Composite Modification Formula and Molding Process for High Temperature Resistant and Flame Retardant MPP Power Conduit

Abstract

This invention proposes a composite modified formula and molding process for a high-temperature resistant and flame-retardant MPP power pipe, which is made from the following raw materials in parts by weight: 65-80 parts polypropylene resin, 7.5-9.5 parts glass fiber, 11-13 parts coupling agent, 15-25 parts flame retardant, 0.5-1 part antioxidant, 4-10 parts toughening agent, 0.5-2.5 parts lubricant, and 0.4-1 part stabilizer. The composite modified formula and molding process of the high-temperature flame-retardant MPP power pipe of this invention, by setting polypropylene resin as the matrix of the pipe and modifying it with coupling agent, improves the interfacial bonding state between inorganic glass fiber, powder flame retardant additives and organic polypropylene resin matrix, improves the dispersion uniformity of inorganic fillers in the resin, and makes up for the shortcomings of pure polypropylene matrix such as insufficient heat resistance, poor flame retardancy and easy brittleness at low temperature. At the same time, under low temperature conditions, the outer pipe wall can preferentially contact the low temperature environment, play a temperature buffering and isolation role, and improve the pipe's adaptability to low temperature environment and long-term service safety.

Description

Technical Field

[0001] This invention relates to the field of MPP power pipe technology, and in particular to a composite modified formula and molding process for a high-temperature resistant and flame-retardant MPP power pipe. Background Technology

[0002] MPP power conduit, also known as modified polypropylene power cable protection pipe, is a special polymer pipe used for the protection of underground high-voltage and low-voltage power cables. It is widely used in core infrastructure scenarios such as municipal road power grid pre-buried, highway power network renovation, urban underground integrated pipe corridor, rail transit supporting power projects, and old urban area cable undergrounding renovation.

[0003] An existing MPP power pipe and its preparation method involve using 85-100 parts PP, 3-7 parts silane coupling agent, 12-18 parts attapulgite, 5-8 parts glass fiber, 2-5 parts aluminum hydroxide, 2-5 parts calcium carbonate, 0.5-0.8 parts antioxidant, and 0.5-0.8 parts lubricant. The resulting MPP power pipe exhibits varying degrees of improvement in tensile and flexural strength. However, glass fiber is an inorganic rigid filler. During melt extrusion, the resin melt cannot completely impregnate and encapsulate the glass fiber, resulting in some fiber ends breaking through the melt surface and becoming exposed. This leads to irregular, fine pitting on the pipe wall after cooling and solidification, accelerating corrosion and reducing the pipe's service life. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the above-mentioned technologies.

[0005] Therefore, one objective of this invention is to propose a composite modified formula and molding process for a high-temperature resistant and flame-retardant MPP power pipe, which can...

[0006] To achieve the above objectives, the present invention provides a composite modified formulation for a high-temperature resistant and flame-retardant MPP power pipe, which is made from the following raw materials in parts by weight: 65-80 parts of polypropylene resin, 7.5-9.5 parts of glass fiber, 11-13 parts of coupling agent, 15-25 parts of flame retardant, 0.5-1 part of antioxidant, 4-10 parts of toughening agent, 0.5-2.5 parts of lubricant, and 0.4-1 part of stabilizer.

[0007] In addition, the composite modification formula and molding process of the high-temperature resistant flame-retardant MPP power pipe proposed above according to the present invention can also have the following additional technical features:

[0008] Specifically, the coupling agent is one or more combinations of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0009] Specifically, the flame retardant is one or more combinations of phosphonic acid metal salt flame retardants, melamine cyanurate, and ammonium polyphosphate-based intumescent flame retardants.

[0010] Specifically, the antioxidant is one or more combinations of hindered phenolic primary antioxidants, phosphite secondary antioxidants, and thioester secondary antioxidants.

[0011] Specifically, the toughening agent is one or more combinations of maleic anhydride-grafted polyolefin elastomer and maleic anhydride-grafted linear low-density polyethylene.

