阅读说明：本技术 涂液、复合材料及涂膜 (Coating liquid, composite material and coating film ) 是由 泉宽之 高安慧 佐藤直义 横仓亚唯 小竹智彦 于 2020-03-30 设计创作，主要内容包括：一种涂液,含有气凝胶粒子、具有疏水性基的水溶性高分子、及液状介质。(A coating liquid comprises aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium.)

1. A masking liquid comprising:

aerogel particles;

a water-soluble polymer having a hydrophobic group; and

a liquid medium.

2. The dope according to claim 1, wherein the content of the aerogel particles is 70% by volume or more based on the total volume of the solid components.

3. The masking liquid according to claim 1 or 2, wherein the hydrophobic group is an alkyl group having 1 to 26 carbon atoms.

4. The masking liquid according to any one of claims 1 to 3, wherein the water-soluble polymer comprises a cellulose-based resin.

5. The masking liquid according to claim 4, wherein the cellulose-based resin has a structural unit represented by the following formula (A-1),

[ solution 1]

[ in the formula, R^ARepresents a hydrogen atom, an alkyl group, a hydroxyalkyl group, a group represented by the formula-R^A1-O-R^A2The group (R) represented^A1Represents alkanediyl, R^A2Represents an alkyl group);three R^AMay be the same or different from each other; wherein three R^AAt least one of which is alkyl or is represented by-R^A1-O-R^A2Group represented by]。

6. The coating liquid according to any one of claims 1 to 5, wherein the liquid medium is an aqueous solvent containing water.

7. A composite material comprising:

aerogel particles; and

the water-soluble polymer has a hydrophobic group.

8. The composite of claim 7, wherein the aerogel particles are present in an amount of 70% by volume or greater.

9. The composite material according to claim 7 or 8, wherein the hydrophobic group is an alkyl group having a carbon number of 1 to 26.

10. The composite material according to any one of claims 7 to 9, wherein the water-soluble polymer comprises a cellulose-based resin.

11. The composite material according to claim 10, wherein the cellulose-based resin has a structural unit represented by the following formula (A-1),

[ solution 2]

[ in the formula, R^ARepresents a hydrogen atom, an alkyl group, a hydroxyalkyl group, a group represented by the formula-R^A1-O-R^A2The group (R) represented^A1Represents alkanediyl, R^A2Represents an alkyl group); three R^AMay be the same or different from each other; wherein three R^AAt least one of which is alkyl or is represented by-R^A1-O-R^A2Group represented by]。

12. A coated film comprising the composite material according to any one of claims 7 to 11.

Technical Field

The invention relates to a coating liquid, a composite material and a coating film.

Background

Aerogel is known as a material having excellent thermal insulation properties. Further, a method of processing an aerogel into a particulate form to be used as a constituent material of a heat insulator has been proposed (for example, patent documents 1 and 2). Patent document 1 proposes using a particulate aerogel as a filler between resin plates or the like constituting a heat insulating window. Patent document 2 shows the following method: after preparing an aqueous dispersion containing aerogel particles and organic fibers, an intermediate product obtained by evaporating water is further subjected to press molding, thereby producing a heat insulating material (molded body).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012-91943

Patent document 2: japanese patent laid-open No. 2014-35044

Disclosure of Invention

Problems to be solved by the invention

A composite material having a high packing ratio of aerogel particles is expected to have excellent heat resistance. However, when the composite material is applied to a liquid, it may be difficult to disperse the aerogel particles in the coating liquid. Further, a coating film containing such a composite material may have aerogel particles biased or may not have sufficient film strength.

Accordingly, an object of the present invention is to provide a coating liquid which has a high packing ratio of aerogel particles, can form a coating film having excellent film strength, and has excellent dispersibility of aerogel particles. Another object of the present invention is to provide a composite material having a high packing ratio of aerogel particles and excellent film strength during film formation. Further, an object of the present invention is to provide a coating film having a high packing ratio of aerogel particles and excellent film strength.

Means for solving the problems

One aspect of the present invention relates to a coating liquid containing aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium. In such a coating liquid, the dispersibility of the aerogel particles is improved by the water-soluble polymer having a hydrophobic group, and therefore a coating film having sufficient film strength with little deflection of the aerogel particles can be formed.

The aerogel particles may be contained in an amount of 70 vol% or more based on the total volume of the solid components.

The hydrophobic group may be an alkyl group having 1 to 26 carbon atoms.

The water-soluble polymer may contain a cellulose-based resin.

The cellulose-based resin may have a structural unit represented by the following formula (A-1).

[ solution 1]

[ in the formula, R^ARepresents a hydrogen atom, an alkyl group, a hydroxyalkyl group, a group represented by the formula-R^A1-O-R^A2The group (R) represented^A1Represents alkanediyl, R^A2Represents an alkyl group). Three R^AMay be the same or different from each other. Wherein three R^AAt least one of which is alkyl or is represented by-R^A1-O-R^A2Group represented by]

The liquid medium may be an aqueous solvent containing water.

Another aspect of the present invention relates to a composite material containing aerogel particles and a water-soluble polymer having a hydrophobic group.

The aerogel particles can be present in an amount of 70 vol% or more.

The hydrophobic group may be an alkyl group having 1 to 26 carbon atoms.

The water-soluble polymer may contain a cellulose-based resin.

The water-soluble polymer may have a structural unit represented by the following formula (A-1).

[ solution 2]

[ in the formula, R^ARepresents a hydrogen atom, an alkyl group, a hydroxyalkyl group, a group represented by the formula-R^A1-O-R^A2The group (R) represented^A1Represents alkanediyl, R^A2Represents an alkyl group). Three R^AMay be the same or different from each other. Wherein three R^AAt least one of which is alkyl or is represented by-R^A1-O-R^A2Group represented by]

Yet another aspect of the invention relates to a coated film comprising the composite.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a coating liquid which has a high packing ratio of aerogel particles, can form a coating film having excellent film strength, and has excellent dispersibility of aerogel particles. Further, the present invention can provide a composite material having a high packing ratio of aerogel particles and excellent film strength during film formation. Further, the present invention can provide a coating film having a high packing ratio of aerogel particles and excellent film strength.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments. In the present specification, the numerical range expressed by "to" means a range including numerical values described before and after "to" as a minimum value and a maximum value, respectively. "a or B" may include either or both of a and B. The materials exemplified in the present embodiment may be used alone or in combination of two or more unless otherwise specified.

< coating liquid >

The coating liquid of the present embodiment contains aerogel particles, a water-soluble polymer having a hydrophobic group, and a liquid medium. The coating liquid of the present embodiment improves the dispersibility of the aerogel particles by the water-soluble polymer having a hydrophobic group, and thus can form a coating film having sufficient film strength with little deflection of the aerogel particles.

The content of the aerogel particles in the coating liquid may be, for example, 70 vol% or more, preferably 72 vol% or more, and more preferably 74 vol% or more, based on the total volume of the solid content in the coating liquid. The content of the aerogel particles in the coating liquid may be, for example, 99 vol% or less, and preferably 97 vol% or less, based on the total volume of the solid content in the coating liquid.

< aerogel >

In a narrow sense, a dried gel obtained by applying a supercritical drying method to a wet gel is referred to as an aerogel, a dried gel obtained by drying under atmospheric pressure is referred to as a xerogel (xenogel), and a dried gel obtained by freeze-drying is referred to as a cryogel (cryogel), but in the present embodiment, a dried gel of low density obtained is referred to as an "aerogel" regardless of these drying methods of a wet gel. That is, in the present embodiment, the term "aerogel" refers to a broad aerogel "a Gel composed of a microporous solid in which the dispersed phase is a gas (Gel comprising a microporous solid in which the dispersed phase is a gas)". Generally, an aerogel has a fine mesh structure inside thereof, and has a cluster (cluster) structure in which particulate aerogel components of about 2 to 20nm are bonded together. Pores of less than 100nm are present between the skeletons formed by the clusters. As a result, a three-dimensional fine porous structure is formed in the aerogel.

The aerogel of the present embodiment is, for example, silica aerogel containing silica (silica) as a main component. Examples of the silica aerogel include so-called hybrid organic-inorganic (hybrid) silica aerogels in which an organic group (e.g., methyl group) or an organic chain is introduced.

The aerogel according to the present embodiment includes, for example, the following embodiments. By adopting these forms, an aerogel excellent in heat insulating properties, flame retardancy, heat resistance and flexibility can be easily obtained. By adopting each form, an aerogel having heat insulating properties, flame retardancy, heat resistance and flexibility corresponding to each form can be obtained.

(first embodiment)

The aerogel of the present embodiment may have a structure represented by the following general formula (1). The aerogel of the present embodiment may have a structure represented by the following general formula (1a) as a structure including the structure represented by formula (1).

