Heat-resistant flame-retardant PE film and preparation method thereof

Abstract

The application provides a heat-resistant flame-retardant PE film and a preparation method thereof, and belongs to the technical field of polyethylene materials. The PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 10-14 parts of acrylonitrile grafted polyethylene, 30-40 parts of a composite flame retardant, 0.5-2 parts of a lubricant and 0.2-1 parts of an antioxidant, wherein the composite flame retardant is a mixture of brominated triazine and pre-coated red mud, and the pre-coated red mud is prepared by organic coating of red mud. The preparation method is simple and easy for industrial production. Through the combined use of flame-retardant substances and the separate treatment of raw material components, the flame-retardant performance of the flame retardant can be effectively exerted, and the compatibility between the flame retardant and the matrix material is obviously improved. The finally obtained PE film has high flame-retardant performance and mechanical strength, and is expected to be more widely applied in the fields of packaging, building decoration and electronic appliances.

Description

Technical Field

[0001] This invention belongs to the field of polyethylene material technology, specifically relating to a heat-resistant and flame-retardant PE film and its preparation method. Background Technology

[0002] Polyethylene is a highly crystalline, non-polar thermoplastic resin. Polyethylene film is widely used due to its excellent chemical stability, processing performance, and low cost. However, the limiting oxygen index of polyethylene is only 17-18%, making it a flammable material. When burning, it is accompanied by problems such as dripping and large amount of smoke, posing a serious fire hazard.

[0003] In the existing technology, adding flame retardants to the matrix material can give the film product a certain flame retardancy. However, due to the limitations of its own structure and chemical properties, the flame retardant efficiency is low and its inhibitory effect on the combustion process is limited. Moreover, the high addition amount of flame retardant will reduce the strength of the material, making it difficult to obtain polyethylene flame retardant materials with good flame retardancy and high strength. This limits PE film in some application fields with high requirements for both flame retardancy and mechanical strength. Summary of the Invention

[0004] To address the problems existing in the background art, the present invention provides a heat-resistant and flame-retardant PE film and its preparation method, which can effectively utilize the flame-retardant properties of flame retardants, improve flame-retardant efficiency, and enhance the mechanical strength of the material. The resulting flame-retardant PE film has high flame-retardant performance and mechanical strength.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A heat-resistant and flame-retardant PE film, by weight, comprises the following raw material components: 100 parts of polyethylene resin, 10-14 parts of acrylonitrile-grafted polyethylene, 30-40 parts of composite flame retardant, 0.5-2 parts of lubricant, and 0.2-1 parts of antioxidant.

[0006] The composite flame retardant is a mixture of brominated triazine and pre-coated red mud, wherein the pre-coated red mud is prepared by organically coating red mud.

[0007] Furthermore, the mass ratio of bromotriazine to pre-coated red mud in the composite flame retardant is 1.8-2.2:1.

[0008] Furthermore, the preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.1-0.3:4-6 until homogeneous, heat to 40-60℃ and stir for 20-40 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud is roasted at 450-550℃ for 2-4 hours. The roasted red mud is then crushed and sieved through a 300-500 mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing vinylsilane coupling agent, heat to 60-80℃, stir and react for 1-2 hours. After the reaction is complete, remove the solvent to obtain pre-coated red mud.

[0009] Furthermore, in step A3, the vinyl silane coupling agent is one or a mixture of two of vinyltrimethoxysilane and vinyltriethoxysilane.

[0010] Furthermore, in step A3, the amount of vinylsilane coupling agent added to the ethanol solution is 1-3% of the mass of ethanol.

[0011] Furthermore, in step A3, the mass ratio of ethanol solution to pretreated red mud powder is 10:0.5-1.5.

[0012] Furthermore, the preparation of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 60-80 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.2-0.4 parts of sodium dodecylbenzenesulfonate and 35-45 parts of deionized water to the reaction vessel, stir evenly, and then add 1-2 parts of acrylonitrile and 20-30 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.05-0.1 parts of tert-butyl hydroperoxide and 0.01-0.03 parts of ferrous sulfate to the premixed solution in step B1, heat to 40-60℃, and react at a constant temperature for 4-6 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

[0013] Furthermore, the lubricant is one or a mixture of two or more of polyethylene wax, silicone wax, and erucamide.

[0014] Furthermore, the antioxidant is one or a mixture of two or more of antioxidant 1010, antioxidant 1076 and antioxidant 168.