[0012] A composite modification molding process for a high-temperature resistant and flame-retardant MPP power pipe, used in the composite modification formulation of the high-temperature resistant and flame-retardant MPP power pipe according to any one of claims 1-6, includes the following steps:

[0013] S1: Premixing Treatment The first group of polypropylene resin, toughening agent, coupling agent, and alkali-free chopped glass fiber are added to a mixer and stirred to obtain glass fiber-containing composite premix A. The second group of polypropylene resin, toughening agent, and coupling agent are added to a mixer and stirred to obtain glass fiber-free composite premix B. S2: Melting Treatment Premix A and premix B are fed into two twin-screw extruders respectively. Antioxidant, lubricant, stabilizer, and flame retardant are added to the two twin-screw extruders sequentially. Blending modification is completed through segmented temperature control and shear melting to obtain inner layer melt blend material A and outer layer melt blend material B. S3: Granulation Treatment The inner layer molten blend material A and the outer layer molten blend material B are extruded and pelletized respectively, and then screened to obtain composite modified masterbatch A and composite modified masterbatch B; S4: Drying treatment, composite modified masterbatch A and composite modified masterbatch B are dried respectively to obtain dried composite modified masterbatch A and composite modified masterbatch B; S5: Extrusion treatment, composite modified masterbatch A is fed into the main extruder, and composite modified masterbatch B is fed into the auxiliary extruder. Through the co-extrusion nozzle, composite modified masterbatch B is coated on the outside of composite modified masterbatch A in a molten state to obtain a composite tube blank. After water cooling, a high temperature resistant flame retardant MPP power pipe is obtained.

[0014] Specifically, in the S1 premixing process, the preheating temperature of the mixer is controlled at 75-85℃, and the alkali-free chopped glass fiber is added at a low speed in the later stage of premixing.

[0015] Specifically, in the S2 melt treatment and the S5 extrusion treatment, the temperature of the main extruder is 180-205℃, the temperature of the auxiliary extruder is 175-195℃, and the temperature of the co-extrusion die is 200-208℃.

[0016] Specifically, the wall thickness ratio of the inner layer composite modified masterbatch A to the outer layer composite modified masterbatch B is 7:3.

[0017] Specifically, the S4 drying process uses hot air drying at a temperature of 75-85℃ for 4-6 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The composite modification formula and molding process of the high-temperature flame-retardant MPP power pipe of the present invention, by setting polypropylene resin and using polypropylene resin as the matrix of the pipe, combined with coupling agent modification treatment, improves the interfacial bonding state between inorganic glass fiber, powder flame retardant additives and organic polypropylene resin matrix, reduces the interfacial tension between the two phases, improves the dispersion uniformity of inorganic fillers in the resin, avoids filler agglomeration, and by using flame retardants, toughening agents and antioxidants in combination, it makes up for the shortcomings of pure polypropylene matrix in terms of insufficient heat resistance, poor flame retardancy and easy brittleness at low temperature. At the same time, under low temperature conditions, the outer pipe wall can preferentially contact the low temperature environment, play a temperature buffering and isolation role, and improve the pipe's adaptability to low temperature environment and long-term service safety.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0021] Figure 1 A schematic diagram of the composite modification formula and molding process of a high-temperature resistant and flame-retardant MPP power pipe according to an embodiment of the present invention. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] The following describes the composite modification formula and molding process of the high-temperature resistant and flame-retardant MPP power pipe according to an embodiment of the present invention, with reference to the accompanying drawings.

[0024] As mentioned earlier, the glass fiber ends are prone to breaking through the surface of the melt and being exposed to the outside, resulting in irregular small pits forming on the pipe wall after cooling and solidification. This accelerates the corrosion of the pipe and reduces its service life.

[0025] like Figure 1As shown, the composite modified formula and molding process of the high-temperature flame-retardant MPP power pipe of the present invention are made from the following raw materials in parts by weight: 65-80 parts of polypropylene resin, 7.5-9.5 parts of glass fiber, 11-13 parts of coupling agent, 15-25 parts of flame retardant, 0.5-1 part of antioxidant, 4-10 parts of toughening agent, 0.5-2.5 parts of lubricant and 0.4-1 part of stabilizer.

