Coating liquid, composite material, and production method for composite material

Abstract

The present disclosure relates to a coating liquid containing aerogel particles, glass particles, a binder resin, and an aqueous solvent. The coating liquid makes it possible for a composite material containing aerogel particles and a binder resin to be formed with excellent film formation properties.

Description

Coating liquid, composite material, and method for manufacturing composite material

[0001] This disclosure relates to a coating liquid, a composite material, and a method for manufacturing the composite material.

[0002] Aerogel is known as a material with excellent thermal insulation properties. Furthermore, methods have been proposed for processing aerogel into particles and using them as constituent materials for thermal insulation (for example, Patent Documents 1 and 2). Patent Document 1 proposes using particulate aerogel as a filler between resin plates and other materials that constitute a thermal insulation window. Patent Document 2 describes a method for producing thermal insulation (molded body) by preparing an aqueous dispersion containing aerogel particles and organic fibers, and then further press-molding the intermediate product obtained by evaporating the water.

[0003] Japanese Unexamined Patent Publication No. 2012-091943, Japanese Unexamined Patent Publication No. 2014-035044, Japanese Unexamined Patent Publication No. 2000-26609, Japanese Unexamined Patent Publication No. 2012-233110, Japanese Patent No. 5250900

[0004] Composite materials, in which aerogel particles are dispersed in a binder resin, are expected to have expanded applications and uses when made into a liquid coating. However, when such composite materials are made into a liquid coating, there is a problem in that cracks tend to occur during the drying of the coating film. In particular, when applied to curved parts or when thick films are to be made, the shrinkage stress during drying becomes large, and cracks tend to occur.

[0005] Therefore, the present disclosure aims to provide a coating liquid capable of forming a composite material containing aerogel particles and a binder resin with excellent film-forming properties. Furthermore, the present disclosure aims to provide a composite material with minimal cracking. Moreover, the present disclosure aims to provide a method for manufacturing a composite material capable of forming a composite material with minimal cracking.

[0006] This disclosure relates, for example, to the following [1] to

[11] : [1] A coating liquid containing aerogel particles, glass particles, a binder resin, and an aqueous solvent. [2] The coating liquid according to [1], wherein the glass particles include hollow glass particles. [3] The coating liquid according to [1] or [2], further containing a water-soluble polymer. [4] The coating liquid according to [3], wherein the water-soluble polymer has hydrophobic groups. [5] A composite material which is a dried product of any one of the coating liquids according to [1] to [4]. [6] The composite material according to [5], having a thick film portion having a thickness of 1 mm or more. [7] A composite material containing aerogel particles, glass particles, and a binder resin. [8] The composite material according to [7], further containing a water-soluble polymer. [9] The composite material according to [7] or [8], having a thick film portion having a thickness of 1 mm or more.

[10] A method for producing a composite material, comprising: a coating step of applying a coating liquid according to any one of [1] to [4] onto a support to obtain a coating film; and a removal step of removing at least a portion of the aqueous solvent from the coating film to obtain a composite material containing aerogel particles, glass particles and a binder resin.

[11] The method for producing the composite material according to

[10] , wherein the composite material has a thick film portion having a thickness of 1 mm or more.

[0007] This disclosure provides a coating liquid capable of forming a composite material containing aerogel particles and a binder resin with excellent film-forming properties. Furthermore, this disclosure provides a composite material with minimal cracking. Moreover, this disclosure provides a method for manufacturing a composite material capable of forming a composite material with minimal cracking.

[0008] Preferred embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. "A or B" means that either A or B is included, or both are included. Unless otherwise specified, the materials exemplified in these embodiments can be used individually or in combination of two or more.

[0009] (Coating liquid) The coating liquid of this embodiment contains aerogel particles, glass particles, a binder resin, and an aqueous solvent.

[0010] The coating liquid of this embodiment has excellent film-forming properties, and according to the coating liquid of this embodiment, even if the application area is a curved part or the film thickness after drying is 1 mm or more, it is possible to form a composite material while suppressing the occurrence of cracks.

[0011] Because the coating liquid of this embodiment contains aerogel particles, the resulting composite material has excellent heat insulation properties. Therefore, the composite material formed from the coating liquid of this embodiment can be suitably used as a heat insulating material.

[0012] Furthermore, in the coating solution of this embodiment, the use of both aerogel particles and glass particles improves the fluidity of the coating solution compared to the case where only aerogel particles are contained, making it easier to form a uniform coating film. In addition, in the coating solution of this embodiment, the use of both aerogel particles and glass particles as fillers suppresses the adsorption of the binder resin to the filler surface compared to the case where only aerogel particles are used as fillers, allowing the binder resin to function more easily as a matrix. As a result, the coating solution of this embodiment achieves the excellent film-forming properties described above.

[0013] In coatings containing aerogel particles, the aerogel particles may aggregate and form aggregates within the coating. When aerogel particles aggregate in the coating, these aggregates can act as starting points for cracking, potentially leading to cracking during drying. Furthermore, aggregation of aerogel particles in the coating significantly increases the viscosity of the coating, making it difficult to form a uniform coating film. This can also lead to uneven shrinkage stress during drying, potentially causing cracking. In this embodiment, the coating uses both aerogel particles and glass particles, thus suppressing the aggregation of aerogel particles in the coating, and reducing the likelihood of the aforementioned problems caused by aerogel particle aggregates. This is considered one of the factors contributing to its excellent film-forming properties.

[0014] <Aerogel> In a narrow sense, a dry gel obtained by supercritical drying of a wet gel is called an aerogel, a dry gel obtained by drying under atmospheric pressure is called a xerogel, and a dry gel obtained by freeze-drying is called a cryogel. However, in this embodiment, a low-density dry gel obtained by any of these drying methods of a wet gel is called an "aerogel." That is, in this embodiment, "aerogel" means aerogel in a broad sense, "Gel composed of a microporous solid in which the dispersed phase is a gas." Generally, the interior of an aerogel has a mesh-like microstructure and has a cluster structure in which particulate aerogel components of about 2 to 20 nm are bound together. There are pores less than 100 nm in size between the frameworks formed by these clusters. As a result, the aerogel has a three-dimensionally fine, porous structure.

[0015] The aerogel in this embodiment may be, for example, a silica aerogel mainly composed of silica. Examples of silica aerogels include so-called organic-inorganic hybridized silica aerogels into which organic groups (such as methyl groups) or organic chains have been introduced.

[0016] Examples of aerogels in this embodiment include the following embodiments. By adopting these embodiments, it becomes easy to obtain an aerogel with excellent heat insulation, flame retardancy, heat resistance, and flexibility. By adopting each embodiment, an aerogel having heat insulation, flame retardancy, heat resistance, and flexibility according to each embodiment can be obtained.

[0017] (First Embodiment) The aerogel in this embodiment may have a structure represented by the following formula (1). The aerogel according to this embodiment may have a structure represented by the following formula (1a) as a structure that includes the structure represented by formula (1).

[0018] In equations (1) and (1a), R １ and R ２each independently represents an alkyl group or an aryl group, and R ３ and R ４ each independently represents an alkylene group. Here, examples of the aryl group include a phenyl group, a substituted phenyl group, etc. 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, a cyano group, etc. p represents an integer of 1 to 50. In formula (1a), two or more R １ may be the same or different from each other. Similarly, two or more R ２ may be the same or different from each other. In formula (1a), two R ３ may be the same or different from each other. Similarly, two R ４ may be the same or different from each other.

[0019] By introducing the structure represented by formula (1) or formula (1a) into the skeleton of the aerogel as an aerogel component, an aerogel with low thermal conductivity and flexibility can be obtained. From such a viewpoint, in formula (1) and formula (1a), R １ and R ２ each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc. Examples of the alkyl group include a methyl group, etc. Also, in formula (1) and formula (1a), R ３ and R ４ each independently include an alkylene group having 1 to 6 carbon atoms, etc. Examples of the alkylene group include an ethylene group, a propylene group, etc. In formula (1a), p can be 2 to 30, and may be 5 to 20.

[0020] (Second Embodiment) The aerogel in this embodiment may have a ladder-type structure comprising support sections and bridge sections. The bridge sections may have a structure represented by the following formula (2). By introducing such a ladder-type structure as an aerogel component into the aerogel skeleton, heat resistance and mechanical strength can be improved. In this embodiment, the "ladder-type structure" is one having two support sections and bridge sections connecting the support sections (a so-called "ladder" shape). In this embodiment, the aerogel skeleton may consist of a ladder-type structure, but the aerogel may also have a ladder-type structure in part.

[0021] In formula (2), R ５ and R ６ Each of the R groups independently represents an alkyl group or an aryl group, and b represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups and substituted phenyl groups. Examples of substituents on substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, and cyano groups. Note that in formula (2), if b is an integer of 2 or more, there are two or more R groups. ５ Each of them may be the same or different, and similarly, two or more R ６ They may be the same or different.

[0022] By introducing the above structure as an aerogel component into the aerogel skeleton, for example, an aerogel with superior flexibility compared to aerogels having a structure derived from conventional ladder-type silsesquioxane (i.e., a structure represented by the following formula (X)) can be obtained. Silsesquioxane has the following composition formula: (RSio １．５ ) ｎThe polysiloxane has various skeletal structures such as cage-type, ladder-type, and random-type. As shown in formula (X) below, in conventional aerogels having a structure derived from ladder-type silsesquioxane, the crosslinking structure is -O-, but in the aerogel of this embodiment, the crosslinking structure is the structure represented by formula (2) above (polysiloxane structure). However, the aerogel of this embodiment may have a structure derived from silsesquioxane in addition to the structure represented by formula (2).

[0023] In formula (X), R represents a hydroxyl group, an alkyl group, or an aryl group.

[0024] The structure that forms the support column and its chain length, as well as the spacing of the structures that form the bridge, are not particularly limited, but from the viewpoint of further improving heat resistance and mechanical strength, the ladder-type structure may have a ladder-type structure represented by the following formula (3).

[0025] In formula (3), R ５ , R ６ , R ７ and R ８ Each of the following independently represents an alkyl group or an aryl group, a and c independently represent an integer from 1 to 3000, and b represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups and substituted phenyl groups. Examples of substituents on substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, and cyano groups. In formula (3), if b is an integer of 2 or more, there are two or more R ５ Each of them may be the same or different, and similarly, two or more R ６ These may be the same or different. Also, in equation (3), if a is an integer of 2 or more, there may be two or more R ７ These may be the same or different, and similarly, if c is an integer of 2 or more, there may be two or more R ８ These may be the same or different.

[0026] Furthermore, from the perspective of obtaining greater flexibility, in equations (2) and (3), R ５ , R ６, R ７ and R ８ (However, R ７ and R ８ In formula (3) only, a and c can be independently alkyl groups having 1 to 6 carbon atoms, phenyl groups, etc., and examples of alkyl groups include methyl groups, etc. Also, in formula (3), a and c can be independently 6 to 2000, but may also be 10 to 1000. Also, in formulas (2) and (3), b can be 2 to 30, but may also be 5 to 20.

[0027] (Third Embodiment) The aerogel in this embodiment may be a dried product of a wet gel that is a condensate of a sol containing a silicon compound having a hydrolyzable or condensable functional group, and at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group and a hydrolysis product of a silicon compound having a hydrolyzable functional group (obtained by drying a wet gel generated from a sol: a dried product of a wet gel derived from a sol). The aerogel described above may also be obtained by drying a wet gel generated from a sol containing a silicon compound, etc.

[0028] As the silicon compound having a hydrolyzable or 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 or condensable functional group, and the hydrolysis product of a polysiloxane compound having a hydrolyzable functional group (hereinafter, sometimes referred to as the "polysiloxane compound group").

[0029] The functional groups in polysiloxane compounds are not particularly limited, but they can be groups that react with other functional groups or with other functional groups. Examples of hydrolyzable functional groups include alkoxy groups. Examples of condensing functional groups include hydroxyl groups, silanol groups, carboxyl groups, and phenolic hydroxyl groups. Hydroxyl groups may be contained in hydroxyl group-containing groups such as hydroxyalkyl groups. Polysiloxane compounds having hydrolyzable or condensing functional groups may further have reactive groups different from the hydrolyzable and condensing functional groups (functional groups that do not fall under the category of hydrolyzable or condensing functional groups). Examples of reactive groups include epoxy groups, mercapto groups, glycidoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, and amino groups. Epoxy groups may be contained in epoxy group-containing groups such as glycidoxy groups. Polysiloxane compounds having these functional groups and reactive groups may be used alone or in mixtures of two or more types. Among these functional and reactive groups, for example, alkoxy groups, silanol groups, and hydroxyalkyl groups can improve the flexibility of the aerogel. Of these, alkoxy groups and hydroxyalkyl groups can further improve the compatibility of the sol. Furthermore, from the viewpoint of improving the reactivity of the polysiloxane compound and reducing the thermal conductivity of the aerogel, the number of carbon atoms in the alkoxy and hydroxyalkyl groups can be 1 to 6, but from the viewpoint of further improving the flexibility of the aerogel, it may be 2 to 5 or 2 to 4.

