JPWO2018142530A1 - Manufacturing method of structure - Google Patents

Abstract

The present invention relates to a method for manufacturing a structure in which an airgel layer is formed, the method comprising a step of forming an airgel layer from a mist-like sol.

Description

  The present invention relates to a method for manufacturing a structure.

  As an airgel, for example, silica aerogel is known (see, for example, Patent Document 1). Silica airgel is generally produced by a method using a supercritical drying method.

  Patent Document 2 describes that silica xerogel is produced without using a supercritical drying method.

U.S. Pat. No. 4,402,927 JP 2011-93744 A

  By the way, when manufacturing the structure in which the airgel layer was formed, it is required to form an airgel layer with less unevenness with respect to an object which is an object for forming the airgel layer.

  This invention is made | formed in view of said situation, and it aims at providing the manufacturing method of the structure which can suppress the nonuniformity of an airgel layer.

  As a result of intensive studies to achieve the above object, the present inventor has found a method of forming an airgel layer using a mist-like sol, and has completed the present invention.

  The present invention provides a method for producing a structure in which an airgel layer is formed, the method comprising the step of forming an airgel layer from a mist-like sol.

  According to the method for manufacturing a structure according to the present invention, a structure in which unevenness of the airgel layer is suppressed can be manufactured. Moreover, according to the structure manufacturing method according to the present invention, a thick airgel layer can be formed without depending on the shape of the object forming the airgel layer.

  By the way, when producing an airgel by the supercritical drying method, an alcogel and a dispersion medium (solvent used for drying) are introduced into a high-pressure vessel, and the dispersion medium is subjected to a temperature and pressure above its critical point to form a supercritical fluid. Thus, a method of removing the solvent contained in the alcogel is common. Supercritical drying is usually a high pressure process. When supercritical drying is performed in producing airgel, capital investment for special equipment that can withstand supercriticality and much labor and time are required, resulting in high production costs and batch production. Therefore, the production efficiency may not be sufficient. Moreover, when performing supercritical drying, it is thought that the object which forms an airgel layer is limited to the material which can endure supercritical. On the other hand, in one embodiment of the structure manufacturing method according to the present invention, a structure can be obtained without using supercritical drying. Furthermore, the structure manufactured by the method for manufacturing a structure according to the present invention has an excellent function as an airgel and the airgel is prevented from falling off.

  By the way, airgel tends to be very brittle. For example, a mass of airgel may be damaged simply by trying to lift it by hand. On the other hand, conventionally, an airgel sheet using an airgel and a reinforcing material has been devised. However, since the airgel itself is fragile, there are problems in workability such as the sheet is torn by impact or bending work, and the airgel powder is dropped from the sheet. Meanwhile, in the present invention, the sol is selected from the group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may contain at least one kind. According to the airgel layer formed from such a sol, the problem of workability can be easily solved and the heat insulation can be improved. In addition, according to the airgel layer formed from such a sol, the flexibility is improved, so that the aerogel is further prevented from falling off, and the structure including such an airgel layer has the flexibility of the main body. It becomes easy to bend according to.

  The sol may further contain silica particles. Thereby, heat insulation and a softness | flexibility improve further.

  The average primary particle diameter of the silica particles may be 1 to 500 nm. Thereby, heat insulation and a softness | flexibility further improve easily.

  The diameter of the sol droplet may be 0.1 to 1000 μm. According to such a sol, a thick airgel layer can be formed more easily, and cracks in the airgel layer are further suppressed.

  The sol may contain a solvent having a boiling point of less than 200 ° C. According to such a sol, a thick airgel layer can be formed more easily, and cracks in the airgel layer are further suppressed.

  In the manufacturing method, the structure includes a main body and a coating layer that covers at least a part of the surface of the main body, and at least on the coating layer so that the coating layer becomes an intermediate layer. An airgel layer may be formed. Thereby, the adhesiveness of the airgel layer is further improved, and peeling and dropping of the airgel layer are further suppressed.

  The coating layer may contain a filler. Thereby, peeling and dropping of the airgel layer at the time of high temperature use are further suppressed.

  The filler may be an inorganic filler. This improves the heat resistance of the coating layer (intermediate layer) and further suppresses peeling and dropping off under high temperature conditions.

  The content of the filler may be 0.1 to 70% by volume with respect to the total volume of the coating layer. Thereby, heat resistance and the adhesiveness of a main-body part and an airgel layer further improve.

  According to the method for manufacturing a structure according to the present invention, a structure in which unevenness of the airgel layer is suppressed can be manufactured. Moreover, according to the structure manufacturing method of the present invention, a thick airgel layer can be formed without depending on the shape of the main body. Furthermore, the structure manufactured by the method for manufacturing a structure according to the present invention has excellent heat insulating properties, water repellency, specific optical characteristics, and specific electrical characteristics, and airgel drop-off is suppressed. .

It is sectional drawing which shows typically the structure obtained by the manufacturing method of the structure which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the structure obtained by the manufacturing method of the structure which concerns on one Embodiment of this invention. It is a figure which shows the calculation method of the biaxial average primary particle diameter of particle | grains. It is a figure explaining the manufacturing method of the structure concerning one embodiment of the present invention. It is a figure explaining the manufacturing method of the structure concerning one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as the case may be. However, the present invention is not limited to the following embodiments.

<Definition>
In this specification, the numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a numerical range in a certain step may be replaced with the upper limit value or the lower limit value of a numerical range in another step. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples. “A or B” only needs to include either A or B, and may include both. The materials exemplified in the present specification can be used singly or in combination of two or more unless otherwise specified. In the present specification, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. means.

  First, the structure obtained by the structure manufacturing method according to the present embodiment will be described.

<Structure>
FIG. 1 is a cross-sectional view schematically showing a structure obtained by the structure manufacturing method according to the present embodiment. As shown in FIG. 1, the structure (aerogel composite, airgel composite structure) 100 has an airgel layer 5 formed on an object 10 (hereinafter also referred to as “object”) that is an object for forming an airgel layer. Has a structure. The structure 100 may have, for example, a structure in which the airgel layer 5 is integrally formed on the object 10. That is, the structure 100 may include the target object 10 and the airgel layer 5 integrally bonded to the target object 10. In the structure 100, for example, the object 10 and the airgel layer 5 may be integrally fixed. The airgel layer 5 is an airgel layer formed from a mist-like (mist-like) sol. The object 10 is a support part that supports the airgel layer 5, for example. The structure 100 according to the present embodiment is excellent in heat insulation and water repellency, is excellent in unique optical characteristics and electrical characteristics, and is suppressed from falling off the airgel.

  The structure 100 according to the present embodiment is a structure including an airgel layer 5 disposed on at least a part (a part or the whole) of the surface 10a of the object 10, for example. Such a structure 100 is considered to exhibit excellent heat insulating properties, water repellency, unique optical characteristics and electrical characteristics, and to prevent the airgel from falling off. The surface 10a on which the airgel layer 5 is disposed may be a flat surface, a composite plane (combination of inclined surfaces), or a curved surface.

  As illustrated in FIG. 2, the object 10 may include a main body 3 and a covering layer 4 that covers at least a part of the surface of the main body 3. In this case, the airgel layer 5 is formed on at least the coating layer 4 so that the coating layer 4 becomes an intermediate layer.

  FIG. 2 is a cross-sectional view schematically showing a structure obtained by the structure manufacturing method according to the present embodiment. The structure (aerogel composite, airgel composite structure) 200 includes a main body 3 and a coating layer 4 that covers at least a part of the surface of the main body 3 so that the coating layer 4 is an intermediate layer. At least the airgel layer 5 is formed on the coating layer 4. That is, the object 10 may include the main body 3 and the coating layer 4 that covers at least a part of the surface of the main body 3. For example, the structure 200 may include the main body 3 and the airgel layer 5 that is integrally joined to the main body 3 via the coating layer 4 that is an intermediate layer. In the structure 200, the airgel layer 5 may be integrally joined to the main body part 3 via the coating layer 4 serving as an intermediate layer. In the structure 200, the main body 3, the coating layer 4, and the airgel layer 5 may be integrated. The main body 3 is, for example, a support that supports the airgel layer 5. The structure 200 according to the present embodiment is excellent in adhesiveness and adhesion between the main body 3 and the airgel layer 5, and can further suppress the peeling and dropping of the airgel layer 5. The structure 200 is also excellent in the protection performance of the main body 3.

  The structure 200 according to the present embodiment includes, for example, a coating layer (also referred to as “intermediate layer”) 4 disposed on at least a part (a part or the whole) of the surface 3a of the main body 3, and the main body of the coating layer 4 The structure includes an airgel layer 5 disposed on at least a part (a part or the whole) of the surface 4a opposite to the part 3. In the structure 200 according to the present embodiment, the main body 3 and the airgel layer 5 are integrally fixed via a covering layer 4 serving as an intermediate layer. The surface 3a on which the coating layer 4 is disposed may be a flat surface, a composite plane (a combination of inclined surfaces), or a curved surface.

  In FIG. 2, the aspect in which the structure includes the main body portion and the covering layer that covers the main body portion 3 has been described. However, the covering layer is not necessarily required. That is, the target object that forms the airgel layer may be the main body.

  When the object is a main body, the structure is a structure including an airgel layer disposed on at least a part (a part or the whole) of the surface of the main body, and the main body and the airgel layer are directly It has a contact structure. Also in this aspect, the surface of the main body portion on which the airgel layer is disposed may be a flat surface, a composite plane (combination of inclined surfaces), or a curved surface.

  The airgel layer 5 includes a hydrolyzable functional group or a silicon compound having a condensable functional group (silicon compound) and a hydrolysis product (hydrolyzable functional group) of the silicon compound having the hydrolyzable functional group. A silicon compound (silicon) having a hydrolyzable functional group or a condensable functional group, which may be formed from a sol containing at least one selected from the group consisting of hydrolyzed silicon compounds) Compound), and condensation of sol containing at least one selected from the group consisting of hydrolysis products of silicon compounds having hydrolyzable functional groups (silicon compounds in which hydrolyzable functional groups are hydrolyzed) It may be a layer composed of a dried product of a wet gel (a wet gel derived from the sol). That is, the sol comprises at least one selected from the group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. You may contain. When the airgel layer is such, both heat insulation and flexibility can be achieved at a high level, and the airgel can be prevented from dropping off.

{Object}
As described above, the target object that forms the airgel layer may include a main body part and a coating layer that covers at least a part of the surface of the main body part, or may be a main body part. .

(Main body)
Examples of the material constituting the main body include metal, ceramic, glass, resin, and composite materials thereof. For example, the main body may include at least one selected from the group consisting of metal, ceramic, glass, and resin. As the form of the main body, a block shape, a sheet shape, a spherical shape, a fiber shape, or the like can be adopted depending on the purpose or material to be used.

  The metal is not particularly limited, and examples thereof include a single metal, a metal alloy, and a metal on which an oxide film is formed. Examples of the metal include iron, copper, nickel, aluminum, zinc, titanium, chromium, cobalt, tin, gold, and silver. Depending on the material used in the sol production step described later, from the viewpoint of excellent corrosion resistance of the metal surface, simple metals such as titanium, gold and silver; iron and aluminum on which an oxide film is formed can be used as the metal.

  Examples of the ceramic include oxides such as alumina, titania, zirconia, and magnesia; nitrides such as silicon nitride and aluminum nitride; carbides such as silicon carbide and boron carbide; and mixtures thereof.

  Examples of the glass include quartz glass, soda glass, and borosilicate glass.

  Examples of the resin include polyvinyl chloride, polyvinyl alcohol, polystyrene, polyethylene, polypropylene, polyacetal, polymethyl methacrylate, polycarbonate, polyamide, and polyurethane.

