Ultrahigh molecular weight polyethylene material with excellent processability and processing method thereof

Abstract

The invention relates to an ultra-high molecular weight polyethylene material with excellent processability and a processing method thereof, the ultra-high molecular weight polyethylene material with excellent processability comprises the following raw materials by weight: 80-95 parts of ultra-high molecular weight polyethylene, 5-20 parts of hyperbranched polyethylene, 0.3-0.6 part of an antioxidant, 4-8 parts of a filler, and 0.5-2 parts of a lubricant, the branching degree of the hyperbranched polyethylene is 50-130 branched chains / 1000 carbons, the weight-average molecular weight is 660,000-53.40 thousand, the melt index is 3-15g / 10min, and the melting point is 40-80 DEG C. The invention further discloses a preparation method of the hyperbranched polyethylene. The added hyperbranched polyethylene can effectively improve the processability of the ultra-high molecular weight polyethylene on the premise of not greatly reducing the comprehensive performance of the ultra-high molecular weight polyethylene, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic modification, and in particular relates to an ultra-high molecular weight polyethylene material with excellent processing performance and a processing method thereof. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) has super wear resistance, self-lubrication, high strength, stable chemical properties, and strong anti-aging performance. The main product forms include plates, rods, profiles, industrial pipes, fibers, lithium battery separators, etc., and are widely used in the fields of machinery industry, petrochemical industry, new energy materials, and composite materials. However, due to the ultra-long molecular chain of ultra-high molecular weight polyethylene, there are dense inter-chain entanglements inside it, which makes it extremely difficult for its melt to flow and difficult to be molded by conventional extrusion, injection molding, etc., which greatly limits the large-scale production and application of its products.

[0003] In order to solve this problem, blending modification is usually adopted, such as adding low molecular weight polyethylene (LMWPE) or polyolefin elastomer (POE) to UHMWPE to improve the processing performance of UHMWPE. LMWPE and UHMWPE have similar chemical structures, and have good compatibility after blending, and are not prone to phase separation. After blending, the melt viscosity of the blend can be effectively reduced, and the processing performance can be significantly improved. However, the addition of LMWPE will cause a significant decrease in the mechanical properties (such as tensile strength and wear resistance) of the blended material, and the melting point of LMWPE is low, and the heat resistance of the blended material will be significantly affected, limiting the application of the material in high temperature fields.

[0004] POE as a blending modifier can also improve the processing performance of UHMWPE melt, but the addition of POE will significantly reduce the tensile strength and impact properties of the blended material. In addition, the compatibility between POE and UHMWPE is relatively poor, and phase separation may occur at high addition ratios, and additional compatibilizers are usually required. Moreover, the synthesis process of POE is very demanding, including polymerization process, catalyst, α-olefins and other links, there are high technical barriers, the process is complicated and the relevant catalysts are protected by patents. There is currently no large-scale production capacity for 1-octene. Summary of the invention

[0005] The purpose of the present invention is to provide an ultra-high molecular weight polyethylene material with excellent processing performance and a preparation method thereof, which can effectively overcome the problem of difficulty in processing and molding ultra-high molecular weight polyethylene, while retaining the excellent comprehensive properties of ultra-high molecular weight polyethylene to the greatest extent.

[0006] The present invention provides an ultra-high molecular weight polyethylene material with excellent processing performance. The raw material components of the material include, by weight: 80-95 parts of ultra-high molecular weight polyethylene, 5-20 parts of hyperbranched polyethylene, 0.3-0.6 parts of antioxidant, 4-8 parts of filler, and 0.5-2 parts of lubricant;

[0007] The branching degree of the hyperbranched polyethylene is not less than 50 branches / 1000 carbons, the weight average molecular weight is 66,000 to 534,000, the melt index is 3 to 15 g / 10 min, and the melting point is 40 to 80° C.; and the molecular weight of the ultra-high molecular weight polyethylene is 1.5 million to 6 million.

[0008] The present invention also provides a method for processing an ultra-high molecular weight polyethylene material with excellent processing performance, comprising the following steps:

[0009] Step 1, by weight, 80-95 parts of ultra-high molecular weight polyethylene, 5-20 parts of hyperbranched polyethylene, 0.3-0.6 parts of antioxidant, 4-8 parts of filler and 0.5-2 parts of lubricant are added into an internal mixer;

[0010] Step 2, mixing at a speed of 30 to 60 rpm for 5 to 15 minutes at a mixing temperature of 180° C. to 220° C.;

[0011] Step 3, placing the mixed material in a flat vulcanizing machine mold for molding, the molding pressure is 10MPa-20MPa, and hot pressing for 5-20 minutes;

[0012] Step 4: Cool the mold to 50°C to 80°C under pressure, then demould it, place it at room temperature for 24 hours, and use a cutter to cut it into corresponding characterization specimens.

