the pore specific surface area when the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is measured by BET (Kr) is 1.50 m 2 / g or less, the ratio of the crystalline part to the amorphous part, which affects the formation of a high-strength molded body, can be optimized. 2 When the particle size is less than 100 μm, the powder has a small number of pores and is dense, so the ratio of the amorphous part is reduced and the strength tends to be improved.

[0100] In this embodiment, there is no particular limitation on the method for controlling the pore specific surface area within the above range when performing BET (Kr) measurement on ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm. For example, methods of increasing the catalyst activity at the end of polymerization and adjusting the drying temperature and drying time may be considered.

[0101] The specific method for improving the catalyst activity at the end of the polymerization is not particularly limited, and examples thereof include a method of increasing the pressure in the reactor at the end of the polymerization and a method of extending the slurry residence time.

[0102] [Pore volume of ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm measured by mercury porosimetry]

[0103] The ultrahigh molecular weight polyethylene powder of the present embodiment preferably has a pore volume of 0.30 mL / g or more and 1.70 mL / g or less, more preferably 0.30 mL / g or more and 1.30 mL / g or less, further preferably 0.40 mL / g or more and 1.20 mL / g or less, and particularly preferably 0.50 mL / g or more and 1.00 mL or less, when measured by a mercury intrusion meter for an ultrahigh molecular weight polyethylene powder having a particle size of less than 75 μm. Since the ultrahigh molecular weight polyethylene powder of the present embodiment has a pore volume of 0.30 mL / g or more when measured by a mercury intrusion meter for an ultrahigh molecular weight polyethylene powder having a particle size of less than 75 μm, sufficient liquid paraffin is impregnated into the center of the powder before the ultrahigh molecular weight polyethylene powder is dissolved during molding, so that a uniform gel without agglomerates (a substance obtained by melting and fusing the ultrahigh molecular weight polyethylene powders) can be obtained, and as a result, there is a tendency that defects and scale can be suppressed during molding, and a molded body without uneven thickness can be obtained. In addition, the ultra-high molecular weight polyethylene powder of this embodiment also has the following tendency: when it is kneaded with liquid paraffin using a Labo Plastomill mixer, a uniform gel can be obtained even if the kneading time is shortened, and because the liquid paraffin is fully impregnated into the ultra-high molecular weight polyethylene powder, the entanglement of the molecular chains can be untangled in a short time, and the resulting molded body has a tendency to achieve high film strength.

[0104] In addition, for the ultra-high molecular weight polyethylene powder of the present embodiment, the ratio of the crystalline part and the amorphous part, which has an influence on obtaining a high-strength molded body, can be optimized by measuring the pore volume of the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm by a mercury intrusion instrument to be 1.70 mL / g or less. That is, it is considered that when the pore volume is 1.70 mL / g or less, the number of pores is small and the powder is dense, so there is a tendency that the ratio of the amorphous part is reduced and the strength is improved.

[0105] In this embodiment, there is no particular limitation on the method for controlling the pore volume within the above range when measuring ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm using a mercury porosimeter. For example, methods of increasing the catalyst activity at the end of polymerization and adjusting the drying temperature and drying time may be considered.

[0106] The specific method for improving the catalyst activity at the end of the polymerization is not particularly limited, and examples thereof include a method of increasing the pressure in the reactor at the end of the polymerization and a method of extending the slurry residence time.

[0107] [Average pore size when measuring ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm using a mercury porosimeter]

[0108] The ultra-high molecular weight polyethylene powder of the present embodiment preferably has an average pore size of 0.10 μm or more and 0.80 μm or less, more preferably 0.10 μm or more and 0.50 μm or less, further preferably 0.10 μm or more and 0.45 μm or less, and particularly preferably 0.20 μm or more and 0.40 μm or less, when measured by a mercury intrusion meter on an ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm. Since the ultra-high molecular weight polyethylene powder of the present embodiment has an average pore size of 0.10 μm or more when measured by a mercury intrusion meter on an ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm, sufficient liquid paraffin is impregnated into the center of the powder before the ultra-high molecular weight polyethylene powder is dissolved during molding, and thus a uniform gel without agglomerates (a substance obtained by melting and fusing the ultra-high molecular weight polyethylene powders) can be obtained, and as a result, there is a tendency that defects and scale can be suppressed during molding, and a molded body without uneven thickness can be obtained. In addition, the ultra-high molecular weight polyethylene powder of this embodiment also has the following tendency: when it is kneaded with liquid paraffin using a Labo Plastomill mixer, a uniform gel can be obtained even if the kneading time is shortened, and because the liquid paraffin is fully impregnated into the ultra-high molecular weight polyethylene powder, the entanglement of the molecular chains can be untangled in a short time, and the obtained molded body can achieve high film strength.

[0109] In addition, for the ultra-high molecular weight polyethylene powder of the present embodiment, the average pore size when measured by a mercury intrusion instrument on the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is 0.80 μm or less, so that the ratio of the crystalline part and the amorphous part that have an influence on obtaining a high-strength molded body can be optimized. That is, it is considered that when the average pore size is 0.80 μm or less, the pores are small and the powder is dense, so there is a tendency that the ratio of the amorphous part is reduced and the strength is improved.

[0110] In this embodiment, there is no particular limitation on the method for controlling the average pore size within the above range when measuring ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm using a mercury porosimeter. For example, methods of increasing the catalyst activity at the end of polymerization and adjusting the drying temperature and drying time may be considered.

[0111] The specific method for improving the catalyst activity at the end of the polymerization is not particularly limited, and examples thereof include a method of increasing the pressure in the reactor at the end of the polymerization and a method of extending the slurry residence time.

[0112] [Crystallinity of ultra-high molecular weight polyethylene powder]

[0113] The crystallinity of the ultra-high molecular weight polyethylene powder of this embodiment is preferably 70% or more and 82% or less, more preferably 70% or more and 80% or less, further preferably 70% or more and 78% or less, and particularly preferably 70% or more and 75% or less. The crystallinity of the ultra-high molecular weight polyethylene powder of this embodiment is 70% or more, which tends to produce a high-strength molded body. In addition, the crystallinity of the ultra-high molecular weight polyethylene powder of this embodiment is 82% or less, which tends to be easy to mold and have excellent processability.

[0114] In the present embodiment, there is no particular limitation on the method for controlling the crystallinity of the ultrahigh molecular weight polyethylene powder within the above range, and for example, a method of adjusting the drying temperature and the drying time may be considered.

[0115] In the present embodiment, the crystallinity can be measured by the method described in Examples described later.

[0116] [Ratio of ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm]

[0117] For the ultra-high molecular weight polyethylene powder of the present embodiment, when the ultra-high molecular weight polyethylene powder as a whole is set to 100% by mass, the proportion of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm is preferably 35% by mass or less, more preferably 33% by mass or less, and further preferably 30% by mass or less. The lower limit of the proportion of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm is not particularly limited. For example, when the ultra-high molecular weight polyethylene powder as a whole is set to 100% by mass, the lower limit of the proportion of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm is 1% by mass. For the ultra-high molecular weight polyethylene powder of the present embodiment, by making the proportion of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm less than 35% by mass, a uniform gel without agglomeration can be obtained. That is, when the proportion of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm is less than 35% by mass, it is possible to suppress the melting and fusion of the micropowders before the ultra-high molecular weight polyethylene powder swells, so that it is not easy to form agglomerates. From the above, it can be seen that for the ultra-high molecular weight polyethylene powder of this embodiment, by adjusting the proportion of ultra-high molecular weight polyethylene powder with a particle size less than 75 μm to less than 35 mass%, there is a tendency to suppress defects and material scale during molding processing, and to obtain a molded body without uneven thickness.

[0118] In the present embodiment, the ratio of the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm can be measured by the method described in the examples described later.

[0119] [Average particle size of ultra-high molecular weight polyethylene powder (D50)]

[0120] The average particle size (D50) of the ultra-high molecular weight polyethylene powder of the present embodiment is preferably 60 μm or more and 140 μm or less, more preferably 60 μm or more and 120 μm or less, further preferably 60 μm or more and 115 μm or less, and particularly preferably 60 μm or more and 100 μm or less. The average particle size (D50) of the ultra-high molecular weight polyethylene powder of the present embodiment is 60 μm or more, which has the tendency to suppress the melting and fusion of the micropowders before the ultra-high molecular weight polyethylene powder swells to form agglomerates. As a result, the ultra-high molecular weight polyethylene powder of the present embodiment has the tendency to suppress defects and the amount of material scale during molding, and to obtain a molded body without uneven thickness. In addition, the average particle size (D50) of the ultra-high molecular weight polyethylene powder of the present embodiment is 140 μm or less, which has the tendency to suppress poor swelling of coarse powder. As a result, the ultra-high molecular weight polyethylene powder of the present embodiment has the tendency to suppress defects and the amount of material scale during molding, and to obtain a molded body without uneven thickness.

[0121] In the present embodiment, the average particle size (D50) of the ultra-high molecular weight polyethylene powder can be measured by the method described in Examples described later.

[0122] [Titanium content and aluminum content in ultra-high molecular weight polyethylene powder]

[0123] The titanium (Ti) content in the ultra-high molecular weight polyethylene powder of the present embodiment is preferably 0.1 ppm or more and 5.0 ppm or less, more preferably 0.5 ppm or more and 5.0 ppm or less, and further preferably 1.0 ppm or more and 4.0 ppm or less. In addition, the aluminum (Al) content in the ultra-high molecular weight polyethylene powder of the present embodiment is preferably 0.1 ppm or more and 5.0 ppm or less, more preferably 0.1 ppm or more and 4.0 ppm or less, and further preferably 0.1 ppm or more and 3.5 ppm or less.

[0124] For the ultra-high molecular weight polyethylene powder of the present embodiment, by adjusting the titanium content and the aluminum content to such a range, there is a tendency that the thermal stability is more excellent and the long-term stability of the obtained molded body is more excellent. In addition, there is a tendency that can suppress the reaction with the antioxidant or heat stabilizer added during processing, and can suppress the tendency of the molded body coloring caused by the generation of an organic metal complex. In addition, for the ultra-high molecular weight polyethylene powder of the present embodiment, by adjusting the titanium content and the aluminum content to the above range, a wire with uniform wire diameter can be obtained when the fiber is made, and a film with uniform film thickness can be obtained when the film is made. It should be noted that, in general, the tendency of uneven thickness of the molded body caused by the amount of metal from the catalyst residue remaining in the ultra-high molecular weight polyethylene powder is strong. It should be noted that the content of Ti and Al in the ultra-high molecular weight polyethylene powder can be controlled by the productivity of ethylene homopolymer or ethylene polymer per unit catalyst. The productivity of ethylene homopolymer or ethylene polymer can be controlled by the polymerization temperature, polymerization pressure, and slurry concentration of the reactor during manufacturing. That is, in order to improve the productivity of the ethylene homopolymer or ethylene polymer used in the present embodiment, there is no particular limitation, for example, increasing the polymerization temperature, increasing the polymerization pressure and / or increasing the slurry concentration can be cited. As other methods, the amount of aluminum can also be controlled by selecting the type of the co-catalyst component, reducing the concentration of the co-catalyst component, and utilizing acid or alkali to clean the ethylene homopolymer or ethylene polymer when the ethylene homopolymer or ethylene polymer is obtained by polymerization. It should be noted that, in the present embodiment, the determination of the content of Ti and Al can be carried out by the method described in the embodiments described later.

[0125] [Method for producing ultra-high molecular weight polyethylene powder]

[0126] (Catalyst component)

[0127] The catalyst component for producing the ultra-high molecular weight polyethylene powder of the present embodiment is not particularly limited, and examples thereof include common Ziegler-Natta catalysts.

[0128] <Ziegler-Natta catalyst>

[0129] As the Ziegler-Natta catalyst, an olefin polymerization catalyst is preferably an olefin polymerization catalyst comprising a solid catalyst component [A] and an organometallic compound component [B], wherein the solid catalyst component [A] is produced by reacting an organomagnesium compound (A-1) soluble in an inert hydrocarbon solvent represented by the following formula 1 with a titanium compound (A-2) represented by the following formula 2.

[0130] (A-1): (M 1 ) α (Mg) β (R 2) a (R 3 ) b (Y 1 ) c ……Formula 1

[0131] (In Formula 1, M 1 is a metal atom belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table, R 2 and R 3 is a hydrocarbon group having 2 or more and 20 or less carbon atoms, Y 1 is alkoxy, silyloxy, allyloxy, amino, amide, -N=CR 4 ,R 5 、-SR 6 (Among them, R 4 , R 5 and R 6 represents a hydrocarbon group having 1 to 20 carbon atoms. When c is 2, Y 1 α, β, a, b and c are real numbers satisfying the following relationship: 0≤α, 0<β, 0≤a, 0≤b, 0≤c, 0<a+b, 0≤c / (α+β)≤2, nα+2β=a+b+c (where n represents M 1 valence.

[0132] (A-2): Ti(OR 7 ) d X 1 (4-d) ……Formula 2

[0133] (In Formula 2, d is a real number greater than or equal to 0 and less than or equal to 4, R 7 is a hydrocarbon group having 1 to 20 carbon atoms, X 1 is a halogen atom.)

