TW201922930A - Dispersion liquid and aerogel particles - Google Patents

Abstract

The present invention pertains to a dispersion liquid containing aerogel particles that have a specific surface area of 350 m2/g or less, and also containing a dispersion medium.

Description

Dispersions and aerogel particles

The present invention relates to a dispersion and aerogel particles.

Aerogel is known as a material excellent in heat insulation and transparency. Aerogels with such characteristics are being processed into particles and used in various applications. For example, it is proposed to use a particulate aerogel as a filler between resin plates and the like constituting a thermal insulation window (for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2012-91943

[Problems to be Solved by the Invention]

In addition, if a particulate aerogel can be dispersed in a dispersion medium, it can be expected to be used as a dispersion liquid different from the case where the particles themselves are processed. However, when the particulate aerogel described in Patent Document 1 is used, agglomeration occurs in the dispersion medium, and a dispersion liquid cannot be prepared from the beginning.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a dispersion liquid in which aerogel particles are preferably dispersed. Another object of the present invention is to provide aerogel particles for preparing the dispersion. [Means for solving problems]

The present inventors have made intensive studies in order to achieve the above-mentioned object, and as a result, have found that an aerogel particle having a predetermined specific surface area can exhibit excellent dispersibility in a dispersion medium.

The present invention provides a dispersion liquid including aerogel particles having a specific surface area of 350 m ² / g or less; and a dispersion medium. Such a dispersion is different from those containing aerogel particles obtained by a conventional technique and is excellent in dispersibility.

In the present invention, the dispersion medium may include an organic solvent. Thereby, the dispersibility of aerogel particles can be further improved.

In addition, the present invention provides an aerogel particle having a specific surface area of 350 m ² / g or less. As described above, such aerogel particles can exhibit excellent dispersibility in a dispersion medium. Therefore, the aerogel particles of the present invention may also be referred to as aerogel particles for dispersion preparation. [Effect of the invention]

According to the present invention, a dispersion liquid in which aerogel particles are preferably dispersed can be provided. In addition, the present invention can provide aerogel particles for preparing the dispersion.

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In this specification, a numerical range expressed using "~" means a range including the numerical value described before and after "~" as the minimum value and the maximum value, respectively. The "A or B" may include any one of A and B, and may include both. Unless otherwise specified, the materials exemplified in this embodiment may be used alone or in combination of two or more.

<Aerogel> In a narrow sense, a dry gel obtained by using a supercritical drying method on a wet gel is referred to as an aerogel, and a dry gel obtained by drying under atmospheric pressure is referred to as a xerogel ( xerogel), and the dry gel obtained by freeze-drying is referred to as cryogel. However, in this embodiment, regardless of the drying method of the wet gel, the obtained low-density dry gel is condensed. The gel is called "aerogel". That is, in the present embodiment, the "aerogel" refers to an aerogel in a broad sense "a gel consisting of a microporous solid in which the dispersed phase is a gas). " Generally, an aerogel has a mesh-like fine structure inside, and has a cluster structure in which particulate aerogel components of about 2 nm to 20 nm are combined. There are pores smaller than 100 nm between the skeletons formed by the clusters. Thereby, a three-dimensional fine porous structure is formed in the aerogel. The aerogel of the present embodiment is, for example, a silica aerogel containing silica as a main component. Examples of the silica aerogel include a so-called organic-inorganic hybrid silica aerogel into which, for example, an organic group (such as a methyl group) or an organic chain is introduced.

As the aerogel of this embodiment, the following aspects are mentioned. By adopting these aspects, it is easy to obtain an aerogel excellent in heat insulation, flame retardancy, heat resistance, and flexibility. By adopting each aspect, an aerogel having heat insulation, flame retardancy, heat resistance, and flexibility corresponding to each aspect can be obtained.

(First aspect) The aerogel of this embodiment may have a structure represented by the following general formula (1). The aerogel according to this embodiment may have a structure represented by the following general formula (1a) as a structure represented by formula (1). [Chemical 1] [Chemical 2]

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

By introducing the structure represented by the formula (1) or the formula (1a) into the aerogel skeleton as an aerogel component, a soft aerogel having a low thermal conductivity is obtained. From such a viewpoint, in Formula (1) and Formula (1a), R ¹ and R ² each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like. Examples of the alkyl group include a methyl group. Wait. In Formula (1) and Formula (1a), 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 alkylene group and an alkylene group. Wait. In the formula (1a), p may be 2 to 30, or 5 to 20 may be used.