  There is no restriction | limiting in particular in the shape of a main-body part, You may have any surface shape of a plane and a curved surface. Examples of the shape of the main body include a plate shape, a cylindrical shape, a spherical shape, and a rod shape. Examples of the cylindrical main body include piping.

  The surface roughness of the main body may be 100 nm or more, or 500 nm or more from the viewpoint of obtaining a good anchor effect and further improving the adhesion of the airgel layer.

(Coating layer (intermediate layer))
As described above, the object may include a coating layer. Examples of the material constituting the coating layer include organic materials, inorganic materials, and organic-inorganic hybrid materials.

  Examples of the organic material include urethane resin, polyester resin, acrylic resin, phenol resin, epoxy resin, polyimide, polyamideimide, polybenzimidazole, polyetheretherketone, silicone, and composite materials thereof. The organic material includes, for example, at least one selected from the group consisting of urethane resin, polyester resin, acrylic resin, phenol resin, epoxy resin, polyimide, polyamideimide, polybenzimidazole, polyetheretherketone, and silicone. It may be.

  From the viewpoint of improving the adhesion between the main body and the airgel layer, the organic material is, for example, from a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an isocyanate group, a mercapto group, a cyano group, an ester bond, a urethane bond, and an amide bond. A compound containing at least one selected from the group consisting of:

  Examples of the inorganic material include glass, a single metal, a metal alloy, a metal on which an oxide film is formed, ceramic, silicon carbide, silicon nitride, and sodium silicate. The inorganic material includes, for example, at least one selected from the group consisting of glass, simple metal, metal alloy, metal with an oxide film, ceramic, silicon carbide, silicon nitride, and sodium silicate. There may be.

  Examples of the metal include titanium, chromium, aluminum, copper, and platinum.

  Examples of the ceramic include alumina and zirconia.

  The inorganic material may further contain a binder. Examples of the binder include metal alkoxide and water glass.

  Examples of the organic-inorganic hybrid material include a composite material of the organic material and the inorganic material, an epoxy-silica hybrid material, and an acrylic-silica hybrid material.

  The material constituting the coating layer may be an inorganic material or an organic-inorganic hybrid material from the viewpoint of further improving the heat resistance, and the difference in thermal expansion between the main body and the coating layer when used in a high temperature environment. From the viewpoint of reducing and suppressing cracks, an organic-inorganic hybrid material may be used. From the viewpoint of suppressing cracks, a material having a low elastic modulus can also be used as a material constituting the coating layer.

  From the viewpoint of further improving the heat resistance, the coating layer may be, for example, a layer composed of ceramic (ceramic layer) and / or a layer composed of metal (metal layer).

  The said coating layer may contain a filler from a viewpoint which further improves heat resistance, a viewpoint which further suppresses a crack, and a viewpoint which further suppresses peeling and dropping | offset | release of an airgel layer at the time of high temperature use. The reason why the airgel layer is further prevented from peeling and falling off by containing the filler is, for example, that the thermal expansion coefficient of the coating layer is adjusted by containing the filler, and the main body, the coating layer, and the airgel at high temperatures. It is assumed that this is because the difference in thermal expansion coefficient generated between the layers is reduced.

  As said filler, an inorganic filler and an organic filler are mentioned, for example. The filler may be an inorganic filler from the viewpoint of improving the heat resistance of the coating layer and further suppressing peeling and dropping under high temperature conditions, and a thermal cycle when repeatedly used in a high temperature environment. From the viewpoint of improving reliability, an organic filler may be used. There is no restriction | limiting in particular in the shape of a filler, For example, a short fiber form, fine powder form, and a hollow form may be sufficient.

  Examples of the material constituting the inorganic filler include silica, mica, talc, glass, calcium carbonate, quartz, metal hydrate, metal hydroxide, and composite materials thereof. For example, the inorganic filler may include at least one selected from the group consisting of silica, mica, talc, glass, calcium carbonate, quartz, metal hydrate, and metal hydroxide.

  Examples of the metal hydrate include potassium aluminum sulfate 12 hydrate, magnesium nitrate hexahydrate, and magnesium sulfate heptahydrate. Examples of the metal hydroxide include aluminum hydroxide and magnesium hydroxide. The aluminum hydroxide may be boehmite type aluminum hydroxide.

  From the viewpoint of further improving heat resistance and flame retardancy, the inorganic filler may contain silica, glass, or metal hydroxide, and the glass may be glass short fiber or hollow glass. The metal hydroxide may be magnesium hydroxide or boehmite type aluminum hydroxide.

  Examples of the material constituting the organic filler include phosphate ester, polyester, polystyrene, pulp, elastomer, and composite materials thereof. For example, the organic filler may include at least one selected from the group consisting of phosphate ester, polyester, polystyrene, pulp, and elastomer. The pulp may be in the form of pulp floc. The organic filler may contain an elastomer because the thermal expansion difference between the main body and the coating layer is relieved of stress and cracks are easily suppressed.

  Examples of the elastomer include a styrene elastomer, an olefin elastomer, a urethane elastomer, a polybutadiene elastomer, a fluorine elastomer, and a silicone elastomer. Among these, from the viewpoint of further improving heat resistance and water repellency, a fluorine-based elastomer or a silicone-based elastomer can be used as the elastomer.

  The content of the filler contained in the coating layer may be 0.1% by volume or more based on the total volume of the coating layer from the viewpoint of further improving the heat resistance. The content of the filler contained in the coating layer is based on the total volume of the coating layer from the viewpoint of improving workability when forming the coating layer and improving the adhesion between the main body and the airgel layer. 70 volume% or less, 50 volume% or less, 40 volume% or less, or 30 volume% or less. From these viewpoints, the content of the filler contained in the coating layer may be 0.1 to 70% by volume or 0.1 to 50% by volume with respect to the total volume of the coating layer. 0.1-40 volume% may be sufficient and 0.1-30 volume% may be sufficient.

  The coating layer may contain, for example, an adhesion improver, a flame retardant, and an antioxidant.

  Examples of the adhesion improver include urea compounds such as urea silane; and silane coupling agents.

  Examples of the flame retardant include melamine cyanurate and bis (pentabromophenyl) ethane.

  Examples of the antioxidant include an antioxidant made of ceramic powder such as alumina and zirconia and an inorganic binder.

  The thermal decomposition temperature of the coating layer may be 300 ° C. or higher from the viewpoint of further improving the heat resistance. Here, the thermal decomposition temperature of 300 ° C. or higher means that the material is heated at a rate of 10 ° C./temperature in a nitrogen atmosphere using a high-temperature differential thermothermal gravimetric measuring device TG / DTA7300 manufactured by SII Nanotechnology. When measured under the condition of minutes, it means that the temperature when the weight is reduced by 5% is 300 ° C. or higher.

  Even if the thickness of the coating layer is 0.01 μm or more from the viewpoint of reducing damage due to impact and the like, and improving the protection performance of the main body, and further improving the adhesion between the main body and the airgel layer. It may be 0.1 μm or more, or 1 μm or more. From the viewpoint of suppressing cracks during formation of the coating layer, the thickness of the coating layer may be 1000 μm or less, may be less than 1000 μm, or may be 500 μm or less. The thickness of the coating layer may be 100 μm or less from the viewpoint of suppressing cracks due to a difference in thermal expansion between the main body portion and the coating layer and improving the thermal cycle stability. From these viewpoints, the thickness of the coating layer may be 0.01 to 1000 μm, 0.01 to 500 μm, or 0.01 to 100 μm.

  By using a coating layer having a low water absorption rate, it is possible to further reduce the chemical influence of the water-soluble acidic substance or basic substance and inorganic salts on the main body. Specifically, for example, the chemical change (corrosion, modification, etc.) of the main body due to the influence of a sol coating solution described later can be further reduced. That is, it is difficult to be influenced by the conditions for forming the airgel layer and the composition of the sol coating solution, and the structure can be easily manufactured. From these viewpoints, the water absorption rate of the coating layer may be less than 5%, less than 4%, or less than 3%.

  The water absorption rate of the coating layer is a change in mass when a test piece obtained by molding the constituent material of the coating layer into a size of 20 mm × 20 mm × 0.5 mm is left in a constant temperature and humidity chamber at 60 ° C. and 90% RH for 6 hours. Means rate.

  By using a coating layer having a large surface roughness, the adhesion between the coating layer and the airgel layer can be further improved, and peeling and dropping of the airgel layer can be further suppressed. The surface roughness (Ra) of the coating layer may be 200 nm or more, or 300 nm or more from the viewpoint of obtaining a good anchor effect between the coating layer and the airgel layer and further improving the adhesion of the airgel layer. It may be 500 nm or more.

  The surface roughness of the coating layer can be adjusted, for example, by forming a coating layer on the main body and then subjecting the coating layer to polishing (polishing) or roughening (roughening). The polishing process or the roughening process may be a mechanical process or a chemical process. Examples of processing methods include mechanical processing with abrasive grains such as slurry or abrasive; wet etching with acid or base, oxidizing agent or reducing agent; and dry etching with sulfur hexafluoride or carbon tetrafluoride. It is done.

  The coating layer may be a single layer or a plurality of layers.

{Airgel layer}
The airgel layer according to the present embodiment is made of airgel and is formed from a mist-like sol. In a narrow sense, dry gel obtained by using supercritical drying method for wet gel is aerogel, dry gel obtained by drying under atmospheric pressure is xerogel, dry gel obtained by freeze-drying is cryogel and However, in the present embodiment, the obtained low-density dried gel is referred to as “aerogel” regardless of the drying method of the wet gel. That is, in this embodiment, “aerogel” is a gel in a broad sense, “Gel composed of a microporous solid in which the dispersed phase is a gas” (a gel composed of a microporous solid in which the dispersed phase is a gas). "Means. In general, the inside of the airgel has a network-like fine structure, and has a cluster structure in which airgel particles of about 2 to 20 nm (particles constituting the airgel) are bonded. There are pores less than 100 nm between the skeletons formed by these clusters. Thereby, the airgel has a three-dimensionally fine porous structure. In addition, the airgel in this embodiment is a silica airgel which has a silica as a main component, for example. Examples of the silica airgel include so-called organic-inorganic hybrid silica airgel into which an organic group (such as a methyl group) or an organic chain is introduced. The airgel layer may be a layer containing an airgel having a structure derived from polysiloxane.

  The airgel which concerns on this embodiment may have a void | hole smaller than the mean free path | route of gas from a viewpoint which is excellent in heat insulation, and a viewpoint which exhibits a specific electrical property, for example. The primary particle diameter of the airgel according to the present embodiment may be, for example, about several nm from the viewpoint of exhibiting unique optical characteristics.

  The airgel according to the present embodiment includes a silicon compound having a hydrolyzable functional group or a condensable functional group (in the molecule) and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may be a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group. That is, the airgel according to the present embodiment includes a hydrolyzable functional group or a silicon compound having a condensable functional group (in the molecule) and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may be obtained by drying a wet gel produced from a sol containing at least one selected from the group consisting of: By adopting these aspects, the heat insulation and flexibility are further improved. The condensate may be obtained by a condensation reaction of a hydrolysis product obtained by hydrolysis of a silicon compound having a hydrolyzable functional group, and is not a functional group obtained by hydrolysis. It may be obtained by a condensation reaction of a silicon compound having a group. The silicon compound may have at least one of a hydrolyzable functional group and a condensable functional group, and may have both a hydrolyzable functional group and a condensable functional group. In addition, each airgel mentioned later is a group which consists of a hydrolysis product of the silicon compound which has a hydrolyzable functional group or a condensable functional group, and the said hydrolyzable functional group in this way. It may be a dried product of a wet gel that is a condensate of a sol containing at least one selected from the above (obtained by drying a wet gel produced from the sol).

