Method for producing low-entanglement UHMWPE supported Ziegler-Natta catalyst and catalyst
By uniformly distributing MgCl2 and TiCl4 on a SiO2 support, an active center-separated microenvironment was constructed, which solved the entanglement problem of UHMWPE, realized the preparation and performance improvement of low-entanglement UHMWPE, simplified catalyst preparation, and reduced costs.
Patent Information
- Application Number
- CN202511687239.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-01-13
AI Technical Summary
Existing magnesium chloride-supported Ziegler-Natta catalysts have many entanglement points in UHMWPE production, which leads to processing difficulties and performance degradation. Traditional silica gel supports are difficult to meet the requirements of high-performance UHMWPE, and composite catalyst formulations are complex and costly, making them difficult to apply industrially.
Using a macroporous SiO2 support, a supported Ziegler-Natta catalyst was prepared. By utilizing the uniform distribution of MgCl2 and TiCl4 on the SiO2 surface, a microenvironment with separated active centers was constructed to avoid polyethylene chain entanglement, thus preparing low-entanglement UHMWPE.
This method enables the preparation of low-entanglement UHMWPE under industrial polymerization conditions, simplifies the catalyst preparation process, reduces costs, facilitates industrial applications, and improves the processing and mechanical properties of UHMWPE.
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Figure CN121319253A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of catalyst production, in particular to a method for producing a supported Ziegler-Natta catalyst for low entanglement UHMWPE and the catalyst. BACKGROUND
[0002] Ultra-high molecular weight polyethylene (UHMWPE) has unique physical and chemical properties due to its ultra-high molecular weight (>1.0×106 g.mol-1). Compared with conventional plastic products, it has extremely high strength, impact resistance, wear resistance, insulation, chemical corrosion resistance, and biocompatibility, etc. It belongs to high-performance special polyethylene materials. As a high-end polyethylene resin, it plays an important role in the fields of national defense and military industry, biological medicine, pipeline transportation and marine engineering. Since the 1950s, Ziegler-Natta catalysts, metallocene catalysts and post-transition metal catalysts have gradually evolved into three major types of catalytic systems in the olefin polymerization industry. Traditional magnesium chloride supported Ziegler-Natta catalysts (referred to as magnesium chloride supported Z-N catalysts) are widely used in the production of industrial UHMWPE due to their high activity, low cost and easy control. The active sites of magnesium chloride supported Z-N catalysts are randomly and closely distributed on the surface of the carrier. The polyethylene chains grown on the active sites are prone to near-neighbor entanglement, resulting in a large number of entanglement points in existing commercial UHMWPE particles. These entanglement points greatly limit the diffusion and movement behavior of polyethylene molecular chains, resulting in high melt viscosity of UHMWPE, making it difficult to process and form, and easily forming defects in the product, which greatly damages the product performance.
