WO2017038781A1 - Aerogel complex - Google Patents

Abstract

An aerogel complex that is the product of drying a wet gel that is a condensate of a sol that contains silica particles and at least one type of compound selected from the group that consists of polysiloxane compounds represented by general formula (B) and hydrolysis products of said polysiloxane compounds. [In formula (B), R^1b represents an alkyl group, an alkoxy group, or an aryl group, R^2b and R^3b each independently represent an alkoxy group, R^4b and R^5b each independently represent an alkyl group or an aryl group, and m represents an integer from 1 to 50.]

Description

Airgel composite

This disclosure relates to an airgel composite.

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 (thermal insulation, etc.), unique optical properties, and unique electrical properties. 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.

As a method for producing such a silica airgel, a supercritical drying method is known in which a gel-like compound (alcogel) obtained by hydrolyzing and polymerizing alkoxysilane is dried under supercritical conditions of a dispersion medium. (For example, refer to Patent Document 1). In the supercritical drying method, an alcogel and a dispersion medium (solvent used for drying) are introduced into a high-pressure vessel, and the dispersion medium is applied to the supercritical fluid by applying a temperature and pressure above its critical point to form a supercritical fluid. It is a method of removing the solvent. However, since the supercritical drying method requires a high-pressure process, capital investment is required for a special apparatus that can withstand supercriticality, and much labor and time are required.

Therefore, a technique for drying alcogel using a general-purpose method that does not require a high-pressure process has been proposed. As such a method, for example, a method of improving the strength of the resulting alcogel by using a monoalkyltrialkoxysilane and a tetraalkoxysilane in combination at a specific ratio as a gel material and drying at normal pressure is known. (See, for example, Patent Document 2). However, when such atmospheric pressure drying is employed, the gel tends to contract due to stress caused by the capillary force inside the alcogel.

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

As described above, while the problems of the conventional manufacturing process have been studied from various viewpoints, even if any of the above processes is adopted, the obtained airgel is poor in handling and large in size. Because it is difficult, there is a problem in productivity. For example, the agglomerated airgel obtained by the above process may be broken simply by trying to lift it by hand. This is presumably due to the fact that the density of the airgel is low and that the airgel has a pore structure in which fine particles of about 10 nm are weakly connected.

As a method for improving such problems of conventional aerogels, a method of imparting flexibility to the gel by enlarging the pore diameter of the gel to the micrometer scale is conceivable. However, the airgel thus obtained has a problem that the thermal conductivity is greatly increased, and the excellent heat insulating property of the airgel is lost.

The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an airgel composite excellent in heat insulation and flexibility.

As a result of intensive studies to achieve the above object, the present inventor has excellent heat insulation and flexibility as long as it is an airgel composite produced using silica particles and a predetermined polysiloxane compound. Was found to be expressed.

The present disclosure provides a condensation of a sol containing silica particles and at least one selected from the group consisting of a polysiloxane compound represented by the following general formula (B) and a hydrolysis product of the polysiloxane compound. The present invention provides an airgel composite that is a dried product of a wet gel. The airgel composite thus obtained is excellent in heat insulation and flexibility.

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 to 50.

The airgel composite may have a ladder structure including a support portion and a bridge portion, and the bridge portion may have a structure represented by the following general formula (2).

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

The airgel composite can have a ladder structure represented by the following general formula (3).

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

The average primary particle diameter of the silica particles can be 1 to 200 nm. Thereby, it becomes easy to improve heat insulation and a softness | flexibility further.

At this time, the shape of the silica particles may be spherical. The silica particles can be colloidal silica particles. Thereby, further excellent heat insulation and flexibility can be achieved.

In the present disclosure, the sol is selected from the group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. At least one kind can be further contained. Thereby, further excellent heat insulation and flexibility can be achieved.

The dried product can be obtained by drying at a temperature below the critical point of the solvent used for drying the wet gel and under atmospheric pressure. This makes it easier to obtain an airgel composite that is excellent in heat insulation and flexibility.

According to the present disclosure, an airgel composite excellent in heat insulation and flexibility can be provided. That is, it is possible to provide an airgel composite that exhibits excellent heat insulating properties, improves handleability, can be increased in size, and can increase productivity. Thus, the airgel composite excellent in heat insulation and flexibility has a possibility of being used for various purposes. Here, an important point according to the present disclosure is that it becomes easier to control heat insulation and flexibility than conventional aerogels. This is not possible with conventional aerogels that require sacrificing thermal insulation to obtain flexibility or sacrificing flexibility to obtain thermal insulation. The above “excellent in heat insulation and flexibility” does not necessarily mean that both numerical values representing both characteristics are high. For example, “excellent flexibility while maintaining good heat insulation” , “Excellent thermal insulation while maintaining good flexibility” and the like.

It is a figure showing typically the fine structure of the airgel composite concerning one embodiment of this indication. It is a figure which shows the calculation method of the biaxial average primary particle diameter of particle | grains. The surface of the airgel composite in the foil-like support member with the airgel composite obtained in Example 3 is (a) 10,000 times, (b) 50,000 times, (c) 200,000 times, and (d) 350,000. It is the SEM image observed by each magnification. The SEM image which observed the surface of the airgel composite in the foil-shaped support member with an airgel composite obtained in Example 4 at (a) 10,000 times, (b) 50,000 times, and (c) 200,000 times, respectively. It is.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings depending on the cases. However, the present disclosure is not limited to the following embodiment.

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

<Airgel composite>
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. In addition, the airgel composite of the present embodiment has a cluster structure that is a feature of the above airgel while silica particles are composited in the airgel, and has a three-dimensionally fine porous structure. ing.

The airgel composite of this embodiment contains an airgel component and silica particles. Although not necessarily meaning the same concept as this, the airgel composite of the present embodiment can also be expressed as containing silica particles as a component constituting the three-dimensional network skeleton. . The airgel composite of this embodiment is excellent in heat insulation and flexibility as described later. In particular, since the flexibility is excellent, the handling property as an airgel composite is improved and the size can be increased, so that the productivity can be increased. In addition, such an airgel composite is obtained by making silica particles exist in the airgel production environment. And the merit by the presence of silica particles is not only that the heat insulation and flexibility of the composite itself can be improved, but also shortening the time of the wet gel generation process described later, or simplifying the drying process from the washing and solvent replacement process. Is also possible. In addition, shortening of the time of this process and simplification of a process are not necessarily calculated | required when producing the airgel composite 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 coated with the airgel component, etc.) An embodiment is mentioned. Thus, in this embodiment, the airgel composite 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 composite of the present 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 aspect of the airgel composite (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, it is considered that the density, porosity, etc. of the airgel composite can be controlled, and the heat insulating property and flexibility of the airgel composite can be controlled. In addition, the three-dimensional network skeleton of the airgel composite 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 composite 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 composite 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 heat insulation and flexibility as the airgel. That is, in the present embodiment, the airgel composite may have a three-dimensional network skeleton formed by three-dimensionally connecting silica particles randomly through 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 airgel particle 1 may have an average particle size (that is, a secondary particle size) of 2 nm or more, may be 5 nm or more, and may be 10 nm or more. Moreover, the said average particle diameter can be 50 micrometers or less, may be 2 micrometers or less, and may be 200 nm or less. That is, the average particle diameter 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, an airgel composite having excellent flexibility can be easily obtained. On the other hand, when the average particle diameter is 50 μm or less, an airgel composite having excellent heat insulation can be easily obtained. Become. The average particle diameter of the primary particles constituting the airgel particles 1 can be set to 0.1 nm to 5 μm from the viewpoint of easy formation of 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 any 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 particles 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 nm or more, may be 5 nm or more, and may be 20 nm or more. The average primary particle diameter can be 200 nm or less, and may be 100 nm or less. That is, the average primary particle diameter can be 1 to 200 nm, but may be 5 to 200 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 an airgel composite having excellent shrinkage resistance during drying is easily obtained. On the other hand, when the average primary particle diameter is 200 nm or less, it becomes easy to suppress the solid heat conduction of the silica particles, and it becomes easy to obtain an airgel composite excellent in heat insulation.

