WO2017038646A1

WO2017038646A1 - Aerogel composite, and heat-insulating material

Info

Publication number: WO2017038646A1
Application number: PCT/JP2016/074868
Authority: WO
Inventors: 知里吉川; 寛之泉; 智彦小竹; 正人宮武
Original assignee: 日立化成株式会社
Priority date: 2015-08-28
Filing date: 2016-08-25
Publication date: 2017-03-09
Also published as: JP6288382B2; TW201711962A; JP2018087136A; JPWO2017038646A1

Abstract

The present disclosure pertains to: an aerogel composite containing an aerogel component and hollow silica particles; an aerogel composite containing hollow silica particles as a component constituting a three-dimensional mesh skeleton; or an aerogel composite that is the dried product of a wet gel that is the product of a sol containing hollow silica particles and at least one substance selected from the group consisting of: silicon compounds having a hydrolysable functional group or a condensable functional group; and hydrolysates of silicon compounds having said hydrolysable functional group.

Description

Airgel composite and heat insulating material

The present disclosure relates to an airgel composite and a heat insulating material.

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 (such as heat insulation), unique optical characteristics, and unique electrical characteristics. Silica airgel is used, for example, as an electronic substrate material that utilizes the ultra-low dielectric constant characteristics of silica airgel, a heat-insulating material that utilizes the high thermal insulation property of silica airgel, and a light-reflecting material that utilizes the ultra-low refractive index of silica airgel. ing.

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. (For example, refer to 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. The present disclosure also provides a thermal insulation comprising such an airgel composite.

As a result of intensive studies to achieve the above object, the present inventor has demonstrated that excellent heat insulation and flexibility can be expressed if an airgel composite in which hollow silica particles are combined in an airgel. I found it.

The present disclosure provides an airgel composite containing an airgel component and hollow silica particles. The airgel composite of the present disclosure is excellent in heat insulation and flexibility, unlike the airgel obtained by the prior art.

The airgel composite can have a three-dimensional network skeleton formed by an airgel component and hollow silica particles, and pores. Thereby, it becomes easy to improve heat insulation and a softness | flexibility further.

The present disclosure also provides an airgel composite containing hollow silica particles as a component constituting a three-dimensional network skeleton. Such an airgel composite is excellent in heat insulation and flexibility.

The present disclosure is also selected from the group consisting of hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. The airgel composite is a dried product of a wet gel that is a condensate of a sol containing at least one of the above. The airgel composite thus obtained is excellent in heat insulation and flexibility.

The above-described airgel composite also includes hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. It may be a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group consisting of:

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

The average primary particle diameter of the hollow silica particles can be 1 nm to 100 μm. Thereby, it becomes easy to improve heat insulation and a softness | flexibility further.

The hollow silica particles can have a spherical shape. Thereby, aggregation in a sol is easy to be suppressed, and further excellent heat insulation and flexibility can be achieved.

The hollow silica particles may be at least one selected from the group consisting of fused silica particles, fumed silica particles, and colloidal silica particles. Thereby, the further outstanding heat insulation and softness | flexibility can be achieved.

From the viewpoint of further superior heat insulation and flexibility, the compression elastic modulus at 25 ° C. of the airgel composite according to the present disclosure can be 3 MPa or less.

The present disclosure further provides a heat insulating material including the airgel composite. The heat insulating material according to the present disclosure exhibits excellent heat insulating properties and excellent flexibility that is difficult to achieve with conventional heat insulating materials because the airgel composite has excellent heat insulating properties and flexibility. Can do.

According to the present disclosure, an airgel composite excellent in heat insulation and flexibility can be provided. That is, while exhibiting excellent heat insulation properties and excellent flexibility, it is possible to provide an airgel composite that can be handled and improved in size and can be increased in productivity. . Thus, the airgel composite which is excellent in heat insulation and a softness | flexibility has the possibility of being utilized for various uses. The present disclosure can also provide a heat insulating material including the above-described airgel composite and having excellent heat insulating properties and flexibility. Here, an important point according to the present disclosure is that it becomes easier to control heat insulation and flexibility than conventional aerogels. This was not possible with conventional aerogels that required 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.

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 an 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. Between the skeletons formed by the clusters, there are fine pores less than 200 nm, and a three-dimensionally fine porous structure is formed. In addition, the airgel in this embodiment is a silica airgel which has a silica as a main component. Examples of the silica airgel include so-called organic-inorganic hybrid silica airgel into which an organic group (such as a methyl group) or an organic chain is introduced. The airgel composite of the present embodiment has a cluster structure that is a feature of the above-mentioned airgel, even though hollow silica particles are complexed in the airgel, and has a three-dimensionally fine porous structure. is doing.

