JP2018145331A - Aerogel powder dispersion liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous aerogel powder dispersion liquid having excellent dispersibility and dispersion stability.SOLUTION: An aerogel powder dispersion liquid contains aerogel powder, water and a surfactant.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an aqueous airgel powder dispersion.

  Silica airgel is known as a material having low thermal conductivity and heat insulation. Silica airgel is useful as a functional material having excellent functionality (heat insulation, etc.), unique optical properties, unique electrical properties, etc., for example, an electronic substrate utilizing the ultra-low dielectric constant properties of silica airgel It is used as a material, a heat insulating material using the high heat insulating property of silica airgel, a light reflecting material using the ultra-low refractive index of silica airgel, and the like.

  Such an airgel is hydrophobized by end-capping silanol groups present on the surface with a hydrophobic organic group such as a silylating agent. In the case of an airgel powder obtained by powdering an airgel, it is similarly hydrophobized (see, for example, Patent Document 1).

JP-T-2001-504756

  By the way, the airgel powder whose surface has been hydrophobized has good dispersibility in an organic solvent, but is not good in dispersibility in, for example, water or a liquid containing a large amount of water. That is, if the above-mentioned airgel powder is dispersed in an aqueous dispersion medium, it cannot be dispersed or is easily aggregated even if it can be temporarily dispersed, so that a stable dispersion can be obtained. There is a problem of difficulty.

  The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a water-based airgel powder dispersion excellent in dispersibility and dispersion stability.

  As a result of intensive studies to achieve the above object, the present inventor has found that an aqueous airgel powder dispersion excellent in dispersibility and dispersion stability can be obtained by using a surfactant.

  That is, the present disclosure provides an airgel powder dispersion containing airgel powder, water and a surfactant. The aqueous airgel powder dispersion of the present disclosure is excellent in the dispersibility and dispersion stability of the airgel powder that has been subjected to a hydrophobic treatment, which has been difficult with the prior art.

  In the present disclosure, as the airgel powder, those having a contact angle of 90 degrees or more between the powder layer made of the airgel powder and water can be used.

  In the present disclosure, the surfactant may have an alkylene oxide structure. Thereby, dispersibility and dispersion stability are easily improved.

  In the present disclosure, the surfactant may further have a siloxane structure. Thereby, dispersibility and dispersion stability are further improved.

  In the present disclosure, the dispersion may further contain an organic solvent. Thereby, dispersibility and dispersion stability are easily improved.

  In the present disclosure, the content of water in the dispersion medium can be 50% by mass or more. Thereby, it becomes an aqueous dispersion and the burden on the global environment can be remarkably reduced as compared with the solvent dispersion.

  In the present disclosure, the airgel powder may contain an airgel component and silica particles. Thereby, it can suppress that the pore structure of a powder is damaged by the stress applied in a dispersion | distribution process.

  In the present disclosure, the airgel powder may have a three-dimensional network skeleton formed from an airgel component and silica particles, and pores. Thereby, it can suppress that the pore structure of a powder is damaged by the stress applied in a dispersion | distribution process.

  In the present disclosure, the airgel powder may contain silica particles as a component constituting the three-dimensional network skeleton. Thereby, it can suppress that the pore structure of a powder is damaged by the stress applied in a dispersion | distribution process.

  In the present disclosure, the airgel powder includes silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may be a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group. The airgel powder obtained in this way is excellent in flexibility and can suppress the damage of the pore structure of the powder due to the stress applied in the dispersion process.

  In the present disclosure, the silicon compound may further contain a polysiloxane compound having a hydrolyzable functional group or a condensable functional group. Thereby, the further outstanding softness | flexibility can be achieved.

  In the present disclosure, the average primary particle diameter of the silica particles may be 1 to 500 nm. Thereby, it can suppress that the pore structure of a powder is damaged by the stress applied in a dispersion | distribution process.

  At this time, the shape of the silica particles can be spherical. The silica particles can be amorphous silica particles, and the amorphous silica particles can be at least one selected from the group consisting of fused silica particles, fumed silica particles, and colloidal silica particles. . Thereby, it can suppress that the pore structure of a powder is damaged by the stress applied in a dispersion | distribution process.

  In the present disclosure, the average particle diameter D50 of the airgel powder can be 1-1000 μm. Thereby, dispersibility and dispersion stability are easily improved.

  According to the present disclosure, it is possible to provide an aqueous airgel powder dispersion excellent in dispersibility and dispersion stability. Further, by using a specific airgel powder, it is possible to provide a water-based airgel powder dispersion in which a flexible airgel powder is stably dispersed in which the pore structure is not easily damaged by the stress in the dispersion process. A water-based airgel powder dispersion having excellent dispersion stability in which an airgel powder excellent in flexibility is dispersed has a possibility of being used in various applications. Here, an important point according to the present disclosure is that it becomes easy to stably disperse the hydrogel airgel powder without aggregation in a state where the pore structure is not damaged. In the prior art, hydrophobic airgel powder was only applicable to solvent-based dispersions, but according to the present disclosure, it is possible to disperse into water-based waters that have a significantly lower burden on the global environment than solvent-based ones. Become. Furthermore, by using a specific surfactant, it is possible to provide an aqueous airgel powder dispersion with less foaming immediately after dispersion and good defoaming properties after aging. Such a dispersion is easy to handle and has excellent processability.

It is a figure which represents typically the fine structure of the airgel powder which concerns on one Embodiment of this invention. It is a figure which shows the calculation method of the biaxial average primary particle diameter of particle | grains.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings depending on cases.
However, the present disclosure is not limited to the following embodiment. In the present specification, numerical ranges indicated using “to” indicate ranges including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. “A or B” only needs to include one of A and B, and may include both. The materials exemplified in this embodiment can be used singly or in combination of two or more unless otherwise specified.

<Dispersion>
The dispersion liquid of this embodiment is a dispersion of airgel powder in a liquid containing water and a surfactant. That is, in the dispersion system of this embodiment, it can be said that the dispersion medium is a liquid containing water and a surfactant, and the dispersoid is an airgel powder.

  The surfactant can have an alkylene oxide structure such as ethylene oxide or propylene oxide in the molecule. By having an alkylene oxide structure, the hydrophilicity of the surfactant is increased, and the dispersibility and dispersion stability of the airgel powder can be improved. Further, such a surfactant can provide a water-based airgel powder dispersion with little foaming immediately after dispersion and good defoaming properties after aging.

  The surfactant having an alkylene oxide structure in the molecule is not particularly limited. For example, polyoxyethylene alkyl ether surfactants such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene sorbitan monolaurate , Polyoxyethylene sorbitan fatty acid ester surfactants such as polyoxyethylene sorbitan monostearate; polyoxyethylene fatty acid ester surfactants such as polyethylene glycol monolaurate and polyethylene glycol monostearate; polyoxyethylene alkylamines Surfactant; Polyoxyethylene acetylene alcohol surfactant and the like.

  The surfactant can have a siloxane structure in the molecule in addition to the above alkylene oxide structure. By having a siloxane structure, the affinity with the airgel powder having strong hydrophobicity is further increased, and the dispersibility and dispersion stability can be further improved in combination with the alkylene oxide structure having strong hydrophilicity. Further, such a surfactant can provide a water-based airgel powder dispersion with little foaming immediately after dispersion and good defoaming properties after aging.

  Although there is no restriction | limiting in particular as surfactant which has an alkylene oxide structure and a siloxane structure in a molecule | numerator, For example, a both terminal polyether modified siloxane type surfactant, a side chain polyether modified siloxane type surfactant, etc. are mentioned.

