A type of fine particle size, low bulk density ultra-high molecular weight polyethylene powder

Abstract

The present invention provides a class of ultra-high molecular weight polyethylene microparticles having a small particle size and a low bulk density. Specifically, the present invention provides microparticles having the following characteristics: (a) a viscosity-average molecular weight in the range of 1 million to 5 million; (b) at least 90% by weight passing through a 100-mesh sieve; a particle median diameter (d50) of 40 μm < d50 < 80 μm; and (c) a powder bulk density of 0.25 to 0.33 g / cm 3 The ultra-high molecular weight polyethylene particles provided by the present invention are suitable for producing microporous filter materials.

Description

Technical Field

[0001] The present invention relates to a type of ultra-high molecular weight polyethylene particles suitable for manufacturing microporous filter equipment. More specifically, it relates to a type of ultra-high molecular weight polyethylene particles with a viscosity-average molecular weight of 1 to 5 million g / mol, a particle size distribution concentrated in the range (d50) of 40 μm < d50 < 80 μm, and a bulk density of 0.26 to 0.33 g / cm 3 Polyethylene microparticles. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a thermoplastic engineering plastic with the advantages of high impact resistance, extremely high wear resistance, high corrosion resistance, self-lubrication, resistance to environmental stress cracking, safety and hygiene. It can be processed into various products such as plates, pipes, fibers, films, etc. It is mainly used in military applications such as bulletproof vests, bulletproof helmets, bulletproof armor, cut-resistant gloves, as well as high-end fields such as aerospace, marine equipment, rail transportation, medical stents, fine filtration, and lithium battery separators.

[0003] In recent years, the development of polymer microparticles has also made certain progress. Various types of polymer special materials have been widely used in different production fields. The materials involve acrylic resins, styrene resins, melamine resins and polyolefin resins. Ultra-high molecular weight polyethylene resin particles, in particular, are being considered more for various new materials and new uses due to their excellent performance. Using them to prepare microporous materials for filtration and separation processes has become a new application direction for ultra-high molecular weight polyethylene. UHMWPE microporous filter material refers to a material with UHMWPE as an organic matrix, in which a large number of microscopic interconnected pores in the thickness direction are generated on the matrix during the molding process, thereby meeting the needs of various treatment processes. At present, the main methods for preparing UHMWPE microporous materials are sintering method, particle filling method, nuclear track method, melt extrusion stretching method, TIPS method, TIPS-S method, etc. Different molding methods often have a great influence on important parameters such as pore size, distribution and porosity of microporous materials, and will also have a direct effect on their microstructure; on the other hand, the particle size of UHMWPE particles also has a significant impact on the performance of microporous filtration products. When applying the sintering process to prepare microporous filter materials, heat gradually enters the interior of the particles from the surface of the powder particles, and the larger the particles are, the better. The larger the particle size, the longer the time from softening the particle surface to melting inside the particle, and it is easier to form a porous structure, resulting in a large porosity. However, the microporous structure is likely to become irregular, the micropore distribution is also uneven, and the strength decreases accordingly. The finer the particle, the shorter the melting time is, the easier it is to stick together, and the more difficult it is to form a porous structure. The finer and more uniform the microporous structure is, the lower the porosity is, but the strength increases. At the same time, the particle size and the morphology of the particles almost determine the size of the pore size of the prepared product. According to the pore-forming mechanism of the sintering method, UHMWPE particles are stacked on each other, and the gaps between the particles constitute the source of the pores. Therefore, the larger the UHMWPE particle size and the more irregular the particle morphology, the larger the gaps between the particles, resulting in a larger pore size of the product.

[0004] At present, there is still little progress in the development of differentiated and dedicated ultra-high molecular weight polyethylene resin particles for microporous filtration materials. 3 ) still dominates the market, and the particle size range (D50) of polymer microparticle resin is mainly concentrated between 120 microns and 200 microns, or coarse particles above 600 microns. In addition, Mitsui Chemicals also produces an extremely fine UHMWPE powder with a registered trademark of MIPELON. TM The product particles are extremely fine, with an average particle size range of 25μm-30μm, but its bulk density is as high as 0.44g / cm 3. Patent CN200580039390.2 discloses ethylene polymer microparticles and catalysts for their manufacture, wherein at least 95% of the weight ratio of the polymer microparticles passes through a 37-micron mesh sieve, and the median diameter (d50) measured by laser diffraction scattering is 3μm≤d50≤25μm. The bulk density of the particles prepared by this technology is not listed, and the polymer requires a cumbersome step of removing inorganic impurities, and the preparation process of the catalyst reported in this patent method must use regulated toluene as a solvent. The patented technologies we developed in the early stage (202010585230.4, 202010585258.8, 202010583913.6) can obtain ultra-high and ultra-high molecular weight polyethylene resin microparticles with a particle size (d50) of 40μm≤d50≤80μm. The bulk density of the particles prepared by this technology is ≥0.35g / cm 3 , mainly used in the fields of ultra-high molecular weight polyethylene fiber and lithium battery separator. At the same time, the patent (202011019681.8) can obtain a class of particles with a median diameter (d50) of 80μm≤d50≤110μm and a powder bulk density of 0.20-0.30g / cm 3 Ultra-high molecular weight polyethylene powder.

[0005] In summary, based on our previously developed patented technology, by adjusting the catalyst preparation process and the polymerization process, we have newly developed a new type of ultra-high molecular weight polyethylene special resin microparticles with low bulk density, relatively finer particle size, suitable for manufacturing microporous filter equipment with higher filtration accuracy, a special catalyst for manufacturing the microparticles, a preparation method, and a method for catalyzing ethylene polymerization using the catalyst. Summary of the Invention

[0006] The present invention provides a type of microporous filter material suitable for manufacturing microporous filter materials, with a viscosity average molecular weight of 1-5 million g / mol, an average particle size range smaller than that of the commonly used commercial types, a particle size distribution concentrated in (d50) of 40 μm ≤ d50 ≤ 80 μm, and a bulk density of 0.26-0.33 g / cm 3 Ultra-high molecular weight polyethylene particles, a special catalyst for producing the particles, a preparation method, and a method for catalyzing ethylene polymerization using the catalyst.

[0007] In a first aspect of the present invention, there is provided an ultra-high molecular weight polyethylene particle having the following characteristics:

[0008] (a) a viscosity-average molecular weight of 1 to 5 million g / mol;

[0009] (b) ≥90 wt% can pass through a 100-mesh sieve, and the particle median diameter (d50) is 40 μm < d50 < 80 μm.

