CN111732871B - Light high-heat-resistance coating and preparation method thereof - Google Patents

Abstract

The invention provides a light-weight high heat-proof coating and a preparation method thereof. The invention uses epoxy resin as matrix resin, adds high temperature resistant filler, greatly increases the service temperature of the coating, reduces the density of the coating, and obtains a light-weight and high-heat-proof coating, which can be applied to metal parts in a high-temperature working environment and composite surfaces.

Description

Light high-heat-resistance coating and preparation method thereof

Technical Field

The invention relates to the field of epoxy resin coating materials, in particular to a light high-heat-proof epoxy resin coating and a preparation method thereof.

Background

At present, the burning heat-proof coating adopts an ablation heat protection method, the self quality is lost in the ablation process, heat protection is carried out by utilizing mechanisms such as thermal blockage, melting heat absorption, radiation heat dissipation, chemical reaction heat absorption and the like, and the heat protection efficiency is high. Wherein, the carbon-based ablation heat-proof coating takes epoxy resin and phenolic resin as resin matrixes. Under a new heat environment, the ablation rate of the heat-proof coating is too high, so that the heat-proof coating is not suitable for long-time heat protection, the toughness of the carbon-based ablation heat-proof coating is poor, the problems of expansion cracking, debonding from a base material and the like easily occur under the new heat flow environment, and the stability and the reliability of the ablation appearance of the coating are greatly reduced.

Epoxy resin is a variety with the largest application amount in thermosetting resin due to good cohesiveness, heat resistance, chemical resistance and mechanical property, but because the epoxy resin is used as a coating in medium-high temperature environment, the application temperature range is limited, and especially certain disadvantages are brought to the application of structural members with higher temperature and higher dimensional stability requirements in working environment.

Therefore, the development of an epoxy resin heat-proof coating with good dimensional stability and good processing performance is urgently needed.

Disclosure of Invention

In order to solve the problems, the inventor finds that the epoxy resin is used as a resin matrix, and the high-temperature-resistant filler is added, so that the heat resistance and stability of the coating are improved, the heat conductivity coefficient and the density of the coating are reduced, the coating can perform an endothermic reaction with a carbon layer at a high temperature, the heat insulation effect is improved, and the good manufacturability is achieved, thereby completing the invention.

The invention aims to provide a light high-heat-proof coating which is prepared by taking epoxy resin as a matrix and adding high-temperature-resistant filler.

The high temperature resistant filler comprises white carbon black, such as precipitated white carbon black, fumed white carbon black or modified silica aerogel, preferably modified silica aerogel.

The modified silicon dioxide aerogel is prepared by the following method:

step a, adding a silicon source into a solvent, and heating for reaction to obtain a silicon dioxide sol solution;

b, aging the silica sol solution under an alkaline catalyst to obtain a silica aerogel crude product;

and c, post-treating the crude product of the silicon dioxide aerogel to obtain the modified silicon dioxide aerogel.

The refractory filler also includes aluminum hydroxide, such as commercial aluminum hydroxide or modified aluminum hydroxide.

The heat-proof coating also comprises an epoxy diluent, a curing agent and a coupling agent.

The invention also aims to provide a preparation method of the light high-heat-proof coating, which comprises the following steps:

step 1, respectively adding a curing agent and a coupling agent into an epoxy diluent, and uniformly stirring to obtain a mixture a;

step 2, adding a high-temperature-resistant filler into epoxy resin, and heating for reaction to obtain a reactant b;

and 3, uniformly mixing the mixture a and the reactant b to obtain the light high-heat-proof coating.

The invention further aims to provide application of the light high-heat-proof coating to surface protection of metal parts and composite material structural parts in high-temperature working environments.

The invention has the following beneficial effects:

(1) the epoxy resin coating provided by the invention has the advantages of simple process method, easily obtained raw materials and low cost.

