Coating material for heat insulating material, heat insulating coating film and heat insulating material

Abstract

To provide a coating material for a heat insulating material which has excellent dispersibility of a silica aerogel and good coatability, and from which a heat insulating coating film having high durability and excellent heat insulating properties can be formed, and to provide a heat insulating coating film and a heat insulating material obtained from the coating material for a heat insulating material.SOLUTION: The coating material for a heat insulating material of the present invention comprises a silica aerogel (A), a urethane resin emulsion (B), a cellulose nanofiber (C), a nonionic surfactant (D), and water, wherein when the solid content mass of the urethane resin emulsion (B) is B (pts.mass) and the solid content mass of the cellulose nanofiber (C) is C (pts.mass), the value of B / C is 0.5 or more and 20 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a paint for a heat insulating material, a heat insulating coating film, and a heat insulating material. [Background technology]

[0002] Due to the strong promotion of energy conservation, the insulating performance required of insulating materials has been increasing year by year. Insulating materials are indispensable materials in various fields, including buildings such as houses, buildings, and factories, as well as vehicles such as automobiles and electronic devices. Various materials are known as insulating materials, such as inorganic fibers, inorganic foams, and resin-based foams, and silica aerogel is one such material.

[0003] Silica aerogel has a structure in which many silica particles are interconnected, resulting in a very high porosity and excellent thermal insulation properties. Therefore, there has been active development of thermal insulation materials that take advantage of these properties of silica aerogel. Various thermal insulation materials containing silica aerogel are known, and one such material is a thermal insulation material obtained from a thermal insulation paint containing silica aerogel.

[0004] For example, Patent Document 1 discloses that a coating material for heat insulation containing water, silica aerogel, a water-soluble binder, and nanofibers is applied to a substrate to form a silica aerogel-containing coating film on the substrate, which is used as a heat insulating material. In this coating material for heat insulating material, the presence of hydrophilic nanofibers around the silica aerogel makes the silica aerogel more compatible with water, thereby improving the dispersibility of the silica aerogel and achieving high heat insulating properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-065264 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, increasingly high demands have been placed on thermal insulation materials, and it is necessary to improve their thermal insulation performance as much as possible. The same is true for the above-mentioned coating materials for thermal insulation containing silica aerogel, and there is an urgent need to further improve the thermal insulation performance of the thermal insulation materials obtained from such coating materials. Therefore, in coating materials for thermal insulation containing silica aerogel, the challenge is how to further improve the dispersibility of the silica aerogel and how to increase the durability of the coating film obtained from the coating material for thermal insulation.

[0007] The present invention has been made in view of the above, and aims to provide a coating material for thermal insulation that has excellent dispersibility of silica aerogel, good coatability, and is capable of forming a thermal insulation coating film that has high durability and excellent thermal insulation properties. Another aim of the present invention is to provide a thermal insulation coating film and a thermal insulation material obtained from the coating material for thermal insulation. [Means for solving the problem]

[0008] As a result of extensive research to achieve the above-mentioned objective, the inventors discovered that the above-mentioned objective can be achieved by containing a urethane resin emulsion and cellulose nanofibers in a specified ratio and using a nonionic surfactant in combination, thereby completing the present invention.

[0009] That is, the present invention includes, for example, the subject matter described in the following sections. Item 1 Silica aerogel (A), a urethane resin emulsion (B); Cellulose nanofibers (C); Nonionic surfactant (D) Water and Including, When the solid content mass of the urethane resin emulsion (B) is B (parts by mass) and the solid content mass of the cellulose nanofibers (C) is C (parts by mass), A paint for heat insulation with a B / C value of 0.5 or more and 20 or less. Section 2 Item 2. The coating material for heat insulating materials according to Item 1, wherein the urethane resin emulsion (B) is a carbonate-based urethane resin emulsion. Section 3 Item 3. The coating material for heat insulating materials according to Item 1 or 2, wherein the silica aerogel (A) has an average particle size of 1 to 500 μm. Section 4 Item 4. A heat insulating coating film comprising a cured product of the coating material for heat insulating materials according to any one of Items 1 to 3. Section 5 Item 5. A heat insulating material containing the heat insulating coating film according to item 4. [Effects of the Invention]

[0010] The coating material for heat insulating materials of the present invention has excellent dispersibility of silica aerogel and good coatability, and can form a heat insulating coating film having high durability and excellent heat insulating properties.

[0011] The thermal barrier coating of the present invention and a thermal insulating material containing the thermal barrier coating have high durability and excellent thermal insulation properties. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0013] 1.Insulation paint The coating material for heat insulating materials of the present invention contains silica aerogel (A), a urethane resin emulsion (B), cellulose nanofibers (C), a nonionic surfactant (D), and water, and when the solid content mass of the urethane resin emulsion (B) is B (parts by mass) and the solid content mass of the cellulose nanofibers (C) is C (parts by mass), the value of B / C is 0.5 or more and 20 or less.

[0014] The heat insulating coating material of the present invention has excellent dispersibility of silica aerogel and good coatability. Furthermore, the heat insulating coating material of the present invention can form a heat insulating coating film having high durability and excellent heat insulating properties, and therefore can form an excellent heat insulating material. Therefore, the heat insulating coating material of the present invention can be suitably used as a raw material for producing heat insulating materials. Below, each component contained in the heat insulating coating material of the present invention and the heat insulating coating material will be described in order.

[0015] (Silica aerogel (A)) The coating material for heat insulating materials of the present invention contains silica aerogel as an essential component. In this specification, the silica aerogel contained in the coating material for heat insulating materials is referred to as "silica aerogel (A)."

[0016] The type of silica aerogel (A) is not particularly limited, and a wide variety of known silica aerogels can be used. Generally, silica aerogels are formed by silica fine particles of several tens of nanometers forming a network-like microstructure, and have a porous structure with fine pores. The size of the silica aerogel (A) used in the present invention is not particularly limited, and for example, the diameter of the silica fine particles (primary particles) forming the skeleton of the silica aerogel can be about 2 to 5 nm, and the size of the pores formed between the skeletons can be about 10 to 50 nm.