The airgel composite of this embodiment contains an airgel component and hollow silica particles. In the present embodiment, the same concept is not necessarily meant, but the airgel composite of the present embodiment is expressed as containing hollow silica particles as a component constituting the three-dimensional network skeleton. It is also possible to do. 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 hollow silica particles exist in the airgel production environment. And the merit by making hollow silica particles exist is not only that the heat insulation property and flexibility of the composite itself can be improved, but also shortening the time of the wet gel generation step described later, or from the washing and solvent replacement step to the drying step. In some cases, simplification is 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 the present disclosure, the airgel component means a silicone component constituting the airgel composite, and the hollow silica particle means a silica particle having a hollow structure. Here, the silica particle having a hollow structure is a particle in which the outer shell of the particle has a pore structure containing silica, and the inside (inner side than the outer shell) is hollow. Further, since the hollow structure is sometimes called a balloon structure, the particles are also called balloon silica.

In the present embodiment, there are various composite modes of the airgel component and the hollow silica particles. 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 hollow silica particles, it is presumed that flexibility is imparted to the skeleton of the composite.

First, examples of the composite form of the airgel component and the hollow silica particles include an aspect in which an amorphous airgel component is interposed between the hollow silica particles. As such an embodiment, specifically, for example, an embodiment in which the hollow silica particles are coated with a film-like airgel component (silicone component) (an embodiment in which the airgel component encloses the hollow silica particles), the airgel component serves as a binder. A mode in which hollow silica particles are connected to each other, a mode in which an airgel component fills a gap between a plurality of hollow silica particles, a mode of a combination of these modes (clustered hollow silica particles are covered with an airgel component) Various aspects) and the like. Thus, in this embodiment, the airgel composite can have a three-dimensional network skeleton composed of hollow silica particles and an airgel component (silicone component), and the specific mode (form) is not particularly limited.

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 rate of the airgel component tends to vary by varying the number of silanol groups in the hollow 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, pH of the system, etc. of the hollow 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 the hollow silica particles), the following description 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 three-dimensionally randomly connecting airgel particles 1 constituting an airgel component partially through hollow silica particles 2. And pores 3 surrounded by the skeleton. At this time, it is presumed that the hollow 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. In the present embodiment, the airgel composite may have a three-dimensional network skeleton formed by three-dimensionally connecting hollow silica particles via the airgel particles. The hollow 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 hollow silica particle is high. Therefore, in this embodiment, it is considered that the hollow 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 hollow 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. The average particle diameter may be 50 μm or less, may be 2 μm or less, and may be 200 nm or less. That is, the average particle diameter can be 2 nm to 50 μm, and can 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 and 0.5 nm to 200 nm from the viewpoint of easy formation of secondary particles having a low density porous structure. It may be 1 nm to 20 nm.

The form of the hollow silica particles used for producing the airgel composite is not particularly limited, and examples thereof include at least one selected from the group consisting of fused silica particles, fumed silica particles, and colloidal silica particles. As the hollow silica particles, for example, the product name “Thruria” of JGC Catalysts & Chemicals Co., Ltd., the product name “Sirinax” of Nittetsu Mining Co., Ltd. and the like can be obtained commercially. Also, shirasu balloon made from shirasu (for example, “Winlite”, product name of Axes Chemical Co., Ltd., SiO ₂ content 75 to 77 mass%) can be used as the hollow silica particles.

When the hollow silica particles are colloidal silica particles, the pH of the slurry in which the colloidal silica particles are dispersed in a solvent is preferably 8.0 or less. This facilitates control of the gelation reaction when producing the airgel composite.

The solvent in which colloidal silica particles are dispersed can be used without any particular limitation. Examples of the solvent include water, alcohol, hexane, benzene, and toluene.

The lower limit of the refractive index of the hollow silica particles, which is an index of the flexibility, that is, the ratio of the shell in the hollow silica particles, can be 1.20 or more from the viewpoint of toughness, and is 1.25 or more. It may be 1.30 or more. From the viewpoint of flexibility, the upper limit of the refractive index of the hollow silica particles can be 1.50 or less, may be 1.45 or less, and may be 1.40 or less. That is, the refractive index of the hollow silica particles can be 1.20 to 1.50, may be 1.25 to 1.45, and may be 1.30 to 1.40.

The shape of the hollow silica particles 2 is not particularly limited, and examples thereof include a spherical shape, an eyebrows type, and an association type. Among these, the use of spherical particles as the hollow silica particles 2 makes it easy to suppress aggregation in the sol. Since it becomes easy to impart an appropriate strength to the airgel composite and it becomes easy to obtain an airgel composite having excellent shrinkage resistance during drying, the average primary particle diameter of the hollow silica particles can be 1 nm or more, and 5 nm. The above may be sufficient and 10 nm or more may be sufficient. Since it becomes easy to suppress the solid heat conduction of the hollow silica particles and it becomes easy to obtain an airgel composite excellent in heat insulation, the average primary particle diameter of the hollow silica particles can be 100 μm or less, and is 70 μm or less. Or 50 μm or less. That is, the average primary particle diameter of the hollow silica particles 2 can be 1 nm to 100 μm, 5 nm to 70 μm, or 10 nm to 50 μm.