[0013] Compared with the prior art, the invention has the following beneficial effects: by adding a small amount of hyperbranched polyethylene, the disadvantage of difficult processing of ultra-high molecular weight polyethylene can be significantly improved, while the excellent properties of ultra-high molecular weight polyethylene itself, such as high strength and high modulus, can be retained to the greatest extent. In addition, the addition of hyperbranched polyethylene also has a significant toughening and modification effect on ultra-high molecular weight polyethylene. DETAILED DESCRIPTION

[0014] The following examples are given to further illustrate the present invention, but are not intended to limit the scope of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the invention still fall within the scope of protection of the present invention.

[0015] The technical solutions provided in this application are as follows:

[0016] The raw material components of the ultra-high molecular weight polyethylene material with excellent processing performance include, by weight: 80-95 parts of ultra-high molecular weight polyethylene, 5-20 parts of hyperbranched polyethylene, 0.3-0.6 parts of antioxidant, 4-8 parts of filler, and 0.5-2 parts of lubricant.

[0017] A further technical solution is that the branched polyethylene is a type of ethylene homopolymer with a branching degree of not less than 50 branches / 1000 carbons, a branching degree of 50-130 branches / 1000 carbons, a weight average molecular weight of 66,000-534,000, a melt index of 3-15g / 10min, and a melting point of 40-80°C. The synthesis method is mainly obtained by catalyzing ethylene homopolymerization based on the "chain walking mechanism" by a late transition metal catalyst, wherein the late transition metal catalyst is at least one of a diimine nickel or a diimine palladium catalyst, and the catalyst needs to be coordinated with a co-catalyst to catalyze ethylene polymerization to obtain a hyperbranched polyethylene, wherein the co-catalyst includes: any one or more of boron salts, alkylaluminoxanes, diethylaluminum chloride, trimethylaluminum, triisobutylaluminum, and diethylaluminum chloride.

[0018] A further technical solution is that the molecular weight of the ultra-high molecular weight polyethylene UHMWPE is 1.5 million to 6 million.

[0019] A further technical solution is that the antioxidant comprises one or more of antioxidant 1010 and antioxidant 1076; the filler is any one of talc, kaolin or titanium dioxide; and the lubricant is polyethylene wax or stearic acid.

[0020] The processing method of ultra-high molecular weight polyethylene material with excellent processing performance is:

[0021] Add the raw material components into the internal mixer according to the ratio, and mix them for 5 to 15 minutes at a speed of 30 to 60 rpm, and the mixing temperature is 180 to 220 degrees; place the mixed material in a flat vulcanizer mold for molding, the molding temperature is 190 degrees, the molding pressure is 10MPa to 20MPa, and after hot pressing for 5 to 20 minutes, the mold is cooled to 50 to 80 degrees under pressure and then demolded, placed at room temperature for 24 hours, and cut into corresponding characterization specimens using a cutter.

[0022] The principle of this process: In the blend of polyolefin elastomer (POE) and ultra-high molecular weight polyethylene (UHMWPE), the addition of POE changes the originally tight UHMWPE molecular network, making the originally entangled UHMWPE and POE molecular chains entangled. When subjected to force, the molecular chains entangled by the two cannot show excellent ductility like the molecular chains composed entirely of UHMWPE, and therefore break quickly. After the hyperbranched polyethylene elastomer is blended with ultra-high molecular weight polyethylene, the hyperbranched polyethylene exists in the amorphous region between the UHMWPE crystals, destroying the highly entangled grid structure of the UHMWPE segments, having a significant viscosity-reducing effect on ultra-high molecular weight polyethylene, and significantly improving the processing performance of UHMWPE.

[0023] In addition, due to the hyperbranched structure of hyperbranched polyethylene, the originally tightly entangled UHMWPE chains can be entangled with the branches of hyperbranched polyethylene. Moreover, hyperbranched polyethylene can serve as a bridging structure to connect multiple entangled UHMWPE molecular chain regions, improving the effect of the molecular chain segments formed by entanglement of POE without ductility, so while ensuring the improvement of processing performance, other mechanical properties of ultra-high molecular weight polyethylene will not be lost.

[0024] At the same time, since the chemical structures of ultra-high molecular weight polyethylene and hyperbranched polyethylene elastomer are similar, they have good compatibility after blending and are not prone to phase separation. Therefore, a good blending effect can be achieved without adding additional compatibilizers.

