JP6597064B2 - Airgel composite - Google Patents

Description

  The present invention relates to an airgel composite.

  Airgel has excellent physical properties due to its high porosity, and is used in the fields of architecture, automobiles, household appliances, semiconductors, industrial equipment, etc. It may be applicable to catalysts and support materials. It is desirable to add various chemical and physical properties to the airgel in addition to the properties such as heat insulation and flexibility so that the airgel can be suitably used for these wide applications.

  By the way, as a method for producing an 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, see Patent Document 1). In the supercritical drying method, an alcogel and a dispersion medium (solvent used for drying) are introduced into a high-pressure vessel, and the dispersion medium is applied to the supercritical fluid by applying a temperature and pressure above its critical point to form a supercritical fluid. It is a method of removing the solvent. However, since the supercritical drying method requires a high-pressure process, capital investment is required for a special apparatus that can withstand supercriticality, and much labor and time are required.

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

  On the other hand, as a method for producing an airgel that does not require a high-pressure process and has added chemical and physical properties, there is a method using a metal alkoxide and a polysiloxane having a Si—H bond as raw materials (for example, patents). Reference 3). Specifically, by reacting a metal alkoxide and a polysiloxane having a Si—H bond in the presence of a base catalyst, generation of hydrogen gas due to decomposition of Si—H and gelation occur simultaneously, so that shrinkage is suppressed and foaming is performed. It is a technique that can obtain a gel body. However, even if this method is used, it is difficult to impart flexibility necessary for further improving the handleability of the airgel.

U.S. Pat. No. 4,402,927 JP 2011-93744 A JP 2003-267719 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. In addition, as for the method of imparting various suitable chemical and physical properties to such aerogel, it is a matter of course that sufficient studies have not been made.

  This invention is made | formed in view of said situation, and it aims at providing the airgel composite which is not only excellent in a softness | flexibility but is excellent also in ultraviolet-ray shielding property.

  As a result of intensive studies to achieve the above object, the present inventor achieved excellent flexibility as long as it is an airgel composite in which silica particles and metal oxide particles are combined in an airgel component, and It has been found that ultraviolet shielding can be imparted as predetermined chemical and physical properties.

  The present invention provides an airgel composite containing an airgel component, silica particles, and metal oxide particles. Unlike the airgel obtained by the prior art, the airgel composite of the present invention is excellent in flexibility and ultraviolet shielding properties.

  The airgel composite can have a three-dimensional network skeleton formed from an airgel component, silica particles, and metal oxide particles, and pores. Thereby, flexibility is easily improved.

  The present invention also provides an airgel composite containing silica particles and metal oxide particles as components constituting a three-dimensional network skeleton. The airgel composite thus obtained is excellent in flexibility and ultraviolet shielding properties.

  The present invention also includes silica particles and metal oxide particles, and at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group in the molecule and a hydrolysis product of the silicon compound. An airgel composite obtained by drying a wet gel generated from the sol is provided. The airgel composite thus obtained is excellent in flexibility and ultraviolet shielding properties.

  In the present invention, the sol may 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. Thereby, the further outstanding softness | flexibility can be achieved.

  Moreover, the average primary particle diameter of a silica particle can be 1-500 nm. Thereby, it becomes easy to improve a softness | flexibility further.

  At this time, the shape of the silica particles can be spherical. The 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 softness | flexibility can be achieved.

  The metal oxide particles can be at least one selected from the group consisting of cerium oxide particles, titanium oxide particles, and zinc oxide particles. Thereby, the further outstanding ultraviolet-ray shielding property can be achieved.

  At this time, the average primary particle diameter of the metal oxide particles can be 1 to 500 nm. Thereby, flexibility can be maintained.

  In addition, the said drying can be performed under the temperature and atmospheric pressure below the critical point of the solvent used for drying. Thereby, it becomes easier to obtain an airgel composite excellent in flexibility.

  According to the present invention, it is possible to provide an airgel composite that is not only excellent in flexibility but also excellent in ultraviolet shielding properties.

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

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as the case may be. However, the present invention is not limited to the following embodiments.

<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. That is, in the present embodiment, the airgel means “Gel composed 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 are bonded. There are fine pores between the skeletons formed by the clusters, 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 characteristic of the above-mentioned aerogel while the silica particles and metal oxide particles are composited in the airgel, and has a three-dimensionally fine porosity. It has the structure of.

  In this embodiment, it does not necessarily mean the same concept as this, but the airgel composite of this embodiment contains silica particles and metal oxide particles as components constituting the three-dimensional network skeleton. It is also possible to express. The airgel composite of this embodiment is excellent in flexibility as described later. In particular, since the flexibility is excellent, the handling property as an airgel composite is improved and the size can be increased, so that the productivity can be increased. In addition, such an airgel composite is obtained by making silica particles exist in the airgel production environment. The merit of having silica particles is not only that the flexibility of the composite itself can be improved, but also the time for the wet gel generation process described later can be shortened, or the drying process can be simplified from the washing and solvent replacement process. There are also. In addition, shortening of the time of this process and simplification of a process are not necessarily calculated | required when producing the airgel composite which is excellent in a softness | flexibility.

