WO2023035578A1

WO2023035578A1 - Reaction kettle and preparation method for silicon dioxide aerogel thermal insulation composite material

Info

Publication number: WO2023035578A1
Application number: PCT/CN2022/081157
Authority: WO
Inventors: 张和平; 潘月磊; 程旭东; 龚伦伦
Original assignee: 中国科学技术大学先进技术研究院
Priority date: 2021-09-09
Filing date: 2022-03-16
Publication date: 2023-03-16
Also published as: CN113666712A

Abstract

The present application discloses a reaction kettle and a preparation method for a silicon dioxide aerogel thermal insulation composite material. The method comprises the following steps: providing a reaction kettle, wherein the reaction kettle comprises a kettle body and a plurality of ultrasonic device groups, the kettle body is provided with a reaction chamber, the plurality of ultrasonic device groups are arranged on the sidewall of the reaction chamber in an up-down direction, each ultrasonic device group comprises a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are arranged at intervals in the circumferential direction of the reaction chamber; providing a wet gel composite material subjected to aging treatment; placing the wet gel composite material in the reaction chamber, adding a silsesquioxane solution and an acid solution, and performing annular ultrasonic cavitation treatment, so that the liquid in the reaction chamber is emulsified and reacts so as to obtain a modified material; and drying the modified material to obtain the silicon dioxide aerogel thermal insulation composite material.

Description

Reactor and preparation method of silica airgel thermal insulation composite material

This application claims priority to a Chinese patent application with application number 202111060758.0 filed on September 9, 2021, the entire contents of which are hereby incorporated by reference into this application.

technical field

The application relates to the technical field of airgel preparation, in particular to a reaction kettle and a method for preparing a silica airgel thermal insulation composite material.

Background technique

Silica airgel is a nanoporous material with a highly cross-linked silica network structure, which has low density, large specific surface area, small pore size, large porosity, low thermal conductivity and strong adsorption. Based on these properties, silica aerogels are used in thermal insulation materials, catalyst carriers, sound insulation, optical applications, etc. Because silica airgel has poor mechanical properties and is not pressure-resistant, in order to promote the application of silica airgel in the field of thermal insulation, silica airgel is compounded with silica and fiber reinforcement. , prepared into silica airgel thermal insulation composites. Among them, the fiber reinforcement mainly includes fiber materials such as glass fiber, aramid fiber, and mullite fiber.

There are three main methods for the preparation of silica airgel composites: supercritical drying, freeze drying and atmospheric drying. Among them, the development of atmospheric pressure drying method has greatly reduced the production cost of silica airgel, making the large-scale production of silica airgel composite materials possible, and thus widely used.

Since the wet gel composite contains a large amount of water, and the surface modifier is easy to react with water, in order to avoid the loss of the surface modifier, it is necessary to reduce the water content in the wet gel composite. The silica airgel process uses solvent exchange to remove moisture from the material. Specifically, it comprises the following steps: a. the preparation stage of silica wet gel composite material; b. The aging stage of the wet gel composite; c. The solvent exchange and surface hydrophobic modification stage of the wet gel composite; d. The atmospheric pressure drying of the wet gel composite. Solvent exchange and surface hydrophobic modification are time-consuming and solvent-consuming due to the high water content and the poor penetration of solvents into the composites. For example, the patent with publication number CN101973752A discloses a glass fiber reinforced silica airgel composite material and a preparation method thereof. It adopts tetraethyl orthosilicate and methyltrimethoxysilane as co-precursors to prepare wet gel, then after aging the wet gel, it is modified twice with TMCS (trimethylchlorosilane), and finally dried under normal pressure An airgel composite is obtained. However, in this invention, the wet gel requires multiple solvent exchanges with ethanol and n-hexane, which consumes a large amount of solvent and has a long cycle. In addition, the modification process uses the conventional active surface modifier TMCS wet modification, TMCS is difficult to penetrate into the wet gel composite material for modification and the consumption of TMCS is large, the generated by-products cannot be reused, and the consumption of raw materials The cost and the cost of post-solvent recovery treatment are relatively large. The surface modification efficiency of TMCS is also low (preparation cycle > 3 days), and the quality of the obtained airgel composites is average.

technical problem

The main purpose of this application is to propose a preparation method of silica airgel thermal insulation composite material, aiming to solve the problem of consuming too much solvent in the modification stage of the traditional preparation method.

technical solution

In order to achieve the above purpose, the present application proposes a method for preparing a silica airgel thermal insulation composite material, the preparation method of the silica airgel thermal insulation composite material comprises the following steps:

A reaction kettle is provided, the reaction kettle includes a kettle body and a plurality of ultrasonic device groups, the kettle body has a reaction chamber, a plurality of the ultrasonic device groups are arranged on the side wall of the reaction chamber along the up and down direction, each of the ultrasonic The transducer group includes a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are arranged at intervals along the circumference of the reaction chamber;

Provide aged wet gel composites;

placing the wet gel composite material in the reaction chamber, adding a silsesquioxane solution and an acid solution, and performing annular ultrasonic cavitation treatment, so that the liquid in the reaction chamber is emulsified and reacted to obtain a modified Material;

The modified material is dried to obtain a silica airgel thermal insulation composite material.