  Although there is no restriction | limiting in particular in content of surfactant in a dispersion medium, 0.001-10 mass% is preferable. If it is 0.001 mass% or more, dispersibility and dispersion stability can be improved, and if it is 10 mass% or less, it is difficult to impair the function of the airgel powder as a porous body. From the above viewpoint, 0.005 to 5 mass% is more preferable, and 0.01 to 3 mass% is further preferable.

  The dispersion may further contain an organic solvent. By including an organic solvent, dispersibility and dispersion stability are easily improved.

  The organic solvent is not particularly limited as long as it is soluble in water. For example, ketone organic solvents such as acetone; ester organic solvents such as ethyl lactate and γ-butyrolactone; alcohols such as methanol, ethanol and 2-propanol Surfactants; polyhydric alcohol organic solvents such as ethylene glycol and propylene glycol; polyhydric alcohol alkyl ether organic solvents such as ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether and diethylene glycol monomethyl ether; propylene glycol Polyhydric alcohol alkyl ether acetates such as monomethyl ether acetate and diethylene glycol monomethyl ether acetate; N, N-dimethylacetamide, N-methylpi Amide-based organic solvents such as pyrrolidone, and the like. These organic solvents can be used individually by 1 type or in combination of 2 or more types.

  The content of the organic solvent in the dispersion medium can be less than 50% by mass. Thereby, it becomes an aqueous dispersion having water as a main component, and the burden on the global environment can be remarkably reduced as compared with the organic solvent dispersion.

  The content of water in the dispersion medium can be 50% by mass or more. Thereby, it becomes an aqueous dispersion having water as a main component, and the burden on the global environment can be remarkably reduced as compared with the organic solvent dispersion.

  The dispersion liquid of this embodiment can be obtained by dispersing the airgel powder in a liquid containing water and a surfactant. The dispersion method is not particularly limited. For example, an airgel powder, water, a surfactant, and an organic solvent as required are placed in a homogenizer, jet mill, roller mill, bead mill, hammer mill, etc. This can be done by driving at

  Content of the airgel powder in a dispersion liquid can be 0.01-30 mass%. If the content is 0.01% by mass or more, the concentration of the airgel powder is sufficiently secured, and the amount of the dispersion to be used can be reduced. If the content is 30% by mass or less, dispersibility and dispersion stability are achieved. Can be made better. From the above viewpoint, the content is more preferably 0.05 to 20% by mass, and further preferably 0.1 to 10% by mass. In addition, the remainder of content of airgel powder becomes content of the dispersion medium in a dispersion liquid.

<Airgel powder>
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 an airgel has a network-like fine structure, and has a cluster structure in which airgel particles of about 2 to 20 nm (particles constituting the airgel) are bonded. There are pores less than 100 nm between the skeletons formed by these clusters. Thereby, the airgel has a three-dimensionally fine porous structure. In addition, the airgel in this embodiment is a silica airgel which has a silica as a main component, for example. Examples of the silica airgel include so-called organic-inorganic hybrid silica airgel into which an organic group (such as a methyl group) or an organic chain is introduced. Note that the airgel powder of this embodiment (also referred to as a powder (powdered) airgel) has a cluster structure that is characteristic of the airgel, and has a three-dimensionally fine porous structure. It is a powder.

  The airgel powder of this embodiment may be an airgel composite containing silica particles in addition to the airgel component. In addition, although not necessarily meaning the same concept as this, the airgel powder of this embodiment can also be expressed as containing silica particles as a component constituting the three-dimensional network skeleton. The airgel powder of the present embodiment has excellent flexibility, and can provide a flexible airgel powder that is not easily damaged even when stress such as compression is applied. In addition, such an airgel powder is obtained by making a silica particle exist in the manufacturing environment of an airgel. And the merit by making the silica particles exist is not only that the flexibility of the airgel powder itself can be improved, but also the time for the wet gel generation process described later can be shortened, or the drying process can be simplified from the washing and solvent replacement process. There is also. In addition, shortening of the time of this process and simplification of a process are not necessarily calculated | required when producing airgel powder which is excellent in a softness | flexibility.

  In this embodiment, the composite aspect of an airgel component and a silica particle is various. For example, the airgel component may be in an indeterminate form such as a film or may be in the form of particles (aerogel particles). In any embodiment, since the airgel component is in various forms and exists between the silica particles, it is presumed that flexibility is imparted to the skeleton of the composite.

  First, the composite mode of the airgel component and the silica particles includes a mode in which an amorphous airgel component is interposed between the silica particles. As such an embodiment, specifically, for example, an embodiment in which silica particles are coated with a film-like airgel component (silicone component) (an embodiment in which the airgel component encloses silica particles), the airgel component serves as a binder, and the silica particles , A mode in which the airgel component is filled with a plurality of silica particle gaps, a mode of a combination of these modes (a mode in which silica particles arranged in a cluster are covered with the airgel component, etc.) An embodiment is mentioned. Thus, in the present embodiment, the airgel powder can have a three-dimensional network skeleton composed of silica particles and an airgel component (silicone component), and there is no particular limitation on the specific mode (form).

  On the other hand, as will be described later, in the present embodiment, the airgel component may be in the form of a clear particle as shown in FIG.

  The mechanism by which such various aspects occur in the airgel powder of this embodiment is not necessarily clear, but the present inventor speculates that the generation rate of the airgel component in the gelation process is involved. For example, the production speed of the airgel component tends to vary by varying the number of silanol groups in the silica particles. Further, the production rate of the airgel component also tends to fluctuate by changing the pH of the system.

  This suggests that the mode of the airgel powder (size, shape, etc. of the three-dimensional network skeleton) can be controlled by adjusting the size, shape, silanol group number, system pH, etc. of the silica particles. Therefore, the density, porosity, etc. of the airgel composite can be controlled, and the flexibility of the airgel composite can be controlled. In addition, the three-dimensional network skeleton of the airgel powder may be composed of only one kind of the various aspects described above, or may be composed of two or more kinds of aspects.

  Hereinafter, the airgel powder of the present embodiment will be described using FIG. 1 as an example. However, as described above, the present disclosure is not limited to the aspect of FIG. However, for matters common to any of the above aspects (type, size, content, etc. of silica particles), the following descriptions can be referred to as appropriate.

  FIG. 1 is a diagram schematically illustrating a fine structure of an airgel powder according to an embodiment of the present disclosure. As shown in FIG. 1, the airgel composite 10 includes a three-dimensional network skeleton formed by the airgel particles 1 constituting the airgel component being partially linked in a three-dimensional manner through silica particles 2; And pores 3 surrounded by the skeleton. At this time, it is assumed that the silica particles 2 are interposed between the airgel particles 1 and function as a skeleton support that supports the three-dimensional network skeleton. Therefore, it is thought that by having such a structure, moderate strength is imparted to the airgel while maintaining the flexibility as the airgel. That is, in the present embodiment, the airgel powder may have a three-dimensional network skeleton formed by silica particles that are three-dimensionally connected in series via the airgel particles. Silica particles may be covered with airgel particles. In addition, since the said airgel particle (aerogel component) is comprised from a silicon compound, it is guessed that the affinity to a silica particle is high. Therefore, in this embodiment, it is considered that the silica particles were successfully introduced into the three-dimensional network skeleton of the airgel. In this respect, it is considered that the silanol groups of the silica particles also contribute to the affinity between them.

  The airgel particle 1 is considered to be in the form of secondary particles composed of a plurality of primary particles, and is generally spherical. The average particle size (that is, the secondary particle size) of the airgel particles 1 can be 2 nm to 50 μm, but may be 5 nm to 2 μm, or 10 nm to 200 nm. When the airgel particle 1 has an average particle diameter of 2 nm or more, it becomes easy to obtain an airgel powder excellent in flexibility, and when the average particle diameter is 50 μm or less, the dispersibility and dispersion stability of the obtained airgel powder are improved. It becomes easy to improve. The average particle diameter of the primary particles constituting the airgel particles 1 can be 0.1 nm to 5 μm from the viewpoint of easily forming secondary particles having a low-density porous structure. It may be 200 nm, or 1 nm to 20 nm.

