CN102557052A - Method for rapidly preparing low-density silicon oxide aerogel - Google Patents
Method for rapidly preparing low-density silicon oxide aerogel Download PDFInfo
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Abstract
The invention provides a method for rapidly preparing low-density silicon oxide aerogel. The method includes the following steps of: providing SiO2 hydrogel; carrying out microwave irradiation on the SiO2 hydrogel, so that the SiO2 hydrogel is fully gelatinized; carrying out solvent replacement on the obtained fully-gelatinized hydrogel by sequentially using polar solvent and non-polar solvent; and obtaining the low-density silicon oxide aerogel. The method for rapidly preparing the low-density silicon oxide aerogel provided by the invention has the advantages of low production cost, short production time and mass production, and can decrease the density of the obtained aerogel.
Description
Technical field
The invention belongs to the new chemical materials field, be specifically related to a kind of quick technology of preparing of low density silica aerogel.The aerogel material of gained can be widely used in Aeronautics and Astronautics, industrial energy saving, building energy conservation and sound insulation, damping, various fields such as explosion-proof.
Background technology
Gas gel is present the lightest known in the world solid, and its porosity can be up to 99.8%, and bore hole size is at 1～100nm, and specific surface area can be up to 1000m
2/ g, volume density can be at 3～500kg/m
3Between change be a kind of hi-tech, environmental protection, energy-saving and heat-insulating material efficiently, the minimum 0.015W/ (mK) that reaches under its thermal conductivity normal temperature and pressure), be to know minimum a kind of of thermal conductivity in the solid-state material at present.Because the unique texture and the performance of gas gel, this material are expected in extensive fields such as Aeronautics and Astronautics, industrial energy saving, building energy conservation and sound insulation, damping, explosion-proof, environmental protection, energy storage great application prospect is arranged.On August 19th, 2007, the Britain London Sunday Times title of publishing an article, " gas gel will be the material that changes the world ".
Silica aerogel be studied the earliest, also be the aerogel material of at present tool application prospect.Its preparation is raw material (like tetraethoxy, methyl silicate etc.) usually with the organosilicon, and through supercritical process (under HTHP, carrying out), is air with the solvent replacing in the gel.The organosilicon source is with high costs, and the supercritical drying technological operation is complicated, dangerous big, therefore is difficult to realize scale operation and commercialization.
Therefore, adopting raw materials such as industry silicasol, water glass is the silicon source, often press dry drying process and prepares aerosil, is the important directions of current this field development.
Having introduced with the rice hull ash in Chinese patent (application number 200510011378.2) intermediary of Wang Tao application is the silicon source, through the method for washing and organic solvent displacement preparation (non-hydrophobic) silica aerogel.
It is raw material that Ni Xingyuan etc. (Chinese patent, application number 200810042222.4) disclose employing rice hull ash base silica gel, prepares the method for hydrophobic type silica aerogel through solvent exchange, finishing and constant pressure and dry technology.
(Chinese patent, application numbers 200910042159.5) such as Cao Xu light discloses the employing organo-siloxane is raw material, prepares the method for high-specific surface area gas gel through microwave exposure, solvent exchange and constant pressure and dry.
Li Wencui etc. (Chinese patent, application number 201010205734.5) disclose employing inorganic silicon source or the organosilicon source is a raw material, prepare the method for hydrophobic aerogel through processes such as ageing, solvent exchange, finishing and constant pressure and dries, or the like.
Although existing some research reports that prepare silica aerogel about the constant pressure and dry method in patent and the document; But all there is preparation cycle long (basically for 2-20 days) in disclosed method at present; Expend big, higher, the more high defective of production cost of gained gas gel density of solvent and organosilicon reagent amount, be difficult to satisfy requirement of massive production.
In sum, this area lacks that a kind of production cost is low, the PT is short, be produced on a large scale and obtain the reducible gas gel fast preparation method of gas gel density.
