Energy-saving building wall composite material and preparation method thereof

Abstract

The application relates to the technical field of new wall building materials, and discloses a building energy-saving thermal insulation wall composite material and a preparation method thereof. The preparation method of the building energy-saving thermal insulation wall composite material comprises the following steps: loading eutectic hydrated salt in modified diatomite to obtain a diatomite-based phase change material; modifying the diatomite-based phase change material through 3-(2,3-epoxypropoxy) propyl trimethoxysilane and a flame retardant to obtain a functionally modified diatomite-based phase change material; mixing microsilica powder, the functionally modified diatomite-based phase change material, calcium oxide, double-coated foamed polystyrene particles, a polycarboxylic acid-based high-performance water reducing agent and deionized water in proportion, performing mold pressing, standing, demolding and obtaining the building energy-saving thermal insulation wall composite material; the building energy-saving thermal insulation wall composite material has good heat insulation performance and simultaneously has flame retardant performance, and can be used in an outer wall thermal insulation material with high fireproof performance.

Description

Technical Field

[0001] This invention relates to the field of novel wall building materials technology, and in particular to a building energy-saving and heat-insulating wall composite material and its preparation method. Background Technology

[0002] In thermal insulation materials, EPS particles (expanded polystyrene particles) are widely used in lightweight building materials due to their low bulk density, thermal insulation, durability, ease of processing and cost-effectiveness. However, as an organic material, it has poor interfacial compatibility with inorganic material matrices, which can easily lead to uneven dispersion and thus affect the overall performance of building materials.

[0003] Furthermore, with the continuous improvement of national requirements for the fire resistance performance of building materials, the flame-retardant technology of building exterior wall insulation materials has been studied in depth. In 2011, my country promulgated the "Interim Provisions on Fire Prevention of Civil Building Exterior Insulation Systems and Exterior Wall Decorations," which clearly requires that the combustion rating of civil building exterior insulation materials shall not be lower than B2, and in some cases, it shall reach A. However, polystyrene, as an organic carbon compound, has a limiting oxygen index of only 18%, which is a flammable material. When burning, it has characteristics such as shrinkage, melting, and dripping, and the dripping material has secondary ignition properties. This poses a severe challenge to the fire safety of building structures. Therefore, the development of highly efficient flame-retardant polystyrene building energy-saving insulation wall composite materials has become a current research hotspot. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a composite material for energy-saving and thermally insulated building walls, comprising the following steps:

[0005] Step 1: Load eutectic hydrated salt into modified diatomite to obtain diatomite-based phase change material; modify the diatomite-based phase change material with 3-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain surface-modified diatomite-based phase change material.

[0006] Step 2: 4,4'-dihydroxybiphenyl, paraformaldehyde and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane are reacted to obtain a flame retardant; the surface-modified diatomaceous earth-based phase change material is modified by the flame retardant to obtain a functionally modified diatomaceous earth-based phase change material.

[0007] Step 3: Mix microsilica powder, functional modified diatomaceous earth-based phase change material, calcium oxide, double-coated expanded polystyrene particles, polycarboxylate-based high-performance water-reducing agent, and deionized water in a certain proportion to obtain a mixture; place the mixture in a mold, compress it, let it stand, and demold it to obtain a building energy-saving and heat-insulating wall composite material.

[0008] Preferably, in step one, the preparation method of the surface-modified diatomaceous earth-based phase change material is as follows:

[0009] Disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and deionized water were mixed in a mass ratio of 6:4:(6.7-10) and stirred at 55-65℃ until completely dissolved to obtain a eutectic hydrated salt. Modified diatomaceous earth was mixed with the eutectic hydrated salt in a mass ratio of (25-40):(60-75) and stirred at 58-62℃ for 20-40 min. After purification, a diatomaceous earth-based phase change material was obtained.

[0010] 25wt% ammonia, deionized water, and ethanol were mixed in a volume ratio of 0.7:10:30, then diatomaceous earth-based phase change material was added, and the mixture was stirred. 3-(2,3-epoxypropoxy)propyltrimethoxysilane was then added, and the mixture was reacted at 55-65℃ for 1.5-2.5 h. After purification, surface-modified diatomaceous earth-based phase change material was obtained. The volume ratio of 25wt% ammonia to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 7:0.2, and the mass ratio of diatomaceous earth-based phase change material to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 5:(0.2-0.6).