  The silica particles 2 can be used without particular limitation, and examples thereof include amorphous silica particles. Further, the amorphous silica particles include at least one selected from the group consisting of fused silica particles, fumed silica particles, and colloidal silica particles. Among these, colloidal silica particles have high monodispersibility and are easy to suppress aggregation in the sol. Note that the silica particles 2 may be silica particles having a hollow structure, a porous structure, or the like.

  The shape of the silica particle 2 is not particularly limited, and examples thereof include a spherical shape, a cage shape, and an association type. Of these, the use of spherical particles as the silica particles 2 makes it easy to suppress aggregation in the sol. The average primary particle diameter of the silica particles 2 can be 1 to 500 nm, but may be 5 to 300 nm, or 20 to 100 nm. When the average primary particle diameter of the silica particles 2 is 1 nm or more, it becomes easy to impart an appropriate strength to the airgel, and it becomes easy to obtain an airgel powder excellent in shrinkage resistance during drying. On the other hand, when the average primary particle diameter is 500 nm or less, the dispersibility and dispersion stability of the obtained airgel powder are easily improved.

  It is presumed that the airgel particle 1 (aerogel component) and the silica particle 2 are bonded in the form of hydrogen bonding or chemical bonding. At this time, the hydrogen bond or the chemical bond is considered to be formed by the silanol group or reactive group of the airgel particle 1 (aerogel component) and the silanol group of the silica particle 2. Therefore, it is thought that moderate strength is easily imparted to the airgel when the bonding mode is chemical bonding. Considering this, the particles to be combined with the airgel component are not limited to silica particles, and inorganic particles or organic particles having a silanol group on the particle surface can also be used.

The number of silanol groups per gram of silica particles 2 can be 10 × 10 ^{18 to} 1000 × 10 ¹⁸ pcs / g, but may be 50 × 10 ^{18 to} 800 × 10 ¹⁸ pcs / g, or 100 × ¹⁰ 18 ~700 may be a × ^{10 18} cells / g. Since the number of silanol groups per gram of the silica particles 2 is 10 × 10 ¹⁸ / g or more, the airgel powder can have better reactivity with the airgel particles 1 (airgel component) and has excellent shrinkage resistance. It becomes easy to obtain. On the other hand, when the number of silanol groups is 1000 × 10 ¹⁸ atoms / g or less, it is easy to suppress abrupt gelation at the time of sol preparation, and it becomes easy to obtain a homogeneous airgel powder.

  In the present embodiment, the average particle size of particles (average secondary particle size of airgel particles, average primary particle size of silica particles, etc.) is determined using an airgel composite using a scanning electron microscope (hereinafter abbreviated as “SEM”). It can be obtained by directly observing the cross section of the body. For example, the particle diameter of each airgel particle or silica particle can be obtained from the three-dimensional network skeleton based on the diameter of the cross section. The diameter here means the diameter when the cross section of the skeleton forming the three-dimensional network skeleton is regarded as a circle. The diameter when the cross section is regarded as a circle is the diameter of the circle when the area of the cross section is replaced with a circle having the same area. In calculating the average particle diameter, the diameter of a circle is obtained for 100 particles, and the average is taken.

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

  In the airgel powder, the size of the pores 3, that is, the average pore diameter can be 5 to 1000 nm, but may be 25 to 500 nm. When the average pore diameter is 5 nm or more, an airgel powder excellent in flexibility can be easily obtained, and when it is 1000 nm or less, an airgel powder having a fine porous structure can be easily obtained.

  The content of the airgel component contained in the airgel powder can be 4 to 25 parts by mass with respect to 100 parts by mass of the total amount of the airgel powder, but may be 10 to 20 parts by mass. When the content is 4 to 25 parts by mass, an appropriate strength is easily imparted.

  The content of the silica particles contained in the airgel powder can be 1 to 25 parts by mass with respect to 100 parts by mass of the total amount of the airgel powder, but may be 3 to 15 parts by mass. It becomes easy to give moderate intensity | strength to an airgel composite because content is 1-25 mass parts.

  In addition to these airgel components and silica particles, the airgel powder further includes other components such as carbon graphite, aluminum compound, magnesium compound, silver compound, and titanium compound for the purpose of imparting optical properties and thermal properties. May be. The content of other components is not particularly limited, but may be 1 to 5 parts by mass with respect to 100 parts by mass of the total amount of the airgel powder from the viewpoint of sufficiently ensuring the desired effect of the airgel composite.

[Powder shape]
The shape of the airgel powder of the present embodiment is not particularly limited, and may be various shapes. Since the airgel powder in the present embodiment is pulverized to be powdered as described later, the shape of the powder is usually an irregular shape with irregularities on the surface. Of course, a spherical powder or the like may be used. Moreover, panel shape, flake shape, and fiber shape may be sufficient. The powder shape can be obtained by directly observing the airgel powder using SEM.

[Average particle diameter of powder]
Although the average particle diameter D50 of the airgel powder of this embodiment can be 1-1000 micrometers, 3-700 micrometers may be sufficient, or 5-500 micrometers may be sufficient. When the average particle diameter D50 of the airgel powder is 1 μm or more, an airgel powder excellent in dispersibility and handleability is easily obtained. On the other hand, when the average particle diameter D50 is 1000 μm or less, an airgel powder excellent in dispersibility is easily obtained. The average particle diameter of the powder can be adjusted as appropriate depending on the pulverization method, pulverization conditions, sieving and classification.

  The average particle diameter D50 of the powder can be measured by a laser diffraction / scattering method. For example, the airgel powder is added to a solvent (ethanol) in a concentration range of 0.05 to 5% by mass, and the powder is dispersed by vibrating for 15 to 30 minutes with a 50 W ultrasonic homogenizer. Thereafter, about 10 mL of the dispersion is injected into a laser diffraction / scattering particle size distribution measuring apparatus, and the particle size is measured at 25 ° C. with a refractive index of 1.3 and zero absorption. The particle size at an integrated value of 50% (volume basis) in this particle size distribution is defined as the average particle size D50. As a measuring device, for example, Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name) can be used.

[Contact angle of powder with water]
As the airgel powder, those having a contact angle of 90 degrees or more between the powder layer made of airgel powder and water can be used. The contact angle may be 110 degrees or more, or 130 degrees or more. By using an airgel powder in which the contact angle between the powder layer made of airgel powder and water is 90 degrees or more, the airgel powder after removing the dispersion medium exhibits water repellency again, and surface treatment with the dispersion tends to be easy.

  The contact angle between the powder layer made of airgel powder and water can be measured by the θ / 2 method or the tangential method. For example, the airgel powder is transferred onto an adhesive tape to form a powder layer of the airgel powder, a water droplet is dropped on the airgel powder, and the contact angle between the water droplet and the powder layer is measured using a contact angle meter. As a measuring device, for example, DMo-701 (manufactured by Kyowa Interface Science Co., Ltd., product name) can be used.

<Specific embodiment of airgel component>
The airgel powder 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 following aspects are mentioned as an airgel component in the airgel powder of this embodiment. By adopting these aspects, it becomes easy to control the flexibility and dispersibility of the airgel powder to a desired level.

(First aspect)
The airgel powder of this embodiment can have a structure represented by the following general formula (1). The airgel composite powder of the present embodiment can have a structure represented by the following general formula (1a) as a structure including the structure represented by the formula (1).

