CN109503116B - Preparation method of aerogel composite thermal insulation material - Google Patents

Preparation method of aerogel composite thermal insulation material Download PDF

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CN109503116B
CN109503116B CN201811543009.1A CN201811543009A CN109503116B CN 109503116 B CN109503116 B CN 109503116B CN 201811543009 A CN201811543009 A CN 201811543009A CN 109503116 B CN109503116 B CN 109503116B
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silica sol
wet gel
felt
precursor solution
drying
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CN109503116A (en
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王振宇
张成贺
郑维金
任大贵
鹿成洪
刘超
岳耀辉
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Luyang Energy Saving Materials 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
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
    • 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
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/30—Mortars, concrete or artificial stone characterised by specific physical values for heat transfer properties such as thermal insulation values, e.g. R-values
    • C04B2201/32—Mortars, concrete or artificial stone characterised by specific physical values for heat transfer properties such as thermal insulation values, e.g. R-values for the thermal conductivity, e.g. K-factors

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  • Organic Chemistry (AREA)
  • Chemical Or Physical Treatment Of Fibers (AREA)
  • Silicon Compounds (AREA)

Abstract

The invention provides a preparation method of an aerogel composite thermal insulation material, which comprises the following steps: a) mixing a silicon source, hexamethyldisilazane, a pH regulator and a solvent; b) soaking the mixed silica sol precursor solution into a magnesium silicate fiber felt, and standing to form a wet gel felt body; c) and soaking the wet gel felt body into organic siloxane at the temperature of 40-90 ℃, and then drying by microwave to obtain the aerogel composite thermal insulation material. On the basis of improving the formula of the precursor solution, the wet gel felt formed in the step b) is soaked in the organic siloxane solution, so that the impurity removal, aging, solvent exchange and alkylation treatment of the wet gel felt can be synchronously realized, and the preparation period of the material is greatly shortened. Meanwhile, the treatment can also reduce the drying difficulty of the material, and the material can be quickly dried under normal pressure by matching with microwave drying subsequently. In addition, the method does not introduce chloride ions in the preparation process of the material, so that the method has less corrosion to used equipment.

Description

Preparation method of aerogel composite thermal insulation material
Technical Field
The invention belongs to the field of thermal insulation materials, and particularly relates to a preparation method of an aerogel composite thermal insulation material.
Background
The silica aerogel composite thermal insulation material is a novel thermal insulation material which has emerged in recent years, has the normal-temperature thermal conductivity coefficient of less than or equal to 0.023w/(m.k), has obvious advantages compared with the traditional thermal insulation material, has better thermal insulation effect, and is widely used in the fields of aerospace, military industry, metallurgy, petrochemical industry, energy-saving buildings, comprehensive utilization of solar energy and the like.
At present, most of silica aerogel composite heat insulation materials adopt alkali-free glass fiber mats or aluminum silicate fiber mats as base materials, and no matter the glass fiber mats or the aluminum silicate fiber mats are adopted as the base materials of the silica aerogel composite heat insulation materials, tiny glass fibers and aluminum silicate fibers cannot be prevented from escaping from the surface of the base materials in the production and construction processes, the tiny glass fibers and the small aluminum silicate fibers cannot be degraded after being sucked into a human body to cause health hidden troubles, and meanwhile, the environment is polluted to a certain extent. In recent years, people-friendly policies such as 'energy conservation', 'environmental protection', 'low carbon', 'green', 'health' and the like are vigorously advocated in the industrial field and the civil field in China, the requirement for the field of novel heat-insulating materials is continuously improved, magnesium silicate fiber is regarded as a material capable of being degraded by human bodies and is paid attention to, and a silica aerogel composite heat-insulating material is prepared by taking magnesium silicate fiber felt as a base material, so that the magnesium silicate fiber felt is a new hot point in the field of novel heat-insulating materials.
