High-flame-retardant resin layer composite material for steel wire framework polyethylene pipe and preparation method

Abstract

The invention discloses a high-flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe and a preparation method thereof, and the preparation method comprises the following steps: uniformly stirring and mixing high-density polyethylene, low-density polyethylene, a flame retardant, an antioxidant and a compatilizer to obtain a mixture; the flame retardant is a compound of a nano flame retardant and a phosphorus flame retardant; the mixture is subjected to melt blending and granulation, and the polyethylene composite material is obtained; the polyethylene composite material is subjected to injection molding, and the high-flame-retardant resin layer composite material for the steel wire framework polyethylene pipe is obtained. The nano flame retardant is compounded with the phosphorus flame retardant to serve as the composite flame retardant to modify the high-density polyethylene, and the nano flame retardant is large in specific surface area, high in surface activity, good in dispersity and capable of being uniformly dispersed in the high-density polyethylene, so that the mechanical property of the composite material can be improved; and a better flame-retardant effect can be achieved when the flame retardant is compounded with a phosphorus-based flame retardant.

Description

Technical Field

[0001] The present invention relates to the field of polymer material modification and processing, and in particular to a high flame retardant resin layer composite material for a steel wire skeleton polyethylene pipe and a preparation method thereof. Background Art

[0002] Steel wire mesh skeleton plastic (polyethylene) composite pipe is a new type of improved steel skeleton composite pipe. This pipe is also called SRTP pipe (Steel Reinforced Thermoplastic Pipe). It uses high-strength plasticized steel wire skeleton and thermoplastic polyethylene as raw materials. Steel wire is wrapped as the reinforcement of the polyethylene plastic pipe, high-density polyethylene is used as the matrix, and high-performance high-density polyethylene (HDPE) modified adhesive resin is used to tightly combine the steel wire skeleton with the inner and outer high-density polyethylene, so that it has excellent composite effect and has the respective advantages of steel pipe and plastic pipe.

[0003] Because high-density polyethylene (HDPE) consists of only carbon and hydrogen in its molecular chain, it is flammable. In some high-temperature and high-risk environments, its flame retardancy may not meet practical requirements. Coal mines, on the other hand, are high-temperature environments, with temperatures often exceeding 30°C. In deep mines, ground temperatures can reach even higher, reaching 45°C. Therefore, HDPE must be flame-retardant modified for use in mine environments. Improper selection of flame retardants can directly affect the mechanical properties of the formed pipe, which are crucial for steel-wire reinforced polyethylene pipe. Therefore, flame-retardant modification of HDPE without compromising its mechanical properties is crucial. Summary of the Invention

[0004] In order to overcome the problem in the prior art that high-density polyethylene modification cannot take into account both flame retardancy and mechanical properties, the purpose of the present invention is to provide a high flame retardant resin layer composite material for steel wire skeleton polyethylene pipe and a preparation method, which has good flame retardancy and mechanical properties.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe comprises the following steps:

[0007] High-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer are stirred and mixed uniformly to obtain a mixture; the flame retardant is a composite of nano flame retardant and phosphorus flame retardant;

[0008] The mixture is melt-blended and then granulated to obtain a polyethylene composite material;

[0009] The polyethylene composite material is injection molded to obtain a high flame retardant resin layer composite material for a steel wire skeleton polyethylene pipe.

[0010] Furthermore, the mass ratio of high-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer is (50-80): (5-15): (10-30): (1-2): (3-4).

[0011] Furthermore, the nano flame retardant is one or both of nano aluminum hydroxide and nano magnesium hydroxide.

[0012] Furthermore, the phosphorus-based flame retardant is one or both of dimethyl methyl phosphate and triphenyl phosphate.

[0013] Furthermore, when the flame retardant is a mixture of one of dimethyl methyl phosphate and triphenyl phosphate, nano aluminum hydroxide and nano magnesium hydroxide, the mass ratio of dimethyl methyl phosphate and one of triphenyl phosphate, nano aluminum hydroxide and nano magnesium hydroxide is 1: (0.5-2): (1-3).

[0014] Furthermore, the antioxidant is one or more of pentaerythritol β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,6-di-tert-butyl-4-methylphenol.

[0015] Furthermore, the compatibilizer is one or both of maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene.

[0016] Furthermore, the melt blending is carried out in a twin-screw extruder, the temperature of the plasticizing section of the twin-screw extruder is 190-200° C., the temperature of the metering section is 200-220° C., the head temperature is 220-230° C., and the screw speed is 50 r / min.