[0025] Embodiment 1:

[0026] The ultra-high molecular weight polyethylene blend material includes, by weight: 95 parts of ultra-high molecular weight polyethylene, 5 parts of hyperbranched polyethylene, 0.5 parts of antioxidant, 4 parts of filler, and 0.5 parts of lubricant. The hyperbranched polyethylene and ultra-high molecular weight polyethylene powders are mixed by an internal mixer to obtain a blend material. The powder is placed in a mold, hot-pressed with a flat vulcanizer at a temperature of 190 degrees, and taken out after hot pressing for 10 minutes. The sample is naturally cooled to room temperature, placed at room temperature for 24 hours, and cut into corresponding characterization specimens using a cutter.

[0027] Embodiment 2:

[0028] The ultra-high molecular weight polyethylene blend material includes, by weight: 90 parts of ultra-high molecular weight polyethylene, 10 parts of hyperbranched polyethylene, 0.5 parts of antioxidant, 4 parts of filler, and 0.5 parts of lubricant. The hyperbranched polyethylene and ultra-high molecular weight polyethylene powders are mixed by an internal mixer to obtain a blend material. The powder is placed in a mold, hot-pressed with a flat vulcanizer at a temperature of 190 degrees, and taken out after hot pressing for 10 minutes. The sample is naturally cooled to room temperature, placed at room temperature for 24 hours, and cut into corresponding characterization specimens using a cutter.

[0029] Embodiment 3:

[0030] The ultra-high molecular weight polyethylene blend material includes, by weight: 85 parts of ultra-high molecular weight polyethylene, 15 parts of hyperbranched polyethylene, 0.5 parts of antioxidant, 4 parts of filler, and 0.5 parts of lubricant. The hyperbranched polyethylene and ultra-high molecular weight polyethylene powders are mixed by an internal mixer to obtain a blend material. The powder is placed in a mold, hot-pressed with a flat vulcanizer at a temperature of 190 degrees, and taken out after hot pressing for 10 minutes. The sample is naturally cooled to room temperature, placed at room temperature for 24 hours, and cut into corresponding characterization specimens using a cutter.

[0031] Comparative Example 1:

[0032] Place the ultra-high molecular weight polyethylene powder in a mold and hot-press it with a flat vulcanizer at 190 degrees. Take it out after hot pressing for 10 minutes, cool the sample naturally to room temperature, leave it at room temperature for 24 hours, and use a cutter to cut it into corresponding characterization strip specimens.

[0033] Comparative Example 2:

[0034] The ultra-high molecular weight polyethylene blend material includes, by weight: 95 parts of ultra-high molecular weight polyethylene, 5 parts of POE, 0.5 parts of antioxidant, 4 parts of filler, and 0.5 parts of lubricant. The commercially available conventional brand POE and ultra-high molecular weight polyethylene powder are mixed by an internal mixer to obtain a blend material. The powder is placed in a mold and hot-pressed with a flat vulcanizer at a temperature of 190 degrees. After hot pressing for 10 minutes, the sample is taken out and cooled naturally to room temperature. It is placed at room temperature for 24 hours and cut into corresponding characterization specimens using a cutter.

[0035] Sample performance test method:

[0036] Tensile strength and elongation at break performance test:

[0037] According to GBT1040.3-2006 standard, the tensile properties were tested by tensile test using a universal testing machine at a tensile speed of 50 mm / min. The average value of 5 samples was taken as the test result for each group of experiments.

[0038] Capillary rheological properties test:

[0039] A compact desktop high-temperature capillary rheometer was used for high-pressure capillary rheological measurement and analysis. The capillary die aspect ratio was 16, the die diameter was 1 mm, and the test temperature was 200°C.

[0040] Impact strength test:

[0041] According to GB1843-2008 standard, the notched impact strength was tested by using a pendulum impact tester, and the average value was taken for each group of 3 samples.

