Polyvinyl chloride material for transparent high-flame-retardant optical cable and preparation method of polyvinyl chloride material

Abstract

The invention belongs to the technical field of polyvinyl chloride materials, and particularly relates to a transparent high-flame-retardant polyvinyl chloride material for an optical cable and a preparation method of the transparent high-flame-retardant polyvinyl chloride material. 8 to 12 parts of tris (2, 3-dibromopropyl) phosphate; 6 to 10 parts of aluminum hydroxide; 3 to 7 parts of silicon dioxide nanoparticles; 2 to 4 parts of calcium stearate; 5 to 9 parts of dioctyl phthalate; 0.5 to 1.5 parts of an antioxidant 1010; 0.3 to 0.7 part of an ultraviolet absorbent UV-326; 3 to 5 parts of plasticizer TOTM; and 2 to 4 parts of a compatilizer SEBS. By accurately controlling the proportion of all the components and particularly selecting the specific plasticizer TOTM, the antioxidant 1010, the ultraviolet absorbent UV-326 and other components, the flame retardant property and optical transparency of the material are improved, and the mechanical property and long-term stability of the material under complex environmental conditions are enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of polyvinyl chloride materials, and particularly relates to a transparent highly flame-retardant polyvinyl chloride material for optical cables and a preparation method thereof. Background Art

[0002] With the rapid development of communications technology, the requirements for optical cable material performance are increasing. Existing transparent, highly flame-retardant polyvinyl chloride (PVC) materials used in optical cables often struggle to maintain both long-term optical and mechanical stability in environments with extreme humidity fluctuations. Furthermore, during natural degradation, traditional PVC materials may release harmful substances, posing a potential threat to local ecosystems.

[0003] Some solutions currently on the market attempt to improve the performance of PVC materials by adding different types of plasticizers, flame retardants, and stabilizers. For example, some solutions use traditional phthalate plasticizers to enhance the flexibility and processing properties of the material, but these plasticizers may not be sufficiently durable and may migrate into the environment in some cases, causing health and environmental problems. In addition, to improve flame retardancy, many formulations have added brominated flame retardants, such as tris(2,3-dibromopropyl) phosphate (TDBPP). Although this significantly improves the flame retardant effect, the physical and optical properties of the material may still be affected in extreme environments. Summary of the Invention

[0004] The purpose of the present invention is to provide a transparent highly flame-retardant polyvinyl chloride material for optical cables and a preparation method thereof, which will not release harmful substances during the natural degradation process, thereby reducing the negative impact on the ecological environment, so as to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a transparent highly flame-retardant polyvinyl chloride material for optical cables, wherein the polyvinyl chloride material is composed of: polyvinyl chloride: 40-50 parts; tris(2,3-dibromopropyl) phosphate: 8-12 parts; aluminum hydroxide: 6-10 parts; silicon dioxide nanoparticles: 3-7 parts; calcium stearate: 2-4 parts; dioctyl phthalate: 5-9 parts; antioxidant 1010: 0.5-1.5 parts; ultraviolet absorber UV-326: 0.3-0.7 parts; plasticizer TOTM: 3-5 parts; and compatibilizer SEBS: 2-4 parts.

[0006] Preferably, the antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl)phosphite, and n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0007] Preferably, the particle size distribution of the aluminum hydroxide is between 0.5-2 μm.

[0008] Preferably, the average particle size of the silicon dioxide nanoparticles is 20-50 nm.

[0009] Preferably, the plasticizer is selected from one or more of environmentally friendly dioctyl terephthalate, epoxidized soybean oil, and trioctyl trimellitate.

