Coating liquid, method for producing coating film, and coating film

Abstract

The present invention provides a coating liquid, a method for producing a coating film, and a coating film. The coating liquid contains aerogel particles, a liquid medium, a first binder resin, a second binder resin having a solubility in the liquid medium lower than that of the first binder resin, and a fibrous substance having a fiber length of 1.5 mm or more, the content of the second binder resin being greater than that of the first binder resin.

Description

[0001] This application is a divisional application of Chinese patent application No. 201880064402.4, filed on April 16, 2018, entitled "Method for manufacturing coating liquid and coating film and coating film". Technical Field

[0002] This invention relates to a method for manufacturing a coating liquid and a coating film, and the coating film itself. Background Technology

[0003] Aerogels are known as materials with excellent thermal insulation and transparency. Methods have been proposed for processing aerogels with these properties into particle form and using them as constituent materials of thermal insulation materials (e.g., Patent Documents 1 and 2). Patent Document 1 proposes using particle-shaped aerogels as fillers between resin panels or the like that constituting thermal insulation windows. Patent Document 2 shows a method for manufacturing thermal insulation materials (molded bodies) by evaporating water after preparing an aqueous dispersion containing aerogel particles and organic fibers, and further pressing the intermediate product into shape.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-91943

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-35044 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] This invention was made in view of the above circumstances, and its object is to provide a novel coating liquid containing aerogel particles. Another object of this invention is to provide a method for manufacturing a coating film using the coating liquid, and a novel coating film.

[0010] Methods for solving problems

[0011] The present invention provides a coating liquid comprising aerogel particles and a liquid medium.

[0012] This invention provides a component with a specific surface area less than or equal to 350 m² 2 A coating solution containing aerogel particles, adhesive resin, and liquid medium at a concentration of / g. This coating solution differs from coating solutions containing aerogel particles obtained by conventional techniques and yields a superior coating film.

[0013] In the above coating solution, the liquid medium may contain organic solvents. This can further improve the dispersibility of aerogel particles.

[0014] In the above coating solution, the adhesive resin can be at least one selected from the group consisting of epoxy resin, silicone resin, phenolic resin, urea resin, melamine resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, polyamide resin, polyimide resin, cellulose resin, and polyethylene resin. This further improves film-forming properties.

[0015] The present invention also provides a coating liquid comprising aerogel particles, an adhesive resin, a fibrous material with a fiber length greater than or equal to 1.5 mm, and a liquid medium. Compared with coating liquids obtained by conventional techniques, this coating liquid can produce a coating film with excellent thermal insulation properties.

[0016] In the above coating solution, the liquid medium may contain organic solvents. This improves the dispersibility of aerogel particles.

[0017] In the above coating solution, the fiber length of the fibrous material can be set to be less than or equal to 20 mm. This can improve the dispersibility of the fibrous material.

[0018] In the above coating solution, based on the total mass of fibrous material in the solution, the content of fibrous material with a fiber length greater than or equal to 1.5 mm can be set to greater than or equal to 30% by mass. This can further improve the thermal insulation and coating strength.

[0019] The present invention further provides a coating solution comprising aerogel particles, a liquid medium, a first adhesive resin, and a second adhesive resin having a lower solubility in the liquid medium than the first adhesive resin. According to such a coating solution, a coating film with excellent strength and adhesion can be obtained.

[0020] In the above coating solution, the liquid medium can be an aqueous solvent containing water. This improves the dispersibility of the aerogel particles, making it easier to obtain a uniform coating film.

[0021] In the above coating solution, the content of the second adhesive resin can be higher than that of the first adhesive resin. This makes it easier to obtain a coating film with superior strength and adhesion.

[0022] In the above-mentioned coating liquid, the first adhesive resin can be a cellulose-based resin. Therefore, in addition to obtaining a coating film with excellent strength and adhesion, it also has the effect of increasing the viscosity of the coating liquid, making film formation easier.

[0023] In the above coating solution, the second adhesive resin can be a thermoplastic resin. This makes it easy to obtain a coating film with superior adhesion. It should be noted that the second adhesive resin can be an acrylic resin.

[0024] In the above coating solution, the second adhesive resin can be a thermosetting resin, in which case the coating film can further contain a curing agent. This easily yields a coating film with superior strength. It should be noted that the second adhesive resin can be an epoxy resin, in which case the coating film can further contain an epoxy resin curing agent.

[0025] The above-mentioned coating solution may further contain fibrous materials. This makes it easier to obtain a coating film with superior strength.

[0026] In each coating solution of the present invention, the viscosity can be greater than or equal to 1000 mPa·s. This further improves film-forming properties.

[0027] Each coating liquid of the present invention may contain at least one of organic fibers and inorganic fibers. Therefore, it is easy to obtain a coating film with superior strength.

[0028] The present invention also provides a method for manufacturing a coating film, comprising a step of removing a liquid medium from the above-mentioned coating liquid.

[0029] The present invention further provides a component with a specific surface area less than or equal to 350 m² 2 A coating film comprising aerogel particles, an adhesive resin or its cured form thereof, and fibrous material with a fiber length greater than or equal to 1.5 mm is provided. A coating film comprising aerogel particles, a first adhesive resin, and a second adhesive resin or its cured form thereof with a lower solubility in aqueous solvents than the first adhesive resin is also provided. The coating films obtained by the manufacturing method of the present invention and the coating films of the present invention have good film quality.

[0030] Invention Effects

[0031] According to the present invention, a novel coating liquid containing aerogel particles can be provided. The present invention also provides a method for manufacturing a coating film using the coating liquid, and a novel coating film (aerogel coating film). Attached Figure Description

[0032] Figure 1 This diagram illustrates the method of applying a coating liquid onto an object using a spatula. Detailed Implementation

[0033] The preferred embodiments of the present invention will now be described in detail. However, the present invention is not limited to the following embodiments. In this specification, the numerical range represented by "~" indicates a range in which the values ​​before and after "~" are respectively the minimum and maximum values. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in this embodiment may be used alone or in combination of two or more.

[0034] <Aerogel>

[0035] In a narrow sense, a dry gel obtained by supercritical drying of a moistened gel is called an aerogel, a dry gel obtained by drying under atmospheric pressure is called a desiccant, and a dry gel obtained by freeze-drying is called a freeze gel. In this embodiment, regardless of these drying methods for the moistened gel, the resulting low-density dry gel is called an "aerogel." That is, in this embodiment, "aerogel" refers to aerogel in a broad sense, namely, "Gel comprised of a microporous solid in which the dispersed phase is a gas." Generally, aerogels have a mesh-like microstructure inside, with a cluster structure formed by aerogel components of 2-20 nm in size. Pores less than 100 nm exist between the framework formed by these clusters. Thus, the aerogel forms a three-dimensional microporous structure. It should be noted that the aerogel involved in this embodiment is, for example, a silica aerogel with silica as the main component. Examples of silica aerogels include so-called organic-inorganic hybrid silica aerogels incorporating organic groups (such as methyl groups) or organic chains.

[0036] The aerogels involved in this embodiment can be exemplified by the following methods. By employing these methods, aerogels with excellent thermal insulation, flame retardancy, heat resistance, and flexibility can be readily obtained. By employing various methods, aerogels with thermal insulation, flame retardancy, heat resistance, and flexibility in various forms can be obtained.

[0037] (First method)

[0038] The aerogel according to this embodiment may have the structure represented by the following general formula (1). The aerogel according to this embodiment may have the structure represented by the following general formula (1a) as a structure including the structure represented by formula (1).

[0039] [Chemistry 1]

[0040]

[0041] [Chemistry 2]

[0042]

[0043] In equations (1) and (1a), R 1 and R 2 Each can be independently represented as alkyl or aryl, R 3 and R 4Each group independently represents an alkylene group. Here, phenyl, substituted phenyl, etc., can be listed as aryl groups. It should be noted that alkyl, vinyl, mercapto, amino, nitro, cyano, etc., can be listed as substituents for substituted phenyl groups. p represents an integer from 1 to 50. In formula (1a), two or more R groups... 1 Each can be the same or different; similarly, two or more R's can be the same. 2 They can be the same or different. In equation (1a), the two R... 3 They can be the same or different; similarly, two Rs... 4 They can be the same or different.

[0044] By incorporating the structure represented by equation (1) or (1a) as an aerogel component into the aerogel framework, a soft aerogel with low thermal conductivity is achieved. From this perspective, in equations (1) and (1a), R... 1 and R 2 Alkyl groups, phenyl groups, etc., with 1 to 6 carbon atoms can be listed independently, and methyl groups, etc., can be listed as such alkyl groups. Furthermore, in formulas (1) and (1a), R... 3 and R 4 Alkylenes with 1 to 6 carbon atoms can be listed independently, and ethylene, propylene, etc. can be listed as such alkylenes. In formula (1a), p can be set to 2 to 30 or 5 to 20.

[0045] (Second method)

[0046] The aerogel according to this embodiment has a trapezoidal structure with struts and bridges, and the bridges can have a structure represented by the following general formula (2). By introducing such a trapezoidal structure as an aerogel component into the aerogel skeleton, heat resistance and mechanical strength can be improved. It should be noted that in this embodiment, "trapezoidal structure" refers to a structure having two struts and bridges connecting the struts (a structure with a so-called "ladder" shape). In this method, the aerogel skeleton can be composed of a trapezoidal structure, or the aerogel can partially have a trapezoidal structure.

[0047] [Chemistry 3]

[0048]

[0049] In equation (2), R 5 and R 6Each group independently represents an alkyl or aryl group, and b represents an integer from 1 to 50. Examples of aryl groups include phenyl and substituted phenyl groups. Examples of substituents for substituted phenyl groups include alkyl, vinyl, mercapto, amino, nitro, and cyano groups. It should be noted that in formula (2), when b is an integer greater than or equal to 2, two or more R groups... 5 Each can be the same or different; similarly, two or more R's can be the same. 6 They can be the same or different.

[0050] By incorporating the above structure as an aerogel component into the aerogel framework, an aerogel exhibits superior flexibility compared to conventional aerogels with structures derived from ladder-type silsesquioxanes (i.e., structures represented by the following general formula (X)). Silsesquioxanes are those having the compositional formula: (RSiO 1.5 ) n The polysiloxane can have various skeletal structures such as cage-like, ladder-like, and random. It should be noted that, as shown in the following general formula (X), in conventional aerogels with a structure derived from ladder-like silsesquioxanes, the bridging structure is -O-, but in the aerogel involved in this embodiment, the bridging structure is the structure represented by the above general formula (2) (polysiloxane structure). In addition to having the structure represented by general formula (2), the aerogel of this embodiment may also have a structure derived from silsesquioxanes.

[0051] [Chemistry 4]

[0052]

[0053] In formula (X), R represents hydroxyl, alkyl or aryl.

[0054] There are no particular restrictions on the structure that becomes a support and its chain length, as well as the spacing of the structure that becomes a bridging part. However, from the viewpoint of further improving heat resistance and mechanical strength, as a trapezoidal structure, it can have the trapezoidal structure represented by the following general formula (3).

[0055] [Chemistry 5]

[0056]

[0057] In equation (3), R 5 R 6 R 7 and R 8Each of the R groups independently represents an alkyl or aryl group, a and c independently represent integers from 1 to 3000, and b represents an integer from 1 to 50. Here, phenyl, substituted phenyl, etc., can be listed as aryl groups. Additionally, alkyl, vinyl, mercapto, amino, nitro, cyano, etc., can be listed as substituents for substituted phenyl groups. It should be noted that in formula (3), when b is an integer greater than or equal to 2, two or more R groups... 5 Each can be the same or different; similarly, two or more R's can be the same. 6 They can also be the same or different. Furthermore, in equation (3), when a is an integer greater than or equal to 2, two or more R... 7 They can be the same or different. Similarly, when c is an integer greater than or equal to 2, two or more R... 8 They can be the same or different.

