Fire-resistant polyvinyl chloride insulated cable and preparation method thereof

Abstract

The invention discloses a fire-resistant polyvinyl chloride insulated cable and a preparation method thereof, belonging to the technical field of fire-resistant cables, and is used to solve the technical problem in the prior art that the mechanical strength, flame retardancy and fire resistance of polyvinyl chloride insulated cables need to be further improved. The invention comprises at least a cable core and a polyvinyl chloride sheath layer coated on the outside of the cable core, wherein the polyvinyl chloride sheath layer comprises the following components in parts by weight: 60-70 parts of activated polyvinyl chloride, 30-40 parts of methyl vinyl silicone rubber, 25-35 parts of activated filler, 12-16 parts of composite ammonium polyphosphate, 1-2 parts of a vulcanizing agent and 7-8 parts of an additive. The invention reinforces a matrix composed of activated polyvinyl chloride and methyl vinyl silicone rubber by using the activated filler and the composite ammonium polyphosphate, thereby effectively improving not only the mechanical strength and flame retardancy and heat resistance of the polyvinyl chloride insulated cable material but also the fire resistance level thereof.

Description

Technical Field

[0001] The present invention relates to the technical field of fire-resistant cables, and in particular to a fire-resistant polyvinyl chloride insulated cable and a preparation method thereof. Background Art

[0002] In various fields such as construction, electricity, and communications, cables are key carriers of electrical energy and signal transmission. Their performance is directly related to the stable operation and safety of the system. Polyvinyl chloride (PVC) has become an extremely widely used material in insulating cables due to its excellent electrical insulation, mechanical properties, and processing properties. However, traditional PVC insulated cables expose serious fire resistance defects when faced with extreme high temperature environments such as fire.

[0003] In the prior art, an invention patent with publication number CN113881164A discloses a polyvinyl chloride-based fire-resistant and highly flame-retardant cable material and a preparation method thereof. The material comprises the following raw materials in parts by weight: 80-140 parts of PVC resin, 10-20 parts of nitrile rubber, 48-78 parts of plasticizer, 15-35 parts of triazine flame retardant, 5-9 parts of flame retardant synergist, 4.5-8 parts of composite stabilizer, 3-10 parts of hydrotalcite, 16-36 parts of talc, 12-30 parts of nanoclay, 1-4 parts of hyperdispersant, 0.5-3.5 parts of thermoreversible crosslinking agent, 0.8-1.5 parts of lubricant, and 0.4-0.8 parts of silane coupling agent. The material is prepared by high-speed mixing and then double-stage melt extrusion granulation. The cable material of the present invention has the advantages of good shell forming performance, low price, good aging resistance, and high flame retardancy.

[0004] That is, in order to improve the fire resistance and flame retardant properties of PVC cables in the existing technology, flame retardants, plasticizers and other methods are usually adopted to improve their combustion characteristics. However, these methods often have some problems, such as excessive addition of flame retardants resulting in a decrease in the mechanical strength of the cable, or easy migration of plasticizers at high temperatures, affecting the long-term stability of the cable. In addition, the cable is prone to deformation in a high temperature environment, resulting in a decrease in insulation performance. The flame retardant and fire resistance of the cable material needs to be further improved. Summary of the Invention

[0005] The object of the present invention is to provide a fire-resistant polyvinyl chloride insulated cable and a preparation method thereof, so as to solve the technical problem in the prior art that the mechanical strength, flame retardancy and fire resistance of polyvinyl chloride insulated cables need to be further improved.

[0006] The object of the present invention can be achieved by the following technical solution: a fire-resistant polyvinyl chloride insulated cable, comprising at least a cable core and a polyvinyl chloride sheath layer coated on the outside of the cable core, wherein the polyvinyl chloride sheath layer comprises the following components in parts by weight: 60-70 parts of activated polyvinyl chloride, 30-40 parts of methyl vinyl silicone rubber, 25-35 parts of activated filler, 12-16 parts of composite ammonium polyphosphate, 1-2 parts of vulcanizing agent and 7-8 parts of additive additive.

[0007] Furthermore, the vulcanizing agent is composed of dicumyl peroxide and a vulcanization accelerator in a weight ratio of 3:1, the vulcanization accelerator is any one of accelerator TMTM and accelerator TMDM, the additives are composed of a plasticizer, a lubricant, a dispersant, a stabilizer and an antioxidant in a weight ratio of 5:1:2:2:2, the plasticizer is a phthalate, the lubricant is any one of polyethylene wax and ethylene bisstearamide, the dispersant is a stearate, the stabilizer is a calcium zinc stabilizer, and the antioxidant is any one of antioxidant 1035, antioxidant 1520, and antioxidant 1024.

