JP6330974B2 - Airgel composite material - Google Patents

Description

  The present invention relates to a novel airgel composite material, and more particularly to an airgel composite material suitably used as a heat insulating material for construction, for cryogenic containers, for high temperature containers and the like.

  In recent years, as the demand for comfort and energy saving in living spaces has increased, the shape of the object to be insulated tends to be complex, and the installation space for the heat insulating material tends to be narrow. Therefore, the heat insulating material used for them is requested | required of the further improvement of heat insulation performance and thickness reduction.

  As conventional heat insulating materials, foamable heat insulating materials such as urethane foam and phenol foam are known. However, since these materials have higher thermal conductivity than air, in order to further improve the heat insulation, a material that has better heat insulation than air must be developed.

  As a heat insulating material having better heat insulation than air, there is a heat insulating material filled with a low thermal conductive gas in the void forming foam by using chlorofluorocarbon or CFC substitute foaming agent, etc., but low thermal conductive gas leakage due to deterioration with time There is a possibility that the heat insulation performance may be lowered (for example, Patent Document 1 below).

  Moreover, the vacuum heat insulating material which has a core material using an inorganic fiber and a phenol resin binder is known (for example, the following patent document 2). However, in the case of a vacuum heat insulating material, there is a problem that the heat insulating performance is remarkably lowered due to problems such as deterioration with time or scratches on the packaging bag, and further, the heat insulating material is not flexible and cannot be applied to a curved surface in terms of vacuum packaging.

Japanese Patent No. 4084516 Japanese Patent No. 4898157 U.S. Pat. No. 4,402,927

  At present, airgel is known as a material having the lowest thermal conductivity at normal pressure (for example, Patent Document 3). The airgel has a fine porous structure, so that the heat transfer is reduced by suppressing the movement of gas including air. However, general aerogels are very fragile, difficult to handle, and have problems with productivity. For example, a mass of airgel may be damaged simply by trying to lift it by hand.

  As a technique for solving such problems of conventional heat insulating materials, an airgel sheet using an airgel and a reinforcing material has been devised. However, since the airgel itself is fragile, there is a problem of workability such that airgel (aerogel powder or the like) is dropped from the sheet by impact or bending work.

  This invention is made | formed in view of the said situation, and it aims at providing the airgel composite material which has the outstanding heat insulation and can suppress drop-off | omission of an airgel.

  As a result of intensive studies to achieve the above object, the present inventor has found that a silicon compound having a hydrolyzable functional group or a condensable functional group, and a silicon compound having the hydrolyzable functional group, An airgel (aerogel obtained by drying a wet gel generated from the sol) that is a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group consisting of hydrolysis products is porous. The airgel composite material adhering to the base material having a structure has an excellent heat insulating property, and the airgel has flexibility, and is found to be a material with less aerogel falling off (powder falling), The present invention has been completed.

  The present invention includes a base material having a porous structure and an airgel attached to the base material, wherein the airgel has a hydrolyzable functional group or a condensable functional group, and the hydrolysate. Provided is an airgel composite material, which is a dried product of a wet gel which is a condensate of a sol containing at least one selected from the group consisting of hydrolysis products of silicon compounds having degradable functional groups.

  The airgel composite material of the present invention has excellent heat insulating properties as compared with conventional heat insulating materials. Moreover, according to the airgel composite material of this invention, since the airgel has a softness | flexibility, the fall-off of an airgel can be suppressed compared with the conventional heat insulation material. The airgel composite material of the present invention can be bent according to the flexibility of the base material while suppressing the airgel from falling off because the airgel has flexibility.

  By the way, when supercritical drying is performed in producing an airgel, the production cost may be high, or the production efficiency may not be sufficient due to batch production. On the other hand, in one aspect of the airgel composite material of the present invention, the airgel composite material can be obtained without using supercritical drying.

  The sol may further contain silica particles. Thereby, the further outstanding heat insulation and softness | flexibility can be achieved.

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

  The silicon compound may include a silicon compound having an alkoxy group as the hydrolyzable functional group. The alkoxy group may have 1 to 6 carbon atoms.

  The silicon compound may include a silicon compound having a hydroxyalkyl group as the condensable functional group. Carbon number of the said hydroxyalkyl group can be 1-6.

  The silicon compound may include a polysiloxane compound having a hydrolyzable functional group or a condensable functional group.

［式（Ａ）中、Ｒ^１ａはヒドロキシアルキル基を示し、Ｒ^２ａはアルキレン基を示し、Ｒ^３ａ及びＲ^４ａはそれぞれ独立にアルキル基又はアリール基を示し、ｎは１〜５０の整数を示す。］The polysiloxane compound may include a compound 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. . ]

［式（Ｂ）中、Ｒ^１ｂはアルキル基又はアルコキシ基を示し、Ｒ^２ｂ及びＲ^３ｂはそれぞれ独立にアルコキシ基を示し、Ｒ^４ｂ及びＲ^５ｂはそれぞれ独立にアルキル基又はアリール基を示し、ｍは１〜５０の整数を示す。］The polysiloxane compound may include a compound having a structure represented by the following general formula (B).

[In formula (B), R ^1b represents an alkyl group or an alkoxy group, R ^2b and R ^3b each independently represents an alkoxy group, R ^4b and R ^5b each independently represent an alkyl group or an aryl group, m Represents an integer of 1 to 50. ]

［式（１）中、Ｒ^１及びＲ^２はそれぞれ独立にアルキル基又はアリール基を示し、Ｒ^３及びＲ^４はそれぞれ独立にアルキレン基を示す。］The airgel may have a structure represented by the following general formula (1).

[In Formula (1), 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. ]

［式（２）中、Ｒ^５及びＲ^６はそれぞれ独立にアルキル基又はアリール基を示し、ｂは１〜５０の整数を示す。］The airgel may have a ladder structure including a support portion and a bridge portion, and the bridge portion may have a structure represented by the following general formula (2).

[In Formula (2), R ⁵ and R ⁶ each independently represents an alkyl group or an aryl group, and b represents an integer of 1 to 50. ]

［式（３）中、Ｒ^５、Ｒ^６、Ｒ^７及びＲ^８はそれぞれ独立にアルキル基又はアリール基を示し、ａ及びｃはそれぞれ独立に１〜３０００の整数を示し、ｂは１〜５０の整数を示す。］The airgel may have a ladder structure represented by the following general formula (3).

[In Formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group or an aryl group, a and c each independently represent an integer of 1 to 3000, and b represents 1 to 50 Indicates an integer. ]

  In the airgel composite material of the present invention, the holes in the porous structure may be communication holes, and the total volume of the holes may be 50 to 99% by volume of the total volume of the substrate. As a result, the heat insulating property is further improved.

  The airgel composite material according to the present invention may be configured such that the airgel is filled in the communication hole. Thereby, the heat conduction by air is suppressed and heat insulation is further improved.

  The substrate having the porous structure can be a sheet made of a fibrous material having a diameter of 0.1 to 1000 μm. Thereby, the heat conduction by the fibers can be suppressed, and a sufficient space is secured, so that the impregnation property of the sol into the sheet is improved.

