CN108793173B - Method for preparing modified silica aerogel material by adopting external circulation mode and normal pressure drying - Google Patents

Method for preparing modified silica aerogel material by adopting external circulation mode and normal pressure drying Download PDF

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CN108793173B
CN108793173B CN201810865511.8A CN201810865511A CN108793173B CN 108793173 B CN108793173 B CN 108793173B CN 201810865511 A CN201810865511 A CN 201810865511A CN 108793173 B CN108793173 B CN 108793173B
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fiber
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CN108793173A (en
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张和平
潘月磊
程旭东
龚伦伦
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University of Science and Technology of China USTC
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/157—After-treatment of gels
    • C01B33/158—Purification; Drying; Dehydrating
    • C01B33/1585—Dehydration into aerogels
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C01P2006/17—Pore diameter distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/32—Thermal properties

Abstract

The invention provides a preparation method of a modified silica aerogel material, which comprises the following steps of placing an aged silica wet gel material and a modifier precursor into a reaction container, and returning the modifier precursor into the reaction container after the modifier precursor is subjected to external circulation hydrolysis to perform modification reaction to obtain the modified silica aerogel material; the modifier is a modifier which can generate a modifier precursor through a polymerization reaction when meeting water. The invention abandons the traditional process link of organic solvent exchange, adopts an external circulation one-step modification mode, has less organic solvent consumption, low cost and small environmental hazard, avoids the use and waste of the organic solvent in the link, saves a large amount of silane modifiers for the subsequent surface modification process, improves the surface modification efficiency, and reduces the cost and the environmental hazard; the preparation method has the advantages of short preparation period, high efficiency, simple operation and mild reaction conditions, and is suitable for industrial continuous production.

Description

Method for preparing modified silica aerogel material by adopting external circulation mode and normal pressure drying
Technical Field
The invention relates to the technical field of high-performance porous materials, and relates to a preparation method of a modified silicon dioxide aerogel material. In particular to a method for preparing a modified silicon dioxide aerogel material by adopting an external circulation mode and drying at normal pressure.
Background
Aerogel, also called xerogel, is a solid substance form, which is a highly dispersed solid material that is formed by the mutual coalescence of colloidal particles or high polymer molecules into a nanoporous network structure and is filled with gaseous dispersion medium in the pores, and is one of the less dense solids in the existing materials, and has continuous mesoporous pores, which are nanostructures composed of mutually cross-linked nanoparticles or polymer chains with a characteristic diameter of about 10 nm. These nanostructures provide high surface area, relatively large pore volume, low bulk density, low thermal and acoustic conductivity. Because of these excellent characteristics, aerogels are used in the fields of catalysts and carriers thereof, aerospace, molecular sieves, sensors, and electrochemistry. There are many kinds of aerogels, including silicon-based, carbon-based, sulfur-based, metal oxide-based, or metal-based ones, and the common aerogel is silicon-based aerogel (SiO)2Etc.), silica aerogels having excellent heat insulating properties and environmental stability, high porosity, good transparency and good stability are their outstanding generationsTable (7). However, silica aerogels are themselves extremely brittle and can form particle shedding during bending or compression, limiting their practical application to industry. Therefore, the silica aerogel composite material is generally formed by fixing brittle silica aerogel inside a fiber toughening body by using the fiber as the toughening framework. The material overcomes the defect that the silica aerogel is fragile, can be applied to large-area planar wall heat preservation and insulation, can also be applied to pipelines with bent and special structures or other spaces, greatly expands the industrial application field of the silica aerogel material, and has great application prospect.
In the existing production process, the key of preparing the silicon dioxide aerogel composite material is to extract the solution in the framework and replace the solution with air on the premise of keeping the gel framework undamaged. Therefore, the preparation of the silica aerogel composite material is a core technology in the drying process. Currently, methods for preparing silica aerogel composites are classified into supercritical drying methods, atmospheric drying methods, and freeze-drying methods. The supercritical drying method is greatly applied to industrial production due to the simple operation process and excellent silica aerogel forming characteristics. The method forms supercritical fluid by utilizing liquid under high pressure, and theoretically avoids the unbalanced capillary pressure generated on the wall surface of the framework when the liquid in the gel framework is discharged from pores. However, the supercritical drying process has high requirements on equipment, and the later maintenance cost is not low. And the operation requires high temperature and high pressure conditions, so that the danger coefficient is large. Therefore, another alternative method of freeze-drying has received a great deal of attention from scholars. The freeze-drying method requires freezing the gel into ice cubes and then sublimating the ice crystals within the gel under vacuum. The method has the great disadvantage that the solution in the gel skeleton can grow into ice nuclei in the freezing process, and the growth and expansion of the ice nuclei can cause irreversible damage to the skeleton structure. This results in a deterioration of the structural characteristics of the final silica aerogel itself, all of which perform differently than in supercritical dried products. The method which is considered to be the most promising alternative to supercritical drying is the atmospheric drying method. In the normal pressure drying method, the most important is to perform hydrophobic modification on the hydrogel composite material and then dry the hydrogel composite material under the normal pressure condition. The quality of the modification determines the quality of the silica aerogel obtained.
In chinese patent publication No. CN104478394A, a silica aerogel powder is provided, which is obtained by using industrial water glass as a precursor and performing surface modification treatment using trimethylchlorosilane as a silane modifier. And mixing the prepared silicon dioxide aerogel powder and the fiber felt mutually to obtain the fiber reinforced silicon dioxide aerogel composite material. The method has a long preparation period, and the preparation time of a single batch of samples is more than 48 hours. And the powder needs to be dispersed in the pores of the fiber toughening material, the process is difficult, and the condition that the distribution of the silicon dioxide aerogel powder in the inner layer of the fiber is not uniform is easily caused.
In chinese patent publication No. CN102557577A, tetraethyl orthosilicate is used as a silicon source, and glass fiber or cellucotton material is used as a reinforcement, an alkaline catalyst is added after acidification, wet gel is formed after impregnation, solvent exchange and aging are performed in an ethanol solution, trimethylchlorosilane is added for surface modification, and normal pressure drying is performed after washing with normal hexane, so as to obtain the hydrophobic silica aerogel composite material. However, the preparation period of the method is long, and the cost of the precursor tetraethyl orthosilicate is high, so that the method is not beneficial to large-scale industrial production. The trimethylchlorosilane is active in nature, can be hydrolyzed to generate corrosive hydrochloric acid gas when meeting water, and poses serious threats to the environment and operators.
In chinese patent publication No. CN101318659, water glass is used as a silicon source, a fiber material or polyurethane flexible foam is used as a reinforcement, a silicon source sol solution is prepared by using acidic ion exchange resin or inorganic acid as a hydrolysis catalyst, then an alkaline catalyst is added to adjust the pH to a proper range, the reinforcement is immersed in the sol, standing for gelation, aging, organic solvent exchange, and finally an organic silicon compound, such as methyl trimethoxysilane, trimethyl methoxysilane and other modifiers are added to perform surface modification, and the hydrophobic silica aerogel composite material is prepared under normal pressure drying. The prepared silicon dioxide aerogel composite material has good hydrophobic property and heat insulation property. The process requires further optimization of the subsequent modification effect by a laborious exchange process of organic solvents. But the investment cost of the organic solvent is huge, and the solvent is very difficult to recover and reuse after solvent exchange, which increases the production cost and solves the environmental protection problem, thus being not beneficial to industrial popularization and application. And the time of solvent exchange is very long, thereby greatly increasing the preparation period of the silicon dioxide aerogel composite material. Moreover, it can be seen from the conventional methods that the organic solvent is generally used for solvent exchange, especially alcohols such as ethanol, methanol, ethylene glycol or butanol are mostly used, mainly because the alcohol organic solvent can be mutually soluble with water to exchange water. The purpose of the solvent exchange is to displace the water in the silica gel space network, replacing the water in the pores with an organic solvent. And organosilane modifiers such as trimethylchlorosilane and the like can react with water in pores, so that the consumption of the silane modifiers can be greatly reduced after the water in the pores is replaced by an organic solvent. However, when organic solvents such as alcohols are used as solvents for exchanging pore water, the consumption of the silane modifier is still larger than the amount required for actual modification, which causes the loss of the silane surface modifier, and accordingly, the cost is greatly increased, and the popularization and the use of aerogel products are limited.
