High-strength flame-retardant polyethylene cable and preparation method thereof

Abstract

The invention relates to the technical field of polyethylene cables, in particular to a high-strength flame-retardant polyethylene cable and a preparation method thereof.The high-strength flame-retardant polyethylene cable is composed of a copper stranded wire core and a flame-retardant protective layer on the surface of the copper stranded wire core; the flame-retardant protective sleeve is made of a high-strength flame-retardant material; the high-strength flame-retardant material comprises the following components in parts by weight: 80-100 parts of low-density polyethylene, 5-10 parts of a flame retardant, 3-5 parts of a performance additive, 1-1.5 parts of filler, 0.1-0.2 part of a voltage stabilizer, 0.1-0.5 part of an antioxidant, 0.5-1 part of an initiator and 1-5 parts of a lubricant. The amino group on the surface of the silicon dioxide carrier treated by 3-aminopropyltriethoxysilane in the modification additive can be subjected to acid-base interaction with the phosphate group of APP to form chemical bridging; the interface bonding enables the APP and the modification additive to synchronously migrate to the surface of the material during combustion to cooperatively construct a protection layer, so that the problem of protection failure caused by migration rate difference of different flame retardants in a traditional flame-retardant system is solved, and the flame-retardant performance of the cable can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyethylene cables, in particular to a high-strength flame-retardant polyethylene cable and a preparation method thereof. BACKGROUND

[0002] Cables are widely used in the power, communication, construction and other industries, and are closely related to the development of the national economy. They are known as the "tongue" of the national production and are indispensable basic products in the electrified and information-based society. With the development of electric power energy, the demand for wire and cable is rapidly increasing. At the same time, the safety performance of the cable is also continuously improving. This is because it is difficult to extinguish the power fire, and the protective material used to manufacture the cable produces a large amount of toxic smoke during combustion. Under this background, various flame-retardant cable materials have been developed.

[0003] Polymeric materials are widely used in the manufacture of cable protective materials. Traditional cables are mainly based on polyvinyl chloride, but considering environmental protection and fire safety, they are gradually being replaced by polyolefin materials. Among them, polyethylene has excellent insulation and dielectric properties and is a good choice for medium and low voltage cable materials. However, polyethylene is not heat-resistant, easily flammable, and has poor mechanical properties. Therefore, it is often modified by means of reinforcement, filling, and crosslinking to improve its performance. Crosslinking modification is a method in which the molecular chains of polyethylene are connected to each other to form a three-dimensional network structure, thereby improving the mechanical properties. In existing technologies, the methods for forming crosslinked polyethylene mainly include high-energy irradiation crosslinking, silane crosslinking, peroxide crosslinking, and ultraviolet crosslinking. Among them, irradiation crosslinking has easy quality control and high product cleanliness, but it requires large-scale irradiation equipment and is not suitable for traditional cable manufacturing industry production lines. In existing industrial production, peroxide crosslinking is still the main method. The preparation method of flame-retardant crosslinked polyethylene that matches this is mainly to add flame retardants to the base to achieve flame-retardant effect. However, the flame retardants are difficult to disperse uniformly in the polyethylene base, and they are prone to migration and segregation during the heat processing process, resulting in poor flame-retardant effect. Usually, the amount of flame retardant added is large, the flame-retardant effect is general, and too much addition of flame retardant will cause the deterioration of the mechanical properties of the base. SUMMARY

