Flame-retardant thermal insulation foam and preparation method thereof

Abstract

The invention discloses flame-retardant thermal insulation foam and a preparation method, belongs to the technical field of foam processing, and aims to solve the technical problems of poor high temperature resistance, flame retardance and impact resistance of foam in the prior art. The preparation method comprises the following steps: adding modified polyacrylate, a modified flame retardant, toluene, ammonium persulfate and glutaraldehyde into a reaction kettle, raising the temperature of the reaction kettle to 120-130 DEG C, carrying out heat preservation treatment for 3-5 hours, and carrying out post-treatment to obtain flame-retardant foam masterbatch; according to the invention, acrylic monomers are added into modified polyacrylate synthesized by modified polyvinyl alcohol with sulfydryl at one end of a molecular chain, and DOPO and ethylenediamine are used for modifying and synthesizing a flame retardant containing dimer phosphamide, so that the high temperature resistance, flame retardance and structural strength of the new energy battery partition flame-retardant foam are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of foam processing, and in particular to a flame-retardant thermal insulation foam and a preparation method thereof. Background Art

[0002] Foam is a porous structure material made of polymer materials. It is widely used in packaging, cushioning, sound insulation, thermal insulation and other fields. It plays an important role in new energy battery packs and is used for cushioning and shock absorption, heat insulation, flame retardant sealing, etc., to ensure the safety and stability of batteries in various extreme environments.

[0003] However, traditional thermal insulation foam has a low heat resistance temperature and is prone to thermal degradation, softening or even melting in high temperature environments. This may pose a safety hazard to the high temperature environment in new energy battery packs (such as the heat when a high-power battery pack is working). In addition, the thermal insulation foam is easily damaged when impacted and cannot provide effective buffering protection. At the same time, the thermal insulation foam itself is a flammable material and is easily ignited and combustion-supporting when exposed to open flames or high temperatures. In order to improve the flame retardancy, flame retardants are usually added to the foam, but there is a weak interface effect between these flame retardants and the material, which leads to a decrease in the impact resistance of the thermal insulation foam. Therefore, the high temperature resistance, flame retardancy and impact resistance of the foam still face certain technical challenges, which are directly related to the safety of the battery. Summary of the invention

[0004] The object of the present invention is to provide a flame retardant thermal insulation foam and a preparation method thereof, so as to solve the technical problems of poor high temperature resistance, flame retardancy and impact resistance of the foam in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solution: A method for preparing a flame retardant thermal insulation foam, comprising the following steps: S1. Add modified polyacrylate, modified flame retardant, toluene, ammonium persulfate and glutaraldehyde into a reactor, raise the temperature of the reactor to 120-130° C., and perform heat preservation for 3-5 hours, and perform post-treatment to obtain a flame retardant foam masterbatch; S2, adding flame retardant foam masterbatch, azodicarbonamide and xylene into a reactor and stirring, raising the temperature of the reactor to 120-130°C, keeping the temperature for 3-4 hours, and post-treating to obtain a flame retardant foaming liquid; S3, adding flame retardant foaming liquid and modified polypropylene into a reaction kettle and stirring, raising the temperature of the reaction kettle to 120-130°C, and foaming and finishing to obtain flame retardant thermal insulation foam.

[0006] Further, in step S1, the modified polyacrylate, the modified flame retardant, toluene, and glutaraldehyde are used in a ratio of 20-25g:15-20g:150-200mL:5-10mL, and the post-treatment includes: transferring the mixed solution after the reaction to a nitrogen-protected tubular furnace at a temperature of 70-80°C, removing the organic solvent by reduced pressure distillation, washing with anhydrous ethanol, placing it in a drying oven at a temperature of 80°C, and drying to constant weight to obtain a flame retardant foam masterbatch; in step S2, the flame retardant foam masterbatch, azodicarbonamide, and acetone are used in a ratio of 20-3 0g:1-2g:150-160mL, post-treatment includes: lowering the temperature of the reactor to room temperature, adding acetone solution to dilute, filtering with a 100-mesh filter, moving the filtered solution to a vacuum environment for degassing, and standing for 24 hours to obtain a flame retardant foaming liquid; in step S3, the amount ratio of the flame retardant foaming liquid and the modified polypropylene is 100-120mL:80-90g, and the foaming finishing operation includes: heating the mixture to 190-210°C, and foaming by melt extrusion at an extrusion pressure of 0.2-0.3MPa to obtain a flame retardant thermal insulation foam.

[0007] Furthermore, in step S1, the modified polyacrylate preparation method is: butyl acrylate, methyl methacrylate, modified polyvinyl alcohol, potassium persulfate, and xylene are added to a reactor and stirred; under nitrogen protection, the temperature of the reactor is increased to 70-90° C., the reaction is kept warm for 4-5 hours, and the modified polyacrylate is obtained by post-treatment.

