JP5456436B2 - Method for producing silica xerogel - Google Patents

Description

The present invention relates to a process for the preparation of silica xerogel available insulation material or the like.

  Silica xerogel having pores below the mean free path of air molecules does not contain low thermal conductivity foaming gas, has high heat insulation properties, and has the performance of little secular change. Has attracted attention in such fields.

  Silica xerogel uses water glass or an alkoxysilane compound such as tetramethoxysilane as a gel raw material, mixes a solvent such as water or alcohol with a catalyst as necessary, and reacts the gel raw material in the solvent to form a wet gel. After the formation, it can be obtained by evaporating and drying the solvent inside the wet gel.

  However, since the gel skeleton is flexible at the initial stage of drying of the wet gel, an aggregate cluster of silica particles (hereinafter referred to as gel wall) constituting the porous structure of the wet gel and the liquid medium in the wet gel Due to the interfacial tension, the gel wall shrinks when the solvent present on the gel wall evaporates. And when the distance between gel walls becomes close, the silanol groups which exist in a gel wall react, the void | hole diameter of the gel after drying becomes small, and it becomes a thing unsuitable for a heat insulating material use in many cases. For this reason, attempts have been made to keep the interfacial tension between the gel wall and the liquid medium in the wet gel as close to zero as possible, suppress the shrinkage of the wet gel during drying, and maintain the porosity of the wet gel after drying. Yes.

  In order to suppress the shrinkage of the wet gel during drying, attempts have been conventionally made to dry by supercritical extraction using carbon dioxide.

  In Patent Document 1 below, after washing with an organic solvent until the moisture content in the wet gel becomes 5% by weight or less, the gel wall surface is chemically modified with a silylating agent, and the interfacial tension between the gel wall and the solvent is determined. A method for producing a silica airgel is disclosed in which atmospheric pressure drying is performed with a reduced pressure.

  Further, in Patent Document 2 below, (a) a reaction in which a silicon compound having a hydrolyzable functional group and a non-hydrolyzable functional group in a molecule is added to an acidic aqueous solution containing a surfactant to form a sol. And a step of performing the reaction for gelling the sol in one step, and (b) a step of drying the gel formed by the step (a), In the step (a), the acidic aqueous solution further includes a hydrolyzable compound that generates a substance that promotes a reaction of gelling the gel by hydrolysis, and hydrolyzing the hydrolyzable compound makes the sol The gel is reacted, and in step (b), the gel is dried at a temperature and pressure below the supercritical point of the solvent used for drying the gel. Manufacturing method of Le siloxane airgel is disclosed.

Japanese Patent No. 3854645 International Publication WO2007 / 10949 Pamphlet

  However, the supercritical extraction method requires a pressure and a temperature that are higher than the supercritical point of the extraction medium, so that an apparatus that can withstand high temperature and pressure is required, and there is a problem of requiring equipment costs. Furthermore, there was a danger in handling the high-pressure device.

  Moreover, in the said patent document 1, although the interfacial tension of a gel wall and a solvent is reduced by chemically modifying the gel wall surface with a silylating agent, since the silylating agent has low compatibility with water, it is wet. In order to sufficiently modify the surface of the gel, it is necessary to sufficiently substitute the organic solvent. This medium replacement process depends on the diffusion phenomenon, so that the time required for the process becomes longer, a large amount of organic solvent is used in order to increase the efficiency of the medium replacement, and further surface modification with a silylating agent is sufficient. There are problems such as requiring a reaction time for completeness and a washing step for removing the unreacted silylating agent, resulting in a complicated manufacturing process.

  Moreover, in the said patent document 2, although the silicon compound which has a hydrolyzable functional group and a non-hydrolyzable functional group in a molecule | numerator is used as a gel raw material, the bridge | crosslinking density of the gel obtained using this silicon compound As a result, even if the interfacial tension between the gel wall and the liquid medium is reduced due to insufficient strength or rigidity of the gel wall, unless the interfacial tension is reduced to zero as in the supercritical extraction method The gel tended to shrink. Therefore, in Patent Document 2, in order to dry the wet gel at atmospheric pressure, the solvent of the wet gel is replaced with a liquid medium having a low surface tension such as a fluorinated solvent, and the wet gel is dried. Substituting these solvents requires labor and time, and thus there is a problem that the manufacturing process becomes complicated.

Accordingly, an object of the present invention has a smaller pore than the mean free path of the air is to provide a method of manufacturing can be produced silica xerogels low silica xerogel bulk density by a simple manufacturing process.

  As a result of various studies, the inventor has used monoalkyltrialkoxysilane as a gel raw material in combination with tetraalkoxysilane in a specific ratio, so that the solvent substitution of the wet gel and the chemistry of the gel wall surface with the silylating agent are performed. Even without modification, drying in the supercritical extraction method, etc., shrinkage during drying of the wet gel can be suppressed, with a simple manufacturing process, pores smaller than the mean free path of air, and bulk density It has been found that low silica xerogels are obtained.

That is, the silica xerogel of the present invention comprises tetraalkoxysilane and monoalkyltrialkoxysilane in a molar ratio of tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05 to 0.35: 0.65 to 0.95. The gel material contains a condensed and dried product, and has a bulk density of 90 to 200 kg / m ³ and an average pore diameter of 20 to 65 nm.

Since tetraalkoxysilane is hydrolyzed to produce four silanol groups in one molecule, the crosslink density of the wet gel can be increased in the subsequent gelation step, and the strength or rigidity of the gel wall can be increased. In addition, since monoalkyltrialkoxysilane generates three silanol groups in one molecule by a hydrolysis reaction, the crosslink density of the wet gel can be increased in the subsequent gelation step. The wall surface can be coated with a large volume of alkyl groups. For this reason, the condensate of the gel raw material containing tetraalkoxysilane and monoalkyltrialkoxysilane in the above molar ratio has a high crosslinking density, and the gel wall surface is coated with a large volume alkyl group. Therefore, when this condensate (wet gel) is dried, it is possible to prevent the volume from shrinking, and it is possible to produce a silica xerogel having a lower bulk density and a smaller average pore diameter by a simpler production process than before. Further, this silica xerogel has a low bulk density of 90 to 200 kg / m ^3, and furthermore has an average pore diameter of 20 to 65 nm and smaller pores than the mean free path of air, so It is excellent in performance and can be particularly preferably used for applications such as a heat insulating material.