[0026] The polypropylene resin used is homopolymer polypropylene as the base resin for the pipe. The glass fiber is alkali-free chopped glass fiber with a fixed diameter of 10μm and a fixed length of 3mm. The coupling agent is aminopropyltriethoxysilane, a silane coupling agent that can improve the interfacial compatibility between inorganic glass fiber and organic polypropylene matrix. The flame retardant is aluminum phosphonate and melamine cyanurate, compounded in a 2:1 mass ratio to improve the high-temperature flame retardant performance of the MPP power pipe. The antioxidant is a 1:1 mass ratio compounded of di-tert-butylhydroxyphenyl hindered phenolic main antioxidant and a matching auxiliary antioxidant. The toughening agent is maleic anhydride-grafted polyolefin elastomer. The lubricant is polyethylene wax. The stabilizer is calcium stearate and zinc stearate, compounded in a 6:4 mass ratio.

[0027] The present invention will be described in detail below through specific embodiments:

[0028] Example 1:

[0029] The composite modified formulation of the high-temperature resistant and flame-retardant MPP power pipe in this embodiment is as follows:

[0030] A composite modified formula and molding process for a high-temperature resistant and flame-retardant MPP power pipe includes the following components in parts by weight: 72 parts polypropylene resin, 8.5 parts alkali-free chopped glass fiber, 12 parts coupling agent, 20 parts flame retardant, 0.8 parts antioxidant, 7 parts toughening agent, 1.5 parts lubricant, and 0.7 parts stabilizer.

[0031] This technical solution provides a composite modification preparation process for high-temperature resistant and flame-retardant MPP power pipes:

[0032] The specific steps are as follows:

[0033] S1: Premixing treatment: The first group of polypropylene resin, toughening agent, and coupling agent are added to a mixer to ensure thorough mixing of the organic raw materials. Then, the stirring speed is reduced, and alkali-free chopped glass fibers are added while stirring is continued to obtain glass fiber-containing composite premix A. Simultaneously, the second group of polypropylene resin, toughening agent, and coupling agent are added to another mixer and stirred to obtain glass fiber-free composite premix B.

[0034] S2: Melting treatment. Premix A and premix B are fed into the main feed hoppers of two twin-screw extruders. The temperature range from the feed end to the die head of the twin-screw extruder processing premix A is set as follows: 180℃-190℃, 195℃, 200℃, 200℃, 195℃, 190℃, 195℃, with a screw speed of 300 r / min. The temperature range from the feed end to the die head of the twin-screw extruder processing premix B is set as follows: 175℃-185℃, 190℃, 195℃, 195℃, 190℃, 185℃, 190℃, with a screw speed of 280 r / min. During the extrusion process, antioxidants, lubricants, stabilizers, and flame retardants are added to the two extruders sequentially through a side feeding device. The blending modification is completed by shear melting, resulting in inner layer melt blend material A and outer layer melt blend material B.

[0035] S3: Granulation process. The molten strips extruded from the two extruder heads are fed into a water cooling tank at a temperature of 25°C for initial cooling, and then sent to a pelletizer for pelletizing. After pelletizing, the pellets are screened by a vibrating screen to remove unqualified particles that are too large or too small, thus obtaining composite modified masterbatch A and composite modified masterbatch B respectively.

[0036] S4: Drying treatment. Composite modified masterbatch A and composite modified masterbatch B are respectively put into a hot air circulating drying oven. The drying temperature is set to 80℃ and the drying time is 5h. After drying, the moisture content of the masterbatch is tested and controlled below 0.02% to avoid the generation of air bubbles due to moisture evaporation during subsequent extrusion molding, which would affect the compactness of the pipe.

[0037] S5: Extrusion Process. The dried composite modified masterbatch A is fed into the main extruder, and the composite modified masterbatch B is fed into the auxiliary extruder. The heating zone temperatures of the main extruder are set sequentially to 185℃, 190℃, 195℃, 200℃, and 205℃, with a screw speed of 80 r / min. The heating zone temperatures of the auxiliary extruder are set sequentially to 175℃, 180℃, 185℃, 190℃, and 195℃, with a screw speed of 30 r / min. The temperature of the co-extrusion die is set to 205℃, so that the outer layer of composite modified masterbatch B coats the outer layer of composite modified masterbatch A in a molten state. By controlling the extrusion volume of the two extruders, the wall thickness ratio of the inner and outer layers is controlled to be 7:3, and a composite tube blank is obtained by extrusion. The composite tube blank is then water-cooled through a spray cooling water tank to gradually cool down and shape the tube blank. After traction, sizing, and cutting, a high-temperature resistant and flame-retardant MPP power pipe is obtained.

