A method for industrial production of ultra-high molecular weight polyethylene powder having a fine particle size and a low bulk density

Abstract

The present application relates to a kind of industrial production of the method of low bulk density of fine particle size and ultra-high molecular weight polyethylene powder.The reaction kettle used is provided with multiple groups of U-shaped cooling coil and combined stirrer, and by regulating stirring speed and magnesium alcohol ratio, high-activity catalyst with particle size <2 μm is prepared.The catalyst is pre-dispersed in solvent, and then polymerized with ethylene in the presence of static eliminator, to obtain UHMWPE powder with bulk density ≤0.30 g / cm³ and particle size of 30-80 μm.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high molecular weight polymer technology and relates to a method for preparing ultra-high molecular weight polyethylene powder. Specifically, it relates to a method for preparing ultra-high molecular weight polyethylene particles with a particle size smaller than existing ultra-high molecular weight polyethylene particles, no agglomeration between particles, extremely narrow particle size distribution, and high sphericity. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE), a representative of ultra-high molecular weight polyolefins, is widely used in mechanical parts, lining materials, and sporting goods due to its lightweight nature and excellent properties such as wear resistance, impact resistance, chemical resistance, and good self-lubrication. In recent years, the development of UHMWPE microparticles has been active, and they are widely used in various industrial applications. In particular, UHMWPE microparticles with a spherical shape and narrow particle size distribution are used in filters, separation membranes, dispersants, powder coatings, resin modifiers, and coating agents due to their good processability, flowability, and surface properties.

[0003] For example, ultra-high molecular weight polyethylene (UHMWPE) microparticles can be directly used as column packing agents for the efficient separation of chemical or biological substances, or as adsorbents or catalyst supports with high specific surface areas. Additionally, they can be used as carriers for drug delivery and release, or as dispersants to uniformly disperse poorly dispersed microparticles. They can also be used as safe microparticles in cosmetics, providing a pleasant feel on the skin. Furthermore, researchers are actively exploring their application in the field of functional new materials. Examples include components for separators in lithium batteries or lithium-ion secondary batteries, components for optical filters with light diffusion, reflection, and anti-reflection properties, high-performance adhesives for sintered porous bodies such as ceramics, pore-forming materials for breathable membranes, carriers for immobilizing immunochemically active substances, microporous high specific surface area sintered filters, smoothing agents, colorants, matting agents for coatings, light-diffusing additives, insulating fillers, nucleating agents, chromatograph packing materials, and carriers for immunodiagnostic drugs. To endow ultra-high molecular weight polyethylene (UHMWPE) microparticles with more new functional applications and further improve their performance and quality, researchers are dedicated to developing spherical UHMWPE microparticles with smaller particle size, narrower particle size distribution, and no interparticle aggregation. Among these many applications, the use of UHMWPE microparticles as filter materials is a rapidly developing emerging application. However, when preparing filters from UHMWPE through molding, the poor flowability of UHMWPE during melting prevents the use of commonly used melt molding methods. Instead, rotational molding or powder molding methods are used to directly process the polyolefin powder, but the resulting filters have poor filtration performance. In existing technologies, when preparing microfiltration membranes through sintering, only the surface of the raw material particles melts rather than fully melts, resulting in the formation of a network of pores within the filter membrane. The size and distribution of these pores are related to the particle size and distribution of the UHMWPE powder. The impact of UHMWPE particle size on product performance is as follows: the larger the particle size, the greater the porosity, but the microporous structure is prone to becoming irregular, the micropore distribution becomes uneven, and the strength of the filter membrane decreases accordingly; however, the smaller the particle size, the finer and more uniform the microporous structure, and although the porosity decreases, the strength of the filter membrane will increase.

[0004] Low bulk density and fine particle size UHMWPE powder can be sintered to form a microporous structure with small and uniform pore size, making it suitable for high-precision filter materials such as water treatment membranes and lithium battery separators. The close packing of fine particles reduces pore size, improving filtration efficiency and material strength. Furthermore, the fine particle size powder has better flowability, making it suitable for precision molding processes involving complex shapes. For example, it can be used in the medical field for customized artificial joints or surgical instruments, or in the electronics industry for manufacturing miniature insulating components.

