CN114751718B - Method for preparing hydrophobic silica aerogel felt under normal pressure - Google Patents

Method for preparing hydrophobic silica aerogel felt under normal pressure Download PDF

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CN114751718B
CN114751718B CN202210335902.5A CN202210335902A CN114751718B CN 114751718 B CN114751718 B CN 114751718B CN 202210335902 A CN202210335902 A CN 202210335902A CN 114751718 B CN114751718 B CN 114751718B
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hydrophobization
reagent
nitrogen
hydrophobic
drying box
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CN114751718A (en
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张继承
张东生
刘喜宗
姚栋嘉
潘广镇
陈帅
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Gongyi Van Research Yihui Composite Material Co Ltd
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Gongyi Van Research Yihui Composite Material Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B30/00—Compositions for artificial stone, not containing binders
    • C04B30/02—Compositions for artificial stone, not containing binders containing fibrous materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/46—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with organic materials
    • C04B41/49—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes
    • C04B41/4905—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon
    • C04B41/4922—Compounds having one or more carbon-to-metal or carbon-to-silicon linkages ; Organo-clay compounds; Organo-silicates, i.e. ortho- or polysilicic acid esters ; Organo-phosphorus compounds; Organo-inorganic complexes containing silicon applied to the substrate as monomers, i.e. as organosilanes RnSiX4-n, e.g. alkyltrialkoxysilane, dialkyldialkoxysilane
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/60—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only artificial stone
    • C04B41/61—Coating or impregnation
    • C04B41/62—Coating or impregnation with organic materials
    • C04B41/64—Compounds having one or more carbon-to-metal of carbon-to-silicon linkages

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  • Silicon Compounds (AREA)

Abstract

The invention provides a method for preparing a hydrophobic silica aerogel felt under normal pressure, wherein a liquid-phase hydrophobization reagent is promoted to be converted into a gas-phase hydrophobization reagent by preheating nitrogen, and the organic solvent in wet gel can be taken out while the circulating preheating nitrogen and the gas-phase hydrophobization reagent are subjected to hydrophobization treatment, so that the hydrophobic and drying treatment of the wet gel felt is realized. The preparation method provided by the invention can obviously shorten the preparation period of the conventional hydrophobic aerogel, reduce the production cost, and simultaneously can avoid a large amount of solvent replacement after the traditional hydrophobic reaction is completed.

Description

Method for preparing hydrophobic silica aerogel felt under normal pressure
Technical Field
The invention belongs to the technical field of aerogel preparation, and particularly relates to a method for preparing a hydrophobic silica aerogel felt under normal pressure.
Background
The aerogel is a gel material with gas as a dispersion medium, has a highly crosslinked continuous three-dimensional network nano hollow structure inside, and has a large specific surface area (500-1300 m) 2 Per g), low density (30-150 Kg/m) 3 ) High porosity (85-99%), small average pore diameter (2-50 nm), lower thermal conductivity (0.01-0.02W/m.K) than room temperature air and the like, and is a solid material with the lowest thermal conductivity which is generally accepted at present. The silicon dioxide aerogel and the felt body thereof have unique physical and chemical properties, and are widely researched and applied in the aspects of aerospace, chemical engineering, energy-saving buildings, heat insulation, catalyst carriers, optics, acoustics and the like.
The existing preparation technology of the silica aerogel felt is mainly divided into two parts, namely: preparing gel and drying the gel. Silica gel to be dried is prepared by hydrolysis, gelation, aging and hydrophobization treatment of a silicon source, a solvent and a catalyst, and then the aerogel is obtained by drying the gel. The currently common hydrophobization method is to place the treated felt body into a prepared hydrophobization solution for hydrophobization after the gel reaction of the treated felt body is completed, and then take out the treated felt body for drying treatment. Although this method can produce a hydrophobized silica aerogel blanket, it involves many times of solvent substitution in actual production, and has a long reaction period and an increased production cost.
