Homogeneous thermal insulation material and method for its production

Abstract

The application discloses a kind of homogeneous heat-insulating materials and preparation method thereof, belong to heat-insulating material technical field.The material of preparation includes: (1) the mixture of graphene oxide aqueous solution and metal salt, add sodium hydroxide or potassium hydroxide solution to obtain graphene oxide composite inorganic flame retardant solution;(2) to graphene oxide composite inorganic flame retardant solution join surface modifier, obtain the modified graphene oxide composite inorganic flame retardant of powdery;(3) 50-60 parts polyether polyol, 40-50 parts polyester polyol, 3-5 parts uniform foaming agent, 2-3 parts catalyst, 15-18 parts foaming agent, 80-100 parts modified expandable graphite, 160-220 parts modified graphene oxide composite inorganic flame retardant, 15-20 parts organic phosphorus flame retardant and 0.9-1.5 parts water are mixed to obtain mixed liquid;(4) 100-110 parts diisocyanate is added to mixed liquid, after stirring, pour into mould to carry out foaming and curing, i.e.get.The method process is simple, production cost is low and flame-retardant performance, heat-insulating performance, mechanical property and thermal stability are all higher.

Description

[0001] This application claims priority to Chinese Patent Application No. 202410570458.4, filed on May 9, 2024, entitled "A Homogeneous Thermal Insulation Material and a Method for Preparing the Same", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to a homogeneous thermal insulation material and its preparation method, belonging to the field of thermal insulation material technology. Background Technology

[0003] Flame retardants are typically added to the polyurethane matrix to improve the flame retardancy of polyurethane insulation materials. Common flame retardants include halogen compounds, metal hydroxides, expandable graphite, and phosphorus compounds. Graphene oxide, due to its unique chemical stability and certain flame retardant properties, is also increasingly being used by researchers to synergistically enhance the flame retardancy of polyurethane materials. Currently, graphene is mainly combined with other flame retardants through physical mixing or chemical bonding to improve the flame retardant performance and compatibility of the flame retardants.

[0004] For example, patent CN112679938B provides a homogeneous polyurethane foam, which mainly obtains a material with good flame retardant properties by modifying inorganic materials and improving product processes. However, there are still obvious problems: First, the filling ratio of inorganic materials is too high. During the production process, it is difficult to achieve uniform mixing with polyurethane foam due to the high proportion of inorganic fillers, making it difficult to guarantee the homogeneity of the material. At the same time, the mechanical properties are usually greatly affected. Second, the technical solution does not mention the impact on the thermal insulation performance of rigid polyurethane foam matrix. While filling inorganic powder to improve flame retardant properties, it is difficult to take into account the thermal insulation properties. Therefore, the product of this technology does not meet the market demand for energy conservation and environmental protection.

[0005] For example, patent CN106496518A provides a graphene-modified polyurethane insulation board. By premixing graphene and flame retardant to form a white premix, the compatibility between graphene and flame retardant is improved, so as to obtain an insulation board that takes into account both thermal insulation performance and flame retardant performance. However, it only uses a high-speed dispersion method to premix graphite powder, graphene and white premix, and the mixed solution cannot form a uniform and stable state. The flame retardant will settle, and the graphite powder is also prone to forming agglomerates, which greatly affects the mechanical properties of the product.

[0006] Therefore, although existing technologies have improved the flame retardant properties and compatibility of flame retardants to some extent, some problems and drawbacks still exist. First, existing composite methods often require complex process conditions and are costly; second, the flame retardant and thermal insulation properties of existing composite flame retardants still need improvement; and third, existing composite flame retardants may adversely affect other properties of polymer materials (such as mechanical properties and thermal stability). Summary of the Invention

[0007] To address the aforementioned issues, a homogeneous thermal insulation material and its preparation method are provided. The homogeneous thermal insulation material prepared by this method can solve the above-mentioned technical problems. The production process of the thermal insulation material is simple, the production cost is reduced, and it has high flame retardant performance, thermal insulation performance, mechanical properties, and thermal stability.

[0008] According to one aspect of this application, a method for preparing a homogeneous thermal insulation material is provided, comprising the following steps:

[0009] (1) Heat the aqueous solution of graphene oxide to 60-70℃, then add metal salt and stir to obtain a mixed solution. Add sodium hydroxide or potassium hydroxide solution to the mixed solution and stir continuously for 1-2 hours. The molar ratio of metal salt to sodium hydroxide or potassium hydroxide is 1:3-3.5 to obtain a graphene oxide composite inorganic flame retardant solution. The metal salt is selected from aluminum salt and / or magnesium salt.

[0010] (2) Add a surface modifier to the graphene oxide composite inorganic flame retardant solution, modify it at 70-80℃ for 2-3 hours, and then spray dry to obtain powdered modified graphene oxide composite inorganic flame retardant.

[0011] (3) Mix 50-60 parts of polyether polyol, 40-50 parts of polyester polyol, 3-5 parts of foam stabilizer, 2-3 parts of catalyst, 15-18 parts of foaming agent, 80-100 parts of modified expandable graphite, 160-220 parts of modified graphene oxide composite inorganic flame retardant, 15-20 parts of organophosphorus flame retardant and 0.9-1.5 parts of water to obtain a mixed liquid;

[0012] (4) Add 100-110 parts of diisocyanate to the mixed liquid, stir, pour into a mold for foaming and curing, and a homogeneous thermal insulation material is obtained.