The surface structure of the hollow silica particles is not particularly limited, and hollow silica particles in which silanol groups present on the surface are not modified, or hollow silica particles in which some or all of the silanol groups are modified with a cation group, an anion group, a nonion group, or the like. Alternatively, hollow silica particles in which some or all of the silanol groups are substituted with alkoxy groups, hydroxyalkyl groups, or the like can also be used.

It is presumed that the airgel particle 1 (aerogel component) and the hollow 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 other than the silanol groups of the airgel particles 1 (aerogel component) and the silanol groups of the hollow 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 hollow 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 the hollow silica particles 2 can be 10 × 10 ¹⁸ pieces / g or more, may be 50 × 10 ¹⁸ pieces / g or more, and is 100 × 10 ¹⁸ pieces / g or more. May be. The number of silanol groups can be 10000 × 10 ¹⁸ pieces / g or less, 8000 × 10 ¹⁸ pieces / g or less, or 7000 × 10 ¹⁸ pieces / g or less. That is, the number of silanol groups can be 10 × 10 ¹⁸ to 10000 × 10 ¹⁸ pcs / g, 50 × 10 ¹⁸ to 8000 × 10 ¹⁸ pcs / g, or 100 × 10 ¹⁸ to 7000. X10 ¹⁸ pieces / g may be sufficient. When the number of silanol groups per gram of the hollow silica particles 2 is 10 × 10 ¹⁸ pieces / g or more, the hollow silica particles 2 can have better reactivity with the airgel particles 1 (aerogel component), and have a more appropriate strength. Since it is easy to give to a composite, it becomes easy to obtain the airgel composite which is excellent in shrink resistance. On the other hand, when the number of silanol groups is 10000 × 10 ¹⁸ / g or less, it is easy to suppress abrupt gelation at the time of sol preparation, and a homogeneous airgel composite is easily obtained.

In the present embodiment, the average particle size of the particles (the average secondary particle size of the airgel particles and the average primary particle size of the hollow silica particles) 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, from the three-dimensional network skeleton, the particle diameter of each airgel particle or hollow silica particle can be obtained 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.

For hollow silica particles, the average particle diameter can be measured from the 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 dried by nitrogen blowing. Thereafter, the chip is placed on a sample stage for SEM observation, an acceleration voltage of 10 kV is applied, the hollow silica particles are observed at a magnification of 100,000, and an image is taken. 20 hollow silica particles are arbitrarily selected from the obtained image, and the average of the particle diameters of these particles is defined as the average particle diameter. At this time, when the selected silica particles have a shape as shown in FIG. 2, a rectangle (circumscribed rectangle L) that circumscribes the hollow silica particles 2 and has the longest side is guided. 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.

Since the content of the airgel component contained in the airgel composite can be easily imparted with an appropriate strength to the airgel composite, it can be 4 parts by mass or more with respect to 100 parts by mass of the total amount of the airgel composite. It may be greater than or equal to parts by mass. Since the said content becomes easy to acquire better heat insulation, it can be 25 mass parts or less with respect to 100 mass parts of total amounts of an airgel composite, and may be 20 mass parts or less. That is, the content of the airgel component contained in the airgel composite can be 4 to 25 parts by mass with respect to 100 parts by mass of the total amount of the airgel composite, but may be 10 to 20 parts by mass.

The content of the hollow silica particles contained in the airgel composite can easily be imparted with a more appropriate strength to the airgel composite, and therefore can be 1 part by mass or more with respect to 100 parts by mass of the total amount of the airgel composite. It may be 3 parts by mass or more. The content can be 25 parts by mass or less, or 15 parts by mass or less, because it is easy to suppress the solid heat conduction of the hollow silica particles. That is, the content of the hollow silica particles contained in the airgel composite can be 1 to 25 parts by mass with respect to 100 parts by mass of the total amount of the airgel composite, but may be 3 to 15 parts by mass.

In addition to these airgel components and hollow silica particles, the airgel composite may further contain other components such as carbon graphite, an aluminum compound, a magnesium compound, a silver compound, and a 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.

<Specific embodiment of airgel composite>
The airgel composite of the present embodiment includes hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group (in the molecule), and a silicon compound having the hydrolyzable functional group. It may be a dried product of a wet gel that is a condensate of a sol containing at least one selected from the group consisting of hydrolysis products. That is, the airgel composite of this embodiment includes hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group (in the molecule), and silicon having the hydrolyzable functional group. The wet gel produced | generated from the sol containing at least 1 type selected from the group which consists of a hydrolysis product of a compound can be obtained by drying. By adopting these aspects, the heat insulating property and flexibility of the airgel composite are further improved. The condensate may be obtained by a condensation reaction of a hydrolysis product obtained by hydrolysis of a silicon compound having a hydrolyzable functional group, and is not a functional group obtained by hydrolysis. It may be obtained by a condensation reaction of a silicon compound having a group. The silicon compound may have at least one of a hydrolyzable functional group and a condensable functional group, and may have both a hydrolyzable functional group and a condensable functional group. In addition, each airgel composite described later includes hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a silicon compound having the hydrolyzable functional group. A wet gel dried product (obtained by drying a wet gel generated from the sol), which is a condensate of a sol containing at least one selected from the group consisting of hydrolysis products, Also good.