[0003] The key to improve the processing performance and mechanical properties of UHMWPE is to reduce the entanglement degree of polyethylene chain. The chain entanglement structure of polyethylene is closely related to its molecular chain structure (molecular weight, branch chain), aggregate structure (chain entanglement degree) and particle morphology (polyethylene particle size, morphology), and the design of catalyst plays a decisive role in the above polyethylene multi-level structure. In terms of regulating the molecular chain structure, the use of supported composite catalyst (with multiple different active sites) can obtain bimodal UHMWPE with uniform mixing of low molecular weight and ultrahigh molecular weight components. The different active centers on the composite catalyst are dispersed in the surface of the same carrier in close proximity, so that the low / ultrahigh molecular weight polyethylene active chains are mixed in nanoscale during the polymerization process. The compatibility of each component in the bimodal UHMWPE product obtained by this technology is good, which can improve the processing performance of UHMWPE and can be applied to traditional melt processing processes such as extrusion and injection molding. However, the introduction of low molecular weight polyethylene reduces the overall molecular weight of the product, weakening the mechanical properties of UHIMWPE itself. At the same time, the distance between the active centers on the composite catalyst is close, which is easy to interact, reducing the controllability of the polymerization process and effectively regulating the molecular weight and branch chain of the product. Microstructure parameters restrict the improvement of the mechanical properties of the product. In terms of regulating the aggregate structure, the use of silica gel supported catalyst can prepare low entanglement UHMWPE. This method fixes the barrier agent through the hydroxyl group on the surface of the carrier, and then separates the active centers on the surface of the carrier through the steric effect of the barrier agent, thereby hindering the entanglement of polyethylene chains. However, the particle size of the traditional silica carrier is large, which is difficult to meet the requirements of small particle size (<300 μm) of high-performance UHMWPE products. In addition, the barrier agent further reduces the loading capacity of the carrier and the activity of the catalyst. In terms of regulating the particle morphology, in order to obtain ultrafine UHMWPE particles (<80 μm) with significantly improved processing performance, nanoparticles are used as carriers or high-speed stirring is used in the carrier forming process to obtain extremely fine carriers, and then extremely fine catalysts (<10 μm) are prepared for the synthesis of ultrafine UHMWPE. However, these catalyst preparation methods have problems such as complex catalyst formula, high technical requirements and high production cost, which are not conducive to industrial application. Therefore, a method for producing a supported Ziegler-Natta catalyst for low entanglement UHMWPE is needed. SUMMARY
[0004] In view of the above technical problems, the technical scheme adopted by the present application is as follows: a method for producing a supported Ziegler-Natta catalyst for low entanglement UHMWPE, comprising the following steps:
[0005] S1. Preparing a carrier macroporous SiO2;
[0006] S11. The epoxy resin E50 and polyethylene glycol PEG1000, PEG2000 were heated to melt and stirred to form a solution, diethylene triamine was added dropwise, and the solution was kept at 70 °C for 3 h. The obtained solid was washed, and the washed solid was transferred to an oven for drying to obtain a white three-dimensional framework polymer;
[0007] S12. The white three-dimensional framework polymer was mixed with TEOS and kept for 3 h. Ammonia water was added to the sample, and the sample was hydrothermally treated for 12 h. The sample was dried in an oven for 2 h, and then the sample was calcined in a muffle furnace for 30 min to obtain a macroporous SiO2;
[0008] S2. Preparation of a supported catalyst;
[0009] S21. Macroporous SiO2 and BDO were added to a No. 1 reaction flask, and THF was added. The mixture was stirred at 40 °C for 1 h. Anhydrous MgCl2 and ultra-dry THF were added to a No. 2 reaction flask, and the solution was stirred at 60 °C until dissolved. The solution in the No. 2 reaction flask was poured into the No. 1 reaction flask, and a large amount of white solid was precipitated. The mixture was continuously stirred at 40 °C for 2 h. The solid was washed with n-hexane for several times to remove excess THF, and vacuum drying was performed to obtain a macroporous SiO2 / MgCl2 composite;
[0010] S22. The macroporous SiO2 / MgCl2 composite, n-hexane, and TEA were added to a reaction flask, and the slurry was stirred at 60 °C for 2 h. The solid was washed with n-hexane for several times. N-hexane and TiCl4 were added, and the mixture was stirred at 60 °C for 2 h. The solid was washed with n-hexane for several times to remove excess TiCl4, and a macroporous SiO2 / MgCl2 / TiCl4 supported catalyst was obtained;
[0011] S3. Ethylene polymerization;
[0012] S31. N-hexane was added to a reactor, and TEA was added as a cocatalyst at an Al / Ti ratio of 200. The mixture was stirred in a stainless steel autoclave reactor to remove impurities;
[0013] S32. The catalyst was injected into the reactor. The polymerization reaction was first carried out under a continuous ethylene gas stream at a stirring rate of 800 r / min, and the reaction was continued for 30 min. The stainless steel autoclave reactor was raised to 65 °C, and the ethylene pressure was adjusted to 0.40 Mpa. The reaction was continued for 2 h;
[0014] S33. At the end of the polymerization, the gas in the reactor was quickly vented, and the reaction product was collected. The product was dried at 60 °C for 12 h;
[0015] S4. Characterization test;
[0016] Nitrogen adsorption-desorption experiments were performed using a physical adsorption instrument; the specific surface area of the macroporous SiO2 was calculated by the Brunauer-Emmett-Teller (BET) method, and the average pore size was calculated by the Barrett-Joyner-Halenda (BJH) method;
[0017] X-ray diffraction (XRD) tests were performed on the macroporous SiO2 powder using a Bruker GADDS diffractometer;
[0018] The contents of magnesium and titanium elements in the macroporous SiO2 / MgCl2 / TiCl4 supported catalyst were determined by an inductively coupled plasma emission spectrometer;
[0019] The morphology of the catalyst was observed using a scanning electron microscope;
[0020] DSC annealing experiments were performed using a differential scanning calorimeter to characterize the chain entanglement degree of the nascent UHMWPE.
