A high speed extrusion process for flame retardant polyethylene sheaths

Abstract

The application discloses a kind of high-speed extrusion processes of flame-retardant polyethylene sheath, including, low-smoke halogen-free flame-retardant polyethylene is uniformly mixed with additive, and is premixed by twin-screw extruder Processed, the material after mixing is sufficiently dried;Extruder head and screw design optimization;Again screw cylinder double cooling;Select mold type and mold material and optimize;Adjust process parameters, optimize extrusion speed.The application significantly improves the extrusion speed of flame-retardant polyethylene sheath by optimizing the temperature setting of each section of extruder and using advanced mold design, using screw cylinder double cooling cooling mode, realizes the precise control of extruder temperature, ensures the stability of material;Effectively reduce the surface defects such as bamboo joint, ring thinning, hole and other surface defects in the extrusion process, the surface of the produced flame-retardant polyethylene sheath is smooth and dense, without air hole, the quality of section is significantly improved.

Description

Technical Field

[0001] The invention relates to the technical field of sheath preparation, in particular to a high-speed extrusion process for a flame-retardant polyethylene sheath. Background Art

[0002] With the rapid development of modern society and the shortening of the distance between urban and rural areas, the demand for wires and cables has further increased. The requirements for wires and cables have also increased accordingly, such as the ability to prevent flames from burning in the event of a fire, low smoke emission, and no halogen gas release. This has led to the development of halogen-free, low-smoke, flame-retardant cables, which are widely used in high-rise buildings and crowded places. The revised national standard GB / T12706.1-2020 also includes halogen-free, low-smoke, flame-retardant cables. Competition is in the market, and competitiveness is in the field. As a wire and cable manufacturer, how to better control the stability of product quality on site is the unremitting goal of all employees. The extrusion process of halogen-free, low-smoke, flame-retardant sheathing materials is not the same as the extrusion process of polyvinyl chloride, ordinary polyethylene, etc., and is much more complex. However, with long-term exploration and summary, problems will always be solved.

[0003] While the production technology for low-smoke, halogen-free, flame-retardant polyethylene is relatively mature, many technical challenges remain during actual production. These include slow production speeds, low glue output, high extrusion pressures, and high current draws on the extruder. During the production of flame-retardant polyethylene outer sheaths, the extruder's temperature control is unstable, with a significant difference between the set and actual temperatures. The sheath's surface develops a bamboo-like texture, becoming rough, hairy, and porous. Furthermore, the material discharge during extrusion is unstable, resulting in ring-shaped thinning and holes. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the existing flame retardant polyethylene sheath high-speed extrusion process, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is how to provide a high-speed extrusion process for a flame-retardant polyethylene sheath.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] An embodiment of the present invention provides a high-speed extrusion process for a flame-retardant polyethylene sheath, which includes uniformly mixing low-smoke halogen-free flame-retardant polyethylene with additives, premixing the mixture through a twin-screw mixer, and fully drying the mixed material; optimizing the design of the extruder head and the screw; then performing double cooling on the screw and barrel; selecting and optimizing the mold type and mold material; and adjusting the process parameters to optimize the extrusion speed.

[0009] As a preferred solution of the flame-retardant polyethylene sheath high-speed extrusion process described in the present invention, the low-smoke halogen-free flame-retardant polyethylene is uniformly mixed with additives, and pre-mixed through a twin-screw mixer, and the mixed material is fully dried, including: the additives include 25-30% flame retardant, 2-5% charring agent, 0.2-0.5% antioxidant, 0.1-0.3% antistatic agent, 0.2-0.5% lubricant and 2-4% plasticizer; during the initial mixing process, the temperature is controlled below 80°C and the time does not exceed 15 minutes. During the mixing process, the ambient humidity is kept below 50%, the screw speed is set at 200-300rpm, the mixing time is 2-5 minutes, the drying is set at 70-90°C, and the drying time is 4-6 hours.

[0010] As a preferred solution for the high-speed extrusion process of the flame-retardant polyethylene sheath described in the present invention, the optimization of the design of the extruder head and screw includes: optimizing the flow channel depth and width of the colloid in the head, specifically increasing the depth and width by 5 mm each, and designing the flow channel form to reduce dead angles and optimize the material flow path; the screw uses a screw with a length-to-diameter ratio of 20 and a compression ratio of 1:1.3, optimizing the screw groove depth and spiral angle, increasing the melt cavity between the screw and the barrel, and reducing the shear heat and pressure fluctuations of the material during the extrusion process.