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 powder as an airgel component, a flexible airgel powder is obtained. From such a viewpoint, in formula (1) and formula (1a), R ¹ and R ² each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like. A methyl group etc. are mentioned. Moreover, in Formula (1) and Formula (1a), as R < ³ > and R < ⁴ >, a C1-C6 alkylene group etc. are mentioned each independently, As said alkylene group, ethylene group, a propylene group, etc. Is mentioned. In formula (1a), p can be set to 2 to 30, and may be 5 to 20.

(Second embodiment)
The airgel powder of this embodiment can have a ladder type structure provided with a support | pillar part and a bridge | bridging part, and a bridge | bridging part can have a structure represented by following General formula (2). By introducing such a ladder structure as an airgel component into the skeleton of the airgel powder, heat resistance and mechanical strength can be improved. In this embodiment, the “ladder structure” has two struts and bridges connecting the struts (having a so-called “ladder” form). It is. In this embodiment, the skeleton of the airgel composite may have a ladder structure, but the airgel powder 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. In addition, 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 each the same. May be different.

By introducing the above structure as an airgel component into the skeleton of the airgel powder, for example, it has a structure derived from a conventional ladder-type silsesquioxane (that is, a structure represented by the following general formula (X)) ) Airgel powder having flexibility superior to airgel. Silsesquioxane is a polysiloxane having a composition formula: (RSiO _1.5 ) _n and can have various skeleton structures such as a cage type, a ladder type, and a random type. As shown by the following general formula (X), in the airgel having a structure derived from a conventional ladder-type silsesquioxane, the structure of the bridging portion is —O— (having the T unit as a structural unit). However, in the airgel powder of the present embodiment, the structure of the bridge portion is a structure (polysiloxane structure) represented by the general formula (2). However, the airgel composite powder of this embodiment may have a structure derived from silsesquioxane in addition to the structure represented by the general formula (2).

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

There are no particular limitations on the structure to be the strut portion and its chain length, and the interval between the structures to be the bridging portions, but from the viewpoint of further improving the heat resistance and mechanical strength, the ladder 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. In addition, 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} are each 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 the viewpoint of obtaining more excellent flexibility, in formulas (2) and (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ (however, R ⁷ and R ⁸ are only in formula (3)) Each independently includes an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. Moreover, in Formula (3), a and c can be independently 6-2000, but 10-1000 may be sufficient. Moreover, in formula (2) and (3), b can be 2-30, but 5-20 may be sufficient.

(Third embodiment)
The airgel powder of the present embodiment is produced by hydrolysis of silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group (in the molecule), and a silicon compound having a hydrolyzable functional group. A dried product of a wet gel, which is a condensate of a sol containing at least one selected from the group consisting of a product (obtained by drying a wet gel generated from the sol: a dried product of a wet gel derived from a sol ). Note that the airgel composite described so far may also be obtained by drying a wet gel generated from a sol containing silica particles and a silicon compound.

  As the silicon compound having a hydrolyzable functional group or a condensable functional group, a silicon compound (silicon compound) other than the polysiloxane compound described later can be used. That is, the sol is a group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group (excluding a polysiloxane compound) and a hydrolyzed product of the silicon compound having a hydrolyzable functional group. It may contain at least one compound selected from the following (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. Alkyl silicon alkoxide can make the number of hydrolyzable functional groups 3 or less from the viewpoint of improving water resistance. Examples of such alkyl silicon alkoxides include monoalkyltrialkoxysilanes, monoalkyldialkoxysilanes, dialkyldialkoxysilanes, monoalkylmonoalkoxysilanes, dialkylmonoalkoxysilanes, and trialkylmonoalkoxysilanes. Examples thereof include methyltrimethoxysilane, methyldimethoxysilane, dimethyldimethoxysilane, and ethyltrimethoxysilane. Examples of the hydrolyzable functional group include alkoxy groups such as methoxy group and ethoxy group.

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

  A silicon 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). It may further have a functional group (not applicable). Examples of the reactive group include an epoxy group, a mercapto group, a glycidoxy group, a vinyl group, an acryloyl group, a methacryloyl group, and an amino group. The epoxy group may be contained in an epoxy group-containing group such as a glycidoxy group.

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

  Moreover, as a silicon compound having a condensable functional group and having a reactive group, vinylsilane triol, 3-glycidoxypropylsilanetriol, 3-glycidoxypropylmethylsilanediol, 3-methacryloxypropylsilanetriol, 3-methacryloxypropylmethylsilanediol, 3-acryloxypropylsilanetriol, 3-mercaptopropylsilanetriol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2- (aminoethyl) ) -3-Aminopropylmethylsilanediol and the like can also be used.

  Further, bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, ethyltrimethoxysilane, vinyltrimethoxysilane, etc., which are silicon compounds having a hydrolyzable functional group at the molecular end of 3 or less can also be used. .

  Hydrolyzable functional groups or silicon compounds having a condensable functional group (excluding polysiloxane compounds) and hydrolyzed products of silicon compounds having hydrolyzable functional groups may be used alone or in combination of two or more May be used in combination.

  In producing the airgel powder of this embodiment, the silicon compound can contain a polysiloxane compound having a hydrolyzable functional group or a condensable functional group. That is, the sol containing the above-described silicon compound is obtained by hydrolyzing a polysiloxane compound having a hydrolyzable functional group or a condensable functional group (in the molecule) and a polysiloxane compound having a hydrolyzable functional group. It may further contain at least one selected from the group consisting of decomposition products (hereinafter sometimes referred to as “polysiloxane compound group”).

  Although the functional group in a polysiloxane compound etc. is not specifically limited, It can be set as the group which reacts with the same functional group, or reacts with another functional group. Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group include a hydroxyl group, a silanol group, a carboxyl group, and a phenolic hydroxyl group. The hydroxyl group may be contained in a hydroxyl group-containing group such as a hydroxyalkyl group. In addition, the polysiloxane compound having a hydrolyzable functional group or a condensable functional group is different from the above-mentioned reactive group (hydrolyzable functional group and condensation) different from the hydrolyzable functional group and the condensable functional group. May further have a functional group that does not correspond to a functional functional group). These polysiloxane compounds having a functional group and a reactive group may be used alone or in combination of two or more. Among these functional groups and reactive groups, examples of the group that improves the flexibility of the airgel composite include an alkoxy group, a silanol group, and a hydroxyalkyl group. Among these, an alkoxy group and a hydroxyalkyl group Can further improve the compatibility of the sol. Further, from the viewpoint of improving the reactivity of the polysiloxane compound, the number of carbon atoms of the alkoxy group and the hydroxyalkyl group can be 1 to 6, but 2 to 4 from the viewpoint of further improving the flexibility of the airgel powder. May be.

Examples of the polysiloxane compound having a hydroxyalkyl group in the molecule include those having a structure represented by the following general formula (A). By using a polysiloxane compound having a structure represented by the following general formula (A), the structure represented by the general formula (1) and the formula (1a) can be introduced into the skeleton of the airgel powder. .

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. In addition, 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 (A), two R ^{1a s} may be the same or different, and similarly, two R ^{2a s} may be the same or different. In the 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 which is a condensate of a sol containing the polysiloxane compound having the above structure, a flexible airgel powder can be obtained more easily. From such a viewpoint, in formula (A), R ^1a includes a hydroxyalkyl group having 1 to 6 carbon atoms, and examples of the hydroxyalkyl group include a hydroxyethyl group and a hydroxypropyl group. In formula (A), R ^2a includes an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group. In formula (A), R ^3a and R ^4a each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. Moreover, in formula (A), n can be 2-30, but 5-20 may be sufficient.