  The airgel composite material of the present invention can be configured such that the airgel adheres to the fibrous substance. Thereby, since airgel exists in the intersection of the said fibrous substances, the heat conduction between fibrous substances can be suppressed and heat insulation is further improved.

  ADVANTAGE OF THE INVENTION According to this invention, while having the outstanding heat insulation, the airgel composite material which can suppress the omission of an airgel can be provided.

FIG. 1 is a cross-sectional view showing an embodiment of an airgel composite material.

  Hereinafter, embodiments of the present invention will be described in detail. 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.

<Airgel composite material>
The airgel composite material of this embodiment includes a base material having a porous structure (porous base material) and an airgel attached to the base material. The airgel includes a silicon compound having a hydrolyzable functional group or a condensable functional group (silicon compound), and a hydrolysis product of the silicon compound having the hydrolyzable functional group (hydrolyzable functional group). Is a dried product of a wet gel (wet gel derived from the sol) which is a condensate of a sol containing at least one selected from the group consisting of hydrolyzed silicon compounds. That is, the airgel 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. The wet gel produced from the sol containing is dried. The airgel is filled, for example, inside the substrate.

  The airgel composite material of the present embodiment includes, for example, a porous substrate and an airgel layer that covers at least a part of the porous substrate. Fig.1 (a) and FIG.1 (b) are sectional drawings which show embodiment of an airgel composite material. An airgel composite material 100 shown in FIG. 1A and an airgel composite material 200 shown in FIG. 1B include a porous substrate 10 and an airgel layer 20. In FIG. 1 (a), the inside of the porous substrate 10 is filled with airgel, and the entire porous substrate 10 is covered with the airgel layer 20. In FIG. 1B, the airgel layer 20 is disposed on the surface of the porous substrate 10.

  The airgel composite material of this embodiment 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. Airgel (aerogel obtained by drying a wet gel generated from the sol), which is a dried product of a wet gel that is a condensate of sol containing at least one kind, achieves both heat insulation and flexibility can do. In particular, the conventional airgel is excellent in heat insulation, but is fragile and difficult to handle. On the other hand, in the airgel composite material of the present embodiment, the use of the specific airgel improves flexibility, so that it is easy to handle. Can be improved.

  The thickness of the airgel layer can be 200 μm or less, 100 μm or less, 80 μm or less, 50 μm or less, or 30 μm or less. By setting the thickness of the airgel layer to 200 μm or less, powder falling is easily suppressed and the airgel layer is easy to handle. The thickness of the airgel layer can be 1 μm or more, 3 μm or more, 5 μm or more, or 10 μm or more.

  The thickness of the airgel composite material of this embodiment may be 100 mm or less, 10 mm or less, or 1 mm or less. By setting the thickness of the airgel composite material to 100 mm or less, the airgel composite material is easily cut and the workability is improved.

(Aerogel)
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. In other words, in the present embodiment, the airgel means “a gel composed of a microporous solid whose dispersed phase is a gas”, which is an aerogel in a broad sense, that is, “Gel compressed of a microporous solid in which the dispersed phase is a gas”. To do. In general, the inside of the airgel has a network-like fine structure, and has a cluster structure in which airgel particles (particles constituting the airgel) of about 2 to 20 nm are combined. 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. For example, the airgel layer in the present embodiment is a layer composed of airgel. The airgel layer may be a layer containing an airgel having a structure derived from polysiloxane.

  The airgel of the present embodiment is a group consisting of 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 is a dried product of a wet gel that is a condensate of a sol containing at least one selected from the above. That is, the airgel of this embodiment is obtained from 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 can be obtained by drying a wet gel produced from a sol containing at least one selected from the group consisting of: By adopting these embodiments, heat insulation and flexibility are excellent. 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).

  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 of this 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 of this 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 of this embodiment. By adopting these aspects, it becomes easy to obtain an airgel that is further excellent in heat insulation and flexibility. By employ | adopting each aspect, the airgel which has the heat insulation and the softness | flexibility according to each aspect can be obtained.

[First aspect]
The airgel of 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 ( A wet gel which is a condensate of a 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 product. That is, the airgel of this embodiment is a hydrolysis product of a polysiloxane compound having a hydrolyzable functional group or a condensable functional group (in the molecule) and 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. 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 phenolic hydroxyl 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 (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 the formula (A), R ^1a includes, for example, a hydroxyalkyl group having 1 to 6 carbon atoms, specifically, 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 formula (A), n can be set to 2 to 30, and may be 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), examples of R ^1b include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms, and specific examples include a methyl group, a methoxy group, and an ethoxy group. It is done. 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 can be 2 to 30, and may be 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.

  Since it becomes easier to obtain good reactivity, the content of the polysiloxane compound group contained in the sol (the content of the polysiloxane compound having a hydrolyzable functional group or a condensable functional group, and the water The total content of hydrolysis products of polysiloxane compounds having degradable functional groups) can be 1 part by mass or more with respect to 100 parts by mass of the total amount of sol. Alternatively, it may be 4 parts by mass or more, 5 parts by mass or more, or 7 parts by mass or more. Since it becomes easier to obtain good compatibility, the content of the polysiloxane compound group can be 50 parts by mass or less with respect to 100 parts by mass of the total amount of the sol, and may be 30 parts by mass or less. 15 parts by mass or less. That is, the content of the polysiloxane compound group may be 1 to 50 parts by mass with respect to 100 parts by mass of the total amount of sol, may be 3 to 50 parts by mass, and is 4 to 50 parts by mass. 5-50 mass parts may be sufficient, 7-30 mass parts may be sufficient, and 7-15 mass parts may be sufficient.

[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 of this embodiment includes a silicon compound (excluding a polysiloxane compound) having a hydrolyzable functional group or a condensable functional group (in the molecule), and silicon having the hydrolyzable functional group. It may be a dried product of a wet gel that is a condensate of sol containing at least one compound selected from the group consisting of hydrolysis products of compounds (hereinafter sometimes referred to as “silicon compound group”). The number of silicon atoms in the molecule of the silicon compound can 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 resistance, 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, and ethyltrimethoxysilane.

  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-amino Propyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like can also be used.

  Furthermore, bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, etc. can be used as the silicon compound having 3 or less hydrolyzable functional groups at the molecular ends.