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

  First, as a composite aspect of an airgel component and silica particles, an aspect in which an amorphous airgel component is interposed between silica particles and the like can be mentioned. As such an embodiment, specifically, for example, an embodiment in which silica particles or the like are coated with a film-like airgel component (silicone) (an embodiment in which the airgel component encloses silica particles or the like), an airgel component serves as a binder and silica particles A mode in which the airgel component is filled with a plurality of gaps such as silica particles, a mode in which these modes are combined (a mode in which silica particles arranged in a cluster are covered with the airgel component, etc. ), And the like. As described above, in the present embodiment, the airgel composite has a three-dimensional network skeleton that can be composed of silica particles, metal oxide particles, and an airgel component (silicone), and is particularly limited in its specific mode (form). There is no.

  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.

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

  This suggests that the aspect of the airgel composite (size, shape, etc. of the three-dimensional network skeleton) can be controlled by adjusting the size, shape, silanol group number, system pH, etc. of the silica particles, for example. 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, but the present invention is not limited to the embodiment of FIG. 1 as described above. However, for matters common to any of the above-described aspects (type, size, content, etc. of silica particles and the like), the following descriptions can be referred to as appropriate.

  FIG. 1 is a diagram schematically showing the fine structure of an airgel composite according to an embodiment of the present invention. As shown in FIG. 1, the airgel composite 10 has a tertiary structure formed by airgel particles 1, which are airgel components, partially linked in a three-dimensional manner through silica particles 2 and metal oxide particles 4. It has an original mesh skeleton and pores 3 surrounded by the skeleton. At this time, it is assumed that the silica particles 2 and the metal oxide particles 4 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 silica particles and metal oxide particles via airgel particles. Silica particles and metal oxide particles may be coated with airgel particles. In addition, since the said airgel particle (aerogel component) is comprised from silicone, it is guessed that the affinity to a silica particle is high. Therefore, in this embodiment, it is considered that the silica particles were successfully introduced into the three-dimensional network skeleton of the airgel. In this respect, it is considered that the silanol groups of the silica particles also contribute to the affinity between them.

  The airgel particle 1 is considered to be in the form of secondary particles composed of a plurality of primary particles, and is generally spherical. The average particle size (that is, the secondary particle size) of the airgel particles 1 can be 2 nm to 50 μm, but may be 5 nm to 2 μm, or 10 nm to 200 nm. When the airgel particle 1 has an average particle diameter of 2 nm or more, an airgel composite having excellent flexibility can be easily obtained. On the other hand, when the average particle diameter is 50 μm or less, fine pores can be formed, which is high. It becomes easy to obtain an airgel composite having a porosity. The average particle diameter of the primary particles constituting the airgel particles 1 can be 0.1 nm to 5 μm from the viewpoint of easily forming secondary particles having a low-density porous structure. It may be 200 nm, or 1 nm to 20 nm.

  The surface structure of the silica particle 2 is not particularly limited, and the particle in which the silanol group present on the surface is not modified, the silica particle in which the silanol group is modified with a cation group, an anion group, nonionic group, or the like, or the silanol group is an alkoxy group Silica particles substituted with a hydroxyalkyl group can also be used.

  The form of the silica particles used for producing the airgel 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.

  When the silica particles are colloidal silica, the pH of the slurry is preferably 8.0 or less. This facilitates control of the gelation reaction when producing the airgel.

  The solvent in which the colloidal silica is dispersed can be used without particular limitation. For example, water, alcohol, hexane, benzene, toluene and the like can be mentioned.

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

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

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

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

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

  Although content of the airgel component contained in an airgel composite can be 4-25 mass parts with respect to 100 mass parts of total amounts of an airgel composite, 10-20 mass parts may be sufficient. When the content is 4 parts by mass or more, an appropriate strength is easily imparted, and when the content is 25 parts by mass or less, the reaction is easily controlled.

  Although content of the silica particle contained in an airgel composite can be 1-25 mass parts with respect to 100 mass parts of total amounts of an airgel composite, 3-15 mass parts may be sufficient. When the content is 1 part by mass or more, an appropriate strength is easily imparted to the airgel composite, and when the content is 25 parts by mass or less, the gelation reaction can be easily controlled when producing the airgel.

  The airgel composite of the present invention further includes metal oxide particles 4 for the purpose of imparting chemical and physical properties in addition to the airgel component and the silica particles 2. For example, the metal oxide particles 4 may further include at least one selected from the group consisting of cerium oxide particles, titanium oxide particles, and zinc oxide particles for the purpose of imparting ultraviolet shielding properties. Although the mechanism by which such various aspects occur in the airgel composite of the present embodiment is not necessarily clear, the present inventors have found that these metal oxide particles 4 are hydrated in water and the surface is a hydroxyl group (—OH). Therefore, it is considered that the dehydration condensation reaction may occur due to the reaction with the silanol groups on the surface of the silica particles 2.

  Although content of the metal oxide particle contained in an airgel composite can be 1-25 mass parts with respect to 100 mass parts of total amounts of an airgel composite, 3-15 mass parts may be sufficient. When the content is 1 part by mass or more, appropriate chemical / physical properties (for example, ultraviolet shielding) can be easily imparted to the airgel composite, and when the content is 25 parts by mass or less, aggregation between particles can be suppressed. .

  When the metal oxide particles are colloidal particles, the pH of the slurry is preferably 8.0 or less. This facilitates control of the gelation reaction when producing the airgel.

  The solvent in which the metal oxide particles are dispersed can be used without particular limitation. For example, water, alcohol, hexane, benzene, toluene and the like can be mentioned.

