Ultrahigh molecular weight polyethylene as well as preparation method and application thereof

Abstract

The invention relates to the field of high polymer materials, in particular to ultra-high molecular weight polyethylene as well as a preparation method and application thereof. The ultra-high molecular weight polyethylene has a sphere-like morphology, the bulk density is 0.45-0.52 g / cm < 3 >, and the average particle size is 110-150 [mu] m. The ultrahigh molecular weight polyethylene has the characteristics of regular morphology, large molecular weight, narrow distribution and uniform particle size distribution, and is stable and excellent in quality.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly relates to a ultra-high molecular weight polyethylene and its preparation method and application. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) generally refers to polyethylene materials with a viscosity-average molecular weight above 1 million, which have excellent properties such as high strength, impact resistance, abrasion resistance, self-lubrication, chemical corrosion resistance, and low-temperature resistance. The main products include fibers, films, pipes, plates, rods, porous materials, and profiled materials, etc., and are widely used in fields such as aerospace, national defense, rail transit, petrochemical industry, and new energy materials. The relative molecular weight of UHMWPE is much larger than that of general polymers, and the molecular chains are severely entangled with each other, resulting in an extremely high melt viscosity of UHMWPE and very difficult flow. At low shear rates, melt fracture phenomenon will occur, resulting in poor surface properties of the product and difficult processing. The particle size distribution of the UHMWPE powder used for HMWPE plates and pipes is in the range of 90 - 150 μm. With the continuous development of technology, UHMWPE with a narrow particle size distribution and a narrow molecular weight distribution is favored by the market. With the continuous expansion of the application of UHMWPE in markets such as inks and filter membranes, the market demand for UHMWPE ultrafine powder with a particle size of 10 - 30 μm and a narrow molecular weight distribution is gradually increasing. At present, the production of UHMWPE in China mainly uses Z-N catalysts. As the earliest multi-active center catalyst for producing UHMWPE, the particle size of its polymer particles is generally in the range of 100 - 300 μm, which can meet the use of most products. The apparent morphology, particle size distribution, and bulk density of ultra-high molecular weight polyethylene have a great influence on the production process and product storage. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art that the molecular weight of ultra-high molecular weight polyethylene is small and the distribution is wide, and the particle size distribution is uneven, and to provide a ultra-high molecular weight polyethylene and its preparation method and application. This ultra-high molecular weight polyethylene has a complete apparent morphology, a uniform particle size distribution, and a relatively high bulk density.

[0004] To achieve the above purpose, in the first aspect of the present invention, a ultra-high molecular weight polyethylene is provided. This ultra-high molecular weight polyethylene has a spherical-like morphology, a bulk density of 0.45 - 0.52 g / cm 3 , and an average particle size of 110 - 150 μm.

[0005] In the second aspect of the present invention, a preparation method of ultra-high molecular weight polyethylene is provided. This preparation method includes: under solvent conditions, contacting ethylene with a catalyst to carry out a polymerization reaction, and then cooling the temperature step by step, and the reaction product enters solid-liquid separation and drying; the step-by-step cooling includes: for every 1 - 3 °C decrease in temperature, stabilizing for 0.5 - 2 h, and the number of temperature decreases is at least two.

[0006] The third aspect of the present invention provides the application of the ultra-high molecular weight polyethylene described in the first aspect of the present invention and the ultra-high molecular weight polyethylene prepared by the preparation method described in the second aspect in the field of lithium battery separators.

[0007] Through the above technical solutions, the present invention has the following advantages:

[0008] The ultra-high molecular weight polyethylene of the present invention has the characteristics of regular morphology, large molecular weight, narrow distribution, and uniform particle size distribution, and is stable and excellent in quality.

[0009] The method of the present invention can stably produce ultra-high molecular weight polyethylene products with stable and excellent quality in a long cycle through the programmed temperature reduction treatment after the polymerization reaction. Description of the Drawings

[0010] Figure 1 is the SEM image of ultra-high molecular weight polyethylene;

[0011] Figure 2 is the particle size distribution diagram of ultra-high molecular weight polyethylene. Detailed Embodiments

[0012] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0013] The present invention provides an ultra-high molecular weight polyethylene, which has a spherical-like morphology, a bulk density of 0.45 - 0.52 g / cm 3 , and an average particle size of 110 - 150 μm.