[0005] There are many examples of ultra-high molecular weight polyethylene (UHMWPE) micro powder products. For instance, Celanese's GUR2022 and 2126 have particle sizes of 60μm and 30μm respectively, and a bulk density of 0.28g / cm³. 3 Used in porous sintering for the preparation of filters and plastic modifiers. This is proprietary technology.

[0006] Mitsui Chemicals' Mipelon™ ultra-high molecular weight polyethylene micropowder has a particle size of 25-30 μm and a bulk density of less than 0.30 g / cm³. 3 It is used as a modifying additive for rubber, inks, and resins, as well as in sintered filters. It is also proprietary technology.

[0007] CN101061144B first reacts a magnesium alcohol mixture with triethylaluminum in a homogenizer at a speed of 15,000–20,000 rpm to generate a magnesium chloride support with a particle size of 0.95–1.5 μm. This support is then reacted with a non-ceramic catalyst to generate a supported non-ceramic catalyst. This catalyst can be used to obtain ultra-high molecular weight polyethylene powder with a particle size of 3 μm–25 μm. While this method can produce fine-particle-size ultra-high molecular weight polyethylene, the high rotational speed limits its application in large-scale industrial production.

[0008] The shape of ultra-high molecular weight polyethylene (UHMWPE) powder particles is derived from the shape of catalyst particles, a phenomenon known as replication. Typically, when this replication occurs, the average particle size of the polymer is proportional to the catalyst yield (the cube root of the number of grams of polymer produced per gram of catalyst). Based on this proportionality, polymer particles with smaller average particle sizes can be prepared by reducing the catalyst yield, but this results in high catalyst residue in the polymer and high catalyst costs for its production. Therefore, this places stringent requirements on the catalyst. Typically, the metal content, especially titanium atoms, in UHMWPE is required to be below 5 ppm. However, to achieve a UHMWPE microparticle content of less than 5 ppm titanium atoms, the catalytic activity must be at least 2.0 × 10⁻⁶. 5 gPE / gTi or above. Summary of the Invention

[0009] In the industrial production of catalysts, the inventors were surprised to discover that a specially designed reactor could produce catalysts with an average particle size of less than 2.0 μm under normal operation, and the produced ultra-high molecular weight polyethylene had a bulk density of 0.3 g / cm³. 3 the following.

[0010] This invention provides a reactor for preparing an olefin polymerization catalyst, comprising a reactor body and a stirrer; The reactor body is provided with two or more sets of U-shaped cooling coils; for example, 2-6 sets are provided; the U-shaped cooling coils act as guide plates, allowing the stirring speed to be changed arbitrarily; more preferably, two or more sets of U-shaped cooling coils are evenly installed on the inner wall of the reactor body corresponding to the stirring paddle. The agitator includes a combined impeller housed inside the reactor body. For example, the combined impeller consists of a lower high-shear impeller (four-bladed turbine impeller) and an upper low-shear impeller (three-bladed slanted impeller). The upper three-bladed slanted impeller enhances axial circulation and reduces energy consumption; the lower four-bladed turbine impeller strengthens localized bottom shear. The four-bladed turbine impeller is configured for downward flow, while the upward flow of the three-bladed slanted impeller promotes overall reactor circulation. This alternating upward and downward flow (downward-upward-downward) ensures uniform material suspension and prevents solids from settling to the bottom.

[0011] According to an embodiment of the present invention, the reactor body is further provided with a combined filter, consisting of a decanting pipe that can move up and down within the reactor body and a bottom filter. The decanting pipe is a supernatant extraction pipe. The number of bottom filters is two or more, preferably four to six, evenly distributed circumferentially at the bottom of the reactor body. This combined filter can play a synergistic role in filtering the mother liquor. First, a centrifugal pump extracts more than 70% of the mother liquor through the decanting pipe, and then the remaining mother liquor is filtered out by the bottom filter plate. This can greatly shorten the filtration and washing time, accelerate the filtration and washing of the catalyst, and improve production efficiency.

[0012] According to an embodiment of the present invention, the ratio of the radial diameter L of the three-bladed oblique propeller to the diameter D of the reactor, L / D, is 0.1~0.4, preferably 0.2~0.4, and exemplary values ​​are 0.1, 0.15, 0.2, 0.25, 0.3, and 0.4.