[ solution 3]

[ solution 4]

In the formula (1) and the formula (1a), R¹And R²Each independently represents an alkyl group or an aryl group, and R3 and R4 each independently represents an alkylene group. Examples of the aryl group include a phenyl group and a substituted phenyl group. Further, as the substituent of the substituted phenyl group, there may be mentioned: alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. p represents an integer of 1 to 50. In the formula (1a), two or more R¹May be the same or different, and similarly, two or more R²Each may be the same or different. In the formula (1a), two R³Each of which may be the same or different, and similarly, two R' s⁴Each may be the same or different.

By introducing the structure represented by the formula (1) or the formula (1a) into the framework of the aerogel as an aerogel component, the aerogel having low thermal conductivity and flexibility is obtained. In this respect, in the formula (1) and the formula (1a), R is¹And R²The alkyl group is independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, or the like, and the alkyl group is a methyl group or the like. In the formulae (1) and (1a), R is³And R⁴Each independently may be an alkylene group having 1 to 6 carbon atomsExamples of the alkylene group include an ethylene group and a propylene group. In the formula (1a), p may be 2 to 30, or 5 to 20.

(second embodiment)

The aerogel of the present embodiment has a ladder-type structure including pillar portions and bridge portions, and the bridge portions may have a structure represented by the following general formula (2). By introducing such a stepped structure as an aerogel component into the skeleton of the aerogel, heat resistance and mechanical strength can be improved. The "ladder-like structure" in the present embodiment is a structure having two struts and bridges connecting the struts (in the form of a so-called "ladder"). In this form, the skeleton of the aerogel may include a stepped structure, but the aerogel may also partially have a stepped structure.

[ solution 5]

In the formula (2), R⁵And R⁶Each independently represents an alkyl group or an aryl group, and b represents an integer of 1 to 50. Examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, as the substituent of the substituted phenyl group, there can be mentioned: alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. In the formula (2), when b is an integer of 2 or more, two or more R' s⁵May be the same or different, and similarly, two or more R⁶And may be the same or different, respectively.

By introducing the structure into the framework of the aerogel as an aerogel component, for example, the aerogel having more excellent flexibility than an aerogel having a structure derived from a conventional stepped silsesquioxane (i.e., having a structure represented by the following general formula (X)) is obtained. Silsesquioxanes are those having the compositional formula: (RSiO)_1.5)_nThe polysiloxane can have various framework structures such as cage type, ladder type, irregular type and the like. Further, as shown by the following general formula (X), there is a conventional ladder-type silsesquioxaneIn the aerogel having an organosiloxane structure, the structure of the bridging portion is — O-, but in the aerogel of the present embodiment, the structure of the bridging portion is the structure represented by the general formula (2) (polysiloxane structure). The aerogel of this embodiment may have a structure derived from silsesquioxane, in addition to the structure represented by the general formula (2).

[ solution 6]

In the formula (X), R represents hydroxyl, alkyl or aryl.

The structure of the pillar portion, the chain length thereof, and the interval between the structures serving as the bridge portion are not particularly limited, and the ladder-type structure may have a ladder-type structure represented by the following general formula (3) from the viewpoint of further improving heat resistance and mechanical strength.

[ solution 7]

In the formula (3), R⁵、R⁶、R⁷And R⁸Independently represents an alkyl group or an aryl group, a and c independently represent an integer of 1 to 3000, and b represents an integer of 1 to 50. Examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, as the substituent of the substituted phenyl group, there can be mentioned: alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. In the formula (3), when b is an integer of 2 or more, two or more R' s⁵May be the same or different, and similarly, two or more R⁶And may be the same or different, respectively. In the formula (3), when a is an integer of 2 or more, two or more R' s⁷Each of which may be the same or different, and similarly, when c is an integer of 2 or more, two or more R' s⁸Each may be the same or different.

Further, from the viewpoint of obtaining more excellent flexibility, the formulae (2) and (2)In the formula (3), as R⁵、R⁶、R⁷And R⁸(wherein, R⁷And R⁸In the formula (3), each independently includes an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and the alkyl group includes a methyl group and the like. In the formula (3), a and c are each independently 6 to 2000, but may be 10 to 1000. In the formulae (2) and (3), b may be 2 to 30, but may be 5 to 20.

(third embodiment)

The aerogel of the present embodiment may be a dried product of a wet gel (obtained by drying a wet gel produced from a sol) which is a condensate of a sol (sol) containing at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensable functional group and a hydrolyzed product of a silicon compound having a hydrolyzable functional group. The aerogel described above may be obtained by drying a wet gel produced from a sol containing a silicon compound or the like as described above.

As the silicon compound having a hydrolyzable functional group or a condensable functional group, a polysiloxane compound can be used. That is, the sol may contain at least one compound selected from the group consisting of a polysiloxane compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the polysiloxane compound having a hydrolyzable functional group (hereinafter, referred to as "polysiloxane compound group" as appropriate).

The functional groups in the polysiloxane compound are not particularly limited, but may be groups in which the same functional groups react with each other or with other functional groups. Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group include: hydroxyl, silanol, carboxyl, phenolic hydroxyl, and the like. The hydroxyl group may be contained in a hydroxyl group-containing group such as a hydroxyalkyl group. Furthermore, the polysiloxane compound having a hydrolyzable functional group or a condensable functional group may further have a reactive group different from the hydrolyzable functional group and the condensable functional group (a functional group not corresponding to the hydrolyzable functional group and the condensable functional group). Examples of the reactive group include: epoxy, mercapto, glycidyloxy, vinyl, acryloyl, methacryloyl, amino, and the like. The epoxy group may be contained in an epoxy group-containing group such as a glycidyloxy group. The polysiloxane compound having these functional groups and reactive groups can be used alone or in combination of two or more. Among these functional groups and reactive groups, examples of the groups that enhance the flexibility of the aerogel include: alkoxy groups, silanol groups, hydroxyalkyl groups, etc., and among these, alkoxy groups and hydroxyalkyl groups can further improve the compatibility of the sol. In addition, the number of carbon atoms of the alkoxy group and the hydroxyalkyl group may be 1 to 6 from the viewpoint of improving the reactivity of the polysiloxane compound and reducing the thermal conductivity of the aerogel, and may be 2 to 4 from the viewpoint of further improving the flexibility of the aerogel.

Examples of the polysiloxane compound having a hydroxyalkyl group in the molecule include those having a structure represented by the following general formula (a). By using a polysiloxane compound having a structure represented by the following general formula (a), the structures represented by the general formulae (1) and (1a) can be introduced into the framework of the aerogel.

[ solution 8]

In the formula (A), R^1aRepresents hydroxyalkyl, R^2aRepresents an alkylene group, R^3aAnd R^4aEach independently represents an alkyl group or an aryl group, and n represents an integer of 1 to 50. Examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, as the substituent of the substituted phenyl group, there can be mentioned: alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. Further, in the formula (A), two R' s^1aEach of which may be the same or different, and similarly, two R' s^2aEach may be the same or different. In the formula (A), two or more R' s^3aMay be the same or different, and similarly, two or more R^4aEach may be the same or different.

By using as a composition containingThe wet gel (formed from the sol) of the condensate of the sol of the structural polysiloxane compound makes it easier to obtain a soft aerogel having low thermal conductivity. From this viewpoint, in the formula (A), R is^1aExamples of the hydroxyalkyl group 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), R is^2aThe alkylene group may include alkylene groups having 1 to 6 carbon atoms, and the alkylene group may include ethylene group, propylene group, and the like. In the formula (A), R is^3aAnd R^4aThe alkyl group is independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, or the like, and the alkyl group is a methyl group or the like. In the formula (A), n may be 2 to 30, but may be 5 to 20.

As the polysiloxane compound having a structure represented by the above general formula (a), commercially available products can be used, and examples thereof include: x-22-160AS, KF-6001, KF-6002, KF-6003 and the like (all manufactured by shin-Etsu chemical industries, Ltd.), XF42-B0970, Fluid OFOH 702-4% and the like (all manufactured by Momentive, Ltd.), and the like.

Examples of the polysiloxane compound having an alkoxy group in the molecule 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-type structure having a bridging portion represented by the general formula (2) or the general formula (3) can be introduced into the framework of the aerogel.

[ solution 9]

In the formula (B), R^1bRepresents alkyl, alkoxy or aryl, R^2bAnd R^3bEach independently represents an alkoxy group, R^4bAnd R^5bEach independently represents an alkyl group or an aryl group, and m represents an integer of 1 to 50. Examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, as the substituent of the substituted phenyl group, there can be mentioned: alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. Further, in the formula (B), twoR^1bEach of which may be the same or different, two R^2bEach of which may be the same or different, and similarly, two R' s^3bEach may be the same or different. In the formula (B), when m is an integer of 2 or more, two or more R' s^4bMay be the same or different, and similarly, two or more R^5bAnd may be the same or different, respectively.