It is presumed that the airgel particle 1 (aerogel component) and the silica particle 2 are bonded in the form of hydrogen bonding and / or chemical bonding. At this time, hydrogen bonds and / or chemical bonds are considered to be formed by the silanol groups and / or reactive groups of the airgel particles 1 (aerogel components) and the silanol groups of the silica particles 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 It may be × 10 ¹⁸ to 700 × 10 ¹⁸ pieces / g. The number of silanol groups per gram of silica particles 2 is 10 × 10 ¹⁸ pieces / g or more, so that the airgel composite can have better reactivity with the airgel particles 1 (airgel component) and has excellent shrinkage resistance. It becomes easy to obtain a body. On the other hand, when the number of silanol groups is 1000 × 10 ¹⁸ / 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 composite.

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, in the case of colloidal silica particles having a solid concentration of 5 to 40% by mass normally dispersed in water, for example, a chip with a 2 cm square wafer with a pattern wiring is immersed in the dispersion of colloidal silica particles for about 30 seconds. Thereafter, the chip is rinsed with pure water for about 30 seconds and blown with nitrogen. Thereafter, the chip is placed on a sample stage for SEM observation, an acceleration voltage of 10 kV is applied, the silica particles are observed at a magnification of 100,000, and an image is taken. 20 silica particles are arbitrarily selected from the obtained image, and the average of the particle diameters of these particles is defined as the average particle diameter. At this time, when the selected silica 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.

The size of the pores 3 in the airgel composite will be described in the section of [Density and porosity] described later.

The content of the airgel component contained in the airgel composite can be 4 parts by mass or more with respect to 100 parts by mass of the total amount of the airgel composite, but may be 10 parts by mass or more. Moreover, although the said content can be 25 mass parts or less, it may be 20 mass parts or less. That is, the content can be 4 to 25 parts by mass, but may be 10 to 20 parts by mass. When the content is 4 parts by mass or more, an appropriate strength is easily imparted, and when the content is 25 parts by mass or less, good heat insulating properties are easily obtained.

The content of the silica particles contained in the airgel composite can be 1 part by mass or more with respect to 100 parts by mass of the total amount of the airgel composite, but may be 3 parts by mass or more. Moreover, although the said content can be 25 mass parts or less, it may be 15 mass parts or less. That is, the content can be 1 to 25 parts by mass, but may be 3 to 15 parts by mass. When the content is 1 part by mass or more, an appropriate strength is easily imparted to the airgel composite, and when the content is 25 parts by mass or less, solid heat conduction of the silica particles is easily suppressed.

In addition to these airgel components and silica particles, the airgel composite may further contain other components such as carbon graphite, aluminum compound, magnesium compound, silver compound, and titanium compound for the purpose of suppressing heat radiation. The content of other components is not particularly limited, but can be 1 to 5 parts by mass with respect to 100 parts by mass of the total amount of the airgel complex from the viewpoint of sufficiently securing the desired effect of the airgel complex.

The airgel composite of the present embodiment includes silica particles, a polysiloxane compound represented by the following general formula (B), and at least one selected from the group consisting of hydrolysis products of the polysiloxane compound. It is a dried product of a wet gel that is a condensate of the contained sol (formed by drying a wet gel produced from the sol).

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 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 (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 (generated from a sol) that is a condensate of a sol containing the polysiloxane compound having the structure described above or a hydrolysis product thereof, it becomes easier to obtain a flexible airgel composite having low thermal conductivity. From such a viewpoint, in formula (B), examples of R ^1b include an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and the like. As the alkyl group or alkoxy group, A methyl group, a methoxy group, an ethoxy group, etc. are mentioned. In the formula (B), R ^2b and R ^3b each independently include an alkoxy group having 1 to 6 carbon atoms, and examples of the alkoxy group include a methoxy group and an ethoxy group. In the formula (B), R ^4b and R ^5b each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group and the like. In the 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.

In preparing the airgel composite of this embodiment, the sol described above contains (in the molecule) another polysiloxane compound having a hydrolyzable functional group or a condensable functional group, and the hydrolyzable functional group. It can further contain at least one selected from the group consisting of hydrolysis products of other polysiloxane compounds having groups. Hereinafter, at least one selected from the group consisting of the polysiloxane compound represented by the general formula (B) and a hydrolysis product of the polysiloxane compound, a hydrolyzable functional group (in the molecule) or In some cases, “polysiloxane compound having a condensable functional group and at least one selected from the group consisting of hydrolysis products of other polysiloxane compounds having a hydrolyzable functional group” A siloxane compound group).

The functional group in the polysiloxane compound is not particularly limited, but may be a group that reacts with the same functional group or reacts with another functional group. As a hydrolysable functional group, the alkoxy group which the polysiloxane compound which has a structure represented by the said general formula (B) has is mentioned, for example. 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, other polysiloxane compounds having a hydrolyzable functional group or a condensable functional group are reactive groups different from the hydrolyzable functional group and the condensable functional group (hydrolyzable functional group and condensation). May further have a functional group that does not correspond to a functional functional group). 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. 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 and reducing the thermal conductivity of the airgel composite, the number of carbon atoms of the alkoxy group and hydroxyalkyl group can be 1 to 6, but the flexibility of the airgel composite is not limited. It may be 2 to 4 from the viewpoint of further improving.

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

In formula (A), R ^1a represents a hydroxyalkyl group, R ^2a represents an alkylene group, R ^3a and R ^4a each independently represents an alkyl group or an aryl group, and n represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. 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 (generated from a sol) that is a condensate of a sol containing the polysiloxane compound having the above structure, it becomes easier to obtain a flexible airgel composite with low thermal conductivity. From this point of view, 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, a hydroxypropyl group, and the like. In the formula (A), examples of R ^2a include an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group. In the 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. In the formula (A), n can be 2 to 30, but may be 5 to 20.

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, and KF-6003 (all of them) , Manufactured by Shin-Etsu Chemical Co., Ltd.), compounds such as XF42-B0970, Fluid OFOH 702-4% (all manufactured by Momentive).

These hydrolyzable functional groups or other polysiloxane compounds having a condensable functional group, and hydrolysis products of other polysiloxane compounds having a hydrolyzable functional group may be used alone or in two kinds You may mix and use the above.

