CN104231798A - Modified silicon dioxide aerogel microsphere thermal-insulation coating - Google Patents

Abstract

This paper discloses a heat-insulating coating using hydrophobic silica airgel microspheres as heat-insulating fillers. The main steps include first preparing hydrophobic silica airgel microspheres, and then preparing Mixing airgel microspheres with polymer emulsions to prepare thermal insulation coatings. Hydrophobic modification of silica airgel microspheres includes two methods, one is to modify silica wet gel microspheres with halogenated alkanes, and the other is to add water to the mixed solution during the sol preparation stage. Add alkoxysilanes, silazanes or siloxanes. Surfactants are added during coating preparation, which is beneficial to increase the compatibility between hydrophobic silica airgel microspheres and polymer emulsions, improve the dispersibility of microspheres in coatings, thereby improving the quality of coatings and improving the coating quality. thermal insulation performance.

Description

Modified silica airgel microsphere thermal insulation coating

technical field

The invention relates to a novel heat-insulating paint which uses hydrophobic silicon dioxide airgel microspheres as functional fillers. Silica airgel microsphere is a porous amorphous material with an irregular three-dimensional network skeleton structure. The thermal insulation coating prepared with it as the main filler is light and environmentally friendly, has low density and good thermal insulation. The present invention can be widely used in thermal insulation of inner and outer walls and roof surfaces of public buildings such as residential buildings, schools, hospitals, factories, etc., thermal expansion damage protection of large-volume buildings or facilities such as bridges and dams, and protection of ships, trains, buses, etc. The protection of the top sunshine surface and many other fields.

Background technique

Thermal insulation coatings can improve the working environment and reduce energy consumption by preventing heat conduction and reducing the temperature of the coating and the internal environment. Traditional thermal insulation coatings usually use functional fillers as aggregates, rely on adhesives to bond them together, and directly form a protective layer on the surface of equipment or walls to achieve the effect of thermal insulation. Thermal insulation materials commonly used as functional fillers include volcanic ash glass, white jade, basalt, sepiolite, bentonite, perlite, expanded vermiculite, calcium silicate, etc. These materials are high temperature resistant, flame retardant, and have high compressive strength. However, they have strong hygroscopicity, large expansion rate, and poor weather resistance. The coating with them as the main filler has a large shrinkage rate and poor crack resistance. In order to form a stable heat preservation system, sometimes it is necessary to set up a waterproof layer and an outer protective layer.

Silica airgel microsphere is a new type of nanoporous material with controllable structure, its porosity is 80%-99%, the specific surface area is as high as 800-1000m ² ·g ^-1 , and the average pore diameter is 1-50nm. It has the advantages of low thermal expansion coefficient, anti-oxidation, corrosion resistance, good stability, etc. Among them, the extremely low thermal conductivity is the most remarkable feature of silica airgel microspheres. The thermal conductivity of commonly used thermal insulation materials can reach as low as 0.045W/m·k, but the thermal conductivity of silica airgel microspheres can reach 0.01W/m·k, so the use of silica airgel microspheres as fillers Thermal insulation coatings will greatly improve the thermal insulation performance of thermal insulation coatings.

Usually prepared silica airgel microspheres are hydrophilic, and the surface contains a large number of hydroxyl groups, which makes them easy to absorb moisture in the air, breaks up when encountering water, and also increases the thermal conductivity. The thermal insulation coating prepared from this airgel microsphere has strong hygroscopicity and poor weather resistance. As time goes by, the thermal conductivity of the coating increases and the thermal insulation performance drops sharply.

In order to improve the thermal insulation performance of the coating and increase the service life of the coating, the silica airgel microspheres must be hydrophobically modified. The commonly used modification method at present is to add modifiers during the preparation of silica airgel microspheres. Commonly used modifiers include trimethylchlorosilane, methyltrimethoxysilane, hexamethyldisilazane, hexamethyldisilazane, etc. Most of these modifiers have alkyl, aromatic hydrocarbon or alkyl Hydrophobic groups such as oxygen groups are used to modify the silica airgel microspheres by introducing hydrophobic groups to replace the hydroxyl groups on the surface of the microspheres.