  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) can be 5 parts by mass or more with respect to 100 parts by mass of the total amount of the sol. 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 can be 50 parts by mass or less with respect to 100 parts by mass of the total amount of the sol, and may be 30 parts by mass or less. It may be 25 parts by mass or less, or 20 parts by mass or less. That is, the said content of a silicon compound group can be 5-50 mass parts with respect to 100 mass parts of total amounts of sol, may be 10-30 mass parts, and is 12-30 mass parts, 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 can more easily obtain good reactivity, and therefore can be 5 parts by mass or more with respect to 100 parts by mass of the total amount of sol. 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. Since it becomes easier to obtain good compatibility, the sum of the contents can be 50 parts by mass or less, or 30 parts by mass or less, and 25 parts by mass with respect to 100 parts by mass of the sol. Or less. That is, the total sum of the contents can be 5 to 50 parts by mass with respect to 100 parts by mass of the sol, 10 to 30 parts by mass, or 15 to 30 parts by mass. 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 to the content of the silicon compound group (polysiloxane compound group: silicon compound group) can be 1: 0.5 to 1: 4. It may be ˜1: 2, may be 1: 2 to 1: 4, and may be 1: 3 to 1: 4. By setting the ratio of the content of these compounds to 1: 0.5 or more, it becomes easier to obtain good compatibility. By setting the content ratio to 1: 4 or less, it becomes easier to suppress the shrinkage of the gel.

[Third embodiment]
The airgel of this embodiment can have a structure represented by the following general formula (1). The airgel of this embodiment can have a structure represented by the following general formula (1a) as a structure including the structure represented by the 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, a flexible airgel having low thermal conductivity can be easily obtained. 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]
The airgel of the present embodiment may be an airgel having a ladder type structure including a support portion and a bridge portion, and the bridge portion may be an airgel having a structure represented by the following general formula (2). . By introducing such a ladder structure into the airgel skeleton, 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 the chain length, and the interval between the structures to be the bridging part are not particularly limited, but from the viewpoint of further improving the heat resistance and mechanical strength, the ladder type structure has the following general formula ( It may have a ladder 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. Similarly, when c is an integer of 2 or more, 2 or more R ⁸ may be the same or different from each other.

From the viewpoint of obtaining further excellent flexibility, in formula (2) and formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ (wherein R ⁷ and R ⁸ are only in formula (3)) are: It may be independently an alkyl group having 1 to 6 carbon atoms or a phenyl group. The alkyl group may be a methyl group. In formula (3), a and c can be independently 6 to 2000, and may be 10 to 1000. In Formula (2) and Formula (3), b can be set to 2 to 30, and may be 5 to 20.

[Fifth aspect]
The airgel of this embodiment may contain silica particles. The sol that gives the airgel may further contain silica particles. That is, the airgel of this 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. That is, the airgel layer may be composed of a layer obtained by drying a wet gel generated 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 spherical, eyebrows, and association types. 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 can easily be imparted with an appropriate strength to the airgel, and an airgel excellent in shrinkage resistance during drying can be easily obtained. It may be 10 nm or more. On the other hand, since it becomes easy to suppress the solid heat conduction of the silica particles and it becomes easy to obtain an airgel excellent in heat insulating properties, the average primary particle diameter of the silica particles can be 500 nm or less, even if it is 300 nm or less. It may be 250 nm or less. That is, the average primary particle diameter of the silica particles can be 1 to 500 nm, 5 to 300 nm, or 10 to 250 nm.

Since it becomes easy to obtain an airgel excellent in shrinkage resistance, the number of silanol groups per gram of silica particles can be 10 × 10 ¹⁸ pieces / g or more, and may be 50 × 10 ¹⁸ pieces / g or more. It may be 100 × 10 ¹⁸ pieces / g or more. Since it becomes easy to obtain a homogeneous airgel, the number of silanol groups per gram of silica particles can be 1000 × 10 ¹⁸ pieces / g or less, and may be 800 × 10 ¹⁸ pieces / g or less, and 700 × 10 ¹⁸ pieces / g or less may be sufficient. That is, the number of silanol groups per gram of silica particles can be 10 × 10 ^{18 to} 1000 × 10 ¹⁸ pcs / g, or 50 × 10 ^{18 to} 800 × 10 ¹⁸ pcs / g, or 100 × 10 10 ^18-700 may be a × ^{10 18} cells / g.

  Since it becomes easy to impart an appropriate strength to the airgel and it becomes easy to obtain an airgel excellent in shrinkage resistance at the time of drying, the content of the silica particles contained in the sol is 1 mass relative to 100 mass parts of the total amount of the sol. It may be 4 parts by mass or more. Since it becomes easy to suppress the solid heat conduction of the silica particles and it becomes easy to obtain an airgel excellent in heat insulation, the content of the silica particles contained in the sol can be 20 parts by mass or less, and 15 parts by mass or less. It may be 12 parts by mass or less, 10 parts by mass or less, or 8 parts by mass or less. That is, the content of silica particles can be 1 to 20 parts by mass with respect to 100 parts by mass of the total amount of sol, and may be 4 to 15 parts by mass or 4 to 12 parts by mass. 4-10 mass parts may be sufficient and 4-8 mass parts may be sufficient.

[Other aspects]
The airgel of this embodiment can have a structure represented by the following general formula (4). The airgel of the present embodiment contains silica particles and can have a structure represented by the following general formula (4).

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 of the present embodiment can have a structure represented by the following general formula (5). The airgel of the present embodiment contains silica particles and can have a structure represented by the following general formula (5).

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 of this embodiment can have a structure represented by the following general formula (6). The airgel of the present embodiment contains silica particles and can have a structure represented by the following general formula (6).

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 of this 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 of this embodiment may have at least one of the structures represented by the general formulas (4), (5), and (6) without containing silica particles.

(Porous substrate)
“Porous substrate” is a general term for materials containing a large number of pores (micropores), and is classified into microporous materials, mesoporous materials, and macroporous materials depending on the size of the pores. In form, it is referred to as a “porous substrate” regardless of the size of the pores. Examples of the porous substrate include a substrate made of a fibrous material and a substrate that forms a three-dimensional complex skeleton. Specifically, examples of the porous substrate include a nonwoven fabric and a porous sheet having a porous structure. The pores in the porous structure (pores constituting the porous structure) may be communication holes. The communication hole is a state in which the pores (voids) inside the porous substrate and the pores (voids) on the surface of the porous substrate are combined to form a two-dimensional or three-dimensional void network. Means the state. The airgel may be filled in the communication hole.

  The size of the hole indicates the maximum linear distance of the shape formed by the hole on the observation surface when observing the cross-sections of any 10 locations on the substrate along the surface direction of the substrate (direction orthogonal to the thickness direction). . The size of the holes can be 0.1 to 1000 μm. If the size is 0.1 μm or more, the sol coating liquid can be easily impregnated. If the size is 1000 μm or less, it is possible to easily prevent the airgel from dropping out of the holes.

The total volume of the pores (porosity, porosity) may be 50 to 99% by volume of the total volume of the substrate, may be 60 to 99% by volume, and 70 to 99% by volume. There may be. As a result, the heat insulating property is further improved. When the holes in the porous structure are communication holes, the total volume of the holes may satisfy the above range. The volume of the hole can be obtained based on the following formula.
Porosity (volume%) = (1−true volume of substrate / apparent volume of substrate) × 100
True volume of substrate: Volume calculated from density and mass of substrate (material constituting substrate) Apparent volume of substrate: Volume calculated from substrate dimensions

  Examples of the material constituting the porous substrate include organic polymers such as vinyl polymer, polyester, polyacrylonitrile, polysulfone, phenol resin, polyurethane, polyamide, polyimide, and carbon; glass, metal (for example, nickel), metal oxide Examples thereof include inorganic porous materials such as (for example, alumina). Examples of the vinyl polymer include polyolefins (for example, polyethylene and polypropylene), cellulose acetate, nitrocellulose, polytetrafluoroethylene, polycarbonate, polystyrene, polyvinyl alcohol, polyacrylic acid ester, and polyvinyl acetate. As a material constituting the porous substrate, glass, metal or metal oxide (for example, alumina) can be used because it is further excellent in heat resistance, and glass or alumina is used from the point of further reducing thermal conductivity. Can be used.