[0008] Furthermore, the preparation method of the activated polyvinyl chloride is as follows: polyvinyl chloride powder and sodium hydroxide solution are mixed, and the mixture is kept warm for reaction at 140-150° C. for 4-5 hours, and post-processed to obtain the activated polyvinyl chloride.

[0009] The synthetic reaction mechanism of activated polyolefin is:

[0010] During the reaction process, when polyvinyl chloride powder is mixed with sodium hydroxide solution and heated at high temperature, the chlorine atoms on the polyvinyl chloride molecular chain are attacked by sodium hydroxide, and a base-catalyzed dehydrohalogenation reaction occurs, forming olefin double bonds and by-product hydrogen chloride on the polyvinyl chloride molecular chain. The hydrogen chloride and sodium hydroxide undergo acid-base neutralization in the solution to form sodium chloride, which is removed by washing with water to prepare activated polyvinyl chloride modified with unsaturated olefin double bonds.

[0011] Furthermore, the dosage ratio of the polyvinyl chloride powder and the sodium hydroxide solution is 1g:20mL, the particle size of the polyvinyl chloride powder is 200-300μm, and the sodium hydroxide solution is composed of sodium hydroxide, purified water and anhydrous ethanol in a ratio of 1g:5mL:8mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until it is neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain activated polyvinyl chloride.

[0012] Furthermore, the preparation method of the activated filler is: mixing the inorganic filler and the ethanol solution, adding hydrochloric acid to the reaction system, adjusting the pH of the system to 3-4, adding KH-570 and copper sulfate solution to the reaction system, raising the temperature of the reaction system to 70-76°C, keeping the reaction warm for 3-5 hours, and post-treating to obtain the activated filler.

[0013] The synthetic reaction mechanism of activated filler is:

[0014] Fly ash and montmorillonite themselves have a certain pore structure. Ball milling further increases the number and connectivity of their pores, resulting in a porous and high-specific-surface-area inorganic filler. Under acidic conditions, the inorganic filler will partially dissolve, exposing more active sites and increasing the surface activity. The methoxysilane on the KH-570 (γ-methacryloxypropyltrimethoxysilane) molecule is hydrolyzed under acidic conditions to form silanols. The silanols undergo a condensation reaction with the active sites on the surface of the inorganic filler to form Si-O-Si or Si-O-Al bonds, thereby grafting KH-570 onto the surface of the inorganic filler. After the copper sulfate solution is added, the copper ions coordinate with the silanol groups after the hydrolysis of the KH-570 molecules to form stable Cu-O bonds, thereby loading the copper ions on the inorganic filler to prepare an activated filler.

[0015] Furthermore, the amount ratio of the inorganic filler, ethanol solution, KH-570 and copper sulfate solution is 1g:10mL:0.3g:5mL, the inorganic filler is obtained by ball-milling fly ash and montmorillonite in a weight ratio of 2:1 and passing through a 100-mesh sieve, the ethanol solution is composed of anhydrous ethanol and deionized water in a volume ratio of 1:5, and the copper sulfate solution is composed of copper sulfate and deionized water in a volume ratio of 1g:10mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with deionized water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and vacuum dried to constant weight to obtain an activated filler.

[0016] Furthermore, the composite ammonium polyphosphate is obtained by processing the following steps:

[0017] A1. Under an inert gas atmosphere, hexachlorocyclotriphosphazene, p-phenylenediamine, toluene, and a catalyst are mixed, the reaction system temperature is raised to 75-85°C, and the reaction is kept warm for 6-8 hours. Ammonium polyphosphate is added to the reaction system, and the reaction is kept warm for 10-12 hours. Post-treatment is performed to obtain modified ammonium phosphate;

[0018] A2. Under an inert gas atmosphere, the modified ammonium polyphosphate and toluene were mixed, the temperature of the reaction system was raised to 40-50°C, 3-isocyanate propylene was added to the reaction system, and the reaction was kept warm for 60-80 minutes, and post-processed to obtain composite ammonium polyphosphate.

[0019] The synthetic reaction mechanism of composite ammonium polyphosphate is:

[0020] During the reaction, potassium carbonate is used as a catalyst, and the amino group on the p-phenylenediamine molecule acts as a nucleophilic reagent to attack the chlorine atom in the hexachlorocyclotriphosphazene, causing a nucleophilic substitution reaction to generate a cyclic phosphazene-aniline derivative and simultaneously releasing HCl. Ammonium polyphosphate has poor solubility in a toluene mixture system. After the ammonium polyphosphate is mixed with the cyclic phosphazene-aniline derivative as insoluble particles, the cyclic phosphazene-aniline derivative adheres to the ammonium polyphosphate particles to form a coating structure to prepare a modified ammonium phosphate. The amino group or imino group on the modified ammonium phosphate molecule undergoes a condensation reaction with the isocyanate group on the 3-isocyanatopropylene molecule to form an olefin double bond modification on the modified ammonium phosphate molecule to prepare a composite ammonium polyphosphate.

