TW201922961A - Coating liquid, method for manufacturing coating film, and coating film - Google Patents

Abstract

The present invention relates to a coating liquid including aerogel particles having a specific surface area of 350 m2/g or less, a binder resin, and a liquid medium.

Description

Manufacturing method of coating liquid and coating film, and coating film

The present invention relates to a method for producing a coating liquid, a coating film, and a coating film.

As a material excellent in heat insulation and transparency, aerogel is known. Aerogels with such characteristics have been researched and processed into particles to be used in various applications. For example, it is proposed to use a particulate aerogel as a filler between resin plates and the like constituting a thermal insulation window (for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2012-91943

[Problems to be Solved by the Invention] By dispersing a particulate aerogel in a dispersion medium, it can be expected to be used as a coating liquid that is different from the case where the particles themselves are processed. However, the film-forming property (painting adaptability) of the coating liquid prepared using the particulate aerogel described in Patent Document 1 is insufficient, and it is difficult to obtain a good coating film.

The present invention has been made in view of the circumstances described above, and an object thereof is to provide an aerogel particle-containing coating liquid having excellent film-forming properties. Another object of the present invention is to provide a method for producing a coating film and a coating film. [Means for solving problems]

The present inventors have made intensive studies in order to achieve the above-mentioned object, and as a result, have found that, particularly, by using a coating liquid containing aerogel particles having a predetermined specific surface area, a good coating film can be formed.

The present invention provides a coating liquid including aerogel particles having a specific surface area of 350 m ² / g or less, a binder resin, and a liquid medium. Such a coating liquid is different from a coating liquid containing aerogel particles obtained by a conventional technique, and a good coating film can be obtained.

In the present invention, the liquid medium may include an organic solvent. Thereby, the dispersibility of aerogel particles can be further improved.

In the present invention, the binder resin may be selected from the group consisting of epoxy resin, silicone resin, phenol resin, urea resin, melamine resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, At least one of the group consisting of a polyester resin, an acrylic resin, a polyvinyl chloride resin, a polyvinyl acetate resin, a polyamide resin, a polyimide resin, a cellulose resin, and a polyethylene-based resin. Thereby, the film-forming property can be further improved.

In addition, the present invention provides a method for manufacturing a coating film including a step of removing a liquid medium from the coating liquid. Furthermore, the present invention provides a coating film including aerogel particles having a specific surface area of 350 m ² / g or less, and an adhesive resin or a cured body thereof. The coating film obtained by the manufacturing method of this invention and the coating film of this invention have favorable film quality. [Effect of the invention]

According to the present invention, an aerogel particle-containing coating liquid having excellent film-forming properties can be provided. Moreover, this invention can provide the manufacturing method of a coating film, and a coating film (aerogel coating film).

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In this specification, a numerical range expressed using "~" means a range including the numerical value described before and after "~" as the minimum and maximum values, respectively. The "A or B" may include any one of A and B, and may include both. Unless otherwise specified, the materials exemplified in this embodiment may be used alone or in combination of two or more.

<Aerogel> In a narrow sense, a dry gel obtained by using a supercritical drying method on a wet gel is referred to as an aerogel, and a dry gel obtained by drying under atmospheric pressure is referred to as a xerogel ( xerogel), and the dry gel obtained by freeze-drying is referred to as cryogel. However, in this embodiment, regardless of the drying method of the wet gel, the obtained low-density dry gel is condensed. The gel is called "aerogel". That is, in the present embodiment, the "aerogel" refers to an aerogel in a broad sense "a gel consisting of a microporous solid in which the dispersed phase is a gas). " Generally, the inside of an aerogel has a network-like fine structure and a cluster structure in which particulate aerogel components of about 2 nm to 20 nm are combined. There are pores smaller than 100 nm between the skeletons formed by the clusters. As a result, the aerogel has a fine three-dimensional porous structure. The aerogel in the present embodiment is, for example, a silica aerogel containing silica as a main component. Examples of the silica aerogel include a so-called organic-inorganic hybrid silica aerogel into which, for example, an organic group (such as a methyl group) or an organic chain is introduced.

As the aerogel of this embodiment, the following aspects are mentioned. By adopting these aspects, it is easy to obtain an aerogel excellent in heat insulation, flame retardancy, heat resistance, and flexibility. By adopting each aspect, an aerogel having heat insulation, flame retardancy, heat resistance, and flexibility corresponding to each aspect can be obtained.

(First aspect) The aerogel of this embodiment may have a structure represented by the following general formula (1). The aerogel of this embodiment may have a structure represented by the following general formula (1a) as a structure including the structure represented by the formula (1). [Chemical 1] [Chemical 2]

In Formula (1) and Formula (1a), R ¹ and R ² each independently represent an alkyl group or an aryl group, and R ³ and R ⁴ each independently represent an alkylene group. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. p represents an integer of 1 to 50. In the formula (1a), two or more R ¹ may be the same or different, and similarly, two or more R ² may be the same or different. In formula (1a), two R ³ may be the same or different, and similarly, two R ⁴ may be the same or different.

By introducing the structure represented by the formula (1) or the formula (1a) into the aerogel skeleton as an aerogel component, a soft aerogel having a low thermal conductivity is obtained. From such a viewpoint, in Formula (1) and Formula (1a), R ¹ and R ² each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like. Examples of the alkyl group include a methyl group. Wait. In Formula (1) and Formula (1a), R ³ and R ⁴ each independently include an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an alkylene group and an alkylene group. Wait. In the formula (1a), p may be 2 to 30, or 5 to 20 may be used.

(Second Aspect) The aerogel of this embodiment has a stepped structure including a pillar portion and a bridge portion, and the bridge portion may have a structure represented by the following general formula (2). By introducing such a stepped structure into an aerogel skeleton as an aerogel component, heat resistance and mechanical strength can be improved. The "stepped structure" in this embodiment is a person having two struts and bridges that connect the struts to each other (a person having a so-called "ladder"). In this aspect, the skeleton of the aerogel may include a stepped structure, but the aerogel may partially have a stepped structure. [Chemical 3]

In formula (2), R ⁵ and R ⁶ each independently represent an alkyl group or an aryl group, and b represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In addition, in formula (2), when b is an integer of 2 or more, two or more R ⁵ may be the same or different, and similarly, two or more R ⁶ may be the same or different.

When the structure is introduced into the aerogel skeleton as an aerogel component, for example, it has a structure derived from a conventional stepped silsesquioxane (ie, it has a general formula (X) below) The aerogel having the structure shown) has a more flexible aerogel. Silsesquioxane is a polysiloxane with a compositional formula: (RSiO _1.5 ) _n , and can have a variety of skeleton structures such as cage, step, and random. In addition, as shown in the following general formula (X), in an aerogel having a structure derived from a conventional stepped silsesquioxane, the structure of the bridge portion is -O-, but this embodiment In the aerogel of a form, the structure of a bridge part is a structure (polysiloxane structure) represented by the said General formula (2). However, the aerogel in this aspect may have a structure derived from silsesquioxane in addition to the structure represented by the general formula (2). [Chemical 4]

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

The structure serving as the pillar portion and its chain length, and the interval between the structures serving as the bridging portion are not particularly limited. From the viewpoint of further improving heat resistance and mechanical strength, the stepped structure may have the following general formula ( 3) The stepped structure shown. [Chemical 5]

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

Furthermore, from the viewpoint of obtaining more excellent flexibility, in formulas (2) and (3), R ⁵ , R ⁶ , R ^7, and R ⁸ (wherein R ⁷ and R ⁸ are only in formula (3) In ()), independently, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like are mentioned, and examples of the alkyl group include a methyl group and the like. In the formula (3), a and c may be independently set to 6 to 2000, or may be 10 to 1,000. Moreover, in Formula (2) and Formula (3), b may be 2-30, and may be 5-20.

(Third aspect) The aerogel according to this embodiment may be a dried gel of a wet gel that is a condensate of a sol (obtained by drying a wet gel produced by a sol: Dry matter), the sol contains at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensable functional group and a hydrolysate of a silicon compound having a hydrolyzable functional group. The aerogel described above may be obtained by drying a wet gel produced by a sol containing a silicon compound or the like as described above.

As the silicon compound having a hydrolyzable functional group or a condensable functional group, a polysiloxane compound can be used. That is, the sol may contain at least one selected from the group consisting of a polysiloxane compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysate of a polysiloxane compound having a hydrolyzable functional group. Compounds (hereinafter, referred to as the "polysiloxane group" as appropriate).