In one embodiment, the wet gel composite material is placed in the reaction chamber, a silsesquioxane solution and an acid solution are added, and an annular ultrasonic cavitation treatment is performed, so that the liquid in the reaction chamber is emulsified and In the step of reacting to obtain the modified material, the silsesquioxane solution includes one or more of MTMS, DMCS, TMCS, TMBS, TMMS, HMDSO, HMDZ and octamethyltrisiloxane; and/ or,

The acid solution includes one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and the concentration of the acid solution is 0.01-32.5mol/L.

In one embodiment, the wet gel composite material is placed in the reaction chamber, a silsesquioxane solution and an acid solution are added, and an annular ultrasonic cavitation treatment is performed, so that the liquid in the reaction chamber is emulsified and In the step of reacting to obtain the modified material, the power of each ultrasonic transducer is 0.1~4.0KW, and the frequency is 20~30KHz; and/or,

The time for the annular ultrasonic cavitation treatment is 10 to 240 minutes.

In one embodiment, the step of providing an aged wet gel composite comprises:

Dilute the silicon source with water to form a diluent, add acid, and acidify under stirring conditions to obtain a sol solution;

After the pH of the sol solution is adjusted to 3-9 with an alkaline aqueous solution, it is introduced into the fiber reinforcement, left to stand for gelation, and aged to obtain an aged wet gel composite material.

In one embodiment, after diluting the silicon source with water into a diluent, acid is added, and acidified under stirring conditions to obtain a sol solution,

The silicon source includes an aqueous sodium silicate solution, the mass fraction of the aqueous sodium silicate solution is 26-46%, and the modulus is 2.1-4.8; and/or,

The acid includes one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and the concentration of the acid is 0.01~29.8mol/L; and/or,

In the diluent, the volume ratio of water and silicon source is 0.1-10:1, and the volume ratio of the diluent and the acid is 1-24:1; and/or,

The temperature of the acidification treatment is 10-70°C, and the acidification time is 0.1-50min.

In one embodiment, after adjusting the pH of the sol solution to 3-9 with an alkaline aqueous solution, introducing it into the fiber reinforcement, standing for gelation, and aging treatment to obtain an aged-treated wet gel composite material middle,

The standing gelation time is 0.01~180min; and/or,

The aging treatment time is 0.1~10h; and/or,

The solute of the alkaline aqueous solution includes ammonia water, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium carbonate or sodium silicate, and the concentration of the alkaline aqueous solution is 0.01-8 mol/L.

In one embodiment, the step of drying the modified material to obtain a silica airgel thermal insulation composite material includes:

Under the condition of 90-200° C., the modified material is blast-dried for 10-180 minutes to obtain a silica airgel thermal insulation composite material.

In addition, this application also proposes a reaction kettle, which is used in the modification process of preparing silica airgel thermal insulation composite materials, and the reaction kettle includes:

The still body has a reaction chamber; and,

A plurality of ultrasonic transducer groups are arranged on the side wall of the reaction chamber along the vertical direction, each of the ultrasonic transducer groups includes a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are spaced along the circumference of the reaction chamber set up.

In one embodiment, the still body includes an outer shell and an inner shell disposed in the outer shell, the inner shell defines the reaction chamber inside, and a gap between the outer shell and the inner shell Cavities for accommodating heat exchange fluid are formed at intervals, and a plurality of ultrasonic devices are assembled on the outer wall of the inner casing.

In one embodiment, the inner casing has a plurality of outer walls connected in sequence, and each of the outer walls is a plane.

Beneficial effect

In the technical scheme provided by this application, the wet gel composite material is modified by using silsesquioxane solution and acid solution, and annular ultrasonic cavitation is performed after adding silsesquioxane solution and acid solution, because the reaction chamber Ultrasonic transducers are installed on the upper, lower and surrounding sides, and the ultrasonic waves can cover the solution and all the wet gel composite materials in the reaction chamber comprehensively and uniformly. An emulsification effect occurs between the semisiloxane solution and the acid solution, and the two solutions fuse with each other in the form of small droplets. With the occurrence of cavitation, the temperature of the solution rises, and the two solutions undergo a violent hydrolysis reaction to generate a large amount of active The surface modifier trimethylsilanol ((CH ₃ ) ₃ -Si-OH), trimethylsilanol is very easy to undergo grafting reaction with Si-OH in the wet gel composite material, thus completing the wet gel material The surface modification process is fast and the thermal conductivity of the obtained silica airgel thermal insulation composite material is <0.02W/m·K, the hydrophobic angle is >165°, and the average specific surface area is >700 m ² /g , the quality is better; at the same time, trimethylsilanol can undergo self-condensation reaction when it meets water to regenerate silsesquioxane, and the generated silsesquioxane can participate in the next cycle reaction process. In this way, only need to add The acid solution can make the modification process continue, greatly reducing the amount of solvent consumed and reducing production costs; moreover, ultrasonic cavitation can generate high temperatures above 5000K and 5.05108 Under the high pressure of Pa, the surface modifier violently impacts and shocks the wet gel composite material under the action of cavitation micro-bubbles, making it easier for the surface modifier to penetrate into the wet gel composite material to complete the modification, further reducing the amount of the modifier. Loss, improved modification efficiency, shortened preparation cycle, and can be used to prepare thick silica airgel thermal insulation composite materials.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only For some embodiments of the present application, those skilled in the art can also obtain other related drawings according to these drawings without creative effort.

