A high abrasion resistant sheath material for cables and a method for its production

Abstract

The application relates to a high-wear-resistance sheath material for cables and a preparation method thereof, and belongs to the technical field of high polymer composite materials. The sheath material comprises, in parts by weight, 100 parts of PVC master batch, 20-30 parts of plasticizer, 2.5-3 parts of heat stabilizer, 0.18-0.22 parts of antioxidant, 2.2-2.8 parts of lubricant, 15-20 parts of magnesium hydroxide powder, 10-20 parts of light calcium powder and 5-10 parts of wear-resistance reinforcing agent. The wear-resistance reinforcing agent is obtained by carrying out amine-ester exchange reaction of mercaptoethylamine and fluorodimethyl ester, introducing double-end mercapto modification, obtaining a modified monomer, and then carrying out addition reaction of the modified monomer and dimethyl glyceryl acrylate to form a chain macromolecular compound, which is the wear-resistance reinforcing agent. The wear-resistance reinforcing agent plays a bridging strengthening role between the anti-wear particles and the PVC matrix, simultaneously forms wear-reducing modification to the anti-wear particles, and endows the sheath material with excellent wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically, it relates to a high wear-resistant sheath material for cables and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is widely used in cable sheathing materials due to its low cost, good processing performance, and excellent electrical insulation properties. However, traditional PVC sheathing materials struggle to meet abrasion resistance requirements in high-wear environments (such as industrial equipment and robot cables).

[0003] To improve wear resistance, a large amount of wear-resistant filler is usually added. However, this will significantly reduce the material's flexibility, tensile strength, and elongation at break. Moreover, these wear-resistant fillers fall off during the wear process and form abrasive particles, further aggravating the wear process. In the prior art, surface treatment technology is used to treat the surface of the wear-resistant filler to improve its dispersion and make the wear more uniform. This can improve the overall wear resistance of the sheath to a certain extent, but it is still difficult to meet the wear resistance requirements in high-wear environments. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide a high wear-resistant sheath material for cables and a method for preparing the same.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A high abrasion-resistant sheath material for cables comprises, by weight: 100 parts PVC masterbatch, 20-30 parts plasticizer, 2.5-3 parts heat stabilizer, 0.18-0.22 parts antioxidant, 2.2-2.8 parts lubricant, 15-20 parts magnesium hydroxide powder, 10-20 parts light calcium carbonate powder, and 5-10 parts abrasion-resistant reinforcing agent.

[0007] The wear-resistant reinforcing agent is prepared by the following method:

[0008] Step A1: Mix difluorodimethyl ester, mercaptoethylamine and dimethyl sulfoxide and remove water under vacuum. Purge with dry nitrogen to constant pressure, add trimethylaluminum and mix well. Heat to 100-120℃ and stir at 60-90 r / min for 4-5.5 h to remove dimethyl sulfoxide and low-boiling substances produced in the reaction, thus obtaining the modified monomer.

[0009] Furthermore, the feed ratio of fluorinated dimethyl ester, mercaptoethylamine, trimethylaluminum and dimethyl sulfoxide is 0.1 mmol: 0.22-0.24 mmol: 60-90 mg: 220-300 mL. Under the catalysis of trimethylaluminum, the active amino group of mercaptoethylamine undergoes an amino-ester exchange reaction with fluorinated dimethyl ester.

[0010] Furthermore, the difluorodimethyl ester is either monofluorodimethyl ester or difluorodimethyl ester, and the resulting wear-resistant reinforcing agent maintains good compatibility with the PVC matrix.

[0011] Preferably, the fluorodimethyl ester is one of dimethyl 2-fluoromalonate and dimethyl difluoromalonate, which has good reactivity.

[0012] Step A2: Mix glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene, heat to 50-60℃, and apply stirring at 90-120 rpm and 150-200 W / m 2 After ultraviolet irradiation and reaction for 3-4 hours to remove toluene, the product is washed with ethanol and dried to obtain the wear-resistant reinforcing agent.

