JP2017178643A - Method for producing aerogel complex, aerogel complex, and support member and heat insulation material with aerogel complex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aerogel complex having excellent heat insulation performance and flexibility.SOLUTION: A method for producing an aerogel complex includes the step for drying wet gel prepared from sol that contains a silica particle dispersion that contains silica particles dispersed therein and has a pH of 8.5 or less, 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.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an airgel composite manufacturing method, an airgel composite, a support member with 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 (thermal insulation, etc.), unique optical properties, and unique electrical properties. For example, an electronic substrate utilizing the ultra-low dielectric constant properties of silica airgel It is used as a material, a heat insulating material using the high heat insulating property of silica airgel, a light reflecting material using the ultra-low refractive index of silica airgel, and the like.

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

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

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

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

  As a technique for improving such problems of conventional aerogels, a method of imparting flexibility to the gel by increasing the pore diameter of the gel to a 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.

  This indication is made in view of said situation, and aims at providing the manufacturing method of the airgel composite excellent in heat insulation and a softness | flexibility. Another object of the present disclosure is to provide an airgel composite excellent in heat insulating properties and flexibility, a support member with an airgel composite formed by supporting the airgel composite, and a heat insulating material.

  As a result of intensive studies to achieve the above object, the present inventor manufactured an airgel composite having excellent heat insulation and flexibility by using a silica particle dispersion having a pH in a predetermined range. I found out that I could do it.

  That is, the present disclosure is a group consisting of a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and a hydrolysis product of the silicon compound. A method for producing an airgel composite comprising the step of drying a wet gel produced from a sol containing at least one selected from the above. According to the manufacturing method of the present disclosure, unlike the airgel obtained by the conventional technique, an airgel composite excellent in heat insulation and flexibility can be manufactured.

  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 heat insulation and softness | flexibility can be achieved.

  The average primary particle diameter of the silica particles may be 1 to 500 nm. Thereby, it becomes easy to improve heat insulation and a softness | flexibility further.

  The silica particles may have a spherical shape. The silica particles may be colloidal silica particles. Thereby, the further outstanding heat insulation and softness | flexibility can be achieved.

  The drying may be performed at a temperature below the critical point of the solvent used for drying and at atmospheric pressure. Thereby, it becomes easier to obtain an airgel composite excellent in heat insulation and flexibility.

  The present disclosure also includes a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and a hydrolysis product of the silicon compound. An airgel composite which is a dried product of a wet gel derived from a sol containing at least one selected from the above. Such an airgel composite has excellent heat insulation and flexibility.

  The present disclosure further provides a support member with an airgel composite comprising the airgel composite and a support member that supports the airgel composite. According to the present disclosure, since the airgel composite has excellent heat insulating properties and flexibility, it can exhibit excellent heat insulating properties and excellent flexibility that is difficult to achieve with conventional airgels.

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

It is a figure showing typically the fine structure of the airgel composite concerning one embodiment of this indication. It is a figure which shows the calculation method of the biaxial average primary particle diameter of particle | grains. It is a figure which shows typically the relationship between pH and reaction rate in the polycondensation reaction of 3-glycidoxypropyl trimethoxysilane. The surface of the airgel composite in the foil-like support member with the airgel composite obtained in Example 4 is (a) 10,000 times, (b) 50,000 times, (c) 200,000 times, and (d) 350,000. It is the SEM image observed by each magnification. The SEM image which observed the surface of the airgel composite in the foil-like support member with an airgel composite obtained in Example 6 at (a) 10,000 times, (b) 50,000 times, and (c) 200,000 times, respectively. It is.

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

<Airgel composite>
The airgel composite of this embodiment includes a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and a hydrolysis product of the silicon compound A wet gel produced from a sol containing at least one selected from the group consisting of: That is, the airgel composite of this embodiment includes a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and hydrolysis of the silicon compound. It may be a dried product of a wet gel derived from a sol containing at least one selected from the group consisting of products.

  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 are combined. Between the skeletons formed by the clusters, there are pores less than 100 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, for example. Examples of the silica airgel include so-called organic-inorganic hybrid silica airgel into which an organic group such as a methyl group or an organic chain is introduced. In addition, the airgel composite of the present embodiment has, for example, a cluster structure which is a feature of the above-mentioned aerogel while silica particles are composited in the airgel, and has a three-dimensionally fine porous structure. The aspect which has may be sufficient.

  The airgel composite of this embodiment contains an airgel component and silica particles. Although not necessarily meaning the same concept as this, the airgel composite of the present embodiment can also be expressed as containing silica particles as a component constituting the three-dimensional network skeleton. . The airgel composite of this embodiment is excellent in heat insulation and flexibility as described later. In particular, since the flexibility is excellent, the handling property as an airgel composite is improved and the size can be increased, so that the productivity can be increased. In addition, such an airgel composite is obtained by making silica particles exist in the airgel production environment. And the merit by the presence of silica particles is not only that the heat insulation and flexibility of the composite itself can be improved, but also shortening the time of the wet gel generation process described later, or simplifying the drying process from the washing and solvent replacement process. Is also possible. In addition, shortening of the time of this process and simplification of a process are not necessarily calculated | required when producing the airgel composite which is excellent in a softness | flexibility.

