Flame-retardant PVC composite material and preparation method thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses a flame-retardant PVC composite material which comprises the following raw materials in parts by weight: 90-100 parts of polyvinyl chloride resin, 2-5 parts of a compatilizer, 30-40 parts of a plasticizer, 1-2 parts of an antioxidant, 5-10 parts of aluminum hydroxide, 2-5 parts of calcium stearate, 4-6 parts of zinc stearate, 2-6 parts of ACR resin, 1-5 parts of a modified heat stabilizer and 6-10 parts of a modified flame retardant. In the application, the preparation of the modified flame retardant can inhibit the combustion of the system through multiple mechanisms, the heat transfer and the combustible gas release are inhibited, and the flame-retardant effect of the system is improved; the preparation of the modified heat stabilizer can inhibit the dehydrochlorination reaction of the PVC and block the free radical chain reaction, the thermal oxidative degradation of the system is delayed, the heat resistance of the system is improved, and the service life of the system is prolonged.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant PVC composite material and its preparation method. Background Technology

[0002] Polyvinyl chloride (PVC) is a polar, non-crystalline polymer widely used in aerospace, construction, and industrial fields due to its advantages such as good insulation, low cost, easy availability, and stable physicochemical properties. However, during long-term use, the performance of PVC materials will age due to the effects of light, heat, and water, including its flame retardant properties. Therefore, flame retardants and heat stabilizers need to be added to improve its flame retardant properties and stability, thereby enhancing the overall performance of the material. Currently, the flame retardants commonly used in PVC materials are mainly classified into several categories, including halogenated, phosphorus-based, nitrogen-based, and inorganic flame retardants. However, each type of flame retardant also has certain limitations in its application. Halogenated flame retardants produce a large amount of toxic and harmful hydrogen halide gas when burning, causing secondary harm to human health and the environment, which is inconsistent with the current trend of green and environmentally friendly development. Phosphorus-based flame retardants often require a high addition amount to achieve the ideal flame retardant effect. Although inorganic flame retardants are environmentally friendly, high filling amounts can easily lead to a decrease in the toughness of the material, making it prone to cracking and other problems during use. In addition, a certain amount of heat stabilizer needs to be added during the PVC molding process to inhibit its dechlorination degradation when heated. The use of traditional lead salt heat stabilizers is gradually being restricted due to heavy metal pollution. Developing efficient, non-toxic, and environmentally friendly flame retardants and heat stabilizers has become one of the current research hotspots.

[0003] Patent application number 202210361367.0 discloses an environmentally friendly flame-retardant PVC / PE composite material and its preparation method. It uses inorganic flame-retardant fillers to improve the flame-retardant performance of the system. However, the inorganic flame retardant requires a relatively high addition amount to achieve the ideal flame-retardant effect, which may potentially affect the material's processing performance and some mechanical properties to a certain extent. Patent application number 201811297660.5 discloses a flame-retardant and smoke-suppressing PVC composite material and its preparation method. It uses phenylphosphonate and antimony trioxide as flame retardants, improving the system's flame-retardant and smoke-suppressing performance. However, phenylphosphonate alone has limited flame-retardant performance and cannot improve the mechanical properties of PVC. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a flame-retardant PVC composite material and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A flame-retardant PVC composite material comprises the following raw materials in parts by weight: 90-100 parts of polyvinyl chloride resin, 2-5 parts of compatibilizer, 30-40 parts of plasticizer, 1-2 parts of antioxidant, 5-10 parts of aluminum hydroxide, 2-5 parts of calcium stearate, 4-6 parts of zinc stearate, 2-6 parts of ACR resin, 1-5 parts of modified heat stabilizer, and 6-10 parts of modified flame retardant.

[0007] The compatibilizer is chlorinated polyethylene, the plasticizer is dioctyl phthalate, and the antioxidant is antioxidant 1010.

[0008] The modified flame retardant is prepared by the following steps:

[0009] Step A1: Mix 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol, stir, react at 80°C for 2 h under nitrogen protection, rotary evaporate and vacuum dry to obtain intermediate product 1.

[0010] Furthermore, the ratio of 4-formylphenylboronic acid, p-aminostyrene, and anhydrous ethanol is 1-3 mol: 1-1.5 mol: 500-700 mL;

[0011] In step A1, 4-formylphenylboronic acid and p-aminostyrene undergo a condensation reaction, introducing an amino group to provide reaction conditions for subsequent substitution reactions. The introduced boric acid group decomposes at high temperature to generate boric acid or boric anhydride, which reacts with hydroxyl-containing compounds to form a BC structure, promoting the formation of a char layer. The char layer has heat insulation and oxygen barrier functions, while inhibiting heat transfer and the release of flammable gases.