[0058] It should be noted that, from the perspective of obtaining superior flexibility, in equations (2) and (3), R is... 5 R 6 R 7 and R 8 (where R) 7 and R 8 In formula (3), alkyl groups, phenyl groups, etc., with 1 to 6 carbon atoms can be listed independently, and methyl groups, etc., can be listed as such alkyl groups. In addition, in formula (3), a and c can be set to 6 to 2000 independently, or they can be set to 10 to 1000. In addition, in formulas (2) and (3), b can be set to 2 to 30, or it can be set to 5 to 20.

[0059] (Third method)

[0060] The aerogel involved in this embodiment can also be a dried product of a sol condensate (a substance obtained by drying a sol-generated sol-derived sol-derived sol-gel), wherein the sol contains at least one selected from the group consisting of a silicon compound having a hydrolyzable or condensational functional group and hydrolysis products of a silicon compound having a hydrolyzable functional group. It should be noted that the aerogel described above can also be a substance obtained by drying a sol-derived sol containing a silicon compound, etc.

[0061] Polysiloxane compounds can be used as silicon compounds having hydrolyzable or condensation functional groups. That is, the sol described above may contain at least one compound selected from the group consisting of polysiloxane compounds having hydrolyzable or condensation functional groups and hydrolysis products of polysiloxane compounds having hydrolyzable functional groups (hereinafter, as appropriate, referred to as the "polysiloxane compound group").

[0062] The functional groups in polysiloxane compounds are not particularly limited and can be groups that react with each other or with other functional groups. Examples of hydrolyzable functional groups include alkoxy groups. Examples of condensation functional groups include hydroxyl, silanol, carboxyl, and phenolic hydroxyl groups. Hydroxyl groups can be included in hydroxyl-containing groups such as hydroxyalkyl groups. It should be noted that polysiloxane compounds having hydrolyzable or condensation functional groups can further have reactive groups (functional groups that are not hydrolyzable or condensation functional groups) that are different from the hydrolyzable and condensation functional groups. Examples of reactive groups include epoxy, mercapto, epoxypropoxy, vinyl, acryloyl, methacryloyl, and amino groups. Epoxy groups can also be included in epoxypropoxy and other epoxy-containing groups. Polysiloxane compounds having these functional groups and reactive groups can be used alone or in combination of two or more. Among these functional groups and reactive groups, examples of groups that enhance the flexibility of aerogels include alkoxy groups, silanol groups, and hydroxyalkyl groups. Alkoxy and hydroxyalkyl groups can further improve the compatibility of the sol. Furthermore, from the viewpoint of improving the reactivity of polysiloxane compounds and reducing the thermal conductivity of aerogels, the carbon number of alkoxy and hydroxyalkyl groups can be set to 1 to 6, or 2 to 4, from the viewpoint of further improving the flexibility of the aerogel.

[0063] Examples of polysiloxane compounds having an intramolecular hydroxyalkyl group include compounds having the structure represented by the following general formula (A). By using a polysiloxane compound having the structure represented by the following general formula (A), the structures represented by general formula (1) and formula (1a) can be introduced into the framework of an aerogel.

[0064] [Chemistry 6]

[0065]

[0066] In formula (A), R 1a Indicates hydroxyalkyl, R 2a R represents an alkylene group. 3a and R 4a Each R group independently represents an alkyl or aryl group, and n represents an integer from 1 to 50. Examples of aryl groups include phenyl and substituted phenyl groups. Examples of substituents for substituted phenyl groups include alkyl, vinyl, mercapto, amino, nitro, and cyano groups. It should be noted that in formula (A), the two R groups... 1a They can be the same or different; similarly, two Rs... 2a Each can be the same or different. Furthermore, in equation (A), two or more R... 3a Each can be the same or different; similarly, two or more R's can be the same. 4a They can be the same or different.

[0067] By using a wetted gel (generated from a sol) that is a condensate of a polysiloxane compound containing the above-described structure, a soft aerogel with low thermal conductivity can be readily obtained. From this perspective, in formula (A), R... 1a Examples of such hydroxyalkyl groups include hydroxyalkyl groups with 1 to 6 carbon atoms, such as hydroxyethyl and hydroxypropyl. Additionally, in formula (A), R... 2a Examples of alkylene groups having 1 to 6 carbon atoms include ethylene and propylene. Additionally, in formula (A), R... 3a and R 4a Alkyl groups, phenyl groups, etc., with 1 to 6 carbon atoms can be listed independently, and methyl groups, etc., can be listed as such alkyl groups. In addition, in formula (A), n can be set to 2 to 30 or 5 to 20.

[0068] As for polysiloxane compounds having the structure represented by the above general formula (A), commercially available products can be used, such as compounds X-22-160AS, KF-6001, KF-6002, KF-6003 (all manufactured by Shin-Etsu Chemical Industry Co., Ltd.), and compounds XF42-B0970, Fluid OFOH 702-4% (all manufactured by Momentive Advanced Materials Japan Co., Ltd.).

[0069] Examples of polysiloxane compounds having an alkoxy group within the molecule include compounds having the structure represented by the following general formula (B). By using a polysiloxane compound having the structure represented by the following general formula (B), a ladder structure having a bridging portion represented by general formula (2) or (3) can be introduced into the framework of an aerogel.

[0070] [Chemistry 7]

[0071]

[0072] In equation (B), R 1b R indicates alkyl, alkoxy, or aryl. 2b and R 3b Each independently represents an alkoxy group, R 4b and R 5b Each R group independently represents an alkyl or aryl group, where m represents an integer from 1 to 50. Examples of aryl groups include phenyl and substituted phenyl groups. Examples of substituents for substituted phenyl groups include alkyl, vinyl, mercapto, amino, nitro, and cyano groups. It should be noted that in formula (B), the two R groups... 1b They can be the same or different, two Rs 2b They can be the same or different; similarly, two Rs... 3bThey can be the same or different. Furthermore, in equation (B), when m is an integer greater than or equal to 2, two or more R... 4b Each can be the same or different; similarly, two or more R's can be the same. 5b They can be the same or different.

[0073] By using a wetted gel (generated from a sol) that is a condensate of a polysiloxane compound containing the above-described structure or its hydrolysis product, a soft aerogel with low thermal conductivity can be readily obtained. From this perspective, in formula (B), R... 1b Examples of alkyl groups having 1 to 6 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms, etc., can be listed. Examples of such alkyl or alkoxy groups include methyl, methoxy, ethoxy, etc. Furthermore, in formula (B), R... 2b and R 3b Alkoxy groups with 1 to 6 carbon atoms can be listed independently, and examples of such alkoxy groups include methoxy and ethoxy groups. Additionally, in formula (B), R... 4b and R 5b Alkyl groups, phenyl groups, etc., with 1 to 6 carbon atoms can be listed independently, and methyl groups, etc., can be listed as alkyl groups. In addition, in formula (B), m can be set to 2 to 30, or 5 to 20.

[0074] Polysiloxane compounds having the structure represented by the above general formula (B) can be obtained by referring appropriately to the manufacturing methods reported in Japanese Patent Application Publication No. 2000-26609, Japanese Patent Application Publication No. 2012-233110, etc.

[0075] It should be noted that alkoxy groups are hydrolyzed; therefore, polysiloxane compounds containing alkoxy groups may exist in the sol as hydrolysis products. Alkoxy-containing polysiloxane compounds and their hydrolysis products can coexist. Furthermore, in polysiloxane compounds containing alkoxy groups, the alkoxy groups in the molecule can be completely or partially hydrolyzed.

[0076] These polysiloxane compounds with hydrolytic or condensation functional groups, and the hydrolysis products of polysiloxane compounds with hydrolytic functional groups, can be used alone or in combination of two or more.

[0077] When preparing the aerogel according to this embodiment, a silicon compound having hydrolyzable or condensational functional groups can be used as the silicon compound, other than the polysiloxane compounds described above. That is, the sol containing the silicon compound may contain, in addition to the polysiloxane compound group described above, or instead of the polysiloxane compound group described above, at least one selected from the group consisting of a silicon compound having hydrolyzable or condensational functional groups (excluding polysiloxane compounds) and hydrolysis products of the silicon compound having hydrolyzable functional groups (hereinafter, as appropriate, referred to as the "silicon compound group"). The number of silicon atoms within the molecule of the silicon compound can be set to 1 or 2.

[0078] There are no particular limitations on silicon compounds that possess hydrolyzable functional groups within the molecule; examples include alkyl siloxanes. From the viewpoint of improving water resistance, the number of hydrolyzable functional groups in alkyl siloxanes can be set to less than or equal to three. Examples of such alkyl siloxanes include monoalkyltrialkoxysilanes, monoalkyldialkoxysilanes, dialkyldialkoxysilanes, monoalkylmonoalkoxysilanes, dialkylmonoalkoxysilanes, and trialkylmonoalkoxysilanes. Specifically, examples include methyltrimethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, and hexyltrimethoxysilane. Here, alkoxy groups such as methoxy and ethoxy can be used as hydrolyzable functional groups.

[0079] As silicon compounds with condensation functional groups, there are no particular limitations, and examples include silanetetraol, methylsilanetriol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, diphenylsilanediol, n-propylsilanetriol, hexylsilanetriol, octylsilanetriol, decylsilanetriol, trifluoropropylsilanetriol, etc.

[0080] Silicon compounds having hydrolytic or condensation functional groups may further have the aforementioned reactive groups (functional groups that do not belong to hydrolytic or condensation functional groups) that are different from the hydrolytic and condensation functional groups.

[0081] As silicon compounds with three or fewer hydrolyzable functional groups and reactive groups, vinyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, etc., can also be used.

[0082] In addition, as silicon compounds having condensation functional groups and reactive groups, vinylsilanetriol, 3-epoxypropoxypropylsilanetriol, 3-epoxypropoxypropylmethylsilanediol, 3-methacryloyloxypropylsilanetriol, 3-methacryloyloxypropylmethylsilanediol, 3-acryloyloxypropylsilanetriol, 3-mercaptopropylsilanetriol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2-(aminoethyl)-3-aminopropylmethylsilanediol, etc., can also be used.

[0083] Furthermore, silicon compounds with three or fewer hydrolyzable functional groups at the molecule's end can also be used, such as bis(trimethoxysilyl)methane, bis(trimethoxysilyl)ethane, bis(trimethoxysilyl)hexane, ethyltrimethoxysilane, vinyltrimethoxysilane, etc.

[0084] Silicon compounds (excluding polysiloxane compounds) having hydrolyzable or condensation functional groups and their hydrolysis products having hydrolyzable functional groups can be used alone or in combination of two or more.

[0085] By using the aforementioned silicon compounds (excluding polysiloxane compounds), structures represented by the following general formulas (4) to (6) can be incorporated into the framework of the aerogel. The aerogel according to this embodiment may have any one of these structures alone or have two or more of them.

[0086] [Chemistry 8]

[0087]

[0088] In equation (4), R 9 This refers to an alkyl group. Here, alkyl groups having 1 to 6 carbon atoms can be listed as examples of alkyl groups, and methyl groups can be listed as examples of such alkyl groups.

[0089] [Chemistry 9]

[0090]

[0091] In equation (5), R 10 and R 11 Each can be independently represented as an alkyl group. Here, alkyl groups having 1 to 6 carbon atoms can be listed as examples of alkyl groups, and methyl groups can be listed as examples of such alkyl groups.

[0092] [Chemistry 10]

[0093]

[0094] In equation (6), R 12This refers to an alkylene group. Here, alkylene groups with 1 to 10 carbon atoms can be listed as examples, and ethylene, hexaneene, etc. can be listed as examples of such alkylene groups.

[0095] (Fourth method)

[0096] From the perspective of further strengthening and achieving further superior thermal insulation and flexibility, the aerogel involved in this embodiment may further contain silica particles in addition to aerogel components. The aerogel containing both aerogel components and silica particles may also be referred to as an aerogel composite. Although the aerogel composite is composed of aerogel components and silica particles, it is considered to possess a cluster structure characteristic of aerogels, exhibiting a three-dimensional, fine, porous structure.

