CN115260346B - Method for preparing small-particle-size ultra-high molecular weight polyethylene powder - Google Patents

Method for preparing small-particle-size ultra-high molecular weight polyethylene powder Download PDF

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CN115260346B
CN115260346B CN202210929248.0A CN202210929248A CN115260346B CN 115260346 B CN115260346 B CN 115260346B CN 202210929248 A CN202210929248 A CN 202210929248A CN 115260346 B CN115260346 B CN 115260346B
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catalyst
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particle size
high molecular
weight polyethylene
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CN115260346A (en
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许学翔
鲁立军
李江涛
邓兆敬
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China Chemical Technology Research Institute
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Abstract

The invention discloses a method for preparing small-particle-size ultrahigh molecular weight polyethylene powder, which is characterized in that magnesium alkoxide prepared by taking in-situ synthesized active magnesium chloride as a catalyst carrier is reacted with titanium tetrachloride and silicon tetrachloride, and a small-particle-size catalyst with good shape can be prepared under the synergistic effect of an anhydride crystallization promoter without an emulsifying machine. The crystallization accelerator has the function of enabling precipitation crystallization of the carrier to be more orderly, so that the prepared catalyst has strong crystallinity, large specific surface area, firm particles and small particle size. The catalyst is pre-dispersed in the solvent in advance to effectively solve the problem of catalyst agglomeration, so that the catalyst with small particle size is obtained, and the ultra-high molecular weight polyethylene is prepared in the presence of the static eliminator. The ultra-high molecular weight polyethylene powder with the particle size of 50-150 mu m can be prepared by the method.

Description

Method for preparing small-particle-size ultra-high molecular weight polyethylene powder
Technical Field
The invention belongs to the technical field of ultra-high molecular weight polymers, relates to a method for preparing ultra-high molecular weight polyethylene powder suitable for various functional materials, and in particular relates to a method for preparing ultra-high molecular weight polyethylene particles, wherein the particle size of the ultra-high molecular weight polyethylene particles is smaller than that of the existing ultra-high molecular weight polyethylene particles, no aggregation exists among the particles, the particle size distribution is extremely narrow, and the sphericity is high.
Background
Ultra-high molecular weight polyolefin represented by ultra-high molecular weight polyethylene (UHMWPE) is widely used for mechanical parts, lining materials, sports goods, and the like, because it is lightweight and has excellent properties such as abrasion resistance, impact resistance, chemical resistance, and self-lubricity. In recent years, development of ultra-high molecular weight polyethylene microparticles is active, and has been widely used for various industrial applications. In particular, polyethylene fine particles having a spherical particle shape and a narrow particle size distribution are used for filters, separation membranes, dispersants, powder coatings, resin modifiers, coating agents, and the like because of their excellent processability, flowability, and surface physical properties.
For example, the ultra-high molecular weight polyethylene fine particles may be used as a column packing for efficient separation of chemical or biological substances, or may be used as an adsorbent or a catalyst carrier having a high specific surface area. In addition, the polymer can be used as a carrier for drug delivery and release, or as a dispersant for uniformly dispersing a poorly dispersible particulate material, and can be used as a highly safe particulate material for cosmetic raw materials that gives good feel to the skin. Furthermore, researchers are actively researching their application in the field of functional new materials. For example, the porous material is used as a separator member for lithium batteries or lithium ion secondary batteries, a high-performance binder having a sintered porous body such as light diffusion, reflection, antireflection optical filter member, ceramics, etc., a pore-forming material such as a porous membrane, a support for fixing immunochemically active substances, a sintered filter having a fine pore and a high specific surface area, a smoothness imparting agent, a toner, a matting agent for paint, an additive for light diffusion, an insulating filler, a crystal nucleating agent, a filler for chromatograph, a support for immunodiagnosis, etc. In order to provide ultra-high molecular weight polyethylene particles with new applications for further functionality and to further improve the performance and quality of ultra-high molecular weight polyethylene particles, researchers have been working to develop spherical ultra-high molecular weight polyethylene particles having smaller particle diameters, narrower particle size distributions, and no aggregation between particles. Among the above uses, the use of ultra-high molecular weight polyethylene particles as a filter material is rapidly developing as an emerging use. However, when a filter is produced by molding an ultrahigh molecular weight polyolefin, since the fluidity of the ultrahigh molecular weight polyolefin is poor when it is melted, the conventional melt molding method cannot be adopted, but the polyolefin powder is directly subjected to a rotational molding method, a powder molding method, or the like, but the filter produced therefrom has poor filtration performance. In the prior art, when the microfiltration membrane is prepared by a sintering method, only the surface of the raw material particles is melted instead of the whole surface, so that the raw material particles are mutually bonded inside the filtration membrane to form network-shaped through holes. And the size and distribution of the network through holes are related to the particle size and distribution of UHMWPE powder. The effect of UHMWPE particle size on product performance is shown by larger particle size and larger aperture ratio, but the micropore structure is easy to become irregular, the micropore distribution is uneven, and the strength of the filter membrane is reduced; however, the smaller the particle diameter, the finer and uniform the microporous structure, and the lower the aperture ratio, but the strength of the filter membrane is increased.
In the preparation of filters by sintering, it is very important to achieve a dense loading of UHMWPE powder in order to make sintering more efficient, which requires a high bulk density of UHMWPE powder (bulk density should be higher than 0.35 g/cm) 3 Even more preferably higher than 0.4g/cm 3 ). And the average particle size (D of the UHMWPE powder 50 ) Is also an important feature (the average particle size (D 50 ) Preferably less than 150 μm, more preferably 100 μm or less). Furthermore, the particle size distribution is often referred to as "span", defined as (D 90 -D 10 )/D 50 Should be low, preferably 1.5 or less, and even more preferably 1.0 or less.
The shape of the ultra-high molecular weight polyethylene powder particles is transformed from the shape of the catalyst particles, also known as replication phenomenon. Typically, when such replication occurs, the average particle size of the polymer is proportional to the catalyst yield, i.e., the cube root in grams of polymer produced per gram of catalyst. See ("Transition Metals and Organometallics as Catalysts for Olefin Polymerization" Kaminsky, W.Sinn, H.Eds.Springer 1988, 209-222.). Based on the above proportionality, small average particle size polymer particles can be produced by reducing catalyst productivity, but this also results in high catalyst residues in the polymer and high catalyst costs required to produce the polymer. This also places stringent demands on the catalyst (higher catalyst activity is required and polymer particle size is below 150 μm, preferably below 100 μm). It is generally required that the metal content, particularly the titanium atom content, in the ultra-high molecular weight polyethylene is 5ppm or less. However, the ultra-high molecular weight polyolefin particles should have a catalytic activity of at least 2.0X10 when they contain less than 5ppm of titanium atoms 5 gPE/gTi.