Disclosure of Invention
In order to solve the problems, the invention provides a method for preparing the hydrophobic silica aerogel felt under normal pressure, which further realizes efficient, low-cost and uniform hydrophobic treatment on the basis of ensuring the good structural performance of the aerogel felt.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for preparing hydrophobic silica aerogel felt under normal pressure is characterized by comprising the following steps: the method comprises the following specific steps:
1. placing the silica wet gel felt in a hydrophobic drying box with a reserved inlet and outlet, and replacing air in the hydrophobic drying box with nitrogen in a mode of vacuumizing and then introducing nitrogen;
2. preheating nitrogen to obtain preheated nitrogen, wherein the temperature of the preheated nitrogen is higher than the boiling point of the hydrophobizing reagent; and continuously introducing and discharging a hydrophobization reagent and preheated nitrogen into the hydrophobic drying box, and simultaneously drying and hydrophobizing the silicon dioxide wet gel felt in the hydrophobic drying box by using the nitrogen and the gas phase hydrophobization reagent in the hydrophobic drying box.
Further, in the second step, the hydrophobization reagent is introduced into the hydrophobization drying box from a reagent tank for storing the hydrophobization reagent; the hydrophobization reagent of the reagent tank introduced into the hydrophobization drying box is a liquid-phase hydrophobization reagent
Or
The hydrophobizing agent introduced into the hydrophobizing drying box from the reagent tank is a gas-phase hydrophobizing agent obtained by heating and evaporating a liquid-phase hydrophobizing agent by using preheated nitrogen, and the introduction time of the hydrophobizing agent is 1 to 24h. The original phase of the hydrophobization reagent is a liquid phase, and the hydrophobization reagent is heated into a gas phase hydrophobization reagent by heating preheated nitrogen in the hydrophobization process.
Furthermore, preheated nitrogen is introduced into a reagent tank for storing the liquid-phase hydrophobization reagent, the liquid-phase hydrophobization reagent in the reagent tank is gasified under the heating of the preheated nitrogen to obtain a gas-phase hydrophobization reagent, and the gas-phase hydrophobization reagent is introduced into the hydrophobization drying box together with the preheated nitrogen through an inlet of the hydrophobization drying box.
Further, preheated nitrogen gas is introduced above the liquid surface of the liquid-phase hydrophobizing agent or inside the liquid.
Furthermore, preheated nitrogen and the liquid-phase hydrophobization reagent in the reagent tank are respectively introduced into the hydrophobization drying box through different inlets, and the liquid-phase hydrophobization reagent in the hydrophobization drying box is gasified under the heating of the preheated nitrogen to obtain the gas-phase hydrophobization reagent.
Further, in the step one, the silica wet gel mat is prepared by preparing a silica sol and immersing the fiber mat in the silica sol, and the preparing step of the silica sol comprises: uniformly mixing a silicon source, ethanol and water, adding a catalyst, and uniformly stirring to obtain a silicon dioxide sol; wherein the silicon-based organic silicon material is prepared by mixing silicon sources, ethanol, water and water in a molar ratio of 1 to (2 to 60) to (0.05 to 30); the silicon source is one or more of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate and alkyl alkoxy silane; the alkyl alkoxy silane comprises one or more of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane, propyl trimethoxy silane and propyl triethoxy silane; the catalyst comprises an alkaline catalyst, wherein the alkaline catalyst is one or a combination of two of sodium hydroxide, potassium hydroxide, ammonia water, ammonium fluoride, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ethanolamine, diethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropanolamine, aniline, o-phenylenediamine, m-phenylenediamine and p-phenylenediamine; the catalyst may also include an acidic catalyst; soaking the fiber felt in the silica sol, and carrying out static aging for 8 to 24h at the temperature of 30 to 60 ℃.
Furthermore, the hydrophobic drying box is a box body, and the outer wall of the hydrophobic drying box is provided with at least two inlets communicated with the interior of the box body; more than one partition board for placing silica wet gel felt can be arranged in the hydrophobic drying box, and a plurality of through holes are formed in the partition board.
Further, the nitrogen is prepared by a nitrogen making machine, and the volume content of the nitrogen is more than 99%; and in the second step, the gas discharged from the hydrophobic drying box is recovered, and the recovered nitrogen gas repeatedly participates in the first step and the second step.