Traditional paints include oil-based paints and water-based paints. Oil-based paints usually contain many organic solvents as dispersion media, such as acetone, formaldehyde, etc. These small molecular substances enter the interior of the silica airgel microspheres or adsorb on the surface of the airgel microspheres, which will lead to a decrease in the thermal conductivity of the microspheres. rise. Water-based paints use water as a solvent or dispersion medium, and at the same time doped polymers to make polymer emulsions. As film-forming substances, they are very suitable as binders for silica airgel microspheres. At the same time, water-based paints Green and environmental protection is the direction of the future development of thermal insulation coatings.

The modified silica airgel microspheres have strong hydrophobicity and high surface tension. After adding the polymer emulsion, mutual repulsion of the interface will inevitably occur, and at the same time, it is difficult for the microspheres to form a uniform dispersion in the coating. , thereby affecting the thermal insulation performance of the coating. In order to solve this problem, an effective way is to add surfactants to the coating. Surfactants are molecules made up of two distinct types of particles. The molecular structure is amphiphilic, one end contains a lipophilic group, and the other end contains a hydrophilic group. It can be oriented in the solution, so that the surface tension of the substance in the solution is significantly reduced. Adding a very small amount of surfactant to the coating can significantly improve the interfacial compatibility between the silica airgel microspheres and the polymer binder, prevent aggregation between the microspheres, and greatly improve the quality of the coating.

In the present invention, the silicon dioxide airgel microsphere uses a modifying agent to carry out hydrophobic modification on the wet gel to obtain completely hydrophobic silicon dioxide airgel micron-sized balls. The thermal insulation coating prepared with this hydrophobically modified silica airgel microsphere as filler has weak hygroscopicity, good weather resistance and long service life. The interface state and dispersion of the microspheres in the coating reduce the thermal conductivity of the thermal insulation coating to 0.05W/m·k, which is better than similar products in the market.

Contents of the invention

The invention provides a new type of heat-insulating coating using hydrophobically modified silica airgel microspheres as heat-insulating fillers. This coating is mainly composed of polymer binder, silica airgel microspheres, additives At the same time, surfactants are added to mix and prepare, the dispersion stability is good, the thermal conductivity is low, and it has the characteristics of environmental protection and energy saving.

The technical scheme adopted in the present invention is:

Mix the selected silicon source with absolute ethanol and deionized water and stir evenly, then add acid as a catalyst, stir to obtain a mixed solution, place the mixed solution in a water bath, and keep it warm for a period of time to obtain a silica sol; The silica sol is sprayed into the oil phase through an atomizer, and continuous stirring is ensured during the atomization process. Via an atomizer, silica sol is injected into the oil in the form of small droplets. In order to ensure that the obtained wet gel microspheres are evenly distributed, the volume of the sol must not exceed 1/5 of the volume of the oil phase. After atomization was completed, ammonia water was added to the mixed solution, and aged at room temperature for two days to obtain silica wet gel microspheres. Filter the silica wet gel microspheres, filter out the oil phase, replace the residual oil phase and organic impurities with n-hexane, and then replace the n-hexane with absolute ethanol to obtain pure silica wet gel microspheres; The modifier performs hydrophobic treatment on the wet gel; adds a mixed solution of deionized water and absolute ethanol to the wet gel microspheres after hydrophobic treatment to clean the modified impurity ions; Add absolute ethanol to replace the deionized water; dry the wet gel microspheres.

Mix surfactant and polymer emulsion, add additives, stir evenly, add dry silica airgel microspheres to the mixture, stir, adjust viscosity, solidify and dry, and obtain silica airgel heat insulation coating.