[0038] Example 2

[0039] A composite modified formula and molding process for a high-temperature resistant and flame-retardant MPP power pipe includes the following components in parts by weight: 80 parts polypropylene resin, 9.5 parts alkali-free chopped glass fiber, 13 parts coupling agent, 25 parts flame retardant, 1 part antioxidant, 10 parts toughening agent, 2.5 parts lubricant, and 1 part stabilizer.

[0040] This technical solution provides a composite modification preparation process for high-temperature resistant and flame-retardant MPP power pipes:

[0041] The specific steps are as follows:

[0042] S1: Premixing treatment: The first group of polypropylene resin, toughening agent, and coupling agent are added to a mixer to ensure thorough mixing of the organic raw materials. Then, the stirring speed is reduced, and alkali-free chopped glass fibers are added while stirring is continued to obtain glass fiber-containing composite premix A. Simultaneously, the second group of polypropylene resin, toughening agent, and coupling agent are added to another mixer and stirred to obtain glass fiber-free composite premix B.

[0043] S2: Melt treatment. Premix A and premix B are fed into the main feed hoppers of two twin-screw extruders, respectively. The twin-screw extruder processing premix A has the following temperature zones from the feed end to the die head: 182℃, 192℃, 197℃, 202℃, 202℃, 197℃, 192℃, 197℃, with a screw speed of 320 r / min to increase shear strength and ensure high filler dispersion. The twin-screw extruder processing premix B... The temperature range from the feed end to the die head is set sequentially as follows: 177℃, 187℃, 192℃, 197℃, 197℃, 192℃, 187℃, 192℃. The screw speed is 300 r / min. During the extrusion process, antioxidants, lubricants, stabilizers, and flame retardants are added sequentially to the two extruders through a side feeding device. The blending modification is completed by shear melting, and inner layer melt blend material A and outer layer melt blend material B are obtained respectively.

[0044] S3: Granulation process. The molten strips extruded from the two extruder heads are fed into a water cooling tank at a temperature of 25°C for initial cooling, and then sent to a pelletizer for pelletizing. After pelletizing, the pellets are screened by a vibrating screen to remove unqualified particles that are too large or too small, thus obtaining composite modified masterbatch A and composite modified masterbatch B respectively.

[0045] S4: Drying treatment. Composite modified masterbatch A and composite modified masterbatch B are respectively put into a hot air circulating drying oven. The drying temperature is set to 82℃ and the drying time is 5.5h. After drying, the moisture content of the masterbatch is tested and controlled below 0.02% to avoid the generation of air bubbles due to moisture evaporation during subsequent extrusion molding, which would affect the compactness of the pipe.

[0046] S5: Extrusion Process. The dried composite modified masterbatch A is fed into the main extruder, and the composite modified masterbatch B is fed into the auxiliary extruder. The heating zone temperatures of the main extruder are set sequentially to 187℃, 192℃, 197℃, 202℃, and 205℃, with a screw speed of 85 r / min. The heating zone temperatures of the auxiliary extruder are set sequentially to 177℃, 182℃, 187℃, 192℃, and 195℃, with a screw speed of 32 r / min. The co-extrusion die temperature is set to 206℃, so that the outer layer of composite modified masterbatch B, in a molten state, coats the outer layer of composite modified masterbatch A. By controlling the extrusion rate of the two extruders, the wall thickness ratio of the inner and outer layers is controlled to be 7:3, and a composite tube blank is obtained by extrusion. The composite tube blank is then water-cooled through a spray cooling water tank to gradually cool down and shape it. After traction, sizing, and cutting, a high-temperature resistant and flame-retardant MPP power pipe is obtained.

[0047] Example 3

[0048] A composite modified formula and molding process for a high-temperature resistant and flame-retardant MPP power pipe includes the following components in parts by weight: 65 parts polypropylene resin, 7.5 parts alkali-free chopped glass fiber, 11 parts coupling agent, 15 parts flame retardant, 0.5 parts antioxidant, 4 parts toughening agent, 0.5 parts lubricant, and 0.4 parts stabilizer.