However, in order to achieve ultra-high molecular weight polyethylene particles having a particle size of 100 μm or less and to maintain a high production efficiency, it is necessary to develop a catalyst having a particle size of less than 5. Mu.m. And as the catalytic activity increases, the particle size of the catalyst is required to be smaller and smaller. However, at present, solid-liquid separation and then drying are generally adopted in the preparation of Ziegler Natta catalysts. The catalyst prepared by the method is easy to harden and agglomerate, and even if stirring with high strength is adopted, the catalyst particles cannot be completely scattered. Thus causing an increase in the particle size of the catalyst particles. And although the slurry catalyst prepared by the non-drying method can prevent agglomeration of particles, the method is not suitable for preservation of the catalyst and is unfavorable for industrial production of the catalyst.
As disclosed in patent document publication No. CN101790547a, a method for preparing ultra-high molecular weight polyethylene particles is disclosed, and the ultra-high molecular weight polyethylene prepared by the method has good flow rate and processability. However, the ultra-high molecular weight polyethylene resin prepared by the method has low molecular weight and low mechanical property, so that the method is not suitable for producing high-strength and high-modulus fibers.
Patent document publication No. CN109627363a discloses a method for preparing a polyolefin catalyst with small particle size by a one-pot method, which adopts a one-pot method to prepare a polyolefin catalyst with small particle size in a reaction kettle equipped with a high shear emulsifying machine. The method can be used for preparing polyolefin catalyst particles with the particle size of 3.7 mu m at least, and the particle size of polyethylene powder prepared by the method is smaller than 125 mu m. However, the particle size of the catalyst is not small enough, and thus the particle size of the polyethylene produced therefrom is not small enough. Thus failing to meet the requirements of filter materials and fiber materials.
Patent document with publication number CN106317273B reports an ultra-high molecular weight ultra-fine particle size polyethylene powder and a method for preparing the same. The polyethylene prepared by the method has the particle size of 45-85 mu m, and the maximum bulk density of the polyethylene is only 0.22g/cm although the particle size is smaller 3 Such low bulk density would severely affect single pot throughput, thus resulting in low commercial efficiency of polyethylene production.
The patent document CN1189486C provides a catalytic system for preparing UHMWPE of high bulk density and good particle morphology by preparing a magnesium-aluminum solution from magnesium halide and aluminum compound in the presence of alcohol, then adding titanium compound and silicon compound after reacting with electron donor to prepare the catalyst. Although the catalyst system has good catalytic activity and the bulk density of the ultra-high molecular weight polyethylene prepared by the catalyst system is relatively high, the particle size of polyethylene powder is 152-179 mu m, and the polyethylene powder in the form is unfavorable for spinning and filter use.
The publication CN1746197a provides a catalytic system for preparing UHMWPE with high bulk density, which uses a catalyst formed by first preparing a support and then supporting titanium, so that the preparation method of the catalyst is cumbersome. And a silicon compound is also required to be added in the preparation of UHMWPE, although the UHMWPE prepared by the method has higher molecular weight, the catalytic activity of the catalyst is not high, and the polymerization time is 4h, and the catalytic activity is only about 3 ten thousand times, so that the time is longer.
The existing preparation of UHMWPE powder not only requires a catalyst to have higher catalytic activity, but also needs to have dynamics stability and long-acting property so as to prevent the polymer from generating oversized particles or undersized particles to the maximum extent and reduce ash content of the polymer, which is particularly important in the preparation of super-strong polyethylene fibers and lithium battery diaphragms. Meanwhile, the polymer is required to have controllable molecular weight and good morphology so as to stabilize the process and improve the running efficiency. This is also the direction of development of ultra-high molecular weight polyethylene catalysts in the future, thus requiring catalysts with higher mechanical attrition strength and good particle morphology.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for preparing small-particle-size ultra-high molecular weight polyethylene powder, which solves the problem of hardening and agglomerating of a catalyst on the premise of keeping high catalytic activity, so as to prepare the ultra-high molecular weight polyethylene with high bulk density, uniform and fine particle size distribution and high and controllable molecular weight.
The invention aims at realizing the following technical scheme:
a process for preparing the small-particle-size ultrahigh-molecular-weight polyethylene powder includes such steps as polymerizing the pre-dispersed Ti catalyst and cocatalyst with olefin polymerizing monomer under the action of static eliminator.
According to an embodiment of the invention, the particle size of the pre-dispersed titanium catalyst and cocatalyst is 1.5 to 4 μm, preferably 1.85 to 3.6 μm, exemplary 1.5 μm, 1.85 μm, 1.90 μm, 1.95 μm, 2.01 μm, 2.03 μm, 2.1 μm, 2.16 μm, 2.22 μm, 2.5 μm, 2.97 μm, 3.0 μm, 3.33 μm, 3.55 μm, 3.6 μm.
According to an embodiment of the present invention, the titanium catalyst may be various types of titanium catalysts for preparing ultra-high molecular weight polyethylene, such as a supported titanium catalyst, and exemplary in-situ active magnesium chloride supported titanium catalyst.
Preferably, the titanium catalyst contains 0.5-5% by mass of Ti; more preferably, the titanium catalyst contains Ti 1.5 to 4.5%; for example, the Ti content is 3.52%, 3.63%, 3.70%, 3.8%, 3.9%, 4.1%, 4.2%.
According to an embodiment of the present invention, the average particle diameter of the titanium catalyst is preferably 0.1 μm or more and 20 μm or less, more preferably 0.2 μm or more and 16 μm or less, still more preferably 0.5 μm or more and 10 μm or less, for example, 2 to 8 μm, and exemplified are 3.1 μm, 5 μm, 5.1 μm, 5.2 μm, 5.3 μm, 6.03 μm, 6.23 μm, 10 μm.