The application publication number 201610203045.8 Chinese invention patent discloses a preparation method of a magnesium silicate fiber felt reinforced silicon dioxide aerogel composite material, the composite material is formed by compounding a magnesium silicate fiber felt and silicon dioxide aerogel, in the preparation process, absolute ethyl alcohol is used for repeatedly replacing a solvent for a gel felt body, and finally, ethanol is used as a supercritical drying medium and is subjected to supercritical drying under the assistance of nitrogen to obtain a finished product. Although the method can be used for preparing the magnesium silicate fiber felt and silicon dioxide aerogel composite thermal insulation material, the supercritical drying equipment adopted in the method has huge investment and overhigh production cost, and is difficult to bear by common enterprises. In order to reduce the production cost, a normal pressure drying method can be adopted to replace supercritical drying. The normal pressure drying method is a drying process for performing gradient heating drying on the alkylated wet gel under the ambient pressure to form an aerogel structure, and has the advantages of small equipment investment and relatively low production cost. However, drying at atmospheric pressure also has a number of problems: for example, repeated solvent replacement of the wet gel is required before drying at atmospheric pressure, resulting in an extended production cycle of the product; for another example, chlorine-containing compounds such as trimethylchlorosilane are mostly used as alkylating agents in normal pressure drying, and the amount of hydrochloric acid by-produced is large, which is easy to corrode production equipment.
Disclosure of Invention
In view of the above, the present invention provides a method for preparing an aerogel composite thermal insulation material, which can greatly shorten the preparation period of a magnesium silicate fiber felt and silica aerogel composite thermal insulation material while maintaining a low production cost, and does not corrode production equipment.
The invention provides a preparation method of an aerogel composite thermal insulation material, which comprises the following steps:
a) mixing a silicon source, hexamethyldisilazane, a pH regulator and a solvent to obtain a silica sol precursor solution;
b) dipping the silica sol precursor solution into a magnesium silicate fiber felt, and standing to form a wet gel felt body;
c) and soaking the wet gel felt body into organic siloxane at the temperature of 40-90 ℃, taking out, and then carrying out microwave heating and drying to obtain the aerogel composite thermal insulation material.
Preferably, in step a), the silicon source comprises one or more of sodium silicate, acidic silica sol, alkaline silica sol, methyl orthosilicate and ethyl orthosilicate.
Preferably, in the step a), the content of the silicon source in the silica sol precursor solution is 0.03-0.3 g/mL;
the content of the hexamethyldisilazane in the silica sol precursor solution is 5-15 vol%.
Preferably, in step a), the solvent includes an alcohol solvent and/or water.
Preferably, in the step a), the mixing temperature is 2-7 ℃.
Preferably, in the step a), the pH value of the silica sol precursor solution is 5-11.
Preferably, in the step b), the standing temperature is 15-40 ℃; and standing for 5-10 min.
Preferably, in step c), the organosiloxane comprises one or more of methyltrimethoxysilane, methyltriethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, hexamethyldisiloxane, dimethyldimethoxysilane and dimethyldiethoxysilane.
Preferably, in the step c), the soaking time is 1-5 hours.
Preferably, in the step c), the microwave heating and drying temperature is 60-150 ℃; the microwave power for microwave heating and drying is 80-130 kW; the microwave heating and drying time is 0.5-2.5 h.
Compared with the prior art, the invention provides a preparation method of an aerogel composite thermal insulation material. The method provided by the invention comprises the following steps: a) mixing a silicon source, hexamethyldisilazane, a pH regulator and a solvent to obtain a silica sol precursor solution; b) dipping the silica sol precursor solution into a magnesium silicate fiber felt, and standing to form a wet gel felt body; c) and soaking the wet gel felt body into organic siloxane at the temperature of 40-90 ℃, taking out, and then carrying out microwave heating and drying to obtain the aerogel composite thermal insulation material. On the basis of improving the formula of the silica sol precursor solution, the wet gel felt formed in the step b) is soaked in the organic siloxane solution at a specific temperature, so that the impurity removal, aging, solvent exchange and alkylation treatment of the wet gel felt can be synchronously realized at one time, and the preparation period of the material is greatly shortened. Meanwhile, the processing can also reduce the drying difficulty of the material, and the material can be quickly dried under normal pressure by matching with microwave heating and drying subsequently without using a supercritical drying technology, so that the production cost of the aerogel composite thermal insulation material can be obviously reduced. In addition, the preparation method provided by the invention does not introduce chloride ions in the whole preparation process, so that the corrosion to used equipment is less. The preparation method provided by the invention has the advantages of short preparation period, low production cost and small equipment loss, and is very suitable for popularization and application in large-scale industrial production of the magnesium silicate fibrofelt and silicon dioxide aerogel composite thermal insulation material. The experimental results show that: when the aerogel composite thermal insulation material is prepared by adopting the method provided by the invention, the total time consumption of impurity removal, aging, solvent exchange, alkylation and normal-pressure drying of the wet gel felt body is less than or equal to 5 hours; the prepared material has good thermal insulation performance, and the thermal conductivity coefficient is less than or equal to 0.025w/(m.k) at 25 ℃.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of an aerogel composite thermal insulation material, which comprises the following steps:
a) mixing a silicon source, hexamethyldisilazane, a pH regulator and a solvent to obtain a silica sol precursor solution;
b) dipping the silica sol precursor solution into a magnesium silicate fiber felt, and standing to form a wet gel felt body;
c) and soaking the wet gel felt body into organic siloxane at the temperature of 40-90 ℃, taking out, and then carrying out microwave heating and drying to obtain the aerogel composite thermal insulation material.