[0010] On the other hand, the present invention provides a method for preparing a transparent highly flame-retardant polyvinyl chloride material for optical cables, comprising the following steps:

[0011] Premixing polyvinyl chloride and tris(2,3-dibromopropyl) phosphate in a high-speed mixer at a temperature of 80-90° C. for 5-10 minutes to obtain a mixture A;

[0012] Aluminum hydroxide was added to mixture A and stirring was continued for 5 minutes;

[0013] Adding silica nanoparticles, calcium stearate, dioctyl phthalate, antioxidant 1010, ultraviolet absorber UV-326, plasticizer TOTM, and compatibilizer SEBS, stirring evenly, and then heating to 110-120° C. for 15 minutes to obtain mixture B;

[0014] The mixture B is fed into a twin-screw extruder, melt-blended at 160-180° C., formed into pellets by the extruder, cooled and dried, and injection-molded to prepare a final product.

[0015] Preferably, the rotation speed of the high-speed mixer is between 800-1200 rpm; the screw speed of the twin-screw extruder is set to 100-200 rpm.

[0016] Preferably, the die temperature of the extruder is between 170-180°C.

[0017] Preferably, during the granule drying process, a fluidized bed dryer is used to dry the granules at a drying temperature of 60-70° C. for 2-3 hours.

[0018] Preferably, the mold temperature during the injection molding process is maintained at 40-50° C. and the injection pressure is 80-120 MPa.

[0019] Technical effects and advantages of the present invention: The transparent highly flame-retardant polyvinyl chloride material for optical cables and the preparation method thereof proposed in the present invention have the following advantages over the prior art:

[0020] By controlling the proportions of the various components, particularly selecting specific ingredients such as plasticizer TOTM, antioxidant 1010, and ultraviolet absorber UV-326, the present invention not only improves the flame retardancy and optical transparency of the material, but also enhances its mechanical properties and long-term stability under complex environmental conditions. More importantly, the material formulation of the present invention does not release harmful substances during natural degradation, thereby reducing the negative impact on the ecological environment. This method provides a new approach for manufacturing high-performance, environmentally friendly optical cables and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a method for preparing a transparent highly flame-retardant polyvinyl chloride material for optical cables. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] The present invention provides a transparent highly flame-retardant polyvinyl chloride material for optical cables, wherein the raw materials of the polyvinyl chloride material include:

[0025] Polyvinyl chloride (PVC): 40 parts;

[0026] Tris(2,3-dibromopropyl) phosphate (TDBPP): 8 parts;

[0027] Aluminum hydroxide (Al(OH)3): 6 parts;

[0028] Silica nanoparticles: 3 parts;

[0029] Calcium stearate (CaSt): 2 parts;

[0030] Dioctyl phthalate (DOP): 5 parts;

[0031] Antioxidant 1010: 0.5 parts;

[0032] Ultraviolet absorber UV-326: 0.3 parts;

[0033] Plasticizer TOTM: 3 parts;

[0034] Compatibilizer SEBS: 2 parts.

[0035] By precisely controlling the proportions of each component, especially adding an appropriate amount of silica nanoparticles, the transparency of the material is effectively improved. The use of a specific ratio of aluminum hydroxide and calcium stearate enhances the mechanical strength of the material, ensuring durability in complex environments. The combination of tris(2,3-dibromopropyl) phosphate and aluminum hydroxide provides excellent flame retardant properties, allowing the material to withstand extreme conditions. The selection of environmentally friendly plasticizers such as TOTM and epoxidized soybean oil avoids the environmental pollution problems that may be caused by traditional plasticizers. At the same time, the use of antioxidants and UV absorbers further extends the service life of the material and reduces the potential harm of waste to the ecosystem.

[0036] In a preferred embodiment, the antioxidant is selected from one or more of the following:

[0037] Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0038] Tris(2,4-di-tert-butylphenyl)phosphite;

[0039] β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0040] The particle size of aluminum hydroxide is distributed at 0.5 μm, the average particle size of silicon dioxide nanoparticles is 20 nm, and the plasticizer is selected from one or more of environmentally friendly dioctyl terephthalate, epoxidized soybean oil, and trioctyl trimellitate.