[0013] Furthermore, the feed ratio of glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene is 0.1 mol: 0.1 mol: 0.1-0.15 g: 0.8-1.2 mL: 150-200 mL. Under the synergistic initiation of dimethyl azobisisobutyrate and photoinitiator 1173, the modified monomer and glyceryl dimethacrylate undergo an addition reaction to form a chain-like macromolecular compound.

[0014] Preferably, the plasticizer is a composite of epoxidized soybean oil and dioctyl phthalate, which synergistically plasticizes PVC and improves the processing performance of the composite material.

[0015] Preferably, the lubricant is selected from microcrystalline wax, which provides good external lubrication and facilitates the extrusion molding of the sheath material.

[0016] Preferably, the fineness of the light calcium carbonate powder is 200-325 mesh, which has both good dispersibility and filling properties within this particle size range.

[0017] A method for preparing a high wear-resistant sheath material for cables includes: premixing PVC masterbatch, plasticizer, heat stabilizer, antioxidant, lubricant and wear-resistant reinforcing agent and feeding them into the main feed port of a twin-screw extruder; premixing magnesium hydroxide micro powder and light calcium carbonate powder and feeding them into the side feed port; plasticizing and extruding at 180-190℃; and pelletizing to obtain the high wear-resistant sheath material.

[0018] The beneficial effects of this invention are:

[0019] This invention, based on the existing PVC cable sheathing system, introduces a wear-resistant reinforcing agent blend to maintain the good strength and toughness of the sheathing material while imparting excellent wear resistance. This wear-resistant reinforcing agent is obtained by an amino-ester exchange reaction between mercaptoethylamine and difluorodimethyl ester, introducing double-terminal thiol modification to obtain a modified monomer. The modified monomer then undergoes an addition reaction with dimethacrylate to form a chain-like macromolecular compound, which is the wear-resistant reinforcing agent. Its main molecular chain contains a large number of ester structures, exhibiting good compatibility with the PVC matrix and easy dispersion during the melting and mixing process, thus playing a certain toughening role. The hydroxyl groups on its side chains react with the chlorine groups on the PVC macromolecules. In this sheath material system, magnesium hydroxide and light calcium carbonate powder particles act as anti-wear particles. The sulfur-containing amide structure on the main chain of the wear-resistant reinforcing agent forms a chelating force with the anti-wear particles, thereby playing a bridging and strengthening role. This makes the anti-wear particles strongly bonded to the matrix, and they are not easy to fall off from the matrix during friction and wear, thus giving full play to their anti-wear role. Thanks to the chelating and compounding effect, the wear-resistant reinforcing agent introduces fluorine structure modification to the surface of the anti-wear particles, reducing the friction coefficient between the anti-wear particles and the friction material, reducing the resistance of the anti-wear particles in friction, reducing the shedding of anti-wear particles, and thus reducing the problem of aggravated wear caused by the shedding of anti-wear particles. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: Preparation of high abrasion-resistant sheath material for cables, as detailed below:

[0022] (1) Preparation of wear-resistant reinforcing agent

[0023] Step A1: Dimethyl 2-fluoromalonate, mercaptoethylamine, and dimethyl sulfoxide were mixed and vacuum dehydrated for 30 min. Dry nitrogen was introduced to restore the pressure to constant, and trimethylaluminum was added and mixed. The mixture was heated to 100 °C and stirred at 60 r / min for 4.5 h. The ratio of 2-fluoromalonate, mercaptoethylamine, trimethylaluminum, and dimethyl sulfoxide was 0.1 mmol: 0.22 mmol: 60 mg: 220 mL. Mercaptoethylamine and dimethyl 2-fluoromalonate underwent an amino-ester exchange reaction. After the reaction was completed, dimethyl sulfoxide and low-boiling substances generated by amino-ester exchange were removed by rotary evaporation under reduced pressure. The substrate was washed with water, the aqueous phase was separated, and the substrate was vacuum dried to obtain the modified monomer.

