Preparation method of heat-shielding flame-retardant composite material

Abstract

The invention belongs to the technical field of building materials, and discloses a preparation method of a heat-shielding flame-retardant composite material, and the method comprises the following steps: preparing a novel core-shell structure acrylate elastic emulsion with excellent performance, and synthesizing a microencapsulated intumescent flame retardant M (Aamp; and P) preparing the heat-shielding flame-retardant composite material. On the basis of environmental protection and flame retardance, the heat-shielding flame-retardant composite material is prepared, and the material has heat insulation and heat preservation effects; the heat-shielding flame-retardant composite material prepared by the method disclosed by the invention not only can achieve the effects of heat insulation, heat preservation and energy conservation, but also can enhance the fireproof and flame-retardant properties of the heat-insulating composite material. The heat-shielding flame-retardant composite material has the characteristics of economy and convenience in use, integrates heat insulation, heat preservation, fire prevention and flame retardance, solves the problem of fire prevention and flame retardance of a heat-preservation material, and has a wide development prospect.

Description

Technical Field

[0001] The present application relates to the technical field of building materials, and more specifically, to a method for preparing a heat shielding and flame retardant composite material. Background Art

[0002] Energy shortage is an indisputable fact at present, and building energy consumption is generated with people's basic needs such as heating and air conditioning, as well as entertainment and work. Building energy conservation is a major issue related to the national economy and people's livelihood, and is an important part of energy conservation. my country's Energy Conservation Law has included building energy conservation in its provisions. At present, the external wall insulation system is one of the main methods of building energy conservation. Putting on a "thermal coat" for the building will save a lot of energy - especially for the renovation of old houses. Therefore, the development of building thermal insulation coatings has great practical significance. Building thermal insulation coatings have the advantages of economy, ease of use and good thermal insulation effect, and are increasingly favored by people, with broad development prospects. Based on this, a new type of functional composite material - heat shielding composite material came into being, which makes the composite material turn to the direction of environmental protection and energy saving.

[0003] However, since traditional building exterior wall insulation materials do not take their fire retardant properties into consideration, the fire retardant properties of building exterior wall insulation materials are poor, and fires are prone to occur during construction and use. Therefore, the fire retardant properties of building exterior wall insulation materials have become one of the key directions of public safety research. It can be seen that the flame retardant and fireproof problems of heat shielding materials have become a bottleneck restricting their development. On the other hand, traditional flame retardant composite materials do not have heat shielding functions, making them ineffective for exterior wall insulation. Therefore, it is particularly important to develop a new type of heat shielding flame retardant composite material, which can not only play the role of heat insulation and energy saving, but also enhance the fire retardant properties of the thermal insulation composite.

[0004] In view of this, we propose a method for preparing a heat shielding flame retardant composite material. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] The purpose of the present application is to provide a method for preparing a heat-shielding flame-retardant composite material, which solves the technical problems raised in the above-mentioned background technology, and achieves the technical effect of not only achieving the effect of heat insulation, heat preservation and energy saving, but also enhancing the fire retardant performance of the thermal insulation composite, thereby solving the problem of poor fire retardancy of current exterior wall insulation materials for buildings.

[0007] 2. Technical solution

[0008] The technical solution of the present application provides a method for preparing a heat shielding flame retardant composite material, comprising the following steps:

[0009] (1) Preparation of core-shell structure acrylic elastic emulsion:

[0010] Raw material preparation: 500g deionized water, 10g emulsifier, 5g pH buffer, 50g seed monomer, 3g initiator, 300g core monomer, 100g shell monomer (polymerized on the core surface formed by the core monomer to form a shell layer to improve the performance of the emulsion) and about 5-10g ammonia water.

[0011] In a four-necked flask equipped with a stirrer, a thermometer, a condenser and a dropping funnel, first add deionized water and start stirring.

[0012] Add emulsifier and pH buffer to the four-necked bottle in sequence, control the stirring speed at 300-400 rpm, and stir for 20-30 minutes to fully dissolve the emulsifier and pH buffer.