The functional group in the polysiloxane compound is not particularly limited, and may be a group that reacts with each other by the same functional group or a group that reacts with other functional groups. Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group include a hydroxyl group, a silanol group, a carboxyl group, and a phenolic hydroxyl group. The hydroxyl group may be contained in a hydroxyl group-containing group such as a hydroxyalkyl group. Furthermore, the polysiloxane compound having a hydrolyzable functional group or a condensable functional group may further have a reactive group different from the hydrolyzable functional group and the condensable functional group. Equivalent functional group). Examples of the reactive group include an epoxy group, a mercapto group, a glycidyloxy group, a vinyl group, an acrylfluorenyl group, a methacrylfluorenyl group, and an amino group. The epoxy group may be contained in an epoxy group-containing group such as a glycidyl group. The polysiloxane compound having these functional groups and reactive groups may be used alone or as a mixture of two or more kinds. Among these functional groups and reactive groups, for example, examples of the group that improves the flexibility of the aerogel include alkoxy, silanol, and hydroxyalkyl groups. Among these groups, alkoxy and hydroxyalkyl groups Group can further improve the compatibility of the sol. In addition, from the viewpoint of improving the reactivity of the polysiloxane compound and lowering the thermal conductivity of the aerogel, the carbon number of the alkoxy group and the hydroxyalkyl group can be set to 1 to 6, which can further improve the flexibility of the aerogel. From the viewpoint of sex, it may be 2 to 4.

Examples of the polysiloxane compound having a hydroxyalkyl group in the molecule include a structure represented by the following general formula (A). By using a polysiloxane compound having a structure represented by the following general formula (A), the structures represented by the general formula (1) and the formula (1a) can be introduced into the aerogel skeleton. [Chemical 6]

In the formula (A), R ^1a represents a hydroxyalkyl group, R ^2a represents an alkylene group, R ^3a and R ^4a each independently represent an alkyl group or an aryl group, and n represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. Moreover, in formula (A), two R ^1a may be the same or different, and similarly, two R ^2a may be the same or different. In addition, in formula (A), two or more R ^3a may be the same or different, and similarly, two or more R ^4a may be the same or different.

By using a moist gel that is a condensate (generated from a sol) of a sol containing a polysiloxane compound having the above structure, it is easier to obtain a soft aerogel having a low thermal conductivity. From such a viewpoint, in the formula (A), R ^1a includes a hydroxyalkyl group having 1 to 6 carbon atoms, and examples of the hydroxyalkyl group include a hydroxyethyl group and a hydroxypropyl group. In the formula (A), R ^2a includes an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an alkylene group and an alkylene group. In formula (A), R ^3a and R ^4a each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group and the like. Moreover, in Formula (A), n may be 2-30, and may be 5-20.

As the polysiloxane compound having a structure represented by the general formula (A), a commercially available product can be used, and examples include compounds such as X-22-160AS, KF-6001, KF-6002, and KF-6003 (all (Made by Shin-Etsu Chemical Industry Co., Ltd.), XF42-B0970, Fluid OFOH 702-4% and other compounds (all manufactured by Japan's Momentive Performance Materials Japan contract company), etc.

Examples of the polysiloxane compound having an alkoxy group in the molecule include a structure represented by the following general formula (B). By using a polysiloxane compound having a structure represented by the following general formula (B), a stepped structure having a bridging portion represented by the general formula (2) or (3) can be introduced into the gas condensate. Glue in the skeleton. [Chemical 7]

In formula (B), R ^1b represents an alkyl group, an alkoxy group, or an aryl group, R ^2b and R ^3b each independently represent an alkoxy group, R ^4b and R ^5b each independently represent an alkyl group or an aryl group, and m represents 1 Integer to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. Furthermore, in formula (B), two R ^1b may be the same or different, two R ^2b may be the same or different, and similarly, two R ^3b may be the same or different. In addition, in formula (B), when m is an integer of 2 or more, two or more R ^4b may be the same or different, and similarly, two or more R ^5b may be the same or different.

By using a moist gel that is a condensate (generated from a sol) of a sol containing the polysiloxane compound or a hydrolyzed product of the structure, it is easier to obtain a soft aerogel having a low thermal conductivity. From such a viewpoint, in the formula (B), R ^1b includes an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and the like. Examples of the alkyl group or alkoxy group include: Methyl, methoxy, ethoxy, etc. In formula (B), R ^2b and R ^3b each independently include an alkoxy group having 1 to 6 carbon atoms, and examples of the alkoxy group include a methoxy group and an ethoxy group. In formula (B), R ^4b and R ^5b each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group and the like. Moreover, in Formula (B), m may be 2-30, and may be 5-20.

The polysiloxane compound having a structure represented by the general formula (B) can be obtained by appropriately referring to production methods reported in Japanese Patent Laid-Open No. 2000-26609, Japanese Patent Laid-Open No. 2012-233110, and the like.

In addition, since the alkoxy group is hydrolyzed, a polysiloxane compound having an alkoxy group may exist as a hydrolysate in the sol, and a polysiloxane compound having an alkoxy group and a hydrolysate thereof may also be mixed. . In addition, in the polysiloxane compound having an alkoxy group, the alkoxy group in the molecule may be entirely hydrolyzed or partially hydrolyzed.

These polysiloxane compounds having a hydrolyzable functional group or a condensable functional group, and the hydrolysates of the polysiloxane compounds having a hydrolyzable functional group can be used alone or in combination of two or more.

When producing the aerogel of this embodiment, as the silicon compound having a hydrolyzable functional group or a condensable functional group, a silicon compound other than the polysiloxane compound described above can be used. That is, the sol containing a silicon compound may contain a silicon compound selected from the group consisting of a hydrolyzable functional group or a condensable functional group in addition to the polysiloxane compound group or in place of the polysiloxane compound group. (Except polysiloxane compounds) and at least one of the group consisting of a hydrolysate of the silicon compound having a hydrolyzable functional group (hereinafter, referred to as a “silicon compound group”). The number of silicon in the molecule in the silicon compound can be set to 1 or 2.

The silicon compound having a hydrolyzable functional group in the molecule is not particularly limited, and examples thereof include alkyl silicon alkoxides. From the viewpoint of improving water resistance, the number of hydrolyzable functional groups of the alkyl alkoxide can be three or less. Examples of such alkoxyalkyl silicon include monoalkyltrialkoxysilane, monoalkyldialkoxysilane, dialkyldialkoxysilane, monoalkylmonoalkoxysilane, and Alkyl monoalkoxysilanes, trialkyl monoalkoxysilanes, and the like, specifically, methyltrimethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, and dimethyldisilane Methoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, etc. Here, examples of the hydrolyzable functional group include alkoxy groups such as a methoxy group and an ethoxy group.

The silicon compound having a condensable functional group is not particularly limited, and examples thereof include silane tetraol, methylsilane triol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, and diphenyl. Silanediol, n-propylsilanetriol, hexylsilyltriol, octylsilyltriol, decylsilyltriol, trifluoropropylsilyltriol, etc.

The silicon compound having a hydrolyzable functional group or a condensable functional group may further have the reactive group (a functional group not equivalent to the hydrolyzable functional group and the condensable functional group) different from the hydrolyzable functional group and the condensable functional group. ).

As the silicon compound having three or less hydrolyzable functional groups and having a reactive group, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl can also be used. Methylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyl Trimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2- (amine Ethyl) -3-aminopropylmethyldimethoxysilane and the like.

In addition, as the silicon compound having a condensable functional group and a reactive group, vinylsilanetriol, 3-glycidoxypropylsilanetriol, and 3-glycidoxypropylmethylsilanedi may also be used. Alcohol, 3-methacryloxypropylsilyltriol, 3-methacryloxypropylmethylsilanediol, 3-acryloxypropylsilyltriol, 3-mercaptopropylsilane Triol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2- (aminoethyl) -3-aminopropylmethylsilanediol Alcohol and so on.

Further, a silicon compound having three or less hydrolyzable functional groups at the molecular end, that is, a ditrimethoxysilylmethane, a ditrimethoxysilylethane, a ditrimethoxysilylhexane, an ethyl group, or the like can also be used. Trimethoxysilane, vinyltrimethoxysilane, etc.