[0021] Furthermore, in step A1, the amount ratio of the hexachlorocyclotriphosphazene, p-phenylenediamine, toluene, catalyst and ammonium polyphosphate is 1g:1g:40mL:0.7g:8g, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, anhydrous ethanol is added to the reaction system, the mixture is stirred for 20-30 minutes, filtered, the filter cake is washed with anhydrous ethanol 3-5 times and then dried, the filter cake is transferred to a drying oven at a temperature of 60-70°C, and vacuum dried to constant weight to obtain modified ammonium phosphate.

[0022] Furthermore, in step A2, the modified ammonium polyphosphate, toluene and 3-isocyanate propylene are used in a ratio of 8g:15mL:1g, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with anhydrous ethanol three times and then dried, the filter cake is transferred to a drying oven at a temperature of 50-60°C, and vacuum dried to constant weight to obtain composite ammonium polyphosphate.

[0023] The present invention also provides a method for preparing a fire-resistant polyvinyl chloride insulated cable. The method for preparing the fire-resistant polyvinyl chloride insulated cable comprises: mixing activated polyvinyl chloride, methyl vinyl silicone rubber, activated filler, composite ammonium polyphosphate, vulcanizing agent and additives, adding the mixture to a twin-screw extruder, melt-extruding and coating the mixture on the outside of the cable core, cooling and curing the mixture, forming a sheath layer on the outside of the cable core, and obtaining the polyvinyl chloride insulated cable.

[0024] Furthermore, the temperatures of the six temperature sections of the twin-screw extruder from the feed end to the discharge end are 175°C, 180°C, 180°C, 180°C, 180°C, and 185°C, respectively.

[0025] The present invention has the following beneficial effects:

[0026] 1. The fire-resistant polyvinyl chloride insulated cable of the present invention is prepared by reinforcing a base material composed of activated polyvinyl chloride containing unsaturated olefin double bonds and methyl vinyl silicone rubber by activating and modifying the filler and then reinforcing it with composite ammonium polyphosphate to form a sheath material for protecting the cable core. In the preparation process, the polyvinyl chloride is activated to introduce unsaturated double bonds into its molecular chain. At the same time, the chlorine atoms on the polyvinyl chloride molecular chain have strong polarity, so that it can be fully mixed with the methyl vinyl silicone rubber and has good reaction activity with the methyl vinyl silicone rubber. and high temperature, it promotes the free radical addition reaction of the olefin double bonds on its molecules to form a complex polyolefin cross-linking network, thereby improving the mechanical strength of the PVC cable sheath material. Moreover, after cross-linking, a complex network structure is formed, which restricts the movement of the molecular chain at high temperature, reduces thermal deformation, and improves its thermal stability. Moreover, the highly cross-linked network structure is more stable at high temperature and not easy to decompose. The composite ammonium polyphosphate and activated filler form a synergistic flame retardant system at high temperature, which cooperates with the cross-linking structure to delay the spread of flame and heat release, further improving the fire resistance of the PVC insulated cable.

[0027] 2. The fire-resistant polyvinyl chloride insulated cable of the present invention uses fly ash and montmorillonite as inorganic fillers and activates and modifies them. Both fly ash and montmorillonite are rigid inorganic fillers with high modulus and thermal stability, can effectively bear stress, and improve the tensile strength of the material. The silane coupling agent grafts organic functional groups on the surface of the filler, thereby enhancing the interfacial bonding between the filler and the PVC matrix and reducing interface defects. The copper ions can coordinate with the functional groups in the PVC molecular chain or silicone rubber to form additional cross-linking points, further improving the strength of the material. The olefin double bonds on the activated filler molecules can cross-link with the activated polyvinyl chloride or silicone rubber molecules, improving the interfacial bonding between the filler and the matrix and reducing interface slip at high temperatures. The silicone rubber itself has high heat resistance, and its synergistic effect with the activated filler further suppresses thermal deformation. During combustion, the fly ash and montmorillonite can form a ceramic protective layer, and the copper ions promote the formation of a carbon layer by catalyzing the oxidation reaction, isolating oxygen and heat, and further improving the fire resistance and flame retardant properties of the cable material.

