Flame-retardant modified polyethylene cable insulation layer and preparation method thereof

Abstract

The invention relates to the technical field of cables, and particularly discloses a flame-retardant modified polyethylene cable insulation layer and a preparation method thereof. The flame-retardant modified polyethylene cable insulating layer comprises the following raw materials in parts by weight: 90-100 parts of polyethylene resin; 30 to 40 parts of EVA resin; 10 to 20 parts of a modified flame retardant; 5-10 parts of aluminum hydroxide micro powder; 5 to 10 parts of barium stearate; 1-5 parts of dimethyl silicone oil; 0.8 to 1.2 parts of a silane coupling agent; 0.5 to 1 part of carbon black; 1-3 parts of an antioxidant; 1-3 parts of a calcium-zinc stabilizer; 1-3 parts of a filler; the modified flame retardant is obtained by modifying melamine cyanurate by aluminum tri-sec-butoxide. According to the cable insulation layer, the modified flame retardant is added, in the combustion process, the modified flame retardant can rapidly form a compact aluminum oxide layer and a carbon layer, the concentration of combustible gas is reduced, the combustion speed is slowed down, and therefore the flame retardant performance of the insulation layer is remarkably improved.

Description

Technical Field

[0001] This application relates to the technical field of cables. More specifically, it relates to a flame-retardant modified polyethylene cable insulation layer and a preparation method thereof. Background Art

[0002] The main function of the cable insulation layer is to prevent current from passing through the wire or cable outer skin into the surrounding environment or other conductors, thereby preventing electrical accidents such as electric shock and short circuit. The insulation layer can ensure the mutual insulation between the conductors in the cable and the surrounding environment or adjacent conductors, ensuring that the current transmitted by the conductor core only propagates along the wire and does not flow to the outside.

[0003] In the related art, the cable insulation layer is usually made of a polyethylene insulation layer. The polyethylene material has excellent electrical insulation performance and chemical corrosion resistance. However, the flame resistance of polyethylene is poor and it is easy to burn under conditions such as high temperature, heat generation, and discharge, thus causing fires, which limits its application in some occasions with strict requirements for flame retardant performance.

[0004] In order to improve the flame retardant performance of the polyethylene insulation layer, this application provides a flame-retardant modified polyethylene cable insulation layer and a preparation method thereof. Summary of the Invention

[0005] This application provides a flame-retardant modified polyethylene cable insulation layer and a preparation method thereof. The flame-retardant modified polyethylene cable insulation layer can enhance the mechanical properties, heat resistance, flame retardant performance, processing performance, and weather resistance of the insulation layer through the blending modification of polyethylene resin and EVA resin and the addition of a modified flame retardant. During the combustion process, the modified flame retardant can quickly form a dense alumina layer and carbon layer, reduce the concentration of combustible gases, and slow down the combustion speed, thus significantly improving the flame retardant performance of the insulation layer.

[0006] A flame-retardant modified polyethylene cable insulation layer provided by this application adopts the following technical solution: A flame-retardant modified polyethylene cable insulation layer, wherein the insulation layer is made of the following raw materials in parts by weight: 90 - 100 parts of polyethylene resin; 30 - 40 parts of EVA resin; 10 - 20 parts of modified flame retardant; 5 - 10 parts of aluminum hydroxide fine powder; 5 - 10 parts of barium stearate; 1 - 5 parts of dimethyl silicone oil; 0.8 - 1.2 parts of silane coupling agent; 0.5 - 1 part of carbon black; 1 - 3 parts of antioxidant; 1 - 3 parts of calcium-zinc stabilizer; 1 - 3 parts of filler; The modified flame retardant is obtained by modifying melamine cyanurate with aluminum tri-sec-butoxide.