[0013] In step (1), a graphene oxide composite inorganic flame retardant is synthesized chemically to improve the dispersibility of the inorganic flame retardant and avoid problems such as incomplete composite and low bonding degree leading to detachment in physical coating methods. Simultaneously, it solves the problem of excessive usage in traditional direct addition methods of inorganic flame retardants, significantly reducing the amount of aluminum hydroxide flame retardant used and improving flame retardant efficiency. In step (2), a surface modifier is used to modify the surface of the graphene oxide composite inorganic flame retardant to obtain a modified graphene oxide composite inorganic flame retardant. This improves the compatibility of the modified graphene oxide composite inorganic flame retardant with the substrate and modified expandable graphite, thereby improving the consistency of the material.

[0014] Graphene oxide possesses an extremely large specific surface area, which is beneficial for improving the compatibility of inorganic flame retardants with polymer materials. Simultaneously, it forms a large-area barrier layer to block heat transfer. This material, based on a modified graphene oxide composite inorganic flame retardant, incorporates modified expandable graphite and organophosphorus flame retardants, achieving a synergistic flame-retardant effect. Furthermore, these substances maintain a stable mixture within the material, resisting sedimentation and agglomeration, thereby improving the material's thermal insulation, mechanical properties, and thermal stability.

[0015] Optionally, the metal salt is an aluminum salt and a magnesium salt in a molar ratio of 1:1.

[0016] Optionally, the aluminum salt is selected from at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate;

[0017] The magnesium salt is selected from at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0018] Optionally, the surface modifier is selected from at least one of titanate, silane and aluminate.

[0019] The weight ratio of the surface modifier to the metal salt is (3-5):1.

[0020] Optionally, the concentration of the graphene oxide aqueous solution is 0.5-0.7%, and the weight ratio of the metal salt to the graphene oxide aqueous solution is 1:(10-150), preferably 1:(50-120).

[0021] Optionally, the foam stabilizer is hydroxyl silicone oil.

[0022] Hydroxyl silicone oil has good compatibility with polyurethane materials. It can reduce the surface tension of the solid-gas phase during the foaming process of polyurethane materials, making the bubbles in the material uniform and dense, thereby improving the thermal insulation performance, mechanical properties and thermal stability of the material, and thus playing a role in uniform foaming and improving the uniformity of bubbles inside the material.

[0023] Optionally, the polyether polyol is selected from polyether triol or polyether tetraol, and the hydroxyl value of the polyether polyol is 350-650 mg KOH / g;

[0024] The polyester polyol is selected from polycaprolactone polyol, polycarbonate polyol or polyacrylate polyol, and the hydroxyl value of the polyester polyol is 350-650 mg KOH / g.

[0025] The catalyst is selected from at least one of dibutyltin dilaurate, bis(dimethylaminoethyl) ether, N,N-dimethylcyclohexylamine, and 1,4-dimethylpiperazine.

[0026] The foaming agent is selected from at least one of n-pentane, n-hexane, and cyclohexane;

[0027] The organophosphorus flame retardant is selected from at least one of dimethyl methylphosphonate, triphenyl phosphite, tributyl phosphate, and tri(β-chloroethyl) phosphate;

[0028] The diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate.

[0029] Organophosphorus flame retardants decompose upon heating to produce phosphoric acid, metaphosphoric acid, and polymetaphosphoric acid. These phosphoric acid-containing substances have strong dehydrating properties, which can dehydrate and carbonize the polymer surface. Since elemental carbon cannot undergo evaporative combustion or decomposition combustion to produce a flame, it has a flame-retardant effect. On the other hand, they generate PO· free radicals upon heating, which can absorb a large number of H·HO· free radicals, thereby interrupting the combustion reaction.

[0030] The modified expandable graphite plays the following roles: first, it can form a tough carbon layer on the surface of polymers, separating combustibles from heat sources; second, it can absorb a large amount of heat during expansion, reducing the temperature of the system; and third, it can release acid radicals in the interlayer during expansion, promoting dehydration and carbonization, and can combine with free radicals generated by combustion to interrupt the chain reaction.

[0031] Optionally, the modified expandable graphite has a particle size of 0.5-10 μm and an expansion coefficient of 250-290 ml / g.

[0032] Optionally, the modification method of the modified expandable graphite is as follows:

[0033] S10: Phosphoric acid and urea are mixed in a molar ratio of (0.5-1):1 and reacted at 80-100℃ to obtain urea phosphate. Expandable graphite, dispersant, and emulsifier are added to the urea phosphate, and stirring is continued at 80-100℃ to obtain a colloid. The colloid is emulsified in an emulsifier and then transferred to a polymerization furnace for polymerization at 150-240℃ and 10-45Kpa to obtain a composite material. The composite material is cooled, dried, and pulverized to obtain intermediate microspheres A.

[0034] S20: The intermediate microsphere A and N-aminoethyl-3-aminopropyltriethoxysilane are mixed in a solvent and heated to 80°C for reaction. The mixture is then filtered, washed, and dried to obtain amino-containing intermediate microsphere B.

[0035] S30: After reacting monomer A, formaldehyde compound and intermediate microsphere B under an acidic catalyst, the mixture is filtered, washed and dried to obtain intermediate microsphere C. The monomer A is selected from at least one of p-acetoxystyrene, diacetone acrylamide and benzenemethylene acetone.

[0036] S40: The intermediate microsphere C is placed in a solution of 3-mercaptopropyltriethoxysilane and reacted under the influence of a free radical initiator. After filtration, washing, and drying, the modified expandable graphite is obtained.