  The shape of the metal oxide particles 4 is not particularly limited, and examples thereof include a spherical shape, an eyebrows type, and an association type. Of these, the use of spherical particles as the metal oxide particles 4 makes it easy to suppress aggregation in the sol. The average primary particle diameter of the metal oxide particles 4 can be 1 to 500 nm, but may be 5 to 250 nm, or 10 to 100 nm. When the average primary particle diameter of the metal oxide particles 4 is 1 nm or more, an appropriate strength is easily imparted to the airgel, and an airgel composite having excellent shrinkage resistance during drying is easily obtained. On the other hand, when the average primary particle diameter is 500 nm or less, sedimentation of the particles is suppressed and it becomes easy to disperse uniformly in the system. As for the metal oxide particles, the average particle diameter can be measured by the same method as that for measuring silica particles as described above.

[Compressive modulus]
In the airgel composite of the present embodiment, the compression modulus at 25 ° C. can be 3 MPa or less, but may be 2 MPa or less, 1 MPa or less, or 0.5 MPa or less. Good. When the compression elastic modulus is 3 MPa or less, it becomes easy to obtain an airgel composite 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.

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

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

<Specific embodiment of airgel component>
The following aspects are mentioned as an airgel component in the airgel composite of this embodiment. By adopting these aspects, it becomes easy to control the heat insulating property and flexibility of the airgel composite to a desired level. However, adopting each of these aspects is not necessarily the purpose of obtaining the airgel composite defined in the present embodiment. By employ | adopting each aspect, the airgel composite which has a 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.

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

In formula (1), R ₁ and R ₂ each independently represent an alkyl group or an aryl group, and R ₃ and R ₄ each independently represent an alkylene group. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. In addition, as a substituent of a substituted phenyl group, an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, a cyano group etc. are mentioned, for example.

By introducing the above structure as an airgel component into the skeleton of the airgel composite, a flexible airgel composite is obtained. From such a viewpoint, in formula (1), R ₁ and R ₂ are each independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, or the like, and the alkyl group is a methyl group or the like. . In formula (1), R ₃ and R ₄ each independently include an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group.

(Second embodiment)
The airgel composite of the present embodiment is an airgel composite having a ladder type 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). There 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. 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 ₆ and R ₇ each independently represent an alkyl group or an aryl group, and b represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Moreover, as a substituent of a substituted phenyl group, an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, a cyano group etc. are mentioned, for example. In formula (2), when b is an integer of 2 or more, two or more R _{6 s} may be the same or different, and similarly two or more R _{7 s} are each the same. May be different.

By introducing the above structure as an airgel component into the skeleton of the airgel complex, for example, it has a structure derived from a conventional ladder-type silsesquioxane (that is, a structure represented by the following general formula (X) An airgel composite having flexibility superior to that of the airgel. In addition, as shown by the following general formula (X), in the airgel having a structure derived from the conventional ladder-type silsesquioxane, the structure of the bridge portion is -O-, but the airgel composite of this embodiment In the body, the structure of the bridging portion is a structure (polysiloxane structure) represented by the general formula (2).

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

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 ( You may have the structure represented by 3).

In formula (3), R ₅ , R ₆ , R ₇ and R ₈ each independently represent an alkyl group or an aryl group, a and c each independently represent an integer of 1 to 3000, and b is 1 to 50 Indicates an integer. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Moreover, as a substituent of a substituted phenyl group, an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, a cyano group etc. are mentioned, for example. In formula (3), when b is an integer of 2 or more, two or more R _{6 s} may be the same or different, and similarly two or more R _{7 s} are each the same. May be different. In Formula (3), when a is an integer of 2 or more, two or more R _{5 s} may be the same or different. Similarly, when c is an integer of 2 or more, 2 or more R ₈ may be the same or different.

From the viewpoint of obtaining more excellent flexibility, in formulas (2) and (3), R ₅ , R ₆ , R ₇ and R ₈ (however, R ₅ and R ₈ are only in formula (3)) Each independently includes an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. Moreover, in Formula (3), a and c can be independently 6-2000, but 10-1000 may be sufficient. Moreover, in formula (2) and (3), b can be 2-30, but 5-20 may be sufficient.

(Third embodiment)
The airgel composite of this embodiment is at least one selected from the group consisting of silica particles and metal oxide particles, a silicon compound having a hydrolyzable functional group in the molecule, and a hydrolysis product of the silicon compound ( Hereinafter, these may be collectively referred to as “silicon compounds and the like”), and may be obtained by drying a wet gel produced from a sol containing the same. The airgel composite described so far may also be obtained by drying a wet gel generated from a sol containing silica particles, metal oxide particles, and a silicon compound. Good.

  The number of silicon atoms in the molecule of the silicon compound can be 1 or 2. Although it does not specifically limit as a silicon compound which has a hydrolyzable functional group in a molecule | numerator, For example, an alkyl silicon alkoxide is mentioned. Alkyl silicon alkoxide can reduce the number of hydrolyzable functional groups to 3 or less from the viewpoint of improving water resistance, and specifically includes, for example, methyltrimethoxysilane, dimethyldimethoxysilane, and ethyltrimethoxysilane. Is mentioned. Here, examples of the hydrolyzable functional group include alkoxy groups such as a methoxy group and an ethoxy group.

  Further, the number of hydrolyzable functional groups is 3 or less, and vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl which are silicon compounds having a reactive group in the molecule. Methyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N- Phenyl-3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like can also be used.

  Further, bistrimethoxysilylmethane, bistrimethoxysilylethane, bistrimethoxysilylhexane, etc., which are silicon compounds having 3 or less hydrolyzable functional groups at the molecular ends can also be used.

