Anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating sucker rod and preparation method thereof

Abstract

The invention discloses an anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod and a preparation method thereof. The special material is prepared from the following components in percentage by weight: 50 to 78 percent of ultrahigh molecular weight polyethylene, 20 to 47 percent of a polyethylene silane grafting material, 0.6 to 2 percent of terminated hydroxyl silicone oil and 1 percent of an antioxidant, the preparation method of the special material comprises the following steps: mixing and granulating the polyethylene silane grafted material and the terminated monohydroxy silicone oil in a twin-screw, and mixing the granulated material with the ultra-high molecular weight polyethylene and the antioxidant in a twin-screw granulator for granulation; the invention has the advantages that the coating layer of the sucker rod can be prevented from cracking under high temperature and severe environments with water and oil, the processing performance is good, pre-crosslinked particles are not easy to appear in the production process, the wear resistance is good, and the sucker rod has a better application prospect.

Description

Technical Field

[0001] The present invention relates to the field of oilfield exploitation equipment, and particularly relates to a special ultra-high molecular weight polyethylene material for preventing cracking, wear resistance, and easy processing for coating sucker rods and a preparation method thereof. Background Art

[0002] A sucker rod is a slender rod, connected to a polished rod at the upper end and a subsurface pump at the lower end. The sucker rod can transmit the power of surface equipment to the subsurface pump, drive the piston movement of the subsurface pump through the up and down movement of the sucker rod, and then pump the liquid produced from the oil layer to the surface. The sucker rod is in a high-temperature, water-containing, saline-alkali environment during operation, and is accompanied by corrosive media such as carbon dioxide, hydrogen sulfide, and bacteria. The harsh working environment exacerbates the corrosion problem of the sucker rod, and the service life of the sucker rod is greatly affected.

[0003] In order to extend the service life of sucker rods, there are usually the following methods. One is to coat a metal alloy on the surface, such as the anti-corrosion and wear-resistant TiCN composite coating and its spraying method and the anti-corrosion and wear-resistant polished rod of a pumping unit in CN107245688B. Another is to coat a polymer material or a composite material of its glass fiber or carbon fiber, such as: polyethylene, the new polyethylene fully coated sucker rod in CN205172453U; nylon, a modified nylon coating anti-corrosion formula and process for a sucker rod head in CN105968795A; polyimide, a high-temperature resistant coated sucker rod in CN112227965A; polyketone, an aliphatic polyketone fully coated sucker rod and its preparation method in CN111205624B, etc.

[0004] Fiber composite materials, the multi-layer structure corrosion-resistant and high-temperature resistant composite material continuous sucker rod and its preparation process in CN109488219B; among them, the coating material modified by ultra-high molecular weight polyethylene has relatively mature technology, good comprehensive performance, and wide application. However, if the formula is unreasonable, the ultra-high molecular weight polyethylene coating layer will crack on the surface during long-term use. The reason is that the shrinkage rate difference between the metal rod and the ultra-high molecular weight polyethylene is very large. After the ultra-high molecular weight coating is applied to the metal sucker rod, the coating layer is in a stressed state for a long time, resulting in stress cracking in a harsh environment of high temperature, oil, and water.

[0005] From a microscopic perspective, its mechanism is that there are fewer tie molecular chains between the lamellae of ultra-high molecular weight polyethylene. In a high-temperature and oil-water environment, under the action of stress, the tie molecules between the lamellae are disentangled or broken. Macroscopically, it is manifested that as the use time increases, small cracks begin to appear on the surface of the coating layer, and the cracks will accelerate growth, resulting in the failure of the coating layer and the sucker rod. Summary of the Invention

[0006] Ultra-high molecular weight polyethylene has a large molecular weight, high viscosity, and is difficult to process. Generally, it needs to be mixed with general polyethylene and additives before processing. However, its wear resistance will decrease accordingly. Generally, its maximum processing temperature is above 250 degrees Celsius.