[0037] In this preparation method, the intermediate microsphere A obtained in step S10 contains ammonium polyphosphate between the graphite layers, which can improve the adhesion between expandable graphite layers, thereby improving the flame retardant effect of expandable graphite. In step S20, N-aminoethyl-3-aminopropyltriethoxysilane is reacted with intermediate microsphere A to obtain intermediate microsphere B. This process can improve the compatibility of intermediate microsphere B with the polyurethane substrate, so that the expandable graphite and the substrate form a uniform and stable state, avoiding the sedimentation and agglomeration of expandable graphite, thereby improving the uniformity of the polymer matrix performance and the uniformity of the flame retardant effect of expandable graphite on the substrate. Secondly, intermediate microsphere B contains NH and NH2 groups, which can absorb toxic gases, reduce the hazard of combustion, and participate in the reaction of isocyanate to form polyurethane, forming chemical bonds with the polyurethane matrix, improving the bonding force between expandable graphite and the substrate, thereby making the flame retardant carbon layer tightly bonded to the substrate, improving the protection of the substrate. Furthermore, in step S30, it can react with monomer A formaldehyde compound to obtain intermediate microsphere C. The intermediate microspheres C prepared in step S30, due to the presence of monomer A, allow expandable graphite to incorporate functional groups such as benzene rings, carbonyl groups, ester groups, and amino groups. The benzene rings reinforce the matrix, improving its mechanical properties. The carbonyl and ester groups further increase compatibility with the polyurethane matrix, while the amino groups further increase the number of bonding sites with the polyurethane matrix and enhance the adsorption of toxic gases. Since monomer A in step S30 contains double bonds, step S40 uses 3-mercaptopropyltriethoxysilane to react with these double bonds, obtaining silane-terminated modified expandable graphite. This further improves the dispersibility and stability of expandable graphite in the matrix and enhances the adhesion between expandable graphite particles, thereby increasing the strength and density of the flame-retardant carbon layer. This effectively adsorbs and blocks toxic gases, reducing their harm to the human body.

[0038] The intermediate microspheres A obtained in step S10 above contain ammonium polyphosphate between the graphite layers, which not only improves the bonding force between expandable graphite layers and increases the strength of the flame-retardant carbon layer, but also, since ammonium polyphosphate itself is flame-retardant, can simultaneously improve the flame-retardant properties of expandable graphite. In steps S20-S40, modified molecular chains are added to the surface of expandable graphite, which firstly enables the adsorption of toxic gases; secondly, improves the compatibility between expandable graphite and the matrix, improves the dispersion uniformity of expandable graphite, avoids sedimentation or agglomeration of expandable graphite, and also improves the performance uniformity of polyurethane composite materials; thirdly, it can chemically bond with the polyurethane matrix, so that the flame-retardant carbon layer is tightly bonded to the matrix, effectively blocking toxic gases, and also improves the density, uniformity and mechanical strength of the flame-retardant carbon layer, which can resist the impact of open flame or heat convection.

[0039] The modified expandable graphite prepared by the above method has a more uniform dispersion characteristic, which can effectively reduce the amount used when it is used as a flame retardant, thereby reducing the density of the material and avoiding the problem of excessive weight and falling off when used as a building exterior wall.

[0040] Optionally, in step S10, the expandable graphite accounts for 5-30% of the weight of urea phosphate, the dispersant accounts for 0.5% of the weight of urea phosphate, and the emulsifier accounts for 0.5% of the weight of urea phosphate.

[0041] In step S10 above, the homogenization emulsification process is used to obtain intermediate microspheres A, which can solve the problem of difficult dispersion of expandable graphite and ammonium polyphosphate emulsion. Under the high shear force of the homogenization emulsifier, numerous small droplets are formed inside the emulsion, realizing the microstructure of expandable graphite particles encapsulated by the ammonium polyphosphate emulsion. During the polymerization process, the expandable graphite particles can be uniformly dispersed, thereby improving the modification effect of ammonium polyphosphate on expandable graphite.

[0042] Because expandable graphite contains ammonium polyphosphate between its layers, which decomposes into ammonia and polyphosphate when heated, the ammonia can dilute the oxygen concentration, and the polyphosphate has good thermal stability. Expandable graphite expands rapidly when heated, which can effectively isolate the oxygen required for combustion. At the same time, its porous structure absorbs combustion fumes, reducing the possibility of re-combustion, and can also effectively isolate the oxygen required for combustion, thus improving the flame retardant properties of the material.

[0043] Optionally, in step S20, the weight ratio of intermediate microsphere A to N-aminoethyl-3-aminopropyltriethoxysilane is 1:(1-2);

[0044] The heating reaction time in step S20 is 8-10 hours.

[0045] Expandable graphite contains a large number of hydroxyl groups on its surface. Through the reaction of N-aminoethyl-3-aminopropyltriethoxysilane and intermediate microsphere A, N-aminoethyl-3-aminopropyltriethoxysilane can be grafted onto the surface of expandable graphite by reacting with hydroxyl groups. The above reaction conditions can increase the reaction rate of N-aminoethyl-3-aminopropyltriethoxysilane with intermediate microsphere A and improve the control of the amount of N-aminoethyl-3-aminopropyltriethoxysilane on the surface of expandable graphite, thereby synergistically improving the effects of modified expandable graphite on flame retardancy, reinforcement, adsorption of toxic gases, and increased density of the matrix.

[0046] If the weight of N-aminoethyl-3-aminopropyltriethoxysilane is too high, the amount of N-aminoethyl-3-aminopropyltriethoxysilane on the surface of expandable graphite will increase. Combined with the reactions in subsequent steps S30 and S40, this will result in too many molecular chains being introduced onto the surface of expandable graphite, which will weaken the bonding force between expandable graphite particles. The flame-retardant carbon layer will still have cracks, and the flame-retardant effect and the barrier effect against toxic gases will be reduced. If the weight of N-aminoethyl-3-aminopropyltriethoxysilane is too low, the modification effect of expandable graphite will be reduced, and the effects of flame retardancy, reinforcement, adsorption of toxic gases, and improvement of density of the matrix will all decrease.