[0010] In another preferred embodiment, the viscosity average molecular weight of the microparticles is 2-3.5 million g / mol.

[0011] In another preferred embodiment, the d50 of the particles is 50 μm < d50 < 70 μm; and / or

[0012] The bulk density of the microparticles is 0.25-0.33 g / cm 3 and / or

[0013] The bulk density of the particles is 0.28-0.31 g / cm 3 ; More preferably 0.29-0.30g / cm 3 .

[0014] The second aspect of the present invention provides a method for preparing the polyethylene microparticles as described in the first aspect of the present invention, which comprises the steps of: contacting a catalyst and a co-catalyst with ethylene / hydrogen to carry out a catalytic polymerization reaction, thereby obtaining the ultra-high molecular weight polyethylene microparticles.

[0015] In another preferred embodiment, the catalyst is catalyst particles, or a catalyst slurry comprising the catalyst particles; the silicon content in the catalyst is 20-40wt%, the magnesium content is 10-30wt%, the aluminum content is 2-4wt%, the titanium content is 2-5wt%, and the chlorine content is 20-60wt%; wherein the silicon content is preferably 25-35wt%, the magnesium content is preferably 12-18wt%, and the titanium content is preferably 3-4wt%.

[0016] In another preferred embodiment, the solid concentration of the catalyst particles in the catalyst solution is 200-250 g / L.

[0017] In another preferred embodiment, the method comprises the steps of:

[0018] (1) In an inert solvent, hydrogen gas at 0.01-0.05 MPa is introduced into a reactor to which a catalyst and a co-catalyst have been added in advance, and then ethylene gas is introduced until the pressure in the reactor reaches 0.2-1.5 MPa. The polymerization reaction is carried out at 40-80°C for 1-3 hours, after which the introduction of ethylene is stopped;

[0019] (2) Lower the temperature in the kettle to below 50°C;

[0020] (3) removing the solvent from the slurry obtained in step (2);

[0021] (4) After vacuum drying, the polyethylene microparticles described in the first aspect of the present invention are obtained.

[0022] In another preferred embodiment, steam stripping is required between step (3) and step (4), that is, the wet material obtained in step (3) is subjected to steam stripping to deeply remove the organic solvent contained in the powder.

[0023] In another preferred embodiment, the catalyst is prepared by the following method:

[0024] (a) contacting a magnesium source with a C1-C10 alcohol and reacting them at 60-120° C., adding nanosilica gel, and homogenizing the mixture under high-speed dispersing stirring and ultrasonic oscillation, and then cooling the mixture to below -30° C. to obtain a precursor slurry PI;

[0025] (b) contacting the precursor slurry PI obtained in step (a) with an alkyl aluminum at a temperature below -30°C, and then heating to 60-120°C and maintaining for 2-6 hours to obtain a precursor slurry P-II;

[0026] (c) cooling the precursor slurry P-II obtained in step (b) to below -30°C, contacting it with an inert hydrocarbon solution of a titanium compound for 0.5-3 hours, and then heating it to 60-120°C and maintaining it for 2-6 hours to obtain a catalyst slurry C-III;

[0027] (d) filtering the catalyst slurry C-III obtained in step (c) to obtain a catalyst.

[0028] In another preferred embodiment, the magnesium source is magnesium chloride, preferably anhydrous magnesium chloride.

[0029] In another preferred embodiment, the method comprises:

[0030] (a) Under inert gas protection, anhydrous magnesium chloride is added to a mixture of an inert hydrocarbon solvent and a C1-C10 alcohol (preferably 2-6 equivalents of a C1-C10 alcohol) containing ≥2 equivalents of magnesium chloride, and the mixture is reacted at 60-120° C. to form a homogeneous solution. Nanosilica gel is added to the mixture and dispersed and homogenized under high-speed dispersing stirring and ultrasonic vibration to prepare a composite carrier, and then the mixture is cooled to below -30° C. to obtain a precursor slurry PI; wherein the cooling rate is preferably 1-10° C. / min; more preferably 1-5° C. / min, and most preferably 1° C. / min. In the above reaction, the amount of anhydrous magnesium chloride is taken as 1 equivalent.

[0031] (b) contacting the precursor slurry PI obtained in step (a) with an alkyl aluminum at a temperature below -30°C for at least 1 hour, and then heating to 60-120°C and maintaining for 2-6 hours to obtain a precursor slurry P-II; wherein the heating rate is preferably 1-10°C / min;

[0032] (c) cooling the precursor slurry P-II obtained in step (b) to below -30°C, contacting it with an inert hydrocarbon solution of a titanium compound for 0.5-3 hours, and then heating it to 60-120°C and maintaining it for 2-6 hours to obtain a catalyst slurry C-III; wherein the cooling rate is preferably 1-10°C / min, and the heating rate is preferably 1-10°C / min;

[0033] (d) filtering the catalyst slurry C-III obtained in step (c) to obtain a catalyst;

[0034] Preferably, the method for preparing the catalyst further comprises the step of: (e) drying the catalyst obtained in step (d) to obtain catalyst powder.

[0035] In another preferred embodiment, the mass ratio of the nano-silica gel to magnesium chloride is 1-3:1.

[0036] In another preferred embodiment, the nano silica gel has the appearance of white powder and a bulk density of less than 0.15 g / cm 3 , the particle size range can be 15 to 100 nm, preferably 30 to 50 nm.

[0037] In another preferred embodiment, in the catalyst preparation, the C1-C10 alcohol in step (a) is selected from the group consisting of methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, 2-ethylhexanol, n-octanol, or a combination thereof; and / or

[0038] In the catalyst preparation, the speed of the high-speed dispersing and stirring homogenizer in step (a) is 1000-6000 rpm, preferably 2000-5500 rpm, more preferably 4000-5000 rpm; and / or

[0039] In the catalyst preparation, the ultrasonic oscillation auxiliary power in step (a) is 600W and the frequency is 40KHz; and / or

[0040] In the catalyst preparation, the alkyl aluminum in step (b) is selected from the group consisting of ethyl aluminum dichloride, diethyl aluminum chloride, triethyl aluminum, triisobutyl aluminum, ethyl aluminum sesquichloride, or butyl aluminum sesquichloride; and / or

[0041] In the catalyst preparation, the molar ratio of the titanium compound to magnesium chloride in step (c) can be 0.3-0.8:1, preferably 0.4-0.6:1, and most preferably 0.5:1.