Further, the hydrophobizing agent is one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, triethylmethoxysilane, triethylethoxysilane, diethyldiethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, methylvinyldimethoxysilane, vinyltrichlorosilane, hexamethyldisiloxane, hexamethyldisilazane, heptamethyldisiloxane, heptamethyldisilazane, chloropropyltriethoxysilane, chloropropylmethyldimethoxysilane, dimethoxybis (2-methylpropyl) silane, bistrimethylsilylmethylsilane, bis (1,2-methyldichlorosilyl) ethane, bis (3732 zxft 32-trichlorosilane) ethane, bis (1,2-methyldimethoxysilyl) ethane, bis (1,2-methyldiethoxy) ethane, bis (3536-zxft) ethane, bis (3536-trichlorosilane) ethyl, bis (3963-triethoxysilane, triethylethylchlorosilane, triethylethyltriethoxysilane, triethylethyldichlorosilane, or triethylchlorosilane.
Furthermore, the hydrophobic rate of the prepared hydrophobic silica aerogel is 99.0-99.3%. The hydrophobic effect is good.
The invention relates to a preparation method for preparing a hydrophobic silica aerogel felt under normal pressure. The specific working process is as follows: preparing nitrogen through a nitrogen generator, and preheating the nitrogen through a nitrogen heater; the original state of the hydrophobization reagent is a liquid phase, the liquid-phase hydrophobization reagent and preheated nitrogen are introduced into a hydrophobization drying box in which a silica wet gel felt is placed, and the preheated nitrogen promotes the liquid-phase hydrophobization reagent entering the hydrophobization drying box to be converted into a gas-phase hydrophobization reagent and diffuse in the hydrophobization drying box; or the preheated nitrogen is directly introduced into the reagent tank, the preheated nitrogen promotes the liquid-phase hydrophobization reagent in the reagent tank to be converted from the liquid phase into the gas phase, and then the gas-phase hydrophobization reagent is introduced into the hydrophobization drying box along with the preheated nitrogen; the circulation of preheated nitrogen enables the organic solvent in the wet gel to be carried out simultaneously with the hydrophobization treatment.
The hydrophobization reagent replenishing tank replenishes the hydrophobization reagent into the reagent tank in real time, and the liquid level of the hydrophobization reagent in the reagent tank is kept basically constant; the preheated nitrogen containing the organic solvent discharged from the hydrophobic drying box is recovered by a solvent recovery device, the recovered solvent is stored in a solvent tank, and the recovered nitrogen can still be recycled to the nitrogen heater for preheating and recycling. The hydrophobic silica aerogel felt prepared under normal pressure has hydrophobic rate of 90.0-99.3%.
The second step can be followed by a drying process, wherein the drying is ethanol supercritical drying and CO 2 One of supercritical drying, atmospheric drying and freeze-drying.
The invention has the beneficial effects that:
1. a method for preparing hydrophobic silica aerogel felt under normal pressure comprises the steps of using preheated nitrogen to promote a liquid-phase hydrophobization reagent to be converted into a gas-phase hydrophobization reagent, enabling the wet gel felt to be subjected to hydrophobization treatment through circulating preheated nitrogen and the gas-phase hydrophobization reagent, and simultaneously bringing out an organic solvent in wet gel to achieve hydrophobization and drying treatment of the silica wet gel felt. The preparation method can obviously shorten the preparation period of the conventional hydrophobic aerogel and reduce the production cost, and the aerogel felt drying process and the aerogel hydrophobic treatment are carried out simultaneously, so that the preparation method is easy to operate, economic and environment-friendly;
2. the liquid-phase hydrophobization reagent is converted into the gas-phase hydrophobization reagent to perform hydrophobization treatment on the silicon dioxide wet gel, and the gas-phase hydrophobization reagent is rapidly diffused in the hydrophobization drying box, so that dead angles are eliminated, the diffusion time is shortened, the using amount of the hydrophobization reagent is reduced, the hydrophobization efficiency is improved, meanwhile, a large amount of solvent replacement after the traditional hydrophobization reaction is completed can be avoided, and the whole preparation process is simple in process;
3. the nitrogen containing the solvent discharged by the hydrophobic drying oven is recycled by the solvent recovery device, and the residual nitrogen can be recycled, so that large-scale continuous production is easy, and high-efficiency and uniform hydrophobic treatment can be realized;
4. the partition board is arranged in the hydrophobic drying box, the plurality of through holes are formed in the partition board, and when the silica wet gel felt is placed on the partition board, the contact area between the preheated nitrogen and the gas-phase hydrophobic reagent in the hydrophobic drying box and the silica wet gel felt is increased, so that the hydrophobic efficiency is improved.