[0047] Optionally, in step S30, the weight ratio of monomer A, formaldehyde compound and intermediate microsphere B is (1-2):(1-3):1;

[0048] The reaction temperature in step S30 is 50-60℃, and the reaction time is 8-12h.

[0049] Preferably, the acidic catalyst is selected from at least one of nicotinic acid, sulfuric acid, acetic acid, and nitric acid.

[0050] The above weight ratio and reaction conditions can improve the reaction efficiency of monomer A, formaldehyde compound and intermediate microsphere B, promote the reaction of monomer A and formaldehyde compound with amino groups in N-aminoethyl-3-aminopropyltriethoxysilane, thereby introducing new functional groups, increasing the number of functional groups in intermediate microsphere B, and thus synergistically improving the flame retardant and reinforcing effects of expandable graphite on the matrix.

[0051] Optionally, monomer A is selected from diacetone acrylamide and benzenemethylene acetone;

[0052] The formaldehyde compounds are selected from trioxymethylene and / or paraoxymethylene.

[0053] Optionally, the molar ratio of diacetone acrylamide to benzene methylene acetone is 3:1.

[0054] Verification showed that when monomer A reacts with formaldehyde compounds and intermediate microspheres B, the attachment of monomer A to microsphere B hinders the continued reaction of monomer A, thus reducing its participation rate. Consequently, in the molecular chain on the surface of intermediate microsphere C, part is capped with monomer A, while the other part is capped with N-aminoethyl-3-aminopropyltriethoxysilane. However, selecting diacetone acrylamide and benzene methylene acetone in a molar ratio of 3:1 as monomer A increases its participation rate, resulting in a reaction rate greater than 98% between N-aminoethyl-3-aminopropyltriethoxysilane and monomer A on the surface of intermediate microsphere B. Furthermore, it simultaneously imparts both amino and benzene ring functional groups to the intermediate microsphere C, enhancing its mechanical strength and chemical bonding with the matrix, thereby achieving a tight and uniform connection between the modified expandable graphite and the matrix.

[0055] Optionally, in step S40, the weight ratio of the intermediate microsphere C to 3-mercaptopropyltriethoxysilane is 1:(5-10);

[0056] Preferably, the free radical initiator is AIBN, the reaction temperature is 60-70℃, and the reaction time is at least 5 hours.

[0057] The surface of the intermediate microsphere C is capped with monomer A, resulting in a large number of double bonds on the surface of the intermediate microsphere. In step S40, the double bonds react with mercapto groups, which can reintroduce siloxane molecular chains into the modified expandable graphite. At this time, both ends of the molecular chains on the surface of the modified expandable graphite are siloxane molecular chains, which can improve the dispersibility and stability of the modified expandable graphite in the matrix. Under the premise of stable dispersion, the uniformity of the reaction between amino groups and isocyanates in the molecular chains on the surface of the modified expandable graphite can be improved, thereby improving the uniformity of chemical bonding with the matrix. The modified expandable graphite is uniformly embedded in the matrix. Under high temperature environment, the modified expandable graphite has a strong bonding force with the matrix and can adsorb and block toxic matrix substances in the matrix in the first time, thereby improving the safety of the material.

[0058] According to another aspect of this application, a homogeneous thermal insulation material prepared by the method described in any of the preceding claims is provided.

[0059] The beneficial effects of this application include, but are not limited to:

[0060] 1. The preparation method of the homogeneous thermal insulation material of this application is simple and has low production cost. The inorganic flame retardant supported on graphene oxide synthesized by chemical method can improve the dispersibility of inorganic flame retardant and its compatibility with other substances, and the performance of the prepared thermal insulation material is improved in all aspects.

[0061] 2. The homogeneous thermal insulation material of this application can solve the problem of excessive usage caused by the direct addition of traditional flame retardants, thereby significantly reducing the amount of inorganic flame retardants used, and improving flame retardant efficiency while reducing the amount of flame retardants used.

[0062] 3. In the homogeneous thermal insulation material of this application, the modified inorganic flame retardant, modified expandable graphite and organophosphorus flame retardant can work together to improve the flame retardant effect of the material. Under the action of the foam leveling agent, the density and uniformity of the foam inside the material can be improved, resulting in a thermal insulation material with excellent performance in all aspects. Detailed Implementation

[0063] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0064] Unless otherwise specified, all raw materials used in the embodiments of this application are purchased commercially, and phosphoric acid is an 85% phosphoric acid solution.

[0065] Unless otherwise specified, the methods used in the embodiments of this application are conventional methods in the prior art.

[0066] The graphene oxide used in Example 2 was prepared using the Hummers method.

[0067] Example 1

[0068] This embodiment relates to the preparation of modified expandable graphite, which includes the following steps:

[0069] S10: Phosphoric acid and urea are mixed in a molar ratio of (0.5-1):1 and reacted at 80-100℃ to obtain urea phosphate. Expandable graphite, dispersant and emulsifier are added to the urea phosphate, and stirring is continued at 80-100℃ to obtain a colloid. The colloid is emulsified in an emulsifier and then transferred to a polymerization furnace for polymerization at 150-240℃ and 10-45Kpa to obtain a composite material. The composite material is cooled, dried and pulverized to obtain intermediate microspheres A.

[0070] S20: Intermediate microsphere A and N-aminoethyl-3-aminopropyltriethoxysilane are mixed in a solvent and heated to 80°C for reaction. After filtration, washing and drying, amino-containing intermediate microsphere B is obtained.