[0042] In another preferred embodiment, no toluene, halogenated hydrocarbons or aromatic hydrocarbons are used in the catalyst preparation step.

[0043] In another preferred embodiment, the titanium compound is selected from the following group: TiCl4, TiR4, or an alkyl complex represented by structural formula I-IV; wherein R is a C1-C6 alkyl, allyl, benzyl, or NMe2, and the alkyl is preferably methyl, ethyl, propyl, or butyl:

[0044]

[0045] Where X is SR 5 or P(R 5 )2;

[0046] R 1 、R 2 、R 3 、R 4 、R 5 Each is independently a substituted or unsubstituted group selected from the group consisting of a C1-C6 alkyl group, a C2-C6 alkenyl group, a C3-C8 cycloalkyl group, a C6-C10 aryl group, a halogenated C3-C8 cycloalkyl group, and a 5-7 membered heteroaryl group;

[0047] or R 3 and R 4 , and the carbon atoms connected thereto together form a 5-7 membered saturated, partially unsaturated or aromatic carbocyclic or heterocyclic ring;

[0048] R 6 Selected from the following group: C1-C6 alkyl, NH2, N(C1-C6 alkyl)2, allyl, benzyl, C1-C6 silyl; the alkyl is preferably methyl, ethyl, propyl or butyl;

[0049] R 7 Selected from the group consisting of C1-C6 alkyl, C2-C6 alkenyl, or C3-C8 cycloalkyl;

[0050] Wherein, the heteroaryl group has 1-3 heteroatoms selected from the following group: N, S(O), P or O;

[0051] Unless otherwise specified, the term "substituted" refers to substitution by one or more (e.g., 2, 3, 4, etc.) substituents selected from the group consisting of halogen, C1-C6 alkyl, halogenated C1-C6 alkyl, C1-C6 alkoxy, and halogenated C1-C6 alkoxy.

[0052] In another preferred embodiment, the titanium complex is a molecule having the following structure:

[0053]

[0054] The third aspect of the present invention provides a microporous filtration product, which is prepared using the ultra-high molecular weight polyethylene particles described in the first aspect of the present invention.

[0055] In another preferred embodiment, the porosity of the microporous filtration product is ≥40%.

[0056] In another preferred embodiment, the filtration accuracy of the microporous filtration product can be as low as 0.30 microns.

[0057] In another preferred embodiment, the solid insoluble matter filtration efficiency of the microporous filtration product is greater than 99.9%.

[0058] In another preferred embodiment, under the water pressure of 0.2 MPa, the water permeability of the microporous filtration product can reach 20m 3 / h.

[0059] A fourth aspect of the present invention provides a method for preparing the product according to the third aspect of the present invention, characterized in that it comprises the steps of:

[0060] (i) using polyethylene wax and calcium stearate as composite additives and uniformly mixing them with the ultra-high molecular weight polyethylene particles of the first aspect of the present invention to obtain a mixed material;

[0061] (ii) placing the mold into a pressureless sintering process;

[0062] (iii) cooling to obtain an ultra-high molecular weight polyethylene microporous filtration product.

[0063] In another preferred embodiment, the mass ratio of the ultra-high molecular weight polyethylene particles: polyethylene wax: calcium stearate is 250-350:2-8:0.8-1.2.

[0064] In another preferred embodiment, the sintering temperature is 180-220°C.

[0065] In another preferred embodiment, the sintering time is 10-20 minutes.

[0066] In another preferred embodiment, the cooling is performed by water cooling.

[0067] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features described in detail below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be listed here one by one. DETAILED DESCRIPTION

[0068] After long and in-depth research, the inventors have produced ultra-high molecular weight polyethylene particles suitable for manufacturing microporous filter equipment with higher filtration accuracy. The prepared polyethylene has a viscosity-average molecular weight of 1-5 million g / mol, at least 90% by weight passes through a 100-mesh sieve, and the particle size distribution is concentrated in the range (d50) of 40 μm ≤ d50 ≤ 80 μm, with a bulk density of 0.26-0.33 g / cm 3 The present invention is based on the above findings and is the result of a special catalyst for producing polyethylene microparticles, a preparation method thereof, and a method for catalyzing ethylene polymerization using the catalyst.

[0069] Ultra-high molecular weight polyethylene microparticles with fine particle size and low bulk density and their preparation

[0070] The present invention provides a class of ultra-high molecular weight polyethylene particles, which meet at least the following characteristics: (a) a viscosity-average molecular weight in the range of 1 million to 5 million; (b) at least 90% by weight passing through a 100-mesh sieve; a particle median diameter (d50) of 40 μm ≤ d50 ≤ 80 μm; and (c) a powder bulk density of 0.26-0.33 g / cm 3 .

[0071] In a preferred embodiment, the viscosity average molecular weight of the microparticles is in the range of 1.5-3.5 million.

[0072] Since the polyethylene microparticles of the present invention have a smaller particle size than the microparticles of the prior art, they are suitable for preparing products requiring ultrafine polyethylene microparticles, such as microporous filtration products.

[0073] The molecular weight of the ultra-high molecular weight polyethylene particles described herein can be conveniently controlled by polymerization conditions: ethylene is catalytically polymerized in the presence of a catalyst and a co-catalyst at 40-80°C, a hydrogen pressure of 0.01-0.05 MPa, and an ethylene pressure of 0.2-2.0 MPa, thereby producing the ultra-high molecular weight polyethylene powder. In a preferred embodiment of the present application, at least 90% by weight of the resulting polyethylene particles pass through a 100-mesh sieve, and 50 μm ≤ d50 ≤ 70 μm.

[0074] The preparation method of the ultra-high molecular weight polyethylene microparticles of the present invention is as follows:

[0075] The obtained product is obtained by contacting a heterogeneous catalyst system consisting of a main catalyst and an alkyl aluminum compound as a cocatalyst with ethylene / hydrogen, and reacting at a hydrogen partial pressure of 0.01-0.05 MPa, an ethylene partial pressure of 0.2 to 2.0 MPa, and a temperature range of 0 to 100°C for 1 to 18 hours. The molar ratio of catalyst to cocatalyst is 1:1-5000, and polymerization can generally be performed for 2 to 6 hours at a molar ratio of 1:10-2000 to maintain optimal catalytic activity, polymer properties, and production costs. A molar ratio of 1:20 to 500 is preferred.