[0134] It should be noted that the inert hydrocarbon solvent used in the reaction of (A-1) and (A-2) is not particularly limited, and specific examples thereof include aliphatic hydrocarbons such as pentane, hexane, and heptane; aromatic hydrocarbons such as benzene and toluene; and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane.

[0135] First, (A-1) is described. (A-1) is shown in the form of an organic magnesium complex soluble in an inert hydrocarbon solvent, and includes all dihydrocarbyl magnesium compounds and complexes of dihydrocarbyl magnesium compounds and other metal compounds. The relationship between the symbols α, β, a, b, and c is nα+2β=a+b+c, which shows the valence of the metal atom and the stoichiometry of the substituent.

[0136] In formula 1, as R2 and R 3 The hydrocarbon group represented by is not particularly limited to a hydrocarbon group having 2 or more and 20 or less carbon atoms, and specifically is an alkyl group, a cycloalkyl group or an aryl group, for example, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, cyclohexyl group, phenyl group, etc. Among them, an alkyl group is preferred. In the case of α>0, the metal atom M 1 As the metal atom, metal atoms belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table can be used, for example, zinc, boron, aluminum, etc. Among them, aluminum and zinc are preferred.

[0137] Magnesium relative to metal atoms M 1 The ratio β / α is not particularly limited, but is preferably 0.1 to 30, and more preferably 0.5 to 10. In the case of using a predetermined organomagnesium compound with α=0, for example, in R 2 In the case of 1-methylpropyl, etc., it is soluble in an inert hydrocarbon solvent, and such a compound also produces satisfactory results in this embodiment. In Formula 1, when α=0, it is recommended that R 2 and R 3 Satisfies any one of the three groups: group (1), group (2) and group (3) shown below.

[0138] Group (1): R 2 and R 3 At least one of them is a secondary or tertiary alkyl group having 4 or more and 6 or less carbon atoms, preferably R 2 and R 3 are all alkyl groups having 4 or more and 6 or less carbon atoms and R 2 and R 3 At least one of them is a secondary alkyl group or a tertiary alkyl group.

[0139] Group (2): R 2 With R 3 are alkyl groups with different carbon number, preferably R 2 is an alkyl group having 2 or 3 carbon atoms and R 3 It is an alkyl group having 4 or more carbon atoms.

[0140] Group (3): R 2 and R 3 At least one of them is a hydrocarbon group having 6 or more carbon atoms, and it is preferred that R 2 and R 3 The total number of carbon atoms contained in the alkyl group is 12 or more.

[0141] These groups are specifically shown below. As the secondary alkyl group or tertiary alkyl group having 4 to 6 carbon atoms in group (1), specifically, for example, 1-methylpropyl group, 2-methylpropyl group, 1,1-dimethylethyl group, 2-methylbutyl group, 2-ethylpropyl group, 2,2-dimethylpropyl group, 2-methylpentyl group, 2-ethylbutyl group, 2,2-dimethylbutyl group, 2-methyl-2-ethylpropyl group, etc. Among them, 1-methylpropyl group is particularly preferred.

[0142] In addition, examples of the alkyl group having 2 or 3 carbon atoms in group (2) include, for example, ethyl, 1-methylethyl, propyl, etc. Among them, ethyl is particularly preferred. In addition, examples of the alkyl group having 4 or more carbon atoms are not particularly limited, and examples thereof include, for example, butyl, pentyl, hexyl, heptyl, octyl, etc. Among them, butyl and hexyl are particularly preferred.

[0143] In addition, the hydrocarbon group having 6 or more carbon atoms in group (3) is not particularly limited, and specific examples thereof include hexyl, heptyl, octyl, nonyl, decyl, phenyl, 2-naphthyl, etc. Among the hydrocarbon groups, alkyl groups are preferred, and among the alkyl groups, hexyl and octyl groups are particularly preferred.

[0144] Generally, when the number of carbon atoms contained in the alkyl group increases, it tends to be easily dissolved in an inert hydrocarbon solvent and has a tendency to increase the viscosity of the solution. Therefore, it is preferred to use an alkyl group with a moderately long chain in operation. It should be noted that the above-mentioned organomagnesium compound can be used after dilution with an inert hydrocarbon solvent, and can be used without problem even if a trace amount of Lewis basic compounds such as ether, ester, amine, etc. is contained or remains in the solution.

[0145] Next, for Y 1 In Formula 1, Y 1 is alkoxy, silyloxy, allyloxy, amino, amide, -N=CR 4 ,R 5 、-SR 6 (Among them, R 4 , R 5 and R 6 Each independently represents any one of a hydrocarbon group having 2 to 20 carbon atoms) and a β-keto acid residue.

[0146] As in Formula 1, R 4 , R 5 and R 6The hydrocarbon group represented by is preferably an alkyl group or an aryl group having 1 to 12 carbon atoms, and particularly preferably an alkyl group or an aryl group having 3 to 10 carbon atoms. There are no particular restrictions, and examples thereof include methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 1,1-dimethylethyl, pentyl, hexyl, 2-methylpentyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylhexyl, 2-ethyl-4-methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, octyl, nonyl, decyl, phenyl, naphthyl, etc. Among them, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl are particularly preferred.

[0147] In addition, in Formula 1, Y 1 Preferably, it is a hydrocarbyloxy group or a silyloxy group. As a hydrocarbyloxy group, there is no particular limitation, and specifically, for example, preferably, a methoxy group, an ethoxy group, a propoxy group, a 1-methylethoxy group, a butoxy group, a 1-methylpropoxy group, a 1,1-dimethylethoxy group, a pentoxy group, a hexoxy group, a 2-methylpentoxy group, a 2-ethylbutoxy group, a 2-ethylpentoxy group, a 2-ethylhexyloxy group, a 2-ethyl-4-methylpentoxy group, a 2-propylheptyloxy group, a 2-ethyl-5-methyloctyloxy group, an octyloxy group, a phenoxy group, a naphthoxy group. Among them, butoxy group, a 1-methylpropoxy group, a 2-methylpentyloxy group, and a 2-ethylhexyloxy group are more preferred. As a silyloxy group, there is no particular limitation, and specifically, for example, preferably, a dimethylhydrogensiloxy group, an ethylmethylhydrogensiloxy group, a diethylhydrogensiloxy group, a trimethylsiloxy group, an ethyldimethylsiloxy group, a diethylmethylsiloxy group, a triethylsiloxy group, and the like. Among them, a dimethylhydrogensiloxy group, an ethylmethylhydrogensiloxy group, a diethylhydrogensiloxy group, and a trimethylsiloxy group are more preferred.

[0148] In this embodiment, the synthesis method of (A-1) is not particularly limited, for example, by making a 2 MgX 1 Japanese R 2 Mg(R 2 The meaning of X is as described above. 1 The organomagnesium compound of the group consisting of halogen) and the organomagnesium compound of the formula M 1 R 3 n Japanese M 1 R 3 (n-1) H(M 1 and R 3 The meaning is as above, n represents M 1 The organic metal compound of the group consisting of (a) is reacted in an inert hydrocarbon solvent at a temperature of 25° C. to 150° C., and then, if necessary, the organic metal compound of the formula Y is reacted in an inert hydrocarbon solvent at a temperature of 25° C. to 150° C. 1 -H(Y 1The meaning is as described above) is as follows: 1 The organic magnesium compound and / or organic aluminum compound having a functional group represented by the formula Y are reacted to synthesize the organic magnesium compound soluble in an inert hydrocarbon solvent and 1 In the case of reacting a compound represented by -H, there is no particular limitation on the order of the reaction. For example, the organic magnesium compound may be added with a compound represented by formula Y 1 -H represented by the method of formula Y 1 Any of the methods of adding an organomagnesium compound to a compound represented by -H, or adding both simultaneously.

[0149] In this embodiment, Y in (A-1) 1 The molar composition ratio c / (α+β) relative to all metal atoms is 0≤c / (α+β)≤2, preferably 0≤c / (α+β)<1. 1 When the molar composition ratio relative to all metal atoms is 2 or less, the reactivity of (A-1) to (A-2) tends to increase.

[0150] Next, (A-2) is described. (A-2) is a titanium compound represented by Formula 2.

[0151] (A-2): Ti(OR 7 ) d X 1 (4 -d) ... Formula 2

[0152] (where d is a real number greater than or equal to 0 and less than or equal to 4, R 7 is a hydrocarbon group having 1 to 20 carbon atoms, X 1 is a halogen atom.)

[0153] In the above formula 2, d is preferably 0 or more and 1 or less, and more preferably 0. 7 The hydrocarbon group represented by is not particularly limited, and specifically, for example, aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, and allyl can be cited; alicyclic hydrocarbon groups such as cyclohexyl, 2-methylcyclohexyl, and cyclopentyl; and aromatic hydrocarbon groups such as phenyl and naphthyl. Among them, aliphatic hydrocarbon groups are preferred. 1 The halogen represented by may be, for example, chlorine, bromine, and iodine. Among them, chlorine is preferred. In this embodiment, (A-2) is particularly preferably titanium tetrachloride. In this embodiment, two or more compounds selected from the above may be used in combination.

[0154] Next, the reaction of (A-1) and (A-2) is described. The reaction is preferably carried out in an inert hydrocarbon solvent, and more preferably in an aliphatic hydrocarbon solvent such as hexane or heptane. There is no particular restriction on the molar ratio of (A-1) to (A-2) in the reaction, and the molar ratio (Ti / Mg) of the Ti atoms contained in (A-2) to the Mg atoms contained in (A-1) is preferably 0.1 or more and 10 or less, and more preferably 0.3 or more and 3 or less. There is no particular restriction on the reaction temperature, and it is preferably carried out in the range of -80°C or more and 150°C or less, and more preferably in the range of -40°C or more and 100°C or less. There is no particular restriction on the order of addition of (A-1) and (A-2), and it can be any of the methods of adding (A-2) after (A-1), adding (A-1) after (A-2), and adding (A-1) and (A-2) at the same time, and the method of adding (A-1) and (A-2) at the same time is preferred. In the present embodiment, the solid catalyst component [A] obtained by the above reaction is used in the form of a slurry using an inert hydrocarbon solvent.

[0155] As another example of the Ziegler-Natta catalyst component used in the present embodiment, the following olefin polymerization catalyst is preferred, wherein the olefin polymerization catalyst comprises a solid catalyst component [C] and an organic metal compound component [B], the solid catalyst component [C] being produced by supporting an organic magnesium compound (C-4) soluble in an inert hydrocarbon solvent represented by Formula 5 and a titanium compound (C-5) represented by Formula 6 on a carrier (C-3), wherein the carrier (C-3) is prepared by reacting an organic magnesium compound (C-1) soluble in an inert hydrocarbon solvent represented by Formula 3 with a chlorinating agent (C-2) represented by Formula 4.

[0156] (C-1): (M 2 ) γ (Mg) δ (R 8 ) e (R 9 ) f (OR 10 ) g ……Formula 3

[0157] (In Formula 3, M 2 is a metal atom belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table, R 8 , R 9 and R 10 Each is a hydrocarbon group having 1 to 20 carbon atoms, and γ, δ, e, f, and g are real numbers satisfying the following relationship: 0≤γ, 0<δ, 0≤e, 0≤f, 0≤g, 0<e+f, 0≤g / (γ+δ)≤2, kγ+2δ=e+f+g (wherein k represents M 2valence.

[0158] (C-2): H h SiCl i R 11 (4-(h+i)) ……Formula 4

[0159] (In Formula 4, R 11 is a hydrocarbon group having 1 or more and 12 or less carbon atoms, and h and i are real numbers satisfying the following relationship: 0<h, 0<i, 0<h+i≤4. )

[0160] (C-4): (M 1 ) α (Mg) β (R 2 ) a (R 3 ) b Y 1 c ……Formula 5

[0161] (In Formula 5, M 1 is a metal atom belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table, R 2 and R 3 is a hydrocarbon group having 2 or more and 20 or less carbon atoms, Y 1 is alkoxy, silyloxy, allyloxy, amino, amide, -N=CR 4 ,R 5 、-SR 6 (Among them, R 4 , R 5 and R 6 represents a hydrocarbon group having 1 to 20 carbon atoms. When c is 2, Y 1 α, β, a, b and c are real numbers satisfying the following relationship: 0≤α, 0<β, 0≤a, 0≤b, 0≤c, 0<a+b, 0≤c / (α+β)≤2, nα+2β=a+b+c (where n represents M 1 valence.

[0162] (C-5): Ti(OR 7 ) d X 1 (4-d) ……Formula 6

[0163] (In Formula 6, d is a real number greater than or equal to 0 and less than or equal to 4, R 7 is a hydrocarbon group having 1 to 20 carbon atoms, X 1 is a halogen atom.)

[0164] First, (C-1) is described. (C-1) is shown in the form of an organic magnesium complex soluble in an inert hydrocarbon solvent, including all dihydrocarbyl magnesium compounds and complexes of dihydrocarbyl magnesium compounds and other metal compounds. The relationship between the symbols γ, δ, e, f and g in Formula 3, kγ+2δ=e+f+g, represents the stoichiometry of the valence of the metal atom and the substituent.