Fig. 1 is the schematic flow chart of an embodiment of the preparation method of the silica airgel thermal insulation composite material provided by the present application;

Figure 2 is a schematic flow diagram of another embodiment of the preparation method of the silica airgel thermal insulation composite material provided by the present application;

Fig. 3 is the structural representation of an embodiment of the reactor provided by the application;

Fig. 4 is the top view of reactor among Fig. 3;

Fig. 5 is the A-A sectional view of reactor among Fig. 4;

Fig. 6 is the scanning electron micrograph of the silica airgel thermal insulation composite material that Fig. 1 method makes;

Fig. 7 is the test diagram of the water droplet hydrophobic angle of the silica airgel thermal insulation composite material prepared by the method of Fig. 1;

Figure 8 is an infrared spectrum detection spectrum of the silica airgel thermal insulation composite material prepared by the method of Figure 1;

Fig. 9 is a physical diagram of the silica airgel thermal insulation composite material prepared by the method in Fig. 1 .

Explanation of reference numbers:

标号 label	名称 name	标号 label	名称 name
100 100	反应釜 Reactor	20 20	超声换能器 ultrasonic transducer
10 10	釜体 Kettle body	101 101	反应腔 reaction chamber
1 1	外壳体 Shell	102 102	容腔 Cavity
2 2	内壳体 Inner shell	30 30	隔板 Partition

The realization, functional features and advantages of the present application will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Embodiments of the present invention

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market. In addition, the meaning of "and/or" appearing in the whole text includes three parallel schemes, taking "A and/or B" as an example, including scheme A, scheme B, or schemes that both A and B satisfy. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist , nor within the scope of protection required by the present application. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of this application.

This application proposes a reaction kettle 100, which can be used in the modification process of preparing silica airgel thermal insulation composite materials. Figures 3 to 5 are specific embodiments of the reaction kettle 100 proposed by this application .

Referring to Fig. 3 to Fig. 5, described reactor 100 comprises still body 10 and a plurality of supersonicator groups, and described still body 10 has reaction chamber 101, and a plurality of described sonicator groups are arranged on described reaction chamber 101 along the up and down direction Each ultrasonic group includes a plurality of ultrasonic transducers 20 , and the plurality of ultrasonic transducers 20 are arranged at intervals along the circumference of the reaction chamber 101 .

The kettle body 10 is roughly in the shape of a pot, and a reaction chamber 101 is formed inside it. The central axis of the reaction chamber 101 is arranged along the vertical direction. The reaction chamber 101 is used to place reaction substances for reaction. The specific shape of the cross-section of the reaction chamber 101 may be circular, elliptical, polygonal, etc., which is not limited in this application. Specifically, in one embodiment, the kettle body 10 includes an outer shell 1 and an inner shell 2 disposed inside the outer shell 1, the inner shell 2 defines the reaction chamber 101 inside, the A cavity 102 for accommodating heat exchange fluid is formed at intervals between the outer shell 1 and the inner shell 2, and a plurality of ultrasonic devices are assembled on the outer wall of the inner shell 2, and the kettle body 10 is designed in this way , a cavity 102 can be formed between the outer shell 1 and the inner shell 2, so that a heat exchange fluid, such as heat exchange oil, heat exchange water, heat exchange gas, etc., can be injected into it, and heat is transferred through the heat exchange fluid, A suitable reaction temperature environment is provided for the reaction chamber 101 . Based on this, a partition 30 can be further arranged on the outer wall of the inner casing 2, and a closed space is formed between the partition 30 and the inner casing 2 for installing the ultrasonic transducer 20, so as to avoid the ultrasonic transducer 20 and the heat exchange fluid, causing safety hazards.

In this embodiment, multiple ultrasonic transducers 20 are provided. Specifically, the reactor 100 includes a plurality of ultrasonic groups, and each ultrasonic group includes a plurality of ultrasonic transducers 20 . During specific setting, a plurality of ultrasonic device groups are arranged on the side wall of described reaction chamber 101 along the up and down direction, like this, can ensure that reaction chamber 101 is fully covered by ultrasonic wave in vertical direction, when wet gel composite material is placed in reaction chamber 101, it is usually placed vertically in a roll shape, and multiple ultrasonic device groups are arranged in the up and down direction, which can make the wet gel composite material as a whole within the range of ultrasonic radiation. Based on this, the coverage range of the ultrasonic set in the up-down direction is not smaller than the space range usually involved by the reactants in the reaction chamber 101, so as to ensure that the ultrasound can fully cover the space range involved in the reactants in the up-down direction.