[0076] The polymerization is generally carried out in an inert organic solvent, such as hydrocarbons, cyclic hydrocarbons, or aromatic hydrocarbons. It can also be carried out in a halogenated solvent, such as ethylene dichloride or chlorobenzene. To facilitate reactor operation, the inert organic solvent can be a hydrocarbon with less than 12 carbon atoms. Examples include, but are not limited to, propane, isobutane, n-pentane, 2-methylbutane, n-hexane, cyclohexane, toluene, chlorobenzene, ethylene dichloride, and mixtures thereof.

[0077] The polymerization temperature is maintained at 0 to 100°C, and can be maintained at 40 to 80°C to achieve good catalytic activity and production capacity.

[0078] Operating within the hydrogen partial pressure of 0.01-0.05 MPa can obtain a more ideal polymer viscosity-average molecular weight and a finer particle size.

[0079] Operating within the polymerization ethylene partial pressure range of 0.2 to 1.5 MPa can obtain better reactor operating parameters and polymers.

[0080] The cocatalyst is an alkylaluminum compound, an alkylaluminoxane, or a weakly coordinating anion. The alkylaluminum compound is preferably selected from AlEt3, AlMe3, Al(i-Bu)3, or AlEt2Cl. The alkylaluminoxane is preferably methylaluminoxane or MMAO (modified methylaluminoxane). The weakly coordinating anion is preferably selected from [B(3,5-(CF3)2C6H3)4]-, -OSO2CF3, or ((3,5-(CF3)2)C6H3)4B-. The catalyst and cocatalyst can be added to the system in any order to proceed with polymerization, preferably AlEt3. The ratio of catalyst to cocatalyst used in the polymerization can be varied. Typically, the polymerization time is 1-18 hours, and the molar ratio of catalyst to cocatalyst is 1:1-5000. Generally, a molar ratio of 1:10-2000 is used for polymerization for 2-6 hours to maintain optimal catalytic activity, polymer properties, and production costs, preferably 1:20-500.

[0081] In a preferred embodiment of the present invention, the catalyst catalyzes ethylene polymerization at 40-80°C, a hydrogen partial pressure of 0.01-0.05 MPa, and an ethylene partial pressure of 0.2-0.8 MPa to obtain ultra-high molecular weight polyethylene particles, and at least 90% by weight of the powder obtained by polymerization passes through a 100-mesh mesh sieve, and the median diameter (d50) measured by laser diffraction scattering method is 40μm≤d50≤80μm, more preferably, 50μm≤d50≤70μm, and the polyethylene viscosity-average molecular weight is 1.5-3.5 million; more preferably, the polyethylene viscosity-average molecular weight is 2-3 million.

[0082] The ultra-high molecular weight polyethylene particles created by the present invention have a bulk density of 0.26-0.33 g / cm 3 , the more preferred bulk density is 0.29-0.30 g / cm 3 , which can be used to prepare microporous filter materials.

[0083] Polyethylene catalyst and its preparation

[0084] The ultra-high molecular weight polyethylene particles with fine particle size and low bulk density of the present invention are prepared by homogenizing a titanium catalyst containing a composite carrier of nano-silica gel and magnesium chloride under conditions of high-speed dispersing stirring and ultrasonic vibration, and then polymerizing the catalyst through ethylene.

[0085] The catalyst is catalyst particles, or a catalyst slurry comprising the catalyst particles; the catalyst has a silicon content of 20-40wt%, a magnesium content of 10-30wt%, an aluminum content of 2-4wt%, a titanium content of 2-5wt%, and a chlorine content of 20-60wt%; the silicon content is preferably 25-35wt%, the magnesium content is preferably 12-18wt%, and the titanium content is preferably 3-4wt%.

[0086] In another preferred embodiment, the concentration of the catalyst particles in the catalyst solution is 200-250 g / L.

[0087] In another preferred embodiment, the catalyst is prepared by the following method:

[0088] (a) Under inert gas protection, anhydrous magnesium chloride is added to a mixture of an inert hydrocarbon solvent and a C1-C10 alcohol (preferably 2-6 equivalents of a C1-C10 alcohol) containing ≥2 equivalents of magnesium chloride, and the mixture is reacted at 60-120° C. to form a homogeneous solution. 1-3 equivalents of nano-silica gel are added to the mixture under high-speed dispersing stirring and ultrasonic vibration to disperse and homogenize the solution to prepare a composite carrier, and then the mixture is cooled to below -30° C. to obtain a precursor slurry PI; wherein the cooling rate is preferably 1-10° C. / min; more preferably 1-5° C. / min, and most preferably 1° C. / min. In the above reaction, the amount of anhydrous magnesium chloride is taken as 1 equivalent.

[0089] (b) contacting the precursor slurry PI obtained in step (a) with an alkyl aluminum at a temperature below -30°C for at least 1 hour, and then heating to 60-120°C and maintaining for 2-6 hours to obtain a precursor slurry P-II; wherein the heating rate is preferably 1-10°C / min;

[0090] (c) cooling the precursor slurry P-II obtained in step (b) to below -30°C, contacting it with an inert hydrocarbon solution of a titanium compound for 0.5-3 hours, and then heating it to 60-120°C and maintaining it for 2-6 hours to obtain a catalyst slurry C-III; wherein the cooling rate is preferably 1-10°C / min, and the heating rate is preferably 1-10°C / min;

[0091] (d) filtering the catalyst slurry C-III obtained in step (c) to obtain a catalyst.

[0092] In another preferred embodiment, the method for preparing the catalyst further comprises the step of: (e) drying the catalyst obtained in step (d) to obtain catalyst powder.

[0093] In another preferred embodiment, in the catalyst preparation, the C1-C10 alcohol in step (a) is preferably methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, 2-ethylhexanol or n-octanol.

[0094] In another preferred embodiment, in the catalyst preparation, the rotation speed of the high-speed dispersing stirring and homogenizing in step (a) is 1000-6000 rpm, preferably 2000-5500 rpm, more preferably 4000-5000 rpm.

[0095] In another preferred embodiment, in the catalyst preparation, the ultrasonic oscillation auxiliary power in step (a) is 600W and the frequency is 40KHz.