[0097] Aerogels containing aerogel components and silica particles can be referred to as dried products of humidified gels, wherein the humidified gel is a condensation product of a sol containing at least one selected from the group consisting of silicon compounds having hydrolyzable or condensational functional groups, and hydrolysis products of silicon compounds having hydrolyzable functional groups, as well as silica particles. Therefore, the descriptions relating to the first to third embodiments can also be appropriately applied to the aerogels involved in this embodiment.

[0098] As silica particles, they can be used without particular restrictions, including amorphous silica particles. Examples of amorphous silica particles include molten silica particles, fumed silica particles, and colloidal silica particles. Among these, colloidal silica particles have high monodispersity and easily suppress aggregation in sols. It should be noted that silica particles can also be those with hollow or porous structures.

[0099] There are no particular limitations on the shape of silica particles; examples include spherical, cocoon-shaped, and associated types. Using spherical particles makes it easier to suppress aggregation in the sol. From the viewpoint of easily imparting moderate strength and flexibility to the aerogel and readily obtaining an aerogel with excellent shrinkage resistance during drying, the average primary particle size of the silica particles can be greater than or equal to 1 nm, greater than or equal to 5 nm, or greater than or equal to 20 nm. From the viewpoint of easily suppressing solid-state thermal conductivity of silica particles and readily obtaining an aerogel with excellent thermal insulation, the average primary particle size of the silica particles can be less than or equal to 500 nm, less than or equal to 300 nm, or less than or equal to 100 nm. From these perspectives, the average primary particle size of silica particles can be 1–500 nm, 5–300 nm, or 20–100 nm.

[0100] In this embodiment, the average particle size of the aerogel component and the average primary particle size of the silica particles can be obtained by directly observing the aerogel using a scanning electron microscope (hereinafter referred to as "SEM"). The term "diameter" here refers to the diameter of the cross-section of a particle exposed in the aerogel when considered as a circle. Furthermore, "diameter when the cross-section is considered as a circle" refers to the diameter of a circle with the same area as the cross-section. It should be noted that when calculating the average particle size, the diameter of the circle is calculated for 100 particles, and the average is taken.

[0101] It should be noted that the average particle size of silica particles can also be determined from the raw material. For example, based on the results obtained by observing any 20 particles via SEM, the biaxial average primary particle size can be calculated as follows: Taking colloidal silica particles, typically dispersed in water at a solid content of 5-40% by mass, as an example, the chip obtained by immersing a patterned wire-lined wafer cut into 2cm squares in the dispersion of colloidal silica particles is immersed for approximately 30 seconds. The chip is then rinsed with pure water for approximately 30 seconds and dried with nitrogen. The chip is then placed on a SEM stage, an accelerating voltage of 10kV is applied, and the silica particles are observed at 100,000x magnification, and images are captured. From the obtained images, 20 silica particles are randomly selected, and the average particle size of these particles is taken as the average particle size.

[0102] From the perspective of easily obtaining aerogels with excellent shrinkage resistance, the number of silanol groups per 1g of silica particles can be greater than or equal to 10 × 10. 18 The number of cells / g can be greater than or equal to 50 × 10⁻⁶. 18 The number of cells / g can also be greater than or equal to 100 × 10 18 1 g of silica particles. From the viewpoint of easily obtaining homogeneous aerogels, the number of silanol groups per 1 g of silica particles can be less than or equal to 1000 × 10⁻⁶. 18 The number of cells / g can be less than or equal to 800 × 10⁻⁶. 18 The number of cells / g can also be less than or equal to 700 × 10⁻⁶. 18 From these perspectives, the number of silanol groups per 1g of silica particles could be 10 × 10⁻⁶. 18 ~1000×10 18 Units / g, which can be 50×10 18 ~800×10 18 pcs / g, or 100×10 18 ~700×10 18 per g.

[0103] From the viewpoint of easily obtaining good reactivity, the content of the polysiloxane compound group contained in the sol (the sum of the content of polysiloxane compounds having hydrolyzable or condensational functional groups and the content of hydrolysis products of polysiloxane compounds having hydrolyzable functional groups) relative to 100 parts by mass of the total sol can be greater than or equal to 5 parts by mass, and greater than or equal to 10 parts by mass. From the viewpoint of easily obtaining good compatibility, the content of the polysiloxane compound group contained in the sol can be less than or equal to 50 parts by mass, and less than or equal to 30 parts by mass, relative to 100 parts by mass of the total sol. From these viewpoints, the content of the polysiloxane compound group contained in the sol can be 5 to 50 parts by mass, or 10 to 30 parts by mass, relative to 100 parts by mass of the total sol.

[0104] When the sol contains silicon compounds (excluding polysiloxane compounds), from the viewpoint of further facilitating good reactivity, the silicon compound group (the sum of the content of silicon compounds having hydrolyzable or condensational functional groups and the content of hydrolysis products of silicon compounds having hydrolyzable functional groups) can be greater than or equal to 5 parts by mass, or greater than or equal to 10 parts by mass, relative to 100 parts by mass of the total sol. From the viewpoint of further facilitating good compatibility, the content of the silicon compound group contained in the sol can be less than or equal to 50 parts by mass, or less than or equal to 30 parts by mass, relative to 100 parts by mass of the total sol. From these viewpoints, the content of the silicon compound group contained in the sol can be 5 to 50 parts by mass, or 10 to 30 parts by mass.

[0105] When the sol contains both polysiloxane compounds and silicon compounds, from the viewpoint of further facilitating good compatibility, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group can be greater than or equal to 1:0.5, or greater than or equal to 1:1. From the viewpoint of further facilitating the suppression of gel shrinkage, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group can be less than or equal to 1:4, or less than or equal to 1:2. From these viewpoints, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group can be 1:0.5 to 1:4, or 1:1 to 1:2.

[0106] When silica particles are included in the sol described above, from the viewpoint of easily imparting appropriate strength to the aerogel and easily obtaining an aerogel with excellent shrinkage resistance during drying, the content of silica particles relative to 100 parts by mass of the total sol can be greater than or equal to 1 part by mass, or greater than or equal to 4 parts by mass. From the viewpoint of easily suppressing the solid-state thermal conductivity of silica particles and easily obtaining an aerogel with excellent thermal insulation properties, the content of silica particles relative to 100 parts by mass of the total sol can be less than or equal to 20 parts by mass, or less than or equal to 15 parts by mass. From these viewpoints, the content of silica particles relative to 100 parts by mass of the total sol can be 1 to 20 parts by mass, or 4 to 15 parts by mass.

[0107] <Aerogel particles>

[0108] The aerogel particles of this embodiment can be obtained, for example, by crushing the block aerogel as described below.

[0109] The specific surface area of ​​aerogel particles can be set to be less than or equal to 350 m². 2 / g, can be less than or equal to 300m 2 / g, can be less than or equal to 250m 2 / g, or less than or equal to 150m 2 / g. Therefore, it is easy to formulate a coating solution with excellent film-forming properties. There is no particular limitation on the lower limit of the specific surface area of ​​the aerogel particles; however, considering the need to inhibit aggregation in the coating solution and improve the filling rate, it can be set to 30m². 2 Approximately / g. Various methods can be considered to adjust the specific surface area of ​​aerogel particles, such as adjusting the amount of aerogel components with the bridging structure represented by general formula (2), adjusting the amount of silica particles, etc.

[0110] Specific surface area can be determined by the BET method. As the measuring device, a gas adsorption capacity measuring device (manufactured by Quantachrome Instruments, Japan, Autosorb-iQ (Autosorb is a registered trademark)) can be used.

[0111] The average particle size D50 of the aerogel particles can be set to 1~1000 μm, 3~700 μm, 5~500 μm, 10~100 μm, or 10~50 μm. By making the average particle size D50 of the aerogel particles greater than or equal to 1 μm, aerogel particles with excellent dispersibility and workability can be easily obtained. On the other hand, by making the average particle size D50 less than or equal to 1000 μm, aerogel particles with excellent dispersibility can be easily obtained. The average particle size of the aerogel particles can be appropriately adjusted by the pulverization method and pulverization conditions, sieves, classification methods, etc.

[0112] The average particle size D50 of aerogel particles can be determined by laser diffraction / scattering. For example, aerogel particles are added to a solvent (ethanol) at a content of 0.05 to 5% by mass, and dispersed using a 50W ultrasonic homogenizer for 15 to 30 minutes. Then, approximately 10 mL of the dispersion is injected into a laser diffraction / scattering particle size distribution measuring device, and the particle size is measured at 25°C with a refractive index of 1.3 and an absorption of 0. The particle size at 50% (volume basis) of the cumulative value of this particle size distribution is then defined as the average particle size D50. For example, a Microtrac MT3000 (manufactured by Nikkiso Co., Ltd.) can be used as the measuring device.

[0113] <Methods for Manufacturing Aerogel Particles>

[0114] There are no particular restrictions on the manufacturing method of aerogel particles; for example, they can be manufactured using the following methods.

[0115] The aerogel particles of this embodiment can be manufactured by a manufacturing method mainly comprising the following steps: a sol generation step; a wet gel generation step, wherein the sol obtained in the sol generation step is gelled and then matured to obtain a wet gel; a washing and solvent replacement step, wherein the wet gel obtained in the wet gel generation step is washed and (as needed) replaced with a solvent; a drying step, wherein the wet gel after washing and solvent replacement is dried; and a pulverizing step, wherein the aerogel obtained by drying is pulverized.

[0116] Alternatively, it can be manufactured using a manufacturing method that mainly includes the following steps: sol generation step; wet gel generation step; wet gel pulverization step, in which the wet gel obtained in the wet gel generation step is pulverized; washing and solvent replacement step; and drying step.

[0117] The obtained aerogel particles can be further homogenized in size through sieving, grading, etc. Dispersibility can be improved by adjusting the particle size. It should be noted that "sol" refers to the state before the gelation reaction occurs; in this embodiment, it refers to the state in which the aforementioned silicon compound and, depending on the circumstances, silica particles are dissolved or dispersed in a solvent. Furthermore, a wetted gel refers to a gel solid in a wetted state that contains a liquid medium but does not exhibit fluidity.

[0118] (Soluble formation process)

[0119] The sol-gel generation process involves mixing a silicon compound and, depending on the situation, silica particles (or a solvent containing silica particles) and subjecting them to a hydrolysis reaction to generate a sol. In this process, an acid catalyst may be further added to the solvent to promote the hydrolysis reaction. Additionally, as shown in Japanese Patent No. 5250900, surfactants, hot-hydrolyzable compounds, etc., may be added to the solvent. Furthermore, for purposes such as suppressing thermal radiation, components such as carbon graphite, aluminum compounds, magnesium compounds, silver compounds, and titanium compounds may be added to the solvent.

[0120] As a solvent, water, or a mixture of water and alcohol, can be used, for example. Examples of alcohols include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and tert-butanol. Among these, methanol, ethanol, and 2-propanol are examples of alcohols with low surface tension and low boiling points, chosen from the perspective of reducing interfacial tension with the gel wall. They can be used alone or in mixtures of two or more.

[0121] For example, when using alcohol as a solvent, the amount of alcohol can be set to 4 to 8 moles, 4 to 6.5 moles, or 4.5 to 6 moles, relative to the total amount of silicon compounds and polysiloxane compounds (1 mole). By setting the amount of alcohol to greater than or equal to 4 moles, good compatibility is further facilitated; and by setting it to less than or equal to 8 moles, gel shrinkage is further suppressed.

[0122] Examples of acid catalysts include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphite, bromic acid, chloric acid, chlorogenic 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 can be used as acid catalysts to further improve the water resistance of the obtained aerogel. Examples of such organic carboxylic acids include acetic acid, but formic acid, propionic acid, oxalic acid, and malonic acid can also be used. They can be used alone or in combination of two or more.

