Coating liquid, method for producing coating liquid, and method for producing composite material

Abstract

A coating liquid comprising: emulsified particles containing a binder resin; aerogel particles; a water-soluble polymer having a hydrophobic group; and a liquid medium. The binder resin contains a structural unit derived from a first monomer having a Tg of less than 0 DEG C in a homopolymer.

Description

Technical Field

[0001] The invention relates to a coating liquid, a method for manufacturing the coating liquid and a method for manufacturing a composite material. Background Art

[0002] Aerogel is known as a material excellent for thermal insulation. In addition, a method of processing aerogel into particles and using it as a constituent material of thermal insulation has been proposed (for example, Patent Documents 1 and 2). Patent Document 1 proposes using particulate aerogel as a filler between resin plates, etc., that constitute thermal insulation windows. Patent Document 2 shows the following method: After preparing an aqueous dispersion containing aerogel particles and organic fibers, water is evaporated, and the intermediate product obtained is further pressurized to form a thermal insulation material (molded body).

[0003] Previous technical literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-091943

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-035044 Summary of the invention

[0007] Technical issues to be solved by the invention

[0008] Composite materials in which aerogel particles are dispersed in a binder resin are expected to be applied to a wider range of objects and uses by being liquid-coated. However, when attempting to liquid-coat the composite material, it is sometimes difficult to evenly disperse the aerogel particles and the binder resin in the coating liquid.

[0009] Furthermore, in order to make the coating liquid applicable to various uses, it is desired to have excellent film-forming properties at low temperatures.

[0010] Therefore, an object of the present invention is to provide a coating liquid having excellent dispersibility of aerogel particles and a binder resin, capable of forming a composite material containing aerogel particles and a binder resin, and having excellent film-forming properties at low temperatures (e.g., below 10° C.). Furthermore, an object of the present invention is to provide a method for producing the coating liquid and a method for producing a composite material using the coating liquid.

[0011] Means for solving technical problems

[0012] The present invention relates to, for example, the following [1] to

[16] . [1]

[0014] A coating liquid comprising:

[0015] emulsified particles, containing a binder resin;

[0016] Aerogel particles;

[0017] A water-soluble polymer having a hydrophobic group; and

[0018] Liquid medium,

[0019] The binder resin includes a structural unit derived from a first monomer having a homopolymer Tg of less than 0°C. [2]

[0021] The coating liquid according to [1], wherein

[0022] At least a portion of the aerogel particles forms aggregates. [3]

[0024] The coating liquid according to [2], wherein

[0025] The average diameter of the agglomerates is 2 to 40 times the average diameter of the aerogel particles. [4]

[0027] The coating solution according to any one of [1] to [3], wherein

[0028] The first monomer is an alkyl (meth)acrylate whose homopolymer Tg is less than 0°C. [5]

[0030] The coating solution according to any one of [1] to [4], wherein

[0031] The binder resin further includes a structural unit derived from a second monomer having a homopolymer Tg of 0° C. or higher. [6]

[0033] The coating solution according to any one of [1] to [5], wherein

[0034] The binder resin has a Tg of 10° C. or less. [7]

[0036] The coating solution according to any one of [1] to [6], wherein

[0037] The emulsified particles further contain a nonionic emulsifier. [8]

[0039] A method for preparing a coating liquid, comprising:

[0040] An emulsion preparation step of preparing an emulsion including emulsified particles containing a binder resin and a first liquid medium;

[0041] a dispersion preparation step of mixing aerogel particles, a water-soluble polymer having a hydrophobic group, and a second liquid medium to obtain a dispersion containing the aerogel particles, the water-soluble polymer, and the second liquid medium; and

[0042] A coating liquid preparation step of mixing the emulsion and the dispersion to obtain a coating liquid,

[0043] The binder resin includes a structural unit derived from a first monomer having a homopolymer Tg of less than 0°C. [9]

[0045] The method for producing a coating liquid according to [8], wherein:

[0046] The dispersion liquid preparation step is a step of mixing the aerogel particles, the water-soluble polymer, and the second liquid medium to aggregate the aerogel particles, and the coating liquid production step is a step of obtaining a coating liquid containing aggregates of the aerogel particles.

[10]

[0048] The method for producing a coating liquid according to [9], wherein:

[0049] The average diameter of the agglomerates is 2 to 40 times the average diameter of the aerogel particles.

[11]

[0051] The method for producing a coating liquid according to any one of [8] to

[10] , wherein:

[0052] The first monomer is an alkyl (meth)acrylate whose homopolymer Tg is less than 0°C.

[12]

[0054] The method for producing a coating liquid according to any one of [8] to

[11] , wherein:

[0055] The binder resin further includes a structural unit derived from a second monomer having a homopolymer Tg of 0° C. or higher.

[13]

[0057] The method for producing a coating liquid according to any one of [8] to

[12] , wherein:

[0058] The binder resin has a Tg of 10° C. or less.

[14]

[0060] The method for producing a coating liquid according to any one of [8] to

[13] , wherein:

[0061] The emulsified particles further contain a nonionic emulsifier.

[15]

[0063] A method for manufacturing a composite material, comprising:

[0064] a coating step of coating the coating solution described in any one of [1] to [7] on a support to obtain a coating film; and

[0065] The removing step removes at least a portion of the liquid medium from the coating film to obtain a composite material.

[16]

[0067] A method for manufacturing a composite material, comprising:

[0068] a coating step of coating the coating liquid produced by the production method described in any one of [8] to

[14] on a support to obtain a coating film; and

[0069] The removing step removes at least a portion of the liquid medium from the coating film to obtain a composite material.

[17]

[0071] A composite material, which is a dried product of the coating solution according to any one of [1] to [7].

[18]

[0073] An article comprising the composite material described in

[17] .

[0074] Effects of the Invention

[0075] According to the present invention, a coating liquid can be provided, which has excellent dispersibility of aerogel particles and a binder resin, can form a composite material containing aerogel particles and a binder resin, and has excellent film-forming properties at low temperatures (e.g., below 10° C.). In addition, according to the present invention, a method for producing the coating liquid and a method for producing a composite material using the coating liquid are provided. DETAILED DESCRIPTION

[0076] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In this specification, the numerical range represented by "~" indicates a range that includes the numerical values ​​recorded before and after "~" as the minimum value and the maximum value, respectively. "A or B" only needs to include any one of A and B, or both. Unless otherwise specified, the materials exemplified in this embodiment can be used alone or in combination of two or more.

[0077] [Coating liquid]

[0078] The coating liquid of this embodiment comprises: emulsified particles containing a binder resin; aerogel particles; a water-soluble polymer having a hydrophobic group; and a liquid medium. In this embodiment, the binder resin contains a structural unit (first structural unit) derived from a first monomer having a homopolymer Tg of less than 0°C.

[0079] The coating liquid of this embodiment disperses the binder resin as emulsified particles. In addition, the coating liquid of this embodiment improves the dispersibility of the aerogel particles by the water-soluble polymer. Therefore, by applying and drying the coating liquid of this embodiment, a uniform composite material containing aerogel particles and a binder resin can be easily formed.

[0080] Furthermore, the binder resin in the coating liquid of the present embodiment contains a structural unit (first structural unit) derived from a first monomer having a homopolymer Tg of less than 0° C. Therefore, the coating liquid of the present embodiment has excellent film-forming properties at low temperatures (eg, 10° C. or less).

[0081] In this embodiment, the aerogel particles may form aggregates.

[0082] When aerogel particles form aggregates, the contact interface between the aerogel particles and the resin component (binder resin) becomes smaller when forming a composite material, which can inhibit the penetration of the resin component into the pores of the aerogel particles, thereby tending to obtain a composite material with higher thermal insulation properties.

[0083] <Emulsified particles>

[0084] The binder resin may be, for example, a polymer of a monomer component having an ethylenically unsaturated bond. Such a binder resin has a structural unit (also referred to as a monomer unit) derived from a monomer component. As a monomer component, for example, acrylic compounds, aromatic vinyl compounds, heterocyclic vinyl compounds, vinyl esters, monoolefins, conjugated dienes, α,β-unsaturated carboxylic acids, vinyl cyanides, etc. having a (meth)acryloyl group may be cited. These may be used alone or in combination of two or more.

[0085] 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 of 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, isobornyl (meth)acrylate and the like.

[0086] Examples of acrylic compounds include polar group-containing acrylic compounds having a (meth)acryloyl group and a polar group (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, phosphoric acid groups, carbonyl groups, and the like.

[0087] Examples of the polar group-containing acrylic compound include compounds in which the alkyl group of an alkyl (meth)acrylate is substituted with a polar group. Examples of such compounds include hydroxyalkyl (meth)acrylates (e.g., hydroxyethyl (meth)acrylate, etc.), dialkylaminoalkyl (meth)acrylates (e.g., dimethylaminoethyl (meth)acrylate, etc.), glycidyl (meth)acrylate, trialkoxysilylalkyl (meth)acrylate, isocyanatoalkyl (meth)acrylates (e.g., 2-isocyanatoethyl (meth)acrylate, etc.), and 2-(meth)acryloyloxyethyl phosphate.

[0088] Examples of the polar group-containing acrylic compound include compounds in which a (meth)acryloyl group is bonded to a polar group, such as (meth)acrylic acid, (meth)acrylamide, n-hydroxymethyl (meth)acrylamide, and diacetone acrylamide.

[0089] Examples of the polar group-containing acrylic compound include diacetone (meth)acrylate, acetoacetoxyalkyl (meth)acrylate (eg, acetoacetoxyethyl (meth)acrylate), and the like.

[0090] Examples of the acrylic compound include acrolein, vinyl alkyl ketone (eg, vinyl methyl ketone, etc.), and the like.

[0091] Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, and ethylvinylbenzene.

[0092] Examples of the heterocyclic vinyl compound include vinyl pyrrolidone, vinyl furan, vinyl thiophene, vinyl oxazoline, and vinyl pyrrole.

[0093] Examples of the vinyl esters include vinyl acetate, vinyl alkylate, vinyl versatate, and the like.

[0094] Examples of the monoolefins include ethylene, propylene, butene, and isobutylene.

[0095] Examples of the conjugated dienes include butadiene, isoprene, and chloroprene.

[0096] Examples of the α,β-unsaturated carboxylic acid include crotonic acid, itaconic acid, maleic acid, fumaric acid, and anhydrides thereof.

[0097] Examples of vinyl cyanides include acrylonitrile and methacrylonitrile.

[0098] From the viewpoint of more significantly exhibiting the effects of the present invention, the monomer component is preferably a compound selected from the group consisting of acrylic compounds, aromatic vinyl compounds, heterocyclic vinyl compounds, and α,β-unsaturated carboxylic acids.

[0099] From the viewpoint of more significantly exerting the effect of the present invention, 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, 95% by mass or more, or 100% by mass, based on the total amount of the monomer component.

[0100] That is, the content of the acrylic compound may be, for example, 50 to 100 mass %, 60 to 100 mass %, 70 to 100 mass %, 80 to 100 mass %, 90 to 100 mass % or 95 to 100 mass % based on the total amount of the monomer components.

[0101] From the viewpoint of more significantly exerting the effect of the present invention, the acrylic compound preferably contains an alkyl (meth)acrylate. The content of the alkyl (meth)acrylate may be, for example, 50% by mass or more based on the total amount of the monomer components, and may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more based on the viewpoint of further improving the water resistance of the composite material. Furthermore, the content of the alkyl (meth)acrylate 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 the monomer components.

[0102] That is, the content of the alkyl (meth)acrylate is based on the total amount of the monomer components, and can be, for example, 50 to 99 mass%, 50 to 97 mass%, 50 to 95 mass%, 60 to 99 mass%, 60 to 97 mass%, 60 to 95 mass%, 70 to 99 mass%, 70 to 97 mass%, 70 to 95 mass%, 80 to 99 mass%, 80 to 97 mass%, 80 to 95 mass%, 90 to 99 mass%, 90 to 97 mass% or 90 to 95 mass%.

[0103] The acrylic compound may further include an acrylic compound containing a polar group. The content of the acrylic compound containing a polar group 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 the monomer components. Furthermore, the content of the acrylic compound containing a polar group 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 the monomer components.

[0104] That is, the content of the polar group-containing acrylic compound can be, for example, 1 to 30 mass%, 1 to 25 mass%, 1 to 20 mass%, 1 to 15 mass%, 1 to 10 mass%, 3 to 30 mass%, 3 to 25 mass%, 3 to 20 mass%, 3 to 15 mass%, 3 to 10 mass%, 5 to 30 mass%, 5 to 25 mass%, 5 to 20 mass%, 5 to 15 mass% or 5 to 10 mass%, based on the total amount of the monomer components.

[0105] The monomer component can 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.

[0106] In this embodiment, the monomer component includes a first monomer having a homopolymer Tg of less than 0°C.