[0011] As a preferred solution of the flame-retardant polyethylene sheath high-speed extrusion process of the present invention, the double cooling of the screw and barrel includes: using 6 750W high-pressure centrifugal fans to air-cool the barrel, and using cooling circulating water to cool the screw, ensuring that the extruder temperature is controlled within the set value ±2°C.

[0012] As a preferred solution for the high-speed extrusion process of the flame-retardant polyethylene sheath described in the present invention, the selection and optimization of the mold type and mold material include: using a semi-extrusion tube mold with a core nozzle length of 15 mm and a mold sleeve bearing wire length of 8 mm, and placing the core head end at 1 / 2 of the mold sleeve bearing diameter, thereby reducing the stretching of the sheath material, so that the surface wrapping of the sheath is denser and the appearance is brighter when the production speed is increased; the mold material is selected to use a mold material with high thermal conductivity and strong wear resistance to reduce the adhesion of the material during the extrusion process.

[0013] As a preferred embodiment of the high-speed extrusion process for the flame-retardant polyethylene sheath of the present invention, the process parameters are adjusted to optimize the extrusion speed, including: adjusting the temperature settings of each section of the extruder according to the material formula, controlling the feed zone at 145-165°C, the compression zone at 150-170°C, the metering zone at 155-175°C, the die zone at 160-180°C, and the cooling zone at <100°C; gradually increasing the extrusion speed, monitoring the changes in current, voltage and pressure, and adjusting the extruder parameters to initially set the extruder speed to 10 rpm, current to 142 A, pressure to 50 bar, glue output to 420 kg / h, and production speed to 4.6 m / min; and gradually optimizing the process to increase the extruder speed to 15 rpm, current to 196 A, pressure to 75 bar, glue output to 578 kg / h, and production speed to 6.0 m / min.

[0014] The beneficial effects of the present invention are as follows: by optimizing the temperature settings of each section of the extruder and adopting advanced mold design, the present invention significantly improves the extrusion speed of the flame-retardant polyethylene sheath, and adopts a cooling method of dual cooling of the screw and barrel to achieve precise control of the extruder temperature and ensure the stability of the material; the present invention effectively reduces surface defects such as bamboo-shaped, ring-shaped thinning, and holes that appear during the extrusion process, and the surface of the flame-retardant polyethylene sheath produced is smooth, dense, and free of pores, and the quality of the cross-section is significantly improved. The optimized screw design and mold material selection reduce the friction between the screw and the barrel during the extrusion process, and reduce the shear heat and flow channel pressure of the material. The mold material used in the present invention has high thermal conductivity and strong wear resistance, which significantly reduces the adhesion and wear of the material to the mold during the extrusion process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0016] Figure 1 This is the process flow chart of the high-speed extrusion process of flame-retardant polyethylene sheath.

[0017] Figure 2 This is a structural diagram of a medium-voltage cross-linked polyethylene insulated, PVC inner sheathed, steel tape armored, low-smoke, halogen-free, flame-retardant polyethylene outer sheathed power cable.

[0018] Figure 3 This is a schematic diagram of the glue dispenser structure before the process technology upgrade.

[0019] Figure 4 This is a schematic diagram of the glue dispenser structure after the process technology is upgraded. DETAILED DESCRIPTION

[0020] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0023] In the description of the present invention, it should be noted that the terms "upper, lower, inner, and outer" and other references to orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] Example 1

[0025] Reference Figures 1-2 , which is an embodiment of the present invention.

[0026] A flame retardant polyethylene sheath high-speed extrusion process:

[0027] The low-smoke, halogen-free, flame-retardant polyethylene and additives were uniformly mixed and pre-mixed in a twin-screw mixer, and the mixed material was fully dried. The additives included 25% flame retardant, 2% charring agent, 0.2% antioxidant, 0.1% antistatic agent, 0.2% lubricant, and 2% plasticizer. During the initial mixing process, the temperature was controlled at 80°C for 15 minutes, the ambient humidity was maintained at 48%, the screw speed was set at 200 rpm, the mixing time was 2 minutes, and the drying temperature was set at 70°C for 4 hours.