Drawings
FIG. 1 is one of the process flow diagrams for the atmospheric preparation of a hydrophobic silica aerogel blanket;
FIG. 2 is a second process flow diagram for the atmospheric preparation of a hydrophobic silica aerogel blanket;
wherein, each reference number in the figure is: 1. a nitrogen making machine; 2. a nitrogen heater; 3. a hydrophobization reagent replenishing tank; 4. a reagent tank; 5. a hydrophobic drying oven; 6. a solvent recovery unit; 7. and (4) a solvent tank.
Detailed Description
In order that those skilled in the art will be able to better understand the technical solutions provided by the present invention, the following description is provided in connection with specific embodiments.
Example 1
Referring to fig. 1, a method for preparing a hydrophobic silica aerogel blanket at atmospheric pressure using an apparatus for preparing a hydrophobic aerogel at atmospheric pressure, the apparatus comprising: the device comprises preparation components such as a nitrogen making machine 1, a nitrogen heater 2, a hydrophobization reagent supplementing tank 3, a reagent tank 4, a hydrophobization drying box 5, a solvent recovery device 6, a solvent tank 7 and the like, wherein the preparation components are connected with valves arranged on the pipelines through a plurality of pipelines with communicating effects, and the valves can control whether the preparation components at two ends of the connected pipelines are communicated or not.
Each hydrophobic drying box 5 comprises two inlets and an outlet, the outer wall of each hydrophobic drying box is wrapped with a heat-insulating layer with heat-insulating and heat-preserving effects, and the heat-insulating layer can be made of one or more of heat-insulating materials such as aerogel felts, aerogel composite boards and foam composite boards. The nitrogen making machine 1 is used for preparing nitrogen and is connected with a nitrogen heater 2 through a pipeline, and the nitrogen heater 2 is connected with an inlet of a hydrophobic drying box 5 through a pipeline; the hydrophobization reagent supplement tank 3 is stored with a prepared liquid phase hydrophobization reagent, is connected with the reagent tank 4 through a pipeline and supplements the hydrophobization reagent into the reagent tank 4 in real time, and the reagent tank 4 is also connected with the other inlet of the hydrophobization drying box 5 through a pipeline. The outlet of the hydrophobic drying box 5 is connected with a solvent recovery device 6 through a pipeline, the liquid obtained by the recovery of the solvent recovery device 6 is stored in a solvent tank 7 through a pipeline for further treatment, and the nitrogen obtained by the recovery of the solvent recovery device 6 is also communicated to the air inlet of the nitrogen heater 2 for recovery and reuse.
The working process is as follows: preparing nitrogen through a nitrogen making machine 1, and then introducing the nitrogen into a nitrogen heater 2 to preheat the nitrogen; respectively introducing preheated nitrogen and a liquid-phase hydrophobizing reagent into a hydrophobizing drying box 5 for placing a silica wet gel felt through different inlets, promoting the liquid-phase hydrophobizing reagent in the hydrophobizing drying box 5 to be converted into a gas-phase hydrophobizing reagent by the preheated nitrogen, diffusing the gas-phase hydrophobizing reagent in the hydrophobizing drying box 5, and taking out an organic solvent in wet gel while carrying out hydrophobizing treatment under the driving of circulation of the preheated nitrogen; meanwhile, the hydrophobization reagent replenishing tank 3 replenishes the hydrophobization reagent into the reagent tank 4 in real time, keeps the liquid level of the solution in the reagent tank 4 basically constant, and controls the pressure in the hydrophobization drying box 5 to be constant as the saturated vapor pressure of the corresponding liquid at the setting temperature of the nitrogen heater 2; and (3) after the nitrogen containing the solvent obtained from the outlet of the hydrophobic drying box 5 passes through the solvent recovery device 6, recovering the solvent, circulating the nitrogen after the solvent is recovered back to the nitrogen heater 2 for preheating again, and then continuously entering the hydrophobic drying box 5 for drying the product and driving the hydrophobic reagent to circulate.