Therefore, how to find a more suitable preparation method of the modified silica aerogel material, which can reduce the consumption of organic solvents, is environment-friendly and green, and reduces the production cost, has become one of the problems to be solved by many application researchers in the industry.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a method for preparing a modified silica aerogel material, which is a method for preparing a modified silica aerogel material by using an external circulation manner and drying at normal pressure, the method replaces a conventional solvent replacement method, does not use organic solvents such as alcohols, has low production cost, short preparation period, simple operation and mild reaction conditions, and is suitable for industrial continuous production, and the prepared silica aerogel material has a super-hydrophobic characteristic, a low thermal conductivity coefficient and excellent mechanical properties.
The invention provides a preparation method of a modified silica aerogel material, which comprises the following steps:
1) placing the aged silica wet gel material and a modifier precursor in a reaction container, and returning the modifier precursor to the reaction container after the modifier precursor is subjected to external circulation hydrolysis to perform modification reaction to obtain a modified silica aerogel material;
the modifier is a modifier which can generate a modifier precursor through a polymerization reaction when meeting water.
Preferably, the modifier precursor comprises a silsesquioxane compound;
the hydrolysis is specifically hydrolysis by adding an auxiliary agent;
the time of the modification reaction is 4-12 h;
the liquid level height of the modifier precursor is less than or equal to the height of the aged silica wet gel material.
Preferably, the step 1) is specifically:
11) placing the aged silicon dioxide wet gel material and the modifier precursor into a reaction container, wherein the reaction container is connected with a second reaction container and is used for liquid phase conveying;
the second reaction container is filled with an auxiliary agent or a mixture of the auxiliary agent and a modifier precursor;
12) carrying out modification reaction, conveying the modifier precursor to a second reaction container, and returning the modifier precursor to the reaction container after hydrolysis;
13) after the modification reaction is finished, drying to obtain a modified silica aerogel material;
the auxiliary agent comprises acid or alkali;
the modifier precursor comprises one or more of methyltrimethoxysilane, dimethylmonochlorosilane, trimethylmonochlorosilane, trimethylbromosilane, trimethylmethoxysilane, tetramethylsilane, hexamethyldisiloxane, hexamethyldisilazane and octamethyltrisiloxane.
Preferably, the acid is one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid;
the acid comprises an acid solution;
the concentration of the acid solution is 0.2-17.8 mol/L;
the alkali is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia water, magnesium hydroxide and aluminum hydroxide;
the base comprises a base solution;
the concentration of the alkali solution is 3-12 mol/L;
the return mode is specifically as follows: spraying into a reaction vessel from top to bottom.
Preferably, the area of the spray is larger than or equal to the cross-sectional area of the aged silica wet gel material;
on the reaction container, a liquid phase outlet is arranged below the liquid level of the reaction container, and a liquid phase inlet is arranged at the top of the reaction container;
on the second reaction vessel, a liquid phase inlet is arranged at the bottom of the second reaction vessel, and a liquid phase outlet is arranged below the liquid level of the second reaction vessel;
in the second reactor, the ratio of the volume of the liquid to the volume of the second reactor is 25-75%;
in the mixture of the auxiliary agent and the modifier precursor, the volume ratio of the modifier precursor to the auxiliary agent is (0.5-20): 1.
preferably, the conveying flow rate is 0.3-2.2 m3/h；
The flow rate of the return is 0.3-2.2 m3/h；
The drying time is 10-240 min;
the drying temperature is 100-200 ℃;
the aged silicon dioxide wet gel material is prepared by the following steps:
a) acidifying a silicon source, water and acid to obtain a sol solution;
b) and (3) adjusting the pH value of the sol solution obtained in the step, performing microwave treatment, and aging to obtain the aged silica wet gel material.
Preferably, the silicon source comprises water glass;
the volume ratio of the silicon source to the water is 1: (0.4 to 7);
the modulus of the water glass is 3.0-3.5;
the acid comprises an acid solution;
the step a) is specifically as follows: mixing a silicon source and water to obtain a diluent, and then acidifying the diluent and an acid solution to obtain a sol solution;
the volume ratio of the diluent to the acid solution is (0.5-20): 1.
preferably, the acid comprises one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid;
the concentration of the acid solution is 0.2-17.8 mol/L;
the time of the acidification treatment is 20-50 min;
the temperature of the acidification treatment is 10-80 ℃.
Preferably, the pH value is 4-7;
the pH value is adjusted by adding alkaline solution;
the alkaline solution comprises one or more of sodium carbonate, ammonia water, sodium hydroxide, sodium bicarbonate, sodium silicate and potassium carbonate;
the concentration of the alkaline solution is 0.5-5 mol/L.
Preferably, the power ratio of the microwave treatment is 0.4-4.0 KW/400mL of sol solution;
the microwave treatment time is 20-450 s;
the method also comprises the step of adding fiber materials before the microwave treatment;
the fiber material comprises one or more of glass fiber, basalt fiber, mullite fiber, aluminum silicate fiber, alumina fiber, ceramic fiber, perlite fiber and high silica fiber;
the volume ratio of the fiber material to the sol solution is (0.1-1.5): 1;
the aging time is 5-48 h.
The invention provides a preparation method of a modified silica aerogel material, which comprises the following steps of placing an aged silica wet gel material and a modifier precursor into a reaction container, and returning the modifier precursor into the reaction container after the modifier precursor is subjected to external circulation hydrolysis to perform modification reaction to obtain the modified silica aerogel material; the modifier is a modifier which can generate a modifier precursor through a polymerization reaction when meeting water. Compared with the prior art, the method aims at solving the problems that in the existing process of preparing the modified silica aerogel material by normal-pressure drying, a common organic solvent exchange method consumes a large amount of alcohol organic solvent, the subsequent modification effect needs to be further optimized through the complicated exchange process of the organic solvent, the investment cost of the organic solvent is huge, the solvent is very difficult to recover and reuse after solvent exchange, the cost is high, the time of solvent exchange is long, and the like, which are not beneficial to industrial popularization and application, and meanwhile, the solvent exchange method still has the defect that the consumption of the silane modifier is larger than the required amount of actual modification.
Based on a large amount of experiments and researches, the key steps for preparing the hydrophobic silica aerogel material are solvent exchange and silane surface modification, and the invention also finds that in the actual exchange process, the exchange of the alcohol organic solvent can not completely exchange water in the pores of the aerogel, so that residual water can react with the silane surface modifier, and the excessive consumption of the modifier is caused. The invention creatively provides a preparation method of a modified silica aerogel material, which abandons the traditional process link of organic solvent exchange, adopts an external circulation one-step modification mode, has low organic solvent consumption, low cost and small environmental hazard, avoids the use and waste of organic solvent in the link, saves a large amount of silane modifier for the subsequent surface modification process, improves the surface modification efficiency, and reduces the cost and the environmental hazard. The preparation method has the advantages of short preparation period and high efficiency.