[0030] Examples of polysiloxane compounds having a hydroxyalkyl group in the molecule include those having the structure represented by the following formula (A). By using a polysiloxane compound having the structure represented by the following formula (A), the structures represented by formulas (1) and (1a) can be introduced into the aerogel skeleton.

[0031] In formula (A), R １ａ R represents a hydroxyalkyl group, ２ａ R indicates an alkylene group. ３ａ and R ４ａEach of the R groups independently represents an alkyl group or an aryl group, and n is an integer from 1 to 50. Here, examples of aryl groups include phenyl groups and substituted phenyl groups. Examples of substituents on substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, and cyano groups. Note that in formula (A), there are two R groups. １ａ Each of them may be the same or different, and similarly, two R ２ａ These may be the same or different. Also, in formula (A), there may be two or more R ３ａ Each of them may be the same or different, and similarly, two or more R ４ａ These may be the same or different.

[0032] By using a wet gel (produced from a sol) which is a condensate of a sol containing a polysiloxane compound of the above structure, it becomes easier to obtain a low thermal conductivity and flexible aerogel. From this viewpoint, in formula (A), R １ａ Examples include hydroxyalkyl groups having 1 to 6 carbon atoms, and examples of such hydroxyalkyl groups include hydroxyethyl groups and hydroxypropyl groups. Also, in formula (A), R ２ａ Examples include alkylene groups having 1 to 6 carbon atoms, and examples of such alkylene groups include ethylene groups and propylene groups. Also, in formula (A), R ３ａ and R ４ａ Examples of these include alkyl groups having 1 to 6 carbon atoms, phenyl groups, etc., and examples of alkyl groups include methyl groups. In formula (A), n can be 2 to 30, but may also be 5 to 20.

[0033] As polysiloxane compounds having the structure represented by the above formula (A), commercially available products can be used, such as compounds like X-22-160AS, KF-6001, KF-6002, KF-6003 (all manufactured by Shin-Etsu Chemical Co., Ltd.), and compounds like XF42-B0970, Fluid OFOH 702-4% (all manufactured by Momentive).

[0034] Examples of polysiloxane compounds having an alkoxy group in the molecule include those having the structure represented by the following formula (B). By using a polysiloxane compound having the structure represented by the following formula (B), a ladder-type structure having a crosslinking portion represented by formula (2) or (3) can be introduced into the aerogel skeleton.

[0035] In formula (B), R １ｂ R represents an alkyl group, an alkoxy group, or an aryl group. ２ｂ and R ３ｂ Each of these independently represents an alkoxy group, R ４ｂ and R ５ｂ Each of these independently represents an alkyl group or an aryl group, and m represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups and substituted phenyl groups. Examples of substituents on substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, and cyano groups. Note that in formula (B), there are two R １ｂ Each of them may be the same or different, and the two R ２ｂ Each of them may be the same or different, and similarly, two R ３ｂ These may be the same or different. Also, in formula (B), if m is an integer of 2 or more, there may be two or more R ４ｂ Each of them may be the same or different, and similarly, two or more R ５ｂ They may be the same or different.

[0036] By using a wet gel (produced from a sol) which is a condensate of a polysiloxane compound having the above structure or a hydrolysis product thereof, it becomes easier to obtain a low thermal conductivity and flexible aerogel. From this viewpoint, in formula (B), R １ｂ Examples include alkyl groups having 1 to 6 carbon atoms and alkoxy groups having 1 to 6 carbon atoms, and examples of such alkyl groups or alkoxy groups include methyl groups, methoxy groups, and ethoxy groups. In addition, in formula (B), R ２ｂ and R ３ｂExamples of these groups include alkoxy groups having 1 to 6 carbon atoms, and examples of such alkoxy groups include methoxy groups and ethoxy groups. In addition, in formula (B), R ４ｂ and R ５ｂ Examples of these include alkyl groups having 1 to 6 carbon atoms, phenyl groups, etc., and examples of alkyl groups include methyl groups. In formula (B), m can be 2 to 30, but may also be 3 to 35 or 5 to 20.

[0037] A polysiloxane compound having the structure represented by formula (B) above can be obtained by appropriately referring to the manufacturing methods reported in Japanese Patent Publication No. 2000-26609, Japanese Patent Publication No. 2012-233110, etc. Alternatively, XR31-B1410 (manufactured by Momentive) can be used as the polysiloxane compound.

[0038] Furthermore, since alkoxy groups are hydrolyzed, polysiloxane compounds containing alkoxy groups may exist as hydrolysis products in the sol, and the polysiloxane compounds containing alkoxy groups and their hydrolysis products may be present together. In addition, in polysiloxane compounds containing alkoxy groups, all of the alkoxy groups in the molecule may be hydrolyzed, or only partially hydrolyzed.

[0039] These polysiloxane compounds having hydrolyzable or condensable functional groups, and the hydrolysis products of polysiloxane compounds having hydrolyzable functional groups, may be used individually or in combination of two or more types.

[0040] In preparing the aerogel in this embodiment, silicon compounds other than the polysiloxane compounds described above can be used as silicon compounds having hydrolyzable or condensing functional groups. That is, the sol containing the above silicon compounds may contain, in addition to or in place of the polysiloxane compounds described above, at least one selected from the group consisting of silicon compounds having hydrolyzable or condensing functional groups (excluding polysiloxane compounds) and hydrolysis products of said silicon compounds having hydrolyzable functional groups (hereinafter, sometimes referred to as the "silicon compound group"). The number of silicon atoms in the silicon compound molecule may be 1 or 2.

[0041] Silicon compounds having hydrolyzable functional groups in their molecules are not particularly limited, but examples include alkylsilicon alkoxides. From the viewpoint of improving water resistance, alkylsilicon alkoxides can have three or fewer hydrolyzable functional groups. Examples of such alkylsilicon alkoxides include monoalkyltrialkoxysilanes, monoalkyldialkoxysilanes, dialkyldialkoxysilanes, monoalkylmonalkoxysilanes, dialkylmonalkoxysilanes, trialkylmonalkoxysilanes, and more specifically, methyltrimethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, etc. Here, examples of hydrolyzable functional groups include alkoxy groups such as methoxy groups and ethoxy groups.

[0042] Silicon compounds having condensing functional groups are not particularly limited, but examples include silanetetraol, methylsilanetriol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, diphenylsilanediol, n-propylsilanetriol, hexylsilanetriol, octylsilanetriol, decylsilanetriol, and trifluoropropylsilanetriol.

[0043] A silicon compound having a hydrolyzable functional group or a condensable functional group may further have reactive groups other than the hydrolyzable functional group and the condensable functional group (functional groups that do not fall under the category of hydrolyzable functional groups and condensable functional groups).

[0044] Silicon compounds having three or fewer hydrolyzable functional groups and possessing reactive groups can also be used, such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane.

[0045] Furthermore, as silicon compounds having condensing functional groups and reactive groups, vinylsilanetriol, 3-glycidoxypropylsilanetriol, 3-glycidoxypropylmethylsilanediol, 3-methacryloxypropylsilanetriol, 3-methacryloxypropylmethylsilanediol, 3-acryloxypropylsilanetriol, 3-mercaptopropylsilanetriol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2-(aminoethyl)-3-aminopropylmethylsilanediol, etc. can also be used.

[0046] Furthermore, silicon compounds with three or fewer hydrolyzable functional groups at the molecular ends, such as bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, ethyltrimethoxysilane, and vinyltrimethoxysilane, can also be used.

[0047] Silicon compounds (excluding polysiloxane compounds) having hydrolyzable or condensable functional groups, and hydrolysis products of such silicon compounds having hydrolyzable functional groups, may be used individually or in combination of two or more types.

[0048] By using the above silicon compounds (excluding polysiloxane compounds), structures represented by the following formulas (4) to (6) can be introduced into the aerogel skeleton. The aerogel in this embodiment may have any of these structures individually or two or more of them.

[0049]

[0050] In formula (4), R ９ represents an alkyl group. Here, examples of alkyl groups include alkyl groups having 1 to 6 carbon atoms, and examples of such alkyl groups include methyl groups.

[0051]

[0052] In formula (5), R １０ and R １１ Each of these independently represents an alkyl group. Here, examples of alkyl groups include alkyl groups having 1 to 6 carbon atoms, and examples of such alkyl groups include methyl groups.

[0053]

[0054] In formula (6), R １２ represents an alkylene group. Here, examples of alkylene groups include alkylene groups having 1 to 10 carbon atoms, and examples of such alkylene groups include ethylene groups and hexylene groups.

[0055] (Fourth Embodiment) In this embodiment, the aerogel may further contain silica particles in addition to the aerogel component, from the viewpoint of further strengthening and achieving even better heat insulation and flexibility. An aerogel containing both the aerogel component and silica particles can also be called an aerogel composite. The aerogel composite, while being a composite of the aerogel component and silica particles, is thought to have the cluster structure characteristic of aerogel and a three-dimensionally fine porous structure.

[0056] An aerogel containing aerogel components and silica particles can be described as a dried wet gel which is a condensate of a sol containing at least one selected from the group consisting of a silicon compound having a hydrolyzable or condensable functional group, and a hydrolysis product of a silicon compound having a hydrolyzable functional group, and silica particles. Therefore, the descriptions relating to the first to third embodiments can be appropriately applied to the aerogel in this embodiment.

[0057] The silica particles can be used without particular restrictions, and examples include amorphous silica particles. Examples of amorphous silica particles include fused silica particles, fumed silica particles, and colloidal silica particles. Of these, colloidal silica particles have high monodispersity and are good at suppressing aggregation in the sol. The silica particles may also have a hollow structure, a porous structure, or the like.

[0058] The shape of the silica particles is not particularly limited and can be spherical, cocoon-shaped, aggregate-shaped, etc. Of these, using spherical particles as silica particles makes it easier to suppress aggregation in the sol. The average primary particle diameter of the silica particles may be 1 nm or more, 5 nm or more, or 20 nm or more, from the viewpoint of easily imparting appropriate strength and flexibility to the aerogel and easily obtaining an aerogel with excellent shrinkage resistance during drying. The average primary particle diameter of the silica particles may be 500 nm or less, 300 nm or less, or 100 nm or less, from the viewpoint of easily suppressing solid heat conduction of the silica particles and easily obtaining an aerogel with excellent heat insulation properties. From these viewpoints, the average primary particle diameter of the silica particles may be 1 to 500 nm, 5 to 300 nm, or 20 to 100 nm.

[0059] In this embodiment, the average particle diameter of the aerogel component and the average primary particle diameter of the silica particles can be obtained by directly observing the aerogel using a scanning electron microscope (hereinafter abbreviated as "SEM"). Here, "diameter" refers to the diameter when the cross-section of the particle exposed on the cross-section of the aerogel is considered to be a circle. Furthermore, "diameter when the cross-section is considered to be a circle" refers to the diameter of a perfect circle when the area of ​​the cross-section is replaced with a perfect circle of the same area. In calculating the average particle diameter, the diameter of the circle is determined for 100 particles and the average is taken.

[0060] Furthermore, the average particle diameter of silica particles can also be measured from the raw material. For example, the biaxial average primary particle diameter can be calculated from the results of observing 20 arbitrary particles using SEM as follows: Specifically, taking colloidal silica particles dispersed in water with a solid content concentration of approximately 5 to 40 mass%, a chip obtained by cutting a patterned wafer into a 2 cm square is immersed in the colloidal silica particle dispersion for about 30 seconds. Then, the chip is rinsed with pure water for about 30 seconds and nitrogen-blown dry. After that, the chip is placed on a sample stage for SEM observation, an acceleration voltage of 10 kV is applied, and the silica particles are observed at a magnification of 100,000 times, and an image is taken. Twenty silica particles are arbitrarily selected from the obtained image, and the average of the particle diameters of those particles is taken as the average particle diameter.

[0061] The number of silanol groups per gram of silica particles is set to 10 × 10 from the viewpoint of easily obtaining an aerogel with excellent shrinkage resistance. １８ It may be more than pieces / g, 50 x 10 １８ It may be more than pieces / g, 100 x 10 １８ The number of particles / g or more may be appropriate. From the viewpoint of easily obtaining a homogeneous aerogel, the number of silanol groups per gram of silica particles should be 1000 × 10⁶. １８ It may be less than or equal to 10 pieces / g, 800 x 10 １８ It may be less than or equal to 700 x 10 １８ The number of particles per gram may be less than or equal to 10 g. From these viewpoints, the number of silanol groups per gram of silica particles is 10 × 10 １８ ~1000 x 10 １８ It may also be pieces / g, 50 x 10１８ ~800 x 10 １８ It may also be pieces / g, 100 x 10 １８ ~700 x 10 １８ It may also be per gram.