In the method provided by the invention, a silicon source, hexamethyldisilazane, a pH regulator and a solvent are first mixed. Wherein the silicon source includes but is not limited to one or more of sodium silicate, acidic silica sol, alkaline silica sol, methyl orthosilicate and ethyl orthosilicate; the pH adjusting agent comprises an acidic pH adjusting agent including but not limited to one or more of sulfuric acid, nitric acid, hydrofluoric acid, acetic acid and oxalic acid, and/or a basic pH adjusting agent including but not limited to one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonia; the solvent includes an alcohol solvent including, but not limited to, one or more of methanol, ethanol, propanol, ethylene glycol, and glycerol, and/or water. In the invention, the content of the silicon source in the silica sol precursor solution is preferably 0.03-0.3 g/mL, and specifically may be 0.03g/mL, 0.035g/mL, 0.04g/mL, 0.042g/mL, 0.045g/mL, 0.048g/mL, 0.05g/mL, 0.055g/mL, 0.06g/mL, 0.062g/mL, 0.065g/mL, 0.068g/mL, 0.07g/mL, 0.08g/mL, 0.09g/mL, 0.1g/mL, 0.15g/mL, 0.2g/mL, 0.23g/mL, 0.24g/mL, 0.25g/mL or 0.3 g/mL. In one embodiment of the present invention, sodium silicate is used as a silicon source, and the sodium silicate is preferably mixed with other raw materials for preparing a silica sol precursor solution in the form of a sodium silicate aqueous solution (also referred to as water glass), wherein the concentration of the water glass is preferably 5-10 wt%, and specifically may be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%; the volume ratio of the water glass to the silica sol precursor solution is preferably (30-70): (70-80), more preferably (40-60): (76-77), specifically 40:76 or 60: 77. In another embodiment provided by the invention, tetraethoxysilane is used as a silicon source, and the volume ratio of tetraethoxysilane to silica sol precursor solution is preferably (10-30): 78.7, specifically 20: 78.7. In the present invention, the content of the hexamethyldisilazane in the silica sol precursor solution is preferably 5 to 15vol%, and specifically may be 5vol%, 5.5 vol%, 6 vol%, 6.2 vol%, 6.5 vol%, 6.7 vol%, 7 vol%, 7.2 vol%, 7.5 vol%, 7.9 vol%, 8 vol%, 8.2 vol%, 8.5 vol%, 8.7 vol%, 9 vol%, 9.2 vol%, 9.5 vol%, 9.7 vol%, 10 vol%, 10.5 vol%, 11 vol%, 11.5 vol%, 12 vol%, 12.5 vol%, 13 vol%, 13.5 vol%, 14 vol%, 14.5 vol%, or 15 vol%. In the present invention, the mixing temperature is preferably 2 to 7 ℃, and specifically may be 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃ or 7 ℃. In the present invention, in order to promote mutual solubility of the silicon source and hexamethyldisilazane, it is preferable to add a certain amount of surfactant during the mixing process, the surfactant including, but not limited to, one or more of cetyltrimethylammonium bromide, oleyl polyoxyethylene ether, and poloxamer. In the present invention, the mixing method and time are not particularly limited, and the raw materials may be mixed uniformly. After the mixing is finished, a silica sol precursor solution is obtained, wherein the pH value of the silica sol precursor solution is preferably 5 to 11, and specifically may be 5, 5.2, 5.4, 5.6, 5.8, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.2, 10.4, 10.6, 10.8 or 11.