  Moreover, the manufacturing method of the silica xerogel of this invention is tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05-0.35: 0.65-in a molar ratio with tetraalkoxysilane and monoalkyltrialkoxysilane. The gel raw material, alcohols, and water contained at a ratio of 0.95 are 4 to 8 moles of the alcohols and 3 to 6 moles of the water with respect to 1 mole of the total amount of the silane compound in the gel raw material. The silane compound in the gel raw material is hydrolyzed to produce a sol, and the resulting sol is gelled, then cured to obtain a wet gel. The obtained wet gel is subjected to normal pressure and / or Or it is characterized by drying under reduced pressure.

  According to the method for producing silica xerogel of the present invention, the silane compound is almost completely hydrolyzed by mixing the gel raw material, water, and alcohols within the specific ranges described above to form a sol. Can proceed to. Then, by gelling and curing the sol, it is possible to obtain a wet gel having a high crosslinking density and a gel wall surface coated with a large volume alkyl group. For this reason, since volume shrinkage can be suppressed when drying the wet gel, a silica xerogel having pores smaller than the mean free path of air and having a low bulk density can be obtained with a simple manufacturing process.

  In the method for producing a silica xerogel of the present invention, it is preferable to hydrolyze a silane compound in the gel raw material at a temperature of 20 to 60 ° C. for 2 to 48 hours to form the sol. It is more preferable to hydrolyze the compound at a temperature of 50 to 60 ° C. for 2 to 8 hours to form the sol. By hydrolyzing in this way, the silane compound can be hydrolyzed almost completely.

  In the method for producing a silica xerogel of the present invention, 0.001 to 0.1 parts by mass of an acid catalyst is added to 100 parts by mass of the total amount of silane compounds in the gel raw material to hydrolyze the silane compound. It is preferable. According to this aspect, since the sol can be obtained in a shorter time by promoting the hydrolysis reaction of the silane compound, the production efficiency of the silica xerogel is improved.

  In the method for producing the silica xerogel of the present invention, the sol is preferably gelated by adding an aqueous base catalyst to the sol at a temperature of 30 to 70 ° C., and the aqueous base catalyst is used in the gel raw material. It is preferable to add 0.5 to 5 parts by mass with respect to 100 parts by mass of the total amount of silane compounds. Moreover, it is preferable to use ammonia as the aqueous base catalyst. According to this aspect, gelation of the sol can be performed in a shorter time, and a wet gel having high strength or rigidity can be obtained in a shorter time. In addition, since ammonia is highly volatile and hardly remains in silica xerogel, silica xerogel having excellent water resistance can be obtained by using ammonia as an aqueous base catalyst.

  In the method for producing a silica xerogel of the present invention, it is preferable to perform the curing at a temperature of 30 to 70 ° C. to obtain the wet gel. According to this aspect, the silica particles constituting the wet gel are strongly bonded to each other. As a result, the strength or rigidity of the gel wall is improved, and shrinkage during drying can be more effectively suppressed.

  In the method for producing a silica xerogel of the present invention, it is preferable to perform the gelation of the sol and subsequent curing for a total of 4 to 75 hours to obtain the wet gel. By gelling and curing in this way, a wet gel that has high gel wall strength and rigidity and is difficult to shrink during drying can be obtained.

  In the method for producing the silica xerogel of the present invention, the wet gel is dried under a reduced pressure of 1 to 10 kPa at a temperature of 40 to 80 ° C. for 3 to 48 hours, and then under a normal pressure and a temperature of 105 to 105. It is preferable to dry at 200 ° C. for 0.5 to 3.0 hours. First, the wet gel is dried at a temperature of 40 to 80 ° C. under a reduced pressure of 1 to 10 kPa for 3 to 48 hours, so that the bumping phenomenon of the solvent in the wet gel can be suppressed and there is no crack. Silica xerogel with good handleability is easily obtained. And after drying under reduced pressure, by drying at a temperature of 105 to 200 ° C. at a temperature of 105 to 200 hours for 0.5 to 3.0 hours, a springback phenomenon can be caused and the shrinkage of the gel can be suppressed, so the bulk density is low, Silica xerogel having pores smaller than the mean free path of air is easily obtained.

  According to the present invention, it is possible to suppress shrinkage during drying of the wet gel without performing solvent replacement of the wet gel, chemical modification of the gel wall surface with the silylating agent, drying in the supercritical extraction method, etc. A silica xerogel having pores smaller than the mean free path of air and having a low bulk density can be produced with a simpler production process.

It is a picked-up image (90,000 times) of the scanning x-microscope of the silica xerogel of Example 6. 10 is a scanning electron microscope image (90,000 times) of the silica xerogel of Example 9. It is a picked-up image (100,000 times) of the scanning x-microscope of the silica xerogel of Example 12.

(Silica xerogel)
In the silica xerogel of the present invention, the tetraalkoxysilane and the monoalkyltrialkoxysilane are in a molar ratio of tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05 to 0.35: 0.65 to 0.95. Condensed and dried products of gel materials contained in

Tetraalkoxysilane is hydrolyzed to produce four silanol groups in one molecule, and the silanol groups undergo a condensation reaction in the subsequent gelation step. It has the function of increasing the crosslink density of the product (wet gel) and increasing the strength or rigidity of the gel wall.
In addition, monoalkyltrialkoxysilane generates three silanol groups in one molecule by hydrolysis reaction and crosslinks in a three-dimensional network in the subsequent gelation process, so the strength of the gel wall of the condensate (wet gel) Alternatively, the rigidity can be increased. Furthermore, the gel wall surface of the condensate (wet gel) can be coated with an alkyl group having a large volume to reduce the interfacial tension with the liquid medium in the condensate (wet gel).
Therefore, a gel raw material containing tetraalkoxysilane and monoalkyltrialkoxysilane in a molar ratio of tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05 to 0.35: 0.65 to 0.95 The condensate has a high crosslinking density, and the surface of the gel wall is coated with a large volume alkyl group, so that volume shrinkage when the condensate (wet gel) is dried can be suppressed.

  Examples of the tetraalkoxysilane used as the gel raw material include tetramethoxysilane, tetraethoxysilane, tetra n-propoxysilane, and tetra n-butoxysilane. Tetramethoxysilane and tetraethoxysilane are preferred in terms of workability such as completion of the hydrolysis reaction and shortening of the time required for the gelation reaction. Furthermore, tetraethoxysilane is more preferable from the viewpoint of sol stability.