[0012] Step A2: Mix intermediate product 1, diphenyl phosphite and toluene, react at 80°C for 8 hours under nitrogen protection, filter, wash and vacuum dry to obtain intermediate product 2;

[0013] Furthermore, the ratio of intermediate product 1, diphenyl phosphite, and toluene is 1-1.3 mol: 1-2 mol: 100-150 mL;

[0014] In step A2, intermediate product 1 and diphenyl phosphite undergo an addition reaction, introducing a diphenyl phosphate group. The free radicals generated by the decomposition of this structure can capture active free radicals in the combustion chain reaction, interrupting the combustion chain reaction; at the same time, it weakens the intermolecular forces and improves the mechanical properties of the material.

[0015] Step A3: Mix 1 / 3 part of intermediate product 2 with 15wt% sodium hydroxide aqueous solution, add it to a mixed solution of cyanuric chloride and toluene, react at 0℃ for 2h, then add 2 / 3 part of intermediate product 2, reflux at 80℃ for 10h, after the reaction is completed, add water for extraction and concentration to obtain the modified flame retardant.

[0016] Furthermore, the ratio of intermediate product 2, sodium hydroxide aqueous solution, cyanuric chloride, and toluene is 0.6-1 mol: 150 mL: 0.2-0.3 mol: 200 mL;

[0017] In step A3, intermediate product 2 undergoes a substitution reaction with cyanuric chloride, introducing a triazine ring structure. When heated and decomposed, it releases non-flammable gases such as ammonia, diluting the concentration of flammable gases. At the same time, it reduces the combustion rate, captures active free radicals in the combustion chain reaction, slows down the combustion rate, and can also work synergistically with phosphorus and nitrogen elements to reduce the heat release rate.

[0018] The modified heat stabilizer is prepared by the following steps:

[0019] Step B1: Mix 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol and acetone, and heat under reflux at 55°C. After the reaction is complete by TLC (thin-layer chromatography), filter, distill under reduced pressure, purify and rotary evaporate to obtain maleimide derivative.

[0020] Furthermore, the ratio of 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone is 1-2 mol: 2-3.5 mol: 3-5 mol: 700-800 mL;

[0021] In step B1, 3,4-dibromo-1H-pyrrole-2,5-dione and 3-bromo-1-propanol undergo a substitution reaction to introduce hydroxyl groups into the system, providing reaction conditions for the subsequent hydrazylation reaction. At the same time, the introduced maleimide structure can form a synergistic effect with metal soaps, improving the heat resistance of PVC.

[0022] Step B2: Mix maleimide derivative, triethylamine and methanol, add mercaptoacetic acid, stir at room temperature, determine the end of the reaction by TLC, extract, dry, filter, concentrate under reduced pressure, column chromatography, and rotary evaporation to obtain carboxylic acid maleimide derivative;

[0023] Furthermore, the ratio of maleimide derivative, triethylamine, methanol, and thioglycolic acid is 0.5-1.5 mol: 1-3 mol: 600-700 mL: 1-3 mol;

[0024] In step B2, the bromine atom in the maleimide derivative and the thiol group in mercaptoacetic acid undergo a substitution reaction, introducing a carboxylic acid group and providing reaction conditions for the subsequent addition reaction.

[0025] Step B3: Mix the carboxylic acid maleimide derivative with ethanol, add phenylhydrazine, reflux at 80°C for 4 hours, then react at room temperature for 2 hours, precipitate, filter, and wash to obtain phenylhydrazine maleimide derivative;

[0026] Furthermore, the ratio of carboxylic acid maleimide derivatives, ethanol, and phenylhydrazine is 0.5-0.8 mol: 450 mL: 0.7-1 mol;

[0027] In step B3, the carboxylic acid maleimide derivative and phenylhydrazine undergo a substitution reaction, introducing the hydrazine group and benzene ring into the system. This allows the hydrazine group to react with the hydrogen chloride produced by the decomposition of PVC, converting it into a harmless substance, thereby blocking the chain degradation reaction and increasing the thermal decomposition temperature of the system.

