WO2019171543A1 - Method for producing aerogel, aerogel, aerogel block, and polysiloxane compound - Google Patents

Abstract

The present invention relates to a method for producing an aerogel provided with a sol generation step for generating a sol containing a silicon compound or a hydrolysis product of a silicon compound, a wet gel generation step for gelling the sol to obtain a wet gel, and a drying step for drying the wet gel to obtain an aerogel, the silicon compound including a polysiloxane compound having a structure represented by general formula (S). [In formula (S), R1s each independently represent an alkyl group or aryl group, R2s each independently represent an alkyl group, aryl group, or hydrogen, ns represents an integer of 2 or higher, ms represents an integer of 2 or higher, and ls represents an integer of 2 or higher.]

Description

Airgel production method, airgel, airgel block and polysiloxane compound

The present invention relates to an airgel production method, an airgel, an airgel block, and a polysiloxane compound.

Silica airgel is known as a material having low thermal conductivity and heat insulation. Silica airgel is useful as a functional material having excellent functionality (thermal insulation, etc.), unique optical properties, and unique electrical properties. For example, an electronic substrate utilizing the ultra-low dielectric constant properties of silica airgel It is used as a material, a heat insulating material using the high heat insulating property of silica airgel, a light reflecting material using the ultra-low refractive index of silica airgel, and the like. As a method for producing such a silica aerogel, for example, a supercritical drying method (for example, a patent) in which a gel compound (alcogel) obtained by hydrolyzing and polymerizing alkoxysilane is dried under supercritical conditions of a dispersion medium. Document 1) or a method of improving the strength of the alcogel and drying at normal pressure (for example, see Patent Document 2) is known.

U.S. Pat. No. 4,402,927 JP 2011-93744 A

Incidentally, an airgel obtained by a conventionally known production method has a certain degree of visible light permeability, but is extremely low in strength and brittle. On the other hand, if it is attempted to increase the strength of such an airgel based on conventional knowledge, the visible light transmittance is extremely lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing an airgel capable of achieving both good visible light transmittance and strength. Another object of the present invention is to provide an airgel obtained by such a production method, an airgel block containing the airgel, and an airgel-forming polysiloxane compound for obtaining the airgel.

As a result of intensive studies in order to achieve the above object, the present inventors have found that it is important to use a specific polysiloxane compound, and have completed the present invention.

　式（Ｓ）中、Ｒ^１ｓはそれぞれ独立にアルキル基又はアリール基を示し、Ｒ^２ｓはそれぞれ独立にアルキル基、アリール基又は水素を示し、ｎｓは２以上の整数を示し、ｍｓは２以上の整数を示し、ｌｓは２以上の整数を示す。 The present invention includes a sol production step for producing a sol containing a silicon compound or a hydrolysis product of the silicon compound, a wet gel production step for obtaining a wet gel by gelling the sol, and drying the wet gel to obtain an airgel. A method for producing an airgel comprising a polysiloxane compound having a structure represented by the following general formula (S). With such a production method, an airgel capable of achieving both good visible light transmittance and strength can be obtained.

In the formula (S), R ^1s independently represents an alkyl group or an aryl group, R ^2s independently represents an alkyl group, an aryl group or hydrogen, ns represents an integer of 2 or more, and ms is 2 or more. Represents an integer, and ls represents an integer of 2 or more.

In the production method of the present invention, the silicon compound may further contain at least one of a trifunctional silane monomer and a silane oligomer. Here, the trifunctional silane monomer has a silicon atom to which three hydrolyzable functional groups or condensable functional groups are bonded, and the silane oligomer has three oxygen atoms with respect to the total number of silicon atoms. And 50% or more of silicon atoms bonded to each other. Thereby, while being able to improve intensity | strength more, it becomes easy to suppress generation | occurrence | production of volume shrinkage and a crack in a drying process. In particular, by suppressing the volume shrinkage and the generation of cracks, an airgel block having good visible light permeability and heat insulating properties can be easily obtained.

The present invention also provides an airgel block having a visible light transmittance of 65% or more and a bending fracture energy per unit volume of 0.30 mJ / cm ³ or more. Such an airgel block can be said to have both visible light transmittance and strength at a very high level.

　式（Ｓ_１）中、Ｒ^１ｓはそれぞれ独立にアルキル基又はアリール基を示し、ｍｓは２以上の整数を示す。 The airgel block of the present invention can include an airgel having a structure represented by the following general formula (S ₁ ). The following structure may be a structure derived from the above general formula (S) used for obtaining an airgel capable of achieving both good visible light transmittance and strength.

In the formula (S ₁ ), R ^1s independently represents an alkyl group or an aryl group, and ms represents an integer of 2 or more.

　式（Ｓ）中、Ｒ^１ｓはそれぞれ独立にアルキル基又はアリール基を示し、Ｒ^２ｓはそれぞれ独立にアルキル基、アリール基又は水素を示し、ｎｓは２以上の整数を示し、ｍｓは２以上の整数を示し、ｌｓは２以上の整数を示す。 The present invention also provides an airgel that is a dried product of a wet gel that is a condensate of a sol containing a hydrolysis product of a polysiloxane compound having a structure represented by the following general formula (S). Such an airgel can achieve both good visible light transmittance and strength.

In the formula (S), R ^1s independently represents an alkyl group or an aryl group, R ^2s independently represents an alkyl group, an aryl group or hydrogen, ns represents an integer of 2 or more, and ms is 2 or more. Represents an integer, and ls represents an integer of 2 or more.

　式（Ｓ）中、Ｒ^１ｓはそれぞれ独立にアルキル基又はアリール基を示し、Ｒ^２ｓはそれぞれ独立にアルキル基、アリール基又は水素を示し、ｎｓは２以上の整数を示し、ｍｓは２以上の整数を示し、ｌｓは２以上の整数を示す。 The present invention further provides an airgel-forming polysiloxane compound having a structure represented by the following general formula (S). A polysiloxane compound having a structure represented by the following general formula (S) is particularly useful for obtaining an airgel having both good visible light transmittance and strength, and such a polysiloxane compound is used for forming an airgel. An example of conventional use as a material for the above has not been confirmed.

In the formula (S), R ^1s independently represents an alkyl group or an aryl group, R ^2s independently represents an alkyl group, an aryl group or hydrogen, ns represents an integer of 2 or more, and ms is 2 or more. Represents an integer, and ls represents an integer of 2 or more.

According to the present invention, it is possible to provide a method for producing an airgel capable of achieving both good visible light transmittance and strength. The present invention can also provide an airgel obtained by such a production method, an airgel block containing the airgel, and an airgel-forming polysiloxane compound for obtaining the airgel.

Hereinafter, preferred embodiments of the present invention will be described. This will be described in detail. However, the present invention is not limited to the following embodiments. In this specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. “A or B” only needs to include one of A and B, and may include both. The materials exemplified in this embodiment can be used singly or in combination of two or more unless otherwise specified.

<Method for producing airgel>
The method for producing an airgel according to this embodiment includes a sol that generates a sol containing a silicon compound or a hydrolysis product of the silicon compound (at least one selected from the group consisting of a silicon compound and a hydrolysis product of the silicon compound). A production step, a wet gel production step of gelling the sol to obtain a wet gel, and a drying step of drying the wet gel to obtain an airgel. More specifically, the airgel manufacturing method according to the present embodiment can further include a washing step of washing the wet gel as a pre-step of the drying step.

The sol means a state before the gelation reaction occurs, and in the present embodiment, it means a state in which the silicon compound or a hydrolysis product of the silicon compound is dissolved or dispersed in the liquid medium. The wet gel means a gel solid in a wet state that contains a liquid medium but does not have fluidity.