(2) According to the invention, the white carbon black, especially the modified silica aerogel is used as the heat-resistant filler and added into the epoxy resin matrix, so that the heat conductivity and density are reduced, and the light heat-proof effect of the coating can be realized.

(3) The modified silica aerogel in the invention effectively grafts the coupling agent by doping the dual silicon source and the epoxy resin, and effectively improves the strength and the compatibility of the modified silica aerogel in the epoxy resin, thereby effectively improving the mechanical property of the coating.

(4) The modified aluminum hydroxide is added, so that the heat resistance of the coating is further improved, and the modified aluminum hydroxide can be better blended and dispersed in the epoxy resin through particle size control and surface modification, so that the adverse effect of the aluminum hydroxide on the mechanical property of the coating is effectively reduced.

(5) The light heat-proof coating obtained by the invention has low density and effectively improved heat-resistant temperature.

Detailed Description

The present invention will now be described in detail by way of specific embodiments, and features and advantages of the present invention will become more apparent and apparent from the following description.

The light high-heat-proof coating is prepared by taking epoxy resin as a matrix and adding high-temperature-resistant filler.

The light high-heat-proof coating provided by the invention comprises the following components in parts by weight:

100 parts of epoxy resin, namely 100 parts of epoxy resin,

3-27 parts of high-temperature resistant filler, preferably 6-18 parts, and more preferably 6-14 parts.

The epoxy resin is preferably a bisphenol A type epoxy resin, and more preferably an E-51 epoxy resin.

The high-temperature-resistant filler comprises white carbon black, such as precipitated white carbon black, gas-phase white carbon black or modified silica aerogel, which can be obtained by commercial purchase or self-manufacture, preferably is modified silica aerogel, and the weight fraction of the modified silica aerogel is 2-15 parts, preferably 4-10 parts, and more preferably 4-8 parts.

The commercially available white carbon black is used after being ground, and the average particle size of the commercially available white carbon black is 75-125 nm, preferably 85-115 nm, and more preferably 95-105 nm. The white carbon black can improve the mechanical property of the coating at high temperature and reduce the density of the coating at the same time, thereby achieving the light effect.

In a preferred embodiment of the present invention, the white carbon black is modified silica aerogel. The modified silicon dioxide aerogel is prepared by the following method:

step a, adding a silicon source into a solvent, and heating for reaction to obtain a silica sol solution.

The silicon source is selected from silicate, such as methyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), siloxane, such as one or more of Polysiloxane (PEDS), methyltrimethoxysilane (MTMS), Methyltriethoxysilane (MTES), dimethyldiethoxysilane (DDS), Hexadecyltrimethoxysilane (HDTMS), Phenyltriethoxysilane (PTES), preferably selected from silicate and siloxane composite silicon sources, more preferably silicate and MTES composite silicon sources or silicate and PTES composite silicon sources.

The solvent is one or more of alcohol solvents or water, preferably one or more of ethanol, methanol, propanol or water, and more preferably a mixed solution of ethanol and water.

The reaction is carried out under the condition of a catalyst, and the catalyst is an acid catalyst and is selected from hydrochloric acid or nitric acid.

The reaction temperature is 45-70 ℃, preferably 50-65 ℃, and more preferably 55-60 ℃.

The reaction time is 2-6 h, preferably 2-5 h, and more preferably 3-4 h.

The molar ratio of the silicon source to the catalyst is 1 (0.005-0.15), preferably 1 (0.01-0.12), and more preferably 1 (0.02-0.09).

The ratio of the silicon source to the solvent is 1 (10-30), preferably 1 (12-25), and more preferably 1 (15-20).

In a preferred embodiment of the present invention, the silicon source is a silicate and Phenyltriethoxysilane (PTES) composite silicon source, such as Tetraethoxysilane (TEOS) and Phenyltriethoxysilane (PTES), wherein the molar ratio of silicate to Phenyltriethoxysilane (PTES) is 1 (0.2-1.2), preferably 1 (0.2-1.0), and more preferably 1 (0.4-0.8). After the reaction, a silica sol solution was obtained.