[0008] Furthermore, the amount ratio of butyl acrylate, methyl methacrylate, potassium persulfate and xylene is 2-3g:20-30mL:1-2mL:100-200mL, the mass fraction of potassium persulfate aqueous solution is 0.1wt%, and the post-treatment includes: raising the temperature of the reactor to 70-80°C, removing unreacted products and low-boiling substances by reduced pressure distillation, washing with anhydrous ethanol, filtering, placing the filter cake in a vacuum drying oven at 80°C, and drying to constant weight to obtain modified polyacrylate.

[0009] Furthermore, the modified polyvinyl alcohol is obtained by processing the following steps: A1. Add vinyl acetate, azobisisobutyronitrile and thioacetic acid into a reaction kettle and stir. Under nitrogen protection, raise the temperature of the reaction kettle to 40-60°C, keep the temperature for 1 hour, and perform post-treatment to obtain an intermediate. The reaction equation for preparing the intermediate is:

[0010] The reaction principle of the intermediate is: During the reaction, the N=N double bond of the initiator azobisisobutyronitrile breaks under heating conditions to form two carbon free radicals and release nitrogen. The newly formed free radicals continue to attack another vinyl acetate monomer, and the above process is repeated to form a growing polymer chain. The carbon free radical at the end of the chain combines with the hydrogen atom of thioacetic acid to form a carbon-hydrogen single bond, and the chain growth is terminated. The SH bond of thioacetic acid breaks to form a thioacetyl free radical intermediate.

[0011] A2. Add the intermediate and methanol solution into a reactor. Under nitrogen protection, raise the temperature of the reactor to 40-60°C and keep the temperature for 48 hours. Post-process and obtain modified polyvinyl alcohol.

[0012] The reaction equation for preparing modified polyvinyl alcohol is:

[0013] The reaction principle of modified polyvinyl alcohol is: During the reaction, the acetate group and the terminal thioacetate group in polyvinyl acetate are hydrolyzed into hydroxyl and thiol groups under the conditions of methanol hydrolysis, and acetic acid and thioacetic acid are released respectively. Thioacetic acid is further decomposed into hydrogen sulfide and acetic acid. There is an excess of methanol in the system, so acetic acid and thioacetic acid are esterified into methyl acetate and methyl thioacetate to generate modified polyvinyl alcohol with thiol groups at the ends of the polyvinyl alcohol chains.

[0014] Further, in step A1, the amount ratio of vinyl acetate, azobisisobutyronitrile and thioacetic acid is 160-180mL: 0.15-0.2g: 0.5-1g, and the post-treatment includes: after the reaction is completed, transferring it to an environment with a temperature of 0°C to terminate the reaction, raising the temperature of the reactor to 70-80°C, removing the organic solvent by vacuum distillation, washing with anhydrous ethanol, filtering, placing the filter cake in a vacuum drying oven at 80°C, and drying to constant weight to obtain an intermediate; in step A2, the The dosage ratio of the intermediate and the methanol solution is 50-60g:500-600mL, the methanol solution is composed of sodium hydroxide and methanol in a dosage ratio of 25g:500mL, and the post-treatment includes: after the reaction is completed, lowering the temperature of the reactor to room temperature, adding ethylene acid solution, adjusting the pH of the system to 7, raising the temperature of the reactor to 70-80°C, removing methanol by reduced pressure distillation, washing with anhydrous ethanol, filtering, placing the filter cake in a vacuum drying oven at 80°C, and drying to constant weight to obtain modified polyvinyl alcohol.

[0015] Furthermore, in step S1, the preparation method of the modified flame retardant is: adding DOPO, ethylenediamine, triethylamine, and dichloromethane into a reactor and stirring, the amount ratio of DOPO, ethylenediamine, triethylamine, dichloromethane, and carbon tetrachloride is 60-65g:8-9g:30-35g:300-400ml:48-50g, under nitrogen protection, waiting for DOPO to be completely dissolved, placing it in an ice-salt bath environment to cool for 1h, adding carbon tetrachloride dropwise, the reaction temperature is 10-15°C, and the reaction is 10-12h. The post-treatment includes: after the reaction is completed, pouring the reacted mixed solution into an ethanol solution for precipitation, filtering, washing the filter cake with an ethanol solution for 5 times to dry it, placing the filter cake in a 50°C vacuum drying oven, and drying it to constant weight to obtain a modified flame retardant.

[0016] The reaction equation for preparing the modified flame retardant is:

[0017] Where: The reaction principle of modified flame retardant is: During the reaction, the oxygen atom on the phosphorus-oxygen double bond in DOPO is attacked by carbon tetrachloride to form a transition state. Under the catalysis of triethylamine, a chloride ion is replaced to form a chlorinated derivative of DOPO, and chloroform is released at the same time. The nitrogen atom on the amino group of ethylenediamine has a lone pair of electrons and attacks the phosphorus atom on DOPO-Cl as a nucleophile to form a tetrahedral intermediate, releasing a chloride ion to form DOPO-amine. The nitrogen atom on the unreacted amino group on the DOPO-amine molecule has a lone pair of electrons and attacks the phosphorus atom on another DOPO-Cl as a nucleophile again, resulting in an aminolysis reaction similar to the previous step to generate a modified flame retardant.