  Monoalkyltrialkoxysilane used as a gel raw material is monomethyltrimethoxysilane, monomethyltriethoxysilane, mono n-propyltrimethoxysilane, mono n-propyltriethoxysilane, monohexyltrimethoxysilane, monohexyltriethoxysilane, mono Examples include decyltrimethoxysilane and monodecyltriethoxysilane. Monomethyltrimethoxysilane and monomethyltriethoxysilane are preferred because they are highly compatible with water when producing a sol and have a high hydrolysis reaction rate. Furthermore, monomethyltrimethoxysilane is more preferable in consideration of economy.

  The molar ratio of tetraalkoxysilane and monoalkyltrialkoxysilane in the gel raw material is tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05 to 0.35: 0.65 to 0.95, and 0.10 -0.30: 0.70-0.90 are preferable, and 0.15-0.25: 0.75-0.85 are more preferable.

  If the molar ratio of tetraalkoxysilane is less than 0.05, the average pore diameter of the resulting silica xerogel tends to be large, and pores larger than the mean free path of air may be formed. This is because the relative proportion of tetraalkoxysilane in the gel raw material decreases, so the strength or rigidity of the gel wall of the condensate (wet gel) decreases, and the monoalkyltrialkoxysilane coated on the gel wall surface It is considered that the pore diameter of the resulting silica xerogel is likely to be widened because it is repelled by the derived alkyl group. Moreover, when the molar ratio of tetraalkoxysilane exceeds 0.35, the bulk density of silica xerogel tends to increase. This is because the relative proportion of tetraalkoxysilane in the gel raw material increases, so the proportion of silanol groups remaining on the gel wall surface of the condensate (wet gel) increases and shrinkage tends to occur during drying. It is thought that.

  The gel raw material may contain dialkyl dialkoxysilane and trialkylmonoalkoxysilane. However, the use of dialkyl dialkoxysilane and trialkylmonoalkoxysilane reduces the relative proportion of tetramethoxysilane in the total amount of silane compound, so the strength or rigidity of the gel wall of the condensate (wet gel) decreases. It becomes easy to do. For this reason, the total amount of the dialkyl dialkoxysilane and the trialkyl monoalkoxysilane is preferably 0.5 mol or less, more preferably 0.25 mol or less, especially not contained, relative to 1 mol of tetraalkoxysilane. preferable.

The silica xerogel of the present invention has a bulk density of 90 to 200 kg / m ³ and an average pore diameter of 20 to 65 nm. The bulk density is preferably from ^{90~180kg / m 3, 90~150kg / m} 3 and more preferably. Moreover, 20-50 nm is preferable and, as for an average hole diameter, 30-45 nm is more preferable. The specific surface area is preferably from 600~800m ² / g, more preferably 650~800m ² / g. If the bulk density, average pore diameter, and specific surface area of the silica xerogel are in the above ranges, they are excellent as heat insulating properties and therefore suitable as heat insulating materials.

In order to adjust the bulk density and average pore size of silica xerogel, it is necessary to adjust the type of solvent used in the sol formation of the gel raw material, the quantitative ratio of the gel raw material, the gelation condition of the sol, the drying condition of the gel, etc. Easy to adjust.
In addition, the value of the bulk density in the present invention means a value measured by an electronic hydrometer according to the Archimedes method. Moreover, the value of an average hole diameter means the value measured by the nitrogen adsorption method.

(Method for producing silica xerogel)
Next, the manufacturing method of the silica xerogel of this invention is demonstrated.

In the method for producing the silica xerogel of the present invention, tetraalkoxysilane and monoalkyltrialkoxysilane are in a molar ratio of tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05-0.35: 0.65-0. The gel raw material, alcohols, and water contained at a ratio of 95 to 4 to 8 moles of the alcohols and 3 to 6 moles of the water with respect to 1 mole of the total amount of the silane compound in the gel raw material. A sol generating step of mixing and hydrolyzing the silane compound in the gel raw material to generate a sol; and a wet gel generating step of gelling the sol obtained in the sol generating step and then curing to obtain a wet gel; The wet gel obtained in the wet gel production step is mainly composed of a drying step for drying under normal pressure and / or reduced pressure.
In the present invention, the sol is a form in which the silane compound in the gel raw material is converted to a silanol group by hydrolysis, and before the condensation reaction between the silanol groups occurs, and is dissolved or dispersed in the solvent. Means the state. In addition, the wet gel means a silica gel solid in a wet state that contains a liquid medium of alcohols and water but does not have fluidity.
Hereinafter, each process of the manufacturing method of the silica xerogel of this invention is demonstrated.

[Sol generation process]
In the production method of the present invention, tetraalkoxysilane and monoalkyltrialkoxysilane are used as a gel raw material in a molar ratio of tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05 to 0.35: 0.65 to 0. .95, preferably 0.10 to 0.30: 0.70 to 0.90, more preferably 0.15 to 0.25: 0.75 to 0.85.

  As described above, tetraalkoxysilane is hydrolyzed to generate four silanol groups in one molecule, so that in the subsequent gelation step, the crosslink density of the wet gel is increased, and the strength or rigidity of the gel wall is increased. Can be increased. In addition, since monoalkyltrialkoxysilane generates three silanol groups in one molecule by a hydrolysis reaction, the crosslink density of the wet gel can be increased in the subsequent gelation step. The wall surface can be coated with a large volume of alkyl groups. For this reason, by using a gel raw material containing tetraalkoxysilane and monoalkyltrialkoxysilane in the above molar ratio, the gel wall has high strength or rigidity, and the gel wall surface is covered with a large volume alkyl group. A gel can be produced.

  In the present invention, the gel raw material may contain a dialkyl dialkoxysilane and a trialkylmonoalkoxysilane, but the inclusion of these reduces the relative proportion of tetraalkoxysilane, so that the dialkyl dialkoxy is reduced. The total amount of silane and trialkylmonoalkoxysilane is preferably 0.5 mol or less, more preferably 0.25 mol or less, and particularly preferably not contained per 1 mol of tetraalkoxysilane.

  In order to reduce the bulk density of the resulting silica xerogel or increase the average pore diameter, it is preferable to use a gel raw material in which the relative proportion of tetraalkoxysilane is lowered within the above-described range. Further, in order to increase the bulk density of the silica xerogel obtained or to reduce the average pore diameter, it is preferable to use a gel raw material in which the relative proportion of tetraalkoxysilane is increased within the above-described range.

