A method for processing ultra-high molecular weight polyethylene powder

Abstract

This invention belongs to the field of polymer preparation technology and discloses a method for processing ultra-high molecular weight polyethylene (UHMWPE) powder. The method includes: dispersing the UHMWPE powder in a solvent, heating and melting it under stirring conditions, cooling, separating, and drying to obtain spherical UHMWPE particles; the solvent contains both polar and non-polar solvents, with the polar solvent accounting for more than 50% by volume. This invention's method can transform UHMWPE powder particles of different sizes into spherical particles.

Description

Technical Field

[0001] This invention belongs to the field of polymer preparation technology, and more specifically, relates to a method for processing ultra-high molecular weight polyethylene powder. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a thermoplastic material with special properties, generally having a molecular weight of over 1.5 million. Due to its high molecular weight, it has high melt viscosity and is essentially non-flowing, making it difficult to granulate; therefore, the product is usually in the form of powder or granules.

[0003] Generally, the production of ultra-high molecular weight polyethylene (UHMWPE) is basically the same as that of conventional polyethylene. The production process of conventional polyethylene can also be used to produce UHMWPE. Currently, it is commonly used in the pulp polyethylene process, mainly by adjusting the amount of hydrogen added or other parameters to obtain UHMWPE products.

[0004] Catalysts commonly used in conventional polyethylene can also be used in the polymerization of UHMWPE. These catalysts are primarily zinc (Zn) catalysts, but metallocene-based single-active-center catalysts are also used. The production process using Zn catalysts generally involves the polymerization of ethylene monomers into polyethylene under specific temperature and pressure conditions, either in a solvent or without solvent. The resulting polyethylene is a powder with a surface morphology similar to the catalyst and exhibits a "replication effect." For conventional polyethylene, the powder is typically melt-granulated to produce resin products. For UHMWPE, the powder is graded to obtain different powder products.

[0005] Since UHMWPE products are generally in the form of powder or granules, particle shape, size, and bulk density are the main control parameters. The ideal particle shape is spherical to ensure product flowability, and the particle size and bulk density should ideally be controllable to meet different needs.

[0006] In the existing technology, there are few reported methods for preparing UHMWPE spherical particles. A possible approach is to prepare spherical catalysts, and then replicate the catalyst morphology into spherical UHMWPE particles during ethylene polymerization. However, this method involves particle breakage during polymerization, which cannot guarantee the uniformity of the spherical shape, and the resulting powder particles can only approximate spherical shapes. There are also reports of preparing UHMWPE spherical particles by grinding powder particles, but this also suffers from uniformity issues and is more costly. In summary, the existing technology has not yet effectively solved the problem of preparing UHMWPE spherical particles. Summary of the Invention

[0007] In view of the above situation, the purpose of this invention is to provide a method for processing ultra-high molecular weight polyethylene powder. This method utilizes the melt characteristics of UHMWPE powder at high temperatures to transform UHMWPE powder particles of different sizes into spherical particles, and the operation is simple.

[0008] This invention provides a method for processing ultra-high molecular weight polyethylene powder, the method comprising: dispersing ultra-high molecular weight polyethylene powder in a solvent, heating and melting it under stirring conditions, cooling, separating and drying it to obtain spherical particles of ultra-high molecular weight polyethylene.

[0009] The solvent contains both polar and non-polar solvents, with the polar solvent accounting for more than 50% of the total volume.

[0010] The processing method of the present invention can transform UHMWPE powder particles of different particle sizes into spherical particles. The processing method is simple and low in cost.

[0011] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0012] Figure 1 The UHMWPE spherical particles obtained in Example 1.

[0013] Figure 2 The UHMWPE spherical particles obtained in Example 2. Detailed Implementation

[0014] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0015] This invention provides a method for processing ultra-high molecular weight polyethylene powder, the method comprising: dispersing ultra-high molecular weight polyethylene powder in a solvent, heating and melting it under stirring conditions, cooling, separating and drying it to obtain spherical particles of ultra-high molecular weight polyethylene.

[0016] The solvent contains both polar and non-polar solvents, with the polar solvent accounting for more than 50% of the total volume.

[0017] The ultra-high molecular weight polyethylene powder in this invention uses materials commonly found in the art. Preferably, the viscosity-average molecular weight of the ultra-high molecular weight polyethylene powder is 1.7 million or more.

[0018] The solvent in this invention is a mixed solvent, that is, a mixture of polar solvent and non-polar solvent. The polar solvent can be an alcohol compound, an amine compound or an alkanolamine compound, such as methanol, ethanol, tetrahydrofuran, DMF, triethanolamine, etc.

[0019] Preferably, the polar solvent accounts for more than 80% of the total volume of the solvent. More preferably, the volume ratio of the polar solvent to the non-polar solvent is 5-20:100. Using a suitable solvent ratio results in better sphericity of the particles, making them closer to spherical shapes.