[0028] Step B4: Mix phenylhydrazine maleimide derivative, sulfoxide and N,N-dimethylformamide, stir at 50°C for 4 h, distill under reduced pressure, dry, and redisperse in acetonitrile to form solution 1. Mix potassium thiocyanate, acetonitrile and polyethylene glycol-400, stir, and add dropwise to solution 1. After stirring for 40 min, add aniline, stir for 3-4 h, extract and column chromatography to obtain the modified heat stabilizer.

[0029] Furthermore, in solution 1, the ratio of phenylhydrazine maleimide derivative, sulfoxide, N,N-dimethylformamide, and acetonitrile is 0.2-0.4 mol; 5-6 mol: 15-20 mL: 100 mL; and in the modified heat stabilizer, the ratio of potassium thiocyanate, acetonitrile, polyethylene glycol-400, aniline, and solution 1 is 1-1.2 mol: 300 mL: 15-20 mL: 0.5-1 mol: 105-115 mL.

[0030] In step B4, the carboxyl group in the phenylhydrazine maleimide derivative is activated and thiolated, and then undergoes a nucleophilic addition reaction with aniline to introduce a thiourea structure. This structure can react with the metal chlorides produced by PVC pyrolysis to form a stable complex, which inhibits the dehydrochlorination reaction of PVC, delays the thermal oxidative degradation of the system, and thus improves the system's heat aging resistance.

[0031] A method for preparing a flame-retardant PVC composite material includes the following steps:

[0032] Step S1: Weigh the raw materials according to the weight ratio, take polyvinyl chloride resin and zinc stearate, add them to a high-speed mixer and mix at 85-95℃ for 8-10 minutes. Then add compatibilizer, plasticizer, antioxidant, aluminum hydroxide, calcium stearate, ACR resin, modified heat stabilizer and modified flame retardant to the high-speed mixer in sequence and mix for 8-10 minutes at 85-95℃. Discharge and cool to obtain PVC composite material.

[0033] Step S2: The PVC composite material is melt-extruded and blended using a twin-screw extruder, cooled by water and then granulated. The granules are dried in a blower drying oven until the moisture content is below 3%, then taken out and put into a horizontal injection molding machine to obtain standard samples through injection molding.

[0034] The beneficial effects of this invention are:

[0035] The flame-retardant PVC composite material of this invention can be widely used in fields such as wire and cable, electronic component housings, and vehicle interior trim. By adding modified flame retardants and modified heat stabilizers during the preparation of the PVC composite material, combustion can be inhibited through multiple mechanisms, heat and oxygen can be blocked, and thermal stability can be significantly improved, reducing the release of toxic substances during thermal degradation. Compared with existing technologies, the flame-retardant PVC composite material prepared by this invention improves the flame-retardant performance of the material without reducing its mechanical properties, effectively delaying the degradation of material performance, meeting the application requirements of flame retardancy, safety, and stability, possessing strong practical value and competitive advantages, and showing broad application prospects.

[0036] The modified flame retardant of this invention first utilizes a condensation reaction between 4-formylphenylboronic acid and p-aminostyrene. The introduced boric acid group decomposes at high temperature to generate boric acid or boric anhydride, which reacts with hydroxyl-containing compounds to form a BC structure, promoting the formation of a char layer. This char layer provides heat insulation and oxygen barrier functions, while simultaneously inhibiting heat transfer and the release of flammable gases. Next, an addition reaction introduces a diphenyl phosphate group. The free radicals generated by the decomposition of this structure can capture active free radicals in the combustion chain reaction, interrupting the combustion chain reaction; simultaneously, it weakens intermolecular forces, improving the mechanical properties of the material. Finally, a substitution reaction introduces a triazine ring structure, which releases non-flammable gases such as ammonia upon thermal decomposition, diluting the concentration of flammable gases, while simultaneously reducing the combustion rate, capturing active free radicals in the combustion chain reaction, slowing down the combustion rate, and also acting synergistically with phosphorus and nitrogen elements to reduce the heat release rate.