When the average particle diameter is 0.1 μm or more, the resulting ethylene polymer particles tend to be free from problems such as scattering and adhesion. When the average particle diameter is 20 μm or less, problems such as sedimentation of the ethylene polymer particles in the polymerization system, clogging of the pipeline in the post-treatment step of the ethylene polymer, and the like, which are caused by the excessively large particles, can be prevented. Therefore, the average particle size distribution of the catalyst system is preferably as narrow as possible.
According to an embodiment of the present invention, the ratio of the total mass of the titanium catalyst and the cocatalyst to the amount of the olefin polymerization monomer is 1: (2-3.0X10) 4 )。
According to an embodiment of the present invention, the cocatalyst may be dispersed in a solvent to obtain a cocatalyst solution, and then the titanium catalyst may be added. Preferably, the pre-dispersion time is 1 to 12 hours, preferably 2 to 5 hours, and exemplary is 1, 2, 5, 8, 10, 12 hours.
Preferably, the solvent used for the pre-dispersion is an alkane solvent, and for example, at least one of pentane, hexane, heptane, octane and decane may be used.
According to an embodiment of the invention, the molar ratio of aluminium in the cocatalyst to titanium in the titanium catalyst is between 10 and 800, preferably between 50 and 200, more preferably between 80 and 160, exemplary 10, 30, 50, 80, 100, 160, 200, 500, 800.
According to an embodiment of the present invention, the static eliminator is selected from one, two or more of hydrogen, aluminum stearate, calcium stearate, magnesium stearate, polyoxyethylene lauryl ether, polyvinylpyrrolidone and Stadis 450.
Preferably, when the static eliminator is selected from hydrogen, the mass ratio of the olefin polymerization monomer to hydrogen is (20000 to 10000): 1, preferably (15000 to 10000): 1, exemplary is 20000: 1. 15000: 1. 12000: 1. 10000:1.
in the invention, the hydrogen as the static eliminator can be used alone or in combination with other static eliminator. Preferably, when the static eliminator is selected from one of aluminum stearate, calcium stearate, magnesium stearate, polyoxyethylene lauryl ether, polyvinylpyrrolidone, stadis450, it is used in an amount of 200 to 1000ppm, preferably 300 to 800ppm, and most preferably 400 to 600ppm relative to the total amount of the solvent in the reactor.
According to an embodiment of the present invention, the polymerization reaction temperature is 30 to 90 ℃, preferably 40 to 80 ℃, and exemplary is 30 ℃, 40 ℃, 60 ℃, 80 ℃, 90 ℃; the polymerization reaction pressure is as follows: 0.1 to 1.0MPa, preferably 0.2 to 0.8MPa, and exemplary are 0.1MPa, 0.2MPa, 0.5MPa, 0.8MPa, and 1.0MPa.
According to an embodiment of the present invention, the preparation method of the titanium catalyst comprises the steps of: mixing an active magnesium chloride compound with an organic alcohol compound, an electron donor ester compound and an alkoxy silicon compound, and carrying out contact reaction on anhydride serving as a crystallization promoter, an optional titanium compound and the silicon compound to obtain the compound with the structure shown in the formula I.
Preferably, the molar ratio of active magnesium chloride compound to organic alcohol compound is 1:0.5-6, preferably 1:2-4, exemplary 1:0.5, 1:1, 1:2, 1:4, 1:6.
According to an embodiment of the present invention, the active magnesium chloride compound has a structure represented by the following formula I:
(MgCl 2 )(R 1 MgCl) a Mg b [Ti(OR 2 ) 4 )] c [Si(OR 3 ) 4 ] d
i is a kind of
Wherein:
R 1 、R 2 、R 3 identical or different, independently of one another, from C 1-12 Alkyl, preferably C 1-6 Alkyl groups such as methyl, ethyl, propyl, n-butyl (Bu);
a is 0.02-1, illustratively a = 0.02, 0.05, 0.1, 0.2, 0.5, 0.55, 0.58, 0.59, 0.8, 1;
b is 0-0.5, illustratively b=0, 0.05, 0.08, 0.1, 0.2, 0.5;
c is 0-0.8, illustratively c=0, 0.05, 0.07, 0.1, 0.2, 0.5;
d is 0-0.8, illustratively d=0, 0.05, 0.08, 0.1, 0.23, 0.5.
For example, the active magnesium chloride compound may be (MgCl 2 )(BuMgCl) 0.59 Or (MgCl) 2 )(BuMgCl) 0.58 Mg 0.08 [Ti(OC 4 H 9 ) 4 )] 0.07 [Si(OC 2 H 5 ) 4 ] 0.23 。
Preferably, the active magnesium chloride is prepared by activating magnesium powder with elemental iodine and then reacting the magnesium powder with chloralkane; or adding titanate and silicate to react while adding elemental iodine to perform the activation to prepare the active magnesium chloride; preferably, the reaction conditions of the active magnesium chloride are: under nitrogen protection and anhydrous conditions.
Preferably, the organic alcohol compound is ROH, wherein: r is C 2 ～C 16 An alkyl group; for example, the organic alcohol is one, two or more of ethanol, propanol, butanol, hexanol, 2-methyl-forming alcohol, n-heptanol, isooctanol and n-octanol.
In the invention, the crystallization accelerator is added into the reaction to promote the crystallization of magnesium chloride, and the crystallization is better, so that the crystal is firmer.
Preferably, the crystallization promoter is selected from the group consisting of norbornene dianhydride, phthalic anhydride, maleic anhydride and mixtures thereof; norbornene dianhydride is preferred.
Preferably, the crystallization promoter is used in an amount of 0.02 to 0.1mol, and exemplified by 0.02mol, 0.05mol, 0.08mol, 0.1mol, per mol of active magnesium chloride.
The ester compound used as an electron donor in the present invention may be at least one selected from unsaturated fatty acid esters containing at least one hydroxyl group, aliphatic mono-and polyesters containing at least one hydroxyl group, aromatic ester compounds containing at least one hydroxyl group and alicyclic esters containing at least one hydroxyl group.