[0062] The amount of polysiloxane compounds contained in the above sol (the sum of the amount of polysiloxane compounds having hydrolyzable or condensing functional groups, and the amount of hydrolysis products of polysiloxane compounds having hydrolyzable functional groups) may be 5 parts by mass or more, or 10 parts by mass or more, per 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating good reactivity. The amount of polysiloxane compounds contained in the above sol may be 50 parts by mass or less, or 30 parts by mass or less, per 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating good compatibility. From these viewpoints, the amount of polysiloxane compounds contained in the above sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass, per 100 parts by mass of the total amount of the sol.

[0063] If the above sol contains silicon compounds (excluding polysiloxane compounds), the silicon compound group (the sum of the content of silicon compounds having hydrolyzable or condensing functional groups, and the content of hydrolysis products of silicon compounds having hydrolyzable functional groups) may be 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more per 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating good reactivity. The content of the silicon compound group contained in the above sol may be 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less per 100 parts by mass of the total amount of the sol, from the viewpoint of further facilitating good compatibility.

[0064] When the sol contains both polysiloxane compounds and silicon compounds, the ratio of the polysiloxane compound content to the silicon compound content may be 1:0.5 or higher, 1:0.7 or higher, or 1:1 or higher, from the viewpoint of further facilitating good compatibility. The ratio of the polysiloxane compound content to the silicon compound content may be 1:4 or lower, 1:3 or lower, or 1:2 or lower, from the viewpoint of further facilitating the suppression of gel shrinkage. From these viewpoints, the ratio of the polysiloxane compound content to the silicon compound content may be 1:0.5 to 1:4, 1:0.7 to 1:3, or 1:1 to 1:2.

[0065] If the above sol contains silica particles, the silica particle content may be 1 part by mass or more, 2 parts by mass or more, or 4 parts by mass or more per 100 parts by mass of the total amount of sol, from the viewpoint of making it easier to impart appropriate strength to the aerogel and to obtain an aerogel with excellent shrinkage resistance during drying. The silica particle content may be 20 parts by mass or less, 17 parts by mass or less, or 15 parts by mass or less per 100 parts by mass of the total amount of sol, from the viewpoint of making it easier to suppress the solid heat conduction of silica particles and to obtain an aerogel with excellent heat insulation properties. From these viewpoints, the silica particle content may be 1 to 20 parts by mass, 2 to 17 parts by mass or 4 to 15 parts by mass per 100 parts by mass of the total amount of sol.

[0066] <Aerogel Particles> The aerogel particles in this embodiment can be obtained, for example, by crushing bulk aerogel as described below.

[0067] The average particle size D50 (also called the average diameter) of the aerogel particles can be 0.1 to 1000 μm, but may also be 0.5 to 700 μm, 1 to 500 μm, 3 to 100 μm, or 5 to 50 μm. A larger average particle size D50 of the aerogel particles makes it easier to obtain aerogel particles with superior dispersibility and handling properties. On the other hand, a smaller average particle size D50 makes it easier to obtain aerogel particles with superior dispersibility. The average particle size of the aerogel particles can be appropriately adjusted by the grinding method and conditions, sieving, classification method, etc.

[0068] The average particle size D50 of aerogel particles can be measured by laser diffraction / scattering. For example, aerogel particles are added to a solvent (ethanol) to a content of 0.05 to 5% by mass, and the aerogel particles are dispersed by vibrating them in a 50W ultrasonic homogenizer for 15 to 30 minutes. Then, about 10 mL of the dispersion is injected into a laser diffraction / scattering particle size distribution analyzer, and the particle size is measured at 25°C with a refractive index of 1.3 and absorption of 0. The particle size at 50% of the cumulative value (by volume) in this particle size distribution is defined as the average particle size D50. As a measuring device, for example, Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name) can be used.

[0069] Furthermore, commercially available aerogel particles can also be used. Examples of commercially available aerogel particles include ENOVA MT1100 (manufactured by CABOT Corporation) and AeroVa (manufactured by JIS AEROGEL CORPORATION).

[0070] <Method for Manufacturing Aerogel Particles> The method for manufacturing aerogel particles is not particularly limited, but they can be manufactured by, for example, the following method.

[0071] The aerogel particles of this embodiment can be manufactured by a manufacturing method mainly comprising: a sol generation step; a wet gel generation step in which the sol obtained in the sol generation step is gelled and then matured to obtain a wet gel; a washing and solvent replacement step in which the wet gel obtained in the wet gel generation step is washed and (if necessary) solvent replaced; a drying step in which the washed and solvent replaced wet gel is dried; and a grinding step in which the aerogel obtained by drying is ground.

[0072] Alternatively, the product may be manufactured by a manufacturing method mainly comprising a sol generation step, a wet gel generation step, a wet gel pulverization step for pulverizing the wet gel obtained in the wet gel generation step, a washing and solvent replacement step, and a drying step.

[0073] The resulting aerogel particles can be further standardized in size by sieving, classification, etc. Standardizing the particle size can improve dispersibility. Note that "sol" refers to the state before the gelation reaction occurs, and in this embodiment, it means the state in which the silicon compound and, optionally, silica particles are dissolved or dispersed in the solvent. Furthermore, a wet gel refers to a wet gel solid that contains a liquid medium but does not have fluidity.

[0074] (Sol Production Process) The sol production process involves mixing a silicon compound with, optionally, silica particles (which may be a solvent containing silica particles) and carrying out a hydrolysis reaction to produce a sol. In this process, an acid catalyst may be added to the solvent to promote the hydrolysis reaction. Furthermore, as shown in Japanese Patent Publication No. 5250900, surfactants, thermally hydrolyzable compounds, etc., may be added to the solvent. In addition, components such as carbon graphite, aluminum compounds, magnesium compounds, silver compounds, and titanium compounds may be added to the solvent for purposes such as suppressing heat radiation.

[0075] As a solvent, for example, water or a mixture of water and alcohol can be used. Examples of alcohols include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol. Among these, methanol, ethanol, and 2-propanol are examples of alcohols with low surface tension and low boiling points that reduce interfacial tension with the gel wall. These may be used individually or in mixtures of two or more types.

[0076] For example, when using alcohol as a solvent, the amount of alcohol can be 4 to 8 moles per 1 mole of the total amount of silicon compounds and polysiloxane compounds, but it may also be 4 to 6.5 moles, or 4.5 to 6 moles. Increasing the amount of alcohol to 4 moles or more makes it easier to obtain good compatibility, and decreasing it to 8 moles or less makes it easier to further suppress gel shrinkage.

[0077] Examples of acid catalysts include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromate, 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, organic carboxylic acids are particularly effective in improving the water resistance of the resulting aerogel. While acetic acid is a suitable organic carboxylic acid, formic acid, propionic acid, oxalic acid, malonic acid, etc., may also be used. These may be used individually or in combination of two or more types.

[0078] By using an acid catalyst, the hydrolysis reaction of silicon compounds can be accelerated, allowing for the acquisition of a sol in a shorter time.

[0079] The amount of acid catalyst added can be 0.001 to 0.1 parts by mass per 100 parts by mass of the total amount of polysiloxane compounds and silicon compounds.

[0080] Nonionic surfactants, ionic surfactants, and the like can be used as surfactants. These may be used individually or in combination of two or more types.

[0081] Examples of nonionic surfactants that can be used include compounds containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly composed of alkyl groups, and compounds containing a hydrophilic portion such as polyoxypropylene. Examples of compounds containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly composed of alkyl groups include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene alkyl ether. Examples of compounds containing a hydrophilic portion such as polyoxypropylene include polyoxypropylene alkyl ether and block copolymers of polyoxyethylene and polyoxypropylene.

[0082] Examples of ionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. Examples of cationic surfactants include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, while examples of anionic surfactants include sodium dodecylsulfonate. Examples of amphoteric surfactants include amino acid-based surfactants, betaine-based surfactants, and amine oxide-based surfactants. Examples of amino acid-based surfactants include acyl glutamic acid. Examples of betaine-based surfactants include lauryldimethylaminoacetic acid betaine and stearyldimethylaminoacetic acid betaine. Examples of amine oxide-based surfactants include lauryldimethylamine oxide.

[0083] These surfactants are thought to reduce the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer during the wet gel formation process described later, thereby suppressing phase separation.

[0084] The amount of surfactant added depends on the type of surfactant, or the type and amount of silicon compound, but for example, it can be 1 to 100 parts by mass per 100 parts by mass of the total amount of polysiloxane compounds and silicon compounds. Alternatively, the amount may be 5 to 60 parts by mass.

[0085] Thermally hydrolyzable compounds are thought to generate a base catalyst upon thermal hydrolysis, making the reaction solution basic and promoting the sol-gel reaction in the wet gel formation step described later. Therefore, the thermally hydrolyzable compounds are not particularly limited as long as they can make the reaction solution basic after hydrolysis, and examples include urea; acid amides such as formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, and N,N-dimethylacetamide; and cyclic nitrogen compounds such as hexamethylenetetramine. Among these, urea is particularly likely to produce the above-mentioned promoting effect.

[0086] The amount of thermally hydrolyzable compound added is not particularly limited, as long as it is sufficient to adequately promote the sol-gel reaction in the wet gel formation step described later. For example, when urea is used as the thermally hydrolyzable compound, the amount added can be 1 to 200 parts by mass per 100 parts by mass of the total amount of polysiloxane compounds and silicon compounds. The amount added may be 2 to 150 parts by mass. Adding 1 part by mass or more makes it easier to obtain good reactivity, and adding 200 parts by mass or less makes it easier to further suppress crystal precipitation and the decrease in gel density.

[0087] The hydrolysis in the sol formation process depends on the type and amount of silicon compound, silica particles, acid catalyst, surfactant, etc., in the mixture, but it may be carried out for 10 minutes to 24 hours at a temperature of 20 to 60°C, or for 5 minutes to 8 hours at a temperature of 50 to 60°C. This ensures that the hydrolyzable functional groups in the silicon compound are sufficiently hydrolyzed, and the hydrolysis product of the silicon compound can be obtained more reliably.

[0088] However, when a thermally hydrolyzable compound is added to the solvent, the temperature environment of the sol formation process may be adjusted to a temperature that suppresses the hydrolysis of the thermally hydrolyzable compound and inhibits the gelation of the sol. The temperature at this time can be any temperature that can suppress the hydrolysis of the thermally hydrolyzable compound. For example, when urea is used as the thermally hydrolyzable compound, the temperature environment of the sol formation process can be 0 to 40°C, but it may also be 10 to 30°C.

[0089] (Wet Gel Formation Process) The wet gel formation process involves gelling the sol obtained in the sol formation process and then maturing it to obtain a wet gel. In this process, a base catalyst can be used to promote gelation.

[0090] Examples of 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, and silver(I) carbonate; bicarbonates 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; basic sodium phosphate salts such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, and diethylamine. Aliphatic amines such as 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)propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, and triethanolamine; nitrogen-containing heterocyclic compounds such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, and imidazole and its derivatives. Among these, ammonium hydroxide (aluminum ammonia) is superior in that it is highly volatile, does not easily remain in the aerogel particles after drying, thus not impairing water resistance, and is also economical. The above base catalysts may be used alone or in mixtures of two or more types.

[0091] By using a base catalyst, the dehydration condensation reaction or dealcoholization condensation reaction of silicon compounds and silica particles in the sol can be accelerated, allowing the sol to gel in a shorter time. This also allows for the production of a wet gel with higher strength (rigidity). In particular, since ammonia is highly volatile and does not easily remain in aerogel particles, using ammonia as a base catalyst allows for the production of aerogel particles with superior water resistance.

[0092] The amount of base catalyst added can be 0.5 to 5 parts by mass per 100 parts by mass of the total amount of polysiloxane compounds and silicon compounds, but it may also be 1 to 4 parts by mass. Adding 0.5 parts by mass or more allows gelation to occur in a shorter time, while adding 5 parts by mass or less further suppresses the decrease in water resistance.

[0093] The gelation of the sol in the wet gel formation process may be carried out in a sealed container to prevent the solvent and base catalyst from volatilizing. The gelation temperature can be 30 to 90°C, but it may also be 40 to 80°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. Furthermore, by setting the gelation temperature to 90°C or lower, the volatilization of the solvent (especially alcohol) is more easily suppressed, allowing gelation to occur while suppressing volume shrinkage.