[0007] The polyethylene silane grafted material has silane grafted on its polyethylene molecular chain. After it is processed into a product, under the action of high temperature and water, the silanes crosslink with each other, connecting the molecular chains between the polyethylene lamellae with silicon-oxygen bonds. This greatly improves the crack resistance, strength at high temperature, and wear resistance of polyethylene. However, when processing silane-grafted polyethylene, it is sensitive to high temperature. Generally, the maximum processing temperature does not exceed 220 degrees Celsius. Exceeding this temperature or staying at a high temperature for too long will easily form pre-crosslinked particles, resulting in abnormal molding, rough surface, and deteriorated performance.

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a special material for anti-cracking, wear-resistant, and easy-to-process ultra-high molecular weight polyethylene for coating sucker rods and its preparation method. The components of the special material are: 50 wt%-78 wt% of ultra-high molecular weight polyethylene, 20 wt %-47 wt % of polyethylene silane grafted material, 0.6 wt %-2 wt % of end-capped hydroxy silicone oil, and 1 wt % of antioxidant. The preparation method of the special material is as follows: First, the polyethylene silane grafted material and the end-capped mono-hydroxy silicone oil are mixed and granulated in a twin-screw extruder, and then the granulated material is mixed with ultra-high molecular weight polyethylene and antioxidant in a twin-screw granulator for granulation. The advantages of the present invention are that it can prevent the coating layer of the sucker rod from cracking in a harsh environment of high temperature, water, and oil, has good processing performance, is not prone to pre-crosslinked particles during production, has good wear resistance, and has good application prospects.

[0009] In the present invention, the polyethylene silane grafted material and the mono-end-capped hydroxy silicone oil are first melted and melt-blended in a twin-screw granulator to react with each other, making the reactive groups of the polyethylene silane grafted material become passivated, and the crosslinking reaction rate is greatly reduced at high temperature. The mono-end-capped hydroxy silicone oil can also act as a lubricant to reduce frictional loss. Then, it is melt-blended with ultra-high molecular weight polyethylene at high temperature to obtain a special material for anti-cracking, wear-resistant, and easy-to-process ultra-high molecular weight polyethylene for coating sucker rods. The material obtained in this way combines the advantages of ultra-high molecular weight polyethylene and polyethylene silane grafted material. During use, under the action of water and high temperature, the silane-crosslinked polyethylene grafted materials crosslink with each other, having very good wear resistance and anti-cracking performance, and also maintaining good processing performance.

[0010] To achieve the above technical effects, the following technical solutions are adopted: A special material for anti-cracking, wear-resistant, and easy-to-process ultra-high molecular weight polyethylene for coating sucker rods, with the following components: Ultra-high molecular weight polyethylene 50 - 78%; Polyethylene silane grafting material 20% - 47%; End-capped monohydroxy silicone oil 0.6% - 2%; Antioxidant 1%; The mass ratio of the end-capped monohydroxy silicone oil to the polyethylene silane grafting material is not less than 0.03. The main reason is that all crosslinking groups have enough silicone oil to react with them.

[0011] Furthermore, the molecular weight of the ultra-high molecular weight polyethylene is 1 million - 7 million; the density is 0.930 g / cm 3 - 0.945 g / cm 3 。

[0012] Furthermore, the ultra-high molecular weight polyethylene is a mixture of one or two or more different molecular weight ultra-high molecular weight polyethylenes.

[0013] Furthermore, the crosslinking degree of the polyethylene silane grafting material is 70% - 90%; the density is 0.938 g / cm 3 - 0.960 g / cm 3 。

[0014] Furthermore, the molecular weight of the end-capped monohydroxy silicone oil is 1000 - 30000.

[0015] Furthermore, the structural formula of the end-capped monohydroxy silicone oil is: 。

[0016] Furthermore, the antioxidant is a general antioxidant for polyethylene.

[0017] Furthermore, the antioxidant is one or more of 1010 and 168.

[0018] Furthermore, the preparation method is: First, mix and pelletize the polyethylene silane grafting material and the end-capped monohydroxy silicone oil in a twin-screw extruder, and then mix the pelletized material with the ultra-high molecular weight polyethylene and the antioxidant and pelletize them in a twin-screw granulator; obtain the special material for anti-cracking, wear-resistant, and easy-to-process ultra-high molecular weight polyethylene for coated sucker rods.