By using a wet gel (formed from a sol) which is a condensate of a sol containing a polysiloxane compound having the above structure or a hydrolysis product thereof, an aerogel having low thermal conductivity and flexibility can be more easily obtained. From this viewpoint, in the formula (B), R is^1bExamples of the alkyl group or the alkoxy group include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms, and examples of the alkyl group or the alkoxy group include: methyl, methoxy, ethoxy, and the like. In the formula (B), R is^2bAnd R^3bThe alkoxy group is independently 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 is^4bAnd R^5bThe alkyl group is independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, or the like, and the alkyl group is a methyl group or the like. In the formula (B), m may 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 Japanese patent laid-open Nos. 2000-26609 and 2012-233110. As the polysiloxane compound, XR31-B1410 (manufactured by Momentive Co., Ltd.) can be used.

Further, since the alkoxy group is hydrolyzed, the polysiloxane compound having the alkoxy group may exist as a hydrolysis product in the sol, and the polysiloxane compound having the alkoxy group and the hydrolysis product thereof may be mixed together. In addition, in the polysiloxane compound having an alkoxy group, the alkoxy group in the molecule may be hydrolyzed entirely or partially.

These hydrolyzable or condensable functional group-containing polysiloxane compounds and hydrolysis products of hydrolyzable or condensable functional group-containing polysiloxane compounds may be used alone or in combination of two or more.

In the production of the aerogel according to the present embodiment, as the silicon compound having a hydrolyzable functional group or a condensable functional group, a silicon compound other than the polysiloxane compound can be used. That is, the silicon compound-containing sol may contain the silicon compound in addition to or instead of the polysiloxane compound group, and the silicon compound-containing sol may contain at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensable functional group (excluding a polysiloxane compound) and a hydrolysis product of the silicon compound having a hydrolyzable functional group (hereinafter, referred to as "silicon compound group" as appropriate). The number of silicon in the molecule of the silicon compound may be 1 or 2.

The silicon compound having a hydrolyzable functional group in the molecule is not particularly limited, and examples thereof include alkoxysilanes. From the viewpoint of improving the water resistance, the number of hydrolyzable functional groups in the alkoxysilanes is three or less. Examples of such alkoxysilanes include: monoalkyltrialkoxysilanes, monoalkyldialkoxysilanes, dialkyldialkoxysilanes, monoalkylmonoalkoxysilanes, dialkylmonoalkoxysilanes, trialkylmonoalkoxysilanes and the like, and specific examples thereof include: methyltrimethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, etc. Examples of the hydrolyzable functional group include alkoxy groups such as methoxy and ethoxy.

The silicon compound having a condensable functional group is not particularly limited, and examples thereof include: silanetetraols, methylsilanetriol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, diphenylsilanediol, n-propylsilanetriol, hexylsilanetriol, octylsilanetriol, decylsilanetriol, trifluoropropylsilanetriol, and the like.

The silicon compound having a hydrolyzable functional group or a condensable functional group may further have a reactive group (a functional group not corresponding to the hydrolyzable functional group or the condensable functional group) different from the hydrolyzable functional group or the condensable functional group.

As the silicon compound having three or less hydrolyzable functional groups and having a reactive group, there can be used: vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane and the like.

As the silicon compound having a condensable functional group and a reactive group, there can be used: vinylsilane triol, 3-glycidoxypropylsilane triol, 3-glycidoxypropylmethylsilane diol, 3-methacryloxypropylsilane triol, 3-methacryloxypropylmethylsilane diol, 3-acryloxypropylsilane triol, 3-mercaptopropylsilane triol, 3-mercaptopropylmethylsilane diol, N-phenyl-3-aminopropylsilane triol, N-2- (aminoethyl) -3-aminopropylmethylsilane diol and the like.

Further, silicon compounds having three or less hydrolyzable functional groups at the molecular end, i.e., bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, ethyltrimethoxysilane, vinyltrimethoxysilane, and the like, may also be used.

The silicon compound having a hydrolyzable functional group or a condensable functional group (excluding a polysiloxane compound) and a hydrolysis product of the silicon compound having a hydrolyzable functional group may be used alone or in combination of two or more.

By using the silicon compound (other than the polysiloxane compound), the structures represented by the following general formulae (4) to (6) can be introduced into the skeleton of the aerogel. The aerogel of the present embodiment may have any one of these structures alone or two or more of them.

[ solution 10]

In the formula (4), R⁹Represents an alkyl group. Here, the alkyl group includes an alkyl group having 1 to 6 carbon atoms, and the alkyl group includes a methyl group.

[ solution 11]

In the formula (5), R¹⁰And R¹¹Each independently represents an alkyl group. Here, the alkyl group includes an alkyl group having 1 to 6 carbon atoms, and the alkyl group includes a methyl group.

[ solution 12]

In the formula (6), R¹²Represents an alkylene group. The alkylene group includes alkylene groups having 1 to 10 carbon atoms, and the alkylene group includes ethylene and hexylene.

(fourth embodiment)

In view of further strengthening and further achieving excellent heat insulation and flexibility, the aerogel degassed gel component of the present embodiment may further contain silica particles in addition to the silica particles. An aerogel containing an aerogel component and silica particles may also be referred to as an aerogel composite. Although the aerogel composite is formed by compounding the aerogel component and the silica particles, it is considered that the aerogel composite has a cluster structure which is a characteristic of the aerogel and has a three-dimensional fine porous structure.

The aerogel containing the aerogel component and the silica particles may be referred to as a dry product of a wet gel which is a condensate of a sol containing silica particles and at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensable functional group and a hydrolysis product of the silicon compound having a hydrolyzable functional group. Therefore, the descriptions of the first to third embodiments can be applied to the aerogel of the present embodiment as appropriate.

The silica particles are not particularly limited and include amorphous silica particles and the like. As the amorphous silica particles, there can be mentioned: fused silica particles, fumed silica particles, colloidal silica particles, and the like. Among these, colloidal silica particles have high monodispersity and are easily inhibited from aggregating in a sol. The silica particles may have a hollow structure, a porous structure, or the like.

The shape of the silica particles is not particularly limited, and examples thereof include spherical, cocoon-shaped, and associated type. Among these, the use of spherical particles as silica particles makes it easy to suppress aggregation in the sol. From the viewpoint of easily imparting appropriate strength and flexibility to the aerogel and easily obtaining an aerogel excellent in shrinkage resistance at the time of drying, the average primary particle diameter of the silica particles may be 1nm or more, may be 5nm or more, or may be 20nm or more. From the viewpoint of easily suppressing solid heat conduction of the silica particles and easily obtaining an aerogel excellent in heat insulating property, the average primary particle diameter of the silica particles may be 500nm or less, may be 300nm or less, or may be 100nm or less. From these viewpoints, the average primary particle diameter of the silica particles may be from 1nm to 500nm, or from 5nm to 300nm, or from 20nm to 100 nm.

In the present embodiment, the average particle size of the aerogel component and the average primary particle size of the silica particles can be obtained by directly observing the aerogel with a scanning electron microscope (hereinafter, abbreviated as "sem" (scanning electron microscope)). The "diameter" referred to herein means a diameter when a cross section of a particle exposed on a cross section of the aerogel is regarded as a circle. The "diameter when the cross section is regarded as a circle" is the diameter of a perfect circle when the area of the cross section is replaced with a perfect circle having the same area. When the average particle size is calculated, the diameter of a circle is obtained for 100 particles, and the average value is obtained.

The average particle diameter of the silica particles can also be measured from the starting material. For example, the biaxial average primary particle size is calculated as follows from the results of observation of arbitrary 20 particles by SEM. That is, in the case of colloidal silica particles which are dispersed in water and have a solid content concentration of about 5 to 40 mass% in general, a chip obtained by cutting a wafer with pattern wiring into a 2cm square is immersed in a dispersion of colloidal silica particles for about 30 seconds, and then the chip is rinsed with pure water for about 30 seconds and nitrogen-blown (nitro-gen blow) dried. Then, the chip was placed on a sample stage for SEM observation, and the silica particles were observed at a magnification of 10 ten thousand times by applying an acceleration voltage of 10kV, and an image was taken. From the obtained image, 20 silica particles were arbitrarily selected, and the average of the particle diameters of these particles was defined as an average particle diameter.

The number of silanol groups per 1g of silica particles may be 10 × 10 from the viewpoint of easily obtaining an aerogel excellent in shrinkage resistance¹⁸More than one/g, also can be 50X 10¹⁸At least one unit/g, or 100X 10¹⁸More than one per gram. The number of silanol groups per 1g of silica particles may be 1000X 10 from the viewpoint of easy obtainment of a homogeneous aerogel¹⁸Less than one/g, and may be 800X 10¹⁸Less than or equal to 700 x 10¹⁸The number per gram is below. From these viewpoints, the number of silanol groups per 1g of the silica particles may be 10X 10¹⁸Per g-1000 x 10¹⁸Per g, also 50X 10¹⁸Per g-800X 10¹⁸Or 2, or 100X 10¹⁸Per g-700 x 10¹⁸Per gram.