[0028] The extruder head and screw design were optimized. The depth and width of the flow channel for the colloid inside the die were optimized, with the specific depth and width increased by 5mm each. The flow channel form was also redesigned to reduce dead angles and optimize the material flow path. The screw used an aspect ratio of 20 and a compression ratio of 1:1.3. The screw groove depth and helix angle were optimized to increase the melt cavity between the screw and the barrel, reducing shear heat and pressure fluctuations of the material during the extrusion process.

[0029] The screw and barrel are double-cooled, using 6 750W high-pressure centrifugal fans to cool the barrel, and cooling circulating water to cool the screw, ensuring that the extruder temperature is controlled within the set value ±2°C;

[0030] The mold type and mold material were selected and optimized. A semi-extrusion tube mold was used, with a core nozzle length of 15mm and a sleeve support wire length of 8mm. The core head was placed at 1 / 2 of the sleeve support diameter, which reduced the stretching of the jacket material. As a result, the jacket surface was more densely wrapped and the appearance was brighter when the production speed was increased. The mold material was selected to use a mold material with high thermal conductivity and strong wear resistance to reduce material adhesion during the extrusion process.

[0031] Adjust the process parameters, optimize the extrusion speed, adjust the temperature settings of each section of the extruder according to the material formula, control the feeding zone at 145°C, the compression zone at 150°C, the metering zone at 155°C, the die zone at 160°C, and the cooling zone at 100°C; gradually increase the extrusion speed, monitor the changes in current, voltage and pressure, and adjust the extruder parameters. Initially set the extruder speed: 10rpm, current: 142A, pressure: 50bar, glue output: 420kg / h, production speed: 4.6m / min; gradually optimize the process, the extruder speed is increased to 15rpm, current: 196A, pressure: 75bar, glue output: 578kg / h, production speed: 6.0m / min.

[0032] Example 2

[0033] A flame retardant polyethylene sheath high-speed extrusion process:

[0034] The low-smoke, halogen-free, flame-retardant polyethylene and additives were uniformly mixed and pre-mixed in a twin-screw mixer, and the mixed material was fully dried. The additives included 26% flame retardant, 3% char-forming agent, 0.3% antioxidant, 0.15% antistatic agent, 0.25% lubricant, and 2.4% plasticizer. During the initial mixing process, the temperature was controlled at 75°C for 13 minutes, the ambient humidity was maintained at 45%, the screw speed was set at 220 rpm, the mixing time was 3 minutes, and the drying was set at 75°C for 4.2 hours.

[0035] The extruder head and screw design were optimized. The depth and width of the flow channel for the colloid inside the die were optimized, with the specific depth and width increased by 5mm each. The flow channel form was also redesigned to reduce dead angles and optimize the material flow path. The screw used an aspect ratio of 20 and a compression ratio of 1:1.3. The screw groove depth and helix angle were optimized to increase the melt cavity between the screw and the barrel, reducing shear heat and pressure fluctuations of the material during the extrusion process.

[0036] The screw and barrel are double-cooled, using 6 750W high-pressure centrifugal fans to cool the barrel, and cooling circulating water to cool the screw, ensuring that the extruder temperature is controlled within the set value ±2°C;

[0037] The mold type and mold material were selected and optimized. A semi-extrusion tube mold was used, with a core nozzle length of 15mm and a sleeve support wire length of 8mm. The core head was placed at 1 / 2 of the sleeve support diameter, which reduced the stretching of the jacket material. As a result, the jacket surface was more densely wrapped and the appearance was brighter when the production speed was increased. The mold material was selected to use a mold material with high thermal conductivity and strong wear resistance to reduce material adhesion during the extrusion process.

[0038] Adjust the process parameters, optimize the extrusion speed, adjust the temperature settings of each section of the extruder according to the material formula, control the feeding zone at 150°C, the compression zone at 155°C, the metering zone at 160°C, the die zone at 165°C, and the cooling zone at 95°C; gradually increase the extrusion speed, monitor the changes in current, voltage and pressure, and adjust the extruder parameters. Initially set the extruder speed: 10rpm, current: 142A, pressure: 50bar, glue output: 420kg / h, production speed: 4.6m / min; gradually optimize the process, the extruder speed is increased to 15rpm, current: 196A, pressure: 75bar, glue output: 578kg / h, production speed: 6.0m / min.