Preferably, the unsaturated fatty acid ester containing at least one hydroxyl group may be selected from at least one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and pentaerythritol triacrylate, for example;
preferably, the aliphatic mono-and polyesters containing at least one hydroxyl group may be, for example, at least one of 2 hydroxyethyl acetate, methyl 3-hydroxybutyrate, ethyl 3-hydroxybutyrate, methyl 2 hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl 3-hydroxy-2-methylpropionate, ethyl 2, 2-dimethyl-3-hydroxypropionate, ethyl 6-hydroxycaproate, t-butyl 2-hydroxyisobutyrate, 3-hydroxydi-acid ethyl ester, ethyl lactate, isopropyl lactate, butyl isobutyl lactate, ethyl mandelate , dimethyl ethyl tartrate, dibutyl tartrate, diethyl citrate, triethyl citrate, ethyl 2-hydroxycaproate and diethyl bis (hydroxymethyl) malonate;
Preferably, the aromatic ester compound containing at least one hydroxyl group may be at least one of 2-hydroxyethyl benzoate, 2-hydroxyethyl salicylate-4- (hydroxymethyl) benzoate, methyl 4-hydroxybenzoate, ethyl 3-hydroxybenzoate, 4-methyl salicylate, ethyl salicylate, phenyl salicylate, propyl 4-hydroxybenzoate, phenyl 3-hydroxynaphthoate, monoethylene glycol monobenzoate, diethylene glycol monobenzoate, triethylene glycol benzoate, and the like;
preferably, the alicyclic ester containing at least one hydroxyl group may be, for example, hydroxybutyl lactone.
Preferably, the ester compound is used in an amount of 0.01 to 2.0mo1, preferably 0.05 to 1.0mo1, and exemplified by 0.01mol, 0.03mol, 0.04mol, 0.08mol, 0.1mol, 0.2mol, 0.5mol, 0.8mol, 1.0mol, 1.5mol, 2.0mol, per mol of active magnesium chloride.
For the silicon compound having an alkoxy group used as another electron donor in the present invention, it is preferable to have a structure represented by the following formula II:
R 1n Si(OR 2 ) 4n
II (II)
Wherein:
R 1 and R is 2 Identical or different, independently of one another, from hydrocarbons having from 1 to 12 carbon atoms, preferably C 1-8 Alkyl groups such as H, methyl, ethyl, propyl;
n is more than or equal to 1 and is an integer; for example n is an integer in the range of 1-10; illustratively, n=1, 2,3.
Preferably, the method comprises the steps of, the silicon compound having an alkoxy group may be selected from, for example, dimethyldimethoxysilane, dipropyldimethoxysilane, diisopropyldimethoxysilane, isobutyldimethoxysilane, dibutyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylisopropyldimethoxysilane, cyclopentylisopropyldimethoxysilane, cyclopentylbutyldimethoxysilane, cyclopentyldimethoxysilane, dicyclopentyldimethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, γ -chloropropyltrimethoxysilane, γ - (2, 3-epoxypropoxy) propyltrimethoxysilane, dimethyldiethoxysilane, dipropyldiethoxysilane, diisopropyldiethoxysilane, isobutyldiethoxysilane, dibutyldiethoxysilane, cyclohexylmethyldiethoxysilane, cyclohexylisopropyldiethoxysilane, cyclopentylisopropyldiethoxysilane, cyclopentyldiethoxysilane, dicyclopentyldiethoxysilane, diphenyldiethoxysilane, triethoxysilane, triethylethoxysilane, and at least one of the group of tetraethoxysilanes.
Preferably, the silicon compound having an alkoxy group is used in an amount of 0.05 to 1.0mo1, and exemplified by 0.01mol, 0.03mol, 0.05mol, 0.08mol, 0.12mol, 0.16mol, 0.2mol, 0.5mol, 0.8mol, 1.0mol, 1.5mol, 2.0mol, per mol of active magnesium chloride.
According to an embodiment of the present invention, the ester compound, the silicon compound having an alkoxy group may be added to the reaction system in one, two or more times, preferably in two times.
Preferably, the titanium compound is used in an amount of 0.2 to 36.5mol per mol of active magnesium chloride.
Preferably, the titanium compound has a structure as shown in formula III: tiX (TiX) 4
Formula III
Wherein X is selected from Cl, br and I.
For example, the titanium compound is at least one selected from titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, and the like.
Preferably, the silicon compound is used in an amount of 0.05 to 9.0mol per mol of active magnesium chloride.
Preferably, the silicon compound is selected from SiCl 4 。
Preferably, the preparation method of the titanium catalyst comprises the following steps:
(1) In a hydrocarbon solvent, reacting active magnesium chloride with an organic alcohol compound to obtain a magnesium alkoxide reaction solution;
(2) Reacting the magnesium alkoxide reaction solution prepared in the step (1) with an electron donor ester compound, a silicon compound having an alkoxy group and a crystallization accelerator;
(3) Mixing the reaction solution obtained in the step (2) with a titanium compound and a silicon compound to perform a pre-load titanium reaction;
(4) And (3) mixing the reaction solution obtained in the step (3) with an electron donor ester compound and a silicon compound with alkoxy to react to obtain the compound with the structure shown in the formula I.
Preferably, in step (1), the hydrocarbon solvent is C 4～18 Aliphatic hydrocarbons, preferably C 6～12 Aliphatic hydrocarbons.
Preferably, in step (1), 0.2 to 1.0L of hydrocarbon solvent, illustratively 0.2L, 0.5L, 0.8L, 1.0L, is used per mole of active magnesium chloride.
Preferably, in step (1), the temperature of the reaction is 50 to 180 ℃, illustratively 50 ℃, 80 ℃, 100 ℃, 130 ℃, 150 ℃, 180 ℃; the reaction time is 0.5 to 5 hours, and is exemplified by 0.5 hours, 1 hour, 2 hours, and 5 hours.
Preferably, in step (2), the temperature of the reaction is 20 to 100 ℃, illustratively 20 ℃, 50 ℃, 65 ℃, 80 ℃, 100 ℃; the reaction time is 0.5 to 2 hours, and is exemplified by 0.5 hours, 1 hour, and 2 hours.
Preferably, in step (3), the temperature of the reaction is from-20 to 10 ℃, preferably from-10 to 5 ℃, more preferably from-5 to 2 ℃, and is exemplified by-20 ℃, -10 ℃, -5 ℃, 0 ℃, 2 ℃, 5 ℃; the reaction time is 0.5 to 5 hours, preferably 0.5 to 3 hours, and exemplified by 0.5 hours, 1 hour, 2 hours, 3 hours, 5 hours.