From the viewpoint of more easily obtaining good reactivity, the content of the polysiloxane compound group contained in the sol (the sum of the content of the polysiloxane compound having a hydrolyzable functional group or a condensable functional group and the content of the hydrolysis product of the polysiloxane compound having a hydrolyzable functional group) may be 5 parts by mass or more and may be 10 parts by mass or more, with respect to 100 parts by mass of the total amount of the sol. From the viewpoint of more easily obtaining good compatibility, the content of the polysiloxane compound group contained in the sol may be 50 parts by mass or less, or may be 30 parts by mass or less, with respect to 100 parts by mass of the total amount of the sol. From these viewpoints, the content of the polysiloxane compound group contained in the sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass, relative to 100 parts by mass of the total amount of the sol.

In the case where the sol contains a silicon compound (excluding a polysiloxane compound), from the viewpoint of more easily obtaining good reactivity, the silicon compound group (the sum of the content of the silicon compound having a hydrolyzable functional group or a condensable functional group and the content of the hydrolysis product of the silicon compound having a hydrolyzable functional group) may be 5 parts by mass or more and may be 10 parts by mass or more, relative to 100 parts by mass of the total amount of the sol. From the viewpoint of more easily obtaining good compatibility, the content of the silicon compound group contained in the sol may be 50 parts by mass or less, or may be 30 parts by mass or less, with respect to 100 parts by mass of the total amount of the sol. From these viewpoints, the content of the silicon compound group contained in the sol may be 5 to 50 parts by mass, or may be 10 to 30 parts by mass.

In the case where the sol contains both the polysiloxane compound group and the silicon compound group, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1: 0.5 or more, and may be 1: 1 or more. From the viewpoint of more easily suppressing the shrinkage of the gel, the ratio of the content of the silicone compound group to the content of the silicon compound group may be 1: 4 or less, and may be 1: 2 or less. In these respects, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1: 0.5-1: 4, can also be 1: 1-1: 2.

when the silica particles are contained in the sol, the content of the silica particles may be 1 part by mass or more and may be 4 parts by mass or more with respect to 100 parts by mass of the total amount of the sol, from the viewpoint of easily imparting appropriate strength to the aerogel and easily obtaining an aerogel excellent in shrinkage resistance at the time of drying. From the viewpoint of easily suppressing solid heat conduction of the silica particles and easily obtaining an aerogel excellent in heat insulating property, the content of the silica particles may be 20 parts by mass or less, or may be 15 parts by mass or less, relative to 100 parts by mass of the total amount of the sol. From these viewpoints, the content of the silica particles may be 1 to 20 parts by mass, or 4 to 15 parts by mass, relative to 100 parts by mass of the total amount of the sol.

< aerogel particles >

The aerogel particles of the present embodiment can be obtained by pulverizing a bulk (bulk) aerogel, for example, as described later.

The average particle diameter D50 of the aerogel particles may be 1 to 1000. mu.m, but may be 3 to 700. mu.m, 5 to 500. mu.m, 10 to 100. mu.m, or 10 to 50 μm. When the average particle diameter D50 of the aerogel particles is 1 μm or more, aerogel particles excellent in dispersibility, handling properties, and the like can be easily obtained. On the other hand, aerogel particles having excellent dispersibility can be easily obtained by setting the average particle diameter D50 to 1000 μm or less. The average particle diameter of the aerogel particles can be suitably adjusted by a pulverization method, pulverization conditions, a method of sieving or classification, and the like.

The average particle diameter D50 of the aerogel particles can be measured by a laser diffraction-scattering method. For example, the dispersion of aerogel particles is performed by adding the aerogel particles to a solvent (ethanol) so that the content of the aerogel particles becomes 0.05 to 5 mass%, and vibrating the mixture for 15 to 30 minutes by a 50W ultrasonic homogenizer. Then, about 10mL of the dispersion was injected into a laser diffraction-scattering particle size distribution measuring apparatus, and the refractive index was set to 1.3 at 25 ℃ and the absorption was 0, thereby measuring the particle size. Then, the particle diameter at the integrated value of 50% (volume basis) in the particle diameter distribution was set as an average particle diameter D50. For example, macchian (Microtrac) MT3000 (product name, manufactured by japanese food products corporation) can be used as the measuring device.

Further, commercially available aerogel particles can be used. Commercially available products of AEROGEL particles include, for example, ENOVA (ENOVA) IC3100 (manufactured by CABOT CORPORATION), alova (AeroVa) (manufactured by geos AEROGEL CORPORATION), and the like.

< method for producing aerogel particles >

The method for producing the aerogel particles is not particularly limited, and the aerogel particles can be produced by the following method, for example.

The aerogel particles of the present embodiment can be produced by a production method mainly including the steps of: a sol generation step; a wet gel generation step of gelling the sol obtained in the sol generation step and then aging the gelled sol to obtain a wet gel; a washing and solvent replacement step of washing and (if necessary) solvent replacement of the wet gel obtained in the wet gel generation step; a drying step of drying the wet gel subjected to cleaning and solvent displacement; and a pulverization step of pulverizing the aerogel obtained by the drying.

In addition, the present invention can also be manufactured by a manufacturing method mainly including the steps of: a sol generation step; a wet gel generation step; a wet gel pulverization step of pulverizing the wet gel obtained in the wet gel generation step; cleaning and solvent replacement; and a drying step.

The aerogel particles obtained can be further made uniform in size by sieving, classifying, and the like. The dispersibility can be improved by adjusting the particle size. The "sol" is a state before the occurrence of the gelation reaction, and in the present embodiment, means a state in which the silicon compound and the optional silica particles are dissolved or dispersed in a solvent. The wet gel is a wet gel solid component that contains a liquid medium but has no fluidity.

(Sol production step)

The sol generating step comprises the following steps: the silicon compound and optionally silica particles (which may be a solvent containing silica particles) are mixed and subjected to a hydrolysis reaction to form a sol. In this step, an acid catalyst may be further added to the solvent in order to promote the hydrolysis reaction. Further, as shown in japanese patent No. 5250900, a surfactant, a thermally hydrolyzable compound, or the like may be added to the solvent. Further, for the purpose of suppressing heat ray radiation, etc., carbon graphite, an aluminum compound, a magnesium compound, a silver compound, a titanium compound, etc. may be added to the solvent.

As the solvent, for example, water or a mixture of water and alcohol can be used. Examples of the alcohol include: methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, etc. Among these, in terms of reducing the interfacial tension with the gel wall, as alcohols having a low surface tension and a low boiling point, there are mentioned: methanol, ethanol, 2-propanol, and the like. These may be used alone or in combination of two or more.

For example, when an alcohol is used as the solvent, the amount of the alcohol may be 4 to 8 moles, but may be 4 to 6.5 moles, or may be 4.5 to 6 moles, based on 1 mole of the total amount of the silicon compound group and the polysiloxane compound group. By setting the amount of the alcohol to 4 moles or more, good compatibility is more easily obtained, and by setting the amount to 8 moles or less, shrinkage of the gel is more easily suppressed.

As the acid catalyst, there can be mentioned: inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, and hypochlorous acid; acidic phosphates such as acidic aluminum phosphate, acidic magnesium phosphate, and acidic zinc phosphate; and 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. Among these, as an acid catalyst for further improving the water resistance of the obtained aerogel, an organic carboxylic acid is exemplified. The organic carboxylic acid may be acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, or the like. These may be used alone or in combination of two or more.

By using an acid catalyst, the hydrolysis reaction of the silicon compound can be promoted, and the sol can be obtained in a shorter time.

The amount of the acid catalyst to be added may be set to 0.001 to 0.1 parts by mass relative to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group.

As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. These may be used alone or in combination of two or more.

As the nonionic surfactant, for example, there can be used: and compounds containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly containing an alkyl group, and compounds containing a hydrophilic portion such as polyoxypropylene. Examples of the compound containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly containing an alkyl group include: polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene alkyl ether, and the like. Examples of the compound containing a hydrophilic portion such as polyoxypropylene include polyoxypropylene alkyl ethers and block copolymers of polyoxyethylene and polyoxypropylene.

Examples of the ionic surfactant include: cationic surfactants, anionic surfactants, zwitterionic surfactants, and the like. Examples of the cationic surfactant include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and examples of the anionic surfactant include sodium dodecylsulfonate. Further, examples of the zwitterionic surfactant include: amino acid-based surfactants, betaine-based surfactants, amine oxide-based surfactants, and the like. Examples of the amino acid surfactant include acyl glutamic acid. Examples of the betaine-type surfactant include lauryl dimethyl glycine betaine and stearyl dimethyl glycine betaine. Examples of the amine oxide surfactant include lauryl dimethylamine oxide.