[0123] By using an acid catalyst, the hydrolysis reaction of silicon compounds can be accelerated to obtain a sol in a shorter time.

[0124] The amount of acid catalyst added can be set to 0.001 to 0.1 parts by mass relative to the total amount of polysiloxane compounds and silicon compounds (100 parts by mass).

[0125] As surfactants, nonionic surfactants, ionic surfactants, etc., can be used. They can be used alone or in combination of two or more.

[0126] As nonionic surfactants, compounds containing a hydrophilic portion such as polyethylene oxide and a hydrophobic portion mainly composed of alkyl groups, and compounds containing a hydrophilic portion such as polypropylene oxide, can be used. Examples of compounds containing a hydrophilic portion such as polyethylene oxide and a hydrophobic portion mainly composed of alkyl groups include polyethylene oxide nonylphenyl ether, polyethylene oxide octylphenyl ether, and polyethylene oxide alkyl ether. Examples of compounds containing a hydrophilic portion such as polypropylene oxide include polypropylene alkyl ether and block copolymers of polyethylene oxide and polypropylene oxide.

[0127] Examples of ionic surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. Examples of cationic surfactants include hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride; examples of anionic surfactants include sodium dodecyl sulfonate. Additionally, 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 dimethylaminoacetic acid betaine and stearyl dimethylaminoacetic acid betaine. Examples of amine oxide-based surfactants include lauryl dimethylamine oxide.

[0128] These surfactants are believed to play the following role: in the wet gel formation process described later, they reduce the difference in chemical affinity between the solvent in the reaction system and the gradually growing siloxane polymer, thereby inhibiting phase separation.

[0129] The amount of surfactant added also depends on the type of surfactant, or the type and amount of silicon compound, but for example, it can be set to 1 to 100 parts by mass relative to 100 parts by mass of the total amount of polysiloxane compound group and silicon compound group. It should be noted that this amount can also be 5 to 60 parts by mass.

[0130] It is believed that hot-hydrolyzable compounds generate alkaline catalysts through hot water hydrolysis, making the reaction solution alkaline and promoting the sol-gel reaction in the subsequent wet gel formation process. Therefore, there are no particular limitations on the hot-hydrolyzable compounds, as long as they can make the reaction solution alkaline after hydrolysis. Examples include urea; 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, in particular, readily exhibits the aforementioned promoting effect.

[0131] There is no particular limitation on the amount of the hot-hydrolyzable compound added, as long as it sufficiently promotes the sol-gel reaction in the subsequent wet gel formation process. For example, when using urea as the hot-hydrolyzable compound, its addition amount can be set to 1 to 200 parts by mass relative to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. It should be noted that this addition amount can also be 2 to 150 parts by mass. By setting the addition amount to greater than or equal to 1 part by mass, it is easier to obtain good reactivity; furthermore, by setting it to less than or equal to 200 parts by mass, it is easier to suppress crystal precipitation and the decrease in gel density.

[0132] The hydrolysis process in the sol-gel formation also depends on the type and amount of silicon compounds, silica particles, acid catalysts, surfactants, etc., in the mixture. For example, it can be carried out at a temperature of 20~60℃ for 10 minutes to 24 hours, or at a temperature of 50~60℃ for 5 minutes to 8 hours. This allows for the complete hydrolysis of the hydrolyzable functional groups in the silicon compounds, resulting in a more reliable yield of the hydrolysis products of the silicon compounds.

[0133] In cases where a hot-hydrolyzable compound is added to the solvent, the temperature environment of the sol-gel formation process can be adjusted to a temperature that inhibits the hydrolysis of the hot-hydrolyzable compound and suppresses the gelation of the sol. This temperature can be any temperature, as long as it inhibits the hydrolysis of the hot-hydrolyzable compound. For example, when using urea as the hot-hydrolyzable compound, the temperature environment of the sol-gel formation process can be set to 0~40℃ or 10~30℃.

[0134] (Wet gel formation process)

[0135] The wet gel formation process involves gelling the sol obtained in the sol formation process and then aging it to obtain a wet gel. In this process, an alkaline catalyst can be used to promote gelation.

[0136] Examples of alkaline catalysts include: carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper(II) carbonate, iron(II) carbonate, and silver(I) carbonate; bicarbonates such as calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, and ammonium bicarbonate; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; basic sodium phosphates such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; and allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, and ethylamine. Aliphatic amines such as diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3-(diethylamino)propylamine, di(2-ethylhexyl)amine, 3-(dibutylamino)propylamine, tetramethylethylenediamine, tert-butylamine, sec-butylamine, propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, and triethanolamine; and nitrogen-containing heterocyclic compounds such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, and imidazole and its derivatives. Among these, ammonium hydroxide (ammonia water) is superior in terms of water resistance and economy due to its high volatility and reluctance to remain in the dried aerogel particles. The above-mentioned alkaline catalysts can be used alone or in combination of two or more.

[0137] By using an alkaline catalyst, the dehydration condensation or dealcoholization condensation reactions of silicon compounds and silica particles in the sol can be promoted, enabling sol gelation in a shorter time. Furthermore, this results in a wetted gel with higher strength (rigidity). In particular, ammonia's high volatility and reluctance to remain in aerogel particles allow for the use of ammonia as an alkaline catalyst, leading to aerogel particles with superior water resistance.

[0138] The amount of alkali catalyst added can be set to 0.5-5 parts by mass or 1-4 parts by mass relative to the total amount of polysiloxane compounds and silicon compounds (100 parts by mass). By setting it to greater than or equal to 0.5 parts by mass, gelation can be carried out in a shorter time, and by setting it to less than or equal to 5 parts by mass, the decrease in water resistance can be further suppressed.

[0139] The gelation of the sol in the wet gel formation process can be carried out in a sealed container to avoid the evaporation of solvents and alkaline catalysts. The gelation temperature can be set to 30~90℃ or 40~80℃. By setting the gelation temperature to greater than or equal to 30℃, gelation can be carried out in a shorter time, resulting in a wet gel with higher strength (rigidity). Furthermore, by setting the gelation temperature to less than or equal to 90℃, the evaporation of solvents (especially alcohols) is easily suppressed, thus allowing gelation to be carried out while simultaneously suppressing volume shrinkage.

[0140] The curing process for forming the wet gel can also be carried out in a sealed container to prevent the evaporation of solvents and alkaline catalysts. Through curing, the bonding between the components constituting the wet gel strengthens, resulting in a wet gel with high strength (rigidity) sufficient to suppress shrinkage during drying. The curing temperature can be set to 30–90°C or 40–80°C. Setting the curing temperature to greater than or equal to 30°C yields a wet gel with higher strength (rigidity), while setting it to less than or equal to 90°C facilitates the suppression of solvent (especially alcohol) evaporation, thus enabling gelation while simultaneously suppressing volume shrinkage.

[0141] It should be noted that, since it is difficult to determine the end time of gelation of the sol in most cases, the gelation and subsequent curing of the sol can be carried out continuously in a series of operations.

[0142] The gelation and curing times can be appropriately set according to the gelation and curing temperatures. The gelation time is particularly shortened when the sol contains silica particles compared to when it does not. This is presumably 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. It should be noted that the gelation time can be set to 10–120 minutes or 20–90 minutes. Setting the gelation time to 10 minutes or more easily yields a homogeneous, wetted gel, while setting it to 120 minutes or less simplifies the subsequent washing, solvent replacement, and drying processes. It should also be noted that the total gelation and curing time can be set to 4–480 hours or 6–120 hours. By setting the combined gelation and curing times to 4 hours or more, a wetting gel with higher strength (rigidity) can be obtained; by setting it to 480 hours or less, the curing effect can be maintained more easily.

[0143] To reduce the density of the obtained aerogel particles or increase the average pore size, the gelation temperature and maturation temperature may be increased within the above-mentioned range, or the total gelation time and maturation time may be extended within the above-mentioned range. Conversely, to increase the density of the obtained aerogel particles or decrease the average pore size, the gelation temperature and maturation temperature may be decreased within the above-mentioned range, or the total gelation time and maturation time may be shortened within the above-mentioned range.

[0144] (Wet gel pulverization process)

[0145] In the case of a wet gel pulverization process, the wet gel obtained in the wet gel formation process is pulverized. Pulverization can be performed, for example, by loading the wet gel into a Henschel mixer, or by performing the wet gel formation process within a mixer, and operating the mixer under appropriate conditions (rotation speed and time). Alternatively, more simply, the wet gel can be loaded into a sealable container, or by performing the wet gel formation process within a sealable container, and by agitating it using a vibrator or other oscillating device for an appropriate time. It should be noted that the particle size of the wet gel can also be adjusted as needed using an air jet mill, roller mill, bead mill, etc.

[0146] (Washing and solvent replacement process)

[0147] The washing and solvent replacement process comprises the following steps: a washing step (washing step) of the wetted gel obtained through the wetted gel formation step or the wetted gel pulverization step; and a solvent replacement step (solvent replacement step) of replacing the washing liquid in the wetted gel with a solvent suitable for drying conditions (the drying step described later). The washing and solvent replacement process can also be implemented in a form where only the solvent replacement step is performed without washing the wetted gel. However, from the viewpoint of reducing unreacted substances, byproducts, and other impurities in the wetted gel, and thus producing aerogel particles with higher purity, washing the wetted gel is also acceptable.

[0148] In the washing process, the wetted gel obtained through the wetted gel formation process or the wetted gel pulverization process is washed. This washing can be repeated, for example, using water or an organic solvent. Heating can be used to improve washing efficiency.

[0149] As organic solvents, various organic solvents can be used, including methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, dichloromethane, N,N-dimethylformamide, dimethyl sulfoxide, acetic acid, and formic acid. These organic solvents can be used alone or in mixtures of two or more.

[0150] In the solvent replacement process described later, a solvent with low surface tension can be used to suppress gel shrinkage caused by drying. However, solvents with low surface tension generally have very low miscibility with water. Therefore, when using a solvent with low surface tension in the solvent replacement process, hydrophilic organic solvents that have high miscibility with both water and low surface tension solvents can be listed as organic solvents used in the washing process. It should be noted that the hydrophilic organic solvent used in the washing process can serve as a pre-replacement for the solvent replacement process. Among the aforementioned organic solvents, examples of hydrophilic organic solvents include methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone. It should be noted that methanol, ethanol, and methyl ethyl ketone are excellent in terms of economic efficiency.

[0151] The amount of water or organic solvent used in the washing process can be set to a level sufficient to fully displace and wash the solvent in the wetted gel. This amount can be set to 3 to 10 times the volume of the wetted gel. Washing can be repeated until the water content in the washed wetted gel is less than or equal to 10% by mass relative to the mass of silica.

[0152] The temperature environment in the washing process can be set to be less than or equal to the boiling point of the solvent used for washing. For example, when using methanol, the temperature can be set to 30-60°C.

[0153] In the solvent replacement process, to suppress the shrinkage of the aerogel during the drying process, the solvent in the washed, wetted gel is replaced with a predetermined replacement solvent. At this time, heating can be used to improve the replacement efficiency. Specifically, as a replacement solvent, when drying is carried out at atmospheric pressure and the temperature is below the critical point of the solvent used for drying, solvents with low surface tension, as described later, can be used. On the other hand, in the case of supercritical drying, examples of replacement solvents include ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, or a mixture of two or more of these.