In a preferred mode of the invention, epoxy resin is added into the reaction system to perform doping modification on the silica sol. Preferably, the epoxy resin is bisphenol A epoxy resin, such as E-51 epoxy resin, and the mass molar ratio of the epoxy resin to silicate ester is (0.1-8) g:1mol, preferably (0.5-5) g:1mol, and more preferably (1-2.5) g:1 mol. At this time, an epoxy-doped silica sol solution was obtained after the reaction was completed.

And b, aging the silica sol solution under an alkaline catalyst to obtain a silica aerogel crude product.

Preferably, the silica sol solution is first atomized in the oil phase and then the mixture of the oil phase and the silica sol solution is aged.

The aging is carried out in the presence of ammonia water, and a crude product of the silicon dioxide aerogel is obtained after aging.

And c, post-treating the crude product of the silicon dioxide aerogel to obtain the modified silicon dioxide aerogel.

The post-treatment comprises cleaning, surface modification and drying.

The cleaning is carried out by cleaning the silica aerogel crude product with a nonpolar organic solvent such as n-hexane.

The surface modification is to carry out surface modification on the cleaned silicon dioxide aerogel by utilizing a sulfur-containing silane coupling agent. According to the invention, the sulfur-containing silane coupling agent is used for surface modification in normal hexane, so that the silica aerogel with a high grafting rate of the coupling agent can be obtained, and the modified silica aerogel can be well dispersed in a resin matrix, thereby improving the heat resistance of the coating and reducing the density of the coating.

The drying is normal-pressure temperature programmed drying, the drying temperature of the first stage is 20-30 ℃, the drying temperature of the second stage is 55-65 ℃, the drying temperature of the third stage is 65-75 ℃, and the drying temperature of the fourth stage is 75-85 ℃. Compared with a supercritical drying method, the drying process provided by the invention is more beneficial to industrial and large-scale production and has lower cost.

In addition, the surface modification and the epoxy resin doping carried out aiming at the heat-resistant coating can enable the modified silica aerogel to be uniformly dispersed in the coating, and meanwhile, the modified silica aerogel has low heat conductivity and can realize good heat insulation effect.

The high-temperature-resistant filler also comprises aluminum hydroxide, such as industrial aluminum hydroxide or modified aluminum hydroxide, preferably modified aluminum hydroxide, and the weight portion of the aluminum hydroxide is 1-12 parts, preferably 2-8 parts, and more preferably 2-6 parts.

Preferably, the aluminum hydroxide is modified by a coupling agent to obtain the modified aluminum hydroxide.

In the invention, the aluminum hydroxide raw material is ground to obtain aluminum hydroxide powder, and after grinding, the aluminum hydroxide powder is micron-sized aluminum hydroxide or nano-sized aluminum hydroxide with the particle size of less than 10 mu m.

In the invention, the aluminum hydroxide raw material is subjected to surface modification: and adding the pretreated and dried aluminum hydroxide raw material into a solvent, adding a modifier, reacting, filtering a sample, and performing aftertreatment drying to obtain the modified aluminum hydroxide.

The modifier is a coupling agent selected from a silane coupling agent or a titanate coupling agent.

In the present invention, other conditions for modifying aluminum hydroxide are not specifically limited.

According to the invention, the density of the epoxy resin is reduced by adding the white carbon black into the epoxy resin, the heat resistance is improved, and a certain amount of aluminum hydroxide is added, so that water is liberated by decomposing the aluminum hydroxide at high temperature, and a coating structure with pores is formed. When the outside temperature reaches more than 200 ℃, the water generated by decomposing the aluminum hydroxide is gasified to form air holes in the coating, thereby achieving a certain heat insulation effect.