[0011] In the above process, disodium hydrogen phosphate dodecahydrate and sodium carbonate decahydrate are mixed in a mass ratio of 6:4 to form a eutectic hydrate salt. The phase transition temperature of the eutectic hydrate salt is about 24.3℃, which can be used as a phase change material in building wall materials. The eutectic hydrate salt is loaded into the porous structure of modified diatomaceous earth by impregnation to obtain a diatomaceous earth-based phase change material with good thermal insulation performance and certain flame retardant properties. Next, the presence of abundant hydroxyl groups on the surface of modified diatomaceous earth allows it to combine with silanols obtained from the hydrolysis of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, attaching 3-(2,3-epoxypropoxy)propyltrimethoxysilane to the surface of the diatomaceous earth-based phase change material, thereby introducing epoxy groups onto the surface of the diatomaceous earth-based phase change material.

[0012] Preferably, in step one, the method for preparing the modified diatomaceous earth is as follows:

[0013] Glucose and deionized water were mixed at a mass ratio of 1:10 and stirred at 28-32℃ for 20-40 min to obtain a glucose solution. Pre-dried diatomaceous earth was mixed with the glucose solution at a mass ratio of (5-10):(55-110) and stirred at 28-32℃ at a speed of 300-400 r / min for 4-6 h. The mixture was then vacuum filtered and dried to obtain a precursor. The precursor was heated to 300-400℃ at a rate of 5℃ / min in a nitrogen atmosphere and held for 100-150 min to obtain modified diatomaceous earth.

[0014] In the above process, diatomaceous earth is a natural clay mineral that is abundant and inexpensive. Studies have shown that diatomaceous earth has advantages such as high specific surface area, high porosity, non-toxicity, heat resistance, and flame retardancy. Moreover, the surface of diatomaceous earth contains abundant silanol groups, which enhances its ability to adsorb inorganic salt hydrates. In order to improve its ability to load phase change materials, this invention forms carbon particles on the surface of diatomaceous earth by carbonizing glucose. Compared with the diatomaceous earth before modification, the carbon particle modified diatomaceous earth forms a porous microstructure with a significantly increased specific surface area and pore volume, thereby having better load-bearing capacity and thermal insulation ability.

[0015] Preferably, in step two, the method for preparing the flame retardant is as follows:

[0016] 4,4'-dihydroxybiphenyl, paraformaldehyde, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were added to N,N-dimethylformamide and reacted at 85-95°C for 1.5-2.5 h under a nitrogen atmosphere to obtain a flame retardant; wherein the mass ratio of 4,4'-dihydroxybiphenyl, paraformaldehyde, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and N,N-dimethylformamide was (13.9-27.9):(9-18):(18.6-37.2):(150-250);

[0017] In the above process, 4,4'-dihydroxybiphenyl, paraformaldehyde, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane are used as raw materials to produce a flame retardant containing flame-retardant nitrogen, silicon, oxazine ring, and biphenyl structure through reaction.

[0018] Preferably, in step two, the preparation method of the functionally modified diatomaceous earth-based phase change material is as follows:

[0019] Surface-modified diatomaceous earth-based phase change material was added to N,N-dimethylformamide and stirred. Then, a flame retardant was added, and the mixture was reacted at 75-85℃ for 16-20 hours. After purification, functionally modified diatomaceous earth-based phase change material was obtained. The mass ratio of the surface-modified diatomaceous earth-based phase change material, N,N-dimethylformamide, and flame retardant was (10-15):(200-300):(12.4-18.6).

[0020] In the above process, the epoxy groups on the surface of the surface-modified diatomaceous earth-based phase change material react with the amino groups in the flame retardant, grafting the flame retardant onto the surface-modified diatomaceous earth-based phase change material, thus obtaining a functionally modified diatomaceous earth-based phase change material. The flame-retardant nitrogen and silicon elements in the flame retardant work synergistically with diatomaceous earth to have a good flame-retardant effect. The rigid structure of biphenyl in the flame retardant can improve the mechanical properties of the functionally modified diatomaceous earth-based phase change material. During combustion, at high temperatures, the rigidity of the biphenyl structure also helps to stabilize the char layer and improve its quality. The cross-linked structure formed by the ring-opening polymerization of oxazine rings can stabilize the char layer and enhance its density. The combined effect of these two factors reduces the release of heat and smoke, effectively prevents the spread of oxygen and heat, and reduces the generation and diffusion of flammable gases, giving the functionally modified diatomaceous earth-based phase change material excellent thermal insulation, flame retardant, and mechanical properties.

