A method for preparing renewable bio-based plant oil-toughened SiO2 aerogel

Abstract

The application provides a preparation method of renewable bio-based plant oil toughened SiO2 aerogel, which comprises the steps of preparing a binary grafting linear copolymer, preparing a polyallylsiloxane polymer, preparing a wet gel, and preparing SiO2 aerogel through supercritical CO2 drying. The preparation method of the renewable bio-based plant oil toughened SiO2 aerogel provided by the application uses renewable bio-based epoxy soybean oil and castor oil derivative ricinoleic acid as monomers to prepare a binary grafting linear copolymer through ring-opening polycondensation reaction as a toughening agent, uses allyl siloxane as a monomer to prepare a polyallyl siloxane through a free radical polymerization reaction as a silica aerogel silicon source, under the action of a catalyst, uses the toughening agent to perform crosslinking reaction on the silica wet gel to form a three-dimensional flexible network structure, so as to buffer external impact and internal shrinkage in the supercritical drying CO2 drying process, and finally, the SiO2 aerogel with large size, high transparency and low thermal conductivity is prepared.

Description

Technical Field

[0001] This invention belongs to the technical field of aerogel material preparation methods, and relates to a method for preparing renewable bio-based plant oil-toughened SiO2 aerogel. Background Technology

[0002] Traditional building exterior wall insulation materials, due to their high heat transfer coefficient, account for 40% of total social energy consumption, resulting in significant energy waste and ineffective energy loss. Aerogel, an ultralight, amorphous solid material composed of nanoparticles with a continuous three-dimensional nanoporous network structure and filled with a gaseous dispersion medium, possesses characteristics such as controllable nanoscale structure, high specific surface area, low density, high porosity, and low thermal conductivity, which can solve the problems of traditional materials in the field of building insulation. However, silica aerogel materials are difficult to mold due to cracking and curling caused by structural shrinkage during the drying process, which greatly limits its application and promotion in the construction field.

[0003] To overcome the brittleness of aerogels, Mayumi K et al. used isocyanates, Leventis, N et al. used epoxides, and Randall JP and Maleki H et al. used crosslinking of polyimide and polyacrylate to improve the toughness of aerogels, developing many robust silica-based composite aerogels. However, unlike natural silica aerogels, which have high visible light transparency, high specific surface area, and low density, traditional silica aerogel modification methods often lead to phase separation during two-phase blending due to poor compatibility. This results in a rough microstructure or inhomogeneity, reducing transparency, increasing density and thermal conductivity, and increasing opacity in the visible light region. Consequently, silica aerogels exhibit lower specific surface area and higher density, limiting their application in ultra-insulating materials, especially transparent window insulation. Improving the uniform dispersion and compatibility of organic compounds in silica aerogels to achieve toughening effects is one of the development directions for aerogels, and is of great significance for the practical application of large-size transparent / transparent aerogel composite glass, an important product for thermal protection of building exterior walls in my country. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing renewable bio-based plant oil-toughened SiO2 aerogel, thereby improving the light transmittance of the aerogel.

[0005] A method for preparing renewable bio-based plant oil-toughened SiO2 aerogel, the specific steps of which are as follows:

[0006] S1. Mix ricinoleic acid and epoxidized soybean oil in a heating container, fill with inert gas, add initiator one, and react at 160-180℃ for 30-150 min to obtain a binary grafted linear copolymer.

[0007] S2. Place allyl siloxane monomers in a heating container, fill with inert gas, add initiator II, and react at 90-130°C for 48-72 hours to obtain polyallyl siloxane polymers;

[0008] S3. The binary grafted linear copolymer and polyallylsiloxane polymer obtained in steps S1 and S2 are mixed with water and solvent and placed in a heating container. After adding a catalyst, the mixture is reacted at 75-100℃ for 5-70 minutes to form a wet gel. The wet gel is then aged and replaced with solvent and dried with supercritical CO2 to obtain SiO2 aerogel.

