WO2020241620A1

WO2020241620A1 - Aerogel complex

Info

Publication number: WO2020241620A1
Application number: PCT/JP2020/020679
Authority: WO
Inventors: 昇川瀬; 正洋山地
Original assignee: ティエムファクトリ株式会社
Priority date: 2019-05-27
Filing date: 2020-05-26
Publication date: 2020-12-03
Also published as: JP2020193316A; JP6683870B1; TW202104440A

Abstract

The purpose of the present invention is to provide an aerogel complex having suppressed aerogel shedding, even when applied to a curved surface. [Solution] The purpose is achieved by an aerogel complex comprising at least a porous resin base material and an aerogel. The aerogel comprises a hydrolyzed condensate of a silane compound. The silane compound fulfills 0 < Qx < 50, 50 ≤ Tx < 100, and 0 ≤ Dx < 30 (where Qx + Tx + Dx = 100), when the mass percentages of a tetrafunctional silane compound, a trifunctional silane compound, and a bifunctional silane compound are Qx, Tx, and Dx, respectively.

Description

Airgel complex

The present invention relates to a novel airgel composite, and more particularly to an airgel composite used as a heat insulating material for construction such as a heat insulating window material for a house, a cryogenic container, and a high temperature container.

Conventionally, a gel-dried product having a siloxane bond called airgel is known (Patent Document 1). Specifically, a sol was formed by hydrolyzing a monomer solution of a silane compound (solvent: water and / or an organic solvent), and a gel (condensation compound) was formed by subjecting the sol to a condensation reaction. After that, the gel is dried to obtain an aerogel (gel dried sol) having a large number of pores.

Here, the pores of the airgel have a pore diameter equal to or smaller than, for example, the mean free path (Mean Free Path [MFP]) of the element molecules constituting the air at atmospheric pressure. Therefore, heat exchange with air is hardly performed inside the airgel, and the airgel has an excellent potential as a heat insulating material, and its heat insulating effect is said to exceed the vacuum.

On the other hand, airgel is very brittle and difficult to handle, so when actually using it as a heat insulating material, a technology is proposed to obtain a form as an easy-to-use heat insulating material by combining it with other materials instead of airgel alone. Has been done. For example, in Patent Document 2, an airgel composite is formed by combining an airgel with a material made of another glass non-woven fabric or a metal sheet to form a sheet, which overcomes brittleness and further suppresses the airgel from falling off from other materials. Proposed.

Japanese Patent No. 5250900 JP-A-2018-111803

However, although the technique of Patent Document 2 improves the handleability to some extent, it still lacks flexibility as a sheet-like material. Therefore, when the airgel composite is applied to a curved surface, the airgel constitutes the airgel composite. The problem of falling off from other materials (for example, powder falling off) has not been sufficiently solved.

An object of the present invention is to provide an airgel composite in which airgel shedding is suppressed even when applied to a curved surface.

An object of the present invention has been achieved by:
1. 1. An aerogel complex composed of at least a porous resin substrate and an airgel, the airgel is composed of a hydrolyzed condensate of a silane compound, and the silane compound is a tetrafunctional silane compound, a trifunctional silane compound and a bifunctional silane compound. An airgel complex in which 0 <Qx <50, 50 ≦ Tx <100, 0 ≦ Dx <30 (where Qx + Tx + Dx = 100), where the mass percentages of are Qx, Tx, and Dx, respectively.
2. 2. The airgel composite according to 1 above, wherein the porous resin substrate is a fibrous resin substrate or a foamed resin substrate.

According to the present invention, it is possible to provide an airgel composite having excellent heat insulating properties, a large area (for example, 400 cm ² or more) and excellent flexibility in the form of a plate or a film, and a method for producing the same.

It is a figure which shows the mass percentage of the preferable silane compound composition which forms the airgel of this invention.

Hereinafter, embodiments of the present invention will be described.
<Airgel complex>
The airgel composite of the present invention is an airgel composite composed of at least a porous resin substrate and an airgel, and the airgel is composed of a hydrolyzate of a silane compound, and the silane compound is a tetrafunctional silane compound, 3 When the mass percentages of the functional silane compound and the bifunctional silane compound are Qx, Tx, and Dx, respectively, the airgel complex is 0 <Qx <50, 50 ≦ Tx <100, 0 ≦ Dx <30 (where Qx + Tx + Dx = 100). It is characterized by being. Further, the porous resin substrate is a fibrous resin substrate or a foamed resin substrate.