(Sol generation process)
Specifically, the sol generation step includes a sol containing a polysiloxane compound having a structure represented by the following general formula (S), or a sol containing a hydrolysis product of the polysiloxane compound by hydrolyzing the polysiloxane compound. , Is a step of generating. In such a production method, an airgel having both good visible light transmittance and strength can be obtained by using a specific polysiloxane compound. The inventors infer the reason why such an excellent effect is obtained as follows. That is, with respect to the visible light transmittance, the polyfunctional silicon units at both ends in the general formula (S) are easy to obtain a microporous structure having a diameter equal to or smaller than the wavelength of visible light, which causes a decrease in the visible light transmittance. It is considered that an airgel in which Mie scattering hardly occurs is obtained. As for strength, flexibility is ensured by the central diorganosiloxane unit in the general formula (S), and rigidity is expressed by the polyfunctional silicon units at both ends of the unit, resulting in a high-strength airgel skeleton. Is considered to have been obtained. Note that by using a polysiloxane compound having a structure represented by formula (S), it can be introduced the structure represented by the general formula (S ₁₎ to be described later in the backbone of the airgel.

In the formula (S), R ^1s independently represents an alkyl group or an aryl group, and R ^2s independently represents an alkyl group, an aryl group or hydrogen. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In the formula (S), two or more R ^1s may be the same or different, and similarly, two R ^2s may be the same or different. In formula (S), ns represents an integer of 2 or more, ms represents an integer of 2 or more, and ls represents an integer of 2 or more.

R ^1s and R ^2s are each independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, or the like from the viewpoint of easily forming an airgel having both good visible light transmittance and strength. Examples of the alkyl group include a methyl group. From the same viewpoint, ns can be an integer of 3 or more, can be an integer of 4 or more, and the upper limit thereof can be 20. ms can be an integer greater than or equal to 3, with an upper limit of 30. ls can be an integer of 3 or more, can be an integer of 4 or more, and the upper limit thereof can be 20. ns and ls may be the same.

When R ^2s is an alkyl group, the polysiloxane compound has an alkoxy group. In this step, the alkoxy group in the molecule may be hydrolyzed, in which case all of the alkoxy groups may be hydrolyzed or partially hydrolyzed. That is, the polysiloxane compound having an alkoxy group and the hydrolysis product thereof may be mixed.

In the sol production step, other silicon compounds other than the specific polysiloxane compound can be further used. Examples of such other silicon compounds include other polysiloxane compounds having a hydrolyzable reactive group or a condensable functional group (provided that the proportion of T units described below is less than 50%, or the number of silicon atoms More than 100). Examples of the hydrolyzable reactive group include an alkoxy group. Specific examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. From the viewpoint of the reaction rate of the hydrolysis reaction, a methoxy group and an ethoxy group. Is preferred. Examples of condensable functional groups include hydroxyl groups (including hydroxyl-containing groups such as hydroxyalkyl groups), silanol groups, and the like. In addition, it is easy to improve the softness | flexibility and toughness of airgel by further using another polysiloxane compound.

Examples of the polysiloxane compound having a hydroxyl group (hydroxyalkyl group) (excluding those having a structure represented by the above general formula (S)) include those having a structure represented by the following general formula (A). It is done. By using a polysiloxane compound having a structure represented by the following general formula (A), the structure represented by the following general formula (1) and formula (1a) can be introduced into the skeleton of the airgel. .

In formula (A), R ^1a represents a hydroxyalkyl group, R ^2a represents an alkylene group, R ^3a and R ^4a each independently represents an alkyl group or an aryl group, and n represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In the formula (A), two R ^{1a s} may be the same or different, and similarly, two R ^{2a s} may be the same or different. In the formula (A), two or more R ^{3a s} may be the same or different, and similarly two or more R ^{4a s} may be the same or different.

In formula (A), examples of R ^1a include a hydroxyalkyl group having 1 to 6 carbon atoms, and examples of the hydroxyalkyl group include a hydroxyethyl group and a hydroxypropyl group. In the formula (A), examples of R ^2a include an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group. In the formula (A), R ^3a and R ^4a each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. In the formula (A), n can be 2 to 30, but may be 5 to 20.

As the polysiloxane compound having the structure represented by the general formula (A), a commercially available product can be used, and compounds such as X-22-160AS, KF-6001, KF-6002, and KF-6003 (all of them) , Manufactured by Shin-Etsu Chemical Co., Ltd.), compounds such as XF42-B0970, Fluid OFOH 702-4% (all manufactured by Momentive Performance Materials Japan GK).

Examples of the polysiloxane compound having an alkoxy group (excluding those having a structure represented by the above general formula (S)) include those having a structure represented by the following general formula (B). By using a polysiloxane compound having a structure represented by the following general formula (B), a ladder structure having a bridge portion represented by the following general formula (2) or (3) can be formed in the skeleton of the airgel. Can be introduced.

In formula (B), R ^1b represents an alkyl group, an alkoxy group or an aryl group, R ^2b and R ^3b each independently represent an alkoxy group, and R ^4b and R ^5b each independently represent an alkyl group or an aryl group. , M represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In the formula (B), two R ^{1b s} may be the same or different from each other, and two R ^{2b s} may be the same or different from each other, and similarly two R ^{1b s. 3b} may be the same or different. In the formula (B), when m is an integer of 2 or more, two or more R ^{4b s} may be the same or different, and similarly two or more R ^{5b s} are each the same. May be different.

In the formula (B), examples of R ^1b include an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and the alkyl group or alkoxy group includes a methyl group, a methoxy group, and an ethoxy group. Etc. In the formula (B), R ^2b and R ^3b each independently include an alkoxy group having 1 to 6 carbon atoms, and examples of the alkoxy group include a methoxy group and an ethoxy group. In the formula (B), R ^4b and R ^5b each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group and the like. In the formula (B), m can be 2 to 30, but may be 5 to 20.

The polysiloxane compound having the structure represented by the general formula (B) can be obtained by appropriately referring to the production methods reported in JP-A Nos. 2000-26609 and 2012-233110. .

Also, as the polysiloxane compound having an alkoxy group, for example, silicate oligomers such as methyl silicate oligomer and ethyl silicate oligomer can be used. Examples of such silicate oligomers include methyl silicate 51, methyl silicate 53A, ethyl silicate 40, and ethyl silicate 48 (all manufactured by Colcoat Co., Ltd.).

In addition, examples of the other silicon compounds include silane monomers having a hydrolyzable functional group or a condensable functional group. Examples of the hydrolyzable functional group and the condensable functional group include the same groups as those exemplified above. Note that the silane monomer can also be referred to as a silicon compound having no siloxane bond (Si—O—Si). In addition, it is easy to improve the softness | flexibility and toughness of an airgel by further using a silane monomer.

Examples of the silane monomer having a hydrolyzable functional group include monoalkyltrialkoxysilane, monoaryltrialkoxysilane, monoalkyldialkoxysilane, monoaryl dialkoxysilane, dialkyl dialkoxysilane, diaryl dialkoxysilane, Examples thereof include alkyl monoalkoxy silane, monoaryl monoalkoxy silane, dialkyl monoalkoxy silane, diaryl monoalkoxy silane, trialkyl monoalkoxy silane, triaryl monoalkoxy silane, and tetraalkoxy silane. Specifically, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, tetraethoxy Silane etc. are mentioned.