[0009] Further, in step S1, the acid value of the castor oil is 175-190, and the epoxy value of the epoxidized soybean oil is 0.3mol-0.8mol / 100g.

[0010] Further, in step S1, the initiator is any one of 2-dimethylaminopyridine, 4-dimethylaminopyridine, and 4-methylaminopyridine.

[0011] Further, in step S1, the weight ratio of ricinoleic acid: epoxidized soybean oil: initiator is equal to 1:(1.5-10):(0.005-0.01).

[0012] Further, in step S2, the allylsiloxane monomer is any one of allyltrimethoxysiloxane, allyldimethoxysiloxane, allylmonomethoxysiloxane, allyltriethoxysiloxane, allyldiethoxysiloxane, and allylmonoethoxysiloxane.

[0013] Further, in step S2, the initiator two is any one of benzoyl peroxide, dicumyl peroxide, and di-tert-butyl peroxide, and the weight ratio of allyl siloxane monomer to initiator two is equal to 1: (0.0025~0.005).

[0014] Further, in step S3, the solvent is any one of methanol, ethanol, benzyl alcohol, and toluene; and the catalyst is any one of ammonia and tetramethylammonium hydroxide.

[0015] Further, in step S3, the volume ratio of solvent: polyallylsiloxane polymer: binary grafted linear copolymer: water: catalyst is 1:(0.15~0.3):(0.05~0.1):(0.01~0.03):(0.002~0.003); the replacement aging solvent is any one of methanol, ethanol, benzyl alcohol, and toluene, the replacement aging time is 8h~12h, and the replacement aging temperature is 55℃~85℃.

[0016] Furthermore, in step S3, the supercritical CO2 drying pressure is 12MPa~15MPa, the drying temperature is 60℃~80℃, and the drying time is 6h~8h.

[0017] Further, in step S1, the binary grafted linear copolymer has an average molecular weight of 2500-9000 and a viscosity of 1000 mPa.s-4700 mPa.s; in step S2, the polyallylsiloxane polymer has an average molecular weight of 20000-35000 and a viscosity of 8500 mPa.s-15000 mPa.s.

[0018] The present invention provides a method for preparing renewable bio-based vegetable oil-toughened SiO2 aerogel. A binary grafted linear copolymer is prepared via ring-opening polycondensation using renewable bio-based epoxidized soybean oil and castor oil derivative ricinoleic acid as monomers, serving as a toughening agent. Allylsiloxane is prepared via free radical polymerization as a silicon source for the silica aerogel. Under the action of a catalyst, the toughening agent is used to crosslink the silica wet gel to form a three-dimensional flexible network structure, buffering external impacts and internal shrinkage during supercritical CO2 drying. This method yields a large-size, highly transparent, and low thermal conductivity SiO2 aerogel. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings:

[0020] Figure 1 This is a schematic diagram of the reaction principle of binary grafted linear copolymers.

[0021] Figure 2 This is a schematic diagram illustrating the reaction principle of polyallylsiloxane polymers.

[0022] Figure 3 This is a schematic diagram of the SiO2 aerogel reaction principle.

[0023] Figure 4 This is a size diagram of the SiO2 aerogel prepared in Example 3;

[0024] Figure 5 The image shows the transmittance of the SiO2 aerogel prepared in Example 3. Detailed Implementation

[0025] To further illustrate the concept of this invention, specific embodiments will be provided below for detailed explanation. These embodiments are merely illustrative and explanatory and should not be construed as limiting the scope of protection of this invention. All technologies implemented based on the content of this invention are covered within the scope of protection intended by this invention. Example 1

[0026] According to the mass ratio, ricinoleic acid with an acid value of 175 and epoxide soybean oil with an epoxy value of 0.3 mol / 100g were mixed in a ratio of 1:1.5 and placed in a heating container. After filling with inert gas, 0.05 parts of 4-dimethylaminopyridine were added as initiator one, and the reaction was carried out at 160℃ for 80 min to obtain a binary grafted linear copolymer. The reaction principle is as follows. Figure 1 As shown, its average molecular weight is 2800 and its viscosity is 1250 mPa·s.