In producing the airgel composite of this embodiment, the sol containing the polysiloxane compound group may further contain a silicon compound (silicon compound) other than the polysiloxane compound. That is, the sol includes a hydrolyzable functional group or a silicon compound having a condensable functional group (excluding a polysiloxane compound) and hydrolyzing the silicon compound having the hydrolyzable functional group. It may further contain at least one selected from the group consisting of decomposition products (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.

The silicon compound having a hydrolyzable functional group is not particularly limited, and examples thereof include alkyl silicon alkoxides. 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.

The silicon compound having a hydrolyzable functional group or a condensable functional group has the above-mentioned reactive group (hydrolyzable functional group and condensable functional group) different from the hydrolyzable functional group and the condensable functional group. It may further have a functional group not corresponding to the 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-amino Propyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like can also be used.

Further, 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. .

The silicon compound having a hydrolyzable functional group or a condensable functional group, and the hydrolysis product of the silicon compound having a hydrolyzable functional group may be used alone or in combination of two or more. Good.

Content of polysiloxane compound group contained in the sol (content of polysiloxane compound having hydrolyzable functional group or condensable functional group, and hydrolysis of polysiloxane compound having hydrolyzable functional group) The sum of the product contents) can be 5 parts by mass or more and 100 parts by mass or more with respect to 100 parts by mass of the sol. The content can be 50 parts by mass or less, or 30 parts by mass or less with respect to 100 parts by mass of the total amount of sol. That is, the content of the polysiloxane compound group may 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 silicon compound, the content of the polysiloxane compound group and the content of the silicon compound group (content of the silicon compound having a hydrolyzable functional group or a condensable functional group, and The total of the hydrolyzable functional group silicon product hydrolysis products) can be 5 parts by mass or more with respect to 100 parts by mass of the sol. There may be. The total content can be 50 parts by mass or less, or 30 parts by mass or less, with respect to 100 parts by mass of the total amount of sol. That is, the total content may 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. 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 polysiloxane compound group to the content of the silicon compound group can be 1: 0.5 to 1: 4, but may be 1: 1 to 1: 2. . When the ratio of the content of these compounds is 1: 0.5 or more, good compatibility is further easily obtained, and when the ratio is 1: 4 or less, gel shrinkage is further easily suppressed.

The content of the silica particles contained in the sol can be 1 part by mass or more with respect to 100 parts by mass of the total amount of the sol, and may be 4 parts by mass or more. The content can be 20 parts by mass or less, or 15 parts by mass or less, with respect to 100 parts by mass of the total amount of sol. That is, the content of silica particles can be 1 to 20 parts by mass with respect to 100 parts by mass of the total amount of sol, but may be 4 to 15 parts by mass. By setting the content to 1 part by mass or more, it becomes easy to impart an appropriate strength to the airgel, and it becomes easy to obtain an airgel composite having excellent shrinkage resistance during drying. Moreover, it becomes easy to suppress the solid heat conduction of a silica particle by making content 20 mass parts or less, and it becomes easy to obtain the airgel composite excellent in heat insulation. In addition, the aspect of the silica particle contained in the said sol is as having demonstrated in the term of the said airgel composite.

<Specific embodiment of airgel composite>
The airgel composite of the present embodiment comprises silica particles, at least one selected from the group consisting of the polysiloxane compound represented by the general formula (B), and a hydrolysis product of the polysiloxane compound. It is a dried product of a wet gel that is a condensate of the contained sol (obtained by drying the wet gel produced from the above sol). In addition, as above-mentioned, the said condensate is obtained by the condensation reaction of the hydrolysis product obtained by hydrolysis of the polysiloxane compound represented by the said general formula (B) which has a hydrolysable functional group. However, the condensate is not a condensation reaction of a hydrolysis product obtained by hydrolysis of another polysiloxane compound having a hydrolyzable functional group or a silicon compound, or a functional group obtained by hydrolysis. It may be obtained with a condensation reaction of other polysiloxane compounds or silicon compounds having a condensable functional group. Other polysiloxane compounds and silicon compounds only need to have at least one of a hydrolyzable functional group and a condensable functional group, and have both a hydrolyzable functional group and a condensable functional group. It may be.

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

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

The airgel composite of the present embodiment can have a ladder structure including a column portion and a bridge portion, and the bridge portion can have a structure represented by the following general formula (2). By introducing such a ladder structure as an airgel component into the skeleton of the airgel composite, heat resistance and mechanical strength can be improved. By using the polysiloxane compound having the structure represented by the general formula (B), a ladder structure having a bridge portion represented by the general formula (2) is introduced into the skeleton of the airgel composite. Can do. 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 composite may partially have a ladder structure.

In formula (2), R ⁵ and R ⁶ each independently represents an alkyl group or an aryl group, and b represents an integer of 1 to 50. 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 complex, for example, it has a structure derived from a conventional ladder-type silsesquioxane (that is, a structure represented by the following general formula (X) An airgel composite having flexibility superior to that of the 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 in the following general formula (X), in an 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). In the airgel composite of this embodiment, the structure of the bridge portion is a structure (polysiloxane structure) represented by the general formula (2). However, the airgel of this embodiment may have a structure derived from silsesquioxane in addition to the structure represented by the general formula (2).

In the 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 the formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group or an aryl group, a and c each independently represents 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. In the formula (3), a and c can be independently 6 to 2000, but may be 10 to 1000. In the formulas (2) and (3), b can be 2 to 30, but may be 5 to 20.

The airgel composite of this embodiment may have a structure represented by the following general formula (1). The airgel composite of this embodiment can have a structure represented by the following general formula (1a) as a structure including the structure represented by the formula (1). By using the polysiloxane compound having the structure represented by the general formula (A), the structures represented by the formulas (1) and (1a) can be introduced into the skeleton of the airgel composite.

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 represents an integer of 1 to 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 composite as an airgel component, a flexible airgel composite with low thermal conductivity is obtained. From such a viewpoint, in the formula (1) and the 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. And a methyl group. In the formulas (1) and (1a), R ³ and R ⁴ each independently include an alkylene group having 1 to 6 carbon atoms, and the alkylene group includes an ethylene group, a propylene group, and the like. Can be mentioned. In the formula (1a), p can be 2 to 30, and can be 5 to 20.

The airgel composite of the present embodiment 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 composite of the present embodiment 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, 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 composite of this embodiment can have a structure represented by the following general formula (6).

In formula (8), R ¹² represents an alkylene group. Here, examples of the alkylene group include alkylene groups having 1 to 10 carbon atoms, and examples of the alkylene group include an ethylene group and a hexylene group.

<Physical properties of airgel composite>
[Thermal conductivity]
In the airgel composite of the present embodiment, the thermal conductivity at 25 ° C. under atmospheric pressure can be 0.03 W / m · K or less, but may be 0.025 W / m · K or less, or It may be 0.02 W / m · K or less. When the thermal conductivity is 0.03 W / m · K or less, it is possible to obtain a heat insulating property higher than that of the polyurethane foam which is a high performance heat insulating material. The lower limit value of the thermal conductivity is not particularly limited, but can be set to 0.01 W / m · K, for example.