[0013] Then slowly add the seed monomer dropwise for pre-emulsification, control the dropwise addition speed at 1-2 mL / min, and keep the stirring speed at 300-400 rpm during the dropwise addition. After the dropwise addition is completed, continue stirring for 30-60 minutes to ensure that the seed monomer is fully dispersed to form a stable pre-emulsion.

[0014] Then adjust the stirring speed to 180 rpm to 200 rpm, place the four-necked bottle in a water bath, and start heating. Raise the temperature to 75°C. When the temperature reaches 75°C and the stirring speed is stable, use a dropping funnel to slowly add the prepared initiator solution, and control the dropping speed at 0.5-1 mL / min.

[0015] Closely observe the color change of the emulsion. After the emulsion turns blue, continue to stir steadily at 75°C for 0.5 to 2.5 hours to obtain the seed emulsion.

[0016] After the seed emulsion is prepared, the core monomer is added dropwise at a rate of 2-3 mL / min; and the initiator is added dropwise every half an hour, with the amount added each time being 10%-15% of the total amount of the initiator.

[0017] After the core monomer is added, the mixture composed of the shell monomer is added, and the initiator is added every half an hour, and the amount added each time is 10%-15% of the total amount of the initiator. Stirring is continued, the temperature is maintained at about 75°C, and the shell monomer addition time is controlled to be 2-3 hours, so that the shell monomer is polymerized on the surface of the core particles.

[0018] After the monomer addition is completed, the temperature is raised to 80°C and kept for 1 to 3 hours to ensure complete reaction. The temperature is lowered to below 50°C, and the pH is adjusted to 7 to 8 with ammonia water. The drop rate is controlled at 0.5-1 mL / min. Filter with a filter with a pore size of 100-200 mesh, and collect the filtered emulsion in a clean container to obtain a core-shell acrylic elastic emulsion with a soft inner and hard outer surface.

[0019] (2) Synthesis of microencapsulated intumescent flame retardant M (A&P): Add distilled water (50 ml) to a three-necked flask equipped with a stirrer and a thermometer, and start the stirring device to form a stable vortex.

[0020] Slowly add 10 grams of melamine, and after melamine is basically dissolved or evenly dispersed in distilled water, slowly drop a calculated amount of 37% formaldehyde aqueous solution (with a molar ratio of 3:1 to melamine). During the dropwise addition, pay attention to the state of the reaction solution to avoid excessive local concentration due to too fast dropwise addition, which affects the uniformity of the reaction. While stirring, adjust the pH to 8-9 with 10% Na2C03 aqueous solution. Continue stirring for a while to make the ions in the solution evenly distributed.

[0021] Turn on the heating device and raise the temperature to 80°C. The heating speed should not be too fast and should be controlled at about 1-2°C per minute to prevent the reaction from being too intense. After 1.5 hours of heat preservation reaction, the experiment is ended to obtain a transparent MF prepolymer aqueous solution. Stir continuously during the period to ensure that the reaction is fully carried out. The reaction progress can be preliminarily judged by observing the changes in the properties of the reaction liquid such as viscosity and color.

[0022] The acid source and the carbon source are mixed in a certain proportion, and the mixture of the acid source and the carbon source is dispersed in a solution such as methanol or ethanol. A magnetic stirring method is used, the rotation speed is controlled at 300-800 rpm, and the stirring time is about 30-60 minutes.

[0023] At room temperature, add an appropriate amount of MF prepolymer solution to the dispersed acid source and carbon source mixed solution (mass ratio 0.2-0.4:1). During the addition process, stir while adding to ensure thorough mixing.

[0024] The pH value of the mixed solution was adjusted to 3-4 with concentrated sulfuric acid.