[0015] A method for preparing a heat-resistant and flame-retardant PE film includes the following steps: S1. Add acrylonitrile-grafted polyethylene to the composite flame retardant and mix evenly to obtain a premix; S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and cooled to obtain a heat-resistant and flame-retardant PE film.

[0016] This application has the following beneficial effects: 1. The preparation method provided by this invention is simple and easy to industrialize. By using flame retardant substances in combination and treating the raw material components separately, the flame retardant properties of the flame retardant can be effectively utilized, the flame retardant efficiency can be improved, the compatibility between the flame retardant and the matrix material can be improved, and the dispersion ability of the flame retardant substances can be enhanced. Ultimately, the PE film obtained has high flame retardant properties and mechanical strength, meeting the dual requirements of flame retardancy and mechanical strength of film materials in different fields.

[0017] 2. In the composite flame retardant of this invention, red mud, which is an industrial waste residue, is used in combination with the novel flame retardant brominated triazine to achieve a combination of organic and inorganic flame retardancy. This allows the two to complement each other effectively, which not only improves the flame retardant efficiency and enhances its fluidity and processing performance in the polymer matrix, but also improves the compatibility of the red mud with brominated triazine after organic coating. This results in a more uniform dispersion of the flame retardant material in the resin matrix, effectively reducing the impact of the flame retardant on the mechanical properties of the film, while fully leveraging the flame retardant effect of the flame retardant.

[0018] 3. In the preparation of acrylonitrile-grafted polyethylene, the introduction of polar cyano groups (-CN) enables the resin matrix to fuse well with triazobromobromotriazine, which has a certain polarity, thus improving the interfacial bonding performance between materials. This enhances the mechanical strength of the PE film while also improving its flame retardant properties. In addition, the vinyl silane coupling agent forms an organic coating layer on the surface of red mud. Both the vinyl groups in the vinyl silane molecule and the cyano groups in the acrylonitrile molecule have certain polarity and reactivity. When the groups are close to each other, they interact with each other. When the two are mixed, a tightly adsorbed layer is formed at the interface, which can effectively reduce the migration and shedding of the flame retardant during the combustion process. This helps to protect the matrix material and improve the flame retardant effect, further enhancing the flame retardant performance of the film material. Detailed Implementation

[0019] The present application will be further described in detail below with reference to the embodiments.

[0020] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0021] Example 1 A heat-resistant and flame-retardant PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 12 parts of acrylonitrile-grafted polyethylene, 35 parts of composite flame retardant, 1 part of lubricant, and 0.5 parts of antioxidant. The composite flame retardant is a mixture of brominated triazine and pre-coated red mud in a 2:1 mass ratio. The lubricant is polyethylene wax, and the antioxidant is antioxidant 1010. The specific preparation process includes the following steps: S1. Weigh each raw material component by weight, add acrylonitrile-grafted polyethylene to the composite flame retardant, mix evenly, and obtain a premix. S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and then cooled to obtain a heat-resistant and flame-retardant PE film; The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.2:5 until homogeneous, heat to 50℃ and stir for 30 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud was calcined at 500℃ for 3 hours. The calcined red mud was then crushed and sieved through a 400-mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing a vinyl silane coupling agent. The amount of vinyl silane coupling agent added to the ethanol solution is 2% of the mass of ethanol. The mass ratio of ethanol solution to pretreated red mud powder is 10:1. Heat to 70°C and stir for 1.5 h. After the reaction is complete, remove the solvent to obtain pre-coated red mud. The vinyl silane coupling agent is vinyltrimethoxysilane. The preparation of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 70 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.3 parts of sodium dodecylbenzenesulfonate and 40 parts of deionized water to the reaction vessel and stir evenly. Then add 1.5 parts of acrylonitrile and 25 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.08 parts of tert-butyl hydroperoxide and 0.02 parts of ferrous sulfate to the premixed solution in step B1, heat to 50°C, and react at a constant temperature for 5 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