[0024] Step A2: Glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene are added and mixed. The mixture is heated to 50°C, and stirred at 90 rpm with 150 W / m². 2 The reaction was carried out under ultraviolet irradiation for 3.2 hours. The feed ratio of glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173 and toluene was 0.1 mol: 0.1 mol: 0.1 g: 0.8 mL: 150 mL. The modified monomer reacted with glyceryl dimethacrylate in an addition reaction. After the reaction was completed, toluene was removed by rotary evaporation. The product was then washed with ethanol and dried to obtain the wear-resistant reinforcing agent.

[0025] (2) Preparation of high wear-resistant protective sleeve material

[0026] Ingredients: By weight, 100 parts of PVC masterbatch, using commercially available SG-5 type PVC raw material; 20 parts of plasticizer, using industrial-grade epoxidized soybean oil and dioctyl phthalate in equal weight ratio; 2.5 parts of heat stabilizer, using GP-283 type calcium-zinc heat stabilizer; 0.18 parts of antioxidant, using antioxidant 1076 and antioxidant 168 in a weight ratio of 2:1; 2.2 parts of lubricant, using H3240 type microcrystalline wax; 15 parts of magnesium hydroxide powder, using commercially available flame retardant grade powder; 15 parts of light calcium carbonate powder, using commercially available 200 mesh powder; and 10 parts of wear-resistant reinforcing agent, prepared in this embodiment.

[0027] Mixing: PVC masterbatch, plasticizer, heat stabilizer, antioxidant, lubricant and wear-resistant reinforcing agent are premixed and fed into the main feed port of the twin-screw extruder. Magnesium hydroxide powder and light calcium carbonate powder are premixed and fed into the side feed port. Plasticized extrusion and pelleting are carried out at 180°C to obtain high wear-resistant sheath material.

[0028] Example 2: Preparation of high abrasion-resistant sheath material for cables, as detailed below:

[0029] (1) Preparation of wear-resistant reinforcing agent

[0030] Step A1: Dimethyl difluoromalonate, mercaptoethylamine, and dimethyl sulfoxide were mixed and vacuum dehydrated for 30 min. Dry nitrogen was introduced to restore constant pressure, and trimethylaluminum was added and mixed. The mixture was heated to 120 °C and stirred at 90 r / min for 5 h. The feeding ratio of dimethyl difluoromalonate, mercaptoethylamine, trimethylaluminum, and dimethyl sulfoxide was 0.1 mmol: 0.24 mmol: 90 mg: 300 mL. Mercaptoethylamine and dimethyl difluoromalonate underwent an amino-ester exchange reaction. After the reaction was completed, dimethyl sulfoxide and low-boiling substances generated by amino-ester exchange were removed by rotary evaporation under reduced pressure. The substrate was washed with water, the aqueous phase was separated, and the substrate was vacuum dried to obtain the modified monomer.

[0031] Step A2: Glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene are added and mixed. The mixture is heated to 60°C, and stirred at 120 rpm with 200 W / m² heat. 2 The reaction was carried out under ultraviolet irradiation for 3.6 hours. The feed ratio of glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173 and toluene was 0.1 mol: 0.1 mol: 0.15 g: 1.2 mL: 200 mL. The modified monomer reacted with glyceryl dimethacrylate in an addition reaction. After the reaction was completed, toluene was removed by rotary evaporation. The product was then washed with ethanol and dried to obtain the wear-resistant reinforcing agent.