Therefore, this area press for exploitation low, PT of a kind of production cost short, be produced on a large scale and obtain the reducible gas gel fast preparation method of gas gel density.
Summary of the invention
The objective of the invention is to obtain that a kind of production cost is low, the PT is short, be produced on a large scale and obtain the reducible gas gel fast preparation method of gas gel density.
The present invention provides a kind of quick method for preparing the low density silica aerogel, and said method comprises the steps:
SiO is provided
2Hydrogel;
To said SiO
2Hydrogel carries out microwave exposure, makes it reach complete gelation;
With polar solvent and non-polar solvent the hydrogel of resulting complete gelation is carried out solvent exchange successively; Obtain the low density silica aerogel.
Adopt the SiO of present method preparation
2The density of gas gel can reach 0.03-0.2g/cm
3, specific surface area is 500-800m
2/ g has significant hydrophobic character.
In an embodiment of the present invention, in the said microwave exposure process, the microwave exposure power that every ml mixture is accepted is 0.1-1000W, preferred 0.5-100W; Irradiation time is 1 second-10 hours, preferred 30 seconds-30 minutes.
In an embodiment of the present invention, said polar solvent adopts alcoholic solvent, is preferably the monobasic or the polyvalent alcohol that can dissolve each other with water, more preferably methyl alcohol, ethanol, propyl alcohol, n-propyl alcohol, Virahol, propyl carbinol, isopropylcarbinol, terepthaloyl moietie or USP Kosher.
In an embodiment of the present invention, the surface tension of said non-polar solvent is less than 30mN/m, preferred acetone, hexanaphthene, normal hexane, n-heptane or its combination.
In an embodiment of the present invention, the processing mode of said solvent exchange is one or more that soak, reflux or wash, and the treatment time is respectively 0.1-24 hour (preferred 0.5-4 hour), and treatment temp is room temperature-99 ℃ (preferably 40-85 a ℃).
In an embodiment of the present invention, said solvent exchange process adopts strengthens solvent exchange technology, promptly in polar solvent or non-polar solvent, adds planar water or pure siccative in a large number.
In an embodiment of the present invention, said siccative is selected from silica gel, molecular sieve, unslaked lime, smectite, attapulgite or its combination.
In an embodiment of the present invention, the volume ratio of the hydrogel of said siccative and complete gelation is 0.1-10: 1.
In an embodiment of the present invention, said SiO
2The raw material of hydrogel prepares through following mode:
(1) with ion exchange resin or acid sodium silicate aqueous solution is carried out acidification, making its pH value is the 2-3 scope;
(2) add the appropriate bases catalyzer, to obtain said SiO
2Hydrogel.
In an embodiment of the present invention, resulting low density silica aerogel carries out following aftertreatment:
Adopt silane coupling agent that said low density silica aerogel is carried out surface-treated;
The low density silica aerogel of resulting surface-treated can randomly carry out constant pressure and dry, obtains the low density gas gel product of hydrophobic type.
Embodiment
The present invention is directed to an above-mentioned difficult problem; Develop a kind of gas gel fast preparation method of using cheap water glass as the silicon source; Utilize microwave exposure to promote gelling; Utilize to strengthen the exchange of solvent exchange technology accelerated solvent, effectively shortened the production cycle, and and then prepare density through constant pressure and dry and be lower than 0.1g/cm
3Hydrophobicity gas gel product.Accomplished the present invention on this basis.
Among the present invention, term " contains " or the various compositions of " comprising " expression can be applied in mixture of the present invention or the compsn together.Therefore, term " mainly by ... form " be included in " by ... composition " that term " contains " or in " comprising ".
Below detail to various aspects of the present invention:
Inventive concept of the present invention is:
Adopting water glass, industry silicasol or sodium silicate aqueous solution with low cost is the silicon source; Substitute the organosilicon source of expensive; Adopt the microwave exposure technology to promote gel agglomerative process simultaneously; Adopt and strengthen solvent exchange technology raising solvent exchange efficient, thereby realize producing the purpose of high quality, low density silica aerogel within a short period of time, and effectively reduce its production cost.