  These silicon compounds may be used alone or in combination of two or more.

  In producing the airgel composite of this embodiment, the sol containing the silicon compound or the like is selected from the group consisting of a polysiloxane compound having a reactive group in the molecule and a hydrolysis product of the polysiloxane compound. At least one kind (hereinafter, these may be collectively referred to as “polysiloxane compounds and the like”).

  The reactive group in the polysiloxane compound or the like is not particularly limited, but may be a group that reacts with the same reactive group or a group that reacts with another reactive group. For example, an alkoxy group, a silanol group, a hydroxy group Examples thereof include an alkyl group, an epoxy group, a polyether group, a mercapto group, a carboxyl group, and a phenol group. You may use the polysiloxane compound which has these reactive groups individually or in mixture of 2 or more types. Examples of the reactive group include an alkoxy group, a silanol group, a hydroxyalkyl group, and a polyether group from the viewpoint of improving the flexibility of the airgel composite. Among these, the alkoxy group or the hydroxyalkyl group is a sol. The compatibility can be further improved. Moreover, from a viewpoint of the reactivity improvement of a polysiloxane compound, carbon number of an alkoxy group and a hydroxyalkyl group can be 1-6, but it is 2-4 from a viewpoint which improves the softness | flexibility of an airgel composite more. There may be.

Examples of the polysiloxane compound having a hydroxyalkyl group in the molecule include those having a structure represented by the following general formula (4). By using a polysiloxane compound having a structure represented by the following general formula (4), the structure represented by the general formula (1) can be introduced into the skeleton of the airgel composite.

In formula (4), R ₉ represents a hydroxyalkyl group, R ₁₀ represents an alkylene group, R ₁₁ and R ₁₂ 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. Moreover, as a substituent of a substituted phenyl group, an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, a cyano group etc. are mentioned, for example. In the formula (4), two R _{9 s} may be the same or different from each other, and similarly two R _{10 s} may be the same or different from each other. In formula (4), two or more R _{11 s} may be the same or different, and similarly two or more R _{12 s} may be the same or different.

By using a wet gel generated from a sol containing a polysiloxane compound or the like having the above structure, it becomes easier to obtain a flexible airgel composite. From such a viewpoint, in formula (4), R ₉ includes a hydroxyalkyl group having 1 to 6 carbon atoms, and the hydroxyalkyl group includes a hydroxyethyl group, a hydroxypropyl group, and the like. In Formula (4), R ₁₀ includes an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an ethylene group and a propylene group. In formula (4), R ₁₁ and R ₁₂ each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. Moreover, in Formula (4), although n can be set to 2-30, 5-20 may be sufficient.

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

Examples of the polysiloxane compound having an alkoxy group in the molecule include those having a structure represented by the following general formula (5). By using a polysiloxane compound having a structure represented by the following general formula (5), a ladder structure having a bridge portion represented by the general formula (2) is introduced into the skeleton of the airgel composite. be able to.

In the formula (5), R ₁₄ represents an alkyl group or an alkoxy group, R ₁₅ and R ₁₆ each independently represent an alkoxy group, R ₁₇ and R ₁₈ each independently represent an alkyl group or an aryl group, and m is An integer of 1 to 50 is shown. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Moreover, as a substituent of a substituted phenyl group, an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, a cyano group etc. are mentioned, for example. In the formula (5), two R _{14 s} may be the same or different, and two R _{15 s} may be the same or different. Similarly, two R 14 Each ₁₆ may be the same or different. In the formula (5), when m is an integer of 2 or more, two or more R _{17 s} may be the same or different, and similarly two or more R ₁₈ are each the same. May be different.

By using a wet gel generated from a sol containing a polysiloxane compound or the like having the above structure, it becomes easier to obtain a flexible airgel composite. From such a viewpoint, in formula (5), R ₁₄ includes an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and the like, and the alkyl group or alkoxy group includes a methyl group. , A methoxy group, an ethoxy group, and the like. In formula (5), R ₁₅ and R ₁₆ each independently include an alkoxy group having 1 to 6 carbon atoms, and examples of the alkoxy group include a methoxy group and an ethoxy group. In formula (5), R ₁₇ and R ₁₈ each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group. Moreover, in Formula (5), m can be 2-30, but 5-20 may be sufficient.

  The polysiloxane compound having the structure represented by the general formula (5) can be obtained by appropriately referring to the production methods reported in, for example, JP-A Nos. 2000-26609 and 2012-233110. Can do.

  Since the alkoxy group is hydrolyzed, the polysiloxane compound having an alkoxy group in the molecule may exist as a hydrolysis product in the sol. The polysiloxane compound having an alkoxy group in the molecule and Decomposition products may be mixed. Further, in the polysiloxane compound having an alkoxy group in the molecule, all of the alkoxy groups in the molecule may be hydrolyzed or partially hydrolyzed.

  These polysiloxane compounds may be used alone or in admixture of two or more.

  Although content, such as a silicon compound contained in the said sol, can be 5-50 mass parts with respect to 100 mass parts of total amounts of sol, 10-30 mass parts may be sufficient. By making it 5 parts by mass or more, it becomes easy to obtain good reactivity, and by making it 50 parts by mass or less, it becomes easy to obtain good compatibility.