[0017] Furthermore, the injection molding is carried out in an injection molding machine, the temperature of the feeding section of the injection molding machine is 190-200° C., the temperature of the plasticizing section is 200-220° C., the temperature of the head is 220-230° C., and the plasticizing length is 65-75 mm.

[0018] The invention discloses a high flame retardant resin layer composite material for a steel wire skeleton polyethylene pipe.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses a nano flame retardant compounded with a phosphorus flame retardant as a composite flame retardant to modify high-density polyethylene. The nano flame retardant has a large specific surface area, high surface activity, and good dispersibility. It can be evenly dispersed in high-density polyethylene, thereby improving the mechanical properties of the composite material. Moreover, compounding with the phosphorus flame retardant will achieve a better flame retardant effect. At the same time, low-density polyethylene with good fluidity is introduced to improve the processing performance of the composite material. The high-density polyethylene composite material prepared using this formula can simultaneously possess high mechanical properties and high flame retardant properties, and is a composite material suitable for steel wire skeleton polyethylene pipes. When applied to high-risk environments such as coal mines, it can reduce the risk factor during equipment operation and avoid accidents. DETAILED DESCRIPTION

[0021] The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0022] The present invention provides a method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe, and the specific preparation steps are as follows:

[0023] (1) Weigh 50-80 parts of high-density polyethylene (HDPE), 5-15 parts of low-density polyethylene (LDPE), 10-30 parts of flame retardant, 1-2 parts of antioxidant and 3-4 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer by a high-speed mixer to obtain a mixture.

[0024] The flame retardant is a mixture of a nano flame retardant and a phosphorus-based flame retardant; the flame retardant is two or more of dimethyl methyl phosphate, triphenyl phosphate, nano-aluminum hydroxide, and nano-magnesium hydroxide. Nano-aluminum hydroxide and nano-magnesium hydroxide are nano flame retardants, while dimethyl methyl phosphate and triphenyl phosphate are phosphorus-based flame retardants. Preferably, the flame retardant is a mixture of one or both of dimethyl methyl phosphate and triphenyl phosphate with one or both of nano-aluminum hydroxide and nano-magnesium hydroxide.

[0025] The antioxidant is one or more of pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, n-octadecyl beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,6-di-tert-butyl-4-methylphenol.

[0026] The compatibilizer is one or both of maleic anhydride grafted polyethylene (PE-g-MAH) and maleic anhydride grafted polypropylene (PP-g-MAH).

[0027] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified particulate composite material is obtained, and the above-mentioned particulate composite material is dried in a blast drying oven at 60°C for 6 hours to obtain a modified high-flame retardant high-density polyethylene composite material.

[0028] (3) The modified high-flame-retardant high-density polyethylene composite material particles obtained in step (2) are fed into an injection molding machine and injection-molded into strips. The feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, and the plasticizing length is 65-75mm. After the mold is cooled and opened, a high-flame-retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0029] The following are specific examples.

[0030] Example 1

[0031] (1) Weigh 50 parts of high-density polyethylene, 15 parts of low-density polyethylene, 30 parts of flame retardant, 2 parts of antioxidant, and 3 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer uniformly using a high-speed mixer.

[0032] The flame retardant is a blend of dimethyl methyl phosphate, nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:0.5:1.

[0033] The antioxidant is a blend of pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and n-octadecyl beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, with a mixing mass ratio of 1:1.

[0034] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0035] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified particulate composite material is obtained, and the above-mentioned particulate composite material is dried in a blast drying oven at 60°C for 6 hours to obtain a modified high-flame retardant high-density polyethylene composite material.

[0036] (3) The high-density polyethylene composite material particles obtained in step (2) are put into an injection molding machine, the feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, the plasticizing length is 65mm, and after the mold is cooled and opened, a high flame retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0037] Example 2

[0038] (1) Weigh 65 parts of high-density polyethylene, 10 parts of low-density polyethylene, 20 parts of flame retardant, 1.5 parts of antioxidant, and 3.5 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant, and compatibilizer uniformly using a high-speed mixer.

[0039] The flame retardant is a blend of triphenyl phosphate, nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:1:1.

[0040] The antioxidant is a blend of pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,6-di-tert-butyl-4-methylphenol, with a mixing mass ratio of 1:1.

[0041] The compatibilizer is maleic anhydride grafted polypropylene (PP-g-MAH).

[0042] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified high-flame-retardant high-density polyethylene composite material is obtained.