The airgel composite of the present invention (hereinafter, also simply referred to as a composite) may be in a state in which the porous resin substrate and the airgel can be handled as one integrated substance regardless of the production method. For example, a state in which a bond between a functional group on the fiber surface and a functional group on the airgel surface by a chemical interaction, or a bond by an intermolecular interaction between a fiber surface and an airgel encloses a porous resin substrate. The state of adhesion and the like can be mentioned as a preferable embodiment, and particularly preferably, the airgel is present in the pores of the porous resin substrate.

Since it is composited, the airgel and the porous resin substrate are not easily separated in normal handling, powder dropout is suppressed, and it can be handled as a single integrated substance.

In particular, since the airgel composite of the present invention has flexibility as an airgel composite, it is intended to optimize the silane compound to be mixed in order to produce an airgel, and the production method is not limited. As a specific production method, for example, there is a case where a sol generation step, a wet gel formation / molding step, a solvent exchange step and a drying step are performed in this order.

The size of the airgel composite of the present invention is not particularly limited, but the desired size can be obtained by appropriately selecting the bulk size of the porous resin substrate. For example, the size can be 3000 mm in length, 3000 mm in width, and 100 mm in thickness. It can also be rolled into a width of 2000 mm.

The thickness of the airgel layer itself in the airgel composite of the present invention can be appropriately selected, but is 100 μm to 100 mm, preferably 500 μm to 40 mm, and more preferably 1 mm to 20 mm. The thickness of the airgel layer can be appropriately selected in relation to the heat insulating property and the powder removing performance of the airgel from the porous resin substrate.

The airgel composite can be formed into a sheet or film, but in that case, it can be further combined with another film, sheet or the like. For example, it is preferable to combine it with an aluminum sheet.

The airgel composite can be appropriately composited from the viewpoint of handling the porous resin substrate, but it is preferable to appropriately composite the airgel composite in the range of 10 to 1000 parts by mass with respect to 100 parts by mass of the airgel.

<Porous resin substrate>
In the present invention, the porous resin substrate refers to a fibrous resin substrate or a foamed resin substrate, and specifically, a fibrous material, a non-woven fabric, a fiber sheet, felt, a foam, or the like itself maintains a three-dimensional shape. There are things that are done. The porosity is preferably 95% to 99.9% and the density is preferably 0.01 to 0.4 g / cm ³ ^.

Examples of the resin of the porous resin substrate include nylon, polyester, polypropylene, polyacrylonitrile, vinylon, polyolefin, polyurethane, polystyrene, rayon, carbon fiber and the like. Commercially available products can be used as the fibrous resin substrate and the foamed resin substrate of the present invention.

<Manufacturing method of airgel complex>
The aerogel composite of the present embodiment has, for example, a sol generation step of producing a sol for forming an aerogel, an impregnation step of impregnating a porous resin substrate with the sol obtained in the sol generation step, and gelling the sol. A gel formation step of obtaining a wet gel, a aging step of curing a porous resin substrate whose voids are filled with a sol or a wet gel, and a washing / solvent replacement step of washing and / or solvent replacing the cured composite. It can be produced by a production method mainly comprising a drying step of washing and / or drying the solvent-substituted composite. The gel formation step may be performed after the impregnation step, or the impregnation step may be performed after the gel formation step.

Further, the porous resin substrate is dispersed in the above sol coating solution in advance, and a porous resin substrate in which airgel is immersed is prepared through an aging step, a washing / solvent replacement step, and a drying step, and this is made into a non-woven fabric. It is also possible to form an airgel composite with a porous resin substrate.
The airgel composite and the method for producing the airgel composite in the present invention will be specifically described below.

(1) Silane Compound The aerogel forming the aerogel composite of the present invention has, as a silane compound, when the mass percentages of the tetrafunctional silane compound, the trifunctional silane compound and the bifunctional silane compound are Qx, Tx and Dx, respectively. , 0 <Qx <50, 50 ≦ Tx <100, 0 ≦ Dx <30 (where Qx + Tx + Dx = 100) are hydrolyzed and condensed.