The airgel composite of the present embodiment can contain 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.

Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group (excluding the functional group corresponding to the hydrolyzable functional group) include a hydroxyl group, a silanol group, a carboxyl group, and a phenolic hydroxyl group. The hydroxyl group may be contained in a hydroxyl group-containing group such as a hydroxyalkyl group. Each of the hydrolyzable functional group and the condensable functional group may be used alone or in admixture of two or more.

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

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

As the silicon compound having a hydrolyzable functional group or a condensable functional group, a silicon compound (silicon compound) other than the polysiloxane compound described later can be used. That is, the airgel composite of this embodiment includes hollow silica particles, a silicon compound (excluding a polysiloxane compound) having a hydrolyzable functional group or a condensable functional group (inside the molecule), and the hydrolysis Wet gel dried product which is a condensate of sol containing at least one compound selected from the group consisting of hydrolysis products of silicon compounds having functional functional groups (hereinafter sometimes referred to as “silicon compound group”) It may be. 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. In the alkyl silicon alkoxide, from the viewpoint of improving water resistance, the number of hydrolyzable functional groups may be 3 or less, or 2 to 3. Examples of the alkyl silicon alkoxide include monoalkyltrialkoxysilane, monoalkyldialkoxysilane, dialkyldialkoxysilane, monoalkylmonoalkoxysilane, dialkylmonoalkoxysilane and trialkylmonoalkoxysilane. Examples of the alkyl silicon alkoxide include methyltrimethoxysilane, methyldimethoxysilane, dimethyldimethoxysilane, and ethyltrimethoxysilane.

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

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

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

As a silicon compound having a condensable functional group and having the above-mentioned 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.

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

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

In preparing the airgel composite of the present embodiment, the silicon compound can include a polysiloxane compound having a hydrolyzable functional group or a condensable functional group. That is, the sol containing the silicon compound can further contain at least one selected from the group consisting of a polysiloxane compound having a reactive group in the molecule and a hydrolysis product of the polysiloxane compound.

The airgel composite of the present embodiment includes hollow silica particles, a polysiloxane compound having a hydrolyzable functional group or a condensable functional group (in the molecule), and the polysiloxane having the hydrolyzable functional group. A sol containing at least one compound selected from the group consisting of a hydrolysis product of a compound (polysiloxane compound in which the hydrolyzable functional group is hydrolyzed) (hereinafter sometimes referred to as “polysiloxane compound group”). It may be a dried product of a wet gel which is a condensate. That is, the airgel composite of this embodiment has hollow silica particles, a polysiloxane compound having a hydrolyzable functional group or a condensable functional group (in the molecule), and the hydrolyzable functional group. It may be obtained by drying a wet gel produced from a sol containing at least one selected from the group consisting of hydrolysis products of polysiloxane compounds.

The functional group in the polysiloxane compound group is not particularly limited, but may be a group that reacts with the same functional group or reacts with another functional group. Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group include a hydroxyl group, a silanol group, a carboxyl group, and a phenolic hydroxyl group. The hydroxyl group may be contained in a hydroxyl group-containing group such as a hydroxyalkyl group. The polysiloxane compound having a hydrolyzable functional group or a condensable functional group is different from the above-mentioned reactive group (hydrolyzable functional group and condensable functional group). You may further have a functional group which does not correspond to a functional group. These polysiloxane compounds having a functional group and a reactive group may be used alone or in combination of two or more. Among these functional groups and reactive groups, examples of the group that improves the flexibility of the airgel composite include an alkoxy group, a silanol group, and a hydroxyalkyl group. Among these, an alkoxy group and a hydroxyalkyl group Can further improve the compatibility of the sol. Further, from the viewpoint of improving the reactivity of the polysiloxane compound 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 compounds having a structure represented by the following general formula (A).

In formula (A), R ^1a represents a hydroxyalkyl group, R ^2a represents an alkylene group, R ^3a and R ^4a each independently represents an alkyl group or an aryl group, and n represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In formula (A), two R ^{1a s} may be the same or different, and similarly, two R ^{2a s} may be the same or different. In formula (A), two or more R ^{3a s} may be the same or different, and similarly, two or more R ^{4a s} may be the same or different.

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

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

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

In formula (B), R ^1b represents an alkyl group, an alkoxy group or an aryl group, R ^2b and R ^3b each independently represent an alkoxy group, and R ^4b and R ^5b each independently represent an alkyl group or an aryl group. , M represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In the formula (B), two R ^{1b s} may be the same or different, and two R ^{2b s} may be the same or different. Similarly, R ^3b may be the same or different. In the formula (B), when m is an integer of 2 or more, two or more R ^4b may be the same or different, and similarly, two or more R ^5b may be the same. May be different.