[0154] Solvents with low surface tension include those with a surface tension of less than or equal to 30 mN / m at 20°C. It should be noted that this surface tension can be less than or equal to 25 mN / m, or it can be less than or equal to 20 mN / m. Examples of solvents with low surface tension include aliphatic hydrocarbons such as pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3-methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), and 1-pentene (16.0); aromatic hydrocarbons such as benzene (28.9), toluene (28.5), m-xylene (28.7), and p-xylene (28.3); and dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), and 2- Halogenated hydrocarbons such as propane (18.1); ethers such as diethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ethyl ether (20.8), and 1,2-dimethoxyethane (24.6); ketones such as acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), and diethyl ketone (25.3); 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 represent the surface tension at 20°C, in mN / m). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and excellent environmental performance. Furthermore, hydrophilic organic solvents such as acetone, methyl ethyl ketone, and 1,2-dimethoxyethane can also be used as organic solvents in the aforementioned washing process. It should be noted that, further from the perspective of facilitating drying in the drying process described later, solvents with a boiling point of less than or equal to 100°C at normal pressure can be used. The aforementioned solvents can be used alone or in mixtures of two or more.

[0155] The amount of solvent used in the solvent replacement process can be set to a level sufficient to fully replace the solvent in the washed, wetted gel. This amount can be set to 3 to 10 times the volume of the wetted gel.

[0156] The temperature environment in the solvent displacement process can be set to be less than or equal to the boiling point of the solvent used for displacement. For example, when using heptane, the temperature can be set to 30-60°C.

[0157] It should be noted that when the gel contains silica particles, the solvent replacement step is not necessary. The inferred mechanism is as follows: the silica particles act as a support for the three-dimensional mesh-like framework, thus supporting the framework and suppressing gel shrinkage during the drying process. Therefore, it is considered that the gel can be directly supplied to the drying process without replacing the solvent used for washing.

[0158] (Drying process)

[0159] In the drying process, the moistened gel, which has been washed and (if necessary) replaced with solvent as described above, is dried. This yields an aerogel (aerogel block or aerogel particles). In other words, an aerogel obtained by drying the moistened gel generated from the sol described above is possible.

[0160] There are no particular limitations on the drying method; known methods such as atmospheric pressure drying, supercritical drying, or freeze drying can be used. Among these methods, atmospheric pressure drying or supercritical drying is preferred from the viewpoint of easily producing low-density aerogels. Furthermore, atmospheric pressure drying is preferred from the viewpoint of enabling low-cost production. It should be noted that in this embodiment, atmospheric pressure refers to 0.1 MPa (atmospheric pressure).

[0161] Aerogels can be obtained by drying a wetted gel, after washing and (if necessary) solvent displacement, at a temperature below the critical point of the solvent used for drying and at atmospheric pressure. The drying temperature varies depending on the type of solvent used for displacement (or washing if solvent displacement is not performed), and can be set between 20 and 150°C, especially considering that high-temperature drying accelerates solvent evaporation and can sometimes cause large cracks in the gel. It should be noted that this drying temperature can also be between 60 and 120°C. Furthermore, the drying time varies depending on the volume of the wetted gel and the drying temperature, and can be set between 4 and 120 hours. It should be noted that applying pressure below the critical point to accelerate drying, within a range that does not impede productivity, is also included in atmospheric pressure drying.

[0162] Alternatively, aerogels can also be obtained by supercritical drying of a wetted gel that has been washed and (if necessary) replaced with a solvent. Supercritical drying can be performed by known methods. For example, methods for supercritical drying include removing the solvent at a temperature and pressure greater than or equal to the critical point of the solvent contained in the wetted gel. Alternatively, methods for supercritical drying include immersing the wetted gel in liquid carbon dioxide at, for example, 20–25°C and 5–20 MPa, thereby replacing all or part of the solvent contained in the wetted gel with carbon dioxide, which has a critical point lower than that of the solvent, and then removing the carbon dioxide alone or a mixture of carbon dioxide and solvent.

[0163] The aerogel obtained by such atmospheric or supercritical drying can be further dried at atmospheric pressure and 105–200 °C for 0.5–2 hours. This readily yields an aerogel with low density and small pores. The additional drying can be carried out at atmospheric pressure and 150–200 °C.

[0164] (Grinding process)

[0165] Aerogel particles are obtained by pulverizing the aerogel (aerogel block) obtained through drying without performing a wetting and pulverizing process. For example, this can be done by placing the aerogel in an air jet mill, roller mill, bead mill, hammer mill, etc., and running it at an appropriate speed and time.

[0166] <Coating>

[0167] The coating liquid comprises aerogel particles and a liquid medium. The pores of the aerogel particles in the coating liquid can be filled by the liquid medium. More specifically, the first to third coating liquids shown below can be cited as examples of this coating liquid. It should be noted that the coating liquid with high viscosity (e.g., greater than or equal to 1000 mPa·s) can be referred to as a paste.

[0168] (First coat)

[0169] The first coating solution contains substances with a specific surface area less than or equal to 350m². 2 / g of aerogel particles, adhesive resin, and liquid medium. The first coating liquid may also be referred to as a mixture of the above-mentioned aerogel particles, adhesive resin, and liquid medium.

[0170] In the first coating solution, the specific surface area of ​​the aerogel particles is less than or equal to 350 m². 2 / g. Therefore, a coating solution with excellent film properties can be prepared. The reasoning may not be clear, but the inventors speculate as follows: It is believed that the specific surface area of ​​the aerogel particles determines the adsorption force (adsorption amount) on the binder resin. Therefore, if the specific surface area is too large, the liquid medium and the binder resin are drawn into the porous aerogel particles, making it difficult to maintain an appropriate amount of binder resin on the surface of the aerogel particles in the coating solution state. Consequently, during the drying of the coating solution, the binder resin cannot be used to fully bond the aerogel particles, and a coating film with good film properties cannot be obtained. In contrast, it is believed that if the specific surface area of ​​the aerogel particles is within the above-mentioned range, an appropriate amount of binder resin can be maintained on the surface of the aerogel particles, thus enabling the formation of a coating film in which the aerogel particles are suitably bonded by the binder resin.

[0171] Adhesive resins have the function of binding aerogel particles together after the coating film is formed. Examples of adhesive resins include epoxy resins, silicone resins, phenolic resins, urea resins, melamine resins, polyurethane resins, polyethylene resins, polypropylene resins, polystyrene resins, polyester resins, acrylic resins (including polymers with acrylates or methacrylates as the main structural units), polyvinyl chloride resins, polyvinyl acetate resins, polyamide resins, polyimide resins, cellulose-based resins, and polyethylene-based resins. Additionally, acrylic resins (including polymers with acrylic acid, acrylates, methacrylic acid, and methacrylates as structural units), polyvinyl alcohol, polyethylene oxide, and polyethylene glycol can also be used as adhesive resins. Among these, silicone resins, acrylic resins, phenolic resins, and polyester resins are suitable for use from the viewpoint of heat resistance and toughness.

[0172] It should be noted that examples of cellulose-based resins include hydroxypropyl methylcellulose, carboxymethyl cellulose ammonium, and hydroxyethyl methylcellulose. Additionally, examples of polyethylene-based resins include polyvinyl alcohol and polyvinylpyrrolidone.

[0173] Examples of acrylic resins include polyacrylic acid, acrylic copolymers, polyacrylates, and acrylate copolymers.

[0174] When the adhesive resin is a thermosetting resin, the coating liquid may further contain a curing agent. There are no particular limitations on the curing agent, which can be appropriately varied depending on the type of thermosetting resin. For example, when the thermosetting resin is an epoxy resin, known epoxy resin curing agents can be used as the curing agent. Examples of epoxy resin curing agents include amine-based curing agents, anhydride-based curing agents, and polyamide-based curing agents. From a reactivity point of view, amine-based curing agents and polyamide-based curing agents can be suitably used.

[0175] As a liquid medium, water and organic solvents can be included. As for organic solvents, there are no particular limitations as long as they can disperse the aerogel particles; examples include aromatic hydrocarbons such as toluene, xylene, mesitylene, cumene, and p-isopropylbenzene; aliphatic hydrocarbons such as hexane, heptane, and pentane; and diethyl ether, tetrahydrofuran, and 1,4-diethyl ether. Ethers such as alkanes; alcohols such as methanol, ethanol, isopropanol, butanol, ethylene glycol, and propylene glycol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone; esters such as methyl acetate, ethyl acetate, and butyl acetate; and amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. Among these, alcohols and ketones are suitable from the perspective of volatility and boiling point, especially alcohols. Alcohols and ketones are also suitable when used in combination with these components because they are easily miscible with water and water-based resins.

[0176] The coating liquid may also contain other components such as tackifiers, fibrous substances, pigments, leveling agents, and film-forming aids.

[0177] Tackifiers increase the viscosity of coatings, resulting in better coatability. Examples of tackifiers include organic polymers, fumed silica, layered inorganic additives, and particulate clay minerals.

[0178] Fibrous materials can exhibit anchoring properties between aerogel particles after coating film formation, further enhancing coating film strength. There are no particular limitations on fibrous materials; both organic and inorganic fibers can be included. Examples of organic fibers include polyamide fibers, polyimide fibers, polyvinyl alcohol fibers, polyvinylidene chloride fibers, polyvinyl chloride fibers, polyester fibers, polyacrylonitrile fibers, polyethylene fibers, polypropylene fibers, polyurethane fibers, phenolic fibers, polyether ester fibers, polylactic acid fibers, and polycarbonate fibers. Examples of inorganic fibers include glass fibers, carbon fibers, ceramic fibers, and metal fibers.

[0179] Considering factors such as dispersibility, aerogel particle loading, and coating viscosity, the aerogel particle content in the coating can be set to 0.1–30% by mass, or 1–25% by mass. Furthermore, considering suitability for application using a spatula or similar tool, the aerogel particle content in the coating can be greater than or equal to 2% by mass, or greater than or equal to 3% by mass.

[0180] Considering the adhesion between aerogel particles and the thermal insulation of the coating, the content of the adhesive resin in the coating liquid can be set to 1~40% by mass or 1~30% by mass.

[0181] The content of the binder resin in the coating liquid can be set to, for example, greater than or equal to 5 parts by mass, greater than or equal to 10 parts by mass, greater than or equal to 15 parts by mass, or greater than or equal to 20 parts by mass relative to 100 parts by mass of aerogel particles. This allows the aerogel particles to be easily and firmly bonded by the binder resin, further improving the strength of the coating film.

[0182] Furthermore, the content of the adhesive resin relative to 100 parts by mass of aerogel particles can be set to less than or equal to 150 parts by mass, less than or equal to 130 parts by mass, less than or equal to 100 parts by mass, or less than or equal to 90 parts by mass. This increases the proportion of aerogel particles in the coating film, further improving the thermal insulation of the coating film.

[0183] Considering the dispersibility and good anchoring performance of the coating solution, the content of fibrous material in the coating solution can be set to 1~50% by mass or 1~30% by mass.

[0184] The content of fibrous material in the coating solution can be set to greater than or equal to 5 parts by mass, greater than or equal to 7 parts by mass, or greater than or equal to 9 parts by mass relative to 100 parts by mass of aerogel particles. This easily achieves the anchoring effect brought about by the fibrous material, further improving the coating strength.

[0185] Furthermore, the content of fibrous material relative to 100 parts by mass of aerogel particles can be set to less than or equal to 50 parts by mass, less than or equal to 35 parts by mass, less than or equal to 25 parts by mass, less than or equal to 20 parts by mass, or less than or equal to 15 parts by mass. This increases the proportion of aerogel particles in the coating film, further improving the thermal insulation of the coating film.

[0186] The content of the tackifier can be appropriately adjusted to achieve the desired viscosity of the coating solution (e.g., greater than or equal to 1000 mPa·s). Since the viscosity of the coating solution can also be further increased by incorporating an adhesive resin, in this case, it is not necessarily necessary to incorporate a tackifier.

[0187] (Second coat)

[0188] The second coating liquid comprises aerogel particles, adhesive resin, fibrous material with a fiber length greater than or equal to 1.5 mm, and a liquid medium. The second coating liquid may also be referred to as a mixture of the aforementioned aerogel particles, adhesive resin, fibrous material with a fiber length greater than or equal to 1.5 mm, and liquid medium. The second coating liquid will be described below, but details that overlap with the description of the first coating liquid will be appropriately omitted.