The modifying agent used in the above-mentioned preparation of silica airgel is halosilane, and some types are listed as follows:

a. X ₃ Si(C _n H _2n+1 ) and X ₃ Si(C _n H _2n-1 ) type halogenated organosilanes, X=Cl, Br, n=1-20.

b. X ₂ (R')Si(C _n H _2n+1 ) type and X ₂ (R')Si (C _n H _2n-1 ) type haloorganosilane, X=Cl, Br, R'=such as Such as methyl, ethyl, n-propyl, butyl alkyl or cycloalkyl, n=1-20.

c. X (R') ₂ Si (C _n H _2n+1 ) type and X (R') ₂ Si (C _n H _2n-1 ) type haloorganosilane, X=Cl, Br, R'=such as Such as methyl, ethyl, n-propyl, butyl alkyl or cycloalkyl, n=1-20.

d. X ₃ Si(CH ₂ )m-R' type haloorganosilane, X=Cl, Br, m=0.1-20, R'=methyl, aryl (such as -C ₆ H ₅ , substituted benzene base), -C ₄ F ₉ , -OCF ₂ -CHF-CF ₃ , -C ₆ F ₁₃ , -O-CF ₂ -CHF ₂ , -NH ₂ , -N ₃ , -SCN, -CH=CH ₂ , -NH-CH ₂ -CH ₂ -NH ₂ , -N-(CH ₂ -CH ₂ -NH ₂ ) ₂ , -OOC(CH ₃ )C=CH ₂ , -OCH ₂ -CH(O)CH ₂ , - NH-CO-N-CO-(CH ₂ ), -NH-COO-CH ₃ , -NH-COO-CH ₂ -CH ₃ , NH-(NH ₂ ) ₃ Si(OR) ₃ , -S _X -( CH ₂ ) ₃ Si(OR) ₃ , -SH

e. (R)X ₂ Si(CH ₂ ) _m - R' type haloorganosilane, X=Cl, Br, R=alkyl such as methyl, ethyl, propyl, m=0.1-20, R = methyl, aryl (eg -C ₆ H ₅ , substituted phenyl), -C ₄ F ₉ , -OCF ₂ -CHF-CF ₃ , -C ₆ F ₁₃ , -O-CF ₂ -CHF ₂ , -NH ₂ , -N ₃ , -SCN, -CH=CH ₂ , -NH-CH ₂ -CH ₂ -NH ₂ , -N-(CH ₂ -CH ₂ -NH ₂ ) ₂ , -OOC(CH ₃ ) C=CH ₂ , -OCH ₂ -CH(O)CH ₂ , -NH-CO-N-CO-(CH ₂ ), -NH-COO-CH ₃ , -NH-COO-CH ₂ -CH ₃ , NH -(NH ₂ ) ₃ Si(OR) ₃ (the R group can be methyl, ethyl, propyl, butyl), -S _X -(CH ₂ ) ₃ Si(OR) ₃ (the R group Can be methyl, ethyl, propyl, butyl), -SH

f. (R) ₂ XSi(CH ₂ ) _m -R' type haloorganosilane, X=Cl, Br, m=0.1-20, R'=methyl, aryl (such as -C ₆ H ₅ , substituted phenyl), -C ₄ F ₉ , -OCF ₂ -CHF-CF ₃ , -C ₆ F ₁₃ , -O-CF ₂ -CHF ₂ , -NH ₂ , -N ₃ , -SCN, -CH=CH ₂ , -NH-CH ₂ -CH ₂ -NH ₂ , -N-(CH ₂ -CH ₂ -NH ₂ ) ₂ , -OOC(CH ₃ )C=CH ₂ , -OCH ₂ -CH(O)CH ₂ , -NH-CO-N-CO-(CH ₂ ), -NH-COO-CH ₃ , -NH-COO-CH ₂ -CH ₃ , NH-(NH ₂ ) ₃ Si(OR) ₃ , -S _X -(CH ₂ ) ₃ Si(OR) ₃ , -SH.

In addition, alkoxysilane, silazane or siloxane can also be used as a modifier for hydrophobic modification. The technical scheme of using this modifier to prepare airgel thermal insulation coatings is:

Mix silicon source, absolute ethanol, and deionized water in a certain proportion, stir evenly, then add acid as a catalyst, stir evenly to obtain a mixed solution, put the mixed solution in a constant temperature water bath, and after a period of time, add modified agent, stir evenly, and then keep the solution in a water bath for a period of time; spray the silica sol into the oil phase by atomization, and keep stirring during the atomization process. Through the atomizer, the silica sol is present in the oil in the form of small droplets. After the atomization is completed, add ammonia water to the mixed solution of sol and oil, and age for several days to obtain silica wet gel microspheres; filter off the excess oil phase in the mixed solution, and replace the residual oil and organic impurities with n-hexane , and then replace n-hexane with absolute ethanol to obtain pure silica wet gel microspheres, and dry the wet gel microspheres.