Examples of the silane monomer having a condensable functional group include silane tetraol, methyl silane triol, dimethyl silane diol, phenyl silane triol, phenyl methyl silane diol, diphenyl silane diol, n-propyl silane triol, hexyl silane triol, octyl. Examples thereof include silane triol, decyl silane triol, and trifluoropropyl silane triol.

The silane monomer may further have a reactive group different from the hydrolyzable functional group and the condensable functional group. Examples of the reactive group include an epoxy group, a mercapto group, a glycidoxy group, a vinyl group, an acryloyl group, a methacryloyl group, and an amino group. The epoxy group may be contained in an epoxy group-containing group such as a glycidoxy group.

Examples of silane monomers having hydrolyzable functional groups and reactive groups include vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethyl. Methoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N Examples include -2- (aminoethyl) -3-aminopropylmethyldimethoxysilane.

Examples of the silane monomer having a condensable functional group and a reactive group include vinyl silane triol, 3-glycidoxypropyl silane triol, 3-glycidoxypropyl methyl silane diol, 3-methacryloxypropyl silane triol, 3- Methacryloxypropylmethylsilanediol, 3-acryloxypropylsilanetriol, 3-mercaptopropylsilanetriol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2- (aminoethyl)- Examples include 3-aminopropylmethylsilanediol.

The silane monomer may have two or more silicon atoms, and examples of such silane monomer include bistrimethoxysilylmethane, bistrimethoxysilylethane, and bistrimethoxysilylhexane.

Among the above silane monomers, in particular, a trifunctional silane monomer, that is, a monomer having a silicon atom bonded with three hydrolyzable functional groups or three condensable functional groups can further improve the strength. It becomes easy to suppress the volume shrinkage and the generation of cracks in the drying process. Examples of the trifunctional silane monomer include the above-mentioned methyltrimethoxysilane, methylsilanetriol, and bistrimethoxysilylmethane.

In addition, examples of the other silicon compounds include silane oligomers. A silane oligomer is a polymer of a silane monomer, and has a structure in which a plurality of silicon atoms are linked through oxygen atoms. In the present specification, the silane oligomer indicates a polymer having 2 to 100 silicon atoms in one molecule. The silane oligomer may be, for example, one or more polymers of the above silane monomers. In addition, by further using a silane oligomer, the strength can be further improved, and volume shrinkage and cracking in the drying process can be easily suppressed. In particular, by suppressing the volume shrinkage and the generation of cracks, an airgel block having good visible light permeability and heat insulating properties can be easily obtained.

The silicon atom contained in the silane oligomer is a silicon atom bonded to one oxygen atom (M unit), a silicon atom bonded to two oxygen atoms (D unit), a silicon atom bonded to three oxygen atoms ( A distinction can be made between T units) and silicon atoms bonded to four oxygen atoms (Q units). Examples of the M unit, the D unit, the T unit, and the Q unit include the following formulas (M), (D), (T), and (Q), respectively.

In the above formula, R represents an atom other than an oxygen atom bonded to silicon (such as a hydrogen atom) or an atomic group (such as an alkyl group). Information on the content of these units can be obtained by Si-NMR.

As the silane oligomer, those having 50% or more of silicon atoms (T units) bonded to three oxygen atoms can be used with respect to the total number of silicon atoms. In particular, a polymer of a silane monomer containing a certain amount or more of alkyltrialkoxysilane which is a trifunctional silane monomer is preferable. In the silane oligomer, the proportion of the T unit is preferably 60% or more, more preferably 70% or more, and may be 100%.

The silane oligomer preferably has an alkyl group or an aryl group as R in the above formulas (M), (D), (T) and (Q).

Examples of the alkyl group include an alkyl group having 1 to 6 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Among these, a methyl group and an ethyl group are preferable, and a methyl group is more preferable.

Examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. As the aryl group, a phenyl group is preferable.

The silane oligomer has a hydrolyzable functional group, and may be hydrolyzed in the sol production step. It is considered that when this hydrolyzable functional group is hydrolyzed, a silanol group is generated. Examples of the hydrolyzable functional group include an alkoxy group.

The weight average molecular weight of the silane oligomer may be, for example, 200 or more, preferably 400 or more, more preferably 600 or more. Moreover, the weight average molecular weight of a silane oligomer may be 10,000 or less, for example, Preferably it is 7000 or less, More preferably, it is 5000 or less. In addition, in this specification, a weight average molecular weight shows the weight average molecular weight of standard polystyrene conversion measured by gel permeation chromatography (GPC).

Commercially available products may be used as the silane oligomer. For example, XR31-B1410, XC96-B0446 (all manufactured by Momentive Performance Materials Japan GK), KR-500, KR-515, X-40- 9225, KC-89S (all manufactured by Shin-Etsu Chemical Co., Ltd.), SR-2402, AY42-163 (all manufactured by Toray Dow Corning Co., Ltd.) and the like.

The content of the silicon compound contained in the sol may be 5 parts by mass or more and 10 parts by mass or more with respect to 100 parts by mass of the total amount of the sol from the viewpoint of easily obtaining good reactivity. Good. The content of the silicon compound contained in the sol may be 50 parts by mass or less and 40 parts by mass or less with respect to 100 parts by mass of the total amount of the sol from the viewpoint of easily obtaining good compatibility. Good.

Among the silicon compounds used in the sol generation step, the content of the polysiloxane compound having the structure represented by the general formula (S) is from the viewpoint that it is easy to achieve both good visible light transmittance and strength. Based on the total amount of the compound, it can be 5% by mass or more, 8% by mass or more, or 10% by mass or more. In addition, the upper limit of the content can be 95% by mass or less from the viewpoint of enhancing the compatibility of the sol and easily obtaining an airgel having good visible light permeability, and even if it is 90% by mass or less. Good.

In the sol production step, when another polysiloxane compound is further used as the silicon compound, the amount of the other polysiloxane compound is based on 100 parts by mass of the polysiloxane compound having the structure represented by the general formula (S). It may be 1500 parts by mass or less, may be 1300 parts by mass or less, and may be 1000 parts by mass or less. The amount of the other polysiloxane compound can be, for example, 1 part by mass or more with respect to 100 parts by mass of the polysiloxane compound having the structure represented by the general formula (S). It may be 10 mass parts or more.

In the sol production step, when a silane monomer is further used as the silicon compound, the amount of the silane monomer is 1500 parts by mass or less with respect to 100 parts by mass of the polysiloxane compound having the structure represented by the general formula (S). 1300 parts by mass or less, or 1000 parts by mass or less. Moreover, the quantity of a silane monomer can be 1 mass part or more with respect to 100 mass parts of polysiloxane compounds which have a structure represented by the said general formula (S), for example, even if it is 5 mass parts or more. It may be 10 parts by mass or more.

In the sol production step, when a silane oligomer is further used as the silicon compound, the amount of the silane oligomer is 1500 parts by mass or less with respect to 100 parts by mass of the polysiloxane compound having the structure represented by the general formula (S). 1300 parts by mass or less, or 1000 parts by mass or less. Moreover, the quantity of a silane oligomer can be 1 mass part or more with respect to 100 mass parts of polysiloxane compounds which have a structure represented by the said general formula (S), for example, even if it is 5 mass parts or more. It may be 10 parts by mass or more.

In the sol production step, for example, a solvent is used for mixing and optionally hydrolyzing the silicon compound. As the solvent, for example, water or an organic solvent miscible with water can be used. Examples of the organic solvent miscible with water include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, t-butanol, acetone, N, N-dimethylformamide and the like. However, it is not limited to these. Among these, good visible light transmittance can be easily obtained by using N, N-dimethylformamide. The reason for this is not clear, but it is presumed that the aggregation of silica particles (individual particles constituting the airgel) is suppressed by electrostatic interaction in the reaction solvent during gelation. Is done. You may use these individually or in mixture of 2 or more types.