[0027] One part by mass of allyltrimethoxysiloxane monomer was placed in a heating container, filled with inert gas, and then 0.0025 parts of benzoyl peroxide were added as initiator 2. The reaction was carried out at 110°C for 48 hours to obtain polyallylsiloxane polymer. The reaction principle is as follows: Figure 2 As shown, its average molecular weight is 22,000 and its viscosity is 9,000 mPa·s.

[0028] Methanol, polyallyltrimethoxysiloxane polymer, binary grafted linear copolymer, and water were mixed in a volume ratio of 1:0.1:0.05:0.01. Then, 0.002 parts of ammonia were added, and the mixture was reacted at 80℃ for 50 min to form a wet gel. The wet gel was aged in methanol solvent for 10 h at 60℃, followed by supercritical CO2 drying for 8 h at a pressure of 13.5 MPa and a temperature of 70℃, ultimately yielding SiO2 aerogel. The reaction principle is as follows: Figure 3 As shown, the thermal conductivity of the SiO2 aerogel was tested to be 0.0023 W / (mk), and the light transmittance was 29.5%. Example 2

[0029] According to the mass ratio, ricinoleic acid with an acid value of 190 and epoxidized soybean oil with an epoxy value of 0.3 mol / 100g were mixed at a ratio of 1:10 and placed in a heating container. After filling with inert gas, 0.05 parts of 2-dimethylaminopyridine were added as initiator one, and the reaction was carried out at 170℃ for 50 min to obtain a binary grafted linear copolymer with an average molecular weight of 3500 and a viscosity of 1600 mPa·s.

[0030] One part by mass of allyltriethoxysiloxane monomer was placed in a heating container, and after being filled with inert gas, 0.0025 parts of benzoyl peroxide was added as initiator II. The reaction was carried out at 120°C for 48 hours to obtain polyallylsiloxane polymer with an average molecular weight of 25,000 and a viscosity of 12,300 mPa·s.

[0031] Ethanol, polyallyltriethoxysiloxane polymer, binary grafted linear copolymer, and water were mixed in a volume ratio of 1:0.3:0.1:0.03. Then, 0.0025 parts of ammonia were added, and the mixture was reacted at 80℃ for 20 min to form a wet gel. The wet gel was aged in ethanol solvent for 12 h at 60℃, followed by supercritical CO2 drying for 8 h at a pressure of 14 MPa and a temperature of 70℃, finally yielding SiO2 aerogel. The thermal conductivity of this SiO2 aerogel was measured to be 0.0019 W / (mK), and its light transmittance was 43.6%. Example 3

[0032] According to the mass ratio, ricinoleic acid with an acid value of 180 and epoxidized soybean oil with an epoxy value of 0.6 mol / 100g were mixed in a 1:5 ratio and placed in a heating container. After filling with inert gas, 0.05 parts of 2-dimethylaminopyridine were added as initiator one, and the reaction was carried out at 180℃ for 30 min to obtain a binary grafted linear copolymer with an average molecular weight of 5500 and a viscosity of 2800 mPa·s.

[0033] One part by mass of allyltrimethoxysiloxane monomer was placed in a heating container, and after being filled with inert gas, 0.0025 parts of di-tert-butyl peroxide was added as initiator II. The reaction was carried out at 120°C for 72 h to obtain polyallylsiloxane polymer with an average molecular weight of 31,200 and a viscosity of 14,700 mPa·s.

[0034] Benzyl alcohol, polyallyltrimethoxysiloxane polymer, binary grafted linear copolymer, and water were mixed in a volume ratio of 1:0.2:0.1:0.02. Then, 0.0025 parts of tetramethylammonium hydroxide were added, and the mixture was reacted at 90℃ for 13 min to form a wet gel. The wet gel was aged in ethanol solvent for 8 h at 70℃, followed by supercritical CO2 drying for 6 h at a pressure of 15 MPa and a temperature of 80℃, finally yielding SiO2 aerogel. Figure 4 , Figure 5 As shown, the thermal conductivity of the SiO2 aerogel was tested to be 0.0027 W / (mk), and the light transmittance was 78.9%.