[0107] As the first monomer, a compound selected from the group consisting of acrylic compounds, aromatic vinyl compounds, heterocyclic vinyl compounds and α,β-unsaturated carboxylic acids is preferred.

[0108] From the viewpoint of more significantly exerting the effects of the present invention, the first monomer preferably contains an acrylic compound, more preferably contains an alkyl (meth)acrylate, and further preferably contains an alkyl acrylate.

[0109] Examples of the first monomer include alkyl acrylates such as ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, propyl acrylate, and lauryl acrylate; alkyl methacrylates such as 2-ethylhexyl methacrylate, isodecyl methacrylate, and n-lauryl methacrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and 2-hydroxyethyl methacrylate. In addition, examples of the first monomer include methoxyethyl acrylate, ethoxyethoxyethyl acrylate, and the like.

[0110] In the present embodiment, the acrylic compound may further include a second monomer having a homopolymer Tg of 0° C. or higher.

[0111] The second monomer is preferably a compound selected from the group consisting of acrylic compounds, aromatic vinyl compounds, heterocyclic vinyl compounds, and α,β-unsaturated carboxylic acids.

[0112] Examples of the second monomer include methyl acrylate, alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate, (meth)acrylic acid, styrene, etc. Examples of the second monomer include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, maleic acid, and itaconic acid.

[0113] The content of the first monomer and the second monomer is not particularly limited, and can be appropriately selected so that the glass transition temperature (Tg) of the binder resin is within the preferred range described below. The glass transition temperature (Tg) of the binder resin can be measured by the method described in the examples described below.

[0114] In addition, the glass transition temperature (Tg) of the binder resin can be calculated by the FOX formula based on the weight ratio of each monomer unit constituting the binder resin and the Tg of the homopolymer of each monomer. The content of the first monomer and the second monomer can be appropriately selected so that the glass transition temperature (Tg) of the binder resin is within a preferred range with reference to the value calculated by the FOX formula.

[0115] The glass transition temperature (Tg) of the binder resin may be, for example, 25°C or less, and is preferably 20°C or less, and more preferably 15°C or less from the viewpoint of further improving film-forming properties. Furthermore, from the viewpoint of better film-forming properties at low temperatures, the glass transition temperature (Tg) of the binder resin is preferably 10°C or less, more preferably 8°C or less, and may be 6°C or less. The lower limit of the glass transition temperature (Tg) of the binder resin is not particularly limited, and may be, for example, -40°C or more, or -20°C or more.

[0116] That is, the glass transition temperature (Tg) of the binder resin can be, for example, -40 to 25°C, -40 to 20°C, -40 to 15°C, -40 to 10°C, -40 to 8°C, -40 to 6°C, -20 to 25°C, -20 to 20°C, -20 to 15°C, -20 to 10°C, -20 to 8°C or -20 to 6°C.

[0117] 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. By the emulsion polymerization, emulsified particles containing the binder resin and the emulsifier are formed.

[0118] The emulsifier may be any known emulsifier as long as it can emulsify the binder resin. Examples of the emulsifier include anionic emulsifiers and nonionic emulsifiers.

[0119] From the viewpoint of easily obtaining a coating liquid with low corrosiveness to metals, the emulsifier is preferably a nonionic emulsifier. By selecting a nonionic emulsifier, it is believed that corrosion of metals caused by ions contained in other emulsifiers (eg, anionic emulsifiers) is suppressed.

[0120] The nonionic emulsifier may be any known nonionic emulsifier as long as it can emulsify the binder resin. Examples of the nonionic emulsifier include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenol ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, etc., preferably polyoxyalkylene alkyl ethers, more preferably polyoxyethylene alkyl ethers.

[0121] From the viewpoint of making the binder resin more easily emulsified, the HLB value of the emulsifier is preferably 13 or more, more preferably 14 or more, and from the viewpoint of further improving the film-forming property of the coating liquid, it is preferably 15 or more, more preferably 16 or more. Furthermore, from the viewpoint of preventing a decrease in the water resistance of the composite material, the HLB value of the emulsifier is preferably 19 or less.

[0122] That is, the HLB value of the emulsifier may be, for example, 13-19, 14-19, 15-19, or 16-19.

[0123] The content of the emulsifier may be, for example, 0.01 parts by mass or more relative to 100 parts by mass of the binder resin, and from the viewpoint of delaying the drying of the coating surface and improving the film-forming property and the core dryness, 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 content of the emulsifier may be, for example, 15 parts by mass or less relative to 100 parts by mass of the 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.

[0124] That is, the content of the emulsifier can be, for example, 0.01 to 15 parts by mass, 0.01 to 12 parts by mass, 0.01 to 10 parts by mass, 0.01 to 8 parts by mass, 0.01 to 6 parts by mass, 0.1 to 15 parts by mass, 0.1 to 12 parts by mass, 0.1 to 10 parts by mass, 0.1 to 8 parts by mass, 0.1 to 6 parts by mass, 0.3 to 15 parts by mass, 0.3 to 12 parts by mass, 0.3 to 10 parts by mass, 0.3 to 8 parts by mass, 0.3 to 6 parts by mass, or 0.6 parts by mass, relative to 100 parts by mass of the binder resin. 5 to 15 parts by mass, 0.5 to 12 parts by mass, 0.5 to 10 parts by mass, 0.5 to 8 parts by mass, 0.5 to 6 parts by mass, 0.7 to 15 parts by mass, 0.7 to 12 parts by mass, 0.7 to 10 parts by mass, 0.7 to 8 parts by mass, 0.7 to 6 parts by mass, 0.9 to 15 parts by mass, 0.9 to 12 parts by mass, 0.9 to 10 parts by mass, 0.9 to 8 parts by mass, 0.9 to 6 parts by mass, 1 to 15 parts by mass, 1 to 12 parts by mass, 1 to 10 parts by mass, 1 to 8 parts by mass or 1 to 6 parts by mass.

[0125] The average particle size of the emulsified particles may be, for example, 50 nm or more, 70 nm or more, 90 nm or more, or 100 nm or more, and may be, for example, 400 nm or less, 350 nm or less, or 300 nm or less.

[0126] That is, the average particle size of the emulsified particles may be, for example, 50 to 400 nm, 50 to 350 nm, 50 to 300 nm, 70 to 400 nm, 70 to 350 nm, 70 to 300 nm, 90 to 400 nm, 90 to 350 nm, 90 to 300 nm, 100 to 400 nm, 100 to 350 nm, or 100 to 300 nm.

[0127] The content of the emulsified particles in the coating liquid may be, for example, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, based on the total amount of the non-volatile components in the coating liquid. Furthermore, the content of the emulsified particles in the coating liquid may be, for example, 80% by mass or less, 75% by mass or less, or 70% by mass or less, based on the total amount of the non-volatile components in the coating liquid.

[0128] The content of the emulsified particles in the coating liquid can be, for example, 30 to 80 mass%, 30 to 75 mass%, 30 to 70 mass%, 35 to 80 mass%, 35 to 75 mass%, 35 to 70 mass%, 40 to 80 mass%, 40 to 75 mass%, 40 to 70 mass%, 45 to 80 mass%, 45 to 75 mass% or 45 to 70 mass%, based on the total amount of non-volatile components in the coating liquid.

[0129] The content of the emulsified particles in the coating liquid can be appropriately adjusted so that the contents of the binder resin and the emulsifier in the composite material are within the preferred ranges described below.

[0130] <Water-soluble polymer>

[0131] The water-soluble polymer only needs to have a hydrophobic group and be water-soluble.

[0132] Examples of the hydrophobic group include an alkyl group (preferably a long-chain alkyl group having 6 to 26 carbon atoms), an ester group, an alkoxy group, a halogen group, etc. Among these, the hydrophobic group is preferably an alkyl group, more preferably a long-chain alkyl group having 6 to 26 carbon atoms, further preferably a long-chain alkyl group having 8 to 26 carbon atoms, further preferably a long-chain alkyl group having 10 to 26 carbon atoms, and may be a long-chain alkyl group having 12 to 26 carbon atoms or a long-chain alkyl group having 15 to 26 carbon atoms.

[0133] Examples of the water-soluble polymer include modified carboxyvinyl polymers, modified polyether urethane, cellulose resins, polyethylene oxide, polyvinyl alcohol, polyacrylic acid salts, polyvinyl pyrrolidone, dextrin resins, chitin resins, chitosan resins, and the like.

[0134] As the water-soluble polymer, a cellulose resin can be preferably used. Examples of the cellulose resin include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and modified products thereof (for example, hydrophobized).

[0135] As the cellulose resin, a cellulose resin having an alkyl group is preferred, and a cellulose resin having a long-chain alkyl group having 6 to 26 carbon atoms is more preferred. According to such a cellulose resin, the effect of the present invention can be more significantly exerted. The long-chain alkyl group preferably has 6 to 26 carbon atoms, more preferably 8 to 26, further preferably 10 to 26, further preferably 12 to 26, further preferably 15 to 26 carbon atoms.

[0136] In the cellulose-based resin, the content of the long-chain alkyl group having 6 to 26 carbon atoms is preferably 0.01 to 5% by mass, more preferably 0.01 to 3% by mass, based on the total amount of the cellulose-based resin.

[0137] As the cellulose-based resin, for example, a cellulose-based resin having a structural unit represented by the following formula (A-1) is preferred.

[0138]

[0139] In formula (A-1), R A represents a hydrogen atom, an alkyl group, a hydroxyalkyl group, -R A1-OR A2 The group represented by (R A1 represents an alkanediyl group or a hydroxyalkanediyl group, R A2 represents an alkyl group. ) or -(R A3 O) n The group represented by H (R A3 represents an alkanediyl group, and n represents an integer greater than or equal to 2. ) 3 R A They can be the same or different. A At least one of them is an alkyl group or -R A1 -OR A2 The group represented.

[0140] In formula (A-1), R A The alkyl group in is preferably an alkyl group having 1 to 26 carbon atoms. A The alkyl group in is more preferably a short-chain alkyl group having 1 to 3 carbon atoms or a long-chain alkyl group having 6 to 26 carbon atoms. The long-chain alkyl group preferably has 8 to 26 carbon atoms, more preferably 10 to 26 carbon atoms, further preferably 12 to 26 carbon atoms, and further preferably 15 to 26 carbon atoms.

[0141] In formula (A-1), R A The hydroxyalkyl group in the above-mentioned group is preferably a hydroxyalkyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkyl group having 1 to 10 carbon atoms, and still more preferably a hydroxyalkyl group having 1 to 5 carbon atoms.

[0142] In formula (A-1), R A1 The alkanediyl group in is preferably an alkanediyl group having 1 to 26 carbon atoms, more preferably an alkanediyl group having 1 to 10 carbon atoms, and still more preferably an alkanediyl group having 1 to 5 carbon atoms. A1 The hydroxyalkanediyl group in is preferably a hydroxyalkanediyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkanediyl group having 1 to 10 carbon atoms, and still more preferably a hydroxyalkanediyl group having 1 to 5 carbon atoms.

[0143] In formula (A-1), R A2 , preferably an alkyl group having 1 to 26 carbon atoms. A2 The alkyl group in is more preferably a short-chain alkyl group having 1 to 3 carbon atoms or a long-chain alkyl group having 6 to 26 carbon atoms, and more preferably a long-chain alkyl group. The long-chain alkyl group preferably has 8 to 26 carbon atoms, more preferably 10 to 26, further preferably 12 to 26, and further preferably 15 to 26 carbon atoms.

[0144] In formula (A-1), R A3 , preferably an alkanediyl group having 2 to 3 carbon atoms, more preferably an alkanediyl group having 3 carbon atoms.

[0145] In formula (A-1), preferably 3 R A At least one of them is a long chain alkyl or 3 R A At least one of them is -R A1 -OR A2 The group represented by R A2 A long chain alkyl group.

[0146] The content of the water-soluble polymer in the coating liquid may be, for example, 0.03% by mass or more based on the total amount of the non-volatile components in the coating liquid, and may be 0.05% by mass or more, 0.07% by mass or more, 0.09% by mass or more, 0.2% by mass or more, 0.4% by mass or more, 0.6% by mass or more, or 0.8% by mass or more from the viewpoint of further improving the dispersibility of the aerogel particles. Furthermore, the content of the water-soluble polymer in the coating liquid may be, for example, 6% by mass or less based on the total amount of the non-volatile components in the coating liquid, and may be 5% by mass or less, 4% by mass or less, or 3% by mass or less from the viewpoint of further improving the water resistance of the composite material.

[0147] That is, the content of the water-soluble polymer in the coating liquid may be, for example, 0.03 to 5% by mass, 0.03 to 4% by mass, 0.03 to 3% by mass, 0.05 to 5% by mass, 0.05 to 4% by mass, 0.05 to 3% by mass, 0.07 to 5% by mass, 0.07 to 4% by mass, 0.07 to 3% by mass, 0.09 to 5% by mass, 0.09 to 4% by mass, 0.09 to 3% by mass, 0.2 to 5% by mass, 0.2 to 4% by mass, 0.2 to 3% by mass, 0.4 to 5% by mass, 0.4 to 4% by mass, 0.4 to 3% by mass, 0.6 to 5% by mass, 0.6 to 4% by mass, 0.6 to 3% by mass, 0.8 to 5% by mass, 0.8 to 4% by mass or 0.8 to 3% by mass, based on the total amount of the non-volatile components in the coating liquid.