The silicon compound (except a polysiloxane compound) having a hydrolyzable functional group or a condensable functional group, and a hydrolysate of the silicon compound having a hydrolyzable functional group may be used alone or as a mixture of two or more.

By using the silicon compound (except a polysiloxane compound), the structure represented by the following general formula (4) to general formula (6) can be introduced into the aerogel skeleton. The aerogel of the present embodiment may have any one of these structures alone, or may have two or more of these structures.

[Chemical 8]

In formula (4), R ⁹ represents an alkyl group. Here, examples of the alkyl group include an alkyl group having 1 to 6 carbon atoms, and examples of the alkyl group include a methyl group.

[Chemical 9]

In formula (5), R ¹⁰ and R ¹¹ each independently represent an alkyl group. Here, examples of the alkyl group include an alkyl group having 1 to 6 carbon atoms, and examples of the alkyl group include a methyl group.

[Chemical 10]

In the formula (6), R ¹² represents an alkylene group. Here, examples of the alkylene group include an alkylene group having 1 to 10 carbon atoms, and examples of the alkylene group include an ethylene group and a hexyl group.

(Fourth aspect) From the viewpoint of further strengthening and toughening and further achieving excellent thermal insulation and flexibility, the aerogel of this embodiment may further contain silica particles in addition to the aerogel component. . An aerogel containing an aerogel component and silica particles may be referred to as an aerogel composite. The aerogel component and the silica particles are composited in the aerogel composite, but it has a cluster structure that is characteristic of the aerogel, and has a three-dimensionally fine and porous structure.

An aerogel containing an aerogel component and silicon dioxide particles can be referred to as a dried product of the wet gel as a condensate of the sol, and the sol contains silicon selected from the group consisting of a hydrolyzable functional group or a condensable functional group. At least one of the group consisting of a compound and a hydrolysate of a silicon compound having a hydrolyzable functional group, and silicon dioxide particles. Therefore, the description about the first aspect to the third aspect is also applicable to the aerogel of this embodiment.

The silica particles can be used without particular limitation, and examples include amorphous silica particles and the like. Examples of the amorphous silica particles include fused silica particles, fumed silica particles, and colloidal silica particles. Among these particles, colloidal silica particles have high monodispersity, and it is easy to suppress aggregation in the sol. The silica particles may be silica particles having a hollow structure, a porous structure, or the like.

The shape of the silica particles is not particularly limited, and examples thereof include a spherical shape, a cocoon shape, and an association type. In these shapes, by using spherical particles as the silica particles, it is easy to suppress aggregation in the sol. From the viewpoint of easily providing an aerogel with moderate strength and flexibility, and easily obtaining an aerogel having excellent shrinkage resistance during drying, the average primary particle diameter of the silica particles may be 1 nm or more, or may be 5 nm or more, or 20 nm or more. From the viewpoint that it is easy to suppress the solid heat conduction of the silicon dioxide particles and to easily obtain an aerogel with excellent thermal insulation properties, the average primary particle diameter of the silicon dioxide particles may be 500 nm or less, or 300 nm or less, or may be Below 100 nm. From these viewpoints, the average primary particle diameter of the silicon dioxide particles may be 1 nm to 500 nm, 5 nm to 300 nm, or 20 nm to 100 nm.

In this embodiment, the average particle diameter of the aerogel component and the average primary particle diameter of the silica particles can be directly measured on the aerogel by using a scanning electron microscope (hereinafter abbreviated as "SEM (scanning electron microscope)"). Obtained by observation. The "diameter" herein refers to a diameter when a cross section of a particle exposed in a cross section of an aerogel is regarded as a circle. The "diameter when the cross section is regarded as a circle" is the diameter of the perfect circle when the area of the cross section is replaced with a perfect circle of the same area. When calculating the average particle diameter, the diameter of a circle was calculated for 100 particles, and the average value was taken.

The average particle diameter of the silicon dioxide particles can also be measured based on the raw materials. For example, the biaxial average primary particle diameter is calculated from the result of observation of arbitrary 20 particles by SEM as follows. In other words, if colloidal silica particles dispersed in water with a solid content concentration of about 5 to 40% by mass are used as an example, crystals with pattern wiring are immersed in a dispersion of colloidal silica particles. After the wafer obtained by circular cutting into a 2 cm square was obtained for about 30 seconds, the wafer was rinsed with pure water for about 30 seconds, and then subjected to nitrogen blow drying. Thereafter, the wafer was placed on a sample stage for SEM observation, an acceleration voltage of 10 kV was applied, and the silica particles were observed at a magnification of 100,000 times, and an image was taken. Twenty silica particles were arbitrarily selected from the obtained image, and the average value of the particle diameters of these particles was taken as the average particle diameter.

From the viewpoint of easily obtaining an aerogel having excellent shrinkage resistance, the number of silanol groups per 1 g of the silica particles may be 10 × 10 ¹⁸ particles / g or more, or 50 × 10 ¹⁸ particles / g or more. Or it may be 100 × 10 ¹⁸ pieces / g or more. From the viewpoint of easily obtaining a homogeneous aerogel, the number of silanol groups per 1 g of the silica particles may be 1,000 × 10 ¹⁸ particles / g or less, or 800 × 10 ¹⁸ particles / g or less, or may be 700 × 10 ¹⁸ pieces / g or less. From these viewpoints, the number of silanol groups per 1 g of the silica particles may be 10 × 10 ¹⁸ particles / g to 1000 × 10 ¹⁸ particles / g, or 50 × 10 ¹⁸ particles / g to 800 × 10. ¹⁸ / g, or may be 100 × 10 ¹⁸ / g to 700 × 10 ¹⁸ / g.

From the viewpoint that it is easier to obtain good reactivity, the content of the polysiloxane compound group (having a hydrolyzable functional group or a condensable functional group) contained in the sol relative to 100 parts by mass of the total amount of the sol The sum of the content of the polysiloxane compound and the content of the hydrolysate of the polysiloxane compound having a hydrolyzable functional group may be 5 parts by mass or more, or 10 parts by mass or more. From the viewpoint that it is easier to obtain good compatibility, the content of the group of polysiloxane compounds contained in the sol may be 50 parts by mass or less with respect to 100 parts by mass of the total amount of the sol. 30 parts by mass or less. From these viewpoints, the content of the polysiloxane compound group contained in the sol may be 5 to 50 parts by mass, or 10 to parts by mass, with respect to 100 parts by mass of the total amount of the sol. 30 parts by mass.

When the sol contains a silicon compound (except a polysiloxane compound), the silicon compound group (has hydrolyzability) with respect to 100 parts by mass of the total amount of the sol from the viewpoint that it is easier to obtain good reactivity. The sum of the content of the silicon compound of the functional group or the condensable functional group and the content of the hydrolysate of the silicon compound having a hydrolyzable functional group may be 5 parts by mass or more, or 10 parts by mass or more. From the viewpoint that it is easier to obtain good compatibility, the content of the group of silicon compounds contained in the sol may be 50 parts by mass or less, or 30 parts by mass with respect to 100 parts by mass of the total amount of the sol. the following. From these viewpoints, the content of the silicon compound group contained in the sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass.

In the case where the sol includes the polysiloxane compound group and the silicon compound group, the content of the polysiloxane compound group and the content of the silicon compound group are more likely to obtain good compatibility. The ratio may be 1: 0.5 or more, or 1: 1 or more. From the viewpoint of making it easier to suppress the shrinkage of the gel, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1: 4 or less, or may be 1: 2 or less. From these viewpoints, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1: 0.5 to 1: 4, or may be 1: 1 to 1: 2.

When silicon dioxide particles are contained in the sol, it is easy to impart a moderate strength to the aerogel, and it is easy to obtain an aerogel having excellent shrinkage resistance during drying, with respect to 100% of the total amount of the sol. The content of the silicon dioxide particles may be 1 part by mass or more, or 4 parts by mass or more. From the viewpoint that it is easy to suppress the solid heat conduction of the silicon dioxide particles and to easily obtain an aerogel having excellent thermal insulation properties, the content of the silicon dioxide particles may be 20 parts by mass or less with respect to 100 parts by mass of the total amount of the sol. It is 15 parts by mass or less. From these viewpoints, the content of the silica particles may be 1 to 20 parts by mass, or 4 to 15 parts by mass with respect to 100 parts by mass of the total amount of the sol.