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

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

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

  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. 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 as described above, the present disclosure is not limited to the aspect of FIG. However, for matters common to any of the above aspects (type, size, content, etc. of silica particles), the following descriptions can be referred to as appropriate.

  FIG. 1 is a diagram schematically illustrating a microstructure 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 connecting airgel particles 1 that are airgel components in random three-dimensionally via silica particles 2, and And pores 3 surrounded by a skeleton. At this time, it is assumed that the silica particles 2 are interposed between the airgel particles 1 and function as a skeleton support that supports the three-dimensional network skeleton. Therefore, it is thought that by having such a structure, moderate strength is imparted to the airgel while maintaining the heat insulation and flexibility as the airgel. In this embodiment, the airgel composite may have a three-dimensional network skeleton formed by three-dimensionally connecting silica particles randomly through the airgel particles. Silica particles may be covered with airgel particles. In addition, since the said airgel particle (aerogel component) is comprised from 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 diameter (that is, the secondary particle diameter) of the airgel particles 1 can be set to 2 nm to 50 μm, for example, but may be 5 nm to 2 μm, or may be 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, for example, from the viewpoint that secondary particles having a low-density porous structure can be easily formed. It may be 5 nm to 200 nm, or 1 nm to 20 nm.

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

  The shape of the silica particle 2 is not particularly limited, and examples thereof include a spherical shape, a cage shape, and an association type. Of these, the use of spherical particles as the silica particles 2 makes it easy to suppress aggregation in the sol. The average primary particle diameter of the silica particles 2 can be set to 1 to 500 nm, for example, 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, it becomes easy to suppress the solid heat conduction of the silica particles, and it becomes easy to obtain an airgel composite excellent in heat insulation.

  It is presumed that the airgel particle 1 (aerogel component) and the silica particle 2 are bonded by taking a hydrogen bond, a chemical bond, or a combination of these bonds. At this time, hydrogen bonds, chemical bonds, or a combination of these bonds are considered to be formed by the silanol groups, reactive groups, or both 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.

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

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

  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, for example, 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, good heat insulating properties are easily obtained.

  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, for example, 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, solid heat conduction of the silica particles is easily suppressed.

  In addition to these airgel components and silica particles, the airgel composite may further contain other components such as carbon graphite, 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 from the viewpoint of sufficiently ensuring the desired effect of the airgel composite, for example, 1 to 5 parts by mass with respect to 100 parts by mass of the total amount of the airgel composite. it can.

The number of silanol groups per gram of the silica particles according to this embodiment may be, for example, 10 × 10 ^{18 to} 1000 × 10 ^18, or 50 × 10 ^{18 to} 800 × 10 ¹⁸ / g. 100 × 10 ^{18 to} 700 × 10 ¹⁸ pieces / g.

[Sol]
As described above, the sol according to the present embodiment includes a silica particle dispersion liquid in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and the hydrolysis of the silicon compound. And at least one selected from the group consisting of decomposition products (hereinafter, these may be collectively referred to as “silicon compounds and the like”).

(Silica particle dispersion)
The silica particles in the silica particle dispersion may be the silica particles described above. The pH of the silica particle dispersion is, for example, 8.0 or less, from the viewpoint that the hydrolysis reaction of the silicon compound and the polysiloxane compound described below is likely to proceed sufficiently and the crosslinking points in the three-dimensional crosslinking reaction are likely to increase. It may be 7.5 or less, or may be 6.5 or less. The pH of the silica particle dispersion may be, for example, 0.5 or more, 1.5 or more, or 2.5 or more from the viewpoint that the three-dimensional crosslinking reaction easily proceeds in a short time. There may be.

  Here, the pH of the silica particle dispersion can be measured with a pH meter (for example, model number: PHL-40, manufactured by Electrochemical Instrument Co., Ltd.). As the pH measurement value, standard buffer solution (phthalate pH buffer solution pH: 4.01 (25 ° C), neutral phosphate pH buffer solution pH: 6.86 (25 ° C), borate pH buffer solution After calibrating three points using the liquid pH: 9.18 (25 ° C.), the electrode is placed in the dispersion, and the value after 2 minutes or more has been stabilized is adopted.

  The present inventors have also speculated that the reason why the upper limit of the pH of the silica particle dispersion is in the above range is as follows. Hereinafter, the polycondensation reaction of 3-glycidoxypropyltrimethoxysilane will be described as an example.

  FIG. 3 is a diagram schematically showing the relationship between pH and reaction rate in the polycondensation reaction of 3-glycidoxypropyltrimethoxysilane. In FIG. 3, the horizontal axis represents pH, and the vertical axis represents log k (k is a reaction rate constant). However, the plots and approximate curves in FIG. 3 are based on predicted values and do not necessarily indicate actual measurement values.

