Method for manufacturing coating liquid and method for manufacturing insulation material

Abstract

A method for preparing a coating solution, comprising: a preparation process for preparing an emulsion containing a polymeric emulsifier, a binder resin, and a liquid medium, and aerogel particles; and a mixing process for mixing the emulsion and aerogel particles prepared in the preparation process to aggregate at least a portion of the aerogel particles, thereby obtaining a coating solution containing aggregates of aerogel particles, a polymeric emulsifier, a binder resin, and a liquid medium.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a coating liquid and a method for manufacturing an insulating material. Background Technology

[0002] Aerogel is known as a material with excellent thermal insulation properties. In addition, methods have been proposed to process aerogel into a particulate form and use it as a constituent material for thermal insulation (e.g., Patent Documents 1 and 2). In Patent Document 1, it is proposed to use particulate aerogel as a filler between resin plates, etc., that constitute an insulating window. In Patent Document 2, a method for manufacturing a thermal insulation material (molded body) is described by preparing an aqueous dispersion containing aerogel particles and organic fibers, and then further press-molding an intermediate product obtained by evaporating water. Prior art literature

[0003] Patent Document 1: Japanese Published Patent Application No. 2012-91943 Patent Document 2: Japanese Published Patent Application No. 2014-35044 The problem to be solved

[0004] Composite materials in which aerogel particles are dispersed within a resin component are expected to exhibit excellent heat resistance. However, when such composite materials are applied as a coating, there has been a problem in that the resin component penetrates into the micropores of the aerogel particles, causing the micropore structure to be lost and reducing thermal insulation, or the strength of the coating film is not sufficiently achieved, making it prone to cracking.

[0005] Accordingly, the present invention aims to provide a method for manufacturing an insulating material that enables obtaining an insulating material having high thermal insulation and high film-forming properties by suppressing the penetration of a resin component into the micropores of aerogel particles. Furthermore, the present invention aims to provide a coating liquid for forming the insulating material and a method for manufacturing the same. means of solving the problem

[0006] One aspect of the present invention relates to a method for preparing a coating solution, comprising: a preparation process for preparing an emulsion containing a polymeric emulsifier, a binder resin, and a liquid medium, and aerogel particles; and a mixing process for mixing the emulsion and the aerogel particles prepared in the preparation process to aggregate at least a portion of the aerogel particles, thereby obtaining a coating solution containing aggregates of the aerogel particles, the polymeric emulsifier, the binder resin, and the liquid medium.

[0007] The coating solution obtained by the above manufacturing method has a reduced contact interface between the aerogel particles and the resin component due to the aggregation of the aerogel particles, thereby suppressing the penetration of the resin component into the fine pores of the aerogel particles. Furthermore, since the coating solution obtained by the above manufacturing method is not composed of aerogel particle aggregates prepared in advance, but rather aggregates the aerogel particles when mixed with other components, the aerogel particles and their aggregates are uniformly dispersed, and the non-uniformity of the coating film and cracking caused by the uneven distribution of aerogel particles can be suppressed. In addition, in the above manufacturing method, since a binder resin emulsified with a polymer-based emulsifier is mixed in advance, the penetration of the resin component into the fine pores of the aerogel particles is further suppressed. Therefore, according to the coating solution obtained by the above manufacturing method, an insulating material having high thermal insulation and high film-forming properties is obtained.

[0008] In addition, in the above manufacturing method, because the binder resin in the emulsion is covered with the polymer emulsifier due to the use of a polymer emulsifier, it is difficult for the fine particles of the binder resin and the aggregates of aerogel particles to come into contact, and it is difficult for the binder resin to enter the gaps within the aggregates of aerogel particles, so it is difficult for the aggregates of aerogel particles to collapse. For this reason, the coating film obtained by the above manufacturing method is easy to maintain without the aggregates of aerogel particles collapsing even when a certain amount of pressure is applied during application, and, for example, a high-pressure application method such as an airless spray can be suitably used.

[0009] In one embodiment, the average diameter of the aggregate may be 2 to 40 times the average diameter of the aerogel particles prepared in the preparation process. By forming such an aggregate, the above-described effect is more pronounced.

[0010] In one embodiment, when the diluted solution obtained by diluting the above-mentioned solution is observed by an optical microscope, the area occupied by the aerogel particles and the aggregates within the field of view may be 50% or more of the area occupied by the aggregates with a diameter of 20 μm or more. By doing so, the above-mentioned effect is more pronounced.

[0011] In one embodiment, the total content of the aerogel particles and aggregates in the above coating liquid may be 70 volume% or more based on the total volume of the solid content. This makes it possible to form an insulating material with even better thermal insulation properties.

[0012] In one embodiment, the mixing process may further involve mixing a water-soluble polymer having hydrophobic groups, and the coating solution may further contain the water-soluble polymer. As a result, the dispersibility of the aerogel particles is further improved, and even when the packing ratio of the aerogel particles is high, it becomes easier to obtain a coating solution in which the aerogel particles and their aggregates are uniformly dispersed.

[0013] Another aspect of the present invention relates to a method for manufacturing an insulating material, comprising a coating process of applying a coating solution prepared by the above manufacturing method onto a support to obtain a coating film, and a removal process of removing at least a portion of the liquid medium from the coating film to obtain an insulating material. According to such a manufacturing method, the penetration of a resin component into the micropores of aerogel particles is suppressed, thereby making it easy to obtain an insulating material having high thermal insulation and high film-forming properties.

[0014] In one embodiment, the volume of the micropores of the insulating material is 0.15 cm 3 It is okay if it is more than / g.

[0015] In one embodiment, the coating process may be a process of applying the coating liquid by a coating method in which the pressure applied to the coating liquid exceeds 1.5 MPa.

[0016] Another aspect of the present invention relates to a coating solution containing aggregates of aerogel particles, a polymer-based emulsifier, a binder resin, and a liquid medium, wherein when a diluted solution of the coating solution is observed by an optical microscope, the area occupied by the aggregates having a diameter of 20 μm or more within the field of view of observation is 50% or more. Effects of the invention

[0017] According to the present invention, a method for manufacturing an insulating material is provided, wherein the penetration of a resin component into the micropores of aerogel particles is suppressed, thereby making it possible to obtain an insulating material having high thermal insulation and high film-forming properties. Furthermore, according to the present invention, a coating solution for forming the insulating material and a method for manufacturing the same are provided. Specific details for implementing the invention

[0018] Suitable embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In this specification, numerical ranges indicated by "~" represent a range that includes the values ​​listed before and after "~" as minimum and maximum values, respectively. "A or B" means that either one of A and B may be included, or both may be included. Unless otherwise specifically stated, the materials exemplified in this embodiment may be used as a single type or in combination of two or more types.

[0019] The method for preparing a coating solution according to the present embodiment comprises a preparation process for preparing an emulsion containing a polymeric emulsifier, a binder resin, and a liquid medium, and aerogel particles, and a mixing process for mixing the emulsion and aerogel particles prepared in the preparation process to aggregate at least a portion of the aerogel particles to obtain a coating solution containing aggregates of aerogel particles, a polymeric emulsifier, a binder resin, and a liquid medium.

[0020] The coating solution obtained by the manufacturing method of the present embodiment has a reduced contact interface between the aerogel particles and the resin component due to the aggregation of the aerogel particles, thereby suppressing the penetration of the resin component into the fine pores of the aerogel particles. Furthermore, while it is conceivable to prepare aggregates of aerogel particles in advance to reduce the contact interface, in this case, it is difficult to disperse the aggregates within the coating solution, and there is a risk that the aggregates may disintegrate due to stirring operations for dispersion. In the present embodiment, by aggregating the aerogel particles when mixing with other components, the aerogel particles and their aggregates are uniformly dispersed, and non-uniformity of the coating film and cracking caused by the uneven distribution of aerogel particles are suppressed. Additionally, in the present embodiment, since a binder resin emulsified with a polymer-based emulsifier is mixed in advance, the penetration of the resin component into the fine pores of the aerogel particles is further suppressed. Therefore, according to the manufacturing method of the present embodiment, a coating solution capable of forming a thermal insulation material having high thermal insulation and high film-forming properties can be obtained.

[0021] In addition, in the manufacturing method of the present embodiment, because the binder resin in the emulsion is covered with the polymer emulsifier due to the use of a polymer emulsifier, it is difficult for the fine particles of the binder resin to come into contact with the aggregates of aerogel particles, and it is difficult for the binder resin to enter the gaps within the aggregates of aerogel particles, so it is difficult for the aggregates of aerogel particles to collapse. Therefore, the coating film obtained by the manufacturing method of the present embodiment is easy to maintain without the aggregates of aerogel particles collapsing even when a certain amount of pressure is applied during application, and, for example, a high-pressure application method such as an airless spray can be suitably used.

[0022] The method for manufacturing an insulating material according to the present embodiment includes a coating process for obtaining a coating film by applying a coating liquid prepared by the above method onto a support, and a removal process for obtaining an insulating material by removing at least a portion of a liquid medium from the coating film. The method for manufacturing an insulating material according to the present embodiment may further include a coating liquid preparation process for obtaining a coating liquid by the above method.

[0023] According to the manufacturing method of the present embodiment, the penetration of the resin component into the micropores of the aerogel particles is suppressed, so that an insulating material having high thermal insulation and high film-forming properties can be easily obtained.

[0024] Aerogel

[0025] In a narrow sense, a dry gel obtained by using a supercritical drying method with respect to a wet gel is called aerogel, a dry gel obtained by drying under atmospheric pressure is called zerogel, and a dry gel obtained by freeze-drying is called cryogel; however, in the present embodiment, a low-density dry gel obtained regardless of the drying method of the wet gel is called "aerogel." That is, in the present embodiment, "aerogel" refers to an aerogel in the broad sense, "Gel comprised of a microporous solid in which the dispersed phase is a gas." Generally, the interior of the aerogel has a mesh-like microstructure and a cluster structure in which particulate aerogel components of about 2 to 20 nm are bonded. Between the frameworks formed by these clusters, there are micropores of less than 100 nm. Thus, the aerogel has a fine porous structure formed in three dimensions.