<Aerogel particles> The aerogel particles of this embodiment can be obtained, for example, by pulverizing a bulk aerogel, as described later.

The specific surface area of the aerogel particles is 350 m ² / g or less. Thereby, a coating liquid having excellent film-forming properties can be prepared. The reason is not necessarily determined, but the inventors and others speculated as follows. The specific surface area of the aerogel particles is considered to be about the adsorption force (adsorption amount) of the binder resin. Therefore, when the specific surface area is too large, the liquid medium enters the aerogel particles having a porous structure together with the binder resin, and it is difficult to allow an appropriate amount of the binder resin to exist in the aerogel in the state of the coating liquid. Particle surface. Accordingly, when the coating liquid is dried, the aerogel particles using the binder resin cannot be sufficiently adhered, and a coating film having a good film quality cannot be obtained. In contrast, if the specific surface area of the aerogel particles is within the above range, it is considered that an appropriate amount of the binder resin can exist on the surface of the aerogel particles, so that the aerogel particles can be formed by the binder resin. A coating film with good adhesion.

From this viewpoint, the specific surface area may be 300 m ² / g or less, 250 m ² / g or less, or 150 m ² / g or less. The lower limit of the specific surface area of the aerogel particles is not particularly limited, and can be set to about 30 m ² / g in terms of suppression of aggregation in the coating liquid and improvement of the filling rate. As a method of adjusting the specific surface area of aerogel particles, various methods are considered, and examples include adjusting the amount of aerogel components having a bridge portion structure represented by the general formula (2), adjusting the amount of silica particles, and the like.

The specific surface area can be measured by the BET method. As the measuring device, a gas adsorption amount measuring device (manufactured by a contract company of Quantachrome Instruments Japan, Autosorb-iQ (Autosorb is a registered trademark)) can be used.

The average particle diameter D50 of the aerogel particles can be set to 1 μm to 1000 μm, but it can also be 3 μm to 700 μm, 5 μm to 500 μm, 10 μm to 100 μm, or 10 μm ～ 50 μm. When the average particle diameter D50 of the aerogel particles is 1 μm or more, it is easy to obtain aerogel particles having excellent dispersibility and handling properties. On the other hand, when the average particle diameter D50 is 1,000 μm or less, it is easy to obtain aerogel particles having excellent dispersibility. The average particle diameter of the aerogel particles can be appropriately adjusted by a pulverization method and pulverization conditions, a method of sieving, and classification.

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

<The manufacturing method of aerogel particles> The manufacturing method of an aerogel particle is not specifically limited, For example, it can manufacture by the following method.

The aerogel particles of this embodiment can be manufactured by a manufacturing method mainly including the following steps: a sol generation step; a wet gel generation step, gelling the sol obtained in the sol generation step, and then aging to obtain a wet gel ; Washing and solvent replacement steps, washing the wet gel obtained in the wet gel generation step and (if necessary) solvent replacement; a drying step, drying the washed and solvent replaced wet gels; and a pulverization step, The aerogel obtained by drying is pulverized.

In addition, it can also be manufactured by a manufacturing method mainly including the following steps: a sol generation step; a wet gel generation step; a wet gel pulverization step, pulverizing the wet gel obtained in the wet gel generation step; washing and solvent replacement Steps; and a drying step.

The size of the obtained aerogel particles can be further made uniform by sieving, classification, and the like. Dispersibility can be improved by adjusting the particle size. The "sol" is a state before a gelation reaction occurs, and in this embodiment, it means a state in which the silicon compound and optionally silica particles are dissolved or dispersed in a solvent. The moist gel refers to a gel solid in a wet state that does not have fluidity although it contains a liquid medium.

(Sol generation step) The sol generation step is a step of mixing a silicon compound and optionally silica particles (also a solvent containing silica particles) and subjecting them to a hydrolysis reaction to generate a sol. In this step, in order to promote the hydrolysis reaction, an acid catalyst may be further added to the solvent. In addition, as shown in Japanese Patent No. 5250900, a surfactant, a thermally hydrolyzable compound, and the like may be added to the solvent. Furthermore, for the purpose of suppressing infrared radiation and the like, components such as carbon graphite, aluminum compounds, magnesium compounds, silver compounds, and titanium compounds may be added to the solvent.

As the solvent, for example, water or a mixed solution of water and alcohol can be used. Examples of the alcohol include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and third butanol. Among these solvents, in terms of reducing the interfacial tension with the gel wall, examples of the alcohol having a low surface tension and a low boiling point include methanol, ethanol, and 2-propanol. These solvents can be used alone or in combination of two or more.

For example, when alcohol is used as the solvent, the amount of alcohol can be set to 4 mol to 8 mol, or 4 mol relative to the total amount of the silicon compound group and the polysiloxane compound group. Ears to 6.5 moles, or 4.5 to 6 moles. By setting the amount of alcohol to 4 mol or more, it is easier to obtain good compatibility, and by setting it to 8 mol or less, it is easier to suppress gel shrinkage.

Examples of the acid catalyst include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, and hypochlorous acid; acidic aluminum phosphate, Acidic phosphates such as acidic magnesium phosphate and acidic zinc phosphate; organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, azelaic acid, etc. Among these acid catalysts, as the acid catalyst which further improves the water resistance of the obtained aerogel, an organic carboxylic acid is mentioned. Examples of the organic carboxylic acid include acetic acid, and formic acid, propionic acid, oxalic acid, and malonic acid may be used. These acid catalysts can be used alone or in combination of two or more.

By using an acid catalyst, the hydrolysis reaction of the silicon compound can be promoted, and a sol can be obtained in a shorter time.

The addition amount of the acid catalyst may be 0.001 to 0.1 parts by mass relative to 100 parts by mass of the total of the polysiloxane compound group and the silicon compound group.

As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. These surfactants can be used alone or in combination of two or more.

As the nonionic surfactant, for example, a compound containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly containing an alkyl group, a compound containing a hydrophilic portion such as polyoxypropylene, and the like can be used. Examples of the compound containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly containing an alkyl group include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene alkyl ether. Examples of the compound containing a hydrophilic portion such as polyoxypropylene include a polyoxypropylene alkyl ether, a block copolymer of polyoxyethylene and polyoxypropylene, and the like.

Examples of the ionic surfactant include a cationic surfactant, an anionic surfactant, and a diionic surfactant. Examples of the cationic surfactant include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride. Examples of the anionic surfactant include sodium dodecylsulfonate. Examples of the diionic surfactant include amino acid-based surfactants, betaine-based surfactants, and amine oxide-based surfactants. Examples of the amino acid-based surfactants include amidinoglutamic acid and the like. Examples of the betaine-based surfactant include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, and the like. Examples of the amine oxide-based surfactant include lauryl dimethylamine oxide.

It is thought that these surfactants play a role in the wet gel formation step described later to reduce the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer, and to suppress phase separation.

Although the amount of the surfactant added depends on the type of the surfactant or the type and amount of the silicon compound, for example, it can be set to 100 parts by mass based on the total amount of the polysiloxane compound group and the silicon compound group. 1 part by mass to 100 parts by mass. The added amount may be 5 to 60 parts by mass.

It is considered that the thermally hydrolyzable compound generates an alkali catalyst by thermal hydrolysis, and makes the reaction solution alkaline to promote the sol-gel reaction in the wet gel generation step described later. Therefore, the thermally hydrolyzable compound is not particularly limited as long as it can make the reaction solution basic after hydrolysis, and examples thereof include urea; formamidine, N-methylformamide, and N, N- Acid amines such as dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, and cyclic nitrogen compounds such as hexamethylenetetramine. Among these compounds, urea is particularly easy to obtain the promoting effect.

The addition amount of the thermally hydrolyzable compound is not particularly limited as long as it is an amount that can sufficiently promote the sol-gel reaction in the wet gel generation step described later. For example, in the case where urea is used as the thermally hydrolyzable compound, the added amount of the urea may be 1 to 200 parts by mass relative to 100 parts by mass of the total of the polysiloxane compound group and the silicon compound group. Parts by mass. In addition, the added amount may be 2 to 150 parts by mass. When the addition amount is 1 part by mass or more, good reactivity is more easily obtained, and when it is 200 parts by mass or less, precipitation of crystals and reduction in gel density are more easily suppressed.