[0039] Example 3

[0040] A flame retardant polyethylene sheath high-speed extrusion process:

[0041] The low-smoke, halogen-free, flame-retardant polyethylene and additives were uniformly mixed and pre-mixed in a twin-screw mixer, and the mixed material was fully dried. The additives included 27% flame retardant, 4% char-forming agent, 0.4% antioxidant, 0.2% antistatic agent, 0.3% lubricant, and 3% plasticizer. During the initial mixing process, the temperature was controlled at 70°C for 10 minutes, the ambient humidity was maintained at 41%, the screw speed was set at 250 rpm, the mixing time was 4 minutes, and the drying was set at 80°C for 5 hours.

[0042] The extruder head and screw design were optimized. The depth and width of the flow channel for the colloid inside the die were optimized, with the specific depth and width increased by 5mm each. The flow channel form was also redesigned to reduce dead angles and optimize the material flow path. The screw used an aspect ratio of 20 and a compression ratio of 1:1.3. The screw groove depth and helix angle were optimized to increase the melt cavity between the screw and the barrel, reducing shear heat and pressure fluctuations of the material during the extrusion process.

[0043] The screw and barrel are double-cooled, using 6 750W high-pressure centrifugal fans to cool the barrel, and cooling circulating water to cool the screw, ensuring that the extruder temperature is controlled within the set value ±2°C;

[0044] The mold type and mold material were selected and optimized. A semi-extrusion tube mold was used, with a core nozzle length of 15mm and a sleeve support wire length of 8mm. The core head was placed at 1 / 2 of the sleeve support diameter, which reduced the stretching of the jacket material. As a result, the jacket surface was more densely wrapped and the appearance was brighter when the production speed was increased. The mold material was selected to use a mold material with high thermal conductivity and strong wear resistance to reduce material adhesion during the extrusion process.

[0045] Adjust the process parameters, optimize the extrusion speed, adjust the temperature settings of each section of the extruder according to the material formula, control the feed zone at 155°C, the compression zone at 160°C, the metering zone at 165°C, the die zone at 170°C, and the cooling zone at 91°C; gradually increase the extrusion speed, monitor the changes in current, voltage and pressure, and adjust the extruder parameters. Initially set the extruder speed: 10rpm, current: 142A, pressure: 50bar, glue output: 420kg / h, production speed: 4.6m / min; gradually optimize the process, the extruder speed is increased to 15rpm, current: 196A, pressure: 75bar, glue output: 578kg / h, production speed: 6.0m / min.

[0046] Example 4

[0047] A flame retardant polyethylene sheath high-speed extrusion process:

[0048] The low-smoke, halogen-free, flame-retardant polyethylene and additives were uniformly mixed and pre-mixed in a twin-screw mixer, and the mixed material was fully dried. The additives included 28% flame retardant, 4.5% charring agent, 0.45% antioxidant, 0.25% antistatic agent, 0.4% lubricant, and 3.5% plasticizer. During the initial mixing process, the temperature was controlled at 65°C for 8 minutes, the ambient humidity was maintained at 38%, the screw speed was set at 280 rpm, the mixing time was 4.5 minutes, and the drying was set at 85°C for 5.5 hours.

[0049] The extruder head and screw design were optimized. The depth and width of the flow channel for the colloid inside the die were optimized, with the specific depth and width increased by 5mm each. The flow channel form was also redesigned to reduce dead angles and optimize the material flow path. The screw used an aspect ratio of 20 and a compression ratio of 1:1.3. The screw groove depth and helix angle were optimized to increase the melt cavity between the screw and the barrel, reducing shear heat and pressure fluctuations of the material during the extrusion process.

[0050] The screw and barrel are double-cooled, using 6 750W high-pressure centrifugal fans to cool the barrel, and cooling circulating water to cool the screw, ensuring that the extruder temperature is controlled within the set value ±2°C;

[0051] The mold type and mold material were selected and optimized. A semi-extrusion tube mold was used, with a core nozzle length of 15mm and a sleeve support wire length of 8mm. The core head was placed at 1 / 2 of the sleeve support diameter, which reduced the stretching of the jacket material. As a result, the jacket surface was more densely wrapped and the appearance was brighter when the production speed was increased. The mold material was selected to use a mold material with high thermal conductivity and strong wear resistance to reduce material adhesion during the extrusion process.