[0018] The mass spectrometry analysis data of the modified flame retardant are: 500.11 (100.0%), 501.12 (30.7%), 502.12 (5.2%).

[0019] Further, the modified polypropylene is processed by the following steps: B1, ethanol, methyltriethoxysilane, ammonia water and deionized water were added into a reaction kettle and stirred for 2 hours, and then post-treated to obtain nano-silicon dioxide; B2. Add nano-silicon dioxide and xylene into an ultrasonic disperser, ultrasonically disperse for 30 minutes, add methyltriethoxysilane, place in an oil bath at 80°C, stir for 4-5 hours, add polypropylene and cyclohexanone, increase the oil bath temperature to 120-130°C, keep warm for reaction for 1-2 hours, and post-treat to obtain modified polypropylene.

[0020] Furthermore, in step B1, the amount ratio of ethanol, methyltriethoxysilane, ammonia water and deionized water is 60ml:4ml:5ml:25ml, and the post-treatment includes: centrifugal drying to obtain nano-silicon dioxide particles with a diameter of 240nm; in step B2, the amount ratio of nano-silicon dioxide, xylene, methyltriethoxysilane, polypropylene and cyclohexanone is 3-5g:100-120mL:10-15mL:40-50g:20-30mL, and the post-treatment includes: lowering the temperature of the reactor to room temperature, pouring the mixed solution after the reaction into ethanol for precipitation, filtering, washing with ethanol, filtering, placing the filter cake in a vacuum drying oven at 80°C, and drying to constant weight to obtain modified polypropylene.

[0021] The invention also provides a flame retardant thermal insulation foam, which is prepared by a method for preparing the flame retardant thermal insulation foam.

[0022] The present invention has the following beneficial effects: 1. Thiol is active and can react with other active sites in the polymer to form a cross-linked structure, thereby improving the adhesion between the adhesive and the battery pack material. At the same time, thiol participates in free radical polymerization to form a three-dimensional network structure, which can enhance the strength and chemical corrosion resistance of the material. Thiol forms disulfide bonds through oxidation reactions to increase the cross-linking density of the polymer. The polarity of thiol can change the surface properties of the polymer and enhance its compatibility with other materials in the battery pack. Butyl acrylate provides flexibility and can absorb the volume expansion and thermal expansion generated by the battery pack during charging and discharging. Methyl methacrylate improves the high temperature resistance of the material and ensures stable performance within the operating temperature range of the battery. The copolymerization of the two can adjust the performance of the polymer to make it both flexible and strong. Therefore, the modified polyacrylate synthesized by introducing modified polyvinyl alcohol with a mercapto group at one end of the molecular chain into acrylate is used as the key matrix of the foam masterbatch, which significantly improves the structural strength and impact resistance of the synthesized foam.

[0023] 2. In the flame retardant containing dimer phosphoramide of the present invention, the phosphorus-hydroxy bond and the phosphorus-N bond can form a protective phosphate layer at high temperature, and the phosphorus-hydroxy bond can be dehydrated to form a phosphate, forming a protective layer barrier to enhance its flame retardant effect. The phosphorus-N bond can also form a stable phosphate layer at high temperature to enhance the thermal stability of its foam, and the ethylenediamine bridging structure enhances the mechanical strength and high temperature resistance of the foam through the bonding between the amino group and the hydroxyl group. In the DOPO and phosphoramide structure, the presence of carbon-carbon bonds provides structural stability and strength. Therefore, by using DOPO phosphoramide and polyacrylate as foam masterbatch, not only the high temperature resistance, combustion flame retardant performance and thermal stability of the new energy battery pack foam can be significantly improved, but also its mechanical properties and environmental protection performance can be improved.

[0024] 3. By using silane coupling agent to modify polypropylene as the foam skeleton, its mechanical properties are maintained while the formed siloxane network structure further enhances the interfacial bonding with fillers such as flame retardants. On this basis, the flame retardant containing dimer phosphoramide exerts a dual flame retardant mechanism, synergistically acting with the hydrophilicity of modified polyvinyl alcohol and the compatibility of the coupling agent, significantly improving the flame retardant properties of the foam. In addition, the hydrophilicity and uniform pore structure of modified polyvinyl alcohol jointly improve the thermal insulation properties of the foam. Finally, the polypropylene modified by silane coupling agent enhances the interfacial bonding and the cross-linking network formed between the modified flame retardant, modified polyvinyl alcohol, and polyacrylate, which together give the foam excellent flame retardant properties, high temperature resistance, and impact resistance. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1 This embodiment provides a method for preparing a flame retardant thermal insulation foam, comprising the following steps: S1. Preparation of modified polyacrylate Weigh: 200 g of butyl acrylate, 2000 mL of methyl methacrylate, 100 mL of 0.1 wt% potassium persulfate aqueous solution, and 10000 mL of xylene, add into a reactor and stir. Under nitrogen protection, the temperature of the reactor is raised to 70°C, and the reaction is kept warm for 4.5 hours. The temperature of the reactor is raised to 75°C, and unreacted products and low-boiling substances are removed by vacuum distillation. The product is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain modified polyacrylate.