[0017] The shape of the silica aerogel (A) may be, for example, particulate, such as spherical particles or irregularly shaped particles, or lumps. When the silica aerogel (A) is formed into particles, the average particle diameter of the silica aerogel is preferably, for example, 1 μm or more and 500 μm or less. That is, the average particle diameter of the silica aerogel (A) is preferably 1 to 500 μm. In this case, the stability and coatability of the coating material for heat insulating materials are likely to be improved, and the durability of the coating film is likely to be increased, making it easy to form a heat insulating material with excellent heat insulating performance.

[0018] The average particle size of the silica aerogel (A) is more preferably 2 μm or more, even more preferably 5 μm or more, and particularly preferably 10 μm or more, and is more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 100 μm or less.

[0019] In the present invention, the average particle size of the silica aerogel (A) refers to a value measured by a laser diffraction method, specifically, a value measured by using a particle size distribution analyzer "SALD-2000" manufactured by Shimadzu Corporation for the coating material for heat insulating materials of the present invention in which the silica aerogel (A) is dispersed.

[0020] The average particle size of the silica aerogel (A) can be adjusted, for example, in step 1 performed in the method for preparing a coating material for heat insulating materials described later. Specifically, the average particle size of the silica aerogel (A) can be adjusted by the stirring conditions performed in step 1 as described later.

[0021] The specific surface area of ​​the silica aerogel (A) measured by the BET method is not particularly limited, and is, for example, 400 m 2 / g or more 1000m 2 / g or less.

[0022] The method for producing the silica aerogel (A) is not particularly limited, and it can be obtained by drying a wet silica gel. In this case, the drying method can be, for example, atmospheric drying or supercritical drying.

[0023] The silica aerogel (A) can be obtained from a commercially available product, such as silica aerogel particles "P-200" manufactured by Cabot Corporation.

[0024] (Urethane resin emulsion (B)) The heat insulating paint of the present invention contains a urethane resin emulsion as an essential component. In this specification, the urethane resin emulsion contained in the heat insulating paint is referred to as "urethane resin emulsion (B)."

[0025] Although the term "urethane resin emulsion (B)" originally refers to a dispersion of urethane resin in water or the like, in the heat insulating paint of the present invention, it is not possible to distinguish between the water or the like contained in the urethane resin emulsion (B) and the water contained in the heat insulating paint. Therefore, in the heat insulating paint of the present invention, the term "urethane resin emulsion (B)" refers to the urethane resin particles themselves, and the solvent, such as water, is not taken into consideration. However, as will be described later, when producing the heat insulating paint of the present invention, urethane resin particles dispersed in a solvent, such as water (aqueous polyurethane resin dispersion) are used to incorporate the urethane resin emulsion (B).

[0026] The urethane resin constituting the urethane resin emulsion (B) can be a reaction product (polyaddition product) of a polyol and a polyisocyanate. The polyol is a compound having two or more hydroxyl groups in the molecule, such as polycarbonate polyol, polyester polyol, polyhydric alcohol, polyether polyol, polyether ester polyol, polyolefin polyol, polyacrylic polyol, polyacetal polyol, polybutadiene polyol, polysiloxane polyol, fluorine polyol, or the like, which has two or more hydroxyl groups at the molecular end or in the molecule.

[0027] The polycarbonate polyol is preferably a polycarbonate diol, more preferably a polycarbonate diol derived from an aliphatic diol (-ROCOO-, where R represents an aliphatic group). Specific examples of such aliphatic diols include aliphatic diols having 1 to 10 carbon atoms, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,3-propylene glycol, 1,2-propylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, and neopentyl glycol.

[0028] Examples of the polyester polyol include esterified condensates obtained by reacting a low-molecular-weight polyol such as the above-mentioned aliphatic diol with a polycarboxylic acid. Examples of the polycarboxylic acid include succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and tetrahydrofuran acid. Two or more of these may be used in combination.

[0029] The polyhydric alcohol is not particularly limited, and examples thereof include ethylene glycol, diethylene glycol, butanediol, propylene glycol, hexanediol, bisphenol A, bisphenol B, bisphenol S, hydrogenated bisphenol A, dibromobisphenol A, 1,4-cyclohexanedimethanol, dihydroxyethyl terephthalate, hydroquinone dihydroxyethyl ether, trimethylolpropane, glycerin, and pentaerythritol.

[0030] Examples of the polyether polyol include alkylene derivatives of polyhydric alcohols, polytetramethylene glycol, and polythioether polyols.

[0031] The polyolefin polyol is not particularly limited, but examples thereof include polybutadiene polyol, polyisoprene polyol, and hydrogenated polyols thereof.

[0032] The polyol is preferably at least one selected from the group consisting of polycarbonate polyols and polyester polyols. In this case, the stability and coatability of the heat insulating coating material are likely to be improved, and the durability of the coating film is likely to be increased, making it easy to form a heat insulating material with excellent heat insulating performance. The polyol is particularly preferably polycarbonate polyol.

[0033] Therefore, in the coating material for heat insulating materials of the present invention, the urethane resin emulsion (B) is preferably at least one selected from the group consisting of carbonate-based urethane resin emulsions and ester-based urethane resin emulsions, and is particularly preferably a carbonate-based urethane resin emulsion.

[0034] The polyisocyanate is not particularly limited, and any polyisocyanate commonly used in the art can be used, including, for example, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and araliphatic polyisocyanates.

[0035] Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate.

[0036] Examples of the alicyclic polyisocyanate include isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatemethyl)cyclohexane.

[0037] Examples of aromatic polyisocyanates include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.

[0038] Examples of aromatic aliphatic polyisocyanates include dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, and α,α,α,α-tetramethylxylylene diisocyanate. Also included are modified products such as dimers, trimers, and biuretized isocyanates of these organic polyisocyanates. These can be used alone or in combination of two or more.

[0039] In the urethane resin emulsion (B), the number average molecular weight of the urethane resin is, for example, 10,000 or more and 500,000 or less.