At the same time, the plurality of ultrasonic transducers 20 of each ultrasonic group are arranged at intervals along the circumferential direction of the reaction chamber 101, so that it can be ensured that the ultrasonic waves can cover the circumferential direction of the reaction chamber 101. When the wet gel composite material is placed in the reaction chamber 101, the multiple ultrasonic transducers 20 arranged along the circumferential direction can make the wet gel composite material be in the ultrasonic range everywhere in the circumferential direction. Based on this, a plurality of ultrasonic transducers 20 are arranged around the reaction chamber 101 .

When the reaction kettle 100 is used in the following modification process for preparing silica airgel thermal insulation composite materials, it mainly plays an annular ultrasonic cavitation role. In order to ensure the reaction effect, the denser the density of the ultrasonic transducers 20, the more Well, considering the reaction effect, energy consumption and equipment cost and other factors, the distance between any two adjacent ultrasonic transducers 20 can be set within the range of 2-6 cm.

The specific shapes of the inner shell 2 and the outer shell 1 are not limited in the present application, based on this, the cavity 102 formed between them can be of any shape. As a preferred embodiment, the inner housing 2 has a plurality of outer walls connected in sequence, and each of the outer walls is flat, so that each ultrasonic transducer 20 can be better and more firmly installed in the inner housing 2 on the outer wall; specifically, referring to Figure 2, in this embodiment, the inner housing 2 is a regular octagon.

In addition, this application also proposes a preparation method of silica airgel thermal insulation composite material, which has low cost, short preparation cycle, simple operation, mild reaction conditions, and the prepared silica airgel thermal insulation composite The material has good hydrophobicity and low thermal conductivity.

Figure 1 and Figure 2 are specific examples of the preparation method of the silica airgel thermal insulation composite material proposed in this application.

Referring to Fig. 1, the preparation method of described silica airgel thermal insulation composite material comprises the following steps:

Step S10, providing a reaction kettle 100, the reaction kettle 100 includes a kettle body 10 and a plurality of ultrasonic device groups, the kettle body 10 has a reaction chamber 101, and a plurality of the ultrasonic device groups are arranged in the reaction chamber along the vertical direction 101 , each ultrasonic group includes a plurality of ultrasonic transducers 20 , and the plurality of ultrasonic transducers 20 are arranged at intervals along the circumference of the reaction chamber 101 .

The reaction kettle 100 has all the technical features of the above-mentioned embodiments, which will not be repeated here.

Step S20, providing an aging-treated wet gel composite material.

Wherein, the wet gel composite material may be any wet gel composite material formed by combining silicon dioxide and fiber reinforcement. The material can be purchased as a finished product on the market, or can be prepared by itself.

Referring to Fig. 2, in some embodiments, step S20 can be implemented according to the following steps:

Step S21, after diluting the silicon source with water to form a diluent, adding an acid, and acidifying under stirring conditions to obtain a sol solution.

Wherein, the silicon source refers to silicon-containing raw materials, for example, silicon dioxide, tetramethylsilane, water glass and the like. Specifically, in this embodiment, the silicon source includes sodium silicate aqueous solution, the mass fraction of the sodium silicate aqueous solution is 26-46%, and the modulus is 2.1-4.8.

Wherein, the acid includes one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and the concentration of the acid is 0.01-29.8mol/L. It should be noted that the concentration of the above-mentioned acid refers to the total concentration of all solutes in the solution, for example, when the acid is a mixture of hydrochloric acid and nitric acid, its concentration is the total molar concentration of HCl and HNO ₃ .

The concentration of diluent, degree of acidification and acidification conditions will all affect the quality of the sol solution, and then affect the quality of the wet gel composite. In view of this, during specific implementation, in the dilution liquid, the volume ratio of water and silicon source is 0.1～10:1, mix water and silicon source according to above-mentioned volume ratio to obtain the dilution liquid of suitable concentration; The dilution liquid based on this concentration , the volume ratio of the diluent to the acid is 1 to 24:1 to control the degree of acidification.

In addition, the temperature of the acidification treatment is 10-70° C., and the acidification time is 0.1-50 minutes.

Step S22, after adjusting the pH of the sol solution to 3-9 with an alkaline aqueous solution, introducing it into the fiber reinforcement, standing for gelation, and aging treatment to obtain an aged wet gel composite material.

Wherein, the solute of the alkaline aqueous solution includes ammonia water, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium carbonate or sodium silicate, and the concentration of the alkaline aqueous solution is 0.01~8mol/L; the fiber reinforcement Including glass fiber, aramid fiber, mullite fiber and other fiber materials, this article takes glass fiber as an example to illustrate. The standing gelation time is 0.01-180min; the aging treatment method is to place the gelled wet gel composite material at room temperature for aging for a period of time, specifically, the aging treatment time is 0.1-180min. 10h.

Step S30, placing the wet gel composite material in the reaction chamber 101, adding a silsesquioxane solution and an acid solution, and performing annular ultrasonic cavitation treatment, so that the liquid in the reaction chamber 101 is emulsified and generated reaction to obtain modified materials.

Wherein, the silsesquioxane solution includes MTMS (methyltrimethoxysilane), DMCS (dimethylchlorosilane), TMCS (trimethylchlorosilane), TMBS (trimethylbromosilane), TMMS ( One or more of trimethylmethoxysilane), HMDSO (hexamethyldisiloxane), HMDZ (hexamethyldisilazane), and octamethyltrisiloxane; the acid includes hydrochloric acid , hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and the concentration of the acid solution is 0.01~32.5mol/L.