[0148] The content of the water-soluble polymer in the coating liquid may be, for example, 0.1 parts by mass or more relative to 100 parts by mass of the aerogel particles, and from the viewpoint of further improving the dispersibility of the aerogel particles, may be 0.5 parts by mass or more, 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more. Furthermore, from the viewpoint of further improving the water resistance of the composite material, the content of the water-soluble polymer in the coating liquid may be, for example, 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less relative to 100 parts by mass of the aerogel particles.

[0149] That is, the content of the water-soluble polymer in the coating liquid can be, for example, 0.1 to 20 parts by mass, 0.1 to 15 parts by mass, 0.1 to 10 parts by mass, 0.5 to 20 parts by mass, 0.5 to 15 parts by mass, 0.5 to 10 parts by mass, 1 to 20 parts by mass, 1 to 15 parts by mass, 1 to 10 parts by mass, 2 to 20 parts by mass, 2 to 15 parts by mass, 2 to 10 parts by mass, 3 to 20 parts by mass, 3 to 15 parts by mass or 3 to 10 parts by mass, relative to 100 parts by mass of the aerogel particles.

[0150] The content of the water-soluble polymer in the coating liquid can be appropriately adjusted so that the content of the water-soluble polymer in the composite material is within the preferred range described below.

[0151] <Aerogel>

[0152] In the present embodiment, the term "aerogel" refers to aerogel in a broad sense, that is, "gel comprised of a microporous solid in which the dispersed phase is a gas".

[0153] The aerogel of the present embodiment is, for example, a silica aerogel having silica as a main component. Examples of the silica aerogel include so-called organic-inorganic hybrid silica aerogels into which organic groups (such as methyl groups) or organic chains are introduced.

[0154] The aerogel of the present embodiment may be in the following forms, for example. By adopting each form, an aerogel having heat insulation, flame retardancy, heat resistance, and flexibility corresponding to each form can be obtained.

[0155] (First Form)

[0156] The aerogel of the present embodiment may have a structure represented by the following general formula (1). The aerogel according to the present embodiment may have a structure represented by the following general formula (1a) as a structure including the structure represented by the formula (1).

[0157]

[0158] In formula (1) and formula (1a), R 1 and R 2 Each independently represents an alkyl group or an aryl group, R 3 and R 4 Each independently represents an alkylene group. Here, examples of the aryl group include phenyl and substituted phenyl groups. In addition, examples of the substituent of the substituted phenyl group include alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. p represents an integer of 1 to 50. In formula (1a), two or more R1 Each may be the same or different. Similarly, two or more R 2 Each may be the same or different. In formula (1a), two R 3 They can be the same or different. Similarly, the two R 4 Each may be the same or different.

[0159] By introducing the structure represented by the above formula (1) or formula (1a) as an aerogel component into the skeleton of the aerogel, a low thermal conductivity and soft aerogel is obtained. From this point of view, in formula (1) and formula (1a), R 1 and R 2 , and R can be independently exemplified by an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and examples of the alkyl group include a methyl group, etc. Furthermore, in formula (1) and formula (1a), R 3 and R 4 , each independently includes an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include ethylene and propylene. In formula (1a), p can be 2 to 30, or 5 to 20.

[0160] (Second Form)

[0161] The aerogel of this embodiment has a ladder-type structure having a support portion and a bridge portion, and the bridge portion can have a structure represented by the following general formula (2). By introducing this ladder-type structure as an aerogel component into the skeleton of the aerogel, the heat resistance and mechanical strength can be improved. In addition, in this embodiment, the "ladder-type structure" is a structure having two support portions (struts) and bridge portions (bridges) connecting the support portions to each other (a structure having the shape of a so-called "ladder"). In this form, the skeleton of the aerogel can be formed by a ladder-type structure, but the aerogel can also partially have a ladder-type structure.

[0162]

[0163] In formula (2), R 5 and R 6 Each independently represents an alkyl group or an aryl group, and b represents an integer of 1 to 50. Here, examples of the aryl group include phenyl and substituted phenyl groups. Also, examples of the substituent of the substituted phenyl group include alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. In addition, in formula (2), when b is an integer greater than 2, two or more R 5 Each may be the same or different. Similarly, two or more R 6 Each may be the same or different.

[0164] By introducing the above structure as an aerogel component into the skeleton of the aerogel, an aerogel having better flexibility than, for example, a conventional aerogel having a structure derived from ladder-type siloxane can be obtained.

[0165] The structures that become the pillar parts and their chain lengths, and the intervals between the structures that become the bridge parts are not particularly limited, but from the viewpoint of further improving heat resistance and mechanical strength, the ladder structure may have a ladder structure represented by the following general formula (3).

[0166]

[0167] In formula (3), R 5 , R 6 , R 7 and R 8 Each of a and c independently represents an alkyl group or an aryl group, each of a and c independently represents an integer of 1 to 3000, and b represents an integer of 1 to 50. Here, examples of the aryl group include phenyl and substituted phenyl groups. Also, examples of the substituent of the substituted phenyl group include alkyl, vinyl, mercapto, amino, nitro, cyano, and the like. In addition, in formula (3), when b is an integer greater than 2, two or more R 5 Each may be the same or different. Similarly, two or more R 6 Each may be the same or different. In formula (3), when a is an integer greater than 2, two or more R 7 Each may be the same or different. Similarly, when c is an integer greater than 2, two or more R 8 Each may be the same or different.

[0168] In addition, from the viewpoint of obtaining more excellent flexibility, in formulas (2) and (3), R 5 , R 6 , R 7 and R 8 (Among them, R 7 and R 8 Only present in formula (3)), each independently includes an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and examples of the alkyl group include a methyl group, etc. In formula (3), a and c can each independently be 6 to 2000, but can also be 10 to 1000. In formulas (2) and (3), b can be 2 to 30, but can also be 5 to 20.

[0169] (Third Form)

[0170] The aerogel of the present embodiment may be a dried product of a wet gel of a condensate of a sol containing at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensate of a silicon compound having a hydrolyzable functional group (a product obtained by drying a wet gel generated from a sol). In addition, the aerogel described so far may also be an aerogel obtained by drying a wet gel generated from a sol containing a silicon compound or the like.

[0171] As the silicon compound having a hydrolyzable functional group or a condensable functional group, a polysiloxane compound can be used. That is, the sol can contain at least one compound selected from the group consisting of a polysiloxane compound having a hydrolyzable functional group or a condensable functional group and a hydrolyzate of a polysiloxane compound having a hydrolyzable functional group (hereinafter referred to as "polysiloxane compound group" depending on the case).

[0172] The functional group in the polysiloxane compound is not particularly limited, and can be set as a group that reacts between the same functional groups or with other functional groups. As a hydrolyzable functional group, an alkoxy group can be mentioned. As a condensable functional group, a hydroxyl group, a silanol group, a carboxyl group, a phenolic hydroxyl group, etc. can be mentioned. The hydroxyl group can be included in a group containing a hydroxyl group such as a hydroxyalkyl group. In addition, the polysiloxane compound having a hydrolyzable functional group or a condensable functional group can also have a reactive group different from the hydrolyzable functional group and the condensable functional group (a functional group that does not belong to the hydrolyzable functional group and the condensable functional group). As a reactive group, an epoxy group, a mercapto group, a glycidyloxy group, a vinyl group, an acryloyl group, a methacryloyl group, an amino group, etc. can be mentioned. An epoxy group can be included in a group containing an epoxy group such as a glycidyloxy group. The polysiloxane compound having these functional groups and reactive groups can be used alone or in combination of two or more. Among these functional groups and reactive groups, for example, as a group that improves the flexibility of the aerogel, there can be mentioned alkoxy groups, silanol groups, hydroxyalkyl groups, etc. Among these, alkoxy groups and hydroxyalkyl groups can further improve the compatibility of the sol. In addition, from the viewpoint of improving the reactivity of the polysiloxane compound and reducing the thermal conductivity of the aerogel, the number of carbon atoms of the alkoxy group and the hydroxyalkyl group can be set to 1 to 6, but from the viewpoint of further improving the flexibility of the aerogel, it can be 2 to 5, or 2 to 4.

[0173] (Fourth Form)

[0174] From the viewpoint of further strengthening and toughening and achieving further excellent thermal insulation and flexibility, the aerogel involved in this embodiment may contain silica particles in addition to the aerogel component. The aerogel containing the aerogel component and the silica particles can also be called an aerogel composite. In the aerogel composite, although the aerogel component and the silica particles are composited, it is believed that the aerogel still has a cluster structure that is a characteristic of the aerogel and has a three-dimensional fine porous structure.

[0175] The aerogel containing an aerogel component and silica particles can be referred to as a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group consisting of the silicon compound having a hydrolyzable functional group or a condensable functional group and a hydrolyzate of the silicon compound having a hydrolyzable functional group and silica particles. Therefore, the descriptions related to the first to third forms can also be appropriately applied to the aerogel involved in this embodiment.

[0176] As silica particles, any of them can be used without particular limitation, and amorphous silica particles can be cited. As amorphous silica particles, fused silica particles, fumed silica particles, colloidal silica particles, etc. can be cited. Among these, colloidal silica particles have high monodispersity and are easy to suppress aggregation in sol. In addition, as silica particles, silica particles having a hollow structure, a porous structure, etc. can be cited.

[0177] The shape of the silica particles is not particularly limited, and spherical, cocoon-shaped, and associated types can be cited. Among these, by using spherical particles as silica particles, it is easy to suppress agglomeration in the sol. From the viewpoint of easily giving the aerogel appropriate strength and flexibility and easily obtaining an aerogel with excellent shrinkage resistance during drying, the average primary particle size of the silica particles can be 1 nm or more, 5 nm or more, or 20 nm or more. From the viewpoint of easily suppressing the solid thermal conductivity of the silica particles and easily obtaining an aerogel with excellent thermal insulation, the average primary particle size of the silica particles can be 500 nm or less, 300 nm or less, or 100 nm or less. From these viewpoints, the average primary particle size of the silica particles can be 1 to 500 nm, 5 to 300 nm, or 20 to 100 nm.

[0178] In the present embodiment, the average particle size of the aerogel component and the average primary particle size of the silica particles can be obtained by directly observing the aerogel using a scanning electron microscope (hereinafter referred to as "SEM"). The "diameter" mentioned here refers to the diameter when the cross section of the particle exposed on the cross section of the aerogel is regarded as a circle. And, "the diameter when the cross section is regarded as a circle" refers to the diameter of the true circle when the area of ​​the cross section is replaced by a true circle of the same area. In addition, when calculating the average particle size, the diameter of the circle is calculated for 100 particles and the average is taken.

[0179] In addition, the average particle size of the silica particles can also be measured from the raw material. For example, the biaxial average primary particle size is calculated as follows based on the results obtained by observing any 20 particles using SEM. That is, taking colloidal silica particles whose solid content concentration is usually about 5 to 40% by mass and dispersed in water as an example, a chip obtained by cutting a wafer with pattern wiring into 2 cm squares is immersed in a dispersion of colloidal silica particles for about 30 seconds, and then the chip is rinsed with pure water for about 30 seconds and dried by nitrogen blowing. Then, the chip is placed on a sample stage for SEM observation, an acceleration voltage of 10 kV is applied, the silica particles are observed at a magnification of 100,000 times, and an image is taken. From the obtained image, 20 silica particles are randomly selected, and the average of the particle sizes of these particles is taken as the average particle size.

[0180] <Aerogel particles>

[0181] As described later, the aerogel particles in the present embodiment can be obtained by, for example, pulverizing a large mass of aerogel.

[0182] The average particle size (D50) of the aerogel particles (also referred to as the average diameter) can be set to 0.1 to 1000 μm, but can also be 0.5 to 700 μm, 1 to 500 μm, 3 to 100 μm, or 5 to 50 μm. If the average particle size (D50) of the aerogel particles is large, it is easy to obtain aerogel particles with excellent dispersibility and operability. On the other hand, if the average particle size (D50) is small, it is easy to obtain aerogel particles with excellent dispersibility. The average particle size (D50) of the aerogel particles can be appropriately adjusted by a pulverization method and pulverization conditions, sieving, a classification method, etc.

[0183] The average particle size (D50) of aerogel particles can be measured by laser diffraction / scattering method. For example, aerogel particles are added to a solvent (ethanol) in a manner such that the content of aerogel particles becomes 0.05 to 5% by mass, and a 50W ultrasonic homogenizer is vibrated for 15 to 30 minutes to disperse the aerogel particles. Then, about 10 mL of the dispersion is injected into a laser diffraction / scattering particle size distribution measuring device, and the particle size is measured at 25°C with a refractive index of 1.3 and an absorption of 0. Then, the particle size at the cumulative value of 50% (volume basis) in the particle size distribution is set to the average particle size D50. As a measuring device, for example, Microtrac MT3000 (Nikkiso Co., Ltd. manufactured, product name) can be used.