The invention introduces an external circulation modification technology in the link of surface modification, greatly accelerates the reaction process and shortens the whole preparation period. The traditional solvent exchange process needs to be carried out for at least two times and more than two times, each time is not less than 3 hours, the period is very long, and the process is complicated. In addition, in the process, the consumption of the organic solvent is extremely high, the subsequent recovery and purification investment is high, and the production cost is increased. The process abandons the solvent exchange process, directly carries out one-step modification, adopts an external circulation modification technology, fully utilizes the modified by-products, does not waste the solvent, and has good modification effect and short period. The method has good controllability, each link of the silicon dioxide aerogel composite material is controllable and adjustable, an innovative once-through external circulation modification method is used for replacing the traditional organic solvent exchange-modification mode, and the surface modification is more thorough and efficient. In addition, the method is simple and convenient to operate, mild in reaction conditions and suitable for industrial continuous production, and the prepared silicon dioxide aerogel material has the super-hydrophobic characteristic, low heat conductivity coefficient and excellent mechanical properties.
Experimental results show that compared with a traditional normal-pressure drying method, the preparation period of the preparation method provided by the invention is shortened to 25% -40% of the traditional time, the usage amount of the organic solvent is reduced to 14% -30% of the traditional usage amount, and no organic waste liquid is generated; meanwhile, the thermal conductivity coefficient of the prepared silicon dioxide aerogel composite material is 0.014-0.025W/m.K, the average hydrophobic angle reaches 156 degrees, the average pore diameter of the silicon dioxide aerogel is 16.4nm, and the average specific surface area is 683.4m2/g。
Drawings
FIG. 1 is a schematic diagram of the production flow and equipment of the external circulation modification mode in the preparation method provided by the invention;
FIG. 2 is a diagram of a hydrophobic test object of the silica aerogel thermal insulation composite prepared in example 1 of the present invention;
FIG. 3 is a scanning electron microscope image of a silica aerogel thermal insulation composite prepared in example 1 of the present invention;
FIG. 4 is a graph showing the isothermal nitrogen adsorption and desorption curves of the silica aerogel thermal insulation composite prepared in example 2 of the present invention;
FIG. 5 is a pore size distribution diagram of a silica aerogel thermal insulation composite prepared in example 2 of the present invention.
Detailed Description
For a further understanding of the invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are included merely to further illustrate the features and advantages of the invention and are not intended to limit the invention to the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All of the starting materials of the present invention are not particularly limited in their purity, and the present invention preferably employs purity levels commonly used in the art of analytically pure or aerogel materials.
The invention provides a preparation method of a modified silica aerogel material, which comprises the following steps:
1) placing the aged silica wet gel material and a modifier precursor in a reaction container, and returning the modifier precursor to the reaction container after the modifier precursor is subjected to external circulation hydrolysis to perform modification reaction to obtain a modified silica aerogel material;
the modifier is a modifier which can generate a modifier precursor through a polymerization reaction when meeting water.
The modifier is a modifier which can generate a modifier precursor through a polymerization reaction in water. The specific choice of the modifier is not particularly limited in the present invention, and may be selected and adjusted by those skilled in the art according to the actual application, product quality and product properties, as is conventional for hydrophobically modified silica aerogels.
The modifier precursor preferably comprises a silsesquioxane compound, particularly preferably comprises one or more of methyltrimethoxysilane MTMS, dimethylmonochlorosilane DMCS, trimethylmonochlorosilane TMCS, trimethylbromosilane TMBS, trimethylmethoxysilane TMMS, tetramethylsilane TMS, hexamethyldisiloxane HMDSO, hexamethyldisilazane HMDZ and octamethyltrisiloxane, and more preferably MTMS, DMCS, TMCS, TMBS, TMMS, TMS, HMDSO, HMDZ or octamethyltrisiloxane.
The hydrolysis time is not particularly limited in the present invention, and may be selected and adjusted by those skilled in the art according to the practical application, product quality and product performance, and the hydrolysis time is matched with the modification reaction process.
The hydrolysis mode is not particularly limited in the present invention, and may be a conventional hydrolysis mode of the compound, which is well known to those skilled in the art, and can be selected and adjusted by those skilled in the art according to the actual application situation, the product quality and the product performance, and the hydrolysis in the present invention is particularly preferably performed by adding an auxiliary agent. The auxiliary is preferably an acid or base, more preferably an acid or base solution. The acid of the present invention may be one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid, and more preferably hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid or glacial acetic acid. The concentration of the acid solution is preferably 0.2-17.8 mol/L, more preferably 1-15 mol/L, more preferably 3-12 mol/L, more preferably 5-15 mol/L, more preferably 8-12 mol/L. The alkali of the invention can be one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia water, magnesium hydroxide and aluminum hydroxide, and is more preferably sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia water, magnesium hydroxide or aluminum hydroxide. The concentration of the alkali solution is preferably 3-12 mol/L, more preferably 5-10 mol/L, and more preferably 7-8 mol/L.
The conditions of the modification reaction are not particularly limited, and the conditions of the conventional modification reaction of the modified silica aerogel material, which are well known to those skilled in the art, can be selected and adjusted by those skilled in the art according to the actual application condition, the product quality and the product performance, and the time of the modification reaction is preferably 4-12 hours, more preferably 5-11 hours, more preferably 6-10 hours, and more preferably 7-9 hours. The temperature of the modification reaction is preferably normal temperature, and can be 10-40 ℃, or 15-35 ℃, or 20-30 ℃.
In order to ensure the modification process, better improve the performance of the final modified silica aerogel material and complete and refine the whole modification step, the process can be specifically as follows:
11) placing the aged silicon dioxide wet gel material and the modifier precursor into a reaction container, wherein the reaction container is connected with a second reaction container and is used for liquid phase conveying;
the second reaction container is filled with an auxiliary agent or a mixture of the auxiliary agent and a modifier precursor;
12) carrying out modification reaction, conveying the modifier precursor to a second reaction container, and returning the modifier precursor to the reaction container after hydrolysis;
13) and after the modification reaction is finished, drying to obtain the modified silica aerogel material.
According to the invention, firstly, the aged silicon dioxide wet gel material and the modifier precursor are placed in a reaction container, and the reaction container is connected with a second reaction container and used for liquid phase transportation. And the second reaction container is filled with an auxiliary agent or a mixture of the auxiliary agent and a modifier precursor.
The reaction vessel of the present invention is not particularly limited, and may be a conventional reactor known to those skilled in the art, and may be selected and adjusted by those skilled in the art according to the actual application, product quality and product properties, and the reaction vessel of the present invention is preferably a reaction vessel. The second reaction vessel is not particularly limited in the present invention, and may be a conventional reactor known to those skilled in the art, and those skilled in the art can select and adjust the second reaction vessel according to the actual application, product quality and product performance, and the second reaction vessel is preferably a reaction vessel.
In the present invention, the reaction vessel is connected to a second reaction vessel for liquid phase transportation, and the aged silica wet gel material in the reaction vessel is a solid material and is not affected by the connection. The connection according to the invention is preferably a pipe or tube connection. The pipe or line of the present invention is preferably provided with a valve or a pressurizing device, and the present invention is not particularly limited thereto, so as to better facilitate the control of the liquid phase transportation as a final object.