[0094] The maturation process in the wet gel formation step may be carried out in a sealed container to prevent the solvent and base catalyst from volatilizing. Through maturation, the bonds between the components constituting the wet gel strengthen, resulting in a wet gel with sufficient strength (rigidity) to suppress shrinkage during drying. The maturation temperature can be 30 to 90°C, but may also be 40 to 80°C. A maturation temperature of 30°C or higher yields a wet gel with higher strength (rigidity), while a maturation temperature of 90°C or lower makes it easier to suppress the volatilization of the solvent (especially alcohol), thus enabling gelation while suppressing volume shrinkage.

[0095] Since it is often difficult to determine when the gelation of the sol is complete, the gelation of the sol and the subsequent maturation may be carried out in a continuous series of operations.

[0096] The gelation time and maturation time can be appropriately set depending on the gelation temperature and maturation temperature. When silica particles are present in the sol, the gelation time can be shortened compared to when they are not present. This is presumed to be because the silanol groups or reactive groups of the silicon compounds in the sol form hydrogen bonds or chemical bonds with the silanol groups of the silica particles. The gelation time can be 10 to 120 minutes, but may also be 20 to 90 minutes. Setting the gelation time to 10 minutes or more makes it easier to obtain a homogeneous wet gel, and setting it to 120 minutes or less allows for simplification of the drying process from the washing and solvent replacement steps described later. The total gelation and maturation time for the entire process can be 4 to 480 hours, but may also be 6 to 120 hours. Setting the total gelation and maturation time to 4 hours or more makes it possible to obtain a wet gel with higher strength (rigidity), and setting it to 480 hours or less makes it easier to maintain the maturation effect.

[0097] To lower the density of the resulting aerogel particles or increase the average pore size, the gelation temperature and aging temperature may be increased within the above range, or the total gelation and aging time may be increased within the above range. Alternatively, to increase the density of the resulting aerogel particles or decrease the average pore size, the gelation temperature and aging temperature may be lowered within the above range, or the total gelation and aging time may be shortened within the above range.

[0098] (Wet Gel Grinding Process) In the wet gel grinding process, the wet gel obtained in the wet gel generation process is ground. Grinding can be performed, for example, by placing the wet gel in a Henschal mixer, or by performing the wet gel generation process in the mixer and operating the mixer under appropriate conditions (rotation speed and time). Alternatively, a simpler method can be used, such as placing the wet gel in a sealable container, or performing the wet gel generation process in a sealable container and shaking it for an appropriate time using a shaking device such as a shaker. If necessary, the particle size of the wet gel can also be adjusted using a jet mill, roller mill, bead mill, etc.

[0099] (Washing and Solvent Replacement Step) The washing and solvent replacement step comprises a step of washing the wet gel obtained by the wet gel generation step or the wet gel grinding step (washing step) and a step of replacing the washing solution in the wet gel with a solvent suitable for drying conditions (drying step described later) (solvent replacement step). The washing and solvent replacement step can also be carried out in a form in which only the solvent replacement step is performed without washing the wet gel, but from the viewpoint of reducing impurities such as unreacted substances and by-products in the wet gel and enabling the production of aerogel particles of higher purity, the wet gel may be washed.

[0100] In the washing process, the wet gel obtained in the wet gel generation process or the wet gel pulverization process is washed. This washing can be repeated, for example, using water or an organic solvent. Heating during this process can improve washing efficiency.

[0101] Various organic solvents can be used, 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, methylene chloride, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid. These organic solvents may be used individually or in combination of two or more.

[0102] In the solvent replacement step described later, a solvent with low surface tension can be used to suppress gel shrinkage due to drying. However, solvents with low surface tension generally have very low mutual solubility with water. Therefore, when using a solvent with low surface tension in the solvent replacement step, a hydrophilic organic solvent that has high mutual solubility with both water and the low surface tension solvent can be used as the organic solvent in the washing step. The hydrophilic organic solvent used in the washing step can also serve as a pre-replacement for the solvent replacement step. Among the above organic solvents, examples of hydrophilic organic solvents include methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone. Methanol, ethanol, and methyl ethyl ketone are particularly economical.

[0103] The amount of water or organic solvent used in the washing process can be sufficient to adequately replace the solvent in the wet gel and wash it. This amount can be 3 to 10 times the volume of the wet gel. Washing can be repeated until the water content in the wet gel after washing is 10% by mass or less relative to the silica mass.

[0104] The temperature environment during the washing process can be kept below the boiling point of the solvent used for washing. For example, when methanol is used, the temperature can be raised to approximately 30-60°C.

[0105] In the solvent replacement step, the solvent in the washed wet gel is replaced with a predetermined replacement solvent to suppress shrinkage of the aerogel during the drying step. Heating during this process can improve the replacement efficiency. Specifically, as replacement solvents, when drying at atmospheric pressure at a temperature below the critical point of the solvent used for drying, low-surface-tension solvents, as described later, can be used. On the other hand, when performing supercritical drying, examples of replacement solvents include ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, or mixtures of two or more of these.

[0106] Examples of solvents with low surface tension include those with a surface tension of 30 mN / m or less at 20°C. However, this surface tension may also be 25 mN / m or less, or 20 mN / m or less. Examples of solvents with 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); and chloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), and 2-chloropropane (18.1). Examples include chlorohydrocarbons; ethers such as ethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ethyl 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); and 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) (values ​​in parentheses indicate surface tension at 20°C, in units of [mN / m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and excellent working environment. Furthermore, among these, hydrophilic organic solvents such as acetone, methyl ethyl ketone, and 1,2-dimethoxyethane can be used interchangeably with the organic solvent in the above-mentioned cleaning process. Furthermore, among these, solvents with a boiling point of 100°C or lower at atmospheric pressure may be used, as they facilitate drying in the drying process described later. The above solvents may be used alone or in mixtures of two or more types.

[0107] The amount of solvent used in the solvent replacement step can be sufficient to adequately replace the solvent in the wet gel after washing. This amount can be 3 to 10 times the volume of the wet gel.

[0108] The temperature environment during the solvent substitution process can be set to a temperature below the boiling point of the solvent used for substitution. For example, when using heptane, heating to around 30-60°C is sufficient.

[0109] Furthermore, if silica particles are included in the gel, the solvent replacement step is not essential. The presumed mechanism is as follows: The silica particles function as a support for the three-dimensional network-like framework, thereby supporting the framework and suppressing gel shrinkage during the drying process. Therefore, it is thought that the gel can be subjected to the drying process directly without replacing the solvent used for washing. In this way, the use of silica particles makes it possible to simplify the drying process by eliminating the washing and solvent replacement steps.

[0110] (Drying process) In the drying process, the wet gel, which has been washed and (if necessary) solvent-substituted as described above, is dried. This allows aerogel (aerogel block or aerogel particles) to be obtained. That is, an aerogel can be obtained by drying the wet gel produced from the above sol.

[0111] The drying method is not particularly limited, and known methods such as atmospheric pressure drying, supercritical drying, or freeze-drying can be used. Of these, atmospheric pressure drying or supercritical drying can be used from the viewpoint of facilitating the production of low-density aerogels. Furthermore, atmospheric pressure drying can be used from the viewpoint of enabling low-cost production. In this embodiment, atmospheric pressure means 0.1 MPa (atmospheric pressure).

[0112] Aerogel can be obtained by drying a wet gel, which has been washed and (if necessary) solvent-substituted, at atmospheric pressure at a temperature below the critical point of the solvent used for drying. The drying temperature varies depending on the type of solvent substituted (or the solvent used for washing if solvent substitution is not performed), but can be set to 20 to 150°C, considering that drying at high temperatures can accelerate the evaporation rate of the solvent and cause large cracks in the gel. The drying temperature may also be 60 to 120°C. The drying time varies depending on the volume of the wet gel and the drying temperature, but can be 4 to 120 hours. It should be noted that applying a pressure below the critical point to accelerate drying, within a range that does not impede productivity, is also included in atmospheric pressure drying.

[0113] Aerogels can also be obtained by supercritical drying of a wet gel that has been washed and (if necessary) solvent-replaced. Supercritical drying can be carried out by known methods. One method of supercritical drying is to remove the solvent contained in the wet gel at a temperature and pressure above the critical point of the solvent. Alternatively, one method of supercritical drying is to immerse the wet gel in liquefied carbon dioxide under conditions such as 20-25°C and 5-20 MPa, thereby replacing all or part of the solvent contained in the wet gel with carbon dioxide, which has a lower critical point than the solvent, and then remove the carbon dioxide alone or a mixture of carbon dioxide and the solvent.

[0114] The aerogel obtained by such atmospheric pressure drying or supercritical drying may be further dried at 105-200°C for about 0.5-2 hours under atmospheric pressure. This makes it easier to obtain aerogel with lower density and smaller pores. The additional drying may be carried out at 150-200°C under atmospheric pressure.

[0115] (Grinding Process) If a wet gel grinding process is not performed, aerogel particles are obtained by grinding the aerogel (aerogel block) obtained by drying. For example, this can be done by placing the aerogel in a jet mill, roller mill, bead mill, hammer mill, etc., and operating it at an appropriate rotation speed and time.

[0116] <Glass Particles> The glass particles may be solid glass particles or hollow glass particles, and from the viewpoint of further improving the thermal insulation properties of the composite material, hollow glass particles are preferable.

[0117] The average particle size of the glass particles may be, for example, 1000 μm or less, and may also be 500 μm or less, 100 μm or less, or 80 μm or less. A smaller average particle size of glass particles tends to improve the smoothness of the coating film. Alternatively, the average particle size of the glass particles may be, for example, 0.01 μm or more, and may also be 0.1 μm or more, 1 μm or more, or 10 μm or more. A larger average particle size of glass particles tends to suppress the aggregation of glass particles, resulting in a more pronounced effect than described above.

[0118] In this specification, the average particle size of glass particles refers to the median diameter (D50) in the particle size distribution measured by a laser diffraction / scattering particle size distribution analyzer.

[0119] The glass particles may have a hydrophobic surface treatment or may not have a hydrophobic surface treatment, but from the viewpoint of obtaining the above-mentioned effects more significantly, the glass particles may not have a hydrophobic surface treatment.

[0120] When the glass particles are hollow glass particles, the true density of the hollow glass particles is, for example, 0.01 g / cm³. ３ The above is sufficient, and 0.03 g / cm³ ３ Above, 0.05g / cm ３ Above or equal to 0.1 g / cm³ ３ The above is also acceptable. When the true density of hollow glass particles is high, breakage of the hollow glass particles during mixing, application, or drying of the coating liquid is suppressed, and the thermal insulation properties of the composite material tend to improve further. Furthermore, the true density of hollow glass particles is, for example, 0.8 g / cm³. ３ The following may be used: 0.7 g / cm³ ３ Below, 0.6g / cm ３ The following, or 0.5 g / cm³ ３ The following may also apply: When the true density of hollow glass particles is low, the voids in the hollow glass particles become larger, which tends to improve the thermal insulation properties of the composite material.

[0121] In this specification, the true density of hollow glass particles is expressed as the value measured by a gas pycnometer.

[0122] When the glass particles are hollow glass particles, the pressure resistance strength of the hollow glass particles may be, for example, 0.1 MPa or more, 0.5 MPa or more, 1 MPa or more, or 5 MPa or more. When the pressure resistance strength of the hollow glass particles is high, breakage of the hollow glass particles during mixing, application, or drying of the coating liquid is suppressed, and the thermal insulation properties of the composite material tend to improve further. The pressure resistance strength of the hollow glass particles may be, for example, 500 MPa or less, or 200 MPa or less.

[0123] In this specification, the pressure resistance strength of hollow glass particles is expressed as the pressure resistance strength at 80% remaining, measured by a compression test as specified in JIS Z 8844:2019 Method for Measuring the Fracture Strength and Deformation Strength of Fine Particles.

[0124] <Binder Resin> Examples of binder resins include epoxy resin, silicone resin, phenolic resin, urea resin, melamine resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, polyamide resin, polyimide resin, and polyvinyl resin. Among these, silicone resin, acrylic resin, phenolic resin, and polyester resin can be suitably used from the viewpoint of heat resistance and toughness.

[0125] The binder resin may be a resin insoluble in water. The binder resin may be present in the coating liquid as emulsion particles. That is, the coating liquid may contain emulsion particles containing the binder particles. Preferred embodiments of the binder resin in emulsion particles will be described in detail below.

[0126] The binder particles contained in the emulsion particles may be, for example, polymers of monomer components having ethylenically unsaturated bonds. Such binder resins have structural units (also called monomer units) derived from the monomer components. Examples of monomer units include acrylic compounds having (meth)acryloyl groups, aromatic vinyl compounds, heterocyclic vinyl compounds, vinyl esters, monoolefins, conjugated diolefins, α,β-unsaturated carboxylic acids, vinyl cyanides, and the like. These may be used individually or in combination of two or more.