[0021] Further, the S11 comprises the following steps: 4.0 g of epoxy resin E50 and 6.5 g of polyethylene glycol PEG1000, 1.5 g of polyethylene glycol PEG2000 are heated to melting at 120°C and stirred to form a solution, 1.25 g of diethylene triamine is added dropwise to produce a yellow solid, 70°C oil bath for 3h, the generated yellow solid is washed with 80°C hot water, the washed solid is transferred to a 60°C oven for drying for 12h to obtain a white three-dimensional skeleton polymer.
[0022] Further, the S12 comprises the following steps: the obtained white three-dimensional skeleton polymer is mixed with 5.0 g of TEOS for 3h, then 10 mL of ammonia is added to the sample, and the sample is hydrothermally treated at 50°C for 12h, then the sample is placed in a 60°C oven for drying for 2h, finally, the sample is placed in a muffle furnace for calcination at 800°C for 30min to obtain macroporous SiO2; the macroporous SiO2 is ground and activated at 600°C under an argon atmosphere for 6h, and then transferred to a glove box for storage for standby use.
[0023] Further, the S21 comprises the following steps: adding macroporous SiO2 into a No. 1 reaction flask, adding BDO at a ratio of 0.5 mL BDO / g SiO2, adding 10 mL THF, stirring at 40°C for 1 h, adding anhydrous MgCl2 and 30 mL super-dry THF into a No. 2 reaction flask, stirring at 60°C until the anhydrous MgCl2 is dissolved, pouring the solution in the No. 2 reaction flask into the No. 1 reaction flask, recrystallizing the MgCl2 on the surface of the macroporous SiO2 due to the strong coordination between MgCl2 and BDO, precipitating a large amount of white solid, continuing to stir at 40°C for 2 h, then washing the solid with 30 mL n-hexane three times to remove the excess THF, and vacuum drying to obtain a macroporous SiO2 / MgCl2 composite.
[0024] Further, the S22 comprises the following steps: adding 1 g MgCl2 / SiO2 composite, 30 mL n-hexane and 5 mL EA into a reaction flask, stirring the slurry at 60°C for 2 h to remove the excess BDO in the macroporous SiO2 / MgCl2 composite, then washing the solid with 30 mL n-hexane three times, finally adding 30 mL n-hexane and 0.1 mL TiCl4, stirring at 60°C for 2 h, and finally washing the solid with 30 mL n-hexane three times to remove the excess TiCl4, thereby obtaining a macroporous SiO2 / MgCl2 / TiCl4 supported catalyst.
[0025] Further, the ethylene polymerization reaction is carried out in a 1.0 L stainless steel autoclave reactor equipped with a mechanical stirrer and a temperature control device.