[0013] Preferably, the ratio of the diameter l of the four-bladed turbine propeller to the diameter D of the reactor is l / D = 0.15~0.4, more preferably 0.2~0.3, for example 0.25; Preferably, the distance between the three-bladed oblique propeller and the four-bladed turbine propeller is 1.4 to 1.6 times the diameter of the four-bladed turbine propeller, and most preferably 1.5 times. This distance can avoid flow field interference.

[0014] According to an embodiment of the present invention, the stirrer further includes a drive unit for adjusting the stirring speed of the stirring paddle, thereby obtaining a catalyst with the desired particle size by controlling the stirring speed (preferably 150~300 rpm).

[0015] According to an embodiment of the present invention, the catalyst preparation reactor is mainly used for titanium-supported reactions.

[0016] According to embodiments of the present invention, the average particle size of the catalyst is less than 2.0 μm, for example, less than 1.6 μm, less than 1.0 μm, or 0.5 to 1.6 μm; and / or, the particle size range of the catalyst is 700 nm to 3.0 μm, for example, 700 nm to 2.5 μm.

[0017] The present invention also provides the application of the above-mentioned olefin polymerization catalyst preparation reactor in the preparation of olefin polymers (e.g., ultra-high molecular weight polyethylene); The median particle size D of the olefin polymer (e.g., ultra-high molecular weight polyethylene) 50 The thickness is 30~100μm, preferably 30~80μm; The bulk density of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is ≤0.3 g / cm³. 3 For example, not less than 0.2g / cm 3 And less than 0.3g / cm 3 .

[0018] According to embodiments of the present invention, the particle size distribution (i.e., D) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... 90 -D 10 () / D50)≥0.9, for example 0.9~0.96.

[0019] According to an embodiment of the present invention, the viscosity-average molecular weight (M0.05) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... η ×10 4 The range is 520~600, for example, 540~580.

[0020] The present invention also provides a method for preparing an olefin polymer (e.g., ultra-high molecular weight polyethylene), comprising the following steps: (1) The catalyst was prepared using the above-mentioned olefin polymerization catalyst preparation reactor; Preferably, the average particle size of the catalyst is less than 2.0 μm, for example, less than 1.6 μm, less than 1.0 μm, or 0.5~1.6 μm; and / or, the particle size range of the catalyst is 700 nm~3.0 μm, for example, 700 nm~2.5 μm; (2) The catalyst system containing the catalyst in step (1) is subjected to polymerization reaction with an olefin monomer (e.g., ethylene) to prepare the olefin polymer (e.g., ultra-high molecular weight polyethylene). The olefin polymer (e.g., ultra-high molecular weight polyethylene) has the limitations shown above.

[0021] According to an embodiment of the present invention, the catalyst contains, by mass percentage, 4-7% Ti, 15-18% Mg, and 0.15-0.3% Si; for example, 4.5-6.5% Ti, 15.5-17.0% Mg, and 0.18-0.26% Si.

[0022] According to an embodiment of the present invention, step (1) includes: reacting active magnesium chloride with an alkyl alcohol (e.g., isooctyl alcohol) in a hydrocarbon solvent (e.g., decane), then adding a silane electron donor (e.g., γ-chloropropyltrimethoxysilane) and an acid anhydride (e.g., norbornene anhydride) to the system, and continuing the reaction to obtain an alcoholic solution; reacting the alcoholic solution with a titanium compound and a silane electron donor (e.g., γ-chloropropyltrimethoxysilane) to preload titanium to obtain a preloaded titanium catalyst component; filtering, washing, and drying the preloaded titanium catalyst component to obtain a catalyst.

[0023] According to an embodiment of the present invention, the catalyst system comprises the above-described catalyst and organoaluminum compound R. 3- m A1X m Where X is a halogen and R is a C 1~12 Alkyl (e.g., C) 1~6 Alkyl groups, exemplified by methyl, ethyl, propyl, isopropyl, butyl, and isobutyl, with m being an integer from 0 to 2.

[0024] According to an embodiment of the present invention, the molar ratio of aluminum in the organoaluminum compound to titanium in the catalyst active component is 10 to 300, preferably 10 to 150, and more preferably 30 to 100.