  Moreover, such an airgel is considered to be excellent in heat insulation and have a very low refractive index. Therefore, for example, it is considered that it can be used for a heat insulating material, a light reflecting material, and the like.

  Since conventional silica airgel is generally hydrophilic, it is easy to absorb water, and it is considered that the function as an airgel is likely to be lowered. Airgel according to the present embodiment (at least selected from the group consisting of hydrolyzable functional groups or silicon compounds having a condensable functional group, and hydrolysis products of silicon compounds having the hydrolyzable functional group) It is considered that an airgel formed from a sol containing one kind is unlikely to deteriorate in function due to water absorption.

  The airgel layer contains at least one selected from the group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may be a layer composed of a dried product of a wet gel that is a condensate of the sol. That is, the airgel layer is at least one selected from the group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may be composed of a layer formed by drying a wet gel produced from a sol containing.

  The airgel according to the present embodiment can contain polysiloxane having a main chain including a siloxane bond (Si—O—Si). The airgel can have the following M unit, D unit, T unit or Q unit as a structural unit.

  In the above formula, R represents an atom (hydrogen atom or the like) or an atomic group (alkyl group or the like) bonded to a silicon atom. The M unit is a unit composed of a monovalent group in which a silicon atom is bonded to one oxygen atom. The D unit is a unit composed of a divalent group in which a silicon atom is bonded to two oxygen atoms. The T unit is a unit composed of a trivalent group in which a silicon atom is bonded to three oxygen atoms. The Q unit is a unit composed of a tetravalent group in which a silicon atom is bonded to four oxygen atoms. Information on the content of these units can be obtained by Si-NMR.

The airgel according to the present embodiment may contain silsesquioxane. Silsesquioxane is a polysiloxane having the above T unit as a structural unit, and has a composition formula: (RSiO _1.5 ) _n . Silsesquioxane can have various skeletal structures such as a cage type, a ladder type, and a random type.

  Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group (excluding the functional group corresponding to the hydrolyzable 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. Each of the hydrolyzable functional group and the condensable functional group may be used alone or in admixture of two or more.

  The silicon compound can include a silicon compound having an alkoxy group as a hydrolyzable functional group, and can also include a silicon compound having a hydroxyalkyl group as a condensable functional group. The silicon compound can have at least one selected from the group consisting of an alkoxy group, a silanol group, a hydroxyalkyl group and a polyether group from the viewpoint of further improving the flexibility of the airgel. The silicon compound can have at least one selected from the group consisting of an alkoxy group and a hydroxyalkyl group from the viewpoint of improving the compatibility of the sol.

  From the viewpoint of improving the reactivity of the silicon compound and reducing the thermal conductivity of the airgel, the number of carbon atoms of the alkoxy group and the hydroxyalkyl group can be 1 to 6, and the viewpoint of further improving the flexibility of the airgel 2-4 may be sufficient. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. Examples of the hydroxyalkyl group include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

  The following aspects are mentioned as an airgel which concerns on this embodiment. By adopting these aspects, it becomes easy to obtain an airgel excellent in water repellency and flexibility. By employing each aspect, an airgel having water repellency and flexibility according to each aspect can be obtained.

(First aspect)
The airgel according to the present embodiment includes a polysiloxane compound having a hydrolyzable functional group or a condensable functional group (in the molecule), and a hydrolysis product of the polysiloxane compound having the hydrolyzable functional group. Wet which is a condensate of sol containing at least one compound selected from the group consisting of (the hydrolyzable functional group hydrolyzed polysiloxane compound) (hereinafter sometimes referred to as “polysiloxane compound group”) It may be a dried gel. For example, the airgel according to the present embodiment includes a hydrolyzable functional group or a polysiloxane compound having a condensable functional group (in the molecule) and hydrolysis of the polysiloxane compound having the hydrolyzable functional group. It may be obtained by drying a wet gel produced from a sol containing at least one selected from the group consisting of products. That is, the airgel layer is composed of a polysiloxane compound having a hydrolyzable functional group or a condensable functional group (in the molecule) and a hydrolysis product of the polysiloxane compound having the hydrolyzable functional group. It may be formed from a sol containing at least one selected from the group. In addition, each airgel mentioned later is also from the hydrolysis product of the polysiloxane compound which has a hydrolyzable functional group or a condensable functional group, and the polysiloxane compound which has the said hydrolyzable functional group in this way. It may be a wet gel dried product (obtained by drying a wet gel generated from the sol), which is a condensate of a sol containing at least one selected from the group.

  The airgel layer is at least one selected from the group consisting of a hydrolyzable functional group or a polysiloxane compound having a condensable functional group, and a hydrolysis product of the polysiloxane compound having a hydrolyzable functional group. It may be a layer composed of a dried product of a wet gel that is a condensate of sol containing That is, the airgel layer is selected from the group consisting of a hydrolyzable functional group or a polysiloxane compound having a condensable functional group, and a hydrolysis product of the polysiloxane compound having a hydrolyzable functional group. You may be comprised by the layer formed by drying the wet gel produced | generated from the sol containing at least 1 type.

  A polysiloxane compound having a hydrolyzable functional group or a condensable functional group is a reactive group different from the hydrolyzable functional group and the condensable functional group (hydrolyzable functional group and condensable functional group). May further have a functional group that does not fall under. The reactive group is not particularly limited, and examples thereof include an epoxy group, a mercapto group, a glycidoxy group, a vinyl group, an acryloyl group, a methacryloyl group, and an amino group. The epoxy group may be contained in an epoxy group-containing group such as a glycidoxy group. You may use the polysiloxane compound which has the said reactive group individually or in mixture of 2 or more types.

  Examples of the polysiloxane compound having a hydroxyalkyl group include compounds having a structure represented by the following general formula (A).

In formula (A), R ^1a represents a hydroxyalkyl group, R ^2a represents an alkylene group, R ^3a and R ^4a each independently represents 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. In formula (A), two R ^{1a s} may be the same or different, and similarly, two R ^{2a s} may be the same or different. In formula (A), two or more R ^{3a s} may be the same or different, and similarly, two or more R ^{4a s} may be the same or different.

By using a wet gel that is a condensate of a sol containing a polysiloxane compound having the above structure (wet gel generated from the sol), it is excellent in water repellency, and it is easier to obtain a flexible airgel with low thermal conductivity. . From the same viewpoint, the following features may be satisfied. In the formula (A), examples of R ^1a include a hydroxyalkyl group having 1 to 6 carbon atoms, and specifically include a hydroxyethyl group and a hydroxypropyl group. In formula (A), examples of R ^2a include an alkylene group having 1 to 6 carbon atoms, and specific examples include an ethylene group and a propylene group. In formula (A), R ^3a and R ^4a may each independently be an alkyl group having 1 to 6 carbon atoms or a phenyl group. The alkyl group may be a methyl group. In the formula (A), n may be 2 to 30, or 5 to 20.

  As the polysiloxane compound having the structure represented by the general formula (A), commercially available products can be used. For example, compounds such as X-22-160AS, KF-6001, KF-6002, KF-6003 and the like ( In any case, Shin-Etsu Chemical Co., Ltd.) and compounds such as XF42-B0970 and Fluid OFOH 702-4% (all manufactured by Momentive Co., Ltd.) can be mentioned.

  Examples of the polysiloxane compound having an alkoxy group include compounds having a structure represented by the following general formula (B).

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, and R ^4b and R ^5b each independently represent an alkyl group or an aryl group. , M represents an integer of 1-50. 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 the formula (B), two R ^{1b s} may be the same or different, and two R ^{2b s} may be the same or different. Similarly, R ^3b may be the same or different. In the 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. May be different.

By using a wet gel (wet gel generated from the sol) that is a condensate of a sol containing the polysiloxane compound having the above structure or a hydrolysis product thereof, it becomes easier to obtain a flexible airgel having low thermal conductivity. . From the same viewpoint, the following features may be satisfied. In formula (B), R ^1b includes, for example, an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms. Specifically, a methyl group, a methoxy group, and an ethoxy group include Can be mentioned. In formula (B), R ^2b and R ^3b may each independently be an alkoxy group having 1 to 6 carbon atoms. Examples of the alkoxy group include a methoxy group and an ethoxy group. In formula (B), R ^4b and R ^5b may each independently be an alkyl group having 1 to 6 carbon atoms or a phenyl group. The alkyl group may be a methyl group. In the formula (B), m may be 2 to 30, or 5 to 20.

  The polysiloxane compound having the structure represented by the general formula (B) can be obtained by appropriately referring to the production methods reported in, for example, JP-A Nos. 2000-26609 and 2012-233110. Can do.

  In addition, since the alkoxy group is hydrolyzed, the polysiloxane compound having an alkoxy group may exist as a hydrolysis product in the sol. The polysiloxane compound having an alkoxy group and the hydrolysis product are It may be mixed. In the polysiloxane compound having an alkoxy group, all of the alkoxy groups in the molecule may be hydrolyzed or partially hydrolyzed.

  Each of the hydrolyzable functional group or the polysiloxane compound having a condensable functional group and the hydrolysis product of the polysiloxane compound having the hydrolyzable functional group may be used alone or in combination of two or more. May be used.

  Content of polysiloxane compound group contained in the sol (content of polysiloxane compound having hydrolyzable functional group or condensable functional group, and water content of polysiloxane compound having hydrolyzable functional group) The total content of the decomposition products) may be 1 part by mass or 3 parts by mass or more with respect to 100 parts by mass of the total amount of sol, from the viewpoint of further easily obtaining good reactivity. Alternatively, it may be 4 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more. The content of the polysiloxane compound group may be 50 parts by mass or less, or 30 parts by mass or less with respect to 100 parts by mass of the total amount of sol, from the viewpoint of further easily obtaining good compatibility. 15 parts by mass or less. From these viewpoints, the content of the polysiloxane compound group may be 1 to 50 parts by mass, 3 to 50 parts by mass, or 4 to 50 parts by mass with respect to 100 parts by mass of the sol. May be 5 to 50 parts by mass, 7 to 30 parts by mass, 10 to 30 parts by mass, or 10 to 15 parts by mass. .

[Second embodiment]
As the silicon compound having a hydrolyzable functional group or a condensable functional group, a silicon compound (silicon compound) other than the polysiloxane compound may be used. That is, the airgel according to the present embodiment has (in the molecule) a hydrolyzable functional group or a silicon compound having a condensable functional group (excluding a polysiloxane compound) and the hydrolyzable functional group. It may be a wet gel dried product which is a condensate of sol containing at least one compound selected from the group consisting of hydrolysis products of silicon compounds (hereinafter sometimes referred to as “silicon compound group”). The number of silicon atoms in the molecule of the silicon compound may be 1 or 2.

  Although it does not specifically limit as a silicon compound which has a hydrolyzable functional group, For example, an alkyl silicon alkoxide is mentioned. In the alkyl silicon alkoxide, from the viewpoint of improving water repellency, the number of hydrolyzable functional groups may be 3 or less, or may be 2 to 3. Examples of the alkyl silicon alkoxide include monoalkyltrialkoxysilane, monoalkyldialkoxysilane, dialkyldialkoxysilane, monoalkylmonoalkoxysilane, dialkylmonoalkoxysilane and trialkylmonoalkoxysilane. Examples of the alkyl silicon alkoxide include methyltrimethoxysilane, methyldimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, and hexyltrimethoxysilane.