[0096] In another preferred embodiment, in the catalyst preparation, the mass ratio of the nano-silica gel to magnesium chloride in step (a) can be selected as 1-3:1, preferably 2-3:1, and most preferably 3:1. The nano-silica gel has an amorphous white powder appearance, a flocculent and reticular quasi-granular structure, and a bulk density of <0.15 g / cm 3 , the particle size range can be 15 to 100 nm, preferably 30 to 50 nm.

[0097] In another preferred embodiment, in the catalyst preparation, the alkylaluminum in step (b) is selected from the group consisting of ethylaluminum dichloride, diethylaluminum chloride, triethylaluminum, triisobutylaluminum, ethylaluminum sesquichloride or butylaluminum sesquichloride.

[0098] In another preferred embodiment, in the catalyst preparation, the molar ratio of the titanium compound to the magnesium chloride in step (c) can be 0.3-0.8:1, preferably 0.4-0.6:1, and most preferably 0.5:1.

[0099] In another preferred embodiment, no toluene, halogenated hydrocarbons or aromatic hydrocarbons are used in the preparation step of the catalyst.

[0100] In another preferred embodiment, the titanium compound is TiCl4 or TiR4, or an alkyl complex shown in structural formula I-IV; wherein R is a C1-C6 alkyl, allyl, benzyl, or NMe2, and the alkyl is preferably a methyl, ethyl, propyl, or butyl group.

[0101]

[0102] Where X is SR 5 or P(R 5 )2;

[0103] R 1 、R 2 、R 3 、R 4 、R 5 Each is independently a substituted or unsubstituted group selected from the group consisting of a C1-C6 alkyl group, a C2-C6 alkenyl group, a C3-C8 cycloalkyl group, a C6-C10 aryl group, a halogenated C3-C8 cycloalkyl group, and a 5-7 membered heteroaryl group;

[0104] or R 3 and R 4 , and the carbon atoms connected thereto together form a 5-7 membered saturated, partially unsaturated or aromatic carbocyclic or heterocyclic ring;

[0105] R 6 Selected from the following group: C1-C6 alkyl, NH2, N(C1-C6 alkyl)2, allyl, benzyl, C1-C6 silyl; the alkyl is preferably methyl, ethyl, propyl or butyl;

[0106] R 7 Selected from the group consisting of C1-C6 alkyl, C2-C6 alkenyl, or C3-C8 cycloalkyl;

[0107] The heteroaryl group has 1 to 3 heteroatoms selected from the group consisting of N, S(O), P, and O on its skeleton.

[0108] Unless otherwise specified, the term "substituted" refers to substitution by one or more (e.g., 2, 3, 4, etc.) substituents selected from the group consisting of halogen, C1-C6 alkyl, halogenated C1-C6 alkyl, C1-C6 alkoxy, and halogenated C1-C6 alkoxy.

[0109] In another preferred embodiment, the titanium complex is a molecule having the following structure:

[0110]

[0111] Ultra-high molecular weight polyethylene microporous filtration products

[0112] The ultra-high molecular weight polyethylene particles with fine particle size and low bulk density can be used to prepare microporous filtration materials. The present invention uses polyethylene wax and calcium stearate as composite additives, which are mixed with the ultra-high molecular weight polyethylene particles in a certain ratio for processing. The mass ratio of ultra-high molecular weight polyethylene particles: polyethylene wax: calcium stearate is 300:5:1. After being evenly mixed, the mixture is loaded into a mold and pressurelessly sintered on a molding press at a sintering temperature of 180-220°C for 10-20 minutes. Finally, water cooling is performed to obtain an ultra-high molecular weight polyethylene microporous filtration product.

[0113] The porosity of the ultra-high molecular weight polyethylene microporous filtration product reaches 40-60%, the micropores are evenly distributed, the minimum filtration accuracy can be equal to 0.30 microns, the solid insoluble matter filtration efficiency is greater than 99.9%, and the permeability is excellent. Under the water pressure of 0.2Mpa, the water penetration can reach 20m 3 / h.

[0114] Compared with the prior art, the main advantages of the present invention include:

[0115] (1) Through catalyst design and adjustment of reaction parameters (especially the adjustment of hydrogen partial pressure), a type of low bulk density ultra-high molecular weight polyethylene microparticles with a smaller particle size was successfully prepared.

[0116] (2) The ultra-high molecular weight polyethylene microparticles obtained in the present invention can be used to prepare products that require fine-particle polyethylene microparticles as raw materials, such as microporous filters, etc., and can achieve higher filtration accuracy and better mechanical strength.

[0117] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0118] The following examples illustrate various aspects of the present invention. Examples provided include polyethylene microparticles, polymerization methods for preparing polyethylene microparticles, microfiltration product methods, and their properties.

[0119] The particle size distribution of polyethylene microparticles was determined using a Malvern S-type particle size analyzer, using n-hexane or ethanol as a dispersant.

[0120] The viscosity-average molecular weight of polyethylene microparticles is measured using a high-temperature viscometer. Generally, 2.5-2.8 mg of sample is weighed and dissolved in 15 mL of decahydronaphthalene. The calculation formula is as follows:

[0121] ηsp=t-t0 / t0

[0122] ηr=t / t0

[0123] c=100*m(g)*ρ135℃ / V(ml)*ρ25℃

[0124] η1=(ηsp+5Inηr) / 6c

[0125] η2=【2(ηsp-ηr)】0.5 / c

[0126]

η

[0127] Mv=4.55×104×

η

[0128] Example 1

[0129] Under dry nitrogen conditions, 15L hexane and 1.5L n-butanol were added to a 30L stainless steel reactor, mixed evenly, and then 350g magnesium chloride was added. The oil bath was heated to 85°C, the stirring speed was controlled to 100rpm, and the reaction was carried out for 2h to a clear uniform solution. 1050g nano-silica gel was added, high-speed dispersion stirring was started, the stirring speed was controlled to 4500rpm, the ultrasonic oscillation auxiliary power was 600W, the frequency was 40KHz, and the composite carrier was prepared by loading. The loading was stirred for 2h, and the cooling rate was set to 1°C / min to cool to below -30°C. The solid was precipitated to obtain a catalyst precursor slurry. The catalyst precursor slurry was cooled to below -30°C, 1L diethylaluminum monochloride was slowly added dropwise for contact reaction for 2h, and then the heating rate was controlled to 1 ℃ / min, heated to 85 ℃ and reacted for 4h; cooled to below -30 ℃ again, 653g of alkyl complex 3 of fourth subgroup metal titanium in 5L hexane solution was added dropwise for complex reaction for 1h, and then the heating rate was controlled to 1 ℃ / min, heated to 85 ℃ and reacted for 4h. After the reaction time was over, sedimentation and filtration were performed, and the filter cake obtained was added with hexane to prepare a slurry to obtain 10L slurry-type ultra-high activity catalyst CAT-1. 100mL of the slurry catalyst was taken and dried to obtain a solid catalyst with a mass of 19.8g. Therefore, the slurry catalyst concentration was calibrated to 198g / L, and the titanium content was measured to be 3.1wt%, the silicon content was 34.0wt%, the magnesium content was 13.0wt%, the aluminum content was 3.5wt%, and the chlorine content was 32.8wt%.