  In the sol generation step, the gel raw material, water, and alcohols are mixed at a specific ratio, and the silane compound in the gel raw material is hydrolyzed to obtain a sol.

  In the silane compound, when water coexists, a hydrolysis reaction proceeds and a silanol group is generated. For example, tetraalkoxysilane is hydrolyzed by the reaction of the following formula (1), and monoalkyltrialkoxysilane is hydrolyzed by the reaction of the following formula (2).

Si (OR) ₄ + 4H ₂ O → Si (OH) ₄ + 4R—OH (1)
R—Si (OR) ₃ + 3H ₂ O → R—Si (OH) ₃ + 3R—OH (2)

  The hydrolysis of the silane compound starts to proceed gradually and is preferably performed for 2 to 48 hours in a temperature environment of 20 to 60 ° C, and more preferably 2 to 8 hours in a temperature environment of 50 to 60 ° C. By performing hydrolysis in this way, the silane compound can be hydrolyzed almost completely.

  The alcohol mixed with the gel material is not particularly limited. Methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol are preferred because of the high drying speed of the resulting wet gel. Of these, methanol, ethanol, and 2-propanol, which are alcohols having a low surface tension and a low boiling point in reducing the interfacial tension with the gel wall, are more preferable.

  The amount of water mixed with the gel raw material is preferably 3 to 6 mol, more preferably 3 to 5 mol, and particularly preferably 3 to 4 mol with respect to 1 mol of the total amount of silane compounds in the gel raw material. Water is necessary to react with the silane compound to produce silanol, and it is considered that the hydrolysis of the silane compound may not sufficiently proceed when the amount of water is less than 3 mol in the above ratio. In this state, when proceeding to the next wet gel generation step, it is considered that the condensation reaction between silanol groups does not proceed, and it is considered that silica having only alkoxy groups converted to silanol groups is generated. Or rigidity becomes inadequate and shrinkage | contraction at the time of drying becomes large. In addition, when the amount of water exceeds 6 mol in the above ratio, it is considered that a highly hydrophobic alkyl group is localized by hydrophobic interaction during gelation of the sol, and a xerogel having a uniform pore size cannot be obtained. There is a case.

  The amount of alcohol mixed with the gel material is preferably 4 to 8 mol, more preferably 4 to 6.5 mol, and particularly preferably 4.5 to 6 with respect to 1 mol of the total amount of silane compounds in the gel material. If the amount of alcohol is less than 4 moles in the above ratio, compatibility with the monoalkyltrialkoxysilane is impaired, and it is considered that hydrolysis proceeds in a heterogeneous state. Therefore, silanes that are not hydrolyzed remain in part, and the strength or rigidity of the resulting wet gel becomes insufficient, and shrinkage during drying increases. On the other hand, if the amount of alcohol exceeds 8 mol in the above ratio, hydrolysis of the silane compound may not sufficiently proceed. In this state, when proceeding to the next wet gel generation step, it is considered that the condensation reaction between silanol groups does not proceed, and it is considered that silica having only alkoxy groups converted to silanol groups is generated. Or rigidity becomes inadequate and shrinkage | contraction at the time of drying becomes large.

  In order to reduce the bulk density of the resulting silica xerogel or increase the average pore diameter, it is preferable to increase the ratio of alcohol and water mixed with the gel raw material within the above-mentioned range. Moreover, in order to raise the bulk density of the silica xerogel obtained or to reduce the average pore size, it is preferable to reduce the amount ratio of alcohol and water mixed with the gel raw material within the above-mentioned range.

  In the sol production step, it is preferable to add an acid catalyst in order to promote the hydrolysis reaction of the silane compound.

  Acid catalysts include hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, odorous acid, chloric acid, chlorous acid, hypochlorous acid and other inorganic acids, acidic phosphoric acid Examples thereof include acidic phosphates such as aluminum, acidic magnesium phosphate and acidic zinc phosphate, and organic carboxylic acids such as acetic acid, propionic acid, oxalic acid, succinic acid, citric acid, malic acid, adipic acid and azelaic acid. Although there is no restriction | limiting in the kind of acid catalyst to be used, Acetic acid, an oxalic acid, and a succinic acid are especially preferable from the point of the water resistance of the silica xerogel obtained.

  The amount of the acid catalyst added is preferably 0.001 to 0.1, more preferably 0.01 to 0.05 parts by mass with respect to 100 parts by mass of the total amount of the silane compound.

  As a method for preparing the sol in the sol production step, a predetermined amount of alcohol is injected into a closed vessel or a reactor equipped with a closed stirrer, and tetraalkoxysilane and monoalkyltrialkoxysilane so that the molar ratio is obtained. Are sequentially added, and then a predetermined amount of water is added so as to achieve the molar ratio, followed by thorough stirring. Moreover, when using an acid catalyst, it is preferable to make it dissolve in water beforehand. Further, the viscosity of the sol may be adjusted to a desired viscosity by adding various inorganic fillers for viscosity adjustment such as acidic clay, silica, alumina, boehmite, zirconia, titania, zinc oxide and the like.

[Wet gel production process]
In the wet gel production step, the sol obtained in the above step is gelled and then cured to obtain a wet gel.

  The gelation of the sol is preferably performed by adding an aqueous base catalyst to the sol and heating to 30 to 70 ° C. The gelation of the sol is preferably performed in a sealed container so that the liquid medium and the aqueous base catalyst do not volatilize.

  The addition amount of the aqueous base catalyst is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the total amount of silane compounds in the gel raw material, and is 1 to 4 from the viewpoint of shortening the gelation time and the water resistance of the resulting silica xerogel. Part by mass is more preferable. When the sol is gelled, by adding an aqueous base catalyst to the sol, dehydration condensation of the silane compound having a silanol group in the sol or, in part, dealcoholization condensation can be promoted, and in a shorter time. The gelation can proceed. If the amount of the aqueous base catalyst added is less than 0.5 parts by mass in the above ratio, the gelation time may take several days, which is not preferable from the viewpoint of productivity or economy. If the amount exceeds 5 parts by mass, the gelation time can be shortened, but the aqueous base catalyst may remain in the obtained silica xerogel, and the water resistance of the silica xerogel may be impaired.