  In the airgel composite material of the present embodiment, for example, the airgel is present in a void portion of a base material made of a fibrous substance or a base material forming a three-dimensional complex skeleton. By taking such a structure, the movement of the air with respect to the thickness direction is suppressed, and the heat insulation is easily improved. Furthermore, since the solid heat conduction path is highly complicated by filling with airgel, it is effective in reducing the heat conductivity.

  The porous substrate may be a sheet (nonwoven fabric, fiber sheet, etc.) made of a fibrous material. In such a porous substrate, for example, airgel is attached to a fibrous substance.

  Fibrous materials include nylon, polyester, polypropylene, polyacrylonitrile, vinylon, polyolefin, polyurethane, rayon, carbon fiber and other organic fibers; glass, rock wool, ceramic and other inorganic fibers; copper, iron, stainless steel, gold, silver And metal fibers such as aluminum. As the fibrous material, inorganic fibers can be used from the viewpoint of further excellent heat resistance, and glass, rock wool, or ceramic can be used from the viewpoint of further reducing the thermal conductivity.

  The diameter (fiber diameter) of the fibrous substance can be 0.1 to 1000 μm, may be 0.1 to 100 μm, and may be 0.1 to 80 μm. Thereby, the heat conduction by the fibers can be easily suppressed, and the voids are sufficiently secured, so that the impregnation of the sol into the sheet is improved. The diameter of the fibrous substance can be measured by observing with a microscope and measured as an average value of the diameters of 10 arbitrarily selected fibers.

<Method for producing airgel composite material>
Next, the manufacturing method of an airgel composite material is demonstrated. The airgel composite material of the present embodiment 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 can be obtained by drying a wet gel (wet gel produced from the sol) which is a condensate of sol containing at least one of the above. The method for producing an airgel composite material of the present embodiment includes a drying step of drying the wet gel, and includes a hydrolyzable functional group or a silicon compound having a condensable functional group, and the hydrolyzable functional group. There may be further provided a gel generation step of obtaining the wet gel by reacting a sol containing at least one selected from the group consisting of hydrolysis products of silicon compounds. The airgel composite material can be produced, for example, by the following method.

  That is, the airgel composite material of the present embodiment includes, for example, a sol generation step for producing a sol for forming an airgel, an impregnation step for impregnating a porous substrate with the sol obtained in the sol generation step, and a sol Gel generation step of gelling to obtain a wet gel, aging step of aging a porous substrate filled with voids with sol or wet gel, and cleaning and / or solvent replacement step of cleaning and / or solvent replacement of the aged composite material And a drying step of drying the washed and / or solvent-substituted composite material. The “sol” is a state before the gelation reaction occurs, and in the present embodiment, the state in which the silicon compound (and if necessary, further silica particles) is dissolved or dispersed in the solvent. means. The gel generation step may be performed after the impregnation step, or the impregnation step may be performed after the gel generation step.

  When using a porous substrate made of a fibrous material, the fibrous material is dispersed in the sol coating solution in advance, and the fibrous material to which the airgel has adhered is passed through an aging step, a washing / solvent replacement step, and a drying step. An airgel composite material can be obtained by preparing a substance and making it into a non-woven fabric.

  In the fibrous material to which the above-mentioned aerogel is attached, the bonding mode such as bonding by the chemical interaction between the functional group on the fiber surface and the functional group on the airgel surface, bonding by intermolecular interaction between the fiber surface and the airgel is limited. Not what you want. Airgel particles (particles constituting the airgel) may be attached to part or the whole of the fiber surface.

  Hereinafter, each process of the manufacturing method of the airgel composite material of this embodiment is demonstrated. In the following description, the case where the airgel is a layered airgel layer is described as an example, but the airgel is not limited to being layered.

(Sol generation process)
The sol generation step is, for example, a step of mixing a silicon compound (and if necessary, further silica particles) and a solvent, performing a hydrolysis reaction, and then performing a sol-gel reaction to obtain a semi-gelled sol coating liquid. is there. In this 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, it is good to contain a silica particle in a sol from a viewpoint of shortening the process time in this process, the gel production | generation process mentioned later, an impregnation process, and an aging process, and making heating and drying temperature low.

  The solvent is not particularly limited as long as good impregnation properties can be obtained in the impregnation step described later, and for example, water or a mixed solution of water and alcohol can be used. Examples of the alcohol include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol and t-butanol. Among these, water can be used because of its high surface tension and low volatility.

  Examples of the acid catalyst include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, and hypochlorous acid; Acid phosphates such as aluminum phosphate, acid magnesium phosphate and acid zinc phosphate; organic such as formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, azelaic acid Carboxylic acids are mentioned. Among these, as an acid catalyst that further improves the water resistance of the obtained airgel composite material, organic carboxylic acids can be used, and specifically include acetic acid, formic acid, propionic acid, oxalic acid and malonic acid, Acetic acid may be used. 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 an acid catalyst can be 0.001-0.1 mass part with respect to 100 mass parts of total amounts of a 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.

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

  As the ionic surfactant, a cationic surfactant, an anionic surfactant, an amphoteric surfactant and the like can be used, and a cationic surfactant or an anionic surfactant may be used. Examples of the cationic surfactant include cetyltrimethylammonium bromide 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 have the effect of reducing the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer and suppressing phase separation in the impregnation step described later. It is considered.

  The addition amount of the surfactant depends on the type of the surfactant or the type and amount of the silicon compound. For example, the addition amount of the surfactant may be 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. Accordingly, 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 And acid amides such as N-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, when urea is used as the thermally hydrolyzable compound, the amount added can be 1 to 200 parts by mass with respect to 100 parts by mass of the total amount of the silicon compound, even if it is 2 to 150 parts by mass. Good. By making the addition amount 1 mass part or more, it becomes easier to obtain good reactivity. By making the addition amount 200 parts by mass or less, it becomes easy to suppress precipitation of crystals and a decrease in gel density.

  The hydrolysis in the sol production step depends on the types and amounts of the silicon compound, silica particles, acid catalyst, surfactant and the like in the mixed solution, but for example, under a temperature environment of 20 to 60 ° C. for 10 minutes to 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, when urea is used as the thermally hydrolyzable compound, the temperature environment of the sol generation step can be 0 to 40 ° C, and may be 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, sec- Aliphatic amines such as tilamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine; morpholine, N -Nitrogen-containing heterocyclic compounds such as methylmorpholine, 2-methylmorpholine, piperazine and derivatives thereof, piperidine and derivatives thereof, imidazole and derivatives thereof, and the like. Among these, ammonium hydroxide (ammonia water) has high volatility and is difficult to remain in the airgel layer after drying, and is excellent in terms of being hard to impair water resistance and economical. You may use said 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 It can be performed in a shorter time. In particular, ammonia is highly volatile and hardly remains in the airgel composite material. Therefore, an airgel composite material with better water resistance can be obtained by using ammonia as the base catalyst.