[0127] Examples of acrylic compounds include alkyl (meth)acrylates. The alkyl group of the alkyl (meth)acrylate may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkyl (meth)acrylate may be, for example, 1 to 20, 1 to 18, 1 to 16, or 1 to 14. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isobolonyl (meth)acrylate, and the like.

[0128] Examples of acrylic compounds include polar group-containing acrylic compounds having a (meth)acryloyl group and a polar group (a polar group other than the (meth)acryloyl group). Examples of polar groups include hydroxyl groups, amino groups, substituted amino groups (e.g., dialkylamino groups, hydroxyalkylamino groups, etc.), amide groups, substituted amide groups (e.g., dialkylamide groups, hydroxyalkylamide groups, etc.), epoxy groups, silyl groups (e.g., trialkoxysilyl groups, etc.), cyano groups, isocyanate groups, phosphate groups, carbonyl groups, etc.

[0129] Examples of acrylic compounds containing polar groups include compounds in which a polar group is substituted on the alkyl group of an alkyl (meth)acrylate. Examples of such compounds include hydroxyalkyl (meth)acrylate (e.g., hydroxyethyl (meth)acrylate), dialkylaminoalkyl (meth)acrylate (e.g., dimethylaminoethyl (meth)acrylate), glycidyl (meth)acrylate, trialkoxysilylalkyl (meth)acrylate, isocyanatoalkyl (meth)acrylate (e.g., 2-isocyanatoethyl (meth)acrylate), and 2-(meth)acryloyloxyethyl acid phosphate.

[0130] Examples of polar group-containing acrylic compounds include compounds in which a (meth)acryloyl group is bonded to a polar group. Examples of such compounds include (meth)acrylic acid, (meth)acrylamide, n-methylol(meth)acrylamide, and diacetone acrylamide.

[0131] Other examples of polar group-containing acrylic compounds include diacetone (meth)acrylate and acetoacetoxyalkyl (meth)acrylate (e.g., acetoacetoxyethyl (meth)acrylate).

[0132] Examples of acrylic compounds include acrolein and vinyl alkyl ketones (e.g., vinyl methyl ketone).

[0133] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, and ethyl vinylbenzene.

[0134] Examples of heterocyclic vinyl compounds include vinylpyrrolidone, vinylfuran, vinylthiophene, vinyloxazoline, and vinylpyrrole.

[0135] Examples of vinyl esters include vinyl acetate, vinyl alkanate, and vinyl versatate.

[0136] Examples of monoolefins include ethylene, propylene, butylene, and isobutylene.

[0137] Examples of conjugated diolefins include butadiene, isoprene, and chloroprene.

[0138] Examples of α,β-unsaturated carboxylic acids include crotonic acid, itaconic acid, maleic acid, fumaric acid, and their anhydrides.

[0139] Examples of vinyl cyanides include acrylonitrile and methacrylonitrile.

[0140] As monomer components, compounds selected from the group consisting of acrylic compounds, aromatic vinyl compounds, heterocyclic vinyl compounds, and α,β-unsaturated carboxylic acids are preferred from the viewpoint of exhibiting the above-mentioned effects more prominently.

[0141] From the viewpoint of achieving the above-mentioned effects more significantly, the monomer component preferably contains an acrylic compound. The content of the acrylic compound may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, or 100% by mass, based on the total amount of the monomer component.

[0142] From the viewpoint of achieving the above-mentioned effects more significantly, the acrylic compound preferably contains an alkyl (meth)acrylate. The alkyl (meth)acrylate content may be, for example, 50% by mass or more based on the total amount of monomer components, and from the viewpoint of further improving the water resistance of the composite material, it may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. In addition, the alkyl (meth)acrylate content may be, for example, 99% by mass or less, 97% by mass or less, or 95% by mass or less based on the total amount of monomer components.

[0143] The acrylic compound may further contain a polar group-containing acrylic compound. The content of the polar group-containing acrylic compound may be, for example, 1% by mass or more, 3% by mass or more, or 5% by mass or more, based on the total amount of monomer components. Furthermore, the content of the polar group-containing acrylic compound may be, for example, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, based on the total amount of monomer components.

[0144] The monomer component may be selected from the group consisting of, for example, methyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylic acid, and styrene.

[0145] The monomer components may be appropriately selected so that the glass transition temperature (Tg) of the binder resin falls within the preferred range described later. The glass transition temperature (Tg) of the binder resin can be measured by the method described in the examples below.

[0146] The glass transition temperature (Tg) of the binder resin can be estimated using FOX's formula, based on the weight ratio of each monomer unit constituting the binder resin and the Tg of the homopolymer of each monomer. Based on the value estimated using FOX's formula, monomer components may be appropriately selected so that the glass transition temperature (Tg) of the binder resin falls within a suitable range.

[0147] The glass transition temperature (Tg) of the binder resin may be, for example, 25°C or lower, and more preferably 20°C or lower, and more preferably 15°C or lower, from the viewpoint of further improving film formation performance. Furthermore, from the viewpoint of even better film formation performance at low temperatures, the glass transition temperature (Tg) of the binder resin may be 10°C or lower, more preferably 8°C or lower, and may also be 6°C or lower. There is no particular lower limit to the glass transition temperature (Tg) of the binder resin, and may be, for example, -40°C or higher, or -20°C or higher.

[0148] The binder resin can be produced, for example, by emulsion polymerization of monomer components in a liquid medium (preferably an aqueous solvent) in the presence of an emulsifier. This emulsion polymerization forms emulsion particles containing the binder resin and the emulsifier.

[0149] The emulsifier can be any emulsifier capable of emulsifying the binder resin, and may be a known emulsifier. Examples of emulsifiers include anionic emulsifiers and nonionic emulsifiers.

[0150] From the viewpoint of obtaining a coating solution with low corrosiveness to metals, it is preferable that the emulsifier be a nonionic emulsifier. By selecting a nonionic emulsifier, it is thought that corrosion of metals caused by ions present in other emulsifiers (e.g., anionic emulsifiers) is suppressed.

[0151] The nonionic emulsifier can be any nonionic emulsifier capable of emulsifying the binder resin, and may be a known nonionic emulsifier. Examples of nonionic emulsifiers include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenol ethers, polyoxyalkylene fatty acid esters, and polyoxyalkylene sorbitan fatty acid esters, with polyoxyalkylene alkyl ethers being preferred and polyoxyethylene alkyl ethers being more preferred.

[0152] The HLB value of the emulsifier is preferably 13 or higher, more preferably 14 or higher, from the viewpoint of facilitating emulsification of the binder resin, and preferably 15 or higher, more preferably 16 or higher, from the viewpoint of improving the film-forming properties of the coating liquid. Furthermore, the HLB value of the emulsifier is preferably 19 or lower, from the viewpoint of preventing a decrease in the water resistance of the composite material.

[0153] The emulsifier content may be, for example, 0.01 parts by mass or more per 100 parts by mass of binder resin, and from the viewpoint of delaying the surface drying of the coating film and improving film formation and core drying properties, it may be 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 0.7 parts by mass or more, 0.9 parts by mass or more, or 1 part by mass or more. Furthermore, the emulsifier content may be, for example, 15 parts by mass or less per 100 parts by mass of binder resin, and from the viewpoint of further improving the water resistance of the composite material, it may be 12 parts by mass or less, 10 parts by mass or less, 8 parts by mass or less, or 6 parts by mass or less.

[0154] The average particle size of the emulsified particles may be, for example, 50 nm or more, and may be 70 nm or more, 90 nm or more, or 100 nm or more. Alternatively, the average particle size of the emulsified particles may be, for example, 400 nm or less, and may be 350 nm or less, or 300 nm or less.

[0155] The amount of emulsified particles in the coating solution may be adjusted as appropriate so that the amounts of binder resin and emulsifier in the composite material fall within the preferred range described later.

[0156] <Water-based solvents> The water-based solvent may be water, or a mixed solvent of water and an organic solvent. The organic solvent may be any solvent that is compatible with water, such as alcohol-based solvents (e.g., methanol, ethanol, isopropyl alcohol, 1-propanol, etc.) or diol-based solvents (e.g., ethylene glycol, diethylene glycol, etc.).

[0157] The proportion of water in the aqueous solvent may be, for example, 60% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, or 100% by mass.

[0158] <Water-soluble polymer> The coating liquid of this embodiment may further contain a water-soluble polymer. The inclusion of a water-soluble polymer in the coating liquid increases its viscosity, which suppresses the floating and sinking of aerogel particles and glass particles, making it easier to maintain a uniform dispersion state.

[0159] Water-soluble polymers preferably have hydrophobic groups. The presence of hydrophobic groups in the water-soluble polymer improves the dispersibility of aerogel particles in the coating solution.

[0160] Examples of hydrophobic groups include alkyl groups (preferably long-chain alkyl groups, such as alkyl groups having 6 to 26 carbon atoms), ester groups, alkoxy groups, and halogen groups. Alkyl groups are preferred as hydrophobic groups, and long-chain alkyl groups are more preferred. Long-chain alkyl groups may be, for example, alkyl groups having 6 to 26 carbon atoms, or alkyl groups having 8 to 26 carbon atoms, 10 to 26 carbon atoms, 12 to 26 carbon atoms, or 15 to 26 carbon atoms.

[0161] Examples of water-soluble polymers include modified carboxyl vinyl polymers, modified polyether urethanes, cellulose resins, polyethylene oxide, polyvinyl alcohol, polyacrylates, polyvinylpyrrolidone, dextrin resins, chitin resins, and chitosan resins.

[0162] Cellulose resins can be suitably used as water-soluble polymers. Examples of cellulose resins include methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, and modified versions obtained by further modifying (e.g., hydrophobizing) these resins.

[0163] As the cellulose resin, a cellulose resin having a hydrophobic group is preferred, a cellulose resin having an alkyl group is more preferred, and a cellulose resin having a long-chain alkyl group is even more preferred. With such a cellulose resin, the above-mentioned effects are more pronounced. The long-chain alkyl group may be, for example, an alkyl group having 6 to 26 carbon atoms, an alkyl group having 8 to 26 carbon atoms, an alkyl group having 10 to 26 carbon atoms, an alkyl group having 12 to 26 carbon atoms, or an alkyl group having 15 to 26 carbon atoms.

[0164] In the cellulose-based resin, the content of the hydrophobic group (for example, an alkyl group having 6 to 26 carbon atoms) may be, based on the total amount of the cellulose-based resin, for example, 0.01% by mass or more, and may also be 0.1% by mass or more. Further, in the cellulose-based resin, the content of the hydrophobic group (for example, an alkyl group having 6 to 26 carbon atoms) may be, based on the total amount of the cellulose-based resin, for example, 5% by mass or less, and may also be 3% by mass or less.

[0165] The cellulose-based resin may be, for example, a resin having a structural unit represented by the following formula (A-1).

[0166] In formula (A-1), R Ａ represents a hydrogen atom, an alkyl group, a hydroxyalkyl group, -R Ａ１ -O-R Ａ２ group represented by (R Ａ１ represents an alkanediyl group or a hydroxyalkanediyl group, and R Ａ２ represents an alkyl group.), or -(R Ａ３ O) ｎ -R Ａ４ group represented by (R Ａ３ represents an alkanediyl group, R Ａ４ represents a hydrogen atom or an alkyl group, and n represents an integer of 2 or more.). Three R Ａ may be the same as or different from each other.

[0167] As the cellulose-based resin, it is preferable that at least one of the three R Ａ in formula (A-1) contains a hydrophobic group (for example, an alkyl group having 6 to 26 carbon atoms).

[0168] The alkyl group in R Ａ is preferably an alkyl group having 1 to 26 carbon atoms. Further, the alkyl group in R Ａ may be, for example, 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 may be, for example, 8 to 26, 10 to 26, 12 to 26, or 15 to 26.

[0169] The R ＡThe hydroxyalkyl group in is preferably a hydroxyalkyl group having 1 to 26 carbon atoms. The number of carbon atoms in the hydroxyalkyl group may be, for example, 1 or more, 2 or more, or 3 or more. Also, the number of carbon atoms in the hydroxyalkyl group may be, for example, 26 or less, 15 or less, 10 or less, or 5 or less.

[0170] R Ａ１ The number of carbon atoms in the alkanediyl group in R may be, for example, 1 or more, or 2 or more. Ａ１ The number of carbon atoms in the alkanediyl group may be, for example, 26 or less, and may be 15 or less, 10 or less, or 5 or less.