[0037] The modified heat stabilizer of this invention first undergoes a substitution reaction with 3,4-dibromo-1H-pyrrole-2,5-dione and 3-bromo-1-propanol. The introduced maleimide structure can form a synergistic effect with metal soaps, improving the heat resistance of PVC. The resulting maleimide derivative undergoes a substitution reaction with mercaptoacetic acid, introducing a carboxylic acid group. Then, it undergoes a substitution reaction with phenylhydrazine, introducing a hydrazine group and a benzene ring into the system. This reacts with hydrogen chloride produced by PVC decomposition, converting it into a harmless substance, thereby blocking the chain degradation reaction and increasing the thermal decomposition temperature of the system. Finally, a nucleophilic addition reaction introduces a thiourea structure, which can react with metal chlorides produced by PVC pyrolysis to form a stable complex, inhibiting the dehydrochlorination reaction of PVC, delaying the thermal oxidative degradation of the system, and thus improving the system's heat aging resistance. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0039] In this embodiment, the compatibilizer is chlorinated polyethylene, the plasticizer is dioctyl phthalate, and the antioxidant is antioxidant 1010.

[0040] Example 1: The modified flame retardant was prepared by the following steps:

[0041] Step A1: Mix 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol, stir, react at 80°C for 2 hours under nitrogen protection, evaporate by rotary evaporation and dry under vacuum to obtain intermediate product 1, the ratio of 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol is 1 mol: 1 mol: 500 mL.

[0042] Step A2: Mix intermediate product 1, diphenyl phosphite and toluene, react at 80°C for 8 hours under nitrogen protection, filter, wash and vacuum dry to obtain intermediate product 2. The ratio of intermediate product 1, diphenyl phosphite and toluene is 1 mol: 1 mol: 100 mL.

[0043] Step A3: Mix 1 / 3 part of intermediate product 2 with 15wt% sodium hydroxide aqueous solution, add it to a mixed solution of cyanuric chloride and toluene, react at 0℃ for 2h, then add 2 / 3 part of intermediate product 2, reflux at 80℃ for 10h, after the reaction is completed, add water for extraction and concentration to obtain the modified flame retardant. The ratio of intermediate product 2, sodium hydroxide aqueous solution, cyanuric chloride and toluene is 0.6mol:150mL:0.2mol:200mL.

[0044] The modified heat stabilizer is prepared using the following steps:

[0045] Step B1: Mix 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone, and heat under reflux at 55°C. After the reaction is complete as determined by TLC, filter, distill under reduced pressure, purify, and rotary evaporate to obtain the maleimide derivative. The molar ratio of 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone is 1 mol: 2 mol: 3 mol: 700 mL.

[0046] Step B2: Mix maleimide derivative, triethylamine and methanol, add mercaptoacetic acid, stir at room temperature, and after the reaction is completed by TLC, extract, dry, filter, concentrate under reduced pressure, column chromatography and rotary evaporation to obtain carboxylic acid maleimide derivative. The ratio of maleimide derivative, triethylamine, methanol and mercaptoacetic acid is 0.5 mol: 1 mol: 600 mL: 1 mol.

[0047] Step B3: Mix the carboxylic acid maleimide derivative and ethanol, add phenylhydrazine, reflux at 80°C for 4 hours, then react at room temperature for 2 hours, precipitate, filter, and wash to obtain phenylhydrazine maleimide derivative. The ratio of carboxylic acid maleimide derivative, ethanol and phenylhydrazine is 0.5 mol: 450 mL: 0.7 mol.

[0048] Step B4: Mix phenylhydrazine maleimide derivative, sulfonium chloride, and N,N-dimethylformamide, stir at 50°C for 4 hours, distill under reduced pressure, dry, and redisperse in acetonitrile to form solution 1. Mix potassium thiocyanate, acetonitrile, and polyethylene glycol-400, stir, and add dropwise to solution 1. Stir for 40 minutes, then add aniline, stir for 3 hours, extract, and perform column chromatography to obtain the modified heat stabilizer. The ratio of phenylhydrazine maleimide derivative, sulfonium chloride, N,N-dimethylformamide, and acetonitrile in solution 1 is 0.2 mol: 5 mol: 15 mL: 100 mL. The ratio of potassium thiocyanate, acetonitrile, polyethylene glycol-400, aniline, and solution 1 in the modified heat stabilizer is 1 mol: 300 mL: 15 mL: 0.5 mol: 105 mL.

[0049] Example 2: The modified flame retardant was prepared by the following steps:

[0050] Step A1: Mix 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol, stir, and react at 80°C for 2 hours under nitrogen protection. After rotary evaporation and vacuum drying, intermediate product 1 is obtained. The ratio of 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol is 2 mol: 1.2 mol: 600 mL.

[0051] Step A2: Mix intermediate product 1, diphenyl phosphite and toluene, react at 80°C for 8 hours under nitrogen protection, filter, wash and vacuum dry to obtain intermediate product 2. The ratio of intermediate product 1, diphenyl phosphite and toluene is 1.1 mol: 1.5 mol: 130 mL.

