Method for preparing thermally-resistant thermally-insulating organosilicon aerogel material on the basis of piers-rubinsztajn reaction

Abstract

Disclosed in the present invention is a method for preparing a thermally-resistant thermally-insulating organosilicon aerogel material on the basis of a Piers-Rubinsztajn reaction. The method comprises: 1, preparing a hydrogen-containing silane-grafted organic resin by means of a Piers-Rubinsztajn reaction; 2, co-hydrolyzing the hydrogen-containing silane-grafted organic resin and alkoxy silane to prepare a silica sol precursor; 3, carrying out a sol-gel reaction to prepare the organosilicon aerogel. The present invention uses the Piers-Rubinsztajn reaction to copolymerize the organosilicon with various types of organic resins and then prepares the organosilicon aerogel by means of the sol-gel method, wherein the organic resin component improves the cohesion force of silica sol nanoparticles during a further gelation process, so that a wet gel can overcome a capillary force so as to be dried under the atmospheric pressure, and the organosilicon component provides excellent thermal resistance and thermal insulation properties. The organosilicon aerogel prepared by the method has a high compressive strength and a low heat conductivity coefficient.

Description

Preparation method of heat-resistant and heat-insulating organosilicon aerogel material based on Piers-Rubinsztajn reaction Technical Field

[0001] The present invention belongs to the field of high temperature resistance, heat insulation and heat protection, and relates to a method for preparing a silicon-based ablative heat-insulating material, and specifically to a method for preparing an integrated heat-resistant and heat-insulating organic silicon aerogel material based on the Piers-Rubinsztajn reaction. Background Art

[0002] As the first aerogel product synthesized in human history, silica aerogel features low density, high specific surface area, and a fine mesoporous structure. Its nanopore size is smaller than the mean free path of air. Due to its nano-aggregated structure, silica aerogel infinitely extends the conduction path, effectively reducing heat and sound conduction. Its infinite baffle effect effectively reduces its thermal radiation, making it widely used in thermal insulation and soundproofing. Furthermore, because the silicon oxide that makes up silica aerogel has a low dielectric constant and adjustable porosity, it has a tunable dielectric constant between 1 and 3. This allows it to be combined with quartz / alumina blended fibers to produce high-temperature resistant, broadband, and wave-transmitting insulation tiles. Silica aerogel boasts an extremely long service life, excellent thermal insulation properties, and exceptional fire resistance, making it widely used in the aerospace industry.

[0003] Although silica aerogel has so many advantages, the initial nanoparticles of silica aerogel are connected into beaded clusters in different directions during the gel-gel process, and further accumulate into submicron and micron-sized aggregates; the beaded spheres that make up the aggregates have weak interfacial interactions and a "thin neck" structure. These shortcomings make silica aerogel extremely susceptible to capillary action and structural collapse during the drying process, and the texture is hard and brittle after drying, making it difficult to use as a structural material.

[0004] Traditional silica aerogel thermal insulation materials are no longer able to meet the needs of rapidly advancing industry. To enhance the mechanical properties of silica aerogels, researchers currently use three-dimensional fiber braids or heterogeneous nanocosols to improve the brittleness of silica aerogels. Prefabricated fiber braids impregnated with silica sol can improve the brittleness of the silica sol by transferring stress through the fibers. However, during the gelation and subsequent drying process, the silica sol adsorbs on the surface of the fiber braid, resulting in a loss of specific surface area. Furthermore, after aging, heterogeneous nanosols and silica sols still retain a large number of beaded, narrow-necked structures, which cannot fundamentally improve the brittleness of silica aerogels. Summary of the Invention

[0005] In order to prepare silicon-based aerogels with excellent mechanical properties, the present invention provides a method for preparing heat-resistant and heat-insulating silicone aerogel materials based on the Lewis acid-catalyzed Piers-Rubinsztajn reaction. Organic polymers are introduced into the silicone structure through molecular structure design. During the sol-gel reaction, the rich polar groups of the organic resin increase the cohesive force between the silica sol nanoparticles, forming a silica aerogel with a special micromorphology. The aerogel can be dried at room temperature and pressure and has a compressive strength of more than 20 MPa.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a heat-resistant and heat-insulating organosilicon aerogel material based on the Piers-Rubinsztajn reaction comprises the following steps:

[0008] Step 1: Preparation of Hydrosilane-Grafted Organic Resin by Piers-Rubinsztajn Reaction