(Second Aspect) The aerogel of this embodiment has a ladder-type structure including a pillar portion and a bridge portion, and the bridge portion may have a structure represented by the following general formula (2). By introducing such a stepped structure into an aerogel skeleton as an aerogel component, heat resistance and mechanical strength can be improved. The "stepped structure" in this embodiment is a person having two struts and bridges that connect the struts to each other (a person having a so-called "ladder"). In this aspect, the aerogel skeleton may include a stepped structure, but the aerogel may partially have a stepped structure. [Chemical 3]

In formula (2), R ⁵ and R ⁶ each independently represent an alkyl group or an aryl group, and b represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In addition, in formula (2), when b is an integer of 2 or more, two or more R ⁵ may be the same or different, and similarly, two or more R ⁶ may be the same or different.

By introducing the structure into the aerogel skeleton as an aerogel component, for example, it has a structure derived from a conventional stepped silsesquioxane (ie, it has a general formula The aerogel having the structure represented by (X) is an aerogel having more excellent flexibility. Silsesquioxane is a polysiloxane with a compositional formula: (RSiO _1.5 ) _n , and can have a variety of skeleton structures such as cage, step, and random. In addition, as shown in the following general formula (X), in an aerogel having a structure derived from a conventional stepped silsesquioxane, the structure of the bridge portion is -O-, but this embodiment In the aerogel of a form, the structure of a bridge part is a structure (polysiloxane structure) represented by the said General formula (2). Among them, the aerogel in this aspect may have a structure derived from silsesquioxane in addition to the structure represented by the general formula (2). [Chemical 4]

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

The structure serving as the pillar portion and its chain length, and the interval between the structures serving as the bridging portion are not particularly limited. From the viewpoint of further improving heat resistance and mechanical strength, the stepped structure may have the following general formula (3) The represented stepped structure. [Chemical 5]

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 represents an integer of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. In addition, in formula (3), when b is an integer of 2 or more, two or more R ⁵ may be the same or different, and similarly, two or more R ⁶ may be the same or different. In addition, in the formula (3), when a is an integer of 2 or more, two or more R ⁷ may be the same or different. Similarly, when c is an integer of 2 or more, two or more R ⁷ may be the same. R ⁸ may be the same or different.

Furthermore, from the viewpoint of obtaining more excellent flexibility, in formulas (2) and (3), R ⁵ , R ⁶ , R ^7, and R ⁸ (wherein R ⁷ and R ⁸ are only in formula (3) In ()), independently, an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like are mentioned, and examples of the alkyl group include a methyl group and the like. In the formula (3), a and c may be independently set to 6 to 2000, but may be 10 to 1,000. In addition, in Formula (2) and Formula (3), b may be 2-30, but may be 5-20.

(Third Aspect) The aerogel of the present embodiment may be a dried gel of a wet gel as a condensate of a sol (obtained by drying a wet gel generated from a sol: a sol A dry product of a wet gel), and the sol contains at least one selected from the group consisting of a silicon compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysate of a silicon compound having a hydrolyzable functional group. The aerogel described above may be obtained by drying a wet gel produced from a sol containing a silicon compound or the like as described above.

As the silicon compound having a hydrolyzable functional group or a condensable functional group, a polysiloxane compound can be used. That is, the sol may contain at least one selected from the group consisting of a polysiloxane compound having a hydrolyzable functional group or a condensable functional group, and a hydrolysate of a polysiloxane compound having a hydrolyzable functional group. Compounds (hereinafter, referred to as the "polysiloxane group" as appropriate).