[0043] (3) The high-density polyethylene composite material particles obtained in step (2) are put into an injection molding machine, the feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, the plasticizing length is 71mm, and after the mold is cooled and opened, a high flame retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0044] Example 3

[0045] (1) Weigh 65 parts of high-density polyethylene, 10 parts of low-density polyethylene, 20 parts of flame retardant, 1.5 parts of antioxidant, and 3.5 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant, and compatibilizer uniformly using a high-speed mixer.

[0046] The flame retardant is a blend of dimethyl methyl phosphate, nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:2:2.

[0047] The antioxidant is pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0048] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0049] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified high-flame-retardant high-density polyethylene composite material is obtained.

[0050] (3) The high-density polyethylene composite material particles obtained in step (2) are put into an injection molding machine, the feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, the plasticizing length is 75mm, and after the mold is cooled and opened, a high flame retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0051] Example 4

[0052] (1) Weigh 65 parts of high-density polyethylene, 10 parts of low-density polyethylene, 20 parts of flame retardant, 1.5 parts of antioxidant and 3.5 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer in a high-speed mixer.

[0053] The flame retardant is a blend of dimethyl methyl phosphate, nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:1:3.

[0054] The antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate.

[0055] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0056] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified high-flame-retardant high-density polyethylene composite material is obtained.

[0057] (3) The high-density polyethylene composite material particles obtained in step (2) are put into an injection molding machine, the feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, the plasticizing length is 71mm, and after the mold is cooled and opened, a high flame retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0058] Example 5

[0059] (1) Weigh 80 parts of high-density polyethylene, 5 parts of low-density polyethylene, 10 parts of flame retardant, 1 part of antioxidant, and 4 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant, and compatibilizer uniformly using a high-speed mixer.

[0060] The flame retardant is a blend of dimethyl methyl phosphate, triphenyl phosphate, nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:1:1:1.

[0061] The antioxidant is a mixture of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,6-di-tert-butyl-4-methylphenol, with a mixing mass ratio of 1:1.

[0062] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0063] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified high-flame-retardant high-density polyethylene composite material is obtained.

[0064] (3) The high-density polyethylene composite material particles obtained in step (2) are put into an injection molding machine, the feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, the plasticizing length is 71mm, and after the mold is cooled and opened, a high flame retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0065] Comparative Example 1

[0066] Different from Example 1, in this comparative example, the raw materials are calculated by weight, and 80 parts of high-density polyethylene, 15 parts of low-density polyethylene, 2 parts of antioxidant and 3 parts of compatibilizer are weighed, and the high-density polyethylene, low-density polyethylene, antioxidant and compatibilizer are stirred and mixed uniformly by a high-speed mixer.

[0067] The antioxidant is a blend of pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and n-octadecyl beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and the mixing mass ratio is 1:1.

[0068] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0069] Comparative Example 2

[0070] Different from Example 1, in this comparative example, the raw materials are calculated by weight, and 65 parts of high-density polyethylene, 30 parts of flame retardant, 2 parts of antioxidant, and 3 parts of compatibilizer are weighed, and the high-density polyethylene, antioxidant and compatibilizer are stirred and mixed uniformly by a high-speed mixer.

[0071] The flame retardant is a blend of dimethyl methyl phosphate, nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:1:1.

[0072] The antioxidant is a blend of pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and n-octadecyl beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and the mixing mass ratio is 1:1.

[0073] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0074] Comparative Example 3

[0075] (1) Weigh 80 parts of high-density polyethylene, 5 parts of low-density polyethylene, 10 parts of flame retardant, 1 part of antioxidant, and 4 parts of compatibilizer by weight, and stir and mix the high-density polyethylene, low-density polyethylene, flame retardant, antioxidant, and compatibilizer uniformly using a high-speed mixer.

[0076] The flame retardant is a blend of nano-aluminum hydroxide and nano-magnesium hydroxide, and the mixing mass ratio is 1:1.

[0077] The antioxidant is a mixture of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,6-di-tert-butyl-4-methylphenol, with a mixing mass ratio of 1:1.

[0078] The compatibilizer is maleic anhydride grafted polyethylene (PE-g-MAH).

[0079] (2) The mixture obtained in step (1) is put into a twin-screw extruder for melt blending, the temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min. After water cooling and cutting and granulation, a modified high-flame-retardant high-density polyethylene composite material is obtained.

[0080] (3) The high-density polyethylene composite material particles obtained in step (2) are put into an injection molding machine, the feeding section temperature is 190-200°C, the plasticizing section temperature is 200-220°C, the head temperature is 220-230°C, the plasticizing length is 71mm, and after the mold is cooled and opened, a high flame retardant resin layer composite material for a strip-shaped steel wire skeleton polyethylene pipe is obtained.