The specific proportion of the mixture of the assistant and the modifier precursor is not particularly limited, and a person skilled in the art can select and adjust the mixture according to the actual application condition, the product quality and the product performance, wherein in the mixture of the assistant and the modifier precursor, the volume ratio of the modifier precursor to the assistant is preferably (0.5-20): 1, more preferably (2.5 to 18): 1, more preferably (5.5 to 15): 1, more preferably (8.5 to 12): 1.
in the present invention, before or during the modification reaction, the second reaction vessel contains an auxiliary, or a mixture of an auxiliary and a modifier precursor, more preferably a mixture of an auxiliary and a modifier precursor. In the invention, the auxiliary agent is acid or alkali, specifically acid solution or alkali solution, and when the mixture of the auxiliary agent and the modifier precursor is contained in the second reaction container, the auxiliary agent and the modifier precursor are subjected to hydrolysis reaction under the stirring condition to obtain the modifier. The modifier is organic matter and is insoluble with the assistant to form layered mixture, the upper layer is modifier area and the lower layer is acid solution or alkali solution area. The stirring speed of the invention is preferably 50-280 r/min, more preferably 100-230 r/min, and more preferably 150-180 r/min.
The hydrolysis process and the conveying process occur simultaneously or in advance of the conveying process, the invention is not strictly limited, preferably the hydrolysis process and the conveying process occur simultaneously, at the moment, the modifier precursor in the reaction container is conveyed into a second reaction container, more preferably enters from the bottom of the second reaction container, and directly enters into the lower layer of the second reaction container, namely an auxiliary agent area, so that the hydrolysis reaction is carried out together to obtain the modifier; the modifier is lighter than the assistant solution and then enters the upper layer of the reactor, namely a modifier area, to form the external circulation of a modifier precursor.
In the present invention, the reaction vessel is connected with a second reaction vessel, and is used for liquid phase delivery, and on the reaction vessel, a liquid phase outlet, namely the liquid phase outlet used for modifier precursor delivery, is arranged below the liquid level of the reaction vessel, so as to facilitate liquid phase delivery, and is more preferably arranged at the bottom of the reaction vessel. On the reaction vessel, a liquid phase inlet, i.e., a liquid phase inlet through which the modifier after hydrolysis of the modifier precursor returns, is preferably arranged at the top of the reaction vessel, so as to facilitate modification of the silica aerogel material.
In the present invention, the second reaction vessel is connected with the reaction vessel and is used for liquid phase delivery, and on the second reaction vessel, the liquid phase inlet, i.e. the liquid phase outlet for inputting the modifier precursor, is preferably arranged at the bottom of the second reaction vessel, and may also be arranged below the liquid level of the auxiliary agent area of the second reaction vessel, so that the hydrolysis reaction of the modifier precursor and the auxiliary agent is an optimal scheme. The liquid phase outlet of the second reaction vessel, namely the liquid phase outlet of the modifier precursor after hydrolysis, is preferably arranged below the liquid level of the second reaction vessel, more preferably arranged in the modifier region below the liquid level of the second reaction vessel, so that the modifier after hydrolysis can be better returned to the reaction vessel.
The proportion of the liquid in the reactor and the second reactor is not particularly limited, and the liquid is loaded in a most suitable amount in a conventional container well known to those skilled in the art, and the loading can be selected and adjusted by those skilled in the art according to the actual application, the product quality and the product performance, and the ratio of the volume of the liquid in the second reactor is 25-75%, more preferably 35-65%, and still more preferably 45-55%.
In the invention, a modifier precursor is placed in the reaction container, and in order to further ensure the effect of the modification reaction, the liquid level height of the modifier precursor is preferably less than or equal to the height of the aged silica wet gel material, and more preferably, the liquid level height of the modifier precursor is preferably less than the height of the aged silica wet gel material, so as to ensure that the modifier subsequently returned to the reaction container can be better in full contact with the aged silica wet gel material.
The invention then carries out a modification reaction, and simultaneously the modifier precursor is conveyed into a second reaction vessel and returned to the reaction vessel after hydrolysis.
The conveying mode and parameters of the liquid are not particularly limited, and the conveying mode and parameters of the liquid are selected and adjusted by a person skilled in the art according to the actual production situation, the product quality and the product performance, and are preferably conveyed through a pipe or a pipeline connecting the reaction container and the second reaction container. The conveying flow rate of the invention is preferably 0.3-2.2 m3More preferably 0.5 to 2.0m3More preferably 0.8 to 1.7 m/h3More preferably 1.0 to 1.5m3/h。
The present invention is not particularly limited in the way and parameters of the transportation, and the transportation way and parameters of the conventional liquid, which are well known to those skilled in the art, can be selected and adjusted by those skilled in the art according to the actual production situation, product quality and product performance, and the transportation way of the present invention is preferably through a pipe or a pipeline connecting the reaction vessel and the second reaction vessel. The conveying flow rate of the invention is preferably 0.3-2.2 m3More preferably 0.5 to 2.0m3More preferably 0.8 to 1.7 m/h3More preferably 1.0 to 1.5m3/h。
The returning route and parameters are not particularly limited in the present invention, and can be selected and adjusted by those skilled in the art according to actual production conditions, product quality and product performance by using the returning route and parameters of conventional liquid well known to those skilled in the art, and the returning route of the present invention is preferably through the second reaction vessel and the second reaction vesselThe return is made by a pipe or tubing to which the reaction vessels are connected. The return flow rate of the invention is preferably 0.3-2.2 m3More preferably 0.5 to 2.0m3More preferably 0.8 to 1.7 m/h3More preferably 1.0 to 1.5m3/h。
In order to better return the modifier after hydrolysis of the modifier precursor to the reaction vessel for modifying the silica aerogel material and providing the structure and performance of the final product, the mode after returning to the reactor is specifically preferably as follows: spraying into a reaction vessel from top to bottom. The concrete parameters and conditions of the spraying are not particularly limited, the spraying conditions and parameters known by the technicians in the field can be selected and adjusted according to the practical application condition, the product quality and the product performance, and the spraying area of the spraying is preferably more than or equal to the cross-sectional area of the aged silica wet gel material, so that the modifier with extremely high activity can be sprayed on the top of the silica wet gel material in the form of small liquid beads and fully contacts and reacts with the silica gel on the surface of the material from top to bottom to achieve the purpose of surface modification. The cross-sectional area of the silica wet gel material is not a specific area in a specific direction, the cross-sectional area is related to the placement direction of the silica wet gel material in the reaction vessel, and the silica wet gel material is placed in the reaction vessel and is directly opposite to the area above the reaction vessel, namely the cross-sectional area of the silica wet gel material.
After the modification reaction is finished, the modified silica aerogel material is obtained by drying.
The drying mode and parameters are not particularly limited in the present invention, and can be selected and adjusted by those skilled in the art according to actual production conditions, product quality and product performance in the conventional drying mode and parameters well known to those skilled in the art, and the drying mode in the present invention is preferably air-blast drying. The drying time is preferably 10-240 min, more preferably 40-210 min, more preferably 70-180 min, and more preferably 100-150 min. The drying temperature is preferably 100-200 ℃, more preferably 120-180 ℃, and more preferably 140-160 ℃.
The source of the aged silica wet gel material is not particularly limited by the invention, and the aged silica wet gel material is prepared by a conventional preparation method of the aged silica wet gel material known to a person skilled in the art or is commercially available, and the person skilled in the art can select and adjust the aged silica wet gel material according to the actual application condition, the product quality and the product performance, the invention is a complete and optimized preparation process, the performance of the silica aerogel material is further improved, and the aged silica wet gel material is particularly and preferably prepared by the following steps:
a) acidifying a silicon source, water and acid to obtain a sol solution;
b) and (3) adjusting the pH value of the sol solution obtained in the step, performing microwave treatment, and aging to obtain the gel material.
The invention firstly carries out acidification treatment on a silicon source, water and acid to obtain sol solution.
According to the invention, firstly, water glass, an acidic catalyst and water are subjected to hydrolysis reaction to obtain the silica sol.