[0004] To solve the problems mentioned in the background, the present application provides a high-strength flame-retardant polyethylene cable and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: A high-strength flame-retardant polyethylene cable is composed of a copper stranded core and a flame-retardant protective layer on the surface of the core. The flame-retardant protective sleeve is made of high-strength flame-retardant material. The high-strength flame-retardant material comprises, by weight: 80-100 parts of low-density polyethylene, 5-10 parts of flame retardant, 3-5 parts of modification aid, 1-1.5 parts of filler, 0.1-0.2 parts of voltage stabilizer, 0.1-0.5 parts of antioxidant, 0.5-1 parts of initiator, and 1-5 parts of lubricant. Preferably, the flame retardant is modified ammonium polyphosphate, and a preparation method of the modified ammonium polyphosphate comprises the following steps: S1, 100 parts of ammonium polyphosphate (APP) powder is added to a high-speed mixer, 0.5-1 parts of PEG dispersant is added, and stirring is performed at a speed of 1000-1500 r / min for 15-20 min; S2, 3-5 parts of vinyl trimethoxysilane is uniformly mixed with 10-15 parts of anhydrous ethanol to prepare a silane coupling agent solution, a stirring device is started, the speed is controlled at 300-500 r / min, the silane coupling agent solution is slowly added to S1, and the dropping time is controlled at 30-45 min; S3, after the dropping is completed, the temperature is raised to 60-70℃, and reflux reaction is performed for 2-3 h, during which the methoxy of the vinyl trimethoxysilane is hydrolyzed to form silanol, which reacts with the hydroxyl on the surface of the ammonium polyphosphate to introduce vinyl on the surface of the APP and form a preliminary modification layer, and part of the APP surface acidity is neutralized; S4, 5-8 parts of tetraethyl orthosilicate (TEOS) is mixed with 15-20 parts of anhydrous ethanol, 0.5-1 parts of glacial acetic acid is slowly added as a catalyst after uniform stirring, and stirring is continued for 15-20 min to obtain a clear and transparent sol precursor solution, the sol precursor solution is slowly added to the APP system treated by the silane coupling agent at a speed of 1-2 drops / s at 60-70℃, and the dropping time is 1-2 h; S5, after the dropping is completed, the stirring reaction is continued for 3-4 h, during which the TEOS hydrolyzes and condenses under the action of the catalyst to form a polysiloxane (-Si-O-Si-) network structure, which gradually coats on the surface of the APP, the polysiloxane layer further shields the acidic groups of the APP, reduces the acid value, and enhances the interfacial bonding force with the organic material; S6, after the reaction is completed, the product is filtered through a Buchner funnel, washed with anhydrous ethanol for 3-5 times to remove unreacted raw materials and byproducts, ensure the purity of the product, and transfer the washed product to a vacuum drying oven for drying at 60-80℃, a vacuum degree of -0.08 MPa to -0.1 MPa for 12-16 h to fully dry the product, thereby obtaining low-acid-value modified APP.

[0006] Preferably, the preparation method of the modification aid comprises the following steps: S1-1, refluxing reaction of adding silica powder into 3-aminopropyl triethoxysilane ethanol solution, filtering and washing to obtain silica carrier; S1-2, adding silica carrier into tea polyphenol aqueous solution, ultrasonic dispersion, adjusting pH to be less than or equal to 6.0, stirring reaction, then adding propyl gallate and composite catalyst, continuing to stir reaction, adding vitamin C powder in the middle of reaction, filtering and vacuum drying after reaction to obtain modified carrier; S1-3, adding modified carrier, chitosan quaternary ammonium salt and alkyl glycoside into deionized water, stirring and dispersing, adding benzylpropyl emulsion dropwise, heating and adjusting pH to react, then adding glycerol, homogenizing under nitrogen protection and controlling temperature to be less than or equal to 80 DEG C to prepare modified auxiliary agent.

[0007] Preferably, the composite catalyst in step S1-2 is composed of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide with a molar ratio of 1: (0.5-1).

[0008] Preferably, the filler is 1000-1200 mesh super-fine aluminum nitride powder.

[0009] Preferably, the voltage stabilizer is m-aminobenzoic acid.

[0010] Preferably, the antioxidant is a mixture of antioxidant 1010 and antioxidant 1098 with a mass ratio of 3:2.

[0011] Preferably, the initiator is tert-butyl peroxybenzoate; the lubricant is stearic acid monoglyceride.

[0012] A preparation method of high-strength flame-retardant polyethylene cable, further comprising the following steps: Step S2-1: mixing low-density polyethylene, antioxidant and lubricant according to the weight parts, and mixing under nitrogen protection, heating to 115-125 DEG C and mixing to melt to prepare raw rubber; Step S2-2: mixing flame retardant, modified auxiliary agent, filler and voltage stabilizer, then adding into raw rubber, continuing to heat to 160-180 DEG C and mixing for 15-20 min, then adding initiator and mixing, then extruding to coat on the surface of copper stranded wire, spraying and cooling to shape to prepare raw rubber cable; Step S2-3: placing raw rubber cable in vulcanization tunnel furnace to crosslink and cure to form flame-retardant protective layer, cooling to room temperature to prepare high-strength flame-retardant polyethylene cable.

[0013] Compared with the prior art, the present application has the following beneficial effects: 1. In this invention, low-density polyethylene (LDPE) is used as the base material, which has good processing fluidity and flexibility. Its compatibility with modified ammonium polyphosphate and modified additives can be improved by using ultrafine aluminum nitride powder as filler. Modified ammonium polyphosphate, as a phosphorus-based flame retardant, decomposes at high temperatures to generate polyphosphoric acid, which catalyzes the dehydration of LDPE into char. It forms a phosphorus-carbon-nitrogen synergistic flame retardant system with tea polyphenols and chitosan quaternary ammonium salts in the modified additives. The phosphorus system promotes carbonization, while the nitrogen system releases inert gases. At the same time, the silica carrier contained in the modified additives can enhance the char layer structure and form an inorganic skeleton-organic char layer composite barrier with the polyphosphoric acid of APP, thereby significantly improving the flame retardant durability.