Add additives and surfactants to the polymer emulsion, stir evenly, add dry silica airgel microspheres to the mixed solution, stir, adjust viscosity, cure and dry, and obtain silica airgel thermal insulation coating .

These modifiers can be used alone or in combination, and some of their types are as follows:

a. Organosilanes of the (RO) ₃ Si(C _n H _2n+1 ) and (RO) ₃ Si(C _n H _2n-1 ) type, R = such as e.g. methyl, ethyl, n-propyl, isopropyl Base, butyl silane, n=1-20

b. Organosilanes of type R' _x (RO ₎ y Si(C _n H _2n+1 ) and (RO) ₃ Si(C _n H _2n+1 ), R = such as for example methyl, ethyl, n-propyl , isopropyl, butyl silane, R'=such as methyl, ethyl, n-propyl, isopropyl, butyl silane or cycloalkyl, n=1-20, x+y=3, or x=1.2 or y=1.2

c. (RO) ₃ Si(CH ₂ ) _m -R' type organosilane, R=alkyl such as methyl, ethyl, propyl, m=0.1-20, R'=methyl, aryl (such as -C ₆ H ₅ , substituted phenyl), -C ₄ F ₉ , -OCF ₂ -CHF-CF ₃ , -C ₆ F ₁₃ , -O-CF ₂ -CHF ₂ , -NH ₂ , -N ₃ , -SCN, -CH=CH ₂ , -NH-CH ₂ -CH ₂ -NH ₂ , -N-(CH ₂ -CH ₂ -NH ₂ ) ₂ , -OOC(CH ₃ )C=CH ₂ , -OCH ₂ -CH(O)CH ₂ , -NH-CO-N-CO-(CH ₂ ), -NH-COO-CH ₃ , -NH-COO-CH ₂ -CH ₃ , NH-(NH ₂ ) ₃ Si( OR) ₃ , -S _X -(CH ₂ ) ₃ Si(OR) ₃ , -SH, -NR'R''R'''(R'=alkyl,aryl;R''=H, alkyl , aryl; R'''= H, alkyl, aryl, benzyl)

d. R'R ₂ Si-N-SiR ₂ (H)R' type silazane, R=alkyl, vinyl, aryl, R'=alkyl, vinyl, aryl

e. Cyclic polysilazanes of D3, D4, and D5 types, wherein D3, D4, and D5 are cyclic polysiloxanes with 3, 4, and 5 -O-Si(CH ₃ ) ₂ -types.

The silicon sources used in the preparation of the silica sol in the present invention are silicate esters (including ethyl orthosilicate, methyl orthosilicate, etc.), silica sol and water glass. The used acid includes nitric acid, hydrochloric acid, hydrofluoric acid, oxalic acid and the like or a mixture of several of them.

Silicon source used in the present invention, deionized water, the mass fraction of dehydrated alcohol are respectively 10%～60%, 8%～72%, 25%～82%, acid is the catalyzer of tetraethyl orthosilicate hydrolysis, consumption is 1‰-4‰ of the mixed solution volume, the ammonia water is the gel catalyst, and the ammonia water content is 3‰-10‰ of the mixed solution volume. The water bath is kept at 30°C to 90°C, and the water bath time is 0 to 6 days.

The oil phase used in the present invention can be selected from general vegetable blending oil, silicone oil, etc., and has a certain viscosity.

The rotation speed used in the atomization of the present invention is 300r/min-2000r/min.

The present invention cleans the residual oil phase and organic impurities, the amount of n-hexane is not less than 1/10 of the volume of the cleaning solution, and the cleaning is performed 2 to 12 times a day for 1 to 8 days. Wash n-hexane with absolute ethanol, the amount of ethanol is not less than 1/10 of the n-hexane to be cleaned, 2-12 times a day for 1-8 days.

The content of modifier used in the present invention is 40%-180% of the volume of the selected silicon source.