[0184] Furthermore, commercially available products may be used as aerogel particles. Examples of commercially available aerogel particles include ENOVA MT1100 (manufactured by CABOT CORPORATION) and AeroVa (manufactured by JIOS AEROGEL CORPORATION).

[0185] In this embodiment, the amount of aerogel particles in the coating liquid is preferably 70% by volume or more, more preferably 72% by volume or more, and even more preferably 74% by volume or more, based on the content of aerogel particles in the composite material based on the total volume of the composite material. In addition, the amount of aerogel particles in the coating liquid may be, for example, 99% by volume or less, 98% by volume or less, or 97% by volume or less, based on the content of aerogel particles in the composite material based on the total volume of the composite material.

[0186] That is, the amount of aerogel particles in the coating liquid can be 70 to 99 volume %, 70 to 98 volume %, 70 to 97 volume %, 72 to 99 volume %, 72 to 98 volume %, 72 to 97 volume %, 74 to 99 volume %, 74 to 98 volume % or 74 to 97 volume % of the aerogel particles in the composite material based on the total volume of the composite material.

[0187] <Method for producing aerogel particles>

[0188] The method for producing the aerogel particles is not particularly limited, and the aerogel particles can be produced, for example, by the following method.

[0189] The aerogel particles of the present embodiment can be produced by the following production method, which mainly includes: a sol generation step; a wet gel generation step, in which the sol obtained in the sol generation step is gelled and then aged 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) the solvent is replaced; a drying step, in which the wet gel after washing and solvent replacement is dried; and a pulverizing step, in which the aerogel obtained by drying is pulverized.

[0190] Furthermore, the production can also be carried out by a production method mainly comprising a sol production step, a wet gel production step, a wet gel pulverizing step of pulverizing the wet gel obtained in the wet gel production step, a washing and solvent replacement step, and a drying step.

[0191] The size of the obtained aerogel particles can be further adjusted by sieving, grading, etc. By adjusting the size of the particles, the dispersibility can be improved. In addition, "sol" refers to the state before the gelation reaction occurs, and in this embodiment, it refers to the state in which the above-mentioned silicon compound and the silicon dioxide particles contained as appropriate are dissolved or dispersed in the solvent. In addition, wet gel refers to a gel solid in a wet state that does not have fluidity despite containing a liquid medium.

[0192] (Sol generation process)

[0193] The sol generation process is a process of generating a sol after mixing a silicon compound and silicon dioxide particles (or a solvent containing silicon dioxide particles) as appropriate and performing a hydrolysis reaction. In this process, an acid catalyst may be added to the solvent to promote the hydrolysis reaction. In addition, as shown in Japanese Patent Gazette No. 5250900, a surfactant, a thermal hydrolyzable compound, etc. may also be added to the solvent. In addition, for the purpose of suppressing thermal radiation, components such as carbon graphite, aluminum compounds, magnesium compounds, silver compounds, and titanium compounds may be added to the solvent.

[0194] As the solvent, for example, water or a mixed solution of water and alcohol can be used. As the alcohol, methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, etc. can be mentioned. Among these, from the viewpoint of reducing the interfacial tension with the gel wall, methanol, ethanol, 2-propanol, etc. can be mentioned as alcohols with low surface tension and low boiling point. These can be used alone or in combination of two or more.

[0195] For example, when alcohol is used as a solvent, the amount of alcohol can be 4 to 8 mol, but may also be 4 to 6.5, or 4.5 to 6 mol, relative to 1 mol of the total amount of the silicon compound group and the polysiloxane compound group. By setting the amount of alcohol to 4 mol or more, it is easier to obtain good compatibility, and by setting it to 8 mol or less, it is easier to further suppress the shrinkage of the gel.

[0196] As the acid catalyst, there can be cited inorganic acids such as fluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, hypochlorous acid, etc.; acidic phosphates such as acidic aluminum phosphate, acidic magnesium phosphate, acidic zinc phosphate, etc.; organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid, etc. Among these, as an acid catalyst for further improving the water resistance of the obtained aerogel, organic carboxylic acids can be cited. As the organic carboxylic acid, acetic acid can be cited, but it can also be formic acid, propionic acid, oxalic acid, malonic acid, etc. These can be used alone or in combination of two or more.

[0197] By using an acid catalyst, the hydrolysis reaction of the silicon compound can be accelerated to obtain a sol in a shorter time.

[0198] The amount of the acid catalyst added can be 0.001 to 0.1 parts by mass based on 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group.

[0199] As the surfactant, a nonionic surfactant, an ionic surfactant, etc. can be used, and these can be used alone or in combination of two or more.

[0200] As the nonionic surfactant, for example, a compound containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group, a compound containing a hydrophilic part such as polyoxypropylene, etc. can be used. As the compound containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene alkyl ether, etc. can be mentioned. As the compound containing a hydrophilic part such as polyoxypropylene, polyoxypropylene alkyl ether, a block copolymer of polyoxyethylene and polyoxypropylene, etc. can be mentioned.

[0201] As ionic surfactants, cationic surfactants, anionic surfactants, zwitterionic surfactants, etc. can be mentioned. As cationic surfactants, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, etc. can be mentioned, and as anionic surfactants, sodium dodecylsulfonate, etc. can be mentioned. In addition, as zwitterionic surfactants, amino acid surfactants, betaine surfactants, amine oxide surfactants, etc. can be mentioned. As amino acid surfactants, for example, acyl glutamic acid, etc. can be mentioned. As betaine surfactants, for example, lauryl dimethylaminoacetic acid betaine, stearyl dimethylaminoacetic acid betaine, etc. can be mentioned. As amine oxide surfactants, for example, lauryl dimethylamine oxide can be mentioned.

[0202] These surfactants are considered to play a role in reducing the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer and inhibiting phase separation in the wet gel formation step described later.

[0203] The amount of the surfactant added depends on the type of the surfactant or the type and amount of the silicon compound, and can be, for example, 1 to 100 parts by mass relative to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. Alternatively, the amount can be 5 to 60 parts by mass.

[0204] It is believed that the thermally hydrolyzable compound generates an alkali catalyst by thermally hydrolyzing, making the reaction solution alkaline, thereby promoting the sol-gel reaction in the wet gel formation step described later. Therefore, the thermally hydrolyzable compound is not particularly limited as long as it is a compound that can make the reaction solution alkaline after hydrolysis, and examples thereof include urea; acid amides such as formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, and N,N-dimethylacetamide; cyclic nitrogen compounds such as hexamethylenetetramine, etc. Among these, urea is particularly likely to achieve the above-mentioned promotion effect.

[0205] The amount of the thermally hydrolyzable compound added is not particularly limited as long as it is an amount that can sufficiently promote the sol-gel reaction in the wet gel formation step described later. For example, when urea is used as the thermally hydrolyzable compound, its amount added can be set to 1 to 200 parts by mass relative to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. In addition, the amount added can also be 2 to 150 parts by mass. By setting the amount added to 1 part by mass or more, it is easier to obtain good reactivity, and by setting it to 200 parts by mass or less, it is easier to further suppress the precipitation of crystals and the decrease in gel density.

[0206] The hydrolysis in the sol generation step also depends on the types and amounts of the silicon compound, silicon dioxide particles, acid catalyst, surfactant, etc. in the mixed solution, and can be carried out, for example, 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. In this way, the hydrolyzable functional groups in the silicon compound are fully hydrolyzed, and the hydrolysis product of the silicon compound can be obtained more reliably.

[0207] However, when a thermally hydrolyzable compound is added to the solvent, the temperature environment of the sol generation process can be adjusted to a temperature that suppresses the hydrolysis of the thermally hydrolyzable compound and suppresses the gelation of the sol. The temperature at this time can be any temperature as long as it 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 generation process can be set to 0 to 40°C, but it can also be 10 to 30°C.

[0208] (Wet gel forming step)

[0209] The wet gel forming step is a step of gelling the sol obtained in the sol forming step and then aging it to obtain a wet gel. In this step, an alkali catalyst may be used to promote gelation.

[0210] Examples of the base catalyst 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 hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, and ammonium hydrogen carbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; alkaline sodium phosphates such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, and the like. Aliphatic amines such as amine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3-(diethylamino)propylamine, di-2-ethylhexylamine, 3-(dibutylamino)propylamine, tetramethylethylenediamine, tert-butylamine, sec-butylamine, propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine, etc.; nitrogen-containing heterocyclic compounds such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, imidazole and its derivatives, etc. Among these, ammonium hydroxide (ammonia water) is excellent in terms of high volatility, difficulty in remaining in the aerogel particles after drying, and is not easy to damage water resistance, and is also excellent in terms of economy. The above-mentioned base catalysts can be used alone or in combination of two or more.

[0211] By using an alkali catalyst, the dehydration condensation reaction or dealcoholization condensation reaction of the silicon compound and the silica particles in the sol can be promoted, and the sol can be gelled in a shorter time. In addition, a wet gel with higher strength (rigidity) can be obtained. In particular, ammonia is difficult to remain in the aerogel particles due to its high volatility, so by using ammonia as an alkali catalyst, aerogel particles with better water resistance can be obtained.

[0212] The amount of the base catalyst added can be 0.5 to 5 parts by mass relative to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group, but may also be 1 to 4 parts by mass. When it is 0.5 parts by mass or more, gelation can be performed in a shorter time, and when it is 5 parts by mass or less, the decrease in water resistance can be further suppressed.

[0213] The gelation of the sol in the wet gel forming step can be carried out in a closed container to prevent the solvent and the alkali catalyst from volatilizing. The gelation temperature can be set to 30 to 90°C, but it can also be 40 to 80°C. By setting the gelation temperature to 30°C or above, gelation can be carried out in a shorter time, and a wet gel with higher strength (rigidity) can be obtained. In addition, by setting the gelation temperature to 90°C or below, it is easy to suppress the volatilization of the solvent (especially alcohol), so that gelation can be carried out while suppressing volume shrinkage.

[0214] The aging in the wet gel production process can be carried out in a closed container to prevent the solvent and the alkali catalyst from volatilizing. Through aging, the bonding of the components constituting the wet gel is strengthened, and as a result, a wet gel with high strength (rigidity) sufficient to suppress shrinkage during drying can be obtained. The aging temperature can be set to 30 to 90°C, but it can also be 40 to 80°C. By setting the aging temperature to above 30°C, a wet gel with higher strength (rigidity) can be obtained, and by setting the aging temperature to below 90°C, it is easy to suppress the volatilization of the solvent (especially alcohol), so that gelation can be performed while suppressing volume shrinkage.

[0215] In addition, since it is often difficult to determine the point in time when the gelation of the sol is completed, the gelation of the sol and the subsequent aging may be performed continuously through a series of operations.

[0216] The gelation time and the aging time can be appropriately set according to the gelation temperature and the aging temperature. When silica particles are included in the sol, the gelation time can be particularly shortened compared to the case where they are not included. The reason is presumed to be due to the silanol group or reactive group of the silicon compound in the sol forming a hydrogen bond or chemical bond with the silanol group of the silica particles. In addition, the gelation time can be set to 10 to 120 minutes, but it can also be 20 to 90 minutes. By setting the gelation time to more than 10 minutes, it is easy to obtain a homogeneous wet gel, and by setting it to less than 120 minutes, the washing and solvent replacement steps described later can be simplified to the drying step. In addition, as a whole of the gelation and aging process, the total time of the gelation time and the aging time can be set to 4 to 480 hours, but it can also be 6 to 120 hours. By setting the total of the gelation time and the aging time to more than 4 hours, a wet gel with higher strength (rigidity) can be obtained, and by setting it to less than 480 hours, it is easier to maintain the aging effect.

[0217] In order to reduce the density of the obtained aerogel particles or increase the average pore diameter, the gelation temperature and the aging temperature may be increased within the above range, or the total time of the gelation time and the aging time may be extended within the above range. In addition, in order to increase the density of the obtained aerogel particles or reduce the average pore diameter, the gelation temperature and the aging temperature may be reduced within the above range, or the total time of the gelation time and the aging time may be shortened within the above range.

[0218] (Wet gel pulverization process)

[0219] When the wet gel pulverizing step is performed, the wet gel obtained in the wet gel generating step is pulverized. The pulverizing can be performed, for example, by placing the wet gel in a Henschel-type mixer, or performing the wet gel generating step in the mixer, and operating the mixer under appropriate conditions (rotation speed and time). Moreover, more simply, the pulverizing can be performed by placing the wet gel in a sealable container, or performing the wet gel generating step in a sealable container, and oscillating the wet gel for an appropriate time using an oscillating device such as a vibrator. In addition, as needed, the particle size of the wet gel can also be adjusted using a jet mill, a roller mill, a bead mill, or the like.