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

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

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

These polysiloxane compound groups may be used alone or in combination of two or more.

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

When the sol contains a polysiloxane compound group, it becomes easier to obtain good reactivity. Therefore, the content of the polysiloxane compound group contained in the sol (hydrolyzable functional group or condensable functional group) The total content of the polysiloxane compound and the total hydrolysis product content of the polysiloxane compound having a hydrolyzable functional group is 1 part by mass or more with respect to 100 parts by mass of the total amount of the sol. 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more. Since it becomes easier to obtain good compatibility, the content of the polysiloxane compound group can be 50 parts by mass or less with respect to 100 parts by mass of the total amount of the sol, and may be 30 parts by mass or less. 15 parts by mass or less. That is, the content of the polysiloxane compound group can be 1 to 50 parts by weight, or 3 to 50 parts by weight, or 5 to 50 parts by weight with respect to 100 parts by weight of the total sol. It may be 7 to 30 parts by mass, 10 to 30 parts by mass, or 10 to 15 parts by mass.

The total of the content of the silicon compound group and the content of the polysiloxane compound group can further easily obtain good reactivity, and therefore can be 5 parts by mass or more with respect to 100 parts by mass of the sol. It may be greater than or equal to 15 parts by weight. Since it becomes easier to obtain good compatibility, the sum of the contents can be 50 parts by mass or less, or 30 parts by mass or less, and 25 parts by mass with respect to 100 parts by mass of the sol. Or less. That is, the total content can be 5 to 50 parts by mass with respect to 100 parts by mass of the sol, 10 to 30 parts by mass, or 15 to 25 parts by mass. .

The ratio of the content of the silicon compound group to the content of the polysiloxane compound group (silicon compound group: polysiloxane compound group) may be 0.5: 1 to 4: 1. It may be ˜2: 1, may be 2: 1 to 4: 1, and may be 3: 1 to 4: 1. By setting the ratio of the content of these compounds to 0.5: 1 or more, it becomes easier to obtain good compatibility. By making the content ratio 4: 1 or less, it becomes easier to further suppress the shrinkage of the gel.

The content of the hollow silica particles contained in the sol makes it easy to impart an appropriate strength to the airgel composite and makes it easy to obtain an airgel composite having excellent shrinkage resistance during drying. Therefore, the total amount of sol is 100 parts by mass. On the other hand, it can be 1 part by mass or more, may be 4 parts by mass or more, and may be 6 parts by mass or more. Since it becomes easy to suppress the solid heat conduction of the hollow silica particles and it becomes easy to obtain an airgel composite having excellent heat insulation, the content of the hollow silica particles can be 20 parts by mass or less, and 15 parts by mass or less. It may be 10 parts by mass or less. That is, the content of the hollow silica particles contained in the sol can be 1 to 20 parts by mass with respect to 100 parts by mass of the sol, but may be 4 to 15 parts by mass, A mass part may be sufficient.

Examples of the airgel component in the airgel composite of the present embodiment include the following modes. By adopting these aspects, it becomes easy to control the heat insulating property and flexibility of the airgel composite to a desired level. By employ | adopting each aspect, the airgel composite which has the heat conductivity and compression elastic modulus according to each aspect can be obtained. Therefore, the airgel composite which has the heat insulation according to a use and a softness | flexibility can be provided.

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

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, it becomes a flexible airgel composite with low thermal conductivity. From the same viewpoint, the following features may be satisfied. In formula (1) and formula (1a), R ¹ and R ² may each independently be an alkyl group having 1 to 6 carbon atoms or a phenyl group. Examples of the alkyl group include a methyl group. In formula (1) and formula (1a), R ³ and R ⁴ may each independently be an alkylene group having 1 to 6 carbon atoms. Examples of the alkylene group include an ethylene group and a propylene group. In the formula (1a), p can be 2 to 30, and can be 5 to 20.

The airgel composite of the present embodiment is an airgel composite having a ladder structure including a support portion and a bridge portion, and the airgel composite having a structure in which the bridge portion is represented by the following general formula (2). It may be. 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 including a bridge portion having the structure represented by the general formula (2) is introduced into the skeleton of the airgel. be able to. In 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. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In formula (2), when b is an integer of 2 or more, two or more R ^{5 s} may be the same or different, and similarly, two or more R ^{6 s} are the same. Or different.

By introducing the above structure 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 the above T unit as a structural unit, and has a composition formula: (RSiO _1.5 ) _n . Silsesquioxane can have various skeletal structures such as a cage type, a ladder type, and a random type. As shown by the following general formula (X), in the airgel having a structure derived from a conventional ladder-type silsesquioxane, the structure of the bridge portion is —O—, but in the airgel composite of this embodiment, The structure of the bridge portion is a structure (polysiloxane structure) represented by the general formula (2). The airgel composite of this embodiment may further have a structure derived from silsesquioxane in addition to the structures represented by the general formulas (1) to (3).