[0014] The ultra-high molecular weight polyethylene of the present invention has the characteristics of regular morphology, large molecular weight, narrow distribution, and uniform particle size distribution, and is stable and excellent in quality.

[0015] According to a preferred embodiment of the present invention, the bulk density of the ultra-high molecular weight polyethylene is 0.45 - 0.50 g / cm 3 .

[0016] According to a preferred embodiment of the present invention, the average particle size of the ultra-high molecular weight polyethylene is 140 - 150 μm.

[0017] According to a preferred embodiment of the present invention, the viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 30 - 3 million g / mol.

[0018] The present invention provides a method for preparing ultra-high molecular weight polyethylene, which includes: under solvent conditions, bringing ethylene into contact with a catalyst to carry out a polymerization reaction, cooling the temperature stepwise, and subjecting the reaction product to solid-liquid separation and drying; the stepwise temperature reduction includes: for every 1-3 °C reduction in temperature, stabilizing for 0.5-2 h, and the number of temperature reduction times is at least two times.

[0019] Through the stepwise temperature reduction treatment after the polymerization reaction, the method of the present invention can stably produce ultra-high molecular weight polyethylene products with stable and excellent quality for a long period.

[0020] According to a preferred embodiment of the present invention, the catalyst includes a magnesium chloride carrier, elemental titanium and elemental aluminum supported on the carrier, and the molar ratio of elemental aluminum to elemental titanium in the catalyst is 2-8:1, preferably 5-6:1. By adopting the foregoing preferred scheme, the catalyst can release its activity to the greatest extent in the reactor, and further produce the ultra-high molecular weight polyethylene with stable quality of the present invention, without causing problems such as reactor caking or explosion polymerization due to violent reaction.

[0021] In the present invention, there is no special requirement for the contents of elemental titanium and elemental aluminum in the catalyst, as long as the object of the present invention can be achieved.

[0022] In the present invention, elemental titanium in the catalyst is provided by titanium halide, such as titanium tetrachloride, and elemental aluminum is provided by alkyl aluminum, such as triethyl aluminum.

[0023] In the present invention, in order to further improve the quality of ultra-high molecular weight polyethylene, according to a preferred embodiment of the present invention, the particle size range of the ground catalyst carrier magnesium chloride is reduced to 3-5 μm, uniformly dispersed and the loading amount of active centers is reduced, and the activity of the catalyst is controlled to be 10000-15000 gPE / gCat under the conditions of reacting at 80 °C and 0.5 MPa for 2 h.

[0024] According to a preferred embodiment of the present invention, the conditions of the polymerization reaction include: the reaction temperature is 30-100 °C, preferably 50-80 °C. By adopting the foregoing preferred scheme, the ultra-high molecular weight polyethylene with stable quality of the present invention can be further produced, without causing problems such as reactor caking or explosion polymerization due to violent reaction.

[0025] According to a preferred embodiment of the present invention, the conditions of the polymerization reaction include: the reaction pressure is 0.25-1.0 MPa. By adopting the foregoing preferred scheme, the ultra-high molecular weight polyethylene with stable quality of the present invention can be further produced, without causing problems such as reactor caking or explosion polymerization due to violent reaction.

[0026] According to a preferred embodiment of the present invention, the conditions for the polymerization reaction include: the reaction time is 3-5 hours. By adopting the foregoing preferred scheme, sufficient conditions can be provided for the action of the catalyst, promoting the growth of the polymer molecular weight, and further producing the ultra-high molecular weight polyethylene with stable quality of the present invention.

[0027] According to a preferred embodiment of the present invention, the number of temperature decreases during the programmed temperature decrease is 2-4 times. By adopting the foregoing preferred scheme, the quality of the ultra-high molecular weight polyethylene product can be further improved.

[0028] According to a preferred embodiment of the present invention, the polymerization reaction includes first performing a first polymerization reaction and then performing a second polymerization reaction. By adopting the foregoing preferred scheme, the quality of the ultra-high molecular weight polyethylene can be further improved.

[0029] In the present invention, as long as the object of the present invention can be achieved, the solvent can be a conventional choice in the art. According to a preferred embodiment of the present invention, the solvent is an organic solvent.

[0030] According to a preferred embodiment of the present invention, the solvent is at least one of n-hexane, cyclohexane, and heptane.

