Process for the preparation of heat resistant thermally insulated silicone aerogel materials based on the piers-rubinsztajn reaction

Abstract

The application discloses a preparation method of heat-resistant and heat-insulating organic silicon aerogel material based on Piers-Rubinsztajn reaction, and the method is as follows: I. preparing hydrogen-containing silane grafted organic resin through Piers-Rubinsztajn reaction; II. preparing silicon sol precursor through co-hydrolysis of the hydrogen-containing silane grafted organic resin and alkoxysilane; III. preparing organic silicon aerogel through sol-gel reaction. The Piers-Rubinsztajn reaction can be used to copolymerize organic silicon and a wide range of organic resins, and the silicon aerogel is prepared through the sol-gel method, wherein the organic resin component increases the cohesion of the silicon sol nanoparticles in the further gel process, so that the wet gel can overcome the capillary force effect and be dried at normal pressure; and the organic silicon component provides excellent heat resistance and heat insulation performance. The organic silicon aerogel prepared through the method has high compressive strength and low thermal conductivity.

Description

Technical Field

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

[0002] As the first aerogel product synthesized in human history, silica aerogel is characterized by low density, high specific surface area, and a fine mesoporous structure. Its nanopore size is smaller than the mean free path of air. Furthermore, due to the infinitely extended conduction path caused by the nano-aggregate structure of silica aerogel, it effectively reduces heat and sound conduction. The infinite baffle effect also effectively reduces heat radiation, making it widely used in thermal insulation and soundproofing. In addition, because silica, the constituent of silica aerogel, has a low dielectric constant and adjustable porosity, it possesses an adjustable dielectric constant within the range of 1 to 3. This allows it to be composited with quartz / alumina blended fibers to produce high-temperature resistant, broadband, and wave-transparent insulating tiles. Silica aerogel also boasts an extremely long service life, excellent thermal insulation performance, and superb fire resistance, making it widely used in the aerospace field.

[0003] Although silica aerogels have many advantages, during the gel-gel process, the initial nanoparticles connect in different directions to form beaded clusters, which further accumulate into submicron and micron-sized aggregates. The beaded spheres that make up the aggregates have weak interfacial interactions and a "neck" structure. These disadvantages make silica aerogels extremely susceptible to capillary action during drying, causing structural collapse. After drying, they are hard and brittle, making them difficult to use as structural materials.

[0004] Traditional silica aerogel thermal insulation materials can no longer meet the needs of rapidly advancing industry. To enhance the mechanical properties of silica aerogels, researchers currently use three-dimensional fiber braids or heterogeneous nanosols to improve their brittleness. While pre-fabricated fiber braids impregnated with silica sol can improve the brittleness of silica sol through stress transfer via the fibers, the silica sol adsorbs onto the surface of the fiber braid during gelation and subsequent drying, leading to a loss of specific surface area. Heterogeneous nanosols and silica sols, even after aging, still exhibit numerous beaded neck structures, failing to fundamentally improve the brittleness of silica aerogels. Summary of the Invention

[0005] To prepare silica-based aerogels with excellent mechanical properties, this invention provides a method for preparing heat-resistant and heat-insulating organosilicon aerogel materials based on the Piers-Rubinsztajn reaction catalyzed by Lewis acids. By designing the molecular structure, organic polymers are introduced into the organosilicon structure. During the sol-gel reaction, the abundant polar groups of the organic resin increase the cohesive force between silica sol nanoparticles, forming a silica aerogel with a special microstructure. It can be dried at room temperature and pressure and has a compressive strength of over 20 MPa.

[0006] The objective of this invention is achieved through the following technical solution:

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

[0008] Step 1: Piers-Rubinsztajn reaction to prepare hydrogen-silane-grafted organic resins

[0009] Hydrosilane, organic resin, Lewis acid catalyst, and organic solvent A were uniformly mixed and subjected to a Piers-Rubinsztajn reaction at 20–100 °C. After 24–72 h of reaction, the Lewis acid catalyst was removed from the system using a molecular sieve, and the hydrosilane-grafted organic resin was obtained by vacuum distillation. Wherein:

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

[0011] The hydrogen-containing silane is one or more of the following: triethoxysilane, trimethoxysilane, n-butane, methyldichlorosilane, triphenylhydrosilane, tetramethylcyclotetrasilane, tetramethyldisiloxane, 1,4-di(dimethylsilyl)benzene, diphenylsilane, 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane;

[0012] The organic resin is one or more of the following: 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 the following: aluminum chloride, boron trifluoride, trimethylaluminum, aluminum nitrate, tripentafluorophenylborane, phenylboronic acid, aminophenylboronic acid, ferric chloride, trifluoromethanesulfonic acid, and zinc chloride.

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

[0015] Step 2: Prepare silica sol precursor by co-hydrolyzing hydrogen-silane-grafted organic resin with alkoxysilane.