[0007] By adopting the above technical solution, a interpenetrating network structure can be formed through the blend modification of polyethylene resin and EVA resin, enhancing the mechanical properties and heat resistance of the insulating layer. At the same time, the vinyl acetate units in the EVA resin can copolymerize with the ethylene units in the polyethylene resin to form a more compact molecular chain structure, thereby improving the flame retardancy of the insulating layer. In addition, the addition of EVA resin can also improve the processing performance and weather resistance of the insulating layer. By adding the modified flame retardant, during the combustion process, MCA in the modified flame retardant decomposes when heated, generating and gases such as. These gases rapidly diffuse within the combustion zone, occupying the space originally occupied by the combustible gases, thereby reducing the concentration of combustible gases and slowing down the combustion rate. In addition, during the combustion process, aluminum tri-sec-butoxide in the modified flame retardant will form a dense aluminum oxide layer on the surface of the insulating layer material. This aluminum oxide layer has excellent heat insulation performance and can effectively prevent heat from transferring into the interior of the insulating layer, thereby slowing down the heating rate of the material. At the same time, the aluminum oxide layer can also prevent or delay the outward diffusion of small molecule combustibles from the interior of the insulating layer, preventing them from coming into contact with oxygen in the air and burning. In addition, the aluminum oxide layer can also promote the formation of a carbon layer, increasing the thickness and density of the carbon layer, further improving the flame retardancy of the insulating layer.

[0008] The polyethylene cable insulating layer prepared with this modified flame retardant shows excellent performance in terms of flame retardancy. Specifically, during the combustion process, a dense aluminum oxide layer and a carbon layer can be rapidly formed on this insulating layer, effectively preventing the spread of fire. At the same time, due to the gas-phase flame retardant effect of the modified flame retardant, the concentration of combustible gases in the combustion zone has been significantly reduced, and the combustion rate has been effectively controlled. Therefore, this insulating layer shows excellent flame retardant performance in the flame retardancy test and can meet the flame retardant requirements of the cable.

[0009] Optionally, the modified flame retardant is prepared by the following method: A. Mix β-alanine, acetone, melamine cyanurate and deionized water, and adjust the pH value of the mixed system to 10 with ammonia water to obtain a premixed solution; B. Add an emulsifier to the premixed solution, raise the temperature to 50 °C, stir and react at a rate of 500 r / min for 10 - 20 min, then add aluminum tri-sec-butoxide, raise the temperature to 60 °C, continue stirring for 2 - 4 h, and then filter, wash and dry to obtain the modified flame retardant.

[0010] By adopting the above technical solution, during the preparation process, the mixing of β-alanine, acetone, melamine cyanurate and deionized water, as well as the adjustment of the pH value, provide a good environment for the subsequent emulsification reaction and modification reaction. The addition of the emulsifier and the control of the stirring reaction conditions ensure the uniform dispersion and size control of the modified flame retardant particles.

[0011] β-alanine is beneficial to promoting the uniform dispersion of acetone and melamine cyanurate in deionized water. Acetone, as an auxiliary raw material, enhances the compatibility between the modified flame retardant and the polyethylene resin. The role of the emulsifier is to disperse raw materials such as melamine cyanurate and aluminum tri-sec-butoxide into tiny particles, improving their uniform dispersion in the insulating layer. The stirring reaction conditions control the particle size and morphology of the modified flame retardant, thereby enhancing its flame retardant effect in the insulating layer.

[0012] Optionally, the mass ratio of β-alanine, acetone, melamine cyanurate and deionized water in step A is (0.15 - 0.25):2:1:10.

[0013] Optionally, the emulsifier is sodium alkyl sulfonate, and the addition amount of the emulsifier is 2.5% - 5% of the mass of melamine cyanurate.

[0014] Optionally, the addition amount of the aluminum tri-sec-butoxide is 7% - 15% of the mass of melamine cyanurate.

[0015] Optionally, the antioxidant is a hindered phenol antioxidant.

[0016] Optionally, the melt index of the polyethylene resin is 2 - 3.5 g / min; the EVA resin is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 12% - 18%, and the melt index of the EVA resin is 3 - 5 g / 10 min.