[0189] The second coating liquid contains fibrous material with a fiber length greater than or equal to 1.5 mm. This improves the coating strength and ensures the thermal insulation of the coating. The reasoning may not be clear, but the inventors speculate as follows: Generally, when manufacturing a pressed molded body like in Patent Document 2, it is preferable to randomly orient the fibers within the molded body to further ensure the strength of the molded body. The use of short fibers in Patent Document 2 is thought to be because short fibers are easier to randomly orient compared to long fibers. However, in the case of manufacturing a thin film-like molded body, random fiber orientation easily creates heat paths formed by the fibers in the thickness direction (the direction where thermal insulation is desired), resulting in compromised thermal insulation in the thickness direction. In contrast, the coating liquid of this embodiment contains long fibers. It is speculated that when forming a thin coating film on the surface of an object using the coating liquid, the intentional use of long fibers (fibrous material with a fiber length greater than or equal to 1.5 mm) facilitates in-plane orientation of the fibers. Therefore, it is believed that this improves the strength in the planar direction and maintains high thermal insulation in the thickness direction.

[0190] From this perspective, the fiber length can be set to be greater than or equal to 2 mm, greater than or equal to 2.5 mm, or greater than or equal to 3 mm. On the other hand, there is no particular upper limit to the fiber length, but from the viewpoint of dispersibility in the coating liquid, it can be set to 20 mm.

[0191] Considering factors such as dispersibility in the coating solution and good anchoring function, the fiber diameter of fibrous materials can be set to 0.01~100μm.

[0192] The content of fibrous material in the coating solution is as described above. Furthermore, based on the total mass of the fibrous material, the content of fibers with a length greater than or equal to 1.5 mm can be set to greater than or equal to 30% by mass, or greater than or equal to 50% by mass. The upper limit of this content can be set to 100% by mass (i.e., substantially all fibrous material in the coating solution has a fiber length greater than or equal to 1.5 mm).

[0193] (Third coat)

[0194] The third coating liquid comprises aerogel particles, a liquid medium, a first adhesive resin, and a second adhesive resin. The third coating liquid may also be referred to as a mixture of aerogel particles, a liquid medium, a first adhesive resin, and a second adhesive resin. The third coating liquid will be described below, but content that overlaps with the descriptions of the first and second coating liquids will be appropriately omitted.

[0195] The first adhesive resin and the second adhesive resin have the function of binding aerogel particles together after the coating film is formed. Both the first adhesive resin and the second adhesive resin are soluble in a liquid medium, but the first adhesive resin has a higher solubility in the liquid medium than the second adhesive resin.

[0196] By including such a first adhesive resin and a second adhesive resin in the coating liquid, a coating film with excellent strength and adhesion is obtained. The reasoning may not be clear, but the inventors speculate as follows: Because the first and second adhesive resins have different solubilities in the liquid medium, during the drying process (the process of removing the liquid medium) during coating film formation, the second adhesive resin saturates with the liquid medium before the first adhesive resin, and the second adhesive resin tends to precipitate first. It is believed that due to this difference in solubility, a characteristic adhesive structure is formed during coating film formation, resulting in excellent coating film strength and adhesion.

[0197] The exact structure of the aforementioned characteristic adhesive is not yet fully understood, but it is hypothesized, for example, that the second adhesive resin is first bonded to the aerogel particles (and the fibrous material described later), and the first adhesive resin, with the aid of the second adhesive resin, bonds the aerogel particles together (or between the aerogel particles and the fibrous material, or between the fibrous materials), thereby achieving excellent coating strength and adhesion. Alternatively, it is also thought that the second adhesive resin is granular and fills the spaces between the aerogel particles, and is then bonded by the first adhesive resin, thus firmly bonding the aerogel particles together.

[0198] The above-mentioned resins can be listed as adhesive resins. The first adhesive resin and the second adhesive resin can be selected from these resins, and more specifically, from the resins described later.

[0199] In this embodiment, it is preferable that the content of the second adhesive resin is greater than the content of the first adhesive resin. This allows the aforementioned effects to be achieved more significantly. The content of the second adhesive resin relative to 100 parts by weight of the first adhesive resin is preferably more than 100 parts by weight, more preferably greater than or equal to 150 parts by weight, and can be greater than or equal to 200 parts by weight, greater than or equal to 300 parts by weight, greater than or equal to 400 parts by weight, or greater than or equal to 600 parts by weight.

[0200] In addition, from the viewpoint of excellent thermal insulation performance, the content of the second adhesive resin relative to 100 parts by weight of the first adhesive resin can be less than or equal to 800 parts by weight, preferably less than or equal to 700 parts by weight, less than or equal to 600 parts by weight, less than or equal to 500 parts by weight, or less than or equal to 400 parts by weight.

[0201] Considering the adhesion between aerogel particles and the thermal insulation of the coating, the total content of the first adhesive resin and the second adhesive resin in the coating liquid can be set to 1~40% by mass or 1~30% by mass.

[0202] The total content of the first adhesive resin and the second adhesive resin, for example, relative to 100 parts by weight of aerogel particles, can be greater than or equal to 5 parts by weight, preferably greater than or equal to 10 parts by weight, more preferably greater than or equal to 15 parts by weight, and even more preferably greater than or equal to 20 parts by weight. As a result, the aerogel particles are easily and firmly bonded by the adhesive resin, further improving the strength of the coating film.

[0203] Furthermore, the total content of the first adhesive resin and the second adhesive resin, for example, relative to 100 parts by weight of aerogel particles, can be less than or equal to 150 parts by weight, preferably less than or equal to 130 parts by weight, more preferably less than or equal to 100 parts by weight, and even more preferably less than or equal to 90 parts by weight. As a result, the proportion of aerogel particles in the coating film increases, and the thermal insulation of the coating film is further improved.

[0204] The first adhesive resin has the function of binding aerogel particles together after the coating film is formed, and any resin that can dissolve in a liquid medium is acceptable. For example, when the liquid medium is an aqueous solvent, examples of first adhesive resins include cellulose resins, polyvinyl alcohol, polyvinylpyrrolidone, acrylic resins, polyethylene oxide, and polyethylene glycol. Among these, cellulose resins, polyvinylpyrrolidone, and acrylic resins are suitable from the viewpoint of excellent tackifying properties.

[0205] The second adhesive resin can be any resin that is soluble in a liquid medium and has a lower solubility in the liquid medium than the first adhesive resin. The second adhesive resin can be a thermoplastic resin or a thermosetting resin.

[0206] Examples of thermoplastic resins include acrylic resins, polyvinyl alcohol, polypropylene, and polyvinyl chloride. From an operational point of view, acrylic resins and polyvinyl alcohol are suitable for use.

[0207] Examples of thermosetting resins include epoxy resins, silicone resins, and polyurethanes. Among these, epoxy resins and silicone resins are suitable for use from the viewpoint of excellent heat resistance.

[0208] When the second adhesive resin is a thermosetting resin, the coating film may further contain a curing agent. There are no particular limitations on the curing agent, and it can be appropriately changed depending on the type of thermosetting resin. For example, when the thermosetting resin is an epoxy resin, a known epoxy resin curing agent can be used. Examples of epoxy resin curing agents include amine-based curing agents, anhydride-based curing agents, and polyamide-based curing agents. From a reactivity point of view, amine-based and polyamide-based curing agents are suitable.

[0209] Examples of liquid media include water and organic solvents, as described above. In a preferred embodiment, the liquid medium is preferably an aqueous solvent containing water. The aqueous solvent can be water or a mixture of water and an organic solvent. With such a liquid medium, the dispersibility of aerogel particles is improved, and a uniform coating film is easily obtained.

[0210] The coating liquid of this embodiment can be widely applied to everything from large-scale facilities such as factories and power plants to small and medium-sized equipment such as home appliances and automobiles, and can reduce energy loss in various situations.

[0211] <Coating manufacturing method and coating>

[0212] The method for manufacturing a coating film (coating film forming method) includes a step of removing the liquid medium from a coating liquid containing aerogel particles and a liquid medium. More specifically, the method for manufacturing a coating film may include the steps of: applying the aforementioned coating liquid onto an object; and removing the liquid medium from the coating liquid applied to the object.

[0213] There are no particular limitations on the method of applying the coating liquid to the object, such as dip coating, spray coating, spin coating, and roller coating. When the coating film is formed, the coated liquid can be placed in an environment of 0~40°C, or the coated liquid can be heated (e.g., 40~150°C), depressurized (e.g., less than or equal to 10000 Pa), or both.

[0214] It should be noted that the coating liquid in this embodiment can also be of high viscosity (paste-like), therefore, as Figure 1 As shown, a spatula (metal scraper) or similar tool can be used to apply the coating liquid to the object. Figure 1 In this process, a trowel is used to apply the coating liquid to the bends of the pipe. With the coating liquid of this embodiment, a coating film of a thickness difficult to achieve with conventional insulating coatings can be formed in a short time. Specifically, with such a coating liquid, a coating film of at least approximately 2 mm thickness can be formed in a single application, achieving extremely high work efficiency compared to conventional coatings that can only achieve a coating film of approximately 0.5 mm thickness. It should be noted that because the coating liquid contains aerogel particles, a coating film with superior insulating properties compared to conventional insulating coatings can be obtained.

[0215] When using the first coating liquid, it is possible to obtain a coating with a specific surface area of ​​less than or equal to 350 m². 2 A first coating film comprising / g of aerogel particles and an adhesive resin (or its cured form). The first coating film may contain 40-95% by mass of aerogel particles and 1-50% by mass of adhesive resin (or its cured form).

[0216] When using the second coating liquid, a second coating film comprising aerogel particles, an adhesive resin (or its cured form), and fibrous material with a fiber length greater than or equal to 1.5 mm can be obtained. The second coating film may contain 40 to 95% by mass of aerogel particles, 1 to 40% by mass of adhesive resin (or its cured form), and 1 to 50% by mass of fibrous material with a fiber length greater than or equal to 1.5 mm.

[0217] When using the third coating liquid, it is possible to obtain a third coating film comprising aerogel particles, a first adhesive resin, and a second adhesive resin (or their cured form).

[0218] The content of aerogel particles in the coating film can be set to, for example, greater than or equal to 40% by mass, greater than or equal to 50% by mass, greater than or equal to 60% by mass, or greater than or equal to 70% by mass. This further improves the thermal insulation of the coating film. Alternatively, the content of aerogel particles in the coating film can be set to, for example, less than or equal to 95% by mass, or less than or equal to 90% by mass. This tends to facilitate coating film formation.

[0219] Specifically, for the third coating, the content of the first adhesive resin in the coating relative to 100 parts by weight of aerogel particles can, for example, be greater than or equal to 2 parts by weight, preferably greater than or equal to 5 parts by weight, and more preferably greater than or equal to 8 parts by weight. Alternatively, the content of the first adhesive resin in the coating relative to 100 parts by weight of aerogel particles can, for example, be less than or equal to 20 parts by weight, preferably less than or equal to 17 parts by weight, and more preferably less than or equal to 15 parts by weight.

[0220] Specifically, for the third coating, the content of the second adhesive resin (or its cured form) in the coating, relative to 100 parts by weight of aerogel particles, can be, for example, greater than or equal to 10 parts by weight, preferably greater than or equal to 15 parts by weight, or also greater than or equal to 20 parts by weight. Alternatively, the content of the second adhesive resin (or its cured form) in the coating, relative to 100 parts by weight of aerogel particles, can be, for example, less than or equal to 100 parts by weight, preferably less than or equal to 80 parts by weight, less than or equal to 60 parts by weight, or less than or equal to 40 parts by weight.

[0221] There are no particular restrictions on the thickness of the coating; for example, it can be set to 0.01~5mm.