[0052] Adjust the process parameters, optimize the extrusion speed, adjust the temperature settings of each section of the extruder according to the material formula, control the feeding zone at 160°C, the compression zone at 165°C, the metering zone at 170°C, the die zone at 175°C, and the cooling zone at 88°C; gradually increase the extrusion speed, monitor the changes in current, voltage and pressure, and adjust the extruder parameters. Initially set the extruder speed: 10rpm, current: 142A, pressure: 50bar, glue output: 420kg / h, production speed: 4.6m / min; gradually optimize the process, the extruder speed is increased to 15rpm, current: 196A, pressure: 75bar, glue output: 578kg / h, production speed: 6.0m / min.

[0053] Example 5

[0054] A flame retardant polyethylene sheath high-speed extrusion process:

[0055] The low-smoke, halogen-free, flame-retardant polyethylene and additives were uniformly mixed and pre-mixed in a twin-screw mixer, and the mixed material was fully dried; the additives included 30% flame retardant, 5% charring agent, 0.5% antioxidant, 0.3% antistatic agent, 0.5% lubricant, and 4% plasticizer; during the initial mixing process, the temperature was controlled at 60°C for 6 minutes, the ambient humidity was maintained at 35%, the screw speed was set at 300 rpm, the mixing time was 5 minutes, and the drying was set at 90°C for 6 hours;

[0056] The extruder head and screw design were optimized. The depth and width of the flow channel for the colloid inside the die were optimized, with the specific depth and width increased by 5mm each. The flow channel form was also redesigned to reduce dead angles and optimize the material flow path. The screw used an aspect ratio of 20 and a compression ratio of 1:1.3. The screw groove depth and helix angle were optimized to increase the melt cavity between the screw and the barrel, reducing shear heat and pressure fluctuations of the material during the extrusion process.

[0057] The screw and barrel are double-cooled, using 6 750W high-pressure centrifugal fans to cool the barrel, and cooling circulating water to cool the screw, ensuring that the extruder temperature is controlled within the set value ±2°C;

[0058] The mold type and mold material were selected and optimized. A semi-extrusion tube mold was used, with a core nozzle length of 15mm and a sleeve support wire length of 8mm. The core head was placed at 1 / 2 of the sleeve support diameter, which reduced the stretching of the jacket material. As a result, the jacket surface was more densely wrapped and the appearance was brighter when the production speed was increased. The mold material was selected to use a mold material with high thermal conductivity and strong wear resistance to reduce material adhesion during the extrusion process.

[0059] Adjust the process parameters, optimize the extrusion speed, adjust the temperature settings of each section of the extruder according to the material formula, control the feeding zone at 165°C, the compression zone at 170°C, the metering zone at 175°C, the die zone at 180°C, and the cooling zone at 85°C; gradually increase the extrusion speed, monitor the changes in current, voltage and pressure, and adjust the extruder parameters. Initially set the extruder speed: 10rpm, current: 142A, pressure: 50bar, glue output: 420kg / h, production speed: 4.6m / min; gradually optimize the process, the extruder speed is increased to 15rpm, current: 196A, pressure: 75bar, glue output: 578kg / h, production speed: 6.0m / min.

[0060] Control Example

[0061] The actual production conditions before and after the implementation of the invention method were compared, as shown in Tables 1 and 2.

[0062]

[0063] Table 1: Before implementation of the invention method

[0064] Table 1 shows the WDZA-YJV22 26 / 35kV 3×240mm produced before the implementation of the invention method 2 When the extruder speed is turned to 25 rpm, the cable surface becomes rough and not smooth, and there are a lot of pores on the cross section.

[0065]

[0066] Table 2: After implementation of the invention method

[0067] Table 2 shows the production of WDZA-YJV22 26 / 35kV 3×240mm after replacing the die head, upgrading the colloid flow channel, using a new low-smoke, halogen-free, flame-retardant screw, and a semi-extrusion die with a low stretch ratio. 2 The parameters of the cable are analyzed and summarized in the table. For the production of cables of the same model and specifications, the current and pressure of the extruder at the same speed are significantly reduced after upgrading the colloid flow channel and using a new low-smoke halogen-free flame-retardant screw and a semi-extrusion die with a low stretch ratio. The glue output, production speed and surface quality are significantly improved.