[0028] 3. The fire-resistant polyvinyl chloride insulated cable of the present invention is prepared by coating a modified cyclic phosphazene-aniline derivative on the outside of ammonium polyphosphate and then modifying the unsaturated olefin double bond to obtain a composite ammonium polyphosphate. The cyclic phosphazene-aniline derivative contains functional groups such as phosphorus, nitrogen, and a benzene ring. These functional groups have a certain polarity. Due to the presence of the benzene ring, the derivative has a certain degree of similarity with the molecular structure of PVC. It interacts with the PVC molecular chain through π-π interaction or van der Waals force, thereby improving the dispersibility of the composite ammonium polyphosphate in the sheath layer cable material. The unsaturated double bonds modified on the particles serve as reactive sites to promote intermolecular crosslinking of the polyvinyl chloride sheath layer material. The ammonium polyphosphate itself has high thermal stability. The composite material can form a protective layer at high temperatures to reduce thermal deformation. At the same time, the phosphorus and nitrogen elements in the composite can promote the formation of a carbon layer in the sheath layer material at high temperatures, improving thermal stability and thus reducing thermal deformation rate. The composite ammonium polyphosphate and the activated filler form a double protective layer at high temperatures, further improving the flame retardancy and fire resistance of the polyvinyl chloride insulated cable. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] In this application, polyvinyl chloride powder was selected from Shandong Ousheng Chemical Co., Ltd., model number XH817089ZNH6, with a particle size of 200-300 μm;

[0031] In this application, the methyl vinyl silicone rubber is selected from Hubei Xingyan New Material Technology Co., Ltd., with a molecular weight of 480,000-800,000 and a vinyl content of 0.03-5.0;

[0032] In this application, the CAS number of the accelerator TMTM is 97-74-5;

[0033] In this application, the CAS number of the accelerator TMDM is 137-26-8;

[0034] In this application, the polyethylene wax is selected from Shanghai Zhenlishi Network Technology Co., Ltd., model AC-629A, and the acid value is 15mgKOH / g;

[0035] In this application, the calcium zinc stabilizer is selected from Jinan Junteng Chemical Co., Ltd., and the product name is composite heat stabilizer.

[0036] Example 1

[0037] This embodiment provides a method for preparing a fire-resistant polyvinyl chloride insulated cable, comprising the following steps:

[0038] S1. Preparation of activated polyvinyl chloride

[0039] Mix sodium hydroxide, purified water, and anhydrous ethanol in a ratio of 1 g: 5 mL: 8 mL to obtain a sodium hydroxide solution for later use.

[0040] Weigh: 500 g of polyvinyl chloride powder and 1000 mL of sodium hydroxide solution, add them into a polytetrafluoroethylene-lined three-necked flask, seal it and stir, fix the three-necked flask in an oil bath pot with an oil bath temperature of 140°C, keep warm and react for 4 hours, lower the temperature of the three-necked flask to room temperature, filter it, wash the filter cake with purified water until it is neutral and then dry it, transfer the filter cake to a drying oven at a temperature of 60°C, and vacuum dry it to constant weight to obtain activated polyvinyl chloride.

[0041] S2. Preparation of activated filler

[0042] Fly ash and montmorillonite were mixed in a weight ratio of 2:1, ball-milled, and passed through a 100-mesh sieve to obtain an inorganic filler for later use;

[0043] Mix anhydrous ethanol and deionized water in a volume ratio of 1:5 to obtain an ethanol solution for later use;

[0044] Mix anhydrous copper sulfate and deionized water at a ratio of 1 g:10 mL to obtain a copper sulfate solution for later use.

[0045] Weigh: 100 g of inorganic filler and 1000 mL of ethanol solution are added to a three-necked flask and stirred. 1 mol / L hydrochloric acid is added to the three-necked flask to adjust the pH of the system to 3. 30 g of KH-570 and 500 mL of copper sulfate solution are added to the three-necked flask. The temperature of the three-necked flask is raised to 70°C and kept warm for 3 hours. The temperature of the three-necked flask is lowered to room temperature and filtered. The filter cake is washed with deionized water until neutral and then dried. The filter cake is transferred to a drying oven at a temperature of 70°C and vacuum dried to constant weight to obtain an activated filler.

[0046] S3. Preparation of composite ammonium polyphosphate

[0047] Weigh: 20 g of hexachlorocyclotriphosphazene, 20 g of p-phenylenediamine, 800 mL of toluene and 14 g of catalyst potassium carbonate are added to a three-necked flask protected by nitrogen and stirred. The temperature of the three-necked flask is raised to 75° C. and the reaction is kept warm for 6 hours. 160 g of ammonium polyphosphate is added to the three-necked flask and the reaction is kept warm for 10 hours. The temperature of the three-necked flask is lowered to room temperature. 600 mL of anhydrous ethanol is added to the three-necked flask and stirred for 20 minutes. The filter cake is washed with anhydrous ethanol three times and then dried. The filter cake is transferred to a drying oven at a temperature of 60° C. and vacuum dried to constant weight to obtain modified ammonium phosphate;

[0048] Weigh: 80 g of modified ammonium polyphosphate and 300 mL of toluene are added to a nitrogen-protected three-necked flask and stirred. The temperature of the three-necked flask is raised to 40 ° C. 10 g of 3-isocyanate propylene is added to the three-necked flask and kept warm for 60 minutes. The temperature of the three-necked flask is lowered to room temperature, filtered, and the filter cake is washed with anhydrous ethanol three times and then dried. The filter cake is transferred to a drying oven at a temperature of 50 ° C. and vacuum dried to constant weight to obtain composite ammonium polyphosphate.