[0040] The method for producing the urethane resin emulsion (B) is not particularly limited, and for example, a wide variety of known production methods can be used. For example, the urethane resin emulsion (B) can be obtained by a production method utilizing emulsification dispersion.

[0041] Examples of methods for producing aqueous polyurethane resin dispersions using emulsification include mixing a polyol and a polyisocyanate to prepare a urethane prepolymer, and then emulsifying and dispersing the urethane prepolymer. This allows for the preparation of an aqueous polyurethane resin dispersion containing a urethane resin, thereby obtaining the urethane resin emulsion (B) contained in the heat-insulating coating material. This mixing process can be carried out in a solvent. Such a solvent is preferably inert to isocyanate groups and capable of dissolving the resulting urethane prepolymer. Examples of suitable solvents include dioxane, methyl ethyl ketone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, acetone, toluene, dioxane, ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate.

[0042] The above mixing process promotes the reaction between the polyol and polyisocyanate, resulting in the production of a urethane prepolymer. After the urethane prepolymer is produced, the above-described emulsification and dispersion are carried out. Before the emulsification and dispersion, a neutralization treatment can be carried out using a neutralizing agent, if necessary. Examples of neutralizing agents include nonvolatile bases such as sodium hydroxide and potassium hydroxide, tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, and triethanolamine, and volatile bases such as ammonia.

[0043] A blocking agent can be added to the urethane prepolymer solution before or after the neutralization treatment, or preferably simultaneously with the neutralization treatment. The blocking agent reacts with the remaining NCO groups to terminate the reaction. This makes it easier to adjust the molecular weight of the urethane resin. A wide variety of known blocking agents can be used, including, for example, compounds having a monofunctional active hydrogen group, such as monohydric alcohol compounds and monohydric amino compounds (e.g., dibutylamine).

[0044] The method for emulsifying and dispersing is not particularly limited, and a wide variety of known methods can be used. For example, the urethane prepolymer can be emulsified and dispersed by mixing a solution of the urethane prepolymer with an aqueous solvent and applying shear using an emulsifying and dispersing machine such as a homogenizer. The aqueous solvent may contain the neutralizing agent as needed.

[0045] A chain extender can be added simultaneously with or after the emulsification and dispersion to extend the chains. This generates urea bonds through an interfacial polymerization reaction between the isocyanate groups in the emulsion micelles and the chain extender, thereby improving the crosslinking density within the emulsion micelles and forming a three-dimensional crosslinked structure. Examples of chain extenders include diamine compounds and polyamine compounds. Examples of diamine compounds include ethylenediamine, trimethylenediamine, piperazine, isophoronediamine, diethylenetriamine, dipropylenetriamine, and amino group-containing silane coupling agents. Examples of polyamine compounds include diethylenetriamine, dipropylenetriamine, and triethylenetetramine. Other polyamines may also be polycarbodiimide compounds, such as Nisshinbo Chemical's Carbodilite aqueous resin crosslinking agent.

[0046] The urethane resin emulsion (B) can be obtained from commercial products, for example, the Superflex (registered trademark) series from Daiichi Kogyo Seiyaku Co., Ltd.

[0047] (Cellulose nanofiber (C)) The coating material for thermal insulation materials of the present invention contains cellulose nanofibers as an essential component. In this specification, the cellulose nanofibers contained in the coating material for thermal insulation materials are referred to as "cellulose nanofibers (C)."

[0048] The cellulose nanofibers (C) that can be used satisfy the following (a) to (c): (a) The number average fiber diameter is 3 nm or more and 100 nm or less. (b) It has a cellulose type I crystal structure. (c) The average aspect ratio is between 2 and 5000.

[0049] The number-average fiber diameter (a) is more preferably 50 nm or less, even more preferably 30 nm or less, and may be 10 nm or less. The number-average fiber diameter can be measured as follows. Specifically, an aqueous dispersion of cellulose nanofibers with a solid content of 0.05 to 0.1 mass % is prepared, and the aqueous dispersion is cast onto a hydrophilically treated carbon film-coated grid to prepare a sample for observation with a transmission electron microscope (TEM). When fibers with large diameters are included, a scanning electron microscope (SEM) image of the surface cast onto glass may be observed. The observation sample may also be negatively stained, for example, with 2 mass % uranyl acetate. Then, electron microscope images are observed at magnifications of 5,000x, 10,000x, or 50,000x, depending on the size of the constituent fibers. In this case, an axis of any vertical or horizontal image width is assumed within the obtained image, and the sample and observation conditions (magnification, etc.) are adjusted so that 20 or more fibers intersect with this axis. After obtaining an observation image that satisfies these conditions, two random axes are drawn vertically and horizontally on each image, and the fiber diameters of the fibers intersecting the axes are visually read. In this way, at least three non-overlapping images of the surface are taken with the electron microscope, and the fiber diameter values ​​of the fibers intersecting the two axes are read (thus, information on the diameters of at least 20 fibers x 2 x 3 = 120 fibers is obtained). The arithmetic mean of the fiber diameters obtained in this way is taken as the number-average fiber diameter.

[0050] The presence of the cellulose type I crystal structure (b) above can be identified by the presence of typical peaks at two positions, around 2θ=14° to 17° and around 2θ=22° to 23°, in the diffraction profile obtained by wide-angle X-ray diffraction image measurement.