[0025] According to an embodiment of the present invention, step (1) includes: (a) Preparation of magnesium chloride alcohol solution: active magnesium chloride, hydrocarbon solvent (e.g., decane) and isooctanol are mixed at an alcohol-to-magnesium ratio of 4.3, and a silane electron donor (e.g., γ-chloropropyltrimethoxysilane) and norbornyl anhydride are added. The mixture is kept at a constant temperature to obtain the alcohol solution. (b) Supported titanium catalyst: The alcohol solution was added dropwise to titanium tetrachloride at -10°C and a stirring speed of 150~300 r / min. The temperature was raised to 110°C and a silane electron donor (e.g. γ-chloropropyltrimethoxysilane) was added. After the reaction, the mixture was filtered, washed, and dried to obtain a catalyst with an average particle size of <2 μm.

[0026] According to an embodiment of the present invention, the catalyst system needs to be pre-dispersed in a solvent. Preferably, the co-catalyst can be first dispersed in a solvent to obtain a co-catalyst solution; Preferably, the pre-dispersion time is 1-3 hours, more preferably 2 hours; Preferably, the solvent used for pre-dispersion is hexane.

[0027] According to an embodiment of the present invention, the polymerization reaction is carried out in the presence of an antistatic agent. Preferably, the antistatic agent is selected from one, two or more of hydrogen, calcium stearate, magnesium stearate, lauryl alcohol polyoxyethylene ether, polyvinylpyrrolidone, and Stadis 450.

[0028] Preferably, when the static eliminator is selected from any one of calcium stearate, magnesium stearate, lauryl alcohol polyoxyethylene ether, polyvinylpyrrolidone, and Stadis 450, its dosage is 50 to 300 ppm relative to the total amount of solvent in the polyolefin reactor, preferably 150 to 200 ppm, and most preferably 100 to 150 ppm.

[0029] According to an embodiment of the present invention, the temperature of the polymerization reaction is 30~90℃, preferably 40~80℃; the pressure of the polymerization reaction is 0.1~1.0MPa, preferably 0.2~0.8MPa.

[0030] According to an embodiment of the present invention, step (2) includes: pre-dispersing the catalyst in a solvent for 1-3 hours, adding it to a polymerization reactor, and passing it through an ethylene polymerization reactor under the conditions of an antistatic agent (50-300 ppm), a temperature of 40-80°C, and a pressure of 0.2-0.8 MPa to obtain UHMWPE powder with a bulk density of <0.3 g / cm³ and a particle size of 30-80 μm.

[0031] The present invention also provides olefin polymers, such as ultra-high molecular weight polyethylene, prepared by the preparation method described above.

[0032] According to an embodiment of the present invention, the olefin polymer is granular ultra-high molecular weight polyethylene (UHMWPE).

[0033] According to an embodiment of the present invention, the median particle size D50 of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is 30-100 μm, preferably 30-80 μm; The bulk density of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is ≤0.3 g / cm³. 3 For example, not less than 0.2g / cm 3 And less than 0.3g / cm 3 .

[0034] According to embodiments of the present invention, the particle size distribution (i.e., D) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... 90 -D 10 () / D50)≥0.9, for example 0.9~0.96.

[0035] According to an embodiment of the present invention, the viscosity-average molecular weight of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is (520~600) × 10⁻⁶.4 For example, (540~580)×10 4 .

[0036] Formula for calculating viscosity-average molecular weight: M η = 5.37 × 10 4 ×[η] 1.49 .

[0037] According to an embodiment of the present invention, the intrinsic viscosity (η) of the olefin polymer is at least 4 dl / g.

[0038] According to an embodiment of the present invention, the residual Ti content of the olefin polymer is less than 10 ppm.

[0039] According to an embodiment of the present invention, the total ash content of the olefin polymer is less than 500 ppm.

[0040] According to an embodiment of the present invention, the olefin polymer has a content of 220~300 g / cm³. 3 The apparent bulk density.

[0041] The beneficial effects of this invention: (1) The inventors of this invention unexpectedly discovered that small-particle-size catalysts can be prepared by using a specially designed reactor, resulting in catalysts with large specific surface area and small particle size. The produced catalyst precursor has advantages such as high catalytic activity and stable and controllable kinetic curves. The ultra-high molecular weight polyethylene prepared using it has low bulk density, uniform and fine particle size distribution, and high and controllable molecular weight. This solves the problem of industrial production of small-particle-size catalysts.