[0026] The aerogel according to the present embodiment is, for example, a silica aerogel with silica as the main component. Examples of silica aerogels include, for example, so-called organic-inorganic hybridized silica aerogels in which organic groups (such as methyl groups) or organic chains have been introduced.

[0027] Examples of aerogels according to the present embodiment include the following embodiments. By adopting these embodiments, it becomes easy to obtain an aerogel with excellent thermal insulation, flame retardancy, heat resistance, and flexibility. By adopting each embodiment, an aerogel having thermal insulation, flame retardancy, heat resistance, and flexibility according to each embodiment can be obtained.

[0028] (First mode)

[0029] The aerogel according to 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 including the structure represented by formula (1), and may have a structure represented by the following general formula (1a).

[0030] [Chemical Formula 1]

[0031]

[0032] [Chemical Formula 2]

[0033]

[0034] Among Equations (1) and (1a), R 1 and R 2 Each independently represents an alkyl group or an aryl group, and R 3 and R 4 Each represents an alkylene group independently. Here, aryl groups may include phenyl groups, substituted phenyl groups, etc. Additionally, substituents for substituted phenyl groups may include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, cyano groups, etc. p represents an integer from 1 to 50. In formula (1a), two or more R 1 Each may be the same or different, and identically, two or more R2 may be the same or different. In Equation (1a), the two R 3 They may be the same or different, and identically, 2 Rs 4 Each may be the same or different.

[0035] By introducing the structure represented by the above formula (1) or formula (1a) into the framework of the aerogel as an aerogel component, a flexible aerogel with low thermal conductivity is obtained. In this regard, among formulas (1) and (1a), R 1 and R 2 As, each can independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and the alkyl group can include a methyl group, etc. Also, in Formula (1) and Formula (1a), R 3 and R 4 Each of the alkylene groups may independently have 1 to 6 carbon atoms, and the alkylene groups may include ethylene groups, propylene groups, etc. In formula (1a), p may be 2 to 30 and may be 5 to 20.

[0036] (Second mode)

[0037] The aerogel according to the present embodiment has a ladder-type structure having struts and bridges, and the bridges may have a structure represented by the following general formula (2). By introducing such a ladder-type structure into the framework of the aerogel as an aerogel component, heat resistance and mechanical strength can be improved. In addition, in the present embodiment, "ladder-type structure" refers to having two struts and bridges connecting the struts (having the shape of a so-called "ladder"). In the present embodiment, the framework of the aerogel may be formed as a ladder-type structure, but the aerogel may partially have a ladder-type structure.

[0038] [Chemical Formula 3]

[0039]

[0040] In Equation (2), R 5 and R 6 Each represents an alkyl group or an aryl group independently, and b represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups, substituted phenyl groups, etc. Also, examples of substituents for substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, cyano groups, etc. Additionally, in Formula (2), when b is an integer of 2 or more, two or more R 5 may be the same or different, and 2 or more identical R 6 They may be the same or different.

[0041] By introducing the above structure into the framework of the aerogel as an aerogel component, for example, an aerogel is obtained having superior flexibility compared to an aerogel having a structure derived from conventional ladder-type silsesquioxane (i.e., having a structure represented by the following general formula (X)). Silsesquioxane is composed of: (RSiO 1.5 ) n It is a polysiloxane having [the structure] and can have various skeletal structures such as cage type, ladder type, and random type. In addition, as shown by the following general formula (X), in an aerogel having a structure derived from a conventional ladder-type silsesquioxane, the structure of the crosslinking part is -O-, but in the aerogel according to the present embodiment, the structure of the crosslinking part is a structure (polysiloxane structure) represented by the above general formula (2). However, the aerogel of the present embodiment may additionally have a structure derived from silsesquioxane in addition to the structure represented by the general formula (2).

[0042] [Chemical Formula 4]

[0043]

[0044] In formula (X), R represents a hydroxyl group, an alkyl group, or an aryl group.

[0045] The structure that serves as the supporting part, the length of the chain, and the spacing of the structure that serves as the crosslinking part are not particularly limited, but in order to further improve heat resistance and mechanical strength, the ladder-type structure may have a ladder-type structure represented by the following general formula (3).

[0046] [Chemical Formula 5]

[0047]

[0048] In Equation (3), R 5 , R 6 , R 7 and R 8 Each represents an alkyl group or an aryl group independently, a and c each represent an integer from 1 to 3000 independently, and b represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups, substituted phenyl groups, etc. Also, examples of substituents for substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, cyano groups, etc. Additionally, in formula (3), when b is an integer of 2 or more, 2 or more R 5 may be the same or different, and 2 or more identical R 6 Each may be the same or different. Also, in Equation (3), when a is an integer greater than or equal to 2, two or more R 7 They may be the same or different, and identically, if c is an integer greater than or equal to 2, two or more R 8 Each can be the same or different.

[0049] In addition, in terms of obtaining greater flexibility, among equations (2) and (3), R 5 , R 6 , R 7 and R 8 (where R 7 and R 8(Only in Formula (3)) can be independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc., and the alkyl group can be a methyl group, etc. Also, in Formula (3), a and c can each be independently 6 to 2000, but can be 10 to 1000. Also, in Formulas (2) and (3), b can be 2 to 30, but can be 5 to 20.

[0050] (Third mode)

[0051] The aerogel according to the present embodiment may be a dried product of a wet gel that is a condensation product of a sol containing at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensation functional group, and a hydrolysis product of a silicon compound having a hydrolyzable functional group (obtained by drying a wet gel produced from a sol: a dried product of a wet gel derived from a sol). In addition, the aerogel described so far may also be obtained by drying a wet gel produced from a sol containing a silicon compound, etc.

[0052] As a silicon compound having a hydrolyzable functional group or a condensation functional group, a polysiloxane compound may be used. That is, the sol may contain at least one compound selected from the group consisting of a polysiloxane compound having a hydrolyzable functional group or a condensation functional group, and a hydrolysis product of a polysiloxane compound having a hydrolyzable functional group (hereinafter referred to as the "polysiloxane compound group" as an example).

[0053] The functional groups in polysiloxane compounds are not particularly limited, but may be groups that react with the same functional groups or with different functional groups. Examples of hydrolyzable functional groups include alkoxy groups. Examples of condensation functional groups include hydroxyl groups, silanol groups, carboxyl groups, phenolic hydroxyl groups, etc. Hydroxyl groups may be included in hydroxyl-containing groups such as hydroxyalkyl groups. Furthermore, polysiloxane compounds having hydrolyzable or condensation functional groups may additionally have reactive groups different from the hydrolyzable or condensation functional groups (functional groups that do not correspond to hydrolyzable or condensation functional groups). Examples of reactive groups include epoxy groups, mercapto groups, glycidoxy groups, vinyl groups, acryloyl groups, methacryloyl groups, amino groups, etc. Epoxy groups may be included in epoxy-containing groups such as glycidoxy groups. Polysiloxane compounds having these functional groups and reactive groups may be used alone or in a mixture of two or more types. Among these functional groups and reactive groups, for example, alkoxy groups, silanol groups, hydroxyalkyl groups, etc., can be used as groups that improve the flexibility of the aerogel, and among these, alkoxy groups and hydroxyalkyl groups can further improve the compatibility of the sol. Also, from the perspective of improving the reactivity of the polysiloxane compound and reducing the thermal conductivity of the aerogel, the number of carbon atoms in the alkoxy groups and hydroxyalkyl groups may be 1 to 6, but from the perspective of further improving the flexibility of the aerogel, it may be 2 to 5 or 2 to 4.

[0054] Polysiloxane compounds having a hydroxyalkyl group within the molecule may be those having a structure represented by the following general formula (A). By using a polysiloxane compound having a structure represented by the following general formula (A), the structure represented by general formula (1) and formula (1a) can be introduced into the framework of an aerogel.

[0055] [Chemical Formula 6]

[0056]

[0057] In Equation (A), R 1a represents a hydroxyalkyl group, and R 2a represents an alkylene group, and R 3a and R 4a Each represents an alkyl group or an aryl group independently, and n represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups, substituted phenyl groups, etc. Also, examples of substituents for substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, cyano groups, etc. Additionally, in formula (A), 2 R 1a may be the same or different, and identically 2 R 2a may be the same or different. Also, in Equation (A), two or more R 3a may be the same or different, and 2 or more identical R 4a Each may be the same or different.

[0058] By using a wet gel (generated from a sol) which is a condensate of a sol containing a polysiloxane compound of the above structure, it becomes easier to obtain a flexible aerogel with low thermal conductivity. In this regard, R in Formula (A) 1a Examples of such groups include hydroxyalkyl groups having 1 to 6 carbon atoms, and examples of such hydroxyalkyl groups include hydroxyethyl groups, hydroxypropyl groups, etc. Also, in formula (A), R 2a Examples of such groups include alkylene groups having 1 to 6 carbon atoms, and examples of such alkylene groups include ethylene groups, propylene groups, etc. Also, in formula (A), R 3a and R 4a As for each, independently, alkyl groups having 1 to 6 carbon atoms, phenyl groups, etc., may be used, and methyl groups, etc., may be used as the alkyl groups. Also, in formula (A), n may be 2 to 30, but may be 5 to 20.

[0059] As polysiloxane compounds having a structure represented by the above general formula (A), commercially available products may be used, such as compounds X-22-160AS, KF-6001, KF-6002, KF-6003 (all manufactured by Shin-Etsu Chemical Co., Ltd.), compounds XF42-B0970, Fluid OFOH 702-4% (all manufactured by Momentive Co., Ltd.).

[0060] Examples of polysiloxane compounds having alkoxy groups within the molecule include those having a structure represented by the following general formula (B). By using a polysiloxane compound having a structure represented by the following general formula (B), a ladder-type structure having a crosslinking part represented by general formula (2) or (3) can be introduced into the framework of the aerogel.