[0014] 2. The polyphosphoric acid (HPO3) produced by the decomposition of modified APP in this invention. n The olefin structure combines with hydrogen on the LDPE molecular chain to initiate a dehydration reaction. The resulting olefin structure cross-links under the action of a composite catalyst in the modifying agent to form an aromatic carbon skeleton. The NH3 and CO2 produced by the decomposition of chitosan quaternary ammonium salt and the H2O released by APP together expand the carbon layer, while silica micropowder fills the pores of the carbon layer as an inorganic reinforcing phase to improve the structural strength. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The low-density polyethylene was purchased from Shanghai Xinlisheng Plastics Co., Ltd., model number 4404G. m-Aminobenzoic acid was purchased from Aladdin, CAS No.: 99-05-8; tert-butyl peroxide was purchased from Aladdin, CAS No.: 614-45-9; The glyceryl monostearate was purchased from Aladdin, CAS No.: 31566-31-1; Silica micro powder was purchased from Sichuan Hongjianxin Technology Co., Ltd., CAS No.: 60676-86-0; 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was purchased from Aladdin, CAS No.: 25952-53-8; N-hydroxysuccinimide was purchased from Aladdin, CAS No.: 6066-82-6.

[0017] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0018] Preparation Example 1 The flame retardant is modified ammonium polyphosphate, and a preparation method of the modified ammonium polyphosphate comprises the following steps: S1, 100 parts of APP powder are added into a high-speed stirrer, and 0.5 parts of PEG dispersant is added, and stirring is performed at a rotating speed of 1000 r / min for 15 min; S2, 3 parts of vinyl trimethoxysilane are uniformly mixed with 10 parts of anhydrous ethanol to prepare a silane coupling agent solution, a stirring device is started, the rotating speed is controlled to be 300 r / min, the silane coupling agent solution is slowly added into S1, and the dropping time is controlled to be 30 min; S3, after the dropping is completed, the temperature is increased to 60 DEG C, and reflux reaction is performed for 2 h, in this process, methoxy of the vinyl trimethoxysilane is hydrolyzed to generate silanol; S4, 5 parts of TEOS are mixed with 15 parts of anhydrous ethanol, 0.5 parts of glacial acetic acid is slowly added as a catalyst after uniform stirring, and stirring is continuously performed for 15 min, a clear and transparent sol precursor solution is obtained, and the sol precursor solution is slowly added into the APP system treated by the silane coupling agent at a speed of 1 drop / s under the condition that the temperature is 60 DEG C, and the dropping time is 1 h; S5, after the dropping is completed, stirring reaction is continuously performed for 3 h, and hydrolysis and polycondensation reaction of TEOS occurs under the action of the catalyst; S6, after the reaction is completed, the product is filtered through a Buchner funnel, washed with anhydrous ethanol for three times, and unreacted raw materials and by-products are removed, so that the product purity is ensured, the washed product is transferred into a vacuum drying oven, and the product is fully dried under the condition that the temperature is 60 DEG C and the vacuum degree is -0.08 MPa for 12 h, so that the low-acid-value modified APP is obtained.

[0019] Preparation Example 2 The flame retardant is modified ammonium polyphosphate, and a preparation method of the modified ammonium polyphosphate comprises the following steps: S1, 100 parts of APP powder are added into a high-speed stirrer, and 0.5 parts of PEG dispersant is added, and stirring is performed at a rotating speed of 1000 r / min for 15 min; S2, 3 parts of vinyl trimethoxysilane are uniformly mixed with 10 parts of anhydrous ethanol to prepare a silane coupling agent solution, a stirring device is started, the rotating speed is controlled to be 300 r / min, the silane coupling agent solution is slowly added into S1, and the dropping time is controlled to be 30 min; S3, after the dropping is completed, the temperature is increased to 60 DEG C, and reflux reaction is performed for 2 h, in this process, methoxy of the vinyl trimethoxysilane is hydrolyzed to generate silanol; S4, 6 parts of TEOS were mixed with 17 parts of anhydrous ethanol, and after uniform stirring, 0.5 parts of glacial acetic acid was slowly added as a catalyst, and stirring was continued for 20 min to obtain a clear and transparent sol precursor solution, the sol precursor solution was slowly added to the APP system treated with silane coupling agent at a speed of 2 drops / sec at 65℃, and the dropping time was 2h; S5, after the completion of dropping, the reaction was continued for 4h, during which the TEOS hydrolyzed and polycondensed under the action of the catalyst; S6, after the reaction was completed, the product was filtered through a Buchner funnel, washed with anhydrous ethanol 4 times to remove unreacted raw materials and byproducts, and ensure the purity of the product, and the washed product was transferred to a vacuum drying oven, dried at 70℃ under a vacuum degree of-0.09MPa for 15h to fully dry the product, and a low-acid-value modified APP was obtained.