[0049] S4. Preparation of polyvinyl chloride insulated cables

[0050] Dicumyl peroxide and vulcanization accelerator TMTM were mixed uniformly in a weight ratio of 3:1 to obtain a vulcanizing agent, which was set aside;

[0051] Dibutyl phthalate, polyethylene wax, calcium stearate, calcium zinc stabilizer and antioxidant 1035 were mixed uniformly in a weight ratio of 5:1:2:2:2 to obtain an additive, which was set aside;

[0052] The following materials were weighed in parts by weight: 60 parts of activated polyvinyl chloride, 30 parts of methyl vinyl silicone rubber, 25 parts of activated filler, 12 parts of composite ammonium polyphosphate, 1 part of vulcanizing agent and 7 parts of additives, mixed and added into a twin-screw extruder. The temperatures of the six temperature zones of the twin-screw extruder from the feed end to the discharge end were 175°C, 180°C, 180°C, 180°C, 180°C and 185°C, respectively. After melt mixing in the twin-screw extruder for 6 minutes, the mixture was melt extruded and coated on the outside of the cable core. The mixture was cooled and solidified to form a sheath layer on the outside of the cable core to obtain a polyvinyl chloride insulated cable.

[0053] Example 2

[0054] This embodiment provides a method for preparing a fire-resistant polyvinyl chloride insulated cable, comprising the following steps:

[0055] S1. Preparation of activated polyvinyl chloride

[0056] Mix sodium hydroxide, purified water, and anhydrous ethanol in a ratio of 1 g: 5 mL: 8 mL to obtain a sodium hydroxide solution for later use.

[0057] Weigh: 500 g of polyvinyl chloride powder and 1000 mL of sodium hydroxide solution, add them into a polytetrafluoroethylene-lined three-necked flask, seal it and stir it, fix the three-necked flask in an oil bath pot with an oil bath temperature of 145°C, keep it warm and react for 4.5 hours, lower the temperature of the three-necked flask to room temperature, filter it, wash the filter cake with purified water until it is neutral and then dry it, transfer the filter cake to a drying oven at a temperature of 65°C, and vacuum dry it to constant weight to obtain activated polyvinyl chloride.

[0058] S2. Preparation of activated filler

[0059] Fly ash and montmorillonite were mixed in a weight ratio of 2:1, ball-milled, and passed through a 100-mesh sieve to obtain an inorganic filler for later use;

[0060] Mix anhydrous ethanol and deionized water in a volume ratio of 1:5 to obtain an ethanol solution for later use;

[0061] Mix anhydrous copper sulfate and deionized water at a ratio of 1 g:10 mL to obtain a copper sulfate solution for later use.

[0062] Weigh: 100 g of inorganic filler and 1000 mL of ethanol solution are added to a three-necked flask and stirred. 1 mol / L hydrochloric acid is added to the three-necked flask to adjust the pH of the system to 3.5. 30 g of KH-570 and 500 mL of copper sulfate solution are added to the three-necked flask. The temperature of the three-necked flask is raised to 73°C and kept warm for 4 hours. The temperature of the three-necked flask is lowered to room temperature and filtered. The filter cake is washed with deionized water until neutral and then dried. The filter cake is transferred to a drying oven at a temperature of 75°C and vacuum dried to constant weight to obtain an activated filler.

[0063] S3. Preparation of composite ammonium polyphosphate

[0064] Weigh: 20 g of hexachlorocyclotriphosphazene, 20 g of p-phenylenediamine, 800 mL of toluene and 14 g of catalyst potassium carbonate are added to a three-necked flask protected by nitrogen and stirred. The temperature of the three-necked flask is raised to 80° C. and the reaction is kept warm for 7 hours. 160 g of ammonium polyphosphate is added to the three-necked flask and the reaction is kept warm for 11 hours. The temperature of the three-necked flask is lowered to room temperature. 600 mL of anhydrous ethanol is added to the three-necked flask and stirred for 25 minutes. The filter cake is washed with anhydrous ethanol 4 times and then dried. The filter cake is transferred to a drying oven at a temperature of 65° C. and vacuum dried to constant weight to obtain modified ammonium phosphate;

[0065] Weigh: 80 g of modified ammonium polyphosphate and 300 mL of toluene are added to a nitrogen-protected three-necked flask and stirred. The temperature of the three-necked flask is raised to 45 ° C. 10 g of 3-isocyanate propylene is added to the three-necked flask. The reaction is kept warm for 70 minutes. The temperature of the three-necked flask is lowered to room temperature, filtered, and the filter cake is washed three times with anhydrous ethanol and then dried. The filter cake is transferred to a drying oven at a temperature of 55 ° C. and vacuum dried to constant weight to obtain composite ammonium polyphosphate.