[0041] The above-mentioned method of using polyvinyl chloride material for transparent high flame retardant optical cable is as follows: Figure 1 As shown, the following steps are included:

[0042] Polyvinyl chloride and tris(2,3-dibromopropyl) phosphate were premixed in a high-speed mixer at 80° C. for 5 minutes to obtain a mixture A; the rotation speed of the high-speed mixer was set to 800 rpm.

[0043] Aluminum hydroxide was added to mixture A and stirring was continued for 5 minutes.

[0044] Silica nanoparticles, calcium stearate, dioctyl phthalate, antioxidant 1010, ultraviolet absorber UV-326, plasticizer TOTM and compatibilizer SEBS were added, stirred evenly and then heated to 110° C. for 15 minutes to obtain mixture B.

[0045] The mixture B was fed into a twin-screw extruder, melt-blended at 160° C., and formed into pellets by the extruder.

[0046] The obtained granules were cooled and dried, and then dried in a fluidized bed dryer at a drying temperature of 60° C. for 2 hours.

[0047] The pellets were injection molded to prepare a final product, wherein the die head temperature of the extruder was controlled at 170° C., the mold temperature was maintained at 40° C., and the injection pressure was 80 MPa.

[0048] The transparent highly flame-retardant polyvinyl chloride material for optical cables provided by the present invention not only has excellent physical and chemical properties, but also takes environmental protection requirements into account, and is suitable for various high-end application scenarios.

[0049] Example 2

[0050] The present invention provides a transparent highly flame-retardant polyvinyl chloride material for optical cables, wherein the raw materials of the polyvinyl chloride material include:

[0051] Polyvinyl chloride (PVC): 45 parts;

[0052] Tris(2,3-dibromopropyl) phosphate (TDBPP): 10 parts;

[0053] Aluminum hydroxide (Al(OH)3): 8 parts;

[0054] Silica nanoparticles: 5 parts;

[0055] Calcium stearate (CaSt): 3 parts;

[0056] Dioctyl phthalate (DOP): 7 parts;

[0057] Antioxidant 1010: 1 part;

[0058] Ultraviolet absorber UV-326: 0.5 parts;

[0059] Plasticizer TOTM: 4 parts;

[0060] Compatibilizer SEBS: 3 parts.

[0061] In a preferred embodiment, the antioxidant is selected from one or more of the following:

[0062] Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0063] Tris(2,4-di-tert-butylphenyl)phosphite;

[0064] β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0065] The particle size of aluminum hydroxide is distributed at 1.5 μm, the average particle size of silicon dioxide nanoparticles is 35 nm, and the plasticizer is selected from one or more of environmentally friendly dioctyl terephthalate, epoxidized soybean oil, and trioctyl trimellitate.

[0066] The above-mentioned method of using polyvinyl chloride material for transparent high flame retardant optical cable is as follows: Figure 1 As shown, the following steps are included:

[0067] Polyvinyl chloride and tris(2,3-dibromopropyl) phosphate were premixed in a high-speed mixer at 85° C. for 7 minutes to obtain a mixture A; the rotation speed of the high-speed mixer was set to 1000 rpm.

[0068] Aluminum hydroxide was added to mixture A and stirring was continued for 5 minutes.

[0069] Silica nanoparticles, calcium stearate, dioctyl phthalate, antioxidant 1010, ultraviolet absorber UV-326, plasticizer TOTM and compatibilizer SEBS were added, stirred evenly and then heated to 115° C. for 15 minutes to obtain mixture B.

[0070] The mixture B was fed into a twin-screw extruder, melt-blended at 170° C., and formed into pellets by the extruder.

[0071] The obtained granules were cooled and dried, and then dried in a fluidized bed dryer at a drying temperature of 65° C. for 2.5 hours.

[0072] The pellets were injection molded to prepare a final product, wherein the die head temperature of the extruder was controlled at 175° C., the mold temperature was maintained at 45° C., and the injection pressure was 100 MPa.

[0073] This formula and preparation method further optimizes the performance of transparent highly flame-retardant polyvinyl chloride materials for optical cables, specifically:

[0074] Enhanced flame retardancy: Increasing the proportion of tris(2,3-dibromopropyl) phosphate to 10 parts and using aluminum hydroxide with a specific particle size distribution significantly improves the flame retardancy of the material, enabling it to remain stable in more harsh environments.