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

Examples of the polysiloxane compound having an alkoxy group include those having a structure represented by the following general formula (B). By using a polysiloxane compound having a structure represented by the following general formula (B), a ladder structure having a bridge portion represented by the general formula (2) is introduced into the skeleton of the airgel powder. Can do.

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. In addition, 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 from each other, and two R ^{2b s} may be the same or different from each other, and similarly two R ^{1b s. 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 s} may be the same or different, and similarly two or more R ^{5b s} are each the same. May be different.

By using a wet gel that is a condensate of a sol containing the polysiloxane compound having the above structure or a hydrolysis product thereof, a flexible airgel powder can be obtained more easily. From such a viewpoint, in formula (B), as R ^1b , an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and the like can be given. As the alkyl group or alkoxy group, A methyl group, a methoxy group, an ethoxy group, etc. are mentioned. In formula (B), R ^2b and R ^3b each independently include an alkoxy group having 1 to 6 carbon atoms, and examples of the alkoxy group include a methoxy group and an ethoxy group. Moreover, in Formula (B), as R ^<4b> and R ^<5b >, a C1-C6 alkyl group, a phenyl group, etc. are mentioned each independently, A methyl group etc. are mentioned as the said alkyl group. Moreover, in formula (B), m can be 2 to 30, but 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, and the polysiloxane compound having an alkoxy group and the hydrolysis product are mixed. You may do it. In the polysiloxane compound having an alkoxy group, all of the alkoxy groups in the molecule may be hydrolyzed or partially hydrolyzed.

  These polysiloxane compounds having hydrolyzable functional groups or condensable functional groups, and the hydrolysis products of polysiloxane compounds having hydrolyzable functional groups may be used alone or in combination of two or more. May be used.

  Content of silicon compound group contained in the sol (content of silicon compound having hydrolyzable functional group or condensable functional group, and hydrolysis product of silicon compound having hydrolyzable functional group) The total content) can be 5 to 50 parts by mass with respect to 100 parts by mass of the sol, but may be 10 to 30 parts by mass. By making it 5 parts by mass or more, it becomes easy to obtain good reactivity, and by making it 50 parts by mass or less, it becomes easy to obtain good compatibility.

  Further, when the sol further contains a polysiloxane compound, the content of the silicon compound group and the content of the polysiloxane compound group (content of the polysiloxane compound having a hydrolyzable functional group or a condensable functional group) , And the total of the hydrolysis product content of the polysiloxane compound having a hydrolyzable functional group) can be 5 to 50 parts by mass with respect to 100 parts by mass of the sol, 10-30 mass parts may be sufficient. When the total content is 5 parts by mass or more, good reactivity is further easily obtained, and when it is 50 parts by mass or less, good compatibility is further easily obtained. At this time, the ratio of the content of the silicon compound group and the content of the polysiloxane compound group may be 0.5: 1 to 4: 1, but may be 1: 1 to 2: 1. . When the ratio of the content of these compounds is 0.5: 1 or more, good compatibility is further easily obtained, and when the ratio is 4: 1 or less, gel shrinkage is further easily suppressed.

  Although content of the silica particle contained in the said sol can be 1-20 mass parts with respect to 100 mass parts of total amounts of sol, 4-15 mass parts may be sufficient. By setting the content to 1 to 20 parts by mass, it becomes easy to impart an appropriate strength to the airgel, and it becomes easy to obtain an airgel powder having excellent shrinkage resistance during drying.

(Other aspects)
The airgel powder of the present embodiment can have a structure represented by the following general formula (4). The airgel composite powder 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. Here, examples of the alkyl group include an alkyl group having 1 to 6 carbon atoms, and examples of the alkyl group include a methyl group.

The airgel powder of the present embodiment can have a structure represented by the following general formula (5). The airgel composite powder 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. Here, as an alkyl group, a C1-C6 alkyl group etc. are mentioned, A methyl group etc. are mentioned as the said alkyl group.

The airgel powder of the present embodiment can have a structure represented by the following general formula (6). The airgel composite powder 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. Here, examples of the alkylene group include an alkylene group having 1 to 10 carbon atoms, and examples of the alkylene group include an ethylene group and a hexylene group.

<Method for producing airgel powder>
Next, the manufacturing method of airgel powder is demonstrated. Although the manufacturing method of airgel powder is not specifically limited, For example, it can manufacture with the following method.

  That is, the airgel powder of the present embodiment includes a sol production step, a wet gel production step in which the sol obtained in the sol production step is gelled and then aged to obtain a wet gel, and the wet gel obtained in the wet gel production step. The washing and solvent substitution steps for washing the gel and solvent replacement (if necessary), the drying step for drying the wet gel after washing and solvent substitution, and the block crushing step for crushing the airgel block obtained by drying mainly It can manufacture with the manufacturing method provided.

  In addition, the manufacturing mainly includes a sol generation step, the wet gel generation step, a wet gel pulverization step for pulverizing the wet gel obtained in the wet gel generation step, the washing and solvent replacement step, and the drying step. You may manufacture by the method.

  The obtained airgel powder can be further arranged in size by sieving or classification. When the size of the powder is adjusted, the handleability can be improved. The “sol” is a state before the gelation reaction occurs, and in the present embodiment, the silicon compound group, and in some cases, the polysiloxane compound group, and silica particles are dissolved or dispersed in a solvent. Means the state. The wet gel means a gel solid in a wet state that contains a liquid medium but does not have fluidity.

  Hereinafter, each process of the manufacturing method of the airgel powder of this embodiment is demonstrated.

(Sol generation process)
A sol production | generation process is a process which mixes the above-mentioned silicon compound, the polysiloxane compound by the case, and the solvent containing a silica particle or a silica particle, and hydrolyzes it, and produces | generates a sol. 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, components such as carbon graphite, an aluminum compound, a magnesium compound, a silver compound, and a titanium compound may be added to the solvent for the purpose of imparting optical characteristics and thermal characteristics.

  As the solvent, for example, water or a mixed solution of water and alcohols can be used. Examples of alcohols include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol. Among these, methanol, ethanol, 2-propanol etc. are mentioned as alcohol with a low surface tension and a low boiling point at the point which reduces the interfacial tension with a gel wall. You may use these individually or in mixture of 2 or more types.

  For example, when alcohol is used as the solvent, the amount of alcohol can be 4 to 8 moles with respect to 1 mole of the total amount of the silicon compound group and the polysiloxane compound group, but it is 4 to 6.5. It may be 4.5 to 6 mol. By making the amount of alcohols 4 mol or more, it becomes easier to obtain good compatibility, and by making it 8 mol or less, it becomes easier to suppress gel shrinkage.

  Examples of the acid catalyst include hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, hypochlorous acid, and other inorganic acids; acidic phosphoric acid Acidic phosphates such as aluminum, acidic magnesium phosphate and acidic zinc phosphate; organic carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid and azelaic acid Etc. Among these, an organic carboxylic acid is mentioned as an acid catalyst which improves the water resistance of the airgel composite obtained more. Examples of the organic carboxylic acids include acetic acid, but may be formic acid, propionic acid, oxalic acid, malonic acid and the like. You may use these individually or in mixture of 2 or more types.

  By using an acid catalyst, the hydrolysis reaction of the silicon compound and the polysiloxane 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 group and a polysiloxane compound group.

  As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. You may use these 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 nonyl phenyl ether, polyoxyethylene octyl phenyl 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.

  Examples of the ionic surfactant include a cationic surfactant, an anionic surfactant, and an amphoteric surfactant. Examples of the cationic surfactant include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and examples of the anionic surfactant include sodium dodecylsulfonate. Examples of amphoteric surfactants include amino acid surfactants, betaine surfactants, amine oxide surfactants, and the like. Examples of amino acid surfactants include acyl glutamic acid. Examples of betaine surfactants include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, and the like. 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 wet gel formation process described later. It is considered to be.