  The addition amount of a base catalyst can be 0.5-5 mass parts with respect to 100 mass parts of total amounts of a silicon compound (polysiloxane compound group and silicon compound group), and may be 1-4 mass parts. . By making the addition amount of the base catalyst 0.5 parts by mass or more, gelation can be performed in a shorter time. By making the addition amount of the base catalyst 5 parts by mass or less, it is possible to easily suppress a decrease in water resistance.

(Impregnation process)
The impregnation step is, for example, a step of filling the sol coating liquid into a porous substrate or adhering it to a raw material fiber of a nonwoven fabric. Specifically, a dipping method in which the material of the porous base material is immersed in the sol coating liquid or a coating method in which the sol coating liquid is applied to the porous base material can be mentioned. The impregnation method is not limited, and a suitable method can be selected according to physical properties such as the size, shape, and elastic modulus of the porous substrate.

  Regarding the method of treating the sol coating liquid on the raw material fibers of the nonwoven fabric, for example, a wet method in which the fibers are put into a container containing the sol coating liquid and the fibers are surface-treated by heating and stirring for a predetermined time, and the fibers are mixed with a stirrer. A dry method in which a sol coating solution is added while stirring at high speed to uniformly treat the fiber surface can be mentioned. The method for treating the sol coating solution on the fiber is not particularly limited, but a wet method can be used because the sol coating solution is easy to uniformly treat the fiber surface.

  As the coating method (coating machine), a die coater, a comma coater, a bar coater, a kiss coater, a roll coater, etc. can be used, and it is appropriately used depending on the material or thickness of the porous substrate, the viscosity or the coating amount of the sol coating solution, etc. . As the heating / drying method, heating, hot air blowing, or the like can be used.

  The heating / drying conditions after applying the sol coating liquid to the porous substrate are, for example, heating / drying so that the moisture content of the airgel layer after heating / drying is 10% by mass or more (for example, 50% by mass or more). Let By setting the water content to 10% by mass or more, it becomes easy to obtain adhesiveness with the porous substrate.

  The heating / drying temperature varies depending on the amount of water and / or the amount of the organic solvent in the sol coating liquid, the boiling point of the organic solvent, etc., but can be set to, for example, 50 to 150 ° C, or 60 to 120 ° C. Good. By setting the heating / drying temperature to 50 ° C. or higher, gelation can be performed in a shorter time. By setting the heating / drying temperature to 150 ° C. or lower, it becomes easy to obtain adhesion with the porous substrate.

  The heating / drying time varies depending on the heating / drying temperature, but may be, for example, 0.2 to 10 minutes, or may be 0.5 to 8 minutes. By setting the heating / drying time to 0.2 minutes or more, the airgel layer is easily formed. By setting the heating / drying time to 10 minutes or less, it becomes easy to obtain adhesion with the porous substrate. As the heating / drying conditions, suitable heating / drying conditions can be appropriately set by simple experiments in advance.

  A separator can be laminated on both surfaces of the porous substrate. By laminating the separator, it is possible to prevent transfer or contamination of the uncured sol in the conveyance of the porous substrate and other processes. Examples of the method of laminating the separator in the impregnation step include a method of laminating after impregnating the sol coating liquid, and a method of laminating after heating and drying. Examples of the separator include inorganic fibers such as glass nonwoven fabric and glass cloth; organic fibers such as polyimide, polyamideimide, and polyester; base film made of polyolefin, polyester, polycarbonate, polyimide, and the like; release paper; copper foil, aluminum foil, and the like Can be mentioned. Note that the separator may be subjected to a release treatment in addition to the mat treatment and the corona treatment. Among these, when laminating after impregnating the sol coating liquid, a base film made of polyolefin, polyester, polycarbonate, polyimide, or the like can be used from the viewpoint of keeping the water content of the airgel layer high. In addition, when laminating after heating and drying, inorganic fibers such as glass nonwoven fabric and glass cloth; organics such as polyimide, polyamideimide, and polyester, from the viewpoint that they do not need to be peeled off in the aging step and washing / solvent replacement step described later. A fiber etc. can be used.

(Gel generation process)
The gel generation step is a step of obtaining a wet gel by gelling the sol obtained in the sol generation step. In this step, a base catalyst can be used to promote gelation. Since it is often difficult to determine the end point of gelation of the sol, gelation of the sol and subsequent aging may be performed in a series of operations.

  The gelation of the sol in the gel generation step may be performed in a sealed container so that the solvent and the base catalyst do not volatilize. The gelation temperature can be 30-90 ° C, but it may be 40-80 ° C. By setting the gelation temperature to 30 ° C. or higher, gelation can be performed in a shorter time, and a wet gel with high strength can be obtained. By setting the gelation temperature to 90 ° C. or less, it becomes easy to suppress the volatilization of the solvent (particularly alcohol), and thus gelation can be performed while suppressing volume shrinkage.

(Aging process)
The aging step is a step of aging the composite material obtained by the impregnation step or the gel generation step by heating. In this step, from the viewpoint of easily suppressing a decrease in adhesiveness between the airgel layer and the porous substrate, the airgel layer is preferably aged so that the water content is 10% by mass or more, and is 50% by mass or more. It is better to age. The aging method is not particularly limited as long as the above range is satisfied.For example, a method of aging the composite material in a sealed atmosphere, and a constant temperature and humidity chamber that can suppress a decrease in moisture content due to heating, etc. A method of aging is mentioned.

  The aging temperature can be, for example, 40 to 90 ° C, and may be 50 to 80 ° C. By setting the aging temperature to 40 ° C. or more, the aging time can be shortened. By setting the aging temperature to 90 ° C. or lower, it is possible to suppress a decrease in moisture content.

  The aging time can be, for example, 1 to 48 hours, or 3 to 24 hours. By setting the aging time to 1 hour or longer, further excellent heat insulation can be obtained. By setting the aging time to 48 hours or less, high adhesion to the porous substrate can be obtained.

(Washing / solvent replacement process)
The washing / solvent replacement step is a step having a step of washing the composite material obtained by the aging step (washing step) and a step of substitution with a solvent suitable for the drying step described later (solvent substitution step). The washing and solvent replacement technique is not particularly limited, and for example, continuous treatment can be performed using a plurality of washing tanks and / or solvent replacement tanks in a roll-to-roll manner. The washing / solvent replacement step can be performed in a form in which only the solvent replacement step is performed without performing the step of cleaning the composite material, but it reduces impurities such as unreacted substances and by-products in the airgel layer, and more. From the viewpoint of enabling the production of a highly pure airgel composite material, the aged airgel layer may be washed.