Compared with existing airgels, it is possible to produce airgels with less powder falling and lower density, and as a result, the heat insulating properties are improved, and in addition, for curved surfaces that could not be applied in Patent Document 2, Moreover, it is possible to produce an airgel composite having a large area of 400 cm ² (for example, 20 cm square) or more in the form of a plate, a film or a sheet.

Here, the bifunctional silane compound is a silane compound having two siloxane bonds, and the trifunctional silane compound is a silane compound having three siloxane bonds, and 4 The functional silane compound is a silane compound having 4 siloxane bonds.

Examples of the bifunctional silane compound include dialkoxysilane and diacetoxysilane. A desirable embodiment of the dialkoxysilane is that the alkoxy group has 1 to 9 carbon atoms. Specific examples thereof include dimethyldimethoxysilane, diethyldimethoxysilane, and diisobutyldimethoxysilane. These compounds may be used alone or in combination of two or more. In the present invention, it is particularly preferable to use dimethyldimethoxysilane (DMDMS) as the bifunctional silane compound.

Examples of the trifunctional silane compound include trialkoxysilane and triacetoxysilane. A desirable embodiment of the trialkoxysilane is that the alkoxy group has 1 to 9 carbon atoms. For example, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, pentiltriethoxysilane, hexyltriethoxysilane. Examples thereof include silane and octylriethoxysilane. These compounds may be used alone or in combination of two or more. In the present invention, it is particularly preferable to use methyltrimethoxysilane (MTMS) as the trifunctional silane compound.

Examples of the tetrafunctional silane compound include tetraalkoxysilane and tetraacetoxysilane. A desirable embodiment of the tetraalkoxysilane is that the alkoxy group has 1 to 9 carbon atoms. For example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane and the like can be mentioned. These silane compounds may be used alone or in combination of two or more. In the present invention, it is particularly preferable to use tetramethoxysilane (TMS) as the tetrafunctional silane compound.

(2) Appropriate Range of Silane Compound FIG. 1 shows the appropriate range of Qx, Tx and Dx, which are the mass percentages of the tetrafunctional silane compound, the trifunctional silane compound and the bifunctional silane compound, which are the silane compounds of the present invention. It is shown in a triangular diagram having Qx, Tx and Dx as coordinate axes, and the region I shown in FIG. 1 is an appropriate range of Qx, Tx and Dx.

Region I shown in FIG. 1 has four vertices a to d and is a trapezoidal segmented region (hatched region with a downward-sloping diagonal line). Since none of the vertices a to d is included in the region I, they are indicated by "○ (white circles)". Further, the straight line connecting the apex a and the vertex b and the straight line connecting the apex b and the apex c are included in the region I, and the straight line connecting the apex c and the apex d and between the apex d and the apex a. The straight line connecting the above is not included in the region I.

Further, in the method for producing airgel of the first embodiment, the mass percentages of the tetrafunctional silane compound, the trifunctional silane compound and the bifunctional silane compound are Qx, Tx and Dx, respectively, with Qx, Tx and Dx as coordinate axes. When plotting on the triangular diagram (Qx, Tx, Dx), point A (5,95,0), point B (40,60,0), point C (40,55,5), and D Six straight lines connecting points (30, 55, 15), E points (15, 70, 15), F points (5, 90, 5), and A points (5, 95, 0) in this order. It is preferable that it is within the range surrounded by (region II in FIG. 1) from the viewpoint of heat insulating properties.

The region II shown in FIG. 1 has six vertices A to F and is a region partitioned in a hexagonal shape (a region hatched by a diagonal line rising to the right). Since all of the vertices A to F are included in the region II, they are indicated by “● (black circle)”, and six straight lines connecting these vertices A to F are also included in the region II.

(3) Each step of the airgel manufacturing process (3-1) Sol generation step The sol for producing the airgel of the airgel composite of the present invention is a raw material containing a silane compound (main raw material) in a predetermined solution. Is added, and the mixture is produced in a step including a sol forming step of stirring and mixing.

(3-1-1) Sub-materials and sol formation conditions in the sol formation step In the sol formation step, a bifunctional silane compound, a trifunctional silane compound, and in some cases a tetrafunctional silane compound are mixed at the above-mentioned predetermined mixing ratio as a main raw material. Then, prepare a solution containing water and a surfactant. By this preparation, the silane compound is hydrolyzed to produce a sol containing a siloxane bond. The solution to be prepared may contain an acid and / or an organic solvent.