[0066] S4. Preparation of polyvinyl chloride insulated cables

[0067] Dicumyl peroxide and vulcanization accelerator TMDM are mixed uniformly in a weight ratio of 3:1 to obtain a vulcanizing agent, which is set aside;

[0068] Dioctyl phthalate, ethylene bisstearamide, magnesium stearate, calcium zinc stabilizer and antioxidant 1520 were mixed uniformly in a weight ratio of 5:1:2:2:2 to obtain an additive, and the mixture was set aside;

[0069] The following materials were weighed in parts by weight: 65 parts of activated polyvinyl chloride, 35 parts of methyl vinyl silicone rubber, 30 parts of activated filler, 14 parts of composite ammonium polyphosphate, 1.5 parts of vulcanizing agent and 7.5 parts of additives, mixed and added into a twin-screw extruder. The temperatures of the six temperature zones of the twin-screw extruder from the feed end to the discharge end were 175°C, 180°C, 180°C, 180°C, 180°C and 185°C, respectively. After melt mixing in the twin-screw extruder for 7 minutes, the mixture was melt extruded and coated on the outside of the cable core. The mixture was cooled and solidified to form a sheath layer on the outside of the cable core to obtain a polyvinyl chloride insulated cable.

[0070] Example 3

[0071] This embodiment provides a method for preparing a fire-resistant polyvinyl chloride insulated cable, comprising the following steps:

[0072] S1. Preparation of activated polyvinyl chloride

[0073] Mix sodium hydroxide, purified water, and anhydrous ethanol in a ratio of 1 g: 5 mL: 8 mL to obtain a sodium hydroxide solution for later use.

[0074] Weigh: 500 g of polyvinyl chloride powder and 1000 mL of sodium hydroxide solution, add them into a polytetrafluoroethylene-lined three-necked flask, seal it and stir, fix the three-necked flask in an oil bath pot with an oil bath temperature of 150°C, keep warm and react for 5 hours, lower the temperature of the three-necked flask to room temperature, filter it, wash the filter cake with purified water until it is neutral and then dry it, transfer the filter cake to a drying oven at a temperature of 70°C, and vacuum dry it to constant weight to obtain activated polyvinyl chloride.

[0075] S2. Preparation of activated filler

[0076] Fly ash and montmorillonite were mixed in a weight ratio of 2:1, ball-milled, and passed through a 100-mesh sieve to obtain an inorganic filler for later use;

[0077] Mix anhydrous ethanol and deionized water in a volume ratio of 1:5 to obtain an ethanol solution for later use;

[0078] Mix anhydrous copper sulfate and deionized water at a ratio of 1 g:10 mL to obtain a copper sulfate solution for later use.

[0079] Weigh: 100 g of inorganic filler and 1000 mL of ethanol solution are added to a three-necked flask and stirred. 1 mol / L hydrochloric acid is added to the three-necked flask to adjust the pH of the system to 4. 30 g of KH-570 and 500 mL of copper sulfate solution are added to the three-necked flask. The temperature of the three-necked flask is raised to 76°C and kept warm for 5 hours. The temperature of the three-necked flask is lowered to room temperature and filtered. The filter cake is washed with deionized water until neutral and then dried. The filter cake is transferred to a drying oven at 80°C and vacuum dried to constant weight to obtain an activated filler.

[0080] S3. Preparation of composite ammonium polyphosphate

[0081] Weigh: 20 g of hexachlorocyclotriphosphazene, 20 g of p-phenylenediamine, 800 mL of toluene and 14 g of catalyst potassium carbonate are added to a three-necked flask protected by nitrogen and stirred. The temperature of the three-necked flask is raised to 85° C. and the reaction is kept warm for 8 hours. 160 g of ammonium polyphosphate is added to the three-necked flask and the reaction is kept warm for 12 hours. The temperature of the three-necked flask is lowered to room temperature. 600 mL of anhydrous ethanol is added to the three-necked flask and stirred for 30 minutes. The filter cake is washed with anhydrous ethanol 5 times and then dried. The filter cake is transferred to a drying oven at a temperature of 70° C. and vacuum dried to constant weight to obtain modified ammonium phosphate;

[0082] Weigh: 80 g of modified ammonium polyphosphate and 300 mL of toluene are added to a nitrogen-protected three-necked flask and stirred. The temperature of the three-necked flask is raised to 50 ° C. 10 g of 3-isocyanate propylene is added to the three-necked flask and kept warm for 80 minutes. The temperature of the three-necked flask is lowered to room temperature, filtered, and the filter cake is washed with anhydrous ethanol three times and then dried. The filter cake is transferred to a drying oven at a temperature of 60 ° C. and vacuum dried to constant weight to obtain composite ammonium polyphosphate.