  Moreover, when the said sol further contains a polysiloxane compound etc., the sum total of content, such as a silicon compound etc. and a polysiloxane compound, can be 5-50 mass parts with respect to 100 mass parts of total amounts of sol. However, 10-30 mass parts may be sufficient. When the total content is 5 parts by mass or more, good reactivity is further easily obtained, and when it is 50 parts by mass or less, good compatibility is further easily obtained. At this time, the ratio of the content of the silicon compound or the like and the content of the hydrolysis product such as the polysiloxane compound can be 0.5: 1 to 4: 1, but is 1: 1 to 2: 1. It may be. When the ratio of the content of these compounds is 0.5: 1 or more, good compatibility is further easily obtained, and when the ratio is 4: 1 or less, gel shrinkage is further easily suppressed.

  Although content of the silica particle contained in the said sol can be 1-20 mass parts with respect to 100 mass parts of total amounts of sol, 4-15 mass parts may be sufficient. By setting the content to 1 part by mass or more, it becomes easy to impart an appropriate strength to the airgel, and it becomes easy to obtain an airgel composite having excellent shrinkage resistance during drying. Moreover, it becomes easy to suppress the solid heat conduction of a silica particle by making content 20 mass parts or less, and it becomes easy to obtain the airgel composite excellent in heat insulation. On the other hand, the content of the metal oxide particles contained in the sol may be 1 to 20 parts by mass with respect to 100 parts by mass of the sol, but may be 2 to 10 parts by mass. By setting the content to 1 part by mass or more, it becomes easy to obtain an airgel excellent in ultraviolet shielding property. Moreover, it becomes easy to obtain an airgel with a high porosity by making content 20 mass parts or less.

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

In the formula (6), R ₁₉ represents an alkyl group. Here, examples of the alkyl group include an alkyl group having 1 to 6 carbon atoms, and examples of the alkyl group include a methyl group.

The airgel composite of this embodiment can have a structure represented by the following general formula (7).

In formula (7), R ₂₀ and R ₂₁ each independently represents an alkyl group. Here, examples of the alkyl group include an alkyl group having 1 to 6 carbon atoms, and examples of the alkyl group include a methyl group.

The airgel composite of this embodiment can have a structure represented by the following general formula (8).

In formula (8), R ₂₂ represents an alkylene group. Here, examples of the alkylene group include an alkylene group having 1 to 10 carbon atoms, and examples of the alkylene group include an ethylene group and a hexylene group.

<Method for producing airgel 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 and the like, the polysiloxane compound and the like, the hollow silica particles, and the metal oxide 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.

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

(Sol generation process)
The sol generation step is performed by mixing the above-described silicon compound, optionally a polysiloxane compound, a silica particle and / or a solvent containing silica particles, and a metal oxide particle and / or a solvent containing metal oxide particles, and adding water. It is a process of generating sol by decomposing. In this step, an acid catalyst may be further added to the solvent in order to promote the hydrolysis reaction. Further, as shown in Japanese Patent No. 5250900, a surfactant, a thermally hydrolyzable compound, and the like can be added to the solvent.

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

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

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

  By using an acid catalyst, the hydrolysis reaction of the silicon compound and the polysiloxane compound is promoted, and a sol can be obtained in a shorter time.

  The addition amount of an acid catalyst can be 0.001-0.1 mass part with respect to 100 mass parts of total amounts of a silicon compound and a polysiloxane 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.

  Examples of the nonionic surfactant include those containing a hydrophilic part such as polyoxyethylene and a hydrophobic part mainly composed of an alkyl group, and those containing a hydrophilic part such as polyoxypropylene. Examples of those 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. As what contains hydrophilic parts, such as polyoxypropylene, the polyoxypropylene alkyl ether, the block copolymer of polyoxyethylene and polyoxypropylene, etc. are mentioned.

  Examples of the ionic surfactant include a cationic surfactant, an anionic surfactant, and an amphoteric surfactant. Examples of the cationic surfactant include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride, and examples of the anionic surfactant include sodium dodecylsulfonate. Examples of amphoteric surfactants include amino acid surfactants, betaine surfactants, amine oxide surfactants, and the like. Examples of amino acid surfactants include acyl glutamic acid. Examples of betaine surfactants include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, and the like. Examples of the amine oxide surfactant include lauryl dimethylamine oxide.

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

  The addition amount of the surfactant depends on the kind of the surfactant, or the kind and amount of the silicon compound and the polysiloxane compound, but for example, 1 to 100 with respect to 100 parts by mass of the total amount of the silicon compound and the polysiloxane compound. It can be a mass part. In addition, 5-60 mass parts may be sufficient as the addition amount.

  The thermohydrolyzable compound is considered to generate a base catalyst by thermal hydrolysis to make the reaction solution basic, and to promote the sol-gel reaction in the wet gel generation process described later. Therefore, the thermohydrolyzable compound is not particularly limited as long as it is a compound that can make the reaction solution basic after hydrolysis. Urea; formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N -Acid amides such as methylacetamide and N, N-dimethylacetamide; cyclic nitrogen compounds such as hexamethylenetetramine and the like. Among these, urea is particularly easy to obtain the above-mentioned promoting effect.

  The amount of the thermally hydrolyzable compound added is not particularly limited as long as it is an amount that can sufficiently promote the sol-gel reaction in the wet gel generation step described later. For example, when urea is used as the thermally hydrolyzable compound, the amount added can be 1 to 200 parts by mass with respect to 100 parts by mass of the total amount of the silicon compound and the polysiloxane 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, and by making it 200 mass parts or less, it becomes easier to further suppress the precipitation of crystals and the decrease in gel density.