Thermal conductivity can be measured by a steady method. Specifically, it can be measured using, for example, a steady-state thermal conductivity measuring device “HFM436 Lambda” (manufactured by NETZSCH, product name, HFM436 Lambda is a registered trademark). The outline of the thermal conductivity measurement method using the steady method thermal conductivity measuring apparatus is as follows.

(Preparation of measurement sample)
The airgel composite is processed into a size of 150 mm × 150 mm × 100 mm using a blade having a blade angle of about 20 to 25 degrees to obtain a measurement sample. In addition, although the recommended sample size in HFM436Lambda is 300 mm × 300 mm × 100 mm, the thermal conductivity when measured with the above sample size is the same value as the thermal conductivity when measured with the recommended sample size. Confirmed. Next, in order to ensure parallelism of the surface, the measurement sample is shaped with a sandpaper of # 1500 or more as necessary. Then, before the thermal conductivity measurement, the measurement sample is dried at 100 ° C. for 30 minutes under atmospheric pressure using a constant temperature dryer “DVS402” (manufactured by Yamato Scientific Co., Ltd., product name). The measurement sample is then transferred into a desiccator and cooled to 25 ° C. Thereby, the measurement sample for thermal conductivity measurement is obtained.

(Measuring method)
The measurement conditions are an atmospheric pressure and an average temperature of 25 ° C. The measurement sample obtained as described above is sandwiched between the upper and lower heaters with a load of 0.3 MPa, the temperature difference ΔT is set to 20 ° C., and the guard sample is adjusted so as to obtain a one-dimensional heat flow. Measure upper surface temperature, lower surface temperature, etc. And the thermal resistance _RS of a measurement sample is calculated | required from following Formula.
R _S = N ((T _U −T _L ) / Q) −R _O
Wherein, T _U represents a measurement sample top surface temperature, T _L represents the measurement sample lower surface temperature, R _O represents the thermal contact resistance of the upper and lower interfaces, Q is shows the heat flux meter output. N is a proportionality coefficient, and is obtained in advance using a calibration sample.

From the obtained thermal resistance _RS , the thermal conductivity λ of the measurement sample is obtained from the following equation.
λ = d / R _S
In formula, d shows the thickness of a measurement sample.

[Compressive modulus]
In the airgel composite of the present embodiment, the compression modulus at 25 ° C. can be 3 MPa or less, but may be 2 MPa or less, 1 MPa or less, or 0.5 MPa or less. Good. When the compression elastic modulus is 3 MPa or less, it becomes easy to obtain an airgel composite excellent in handleability. In addition, the lower limit value of the compression elastic modulus is not particularly limited, but may be 0.05 MPa, for example.

[Deformation recovery rate]
In the airgel composite of this embodiment, the deformation recovery rate at 25 ° C. can be 90% or more, but may be 94% or more, or 98% or more. When the deformation recovery rate is 90% or more, it becomes easier to obtain excellent strength, excellent flexibility for deformation, and the like. Note that the upper limit value of the deformation recovery rate is not particularly limited, but may be, for example, 100% or 99%.

[Maximum compression deformation rate]
In the airgel composite of this embodiment, the maximum compressive deformation rate at 25 ° C. can be 80% or more, but may be 83% or more, or 86% or more. When the maximum compressive deformation rate is 80% or more, it becomes easier to obtain excellent strength, excellent flexibility for deformation, and the like. The upper limit value of the maximum compressive deformation rate is not particularly limited, but may be 90%, for example.

These compression elastic modulus, deformation recovery rate, and maximum compression deformation rate can be measured using a small desktop tester “EZTest” (manufactured by Shimadzu Corporation, product name). An outline of a method for measuring the compression modulus and the like using a small desktop testing machine is as follows.

(Preparation of measurement sample)
Using a blade with a blade angle of about 20 to 25 degrees, the airgel composite is processed into a 7.0 mm square cube (die shape) to obtain a measurement sample. Next, in order to ensure parallelism of the surface, the measurement sample is shaped with a sandpaper of # 1500 or more as necessary. Before measurement, the measurement sample is dried at 100 ° C. for 30 minutes under atmospheric pressure using a constant temperature dryer “DVS402” (manufactured by Yamato Scientific Co., Ltd., product name). The measurement sample is then transferred into a desiccator and cooled to 25 ° C. Thereby, a measurement sample for measuring the compression elastic modulus, deformation recovery rate, and maximum compression deformation rate is obtained.

(Measuring method)
A 500N load cell is used. A stainless upper platen (φ20 mm) and a lower platen plate (φ118 mm) are used as a compression measurement jig. A measurement sample is set between these jigs, compressed at a speed of 1 mm / min, and the displacement of the measurement sample size at 25 ° C. is measured. The measurement is terminated when a load exceeding 500 N is applied or when the measurement sample is destroyed. Here, the compressive strain ε can be obtained from the following equation.
ε = Δd / d1
In the formula, Δd represents the displacement (mm) of the thickness of the measurement sample due to the load, and d1 represents the thickness (mm) of the measurement sample before the load is applied.
The compressive stress σ (MPa) can be obtained from the following equation.
σ = F / A
In the formula, F represents the compressive force (N), and A represents the cross-sectional area (mm ² ) of the measurement sample before applying a load.

The compression elastic modulus E (MPa) can be obtained from the following equation in the compression force range of 0.1 to 0.2 N, for example.
E = (σ ₂ −σ ₁ ) / (ε ₂ −ε ₁ )
In the formula, σ ₁ indicates a compressive stress (MPa) measured at a compressive force of 0.1 N, σ ₂ indicates a compressive stress (MPa) measured at a compressive force of 0.2 N, and ε ₁ indicates a compressive stress. The compressive strain measured at σ ₁ is shown, and ε ₂ shows the compressive strain measured at the compressive stress σ ₂ .

On the other hand, the deformation recovery rate and the maximum compressive deformation rate are d1, the thickness of the measurement sample before applying the load, d2, the thickness of the measurement sample at the time when the maximum load of 500 N is applied, or the measurement sample is destroyed, and the load is removed. Then, the thickness of the measurement sample can be calculated according to the following formula, where d3 is the thickness.
Deformation recovery rate = (d3-d2) / (d1-d2) × 100
Maximum compression deformation rate = (d1−d2) / d1 × 100

In addition, these thermal conductivity, compression elastic modulus, deformation recovery rate, and maximum compression deformation rate can be appropriately adjusted by changing the production conditions, raw materials, etc. of the airgel composite described later.

[Density and porosity]
In the airgel composite of the present embodiment, 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 composite excellent in flexibility can be easily obtained, and when it is 1000 nm or less, an airgel composite excellent in heat insulation can be easily obtained.

In airgel composite of this embodiment, the density may be 0.05 ~ 0.25g / cm ³ at 25 ° C., or may be 0.1 ~ 0.2g / cm ^3. When the density is 0.05 g / cm ³ or more, more excellent strength and flexibility can be obtained, and when it is 0.25 g / cm ³ or less, more excellent heat insulation can be obtained. it can.