[0051] The average aspect ratio (c) above is more preferably 50 or more, even more preferably 100 or more, and may be 200 or more. The average aspect ratio is more preferably 1000 or less, and may be 500 or less. The average aspect ratio can be measured as follows. That is, the number average fiber diameter is calculated according to the method described above. The number average fiber length of the cellulose nanofibers is also calculated from the same observation image. Specifically, the length from the start point to the end point of at least 10 fibers (fiber length) is visually read. For branched fibers, the length of the longest part of the fiber is taken as the fiber length. The arithmetic mean of the fiber lengths obtained in this way is calculated and this is taken as the number average fiber length. Using these values, the average aspect ratio is calculated according to the following formula. Average aspect ratio = number average fiber length (nm) / number average fiber diameter (nm)

[0052] The cellulose nanofibers (C) may have anionic functional groups. Examples of anionic functional groups include at least one selected from the group consisting of carboxyl groups, phosphate groups, sulfonic acid groups, nitrate groups, borate groups, and sulfate groups. In this specification, the term "carboxyl group" refers not only to the acid form (-COOH) but also to the salt form, i.e., carboxylate salt group (-COOX, where X is a cation that forms a salt with a carboxylic acid), and the acid and salt forms may be mixed. Similarly, the term "phosphate group, sulfonic acid group, nitrate group, borate group, and sulfate group" refers to the acid form as well as the salt form, and the acid and salt forms may be mixed. The salt is not particularly limited, and examples include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, onium salts such as ammonium salts and phosphonium salts, and amine salts such as primary amines, secondary amines, and tertiary amines.

[0053] The amount of anionic functional groups in the cellulose nanofibers (C) is, for example, 0.5 to 3.0 mmol / g per dry mass of the cellulose nanofibers (C). For example, when the anionic functional groups are carboxy groups, the amount of anionic functional groups can be measured using a cellulose nanofiber-containing slurry prepared to a concentration of 0.1 to 1 mass%. Specifically, 60 mL of the slurry is prepared, and the pH is adjusted to about 2.5 with a 0.1 mol / L aqueous hydrochloric acid solution. Then, a 0.05 mol / L aqueous sodium hydroxide solution is added dropwise, and electrical conductivity is measured. This is continued until the pH reaches about 11, and the amount of sodium hydroxide (V) consumed in the neutralization stage of the weak acid, where the change in electrical conductivity is gradual, is used to calculate the electrical conductivity using the following formula: Amount of anionic functional groups (mmol / g) = V (mL) × [0.05 / mass of cellulose nanofiber (g)] The phosphate group can also be measured by the same electrical conductivity measurement. Other anion groups can also be measured by known methods.

[0054] The cellulose nanofiber (C) preferably has a carboxy group as an anionic functional group, and examples thereof include oxidized cellulose nanofibers obtained by oxidizing the hydroxyl groups of the glucose units in the cellulose molecules, and carboxymethylated cellulose nanofibers obtained by carboxymethylating the hydroxyl groups of the glucose units in the cellulose molecules.

[0055] Oxidized cellulose nanofibers include those in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule has been selectively oxidized to a carboxyl group. These oxidized cellulose nanofibers can be obtained by oxidizing natural cellulose, such as wood pulp, with a co-oxidant in the presence of an N-oxyl compound, followed by defibration (refining). The N-oxyl compound used is a compound containing a nitroxy radical, which is commonly used as an oxidation catalyst. For example, a piperidine nitroxyoxy radical is used, with 2,2,6,6-tetramethylpiperidinoxy radical (TEMPO) or 4-acetamido-TEMPO being particularly preferred. TEMPO-oxidized cellulose nanofibers are generally referred to as TEMPO-oxidized cellulose nanofibers (TOCN). The oxidized cellulose nanofibers may also contain aldehyde or ketone groups in addition to the carboxyl groups.

[0056] The cellulose nanofibers (C) can be obtained, for example, by known production methods or can be obtained from commercially available products. Examples of commercially available cellulose nanofibers (C) include the "Leocrysta" (registered trademark) series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0057] (Nonionic surfactant (D)) The heat insulating paint of the present invention contains a nonionic surfactant as an essential component. In this specification, the nonionic surfactant contained in the heat insulating paint is referred to as "nonionic surfactant (D)".

[0058] If the coating material for heat insulating materials of the present invention does not contain the nonionic surfactant (D), the dispersibility of the silica aerogel (A) decreases, the coatability is impaired, and the durability of the coating film also decreases, so that the desired heat insulating performance cannot be obtained.

[0059] The type of nonionic surfactant (D) is not particularly limited, and for example, a wide range of known nonionic surfactants can be used in the present invention.

[0060] Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, sucrose fatty acid esters, and fatty acid alkanolamides.

[0061] More specific examples of nonionic surfactants include polyoxyalkylene alkyl ethers, in which the primary alkyl group has 20 or fewer carbon atoms (more preferably 8 to 16 carbon atoms, and even more preferably 8 to 12 carbon atoms). Examples include polyoxyalkylene lauryl ethers such as polyoxyethylene lauryl ether and polyoxyethylene polyoxypropylene lauryl ether; polyoxyalkylene isodecyl ethers such as polyoxyethylene isodecyl ether and polyoxyethylene polyoxypropylene isodecyl ether; polyoxyalkylene branched decyl ethers such as polyoxyethylene branched decyl ether and polyoxyethylene polyoxypropylene branched decyl ether; polyoxyalkylene block polymers such as polyoxyethylene polyoxypropylene block polymers; and polyoxyalkylene styrenated phenyl ethers such as polyoxyethylene styrenated phenyl ether. These may be used alone or in combination. Here, "the primary alkyl group has 20 or fewer carbon atoms" means that at least 60 mol% of the alkyl groups have 20 or fewer carbon atoms. The "oxyalkylene" preferably has 2 to 4 carbon atoms and contains at least an oxyethylene group.

[0062] The nonionic surfactant (D) can be obtained, for example, by a known production method, or can be obtained from a commercially available product. Examples of commercially available nonionic surfactants (D) include the "Noigen" (registered trademark) series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0063] (Paint for heat insulation materials) The heat insulating coating material of the present invention contains silica aerogel (A), urethane resin emulsion (B), cellulose nanofiber (C), nonionic surfactant (D), and water as essential components. The heat insulating coating material of the present invention may also contain other components as long as the effects of the present invention are not impaired. Examples of other components include pH adjusters, thickeners, light stabilizers, antioxidants, preservatives, flame retardants, pigments, colorants, mildew inhibitors, and lubricants. One or more of these additives may be contained in the heat insulating coating material.