[0031] In the present invention, the methods of solid-liquid separation and drying can be conventional technical choices in the art. For example, the solid-liquid separation can be filtration, suction filtration, etc.; the drying can be vacuum drying, the drying temperature is 90-110 °C; the drying time is 1-3 h.

[0032] The present invention provides an application of the ultra-high molecular weight polyethylene as described above in the field of lithium battery diaphragms.

[0033] The present invention will be described in detail below through examples.

[0034] In the following examples:

[0035] The polymer particle size distribution was measured with reference to GB / T 19077-2016;

[0036] The polymer bulk density was measured with reference to GB / T 1636-2008;

[0037] The average particle size of the polymer particles was measured with reference to GB / T 19077-2016;

[0038] The molecular weight was measured with a viscosity-average molecular weight measuring instrument;

[0039] The apparent morphology was measured with an electron microscope;

[0040] The catalyst activity was measured under the conditions of reacting at 80 °C and 0.5 MPa for 2 h.

[0041] Unless otherwise specified, the raw materials are all commercially available products.

[0042] Example 1

[0043] Preparation of ultra-high molecular weight polyethylene: A 1 L autoclave was purged three times with nitrogen and ethylene. Under vacuum conditions, 500 mL of n-hexane was added to the autoclave, and then a catalyst with a particle size range of 3 - 5 μm and an activity of 12000 gPE / gCat (magnesium chloride support, elemental titanium and elemental aluminum supported on the support, and the molar ratio of elemental aluminum to elemental titanium in the catalyst was 6:1) was added. The pipeline was rinsed with a small amount of hexane, stirred, heated to 50 °C, and ethylene was introduced for polymerization for 2 h. Then the reaction kettle was heated to 80 °C and the reaction continued for 2 h. During the reaction process, the polymerization pressure was controlled to be maintained at 0.3 MPa. Then the temperature was gradually lowered from 80 °C to 74 °C, and it was stabilized for 1 hour every time the temperature was lowered by 2 °C. After the temperature reduction was completed, filtration was carried out, and drying was carried out under vacuum at 100 °C to constant weight to obtain an ultra-high molecular weight polyethylene product. The product had a spherical-like morphology by electron microscopy test, and the SEM image was as Figure 1 shown; the degree of polymerization was 1.5 million g / mol. Other test results are shown in Table 1, and the particle size distribution diagram was as Figure 2 shown.

[0044] Example 2

[0045] Same as Example 1, except that: the temperature was gradually lowered from 80 °C to 74 °C and stabilized for 2 h. After completion, filtration was carried out, and drying was carried out under vacuum to constant weight to obtain an ultra-high molecular weight polyethylene product. The product had a spherical-like morphology by electron microscopy test, and the degree of polymerization was 1 million g / mol. Other test results are shown in Table 1. The particle size distribution diagram was similar to Figure 2 that.

[0046] Example 3

[0047] Same as Example 1, except that: the molar ratio of elemental aluminum to elemental titanium in the catalyst was 5:1; the polymerization pressure was controlled to be maintained at 0.8 MPa during the reaction process.

[0048] After the temperature reduction was completed, filtration was carried out, and drying was carried out under vacuum to constant weight to obtain an ultra-high molecular weight polyethylene product. The product had a spherical-like morphology by electron microscopy test, and the degree of polymerization was 1.4 million g / mol. Other test results are shown in Table 1. The particle size distribution diagram was similar to Figure 2 that.

[0049] Example 4

[0050] Same as Example 1, except that: it was first heated to 30 °C and ethylene was introduced for polymerization for 2 h, and then the reaction kettle was heated to 100 °C and the reaction continued for 2 h.

[0051] After the temperature reduction is completed, filtration is carried out, and drying is performed under vacuum at 100 °C until a constant weight is obtained to obtain an ultra-high molecular weight polyethylene product. The product has a spherical-like morphology as tested by electron microscopy, and the degree of polymerization is 2 million g / mol. Other test results are shown in Table 1. The particle size distribution diagram is similar to that of Figure 2 Similar.