[0165] In the above formula 3, R 8 or R 9 The hydrocarbon group represented by is not particularly limited, and specifically, each is an alkyl group, a cycloalkyl group or an aryl group, and examples thereof include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, and phenyl. Among them, R is preferably 8 and R 9 Each is an alkyl group. In the case of α>0, the metal atom M 2 As the metal atom, metal atoms belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table can be used, for example, zinc, boron, aluminum, etc. Among them, aluminum and zinc are particularly preferred.

[0166] Magnesium relative to metal atoms M 2 The ratio δ / γ is not particularly limited, but is preferably 0.1 to 30, and more preferably 0.5 to 10. In addition, when a predetermined organomagnesium compound having γ=0 is used, for example, in R 8 In the case of 1-methylpropyl, etc., it is soluble in an inert hydrocarbon solvent, and such a compound also produces satisfactory results in this embodiment. In Formula 3, when γ=0, it is recommended that R 8 and R 9 It is any one of the three groups: group (1), group (2) and group (3) shown below.

[0167] Group (1): R 8 and R 9 At least one of them is a secondary or tertiary alkyl group having 4 or more and 6 or less carbon atoms, preferably R 8 and R 9 The number of carbon atoms is 4 or more and 6 or less and R 8 and R 9 At least one of them is a secondary alkyl group or a tertiary alkyl group.

[0168] Group (2): R 8 With R 9 are alkyl groups with different carbon number, preferably R 8 is an alkyl group having 2 or 3 carbon atoms and R 9 It is an alkyl group having 4 or more carbon atoms.

[0169] Group (3): R 8 and R9 At least one of them is a hydrocarbon group having 6 or more carbon atoms, preferably R 8 and R 9 The total number of carbon atoms contained in the alkyl group is 12 or more.

[0170] These groups are specifically shown below. As the secondary alkyl or tertiary alkyl group having 4 to 6 carbon atoms in group (1), specifically, for example, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, 2-methylbutyl, 2-ethylpropyl, 2,2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2,2-dimethylbutyl, 2-methyl-2-ethylpropyl, etc. can be used. Among them, 1-methylpropyl is particularly preferred.

[0171] In addition, examples of the alkyl group having 2 or 3 carbon atoms in group (2) include ethyl, 1-methylethyl, propyl, etc. Among them, ethyl is particularly preferred. In addition, there are no particular restrictions on the alkyl group having 4 or more carbon atoms, and specific examples include butyl, pentyl, hexyl, heptyl, octyl, etc. Among them, butyl and hexyl are particularly preferred.

[0172] In addition, the hydrocarbon group having 6 or more carbon atoms in group (3) is not particularly limited, and specific examples thereof include hexyl, heptyl, octyl, nonyl, decyl, phenyl, 2-naphthyl, etc. Among the hydrocarbon groups, alkyl groups are preferred, and among the alkyl groups, hexyl and octyl groups are particularly preferred.

[0173] Generally, when the number of carbon atoms contained in the alkyl group increases, it tends to be easily dissolved in an inert hydrocarbon solvent and the viscosity of the solution tends to increase. Therefore, it is preferred to use an alkyl group with a moderately long chain in operation. It should be noted that the above-mentioned organomagnesium compound is used in the form of an inert hydrocarbon solution, and can be used without problem even if a trace amount of Lewis basic compounds such as ethers, esters, and amines are contained or remain in the solution.

[0174] Next, the alkoxy group (OR 10 ) is explained. 10 The hydrocarbon group represented by is preferably an alkyl group or aryl group having 1 to 12 carbon atoms, and particularly preferably an alkyl group or aryl group having 3 to 10 carbon atoms. 10 , there are no particular restrictions, and specifically, for example, methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 1,1-dimethylethyl, pentyl, hexyl, 2-methylpentyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylhexyl, 2-ethyl-4-methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, octyl, nonyl, decyl, phenyl, naphthyl, etc. Among them, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl are particularly preferred.

[0175] In this embodiment, the synthesis method of (C-1) is not particularly limited, and the following method is preferred: 8 MgX 1 Japanese R 8 Mg(R 8 The meaning of X is as described above. 1 The organomagnesium compound of the group consisting of halogen atoms and the organic magnesium compound of the formula M 2 R 9 k Japanese M 2 R 9 (k-1) H(M 2 , R 9 and k are as described above) in an inert hydrocarbon solvent at a temperature of 25°C to 150°C, and then reacted with a 9 (R 9 The meaning is as described above) represented by a hydrocarbon alcohol or a hydrocarbon soluble in an inert hydrocarbon solvent having R 9 The hydrocarbyl group represented by the hydrocarbyl group is reacted with a magnesium alkoxide compound and / or an aluminum alkoxide compound.

[0176] In the case of reacting an organomagnesium compound soluble in an inert hydrocarbon solvent with an alcohol, there is no particular limitation on the order of the reaction, and any of a method of adding alcohol to the organomagnesium compound, a method of adding the organomagnesium compound to the alcohol, or a method of adding both simultaneously can be used. In the present embodiment, there is no particular limitation on the reaction ratio of the organomagnesium compound soluble in an inert hydrocarbon solvent and the alcohol, and as a result of the reaction, the molar composition ratio of the hydrocarbyloxy group to the total metal atoms in the obtained organomagnesium compound containing a hydrocarbyloxy group, g / (γ+δ), is 0≤g / (γ+δ)≤2, preferably 0≤g / (γ+δ)<1.

[0177] Next, (C-2) is described. (C-2) is a silicon chloride compound represented by Formula 4 having at least one Si—H bond.

[0178] (C-2): H h SiCl i R 11 (4-(h+i)) ……Formula 4

[0179] (In Formula 4, R 11 is a hydrocarbon group having 1 or more and 12 or less carbon atoms, and h and i are real numbers satisfying the following relationship: 0<h, 0<i, 0<h+i≤4. )

[0180] In formula 4, R 11The hydrocarbon group represented by is not particularly limited, and specifically, it is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group, for example, methyl, ethyl, propyl, 1-methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl, etc. Among them, an alkyl group having 1 to 10 carbon atoms is preferred, and an alkyl group having 1 to 3 carbon atoms such as methyl, ethyl, propyl, 1-methylethyl, etc. is more preferred. In addition, h and i are numbers that satisfy the relationship of h+i≤4 and are greater than 0, and i is preferably 2 to 3.

[0181] There are no particular limitations on these compounds, and specific examples thereof include HSiCl3, HSiCl2CH3, HSiCl2C2H5, HSiCl2(C3H7), HSiCl2(2-C3H7), HSiCl2(C4H9), HSiCl2(C6H5), HSiCl2(4-Cl-C6H4), HSiCl2(CH=CH2), HSiCl2(CH2C6H5), HSiCl2(1-C 10 H7), HSiCl2(CH2CH=CH2), H2SiCl(CH3), H2SiCl(C2H5), HSiCl(CH3)2, HSiCl(C2H5)2, HSiCl(CH3)(2-C3H7), HSiCl(CH3)(C6H5), HSiCl(C6H5)2, etc. A silicon chloride compound containing these compounds or a mixture of two or more selected from these compounds is used. Among them, HSiCl3, HSiCl2CH3, HSiCl(CH3)2, HSiCl2(C3H7) are preferred, and HSiCl3 and HSiCl2CH3 are more preferred.

[0182] Next, the reaction of (C-1) and (C-2) is described. During the reaction, it is preferred to use an inert hydrocarbon solvent, chlorinated hydrocarbons such as 1,2-dichloroethane, o-dichlorobenzene, dichloromethane, ether medium such as ether, tetrahydrofuran, or a mixed medium thereof to dilute (C-2) before use. Among them, from the perspective of catalyst performance, an inert hydrocarbon solvent is more preferred. There is no particular restriction on the reaction ratio of (C-1) to (C-2), and the silicon atoms contained in (C-2) are preferably 0.01 mol or more and 100 mol or less relative to 1 mol of magnesium atoms contained in (C-1), and more preferably 0.1 mol or more and 10 mol or less.

[0183] There is no particular limitation on the reaction method of (C-1) and (C-2). It can be a method of simultaneously introducing (C-1) and (C-2) into a reactor while reacting them, a method of introducing (C-1) into a reactor after (C-2) is introduced into a reactor in advance, or a method of introducing (C-2) into a reactor after (C-1) is introduced into a reactor in advance. Among them, it is preferred to introduce (C-2) into a reactor in advance and then introduce (C-1) into a reactor. For the carrier (C-3) obtained by the above reaction, it is preferably separated by filtration or decantation, and then fully washed with an inert hydrocarbon solvent to remove unreacted substances or by-products.

[0184] The reaction temperature of (C-1) and (C-2) is not particularly limited, but is preferably 25°C to 150°C, more preferably 30°C to 120°C, and even more preferably 40°C to 100°C. In a method of adding (C-1) and (C-2) simultaneously into a reactor while reacting them, it is preferred to adjust the temperature of the reactor to a predetermined temperature in advance, and adjust the temperature in the reactor to a predetermined temperature while adding them simultaneously, thereby adjusting the reaction temperature to a predetermined temperature. In a method of introducing (C-2) into a reactor in advance and then introducing (C-1) into the reactor, it is preferred to adjust the temperature of the reactor into which the silicon chloride compound has been introduced to a predetermined temperature, and adjust the temperature in the reactor to a predetermined temperature while introducing the organomagnesium compound into the reactor, thereby adjusting the reaction temperature to a predetermined temperature. In a method in which (C-2) is introduced into a reactor after (C-1) has been previously introduced into the reactor, it is preferred to adjust the temperature of the reactor into which (C-1) has been introduced to a predetermined temperature, and to adjust the temperature inside the reactor to a predetermined temperature simultaneously with the introduction of (C-2) into the reactor, thereby adjusting the reaction temperature to a predetermined temperature.

[0185] Next, the organomagnesium compound (C-4) is described. As (C-4), the organomagnesium compound represented by the above formula 5 is preferred.

[0186] (C-4): (M 1 ) α (Mg) β (R 2 ) a (R 3 ) b Y 1 c ……Formula 5

[0187] (In Formula 5, M 1 is a metal atom belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table, R2 and R 3 is a hydrocarbon group having 2 or more and 20 or less carbon atoms, Y 1 is alkoxy, silyloxy, allyloxy, amino, amide, -N=CR 4 ,R 5 、-SR 6 (Among them, R 4 , R 5 and R 6 represents a hydrocarbon group having 1 to 20 carbon atoms. When c is 2, Y 1 α, β, a, b and c are real numbers satisfying the following relationship: 0≤α, 0<β, 0≤a, 0≤b, 0<a+b, 0≤c / (α+β)≤2, nα+2β=a+b+c (wherein n represents M 1 valence.

[0188] The amount of (C-4) used is preferably 0.1 to 10, more preferably 0.5 to 5, in terms of the molar ratio of the magnesium atoms contained in (C-4) to the titanium atoms contained in (C-5).

[0189] The reaction temperature of (C-4) and (C-5) is not particularly limited, but is preferably -80°C to 150°C, more preferably -40°C to 100°C.

[0190] There is no particular limitation on the concentration of (C-4) when used, but it is preferably 0.1 mol / L or more and 2 mol / L or less, and more preferably 0.5 mol / L or more and 1.5 mol / L or less, based on the titanium atoms contained in (C-4). It should be noted that an inert hydrocarbon solvent is preferably used for dilution of (C-4).

[0191] The order of adding (C-4) and (C-5) to (C-3) is not particularly limited, and any of the methods of adding (C-5) after (C-4), adding (C-4) after (C-5), and adding (C-4) and (C-5) simultaneously may be used. Among them, the method of adding (C-4) and (C-5) simultaneously is preferred. The reaction of (C-4) and (C-5) is carried out in an inert hydrocarbon solvent, preferably an aliphatic hydrocarbon solvent such as hexane or heptane. The catalyst thus obtained is used in the form of a slurry obtained using an inert hydrocarbon solvent.

[0192] Next, (C-5) will be described. In this embodiment, (C-5) is a titanium compound represented by the above formula 6.

[0193] (C-5): Ti(OR 7 ) d X1 (4-d) ……Formula 6

[0194] (In Formula 6, d is a real number greater than or equal to 0 and less than or equal to 4, R 7 is a hydrocarbon group having 1 to 20 carbon atoms, X 1 is a halogen atom.)

[0195] As in Formula 6, R 7 The hydrocarbon group represented by is not particularly limited, and specifically, for example, aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, and allyl can be cited; alicyclic hydrocarbon groups such as cyclohexyl, 2-methylcyclohexyl, and cyclopentyl; and aromatic hydrocarbon groups such as phenyl and naphthyl. Among them, aliphatic hydrocarbon groups are preferred. 1 The halogen represented by is not particularly limited, and specifically, for example, chlorine, bromine, and iodine can be listed. Among them, chlorine is preferred. One (C-5) selected from the above substances can be used alone, or two or more (C-5) selected from the above substances can be used in combination.

[0196] The amount of (C-5) used is not particularly limited, but is preferably 0.01 to 20, particularly preferably 0.05 to 10, in terms of molar ratio relative to the magnesium atoms contained in the support (C-3).