[0064] In the coating material for heat insulating materials of the present invention, when the solid content mass of the urethane resin emulsion (B) contained in the coating material for heat insulating materials is B (parts by mass) and the solid content mass of the cellulose nanofibers (C) contained in the coating material for heat insulating materials is C (parts by mass), as described above, the value of B / C is 0.5 or more and 20 or less. As a result, the coating material for heat insulating materials of the present invention has excellent dispersibility of silica aerogel and good coatability, and can form a heat insulating coating film having high durability and excellent heat insulating properties.

[0065] If the above-mentioned B / C value is less than 0.5, the durability of the coating film obtained from the coating material for heat insulating materials of the present invention will be reduced, and the desired heat insulating performance will not be obtained. On the other hand, if the B / C value exceeds 20, the dispersibility of the silica aerogel (A) in the coating material for heat insulating materials of the present invention will be reduced, the coatability will be impaired, and the durability of the coating film will also be reduced, making it impossible to obtain the desired heat insulating performance.

[0066] The above-mentioned B / C value is preferably 1 or more, more preferably 3 or more, even more preferably 4.5 or more, particularly preferably 4.8 or more, and is preferably 19 or less, more preferably 18 or less, even more preferably 16 or less, particularly preferably 15 or less.

[0067] Here, the total mass of the solid content mass of the silica aerogel (A), the solid content mass of the urethane resin emulsion (B), the solid content mass of the cellulose nanofiber (C), the solid content mass of the nonionic surfactant (D), and water contained in the coating material for heat insulating materials of the present invention is referred to as the "total mass M."

[0068] The solid content mass of the urethane resin emulsion (B) per 100 parts by mass of the total mass M is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and particularly preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

[0069] The solid content mass of cellulose nanofibers (C) per 100 parts by mass of the total mass M is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, and particularly preferably 0.1 parts by mass or more, and is preferably 3 parts by mass or less, more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less, and particularly preferably 0.5 parts by mass or less.

[0070] The solid content mass of the silica aerogel (A) per 100 parts by mass of the total mass M is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, particularly preferably 2 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 8 parts by mass or less.

[0071] The solid content mass of the nonionic surfactant (D) per 100 parts by mass of the total mass M is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, and particularly preferably 1 part by mass or less.

[0072] The coating material for heat insulating materials of the present invention preferably has a solids concentration of 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, and particularly preferably 3% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less.

[0073] In the heat insulating paint of the present invention, the total mass of the silica aerogel (A), urethane resin emulsion (B), cellulose nanofibers (C), nonionic surfactant (D), and water is preferably 50 mass% or more, more preferably 70 mass% or more, even more preferably 90 mass% or more, and particularly preferably 95 mass% or more, based on the total mass of the heat insulating paint. The heat insulating paint of the present invention may consist only of the silica aerogel (A), urethane resin emulsion (B), cellulose nanofibers (C), nonionic surfactant (D), and water.

[0074] The heat insulating coating material of the present invention contains silica aerogel (A), urethane resin emulsion (B), cellulose nanofiber (C), and nonionic surfactant (D), and therefore has excellent dispersibility of the silica aerogel and good coatability. In particular, the heat insulating coating material of the present invention can be easily applied to a substrate without dripping, and can form a coating film in which each component is uniformly dispersed, thereby demonstrating excellent heat insulating performance.

[0075] Furthermore, the coating material for heat insulating materials of the present invention can form a heat insulating coating film having high durability and excellent heat insulating properties, and can form an excellent heat insulating material. In particular, since the silica aerogel (A) is less likely to fall off from the heat insulating coating film, the heat insulating material can maintain its excellent heat insulating performance for a longer period of time.

[0076] Therefore, the coating material for heat insulating materials of the present invention can be suitably used as a raw material for producing heat insulating materials.

[0077] (Method for preparing paint for heat insulating materials) The method for preparing the heat insulating coating material of the present invention is not particularly limited, and for example, a wide variety of known methods can be employed. For example, the heat insulating coating material of the present invention can be prepared by mixing predetermined raw materials in predetermined amounts. Preferably, the heat insulating coating material of the present invention can be prepared by a production method including: Step 1: mixing the silica aerogel (A), the cellulose nanofibers (C), the nonionic surfactant (D), and the water in predetermined amounts to prepare a dispersion of the silica aerogel (A); and Step 2: mixing the dispersion of the silica aerogel (A) obtained in Step 1 with the urethane resin emulsion (B) to obtain the heat insulating coating material.

[0078] Step 1 is a step for preparing a dispersion of silica aerogel (A). Such a dispersion can be prepared by mixing silica aerogel (A), cellulose nanofibers (C), a nonionic surfactant (D), and water in predetermined amounts to prepare a mixture, and then stirring the mixture. The method for preparing the mixture is not particularly limited, and for example, any known mixing method can be widely used.

[0079] When preparing the mixed solution, the mixing ratio of the silica aerogel (A), the cellulose nanofibers (C), the nonionic surfactant (D), and the water can be adjusted within an appropriate range depending on, for example, the amount of each component and the solid content concentration contained in the desired heat insulating material coating material.

[0080] The method for stirring the mixture is not particularly limited, and for example, any known stirring means can be widely used. Specifically, the mixture is stirred while applying shear using an emulsifying / dispersing device such as a homomixer or homogenizer, thereby obtaining a dispersion of silica aerogel (A). In this case, the average particle size of the silica aerogel (A) can be controlled depending on the magnitude of shear applied to the mixture. An example of an emulsifying / dispersing device is the homomixer "Laborution" manufactured by PRIMIX.

[0081] When preparing a dispersion of silica aerogel (A) using an emulsifying / dispersing device, the average particle size of the silica aerogel (A) can be controlled, for example, by adjusting the stirring rotation speed. The stirring rotation speed of the emulsifying / dispersing device can be set to 1,000 to 30,000 rpm, preferably 2,000 to 20,000 rpm, more preferably 3,000 to 10,000 rpm, and particularly preferably 4,000 to 9,000 rpm. By adjusting the stirring rotation speed to these values, a dispersion of silica aerogel (A) having an average particle size of 1 μm or more and 500 μm or less can be easily obtained. The stirring time using the emulsifying / dispersing device is not particularly limited and can be set within an appropriate range depending on the stirring rotation speed, for example, 30 to 180 minutes.