[0019] Furthermore, the specific method of first mixing and pelletizing the polyethylene silane grafting material and the end-capped monohydroxy silicone oil in a twin-screw extruder is: The polyethylene silane grafting material and the end-capped hydroxyl silicone oil are mixed and pelletized in a twin-screw extruder. The processing temperature is 160 - 210°C. The twin-screw extruder has a total of nine zones, and the temperature settings for each zone are as follows: Zone 1: 160°C, Zone 2: 160 - 180°C, Zone 3: 170 - 190°C, Zone 4: 170 - 190°C, Zone 5: 170 - 190°C, Zone 6: 180 - 200°C, Zone 7: 180 - 210°C, Zone 8: 180 - 210°C, Zone 9: 180 - 210°C, and the die head: 180 - 210°C. The screw speed during the melt extrusion process is 250 - 400 rpm. The end-capped mono-hydroxy silicone oil can passivate the reactive groups of the silane-grafted polyethylene and prevent the occurrence of crosslinking reactions at high temperatures.

[0020] The specific method for mixing the pelletized material with ultra-high molecular weight polyethylene and antioxidant and then pelletizing in a twin-screw granulator is as follows: Pelletizing is carried out in a twin-screw extruder. The temperature settings for each zone are as follows: Zone 1: 190 - 200°C, Zone 2: 190 - 210°C, Zone 3: 190 - 210°C, Zone 4: 200 - 220°C, Zone 5: 200 - 220°C, Zone 6: 220 - 240°C, Zone 7: 240 - 260°C, Zone 8: 250 - 270°C, Zone 9: 260 - 280°C, and the die head: 260 - 280°C. Normal extrusion is carried out at 190 - 280°C to coat the sucker rod. Pre-crosslinking is not likely to occur during the processing. In use, the silane-grafted polyethylene will crosslink in an environment of high temperature and water, greatly improving the wear resistance and crack resistance of the coating layer.

[0021] The beneficial effects of the present invention are as follows: The present invention provides a special material for coating sucker rods with anti-cracking, wear-resistant, and easy-to-process ultra-high molecular weight polyethylene and a preparation method thereof. The components of the special material are: 50 wt% - 78 wt% of ultra-high molecular weight polyethylene, 20 wt% - 47 wt% of polyethylene silane grafting material, 0.6 wt% - 2 wt% of end-capped hydroxyl silicone oil, and 1 wt% of antioxidant. The preparation method of the special material is: first, mix the polyethylene silane grafting material and the end-capped mono-hydroxy silicone oil in a twin-screw extruder for pelletizing, and then mix the pelletized material with ultra-high molecular weight polyethylene and antioxidant and pelletize in a twin-screw granulator. The advantages of the present invention are that it can prevent the coating layer of the sucker rod from cracking in a harsh environment of high temperature, water, and oil, has good processing performance, is not likely to produce pre-crosslinked particles during production, has good wear resistance, and has good application prospects.

[0022] First, the polyethylene silane grafting material and the mono-capped hydroxyl silicone oil are melted and melt-blended in a twin-screw granulator and react with each other, making the reactive groups of the polyethylene silane grafting material become passivated, and at high temperatures, the rate of the cross-linking reaction is greatly reduced. The mono-capped hydroxyl silicone oil can also act as a lubricant to reduce frictional losses. Then, it is melt-blended with ultra-high molecular weight polyethylene at high temperatures to obtain a special material for coating sucker rods, which has crack resistance, wear resistance, and easy processing. The material obtained in this way combines the advantages of ultra-high molecular weight polyethylene and polyethylene silane grafting material. During use, under the action of water and high temperatures, the silane cross-linked polyethylene grafting materials cross-link with each other, having very good wear resistance and crack resistance, and also maintaining good processing performance. Detailed implementation mode

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further descriptions of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing specific implementation modes and are not intended to limit the exemplary implementation modes according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0026] Example 1: Calculated based on a total mass fraction of 100%, the mass fractions of each component are as follows: Ultra-high molecular weight polyethylene with a molecular weight of 3 million accounts for 68 wt% of the total mass of the substance; polyethylene silane grafting material with a maximum cross-linking degree of 80% accounts for 30 wt% of the total mass of the substance; capped mono-hydroxy silicone oil with a molecular weight of 1000 accounts for 1 wt% of the total mass of the substance; the antioxidant is a 1:1 mixture of 1010 and 168; the antioxidant accounts for 1 wt% of the total mass of the substance.