[0021] Preferably, in step three, the content of each component in the mixture, by weight, is as follows: 132-168 parts of microsilica powder, 66-84 parts of functionally modified diatomaceous earth-based phase change material, 85-105 parts of calcium oxide, 14.3-18.5 parts of double-coated expanded polystyrene particles, 3.8-4.6 parts of polycarboxylate-based high-performance water-reducing agent, and 92.1-113.7 parts of deionized water.

[0022] Preferably, in step three, the molding conditions are: temperature 120-150℃, pressure 2.9-3.3MPa; and the settling time is 2-3 hours.

[0023] In the above process, the silica powder and calcium oxide in the mixture can undergo a chemical reaction during the molding process. The functional modified diatomaceous earth-based phase change material and the double-coated expanded polystyrene particles in the mixture can participate in the reaction as silica and calcium substances, and are uniformly dispersed in the mixture. They can also be used as functional fillers to improve the mechanical properties, flame retardancy and thermal insulation performance of building energy-saving and heat-insulating wall composite materials.

[0024] Preferably, in step three, the method for preparing the double-coated expanded polystyrene particles includes the following steps:

[0025] Step S1: In a nitrogen atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to toluene and heated to 90-100℃. Then, 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added and reacted for 5-7 hours. After evaporation, deionized water and ethanol are added, and the mixture is heated to 75-85℃ and maintained for 4.5-5.5 hours. After evaporation, flame-retardant polysiloxane is obtained.

[0026] Step S2: Add expanded polystyrene particles to flame-retardant polysiloxane and stir at 23-25℃ for 1-2 hours. Then add nano-silica and continue stirring for 1-2 hours. Cure the treated expanded polystyrene particles at 70-80℃ for 30-60 minutes to obtain double-coated expanded polystyrene particles. The mass ratio of expanded polystyrene particles, flame-retardant polysiloxane, and nano-silica is (10-20):(2-4):(4-10).

[0027] In the above process, the epoxy group of 3-(2,3-epoxypropoxy)propyltrimethoxysilane undergoes ring-opening reaction with the active hydrogen of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to obtain a siloxane containing flame-retardant phosphorus / silicon elements and hydroxyl groups. The siloxane then undergoes further polycondensation to form a flame-retardant polysiloxane. This polysiloxane exhibits excellent adhesion; therefore, the flame-retardant polysiloxane of this invention can be used both as a flame retardant and as a binder, firmly adhering it to expanded polystyrene particles. The adhesive properties of flame-retardant polysiloxane and its hydroxyl groups facilitate the adsorption of nano-silica, thereby achieving a double-layer coating of flame-retardant polysiloxane and nano-silica on expanded polystyrene particles. Depositing nano-silica on expanded polystyrene particles can, on the one hand, give the double-layer coated expanded polystyrene particles better flame-retardant properties, and on the other hand, nano-silica can react with calcium oxide and improve the interfacial compatibility between the double-layer coated expanded polystyrene particles and calcium oxide and microsilica powder.

[0028] Preferably, in step S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, toluene, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, deionized water and ethanol is (25-50):(30-50):(10.5-21):(30-50):(40-66).

[0029] Preferably, in step S1, the expanded polystyrene particles are obtained by pre-foaming polystyrene beads by heating them in a steam environment for 180 seconds, and then placing them at room temperature (23-25°C) for 24 hours.

[0030] The energy-saving and heat-insulating wall composite material is prepared by the aforementioned method.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The building energy-saving and heat-insulating wall composite material of the present invention contains functional modified diatomaceous earth-based phase change material and double-coated expanded polystyrene particles. Both can participate in the reaction as siliceous and calcareous substances, and be uniformly dispersed in the mixture. They can also be used as functional fillers to improve the mechanical properties, flame retardancy and thermal insulation performance of the building energy-saving and heat-insulating wall composite material.

[0033] 2. The functionally modified diatomaceous earth-based phase change material of the present invention is obtained by grafting a flame retardant onto a surface-modified diatomaceous earth-based phase change material. The flame retardant of the present invention contains flame-retardant nitrogen, silicon, oxazine rings, and biphenyl structures. The flame-retardant nitrogen and silicon elements in the flame retardant work synergistically with diatomaceous earth to have a good flame-retardant effect. The rigid structure of biphenyl in the flame retardant can improve the mechanical properties of the functionally modified diatomaceous earth-based phase change material. The biphenyl structure and oxazine ring work together to improve the flame-retardant effect. Furthermore, the surface-modified diatomaceous earth-based phase change material of the present invention uses glucose carbonization-modified diatomaceous earth as the matrix and loads a eutectic hydrate of disodium hydrogen phosphate dodecahydrate and sodium carbonate decahydrate. The modified diatomaceous earth has a significantly increased specific surface area and pore volume, thus having better load-bearing capacity and thermal insulation capacity.