[0171] R Ａ１ The number of carbon atoms in the hydroxyalkanediyl group in R may be, for example, 1 or more, 2 or more, or 3 or more. Ａ１ The number of carbon atoms in the hydroxyalkanediyl group in this product may be, for example, 26 or less, and may also be 15 or less, 10 or less, or 5 or less.

[0172] R Ａ２ In R, alkyl groups having 1 to 26 carbon atoms are preferred. Ａ２ The alkyl group in may be, for example, 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 in the long-chain alkyl group may be, for example, 8 to 26, 10 to 26, 12 to 26, or 15 to 26.

[0173] R Ａ３ The number of carbon atoms in the alkanediyl group in R may be, for example, 1 or more, or 2 or more. Ａ１ The number of carbon atoms in the alkanediyl group may be, for example, 26 or less, and may be 15 or less, 10 or less, 5 or less, or 3 or less.

[0174] R Ａ４ In R, alkyl groups having 1 to 26 carbon atoms are preferred. Ａ４The alkyl group in may be, for example, 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 in the long-chain alkyl group may be, for example, 8 to 26, 10 to 26, 12 to 26, or 15 to 26.

[0175] <Fibrous material> The coating liquid of this embodiment may further contain a fibrous material. The fibrous material can function as an anchor between aerogel particles, further improving the strength of the composite material.

[0176] The fibrous material is not particularly limited and may be organic or inorganic fiber.

[0177] Examples of organic fibers include polyamide fibers, polyimide fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, polyvinyl chloride fibers, polyester fibers, polyacrylonitrile fibers, polyethylene fibers, polypropylene fibers, polyurethane fibers, phenolic fibers, polyether ester fibers, polylactic acid fibers, and polycarbonate fibers.

[0178] Examples of inorganic fibers include glass fibers, carbon fibers, ceramic fibers, and metal fibers.

[0179] As for the fibrous material, glass fibers are preferred from the viewpoint of strength, heat resistance, etc.

[0180] The fiber diameter of the fibrous material may be, for example, 0.1 μm or more, and from the viewpoint of the strength of the fibrous material, it may be 1 μm or more, 3 μm or more, or 5 μm or more. Alternatively, the fiber diameter of the fibrous material may be, for example, 100 μm or less, and from the viewpoint of frequency of presence in the coating liquid or composite material, it may be 80 μm or less, 50 μm or less, or 30 μm or less.

[0181] The fiber length of the fibrous material may be, for example, 0.1 mm or more, and from the viewpoint of further improving the strength of the composite material, it may be 0.5 mm or more, 1 mm or more, or 2 mm or more. Alternatively, the fiber length of the fibrous material may be, for example, 20 mm or less, and from the viewpoint of making it less likely to re-aggregate in the coating liquid, it may be 10 mm or less, 8 mm or less, or 5 mm or less.

[0182] The coating liquid of this embodiment may further contain other components besides those mentioned above. Examples of other components include thickeners, pigments, leveling agents, and so on.

[0183] Examples of thickening agents include fine particles of fumed silica and clay minerals.

[0184] <Content of each component> In the coating liquid of this embodiment, the total content of aerogel particles and glass particles may be, for example, 70% by volume or more, 75% by volume or more, or 80% by volume or more, based on the total volume of solids. The coating liquid of this embodiment has excellent film-forming properties due to the combined use of aerogel particles and glass particles, and even with a high-filling composition with a large total content of aerogel particles and glass particles, a composite material can be formed with good film-forming properties. Furthermore, in the coating liquid of this embodiment, the total content of aerogel particles and glass particles may be, for example, 99% by volume or less, 97% by volume or less, 95% by volume or less, or 90% by volume or less, based on the total volume of solids.

[0185] In the coating solution of this embodiment, the proportion of glass particles to the total amount of aerogel particles (the content of glass particles relative to the total amount of aerogel particles and glass particles) may be, for example, 5% by volume or more, and may be 10% by volume or more, 20% by volume or more, 30% by volume or more, or 40% by volume or more. That is, the proportion of aerogel particles to the total amount of aerogel particles and glass particles (the content of aerogel particles relative to the total amount of aerogel particles and glass particles) may be, for example, 95% by volume or less, and may be 90% by volume or less, 80% by volume or less, 70% by volume or less, or 60% by volume or less. When the proportion of glass particles is high (the proportion of aerogel particles is low), film formation performance is further improved and cracking in the composite material tends to be more significantly suppressed.

[0186] Furthermore, in the coating liquid of this embodiment, the proportion of glass particles to the total amount of aerogel particles and glass particles (the content of glass particles based on the total amount of aerogel particles and glass particles) may be, for example, 90 vol% or less, 80 vol% or less, 70 vol% or less, or 60 vol% or less. That is, the proportion of aerogel particles to the total amount of aerogel particles and glass particles (the content of aerogel particles based on the total amount of aerogel particles and glass particles) may be, for example, 10 vol% or more, 20 vol% or more, 30 vol% or more, or 40 vol% or more. When the proportion of glass particles is low (the proportion of aerogel particles is high), the thermal insulation performance of the aerogel particles is more pronounced, and the thermal insulation performance of the composite material tends to improve further.

[0187] In the coating liquid of this embodiment, the binder resin content may be, for example, 1 vol% or more based on the total volume of solids, and may also be 3 vol% or more, 5 vol% or more, or 10 vol% or more. A higher binder resin content tends to improve film formation and further suppress cracking in the composite material. Alternatively, in the coating liquid of this embodiment, the binder resin content may be, for example, 30 vol% or less based on the total volume of solids, and may also be 25 vol% or less, or 20 vol% or less. A lower binder resin content tends to further improve the thermal insulation properties of the composite material.

[0188] Furthermore, the upper limit of the numerical range for the binder resin content in the coating solution may be appropriately adjusted so that the total amount of solids in the coating solution is 100% by volume.

[0189] In the coating solution of this embodiment, the total amount of aerogel particles, glass particles, and binder resin may be, for example, more than 80% by volume, and may be 85% or more, 90% or more, or 92% or more by volume, based on the total amount of solids in the coating solution. This will result in the above-mentioned effects being more pronounced.

[0190] The content of the aqueous solvent in the coating liquid of this embodiment may be appropriately changed depending on the desired viscosity of the coating liquid. For example, the content of the aqueous solvent may be such that the solid content concentration of the coating liquid falls within the preferred range described later.

[0191] The solid content concentration of the coating liquid in this embodiment may be, for example, 20% by mass or more, 25% by mass or more, 28% by mass or more, or 30% by mass or more. Alternatively, the solid content concentration of the coating liquid in this embodiment may be, for example, 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less.

[0192] When the coating liquid of this embodiment contains a water-soluble polymer, the content of the water-soluble polymer may be, for example, 0.01% by volume or more, 0.05% by volume or more, 0.1% by volume or more, or 0.15% by volume or more, based on the total volume of solids in the coating liquid. A higher content of water-soluble polymer tends to improve the dispersibility of aerogel particles and increase the viscosity of the coating liquid, further suppressing the buoyancy of aerogel particles and glass particles. Alternatively, the content of the water-soluble polymer may be, for example, 5% by volume or less, 3% by volume or less, 1% by volume or less, or 0.5% by volume or less, based on the total volume of solids in the coating liquid. A lower content of water-soluble polymer tends to lower the viscosity of the coating liquid and facilitate the formation of a coating film.

[0193] When the coating liquid of this embodiment contains fibrous material, the content of fibrous material may be, for example, 0.01% by volume or more, 0.1% by volume or more, 0.3% by volume or more, or 0.5% by volume or more, based on the total volume of solids in the coating liquid. A higher content of fibrous material tends to improve the strength of the composite material. Alternatively, the content of fibrous material may be, for example, 5% by volume or less, 3% by volume or less, 1% by volume or less, or 0.8% by volume or less, based on the total volume of solids in the coating liquid. A lower content of fibrous material tends to result in a relatively larger amount of aerogel particles in the composite material, which tends to improve the heat insulation properties.

[0194] In the coating liquid of this embodiment, the total amount of aerogel particles, glass particles, binder resin, water-soluble polymer, and fibrous material may be, for example, 90% by volume or more, 95% by volume or more, 97% by volume or more, or 99% by volume or more, or 100% by volume, based on the total amount of solids in the coating liquid. That is, in the coating liquid of this embodiment, the content of other components other than aerogel particles, glass particles, binder resin, water-soluble polymer, and fibrous material may be, for example, 10% by volume or less, 5% by volume or less, 3% by volume or less, or 1% by volume or less, or 0% by volume, based on the total amount of solids in the coating liquid.

[0195] <Method for Manufacturing the Coating Liquid> The method for manufacturing the coating liquid of this embodiment is not particularly limited. The coating liquid of this embodiment may be manufactured by a manufacturing method that includes a mixing step of mixing a composition (1) containing aerogel particles, glass particles and an aqueous solvent with a composition (2) containing a binder resin and an aqueous solvent to obtain the coating liquid.

[0196] Composition (1) may further contain a water-soluble polymer. Furthermore, composition (1) may further contain glass fibers.

[0197] The above manufacturing method may further include, for example, a step (i) of preparing a composition (1-1) containing a water-soluble polymer and an aqueous solvent, and a step (ii) of mixing the composition (1-1) with aerogel particles and glass particles.

[0198] Composition (1-1) may further contain glass fibers.

[0199] Step (i) may be, for example, a step of stirring and mixing a water-soluble polymer, an aqueous solvent, and (if necessary, glass fibers). The stirring conditions are not particularly limited, but from the viewpoint of suppressing damage to the glass fibers, low-speed, low-shear conditions are preferred.

[0200] In step (i), hot water (for example, water at 40°C or higher) may be used as at least a portion of the aqueous solvent. This reduces the viscosity of the mixed solution of the water-soluble polymer and the aqueous solvent (composition (1-1)), making the mixed solution more uniform and facilitating the dispersion of glass fibers.

[0201] Step (ii) may be, for example, a step of mixing composition (1-1) with glass particles, and then mixing in aerogel particles. With this mixing order, the viscosity of composition (1-1) decreases due to the mixing of glass particles, making it easier to mix in aerogel particles, and further suppressing damage to aerogel particles, glass particles, glass fibers, etc. during mixing.

[0202] Step (ii) may be a step of stirring and mixing composition (1-1), glass particles, and aerogel particles. The stirring conditions are not particularly limited, but from the viewpoint of suppressing breakage of the glass particles and aerogel particles, low speed and low shear are preferred.

[0203] In step (ii), the presence of glass particles suppresses aggregation of aerogel particles, making it easier for the aerogel particles to disperse without forming aggregates.

[0204] Composition (2) may be, for example, a composition containing emulsion particles including a binder resin and an aqueous solvent.

[0205] The above manufacturing method may further include, for example, a step (iii) of obtaining a composition (2) containing emulsion particles including a binder resin and an aqueous solvent by emulsion polymerization.

[0206] In step (iii), the method of emulsion polymerization is not particularly limited and may be appropriately selected from known methods.

[0207] The mixing step may be a step of stirring and mixing composition (1) and composition (2). The stirring conditions are not particularly limited, but from the viewpoint of suppressing damage to glass particles, aerogel particles, and glass fibers, low speed and low shear are preferred.

[0208] According to the coating liquid of this embodiment, even when applied to a curved area or when the film thickness after drying is 1 mm or more, a composite material can be formed while suppressing the occurrence of cracks. Since this composite material contains aerogel particles and has excellent heat insulation properties, it can be suitably used as a heat insulating material.

[0209] (Composite Material) The composite material of this embodiment contains aerogel particles, glass particles, and a binder resin. The composite material of this embodiment may further contain a water-soluble polymer. The composite material of this embodiment may further contain glass fibers.

[0210] Examples of components contained in the composite material of this embodiment include those that are the same as the components in the coating liquid described above.

[0211] In the composite material of this embodiment, the total content of aerogel particles and glass particles may be, for example, 70% by volume or more, 75% by volume or more, or 80% by volume or more, based on the total volume of the composite material. Furthermore, in the composite material of this embodiment, the total content of aerogel particles and glass particles may be, for example, 99% by volume or less, 97% by volume or less, 95% by volume or less, or 90% by volume or less, based on the total volume of the composite material.

[0212] In the composite material of this embodiment, the proportion of glass particles to the total amount of aerogel particles and glass particles (the content of glass particles based on the total amount of aerogel particles and glass particles) may be, for example, 5 volume% or more, 10 volume% or more, 20 volume% or more, 30 volume% or more, or 40 volume% or more. That is, the proportion of aerogel particles to the total amount of aerogel particles and glass particles (the content of aerogel particles based on the total amount of aerogel particles and glass particles) may be, for example, 95 volume% or less, 90 volume% or less, 80 volume% or less, 70 volume% or less, or 60 volume% or less.