The heat-proof coating also comprises an epoxy diluent, a curing agent and a coupling agent:

30 to 60 parts of epoxy diluent, preferably 40 to 50 parts, more preferably 42 to 45 parts,

10 to 30 parts of curing agent, preferably 15 to 25 parts, more preferably 18 to 22 parts,

0.5 to 5 parts of a coupling agent, preferably 0.5 to 3 parts, more preferably 0.5 to 2 parts,

the coupling agent is selected from one or more of zirconium coupling agents, silane coupling agents or titanate coupling agents, preferably selected from one or more of titanate coupling agents or silane coupling agents, more preferably selected from one or more of titanate coupling agents, such as titanate coupling agent HY311 (bis (dioctyloxypyrophosphate) ethylene titanate), titanate coupling agent NDZ-201 (isopropyltris (dioctylpyrophosphate) titanate), and butyl titanate. The inorganic powder can be uniformly mixed in the resin by adding the coupling agent, and particularly the coating and the surface of the metal or the composite material have better binding force.

The curing agent is selected from organic acid anhydride curing agents, organic hydrazide curing agents, amine complex Lewis acids or dicyandiamide curing agents, preferably selected from amine complex Lewis acids or dicyandiamide curing agents, and more preferably selected from dicyandiamide curing agents. The dicyandiamide curing agent has moderate curing temperature, belongs to a medium-temperature curing system and achieves the purpose of reducing the curing temperature of the coating.

The epoxy diluent is selected from reactive diluents, preferably from one or more of butyl glycidyl ether, 1, 4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, phenyl glycidyl ether, polypropylene glycol diglycidyl ether, fatty glycidyl ether, benzyl glycidyl ether, 1, 6-hexanediol diglycidyl ether, propylene oxide o-tolyl ether, o-tolyl glycidyl ether or neopentyl glycol diglycidyl ether, and more preferably butyl glycidyl ether. The epoxy diluent can reduce the viscosity of an epoxy resin curing system, and the active diluent component can participate in crosslinking to increase the fluidity and improve the processing performance of the coating material.

The preparation method of the light high-heat-proof coating specifically comprises the following steps:

step 1, respectively adding a curing agent and a coupling agent into an epoxy diluent, and uniformly stirring to obtain a mixture a.

The stirring speed is 1500-4500 r/min, preferably 2000-4000 r/min, and more preferably 2500-3500 r/min; the stirring time is 20-80 min, preferably 30-70 min, and more preferably 40-60 min; the standing time is 8-28 h, preferably 12-24 h, and more preferably 9-20 h.

And 2, adding the high-temperature-resistant filler into the epoxy resin, and heating for reaction to obtain a reactant b.

The stirring speed is 1500-4500 r/min, preferably 2000-4000 r/min, and more preferably 2500-3500 r/min; the stirring time is 20-80 min, preferably 30-70 min, and more preferably 40-60 min; the heating temperature is 30-70 ℃, preferably 40-60 ℃, and more preferably 50-65 ℃. The viscosity of the epoxy resin can be reduced by moderate heating, and the epoxy resin and the high-temperature resistant filler are uniformly mixed.

And 3, uniformly mixing the mixture a and the reactant b to obtain the light high-heat-proof coating.

The stirring speed is 1500-4500 r/min, preferably 2000-4000 r/min, and more preferably 2500-3500 r/min; the stirring time is 20-80 min, preferably 30-70 min, and more preferably 40-60 min.

The light-weight high-heat-proof coating material needs to be cured under high-temperature conditions when in use. The curing temperature is 120 ℃ to 150 ℃, preferably 125 ℃ to 135 ℃, and more preferably 130 ℃.

The light high-heat-resistant epoxy resin coating provided by the invention is simple in process method, easy in raw material obtaining and low in cost. The modified silica aerogel used in the invention has low thermal conductivity, good heat resistance, high strength and low density, can be uniformly dispersed in matrix resin, and is added with micron-sized modified aluminum hydroxide or nano-sized aluminum hydroxide with the particle size of less than 10 microns, so that the heat resistance of the coating is further improved, the density of the coating is greatly reduced, the preparation process is easy to realize, and the industrial production is facilitated.