[0032] (2) Preparation of high wear-resistant protective sleeve material

[0033] Ingredients: By weight, 100 parts of PVC masterbatch, using commercially available SG-5 type PVC raw material; 30 parts of plasticizer, using industrial-grade epoxidized soybean oil and dioctyl phthalate in equal weight ratio; 3 parts of heat stabilizer, using GP-283 type calcium-zinc heat stabilizer; 0.22 parts of antioxidant, using antioxidant 1076 and antioxidant 168 in a weight ratio of 2:1; 2.4 parts of lubricant, using H3240 type microcrystalline wax; 20 parts of magnesium hydroxide powder, using commercially available flame retardant grade powder; 10 parts of light calcium carbonate powder, using commercially available 200 mesh powder; and 5 parts of wear-resistant reinforcing agent, prepared in this embodiment.

[0034] Mixing: PVC masterbatch, plasticizer, heat stabilizer, antioxidant, lubricant and wear-resistant reinforcing agent are premixed and fed into the main feed port of the twin-screw extruder. Magnesium hydroxide powder and light calcium carbonate powder are premixed and fed into the side feed port. Plasticized extrusion and pelleting are carried out at 190°C to obtain high wear-resistant sheath material.

[0035] Example 3: Preparation of high abrasion-resistant sheath material for cables, as detailed below:

[0036] (1) Preparation of wear-resistant reinforcing agent

[0037] Step A1: Dimethyl 2-fluoromalonate, mercaptoethylamine, and dimethyl sulfoxide were mixed and vacuum dehydrated for 30 min. Dry nitrogen was introduced to restore constant pressure, and trimethylaluminum was added and mixed. The mixture was heated to 100 °C and stirred at 60 r / min for 4 h. The feeding ratio of dimethyl 2-fluoromalonate, mercaptoethylamine, trimethylaluminum, and dimethyl sulfoxide was 0.1 mmol: 0.23 mmol: 70 mg: 240 mL. Mercaptoethylamine and dimethyl 2-fluoromalonate underwent an amino-ester exchange reaction. After the reaction was completed, dimethyl sulfoxide and low-boiling substances generated by amino-ester exchange were removed by rotary evaporation under reduced pressure. The substrate was washed with water, the aqueous phase was separated, and the substrate was vacuum dried to obtain the modified monomer.

[0038] Step A2: Glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene are added and mixed. The mixture is heated to 50°C, and stirred at 90 rpm with 150 W / m². 2 The reaction was carried out under ultraviolet irradiation for 3 hours. The feed ratio of glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173 and toluene was 0.1 mol: 0.1 mol: 0.12 g: 1 mL: 170 mL. The modified monomer reacted with glyceryl dimethacrylate in an addition reaction. After the reaction was completed, toluene was removed by rotary evaporation. The product was then washed with ethanol and dried to obtain the wear-resistant reinforcing agent.

[0039] (2) Preparation of high wear-resistant protective sleeve material

[0040] Ingredients: By weight, 100 parts of PVC masterbatch, made from commercially available SG-5 type PVC raw material; 25 parts of plasticizer, made from industrial-grade epoxidized soybean oil and dioctyl phthalate in equal weight ratio; 2.7 parts of heat stabilizer, made from GP-283 type calcium-zinc heat stabilizer; 0.2 parts of antioxidant, made from antioxidant 1076 and antioxidant 168 in a weight ratio of 2:1; 2.8 parts of lubricant, made from H3240 type microcrystalline wax; 18 parts of magnesium hydroxide powder, made from commercially available flame retardant grade powder; 20 parts of light calcium carbonate powder, made from commercially available 325 mesh powder; and 8 parts of wear-resistant reinforcing agent, prepared in this embodiment.

[0041] Mixing: PVC masterbatch, plasticizer, heat stabilizer, antioxidant, lubricant and wear-resistant reinforcing agent are premixed and fed into the main feed port of the twin-screw extruder. Magnesium hydroxide powder and light calcium carbonate powder are premixed and fed into the side feed port. Plasticized extrusion and pelleting are carried out at 180°C to obtain high wear-resistant sheath material.