  The hydrolysis in the sol production step depends on the type and amount of silicon compound, polysiloxane compound, silica particles, metal oxide particles, acid catalyst, surfactant, etc. in the mixed solution, but for example 20 to 60 ° C. May be performed for 10 minutes to 24 hours under a temperature environment of 5 minutes to 8 hours under 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.

  However, when a thermohydrolyzable compound is added to the solvent, the temperature environment of the sol generation step may be adjusted to a temperature that suppresses hydrolysis of the thermohydrolyzable compound and suppresses gelation of the sol. . The temperature at this time may be any temperature as long as the hydrolysis of the thermally hydrolyzable compound can be suppressed. For example, when urea is used as the thermohydrolyzable compound, the temperature environment of the sol generation step can be 0 to 40 ° C, but may be 10 to 30 ° C.

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

  Base catalysts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; ammonium compounds such as ammonium hydroxide, ammonium fluoride, ammonium chloride, and ammonium bromide; sodium metaphosphate Basic sodium phosphates such as sodium pyrophosphate and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3 -(Diethylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, t-butylamine, sec- Aliphatic amines such as tilamine, propylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine; morpholine, N -Nitrogen-containing heterocyclic compounds such as methylmorpholine, 2-methylmorpholine, piperazine and derivatives thereof, piperidine and derivatives thereof, imidazole and derivatives thereof, and the like. Among these, ammonium hydroxide (ammonia water) is excellent in that it has high volatility and does not remain in the airgel composite after drying, and thus does not impair water resistance, and is economical. You may use said base catalyst individually or in mixture of 2 or more types.

  By using a base catalyst, it is possible to accelerate the dehydration condensation reaction and / or dealcoholization condensation reaction of the silicon compound, polysiloxane compound, etc., and silica particles in the sol, and the sol is gelled in a shorter time. be able to. Thereby, a wet gel with higher strength (rigidity) can be obtained. In particular, ammonia has high volatility and hardly remains in the airgel composite. Therefore, by using ammonia as a base catalyst, an airgel composite having better water resistance can be obtained.

  Although the addition amount of a base catalyst can be 0.5-5 mass parts with respect to 100 mass parts of total amounts, such as a silicon compound etc. and a polysiloxane compound, 1-4 mass parts may be sufficient. By setting it as 0.5 mass part or more, gelatinization can be performed in a short time, and a water resistance fall can be suppressed more by setting it as 5 mass part or less.

  The gelation of the sol in the wet gel generation step may be performed in a sealed container so that the solvent and the base catalyst do not volatilize. The gelation temperature can be 30-90 ° C, but it may be 40-80 ° C. By setting the gelation temperature to 30 ° C. or higher, gelation can be performed in a shorter time, and a wet gel with higher strength (rigidity) can be obtained. Moreover, since it becomes easy to suppress volatilization of a solvent (especially alcohols) by making gelation temperature into 90 degrees C or less, it can gelatinize, suppressing volume shrinkage.

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

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

  Although the gelation time and the aging time differ depending on the gelation temperature and the aging temperature, in 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 for this is presumed that the silanol groups and / or reactive groups possessed by the polysiloxane compounds and the like in the sol form hydrogen bonds and / or chemical bonds with the silanol groups of the hollow silica particles. . The gelation time can be 10 to 120 minutes, but may be 20 to 90 minutes. By setting the gelation time to 10 minutes or more, it becomes easy to obtain a homogeneous wet gel, and by setting it to 120 minutes or less, the drying process can be simplified from the washing and solvent replacement process described later. In addition, as a whole process of gelation and aging, the total time of the gelation time and the aging time can be 4 to 480 hours, but may be 6 to 120 hours. By setting the total gelation time and aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, the effect of aging can be more easily maintained.

  In order to decrease the density of the obtained airgel composite or increase the average pore diameter, the gelation temperature and the aging temperature are increased within the above range, or the total time of the gelation time and the aging time is increased within the above range. May be. Further, in order to increase the density of the obtained airgel composite or to reduce the average pore diameter, the gelation temperature and the aging temperature are reduced within the above range, or the total time of the gelation time and the aging time is within the above range. It can be shortened.

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

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

  As organic solvents, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, methylene chloride , N, N-dimethylformamide, dimethyl sulfoxide, acetic acid, formic acid, and other various organic solvents can be used. You may use said organic solvent individually or in mixture of 2 or more types.

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

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

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

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

  Examples of the low surface tension solvent include those having a surface tension at 20 ° C. of 30 mN / m or less. The surface tension may be 25 mN / m or less, or 20 mN / m or less. Examples of the low surface tension solvent include pentane (15.5), hexane (18.4), heptane (20.2), octane (21.7), 2-methylpentane (17.4), 3- Aliphatic hydrocarbons such as methylpentane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), 1-pentene (16.0); (28.9), toluene (28.5), m-xylene (28.7), p-xylene (28.3) and other aromatic hydrocarbons; dichloromethane (27.9), chloroform (27.2) ), Carbon tetrachloride (26.9), 1-chloropropane (21.8), 2-chloropropane (18.1) and other halogenated hydrocarbons; ethyl ether (17.1), propyl ether (20.5) ), Isop Ethers such as pyrether (17.7), butyl ethyl ether (20.8), 1,2-dimethoxyethane (24.6); acetone (23.3), methyl ethyl ketone (24.6), methyl propyl ketone (25.1), ketones such as diethyl ketone (25.3); methyl acetate (24.8), ethyl acetate (23.8), propyl acetate (24.3), isopropyl acetate (21.2), Examples include esters such as isobutyl acetate (23.7), ethyl butyrate (24.6), etc. (in parentheses indicate surface tension at 20 ° C., and the unit is [mN / m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have a low surface tension and an excellent working environment. Among these, by using a hydrophilic organic solvent such as acetone, methyl ethyl ketone, or 1,2-dimethoxyethane, it can be used as the organic solvent in the washing step. Among these, those having a boiling point of 100 ° C. or less at normal pressure may be used because they can be easily dried in the drying step described later. You may use said solvent individually or in mixture of 2 or more types.