[0052] Example 5

[0053] Same as Example 1, except that after stirring, the reaction kettle is heated to 80 °C for polymerization for 4 h, and the polymerization pressure is controlled to be maintained at 0.3 MPa during the reaction process. Then, the temperature is gradually reduced from 80 °C to 74 °C, and it is stabilized for 1 hour for every 2 °C reduction. After the temperature reduction is completed, filtration is carried out, and drying is performed under vacuum at 100 °C until a constant weight is obtained to obtain an ultra-high molecular weight polyethylene product. The product has a spherical-like morphology as tested by electron microscopy, and the degree of polymerization is 1.2 million g / mol. Other test results are shown in Table 1. The particle size distribution diagram is similar to that of Figure 2 Similar.

[0054] Example 6

[0055] Same as Example 1, except that the molar ratio of element aluminum to element titanium in the catalyst is 3:1.

[0056] The product has a spherical-like morphology as tested by electron microscopy, and the degree of polymerization is 0.9 million g / mol. Other test results are shown in Table 1. The particle size distribution diagram is similar to that of Figure 2 Similar.

[0057] Example 7

[0058] Same as Example 1, except that it is first heated to 60 °C and ethylene is introduced for polymerization for 2 h,

[0059] The product has a spherical-like morphology as tested by electron microscopy, and the degree of polymerization is 1.5 million g / mol. Other test results are shown in Table 1. The particle size distribution diagram is similar to that of Figure 2 Similar.

[0060] Comparative Example 1

[0061] Same as Example 1, except that after the polymerization reaction is completed, no programmed temperature reduction treatment is carried out, and filtration is directly carried out, and drying is performed under vacuum at 100 °C until a constant weight is obtained to obtain an ultra-high molecular weight polyethylene product. The product does not have a spherical-like morphology as tested by electron microscopy, and the degree of polymerization is 1.4 million g / mol. The test results are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A ultra-high molecular weight polyethylene, characterized in that, The ultra-high molecular weight polyethylene has a spherical-like morphology, a bulk density of 0.45 - 0.52 g / cm 3 , and an average particle size of 110 - 150 μm.

2. The ultra-high molecular weight polyethylene according to claim 1, wherein, The bulk density of the ultra-high molecular weight polyethylene is 0.45 - 0.50 g / cm 3 , and / or the average particle size of the ultra-high molecular weight polyethylene is 140 - 150 μm.

3. The ultra-high molecular weight polyethylene according to claim 1 or 2, wherein, the viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 30 - 3 million g / mol.

4. A preparation method of ultra-high molecular weight polyethylene, characterized in that, The preparation method includes: under solvent conditions, contacting ethylene with a catalyst to carry out a polymerization reaction, cooling the temperature stepwise, and subjecting the reaction product to solid-liquid separation and drying; The stepwise temperature reduction includes: for every 1 - 3 °C of temperature reduction, stabilizing for 0.5 - 2 h, and the number of temperature reduction times is at least two.

5. The preparation method according to claim 4, wherein, The catalyst includes a magnesium chloride carrier, elemental titanium and elemental aluminum supported on the carrier, and the molar ratio of elemental aluminum to elemental titanium in the catalyst is 2 - 8:1, preferably 5 - 6:

1.

6. The preparation method according to claim 4 or 5, wherein, the particle size range of the catalyst is 3 - 5 μm; and / or the activity of the catalyst is 10,000 - 15,000 gPE / gCat under the conditions of reacting at 80 °C and 0.5 MPa for 2 h.

7. The preparation method according to any one of claims 4 - 6, wherein, the conditions of the polymerization reaction include: the reaction temperature is 30 - 100 °C; and / or the reaction pressure is 0.25 - 1.0 MPa; and / or the reaction time is 3 - 5 hours; and / or the number of temperature reduction times in the stepwise temperature reduction is 2 - 4 times.

8. The preparation method according to any one of claims 4-7, wherein The polymerization reaction includes first carrying out a first polymerization reaction and then a second polymerization reaction. Preferably, the temperature of the second polymerization reaction is 30 - 50 °C higher than that of the first polymerization reaction.

9. The preparation method according to any one of claims 4-8, wherein, The solvent is an organic solvent, preferably at least one of n-hexane, cyclohexane, and heptane.

10. The application of the ultra-high molecular weight polyethylene according to any one of claims 1 - 3 and the ultra-high molecular weight polyethylene prepared by the preparation method according to any one of claims 4 - 9 in the field of lithium battery separators.

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