[0130]

[0131] Example 2

[0132] Under dry nitrogen conditions, 15L hexane and 1.5L n-butanol were added to a 30L stainless steel reactor, mixed evenly, and then 350g magnesium chloride was added. The oil bath was heated to 85°C, the stirring speed was controlled to 100rpm, and the reaction was carried out for 2h to a clear uniform solution. 1050g nano-silica gel was added, high-speed dispersion stirring was started, the stirring speed was controlled to 4500rpm, the ultrasonic oscillation auxiliary power was 600W, the frequency was 40KHz, and the composite carrier was prepared by loading. The loading was stirred for 2h, and the cooling rate was set to 1°C / min to cool to below -30°C. The solid was precipitated to obtain a catalyst precursor slurry. The catalyst precursor slurry was cooled to below -30°C, 1L diethylaluminum monochloride was slowly added dropwise for contact reaction for 2h, and then the heating rate was controlled to 1 ℃ / min, heated to 85 ℃ and reacted for 4h; cooled to below -30 ℃ again, 1361g of alkyl complex 5 of fourth subgroup metal titanium in 5L hexane solution was added dropwise for complex reaction for 1h, and then the heating rate was controlled to be 1 ℃ / min, heated to 85 ℃ and reacted for 4h. After the reaction time was over, sedimentation and filtration were performed, and the filter cake obtained was added with hexane to prepare a slurry to obtain 10L slurry-type ultra-high activity catalyst CAT-2. 100mL of the slurry catalyst was taken and dried to obtain a solid catalyst with a mass of 22.6g. Therefore, the slurry catalyst concentration was calibrated to 226g / L, and the titanium content was measured to be 3.6wt%, the silicon content was 34.8wt%, the magnesium content was 12.1wt%, the aluminum content was 2.6wt%, and the chlorine content was 33.5wt%.

[0133]

[0134] Example 3

[0135] Under dry nitrogen conditions, 15L hexane and 1.5L n-butanol were added to a 30L stainless steel reactor, mixed well, and then 350g magnesium chloride was added. The oil bath was heated to 85°C, the stirring speed was controlled to 100rpm, and the reaction was carried out for 2h to a clear uniform solution. 1050g nanosilica gel was added, high-speed dispersion stirring was started, the stirring speed was controlled to 4500rpm, the ultrasonic oscillation auxiliary power was 600W, the frequency was 40KHz, and the composite carrier was prepared by loading. The loading was stirred for 2h, and the cooling rate was set to 1°C / min to cool to below -30°C, and the solid was precipitated to obtain a catalyst precursor slurry. The catalyst precursor slurry was cooled to below -30°C, and 1L diethylaluminum monochloride was slowly added dropwise for contact reaction for 2h, and then the heating rate was controlled to 1 ℃ / min, heated to 85 ℃ for 4h; cooled to below -30 ℃ again, 1358g of the fourth subgroup metal titanium alkyl complex 7 in 5L hexane solution was added dropwise for complexation reaction for 1h, and then the heating rate was controlled to 1 ℃ / min, heated to 85 ℃ for 4h. After the reaction time was over, the mixture was sedimented and filtered, and the filter cake was added with hexane to form a slurry to obtain 10L slurry-type ultra-high activity catalyst CAT-3. 100mL of the slurry catalyst was taken and dried to obtain a solid catalyst with a mass of 21.1g. Therefore, the slurry catalyst concentration was calibrated to 211g / L, and the titanium content was measured to be 3.3wt%, the silicon content was 32.9wt%, the magnesium content was 12.4wt%, the aluminum content was 3.6wt%, and the chlorine content was 35.0wt%.

[0136]

[0137] Example 4

[0138] Under dry nitrogen conditions, 15L hexane and 1.5L n-butanol were added to a 30L stainless steel reactor, mixed well, and then 350g magnesium chloride was added. The oil bath was heated to 85°C, the stirring speed was controlled to 100rpm, and the reaction was carried out for 2h to a clear uniform solution. 1050g nano-silica gel was added, high-speed dispersion stirring was started, the stirring speed was controlled to 4500rpm, the ultrasonic oscillation auxiliary power was 600W, the frequency was 40KHz, and the composite carrier was prepared by loading. The loading was stirred for 2h, and the cooling rate was set to 1°C / min and the temperature was lowered to below -30°C. The solid was precipitated to obtain a catalyst precursor slurry. The catalyst precursor slurry was cooled to below -30°C, 1L diethylaluminum monochloride was slowly added dropwise for contact reaction for 2h, and then the reaction temperature was controlled to 1000rpm. The temperature was raised at a rate of 1°C / min to 85°C for 4 hours; the temperature was lowered to below -30°C again, and a 5L hexane solution of 1000g titanium tetrachloride was added dropwise for a complexation reaction for 1 hour. The temperature was then raised at a rate of 1°C / min to 85°C for 4 hours. After the reaction time was over, the mixture was filtered and the filter cake was added with hexane to form a slurry to obtain 10L of a slurry-type ultra-high activity catalyst CAT-4. 100mL of the slurry catalyst was taken and dried to obtain a solid catalyst with a mass of 20.2g. Therefore, the concentration of the slurry catalyst was calibrated to 202g / L. The titanium content was 3.1wt%, the silicon content was 32.9wt%, the magnesium content was 14.1wt%, the aluminum content was 3.8wt%, and the chlorine content was 33.6wt%.