  In the washing step, the composite material obtained in the aging step can be repeatedly washed with 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 described later, a low surface tension solvent can 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, among the above organic solvents, hydrophilic organic solvents such as methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone can be used, and methanol, ethanol, or methyl ethyl ketone may be used from the economical point of view. .

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

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

  In the solvent replacement step, the solvent in the washed airgel layer can be replaced with a predetermined replacement solvent in order to suppress shrinkage of the airgel layer in the drying step described later. At this time, the replacement efficiency can be improved by heating. Specific examples of the solvent for substitution include a low surface tension solvent described later in the drying step when drying is performed under atmospheric pressure at a temperature lower than the critical point of the solvent used for drying. On the other hand, when supercritical drying is performed, as a replacement solvent, for example, ethanol, methanol, 2-propanol, dichlorodifluoromethane, or carbon dioxide may be used alone, or a mixture of two or more of these may be used. Also good.

  Examples of the low surface tension solvent include a solvent having a surface tension at 20 ° C. of 30 mN / m or less. The surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of the low surface tension solvent include pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 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); methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), Examples include esters such as isobutyl acetate (23.7) and ethyl butyrate (24.6). The parenthesis indicates the surface tension at 20 ° C., and the unit is [mN / m]. Among these, aliphatic hydrocarbons (hexane, heptane, etc.) are excellent in low surface tension and work environment. 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 at normal pressure of 100 ° C. or less may be used because it is easy to dry in the drying step described later. You may use said solvent individually or in mixture of 2 or more types.

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

  The temperature in the solvent substitution step can be a temperature not higher than the boiling point of the solvent used for substitution, and can be, for example, about 30 to 60 ° C.

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

  When separators are laminated in the impregnation step, the separator can be extracted before the washing step and laminated again after the solvent substitution step from the viewpoint of improving the efficiency of washing the airgel layer and replacing the solvent. As a separator, by processing with a composite material without performing extraction, in the washing / solvent replacement step to the drying step, it is possible to suppress a decrease in efficiency of washing the airgel layer and solvent substitution, and drying in the drying step described later A glass nonwoven fabric, organic fiber, etc. can be used from a viewpoint which can suppress the fall of efficiency.

(Drying process)
In the drying step, the composite material that has been washed and / or solvent-substituted as described above is dried. Thereby, the final airgel composite material 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 pressure drying or supercritical drying can be used from the viewpoint of easy production of a low-density airgel layer. Also, atmospheric drying can be used from the viewpoint of being able to produce at low cost. In the present embodiment, the normal pressure means 0.1 MPa (atmospheric pressure).

  The airgel composite material of this embodiment can be obtained by drying the washed and / or solvent-substituted composite material at a temperature below the critical point of the solvent used for drying under atmospheric pressure. 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 porous substrate, but can be 60 to 180 ° C., and is 90 to 150. It may be ° C. The drying time varies depending on the capacity of the airgel layer and the drying temperature, but can be 2 to 48 hours. In the present embodiment, drying can be accelerated by applying pressure within a range that does not impair productivity.

  In the manufacturing method of the airgel composite material of this embodiment, you may pre-dry before a drying process from a viewpoint of improving the drying efficiency in normal-pressure drying. Although it does not restrict | limit especially as a pre-drying method, For example, if it is a roll-to-roll system, it can also perform continuously from a washing | cleaning and solvent substitution process to a drying process. The pre-drying temperature can be 60 to 180 ° C, and may be 90 to 150 ° C. The pre-drying time can be 1 to 30 minutes. Note that the composite material obtained by such pre-drying can be further dried in the drying step.

  When separators are laminated in the washing / solvent replacement step, the separators can be extracted before pre-drying and laminated again after pre-drying from the viewpoint of drying efficiency and transport efficiency. Moreover, when performing continuously from a washing | cleaning and solvent substitution process to a drying process, a separator can be extracted before a washing | cleaning process, and a separator can be laminated | stacked again after pre-drying. As a separator laminated after pre-drying, a glass nonwoven fabric, organic fiber, etc. can be used from a viewpoint which can suppress the fall of the drying efficiency in a drying process.

  The airgel composite material of the present embodiment can also be obtained by supercritical drying of a cleaned and / or solvent-substituted composite material. 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. Is substituted with carbon dioxide having a lower critical point than that of the solvent, and then carbon dioxide alone or a mixture of carbon dioxide and the solvent is removed.

  The airgel composite material of the present embodiment described as described above includes 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. An airgel (aerogel obtained by drying a wet gel generated from the sol) that is a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group, and a substrate having a porous structure It is possible to form an airgel sheet and board, which has been conventionally difficult to handle. Because of such advantages, the airgel composite material of the present embodiment can be applied to a use as a heat insulating material in a cryogenic container, a space field, an architectural field, an automobile field, a home appliance field, a semiconductor field, an industrial facility, and the like. Further, the airgel composite material of the present embodiment can be used for water repellent, sound absorbing, static vibration, catalyst support, etc., in addition to the use as a heat insulating material.

  Next, the present invention will be described in more detail with reference to the following examples, but these examples do not limit the present invention in any way. In the following, the airgel sheet having the structure represented by the general formula (2) has a ladder structure including a support portion and a bridge portion, and the bridge portion is represented by the general formula (2). Has a structure.

<Production of airgel composite material>
Example 1
[Sol coating solution 1]
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 120.0 parts by mass, and methanol. 80.0 parts by mass and 0.10 parts by mass of acetic acid as an acid catalyst were mixed to obtain a mixture. To this mixture, 60.0 parts by mass of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: LS-530, hereinafter abbreviated as “MTMS”) and dimethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Product name: LS-520 (hereinafter abbreviated as “DMDMS”) 40.0 parts by mass was added and reacted at 25 ° C. for 2 hours. To this, 40.0 parts by mass of 5% ammonia water was added as a base catalyst to obtain a sol coating solution 1.

[Aerogel sheet 1]
The sol coating solution 1 is put into a vat, and a glass nonwoven fabric (product length: MGP BMS-5, manufactured by Nippon Sheet Glass Co., Ltd., product length: 1.5 μm, void) is 300 mm × (width) 200 mm × (thickness) 3 mm. The sol coating solution 1 was impregnated with the sol coating solution 1. After confirming that the glass nonwoven fabric was sufficiently impregnated with the sol coating solution 1 and that the glass nonwoven fabric was submerged in the sol coating solution, it was gelled at 60 ° C. for 30 minutes to obtain an airgel sheet. Thereafter, the obtained airgel sheet (wet gel) was transferred to a sealed container and aged at 60 ° C. for 12 hours.

  Thereafter, the aged airgel sheet 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 airgel sheet 1 having the structure represented by the above general formulas (4) and (5) was obtained by drying the washed and solvent-substituted airgel sheet at 120 ° C. for 6 hours under normal pressure.