  As shown in FIG. 3, it is considered that the polycondensation rate of 3-glycidoxypropyltrimethoxysilane is remarkably increased when the pH of the system is high. That is, when the pH of the silica particle dispersion is high, the pH of the system also increases, and the polycondensation rate of the silane component is considered to be remarkably increased. On the other hand, when the pH of the silica particle dispersion is moderately low, the pH of the system is also moderately lowered, and the polycondensation rate of the silane component is considered to be moderately slow. Therefore, when the pH of the silica particle dispersion is moderately low, gelation is unlikely to occur at a stage prior to the formation of the wet gel, and a good wet gel is likely to be produced.

  The degree of association of the silica particles in the silica particle dispersion may be, for example, 2.0 or less, 1.8 or less, from the viewpoint that the three-dimensional crosslinking reaction easily proceeds in a short time. .7 or less. When the degree of association is in such a range, the specific surface area of the particles is appropriately increased, so that the contact area with the silane component is increased, and the above effect is likely to be obtained. The degree of association of the silica particles in the silica particle dispersion is, for example, from the viewpoint that the hydrolysis reaction of the silicon compound and the polysiloxane compound described later is sufficiently advanced and the crosslinking points in the three-dimensional crosslinking reaction are likely to increase. It may be 0 or more, 1.2 or more, or 1.3 or more. When the degree of association is in such a range, the above-mentioned effect is likely to be obtained because the specific surface area of the particles is appropriately reduced.

  Here, in this specification, the degree of association of the silica particles in the silica particle dispersion is the ratio between the average particle diameter of the secondary particles of the silica particles in the silica particle dispersion and the biaxial average primary particle diameter of the silica particles. (Average particle diameter of secondary particles / biaxial average primary particle diameter). The average particle diameter of the secondary particles of the silica particles is a value obtained by measuring the silica particle dispersion with a particle size distribution meter by a dynamic light scattering method. The biaxial average primary particle size is a value determined by the above-described method.

(Silicon compounds, etc.)
The number of silicon atoms in the molecule of the silicon compound can be set to 1 or 2, for example. 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. The alkyl silicon alkoxide may have 3 or less hydrolyzable functional groups from the viewpoint of improving water resistance. Examples of such alkyl silicon alkoxides include methyltrimethoxysilane, dimethyldimethoxysilane, and ethyltrimethoxysilane. 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. In addition, 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 set to 1 to 6, for example. It may be 2 to 4 from the viewpoint of further improving the flexibility.

  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) described later 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 with low thermal conductivity. 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), n can be set to 2-30, for example, but may be 5-20.

  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 type structure having a bridge portion represented by the following general formulas (2) and (3) can be obtained from the airgel composite. It can be introduced into the skeleton.

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 with low thermal conductivity. 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 set to 2-30, for example, but may be 5-20.

  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, it may be 10-30 mass parts, for example. When the content is 5 parts by mass or more, good reactivity is easily obtained, and when the content is 50 parts by mass or less, good compatibility is easily obtained.

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

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

<Specific embodiment of airgel composite>
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 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 this embodiment may have a structure represented by the following general formula (1), for example.

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 having low thermal conductivity 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.

  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-type 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.

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

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 may have a structure represented by the following general formula (7), for example.

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 may have a structure represented by the following general formula (8), for example.

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.

<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, for example, 0.03 W / m · K or less, but even if it is 0.025 W / m · K or less. It may be 0.02 W / m · K or less. When the thermal conductivity is 0.03 W / m · K or less, it is possible to obtain a heat insulating property higher than that of the polyurethane foam which is a high performance heat insulating material. The lower limit value of the thermal conductivity is not particularly limited, but can be set to 0.01 W / m · K, for example.

  The thermal conductivity can be measured by a steady method. Specifically, it can be measured using, for example, a steady-state thermal conductivity measuring device “HFM436 Lambda” (manufactured by NETZSCH, product name, HFM436 Lambda is a registered trademark). The outline of the 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 modulus at 25 ° C. can be, for example, 3 MPa or less, but may be 2 MPa or less, 1 MPa or less, or 0.5 MPa or less. May be. 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.

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

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

  These compression elastic modulus, deformation recovery rate, and maximum compression deformation rate can be measured using a small tabletop 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 elastic modulus, deformation recovery rate, and maximum compression deformation rate is obtained.

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

The compression elastic modulus E (MPa) can be obtained from the following equation in 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 .

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

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

[Density and porosity]
In the airgel composite of the present embodiment, the size of the pores 3, that is, the average pore diameter can be, for example, 5 to 1000 nm, but may be 25 to 500 nm. When the average pore diameter is 5 nm or more, an airgel composite excellent in flexibility can be easily obtained, and when it is 1000 nm or less, an airgel composite excellent in heat insulation can be easily obtained.

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

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

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

<Method for producing airgel composite>
Next, an embodiment of a method for producing an airgel composite will be described.