[0068] In summary, the research and development method of the high-speed extrusion process of the flame-retardant polyethylene sheath of the present invention changes the depth, width and flow channel form of some colloid flow channels in the head of the sheath extruder, adopts a cooling method of double cooling of the screw and barrel, uses a length-to-diameter ratio (L / D) of 20, a compression ratio of 1:1.3, deepens the screw groove depth, increases the screw helix angle, and is equipped with a new low-smoke halogen-free flame-retardant screw with a low stretch ratio. It solves the problems of slow production speed, low glue output, high extrusion pressure and high current of the extruder during production when producing low-smoke halogen-free flame-retardant polyethylene; poor extruder temperature control stability, large difference between the set temperature and the actual temperature, and bamboo-like, rough and hairy extrusion surface with pores, unstable material discharge during extrusion, and the occurrence of annular thinning and holes, thereby truly achieving the goal of high-speed and stable production of low-smoke halogen-free flame-retardant polyethylene.

[0069] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A flame retardant polyethylene sheath high-speed extrusion process, characterized in that: include: The low-smoke halogen-free flame-retardant polyethylene and the additives are uniformly mixed and pre-mixed through a twin-screw mixer, and the mixed materials are fully dried; Optimize the design of extruder head and screw; Then double-cool the screw and barrel; Select mold type and mold material and optimize them; Adjust process parameters and optimize extrusion speed; The optimization of the extruder head and screw design includes: The depth and width of the flow channel for the colloid inside the die head have been optimized, with the specific depth and width increased by 5mm each. The flow channel form is also redesigned to reduce dead angles and optimize the material flow path. The screw uses a length-to-diameter ratio of 20 and a compression ratio of 1:1.

3. The screw groove depth and helix angle are optimized to increase the melt cavity between the screw and the barrel, reducing shear heat and pressure fluctuations during the extrusion process. The selection and optimization of mold type and mold material include: A semi-extrusion tube die is used, with a die core nozzle length of 15mm and a die sleeve bearing wire length of 8mm. The die core head is placed at 1 / 2 of the die sleeve bearing diameter, which reduces the stretching of the sheath material. As a result, the sheath surface is more densely wrapped and the appearance is brighter when the production speed is increased. The die material is selected with high thermal conductivity and strong wear resistance to reduce the adhesion of the material during the extrusion process. The process parameters are adjusted to optimize the extrusion speed, including: According to the material formula, adjust the temperature setting of each section of the extruder, and control the feeding zone at 145-165℃. The compression zone is controlled at 150-170℃, the metering zone is controlled at 155-175℃, and the die zone is controlled at 160-180℃. The cooling zone was <100°C; the extrusion speed was gradually increased, and the changes in current, voltage, and pressure were monitored. By adjusting the extruder parameters, the initial settings were: extruder speed: 10 rpm, current: 142 A, pressure: 50 bar, glue output: 420 kg / h, and production speed: 4.6 m / min; during the gradual optimization process, the extruder speed was increased to 15 rpm, current: 196 A, pressure: 75 bar, glue output: 578 kg / h, and production speed: 6.0 m / min.

2. The flame retardant polyethylene sheath high-speed extrusion process according to claim 1, characterized in that: The low-smoke halogen-free flame-retardant polyethylene and the additive are uniformly mixed, pre-mixed by a twin-screw mixer, and the mixed material is fully dried, including: The additives include 25-30% flame retardant, 2-5% carbonizing agent, 0.2-0.5% antioxidant, 0.1-0.3% antistatic agent, 0.2-0.5% lubricant and 2-4% plasticizer; during the initial mixing process, the temperature is controlled below 80°C and the time does not exceed 15 minutes. During the mixing process, the ambient humidity is kept below 50%, the screw speed is set at 200-300rpm, the mixing time is 2-5 minutes, and the drying is set at 70-90°C for 4-6 hours.

3. The flame retardant polyethylene sheath high-speed extrusion process according to claim 1, characterized in that: The double cooling of the screw barrel comprises: Six 750W high-pressure centrifugal fans are used to cool the barrel, and cooling circulating water is used to cool the screw to ensure that the extruder temperature is controlled within the set value ±2°C.

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