[0082] In step 2, the dispersion of silica aerogel (A) obtained in step 1 is mixed with the urethane resin emulsion (B). By this mixing, the coating material for heat insulating materials of the present invention can be obtained.

[0083] The urethane resin emulsion (B) used in step 2 can be the aforementioned polyurethane resin aqueous dispersion, i.e., a dispersion in which a urethane resin is dispersed in an aqueous solvent. Therefore, in step 2, a dispersion of silica aerogel (A) and the polyurethane resin aqueous dispersion are mixed. Examples of the aqueous solvent contained in the polyurethane resin aqueous dispersion include water, lower alcohols having about 1 to 3 carbon atoms, and mixed solvents thereof, with water being preferred.

[0084] The polyurethane resin aqueous dispersion can be obtained, for example, by the above-mentioned method using emulsification dispersion, or can be obtained from a commercially available product, such as the Superflex (registered trademark) series from Dai-ichi Kogyo Seiyaku Co., Ltd.

[0085] The solid content concentration of the polyurethane resin aqueous dispersion is, for example, 20 to 50 mass %, and preferably 30 to 45 mass %.

[0086] In step 2, the method for mixing the dispersion of silica aerogel (A) and the aqueous polyurethane resin dispersion is not particularly limited, and for example, a wide variety of known mixing means can be used. For example, as in step 1, the dispersion of silica aerogel (A) and the aqueous polyurethane resin dispersion can be mixed using an emulsifying and dispersing device such as a homomixer or a homogenizer.

[0087] When the dispersion of silica aerogel (A) and the aqueous dispersion of polyurethane resin are mixed using an emulsifying and dispersing device, the stirring speed can be, for example, 1,000 to 20,000 rpm, preferably 2,000 to 10,000 rpm. The stirring time is not particularly limited and can be set within an appropriate range depending on the stirring speed, for example, 0.1 to 30 minutes.

[0088] The coating material for heat insulating materials of the present invention can be obtained through the above steps 1 and 2. The method for producing a coating material for heat insulating materials of the present invention may include other steps in addition to steps 1 and 2, or may consist of only steps 1 and 2. The coating material for heat insulating materials of the present invention can also be prepared by a method other than the method including steps 1 and 2.

[0089] 2. Heat insulating coatings and materials The heat insulating coating material of the present invention can be used to form a heat insulating coating film. For example, the heat insulating coating material of the present invention can be used to form a cured product of the heat insulating coating material on the surface of a substrate, and the cured product can be used as a heat insulating coating film. In addition, the heat insulating coating film formed on a substrate can be used as a heat insulating material.

[0090] The thermal insulation coating film contains the cured product of the thermal insulation paint of the present invention, and therefore has high durability and excellent thermal insulation performance. In particular, since the silica aerogel (A) is less likely to fall off from the thermal insulation coating film, the thermal insulation coating film can maintain its excellent thermal insulation performance for a longer period of time.

[0091] Since the thermal insulation coating film is made of a cured product of the thermal insulation paint of the present invention, it can be obtained, for example, by curing the thermal insulation paint of the present invention. Specifically, the thermal insulation coating film can be obtained by applying the thermal insulation paint of the present invention to a substrate to form a coating film on the substrate surface, and then curing the coating film to form a cured product. Alternatively, the thermal insulation coating film can be formed on the substrate surface by immersing the substrate in the thermal insulation paint of the present invention. In this case, a cured product of the thermal insulation paint of the present invention is also formed on the substrate surface.

[0092] Examples of the substrate include fiber substrates such as cloth, nonwoven fabric, woven fabric, and fabric; films and substrates made of resin, etc.; inorganic plates; metal plates; etc. The substrate may be a porous material.

[0093] The method for applying the coating material for heat insulating materials of the present invention to a substrate to form a coating film is not particularly limited, and for example, known coating means such as an applicator, bar coater, die coater, Comma Coater (registered trademark), or roll coater can be used. Alternatively, the coating material for heat insulating materials of the present invention can be applied to a substrate by a method such as spraying. In particular, the coating material for heat insulating materials of the present invention contains the above-mentioned predetermined components in predetermined proportions, and therefore has excellent dispersion stability and coatability of the silica aerogel (A). Therefore, the coating material can be easily applied to a substrate, and a coating film in which each component is uniformly dispersed can be formed.

[0094] The coating film formed on the substrate is subjected to a drying treatment, whereby volatile components such as water are dried and the coating film is converted into a cured product. Such a cured product contains the solid components of silica aerogel (A), urethane resin emulsion (B), cellulose nanofibers (C), and nonionic surfactant (D). The drying treatment can be carried out at a temperature of, for example, 50 to 150°C, and preferably 70 to 120°C.

[0095] The cured product of the heat insulating coating material thus formed can be obtained as a heat insulating coating film. The content ratios of the silica aerogel (A), urethane resin emulsion (B), cellulose nanofibers (C), and nonionic surfactant (D) contained in the heat insulating coating material can be considered to be the same as the content ratios of the silica aerogel (A), urethane resin emulsion (B), cellulose nanofibers (C), and nonionic surfactant (D) contained in the heat insulating coating material of the present invention. Therefore, the above-mentioned B / C value in the heat insulating coating material is also 0.5 or more and 20 or less.

[0096] The thermal insulation material of the present invention can be formed using the thermal insulation coating. Therefore, the thermal insulation material of the present invention can include, for example, the substrate and the thermal insulation coating. The thermal insulation material of the present invention may consist of only the thermal insulation coating, or may consist of only the substrate and the thermal insulation coating, or may combine the substrate and the thermal insulation coating with other components.

[0097] The heat insulating material of the present invention contains a multi-heat insulating coating film formed from the heat insulating paint of the present invention, and therefore has high durability and excellent heat insulating performance.