  Examples of the aqueous base catalyst include lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide and other alkali metal hydroxides, ammonium hydroxide, ammonium fluoride, ammonium chloride, ammonium bromide and other ammonium compounds, Basic sodium phosphate such as sodium phosphate, sodium pyrophosphate, sodium polyphosphate, allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine , 3- (diethylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, t-butylamine, ec-Butylamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine and other aliphatic amines, morpholine And nitrogen-containing heterocyclic compounds such as N-methylmorpholine, 2-methylmorpholine, piperazine and derivatives, piperidine and derivatives, imidazole and derivatives. Among these, highly volatile ones are preferable from the viewpoint that they hardly remain in the dried silica xerogel and do not impair the water resistance, and more preferably ammonium hydroxide (ammonia water) from the viewpoint of economy.

  The aqueous base catalyst is preferably used in the form of an aqueous solution from the viewpoint of workability. And when using an aqueous base catalyst with the form of aqueous solution, it is preferable to use it, adjusting the density | concentration so that the quantity of the water added to sol may be 50 mass parts or less with respect to 100 mass parts of sol, More preferably, it is 50 mass parts or less, More preferably, it is 30 mass parts or less. As described above, since the methyl group in the monoalkyltrialkoxysilane has high hydrophobicity, when a large amount of water is added to the sol, it is localized by hydrophobic interaction and a homogeneous low density silica xerogel is formed. It may not be obtained.

  The gelation temperature of the sol is preferably 30 to 70 ° C, and more preferably 40 to 65 ° C. When the gelation temperature is less than 30 ° C., it takes time until the sol is completely gelled, and the strength of the generated wet gel is low and may shrink greatly during drying. Therefore, the desired silica xerogel May not be obtained. In addition, when the gelation temperature exceeds 70 ° C., a phenomenon in which the solvent (particularly alcohols) is volatilized and separated is observed, and the volume of the wet gel obtained thereby decreases, and the desired silica xerogel cannot be obtained. There is a case.

  The gelation time varies depending on the gelation temperature and the curing condition time after gelation described below, but the total gelation time and the curing time described below are preferably 4 to 75 hours, and preferably 6 to 48 hours. . In this way, by performing gelation and curing, a wet gel that has high gel wall strength and rigidity and is difficult to shrink during drying can be obtained.

  In this way, after the sol is gelled, it is further cured (aged) while being heated in a state where it is placed in a closed container. Thereby, the coupling | bonding of the silica particles which comprise a wet gel becomes strong, As a result, the intensity | strength or rigidity of a gel wall is improved and the shrinkage | contraction at the time of drying is suppressed.

  The curing temperature is preferably 30 to 70 ° C, and more preferably 40 to 60 ° C. If the curing temperature is less than 30 ° C., it takes a long time to obtain sufficient gel wall strength to suppress shrinkage during drying, which is not preferable in terms of productivity. When the curing temperature exceeds 70 ° C., the solvent (particularly alcohols) is volatilized and separated, and the volume of the resulting wet gel is reduced, so that the desired silica xerogel cannot be obtained. There is a case.

  The curing time is preferably 4 to 72 hours, and more preferably 12 to 24 hours. If the curing time is less than 4 hours, the gel wall strength may not be sufficiently improved. If the curing time exceeds 72 hours, the effect of curing in improving the gel wall strength is poor, and conversely, the productivity is impaired. There is.

  In addition, since it is often difficult to determine the end point of gelation of the sol, gelation of the sol and subsequent curing may be performed in a series of operations.

  In order to reduce the bulk density of the resulting silica xerogel or increase the average pore diameter, the gelation temperature and curing temperature are increased within the above range, or the total time of gelation time and curing time is increased within the above range. It is preferable to do. In addition, in order to increase the bulk density of the silica xerogel obtained and to reduce the average pore diameter, the gelation temperature and the curing temperature are lowered within the above range, or the total time of the gelation time and the curing time is within the above range. It is preferable to shorten the length.

[Drying process]
In the drying step, heating is performed to volatilize the medium in the wet gel obtained in the step.

Although there is no limitation on the drying temperature and drying time, rapid heating may cause the medium in the wet gel to bump and cause large cracks in the gel. For example, when a cracked silica xerogel is used for a heat insulating material, the crack may cause conduction heat transfer of air, thereby impairing the heat insulation property or becoming powdery and handling properties may be impaired.
Therefore, in order to suppress the generation of cracks, the drying process is performed at a temperature of 40 to 80 ° C. under a reduced pressure of 1 to 10 kPa for 3 to 48 hours (under reduced pressure drying), and then at a normal pressure and at a temperature of 105. It is preferable to dry (normal pressure drying) at -200 degreeC for 0.5 to 3.0 hours.

  The purpose of the drying under reduced pressure is to quickly remove the medium in the wet gel while suppressing the bumping. If the temperature and pressure are within the above ranges, the bumping phenomenon of the wet gel medium can be suppressed. This makes it easy to obtain a silica xerogel having no cracks and good handleability. The temperature, pressure, and drying time during drying under reduced pressure are preferably adjusted as appropriate within the above ranges, and may be dried under reduced pressure at a pressure of 1 to 5 kPa at a temperature of 40 to 60 ° C. for 6 to 24 hours. preferable.

  The gel after drying under reduced pressure tends to shrink, but when dried under normal pressure at a temperature of 105 to 200 ° C., it causes a springback phenomenon, has a low bulk density, and is smaller than the mean free path of air. A silica xerogel having pores is easily obtained. The normal pressure drying is preferably performed at 150 to 200 ° C. for 0.5 to 2 hours under normal pressure. In the present invention, the normal pressure means 0.1 MPa.

The silica xerogel of the present invention thus obtained can reduce the number of steps compared to the conventional production method, is excellent in productivity, and has a very low bulk density of 90 to 200 kg / m ³ , It has pores smaller than the mean free path of air with an average pore diameter of 20 to 65 nm, has excellent heat insulation performance, and is preferable for applications such as heat insulating materials in the construction field, home appliances, industrial equipment, etc. Applicable. Moreover, it can use preferably for uses, such as a catalyst carrier other than the use of a heat insulating material.

  When the silica xerogel of the present invention is used for, for example, a heat insulating material, the silica xerogel is dispersed in a solvent such as a urethane foam and formed into a target product, or other heat insulating materials such as an inorganic fiber heat insulating material. It can be used by coating the material.