[0025] Turn on the heating device, slowly heat the solution to 70-90℃, and keep it at this temperature for 1-3 hours. During the insulation process, continue to stir, and observe the changes in the transparency, color, precipitation, etc. of the solution to judge the progress of the reaction. Then stir and cool to room temperature, filter, and wash with a large amount of distilled water. After filtering, dry at 100℃ for 24 hours to obtain the flame retardant M (A&P) powder.

[0026] (3) Preparation of heat shielding flame retardant composite materials:

[0027] Initial mixing and stirring: Open the mixing tank and pour 400g of deionized water into the mixing tank. Add 5g of mildew inhibitor and stir evenly. Then add 30g of ethylene glycol and continue stirring. Add 10g of hydroxyethyl cellulose and stir until completely dissolved. Add 8g of wetting and dispersing agent and stir evenly. Add 3g of partial defoaming agent and stir for several minutes. Add 150g of titanium dioxide and 100g of homemade microencapsulated flame retardant M (A&P) in turn. Note that the addition process should be as slow as possible to avoid caking. Set the stirring speed to 800-1000r / min and stir for 20 minutes to fully mix the raw materials.

[0028] Grinding: Carefully transfer the preliminarily stirred mixture to the grinder. Set the grinding time to 1.5 hours. The grinding media of the grinder refines and disperses the solid particles in the material to improve the uniformity and stability of the slurry.

[0029] Secondary stirring and adding remaining raw materials: Place the ground slurry into a high-speed disperser, set the stirring speed to 800-1000r / min, and stir thoroughly for 15-20 minutes. Reduce the stirring speed to 200-400r / min, slowly add 20g of film-forming aid, stirring while adding. Then add 200g of emulsion and continue to stir evenly. Add 2g of partial defoamer and stir for several minutes to eliminate bubbles. Slowly add 2g of ammonia water and pay attention to the changes in the system. Add 10g of thickener and stir until the appropriate viscosity is reached. Finally, add 60g of thermal insulation material and stir evenly.

[0030] After all the raw materials are added and stirred evenly, the heat shielding flame retardant composite material is prepared. Finally, the heat shielding flame retardant composite material is prepared.

[0031] As an optional scheme of the present invention, the emulsifier in step (1) is an anionic emulsifier such as sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl biphenyl ether disulfonate, disodium nonylphenol polyoxyethylene ether succinic acid monoester sulfonate, and disodium succinic acid monoester sulfonate, while the nonionic emulsifier is polyethylene glycol octylphenyl ether, fatty alcohol polyoxyethylene ether, fatty acid polyethoxylated ester, fatty amine polyoxyethylene ether, etc. The total amount of emulsifier accounts for 3% to 6% of the total amount of monomers (mass fraction, the same below); the anionic to nonionic ratio is between 1:2 and 2:1. Sodium bicarbonate is selected as the pH buffer, and the amount is 0.2% to 0.5% of the total weight of the monomers to stabilize the pH value between 5 and 6. The water bath temperature is 40 to 60°C, the stirring speed is 500-1000rpm, and the stirring time is 20-60 minutes. The seed monomer is selected as a soft monomer such as ethyl acrylate, butyl acrylate, and isooctyl acrylate. The initiator is selected from persulfates such as ammonium persulfate and potassium persulfate. The shell monomer is selected from hard monomers such as methyl acrylate, vinyl acetate, styrene, methyl methacrylate, acrylamide, etc.

[0032] As an optional solution of the present invention, in step (2), the acid source is selected from phosphoric acid, sulfuric acid, boric acid, ammonium phosphate, ammonium polyphosphate, etc.; the carbon source is selected from carbon-rich polyhydroxy compounds, such as starch, dextrin, pentaerythritol and its derivatives, etc. The ratio of the acid source to the carbon source mixture is 2:1-5:1 by mass.

[0033] As an optional solution of the present invention, the thermal insulation material in step (3) includes hollow glass microspheres, aluminum silicate fibers, asbestos fibers, expanded perlite, rock wool, glass wool, etc.