Although the hydrolysis in the sol-generating step also depends on the type and amount of silicon compounds, silicon dioxide particles, acid catalysts, and surfactants in the mixed solution, it can be performed at a temperature of 20 ° C to 60 ° C for 10 minutes ～ 24 hours, or 5 minutes to 8 hours in a temperature environment of 50 ° C to 60 ° C. Thereby, the hydrolyzable functional group in a silicon compound is fully hydrolyzed, and the hydrolyzate of a silicon compound can be obtained more reliably.

Among them, when a thermally hydrolyzable compound is added to the solvent, the temperature environment of the sol generation step may be adjusted to a temperature that suppresses hydrolysis of the thermally hydrolyzable compound and suppresses gelation of the sol. The temperature at this time may be any temperature as long as it can suppress the hydrolysis of the thermally hydrolyzable compound. For example, in the case where urea is used as the thermally hydrolyzable compound, the temperature environment of the sol generation step may be 0 ° C to 40 ° C, or 10 ° C to 30 ° C.

(Wet Gel Generation Step) The wet gel generation step is a step of gelling the sol obtained in the sol generation step and then curing to obtain a wet gel. In this step, an alkali catalyst may be used in order to promote gelation.

Examples of the alkali catalyst include carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper (II) carbonate, iron (II) carbonate, and silver (I) carbonate. ; Bicarbonates such as calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, etc .; alkali hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide; ammonium hydroxide, fluoride Ammonium compounds such as ammonium, ammonium chloride, and ammonium bromide; basic sodium phosphates such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropyl Methylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3- (diethylamine) Methylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, third butylamine, second butylamine, propyl Methylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine Other aliphatic amines; morpholine, N -Nitrogen-containing heterocyclic compounds such as methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and its derivatives, imidazole and its derivatives, and the like. Among these alkali catalysts, ammonium hydroxide (aqueous ammonia) is excellent in terms of economy because it has a high volatility and it is difficult to remain in the aerogel particles after drying, and it is difficult to impair water resistance. The alkali catalyst may be used alone or as a mixture of two or more kinds.

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

The addition amount of the alkali catalyst may be 0.5 to 5 parts by mass, or 1 to 4 parts by mass with respect to 100 parts by mass of the total of the polysiloxane compound group and the silicon compound group. By setting it to 0.5 parts by mass or more, gelation can be performed in a shorter period of time, and by setting it to 5 parts by mass or less, a decrease in water resistance can be further suppressed.

The gelation of the sol in the wet gel generation step may be performed in a closed container so as not to volatilize the solvent and the alkali catalyst. The gelation temperature can be set to 30 ° C to 90 ° C, or 40 ° C to 80 ° C. By setting the gelation temperature to 30 ° C or higher, gelation can be performed in a shorter time, and a wet gel with higher strength (rigidity) can be obtained. In addition, by setting the gelation temperature to 90 ° C. or lower, volatilization of a solvent (especially an alcohol) is easily suppressed, and thus gelation can be performed while suppressing volume shrinkage.

The aging in the wet gel formation step may also be performed in a closed container so that the solvent and the alkali catalyst are not volatilized. By aging, the binding of the components constituting the wet gel becomes stronger, and as a result, a wet gel having a high strength (rigidity) sufficient to suppress shrinkage during drying can be obtained. The aging temperature can be set to 30 ° C to 90 ° C, or 40 ° C to 80 ° C. By setting the curing temperature to 30 ° C or higher, a wet gel with higher strength (rigidity) can be obtained. By setting the curing temperature to 90 ° C or lower, the volatilization of the solvent (especially alcohol) can be easily suppressed, so it can be suppressed at the same time. Gelation was performed while shrinking the volume.

In addition, since it is difficult to discriminate the gelation end time of the sol in many cases, the gelation of the sol and the subsequent aging may be continuously performed in a series of operations.

The gelation time and aging time can be appropriately set according to the gelation temperature and the aging temperature. When the silica particles are contained in the sol, the gelation time can be shortened, as compared with the case where the silica particles are not contained. The reason is speculated that the silanol group or reactive group of the silicon compound in the sol forms a hydrogen bond or a chemical bond with the silanol group of the silicon dioxide particle. The gelation time can be set to 10 minutes to 120 minutes, or 20 minutes to 90 minutes. By setting the gelation time to 10 minutes or more, it is easy to obtain a homogeneous wet gel. By setting the gelation time to 120 minutes or less, the cleaning and solvent replacement steps to the drying steps described later can be simplified. In addition, as a whole step of gelation and aging, the total time of the gelation time and the aging time may be set to 4 hours to 480 hours, or may be 6 hours to 120 hours. By setting the total of the gelation time and the aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, it is easier to maintain the effect of aging.

In order to reduce the density of the obtained aerogel particles or increase the average pore diameter, it is also possible to increase the gelation temperature and the maturation temperature within the range, or to extend the gelation time and the maturation time within the range. Total time. In addition, in order to increase the density of the obtained aerogel particles or reduce the average pore diameter, the gelation temperature and the aging temperature may be reduced within the range, or the gelation time and the aging time may be shortened within the range. The total time of time.

(Wet gel pulverizing step) When the wet gel pulverizing step is performed, the wet gel obtained in the wet gel generating step is pulverized. The pulverization can be performed, for example, by putting the wet gel into a Henschel mixer or performing the wet gel generation step in the mixer, and the mixer is placed under moderate conditions (speed and time). ). In addition, more simply, it can be carried out by putting the wet gel into a sealable container or performing the wet gel generation step in the sealable container, and using an oscillation device such as a vibrator for a moderate time. oscillation. Furthermore, if necessary, the particle size of the wet gel can be adjusted by using a jet mill, a roll mill, a bead mill, or the like.

(Washing and solvent replacement step) The washing and solvent replacement step is a step having a step of washing the wet gel obtained by the wet gel generation step or the wet gel pulverization step (washing step); and A step (solvent replacement step) of replacing the cleaning solution in the wet gel with a solvent suitable for drying conditions (the drying step described later). The cleaning and solvent replacement steps may be performed without the step of cleaning the wet gel, and only by performing the solvent replacement step. However, impurities such as unreacted substances and by-products in the wet gel can be reduced, and higher purity can be produced. From the viewpoint of aerogel particles, the wet gel can also be washed.

In the washing step, the wet gel obtained by the wet gel generation step or the wet gel pulverization step is washed. This washing can be performed repeatedly using, for example, water or an organic solvent. In this case, the cleaning efficiency can be improved by heating.

As the organic solvent, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, Various organic solvents such as toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, dichloromethane, N, N-dimethylformamide, dimethylmethane, acetic acid and formic acid. The organic solvents may be used alone or as a mixture of two or more.

In the solvent replacement step described later, in order to suppress shrinkage of the gel caused by drying, a solvent having a low surface tension can be used. However, low surface tension solvents often have very low mutual solubility with water. Therefore, when a low surface tension solvent is used in the solvent replacement step, examples of the organic solvent used in the cleaning step include hydrophilic organic solvents that have high mutual solubility with respect to both water and low surface tension solvent. . Furthermore, the hydrophilic organic solvent used in the washing step can perform a pre-replacement function for performing the solvent replacement step. Among the organic solvents, examples of the hydrophilic organic solvent include methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone. Furthermore, methanol, ethanol, and methyl ethyl ketone are excellent in terms of economic efficiency.

The amount of water or organic solvent used in the washing step may be an amount sufficient to replace and clean the solvent in the wet gel. This amount can be set to 3 to 10 times the capacity of the wet gel. It can be repeatedly washed until the moisture content in the wet gel after washing becomes 10% by mass or less with respect to the mass of the silica.

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

In the solvent replacement step, in order to suppress shrinkage of the aerogel in the drying step, the solvent of the washed wet gel is replaced with a predetermined replacement solvent. In this case, the replacement efficiency can be improved by heating. As the replacement solvent, specifically, when the drying step is performed at a temperature lower than the critical point of the solvent used for drying under atmospheric pressure, a solvent having a low surface tension described below may be mentioned. On the other hand, in the case of performing supercritical drying, examples of the replacement solvent include ethanol, methanol, 2-propanol, dichlorodifluoromethane, and carbon dioxide, or by mixing two or more of these solvents and Into a solvent.