[0026] Further, the S31 comprises the following steps: before polymerization, heating the reactor to 100°C under vacuum for more than 24 h, then repeatedly purging with nitrogen, then reducing the temperature of the reactor to room temperature, adding 350 mL n-hexane into the reactor, adding TEA as a cocatalyst at an Al / Ti ratio of 200, stirring in the stainless steel autoclave reactor for 10 min to remove possible impurities, and then injecting 20±5 mg of the catalyst into the reactor.
[0027] Further, the S32 comprises the following steps: the polymerization reaction is first carried out under a continuous ethylene gas flow at 0.10 MPa, the stirring rate is 800 r / min, the reaction lasts for 30 min, then the stainless steel autoclave reactor is raised to 65°C, the ethylene pressure is adjusted to 0.40 MPa, and the reaction lasts for 2 h.
[0028] Further, the S33 comprises the following steps: at the end of the polymerization, the gas in the autoclave is quickly vented, the reaction product is collected, and then dried at 60°C for 12 h.
[0029] The catalyst prepared by any of the above methods, the loading of Ti element on the catalyst corresponding to the macroporous SiO2 carrier is 2wt%-9wt%, the loading of Mg element is 2wt%-9wt%, the specific surface area of the macroporous SiO2 carrier is 20-200m 2 / g, the average pore size is 5-100nm, and the average pore volume is 0.05-0.5cm 3 / g.
[0030] The beneficial effects of the present application compared with the prior art are: (1) the present application discloses a macroporous SiO2 carrier, which has a very high specific surface area, and under a high MgCl2 loading, the uniform distribution of MgCl2 on the SiO2 carrier can still be achieved, the high-distributed MgCl2 fixes the Ti active sites through Mg-Cl-Ti chemical bonds, and the dispersion of Ti is improved through the uniform distribution of MgCl2 to reduce the adjacent entanglement phenomenon, and the preparation of low-entanglement UHMWPE under industrial polymerization conditions is realized; (2) in order to avoid the adjacent entanglement of polyethylene chains, the present application does not use MgCl2 with extremely small particle size as the carrier, but uniformly loads MgCl2 on the macroporous high-specific-surface-area SiO2, the lattice defect surface of the catalytic active site Ti is combined with MgCl2, and a microenvironment of active center separation is constructed, and a low-entanglement UHMWPE product is synthesized, solving the challenge faced by the Z-N catalyst system in regulating the formation of chain entanglement; (3) the catalyst preparation method of the present application is simple, the catalyst formula is simple, the preparation technical requirements are low, and the production cost is low, which is conducive to industrial application. BRIEF DESCRIPTION OF DRAWINGS
[0031] Figure 1 is the nitrogen adsorption-desorption curve of the macroporous SiO2 of the present application;
[0032] Figure 2 is the pore size distribution graph of the macroporous SiO2 of the present application;
[0033] Figure 3 is the XRD test graph of the catalyst and the macroporous SiO2 carrier of the present application;
[0034] Figure 4 is the SEM test graph of the catalyst of the present application;
[0035] Figure 5 is the comparison graph of the self-made sample and three groups of commercial samples in the second heating curve. DETAILED DESCRIPTION
[0036] The technical solutions of the present application will be further described below by means of specific embodiments.
[0037] Example 1
[0038] A method for producing a supported Ziegler Natta catalyst for low entangled UHMWPE, comprising the following steps:
[0039] S1. Preparation of carrier macroporous SiO2;
[0040] S11. 4.0 g of epoxy resin E50 and 6.5 g of polyethylene glycol PEG1000, 1.5 g of PEG2000 were heated to melt at 120°C and stirred to form a solution, then 1.25 g of diethylenetriamine was added dropwise, a yellow solid was generated after the addition of diethylenetriamine, and the yellow solid was washed with 80°C hot water after being oil-soluble at 70°C for 3 h, and then the washed solid was transferred to a 60°C oven for drying for 12 h to obtain a white three-dimensional skeleton polymer.