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. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In Formula (3), when b is an integer of 2 or more, two or more R ^{5 s} may be the same or different, and similarly, two or more R ^{6 s} may be the same. May be different. In formula (3), when a is an integer of 2 or more, two or more R ^{7 s} may be the same or different. Similarly, when c is an integer of 2 or more, 2 or more R ⁸ may be the same or different from each other.

From the viewpoint of obtaining better flexibility, in formula (2) and formula (3), R ⁵ , R ⁶ , R ⁷ and R ⁸ (however, R ⁷ and R ⁸ are only in formula (3)) are: Each may be independently an alkyl group having 1 to 6 carbon atoms or a phenyl group. Examples of the alkyl group include a methyl group. In the formula (3), a and c can be independently 6 to 2000, and may be 10 to 1000. In the formulas (2) and (3), b 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). The airgel composite of the present embodiment contains silica particles and can have a structure represented by the following general formula (4).

In formula (4), R ⁹ represents an alkyl group. Examples of the alkyl group include alkyl groups having 1 to 6 carbon atoms, and specific examples include a methyl group.

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

In formula (5), R ¹⁰ and R ¹¹ each independently represent an alkyl group. Examples of the alkyl group include alkyl groups having 1 to 6 carbon atoms, and specific examples include a methyl group.

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

In the formula (6), R ¹² represents an alkylene group. Examples of the alkylene group include an alkylene group having 1 to 10 carbon atoms, and specific examples 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, or 0.025 W / m · K or less. It may be 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. The thermal conductivity 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 measurement method of the thermal conductivity using the steady method thermal conductivity measuring device 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 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. 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 this embodiment, the compression elastic modulus at 25 ° C. can be 3 MPa or less, 2 MPa or less, 1 MPa or less, or 0.5 MPa or less. . When the compression elastic modulus is 3 MPa or less, it becomes easy to obtain an airgel composite having excellent handleability. In addition, the lower limit value of the compression elastic modulus is not particularly limited, but may be 0.05 MPa, for example.

Compressive modulus can be measured using a small desktop testing machine “EZTest” (manufactured by Shimadzu Corporation, product name). The outline of the measurement method such as compression modulus using a small tabletop 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 modulus 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 .

In addition, these heat conductivity and compression elastic modulus can be suitably adjusted by changing the manufacturing conditions, raw materials, etc. of an airgel composite.

<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 silicon compound (silicon compound group and / or polysiloxane compound group) and the hollow silica particles are in a solvent. Means dissolved or dispersed. 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 of mixing the above-mentioned silicon compound and the solvent containing a hollow silica particle and / or a hollow silica particle, and making it hydrolyze and producing | generating a sol. In this step, an acid catalyst may be further added to the solvent in order to promote the hydrolysis reaction. Further, as disclosed in Japanese Patent No. 5250900, a surfactant, a thermohydrolyzable compound, or the like can be added to the solvent. Furthermore, components such as carbon graphite, an aluminum compound, a magnesium compound, a silver compound, and a titanium compound may be added to the solvent for the purpose of 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 silicon compounds (silicon compound group and polysiloxane compound group), but 4 to 6.5. It may be a mole or 4.5 to 6 mole. By making the amount of alcohols 4 mol or more, it becomes easier to obtain good compatibility, and by making the amount 8 mol or less, it becomes easier to suppress gel shrinkage.

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

By using an acid catalyst, the hydrolysis reaction of the silicon compound 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 silicon compound.

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, or a compound containing a hydrophilic part such as polyoxypropylene 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.

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

These surfactants have the effect of reducing the difference in chemical affinity between the solvent in the reaction system and the growing siloxane polymer and suppressing phase separation in the wet gel formation process described later. It is considered to be.

The amount of surfactant added depends on the type of surfactant or the type and amount of silicon compound (silicon compound group and polysiloxane compound group). For example, the total amount of silicon compound is 100 parts by mass. The amount may be 1 to 100 parts by mass, and 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; and cyclic nitrogen compounds such as hexamethylenetetramine. 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 of the total amount of the silicon compound. 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. By making the addition amount 200 parts by mass or less, it becomes easier to suppress the precipitation of crystals and the decrease in gel density.

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

When adding a thermohydrolyzable compound in 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 water resistance, and further, it is economical. You may use said base catalyst individually or in mixture of 2 or more types.