These surfactants are considered to play the following roles in the wet gel formation step described later: reduce the difference in chemical affinity between the solvent and the growing siloxane polymer in the reaction system, and inhibit phase separation.

The amount of the surfactant to be added is also influenced by the kind of the surfactant or the kind and amount of the silicon compound, and may be set to 1 part by mass to 100 parts by mass, for example, relative to 100 parts by mass of the total amount of the silicone compound group and the silicon compound group. The amount may be 5 to 60 parts by mass.

It is believed that the thermally hydrolyzable compound generates a base catalyst by thermal hydrolysis, and makes the reaction solution alkaline, thereby promoting the sol-gel reaction in the wet gel formation step described later. Therefore, the thermally hydrolyzable compound is not particularly limited as long as it is a compound capable of making the reaction solution basic after hydrolysis, and examples thereof include: urea; acid amides such as formamide, N-methylformamide, N-dimethylformamide, acetamide, N-methylacetamide, and N, N-dimethylacetamide; and cyclic nitrogen compounds such as hexamethylenetetramine. Of these, urea in particular is easy to obtain the accelerating effect.

The amount of the thermally hydrolyzable compound added is not particularly limited as long as it is an amount sufficient to promote a sol-gel reaction in the wet gel formation step described later. For example, when urea is used as the thermally hydrolyzable compound, the amount of urea added may be 1 to 200 parts by mass per 100 parts by mass of the total amount of the silicone compound group and the silicon compound group. The amount may be 2 to 150 parts by mass. By setting the amount to 1 part by mass or more, good reactivity is more easily obtained, and by setting the amount to 200 parts by mass or less, precipitation of crystals and decrease in gel density are more easily suppressed.

The hydrolysis in the sol-forming step is also affected by the kind and amount of the silicon compound, silica particles, acid catalyst, surfactant and the like in the mixed solution, and may be carried out, for example, at a temperature of 20 to 60 ℃ for 10 minutes to 24 hours, or at a temperature of 50 to 60 ℃ for 5 minutes to 8 hours. Thus, the hydrolyzable functional group in the silicon compound is sufficiently hydrolyzed, and the hydrolysis product of the silicon compound can be obtained more reliably.

However, when the thermally hydrolyzable compound is added to the solvent, the temperature environment in the sol-forming step may be adjusted to a temperature at which the hydrolysis of the thermally hydrolyzable compound is suppressed and the gelation of the sol is suppressed. The temperature at this time may be any temperature as long as it is a temperature at which hydrolysis of the thermally hydrolyzable compound can be suppressed. For example, when urea is used as the thermally hydrolyzable compound, the temperature environment in the sol-forming step may be 0 to 40 ℃, but may be 10 to 30 ℃.

(Wet gel formation step)

The wet gel generation step is as follows: the sol obtained in the sol-generating step is gelled and then aged to obtain a wet gel. In this step, an alkali catalyst may be used in order to promote gelation.

As the base catalyst, there can be mentioned: carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper (II) carbonate, iron (II) carbonate, and silver (I) carbonate; bicarbonate salts such as calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, and ammonium bicarbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride and ammonium bromide; alkaline sodium phosphate salts such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; aliphatic amines such as allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3- (diethylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, tert-butylamine, sec-butylamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, and triethanolamine; and nitrogen-containing heterocyclic compounds such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and derivatives thereof, piperidine and derivatives thereof, and imidazole and derivatives thereof. Among these, ammonium hydroxide (ammonia water) is excellent in the following respects: since the volatility is high, it is difficult to remain in the aerogel particles after drying, and the water resistance is difficult to be impaired; and economic aspects. The base catalyst may be used alone or in combination of two or more.

By using the alkali catalyst, the dehydration condensation reaction or dealcoholization condensation reaction of the silicon compound and the silica particles in the sol can be promoted, and gelation of the sol can be performed in a shorter time. In addition, a wet gel having higher strength (rigidity) can be obtained. In particular, ammonia has high volatility and is less likely to remain in the aerogel particles, and therefore, by using ammonia as the alkali catalyst, aerogel particles having more excellent water resistance can be obtained.

The amount of the alkali catalyst to be added may be 0.5 to 5 parts by mass, but may be 1 to 4 parts by mass, based on 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. When the amount is 0.5 parts by mass or more, gelation can be performed in a shorter time, and when the amount is 5 parts by mass or less, deterioration of water resistance can be further suppressed.

The gelation of the sol in the wet gel formation step can be carried out in a closed vessel so that the solvent and the alkali catalyst do not volatilize. The gelation temperature may be set to 30 to 90 ℃ but may be 40 to 80 ℃. By setting the gelation temperature to 30 ℃ or higher, gelation can be performed in a shorter time, and a wet gel having higher strength (rigidity) can be obtained. Further, since the gelation temperature is set to 90 ℃ or lower, volatilization of the solvent (particularly alcohol) is easily suppressed, and gelation can be performed while suppressing volume shrinkage.

The aging in the wet gel formation step may be performed in a closed vessel so that the solvent and the alkali catalyst do not volatilize. By aging, the binding of the components constituting the wet gel becomes strong, and as a result, a wet gel having high strength (rigidity) sufficient for suppressing shrinkage at the time of drying can be obtained. The curing temperature may be set to 30 to 90 ℃ but may be 40 to 80 ℃. By setting the aging temperature to 30 ℃ or higher, a wet gel having higher strength (rigidity) can be obtained, and by setting the aging temperature to 90 ℃ or lower, volatilization of a solvent (particularly alcohol) can be easily suppressed, and thus gelation can be achieved while volume shrinkage is suppressed.

Further, since it is often difficult to determine the time point at which gelation of the sol ends, gelation of the sol and subsequent aging can be continuously performed in a series of operations.

The gelation time and the aging time can be appropriately set according to the gelation temperature and the aging temperature. In particular, the gelation time can be shortened when the sol contains silica particles, as compared with the case where the sol does not contain silica particles. The reason is presumed to be: the silanol group or reactive group of the silicon compound in the sol forms a hydrogen bond or a chemical bond with the silanol group of the silica particles. The gelation time may be 10 to 120 minutes, but may be 20 to 90 minutes. By setting the gelation time to 10 minutes or more, a homogeneous wet gel is easily obtained, and by setting to 120 minutes or less, the cleaning and solvent replacement steps to the drying step described later can be simplified. The total time of the gelation time and the aging time may be 4 to 480 hours, but may be 6 to 120 hours, as the whole gelation and aging step. By setting the total of the gelation time and the aging time to 4 hours or more, a wet gel having higher strength (rigidity) can be obtained, and by setting the total to 480 hours or less, the effect of aging can be more easily maintained.

In order to decrease the density of the obtained aerogel particles or increase the average pore diameter, the gelation temperature and the aging temperature may be increased within the above ranges, or the total time of the gelation time and the aging time may be increased within the above ranges. In addition, in order to increase the density of the obtained aerogel particles or to decrease the average pore diameter, the gelation temperature and the aging temperature may be decreased within the above ranges, or the total time of the gelation time and the aging time may be shortened within the above ranges.

(Wet gel pulverization step)

In the case of performing the wet gel pulverization step, the wet gel obtained in the wet gel generation step is pulverized. The pulverization can be carried out, for example, by: the wet gel formation step is carried out by putting the wet gel into a Henschel (Henschel) type mixer or in a mixer, and the mixer is operated under moderate conditions (rotation speed and time). In addition, the wet gel may be more easily produced by placing the wet gel in a sealable container or performing the wet gel producing step in a sealable container and oscillating the wet gel for a suitable period of time by using an oscillating device such as a vibrator. Further, if necessary, the particle size of the wet gel may be adjusted by using a jet mill, a roll mill, a bead mill, or the like.

(cleaning and solvent replacement step)

The cleaning and solvent replacement step is a step comprising: a step of washing the wet gel obtained by the wet gel generation step or the wet gel pulverization step (washing step); and a step (solvent replacement step) of replacing the cleaning solution in the wet gel with a solvent suitable for the drying conditions (drying step described later). The washing and solvent replacement step may be performed in a form in which only the solvent replacement step is performed without performing the step of washing the wet gel, but the wet gel may be washed from the viewpoint of reducing impurities such as unreacted products and by-products in the wet gel and producing aerogel particles having a higher purity.

In the washing step, the wet gel obtained in the wet gel generation step or the wet gel pulverization step is washed. The washing may be repeated using, for example, water or an organic solvent. At this time, the cleaning efficiency can be improved by heating.