[0041] S12. The obtained white three-dimensional skeleton polymer was mixed with 5.0 g of TEOS for 3 h, then 10 mL of ammonia was added to the sample, and the sample was hydrothermally treated at 50°C for 12 h, then the sample was placed in a 60°C oven for drying for 2 h; finally, the sample was placed in a muffle furnace at 800°C for calcination for 30 min to obtain macroporous SiO2; After grinding, the macroporous SiO2 was activated at 600°C under argon atmosphere for 6 h, and then transferred to a glove box for storage.
[0042] S2. Preparation of supported catalyst;
[0043] S21. 0.5 g of macroporous SiO2 was added to a No. 1 reaction bottle, BDO was added at a ratio of 0.5 mL BDO / g SiO2, and 10 mL of THF was added, and the mixture was stirred at 40°C for 1 h, while 1.5 g of anhydrous MgCl2 and 30 mL of super-dry THF were added to a No. 2 reaction bottle (the mass ratio of SiO2 to MgCl2 was 1:3, and the ratio of SiO2 to BDO was 1 g SiO2 / 0.5 mL BDO, and the amount of THF as a solvent was proportionally increased), and the mixture was stirred at 60°C until dissolved; the solution in the No. 2 reaction bottle was poured into the No. 1 reaction bottle, and due to the strong coordination between MgCl2 and BDO, MgCl2 could mainly recrystallize on the surface of macroporous SiO2, and a large amount of white solid was precipitated, and the mixture was continuously stirred at 40°C for 2 h, then the solid was washed with 30 mL of n-hexane three times to remove excess THF, and the macroporous SiO2 / MgCl2 composite was obtained by vacuum drying.
[0044] S22. Subsequently, 1 g of MgCl2 / SiO2 composite, 30 mL of n-hexane and 5 mL of TEA were added into the reaction bottle, and the slurry was stirred at 60°C for 2 h to remove the excess BDO in the macroporous SiO2 / MgCl2 composite, then the solid was washed three times with 30 mL of n-hexane each time, finally 30 mL of n-hexane and 0.1 mL of TiCl4 were added, and the mixture was stirred at 60°C for 2 h, and finally the solid was washed three times with 30 mL of n-hexane each time to remove the excess TiCl4, thereby obtaining the macroporous SiO2 / MgCl2 / TiCl4 supported catalyst.
[0045] S3. Ethylene polymerization: The ethylene polymerization reaction was carried out in a 1.0 L stainless steel autoclave reactor equipped with a mechanical stirrer and a temperature control device.
[0046] S31. Before polymerization, the reactor was heated to 100°C under vacuum for 24 h or more, then repeatedly purged with nitrogen, after which the temperature of the reactor was reduced to room temperature, 350 mL of n-hexane was added into the reactor, and TEA was added as a cocatalyst at an Al / Ti ratio of 200, then the stainless steel autoclave reactor was stirred for 10 min to remove possible impurities, and then 20±5 mg of the catalyst was injected into the reactor.
[0047] S32. The polymerization reaction was first carried out under a continuous ethylene gas flow of 0.10 MPa at a stirring rate of 800 r / min for 30 min, then the stainless steel autoclave reactor was raised to 65°C, and the ethylene pressure was adjusted to 0.40 MPa, and the reaction was continued for 2 h.
[0048] S33. At the end of the polymerization, the autoclave was quickly vented, the reaction product was collected, and the product was dried at 60°C for 12 h.
[0049] S4. Characterization test;
[0050] Nitrogen adsorption-desorption experiments were carried out at 77 K using a Micromeritics ASAP 2020 physical adsorption instrument, the specific surface area of the macroporous SiO2 was calculated by the Brunauer-Emmett-Teller (BET) method, the average pore size was calculated by the Barrett-Joyner-Halenda (BJH) method, and the material was subjected to a degassing treatment before the nitrogen adsorption-desorption experiment, the degassing temperature was 400°C, and the degassing time was 6 h.