[0071] S30: After reacting monomer A, formaldehyde compound and intermediate microsphere B under an acidic catalyst, the mixture is filtered, washed and dried to obtain intermediate microsphere C. Monomer A is selected from at least one of p-acetoxystyrene, diacetone acrylamide and benzenemethylene acetone.

[0072] S40: The intermediate microsphere C is placed in a solution of 3-mercaptopropyltriethoxysilane and reacted under the influence of a free radical initiator. After filtration, washing, and drying, the modified expandable graphite is obtained.

[0073] Modified expandable graphite 1#-8# and comparative modified expandable graphite D1#-D4# were prepared according to the above preparation steps, as detailed below:

[0074] Modified expandable graphite #1

[0075] The preparation method of this modified expandable graphite 1# includes the following steps:

[0076] S10: Phosphoric acid and urea in a molar ratio of 0.5:1 are mixed and reacted at 100°C to obtain urea phosphate. Expandable graphite, dispersant, and emulsifier are added to the urea phosphate. The expandable graphite accounts for 5% of the weight of urea phosphate, the dispersant accounts for 0.5% of the weight of urea phosphate, and the emulsifier accounts for 0.5% of the weight of urea phosphate. The mixture is stirred at 100°C to obtain a colloid. The colloid is emulsified in the emulsifier and then transferred to a polymerization furnace for polymerization at 240°C and 10 kPa to obtain a composite material. The composite material is cooled, dried, and pulverized to obtain intermediate microspheres A with a particle size of 0.5 μm.

[0077] S20: Mix intermediate microspheres A and N-aminoethyl-3-aminopropyltriethoxysilane in N,N-dimethylformamide at a weight ratio of 1:1 and heat to 80°C. React under nitrogen protection for 10 h. Filter, wash and dry to obtain amino-containing intermediate microspheres B.

[0078] S30: P-acetoxystyrene, trioxymethylene and intermediate microsphere B in a weight ratio of 1:1:1 were mixed in methanol, and 37% concentrated hydrochloric acid was slowly added dropwise. The amount of concentrated hydrochloric acid added was 30% of the weight of intermediate microsphere B. The reaction was then carried out at 50°C and under nitrogen protection for 12 hours. The reaction solution was neutralized to neutral with sodium bicarbonate, filtered, washed and dried to obtain intermediate microsphere C.

[0079] S40: The intermediate microspheres C with a weight ratio of 1:5 were placed in a solution of 3-mercaptopropyltriethoxysilane. The solvent used was a mixed solvent of ethanol and water with a volume ratio of 5:1. Then, 1% AIBN by weight of the intermediate microspheres was added. After reacting at 70°C under nitrogen protection for 5 hours, the modified expandable graphite 1# was obtained by filtration, washing and drying.

[0080] Modified expandable graphite #2

[0081] The preparation method of this modified expandable graphite 2# includes the following steps:

[0082] S10: Phosphoric acid and urea in a molar ratio of 1:1 are mixed and reacted at 80°C to obtain urea phosphate. Expandable graphite, dispersant, and emulsifier are added to the urea phosphate. The expandable graphite accounts for 30% of the weight of urea phosphate, the dispersant accounts for 0.5% of the weight of urea phosphate, and the emulsifier accounts for 0.5% of the weight of urea phosphate. The mixture is stirred at 80°C to obtain a colloid. The colloid is emulsified in the emulsifier and then transferred to a polymerization furnace for polymerization at 150°C and 45 kPa to obtain a composite material. The composite material is cooled, dried, and pulverized to obtain intermediate microspheres A with a particle size of 10 μm.

[0083] S20: Intermediate microspheres A and N-aminoethyl-3-aminopropyltriethoxysilane in a weight ratio of 1:2 were mixed in N,N-dimethylformamide and heated to 80°C. The reaction was carried out under nitrogen protection for 8 hours. After filtration, washing, and drying, amino-containing intermediate microspheres B were obtained. The reaction equation is as follows:

[0084]

[0085] S30: Monomer A, trioxymethylene, and intermediate microspheres B in a weight ratio of 2:3:1 were mixed in methanol, and 37% concentrated hydrochloric acid was slowly added dropwise. The amount of concentrated hydrochloric acid added was 30% of the weight of intermediate microspheres B. The mixture was then reacted at 60°C under nitrogen protection for 8 hours. The reaction solution was neutralized to neutral with sodium bicarbonate, filtered, washed, and dried to obtain intermediate microspheres C. Monomer A was selected from diacetone acrylamide and benzenemethylene acetone in a molar ratio of 3:1. The reaction equation is as follows:

[0086]

[0087] Where R represents monomer A, and both amino groups in the intermediate microsphere B can participate in the reaction to obtain two compounds with structures of formula 1 and formula 2. In the above reaction, the compound with structure 1 accounts for more than 70%.

[0088] S40: The intermediate microspheres C with a weight ratio of 1:10 were placed in a solution of 3-mercaptopropyltriethoxysilane. The solvent used was a mixed solvent of ethanol and water with a volume ratio of 5:1. Then, 1% AIBN by weight of the intermediate microspheres was added. After reacting at 60°C under nitrogen protection for 8 hours, the mixture was filtered, washed, and dried to obtain modified expandable graphite 2#. In this step, the carbon-carbon double bond in monomer A and 3-mercaptopropyltriethoxysilane undergo an addition reaction.

[0089] Modified expandable graphite #3

[0090] The difference between this modified expandable graphite 3# and modified expandable graphite 2# is that in step S10, expandable graphite accounts for 40% of the weight of urea phosphate, while the remaining steps are the same as those of modified expandable graphite 2#.