The silicon source used in the present invention is not particularly limited, and may be selected and adjusted by those skilled in the art according to actual production conditions, product quality and product properties, and may be used for preparing silica aerogel. The parameters of the water glass are not particularly limited, and the parameters of the water glass for preparing the silica aerogel, which are well known to those skilled in the art, can be selected and adjusted by those skilled in the art according to actual production conditions, product quality and product performance, the water glass is preferably industrial water glass, and the modulus of the water glass is preferably 3.0-3.5, more preferably 3.1-3.4, and more preferably 3.2-3.3. The water glass of the invention is preferably a sodium silicate aqueous solution with the mass fraction of 30 wt% -37 wt%, more preferably 31 wt% -36 wt%, and more preferably 32 wt% -35 wt%.
The amount of the water added in the present invention is not particularly limited, and may be any conventional amount well known to those skilled in the art, and those skilled in the art can select and adjust the amount according to actual production conditions, product quality and product performance, and the volume ratio of the silicon source to the water in the present invention is preferably 1: (0.4 to 7), more preferably 1: (1.4-6), more preferably 1: (2.4-5), more preferably 1: (3.4-4).
The selection of the acid is not particularly limited in the present invention, and may be performed by a conventional acid for such a reaction, which is well known to those skilled in the art, and can be selected and adjusted by those skilled in the art according to actual production conditions, product quality, and product properties, and the acid of the present invention preferably includes one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, nitric acid, oxalic acid, and glacial acetic acid, and more preferably hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid, or glacial acetic acid.
The adding mode of the acid is not particularly limited, and the acid can be used in a conventional using mode known by a person skilled in the art, and the person skilled in the art can select and adjust the acid according to the actual production condition, the product quality and the product performance, and the acid preferably comprises an acid solution, wherein the concentration of the acid solution is 0.2-17.8 mol/L, more preferably 1-15 mol/L, more preferably 3-12 mol/L, more preferably 5-15 mol/L, and more preferably 8-12 mol/L.
For further complete and refined preparation process, the step a) is preferably as follows: mixing a silicon source and water to obtain a diluent, and then acidifying the diluent and an acid solution to obtain a sol solution.
The addition amount of the acid is not particularly limited, and the acid can be used in conventional amounts well known to those skilled in the art, and can be selected and adjusted by those skilled in the art according to actual production conditions, product quality and product performance, and the volume ratio of the diluent to the acid solution is preferably (0.5-20): 1, more preferably (2.5 to 18): 1 is more preferably (5-15): 1, more preferably (8-12): 1.
the process and conditions of the acidification treatment are not particularly limited, and the conventional process and conditions of the reaction well known to those skilled in the art can be used, and the skilled in the art can select and adjust the acidification treatment time according to the actual production condition, the product quality and the product performance, wherein the acidification treatment time is preferably 20-50 min, more preferably 25-45 min, and more preferably 30-40 min. The temperature of the acidification treatment is preferably 10-80 ℃, more preferably 20-70 ℃, more preferably 30-60 ℃, and more preferably 40-50 ℃. The acidification treatment process of the present invention is preferably carried out with constant stirring.
Finally, the pH value of the sol solution obtained in the step is adjusted, and the gel material is obtained after microwave treatment and aging.
The manner of adjusting the pH value is not particularly limited in the present invention, and may be selected and adjusted by those skilled in the art according to the actual production situation, the product quality and the product performance in the conventional manner of adjusting the pH value of such reaction, which is well known to those skilled in the art, and the manner of adjusting the pH value in the present invention is preferably to adjust the pH value by adding an alkaline solution. The alkaline solution of the present invention preferably includes one or more of sodium carbonate, ammonia, sodium hydroxide, sodium bicarbonate, sodium silicate and potassium carbonate, and more preferably sodium carbonate, ammonia, sodium hydroxide, sodium bicarbonate, sodium silicate or potassium carbonate. The concentration of the alkaline solution is preferably 0.5-5 mol/L, more preferably 1.5-4 mol/L, and more preferably 2.5-3 mol/L.
The specific pH value after adjustment is not particularly limited, and the required pH value known by the skilled in the art can be selected and adjusted by the skilled in the art according to the actual production condition, the product quality and the product performance, and the pH value after adjustment is preferably 4-7, more preferably 4.5-6.5, and more preferably 5-6.
In order to further widen the application field of the silica aerogel material and further improve the comprehensive performance of the final material, the method preferably further comprises a step of adding a fiber material before the microwave treatment, namely the modified silica aerogel material preferably further comprises a modified silica aerogel composite material. The specific selection and addition amount of the fiber material are not particularly limited in the present invention, and may be conventional fiber materials and addition amounts well known to those skilled in the art for preparing silica aerogel composite materials, and those skilled in the art may select and adjust the fiber materials according to actual application, product quality and product performance, and the fiber material of the present invention preferably includes one or more of glass fiber, basalt fiber, mullite fiber, aluminosilicate fiber, alumina silicate fiber, alumina fiber, ceramic fiber, perlite fiber and high silica fiber, and more preferably glass fiber, basalt fiber, mullite fiber, alumina silicate fiber, alumina fiber, ceramic fiber, perlite fiber or high silica fiber. The volume ratio of the fiber material to the sol solution is preferably (0.1-1.5): 1, more preferably (0.3 to 1.2): 1, more preferably (0.5 to 1.0): 1, more preferably (0.6 to 0.9): 1; the fibrous material of the present invention is preferably a fibrous mat or mass.
The invention further improves the performance of the final aerogel product, reduces the gelation time, breaks through the conventional standing gelation way, and particularly adopts microwave irradiation treatment for gelation in the cross-linking gelation process of silica sol. The microwave treatment power ratio is preferably 0.4-4.0 KW/400mL, more preferably 0.9-3.5 KW/400mL, more preferably 1.4-3.0 KW/400mL, and more preferably 1.9-2.5 KW/400 mL. The time for the microwave treatment is preferably 20 to 450s, more preferably 70 to 400s, more preferably 120 to 350s, more preferably 150 to 300s, and more preferably 200 to 250 s.
The invention is based on the fact that the mutual polycondensation reaction of Si-OH can be generated under the action of a proper alkaline catalyst, so as to form a mutual cross-linking and intricate space porous structure, and the orthosilicate molecule is a dipolar molecule, and when the microwave is radiated, the dipolar orthosilicate molecule can generate violent spin and movement under the action of an alternating electric field of the microwave. The extremely large number of the orthosilicate molecules collide and rub with each other violently, the dehydration polymerization reaction between Si and OH is accelerated, and the time of the sol-gel process is greatly shortened. And the skeleton structure of the gel is more stable and is not easy to collapse compared with the traditional standing gel mode.
The aging method and conditions are not particularly limited in the present invention, and may be selected and adjusted by those skilled in the art according to the actual production conditions, product quality and product properties, and the aging method is preferably static aging. The aging time is preferably 5-48 h, more preferably 15-38 h, and more preferably 25-28 h. The temperature of the aging is preferably room temperature, more preferably 10-40 ℃, more preferably 15-35 ℃, and more preferably 20-30 ℃.