  The method for producing an airgel composite of the present embodiment includes a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and the hydrolysis of the silicon compound. And a step of drying a wet gel produced from a sol containing at least one selected from the group consisting of degradation products. According to such a manufacturing method, unlike the airgel obtained by the prior art, an airgel composite excellent in heat insulation and flexibility can be manufactured.

  Here, the specific mode of the sol in the above step is the same as that of the sol described above, for example. The sol further contains 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 from the viewpoint of achieving further excellent heat insulation and flexibility. You may do it. Further, the average primary particle diameter of the silica particles may be, for example, 1 to 500 nm from the viewpoint of further improving heat insulation and flexibility. Further, from the viewpoint of achieving excellent heat insulation and flexibility, the shape of the silica particles may be spherical, and the silica particles may be colloidal silica particles.

  The drying may be performed at a temperature below the critical point of the solvent used for drying and at atmospheric pressure from the viewpoint of easily obtaining an airgel composite excellent in heat insulation and flexibility.

  The method for producing an airgel composite of the present embodiment includes a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and the hydrolysis of the silicon compound. A sol production step for producing a sol containing at least one selected from the group consisting of degradation products, a wet gel production step for producing a wet gel from the sol, and a drying step for drying the wet gel; May be provided.

  Hereinafter, although the manufacturing method of an airgel composite is demonstrated in detail using a specific example, the manufacturing method of the airgel composite of this embodiment is not limited to this.

  The airgel composite of the present embodiment includes, for example, the sol generation step, the wet gel generation step, and a step of cleaning and (if necessary) replacing the wet gel obtained in the wet gel generation step (cleaning and solvent). It can be produced by a production method mainly comprising a substitution step) and a drying step for 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, in some cases a polysiloxane compound and the like, and silica particles are dissolved or dispersed in a solvent. Means state. The wet gel means a gel solid in a wet state that contains a liquid medium but does not have fluidity.

  Hereinafter, each step will be described.

(Sol generation process)
In the sol production step, for example, the above-described silicon compound, the above-described silica particle dispersion, and optionally a polysiloxane compound or a solvent are mixed and hydrolyzed to produce a sol. In this step, an acid catalyst may be further added 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. Furthermore, components such as carbon graphite, aluminum compounds, magnesium compounds, silver compounds, and titanium compounds may be added for the purpose of suppressing heat ray 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, 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, for example, 4 to 8 mol with respect to 1 mol of the total amount of the silicon compound and the polysiloxane compound, and is 4 to 6.5. It may be 4.5 to 6 mol. By making the amount of alcohols 4 mol or more, it becomes easier to obtain good compatibility, and by making the amount 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, for example.

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

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

  The amount of the thermally hydrolyzable compound added is not particularly limited as long as it is an amount that can sufficiently promote the sol-gel reaction in the wet gel generation step described later. For example, when urea is used as the thermally hydrolyzable compound, the amount added can be, for example, 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.

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

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

(Wet gel production process)
In the wet gel production step, for example, the sol obtained in the sol production step is gelled and then aged to produce 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 is highly volatile and does not remain in the airgel composite after drying, so that it 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, dealcoholization condensation reaction, or both of the silicon compound, polysiloxane compound, etc., and silica particles in the sol. It can be performed in a shorter time. 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 the addition amount to 0.5 parts by mass or more, gelation can be performed in a shorter time, and by setting the addition amount to 5 parts by mass or less, a decrease in water resistance can be suppressed.

  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, for example, 30 to 90 ° C, but 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, but may be 40 to 80 ° C. By setting the aging temperature to 30 ° C. or higher, a wet gel with higher strength (rigidity) can be obtained, and by setting the aging temperature to 90 ° C. or lower, volatilization of the solvent (especially alcohols) can be easily suppressed. Therefore, it can be gelled while suppressing volume shrinkage.

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

  Although the gelation time and the aging time differ depending on the gelation temperature and the aging temperature, in the present embodiment, since the sol contains silica particles, the gelation time is particularly compared with the conventional method for producing an airgel. Can be shortened. The reason for this is presumed that the silanol groups or reactive groups possessed by the polysiloxane compounds and the like in the sol form hydrogen bonds or chemical bonds with the silanol groups of the silica particles. The gelation time can be, for example, 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, for example, 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.

  Examples of the organic solvent 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, Various organic solvents such as methylene chloride, N, N-dimethylformamide, dimethyl sulfoxide, acetic acid and formic acid 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, for example, 3 to 10 times the amount of the 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 in terms of easier drying 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, for example, 3 to 10 times the amount of the wet gel volume.

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

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

(Drying process)
In the drying step, the wet gel subjected to washing and solvent replacement (if necessary) 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).

  As described above, the drying step is performed, for example, at a temperature below the critical point of the solvent used for drying and at atmospheric pressure. The drying temperature varies depending on the type of substituted solvent (the solvent used for washing if solvent substitution is not performed), but especially when drying at a high temperature increases the evaporation rate of the solvent and causes large cracks in the gel. In view of the fact that there is, for example, the temperature can be 20 to 150 ° C. 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, for example. 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 drying method may be, for example, supercritical drying. 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.