[0020] Preparation Example 3 The flame retardant is a modified ammonium polyphosphate, and the preparation method of the modified ammonium polyphosphate comprises the following steps: S1, 100 parts of APP powder were added to a high-speed stirrer, and 1 part of PEG dispersant was added, and stirring was carried out at a speed of 1500r / min for 20 min; S2, 5 parts of vinyltrimethoxysilane were mixed with 15 parts of anhydrous ethanol to prepare a silane coupling agent solution, and a stirring device was started, and the stirring speed was controlled at 500r / min, and the silane coupling agent solution was slowly added to S1, and the dropping time was controlled at 45 min; S3, after the completion of dropping, the temperature was raised to 70℃, and refluxing was carried out for 3h, during which the methoxy group of vinyltrimethoxysilane was hydrolyzed to form silanol; S4, 8 parts of TEOS were mixed with 20 parts of anhydrous ethanol, and after uniform stirring, 1 part of glacial acetic acid was slowly added as a catalyst, and stirring was continued for 20 min to obtain a clear and transparent sol precursor solution, the sol precursor solution was slowly added to the APP system treated with silane coupling agent at a speed of 2 drops / sec at 70℃, and the dropping time was 2h; S5, after the completion of dropping, the reaction was continued for 4h, during which the TEOS hydrolyzed and polycondensed under the action of the catalyst; S6, after the reaction was completed, the product was filtered through a Buchner funnel, washed with anhydrous ethanol 5 times to remove unreacted raw materials and byproducts, and ensure the purity of the product, and the washed product was transferred to a vacuum drying oven, dried at 80℃ under a vacuum degree of-0.1MPa for 16h to fully dry the product, and a low-acid-value modified APP was obtained.

[0021] Preparation Example 4 The preparation method of the modified additive comprises the following steps: S1-1, 10 parts of silica powder is added to 30 parts of 20% 3-aminopropyl triethoxysilane ethanol solution at 80℃ for reflux reaction for 3h, filtration, washing to obtain silica carrier; S1-2, 15 parts of silica carrier is added to 40 parts of 20% tea polyphenol aqueous solution, ultrasonic dispersion, then pH is adjusted to ≤6.0, stirring reaction for 2h, then 2 parts of propyl gallate and 0.5 parts of composite catalyst are added, continue to stir reaction, 1.5 parts of vitamin C powder is added intermittently during the reaction, after reaction, filtration, vacuum drying to obtain modified carrier; S1-3, 12 parts of modified carrier, 3 parts of chitosan quaternary ammonium salt and 1 part of alkyl glycoside are added to 50 parts of deionized water for stirring and dispersion, 5 parts of styrene-acrylate emulsion is added dropwise, temperature is raised to 60℃ and pH is adjusted to 7.0 for reaction, then 1.5 parts of glycerol is added, homogenization treatment is carried out under nitrogen protection for 30min and temperature is controlled to ≤80℃, to obtain modified adjuvant.

[0022] The composite catalyst in step S1-2 is composed of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide with a molar ratio of 1:0.5.

[0023] Preparation Example 5 The preparation method of the modified adjuvant comprises the following steps: S1-1, 10 parts of silica powder is added to 30 parts of 20% 3-aminopropyl triethoxysilane ethanol solution at 80℃ for reflux reaction for 3h, filtration, washing to obtain silica carrier; S1-2, 15 parts of silica carrier is added to 40 parts of 20% tea polyphenol aqueous solution, ultrasonic dispersion, then pH is adjusted to ≤6.0, stirring reaction for 2h, then 2 parts of propyl gallate and 0.5 parts of composite catalyst are added, continue to stir reaction, 1.5 parts of vitamin C powder is added intermittently during the reaction, after reaction, filtration, vacuum drying to obtain modified carrier; S1-3, 12 parts of modified carrier, 3 parts of chitosan quaternary ammonium salt and 1 part of alkyl glycoside are added to 50 parts of deionized water for stirring and dispersion, 5 parts of styrene-acrylate emulsion is added dropwise, temperature is raised to 60℃ and pH is adjusted to 7.0 for reaction, then 1.5 parts of glycerol is added, homogenization treatment is carried out under nitrogen protection for 30min and temperature is controlled to ≤80℃, to obtain modified adjuvant.

[0024] The composite catalyst in step S1-2 is composed of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide with a molar ratio of 1:0.8.