Preferably, in the step (4), the reaction solution obtained in the step (3) is heated to 60 to 130 ℃, preferably 80 to 100 ℃, and the reaction is continued for 1 to 6 hours, preferably 1 to 4 hours.
Preferably, in the step (4), the reaction temperature is raised to 60-130 ℃ within 1-4 hours; and then reacted with a mixture of an electron donor ester compound and an alkoxy group silicon compound.
Preferably, in the step (4), the amount of the electron donor is 1/10 to 1/2, preferably 1/8 to 1/4, and exemplary is 1/10, 1/8, 1/6, 1/4, 1/3, and 1/2 of the amount of the electron donor in the step (2).
Preferably, the preparation method further comprises the steps of filtering the reaction liquid obtained in the step (4), washing with a solvent and drying to obtain the titanium catalyst.
According to an embodiment of the present invention, the specific surface area of the titanium catalyst is 85 to 110m 2 /g。
According to an embodiment of the invention, the pore volume of the titanium catalyst is 50-70 mL/g.
According to an embodiment of the invention, the cocatalyst is a metal organic compound, preferably an organoaluminium compound; more preferably, the organoaluminum compound has a structure represented by the formula:
R 3-n AlX n ，
wherein:
x is halogen, exemplary F, cl, br, I;
r is C1-C12 alkyl, and is exemplified by methyl, ethyl, and propyl;
n is an integer of 0 to 2; exemplary are 0, 1, 2.
The invention also provides small-particle-size ultra-high molecular weight polyethylene powder prepared by the preparation method.
According to an embodiment of the invention, the small particle size ultra high molecular weight polyethylene powder (UHMWPE) has a median particle size D50 of 50 to 150 μm, preferably 50 to 100 μm, more preferably 50 to 80 μm, exemplified by 50 μm, 50.5 μm, 52 μm, 55 μm, 60 μm, 62.7 μm, 66.5 μm, 71.3 μm, 75 μm, 80 μm, 88.3 μm, 90 μm, 98.3 μm, 100 μm, 110 μm, 120 μm, 150 μm.
According to an embodiment of the invention, the small particle size ultra high molecular weight polyethylene powder has an intrinsic viscosity (η) of at least 4dl/g.
According to an embodiment of the invention, the small particle size ultra high molecular weight polyethylene powder has a residual Ti-content of less than 10ppm.
According to an embodiment of the invention, the small particle size ultra high molecular weight polyethylene powder has a total ash content of less than 1000ppm.
According to an embodiment of the present invention, the small particle size ultra high molecular weight polyethylene powder has not less than 0.3g/cm 3 The apparent bulk density of (C) is preferably 0.3 to 0.4g/cm 3 。
The invention has the beneficial effects that:
(1) The inventor of the present invention has unexpectedly found that by using in situ synthesized active magnesium chloride as a catalyst carrier, the active magnesium chloride prepared by the present invention has a larger specific surface area unlike ordinary anhydrous magnesium chloride. The magnesium alkoxide prepared by using the active magnesium chloride as a catalyst carrier of the invention is reacted with titanium tetrachloride and silicon tetrachloride, and a small-particle-size catalyst with good shape can be prepared under the synergistic effect of an anhydride crystallization promoter without the existence of an emulsifier. The crystallization accelerator has the function of enabling precipitation crystallization of the carrier to be more orderly, so that the prepared catalyst has strong crystallinity, large specific surface area, firm particles and small particle size. The catalyst containing the novel carrier has the advantages of controlling the catalyst dynamics and the polymer molecular weight, along with firm particles, high catalytic activity, stable and controllable dynamic curve and the like, and the ultra-high molecular weight polyethylene prepared by using the catalyst has higher bulk density, uniform and fine particle size distribution, high and controllable molecular weight. Therefore, the problems that the catalyst is easy to harden in the drying process and the catalyst with small particle size easily generates static electricity to cause kettle sticking in the process of preparing the ultra-high molecular weight polyethylene, thereby influencing the production efficiency are solved.
(2) The inventors of the present invention have also unexpectedly found that: the catalyst is pre-carried out in a solventAfter pre-dispersion, the catalyst with smaller particle size and higher catalytic activity can be obtained, thereby effectively solving the problem of agglomeration of the catalyst. The catalyst with small particle size of the invention can be used for preparing ultra-high molecular weight polyethylene powder with particle size of 50-100 mu m, and under the synergistic effect of static eliminator, not only can static adhesion phenomenon be eliminated, but also the bulk density of the prepared polyethylene polymer in smaller particle size state can be stabilized at 0.30g/cm 3 Above, even up to 0.40g/cm 3 Thereby greatly improving the particle morphology of the ultra-high molecular weight polyethylene powder. The ultra-high molecular weight polyethylene with higher bulk density, uniform and fine particle size distribution, high molecular weight and controllability is prepared under the combined action of the small-particle-size catalyst, the pre-dispersion and the static eliminator.
(3) The catalyst of the present invention can be used to simply and practically produce an ultra-high molecular weight ethylene polymer and a molded article using the ultra-high molecular weight ethylene polymer, wherein the ultra-high molecular weight ethylene polymer powder can improve the performance and productivity of a molded article such as a filter for a secondary battery, a separator, a fiber, a compression molded article, a plunger extrusion, a woven fiber, a textile, or the like using the ultra-high molecular weight polyethylene.
Detailed Description
The technical scheme of the invention will be further described in detail below with reference to specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
Unless otherwise indicated, the starting materials and reagents used in the following examples were either commercially available or may be prepared by known methods.
Carrier preparation example 1
0.2mol of magnesium powder is put into a 500mL three-necked flask which is replaced by nitrogen, and 100mL of decane, 0.02g of iodine and 20mL of n-butyl chloride are added; heating to 75deg.C, stirring and activating for 2 hr, dropwise adding 1mol of dry n-butane chloride (obvious reaction can be observed), and continuingReacting for 3h, filtering, washing the obtained solid with hexane, and drying to obtain active MgC1 2 A carrier.