[0139] Example 5

[0140] Under dry nitrogen conditions, 15L hexane and 1.5L n-butanol were added to a 30L stainless steel reactor, mixed well, and then 350g magnesium chloride was added. The oil bath was heated to 85°C, the stirring speed was controlled to 100rpm, and the reaction was carried out for 2h to a clear uniform solution; 1050g nanosilica gel was added, high-speed dispersion stirring was started, the stirring speed was controlled to 4500rpm, the ultrasonic oscillation auxiliary power was 600W, the frequency was 40KHz, and the composite carrier was prepared by loading. The loading was stirred for 2h, and the cooling rate was set to 1°C / min and cooled to below -30°C. The solid was precipitated to obtain a catalyst precursor slurry; the catalyst precursor slurry was cooled to below -30°C, and 1L monochlorodiethylaluminum was slowly added dropwise for contact reaction for 2h, and then the heating rate was controlled to 1°C / min and the temperature was raised to 85°C for reaction for 4h; the temperature was cooled to below -30°C again and 760g The complexation reaction of 5L hexane solution of TiBn4 was carried out for 1h, and then the heating rate was controlled to be 1℃ / min, and the temperature was raised to 85℃ for reaction for 4h. After the reaction time, the solution was filtered and the filter cake was added with hexane to form a slurry, thereby obtaining 10L slurry-type ultra-high activity catalyst CAT-5. 100mL of the slurry catalyst was taken and dried to obtain a solid catalyst with a mass of 20.4g. Therefore, the concentration of the slurry catalyst was calibrated to 204g / L. The titanium content was 3.8wt%, the silicon content was 35.0wt%, the magnesium content was 12.5wt%, the aluminum content was 3.6wt%, and the chlorine content was 37.0wt%.

[0141] Example 6

[0142] Catalysts CAT-1 to CAT-5 for ethylene polymerization

[0143] A 30 L stainless steel stirred polymerization kettle was successively purged with N2, AlEt3 (10 mL) was added to the kettle using 8 kg hexane under 0.4 MPa nitrogen, the stirring speed was controlled at 250 rpm, and the temperature in the kettle was preheated to about 60°C. Then, 30 mg of CAT was flushed into the polymerization kettle using 2 kg hexane under 0.4 MPa nitrogen pressure and activated for 10 min. Then, the nitrogen pressure in the kettle was removed, hydrogen was introduced to bring the pressure in the kettle to 0.01-0.05 MPa, and ethylene gas was introduced to bring the pressure in the kettle to 0.8 MPa. The temperature in the kettle was controlled at 60°C. After 2 h of polymerization, the introduction of ethylene was stopped, and the temperature in the kettle was lowered to below 50°C using a circulating constant temperature oil bath. The gas in the system was vented and the material was discharged. After drying, a granular polymer was obtained. The specific results are shown in Table 1.

[0144] Table 1

[0145]

[0146] Example 7

[0147] Industrial production equipment trial production experiment

[0148] 32m 3 A stainless steel stirred polymerization kettle was purged with nitrogen three times and ethylene twice, and 10 tons of hexane and 50 kg of a 1% Et3Al hexane solution were added. 175 mL of catalyst CAT-1 (containing approximately 35 g of solid catalyst) was then pressurized into the reactor with nitrogen at one time. The nitrogen pressure in the reactor was removed, and hydrogen was introduced to bring the pressure in the reactor to 0.02 MPa. Ethylene gas was then introduced to bring the pressure in the reactor to 0.8 MPa. The temperature in the reactor was controlled at 60°C. After the polymerization reaction lasted for 2.5 hours, the ethylene was stopped and the material was discharged to a filter kettle. After oil washing in the filter kettle, the material was vacuum dried for about 3 hours, and the product polyethylene microparticles was packaged. The specific results are shown in Table 2 below.

[0149] Table 2

[0150]

[0151]

[0152] Example 8 Preparation of Microporous Filtration Products from Ultra-High Molecular Weight Polyethylene Microparticles

[0153] The ultra-high molecular weight polyethylene particles of batch 1 of Example 8 were used to prepare microporous filter materials. 30 g of ultra-high molecular weight polyethylene particles, 0.5 g of polyethylene wax, and 0.1 g of calcium stearate were weighed and placed in a beaker, stirred and mixed evenly, loaded into a mold and pressurelessly sintered on a molding machine at a sintering temperature of 180-220 ° C and a sintering time of 10-20 min. Finally, water was passed through the mold to cool the ultra-high molecular weight polyethylene microporous filter product. The solid insoluble matter filtration efficiency was greater than 99.9%, the permeability was excellent, the pressure difference before and after the filter was controlled to be less than 0.2 MPa, and the pure water throughput reached 20 m 3 / h, the performance test of microporous filtration products is as follows:

[0154]

[0155] From the above results, it can be seen that the ultra-high molecular weight polyethylene particles of the present invention, when made into products, have a higher filtration accuracy than the ultra-high molecular weight polyethylene particles of the prior art, and the lowest can be as low as 0.30 μm.

[0156] All documents mentioned in this application are incorporated herein by reference, just as if each document were incorporated herein by reference individually. It should also be understood that after reading the above teachings of the present invention, those skilled in the art may make various changes or modifications to the present invention, and that such equivalents also fall within the scope of the claims appended hereto.

Claims

1. A low bulk density ultra-high molecular weight polyethylene microparticle, characterized in that: The microparticles have the following characteristics: (a) Viscosity average molecular weight of 1 to 5 million g / mol; (b) ≥90 wt% can pass through a 100-mesh sieve, and the particle median diameter d50 is 40 μm < d50 < 80 μm; (c) The bulk density of the microparticles is 0.26-0.33 g / cm 3 ; The method for preparing the microparticles comprises the following steps: contacting a catalyst and a co-catalyst with ethylene / hydrogen to carry out a catalytic polymerization reaction, thereby obtaining the ultra-high molecular weight polyethylene microparticles; Wherein, the catalyst is prepared by the following method: (a) contacting a magnesium source with a C1-C10 alcohol and reacting them at 60-120°C, adding nanosilica gel, and homogenizing the mixture under high-speed dispersing stirring and ultrasonic oscillation, followed by cooling to below -30°C to obtain a precursor slurry PI; (b) contacting the precursor slurry PI obtained in step (a) with an alkyl aluminum at a temperature below -30°C, and then heating to 60-120°C and maintaining for 2-6 hours to obtain a precursor slurry P-II; (c) cooling the precursor slurry P-II obtained in step (b) to below -30°C, contacting it with an inert hydrocarbon solution of a titanium compound for 0.5-3 hours, and then heating it to 60-120°C and maintaining it for 2-6 hours to obtain a catalyst slurry C-III; (d) filtering the catalyst slurry C-III obtained in step (c) to obtain a catalyst.