[0025] Preparation Example 6 The preparation method of the modified adjuvant comprises the following steps: S1-1, 10 parts of silica powder was added to 30 parts of 20% 3-aminopropyl triethoxysilane ethanol solution at 85°C and refluxed for 4h, then filtered and washed to obtain a silica carrier; S1-2, 15 parts of silica carrier was added to 40 parts of 20% tea polyphenol aqueous solution, ultrasonic dispersion was performed, then pH was adjusted to be less than or equal to 6.0, stirring was performed for 4h, then 2 parts of propyl gallate and 0.5 parts of a composite catalyst were added, stirring was continuously performed, 1.5 parts of vitamin C powder was added at intervals during the reaction, then the reaction was completed, and the modified carrier was obtained by filtering and vacuum drying; S1-3, 12 parts of the modified carrier, 3 parts of chitosan quaternary ammonium salt and 1 part of alkyl glycoside were added to 50 parts of deionized water and stirred and dispersed, 5 parts of styrene-acrylate emulsion was added dropwise, temperature was increased to 65°C, pH was adjusted to 7.0, and reaction was performed, then 1.5 parts of glycerol was added, homogenization treatment was performed for 30min under nitrogen protection, and the temperature was controlled to be less than or equal to 80°C, thereby obtaining a modified additive.

[0026] The composite catalyst in step S1-2 is composed of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide in a molar ratio of 1:1. Example 1

[0027] A preparation method of a high-strength flame-retardant polyethylene cable further includes the following steps: Step S2-1: 80 parts of low-density polyethylene, 0.1 parts of an antioxidant and 1 part of stearic acid monoglyceride were mixed, and the mixture was melt-kneaded to be molten under nitrogen protection at a temperature of 115°C, thereby preparing a raw rubber; the antioxidant was a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 5 parts of the modified ammonium polyphosphate prepared in Preparation Example 1, 3 parts of the modified additive prepared in Preparation Example 4, 1 part of 1000-mesh ultra-fine aluminum nitride powder and 0.1 parts of m-aminobenzoic acid were mixed and then added to the raw rubber, the temperature was further increased to 160°C, and the mixture was stirred for 15min, then 0.5 parts of t-butyl peroxybenzoate was added and mixed, and then the raw rubber cable was extruded and coated on the surface of the copper strand, and then the cable was sprayed and cooled to be shaped, thereby preparing a raw rubber cable; Step S2-3: the raw rubber cable was placed in a vulcanization tunnel furnace to form a flame-retardant protective layer, and then the cable was cooled to room temperature, thereby preparing a high-strength flame-retardant polyethylene cable. Example 2

[0028] A preparation method of a high-strength flame-retardant polyethylene cable further includes the following steps: Step S2-1: 80 parts of low-density polyethylene, 0.1 parts of an antioxidant and 1 part of stearic acid monoglyceride were mixed, and the mixture was melt-kneaded to be molten under nitrogen protection at a temperature of 115°C, thereby preparing a raw rubber; the antioxidant was a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 5 parts of modified ammonium polyphosphate prepared in Preparation Example 1, 3 parts of modified auxiliary prepared in Preparation Example 5, 1 part of 1000 mesh ultra-fine aluminum nitride powder and 0.1 part of m-aminobenzoic acid were mixed and then added to the raw rubber, and the temperature was continued to rise to 170°C for 17 minutes, and then 0.5 parts of tert-butyl peroxybenzoate was added and mixed, and then extruded and coated on the surface of the copper strand, and then spray-cooled and shaped to form a raw rubber cable; Step S2-3: The raw rubber cable was placed in a vulcanization tunnel furnace to crosslink and cure to form a flame-retardant protective layer, and then cooled to room temperature to form a high-strength flame-retardant polyethylene cable. Example 3

[0029] A method for preparing a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 80 parts of low-density polyethylene, 0.1 parts of an antioxidant, and 1 parts of stearic acid monoglyceride were mixed and melt-kneaded under nitrogen protection at a temperature of 115°C to form a raw rubber; the antioxidant was a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 5 parts of modified ammonium polyphosphate prepared in Preparation Example 1, 3 parts of modified auxiliary prepared in Preparation Example 5, 1 part of 1000 mesh ultra-fine aluminum nitride powder and 0.1 part of m-aminobenzoic acid were mixed and then added to the raw rubber, and the temperature was continued to rise to 170°C for 17 minutes, and then 0.5 parts of tert-butyl peroxybenzoate was added and mixed, and then extruded and coated on the surface of the copper strand, and then spray-cooled and shaped to form a raw rubber cable; Step S2-3: The raw rubber cable was placed in a vulcanization tunnel furnace to crosslink and cure to form a flame-retardant protective layer, and then cooled to room temperature to form a high-strength flame-retardant polyethylene cable. Example 4