The results show that through elemental analysis: the composition of the carrier prepared in this example was (MgCl) 2 )(BuMgCl) 0.59 。
Preparation of catalyst example 1
0.5mol (calculated as Mg) of active MgC1 2 200mL decane and 260mL isooctanol (1.67 mol) are heated to 130 ℃ for reaction for 60 minutes, the temperature is reduced to 65 ℃, 0.03mol 2-hydroxyethyl methacrylate, 0.12mol tetraethoxysilane and 0.010mol norbornene dianhydride are added at the temperature for continuous reaction for 60 minutes, and the mixture is obtained after cooling to room temperature. At 0deg.C, stirring at 1000 rpm, and slowly dripping the above mixture into 1.5L TiC1 for 90 min 4 And 0.5L SiCl 4 After the completion of the dropwise addition, the temperature was kept at 0℃for 60 minutes, and then the temperature was slowly raised to 90℃over 120 minutes, and after 0.01mol of 2-hydroxyethyl methacrylate and 0.04mol of tetraethoxysilane electron donor were added at this temperature, the reaction was continued for 120 minutes to obtain a solid catalyst (after stopping stirring, it was found that the sedimentation rate of the solid catalyst particles was very high). After the reaction, the solid catalyst was filtered off by heating. Washing with hexane 5 times, adding 1.0L hexane each time, until the filtrate is colorless, wherein the free titanium content is less than 0.3mg/mL, and drying to obtain solid.
The titanium content of the catalyst prepared in this example was 3.8% as measured by X-ray fluorescence. The average particle size of the catalyst was measured using laser light scattering and was 5.2 μm.
Preparation of catalyst example 2
0.5mol (calculated as Mg) of active MgC1 2 200mL decane and 260mL isooctanol (1.67 mol) are heated to 130 ℃ for reaction for 60 minutes, cooled to 65 ℃, and 0.05mol 2-hydroxyethyl methacrylate, 0.1mol tetraethoxysilane and 0.01mol norbornene dianhydride are added at the temperature for continuous reaction for 60 minutes, and then the mixture is obtained after cooling to room temperature. At 0deg.C, stirring at 1000 rpm, and slowly dripping the above mixture into 2.0L TiC1 for 90 min 4 In which the mixture is maintained after the dripping is finishedThe temperature was set at 0℃for 60 minutes, then the temperature was slowly raised to 90℃over 120 minutes, and after 0.05mol of tetraethoxysilane electron donor was added at this temperature, the reaction was continued for 120 minutes to obtain a solid catalyst (after stopping stirring, it was found that the settling rate of the solid catalyst particles was very fast). After the reaction, the solid catalyst was filtered off by heating. Washing with hexane 5 times, adding 1.0L hexane each time, until the filtrate is colorless, wherein the free titanium content is less than 0.3mg/mL, and drying to obtain solid.
The titanium content of the catalyst prepared in this example was 3.7% as measured by X-ray fluorescence. The average particle size of the catalyst was measured using laser light scattering and was 5.1. Mu.m.
Preparation of catalyst example 3
0.5mol (calculated as Mg) of active MgC1 2 200mL decane and 260mL isooctanol (1.67 mol), heating to 130 ℃ for reaction for 60 minutes, cooling to 65 ℃, adding 0.075mol 2-hydroxyethyl methacrylate, 0.075mol tetraethoxysilane and 0.010mol norbornene dianhydride at the temperature, continuing to react for 60 minutes, and cooling to room temperature to obtain a mixed solution. At 0deg.C, stirring at 1000 rpm, and slowly dripping the above mixture into 2.0L TiC1 for 90 min 4 After the completion of the dropwise addition, the temperature was maintained at 0℃for 60 minutes, and then the temperature was slowly raised to 90℃over 120 minutes, and after 0.05mol of tetraethoxysilane electron donor was added at this temperature, the reaction was continued for 120 minutes to obtain a solid catalyst (after the stirring was stopped, it was found that the sedimentation rate of the solid catalyst particles was very high). After the reaction, the solid catalyst was filtered off by heating. Washing with hexane for 5 times, adding 1.0L of hexane each time until the filtrate is colorless, wherein the content of free titanium is less than 0.3mg/mL, and drying to obtain the solid catalyst.
The titanium content of the catalyst prepared in this example was 3.9% as measured by X-ray fluorescence. The average particle size of the catalyst was measured using laser light scattering and was 5.3 μm.
Preparation of catalyst example 4
0.5mol (calculated as Mg) of active MgC1 2 200mL decane and 260mL isooctanol (0.167 mol), heating to 130 ℃ for reaction for 60 minutes, cooling to 65 ℃, and heating to the same temperature0.03mol of 2-hydroxyethyl methacrylate and 0.012mol of gamma-chloropropyl triethoxysilane are added under the condition of the temperature, 0.01mol of norbornene dianhydride is added for continuous reaction for 60 minutes, and the mixture is obtained after cooling to room temperature. At 0deg.C, stirring at 1000 rpm, and slowly dripping the above mixture into 2.0L TiC1 for 90 min 4 After the completion of the dropwise addition, the temperature was kept at 0℃for 60 minutes, then the temperature was slowly raised to 90℃over 120 minutes, and after 0.05mol of gamma-chloropropyl triethoxysilane as an electron donor was added at this temperature, the reaction was continued for 120 minutes to obtain a solid catalyst (after stopping stirring, it was found that the sedimentation rate of the solid catalyst particles was very high). After the reaction, the solid catalyst was filtered off by heating. Washing with hexane for 5 times, adding 1.0L of hexane each time until the filtrate is colorless, wherein the content of free titanium is less than 0.3mg/mL, and drying to obtain the solid catalyst.
The titanium content of the catalyst prepared in this example was found to be 4.1% by X-ray fluorescence. The average particle size of the catalyst was measured using laser light scattering and was 5.2 μm.
Preparation of catalyst example 5
In comparison with the preparation of catalyst example 1, the only difference is that: titanium tetrachloride TiC1 4 The dosage is adjusted to be 1.0L, and silicon tetrachloride SiCl 4 The amount was adjusted to 1.0L.
The titanium content of the catalyst prepared in this example was found to be 4.1% by X-ray fluorescence. The catalyst was measured to have an average particle size of 6.03 μm using laser light scattering.
Preparation of catalyst example 6
In comparison with the preparation of catalyst example 1, the only difference is that: titanium tetrachloride TiC1 4 The amount was adjusted to 1.8L and the amount of silicon tetrachloride was adjusted to 0.20L.