  The silicon compound having a condensable functional group is not particularly limited. For example, silane tetraol, methyl silane triol, dimethyl silane diol, phenyl silane triol, phenyl methyl silane diol, diphenyl silane diol, n-propyl silane triol, Examples include hexyl silane triol, octyl silane triol, decyl silane triol, and trifluoropropyl silane triol.

  The number of hydrolyzable functional groups is 3 or less, and as a silicon compound having a reactive group, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3 -Methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyl Trimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like can also be used.

  As a silicon compound having a condensable functional group and having the above-mentioned reactive group, vinyl silane triol, 3-glycidoxy propyl silane triol, 3-glycidoxy propyl methyl silane diol, 3-methacryloxy propyl silane triol, 3-methacryloxypropylmethylsilanediol, 3-acryloxypropylsilanetriol, 3-mercaptopropylsilanetriol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2- (aminoethyl) ) -3-Aminopropylmethylsilanediol and the like can also be used.

  As the alkyl silicon alkoxide, bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, bistrimethoxysilyloctane, or the like, which is a silicon compound having more than three hydrolyzable functional groups at the molecular terminals, may be used. it can.

  Each of the hydrolyzable functional group or the silicon compound having a condensable functional group (excluding the polysiloxane compound) and the hydrolyzate of the silicon compound having the hydrolyzable functional group, either alone or 2 You may mix and use a kind or more.

  Content of silicon compounds contained in the sol (contents of silicon compounds having hydrolyzable functional groups or condensable functional groups (excluding polysiloxane compounds) contained in the sol because it becomes easier to obtain good reactivity. And the total content of hydrolysis products of the silicon compound having a hydrolyzable functional group) may be 5 parts by mass or more with respect to 100 parts by mass of the sol, or 10 parts by mass or more. It may be 12 mass parts or more, 15 mass parts or more, or 18 mass parts or more. Since it becomes easier to obtain good compatibility, the content of the silicon compound group may be 50 parts by mass or less, or 30 parts by mass or less, based on 100 parts by mass of the sol. It may be 25 parts by mass or less, or 20 parts by mass or less. That is, the content of the silicon compound group may be 5 to 50 parts by mass, 10 to 30 parts by mass, or 12 to 30 parts by mass with respect to 100 parts by mass of the sol. 15-25 mass parts may be sufficient and 18-20 mass parts may be sufficient.

  The sum of the content of the polysiloxane compound group and the content of the silicon compound group may be 5 parts by mass or more with respect to 100 parts by mass of the sol from the viewpoint of further easily obtaining good reactivity. It may be 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, or 22 parts by mass or more. The sum of the content of the polysiloxane compound group and the content of the silicon compound group may be 50 parts by mass or less with respect to 100 parts by mass of the total amount of the sol, from the viewpoint of easily obtaining good compatibility. 30 parts by mass or less, or 25 parts by mass or less. From these viewpoints, the sum of the content of the polysiloxane compound group and the content of the silicon compound group may be 5 to 50 parts by mass with respect to 100 parts by mass of the sol, or 10 to 30 parts by mass. May be sufficient, 15-30 mass parts may be sufficient, 20-30 mass parts may be sufficient, and 22-25 mass parts may be sufficient.

  The ratio of the content of the polysiloxane compound group and the content of the silicon compound group (polysiloxane compound group: silicon compound group) is 1: 0.5 or more from the viewpoint of further easily obtaining good compatibility. Or 1: 1 or more, 1: 2 or more, or 1: 3 or more. The ratio of the content of the polysiloxane compound group to the content of the silicon compound group (polysiloxane compound group: silicon compound group) is 1: 5 or less from the viewpoint of further easily suppressing gel shrinkage. It may be 1: 4 or less, or 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 (polysiloxane compound group: silicon compound group) may be 1: 0.5 to 1: 5. It may be 1: 0.5 to 1: 4, may be 1: 1 to 1: 2, may be 1: 2 to 1: 4, and may be 1: 3 to 1: 4. It may be.

[Third embodiment]
The airgel according to the present embodiment can have a structure represented by the following general formula (1). The airgel which concerns on this embodiment can have a structure represented by the following general formula (1a) as a structure containing the structure represented by Formula (1). By using the polysiloxane compound having the structure represented by the general formula (A), the structures represented by the formulas (1) and (1a) can be introduced into the skeleton of the airgel.

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 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. p shows the integer of 1-50. In formula (1a), two or more R ^{1 s} may be the same or different, and similarly, two or more R ^{2 s} may be the same or different. In formula (1a), two R ^{3 s} may be the same or different, and similarly, two R ^{4 s} may be the same or different.

By introducing the structure represented by the above formula (1) or formula (1a) into the skeleton of the airgel, it is possible to easily obtain a flexible airgel having excellent water repellency and low thermal conductivity. From the same viewpoint, the following features may be satisfied. In Formula (1) and Formula (1a), R ¹ and R ² may each independently be an alkyl group having 1 to 6 carbon atoms or a phenyl group. The alkyl group may be a methyl group. In formula (1) and formula (1a), R ³ and R ⁴ may each independently be an alkylene group having 1 to 6 carbon atoms. The alkylene group may be an ethylene group or a propylene group. In formula (1a), p can be set to 2 to 30, and may be 5 to 20.

[Fourth aspect]
Even if the airgel which concerns on this embodiment is an airgel which has a ladder type structure provided with a support | pillar part and a bridge | bridging part, and a bridge | bridging part has a structure represented by following General formula (2), Good. By introducing such a ladder structure into the skeleton of the airgel, heat resistance and mechanical strength can be easily improved. By using the polysiloxane compound having the structure represented by the general formula (B), a ladder structure including a bridge portion having the structure represented by the general formula (2) is introduced into the skeleton of the airgel. be able to. In the present embodiment, the “ladder structure” is a structure having two struts and bridges connecting the struts (a structure having a so-called “ladder” form). ). In this embodiment, the airgel skeleton may have a ladder structure, but the airgel may partially have a ladder structure.

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 formula (2), when b is an integer of 2 or more, two or more R ^{5 s} may be the same or different, and similarly, two or more R ^{6 s} are the same. Or different.

  By introducing the above structure into the skeleton of the airgel, for example, the airgel has a structure derived from a conventional ladder-type silsesquioxane (that is, has a structure represented by the following general formula (X)). It becomes the airgel which has the outstanding softness | flexibility. In addition, as shown in the following general formula (X), in the airgel having a structure derived from a conventional ladder-type silsesquioxane, the structure of the bridge portion is —O—. The structure of the hanging portion is a structure (polysiloxane structure) represented by the general formula (2).

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

  The structure to be the strut part and its chain length, and the interval of the structure to be the bridging part are not particularly limited, but from the viewpoint of further improving the heat resistance and mechanical strength, the ladder structure has the following general formula: You may have the ladder type structure represented by (3).

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 is 1 to 50 Indicates an integer. 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 Formula (3), when b is an integer of 2 or more, two or more R ^{5 s} may be the same or different, and similarly, two or more R ^{6 s} may be the same. May be different. In formula (3), when a is an integer of 2 or more, two or more R ^{7 s} may be the same or different. In formula (3), when c is an integer of 2 or more, two or more R ^{8 s} may be the same or different.

Further, from the viewpoint of obtaining excellent water repellency and flexibility, in formula (2) and formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ (where R ⁷ and R ⁸ are in formula (3)). Only) may be each independently an alkyl group having 1 to 6 carbon atoms or a phenyl group. The alkyl group may be a methyl group. In the formula (3), a and c may be independently 6 to 2000 or 10 to 1000. In Formula (2) and Formula (3), b may be 2-30 or 5-20.

[Fifth aspect]
The airgel according to the present embodiment may contain silica particles from the viewpoint of further toughening the airgel layer and further achieving excellent heat insulation and flexibility. The sol that gives the airgel may further contain silica particles. That is, the airgel according to the present embodiment may be a dried product of a wet gel that is a condensate of a sol containing silica particles (obtained by drying a wet gel generated from the sol). The airgel layer may be a layer composed of a dried product of a wet gel that is a condensate of a sol containing silica particles. For example, the airgel layer may be composed of a layer obtained by drying a wet gel generated from a sol containing silica particles. That is, the airgel layer may be formed from a sol containing silica particles. In addition, the airgel described so far is also a dried product of a wet gel that is a condensate of a sol containing silica particles (obtained by drying a wet gel generated from the sol). May be.

  The silica particles can be used without particular limitation, and examples thereof include amorphous silica particles. Examples of the amorphous silica particles include fused silica particles, fumed silica particles, and colloidal silica particles. Among these, colloidal silica particles have high monodispersity and are easy to suppress aggregation in the sol.

  The shape of the silica particles is not particularly limited, and examples thereof include a spherical shape, a cage shape, and an association type. Among these, by using spherical particles as silica particles, it becomes easy to suppress aggregation in the sol. The average primary particle diameter of the silica particles may be 1 nm or more, or 5 nm or more from the viewpoint of easily providing an airgel with suitable strength and flexibility and excellent shrinkage resistance during drying. It may be 10 nm or more, or 20 nm or more. The average primary particle size of the silica particles may be 500 nm or less, may be 300 nm or less, may be 300 nm or less, and may be 250 nm or less, from the viewpoint of easily suppressing solid heat conduction of the silica particles and easily obtaining an airgel excellent in heat insulating properties. Or 100 nm or less. From these viewpoints, the average primary particle diameter of the silica particles may be 1 to 500 nm, 5 to 300 nm, 10 to 250 nm, or 20 to 100 nm.

  In the present embodiment, the average particle size of the particles (average primary particle size of silica particles, etc.) is obtained by directly observing the cross section of the airgel layer using a scanning electron microscope (hereinafter abbreviated as “SEM”). be able to. For example, the particle size of each airgel particle or silica particle can be obtained from the mesh-like microstructure inside the airgel based on the diameter of the particles exposed in the cross section of the airgel layer. The “diameter” here means a diameter when the cross section of the particle exposed in the cross section of the airgel layer is regarded as a circle. The “diameter when the cross section is regarded as a circle” is the diameter of the true circle when the area of the cross section is replaced with a true circle having the same area. In calculating the average particle diameter, the diameter of a circle is obtained for 100 particles, and the average is taken.

  In addition, the average particle diameter of a silica particle can be measured from a raw material. For example, the biaxial average primary particle diameter is calculated as follows from the result of observing 20 arbitrary particles by SEM. That is, taking as an example colloidal silica particles having a solid content concentration of 5 to 40% by mass dispersed in water, a chip obtained by cutting a 2 cm square wafer with a pattern wiring into a dispersion of colloidal silica particles. After soaking for 30 seconds, the chip is rinsed with pure water for about 30 seconds and blown with nitrogen. Thereafter, the chip is placed on a sample stage for SEM observation, an acceleration voltage of 10 kV is applied, the silica particles are observed at a magnification of 100,000, and an image is taken. 20 silica particles are arbitrarily selected from the obtained image, and the average of the particle diameters of these particles is defined as the average particle diameter. At this time, when the selected silica particles have a shape as shown in FIG. 3, a rectangle (circumscribed rectangle L) circumscribing the silica particles P and arranged so that the long side is the longest is led. And the long side of the circumscribed rectangle L is X, the short side is Y, and the biaxial average primary particle diameter is calculated as (X + Y) / 2, and is defined as the particle diameter of the particle.