[0042] Test results table project Apparent viscosity Pa.s (shear rate 1 / s) Apparent viscosity Pa.s (shear rate 10 / s) Tensile strength / MPa Elongation at break / % <![CDATA[Impact strength kJ / m 2 > Example 1 13000 6000 25.2 230 58 Example 2 20000 8000 23.8 162 35 Example 3 25000 6500 15.0 105 33 Comparative Example 1 100000 / 40.5 350 90 Comparative Example 2 20000 8000 10.8 150 22

[0043] By comparing Example 1, Example 2 and Example 3 with Comparative Example 1, it is found that the introduction of hyperbranched polyethylene can significantly reduce the apparent viscosity of ultra-high molecular weight polyethylene at different shear rates, because the hyperbranched structure of the hyperbranched polyethylene destroys the highly entangled grid structure of the UHMWPE segment, and has a significant viscosity reduction effect on ultra-high molecular weight polyethylene. At the same time, when a small amount of hyperbranched polyethylene is added, the apparent viscosity is greatly reduced, and the tensile strength is reduced to half of the original 25.2Mpa, and has a certain toughness, still meeting the requirements of most plastic mechanical properties. In addition, when introducing different numbers of hyperbranched polyethylene, a small amount of hyperbranched polyethylene can achieve the goal, and as the amount of hyperbranched polyethylene increases, the apparent viscosity of the blended material does not change much, and other mechanical strengths are gradually reduced.

[0044] By comparing Example 1 with Comparative Examples 1 and 2, it is found that both the hyperbranched polyethylene in the present invention and the commercially available conventional grade of POE can significantly reduce the apparent viscosity of UHMWPE, but compared with POE, the introduction of hyperbranched polyethylene has less loss on other properties of UHMWPE. It can be seen from the table that the tensile strength and impact strength of the hyperbranched polyethylene and UHMWPE blend are almost twice that of POE and UHMWPE, so the performance of the hyperbranched polyethylene and UHMWPE blend is better.

[0045] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. An ultra-high molecular weight polyethylene material with excellent processing performance, characterized in that: The raw material components of the material include, by weight: 80 to 95 parts of ultra-high molecular weight polyethylene, 5 to 20 parts of hyperbranched polyethylene, 0.3 to 0.6 parts of antioxidant, 4 to 8 parts of filler, and 0.5 to 2 parts of lubricant; The branching degree of the hyperbranched polyethylene is not less than 50 branches / 1000 carbons, the weight average molecular weight is 66,000 to 534,000, the melt index is 3 to 15 g / 10 min, and the melting point is 40 to 80° C.; and the molecular weight of the ultra-high molecular weight polyethylene is 1.5 million to 6 million.

2. The ultra-high molecular weight polyethylene material with excellent processing performance according to claim 1, characterized in that: The antioxidant is one or more of antioxidant 1010 and antioxidant 1076.

3. The ultra-high molecular weight polyethylene material with excellent processing performance according to claim 1, characterized in that: The filler is any one of talc, kaolin or titanium dioxide.

4. The ultra-high molecular weight polyethylene material with excellent processing performance according to any one of claims 1 to 3, characterized in that: The lubricant is polyethylene wax or stearic acid.

5. A method for processing ultra-high molecular weight polyethylene material with excellent processing performance, characterized in that: The following steps are involved: Step 1, by weight, 80-95 parts of ultra-high molecular weight polyethylene, 5-20 parts of hyperbranched polyethylene, 0.3-0.6 parts of antioxidant, 4-8 parts of filler and 0.5-2 parts of lubricant are added into an internal mixer; Step 2, mixing at a speed of 30 to 60 rpm for 5 to 15 minutes at a mixing temperature of 180° C. to 220° C.; Step 3, placing the mixed material in a flat vulcanizing machine mold for molding, the molding pressure is 10MPa-20MPa, and hot pressing for 5-20 minutes; Step 4: Cool the mold to 50°C to 80°C under pressure, then demould it, place it at room temperature for 24 hours, and use a cutter to cut it into corresponding characterization specimens.

6. The method for processing ultra-high molecular weight polyethylene material with excellent processing performance according to claim 5, characterized in that: The branching degree of the hyperbranched polyethylene is 50 to 130 branches / 1000 carbons, the weight average molecular weight is 66,000 to 534,000, the melt index is 3 to 15 g / 10 min, and the melting point is 40 to 80° C.

7. The method for processing ultra-high molecular weight polyethylene material with excellent processing performance according to claim 5, characterized in that: The molecular weight of the ultra-high molecular weight polyethylene is 1.5 million to 6 million.

8. The method for processing an ultra-high molecular weight polyethylene material with excellent processing performance according to claim 6 or 7, characterized in that: The antioxidant is one or more of antioxidant 1010 and antioxidant 1076.

9. The method for processing ultra-high molecular weight polyethylene material with excellent processing performance according to claim 8, characterized in that: The filler is any one of talc, kaolin or titanium dioxide.

10. The method for processing an ultra-high molecular weight polyethylene material with excellent processing performance according to claim 5, 8 or 9, characterized in that: The lubricant is polyethylene wax or stearic acid.