[0017] This application also provides a preparation method for a flame retardant modified polyethylene cable insulating layer, adopting the following technical solution: A preparation method for a flame retardant modified polyethylene cable insulating layer, comprising the following steps: S1. Mix the polyethylene resin, EVA resin, aluminum hydroxide fine powder, barium stearate, dimethyl silicone oil, silane coupling agent, carbon black, antioxidant, calcium-zinc stabilizer and filler evenly according to the weight portion ratio to obtain a mixed material; S2. Add the mixed material into an extruder and carry out melt blending at 185°C - 200°C and a pressure of 90 MPa - 110 MPa to form a melt blend; S3. Add the modified flame retardant to the melt blend, continue melt blending at 180°C - 200°C and a pressure of 90 MPa - 110 MPa, then extrude through a die, and obtain a flame-retardant modified polyethylene cable insulation layer after cooling and solidification.

[0018] In summary, the present application has the following beneficial effects: 1. Since the present application uses the blend modification of polyethylene resin and EVA resin, the blend modification of polyethylene resin and EVA resin can form an interpenetrating network structure, enhancing the mechanical properties and heat resistance of the insulation layer. At the same time, the vinyl acetate units in the EVA resin can copolymerize with the ethylene units in the polyethylene resin to form a more compact molecular chain structure, thereby improving the flame retardancy of the insulation layer. By adding the modified flame retardant, during the combustion process, the modified flame retardant can effectively slow down the combustion rate, and moreover, aluminum tri-sec-butoxide in the modified flame retardant will form a dense aluminum oxide layer on the surface of the insulation layer material during the combustion process. This aluminum oxide layer has excellent heat insulation performance and can effectively prevent heat from transferring into the interior of the insulation layer, thereby further enhancing the flame retardant effect of the insulation layer. In addition, the aluminum oxide layer can also promote the formation of a carbon layer, increasing the thickness and density of the carbon layer, and further improving the flame retardancy of the insulation layer.

[0019] 2. In the present application, the modified flame retardant is obtained by modifying melamine cyanurate with aluminum tri-sec-butoxide. β-Alanine is beneficial to promoting the uniform dispersion of acetone and melamine cyanurate in deionized water, and acetone, as an auxiliary raw material, enhances the compatibility between the modified flame retardant and the polyethylene resin. The role of the emulsifier is to disperse raw materials such as melamine cyanurate and aluminum tri-sec-butoxide into tiny particles, improving their uniform dispersion in the insulation layer. The stirring reaction conditions control the particle size and morphology of the modified flame retardant, thereby enhancing its flame retardant effect in the insulation layer. Specific Embodiments

[0020] The following further elaborates the present application in conjunction with embodiments.

[0021] Preparation Example of Modified Flame Retardant Preparation Example 1 The modified flame retardant is obtained by the following method: A. Mix β-alanine, acetone, melamine cyanurate, and deionized water according to a mass ratio of 0.15:2:1:10, and adjust the pH value of the mixed system to 10 with ammonia water to obtain a premixed solution; B. Add sodium alkyl sulfonate to the premixed solution. The addition amount of sodium alkyl sulfonate is 2.5% of the mass of melamine cyanurate. Then raise the temperature to 50 °C and stir and react at a rate of 500 r / min for 10 min. Then add aluminum tri-sec-butoxide. The addition amount of aluminum tri-sec-butoxide is 7% of the mass of melamine cyanurate. Raise the temperature to 60 °C and continue stirring for 2 h. Then filter, wash, and dry to obtain the modified flame retardant.

[0022] Preparation Example 2 The modified flame retardant is obtained by the following method: A. Mix β-alanine, acetone, melamine cyanurate, and deionized water according to a mass ratio of 0.2:2:1:10, and adjust the pH value of the mixed system to 10 with ammonia water to obtain a premixed solution; B. Add sodium alkyl sulfonate to the premixed solution. The addition amount of sodium alkyl sulfonate is 3.5% of the mass of melamine cyanurate. Then raise the temperature to 50 °C and stir and react at a rate of 500 r / min for 15 min. Then add aluminum tri-sec-butoxide. The addition amount of aluminum tri-sec-butoxide is 10% of the mass of melamine cyanurate. Raise the temperature to 60 °C and continue stirring for 3 h. Then filter, wash, and dry to obtain the modified flame retardant.