[0034] 3. In this invention, flame-retardant polysiloxane and nano-silica are sequentially coated onto expanded polystyrene particles by mechanical stirring to obtain double-layer coated expanded polystyrene particles. The flame-retardant polysiloxane of this invention can act as both a flame retardant and a binder, firmly adhering to the expanded polystyrene particles. Furthermore, the adhesiveness of the flame-retardant polysiloxane and its hydroxyl groups facilitate the adsorption of nano-silica, thereby achieving the coating of nano-silica. Depositing nano-silica onto the expanded polystyrene particles can, on the one hand, give the double-layer coated expanded polystyrene particles better flame-retardant properties, and on the other hand, nano-silica can react with calcium oxide and improve the interfacial compatibility between the double-layer coated expanded polystyrene particles and the inorganic matrix, thereby improving the overall performance of the building energy-saving and thermal insulation wall composite material. Attached Figure Description

[0035] Figure 1 This is a process flow diagram of the preparation process of the building energy-saving and heat-insulating wall composite material containing the present invention;

[0036] Figure 2 This is a schematic diagram illustrating the synthesis of the flame retardant of the present invention;

[0037] Figure 3 This is a schematic diagram of the synthesis of flame-retardant polysiloxane according to the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment discloses a method for preparing double-layer coated expanded polystyrene particles, including the following steps:

[0041] Step S1: In a nitrogen atmosphere, 37.5 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added to 40 g of toluene and heated to 95 °C. Then, 15.8 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added, and the temperature was kept constant for 6 h. After the reaction was completed, the solvent was evaporated, and then 40 g of deionized water and 53 g of ethanol were added. The mixture was heated to 80 °C and kept for 5 h. After the reaction was completed, the ethanol and deionized water were evaporated to remove them, and flame-retardant polysiloxane was obtained.

[0042] Step S2: Pre-foam the polystyrene beads by heating them in a steam environment for 180 seconds, and then place them at room temperature (24°C) for 24 hours to obtain foamed polystyrene particles. Add 15g of foamed polystyrene particles to 3g of flame-retardant polysiloxane and stir at 24°C for 1.5 hours. Then add 7g of nano-silica and continue stirring for 1.5 hours. Cure the treated foamed polystyrene particles at 75°C for 45 minutes to obtain double-coated foamed polystyrene particles.

[0043] Example 2

[0044] This embodiment discloses a method for preparing a composite material for energy-saving and thermally insulated building walls, including the following steps:

[0045] Step 1: Vacuum-dry diatomaceous earth at 100℃ and 5kPa for 12 hours to obtain pre-dried diatomaceous earth; mix glucose and deionized water at a mass ratio of 1:10 and stir at 28℃ for 40 minutes to obtain a glucose solution; add 5g of pre-dried diatomaceous earth to 55g of glucose solution and stir at 300r / min at 28℃ for 6 hours, vacuum filter, and dry the filter residue at 70℃ to constant weight to obtain the precursor; heat the precursor to 300℃ at a rate of 5℃ / min in a nitrogen atmosphere and hold for 150 minutes to obtain modified diatomaceous earth;

[0046] Disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and deionized water were mixed in a mass ratio of 6:4:10 and stirred at 55°C until completely dissolved to obtain a eutectic hydrated salt. Modified diatomite was mixed with the eutectic hydrated salt in a mass ratio of 25:75 and stirred at 58°C for 40 min. The mixture was then vacuum filtered, and the resulting solid product was dried at 20°C to obtain a diatomite-based phase change material.

[0047] 25wt% ammonia, deionized water, and ethanol were mixed in a volume ratio of 0.7:10:30. Diatomaceous earth-based phase change material was then added, and the mixture was stirred for 20 min. Next, 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added, and the mixture was reacted at 55°C for 2.5 h with stirring. After the reaction was complete, the precipitate was collected by centrifugation, washed with ethanol, and dried to obtain the surface-modified diatomaceous earth-based phase change material. The volume ratio of 25wt% ammonia to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 7:0.2, and the mass ratio of the diatomaceous earth-based phase change material to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 5:0.2.

[0048] Step 2: Add 13.9g of 4,4'-dihydroxybiphenyl, 9g of paraformaldehyde, and 18.6g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane to 150g of N,N-dimethylformamide. React at 85°C for 2.5h under a nitrogen atmosphere. After the reaction is complete, remove the solvent by rotary evaporation to obtain the flame retardant.