[0197] The reaction temperature of (C-5) is not particularly limited, but is preferably in the range of -80°C to 150°C, and more preferably in the range of -40°C to 100°C.

[0198] In this embodiment, there is no particular limitation on the method for loading (C-5) on (C-3). A method of reacting an excess amount of (C-5) relative to (C-3) or a method of efficiently loading (C-5) by using a third component can be used. Preferably, a method of loading (C-5) by reacting (C-5) with an organomagnesium compound (C-4) can be used.

[0199] Next, the organometallic compound component [B] used in the present embodiment is described. The solid catalyst component used in the present embodiment becomes a highly active polymerization catalyst by combining with the organometallic compound component [B]. The organometallic compound component [B] is sometimes also referred to as a "co-catalyst". As the organometallic compound component [B], a compound containing a metal belonging to the group consisting of Group 1, Group 2, Group 12 and Group 13 of the periodic table is preferred, and an organoaluminum compound and / or an organomagnesium compound are particularly preferred.

[0200] As the organoaluminum compound, it is preferred to use a compound represented by the following Formula 7 alone or in combination.

[0201] AHr 12 j Z 1 (3-j) ……Formula 7

[0202] (In Formula 7, R 12 is a hydrocarbon group having 1 to 20 carbon atoms, Z 1 is a group belonging to the group consisting of hydrogen, halogen, hydrocarbonoxy, allyloxy and siloxy, and j is a number of 2 or more and 3 or less. )

[0203] In the above formula 7, R 12 The hydrocarbon group having 1 or more and 20 or less carbon atoms represented by is not particularly limited, and specifically includes aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and alicyclic hydrocarbon groups, for example, preferably trialkylaluminum such as trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, tri(2-methylpropyl)aluminum (or triisobutylaluminum), tripentylaluminum, tri(3-methylbutyl)aluminum, trihexylaluminum, trioctylaluminum, and tridecylaluminum; aluminum halide compounds such as diethylaluminum chloride, ethylaluminum dichloride, bis(2-methylpropyl)aluminum chloride, ethylaluminum sesquichloride, and diethylaluminum bromide; alkoxide aluminum compounds such as ethoxydiethylaluminum and butoxybis(2-methylpropyl)aluminum; siloxyaluminum compounds such as dimethylhydrogensilyloxydimethylaluminum, ethylmethylhydrogensilyloxydiethylaluminum, and ethyldimethylsilyloxydiethylaluminum; and mixtures thereof. Among them, trialkylaluminum compounds are particularly preferred.

[0204] As the organic magnesium compound, an organic magnesium compound represented by the above-mentioned Formula 3 which is soluble in an inert hydrocarbon solvent is preferred.

[0205] (M 2 ) γ (Mg) δ (R 8 ) e (R 9 ) f (OR 10 ) g ……Formula 3

[0206] (In Formula 3, M 2 is a metal atom belonging to the group consisting of Group 12, Group 13 and Group 14 of the periodic table, R 8 , R 9 and R 10 Each is a hydrocarbon group having 1 to 20 carbon atoms, and γ, δ, e, f, and g are real numbers satisfying the following relationship: 0≤γ, 0<δ, 0≤e, 0≤f, 0≤g, 0<e+f, 0≤g / (γ+δ)≤2, kγ+2δ=e+f+g (wherein k represents M 2 valence.

[0207] The organomagnesium compound is shown in the form of an organomagnesium complex soluble in an inert hydrocarbon solvent, including all dialkylmagnesium compounds and complexes of dialkylmagnesium compounds and other metal compounds. 2 , R 8 , R 9 , OR 10 As described above, the solubility of the organomagnesium compound in the inert hydrocarbon solvent is preferably higher, and therefore, δ / γ is preferably in the range of 0.5 or more and 10 or less. In addition, M is further preferably 2 Aluminum compounds.

[0208] The combination ratio of the solid catalyst component and the organometallic compound component [B] is not particularly limited, but the organometallic compound component [B] is preferably 1 mmol or more and 3000 mmol or less per 1 g of the solid catalyst component.

[0209] (Polymerization conditions)

[0210] The polymerization temperature in the method for producing the ultrahigh molecular weight polyethylene powder of the present embodiment is usually 30° C. or higher and 100° C. or lower. When the polymerization temperature is 30° C. or higher, there is a tendency that the production can be more efficiently performed industrially. On the other hand, when the polymerization temperature is 100° C. or lower, there is a tendency that the operation can be continuously and more stably performed.

[0211] In addition, the polymerization pressure in the method for producing the ultra-high molecular weight polyethylene powder of the present embodiment is usually above normal pressure and below 2 MPa. The polymerization pressure is preferably above 0.1 MPa, more preferably above 0.12 MPa, and preferably below 1.5 MPa, more preferably below 1.0 MPa. When the polymerization pressure is above normal pressure, there is a tendency to be able to produce more efficiently in industry, and when the polymerization pressure is below 2 MPa, there is a tendency to be able to suppress local heating caused by the rapid polymerization reaction when the catalyst is introduced, and to be able to stably produce polyethylene.

[0212] Polymerization reaction can be carried out by any method in intermittent, semi-continuous, continuous, preferably polymerize in continuous. By continuously supplying ethylene gas, solvent, catalyst etc. in the polymerization system, and continuously discharging together with the generated polyethylene, it is possible to suppress the local high temperature state caused by the reaction of rapid ethylene, and the polymerization system becomes more stable. When ethylene reacts under a uniform state in the system, it is possible to suppress the generation of side chains, double bonds etc. in the polymer chain, and it is difficult for polyethylene to be low molecular weight or crosslinked, therefore, the residual unmelted material is reduced when the ultra high molecular weight polyethylene powder is melted or melted, and it is possible to suppress coloring, and it is also difficult to produce the problems such as mechanical properties reduction. Therefore, it is preferred that the continuous type becomes more uniform in the polymerization system.

[0213] In addition, polymerization can also be divided into two or more stages with different reaction conditions. In addition, for example, as described in the specification of German Patent Application Publication No. 3127133, the intrinsic viscosity of the obtained polyethylene can be adjusted by making hydrogen exist in the polymerization system or changing the polymerization temperature. By adding hydrogen as a chain transfer agent in the polymerization system, the intrinsic viscosity can be controlled within an appropriate range. When hydrogen is added in the polymerization system, the mole fraction of hydrogen is preferably 0 mol% or more and 30 mol% or less, more preferably 0 mol% or more and 25 mol% or less, and further preferably 0 mol% or more and 20 mol% or less. It should be noted that in the present embodiment, in addition to each component as described above, other known components useful for the manufacture of polyethylene can also be included.

[0214] When the ultra-high molecular weight polyethylene powder of the present embodiment is obtained by polymerization, in order to suppress the adhesion of the polymer on the polymerization reactor, an antistatic agent such as Stadis450 manufactured by Associated Octel (agent Maruwa Bussan) can also be used. Stadis450 can be diluted in an inert hydrocarbon medium and added to the polymerization reactor using a pump or the like. For the amount of antistatic agent such as Stadis450 added at this time, it is preferably added in an amount within the range of 0.10 ppm or more and 20 ppm or less relative to the production amount of polyethylene per unit time, and more preferably in an amount within the range of 0.20 ppm or more and 10 ppm or less.

[0215] In the method for producing the ultrahigh molecular weight polyethylene powder of the present embodiment, it is preferred to increase the pressure in the reactor and increase the amount of ethylene introduced at the end of the polymerization.

[0216] Usually, when the catalyst is introduced into the system, the reaction reacts violently at the initial stage, and then the reaction activity gradually decreases. The polymer chains generated at the initial stage of the reaction are squeezed outward from the center of the catalyst (the center of the powder). Therefore, there are polymer chains generated at the initial stage of the reaction on the surface of the powder. The catalyst activity decreases at the end of the reaction, so the polymer is slowly generated. Therefore, the powder structure (the pores on the powder surface are large, and the pores in the center of the powder are small) and the polyethylene properties (the ratio of the crystalline part and the amorphous part) are different at the surface and center of the powder. Therefore, it is believed that by increasing the pressure in the reactor at the end of the polymerization or increasing the amount of ethylene introduced, it is possible to adjust the pores in the center and surface of the powder to become larger.

[0217] In addition, it is preferred to appropriately adjust the drying temperature and drying time. Specifically, the following three-stage drying is preferred. The first stage is preferably to spray a mixed solution of water: methanol = 20:80 into the dryer, and to make it infiltrate into the ultra-high molecular weight polyethylene powder while drying at a high temperature of the crystallization temperature ±5°C for a time equivalent to 1 / 4 of the total drying time; the second stage is preferably to dry at a temperature of 90°C or more and 105°C or less for a time equivalent to 2 / 4 of the total drying time; the third stage is preferably to dry at a low temperature of 60°C or more and less than 90°C for a time equivalent to 1 / 4 of the total drying time. In the first stage, the pore size and pore volume of the center and surface of the ultra-high molecular weight polyethylene powder can be adjusted by volatilizing methanol and water in sequence. In addition, when drying is continued at a high temperature, the ultra-high molecular weight polyethylene powder is annealed, and the balance of the pore size and pore volume of the center and surface of the ultra-high molecular weight polyethylene powder is destroyed. Therefore, the drying time of the first stage is preferably equivalent to 1 / 4 of the total drying time, and the temperature is preferably lowered after the second stage. However, when the temperature is lowered to a low temperature all at once, the balance of the ratio of the crystalline part and the amorphous part in the center and the surface of the ultra-high molecular weight polyethylene powder is destroyed, so it is preferred to dry at an intermediate temperature like the second stage for a time equivalent to 2 / 4 of the total drying time, and dry at a low temperature in the third stage.

[0218] As described above, by adjusting the polymerization conditions, the ultrahigh molecular weight polyethylene powder of the present embodiment can be obtained.

[0219] [additive]

[0220] The ultra-high molecular weight polyethylene powder of this embodiment may be added with additives such as a slip agent, a neutralizer, an antioxidant, a light stabilizer, an antistatic agent, and a pigment as needed.

[0221] There are no particular restrictions on the lubricant or neutralizer, and examples thereof include aliphatic hydrocarbons, higher fatty acids, higher fatty acid metal salts, fatty acid esters of alcohols, waxes, higher fatty acid amides, silicone oils, rosin, etc. The content of the lubricant or neutralizer is not particularly limited, but is 5000 ppm or less, preferably 4000 ppm or less, and more preferably 3000 ppm or less.

[0222] The antioxidant is not particularly limited, but is preferably a phenolic compound or a phenolic phosphorus-containing compound, for example. Specifically, examples include: phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol (butylhydroxytoluene), octadecyl 3-(4-hydroxy-3,5-di-tert-butylphenyl) propionate, and tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane; phenolic phosphorus-containing antioxidants such as 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphophetidine; and phosphorus-containing antioxidants such as 4,4'-biphenylene diphosphite tetrakis(2,4-di-tert-butylphenyl) ester, tris(2,4-di-tert-butylphenyl) phosphite, and cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl phosphite).

[0223] In the ultra-high molecular weight polyethylene powder involved in the present embodiment, when the total amount of the ultra-high molecular weight polyethylene powder and the liquid paraffin is set to 100 parts by mass, the amount of the antioxidant is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, further preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less. When the antioxidant is 5 parts by mass or less, the deterioration of polyethylene can be suppressed, so that embrittlement, discoloration, reduction in mechanical properties, etc. are not likely to occur, and the long-term stability is more excellent.

[0224] The light stabilizer is not particularly limited, and examples thereof include benzotriazole-based light stabilizers such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole and 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole; and hindered amine-based light stabilizers such as di(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and poly{[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}. The content of the light stabilizer is not particularly limited, but is 5000 ppm or less, preferably 3000 ppm or less, and more preferably 2000 ppm or less.

[0225] The antistatic agent is not particularly limited, and examples thereof include aluminosilicate, kaolin, clay, natural silica, synthetic silica, silicates, talc, diatomaceous earth, and the like; and glycerol fatty acid esters.

[0226] [Molding body]

[0227] The ultra-high molecular weight polyethylene powder of the present embodiment can be molded by various methods. In addition, the molded body of the present embodiment can be obtained by molding the above-mentioned ultra-high molecular weight polyethylene powder. The molded body of the present embodiment can be used for various purposes. As a specific example of the molded body of the present embodiment, there is no restriction, for example, it is suitable as a microporous membrane for secondary battery separators, a microporous membrane for lithium ion secondary battery separators, a sintered body, a high-strength fiber, etc. As a method for manufacturing a microporous membrane, there is no particular restriction, for example, the following processing method can be cited: in a wet method using a solvent, an extruder provided with a T-die is used, and after extrusion, stretching, extraction, and drying.

[0228] In addition, utilizing the excellent characteristics of high molecular weight ethylene polymers such as wear resistance, high sliding properties, high strength, and high impact resistance, it can also be used for a molded body (sintered body) obtained by sintering the above-mentioned ultra-high molecular weight polyethylene powder.

[0229] The method for producing the high-strength fiber is not particularly limited, and an example thereof includes a method in which liquid paraffin and the ultra-high molecular weight polyethylene powder are kneaded and spun, and then heated and stretched to obtain the high-strength fiber.