The surfactant contributes to the formation of the bulk portion and the pore portion constituting the airgel described later in the gel formation process described later. As the surfactant that can be used in the production of airgel, a nonionic surfactant, an ionic surfactant and the like can be used. Examples of the ionic surfactant include a cationic surfactant, an anionic surfactant, and a zwitterionic surfactant.

Of these, nonionic surfactants can be preferably used. The amount of the surfactant added to the prepared solution depends on the type and mixing ratio of the silane compound and the type of the surfactant, but is 0.001 to 100% by mass with respect to 100 parts by mass of the total amount of the silane compound as the main raw material. It can be used in the range of parts, preferably in the range of 0.01 to 90 parts by mass, and more preferably in the range of 0.1 to 80 parts by mass.

The acid acts as a catalyst during hydrolysis and can accelerate the reaction rate of hydrolysis. Specific examples of acids include inorganic acids, organic acids and organic acid salts.

Examples of the inorganic acid include hydrochloric acid, sulfuric acid, sulfite, nitric acid, hydrofluoric acid, phosphoric acid, phosphorous acid, hypochlorous acid, bromic acid, chloric acid, chlorous acid, hypochlorous acid and the like.

Examples of organic acids include carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid.

As the organic acid salt, acidic aluminum phosphate, acidic magnesium phosphate, acidic zinc phosphate and the like can be used. These acids may be used alone or in combination of two or more. In the present invention, it is preferable to use acetic acid, which is an organic acid, as the acid.

Further, as the concentration of acid added to the entire solution to be prepared, a range of 0.0001 mol / L to 0.1 mol / L, particularly a range of 0.0005 mol / L to 0.05 mol / L can be preferably used, and 0. The range of .001 mol / L to 0.01 mol / L can be further preferably used.

As the organic solvent, alcohols such as methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol can be used. These may be used alone or in admixture of two or more. From the viewpoint of compatibility, the amount of the organic solvent added to the prepared solution may be in the range of 4 mol to 10 mol, particularly in the range of 4.5 mol to 9 mol, with respect to the total amount of 1 mol of the silane compound as the main raw material. It is preferably in the range of 5 mol to 8 mol, and is particularly preferable.

The solution temperature and time required for the sol formation step depend on the type and amount of the silane compound, surfactant, water, acid, nitrogen compound, organic solvent, etc. in the mixed solution, and are, for example, 0 ° C to 70 ° C. The treatment may be in the range of 0.05 hours to 48 hours under the temperature environment of 20 to 50 ° C., and the treatment is preferably performed for 0.1 hours to 24 hours under the temperature environment of 20 to 50 ° C. As a result, the silane compound is hydrolyzed to form a colloid, and a liquid sol can be produced as a whole.

It should be noted that the auxiliary material and / or the decomposition product of the auxiliary material used in the sol generation step can be mixed as an unavoidable component in the produced airgel.

(3-1-2) Invasion Step The porous resin substrate of the present invention can be immersed in a sol in this step. The immersion is preferably performed so that the entire porous resin substrate is immersed in the sol. It is also preferable to give vibration so that the sol is immersed even inside the porous resin substrate.

(3-2) Wet gel formation / molding process (curing process)
The wet gel formation / molding step is a step of adding a basic catalyst to the liquid sol produced in the above-mentioned sol formation step, and a step of pouring a solution to which the basic catalyst is added into a mold for obtaining a desired shape. By curing the solution inside the mold, it can be roughly divided into the steps of producing a wet gel.

Examples of the basic catalyst include ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride and ammonium bromide, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and cesium hydroxide, and metaphosphoric acid. Basic sodium phosphate salts such as sodium, sodium pyrophosphate, 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-butylamine, propylamine, 3- (methylamino) propylamine, 3- Aliper amines such as (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine, morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and its derivatives, piperidine and Examples thereof include nitrogen-containing heterocyclic compounds such as the derivative, imidazole and the derivative thereof. The basic catalyst may be used alone or in combination of two or more.

The basic catalyst may be a nitrogen compound that generates a basic catalyst by heating. The nitrogen compound is added as a compound that generates a basic catalyst during heating in the wet gel formation / molding step. Specific examples thereof include amide compounds such as urea, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, and heterocyclic compounds such as hexamethylenetetramine. be able to. Of these, urea can be preferably used in the wet gel production step in terms of increasing the production rate.