[0027] S2. Preparation of modified polyvinyl alcohol Weigh: 16000mL of vinyl acetate, 15g of azobisisobutyronitrile, and 50g of thioacetic acid, add them into a reactor and stir. Under nitrogen protection, the temperature of the reactor is raised to 50°C, and the reaction is kept warm for 1h. After the reaction is completed, it is transferred to an environment with a temperature of 0°C to terminate the reaction. The temperature of the reactor is raised to 75°C, and the organic solvent is removed by vacuum distillation. The mixture is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain an intermediate. Mix sodium hydroxide and methanol in a ratio of 25 g:500 mL to obtain a methanol solution for later use; Ethylene acid and deionized water were mixed evenly at a ratio of 2 g:100 mL to obtain an ethylene acid solution for later use; Weigh: 500 g of the intermediate and 50,000 mL of methanol solution are added to a reactor. Under nitrogen protection, the temperature of the reactor is raised to 50°C and the reaction is kept warm for 48 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, ethylene acid solution is added, and the pH of the system is adjusted to 7. The temperature of the reactor is raised to 75°C, and methanol is removed by vacuum distillation. The product is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain modified polyvinyl alcohol.

[0028] S3. Preparation of modified flame retardant Weigh: 600g of DOPO, 80g of ethylenediamine, 300g of triethylamine, and 3000mL of dichloromethane, add into the reactor and stir. Under nitrogen protection, wait until DOPO is completely dissolved, place in an ice-salt bath environment to cool for 1h, add 480g of carbon tetrachloride dropwise, the reaction temperature is 10°C, and the reaction is carried out for 11h. After the reaction is completed, pour the mixed solution after the reaction into an ethanol solution for precipitation, filter, wash the filter cake with ethanol solution 5 times and then dry it, place the filter cake in a 50°C vacuum drying oven, and dry it to constant weight to obtain a modified flame retardant.

[0029] S4. Preparation of flame retardant foaming liquid Weigh: 200g of modified polyacrylate, 150g of modified flame retardant, 1500mL of toluene, and 50mL of glutaraldehyde, add them into a reactor, raise the temperature of the reactor to 125°C, and keep it warm for 4h. Transfer the mixed solution after the reaction to a nitrogen-protected tubular furnace at 75°C, distill under reduced pressure to remove the organic solvent, wash with anhydrous ethanol, place in a drying oven at 80°C, and dry to constant weight to obtain a flame-retardant foam masterbatch; Weigh: 200g of flame-retardant foam masterbatch, 10g of azodicarbonamide, and 1500mL of acetone, add into the reactor and stir, raise the temperature of the reactor to 125°C, and keep warm for 3.5h, lower the temperature of the reactor to room temperature, add acetone solution to dilute, filter with a 100-mesh filter, move the filtered solution to a vacuum environment for degassing, and let it stand for 24h to obtain a flame-retardant foaming liquid.

[0030] S5. Preparation of flame-retardant thermal insulation foam Weigh: 600 mL of ethanol, 40 mL of methyltriethoxysilane, 50 mL of ammonia water, and 250 mL of deionized water, add them into a reaction kettle, stir for 2 h, and centrifuge to dry to obtain nano-silicon dioxide particles with a diameter of 240 nm; Weigh: 300 g of nano-silica, 10000 mL of xylene, add 1000 mL of methyltriethoxysilane, place in an oil bath pot at 80°C, stir for 4.5 h, add 4000 g of polypropylene and 2000 mL of cyclohexanone, raise the oil bath temperature to 125°C, keep warm for 1.2 h, lower the temperature of the reactor to room temperature, pour the mixed solution after the reaction into ethanol for precipitation, filter, wash with ethanol, filter, place the filter cake in a vacuum drying oven at 80°C, and dry to constant weight to obtain modified polypropylene; Weigh: 1000 mL of flame-retardant foaming liquid and 800 g of modified polypropylene are added into a reactor and stirred. The temperature of the reactor is raised to 120° C. The foaming finishing operation includes: heating the mixture to 190° C., and foaming by melt extrusion at an extrusion pressure of 0.2 MPa to obtain a flame-retardant thermal insulation foam.