As the organic solvent, there can be used: various organic solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1, 2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, dichloromethane, N-dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid. The organic solvent may be used alone or in combination of two or more.

In the solvent substitution step described later, a solvent having a low surface tension is used in order to suppress the shrinkage of the gel due to drying. However, a solvent with low surface tension generally has very low mutual solubility with water. Therefore, in the case where a solvent with a low surface tension is used in the solvent substitution step, the organic solvent used in the washing step may be a hydrophilic organic solvent having high mutual solubility in both water and the solvent with a low surface tension. Furthermore, the hydrophilic organic solvent used in the washing step can serve as a pre-substitution for the solvent substitution step. Among the organic solvents, examples of the hydrophilic organic solvent include: methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, and the like. Further, methanol, ethanol, methyl ethyl ketone, and the like are excellent in economical efficiency.

The amount of water or organic solvent used in the washing step may be an amount sufficient to replace the solvent in the wet gel and wash the gel. The amount may be set to an amount of 3 to 10 times the capacity of the wet gel. The washing may be repeated until the water content in the washed wet gel becomes 10 mass% or less with respect to the mass of silica.

The temperature environment in the washing step may be a temperature equal to or lower than the boiling point of the solvent used for washing, and for example, in the case of using methanol, the temperature may be increased to about 30 to 60 ℃.

In the solvent replacement step, the solvent of the wet gel after washing is replaced with a predetermined solvent for replacement in order to suppress the shrinkage of the aerogel in the drying step. In this case, the replacement efficiency can be improved by heating. Specifically, when the solvent for substitution is dried under atmospheric pressure at a temperature lower than the critical point of the solvent used in the drying step, a solvent with a low surface tension as described later can be used. On the other hand, in the case of supercritical drying, examples of the solvent for substitution include: ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, etc., or a mixture of two or more of these solvents.

As the solvent having a low surface tension, a solvent having a surface tension of 30mN/m or less at 20 ℃ may be mentioned. Further, the surface tension may be 25mN/m or less, or may be 20mN/m or less. Examples of the solvent having a low surface tension include: aliphatic hydrocarbons such as pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3-methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), and 1-pentene (16.0); aromatic hydrocarbons such as benzene (28.9), toluene (28.5), m-xylene (28.7), and p-xylene (28.3); halogenated hydrocarbons such as dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), and 2-chloropropane (18.1); ethers such as diethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ether (20.8), and 1, 2-dimethoxyethane (24.6); ketones such as acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), and diethyl ketone (25.3); esters such as methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), isobutyl acetate (23.7), and ethyl butyrate (24.6) (in parentheses, the surface tension at 20 ℃ is represented by [ mN/m ]). Of these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and excellent work environment properties. Of these, a hydrophilic organic solvent such as acetone, methyl ethyl ketone, and 1, 2-dimethoxyethane is used, and thus the organic solvent used in the washing step can be used as well. Among these, a solvent having a boiling point of 100 ℃ or lower under normal pressure may be used in order to facilitate drying in the drying step described later. The solvents may be used alone or in combination of two or more.

The amount of the solvent used in the solvent substitution step may be an amount sufficient to substitute the solvent in the wet gel after washing. The amount may be set to an amount of 3 to 10 times the capacity of the wet gel.

The temperature environment in the solvent substitution step may be a temperature equal to or lower than the boiling point of the solvent used for the substitution, and for example, in the case of using heptane, the temperature may be increased to about 30 to 60 ℃.

In the case where the gel contains silica particles, the solvent replacement step is not essential. The mechanism is presumed as follows. That is, the silica particles function as a support for a three-dimensional network-like skeleton, and the skeleton is supported, whereby the shrinkage of the gel in the drying step is suppressed. Therefore, it is considered that the gel may be directly applied to the drying step without replacing the solvent for washing. Thus, by using silica particles, simplification of the washing and solvent replacement steps to the drying step can be achieved.

(drying step)

In the drying step, the wet gel that has been washed and (if necessary) solvent-displaced is dried as described above. Thus, aerogels (aerogel blocks or aerogel particles) can be obtained. Namely, an aerogel obtained by drying a wet gel produced from the sol can be obtained.

The drying method is not particularly limited, and known methods such as atmospheric drying, supercritical drying, and freeze drying can be used. Among these methods, atmospheric drying or supercritical drying can be used from the viewpoint of ease of production of low-density aerogel. Further, from the viewpoint of production at low cost, atmospheric drying may be used. In the present embodiment, the normal pressure means 0.1MPa (atmospheric pressure).

Aerogels can be obtained by drying wet gels, which have been washed and, if necessary, solvent-displaced, at a temperature below the critical point of the solvent used in drying and at atmospheric pressure. The drying temperature differs depending on the type of solvent to be replaced (solvent used for cleaning in the case where no solvent replacement is performed), but may be 20 to 150 ℃ in view of the fact that drying at high temperature increases the evaporation rate of the solvent and causes large cracks in the gel. Furthermore, the drying temperature can also be 60-120 ℃. The drying time may be set to 4 to 120 hours, depending on the volume of the wet gel and the drying temperature. Further, the case where drying is accelerated by applying a pressure less than the critical point within a range not to impair productivity is also included in the atmospheric drying.

Alternatively, the aerogel may be obtained by subjecting a wet gel which has been washed and (if necessary) solvent-displaced to supercritical drying. Supercritical drying can be carried out by a known method. As a method for performing supercritical drying, for example, a method of removing a solvent by a temperature and a pressure equal to or higher than the critical point of the solvent contained in the wet gel can be cited. Alternatively, the supercritical drying method may be carried out by the following method: the wet gel is immersed in liquefied carbon dioxide under conditions of, for example, 20 to 25 ℃ and 5 to 20MPa, whereby all or a part of the solvent contained in the wet gel is replaced with carbon dioxide having a critical point lower than that of the solvent, and then the carbon dioxide is removed alone or a mixture of the carbon dioxide and the solvent is removed.

The aerogel obtained by such atmospheric drying or supercritical drying may be additionally dried at 105 to 200 ℃ for about 0.5 to 2 hours under atmospheric pressure. Thereby, an aerogel having a low density and small pores is more easily obtained. The additional drying may be carried out at 150 to 200 ℃ under normal pressure.

(crushing step)

The aerogel (aerogel block) obtained by drying is pulverized without performing the wet gel pulverization step, thereby obtaining aerogel particles. For example, this can be done by placing the aerogel into a jet mill, roller mill, bead mill, hammer mill, etc. and running at moderate rotational speeds and times.

< Water-soluble Polymer >

In the present embodiment, the water-soluble polymer may have a hydrophobic group and may have water solubility.

Examples of the hydrophobic group include: an alkyl group (preferably a long-chain alkyl group having 6 to 26 carbon atoms), an ester group, an alkoxy group, a halogen, and the like. Among these, the hydrophobic group is preferably an alkyl group, more preferably a long-chain alkyl group having 8 to 26 carbon atoms, still more preferably a long-chain alkyl group having 10 to 26 carbon atoms, yet more preferably a long-chain alkyl group having 12 to 26 carbon atoms, and may be a long-chain alkyl group having 15 to 26 carbon atoms.

Examples of the water-soluble polymer include: modified carboxyvinyl polymers, modified polyether urethanes, cellulose-based resins, polyethylene oxides, polyvinyl alcohols, polyacrylates, polyvinyl pyrrolidones, dextrin-based resins, chitin-based resins, chitosan-based resins, and the like.

As the water-soluble polymer, a cellulose-based resin can be preferably used. Examples of the cellulose-based resin include: methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and modified products obtained by further modifying (e.g., hydrophobizing) these.

The cellulose resin is preferably a cellulose resin having an alkyl group, and more preferably a cellulose resin having a long-chain alkyl group having 6 to 26 carbon atoms. The effect of the present invention can be more remarkably exhibited by such a cellulose-based resin. The number of carbon atoms of the long chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

The cellulose resin is preferably a cellulose resin having a structural unit represented by the following formula (A-1), for example.

[ solution 13]

In the formula (A-1), R^ARepresents a hydrogen atom, an alkyl group, a hydroxyalkyl group, -R^A1-O-R^A2The group (R) represented^A1Represents alkanediyl or hydroxyalkanediyl, R^A2Represents an alkyl group). Three R^AMay be the same or different from each other. Wherein three R^AAt least one of which is alkyl or-R^A1-O-R^A2The indicated radicals.

In the formula (A-1), as R^AThe alkyl group in (1) is preferably an alkyl group having 1 to 26 carbon atoms. In addition, R^AThe alkyl group in (1) is more preferably a short-chain alkyl group having 1 to 3 carbon atoms or a long-chain alkyl group having 6 to 26 carbon atoms. The number of carbon atoms of the long chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

In the formula (A-1), as R^AThe hydroxyalkyl group in (1) is preferably a hydroxyalkyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkyl group having 1 to 10 carbon atoms, and still more preferably a hydroxyalkyl group having 1 to 5 carbon atoms.