In the airgel composite of this embodiment, the porosity at 25 ° C. can be 85 to 95%, but it may be 87 to 93%. When the porosity is 85% or more, more excellent heat insulating properties can be obtained, and when it is 95% or less, more excellent strength and flexibility can be obtained.

Regarding the airgel composite, the average pore diameter, density and porosity of pores (through holes) continuous in a three-dimensional network can be measured by a mercury intrusion method according to DIN 66133. As a measuring device, for example, Autopore IV9520 (manufactured by Shimadzu Corporation, product name) can be used.

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

That is, the airgel composite of the present embodiment was obtained in the sol generation step, the wet gel generation step in which the sol obtained in the sol generation step was gelled and then aged to obtain a wet gel, and the wet gel generation step. The wet gel can be produced by a production method mainly comprising a step of washing and (if necessary) replacing the solvent with a solvent and a drying step of drying the wet gel after washing and solvent substitution. The “sol” is a state before the gelation reaction occurs, and in the present embodiment, the polysiloxane compound group, and optionally the silicon 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.

Hereafter, each process of the manufacturing method of the airgel composite of this embodiment is demonstrated.

(Sol generation process)
A sol production | generation process is a process which mixes the above-mentioned polysiloxane compound, the silicon compound depending on the case, and the silica particle and / or the solvent containing a silica particle, and hydrolyzes it, and produces | generates 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 suppressing heat radiation.

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, alcohols having a low surface tension and a low boiling point in terms of reducing the interfacial tension with the gel wall include methanol, ethanol, 2-propanol and the like. You may use these individually or in mixture of 2 or more types.

For example, when alcohols are used as the solvent, the amount of alcohols can be 4 to 8 mol with respect to 1 mol of the total amount of the polysiloxane compound group and the silicon compound group, but it can be 4 to 6.5. Or 4.5 to 6 moles. 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 polysiloxane compound and the silicon compound is promoted, and a sol can be obtained in a shorter time.

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

As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. 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 polysiloxane compound group and the silicon compound group. For example, the total amount of the polysiloxane compound group and the silicon compound group is 100 parts by mass. 1 to 100 parts by mass. The added amount may be 5 to 60 parts by mass.

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. Accordingly, the thermohydrolyzable compound is not particularly limited as long as it 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 addition amount of the thermohydrolyzable compound is not particularly limited as long as it 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 polysiloxane compound group and the silicon 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.

The hydrolysis in the sol production step depends on the types and amounts of the polysiloxane compound, silicon compound, silica particles, acid catalyst, surfactant, etc. in the mixed solution, but for example in a temperature environment of 20-60 ° C. The treatment may be performed for 10 minutes to 24 hours, or in a temperature environment of 50 to 60 ° C. for 5 minutes to 8 hours. Thereby, the hydrolyzable functional group in a polysiloxane compound and a silicon compound is fully hydrolyzed, and the hydrolysis product of a polysiloxane compound and the hydrolysis product of a silicon 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 thermally hydrolyzable compound, the temperature environment of the sol production 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; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; sodium metaphosphate Basic sodium phosphates such as sodium pyrophosphate and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3 -(Diethylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, t-butylamine, sec Aliphatic amines such as butylamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine; morpholine, N -Nitrogen-containing heterocyclic compounds such as methylmorpholine, 2-methylmorpholine, piperazine and derivatives thereof, piperidine and derivatives thereof, imidazole and derivatives thereof, and the like. Among these, ammonium hydroxide (ammonia water) is excellent in that it has high volatility and does not easily remain in the airgel composite after drying, so that it is difficult to impair the water resistance, and 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 and / or the dealcoholization condensation reaction of the polysiloxane compound group, the silicon compound group, and the silica particles in the sol can be promoted, and the gelation of the sol can be performed in a shorter time. It can be carried out. Thereby, a wet gel with higher strength (rigidity) can be obtained. In particular, ammonia has high volatility and hardly remains in the airgel composite. Therefore, by using ammonia as a base catalyst, an airgel composite having better water resistance can be obtained.

The addition amount of the base catalyst can be 0.5 to 5 parts by mass with respect to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group, but may be 1 to 4 parts by mass. 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 to 90 ° C., but it may be 40 to 80 ° C. By setting the gelation temperature to 30 ° C. or higher, gelation can be performed in a shorter time, and a wet gel with higher strength (rigidity) can be obtained. 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.

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

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 and / or reactive groups of the polysiloxane compound, silicon compound, etc. in the sol form hydrogen bonds and / 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. Note that the total time of the gelation time and the aging time in the entire gelation and aging process 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 decrease the density of the obtained airgel composite 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. May be. Further, in order to increase the density of the obtained airgel composite or to 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 can be shortened.

(Washing and solvent replacement process)
The washing and solvent replacement step is a step of washing the wet gel obtained by the wet gel generation step (washing step), and a step of replacing the washing liquid in the wet gel with a solvent suitable for the drying conditions (the drying step described later). It is a process which has (solvent substitution process). 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 From the viewpoint of enabling the production of a highly pure airgel composite, the wet gel may be washed. In the present embodiment, since the silica particles are contained in the gel, the solvent replacement step is not necessarily essential as described later.

In the washing step, the wet gel obtained in the wet gel production 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.

Organic solvents include 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 later, a low surface tension solvent can be used in order 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 hydrophilic organic solvents include methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone. 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 an amount that can be sufficiently washed by replacing the solvent in the wet gel. The amount can be 3 to 10 times the volume of the wet gel. 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 a temperature not higher than the boiling point of the solvent used for washing. For example, when methanol is used, the temperature can be raised 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 mixture of two or more thereof.

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); Aromatic hydrocarbons such as (28.9), toluene (28.5), m-xylene (28.7), p-xylene (28.3); 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, 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 volume of the wet gel.

The temperature environment in the solvent replacement step can be 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 increased to about 30 to 60 ° C.

In this 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 composite can be finally obtained. That is, an airgel composite formed 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 composite. 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 composite of the present embodiment 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 under 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 the fact that the temperature is 20 to 150 ° C. The drying temperature may be 60 to 120 ° C. The drying time varies depending on the wet gel volume and the drying temperature, but can be 4 to 120 hours. In the present embodiment, it is also included in the atmospheric pressure drying to accelerate the drying by applying a pressure less than the critical point within a range not inhibiting the productivity.

The airgel composite of the present embodiment can also be obtained by supercritical drying a wet gel that has been washed and (if necessary) solvent-substituted. 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 for 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, at 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 composite 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. Additional drying may be performed at 150 to 200 ° C. under normal pressure.

<Support member with airgel composite>
By forming the airgel composite of this embodiment on a predetermined support member, it can be used as a support member with an airgel composite. That is, the support member with an airgel composite includes the airgel composite described so far and the support member that supports the airgel composite. Such a support member with an airgel composite can exhibit high heat insulation and excellent flexibility.

Examples of the support member include a film-like support member, a sheet-like support member, a foil-like support member, and a porous support member.

The film-like support member is a member obtained by forming a polymer raw material into a thin film, and examples thereof include organic films such as PET and polyimide, glass films, and the like (including metal vapor deposited films).