When the present invention adopts halosilane as modifier, the halogen ion after modifier treatment is cleaned with the mixed solution of deionized water and deionized water, the volume ratio of absolute ethanol and deionized water is 1:1～1:10, 1 Clean once every 5 days, and clean 2 to 7 times in total. After cleaning, use silver nitrate solution for detection. If there is precipitation, continue cleaning.

The tensio-active agent that the present invention adopts mainly plays following effect:

1. Promote the wetting of the polymer emulsion to the hydrophobic silica airgel microspheres and improve the interface condition;

2. Improve the dispersion of hydrophobic silica airgel microspheres in the coating;

3. Improve the storage stability of paint and reduce waste.

Surfactants used in the present invention are divided into polymer electrolytes according to molecular structure, such as anionic polycarboxylic acid, sodium hexametaphosphate, etc., inorganic polymeric alkali salts, such as polycarboxylate ammonium salt, dipolyisobutylene sodium maleate Salt, etc., polymers, such as BYK-154 (acrylic acid polymer), BYK-181 (polymer block copolymer), etc.

The binder used in the present invention is a polymer emulsion, such as epoxy resin, pure acrylic emulsion, polyurethane, etc., and the coating additives used are all commercially available. The polymer emulsion accounts for 10% to 95% of the total volume of the coating, the volume fraction of airgel microspheres accounts for 5% to 90%, the content of surfactant is 0.1‰ to 5‰ of the total mass of the coating, and the sum of other additives is not More than 2‰ of paint quality.

The beneficial effects of the heat-insulating coating prepared by the present invention:

Silica airgel microspheres are lightweight thermal insulation materials, and their thermal conductivity can reach 0.01W/m·k. The coatings using it as thermal insulation fillers have good thermal insulation properties; the hydrophobic silica airgel microspheres are resistant to heat Corrosion, anti-oxidation, and strong water resistance, the thermal insulation coating prepared has poor hygroscopicity, good washing resistance, weather resistance, and long service life; the addition of surface activity improves the interface state of the coating, and hydrophobic silica airgel microspheres The dispersion state in the coating improves the physical properties and thermal insulation performance of the coating.

Detailed ways

Example 1

(1) Preparation of silica sol: use 208.33g of tetraethyl orthosilicate as the silicon source, mix ethyl orthosilicate with 92.14g of absolute ethanol, and stir evenly to obtain a mixed solution ①; another 92.14g of Mix water ethanol with 72g deionized water, then add 1ml of 2w% nitric acid, stir evenly to obtain a mixed solution ②, mix the mixed solutions ① and ② and stir for about 5 minutes to obtain the final mixed solution, place the mixed solution in In a 60°C water bath, keep warm for two hours;

(2) Preparation of silica wet gel microspheres: Silica sol was introduced into the nebulizer through the drainage tube, and the 0.1mm atomizer nozzle was immersed in 500ml peanut oil. The peanut oil was kept stirring, and the atomizer switch was turned on. During the atomization process, a stirring speed of 800 r/min was maintained. Through an atomizer, the silica sol gel is injected into the peanut oil in the form of small droplets. The volume of the sol infused with peanut oil was 100 ml. After the atomization is completed, add 3ml of 20w% ammonia water to the mixed solution of sol and peanut oil, and age at room temperature for two days to obtain silica wet gel microspheres;

(3) Hydrophobic modification of wet gel microspheres: pass silica wet gel microspheres through a filter funnel, filter out peanut oil, and replace residual peanut oil and organic impurities with 150ml of n-hexane, 3 times a day for a total of 3 days , and then replace n-hexane with 100ml of absolute ethanol, 3 times a day, for a total of 3 days to obtain pure silica wet gel microspheres; use trimethylchlorosilane (analytical pure) to hydrophobically treat the wet gel, The volume ratio of trimethylchlorosilane to wet gel is 1:5, treated once every two days, and modified for 4 days;