[0009] The hydrosilane, organic resin, Lewis acid catalyst and organic solvent A are uniformly mixed, and Piers-Rubinsztajn reaction is carried out at 20-100° C. After the reaction for 24-72 hours, the Lewis acid catalyst in the system is removed using molecular sieves, and the organic resin grafted with the hydrosilane is obtained by vacuum distillation; wherein:

[0010] The hydrosilane and the organic resin undergo a Piers-Rubinsztajn reaction under the catalysis of a Lewis acid, wherein the molar ratio of Si-H in the hydrosilane to the active hydrogen-containing functional groups in the organic resin is 0.8 to 2.1, the amount of the Lewis acid catalyst is 0.01 to 0.5% of the total mass of the materials, and the amount of the organic solvent A is 0.5 to 2 times the total mass of the hydrosilane and the organic resin;

[0011] The hydrogen-containing silane is one or more of triethoxysilane, trimethoxysilane, n-butylsilane, methyldichlorosilane, triphenylhydrosilane, tetramethylcyclotetrasilane, tetramethyldisiloxane, 1,4-bis(dimethylsilyl)benzene, diphenylsilane, 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane, etc.;

[0012] The organic resin is one or more of phenolic resin, urea-formaldehyde resin, acrylate resin, epoxy resin, polyurethane resin, melamine-formaldehyde resin, polyamic acid, polyamide, etc.;

[0013] The Lewis acid catalyst is one or more of aluminum chloride, boron trifluoride, trimethylaluminum, aluminum nitrate, trispentafluorophenylborane, phenylboric acid, aminophenylboric acid, ferric chloride, trifluoromethanesulfonic acid, zinc chloride, etc.;

[0014] The organic solvent A is one or more of pyridine, tetrahydropyridine, pyrrole, N-methylpyrrolidone, tetrahydrofuran, methanol, ethanol, N,N'-dimethylformamide, propylenediamine, ethylenediamine, acetonitrile, chlorobenzene, chloroform, etc.;

[0015] Step 2: Hydrogen silane grafted organic resin and alkoxysilane are co-hydrolyzed to prepare silica sol precursor

[0016] The organic resin grafted with hydrogen silane obtained in step 1 is uniformly mixed with alkoxysilane, and an acid catalyst, organic solvent B and deionized water are added. The temperature is raised to 80-100° C. and heated for 20-200 minutes to obtain an organic resin-modified silicone resin, i.e., an organic silica sol precursor, wherein:

[0017] The molar ratio of the hydrogen-containing silane-grafted organic resin to the alkoxysilane is 0.2 to 1.5, the amount of the acid catalyst is 0.01% to 3% of the total mass of the material, the amount of the organic solvent B is 0.5 to 3 times the total mass of the organic resin and the alkoxysilane, and the amount of deionized water is 2 to 5 times the molar amount of the silane alkoxy group;

[0018] The alkoxysilane is a mixture of methyltrimethoxysilane, dimethyldimethoxysilane and phenyltrimethoxysilane, and the mass ratio of methyltrimethoxysilane, dimethyldimethoxysilane and phenyltrimethoxysilane is 10-20:5-10:10-20;

[0019] The organic solvent B is one or more of toluene, xylene, petroleum ether, chloroform, tetrahydrofuran, methanol, ethanol, n-butanol, acetone, etc.;

[0020] The acid catalyst is one or more of hydrochloric acid, sulfuric acid, acetic acid, nitric acid, phosphoric acid, polyphosphoric acid, p-toluenesulfonic acid, oxalic acid, permanganic acid, ferric acid, metaaluminic acid, carbonic acid, boric acid, etc.;

[0021] Step 3: Preparation of organosilicon aerogel by sol-gel reaction

[0022] The organic resin modified silicone resin obtained in step 2 is mixed with a surfactant, an organic solvent C, and a gel catalyst to form a silica sol. The silica sol is subjected to a gelation-aging-washing-room temperature drying process under the action of the gel catalyst to obtain an organosilicon aerogel. The wet gel can be dried without solvent replacement and supercritical drying, wherein:

[0023] The amount of the surfactant added is 0.05-5% of the total material mass, the amount of the organic solvent C is 4-20 times the mass of the organic resin-modified silicone resin, and the amount of the gel catalyst added is 0.1-10% of the total material mass;