The titanium content of the catalyst prepared in this example was 3.8% as measured by X-ray fluorescence. The average particle size of the catalyst was measured using laser light scattering and was 5.13 μm.
Preparation of catalyst example 7
In comparison with the preparation of catalyst example 1, the only difference is that: norbornene dianhydride is modified to phthalic anhydride.
The titanium content of the catalyst prepared in this example was found to be 4.2% by X-ray fluorescence. The catalyst was measured to have an average particle size of 6.23 μm using laser light scattering.
Comparative preparation of catalyst example 1
In comparison with the preparation of catalyst example 1, the only difference is that: active magnesium chloride MgC1 2 The carrier was adjusted to commercially available anhydrous magnesium chloride.
The titanium Ti content of the catalyst prepared by this comparative example was 4.8% as measured by the X-ray fluorescence method. The average particle size of the catalyst measured using laser light scattering was 10.12 μm.
Example 1
In a 500L stainless steel autoclave, after nitrogen substitution, 350L of dehydrated hexane and 1mol/L of a hexane solution of triethylaluminum (30 in terms of Al/Ti molar ratio) were sequentially added, and the mixture was fed into a polymerization vessel. Catalyst preparation 2.0g of the catalyst prepared in example 1 was taken, 100mL of hexane was added and pre-dispersed for 3 hours (the average particle size of the catalyst was measured as 2.03 μm by laser light scattering with a small amount of slurry). Adding the dispersed catalyst into a polymerization kettle, heating to 60 ℃ at the stirring speed of 500 r/min, continuously adding ethylene (21 kg/h) and hydrogen (1.75 g/h) (ethylene/hydrogen mass ratio 12000) into the reactor, polymerizing for 2h at 65 ℃ while maintaining the ethylene flow (21 kg/h) under the kettle pressure of 0.4-0.5 MPa (gauge pressure), cooling to room temperature, discharging and drying to obtain the UHMWPE polyethylene product. After the polymerization is finished, the phenomenon that polyethylene particles adhere to walls does not exist in the polymerization kettle.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Example 2
In comparison with example 1, the difference is that: after 3 hours of pre-dispersion of the catalyst, 2.0g of calcium stearate was added and stirring was continued for 10 minutes (a small amount of slurry was taken and the average particle size of the catalyst was 1.95 μm as measured by laser light scattering). After the polymerization is finished, the inside of the polymerization kettle is very clean, and almost no polyethylene particles exist in the kettle.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Example 3
In comparison with example 1, the difference is that: after 3 hours of pre-dispersion of the catalyst, 2.0g of aluminum stearate was added and stirring was continued for 10 minutes (a small amount of slurry was taken and the average particle size of the catalyst was 1.90 μm as measured by laser light scattering). After the polymerization is finished, the inside of the polymerization kettle is very clean, and almost no polyethylene particles exist in the kettle.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Example 4
In comparison with example 1, the difference is that: after 3 hours of pre-dispersion of the catalyst, 2.0g of Stadis450 was added and stirring was continued for 10 minutes (the average particle size of the catalyst was 1.85 μm as measured by laser light scattering with a small amount of slurry). After the polymerization is finished, the inside of the polymerization kettle is very clean, and almost no polyethylene particles exist in the kettle.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Example 5
In comparison with example 1, the difference is that: the catalyst was pre-dispersed for 1h (the average particle size of the catalyst was 3.55 μm as measured by laser scattering with a small amount of slurry). After the polymerization is finished, the inside of the polymerization kettle is very clean, and almost no polyethylene particles exist in the kettle.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Example 6
In comparison with example 1, the difference is that: the catalyst was pre-dispersed for 12 hours (the average particle size of the catalyst was 2.01 μm as measured by laser scattering with a small amount of slurry). After the polymerization is finished, the inside of the polymerization kettle is very clean, and almost no polyethylene particles exist in the kettle.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Example 7
In comparison with example 1, the difference is that: the catalyst amount was 1.5g. The average particle size of the laser light scattering measurement catalyst was 2.11. Mu.m. During polymerization, the kettle pressure is 0.5-0.6 MPa (gauge pressure).
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Examples 8 to 13
In comparison with example 1, the difference is that: the catalysts were the catalysts prepared in examples 2, 3, 4, 5, 6, and 7, respectively.
The UHMWPE polyethylene product prepared in this example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle size and particle size distribution, and the like, and the results are shown in table 1 in detail.
Comparative example 1
In comparison with example 1, the difference is that: the catalyst was the catalyst prepared in comparative preparation example 1. The average particle size of the catalyst after pre-dispersion was measured by laser light scattering and found to be 6.01. Mu.m. The catalyst loading was 3.0g.
The UHMWPE polyethylene product prepared in this comparative example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle diameter and particle diameter distribution, and the like, and the results are shown in table 1 in detail.
Comparative example 2
In comparison with example 1, the difference is that: the catalyst is not pre-dispersed.
The UHMWPE polyethylene product prepared in this comparative example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle diameter and particle diameter distribution, and the like, and the results are shown in table 1 in detail.
Comparative example 3
In comparison with example 1, the difference is that: no hydrogen was added. After the polymerization is finished, relatively more polyethylene particles are arranged in the polymerization kettle, and the kettle sticking phenomenon exists.
The UHMWPE polyethylene product prepared in this comparative example was subjected to catalyst activity measurement, bulk density measurement, viscosity average molecular weight measurement, measurement of average particle diameter and particle diameter distribution, and the like, and the results are shown in table 1 in detail.
The catalyst activity, bulk density, viscosity average molecular weight, average particle size and particle size distribution of the UHMWPE polyethylene product were determined as follows:
catalyst activity = mass of polyethylene product obtained/mass of catalyst
Bulk density was measured using ASTM-D-1895 method.
Polyethylene particle size is determined by a laser particle analyzer (Mastersizer X, malvern), where D10, D50 and D90 distributions refer to the particle sizes at each of the percentages 10, 50 and 90. D50 is defined as the average particle size and the particle size distribution is defined as (D90-D10)/D50.
Viscosity average molecular weight was determined by high Wen Xingwu viscometer method according to ASTM D4020-05, capillary inner diameter of 0.53mm, and M was used η ＝5.37×10 4 ·[η] 1.37 And (5) performing calculation.