Examples of the low surface tension solvent include solvents having a surface tension of 20 mN / m or less at 20 ° C. The surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of the low surface tension solvent include pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), and 3-methylpentane. Aliphatic hydrocarbons such as alkane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), 1-pentene (16.0); benzene (28.9), toluene (28.5 ), M-xylene (28.7), para-xylene (28.3) and other aromatic hydrocarbons; dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), 2 -Halogenated hydrocarbons such as chloropropane (18.1); diethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ether (20.8), 1,2-dimethoxyethane (24.6), etc. Ethers; ketones such as acetone (23.3), methyl ethyl ketone (24.6), methylpropyl ketone (25.1), diethyl ketone (25.3); methyl acetate (24.8), ethyl acetate (23.8) , Propyl acetate (24.3), isopropyl acetate (21.2), isobutyl acetate (23.7), ethyl butyrate (24.6) and other esters (the brackets indicate the surface tension at 20 ° C, the unit is [mN / m]). Among these solvents, aliphatic hydrocarbons (such as hexane and heptane) have a low surface tension and are excellent in working environment. Among these solvents, by using a hydrophilic organic solvent such as acetone, methyl ethyl ketone, or 1,2-dimethoxyethane, the solvent can also be used as the organic solvent in the cleaning step. Among these solvents, a solvent having a boiling point of 100 ° C. or lower at normal pressure can be used in terms of ease of drying in a drying step described later. The solvents may be used alone or as a mixture of two or more.

The amount of the solvent used in the solvent replacement step may be an amount sufficient to replace the solvent in the wet gel after washing. This amount can be set to 3 to 10 times the capacity of the wet gel.

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

When the silica particles are contained in the gel, the solvent replacement step is not necessary. The speculated mechanism is as follows. That is, the silicon dioxide particles function as a support for a three-dimensional network skeleton, and the skeleton is supported, and the shrinkage of the gel in the drying step is suppressed. Therefore, it is considered that the gel can be directly delivered to the drying step without replacing the solvent used for washing. In this way, by using silicon dioxide particles, the cleaning and solvent replacement steps to the drying step can be simplified.

(Drying step) In the drying step, the wet gel that has been washed and (if necessary) replaced with a solvent is dried. Thereby, an aerogel (aerogel block or aerogel particle) can be obtained. That is, it is possible to obtain an aerogel obtained by drying a wet gel generated from the sol.

The method of drying is not particularly limited, and known atmospheric pressure drying, supercritical drying, or freeze drying can be used. Among these methods, normal-pressure drying or supercritical drying can be used from the viewpoint of easily producing a low-density aerogel. In addition, from the viewpoint that production can be performed at low cost, atmospheric pressure drying can be used. In this embodiment, the normal pressure means 0.1 MPa (atmospheric pressure).

Aerogels can be obtained by drying the wet gel that has been washed and (if necessary) replaced with a solvent at a temperature lower than the critical point of the solvent used for drying under atmospheric pressure. The drying temperature varies depending on the type of the solvent to be replaced (the solvent used for cleaning without solvent replacement), but in view of the existence of drying at a particularly high temperature, the evaporation rate of the solvent is accelerated and large cracks occur in the gel. In the case, it can be set to 20 ° C to 150 ° C. The drying temperature may be 60 ° C to 120 ° C. The drying time varies depending on the capacity of the wet gel and the drying temperature, and it can be set to 4 to 120 hours. Furthermore, the case where drying is accelerated by applying a pressure below the critical point within a range that does not impede productivity is also included in normal pressure drying.

In addition, aerogels can also be obtained by supercritical drying the wet gel that has been washed and (if necessary) replaced with a solvent. Supercritical drying can be performed by a known method. Examples of the method for performing supercritical drying include a method of removing a solvent at a temperature and pressure higher than a critical point of a solvent contained in a wet gel. Alternatively, as a method for performing supercritical drying, there can be mentioned a method in which a wet gel is immersed in liquefied carbon dioxide under conditions of, for example, 20 ° C to 25 ° C and about 5 MPa to 20 MPa. After all or a part of the contained solvent is replaced with carbon dioxide having a critical point lower than the solvent, the carbon dioxide is removed alone, or a mixture of carbon dioxide and the solvent is removed.

The aerogel obtained by such normal-pressure drying or supercritical drying can be further dried at 105 ° C to 200 ° C for about 0.5 to 2 hours under normal pressure. This makes it easier to obtain an aerogel having a low density and small pores. The additional drying may be performed at 150 ° C to 200 ° C under normal pressure.

(Grinding step) Without performing the wet gel pulverizing step, the aerogel (aerogel block) obtained by drying is pulverized to obtain aerogel particles. For example, it can be performed by putting aerogel into a jet mill, a roll mill, a bead mill, a hammer mill, and the like, and operating at a moderate rotation speed and time.

<Coating liquid> The coating liquid contains the aerogel particles having a specific surface area of 350 m ² / g or less, a binder resin, and a liquid medium. The coating liquid may also be a mixture of the aerogel particles, a binder resin, and a liquid medium. The pores of the aerogel particles in the coating liquid may be filled with a liquid medium. Furthermore, those having a high viscosity (for example, 1000 mPa · s or more) in the coating liquid may be referred to as a paste.

The binder resin has a function of adhering aerogel particles to each other after a coating film is formed. Examples of the binder resin include epoxy resin, silicone resin, phenol resin, urea resin, melamine resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, and polyester resin. , Acrylic resin (polymer containing acrylate or methacrylate as the main structural unit), polyvinyl chloride resin, polyvinyl acetate resin, polyamide resin, polyimide resin, cellulose resin, polymer Vinyl resin, etc. In addition, as the binder resin, an acrylic resin (a polymer including acrylic acid, acrylate, methacrylic acid, and methacrylic acid salt as a structural unit), polyvinyl alcohol, polyethylene oxide, and polyethylene glycol can also be used. Alcohol and so on. Among these adhesive resins, silicone resins, acrylic resins, phenol resins, and polyester resins can be preferably used from the viewpoints of heat resistance and toughness.

Examples of the cellulose-based resin include hydroxypropylmethyl cellulose, carboxymethyl cellulose ammonium, and hydroxyethyl methyl cellulose. Examples of the polyvinyl resin include polyvinyl alcohol and polyvinylpyrrolidone.

Examples of the acrylic resin include polyacrylic acid, an acrylic copolymer, a polyacrylate, and an acrylate copolymer.

When the binder resin is a thermosetting resin, the coating liquid may further contain a curing agent. The curing agent is not particularly limited, and can be appropriately changed according to the type of the thermosetting resin. For example, when the thermosetting resin is an epoxy resin, a known epoxy resin curing agent can be used as the curing agent. Examples of the epoxy resin hardener include amine-based hardeners, acid anhydride-based hardeners, and polyamine-based hardeners. From the viewpoint of reactivity, amine-based hardeners and polyamines are preferably used. Department of hardener.

Examples of the liquid medium include water and organic solvents. The organic solvent is not particularly limited as long as it can disperse the aerogel particles, and examples thereof include aromatics such as toluene, xylene, mesitylene, cumene, and p-cymene. Hydrocarbons; aliphatic hydrocarbons such as hexane, heptane, pentane; ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane; methanol, ethanol, isopropanol, butanol, ethylene glycol, propylene glycol, etc. Alcohols; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone; methyl acetate, ethyl acetate, butyl acetate And other esters; N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, and other amines. Among these, from the viewpoints of volatility and boiling point, alcohols and ketones can be used, and alcohols can be particularly preferably used. Alcohols and ketones are easy to mix with water, water-based resins, etc., so they are also preferred when used in combination with these ingredients.

The coating liquid may further contain components other than the binder resin and the liquid medium. Examples of the other components include a thickener, a fibrous substance, a pigment, a leveling agent, and a film-forming aid.

The thickener can increase the viscosity of the coating liquid and make the coating property better with respect to the object. Examples of the thickener include fine particles such as organic polymers, fumed silica, layered inorganic additives, and clay minerals.

The fibrous substance can exhibit the anchoring function between aerogel particles after the formation of the coating film, and can further improve the strength of the coating film. The fibrous substance is not particularly limited, and examples thereof include organic fibers and inorganic fibers. Examples of the organic fiber include a polyamide fiber, a polyimide fiber, a polyvinyl alcohol fiber, a polyvinylidene chloride fiber, a polyvinyl chloride fiber, a polyester fiber, and polyacrylonitrile. Fiber, polyethylene fiber, polypropylene fiber, polyurethane fiber, phenol fiber, polyether ester fiber, polylactic acid fiber, polycarbonate fiber, and the like. Examples of the inorganic fiber include glass fiber, carbon fiber, ceramic fiber, and metal fiber.