Examples

Example 1

40 parts of butyl glycidyl ether, 20 parts of dicyandiamide and 1 part of HY311 titanate coupling agent are mixed and mechanically stirred for 30min, and then ultrasonic oscillation is carried out for 60min and then the mixture is kept stand for 24 hours at normal temperature in a vacuum drying oven.

And (3) carrying out first-step grinding on the white carbon black by using a universal grinder to enable the aggregate particle size to reach about 5 microns, and then feeding the primarily ground white carbon black into a sand mill or an efficient dispersion machine to carry out second-step grinding, so that the average particle size of the white carbon black is reduced to 100 nm.

Grinding industrial aluminum hydroxide by using a universal grinder to obtain aluminum hydroxide powder with the average particle size of about 5 mu m, and drying at 120 ℃ for 6 hours.

Taking 100 parts of E-51 bisphenol A epoxy resin, 4 parts of white carbon black and 2 parts of industrial aluminum hydroxide, mechanically stirring at the stirring speed of 3000r/min, heating to 50 ℃, and stirring for 60min for later use.

And mixing the two mixed liquids, mechanically stirring at 3000r/min for 60min, and storing in a refrigerator for later use.

Example 2

40 parts of butyl glycidyl ether, 20 parts of dicyandiamide and 1 part of HY311 titanate coupling agent are mixed and mechanically stirred for 40min, then ultrasonic oscillation is carried out for 60min, and then the mixture is kept stand for 24 hours in a vacuum drying oven.

And (3) carrying out first-step grinding on the white carbon black by using a universal grinder to enable the aggregate particle size to reach about 5 microns, and then feeding the primarily ground white carbon black into a sand mill or an efficient dispersion machine to carry out second-step grinding, so that the average particle size of the white carbon black is reduced to 100 nm.

Grinding industrial aluminum hydroxide by using a universal grinder to obtain aluminum hydroxide powder with the average particle size of about 5 mu m, then sending the primarily ground aluminum hydroxide powder into a sand mill or an efficient dispersion machine for secondary grinding, reducing the average particle size of white carbon black to 100nm, and drying at 120 ℃ for 6 hours.

100 parts of E-51 bisphenol A epoxy resin, 4 parts of white carbon black and 3 parts of industrial aluminum hydroxide are mixed and mechanically stirred at the stirring speed of 2000r/min, heated to 50 ℃ and reserved for 30 min.

Mixing the above two liquids, mechanically stirring at 3000r/min, and storing in refrigerator.

Example 3

The ethyl orthosilicate, the phenyltriethoxysilane, the ethanol and the deionized water are respectively measured according to the molar weight of 1mol:0.6mol:10mol:8mol, stirred and mixed, 2mL of nitric acid with the mass fraction of 65% is added, and the mixture is reacted in a water bath at 60 ℃ for 4 hours. Then 1.5g of bisphenol A epoxy resin E-51 is added, and the mixture is kept stirring for 1 hour under the condition of heat preservation, thus obtaining the silica sol doped with the epoxy resin.

And spraying the silica sol doped with the epoxy resin into the peanut oil by an atomizer, wherein the volume of the sprayed sol is not more than one fifth of that of the peanut oil every time. And then adding 2% ammonia water by mass into the mixture of the peanut oil bath sol, taking the amount of ammonia water as the standard for starting to generate gel in the mixed solution, waiting for 10 minutes to naturally gel, standing for 24 hours, performing suction filtration, and separating to obtain the crude product of the epoxy resin-doped silicon dioxide aerogel. Adding n-hexane, fully mixing and cleaning, dispersing in 600mL of n-hexane solution again, adding 2.4g of silane coupling agent Si747, stirring at room temperature for 4h to obtain surface-modified silica sol, filtering, drying at 30 ℃ for 1h, drying at 60 ℃, 70 ℃ and 80 ℃ for 2h respectively to obtain the modified silica aerogel.