Technique means of the present invention comprises:
Water glass or sodium silicate solution with different moduluses are starting material; With deionized water it is diluted to the sodium silicate solution that mass concentration is 1-30% (preferred 3-10%); With strong acid ion exchange resin or diluted acid it is carried out ion exchange then, make its pH value be reduced to the 2-3 scope; In filtrating, add the appropriate bases catalyzer, make its pH value be 4-12 (preferred 5-9), gelling after for some time.Place microwave generator to carry out microwave exposure the silica gel after the gelling, with pure and mild organic solvent it is carried out solvent exchange respectively then, obtain organogel; This organogel is carried out constant pressure and dry, can arrive non-hydrophobic type silica aerogel; As this organogel is further carried out surface-treated with organosilicon reagent, often press dry dry, the silica aerogel that can obtain having superhydrophobic property.
More specifically, the invention discloses a kind of is the silicon source with cheap water glass, utilizes microwave exposure and strengthens the solvent exchange technology, under condition of normal pressure, prepares the method for low density silica aerogel fast.The steps include: (1) with ion exchange resin or acid sodium silicate aqueous solution is carried out acidification, making its pH value is the 2-3 scope; (2) add the appropriate bases catalyzer, to obtain SiO
2Hydrogel; (3) hydrogel is carried out microwave exposure, impel its complete gelation; (4) with alcohol, organic solvent hydrogel is carried out solvent exchange successively; (5) adopt silane coupling agent that wet gel is carried out surface-treated; (6) constant pressure and dry obtains final gas gel.
Method characteristics of the present invention are that (1) is at SiO
2After the colloidal sol gelling it is carried out microwave exposure, promote its complete gelation, thereby avoid very long gel ageing process; (2) adopt reinforcement solvent exchange technology, thereby significantly reduce the solvent exchange time, and save the organosilicon reagent consumption.Adopt the SiO of present method preparation
2The density of gas gel can reach 0.03-0.2g/cm
3, specific surface area is 500-800m
2/ g has significant hydrophobic character.Because use cheap water glass to be raw material, and adopted reinforcement solvent exchange technology, the present invention can prepare the hydrophobic silica aerogel of low density, high-specific surface area in 1 day, be fit to large-scale production and application.
Below detail to various aspects of the present invention:
The reaction method general introduction
A kind of quick method for preparing the low density silica aerogel of the present invention, said method comprises the steps:
SiO is provided
2Hydrogel;
To said SiO
2Hydrogel carries out microwave exposure, makes it reach complete gelation;
With alcoholic solvent and non-polar solvent the hydrogel of resulting complete gelation is carried out solvent exchange successively; Obtain the low density silica aerogel.
Described microwave exposure step and solvent swap step can make the low density silica aerogel fast.Adopt the SiO of present method preparation
2The density of gas gel can reach 0.03-0.2g/cm
3In embodiment, SiO
2The density of gas gel can reach 0.03-0.2g/cm
3, specific surface area is 500-800m
2/ g has significant hydrophobic character.
(1) preparation of silica hydrogel
Service water glass or the sodium silicate aqueous solution of choosing different moduluses are the silicon source, and it is mixed with appropriate amount of deionized water (or tap water), and obtaining mass concentration is the sodium silicate aqueous solution (A) of 1-30% (preferred 3-10%).Wherein the modulus scope of water glass or sodium silicate solution is 1.0-3.5.