In addition, a solvent having a low surface tension can be further added to the above mixed solvent. Examples of the low surface tension solvent include those having a surface tension at 20 ° C. of 30 mN / m or less. The surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of the low surface tension solvent include pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3- Aliphatic hydrocarbons such as methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), 1-pentene (16.0); Aromatic hydrocarbons such as (28.9), toluene (28.5), m-xylene (28.7), p-xylene (28.3); dichloromethane (27.9), chloroform (27.2) ), Carbon tetrachloride (26.9), 1-chloropropane (21.8), 2-chloropropane (18.1) and other halogenated hydrocarbons; ethyl ether (17.1), propyl ether (20.5) ), Isop Ethers such as pyrether (17.7), butyl ethyl ether (20.8), 1,2-dimethoxyethane (24.6); acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), ketones such as diethyl ketone (25.3); methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), Examples include esters such as isobutyl acetate (23.7), ethyl butyrate (24.6), etc. (in parentheses indicate surface tension at 20 ° C., and the unit is [mN / m]). You may use said solvent individually or in mixture of 2 or more types.

In the sol production step, the silicon compound may be hydrolyzed by using water and an organic solvent miscible with water as the solvent. The solvent may contain an acid catalyst for promoting the hydrolysis reaction.

Acid catalysts include hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, hypochlorous acid and other inorganic acids; acidic phosphoric acid Acidic phosphates such as aluminum, acidic magnesium phosphate, and acidic zinc phosphate; organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid Etc. Among these, organic carboxylic acid is mentioned as an acid catalyst which improves the water resistance of the airgel obtained more. Examples of the organic carboxylic acid include acetic acid, but formic acid, propionic acid, oxalic acid, malonic acid, and the like may be used.

The addition amount of the acid catalyst is not particularly limited, but may be, for example, 0.001 to 10 parts by mass with respect to 100 parts by mass of the total amount of the silicon compound.

In the sol production step, as shown in Japanese Patent No. 5250900, a surfactant, a thermally hydrolyzable compound, or the like can be added to the solvent. As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. You may use these individually or in mixture of 2 or more types.

As the nonionic surfactant, for example, a compound containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group, a compound containing a hydrophilic part such as polyoxypropylene, and the like can be used. Examples of the compound containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene alkyl ether and the like. Examples of the compound having a hydrophilic portion such as polyoxypropylene include polyoxypropylene alkyl ether, a block copolymer of polyoxyethylene and polyoxypropylene, and the like.

Examples of the ionic surfactant include a cationic surfactant, an anionic surfactant, and an amphoteric surfactant. Examples of the cationic surfactant include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and examples of the anionic surfactant include sodium dodecylsulfonate. Examples of amphoteric surfactants include amino acid surfactants, betaine surfactants, amine oxide surfactants, and the like. Examples of amino acid surfactants include acyl glutamic acid. Examples of betaine surfactants include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, and the like. Examples of the amine oxide surfactant include lauryl dimethylamine oxide.

These surfactants have the effect of reducing the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer and suppressing phase separation in the wet gel formation process described later. It is considered to be. When an organic solvent miscible with water, such as alcohol or N, N-dimethylformamide, is used as the solvent, it is considered that these organic solvents have the same effect as the above-mentioned effect by the surfactant. A wet gel can be suitably formed without adding a surfactant.

The thermohydrolyzable compound is considered to generate a base catalyst by thermal hydrolysis to make the reaction solution basic and to promote the sol-gel reaction in the wet gel generation process described later. Accordingly, the thermohydrolyzable compound is not particularly limited as long as it can make the reaction solution basic after hydrolysis. Urea; formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N -Acid amides such as methylacetamide and N, N-dimethylacetamide; cyclic nitrogen compounds such as hexamethylenetetramine and the like. Among these, urea is particularly easy to obtain the above-mentioned promoting effect.

In the sol production process, components such as carbon graphite, aluminum compound, magnesium compound, silver compound, titanium compound are added to the solvent within the range where visible light transmission and strength are not impaired for the purpose of suppressing heat ray radiation. Also good. In addition, for the purpose of further improving the strength, nanoparticles composed of silica, alumina, etc., nanofibers composed of silica, alumina, cellulose, etc. are added to the solvent as long as visible light permeability is not impaired. You can also

Hydrolysis in the sol production step depends on the type and amount of the silicon compound, acid catalyst and the like in the mixed solution, but may be performed, for example, in a temperature environment of 20 to 80 ° C. for 10 minutes to 24 hours. The reaction may be performed in a temperature environment of ˜60 ° C. for 5 minutes to 8 hours. Thereby, the hydrolyzable functional group in a silicon compound is fully hydrolyzed, and the hydrolysis product of a silicon compound can be obtained more reliably.

However, when a thermohydrolyzable compound is added to the solvent, the temperature environment of the sol generation step may be adjusted to a temperature that suppresses hydrolysis of the thermohydrolyzable compound and suppresses gelation of the sol. . The temperature at this time may be any temperature as long as the hydrolysis of the thermally hydrolyzable compound can be suppressed. For example, when urea is used as the thermally hydrolyzable compound, the temperature environment of the sol production step can be 0 to 40 ° C., but may be 10 to 30 ° C.

In the sol production step, a sol containing a silicon compound or a hydrolysis product of the silicon compound is produced. It can also be said that the hydrolysis product is a product in which a part or all of the hydrolyzable functional group of the silicon compound is hydrolyzed. In the sol production step, part or all of the silicon compound may be hydrolyzed, but as described above, hydrolysis of the silicon compound is not essential. The silicon compound may be hydrolyzed in the wet gel formation step described later.

(Wet gel production process)
The wet gel generation step is a step of obtaining a wet gel by gelling the sol obtained in the sol generation step. More specifically, it is a step of obtaining a wet gel by gelling a sol while obtaining a hydrolysis product of a silicon compound, or by gelling a sol containing a hydrolysis product of a silicon compound. This step may be a step of gelling the sol and then aging to obtain a wet gel. In this step, a base catalyst can be used to promote hydrolysis and gelation.

Base catalysts include carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper (II) carbonate, iron (II) carbonate, silver (I) carbonate; hydrogen carbonate Bicarbonates such as calcium, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide; tetramethylammonium hydroxide, hydroxide Tetraalkylammonium hydroxides such as tetraethylammonium; Metal hydroxides such as magnesium hydroxide and calcium hydroxide; Ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; Sodium metaphosphate, pyro Sodium phosphate Basic sodium phosphate such as 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, sec-butylamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propyl Aliphatic amines such as amine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine; Emissions, N- methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, and the like imidazoles and nitrogen-containing heterocyclic compounds such as derivatives. You may use said base catalyst individually or in mixture of 2 or more types.

By using the base catalyst, the hydrolysis reaction and dehydration condensation reaction or dealcoholization condensation reaction of the silicon compound in the sol can be promoted, and the sol can be gelled in a shorter time. Thereby, a wet gel with higher strength (rigidity) can be obtained. In particular, by using a strong base catalyst such as a hydroxide of an alkali metal, tetraalkylammonium or the like, visible light permeability and strength can be easily improved.

The addition amount of the base catalyst can be 0.1 to 10 parts by mass with respect to 100 parts by mass of the total amount of the silicon compound used in the sol production step, but may be 0.5 to 5 parts by mass. By setting it as 0.1 mass part or more, it becomes easy to improve an intensity | strength, and when it is set as 10 mass parts or less, it becomes easy to suppress a fall of visible light permeability.