[0081] Flame retardant performance test: The vertical burning test method was used in accordance with GB / T 2408-2008 "Determination of combustion properties of plastics - Horizontal and vertical methods". Five specimens were tested for each set of examples and comparative examples, and the average value was calculated.

[0082] Tensile strength test: The test was conducted in accordance with GB / T 1040.2-2006 “Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics”. Five specimens were tested for each set of examples and comparative examples, and the average value was taken.

[0083] Bending strength test: The bending strength was tested according to GB / T 9341-2008 “Determination of flexural properties of plastics”. Five specimens were tested for each set of examples and comparative examples, and the average value was taken.

[0084] Impact strength test: The impact strength test was conducted in accordance with GB / T 1843-2008 “Plastics — Determination of Izod Impact Strength”. Five specimens were tested for each set of examples and comparative examples, and the average value was taken.

[0085] Table 1 Material performance test results

[0086]

[0087] The highly flame-retardant high-density polyethylene composite materials prepared in Examples 1-4 and Comparative Examples 1-3 of the present invention have uniform texture and are free of holes.

[0088] From the test data in Table 1, it can be seen that in Comparative Example 1, when no flame retardant is added, the flame retardant effect of the spline is poor. In Comparative Example 2, no low-density polyethylene is added during extrusion and injection molding, which is poor in fluidity, and is not conducive to processing. Therefore, the addition of low-density polyethylene can improve the processing performance of the composite material. In Comparative Example 3, the addition of nano flame retardants (nano aluminum hydroxide and nano magnesium hydroxide) can effectively improve the flame retardant properties of high-density polyethylene, but the flame retardant effect is not as good as that of the composite material with the addition of phosphorus flame retardant. However, the nano flame retardant can maintain the mechanical properties of the raw materials to a greater extent. Therefore, mixing the nano flame retardant and the phosphorus flame retardant as a compound flame retardant can not only improve the flame retardant properties of the high-density polyethylene composite material, but also retain the mechanical properties of the material to a greater extent.

[0089] The above description is merely a description of the preferred embodiment of the present invention and is not to be construed as limiting the claims. The present invention is not limited to the above embodiment, and variations in the specific structure are permitted. Any variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0090] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe, characterized in that: The following steps are involved: High-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer are stirred and mixed uniformly to obtain a mixture; the flame retardant is a composite of nano flame retardant and phosphorus flame retardant; The mixture is melt-blended and then granulated to obtain a polyethylene composite material; The polyethylene composite material is injection molded to obtain a high flame retardant resin layer composite material for a steel wire skeleton polyethylene pipe.

2. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 1, characterized in that: The mass ratio of high-density polyethylene, low-density polyethylene, flame retardant, antioxidant and compatibilizer is (50-80): (5-15): (10-30): (1-2): (3-4).

3. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 1, characterized in that: The nano flame retardant is one or two of nano aluminum hydroxide and nano magnesium hydroxide.

4. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 3, characterized in that: The phosphorus-based flame retardant is one or both of dimethyl methyl phosphate and triphenyl phosphate.

5. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 4, characterized in that: When the flame retardant is a mixture of one of dimethyl methyl phosphate and triphenyl phosphate, nano aluminum hydroxide and nano magnesium hydroxide, the mass ratio of dimethyl methyl phosphate and one of triphenyl phosphate, nano aluminum hydroxide and nano magnesium hydroxide is 1: (0.5-2): (1-3).

6. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 1, characterized in that: The antioxidant is one or more of pentaerythritol beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, n-octadecyl beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,6-di-tert-butyl-4-methylphenol.

7. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 1, characterized in that: The compatibilizer is one or both of maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene.

8. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 1, characterized in that: The melt blending is carried out in a twin-screw extruder. The temperature of the plasticizing section of the twin-screw extruder is 190-200°C, the temperature of the metering section is 200-220°C, the head temperature is 220-230°C, and the screw speed is 50r / min.

9. The method for preparing a highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe according to claim 1, characterized in that: Injection molding is carried out in an injection molding machine. The temperature of the feeding section of the injection molding machine is 190-200°C, the temperature of the plasticizing section is 200-220°C, the temperature of the head is 220-230°C, and the plasticizing length is 65-75mm.

10. A highly flame-retardant resin layer composite material for a steel wire skeleton polyethylene pipe prepared according to the method of any one of claims 1 to 9.

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