[0083] S4. Preparation of polyvinyl chloride insulated cables

[0084] Dicumyl peroxide and vulcanization accelerator TMTM were mixed uniformly in a weight ratio of 3:1 to obtain a vulcanizing agent, which was set aside;

[0085] Diethyl phthalate, polyethylene wax, zinc stearate, calcium zinc stabilizer and antioxidant 1024 were mixed uniformly in a weight ratio of 5:1:2:2:2 to obtain an additive, and the mixture was set aside;

[0086] The following materials were weighed in parts by weight: 70 parts of activated polyvinyl chloride, 40 parts of methyl vinyl silicone rubber, 35 parts of activated filler, 16 parts of composite ammonium polyphosphate, 2 parts of vulcanizing agent and 8 parts of additives, mixed and added into a twin-screw extruder. The temperatures of the six temperature zones of the twin-screw extruder from the feed end to the discharge end were 175°C, 180°C, 180°C, 180°C, 180°C and 185°C, respectively. After melt mixing in the twin-screw extruder for 8 minutes, the mixture was melt extruded and coated on the outside of the cable core. The mixture was cooled and solidified to form a sheath layer on the outside of the cable core to obtain a polyvinyl chloride insulated cable.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 3 is that step S2 is eliminated, and the activated filler in step S4 is replaced by the inorganic filler in step S2.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 3 is that in step S2, no copper sulfate solution is added.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 3 is that step S3 is eliminated, and the ammonium polyphosphate in step S3 is used instead of the composite ammonium polyphosphate in step S4.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 3 is that the modified ammonium polyphosphate in step S3 is used instead of the composite ammonium polyphosphate in step S4.

[0095] Performance testing:

[0096] The tensile strength, tensile strain at break, thermal deformation, and room temperature oxygen index of the sheath layer materials of the polyvinyl chloride insulated cable samples prepared in Examples 1-3 and Comparative Examples 1-4 were measured with reference to Standard T / SHPTA 006-2021 “Soft polyvinyl chloride flame retardant sheath materials for wires and cables”;

[0097] The fire resistance levels of the polyvinyl chloride insulated cable samples prepared in Examples 1-3 and Comparative Examples 1-4 were determined with reference to Standard XF 306.2-2007 "Classification and Requirements for Flame Retardant and Fire Resistant Cables - Plastic Insulation - Part 2: Fire Resistant Cables". The specific test results are shown in Table 1 below.

[0098] Table 1-Performance test data of the sample

[0099]

[0100] Performance testing:

[0101] A comparative analysis of the performance test data in Table 1 above shows that the tensile strength of the sheath layer of the polyvinyl chloride insulated cable sample prepared by the present invention reaches 20.43 MPa, the tensile strain at break reaches 269.15%, the thermal deformation is reduced to 18.9%, the room temperature oxygen index reaches 39.4%, and the fire resistance level of the polyvinyl chloride insulated cable sample reaches Class IIA. All performance test data are better than those of the comparative example, indicating that the present invention uses a base material composed of activated polyvinyl chloride modified with olefin double bonds and methyl vinyl silicone rubber, and then reinforces the base material with activated fillers and composite ammonium polyphosphate, which not only effectively improves the mechanical strength and flame retardant and heat resistance of the polyvinyl chloride insulated cable material, but also improves its fire resistance level.

[0102] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fire-resistant polyvinyl chloride insulated cable comprising at least a cable core and a polyvinyl chloride sheath layer covering the cable core, characterized in that: The polyvinyl chloride sheath layer comprises the following components in parts by weight: 60-70 parts of activated polyvinyl chloride, 30-40 parts of methyl vinyl silicone rubber, 25-35 parts of activated filler, 12-16 parts of composite ammonium polyphosphate, 1-2 parts of vulcanizing agent and 7-8 parts of additive additive; The preparation method of the activated polyvinyl chloride comprises: mixing polyvinyl chloride powder and sodium hydroxide solution, carrying out heat preservation reaction for 4-5 hours at 140-150° C., and performing post-treatment to obtain the activated polyvinyl chloride; The activated filler is prepared by mixing an inorganic filler and an ethanol solution, adding hydrochloric acid to the reaction system to adjust the pH of the system to 3-4, adding KH-570 and a copper sulfate solution to the reaction system, raising the temperature of the reaction system to 70-76° C., keeping the temperature for reaction for 3-5 hours, and post-treating to obtain the activated filler; The composite ammonium polyphosphate is obtained by processing the following steps: A1. Under an inert gas atmosphere, hexachlorocyclotriphosphazene, p-phenylenediamine, toluene, and a catalyst are mixed, the reaction system temperature is raised to 75-85°C, and the reaction is kept warm for 6-8 hours. Ammonium polyphosphate is added to the reaction system, and the reaction is kept warm for 10-12 hours. After post-treatment, modified ammonium polyphosphate is obtained. A2. Under an inert gas atmosphere, the modified ammonium polyphosphate and toluene were mixed, the temperature of the reaction system was raised to 40-50°C, 3-isocyanate propylene was added to the reaction system, and the reaction was kept warm for 60-80 minutes, and post-processed to obtain composite ammonium polyphosphate.