[0035] There are many methods and approaches that can realize the technical solution of this invention, and the above are merely preferred embodiments provided by way of example. Those skilled in the art can conceive of many modifications, alterations, and substitutions without departing from this invention. It should be understood that various alternatives to the embodiments of this invention described herein can be employed in the practice of this invention. The appended claims are intended to define the scope of this invention and therefore cover the methods within the scope of these claims and their equivalents. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

Claims

1. A method for preparing a renewable bio-based plant oil-toughened SiO2 aerogel, characterized in that: Includes the following steps: S1. Mix ricinoleic acid and epoxidized soybean oil in a heating container, fill with inert gas, add initiator one, and react at 160-180℃ for 30-150 min to obtain a binary grafted linear copolymer. S2. Place allyl siloxane monomers in a heating container, fill with inert gas, add initiator II, and react at 90-130°C for 48-72 hours to obtain polyallyl siloxane polymers. S3. The binary grafted linear copolymer and polyallylsiloxane polymer obtained in steps S1 and S2 are mixed with water and solvent and placed in a heating container. After adding a catalyst, the mixture is reacted at 75-100℃ for 5-70 minutes to form a wet gel. The wet gel is then aged and replaced with solvent and dried with supercritical CO2 to obtain SiO2 aerogel.

2. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 1, characterized in that: In step S1, the acid value of the castor oil is 175-190, and the epoxy value of the epoxidized soybean oil is 0.3mol-0.8mol / 100g.

3. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 1, characterized in that: In step S1, the initiator is any one of 2-dimethylaminopyridine, 4-dimethylaminopyridine, or 4-methylaminopyridine.

4. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 3, characterized in that: In step S1, the weight ratio of ricinoleic acid: epoxidized soybean oil: initiator one is equal to 1:(1.5-10):(0.005-0.01).

5. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 1, characterized in that: In step S2, the allylsiloxane monomer is any one of allyltrimethoxysiloxane, allyldimethoxysiloxane, allylmonomethoxysiloxane, allyltriethoxysiloxane, allyldiethoxysiloxane, or allylmonoethoxysiloxane.

6. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 5, characterized in that: In step S2, the second initiator is any one of benzoyl peroxide, dicumyl peroxide, or di-tert-butyl peroxide, and the weight ratio of allyl siloxane monomer to the second initiator is equal to 1:(0.0025~0.005).

7. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 1, characterized in that: In step S3, the solvent is any one of methanol, ethanol, benzyl alcohol, or toluene; the catalyst is any one of ammonia or tetramethylammonium hydroxide.

8. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 7, characterized in that: In step S3, the volume ratio of solvent: polyallylsiloxane polymer: binary grafted linear copolymer: water: catalyst is 1:(0.15~0.3):(0.05~0.1):(0.01~0.03):(0.002~0.003); the replacement aging solvent is any one of methanol, ethanol, benzyl alcohol or toluene, the replacement aging time is 8h~12h, and the replacement aging temperature is 55℃~85℃.

9. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 8, characterized in that: In step S3, the supercritical CO2 drying pressure is 12MPa~15MPa, the drying temperature is 60℃~80℃, and the drying time is 6h~8h.

10. The method for preparing renewable bio-based plant oil-toughened SiO2 aerogel according to claim 1, characterized in that: The binary grafted linear copolymer obtained in step S1 has an average molecular weight of 2500-9000 and a viscosity of 1000 mPa·s-4700 mPa·s; the polyallylsiloxane polymer obtained in step S2 has an average molecular weight of 20000-35000 and a viscosity of 8500 mPa·s-15000 mPa·s.

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