  The amount of the solvent used in the solvent replacement step can be an amount that can sufficiently replace the solvent in the wet gel after washing. The amount can be 3 to 10 times the amount of wet gel volume.

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

  In the present embodiment, since the 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 shrinkage in the drying process, the solvent of the wet gel is replaced with a predetermined replacement solvent (a low surface tension solvent), but in this embodiment, the hollow silica particles (and metal oxides) are replaced. The product particles) function as a support for a three-dimensional network-like skeleton, whereby the skeleton is supported and gel shrinkage in the drying process is suppressed. Therefore, it is considered that the gel can be directly subjected to the drying step without replacing the solvent used for washing. Thus, in this embodiment, 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 washed and solvent-substituted (if necessary) is dried as described above. 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 this embodiment can be obtained by drying a wet gel that has been washed and (if necessary) solvent-substituted at a temperature below the critical point of the solvent used for drying under atmospheric pressure. The drying temperature varies depending on the type of substituted solvent (the solvent used for washing if solvent substitution is not performed), but especially when drying at a high temperature increases the evaporation rate of the solvent and causes large cracks in the gel. In view of that there is, it can be 20-150 degreeC. The drying temperature may be 60 to 120 ° C. Moreover, although drying time changes with the capacity | capacitances and drying temperature of a wet gel, it can be 4 to 120 hours. In the present embodiment, it is also included in the atmospheric pressure drying that the drying is accelerated by applying a pressure less than the critical point within a range not inhibiting the productivity.

  The airgel composite of this embodiment can also be obtained by supercritically drying a wet gel that has been washed and (if necessary) solvent-substituted. Supercritical drying can be performed by a known method. Examples of the supercritical drying method include a method of removing the solvent at a temperature and pressure higher than the critical point of the solvent contained in the wet gel. Alternatively, as a method of supercritical drying, all or part of the solvent contained in the wet gel is obtained by immersing the wet gel in liquefied carbon dioxide, for example, under conditions of about 20 to 25 ° C. and about 5 to 20 MPa. And carbon dioxide having a lower critical point than that of the solvent, and then removing carbon dioxide alone or a mixture of carbon dioxide and the solvent.

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

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

  Table 1 shows the silica particle-containing raw material (colloidal silica) and ceria particle-containing raw material (colloidal ceria) used in this example.

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

[Production of airgel]
Example 1
Silica 1 is added to an aqueous solution obtained by mixing 201.7 parts by mass of water and 20.0 parts by mass of hexadecyltrimethylammonium bromide (Wako Pure Chemical Industries, Ltd., hereinafter abbreviated as “CTAB”) as an ionic surfactant. 0.5 parts by mass (silica particles: 21.3 parts by mass, water: 85.2 parts by mass), 92.3 parts by mass of ceria 1 (ceria particles: 21.3 parts by mass, water: 71.0 parts by mass), 60.0 parts by mass of methyltrimethoxysilane (product name: KBM-13, manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter abbreviated as “MTMS”) and dimethoxydimethylsilane (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter “DMDMS”) 20.0 parts by mass) 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. 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 Aerogel 1.

(Example 2)
In an aqueous solution in which 21.2 parts by mass of water and 20.0 parts by mass of CTAB as an ionic surfactant are mixed, 142.0 parts by mass of silica 1 (silica particles: 28.4 parts by mass, water: 113.6 parts by mass) Part), 47.3 parts by weight of ceria 1 (ceria particles: 14.2 parts by weight, water: 33.1 parts by weight), 60.0 parts by weight of MTMS and 20.0 parts by weight of DMDMS as a silicon compound, As the siloxane compound, 20.0 parts by mass of the above polysiloxane compound A was added and stirred at 25 ° C. for 30 minutes to obtain a sol. After the obtained sol was gelled at 60 ° C., an airgel 2 was obtained in the same manner as in Example 1.

(Example 3)
106.5 parts by mass of silica 1 (silica particles: 21.3 parts by mass, water: 85.2 parts by mass) in an aqueous solution in which 201.7 parts by mass of water and 20.0 parts by mass of CTAB as an ionic surfactant were mixed. Part), 92.3 parts by mass of ceria 2 (ceria particles: 21.3 parts by mass, water: 71.0 parts by mass), 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as a silicon compound, poly As the siloxane compound, 20.0 parts by mass of the above polysiloxane compound A was added and stirred at 25 ° C. for 30 minutes to obtain a sol. After the obtained sol was gelled at 60 ° C., an airgel 3 was obtained in the same manner as in Example 1.