The parameters of the modified silica aerogel are not particularly limited, and a person skilled in the art can prepare the modified silica aerogel by referring to the above method, and the person skilled in the art can select and adjust the modified silica aerogel according to the actual application condition, the product quality and the product performance, and the thermal conductivity of the modified silica aerogel is preferably 0.014-0.025W/(m · K), more preferably 0.017-0.023W/(m · K), and more preferably 0.019-0.021W/(m · K). The average hydrophobic angle of the modified silica aerogel is preferably 150-190 degrees, more preferably 160-180 degrees, and more preferably 165-175 degrees. The average pore diameter of the silicon dioxide aerogel is preferably 4-30 nm, more preferably 9-25 nm, and more preferably 14-20 nm. The average specific surface area of the modified silicon dioxide aerogel is preferably 450-900 m2(iv)/g, more preferably 550 to 800m2A concentration of 650 to 700m is more preferable2/g。
In order to better perfect and optimize the preparation method of the modified silica aerogel material, the preparation method of the invention specifically comprises the following steps:
I. diluting industrial water glass with water, and then carrying out acidification treatment to obtain sol solution;
II. Adjusting the pH value of the sol solution obtained in the step I to be 4-7 by using an alkaline aqueous solution, introducing the sol solution into a prepared fiber composite material, and treating the fiber composite material by using microwaves to obtain a gel composite material;
III, rolling the gel composite material obtained in the step II, placing the rolled gel composite material into a reaction kettle ①, standing and aging;
and IV, taking silsesquioxane as a mixed solution A, preparing a mixed solution of silsesquioxane and acid liquor as a mixed solution B, respectively introducing the mixed solution A and the mixed solution B into a reaction kettle and a second reaction kettle ②, mutually conveying the mixed solution to carry out external circulation modification, taking out the wet gel composite material after modification, and carrying out air-blast drying treatment to obtain the hydrophobic hybrid silica aerogel, wherein the total volume of the mixed solution A is the final volume of the gel composite material (felt) just immersed in the reaction kettle, and the diameter of a spray head of the reaction kettle ① is larger than that of the rolled wet gel felt.
See the following equations (1) to (3):
Figure BDA0001750831350000181
the reaction mechanism of the invention is briefly described by adopting specific compounds in the reaction formulas I to III, and in the invention, water glass is subjected to acidification treatment and then undergoes hydrolysis reaction to obtain orthosilicic acid, which is shown in reaction (1); under the action of proper alkaline catalyst, the silicic acid molecules can generate mutual polycondensation reaction between Si and OH, thereby forming a mutual cross-linking and intricate spatial porous structure. The orthosilicate molecule is a dipolar molecule, and when microwaves are applied for irradiation, the dipolar orthosilicate molecule can generate violent spin and movement under the action of an alternating electric field of the microwaves. The extremely large number of the orthosilicate molecules collide and rub with each other violently, the dehydration polymerization reaction between Si and OH is accelerated, and the time of the sol-gel process is greatly shortened, as shown in reaction (2). And the skeleton structure of the gel is more stable and is not easy to collapse compared with the traditional standing gel mode.
The invention then rolls the wet gel felt pad and soaks in silsesquioxane, utilizes the external circulation modification mode to introduce the modifier chlorosilane generated after the mixed liquid in the reaction kettle ② reacts into the reaction kettle ① in which the wet gel felt pad is placed, and utilizes the spray head to uniformly spray the modifier on the wet gel felt pad in the form of small water beads, the modifier is fully contacted with the wet gel felt pad from top to bottom, the modification process is fully performed, then some byproduct siloxane generated after modification is conveyed back to the reaction kettle ②, the modifier is hydrolyzed with the acid liquid in the reaction kettle ②, thereby obtaining the modifier and sequentially circulating.
Referring to fig. 1, fig. 1 is a schematic diagram of a production process and equipment of an external circulation modification mode in a preparation method provided by the invention, wherein ① is a reaction kettle, ② is a second reaction kettle, 1 is a mixed solution a, 2 is a spray head, 3 is an aged wet gel material, 4 is a mixed solution B, fig. 1 is mainly divided into two reaction kettles ②, ② is filled with the mixed solution B which is a mixed solution of silsesquioxane and an acid solution, and is provided with a stirring paddle to promote the reaction of the silsesquioxane and the acid solution, so that a modifier chlorosilane is continuously generated, etc., ① is filled with a gel composite material and the mixed solution a, the mixed solution a is a silsesquioxane compound, the modifier in ② is introduced into ①, the spray head is thrown to be uniformly sprayed on a felt pad of ① in the form of small liquid beads, the silane compound reacts with a silicon hydroxyl group on wet gel from top to bottom, the purpose of surface grafting modification is achieved, chlorosilane which is not reacted and is in contact with water to form a silsesquioxane by-product by direct polymerization, the silsesquioxane is formed in a reaction kettle ①, the reaction kettle, and the utilization rate of the modifier is greatly increased, and the acid solution is greatly increased.
The steps of the invention provide a method for preparing the modified silica aerogel material by adopting an external circulation mode and drying at normal pressure. The invention abandons the traditional process link of organic solvent exchange, has less consumption of the organic solvent, low cost and small environmental hazard, adopts an external circulation one-step modification mode, avoids the use and waste of the organic solvent in the link, saves a large amount of silane modifiers for the subsequent surface modification process, improves the surface modification efficiency, and reduces the cost and the environmental hazard. The preparation method has the advantages of short preparation period and high efficiency. The invention introduces microwave technology and external circulation modification technology in the two links of sol-gel and surface modification, greatly accelerates the reaction process and shortens the whole preparation period. The traditional solvent exchange process needs to be carried out for at least two times and more than two times, each time is not less than 3 hours, the period is very long, and the process is complicated. In addition, in the process, the consumption of the organic solvent is extremely high, the subsequent recovery and purification investment is high, and the production cost is increased. The process abandons the solvent exchange process, directly carries out one-step modification, adopts an external circulation modification technology, fully utilizes the modified by-products, does not waste the solvent, and has good modification effect and short period. The invention has good controllability. In the invention, each link of the silicon dioxide aerogel composite material is controllable and adjustable. Microwave technology assistance is introduced, and the traditional organic solvent exchange-modification mode is replaced by an innovative once-through external circulation modification method, so that the surface modification is more thorough and efficient. In addition, the method is simple and convenient to operate, mild in reaction conditions and suitable for industrial continuous production, and the prepared silicon dioxide aerogel material has the super-hydrophobic characteristic, low heat conductivity coefficient and excellent mechanical properties.
Experimental results show that compared with a traditional normal-pressure drying method, the preparation period of the preparation method provided by the invention is shortened to 25% -40% of the traditional time, the usage amount of the organic solvent is reduced to 14% -30% of the traditional usage amount, and no organic waste liquid is generated; meanwhile, the thermal conductivity coefficient of the prepared silicon dioxide aerogel composite material is 0.014-0.025W/m.K, the average hydrophobic angle reaches 156 degrees, the average pore diameter of the silicon dioxide aerogel is 16.4nm, and the average specific surface area is 683.4m2/g。
For further illustration of the present invention, the following will describe the preparation method of a modified silica aerogel material in detail with reference to the following examples, but it should be understood that these examples are carried out on the premise of the technical scheme of the present invention, and the detailed embodiments and specific procedures are given, only for further illustration of the features and advantages of the present invention, not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
I, diluting water glass with water, and fully mixing and stirring 1.2L of water glass and 6L of water uniformly to obtain a diluted solution of the water glass. The diluted solution of water glass was slowly introduced into 244mL of a 10M hydrochloric acid solution to obtain a sol solution.
And II, adjusting the pH value of the sol solution obtained in the step I to 5.0 by using a 3M sodium hydroxide aqueous solution, stirring for a plurality of minutes, and then soaking the glass fiber felt pad into the sol solution. And after the sol solution is fully soaked, taking out the glass fiber felt pad, and performing microwave irradiation treatment on the glass fiber felt pad to obtain the gel composite material, wherein the microwave irradiation power is 0.4KW, and the microwave irradiation treatment time is 150 s.
III, rolling the gel composite material obtained in the step II, putting the rolled gel composite material into a reaction kettle ①, aging at room temperature for 5 hours, and then adding an HMDSO solution into the kettle until the wet gel composite material is just immersed.