Hereinafter, the present invention will be described in more detail with reference to examples. The bulk density and average pore diameter of the silica xerogel obtained in each example were measured as follows.
-Bulk density measurement method: Measured with an electronic hydrometer according to the Archimedes method.
Measurement method of average pore diameter and measurement method of specific surface area: Measurement was performed by a nitrogen adsorption method with a surface area measuring device (Nippon Bell).

(Example 1)
As a silane compound, a gel raw material (tetramethoxysilane: methyltrimethoxysilane = 0.05: 0.95) containing 3.8 parts by mass of tetramethoxysilane and 64.6 parts by mass of methyltrimethoxysilane; , 27 parts by weight of water (3 moles relative to 1 mole of the total amount of silane compounds) and 64 parts by weight of methanol (4 moles relative to 1 mole of the total amount of silane compounds) are mixed and reacted at 23 ° C. for 24 hours. Obtained.
13.68 parts by mass of 5% strength aqueous ammonia as an aqueous base catalyst was added to the obtained sol and gelled at 30 ° C. for 2 hours, followed by curing at 30 ° C. for 72 hours to obtain a wet gel.
The obtained wet gel was dried at 80 ° C. for 6 hours under normal pressure, and then dried at 150 ° C. for 1 hour to obtain a silica xerogel.
The resulting silica xerogel had a bulk density of 152 kg / m ³ , an average pore diameter of 40 nm, and a specific surface area of 716 m ² / g.

(Example 2)
As a silane compound, a gel raw material containing 36.4 parts by mass of tetraethoxysilane and 57.85 parts by mass of methyltriethoxysilane (in molar ratio, tetraethoxysilane: methyltriethoxysilane = 0.35: 0.65); , 36 parts by weight of water (4 moles relative to 1 mole of the total amount of silane compounds) and 138 parts by weight of ethanol (6 moles relative to 1 mole of the total amount of silane compounds) are mixed, and oxalic acid is added to the total amount of silane compounds as an acid catalyst. To 100 parts by mass, 0.0009 part by mass was added and reacted at 23 ° C. for 24 hours to obtain a sol.
To the obtained sol, 47.1 parts by mass of a 10% aqueous ammonium fluoride solution as an aqueous base catalyst was added and gelled at 60 ° C. for 0.5 hour, and then cured at 60 ° C. for 6 hours to obtain a wet gel. It was.
The obtained wet gel was dried at 50 ° C. for 6 hours under reduced pressure of 3 kPa, and then dried at 160 ° C. for 1 hour under normal pressure to obtain silica xerogel.
The obtained silica xerogel had a bulk density of 175 kg / m ³ , an average pore diameter of 33 nm, and a specific surface area of 668 m ² / g.

(Example 3)
As a silane compound, a gel material containing 15.6 parts by mass of tetraethoxysilane and 57.8 parts by mass of methyltrimethoxysilane (in terms of molar ratio, tetraethoxysilane: methyltrimethoxysilane = 0.15: 0.85); , 54 parts by weight of water (6 moles relative to 1 mole of the total amount of silane compounds) and 240 parts by weight of 2-propanol (8 moles relative to 1 mole of the total amount of silane compounds) are mixed and acetic acid is used as the acid catalyst. 0.0014 mass part was added with respect to 100 mass parts of whole quantity, and it was made to react at 23 degreeC for 24 hours, and obtained sol.
44.04 parts by mass of 5% aqueous ammonia as an aqueous base catalyst was added to the obtained sol and gelled at 60 ° C. for 0.7 hours, and then cured at 60 ° C. for 18 hours to obtain a wet gel.
The obtained wet gel was dried at 40 ° C. for 24 hours under a reduced pressure of 2 kPa, and then dried at 105 ° C. for 3 hours under normal pressure to obtain a silica xerogel.
The resulting silica xerogel had a bulk density of 95 kg / m ³ , an average pore diameter of 28 nm, and a specific surface area of 753.6 m ² / g.

(Example 4)
As a silane compound, a gel material containing 15.6 parts by mass of tetraethoxysilane and 75.65 parts by mass of methyltriethoxysilane (in terms of molar ratio, tetraethoxysilane: methyltriethoxysilane = 0.15: 0.85); 31.5 parts by mass of water (3.5 mol with respect to 1 mol of the total amount of silane compounds) and 128 parts by mass of methanol (8 mol with respect to 1 mol of the total amount of silane compounds) are mixed, and oxalic acid is used as the acid catalyst. A sol was obtained by adding 0.012 parts by mass with respect to 100 parts by mass of the total amount of the silane compound and reacting at 23 ° C. for 24 hours.
To the obtained sol, 36.5 parts by mass of a 5% morpholine aqueous solution as an aqueous base catalyst was added and gelled at 70 ° C. for 0.5 hour, and then cured at 60 ° C. for 24 hours to obtain a wet gel.
The obtained wet gel was dried at 40 ° C. for 48 hours under reduced pressure of 10 kPa, and then dried at 200 ° C. for 0.5 hours under normal pressure to obtain silica xerogel.
The obtained silica xerogel had a bulk density of 160 kg / m ³ , an average pore diameter of 29 nm, and a specific surface area of 679.3 m ² / g.

(Example 5)
As a silane compound, a gel material containing 20.8 parts by mass of tetraethoxysilane and 65.6 parts by mass of n-propyltrimethoxysilane (in molar ratio, tetraethoxysilane: n-propyltrimethoxysilane = 0.20: 0 .80), 36 parts by weight of water (4 moles relative to 1 mole of the total amount of silane compounds) and 115 parts by weight of ethanol (5 moles relative to 1 mole of the total amount of silane compounds) are mixed and reacted at 60 ° C. for 4 hours. To obtain a sol.
34.56 parts by mass of a 5% strength aqueous potassium hydroxide solution as an aqueous base catalyst was added to the obtained sol, gelled at 70 ° C. for 0.5 hour, and then cured at 70 ° C. for 6 hours to obtain a wet gel. It was.
The obtained wet gel was dried at 80 ° C. for 4 hours under reduced pressure of 5 kPa, and then dried at 180 ° C. for 1 hour under normal pressure to obtain silica xerogel.
The resulting silica xerogel had a bulk density of 156 kg / m ³ , an average pore diameter of 48 nm, and a specific surface area of 652.7 m ² / g.