[0042] Example 4: Preparation of high abrasion-resistant sheath material for cables, as detailed below:

[0043] (1) Preparation of wear-resistant reinforcing agent

[0044] Step A1: Dimethyl difluoromalonate, mercaptoethylamine, and dimethyl sulfoxide were mixed and vacuum dehydrated for 30 min. Dry nitrogen was introduced to restore the pressure to constant, and trimethylaluminum was added and mixed. The mixture was heated to 115 °C and stirred at 90 r / min for 5.5 h. The ratio of dimethyl difluoromalonate, mercaptoethylamine, trimethylaluminum, and dimethyl sulfoxide was 0.1 mmol: 0.24 mmol: 80 mg: 280 mL. Mercaptoethylamine and dimethyl difluoromalonate underwent an amino-ester exchange reaction. After the reaction was completed, dimethyl sulfoxide and low-boiling substances generated by amino-ester exchange were removed by rotary evaporation under reduced pressure. The substrate was washed with water, the aqueous phase was separated, and the substrate was vacuum dried to obtain the modified monomer.

[0045] Step A2: Glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene are added and mixed. The mixture is heated to 60°C, and stirred at 120 rpm with 200 W / m² heat. 2 The reaction was carried out under ultraviolet irradiation for 4 hours. The feed ratio of glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173 and toluene was 0.1 mol: 0.1 mol: 0.13 g: 1.1 mL: 180 mL. The modified monomer reacted with glyceryl dimethacrylate in an addition reaction. After the reaction was completed, toluene was removed by rotary evaporation. The product was then washed with ethanol and dried to obtain the wear-resistant reinforcing agent.

[0046] (2) Preparation of high wear-resistant protective sleeve material

[0047] Ingredients: By weight, 100 parts of PVC masterbatch, using commercially available SG-5 type PVC raw material; 28 parts of plasticizer, using industrial-grade epoxidized soybean oil and dioctyl phthalate in equal weight ratio; 2.7 parts of heat stabilizer, using GP-283 type calcium-zinc heat stabilizer; 0.19 parts of antioxidant, using antioxidant 1076 and antioxidant 168 in a weight ratio of 2:1; 2.6 parts of lubricant, using H3240 type microcrystalline wax; 16 parts of magnesium hydroxide powder, using commercially available flame retardant grade powder; 17 parts of light calcium carbonate powder, using commercially available 325 mesh powder; and 7 parts of wear-resistant reinforcing agent, prepared in this embodiment.

[0048] Mixing: PVC masterbatch, plasticizer, heat stabilizer, antioxidant, lubricant and wear-resistant reinforcing agent are premixed and fed into the main feed port of the twin-screw extruder. Magnesium hydroxide powder and light calcium carbonate powder are premixed and fed into the side feed port. Plasticized extrusion and pelleting are carried out at 190°C to obtain high wear-resistant sheath material.

[0049] Comparative Example 1, referring to Example 4, replaces the wear-resistant reinforcing agent with 1.2 parts of tridecafluorooctyltrimethoxysilane, and the rest of the implementation process is exactly the same.

[0050] Comparative Example 2, referring to Comparative Example 1, increased the amount of plasticizer to 35 parts, magnesium hydroxide micro powder to 22 parts, light calcium carbonate powder to 25 parts, and tridecafluorooctyltrimethoxysilane to 1.6 parts, with the rest of the implementation process being exactly the same.

[0051] The high-wear-resistant sheath material prepared above was hot-pressed into sheets at 170℃ and 5MPa, and samples were taken. The coefficient of friction was tested according to GB / T 40721-2021 standard, with the friction surface material being aluminum alloy. The wear coefficient of the samples was tested using the drop shot method to simulate dragging wear during cable use, according to ASTM D968-22 standard. A sandblasting wear test was also conducted on the samples, using 100-mesh machine-made abrasive for 60 seconds, and the roughness change rate and wear amount before and after wear were measured. Specific test results are shown in Table 1.