(4) Drying of wet gel microspheres: Add a mixed solution of deionized water and absolute ethanol to the wet gel microspheres after hydrophobic treatment, clean the chloride ions after trimethylchlorosilane treatment, deionized water The volume ratio with absolute ethanol is 1:1. Wash 3 times a day for 3 days. Then use 6w% silver nitrate solution to detect whether there are chloride ions, if there is precipitation, continue to wash. Make sure that the chloride ions are cleaned, add absolute ethanol to the wet gel microspheres, and replace them with deionized water, 3 times a day, for a total of 3 days. Silica wet gel microspheres are dried at normal temperature;

(5) Preparation of silica airgel microsphere thermal insulation coating: add dispersant, wetting agent, defoamer, leveling agent and other additives to 20g of pure acrylic emulsion, and then add anionic surfactant alkyl Sodium benzenesulfonate, stirred evenly, added 6 g of modified silica airgel microspheres to the mixed solution, stirred, added a thickener to adjust viscosity, and obtained silica airgel heat-insulating coating. The additive content is 0.01g, and the surfactant content is 0.01g;

(6) Use the Hot disk TPS 2500S thermal conductivity measuring instrument to test the thermal conductivity. The thermal conductivity of the silica airgel microsphere thermal insulation coating is 0.04866 W/(m K).

Example 2

(1) Preparation of silica sol: Mix absolute ethanol and deionized water in a certain proportion, and then add tetraethyl orthosilicate to the mixture, in which ethyl orthosilicate, deionized water, and absolute ethanol The masses were 208.33g, 72g, and 322.49g, and then 1ml of 2w% nitric acid was added and stirred evenly to obtain the final mixed solution. The mixed solution was placed in a 60°C water bath and kept warm for two hours;

(2) Preparation of silica wet gel microspheres: Silica sol is introduced into the atomizer through the drainage tube, immerse the 0.1mm atomizer nozzle in 500ml of silicone oil, keep the silicone oil in a stirring state, and turn on the switch of the atomizer. During the atomization process, a stirring speed of 900 r/min was maintained. Through the atomizer, the silica sol exists in the silicone oil in the form of small droplets. The volume of the sol injected with silicone oil was 100ml. After the atomization is completed, add 3ml of 20w% ammonia water to the mixed solution of sol and silicone oil, and age at room temperature for two days to obtain silica wet gel microspheres;

(3) Hydrophobic modification of wet gel microspheres: filter, filter out the silicone oil in the mixture, replace the residual silicone oil and organic impurities with n-hexane, 3 times a day, for a total of 3 days, and then replace the n-hexane with absolute ethanol alkane, 3 times a day, for a total of 3 days, to obtain pure silica wet gel microspheres; use trimethylchlorosilane (analytical pure) to hydrophobically treat the wet gel, trimethylchlorosilane and wet gel The volume ratio is 1:5, treated once every two days, and modified for 4 days;

(4) Drying of wet gel microspheres: Add a mixed solution of deionized water and absolute ethanol to the wet gel microspheres after hydrophobic treatment, clean the chloride ions after trimethylchlorosilane treatment, deionized water Both the volume of the solution and the volume of absolute ethanol are 400ml to wash 3 times a day for 3 days. Then use 6w% silver nitrate solution to detect whether there are chloride ions, if there is precipitation, continue to wash. After ensuring that the chloride ions are cleaned, add absolute ethanol to the wet gel microspheres to replace the deionized water. The amount of absolute ethanol is 150ml, 3 times a day, for a total of 3 days. The wet gel microspheres are dried by a supercritical carbon dioxide device;

(5) Preparation of airgel thermal insulation coating: Mix cetyltrimethylammonium chloride (bromide) (cationic surfactant 1631) with dispersant, wetting agent, defoamer, leveling agent and other auxiliary agents Add the surfactant to 20g of epoxy resin emulsion, the content of surfactant and auxiliary agent is 0.01g, stir evenly, add 6g of modified silica airgel microspheres to the mixed solution, stir, add 0.01g thickener to adjust Viscosity, stirring for 3 minutes, adding 2g of curing agent, stirring, drying and curing at room temperature for three days to obtain silica airgel thermal insulation coating;

(6) Use the Hot disk TPS 2500S thermal conductivity measuring instrument to detect the thermal conductivity. The thermal conductivity of the silica airgel microsphere thermal insulation coating is 0.06098 W/(m·K).