<Support member with airgel composite>
The support member with an airgel composite of the present embodiment includes the airgel composite described so far and a support member that supports the airgel composite. Such a support member with an airgel composite can exhibit high heat insulation and excellent flexibility.

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

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

  The sheet-like support member is formed by molding at least one fiber-shaped raw material selected from the group consisting of organic, inorganic, and metal. Paper, non-woven fabric (including glass mat), organic fiber cloth, glass cloth, etc. Can be mentioned.

  The foil-shaped support member is a metal raw material formed into a thin film, and examples thereof include aluminum foil and copper foil.

  The porous support member has a porous structure made of at least one selected from the group consisting of organic, inorganic and metal as a raw material, and is made of a porous organic material (for example, polyurethane foam), a porous inorganic material (for example, , Zeolite sheets), porous metal materials (for example, porous metal sheets, porous aluminum sheets) and the like.

  The support member with an airgel composite can be produced, for example, as follows. First, a sol is prepared according to the sol generation process described above. After applying this onto the support member using a film applicator or the like, or impregnating the support member with the film applicator, a film-like support member with a wet gel is obtained according to the wet gel generation step described above. Then, the film-like support member with wet gel obtained is washed and (if necessary) solvent-replaced according to the above-described washing and solvent-replacement step, and then dried according to the above-described drying step. Can be obtained.

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

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

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

<Insulation material>
The 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 also 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 with reference to the following examples, but these examples do not limit the present disclosure.

Example 1
[Wet gel, airgel composite]
60.0 parts by mass of methyltrimethoxysilane LS-530 (manufactured by Shin-Etsu Chemical Co., Ltd., product name: hereinafter abbreviated as “MTMS”) and dimethyldimethoxysilane LS-520 (manufactured by Shin-Etsu Chemical Co., Ltd., product) Name: hereinafter referred to as “DMDMS”) is 40.0 parts by mass, and PL-2L (hereinafter referred to as “silica particle-containing raw material” in some cases) as a silica particle dispersion (hereinafter referred to as “silica particle-containing raw material”) is described in Table 1. 100.0 parts by mass of the silica particle-containing raw material), 40.0 parts by mass of water and 80.0 parts by mass of methanol were mixed, and 0.10 parts by mass of acetic acid as an acid catalyst was added thereto. The reaction was carried out at 0 ° C. for 2 hours to obtain sol 1. 40.0 parts by mass of 5% strength aqueous ammonia as a base catalyst was added to the obtained sol 1, gelled at 60 ° C., and then aged at 80 ° C. for 24 hours to obtain wet gel 1.

  Then, the obtained wet gel 1 was immersed in 2500.0 parts by mass of methanol and washed at 60 ° C. for 12 hours. This washing operation was performed 3 times while exchanging with fresh methanol. Next, the washed wet gel was immersed in 2500.0 parts by mass of heptane, which is a low surface tension solvent, and solvent substitution was performed at 60 ° C. for 12 hours. This solvent replacement operation was performed three times while exchanging with new heptane. The washed and solvent-substituted wet gel is dried at 40 ° C. for 96 hours under normal pressure, and then further dried at 150 ° C. for 2 hours, thereby being represented by the above general formulas (6) and (7). An airgel composite 1 having a structure was obtained.

[Support member with airgel composite]
A film-like support member with an airgel composite The sol 1 is formed into a film made of polyethylene terephthalate (longitudinal) 300 mm × (horizontal) 270 mm × (thickness) 12 μm so that the thickness after gelation is 40 μm (tester) PI-1210) manufactured by Sangyo Co., Ltd. was applied, gelled at 60 ° C. for 3 hours, and then aged at 80 ° C. for 24 hours to obtain a film-like support member 1 with a wet gel.

  Thereafter, the obtained film-like support member 1 with wet gel was immersed in 100 mL of methanol and washed at 60 ° C. for 2 hours. Next, the washed film-like support member with wet gel was immersed in 100 mL of methyl ethyl ketone, and the solvent was replaced at 60 ° C. for 2 hours. This solvent replacement operation was performed twice while exchanging with new methyl ethyl ketone. The washed and solvent-substituted film-like support member with a wet gel was dried at 120 ° C. for 6 hours under normal pressure to obtain a film-like support member 1 with an airgel composite.

-Sheet-like support member with an airgel composite The sol 1 is placed in an E glass cloth of (length) 300 mm x (width) 270 mm x (thickness) 100 µm so that the thickness of the sheet-like support member after gelation is 120 µm. After impregnation and gelation at 60 ° C. for 3 hours, aging at 80 ° C. for 24 hours yielded a sheet-like support member 1 with a wet gel.