[0030] A method for preparing a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 80 parts of low-density polyethylene, 0.1 parts of an antioxidant, and 1 parts of stearic acid monoglyceride were mixed and melt-kneaded under nitrogen protection at a temperature of 115°C to form a raw rubber; the antioxidant was a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 5 parts of modified ammonium polyphosphate prepared in Preparation Example 1, 3 parts of modified auxiliary prepared in Preparation Example 5, 1 part of 1000 mesh ultra-fine aluminum nitride powder and 0.1 part of m-aminobenzoic acid were mixed and then added to the raw rubber, and the temperature was continued to rise to 170°C for 17 minutes, and then 0.5 parts of tert-butyl peroxybenzoate was added and mixed, and then extruded and coated on the surface of the copper strand, and then spray-cooled and shaped to form a raw rubber cable; Step S2-3: The raw rubber cable was placed in a vulcanization tunnel furnace to crosslink and cure to form a flame-retardant protective layer, and then cooled to room temperature to form a high-strength flame-retardant polyethylene cable. Example 5

[0031] A preparation method of a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 90 parts of low-density polyethylene, 0.3 parts of an antioxidant, and 3 parts of stearic acid monoglyceride are mixed, and under nitrogen protection, the temperature is raised to 115°C for compounding to melt, to prepare a raw rubber; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 7 parts of modified ammonium polyphosphate prepared in Preparation Example 2, 4 parts of modified auxiliary prepared in Preparation Example 5, 1.2 parts of 1100-mesh ultra-fine aluminum nitride powder, and 0.2 parts of m-aminobenzoic acid are mixed and then added to the raw rubber, and the temperature is continuously raised to 160°C for mixing for 15 minutes, and then 0.8 parts of t-butyl peroxybenzoate is added for mixing, and then extruded to coat the surface of the copper strand, sprayed and cooled to shape, to prepare a raw rubber cable; Step S2-3: The raw rubber cable is placed in a vulcanization tunnel furnace for crosslinking and curing to form a flame-retardant protective layer, and cooled to room temperature, to prepare a high-strength flame-retardant polyethylene cable. Example 6

[0032] A preparation method of a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 90 parts of low-density polyethylene, 0.3 parts of an antioxidant, and 3 parts of stearic acid monoglyceride are mixed, and under nitrogen protection, the temperature is raised to 115°C for compounding to melt, to prepare a raw rubber; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 7 parts of modified ammonium polyphosphate prepared in Preparation Example 2, 4 parts of modified auxiliary prepared in Preparation Example 5, 1.2 parts of 1100-mesh ultra-fine aluminum nitride powder, and 0.2 parts of m-aminobenzoic acid are mixed and then added to the raw rubber, and the temperature is continuously raised to 160°C for mixing for 15 minutes, and then 0.8 parts of t-butyl peroxybenzoate is added for mixing, and then extruded to coat the surface of the copper strand, sprayed and cooled to shape, to prepare a raw rubber cable; Step S2-3: The raw rubber cable is placed in a vulcanization tunnel furnace for crosslinking and curing to form a flame-retardant protective layer, and cooled to room temperature, to prepare a high-strength flame-retardant polyethylene cable. Example 7

[0033] A preparation method of a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 90 parts of low-density polyethylene, 0.3 parts of an antioxidant, and 3 parts of stearic acid monoglyceride are mixed, and under nitrogen protection, the temperature is raised to 115°C for compounding to melt, to prepare a raw rubber; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 10 parts of modified ammonium polyphosphate prepared in Preparation Example 3, 5 parts of modified auxiliary prepared in Preparation Example 4, 1.5 parts of 1200 mesh ultra-fine aluminum nitride powder and 0.2 parts of m-aminobenzoic acid were mixed and added to the raw rubber, and then the temperature was raised to 180°C for 20 minutes, 1 part of tert-butyl peroxybenzoate was added and mixed, and then extruded to coat the surface of the copper strand, sprayed and cooled to shape, and the raw rubber cable was prepared; Step S2-3: The raw rubber cable was placed in a vulcanization tunnel furnace to crosslink and cure to form a flame-retardant protective layer, and cooled to room temperature to prepare a high-strength flame-retardant polyethylene cable. Example 8

[0034] A method for preparing a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 100 parts of low-density polyethylene, 0.5 parts of antioxidant and 5 parts of stearic acid monoglyceride were mixed and melt-kneaded under nitrogen protection at a temperature of 125°C to prepare a raw rubber; the antioxidant was a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 8 parts of modified ammonium polyphosphate prepared in Preparation Example 3, 3 parts of modified auxiliary prepared in Preparation Example 5, 1.5 parts of 1200 mesh ultra-fine aluminum nitride powder and 0.2 parts of m-aminobenzoic acid were mixed and added to the raw rubber, and then the temperature was raised to 175°C for 20 minutes, 1 part of tert-butyl peroxybenzoate was added and mixed, and then extruded to coat the surface of the copper strand, sprayed and cooled to shape, and the raw rubber cable was prepared; Step S2-3: The raw rubber cable was placed in a vulcanization tunnel furnace to crosslink and cure to form a flame-retardant protective layer, and cooled to room temperature to prepare a high-strength flame-retardant polyethylene cable. Example 9