The amount of the basic catalyst added is preferably 0.5 to 5 parts by mass and particularly preferably 1 to 4 parts by mass with respect to 100 parts by mass of the total amount of the main raw material. If the addition amount is less than 0.5 parts by mass, the reaction cannot proceed from the sol to the wet gel, and if it exceeds 5 parts by mass, the reaction is too fast, and the whole may cause non-uniformity inside the mold. ..

Among these, the aqueous ammonium hydroxide solution is preferable because it has a high reaction promoting effect as a catalyst and can form a reaction from the sol to the wet gel in a short time and with few defects. In addition, since the aqueous ammonium hydroxide solution is highly volatile, it is also excellent in that it volatilizes in the solvent exchange step and the drying step described later and does not easily remain in the airgel.

The amount added in the case of the nitrogen compound is not particularly limited, but for example, the amount of the nitrogen compound added is preferably in the range of 1 to 200 parts by mass with respect to 100 parts by mass of the total amount of the silane compound as the main raw material. It is more preferable to use the range of 2 to 150 parts by mass. The porous resin substrate of the present invention can also be immersed in a sol in this step.

The step of pouring the solution to which the basic catalyst is added into the mold is a step of obtaining the desired shape of the airgel product. Any of metal, synthetic resin, wood, and paper can be used as the mold, but synthetic resin can be preferably used in that it has both flatness and releasability of the shape. Examples of the synthetic resin include polystyrene, polyethylene, and polypropylene.

Since the mold is for obtaining the desired shape of the airgel product, it reflects the shape obtained by reversing the unevenness of the shape of the desired airgel product. For example, when the desired shape of the airgel product is a plate shape (rectangular parallelepiped), a concave tray having an opening at one end can be used as a mold.

Further, the mold may be a combination mold composed of a plurality of molds, such as a so-called injection molding mold. As an example, there is a two-sheet combination type in which a concave type and a convex type are used facing each other, and a combination type in which the inner surface of the concave type and the outer surface of the convex type are separated by a predetermined interval may be used. As a result, the solution (a solution consisting of a sol and a basic catalyst) may be poured into a combinatorial interior space and sealed for a predetermined time.

When a concave tray with an opening at one end is used as a mold, a flat plate (plate) covering the entire open (flat) surface of the concave tray is prepared as the second mold, and the open surface of the concave tray and the second mold are used. It may be used as a combination type of two sheets so that the two sheets face each other. As a result, the solution (solution consisting of a sol and a basic catalyst) may be poured into the combination type and sealed for a predetermined time.

Following the step of filling the mold with the solution to which the basic catalyst is added, there is a molding step of curing the solution inside the mold to generate a wet gel and molding along the shape of the inner wall of the mold.

Curing is to proceed the reaction from the sol to the wet gel with a predetermined energy over a predetermined time. An example of energy is heat (temperature), where heating at 30-90 ° C, preferably 40-80 ° C is used. The heating may be heater heating or steam heating with water or an organic solvent.

Further, as another example of energy, application of electromagnetic waves such as infrared rays, ultraviolet rays, microwaves, and gamma rays, application of electron beams, and the like can be mentioned. These energies may be used alone or in combination with a plurality of means.

The time required for curing depends on the composition of the silane compound, the type and amount of surfactant, water, acid, nitrogen compound, organic solvent, basic catalyst, etc., and the type and density of energy. The period is between 01 hours and 7 days. When the type of basic catalyst and the type of energy are optimized, gelation may be completed in 0.01 to 24 hours.

The curing may be a curing that changes heat (temperature) and time in multiple stages. The material used in the wet gel formation / molding step and / or the decomposition product of the material may be mixed as an unavoidable component in the produced airgel.

(1-3) Solvent exchange step The solvent exchange step is a step of exchanging water and / or an organic solvent existing on the surface and inside of the wet gel with an organic solvent suitable for short-time drying, but in a subsequent drying step. This is a process that may be omitted if a long time may be required. Further, the solvent exchange step may be performed after being taken out from the above-mentioned mold, or may be performed in the mold.

Further, prior to the solvent exchange step, a washing treatment may be performed to wash away the acid used for sol formation, the catalyst used for wet gel formation, the reaction by-product, and the like. An organic solvent can be widely used for the cleaning treatment. For example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, 1-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, xylene, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate. , Tetrahydrofuran, methylene chloride, N, N-dimethylformamide, dimethylsulfoxide, acetic acid, formic acid and various other organic solvents can be used. The above organic solvent may be used alone or in combination of two or more.