[0213] Furthermore, in the composite material of this embodiment, the proportion of glass particles to the total amount of aerogel particles and glass particles (the content of glass particles based on the total amount of aerogel particles and glass particles) may be, for example, 90 volume% or less, 80 volume% or less, 70 volume% or less, or 60 volume% or less. That is, the proportion of aerogel particles to the total amount of aerogel particles and glass particles (the content of aerogel particles based on the total amount of aerogel particles and glass particles) may be, for example, 10 volume% or more, 20 volume% or more, 30 volume% or more, or 40 volume% or more.

[0214] In the composite material of this embodiment, the binder resin content may be, for example, 1 volume% or more, 3 volume% or more, 5 volume% or more, or 10 volume% or more, based on the total volume of the composite material. Alternatively, in the composite material of this embodiment, the binder resin content may be, for example, 30 volume% or less, 25 volume% or less, or 20 volume% or less, based on the total volume of the composite material.

[0215] Furthermore, the upper limit of the numerical range for the binder resin content in the composite material may be adjusted as appropriate so that the total amount of each component in the composite material equals 100% by volume.

[0216] When the composite material of this embodiment contains a water-soluble polymer, the content of the water-soluble polymer may be, for example, 0.01% by volume or more, 0.05% by volume or more, 0.1% by volume or more, or 0.15% by volume or more, based on the total volume of the composite material. Alternatively, the content of the water-soluble polymer may be, for example, 5% by volume or less, 3% by volume or less, 1% by volume or less, or 0.5% by volume or less, based on the total volume of the composite material.

[0217] When the composite material of this embodiment contains fibrous material, the content of fibrous material may be, for example, 0.01% by volume or more, 0.1% by volume or more, 0.3% by volume or more, or 0.5% by volume or more, based on the total volume of the composite material. Alternatively, the content of fibrous material may be, for example, 5% by volume or less, 3% by volume or less, 1% by volume or less, or 0.8% by volume or less, based on the total volume of the composite material.

[0218] In the composite material of this embodiment, the total amount of aerogel particles, glass particles, binder resin, water-soluble polymer, and fibrous material may be, for example, 90% by volume or more, 95% by volume or more, 97% by volume or more, or 99% by volume or more, or 100% by volume, based on the total amount of the composite material. That is, in the composite material of this embodiment, the content of other components other than aerogel particles, glass particles, binder resin, water-soluble polymer, and fibrous material may be, for example, 10% by volume or less, 5% by volume or less, 3% by volume or less, or 1% by volume or less, or 0% by volume, based on the total amount of the composite material.

[0219] The composite material of this embodiment may be the dried product of the coating liquid described above. That is, the composite material of this embodiment may be formed, for example, by removing at least a portion of the aqueous solvent from the coating film of the coating liquid described above.

[0220] The composite material of this embodiment may have a thick film portion having a thickness of 1 mm or more. The thickness of the thick film portion may be, for example, 1 mm or more, 3 mm or more, or 5 mm or more. Alternatively, the thickness of the thick film portion may be, for example, 30 mm or less, or 20 mm or less.

[0221] The composite material of this embodiment has pores resulting from aerogel particles (and possibly hollow glass particles). The pore volume of the composite material is, for example, 0.01 cm³. ３ It may be 0.03 cm or more per gram. ３ / g or more, 0.05cm ３ / g or more, 0.07cm ３ / g or more, or 0.09 cm ３ It may be greater than or equal to / g. Also, the pore volume of the composite material may be, for example, 10 cm³. ３ It may be less than or equal to / g, and 5cm ３ / g or less, 3cm ３ / g or less, 1cm ３ / g or less, or 0.5cm ３ It may be less than / g.

[0222] The thermal conductivity of the composite material in this embodiment may be, for example, 0.06 W / (m·K) or less, 0.05 W / (m·K) or less, or 0.04 W / (m·K) or less. Alternatively, the thermal conductivity of the composite material in this embodiment may be, for example, 0.02 W / (m·K) or more, or 0.025 W / (m·K) or more.

[0223] The composite material of this embodiment can be manufactured by a manufacturing method that includes, for example, a coating step of applying the above-mentioned coating liquid onto a support to obtain a coating film, and a removal step of removing at least a portion of the aqueous solvent from the coating film to obtain a composite material.

[0224] The support to which the coating liquid is applied is not particularly limited. The support may be peeled off from the composite material after its manufacture, or it may be used without being peeled off from the composite material. The support may, for example, be the object to which the composite material is applied. The material constituting the support is not particularly limited and may be, for example, metal, ceramic, glass, resin, or mixtures thereof. Furthermore, the form of the support may be appropriately selected according to the intended use, material, etc., and may be, for example, block-shaped, sheet-shaped, powder-shaped, fibrous, etc.

[0225] In the coating process, the method of applying the coating solution is not particularly limited and may be, for example, dip coating, spray coating, spin coating, roll coating, etc.

[0226] The thickness of the coating film is not particularly limited and may be adjusted as appropriate so that the thickness of the composite material after drying is the desired thickness. In this embodiment, since the above-described coating liquid is used, even when a thick coating film is applied, cracking during drying is significantly suppressed, and a composite material with fewer cracks can be formed. The coating film may, for example, have a maximum thickness of 2 mm or more, or a maximum thickness of 5 mm or more. The maximum thickness of the coating film may be 30 mm or less, or 20 mm or less.

[0227] The method for removing the aqueous solvent from the coating film is not particularly limited and may include, for example, heat treatment (e.g., heating to 40 to 150°C), reduced pressure treatment (e.g., treatment under reduced pressure of 10,000 Pa or less), or a method that performs both of these treatments.

[0228] The composite material of this embodiment possesses excellent thermal insulation, heat resistance, and flame retardancy derived from aerogel. Therefore, this composite material can be applied as a thermal insulation material in cryogenic containers, space applications, construction, automotive, home appliances, semiconductors, industrial equipment, and other uses. In addition to its use as a thermal insulation material, this composite material can also be used as a water-repellent, sound-absorbing, vibration-damping, and catalyst support material.

[0229] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above.

[0230] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0231] (Example 1) (1) Emulsion production In a reaction vessel equipped with a stirring device, thermometer, condenser and dropping funnel, 160 parts by mass of ion-exchanged water and 1.2 parts by mass of a nonionic emulsifier (Emulgen 1150S-60, a 60% aqueous solution of polyoxyethylene alkyl ether, manufactured by Kao Corporation, HLB value: 18.5) were charged and stirred, and after raising the temperature to 65°C, dissolved oxygen was removed by venting nitrogen into the reaction vessel.

[0232] Next, 274 parts by mass of butyl acrylate, 173.5 parts by mass of methyl methacrylate, 24 parts by mass of 2-hydroxyethyl methacrylate, 9 parts by mass of methacrylic acid, 215 parts by mass of deionized water, and 48.8 parts by mass of nonionic emulsifier (Emulgen 1150S-60, a 60% aqueous solution of polyoxyethylene alkyl ether, manufactured by Kao Corporation, HLB value: 18.5) were mixed and emulsified in a homomixer to obtain a monomer emulsion.

[0233] Three percent of this monomer emulsion was added to the reaction vessel under stirring, and 0.7 parts by mass of "Triganox A-W70" (manufactured by Kayaku Nurion Co., Ltd., a 70% aqueous solution of tert-butyl hydroperoxide) and 0.23 parts by mass of ascorbic acid were added as radical polymerization initiators, and the mixture was reacted for 15 minutes. Next, the remaining 97% monomer emulsion, a solution of 0.9 parts by mass of "Triganox A-W70" dissolved in 60 parts by mass of deionized water, and a solution of 0.37 parts by mass of ascorbic acid dissolved in 60 parts by mass of deionized water were each added dropwise to the reaction vessel over 4 hours and reacted. After the dropwise addition was complete, the mixture was stirred at 65°C for 1 hour, then cooled to below 40°C, and 2.9 parts by mass of 26% aqueous ammonia was added as a neutralizing agent. This yielded an emulsion containing emulsion particles containing a binder resin and a nonionic emulsifier, and water.

[0234] The properties of the emulsion were as follows: • Non-volatile content: 49.5% by mass • Viscosity at 23°C: 35 mPa·s • pH at 23°C: 8.6 • Minimum film formation temperature (MFT): 5°C • Glass transition temperature of the binder resin: 9°C • Average particle size of emulsion particles: 210 nm

[0235] [Measurement of Non-Volatile Content Concentration of Emulsion] 1 g of emulsion was weighed and placed on a 5 cm diameter aluminum dish, then placed in a drying oven. The emulsion was dried for 1 hour at 1 atmosphere (1013 hPa) and 105°C while circulating the air inside the oven, and the mass of the remaining components was measured. The mass ratio (mass%) of the above components remaining after drying to the mass of the emulsion before drying (1 g) was calculated and defined as the non-volatile content concentration (mass%).

[0236] [Measurement of emulsion viscosity] A BL-type viscometer was used as the measuring instrument, and the viscosity was measured under the conditions of a temperature of 23°C and a rotation speed of 60 rpm.

[0237] [Measurement of Emulsion pH] The pH at 23°C was measured using a pH meter (HM-30G, glass electrode type hydrogen ion concentration indicator, manufactured by Toa DKK Co., Ltd.).

[0238] [Measurement of average particle size of emulsified particles] At 23°C, the average particle size (d50) of emulsified particles was measured using dynamic light scattering (DLS) with a MICROTRAC UPA150 (manufactured by Microtrac Bell Co., Ltd.).

[0239] [Measurement of Minimum Film Forming Temperature (MFT)] An emulsion was applied to the measuring surface of a thermal gradient type MFT measuring instrument using a 0.3 mm applicator and dried in a windless environment. The MFT was measured by visually observing for cracks in the dried film that indicated poor film formation.

[0240] [Glass transition temperature (Tg) of binder resin] The glass transition temperature (Tg) of the binder resin was determined by measuring the temperature dependence of the loss tangent using a rheometer (MCR-102, manufactured by Anton Paar). Specifically, a 12 mm diameter parallel plate was used, and the measurement conditions were vibration mode with a frequency of 1 Hz and a strain of 2%. After taking a small amount of emulsion onto the measurement plate, the plate was brought into contact with the resin, and the temperature was increased from 30°C to 180°C at a rate of 10°C / min to remove volatile components from the emulsion and to ensure the resin adhered to the plate. Next, the temperature was decreased from 180°C to 0°C at a rate of 2°C / min, and the loss tangent was measured at intervals of 1 point / °C. The temperature at which the loss tangent was maximum was defined as the glass transition temperature.

[0241] (2) Preparation of coating solution In a 500 mL separable flask, 1 part by mass of 90 L of San Jerose (manufactured by Daido Chemical Industries, Ltd.) as a water-soluble polymer, 8 parts by mass of isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., reagent), 82 parts by mass of hot water (70°C), and 4 parts by mass of glass fiber (manufactured by Nitto Boseki Co., Ltd., product name: CS 3J-891) were placed and stirred at 200 rpm for 1 minute using a mechanical stirrer to obtain a dispersion. Subsequently, while cooling the flask in an ice bath, the 90 L of San Jerose was dissolved by stirring at 200 rpm using a mechanical stirrer to obtain Pregel, which is an aqueous solution of 90 L of San Jerose. In a planetary mixer (Primix, 2P-1 model), 95 parts by mass of the above Pregel and hollow glass particles (i) (3M, product name: Glass Bubbles K1, average particle size (D50) 65 μm, true density 0.13 g / cm³) are mixed. ３) was added in 6.5 parts by mass and stirred at 25 rpm for 5 minutes. Subsequently, 15 parts by mass of aerogel particles (i) (manufactured by CABOT, product name: ENOVA MT1100, particle diameter 2-24 μm, average particle diameter (D50) 10 μm) was added and stirred at 25 rpm for 10 minutes. Subsequently, 86 parts by mass of the emulsion obtained in (1) was added and stirred at 25 rpm for 15 minutes to obtain the coating solution. In the coating solution, based on the total volume of solids, the total content of hollow glass particles and aerogel particles was 84.9 volume% (hollow glass particle content was 21.2 volume%, aerogel particle content was 63.7 volume%), the water-soluble polymer content was 0.3 volume%, and the binder resin content was 14.1 volume%.

[0242] (3) Manufacturing and evaluation of composite materials Using the coating liquid obtained in (2), composite materials (insulating materials) were manufactured and evaluated using the following method. The results are shown in Table 1.