A method for preparing hydrophobic silica aerogel felt under normal pressure comprises the following preparation steps:
(1) Uniformly mixing a silicon source, ethanol and water, adding a catalyst, and uniformly stirring to obtain silicon dioxide sol; wherein, the silicon source, ethanol and water are mixed according to the mol ratio of 1: 40: 15; the silicon source is methyltrimethoxysilane, the catalyst is ammonia water solution, the pH value of the silicon dioxide sol is adjusted to 8, then acid catalyst hydrochloric acid is added, and the pH value of the solution is adjusted to 4;
(2) Soaking the fiber felt in the silica sol obtained in the step (1) for 18 hours, and then standing and aging at 30 ℃ for 24 hours;
(3) Placing the silicon dioxide wet gel felt obtained in the step (2) in a hydrophobic drying box 5 of a device, vacuumizing the hydrophobic drying box 5 by using nitrogen prepared by a vacuum pump and a nitrogen making machine 1, and then conducting nitrogen treatment, wherein the nitrogen treatment is conducted for 2~4 times in a circulating manner, so that the air in the hydrophobic drying box 5 is completely replaced, the number of the hydrophobic drying boxes 5 can be three, the concentration (volume content) of the nitrogen prepared by the nitrogen making machine 1 is more than 99%, and a nitrogen heater 2 preheats the nitrogen by using an electric heating manner;
(4) Opening valves on pipelines between the hydrophobic drying box 5 and the nitrogen heater 2 and between the hydrophobic drying box 5 and the reagent tank 4, introducing preheated nitrogen and a hydrophobizing reagent into the hydrophobic drying box 5 in which the silica wet gel felt is placed through different inlets, evaporating the hydrophobizing reagent through the preheated nitrogen and promoting the gas-phase hydrophobizing reagent to diffuse in the hydrophobic drying box 5, and simultaneously drying and hydrophobizing the silica wet gel felt, wherein the treatment time is 8 hours (the time when the hydrophobizing reagent starts to be gasified is taken as the starting time);
(5) Subjecting the felt body obtained in the step (4) to CO 2 And (5) performing supercritical drying treatment to obtain the hydrophobic silica aerogel felt.
The solvent recovery device 6 recovers in a mode that an evaporative cooler is matched with a gas-liquid separator, the evaporative cooler is arranged between an outlet of the hydrophobic drying box 5 and the gas-liquid separator, mixed gas discharged from the outlet of the hydrophobic drying box 5 is cooled by the evaporative cooler firstly, gas components such as a hydrophobization reagent in the mixed gas and an organic solvent gasified in original wet gel are liquefied under the condensation action, and the rest gas is introduced into the gas-liquid separator for further gas-liquid separation, so that the separation of nitrogen and the rest components is realized. The separated nitrogen is circulated back to the nitrogen heater 2 to preheat the nitrogen and continuously enters the hydrophobic drying box 5 for use.
The nitrogen heater 2 adopts an electric heating mode, the hydrophobizing agent is hexamethyldisiloxane, and the heating temperature of the nitrogen heater 2 is set to be 101 ℃.
Detecting the hydrophobic rate of the hydrophobic silica aerogel felt by adopting a water soaking mode, wherein the soaking time is more than 5min; the hydrophobic silica aerogel felt was found to have a water repellency of 99.0%.