[0049] 10g of surface-modified diatomite-based phase change material was added to 200g of N,N-dimethylformamide and stirred for 20min. Then, 12.4g of flame retardant was added and reacted at 75℃ for 20h. After the reaction was completed, the precipitate was collected by centrifugation. The precipitate was washed with ethanol and dried to obtain the functionally modified diatomite-based phase change material.

[0050] Step 3: By weight, take 132 parts of microsilica powder, 66 parts of functional modified diatomaceous earth-based phase change material, 85 parts of calcium oxide, 14.3 parts of double-coated expanded polystyrene particles, 3.8 parts of polycarboxylate-based high-performance water-reducing agent, and 92.1 parts of deionized water and mix them to obtain a mixture. Place the mixture in a mold and mold it at a temperature of 120℃ and a pressure of 2.9MPa. Let it stand for 3 hours and then demold to obtain a building energy-saving and thermal insulation wall composite material.

[0051] Example 3

[0052] This embodiment discloses a method for preparing a composite material for energy-saving and thermally insulated building walls, including the following steps:

[0053] Step 1: Vacuum-dry diatomaceous earth at 110℃ and 5kPa for 10h to obtain pre-dried diatomaceous earth; mix glucose and deionized water at a mass ratio of 1:10 and stir at 32℃ for 20min to obtain a glucose solution; add 10g of pre-dried diatomaceous earth to 110g of glucose solution and stir at 300r / min at 32℃ for 4h, vacuum filter, and dry the filter residue at 80℃ to constant weight to obtain the precursor; heat the precursor to 400℃ at a rate of 5℃ / min in a nitrogen atmosphere and hold for 100min to obtain modified diatomaceous earth;

[0054] Disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and deionized water were mixed in a mass ratio of 6:4:6.7 and stirred at 55-65℃ until completely dissolved to obtain a eutectic hydrated salt. Modified diatomite was mixed with the eutectic hydrated salt in a mass ratio of 40:75 and stirred at 62℃ for 20 min. The mixture was then vacuum filtered, and the resulting solid product was dried at 23℃ to obtain a diatomite-based phase change material.

[0055] 25wt% ammonia, deionized water, and ethanol were mixed in a volume ratio of 0.7:10:30. Diatomaceous earth-based phase change material was then added, and the mixture was stirred for 40 min. Next, 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added, and the mixture was reacted at 65°C for 1.5 h with stirring. After the reaction was complete, the precipitate was collected by centrifugation, washed with ethanol, and dried to obtain the surface-modified diatomaceous earth-based phase change material. The volume ratio of 25wt% ammonia to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 7:0.2, and the mass ratio of the diatomaceous earth-based phase change material to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 5:0.6.

[0056] Step 2: Add 27.9g of 4,4'-dihydroxybiphenyl, 18g of paraformaldehyde, and 37.2g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane to 250g of N,N-dimethylformamide. React at 95°C for 1.5h under a nitrogen atmosphere. After the reaction is complete, remove the solvent by rotary evaporation to obtain the flame retardant.

[0057] 15g of surface-modified diatomite-based phase change material was added to 300g of N,N-dimethylformamide and stirred for 40min. Then, 18.6g of flame retardant was added and reacted at 85℃ for 16h. After the reaction was completed, the precipitate was collected by centrifugation. The precipitate was washed with ethanol and dried to obtain the functionally modified diatomite-based phase change material.

[0058] Step 3: By weight, take 168 parts of microsilica powder, 84 parts of functional modified diatomaceous earth-based phase change material, 105 parts of calcium oxide, 18.5 parts of double-coated expanded polystyrene particles, 4.6 parts of polycarboxylate-based high-performance water-reducing agent, and 113.7 parts of deionized water and mix them to obtain a mixture. Place the mixture in a mold and mold it at a temperature of 150℃ and a pressure of 3.3MPa. Let it stand for 2 hours, then demold to obtain a building energy-saving and thermal insulation wall composite material.

[0059] Example 4

[0060] This embodiment discloses a method for preparing a composite material for energy-saving and thermally insulated building walls, including the following steps:

[0061] Step 1: Vacuum-dry diatomaceous earth at 105℃ and 5kPa for 11 hours to obtain pre-dried diatomaceous earth; mix glucose and deionized water at a mass ratio of 1:10 and stir at 30℃ for 30 minutes to obtain a glucose solution; add 7.5g of pre-dried diatomaceous earth to 82.5g of glucose solution and stir at 350r / min at 30℃ for 5 hours, vacuum filter, and dry the filter residue at 75℃ to constant weight to obtain the precursor; heat the precursor to 350℃ at a rate of 5℃ / min in a nitrogen atmosphere and hold for 125 minutes to obtain modified diatomaceous earth;

[0062] Disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and deionized water were mixed in a mass ratio of 6:4:8.4 and stirred at 60°C until completely dissolved to obtain a eutectic hydrated salt. Modified diatomaceous earth was mixed with the eutectic hydrated salt in a mass ratio of 32.5:67.5 and stirred at 60°C for 30 min. The mixture was then vacuum filtered, and the resulting solid product was dried at 22°C to obtain a diatomaceous earth-based phase change material.