[0243] [Crack evaluation at 23°C] A frame measuring 40 mm in length and width and 2 mm in thickness was prepared on aluminum foil (manufactured by UACJ Corporation, product name: Myfoil Thick Type 50, thickness: 50 μm) using fluororesin, and the coating liquid was applied to the inside of the frame using a spatula. Next, the frame was left in a low-temperature constant temperature and humidity chamber (HIFLEX FX411N, manufactured by Kusumoto Kasei Co., Ltd.) set to 23°C and 60% RH for 12 hours to remove the liquid medium from the coating liquid and obtain a composite material. The degree of cracking of the obtained composite material was evaluated as follows: A if there were no cracks throughout, B if there were cracks in some parts, and C if there were cracks throughout.

[0244] [Crack Evaluation on a 90° Bending Surface] An aluminum plate (Standard Test Piece, A5052P, 0.8 mm thick, 50 mm wide, 100 mm long) was bent at a point where its longitudinal direction was divided in a 6:4 ratio, resulting in a radius of curvature of 1 mm and a bending angle of 90 degrees, to be used as the evaluation substrate. A 2 mm thick Teflon spacer made of fluororesin was prepared on the side edge of the evaluation substrate, and the coating liquid was applied between the spacers using a spatula. Next, the substrate was left in a low-temperature constant temperature and humidity chamber (HIFLEX FX411N, manufactured by Kusumoto Kasei Co., Ltd.) set to 23°C and 60% RH for 12 hours to remove the liquid medium from the coating liquid and obtain a composite material. The degree of cracking of the obtained composite material was evaluated as follows: A if there were no cracks throughout, B if there were cracks in some areas, and C if there were cracks throughout.

[0245] [Evaluation of Thermal Conductivity] A frame measuring 200 mm in length and width and 3 mm in thickness, made of fluororesin, was prepared on aluminum foil (manufactured by UACJ Corporation, product name: Myfoil Thick Type 50, thickness: 50 μm), and the coating liquid was applied to the inside of the frame using a spatula. After leaving it at room temperature (23°C) for 12 hours, the liquid medium was removed from the coating liquid to obtain a composite material with a thickness of 1.5 mm. Furthermore, this operation was repeated to obtain a composite material with a thickness of 3.0 mm. The thermal conductivity of the obtained composite material was measured using a steady-state method with a thermal conductivity measuring device "HFM-446" (manufactured by NETZSCH, product name).

[0246] (Example 2) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the amount of Sanjelose 90 L was changed to 0.8 parts by mass, the amount of hollow glass particles (i) was changed to 13 parts by mass, the amount of aerogel particles (i) was changed to 10 parts by mass, and the stirring conditions after emulsion addition were changed to 25 rpm for 15 minutes and 50 rpm for 5 minutes. In the coating solution, the total content of hollow glass particles and aerogel particles was 85.0 volume% (42.5 volume% of hollow glass particles and 42.5 volume% of aerogel particles), the content of water-soluble polymer was 0.3 volume%, and the content of binder resin was 14.2 volume%.

[0247] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0248] (Example 3) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the amount of Sanjelose 90 L was changed to 1.2 parts by mass, the amount of hollow glass particles (i) was changed to 19.5 parts by mass, the amount of aerogel particles (i) was changed to 5 parts by mass, and the stirring conditions after emulsion addition were changed to 25 rpm for 15 minutes and 50 rpm for 10 minutes. In the coating solution, the total content of hollow glass particles and aerogel particles was 84.9 vol% (63.7 vol% of hollow glass particles and 21.2 vol% of aerogel particles), the content of water-soluble polymer was 0.4 vol%, and the content of binder resin was 14.1 vol%.

[0249] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0250] (Example 4) Instead of hollow glass particles (i), 25 parts by mass of hollow glass particles (ii) (3M, product name: Glass Bubbles K25, average particle size (D50) 55 μm, true density 0.25 g / cm³) were used. ３ A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the following was done: the amount of aerogel particles (i) was changed to 10 parts by mass, and the stirring conditions after emulsion addition were changed to 25 rpm for 15 minutes and 50 rpm for 30 minutes. In the coating solution, the total content of hollow glass particles and aerogel particles was 84.8 vol% (42.4 vol% of hollow glass particles and 42.4 vol% of aerogel particles), the content of water-soluble polymer was 0.4 vol%, and the content of binder resin was 14.1 vol%.

[0251] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0252] (Example 5) Instead of hollow glass particles (i), 46 parts by mass of hollow glass particles (iii) (3M, product name: Glass Bubbles iM16K, average particle size (D50) 20 μm, true density 0.46 g / cm³) were used. ３A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the amount of aerogel particles (i) was changed to 10 parts by mass and the stirring conditions after emulsion addition were changed to 25 rpm for 15 minutes and 50 rpm for 15 minutes. In the coating solution, the total content of hollow glass particles and aerogel particles was 84.8 vol% (42.4 vol% of hollow glass particles and 42.4 vol% of aerogel particles), the content of water-soluble polymer was 0.4 vol%, and the content of binder resin was 14.1 vol%.

[0253] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0254] (Example 6) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the isopropyl alcohol was changed to a mixed solution of 4 parts by mass of isopropyl alcohol and 4 parts by mass of diethylene glycol, the amount of hollow glass particles (i) was changed to 13 parts by mass, and the amount of aerogel particles (i) was changed to 10 parts by mass. In the coating solution, the total content of hollow glass particles and aerogel particles was 84.8 vol% (42.4 vol% of hollow glass particles and 42.4 vol% of aerogel particles), the content of water-soluble polymer was 0.4 vol%, and the content of binder resin was 14.1 vol%.

[0255] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0256] (Example 7) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the amount of hollow glass particles (i) was changed to 13 parts by mass, and 10 parts by mass of aerogel particles (ii) (manufactured by JIS, product name: JIS AeroVa, particle diameter 2 to 30 μm, average particle diameter (D50) 8 μm) were added in place of aerogel particles (i). In the coating solution, the total content of hollow glass particles and aerogel particles was 84.9 volume%, based on the total volume of solids (hollow glass particle content was 21.2 volume%, aerogel particle content was 63.7 volume%), the water-soluble polymer content was 0.3 volume%, and the binder resin content was 14.1 volume%.

[0257] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0258] (Example 8) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the amount of hollow glass particles (i) was changed to 25 parts by mass, and 10 parts by mass of aerogel particles (iii) (particle diameter 2 to 100 μm, average particle diameter (D50) 40 μm) were added in place of aerogel particles (i). In the coating solution, the total content of hollow glass particles and aerogel particles was 83.7 volume% (45.7 volume% of hollow glass particles, 38.0 volume% of aerogel particles), the content of water-soluble polymer was 0.4 volume%, and the content of binder resin was 15.2 volume%.

[0259] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0260] The aerogel particles (iii) were manufactured by the following method. <Preparation of aerogel particles (iii)> 100.0 parts by mass of PL-2L (manufactured by Fuso Chemical Industries, Ltd., product name) as a silica particle-containing raw material, 80.0 parts by mass of water, 0.5 parts by mass of acetic acid as an acid catalyst, 1.0 part by mass of cetyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd.) as a cationic surfactant, and 150.0 parts by mass of urea as a thermally hydrolyzable product were mixed together. To this, 60.0 parts by mass of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM-13), 20.0 parts by mass of dimethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KMB-22), and 20.0 parts by mass of a bifunctional alkoxy-modified polysiloxane compound (hereinafter referred to as "polysiloxane compound A") were added as silicon compounds, and the mixture was reacted at 25°C for 2 hours to obtain a sol. The obtained sol was gelled at 60°C and then aged at 60°C for 48 hours to obtain a wet gel. The above-mentioned "Polysiloxane Compound A" was synthesized as follows: First, in a 1-liter three-necked flask equipped with a stirrer, thermometer, and Liebig condenser, 100.0 parts by mass of dimethylpolysiloxane XC96-723 (product name, manufactured by Momentive Performance Materials Japan LLC), which has silanol groups at both ends, 181.3 parts by mass of methyltrimethoxysilane, and 0.50 parts by mass of t-butylamine were mixed and reacted at 30°C for 5 hours. After that, this reaction solution was heated at 140°C for 2 hours under a reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining a polysiloxane compound modified with bifunctional alkoxy at both ends (Polysiloxane Compound A). Subsequently, the obtained wet gel was transferred to a plastic bottle, sealed, and then pulverized at 27,000 rpm for 10 minutes using an extreme mill (MX-1000XTS, manufactured by AS ONE Corporation) to obtain particulate wet gel. The obtained particulate wet gel was immersed in 2500.0 parts by mass of methanol and washed at 25°C for 24 hours. This washing operation was repeated a total of three times, with the methanol being replaced each time. Next, the washed particulate wet gel was immersed in 2500.0 parts by mass of heptane, a low surface tension solvent, and the solvent was replaced at 25°C for 24 hours. This solvent replacement operation was repeated a total of three times, with the methanol being replaced each time.The washed and solvent-replaced particulate wet gel was dried at 40°C for 96 hours under normal pressure, and then dried further at 150°C for 2 hours. Finally, it was passed through a sieve (manufactured by Tokyo Screen Co., Ltd., mesh size 45 μm, wire diameter 32 μm) to obtain aerogel particles (iii).

[0261] (Example 9) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that 265 parts by mass of glass particles (iv) (manufactured by Unitika Glass Beads Co., Ltd., product name: UBS-0010E, particle size 1 to 10 μm) were added instead of hollow glass particles (i), and the amount of aerogel particles was changed to 10 parts by mass. In the coating solution, the total content of glass particles and aerogel particles was 85.0 volume% based on the total volume of solids (the content of glass particles was 42.9 volume%, the content of aerogel particles was 42.1 volume%), the content of water-soluble polymer was 0.4 volume%, and the content of binder resin was 14.0 volume%.

[0262] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0263] (Comparative Example 1) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that hollow glass particles (i) were not included and the amount of aerogel particles (i) was changed to 20 parts by mass. In the coating solution, the content of aerogel particles was 84.9% by volume, the content of water-soluble polymer was 0.7% by volume, and the content of binder resin was 14.1% by volume, based on the total volume of solids.

[0264] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0265] (Comparative Example 2) A coating solution was obtained in the same manner as in "(2) Production of coating solution" of Example 1, except that the amount of hot water was changed to 164 parts by mass, hollow glass particles (i) were omitted, and the amount of aerogel particles (i) was changed to 20 parts by mass. In the coating solution, the content of aerogel particles was 84.9% by volume, the content of water-soluble polymer was 0.7% by volume, and the content of binder resin was 14.1% by volume, based on the total volume of solids.

[0266] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0267] (Comparative Example 3) The coating solution was manufactured in the same manner as in Example 1, "(2) Manufacture of Coating Solution," except that the amount of Sanjelose 90 L was changed to 0.5 parts by mass, the amount of hot water was changed to 164 parts by mass, hollow glass particles (i) were omitted, and the amount of aerogel particles (i) was changed to 20 parts by mass. However, in Comparative Example 3, the viscosity increased significantly after the addition of aerogel particles, making stirring after emulsion addition difficult, and making it difficult to manufacture a uniform coating solution.

[0268] (Comparative Example 4) A coating solution was obtained in the same manner as in Example 1, "(2) Preparation of Coating Solution," except that the isopropyl alcohol was changed to a mixed solution of 4 parts by mass of isopropyl alcohol and 4 parts by mass of diethylene glycol, the amount of hot water was changed to 164 parts by mass, the hollow glass particles (i) were omitted, and the amount of aerogel particles (i) was changed to 20 parts by mass. In the coating solution, the content of aerogel particles was 84.9% by volume, the content of water-soluble polymer was 0.7% by volume, and the content of binder resin was 14.1% by volume, based on the total volume of solids.

[0269] Using the obtained coating solution, composite materials were manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0270]

[0271]

[0272]

Claims

A coating liquid containing aerogel particles, glass particles, a binder resin, and an aqueous solvent. 　 The coating liquid according to claim 1, wherein the glass particles include hollow glass particles. 　 The coating liquid according to claim 1, further containing a water-soluble polymer. 　 The coating solution according to claim 3, wherein the water-soluble polymer has a hydrophobic group. 　 A composite material which is a dried product of a coating liquid according to any one of claims 1 to 4. 　 The composite material according to claim 5, having a thick film portion having a thickness of 1 mm or more. 　 A composite material containing aerogel particles, glass particles, and a binder resin. 　 The composite material according to claim 7, further containing a water-soluble polymer. 　 The composite material according to claim 7, having a thick film portion having a thickness of 1 mm or more. 　 A coating step of applying the coating liquid according to any one of claims 1 to 4 onto a support to obtain a coating film, A removal step of removing at least a portion of the aqueous solvent from the coating film to obtain a composite material containing aerogel particles, glass particles, and a binder resin, A method for manufacturing composite materials, including 　 The manufacturing method according to claim 10, wherein the composite material has a thick film portion having a thickness of 1 mm or more.

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