2. A fire-resistant polyvinyl chloride insulated cable according to claim 1, characterized in that: The vulcanizing agent is composed of dicumyl peroxide and a vulcanization accelerator in a weight ratio of 3:1, the vulcanization accelerator is any one of accelerator TMTM and accelerator TMDM, the additives are composed of a plasticizer, a lubricant, a dispersant, a stabilizer and an antioxidant in a weight ratio of 5:1:2:2:2, the plasticizer is a phthalate, the lubricant is any one of polyethylene wax and ethylene bisstearamide, the dispersant is a stearate, the stabilizer is a calcium zinc stabilizer, and the antioxidant is any one of antioxidant 1035, antioxidant 1520, and antioxidant 1024.

3. A fire-resistant polyvinyl chloride insulated cable according to claim 1, characterized in that: The polyvinyl chloride powder and the sodium hydroxide solution are used in a ratio of 1 g:20 mL, the particle size of the polyvinyl chloride powder is 200-300 μm, and the sodium hydroxide solution is composed of sodium hydroxide, purified water, and anhydrous ethanol in a ratio of 1 g:5 mL:8 mL. The post-treatment includes: after the reaction is completed, lowering the temperature of the reaction system to room temperature, filtering, washing the filter cake with purified water until it is neutral, and then drying it, transferring the filter cake to a drying oven at a temperature of 60-70° C., and vacuum drying it to constant weight to obtain activated polyvinyl chloride.

4. A fire-resistant polyvinyl chloride insulated cable according to claim 1, characterized in that: The inorganic filler, ethanol solution, KH-570 and copper sulfate solution are used in a ratio of 1g:10mL:0.3g:5mL. The inorganic filler is obtained by ball-milling fly ash and montmorillonite in a weight ratio of 2:1 and passing through a 100-mesh sieve. The ethanol solution is composed of anhydrous ethanol and deionized water in a volume ratio of 1:

5. The copper sulfate solution is composed of copper sulfate and deionized water in a volume ratio of 1g:10mL. The post-treatment includes: after the reaction is completed, lowering the temperature of the reaction system to room temperature, filtering, washing the filter cake with deionized water until it is neutral and then drying it, transferring the filter cake to a drying oven at a temperature of 70-80°C, and vacuum drying it to constant weight to obtain the activated filler.

5. A fire-resistant polyvinyl chloride insulated cable according to claim 1, characterized in that: In step A1, the amount ratio of the hexachlorocyclotriphosphazene, p-phenylenediamine, toluene, catalyst and ammonium polyphosphate is 1g:1g:40mL:0.7g:8g. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, anhydrous ethanol is added to the reaction system, the mixture is stirred for 20-30 minutes, filtered, the filter cake is washed with anhydrous ethanol 3-5 times and then dried, and the filter cake is transferred to a drying oven at a temperature of 60-70°C and vacuum dried to constant weight to obtain modified ammonium polyphosphate.

6. A fire-resistant polyvinyl chloride insulated cable according to claim 1, characterized in that: In step A2, the modified ammonium polyphosphate, toluene and 3-isocyanate propylene are used in a ratio of 8g:15mL:1g, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with anhydrous ethanol three times and then dried, and the filter cake is transferred to a drying oven at a temperature of 50-60°C and vacuum dried to constant weight to obtain composite ammonium polyphosphate.

7. A method for preparing a fire-resistant polyvinyl chloride insulated cable according to any one of claims 1 to 6, characterized in that: The preparation method of the fire-resistant polyvinyl chloride insulated cable comprises the following steps: mixing activated polyvinyl chloride, methyl vinyl silicone rubber, activated filler, composite ammonium polyphosphate, vulcanizing agent and additives, adding the mixture into a twin-screw extruder, melt-extruding and coating the mixture on the outside of a cable core, cooling and curing the mixture, forming a sheath layer on the outside of the cable core, and obtaining the polyvinyl chloride insulated cable.

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