[0220] (Cleaning and solvent replacement process)

[0221] The washing and solvent replacement step is a step including: a step of washing the wet gel obtained by the wet gel forming step or the wet gel pulverizing step (washing step); and a step of replacing the washing liquid in the wet gel with a solvent suitable for the drying conditions (the drying step described later) (solvent replacement step). The washing and solvent replacement step can be carried out by performing only the solvent replacement step without performing the step of washing the wet gel. However, from the viewpoint of reducing impurities such as unreacted substances and by-products in the wet gel and enabling the production of aerogel particles with higher purity, the wet gel may be washed.

[0222] In the washing step, the wet gel obtained in the wet gel generation step or the wet gel crushing step is washed. This washing can be repeatedly performed using water or an organic solvent, for example. At this time, the washing efficiency can be improved by heating.

[0223] As the organic solvent, various organic solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, dichloromethane, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, formic acid, etc. can be used. The above organic solvents can be used alone or in combination of two or more.

[0224] In the solvent replacement process described later, in order to suppress the shrinkage of the gel caused by drying, a solvent with low surface tension can be used. However, the mutual solubility of the solvent with low surface tension with water is usually very low. Therefore, when a solvent with low surface tension is used in the solvent replacement process, as the organic solvent used in the cleaning process, a hydrophilic organic solvent with high mutual solubility in both water and the solvent with low surface tension can be cited. In addition, the hydrophilic organic solvent used in the cleaning process can play a role in the pre-replacement of the solvent replacement process. Among the above-mentioned organic solvents, as the hydrophilic organic solvent, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, etc. can be cited. In addition, methanol, ethanol, methyl ethyl ketone, etc. are excellent in economy.

[0225] The amount of water or organic solvent used in the washing step can be set to an amount that can fully replace and wash the solvent in the wet gel. The amount can be set to an amount of 3 to 10 times the volume of the wet gel. Washing can be repeated until the water content in the wet gel after washing becomes less than 10% by mass relative to the mass of silica.

[0226] The temperature environment in the cleaning step can be set to a temperature lower than the boiling point of the solvent used in the cleaning. For example, when methanol is used, the temperature can be set to about 30 to 60°C.

[0227] In the solvent replacement process, in order to suppress the shrinkage of the aerogel in the drying process, the solvent of the washed wet gel is replaced with a specified replacement solvent. At this time, the replacement efficiency can be improved by heating. As the replacement solvent, specifically, in the drying process, when drying is performed at a temperature lower than the critical point of the solvent used in the drying and at atmospheric pressure, a low surface tension solvent described later can be cited. On the other hand, when supercritical drying is performed, as the replacement solvent, for example, ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, etc. or a solvent obtained by mixing two or more of them can be cited.

[0228] Examples of low surface tension solvents include solvents having a surface tension of 30 mN / m or less at 20°C. The surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of low surface tension solvents 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); dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), 2- Halogenated hydrocarbons such as chloropropane (18.1); ethers such as ethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ethyl ether (20.8), 1,2-dimethoxyethane (24.6); ketones such as acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), diethyl ketone (25.3); esters such as methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), isobutyl acetate (23.7), ethyl butyrate (24.6), etc. (The surface tension at 20°C is expressed in [mN / m] in parentheses). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and are excellent in working environment. Among these, hydrophilic organic solvents such as acetone, methyl ethyl ketone, and 1,2-dimethoxyethane can be used as organic solvents in the above-mentioned washing step. In addition, among these, solvents having a boiling point of 100° C. or less under normal pressure can be used from the viewpoint of further facilitating drying in the drying step described later. The above-mentioned solvents can be used alone or in combination of two or more.

[0229] The amount of the solvent used in the solvent replacement step can be set to an amount that can sufficiently replace the solvent in the wet gel after washing, and can be set to an amount that is 3 to 10 times the volume of the wet gel.

[0230] The temperature environment in the solvent replacement step can be set to a temperature lower than the boiling point of the solvent used in the replacement. For example, when heptane is used, the temperature can be set to about 30 to 60°C.

[0231] In addition, when silica particles are included in the gel, the solvent replacement process is not necessary. As an inferred mechanism, it is described as follows. That is, the silica particles act as a support for the three-dimensional mesh skeleton and the skeleton is supported, and the shrinkage of the gel in the drying process is suppressed. Therefore, it can be considered that the gel can be directly supplied to the drying process without replacing the solvent used in the cleaning. In this way, by using silica particles, the cleaning and solvent replacement process can be simplified to the drying process.

[0232] (Drying process)

[0233] In the drying step, the wet gel after washing and (if necessary) solvent replacement as described above is dried. Thus, an aerogel (aerogel block or aerogel particles) can be obtained. That is, an aerogel formed by drying the wet gel generated from the above sol can be obtained.

[0234] The drying method is not particularly limited, and known normal pressure drying, supercritical drying or freeze drying can be used. Among these, normal pressure drying or supercritical drying can be used from the viewpoint of easy production of low-density aerogel. In addition, normal pressure drying can be used from the viewpoint of low-cost production. In addition, in the present embodiment, normal pressure refers to 0.1 MPa (atmospheric pressure).

[0235] Aerogel can be obtained by drying the wet gel after washing and (if necessary) solvent replacement at a temperature below the critical point of the solvent used in drying and under atmospheric pressure. The drying temperature varies depending on the type of solvent replaced (the solvent used in washing when solvent replacement is not performed), and can be set to 20 to 150°C, especially in view of the fact that drying at high temperature accelerates the evaporation rate of the solvent and sometimes produces large cracks in the gel. In addition, the drying temperature can also be 60 to 120°C. In addition, the drying time varies depending on the capacity of the wet gel and the drying temperature, and can be set to 4 to 120 hours. In addition, accelerating the drying by applying a pressure below the critical point within a range that does not hinder productivity is also included in normal pressure drying.

[0236] Aerogel can also be obtained by supercritically drying the wet gel after washing and (if necessary) solvent replacement. Supercritical drying can be performed by a known method.

[0237] As a method for supercritical drying, for example, a method of removing the solvent at a temperature and pressure above the critical point of the solvent contained in the wet gel can be cited. Alternatively, as a method for supercritical drying, the following method can be cited: the wet gel is immersed in liquefied carbon dioxide, for example, under the conditions of 20 to 25° C. and 5 to 20 MPa to replace all or part of the solvent contained in the wet gel with carbon dioxide having a critical point lower than that of the solvent, and then the carbon dioxide is removed alone or a mixture of carbon dioxide and the solvent is removed.

[0238] The aerogel obtained by such normal pressure drying or supercritical drying can be further dried at normal pressure and 105 to 200° C. for about 0.5 to 2 hours. In this way, it is easier to obtain an aerogel with low density and small pores. The additional drying can also be performed at normal pressure and 150 to 200° C.

[0239] (Crushing process)

[0240] When the wet gel pulverization step is not performed, the aerogel (aerogel block) obtained by drying is pulverized to obtain aerogel particles. For example, the aerogel can be placed in a jet mill, a roll mill, a bead mill, a hammer mill, etc., and operated at an appropriate rotation speed and time.

[0241] <Liquid medium>

[0242] As the liquid medium, an aqueous solvent containing water is preferred. In addition to water, the aqueous solvent may contain an organic solvent. As long as the organic solvent is compatible with water, examples thereof include alcohols such as methanol, ethanol, isopropanol, butanol, ethylene glycol, and propylene glycol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and methyl ethyl ketone; carboxylic acids such as acetic acid and propionic acid; nitrogen-containing compounds such as acetonitrile, dimethylformamide, and triethylamine.

[0243] In this embodiment, the content of the liquid medium in the coating liquid is not particularly limited and can be appropriately changed according to the desired viscosity of the coating liquid, etc. For example, the content of the liquid medium may be such that the nonvolatile component concentration of the coating liquid falls within the preferred range described below.

[0244] The nonvolatile component concentration of the coating liquid may be, for example, 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more. Also, the nonvolatile component concentration of the coating liquid may be, for example, 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less.

[0245] That is, the nonvolatile component concentration of the coating liquid can be, for example, 10 to 70 mass%, 10 to 60 mass%, 10 to 50 mass%, 15 to 70 mass%, 15 to 60 mass%, 15 to 50 mass%, 20 to 70 mass%, 20 to 60 mass% or 20 to 50 mass%.

[0246] <Other ingredients>

[0247] In the present embodiment, the coating liquid may further contain other components besides the above components.

[0248] The coating liquid of the present embodiment may further contain, for example, a thickener, a fibrous substance, a pigment, a leveling agent, and the like.

[0249] Examples of the thickener include fine particles such as fumed silica and clay minerals.

[0250] The fibrous material acts as an anchor between the aerogel particles, and can further improve the strength of the composite material. The fibrous material is not particularly limited and can be an organic fiber or an inorganic fiber. As organic fibers, for example, 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, polycarbonate fibers, etc. can be cited. As inorganic fibers, for example, glass fibers, carbon fibers, ceramic fibers, metal fibers, etc. can be cited.

[0251] In the present embodiment, the coating liquid may contain a fibrous substance having a fiber length of 1.5 mm or more, thereby improving the strength of the composite material formed by the coating liquid, and even in the case where the composite material is film-shaped, there is a tendency to ensure sufficient thermal insulation. The reason is not certain, but the inventors speculate as follows. Generally, in order to ensure the strength of the formed body, it is preferred that the fibers are randomly oriented in the formed body. In patent document 2, short fibers are used, which is believed to be because short fibers are easily randomly oriented compared to long fibers. However, when making a thin film-shaped formed body, if the short fibers are randomly oriented, a heat conduction path (heat path) based on the fiber is easily formed in the thickness direction (the direction in which thermal insulation is desired), and sometimes the thermal insulation in the thickness direction is impaired. In the present embodiment, it is believed that by deliberately setting the fibrous substance contained in the coating liquid to a long fiber (a fibrous substance having a fiber length of 1.5 mm or more), when forming a thin film-shaped composite material, the fibrous substance is easily oriented in the surface direction, which can improve the strength in the surface direction while fully ensuring the thermal insulation in the thickness direction.

[0252] From the viewpoint of more significantly obtaining the above-mentioned effects, the fiber length of the fibrous material may be 2 mm or more, 2.5 mm or more, or 3 mm or more. On the other hand, from the viewpoint of dispersibility in the coating liquid and expellability by spraying, etc., the fiber length of the fibrous material may be, for example, 20 mm or less, or 15 mm or less, or 10 mm or less.

[0253] That is, the fiber length of the fibrous material can be, for example, 1.5-20 mm, 1.5-10 mm, 1.5-10 mm, 2-20 mm, 2-15 mm, 2-10 mm, 2.5-20 mm, 2.5-15 mm, 2.5-10 mm, 3-20 mm, 3-15 mm or 3-10 mm.

[0254] From the viewpoint of dispersibility in the coating liquid and obtaining a good anchoring function, the fiber diameter of the fibrous substance may be, for example, 0.01 to 100 μm.

[0255] The content of the fibrous substance in the coating liquid may be, for example, 0.1% by mass or more based on the total amount of the non-volatile components in the coating liquid, and may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more from the viewpoint of further improving the film-forming property. Furthermore, the content of the fibrous substance in the coating liquid may be, for example, 20% by mass or less based on the total amount of the non-volatile components in the coating liquid, and may be, for example, 15% by mass or less or 10% by mass or less from the viewpoint of further improving the coating stability.

[0256] That is, the content of the fibrous substance in the coating liquid is based on the total amount of non-volatile components in the coating liquid, and can be, for example, 0.1 to 20 mass%, 0.1 to 15 mass%, 0.1 to 10 mass%, 0.5 to 20 mass%, 0.5 to 15 mass%, 0.5 to 10 mass%, 1 to 20 mass%, 1 to 15 mass%, 1 to 10 mass%, 3 to 20 mass%, 3 to 15 mass% or 3 to 10 mass%.

[0257] Furthermore, the content of the fibers (fibrous substances having a fiber length of 1.5 mm or more) may be, for example, 30% by mass or more, or 50% by mass or more, based on the total amount of the fibrous substances. The upper limit of the content is not particularly limited, and may be 100% by mass (i.e., the fiber length of all fibrous substances in the coating solution is 1.5 mm or more).

[0258] The content of the fibrous substance in the coating liquid can be appropriately adjusted so that the content of the fibrous substance in the composite material is within the preferred range described below.

[0259] The chloride ion content in the coating liquid of the present embodiment may be, for example, 50 mass ppm or less, and from the viewpoint of further suppressing corrosion to metals, may be 30 mass ppm or less, 10 mass ppm or less, 5 mass ppm or less, or 1 mass ppm or less.