[0063] 25wt% ammonia, deionized water, and ethanol were mixed in a volume ratio of 0.7:10:30. Diatomaceous earth-based phase change material was then added, and the mixture was stirred for 30 min. Next, 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added, and the mixture was reacted at 60 °C for 2 h with stirring. After the reaction was complete, the precipitate was collected by centrifugation, washed with ethanol, and dried to obtain the surface-modified diatomaceous earth-based phase change material. The volume ratio of 25wt% ammonia to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 7:0.2, and the mass ratio of the diatomaceous earth-based phase change material to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 5:0.4.

[0064] Step 2: Add 20.9g of 4,4'-dihydroxybiphenyl, 13.5g of paraformaldehyde, and 27.9g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane to 200g of N,N-dimethylformamide. React at 90°C for 2 hours under a nitrogen atmosphere. After the reaction is complete, remove the solvent by rotary evaporation to obtain the flame retardant.

[0065] 12.5g of surface-modified diatomite-based phase change material was added to 250g of N,N-dimethylformamide and stirred for 30min. Then, 15.5g of flame retardant was added and reacted at 80℃ for 18h. After the reaction was completed, the precipitate was collected by centrifugation. The precipitate was washed with ethanol and dried to obtain the functionally modified diatomite-based phase change material.

[0066] Step 3: By weight, take 150 parts of microsilica powder, 75 parts of functional modified diatomaceous earth-based phase change material, 95 parts of calcium oxide, 16.4 parts of double-coated expanded polystyrene particles, 4.2 parts of polycarboxylate-based high-performance water-reducing agent, and 102.9 parts of deionized water and mix them to obtain a mixture. Place the mixture in a mold and mold it at a temperature of 135℃ and a pressure of 3.1MPa. Let it stand for 2.5 hours, then demold to obtain a building energy-saving and thermal insulation wall composite material.

[0067] The double-coated expanded polystyrene particles in Examples 2-4 above are the double-coated expanded polystyrene particles prepared in Example 1.

[0068] Comparative Example 1

[0069] Compared with Example 4, Comparative Example 1 used pre-dried diatomaceous earth instead of modified diatomaceous earth in the process of preparing diatomaceous earth-based phase change materials, while other conditions remained unchanged.

[0070] Comparative Example 2

[0071] Compared with Example 4, Comparative Example 2 used surface-modified diatomaceous earth-based phase change material instead of functionally modified diatomaceous earth-based phase change material in the process of preparing building energy-saving and heat-insulating wall composite material, while keeping other conditions unchanged.

[0072] Comparative Example 3

[0073] Compared with Example 4, Comparative Example 3 used expanded polystyrene particles instead of double-coated expanded polystyrene particles in the process of preparing building energy-saving and heat-insulating wall composite materials, while keeping other conditions unchanged.

[0074] In the above examples and comparative examples, paraformaldehyde with a purity ≥95% was sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.; diatomaceous earth, branded as Wokai, was sourced from Sinopharm Chemical Reagent Co., Ltd.; polystyrene beads with a particle size of 0.3-0.5 mm were sourced from Dongguan Shenghao Plastic Raw Materials Co., Ltd.; nano-silica with an average particle size of 20 nm was sourced from Nangong Harbin Institute of Technology New Materials Technology Co., Ltd.; microsilica powder, 1250 mesh, was sourced from Lingshou Yuanda Mica Factory; and polycarboxylate-based high-performance water-reducing agent with a water reduction rate ≥25% was sourced from Suzhou Xinhua East Chemical Co., Ltd.

[0075] Experimental Example

[0076] Performance tests were conducted on the building energy-saving and thermal insulation wall composite material samples prepared in Examples 2-4 and Comparative Examples 1-3.