[0052] Step A3: Mix 1 / 3 part of intermediate product 2 with 15wt% sodium hydroxide aqueous solution, add it to a mixed solution of cyanuric chloride and toluene, react at 0℃ for 2h, then add 2 / 3 part of intermediate product 2, reflux at 80℃ for 10h, after the reaction is completed, add water for extraction and concentration to obtain the modified flame retardant. The ratio of intermediate product 2, sodium hydroxide aqueous solution, cyanuric chloride and toluene is 0.7mol:150mL:0.25mol:200mL.

[0053] The modified heat stabilizer is prepared using the following steps:

[0054] Step B1: Mix 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone, and heat under reflux at 55°C. After the reaction is complete as determined by TLC, filter, distill under reduced pressure, purify, and rotary evaporate to obtain the maleimide derivative. The molar ratio of 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone is 1.5 mol: 2.5 mol: 4 mol: 750 mL.

[0055] Step B2: Mix maleimide derivative, triethylamine and methanol, add mercaptoacetic acid, stir at room temperature, and after the reaction is completed by TLC, extract, dry, filter, concentrate under reduced pressure, column chromatography and rotary evaporation to obtain carboxylic acid maleimide derivative. The ratio of maleimide derivative, triethylamine, methanol and mercaptoacetic acid is 1 mol: 2 mol: 650 mL: 2 mol.

[0056] Step B3: Mix the carboxylic acid maleimide derivative and ethanol, add phenylhydrazine, reflux at 80°C for 4 hours, then react at room temperature for 2 hours, precipitate, filter, and wash to obtain phenylhydrazine maleimide derivative. The ratio of carboxylic acid maleimide derivative, ethanol and phenylhydrazine is 0.6 mol: 450 mL: 0.8 mol.

[0057] Step B4: Mix phenylhydrazine maleimide derivative, sulfonium chloride, and N,N-dimethylformamide, stir at 50°C for 4 hours, distill under reduced pressure, dry, and redisperse in acetonitrile to form solution 1. Mix potassium thiocyanate, acetonitrile, and polyethylene glycol-400, stir, and add dropwise to solution 1. Stir for 40 minutes, then add aniline, stir for 3.5 hours, extract, and perform column chromatography to obtain the modified heat stabilizer. The ratio of phenylhydrazine maleimide derivative, sulfonium chloride, N,N-dimethylformamide, and acetonitrile in solution 1 is 0.3 mol: 5.5 mol: 18 mL: 100 mL. The ratio of potassium thiocyanate, acetonitrile, polyethylene glycol-400, aniline, and solution 1 in the modified heat stabilizer is 1.1 mol: 300 mL: 18 mL: 0.7 mol: 110 mL.

[0058] Example 3: The modified flame retardant was prepared by the following steps:

[0059] Step A1: Mix 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol, stir, react at 80°C for 2 hours under nitrogen protection, rotary evaporate and vacuum dry to obtain intermediate product 1. The ratio of 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol is 3 mol: 1.5 mol: 700 mL.

[0060] Step A2: Mix intermediate product 1, diphenyl phosphite and toluene, react at 80°C for 8 hours under nitrogen protection, filter, wash and vacuum dry to obtain intermediate product 2. The ratio of intermediate product 1, diphenyl phosphite and toluene is 1.3 mol: 2 mol: 150 mL.

[0061] Step A3: Mix 1 / 3 part of intermediate product 2 with 15wt% sodium hydroxide aqueous solution, add it to a mixed solution of cyanuric chloride and toluene, react at 0℃ for 2h, then add 2 / 3 part of intermediate product 2, reflux at 80℃ for 10h, after the reaction is completed, add water for extraction and concentration to obtain the modified flame retardant. The ratio of intermediate product 2, sodium hydroxide aqueous solution, cyanuric chloride and toluene is 1mol:150mL:0.3mol:200mL.

[0062] The modified heat stabilizer is prepared using the following steps:

[0063] Step B1: Mix 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone, and heat under reflux at 55°C. After the reaction is complete as determined by TLC, filter, distill under reduced pressure, purify, and rotary evaporate to obtain the maleimide derivative. The molar ratio of 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone is 2 mol: 3.5 mol: 5 mol: 800 mL.