[0020] According to the present invention, the nonpolar solvent is a saturated hydrocarbon, such as n-hexane, toluene, benzene, decane, decahydronaphthalene, etc.

[0021] In this invention, the heating and melting treatment is performed at a temperature of 90-200°C for 1-3 hours. Preferably, the heating and melting treatment is performed at a temperature of 150-200°C for 1.5-2 hours.

[0022] Parameters not specified in this invention are all conventional techniques in the field.

[0023] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0024] In the following embodiments and comparative examples:

[0025] Polymer molecular weight (Mw): Viscosity method;

[0026] Average particle size and aspect ratio of polymer: The average particle size and aspect ratio of polymer were obtained using optical image analysis software.

[0027] Examples 1-3 illustrate the processing method of ultra-high molecular weight polyethylene powder of the present invention.

[0028] Example 1

[0029] 0.5 g of ultra-high molecular weight polyethylene powder with a viscosity-average molecular weight of 3.5 million was added to a 250 mL reactor. A mixed solvent of 100 mL anhydrous ethanol and 5 mL decahydronaphthalene was added. The mixture was heated to 160 °C under stirring and maintained for 2 hours. Then, the temperature was lowered to 30 °C over 1.5 hours. After separation and drying, spherical particles were obtained. The aspect ratio of the particles was 0.93.

[0030] Example 2

[0031] 0.2 g of ultra-high molecular weight polyethylene powder with a viscosity-average molecular weight of 6.3 million was added to a 250 mL reactor. A mixed solvent of 100 mL anhydrous methanol and 10 mL decane was added. The mixture was heated to 180 °C under stirring and maintained for 1.5 hours. Then, it was cooled to 30 °C within 1 hour. After separation and drying, spherical particles were obtained. The aspect ratio of the particles was 0.92.

[0032] Example 3

[0033] 0.5 g of ultra-high molecular weight polyethylene powder with a viscosity-average molecular weight of 5.2 million was added to a 250 mL reactor. A mixed solvent of 100 mL triethanolamine and 20 mL toluene was added. The mixture was heated to 170 °C under stirring and maintained for 2 hours. Then, the temperature was lowered to 30 °C over 0.5 hours. After separation and drying, spherical particles were obtained. The aspect ratio of the particles was 0.93.

[0034] Comparative Example 1

[0035] 0.5 g of ultra-high molecular weight polyethylene powder with a viscosity-average molecular weight of 3.5 million was added to a 250 mL reactor, along with 100 mL of anhydrous ethanol solvent. The mixture was heated to 160 °C under stirring and maintained for 2 hours. Then, it was cooled to 30 °C over 1.5 hours. After separation and drying, granules were obtained. The aspect ratio of the granules was 0.64.

[0036] Comparative Example 2

[0037] Add 0.5 g of ultra-high molecular weight polyethylene powder with a viscosity-average molecular weight of 3.5 million to a 250 ml reactor, add 100 ml of decahydronaphthalene solvent, heat to 160 °C under stirring, maintain for 2 hours, and then cool to 30 °C within 1.5 hours. The system is a flocculent suspension.

[0038] The aspect ratio of the spherical particles in the examples and comparative examples, combined with... Figure 1 and Figure 2 It is known that the method of the present invention can transform UHMWPE powder particles of different particle sizes into spherical particles.

[0039] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for processing ultra-high molecular weight polyethylene powder, characterized in that, The processing method includes: dispersing ultra-high molecular weight polyethylene powder in a solvent, heating and melting it under stirring conditions, cooling, separating and drying it to obtain spherical particles of ultra-high molecular weight polyethylene; The solvent contains both polar and non-polar solvents, with the polar solvent comprising more than 50% by volume. The polar solvent is an alcohol, an amine, or an alkanolamine. The nonpolar solvent is a saturated hydrocarbon.

2. The method for processing ultra-high molecular weight polyethylene powder according to claim 1, wherein, The viscosity-average molecular weight of the ultra-high molecular weight polyethylene powder is over 1.7 million.

3. The method for processing ultra-high molecular weight polyethylene powder according to claim 1, wherein, The polar solvent accounts for more than 80% by volume in the solvent.

4. The method for processing ultra-high molecular weight polyethylene powder according to claim 1, wherein, The temperature for the heating and melting treatment is 90-200℃.

5. The method for processing ultra-high molecular weight polyethylene powder according to claim 4, wherein, The temperature for the heating and melting treatment is 150-200℃.

6. The method for processing ultra-high molecular weight polyethylene powder according to claim 1, wherein, The heating and melting process takes 1-3 hours.

7. The method for processing ultra-high molecular weight polyethylene powder according to claim 6, wherein, The heating and melting process takes 1.5-2 hours.

8. The method for processing ultra-high molecular weight polyethylene powder according to claim 1, wherein, The temperature will drop to 25-35℃ in 0.5-2 hours.

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