[0027] The preparation process is divided into two steps. In the first step, the polyethylene silane grafting material and the capped monohydroxy silicone oil are added to a twin-screw extruder for melt blending and pelletizing. The processing temperature is between 160 and 210 degrees. The twin-screw extruder has a total of nine zones, and the temperature settings for each zone are as follows: Zone 1: 160 °C, Zone 2: 160 - 180 °C, Zone 3: 170 - 190 °C, Zone 4: 170 - 190 °C, Zone 5: 170 - 190 °C, Zone 6: 180 - 200 °C, Zone 7: 180 - 210 °C, Zone 8: 180 - 210 °C, Zone 9: 180 - 210 °C, and the head: 180 - 210 °C. The rotational speed of the twin-screw during the melt extrusion process is 250 - 400 rpm.

[0028] In the second step, the prepared material, ultra-high molecular weight polyethylene, and antioxidant are again melt blended and pelletized in a twin-screw extruder. The temperature settings for each zone are as follows: Zone 1: 190 - 200 °C, Zone 2: 190 - 210 °C, Zone 3: 190 - 210 °C, Zone 4: 200 - 220 °C, Zone 5: 200 - 220 °C, Zone 6: 220 - 240 °C, Zone 7: 240 - 260 °C, Zone 8: 250 - 270 °C, Zone 9: 260 - 280 °C, and the head: 260 - 280 °C. The rotational speed of the twin-screw during the melt extrusion process is 250 - 400 rpm. Normal extrusion is carried out at 190 - 280 °C to coat the sucker rod.

[0029] Compared with Example 1, in other examples, only the component ratios are different, and the preparation methods are the same. The component ratios are summarized in Table 1: Table 1 Mass fractions of components in each example

[0030] For Comparative Example 1 and Comparative Example 2, after the raw materials and antioxidant are blended, they are directly pressed into tablets on a molding press to prepare test samples for testing. For Comparative Examples 3 - 7, compared with Example 1, only the component ratios are different, and the preparation methods are the same. The component ratios are summarized in Table 2: Table 2 Mass fractions of components in each comparative example

[0031] Perform performance tests on the above examples and comparative examples: For the test samples of stress cracking resistance performance and mass wear performance, test specimens are prepared by the method of molding pressing according to the regulations of relevant standards, and then treated in water at 95 °C for 48 h for cross-linking reaction. Then the samples are taken out and the stress cracking resistance and sliding friction wear tests are carried out according to relevant test standards.

[0032] Stress cracking resistance performance: Prepare test specimens and test the stress resistance performance according to the regulations of GB / T1842 Plastics - Methods of test for environmental stress cracking of polyethylene. Mass wear performance: Test samples were prepared and performance tests were conducted in accordance with the provisions of GB / T 3960 Plastics - Methods of sliding friction and wear tests. Extrusion processing performance: The special anti - cracking and easy - processing ultra - high - molecular - weight polyethylene material for coating sucker rods, which had been pelletized, was added to an extruder with a diameter of φ63. The temperatures of its six zones were set at 200°C, 220°C, 240°C, 260°C, 280°C, 280°C, and the head temperature was 280°C. The screw speed of the extruder was 40 rpm. Observe the extrusion situation and the appearance of the extruded strip.

[0033] The performance test results of the examples are listed in Table 3: Table 3 Performance results of each example

[0034] The performance test results of the comparative examples are listed in Table 4: Table 4 Performance results of each comparative example

[0035] It can be seen from Examples 1, 2, and 3 that as the amount of polyethylene silane grafted material increases, the environmental stress cracking resistance increases and the mass wear decreases. However, the processing performance is relatively good. Comparing Examples 1, 4, and 5, the greater the maximum cross - linking degree of the polyethylene silane grafted material, the greater the environmental stress cracking resistance and the lower the mass wear. Comparing Examples 1, 6, and 7, the larger the molecular weight of the ultra - high - molecular - weight polyethylene, the greater the environmental stress cracking resistance and the lower the mass wear. However, the surface of the extruded strip becomes more and more matte, but the extrusion volume is relatively stable. Comparing Examples 1, 8, and 9, with different amounts of silicone oil, the environmental stress cracking resistance remains unchanged and the mass wear decreases. It should be that more silicone oil increases lubrication.