[0023] Preparation Example 3 The modified flame retardant is obtained by the following method: A. Mix β-alanine, acetone, melamine cyanurate, and deionized water according to a mass ratio of 0.25:2:1:10, and adjust the pH value of the mixed system to 10 with ammonia water to obtain a premixed solution; B. Add sodium alkyl sulfonate to the premixed solution. The addition amount of sodium alkyl sulfonate is 5% of the mass of melamine cyanurate. Then raise the temperature to 50 °C and stir and react at a rate of 500 r / min for 20 min. Then add aluminum tri-sec-butoxide. The addition amount of aluminum tri-sec-butoxide is 15% of the mass of melamine cyanurate. Raise the temperature to 60 °C and continue stirring for 3 h. Then filter, wash, and dry to obtain the modified flame retardant.

[0024] Preparation Example 4 The difference between the modified flame retardant and Preparation Example 3 is that in this example, an equal amount of methylcyclosiloxane is used instead of aluminum tri-sec-butoxide.

[0025] Example 1

[0026] A flame-retardant modified polyethylene cable insulation layer, the raw materials and their dosages of each component are shown in Table 1. Among them, the melt index of the polyethylene resin is 2 g / min; the EVA resin is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 12%, and the melt index of the EVA resin is 3 g / 10 min; the modified flame retardant is the modified flame retardant prepared in Preparation Example 1; the antioxidant is the hindered phenol antioxidant 1076; the filler is titanium dioxide.

[0027] A method for preparing a flame-retardant modified polyethylene cable insulation layer is as follows: S1. Mix the polyethylene resin, EVA resin, aluminum hydroxide fine powder, barium stearate, dimethyl silicone oil, silane coupling agent, carbon black, antioxidant, calcium-zinc stabilizer and filler evenly according to the weight part ratio to obtain a mixed material; S2. Add the mixed material into an extruder, and carry out melt blending at 185 °C and a pressure of 90 MPa for 2 h to form a melt blend; S3. Add the modified flame retardant into the melt blend, continue to carry out melt blending at 180 °C and a pressure of 90 MPa for 2 h, and then extrude through a die. After cooling and solidifying, a flame-retardant modified polyethylene cable insulation layer is obtained.

[0028] Example 2

[0029] A flame-retardant modified polyethylene cable insulation layer, the raw materials and their dosages of each component are shown in Table 1. Among them, the melt index of the polyethylene resin is 3 g / min; the EVA resin is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 15%, and the melt index of the EVA resin is 4 g / 10 min; the modified flame retardant is the modified flame retardant prepared in Preparation Example 1; the antioxidant is the hindered phenol antioxidant 1076; the filler is titanium dioxide.

[0030] A method for preparing a flame-retardant modified polyethylene cable insulation layer is as follows: S1. Mix the polyethylene resin, EVA resin, aluminum hydroxide fine powder, barium stearate, dimethyl silicone oil, silane coupling agent, carbon black, antioxidant, calcium-zinc stabilizer and filler evenly according to the weight part ratio to obtain a mixed material; S2. Add the mixed material into an extruder, and carry out melt blending at 190 °C and a pressure of 100 MPa for 1.5 h to form a melt blend; S3. Add the modified flame retardant into the melt blend, continue to carry out melt blending at 190 °C and a pressure of 100 MPa for 1.5 h, and then extrude through a die. After cooling and solidifying, a flame-retardant modified polyethylene cable insulation layer is obtained.