Strong acid ion exchange resin is mixed with the sodium silicate solution (A) of dilution, under room temperature-70 ℃ condition, stirred 1 minute-12 hours, obtain the silicate solution that pH is 2-3 (C).Perhaps, the pH value of A is adjusted to 2-3, obtains (C) equally with diluted acid (B).Wherein strong acid ion exchange resin can be styrene type cation exchange resin, its modified resin or any other cationoid exchange resin; Diluted acid (B) can be hydrochloric acid, sulfuric acid, nitric acid, acetic acid or any inorganic or organic acid of concentration at 0.001-12mol/L.The volume ratio of resin and sodium silicate solution (A) is 1～10: 1 (preferred 1-3: 1).
Resin in the filtering solution (C) obtains clear liquid, adds appropriate bases catalyzer (D) therein, makes pH value to the 4-12 scope (preferred 5-9) of solution, leaves standstill 1 minute-12 hours in room temperature-99 a ℃ condition, obtains silicate gel (E).Alkaline catalysts (D) can discharge OH for any in the aqueous solution
-Inorganic or organic reagent, include but not limited to ammoniacal liquor, sodium hydroxide, Pottasium Hydroxide, thanomin, diethylolamine, trolamine, quadrol or the like.
Silica hydrogel of the present invention can also adopt the various ordinary methods of this area to prepare, or through commercially available acquisition, all can obtain low-density silica aerogel fast through follow-up step.
(2) microwave exposure of hydrogel
(E) places microwave reactor to carry out microwave exposure with silicate gel, and the microwave exposure power that every ml mixture is accepted is 0.1-1000W (preferred 0.5-100W), and irradiation time is 1 second-10 hours (preferred 30 seconds-30 minutes).Silicate gel behind microwave exposure is designated as (F).
Outstanding feature of the present invention is, after silica hydrogel forms, adopts the microwave exposure technology that hydrogel is handled.Microwave heating is a kind ofly to polar molecule even type of heating to be arranged fast, effectively, all; The effective gelatinization process of promotes oxidn silicon gel; The intensity of enhanced oxidation silicon skeleton in very short time, thus the surface tension that solvent evaporation causes effectively resisted, prevent that nano pore from caving in.Simultaneously, the microwave exposure process can make the moisture in the gel duct partly evaporate, thereby reduces the time of solvent exchange to a certain extent, and the UNICOM duct that moisture evaporation forms will help to improve the solvent exchange efficient in the subsequent step.
(3) solvent exchange
Hydrogel (F) is carried out solvent exchange handle, use alcohol (G) and low surface tension organic solvent (H) that (F) handled successively.
One or more that processing mode can be immersion, refluxes or washes, the treatment time is respectively 0.1-24 hour (preferred 0.5-4 hour), and treatment temp is room temperature-99 ℃ (preferred 40-85 a ℃).
Wherein monobasic or the polyvalent alcohol of alcohol (G) for dissolving each other with water includes but not limited to methyl alcohol, ethanol, propyl alcohol, n-propyl alcohol, Virahol, propyl carbinol, isopropylcarbinol, terepthaloyl moietie, USP Kosher or the like.
Organic solvent (H) is the non-polar solvent of surface tension less than 30mN/m, includes but not limited to acetone, hexanaphthene, normal hexane, n-heptane or the like.The organogel that behind solvent exchange, obtains is designated as gel (I).
The solvent exchange process adopt to be strengthened solvent exchange technology, i.e. adding planar water or pure siccative (N) in a large number in alcoholic solution (G) or organic solvent (H) is like silica gel, molecular sieve, unslaked lime, smectite, attapulgite or the like.Siccative (N) is 0.1-10 with the volume ratio of wet gel (F): 1.
As organogel (I) directly being carried out the constant pressure and dry in the 5th step, then get wetting ability silica aerogel (M).
Outstanding feature of the present invention also is; In solvent exchange and surface-treated, modification, can adopt " strengthening the solvent exchange technology "; Promptly use the siccative to absorb water/alcohol in a large number to remove the water or the alcohol of from wet gel, discharging, thereby the peak concentration gradient of assurance solvent diffusion make water or the alcoholic solvent in the gel nano pore can fast as far as possible discharge; Save the solvent exchange time, and effectively reduce the solvent exchange number of times.Therefore, in typical case of the present invention, alcohol-water solvent exchange and organic solvent-alcohol exchange all only needs 1-2 time (traditional method is 3 times basically), and each time length also only needs 1-4 hour (traditional method is 12-24 hour basically).