[0230] Example

[0231] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples, but the present invention is not limited to the following Examples at all.

[0232] In the present application, ethylene and hexane used in Examples and Comparative Examples were dehydrated using MS-3A (manufactured by Showa Union), and hexane was further deoxygenated by degassing under reduced pressure using a vacuum pump before use.

[0233] [Measurement method and conditions]

[0234] The physical properties of the ultra-high molecular weight polyethylene powders of Examples and Comparative Examples were measured by the following methods.

[0235] (1) Viscosity average molecular weight (Mv)

[0236] The viscosity average molecular weight Mv of the ultrahigh molecular weight polyethylene powders obtained in Examples and Comparative Examples was determined by the method shown below in accordance with ISO 1628-3 (2010).

[0237] First, weigh 20 mg of ultra-high molecular weight polyethylene powder in a dissolving tube, replace the dissolving tube with nitrogen, then add 20 mL of decalin (decalin with 1 g / L of 2,6-di-tert-butyl-4-methylphenol added), and stir at 150°C for 2 hours to dissolve the ultra-high molecular weight polyethylene powder. The solution was measured for the falling time (ts) between the markings using a Cannon-Fenske viscometer (manufactured by Shibata Scientific Instruments Co., Ltd.: product model -100) in a constant temperature bath at 135°C. Similarly, the falling time (ts) between the markings was measured for samples obtained by changing the amount of ultra-high molecular weight polyethylene powder to 10 mg, 5 mg, and 2 mg. The falling time (tb) of decalin alone without adding ultra-high molecular weight polyethylene powder as a blank was measured. The reduced viscosity (ηsp / C) of the ultra-high molecular weight polyethylene powder was calculated according to the following formula.

[0238] ηsp / C=(ts / tb-1) / 0.1(unit: dL / g)

[0239] The relationship between the concentration (C) (unit: g / dL) and the reduced viscosity (ηsp / C) of the ultra-high molecular weight polyethylene powder was plotted, and an approximate linear equation was derived by the least squares method, and the intrinsic viscosity ([η]) was obtained by extrapolation to a concentration of 0. Next, the viscosity average molecular weight (Mv) was calculated from the value of the intrinsic viscosity [η] using the following formula A.

[0240] Mv=(5.34×10 4 )×[η] 1.49 (Formula A)

[0241] (2) Swelling start temperature and dissolution start temperature

[0242] While confirming with an optical microscope, arbitrarily select 1 ultra-high molecular weight polyethylene powder with a major axis and a minor axis of 120 μm or more and 130 μm or less. Place the selected 1 ultra-high molecular weight polyethylene powder (hereinafter also referred to as "measurement particle") on a cover glass (manufactured by Marienfeld, Deckglaser cover glass, 24 mm × 24 mm), and use a 2 mL dropper to drop 1 drop of liquid paraffin (liquid paraffin manufactured by Matsumura Institute of Petroleum Co., Ltd. (product name: SMOIL P-350P)) onto the measurement particle. Then, place another cover glass (manufactured by Matsunami Glass Industry Co., Ltd., TROPHY micro cover glass, 18 mm × 18 mm) on it to sandwich the measurement particle in the middle. Then, place the cover glass sandwiching the measurement particle on a heating stage, and use an optical microscope with a camera to observe the process of heating the measurement particle from room temperature to 150 °C under the following heating conditions. Take an observation image of the measurement particle every 6 seconds during the heating step. After the measurement is completed, use image analysis software (manufactured by Asahi Kasei, A Image-kun, version 2.50) to calculate the equivalent circle diameter of the measurement particle based on each observation image, and judge the swelling start temperature and dissolution start temperature as follows.

[0243] (Heating conditions)

[0244] Heating rate in the range of 35 °C to 80 °C: 8 °C / minute

[0245] Heating rate in the range of 80 °C to 150 °C: 5 °C / minute

[0246] It should be noted that the heating rate from room temperature to 35 °C is set to 5 °C / minute

[0247] [Swelling start temperature]

[0248] Use image analysis software (manufactured by Asahi Kasei, A Image-kun, version 2.50) to calculate the equivalent circle diameter of the measurement particle based on the observation images obtained by photographing the measurement particle. Based on the equivalent circle diameter of the measurement particle at 80 °C, in the temperature range above 80 °C and below 150 °C, the lowest temperature at which the equivalent circle diameter of the measurement particle increases by 1% or more is taken as the swelling start temperature. It should be noted that the average value of three measurements is taken as the final swelling start temperature. The equivalent circle diameter of the measurement particle at each temperature is plotted to create a graph.

[0249] [Dissolution start temperature]

[0250] Use image analysis software to calculate the equivalent circle diameter of the measurement particle based on the observation images obtained by photographing the measurement particle, and take the measurement temperature when the equivalent circle diameter of the measurement particle shows the maximum value as the dissolution start temperature. It should be noted that the average value of three measurements is taken as the final dissolution start temperature.

[0251] (3) Liquid paraffin impregnation rate (weight increase rate)

[0252] 10g of ultra-high molecular weight polyethylene powder and 30g of liquid paraffin (liquid paraffin manufactured by Matsumura Petroleum Research Institute Co., Ltd. (product name: SMOIL P-350P)) were mixed at a stirring speed of 50rpm for 3 minutes to prepare a sample. The prepared sample was placed in a metal container, covered with aluminum foil, and placed at 70°C for 3 hours. Next, the sample was dried under reduced pressure at 110°C / reduced pressure (-0.1MPaG) for 5 hours. Then, the sample was washed and filtered three times using 10g of hexane, then air-dried for more than 24 hours, and the weight of the ultra-high molecular weight polyethylene powder was measured. It should be noted that the washing and filtering operation refers to the following operation: filter paper is placed in a funnel, the sample is poured onto the filter paper, and 10g of hexane is poured from it to wash and filter. The liquid paraffin (LP) impregnation rate (weight increase rate) was calculated by the following formula from the increase rate of the weight of the ultra-high molecular weight polyethylene powder after impregnation with liquid paraffin (weight after impregnation) relative to the original weight of the ultra-high molecular weight polyethylene powder (weight before impregnation).

[0253] Liquid paraffin impregnation rate (%) = (weight after impregnation - weight before impregnation) / weight before impregnation × 100

[0254] (4) Select ultra-high molecular weight polyethylene powder with a particle size less than 75 μm

[0255] The ultra-high molecular weight polyethylene powder was classified using sieves having mesh sizes of 710 μm, 500 μm, 425 μm, 355 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, and 53 μm according to JIS Z8801.

[0256] From each fraction of the classified ultra-high molecular weight polyethylene powder, powder having a particle size of less than 75 μm was taken out.

[0257] (5) Pore specific surface area measured by BET method

[0258] About 1 g of the ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm selected in the above (4) was placed in a glass tube and heated for vacuum degassing at 70°C for about 18 hours under a reduced pressure of about 100 mTorr. Then, for the ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm, a multi-sample high-performance specific surface area / pore distribution measuring device (trade name: 3Flex, manufactured by Micromeritics Instruments) was used to measure the adsorption isotherm at -196°C using krypton as the adsorption gas, and the pore specific surface area (particle size less than 75 μm; pore specific surface area (m2 / g)).

[0259] (6) Pore volume and pore diameter measured by mercury porosimetry

[0260] The pore volume (particle size less than 75 μm; pore volume (mL / g)) and pore distribution of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm selected in (4) above were measured using AutoPore IV9500 manufactured by Shimadzu Corporation as a mercury porosimeter. Based on the obtained pore distribution, the average pore size (particle size less than 75 μm; average pore size (μm)) of the ultra-high molecular weight polyethylene powder with a particle size less than 75 μm was calculated.

[0261] It should be noted that, as a pretreatment, 0.5 g of the ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm selected in (4) above is placed in the sample cell, degassed and dried at room temperature in the low-pressure measuring section, and then the sample container is filled with mercury. The mercury is pressed into the pores of the sample by slowly applying pressure (high-pressure section).

[0262] The pressure conditions were set as follows.

[0263] Low pressure part: measured at 69Pa (0.01psia) N2 pressure

[0264] High pressure part: 21MPa~228MPa (3000pisa~33000pisa)

[0265] (7) Crystallinity of ultra-high molecular weight polyethylene powder obtained by X-ray measurement

[0266] The crystallinity of the ultra-high molecular weight polyethylene powder was measured by wide angle X-ray scattering (WAXS) under the following conditions.

[0267] Ultima-IV manufactured by Rigaku Corporation was used for the measurement. Cu-Kα rays were incident on the ultra-high molecular weight polyethylene powder as a sample, and the diffracted light was detected by D / tex Uitra. The measurement conditions were as follows: the distance between the sample and the detector was 285 mm, the excitation voltage was 40 kV, and the current was 40 mA. The optical system used a focusing optical system, and the slit conditions were DS = 1 / 2°, SS = open, and the vertical slit = 10 mm.

[0268] (8) Proportion of ultra-high molecular weight polyethylene powder particles with a particle size of less than 75 μm

[0269] Regarding the proportion of particles with a particle size of less than 75 μm in the entire ultra-high molecular weight polyethylene powder particles (hereinafter also referred to as "particles") (the proportion of particles with a particle size of less than 75 μm), 100 g of the particles were classified using 10 sieves specified in JIS Z8801 (sieve hole sizes: 710 μm, 500 μm, 425 μm, 355 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 53 μm), and then the weight of the particles passing through the sieve with a mesh size of 75 μm relative to the weight of all particles (ultra-high molecular weight polyethylene powder) was calculated.

[0270] The ratio (mass %) of particles having a particle size of less than 75 μm was calculated using the following formula from the weight of particles passing through a sieve having a mesh size of 75 μm obtained above.

[0271] Ratio of particles with a particle size of less than 75 μm (mass %) = [weight of particles passing through a sieve with a mesh size of 75 μm (g)] / [weight of all particles (ultra-high molecular weight polyethylene powder) 100 (g)] × 100

[0272] (9) Average particle size of ultra-high molecular weight polyethylene powder (D50)

[0273] Regarding the average particle size of the polyethylene powder, 100 g of particles were classified using 10 sieves specified in JIS Z8801 (sieve hole sizes: 710 μm, 500 μm, 425 μm, 355 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, and 53 μm). The weight of the particles remaining on each sieve was integrated from the side with the smaller sieve hole size, and in the resulting integral curve, the particle size at which 50% of the weight was reached was taken as the average particle size.

[0274] (10) Ti and Al content in ultra-high molecular weight polyethylene powder

[0275] The ultra-high molecular weight polyethylene powder was decomposed under pressure using a microwave decomposition device (model ETHOS TC, manufactured by Milestone General), and the element concentrations of titanium (Ti) and aluminum (Al) as metals contained in the ultra-high molecular weight polyethylene powder were measured using an internal standard method and ICP-MS (inductively coupled plasma mass spectrometer, model X series X7, manufactured by Thermo Fisher Scientific).

[0276] (11) Method for producing microporous membrane for secondary battery separator

[0277] A microporous membrane for a secondary battery separator was produced using ultra-high molecular weight polyethylene powder as described below.

[0278] When the total amount of the ultra-high molecular weight polyethylene powder and the liquid paraffin is 100 parts by mass, 30 to 40 parts by mass of the ultra-high molecular weight polyethylene powder, 60 to 70 parts by mass of the liquid paraffin (liquid paraffin manufactured by Matsumura Petroleum Research Institute Co., Ltd. (product name: SMOIL P-350P)), and 1 part by mass of an antioxidant (tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane (product name: ANOX20) manufactured by Ooko Chemical Japan Co., Ltd.) are blended to prepare a slurry.

[0279] The obtained slurry was replaced with nitrogen and then fed into a twin-screw extruder (main model: 2D25S) for a Labo Plastomill kneader (main model: 30C150) manufactured by Toyo Seiki Co., Ltd. through a feeder under a nitrogen atmosphere, kneaded at 200° C., and then extruded from a T-die provided at the front end of the extruder. It was then immediately cooled and solidified using a casting roll cooled to 25° C. and formed into a gel-like sheet.

[0280] The gel-like sheet was stretched to 7×7 times at 120°C using a biaxial synchronous stretching machine, and then the stretched film was immersed in methyl ethyl ketone or hexane to extract and remove liquid paraffin, and then vacuum dried for more than 24 hours. Then, it was heat-set at 125°C for 3 minutes to obtain a microporous membrane for a secondary battery separator.

[0281] (12) Amount of material scale during the manufacture of microporous membranes for secondary battery separators

[0282] When the film forming operation was performed for 1 hour by the method described in the above (11), the amount of scale adhering to the front end of the extruder was visually determined.

[0283] (Evaluation Criteria)

[0284] ◎(Good) ... No material scale.

[0285] ○(Normal) ... Material scale exists (little).

[0286] ×(bad)...there is material scale (a lot).

[0287] (13) Uneven film thickness of microporous membrane for secondary battery separator

[0288] The microporous membrane for secondary battery separator is manufactured by the method described in (11) above, and the film thickness of the obtained microporous membrane is measured at room temperature 23°C using a micro thickness gauge (type KBM (registered trademark)) manufactured by Toyo Seiki Co., Ltd. Any 10 positions are selected for measurement in an even manner throughout the membrane for each 1m of the membrane, and a total of 50 positions in the 5m membrane are measured, and the average film thickness is calculated. The average film thickness is greater than 5μm and less than 20μm. Taking the average film thickness as a benchmark, the uneven film thickness of the microporous membrane is evaluated as follows.