[0024] The surfactant is one or more of cetyltrimethylammonium bromide, octadecyltrimethylammonium bromide, polysorbate, polyethylene glycol, polyvinyl alcohol, polyoxyethylene ethyl ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, etc.;

[0025] The organic solvent C is one or more of toluene, acetone, xylene, ethanol, methanol, glycerol, isopropanol, dimethyl sulfoxide, tetrahydrofuran, dioxane, acetonitrile, etc.;

[0026] The gel catalyst is one or more of urotropine, polyetheramine, polyamide, triethylenetetramine, diethylenetriamine, triethylamine, hexadecyl ammonium bromide, ammonia water, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminopropylmethyldimethoxysilane, etc.;

[0027] The gelling temperature is 80-180° C. and the gelling time is 24-72 hours;

[0028] The aging temperature is 50-100° C., and the aging time is 24-72 hours.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] The organosilicon aerogel prepared by this method exhibits excellent mechanical and thermal insulation properties. Organosilicon can be copolymerized with a wide range of organic resins via the Piers-Rubinsztajn reaction. The aerogel is then prepared via a sol-gel method. The organic resin component increases the cohesive force of the silica sol nanoparticles during the gelation process, enabling the wet gel to overcome capillary forces and dry under normal pressure. The organosilicon component, on the other hand, provides excellent heat resistance and thermal insulation. The organosilicon aerogel prepared by this method exhibits high compressive strength and low thermal conductivity, making it suitable as a primary component of thermal insulation materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a scanning electron microscope photograph of the silica aerogel prepared in Example 1.

[0032] FIG2 shows the thermal conductivity of the silica aerogel prepared in Example 1 at different temperatures.

[0033] FIG3 is a compressive stress-strain curve of the silica aerogel prepared in Example 1. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0035] Example 1:

[0036] Step 1: Preparation of Hydrosilane-Grafted Organic Resin by Piers-Rubinsztajn Reaction

[0037] 20 parts by weight of tetramethylcyclotetrasilane, 10 parts by weight of resol phenolic resin, 40 parts of tetrahydrofuran, and 0.25 parts of aluminum chloride were added to a stirrer, and a Piers-Rubinsztajn reaction was carried out at 25°C. After 72 hours, the aluminum chloride catalyst in the reaction system was removed using mesoporous alumina, and a colorless and viscous hydrogen-containing silane-grafted phenolic resin was obtained by distillation under reduced pressure.

[0038] Step 2: Hydrogen silane grafted organic resin and alkoxysilane are co-hydrolyzed to prepare silica sol precursor

[0039] 10 parts by weight of a hydrogenated silane-grafted phenolic resin, 20 parts by weight of methyltrimethoxysilane, 5 parts by weight of dimethyldimethoxysilane, 10 parts by weight of phenyltrimethoxysilane and 45 parts by weight of toluene were added into a stirrer, 25 parts by weight of deionized water and 0.5 to 5 parts by weight of concentrated hydrochloric acid were added dropwise, and the mixture was reacted at 80° C. for 150 minutes. The organic phase was taken and distilled under reduced pressure to obtain a silica sol precursor.

[0040] Step 3: Preparation of organosilicon aerogel by sol-gel reaction

[0041] Take 20 parts by weight of silica sol precursor, add 80 parts by weight of methanol, 3 parts by weight of polyethylene glycol, and 5 parts by weight of triethylenetetramine, react in a reactor at 80°C for 12 hours and then at 150°C for 12 hours. After the reaction, age the wet gel at 100°C for 72 hours. After aging, let the reactor cool naturally, take out the wet gel and evaporate the solvent at room temperature for 24 to 72 hours.

[0042] The microscopic morphology of the organosilicon aerogel in Figure 1 shows that the aerogel prepared in this example lacks a distinct beaded, narrow-necked structure and instead possesses a rich pore structure. Furthermore, the thermal conductivity of the aerogel samples at different temperatures, shown in Figure 2, demonstrates that the organosilicon aerogel prepared in this example based on the Piers-Rubinsztajn reaction exhibits excellent thermal insulation properties and can be used as a heat-insulating material. Figure 3 demonstrates that the aerogel products prepared in this example exhibit good flexibility and compressive strength, with a compressive strength exceeding 20 MPa.