[0061] [Chemical Formula 7]

[0062]

[0063] In Equation (B), R 1b represents an alkyl group, an alkoxy group, or an aryl group, and R 2b and R 3b Each independently represents an alkoxy group, and R 4b and R 5b Each represents an alkyl group or an aryl group independently, and m represents an integer from 1 to 50. Here, examples of aryl groups include phenyl groups, substituted phenyl groups, etc. Also, examples of substituents for substituted phenyl groups include alkyl groups, vinyl groups, mercapto groups, amino groups, nitro groups, cyano groups, etc. Additionally, in formula (B), 2 R 1b may be the same or different, and 2 R 2b may be the same or different, and identically 2 R 3b may be the same or different. Also, in Equation (B), when m is an integer greater than or equal to 2, 2 or more R 4b may be the same or different, and 2 or more identical R 5bThey may be the same or different.

[0064] By using a wet gel (generated from a sol) which is a condensate of a sol containing a polysiloxane compound of the above structure or its hydrolysis product, it becomes easier to obtain a flexible aerogel with low thermal conductivity. In this regard, R in Formula (B) 1b Examples include alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, etc., and examples of said alkyl groups or alkoxy groups include methyl groups, methoxy groups, ethoxy groups, etc. Also, in formula (B), R 2b and R 3b As, each independently, examples include alkoxy groups having 1 to 6 carbon atoms, and examples of said alkoxy groups include methoxy groups, ethoxy groups, etc. Also, in formula (B), R 4b and R 5b As for each, independently, alkyl groups having 1 to 6 carbon atoms, phenyl groups, etc., may be used, and methyl groups, etc., may be used as the alkyl groups. Also, in formula (B), m may be 2 to 30, but may be 3 to 35 or 5 to 20.

[0065] A polysiloxane compound having a structure represented by the above general formula (B) can be obtained by appropriately referring to the manufacturing methods reported in Japanese Patent Publication No. 2000-26609, Japanese Patent Publication No. 2012-233110, etc. In addition, XR31-B1410 (manufactured by Momentive) may be used as the polysiloxane compound.

[0066] Furthermore, since alkoxy groups undergo hydrolysis, polysiloxane compounds having alkoxy groups may exist as hydrolysis products in the sol, and the polysiloxane compounds having alkoxy groups and their hydrolysis products may coexist. Additionally, regarding the polysiloxane compounds having alkoxy groups, all of the alkoxy groups in the molecule may be hydrolyzed, or they may be partially hydrolyzed.

[0067] These polysiloxane compounds having hydrolyzable functional groups or condensation functional groups, and the hydrolysis products of polysiloxane compounds having hydrolyzable functional groups may be used alone or in a mixture of two or more types.

[0068] In preparing the aerogel according to the present embodiment, silicon compounds other than the polysiloxane compounds described above may be used as silicon compounds having hydrolyzable functional groups or condensation functional groups. That is, the sol containing the silicon compounds described above may contain at least one selected from the group consisting of silicon compounds having hydrolyzable functional groups or condensation functional groups (excluding polysiloxane compounds) and hydrolysis products of said silicon compounds having hydrolyzable functional groups (hereinafter referred to as the "silicon compound group" as applicable), in addition to the polysiloxane compound group described above, or instead of the polysiloxane compound group described above. The number of silicon atoms in the molecule of the silicon compounds may be 1 or 2.

[0069] Silicon compounds having hydrolyzable functional groups within the molecule are not particularly limited, but examples include alkyl silicon alkoxides. Alkyl silicon alkoxides may have three or fewer hydrolyzable functional groups to improve water resistance. Examples of such alkyl silicon alkoxides include monoalkyltrialkoxysilane, monoalkyldialkoxysilane, dialkyldialkoxysilane, monoalkylmonoalkoxysilane, dialkylmonoalkoxysilane, trialkylmonoalkoxysilane, and specifically, methyltrimethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, etc. Here, hydrolyzable functional groups may include alkoxy groups such as methoxy groups and ethoxy groups.

[0070] Silicon compounds having condensation functional groups are not particularly limited, but examples include silanetetraol, methylsilanetriol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, diphenylsilanediol, n-propylsilanetriol, hexylsilanetriol, octylsilanetriol, decylsilanetriol, trifluoropropylsilanetriol, etc.

[0071] Silicon compounds having hydrolyzable functional groups or condensation functional groups may additionally have the aforementioned reactive groups (functional groups that do not correspond to hydrolyzable functional groups and condensation functional groups) which are different from hydrolyzable functional groups and condensation functional groups.

[0072] Silicon compounds having three or fewer hydrolyzable functional groups and reactive groups, such as vinyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyl trimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, etc., may also be used.

[0073] In addition, silicon compounds having condensation functional groups and reactive groups, such as vinyl silane triol, 3-glycidoxypropyl silane triol, 3-glycidoxypropylmethylsilanediol, 3-methacryloxypropyl silane triol, 3-methacryloxypropylmethylsilanediol, 3-acryloxypropyl silane triol, 3-mercaptopropyl silane triol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropyl silane triol, N-2-(aminoethyl)-3-aminopropylmethylsilanediol, etc., can also be used.

[0074] In addition, silicon compounds having three or fewer hydrolyzable functional groups at the molecular ends, such as bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, ethyltrimethoxysilane, and vinyltrimethoxysilane, can also be used.

[0075] Silicon compounds having hydrolyzable functional groups or condensation functional groups (excluding polysiloxane compounds), and hydrolysis products of said silicon compounds having hydrolyzable functional groups may be used alone or in a mixture of two or more types.

[0076] By using the above silicon compounds (excluding polysiloxane compounds), structures represented by the following general formulas (4) to (6) can be introduced into the framework of the aerogel. The aerogel according to the present embodiment may have any one of these structures alone or two or more types.

[0077] [Chemical Formula 8]

[0078]

[0079] In Equation (4), R 9 represents an alkyl group. Here, examples of alkyl groups include alkyl groups having 1 to 6 carbon atoms, and examples of alkyl groups include methyl groups.

[0080] [Chemical Formula 9]

[0081]

[0082] In Equation (5), R 10 and R 11 Each represents an alkyl group independently. Here, examples of alkyl groups include alkyl groups having 1 to 6 carbon atoms, and examples of alkyl groups include methyl groups.

[0083] [Chemical Formula 10]

[0084]

[0085] In Equation (6), R 12represents an alkylene group. Here, examples of alkylene groups include alkylene groups having 1 to 10 carbon atoms, and examples of such alkylene groups include ethylene groups, hexylene groups, etc.

[0086] (Fourth mode)

[0087] The aerogel according to the present embodiment may further contain silica particles in addition to the aerogel components in order to achieve greater toughness and superior thermal insulation and flexibility. An aerogel containing aerogel components and silica particles may be referred to as an aerogel composite. The aerogel composite is thought to have a cluster structure characteristic of aerogels, while having a cluster structure formed by the aerogel components and silica particles, and having a fine porous structure in three dimensions.

[0088] An aerogel containing aerogel components and silica particles can be described as a dried product of a wet gel which is a condensation product of a sol containing silica particles and at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensation functional group as described above, and a hydrolysis product of a silicon compound having a hydrolyzable functional group. Accordingly, the descriptions relating to the first to third embodiments may be appropriately applied to the aerogel relating to the present embodiment.

[0089] As for silica particles, they can be used without particular restrictions, and examples include amorphous silica particles. Examples of amorphous silica particles include fused silica particles, fumed silica particles, and colloidal silica particles. Among these, colloidal silica particles have high monodispersity, making it easy to suppress aggregation in the sol. In addition, as for silica particles, silica particles having a hollow structure, a porous structure, etc. may also be used.

[0090] The shape of the silica particles is not particularly limited and may include spherical, cocoon-shaped, or associative shapes. Among these, using spherical particles as silica particles makes it easier to suppress aggregation in the sol. The average primary particle size of the silica particles may be 1 nm or more, 5 nm or more, or 20 nm or more, from the perspective that it is easier to impart appropriate strength and flexibility to the aerogel and obtain an aerogel with excellent shrinkage resistance during drying. The average primary particle size of the silica particles may be 500 nm or less, 300 nm or less, or 100 nm or less, from the perspective that it is easier to suppress solid thermal conductivity of the silica particles and obtain an aerogel with excellent thermal insulation. From these perspectives, the average primary particle size of the silica particles may be 1 to 500 nm, 5 to 300 nm, or 20 to 100 nm.

[0091] In this embodiment, the average particle size of the aerogel component and the average primary particle size of the silica particle can be obtained by directly observing the aerogel using a scanning electron microscope (hereinafter abbreviated as "SEM"). The term "diameter" as used herein refers to the diameter when the cross-section of a particle exposed to the cross-section of the aerogel is considered as a circle. Furthermore, "diameter when the cross-section is considered as a circle" refers to the diameter of the circle when the area of ​​the cross-section is replaced with a circle of the same area. Additionally, in calculating the average particle size, the diameter of the circle is determined for 100 particles, and the average is taken.

[0092] In addition, the average particle size of silica particles can also be measured from the raw material. For example, the biaxial average primary particle size is calculated as follows from the results of observing 20 arbitrary particles using SEM. That is, taking colloidal silica particles dispersed in water with a typical solid content concentration of about 5 to 40 mass% as an example, a chip obtained by cutting a wafer with attached pattern wiring into a square with sides of 2 cm is immersed in the dispersion of colloidal silica particles for about 30 seconds, then the chip is rinsed with pure water for about 30 seconds and dried with a nitrogen blower. Afterward, 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 those particles is taken as the average particle size.

[0093] The number of silanol groups per gram of silica particles is 10×10, in terms of making it easier to obtain aerogels with excellent shrinkage resistance. 18 It may be more than 1 / g, and 50×10 18 It may be more than pieces / g, and 100×10 18 It may be at least one / g. From the perspective of facilitating the attainment of a homogeneous aerogel, the number of silanol groups per 1g of silica particles is 1000 × 10⁻⁶. 18 It may be less than or equal to pieces / g, and 800×10 18 It may be less than or equal to pieces / g, and 700×10 18 It may be less than or equal to pieces / g. In this regard, the number of silanol groups per 1g of silica particles is 10×10 18 ~1000×10 18 It can be pieces / g, or 50×10 18 ~800×10 18 It may be pieces / g, and 100×10 18 ~700×10 18 It can be g.