The gelation of the sol in the wet gel generation step may be performed in a sealed container so that the solvent and the base catalyst do not volatilize. The gelation temperature can be 30 to 100 ° C., but it may be 40 to 90 ° C. By setting the gelation temperature to 30 ° C. or higher, gelation can be performed in a shorter time, and a wet gel with higher strength (rigidity) can be obtained. Moreover, since it becomes easy to suppress volatilization of a solvent (especially water or alcohol) by making gelation temperature into 100 degrees C or less, it can gelatinize, suppressing volume shrinkage.

The aging in the wet gel generation step may be performed in a sealed container so that the solvent and the base catalyst do not volatilize. By aging, the components of the wet gel are strongly bonded, and as a result, a wet gel having a high strength (rigidity) sufficient to suppress shrinkage during drying can be obtained. The aging temperature can be 30 to 100 ° C., but it may be 40 to 90 ° C. By setting the aging temperature to 30 ° C. or higher, a wet gel with higher strength (rigidity) can be obtained, and by setting the aging temperature to 100 ° C. or lower, volatilization of the solvent (especially water or alcohol) can be easily suppressed. Therefore, it can be gelled while suppressing volume shrinkage.

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

Gelling time and aging time can be appropriately set depending on the gelation temperature and aging temperature. The gel time can be 3 to 120 minutes, but may be 5 to 90 minutes. By setting the gelation time to 3 minutes or more, it becomes easy to obtain a homogeneous wet gel, and by setting it to 120 minutes or less, the drying process can be simplified from the washing process described later. Note that the total time of the gelation time and the aging time in the entire gelation and aging process can be 4 to 480 hours, but may be 6 to 200 hours. By setting the total gelation time and aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, the effect of aging can be more easily maintained.

In order to reduce the density of the obtained airgel particles or increase the average pore diameter, the gelation temperature and the aging temperature are increased within the above range, or the total time of the gelation time and the aging time is increased within the above range. Also good. Further, in order to increase the density of the obtained airgel or reduce the average pore diameter, the gelation temperature and the aging temperature are reduced within the above range, or the total time of the gelation time and the aging time is shortened within the above range. May be.

(Washing process)
The washing step is a step of washing the wet gel obtained in the wet gel production step. In the washing step, solvent substitution may be further performed in which the washing liquid in the wet gel is substituted with a solvent suitable for the drying conditions (the drying step described later).

In the washing step, the wet gel obtained in the wet gel production step is washed. The washing can be repeatedly performed using, for example, water or an organic solvent. At this time, washing efficiency can be improved by heating.

Organic solvents include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, methylene chloride , N, N-dimethylformamide, dimethyl sulfoxide, acetic acid, formic acid, and other various organic solvents can be used. You may use said organic solvent individually or in mixture of 2 or more types.

In solvent replacement, a low surface tension solvent can be used to suppress gel shrinkage due to drying. However, low surface tension solvents generally have very low mutual solubility with water. Therefore, when a low surface tension solvent is used in solvent replacement, the organic solvent used for washing includes a hydrophilic organic solvent having high mutual solubility in both water and a low surface tension solvent. In addition, the hydrophilic organic solvent used in washing | cleaning can play the role of the preliminary substitution for solvent substitution. Among the above organic solvents, examples of hydrophilic organic solvents include methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone. Methanol, ethanol, methyl ethyl ketone and the like are excellent in terms of economy.

As the amount of water or organic solvent used for washing, the solvent in the wet gel can be sufficiently replaced and washed. The amount can be 3 to 10 times the volume of the wet gel.

The temperature environment in washing can be a temperature below the boiling point of the solvent used for washing. For example, when methanol is used, the temperature can be raised to about 30 to 60 ° C.

In solvent replacement, the solvent of the washed wet gel is replaced with a predetermined replacement solvent in order to suppress the shrinkage of the airgel in the drying process. At this time, the replacement efficiency can be improved by heating. Specific examples of the solvent for substitution include a low surface tension solvent described later in the drying step when drying is performed under atmospheric pressure at a temperature lower than the critical point of the solvent used for drying. On the other hand, when performing supercritical drying, examples of the substitution solvent include ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, and the like, or a mixture of two or more thereof.

Examples of the low surface tension solvent include a solvent having a surface tension at 20 ° C. of 30 mN / m or less. The surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of the low surface tension solvent include pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3- Aliphatic hydrocarbons such as methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), 1-pentene (16.0); Aromatic hydrocarbons such as (28.9), toluene (28.5), m-xylene (28.7), p-xylene (28.3); dichloromethane (27.9), chloroform (27.2) ), Carbon tetrachloride (26.9), 1-chloropropane (21.8), 2-chloropropane (18.1) and other halogenated hydrocarbons; ethyl ether (17.1), propyl ether (20.5) ), Isop Ethers such as pyrether (17.7), butyl ethyl ether (20.8), 1,2-dimethoxyethane (24.6); acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), ketones such as diethyl ketone (25.3); methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), Examples include esters such as isobutyl acetate (23.7), ethyl butyrate (24.6), etc. (in parentheses indicate surface tension at 20 ° C., and the unit is [mN / m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have a low surface tension and an excellent working environment. Among these, by using a hydrophilic organic solvent such as acetone, methyl ethyl ketone, 1,2-dimethoxyethane, it can be used as an organic solvent at the time of washing. Among these, a solvent having a boiling point of 100 ° C. or less at normal pressure may be used because it is easy to dry in the drying step described later. You may use said solvent individually or in mixture of 2 or more types.

The amount of the solvent used for solvent replacement can be an amount that can sufficiently replace the solvent in the wet gel after washing. The amount can be 3 to 10 times the volume of the wet gel.

The temperature environment in the solvent replacement can be a temperature not higher than the boiling point of the solvent used for the replacement. For example, when heptane is used, the temperature can be set to about 30 to 60 ° C.

(Drying process)
In the drying step, the airgel can be obtained by drying the wet gel (after the washing step). That is, an airgel obtained by drying a wet gel generated from the sol can be obtained.

The drying method is not particularly limited, and known atmospheric pressure drying, supercritical drying, or freeze drying can be used. Among these, lyophilization or supercritical drying can be used from the viewpoint of easy production of a low-density airgel. Further, from the viewpoint that production is possible at low cost, atmospheric pressure drying can be used. In the present embodiment, the normal pressure means 0.1 MPa (atmospheric pressure).

Airgel can be obtained by drying a wet gel at a temperature below the critical point of the solvent in the wet gel under atmospheric pressure. Although the drying temperature varies depending on the type of solvent in the wet gel, it should be 20 to 180 ° C. in view of the fact that drying at a high temperature increases the evaporation rate of the solvent and may cause large cracks in the gel. Can do. The drying temperature may be 30 to 150 ° C. The drying time varies depending on the wet gel volume and the drying temperature, and can be 4 to 300 hours. It should be noted that atmospheric pressure drying also includes speeding up drying by applying a pressure less than the critical point within a range that does not impair productivity.

Airgel can also be obtained by supercritical drying of a wet gel. Supercritical drying can be performed by a known method. Examples of the supercritical drying method include a method of removing the solvent at a temperature and pressure higher than the critical point of the solvent contained in the wet gel. Alternatively, as a method for supercritical drying, all or part of the solvent contained in the wet gel is obtained by immersing the wet gel in liquefied carbon dioxide, for example, at about 20 to 25 ° C. and about 5 to 20 MPa. And carbon dioxide having a lower critical point than that of the solvent, and then removing carbon dioxide alone or a mixture of carbon dioxide and the solvent.