[0035] A method for preparing a high-strength flame-retardant polyethylene cable further comprises the following steps: Step S2-1: 100 parts of low-density polyethylene, 0.5 parts of antioxidant and 5 parts of stearic acid monoglyceride were mixed and melt-kneaded under nitrogen protection at a temperature of 125°C to prepare a raw rubber; the antioxidant was a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:2; Step S2-2: 9 parts of modified ammonium polyphosphate prepared in Preparation Example 3, 4 parts of modified auxiliary prepared in Preparation Example 6, 1.5 parts of 1200 mesh ultra-fine aluminum nitride powder and 0.2 parts of m-aminobenzoic acid were mixed and added to the raw rubber, and then the temperature was raised to 180°C for 18 minutes, 1 part of tert-butyl peroxybenzoate was added and mixed, and then extruded to coat the surface of the copper strand, sprayed and cooled to shape, and the raw rubber cable was prepared; Step S2-3: The raw rubber cable was placed in a vulcanization tunnel furnace to crosslink and cure to form a flame-retardant protective layer, and cooled to room temperature to prepare a high-strength flame-retardant polyethylene cable.

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is that the modified ammonium polyphosphate prepared in Preparation Example 1 is replaced by a common commercially available ammonium polyphosphate, which is purchased from Aladdin, CAS No.: 68333-79-9.

[0037] Comparative Example 2 The difference between this comparative example and Example 1 is that the modified ammonium polyphosphate prepared in Preparation Example 1 is not added.

[0038] Comparative Example 3 The difference between this comparative example and Example 1 is that the modified auxiliary prepared in Preparation Example 4 is replaced by a common commercially available silica powder, which is purchased from Sichuan Hongjianxin Technology Co., Ltd., CAS No.: 60676-86-0.

[0039] Comparative Example 4 The difference between this comparative example and Example 1 is that the modified auxiliary prepared in Preparation Example 4 is not added.

[0040] Comparative Example 5 The difference between this comparative example and Example 1 is that both the modified ammonium polyphosphate prepared in Preparation Example 1 and the modified auxiliary prepared in Preparation Example 4 are not added.

[0041] Examples 1-9 and Comparative Examples 1-5 are subjected to performance tests, and the results are shown in Table 1: Standard samples are prepared according to GB / T 2406-2008 and tested for oxygen index; Standard samples are prepared according to UL-94 and tested for flame retardant grade; Standard samples are prepared according to GB / T 1040-2006 and tested for tensile strength.

[0042] Table 1 Test item Flame retardant class Oxygen index (%) Tensile strength (MPa) Example 1 V-0 32.8 25.5 Example 2 V-0 32.6 25.2 Example 3 V-0 32.3 25.4 Example 4 V-0 32.5 25.3 Example 5 V-0 32.1 25.5 Example 6 V-0 31.8 25.6 Example 7 V-0 32.2 25.2 Example 8 V-0 32.3 25.3 Example 9 V-0 32.5 25.1 Comparative Example 1 V-1 27.5 20.7 Comparative Example 2 V-3 24.1 18.9 Comparative Example 3 V-1 28.8 19.1 Comparative Example 4 V-2 27.6 16.9 Comparative Example 5 V-4 13.5 12.7 In summary, the high-strength flame-retardant polyethylene cables prepared in Examples 1-9 have excellent flame-retardant properties and tensile strength, and the comprehensive performance is better than that of the polyethylene cables prepared in the comparative examples, especially in Comparative Example 2, where the modified ammonium polyphosphate is not added, directly leading to a flame-retardant grade of V-3, and in Comparative Example 4, where the modified auxiliary is not added, resulting in a significant decrease in flame-retardant properties and tensile strength. The silica carrier treated with 3-aminopropyl triethoxysilane in the modified auxiliary can interact with the phosphate groups of APP through acid-base interaction to form a chemical bridge. This interfacial bonding enables APP and the modified auxiliary to migrate synchronously to the material surface during combustion, thereby building a protective layer and solving the problem of protective failure caused by the difference in migration rate of different flame retardants in traditional flame-retardant systems, thereby greatly improving the flame-retardant properties of the cable.

[0043] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A high strength flame retardant polyethylene cable consisting of a copper strand core and a flame retardant sheath on the surface of the core, characterized in that, The fireproof protective layer is made of high-strength fireproof material, which comprises, in parts by weight: Low-density polyethylene 80-100 parts, flame retardant 5-10 parts, modified auxiliary 3-5 parts, filler 1-1.5 parts, voltage stabilizer 0.1-0.2 parts, antioxidant 0.1-0.5 parts, initiator 0.5-1 parts and lubricant 1-5 parts.