[0289] (Evaluation Criteria)

[0290] ◎ indicates very good, with the variation relative to the average film thickness being less than ±3 μm.

[0291] ○ indicates that there is no problem and the variation with respect to the average film thickness is greater than or equal to ±3 μm and less than ±5 μm.

[0292] × indicates a difference, and the variation with respect to the average film thickness is ±5 μm or more.

[0293] (14) Puncture strength of microporous membranes for secondary battery separators

[0294] The gel-like sheet obtained by the method described in (11) above was stretched to 7×7 times at 120°C using a biaxial synchronous stretching machine. The obtained stretched film was subjected to a puncture test using the "KES-G5 Portable Compression Tester" (trademark), a product of Kado Technology Co., Ltd., under the conditions of a curvature radius of 0.5 mm at the front end of the needle and a puncture speed of 2 mm / sec, and the maximum puncture load (N) was measured. If the maximum puncture load (N) is 3.0 N or more, it means that the strength is sufficiently excellent. The evaluation criteria are as follows.

[0295] (Evaluation Criteria)

[0296] ◎ (good), the maximum puncture load (N) is 3.5N or more.

[0297] ○(Normal), maximum puncture load (N) is greater than or equal to 3.0N and less than 3.5N.

[0298] ×(bad), maximum puncture load (N) is less than 3.0N.

[0299] (15) Number of wrinkles in microporous membrane for secondary battery separator

[0300] The number of wrinkles of the microporous membrane obtained by the method described in (11) above was visually measured. The evaluation criteria are as follows.

[0301] (Evaluation Criteria)

[0302] ◎ (Good): The number of wrinkles is 30 or less / 1000m 2

[0303] ○(Normal): The number of wrinkles is 31 or more and 50 or less / 1000m 2

[0304] × (bad): The number of wrinkles is 51 or more / 1000 m 2

[0305] (16) Method for producing high-strength fiber

[0306] High strength fibers were produced using ultra high molecular weight polyethylene powder as described below.

[0307] When the total amount of the ultra-high molecular weight polyethylene powder and the liquid paraffin is 100 parts by mass, 5 to 10 parts by mass of the ultra-high molecular weight polyethylene powder, 90 to 95 parts by mass of the liquid paraffin (liquid paraffin (product name: SMOIL P-350P) manufactured by Matsumura Petroleum Research Institute Co., Ltd.), and 1 part by mass of an antioxidant (tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane (product name: ANOX20) manufactured by Oho Chemical Japan Co., Ltd.) are blended to prepare a slurry.

[0308] Next, the slurry was vacuum degassed while being stirred at 80° C. for 1 hour or longer, and then introduced into an extruder. The slurry was kneaded in a nitrogen atmosphere, and the oxygen concentration was set to 0.1% by volume or less.

[0309] As the extruder into which the slurry was introduced, a twin-screw extruder (main body model: 2D25S) for a Labo Plastomill kneader (main body model: 30C150) manufactured by Toyo Seiki Co., Ltd. was used, and kneading and spinning operations were performed.

[0310] The temperature at which the slurry is kneaded in the extruder is 140° C. or higher and 320° C. or lower, and the melt residence time in the extruder is 5 minutes or higher and 30 minutes or lower.

[0311] Then, spinning is performed by a spinneret installed at the front end of the extruder under the conditions of a spinneret temperature of 140°C to 250°C, a discharge rate of 0.5 g / min to 2.0 g / min, and a spinneret hole diameter of 0.3 mm to 1.5 mm.

[0312] Next, the discharged filaments containing liquid paraffin are placed in a water bath at 5°C to 15°C via an air gap of 3 to 5 cm, and are rapidly cooled while being wound at a winding speed of 20 m / min to 50 m / min.

[0313] Next, the liquid paraffin is removed from the silk, the silk is immersed in a solvent such as hexane to perform an extraction operation, and then the silk is vacuum dried for 24 hours or more.

[0314] The obtained yarn was brought into contact with a metal heater so that the temperature of the yarn reached 100°C or higher and 140°C or lower, and primary stretching was performed, and the drawn yarn was wound. Next, the drawn yarn was brought into contact with a metal heater so that the drawn yarn reached 140°C or higher and 160°C or lower, and secondary stretching was performed, and the yarn was stretched until it was about to break, thereby obtaining a drawn yarn. The uniformity of the yarn diameter of the obtained drawn yarn (high-strength fiber) was evaluated as follows.

[0315] (17) Amount of material scale during high-strength fiber manufacturing

[0316] When the membrane forming operation was performed for 1 hour by the method described in the above (16), the amount of scale attached near the spinneret was visually determined.

[0317] (Evaluation Criteria)

[0318] ◎(Good) ... No material scale.

[0319] ○(Normal) ... Material scale exists (little).

[0320] ×(bad)...there is material scale (a lot).

[0321] (18) Uneven wire diameter of high-strength fibers

[0322] Ten yarns (high-strength fibers) spun by the method described in (16) above and stretched to the breaking limit were prepared, and the average yarn diameter was calculated with n = 10. The average yarn diameter of the high-strength fibers was 10 μm or more and 20 μm or less. The yarn diameter unevenness of the high-strength fibers was evaluated as follows based on the average yarn diameter.

[0323] (Evaluation Criteria)

[0324] ◎ means very good, with the variation relative to the average wire diameter being less than ±5μm.

[0325] ○ indicates that there is no problem and the variation relative to the average wire diameter is greater than or equal to ±5 μm and less than ±10 μm.

[0326] × indicates a difference, and the variation with respect to the average wire diameter is ±10 μm or more.

[0327] (19)Tensile breaking strength of high-strength fibers

[0328] Ten yarns spun by the method described in the above (16) were prepared, and the tensile strength at break was calculated with n = 10. The method for calculating the tensile strength at break is as follows.

[0329] The yarn stretched to the breaking limit was stretched at room temperature until it broke, and the tensile breaking strength was calculated by dividing the maximum load value applied to the yarn at this time by the fineness. 4 The weight of the yarn per m is expressed in dtex. The tensile strength at break of the high-strength fiber is evaluated according to the following criteria.

[0330] (Evaluation Criteria)

[0331] ◎(Good) ... Breaking strength is 30 cN / dtex or more.

[0332] ○(Normal) ... Breaking strength is 20 cN / dtex or more and less than 30 cN / dtex.

[0333] × (poor) ... breaking strength is less than 20 cN / dtex.

[0334] [Catalyst synthesis method]

[0335] [Preparation of solid catalyst component [A]]

[0336] (1) Synthesis of raw material (a-1)

[0337] 1 mol / L of Mg6(C4H9) was added to an 8L stainless steel autoclave that had been fully purged with nitrogen. 12 2000 mL of a hexane solution of Al(C2H5)3 (equivalent to 2000 mmol in terms of the total amount of magnesium and aluminum) was added, and 240 mL of a hexane solution of 8.33 mol / L methyl hydrogen polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) was pumped while stirring at 80°C, and stirring was continued at 80°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and the resulting reaction solution was used as raw material (a-1). The total concentration of magnesium and aluminum in raw material (a-1) was 0.786 mol / L.

[0338] (2) 1600 mL of hexane was added to an 8 L stainless steel autoclave after nitrogen substitution, and 800 mL of a 1 mol / L titanium tetrachloride hexane solution and 800 mL of the raw material (a-1) were added simultaneously over 5 hours while stirring at 10° C. The reaction was continued at 10° C. for 1 hour. After the reaction was completed, the supernatant of the obtained reaction solution was removed and washed 4 times with hexane to remove unreacted raw material components, thereby preparing a solid catalyst component [A].

[0339] [Preparation of solid catalyst component [B]]

[0340] (1) Synthesis of raw material (b-1)

[0341] 1 mol / L of Mg6(C4H9) was added to an 8L stainless steel autoclave that had been fully purged with nitrogen. 12 2000mL of Al(C2H5)3 hexane solution (equivalent to 2000 mmol in terms of the total amount of magnesium and aluminum) was added dropwise with 146mL of 5.47mol / L n-butanol hexane solution for 3 hours while stirring at 50°C. After the addition, the pipeline was cleaned with 300mL of hexane. Then, stirring was continued at 50°C for 2 hours. After the reaction was completed, it was cooled to room temperature and the resulting reaction solution was used as raw material (b-1). The raw material (b-1) had a total concentration of 0.704mol / L of magnesium and aluminum.

[0342] (2) Synthesis of raw material (b-2)

[0343] 1 mol / L of Mg6(C4H9) was added to an 8L stainless steel autoclave that had been fully purged with nitrogen. 12 2000 mL of a hexane solution of Al(C2H5)3 (equivalent to 2000 mmol in terms of the total amount of magnesium and aluminum) was added, and 240 mL of a hexane solution of 8.33 mol / L methyl hydrogen polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) was pumped while stirring at 80°C, and stirring was continued at 80°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and the resulting reaction solution was used as raw material (b-2). The total concentration of magnesium and aluminum in raw material (b-2) was 0.786 mol / L.

[0344] (3) (B-1) Synthesis of carrier

[0345] 1000 mL of a 1 mol / L hexane solution of hydroxytrichlorosilane was added to an 8 L stainless steel autoclave after full nitrogen substitution, and 1340 mL of a hexane solution of an organic magnesium compound of the raw material (b-1) (equivalent to 943 mmoles of magnesium) was added dropwise at 65° C. for 3 hours, and then the reaction was continued while stirring at 65° C. for 1 hour. After the reaction was completed, the supernatant of the obtained reaction solution was removed and washed 4 times with 1800 mL of hexane to obtain a carrier (B-1). The carrier was analyzed, and the magnesium contained in 1 g of solid was 7.5 mmoles.

[0346] (4) 1970 mL of hexane slurry containing 110 g of the above-mentioned (B-1) carrier was stirred at 10° C. for 3 hours while adding 103 mL of a 1 mol / L titanium tetrachloride hexane solution and 131 mL of the raw material (b-2). After the addition, the reaction was continued at 10° C. for 1 hour. After the reaction was completed, the supernatant of the obtained reaction solution was removed and washed with hexane 4 times to remove the unreacted raw material components, thereby obtaining a solid catalyst component [B].

[0347] [Example 1]

[0348] (Polyethylene polymerization process)

[0349] Hexane, ethylene, hydrogen and catalyst are continuously supplied to a container-type 300L polymerization reactor (1) with a stirring device. The polymerization pressure is 0.5MPa. The polymerization temperature is maintained at 83°C by jacket cooling. Hexane is supplied from the bottom of the polymerization reactor (1) at a rate of 40L / hour. A solid catalyst component [A] is used as a catalyst, and a mixture of triisobutylaluminum and diisobutylaluminum hydride (a mixture in a mass ratio of 9:1, respectively) is used as a co-catalyst. The solid catalyst component [A] is added from the middle of the liquid surface and the bottom of the polymerization reactor (1) at a rate of 0.2g / hour, and the co-catalyst is added from the middle of the liquid surface and the bottom of the polymerization reactor (1) at a rate of 10mmol / hour. The production rate of polyethylene is 14kg / hour. Hydrogen is continuously supplied by a pump so that the hydrogen concentration relative to ethylene in the gas phase is 11.0 mol%. It should be noted that hydrogen is supplied to the gas phase, and ethylene is supplied from the bottom of the polymerization reactor (1). The catalyst activity is 50000 g-PE / g-solid catalyst component [A]. Next, the polymerization slurry is continuously extracted into a flash tank at a pressure of 0.05 MPa and a temperature of 83°C to keep the liquid level of the polymerization reactor constant, and then the polymerization slurry is supplied to a container-type 300L polymerization reactor (2) at a pressure of 0.8 MPa and a temperature of 83°C by a slurry pump for the second step polymerization, and then the unreacted ethylene and hydrogen are separated. The catalyst activity is 70000 g-PE / g-solid catalyst component [A]. It should be noted that the polymerization slurry residence time of the first step is 1 hour, and the polymerization slurry residence time of the second step is 4 hours.

[0350] Next, the polymerized slurry was continuously fed to a centrifuge so that the liquid level in the polymerization reactor was kept constant, and the polyethylene powder was separated from the solvent and the like. At this time, the content of the solvent and the like relative to the polyethylene powder was 87% by mass.

[0351] The separated polyethylene powder is dried in the following three stages while blowing nitrogen. As the front-end drying, drying is performed at 115°C for a time equivalent to 1 / 4 of the total drying time. At this time, a mixed solution of water: methanol = 20:80 is sprayed into the dryer to infiltrate the ultra-high molecular weight polyethylene powder and deactivate the catalyst and the co-catalyst. As the middle-end drying, drying is performed at 95°C for a time equivalent to 2 / 4 of the total drying time, and as the rear-end drying, drying is performed at 80°C for a time equivalent to 1 / 4 of the total drying time. It should be noted that the overall drying time is 2 hours.