The annular ultrasonic cavitation treatment refers to opening a plurality of ultrasonic transducers 20 in the reactor 100. Since the plurality of ultrasonic transducers 20 surround the reaction chamber 101 in all directions in the up-down direction and the circumferential direction, it is possible to play an annular The effect of ultrasound; under the joint action of multiple ultrasonic transducers 20, the silsesquioxane solution and the acid solution in the reaction chamber 101 can undergo cavitation. Specifically, ultrasonic cavitation means that under the action of ultrasonic pressure waves, the average distance between liquid phase molecules changes with the continuous vibration of molecules. When the liquid is in the negative pressure half cycle of ultrasonic alternating sound pressure, the pressure Under the action of a sufficiently strong negative pressure, the mutual attraction between liquid phase molecules is broken. When the distance between molecules exceeds the critical molecular distance of the substance in the liquid state, the liquid will break and generate holes, forming cavitation nuclei. After that, the cavitation nucleus in the sound field absorbs energy continuously, vibrates, expands, contracts, and finally bursts and collapses. During the cavitation process, the energy accumulated by the cavitation nucleus is released rapidly, and extreme physical conditions such as high temperature above 5000K, high pressure above 100MPa, shock wave and micro jet are generated in the tiny space where cavitation occurs.

In this embodiment, the silsesquioxane solution and the acid solution are two kinds of immiscible solutions, and stratification will occur in the reaction chamber 101. Among them, the silsesquioxane solution has a low density and is generally located in the upper layer, and the acid solution High density, generally located in the lower layer. Under the action of annular ultrasonic cavitation, a severe emulsification effect occurs between the silsesquioxane solution and the acid solution, and the two solutions fuse with each other in the form of small droplets. Subsequently, with the occurrence of cavitation, the temperature of the solution increased, and the two solutions underwent a violent hydrolysis reaction to generate a large amount of active surface modifier trimethylsilanol ((CH ₃ ) ₃ -Si-OH). Trimethylsilanol can undergo self-condensation reaction with water to regenerate silsesquioxane, thereby continuously consuming the water in the wet gel composite and reducing its water content. At the same time, the generated silsesquioxane can participate in The next cyclic reaction process is repeated until the moisture in the wet gel composite is reacted. During this period, only the acid solution is added to allow the reaction to continue, thereby greatly reducing the cost of water removal while achieving The amount of solvent reduces the production cost; at the same time, trimethylsilanol is very easy to undergo grafting reaction with Si-OH in the wet gel composite material, thereby completing the surface modification process of the wet gel material, the modification speed is fast and The thermal conductivity of the obtained silica airgel thermal insulation composite material is <0.02W/m·K, the hydrophobic angle is >165°, the average specific surface area is >700 m ² /g, and the quality is good.

The wet gel composite material has a block structure, and it is difficult for external modifiers to enter the block for deep modification, resulting in the use of a large amount of modifiers and the greatly prolonged modification time. In this method, the ring-shaped ultrasonic technology modification method is adopted, and the ultrasonic wave can promote the uniform coexistence (emulsification) of immiscible solutions. At the same time, the high-frequency oscillation provided by the ultrasound produces cavitation effect in the reaction solvent, which can generate a high temperature above 5000K and a high pressure of 5.0510 ⁸ Pa in a very small space and a very short time. Under the action of cavitation micro-bubbles, the wet gel composite material is violently impacted and shocked, making it easier for the surface modifier to penetrate into the wet gel composite material to complete the modification, which further reduces the loss of the modifier, improves the modification efficiency, and shortens the The preparation cycle is shortened, and it can be used to prepare thicker silica airgel thermal insulation composite materials.

Specifically, the power of each of the ultrasonic transducers 20 is 0.1-4.0KW, and the frequency is 20-30KHz, so that ultrasonic cavitation can be realized; the time for the annular ultrasonic cavitation treatment is 10-240min, and during specific implementation, Depending on the size, thickness and moisture content of the wet gel composite, the time can be adapted.

Step S40, drying the modified material to obtain a silica airgel thermal insulation composite material.

During specific implementation, step S40 includes:

In step S41, the modified material is blast-dried for 10-180 minutes under the condition of 90-200° C. to obtain a silica airgel thermal insulation composite material.

In the technical scheme provided by this application, the wet gel composite material is modified by using silsesquioxane solution and acid solution, and annular ultrasonic cavitation is performed after adding silsesquioxane solution and acid solution, because the reaction chamber Ultrasonic transducers 20 are arranged on the upper, lower and surrounding sides of 101. Ultrasonic waves can fully and uniformly cover the solution and all wet gel composite materials in the reaction chamber 101. Under the action of ultrasonic cavitation, the silsesquioxane solution and acid The solution can quickly react to generate a modifier, which can quickly penetrate into the wet gel composite material and modify it. The modified silica airgel thermal insulation composite material is shown in Figure 9, which has the following properties: The microstructure shown in Figure 6, it can be seen from Figure 6 that the three-dimensional network structure of the airgel is evenly distributed, the pore size is distributed in the range of mesopores (2-50nm), and it has good thermal insulation performance, which shows that the airgel The silica airgel thermal insulation composite material prepared by the application method has good structure and thermal insulation performance; at the same time, the infrared spectrum of the silica airgel thermal insulation composite material is shown in Figure 8, from the spectrum It can be seen that under the treatment of ultrasonic modification, the Si-OH of the silica airgel was successfully grafted and replaced by Si-O-Si-(CH ₃ ) ₃ , indicating that the method of this application has realized the anti-wetting Surface modification of adhesive composite materials, and the modified product has an efficient hydrophobic modification effect.