[0036] When Example 1 is compared with Comparative Examples 1 and 2, the normal properties of ultra-high molecular weight polyethylene and polyethylene silane grafted material are shown in Comparative Example 1 and Comparative Example 2. The stress cracking resistance of Example 1 is much better than that of ultra-high molecular weight polyethylene. Crosslinked polyethylene has the best cracking resistance because the molecular chains are connected by chemical bonds. The wear resistance of Example 1 is better than that of ultra-high molecular weight polyethylene and polyethylene silane grafted material because of the presence of single-capped hydroxy silicone oil lubricant. However, the processing properties of Comparative Examples 1 and 2 are very poor. The ultra-high molecular weight polyethylene is not plasticized, and there are many crosslinked large and small particles during the extrusion of silane crosslinked polyethylene. When Comparative Example 3 is compared with Comparative Example 1, single-capped hydroxy silicone oil is added, and there are two more twin-screw extrusion processes. When Comparative Example 3 is compared with Example 1, all properties of Comparative Example 3 are much worse than those of Example 1. When Comparative Example 2 is compared with Comparative Example 1, except for a certain degree of improvement in wear resistance, other properties are not much different. Single-capped hydroxy silicone oil improves the wear resistance. When Comparative Example 4 is compared with Comparative Example 2, silicone oil is added in terms of composition, and there are two more twin-screw extrusion processes. When Comparative Example 4 is compared with Example 1, all properties are very poor. Because many large and small crosslinked particles are generated during high-temperature extrusion, these particles cause stress concentration, so the performance is very poor. When Comparative Example 4 is compared with Comparative Example 2, since Comparative Example 2 does not undergo high-temperature extrusion and there are no pre-crosslinked particles causing stress concentration, the performance of Comparative Example 2 is the performance of the material itself, and the performance is better than that of Comparative Example 4. When Example 1 is compared with Comparative Example 5, Example 1 uses ultra-high molecular weight polyethylene as the continuous phase, while Comparative Example 5 uses silane grafted polyethylene as the continuous phase. Since silane grafted polyethylene crosslinks during processing and contains too many pre-crosslinked particles, during the wear process, some particles are peeled off, making the wear surface rough and the wear resistance very poor, and the mass loss increases greatly. The processing performance is also very poor. Due to stress concentration caused by pre-crosslinked particles, the cracking resistance is also poor. When Example 1 is compared with Comparative Example 6 and Comparative Example 7, Comparative Example 7 does not have single-capped hydroxy silicone oil lubricant, and the addition amount of single-capped hydroxy silicone oil lubricant in Comparative Example 6 is insufficient. Due to the generation of pre-crosslinked particles, the environmental stress cracking resistance, wear resistance and processing performance of Example 1 are better than those of Comparative Example 6, and Comparative Example 6 is better than Comparative Example 7.

[0037] In summary, the present invention discloses a special material for anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene for coating sucker rods and a preparation method thereof. The components of the special material are as follows: 50 wt% - 78 wt% of ultra-high molecular weight polyethylene, 20 wt% - 47 wt% of polyethylene silane grafting material, 0.6 wt% - 2 wt% of end-capped hydroxy silicone oil, and 1 wt% of antioxidant. The preparation method of the special material is as follows: First, the polyethylene silane grafting material and the end-capped mono-hydroxy silicone oil are mixed and granulated in a twin-screw extruder, and then the granulated material is mixed with ultra-high molecular weight polyethylene and antioxidant in a twin-screw granulator for granulation. The advantages of the present invention are that it can prevent the coating layer of the sucker rod from cracking in harsh environments with high temperature, water and oil, has good processing performance, is not prone to pre-crosslinked particles during production, has good wear resistance, and has good application prospects.