[0034] 3. Beneficial effects

[0035] One or more technical solutions provided in the technical solution of this application have at least the following technical effects or advantages:

[0036] The heat shielding flame retardant composite material prepared by the preparation method of the heat shielding flame retardant composite material of the present invention can not only play the effect of heat insulation and energy saving, but also can enhance the fire retardant performance of the heat insulation composite. The heat shielding flame retardant composite material is economical and easy to use, integrates heat insulation and fire retardant, solves the problem of fire retardant of building exterior wall insulation materials, and has broad development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a scanning electron microscope photograph of the heat shielding and flame retardant composite material prepared by the method of the present invention. DETAILED DESCRIPTION

[0038] The present application is further described in detail below in conjunction with the accompanying drawings.

[0039] Reference Figure 1 Embodiment 1: The present invention provides a method for preparing a heat shielding flame retardant composite material, comprising the following steps:

[0040] (1) Preparation of core-shell acrylic elastic emulsion: Add 0.5g NaHCO3 (0.2%-0.5%), 1g SDS (sodium dodecyl sulfate) (0.5%), 0.8g OP-10 (0.4%) and 150g deionized water (75%) into a 250ml four-necked bottle, and stir for 30min in a 50℃ water bath at 700rpm. NaHCO3 is used as a pH buffer to maintain the pH stability of the reaction system and prevent pH fluctuations from causing adverse effects on the reaction; SDS and OP-10 are used as emulsifiers to reduce surface tension and better emulsify to form a stable emulsion.

[0041] Then slowly drop 20g of acrylate seed monomer (10%) for pre-emulsification. Adjust the stirring speed to 180rpm-200rpm, raise the temperature to 75°C, and add the prepared initiator-ammonium persulfate solution after the temperature and speed are stable. After the emulsion turns blue and stabilizes for 1.5 hours, the seed emulsion is obtained.

[0042] The remaining 10 grams of core monomer (total acrylate seed monomer is 10%) are added dropwise, and the initiator is added dropwise every half an hour. 15 grams (7.5%) of a mixture consisting of methyl methacrylate: styrene shell monomer 2:1 are added dropwise, and the initiator is added dropwise every half an hour (total initiator is 0.2 grams, 0.1%). The core monomer and the shell monomer are gradually polymerized under the action of the initiator to form a core-shell structure, in which the core monomer provides softness and elasticity, and the methyl methacrylate and styrene shell monomers can provide hardness, strength and other properties for the final product.

[0043] After the monomer addition is completed, the temperature is raised to 80°C and kept for 2 hours to make the reaction more complete. The temperature is lowered to below 50°C, and the pH is adjusted to 7-8 with ammonia water to neutralize the acidic substances in the reaction system. The material is filtered to obtain a core-shell structure acrylic elastic emulsion.

[0044] (2) Add distilled water (50 ml), melamine (10 g), 37% formaldehyde aqueous solution (molar ratio to melamine is 3:1) to a 250 ml three-necked flask equipped with a stirrer and a thermometer, and adjust the pH to 8-9 with a 10% Na2C03 aqueous solution. Melamine and formaldehyde undergo polycondensation under alkaline conditions to form a melamine formaldehyde resin (MF) prepolymer. The alkaline environment is conducive to the nucleophilic addition reaction of formaldehyde to form hydroxymethyl melamine, which is a key intermediate in the subsequent polycondensation reaction. Stir, heat to 80°C, and heat for 1.5 hours before the experiment is terminated. It can promote the reaction, so that melamine and formaldehyde react fully to obtain a MF prepolymer with a certain degree of polymerization. After the reaction is completed, distilled water is used to prepare the system to 100 ml for standby use to form a transparent MF prepolymer aqueous solution.