  Then, the obtained sheet-like support member 1 with wet gel was immersed in 300 mL of methanol and washed at 60 ° C. for 2 hours. Next, the washed sheet-like support member with wet gel was immersed in 300 mL of methyl ethyl ketone, and the solvent was replaced at 60 ° C. for 2 hours. This solvent replacement operation was performed twice while exchanging with new methyl ethyl ketone. The washed and solvent-substituted sheet-like support member with a wet gel was dried at 120 ° C. for 8 hours under normal pressure to obtain a sheet-like support member 1 with an airgel composite.

-Foil-like support member with airgel composite The sol 1 is applied to a (longitudinal) 300 mm x (horizontal) 270 mm x (thickness) 12 µm aluminum foil using a film applicator so that the thickness after gelation is 40 µm. Then, after gelling at 60 ° C. for 3 hours, it was aged at 80 ° C. for 24 hours to obtain a foil-like support member 1 with a wet gel.

  Thereafter, the obtained foil-like support member 1 with wet gel was immersed in 100 mL of methanol and washed at 60 ° C. for 2 hours. Next, the washed foil-like support member with wet gel was immersed in 100 mL of methyl ethyl ketone, and solvent substitution was performed at 60 ° C. for 2 hours. This solvent replacement operation was performed twice while exchanging with new methyl ethyl ketone. The washed and solvent-substituted foil-like support member with a wet gel was dried at 120 ° C. for 6 hours under normal pressure to obtain a foil-like support member 1 with an airgel composite.

-Porous support member with airgel composite The above sol 1 is made into a flexible urethane foam of (length) 300 mm x (width) 270 mm x (thickness) 10 mm so that the thickness of the porous support member after gelation becomes 10 mm. After impregnating and gelling at 60 ° C. for 3 hours, it was aged at 80 ° C. for 24 hours to obtain a porous support member 1 with wet gel.

  Then, the obtained porous support member 1 with wet gel was immersed in 300 mL of methanol and washed at 60 ° C. for 2 hours. Next, the washed porous support member with wet gel was immersed in 300 mL of methyl ethyl ketone, and the solvent was replaced at 60 ° C. for 2 hours. This solvent replacement operation was performed twice while exchanging with new methyl ethyl ketone. The porous support member 1 with an airgel composite was obtained by drying the washed and solvent-substituted porous support member with a wet gel at 120 ° C. for 10 hours under normal pressure.

(Example 2)
[Wet gel, airgel composite]
100.0 parts by mass of PL-2L as a silica particle-containing raw material, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, cetyltrimethylammonium bromide as a cationic surfactant (Wako Pure Chemical Industries, Ltd.) Co., Ltd .: hereinafter abbreviated as “CTAB”) is mixed with 20.0 parts by mass of urea and 120.0 parts by mass of urea as a thermohydrolyzable compound, and then 70.0 parts by mass of MTMS and 30 parts of DMDMS as silicon compounds. 0.0 part by mass was added and reacted at 25 ° C. for 2 hours to obtain sol 2. The obtained sol 2 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 2. Then, the airgel composite 2 which has the structure represented by the said General formula (6) and (7) was obtained like Example 1 using the obtained wet gel 2. FIG.

[Support member with airgel composite]
In the same manner as in Example 1, using the sol 2, a film-like support member 2 with an airgel composite, a sheet-like support member 2 with an airgel composite, a foil-like support member 2 with an airgel composite, and a porous with an airgel composite A quality support member 2 was obtained.

(Example 3)
[Wet gel, airgel composite]
200.0 parts by mass of PL-5 as a silica particle-containing raw material, 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. urea as a thermohydrolyzable compound. 0 parts by mass was mixed, and 60.0 parts by mass of MTMS and 40.0 parts by mass of DMDMS were added as silicon compounds to this and reacted at 25 ° C. for 2 hours to obtain sol 3. The obtained sol 3 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 3. Then, the airgel composite 3 which has the structure represented by the said General formula (6) and (7) was obtained like Example 1 using the obtained wet gel 3. FIG.

[Support member with airgel composite]
Using the sol 3, as in Example 1, a film-like support member 3 with an airgel composite, a sheet-like support member 3 with an airgel composite, a foil-like support member 3 with an airgel composite, and a porous with an airgel composite A quality support member 3 was obtained.

Example 4
[Wet gel, airgel composite]
100.0 parts by mass of PL-2L as a silica particle-containing raw material, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant and thermal hydrolysis 120.0 parts by mass of urea was mixed as a decomposable compound, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as silicon compounds, and 20.0 parts by mass of polysiloxane compound A as a polysiloxane compound. In addition, sol 4 was obtained by reacting at 25 ° C. for 2 hours. The obtained sol 4 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 4. Then, the airgel composite 4 which has the structure represented by the said General formula (3), (6) and (7) was obtained like Example 1 using the obtained wet gel 4. FIG.