In the formula (A-1), R^A1The alkanediyl group in (1) is preferably an alkanediyl group having 1 to 26 carbon atoms, more preferably an alkanediyl group having 1 to 10 carbon atoms, and still more preferably an alkanediyl group having 1 to 5 carbon atoms. In addition, R^A1The hydroxyalkanediyl group in (1) is preferably a hydroxyalkanediyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkanediyl group having 1 to 10 carbon atoms, and still more preferably a hydroxyalkanediyl group having 1 to 5 carbon atoms.

In the formula (A-1), as R^A2Preferably, the alkyl group has 1 to 26 carbon atoms. In addition, R^A2The alkyl group in (1) is more preferably a C1 groupA short-chain alkyl group having 3 or a long-chain alkyl group having 6 to 26 carbon atoms, and more preferably a long-chain alkyl group. The number of carbon atoms of the long chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

In the formula (A-1), three R are preferred^AAt least one of which is a long chain alkyl group, or three R^AAt least one of which is-R^A1-O-R^A2A group represented by^A2Is a long chain alkyl group.

The cellulose resin preferably contains a long-chain alkyl group having 6 to 26 carbon atoms in an amount of 0.01 to 5% by mass, more preferably 0.01 to 3% by mass, based on the total amount of the cellulose resin.

In the coating liquid of the present embodiment, the content of the water-soluble polymer may be, for example, 0.01 vol% or more, preferably 0.1 vol% or more, and more preferably 0.3 vol% or more, based on the total volume of solid components in the coating liquid. The content of the water-soluble polymer may be, for example, 10 vol% or less, preferably 5 vol% or less, and more preferably 3 vol% or less, based on the total volume of the solid content in the coating liquid.

< liquid medium >

The liquid medium is preferably an aqueous solvent containing water. The aqueous solvent may contain an organic solvent in addition to water. The organic solvent may be any organic solvent having compatibility with water, and examples thereof include: alcohols such as methanol, ethanol, isopropanol, butanol, ethylene glycol, and propylene glycol; ethers such as diethyl ether, tetrahydrofuran, and 1, 4-dioxane; ketones such as acetone and methyl ethyl ketone; carboxylic acids such as acetic acid and propionic acid; and nitrogen-containing compounds such as acetonitrile, dimethylformamide and triethylamine.

The content of the liquid medium in the coating liquid of the present embodiment is not particularly limited, and may be appropriately changed depending on the viscosity of the coating liquid and the like. For example, the content of the liquid medium may be such that the solid content concentration of the coating liquid falls within a preferable range described later.

The solid content concentration of the coating liquid may be, for example, 10 mass% or more, preferably 15 mass% or more, and more preferably 20 mass% or more. The solid content concentration of the coating liquid may be, for example, 70 mass% or less, preferably 60 mass% or less, and more preferably 50 mass% or less.

< other ingredients >

The coating liquid of the present embodiment may further contain components other than the aerogel particles, the water-soluble polymer, and the liquid medium.

The coating liquid of the present embodiment may further contain a binder resin, for example. Examples of the binder resin include: epoxy resins, silicone resins, phenol resins, urea resins, melamine resins, polyurethane resins, polyethylene resins, polypropylene resins, polystyrene resins, polyester resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, polyamide resins, polyimide resins, polyvinyl-based resins, and the like. Among these, silicone resins, acrylic resins, phenol resins, polyester resins, and the like are preferably used from the viewpoint of heat resistance and toughness.

When the coating liquid of the present embodiment contains a binder resin, the content of the binder resin may be, for example, 30 vol% or less, preferably 28 vol% or less, and more preferably 25 vol% or less, based on the total volume of solid components. The content of the binder resin may be, for example, 0.1 vol% or more, or 1 vol% or more based on the total volume of the solid content.

The composite material of the present embodiment may further contain a thickener, a fibrous material, a pigment, a leveling agent, and the like as other components.

Examples of the thickener include fumed silica, clay mineral, and other fine particles.

The fibrous material can exhibit an anchoring function between aerogel particles, and can further improve the strength of a coating film brought by the composite material. The fibrous material is not particularly limited, and organic fibers and inorganic fibers are exemplified. Examples of the organic fibers include: polyamide-based fibers, polyimide-based fibers, polyvinyl alcohol-based fibers, polyvinylidene chloride-based fibers, polyvinyl chloride-based fibers, polyester-based fibers, polyacrylonitrile-based fibers, polyethylene-based fibers, polypropylene-based fibers, polyurethane-based fibers, phenol-based fibers, polyether-based fibers, polylactic acid-based fibers, polycarbonate-based fibers, and the like. Examples of the inorganic fibers include: glass fibers, carbon fibers, ceramic fibers, metal fibers, and the like.

According to the coating liquid of the present embodiment, a coating film including a composite material described later can be easily formed by applying the coating liquid and removing the liquid medium.

The method of applying the coating liquid is not particularly limited, and examples thereof include dip coating, spray coating, spin coating, roll coating, and the like.

The method for removing the liquid medium from the coating liquid to be applied is not particularly limited, and examples thereof include a method of performing a heat treatment (for example, 40 ℃ C. to 150 ℃ C.), a reduced pressure treatment (for example, 10000Pa or less), or both of these treatments.

The object to which the coating liquid is applied is not particularly limited. The material constituting the object may be, for example, metal, ceramic, glass, resin, or a composite material thereof. The form of the object may be appropriately selected depending on the purpose of use, material, and the like, and may be, for example, a block form, a sheet form, a powder form, a fiber form, and the like.

< composite Material, coating film >

The composite material of the present embodiment contains aerogel particles and a water-soluble polymer. The composite material according to the present embodiment may be a composite material in which the liquid medium is removed from the coating liquid. That is, the same components as those in the coating liquid can be exemplified as the components in the composite material, and the content of the components in the composite material can be the same as that in the coating liquid.

The coating film of the present embodiment includes the composite material. The coating film of the present embodiment can be formed by applying the coating liquid and removing the liquid medium.

The thickness of the coating film is not particularly limited, and may be, for example, 0.01mm to 30mm, or 0.1mm to 20 mm.

The composite material and the coating film of the present embodiment have excellent heat insulating properties, heat resistance, flame retardancy, and the like, which are derived from the aerogel. Therefore, the composite material and the coating film can be suitably used for applications as a heat insulator in a cryogenic container, the space field, the building field, the automobile field, the household appliance field, the semiconductor field, industrial equipment, and the like. The composite material and the coating film can be used as a water repellent, a sound absorber, a vibration stabilizer, a catalyst carrier, and the like, in addition to the use as a heat insulator.

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

Examples

The present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples.

< production example 1 >

(preparation of aerogel particles A)

100.0 parts by mass of PL-2L (manufactured by Futsun chemical industries, Ltd., product name), 80.0 parts by mass of water, 0.5 parts by mass of acetic acid as an acid catalyst, 1.0 parts by mass of cetyltrimethylammonium bromide as a cationic surfactant (manufactured by Wako pure chemical industries, Ltd.), and 150.0 parts by mass of urea as a pyrohydrolyzable compound were mixed, and 60.0 parts by mass of methyltrimethoxysilane (manufactured by shin chemical industries, Ltd., product name: KBM-13), 20.0 parts by mass of dimethyldimethoxysilane (manufactured by shin chemical industries, Ltd., product name: KBM-22) as a silicon compound, 20.0 parts by mass of a both-terminal bifunctional alkoxy-modified polysiloxane compound having a structure represented by the general formula (B) (hereinafter, referred to as "polysiloxane compound a") at 25 ℃ for 2 hours to obtain a sol. The obtained sol was gelled at 60 ℃ and then aged at 60 ℃ for 48 hours to obtain a wet gel.

Further, the "polysiloxane compound A" was synthesized in the following manner. First, 100.0 parts by mass of dimethylpolysiloxane XC96-723 (product name, manufactured by Momentive Performance Materials Japan) having silanol groups at both ends thereof, 181.3 parts by mass of methyltrimethoxysilane, and 0.50 part by mass of t-butylamine were mixed in a 1 liter three-necked flask equipped with a stirrer, a thermometer, and a Dietz cooler and reacted at 30 ℃ for 5 hours. Then, the reaction solution was heated under a reduced pressure of 1.3kPa at 140 ℃ for 2 hours to remove volatile components, thereby obtaining a both-terminal bifunctional alkoxy-modified polysiloxane compound (polysiloxane compound a).