Example 3

(1) Preparation of silica sol: Mix 460.7g of absolute ethanol with 72g of deionized water, then add 288.33g of ethyl orthosilicate to the mixture, then add 1ml of 2w% nitric acid, stir well, Put the mixed solution in a 60°C water bath, add 118.62g of dimethyldiethoxysilane to the mixed solution after 8 minutes, and keep the mixed solution for two hours;

(2) Preparation of silica wet gel microspheres: Silica sol was introduced into the nebulizer through a drainage tube, and a 0.3mm nebulizer nozzle was used. Use peanut oil as the oil phase, keep the rotation speed of the peanut oil at 800r/min, and spray the silica sol into the peanut oil. During the atomization process, a stirring speed of 800 r/min was maintained. The volume of sol sprayed into 500ml peanut oil is 100ml. After the atomization is completed, add 3ml of 20w% ammonia water to the mixture of sol and peanut oil, and age at room temperature for two days to obtain silica wet gel microspheres;

(3) Drying of wet gel microspheres: filter, filter out the peanut oil in the mixture, replace the residual oil and organic impurities with n-hexane, 3 times a day, for a total of 3 days, and then replace n-hexane with absolute ethanol, 3 times a day, a total of 3 days of replacement, to obtain pure silica wet gel microspheres. The wet gel microspheres are dried by a supercritical ethanol device;

(4) Preparation of airgel thermal insulation coating: use 0.015g fatty acid methyl ester polyoxyethylene ether FMEE as surfactant, mix it with 0.01g dispersant, wetting agent, defoamer, leveling agent, etc. Add additives to 20g of epoxy resin emulsion, stir evenly, then add 5g of modified silica airgel microspheres, stir, add 0.01g thickener to adjust viscosity, stir for 3 minutes, dry and solidify at room temperature for three days , to obtain silica airgel thermal insulation coating;

(5) The thermal conductivity was tested with the Hot disk TPS 2500S thermal conductivity measuring instrument, and the thermal conductivity of the silica airgel microsphere thermal insulation coating was 0.06980 W/(m·K). the

Claims (8)

1. hydrophobic silica aerogel thermal insulating coating, primarily of polymer emulsion, hydrophobic silica aerogel microballoon and auxiliary agent composition, with the addition of tensio-active agent simultaneously.

2. hydrophobic silica aerogel thermal insulating coating according to claim 1, it is characterized in that a large amount of hydrophobic grouping is all contained in the surface of the silica aerosil microballoon adopted and inside, whole microballoon has complete hydrophobicity.

3. hydrophobic silica aerogel thermal insulating coating according to claim 1, key is the hydrophobically modified to silica aerosil microballoon, the present invention proposes two kinds of methods, first the first prepare silica wet gel microballoon, then be that properties-correcting agent carries out hydrophobically modified to silica wet gel microballoon with halogenated silanes, the second prepares the initial stage at colloidal sol, with the preparation for properties-correcting agent participation colloidal sol of organoalkoxysilane, silazane or siloxanes, finally obtain hydrophobic silica aerosil microballoon.

4. hydrophobic silica aerogel according to claim 3, when it is characterized in that silica aerosil microballoon modification, properties-correcting agent used is one or more in halogenated silanes, organoalkoxysilane, silazane or siloxanes.

5. hydrophobic silica aerogel according to claim 3, it is characterized in that halogenated silanes uses after silica wet gel microballoon completes, organoalkoxysilane, silazane or siloxanes use in silicon dioxide gel preparation process.

6. hydrophobic silica aerogel thermal insulating coating according to claim 1, is characterized in that have employed tensio-active agent.

7. tensio-active agent according to claim 6, is characterized in that tensio-active agent is polymer dielectric class, one or more in inorganic polymeric alkali salt class and high molecular polymer class.

8. hydrophobic silica aerogel thermal insulating coating according to claim 1, it is characterized in that polymer emulsion accounts for 10% ~ 95% of coating cumulative volume, the volume fraction of silica aerosil microballoon accounts for 5% ~ 90%, surfactant content is 0.1 ‰ ~ 5 ‰ of coating total mass, and other auxiliary agent sums are no more than 2 ‰ of coating quality.