Example 2
The parts and connections were made as in example 1. A method for preparing hydrophobic silica aerogel felt under normal pressure is prepared by preparation equipment such as a nitrogen making machine 1, a nitrogen heater 2, a hydrophobization reagent supplement tank 3, a reagent tank 4, a hydrophobization drying box 5, a solvent recovery device 6 and a solvent tank 7, and comprises the following preparation steps:
(1) Uniformly mixing a silicon source, ethanol and water, adding a catalyst, and uniformly stirring to obtain a silicon dioxide sol; wherein, the silicon source, ethanol and water are mixed according to the mol ratio of 1: 6: 2; the silicon source is tetraethoxysilane and methyl orthosilicate, and the catalyst is ammonium fluoride solution;
(2) Soaking the fiber felt in the silica sol obtained in the step (1) for 12 hours, and then statically aging at 60 ℃ for 8h;
(3) Placing the wet silica gel felt obtained in the step (2) into a hydrophobic drying box 5 of a device, wherein the nitrogen heater 2 is not turned on, vacuumizing the hydrophobic drying box 5 at normal temperature, introducing nitrogen, circulating 2~4 times to ensure that air in the hydrophobic drying box 5 is completely replaced, wherein the hydrophobic drying box 5 is a box body with an inlet and an outlet reserved, three groups of partition plates are arranged in parallel along the inner edge of the box body, a plurality of partition plates convenient for nitrogen concentration to be more than 99% can be arranged on each group of partition plates, and the nitrogen heater 2 adopts an electric heating mode;
(4) And introducing preheated nitrogen and a hydrophobizing agent into a hydrophobizing drying box 5 in which the silicon dioxide wet gel felt is placed, promoting the hydrophobizing agent to diffuse in the hydrophobizing drying box 5 by preheating the nitrogen, and simultaneously drying and hydrophobizing the aerogel felt for 3 hours to obtain the hydrophobic silicon dioxide aerogel felt. And recovering the solvent, and circulating the residual nitrogen to the nitrogen heater 2 to preheat the nitrogen and continuously enter the hydrophobic drying box 5 for use.
Wherein the hydrophobization reagent is methyl trimethoxy silane, and the heating temperature of the nitrogen heater 2 is 102 ℃.
Detecting hydrophobicity by adopting a water soaking mode; the hydrophobic silica aerogel felt was found to have a hydrophobic content of 96%.
Example 3
Referring to fig. 2, a method of preparing a hydrophobic silica aerogel blanket at atmospheric pressure by an apparatus for preparing a hydrophobic aerogel at atmospheric pressure, the apparatus comprising: nitrogen generator 1, nitrogen heater 2, hydrophobization reagent make-up jar 3, reagent jar 4, hydrophobic drying cabinet 5, solvent recovery unit 6, solvent jar 7, a plurality of pipeline and valve.
The difference from example 1 is that: the nitrogen heater 2 respectively transmits nitrogen to the inlet of the hydrophobic drying box 5 and the reagent tank 4 through two pipelines and valves arranged on the pipelines.
The working process is as follows: the nitrogen is prepared by the nitrogen generator 1, firstly, the nitrogen heater 2 is not started, the valve on the pipeline between the nitrogen heater 2 and the reagent tank 4 is closed, the pipeline between the nitrogen heater 2 and the hydrophobic drying box 5 is kept smooth, the air in the hydrophobic drying box 5 is replaced by the nitrogen in a nitrogen introducing mode after vacuumizing, and the valve on the pipeline between the nitrogen heater 2 and the hydrophobic drying box 5 is closed after the replacement is finished. Opening the nitrogen heater 2, and simultaneously opening a valve on a pipeline between the nitrogen heater 2 and the reagent tank 4 to keep the connectivity between the nitrogen heater 2 and the reagent tank 4; the preheated nitrogen heated by the nitrogen heater 2 is introduced into the reagent tank 4, the hydrophobizing reagent is evaporated from the liquid-phase hydrophobizing reagent to the gas-phase hydrophobizing reagent by the temperature of the preheated nitrogen, and then the preheated nitrogen and the gas-phase hydrophobizing reagent are introduced into the hydrophobizing drying oven 5 in which the silica wet gel mat is placed through a pipeline, and the organic solvent in the wet gel is carried out while the gas-phase hydrophobizing treatment is carried out. In the process, the hydrophobization reagent replenishing tank 3 replenishes the hydrophobization reagent into the reagent tank 4 in real time so as to keep the liquid level of the solution in the reagent tank 4 basically constant; the obtained preheated nitrogen containing the solvent continues to participate in the circulation after passing through the solvent recovery device 6.