[0075] Improved optical properties: Selecting silica nanoparticles of appropriate particle size (average particle size 35nm) can effectively improve the transparency of the material while avoiding scattering caused by particles that are too large.

[0076] Excellent mechanical strength: Adjusting the proportions of each component, especially increasing the content of calcium stearate and dioctyl phthalate, enhances the mechanical strength and flexibility of the material, ensuring its durability during long-term use.

[0077] Environmentally friendly: The use of environmentally friendly plasticizers such as TOTM and epoxidized soybean oil not only improves the durability and processing properties of the material, but also reduces negative impacts on the environment. The use of antioxidants and UV absorbers also extends the service life of the material and reduces the potential harm of waste to the ecosystem.

[0078] In summary, the transparent highly flame-retardant polyvinyl chloride material for optical cable provided in this embodiment achieves excellent physical and chemical properties and environmental characteristics by precisely controlling the raw material composition and preparation process parameters, and is suitable for manufacturing high-performance, long-life optical cable products.

[0079] Example 3

[0080] The present invention provides a transparent highly flame-retardant polyvinyl chloride material for optical cables, wherein the raw materials of the polyvinyl chloride material include:

[0081] Polyvinyl chloride (PVC): 50 parts;

[0082] Tris(2,3-dibromopropyl) phosphate (TDBPP): 12 parts;

[0083] Aluminum hydroxide (Al(OH)3): 10 parts;

[0084] Silica nanoparticles: 7 parts;

[0085] Calcium stearate (CaSt): 4 parts;

[0086] Dioctyl phthalate (DOP): 9 parts;

[0087] Antioxidant 1010: 1.5 parts;

[0088] Ultraviolet absorber UV-326: 0.7 parts;

[0089] Plasticizer TOTM: 5 parts;

[0090] Compatibilizer SEBS: 4 parts.

[0091] In a preferred embodiment, the antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl)phosphite, and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0092] In a preferred embodiment, the particle size distribution of the aluminum hydroxide is 2 μm.

[0093] In a preferred embodiment, the average particle size of the silicon dioxide nanoparticles is 50 nm.

[0094] In a preferred embodiment, the plasticizer is selected from one or more of environmentally friendly dioctyl terephthalate, epoxidized soybean oil, and trioctyl trimellitate.

[0095] The above-mentioned method of using polyvinyl chloride material for transparent high flame retardant optical cable is as follows: Figure 1 As shown, the following steps are included:

[0096] Polyvinyl chloride and tris(2,3-dibromopropyl) phosphate were premixed in a high-speed mixer at 90° C. for 10 minutes to obtain a mixture A; the rotation speed of the high-speed mixer was set to 1200 rpm.

[0097] Aluminum hydroxide was added to mixture A and stirring was continued for 5 minutes.

[0098] Silica nanoparticles, calcium stearate, dioctyl phthalate, antioxidant 1010, ultraviolet absorber UV-326, plasticizer TOTM and compatibilizer SEBS were added, stirred evenly and then heated to 120° C. for 15 minutes to obtain mixture B.

[0099] The mixture B was fed into a twin-screw extruder, melt-blended at 180° C., and formed into pellets by the extruder.

[0100] The obtained granules were cooled and dried, and then dried in a fluidized bed dryer at a drying temperature of 70° C. for 3 hours.

[0101] The pellets were injection molded to prepare a final product, wherein the die head temperature of the extruder was controlled at 180° C., the mold temperature was maintained at 50° C., and the injection pressure was 120 MPa.

[0102] Technical Effects

[0103] This formula and preparation method further optimizes the performance of transparent highly flame-retardant polyvinyl chloride materials for optical cables, specifically:

[0104] Excellent flame retardancy: Increasing the proportion of tris(2,3-dibromopropyl) phosphate to 12 parts and using aluminum hydroxide with a larger particle size distribution (2μm) significantly improves the flame retardancy of the material, allowing it to remain stable in extreme environments.