[0049] This technical solution provides a composite modification preparation process for high-temperature resistant and flame-retardant MPP power pipes:

[0050] The specific steps are as follows:

[0051] S1: Premixing treatment: The first group of polypropylene resin, toughening agent, and coupling agent are added to a mixer to ensure thorough mixing of the organic raw materials. Then, the stirring speed is reduced, and alkali-free chopped glass fibers are added while stirring is continued to obtain glass fiber-containing composite premix A. Simultaneously, the second group of polypropylene resin, toughening agent, and coupling agent are added to another mixer and stirred to obtain glass fiber-free composite premix B.

[0052] S2: Melting treatment. Premix A and premix B are fed into the main feed hoppers of two twin-screw extruders, respectively. The twin-screw extruder processing premix A has its temperature zones from the feed end to the die head set sequentially as follows: 178℃, 188℃, 193℃, 198℃, 198℃, 193℃, 188℃, 193℃, with a screw speed of 280 r / min to avoid excessive shearing. The twin-screw extruder processing premix B starts from the feed end... The temperature ranges to the die head are set sequentially as follows: 173℃, 183℃, 188℃, 193℃, 193℃, 188℃, 183℃, and 188℃. The screw speed is 260 r / min. During the extrusion process, antioxidants, lubricants, stabilizers, and flame retardants are added sequentially to the two extruders through a side feeding device. The blending modification is completed through shear melting, resulting in inner layer melt blend material A and outer layer melt blend material B.

[0053] S3: Granulation process. The molten strips extruded from the two extruder heads are fed into a water cooling tank at a temperature of 25°C for initial cooling, and then sent to a pelletizer for pelletizing. After pelletizing, the pellets are screened by a vibrating screen to remove unqualified particles that are too large or too small, thus obtaining composite modified masterbatch A and composite modified masterbatch B respectively.

[0054] S4: Drying treatment. Composite modified masterbatch A and composite modified masterbatch B are respectively put into a hot air circulating drying oven. The drying temperature is set to 78℃ and the drying time is 4.5h. After drying, the moisture content of the masterbatch is tested and controlled below 0.02% to avoid the generation of air bubbles due to moisture evaporation during subsequent extrusion molding, which would affect the compactness of the pipe.

[0055] S5: Extrusion Process. The dried composite modified masterbatch A is fed into the main extruder, and the composite modified masterbatch B is fed into the auxiliary extruder. The heating zone temperatures of the main extruder are set sequentially to 183℃, 188℃, 193℃, 198℃, and 203℃, with a screw speed of 75 r / min. The heating zone temperatures of the auxiliary extruder are set sequentially to 173℃, 178℃, 183℃, 188℃, and 193℃, with a screw speed of 28 r / min. The temperature of the co-extrusion die is set to 204℃, so that the outer layer of composite modified masterbatch B is uniformly coated on the outer layer of composite modified masterbatch A in a molten state. By controlling the extrusion volume of the two extruders, the wall thickness ratio of the inner and outer layers is controlled to be 7:3. The composite tube blank is then extruded and cooled by water spray cooling water tank to gradually cool down and shape the tube blank. After traction, sizing, and cutting, a high-temperature resistant and flame-retardant MPP power pipe is obtained.

[0056] In summary, the composite modified formula and molding process of the high-temperature flame-retardant MPP power pipe of the present invention, by setting polypropylene resin as the matrix of the pipe and modifying it with coupling agent, improves the interfacial bonding state between inorganic glass fiber, powder flame retardant additives and organic polypropylene resin matrix, reduces the interfacial tension between the two phases, improves the dispersion uniformity of inorganic fillers in the resin, avoids filler agglomeration, and compensates for the shortcomings of pure polypropylene matrix in terms of insufficient heat resistance, poor flame retardancy and easy brittleness at low temperature by using flame retardants, toughening agents and antioxidants in combination. At the same time, under low temperature conditions, the outer pipe wall can preferentially contact the low temperature environment, play a temperature buffering and isolation role, and improve the pipe's adaptability to low temperature environment and long-term service safety.