The sheet-like support member is a member obtained by molding an organic, inorganic, and / or metal fiber raw material, and examples thereof include paper, nonwoven fabric (including glass mat), organic fiber cloth, and glass cloth.

The foil-like support member is a member obtained by forming a metal raw material into a thin film, and examples thereof include aluminum foil and copper foil.

The porous support member is a member having a porous structure made of organic, inorganic and / or metal as a raw material, and is made of a porous organic material (for example, polyurethane foam), a porous inorganic material (for example, zeolite sheet), or porous. Examples thereof include metal materials (for example, porous metal sheets and porous aluminum sheets).

The support member with the airgel composite can be produced, for example, as follows. First, a sol is prepared according to the sol generation process described above. After applying the sol onto the support member using a film applicator or the like, or impregnating the sol with the support member, a support member with a wet gel is obtained according to the above-described wet gel generating step. And the support member with an airgel composite is obtained by performing washing | cleaning and solvent substitution (if needed) according to the above-mentioned washing | cleaning and solvent substitution process, and also drying according to the above-mentioned drying process. be able to.

The thickness of the airgel composite formed on the film-like support member or the foil-like support member can be 1 to 200 μm, but may be 10 to 100 μm, or 30 to 80 μm. When the thickness is 1 μm or more, it is easy to obtain good heat insulating properties, and when it is 200 μm or less, flexibility is easily obtained.

The airgel composite of the present embodiment described as described above has excellent heat insulating properties and flexibility, which has been difficult to achieve with conventional airgel, by containing an airgel component and silica particles. The particularly excellent flexibility made it possible to form an airgel composite layer on a film-like support member and a foil-like support member, which had been difficult to achieve in the past. Therefore, the support member with an airgel composite of the present embodiment has high heat insulating properties and excellent flexibility. In addition, also in the aspect which impregnates a sheet-like support member and a porous support member with sol, it is possible to suppress the powder falling of an airgel composite at the time of handling after drying.

From such advantages, the airgel composite and the support member with the airgel composite of the present embodiment can be applied to a use as a heat insulating material in an architectural field, an automobile field, a home appliance, a semiconductor field, an industrial facility, and the like. Moreover, the airgel composite of this embodiment can be used as a coating additive, cosmetics, antiblocking agent, catalyst carrier, etc., in addition to its use as a heat insulating material.

<Insulation material>
The airgel composite of this embodiment can be used as a heat insulating material. Such a heat insulating material has high heat insulating properties and excellent flexibility. In addition, the airgel composite obtained by the manufacturing method of the said airgel composite can be made into a heat insulating material as it is (processed into a predetermined shape as needed).

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

(Example 1) [wet gel, airgel composite]
As a silica particle-containing raw material, PL-06L (details of PL-06L are described in Table 1. The same applies to the silica particle-containing raw material) 200.0 parts by mass, acetic acid as an acid catalyst 0.10 parts by mass, a cationic system 20.0 parts by mass of cetyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd .: hereinafter abbreviated as “CTAB”) as a surfactant and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed. 80.0 parts by mass of methyltrimethoxysilane LS-530 (manufactured by Shin-Etsu Chemical Co., Ltd., product name: hereinafter abbreviated as “MTMS”) as a silicon compound and a structure represented by the above general formula (B) as a polysiloxane compound 20.0 parts by mass of bifunctional alkoxy-modified polysiloxane compound having both ends (hereinafter referred to as “polysiloxane compound A”) Allowed to react for 2 hours to obtain a sol 1 ° C.. The obtained sol 1 was 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 was immersed in 2500.0 parts by mass of methanol and washed at 60 ° C. for 12 hours. This washing operation was performed 3 times while exchanging with fresh methanol. Next, the washed 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 60 ° C. for 12 hours. This solvent replacement operation was performed three times while exchanging with new heptane. The washed and solvent-substituted wet gel is dried under normal pressure at 40 ° C. for 96 hours, and then further dried at 150 ° C. for 2 hours, whereby the structures represented by the above general formulas (3) and (4) The airgel composite 1 which has this was obtained.

The “polysiloxane compound A” was synthesized as follows. First, 100.0 masses of dimethylpolysiloxane XC96-723 (product name, manufactured by Momentive) having silanol groups at both ends in a 1-liter three-necked flask equipped with a stirrer, a thermometer, and a Dimroth condenser. Parts, 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 2) [Wet gel, airgel composite]
100.0 parts by mass of PL-20 as a raw material containing silica particles, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and hot water addition 120.0 parts by mass of urea as a decomposable compound, 60.0 parts by mass of MTMS as a silicon compound, and trifunctional alkoxy modification at both ends having a structure represented by the above general formula (B) as a polysiloxane compound 40.0 parts by mass of a polysiloxane compound (hereinafter referred to as “polysiloxane compound B”) was added and reacted at 25 ° C. for 2 hours to obtain sol 2. The obtained sol 2 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 2. Then, the airgel composite 2 which has the structure represented by the said General formula (2) and (4) was obtained like Example 1 using the obtained wet gel 2. FIG.

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

(Example 3) [wet gel, airgel composite]
100.0 parts by mass of PL-2L as a raw material containing silica particles, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and hot water addition 120.0 parts by mass of urea was mixed as a decomposable compound, and 60.0 parts by mass of MTMS as a silicon compound and dimethyldimethoxysilane LS-520 (manufactured by Shin-Etsu Chemical Co., Ltd., product name: hereinafter abbreviated as “DMDMS”) ) And 20.0 parts by mass of polysiloxane compound A as a polysiloxane compound were added and reacted at 25 ° C. for 2 hours 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. Thereafter, an airgel composite 3 having a structure represented by the general formulas (3), (4) and (5) was obtained in the same manner as in Example 1 by using the obtained wet gel 3.

(Example 4) [wet gel, airgel composite]
143.0 parts by mass of ST-OZL-35 as a raw material containing silica particles, 57.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, 120.0 parts by mass of urea was mixed as a thermally hydrolyzable compound, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as silicon compounds, and 20.0 parts of polysiloxane compound B as a polysiloxane compound. Mass part was added and reacted at 25 ° C. for 2 hours to obtain sol 4. The obtained sol 4 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 4. Thereafter, an airgel composite 4 having a structure represented by the general formulas (2), (4) and (5) was obtained in the same manner as in Example 1 by using the obtained wet gel 4.

(Example 5)
100.0 parts by mass of PL-2L as a raw material containing silica particles, 50.0 parts by mass of ST-OZL-35, 50.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, cationic surface activity 20.0 parts by mass of CTAB as an agent, 120.0 parts by mass of urea as a thermally hydrolyzable compound, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as a silicon compound, and a polysiloxane compound As a result, 20.0 parts by mass of polysiloxane compound A was added and reacted at 25 ° C. for 2 hours to obtain sol 5. The obtained sol 5 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 5. Then, the airgel composite 5 which has the structure represented by the said General formula (3), (4) and (5) was obtained like Example 1 using the obtained wet gel 5. FIG.