[0042] (2) The inventors of this invention also unexpectedly discovered that pre-dispersing the above-mentioned catalyst in a solvent effectively solved the problem of catalyst agglomeration. Using the small-particle-size catalyst of this invention, ultra-high molecular weight polyethylene powder with a particle size of 30-80 μm can be prepared. Simultaneously, with the synergistic effect of the electrostatic eliminator, not only can the electrostatic sticking phenomenon be eliminated, but the bulk density of the prepared polyethylene polymer is also 0.30 g / cm³. 3 The present invention utilizes a small-particle-size catalyst, pre-dispersion agent, and electrostatic eliminator to produce ultra-high molecular weight polyethylene with low bulk density, uniform and fine particle size distribution, and high and controllable molecular weight. Attached Figure Description

[0043] Figure 1 Prepare reaction vessel for catalyst; Attached reference numerals: 1-reactor body, 2-U-shaped cooling coil, 3-combined agitator, 4-decanting pipe, 5-bottom filter.

[0044] Figure 2 Here is an electron microscope image of the catalyst from Example 1; Figure 3 Here is an electron microscope image of the UHMWPE product from Example 1; Figure 4 Here is an electron microscope image of the catalyst from Example 2; Figure 5 Here is an electron microscope image of the UHMWPE product from Example 2; Figure 6 Here is an electron microscope image of the catalyst in Example 3; Figure 7 Example 3: Electron micrograph of the UHMWPE product; Figure 8 Electron micrograph of the catalyst in Comparative Example 1; Figure 9 Electron micrograph of Comparative Example 1 UHMWPE product; Figure 10 Electron microscope images of Comparative Example 2 UHMWPE product; Figure 11 Electron micrograph of catalyst in Comparative Example 3; Figure 12 Electron micrograph of Comparative Example 3 UHMWPE product. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0046] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0047] The methods for measuring catalyst particle size and bulk density of UHMWPE products, measuring viscosity-average molecular weight, and determining average particle size and particle size distribution are as follows: Catalyst particle size was tested using Hitachi 8100.

[0048] The bulk density of polyethylene was determined using the ASTM-D-1895 method.

[0049] The particle size of polyethylene was determined using a laser particle analyzer (MastersizerX, Malvern), where D... 10 D 50 and D 90 Distribution refers to the particle size at percentages of 10%, 50%, and 90%. (D) 50 Defined as average particle size, particle size distribution is defined as (D 90 -D 10 ) / D50 .

[0050] Viscosity was determined using a high-temperature Ubbelohde viscometer method according to ASTM D4020-05 standard, with a capillary inner diameter of 0.53 mm and an M... η =5.37×10 4 ·[η] 1.49 Perform the calculation.

[0051] The following examples illustrate the preparation of pre-supported titanium catalyst components. Figure 1 The catalyst preparation reactor shown includes: reactor body 1, stirrer, two sets of U-shaped cooling coils 2 installed on the inner wall of reactor body 1, and combined filter; The agitator includes a combined agitator blade 3: the upper layer is a three-bladed inclined blade (upward-folding setting to enhance axial circulation, its structure is not shown in the figure), and the lower layer is a four-bladed turbine blade (downward-pressing flow direction to enhance bottom shear, its structure is not shown in the figure). The uniform suspension is achieved by alternating up and down flow directions (downward-upward-downward) to avoid solids settling to the bottom. The ratio of the radial diameter l of the four-bladed turbine propeller to the diameter D of the reactor is l / D = 0.15~0.4, and the ratio in the following example is 0.25; The ratio of the radial diameter L of the three-bladed oblique propeller to the diameter D of the reactor is L / D = 0.1~0.4, and the ratio in the following example is 0.25; The distance between the two stirring blades is 1.4 to 1.6 times the diameter of the four-bladed turbine blade. In the following example, the value is 1.5. This distance can avoid flow field interference. Combined filter: includes a vertically movable decanting pipe 4 and a bottom filter 5; the number of bottom filters is four, evenly arranged circumferentially at the bottom of the reactor body.

[0052] Example 1 I. Catalyst Preparation: In the first step, 30 kg of activated magnesium chloride, 260 L of decane, and 213 L of isooctanol were added to the alcohol preparation vessel, controlling the magnesium-to-alcohol ratio at 4.3. The temperature was raised to 130 °C and held for 3 hours. Then, the temperature was lowered to 65 °C, and 11 L of γ-chloropropyltrimethoxysilane electron donor and 5.7 kg of norbornene anhydride were added. The mixture was held for 1 hour to obtain the magnesium chloride alcohol solution.