[0016] The hydrogen-containing silane-grafted organic resin obtained in step one is uniformly mixed with alkoxysilane, and an acid catalyst, organic solvent B, and deionized water are added. The mixture is heated to 80–100°C for 20–200 min to obtain an organic resin-modified silicone resin, i.e., an organosilicon sol precursor.

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

[0018] The alkoxysilane is a mixture of methyltrimethoxysilane, dimethyldimethoxysilane and phenyltrimethoxysilane, wherein 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 the following: hydrochloric acid, sulfuric acid, acetic acid, nitric acid, phosphoric acid, polyphosphoric acid, p-toluenesulfonic acid, oxalic acid, permanganic acid, ferric acid, aluminic acid, carbonic acid, and boric acid.

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

[0022] The organic resin-modified silicone resin obtained in step two was combined with a surfactant, organic solvent C, and a gel catalyst to form a silica sol. The silica sol underwent gelation-aging-washing-room temperature drying treatment under the action of the gel catalyst to obtain an organosilicon aerogel. The wet gel could be dried without solvent replacement and supercritical drying.

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

[0024] The surfactant is one or more of the following: hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, polysorbate, polyethylene glycol, polyvinyl alcohol, polyoxyethylene ethyl ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, 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 the following: hexamethylenetetramine, polyetheramine, polyamide, triethylenetetramine, diethylenetriamine, triethylamine, hexadecylammonium bromide, ammonia, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, and aminopropylmethyldimethoxysilane.

[0027] The gelation temperature is 80–180℃, and the gelation time is 24–72 h;

[0028] The aging temperature is 50–100℃, 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 invention possesses excellent mechanical and thermal insulation properties. Organosilicon can be copolymerized with a wide range of organic resins via the Piers-Rubinsztajn reaction, and the aerogel is prepared using the sol-gel method. During the further gelation process, the organic resin component increases the cohesive force of the silica sol nanoparticles, enabling the wet gel to overcome capillary forces and dry at normal pressure. The organosilicon component provides excellent heat resistance and thermal insulation properties. The organosilicon aerogel prepared by this method exhibits high compressive strength and low thermal conductivity, making it suitable as a major component of thermal insulation materials. Attached Figure Description

[0031] Figure 1 Scanning electron microscope image of the silica aerogel prepared in Example 1.

[0032] Figure 2 Thermal conductivity of the silica aerogel prepared in Example 1 at different temperatures.

[0033] Figure 3 The compressive stress-strain curve of the silica aerogel prepared in Example 1. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0035] Example 1:

[0036] Step 1: Piers-Rubinsztajn reaction to prepare hydrogen-silane-grafted organic resins

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

[0038] Step 2: Prepare silica sol precursor by co-hydrolyzing hydrogen-silane-grafted organic resin with alkoxysilane.

[0039] Ten parts by weight of phenolic resin grafted with hydrogen-containing silane, 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 to a stirrer. 25 parts by weight of deionized water and 0.5 to 5 parts by weight of concentrated hydrochloric acid were added dropwise. The mixture was reacted at 80°C for 150 min. The organic phase was then distilled under reduced pressure to obtain the silica sol precursor.

[0040] Step 3: Preparation of organosilicon aerogel via 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 h and at 150°C for 12 h. After the reaction is completed, age the wet gel at 100°C for 72 h. After aging, allow the reactor to cool naturally and take out the wet gel to evaporate the solvent at room temperature for 24-72 h.

[0042] from Figure 1 The microstructure of the organosilicon aerogel shows that the aerogel prepared in this embodiment does not exhibit a distinct beaded neck structure, but rather a rich porous structure. Furthermore, Figure 2 The thermal conductivity of the aerogel samples shown at different temperatures indicates that the organosilicon aerogel prepared based on the Piers-Rubinsztajn reaction in this embodiment has excellent thermal insulation properties and can be used as a thermal insulation material. Figure 3 This indicates that the aerogel product prepared in this embodiment has good flexibility and compressive strength, with a compressive strength higher than 20 MPa.

[0043] Example 2:

[0044] Step 1: Piers-Rubinsztajn reaction to prepare hydrogen-silane-grafted organic resins

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

[0046] Step 2: Prepare silica sol precursor by co-hydrolyzing hydrogen-silane-grafted organic resin with alkoxysilane.

[0047] Eight parts by weight of hydrosilane-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 to a stirrer. 40 parts by weight of deionized water and 0.5 parts by weight of concentrated sulfuric acid were added dropwise. The reaction was carried out at 80°C for 200 min. The organic phase was then distilled under reduced pressure to obtain the silica sol precursor.

[0048] Step 3: Preparation of organosilicon aerogel via 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, react 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 24-72 hours.

[0050] Example 3:

[0051] Step 1: Piers-Rubinsztajn reaction to prepare hydrogen-silane-grafted organic resins

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

[0053] Step 2: Prepare silica sol precursor by co-hydrolyzing hydrogen-silane-grafted organic resin with alkoxysilane.