The number of silanol groups per gram of silica particles may be 10 × 10 ¹⁸ pieces / g or more, or 50 × 10 ¹⁸ pieces / g or more from the viewpoint of easily obtaining an airgel having excellent shrinkage resistance. 100 × 10 ¹⁸ pieces / g or more. The number of silanol groups per gram of silica particles may be 1000 × 10 ¹⁸ pieces / g or less, may be 800 × 10 ¹⁸ pieces / g or less, and 700 × It may be 10 ¹⁸ pieces / g or less. From these viewpoints, the number of silanol groups per gram of the silica particles may be 10 × 10 ^{18 to} 1000 × 10 ¹⁸ pcs / g, or 50 × 10 ^{18 to} 800 × 10 ¹⁸ pcs / g. 100 × 10 ^{18 to} 700 × 10 ¹⁸ pieces / g.

  The content of the silica particles contained in the sol is 1 mass with respect to 100 mass parts of the total amount of the sol from the viewpoint of easily imparting an appropriate strength to the airgel and easily obtaining an airgel excellent in shrinkage resistance during drying. Or 4 parts by mass or more. The content of the silica particles contained in the sol is 20 parts by mass or less with respect to 100 parts by mass of the total amount of the sol, from the viewpoint of easily suppressing the solid heat conduction of the silica particles and easily obtaining an airgel excellent in heat insulation. It may be 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, or 8 parts by mass or less. From these viewpoints, the content of the silica particles contained in the sol may be 1 to 20 parts by mass or 4 to 15 parts by mass with respect to 100 parts by mass of the sol. 12 mass parts may be sufficient, 4-10 mass parts may be sufficient, and 4-8 mass parts may be sufficient.

[Other aspects]
The airgel according to the present embodiment can have a structure represented by the following general formula (4). The airgel which concerns on this embodiment can have a structure represented by following General formula (4) while containing a silica particle.

In formula (4), R ⁹ represents an alkyl group. As an alkyl group, a C1-C6 alkyl group is mentioned, for example, A methyl group is mentioned specifically ,.

  The airgel according to the present embodiment can have a structure represented by the following general formula (5). The airgel which concerns on this embodiment can have a structure represented by following General formula (5) while containing a silica particle.

In formula (5), R ¹⁰ and R ¹¹ each independently represent an alkyl group. As an alkyl group, a C1-C6 alkyl group is mentioned, for example, A methyl group is mentioned specifically ,.

  The airgel according to the present embodiment can have a structure represented by the following general formula (6). The airgel which concerns on this embodiment can have a structure represented by following General formula (6) while containing a silica particle.

In the formula (6), R ¹² represents an alkylene group. As an alkylene group, a C1-C10 alkylene group is mentioned, for example, Specifically, an ethylene group and a hexylene group are mentioned.

  The airgel according to the present embodiment may have a structure derived from polysiloxane. Examples of the structure derived from polysiloxane include structures represented by the above general formula (1), (2), (3), (4), (5), or (6). The airgel which concerns on this embodiment may have at least 1 type among the structures represented by the said General formula (4), (5) and (6), without containing a silica particle.

  The thickness of the airgel layer can be 1 μm or more, 2 μm or more, 3 μm or more, or 10 μm or more because it is easy to ensure the reliability of the airgel layer. 30 μm or more. The thickness of the airgel layer may be 5000 μm or less, 4000 μm or less, 3000 μm or less, or 1000 μm or less from the viewpoint of shortening the later-described washing and solvent replacement step. 500 μm or less, or 250 μm or less. From these viewpoints, the thickness of the airgel layer may be 1 to 5000 μm, 2 to 4000 μm, 3 to 3000 μm, 10 to 1000 μm, 10 to 500 μm. It may be 30 to 250 μm.

<Method for manufacturing structure>
Next, a method for manufacturing the structure will be described.

  The structure manufacturing method according to the present embodiment is a structure manufacturing method in which an airgel layer is formed, and a step of forming an airgel layer from a mist-like sol (hereinafter, also referred to as “airgel layer forming step”). It is a method provided with. The mist sol may be, for example, a mist form of the sol described above. According to this manufacturing method, a structure in which unevenness of the airgel layer is suppressed can be manufactured. Moreover, according to this manufacturing method, a thick airgel layer can be formed without depending on the shape of the main body, and the thickness of the airgel layer can be easily controlled. In general, when the airgel is thickened, cracks tend to easily occur. However, according to such a manufacturing method, cracks are reduced. According to the structure manufacturing method according to the present embodiment, even when the shape of the object is complicated, it is difficult for the airgel to be defective, so that the reliability of the performance as the airgel can be kept high.

  Moreover, according to the structure manufacturing method according to the present embodiment, since stress due to capillary force inside the gel is difficult to occur, gel contraction is difficult to occur, and the reliability as an airgel tends to be maintained.

  The airgel layer forming step may be, for example, a step of forming an airgel layer from the sol layer after forming the sol layer from a mist in the form of a mist.

  Specifically, for example, as shown in FIG. 4, after preparing an object 10 that is an object for forming an airgel layer (FIG. 4A), a sol in the form of mist ( After forming the sol layer 5a from the “sol coating solution” (FIG. 4B), the airgel layer 5 is formed from the sol layer 5a (FIG. 4C). If the object is only the main body, after preparing the main body, the sol may be applied directly to the main body.

  In the structure manufacturing method according to the present embodiment, the structure includes a main body portion and a covering layer that covers at least a part of the surface of the main body portion, and the covering layer serves as an intermediate layer. In addition, an airgel layer may be formed on at least the coating layer. That is, when the target object that forms the airgel layer includes the main body part and the covering layer, for example, as shown in FIG. 5, the target object 10 including the main body part 3 and the covering layer 4 is prepared. After forming the sol layer 5a from the mist in the form of mist (FIG. 5 (b)) on the coating layer 4 so that the coating layer 4 becomes an intermediate layer (FIG. 5 (a)), the sol layer The airgel layer 5 is formed from 5a (FIG.5 (c)). Thereby, the adhesiveness of the airgel layer is further improved, and peeling and dropping of the airgel layer are further suppressed. In addition, the aspect regarding a main-body part and a coating layer is as having mentioned above.

  4 and 5 show the form in which the airgel layer is formed after the sol layer is formed, the airgel layer may be formed simultaneously with the application of the sol.

  Hereinafter, a specific example of the structure manufacturing method according to the present embodiment will be described in more detail. However, the manufacturing method of the structure is not limited to the following method.

  The structure according to the present embodiment includes, for example, a preparation step for preparing an object, a sol generation step for producing a sol for forming an airgel, and a sol obtained in the sol generation step in a mist form. A contact process for obtaining a structure by forming an airgel layer integrally bonded to the object by contacting the object, an aging process for aging the structure obtained in the contact process, and an aged structure It can be produced by a production method mainly comprising a step of washing and / or solvent replacement of the body and a drying step of drying the washed and / or solvent-substituted structure. In the contact step, the mist-like sol may be contacted with the object and then dried as necessary. Here, the specific example of the process of forming an airgel layer from mist-like sol includes the said contact process, for example. Further, the “sol” is a state before the gelation reaction occurs, and in the present embodiment, for example, a silicon compound (and if necessary, further silica particles) is dissolved or dispersed in a solvent. Means state.

  Hereinafter, each step will be described.

{Preparation process}
In the preparation step, for example, a main body part or a main body part on which a coating layer is formed is prepared. The coating layer can be formed by, for example, a coating layer forming step of forming a coating layer on the main body portion.

(Coating layer forming process)
A coating layer formation process is a process of making the composition for coating layer formation contact the base material used as a main-body part, for example, and forming a coating layer on a main-body part. Specifically, for example, the composition for forming a coating layer is brought into contact with the substrate, and if necessary, the coating layer is formed on the surface of the substrate by heating and drying. The composition for forming a coating layer may be a liquid composition such as a primer solution or a sheet-like composition such as an adhesive sheet.

  The contact method is appropriately selected depending on the type of the coating layer forming composition, the thickness of the coating layer, or the shape of the substrate. For example, when the composition for forming a coating layer is a sheet-like composition, a method of laminating on a substrate can be used, and when the composition for forming a coating layer is a liquid composition, for example, dip coating Spray coating, spin coating, roll coating, etc. can be used.

  The contact method is selected from the viewpoint of film formability or manufacturing cost. For example, if it is a sheet-like or fibrous base material, dip coating or roll coating can be used. If it is a block-like or spherical base material, dip coating or spray coating can be used.

  In the coating layer forming step, heat treatment may be performed from the viewpoint of drying and fixing the composition for forming the coating layer, and washing and / or drying from the viewpoint of removing impurities and improving the adhesion of the coating layer. May be performed. Further, for the purpose of adjusting the surface roughness of the coating layer, the surface of the coating layer may be subjected to polishing treatment and / or roughening treatment.

{Sol generation process}
In the sol production step, for example, a silicon compound (if necessary, further silica particles) and a solvent are mixed and a hydrolysis reaction is performed, and then a sol-gel reaction is performed to obtain a semi-gelled sol coating liquid. It is. In the sol production step, an acid catalyst may be further added to the solvent in order to promote the hydrolysis reaction. Further, as disclosed in Japanese Patent No. 5250900, a surfactant, a thermohydrolyzable compound, or the like can be added to the solvent. Furthermore, a base catalyst may be added to promote the gelation reaction. In addition, you may contain a silica particle in a sol from a viewpoint of shortening the process time in a sol production | generation process, a contact process, and an aging process, and reducing a heating temperature and a drying temperature.

  The boiling point of the solvent may be less than 200 ° C., 170 ° C. or less, or 150 ° C. or less from the viewpoint of obtaining good coatability in the contacting step. That is, the sol may contain a solvent having a boiling point of less than 200 ° C., may contain a solvent having a boiling point of 170 ° C. or less, and may contain a solvent having a boiling point of 150 ° C. or less. According to the sol containing such a solvent, a thick airgel layer can be formed more easily, and cracks in the airgel layer are further suppressed. The reason for this is that if the solvent is such, after the mist-like sol comes into contact with the main body or the coating layer, the solvent easily evaporates from the sol in a short time and becomes a wet gel. This is presumably because the film thickness tends to increase.

  The solvent may have a high surface tension from the viewpoint of improving the coating film formability and from the viewpoint of easy film thickness control. The solvent may have a low volatility from the viewpoint of suppressing changes in the sol viscosity and resin content and improving storage stability. Examples of the solvent that satisfies these characteristics include water or a mixed solution of water and alcohol. Examples of the alcohol include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol and t-butanol. Among these, water may be used because it has a high surface tension and low volatility.

  Examples of the acid catalyst include hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, hypochlorous acid, and other inorganic acids; Acid phosphates such as aluminum phosphate, acid magnesium phosphate, acid zinc phosphate; organics such as formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, azelaic acid Carboxylic acid is mentioned. Among these, as the acid catalyst, an organic carboxylic acid can be used from the viewpoint of further improving the water resistance of the resulting structure. Specifically, acetic acid, formic acid, propionic acid, oxalic acid and malonic acid are used. May be acetic acid. You may use an acid catalyst individually or in mixture of 2 or more types.

  By using an acid catalyst, the hydrolysis reaction of the silicon compound is 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 with respect to 100 parts by mass of the total amount of the silicon compound.

  As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. You may use surfactant individually or in mixture of 2 or more types.

  Examples of the nonionic surfactant include those containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group, and those containing a hydrophilic part such as polyoxypropylene. Examples of those containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene alkyl ether. Examples of those containing a hydrophilic portion such as polyoxypropylene include polyoxypropylene alkyl ethers, block copolymers of polyoxyethylene and polyoxypropylene, and the like.