[0053] The second step is to add 1200L of titanium tetrachloride to 2m 3 Reactor ( Figure 1In this process, refrigerant was introduced into a U-shaped cooling coil, and the stirrer was turned on at a stirring speed of 300 r / min. After cooling the reactor to 10°C, magnesium chloride-alcohol mixture was slowly added to the reactor over 6 hours. After the magnesium chloride-alcohol mixture was added, the temperature was raised to 0°C over 60 minutes, then maintained at 0°C for 60 minutes, and then slowly raised to 110°C over 240 minutes. At this temperature, 3.3 L of the same silane electron donor (i.e., γ-chloropropyltrimethoxysilane) was added, and the reaction continued for 120 minutes to obtain the pre-loaded titanium catalyst component. After the reaction was completed, the mother liquor was filtered out. The solid catalyst was washed with 500 L of hexane at 50°C each time until the filtrate was basically colorless and the free titanium content was less than 0.3 mg / mL. The catalyst slurry was transferred to a drying vessel and dried under vacuum for 2 hours to obtain 40 kg of solid catalyst. Catalyst elemental analysis: by mass percentage, Ti: 5.61%, Mg: 16.83%, Si: 0.24%. Electron microscopy revealed an average particle size of 900 nm. Results are as follows: Figure 2 As shown.

[0054] II. Ethylene polymerization: At 13m 3 In a stainless steel autoclave, after nitrogen purging, 8.5 ml of dehydrated hexane was sequentially added. 3 A hexane solution of triethylaluminum (Al / Ti molar ratio of 30) was added to the polymerization reactor. 80g of the catalyst prepared in Example 1 was added to 1000L of hexane in a catalyst preparation tank and pre-dispersed for 0.5h. Then, 8.5g of Stadis 450 antistatic agent was added, followed by the addition of the pre-dispersed catalyst to the polymerization reactor. The reactor was heated to 65℃ with a stirring speed of 200 rpm, and ethylene (600kg / h) was continuously added. The reactor pressure was 0.4~0.5MPa (gauge pressure). The polymerization reaction was carried out at 75℃ while maintaining an ethylene flow rate of 600kg / h. When the cumulative ethylene flow rate reached 2500kg, the ethylene addition was stopped, and the reactor pressure was reduced to 0.15MPa using suction pressure. The reactor was then cooled to room temperature, and the product was discharged and dried to obtain UHMWPE polyethylene.

[0055] The bulk density, viscosity-average molecular weight, average particle size, and particle size distribution of the UHMWPE polyethylene product prepared in this embodiment were measured. Detailed results are shown in Table 1. Electron micrographs of the product are shown below. Figure 3 The average particle size of polyethylene was calculated to be 33.1 μm.

[0056] Example 2 I. Catalyst Preparation: The preparation method was the same as in Example 1, except that the stirring speed in the second step was 200 rpm. After vacuum drying, 39 kg of solid catalyst was obtained. Elemental analysis of the catalyst: Ti: 5.83%, Mg: 16.15%, Si: 0.21%. Electron microscopy showed that the average particle size of the catalyst was 1.53 μm. The results are as follows... Figure 4 As shown.

[0057] II. Ethylene Polymerization: The 1.53 μm catalyst described above was used, and all other procedures were the same as in Example 1. The average particle size of the UHMWPE polyethylene product under electron microscopy was 53.5 μm, see [link to example]. Figure 5 The aggregated data is shown in Table 1.

[0058] Example 3 Catalyst preparation: Same as in Example 1, except that the stirring speed in the second step was 150 rpm. After vacuum drying, 38.3 kg of solid catalyst was obtained. Elemental analysis of the catalyst: Ti: 6.08%, Mg: 16.01%, Si: 0.19%. The average particle size of the catalyst measured by electron microscopy was 1.99 μm. The results are as follows. Figure 6 As shown.

[0059] Ethylene polymerization: The 1.99 μm catalyst described above was used, and all other procedures were the same as in Example 1. The average particle size under electron microscopy was 75.9 μm. (See attached image). Figure 7 The aggregated data is shown in Table 1.

[0060] Comparative Example 1 Similar to Example 1, except that the alkoxide-to-magnesium ratio was controlled at 2.8. After vacuum drying, 38 kg of solid catalyst was obtained. Elemental analysis showed: Ti: 6.43%, Mg: 15.75%, Si: 0.18%. Electron microscopy revealed that the average particle size of the catalyst was 1.68 μm. The results are as follows. Figure 8 As shown.