[0098] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in the embodiments of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification. [Example]

[0099] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0100] Example 1 A coating material for heat insulating materials containing silica aerogel (A), urethane resin emulsion (B), cellulose nanofiber (C), nonionic surfactant (D), and water was prepared according to the formulation conditions of Example 1 shown in Table 1. Specifically, the coating material for heat insulating materials was prepared as follows: First, a mixture was prepared by mixing 5.0 parts by solids of Cabot Corporation's silica aerogel particles "P-200" as the silica aerogel (A), 0.4 parts by solids of Dai-ichi Kogyo Seiyaku Co., Ltd.'s TEMPO-oxidized cellulose nanofiber "Leocrysta I-2SX" (solids concentration 2% by mass, number-average fiber diameter 3 nm) as the cellulose nanofiber (C), 0.5 parts by solids of Dai-ichi Kogyo Seiyaku Co., Ltd.'s nonionic surfactant "Noigen LF-60X" (polyoxyalkylene alkyl ether) as the nonionic surfactant (D), and water (pure water). This mixture was stirred at 8000 rpm for 120 minutes with a homomixer (Laborution, manufactured by PRIMIX) to prepare a dispersion of silica aerogel (A) (Step 1).

[0101] Next, the entire dispersion of silica aerogel (A) obtained in step 1 was mixed with 0.2 parts by solids of "Superflex 460" (solids concentration 38% by mass), a carbonate-based polyurethane resin aqueous dispersion manufactured by Daiichi Kogyo Seiyaku Co., Ltd., as the urethane resin emulsion (B). The mixture was stirred at 5,000 rpm in a homomixer for 5 minutes and then degassed to obtain a coating material for heat insulating materials with a solids concentration of 6.1% by mass (step 2). The amount of water shown in Table 1 is the total amount of water contained in the dispersion of silica aerogel (A) and the polyurethane resin aqueous dispersion (the same applies to Table 2 below).

[0102] Example 2 As shown in Table 1, a coating material for heat insulating materials having a solid content concentration of 7.8 mass % was obtained in the same manner as in Example 1, except that the amount of urethane resin emulsion (B) used was changed to 1.9 mass parts in terms of solid content.

[0103] Example 3 As shown in Table 1, a coating material for heat insulating materials with a solid content concentration of 7.6 mass % was obtained in the same manner as in Example 2, except that the amount of cellulose nanofiber (C) used was changed to 0.2 mass parts in terms of solid content.

[0104] Example 4 As shown in Table 1, a coating material for heat insulating materials with a solid content concentration of 7.5 mass % was obtained in the same manner as in Example 2, except that the amount of cellulose nanofiber (C) used was changed to 0.1 mass parts in terms of solid content.

[0105] Example 5 As shown in Table 1, a coating material for heat insulating materials having a solid content concentration of 3.5 mass % was obtained in the same manner as in Example 4, except that the amount of silica aerogel (A) used was changed to 1.0 mass part in terms of solid content.

[0106] Example 6 A coating material for heat insulating materials with a solid content of 7.8% by mass was obtained in the same manner as in Example 2, except that the urethane resin emulsion (B) was changed to 1.8 parts by mass of "Superflex 210" (solid content concentration 35% by mass), an ester-based polyurethane resin aqueous dispersion from Daiichi Kogyo Seiyaku Co., Ltd.

[0107] Example 7 A coating material for heat insulating materials having a solids concentration of 7.8% by mass was obtained in the same manner as in Example 2, except that the nonionic surfactant (D) was changed to "Noigen EA-167" (polyoxyethylene styrenated phenyl ether), a nonionic surfactant manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0108] Example 8 To 2 g of softwood pulp, 150 ml of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO were added and thoroughly stirred to disperse the mixture. Then, a 13 wt. % aqueous solution of sodium hypochlorite (co-oxidant) was added to 1.0 g of pulp so that the sodium hypochlorite content was 10 mmol / g, and the reaction was initiated. As the reaction progressed, the pH decreased, so 0.5 N aqueous solution of sodium hydroxide was added dropwise to maintain the pH at 10-11, and the reaction was continued until no further change in pH was observed (reaction time: 120 minutes). After the reaction was completed, the mixture was neutralized with 0.1 N hydrochloric acid, and then purified by repeated filtration and washing with water to prepare cellulose fibers with oxidized surfaces. The solids concentration was adjusted to 2.0% by mass, and a 24% aqueous sodium hydroxide solution was added to adjust the pH to 7.0. The mixture was then subjected to one pass at 50 MPa using a high-pressure disperser (Microfluidizer M-110, manufactured by Microfluidics Corporation) to prepare cellulose nanofibers (number average fiber diameter 20 nm). A coating material for heat insulating materials with a solids concentration of 7.8% by mass was obtained in the same manner as in Example 2, except that the cellulose nanofibers were used as cellulose nanofibers (C).

[0109] Example 9 As shown in Table 1, a coating material for heat insulating materials having a solid content of 7.8 mass % was obtained in the same manner as in Example 2, except that in step 1, the mixed solution was stirred with a homomixer at 3000 rpm for 60 minutes to prepare a dispersion of silica aerogel (A).

[0110] Example 10 As shown in Table 1, a coating material for heat insulating materials having a solid content of 7.8 mass % was obtained in the same manner as in Example 2, except that in step 1, the mixed solution was stirred with a homomixer at 10,000 rpm for 180 minutes to prepare a dispersion of silica aerogel (A).

[0111] (Comparative Example 1) As shown in Table 2, a coating material for heat insulating materials having a solid content concentration of 6.0 mass % was obtained in the same manner as in Example 1, except that the amount of urethane resin emulsion (B) used was changed to 0.1 mass parts in terms of solid content.

[0112] (Comparative Example 2) As shown in Table 2, a coating material for heat insulating materials with a solid content concentration of 7.5 mass % was obtained in the same manner as in Example 2, except that the amount of cellulose nanofiber (C) used was changed to 0.08 mass parts in terms of solid content.