[0222] Because the aerogel particles in this embodiment are hydrophobic, the coating film exhibits excellent water-repellent properties. That is, performance degradation due to water content in the coating film (e.g., reduced thermal insulation) is unlikely to occur, reducing the frequency of coating film replacement. Furthermore, due to the excellent water-repellent properties, there is no need for an external casing to protect the coating film. Water repellency can be evaluated by measuring the contact angle between the coating film and water. The contact angle can be set to be greater than or equal to 90°, greater than or equal to 110°, or greater than or equal to 130°. The contact angle of the coating film can be adjusted, for example, by the content of aerogel particles in the coating film, the type and content of the liquid medium, etc.

[0223] The coating exhibits good heat resistance. Heat resistance can be evaluated by measuring the temperature at which the coating weight decreases by 5%. For example, using a differential thermogravimetric analyzer, with the temperature increased to 500°C at a heating rate of 10°C / min, the temperature at which the weight decreases by 5% can be set to be greater than or equal to 150°C, greater than or equal to 200°C, or greater than or equal to 250°C. The heat resistance of the coating can be adjusted, for example, by the type of adhesive resin and its content in the coating.

[0224] There are no particular restrictions on the materials used to constitute the object; examples include metals, ceramics, glass, resins, and their composite materials. The form of the object can be appropriately selected based on its intended use or the material itself; examples include block, sheet, powder, and fibrous forms.

[0225] It should be noted that the shape of the object can also be more complex. Even for objects that are difficult to install planar insulation materials such as sheet or plate shapes, such as components with complex shapes or pipes with bends, an insulation layer can be formed on their surface as long as the coating liquid of this embodiment is used.

[0226] The coating possesses excellent thermal insulation, heat resistance, flame retardancy, and water repellency derived from aerogels. Due to these advantages, the coating can be used as an insulation material in cryogenic containers, aerospace applications, construction, automotive (e.g., insulation materials for automotive parts), home appliances, semiconductors, and industrial equipment (e.g., insulation materials for various piping systems in factories and power plants). It should be noted that, in addition to its use as an insulation material, the coating can also be used as a water-repellent material, sound-absorbing material, vibration damping material, and catalyst support material.

[0227] Example

[0228] The present invention will now be described in further detail through the following embodiments, but these embodiments do not limit the present invention.

[0229] <Experiment 1>

[0230] (Preparation of aerogel particles A)

[0231] 100.0 parts by weight of PL-2L (manufactured by Fuso Chemical Industry Co., Ltd., product name) containing silica particles, 80.0 parts by weight of water, 0.5 parts by weight of acetic acid as an acid catalyst, 1.0 part by weight of hexadecyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries Co., Ltd.) as a cationic surfactant, and 150.0 parts by weight of urea as a hot hydrolyzable compound were mixed together. 60.0 parts by weight of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KBM-13) as a silicon compound, 20.0 parts by weight of dimethyldimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KBM-22), and 20.0 parts by weight of a difunctional alkoxy-modified polysiloxane compound having the structure represented by the above general formula (B) (hereinafter referred to as "polysiloxane compound A") were added to the mixture. The mixture was reacted at 25°C for 2 hours to obtain a sol. The obtained sol was gelled at 60°C and then cured at 60°C for 48 hours to obtain a moist gel.

[0232] It should be noted that the above-mentioned "polysiloxane compound A" was synthesized as follows: First, in a 1-liter three-necked flask equipped with a stirrer, thermometer, and serpentine condenser, 100.0 parts by weight of dimethylpolysiloxane XC96-723 (manufactured by Momentive Materials Japan Co., Ltd., product name) with silanol groups at both ends, 181.3 parts by weight of methyltrimethoxysilane, and 0.50 parts by weight of tert-butylamine were mixed and reacted at 30°C for 5 hours. Then, the reaction solution was heated at 140°C for 2 hours under reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining the polysiloxane compound modified with difunctional alkoxy groups at both ends (polysiloxane compound A).

[0233] The obtained wetted gel was then transferred into a plastic bottle, sealed, and pulverized at 27,000 rpm for 10 minutes using an Extreme Mill (AS ONE Co., Ltd., MX-1000XTS) to obtain particulate wetted gel. The obtained particulate wetted gel was immersed in 2500 parts by weight of methanol and washed at 25°C for 24 hours. This washing operation was repeated a total of 3 times, replacing the methanol with fresh methanol. Next, the washed particulate wetted gel was immersed in 2500 parts by weight of heptane as a low surface tension solvent and solvent-displaced at 25°C for 24 hours. This solvent-displacement operation was repeated a total of 3 times, replacing the heptane with fresh heptane. The washed and solvent-displaced particulate wetted gel was dried at 40°C for 96 hours under normal pressure, and then further dried at 150°C for 2 hours. Finally, the particles were sieved (manufactured by Tokyo SCREEN Co., Ltd., with a mesh size of 45 μm and a wire diameter of 32 μm) to obtain aerogel particles A having the structures represented by the above general formulas (3), (4) and (5).

[0234] (Preparation of Aerogel Particles B)

[0235] Prepare JIOS AeroVa (registered trademark, manufactured by JIOS AEROGEL CORPORATION, product name) as aerogel particles B.

[0236] (Example 1-1)

[0237] In a 300mL detachable flask, 10g of aerogel particles A, 1g of glass fiber (manufactured by Nitto Boshoku Co., Ltd., CS3 PE-908, average fiber length 3mm), 35g of isopropanol (manufactured by Wako Pure Chemical Industries, Ltd., reagent), and 1g of carboxymethyl cellulose ammonium (Wako Pure Chemical Industries, Ltd., reagent) were taken and stirred at 150rpm for 15 minutes using a mechanical stirrer to obtain an isopropanol dispersion. Next, 50g of water was added to this dispersion to dissolve the carboxymethyl cellulose ammonium, yielding coating solution 1-1.

[0238] (Other embodiments and comparative examples)

[0239] Except for changing the raw materials and quantities of the coating solution as shown in Table 1, the coating solutions were prepared in the same manner as in Examples 1-1 to obtain coating solutions 1-2 to 1-5. The viscosity of the coating solutions in all examples exceeded 10000 mPa·s.

[0240] [Table 1]

[0241]

[0242] *CMC-NH4: Manufactured by Wako Pure Chemical Industries, Ltd., carboxymethyl cellulose ammonium

[0243] Fiberglass: Nitto Boshoku Co., Ltd., CS 3 PE-908, average fiber length 3mm

[0244] Vinylon fiber: Manufactured by Kuraray Co., Ltd., VPB303, average fiber length 3mm

[0245] (Specific surface area measurement)

[0246] The BET specific surface area of ​​aerogel particles was determined using a gas adsorption capacity measuring device (Kunta Instruments Japan Co., Ltd., Autosorb-iQ (Autosorb is a registered trademark)). The specific surface area of ​​aerogel particle A was 125 m². 2 / g, the specific surface area of ​​aerogel particles B is 716m². 2 / g.

[0247] (Average particle size determination)

[0248] Aerogel particles were added to ethanol at a concentration of 0.5% by mass, and the mixture was vibrated for 20 minutes using a 50W ultrasonic homogenizer to prepare a dispersion. 10 mL of the resulting dispersion was injected into a Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name), and the particle size was measured at 25°C with a refractive index of 1.3 and absorbance of 0. The particle size at the 50% cumulative value (volume basis) of the obtained particle size distribution was then defined as the average particle size D50. The average particle size D50 for aerogel particle A was 20 μm, and the average particle size D50 for aerogel particle B was 8.7 μm.

[0249] (Film-forming property evaluation)

[0250] The coating solutions of the examples and comparative examples were applied to aluminum foil using a metal scraper to a thickness of 2 mm. The solution was then heated at 120°C for 1 hour to remove the liquid medium, resulting in a coating film. The film-forming properties of the coating solution were evaluated by visual inspection. Specifically, a good appearance without cracks was evaluated as good film-forming properties, while cracks were evaluated as poor film-forming properties. The evaluation results are shown in Table 2.

[0251] [Table 2]

[0252]

[0253] It should be noted that, for Examples 1-1 and 1-2, after cutting the coating obtained in the film-forming property evaluation together with the aluminum foil into 30cm×30cm pieces and removing the aluminum foil, the aluminum foil could be peeled off without damaging the coating. Furthermore, the thermal insulation of the coating was evaluated using a steady-state method, and the results showed a sufficiently low thermal conductivity (32~35mW / m·K).

[0254] (Water repellency evaluation)

[0255] The water repellency of the coating obtained in Example 1-1 was evaluated by measuring the contact angle with water. The coating was processed into a size of 50 × 50 mm as a test sample. Approximately 3 μL of pure water was then dropped onto the surface of the test sample, and the contact angle was measured after 5 minutes. A contact angle meter (NiCK Corporation, LSE-B100) was used as the measuring apparatus. The contact angle of the coating was 145°.

[0256] (Heat resistance evaluation)

[0257] The heat resistance was evaluated using the coating obtained in Example 1-1. First, the obtained coating was peeled off from the aluminum foil and used as a test sample. A differential thermogravimetric analyzer (TG / DTA STA7300, Hitachi Advanced Technology Co., Ltd.) was used as the testing apparatus. The temperature was increased to 500°C at a heating rate of 10°C / min, and the temperature at which the weight decreased by 5% was recorded. It should be noted that, to eliminate weight changes due to water evaporation, the weight of the coating at 100°C was set as the baseline weight (zero point). The temperature at which the coating weight decreased by 5% was 320°C.

[0258] (Evaluation of thermal insulation performance)

[0259] The thermal insulation performance of the coating obtained using the coating solution from Example 1-1 was evaluated. First, the coating solution was applied to an anodized aluminum plate (50×50mm, 0.5mm thickness) using a metal scraper to achieve the specified thickness. After drying the coating solution at room temperature (25°C) for 2 hours, it was further dried for 2 hours using a dryer heated to 60°C (PERFECTOVEN SPHH-301, manufactured by ESPEC Corporation), preparing multiple evaluation samples with different coating thicknesses. To obtain a thicker coating, a single coating was applied, followed by drying at room temperature for 2 hours, and then a second coating was applied. This process was repeated until the desired thickness was obtained. It should be noted that a coating thickness of approximately 2mm can be obtained with a single coating. The evaluation samples were placed with the aluminum plate side facing a glass heater (BLAST Corporation, S-101), and the temperature was raised to 150°C. The surface temperature of the evaluation sample (coating surface temperature) was measured using an infrared thermal imager (APISTE Corporation, FSV-1200-L16) after being held at 150°C for 1 hour. The surface temperature was 150°C in the uncoated state (coating thickness 0 mm). As the coating thickness increased to 1.0 mm, 2.0 mm, 5.0 mm, and 10.0 mm, the surface temperature decreased to 130°C, 100°C, 75°C, and 60°C, respectively.

[0260] <Experiment 2>

[0261] (Example 2-1)

[0262] In a 300mL detachable flask, 10g of aerogel particles prepared using the same steps as in Experiment 1 ("Preparation of Aerogel Particles A"), 5g of aramid fiber (manufactured by Teijin Corporation, TECHNORA, average fiber length 6mm), 100g of isopropanol (manufactured by Wako Pure Chemical Industries, Ltd., reagent), and 2g of carboxymethyl cellulose ammonium (manufactured by Wako Pure Chemical Industries, Ltd., reagent) were taken and stirred at 150rpm for 15 minutes using a mechanical stirrer to obtain an isopropanol dispersion. Next, 100g of water was added to this dispersion to dissolve the carboxymethyl cellulose ammonium, yielding coating solution 2-1.

[0263] (Other embodiments and comparative examples)

[0264] Except for changing the formulation materials and quantities of the coating solution as shown in Table 3, the coating solution was prepared in the same manner as in Example 2-1, resulting in coating solutions 2-2 to 2-7. The viscosity of the coating solutions in all examples exceeded 10000 mPa·s. It should be noted that in Examples 2-6, 2g PVA and 98g water mean that 100g of 2wt% PVA aqueous solution was used to replace carboxymethyl cellulose ammonium and water.