(4) surface-treated
Dosage of silane coupling agent of the present invention can be controlled in lower level.For example, adopt organo silane coupling agent (J) that organogel (I) is carried out surface-treated, the volume ratio of silane coupling agent (J), organogel (I), solvent (H) is 0.01-10: 1: 1-10.
In an embodiment; Adopt organo silane coupling agent (J) that organogel (I) is carried out surface-treated; The volume ratio of silane coupling agent (J), organogel (I), solvent (H) is 0.01-10: 1: 1-10; Treatment temp is room temperature-99 ℃ (preferred 40-85 a ℃), and the treatment time is 0.1-24 hour (preferred 0.5-4 hour), one or more that processing mode can be immersion, refluxes or washes.
The general formula of silane coupling agent (J) is RSiX
3In the formula: R is an organic group; Like vinyl, amino, epoxy group(ing), methacryloxy, sulfydryl or urea groups etc., X is the group of some facile hydrolysis, like chlorine, methoxyl group, oxyethyl group, methoxy ethoxy, acetoxyl group etc.; Therefore, silane coupling agent (J) includes but not limited to trimethylchlorosilane, hexamethyldisilazane, IPOTMS isopropyloxy trimethylsilane, hexamethyldisiloxane or the like.
Gel after surface-treated cleans 1-10 time with organic solvent (H), and treatment temp is room temperature-99 ℃ (preferred 40-85 a ℃), and the treatment time is 0.1-24 hour (preferred 0.5-4 hour), one or more that processing mode can be immersion, refluxes or washes.The organogel of gained is designated as (K).
Surface-treated and organic solvent cleaning process subsequently can adopt the reinforcement solvent exchange technology similar with step (three).
Characteristics of the present invention are that also in the surface-treated process of organogel (I), dosage of silane coupling agent can be controlled in lower level, and the hydrophobic effect of the gas gel that obtains is constant.This cost for effective reduction gas gel product is significant.
(5) constant pressure and dry
Under normal pressure, organogel (K) is carried out drying; Remove the organic solvent in the hole; Drying temperature is room temperature-250 ℃ (preferred 60-200 a ℃), and the treatment time is 0.5-24 hour (preferred 1-4 hour), and type of heating can be baking oven for heating, ir lamp heating or other type of heating.The gained gel is final product hydrophobic type silica aerogel (L) after drying.
Characteristics of the present invention are that also the silica aerogel of the hydrophobic or non-hydrophobic type that the employing method for preparing obtains all has lower tap density (0.03-0.2g/cm
3), especially be fit to preparation density at 0.1g/cm
3Following silica aerogel, and low-density gas gel often has lower thermal conductivity and better thermal insulation, exhausted sound effective value, practicality is better.
Specify like nothing, various raw materials of the present invention all can obtain through commercially available; Or prepare according to the ordinary method of this area.Only if definition or explanation are arranged in addition, the same meaning that all specialties used herein and scientific words and those skilled in the art are familiar with.Any in addition with the institute similar content of putting down in writing or the equalization method and material all can be applicable in the inventive method.
Above-mentioned compound method is the synthetic route of part of compounds of the present invention; According to above-mentioned example; Those skilled in the art can synthesize other compounds of the present invention through the adjustment diverse ways, and perhaps, those skilled in the art can synthesize compound of the present invention according to existing known technology.
Other aspects of the present invention are because the disclosure of this paper is conspicuous to those skilled in the art.
Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment only to be used to the present invention is described and be not used in the restriction scope of the present invention.The experimental technique of unreceipted actual conditions in the following example is measured according to national standard usually.If there is not a corresponding national standards, then carry out according to general international standard, normal condition or according to the condition that manufacturer advises.Unless otherwise indicated, otherwise all umbers are weight part, and all per-cents are weight percentage, and described polymericular weight is a number-average molecular weight.
Only if definition or explanation are arranged in addition, the same meaning that all specialties used herein and scientific words and those skilled in the art are familiar with.Any in addition with the institute similar content of putting down in writing or the equalization method and material all can be applicable in the inventive method.
Embodiment 1:
Choosing modulus and be 3.0 service water glass is 2 milliliters in silicon source, mixes with 8 ml deionized water, obtains mass concentration and be 5% sodium silicate aqueous solution (A).The strong acid ion exchange resin that with volume ratio is 1: 1 mixes with sodium silicate solution (A), stirs at ambient temperature 3-5 minute, obtains the silicate solution that pH is 2-3 (C).Filter (C) and get clear liquid, add proper ammonia (D) therein, the pH value that makes solution is to the 5-6 scope, and room temperature condition leaves standstill and got silicate gel (E) in 10 minutes.
(E) places microwave reactor to carry out microwave exposure with silicate gel, and the microwave exposure power that every ml mixture is accepted is 20W, and irradiation time is 6 minutes, gets silicate gel (F).
Use ethanol (G) and hexanaphthene (H) that hydrogel (F) is soaked under 65 ℃ successively, the time was respectively 2 hours.Add at (G) or (H) and the 4A molecular sieve of wet gel simultaneously with volume.Obtain organogel (I).
Adopt trimethylchlorosilane (J) that organogel (I) is carried out surface-treated, the volume ratio of trimethylchlorosilane (J), organogel (I), solvent (H) is 0.1: 1: 3, and treatment temp is 65 ℃, and the treatment time is 2 hours, and processing mode can be immersion.With hexanaphthene soaking and washing gained modified gel 1 time, temperature is 65 ℃, and the treatment time is 2 hours, obtains organogel (K).
Organogel (K) is placed 200 ℃ of baking ovens oven dry 2 hours, get final product the hydrophobic type silica aerogel.Through test, its density is 0.037g/cm
3, specific surface area is 1177m
2/ g, pore size distribution peak value are 11 nanometers.
Embodiment 2:
Choosing modulus and be 3.0 service water glass is 20 milliliters in silicon source, mixes with 80 ml deionized water, obtains mass concentration and be 5% sodium silicate aqueous solution (A).The strong acid ion exchange resin that with volume ratio is 1: 1 mixes with sodium silicate solution (A), stirs at ambient temperature 3-5 minute, obtains the silicate solution that pH is 2-3 (C).Filter (C) and get clear liquid, add proper ammonia (D) therein, the pH value that makes solution is to the 5-6 scope, and room temperature condition leaves standstill and got silicate gel (E) in 10 minutes.
(E) places microwave reactor to carry out microwave exposure with silicate gel, and the microwave exposure power that every ml mixture is accepted is 20W, and irradiation time is 6 minutes, gets silicate gel (F).
Use ethanol (G) and hexanaphthene (H) that hydrogel (F) is soaked under 65 ℃ successively, the time was respectively 8 hours.Add at (G) or (H) and the 4A molecular sieve of wet gel simultaneously with volume.Obtain organogel (I).
Adopt trimethylchlorosilane (J) that organogel (I) is carried out surface-treated, the volume ratio of silane coupling agent (J), organogel (I), solvent (H) is 0.3: 1: 3, and treatment temp is 65 ℃, and the treatment time is 3 hours, and processing mode can be backflow.With hexanaphthene soaking and washing gained modified gel 1 time, temperature is 65 ℃, and the treatment time is 2 hours, obtains organogel (K).