[0022] Example 2 A heat-resistant and flame-retardant PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 10 parts of acrylonitrile-grafted polyethylene, 30 parts of composite flame retardant, 0.5 parts of lubricant, and 0.2 parts of antioxidant. The composite flame retardant is a mixture of brominated triazine and pre-coated red mud in a mass ratio of 1.8:1. The lubricant is silicone wax, and the antioxidant is antioxidant 1076. The specific preparation process includes the following steps: S1. Weigh each raw material component by weight, add acrylonitrile-grafted polyethylene to the composite flame retardant, mix evenly, and obtain a premix. S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and then cooled to obtain a heat-resistant and flame-retardant PE film; The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.1:4 until homogeneous, heat to 40℃ and stir for 40 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud was calcined at 450℃ for 4 hours. The calcined red mud was then crushed and sieved through a 300-mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing a vinyl silane coupling agent. The amount of vinyl silane coupling agent added to the ethanol solution is 1% of the mass of ethanol. The mass ratio of ethanol solution to pretreated red mud powder is 10:0.5. Heat to 60°C and stir for 2 hours. After the reaction is complete, remove the solvent to obtain pre-coated red mud. The vinyl silane coupling agent is vinyltriethoxysilane. The preparation of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 60 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.2 parts of sodium dodecylbenzenesulfonate and 35 parts of deionized water to the reaction vessel and stir evenly. Then add 1 part of acrylonitrile and 20 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.05 parts of tert-butyl hydroperoxide and 0.01 parts of ferrous sulfate to the premixed solution in step B1, heat to 40°C, and react at a constant temperature for 6 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

[0023] Example 3 A heat-resistant and flame-retardant PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 14 parts of acrylonitrile-grafted polyethylene, 40 parts of composite flame retardant, 2 parts of lubricant, and 1 part of antioxidant. The composite flame retardant is a mixture of brominated triazine and pre-coated red mud in a mass ratio of 2.2:1. The lubricant is erucamide, and the antioxidant is antioxidant 168. The specific preparation process includes the following steps: S1. Weigh each raw material component by weight, add acrylonitrile-grafted polyethylene to the composite flame retardant, mix evenly, and obtain a premix. S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and then cooled to obtain a heat-resistant and flame-retardant PE film; The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.3:6 until homogeneous, heat to 60℃ and stir for 20 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud was calcined at 550℃ for 2 hours. The calcined red mud was then crushed and sieved through a 500-mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing a vinyl silane coupling agent. The amount of vinyl silane coupling agent added to the ethanol solution is 3% of the mass of ethanol. The mass ratio of ethanol solution to pretreated red mud powder is 10:1.5. Heat to 80°C and stir for 1 hour. After the reaction is complete, remove the solvent to obtain pre-coated red mud. The vinyl silane coupling agent is vinyltrimethoxysilane. The preparation of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 80 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.4 parts of sodium dodecylbenzenesulfonate and 45 parts of deionized water to the reaction vessel and stir evenly. Then add 2 parts of acrylonitrile and 30 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.1 parts of tert-butyl hydroperoxide and 0.03 parts of ferrous sulfate to the premixed solution from step B1, heat to 60°C, and react at a constant temperature for 4 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

[0024] Example 4 A heat-resistant and flame-retardant PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 14 parts of acrylonitrile-grafted polyethylene, 30 parts of composite flame retardant, 2 parts of lubricant, and 0.2 parts of antioxidant. The composite flame retardant is a mixture of brominated triazine and pre-coated red mud in a mass ratio of 2.2:1. The lubricant is polyethylene wax, and the antioxidant is antioxidant 1076. The specific preparation process includes the following steps: S1. Weigh each raw material component by weight, add acrylonitrile-grafted polyethylene to the composite flame retardant, mix evenly, and obtain a premix. S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and then cooled to obtain a heat-resistant and flame-retardant PE film; The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.1:6 until homogeneous, heat to 40℃ and stir for 40 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud was calcined at 450℃ for 4 hours. The calcined red mud was then crushed and sieved through a 300-mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing a vinyl silane coupling agent. The amount of vinyl silane coupling agent added to the ethanol solution is 3% of the mass of ethanol. The mass ratio of ethanol solution to pretreated red mud powder is 10:0.5. Heat to 80°C and stir for 1 hour. After the reaction is complete, remove the solvent to obtain pre-coated red mud. The vinyl silane coupling agent is vinyltrimethoxysilane. The preparation of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 80 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.2 parts of sodium dodecylbenzenesulfonate and 45 parts of deionized water to the reaction vessel and stir evenly. Then add 1 part of acrylonitrile and 20 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.1 parts of tert-butyl hydroperoxide and 0.01 parts of ferrous sulfate to the premixed solution in step B1, heat to 60°C, and react at a constant temperature for 4 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