[0091] Modified expandable graphite #4

[0092] The difference between this modified expandable graphite 4# and modified expandable graphite 2# is that in step S20, the weight ratio of the intermediate microsphere A and N-aminoethyl-3-aminopropyltriethoxysilane is 1:0.5, while the remaining steps are the same as those for modified expandable graphite 2#.

[0093] Modified expandable graphite #5

[0094] The difference between this modified expandable graphite 5# and modified expandable graphite 2# is that the weight ratio of monomer A, formaldehyde compound and intermediate microsphere B in step S30 is 0.8:3:1, while the remaining steps are the same as those for modified expandable graphite 2#.

[0095] Modified expandable graphite #6

[0096] The difference between this modified expandable graphite 6# and modified expandable graphite 2# is that in step S30, monomer A is selected from diacetone acrylamide and benzene methylene acetone in a molar ratio of 1:3, while the remaining steps are the same as those for modified expandable graphite 2#.

[0097] Modified expandable graphite #7

[0098] The difference between this modified expandable graphite 7# and modified expandable graphite 2# is that in step S40, the weight ratio of the intermediate microsphere C and 3-mercaptopropyltriethoxysilane is 1:3, while the remaining steps are the same as those for modified expandable graphite 2#.

[0099] Modified expandable graphite #8

[0100] The difference between this modified expandable graphite 8# and modified expandable graphite 2# is that the particle size of the intermediate microsphere A is 15μm, while the other steps are the same as those of modified expandable graphite 2#.

[0101] Comparison of modified expandable graphite D1#

[0102] The difference between modified expandable graphite D1# and modified expandable graphite 2# is that step S10 is omitted. In step S20, expandable graphite with N-aminoethyl-3-aminopropyltriethoxysilane at a weight ratio of 1:2 is reacted directly, and the particle size of the expandable graphite is 10 μm. The remaining steps are the same as those of modified expandable graphite 2#.

[0103] Comparison of modified expandable graphite D2#

[0104] The difference between this comparative modified expandable graphite D2# and modified expandable graphite 2# is that steps S20-S40 were not performed, and the intermediate microsphere A is the final modified expandable graphite. The remaining steps are the same as those for modified expandable graphite 2#.

[0105] Comparison of modified expandable graphite D3#

[0106] The difference between this comparative modified expandable graphite D3# and modified expandable graphite 2# is that step S40 was not performed, and the intermediate microsphere C is the final modified expandable graphite. The remaining steps are the same as those for modified expandable graphite 2#.

[0107] Comparison of modified expandable graphite D4#

[0108] The difference between this comparative modified expandable graphite D4# and modified expandable graphite 2# is that in step S20, 3-aminopropyltriethoxysilane is used instead of N-aminoethyl-3-aminopropyltriethoxysilane, while the remaining steps are the same as those for modified expandable graphite 2#.

[0109] Test Example 1

[0110] Gas adsorption tests were performed on the modified expandable graphite prepared above. The test results are shown in Table 1. The test methods are as follows:

[0111] Experimental group: 1g of modified expandable graphite was placed in the non-combustible plate of the reactor. A polyurethane board (5cm long * 5cm wide * 1cm thick) without flame retardant was fixedly suspended in the reactor. Oxygen was introduced into the reactor (100ml / min). The polyurethane board was ignited using a ignition device until it was completely burned. The concentrations of HCN, CO2, CO, NO, and NO2 in the reactor were tested.

[0112] Blank group: Polyurethane boards of the same material and size were fixedly suspended in the reactor. Nothing was placed in the non-combustible board. After combustion, the concentrations of HCN, CO2, CO, NO and NO2 in the reactor were recorded.

[0113] Both the experimental and blank groups of polyurethane boards were prepared by placing polyether polyol, foaming agent, catalyst, foaming agent, and water in a container with a weight ratio of 75:2.7:1.5:1.5:1. The mixture was stirred at high speed for 2 minutes to obtain a homogeneous liquid. Then, PAPI was added and stirred at high speed for 20 seconds to obtain a mixture with a weight ratio of PAPI to water of 100:1. The mixture was then quickly poured into a mold for foaming. The temperature of the closed mold was controlled at 65℃ and the curing time was maintained for 30 minutes. After foaming, the mold was opened and the board was cut into pieces with a length of 5cm, a width of 5cm, and a thickness of 1cm.

[0114] The modified expandable graphite prepared in Example 1 was subjected to experimental group tests in sequence. The adsorption rates of various gases were calculated by comparing the tested gas concentrations with those of the blank group. The calculation method is as follows:

[0115] HCN adsorption rate = (HCN concentration in blank group - HCN concentration in experimental group) / HCN concentration in blank group * 100;

[0116] CO2 adsorption rate = (CO2 concentration in blank group - CO2 concentration in experimental group) / CO2 concentration in blank group * 100;

[0117] CO adsorption rate = (CO concentration in blank group - CO concentration in experimental group) / CO concentration in blank group * 100;

[0118] NO adsorption rate = (NO concentration in blank group - NO concentration in experimental group) / NO concentration in blank group * 100;

[0119] NO2 adsorption rate = (NO2 concentration in blank group - NO2 concentration in experimental group) / NO2 concentration in blank group * 100.

[0120] Table 1

[0121]

[0122] According to the data in Table 1, modified expandable graphite can adsorb HCN, CO2, CO, NO, and NO2. Therefore, when it is used in polyurethane boards, it can adsorb and block the toxic gases generated in the early stage of combustion, reducing the combustion hazard.