  The addition amount of the surfactant depends on the kind of the surfactant, or the kind and amount of the silicon compound group and the polysiloxane compound group. For example, the total amount of the silicon compound group and the polysiloxane compound group is 100 parts by mass. 1 to 100 parts by mass. In addition, 5-60 mass parts may be sufficient as the addition amount.

The thermohydrolyzable compound is considered to generate a base catalyst by thermal hydrolysis to make the reaction solution basic, and to promote the sol-gel reaction in the wet gel generation process described later. Therefore, the thermohydrolyzable compound is not particularly limited as long as it is a compound that can make the reaction solution basic after hydrolysis. Urea; formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N -Acid amides such as methylacetamide and N, N-dimethylacetamide; cyclic nitrogen compounds such as hexamethylenetetramine and the like.
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 in the wet gel generation step described later. 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 as the total amount of the silicon compound group and the polysiloxane compound group. The added amount may be 2 to 150 parts by mass. By making the addition amount 1 mass part or more, it becomes easier to obtain good reactivity, and by making it 200 mass parts or less, it becomes easier to further suppress the precipitation of crystals and the decrease in gel density.

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

  However, when a thermohydrolyzable compound is added to the solvent, the temperature environment of the sol generation step may be adjusted to a temperature that suppresses hydrolysis of the thermohydrolyzable compound and suppresses gelation of the 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 thermohydrolyzable compound, the temperature environment of the sol generation step can be 0 to 40 ° C, but may be 10 to 30 ° C.

(Wet gel production process)
The wet gel generation step is a step in which the sol obtained in the sol generation step is gelled and then aged to obtain a wet gel. In this step, a base catalyst can be used to promote gelation.

  Base catalysts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkali carbonates such as sodium carbonate and potassium carbonate; alkaline carbonates such as sodium bicarbonate and potassium bicarbonate Ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; basic sodium phosphate salts such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine , Diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3- (diethylamino) propylamine, di-2-ethylhe Silamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, t-butylamine, sec-butylamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethyl Aliphatic amines such as ethanolamine, methyldiethanolamine, diethanolamine, triethanolamine; nitrogen-containing heterocyclic rings such as morpholine, N-methylmorpholine, 2-methylmorpholine, piperazine and derivatives thereof, piperidine and derivatives thereof, imidazole and derivatives thereof Examples thereof include compounds. Among these, ammonium hydroxide (ammonia water) is excellent in that it has high volatility and does not easily remain in the airgel powder after drying, so that water resistance is not easily lost, and further, it is 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 or dealcoholization condensation reaction of the silicon compound, polysiloxane compound, and silica particles in the sol can be promoted, and the sol can be gelled in a shorter time. . Thereby, a wet gel with higher strength (rigidity) can be obtained.

  Although 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 group and a polysiloxane compound group, 1-4 mass parts may be sufficient. By setting it as 0.5 mass part or more, gelatinization can be performed in a short time, and a water resistance fall can be suppressed more by setting it as 5 mass part or less.

  The gelation of the sol in the wet 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 higher strength (rigidity) can be obtained. Moreover, since it becomes easy to suppress volatilization of a solvent (especially alcohol) by making gelation temperature into 90 degrees C or less, it can gelatinize, suppressing volume shrinkage.

  The aging in the wet gel generation step may be performed in a sealed container so that the solvent and the base catalyst do not volatilize. By aging, the components of the wet gel are strongly bonded, and as a result, a wet gel having a high strength (rigidity) sufficient to suppress shrinkage during drying can be obtained. The aging temperature can be 30 to 90 ° C, but it may be 40 to 80 ° C. By setting the aging temperature to 30 ° C. or higher, a wet gel with higher strength (rigidity) can be obtained, and by setting the aging temperature to 90 ° C. or lower, volatilization of the solvent (especially alcohols) can be easily suppressed. Therefore, it can be gelled while suppressing volume shrinkage.

  Since it is often difficult to determine the sol gelation end point, sol gelation and subsequent aging may be performed in a series of operations.

  Although the gelation time and the aging time differ depending on the gelation temperature and the aging temperature, in the present embodiment, since the sol contains silica particles, the gelation time is particularly compared with the conventional method for producing an airgel. Can be shortened. The reason for this is presumed that the silanol groups or reactive groups of the silicon compound, polysiloxane compound, etc. in the sol form hydrogen bonds or chemical bonds with the silanol groups of the silica particles. The gelation time can be 10 to 120 minutes, but may be 20 to 90 minutes. By setting the gelation time to 10 minutes or more, it becomes easy to obtain a homogeneous wet gel, and by setting it to 120 minutes or less, the drying process can be simplified from the washing and solvent replacement process described later. In addition, as a whole process of gelation and aging, the total time of the gelation time and the aging time can be 4 to 480 hours, but may be 6 to 120 hours. By setting the total gelation time and aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, the effect of aging can be more easily maintained.

  In order to reduce the density of the obtained airgel powder or increase the average pore diameter, the gelation temperature and the aging temperature are increased within the above range, or the total time of the gelation time and the aging time is increased within the above range. Also good. In addition, in order to increase the density of the obtained airgel powder or reduce the average pore diameter, the gelation temperature and the aging temperature are reduced within the above range, or the total time of the gelation time and the aging time is within the above range. It may be shortened.

(Wet gel grinding process)
When performing the wet gel pulverization step, the wet gel obtained in the wet gel production step is pulverized. The pulverization can be carried out, for example, by putting the wet gel in a Hench type mixer or by performing a wet gel production process in the mixer and operating the mixer under appropriate conditions (rotation speed and time). More simply, the wet gel is put into a sealable container, or the wet gel generation process is performed in the sealable container, and the mixture is shaken for an appropriate time using a shaker such as a shaker. Can do. If necessary, the particle size of the wet gel can be adjusted using a jet mill, a roller mill, a bead mill or the like.

(Washing and solvent replacement process)
The washing and solvent replacement step is suitable for the step of washing the wet gel obtained by the wet gel generation step or the wet gel pulverization step (washing step) and the washing liquid in the wet gel for drying conditions (the drying step described later). This is a step having a step of replacing with a solvent (solvent replacement step). The washing and solvent replacement step can be performed in a form in which only the solvent replacement step is performed without performing the step of washing the wet gel, but the impurities such as unreacted substances and by-products in the wet gel are reduced, and more The wet gel may be washed from the viewpoint of enabling production of a highly pure airgel powder. In this embodiment, since the silica particles are contained in the gel, the solvent replacement step after the washing step is not necessarily essential as will be described later.

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

  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 said organic solvent individually or in mixture of 2 or more types.

  In the solvent replacement step described below, a low surface tension solvent can be used to suppress gel shrinkage due to drying. However, low surface tension solvents generally have very low mutual solubility with water. Therefore, when using a low surface tension solvent in the solvent replacement step, examples of the organic solvent used in the washing step include hydrophilic organic solvents having high mutual solubility in both water and a low surface tension solvent. Note that the hydrophilic organic solvent used in the washing step can serve as a preliminary replacement for the solvent replacement step. Among the above organic solvents, examples of the hydrophilic organic solvent include methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, and the like. Methanol, ethanol, methyl ethyl ketone and the like are excellent in terms of economy.

  The amount of water or organic solvent used in the washing step can be set to an amount that can sufficiently wash the solvent in the wet gel and wash it. The amount can be 3 to 10 times the amount of wet gel volume. The washing can be repeated until the moisture content in the wet gel after washing is 10% by mass or less with respect to the silica mass.