[0352] 500 ppm of calcium stearate (manufactured by Dainichi Chemical Co., Ltd.) was added to the obtained ultra-high molecular weight polyethylene powder and uniformly mixed using a Henschel mixer. The obtained ultra-high molecular weight polyethylene powder was sieved with a sieve having a mesh size of 425 μm to remove the powder that did not pass through the sieve, thereby obtaining an ultra-high molecular weight polyethylene powder. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0353] (Method for producing microporous membrane for secondary battery separator)

[0354] Relative to the total of 100 parts by mass of the obtained ultra-high molecular weight polyethylene powder and liquid paraffin, the amount of the ultra-high molecular weight polyethylene powder is set to 40 parts by mass, and the amount of the liquid paraffin is set to 60 parts by mass, and a microporous membrane for a secondary battery separator is manufactured by the method described in (11). The evaluation results of the obtained microporous membrane are shown in Table 1.

[0355] [Example 2]

[0356] (Polyethylene polymerization process)

[0357] The same procedure as in Example 1 was followed except that 0.4 mol % of 1-butene relative to ethylene was introduced from the gas phase to obtain an ultrahigh molecular weight polyethylene powder of Example 2. The viscosity average molecular weight of the obtained ultrahigh molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0358] (Method for producing microporous membrane for secondary battery separator)

[0359] The microporous membrane of Example 2 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0360] [Example 3]

[0361] (Polyethylene polymerization process)

[0362] Using solid catalyst component [B] as the catalyst, using Mg6(C4H9) 12The same method as in Example 1 was used except that Al(C2H5)3 was used as a co-catalyst, the temperature was set to 70°C and the pressure was set to 0.4 MPa in the first polymerization step, the temperature was set to 70°C and the pressure was set to 0.7 MPa in the second polymerization step, 0.25 mol % of 1-butene relative to ethylene was introduced from the gas phase, and the hydrogen concentration relative to ethylene in the gas phase was set to 0.20 mol %, thereby obtaining the ultra-high molecular weight polyethylene powder of Example 3. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 300×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0363] (Method for producing high-strength fiber)

[0364] The conditions were set as follows, with the ultra-high molecular weight polyethylene powder being added in an amount of 10 parts by mass and the liquid paraffin being added in an amount of 90 parts by mass relative to a total of 100 parts by mass of the obtained ultra-high molecular weight polyethylene powder and liquid paraffin, and high-strength fibers were produced by the method described in (16) above. The evaluation results of the obtained high-strength fibers are shown in Table 1.

[0365] (each condition)

[0366] Slurry stirring temperature: 80℃

[0367] Slurry stirring time: 1 hour

[0368] Mixing temperature in extruder: 200°C

[0369] Melt residence time in extruder: 10 minutes

[0370] Spinneret temperature: 200°C,

[0371] The amount of filament ejected from the extruder: 0.5 g / min

[0372] Spinneret aperture: 1.0mm

[0373] Air gap: 4cm

[0374] Temperature of water bath when quenching silk: 5°C

[0375] Winding speed: 30m / min

[0376] Vacuum drying time: 24 hours

[0377] The temperature of the wire when it contacts the metal heater during the first stretch: 120°C

[0378] Wire temperature when in contact with metal heater during secondary drawing: 140°C

[0379] [Example 4]

[0380] (Polyethylene polymerization process)

[0381] Using solid catalyst component [B] as the catalyst, using Mg6(C4H9) 12 The same method as in Example 1 was used except that Al(C2H5)3 was used as a co-catalyst, the temperature was set to 60°C and the pressure was set to 0.4 MPa in the first polymerization step, the temperature was set to 60°C and the pressure was set to 0.7 MPa in the second polymerization step, and the hydrogen concentration relative to ethylene in the gas phase was set to 0.20 mol %, thereby obtaining an ultra-high molecular weight polyethylene powder of Example 4. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 660×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0382] (Method for producing high-strength fiber)

[0383] The high-strength fiber of Example 4 was obtained in the same manner as in Example 3 except that the blending amount of the ultra-high molecular weight polyethylene powder was set to 5 parts by mass and the blending amount of the liquid paraffin was set to 95 parts by mass relative to the total of 100 parts by mass of the obtained ultra-high molecular weight polyethylene powder and liquid paraffin. The evaluation results of the obtained high-strength fiber are shown in Table 1.

[0384] [Example 5]

[0385] (Polyethylene polymerization process)

[0386] The same procedure as in Example 1 was followed except that the first step polymerization slurry retention time was changed to 4 hours and the second step polymerization slurry retention time was changed to 1 hour to obtain an ultra-high molecular weight polyethylene powder of Example 5. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0387] (Method for producing microporous membrane for secondary battery separator)

[0388] The microporous membrane of Example 5 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0389] [Example 6]

[0390] (Polyethylene polymerization process)

[0391] The ultra-high molecular weight polyethylene powder of Example 6 was obtained in the same manner as in Example 1 except that the pressure during the second step polymerization was changed to 0.5 MPa. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0392] (Method for producing microporous membrane for secondary battery separator)

[0393] The microporous membrane of Example 6 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0394] [Example 7]

[0395] (Polyethylene polymerization process)

[0396] The same procedure as in Example 1 was followed except that the first step polymerization slurry retention time was changed to 4 hours, the second step polymerization slurry retention time was changed to 1 hour, and the front stage drying temperature was changed to 90°C to obtain an ultra-high molecular weight polyethylene powder of Example 7. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0397] (Method for producing microporous membrane for secondary battery separator)

[0398] The microporous membrane of Example 7 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0399] [Example 8]

[0400] (Polyethylene polymerization process)

[0401] The ultra-high molecular weight polyethylene powder of Example 8 was obtained in the same manner as in Example 1 except that the post-stage drying temperature was changed to 110°C. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0402] (Method for producing microporous membrane for secondary battery separator)

[0403] The microporous membrane of Example 8 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0404] [Example 9]

[0405] (Polyethylene polymerization process)

[0406] Using solid catalyst component [B] as the catalyst, using Mg6(C4H9) 12 The same method as in Example 1 was used except that Al(C2H5)3 was used as a co-catalyst, the temperature was set to 70°C and the pressure was set to 0.4 MPa in the first polymerization step, the temperature was set to 70°C and the pressure was set to 0.7 MPa in the second polymerization step, and the hydrogen concentration relative to ethylene in the gas phase was set to 0.20 mol %, thereby obtaining an ultra-high molecular weight polyethylene powder of Example 9. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 300×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0407] (Method for producing high-strength fiber)

[0408] High-strength fibers were produced in the same manner as in Example 3 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained high-strength fibers.

[0409] [Comparative Example 1]

[0410] (Polyethylene polymerization process)

[0411] The polymerization was carried out in the same manner as in Example 1 except that the temperature was set to 85° C. and the concentration of hydrogen relative to ethylene in the gas phase was set to 30.0 mol % in the first and second steps of polymerization, thereby obtaining an ultra-high molecular weight polyethylene powder (fusion solidified) of Comparative Example 1. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 3×10 4 In addition, since the obtained ultra-high molecular weight polyethylene powder was fused and solidified, various properties were not measured.

[0412] (Method for producing microporous membrane for secondary battery separator)

[0413] A membrane was formed in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used, but no microporous membrane could be obtained.

[0414] [Comparative Example 2]

[0415] (Polyethylene polymerization process)

[0416] Using solid catalyst component [B] as the catalyst, using Mg6(C4H9) 12 The same method as in Example 1 was used except that Al(C2H5)3 was used as a co-catalyst, the temperature was set to 50°C and the pressure was set to 0.3 MPa in the first polymerization step, the temperature was set to 50°C and the pressure was set to 0.6 MPa in the second polymerization step, and the hydrogen concentration relative to ethylene in the gas phase was set to 0.005 mol %, thereby obtaining an ultra-high molecular weight polyethylene powder of Comparative Example 2. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 1200×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0417] (Method for producing microporous membrane for secondary battery separator)

[0418] The microporous membrane of Comparative Example 2 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0419] [Comparative Example 3]

[0420] (Polyethylene polymerization process)

[0421] Hexane, ethylene, hydrogen and catalyst are continuously supplied to a container-type 300L polymerization reactor (1) with a stirring device. The polymerization pressure is 0.5MPa. The polymerization temperature is maintained at 83°C by jacket cooling. Hexane is supplied from the bottom of the polymerization reactor (1) at a rate of 40L / hour. A solid catalyst component [A] is used as a catalyst, and a mixture of triisobutylaluminum and diisobutylaluminum hydride (a mixture in a mass ratio of 9:1, respectively) is used as a co-catalyst. The solid catalyst component [A] is added from the middle of the liquid surface and the bottom of the polymerization reactor (1) at a rate of 0.2g / hour, and the co-catalyst is added from the middle of the liquid surface and the bottom of the polymerization reactor (1) at a rate of 10mmol / hour. The production rate of polyethylene is 14kg / hour. Hydrogen is continuously supplied by a pump so that the hydrogen concentration relative to ethylene in the gas phase is 11.0 mol%. It should be noted that hydrogen is supplied to the gas phase, and ethylene is supplied from the bottom of the polymerization reactor (1). The catalyst activity is 50000 g-PE / g-solid catalyst component [A]. Next, the polymerization slurry is continuously extracted into a flash tank at a pressure of 0.05 MPa and a temperature of 83°C to keep the liquid level of the polymerization reactor constant, and then the polymerization slurry is supplied to a container-type 300L polymerization reactor (2) at a pressure of 0.5 MPa and a temperature of 83°C by a slurry pump for the second step polymerization, and then the unreacted ethylene and hydrogen are separated. The catalyst activity is 50000 g-PE / g-solid catalyst component [A]. It should be noted that the polymerization slurry residence time of the first step is 1 hour, and the polymerization slurry residence time of the second step is 4 hours.

[0422] Next, the polymerized slurry was continuously fed to a centrifuge so that the liquid level in the polymerization reactor was kept constant, and the polyethylene powder was separated from the solvent and the like. At this time, the content of the solvent and the like relative to the polyethylene powder was 87% by mass.

[0423] The separated polyethylene powder was dried in the following three stages while blowing nitrogen. As the front-end drying, the powder was dried at 90°C for 1 / 4 of the total drying time. At this time, water was sprayed into the dryer to deactivate the catalyst and the co-catalyst. As the middle-end drying, the powder was dried at 100°C for 1 / 4 of the total drying time, and as the rear-end drying, the powder was dried at 110°C for 2 / 4 of the total drying time. It should be noted that the overall drying time was 2 hours.

[0424] 500 ppm of calcium stearate (manufactured by Dainichi Chemical Co., Ltd.) was added to the obtained ultra-high molecular weight polyethylene powder and uniformly mixed using a Henschel mixer. The obtained ultra-high molecular weight polyethylene powder was sieved with a sieve having a mesh size of 425 μm to remove the powder that did not pass through the sieve, thereby obtaining an ultra-high molecular weight polyethylene powder. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0425] (Method for producing microporous membrane for secondary battery separator)

[0426] The microporous membrane of Comparative Example 3 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0427] [Comparative Example 4]

[0428] (Polyethylene polymerization process)

[0429] Hexane, ethylene, hydrogen and catalyst are continuously supplied to a container-type 300L polymerization reactor (1) with a stirring device. The polymerization pressure is 0.5MPa. The polymerization temperature is maintained at 83°C by jacket cooling. Hexane is supplied from the bottom of the polymerization reactor (1) at a rate of 40L / hour. A solid catalyst component [A] is used as a catalyst, and a mixture of triisobutylaluminum and diisobutylaluminum hydride (a mixture in a mass ratio of 9:1, respectively) is used as a co-catalyst. The solid catalyst component [A] is added from the middle of the liquid surface and the bottom of the polymerization reactor (1) at a rate of 0.2g / hour, and the co-catalyst is added from the middle of the liquid surface and the bottom of the polymerization reactor (1) at a rate of 10mmol / hour. The production rate of polyethylene is 14kg / hour. Hydrogen is continuously supplied by a pump so that the hydrogen concentration relative to ethylene in the gas phase is 11.0 mol%. It should be noted that hydrogen is supplied to the gas phase, and ethylene is supplied from the bottom of the polymerization reactor (1). The catalyst activity was 50000 g-PE / g-solid catalyst component [A]. Next, the polymerization slurry was continuously extracted into a flash tank at a pressure of 0.05 MPa and a temperature of 83°C to keep the liquid level in the polymerization reactor constant, and unreacted ethylene and hydrogen were separated.

[0430] Next, the polymerized slurry was continuously fed to a centrifuge so that the liquid level in the polymerization reactor was kept constant, and the polyethylene powder was separated from the solvent and the like. At this time, the content of the solvent and the like relative to the polyethylene powder was 87% by mass.