Of these, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, etc., which are soluble in both water and organic solvents, are used alone or in combination of two or more.

In the solvent exchange step, the water (or organic solvent) on the surface and inside of the wet gel is replaced with an organic solvent having a surface tension of 45 mN / m or less at 20 ° C. in order to suppress shrinkage damage of the gel in the subsequent drying step. .. Examples thereof include dimethyl sulfoxide (43.5 mN / m), cyclohexane (25.2 mN / m), isopropyl alcohol (21 mN / m), heptane (20.2 mN / m), pentane (15.5 mN / m) and the like. ..

The organic solvent used in the solvent exchange step has a surface tension at 20 ° C. of 45 mN / m or less, 40 mN / m or less, 35 mN / m or less, 30 mN / m or less, 25 mN / m or less, 20 mN / m or less, 15 mN / m or less. , 5 mN / m or more, 10 mN / m or more, 15 mN / m or more, 20 mN / m or more. Among these, it is particularly preferable to use an organic solvent containing an aliphatic hydrocarbon whose surface tension at 20 ° C. is in the range of 20 to 40 mN / m. The organic solvent can be used alone or in combination of two or more.

The amount of solvent used in the solvent exchange step depends on the temperature at which the solvent is exchanged and the device (container), but it is desirable to use an amount 2 to 100 times the volume of the wet gel. The solvent exchange is not limited to once, and may be performed a plurality of times. Further, the solvent exchange method may be any of total substitution, partial substitution, and cyclic substitution.

Further, when the solvent exchange is performed a plurality of times, the type, temperature, and treatment time of the organic solvent may be set independently for each time. The material used in the solvent exchange step and / or the decomposition product of the material may be mixed as an unavoidable component in the produced airgel.

(1-4) Drying Step The drying step is a step of drying the above-mentioned solvent-exchanged wet gel to obtain an airgel having predetermined properties. Although the drying method is not particularly limited, the supercritical drying method has problems that the equipment becomes large, the manufacturing cost is extremely high, and mass production is difficult. Therefore, the supercritical drying method of the present invention is supercritical. It is preferable to use the atmospheric pressure drying method without applying the critical drying method.

Note that the atmospheric pressure refers to the surface pressure of 300 hPa to 1100 hPa, and as long as it is on the surface of the earth, there is no limitation on the altitude at which the present invention is carried out. In other words, as a drying method, the present invention also includes drying under reduced pressure to about 300 hPa.

From the above, by going through the steps (1-1) to (1-4) described above, an airgel composite having few defects such as powder falling can be produced, and as a result, the heat insulating properties are improved. In addition, it is possible to produce an airgel composite having a large area of 400 cm ² (for example, 20 cm square) or more in the form of a plate or a film on a curved surface which cannot be applied in Patent Document 2.

(1-5) Other Steps The above-mentioned manufacturing method has described a method for manufacturing an airgel composite having a plate (or rectangular parallelepiped) shape or a film shape, but the present invention is not limited to this, and the plate shape is not limited to this. Processing from the airgel composite into a desired shape can be included as an optional step. For example, it can be processed from a plate (or a rectangular parallelepiped) into various shapes such as a rectangular or circular plate or film, a cube, a sphere, a cylinder, a pyramid, or a cone. Known machining such as wire cutting and laser cutting can be used as the processing method.

Further, the airgel composite of the present invention may include processing from a rectangular parallelepiped airgel composite into a particulate airgel composite as an optional step. As a processing method, a known crusher (crusher) such as a jaw crusher, a roll crusher, and a ball mill can be used.

(2) Structure of Airgel Constituting Airgel Complex The macro structure of the airgel of the airgel complex of the present invention will be described.

(2-1) Internal structure of airgel The airgel constituting the airgel composite of the present invention has a bulk portion (gel skeleton) filled with solid matter and 3 in the bulk portion when the structure is observed microscopically. It is mainly composed of through holes penetrating in a three-dimensional network, and forms a three-dimensional network as a whole.

The three-dimensional network of airgel of the present invention can be judged by observing with a scanning electron microscope, and the diameter of the through hole of the three-dimensional network structure and the cross-sectional area of the gel skeleton are three-dimensional network-like. The central pore diameter of the through pores (pores), the diameter when the cross section of the skeleton is regarded as a circle, the density, and the porosity can be continuously measured and calculated by the mercury injection method.