[0094] The content of the polysiloxane compound group included in the above sol (the total sum of the content of polysiloxane compounds having hydrolyzable functional groups or condensation functional groups, and the content of hydrolysis products of polysiloxane compounds having hydrolyzable functional groups) may be 5 parts by mass or more, or 10 parts by mass or more, per 100 parts by mass of the total amount of sol, from the viewpoint that it is easier to obtain good reactivity. The content of the polysiloxane compound group included in the above sol may be 50 parts by mass or less, or 30 parts by mass or less, per 100 parts by mass of the total amount of sol, from the viewpoint that it is easier to obtain good compatibility. From these perspectives, the content of the polysiloxane compound group included in the above sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass, per 100 parts by mass of the total amount of sol.

[0095] In the case where the above sol contains a silicon compound (excluding polysiloxane compounds), the silicon compound group (the sum of the content of silicon compounds having hydrolyzable functional groups or condensation functional groups, and the content of hydrolysis products of silicon compounds having hydrolyzable functional groups) may be 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more per 100 parts by mass of the total amount of sol, in order to make it easier to obtain good reactivity. The content of the silicon compound group included in the above sol may be 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less per 100 parts by mass of the total amount of sol, in order to make it easier to obtain good compatibility.

[0096] When the sol contains a polysiloxane group of compounds and a silicon group of compounds together, the ratio of the content of the polysiloxane group of compounds to the content of the silicon group of compounds may be 1:0.5 or higher, 1:0.7 or higher, or 1:1 or higher, from the perspective that good compatibility is more easily obtained. The ratio of the content of the polysiloxane group of compounds to the content of the silicon group of compounds may be 1:4 or lower, 1:3 or lower, or 1:2 or lower, from the perspective that gel shrinkage is more easily suppressed. From these perspectives, the ratio of the content of the polysiloxane group of compounds to the content of the silicon group of compounds may be 1:0.5 to 1:4, 1:0.7 to 1:3, or 1:1 to 1:2.

[0097] In the case where silica particles are included in the above sol, the content of silica particles may be 1 part by mass or more, 2 parts by mass or more, or 4 parts by mass or more, based on the view that it is easier to impart appropriate strength to the aerogel and thus easier to obtain an aerogel with excellent shrinkage resistance during drying. The content of silica particles may be 20 parts by mass or less, 17 parts by mass or less, or 15 parts by mass or less, based on the view that it is easier to suppress solid thermal conductivity of the silica particles and thus easier to obtain an aerogel with excellent thermal insulation properties, based on the view that it is easier to suppress solid thermal conductivity of the silica particles. In these viewpoints, the content of silica particles may be 1 to 20 parts by mass, 2 to 17 parts by mass, or 4 to 15 parts by mass, based on the view that it is easier to obtain an aerogel with excellent thermal insulation properties.

[0098] Aerogel particles

[0099] The aerogel particles in this embodiment can be obtained, for example, by crushing bulk aerogel as described below.

[0100] The average particle size D50 (also called the average diameter) of the aerogel particles can be 0.1 to 1000 μm, but it may 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 easier to obtain aerogel particles with excellent dispersibility and handling properties. On the other hand, if the average particle size D50 is small, it is easier to obtain aerogel particles with excellent dispersibility. The average particle size of the aerogel particles can be appropriately adjusted by the grinding method and grinding conditions, sieve, classification method, etc.

[0101] The average particle size D50 of aerogel particles can be measured by the laser diffraction and scattering method. For example, aerogel particles are added to a solvent (ethanol) such that the content is 0.05 to 5 mass%, and the aerogel particles are dispersed by vibrating with a 50W ultrasonic homogenizer for 15 to 30 minutes. Afterward, about 10 mL of the dispersion is injected into a laser diffraction and scattering particle size distribution measuring device, and the particle size is measured at 25°C with a refractive index of 1.3 and absorption of 0. Then, the particle size at 50% (by volume) of the integrated value in this particle size distribution is defined as the average particle size D50. As a measuring device, for example, the Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name) can be used.

[0102] In addition, commercially available products may be used as aerogel particles. Examples of commercially available aerogel particles include ENOVA MT1100 (manufactured by CABOT), AeroVa (manufactured by JIOS AEROGEL CORPORATION), etc.

[0103] In the present embodiment, the amount of aerogel particles is preferably such that the total content of aerogel particles and aggregates in the coating solution is 70 volume% or more based on the total volume of solids, more preferably such that it is 75 volume% or more, and even more preferably such that it is 80 volume% or more. Additionally, the amount of aerogel particles may be such that the total content of aerogel particles and aggregates in the coating solution is, for example, 99 volume% or less based on the total volume of solids, 95 volume% or less, or 90 volume% or less.

[0104] Method for manufacturing aerogel particles

[0105] The method for manufacturing aerogel particles is not particularly limited, but, for example, can be manufactured by the following method.

[0106] The aerogel particles of the present embodiment can be manufactured by a manufacturing method mainly comprising: a sol generation process; a wet gel generation process in which the sol obtained from the sol generation process is gelled and then aged to obtain a wet gel; a washing and solvent exchange process in which the wet gel obtained from the wet gel generation process is washed and (if necessary) solvent exchanged; a drying process in which the wet gel obtained from the washing and solvent exchanged is dried; and a grinding process in which the aerogel obtained by drying is ground.

[0107] In addition, it may be manufactured by a manufacturing method mainly comprising a sol generation process, a wet gel generation process, a wet gel grinding process for grinding the wet gel obtained from the wet gel generation process, a washing and solvent exchange process, and a drying process.

[0108] The size of the obtained aerogel particles can be further adjusted by sieving, classification, etc. Dispersibility can be improved by adjusting the particle size. In addition, "sol" refers to a state prior to the occurrence of a gelation reaction, and in this embodiment, it refers to a state in which the silicon compound and, in some cases, silica particles are dissolved or dispersed in a solvent. Furthermore, "wet gel" refers to a gel solid in a wet state that contains a liquid medium but does not possess fluidity.

[0109] (Sol generation process)

[0110] The sol generation process is a process of mixing a silicon compound with, in some cases, silica particles (which may be a solvent containing silica particles) and performing a hydrolysis reaction to produce a sol. In this process, an acid catalyst may be added to the solvent to promote the hydrolysis reaction. Also, as shown in Japanese Patent Publication No. 5250900, a surfactant, a thermohydrolyzable compound, etc. may 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.

[0111] As a solvent, for example, water or a mixture of water and alcohol may be used. Examples of alcohols include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, t-butanol, etc. Among these, alcohols with low surface tension and low boiling points that reduce interfacial tension with the gel wall include methanol, ethanol, 2-propanol, etc. These may be used individually or in a mixture of two or more types.

[0112] For example, when alcohol is used as a solvent, the amount of alcohol can be 4 to 8 moles per 1 mole of the total amount of silicon compound group and polysiloxane compound group, but it can also be 4 to 6.5 moles or 4.5 to 6 moles. By using 4 moles or more of alcohol, it becomes easier to obtain good compatibility, and by using 8 moles or less, it becomes easier to suppress gel shrinkage.

[0113] Examples of acid catalysts include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfite, phosphoric acid, phosphorus, hypophosphorus, bromic acid, chloric acid, hypochlorous acid, and hypochlorous acid; acidic phosphates such as acidic aluminum phosphate, acidic magnesium phosphate, and acidic zinc phosphate; and organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid. Among these, organic carboxylic acids may be used as acid catalysts to further improve the water resistance of the resulting aerogel. Examples of such organic carboxylic acids include acetic acid, but formic acid, propionic acid, oxalic acid, and malonic acid may also be used. These may be used individually or in a mixture of two or more types.

[0114] By using an acid catalyst, the hydrolysis reaction of silicon compounds can be promoted, allowing a sol to be obtained in a shorter time.

[0115] The amount of acid catalyst added can be 0.001 to 0.1 parts by mass per 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group.

[0116] As surfactants, nonionic surfactants, ionic surfactants, etc. may be used. These may be used alone or in a mixture of two or more types.

[0117] As nonionic surfactants, for example, compounds containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of alkyl groups, or compounds containing a hydrophilic part such as polyoxypropylene, may be used. Examples of compounds containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of alkyl groups include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene alkyl ether. Examples of compounds containing a hydrophilic part such as polyoxypropylene include polyoxypropylene alkyl ether and block copolymers of polyoxyethylene and polyoxypropylene.

[0118] Examples of ionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. Examples of cationic surfactants include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and examples of anionic surfactants include sodium dodecylsulfonate. In addition, examples of amphoteric surfactants include amino acid-based surfactants, betaine-based surfactants, and amine oxide-based surfactants. Examples of amino acid-based surfactants include acylglutamic acid. Examples of betaine-based surfactants include lauryl dimethylaminoacetate betaine and stearyl dimethylaminoacetate betaine. Examples of amine oxide-based surfactants include lauryl dimethylamine oxide.

[0119] These surfactants are thought to have the effect of suppressing phase separation by reducing the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer in the wet gel generation process described later.

[0120] The amount of surfactant added depends on the type of surfactant or the type and amount of silicon compound, but, for example, it can be 1 to 100 parts by mass per 100 parts by mass of the total amount of polysiloxane compound group and silicon compound group. In addition, the same amount added may be 5 to 60 parts by mass.

[0121] It is believed that thermohydrolyzable compounds generate a base catalyst upon thermohydrolysis, thereby making the reaction solution basic and promoting the sol-gel reaction in the wet gel formation process described later. Therefore, as for these thermohydrolyzable compounds, any compound capable of making the reaction solution basic after hydrolysis is not particularly limited and may include urea; acid amides such as formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, and N,N-dimethylacetamide; and cyclic nitrogen compounds such as hexamethylenetetramine. Among these, urea is particularly effective in obtaining the aforementioned promoting effect.

[0122] The amount of thermohydrolyzable compound added is not particularly limited as long as it is an amount sufficient to promote the sol-gel reaction in the wet gel generation process described later. For example, when urea is used as the thermohydrolyzable compound, the amount added can be 1 to 200 parts by mass with respect to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. In addition, the same amount added may be 2 to 150 parts by mass. By adding an amount of 1 part by mass or more, it becomes easier to obtain good reactivity, and by adding an amount of 200 parts by mass or less, it becomes easier to suppress the precipitation of crystals and the decrease in gel density.