Example 4
In an aqueous solution in which 21.2 parts by mass of water and 20.0 parts by mass of CTAB as an ionic surfactant were mixed, 142.0 parts by mass of silica 1 (silica particles: 28.4 parts by mass, water: 113.6 parts by mass) Part), 47.3 parts by weight of ceria 2 (ceria particles: 14.2 parts by weight, water: 33.1 parts by weight), 60.0 parts by weight of MTMS and 20.0 parts by weight of DMDMS as silicon compounds, poly As the siloxane compound, 20.0 parts by mass of the above polysiloxane compound A was added and stirred at 25 ° C. for 30 minutes to obtain a sol. After the obtained sol was gelled at 60 ° C., an airgel 4 was obtained in the same manner as in Example 1.

(Comparative Example 1)
In an aqueous solution in which 258.8 parts by mass of water and 20.0 parts by mass of CTAB as an ionic surfactant are mixed, 141.7 parts by mass of ceria 1 (ceria particles: 42.5 parts by mass, water: 99.2 parts by mass) Part), 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS, 20.0 parts by mass of the above polysiloxane compound A as a polysiloxane compound, and stirred at 25 ° C. for 30 minutes to obtain a sol It was. After the obtained sol was gelled at 60 ° C., an airgel 5 was obtained in the same manner as in Example 1.

(Comparative Example 2)
In an aqueous solution obtained by mixing 258.8 parts by mass of water and 20.0 parts by mass of CTAB as an ionic surfactant, 141.7 parts by mass of ceria 2 (ceria particles: 42.5 parts by mass, water: 99.2 parts by mass) Part), 60.0 parts by mass of MTMS as a silicon compound and 20.0 parts by mass of DMDMS, 20.0 parts by mass of the above polysiloxane compound A as a polysiloxane compound, and stirred at 25 ° C. for 30 minutes to obtain a sol It was. After the obtained sol was gelled at 60 ° C., an airgel 6 was obtained in the same manner as in Example 1.

(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. 100.0 parts by mass of MTMS as a silicon compound was added and reacted at 25 ° C. for 2 hours 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 7 was obtained like Example 1 using the obtained wet gel.

  Table 2 summarizes the drying method, the types and addition amounts of Si raw materials (silicon compounds and polysiloxane compounds), the addition amounts of silica particles and ceria particles in each Example and Comparative Example.

[Evaluation of shrinkage resistance and compression modulus]
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. Table 3 summarizes the evaluation results of the airgel composite and the airgel in the atmospheric pressure drying of the methanol-substituted gel, and the compression elastic modulus of the airgel composite.

(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 at 100 ° C. for 3 hours using an incubator with a safety door “SPH (H) -202” (product name, manufactured by ESPEC CORP.), And then further 150 ° C. And dried for 2 hours to obtain a sample after drying (especially the solvent evaporation rate is not controlled). Here, the volume shrinkage ratio SV before and after drying of the sample was obtained from the following equation. When the volume shrinkage ratio SV was 5% or less, it was evaluated as “no contraction”, and when it was 5% or more, it was evaluated as “shrinkage”. When the sample had been crushed after drying, it was evaluated as “crushed”.
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 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 (die 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 compression modulus E (MPa) was determined from the following formula 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 .

  In Examples 1-4, the airgel composite excellent in shrinkage resistance and compression elastic modulus could be obtained.

[Evaluation of UV shielding properties]
The airgel composite produced without being pulverized by the above measurement was evaluated for ultraviolet shielding property by the following measurement method. Table 4 shows the results.

(3) Evaluation of UV shielding property Newspaper was cut into 10 cm × 10 cm and placed on the east side of the room, on the window where natural light shines. The airgel composite processed into 3 cm x 3 cm x 0.5 cm was put on it, and the state as it was was maintained for 40 days. After 40 days, the airgel composite was removed, and the color of the newspaper on the part where the airgel composite was placed was confirmed. When there was no discoloration of the newspaper before and after the experiment, it was A, and when the newspaper discolored yellow, it was B.

  From Tables 3 and 4, the airgel composites obtained in the examples were excellent in shrinkage resistance, flexible, and ultraviolet shielding properties.

  On the other hand, since Comparative Examples 1 and 2 were crushed during solvent substitution with methanol, it was difficult to obtain a block gel. Further, Comparative Example 3 could not obtain the effects of shrinkage resistance, flexibility and ultraviolet shielding properties.

DESCRIPTION OF SYMBOLS 1 ... Airgel particle, 2 ... Silica particle, 3 ... Fine hole, 4 ... Metal oxide particle, 10 ... Airgel composite, L ... circumscribed rectangle.

Claims (6)

Containing airgel components, silica particles and metal oxide particles,
The airgel component has a ladder type structure including a column part and a bridge part, and the bridge part has a structure represented by the following general formula (2),
An airgel composite, wherein the metal oxide particles are at least one selected from the group consisting of cerium oxide particles, titanium oxide particles, and zinc oxide particles.

[In Formula (2), R ₆ and R ₇ each independently represent an alkyl group or an aryl group, and b represents an integer of 1 to 50. In the formula (2), when b is an integer of 2 or more, two or more R _{6 s} may be the same or different, and similarly two or more R _{7 s} may be the same or different. It may be. ]   The airgel composite according to claim 1, comprising a three-dimensional network skeleton formed from the airgel component, the silica particles, and the metal oxide particles, and pores. The airgel composite according to claim 1 or 2 , wherein the silica particles have an average primary particle diameter of 1 to 500 nm. The airgel composite according to any one of claims 1 to 3 , wherein the silica particles have a spherical shape. The airgel composite according to any one of claims 1 to 4 , wherein the 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 5 , wherein an average primary particle diameter of the metal oxide particles is 1 to 500 nm.