(Example 2)
[Sol coating liquid 2]
ST-OZL-35 (product name, average primary particle size: 100 nm, solid content: 35% by mass) 100.0 parts by mass and 100.0 parts by mass of water as a silica particle-containing raw material 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB (cetyltrimethylammonium bromide) as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound To obtain a mixture. To this mixture, 60.0 parts by mass of MTMS as a silicon compound, and X-22-160AS (product name, manufactured by Shin-Etsu Chemical Co., Ltd.) as a polysiloxane compound having a structure represented by the above general formula (A) 20.0 parts by mass were 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 2.

[Aerogel sheet 2]
Using the sol coating liquid 2, an airgel sheet 2 having a structure represented by the general formulas (1), (1a), (2), (4) and (5) in the same manner as in Example 1. Obtained.

(Example 3)
[Sol coating solution 3]
100.0 parts by mass of PL-2L as a raw material containing silica particles, 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 As a heat hydrolyzable compound, 120.0 parts by mass of urea was mixed to obtain a mixture. In this mixture, 80.0 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”) 20.0 parts by mass of A)) 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.

  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 parts by mass of t-butylamine were mixed and reacted at 30 ° C. for 5 hours. Thereafter, this reaction solution was heated at 140 ° C. under reduced pressure of 1.3 kPa for 2 hours to remove volatile components, thereby obtaining a bifunctional alkoxy-modified polysiloxane compound (polysiloxane compound A) at both ends.

[Aerogel sheet 3]
Using the sol coating liquid 3, an airgel sheet 3 having a structure represented by the general formulas (2), (3), (4) and (5) was obtained in the same manner as in Example 1.

Example 4
[Sol coating solution 4]
100.0 parts by mass of PL-2L 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 mixture. In this mixture, 60.0 parts by mass of MTMS as a silicon compound and a trifunctional alkoxy-modified polysiloxane compound having both ends as a polysiloxane compound having a structure represented by the above general formula (B) (hereinafter referred to as “polysiloxane compound”) 40.0 parts by mass of B) was added, and the mixture was 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 4.

  The “polysiloxane compound B” was synthesized as follows. First, in a 1 L three-necked flask equipped with a stirrer, a thermometer, and a Dimroth condenser, 100.0 parts by mass of XC96-723, 202.6 parts by mass of tetramethoxysilane, and 0 of t-butylamine were added. 50 parts by mass were mixed and reacted at 30 ° C. for 5 hours. Thereafter, this reaction solution was heated at 140 ° C. under reduced pressure of 1.3 kPa for 2 hours to remove volatile components, thereby obtaining a trifunctional alkoxy-modified polysiloxane compound (polysiloxane compound B) at both ends.

[Aerogel sheet 4]
Using the sol coating liquid 4, an airgel sheet 4 having a structure represented by the general formulas (2), (3), (4) and (5) was obtained in the same manner as in Example 1.

(Example 5)
[Sol coating solution 5]
100.0 parts by mass of PL-2L as a raw material containing silica particles, 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 As a heat hydrolyzable compound, 120.0 parts by mass of urea was mixed to obtain a mixture. To this mixture, 60.0 parts by mass of MTMS and 40.0 parts by mass of DMDMS were added as silicon compounds 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 solution 5.

[Aerogel sheet 5]
Except for using the sol coating solution 5 and using a glass nonwoven fabric (manufactured by Olivest Co., Ltd., product name: Boroid GMU, fiber diameter: 13 μm, porosity: 95% by volume), the above general formula is used. The airgel sheet 5 having the structure represented by (4) and (5) was obtained.

(Example 6)
[Sol coating liquid 6]
100.0 parts by mass of PL-2L as a raw material containing silica particles, 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 As a heat hydrolyzable compound, 120.0 parts by mass of urea was mixed to obtain a mixture. To this mixture, 60.0 parts by mass of MTMS as a silicon compound, 20.0 parts by mass of DMDMS, and 20.0 parts by mass of X-22-160AS as a polysiloxane compound were added 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 6.

[Aerogel sheet 6]
In the same manner as in Example 1 except that the sol coating liquid 6 and a glass nonwoven fabric (boroid GMU) were used, the above general formulas (1), (1a), (2), (4) and (5) An airgel sheet 6 having the structure shown was obtained.

(Example 7)
[Sol coating liquid 7]
100.0 parts by mass of PL-2L as a raw material containing silica particles, 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 As a heat hydrolyzable compound, 120.0 parts by mass of urea was mixed to obtain a mixture. To this mixture, 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS and 20.0 parts by mass of polysiloxane compound A as a polysiloxane compound were added 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.

[Aerogel sheet 7]
A structure represented by the above general formulas (2), (3), (4) and (5) in the same manner as in Example 1 except that the sol coating liquid 7 is used and a glass nonwoven fabric (boroid GMU) is used. An airgel sheet 7 having the following was obtained.

(Example 8)
[Sol coating 8]
100.0 parts by mass of PL-2L as a raw material containing silica particles, 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 As a heat hydrolyzable compound, 120.0 parts by mass of urea was mixed to obtain a mixture. To this mixture, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as a silicon compound and 20.0 parts by mass of polysiloxane compound B as a polysiloxane compound were added 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 8.

[Aerogel sheet 8]
In a flask, 100 parts by mass of glass fiber (manufactured by Nippon Electric Glass Co., Ltd., product name: ECS03T-187, fiber diameter: 13 μm) was added to 100 parts by mass of the sol coating liquid 8 at 60 ° C. for 60 minutes. After stirring at 200 rpm, the obtained glass fiber dispersion sol was transferred to a sealed container and aged at 60 ° C. for 8 hours.

  Thereafter, the washing / solvent replacement step and the drying step are performed in the same manner as in Example 1, and the glass fiber to which the airgel having the structure represented by the general formulas (2), (3), (4) and (5) is attached is attached. was gotten.

40 L of a dispersion composed of the obtained glass fiber, water, and 0.1% by mass of a surfactant (polyoxyethylene lauryl ether) was prepared, and the dispersion was put into a papermaking apparatus. As a papermaking apparatus, an apparatus comprising an upper papermaking tank (capacity 30L) and a lower water tank (capacity 10L) provided with a stirrer with a rotor blade, and a porous support is provided between the papermaking tank and the water tank. Was used. First, the dispersion was stirred using a stirrer until air microbubbles were generated. Thereafter, the glass fiber whose mass was adjusted so as to have a desired basis weight was put into a dispersion liquid in which fine air bubbles were dispersed, and stirred to obtain a slurry in which the glass fiber to which the airgel was adhered was dispersed. Next, the slurry was sucked from the water storage tank and dehydrated through a porous support to obtain a fiber paper product. The papermaking product was dried with a hot air dryer at 150 ° C. for 2 hours to obtain an airgel sheet 8 having a basis weight of 100 g / m ² and a porosity of 90% by volume.

Example 9
[Sol coating liquid 9]
143.0 parts by mass of ST-OZL-35 as a silica particle-containing raw material, 57.0 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 120.0 mass parts of urea was mixed as a thermohydrolyzable compound, and the mixture was obtained. To this mixture, 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS and 20.0 parts by mass of polysiloxane compound A as a polysiloxane compound were added and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 2.0 hours to obtain a sol coating liquid 9.