[0123] The hydrolysis of the sol-forming process depends on the type and amount of silicon compounds, silica particles, acid catalysts, surfactants, etc. in the mixture, but, for example, it may be carried out for 10 minutes to 24 hours under a temperature environment of 20 to 60°C, or for 5 minutes to 8 hours under a temperature environment of 50 to 60°C. By doing so, the hydrolyzable functional groups in the silicon compounds are sufficiently hydrolyzed, and the hydrolysis product of the silicon compounds can be obtained more reliably.

[0124] However, when a thermohydrolyzable compound is added to the solvent, the temperature environment of the sol formation process may be controlled to a temperature that inhibits the hydrolysis of the thermohydrolyzable compound and thus inhibits gelation of the sol. At this time, any temperature may be used as long as it inhibits the hydrolysis of the thermohydrolyzable compound. For example, when urea is used as the thermohydrolyzable compound, the temperature environment of the sol formation process may be 0 to 40°C, but it may also be 10 to 30°C.

[0125] (Wet gel formation process)

[0126] The wet gel production process is a process of gelling the sol obtained from the sol production process and then aging it to obtain a wet gel. In this process, a base catalyst may be used to promote gelation.

[0127] As base catalysts, carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper(II) carbonate, iron(II) carbonate, silver(I) carbonate; bicarbonates such as calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, ammonium bromide; basic sodium phosphates such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; Examples include aliphatic amines such as allylamine, diallylamine, trialylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3-(diethylamino)propylamine, di-2-ethylhexylamine, 3-(dibutylamino)propylamine, tetramethylethylenediamine, t-butylamine, sec-butylamine, propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, and triethanolamine; nitrogen-containing heterocyclic compounds such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, imidazole and its derivatives. Among these, ammonium hydroxide (ammonia water) is superior in terms of its high volatility, which makes it difficult to remain in the aerogel particles after drying, thus making it difficult to impair water resistance, and furthermore, in terms of economic efficiency. The above-mentioned base catalyst may be used alone or in a mixture of two or more types.

[0128] By using a base catalyst, the dehydration condensation reaction or dealolysis condensation reaction of silicon compounds and silica particles in the sol can be promoted, allowing the gelation of the sol to be performed in a shorter time. In addition, a wet gel with higher strength (stiffness) can be obtained. In particular, since ammonia is highly volatile and difficult to remain in the aerogel particles, aerogel particles with better water resistance can be obtained by using ammonia as a base catalyst.

[0129] The amount of base catalyst added can be 0.5 to 5 parts by mass per 100 parts by mass of the total amount of the polysiloxane group of compounds and the silicon group of compounds, but it may also be 1 to 4 parts by mass. By using 0.5 parts by mass or more, gelation can be performed in a shorter time, and by using 5 parts by mass or less, the decrease in water resistance can be further suppressed.

[0130] In the process of producing a wet gel, the gelation of the sol may be carried out in a sealed container so that the solvent and base catalyst do not volatilize. The gelation temperature may be 30 to 90°C, but may also be 40 to 80°C. By setting the gelation temperature to 30°C or higher, gelation can be performed in a shorter time, and a wet gel with higher strength (stiffness) can be obtained. In addition, by setting the gelation temperature to 90°C or lower, it becomes easier to suppress the volatilization of the solvent (especially alcohol), so gelation can be performed while suppressing volume shrinkage.

[0131] In the process of producing a wet gel, aging may be carried out in a sealed container so that the solvent and base catalyst do not volatilize. Through aging, the bonding of the components constituting the wet gel is strengthened, and as a result, a wet gel with high strength (stiffness) sufficient to suppress shrinkage during drying can be obtained. The aging temperature may be 30 to 90°C, but may also be 40 to 80°C. By setting the aging temperature to 30°C or higher, a wet gel with higher strength (stiffness) can be obtained, and by setting the aging temperature to 90°C or lower, it becomes easier to suppress the volatilization of the solvent (especially alcohol), so gelation can be performed while suppressing volume shrinkage.

[0132] In addition, since it is often difficult to determine the end point of gelation of the sol, the gelation of the sol and subsequent maturation may be performed as a continuous series of operations.

[0133] The gelation time and aging time can be appropriately set according to the gelation temperature and aging temperature. When silica particles are included in the sol, the gelation time can be shortened in particular compared to when they are not included. This is presumed to be because the silanol groups or reactive groups of the silicon compounds in the sol form hydrogen bonds or chemical bonds with the silanol groups of the silica particles. Additionally, the gelation time can be 10 to 120 minutes, but it may also be 20 to 90 minutes. By making the gelation time 10 minutes or more, it becomes easier to obtain a homogeneous wet gel, and by making it 120 minutes or less, it becomes possible to simplify the drying process from the washing and solvent exchange processes described later. Furthermore, as the entire gelation and aging process, the total time of the gelation time and aging time may be 4 to 480 hours, but it may also be 6 to 120 hours. By making the total of the gelation time and the aging time 4 hours or more, a wet gel with higher strength (stiffness) can be obtained, and by making it 480 hours or less, it becomes easier to maintain the effect of aging.

[0134] In order to lower the density of the aerogel particles obtained or to increase the average micropore diameter, the gelation temperature and aging temperature may be increased within the above range, or the total time of gelation and aging may be increased within the above range. In addition, in order to increase the density of the aerogel particles obtained or to decrease the average micropore diameter, the gelation temperature and aging temperature may be lowered within the above range, or the total time of gelation and aging may be shortened within the above range.

[0135] (Wet gel grinding process)

[0136] When performing a wet gel grinding process, the wet gel obtained from the wet gel generation process is ground. Grinding can be performed, for example, by placing the wet gel into a Henschel-type mixer, or by performing the wet gel generation process inside the mixer and operating the mixer under appropriate conditions (rotation speed and time). Alternatively, more simply, grinding can be performed by placing the wet gel into a sealable container, or by performing the wet gel generation process inside a sealable container and shaking for an appropriate time using a shaking device such as a shaker. Additionally, if necessary, the particle size of the wet gel can be adjusted using a jet mill, roller mill, bead mill, etc.

[0137] (Cleaning and solvent displacement process)

[0138] The washing and solvent exchange process is a process comprising a washing process (washing process) for washing a wet gel obtained by a wet gel generation process or a wet gel grinding process, and a process (solvent exchange process) for replacing the washing solution in the wet gel with a solvent suitable for drying conditions (drying process described later). The washing and solvent exchange process can be carried out in a form where only the solvent exchange process is performed without performing the washing process for the wet gel, but the wet gel may be washed from the perspective of reducing impurities such as unreacted materials and by-products in the wet gel and enabling the production of aerogel particles of higher purity.

[0139] In the cleaning process, the wet gel obtained by the wet gel generation process or the wet gel grinding process is cleaned. The cleaning can be performed repeatedly, for example, using water or an organic solvent. At this time, the cleaning efficiency can be improved by heating.

[0140] As organic solvents, 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, methylene chloride, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid may be used. The above organic solvents may be used alone or in a mixture of two or more types.

[0141] In the solvent exchange process described below, a low surface tension solvent may be used to suppress shrinkage of the gel caused by drying. However, low surface tension solvents generally have very low mutual solubility with water. Therefore, when using a low surface tension solvent in the solvent exchange process, a hydrophilic organic solvent having high mutual solubility with both water and the low surface tension solvent may be used as the organic solvent in the cleaning process. Furthermore, the hydrophilic organic solvent used in the cleaning process can serve as a preliminary exchange for the solvent exchange process. Among the above organic solvents, examples of hydrophilic organic solvents include methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, etc. Additionally, methanol, ethanol, methyl ethyl ketone, etc. are excellent in terms of economic efficiency.

[0142] The amount of water or organic solvent used in the cleaning process can be an amount sufficient to sufficiently replace the solvent in the wet gel and clean it. This amount can be 3 to 10 times the volume of the wet gel. The cleaning can be repeated until the water content in the wet gel after cleaning is 10 mass% or less relative to the mass of silica.

[0143] The temperature environment in the cleaning process can be set to a temperature below the boiling point of the solvent used for cleaning, and for example, when using methanol, it can be heated to about 30 to 60°C.

[0144] In the solvent exchange process, the solvent of the washed wet gel is replaced with a predetermined exchange solvent to suppress shrinkage of the aerogel during the drying process. At this time, the exchange efficiency can be improved by heating. Specifically, as the exchange solvent, when drying is performed under atmospheric pressure at a temperature below the critical point of the solvent used for drying during the drying process, a solvent with low surface tension described later may be used. On the other hand, when supercritical drying is performed, as the exchange solvent, examples include ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, etc., or a solvent in which two or more of these are mixed.

[0145] As a solvent with low surface tension, a solvent having a surface tension of 30 mN / m or less at 20°C may be used. Additionally, the surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of solvents with low surface tension include aliphatic hydrocarbons such as pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3-methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), and 1-pentene (16.0); aromatic hydrocarbons such as benzene (28.9), toluene (28.5), m-xylene (28.7), and p-xylene (28.3); Halogenated hydrocarbons such as dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), 2-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); Examples include esters such as methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), isobutyl acetate (23.7), and ethyl butyrate (24.6) (the values ​​in parentheses indicate surface tension at 20°C, and the unit is [mN / m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and excellent working environment properties. Furthermore, among these, hydrophilic organic solvents such as acetone, methyl ethyl ketone, and 1,2-dimethoxyethane can be used in combination with the organic solvent in the cleaning process. Additionally, among these, a solvent with a boiling point of 100°C or lower at atmospheric pressure may be further used, as drying is easier in the drying process described later. The above solvents may be used alone or in a mixture of two or more types.

[0146] The amount of solvent used in the solvent exchange process can be an amount sufficient to sufficiently replace the solvent in the wet gel after washing. This amount can be 3 to 10 times the volume of the wet gel.

[0147] The temperature environment in the solvent exchange process can be set to a temperature below the boiling point of the solvent used for exchange, and for example, when using heptane, it can be heated to about 30 to 60°C.