A method for preparing hydrophobic silica aerogel felt under normal pressure comprises the following preparation steps:
(1) Uniformly mixing a silicon source, ethanol and water, adding a catalyst, and uniformly stirring to obtain silicon dioxide sol; wherein, the silicon source, ethanol and water are mixed according to the mol ratio of 1: 60: 30; the silicon source is three of dimethyl dimethoxy silane, methyl triethoxy silane and dimethyl diethoxy silane, and the catalyst is ammonia water and ammonium fluoride aqueous solution;
(2) Soaking a fiber felt in the silica sol obtained in the step (1) for 24 hours, and then statically aging at 40 ℃ for 12 hours;
(3) Placing the wet silica gel felt obtained in the step (2) into a hydrophobic drying box 5 of a device, wherein the nitrogen heater 2 is not turned on, vacuumizing the hydrophobic drying box 5 at normal temperature, introducing nitrogen for 2 times to ensure that air in the hydrophobic drying box 5 is completely replaced, wherein the number of the hydrophobic drying boxes 5 in the normal-pressure drying device is 6, the nitrogen concentration is more than 99%, and the nitrogen heater 2 adopts a gas heating mode;
(4) The preheated nitrogen is introduced into a reagent tank 4, the hydrophobization reagent is promoted to evaporate from a liquid-phase hydrophobization reagent into a gas-phase hydrophobization reagent by the preheated nitrogen, the pressure in the reagent tank 4 is controlled to be constant to be the saturated vapor pressure of the corresponding liquid at the heating temperature of the nitrogen heater 2, then the preheated nitrogen and the gasified hydrophobization reagent are introduced into a hydrophobization drying box 5 which is used for placing a silica wet gel felt together, the drying and the hydrophobization treatment are simultaneously carried out, the treatment time (the time for starting the gasification of the hydrophobization reagent is taken as the starting time) is 10h, the solvent and the gas are respectively recovered after the treatment, and the residual nitrogen is circulated back to the nitrogen heater 2 for preheating the nitrogen.
Wherein the hydrophobizing agent is tetraethoxysilane, and the heating temperature of the nitrogen heater 2 is 168.1 ℃.
Detecting the hydrophobic rate by adopting a water soaking mode, wherein the soaking time is more than 5min; the hydrophobic silica aerogel felt was found to have a hydrophobicity of 99.3%.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A method for preparing hydrophobic silica aerogel felt under normal pressure is characterized by comprising the following steps:
the method comprises the following specific steps:
1. placing the silica wet gel felt in a hydrophobic drying box with a reserved inlet and outlet, and replacing air in the hydrophobic drying box with nitrogen in a mode of vacuumizing and then introducing nitrogen;
2. preheating nitrogen, wherein the temperature of the obtained preheated nitrogen is higher than the boiling point of the hydrophobization reagent; continuously introducing and discharging a hydrophobization reagent and preheated nitrogen into the hydrophobic drying box, and drying and hydrophobizing the silicon dioxide wet gel felt by the nitrogen and the gas phase hydrophobization reagent in the hydrophobic drying box;
the gas-phase hydrophobization reagent is obtained by preheating nitrogen to promote the transformation of a liquid-phase hydrophobization reagent; the hydrophobicity of the prepared hydrophobic silica aerogel is 90.0 to 99.3 percent.
2. The method for preparing hydrophobic silica aerogel felt under atmospheric pressure according to claim 1, wherein: in the second step, the hydrophobization reagent is introduced into the hydrophobization drying box from a reagent tank for storing the hydrophobization reagent; the hydrophobization reagent which is introduced into the hydrophobization drying box from the reagent tank is a liquid-phase hydrophobization reagent;
or
The hydrophobization reagent which is introduced into the hydrophobization drying box from the reagent tank is a gas-phase hydrophobization reagent which is obtained by preheating nitrogen and heating a liquid-phase hydrophobization reagent, and the introduction time of the hydrophobization reagent is 1 to 24h.