The bulk part is composed of a continuum in which solids form a three-dimensional network by siloxane bonds. In a three-dimensional network, the average length of one side when a grid, which is the smallest unit of a network, is approximated by a cube is 2 nm or more and 25 nm or less. The average length of one side is preferably 2 nm or more, 5 nm or more, 7 nm or more, 10 nm or more, and 25 nm or less, 20 nm or less, and 15 nm or less.

Further, the pore portion has a tubular shape penetrating the inside of the bulk portion, and the average inner diameter when the pore is approximated by a tube and the inner diameter of the tube is approximated by a circle is 5 nm or more and 100 nm or less. The average inner diameter of the pores is preferably 5 nm or more, 7 nm or more, 10 nm or more, 20 nm or more, 30 nm or more, 50 nm or more, and 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less. Here, the inner diameter of the tube has a dimension equal to or less than the mean free path (MFP) of the element molecules constituting air at atmospheric pressure.

Further, the porosity of the airgel, that is, the ratio of the volume of the pores to the total volume of the airgel is 70% or more. As an example of the porosity, it may be 75% or more, 80% or more, 85% or more, 90% or more.

The airgel of the present invention may include a structure other than the bulk portion and the pore portion described above as long as it satisfies the physical properties described later. As an example, a void different from the above-mentioned pore portion may be included.

Further, as another example, water, an organic solvent, a surfactant, a catalyst, and decomposition products thereof that remain as unavoidable components in production can be included as long as the physical properties described later are satisfied. Further, as another example, as long as the physical properties described later are satisfied, dust mixed from the manufacturing space or the manufacturing apparatus can be included as an unavoidable component in manufacturing.

Further, the airgel composite of the present invention may contain components to be added with the intention of imparting functionality, improving appearance, imparting decorativeness, etc., in addition to the above-mentioned constitution. For example, antistatic agents, lubricants, inorganic pigments, organic pigments, inorganic dyes, and organic dyes can be included. These can be contained in each of the porous resin substrate and the airgel.

(2-2) Airgel Density The airgel of the present invention has a density as low as 0.15 g / cm ³ or less. Here, the density is obtained by the mercury intrusion method. The lower the density of airgel, the lower the thermal conductivity, and the higher the heat insulating property. Since the airgel of the present invention has a density of 0.15 g / cm ³ or less, the thermal conductivity is as small as 0.01 W / m · K or less.

From such an advantage, the airgel composite of the present embodiment can be applied to applications as a heat insulating material in a cryogenic container, a space field, a building field, an automobile field, a home appliance field, a semiconductor field, an industrial facility, and the like. In addition to the use as a heat insulating material, the airgel composite material of the present embodiment can be used for water repellency, sound absorption, static vibration, catalyst support, and the like.

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.

<Preparation of airgel complex>
(Experimental Example 1)
As a surfactant, 3.28 g of a nonionic surfactant (BASF Shi Co., Ltd .: Pluronic PE9400) was dissolved in 28.96 g of a 0.005 mol / L acetic acid aqueous solution, and then urea (Nacalai Tesque) was further used as a hydrolyzable compound. (Made by Tesque) 4.00 g was added and dissolved. After 10.0 g of the silane compound as the main raw material was added to this aqueous solution, the mixture was stirred and mixed at room temperature for 60 minutes to carry out a hydrolysis reaction of the silane compound to generate a sol.

The silane compound may be abbreviated as methyltrimethoxysilane (MTMS), which is a trifunctional silane compound, dimethyldimethoxysilane (DMDMS), which is a bifunctional silane compound, and tetramethoxysilane (hereinafter, TMOS), which is a tetrafunctional silane compound. ), And added at a mass percentage Dx of the bifunctional silane compound, a mass percentage Tx of the trifunctional silane compound, and a mass percentage Qx of the tetrafunctional silane compound = 10:65:25.

Then, the generated sol was transferred to a sealable container (W × D × H = 60 mm × 110 mm × 20 mm), and a polyester non-woven fabric (W × D × H = 55 mm × 105 mm × 5 mm) was placed therein as a porous resin substrate. It was sufficiently immersed, sealed, allowed to stand at 60 ° C., and gelled to form a wet gel.