[0260] The content of sulfate ions in the coating liquid of the present embodiment may be, for example, 50 mass ppm or less, and from the viewpoint of further suppressing corrosion to metals, may be 30 mass ppm or less, 10 mass ppm or less, 5 mass ppm or less, or 1 mass ppm or less.

[0261] In this embodiment, the above-mentioned preferred range can be achieved by using a substance containing a small amount (or no) of chloride ions and sulfate ions for each component in the coating liquid. In addition, in this embodiment, since a nonionic emulsifier is used as an emulsifier, it is easier to adjust the content of chloride ions and sulfate ions to the above-mentioned preferred range compared to the case of using an anionic emulsifier.

[0262] [Method for producing coating liquid]

[0263] In the present embodiment, the coating liquid can be produced by a production method including an emulsion preparation step, a dispersion preparation step, and a coating liquid production step.

[0264] The emulsion preparation step is a step of preparing an emulsion including emulsified particles containing a binder resin and a first liquid medium.

[0265] The emulsion preparation step may be, for example, a step of performing emulsion polymerization of the monomer components in the first liquid medium in the presence of an emulsifier to obtain the emulsion.

[0266] Examples of the first liquid medium include the same liquid medium as described above. The first liquid medium is preferably an aqueous solvent.

[0267] Emulsion polymerization can be carried out, for example, by the following steps: step (i), mixing the monomer component and the emulsifier in the first liquid medium to obtain a monomer emulsion; and step (ii), mixing the monomer emulsion and a free radical polymerization initiator to carry out emulsion polymerization of the monomer component.

[0268] In step (i), the amount of the emulsifier may be, for example, 0.01 parts by mass or more, 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, based on 100 parts by mass of the monomer component. In step (i), the amount of the emulsifier may be, for example, 15 parts by mass or less, 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, based on 100 parts by mass of the monomer component.

[0269] That is, in step (i), the amount of the emulsifier may be, for example, 0.01 to 15 parts by mass, 0.01 to 12 parts by mass, 0.01 to 10 parts by mass, 0.01 to 8 parts by mass, 0.01 to 6 parts by mass, 0.1 to 15 parts by mass, 0.1 to 12 parts by mass, 0.1 to 10 parts by mass, 0.1 to 8 parts by mass, 0.1 to 6 parts by mass, 0.3 to 15 parts by mass, 0.3 to 12 parts by mass, 0.3 to 10 parts by mass, 0.3 to 8 parts by mass, 0.3 to 6 parts by mass, relative to 100 parts by mass of the monomer component. , 0.5-15 parts by mass, 0.5-12 parts by mass, 0.5-10 parts by mass, 0.5-8 parts by mass, 0.5-6 parts by mass, 0.7-15 parts by mass, 0.7-12 parts by mass, 0.7-10 parts by mass, 0.7-8 parts by mass, 0.7-6 parts by mass, 0.9-15 parts by mass, 0.9-12 parts by mass, 0.9-10 parts by mass, 0.9-8 parts by mass, 0.9-6 parts by mass, 1-15 parts by mass, 1-12 parts by mass, 1-10 parts by mass, 1-8 parts by mass or 1-6 parts by mass.

[0270] The radical polymerization initiator is not particularly limited as long as it is a polymerization initiator that can start emulsion polymerization of the monomer components, and can be appropriately selected from known radical polymerization initiators.

[0271] Examples of the radical polymerization initiator include hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, 4,4′-azobis(4-cyanovaleric acid), and 2,2′-azobis[N-(2-hydroxyethyl)-2-methylpropionamide].

[0272] In step (ii), the amount of the radical polymerization initiator may be, for example, 0.001 parts by mass or more, 0.01 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more, relative to 100 parts by mass of the monomer component. In addition, in step (ii), the amount of the radical polymerization initiator may be, for example, 5 parts by mass or less, 3 parts by mass or less, 2 parts by mass or less, or 1 part by mass or less, relative to 100 parts by mass of the monomer component.

[0273] That is, in step (ii), the amount of the radical polymerization initiator may be, for example, 0.001 to 5 parts by mass, 0.001 to 3 parts by mass, 0.001 to 2 parts by mass, 0.001 to 1 part by mass, 0.01 to 5 parts by mass, 0.01 to 3 parts by mass, 0.01 to 2 parts by mass, 0.01 to 1 part by mass, 0.05 to 5 parts by mass, 0.05 to 3 parts by mass, 0.05 to 2 parts by mass, 0.05 to 1 part by mass, 0.1 to 5 parts by mass, 0.1 to 3 parts by mass, 0.1 to 2 parts by mass, or 0.1 to 1 part by mass, based on 100 parts by mass of the monomer component.

[0274] In step (ii), a reducing agent may be used together with the free radical polymerization initiator as required. Thus, the generation of free radicals of the free radical polymerization initiator is promoted. Examples of the reducing agent include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, and glucose; reducing inorganic compounds such as thiourea dioxide and hydrazine.

[0275] In step (ii), after the emulsion polymerization is completed, neutralization may be performed with a neutralizer. The neutralizer is not particularly limited and may be a known neutralizer. Examples of the neutralizer include aqueous ammonia, morpholine, 2-amino-2-methyl-1-propanol, triethylamine, triethanolamine, sodium hydroxide, potassium hydroxide, and the like. The amount of the neutralizer is not particularly limited and may be appropriately adjusted, for example, so that the pH of the obtained emulsion is 7 to 11 (preferably 8 to 10).

[0276] The emulsion obtained in step (ii) contains emulsified particles containing a binder resin. The average particle size of the emulsified particles in the emulsion may be, for example, 50 nm or more, 70 nm or more, 90 nm or more, or 100 nm or more. Furthermore, the average particle size of the emulsified particles in the emulsion may be, for example, 400 nm or less, 350 nm or less, or 300 nm or less.

[0277] That is, the average particle size of the emulsified particles in the emulsion can be, for example, 50 to 400 nm, 50 to 350 nm, 50 to 300 nm, 70 to 400 nm, 70 to 350 nm, 70 to 300 nm, 90 to 400 nm, 90 to 350 nm, 90 to 300 nm, 100 to 400 nm, 100 to 350 nm or 100 to 300 nm.

[0278] In the present specification, the average particle size of emulsified particles in the emulsion refers to a value measured at 23° C. by a dynamic light scattering method (DLS) using MICROTRACUPA150 (manufactured by Microtrac BEL Corp.).

[0279] The minimum film-forming temperature (MFT) of the emulsion obtained in step (ii) may be, for example, 25°C or less, preferably 20°C or less, and more preferably 15°C or less from the viewpoint of further improving film-forming properties. Furthermore, from the viewpoint of better film-forming properties at low temperatures, the minimum film-forming temperature (MFT) of the emulsion is preferably 10°C or less, more preferably 8°C or less, and may be 6°C or less. The lower limit of the minimum film-forming temperature (MFT) of the emulsion is not particularly limited. In addition, when the coating contains an aqueous solvent, the MFT below 0°C cannot be measured.

[0280] The dispersion liquid preparation step is a step of mixing aerogel particles, a water-soluble polymer, and a second liquid medium to obtain a dispersion liquid containing aerogel particles, a water-soluble polymer, and the second liquid medium.

[0281] The dispersion preparation step may be a step of mixing aerogel particles, a water-soluble polymer, and a second liquid medium so that the aerogel particles aggregate, thereby obtaining a dispersion containing aggregates of aerogel particles, a water-soluble polymer, and a second liquid medium.

[0282] The second liquid medium may be the same liquid medium as the above-mentioned liquid medium. The second liquid medium is preferably an aqueous solvent.

[0283] In the dispersion preparation step, the amount of the water-soluble polymer may be, for example, 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more, based on 100 parts by mass of the aerogel particles. In addition, in the dispersion preparation step, the amount of the water-soluble polymer may be, for example, 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less, based on 100 parts by mass of the aerogel particles.

[0284] That is, in the dispersion preparation step, the amount of the water-soluble polymer can be, for example, 0.1 to 20 parts by mass, 0.1 to 15 parts by mass, 0.1 to 10 parts by mass, 0.5 to 20 parts by mass, 0.5 to 15 parts by mass, 0.5 to 10 parts by mass, 1 to 20 parts by mass, 1 to 15 parts by mass, 1 to 10 parts by mass, 2 to 20 parts by mass, 2 to 15 parts by mass, 2 to 10 parts by mass, 3 to 20 parts by mass, 3 to 15 parts by mass or 3 to 10 parts by mass based on 100 parts by mass of the aerogel particles.

[0285] In the dispersion preparation step, the mixing method is not particularly limited, and mixing can be performed by, for example, stirring.

[0286] The stirring speed will affect the size of the aggregate. The greater the stirring speed, the greater the shear stress, so the size of the aggregate tends to decrease. Therefore, from the viewpoint of obtaining an aggregate of a preferred size described later, it is preferred to mix at a slow stirring speed.

[0287] In addition, the viscosity during mixing also affects the size of the agglomerate. Even at the same stirring speed, the shear stress will also change according to the viscosity. If the viscosity is high, a greater shear stress is applied, and the agglomerate is downsized. On the other hand, if the viscosity is low, the shear stress decreases, and the agglomerate tends to become larger. Therefore, by adjusting the stirring speed according to the viscosity, the size of the desired agglomerate can be achieved.

[0288] Furthermore, the amount of liquid medium during mixing will also affect the size of the agglomerates. Although the final composition is the same, the size of the agglomerates is different between the method (i) of adding all the liquid medium from the initial mixing stage and the method (ii) of adding the liquid medium after mixing with a small amount of liquid medium at the initial mixing stage. The initial viscosity of the method (ii) is higher than that of the method (i). Therefore, the agglomerates of the method (ii) tend to be smaller than those of the method (i). By using these methods according to the composition, mixing device (stirring device) and other conditions, agglomerates of the desired size can be formed.

[0289] The size of the aggregates in the dispersion is not particularly limited, and can be appropriately adjusted so that the size of the aggregates in the coating liquid is within the preferred range described below.

[0290] The coating liquid production step is a step of mixing the emulsion and the dispersion to obtain the coating liquid.

[0291] In the coating liquid production process, the mixing method is not particularly limited, and mixing may be performed by stirring, for example.

[0292] The mixing method in the coating liquid production step can be appropriately adjusted, similar to the mixing method in the dispersion preparation step, so that the size of the agglomerates of the aerogel particles falls within the preferred range described below.

[0293] The average diameter of the agglomerates may be, for example, 20 μm or more, or 30 μm or more. If the average diameter of the agglomerates is large, the contact interface between the aerogel and the binder resin becomes smaller, and the penetration of the resin into the pores of the aerogel is further suppressed. The average diameter of the agglomerates may be, for example, 300 μm or less, or 200 μm or less or 150 μm or less. If the average diameter of the agglomerates is small, the decrease in film strength caused by the continuity of relatively brittle aerogels is suppressed, and a stronger composite material is easily obtained.

[0294] That is, the average diameter of the aggregates may be, for example, 20 to 300 μm, 20 to 200 μm, 20 to 150 μm, 30 to 300 μm, 30 to 200 μm, or 30 to 150 μm.

[0295] The average diameter of the agglomerates can be more than 2 times, or more than 3 times, the average diameter of the aerogel particles. If the average diameter of the agglomerates is large, the contact interface between the aerogel and the binder resin becomes smaller, and the penetration of the resin into the pores of the aerogel is further suppressed. In addition, the average diameter of the agglomerates can be less than 30 times, or less than 20 times, or less than 15 times the average diameter of the aerogel particles. If the average diameter of the agglomerates is small, the reduction in film strength caused by the continuity of the relatively brittle aerogel is suppressed, and a more solid composite material is easily obtained.

[0296] That is, the average diameter of the aggregates may be 2 to 30 times, 2 to 20 times, 2 to 15 times, 3 to 30 times, 3 to 20 times, or 3 to 15 times the average diameter of the aerogel particles.

[0297] In addition, in this specification, the average diameter of aggregates refers to a value measured by the following method.

[0298] [Method for measuring the average diameter of aggregates in coating liquid]

[0299] Take about 20g of the coating liquid in a 100mL plastic cup, stir with a spatula and add water in an amount of 2g each time, thereby gradually making it compatible and diluting it. Take the diluted sample on a glass plate and use an optical microscope (manufactured by OLYMPUS, model: BX51) to obtain a microscope photo of the sample. Use the image editing software ImageJ to analyze the obtained microscope photos and find the diameters of multiple agglomerates in the microscope photos. The average value of the obtained values ​​is used as the average diameter of the agglomerates.

[0300] In this specification, the average diameter of aerogel particles has the same meaning as the average particle size (D50) of the aerogel particles described above.

[0301] In this embodiment, when the diluted liquid obtained by diluting the coating liquid is observed using an optical microscope, the area occupied by agglomerates with a diameter of 20 μm or more (more preferably agglomerates with a diameter of 50 μm or more) of the aerogel particles (including agglomerates) within the observation field of view is preferably 50% or more, more preferably 60% or more, further preferably 70% or more, and may also be 100%.