[0057] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A composite modified formula for a high-temperature resistant and flame-retardant MPP power pipe, characterized in that, Made from the following raw materials in parts by weight: The composition includes 65-80 parts polypropylene resin, 7.5-9.5 parts glass fiber, 11-13 parts coupling agent, 15-25 parts flame retardant, 0.5-1 part antioxidant, 4-10 parts toughening agent, 0.5-2.5 parts lubricant, and 0.4-1 part stabilizer.

2. The composite modified formula and molding process of the high-temperature resistant flame-retardant MPP power pipe according to claim 1, characterized in that, The coupling agent is one or more combinations of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

3. The composite modified formula and molding process of the high-temperature resistant flame-retardant MPP power pipe according to claim 2, characterized in that, The flame retardant is one or more combinations of phosphonic acid metal salt flame retardants, melamine cyanurate, and ammonium polyphosphate intumescent flame retardants.

4. The composite modified formula and molding process of the high-temperature resistant and flame-retardant MPP power pipe according to claim 3, characterized in that, The antioxidant is one or more combinations of hindered phenolic primary antioxidants, phosphite secondary antioxidants, and thioester secondary antioxidants.

5. The composite modified formula and molding process of the high-temperature resistant flame-retardant MPP power pipe according to claim 4, characterized in that, The toughening agent is one or more combinations of maleic anhydride-grafted polyolefin elastomer and maleic anhydride-grafted linear low-density polyethylene.

6. A composite modification molding process for a high-temperature resistant and flame-retardant MPP power pipe, characterized in that, The composite modified formulation for the high-temperature resistant and flame-retardant MPP power pipe according to any one of claims 1-6 includes the following steps: S1: Premixing treatment The first group of polypropylene resin, toughening agent, coupling agent and alkali-free chopped glass fiber were put into a mixer and stirred to obtain glass fiber-containing composite premix A. The second group of polypropylene resin, toughening agent and coupling agent were put into a mixer and stirred to obtain glass fiber-free composite premix B. S2: Melting treatment Premix A and premix B are fed into two twin-screw extruders respectively, and antioxidants, lubricants, stabilizers and flame retardants are added to the two twin-screw extruders in sequence. The blending modification is completed by segmented temperature control and shear melting to obtain inner layer melt blend material A and outer layer melt blend material B. S3: Granulation Process The inner layer melt blend material A and the outer layer melt blend material B are extruded and pelletized, and then screened to obtain composite modified masterbatch A and composite modified masterbatch B. S4: Drying process Composite modified masterbatch A and composite modified masterbatch B were dried separately to obtain dried composite modified masterbatch A and composite modified masterbatch B; S5: Extrusion Processing Composite modified masterbatch A is fed into the main extruder, and composite modified masterbatch B is fed into the auxiliary extruder. Through the co-extrusion nozzle, composite modified masterbatch B is coated onto the outside of composite modified masterbatch A in a molten state to obtain a composite tube blank. After water cooling, a high-temperature resistant and flame-retardant MPP power pipe is obtained.

7. The composite modification molding process for the high-temperature resistant and flame-retardant MPP power pipe according to claim 6, characterized in that, In the S1 premixing process, the preheating temperature of the mixer is controlled at 75-85℃, and the alkali-free chopped glass fiber is added at a low speed in the later stage of premixing.

8. The composite modification molding process for the high-temperature resistant and flame-retardant MPP power pipe according to claim 7, characterized in that, In the S2 melt treatment and the S5 extrusion treatment, the temperature of the main extruder is 180-205℃, the temperature of the auxiliary extruder is 175-195℃, and the temperature of the co-extrusion die is 200-208℃.

9. The composite modification molding process for the high-temperature resistant and flame-retardant MPP power pipe according to claim 8, characterized in that, The wall thickness ratio of the inner layer composite modified masterbatch A to the outer layer composite modified masterbatch B is 7:

3.

10. The composite modified formula and molding process of the high-temperature resistant flame-retardant MPP power pipe according to claim 9, characterized in that, The S4 drying process uses hot air drying at a temperature of 75-85℃ for 4-6 hours.

Images