2. The polyethylene microparticles according to claim 1, wherein The viscosity average molecular weight of the microparticles is 2 to 3.5 million g / mol.

3. The polyethylene microparticles according to claim 1, wherein The d50 of the microparticles is 50 μm < d50 < 70 μm; and / or The bulk density of the particles is 0.28-0.31 g / cm 3 .

4. The polyethylene microparticles according to claim 1, wherein The bulk density of the particles is 0.29-0.30 g / cm 3 .

5. A method for preparing polyethylene microparticles according to claim 1, characterized in that: The method comprises the following steps: contacting a catalyst and a co-catalyst with ethylene / hydrogen to carry out a catalytic polymerization reaction, thereby obtaining the ultra-high molecular weight polyethylene particles; The catalyst is prepared by the following method: (a) contacting a magnesium source with a C1-C10 alcohol and reacting them at 60-120°C, adding nanosilica gel, and homogenizing the mixture under high-speed dispersing stirring and ultrasonic oscillation, followed by cooling to below -30°C to obtain a precursor slurry PI; (b) contacting the precursor slurry PI obtained in step (a) with an alkyl aluminum at a temperature below -30°C, and then heating to 60-120°C and maintaining for 2-6 hours to obtain a precursor slurry P-II; (c) cooling the precursor slurry P-II obtained in step (b) to below -30°C, contacting it with an inert hydrocarbon solution of a titanium compound for 0.5-3 hours, and then heating it to 60-120°C and maintaining it for 2-6 hours to obtain a catalyst slurry C-III; (d) filtering the catalyst slurry C-III obtained in step (c) to obtain a catalyst.

6. The method according to claim 5, wherein The method comprises the steps of: (1) In an inert solvent, first introduce 0.01-0.05 MPa of hydrogen into a reactor in which catalyst and co-catalyst have been added, and then introduce ethylene gas to make the pressure in the reactor reach 0.2-1.5 MPa. o C for 1-3 h; (2) Lower the temperature in the kettle to 50 o C or below; (3) removing the solvent from the slurry obtained in step (2); (4) After vacuum drying, the polyethylene microparticles as claimed in claim 1 are obtained.

7. The method according to claim 5, wherein The catalyst is catalyst particles, or a catalyst slurry comprising the catalyst particles; the catalyst has a silicon content of 20-40 wt%, a magnesium content of 10-30 wt%, an aluminum content of 2-4 wt%, a titanium content of 2-5 wt%, and a chlorine content of 32.8-60 wt%.

8. The method according to claim 5, wherein The method includes: (a) Under inert gas protection, anhydrous magnesium chloride is added to a mixture of an inert hydrocarbon solvent and a C1-C10 alcohol containing ≥2 equivalents of magnesium chloride, and the mixture is reacted at 60-120°C to form a homogeneous solution. Nanosilica gel is added to the mixture and dispersed and homogenized under high-speed dispersing stirring and ultrasonic vibration to prepare a composite carrier. The mixture is then cooled to below -30°C to obtain a precursor slurry PI; the cooling rate is 1-10°C / min. In the above reaction, the amount of anhydrous magnesium chloride is taken as 1 equivalent. (b) contacting the precursor slurry PI obtained in step (a) with an alkyl aluminum at a temperature below -30°C for at least 1 hour, and then heating to 60-120°C and maintaining the temperature for 2-6 hours to obtain a precursor slurry P-II; wherein the heating rate is 1-10°C / min; (c) cooling the precursor slurry P-II obtained in step (b) to below -30°C, contacting it with an inert hydrocarbon solution of a titanium compound for 0.5-3 hours, and then heating it to 60-120°C and maintaining it for 2-6 hours to obtain a catalyst slurry C-III; wherein the cooling rate is 1-10°C / min and the heating rate is 1-10°C / min; (d) filtering the catalyst slurry C-III obtained in step (c) to obtain a catalyst.

9. The method according to claim 8, wherein In step (a), the equivalent weight of the C1-C10 alcohol is 2-6 equivalents.

10. The method according to claim 8, wherein In step (a), the cooling rate is 1-5°C / min.

11. The method according to claim 8, wherein In step (a), the cooling rate is 1°C / min.

12. The method according to claim 8, wherein The method for preparing the catalyst further comprises the step of: (e) drying the catalyst obtained in step (d) to obtain catalyst powder.

13. The method according to claim 8, wherein In the catalyst preparation, the C1-C10 alcohol in step (a) is selected from the group consisting of methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, 2-ethylhexanol, n-octanol, or a combination thereof; and / or In the catalyst preparation, the speed of the high-speed dispersing and stirring homogenizing in step (a) is 1000-6000 rpm; and / or In the catalyst preparation, the ultrasonic oscillation auxiliary power in step (a) is 600W and the frequency is 40KHz; and / or In the catalyst preparation, the alkyl aluminum in step (b) is selected from the group consisting of ethyl aluminum dichloride, diethyl aluminum chloride, triethyl aluminum, triisobutyl aluminum, ethyl aluminum sesquichloride, or butyl aluminum sesquichloride; and / or In the catalyst preparation, the molar ratio of the titanium compound to magnesium chloride in step (c) is 0.3-0.8:

1.

14. The method according to claim 8, wherein In the catalyst preparation, the rotation speed of the high-speed dispersing and stirring homogenizing in step (a) is 2000-5500 rpm; and / or In the catalyst preparation, the molar ratio of the titanium compound to magnesium chloride in step (c) is 0.4-0.6:

1.

15. The method according to claim 8, wherein In the catalyst preparation, the speed of the high-speed dispersing and stirring homogenizing in step (a) is 4000-5000 rpm; and / or In the catalyst preparation, the molar ratio of the titanium compound to magnesium chloride in step (c) is 0.5:

1.

16. A microporous filtration product, characterized in that: The product is prepared using the ultra-high molecular weight polyethylene particles described in any one of claims 1-4.

17. A method for preparing the product according to claim 16, characterized in that: Including steps: (i) using polyethylene wax and calcium stearate as composite additives and uniformly mixing them with the ultra-high molecular weight polyethylene particles according to any one of claims 1 to 4 to obtain a mixed material; (ii) placing the mixed material into a mold for pressureless sintering; (iii) cooling to obtain an ultra-high molecular weight polyethylene microporous filtration product.

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