[0077] I. Flame retardant performance test: The flammability rating of each group of samples was tested according to GB 8624-2012 "Classification of Burning Performance of Building Materials and Products";

[0078] II. Mechanical performance testing: The compressive strength of each group of samples was tested according to GB / T 5486—2008 "Test Methods for Inorganic Rigid Thermal Insulation Products";

[0079] III. Thermal Insulation Performance Test: A small room model was constructed using samples of various building energy-saving thermal insulation wall composite materials and polystyrene foam. The small room model consisted of 4 pieces of polystyrene foam (external dimensions 26×26×26cm). 3 The internal dimensions are 20×20×20cm. 3 ) and 2 samples of building energy-saving and heat-insulating wall composite materials (20×20×20cm in size). 3 The test consisted of two samples of building energy-saving and heat-insulating wall composite materials, which were placed on the parallel surface of a small room. An 800W heat source was installed 30cm away from the sample. Two thermocouples were placed at the center of the small room and the center of the surface of the sample. After heating for 600s, the temperature on the outer wall of the room was recorded.

[0080] The test results are shown in Table 1:

[0081] Table 1

[0082] ;

[0083] As shown in Table 1, the building energy-saving and thermal insulation wall composite materials prepared in Examples 2-4 of this invention have excellent flame retardant, thermal insulation, and mechanical properties. A comparison between Comparative Example 1 and Example 4 shows that this invention forms carbon particles on the surface of diatomaceous earth through glucose carbonization. Compared with the unmodified diatomaceous earth, the carbon particle-modified diatomaceous earth forms a porous microstructure with significantly increased specific surface area and pore volume, thus exhibiting better load-bearing capacity and thermal insulation capabilities. A comparison between Comparative Example 2 and Example 4 shows that grafting flame retardants onto surface-modified diatomaceous earth-based phase change materials results in a synergistic effect between the flame-retardant nitrogen and silicon elements in the flame retardant and diatomaceous earth, exhibiting excellent flame retardant properties. The rigid structure of biphenyl in the flame retardant improves the mechanical properties of the functionally modified diatomaceous earth-based phase change material. During combustion, at high temperatures, the rigidity of the biphenyl structure also helps stabilize the char layer and improve its quality. The cross-linked structure formed by the ring-opening polymerization of oxazine rings stabilizes the char layer and enhances its density. Together, these factors reduce heat and smoke release. Effectively preventing the spread of oxygen and heat, and reducing the generation and diffusion of flammable gases, the functionally modified diatomaceous earth-based phase change material possesses excellent flame retardant and mechanical properties. A comparison of Comparative Example 3 and Example 4 shows that by sequentially coating flame-retardant polysiloxane and nano-silica onto expanded polystyrene particles using mechanical stirring, a double-layer coated expanded polystyrene particle is obtained. The flame-retardant polysiloxane of this invention can act as both a flame retardant and a binder, firmly adhering to the expanded polystyrene particles. Furthermore, the adhesiveness of the flame-retardant polysiloxane and its hydroxyl groups facilitate the adsorption of nano-silica, thereby achieving nano-silica coating. Depositing nano-silica onto expanded polystyrene particles not only improves the flame retardant properties of the double-layer coated expanded polystyrene particles but also allows the nano-silica to react with calcium oxide, improving the interfacial compatibility between the double-layer coated expanded polystyrene particles and the inorganic matrix, thus improving the overall performance of the building energy-saving and thermal insulation wall composite material.

[0084] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite material for energy-saving and thermally insulated building walls, characterized in that, Includes the following steps: Step 1: Load eutectic hydrated salt into modified diatomite to obtain diatomite-based phase change material; modify the diatomite-based phase change material with 3-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain surface-modified diatomite-based phase change material. Step 2: 4,4'-dihydroxybiphenyl, paraformaldehyde and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane are reacted to obtain a flame retardant; the surface-modified diatomaceous earth-based phase change material is modified by the flame retardant to obtain a functionally modified diatomaceous earth-based phase change material. Step 3: Mix microsilica powder, functional modified diatomaceous earth-based phase change material, calcium oxide, double-coated expanded polystyrene particles, polycarboxylate-based high-performance water-reducing agent, and deionized water in a certain proportion to obtain a mixture; place the mixture in a mold, compress it, let it stand, and demold it to obtain a building energy-saving and heat-insulating wall composite material. In step one, the preparation method of the surface-modified diatomaceous earth-based phase change material is as follows: Disodium hydrogen phosphate dodecahydrate, sodium carbonate decahydrate, and deionized water were mixed in a mass ratio of 6:4:(6.7-10) and stirred at 55-65℃ until completely dissolved to obtain a eutectic hydrated salt. Modified diatomaceous earth was mixed with the eutectic hydrated salt in a mass ratio of (25-40):(60-75) and stirred at 58-62℃ for 20-40 min. After purification, a diatomaceous earth-based phase change material was obtained. 25wt% ammonia, deionized water, and ethanol were mixed in a volume ratio of 0.7:10:30, then diatomaceous earth-based phase change material was added, and the mixture was stirred. 3-(2,3-epoxypropoxy)propyltrimethoxysilane was then added, and the mixture was reacted at 55-65℃ for 1.5-2.5 h. After purification, surface-modified diatomaceous earth-based phase change material was obtained. The volume ratio of 25wt% ammonia to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 7:0.2, and the mass ratio of diatomaceous earth-based phase change material to 3-(2,3-epoxypropoxy)propyltrimethoxysilane was 5:(0.2-0.6). In step one, the method for preparing the modified diatomaceous earth is as follows: Glucose and deionized water were mixed at a mass ratio of 1:10 and stirred at 28-32℃ for 20-40 min to obtain a glucose solution. Pre-dried diatomaceous earth was mixed with the glucose solution at a mass ratio of (5-10):(55-110) and stirred at 28-32℃ at a speed of 300-400 r / min for 4-6 h. The mixture was then vacuum filtered and dried to obtain a precursor. The precursor was heated to 300-400℃ at a rate of 5℃ / min in a nitrogen atmosphere and held for 100-150 min to obtain modified diatomaceous earth.