[0051] As Figure 1As shown in the figure, the N2 adsorption isotherm and pore size distribution of macroporous SiO2, the adsorption isotherm of macroporous SiO2 shows gradual adsorption kinetics, and there is no adsorption saturation, which reflects the type IV isotherm; in addition, macroporous SiO2 shows a rapid adsorption and desorption rate at relatively low pressure, indicating that the resistance to N2 transmission inside the macroporous SiO2 particles is small.
[0052] As shown in the figure, the pore volume and pore size of macroporous SiO2 are shown, and the BET results of macroporous SiO2 are shown in Table 1. Macroporous SiO2 has a large pore size and pore volume, which is beneficial to the uniform distribution of catalytically active sites. Figure 2
[0053] Table 1 BET results of macroporous SiO2
[0054] The macroporous SiO2 powder was tested by X-ray diffraction (XRD) using a Bruker GADDS diffractometer, using CuKβ radiation, scanning range 5-90°, step size 0.02°.
[0055] As shown in the figure, the pore volume and pore size of macroporous SiO2 are shown, and the BET results of macroporous SiO2 are shown in Table 1. Macroporous SiO2 has a large pore size and pore volume, which is beneficial to the uniform distribution of catalytically active sites. Figure 3 As shown in the figure, the macroporous SiO2 support has a hump peak near 22° (corresponding to the crystal form of SiO2), which proves that the macroporous SiO2 synthesized is a typical SiO2 structure. After loading TiCl4, peaks appear near 12°, 29-32° and 50.5° (corresponding to the resonance of δ-MgCl2 crystal form), indicating that the MgCl2 loaded has good activation effect, α-MgCl2 is converted to δ-MgCl2 crystal form, and the intensity near 29-32° (104) and 50.5° (110) is high, indicating that there are a large number of defect surfaces in the MgCl2 crystal, which is beneficial to the immobilization of Ti, forming a TiClx-MgCl2 combination, and the intensity of the characteristic peak of SiO2 is weakened, indicating that δ-MgCl2 covers SiO2 well.
[0056] The content of magnesium and titanium elements in macroporous SiO2 / MgCl2 / TiCl4 supported catalyst was determined by inductively coupled plasma emission spectrometer (ICP, Varian 730-ES, USA); before analysis, the sample was dispersed in 5 mL nitric acid (12 wt%) and dissolved at 100°C for 12 h; the mass fraction of magnesium and titanium elements in macroporous SiO2 / MgCl2 / TiCl4 supported catalyst was 6.726% and 6.769%, respectively.
[0057] The morphology of the catalyst was observed using a scanning electron microscope (SEM, Hitachi S-4700, Japan), and the sample was treated with platinum sputtering before testing. The elemental content and surface elemental distribution of the catalyst were determined by X-ray energy dispersive spectrometer (EDX).
[0058] As Figure 4 shown in the SEM images, the morphology of the catalysts is shown, from which it can be seen that MgCl2 achieves effective coverage on the surface of the macroporous SiO2, and achieves uniform distribution of the metal active sites on the surface of the catalyst with a certain interval, thus proving that the catalyst can keep the polyethylene chains growing on the metal active sites at a certain interval during polymerization, and can produce low entangled UHMWPE.
[0059] DSC annealing experiment was performed by using a differential scanning calorimeter (DSC8000, Perkin, USA) to characterize the chain entanglement degree of the nascent UHMWPE, and the temperature variation program was divided into five stages: ① heating from 30℃ to 130℃ at a rate of 10℃ / min; ② heating from 130℃ to 138℃ at a rate of 1.0℃ / min; ③ annealing at 138℃ for 3h; ④ cooling from 138℃ to 30℃ at a rate of 10℃ / min and keeping for 1min; ⑤ heating from 30℃ to 160℃ at a rate of 10℃ / min, which is divided into low-temperature annealing, cooling crystallization and secondary heating processes in turn, and the nitrogen flow rate is 50mL / min. The higher the proportion of the low-temperature peak area in the secondary heating process, the lower the entanglement degree of the UHMWPE.