[0064] Step B2: Mix maleimide derivative, triethylamine and methanol, add mercaptoacetic acid, stir at room temperature, and after the reaction is completed by TLC, extract, dry, filter, concentrate under reduced pressure, column chromatography and rotary evaporation to obtain carboxylic acid maleimide derivative. The ratio of maleimide derivative, triethylamine, methanol and mercaptoacetic acid is 1.5 mol: 3 mol: 700 mL: 3 mol.

[0065] Step B3: Mix the carboxylic acid maleimide derivative and ethanol, add phenylhydrazine, reflux at 80°C for 4 hours, then react at room temperature for 2 hours, precipitate, filter, and wash to obtain phenylhydrazine maleimide derivative. The ratio of carboxylic acid maleimide derivative, ethanol and phenylhydrazine is 0.8 mol: 450 mL: 1 mol.

[0066] Step B4: Mix phenylhydrazine maleimide derivative, sulfonium chloride, and N,N-dimethylformamide, stir at 50°C for 4 hours, distill under reduced pressure, dry, and redisperse in acetonitrile to form solution 1. Mix potassium thiocyanate, acetonitrile, and polyethylene glycol-400, stir, and add dropwise to solution 1. Stir for 40 minutes, then add aniline, stir for 4 hours, extract, and perform column chromatography to obtain the modified heat stabilizer. The ratio of phenylhydrazine maleimide derivative, sulfonium chloride, N,N-dimethylformamide, and acetonitrile in solution 1 is 0.4 mol: 6 mol: 20 mL: 100 mL. The ratio of potassium thiocyanate, acetonitrile, polyethylene glycol-400, aniline, and solution 1 in the modified heat stabilizer is 1.2 mol: 300 mL: 20 mL: 1 mol: 115 mL.

[0067] Example 4: A method for preparing a flame-retardant PVC composite material, comprising the following steps:

[0068] 90 parts of polyvinyl chloride resin, 2 parts of compatibilizer, 30 parts of plasticizer, 1 part of antioxidant, 5 parts of aluminum hydroxide, 2 parts of calcium stearate, 4 parts of zinc stearate, 2 parts of ACR resin, 1 part of modified heat stabilizer prepared in Example 1, and 6 parts of modified flame retardant prepared in Example 1.

[0069] Step S1: Weigh the raw materials according to the weight ratio, take polyvinyl chloride resin and zinc stearate, add them to a high-speed mixer and mix at 85°C for 8 minutes. Then add compatibilizer, plasticizer, antioxidant, aluminum hydroxide, calcium stearate, ACR resin, modified heat stabilizer prepared in Example 1 and modified flame retardant prepared in Example 1 to the high-speed mixer in sequence, mix for 8 minutes at 85°C, unload and cool to obtain PVC composite material.

[0070] Step S2: The PVC composite material is melt-extruded and blended using a twin-screw extruder, cooled by water and then granulated. The granules are dried in a blower drying oven until the moisture content is below 3%, then taken out and put into a horizontal injection molding machine to obtain standard samples through injection molding.

[0071] Example 5: A method for preparing a flame-retardant PVC composite material, comprising the following steps:

[0072] 95 parts polyvinyl chloride resin, 3 parts compatibilizer, 35 parts plasticizer, 1.5 parts antioxidant, 8 parts aluminum hydroxide, 4 parts calcium stearate, 5 parts zinc stearate, 4 parts ACR resin, 3 parts modified heat stabilizer prepared in Example 2, and 8 parts modified flame retardant prepared in Example 2.

[0073] Step S1: Weigh the raw materials according to the weight ratio, take polyvinyl chloride resin and zinc stearate, add them to a high-speed mixer and mix at 90°C for 9 minutes. Then add compatibilizer, plasticizer, antioxidant, aluminum hydroxide, calcium stearate, ACR resin, modified heat stabilizer prepared in Example 2 and modified flame retardant prepared in Example 2 to the high-speed mixer in sequence, mix for 9 minutes at 90°C, unload and cool to obtain PVC composite material.

[0074] Step S2: The PVC composite material is melt-extruded and blended using a twin-screw extruder, cooled by water and then granulated. The granules are dried in a blower drying oven until the moisture content is below 3%, then taken out and put into a horizontal injection molding machine to obtain standard samples through injection molding.

[0075] Example 6: A method for preparing a flame-retardant PVC composite material, comprising the following steps:

[0076] 100 parts of polyvinyl chloride resin, 5 parts of compatibilizer, 40 parts of plasticizer, 2 parts of antioxidant, 10 parts of aluminum hydroxide, 5 parts of calcium stearate, 6 parts of zinc stearate, 6 parts of ACR resin, 5 parts of modified heat stabilizer prepared in Example 3, and 10 parts of modified flame retardant prepared in Example 3.