[0431] The separated polyethylene powder was dried in the following three stages while blowing nitrogen. As the front-stage drying, drying was performed at 90°C for a time equivalent to 1 / 4 of the total drying time. At this time, water was sprayed into the dryer to deactivate the catalyst and the co-catalyst. As the middle-stage drying, drying was performed at 100°C for a time equivalent to 1 / 4 of the total drying time, and as the rear-stage drying, drying was performed at 120°C for a time equivalent to 2 / 4 of the total drying time. It should be noted that the overall drying time was 2 hours. 500 ppm of calcium stearate (manufactured by Dainichi Chemical Co., Ltd.) was added to the obtained ultra-high molecular weight polyethylene powder, and the mixture was uniformly mixed using a Henschel mixer. The obtained ultra-high molecular weight polyethylene powder was sieved with a mesh size of 425 μm to remove the powder that did not pass through the sieve, thereby obtaining an ultra-high molecular weight polyethylene powder. The viscosity average molecular weight of the obtained ultra-high molecular weight polyethylene powder was 30×10 4 In addition, the properties of the obtained ultra-high molecular weight polyethylene powder were measured by the above-mentioned method. The measurement results are shown in Table 1.

[0432] (Method for producing microporous membrane for secondary battery separator)

[0433] The microporous membrane of Comparative Example 4 was obtained in the same manner as in Example 1 except that the obtained ultrahigh molecular weight polyethylene powder was used. Table 1 shows the evaluation results of the obtained microporous membrane.

[0434]

[0435] This application is based on Japanese patent application (Japanese Patent Application No. 2020-051302) filed on March 23, 2020, the contents of which are incorporated herein by reference.

[0436] Industrial Applicability

[0437] The ultra-high molecular weight polyethylene powder of the present invention can produce a uniform gel with excellent solubility in a solvent, and it is also easy to remove bubbles in the powder, so that a polyethylene powder with excellent processability can be obtained. As a result, the ultra-high molecular weight polyethylene powder of the present invention can provide, for example, a molded body, a stretched molded body, a microporous film, and a fiber with excellent uniformity, and has industrial applicability.

Claims

1. An ultra-high molecular weight polyethylene powder, wherein: The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 10×10 4 Above and 1000×10 4 the following, The difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder determined by the following method is 3° C. or more and 25° C. or less, and The liquid paraffin impregnation rate (weight increase rate) of the ultra-high molecular weight polyethylene powder determined by the following method is 0.5% or more and 5.0% or less, [Method for measuring swelling onset temperature and dissolution onset temperature] While confirming with an optical microscope, a particle of ultra-high molecular weight polyethylene powder having a long diameter and a short diameter of 120 μm or more and 130 μm or less is randomly selected, and the selected particle of ultra-high molecular weight polyethylene powder (hereinafter also referred to as "measurement particle") is placed on a cover glass, and a drop of liquid paraffin is dripped onto the measurement particle using a 2 mL dropper, and then a cover glass is placed to sandwich the measurement particle. Then, the cover glass sandwiching the measurement particle is placed on a heating table, and an optical microscope with a camera is used to observe the process of heating the measurement particle from room temperature to 150° C. under the following heating conditions. During the heating step, an observation image of the measurement particle is captured every 6 seconds. After the measurement is completed, the equivalent circle diameter of the measurement particle is calculated from each observation image using image analysis software, and the swelling start temperature and the dissolution start temperature are determined as follows. (Temperature rising conditions) Heating rate from room temperature to 35°C: 5°C / min Heating rate within the range of 35℃~80℃: 8℃ / min Heating rate within the range of 80℃~150℃: 5℃ / min [Swelling start temperature] The equivalent circle diameter of the measured particle is calculated from the observation image obtained by photographing the measured particle using image analysis software. The equivalent circle diameter of the measured particle at 80°C is used as a reference. In the temperature range of 80°C to 150°C, the lowest temperature at which the equivalent circle diameter of the measured particle increases by 1% or more is used as the swelling start temperature. The average value of three such measurements is used as the final swelling start temperature. [Melting start temperature] The equivalent circle diameter of the measured particle is calculated from the observation image obtained by photographing the measured particle using image analysis software, and the measured temperature when the equivalent circle diameter of the measured particle shows the maximum value is taken as the dissolution start temperature, and the average value of the three measurements is taken as the final dissolution start temperature. [Calculation method of liquid paraffin impregnation rate (weight increase rate)] 10 g of ultra-high molecular weight polyethylene powder and 30 g of liquid paraffin were mixed to prepare a sample, and the prepared sample was placed in a metal container, covered with aluminum foil, and placed at 70°C for 3 hours. Then, the sample was dried under reduced pressure at 110°C / reduced pressure (-0.1 MPaG) for 5 hours. Then, the sample was washed and filtered three times using 10 g of hexane, and then air-dried for more than 24 hours. The weight of the ultra-high molecular weight polyethylene powder was measured, and the liquid paraffin (LP) impregnation rate (weight increase rate) was calculated by the following formula based on the increase rate of the weight of the ultra-high molecular weight polyethylene powder after impregnation with liquid paraffin (weight after impregnation) relative to the original weight of the ultra-high molecular weight polyethylene powder (weight before impregnation). Liquid paraffin impregnation rate (%) = (weight after impregnation - weight before impregnation) / weight before impregnation × 100.

2. The ultra-high molecular weight polyethylene powder according to claim 1, wherein The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 10×10 4 Above and 900×10 4 the following.

3. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 10×10 4 Above and 800×10 4 the following.

4. The ultra-high molecular weight polyethylene powder according to claim 1, wherein The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is greater than or equal to 10×10 4 And less than 300×10 4 .

5. The ultra-high molecular weight polyethylene powder according to claim 4, wherein The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 10×10 4 Above and 200×10 4 the following.

6. The ultra-high molecular weight polyethylene powder according to claim 1, wherein The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 300×10 4 Above and 1000×10 4 the following.

7. The ultra-high molecular weight polyethylene powder according to claim 6, wherein The viscosity average molecular weight (Mv) of the ultra-high molecular weight polyethylene powder is 300×10 4 Above and 800×10 4 the following.

8. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder is 4° C. or more.

9. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder is 5° C. or more.

10. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder is 7° C. or more.

11. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The difference between the swelling start temperature and the dissolution start temperature of the ultra-high molecular weight polyethylene powder is 20° C. or less.

12. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The ultra-high molecular weight polyethylene powder has a liquid paraffin impregnation rate (weight increase rate) of 1.0% or more and 4.5% or less.

13. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The ultra-high molecular weight polyethylene powder has a liquid paraffin impregnation rate (weight increase rate) of 2.0% or more and 4.5% or less.

14. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: When the BET method based on krypton gas adsorption was used to measure ultra-high molecular weight polyethylene powder with a particle size of less than 75 μm, the pore specific surface area was 0.10 m 2 / g or more and 1.50m 2 / g or less.

15. The ultra-high molecular weight polyethylene powder according to claim 14, wherein The pore specific surface area is 0.10m 2 / g or more and 1.40m 2 / g or less.

16. The ultra-high molecular weight polyethylene powder according to claim 14, wherein The pore specific surface area is 0.20m 2 / g or more and 1.20m 2 / g or less.

17. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: When an ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is measured using a mercury porosimeter, the pore volume is 0.30 mL / g or more and 1.70 mL / g or less.

18. The ultra-high molecular weight polyethylene powder according to claim 17, wherein The pore volume is 0.30 mL / g or more and 1.30 mL / g or less.

19. The ultra-high molecular weight polyethylene powder according to claim 17, wherein: The pore volume is 0.40 mL / g or more and 1.20 mL / g or less.

20. The ultra-high molecular weight polyethylene powder according to claim 17, wherein The pore volume is 0.50 mL / g or more and 1.00 mL / g or less.

21. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: When an ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is measured using a mercury porosimeter, the average pore size is 0.10 μm or more and 0.80 μm or less.

22. The ultra-high molecular weight polyethylene powder according to claim 21, wherein The average pore diameter is 0.10 μm or more and 0.50 μm or less.

23. The ultra-high molecular weight polyethylene powder according to claim 21, wherein The average pore diameter is 0.10 μm or more and 0.45 μm or less.

24. The ultra-high molecular weight polyethylene powder according to claim 21, wherein The average pore diameter is 0.20 μm or more and 0.40 μm or less.

25. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The crystallinity of the ultra-high molecular weight polyethylene powder is greater than or equal to 70% and less than 82%.

26. The ultra-high molecular weight polyethylene powder according to claim 25, wherein The ultra-high molecular weight polyethylene powder has a crystallinity of 70% or more and 80% or less.

27. The ultra-high molecular weight polyethylene powder according to claim 25, wherein The ultra-high molecular weight polyethylene powder has a crystallinity of 70% or more and 78% or less.

28. The ultra-high molecular weight polyethylene powder according to claim 25, wherein The ultra-high molecular weight polyethylene powder has a crystallinity of 70% or more and 75% or less.

29. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: When the entire ultra-high molecular weight polyethylene powder is taken as 100 mass %, the proportion of the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is 35 mass % or less.

30. The ultra-high molecular weight polyethylene powder according to claim 29, wherein When the entire ultra-high molecular weight polyethylene powder is taken as 100 mass %, the proportion of the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is 33 mass % or less.

31. The ultra-high molecular weight polyethylene powder according to claim 29, wherein When the entire ultra-high molecular weight polyethylene powder is taken as 100 mass %, the proportion of the ultra-high molecular weight polyethylene powder having a particle size of less than 75 μm is 30 mass % or less.

32. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The ultra-high molecular weight polyethylene powder has an average particle size (D50) of 60 μm or more and 140 μm or less.

33. The ultra-high molecular weight polyethylene powder according to claim 32, wherein: The average particle size (D50) of the ultra-high molecular weight polyethylene powder is 60 μm or more and 120 μm or less.

34. The ultra-high molecular weight polyethylene powder according to claim 32, wherein: The average particle size (D50) of the ultra-high molecular weight polyethylene powder is 60 μm or more and 115 μm or less.

35. The ultra-high molecular weight polyethylene powder according to claim 32, wherein The average particle size (D50) of the ultra-high molecular weight polyethylene powder is 60 μm or more and 100 μm or less.

36. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The titanium content in the ultra-high molecular weight polyethylene powder is 0.1 ppm or more and 5.0 ppm or less.

37. The ultra-high molecular weight polyethylene powder according to claim 36, wherein The titanium content in the ultra-high molecular weight polyethylene powder is 0.5 ppm or more and 5.0 ppm or less.

38. The ultra-high molecular weight polyethylene powder according to claim 36, wherein The titanium content in the ultra-high molecular weight polyethylene powder is 1.0 ppm or more and 4.0 ppm or less.

39. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The aluminum content in the ultra-high molecular weight polyethylene powder is 0.1 ppm or more and 5.0 ppm or less.

40. The ultra-high molecular weight polyethylene powder according to claim 39, wherein The aluminum content in the ultra-high molecular weight polyethylene powder is 0.1 ppm or more and 4.0 ppm or less.

41. The ultra-high molecular weight polyethylene powder according to claim 39, wherein The aluminum content in the ultra-high molecular weight polyethylene powder is 0.1 ppm or more and 3.5 ppm or less.

42. The ultra-high molecular weight polyethylene powder according to claim 1 or 2, wherein: The ultra-high molecular weight polyethylene powder is a powder containing an ethylene homopolymer and / or a copolymer of ethylene and an olefin copolymerizable with ethylene.

43. The ultra-high molecular weight polyethylene powder according to claim 42, wherein The olefin copolymerizable with ethylene is selected from α-olefins having 3 to 15 carbon atoms, cyclic olefins having 3 to 15 carbon atoms, 1 (Here, R 1 is an aryl group having 6 to 12 carbon atoms), and at least one comonomer selected from the group consisting of a linear, branched or cyclic diene having 3 to 15 carbon atoms.

44. The ultra-high molecular weight polyethylene powder according to claim 43, wherein The α-olefin is at least one selected from the group consisting of propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, and 1-tetradecene.

45. The ultra-high molecular weight polyethylene powder according to claim 42, wherein The content of the comonomer unit in the copolymer is 0.01 mol % or more and 5 mol % or less.

46. ​​The ultra-high molecular weight polyethylene powder according to claim 45, wherein The content of the comonomer unit in the copolymer is 0.01 mol % or more and 2 mol % or less.

47. The ultra-high molecular weight polyethylene powder according to claim 45, wherein The content of the comonomer unit in the copolymer is 0.01 mol % or more and 1 mol % or less.

48. A molded body, wherein The molded body is obtained by molding the ultra-high molecular weight polyethylene powder according to any one of claims 1 to 47.

49. The molded article according to claim 48, wherein The molded body is a microporous membrane, a high-strength fiber or a sintered body.

50. The molded article according to claim 49, wherein The molded body is a microporous membrane for a secondary battery separator.

51. The molded article according to claim 49 or 50, wherein The molded body is a microporous membrane for a lithium ion secondary battery separator.

52. The molded article according to claim 49 or 50, wherein The microporous membrane has a thickness variation of less than ±5 μm relative to an average thickness.

53. The molded article according to claim 49 or 50, wherein The maximum puncture load of the microporous membrane is greater than 3.0N.

54. The molded article according to claim 49 or 50, wherein The number of wrinkles of the microporous membrane is 50 or less / 1000 m 2 .

55. The molded article according to claim 49, wherein The variation of the fiber diameter of the high-strength fiber relative to the average fiber diameter is less than ±10 μm.

56. The molded article according to claim 49, wherein The tensile breaking strength of the high-strength fiber is greater than or equal to 20 cN / dtex.

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