Then, the obtained wet gel was transferred to a plastic bottle and sealed, and then pulverized at 27,000rpm for 10 minutes using a limit Mill (Extreme Mill) (MX-1000 XTS, manufactured by AS ONE corporation) to obtain a wet gel in the form of particles. The obtained wet gel in the form of particles was immersed in 2500.0 parts by mass of methanol, and washed at 25 ℃ for 24 hours. The washing operation was performed three times in total while changing to new methanol. Next, the washed wet gel in the form of particles was immersed in 2500.0 parts by mass of heptane, which is a low surface tension solvent, and solvent substitution was performed at 25 ℃ for 24 hours. The solvent replacement operation was performed three times in total while changing to fresh heptane. The wet gel in the form of particles after washing and solvent replacement was dried at 40 ℃ for 96 hours under normal pressure, and then further dried at 150 ℃ for 2 hours. Finally, the solution was applied to a sieve (45 μm in pore diameter, 32 μm in wire diameter, manufactured by tokyo screen corporation), thereby obtaining aerogel particles a having the structures represented by the general formulae (3), (4), and (5).

< example 1 >

(preparation of masking liquid)

In a 500mL separable flask, 4 parts by mass of water-soluble polymer, i.e., sanggilose (Sangelose)90L (manufactured by macrochemical industries, ltd.), 20 parts by mass of isopropyl alcohol (and reagent manufactured by Wako pure chemical industries, ltd.), and 350 parts by mass of hot liquid were taken, and stirred at 200rpm for 1 minute using a mechanical stirrer, thereby obtaining a dispersion. Then, while the flask was cooled with an ice-water bath, 90L of sanggilos (Sangelose) was dissolved with a mechanical stirrer at 200rpm to obtain a pregel as an aqueous solution of 90L of sanggilos (Sangelose). 374 parts by mass of the pregel and 100 parts by mass of an acrylic resin (product name: KH-CT-865, manufactured by Hitachi chemical Co., Ltd.) were mixed by a planetary mixer (2P-1 type, manufactured by Promega corporation) at 100 rpm. Then, 100 parts by mass of the aerogel particles a were divided into 5 times, and added while stirring at 100rpm, thereby obtaining a coating liquid. In the coating liquid, the content of aerogel particles was 85.2 vol%, the content of water-soluble polymer was 0.6 vol%, and the content of binder resin was 14.2 vol%, based on the total volume of solid components.

The obtained coating liquid was visually observed, and the dispersibility was evaluated by taking a case where the aerogel particles were well dispersed as a and a case where the aerogel particles were separated, aggregated, or precipitated as B. The results are shown in Table 1.

(formation of coating film)

The coating liquid was applied to an aluminum foil (product name: hemp iridoid thickness model 50, thickness: 50 μm) with a thickness of 2mm or 3mm by a metal spatula. Then, the resultant was left at room temperature of 23 ℃ for 12 hours, and the liquid medium was removed from the coating liquid, thereby obtaining a coating film with an aluminum foil. The aluminum foil was peeled from the obtained coating film with aluminum foil to obtain a coating film for performance evaluation. The tensile strength and heat insulating property of the obtained coating film were measured by the following methods.

(measurement of tensile Strength)

The obtained coating film was processed into a size of 2mm × 5mm × 50mm as a measurement sample. As the measuring apparatus, a small bench test machine "EZTest" (product name, manufactured by Shimadzu corporation) was used. Further, 500N is used for the load unit. The sample was set with a screw type flat jig disposed vertically with the distance between the top and bottom set at 25mm, and the sample was stretched at a speed of 2.5 mm/min. The measurement is set to end at the point in time when the sample breaks.

(measurement of thermal insulation)

The obtained coating film was processed into a size of 200mm × 200mm × 3mm as a measurement sample. The thermal conductivity of the obtained coating film was measured by a steady state method using a thermal conductivity measuring device "HFM-446" (manufactured by NETZSCH corporation, product name). The results are shown in Table 1.

< example 2 >

(preparation of masking liquid)

In a 500mL separable flask, 1 part by mass of sang Ji Luo (Sangelose)90L (manufactured by Dazai Kagaku Kogyo Co., Ltd.), 20 parts by mass of isopropyl alcohol (and Wako pure chemical industries, Ltd., reagent) and 250 parts by mass of hot liquid were taken, and stirred at 200rpm for 1 minute using a mechanical stirrer, thereby obtaining a dispersion. Then, while the flask was cooled with an ice-water bath, 90L of sanggilos (Sangelose) was dissolved with a mechanical stirrer at 200rpm to obtain a pregel as an aqueous solution of 90L of sanggilos (Sangelose). The pregel (271 parts by mass) was mixed with 200 parts by mass of an acrylic resin (product name: bunko DV759-EF, manufactured by dean son (DIC) gmbh) in a planetary mixer (model 2P-1, manufactured by planomile (Primix)) at 100 rpm. Then, 100 parts by mass of an Aerogel powder (manufactured by geos Aerogel (jis os Aerogel) corporation, mugwar (AeroVa)) was divided into 5 times, and the divided powder was added while stirring at 100rpm to obtain a coating liquid. In the coating liquid, the content of aerogel particles was 88.1 vol%, the content of water-soluble polymer was 0.1 vol%, and the content of binder resin was 11.7 vol%, based on the total volume of solid components.

The obtained coating liquid was visually observed, and the dispersibility was evaluated by taking a case where the aerogel particles were well dispersed as a and a case where the aerogel particles were separated, aggregated, or precipitated as B. The results are shown in Table 1.

(formation of coating film)

The coating liquid was applied to an aluminum foil (product name: Muyingoluo thickness model 50, thickness: 50 μm) with a thickness of 2mm or 3mm by an airless spray gun (ULTRA, manufactured by Graco). Then, the resultant was left at room temperature of 23 ℃ for 12 hours, and the liquid medium was removed from the coating liquid, thereby obtaining a coating film with an aluminum foil. The aluminum foil was peeled from the obtained coating film with aluminum foil to obtain a coating film for performance evaluation. The tensile strength and heat insulating property of the obtained coating film were measured by the same method as in example 1. The results are shown in Table 1.

< example 3 >

(preparation of masking liquid)

In a 500mL separable flask, 10 parts by mass of Natrosol Plus Grade (manufactured by Aqualon corporation), 10 parts by mass of isopropyl alcohol (manufactured by wako pure chemical industries, ltd., reagent), and 50 parts by mass of water were taken, and stirred at 500rpm for 10 minutes using a mechanical stirrer, to obtain a pregel. 70 parts by mass of the pre-gel and 500 parts by mass of a silicone resin (product name: Polon) -MF-56, manufactured by shin-Etsu chemical Co., Ltd.) were mixed in a planetary mixer (2P-1 type, manufactured by Provisions Raclex Co., Ltd.) and stirred at 100 rpm. Then, 100 parts by mass of aerogel powder (ENOVA) IC3100, manufactured by CABOT corporation) was divided into 5 portions and added while stirring at 100rpm, thereby obtaining a coating liquid. In the coating liquid, the content of aerogel particles was 74.1 vol%, the content of water-soluble polymer was 1.2 vol%, and the content of binder resin was 24.7 vol%, based on the total volume of solid components.

The obtained coating liquid was visually observed, and the dispersibility was evaluated by taking a case where the aerogel particles were well dispersed as a and a case where the aerogel particles were separated, aggregated, or precipitated as B. The results are shown in Table 1.

(formation of coating film)

The coating liquid was applied to an aluminum foil (product name: hemp iridoid thickness model 50, thickness: 50 μm) with a thickness of 2mm or 3mm by a metal spatula. Then, the resultant was left at room temperature of 23 ℃ for 12 hours, and the liquid medium was removed from the coating liquid, thereby obtaining a coating film with an aluminum foil. The aluminum foil was peeled from the obtained coating film with aluminum foil to obtain a coating film for performance evaluation. The tensile strength and heat insulating property of the obtained coating film were measured by the same method as in example 1. The results are shown in Table 1.

< comparative example 1 >

A coating solution was obtained by dividing 100 parts by mass of aerogel particles A into 5 times with a planetary mixer (2P-1 type manufactured by Ponkoe (DIC) DV750-EF, product name: Bonkote DV) 200 parts by mass, manufactured by Dian-Ci-George (Primix), and adding the divided aerogel particles while stirring at 100 rpm.

The obtained coating liquid was visually observed, and the dispersibility was evaluated by taking a case where the aerogel particles were well dispersed as a and a case where the aerogel particles were separated, aggregated, or precipitated as B. The results are shown in Table 1.

(formation of coating film)

The coating liquid obtained in comparative example 1 was used to try to form a coating film, but since aerogel particles were separated in the coating liquid, it was difficult to form a uniform coating film.

[ Table 1]

	Example 1	Example 2	Example 3	Comparative example 1
					Dispersibility of coating liquid	A	A	A	B
Tensile Strength (MPa) of coating film	0.4	0.3	0.2	-
					Heat insulation of coating film (mW/m. K)	32	27	30	-