[0302] In addition, in this specification, the dilution obtained by diluting the coating liquid and the method for observing the dilution can be the same as the sample prepared in the above-mentioned [Method for measuring the average diameter of agglomerates in the coating liquid] and the method for observing the sample. In addition, the "area within the observation field of view" is obtained by analyzing the microscope photograph using the image editing software ImageJ.

[0303] <Method for producing composite materials>

[0304] In this embodiment, the composite material can be manufactured by a manufacturing method including the following steps: a coating step of coating the coating liquid on a support to obtain a coating film; and a removal step of removing at least a portion of the liquid medium from the coating film to obtain the composite material. That is, the composite material of this embodiment can be a dried product of the coating liquid.

[0305] The composite material of the present embodiment may be, for example, a composite material including a binder resin, aerogel particles, and a water-soluble polymer having a hydrophobic group.

[0306] In this embodiment, by using the above coating liquid, a composite material in which aerogel particles and binder particles are appropriately dispersed can be easily obtained. In addition, in this embodiment, by using the above coating liquid, a composite material in a good film shape can be obtained even when the coating process is performed at a low temperature (e.g., below 10°C).

[0307] The support to which the coating liquid is applied is not particularly limited. The support may be peeled off from the composite material after the composite material is manufactured, or may be used without being peeled off from the composite material. The support may be, for example, an applicable object of the composite material. The material constituting the support is not particularly limited, and may be, for example, a material formed of metal, ceramic, glass, resin, and a mixture thereof. Furthermore, the form of the support may be appropriately selected according to the purpose of use, material, etc., and may be, for example, block, sheet, powder, fiber, etc.

[0308] The coating method of the coating liquid is not particularly limited, and examples thereof include dip coating, spray coating, spin coating, and roll coating.

[0309] As a coating method for the coating liquid, a coating method in which the pressure applied to the coating liquid is 1.5 MPa or less is preferred. According to this coating method, the crushing of the agglomerates in the coating liquid caused by the load during coating is suppressed, and the agglomerates produce the above-mentioned effect more significantly. For example, coating methods such as roller coating, trowel coating, and air spray coating are preferred because they can easily reduce the pressure applied to the coating liquid.

[0310] In the removing step, at least a portion of the liquid medium is removed from the coating film, thereby forming a composite material containing the binder resin, the aerogel particles, and the water-soluble polymer.

[0311] The method of removing the liquid medium from the coating film is not particularly limited, and examples thereof include a method of performing a heating (eg, 40 to 150° C.) treatment, a reduced pressure (eg, 10000 Pa or less) treatment, or both.

[0312] The thickness of the composite material is not particularly limited, and may be, for example, 0.05 mm or more, 0.1 mm or more, 0.5 mm or more, or 1 mm or more. Also, the thickness of the composite material may be, for example, 30 mm or less, 20 mm or less, 10 mm or less, or 5 mm or less.

[0313] That is, the thickness of the composite material can be, for example, 0.05 to 30 mm, 0.05 to 20 mm, 0.05 to 10 mm, 0.05 to 5 mm, 0.1 to 30 mm, 0.1 to 20 mm, 0.1 to 10 mm, 0.1 to 5 mm, 0.5 to 30 mm, 0.5 to 20 mm, 0.5 to 10 mm, 0.5 to 5 mm, 1 to 30 mm, 1 to 20 mm, 1 to 10 mm or 1 to 5 mm.

[0314] The composite material has pores caused by the aerogel particles. From the viewpoint of obtaining higher thermal insulation, the pore volume of the composite material is preferably 0.15 cm 3 / g or more, more preferably 0.20cm 3 / g or more, more preferably 0.60cm 3 / g or more. The upper limit of the pore volume of the composite material is not particularly limited. The pore volume of the composite material may be, for example, 5.0 cm 3 / g or less.

[0315] That is, the pore volume of the composite material can be, for example, 0.15 to 5.0 cm 3 / g, 0.20~5.0cm 3 / g or 0.60~5.0cm 3 / g.

[0316] The thermal conductivity of the composite material is, for example, 0.05 W / (m·K) or less, preferably 0.04 W / (m·K) or less, and more preferably 0.035 W / (m·K) or less. The lower limit of the thermal conductivity of the composite material is not particularly limited. The thermal conductivity of the composite material may be, for example, 0.01 W / (m·K) or more.

[0317] That is, the thermal conductivity of the composite material may be, for example, 0.01 to 0.05 W / (m·K), 0.01 to 0.04 W / (m·K), or 0.01 to 0.035 W / (m·K).

[0318] The composite material of the present embodiment has excellent thermal insulation derived from aerogel. Therefore, the composite material can be suitable for use as a thermal insulation material in the fields of construction such as extremely low temperature containers, space fields, pipelines, outer walls, automobile fields such as automobile air conditioning units, engines, home appliances such as refrigerators and freezers, semiconductor fields, pipelines, storage tanks and other industrial equipment, etc. In addition to the use of composite materials as thermal insulation materials, they can also be used as waterproof materials, sound absorbing materials, vibration damping materials, catalyst carrier materials, etc. In addition, the composite material of the present embodiment has excellent bending resistance. Therefore, the composite material of the present embodiment can be preferably used for applications to supports with curved surfaces, applications on supports with curved surfaces, configurations on curved surfaces, winding around cylindrical portions, etc.

[0319] The composite material of the present embodiment can be preferably used for applications in contact with a heat source.

[0320] The article of the present embodiment may include, for example, a heat source and a composite material in thermal contact with the heat source.

[0321] As mentioned above, although the preferred embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment.

[0322] Example

[0323] Hereinafter, the present invention will be described in further detail using examples, but the present invention is not limited to these examples.

[0324] (Example 1)

[0325] (1) Manufacture of emulsion

[0326] In a reaction container equipped with a stirring device, a thermometer, a cooling tube and a dropping funnel, 160 parts by mass of ion exchange 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 placed, stirred, and after heating to 65° C., the reaction container was ventilated with nitrogen to remove dissolved oxygen.

[0327] 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 ion-exchanged water, and 48.8 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 mixed and emulsified in a homogenizer to obtain a monomer emulsion.

[0328] 3% of the monomer emulsion was stirred and added to the above reaction vessel, and 0.7 parts by mass of "Trigonox A-W70" (manufactured by KAYAKU NOURYON CORPORATION, 70% aqueous solution of tert-butyl hydroperoxide) and 0.23 parts by mass of ascorbic acid were added as free radical polymerization initiators, and the mixture was reacted for 15 minutes. Next, the remaining 97% of the monomer emulsion, a solution of 0.9 parts by mass of "Trigonox AW70" dissolved in 60 parts by mass of ion exchange water, and a solution of 0.37 parts by mass of ascorbic acid dissolved in 60 parts by mass of ion exchange water were added dropwise to the reaction vessel over 4 hours to react. After the addition was completed, the mixture was further stirred at 65°C for 1 hour, cooled to below 40°C, and 2.9 parts by mass of ammonia water with a concentration of 26% was added as a neutralizer. Thus, an emulsion containing a binder resin, emulsified particles containing a nonionic emulsifier, and water was obtained.

[0329] The properties of the emulsion are as follows.

[0330] Non-volatile content: 49.5% by mass

[0331] Viscosity at 23°C: 35mPa·s

[0332] pH at 23°C: 8.6

[0333] Minimum film forming temperature (MFT): 5°C

[0334] ·Glass transition temperature of binder resin: 9°C

[0335] The average particle size of emulsion particles: 210nm

[0336] [Determination of non-volatile content of emulsion]

[0337] 1 g of the emulsion was weighed, placed on an aluminum pan with a diameter of 5 cm, and placed in a desiccator. The emulsion was dried at 1 atmosphere (1013 hPa) and 105°C for 1 hour while circulating the air in the desiccator, and the mass of the remaining components was measured. The mass ratio (mass %) of the above components remaining after drying relative to the mass (1 g) of the emulsion before drying was calculated as the non-volatile component concentration (mass %).

[0338] [Measurement of viscosity of emulsion]

[0339] A BL type viscometer was used as a measuring instrument, and the measurement was performed under the conditions of a temperature of 23° C. and a rotation speed of 60 rpm.

[0340] [Measurement of pH of emulsion]

[0341] The pH at 23° C. was measured using a pH meter (manufactured by DKK-TOA CORPORATION, glass electrode hydrogen ion concentration indicator HM-30G).

[0342] [Measurement of average particle size of emulsified particles]

[0343] The average particle size (d50) of the emulsified particles was measured at 23°C by dynamic light scattering (DLS) using MICROTRAC UPA150 (manufactured by Microtrac BEL Corp.).

[0344] [Determination of minimum film forming temperature (MFT)]

[0345] The emulsion was applied to the measuring surface of the thermal gradient MFT measuring device using a 0.3 mm applicator and dried in a windless environment. The dried film was visually observed for cracks and film formation defects, and the MFT was measured.

[0346] [Glass transition temperature (Tg) of binder resin]

[0347] The glass transition temperature (Tg) of the binder resin is determined by measuring the temperature dependence of the loss tangent using a rheometer (MCR-102, manufactured by Anton Paar GmbH). Specifically, a parallel flat plate with a diameter of 12 mm is used, and the measurement conditions are a frequency of 1 Hz and a strain of 2% in the vibration mode. After a small amount of the emulsion is dispensed onto the measurement plate, it is brought into contact with the plate and heated from 30°C to 180°C at a rate of 10°C / min to remove the volatile components of the emulsion and make the resin and the plate closely attached. Next, the temperature is lowered from 180°C to 0°C at a rate of 2°C / min, and the loss tangent is measured at intervals of 1 point / °C, and the temperature at which the loss tangent is the largest is taken as the glass transition temperature.

[0348] (2) Manufacture of coating liquid

[0349] In a 500 mL separable flask, 1 part by mass of Sanjielose 90L (manufactured by Daido Chemical Industry Co., Ltd.) as a water-soluble polymer, 9 parts by mass of isopropyl alcohol (manufactured by FUJIFILM Wako Pure Chemical Corporation, reagent), 179 parts by mass of hot water, and 4 parts by mass of glass fiber (manufactured by Nitto Boseki Co., Ltd., product name: CS3J-891) were taken, and stirred at 200 rpm for 1 minute using a mechanical stirrer to obtain a dispersion. Then, the flask was cooled in an ice water bath and stirred at 200 rpm using a mechanical stirrer to dissolve Sangelose 90L, and a pre-gel as an aqueous solution of Sangelose 90L was obtained. In a planetary mixer (manufactured by PRIMIX Corporation, Model 2P-1), 188 parts by mass of the pregel and 21 parts by mass of aerogel particles (manufactured by CABOT, product name: ENOVA MT1100, particle diameter 2 to 24 μm, average particle diameter (D50) 10 μm) were added and stirred at 25 rpm for 10 minutes. Next, 86 parts by mass of the emulsion obtained in (1) was added and stirred at 25 rpm for 15 minutes to obtain a coating liquid.

[0350] In addition, the content of aerogel particles in the coating liquid was 84.9% by volume based on the total volume of solid components, and the content of water-soluble polymers in the coating liquid was 1.5% by mass based on the total amount of non-volatile components, and the content of emulsified particles (the total amount of binder resin and emulsifier) ​​was 61.5% by mass.

[0351] The average diameter of the agglomerates of the aerogel particles in the obtained coating liquid was measured by the following method. The results are shown in Table 1.

[0352] <Measurement of average diameter of aerogel particle aggregates>

[0353] About 20 g of the coating liquid was placed in a 100 mL plastic cup, stirred with a spatula, and water was added in an amount of 2 g each time, while it was gradually mixed and diluted. The diluted sample was placed on a glass plate, and an optical microscope (manufactured by OLYMPUS, model: BX51) was used to observe the agglomerates of aerogel particles in the coating liquid, and a microscope photograph was obtained. The obtained microscope photograph was analyzed using the image editing software ImageJ to obtain the average diameter of the agglomerates of the aerogel particles.

[0354] <Determination of chloride ion and sulfate ion content>

[0355] About 2.0 g of the coating liquid and about 20.0 g of ultrapure water were placed in a Teflon (registered trademark) container, and heated and extracted at 100°C for 2 hours. After cooling, centrifugation was performed at 15,000 rpm for 1 hour, and the supernatant was subjected to solid phase extraction and ultrafiltration as a measurement sample. Using an ion chromatograph (manufactured by Thermo Fisher Scientific KK, product name: ICS-2000) equipped with an anion exchange column (manufactured by Thermo Fisher Scientific KK, product name: AS20), the ion content was measured under the conditions of column temperature 30°C, flow rate 1.0 mL / min, injection volume 25 μL, and the gradient of potassium hydroxide solution set to 5 mM at 0 to 5 minutes, 30 mM at 15 minutes, and 55 mM at 20 minutes. The chloride ion content was evaluated based on the peak detected at a retention time of 10.8 minutes, and the sulfate ion content was evaluated based on the peak detected at a retention time of 16.1 minutes.