Further, the hydrophobic performance of the silica airgel thermal insulation composite material was investigated, and the results are shown in Figure 7. It can be seen from the water droplet hydrophobic angle test chart that the silica airgel thermal insulation composite material The average hydrophobic angle is as high as 173°, which shows that the silica airgel thermal insulation composite material prepared by the method of the present application has excellent hydrophobic performance, reaches superhydrophobicity, and has a broader practical application range.

The technical solutions of the present application will be described in further detail below in conjunction with specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present application and are not intended to limit the present application.

The following examples all use the reactor 100 as shown in FIG. 3 to FIG. 5 to carry out the reaction.

Example 1

1. Take 34 mL of water glass, dilute it with 215 mL of water, introduce 192 mL of the diluted solution into 8 mL of 11.7 mol/L hydrochloric acid solution, and acidify at 30°C for 10 minutes to obtain a sol solution. Among them, water glass is an aqueous solution of sodium silicate with a mass fraction of 36% and a modulus of 2.1 to 4.8.

II. Adjust the pH of the sol solution obtained in I to 5.0 with 3.7 mol/L NaOH aqueous solution, stir for 2 minutes, introduce it into the glass fiber composite material, and let it stand for 2 minutes to gel.

Ⅲ. Put the wet gel composite material obtained in Ⅱ into the annular ultrasonic reactor and let it stand for aging for 0.1h. Then, add 54mL of 12mol/L HCl solution and 100mL of HMDSO, and perform annular ultrasonic cavitation treatment for 60min. The power of the ultrasonic transducer is 1.0KW and the frequency is 20KHz.

Ⅳ. Take the modified gel composite material in Ⅲ, place it in a forced air oven and dry it for 20 minutes at 150° C. to obtain a superhydrophobic silica airgel thermal insulation composite material.

The thermal conductivity of the silica airgel thermal insulation composite point is 0.017W/m·K, the hydrophobic angle is 173°, the average specific surface area is 705.3m ² /g, and the thickness of the composite material is 1.5cm.

Example 2

Ⅰ. Take 34 mL of water glass, dilute it with 78 mL of water, introduce all the diluted solution into 17.5 mL of 5.8 mol/L oxalic acid solution, and acidify at 30°C for 10 minutes to obtain a sol solution. Among them, water glass is an aqueous solution of sodium silicate with a mass fraction of 36% and a modulus of 2.1 to 4.8.

II. Adjust the pH of the sol solution obtained in I to 4.8 with 3.7 mol/L ammonia solution, stir for 2 minutes, introduce it into the glass fiber composite material, and let it stand for 10 minutes to gel.

Ⅲ. Put the wet gel composite material obtained in Ⅱ into an annular ultrasonic reactor and seal it for aging for 0.2h, then add 44.5mL of 18.4mol/L sulfuric acid solution and 150mL MTMS, conduct ring ultrasonic cavitation treatment for 45min. The power of the ultrasonic transducer is 2.0KW and the frequency is 25KHz.

The thermal conductivity of the silica airgel thermal insulation composite point is 0.018W/m·K, the hydrophobic angle is 174°, the average specific surface area is 728m ² /g, and the thickness of the composite material is 1.5cm.

Example 3

Ⅰ. Take 34 mL of water glass, dilute it with 340 mL of water, introduce 160 mL of the diluted solution into 16 mL of a mixed solution of 29.8 mol/L hydrofluoric acid, hydrobromic acid and glacial acetic acid, and acidify at 20°C for 10 minutes to obtain a sol liquid. Among them, water glass is an aqueous solution of sodium silicate with a mass fraction of 46% and a modulus of 2.1 to 4.8.

II. Adjust the pH of the sol solution obtained in I to 5.5 with 5 mol/L sodium bicarbonate aqueous solution, stir for 2 minutes, introduce it into the glass fiber composite material, and let it stand for 180 minutes to gel.

Ⅲ. Put the wet gel composite material obtained in Ⅱ into the ring-shaped ultrasonic reactor and let it stand for aging for 1h, then add 54mL of 0.01mol/L mixed solution of hydrofluoric acid, hydrobromic acid and glacial acetic acid and 100mL DMCS The mixed solution of , TMCS and TMBS was subjected to annular ultrasonic cavitation treatment for 30 minutes. The power of the ultrasonic transducer is 0.1KW and the frequency is 26KHz.

Ⅳ. Take the modified gel composite material in Ⅲ, place it in a forced air oven and dry it for 180 minutes at 90°C to obtain a superhydrophobic silica airgel thermal insulation composite material.