[0031] Example 2 This embodiment provides a method for preparing a flame retardant thermal insulation foam, comprising the following steps: S1. Preparation of flame retardant foam masterbatch Weigh: 250g of butyl acrylate, 2500mL of methyl methacrylate, 150mL of 0.1wt% potassium persulfate aqueous solution, and 15000mL of xylene, add into the reactor and stir. Under nitrogen protection, the temperature of the reactor is raised to 80°C, and the reaction is kept warm for 4.5h. The mass fraction of the potassium persulfate aqueous solution is 0.1wt%. The temperature of the reactor is raised to 75°C, and unreacted products and low-boiling substances are removed by vacuum distillation. The product is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain modified polyacrylate.

[0032] S2. Preparation of modified polyvinyl alcohol Weigh: 17000mL of vinyl acetate, 17g of azobisisobutyronitrile, and 70g of thioacetic acid, add them into a reactor and stir. Under nitrogen protection, the temperature of the reactor is raised to 50°C, and the reaction is kept warm for 1h. After the reaction is completed, it is transferred to an environment with a temperature of 0°C to terminate the reaction. The temperature of the reactor is raised to 75°C, and the organic solvent is removed by vacuum distillation. The mixture is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain an intermediate. Mix sodium hydroxide and methanol in a ratio of 25 g:500 mL to obtain a methanol solution for later use; Ethylene acid and deionized water were mixed evenly at a ratio of 2 g:100 mL to obtain an ethylene acid solution for later use; Weigh: 550 g of the intermediate and 55000 mL of methanol solution are added to the reactor. Under nitrogen protection, the temperature of the reactor is raised to 50°C and the reaction is kept warm for 48 hours. After the reaction is completed, the temperature of the reactor is lowered to room temperature, ethylene acid solution is added, and the pH of the system is adjusted to 7. The temperature of the reactor is raised to 75°C, and methanol is removed by vacuum distillation. The product is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain modified polyvinyl alcohol.

[0033] S3. Preparation of modified flame retardant Weigh: add 620g of DOPO, 85g of ethylenediamine, 320g of triethylamine, and 3500mL of dichloromethane into a reactor and stir. Under nitrogen protection, wait until DOPO is completely dissolved, place it in an ice-salt bath environment to cool for 1h, add 490g of carbon tetrachloride dropwise, the reaction temperature is 12°C, and the reaction is carried out for 11h. After the reaction is completed, pour the mixed solution after the reaction into an ethanol solution for precipitation, filter, wash the filter cake with ethanol solution 5 times, then drain it, place the filter cake in a 50°C vacuum drying oven, and dry it to constant weight to obtain a modified flame retardant.

[0034] S4. Preparation of flame retardant foaming liquid Weigh: 250g of modified polyacrylate, 180g of modified flame retardant, 1800mL of toluene, and 70mL of glutaraldehyde, add them into a reactor, raise the temperature of the reactor to 125°C, and keep it warm for 4h. Transfer the mixed solution after the reaction to a nitrogen-protected tubular furnace at 75°C, remove the organic solvent by reduced pressure distillation, wash with anhydrous ethanol, place in a drying oven at 80°C, and dry to constant weight to obtain a flame retardant foam masterbatch; Weigh: 250g of flame-retardant foam masterbatch, 15g of azodicarbonamide, and 1500mL of acetone, add into the reactor and stir, raise the temperature of the reactor to 125°C, and keep warm for 3.4h, lower the temperature of the reactor to room temperature, add acetone solution to dilute, filter with a 100-mesh filter, move the filtered solution to a vacuum environment for degassing, and let it stand for 24h to obtain a flame-retardant foaming liquid.

[0035] S5. Preparation of flame-retardant thermal insulation foam Weigh: 650 mL of ethanol, 45 mL of methyltriethoxysilane, 60 mL of ammonia water, and 280 mL of deionized water, add them into a reaction kettle and stir for 2 h, and centrifuge and dry to obtain nano-silicon dioxide particles with a diameter of 240 nm; Weigh: 400 g of nano-silicon dioxide, 11000 mL of xylene, add 1200 mL of methyltriethoxysilane, place in an oil bath pot at 80°C, stir for 4.5 h, add 4500 g of polypropylene and 2500 mL of cyclohexanone, raise the oil bath temperature to 125°C, keep warm for 1.5 h, lower the temperature of the reactor to room temperature, pour the mixed solution after the reaction into ethanol for precipitation, filter, wash with ethanol, filter, place the filter cake in a vacuum drying oven at 80°C, and dry to constant weight to obtain modified polypropylene; Weigh: 1100 mL of flame-retardant foaming liquid and 850 g of modified polypropylene are added into a reactor and stirred. The temperature of the reactor is raised to 125° C. The foaming finishing operation includes: heating the mixture to 200° C., and foaming by melt extrusion at an extrusion pressure of 0.3 MPa to obtain a flame-retardant thermal insulation foam.