[0123] Example 2

[0124] This embodiment relates to a method for preparing a homogeneous thermal insulation material, including the following steps:

[0125] (1) Heat the aqueous solution of graphene oxide to 60-70℃, then add metal salt and stir to obtain a mixed solution. Add sodium hydroxide or potassium hydroxide solution to the mixed solution and stir continuously for 1-2 hours. The molar ratio of metal salt to sodium hydroxide or potassium hydroxide is 1:3-3.5 to obtain a graphene oxide composite inorganic flame retardant solution. The metal salt is selected from aluminum salt and / or magnesium salt.

[0126] (2) Add a surface modifier to the graphene oxide composite inorganic flame retardant solution, modify it at 70-80℃ for 2-3 hours, and then spray dry to obtain powdered modified graphene oxide composite inorganic flame retardant.

[0127] (3) Mix 50-60 parts of polyether polyol, 40-50 parts of polyester polyol, 3-5 parts of foam stabilizer, 2-3 parts of catalyst, 15-18 parts of foaming agent, 80-100 parts of modified expandable graphite, 160-220 parts of modified graphene oxide composite inorganic flame retardant, 15-20 parts of organophosphorus flame retardant and 0.9-1.5 parts of water to obtain a mixed liquid;

[0128] (4) Add 100-110 parts of diisocyanate to the mixed liquid, stir, pour into a mold for foaming and curing, and a homogeneous thermal insulation material is obtained.

[0129] Materials 1#-6# and comparative materials D1#-D2# were prepared according to the above preparation method. The specific preparation method is as follows:

[0130] Material 1#

[0131] Preparation of modified expandable graphite:

[0132] Expandable graphite with a particle size of 0.5 μm was placed in a solution of 3-aminopropyltriethoxysilane with a weight ratio of 10:1. The mixture was stirred at 60 °C for 3 h, and then centrifuged and dried to obtain modified expandable graphite.

[0133] The preparation of material 1# includes the following steps:

[0134] (1) Heat 0.07% graphene oxide aqueous solution to 60°C, then add aluminum nitrate and stir to obtain a mixed solution. The weight ratio of aluminum nitrate to graphene oxide aqueous solution is 1:10. Add sodium hydroxide solution to the mixed solution and stir continuously for 1 hour. The molar ratio of aluminum nitrate to sodium hydroxide is 1:3 to obtain graphene oxide composite inorganic flame retardant solution.

[0135] (2) 3-aminopropyltriethoxysilane was added to the graphene oxide composite inorganic flame retardant solution. The weight ratio of 3-aminopropyltriethoxysilane to aluminum nitrate was 3:1. The modification was carried out at 80°C for 2 hours, and then spray-dried to obtain powdered modified graphene oxide composite inorganic flame retardant.

[0136] (3) Mix 50 parts of polyether triol (hydroxyl value of 350 mg KOH / g), 40 parts of polycaprolactone polyol (hydroxyl value of 650 mg KOH / g), 3 parts of hydroxyl silicone oil, 2 parts of dibutyltin dilaurate, 15 parts of n-pentane, 80 parts of modified expandable graphite, 160 parts of modified graphene oxide composite inorganic flame retardant, 15 parts of triphenyl phosphite and 0.9 parts of water to obtain a mixed liquid;

[0137] (4) Add 100 parts of hexamethylene diisocyanate to the mixed liquid, stir and pour into a mold, foam and mature at 65°C to obtain a homogeneous thermal insulation material.

[0138] Material 2#

[0139] The particle size of expandable graphite is 10μm. The steps and dosage of modifying expandable graphite are the same as those for material 1#.

[0140] The preparation of material 2# includes the following steps:

[0141] (1) Heat 0.05% graphene oxide aqueous solution to 70°C, then add magnesium sulfate and stir to obtain a mixed solution. The weight ratio of magnesium sulfate to graphene oxide aqueous solution is 1:150. Add potassium hydroxide solution to the mixed solution and stir continuously for 2 hours. The molar ratio of magnesium nitrate to potassium hydroxide is 1:3.5 to obtain graphene oxide composite inorganic flame retardant solution.

[0142] (2) 3-aminopropyltriethoxysilane was added to the graphene oxide composite inorganic flame retardant solution. The weight ratio of 3-aminopropyltriethoxysilane to aluminum nitrate was 5:1. The modification was carried out at 70°C for 3 hours, and then spray-dried to obtain powdered modified graphene oxide composite inorganic flame retardant.

[0143] (3) Mix 60 parts of polyether tetraol (hydroxyl value of 400 mg KOH / g), 50 parts of polycarbonate polyol (hydroxyl value of 400 mg KOH / g), 5 parts of hydroxyl silicone oil, 3 parts of dibutyltin dilaurate, 18 parts of n-pentane, 100 parts of modified expandable graphite, 220 parts of modified graphene oxide composite inorganic flame retardant, 20 parts of dimethyl methylphosphonate and 1.5 parts of water to obtain a mixed liquid;

[0144] (4) Add 110 parts of hexamethylene diisocyanate to the mixed liquid, stir and pour into a mold, foam and cure at 65°C to obtain a homogeneous thermal insulation material.

[0145] Material 3#

[0146] The difference between Material 3 and Material 2 is that aluminum chloride and magnesium chloride in a molar ratio of 1:1 replace magnesium sulfate; otherwise, they are the same as Material 2.

[0147] Material 4#

[0148] The difference between Material 4# and Material 3# is that Material 4# uses the modified expandable graphite 2# from Example 1 as the modified expandable graphite, while the rest is the same as Material 3#.