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

  In the solvent replacement step, the solvent of the washed wet gel is replaced with a predetermined replacement solvent in order to suppress shrinkage 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 performing supercritical drying, examples of the substitution solvent include ethanol, methanol, 2-propanol, dichlorodifluoromethane, carbon dioxide, and the like, or a solvent obtained by mixing two or more of these.

  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), ethyl butyrate (24.6), etc. (in parentheses indicate surface tension at 20 ° C., and the unit is [mN / m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have a low surface tension and an excellent working 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 of 100 ° C. or less at normal pressure 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 wet gel after washing. The amount can be 3 to 10 times the amount of wet gel volume.

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

  In the present embodiment, since the silica particles are contained in the gel, the solvent replacement step is not necessarily essential as described above. The inferred mechanism is as follows. That is, conventionally, in order to suppress shrinkage in the drying process, the solvent of the wet gel is replaced with a predetermined replacement solvent (a low surface tension solvent), but in this embodiment, the silica particles are in a three-dimensional network shape. By functioning as a skeleton support, the skeleton is supported, and the shrinkage of the gel in the drying step is suppressed. Therefore, it is considered that the gel can be directly subjected to the drying step without replacing the solvent used for washing. Thus, in this embodiment, the drying process can be simplified from the washing and solvent replacement process. However, this embodiment does not exclude performing the solvent substitution step at all.

(Drying process)
In the drying step, the wet gel that has been washed and solvent-substituted (if necessary) as described above is dried. Thereby, an airgel block or powder can be obtained. That is, an airgel obtained by drying a wet gel generated from the sol can be obtained.

  The drying method is not particularly limited, and known atmospheric pressure drying, supercritical drying, or freeze drying can be used. Among these, atmospheric drying or supercritical drying can be used from the viewpoint of easy production of a low-density airgel block or powder. Further, from the viewpoint that production is possible at low cost, atmospheric pressure drying can be used. In the present embodiment, the normal pressure means 0.1 MPa (atmospheric pressure).

  The airgel block or powder can be obtained by drying a wet gel that has been washed and solvent-substituted (if necessary) at a temperature below the critical point of the solvent used for drying at atmospheric pressure. The drying temperature varies depending on the type of substituted solvent (the solvent used for washing if solvent substitution is not performed), but especially when drying at a high temperature increases the evaporation rate of the solvent and causes large cracks in the gel. In view of that there is, it can be 20-150 degreeC. The drying temperature may be 60 to 120 ° C. Moreover, although drying time changes with the capacity | capacitances and drying temperature of a wet gel, it can be 4 to 120 hours. In the present embodiment, it is also included in the atmospheric pressure drying that the drying is accelerated by applying a pressure less than the critical point within a range not inhibiting the productivity.

  The airgel block or powder can also be obtained by supercritical drying of a washed and solvent-substituted wet gel (if necessary). 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 wet gel. Alternatively, as a method of supercritical drying, all or part of the solvent contained in the wet gel is obtained by immersing the wet gel in liquefied carbon dioxide, for example, under conditions of about 20 to 25 ° C. and about 5 to 20 MPa. And carbon dioxide having a lower critical point than that of the solvent, and then removing carbon dioxide alone or a mixture of carbon dioxide and the solvent.

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

(Block grinding process)
When performing a block crushing process, airgel powder is obtained by grind | pulverizing the airgel block obtained by drying. For example, it can be carried out by putting the airgel composite in a jet mill, roller mill, bead mill, hammer mill or the like and operating at an appropriate rotation speed and time.

  The airgel powder in this embodiment includes a hydrophobic carbon-silicon bond derived from polysiloxane or alkyl silicon alkoxide used as a raw material. Therefore, such an airgel powder can be said to be a hydrophobized (hydrophobic) airgel powder.

  Next, the present disclosure will be described in more detail with reference to the following examples, but these examples do not limit the present disclosure.

(Airgel powder production example 1)
60.0 parts by mass of methyltrimethoxysilane LS-530 (manufactured by Shin-Etsu Chemical Co., Ltd., product name: hereinafter abbreviated as “MTMS”) and dimethyldimethoxysilane LS-520 (manufactured by Shin-Etsu Chemical Co., Ltd., product) Name: “DMDMS” hereinafter) 40.0 parts by mass, and spherical colloidal silica PL-2L (manufactured by Fuso Chemical Industries, Ltd., product name, average primary particle size 20 nm, solid content 20% by mass) 100.0 parts by mass, 40.0 parts by mass of water and 80.0 parts by mass of methanol, 0.10 parts by mass of acetic acid as an acid catalyst was added thereto, and reacted at 25 ° C. for 2 hours to obtain sol 1 Got. To the obtained sol 1, 40.0 parts by mass of ammonia water having a concentration of 5% by mass as a base catalyst was added, gelled at 60 ° C., and then aged at 80 ° C. for 24 hours to obtain a wet gel 1.

  Thereafter, the obtained wet gel 1 is transferred to a plastic bottle, sealed, and then pulverized at 27,000 rpm for 10 minutes using an Extreme Mill MX-1000XTS (manufactured by ASONE Co., Ltd.) to form a particulate wet gel. 1 was obtained. The obtained particulate wet gel 1 was immersed in 2500.0 parts by mass of methanol and washed at 25 ° C. for 24 hours. This washing operation was performed a total of three times while exchanging with fresh methanol. Next, the washed particulate wet gel was immersed in 2500.0 parts by mass of heptane, which is a low surface tension solvent, and solvent substitution was performed at 25 ° C. for 24 hours. This solvent replacement operation was performed three times in total while exchanging with new heptane. The washed and solvent-substituted particulate wet gel was dried at 40 ° C. for 96 hours under normal pressure, and then further dried at 150 ° C. for 2 hours. Finally, the airgel powder P-1 which has a structure represented by the said General formula (4) and (5) was obtained by sieving (The Tokyo screen make, the opening of 45 micrometers, wire diameter 32 micrometers).

  The obtained airgel powder P-1 is transferred to a double-sided tape affixed on a slide glass to form a powder layer of airgel powder. Contact angle meter DMo-701 (product name, manufactured by Kyowa Interface Science Co., Ltd.) Was used to measure the contact angle between water and the powder layer. The contact angle was calculated using the θ / 2 method, and the amount of water dropped was 3 μL. The contact angle between the powder layer made of airgel powder P-1 and water was 146 degrees.

(Airgel powder preparation example 2)
60.0 parts by mass of MTMS as a silicon compound, 40.0 parts by mass of bistrimethoxysilyl hexane “KBM-3066” (manufactured by Shin-Etsu Chemical Co., Ltd., product name), and spherical colloidal silica ST- 57.0 parts by mass of OZL-35 (manufactured by Nissan Chemical Industries, product name, average primary particle size 100 nm, solid content 35% by mass), 83.0 parts by mass of water and 80.0 parts by mass of methanol were mixed. 0.10 parts by mass of acetic acid as an acid catalyst and 20.0 parts by mass of cetyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd .: hereinafter abbreviated as “CTAB”) as a cationic surfactant were added at 25 ° C. A sol 2 was obtained by reacting for 2 hours. 40.0 parts by mass of 5% aqueous ammonia as a base catalyst was added to the obtained sol 2, gelled at 60 ° C., and then aged at 80 ° C. for 24 hours to obtain wet gel 2. Then, using the obtained wet gel 2, airgel powder P-2 having a structure represented by the general formulas (4) and (6) was obtained in the same manner as in Example 1. The contact angle between the powder layer made of airgel powder P-2 and water was measured by the same method as in Production Example 1 and found to be 144 degrees.