[0036] Example 3 This embodiment provides a method for preparing a flame retardant thermal insulation foam, comprising the following steps: S1. Preparation of modified polyacrylate Weigh: 300 g of butyl acrylate, 3000 mL of methyl methacrylate, 200 mL of 0.1 wt% potassium persulfate aqueous solution, and 20000 mL of xylene, add into a reactor and stir. Under nitrogen protection, the temperature of the reactor is raised to 90°C, and the reaction is kept warm for 5 hours. The mass fraction of the potassium persulfate aqueous solution is 0.1 wt%. The temperature of the reactor is raised to 80°C, and unreacted products and low-boiling substances are removed by vacuum distillation. The mixture is washed with anhydrous ethanol and filtered. The filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain modified polyacrylate.

[0037] S2. Preparation of modified polyvinyl alcohol Weigh: 18000mL of vinyl acetate, 20g of azobisisobutyronitrile, and 100g of thioacetic acid, add them into a reactor and stir. Under nitrogen protection, the temperature of the reactor is raised to 60°C, and the reaction is kept warm for 1h. After the reaction is completed, it is transferred to an environment with a temperature of 0°C to terminate the reaction. The temperature of the reactor is raised to 80°C, and the organic solvent is removed by vacuum distillation. The mixture is washed with anhydrous ethanol, filtered, and the filter cake is placed in a vacuum drying oven at 80°C and dried to constant weight to obtain an intermediate; Mix sodium hydroxide and methanol in a ratio of 25 g:500 mL to obtain a methanol solution for later use; Ethylene acid and deionized water were mixed evenly at a ratio of 2 g:100 mL to obtain an ethylene acid solution for later use; Weigh: 600g of the intermediate and 60000mL of methanol solution, where the methanol solution is composed of a mixture of sodium hydroxide and methanol in a dosage ratio of 25g:500mL, add them into a reactor, and under nitrogen protection, raise the temperature of the reactor to 60°C and keep the reaction warm for 48h. After the reaction is completed, lower the temperature of the reactor to room temperature, add ethylene acid solution, adjust the system pH to 7, raise the temperature of the reactor to 80°C, remove methanol by reduced pressure distillation, wash with anhydrous ethanol, filter, place the filter cake in a vacuum drying oven at 80°C, and dry to constant weight to obtain modified polyvinyl alcohol.

[0038] S3. Preparation of modified flame retardant Weigh: add 650g of DOPO, 90g of ethylenediamine, 350g of triethylamine, and 4000mL of dichloromethane into a reactor and stir. Under nitrogen protection, wait until DOPO is completely dissolved, place it in an ice-salt bath environment to cool for 1h, add 500g of carbon tetrachloride dropwise, the reaction temperature is 15°C, and the reaction is carried out for 12h. After the reaction is completed, pour the mixed solution after the reaction into an ethanol solution for precipitation, filter, wash the filter cake with ethanol solution 5 times, then drain it, place the filter cake in a 50°C vacuum drying oven, and dry it to constant weight to obtain a modified flame retardant.

[0039] S4. Preparation of flame retardant foaming liquid Weigh: 250g of modified polyacrylate, 200g of modified flame retardant, 2000mL of toluene, and 100mL of glutaraldehyde, add them into a reactor, raise the temperature of the reactor to 130°C, and keep it warm for 5h. Transfer the mixed solution after the reaction to a nitrogen-protected tubular furnace at 80°C, distill under reduced pressure to remove the organic solvent, wash with anhydrous ethanol, place in a drying oven at 80°C, and dry to constant weight to obtain a flame retardant foam masterbatch; Weigh: 300g of flame-retardant foam masterbatch, 20g of azodicarbonamide, and 1600mL of acetone, add into the reactor and stir, raise the temperature of the reactor to 130°C, keep warm for 4h, lower the temperature of the reactor to room temperature, add acetone solution to dilute, filter with a 100-mesh filter, move the filtered solution to a vacuum environment for degassing, and let it stand for 24h to obtain a flame-retardant foaming liquid.

[0040] S5. Preparation of flame-retardant thermal insulation foam Weigh: 700 mL of ethanol, 50 mL of methyltriethoxysilane, 70 mL of ammonia water, and 300 mL of deionized water, add them into a reaction kettle and stir for 2 h, and centrifuge and dry to obtain nano-silicon dioxide particles with a diameter of 240 nm; Weigh: 500 g of nano-silica, 12000 mL of xylene, add 1500 mL of methyltriethoxysilane, place in an oil bath pot at 80°C, stir for 5 hours, add 5000 g of polypropylene and 3000 mL of cyclohexanone, raise the oil bath temperature to 130°C, keep warm for 2 hours, lower the temperature of the reactor to room temperature, pour the mixed solution after the reaction into ethanol for precipitation, filter, wash with ethanol, filter, place the filter cake in a vacuum drying oven at 80°C, and dry to constant weight to obtain modified polypropylene; Weigh: 1200 mL of flame-retardant foaming liquid and 900 g of modified polypropylene are added into a reactor and stirred. The temperature of the reactor is raised to 130° C. The foaming finishing operation includes: heating the mixture to 210° C., and foaming by melt extrusion at an extrusion pressure of 0.3 MPa to obtain a flame-retardant thermal insulation foam.