Organogel (K) is placed 200 ℃ of baking ovens oven dry 1 hour, get final product the hydrophobic type silica aerogel.Through test, its density is 0.047g/cm
3
Embodiment 3:
Choosing modulus and be 3.0 service water glass is 2 milliliters in silicon source, mixes with 8 ml deionized water, obtains mass concentration and be 5% sodium silicate aqueous solution (A).The strong acid ion exchange resin that with volume ratio is 1: 1 mixes with sodium silicate solution (A), stirs at ambient temperature 3-5 minute, obtains the silicate solution that pH is 2-3 (C).Filter (C) and get clear liquid, add proper ammonia (D) therein, the pH value that makes solution is to the 5-6 scope, and room temperature condition leaves standstill and got silicate gel (E) in 5 minutes.
(E) places microwave reactor to carry out microwave exposure with silicate gel, and the microwave exposure power that every ml mixture is accepted is 20W, and irradiation time is 6 minutes, gets silicate gel (F).
Use ethanol (G) and hexanaphthene (H) that hydrogel (F) is soaked under 65 ℃ successively, the time was respectively 2 hours.Add at (G) or (H) and the 4A molecular sieve of wet gel simultaneously with volume.Obtain organogel (I).
Adopt trimethylchlorosilane (J) that organogel (I) is carried out surface-treated, the volume ratio of trimethylchlorosilane (J), organogel (I), solvent (H) is 0.1: 1: 3, and treatment temp is 65 ℃, and the treatment time is 4 hours, and processing mode can be immersion.With hexanaphthene soaking and washing gained modified gel 1 time, temperature is 65 ℃, and the treatment time is 3 hours, obtains organogel (K).
Organogel (K) is placed 200 ℃ of baking ovens oven dry 3 hours, get final product the hydrophobic type silica aerogel.Through test, its density is 0.084g/cm
3
Embodiment 4:
All raw materials and technology are all identical with embodiment 3, but change microwave irradiation time into 10 minutes.The density of gained gas gel is 0.127g/cm
3
Embodiment 5:
The delivery number is that 3.0 service water glass is 1.4 milliliters in silicon source, mixes with 8.6 ml deionized water, obtains mass concentration and be 3.5% sodium silicate aqueous solution (A).The strong acid ion exchange resin that with volume ratio is 1: 1 mixes with sodium silicate solution (A), stirs at ambient temperature 3-5 minute, obtains the silicate solution that pH is 2-3 (C).Filter (C) and get clear liquid, add proper ammonia (D) therein, the pH value that makes solution is to the 5-6 scope.
Place microwave reactor to carry out microwave exposure hydrosol of silicic acid, the microwave exposure power that every ml mixture is accepted is 20W, and irradiation time is 7 minutes, gets silicate gel (F).
Other technological processs are all identical with embodiment 3.The density of gained gas gel is 0.1035g/cm
3
Embodiment 6:
The delivery number is that 3.0 service water glass is 20 milliliters in silicon source, mixes with 80 ml deionized water, obtains mass concentration and be 5% sodium silicate aqueous solution (A).The strong acid ion exchange resin that with volume ratio is 1: 1 mixes with sodium silicate solution (A), stirs at ambient temperature 3-5 minute, obtains the silicate solution that pH is 2-3 (C).Filter (C) and get clear liquid, add proper ammonia (D) therein, the pH value that makes solution is to the 5-6 scope, and room temperature condition leaves standstill and got silicate gel (E) in 10 minutes.
(E) places microwave reactor to carry out microwave exposure with silicate gel, and the microwave exposure power that every ml mixture is accepted is 20W, and irradiation time is 6 minutes, gets silicate gel (F).
Use ethanol (G) and hexanaphthene (H) that hydrogel (F) is carried out solvent exchange successively under 65 ℃, each repeats 2 times, and each time length was respectively 4 hours, got organogel (I).