2. The preparation method of the building energy-saving and thermal insulation wall composite material according to claim 1, characterized in that, In step two, the method for preparing the flame retardant is as follows: 4,4'-dihydroxybiphenyl, paraformaldehyde, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were added to N,N-dimethylformamide and reacted at 85-95°C for 1.5-2.5 h under a nitrogen atmosphere to obtain a flame retardant; wherein the mass ratio of 4,4'-dihydroxybiphenyl, paraformaldehyde, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and N,N-dimethylformamide was (13.9-27.9):(9-18):(18.6-37.2):(150-250).

3. The preparation method of the building energy-saving and thermal insulation wall composite material according to claim 1, characterized in that, In step two, the preparation method of the functionally modified diatomaceous earth-based phase change material is as follows: Surface-modified diatomaceous earth-based phase change material was added to N,N-dimethylformamide and stirred. Then, a flame retardant was added, and the mixture was reacted at 75-85℃ for 16-20 hours. After purification, functionally modified diatomaceous earth-based phase change material was obtained. The mass ratio of the surface-modified diatomaceous earth-based phase change material, N,N-dimethylformamide, and flame retardant was (10-15):(200-300):(12.4-18.6).

4. The preparation method of the building energy-saving and thermal insulation wall composite material according to claim 1, characterized in that, In step three, the contents of each component in the mixture, by weight, are as follows: 132-168 parts of microsilica powder, 66-84 parts of functionally modified diatomaceous earth-based phase change material, 85-105 parts of calcium oxide, 14.3-18.5 parts of double-coated expanded polystyrene particles, 3.8-4.6 parts of polycarboxylate-based high-performance water-reducing agent, and 92.1-113.7 parts of deionized water.

5. The method for preparing the building energy-saving and thermal insulation wall composite material according to claim 1, characterized in that, In step three, the molding conditions are: temperature 120-150℃, pressure 2.9-3.3MPa; and the settling time is 2-3h.

6. The method for preparing the building energy-saving and thermal insulation wall composite material according to claim 1, characterized in that, In step three, the method for preparing the double-layer coated expanded polystyrene particles includes the following steps: Step S1: In a nitrogen atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to toluene and heated to 90-100℃. Then, 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added and reacted for 5-7 hours. After evaporation, deionized water and ethanol are added, and the mixture is heated to 75-85℃ and maintained for 4.5-5.5 hours. After evaporation, flame-retardant polysiloxane is obtained. Step S2: Add expanded polystyrene particles to flame-retardant polysiloxane and stir at 23-25℃ for 1-2 hours. Then add nano-silica and continue stirring for 1-2 hours. Cure the treated expanded polystyrene particles at 70-80℃ for 30-60 minutes to obtain double-coated expanded polystyrene particles. The mass ratio of expanded polystyrene particles, flame-retardant polysiloxane, and nano-silica is (10-20):(2-4):(4-10).

7. The method for preparing the building energy-saving and thermal insulation wall composite material according to claim 6, characterized in that, In step S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, toluene, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, deionized water and ethanol is (25-50):(30-50):(10.5-21):(30-50):(40-66).

8. A building energy-saving and heat-insulating wall composite material prepared by the preparation method of the building energy-saving and heat-insulating wall composite material as described in any one of claims 1-7.

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