From the viewpoints of dispersibility, the filling amount of aerogel particles, and the viscosity of the coating liquid, the content of the aerogel particles in the coating liquid may be 0.1% to 30% by mass, or 1% to 25% by mass. quality%. In addition, the content of the aerogel particles in the coating liquid may be 2% by mass or more, or 3% by mass or more from the viewpoint of being suitable for coating using a trowel.

From the viewpoints of the adhesion of aerogel particles to each other and the thermal insulation of the coating film, the content of the binder resin in the coating liquid may be 1% to 40% by mass, or 1% to 30% by mass. .

For example, with respect to 100 parts by mass of aerogel particles, the content of the binder resin in the coating liquid may be set to 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, and 20 parts by mass. More than. Thereby, the aerogel particles are easily and firmly adhered by the adhesive resin, and the strength of the coating film is further improved.

In addition, for example, the content of the binder resin may be 150 parts by mass or less, or 130 parts by mass or less, or 100 parts by mass or less, and 90 parts by mass or less with respect to 100 parts by mass of the aerogel particles. Thereby, the ratio of the aerogel particle in a coating film becomes high, and the heat insulation property of a coating film is further improved.

From the viewpoints of dispersibility in the coating liquid and good performance of the anchoring function, the content of the fibrous substance in the coating liquid may be 1 to 50% by mass, or 1 to 30% by mass. quality%.

For example, the content of the fibrous substance in the coating liquid may be 5 parts by mass or more, may be 7 parts by mass or more, and may be 9 parts by mass or more with respect to 100 parts by mass of the aerogel particles. Thereby, the anchoring effect of the fibrous substance is easily obtained, and the strength of the coating film is further improved.

In addition, for example, the content of the fibrous substance may be 50 parts by mass or less with respect to 100 parts by mass of the aerogel particles, 35 parts by mass or less, 25 parts by mass or less, and 20 parts by mass or less. It may be 15 parts by mass or less. Thereby, the ratio of the aerogel particle in a coating film becomes high, and the heat insulation property of a coating film is further improved.

The content of the tackifier can be appropriately adjusted in such a manner that the viscosity of the coating liquid (for example, 1000 mPa · s or more) is desired. The viscosity of the coating liquid can also be increased by blending a binder resin, so it is not necessary to blend a tackifier in such cases.

The coating liquid of this embodiment can be widely applied to, for example, large-scale facilities such as factories and power stations to medium-sized and small-sized appliances such as home appliances and automobiles, and can reduce energy consumption under various conditions.

<Manufacturing method and coating film of coating film> The manufacturing method (coating film forming method) of the coating film includes self-containing aerogel particles having a specific surface area of 350 m ² / g or less, an adhesive resin, and a liquid medium. The step of removing the liquid medium from the coating liquid. More specifically, the method for producing a coating film may include a step of applying the coating liquid to an object, and a step of removing a liquid medium from the coating liquid applied to the object.

The method for applying the coating liquid to the object is not particularly limited, and examples thereof include dip coating, spray coating, spin coating, and roll coating. When forming a coating film, the coated coating liquid may be left in an environment of 0 ° C to 40 ° C, or the coated coating liquid may be heated (for example, 40 ° C to 150 ° C), and reduced in pressure. (For example, 10,000 Pa or less), or both.

In addition, since the coating liquid of this embodiment can also have a high viscosity (paste), as shown in FIG. 1, the coating liquid can be applied to an object using a trowel (metal spatula) or the like. In FIG. 1, a coating solution is applied to a bent portion of a pipe using a trowel. According to the coating liquid of this embodiment, it is possible to form a coating film having a thickness that is difficult to achieve with a conventional heat-insulating coating material in a short time. Specifically, in the case of such a coating liquid, a coating film having a thickness of at least about 2 mm can be formed by a single coating, which can be achieved compared with a conventional coating material that only obtains a coating film having a thickness of about 0.5 mm. Extremely efficient operation. Furthermore, since the coating liquid contains aerogel particles, a coating film having better thermal insulation performance than a conventional thermal insulation coating can be obtained.

Thereby, a coating film containing aerogel particles and a binder resin (or a hardened body thereof) having a specific surface area of 350 m ² / g or less can be obtained. The coating film may include aerogel particles in an amount of 40% to 95% by mass, and may include an adhesive resin (or a cured body thereof) of 1% to 50% by mass.

The content of the aerogel particles in the coating film may be, for example, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more. Thereby, the heat insulation of a coating film is improved further. The content of the aerogel particles in the coating film may be, for example, 95% by mass or less, or 90% by mass or less. Thereby, there exists a tendency for a coating film to be formed easily.

The thickness of the coating film is not particularly limited, and may be, for example, 0.01 mm to 5 mm.

The coating film has good water repellency because the aerogel particles of this embodiment are hydrophobic. That is, it is difficult to cause performance degradation (for example, a decrease in thermal insulation) caused by the water contained in the coating film, and the frequency of replacement of the coating film can be reduced. In addition, with good water repellency, it is not necessary to provide an exterior material for the purpose of protecting the coating film. The water repellency can be evaluated by measuring the contact angle between the coating film and water. The contact angle can be set to 90 ° or more, 110 ° or more, or 130 ° or more. The contact angle of the coating film can be adjusted according to, for example, the content of aerogel particles in the coating film, the type or content of the liquid medium, and the like.

The coating film has good heat resistance. The heat resistance can be evaluated by measuring the temperature at the time of 5% weight loss of the coating film. For example, in the case of using a simultaneous thermo-gravimetric simultaneous measurement device and measuring at a temperature rising rate of 10 ° C./min to 500 ° C., the temperature at a 5% weight reduction can be set to 150 ° C. or higher. It is 200 ° C or higher, and may be 250 ° C or higher. The heat resistance of a coating film can be adjusted according to the kind of adhesive resin, content in a coating film, etc., for example.

The material constituting the object is not particularly limited, and examples thereof include metals, ceramics, glass, resins, and composite materials thereof. The form of the object can be appropriately selected depending on the purpose or material to be used, and examples thereof include a bulk, a sheet, a powder, and a fiber.

Furthermore, the shape of the object may be more complicated. According to the coating liquid of this embodiment, it is also applicable to objects having complicated shapes, pipes having curved portions, and the like, which are difficult to attach a sheet-like or plate-like planar heat insulating material. A heat insulation layer is provided on the surface.

The coating film has excellent thermal insulation, heat resistance, flame retardancy, water repellency, and the like from aerogel. Due to this advantage, this coating film can be applied to extremely low temperature containers, space, construction, automotive (such as thermal insulation materials for automotive parts), home appliances, semiconductors, and industrial equipment (such as factories, power generation) Stations and other piping insulation materials) etc. In addition, the coating film can be used as a water-repellent material, a sound-absorbing material, a stationary vibration material, a catalyst supporting material, and the like, in addition to the use as a heat-insulating material. [Example]

Next, the present invention is further described in detail by the following examples, but these examples do not limit the present invention.

(Production of Aerogel Particles A) 100.0 parts by mass of PL-2L (produced by Fuso Chemical Industry Co., Ltd.) as a raw material containing silica particles, 80.0 parts by mass of water, and an acid catalyst 0.5 parts by mass of acetic acid, 1.0 part by mass of cetyltrimethylammonium bromide (made by Wako Pure Chemical Industries, Ltd.) as a cationic surfactant, and 150.0 parts by mass of urea as a thermally hydrolyzable compound 60.0 parts by mass of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KBM-13) and 20.0 parts by mass of dimethyldimethoxysilane (as a silicon compound) were added to the mixture. Manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KBM-22), 20.0 parts by mass of a two-terminal difunctional alkoxy-modified polysiloxane compound having the structure represented by the general formula (B) (hereinafter, (Referred to as "polysiloxane compound A"), and reacted at 25 ° C for 2 hours to obtain a sol. The obtained sol was gelatinized at 60 ° C, and then aged at 60 ° C for 48 hours to obtain a wet gel.