[0149] Material 5#

[0150] The difference between Material 5# and Material 3# is that Material 5# uses the comparative modified expandable graphite D1# from Example 1 as the modified expandable graphite, while the rest is the same as Material 3#.

[0151] Material 6#

[0152] The difference between Material 6# and Material 3# is that Material 6# uses the comparative modified expandable graphite D2# from Example 1 as the modified expandable graphite, while the rest is the same as Material 3#.

[0153] Comparative material D1#

[0154] The difference between material D1# and material 3# is that the inorganic flame retardant was not coated with graphene oxide and surface modified in steps (1) and (2). In step (3), aluminum hydroxide and magnesium hydroxide with a weight ratio of 1:1 were directly used as inorganic flame retardants. The rest is the same as material 3#.

[0155] Comparison material D2#

[0156] The difference between this comparative material D2# and material 3# is that modified expandable graphite is not added; otherwise, they are the same as material 3#.

[0157] Test Example 2

[0158] The density, thermal conductivity, flame retardancy and mechanical properties of the material prepared in Example 2 were tested, and the results are shown in Table 2 below. The flame retardancy performance was performed in accordance with GB8624-2012 standard.

[0159] Table 2

[0160]

[0161]

[0162] Test Example 3

[0163] The material prepared in Example 2 was placed at 60°C and 50% humidity for 30 days, and then the compressive strength of the material was tested. The test results are shown in Table 3 below. The dimensional stability of the material prepared in Example 2 was tested according to GBT8811-2008. The test results are shown in Table 3 below.

[0164] Table 3

[0165]

[0166] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a homogeneous thermal insulation material, characterized in that, Includes the following steps: (1) Heat the graphene oxide aqueous solution to 60-70℃, then add metal salt and stir to obtain a mixed solution. Add sodium hydroxide or potassium hydroxide solution to the mixed solution and stir continuously for 1-2 hours. The molar ratio of metal salt to sodium hydroxide or potassium hydroxide is 1:3-3.5 to obtain a graphene oxide composite inorganic flame retardant solution. The metal salt is selected from aluminum salt and / or magnesium salt. The concentration of the graphene oxide aqueous solution is 0.5-0.7%. The weight ratio of metal salt to graphene oxide aqueous solution is 1:(10-150). (2) Add a surface modifier to the graphene oxide composite inorganic flame retardant solution, modify it at 70-80℃ for 2-3 hours, and then spray dry to obtain a powdered modified graphene oxide composite inorganic flame retardant. The surface modifier is selected from at least one of titanate, silane and aluminate. (3) Mix 50-60 parts of polyether polyol, 40-50 parts of polyester polyol, 3-5 parts of foam stabilizer, 2-3 parts of catalyst, 15-18 parts of foaming agent, 80-100 parts of modified expandable graphite, 160-220 parts of modified graphene oxide composite inorganic flame retardant, 15-20 parts of organophosphorus flame retardant and 0.9-1.5 parts of water to obtain a mixed liquid, wherein the foam stabilizer is hydroxyl silicone oil; (4) Add 100-110 parts of diisocyanate to the mixed liquid, stir, pour into a mold for foaming and curing, and a homogeneous thermal insulation material is obtained; the modification method of the modified expandable graphite is as follows: S10: Phosphoric acid and urea are mixed in a molar ratio of (0.5-1):1 and reacted at 80-100℃ to obtain urea phosphate. Expandable graphite, dispersant, and emulsifier are added to the urea phosphate, and stirring is continued at 80-100℃ to obtain a colloid. The colloid is emulsified in an emulsifier and then transferred to a polymerization furnace for polymerization at 150-240℃ and 10-45Kpa to obtain a composite material. The composite material is cooled, dried, and pulverized to obtain intermediate microspheres A. S20: The intermediate microsphere A and N-aminoethyl-3-aminopropyltriethoxysilane are mixed in a solvent and heated to 80°C for reaction. The mixture is then filtered, washed, and dried to obtain amino-containing intermediate microsphere B. S30: After reacting monomer A, formaldehyde compound and intermediate microsphere B under an acidic catalyst, the mixture is filtered, washed and dried to obtain intermediate microsphere C. The monomer A is selected from at least one of p-acetoxystyrene, diacetone acrylamide and benzenemethylene acetone. S40: The intermediate microsphere C is placed in a solution of 3-mercaptopropyltriethoxysilane and reacted under the influence of a free radical initiator. After filtration, washing, and drying, the modified expandable graphite is obtained.

2. The preparation method according to claim 1, characterized in that, The metal salts are aluminum and magnesium salts in a molar ratio of 1:

1.

3. The preparation method according to claim 2, characterized in that, The aluminum salt is selected from at least one of aluminum chloride, aluminum sulfate, and aluminum nitrate; The magnesium salt is selected from at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

4. The preparation method according to claim 1, characterized in that, The polyether polyol is selected from polyether triol or polyether tetraol, and the hydroxyl value of the polyether polyol is 350-650 mg KOH / g; The polyester polyol is selected from polycaprolactone polyol or polycarbonate polyol, and the hydroxyl value of the polyester polyol is 350-650 mg KOH / g; The catalyst is selected from at least one of dibutyltin dilaurate, bis(dimethylaminoethyl) ether, N,N-dimethylcyclohexylamine, and 1,4-dimethylpiperazine. The foaming agent is selected from at least one of n-pentane, n-hexane, and cyclohexane; The organophosphorus flame retardant is selected from at least one of dimethyl methylphosphonate, triphenyl phosphite, tributyl phosphate, and tri(β-chloroethyl) phosphate; The diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate.

5. The homogeneous thermal insulation material prepared by the method for preparing homogeneous thermal insulation material according to any one of claims 1-4.

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