[0061] Ethylene polymerization: Same as in Example 1. The average particle size of the UHMWPE polyethylene product under electron microscopy was 63.6 μm, see [link to example]. Figure 9 The aggregated data is shown in Table 1.

[0062] Comparative Example 2 Ethylene polymerization: at 13m 3 In a stainless steel autoclave, after nitrogen purging, 8.5 ml of dehydrated hexane was sequentially added. 3A hexane solution of triethylaluminum (Al / Ti molar ratio of 30) was added to the polymerization reactor. 80g of the catalyst prepared in Example 1 was activated and directly added to the polymerization reactor. The reactor was heated to 65°C with a stirring speed of 200 rpm, and then ethylene (600 kg / h) was continuously added. The reactor pressure was 0.4~0.5 MPa (gauge pressure). The polymerization reaction was carried out at 75°C while maintaining an ethylene flow rate of 600 kg / h. When the cumulative ethylene flow rate reached 2500 kg, the addition of ethylene was stopped. The reactor pressure was reduced to 0.15 MPa using suction pressure, and then cooled to room temperature. After drying, UHMWPE polyethylene product was obtained. The average particle size of the UHMWPE polyethylene product under electron microscopy was 50.9 μm. (See...) Figure 10 The aggregated data is shown in Table 1.

[0063] Comparative Example 3 Catalyst preparation: Laboratory catalyst preparation equipment in this field was used. 0.5 mol (calculated as Mg) of in-situ active magnesium chloride support, 200 mL of decane, and 329 mL of isooctanol (2.1 mol) were mixed and heated to 130 °C for 60 minutes. The mixture was then cooled to 65 °C, at which point 0.15 mol of γ-chloropropyltrimethoxysilane electron donor and 0.15 mol of norbornyl anhydride were added, and the reaction continued for another 60 minutes. After cooling to room temperature, the mixture was slowly added dropwise over 90 minutes at 10 °C to a 5 L reactor containing 2000 mL of TiCl4, with a stirring speed of 1000 rpm. After the addition was complete, the temperature was maintained at 0 °C for 60 minutes, and then slowly increased to 110 °C over 120 minutes. At this temperature, 0.05 mol of the same silane electron donor was added, and the reaction continued for another 120 minutes to obtain the solid catalyst active component. After the reaction was completed, the solid catalyst active component was hot-filtered out. Wash with hexane until the filtrate is essentially colorless, containing less than 0.3 mg / mL of free titanium. After drying, 70 g of solid catalyst active component was obtained. The catalyst active particle size is 2.8 μm. (See attached image) Figure 11 Elemental analysis: Ti: 4.5%, Mg: 17.8%, Si: 0.46%.

[0064] Ethylene polymerization: Same as in Example 1. The average particle size of polyethylene under electron microscopy was 110.5 μm, see [link to example]. Figure 12 The aggregated data is shown in Table 1.

[0065] Table 1

[0066] From the data in Table 1, we can find that: 1. Compared with Comparative Example 1, a high alcohol-magnesium ratio is beneficial to the generation of small particle size catalysts, and controlling the alcohol-magnesium ratio can achieve the purpose of controlling the catalyst particle size. 2. Data from Examples 1, 2, and 3 show that increasing the stirring speed, preferably between 150 and 300 rpm, can reduce the catalyst particle size. By adjusting the stirring speed, the catalyst particle size can be controlled.

[0067] 3. A comparison between Example 1 and Comparative Example 2 shows that the particle size distribution of Comparative Example 2 is much wider, that is, the particle size difference of the product particles is larger. This is due to partial agglomeration. The addition of the static eliminator can reduce the agglomeration of polyethylene powder particles during the polymerization process, making the particle size more uniform, improving the flowability of polyethylene powder, which is beneficial to the later transportation and processing of polyethylene powder, improving production continuity, and reducing safety risks.

[0068] 4. Compared with Example 1, the laboratory equipment conditions could not meet the conditions for industrial production, and thus produced products with small particle size and low bulk density.