(Example 6)
As a silane compound, a gel raw material containing 19.0 parts by mass of tetramethoxysilane and 51.0 parts by mass of methyltrimethoxysilane (in molar ratio, tetramethoxysilane: methyltrimethoxysilane = 0.25: 0.75) 36 parts by weight of water (4 moles relative to 1 mole of the total amount of silane compounds) and 104 parts by weight of ethanol (4.5 moles relative to 1 mole of the total amount of silane compounds) were mixed and reacted at 60 ° C. for 4 hours. A sol was obtained.
To the obtained sol, 11.2 parts by mass of 25% strength aqueous ammonia as an aqueous base catalyst was added, gelled at 50 ° C. for 0.4 hours, and then cured at 30 ° C. for 6 hours to obtain a wet gel.
The obtained wet gel was dried at 60 ° C. for 24 hours under normal pressure, and then dried at 160 ° C. for 1 hour to obtain a silica xerogel.
The obtained silica xerogel had a bulk density of 107 kg / m ³ , an average pore diameter of 39 nm, and a specific surface area of 755.2 m ² / g. Further, the surface of the obtained silica xerogel was observed with a scanning electron microscope. A 90,000 times enlarged view is shown in FIG.

(Example 7)
As a silane compound, a gel raw material containing 19.0 parts by mass of tetramethoxysilane, 34.0 parts by mass of methyltrimethoxysilane, and 20.5 parts by mass of n-propyltrimethoxysilane (in terms of molar ratio, tetramethoxysilane: methyl Trimethoxysilane: n-propyltrimethoxysilane = 0.25: 0.50: 0.25), 54 parts by mass of water (6 mols per 1 mol of the total amount of silane compounds), and 115 parts by mass of ethanol (silane compounds) The total amount of 1 mol was 5 mol) and the mixture was reacted at 60 ° C. for 3 hours to obtain a sol.
To the obtained sol, 7.35 parts by mass of 5% ammonia water as an aqueous base catalyst was added and gelled at 30 ° C. for 3 hours, and then cured at 50 ° C. for 12 hours to obtain a wet gel.
The obtained wet gel was dried at 200 ° C. for 2 hours under normal pressure to obtain a silica xerogel.
The obtained silica xerogel had a bulk density of 104 kg / m ³ , an average pore diameter of 25 nm, and a specific surface area of 776.6 m ² / g.

(Example 8)
As a silane compound, 68.0 parts by mass of methyltrimethoxysilane, 36 parts by mass of water (4 mols per 1 mol of the total amount of silane compounds), and 64 parts by mass of methanol (4 mols per mol of the total amount of silane compounds) Were mixed and reacted at 23 ° C. for 24 hours to obtain a sol.
To the obtained sol, 40.8 parts by mass of 5% aqueous ammonia as an aqueous base catalyst was added, gelled at 60 ° C. for 0.5 hour, and then cured at 30 ° C. for 72 hours to obtain a wet gel.
The obtained wet gel was dried at 50 ° C. for 6 hours under reduced pressure of 3 kPa, and then dried at 160 ° C. for 1 hour under normal pressure to obtain silica xerogel.
The obtained silica xerogel had a bulk density of 139 kg / m ³ , an average pore diameter of 100 nm or more, and a specific surface area of 415.3 m ² / g.

(Example 9)
As a silane compound, a gel material containing 41.6 parts by mass of tetraethoxysilane and 53.4 parts by mass of methyltriethoxysilane (in molar ratio, tetraethoxysilane: methyltriethoxysilane = 0.40: 0.60) , 27 parts by weight of water (3 moles relative to 1 mole of the total amount of silane compounds) and 138 parts by weight of ethanol (6 moles relative to 1 mole of the total amount of silane compounds) are mixed and reacted at 23 ° C. for 24 hours. Obtained.
To the obtained sol, 57.0 parts by mass of 5% ammonia water as an aqueous base catalyst was added and gelled at 60 ° C. for 0.4 hours, and then cured at 60 ° C. for 24 hours to obtain a wet gel.
The obtained wet gel was dried at 50 ° C. for 6 hours under reduced pressure of 3 kPa, and then dried at 160 ° C. for 1 hour under normal pressure to obtain silica xerogel.
The obtained silica xerogel had a bulk density of 205 kg / m ³ , an average pore diameter of 75 nm, and a specific surface area of 497.3 m ² / g. Further, the surface of the obtained silica xerogel was observed with a scanning electron microscope. A 90,000 times enlarged view is shown in FIG.

(Example 10)
As a silane compound, a gel raw material containing 36.4 parts by mass of tetraethoxysilane and 57.85 parts by mass of methyltriethoxysilane (in molar ratio, tetraethoxysilane: methyltriethoxysilane = 0.35: 0.65); , 63 parts by weight of water (7 moles relative to 1 mole of the total amount of silane compounds) and 138 parts by weight of ethanol (6 moles relative to 1 mole of the total amount of silane compounds) are mixed with oxalic acid as the total amount of the silane compounds. 0.0015 mass part was added with respect to 100 mass parts, and it was made to react at 23 degreeC for 24 hours, and obtained sol.
To the obtained sol, 56.55 parts by mass of a 5% morpholine aqueous solution as an aqueous base catalyst was added, gelled at 70 ° C. for 0.5 hour, and then cured at 70 ° C. for 6 hours to obtain a wet gel.
The obtained wet gel was dried at 60 ° C. for 24 hours under normal pressure, and then dried at 160 ° C. for 1 hour to obtain a silica xerogel.
The obtained silica xerogel had a bulk density of 266 kg / m ³ , an average pore diameter of 100 nm or more, and a specific surface area of 349.3 m ² / g.

(Example 11)
As a silane compound, a gel raw material containing 36.4 parts by mass of tetraethoxysilane and 57.85 parts by mass of methyltriethoxysilane (in molar ratio, tetraethoxysilane: methyltriethoxysilane = 0.35: 0.65); , 36 parts by weight of water (4 moles relative to 1 mole of the total amount of silane compounds) and 195.5 parts by weight of ethanol (8.5 moles relative to 1 mole of the total amount of silane compounds) are mixed and acetic acid is used as the acid catalyst. A sol was obtained by adding 0.0015 parts by mass with respect to 100 parts by mass of the total amount of the compounds and reacting at 23 ° C. for 24 hours.
To the obtained sol, 56.55 parts by mass of a 5% morpholine aqueous solution as an aqueous base catalyst was added, gelled at 70 ° C. for 0.5 hour, and then cured at 70 ° C. for 6 hours to obtain a wet gel.
The obtained wet gel was dried at 60 ° C. for 24 hours under normal pressure, and then dried at 160 ° C. for 1 hour to obtain a silica xerogel.
The obtained silica xerogel had a bulk density of 365 kg / m ³ , an average pore diameter of 100 nm or more, and a specific surface area of 326 m ² / g.