[0045] Disperse 60g of a mixture of ammonium polyphosphate and pentaerythritol (mass ratio 3:1) in 150ml of methanol solution. Ammonium polyphosphate is an inorganic flame retardant containing phosphorus and nitrogen, which has a flame retardant effect; pentaerythritol can undergo an esterification reaction during combustion to form a carbon layer, enhancing the flame retardant effect. The combination of the two can play a synergistic flame retardant effect. The mixture of ammonium polyphosphate and pentaerythritol (mass ratio 3:1) determines the synergistic flame retardant effect of the two. Ammonium polyphosphate provides phosphorus and nitrogen elements, and pentaerythritol provides a carbon source. Different ratios will affect the formation of the carbon layer and flame retardant properties during combustion. If the proportion of pentaerythritol is increased, a denser carbon layer may be formed, but too much may affect the mechanical properties of the material; reducing it may reduce the quality of the carbon layer.

[0046] Add an appropriate amount of MF prepolymer solution (mass ratio 0.2-0.4:1) at room temperature, and adjust the pH value of the mixed solution to 3-4 with concentrated sulfuric acid. Under acidic conditions, the MF prepolymer further condenses to form a capsule shell on the surface of the mixture of ammonium polyphosphate and pentaerythritol. Under acidic conditions, the hydroxymethyl in the MF prepolymer undergoes a condensation reaction to form a polymer shell layer on the surface of the ammonium polyphosphate and pentaerythritol particles, wrapping them up to form a microcapsule structure, thereby achieving the purpose of microencapsulation.

[0047] The solution was slowly heated to 70°C and kept at this temperature for 2 hours to promote the complete polycondensation reaction and the formation of the capsule shell. Then, it was stirred and cooled to room temperature, filtered and washed with a large amount of distilled water to remove unreacted substances and impurities. After filtering, it was dried at 100°C for 24 hours to obtain the microencapsulated flame retardant M (A&P) powder. Drying can remove residual solvents and moisture.

[0048] (3) Preparation of heat shielding flame retardant composite material: deionized water (45%-60%), mildew inhibitor (1%-2%), ethylene glycol (10%-15%), hydroxyethyl cellulose (2%-5%), wetting dispersant (1%-3%), part of defoaming agent (total proportion is 0.5%-1%), titanium dioxide (10%-20%), microencapsulated flame retardant M (A&P) (15%-25%) are added into a stirring tank in sequence; the first stirring is performed;

[0049] Start the agitator, set the stirring speed to 800-1000 r / min, and set the stirring time to 20 minutes to ensure that all the raw materials are fully mixed.

[0050] Transfer the slurry after the first stirring from the stirring tank to the grinder. Turn on the grinder and grind for 1.5 hours to further refine the solid particles in the slurry to the required particle size range to ensure the uniformity and stability of the material properties.

[0051] The prepared slurry is placed in a high-speed disperser, which is turned on and stirred at 800-1000 r / min to achieve a fully dispersed state.

[0052] While maintaining stirring, adjust the speed to 200-400r / min. Add the following materials in sequence: film-forming aid (3%-10%), core-shell structure acrylic elastic emulsion (25%-40%), defoamer, ammonia water (0.5%-2%), thickener (1%-15%), hollow glass microspheres (8%-18%) and aluminum silicate fiber (6%-15%), continue stirring for a period of time to make these newly added raw materials evenly dispersed in the slurry. The stirring time can be determined according to the actual situation and is set to 40 minutes. Finally, a heat shielding flame retardant composite material is prepared.