After that, the wet gel was aged by allowing it to stand for 96 hours in succession. Next, the wet gel was taken out from the closed container, immersed in a MeOH solution corresponding to 5 times the volume of the wet gel, and the solvent was exchanged repeatedly 5 times under the condition of 60 ° C. for 8 hours. Immerse in an IPA / hep mixed solution corresponding to 5 times the volume of the wet gel, which is a mixture of isopropyl alcohol (IPA) and heptan (Hep) in a volume ratio of 1: 4 to 1: 3, and 8 at 60 ° C. Further solvent exchange was carried out under time conditions.

After that, the mixture was immersed in a Hep solution corresponding to 5 times the volume of the wet gel, and the solvent was exchanged twice under the condition of 60 ° C. for 8 hours. The methanol and isopropanol used for the solvent exchange were both manufactured by Nacalai Tesque.

Next, the solvent in the wet gel was placed in a container (dryer) whose evaporation rate could be controlled, and drying was started. The drying temperature was set to be equal to or lower than the boiling point of the solvent, and the solvent evaporation rate of the gel exchanged (replaced) with a low surface tension solvent was adjusted to 0.2 g / (h · cm ³ ) from immediately after the start of drying to 4 hours. After that, the solvent evaporation rate was gradually reduced, and when the gel mass became constant, drying was completed to prepare a sheet-shaped airgel composite. Other examples were prepared in the same manner.

(Comparison example)
Comparative Examples 1 and 2 were produced in the same manner as in Example 1. In Comparative Example 3, the same composition as the airgel composite material described in Example 1 of JP-A-2018-11183 (Patent Document 2) was prepared and used.

<Various evaluations>
The airgel complex charges obtained in each Example and Comparative Example were measured and evaluated according to the following conditions. Unless otherwise specified, the measurement was carried out while maintaining an atmosphere of 23 ° C. and 55% RH.

(Evaluation of powder removal property)
[Amount of cutting powder dropped]
Each sample of the airgel composite was prepared so as to have a width of 50 mm, a length of 100 mm, and a thickness of 5 mm, and the amount of powder removed when the length of 10 cm was cut with scissors was measured as the amount of powder removed. The experiment was performed three times and the average value was taken. The results are shown in Table 1.
[Amount of bending powder dropped]
Each sample of the airgel complex was prepared so as to have a width of 50 mm, a length of 100 mm, and a thickness of 5 mm, and was wound around a Φ26 PVC pipe, and the amount of powder dropped at that time was measured. The experiment was performed three times and the average value was taken. The results are shown in Table 1.

From Table 1, it can be seen that the airgel composite of the embodiment of the present invention has a small amount of powder falling off. The airgel composite of Comparative Example 3 (described in Example 1 of Patent Document 1) has already fallen off at the stage of preparing a sample, and the amount of powder fallen is clearly larger than that of the example of the present invention. (More than in Comparative Example 2), and even the reproducibility of the test results was problematic, so the results are not shown in Table 1.

(Experimental Example 2)
An airgel composite having the composition shown in Table 2 was prepared according to the method for producing an airgel composite of Experimental Example 1, and the same evaluation was performed. Although the absolute amount of powder falling is different from that of Experimental Example 1 due to the difficulty in reproducibility of the experiment, sufficient comparison can be made within the same experiment.
In Experimental Example 2, the amount of cut powder dropped 7.5 mg or less was judged to be 〇, the amount of bent powder dropped 5.0 mg or less was judged to be 〇, and the others were marked with x.
The composition having a Dx of more than 30% by mass and the composition not containing Qx had a problem in the progress of the reaction of the airgel itself, and could not be evaluated.

From Table 2, it can be seen that the airgel composites of the examples in the scope of the present invention can produce the airgel composite with good reactivity and the amount of powder falling off is small.

Claims

An aerogel complex composed of at least a porous resin substrate and an airgel, the airgel is composed of a hydrolyzed condensate of a silane compound, and the silane compound is a tetrafunctional silane compound, a trifunctional silane compound and a bifunctional silane compound. An airgel complex in which 0 <Qx <50, 50 ≦ Tx <100, 0 ≦ Dx <30 (where Qx + Tx + Dx = 100), where the mass percentages of are Qx, Tx, and Dx, respectively.
The airgel composite according to claim 1, wherein the porous resin substrate is a fibrous resin substrate or a foamed resin substrate.