The airgel obtained by such normal pressure drying or supercritical drying may be further dried at 105 to 200 ° C. for about 0.5 to 2 hours under normal pressure. This makes it easier to obtain an airgel having a low density and small pores. Additional drying may be performed at 150 to 200 ° C. under normal pressure.

In the manufacturing method according to this embodiment, the wet gel may be formed into a desired shape and then the drying step may be performed. For example, a granular airgel can be obtained by pulverizing the wet gel with a mixer or the like and then performing the drying step. In the manufacturing method which concerns on this embodiment, the process of shape | molding the airgel obtained at the drying process may be further provided. For example, a granular airgel can be obtained by pulverizing the airgel obtained in the drying step.

<Polysiloxane compound>
The polysiloxane compound having the structure represented by the general formula (S) is particularly useful for obtaining an airgel having both good visible light transmittance and strength, and such a polysiloxane compound is used for forming an airgel. An example of conventional use as a material for the above has not been confirmed. Therefore, it can be said that the polysiloxane compound according to the present embodiment is an airgel-forming polysiloxane compound having a structure represented by the general formula (S).

<Aerogel>
The airgel according to this embodiment is a dried product of a wet gel that is a condensate of a sol containing a polysiloxane compound having a structure represented by the general formula (S). The airgel which concerns on this embodiment may be obtained by said manufacturing method, for example. That is, the airgel according to the present embodiment includes a sol generation step for generating a sol containing a silicon compound or a hydrolysis product of the silicon compound, a wet gel generation step for gelling the sol to obtain a wet gel, and a wet gel. An airgel obtained by a production method comprising a polysiloxane compound having a structure represented by the above general formula (S).

In a narrow sense, dry gel obtained by using supercritical drying method for wet gel is aerogel, dry gel obtained by drying under atmospheric pressure is xerogel, dry gel obtained by freeze-drying is cryogel and However, in the present embodiment, the obtained low-density dried gel is referred to as “aerogel” regardless of the drying method of the wet gel. That is, in the present embodiment, the “aerogel” is a broadly defined aerogel “Gel compressed of a microporous solid in which the dispersed phase is a gas (a gel composed of a microporous solid in which the dispersed phase is a gas). "Means. In general, the inside of the airgel has a network-like fine structure, and has a cluster structure in which particulate airgel components of about 2 to 20 nm are combined. There are pores less than 100 nm between the skeletons formed by these clusters. As a result, the airgel has a three-dimensionally fine porous structure. In addition, the airgel which concerns on this embodiment is a silica airgel which has a silica as a main component, for example. Examples of the silica airgel include so-called organic-inorganic hybrid silica airgel into which an organic group (such as a methyl group) or an organic chain is introduced.

Examples of the airgel according to the present embodiment include the following modes. By adopting these aspects, it becomes easy to obtain an airgel excellent in heat insulation, flame retardancy, heat resistance and flexibility. By employ | adopting each aspect, the airgel which has the heat insulation according to each aspect, a flame retardance, heat resistance, and a softness | flexibility can be obtained.

The airgel according to the present embodiment can have a structure represented by the following general formula (S ₁ ).

In the formula (S ₁ ), R ^1s independently represents an alkyl group or an aryl group. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In the formula (S ₁ ), two or more R ^1s may be the same or different. In the formula (S ₁ ), ms represents an integer of 2 or more.

From the viewpoint of easily forming an airgel having both good visible light transmittance and strength, R ^1s includes, independently, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like. Includes a methyl group and the like. From the same viewpoint, ms can be an integer of 2 or more, and the upper limit thereof can be 30.

The airgel according to the present embodiment can have a structure represented by the following general formula (1). The airgel which concerns on this embodiment can have a structure represented by the following general formula (1a) as a structure containing the structure represented by Formula (1).

In formula (1) and formula (1a), R ¹ and R ² each independently represent an alkyl group or an aryl group, and R ³ and R ⁴ each independently represent an alkylene group. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. p represents an integer of 1 to 50. In formula (1a), two or more R ^{1 s} may be the same or different, and similarly, two or more R ^{2 s} may be the same or different. In formula (1a), two R ^{3 s} may be the same or different, and similarly, two R ^{4 s} may be the same or different.

By introducing the structure represented by the above formula (1) or formula (1a) into the skeleton of the airgel as an airgel component, a flexible airgel with low thermal conductivity is obtained. From such a viewpoint, in the formula (1) and the formula (1a), R ¹ and R ² each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like. Groups and the like. In the formulas (1) and (1a), R ³ and R ⁴ each independently include an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group. It is done. In the formula (1a), p can be 2 to 30, and can be 5 to 20.

The airgel which concerns on this embodiment can have a ladder type structure provided with a support | pillar part and a bridge | bridging part, and a bridge | bridging part can have a structure represented by following General formula (2). By introducing such a ladder structure as an airgel component into the airgel skeleton, heat resistance and mechanical strength can be improved. In this embodiment, the “ladder structure” has two struts and bridges connecting the struts (having a so-called “ladder” form). It is. In this embodiment, the skeleton of the airgel may have a ladder structure, but the airgel may partially have a ladder structure.

In formula (2), R ⁵ and R ⁶ each independently represents an alkyl group or an aryl group, and b represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In formula (2), when b is an integer of 2 or more, two or more R ^{5 s} may be the same or different, and similarly two or more R ^{6 s} are each the same. May be different.

By introducing the above structure into the airgel skeleton as an airgel component, for example, it has a structure derived from a conventional ladder-type silsesquioxane (that is, has a structure represented by the following general formula (X)) It becomes the airgel which has the softness | flexibility superior to an airgel. Silsesquioxane is a polysiloxane having a composition formula: (RSiO _1.5 ) _n and can have various skeleton structures such as a cage type, a ladder type, and a random type. In addition, as shown by the following general formula (X), in the airgel having a structure derived from the conventional ladder-type silsesquioxane, the structure of the bridge portion is —O—, but the airgel according to the present embodiment Then, the structure of a bridge part is a structure (polysiloxane structure) represented by the said General formula (2). However, the airgel of this aspect may have a structure derived from silsesquioxane in addition to the structure represented by the general formula (2).

In the formula (X), R represents a hydroxy group, an alkyl group or an aryl group.

There are no particular limitations on the structure to be the strut portion and its chain length, and the interval between the structures to be the bridging portions, but from the viewpoint of further improving the heat resistance and mechanical strength, the ladder structure has the following general formula ( It may have a ladder structure represented by 3).

In the formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group or an aryl group, a and c each independently represents an integer of 1 to 3000, and b is 1 to 50 Indicates an integer. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In formula (3), when b is an integer of 2 or more, two or more R ^{5 s} may be the same or different, and similarly two or more R ^{6 s} are each the same. May be different. In Formula (3), when a is an integer of 2 or more, two or more R ^{7 s} may be the same or different. Similarly, when c is an integer of 2 or more, 2 or more R ⁸ may be the same or different.

From the viewpoint of obtaining more excellent flexibility, in formulas (2) and (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ (however, R ⁷ and R ⁸ are only in formula (3)) Each independently includes an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. In the formula (3), a and c can be independently 6 to 2000, but may be 10 to 1000. In the formulas (2) and (3), b can be 2 to 30, but may be 5 to 20.

Airgel, although the density may be 0.01 ~ 0.5g / cm ³ at 25 ° C., may be 0.05 ~ 0.4g / cm ^3. When the density is 0.01 g / cm ³ or more, more excellent strength and flexibility can be obtained, and when it is 0.5 g / cm ³ or less, more excellent heat insulation can be obtained. it can. The density of the airgel can be measured by the Archimedes method according to the method described in JIS K7112, for example, using an electronic hydrometer SD-200L (product name, manufactured by Alpha Mirage Co., Ltd.).