[0041] Comparative Example 1 The difference between this comparative example and Example 3 is that in step S1, no modified flame retardant is added.

[0042] Comparative Example 2 The difference between this comparative example and Example 3 is that in step S1, modified polyvinyl alcohol is not added.

[0043] Comparative Example 3 The difference between this comparative example and Example 3 is that in step S3, no silane coupling agent is added.

[0044] Performance Test: The flame retardant thermal insulation foams prepared in Examples 1-3 and Comparative Examples 1-3 were tested for their performance, wherein the impact strength of the samples was measured according to standard GB / T 2408 "Determination of impact strength of hard rubber", and the thermal conductivity of the samples was measured according to standard HG / T 3845-2006 "China's test method for combustion performance of plastic materials".

[0045] According to the international standard ISO4589-2017 "Plastics - Determination of flammability by oxygen index method", the oxygen index of the sample is measured to prove its flame retardant performance. The specific test results are shown in Table 1: Table 1-Performance test data of samples

[0046] Data Analysis: It can be seen from the relevant data in Table 1 that, compared with the comparative example, the flame-retardant thermal insulation foam provided by the present invention, by adding acrylate monomers to modified polyvinyl alcohol having a thiol group at one end of the molecular chain to synthesize a modified polyacrylate and modifying DOPO and ethylenediamine to synthesize a flame retardant containing dimer phosphoramide, can further improve the thermal insulation performance, flame retardant performance and structural strength of the foam to improve the performance of the flame-retardant foam for new energy battery partitions, thereby enhancing the safety performance of the battery pack and extending its service life.

[0047] Compared with Examples 1-3, the oxygen index and high temperature resistance of Comparative Example 1 are reduced, indicating that the phosphorus-hydroxy bond can be dehydrated to form a phosphate, which can form a protective layer to enhance its flame retardant effect. The phosphorus-N bond forms a stable phosphate layer at high temperature, which enhances the thermal stability of the foam and improves the flame retardancy of the foam.

[0048] Compared with Examples 1-3, the impact strength of Comparative Example 2 is reduced, indicating that thiol participates in free radical polymerization to form a three-dimensional network structure, which can enhance the strength and chemical corrosion resistance of the material. Thiol forms disulfide bonds through oxidation reaction, increasing the crosslinking density of the polymer, thereby improving the mechanical properties of the foam.

[0049] Compared with Examples 1-3, the oxygen index and impact strength performance of Comparative Example 3 are significantly reduced, indicating that by using silane coupling agent to modify polypropylene as the foam skeleton, its mechanical properties are maintained while the formed siloxane network structure further enhances the interfacial bonding force with fillers such as flame retardants. On this basis, the flame retardant containing dimer phosphoramide exerts a dual flame retardant mechanism, synergistically with the hydrophilicity of modified polyvinyl alcohol and the compatibility of the coupling agent, significantly improving the flame retardant properties of the foam, thereby improving the mechanical properties and flame retardant properties of the foam.

[0050] The flame-retardant thermal insulation foam of the present invention has excellent flame-retardant properties, can effectively prevent the spread of flames, and reduce the risk of thermal runaway of the battery. At the same time, the foam has good thermal insulation properties, can maintain the internal temperature of the battery pack stable, and extend the battery life. In addition, the flame-retardant thermal insulation foam is particularly suitable for partition flame-retardant applications of new energy battery packs, and can be used as an important safety component inside the battery pack to improve the overall safety performance of the battery pack.

[0051] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a flame retardant thermal insulation foam, characterized in that: The following steps are involved: S1. Add modified polyacrylate, modified flame retardant, toluene, ammonium persulfate and glutaraldehyde into a reactor, raise the temperature of the reactor to 120-130° C., and perform heat preservation for 3-5 hours, and perform post-treatment to obtain a flame retardant foam masterbatch; S2, adding flame retardant foam masterbatch, azodicarbonamide and xylene into a reactor and stirring, raising the temperature of the reactor to 120-130°C, keeping the temperature for 3-4 hours, and post-treating to obtain a flame retardant foaming liquid; S3, adding flame retardant foaming liquid and modified polypropylene into a reaction kettle and stirring, raising the temperature of the reaction kettle to 120-130°C, and foaming and finishing to obtain flame retardant thermal insulation foam.