[0113] (Comparative Example 3) As shown in Table 2, a coating material for heat insulating materials with a solid content concentration of 7.1% by mass was obtained in the same manner as in Example 2, except that the amount of cellulose nanofiber (C) used was changed to 0.2 parts by mass in terms of solid content and no nonionic surfactant (D) was used.

[0114] (Evaluation method) [Average particle size of silica aerogel] Using a particle size distribution analyzer (SALD-2000, manufactured by Shimadzu Corporation), the average particle diameter of the coating material for heat insulating materials obtained in each example and comparative example was measured, and the obtained value was taken as the average particle diameter of the silica aerogel (A).

[0115] [Stability (dispersion stability)] 100 g of the heat insulating paint obtained in each Example and Comparative Example was transferred to a sample bottle and stored for one month at 50° C. After storage, the heat insulating paint was visually observed, and the stability (dispersion stability) was evaluated according to the following criteria. ≪Judgment criteria≫ 5: No separation of silica aerogel or water release was observed, and the stability was excellent. 4: Although a slight concentration gradient of silica aerogel was observed, the stability was good. 3: The silica aerogel floated to the surface, and a layer lacking less than 30% of the silica aerogel was observed at the bottom, indicating that the stability was not necessarily good. 2: The silica aerogel floated to the surface, and a layer was observed at the bottom where 30% or more but less than 60% of the silica aerogel was missing, indicating poor stability. 1: The silica aerogel completely floated to the surface, and a layer missing 60% or more of the silica aerogel was observed at the bottom, indicating extremely poor stability.

[0116] [Coatability] 50 g of the heat insulating paint prepared in each Example and Comparative Example was applied to a polyester fabric (film thickness 1 mm) using an applicator (film thickness 0.5 mm), and the formed coating film was visually observed and evaluated for coatability according to the following criteria. ≪Judgment criteria≫ 3: The coating solution did not drip or soak into the fabric, a uniform coating film was obtained, and the coating properties were extremely good. 2: There was some dripping of the coating liquid or soaking into the fabric, but a generally uniform coating film was obtained and the coating properties were good. 1: A uniform coating film was not obtained due to coating solution dripping or soaking into the fabric.

[0117] [Durability] The heat insulating paints obtained in each example and comparative example were applied to a polyester substrate (10 cm long, 5 cm wide, 1 mm thick) using an applicator to form a coating film with a thickness of 0.5 mm. The coating film was dried in an atmosphere at 100°C for 1 hour to harden the coating film and obtain a cured product. This cured product served as a heat insulating coating film, and the substrate with the heat insulating coating film was used as an evaluation sample for heat insulating material. Both ends of the obtained sample were clamped with clips, and the sample was stretched by hand by 5 mm from both ends in the longitudinal direction, held for 3 seconds, and then returned to its original position. This process was repeated 10 times, after which the condition of the heat insulating coating film formed on the evaluation sample was visually observed, and the coatability was evaluated according to the following criteria. ≪Judgment criteria≫ 4: No cracks in the heat insulating coating or loss of silica aerogel were observed, demonstrating extremely excellent durability. 3: Almost no cracking of the heat insulating coating or loss of silica aerogel was observed, demonstrating excellent durability. 2: No silica aerogel was observed to fall off, but cracks were observed in the heat insulating coating, but the durability was acceptable for practical use. 1: Both cracks in the heat insulating coating and loss of silica aerogel were observed, and the durability was extremely poor.

[0118] [Insulation performance] The thermal conductivity (W / (m K)) of the thermal insulation coating formed on the insulation material evaluation sample prepared in the durability evaluation described above was measured to evaluate the thermal insulation performance. Thermal conductivity was measured using a thermal conductivity meter (TCi, manufactured by C-Therm Technologies) in accordance with ASTM D7984.

[0119] (Evaluation results) Tables 1 and 2 show the blending conditions for preparing the heat insulating paints prepared in each Example (Table 1) and Comparative Example (Table 2), as well as the B / C values ​​(solid mass ratios of the urethane resin emulsion (B) and the cellulose nanofibers (C)) and the average particle diameter of the silica aerogel (A) for each heat insulating paint. Table 1 also shows the evaluation results of the heat insulating paints obtained in each Example and Comparative Example, and the evaluation results of the heat insulating coating films formed from the heat insulating paints.

[0120] As can be seen from Table 1, the heat insulating paints obtained in the Examples had excellent silica aerogel dispersibility and good coatability. Furthermore, the heat insulating paints obtained in the Examples were capable of forming heat insulating coating films with high durability and excellent heat insulating properties. On the other hand, the heat insulating paint obtained in Comparative Example 1 had a B / C value below 0.5, resulting in poor coatability and durability. The heat insulating paint obtained in Comparative Example 2 had a B / C value above 20, resulting in poor stability (dispersion stability), coatability, and durability. Furthermore, the heat insulating paint obtained in Comparative Example 3 did not contain a nonionic surfactant, resulting in poor dispersion stability and coatability. It was therefore impossible to measure the average particle size of the silica aerogel (A), and the desired heat insulating coating film could not be formed.

[0121] [Table 1]

[0122] [Table 2]

Claims

1. Silica aerogel (A), a urethane resin emulsion (B); Cellulose nanofibers (C), a nonionic surfactant (D); Water and Including, When the solid content mass of the urethane resin emulsion (B) is B (parts by mass) and the solid content mass of the cellulose nanofibers (C) is C (parts by mass), A paint for heat insulating materials, having a B / C value of 0.5 or more and 20 or less.

2. 2. The coating material for heat insulating materials according to claim 1, wherein the urethane resin emulsion (B) is a carbonate-based urethane resin emulsion.

3. The coating material for heat insulating materials according to claim 1, wherein the silica aerogel (A) has an average particle size of 1 to 500 μm.

4. A heat insulating coating film comprising a cured product of the coating material for heat insulating materials according to any one of claims 1 to 3.

5. A heat insulating material comprising the heat insulating coating film according to claim 4.

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