(Example 6) [wet gel, airgel composite]
The wet gel 5 obtained above was immersed in 2500.0 parts by mass of methanol and washed at 60 ° C. for 12 hours. This washing operation was performed 3 times while exchanging with fresh methanol. Next, the washed wet gel was immersed in 2500.0 parts by mass of 2-propanol, and solvent substitution was performed at 60 ° C. for 12 hours. This solvent replacement operation was performed three times while exchanging with new 2-propanol.

Next, supercritical drying of the solvent-substituted wet gel was performed. The inside of the autoclave was filled with 2-propanol, and a wet gel substituted with solvent was placed. Then, liquefied carbon dioxide gas was sent into the autoclave, and the autoclave was filled with a mixture of 2-propanol and carbon dioxide as a dispersion medium. Thereafter, heating and pressurizing are performed so that the environment in the autoclave is 80 ° C. and 14 MPa, and carbon dioxide in a supercritical state is sufficiently circulated in the autoclave. Then, the pressure is reduced and 2-propanol and dioxide contained in the gel are added. Carbon was removed. In this manner, an airgel composite 6 having a structure represented by the general formulas (3), (4), and (5) was obtained.

(Example 7) [wet gel, airgel composite]
The wet gel 3 obtained above was immersed in 2500.0 parts by mass of methanol and washed at 60 ° C. for 12 hours. This washing operation was performed 3 times while exchanging with fresh methanol. Next, the washed wet gel is dried at 60 ° C. for 2 hours and at 100 ° C. for 3 hours under solvent pressure without solvent substitution, and then further dried at 150 ° C. for 2 hours. The airgel composite 7 having the structure represented by (3), (4) and (5) was obtained.

(Example 8) [wet gel, airgel composite]
Using the wet gel 4 obtained above, an airgel composite 8 having a structure represented by the general formulas (2), (4) and (5) was obtained in the same manner as in Example 7.

Comparative Example 1 [wet gel, aerogel]
200.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed. 100.0 parts by mass of MTMS as a silicon compound was added and reacted at 25 ° C. for 2 hours to obtain Sol 1C. The obtained sol 1C was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 1C. Thereafter, an airgel 1C was obtained in the same manner as in Example 1 by using the obtained wet gel 1C.

(Comparative Example 2) [wet gel, aerogel]
200.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed. As a silicon compound, 80.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS were added and reacted at 25 ° C. for 2 hours to obtain sol 2C. The obtained sol 2C was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 2C. Thereafter, an airgel 2C was obtained in the same manner as in Example 1 using the obtained wet gel 2C.

Comparative Example 3 [wet gel, aerogel]
200.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed. As a silicon compound, 70.0 parts by mass of MTMS and 30.0 parts by mass of DMDMS were added and reacted at 25 ° C. for 2 hours to obtain sol 3C. The obtained sol 3C was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 3C. Thereafter, an airgel 3C was obtained in the same manner as in Example 1 by using the obtained wet gel 3C.

(Comparative Example 4) [wet gel, aerogel]
200.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea as a thermohydrolyzable compound were mixed. As a silicon compound, 60.0 parts by mass of MTMS and 40.0 parts by mass of DMDMS were added and reacted at 25 ° C. for 2 hours to obtain sol 4C. The obtained sol 4C was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 4C. Thereafter, a comparative airgel 4C was obtained in the same manner as in Example 1 by using the obtained wet gel 4C.

Table 1 summarizes the modes of the silica particle-containing raw materials in each example. Table 2 summarizes the drying method, the types and addition amounts of Si raw materials (silicon compounds and polysiloxane compounds), and the addition amounts of silica particle-containing raw materials in each Example and Comparative Example.

[Various evaluations]
The wet gel and airgel composite obtained in each Example and Comparative Example were measured or evaluated according to the following conditions. Summary of gelation time in wet gel formation process, airgel composite and airgel state in atmospheric pressure drying of methanol-substituted gel, and evaluation results of thermal conductivity, compressive elastic modulus, density and porosity of airgel composite and airgel Table 3 shows.

(1) Measurement of gelation time 30 mL of the sol obtained in each Example and Comparative Example was transferred to a 100 mL PP sealed container to obtain a measurement sample. Next, using a constant temperature dryer “DVS402” (manufactured by Yamato Kagaku Co., Ltd., product name) set to 60 ° C., the time from when the measurement sample was introduced to gelation was measured.

(2) State of airgel complex and airgel in atmospheric pressure drying of methanol-substituted gel 30.0 parts by mass of wet gel obtained in each Example and Comparative Example was immersed in 150.0 parts by mass of methanol at 60 ° C. Washing was performed for 12 hours. This washing operation was performed 3 times while exchanging with fresh methanol. Next, the washed wet gel was processed into a size of 100 mm × 100 mm × 100 mm using a blade having a blade angle of about 20 to 25 degrees, and used as a sample before drying. The obtained pre-drying sample was dried at 60 ° C. for 2 hours and at 100 ° C. for 3 hours using a constant temperature chamber “SPH (H) -202” (product name, manufactured by ESPEC CORP.) With a safety door, and then further 150 ° C. And dried for 2 hours to obtain a sample after drying (especially the solvent evaporation rate is not controlled). Here, the volume shrinkage ratio SV before and after drying of the sample was obtained from the following equation. When the volume shrinkage ratio SV was 5% or less, it was evaluated as “no contraction”, and when it was 5% or more, it was evaluated as “shrinkage”.
SV = (V ₀ −V ₁ ) / V ₀ × 100
In the formula, V ₀ represents the volume of the sample before drying, and V ₁ represents the volume of the sample after drying.

(3) Measurement of thermal conductivity Using a blade having a blade angle of about 20 to 25 degrees, the airgel composite and the airgel were processed into a size of 150 mm × 150 mm × 100 mm to obtain a measurement sample. Next, in order to ensure parallelism of the surface, shaping was performed with sandpaper of # 1500 or more as necessary. The obtained measurement sample was dried at 100 ° C. for 30 minutes under atmospheric pressure using a constant temperature dryer “DVS402” (manufactured by Yamato Scientific Co., Ltd., product name) before measuring the thermal conductivity. The measurement sample was then transferred into a desiccator and cooled to 25 ° C. Thereby, the measurement sample for thermal conductivity measurement was obtained.

The thermal conductivity was measured using a steady-state thermal conductivity measuring device “HFM436 Lambda” (manufactured by NETZSCH, product name). The measurement conditions were an average temperature of 25 ° C. under atmospheric pressure. The measurement sample obtained as described above was sandwiched between the upper and lower heaters with a load of 0.3 MPa, the temperature difference ΔT was set to 20 ° C., and the guard sample was adjusted so as to obtain a one-dimensional heat flow. Upper surface temperature, lower surface temperature, etc. were measured. And thermal resistance _RS of the measurement sample was calculated | required from following Formula.
R _S = N ((T _U −T _L ) / Q) −R _O
Wherein, T _U represents a measurement sample top surface temperature, T _L represents the measurement sample lower surface temperature, R _O represents the thermal contact resistance of the upper and lower interfaces, Q is shows the heat flux meter output. Note that N is a proportionality coefficient, and is obtained in advance using a calibration sample.

From the obtained thermal resistance _RS , the thermal conductivity λ of the measurement sample was obtained from the following equation.
λ = d / R _S
In formula, d shows the thickness of a measurement sample.