(Example 12)
As a silane compound, a gel raw material containing 41.6 parts by mass of tetraethoxysilane and 53.4 parts by mass of methyltriethoxysilane (in molar ratio, tetramethoxysilane: methyltrimethoxysilane = 0.4: 0.6) and , 27 parts by weight of water (3 moles relative to 1 mole of the total amount of silane compounds) and 138 parts by weight of ethanol (6 moles relative to 1 mole of the total amount of silane compounds) are mixed and reacted at 60 ° C. for 4 hours. Obtained.
To the obtained sol, 57.0 parts by mass of 5% aqueous ammonia as an aqueous base catalyst was added and gelled at 50 ° C. for 1 hour, and then cured at 50 ° C. for 2 hours to obtain a wet gel.
The obtained wet gel was dried at 80 ° C. for 4 hours under reduced pressure of 5 kPa, and then dried at 180 ° C. for 1 hour under normal pressure to obtain silica xerogel.
The obtained silica xerogel had a bulk density of 440 kg / m ³ , an average pore diameter of 20 nm, and a specific surface area of 544.2 m ² / g. Further, the surface of the obtained silica xerogel was observed with a scanning electron microscope. A 100,000 times magnified view is shown in FIG.

(Example 13)
As a silane compound, a gel raw material containing 41.6 parts by mass of tetraethoxysilane and 53.4 parts by mass of methyltriethoxysilane (in molar ratio, tetramethoxysilane: methyltrimethoxysilane = 0.4: 0.6) and , 27 parts by weight of water (3 moles relative to 1 mole of the total amount of silane compounds) and 138 parts by weight of ethanol (6 moles relative to 1 mole of the total amount of silane compounds) are mixed and reacted at 60 ° C. for 4 hours. Obtained.
To the obtained sol, 57.0 parts by mass of 5% aqueous ammonia was added as an aqueous base catalyst, and gelled at 50 ° C. for 1 hour to obtain a wet gel.
The obtained wet gel was dried at 80 ° C. for 4 hours under reduced pressure of 5 kPa, and then dried at 180 ° C. for 1 hour under normal pressure to obtain silica xerogel.
The obtained silica xerogel had a bulk density of 537 kg / m ³ , an average pore diameter of 15 nm, and a specific surface area of 530.6 m ² / g.
The production conditions of each example and the bulk density and average pore diameter of the obtained xerogel are summarized in Table 1 below.

From the results of Table 1, in Examples 1 to 7 according to the production method of the present invention, silica xerogel having a bulk density of 100 to 200 kg / m ³ , an average pore diameter of 20 to 65 nm, and a specific surface area of 600 to 800 m ² / g is obtained. Was made. These silica xerogels could be preferably used as a heat insulating material.

  On the other hand, in Example 8 using the gel raw material containing no tetraalkoxylane, the average pore diameter was larger than 65 nm. In addition, even when a tetraalkoxysilane and a monoalkyltrialkoxysilane are used in combination, Examples 9 and 12 using gel raw materials in which the molar ratio of the tetraalkoxysilane and the monoalkyltrialkoxysilane is outside the scope of the present invention. No. 13 silica xerogel had a high bulk density. In addition, the silica xerogels of Examples 10 and 11 in which the gel raw material was solated using a solvent having an alcohol amount or water amount outside the scope of the present invention has a large average pore diameter and further becomes a heterogeneous silica xerogel. Therefore, the bulk density was also large. The silica xerogels of Examples 8 to 13 had low heat insulating performance and were not suitable as heat insulating materials.

Claims (10)

A gel raw material containing tetraalkoxysilane and monoalkyltrialkoxysilane in a molar ratio of tetraalkoxysilane: monoalkyltrialkoxysilane = 0.05 to 0.35: 0.65 to 0.95; Alcohols and water are mixed at a ratio of 4 to 8 mol of the alcohol and 3 to 6 mol of the water with respect to 1 mol of the total amount of the silane compound in the gel material, and the silane compound in the gel material is mixed. Is hydrolyzed to form a sol,
The resulting sol is gelled, then cured to obtain a wet gel,
A method for producing a silica xerogel, wherein the obtained wet gel is dried under normal pressure and / or reduced pressure. The method for producing a silica xerogel according to claim 1 , wherein the sol is produced by hydrolyzing the silane compound in the gel raw material at a temperature of 20 to 60 ° C for 2 to 48 hours. The method for producing a silica xerogel according to claim 2 , wherein the sol is produced by hydrolyzing the silane compound in the gel raw material at a temperature of 50 to 60 ° C for 2 to 8 hours. An acid catalyst, relative to the total amount 100 parts by weight of the silane compound of the gel material, by adding 0.001 to 0.1 part by weight, any one of the preceding claims carrying out the hydrolysis of the silane compound A method for producing silica xerogel according to claim 1. The method for producing a silica xerogel according to any one of claims 1 to 4 , wherein the gelation of the sol is performed at a temperature of 30 to 70 ° C by adding an aqueous base catalyst to the sol. Wherein the aqueous base catalyst, relative to the silane compound the total amount 100 parts by weight of the gel material, silica xerogels method according to claim 5 is added 0.5 to 5 parts by weight. The method for producing a silica xerogel according to claim 5 or 6 , wherein ammonia is used as the aqueous base catalyst. The method for producing a silica xerogel according to any one of claims 1 to 7 , wherein the wet gel is obtained by performing the curing at a temperature of 30 to 70 ° C. The method for producing a silica xerogel according to any one of claims 1 to 8 , wherein the wet gel is obtained by performing gelation of the sol and subsequent curing for a total of 4 to 75 hours. The wet gel is dried at a temperature of 40 to 80 ° C. for 3 to 48 hours under a reduced pressure of 1 to 10 kPa, and then at a temperature of 105 to 200 ° C. and 0.5 to 3. The manufacturing method of the silica xerogel of any one of Claims 1-9 dried for 0 hours.