3. The method for preparing the hydrophobic silica aerogel felt under normal pressure according to claim 2, wherein the method comprises the following steps: preheating nitrogen is introduced into a reagent tank for storing the liquid-phase hydrophobization reagent, the liquid-phase hydrophobization reagent in the reagent tank is gasified under the heating of the preheating nitrogen to obtain a gas-phase hydrophobization reagent, and the gas-phase hydrophobization reagent is introduced into a hydrophobization drying box together with the preheating nitrogen through an inlet of the hydrophobization drying box.
4. The method for preparing hydrophobic silica aerogel felt under normal pressure according to claim 3, wherein: preheated nitrogen is introduced above the liquid level of the liquid-phase hydrophobizing agent or inside the liquid.
5. The method for preparing the hydrophobic silica aerogel felt under normal pressure according to claim 2, wherein the method comprises the following steps: preheating nitrogen and a liquid-phase hydrophobization reagent in a reagent tank are respectively introduced into a hydrophobization drying box through different inlets, and the liquid-phase hydrophobization reagent in the hydrophobization drying box is gasified under the heating of the preheating nitrogen to obtain a gas-phase hydrophobization reagent.
6. The method of atmospheric preparation of a hydrophobic silica aerogel blanket of claim 1, wherein: in the first step, the silica wet gel mat is further prepared by the steps of preparing silica sol and dipping the fiber mat in the silica sol, and the step of preparing the silica sol comprises the following steps: uniformly mixing a silicon source, ethanol and water, adding a catalyst, and uniformly stirring to obtain a silicon dioxide sol; wherein the silicon-based material is obtained by mixing silicon source, ethanol, water = 1: 2 to 60: 0.05 to 30 in molar ratio; the silicon source is one or more of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate and alkyl alkoxy silane; the alkyl alkoxy silane comprises one or more of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane, propyl trimethoxy silane and propyl triethoxy silane; the catalyst comprises an alkaline catalyst, wherein the alkaline catalyst is one or a combination of two of sodium hydroxide, potassium hydroxide, ammonia water, ammonium fluoride, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ethanolamine, diethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropanolamine, aniline, o-phenylenediamine, m-phenylenediamine and p-phenylenediamine; the catalyst may also include an acidic catalyst; and (3) soaking the fiber felt in the prepared silicon dioxide sol, and carrying out static aging for 8 to 24h at the temperature of 30 to 60 ℃.
7. The method of atmospheric preparation of a hydrophobic silica aerogel blanket of claim 1, wherein: the hydrophobic drying box is a box body, and the outer wall of the hydrophobic drying box is provided with at least two inlets communicated with the interior of the box body; more than one partition board for placing silica wet gel felt can be arranged in the hydrophobic drying box, and a plurality of through holes are formed in the partition board.
8. The method for preparing hydrophobic silica aerogel felt under atmospheric pressure according to claim 1, wherein: the nitrogen is prepared by a nitrogen making machine, and the volume content of the nitrogen is more than 99 percent; and in the second step, the gas discharged from the hydrophobic drying box is recovered, and the recovered nitrogen gas repeatedly participates in the first step and the second step.
9. The method of claim 8, wherein the method comprises the steps of: the hydrophobization reagent is one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, ethyltrimethoxysilane, diethyldimethoxysilane, triethylmethoxysilane, triethylethoxysilane, diethyldiethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, methylvinyldimethoxysilane, vinyltrichlorosilane, hexamethyldisiloxane, hexamethyldisilazane, heptamethyldisiloxane, heptamethyldisilazane, chloropropyltriethoxysilane, chloropropylmethyldimethoxysilane, dimethoxybis (2-methylpropyl) silane, bistrimethylsilylmethylsilane, bis (1,2-methyldichlorosilyl) ethane, bis (1,2-trichlorosilane) ethane, bis (1,2-methyldimethoxysilyl) ethane, bis (1,2-methyldiethoxy) ethane, bis (3536-trimethoxy zft 3536-trimethoxysilane) ethane, bis (3963-methyldiethoxy) ethane, bis (triethyloctylsilyl) 3926-triethylethylsilane, triethylethylchlorosilane, or trichlorosilanes.
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