IV, then 10L, 12mol/L hydrochloric acid solution and 10L HMDSO are introduced into a reaction kettle ②, the stirring is started, the stirring speed is 60r/min, then the transmission of the mixed liquid between the reaction kettles is started simultaneously, and the transmission flow is set to be 0.6m3H is used as the reference value. And (3) after the external circulation modification is carried out for 6 hours, taking out the composite material, and drying the composite material in a forced air oven at 150 ℃ for 120min to obtain the super-hydrophobic silica aerogel heat-insulation composite material.
The silica aerogel thermal insulation composite material prepared in example 1 of the present invention was characterized.
Referring to fig. 2, fig. 2 is a diagram of a hydrophobic test object of the silica aerogel thermal insulation composite prepared in example 1 of the present invention.
As can be seen from FIG. 2, the silica aerogel thermal insulation composite material has excellent super-hydrophobic property, and the hydrophobic angle is as high as 162.5 degrees. The invention successfully carries out the reaction of surface hydrophobic modification, and has good modification effect and strong hydrophobic capability.
Referring to fig. 3, fig. 3 is a scanning electron microscope image of the silica aerogel thermal insulation composite prepared in example 1 of the present invention.
As can be seen from FIG. 3, the silica aerogel prepared by the present invention has a complete network, uniform particle growth of the silica polymer, strong spatial stereospecificity, uniform pore size, and no occurrence of the phenomena of pore collapse and particle aggregation. These excellent microscopic properties explain the essential reasons for their low thermal conductivity and high specific surface area.
The silica aerogel heat-insulating composite material prepared in the embodiment 1 of the invention is detected. The results show that the thermal conductivity coefficient of the composite material is 0.0249W/m.K, the hydrophobic angle is 162.5 degrees, the average pore diameter of the silica aerogel is 15.3nm, and the average specific surface area is 692.2m2G, total preparation time is about 7.5 hours.
Example 2
A method for preparing a silicon dioxide aerogel composite material by external circulation modification and normal pressure drying comprises the following steps:
i, diluting water glass with water, and fully mixing and stirring 1.2L of water glass and 3.6L of water uniformly to obtain a diluted solution of the water glass. The diluted solution of water glass was slowly introduced into 710mL of a 5M hydrochloric acid solution to obtain a sol solution.
And II, adjusting the pH of the sol solution obtained in the step I to 5.0 by using a diluted water glass solution, wherein the volume ratio of water glass to water is 3: 1. After stirring for several minutes, the glass fiber mat was dipped into the sol solution. And after the sol solution is fully soaked, taking out the glass fiber felt pad, and performing microwave irradiation treatment on the glass fiber felt pad to obtain the gel composite material, wherein the microwave irradiation power is 0.4KW, and the microwave irradiation treatment time is 60 s.
III, rolling the gel composite material obtained in the step II, putting the rolled gel composite material into a reaction kettle ①, aging at room temperature for 5 hours, and then adding an MTMS solution into the kettle until the wet gel composite material is just immersed.
IV, then 5L of sulfuric acid solution of 10mol/L and 10L of HMDSO are introduced into a reaction kettle ②, the stirring is started, the stirring speed is 100r/min, then the transmission of the mixed liquid between the reaction kettles is started simultaneously, and the transmission flow is set to be 1.5m3H is used as the reference value. And (3) after the external circulation modification is carried out for 6 hours, taking out the composite material, and drying the composite material in a forced air oven at 150 ℃ for 120min to obtain the super-hydrophobic silica aerogel heat-insulation composite material.
The performance of the silica aerogel heat-insulating composite material prepared in the embodiment 2 of the invention is detected.
Referring to fig. 4, fig. 4 is a graph showing isothermal nitrogen adsorption and desorption curves of the silica aerogel thermal insulation composite prepared in example 2 of the present invention.
As can be seen from the shape of the isothermal adsorption curve of fig. 4, the adsorption type belongs to the type IV isothermal adsorption curve. As can be seen from the type of the latter ring in the figure, it belongs to the hysteresis loop type H3. This is obtained only in the slit mesopores formed after the particles are stacked. The mesoporous structure is very obvious and is matched with a microscopic image of a scanning electron microscope. The pore structure is very uniform and complete and is a mesoporous structure.
Referring to fig. 5, fig. 5 is a pore size distribution diagram of the silica aerogel thermal insulation composite prepared in example 2 of the present invention. Wherein the Y coordinate represents the pore volume and the X coordinate is the pore size.
As can be seen from fig. 5, the pore size corresponding to the peak of the maximum pore volume was about 16 nm. The pore size of the prepared silicon dioxide aerogel is in the mesoporous range (2-50 nm). This is consistent with the curve analysis of isothermal adsorption and desorption of nitrogen.
Other detection results show that the thermal conductivity coefficient of the composite material is 0.0247W/m.K, the hydrophobic angle is 159.8 degrees, the average pore diameter of the silica aerogel is 15.6nm, and the average specific surface area is 692.7m2The total preparation time is about 8 hours.
Example 3
A method for preparing a silicon dioxide aerogel composite material by external circulation modification and normal pressure drying comprises the following steps:
i, diluting water glass with water, and fully mixing and stirring 1.2L of water glass and 3.6L of water uniformly to obtain a diluted solution of the water glass. The diluted solution of water glass was slowly introduced into 430mL of 6M oxalic acid solution to obtain a sol solution.
And II, adjusting the pH of the sol solution obtained in the step I to 5.0 by using 2M sodium hydroxide solution. After stirring for several minutes, the glass fiber mat was dipped into the sol solution. And after the sol solution is fully soaked, taking out the glass fiber felt pad, and performing microwave irradiation treatment on the glass fiber felt pad to obtain the gel composite material, wherein the microwave irradiation power is 0.9KW, and the microwave irradiation treatment time is 90 s.
III, rolling the gel composite material obtained in the step II, putting the rolled gel composite material into a reaction kettle ①, aging at room temperature for 5 hours, and adding a mixed solution of MTMS and HMDSO into the kettle at a volume ratio of 1:1 until the wet gel composite material is just immersed.
IV, then 5L of sulfuric acid solution of 10mol/L and 10L of HMDSO are introduced into a reaction kettle ②, the stirring is started, the stirring speed is 150r/min, then the transmission of the mixed liquid between the reaction kettles is started simultaneously, and the transmission flow is set to be 1.5m3H is used as the reference value. And (3) after the external circulation modification is carried out for 10 hours, taking out the composite material, and drying the composite material in a forced air oven at 150 ℃ for 120min to obtain the super-hydrophobic silica aerogel heat-insulation composite material.
For the silica prepared in example 3 of the inventionAnd (5) detecting the aerogel heat insulation composite material. The results show that the thermal conductivity coefficient of the composite material is 0.0240W/m.K, the hydrophobic angle is 159.0 degrees, the average pore diameter of the silicon dioxide aerogel is 15.3nm, and the average specific surface area is 693.2m2The total preparation time is about 16 hours.
Example 4
I, diluting water glass with water, and fully mixing and stirring 1.2L of water glass and 6L of water uniformly to obtain a diluted solution of the water glass. The diluted solution of water glass was slowly introduced into 430mL of 6M oxalic acid solution to obtain a sol solution.
And II, adjusting the pH of the sol solution obtained in the step I to 5.0 by using 2M sodium hydroxide solution. After stirring for several minutes, the glass fiber mat was dipped into the sol solution. And after the sol solution is fully soaked, taking out the glass fiber felt pad, and performing microwave irradiation treatment on the glass fiber felt pad to obtain the gel composite material, wherein the microwave irradiation power is 1KW, and the microwave irradiation treatment time is 80 s.
III, rolling the gel composite material obtained in the step II, putting the rolled gel composite material into a reaction kettle ①, aging at room temperature for 5 hours, and adding a mixed solution of DMCS and MTMS into the kettle at a volume ratio of 1:2 until the wet gel composite material is just immersed.