  As the ionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant or the like can be used, and a cationic surfactant or an anionic surfactant may be used. Examples of the cationic surfactant include cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride. Examples of the anionic surfactant include sodium dodecyl sulfonate. Examples of amphoteric surfactants include amino acid surfactants, betaine surfactants, and amine oxide surfactants. Examples of amino acid surfactants include acyl glutamic acid. Examples of betaine surfactants include lauryldimethylaminoacetic acid betaine and stearyldimethylaminoacetic acid betaine. Examples of the amine oxide surfactant include lauryl dimethylamine oxide.

  These surfactants are thought to have the effect of reducing phase separation by reducing the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer in the contacting step. .

  The addition amount of the surfactant depends on the type of the surfactant or the type and amount of the silicon compound. For example, even if the amount is 1 to 100 parts by mass with respect to 100 parts by mass of the total amount of the silicon compound. It may be 5 to 60 parts by mass.

  The thermohydrolyzable compound is considered to generate a base catalyst by thermal hydrolysis, thereby making the reaction solution basic and promoting the sol-gel reaction. The thermohydrolyzable compound is not particularly limited as long as it can make the reaction solution basic after hydrolysis. For example, urea; formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N- Examples include acid amides such as methylacetamide and N, N-dimethylacetamide; and cyclic nitrogen compounds such as hexamethylenetetramine. Among these, urea is particularly easy to obtain the above-mentioned promoting effect.

  The amount of the thermally hydrolyzable compound added is not particularly limited as long as it is an amount that can sufficiently promote the sol-gel reaction. For example, the addition amount of the thermally hydrolyzable compound (urea or the like) may be 1 to 200 parts by mass or 2 to 150 parts by mass with respect to 100 parts by mass of the total amount of the silicon compound. When the addition amount of the thermohydrolyzable compound (urea or the like) is 1 part by mass or more, good reactivity can be further easily obtained, and when it is 200 parts by mass or less, the precipitation of crystals and the gel density are reduced. It becomes easy to suppress the decrease.

  The hydrolysis in the sol production step depends on the type and amount of silicon compound, silica particles, acid catalyst, surfactant, etc. in the mixed solution, but for example, 10 minutes in a temperature environment of 20-60 ° C. It may be performed for 24 hours, or may be performed in a temperature environment of 50 to 60 ° C. for 5 minutes to 8 hours. Thereby, the hydrolyzable functional group in a silicon compound is fully hydrolyzed, and the hydrolysis product of a silicon compound can be obtained more reliably.

  When adding a thermohydrolyzable compound in a solvent, you may adjust the temperature environment of a sol production | generation process to the temperature which suppresses the hydrolysis of a thermohydrolyzable compound and suppresses gelatinization of a sol. The temperature at this time may be any temperature as long as the hydrolysis of the thermally hydrolyzable compound can be suppressed. For example, the temperature environment in the sol production step (for example, the temperature environment when urea is used as the thermohydrolyzable compound) may be 0 to 40 ° C or 10 to 30 ° C.

  Base catalysts include 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; sodium metaphosphate Basic sodium phosphates such as sodium pyrophosphate and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3- (diethylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, t-butylamine, aliphatic amines such as ec-butylamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine; morpholine N-methylmorpholine, 2-methylmorpholine, piperazine and derivatives thereof, piperidine and derivatives thereof, nitrogen-containing heterocyclic compounds such as imidazole and derivatives thereof, and the like. Among these, ammonium hydroxide (ammonia water) can be used from the viewpoint of high volatility and hardly remaining in the airgel layer after drying, and from the viewpoint of not impairing water resistance and economical efficiency. You may use a base catalyst individually or in mixture of 2 or more types.

  By using a base catalyst, the dehydration condensation reaction and / or dealcoholization condensation reaction of the silicon compound (polysiloxane compound group and silicon compound group) and silica particles in the sol can be promoted, and the gelation of the sol Furthermore, it can be performed in a short time. In particular, ammonia is highly volatile and hardly remains in the structure. Therefore, by using ammonia as the base catalyst, a structure having further excellent water resistance can be obtained.

  The addition amount of the base 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 amount of silicon compounds (polysiloxane compound group and silicon compound group). . When the addition amount of the base catalyst is 0.5 parts by mass or more, gelation can be performed in a shorter time, and when it is 5 parts by mass or less, the water repellency is improved.

  In the sol-gel reaction in the sol production step, a semi-gelled sol can be obtained for the purpose of obtaining good coating properties in the contact step. This reaction can be performed in an airtight container so that a solvent and a base catalyst may not volatilize. The gelation temperature depends on the type and amount of silicon compound, silica particles, acid catalyst, surfactant, base catalyst and the like in the sol, but may be 30 to 90 ° C, or 40 to 80 ° C. There may be. When the gelation temperature is 30 ° C. or higher, gelation can be performed in a shorter time. When the gelation temperature is 90 ° C. or less, rapid gelation can be suppressed.

  Although the sol-gel reaction time varies depending on the gelation temperature, in the present embodiment, when silica particles are contained in the sol, the gelation time may be shortened as compared with a sol applied to a conventional aerogel. it can. The reason is presumed that the hydrolyzable functional group or the condensable functional group of the silicon compound in the sol forms hydrogen bonds and / or chemical bonds with the silanol groups of the silica particles. The gelation time may be 10 to 360 minutes or 20 to 180 minutes. When the gelation time is 10 minutes or longer, the viscosity of the sol is improved, and good coating properties are easily obtained in the contact process. It becomes easy to obtain adhesiveness with a part or a coating layer.

{Contact process}
In the contact step, the sol coating liquid (semi-gelled sol coating liquid or the like) obtained in the sol generation step is brought into contact with the main body or the coating layer in the form of a mist to produce a structure (coating). Construction process). Specifically, the sol coating liquid is brought into contact with the main body part or the coating layer in the form of a mist, and the sol coating liquid is gelled by heating and drying as necessary to form the airgel layer of the main body part or the coating layer. Form on the surface. However, the airgel layer is desirably in a state in which an adhesive force with the main body portion or the coating layer is ensured.

  The contact method (such as a coating method) is not particularly limited as long as the sol can be contacted (applied) to the main body or the layer in the form of a mist, and examples thereof include spray coating. According to this method, since the mist generated by spraying only needs to reach the surface to be coated, for example, an airgel layer can be formed also on the inner surface of a cylindrical main body such as a pipe. .

  Sprays used for spray application include, for example, air spray that mists are applied by applying compressed gas, and airless sprays that apply mist by spraying from the spray gun nozzle by applying pressure to the sol. A liquid electrostatic spray that efficiently attaches a mist to an adherend by applying a static voltage can be used.

  The coating method is not limited, and a suitable method can be selected depending on physical properties such as the size, shape, and elastic modulus of the main body or the coating layer.

  When gas is used for spraying, the pressure of the gas used can be adjusted according to the specifications of the air gun and air brush used, for example. The pressure is not particularly limited, but may be, for example, less than 0.5 MPa.

  The thickness of the airgel layer formed in the contacting step can be adjusted by, for example, the pressure of the gas used for spraying, the coating amount of the sol, the viscosity of the sol, the distance between the spray and the main body, and the coating time. Among these, the thickness of the airgel layer may be adjusted by the coating time from the viewpoint of workability. In this case, for example, a calibration curve indicating the relationship between the coating time and the thickness of the semi-cured gel or the thickness of the airgel layer may be created, and thereby the thickness may be controlled.

  The diameter of the mist droplets of the sol may be 0.1 μm or more, from the viewpoint of easily forming a thick airgel layer and further suppressing cracking of the airgel layer, and may be 0.3 μm or more. It may be 0.5 μm or more. From the same viewpoint, the diameter of the sol droplet may be 1000 μm or less, 800 μm or less, or 500 μm or less. From these viewpoints, the diameter of the sol droplet may be 0.1 to 1000 μm, 0.3 to 800 μm, or 0.5 to 500 μm. When the diameter of the droplet is in such a range, it is easy to form a thick airgel layer and the crack of the airgel layer can be further suppressed. For example, a droplet having such a size has a sufficient surface area. Since it is large, it is assumed that the solvent in the sol evaporates in a short time after adhering to the main body or the coating layer, and the sol contracts accordingly.

  If the airgel layer forming part (coating part) and the non-forming part (non-coating part) are adjacent, for example, the non-coating part is masked with a tape or the like, and then the sol is applied to the coating part. May be contacted.

  When masking is applied, from the viewpoint of reducing airgel loss and peeling at the boundary between the coated and non-coated areas, for example, after spray coating, the mask is removed at a semi-cured gel-like timing. May be.

  In the contact step, when heating and drying, these conditions are such that the moisture content of the airgel layer after heating and drying is, for example, 10% by mass from the viewpoint of easily obtaining adhesion between the airgel layer and the main body portion or the coating layer. The conditions may be as described above, or the conditions may be 50% by mass or more.

  The heating and drying temperature varies depending on conditions such as the amount of water in the sol coating liquid, the amount of the organic solvent, the boiling point of the organic solvent, etc., from the viewpoint of shortening the gelation time, for example, may be 50 ° C. or more, It may be 60 ° C. or higher. The heating and drying temperature may be, for example, 150 ° C. or less or 120 ° C. or less from the viewpoint of easily obtaining adhesion between the airgel layer and the main body portion or the coating layer. From these viewpoints, the heating and drying temperature may be, for example, 50 to 150 ° C or 60 to 120 ° C.

  The heating and drying time varies depending on the heating and drying temperature, but may be, for example, 0.2 minutes or more, or 0.5 minutes or more from the viewpoint of ease of forming the airgel layer. The heating and drying time may be, for example, 10 minutes or less or 8 minutes or less from the viewpoint of easily obtaining the adhesion between the airgel layer and the main body portion or the coating layer. From these viewpoints, the heating and drying time may be, for example, 0.2 to 10 minutes or 0.5 to 8 minutes. As for the heating and drying conditions, for example, suitable conditions can be appropriately set by conducting a simple experiment in advance.

  From the viewpoint of increasing the thickness of the airgel layer, coating and drying may be repeated a plurality of times. By repeating the coating and drying, it is easy to adjust the moisture content of the airgel layer after heating and drying, and the film can be easily thickened.

{Aging process}
The aging step is a step of aging the structure obtained by the contact step by heating. In the aging step, the moisture content of the airgel layer after aging may be 10% by mass or more, or 50% by mass or more from the viewpoint of suppressing a decrease in adhesiveness between the airgel layer and the main body portion or the coating layer. May be. The aging method is not particularly limited, and examples thereof include a method of aging the structure in a sealed atmosphere, and a method of aging using a constant temperature and humidity bath that can suppress a decrease in moisture content due to heating.

  The aging temperature may be, for example, 40 to 90 ° C or 50 to 80 ° C. When the aging temperature is 40 ° C. or higher, the aging time can be shortened, and when it is 90 ° C. or lower, a decrease in water content can be suppressed.

  The aging time may be, for example, 1 to 48 hours, or 3 to 24 hours. When the aging time is 1 hour or longer, excellent heat insulating properties can be easily obtained, and when it is 48 hours or shorter, high adhesion between the airgel layer and the main body portion or the coating layer can be obtained.

{Washing and solvent replacement step}
The washing and solvent substitution step is a step having a step of washing the structure obtained by the aging step (washing step) and a step of substitution with a solvent suitable for the drying step (solvent substitution step). The cleaning and solvent replacement method is not particularly limited, and for example, continuous processing can be performed using a plurality of cleaning tanks and / or solvent replacement tanks by conveyor conveyance. The cleaning and solvent replacement step can be carried out in a form in which only the solvent replacement step is performed without performing the step of cleaning the structure, but it is possible to reduce impurities such as unreacted substances and by-products in the airgel layer. The airgel layer can be washed from the viewpoint of enabling production of a highly pure structure.