[0025] Example 5 A heat-resistant and flame-retardant PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 10 parts of acrylonitrile-grafted polyethylene, 35 parts of composite flame retardant, 0.5 parts of lubricant, and 1 part of antioxidant. The composite flame retardant is a mixture of brominated triazine and pre-coated red mud in a mass ratio of 1.8:1. The lubricant is erucamide, and the antioxidant is antioxidant 1076. The specific preparation process includes the following steps: S1. Weigh each raw material component by weight, add acrylonitrile-grafted polyethylene to the composite flame retardant, mix evenly, and obtain a premix. S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and then cooled to obtain a heat-resistant and flame-retardant PE film; The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.3:4 until homogeneous, heat to 60℃ and stir for 20 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud was calcined at 550℃ for 2 hours. The calcined red mud was then crushed and sieved through a 500-mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing a vinyl silane coupling agent. The amount of vinyl silane coupling agent added to the ethanol solution is 1% of the mass of ethanol. The mass ratio of ethanol solution to pretreated red mud powder is 10:1.5. Heat to 60°C and stir for 2 hours. After the reaction is complete, remove the solvent to obtain pre-coated red mud. The vinyl silane coupling agent is vinyltriethoxysilane. The preparation of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 60 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.4 parts of sodium dodecylbenzenesulfonate and 35 parts of deionized water to the reaction vessel and stir evenly. Then add 2 parts of acrylonitrile and 30 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.1 parts of tert-butyl hydroperoxide and 0.03 parts of ferrous sulfate to the premixed solution from step B1, heat to 40°C, and react at a constant temperature for 6 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

[0026] Comparative Example 1 The only difference between this comparative example and Example 1 is that in the raw material composition of the heat-resistant and flame-retardant PE film, the acrylonitrile-grafted polyethylene is not grafted with acrylonitrile, that is, the acrylonitrile-grafted polyethylene is replaced with polyethylene resin, as follows: A heat-resistant and flame-retardant PE film is prepared from the following raw material components: 100 parts of polyethylene resin, 12 parts of polyethylene resin (70 mesh), 35 parts of composite flame retardant, 1 part of lubricant and 0.5 parts of antioxidant.

[0027] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in the preparation of the pre-coated red mud in the composite flame retardant, the red mud was not coated, as detailed below: The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.2:5 until homogeneous, heat to 50℃ and stir for 30 minutes to obtain dealkalized red mud; A2. The dealkalized red mud was roasted at 500℃ for 3 hours. The roasted red mud was then crushed and sieved through a 400-mesh sieve to obtain pre-coated red mud.

[0028] Comparative Example 3 The only difference between this comparative example and Example 1 is that, in the raw material components of the heat-resistant and flame-retardant PE film, the acrylonitrile-grafted polyethylene is not grafted with acrylonitrile, and in the preparation of the pre-coated red mud in the composite flame retardant, the red mud is not coated.

[0029] Proof of effectiveness The flame-retardant PE granules obtained in Examples 1-5 and Comparative Examples 1-3 were used to prepare test samples, and their tensile strength and limiting oxygen index were tested. The specific test results are shown in Table 1. 1. Tensile strength testing shall be conducted according to the method specified in GB / T 1040-2006; 2. The limiting oxygen index was tested according to the method specified in GB / T 2406-2009.

[0030] Table 1

[0031] Results Analysis Analysis of Examples 1-5 and Comparative Examples 1-3, and in conjunction with the data in Table 1, shows that the flame-retardant PE granules prepared in the embodiments of the present invention have a tensile strength of over 21.7 MPa and a limiting oxygen index of over 28.6%. Therefore, it can be seen that the PE film provided by the present invention has high flame-retardant properties and mechanical strength. Specific analysis is as follows: Comparing Comparative Example 1 with Example 1, it can be seen that when polyethylene is not grafted with acrylonitrile in the raw material components of the heat-resistant and flame-retardant PE film, the tensile strength of the obtained flame-retardant PE granules decreases from 22.4 MPa to 20.7 MPa, and the limiting oxygen index decreases from 29.2% to 26.9%. This indicates that by grafting acrylonitrile onto polyethylene, the mechanical strength and flame-retardant properties of the material can be improved. Comparing Comparative Example 2 with Example 1, it can be seen that in the preparation of pre-coated red mud in the composite flame retardant, when the red mud is not coated, the tensile strength of the obtained flame-retardant PE granules decreases from 22.4 MPa to 19.2 MPa, and the limiting oxygen index decreases from 29.2% to 25.8%. This indicates that by coating the red mud, the mechanical strength and flame retardant properties of the material can be improved. A comprehensive analysis of Comparative Examples 1-3 and Example 1 shows that both grafting acrylonitrile onto polyethylene and coating red mud can improve the flame retardant properties of the material. Furthermore, when these two treatments are used in combination, the increase in the limiting oxygen index of the resulting flame-retardant PE granules (the difference between Example 1 and Comparative Example 3) is significantly greater than the sum of the increases when the two treatments are used individually (the sum of the differences between Comparative Examples 1 and 3 and the sum of the differences between Comparative Examples 2 and 3). This indicates that the combination of grafting acrylonitrile onto polyethylene and coating red mud can produce a synergistic effect, significantly improving the flame retardant properties of the flame-retardant PE granules.