IV, then 5L of 10mol/L phosphoric acid solution and 10L of MTMS are introduced into a reaction kettle ②, the stirring is started, the stirring speed is 1500r/min, then the transmission of the mixed liquid between the reaction kettles is started simultaneously, and the transmission flow is set to be 1.0m3H is used as the reference value. And (3) after the external circulation modification is carried out for 8 hours, taking out the composite material, and drying the composite material in a forced air oven at 150 ℃ for 120min to obtain the super-hydrophobic silica aerogel heat-insulation composite material.
The silica aerogel heat-insulating composite material prepared in the embodiment 4 of the invention is detected. The results show that the thermal conductivity coefficient of the composite material is 0.0251W/m.K, the hydrophobic angle is 160.1 degrees, the average pore diameter of the silicon dioxide aerogel is 15.0nm, and the average specific surface area is 690.3m2G, total preparation time is about 15 hours.
While the present invention has been described in detail with respect to a method of preparing modified silica aerogel materials by ambient drying using external circulation, the principles and embodiments of the present invention are described herein using specific examples, which are intended to serve only as an aid in understanding the method of the present invention and its core concepts, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (10)

1. A preparation method of a modified silica aerogel material is characterized by comprising the following steps:
1) placing the aged silica wet gel material and a modifier precursor in a reaction container, and returning the modifier precursor to the reaction container after the modifier precursor is subjected to external circulation hydrolysis to perform modification reaction to obtain a modified silica aerogel material;
the modifier is a modifier which can generate a modifier precursor through a polymerization reaction when meeting water.
2. The method of claim 1, wherein the modifier precursor comprises a silsesquioxane compound;
the hydrolysis is specifically hydrolysis by adding an auxiliary agent;
the time of the modification reaction is 4-12 h;
the liquid level height of the modifier precursor is less than or equal to the height of the aged silica wet gel material.
3. The preparation method according to claim 1, wherein the step 1) is specifically:
11) placing the aged silicon dioxide wet gel material and the modifier precursor into a reaction container, wherein the reaction container is connected with a second reaction container and is used for liquid phase conveying;
the second reaction container is filled with an auxiliary agent or a mixture of the auxiliary agent and a modifier precursor;
12) carrying out modification reaction, conveying the modifier precursor to a second reaction container, and returning the modifier precursor to the reaction container after hydrolysis;
13) after the modification reaction is finished, drying to obtain a modified silica aerogel material;
the auxiliary agent comprises acid or alkali;
the modifier precursor comprises one or more of methyltrimethoxysilane, dimethylmonochlorosilane, trimethylmonochlorosilane, trimethylbromosilane, trimethylmethoxysilane, tetramethylsilane, hexamethyldisiloxane, hexamethyldisilazane and octamethyltrisiloxane.
4. The method according to claim 3, wherein the acid is one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid and glacial acetic acid;
the acid comprises an acid solution;
the concentration of the acid solution is 0.2-17.8 mol/L;
the alkali is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia water, magnesium hydroxide and aluminum hydroxide;
the base comprises a base solution;
the concentration of the alkali solution is 3-12 mol/L;
the return mode is specifically as follows: spraying into a reaction vessel from top to bottom.
5. The method according to claim 4, wherein the area of the spray is equal to or larger than the cross-sectional area of the aged silica wet gel material;
on the reaction container, a liquid phase outlet is arranged below the liquid level of the reaction container, and a liquid phase inlet is arranged at the top of the reaction container;
on the second reaction vessel, a liquid phase inlet is arranged at the bottom of the second reaction vessel, and a liquid phase outlet is arranged below the liquid level of the second reaction vessel;
in the second reactor, the ratio of the volume of the liquid to the volume of the second reactor is 25-75%;
in the mixture of the auxiliary agent and the modifier precursor, the volume ratio of the modifier precursor to the auxiliary agent is (0.5-20): 1.
6. the method according to claim 3, wherein the flow rate of the transportation is 0.3 to 2.2m3/h；
The flow rate of the return is 0.3-2.2 m3/h；
The drying time is 10-240 min;
the drying temperature is 100-200 ℃;
the aged silicon dioxide wet gel material is prepared by the following steps:
a) acidifying a silicon source, water and acid to obtain a sol solution;
b) and (3) adjusting the pH value of the sol solution obtained in the step, performing microwave treatment, and aging to obtain the aged silica wet gel material.
7. The method of claim 6, wherein the silicon source comprises water glass;
the volume ratio of the silicon source to the water is 1: (0.4 to 7);
the modulus of the water glass is 3.0-3.5;
the acid comprises an acid solution;
the step a) is specifically as follows: mixing a silicon source and water to obtain a diluent, and then acidifying the diluent and an acid solution to obtain a sol solution;
the volume ratio of the diluent to the acid solution is (0.5-20): 1.
8. the method of claim 7, wherein the acid comprises one or more of hydrochloric acid, hydrofluoric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, oxalic acid, and glacial acetic acid;
the concentration of the acid solution is 0.2-17.8 mol/L;
the time of the acidification treatment is 20-50 min;
the temperature of the acidification treatment is 10-80 ℃.
9. The method according to claim 6, wherein the pH is 4 to 7;
the pH value is adjusted by adding alkaline solution;
the alkaline solution comprises one or more of sodium carbonate, ammonia water, sodium hydroxide, sodium bicarbonate, sodium silicate and potassium carbonate;
the concentration of the alkaline solution is 0.5-5 mol/L.
10. The preparation method according to any one of claims 6 to 9, wherein the power ratio of the microwave treatment is 0.4 to 4.0KW/400mL sol solution;
the microwave treatment time is 20-450 s;
the method also comprises the step of adding fiber materials before the microwave treatment;
the fiber material comprises one or more of glass fiber, basalt fiber, mullite fiber, aluminum silicate fiber, alumina fiber, ceramic fiber, perlite fiber and high silica fiber;
the volume ratio of the fiber material to the sol solution is (0.1-1.5): 1;
the aging time is 5-48 h.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1636871A (en) * 2004-12-09 2005-07-13 同济大学 Hydrophobic SiO2 aerogel preparing process
US20080081014A1 (en) * 2006-10-02 2008-04-03 Korea Institute Of Energy Research Rapid preparation process of aerogel
CN104909375A (en) * 2015-05-29 2015-09-16 田雷 Method for rapidly preparing hydrophobicsilica aerogel by carbon dioxidesubcritical drying method
CN106865558A (en) * 2017-03-22 2017-06-20 伊科纳诺（北京）科技发展有限公司 Normal pressure prepares the method and obtained aerosil of aerosil
US20170369326A1 (en) * 2015-11-27 2017-12-28 Lg Chem, Ltd. Method of preparing hydrophobic silica aerogel and hydrophobic silica aerogel prepared thereby

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1636871A (en) * 2004-12-09 2005-07-13 同济大学 Hydrophobic SiO2 aerogel preparing process
US20080081014A1 (en) * 2006-10-02 2008-04-03 Korea Institute Of Energy Research Rapid preparation process of aerogel
CN104909375A (en) * 2015-05-29 2015-09-16 田雷 Method for rapidly preparing hydrophobicsilica aerogel by carbon dioxidesubcritical drying method
US20170369326A1 (en) * 2015-11-27 2017-12-28 Lg Chem, Ltd. Method of preparing hydrophobic silica aerogel and hydrophobic silica aerogel prepared thereby
CN106865558A (en) * 2017-03-22 2017-06-20 伊科纳诺（北京）科技发展有限公司 Normal pressure prepares the method and obtained aerosil of aerosil

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