  The “polysiloxane compound A” was synthesized as follows. First, in a 1 liter three-necked flask equipped with a stirrer, a thermometer, and a Dimroth condenser, 100.0 parts by mass of hydroxy-terminated dimethylpolysiloxane “XC96-723” (product name, manufactured by Momentive), methyl 181.3 parts by mass of trimethoxysilane and 0.50 parts by mass of t-butylamine were mixed and reacted at 30 ° C. for 5 hours. Thereafter, this reaction solution was heated at 140 ° C. for 2 hours under reduced pressure of 1.3 kPa to remove volatile components, thereby obtaining a bifunctional alkoxy-modified polysiloxane compound (polysiloxane compound A) at both ends.

[Support member with airgel composite]
Using the sol 4, as in Example 1, a film-like support member 4 with an airgel composite, a sheet-like support member 4 with an airgel composite, a foil-like support member 4 with an airgel composite, and a porous with an airgel composite A quality support member 4 was obtained.

(Example 5)
[Wet gel, airgel composite]
100.0 parts by mass of HL-3L as a silica particle-containing raw material, 100.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and thermal hydrolysis 120.0 parts by mass of urea was mixed as a decomposable compound, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as silicon compounds, and 20.0 parts by mass of polysiloxane compound A as a polysiloxane compound. In addition, sol 5 was obtained by reacting at 25 ° C. for 2 hours. The obtained sol 5 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 5. Then, the airgel composite 5 which has the structure represented by the said General formula (3), (6) and (7) was obtained like Example 1 using the obtained wet gel 5. FIG.

[Support member with airgel composite]
Using the sol 5, as in Example 1, a film-like support member 5 with an airgel composite, a sheet-like support member 5 with an airgel composite, a foil-like support member 5 with an airgel composite, and a porous with an airgel composite A quality support member 5 was obtained.

(Example 6)
[Wet gel, airgel composite]
143.0 parts by mass of ST-OZL-35 as a raw material containing silica particles, 57.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and 120.0 parts by mass of urea was mixed as a thermally hydrolyzable compound, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as silicon compounds, and 20.0 parts of polysiloxane compound B as a polysiloxane compound. A mass part was added and reacted at 25 ° C. for 2 hours to obtain sol 6. The obtained sol 6 was gelled at 60 ° C. and then aged at 80 ° C. for 24 hours to obtain a wet gel 6. Then, the airgel composite 6 which has the structure represented by the said General formula (2), (6) and (7) was obtained like Example 1 using the obtained wet gel 6. FIG.

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

[Support member with airgel composite]
Using the sol 6, as in Example 1, a film-like support member 6 with an airgel composite, a sheet-like support member 6 with an airgel composite, a foil-like support member 6 with an airgel composite, and a porous with an airgel composite A quality support member 6 was obtained.

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

[Supporting member with airgel]
Using the sol 1C, a film-like support member 1C with an airgel, a sheet-like support member 1C with an airgel, a foil-like support member 1C with an airgel, and a porous support member 1C with an airgel were obtained in the same manner as in Example 1.

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

[Supporting member with airgel]
Using the sol 2C, a film-like support member 2C with an airgel, a sheet-like support member 2C with an airgel, a foil-like support member 2C with an airgel, and a porous support member 2C with an airgel were obtained in the same manner as in Example 1.

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

[Supporting member with airgel]
Using the sol 3C, a film-like support member 3C with an airgel, a sheet-like support member 3C with an airgel, a foil-like support member 3C with an airgel, and a porous support member 3C with an airgel were obtained in the same manner as in Example 1.

(Comparative Example 4)
143.0 parts by mass of ST-S as a silica particle-containing raw material, 57.0 parts by mass of water, 0.10 parts by mass of acetic acid as an acid catalyst, 20.0 parts by mass of CTAB as a cationic surfactant, and thermal hydrolysis 120.0 parts by mass of urea was mixed as a decomposable compound, 60.0 parts by mass of MTMS and 20.0 parts by mass of DMDMS as silicon compounds, and 20.0 parts by mass of polysiloxane compound B as a polysiloxane compound. In addition, when reacted at 25 ° C. for 2 hours, gelation occurred and a wet gel could not be prepared.

  The aspect of the silica particle containing raw material in each Example and a comparative example is put together in Table 1, and is shown. Table 2 summarizes the drying method, the types and addition amounts of the Si raw materials (silicon compounds and polysiloxane compounds), and the addition amount of the silica particle-containing raw materials in each Example and Comparative Example.

  In addition, pH of the silica particle containing raw material was measured using the pH meter (the electrochemical meter company make, model number: PHL-40). As the pH measurement value, standard buffer solution (phthalate pH buffer solution pH: 4.01 (25 ° C), neutral phosphate pH buffer solution pH: 6.86 (25 ° C), borate pH buffer solution After calibrating three points using the liquid pH: 9.18 (25 ° C.), the value after the electrode was placed in the dispersion and stabilized after 2 minutes or more was adopted.