  In the washing step, the structure obtained in the aging step can be washed repeatedly using water or an organic solvent.

  As organic solvents, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, methylene chloride , N, N-dimethylformamide, dimethyl sulfoxide, acetic acid, formic acid and other various organic solvents can be used. You may use an organic solvent individually or in mixture of 2 or more types.

  In the solvent replacement step, a low surface tension solvent may be used to suppress shrinkage of the airgel layer due to drying. However, low surface tension solvents generally have very low mutual solubility with water. Therefore, when a low surface tension solvent is used in the solvent replacement step, a hydrophilic organic solvent having high mutual solubility in both water and a low surface tension solvent is used as the organic solvent used in the washing step. it can. Note that the hydrophilic organic solvent used in the washing step can serve as a preliminary replacement for the solvent replacement step. From this, it is possible to use methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone from the viewpoint of being a hydrophilic organic solvent among the above organic solvents, and methanol, ethanol from the viewpoint of being economical. Alternatively, methyl ethyl ketone can be used.

  The amount of water or organic solvent used in the washing step can be an amount that can sufficiently replace the solvent in the airgel layer and can be washed, and is 3 to 10 times the volume of the airgel layer. These solvents can be used. The washing can be repeated until the water content in the airgel layer after washing becomes 10% by mass or less.

  As a temperature environment in the washing step, a temperature not higher than the boiling point of the solvent used for washing can be used. For example, when methanol is used, a temperature of about 30 to 60 ° C. can be used.

  In the solvent replacement step, in order to suppress shrinkage of the airgel layer in the drying step, the solvent of the washed airgel layer can be replaced with a predetermined replacement solvent. At this time, the replacement efficiency can be improved by heating. Specifically, as the replacement solvent, a solvent having a low surface tension, which will be described later, can be used in the drying step when drying under atmospheric pressure at a temperature lower than the critical point of the solvent used for drying. When performing supercritical drying, for example, a solvent such as ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, or the like can be used alone, or a solvent obtained by mixing two or more of these can be used.

  The low surface tension solvent may be a solvent having a surface tension at 20 ° C. of 30 mN / m or less, a solvent of 25 mN / m or less, or a solvent of 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), 3- Aliphatic hydrocarbons such as methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), 1-pentene (16.0); (28.9), toluene (28.5), m-xylene (28.7), p-xylene (28.3) and other aromatic hydrocarbons; dichloromethane (27.9), chloroform (27.2) ), Carbon tetrachloride (26.9), 1-chloropropane (21.8), 2-chloropropane (18.1) and other halogenated hydrocarbons; ethyl ether (17.1), propyl ether (20.5) ), Isop Ethers such as pyrether (17.7), butyl ethyl ether (20.8), 1,2-dimethoxyethane (24.6); acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), ketones such as diethyl ketone (25.3); and methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2) And esters such as isobutyl acetate (23.7) and ethyl butyrate (24.6) (inside the surface tension at 20 ° C. is shown in parentheses, the unit is [mN / m]). Among these, from the viewpoint of achieving low surface tension and excellent working environment, aliphatic hydrocarbons may be used, and hexane or heptane may be used. Among these, by using a hydrophilic organic solvent such as acetone, methyl ethyl ketone, or 1,2-dimethoxyethane, it can be used as the organic solvent in the washing step. Among these, a solvent having a boiling point of 100 ° C. or less at normal pressure may be used from the viewpoint of easy drying in the drying step. Low surface tension solvents may be used alone or in combination of two or more.

  As the amount of the solvent used in the solvent replacement step, an amount that can sufficiently replace the solvent in the airgel layer after washing can be used, and the amount of the solvent is 3 to 10 times the volume of the airgel layer. Can be used.

  As a temperature environment in the solvent substitution step, a temperature not higher than the boiling point of the solvent used for substitution can be used. For example, when heptane is used, a temperature of about 30 to 60 ° C. can be used.

  In the present embodiment, when the sol contains silica particles, the solvent replacement step is not necessarily essential. The inferred mechanism is as follows. In the present embodiment, the silica particles function as a three-dimensional network airgel skeleton support, whereby the skeleton is supported and gel shrinkage in the drying process is suppressed. Therefore, it is considered that the gel can be directly transferred to the drying step without replacing the solvent used for washing. Thus, in this embodiment, it is possible to simplify the washing and solvent replacement step to the drying step.

{Drying process}
In the drying step, the structure that has been washed and solvent-substituted (if necessary) as described above is dried. Thereby, a final structure can be obtained.

  The drying method is not particularly limited, and known atmospheric pressure drying, supercritical drying, or freeze drying can be used. Among these, atmospheric drying or supercritical drying can be used from the viewpoint of easy production of a low-density airgel layer. From the viewpoint of being able to produce at low cost, atmospheric drying can be used. In the present embodiment, “normal pressure” means 0.1 MPa (atmospheric pressure).

  The structure according to the present embodiment can be obtained, for example, by drying a structure after washing and solvent substitution (if necessary) at a temperature below the critical point of the solvent used for drying under atmospheric pressure. it can. The drying temperature varies depending on the type of the substituted solvent (the solvent used for washing when solvent substitution is not performed) or the heat resistance of the main body, but may be 60 to 500 ° C, and 90 to 150 ° C. There may be. The drying time varies depending on the capacity of the airgel layer and the drying temperature, but may be 2 to 48 hours. In the present embodiment, drying can be accelerated by applying pressure within a range that does not impair productivity.

  The structure according to the present embodiment may be pre-dried before the drying step from the viewpoint of improving the drying efficiency in atmospheric drying. The pre-drying temperature may be 60 to 180 ° C or 90 to 150 ° C. The predrying time varies depending on the capacity of the airgel layer and the drying temperature, but may be 1 to 30 minutes.

  As described above, supercritical drying can also be used as a drying method. Supercritical drying can be performed by a known method. Examples of the supercritical drying method include a method of removing the solvent at a temperature and pressure higher than the critical point of the solvent contained in the airgel layer. Alternatively, as a method of supercritical drying, the airgel layer is immersed in liquefied carbon dioxide under conditions of, for example, about 20 to 25 ° C. and about 5 to 20 MPa, so that all or part of the solvent contained in the airgel layer is used. And carbon dioxide having a lower critical point than that of the solvent, and then removing carbon dioxide alone or a mixture of carbon dioxide and the solvent.

  As mentioned above, although one Embodiment of the manufacturing method of the structure which concerns on this embodiment was described, the manufacturing method of a structure is not limited to this embodiment. Moreover, the airgel layer which concerns on this embodiment is applicable to water-repellent uses, such as an architecture field, a clothing field, a motor vehicle field, a household appliance field, a semiconductor field, an industrial facility, for example. Further, the airgel layer can be used for a heat insulating application, a sound absorbing application, a static vibration application, a catalyst supporting application and the like in addition to the application as a water repellent material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples.

(Main body)
The following glass plate, aluminum plate, SUS piping and PET film were prepared as the main body.

Glass plate: Tempax (manufactured by Toshin Rikou Co., Ltd., dimensions: 100 mm x 100 mm x 2 mm)
Aluminum plate: A1035P (manufactured by Takeuchi Metal Foil Powder Industry Co., Ltd., dimensions: 100 mm x 100 mm x 0.5 mm)
SUS piping: SUS316TPD (manufactured by Mori Kogyo Co., Ltd., outer diameter 115 mm × thickness 2 mm × length 50 mm)
PET film: Tetoron G2 (Teijin Limited, dimensions: 100 mm x 100 mm x 0.1 mm)

  In addition, when using SUS piping as a main-body part, formation of the below-mentioned airgel layer (coating layer as needed) was given with respect to the outer surface of piping.

<Examples 1-7>
(Formation of coating layer (hereinafter also referred to as “intermediate layer”))
An intermediate layer 1 and an intermediate layer 2 were formed on the prepared various main body portions in the combinations shown in Table 1 as follows.

[Intermediate layer 1]
KBM-903 (3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name) as a silicone-based primer liquid is applied to the main body, and an air brush (product name: HP-CP, manufactured by Anest Iwata Co., Ltd.). Then, the coating was cured by heating at 90 ° C. for 1 hour to form a 5 μm thick layer (intermediate layer 1) on the main body.

[Intermediate layer 2]
After applying a sodium silicate solution (about 38% by mass) (made by Wako Pure Chemical Industries, Ltd., reagent) as an inorganic primer solution to the main body using a bar coater, heat at 300 ° C. for 2 hours. Then, a 10 μm thick layer (intermediate layer 2) was formed on the main body.

(Sol coating liquid)
[Sol coating solution 1]
As a silica particle-containing raw material, ST-OXS (manufactured by Nissan Chemical Industries, Ltd., product name, average primary particle size: 5 nm, solid content: 10% by mass) is 100.0 parts by mass, water is 50.0 parts by mass, acid catalyst As a mixture, 0.10 parts by mass of acetic acid, 20.0 parts by mass of CTAB as a cationic surfactant and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed to obtain a mixed solution. In this mixed solution, 60.0 parts by mass of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: LS-530, hereinafter abbreviated as “MTMS”) as a silicon compound and dimethyldimethoxysilane (Shin-Etsu Chemical Co., Ltd.) 40.0 parts by mass of the product, product name: LS-520 (hereinafter abbreviated as “DMDMS”) was added, and the mixture was reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 5 hours to obtain a sol coating liquid 1.

[Sol coating liquid 2]
As a silica particle-containing raw material, 100.0 parts by mass of ST-OXS, 100.0 parts by mass of water, and 100.0 parts by mass of methanol were mixed to obtain a mixed solution. To this mixed solution, 80.0 parts by mass of MTMS as a silicon compound and 60.0 parts by mass of KBE-22 (dimethyldiethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name) are added and reacted at 25 ° C. for 2 hours. It was. A sol coating solution 2 was obtained by adding 50.0 parts by mass of 5% aqueous ammonia as a base catalyst.

[Sol coating solution 3]
ST-OZL-35 (manufactured by Fuso Chemical Industry Co., Ltd., product name, average primary particle size: 100 nm, solid content: 35% by mass) as silica particle-containing raw material is 100.0 parts by mass, and water is 200.0 parts by mass. Then, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed to obtain a mixed solution. To this mixed solution, 80.0 parts by mass of KBM-3063 (hexyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name) as a silicon compound and KBM-3086 (1,8-bis (trimethoxysilyl) octane, 80.0 parts by mass of Shin-Etsu Chemical Co., Ltd., product name) was added and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 2 hours to obtain a sol coating solution 3.

[Sol coating solution 4]
As a silica particle-containing raw material, PL-2L (manufactured by Fuso Chemical Industry Co., Ltd., product name, average primary particle size: 20 nm, solid content: 20% by mass) is 100.0 parts by mass, water is 50.0 parts by mass, acid 0.10 parts by mass of acetic acid as a catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed to obtain a mixed solution. In this mixed solution, 60.0 parts by mass of MTMS as a silicon compound, 80.0 parts by mass of KBM-3086, and KF-6001 (Shin-Etsu Chemical Co., Ltd.) as a polysiloxane compound having a structure represented by the above general formula (A) 30.0 parts by mass of a product name manufactured by Kogyo Co., Ltd. was added and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 4 hours to obtain a sol coating solution 4.

[Sol coating solution 5]
100.0 parts by mass of PL-2L as a silica particle-containing raw material, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant and thermal hydrolysis As a decomposable compound, 120.0 parts by mass of urea was mixed to obtain a mixed solution. In this mixed solution, 40.0 parts by mass of MTMS as a silicon compound and a bifunctional alkoxy-modified polysiloxane compound having a structure represented by the above general formula (B) as a polysiloxane compound (hereinafter referred to as “polysiloxane compound A”). 20.0 parts by mass) was added and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 5 hours to obtain a sol coating solution 5.