[0031] Example 3

[0032] A flame-retardant modified polyethylene cable insulation layer, the raw materials and their dosages of each component are shown in Table 1. Among them, the melt index of the polyethylene resin is 3.5 g / min; the EVA resin is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 18%, and the melt index of the EVA resin is 5 g / 10 min; the modified flame retardant is the modified flame retardant prepared in Preparation Example 1; the antioxidant is the hindered phenol antioxidant 1076; the filler is titanium dioxide.

[0033] A method for preparing a flame-retardant modified polyethylene cable insulation layer is as follows: S1. Mix the polyethylene resin, EVA resin, aluminum hydroxide micropowder, barium stearate, dimethyl silicone oil, silane coupling agent, carbon black, antioxidant, calcium-zinc stabilizer and filler evenly according to the weight ratio to obtain a mixed material; S2. Add the mixed material into an extruder, and carry out melt blending at 200 °C and a pressure of 110 MPa for 1 h to form a melt blend; S3. Add the modified flame retardant to the melt blend, continue to carry out melt blending at 200 °C and a pressure of 110 MPa for 1 h, and then extrude through a die. After cooling and solidifying, a flame-retardant modified polyethylene cable insulation layer is obtained.

[0034] Table 1 Raw material components and dosages (kg) of the insulation layer in Examples 1-3 Raw materials Example 1 Example 2 Example 3 Polyethylene resin 90 95 100 EVA resin 30 35 40 Modified flame retardant 10 15 20 Aluminum hydroxide micropowder 5 8 10 Barium stearate 5 8 10 Dimethyl silicone oil 1 3 5 Silane coupling agent 0.8 1.0 1.2 Carbon black 0.5 0.8 1.0 Antioxidant 1 2 3 Calcium-zinc stabilizer 1 2 3 Filler 1 2 3

[0035] Example 4

[0036] A flame-retardant modified polyethylene cable insulation layer, which is different from Example 3 in that the modified flame retardant in this example is the modified flame retardant prepared in Preparation Example 2.

[0037] Example 5

[0038] A flame-retardant modified polyethylene cable insulation layer, which is different from Example 3 in that the modified flame retardant in this example is the modified flame retardant prepared in Preparation Example 3.

[0039] Comparative Example 1 The cable insulation layer prepared in this comparative example was prepared according to the method of Example 1 of the patent with the application number CN201810705533.8 and the patent name "Cable Insulation Layer with Flame Retardancy and Its Preparation Method".

[0040] Comparative Example 2 A flame-retardant modified polyethylene cable insulation layer, which is different from Example 3 in that the modified flame retardant in this example is unmodified melamine cyanurate.

[0041] Comparative Example 3 A flame-retardant modified polyethylene cable insulation layer, which is different from that of Example 3 in that the modified flame retardant in this example is the modified flame retardant prepared in Preparation Example 4.

[0042] Performance detection test Performance tests were carried out on the flame-retardant modified polyethylene cable insulation layers prepared in Examples 1-5 and Comparative Examples 1-3, and the test results are shown in Table 2.

[0043] Table 2 Test results of Examples 1-5 and Comparative Examples 1-3 Item Limiting oxygen index (%) Tensile strength (MPa) Elongation at break (%) Example 1 46 25.6 472 Example 2 45 26.1 475 Example 3 47 26.2 478 Example 4 47 26.8 470 Example 5 49 26.9 474 Comparative example 1 28 19.2 378 Comparative example 2 30 23.4 402 Comparative example 3 29 22.6 396 The limiting oxygen index is an important indicator to measure the flame retardancy of materials, which represents the lowest oxygen concentration at which materials can maintain combustion in a mixed gas of oxygen and nitrogen. The LOI values of Examples 1-5 are all above 45%, much higher than those of Comparative Examples 1-3 (the highest is 30%). This is mainly due to the blend modification of polyethylene resin and EVA resin. The blend modification of polyethylene resin and EVA resin can form an interpenetrating network structure, enhancing the mechanical properties and heat resistance of the insulation layer. At the same time, in combination with the modified flame retardant, aluminum tri-sec-butoxide in the modified flame retardant will form a dense aluminum oxide layer on the surface of the insulation layer material during combustion. This aluminum oxide layer has excellent heat insulation performance and can effectively prevent heat from transferring into the insulation layer, thereby further enhancing the flame retardant effect of the insulation layer. In addition, the aluminum oxide layer can also promote the formation of a carbon layer, increasing the thickness and density of the carbon layer, and further improving the flame retardancy of the insulation layer.