The thermal conductivity of the silica airgel thermal insulation composite point is 0.018W/m·K, the hydrophobic angle is 176°, the average specific surface area is 733m ² /g, and the thickness of the composite material is 1.5cm.

Example 4

1. Take 340 mL of water glass, dilute it with 34 mL of water, introduce 80 mL of the diluted solution into 80 mL of 0.01 mol/L sulfuric acid, and acidify at 70°C for 0.1 min to obtain a sol solution. Among them, water glass is an aqueous solution of sodium silicate with a mass fraction of 26% and a modulus of 2.1 to 4.8.

II. Adjust the pH of the sol solution obtained in I to 9 with 8 mol/L sodium silicate aqueous solution, stir for 2 minutes, introduce it into the glass fiber composite material, and let it stand for 10 minutes to gel.

Ⅲ. Put the wet gel composite material obtained in Ⅱ into an annular ultrasonic reactor and let it stand for aging for 5 hours. Then, add 54mL of a mixed solution of 32.5mol/L phosphoric acid, oxalic acid and glacial acetic acid and 100mL The mixed solution of HMDSO and octamethyltrisiloxane was subjected to annular ultrasonic cavitation treatment for 240min. The power of the ultrasonic transducer is 4.0KW and the frequency is 28KHz.

The thermal conductivity of the silica airgel thermal insulation composite point is 0.018W/m·K, the hydrophobic angle is 168°, the average specific surface area is 861m ² /g, and the thickness of the composite material is 3.0cm.

Example 5

Ⅰ. Take 100mL of water glass, dilute it with 100mL of water, introduce 128ml of the diluted solution into 20mL of 10mol/L phosphoric acid, and acidify at 10°C for 50min to obtain a sol solution. Among them, water glass is an aqueous solution of sodium silicate with a mass fraction of 36% and a modulus of 2.1 to 4.8.

II. Adjust the pH of the sol solution obtained in I to 3 with 0.01 mol/L potassium carbonate aqueous solution, stir for 2 minutes, introduce it into the glass fiber composite material, and let it stand for 0.01 minutes to gel.

Ⅲ. Put the wet gel composite material obtained in Ⅱ into an annular ultrasonic reactor and let it age for 10 hours. Then, add 54mL of 10mol/L nitric acid solution and 100mL TMMS, and perform annular ultrasonic cavitation treatment for 10 minutes. The power of the ultrasonic transducer is 2.0KW and the frequency is 30KHz.

Ⅳ. Take the modified gel composite material in Ⅲ, place it in a forced air oven and dry it for 10 minutes at 200°C to obtain a superhydrophobic silica airgel thermal insulation composite material.

The thermal conductivity of the silica airgel thermal insulation composite point is 0.019W/m·K, the hydrophobic angle is 172°, the average specific surface area is 863m ² /g, and the thickness of the composite material is 1.5cm.

Example 6

Ⅰ. Take 34mL of water glass, dilute it with 215mL of water, introduce 192ml of the diluted solution into 8mL of 11.7mol/L nitric acid, and acidify it at 30°C for 10min to obtain a sol solution. Among them, water glass is an aqueous solution of sodium silicate with a mass fraction of 36% and a modulus of 2.1 to 4.8.

II. Adjust the pH of the sol solution obtained in I to 5.0 with 6mol/L sodium carbonate aqueous solution, stir for 2 minutes, introduce it into the glass fiber composite material, and let it stand for 2 minutes to gel.

Ⅲ. Put the wet gel composite material obtained in Ⅱ into the annular ultrasonic reactor and let it stand for aging for 0.1h. Then, add 54mL of 12mol/L HCl solution and 100mL of HMDZ, and perform annular ultrasonic cavitation treatment for 60min. The power of the ultrasonic transducer is 1.0KW and the frequency is 20KHz.

The thermal conductivity of the silica airgel thermal insulation composite point is 0.017 W/m·K, the hydrophobic angle is 175°, the average specific surface area is 796m ² /g, and the thickness of the composite material is 1.5cm.

Comparative example 1

Except that the setting position of the ultrasonic transducer of the reactor was changed to the bottom of the reaction chamber, other steps were the same as in Example 1.

In this comparative example, the thermal conductivity of the silica airgel thermal insulation composite material point is 0.029W/m·K, the hydrophobic angle is 143°, the average specific surface area is 552 m ² /g, the thickness of the composite material is 1.5cm, and the ultrasonic modification It takes about 5.8 hours.

Comparative example 2

Except that the step after the aging treatment in step III adopts the traditional solvent replacement method, other steps are the same as in Example 1. Among them, the solvent replacement method is as follows: instead of adopting the circular ultrasonic modification method, the obtained wet gel composite material after aging treatment is soaked in 150 mL of ethanol solvent at 50°C for 6.0 hours, and then the above process is repeated after replacing with a new ethanol solvent. times (using 150mL ethanol solvent each time), in order to achieve the purpose of ethanol solvent replacing a large amount of water in the pores of wet gel. Then soak the wet gel composite material after solvent replacement in the strong active surface modifier TMCS to fully modify it for 12 hours, and finally take out the modified wet gel and dry it under normal pressure to obtain the airgel composite material.