[0105] Excellent optical properties: Selecting silica nanoparticles of appropriate particle size (average particle size 50nm) can improve the transparency of the material while avoiding light scattering caused by overly large particles, thereby ensuring the transparency of the material.

[0106] Enhanced mechanical strength: Adjusting the proportions of each component, especially increasing the content of calcium stearate and dioctyl phthalate, enhances the mechanical strength and flexibility of the material, ensuring its durability in long-term use.

[0107] Environmentally friendly: The use of environmentally friendly plasticizers such as TOTM and epoxidized soybean oil not only improves the material's durability and processing properties, but also reduces negative environmental impact. Furthermore, the use of antioxidants and UV absorbers extends the material's service life and reduces the potential harm of waste to the ecosystem.

[0108] Efficient production process: By optimizing mixing time and temperature, and precisely controlling extrusion and injection molding parameters, the efficiency and stability of the production process are ensured, which is conducive to large-scale production and application.

[0109] In summary, the transparent highly flame-retardant polyvinyl chloride material for optical cable provided in this embodiment achieves excellent physical and chemical properties and environmental characteristics by precisely controlling the raw material composition and preparation process parameters, and is suitable for manufacturing high-performance, long-life optical cable products.

[0110] Comparative Example: Comparison with Example 1:

[0111] In order to better demonstrate the advantages of the transparent highly flame-retardant polyvinyl chloride material for optical cables provided by the present invention, the present invention provides a comparative example in which a traditional formula is used to prepare the PVC material and compared with Example 1.

[0112] Comparative example formula and preparation method:

[0113] Raw material composition and ratio:

[0114] Polyvinyl chloride (PVC): 40 parts;

[0115] Traditional phthalate plasticizer (DOP): 5 parts;

[0116] Aluminum hydroxide (Al(OH)3): 6 parts;

[0117] Silica nanoparticles: 3 parts;

[0118] Calcium stearate (CaSt): 2 parts;

[0119] Antioxidant 1010: 0.5 parts;

[0120] Ultraviolet absorber UV-326: 0.3 parts;

[0121] Lack of tris(2,3-dibromopropyl) phosphate (TDBPP), plasticizer TOTM, and compatibilizer SEBS.

[0122] Preparation method:

[0123] Polyvinyl chloride and aluminum hydroxide were premixed in a high-speed mixer at 80° C. for 5 minutes to obtain a mixture A; the rotation speed of the high-speed mixer was set to 800 rpm.

[0124] Silica nanoparticles, calcium stearate, dioctyl phthalate, antioxidant 1010, and ultraviolet absorber UV-326 were added to mixture A, stirred evenly, and then heated to 110° C. for 15 minutes to obtain mixture B.

[0125] The mixture B was fed into a twin-screw extruder, melt-blended at 160° C., pelletized by the extruder, cooled and dried, and injection-molded to prepare a final product.

[0126] Experimental data and effect comparison

[0127] Test items Example 1 Comparative Example Flame retardant performance (UL94 grade) V-0 V-2 Light transmittance (%) 85 78 Tensile strength (MPa) 28 22 Elongation at break (%) 300 220 Thermal stability (min) 60 45 Environmental impact No harmful substances released May release hazardous substances

[0128] Result analysis:

[0129] Flame retardant properties: The material in Example 1 achieved UL94 V-0 rating, while the comparative example only achieved V-2 rating. This indicates that the combination of tris(2,3-dibromopropyl) phosphate (TDBPP) and aluminum hydroxide significantly improved the flame retardant properties of the material.

[0130] Light transmittance: The light transmittance of Example 1 is 85%, while that of the comparative example is only 78%. This shows that the selection and specific particle size distribution of silica nanoparticles are crucial for improving transparency.