[0043] Example 2:

[0044] Step 1: Preparation of Hydrosilane-Grafted Organic Resin by Piers-Rubinsztajn Reaction

[0045] 10 parts by weight of 1,4-bis(dimethylsilyl)benzene, 10 parts by weight of acrylate resin, 40 parts of ethanol, and 0.3 parts of boron trifluoride were added to a stirrer, and a Piers-Rubinsztajn reaction was carried out at 70° C. After 72 hours, the boron trifluoride catalyst in the reaction system was removed using mesoporous alumina, and the hydrogen-containing silane-grafted acrylate resin was obtained by distillation under reduced pressure.

[0046] Step 2: Hydrogen silane grafted organic resin and alkoxysilane are co-hydrolyzed to prepare silica sol precursor

[0047] 8 parts by weight of hydrogenated silane-grafted acrylate resin, 20 parts by weight of methyltrimethoxysilane, 5 parts by weight of dimethyldimethoxysilane, 10 parts by weight of phenyltrimethoxysilane and 30 parts by weight of ethanol were added into a stirrer, 40 parts by weight of deionized water and 0.5 parts by weight of concentrated sulfuric acid were added dropwise, and the mixture was reacted at 80° C. for 200 minutes. The organic phase was taken and distilled under reduced pressure to obtain a silica sol precursor.

[0048] Step 3: Preparation of organosilicon aerogel by sol-gel reaction

[0049] Take 20 parts by weight of silica sol precursor, add 80 parts by weight of tetrahydrofuran, 5 parts by weight of polyethylene glycol, and 5 parts by weight of ammonia water, react in a reactor at 80°C for 12 hours, and then at 150°C for 12 hours. After the reaction is completed, age at 60°C for 72 hours, then allow the reactor to cool naturally, take out the wet gel and evaporate the solvent at room temperature for 24 to 72 hours.

[0050] Example 3:

[0051] Step 1: Preparation of Hydrosilane-Grafted Organic Resin by Piers-Rubinsztajn Reaction

[0052] 5 parts by weight of triethoxysilane, 10 parts by weight of urea-formaldehyde resin, 40 parts of acetone, and 0.15 parts of tris-pentafluorophenylborane were added to a stirrer, and a Piers-Rubinsztajn reaction was carried out at 30° C. After 68 hours, the tris-pentafluorophenylborane catalyst in the reaction system was removed using mesoporous alumina, and the urea-formaldehyde resin grafted with hydrogen-containing silane was obtained by distillation under reduced pressure.

[0053] Step 2: Hydrogen silane grafted organic resin and alkoxysilane are co-hydrolyzed to prepare silica sol precursor

[0054] 8 parts by weight of urea-formaldehyde resin grafted with hydrogen silane, 15 parts by weight of methyltrimethoxysilane, 5 parts by weight of dimethyldimethoxysilane, 20 parts by weight of phenyltrimethoxysilane and 30 parts by weight of chloroform were added into a stirrer, 30 parts by weight of deionized water and 0.5 parts by weight of concentrated nitric acid were added dropwise, and the mixture was reacted at 80°C for 200 minutes. The organic phase was taken and distilled under reduced pressure to obtain a silica sol precursor.

[0055] Step 3: Preparation of organosilicon aerogel by sol-gel reaction

[0056] Take 15 parts by weight of the above-mentioned silica sol precursor, add 75 parts by weight of ethanol, 5 parts by weight of polyethylene glycol, and 5 parts by weight of polyetheramine, and react at 80°C for 12 hours and 150°C for 12 hours in a reactor. After the reaction is completed, age at 80°C for 72 hours, then allow the reactor to cool naturally, take out the wet gel and evaporate the solvent at room temperature for 72 hours.