[0265] [Table 3]

[0266]

[0267] *CMC-NH4: Manufactured by Wako Pure Chemical Industries, Ltd., carboxymethyl cellulose ammonium

[0268] MP-30000: Manufactured by Wako Pure Chemical Industries, Ltd., containing hydroxypropyl methylcellulose.

[0269] Glass fiber A: Manufactured by Nitto Boshoku Co., Ltd., CS 3 PE-908, average fiber length 3mm

[0270] Glass fiber B: Manufactured by Nitto Boshoku Co., Ltd., CS 12 PE-908, average fiber length 12mm

[0271] EFH150-31: Manufactured by Central Glass Fiber Co., Ltd., with an average fiber length of 150 μm and a fiber diameter of 11 μm.

[0272] Vinylon fiber: Manufactured by Kuraray Co., Ltd., VPB303, average fiber length 3mm

[0273] Aromatic polyamide fiber: manufactured by Teijin Corporation, TECHNORA, average fiber length 6mm

[0274] (Thermal conductivity measurement)

[0275] The coating solutions of the examples and comparative examples were applied to aluminum foil using a metal scraper to a thickness of 2 mm. The foil was then heated at 120°C for 1 hour to remove the liquid medium, resulting in coated aluminum foil. The thermal conductivity of the obtained coating was measured using a steady-state method. The results are shown in Table 4.

[0276] (Insulation performance evaluation)

[0277] The coated aluminum foil obtained during the thermal conductivity measurement was placed on a glass heater (BLAST Corporation, S-101) with the aluminum foil on the glass heater side, and the temperature was set to 100°C by a temperature control device (BLAST Corporation, BT-101). The coating amount was 1 μL / cm between the glass heater and the aluminum foil. 2 The coating was then contacted with silicone oil (manufactured by Shin-Etsu Chemical Industry Co., Ltd., KF96-100CS). The temperature of the coating surface was then measured after 5 minutes. The results are shown in Table 4.

[0278] [Table 4]

[0279]

[0280] It should be noted that the coating of the embodiment was cut into 30cm × 30cm pieces together with the aluminum foil, and the aluminum foil was removed. For any coating, the aluminum foil could be peeled off without damaging the coating. On the other hand, the same operation was performed on the coating of the comparative example, and the coating was damaged, leaving coating residue on the aluminum foil. It is believed that because short fibers were used in the comparative example, a greater amount of fibers was required to obtain sufficient coating strength. However, it is believed that with an increased amount of fibers, more thermal paths are formed by the short fibers, thus further increasing the thermal conductivity.

[0281] <Experiment 3>

[0282] (Example A-1)

[0283] 10 parts by mass of hydroxypropyl methylcellulose (manufactured by Matsumoto Oils & Fats Co., Ltd., product name: MP-30000), 10 parts by mass of glass fiber (product name: Chopped strand, fiber diameter: 13 μm, fiber length: 3 mm), 100 parts by mass of aerogel particles prepared by the same steps as "Preparation of Aerogel Particle A" in Experiment 1, 16 parts by mass of acrylic resin (manufactured by Hitachi Chemical Co., Ltd., product name: KH-CT-865), 350 parts by mass of methyl ethyl ketone (MEK), and 200 parts by mass of water were mixed to obtain a coating solution.

[0284] The coating solution was applied to an aluminum foil (manufactured by UACJ Co., Ltd., product name: Myfoil Thick Type 50, thickness: 50μm) to a thickness of 2mm after drying. The foil was then dried for 2 hours using a dryer heated to 60°C (manufactured by ESPEC Co., Ltd., product name: PERFECT OVEN SPHH-301) to obtain a coating film containing aerogel.

[0285] The strength (tensile strength) and adhesive strength (peel strength) of the resulting coating were determined using the following methods. The results are shown in Table 5.

[0286] <Determination of Tensile Strength>

[0287] The obtained coating was processed into a size of 2×5×5mm and used as the test sample. A small benchtop testing machine, "EZTest" (manufactured by Shimadzu Corporation), was used as the testing apparatus. It should be noted that a 500N load sensor was used. Furthermore, a spiral-type flat clamp with an upper and lower arrangement was used, with the distance between the upper and lower parts set to 25mm, to place the sample, and tensile testing was performed at a speed of 2.5mm / min. The test ended when the sample broke.

[0288] <Determination of peel strength>

[0289] The coating film with aluminum foil was cut at 3mm intervals to serve as the test sample. A small benchtop testing machine, "EZTest" (manufactured by Shimadzu Corporation), was used as the testing apparatus. During the test, the sample was fixed with the aluminum foil side facing up, and the aluminum foil was clamped and stretched at a speed of 50mm / min. The test ended when the aluminum foil peeled off from the coating film.

[0290] (Example A-2)

[0291] Except for changing the amount of acrylic resin to 33 parts by mass, the coating solution was prepared in the same manner as in Example A-1. Furthermore, using the obtained coating solution, an aerogel-containing coating film was prepared using the same method as in Example A-1. For the obtained coating film, the coating strength (tensile strength) and adhesive strength (peel strength) were measured using the same method as in Example A-1. The results are shown in Table 5.

[0292] (Example A-3)

[0293] Except for changing the amount of acrylic resin to 66 parts by mass, the coating solution was prepared in the same manner as in Example A-1. Furthermore, using the obtained coating solution, an aerogel-containing coating film was prepared using the same method as in Example A-1. For the obtained coating film, the coating strength (tensile strength) and adhesive strength (peel strength) were measured using the same method as in Example A-1. The results are shown in Table 5.

[0294] (Example B-1)

[0295] A coating solution was prepared by mixing 10 parts by weight of hydroxypropyl methylcellulose (manufactured by Matsumoto Oils & Fats Co., Ltd., product name: MP-30000), 10 parts by weight of glass fiber (product name: Chopped strand, fiber diameter: 13 μm, fiber length: 3 mm), 100 parts by weight of aerogel particles, 16 parts by weight of epoxy resin (manufactured by Mitsubishi Chemical Co., Ltd., product name: jER811), 1.6 parts by weight of triethylenetetramine (TETA, manufactured by Wako Pure Chemical Co., Ltd.) as a curing agent, 350 parts by weight of methyl ethyl ketone (MEK), and 200 parts by weight of water.

[0296] The coating solution was applied to aluminum foil (manufactured by UACJ Corporation, product name: Myfoil Thick Type 50, thickness: 50μm) to a thickness of 2mm after drying, and dried for 2 hours using a dryer heated to 60°C (manufactured by ESPEC Corporation, product name: PERFECT OVEN SPHH-301) to obtain a coating film containing aerogel.

[0297] The resulting coatings were tested for strength (tensile strength) and adhesive strength (peel strength) using the same method as in Example A-1. The results are shown in Table 5.

[0298] (Example B-2)

[0299] Except for changing the amount of epoxy resin to 33 parts by mass and the amount of curing agent to 3.3 parts by mass, the coating solution was prepared in the same manner as in Example B-1. Furthermore, using the obtained coating solution, an aerogel-containing coating film was prepared using the same method as in Example B-1. For the obtained coating film, the film strength (tensile strength) and adhesive strength (peel strength) were measured using the same method as in Example A-1. The results are shown in Table 5.

[0300] (Example B-3)

[0301] Except for changing the amount of epoxy resin to 66 parts by mass and the amount of curing agent to 6.6 parts by mass, the coating solution was prepared in the same manner as in Example B-1. Furthermore, using the obtained coating solution, an aerogel-containing coating film was prepared using the same method as in Example B-1. For the obtained coating film, the film strength (tensile strength) and adhesive strength (peel strength) were measured using the same method as in Example A-1. The results are shown in Table 5.

[0302] It should be noted that the viscosity of the coating liquid in the examples all exceeds 10000 mPa·s.

[0303] (Comparative Example 1)

[0304] Except for the absence of acrylic resin, the coating solution was prepared in the same manner as in Example A-1. Furthermore, using the obtained coating solution, an aerogel-containing coating film was prepared using the same method as in Example A-1. The strength (tensile strength) and adhesive strength (peel strength) of the resulting coating film were measured using the same method as in Example A-1. The results are shown in Table 5.

[0305] In Table 5, "second adhesive resin" represents the content relative to 100 parts by mass of the first adhesive resin, "peel strength" represents the result of the above-mentioned <determination of peel strength>, and "tensile breaking strength" represents the result of the above-mentioned <determination of tensile strength>.

[0306] [Table 5]

[0307]

[0308] For Example A-1, the water repellency was evaluated in the same manner as in Example 1-1. The contact angle of the coating was 123°. Furthermore, for Example A-1, the heat resistance was evaluated in the same manner as in Example 1-1. The temperature at which the coating weight decreased by 5% was 270°C. Further, for Example A-1, the thermal insulation performance was evaluated in the same manner as in Example 1-1. The surface temperature was 150°C in the uncoated state (coating thickness 0 mm), and decreased to 130°C, 110°C, 85°C, and 65°C respectively as the coating thickness increased to 1.0 mm, 2.0 mm, 5.0 mm, and 10.0 mm.

Claims

1. A coating liquid comprising aerogel particles, a liquid medium, a first adhesive resin, a second adhesive resin having a lower solubility in the liquid medium than the first adhesive resin, and a fibrous material with a fiber length greater than or equal to 1.5 mm, wherein the content of the second adhesive resin is greater than the content of the first adhesive resin.

2. The coating liquid according to claim 1, wherein the specific surface area of ​​the aerogel particles is less than or equal to 350 m². 2 / g.

3. The coating liquid according to claim 2, wherein the liquid medium comprises an organic solvent.

4. The coating liquid according to claim 2 or 3, wherein the adhesive resin is at least one selected from the group consisting of epoxy resin, silicone resin, phenolic resin, urea resin, melamine resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, polyamide resin, polyimide resin, cellulose resin, and polyethylene resin.

5. The coating liquid according to claim 1, wherein the liquid medium comprises an organic solvent.

6. The coating liquid according to claim 1 or 5, wherein the fiber length of the fibrous material is less than or equal to 20 mm.

7. The coating liquid according to claim 1 or 5, wherein, based on the total mass of the fibrous material in the coating liquid, the content of the fibrous material with a fiber length greater than or equal to 1.5 mm is greater than or equal to 30% by mass.

8. The coating liquid according to claim 1, wherein the liquid medium is an aqueous solvent containing water.

9. The coating liquid according to claim 1 or 8, wherein the first adhesive resin is a cellulose-based resin.

10. The coating liquid according to claim 1 or 8, wherein the second adhesive resin is a thermoplastic resin.

11. The coating liquid according to claim 10, wherein the second adhesive resin is an acrylic resin.

12. The coating liquid according to claim 1 or 8, wherein the second adhesive resin is a thermosetting resin, and the coating liquid further comprises a curing agent.

13. The coating liquid according to claim 12, wherein the second adhesive resin is an epoxy resin, and the coating liquid further comprises an epoxy resin curing agent.

14. The coating liquid according to claim 1 or 2, wherein the viscosity is greater than or equal to 1000 mPa·s.

15. The coating liquid according to claim 1 or 2, comprising at least one of organic fibers and inorganic fibers.

16. A method for manufacturing a coating film, comprising a step of removing the liquid medium from the coating liquid according to any one of claims 1 to 15.

17. A coating comprising aerogel particles, a first adhesive resin, a second adhesive resin or a cured form thereof having a lower solubility in aqueous solvents than the first adhesive resin, and a fibrous material with a fiber length greater than or equal to 1.5 mm, wherein the content of the second adhesive resin is greater than the content of the first adhesive resin.

18. The coating according to claim 17, wherein the specific surface area of ​​the aerogel particles is less than or equal to 350 m². 2 / g.

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