[0131] Mechanical Properties: The tensile strength and elongation at break of Example 1 were 28 MPa and 300%, respectively, significantly better than the 22 MPa and 220% of the comparative example. This indicates that the plasticizer TOTM and calcium stearate contribute to enhancing the mechanical strength and flexibility of the material.

[0132] Thermal stability: The material of Example 1 remained stable at high temperature for 60 minutes, while the comparative example remained stable for only 45 minutes. This demonstrates the effectiveness of antioxidant 1010 and UV absorber UV-326, which together enhance the thermal stability of the material.

[0133] Environmental impact: The material in Example 1 does not release harmful substances during natural degradation, reducing the negative impact on the ecological environment. However, the comparative example uses traditional phthalate plasticizers, which may release harmful substances during long-term use or disposal.

[0134] The above experimental data demonstrates that the transparent, highly flame-retardant polyvinyl chloride material for optical cable of Example 1 significantly outperforms the conventional formulation of the comparative example in terms of flame retardancy, optical properties, mechanical properties, and environmental performance. Therefore, the present invention provides a high-performance and environmentally friendly polyvinyl chloride material suitable for manufacturing high-end optical cable products.

[0135] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A transparent highly flame-retardant polyvinyl chloride material for optical cables, characterized by: The polyvinyl chloride material comprises: polyvinyl chloride: 40-50 parts; tris(2,3-dibromopropyl) phosphate: 8-12 parts; The raw material composition includes: aluminum hydroxide: 6-10 parts; silicon dioxide nanoparticles: 3-7 parts; calcium stearate: 2-4 parts; dioctyl phthalate: 5-9 parts; antioxidant 1010: 0.5-1.5 parts; ultraviolet absorber UV-326: 0.3-0.7 parts; plasticizer TOTM: 3-5 parts; and compatibilizer SEBS: 2-4 parts.

2. The transparent highly flame-retardant polyvinyl chloride material for optical cable according to claim 1, characterized in that: The antioxidant is selected from one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris(2,4-di-tert-butylphenyl)phosphite, and n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

3. The transparent highly flame-retardant polyvinyl chloride material for optical cable according to claim 1, characterized in that: The particle size distribution of the aluminum hydroxide is between 0.5-2 μm.

4. The transparent highly flame-retardant polyvinyl chloride material for optical cable according to claim 1, characterized in that: The average particle size of the silicon dioxide nanoparticles is 20-50 nm.

5. The transparent highly flame-retardant polyvinyl chloride material for optical cable according to claim 1, characterized in that: The plasticizer is selected from one or more of environmentally friendly dioctyl terephthalate, epoxidized soybean oil, and trioctyl trimellitate.

6. A method for preparing the transparent highly flame-retardant polyvinyl chloride material for optical cable according to any one of claims 1 to 5, characterized in that: The steps include: Premixing polyvinyl chloride and tris(2,3-dibromopropyl) phosphate in a high-speed mixer at a temperature of 80-90° C. for 5-10 minutes to obtain a mixture A; Aluminum hydroxide was added to mixture A and stirring was continued for 5 minutes; Adding silica nanoparticles, calcium stearate, dioctyl phthalate, antioxidant 1010, ultraviolet absorber UV-326, plasticizer TOTM, and compatibilizer SEBS, stirring evenly, and then heating to 110-120° C. for 15 minutes to obtain mixture B; The mixture B is fed into a twin-screw extruder, melt-blended at 160-180° C., formed into pellets by the extruder, cooled and dried, and injection-molded to prepare a final product.

7. The method according to claim 6, characterized in that: The rotation speed of the high-speed mixer is between 800-1200 rpm; the screw rotation speed of the twin-screw extruder is set to 100-200 rpm.

8. The method according to claim 6, wherein: The die temperature of the extruder is between 170-180°C.

9. The method according to claim 6, wherein: During the granule drying process, a fluidized bed dryer is used to dry the granules at a temperature of 60-70° C. for 2-3 hours.

10. The method according to claim 6, wherein: During the injection molding process, the mold temperature is maintained at 40-50°C and the injection pressure is 80-120 MPa.

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