[0053] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a heat shielding flame retardant composite material, characterized in that: The following steps are involved: S1. Preparation of core-shell structured acrylic elastic emulsion: add emulsifier, pH buffer and deionized water into a four-necked bottle, stir in a water bath for a certain period of time; slowly drop seed monomer for pre-emulsification; adjust the stirring speed to 180rpm-200rpm, raise the temperature to 75°C, and add initiator solution after stabilization; wait for the emulsion to turn blue and stabilize for 0.5-2.5 hours to obtain seed emulsion; drop the remaining core monomer and shell monomer mixture, and drop the initiator every half an hour; after the monomer addition is completed, heat to 80°C, keep warm for reaction for 1-3 hours, cool to below 50°C, adjust the pH to 7-8 with ammonia water, filter the material, and obtain a core-shell acrylic elastic emulsion with soft inside and hard outside; S2. Synthesis of microencapsulated intumescent flame retardant M (A&P): Add distilled water (50 ml), melamine (10 g), 37% formaldehyde aqueous solution (molar ratio to melamine is 3:1) to a three-necked flask equipped with a stirrer and a thermometer, and adjust the pH to 8-9 with a 10% Na2C03 aqueous solution; stir and heat to 80°C, keep warm for 1.5 hours to obtain a transparent MF prepolymer aqueous solution; disperse the mixture of the acid source and the carbon source in a methanol or ethanol solution; add an appropriate amount of MF prepolymer solution (mass ratio 0.2-0.4:1) at room temperature, and adjust the pH value of the mixed solution to 3-4 with concentrated sulfuric acid; slowly heat the solution to 70-90°C and keep warm for 1-3 hours; stir and cool to room temperature, filter and wash with a large amount of distilled water; after filtering, dry at 100°C for 24 hours to obtain flame retardant M (A&P) powder; S3. Preparation of heat-shielding flame-retardant composite materials: deionized water, mildewproof agent, ethylene glycol, hydroxyethyl cellulose, wetting dispersant, part of defoaming agent, titanium dioxide, and microencapsulated flame retardant M (A&P) are added to a stirring pot in sequence, stirred at a high speed of 800-1000 r / min for 20 minutes, and ground in a grinder for 1.5 hours; the prepared slurry is placed in a high-speed disperser and stirred thoroughly at 800-1000 r / min; and then a film-forming agent, a core-shell structured acrylic elastic emulsion, part of the defoaming agent, ammonia water, a thickener, and heat-insulating materials are added at 200-400 r / min to prepare a heat-shielding flame-retardant composite material.

2. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: In step S2: 50 ml of distilled water, 10 g of melamine and 37% formaldehyde aqueous solution are added in the following proportions, wherein the molar ratio of 37% formaldehyde aqueous solution to melamine is 3:

1.

3. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: In step S1, the emulsifier is sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, disodium nonylphenol polyoxyethylene ether succinic acid monoester sulfonate or disodium succinic acid monoester sulfonate anionic emulsifier, and the total mass ratio of the emulsifier to the total mass of the monomer is between 3% and 6%; the anionic-nonionic ratio is between 1:2 and 2:

1.

4. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: In step S1, sodium bicarbonate is selected as the pH buffer, and the amount used is 0.2% to 0.5% of the total weight of the monomers, so that the pH value is stabilized between 5 and 6.

5. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: In step S1, the water bath temperature is 40-60°C, the stirring speed is 500-1000 rpm, and the stirring time is 20-60 minutes.

6. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: In step S1, the seed monomer is a soft monomer of ethyl acrylate, butyl acrylate or isooctyl acrylate; the initiator is ammonium persulfate or potassium persulfate; and the shell monomer is a hard monomer of methyl acrylate, vinyl acetate, styrene, methyl methacrylate or acrylamide.

7. The method for preparing the heat shielding flame retardant composite material according to claim 6, characterized in that: In step S2, the ratio of the acid source to the carbon source mixture is 2:1-5:1 by mass.

8. The method for preparing the heat shielding flame retardant composite material according to claim 7, characterized in that: In step S2, the acid source is phosphoric acid, sulfuric acid, boric acid, ammonium phosphate or ammonium polyphosphate; the carbon source is a carbon-rich polyhydroxy compound.

9. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: The polyol is starch, dextrin or pentaerythritol and its derivatives.

10. The method for preparing the heat shielding flame retardant composite material according to claim 1, characterized in that: In step S3, the thermal insulation material includes hollow glass microspheres, aluminum silicate fibers, asbestos fibers, expanded perlite, rock wool or glass wool.

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