[0356] <Crack evaluation of composite materials at 23°C>

[0357] A frame made of fluororesin with a length and width of 40 mm and a thickness of 2 mm was prepared on an aluminum foil (manufactured by UACJ Corporation, product name: My Foil Thick Type 50, thickness: 50 μm), and a coating liquid was applied to the frame using a scraper as an evaluation sample. The evaluation sample was placed in a tank of a low-temperature constant temperature and humidity machine (manufactured by Kanematsu Chemicals Ltd., HIFLEXFX411N) set at 23°C and 60%RH for 12 hours, and the liquid medium was removed from the coating liquid to obtain a composite material. Regarding the obtained composite material, the case where there is no crack as a whole is set as A, the case where there is crack in a part is set as B, and the case where there is crack as a whole is set as C, and the degree of cracking was evaluated.

[0358] <Crack evaluation of composite materials at 10°C>

[0359] A frame made of fluororesin with a length and width of 40 mm and a thickness of 2 mm was prepared on an aluminum foil (manufactured by UACJ Corporation, product name: My Foil Thick Type 50, thickness: 50 μm), and a coating liquid was applied to the frame using a scraper as an evaluation sample. The evaluation sample was placed in a tank of a low-temperature constant temperature and humidity machine (manufactured by Kanematsu Chemicals Ltd., HIFLEXFX411N) set at 10°C and 60% RH for 24 hours, and the liquid medium was removed from the coating liquid to obtain a composite material. Regarding the obtained composite material, the case where there is no crack as a whole is set as A, the case where there is crack in a part is set as B, and the case where there is crack as a whole is set as C, and the degree of cracking was evaluated.

[0360] <Evaluation of pore volume of composite materials>

[0361] A composite material was prepared by the same method as in the above <Crack evaluation of composite material at 23° C.> 100 mg of the obtained composite material was collected and the pore volume was calculated using a high-sensitivity gas adsorption analyzer (AutoSorbiQ, manufactured by Quantachrome).

[0362] <Evaluation of thermal conductivity of composite materials>

[0363] A frame made of fluororesin with a length and width of 200 mm and a thickness of 3 mm was prepared on an aluminum foil (manufactured by UACJ Corporation, product name: My Foil Thick Type 50, thickness: 50 μm), and a coating liquid was applied to the frame using a scraper. After being placed at room temperature of 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 μm. The thermal conductivity of the obtained composite material was measured by a steady-state method using a thermal conductivity measuring device "HFM-446" (manufactured by NETZSCH, product name).

[0364] <Evaluation of Corrosion Resistance of Composite Materials>

[0365] A few mL of the coating solution was dripped onto a carbon steel plate (100 mm × 70 mm × 0.8 mm), and the plate was left at room temperature of 23°C for 12 hours. The liquid medium was removed from the coating solution to form a coating film. Next, the coating film was removed to expose the surface of the carbon steel plate, and the presence of rust was visually inspected. The plate without rust was designated as A, the plate with rust of less than 10% in the coating area was designated as B, and the plate with rust of more than 10% was designated as C. Corrosion (flash rust) was evaluated.

[0366] <Evaluation of weather resistance of composite materials>

[0367] The coating liquid was applied to a carbon steel plate (100 mm × 70 mm × 0.8 mm) by air spraying to a thickness of 2 mm, and then placed at room temperature 23°C for 12 hours. The liquid medium was removed from the coating liquid to obtain a carbon steel plate with a 1 mm thick composite material. Then, an accelerated weathering test was performed for 240 cycles and 1920 hours under the conditions shown below, and whitening was evaluated.

[0368] Cycle conditions (1 cycle)

[0369] (1) Irradiation: 60±3℃ for 4 hours

[0370] (2) Dark / humid at 50±2℃ for 4 hours

[0371] ·Whitening evaluation

[0372] After the pressure-sensitive adhesive tape is strongly pressed against the composite material, it is peeled off and the amount of fine powder attached to the tape is observed. The level is determined according to JIS-K5600-8-6 (level 1 is when there is no adhesion, level 5 is when the fine powder is seamlessly transferred to the entire surface of the tape, and levels 2, 3, and 4 are in the middle, starting from the direction with the least adhesion).

[0373] <Evaluation of flexural resistance of composite materials>

[0374] The thickness of the composite material was set to 1 mm or 2 mm, and a stainless steel plate (100 mm × 70 mm × 0.3 mm) was used as the substrate. In addition, the composite material was manufactured in the same manner as in <Evaluation of Weathering Resistance of Composite Materials> as an evaluation sample. The evaluation sample was bent along a cylindrical mandrel with a diameter of 10 mm, and the presence or absence of cracks and peeling was visually confirmed. The case where no cracks or peeling were confirmed was evaluated as A, and the case where cracks or peeling were confirmed was evaluated as B.

[0375] (Example 2)

[0376] A coating liquid was prepared in the same manner as in Example 1 except that additional stirring was performed at 50 rpm for 3 minutes in a planetary mixer (manufactured by PRIMIX Corporation, Model 2P-1). The obtained coating liquid was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0377] (Example 3)

[0378] A coating liquid was prepared in the same manner as in Example 1 except that additional stirring was performed at 50 rpm for 5 minutes in a planetary mixer (manufactured by PRIMIX Corporation, Model 2P-1). The obtained coating liquid was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0379] (Example 4)

[0380] A coating liquid was prepared in the same manner as in Example 1 except that additional stirring was performed at 50 rpm for 15 minutes in a planetary mixer (manufactured by PRIMIX Corporation, Model 2P-1). The obtained coating liquid was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0381] (Example 5)

[0382] A coating liquid was prepared in the same manner as in Example 1 except that the amount of aerogel particles was changed to 14 parts by mass and the amount of the emulsion was changed to 93 parts by mass. The obtained coating liquid was evaluated in the same manner as in Example 1. Table 2 shows the results.

[0383] (Example 6)

[0384] A coating liquid was prepared in the same manner as in Example 1 except that the aerogel particles were changed to those manufactured by JIOS Corporation, product name: Aerova (average particle size (D50) 17 μm). The coating liquid was evaluated in the same manner as in Example 1, and the results are shown in the table.

[0385] (Example 7)

[0386] (1) Preparation of Aerogel Particles A

[0387] As a raw material containing silica particles, 100.0 parts by mass of PL-2L (manufactured by Fuso Chemical Co., Ltd., product name), 80.0 parts by mass of water, 0.5 parts by mass of acetic acid as an acid catalyst, 1.0 parts by mass of hexadecyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd.) as a cationic surfactant, and 150.0 parts by mass of urea as a thermal hydrolysis product were mixed, and 60.0 parts by mass of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM-13) as a silicon compound, 20.0 parts by mass of dimethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KMB-22), and 20.0 parts by mass of a polysiloxane compound modified with difunctional alkoxy groups at both ends (hereinafter referred to as "polysiloxane compound A") were 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.

[0388] In addition, the above-mentioned "polysiloxane compound A" is synthesized as follows. First, in a 1-liter three-necked flask equipped with a stirrer, a thermometer and a serpentine condenser, 100.0 parts by mass of dimethylpolysiloxane XC96-723 (manufactured by MomentivePerformance Materials Japan LLC, product name) having silanol groups at both ends, 181.3 parts by mass of methyltrimethoxysilane and 0.50 parts by mass of tert-butylamine are mixed and reacted at 30°C for 5 hours. Then, the reaction solution is heated at 140°C for 2 hours under a reduced pressure of 1.3 kPa, and a two-functional alkoxy-modified polysiloxane compound (polysiloxane compound A) at both ends is obtained by removing volatile components.

[0389] Then, the obtained wet gel was transferred to a plastic bottle, sealed, and crushed at 27,000 rpm for 10 minutes using an extreme grinder (manufactured by ASONE Corporation, MX-1000XTS) to obtain a granular wet gel. The obtained granular wet gel was immersed in 2500.0 parts by mass of methanol and washed at 25°C for 24 hours. The washing operation was replaced with new methanol and performed a total of 3 times. Next, the washed granular wet gel was immersed in 2500.0 parts by mass of heptane as a low surface tension solvent, and solvent replacement was performed at 25°C for 24 hours. The solvent replacement operation was replaced with new heptane and performed a total of 3 times. The washed and solvent-replaced granular wet gel was dried at 40°C for 96 hours under normal pressure, and then further dried at 150°C for 2 hours. Finally, the aerogel particles A were obtained by passing through a sieve (manufactured by TOKYOSCREEN CO., LTD., pore size 45 μm, wire diameter 32 μm).

[0390] (2) Manufacture of coating liquid

[0391] A coating liquid was prepared in the same manner as in Example 1 except that the aerogel particles were changed to aerogel particles A. The coating liquid obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

[0392] (Comparative Example 1)

[0393] A coating liquid was prepared in the same manner as in Example 1 except that the emulsion was changed to BONCOAT DV759-EF (Tg of the resin: 15° C.) manufactured by DIC Corporation. The obtained coating liquid was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0394] (Comparative Example 2)

[0395] A coating liquid was prepared in the same manner as in Example 1 except that the emulsion was changed to Boncoat DV759-EF manufactured by DIC Corporation and stirring was performed at 1500 rpm for 5 minutes using a rotation and revolution mixer (manufactured by THINKY, product name: Defoam Rentaro, model: ARE-310). The coating liquid obtained was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0396] (Comparative Example 3)

[0397] A coating liquid was prepared in the same manner as in Example 1 except that the emulsion was changed to Boncoat DV759-EF manufactured by DIC Corporation and stirring was performed at 2000 rpm for 5 minutes using an autorotation-revolution mixer (manufactured by THINKY, product name: Defoam Rentaro, model: ARE-310). The coating liquid obtained was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0398] [Table 1]

[0399]

[0400] [Table 2]

[0401]

[0402] [Table 3]

[0403]

Claims

1. A coating liquid comprising: emulsified particles, containing a binder resin; Aerogel particles; A water-soluble polymer having a hydrophobic group; and Liquid medium, The binder resin includes a structural unit derived from a first monomer having a homopolymer Tg of less than 0°C.

2. The coating liquid according to claim 1, wherein At least a portion of the aerogel particles forms aggregates.

3. The coating liquid according to claim 2, wherein The average diameter of the agglomerates is 2 to 40 times the average diameter of the aerogel particles.

4. The coating liquid according to claim 1, wherein The first monomer is an alkyl (meth)acrylate whose homopolymer Tg is less than 0°C.

5. The coating liquid according to claim 1, wherein The binder resin further includes a structural unit derived from a second monomer having a homopolymer Tg of 0° C. or higher.

6. The coating liquid according to claim 1, wherein The binder resin has a Tg of 10° C. or less.

7. The coating liquid according to claim 1, wherein The emulsified particles further contain a nonionic emulsifier.

8. A method for preparing a coating liquid, comprising: An emulsion preparation step of preparing an emulsion including emulsified particles containing a binder resin and a first liquid medium; a dispersion preparation step of mixing aerogel particles, a water-soluble polymer having a hydrophobic group, and a second liquid medium to obtain a dispersion containing the aerogel particles, the water-soluble polymer, and the second liquid medium; and A coating liquid preparation step of mixing the emulsion and the dispersion to obtain a coating liquid, The binder resin includes a structural unit derived from a first monomer having a homopolymer Tg of less than 0°C.

9. The method for producing a coating liquid according to claim 8, wherein: The dispersion liquid preparation step is a step of mixing the aerogel particles, the water-soluble polymer, and the second liquid medium to aggregate the aerogel particles. The coating liquid manufacturing step is a step of obtaining a coating liquid containing the agglomerates of the aerogel particles.

10. The method for producing a coating liquid according to claim 9, wherein: The average diameter of the agglomerates is 2 to 40 times the average diameter of the aerogel particles.

11. The method for producing a coating liquid according to claim 8, wherein: The first monomer is an alkyl (meth)acrylate whose homopolymer Tg is less than 0°C.

12. The method for producing a coating liquid according to claim 8, wherein: The binder resin further includes a structural unit derived from a second monomer having a homopolymer Tg of 0° C. or higher.

13. The method for producing a coating liquid according to claim 8, wherein: The binder resin has a Tg of 10° C. or less.

14. The method for producing a coating liquid according to claim 8, wherein: The emulsified particles further contain a nonionic emulsifier.

15. A method for manufacturing a composite material, comprising: A coating step, coating the coating liquid according to any one of claims 1 to 7 on a support to obtain a coating film; and The removing step removes at least a portion of the liquid medium from the coating film to obtain a composite material.

16. A method for manufacturing a composite material, comprising: A coating step of coating the coating liquid produced by the production method according to any one of claims 8 to 14 on a support to obtain a coating film; and The removing step removes at least a portion of the liquid medium from the coating film to obtain a composite material.

17. A composite material, which is a dried product of the coating solution according to any one of claims 1 to 7.

18. An article comprising the composite material of claim 17.

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