In the invention, after the silica sol precursor solution is prepared, the silica sol precursor solution is impregnated into a magnesium silicate fiber felt. Wherein the magnesium silicate fiber felt is preferably a magnesium silicate fiber needled felt; the volume weight of the magnesium silicate fiber felt is preferably 70-150 kg/m3Specifically, it may be 70kg/m3、75kg/m3、80kg/m3、85kg/m3、90kg/m3、96kg/m3、100kg/m3、105kg/m3、110kg/m3、115kg/m3、120kg/m3、125kg/m3、128kg/m3、130kg/m3、135kg/m3、140kg/m3、145kg/m3Or 150kg/m3(ii) a The fiber diameter of the magnesium silicate fiber felt is preferably 1-10 μm, and specifically can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm. In the present invention, the impregnation amount of the silica sol precursor solution is not particularly limited, and it is preferable to bring the magnesium silicate fiber mat into a saturated adsorption state. And after the impregnation is finished, standing the magnesium silicate fiber felt impregnated with the silica sol precursor solution. Wherein the temperature of the standing is preferably 15-40 deg.C, and specifically 15 deg.C, 16 deg.C, 17 deg.C, 18 deg.C, 19 deg.C, 20 deg.C, 21 deg.C, 22 deg.C, 23 deg.C, 24 deg.C, 25 deg.C (room temperature), 26 deg.C, 27 deg.C, 28 deg.C, 29 deg.C, 30 deg.C, 31 deg.C, 32 deg.C, 33 deg.C, 34 deg.C; the standing time is preferably 5-10 min, and specifically can be 5min, 5.5min, 6min, 6.5min, 7min, 7.5min, 8min, 8.5min, 9min, 9.5min or 10 min. And in the standing process, the silica sol precursor solution soaked in the magnesium silicate fiber felt is gradually converted into wet gel. And after standing, obtaining the wet gel felt body.
In the invention, after the wet gel felt body is prepared, the wet gel felt body is soaked in organic siloxane at the temperature of 40-90 ℃. Wherein the organosiloxane comprises but is not limited to one or more of methyltrimethoxysilane, methyltriethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, hexamethyldisiloxane, dimethyldimethoxysilane and dimethyldiethoxysilane, preferably hexamethyldisiloxane; the temperature of the organosiloxane may be 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C, 60 deg.C, 65 deg.C, 70 deg.C, 75 deg.C, 80 deg.C, 85 deg.C or 90 deg.C; the soaking time is preferably 1-5 h, and specifically can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5 h. During the soaking process, the wet gel felt body is synchronously subjected to impurity removal, aging, solvent exchange and alkylation treatment in organic siloxane at one time. And after soaking, taking out the wet gel felt body, and carrying out microwave heating and drying. Wherein the temperature of the microwave heating drying is preferably 60-150 ℃, and specifically 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃; the microwave power of the microwave heating drying is preferably 80-130 kW, and specifically can be 80kW, 85kW, 90kW, 95kW, 100kW, 105kW, 110kW, 115kW, 120kW, 125kW or 130 kW; the microwave heating drying is preferably carried out under normal pressure; the microwave heating and drying time is preferably 0.5-2.5 h, and specifically can be 0.5h, 1h, 1.5h, 2h or 2.5 h. And after drying, obtaining the magnesium silicate fiber felt and silicon dioxide aerogel composite thermal insulation material.
On the basis of improving the formula of the silica sol precursor solution, the wet gel felt formed in the step b) is soaked in the organic siloxane solution at a specific temperature, so that the impurity removal, aging, solvent exchange and alkylation treatment of the wet gel felt can be synchronously realized at one time, and the preparation period of the material is greatly shortened. Meanwhile, the processing can also reduce the drying difficulty of the material, and the material can be quickly dried under normal pressure by matching with microwave heating and drying subsequently without using a supercritical drying technology, so that the production cost of the aerogel composite thermal insulation material can be obviously reduced. In addition, the preparation method provided by the invention does not introduce chloride ions in the whole preparation process, so that the corrosion to used equipment is less. The preparation method provided by the invention has the advantages of short preparation period, low production cost and small equipment loss, and is very suitable for popularization and application in large-scale industrial production of the magnesium silicate fibrofelt and silicon dioxide aerogel composite thermal insulation material. The experimental results show that: when the aerogel composite thermal insulation material is prepared by adopting the method provided by the invention, the total time consumption of impurity removal, aging, solvent exchange, alkylation and normal-pressure drying of the wet gel felt body is less than or equal to 5 hours; the prepared material has good thermal insulation performance, and the thermal conductivity coefficient is less than or equal to 0.025w/(m.k) at 25 ℃.
For the sake of clarity, the following examples are given in detail.