  The “polysiloxane compound A” was synthesized as follows. First, 100.0 mass of dimethylpolysiloxane (product name: XC96-723, manufactured by Momentive) having silanol groups at both ends in a 1 L three-necked flask equipped with a stirrer, a thermometer and a Dimroth condenser Part, 181.3 parts by mass of methyltrimethoxysilane and 0.50 part by mass of t-butylamine were mixed and reacted at 30 ° C. for 5 hours. Thereafter, this reaction solution was heated at 140 ° C. for 2 hours under reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining a bifunctional alkoxy-modified polysiloxane compound (polysiloxane compound A) at both ends.

[Sol coating liquid 6]
ST-OZL-35 (manufactured by Fuso Chemical Industry Co., Ltd., product name, average primary particle size: 100 nm, solid content: 35% by mass) as silica particle-containing raw material is 100.0 parts by mass, and water is 100.0 parts by mass. Then, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed to obtain a mixed solution. In this mixed solution, 60.0 parts by mass of KBM-3063 (hexyltrimethoxysilane) as a silicon compound and a bifunctional bifunctional alkoxy-modified polysiloxane compound having a structure represented by the above general formula (B) as a polysiloxane compound 40.0 parts by mass (hereinafter referred to as “polysiloxane compound B”) was added and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 5 hours to obtain a sol coating liquid 6.

  The “polysiloxane compound B” was synthesized as follows. First, 100.0 parts by mass of XC96-723, 202.6 parts by mass of tetramethoxysilane and 0.50 of t-butylamine in a 1 L three-necked flask equipped with a stirrer, a thermometer and a Dimroth condenser. Mass parts were mixed and reacted at 30 ° C. for 5 hours. Then, this reaction liquid was heated at 140 ° C. for 2 hours under a reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining a trifunctional alkoxy-modified polysiloxane compound (polysiloxane compound B) at both ends.

[Sol coating liquid 7]
100.0 parts by mass of ST-OZL-35 as a raw material containing silica particles, 200.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and As a heat hydrolyzable compound, 120.0 parts by mass of urea was mixed to obtain a mixed solution. To this mixed solution, 80.0 parts by mass of KBM-3063 (hexyltrimethoxysilane) and 40.0 parts by mass of DMDMS were added as a silicon compound and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 1.0 hour to obtain a sol coating liquid 7.

(Production of structure (hereinafter also referred to as “airgel composite structure”))
On the main body part or the intermediate layer, the airgel layers 1 to 7 are formed as follows in the combinations shown in Table 1, and the airgel layer joined integrally to the main body part directly or via the intermediate layer. An airgel composite structure comprising:

[Airgel layer 1]
Using a spray gun (manufactured by Anest Iwata Co., Ltd., product name: W-50-124BPG), the sol coating liquid 1 is formed in a mist shape on the main body or intermediate layer so that the thickness after gelation becomes 200 μm. It was applied in the form and gelled at 60 ° C. for 30 minutes to obtain a structure. Thereafter, the obtained structure was transferred to a sealed container and aged at 60 ° C. for 12 hours.

  Thereafter, the aged structure was immersed in 2000 mL of water and washed for 30 minutes. Next, it was immersed in 2000 mL of methanol and washed at 60 ° C. for 30 minutes. Washing with methanol was performed twice more while exchanging with fresh methanol. Next, it was immersed in 2000 mL of methyl ethyl ketone, and solvent substitution was performed at 60 ° C. for 30 minutes. Washing with methyl ethyl ketone was performed twice more while exchanging with new methyl ethyl ketone. The washed and solvent-substituted structure is dried at 120 ° C. for 6 hours under normal pressure, so that the airgel layer 1 including the airgel having the structure represented by the general formulas (4) and (5) (main body) An airgel composite structure provided with an airgel layer integrally bonded directly to the part or via an intermediate layer was obtained.

[Airgel layer 2]
The sol coating liquid 2 is applied in a mist form on the main body or intermediate layer using a spray gun so that the thickness after gelation is 500 μm, and the structure is gelled at 60 ° C. for 30 minutes. Obtained. Thereafter, the obtained structure was transferred to a sealed container and aged at 60 ° C. for 12 hours.

  Thereafter, the washing and solvent replacement step and the drying step are performed in the same manner as the method described in “Airgel layer 1”, and the airgel layer 2 includes the airgel having the structure represented by the general formulas (4) and (5). An airgel composite structure provided with (an airgel layer integrally bonded to the main body directly or via an intermediate layer) was obtained.

[Airgel layer 3]
The sol coating liquid 3 is applied on the main body or intermediate layer in a mist form using a spray gun so that the thickness after gelation becomes 50 μm, and gelled at 60 ° C. for 30 minutes to form a structure. Obtained. Thereafter, the obtained structure was transferred to a sealed container and aged at 60 ° C. for 12 hours.

  Thereafter, the washing and solvent replacement step and the drying step are performed in the same manner as the method described in “Aerogel layer 1”, and the airgel layer 3 (main body portion) having the structure represented by the above general formulas (4) and (5) The airgel composite structure provided with an airgel layer integrally bonded directly or via an intermediate layer.

[Aerogel layer 4]
Except that the sol coating solution 4 was used in place of the sol coating solution 1 and that the thickness after gelation was 100 μm, the above general formula ( 1), an airgel composite structure including an airgel layer 4 (an airgel layer integrally bonded to a main body part directly or via an intermediate layer) containing an airgel having a structure represented by (1a) and (4) Obtained.

[Airgel layer 5]
Except for using the sol coating solution 5 in place of the sol coating solution 1 and adjusting the thickness after gelation to 30 μm, the above general formula ( 2), (3), (4) and the airgel provided with the airgel layer 5 (the airgel layer joined integrally to the main body part directly or through the intermediate layer) containing the airgel having the structure represented by (5) A composite structure was obtained.

[Aerogel layer 6]
Except that the sol coating liquid 6 was used instead of the sol coating liquid 1 and that the thickness after gelation was 250 μm, the above general formula ( The airgel composite structure provided with the airgel layer 6 (the airgel layer integrally joined to the main body part directly or via the intermediate layer) containing the airgel having the structure represented by 2) and (4) was obtained.

[Airgel layer 7]
Except that the sol coating liquid 7 was used instead of the sol coating liquid 1 and the thickness after gelation was 100 μm, the above general formula ( An airgel composite structure provided with an airgel layer 7 (an airgel layer integrally joined to the main body directly or via an intermediate layer) containing an airgel having the structure represented by 4) and (5) was obtained.

<Comparative Example 1>
A foamed urethane foam structure was obtained by applying a foamed urethane foam (manufactured by Henkel Japan Co., Ltd., product name: Sista M5230) to a glass plate as the main body so as to have a thickness of 100 μm.

(Comparative Example 2)
The sol coating liquid 1 was put in a vat, and an aluminum plate as a main body was immersed in the sol coating liquid 1 and taken out, and gelled at 60 ° C. for 30 minutes to obtain a structure having a gel layer thickness of 200 μm. Thereafter, the obtained structure was transferred to a sealed container and aged at 60 ° C. for 12 hours.

  Thereafter, the washing and solvent replacement step and the drying step were performed in the same manner as the method described in “Airgel layer 1” to obtain an airgel composite structure including the airgel layer X1.

(Comparative Example 3)
The sol coating liquid 1 was applied to a SUS pipe as a main body with a brush and gelled at 60 ° C. for 30 minutes to obtain a structure having a gel layer thickness of 200 μm. Thereafter, the obtained structure was transferred to a sealed container and aged at 60 ° C. for 12 hours.

  Thereafter, the washing and solvent replacement step and the drying step were carried out in the same manner as the method described in “Airgel layer 1” to obtain an airgel composite structure including the airgel layer Y1.

<Various evaluations>
(Water repellency evaluation)
For the airgel composite structure obtained in each example and the structure obtained in each comparative example, the airgel layer and the foamed urethane foam layer were placed horizontally, and 100 μL of pure water was dropped with a microsyringe, After leaving still for 10 seconds, the airgel layer and the foamed urethane foam layer were tilted so as to have an angle of 30 ° with respect to the horizontal to remove water droplets. At this time, “A” indicates that no water droplets remain visually, “B” indicates that the water droplets remaining on the structure are less than 10% by volume of the dropped water droplets, and remained on the structure visually. What was 10 volume% or more of the water drop which the water drop hung was evaluated as "C".

(Appearance evaluation)
The airgel composite structure obtained in each example and the airgel layer and the foamed urethane foam layer of the structure obtained in each comparative example were visually evaluated. "A" when the maximum color area on the coated surface is 95% or more of the coated surface and there is no color unevenness of φ2 mm or more, and there is no color unevenness of 50% or more and less than 95% and φ2 mm or more “B” was defined as “B”, and “C” was defined as having color unevenness of less than 50% and φ2 mm or more.

(Heat resistance evaluation)
The airgel composite structure obtained in each example and the structure obtained in each comparative example were placed on a hot plate having a surface temperature of 200 ° C. so that the airgel layer or the foamed urethane foam layer was on the lower surface, and 200 ° C. For 5 minutes. After heating, visual observation was performed and appearance such as deformation, discoloration, and peeling was evaluated. Those having no change by visual observation were determined to have good heat resistance, and those having deformation, discoloration, peeling, etc. were determined to have poor heat resistance.

  From Table 2, it can be seen that the airgel composite structures of the examples are excellent in the results of appearance evaluation, and the unevenness of the airgel layer is suppressed. In addition, the airgel composite structures of the examples also have good water repellency and heat resistance. Therefore, it can be used in a high temperature environment.

  On the other hand, the structures of Comparative Examples 1 to 3 are inferior in appearance and water repellency, and the same effects as in the examples cannot be obtained. Moreover, the structure of Comparative Example 1 is also inferior in heat resistance.

  DESCRIPTION OF SYMBOLS 3 ... Main-body part, 3a ... Surface of main-body part, 5 ... Airgel layer, 5a ... Sol layer, 10 ... Target object, 10a ... Surface of target object, 4 ... Coating layer, 4a ... Opposite side to main-body part of coating layer Surface, 100, 200 ... structure, L ... circumscribed rectangle, P ... silica particles.

Claims (10)

A method for producing a structure in which an airgel layer is formed,
A method for producing a structure, comprising a step of forming an airgel layer from a mist-like sol.   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 hydrolysis product of the silicon compound having the hydrolyzable functional group. The method for manufacturing the structure according to claim 1.   The method for producing a structure according to claim 2, wherein the sol further contains silica particles.   The manufacturing method of the structure of Claim 3 whose average primary particle diameter of the said silica particle is 1-500 nm.   The manufacturing method of the structure as described in any one of Claims 1-4 whose diameter of the droplet of the said sol is 0.1-1000 micrometers.   The method for producing a structure according to any one of claims 1 to 5, wherein the sol contains a solvent having a boiling point of less than 200 ° C.   The structure includes a main body portion and a coating layer that covers at least a part of the surface of the main body portion, and an airgel layer is formed on at least the coating layer so that the coating layer serves as an intermediate layer. The manufacturing method of the structure as described in any one of Claims 1-6.   The method for manufacturing a structure according to claim 7, wherein the coating layer contains a filler.   The method for manufacturing a structure according to claim 8, wherein the filler is an inorganic filler.   The method for manufacturing a structure according to claim 8 or 9, wherein a content of the filler is 0.1 to 70% by volume with respect to a total volume of the coating layer.

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