[Various evaluations]
Regarding the wet gel, airgel composite and support member with airgel composite obtained in each example, and the wet gel, airgel and support member with airgel obtained in each comparative example (excluding Comparative Example 4), the following conditions According to the measurement or evaluation. Summary of gelation time in wet gel formation process, airgel composite and airgel state in atmospheric pressure drying of methanol-substituted gel, and evaluation results of thermal conductivity, compressive elastic modulus, density and porosity of airgel composite and airgel Table 3 summarizes the evaluation results of the 180 ° bending test of the support member with the airgel composite and the support member with the airgel.

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

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

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

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

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

(4) Measurement of compression elastic modulus Using a blade having a blade angle of about 20 to 25 degrees, the airgel composite and the airgel were processed into 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 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 .

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

(6) Flexural resistance test The support member with an airgel composite and the support member with an airgel obtained in each example and comparative example were processed into a width of 50 mm, and the mandrel on the airgel composite layer side according to JIS K5600-1. A test was conducted. A mandrel tester manufactured by Toyo Seiki Seisakusho was used. The presence or absence of cracks and peeling on the airgel composite and the airgel layer when bent 180 ° at a mandrel radius of 1 mm was visually evaluated. And the thing which a crack and peeling did not generate | occur | produce was evaluated as "non-destructive", and the thing which a crack or peeling generate | occur | produced was evaluated as "destructive".

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

  Moreover, 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. Moreover, the support member with an airgel composite of the example had good bending resistance.

  On the other hand, in Comparative Examples 1 to 3, the gelation time in the wet gel generation process was long, and in normal pressure drying using a methanol-substituted gel, the gel contracted and cracks occurred on the surface. Moreover, either thermal conductivity or flexibility was inferior. Furthermore, since the support member with an airgel is brittle with respect to bending, it has been easily broken.

(7) SEM observation The surface of the airgel composite in the foil-like support member with an airgel composite obtained in Example 4 and Example 6 was observed by SEM. FIG. 4 shows the surface of the airgel composite in the foil-like support member with the airgel composite obtained in Example 4, (a) 10,000 times, (b) 50,000 times, (c) 200,000 times, and (d ) SEM images observed at 350,000 times. FIG. 5 shows the surface of the airgel composite in the foil-like support member with the airgel composite obtained in Example 6, respectively (a) 10,000 times, (b) 50,000 times, and (c) 200,000 times. It is the observed SEM image.

  As shown in FIG. 4, it was observed that the airgel composite obtained in Example 4 had a three-dimensional network skeleton (three-dimensionally fine porous structure). The observed particle size was mainly about 20 nm derived from silica particles. Spherical airgel components (aerogel particles) with a particle diameter smaller than that of the silica particles can also be confirmed, but mainly the airgel components do not take a spherical form and cover the silica particles or function as a binder between the silica particles. Observed to be. Thus, since a part of airgel component functions as a binder between silica particles, it is guessed that the intensity | strength of an airgel composite can be improved.

  As shown in FIG. 5, it was observed that the airgel composite obtained in Example 6 also has a three-dimensional network skeleton. However, the cluster structure is unique. In this example, it does not have a structure in which particles and particles are connected in a bead shape as in a normal airgel, and the connection part of particles and particles seems to be densely filled with an airgel component (silicone). It is observed. Moreover, since the particle diameter of the particle | grains derived from a silica particle is significantly larger than the particle diameter of the silica particle itself, it is guessed that the silica particle is coat | covered thickly with the airgel component. Thus, in this example, the airgel component not only functions as a binder between particles, but also covers the entire cluster structure, so it is assumed that the strength of the airgel composite can be further improved. Is done. In Example 6, since ST-OZL-35 used was an acidic sol, an airgel composite was produced with a low pH in the system. Therefore, it is guessed that the production | generation speed | rate of the airgel component became slow and the airgel component in the obtained airgel composite was hard to become a particulate form.

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

Claims (9)

  At least one selected from the group consisting of a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and a hydrolysis product of the silicon compound And a method for producing an airgel composite comprising a step of drying a wet gel produced from a sol containing   The airgel composite according to claim 1, wherein the sol further contains 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. Method.   The manufacturing method of the airgel composite of Claim 1 or 2 whose average primary particle diameter of the said silica particle is 1-500 nm.   The manufacturing method of the airgel composite as described in any one of Claims 1-3 whose shape of the said silica particle is spherical.   The method for producing an airgel composite according to any one of claims 1 to 4, wherein the silica particles are colloidal silica particles.   The method for producing an airgel composite according to any one of claims 1 to 5, wherein the drying is performed at a temperature lower than a critical point of a solvent used for drying and at atmospheric pressure.   At least one selected from the group consisting of a silica particle dispersion in which silica particles are dispersed and having a pH of 8.5 or less, a silicon compound having a hydrolyzable functional group in the molecule, and a hydrolysis product of the silicon compound And an airgel composite that is a dried product of a wet gel derived from a sol containing.   A support member with an airgel composite comprising: the airgel composite according to claim 7; and a support member that carries the airgel composite.   A heat insulating material comprising the airgel composite according to claim 7.