(4) Measurement of compression elastic modulus Using a blade having a blade angle of about 20 to 25 degrees, the airgel composite and the airgel were processed into 7.0 mm square cubes (diced) to obtain measurement samples. Next, in order to ensure parallelism of the surfaces, the measurement sample was shaped with sandpaper of # 1500 or more as necessary. The obtained measurement sample was dried at 100 ° C. for 30 minutes under atmospheric pressure using a constant temperature dryer “DVS402” (manufactured by Yamato Scientific Co., Ltd., product name) before measurement. The measurement sample was then transferred into a desiccator and cooled to 25 ° C. Thereby, the measurement sample for compression elastic modulus measurement was obtained.

As a measuring apparatus, a small tabletop testing machine “EZTest” (manufactured by Shimadzu Corporation, product name) was used. In addition, 500N was used as a load cell. Further, an upper platen (φ20 mm) and a lower platen (φ118 mm) made of stainless steel were used as compression measurement jigs. A measurement sample was set between an upper platen and a lower platen arranged in parallel, and compression was performed at a speed of 1 mm / min. The measurement temperature was 25 ° C., and the measurement was terminated when a load exceeding 500 N was applied or when the measurement sample was destroyed. Here, the strain ε was obtained from the following equation.
ε = Δd / d1
In the formula, Δd represents the displacement (mm) of the thickness of the measurement sample due to the load, and d1 represents the thickness (mm) of the measurement sample before the load is applied.
The compressive stress σ (MPa) was obtained from the following equation.
σ = F / A
In the formula, F represents the compressive force (N), and A represents the cross-sectional area (mm ² ) of the measurement sample before applying a load.

The compressive elastic modulus E (MPa) was obtained from the following equation in the compression force range of 0.1 to 0.2N.
E = (σ ₂ −σ ₁ ) / (ε ₂ −ε ₁ )
In the formula, σ ₁ indicates a compressive stress (MPa) measured at a compressive force of 0.1 N, σ ₂ indicates a compressive stress (MPa) measured at a compressive force of 0.2 N, and ε ₁ indicates a compressive stress. The compressive strain measured at σ ₁ is shown, and ε ₂ shows the compressive strain measured at the compressive stress σ ₂ .

(5) Measurement of density and porosity The density and porosity of pores (through holes) continuous in a three-dimensional network for the airgel composite and the airgel were measured by a mercury intrusion method according to DIN 66133. The measurement temperature was room temperature (25 ° C.), and Autopore IV9520 (manufactured by Shimadzu Corporation, product name) was used as the measurement apparatus.

From Table 3, the airgel composites of the examples had a short gelation time in the wet gel production process and excellent reactivity, and had good shrinkage resistance in atmospheric drying using a methanol-substituted gel. In addition, in this evaluation, it was shown that good shrinkage resistance was shown in any of the examples, that is, a good-quality airgel composite could be obtained without performing the solvent replacement step. .

Also, it can be read that the airgel composites of the examples have small thermal conductivity and compression modulus, and are excellent in both high heat insulation and high flexibility.

On the other hand, in Comparative Examples 1 to 3, the gelation time in the wet gel production process was long, and in normal pressure drying using a methanol-substituted gel, the gel contracted and cracks occurred on the surface. Moreover, either thermal conductivity or flexibility was inferior. In Comparative Example 4, the shrinkage resistance, flexibility and bending resistance were sufficient, but the gelation time was long and the thermal conductivity was large.

(6) SEM observation The surface of the airgel composite obtained in Example 3 and Example 4 was observed by SEM. FIG. 3 shows SEMs in which the surface of the airgel composite obtained in Example 3 was observed at (a) 10,000 times, (b) 50,000 times, (c) 200,000 times, and (d) 350,000 times, respectively. It is an image. FIG. 4 is SEM images obtained by observing the surface of the airgel composite obtained in Example 4 at (a) 10,000 times, (b) 50,000 times, and (c) 200,000 times, respectively.

As shown in FIG. 3, it was observed that the airgel composite obtained in Example 3 had a three-dimensional network skeleton (three-dimensionally fine porous structure). The observed particle size was mainly about 20 nm derived from silica particles. Spherical airgel components (aerogel particles) with a particle diameter smaller than that of the silica particles can also be confirmed, but mainly the airgel components do not take a spherical form and cover the silica particles or function as a binder between the silica particles. Observed to be. Thus, since a part of airgel component functions as a binder between silica particles, it is guessed that the intensity | strength of an airgel composite can be improved.

As shown in FIG. 4, it was observed that the airgel composite obtained in Example 4 also has a three-dimensional network skeleton. However, the cluster structure is unique. In the present embodiment, the structure is such that particles and particles are connected in a bead shape unlike ordinary airgel, and the connection part of particles and particles seems to be packed densely with an airgel component (silicone component). It is observed that there is. Moreover, since the particle diameter of the particle | grains derived from a silica particle is significantly larger than the particle diameter of the silica particle itself, it is guessed that the silica particle is coat | covered thickly with the airgel component. Thus, in this example, the airgel component not only functions as a binder between particles, but also covers the entire cluster structure, so it is assumed that the strength of the airgel composite can be further improved. Is done. In Example 4, since ST-OZL-35 used was an acidic sol, an airgel composite was produced with a low pH in the system. Therefore, it is guessed that the production | generation speed | rate of the airgel component became slow and the airgel component in the obtained airgel composite was hard to become a particulate form.

1 ... airgel particles, 2 ... silica particles, 3 ... pores, 10 ... airgel composite, L ... circumscribed rectangle.

Claims (8)

1. Wet which is a condensate of sol containing silica particles and at least one selected from the group consisting of a polysiloxane compound represented by the following general formula (B) and a hydrolysis product of the polysiloxane compound An airgel composite that is a dried product of a gel.
   

   

   [In the formula (B), R ^1b represents an alkyl group, an alkoxy group or an aryl group, R ^2b and R ^3b each independently represents an alkoxy group, and R ^4b and R ^5b each independently represents an alkyl group or an aryl group. M represents an integer of 1 to 50. ]
2. The airgel composite of Claim 1 which has a ladder type structure provided with a support | pillar part and a bridge | bridging part, and the said bridge | bridging part has a structure represented by following General formula (2).
   

   

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

   

   [In Formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group or an aryl group, a and c each independently represent an integer of 1 to 3000, and b represents 1 to 50 Indicates an integer. ]
4. The airgel composite according to any one of claims 1 to 3, wherein the silica particles have an average primary particle diameter of 1 to 200 nm.
5. The airgel composite according to any one of claims 1 to 4, wherein the silica particles have a spherical shape.
6. The airgel composite according to any one of claims 1 to 5, wherein the silica particles are colloidal silica particles.
7. The sol further includes at least one selected from the group consisting of a hydrolyzable functional group or a silicon compound having a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. The airgel composite according to any one of claims 1 to 6, which is contained.
8. The airgel composite according to any one of claims 1 to 7, wherein the dried product is obtained by drying performed at a temperature below the critical point of a solvent used for drying the wet gel and under atmospheric pressure.
   

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