(Airgel powder production example 3)
100.0 parts by mass of PL-2L as a silica particle-containing raw material, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant and thermal hydrolysis 120.0 parts by mass of urea is mixed as a decomposable compound, 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS, and represented by the above general formula (B) as a polysiloxane compound 20.0 parts by mass of a bifunctional alkoxy-modified polysiloxane compound having a structure at both ends (hereinafter referred to as “polysiloxane compound A”) was added and reacted at 25 ° C. for 2 hours to obtain sol 3. The obtained sol 3 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 3. Then, using the obtained wet gel 3, airgel powder P-3 having a structure represented by the above general formulas (3), (4) and (5) was obtained in the same manner as in Example 1. As a result of measuring the contact angle between the powder layer made of the airgel powder P-3 and water by the same method as in Production Example 1, it was 149 degrees.

  The “polysiloxane compound A” was synthesized as follows. First, dimethylpolysiloxane XC96-723 having a silanol group at both ends in a 1 liter three-necked flask equipped with a stirrer, a thermometer and a Dimroth condenser (product name, manufactured by Momentive Performance Materials) 100.0 parts by mass, 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. for 2 hours under reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining a bifunctional alkoxy-modified polysiloxane compound (polysiloxane compound A) at both ends.

Example 1
0.5 parts by mass of airgel powder P-1, 0.5 parts by mass of polyoxyethylene sorbitan monostearate Rheodor TW-S120V (Kao Corporation, product name) as a surfactant having an alkylene oxide structure, and 41 of water After mixing 6.4 parts by mass with 7.4 parts by mass of 2-propanol, the mixture was stirred at 5,000 rpm for 15 minutes using a homogenizer HG-200 (product name, manufactured by HSIANGTAI), and a dispersion of airgel powder P-1 Got.

(Example 2)
0.5 parts by mass of airgel powder P-1, 0.5 parts by mass of polyoxyethylene acetylene alcohol Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd., product name) as a surfactant having an alkylene oxide structure and 49 of water After mixing parts by mass, a dispersion of airgel powder P-1 was obtained in the same manner as in Example 1.

(Example 3)
0.5 parts by mass of airgel powder P-1 and 0.5 parts by mass of polyether-modified siloxane Silface SAG002 (manufactured by Nissin Chemical Industry Co., Ltd., product name) as a surfactant having an alkylene oxide structure and a siloxane structure After mixing 49 parts by mass of water, a dispersion of airgel powder P-1 was obtained in the same manner as in Example 1.

(Example 4)
0.5 parts by mass of airgel powder P-1 and 0.5 parts by mass of polyether-modified siloxane Silwet L-7608 (product name, manufactured by Momentive Performance Materials) as a surfactant having an alkylene oxide structure and a siloxane structure And after mixing 49 mass parts of water, the dispersion liquid of airgel powder P-1 was obtained by the same method as Example 1.

(Example 5)
2.5 parts by mass of airgel powder P-1 and 0.5 parts by mass of polyether-modified siloxane Silwet L-7608 (product name, manufactured by Momentive Performance Materials) as a surfactant having an alkylene oxide structure and a siloxane structure After mixing 47 parts by mass of water and water, a dispersion of airgel powder P-1 was obtained in the same manner as in Example 1.

(Example 6)
2.5 parts by mass of airgel powder P-2 and 0.5 parts by mass of polyether-modified siloxane Silwet L-7608 (product name, manufactured by Momentive Performance Materials) as a surfactant having an alkylene oxide structure and a siloxane structure After mixing 47 parts by mass of water and water, a dispersion of airgel powder P-2 was obtained in the same manner as in Example 1.

(Example 7)
2.5 parts by mass of airgel powder P-3 and 0.5 parts by mass of polyether-modified siloxane Silwet L-7608 (product name, manufactured by Momentive Performance Materials) as a surfactant having an alkylene oxide structure and a siloxane structure After mixing 47 parts by mass of water and water, a dispersion of airgel powder P-3 was obtained in the same manner as in Example 1.

(Comparative Example 1)
After mixing 0.5 parts by mass of airgel powder P-1 and 49.5 parts by mass of water, the airgel powder P was prepared in the same manner as in Example 1 using a homogenizer HG-200 (product name, manufactured by HSIANGTAI). A dispersion of -1 was obtained.

(Comparative Example 2)
After mixing 0.5 parts by mass of airgel powder P-1, 24.8 parts by mass of water and 24.8 parts by mass of 2-propanol, a dispersion of airgel powder P-1 was prepared in the same manner as in Example 1. Obtained.

  Various evaluations of the aqueous dispersions of the airgel powder obtained above were performed by the procedure described below. The evaluation results are shown in Table 1.

[Dispersibility evaluation]
The appearance of the dispersion immediately after the production was visually confirmed. The sample in which the airgel powder was uniformly dispersed without agglomeration was evaluated as “◯”, and the sample in which the airgel powder was agglomerated but not uniformly dispersed was evaluated as “x”.

[Foaming evaluation]
The height of bubbles generated on the surface of the dispersion immediately after production was measured from the side with a ruler.

[Dispersibility stability evaluation]
The appearance of the dispersion 1 hour after production was visually confirmed. “○” indicates a sample in which airgel powder is uniformly dispersed, “△” indicates a sample in which a part of the dispersed airgel powder settles, and the airgel powder and dispersion medium are completely separated by aggregation or complete sedimentation of the airgel powder. The sample was evaluated as “x”.

[Defoaming evaluation]
The height of the foam remaining on the surface of the dispersion 1 hour after production was measured with a ruler from the side.

  From Table 1, the airgel powder dispersions of Examples 1 to 7 were excellent in dispersibility and dispersion stability. In some cases, the airgel powder settled, but was dispersed without complete separation from the dispersion medium due to aggregation or complete sedimentation. On the other hand, Comparative Examples 1 and 2 were inferior in dispersibility and / or dispersion stability, and could not be uniformly dispersed.

  DESCRIPTION OF SYMBOLS 1 ... Airgel particle, 2 ... Silica particle, 3 ... Fine pore, 10 ... Airgel composite, L ... circumscribed rectangle.

Claims (16)

  An airgel powder dispersion containing airgel powder, water and a surfactant.   The dispersion liquid according to claim 1, wherein the airgel powder includes a powder layer composed of the airgel powder and water having a contact angle of 90 ° or more.   The dispersion according to claim 1 or 2, wherein the surfactant has an alkylene oxide structure.   The dispersion according to claim 3, wherein the surfactant further has a siloxane structure.   Furthermore, the dispersion liquid as described in any one of Claims 1-4 containing an organic solvent.   The dispersion liquid as described in any one of Claims 1-5 whose content of the water in a dispersion medium is 50 mass% or more.   The dispersion liquid according to claim 1, wherein the airgel powder contains an airgel component and silica particles.   The dispersion according to claim 7, wherein the airgel powder has a three-dimensional network skeleton and pores formed from the airgel component and the silica particles.   The dispersion according to any one of claims 1 to 6, wherein the airgel powder contains silica particles as a component constituting a three-dimensional network skeleton.   The airgel powder is selected from the group consisting of silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. The dispersion according to any one of claims 1 to 9, which is a dried product of a wet gel that is a condensate of a sol containing at least one of the above.   The dispersion according to claim 10, wherein the silicon compound further contains a polysiloxane compound having a hydrolyzable functional group or a condensable functional group.   The dispersion liquid as described in any one of Claims 7-11 whose average primary particle diameter of the said silica particle is 1-500 nm.   The dispersion according to any one of claims 7 to 12, wherein the silica particles have a spherical shape.   The dispersion according to any one of claims 7 to 13, wherein the silica particles are amorphous silica particles.   The dispersion according to claim 14, wherein the amorphous silica particles are at least one selected from the group consisting of fused silica particles, fumed silica particles, and colloidal silica particles. The dispersion liquid according to claim 1, wherein the airgel powder has an average particle diameter D50 of 1 to 1000 μm.