2. A high strength flame retardant polyethylene cable according to claim 1, characterized in that, The flame retardant is modified ammonium polyphosphate, and the preparation method of the modified ammonium polyphosphate comprises the following steps: S1, 100 parts of APP powder are added into a high-speed mixer, 0.5-1 parts of PEG dispersant is added at the same time, and stirring is carried out at a speed of 1000-1500 r / min for 15-20 min; S2, 3-5 parts of vinyl trimethoxysilane is uniformly mixed with 10-15 parts of anhydrous ethanol to prepare a silane coupling agent solution, a stirring device is started, the speed is controlled at 300-500 r / min, the silane coupling agent solution is slowly added into S1, and the dropping time is controlled at 30-45 min; S3, after the dropping is completed, the temperature is raised to 60-70 DEG C, and reflux reaction is carried out for 2-3 h; S4, 5-8 parts of TEOS is mixed with 15-20 parts of anhydrous ethanol, after stirring uniformly, 0.5-1 parts of glacial acetic acid is slowly added as a catalyst, and stirring is continued for 15-20 min, a clear and transparent sol precursor solution is obtained, the sol precursor solution is slowly added into the APP system treated by the silane coupling agent at a speed of 1-2 drops / s under the condition of 60-70 DEG C, and the dropping time is 1-2 h; S5, after the dropping is completed, stirring reaction is continued for 3-4 h, during which hydrolysis and polycondensation reaction of TEOS occurs under the action of the catalyst to form a polysiloxane network structure; S6, after the reaction is completed, the product is filtered through a Buchner funnel, washed with anhydrous ethanol for 3-5 times to remove unreacted raw materials and byproducts, the washed product is transferred to a vacuum drying oven, and drying is carried out under the condition of 60-80 DEG C and vacuum degree of-0.08 MPa to-0.1 MPa for 12-16 h to fully dry the product, and low-acid-value modified APP is obtained.

3. A high strength flame retardant polyethylene cable according to claim 1, characterized in that, The preparation method of the modified auxiliary comprises the following steps: S1-1, silica powder is added into 3-aminopropyl triethoxysilane ethanol solution for reflux reaction, filtration and washing to obtain a silica carrier; S1-2, the silica carrier is added into a tea polyphenol aqueous solution, ultrasonic dispersion is carried out, pH is adjusted to be less than or equal to 6.0, stirring reaction is carried out, propyl gallate and a composite catalyst are further added, stirring reaction is continued, vitamin C powder is intermittently added during the reaction, and after the reaction, filtration and vacuum drying are carried out to obtain a modified carrier; S1-3, the modified carrier, chitosan quaternary ammonium salt and alkyl polyglycoside are added into deionized water for stirring and dispersion, benzyl acrylate emulsion is added dropwise, temperature is raised and pH is adjusted for reaction, glycerol is further added, homogenization treatment is carried out under nitrogen protection and temperature is controlled to be less than or equal to 80 DEG C to prepare the modified auxiliary.

4. A high strength flame retardant polyethylene cable according to claim 3, characterized in that, The composite catalyst in step S1-2 is composed of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide with a molar ratio of 1: (0.5-1).

5. A high strength flame retardant polyethylene cable according to claim 1, wherein, The filler is 1000-1200 mesh ultra-micro aluminum nitride powder.

6. A high strength flame retardant polyethylene cable according to claim 1, wherein, The voltage stabilizer is m-aminobenzoic acid.

7. A high strength flame retardant polyethylene cable according to claim 1, wherein, The antioxidant is a mixture of antioxidant 1010 and antioxidant 1098 in a mass ratio of 3:

2.

8. A high strength flame retardant polyethylene cable according to claim 1, wherein, The initiator is tert-butyl peroxybenzoate.

9. A high strength flame retardant polyethylene cable according to claim 1, wherein, The lubricant is stearic acid monoglyceride.

10. A process for the preparation of a high strength flame retardant polyethylene cable as claimed in any one of claims 1 to 9, characterised in that, The following steps are also included: Step S2-1: Mix low-density polyethylene, antioxidant, and lubricant according to the weight parts, melt in an internal mixer under nitrogen protection at a temperature of 115-125°C to produce a raw rubber compound; Step S2-2: Mix flame retardant, modification aid, filler, and voltage stabilizer, then add to the raw rubber compound, continue to heat to 160-180°C and mix for 15-20 minutes, then add the initiator and mix, then extrude and coat on the surface of copper stranded wire, spray cooling and shaping to produce a raw rubber cable; Step S2-3: Place the raw rubber cable in a vulcanization tunnel furnace for crosslinking and curing to form a flame-retardant protective layer, cool to room temperature, and produce a high-strength flame-retardant polyethylene cable.