The thermal conductivity of the airgel at 25 ° C. under atmospheric pressure can be 0.030 W / (m · K) or less, but may be 0.028 W / (m · K) or less, or It may be 025 W / (m · K) or less. When the thermal conductivity is 0.03 W / m · K or less, it is possible to obtain a heat insulating property higher than that of the polyurethane foam which is a high performance heat insulating material. The lower limit value of the thermal conductivity is not particularly limited, but can be set to 0.005 W / m · K, for example. The thermal conductivity can be performed using, for example, a steady-state thermal conductivity measuring device “HFM436 Lambda” (product name, manufactured by NETZSCH).

<Airgel block>
The airgel block can include the aerogel described above. Therefore, the airgel block according to the present embodiment has both visible light transmittance and strength at a very high level.

The visible light transmittance of the airgel block is 65% or more. Here, visible light refers to electromagnetic waves defined by JIS Z8120. The visible light transmittance of the airgel block may be 68% or more, or 70% or more. When the visible light transmittance is 65% or more, it is possible to obtain visible light transmittance comparable to that of glass used in automobiles. The upper limit of the visible light transmittance is not particularly limited, but can be 100%. The visible light transmittance can be measured using, for example, a double beam spectrophotometer “U-2900” (product name, manufactured by Hitachi High-Technologies Corporation) at a measurement wavelength of 550 nm.

The visible light transmittance is, for example, the number of central diorganosiloxane units in the general formula (S) (that is, the value of ms in the formula (S)) and the number of functional groups of the polyfunctional silicon units at both ends (that is, It can be adjusted by changing the values of ns and ls in the formula (S).

The bending fracture energy per unit volume of the airgel block is 0.30 mJ / cm ³ or more. Bending fracture energy per unit volume of the airgel block may be 0.40mJ / cm ³ or more, it may be 0.50 mJ / cm ³ or more. The upper limit of the bending fracture energy per unit volume is not particularly limited, but can be 1000 mJ / cm ³ . The bending fracture energy per unit volume is, for example, tensilon universal material tester (tensile / compression tester) “RTC-1350A” (product name, manufactured by Orientec Co., Ltd.), with the measurement mode set to three-point bending and between fulcrums. The distance can be measured as 20 mm.

The bending fracture energy per unit volume is, for example, in the above general formula (S), the central diorganosiloxane unit that will affect the flexibility, and the polyfunctional silicon that will affect the rigidity of both ends of the unit. It can be adjusted by changing the composition ratio with the unit.

In addition, although the block-shaped airgel which has a certain amount of volume was demonstrated above as a concrete shape of the airgel which concerns on this embodiment, the shape of an airgel is not limited to this. For example, the airgel according to the present embodiment is useful even in a sheet-like airgel having a further reduced thickness.

The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.

Example 1
12 mL of 9-functional alkoxy-modified polysiloxane compound at both ends (hereinafter referred to as “polysiloxane compound S-1”), 20 mL of silane oligomer “KC-89S” (manufactured by Shin-Etsu Chemical Co., Ltd., product name), N, N— After 140 mL of dimethylformamide was mixed and stirred for 10 minutes, 6 mL of tetraethylammonium hydroxide aqueous solution adjusted to 0.75 M was added and further stirred for 1 minute to obtain a sol. The obtained sol was gelled at 80 ° C. and aged for 120 hours to obtain a wet gel.

The obtained wet gel was immersed in 2500 mL of methanol and washed at 60 ° C. for 3 hours. This washing operation was performed twice while exchanging with fresh methanol. Next, the washed wet gel was immersed in 2500 mL of methyl ethyl ketone, and solvent substitution was performed at 60 ° C. for 3 hours. This solvent replacement operation was performed twice while exchanging with new methyl ethyl ketone. Further, the wet gel after solvent replacement with methyl ethyl ketone was immersed in 2500 mL of n-heptane, which is a low surface tension solvent, and solvent replacement was performed again at 60 ° C. over 3 hours. This solvent replacement operation was performed twice while exchanging with new n-heptane. The washed and solvent-substituted wet gel was dried at 30 ° C. for 170 hours under normal pressure, and then further dried at 150 ° C. for 2 hours to obtain an airgel.

The “polysiloxane compound S-1” was synthesized as follows. Hydroxy-terminated dimethylpolysiloxane “XC96-723” (product name, manufactured by Momentive Performance Materials Japan LLC) in a 1 liter three-necked flask equipped with a stirrer, thermometer and Dimroth condenser. By mixing 293.8 parts by mass of “methyl silicate 51” (product name, manufactured by Colcoat Co., Ltd.) and 0.50 parts by mass of t-butylamine and reacting at 30 ° C. for 5 hours, 9 functional groups at both ends An alkoxy-modified polysiloxane compound (polysiloxane compound having 9 alkoxy groups at both ends) was obtained.

(Example 2)
As in Example 1, except that “XR31-B1410” (product name, manufactured by Momentive Performance Materials Japan GK) was used as the silane oligomer instead of “KC-89S”, the airgel was used. Obtained.

(Example 3)
20 mL of polysiloxane compound S-1, 12 mL of silane monomer (methyltrimethoxysilane) “KBM-13” (product name, manufactured by Shin-Etsu Chemical Co., Ltd.) and 140 mL of N, N-dimethylformamide were mixed and stirred for 10 minutes. Then, 6 mL of an aqueous tetraethylammonium hydroxide solution adjusted to 0.75 M was added, and the mixture was further stirred for 1 minute to obtain a sol. The obtained sol was gelled at 80 ° C. and aged for 24 hours to obtain a wet gel. Thereafter, an airgel was obtained in the same manner as in Example 1.

Example 4
16 mL of polysiloxane compound S-1, 16 mL of silane oligomer “KR-500” (manufactured by Shin-Etsu Chemical Co., Ltd., product name) and 140 mL of N, N-dimethylformamide were mixed and stirred for 10 minutes, then 0.75M 6 mL of an adjusted sodium hydroxide aqueous solution was added, and the mixture was further stirred for 1 minute to obtain a sol. The obtained sol was gelled at 80 ° C. and aged for 120 hours to obtain a wet gel. Thereafter, an airgel was obtained in the same manner as in Example 1.

(Example 5)
An airgel was obtained in the same manner as in Example 1 except that an 11-functional alkoxy-modified polysiloxane compound at both ends (hereinafter referred to as “polysiloxane compound S-2”) was used in place of the polysiloxane compound S-1. It was.

The above “polysiloxane compound S-2” was synthesized as follows. In a 1-liter three-necked flask equipped with a stirrer, thermometer and Dimroth condenser, 100 parts by mass of hydroxy-terminated dimethylpolysiloxane “XC96-723”, “methyl silicate 53A” (manufactured by Colcoat Co., Ltd., product name) ) Is mixed with 185.7 parts by mass and t-butylamine at 0.50 parts by mass, and reacted at 30 ° C. for 5 hours, whereby 11 functional alkoxy-modified polysiloxane compounds at both ends (each having 11 alkoxy groups at both ends). Polysiloxane compound).

(Comparative Example 1)
The mixing ratio of “methyl silicate 51”, ethanol, water, and 15N ammonia water is “methyl silicate 51”: ethanol: water: ammonia water = 49.56: 67.06: 52.97: 0.25 (mass ratio) ) Were mixed. After stirring for about 20 seconds, the mixture was allowed to stand and gelled. Thereafter, ethanol was added and aged at 50 ° C. for 72 hours to obtain a wet gel.