Adopt trimethylchlorosilane (J) that organogel (I) is carried out surface-treated, the volume ratio of silane coupling agent (J), organogel (I), solvent (H) is 0.1: 1: 3, and treatment temp is 65 ℃, and the treatment time is 4 hours, and processing mode can be immersion.With hexanaphthene soaking and washing gained modified gel 1 time, temperature is 65 ℃, and the treatment time is 2 hours, obtains organogel (K).
Organogel (K) is placed 200 ℃ of baking oven oven dry 1 hour, obtain the hydrophobic type silica aerogel.Through test, its density is 0.03g/cm
3
The above is merely preferred embodiment of the present invention; Be not in order to limit essence technology contents scope of the present invention; Essence technology contents of the present invention is broadly to be defined in the claim scope of application, and if any technological entity or method that other people accomplish are defined identical with the claim scope of application; Also or a kind of change of equivalence, all will be regarded as and be covered by among this claim scope.
All documents in that the present invention mentions are all quoted as a reference in this application, are just quoted such as a reference separately as each piece document.Should be understood that in addition that after having read foregoing of the present invention those skilled in the art can do various changes or modification to the present invention, these equivalent form of values fall within the application's appended claims institute restricted portion equally.
Claims (10)
1. a method for preparing the low density silica aerogel fast is characterized in that said method comprises the steps:
SiO is provided
2Hydrogel;
To said SiO
2Hydrogel carries out microwave exposure, makes it reach complete gelation;
With polar solvent and non-polar solvent the hydrogel of resulting complete gelation is carried out solvent exchange successively; Obtain the low density silica aerogel.
2. the method for claim 1 is characterized in that, in the said microwave exposure process, the microwave exposure power that every ml mixture is accepted is 0.1-1000W, preferred 0.5-100W; Irradiation time is 1 second-10 hours, preferred 30 seconds-30 minutes.
3. the method for claim 1; It is characterized in that; Said polar solvent adopts alcoholic solvent, is preferably the monobasic or the polyvalent alcohol that can dissolve each other with water, more preferably methyl alcohol, ethanol, propyl alcohol, n-propyl alcohol, Virahol, propyl carbinol, isopropylcarbinol, terepthaloyl moietie or USP Kosher.
4. the method for claim 1 is characterized in that, the surface tension of said non-polar solvent is less than 30mN/m, preferred acetone, hexanaphthene, normal hexane, n-heptane or its combination.
5. the method for claim 1; It is characterized in that; The processing mode of said solvent exchange is one or more that soak, reflux or wash, and the treatment time is respectively 0.1-24 hour (preferred 0.5-4 hour), and treatment temp is room temperature-99 ℃ (preferably 40-85 a ℃).
6. the method for claim 1 is characterized in that, said solvent exchange process adopts strengthens solvent exchange technology, promptly in polar solvent or non-polar solvent, adds planar water or pure siccative in a large number.
7. method as claimed in claim 6 is characterized in that, said siccative is selected from silica gel, molecular sieve, unslaked lime, smectite, attapulgite or its combination.
8. method as claimed in claim 6 is characterized in that, the volume ratio of the hydrogel of said siccative and complete gelation is 0.1-10: 1.
9. the method for claim 1 is characterized in that, said SiO
2The raw material of hydrogel prepares through following mode:
(1) with ion exchange resin or acid sodium silicate aqueous solution is carried out acidification, making its pH value is the 2-3 scope;
(2) add the appropriate bases catalyzer, to obtain said SiO
2Hydrogel.
10. the method for claim 1 is characterized in that, resulting low density silica aerogel carries out following aftertreatment:
Adopt silane coupling agent that said low density silica aerogel is carried out surface-treated;
The low density silica aerogel of resulting surface-treated can randomly carry out constant pressure and dry, obtains the low density gas gel product of hydrophobic type.
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| CN109704349A (en) * | 2019-02-22 | 2019-05-03 | 广州市飞雪材料科技有限公司 | A kind of low-density colour silicon dioxide granule and its preparation with porous structure |
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