[0077] Step S1: Weigh the raw materials according to the weight ratio, take polyvinyl chloride resin and zinc stearate, add them to a high-speed mixer and mix at 95°C for 10 minutes. Then add compatibilizer, plasticizer, antioxidant, aluminum hydroxide, calcium stearate, ACR resin, modified heat stabilizer prepared in Example 3 and modified flame retardant prepared in Example 3 to the high-speed mixer in sequence, mix for 10 minutes at 95°C, unload and cool to obtain PVC composite material.

[0078] Step S2: The PVC composite material is melt-extruded and blended using a twin-screw extruder, cooled by water and then granulated. The granules are dried in a blower drying oven until the moisture content is below 3%, then taken out and put into a horizontal injection molding machine to obtain standard samples through injection molding.

[0079] Comparative Example 1: This comparative example is a flame-retardant PVC composite material. The difference between this example and Example 6 is that zinc borate is used instead of the modified flame retardant prepared in Example 3. All other aspects are the same.

[0080] Comparative Example 2: This comparative example is a flame-retardant PVC composite material. The difference between this example and Example 6 is that epoxidized soybean oil is used instead of the modified heat stabilizer prepared in Example 3. All other aspects are the same.

[0081] Comparative Example 3: This comparative example is a flame-retardant PVC composite material. The difference between this example and Example 6 is that zinc borate is used instead of the modified flame retardant prepared in Example 3, and epoxidized soybean oil is used instead of the modified heat stabilizer prepared in Example 3. All other aspects are the same.

[0082] The performance of the PVC composite materials prepared in Examples 4-6 and Comparative Examples 1-3 was tested:

[0083] The PVC composite material was hot-pressed into sheet samples at 160℃ and 10MPa in a flat vulcanizing machine. The mechanical properties were tested according to GB / T1040.2-2022 standard; the oxygen index was tested according to GB / T 2406.2-2009 standard; and the vertical burning test was conducted according to UL-94.

[0084] Static thermal stability was tested according to the Congo red method in GB / T 2917-2002. The time when the Congo red test paper began to turn blue (i.e., the static thermal stability time) and the color of the sample were recorded. The test was performed in three parallel trials and the average value was taken.

[0085] The test results are shown in Table 1:

[0086] Table 1: Performance Test Results

[0087]

[0088] As can be seen from Table 1, the PVC composite material prepared by this invention has excellent strength, toughness and mechanical properties. The limiting oxygen index of the PVC composite materials prepared in the examples all reached above 38%, and they have flame retardant properties. Their flame retardancy all reached V-0, which is the highest level of flame retardancy. At the same time, it can be seen from the static thermal stability test that the static thermal stability time of the materials in Examples 4-6 is not less than 120 min. It can also be seen from the color change of the materials that Comparative Examples 2 and 3, which changed color the fastest, turned brown after 60 min. Compared with Comparative Examples 1-3, the PVC composite material prepared by this invention has better flame retardant properties, mechanical properties and thermal stability.