Next, the wet gel was transferred into a toluene solution of 5-fold volume 0.2M-hexamethyldisilazane (manufactured by Toray Dow Corning Co., Ltd.), and the toluene solution was repeatedly exchanged for one day and night. Silazane was included. Thereafter, the mixture was heated and stirred at 110 ° C. for about 2 hours to perform a hydrophobization reaction, and then the gel was transferred into ethanol, and ethanol exchange was repeated for one day and night to perform solvent replacement.

Next, this gel was placed in carbon dioxide at 18 ° C. and 5.1 MPa, and the operation of replacing ethanol in the gel with carbon dioxide was performed for 2 to 3 hours. Thereafter, the inside of the system was supercritical conditions of carbon dioxide, 40 ° C. and 8.1 MPa, and supercritical drying was performed for about 24 hours to obtain an airgel.

(Comparative Example 2)
In place of “methyl silicate 51”, “ethyl silicate 40” (product name, manufactured by Colcoat Co., Ltd.) was used, and the mixing ratio was “ethyl silicate 40”: ethanol: water: ammonia water = 120.18: 67. An airgel was obtained in the same manner as in Comparative Example 1 except that the ratio was 06: 52.97: 0.25 (mass ratio).

(Comparative Example 3)
32 mL of “XR31-B1410” and 140 mL of N, N-dimethylformamide were mixed and stirred for 10 minutes, and then 6 mL of tetraethylammonium hydroxide aqueous solution adjusted to 0.75 M was added and further stirred for 1 minute to obtain a sol. . The obtained sol was gelled at 80 ° C. and aged for 120 hours to obtain a wet gel. Thereafter, an airgel was obtained in the same manner as in Example 1.

[Various evaluations]
The airgel obtained in each Example and each Comparative Example was evaluated according to the following conditions. The results are shown in Table 1.

(1) Measurement of density The density of the airgel was measured by Archimedes method according to the method described in JIS K7112. As a measuring device, an electronic hydrometer SD-200L (manufactured by Alpha Mirage Co., Ltd., product name) was used.

(2) Measurement of thermal conductivity The airgel was cut to a size of 150 mm × 150 mm × 10 mm to obtain a block-shaped airgel (aerogel block). In order to ensure parallelism of the surfaces, shaping was performed with sandpaper of # 1500 or more as necessary. The shaped airgel block was dried at 100 ° C. for 30 minutes under atmospheric pressure using a constant temperature dryer “DVS402” (manufactured by Yamato Scientific Co., Ltd., product name), then transferred to a desiccator and cooled to 25 ° C. A measurement sample for thermal conductivity measurement was obtained.
The thermal conductivity was measured using a steady-state thermal conductivity measuring device “HFM436 Lambda” (manufactured by NETZSCH, product name). The measurement conditions were an average temperature of 25 ° C. under atmospheric pressure. The measurement sample is sandwiched between the upper and lower heaters with a load of 0.3 MPa, the temperature difference ΔT is set to 20 ° C., and the upper surface temperature, the lower surface temperature, etc. of the measurement sample are adjusted while adjusting to a one-dimensional heat flow by the guard heater. Was measured. And thermal resistance _RS of the measurement sample was calculated | required from following Formula.
R _S = N ((T _U −T _L ) / Q) −R _O
Wherein, T _U represents a measurement sample top surface temperature, T _L represents the measurement sample lower surface temperature, R _O represents the thermal contact resistance of the upper and lower interfaces, Q is shows the heat flux meter output. Note that N is a proportionality coefficient, and is obtained in advance using a calibration sample.
From the obtained thermal resistance _RS and the thickness d of the measurement sample, the thermal conductivity λ of the measurement sample was obtained from the following equation.
λ = d / R _S

(3) Measurement of bending fracture energy per unit volume A measurement sample was produced in the same manner as the measurement of thermal conductivity. This was used as a measurement sample for three-point bending measurement.
A Tensilon universal material testing machine (tensile / compression testing machine) “RTC-1350A” (product name, manufactured by Orientec Co., Ltd.) was used as a measuring apparatus. The measurement mode was 3-point bending, and the distance between fulcrums was 20 mm. A load was applied from the upper surface of the sample to the center between the fulcrums, and the measurement was completed at the point where the measurement sample was broken (break point). The moving speed of the jig when applying the load was 0.3 mm / min, and the measurement temperature was 25 ° C. Here, the strain ε was obtained from the following equation.
ε = 6 × s × h / L ²
In the formula, s is the displacement (mm) at the breaking point, h is the thickness (mm) of the measurement sample before applying a load, and L is the distance between supporting points (mm).
The breaking bending stress σ (MPa) was obtained from the following equation.
σ = 3 × F × L / 2 × b × h ²
In the formula, F indicates the load (N) at the breaking point, and b indicates the width (mm) of the measurement sample before applying the load.
Then, in the stress-strain curve in which the vertical axis represents stress and the horizontal axis represents strain, the bending fracture energy per unit volume (mJ / cm ³ ) is calculated by calculating the area under the curve up to the breaking point. Asked.

(4) Measurement of visible light transmittance A measurement sample was prepared in the same manner as the measurement of thermal conductivity, except that the size was 20 mm × 25 mm × 10 mm. This was used as a measurement sample for transmittance measurement. As a measuring device, a double beam spectrophotometer “U-2900” (trade name, manufactured by Hitachi High-Technologies Corporation) was used. A 20 mm × 25 mm surface was irradiated with light having a wavelength of 550 nm, and the distance of the light (optical path) was 10 mm. The transmittance when transmitting through (long) was measured (parallel light transmittance).

Claims (6)

A sol production step for producing a sol containing a silicon compound or a hydrolysis product of the silicon compound;
Forming a wet gel by gelling the sol to obtain a wet gel;
A drying step of drying the wet gel to obtain an airgel;
With
The manufacturing method of an airgel in which the said silicon compound contains the polysiloxane compound which has a structure represented with the following general formula (S).

[In the formula (S), R ^1s independently represents an alkyl group or an aryl group, R ^2s independently represents an alkyl group, an aryl group or hydrogen, ns represents an integer of 2 or more, and ms is 2 or more. And ls represents an integer of 2 or more. ] The silicon compound further comprises at least one of a trifunctional silane monomer and a silane oligomer;
The trifunctional silane monomer has a silicon atom to which three hydrolyzable functional groups or condensable functional groups are bonded,
The said silane oligomer is a manufacturing method of Claim 1 which has 50% or more of silicon atoms couple | bonded with three oxygen atoms with respect to the total number of silicon atoms. An airgel block having a visible light transmittance of 65% or more and a bending fracture energy per unit volume of 0.30 mJ / cm ³ or more. Containing airgel having a structure represented by the following general formula (S _1), airgel block according to claim 3.

[In Formula (S ₁ ), R ^1s independently represents an alkyl group or an aryl group, and ms represents an integer of 2 or more. ] An aerogel which is a dried product of a wet gel that is a condensate of a sol containing a hydrolysis product of a polysiloxane compound having a structure represented by the following general formula (S).

[In the formula (S), R ^1s independently represents an alkyl group or an aryl group, R ^2s independently represents an alkyl group, an aryl group or hydrogen, ns represents an integer of 2 or more, and ms is 2 or more. And ls represents an integer of 2 or more. ] An airgel-forming polysiloxane compound having a structure represented by the following general formula (S).

[In the formula (S), R ^1s independently represents an alkyl group or an aryl group, R ^2s independently represents an alkyl group, an aryl group or hydrogen, ns represents an integer of 2 or more, and ms is 2 or more. And ls represents an integer of 2 or more. ]