2. The method for preparing a flame retardant thermal insulation foam according to claim 1, characterized in that: In step S1, the amount ratio of the modified polyacrylate, the modified flame retardant, toluene, and glutaraldehyde is 20-25g:15-20g:150-200mL:5-10mL; in step S2, the amount ratio of the flame retardant foam masterbatch, azodicarbonamide, and acetone is 20-30g:1-2g:150-160mL; in step S3, the amount ratio of the flame retardant foaming liquid and the modified polypropylene is 100-120mL:80-90g, and the foaming finishing operation includes: heating the mixture to 190-210°C, and foaming by melt extrusion at an extrusion pressure of 0.2-0.3MPa to obtain a flame retardant thermal insulation foam.

3. The method for preparing a flame retardant thermal insulation foam according to claim 1, characterized in that: In step S1, the modified polyacrylate preparation method is: butyl acrylate, methyl methacrylate, modified polyvinyl alcohol, potassium persulfate, and xylene are added to a reactor and stirred. Under nitrogen protection, the temperature of the reactor is increased to 70-90° C., and the reaction is kept warm for 4-5 hours, and the modified polyacrylate is obtained by post-treatment.

4. The method for preparing a flame retardant thermal insulation foam according to claim 3, characterized in that: The dosage ratio of butyl acrylate, methyl methacrylate, potassium persulfate aqueous solution and xylene is 2-3 g: 20-30 mL: 1-2 mL: 100-200 mL, and the mass fraction of potassium persulfate aqueous solution is 0.1 wt %.

5. The method for preparing a flame retardant thermal insulation foam according to claim 3, characterized in that: The modified polyvinyl alcohol is obtained by processing the following steps: A1. Add vinyl acetate, azobisisobutyronitrile and thioacetic acid into a reaction kettle and stir. Under nitrogen protection, raise the temperature of the reaction kettle to 40-60°C, keep the temperature for 1 hour, and perform post-treatment to obtain an intermediate. A2. Add the intermediate and methanol solution into a reactor. Under nitrogen protection, raise the temperature of the reactor to 40-60°C and keep the temperature for 48 hours. Post-process and obtain modified polyvinyl alcohol.

6. The method for preparing a flame retardant thermal insulation foam according to claim 5, characterized in that: In step A1, the amount ratio of vinyl acetate, azobisisobutyronitrile and thioacetic acid is 160-180mL:0.15-0.2g:0.5-1g; in step A2, the amount ratio of the intermediate and the methanol solution is 50-60g:500-600mL, and the methanol solution is composed of sodium hydroxide:methanol mixed in a ratio of 25g:500mL.

7. The method for preparing a flame-retardant thermal insulation foam according to claim 1, characterized in that: In step S1, the preparation method of the modified flame retardant is: DOPO, ethylenediamine, triethylamine, and dichloromethane are added into a reaction kettle and stirred, and the dosage ratio of DOPO, ethylenediamine, triethylamine, dichloromethane, and carbon tetrachloride is 60-65g:8-9g:30-35g:300-400ml:48-50g. Under nitrogen protection, DOPO is completely dissolved, placed in an ice-salt bath environment and cooled for 1h, carbon tetrachloride is added dropwise, the reaction temperature is 10-15°C, the reaction is carried out for 10-12h, and the modified flame retardant is obtained by post-treatment.

8. The method for preparing a flame retardant thermal insulation foam according to claim 1, characterized in that: In step S2, the flame retardant foam masterbatch, azodicarbonamide, and acetone are used in an amount ratio of 20-30 g: 1-2 g: 150-160 mL, and the post-treatment includes: lowering the temperature of the reactor to room temperature, adding acetone solution to dilute, filtering with a 100-mesh filter, moving the filtered solution to a vacuum environment for degassing, and standing for 24 hours to obtain a flame retardant foaming liquid; in step S3, the modified polypropylene is processed by the following steps: B1, ethanol, methyltriethoxysilane, ammonia water and deionized water were added into a reaction kettle and stirred for 2 hours, and then post-treated to obtain nano-silicon dioxide; B2. Add nano-silicon dioxide and xylene into an ultrasonic disperser, ultrasonically disperse for 30 minutes, add methyltriethoxysilane, place in an oil bath at 80°C, stir for 4-5 hours, add polypropylene and cyclohexanone, increase the oil bath temperature to 120-130°C, keep warm for reaction for 1-2 hours, and post-treat to obtain modified polypropylene.

9. The method for preparing a flame retardant thermal insulation foam according to claim 8, characterized in that: In step B1, the ratio of ethanol, methyltriethoxysilane, ammonia water and deionized water is 60-70ml:4-5ml:5-7ml:25-30ml; in step B2, the ratio of nano-silica, xylene, methyltriethoxysilane, polypropylene and cyclohexanone is 3-5g:100-120mL:10-15mL:40-50g:20-30mL.

10. A flame retardant thermal insulation foam, characterized in that: The flame retardant thermal insulation foam is prepared by the method for preparing a flame retardant thermal insulation foam as described in any one of claims 1 to 9.

Images