Example 1
(1) Preparing a silica sol precursor:
preparing 8 wt% industrial water glass solution and 20 wt% nitric acid solution with deionized water at 5 deg.c; firstly, injecting 10mL of absolute ethanol with the temperature of 5 ℃ into a stirrer, starting stirring, sequentially adding 6mL of hexamethyldisilazane and 20mL of nitric acid solution, and continuously stirring for 10 min; then 40mL of the industrial water glass solution is added, and the pH value of the silica sol precursor solution is controlled to be 5.4.
(2) Selecting the bulk density of 96kg/m3The magnesium silicate fiber needled felt (the fiber diameter is 2-5 mu m) is taken as a base material, the base material is flatly laid in a closed container at the periphery, and the silica sol precursor solution is poured into the container, so that the magnesium silicate fiber needled felt is saturated and adsorbs the silica sol precursor solution.
(3) And (3) standing the needled felt treated in the step (2) for 10min to form a wet gel felt body.
(4) Transferring the wet gel felt into a closed container, injecting hexamethyldisiloxane, completely immersing the wet gel felt, heating in a water bath at 70 ℃, and preserving heat for 3 hours, wherein the wet gel felt synchronously completes impurity removal, aging, solvent exchange and alkylation treatment at one time in the process.
(5) And (4) taking the wet gel felt treated in the step (4) out of the closed container, wherein the liquid phase in the container contains by-product ammonia water and sodium nitrate impurities. And (3) carrying out normal-pressure microwave drying on the taken-out felt body, wherein the drying temperature is 105 ℃, the microwave heating power is 110kW, and the drying time is 1h, so as to obtain the magnesium silicate fiber felt and silicon dioxide aerogel composite heat-insulating material.
The heat insulation material prepared in the embodiment is detected, and the result shows that: the bulk density was 137kg/m3And the thermal conductivity coefficient at 25 ℃ is 0.025 w/(m.k).
Example 2
(1) Preparing a silica sol precursor:
preparing 8 wt% industrial water glass solution and 20 wt% nitric acid solution with deionized water at 5 deg.c; firstly, injecting 10mL of absolute ethanol with the temperature of 5 ℃ into a stirrer, starting stirring, sequentially adding 6mL of hexamethyldisilazane and 20mL of nitric acid solution, and continuously stirring for 10 min; then 40mL of the industrial water glass solution is added, and the pH value of the silica sol precursor solution is controlled to be 5.4.
(2) Selecting the bulk density as 128kg/m3The magnesium silicate fiber needled felt (the fiber diameter is 2-5 mu m) is taken as a base material, the base material is flatly laid in a closed container at the periphery, and the silica sol precursor solution is poured into the container, so that the magnesium silicate fiber needled felt is saturated and adsorbs the silica sol precursor solution.
(3) And (3) standing the needled felt treated in the step (2) for 10min to form a wet gel felt body.
(4) Transferring the wet gel felt into a closed container, injecting hexamethyldisiloxane, completely immersing the wet gel felt, heating in a water bath at 70 ℃, and preserving heat for 3 hours, wherein the wet gel felt synchronously completes impurity removal, aging, solvent exchange and alkylation treatment at one time in the process.
(5) And (4) taking the wet gel felt treated in the step (4) out of the closed container, wherein the liquid phase in the container contains by-product ammonia water and sodium nitrate impurities. And (3) carrying out normal-pressure microwave drying on the taken-out felt body, wherein the drying temperature is 105 ℃, the microwave heating power is 110kW, and the drying time is 1h, so as to obtain the magnesium silicate fiber felt and silicon dioxide aerogel composite heat-insulating material.
The heat insulation material prepared in the embodiment is detected, and the result shows that: the volume weight is 183kg/m3The thermal conductivity at 25 ℃ is 0.022 w/(m.k).
Example 3
(1) Preparing a silica sol precursor:
preparing 8 wt% industrial water glass solution and 20 wt% nitric acid solution with deionized water at 5 deg.c; injecting 60mL of the industrial water glass solution into a stirrer, starting stirring, adding 0.015g of hexadecyl trimethyl ammonium bromide, continuously stirring for 10min, adding 7.5mL of hexamethyldisilazane, continuously stirring for 10min, finally adding 9.5mL of the nitric acid solution, and controlling the pH value of the silica sol precursor solution to be 10.2.