[0052] Table 1

[0053] Example 1 0.4103 58.0 9.37 32.9 Example 2 0.4329 50.1 10.65 36.5 Example 3 0.4055 56.7 7.89 30.1 Example 4 0.3952 59.4 8.66 27.9 Comparative Example 1 0.3810 29.6 20.42 69.3 Comparative Example 2 0.4291 35.2 14.37 40.7

[0054] As shown in Table 1, the friction coefficient of the sheath material prepared in the example is similar to that of the comparative example after molding. It has a high wear coefficient and low wear amount, exhibiting excellent wear resistance. After wear, the surface becomes smoother and maintains good surface quality.

[0055] Samples were taken from the above-mentioned sheet material and subjected to tensile testing according to GB / T 1040.2-2022 and impact testing according to GB / T1843-2008. The specific test results are shown in Table 2.

[0056] Table 2

[0057]

[0058]

[0059] As shown in Table 2, the sheath material prepared in the example maintains excellent overall strength and toughness after molding. In contrast, in Comparative Example 2, the strength and toughness of the material deteriorated drastically as the amount of wear-resistant particles increased.

[0060] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high abrasion-resistant sheath material for cables, characterized in that, The product comprises, by weight: 100 parts PVC masterbatch, 20-30 parts plasticizer, 2.5-3 parts heat stabilizer, 0.18-0.22 parts antioxidant, 2.2-2.8 parts lubricant, 15-20 parts magnesium hydroxide powder, 10-20 parts light calcium carbonate powder, and 5-10 parts wear-resistant reinforcing agent. The wear-resistant reinforcing agent is prepared by the following method: Step A1: Mix difluorodimethyl ester, mercaptoethylamine and dimethyl sulfoxide and remove water under vacuum. Purge with dry nitrogen to constant pressure, add trimethylaluminum and mix well. Heat to 100-120℃ and stir for 4-5.5 h to obtain the modified monomer. Step A2: Mix glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173, and toluene, and heat to 50-60℃ at 150-200W / m 2 The wear-resistant reinforcing agent is obtained by stirring under ultraviolet light for 3-4 hours.

2. The high abrasion-resistant sheath material for cables according to claim 1, characterized in that, The feed ratio of difluorodimethyl ester, mercaptoethylamine, trimethylaluminum and dimethyl sulfoxide is 0.1 mmol: 0.22-0.24 mmol: 60-90 mg: 220-300 mL.

3. The high abrasion-resistant sheath material for cables according to claim 2, characterized in that, Fluorinated dimethyl esters are either monofluorodimethyl esters or difluorodimethyl esters.

4. The high abrasion-resistant sheath material for cables according to claim 3, characterized in that, Fluorinated dimethyl ester is one of dimethyl 2-fluoromalonate and dimethyl difluoromalonate.

5. The high abrasion-resistant sheath material for cables according to claim 2, characterized in that, The feed ratio of glyceryl dimethacrylate, modified monomer, dimethyl azobisisobutyrate, photoinitiator 1173 and toluene is 0.1mol: 0.1mol: 0.1-0.15g: 0.8-1.2mL: 150-200mL.

6. The high abrasion-resistant sheath material for cables according to claim 1, characterized in that, The plasticizer is a compound of epoxidized soybean oil and dioctyl phthalate.

7. The high abrasion-resistant sheath material for cables according to claim 1, characterized in that, The lubricant is microcrystalline wax.

8. The high abrasion-resistant sheath material for cables according to claim 1, characterized in that, The fineness of light calcium carbonate powder is 200-325 mesh.

9. A method for preparing a high abrasion-resistant sheath material for cables according to any one of claims 1-8, characterized in that, Specifically, PVC masterbatch, plasticizer, heat stabilizer, antioxidant, lubricant and wear-resistant enhancer are premixed and fed into the main feed port of a twin-screw extruder, while magnesium hydroxide powder and light calcium carbonate powder are premixed and fed into the side feed port. The mixture is then plasticized, extruded and pelletized at 180-190℃ to obtain a high wear-resistant sheath material.

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