[Airgel board 9]
While using the said sol coating liquid 9, it replaces with a glass nonwoven fabric, and it is a porous nickel sheet (The product made from Sumitomo Electric Industries, product name: Celmet, thickness: 1.4 mm, nickel basis weight: 420 g / m < ² >, porosity: 97 The airgel board 9 having the structure represented by the general formulas (2), (3), (4) and (5) was obtained in the same manner as in Example 1 except that the volume%) was used.

(Example 10)
[Sol coating solution 10]
As a silica particle-containing raw material, PL-20 (manufactured by Fuso Chemical Industry Co., Ltd., product name, average primary particle size: 200 nm, solid content: 20% by mass) is 100.0 parts by mass, water is 100.0 parts by mass, acid A mixture was obtained by mixing 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. To this mixture, 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS and 20.0 parts by mass of polysiloxane compound A as a polysiloxane compound were added and reacted at 25 ° C. for 2 hours. Thereafter, a sol-gel reaction was performed at 60 ° C. for 2.0 hours to obtain a sol coating solution 10.

[Airgel board 10]
Example 1 except that the sol coating liquid 10 was used and a porous alumina sheet (manufactured by Aszac Co., Ltd., product name: AZP60, average thickness: 700 μm, porosity: 60 vol%) was used instead of the glass nonwoven fabric. Similarly, the airgel board 10 which has a structure represented by the said General Formula (2), (3), (4) and (5) was obtained.

(Comparative Example 1)
While using the sol coating liquid 1, a PET film (product name: G2 manufactured by Teijin DuPont Co., Ltd.) having no porous structure is used in place of the glass nonwoven fabric, and the sol coating liquid 1 is applied to the PET film by a bar coater. The PET core airgel sheet having the structure represented by the above general formulas (4) and (5) was obtained in the same manner as in Example 1 except that the sol coating solution was coated to a thickness of 80 μm.

(Comparative Example 2)
In place of the glass nonwoven fabric, a thin glass having no porous structure (manufactured by Nippon Electric Glass Co., Ltd., product name: OA-10G, thickness: 150 μm) is used, and the sol coating solution 1 is applied to the thin glass with a bar coater. A glass core airgel sheet having the structure represented by the general formulas (4) and (5) was obtained in the same manner as in Example 1 except that the sol coating solution was applied to a thickness of 50 μm.

<Various evaluations>
In accordance with the following conditions, the airgel composite material obtained in each example and comparative example was measured or evaluated.

(Measurement of thickness of airgel layer)
The thickness of the airgel layer covering the substrate on the surface of the substrate was measured. Specifically, using a micrometer (manufactured by Mitutoyo Corporation, product name: CLM1-15QM), measuring the thickness of the airgel composite material with a measuring force of 0.5 N, and reducing the thickness of the porous substrate. Calculated with The results are shown in Table 1.

(Thermal conductivity measurement)
The thermal conductivity measurement was performed using a thermal conductivity measuring device (product name: HC-074) manufactured by Eihiro Seiki Co., Ltd. A 20 cm × 20 cm sample was used as a measurement sample, and the temperature of the upper and lower heat plates was set to 30 ° C. and 10 ° C., respectively, and the thermal conductivity was measured. The results are shown in Table 1.

(Evaluation of powder removal)
The powder-off property of the airgel composite material obtained in each Example and Comparative Example was evaluated. A plurality of the same kind of airgel composite materials are stacked so as to have a length of 30 cm × width of 30 cm × height of 10 to 15 mm, and the four sides of the stacked airgel composite materials in the vertical direction and the horizontal direction are each five times from the top of the table. The amount of powder falling when dropped was measured. A powder having a powder fall amount of 10 mg or less was determined to have a good powder fall off property. The height to be dropped was 5 cm from the table, and dropping vertically was used as a test method for powder fallability. The results are shown in Table 1.

  From Table 1, it can be seen that the airgel composite materials of the examples have good thermal conductivity and a small amount of powder fall off. Therefore, the amount of dust generated during construction of the heat insulating material can be reduced, and the handleability during construction is good. On the other hand, in the comparative example, both the thermal conductivity and the amount of powder fall are inferior.

  DESCRIPTION OF SYMBOLS 10 ... Porous base material, 20 ... Airgel layer, 100,200 ... Airgel composite material.

Claims (16)

A base material having a porous structure, and an airgel attached to the base material,
The airgel 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 hydrolyzate of the silicon compound having the hydrolyzable functional group. dry matter der the wet gel is a condensation product of sol is, and, that having a structure represented by the following general formula (1), airgel composite.

[In Formula (1), 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. ]   The airgel composite according to claim 1, wherein the sol further contains silica particles.   The airgel composite material of Claim 2 whose average primary particle diameter of the said silica particle is 1-500 nm.   The airgel composite material according to any one of claims 1 to 3, wherein the silicon compound includes a silicon compound having an alkoxy group as the hydrolyzable functional group.   The airgel composite material according to claim 4, wherein the alkoxy group has 1 to 6 carbon atoms.   The airgel composite material according to any one of claims 1 to 5, wherein the silicon compound includes a silicon compound having a hydroxyalkyl group as the condensable functional group.   The airgel composite material according to claim 6, wherein the hydroxyalkyl group has 1 to 6 carbon atoms.   The airgel composite material according to any one of claims 1 to 7, wherein the silicon compound includes a polysiloxane compound having a hydrolyzable functional group or a condensable functional group. The airgel composite material according to claim 8, wherein the polysiloxane compound includes a compound 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. . ] The airgel composite material according to claim 8 or 9, wherein the polysiloxane compound includes a compound having a structure represented by the following general formula (B).

[In formula (B), R ^1b represents an alkyl group or an alkoxy group, R ^2b and R ^3b each independently represents an alkoxy group, R ^4b and R ^5b each independently represent an alkyl group or an aryl group, m Represents an integer of 1 to 50. ] The airgel has a ladder type structure including a column part and a bridge part,
The bridging portion has a structure represented by the following general formula (2), airgel composite according to any one of claims 1-10.

[In Formula (2), R ⁵ and R ⁶ each independently represents an alkyl group or an aryl group, and b represents an integer of 1 to 50. ] The airgel composite material according to claim 11 , wherein the airgel has a ladder structure represented by the following general formula (3).

[In Formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group or an aryl group, a and c each independently represent an integer of 1 to 3000, and b represents 1 to 50 Indicates an integer. ] The holes in the porous structure are communication holes,
The airgel composite material according to any one of claims 1 to 12 , wherein a total volume of the pores is 50 to 99% by volume of a total volume of the base material. The airgel composite material according to claim 13 , wherein the airgel is filled in the communication hole. The airgel composite material according to any one of claims 1 to 14 , wherein the substrate having the porous structure is a sheet made of a fibrous substance having a diameter of 0.1 to 1000 µm. The airgel composite material according to claim 15 , wherein the airgel is attached to the fibrous substance.

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