In this comparative example, the thermal conductivity of the silica airgel thermal insulation composite point is 0.025W/m·K, the hydrophobic angle is 161°, the average specific surface area is 653m ² /g, the thickness of the composite material is 1.5cm, and the solvent replacement takes time About 35 hours.

The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. For those skilled in the art, various modifications and changes may be made to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the scope of patent protection of this application.

Claims

A method for preparing a silica airgel thermal insulation composite material, comprising the following steps:

A reaction kettle is provided, the reaction kettle includes a kettle body and a plurality of ultrasonic device groups, the kettle body has a reaction chamber, a plurality of the ultrasonic device groups are arranged on the side wall of the reaction chamber along the up and down direction, each of the ultrasonic The transducer group includes a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are arranged at intervals along the circumference of the reaction chamber;

Provide aged wet gel composites;

placing the wet gel composite material in the reaction chamber, adding a silsesquioxane solution and an acid solution, and performing annular ultrasonic cavitation treatment, so that the liquid in the reaction chamber is emulsified and reacted to obtain a modified Material;

The modified material is dried to obtain a silica airgel thermal insulation composite material.
The preparation method of silica airgel thermal insulation composite material as claimed in claim 1, wherein, described wet gel composite material is placed in described reaction chamber, adds silsesquioxane solution and acid solution, Annular ultrasonic cavitation treatment, so that the liquid in the reaction chamber is emulsified and reacted, and in the step of obtaining the modified material, the silsesquioxane solution includes MTMS, DMCS, TMCS, TMBS, TMMS, HMDSO, HMDZ and one or more of octamethyltrisiloxane; and/or,

The acid solution includes one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and the concentration of the acid solution is 0.01-32.5mol/L.
The preparation method of silica airgel thermal insulation composite material as claimed in claim 1, wherein, described wet gel composite material is placed in described reaction chamber, adds silsesquioxane solution and acid solution, Annular ultrasonic cavitation treatment, so that the liquid in the reaction chamber is emulsified and reacted, and in the step of obtaining the modified material, the power of each ultrasonic transducer is 0.1~4.0KW, and the frequency is 20~30KHz; and /or,

The time for the annular ultrasonic cavitation treatment is 10 to 240 minutes.
The preparation method of silica airgel thermal insulation composite material as claimed in claim 1, wherein, the step of providing the wet gel composite material through aging treatment comprises:

Dilute the silicon source with water to form a diluent, add acid, and acidify under stirring conditions to obtain a sol solution;

After the pH of the sol solution is adjusted to 3-9 with an alkaline aqueous solution, it is introduced into the fiber reinforcement, left to stand for gelation, and aged to obtain an aged wet gel composite material.
The preparation method of silica airgel heat-insulating composite material as claimed in claim 4, wherein, after diluting the silicon source with water into a diluent, adding acid, and acidizing under stirring conditions to obtain the sol solution,

The silicon source includes an aqueous sodium silicate solution, the mass fraction of the aqueous sodium silicate solution is 26-46%, and the modulus is 2.1-4.8; and/or,

The acid includes one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and the concentration of the acid is 0.01~29.8mol/L; and/or,

In the diluent, the volume ratio of water and silicon source is 0.1-10:1, and the volume ratio of the diluent and the acid is 1-24:1; and/or,

The temperature of the acidification treatment is 10-70°C, and the acidification time is 0.1-50min.
The preparation method of silica airgel heat-insulating composite material as claimed in claim 4, wherein, after adjusting the pH of the sol solution to 3-9 with an alkaline aqueous solution, it is introduced into a fiber reinforcement, and the gel is left to stand In the step of aging treatment to obtain the wet gel composite material after aging treatment,

The standing gelation time is 0.01~180min; and/or,

The aging treatment time is 0.1~10h; and/or,

The solute of the alkaline aqueous solution includes ammonia water, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium carbonate or sodium silicate, and the concentration of the alkaline aqueous solution is 0.01-8 mol/L.
The preparation method of silica airgel thermal insulation composite material as claimed in claim 1, wherein, drying described modified material, the step of obtaining silica airgel thermal insulation composite material comprises:

Under the condition of 90-200° C., the modified material is blast-dried for 10-180 minutes to obtain a silica airgel thermal insulation composite material.
A reaction kettle used in the modification process of preparing silica airgel thermal insulation composite materials, wherein the reaction kettle includes:

The still body has a reaction chamber; and,

A plurality of ultrasonic transducer groups are arranged on the side wall of the reaction chamber along the vertical direction, each of the ultrasonic transducer groups includes a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are spaced along the circumference of the reaction chamber set up.
The reactor according to claim 8, wherein the still body comprises an outer shell and an inner shell disposed in the outer shell, the inner shell defines the reaction chamber, the outer shell and the inner shell Cavities for accommodating heat exchange fluid are formed at intervals between the inner shells, and a plurality of ultrasonic devices are assembled on the outer wall of the inner shells.
The reaction kettle according to claim 8, wherein the inner casing has a plurality of outer walls connected in sequence, and each of the outer walls is a plane.