[0069] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A reaction vessel for preparing an olefin polymerization catalyst, characterized in that, The reaction vessel includes a reaction vessel body and a stirrer; The reactor body is equipped with two or more sets of U-shaped cooling coils, which are evenly spaced and installed on the inner wall of the reactor body corresponding to the stirring paddle. The agitator includes a combined agitator blade disposed inside the reactor body; the combined agitator blade consists of a four-bladed turbine blade located in the lower layer and a three-bladed oblique blade located in the upper layer.

2. The reaction vessel according to claim 1, characterized in that, The reactor body is also equipped with a combined filter, which consists of a decanting pipe that can move up and down within the reactor body and a bottom filter.

3. The reaction vessel according to claim 1, characterized in that, The ratio of the radial diameter L of the three-bladed oblique propeller to the diameter D of the reactor is L / D = 0.1~0.4; The ratio of the diameter l of the four-bladed turbine propeller to the diameter D of the reactor is l / D = 0.15~0.4; The distance between the three-bladed oblique propeller and the four-bladed turbine propeller is 1.4 to 1.6 times the diameter of the four-bladed turbine propeller.

4. The reaction vessel according to claim 1, characterized in that, The stirrer also includes a drive unit for adjusting the stirring speed of the stirring paddle. By controlling the rotation speed to 150~300 rpm, a catalyst with the desired particle size can be obtained. The catalyst has an average particle size of less than 2.0 m.

5. The application of the olefin polymerization catalyst preparation reactor according to any one of claims 1-4 in the preparation of olefin polymers (e.g., ultra-high molecular weight polyethylene); The median particle size D of the olefin polymer (e.g., ultra-high molecular weight polyethylene) 50 The thickness is 30~100μm, preferably 30~80μm; The bulk density of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is ≤0.3 g / cm³. 3 For example, not less than 0.2g / cm 3 And less than 0.3g / cm 3 ; Preferably, the particle size distribution (i.e., D0) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... 90 -D 10 () / D50)≥0.9; Preferably, the viscosity-average molecular weight (M) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... η ×10 4 The value is 520~600; Preferably, the intrinsic viscosity η of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is at least 4 dl / g; Preferably, the residual Ti content of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is less than 10 ppm; Preferably, the total ash content of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is less than 500 ppm; Preferably, the olefin polymer (e.g., ultra-high molecular weight polyethylene) has a content of 220-300 g / cm³. 3 The apparent bulk density.

6. A method for preparing an olefin polymer (e.g., ultra-high molecular weight polyethylene), characterized in that, The preparation method includes the following steps: (1) A catalyst is prepared using a reaction vessel for preparing the olefin polymerization catalyst according to any one of claims 1 to 4; Preferably, the average particle size of the catalyst is less than 2.0 μm; (2) The catalyst system containing the catalyst in step (1) is subjected to polymerization reaction with an olefin monomer (e.g., ethylene) to prepare the olefin polymer (e.g., ultra-high molecular weight polyethylene). Preferably, the olefin polymer (e.g., ultra-high molecular weight polyethylene) has the definition shown in claim 5.

7. The preparation method according to claim 6, characterized in that, The catalyst system needs to be pre-dispersed in a solvent; Preferably, the pre-dispersion time is 1-3 hours; Preferably, the solvent used for pre-dispersion is hexane.

8. The preparation method according to claim 6, characterized in that, The polymerization reaction is to be carried out in the presence of an antistatic agent; preferably, the antistatic agent is selected from one, two or more of hydrogen, calcium stearate, magnesium stearate, lauryl alcohol polyoxyethylene ether, polyvinylpyrrolidone and Stadis 450.

9. The preparation method according to claim 6, characterized in that, The median particle size D of the olefin polymer (e.g., ultra-high molecular weight polyethylene) 50 The thickness is 30~100μm, preferably 30~80μm; The bulk density of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is ≤0.3 g / cm³. 3 For example, not less than 0.2g / cm 3 And less than 0.3g / cm 3 ; Preferably, the particle size distribution (i.e., D0) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... 90 -D 10 () / D50)≥0.9; Preferably, the viscosity-average molecular weight (M) of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is... η ×10 4 The value is 520~600; Preferably, the intrinsic viscosity η of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is at least 4 dl / g; Preferably, the residual Ti content of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is less than 10 ppm; Preferably, the total ash content of the olefin polymer (e.g., ultra-high molecular weight polyethylene) is less than 500 ppm; Preferably, the olefin polymer (e.g., ultra-high molecular weight polyethylene) has a content of 220-300 g / cm³. 3 The apparent bulk density.

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