[0060] As Figure 5 shown in Table 2, compared with the three groups of commercial samples, the self-made sample of the application has the largest low-temperature peak area and the smallest high-temperature peak area in the secondary heating curve, indicating that the UHMWPE sample of the application has a lower entanglement degree. By using the normalization algorithm, it is found that the entanglement degree of the UHMWPE sample of the application is significantly lower than that of the commercial UHMWPE sample, which proves that the supported catalyst successfully prepares low-entangled UHMWPE.
[0061] Table 2 Comparison results of self-made sample and three groups of commercial samples
[0062] Sampel Low-temperature peak area (Wg-1) High-temperature peak area (Wg-1) Normalized Value Commercialsample 1 2.55 545.79 0.00465 Commercialsample 2 57.45 378.48 0.1528 Commercialsample 3 78.03 235.98 0.2485 Our Work 472.55 5.48 0.9985
[0063] The molecular weight of the UHMWPE product was tested: the viscosity average molecular weight Mv was 1.58×106g / mol.
[0064] A catalyst prepared by the above method, the proportion of Ti elements supported on the macroporous SiO2 carrier on the catalyst is 2wt%-9wt%, the proportion of Mg elements is 2wt%-9wt%, the specific surface area of the macroporous SiO2 carrier is 20-200m 2 / g, the average pore size is 5-100nm, and the average pore volume is 0.05-0.5cm 3 / g.
Claims
1. A method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE, characterized in that, Includes the following steps: S1. Preparation of macroporous SiO2 support; S11. Epoxy resin E50 and polyethylene glycol PEG1000 and PEG2000 are heated and stirred to form a solution. Diethylenetriamine is added dropwise to produce a yellow solid. The yellow solid is washed and dried to obtain a white three-dimensional skeleton polymer. S12. Mix the white three-dimensional framework polymer with TEOS, add ammonia to the sample, perform hydrothermal treatment, dry the sample, and then calcine the sample to obtain macroporous SiO2. S2. Preparation of supported catalysts; S21. Add macroporous SiO2 and BDO to reaction flask 1, then add THF and stir. At the same time, add anhydrous MgCl2 and ultra-dry THF to reaction flask 2 and stir until dissolved. Pour all the solution in reaction flask 2 into reaction flask 1. At this time, a large amount of white solid precipitates out. Continue stirring and wash the solid with n-hexane several times to remove excess THF. Vacuum dry to obtain macroporous SiO2 / MgCl2 complex. S22. Add the MgCl2 / SiO2 complex, n-hexane, and TEA to a reaction flask and stir. Wash the solid with n-hexane several times. Add n-hexane and TiCl4 and continue stirring. Wash the solid with n-hexane several times to remove excess TiCl4 and obtain a macroporous SiO2 / MgCl2 / TiCl4 supported catalyst. S3. Ethylene polymerization; S31. Add n-hexane to the reactor, add TEA as a co-catalyst, stir in the reactor to remove impurities, and then inject the catalyst into the reactor; S32. The polymerization reaction is first carried out under a continuous ethylene gas flow, and then the reactor temperature is increased and the ethylene pressure is adjusted to carry out a continuous reaction; S33. When the polymerization is complete, quickly vent the gas in the reactor, collect the reaction products, and then dry them.
2. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 1, characterized in that, S11 includes the following steps: 4.0g of epoxy resin E50, 6.5g of polyethylene glycol PEG1000, and 1.5g of polyethylene glycol PEG2000 are heated to melt at 120°C and stirred to form a solution. 1.25g of diethylenetriamine is added dropwise to produce a yellow solid. The solution is then heated in an oil bath at 70°C for 3 hours. The resulting yellow solid is washed with hot water at 80°C. The washed solid is then transferred to an oven at 60°C and dried for 12 hours to obtain a white three-dimensional skeleton polymer.
3. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 2, characterized in that, S12 includes the following steps: the obtained white three-dimensional skeleton polymer is mixed with 5.0g TEOS and kept for 3h, then 10mL ammonia water is added to the sample and hydrothermally heated at 50℃ for 12h, then the sample is placed in a 60℃ oven to dry for 2h, and finally, the sample is placed in a muffle furnace and calcined at 800℃ for 30min to obtain macroporous SiO2; after grinding, the macroporous SiO2 is activated at 600℃ in an argon atmosphere for 6h, and then transferred to a glove box for storage.
4. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 1, characterized in that, S21 includes the following steps: Macroporous SiO2 is added to reaction flask No. 1, BDO is added at a ratio of 0.5 mL BDO / gSiO2, and then 10 mL THF is added. The mixture is magnetically stirred at 40 °C for 1 h. At the same time, anhydrous MgCl2 and 30 mL ultra-dry THF are added to reaction flask No.
2. The mixture is stirred at 60 °C until dissolved. The mass ratio of macroporous SiO2 to anhydrous MgCl2 is 1:
3. The solution in reaction flask No. 2 is poured into reaction flask No.
1. Due to the strong coordination between MgCl2 and BDO, MgCl2 can recrystallize mainly on the surface of macroporous SiO2. At this time, a large amount of white solid precipitates. The mixture is magnetically stirred at 40 °C for 2 h. Then, the solid is washed three times with 30 mL n-hexane each time to remove excess THF. The solid is then vacuum dried to obtain the macroporous SiO2 / MgCl2 complex.
5. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 4, characterized in that, The S22 process includes the following steps: 1g of MgCl2 / SiO2 complex, 30mL of n-hexane, and 5m of LTA are added to a reaction flask. The slurry is stirred at 60°C for 2 hours to remove excess BDO from the macroporous SiO2 / MgCl2 complex. The solid is then washed three times with 30mL of n-hexane each time. Finally, 30mL of n-hexane and 0.1mL of TiCl4 are added, and the mixture is stirred at 60°C for 2 hours. The solid is then washed three times with 30mL of n-hexane each time to remove excess TiCl4, thus obtaining a macroporous SiO2 / MgCl2 / TiCl4 supported catalyst.
6. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 1, characterized in that, The ethylene polymerization reaction of S3 is carried out in a 1.0L stainless steel autoclave reactor equipped with a mechanical stirrer and temperature control equipment.
7. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 6, characterized in that, The S31 includes the following steps: Before polymerization, the reactor is heated to 100°C under vacuum and maintained for more than 24 hours. Then, nitrogen gas is repeatedly purged. After that, the reactor temperature is reduced to room temperature, and 350 mL of n-hexane is added to the reactor. TEA is added as a co-catalyst with Al / Ti=200. The reactor is stirred in a stainless steel autoclave reactor for 10 minutes to remove any possible impurities. 20 ± 5 mg of catalyst is then injected into the reactor.
8. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 7, characterized in that, The S32 includes the following steps: the polymerization reaction is first carried out under a continuous ethylene gas flow of 0.10 MPa, with a stirring rate of 800 r / min, and the reaction lasts for 30 min. Then, the stainless steel autoclave reactor is raised to 65°C and the ethylene pressure is adjusted to 0.40 MPa, and the reaction lasts for 2 h.
9. The method for producing a supported Ziegler-Natta catalyst with low entanglement UHMWPE as described in claim 8, characterized in that, The S33 includes the following steps: when the polymerization is completed, the gas in the high-pressure reactor is quickly vented, the reaction product is collected, and then dried at 60°C for 12 hours.
10. A catalyst prepared by any one of claims 1-9, characterized in that, The catalyst is supported on a macroporous SiO2 support with a Ti element content of 2wt%-9wt% and a Mg element content of 2wt%-9wt%, and the specific surface area of the macroporous SiO2 support is 20-200 m². 2 / g, with an average pore size of 5-100nm and an average pore volume of 0.05-0.5cm³. 3 / g.