Weighing 100g of nano aluminum hydroxide raw material dried for 6 hours at 120 ℃, adding the nano aluminum hydroxide raw material into 650mL of deionized water, adding an absolute ethanol solution containing 2.5g of titanate coupling agent UP-311, stirring for 30min at normal temperature, carrying out suction filtration, and drying at 105 ℃ to obtain the modified aluminum hydroxide.

40 parts of butyl glycidyl ether, 18 parts of dicyandiamide and 1 part of HY311 titanate coupling agent are mixed and mechanically stirred for 30min, and then ultrasonic oscillation is carried out for 60min, and then the mixture is kept stand in a vacuum drying oven at normal temperature for 24 h.

And (2) mechanically stirring 100 parts of bisphenol A epoxy resin E-51100 parts, 8 parts of modified silica aerogel and 6 parts of modified aluminum hydroxide at the stirring speed of 3000r/min, heating to 50 ℃, and stirring for 60min for later use.

And mixing the two mixed liquids, mechanically stirring at 3000r/min for 60min, and storing in a refrigerator for later use.

Example 4

Measuring tetraethoxysilane, phenyl triethoxysilane, ethanol and deionized water according to the molar weight of 1mol:0.6mol:10mol:8mol respectively, stirring and mixing, adding 2mL of nitric acid with the mass fraction of 65%, and reacting in a water bath at 60 ℃ for 4 hours. Then 1.5g of bisphenol A type epoxy resin E-51 is added, and the mixture is kept stirring for 1 hour under the condition of heat preservation, so as to obtain the silica sol doped with the epoxy resin.

And spraying the silica sol doped with the epoxy resin into the peanut oil by an atomizer, wherein the volume of the sprayed sol is not more than one fifth of that of the peanut oil every time. And then adding 2% ammonia water by mass into the mixture of the peanut oil bath sol, taking the amount of ammonia water as the standard for starting to generate gel in the mixed solution, waiting for 10 minutes to naturally gel, standing for 24 hours, performing suction filtration, and separating to obtain the crude product of the epoxy resin-doped silicon dioxide aerogel. Adding n-hexane, fully mixing and cleaning, dispersing in 600mL of n-hexane solution again, adding 2.4g of silane coupling agent Si747, stirring at room temperature for 4h to obtain surface-modified silica sol, filtering, drying at 30 ℃ for 1h, drying at 60 ℃, 70 ℃ and 80 ℃ for 2h respectively to obtain the modified silica aerogel.

Weighing 100g of micron-sized aluminum hydroxide raw material dried for 6 hours at 120 ℃, adding 650mL of deionized water, stirring and mixing, adding 1.5g of vinyltriethoxysilane and 3-chloropropylalkoxysilane based on the mass of the aluminum hydroxide raw material, wherein the mass ratio of the vinyltriethoxysilane to the 3-chloropropylalkoxysilane is 1:12, stirring for 30min at normal temperature, performing suction filtration, and drying at 105 ℃ to obtain the modified aluminum hydroxide.

40 parts of butyl glycidyl ether, 18 parts of dicyandiamide and 0.5 part of HY311 titanate coupling agent are mixed and mechanically stirred for 30min, and then ultrasonic oscillation is carried out for 60min and then the mixture is kept stand for 24 hours at normal temperature in a vacuum drying oven.

Taking 100 parts of E-51 bisphenol A epoxy resin, 7 parts of modified silica aerogel and 5 parts of modified aluminum hydroxide, mechanically stirring at the stirring speed of 3000r/min, heating to 50 ℃, and stirring for 60min for later use.

And mixing the two mixed liquids, mechanically stirring at 3000r/min for 60min, and storing in a refrigerator for later use.

Comparative example

Respectively weighing 100 parts of E-51 bisphenol A epoxy resin and 20 parts of dicyandiamide, mechanically stirring for 60min after mixing, and putting into a refrigerator for storage for later use after mixing.