(2) Selecting the bulk density of 96kg/m3The magnesium silicate fiber needled felt (the fiber diameter is 2-5 mu m) is taken as a base material, the base material is flatly laid in a closed container at the periphery, and the silica sol precursor solution is poured into the container, so that the magnesium silicate fiber needled felt is saturated and adsorbs the silica sol precursor solution.
(3) And (3) standing the needled felt treated in the step (2) for 10min to form a wet gel felt body.
(4) Transferring the wet gel felt into a closed container, injecting hexamethyldisiloxane, completely immersing the wet gel felt, heating in a water bath at 70 ℃, and preserving heat for 3 hours, wherein the wet gel felt synchronously completes impurity removal, aging, solvent exchange and alkylation treatment at one time in the process.
(5) And (4) taking the wet gel felt treated in the step (4) out of the closed container, wherein the liquid phase in the container contains by-product ammonia water and sodium nitrate impurities. And (3) carrying out normal-pressure microwave drying on the taken-out felt body, wherein the drying temperature is 105 ℃, the microwave heating power is 110kW, and the drying time is 1h, so as to obtain the magnesium silicate fiber felt and silicon dioxide aerogel composite heat-insulating material.
The heat insulation material prepared in the embodiment is detected, and the result shows that: the volume weight is 131kg/m3And the thermal conductivity coefficient at 25 ℃ is 0.024 w/(m.k).
Example 4
(1) Preparing a silica sol precursor:
preparing 8 wt% industrial water glass solution and 20 wt% nitric acid solution with deionized water at 5 deg.c; injecting 60mL of the industrial water glass solution into a stirrer, starting stirring, adding 0.015g of hexadecyl trimethyl ammonium bromide, continuously stirring for 10min, adding 7.5mL of hexamethyldisilazane, continuously stirring for 10min, finally adding 9.5mL of the nitric acid solution, and controlling the pH value of the silica sol precursor solution to be 10.2.
(2) Selecting the bulk density as 128kg/m3The magnesium silicate fiber needled felt (the fiber diameter is 2-5 mu m) is taken as a base material, the base material is flatly laid in a closed container at the periphery, and the silica sol precursor solution is poured into the container, so that the magnesium silicate fiber needled felt is saturated and adsorbs the silica sol precursor solution.
(3) And (3) standing the needled felt treated in the step (2) for 10min to form a wet gel felt body.
(4) Transferring the wet gel felt into a closed container, injecting hexamethyldisiloxane, completely immersing the wet gel felt, heating in 70 ℃ water bath, and keeping the temperature for 3h, wherein the wet gel felt synchronously finishes impurity removal, aging, solvent exchange and alkylation treatment at one time in the process
(5) And (4) taking the wet gel felt treated in the step (4) out of the closed container, wherein the liquid phase in the container contains by-product ammonia water and sodium nitrate impurities. And (3) carrying out normal-pressure microwave drying on the taken-out felt body, wherein the drying temperature is 105 ℃, the microwave heating power is 110kW, and the drying time is 1h, so as to obtain the magnesium silicate fiber and silicon dioxide aerogel composite heat-insulating material.
The heat insulation material prepared in the embodiment is detected, and the result shows that: the volume weight is 173kg/m3And the thermal conductivity coefficient at 25 ℃ is 0.021 w/(m.k).
Example 5
(1) Preparing a silica sol precursor:
respectively preparing oxalic acid solution with the concentration of 0.1mol/L and ammonia water solution with the concentration of 0.2mol/L by using deionized water with the temperature of 5 ℃; firstly, injecting 30mL of 5 ℃ absolute ethanol solution into a stirrer, starting stirring, then adding 20mL of tetraethoxysilane, then adding 15mL of 5 ℃ deionized water, continuously stirring for 10min, then adding 6mL of the oxalic acid solution, continuously stirring for 40min, then adding 5.5mL of hexamethyldisilazane, finally adding 2.2mL of the ammonia water solution, and controlling the pH value of the silica sol precursor solution to be 5.6.
(2) Selecting the bulk density of 96kg/m3The magnesium silicate fiber needled felt (the fiber diameter is 2-5 mu m) is taken as a base material, the base material is flatly laid in a closed container at the periphery, and the silica sol precursor solution is poured into the container, so that the magnesium silicate fiber needled felt is saturated and adsorbs the silica sol precursor solution.
(3) And (3) standing the needled felt treated in the step (2) for 5min to form a wet gel felt body.