[0148] In addition, when silica particles are included in the gel, the solvent exchange process is not mandatory. The suspected mechanism is as follows: that is, the silica particles function as a support for a three-dimensional mesh-like framework, thereby supporting the framework and suppressing the shrinkage of the gel during the drying process. Therefore, it is thought that the gel can be provided to the drying process as is without replacing the solvent used for washing. In this way, by using silica particles, the drying process can be simplified from the washing and solvent exchange processes.

[0149] (Drying process)

[0150] In the drying process, the wet gel, which has been washed and (if necessary) solvent-exchanged as described above, is dried. In this way, an aerogel (aerogel block or aerogel particle) can be obtained. That is, an aerogel can be obtained by drying the wet gel produced from the above sol.

[0151] The drying method is not particularly limited and known atmospheric drying, supercritical drying, or freeze-drying methods may be used. Among these, atmospheric drying or supercritical drying may be used from the perspective of facilitating the production of low-density aerogels. Additionally, atmospheric drying may be used from the perspective of enabling production at low cost. Furthermore, in this embodiment, atmospheric pressure refers to 0.1 MPa (atmospheric pressure).

[0152] Aerogels can be obtained by drying a wet gel, which has been washed and (if necessary) solvent-exchanged, under atmospheric pressure at a temperature below the critical point of the solvent used for drying. The drying temperature varies depending on the type of exchanged solvent (or the solvent used for washing if solvent exchange is not performed), but can be set to 20 to 150°C, taking into account that drying at particularly high temperatures accelerates the evaporation rate of the solvent and may cause large cracks in the gel. Additionally, the drying temperature may be 60 to 120°C. Furthermore, the drying time may be 4 to 120 hours, although it varies depending on the volume of the wet gel and the drying temperature. Additionally, accelerating drying by applying pressure below the critical point within a range that does not impair productivity is also considered to be included in atmospheric pressure drying.

[0153] Aerogel can also be obtained by supercritical drying a wet gel that has been washed and (if necessary) solvent-exchanged. Supercritical drying can be performed by known methods.

[0154] As a method of 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 may be cited. Alternatively, as a method of supercritical drying, a method of immersing the wet gel in liquid carbon dioxide under conditions of, for example, 20 to 25°C and 5 to 20 MPa may be cited, thereby replacing 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 removing the carbon dioxide alone or a mixture of carbon dioxide and solvent.

[0155] The aerogel obtained by such atmospheric pressure drying or supercritical drying may also be further dried at 105 to 200°C for about 0.5 to 2 hours under atmospheric pressure. This makes it easier to obtain an aerogel with low density and small micropores. The additional drying may be performed at 150 to 200°C under atmospheric pressure.

[0156] (Grinding process)

[0157] In cases where the wet gel grinding process is not performed, aerogel particles are obtained by grinding the aerogel (aerogel block) obtained by drying. For example, this can be done by placing the aerogel into a jet mill, roller mill, bead mill, hammer mill, etc., and operating it at an appropriate rotational speed and time.

[0158] Emulsion

[0159] In this embodiment, the emulsion may be one in which a binder resin is emulsified with a polymer-based emulsifier in a liquid medium.

[0160] As a liquid medium, an aqueous solvent containing water is preferred. The aqueous solvent may contain an organic solvent in addition to water. The organic solvent may be compatible with water, and examples include alcohols such as methanol, ethanol, isopropanol, butanol, ethylene glycol, and propylene glycol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and methyl ethyl ketone; carboxylic acids such as acetic acid and propionic acid; and nitrogen-containing compounds such as acetonitrile, dimethylformamide, and triethylamine.

[0161] The content of the liquid medium in the emulsion is not particularly limited, but for example, 20 to 900 parts by mass may be added per 100 parts by mass of solid content, or 50 to 250 parts by mass may be added.

[0162] The content of the liquid medium in the coating solution is not particularly limited and may be appropriately changed according to the desired viscosity of the coating solution, etc. For example, the content of the liquid medium in the coating solution may be an amount such that the solid content concentration of the coating solution falls within the suitable range described below. In addition, the liquid medium in the coating solution may be only the liquid medium in the emulsion, or it may include a liquid medium added during or after mixing of the emulsion and the aerogel particles.

[0163] The solid content concentration of the coating liquid may, for example, be 10 mass% or more, preferably 15 mass% or more, and more preferably 20 mass% or more. In addition, the solid content concentration of the coating liquid may, for example, be 70 mass% or less, preferably 60 mass% or less, and more preferably 50 mass% or less.

[0164] The binder resin may be any resin that can be emulsified by a polymer emulsifier in a liquid medium. Examples of binder resins include uretane resin, alkyd resin, silicone resin, acrylic resin, olefin resin, fluoropolymer, vinyl acetate resin, vinyl chloride resin, polyester, polyamide, polyimide, and copolymers of two or more monomers that form these resins. Among these, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, acrylic resin, and silicone resin may be suitably used from the perspective of having better flexibility of the thermal insulation material formed, and vinyl acetate resin may be suitably used from the perspective of having excellent film-forming properties at low temperatures.

[0165] The content of the binder resin in the emulsion is not particularly limited and, for example, may be 20 mass% or more, or 30 mass% or more. In addition, the content of the binder resin in the emulsion may, for example, be 80 mass% or less, or 60 mass% or less.

[0166] The content of binder resin in the coating solution may be, for example, 30 volume% or less based on the total volume of solids, preferably 25 volume% or less, and more preferably 20 volume% or less. In addition, the content of binder resin in the coating solution may be, for example, 1 volume% or more, 5 volume% or more, or 10 volume% or more based on the total volume of solids.

[0167] A polymeric emulsifier is sufficient if it is an emulsifier capable of emulsifying a binder resin in a liquid medium. Furthermore, in this specification, "polymeric emulsifier" refers to an emulsifier formed by the polymerization of monomers (and, if necessary, the modification of the polymer). The polymeric emulsifier may have a molecular weight distribution.

[0168] The number average molecular weight (Mn) of the polymeric emulsifier may be, for example, 1,000 or more, 5,000 or more, 8,000 or more, 10,000 or more, or 20,000 or more. Additionally, the number average molecular weight of the polymeric emulsifier may be, for example, 1,000,000 or less, 50,000 or less, 200,000 or less, 100,000 or less, or 50,000 or less. Furthermore, the number average molecular weight of the polymeric emulsifier represents a value measured by GPC.

[0169] Examples of polymeric emulsifiers include polyvinyl alcohol (PVA) and hydroxyethyl cellulose.

[0170] The content of the polymeric emulsifier in the emulsion may, for example, be 0.001 parts by mass or more per 100 parts by mass of binder resin, and from the perspective of stabilizing the emulsion, it may be 0.01 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more. In addition, the content of the polymeric emulsifier in the emulsion may, for example, be 80 parts by mass or less per 100 parts by mass of binder resin, and from the perspective of viscosity, it may be 20 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less.

[0171] The content of the polymeric emulsifier in the coating solution may, for example, be 0.0001 parts by mass or more per 100 parts by mass of binder resin, and from the perspective of emulsion stabilization, it may be 0.001 parts by mass or more, 0.005 parts by mass or more, or 0.01 parts by mass or more. In addition, the content of the polymeric emulsifier in the coating solution may, for example, be 80 parts by mass or less per 100 parts by mass of binder resin, and from the perspective of ease of handling during mixing, it may be 20 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less.

[0172] The method of manufacturing the emulsion is not particularly limited, and for example, a method of synthesizing a binder resin in the presence of a polymer-based emulsifier in a liquid medium can be cited.

[0173] The emulsion may contain other ingredients in addition to those mentioned above. Examples of other ingredients include fillers, solvents, pigments, dyes, preservatives, defoaming agents, etc.

[0174] Water-soluble polymers

[0175] The coating solution of the present embodiment may further contain a water-soluble polymer having hydrophobic groups. The water-soluble polymer may have hydrophobic groups and also be water-soluble. The water-soluble polymer may be added during or after mixing of the emulsion and the aerogel particles.

[0176] Examples of hydrophobic groups include alkyl groups (preferably long-chain alkyl groups having 6 to 26 carbon atoms), ester groups, alkoxy groups, halogens, etc. Among these, as hydrophobic groups, alkyl groups are preferred, long-chain alkyl groups having 8 to 26 carbon atoms are more preferred, long-chain alkyl groups having 10 to 26 carbon atoms are more preferred, long-chain alkyl groups having 12 to 26 carbon atoms are even more preferred, and long-chain alkyl groups having 15 to 26 carbon atoms may also be used.

[0177] Examples of water-soluble polymers include modified carboxyl vinyl polymers, modified polyether uretaines, cellulose-based resins, polyethylene oxide, polyvinyl alcohol, polyacrylates, polyvinylpyrrolidone, dextrin-based resins, chitin-based resins, chitosan-based resins, etc.

[0178] As a water-soluble polymer, cellulose-based resins can be suitably used. Examples of cellulose-based resins include methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, and modified products obtained by further modifying (e.g., hydrophobizing) these.

[0179] As for the cellulose-based resin, a cellulose-based resin having an alkyl group is preferred, and a cellulose-based resin having a long-chain alkyl group having 6 to 26 carbon atoms is more preferred. With such a cellulose-based resin, the effects of the present invention are more pronounced. The number of carbon atoms of the long-chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

[0180] As for the cellulose-based resin, for example, a cellulose-based resin having a structural unit represented by the following formula (A-1) is preferred.

[0181] [Chemical Formula 11]

[0182]

[0183] In Equation (A-1), R A is, hydrogen atom, alkyl group, hydroxyalkyl group, -R A1 -OR A2 The energy appearing as (R A1 represents an alkanediyl group or a hydroxyalkainediyl group, and R A2 represents an alkyl group.) represents three Rs A They may be identical or different. However, the three Rs A Among them, at least one is an alkyl group or -R A1 -ORA2 It is a form that appears as.