By using a base catalyst, the dehydration condensation reaction and / or dealcoholization condensation reaction of the silicon compound (polysiloxane compound group and silicon compound group) and hollow silica particles in the sol can be promoted, and the sol can be further gelled. It can be done in a short time. Thereby, a wet gel with higher strength (rigidity) can be obtained. In particular, since aqueous ammonia has high volatility and hardly remains in the airgel composite, by using ammonia water as a base catalyst, an airgel composite with 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 silicon compounds (polysiloxane compound group and silicon compound group), and may be 1 to 4 parts by mass. . By making the addition amount of the base catalyst 0.5 parts by mass or more, gelation can be performed in a shorter time. The fall of water resistance can be suppressed more by making the addition amount of a base catalyst into 5 mass parts 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, and 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, for example, 30 to 90 ° C., and 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 this embodiment, since the sol contains hollow silica particles, the gelation is particularly performed as compared with the conventional airgel manufacturing method. Time can be shortened. The reason is that the silanol groups and / or reactive groups other than the silanol groups of the silicon compound group and the polysiloxane compound group in the sol form hydrogen bonds and / or chemical bonds with the silanol groups of the hollow silica particles. I guess there is. The gelation time can be, for example, 10 to 120 minutes, or 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. As the entire gelation and aging process, the total time of the gelation time and the aging time can be, for example, 4 to 480 hours, or 6 to 120 hours. By setting the total of the gelation time and the aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, the effect of aging can be more easily maintained.

In order to reduce the density of the obtained airgel 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 decreased within the above range, or the total time of the gelation time and the aging time is within the above range. It may be shortened within.

(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 hollow 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 said washing | cleaning can be repeatedly performed using water or an organic solvent, for example. 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. From the economical point of view, methanol, ethanol, or methyl ethyl ketone may be used.

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) and ethyl butyrate (24.6). The parenthesis indicates the surface tension at 20 ° C., and the unit is [mN / m]. Among these, aliphatic hydrocarbons (hexane, heptane, etc.) 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 at normal pressure of 100 ° C. or less may be used because it is easy to dry in the drying step described later. You may use said solvent individually or in mixture of 2 or more types.

The amount of the solvent used in the solvent replacement step can be an amount that can sufficiently replace the solvent in the 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 the present embodiment, since the hollow 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 the shrinkage of the gel in the drying process, the solvent of the wet gel is replaced with a predetermined replacement solvent (a low surface tension solvent). By functioning as a support for the original network-like skeleton, the skeleton is supported, and the shrinkage of the gel in the drying process is suppressed. Therefore, it is considered that the gel can be directly subjected to the drying step without replacing the solvent used for washing. Thus, in this embodiment, 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.

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. By performing the drying at a temperature lower than the critical point of the solvent used for drying and at atmospheric pressure, it becomes easier to obtain an airgel composite having excellent heat insulation and flexibility. 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 above, it can be set to 20 to 150 ° C, and 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. Further, as a method of supercritical drying, all or part of the solvent contained in the wet gel is obtained by immersing the wet gel in liquefied carbon dioxide under conditions of, for example, 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.

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 has made it possible to form an airgel composite layer on a film-like support member, a fibrous support member and a foil-like support member, which have been difficult to achieve in the past.

Because of such advantages, 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 heat insulating material of the present embodiment includes the airgel composite described so far, and 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 in any way.

(Hollow silica particle dispersion)
As a hollow silica particle dispersion, product name “Thruria A” of JGC Catalysts & Chemicals Co., Ltd. (average primary particle diameter 50 nm, refractive index 1.30 hollow silica particles 20 mass%, isopropyl alcohol 70 mass% and methanol 10 mass%) Containing) was used.

(Synthesis Example 1)
100.0 parts by mass of hydroxy-terminated dimethylpolysiloxane (product name: XC96-723, manufactured by Momentive), methyltrimethoxysilane in a 1-liter three-necked flask equipped with a stirrer, thermometer and Dimroth condenser Was mixed with 181.3 parts by mass and 0.50 part by mass of t-butylamine and reacted at 30 ° C. for 5 hours. Thereafter, the reaction solution was heated at 140 ° C. for 2 hours under a reduced pressure of 1.3 kPa to remove volatile components, whereby a bifunctional alkoxy-modified polysiloxane compound represented by the above general formula (B) ( Polysiloxane compound A) was obtained.

[Production of airgel]
Example 1
Dispersion of hollow silica particles in an aqueous solution in which 187.5 parts by mass of water and 20.0 parts by mass of cetyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter abbreviated as “CTAB”) as a cationic surfactant are mixed. 213.0 parts by mass of liquid (product name: Thruria A, manufactured by JGC Catalysts and Chemicals Co., Ltd.), methyltrimethoxysilane (product name: KBM-13, manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter abbreviated as “MTMS”) ) 60.0 parts by mass and 20.0 parts by mass of dimethoxydimethylsilane (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as “DMDMS”), 20.0 parts by mass of the polysiloxane compound A as a polysiloxane compound, A sol was obtained by stirring at 25 ° C. for 30 minutes. The obtained sol was gelled at 60 ° C. and then aged at 60 ° C. for 60 hours to obtain a wet gel.