Examples of the experiments

Experimental example 1

The coatings of examples 1, 2, 3 and comparative examples were respectively used to prepare a coating layer with a thickness of 0.5mm, the coating layer was coated on a glass fiber reinforced plastic test piece with a thickness of 1.5mm and a thickness of 100mm × 100mm, and then the glass fiber reinforced plastic test piece was cured at a high temperature of 130 ℃, and finally the coating layer was heated by a quartz lamp to test the back temperature of the composite material, and the test results are shown in table 1.

Table 1 coating insulation effect data

From the data in Table 1, the lightweight high thermal protective coating of the present invention provides better thermal insulation than the E-51 epoxy resin alone.

Experimental example 2

Mechanical property tests were performed on the coatings formed by the coatings in example 1, example 3 and comparative example, and the test results are shown in table 2.

TABLE 2 coating mechanical Properties data

The present invention has been described in detail with reference to specific embodiments and/or illustrative examples, but the description is not intended to limit the invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims (2)

1. The preparation method of the light high-heat-proof coating is characterized in that the coating is prepared by taking epoxy resin as a matrix and adding high-temperature-resistant filler;

the coating comprises the following components in parts by weight:

100 parts of epoxy resin, namely 100 parts of epoxy resin,

6-18 parts of high-temperature-resistant filler;

the epoxy resin is bisphenol A type epoxy resin;

the high-temperature resistant filler comprises modified silica aerogel and modified aluminum hydroxide;

adding the pretreated and dried nano aluminum hydroxide into a solvent, adding a titanate coupling agent, and filtering and drying a sample after reaction to obtain modified aluminum hydroxide;

the modified silicon dioxide aerogel is 4-10 parts by weight, and the modified aluminum hydroxide is 2-8 parts by weight;

the modified silicon dioxide aerogel is prepared by the following method:

step a, adding a silicon source into a solvent, and heating for reaction to obtain a silicon dioxide sol solution;

the silicon source is a silicate and methyl triethoxysilane compound silicon source or a silicate and phenyl triethoxysilane compound silicon source, and the solvent is a mixed solution of ethanol and water; the reaction is carried out under the condition of a hydrochloric acid or nitric acid catalyst; the reaction temperature is 50-65 ℃, and the reaction time is 2-5 h;

adding bisphenol A type epoxy resin into a reaction system, carrying out doping modification on the silica sol, wherein the mass molar ratio of the epoxy resin to silicate ester is (0.5-5) g:1mol, and obtaining an epoxy resin doped silica sol solution after the reaction is finished;

b, atomizing the silica sol solution doped with the epoxy resin in an oil phase, and then aging a mixed solution of the oil phase and the silica sol solution in the presence of ammonia water to obtain a crude product of the silica aerogel;

c, post-treating the crude product of the silicon dioxide aerogel to obtain modified silicon dioxide aerogel; the post-treatment comprises non-polar organic solvent cleaning, surface modification and drying; the surface modification is to carry out surface modification on the cleaned silicon dioxide aerogel in normal hexane by utilizing a sulfur-containing silane coupling agent;

the coating also comprises an epoxy diluent, a curing agent and a coupling agent;

the coupling agent is selected from titanate coupling agents;

the curing agent is selected from amine complex Lewis acid or dicyandiamide curing agent;

the epoxy diluent is butyl glycidyl ether;

the method comprises the following steps:

step 1, respectively adding a curing agent and a coupling agent into an epoxy diluent, and uniformly stirring to obtain a mixture a;

step 2, adding a high-temperature-resistant filler into epoxy resin, and heating for reaction to obtain a reactant b; the heating temperature is 40-60 ℃;

step 3, uniformly mixing the mixture a and the reactant b to obtain the light high-heat-proof coating;

the light high-heat-proof coating needs to be cured at 125-135 ℃ when in use;

the coating is used for surface protection of metal parts and composite material structural parts in a high-temperature working environment.

2. The method of claim 1, wherein the curing agent is a dicyandiamide curing agent.