[0038] In the present invention, the polyethylene silane grafting material and the mono-end-capped hydroxy silicone oil are first melted and melt-blended in a twin-screw granulator to react with each other, making the reactive groups of the polyethylene silane grafting material become passivated, and at high temperature, the rate of the crosslinking reaction is greatly reduced. The mono-end-capped hydroxy silicone oil can also act as a lubricant to reduce frictional losses. Then, it is melt-blended with ultra-high molecular weight polyethylene at high temperature to obtain a special material for anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene for coating sucker rods. The material obtained in this way combines the advantages of ultra-high molecular weight polyethylene and polyethylene silane grafting material. During use, under the action of water and high temperature, the silane-crosslinked polyethylene grafting materials crosslink with each other, having very good wear resistance and anti-cracking performance, and still maintaining good processing performance.

[0039] At this point, those skilled in the art recognize that although the embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived from the content disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and determined to cover all these other variations or modifications.

Claims

1. A special ultra-high molecular weight polyethylene material for coating sucker rods that is crack-resistant, wear-resistant and easy to process, characterized in that: The special material is the following components: Ultra-high molecular weight polyethylene 50-78%; polyethylene silane grafted material 20%-47%; end-capped monohydroxy silicone oil 0.6%-2%; antioxidant 1%; The mass ratio of the end-capped monohydroxy silicone oil to the polyvinyl silane grafted material is not less than 0.

03.

2. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 1, characterized in that: The molecular weight of the ultra-high molecular weight polyethylene is 1 million to 7 million; the density is 0.930 g / cm 3 -0.945 g / cm 3 .

3. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 1, characterized in that: The ultra-high molecular weight polyethylene is a mixture of one or two or more ultra-high molecular weight polyethylenes with different molecular weights.

4. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 1, characterized in that: The crosslinking degree of the polyethylene silane grafted material is 70%-90%; the density is 0.938 g / cm 3 -0.960g / cm 3 .

5. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 1, characterized in that: The molecular weight of the end-capped monohydroxy silicone oil is 1000-30000.

6. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 1, characterized in that: The structural formula of the end-capped monohydroxy silicone oil is: 。 7. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 1, characterized in that: The antioxidant is a general antioxidant for polyethylene.

8. The anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 7, characterized in that: The antioxidant is one or more of 1010 and 168.

9. The method for preparing a special ultra-high molecular weight polyethylene material for coating a sucker rod that is crack-resistant, wear-resistant and easy to process as claimed in claim 1, characterized in that: The preparation method is: Firstly, the polyethylene silane grafted material and the blocked monohydroxy silicone oil are mixed and granulated in a twin-screw extruder, and then the granulated material is mixed with ultra-high molecular weight polyethylene and an antioxidant and granulated in a twin-screw extruder to obtain the anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating the sucker rod.

10. The method for preparing the anti-cracking, wear-resistant and easy-to-process ultra-high molecular weight polyethylene special material for coating a sucker rod as claimed in claim 9, characterized in that: The specific method of mixing the polyethylene silane grafted material and the blocked monohydroxy silicone oil in a twin-screw extruder for granulation is as follows: The polyethylene silane grafted material and the end-capped monohydroxy silicone oil are mixed and granulated in a twin-screw extruder, the processing temperature is 160-210°C, the twin-screw extruder has nine zones, and the temperature setting of each zone is specifically as follows: zone 1 160°C, zone 2 160-180°C, zone 3 170-190°C, zone 4 170-190°C, zone 5 170-190°C, zone 6 180-200°C, zone 7 180-210°C, zone 8 180-210°C, zone 9 180-210°C, and die head 180-210°C; the screw speed during the melt extrusion process is 250-400rpm; The specific method of mixing the granulated material with the ultra-high molecular weight polyethylene and the antioxidant and then granulating in a twin-screw granulator is as follows: Granulation is carried out in a twin-screw extruder, and the temperature setting of each zone is as follows: 190-200°C for zone one, 190-210°C for zone two, 190-210°C for zone three, 200-220°C for zone four, 200-220°C for zone five, 220-240°C for zone six, 240-260°C for zone seven, 250-270°C for zone eight, 260-280°C for zone nine, and 260-280°C for die head; normal extrusion is carried out at 190-280°C to coat the sucker rod.

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