The results of measuring the catalytic activity, bulk density, viscosity average molecular weight, average particle diameter D50 (μm) and particle size distribution ((D90-D10)/D50) of the UHMWPE polyethylene products prepared in examples 1 to 13 and comparative examples 1 to 3 are shown in Table 1 below.
TABLE 1
From the data in table 1, it can be found that:
1. after the catalyst is pre-dispersed, agglomeration can be eliminated, and the particle size of the catalyst is reduced;
2. in the presence of the static eliminator, the static of the polyethylene can be inhibited to obtain polyethylene with small particle size; on the contrary, polyethylene tends to generate static electricity, resulting in an increase in particle size.
3. The particle size of polyethylene is affected by the activity of the catalyst and is in direct proportion to the cube root of the catalyst activity.
4. After the catalyst is dispersed, the particle size is reduced, the specific surface area is increased, the catalytic activity is further increased, and the molecular weight of a polyethylene product can be reduced and the bulk density is reduced under the condition of controlling the ethylene flow.
The small-particle-diameter polyethylene powder produced by the present invention is more suitable as a filler for secondary battery filters, separators, fibers, compression molded articles, plunger extrudates, fiber knits, textiles and other molded articles to improve the performance and productivity thereof.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (12)

1. The method for preparing the small-particle-size ultra-high molecular weight polyethylene powder is characterized by comprising the steps of carrying out polymerization reaction on a pre-dispersed titanium catalyst and a cocatalyst and an olefin polymerization monomer under the action of an electrostatic eliminator to prepare the small-particle-size ultra-high molecular weight polyethylene powder; the particle size of the pre-dispersed titanium catalyst and the pre-dispersed cocatalyst is 1.5-4 mu m;
the titanium catalyst comprises 0.5-5% of Ti in percentage by mass;
the titanium catalyst has an average particle diameter of 0.1 [ mu ] m or more and 10 [ mu ] m or less;
the titanium catalyst is prepared by the following method:
(1) In a hydrocarbon solvent, reacting active magnesium chloride with an organic alcohol compound to obtain a magnesium alkoxide reaction solution;
the active magnesium chloride compound has a structure shown in the following formula I:
(MgCl 2 )(R 1 MgCl) a Mg b [Ti(OR 2 ) 4 )] c [Si(OR 3 ) 4 ] d
i is a kind of
Wherein:
R 1 、R 2 、R 3 identical or different, independently of one another, from C 1-12 Alkyl, a is 0.02-1, b is 0-0.5, c is 0-0.8, d is 0-0.8;
(2) Reacting the magnesium alkoxide reaction solution prepared in the step (1) with an electron donor ester compound, a silicon compound having an alkoxy group and a crystallization accelerator;
(3) Mixing the reaction solution obtained in the step (2) with a titanium compound and a silicon compound to perform a pre-load titanium reaction;
(4) Mixing the reaction solution obtained in the step (3) with an electron donor ester compound and a silicon compound with alkoxy to react to obtain a titanium catalyst;
the molar ratio of aluminum in the cocatalyst to titanium in the titanium catalyst is 10-800;
the static eliminator is one, two or more selected from hydrogen, aluminum stearate, calcium stearate, magnesium stearate, polyoxyethylene lauryl ether, polyvinylpyrrolidone and Stadis 450;
the pre-dispersion time is 1-12 h; the solvent adopted in the pre-dispersion is at least one of pentane, hexane, heptane, octane and decane;
the median particle diameter D50 of the small-particle-diameter ultra-high molecular weight polyethylene powder is 50-100 mu m, and the apparent volume density is 0.3-0.4 g/cm 3 。
2. The method of claim 1, wherein the pre-dispersed titanium catalyst and promoter have a particle size of 1.85 to 3.6 μm;
the titanium catalyst contains 1.5-4.5% of Ti;
The average particle diameter of the titanium catalyst is 0.2 μm or more and 8 μm or less.
3. The process according to claim 1 or 2, wherein the total mass of titanium catalyst and cocatalyst is equal toThe dosage ratio of the olefin polymerization monomers is 1: (2-3.0X10) 4 )。
4. The method of any one of claims 1-2, wherein the pre-dispersion is for a period of 2 to 5 hours.
5. The method of claim 1, wherein the molar ratio of aluminum in the promoter to titanium in the titanium catalyst is from 50 to 200.
6. The method of claim 5, wherein the molar ratio of aluminum in the promoter to titanium in the titanium catalyst is from 80 to 160.
7. The method according to claim 1, wherein when the static eliminator is selected from hydrogen, the mass ratio of the olefin polymerization monomer to hydrogen is (20000 to 10000): 1, a step of;
and/or when the static eliminator is selected from one of aluminum stearate, calcium stearate, magnesium stearate, polyoxyethylene lauryl ether, polyvinylpyrrolidone and Stadis450, the amount thereof is 200-1000 ppm relative to the total amount of the solvent in the reactor.
8. The method according to claim 7, wherein when the static eliminator is selected from hydrogen, the mass ratio of the olefin polymerization monomer to hydrogen is (15000 to 10000): 1, a step of;
When the static eliminator is one selected from aluminum stearate, calcium stearate, magnesium stearate, laureth, polyvinylpyrrolidone and Stadis450, the amount is 300-800 ppm relative to the total amount of the solvent in the reactor.
9. The method according to claim 8, wherein when the static eliminator is selected from one of aluminum stearate, calcium stearate, magnesium stearate, polyoxyethylene lauryl ether, polyvinylpyrrolidone, stadis450, the amount thereof is 400 to 600ppm relative to the total amount of the solvent in the reactor.
10. The method of any one of claims 1-2, wherein the polymerization reaction is at a temperature of 30-90 ℃; the polymerization reaction pressure is as follows: 0.1-1.0 MPa.
11. The method of claim 10, wherein the polymerization reaction is carried out at a temperature of 40 to 80 ℃ and a pressure of 0.2 to 0.8MPa.
12. The method of claim 1, wherein the small particle size ultra high molecular weight polyethylene powder has a median particle size D50 of 50 to 80 μm;
and/or the small particle size ultra high molecular weight polyethylene powder has an intrinsic viscosity (η) of at least 4dl/g;
and/or the residual Ti-content of the small-particle-size ultra-high molecular weight polyethylene powder is lower than 10ppm;
And/or the total ash content of the small-particle-size ultra-high molecular weight polyethylene powder is lower than 1000ppm.
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