[0054] Eight parts by weight of urea-formaldehyde resin grafted with hydrogen-containing 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 to a stirrer. 30 parts by weight of deionized water and 0.5 parts by weight of concentrated nitric acid were added dropwise. The reaction was carried out at 80°C for 200 min. The organic phase was then distilled under reduced pressure to obtain the silica sol precursor.

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

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

Claims

1. A method for preparing a heat-resistant and heat-insulating organosilicon aerogel material based on the Piers-Rubinsztajn reaction, characterized in that... The method includes the following steps: Step 1: Piers-Rubinsztajn reaction to prepare hydrogen-silane-grafted organic resins Hydrogen-containing silane, organic resin, Lewis acid catalyst, and organic solvent A are uniformly mixed and subjected to a Piers-Rubinsztajn reaction at 20–100 °C. After reacting for 24–72 h, the Lewis acid catalyst in the system is removed using a molecular sieve, and the organic resin grafted with hydrogen-containing silane is obtained by vacuum distillation. The molar ratio of Si-H in the hydrogen-containing silane to the functional groups containing active hydrogen in the organic resin is 0.8–2.1, and the amount of Lewis acid catalyst is 0.01–0.5% of the total material mass. Step 2: Prepare silica sol precursor by co-hydrolyzing hydrogen-silane-grafted organic resin with alkoxysilane. The hydrogen-containing silane-grafted organic resin obtained in step one is uniformly mixed with alkoxysilane, and acid catalyst, organic solvent B and deionized water are added. The mixture is heated to 80-100℃ for 20-200 min to obtain organic resin modified silicone resin, i.e., organosilicon sol precursor. The molar ratio of hydrogen-containing silane-grafted organic resin to alkoxysilane is 0.2-1.5, the amount of acid catalyst is 0.01%-3% of the total material mass, and the amount of deionized water is 2-5 times the molar amount of silaneoxy. Step 3: Preparation of organosilicon aerogel via sol-gel reaction The organic resin modified silicone resin obtained in step two is prepared into a silica sol with a surfactant, organic solvent C, and a gel catalyst. The silica sol is subjected to gelation-aging-washing-room temperature drying treatment under the action of the gel catalyst to obtain an organosilicon aerogel. The wet gel can be dried without solvent replacement and supercritical drying. The amount of surfactant added is 0.05-5% of the total material mass, and the amount of gel catalyst added is 0.1-10% of the total material mass.

2. The method for preparing the heat-resistant and heat-insulating organosilicon aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that... The hydrogen-containing silane is one or more of the following: triethoxysilane, trimethoxysilane, n-butane, methyldichlorosilane, triphenylhydrosilane, tetramethylcyclotetrasilane, tetramethyldisiloxane, 1,4-di(dimethylsilyl)benzene, diphenylsilane, and 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane.

3. The method for preparing the heat-resistant and heat-insulating organosilicon aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that... The organic resin is one or more of the following: phenolic resin, urea-formaldehyde resin, acrylate resin, epoxy resin, polyurethane resin, melamine-formaldehyde resin, polyamic acid, and polyamide.

4. The method for preparing the heat-resistant and heat-insulating organosilicon 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, tripentafluorophenylborane, phenylboronic acid, aminophenylboronic acid, ferric chloride, trifluoromethanesulfonic acid, and 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, ferric acid, aluminic acid, carbonic acid, and boric acid.

5. The method for preparing the heat-resistant and heat-insulating organosilicon 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 its amount is 0.5 to 2 times the total mass of the hydrogen-containing silane and organic resin; the organic solvent B is one or more of toluene, xylene, petroleum ether, chloroform, tetrahydrofuran, methanol, ethanol, n-butanol, and acetone, and its amount is 0.5 to 3 times the total mass of the organic resin and alkoxysilane; the organic solvent C is one or more of toluene, acetone, xylene, ethanol, methanol, glycerol, isopropanol, dimethyl sulfoxide, tetrahydrofuran, dioxane, and acetonitrile, and its amount is 4 to 20 times the mass of the silicone resin modified by the organic resin.

6. The method for preparing the heat-resistant and heat-insulating organosilicon 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, wherein the mass ratio of methyltrimethoxysilane, dimethyldimethoxysilane and phenyltrimethoxysilane is 10-20:5-10:10-20.

7. The method for preparing the heat-resistant and heat-insulating organosilicon aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that... The surfactant is one or more of the following: hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, polysorbate, polyethylene glycol, polyvinyl alcohol, polyoxyethylene ethyl ether, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium oleate.

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

9. The method for preparing the heat-resistant and heat-insulating organosilicon aerogel material based on the Piers-Rubinsztajn reaction according to claim 1, characterized in that... The gelation temperature is 80–180℃, and the gelation time is 24–72 h; the aging temperature is 50–100℃, and the aging time is 24–72 h.

10. The application of a heat-resistant and heat-insulating organosilicon aerogel material prepared by the method of any one of claims 1-9 in heat insulation materials.

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