[0184] In Equation (A-1), R A As the alkyl group in [the name], an alkyl group having 1 to 26 carbon atoms is preferred. Also, R A The alkyl group in the above is more preferably a short-chain alkyl group having 1 to 3 carbon atoms, or a long-chain alkyl group having 6 to 26 carbon atoms. The number of carbon atoms of the long-chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

[0185] In Equation (A-1), R A As for the hydroxyalkyl group, a hydroxyalkyl group having 1 to 26 carbon atoms is preferred, a hydroxyalkyl group having 1 to 10 carbon atoms is more preferred, and a hydroxyalkyl group having 1 to 5 carbon atoms is even more preferred.

[0186] In Equation (A-1), R A1 The alkaine diyl group in [the embodiment] is preferably an alkaine diyl group having 1 to 26 carbon atoms, more preferably an alkaine diyl group having 1 to 10 carbon atoms, and even more preferably an alkaine diyl group having 1 to 5 carbon atoms. Also, R A1 The hydroxyalkainediyl group in the above is preferably a hydroxyalkainediyl group having 1 to 26 carbon atoms, more preferably a hydroxyalkainediyl group having 1 to 10 carbon atoms, and even more preferably a hydroxyalkainediyl group having 1 to 5 carbon atoms.

[0187] In Equation (A-1), R A2 As for, an alkyl group having 1 to 26 carbon atoms is preferred. Also, R A2 The alkyl group in the above 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 is more preferably a long-chain alkyl group. The number of carbon atoms of the long-chain alkyl group is preferably 8 to 26, more preferably 10 to 26, even more preferably 12 to 26, and even more preferably 15 to 26.

[0188] In equation (A-1), 3 R A At least one of them is a long-chain alkyl group, or three R A At least one of them is -R A1 -OR A2 It is a mechanism that appears as and is also R A2 It is preferable that the alkyl group be a long-chain alkyl group.

[0189] In the cellulose-based resin, it is preferable that the content of long-chain alkyl groups having 6 to 26 carbon atoms is 0.01 to 5 mass% based on the total amount of the cellulose-based resin, and more preferable that it is 0.01 to 3 mass%.

[0190] In the present embodiment, the content of the water-soluble polymer in the coating solution may be, for example, 0.01 volume% or more based on the total volume of the solids in the coating solution, preferably 0.1 volume% or more, and more preferably 0.3 volume% or more. In addition, the content of the water-soluble polymer may be, for example, 10 volume% or less based on the total volume of the solids in the coating solution, preferably 5 volume% or less, and more preferably 3 volume% or less.

[0191] Other ingredients

[0192] The coating liquid of the present embodiment may further include, as components other than those mentioned above, a thickener, a fibrous material, a pigment, a leveling agent, etc.

[0193] Examples of thickeners include fine particles such as fumed silica and clay minerals.

[0194] Fibrous materials can exhibit an anchoring function between aerogel particles and can further improve the strength of the coating film made of the composite material. Fibrous materials are not particularly limited and include organic fibers and inorganic fibers. Examples of organic fibers include polyamide fibers, polyimide fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, polyvinyl chloride fibers, polyester fibers, polyacrylonitrile fibers, polyethylene fibers, polypropylene fibers, polyurethane fibers, phenol fibers, polyetherester fibers, polylactic acid fibers, polycarbonate fibers, etc. Examples of inorganic fibers include glass fibers, carbon fibers, ceramic fibers, metal fibers, etc.

[0195] Method for preparing the solution

[0196] In the present embodiment, the coating solution is prepared by a manufacturing method comprising: a preparation process for preparing an emulsion containing a polymeric emulsifier, a binder resin, and a liquid medium, and aerogel particles; and a mixing process for mixing the emulsion and aerogel particles prepared in the preparation process to aggregate at least a portion of the aerogel particles, thereby obtaining a coating solution containing aggregates of aerogel particles, a polymeric emulsifier, a binder resin, and a liquid medium.

[0197] In the preparation process, additional components other than the emulsion and aerogel particles (e.g., the aforementioned <water-soluble polymer>, <other components>, etc.) may be prepared.

[0198] In the mixing process, each component prepared in the preparation process is mixed so that the aerogel particles aggregate. The mixing method may be any method that allows the aerogel particles to form aggregates, for example, a method of stirring and mixing each component prepared in the preparation process.

[0199] The stirring speed affects the size of the aggregates. As the stirring speed increases, shear stress is applied to the coating solution, so the size of the aggregates tends to decrease. Therefore, from the perspective of obtaining aggregates of a suitable size as described below, it is desirable to prepare the coating solution with a low stirring speed.

[0200] Furthermore, viscosity during mixing also affects the size of the aggregates. Even at the same stirring speed, the shear stress applied to the coating solution varies depending on the viscosity. If the viscosity is high, greater shear stress is applied to the coating solution, and the aggregates become smaller. On the other hand, if the viscosity of the coating solution is low, the shear stress applied to the solution decreases even at the same stirring speed, and the aggregates become larger. Therefore, by adjusting the stirring speed according to the viscosity of the coating solution, it is possible to produce a coating solution with a desired aggregate size.

[0201] In addition, the size of the aggregates can be changed by additives. Examples of additives that strongly influence the size of the aggregates include surface modifiers, surfactants, and dispersants.

[0202] Surface modifiers and surfactants lower the surface energy of aerogel particles and solutions. The lower the surface energy, the weaker the force attempting to minimize the interface, and thus the size of aggregates tends to decrease. Therefore, the addition of surface modifiers and surfactants lowers the surface energy, thereby reducing the size of aggregates.

[0203] Dispersants inhibit the approach of particles by adhering to the particle surface through electrostatic or steric repulsion. By attaching to the surface of aerogel particles and inhibiting their proximity, the addition of the dispersant causes the aggregates to be reduced in size.

[0204] In addition, the amount of liquid medium used during mixing also affects the size of the aggregates. Even if the composition of the final coating solution is the same, the size of the aggregates differs between (i) the method of adding the entire amount of liquid medium from the beginning of mixing and (ii) the method of mixing with a small amount of liquid medium initially and then adding more liquid medium later. Compared to method (i), method (ii) results in a higher initial viscosity of the coating solution, and if the aforementioned additive is added, its concentration also increases. For this reason, method (ii) tends to produce smaller aggregates compared to method (i). By distinguishing and using these methods according to conditions such as the coating solution composition and the mixing device (stirring device), aggregates of the desired size can be formed.

[0205] As the size of the aggregate increases, the contact interface between the aerogel and the resin component becomes smaller, making it easier to suppress the penetration of the resin component into the micropores of the aerogel. In this regard, in the present embodiment, it is preferable to form aggregates with a diameter of 20 μm or more, more preferable to form aggregates with a diameter of 40 μm or more, and even more preferable to form aggregates with a diameter of 50 μm or more. On the other hand, from the perspective of avoiding a decrease in membrane strength caused by the continuous formation of relatively brittle aerogels, the diameter of the aggregate is preferably 400 μm or less, and more preferable to have a diameter of 300 μm or less.

[0206] In the present embodiment, it is preferable that the average diameter of the aggregate be at least twice the average diameter of the aerogel particles prepared in the preparation process, more preferable that it be at least four times, and even more preferable that it be at least eight times. As a result, the contact interface between the aerogel and the resin component becomes smaller, making it easier to suppress the penetration of the resin component into the micropores of the aerogel. In addition, it is preferable that the average diameter of the aggregate be 40 times or less the average diameter of the aerogel particles prepared in the preparation process, more preferable that it be 30 times or less, and even more preferable that it be 20 times or less. As a result, the decrease in membrane strength caused by the continuous formation of relatively brittle aerogels is suppressed, making it easier to obtain higher membrane strength.

[0207] In addition, in this specification, the average diameter of the aggregate represents a value measured by the following method.

[0208] [Method for measuring the average diameter of aggregates in a liquid]

[0209] Take about 20g of the solution into a 100mL poly cup and dilute it slowly by adding 2g of water at a time while stirring with a spatula. Place the diluted sample on a glass plate and acquire a micrograph of the sample using an optical microscope (OLYMPUS, Model No.: BX51). Analyze the obtained micrograph using image editing software ImageJ and determine the diameters of multiple aggregates within the micrograph. The average of the obtained values ​​is taken as the average diameter of the aggregates.

[0210] Also, in this specification, the average diameter of the aerogel particles has the same meaning as the average particle diameter D50 of the aerogel particles described above.

[0211] In this embodiment, when the diluted solution is observed by an optical microscope, among the area occupied by aerogel particles and aggregates within the field of view, the area occupied by aggregates with a diameter of 20 μm or more (more preferably aggregates with a diameter of 50 μm or more) is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and may be 100%.

[0212] In addition, in this specification, the diluted solution obtained by diluting the plating solution and the method of observing said diluted solution may be the same as the sample prepared in the [method for measuring the average diameter of aggregates in the plating solution] described above and the method of observing said sample. Also, the “area of ​​… within the field of view” is obtained by analyzing the microscope photograph using the image editing software ImageJ.

[0213] Method for manufacturing insulation material

[0214] In the present embodiment, the insulating material is manufactured by a manufacturing method comprising a coating process in which the coating solution is applied onto a support to obtain a coating film, and a removal process in which at least a portion of the liquid medium is removed from the coating film to obtain the insulating material. According to this manufacturing method, aggregates of aerogel particles are formed in the coating solution, and since the penetration of the resin into the aerogel micropores is sufficiently suppressed, an insulating material having high thermal insulation and high film-forming properties is obtained.

[0215] The support to which the coating solution is applied is not particularly limited. The support may be peeled off from the insulation material after manufacturing, or it may be used without being peeled off from the insulation material. For example, the support may be the target of application for the insulation material. The material constituting the support is not particularly limited and may be, for example, metal, ceramic, glass, resin, composite materials thereof, etc. In addition, the shape of the support may be appropriately selected according to the purpose of use, material, etc., and may be, for example, block-shaped, sheet-shaped, powder-shaped, fibrous-shaped, etc.

[0216] The method of applying the coating solution is not particularly limited, and examples include dip coat, spray coat, spin coat, roll coat, etc.

[0217] As for the application method of the coating solution, a method in which the pressure applied to the coating solution is 1.5 MPa or less may be used. With such an application method, the disintegration of aggregates in the coating solution due to the load during application is suppressed. For example, application methods such as roller coating, soldering iron coating, and air spray are preferred because they make it easy to reduce the pressure applied to the coating solution.