Then, the obtained wet gel was immersed in a mixed solution of 1000.0 parts by mass of water and 1500.0 parts by mass of methanol, and washed at 60 ° C. for 3 hours. This washing operation was performed once while exchanging with 2500.0 parts by mass of new methanol. Next, the washed wet gel was immersed in 2500.0 parts by mass of methyl ethyl ketone, which is a low surface tension solvent, and solvent substitution was performed at 60 ° C. for 3 hours. This solvent replacement operation was performed twice while exchanging with new methyl ethyl ketone. The washed and solvent-substituted wet gel was dried at 25 ° C. for 48 hours under normal pressure, and then further dried at 150 ° C. for 2 hours to obtain an airgel composite 1.

(Example 2)
Into an aqueous solution in which 208.8 parts by mass of water and 20.0 parts by mass of CTAB as a cationic surfactant are mixed, 191.7 parts by mass of a hollow silica particle dispersion (product name: Thruria A, manufactured by JGC Catalysts and Chemicals Co., Ltd.) Part, 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS, and 20.0 parts by mass of the polysiloxane compound A as a polysiloxane compound were added and stirred at 25 ° C. for 30 minutes to obtain a sol. . After the obtained sol was gelled at 60 ° C., an airgel composite 2 was obtained in the same manner as in Example 1.

(Example 3)
159.8 parts by mass of hollow silica particle dispersion (product name: Thruria A, manufactured by JGC Catalysts and Chemicals) in an aqueous solution in which 240.7 parts by mass of water and 20.0 parts by mass of CTAB as a cationic surfactant are mixed. Part, 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS, and 20.0 parts by mass of the polysiloxane compound A as a polysiloxane compound were added and stirred at 25 ° C. for 30 minutes to obtain a sol. . After the obtained sol was gelled at 60 ° C., an airgel composite 3 was obtained in the same manner as in Example 1.

(Comparative Example 1)
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 stirred at 25 ° C. for 120 minutes to obtain a sol. The obtained sol was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel. Then, airgel 4 was obtained like Example 1 using the obtained wet gel.

(Comparative Example 2)
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 stirred at 25 ° C. for 120 minutes to obtain a sol. The obtained sol was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel. Then, airgel 5 was obtained like Example 1 using the obtained wet gel.

(Comparative Example 3)
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 stirred at 25 ° C. for 120 minutes to obtain a sol. The obtained sol was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel. Then, airgel 6 was obtained like Example 1 using the obtained wet gel.

Table 1 below collectively shows the drying method, the types and addition amounts of the silicone components (silicon compound and polysiloxane compound), and the addition amount of the hollow silica particle dispersion in each Example and Comparative Example.

[Various evaluations]
The wet gel and airgel composite obtained in each example and the wet gel and airgel obtained in each comparative example were measured or evaluated according to the following conditions. The state of the airgel composite and the airgel in the atmospheric pressure drying of the methanol-substituted gel, and the evaluation results of the thermal conductivity and the compression elastic modulus of the airgel composite and the airgel are collectively shown in Table 2 below.

(1) State of airgel composite 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 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 shrinkage”, and when it exceeded 5%, 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.

(2) Measurement of thermal conductivity Using a blade with 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.

(3) 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 a 7.0 mm square cube (dice shape) to obtain a measurement sample. 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 .

From Table 2, it can be confirmed that the airgel composites of the examples have good shrinkage resistance in atmospheric drying using a methanol-substituted gel. In this evaluation, the fact that good shrinkage resistance was shown in any of the examples showed that a good-quality airgel composite could be obtained without carrying out 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 gel contracted by atmospheric drying using a methanol-substituted gel, cracks were generated on the surface, and either thermal conductivity or flexibility was inferior.

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

Claims

An airgel composite containing an airgel component and hollow silica particles.
The airgel composite according to claim 1, comprising a three-dimensional network skeleton formed by the airgel component and the hollow silica particles, and pores.
An airgel composite containing hollow silica particles as a component constituting a three-dimensional network skeleton.
At least one selected from the group consisting of hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the silicon compound having a hydrolyzable functional group An airgel composite that is a dried product of a wet gel that is a condensate of a sol containing
At least one selected from the group consisting of the hollow silica particles, a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysis product of the silicon compound having the hydrolyzable functional group. The airgel composite according to any one of claims 1 to 3, which is a dried product of a wet gel that is a condensate of a sol containing:
The airgel composite according to claim 4 or 5, wherein the silicon compound includes a polysiloxane compound having a hydrolyzable functional group or a condensable functional group.
The airgel composite according to any one of claims 1 to 6, wherein the hollow silica particles have an average primary particle diameter of 1 nm to 100 µm.
The airgel composite according to any one of claims 1 to 7, wherein the hollow silica particles have a spherical shape.
The airgel composite according to any one of claims 1 to 8, wherein the hollow silica particles are at least one selected from the group consisting of fused silica particles, fumed silica particles, and colloidal silica particles.
The airgel composite according to any one of claims 1 to 9, wherein the compression elastic modulus at 25 ° C is 3 MPa or less.
A heat insulating material comprising the airgel composite according to any one of claims 1 to 10.