The "polysiloxane compound A" was synthesized as follows. First, in a 1-liter three-necked flask equipped with a stirrer, a thermometer, and a Dessert condenser, 100.0 parts by mass of dimethylpolysiloxane XC96-723 (silicon high-tech materials ( Momentive Performance Materials Japan) (manufactured by the contract company, product name), 181.3 parts by mass of methyltrimethoxysilane and 0.50 parts by mass of third butylamine were mixed and reacted at 30 ° C for 5 hours. Thereafter, the reaction solution was heated at 140 kC for 2 hours under a reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining a difunctional alkoxy-modified polysiloxane compound (polysiloxane compound A) at both ends. .

After that, the obtained moist gel was transferred to a plastic bottle and sealed, and then subjected to an Extreme Mill (manufactured by AS ONE Co., Ltd., MX-1000XTS) at 27,000 rpm. It was pulverized for 10 minutes to obtain a particulate wet gel. The obtained particulate wet gel was immersed in 2500.0 parts by mass of methanol, and washed at 25 ° C. for 24 hours. This washing operation was performed a total of 3 times while changing to new methanol. Then, the washed particulate wet gel was immersed in 2500.0 parts by mass of heptane as a low surface tension solvent, and the solvent was replaced at 25 ° C. for 24 hours. This solvent replacement operation was performed a total of 3 times while changing to new heptane. The washed and solvent-replaced particulate wet gel was dried under normal pressure at 40 ° C for 96 hours, and then further dried at 150 ° C for 2 hours. Finally, it was applied to a sieve (manufactured by Tokyo Screen Co., Ltd., with a hole diameter of 45 μm and a wire diameter of 32 μm) to obtain a structure represented by the general formula (3), general formula (4), and general formula (5). Aerogel particles A.

(Preparation of Aerogel Particle B) As the aerogel particle B, JIOS AeroVa (registered trademark, manufactured by JIOS AEROGEL CORPORATION, product name) was prepared.

(Example 1) In a 300 mL separable flask, 10 g of aerogel particles A, glass fibers (manufactured by Nittobo Industries Ltd., CS 3 PE-908, average fiber length 3 mm), 1 g, 35 g of propanol (Wako Pure Chemical Industries, Ltd., reagent) and 1 g of carboxymethyl cellulose ammonium (Wako Pure Chemical Industries, Ltd., reagent), using a mechanical stirrer and stirring at 150 rpm for 15 minutes, Thus, an isopropanol dispersion was obtained. Then, 50 g of water was added to the dispersion liquid, and carboxymethyl cellulose ammonium was dissolved to obtain a coating liquid 1.

(Other Examples and Comparative Examples) A coating liquid was prepared in the same manner as in Example 1 except that the preparation materials and the mixing amount of the coating liquid were changed as shown in Table 1, thereby obtaining coating liquids 2 to 5. The viscosity of the coating liquids in the examples all exceeded 10,000 mPa · s.

[Table 1] (Unit: g) * CMC-NH ₄ : manufactured by Wako Pure Chemical Industries, Ltd., carboxymethyl cellulose ammonium glass fiber: manufactured by Nitto Textile Co., Ltd., CS 3 PE-908, average fiber length 3 mm Vinyl fiber : Kuraray Co., Ltd., VPB303, average fiber length 3 mm

(Specific Surface Area Measurement) The BET specific surface area of the aerogel particles was measured using a gas adsorption amount measuring device (Autosorb-iQ (Autosorb is a registered trademark) manufactured by a contract company of Quantachrome Instruments Japan). The specific surface area of aerogel particle A was 125 m ² / g, and the specific surface area of aerogel particle B was 716 m ² / g.

(Measurement of average particle size) A dispersion was prepared by adding the aerogel particles to ethanol in an amount of 0.5% by mass, and applying a 50 W ultrasonic homogenizer to the mixture for 20 minutes. 10 mL of the obtained dispersion was poured into Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name), and the particle diameter was measured at 25 ° C. with a refractive index of 1.3 and an absorption of 0. Then, the particle diameter at 50% (volume basis) of the cumulative value in the obtained particle size distribution was set as the average particle diameter D50. The average particle diameter D50 of the aerogel particles A is 20 μm, and the average particle diameter D50 of the aerogel particles B is 8.7 μm.

(Evaluation of Film Formability) The coating liquids of Examples and Comparative Examples were applied to aluminum foil using a metal doctor blade so that the thickness became 2 mm. Then, the liquid medium was removed from the coating liquid by heating at 120 ° C. for 1 hour to obtain a coating film. The obtained coating film was visually observed, and the film-forming property of the coating liquid was evaluated. That is, the case where there is no crack and has a good appearance is evaluated as a good film formability, and the case where a crack is generated is evaluated as a poor film formability. The evaluation results are shown in Table 2.

[Table 2]

In addition, regarding Example 1 and Example 2, the coating film obtained in the film-forming evaluation was cut into 30 cm × 30 cm for each aluminum foil, and the aluminum foil was removed. As a result, the coating film could be peeled off without damaging the coating film. Aluminum foil. In addition, when the thermal insulation property of the coating film was evaluated by the steady state method, the thermal conductivity was very low (32 mW / m · K to 35 mW / m · K).

(Water Repellency Evaluation) The water repellency of the coating film obtained in Example 1 was evaluated by measuring the contact angle with water. The coating film was processed into a size of 50 mm × 50 mm as a measurement sample. Then, about 3 μL of pure water was dropped on the surface of the measurement sample, and the contact angle after 5 minutes was measured. As a measuring device, a contact angle meter (Nick Co., Ltd., LSE-B100) was used. The contact angle of the coating film was 145 °.

(Evaluation of heat resistance) The coating film obtained in Example 1 was used to evaluate heat resistance. First, the obtained coating film was peeled from an aluminum foil and used as a measurement sample. As a measuring device, a differential thermogravimetric simultaneous measuring device (Hitachi High-Tech Science Co., Ltd., TG / DTA STA7300) was used to perform the measurement until the temperature was raised to 500 ° C at a rate of 10 ° C / min. , And record the temperature when the weight is reduced by 5%. In addition, since the weight change due to the evaporation of water is excluded, the weight of the coating film at 100 ° C. is taken as the reference weight (zero point). The temperature at which the 5% weight reduction of the coating film was 320 ° C.

(Evaluation of thermal insulation performance) The thermal insulation performance of the coating film obtained using the coating liquid of Example 1 was evaluated. First, using a metal doctor blade, the coating liquid was applied to an aluminum anodized aluminum plate (50 mm × 50 mm, thickness 0.5 mm) so as to have a predetermined thickness. This coating solution was dried at room temperature (25 ° C) for 2 hours, and then dried with a dryer heated to 60 ° C (manufactured by Espec Corporation, PERFECT OVEN SPHH-301) and further After being dried for 2 hours, a plurality of evaluation samples having different coating film thicknesses were prepared. In the case where a thick coating film is obtained, the coating is temporarily applied again, and then dried at room temperature for 2 hours, and then the coating is performed again. Repeat this operation until the desired thickness is obtained. Furthermore, a coating film having a thickness of about 2 mm can be obtained by one coating. The evaluation sample was placed with the side of the aluminum plate facing a glass heater (manufactured by Blast Co., Ltd., S-101), and the temperature was raised to 150 ° C. The temperature of the surface of the evaluation sample (the temperature of the surface of the coating film) after being held at 150 ° C. for 1 hour was measured using an infrared thermometer (manufactured by Apiste Corporation, FSV-1200-L16). As the thickness of the coating film became 1.0 mm, 2.0 mm, 5.0 mm, and 10.0 mm, the surface temperature at 150 ° C decreased without the coating film (the thickness of the coating film was 0 mm) to 130 ° C and 100 ° C. , 75 ° C, 60 ° C.

no

FIG. 1 is a diagram illustrating a method of applying a coating liquid to an object using a trowel.

Claims (5)

A coating liquid comprising aerogel particles having a specific surface area of 350 m ² / g or less, a binder resin, and a liquid medium. The coating liquid according to item 1 of the patent application scope, wherein the liquid medium comprises an organic solvent. The coating liquid according to item 1 or item 2 of the patent application scope, wherein the adhesive resin is selected from the group consisting of epoxy resin, silicone resin, phenol resin, urea resin, melamine resin, and 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 poly At least one of the group consisting of a vinyl resin. A method for manufacturing a coating film, comprising the step of removing the liquid medium from a coating liquid according to any one of claims 1 to 3 of a patent application scope. A coating film comprising aerogel particles having a specific surface area of 350 m ² / g or less, and an adhesive resin or a hardened body thereof.