[0089] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A flame-retardant PVC composite material, characterized in that, The raw materials include the following parts by weight: 90-100 parts of polyvinyl chloride resin, 2-5 parts of compatibilizer, 30-40 parts of plasticizer, 1-2 parts of antioxidant, 5-10 parts of aluminum hydroxide, 2-5 parts of calcium stearate, 4-6 parts of zinc stearate, 2-6 parts of ACR resin, 1-5 parts of modified heat stabilizer, and 6-10 parts of modified flame retardant. The modified flame retardant is prepared by the following steps: Step A1: Mix 4-formylphenylboronic acid, p-aminostyrene and anhydrous ethanol, stir, react at 80°C for 2 h under nitrogen protection, rotary evaporate and vacuum dry to obtain intermediate product 1. Step A2: Mix intermediate product 1, diphenyl phosphite and toluene, react at 80°C for 8 hours under nitrogen protection, filter, wash and vacuum dry to obtain intermediate product 2; Step A3: Mix 1 / 3 part of intermediate product 2 with 15wt% sodium hydroxide aqueous solution, add it to a mixed solution of cyanuric chloride and toluene, react at 0℃ for 2h, then add 2 / 3 part of intermediate product 2, reflux at 80℃ for 10h, after the reaction is completed, add water for extraction and concentration to obtain the modified flame retardant. The modified heat stabilizer is produced by the following steps: Step B1: Mix 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol and acetone, and heat to reflux at 55°C. After the reaction is completed by TLC, filter, distill under reduced pressure, purify and rotary evaporate to obtain maleimide derivative. Step B2: Mix maleimide derivative, triethylamine and methanol, add mercaptoacetic acid, stir at room temperature, determine the end of the reaction by TLC, extract, dry, filter, concentrate under reduced pressure, column chromatography, and rotary evaporation to obtain carboxylic acid maleimide derivative; Step B3: Mix the carboxylic acid maleimide derivative and ethanol, add phenylhydrazine, reflux at 80℃ for 4 hours, then react at room temperature for 2 hours, precipitate, filter, and wash to obtain phenylhydrazine maleimide derivative. The ratio of carboxylic acid maleimide derivative, ethanol and phenylhydrazine is 0.5-0.8 mol: 450 mL: 0.7-1 mol. Step B4: Mix phenylhydrazine maleimide derivative, sulfoxide and N,N-dimethylformamide, stir at 50°C for 4 h, distill under reduced pressure, dry, and redisperse in acetonitrile to form solution 1. Mix potassium thiocyanate, acetonitrile and polyethylene glycol-400, stir, and add dropwise to solution 1. Stir for 40 min, add aniline, stir for 3-4 h, extract and column chromatography to obtain the modified heat stabilizer.

2. The flame-retardant PVC composite material according to claim 1, characterized in that, In step A1, the ratio of 4-formylphenylboronic acid, p-aminostyrene, and anhydrous ethanol is 1-3 mol: 1-1.5 mol: 500-700 mL.

3. The flame-retardant PVC composite material according to claim 1, characterized in that, In step A2, the ratio of intermediate product 1, diphenyl phosphite, and toluene is 1-1.3 mol: 1-2 mol: 100-150 mL.

4. The flame-retardant PVC composite material according to claim 1, characterized in that, In step A3, the ratio of intermediate product 2, sodium hydroxide aqueous solution, cyanuric chloride and toluene is 0.6-1 mol: 150 mL: 0.2-0.3 mol: 200 mL.

5. The flame-retardant PVC composite material according to claim 1, characterized in that, The compatibilizer is chlorinated polyethylene, the plasticizer is dioctyl phthalate, and the antioxidant is antioxidant 1010.

6. The flame-retardant PVC composite material according to claim 1, characterized in that, In step B1, the ratio of 3,4-dibromo-1H-pyrrole-2,5-dione, potassium carbonate, 3-bromo-1-propanol, and acetone is 1-2 mol: 2-3.5 mol: 3-5 mol: 700-800 mL.

7. The flame-retardant PVC composite material according to claim 1, characterized in that, In step B2, the ratio of maleimide derivative, triethylamine, methanol, and thioglycolic acid is 0.5-1.5 mol: 1-3 mol: 600-700 mL: 1-3 mol.

8. The flame-retardant PVC composite material according to claim 1, characterized in that, In step B4, the ratio of phenylhydrazine maleimide derivative, sulfoxide, N,N-dimethylformamide, and acetonitrile in solution 1 is 0.2-0.4 mol; 5-6 mol: 15-20 mL: 100 mL; the ratio of potassium thiocyanate, acetonitrile, polyethylene glycol-400, aniline, and solution 1 in the modified heat stabilizer is 1-1.2 mol: 300 mL: 15-20 mL: 0.5-1 mol: 105-115 mL.

9. A method for preparing the flame-retardant PVC composite material according to any one of claims 1-8, characterized in that, The flame-retardant PVC composite material is prepared by the following steps: Step S1: Weigh the raw materials according to the weight ratio, take polyvinyl chloride resin and zinc stearate, add them to a high-speed mixer and mix at 85-95℃ for 8-10 minutes. Then add compatibilizer, plasticizer, antioxidant, aluminum hydroxide, calcium stearate, ACR resin, modified heat stabilizer and modified flame retardant to the high-speed mixer in sequence and mix for 8-10 minutes at 85-95℃. Discharge and cool to obtain PVC composite material. Step S2: The PVC composite material is melt-extruded and blended using a twin-screw extruder, cooled by water and then granulated. The granules are dried in a blower drying oven until the moisture content is below 3%, then taken out and put into a horizontal injection molding machine to obtain standard samples through injection molding.

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