(4) Transferring the wet gel felt into a closed container, injecting hexamethyldisiloxane, completely immersing the wet gel felt, heating in a water bath at 70 ℃, and preserving heat for 3 hours, wherein the wet gel felt synchronously finishes aging, solvent exchange and alkylation treatment at one time in the process.
(5) And (4) taking the wet gel felt body treated in the step (4) out of the closed container, wherein the liquid phase in the container contains by-products of ammonia water, ammonium oxalate and ethanol. And (3) carrying out normal-pressure microwave drying on the taken-out felt body, wherein the drying temperature is 105 ℃, the microwave heating power is 110kW, and the drying time is 1h, so as to obtain the magnesium silicate fiber and silicon dioxide aerogel composite heat-insulating material.
The heat insulation material prepared in the embodiment is detected, and the result shows that: the volume weight is 142kg/m3And a thermal conductivity of 0.023w/(m.k) at 25 ℃.
Example 6
(1) Preparing a silica sol precursor:
respectively preparing oxalic acid solution with the concentration of 0.1mol/L and ammonia water solution with the concentration of 0.2mol/L by using deionized water with the temperature of 5 ℃; firstly, injecting 30mL of 5 ℃ absolute ethanol solution into a stirrer, starting stirring, then adding 20mL of tetraethoxysilane, then adding 15mL of 5 ℃ deionized water, continuously stirring for 10min, then adding 6mL of the oxalic acid solution, continuously stirring for 40min, then adding 5.5mL of hexamethyldisilazane, finally adding 2.2mL of the ammonia water solution, and controlling the pH value of the silica sol precursor solution to be 5.6.
(2) Selecting the bulk density as 128kg/m3The magnesium silicate fiber needled felt (the fiber diameter is 2-5 mu m) is taken as a base material, the base material is flatly laid in a closed container at the periphery, and the silica sol precursor solution is poured into the container, so that the magnesium silicate fiber needled felt is saturated and adsorbs the silica sol precursor solution.
(3) And (3) standing the needled felt treated in the step (2) for 5min to form a wet gel felt body.
(4) Transferring the wet gel felt into a closed container, injecting hexamethyldisiloxane, completely immersing the gel felt, heating in a water bath at 70 ℃, and preserving heat for 3 hours, wherein the wet gel felt synchronously finishes aging, solvent exchange and alkylation treatment at one time.
(5) And (4) taking the wet gel felt body treated in the step (4) out of the closed container, wherein the liquid phase in the container contains by-products of ammonia water, ammonium oxalate and ethanol. And (3) carrying out normal-pressure microwave drying on the taken-out felt body, wherein the drying temperature is 105 ℃, the microwave heating power is 110kW, and the drying time is 1h, so as to obtain the magnesium silicate fiber and silicon dioxide aerogel composite heat-insulating material.
The heat insulation material prepared in the embodiment is detected, and the result shows that: the volume weight is 188kg/m3And the thermal conductivity coefficient at 25 ℃ is 0.019 w/(m.k))。
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (3)

1. A preparation method of an aerogel composite thermal insulation material comprises the following steps:
a) mixing a silicon source, hexamethyldisilazane, a pH regulator and a solvent to obtain a silica sol precursor solution;
the silicon source comprises one or more of sodium silicate, acidic silica sol, alkaline silica sol, methyl orthosilicate and ethyl orthosilicate; the content of the silicon source in the silica sol precursor solution is 0.03-0.3 g/mL; the content of the hexamethyldisilazane in the silica sol precursor solution is 5-15 vol%; the pH value of the silica sol precursor solution is 5-11;
b) dipping the silica sol precursor solution into a magnesium silicate fiber felt, and standing to form a wet gel felt body;
the standing temperature is 15-40 ℃, and the standing time is 5-10 min;
c) soaking the wet gel felt body into organic siloxane at the temperature of 40-90 ℃, taking out, and then carrying out microwave heating and drying to obtain an aerogel composite thermal insulation material;
the organic siloxane comprises one or more of methyltrimethoxysilane, methyltriethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, hexamethyldisiloxane, dimethyldimethoxysilane and dimethyldiethoxysilane; the soaking time is 1-5 h; the microwave heating and drying temperature is 60-150 ℃, the microwave power is 80-130 kW, and the time is 0.5-2.5 h.
2. The method according to claim 1, wherein the solvent comprises an alcohol solvent and/or water in step a).
3. The method according to claim 1, wherein the mixing temperature in step a) is 2 to 7 ℃.
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