[0044] The cable insulation layer prepared by the traditional method in Comparative Example 1 has low flame retardancy, tensile strength and elongation at break. In Comparative Example 2, unmodified melamine cyanurate was used as the flame retardant. Although the flame retardancy was improved to a certain extent, its effect is still insufficient compared with the modified flame retardant. In Comparative Example 3, methylcyclosiloxane was used to replace aluminum tri-sec-butoxide for modification, but the flame retardant effect was not ideal, indicating that aluminum tri-sec-butoxide plays a key role in the modified flame retardant.

[0045] This specific embodiment is only an explanation of the present application and does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A flame retardant modified polyethylene cable insulation layer, characterized in that: The insulating layer is made of the following raw materials in parts by weight: Polyethylene resin 90-100 parts; 30-40 parts of EVA resin; 10-20 parts of modified flame retardant; 5-10 parts of aluminum hydroxide powder; Barium stearate 5-10 parts; 1-5 parts of dimethyl silicone oil; Silane coupling agent 0.8-1.2 parts; Carbon black 0.5-1 part; 1-3 parts of antioxidant; Calcium zinc stabilizer 1-3 parts; 1-3 parts of filler; The modified flame retardant is obtained by modifying melamine cyanurate with aluminum tri-secondary butoxide.

2. The flame retardant modified polyethylene cable insulation layer according to claim 1, characterized in that: The modified flame retardant is prepared by the following method: A. After mixing β-alanine, acetone, melamine cyanurate and deionized water, the pH value of the mixed system is adjusted to 10 with aqueous ammonia to obtain a premixed solution; B. Add emulsifier to the premixed liquid, heat it to 50°C, stir and react at a rate of 500r / min for 10-20min, then add aluminum tri-sec-butoxide, heat it to 60°C, continue stirring for 2-4h, and then filter, wash and dry to obtain a modified flame retardant.

3. The flame retardant modified polyethylene cable insulation layer according to claim 2, characterized in that: In step A, the mass ratio of β-alanine, acetone, melamine cyanurate and deionized water is (0.15-0.25):2:1:

10.

4. The flame retardant modified polyethylene cable insulation layer according to claim 2, characterized in that: The emulsifier is sodium alkyl sulfonate, and the amount of the emulsifier added is 2.5%-5% of the mass of melamine cyanurate.

5. The flame retardant modified polyethylene cable insulation layer according to claim 2, characterized in that: The amount of aluminum tri-sec-butoxide added is 7%-15% of the mass of melamine cyanurate.

6. The flame retardant modified polyethylene cable insulation layer according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant.

7. The flame retardant modified polyethylene cable insulation layer according to claim 1, characterized in that: The polyethylene resin has a melt index of 2-3.5 g / min; the EVA resin is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 12%-18%, and the melt index of the EVA resin is 3-5 g / 10 min.

8. A method for preparing a flame retardant modified polyethylene cable insulation layer according to any one of claims 1 to 7, characterized in that: The steps include: S1. Evenly mix polyethylene resin, EVA resin, aluminum hydroxide powder, barium stearate, dimethyl silicone oil, silane coupling agent, carbon black, antioxidant, calcium zinc stabilizer and filler according to the weight ratio to obtain a mixed material; S2, adding the mixed material into an extruder, and melt blending at 185° C.-200° C. and 90 MPa-110 MPa pressure to form a melt blend; S3. Add the modified flame retardant to the molten blend, continue melt blending at 180°C-200°C and 90MPa-110MPa pressure, extrude through a die, and obtain a flame retardant modified polyethylene cable insulation layer after cooling and solidification.