[0032] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0033] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A heat-resistant and flame-retardant PE film, characterized in that, By weight, it includes the following raw material components: 100 parts polyethylene resin, 10-14 parts acrylonitrile-grafted polyethylene, 30-40 parts composite flame retardant, 0.5-2 parts lubricant and 0.2-1 parts antioxidant; The composite flame retardant is a mixture of bromotriazine and pre-coated red mud, which is prepared by organically coating red mud. The preparation of pre-coated red mud includes the following: A1. Mix red mud, acetic acid and water in a mass ratio of 1:0.1-0.3:4-6 until homogeneous, heat to 40-60℃ and stir for 20-40 minutes to obtain dealkalized red mud; A2. The dealkali-treated red mud is roasted at 450-550℃ for 2-4 hours. The roasted red mud is then crushed and sieved through a 300-500 mesh sieve to obtain pretreated red mud powder. A3. Add the pretreated red mud powder to an ethanol solution containing vinylsilane coupling agent, heat to 60-80℃, stir and react for 1-2 hours, remove the solvent after the reaction is complete to obtain pre-coated red mud; The mass ratio of bromotriazine to pre-coated red mud in the composite flame retardant is 1.8-2.2:1; In step A3, the amount of vinylsilane coupling agent added to the ethanol solution is 1-3% of the mass of ethanol; In step A3, the mass ratio of ethanol solution to pretreated red mud powder is 10:0.5-1.

5.

2. The heat-resistant and flame-retardant PE film according to claim 1, characterized in that, In step A3, the vinyl silane coupling agent is one or a mixture of vinyltrimethoxysilane and vinyltriethoxysilane.

3. The heat-resistant and flame-retardant PE film according to claim 1, characterized in that, The preparation process of acrylonitrile-grafted polyethylene includes the following steps: B1. Pulverize polyethylene resin to 60-80 mesh to obtain polyethylene powder. Add 10 parts of polyethylene powder, 0.2-0.4 parts of sodium dodecylbenzenesulfonate and 35-45 parts of deionized water to the reaction vessel, stir evenly, and then add 1-2 parts of acrylonitrile and 20-30 parts of ethyl acetate to obtain a premixed solution. B2. Add 0.05-0.1 parts of tert-butyl hydroperoxide and 0.01-0.03 parts of ferrous sulfate to the premixed solution in step B1, heat to 40-60℃, and react at a constant temperature for 4-6 hours to obtain the reaction solution; B3. The reaction solution from step B2 is subjected to vacuum distillation to remove the solvent, cooled and discharged to obtain acrylonitrile-grafted polyethylene.

4. The heat-resistant and flame-retardant PE film according to claim 1, characterized in that, The lubricant is one or a mixture of two or more of polyethylene wax, silicone wax and erucamide.

5. The heat-resistant and flame-retardant PE film according to claim 1, characterized in that, The antioxidant is one or a mixture of two or more of antioxidant 1010, antioxidant 1076 and antioxidant 168.

6. A method for preparing a heat-resistant and flame-retardant PE film, used to prepare the heat-resistant and flame-retardant PE film according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add acrylonitrile-grafted polyethylene to the composite flame retardant and mix evenly to obtain a premix; S2. The premix from step S1, along with other raw material components such as polyethylene resin, lubricant, and antioxidant, is fed into a twin-screw extruder and extruded and granulated through a die and pelletizer to obtain flame-retardant PE granules. S3. The flame-retardant PE granules from step S2 are blown into a film using a blow molding machine and cooled to obtain a heat-resistant and flame-retardant PE film.

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