Claims

1. A preparation method of a heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction, characterized in that The method includes the following steps: Step 1: Preparation of hydrogen-silane-grafted organic resin by Piers-Rubinsztajn reaction The hydrogen silane, organic resin, Lewis acid catalyst and organic solvent A are uniformly mixed, and the Piers-Rubinsztajn reaction is carried out at 20-100 °C for 24-72 h. After the reaction, the Lewis acid catalyst in the system is removed using molecular sieves, and the hydrogen-silane-grafted organic resin is obtained by vacuum distillation. Among them: the molar ratio of Si-H of the hydrogen silane to the functional group containing active hydrogen in the organic resin is 0.8-2.1, and the dosage of the Lewis acid catalyst is 0.01-0.5% of the total material mass; Step 2: Co-hydrolysis of hydrogen-silane-grafted organic resin and alkoxysilane to prepare silica sol precursor The hydrogen-silane-grafted organic resin obtained in Step 1 and the alkoxysilane are uniformly mixed, and an acid catalyst, organic solvent B and deionized water are added. The temperature is raised to 80-100 °C and heated for 20-200 min to obtain an organic resin-modified silicone resin, that is, an organosilica sol precursor. Among them: the molar ratio of the hydrogen-silane-grafted organic resin to the alkoxysilane is 0.2-1.5, the dosage of the acid catalyst is 0.01%-3% of the total material mass, and the dosage of deionized water is 2-5 times the molar amount of silaneoxy; Step 3: Sol-gel reaction to prepare organosilica aerogel The organic resin-modified silicone resin obtained in Step 2, surfactant, organic solvent C and gel catalyst are formulated into silica sol. The silica sol is subjected to gelation-aging-washing-room temperature drying treatment under the action of the gel catalyst to obtain organosilica aerogel. The wet gel can be dried without solvent replacement and supercritical drying. Among them: the addition amount of the surfactant is 0.05-5% of the total material mass, and the addition amount of the gel catalyst is 0.1-10% of the total material mass.

2. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The hydrogen silane is one or more of triethoxysilane, trimethoxysilane, n-butylsilane, methyldichlorosilane, triphenylsilane, tetramethylcyclotetrasilane, tetramethyldisiloxane, 1,4-bis(dimethylsilyl)benzene, diphenylsilane, 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane.

3. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, wherein The organic resin is one or more of phenolic resin, urea-formaldehyde resin, acrylate resin, epoxy resin, polyurethane resin, melamine-formaldehyde resin, polyamic acid, polyamide.

4. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The Lewis acid catalyst is one or more of aluminum chloride, boron trifluoride, trimethylaluminum, aluminum nitrate, pentafluorophenylborane, benzeneboronic acid, aminobenzeneboronic acid, iron chloride, trifluoromethanesulfonic acid, zinc chloride; the acid catalyst is one or more of hydrochloric acid, sulfuric acid, acetic acid, nitric acid, phosphoric acid, polyphosphoric acid, p-toluenesulfonic acid, oxalic acid, permanganic acid, ferrate, metaaluminate, carbonic acid, boric acid.

5. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The organic solvent A is one or more of pyridine, tetrahydropyridine, pyrrole, N-methylpyrrolidone, tetrahydrofuran, methanol, ethanol, N,N'-dimethylformamide, propylenediamine, ethylenediamine, acetonitrile, chlorobenzene, and chloroform, and the dosage is 0.5 to 2 times the total mass of the hydrosilane and the organic resin; the organic solvent B is one or more of toluene, xylene, petroleum ether, chloroform, tetrahydrofuran, methanol, ethanol, n-butanol, and acetone, and the dosage is 0.5 to 3 times the total mass of the organic resin and the alkoxysilane; the organic solvent C is one or more of toluene, acetone, xylene, ethanol, methanol, glycerol, isopropanol, dimethyl sulfoxide, tetrahydrofuran, dioxane, acetonitrile, etc., and the dosage is 4 to 20 times the mass of the silicone resin modified by the organic resin.

6. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The alkoxysilane is a mixture of methyltrimethoxysilane, dimethyldimethoxysilane, and phenyltrimethoxysilane, and the mass ratio of methyltrimethoxysilane, dimethyldimethoxysilane, and phenyltrimethoxysilane is 10 to 20:5 to 10:10 to 20.

7. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The surfactant is one or more of cetyltrimethylammonium bromide, octadecyltrimethylammonium bromide, polysorbate, polyethylene glycol, polyvinyl alcohol, polyoxyethylene ethyl ether, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium oleate.

8. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The gel catalyst is one or more of hexamethylenetetramine, polyetheramine, polyamide, triethylenetetramine, diethylenetriamine, triethylamine, cetylammonium bromide, ammonia water, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, and aminopropylmethyldimethoxysilane.

9. The preparation method of the heat-resistant and heat-insulating organosilica aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that The gel temperature is 80 to 180 °C, and the gel time is 24 to 72 h; the aging temperature is 50 to 100 °C, and the aging time is 24 to 72 h.

10. Application of the heat-resistant and heat-insulating organosilica aerogel material prepared by the method according to any one of claims 1-9 in heat-insulating and heat-proof materials.

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