[0218] In addition, in this embodiment, because the binder resin in the emulsion is covered by the polymer emulsifier due to the use of a polymer emulsifier, it is difficult for the fine particles of the binder resin to come into contact with the aggregates of aerogel particles, and it is difficult for the binder resin to enter the gaps within the aggregates of aerogel particles, making it difficult for the aggregates of aerogel particles to collapse. For this reason, in this embodiment, the aggregates of aerogel particles are easily maintained without collapsing even when a certain amount of pressure is applied during the application of the coating solution. Accordingly, in this embodiment, as a method for applying the coating solution, a coating method in which the pressure applied to the coating solution exceeds 1.5 MPa can also be suitably used. Examples of such coating methods include application by airless spray, die coater, lip coater, etc.

[0219] In the removal process, by removing at least a portion of the liquid medium from the coating film, an insulating material is formed consisting of a composite material containing aggregates of aerogel particles, a binder resin, and a polymer-based emulsifier.

[0220] The method of removing the liquid medium from the coating film is not particularly limited, and examples include heating (e.g., 40 to 150°C), reducing pressure (e.g., 10,000 Pa or less), or performing both of these treatments.

[0221] The thickness of the insulation material is not specifically limited and, for example, can be 0.01 to 30 mm or 0.1 to 20 mm.

[0222] The insulating material has micropores caused by aerogel particles. The volume of the micropores in the insulating material is 0.15 cm², in terms of achieving higher thermal insulation performance. 3 / g or more is desirable, and 0.20cm 3 / g or more is more desirable, and 0.60cm 3 / g or more is more desirable. The upper limit of the micropore volume of the insulation material is not specifically limited. The micropore volume of the insulation material is, for example, 5.0 cm² 3 / g or less is acceptable.

[0223] The thermal conductivity of the insulation 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 insulation material is not particularly limited. The thermal conductivity of the insulation material may be, for example, 0.01 W / (m·K) or more.

[0224] The insulating material produced by the manufacturing method of the present embodiment possesses excellent thermal insulation, heat resistance, flame retardancy, etc. derived from aerogel. Therefore, the insulating material can be applied for use as an insulating material in cryogenic vessels, the space industry, the construction industry, the automotive industry, the home appliance industry, the semiconductor industry, industrial equipment, etc. In addition, the insulating material can be used as a water-repellent material, sound-absorbing material, anti-vibration material, catalyst support material, etc., in addition to its use as an insulating material.

[0225] Although suitable embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

[0226] Examples

[0227] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples.

[0228] (Example 1)

[0229] In a 500 mL separable flask, 6 parts by mass of 90 L of Sangelose (manufactured by Daido Kasei High School Co., Ltd.) as a water-soluble polymer, 46 parts by mass of isopropyl alcohol (manufactured by Fujifilm Wako Junyaku High School Co., Ltd., reagent), and 840 parts by mass of hot water were taken and stirred at 200 rpm for 1 minute using a mechanical stirrer to obtain a dispersion. Subsequently, while cooling the flask with an ice bath, 90 L of Sangelose was dissolved by stirring at 200 rpm using a mechanical stirrer to obtain Pregel, which is an aqueous solution of 90 L of Sangelose. 892 parts by mass of Pregel and 1,000 parts by mass of vinyl acetate emulsion were taken in a planetary mixer (manufactured by Fry Mix Co., Ltd., type 2P-1) and stirred at 100 rpm. Next, 100 parts by mass of aerogel particles (CABOT product, product name: ENOVA MT1100, particle diameter 2-24 μm, average particle diameter (D50) 10 μm) were added, and then stirred at 50 rpm to obtain a coating solution. In addition, the vinyl acetate emulsion was prepared using polyvinyl alcohol (degree of polymerization 1700) as a polymer-based emulsifier, in the same manner as Example 1 of Japanese Patent Publication No. Hei 6-18966. In the coating solution, based on the total volume of solids, the content of aerogel particles was 74.7 volume%, the content of water-soluble polymer was 0.4 volume%, and the content of vinyl acetate resin was 24.9 volume%.

[0230] (Example 2)

[0231] A coating solution was obtained in the same manner as in Example 1, except that the vinyl acetate emulsion was changed to an ethylene-vinyl acetate copolymer emulsion (manufactured by Sumika Chemtex, product name: Sumika Flex 400HQ) prepared using a polyvinyl alcohol-based emulsifier. In addition, based on the total volume of solids in the coating solution, the content of aerogel particles was 72.9 volume%, the content of water-soluble polymer was 0.4 volume%, and the content of ethylene-vinyl acetate copolymer resin was 26.7 volume%.

[0232] (Example 3)

[0233] A coating solution was obtained in the same manner as in Example 1, except that the vinyl acetate emulsion was changed to an ethylene-vinyl acetate-vinyl chloride copolymer emulsion (manufactured by Sumika Chemtex, product name: Sumika Flex 801HQ) prepared using a polyvinyl alcohol-based emulsifier. In addition, based on the total volume of solids in the coating solution, the content of aerogel particles was 74.7 volume%, the content of water-soluble polymer was 0.4 volume%, and the content of ethylene-vinyl acetate-vinyl chloride copolymer resin was 24.9 volume%.

[0234] (Comparative Example 1)

[0235] A coating solution was obtained in the same manner as in Example 1, except that the vinyl acetate emulsion was changed to an acrylic silicone emulsion prepared using a radical polymerizable emulsifier (manufactured by ADEKA, product name: Adecalia Soph SE-10N) in the same manner as in Example 1 of Japanese Patent Publication No. Hei 11-80486. In addition, based on the total volume of solids in the coating solution, the content of aerogel particles was 76.6 volume%, the content of water-soluble polymer was 0.4 volume%, and the content of acrylic silicone resin was 23.0 volume%.

[0236] <Evaluation of Insulation Pressure Resistance>

[0237] On a 70mm × 150mm carbon steel plate coated with commercially available anti-corrosion paint, the coating solution obtained in the example was applied using an airless spray (Graco, Ultra Cordless Airless Handheld, Chip Nozzle FFLP514, Pressure 10MPa) so that the film thickness after drying was 1mm. The liquid medium was removed from the coating solution by leaving it at room temperature (23℃) for 12 hours to obtain an insulating material. Regarding the obtained insulating material, the crack condition was evaluated by designating the one without cracks throughout the insulating material as A, the one with cracks in some parts as B, and the one with cracks throughout as C.

[0238] <Evaluation of Micropore Volume in Insulation Material>

[0239] Insulation material was prepared using the same method as in the above <Evaluation of Cracks in Insulation Material>. 100 mg of the prepared insulation material was collected, and the volume of micropores was calculated using a high-sensitivity gas adsorption analyzer (AutoSorb iQ, manufactured by Quantachrome).

[0240] Evaluation of Thermal Conductivity of Insulation Materials

[0241] A frame made of fluoropolymer with dimensions of 200 mm in width and length and a thickness of 3 mm was prepared on an aluminum foil (manufactured by UACJ Co., Ltd., product name: My Foil Thick Type 50, thickness: 50 μm), and a coating solution was applied into the frame using a spatula. The liquid medium was removed from the coating solution by leaving it at room temperature (23°C) for 12 hours to obtain an insulating material. The thermal conductivity of the obtained insulating material was measured by the normal method using a thermal conductivity measuring device "HFM-446" (manufactured by NETZSCH, product name).

[0242] The results of the above evaluation are shown in Table 1.

[0243] [Table 1]

[0244]

Claims

Claim 1 A method for preparing a coating solution comprising: a preparation process for preparing an emulsion containing a polymer-based emulsifier, a binder resin, and a liquid medium, aerogel particles, and a water-soluble polymer having hydrophobic groups; and a mixing process for mixing the emulsion, the aerogel particles, and the water-soluble polymer having hydrophobic groups prepared in the preparation process to aggregate at least a portion of the aerogel particles to obtain a coating solution containing aggregates of the aerogel particles, the polymer-based emulsifier, the binder resin, the water-soluble polymer having hydrophobic groups, and the liquid medium, wherein the binder resin is at least one selected from the group consisting of vinyl acetate resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate-vinyl chloride copolymer resin, and combinations thereof, and the water-soluble polymer having hydrophobic groups is a cellulose-based resin having an alkyl group having 6 to 26 carbon atoms. Claim 2 A method of manufacturing according to claim 1, wherein the average diameter of the aggregate is 2 to 40 times the average diameter of the aerogel particles prepared in the preparation process. Claim 3 A method of manufacturing according to claim 1 or claim 2, wherein, when the diluted solution obtained by diluting the solution is observed by an optical microscope, the area occupied by the aerogel particles and the aggregates within the field of view is 50% or more of the area occupied by the aggregates with a diameter of 20 μm or more. Claim 4 A method of manufacturing according to claim 1 or claim 2, wherein the total content of the aerogel particles and the aggregates in the coating liquid is 70 volume% or more based on the total volume of the solid content. Claim 5 A method for manufacturing an insulating material, comprising: a coating process of applying a coating solution prepared by the manufacturing method described in claim 1 or claim 2 onto a support to obtain a coating film; and a removal process of removing at least a portion of the liquid medium from the coating film to obtain an insulating material. Claim 6 In claim 5, the volume of the micropores of the insulating material is 0.15 cm 3 A method for manufacturing an insulating material with a value of / g or more. Claim 7 A method for manufacturing an insulating material according to claim 5, wherein the coating process is a coating method in which the pressure applied to the coating liquid exceeds 1.5 MPa. Claim 8 A coating solution comprising aggregates of aerogel particles, a polymer-based emulsifier, a binder resin, a water-soluble polymer having hydrophobic groups, and a liquid medium, wherein when a diluted solution obtained by diluting the coating solution is observed by an optical microscope, the area occupied by the aggregates with a diameter of 20 μm or more within the field of view of observation is 50% or more, the binder resin is at least one selected from the group consisting of vinyl acetate resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate-vinyl chloride copolymer resin, and combinations thereof, and the water-soluble polymer having hydrophobic groups is a cellulose-based resin having an alkyl group having 6 to 26 carbon atoms. Claim 9 delete

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