The functional group in the polysiloxane compound is not particularly limited, but may be a group that reacts with the same functional group or reacts with other functional groups. Examples of the hydrolyzable functional group include an alkoxy group. Examples of the condensable functional group include a hydroxyl group, a silanol group, a carboxyl group, and a phenolic hydroxyl group. The hydroxyl group may be contained in a hydroxyl group-containing group such as a hydroxyalkyl group. Furthermore, the polysiloxane compound having a hydrolyzable functional group or a condensable functional group may further have a reactive group different from the hydrolyzable functional group and the condensable functional group. Equivalent functional group). Examples of the reactive group include an epoxy group, a mercapto group, a glycidyloxy group, a vinyl group, an acrylfluorenyl group, a methacrylfluorenyl group, and an amino group. The epoxy group may be contained in an epoxy group-containing group such as a glycidyl group. The polysiloxane compounds having these functional groups and reactive groups can be used alone or in combination of two or more. Among these functional groups and reactive groups, for example, examples of the group that improves the flexibility of the aerogel include alkoxy, silanol, and hydroxyalkyl groups. Among these groups, alkoxy and hydroxyalkyl groups Group can further improve the compatibility of the sol. In addition, from the viewpoint of improving the reactivity of the polysiloxane compound and lowering the thermal conductivity of the aerogel, the carbon number of the alkoxy group and the hydroxyalkyl group can be set to 1 to 6, which can further improve the flexibility of the aerogel. From the viewpoint of sex, it may be 2 to 4.

Examples of the polysiloxane compound having a hydroxyalkyl group in the molecule include a structure represented by the following general formula (A). By using a polysiloxane compound having a structure represented by the following general formula (A), the structures represented by the general formula (1) and the formula (1a) can be introduced into the aerogel skeleton. [Chemical 6]

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

By using a wet gel (generated from a sol) as a condensate of a sol containing the polysiloxane compound having the structure, it is easier to obtain a low-thermal-conductivity and soft aerogel. From such a viewpoint, in the formula (A), R ^1a includes a hydroxyalkyl group having 1 to 6 carbon atoms, and examples of the hydroxyalkyl group include a hydroxyethyl group and a hydroxypropyl group. In the formula (A), R ^2a includes an alkylene group having 1 to 6 carbon atoms, and examples of the alkylene group include an alkylene group and an alkylene group. In formula (A), R ^3a and R ^4a each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group and the like. In the formula (A), n may be 2 to 30, but may be 5 to 20.

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

Examples of the polysiloxane compound having an alkoxy group in the molecule include a structure represented by the following general formula (B). By using a polysiloxane compound having a structure represented by the following general formula (B), a stepped structure having a bridging portion represented by the general formula (2) or (3) can be introduced into the gas condensate. Glue in the skeleton. [Chemical 7]

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

By using a wet gel (generated from a sol) as a condensate of a sol containing the polysiloxane compound or a hydrolyzed product of the structure, a moist gel (lower thermal conductivity and soft aerogel) is more easily obtained. From such a viewpoint, in the formula (B), R ^1b includes an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and the like. Examples of the alkyl group or alkoxy group include: Methyl, methoxy, ethoxy, etc. In formula (B), R ^2b and R ^3b each independently include an alkoxy group having 1 to 6 carbon atoms, and examples of the alkoxy group include a methoxy group and an ethoxy group. In formula (B), R ^4b and R ^5b each independently include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and the like, and examples of the alkyl group include a methyl group and the like. In the formula (B), m may be 2 to 30, but may be 5 to 20.

The polysiloxane compound having a structure represented by the general formula (B) can be obtained by appropriately referring to production methods reported in Japanese Patent Laid-Open No. 2000-26609, Japanese Patent Laid-Open No. 2012-233110, and the like.

Moreover, as a polysiloxane compound which has an alkoxy group in a molecule | numerator, the thing which has a structure represented by the following general formula (C) is also mentioned. By using a polysiloxane compound having a structure represented by the following general formula (C), heat resistance and mechanical strength can be improved. [Chemical 8]

In formula (C), R ^{1 C} represents an alkyl group, an alkoxy group, or an aryl group, R ^{2 C} and R ^{3 C} each independently represent an alkoxy group, and x and y represent integers of 1 to 50. Here, examples of the aryl group include a phenyl group and a substituted phenyl group. Examples of the substituent of the substituted phenyl group include an alkyl group, a vinyl group, a mercapto group, an amino group, a nitro group, and a cyano group. Furthermore, in formula (C), R ^{1 C} may be the same or different, R ^{2 C} may be the same or different, and similarly, R ^3C may be the same or different.

By using a moist gel (generated from a sol) as a condensate of a sol containing a polysiloxane compound or a hydrolyzed product thereof, it is easier to obtain a soft aerogel with low thermal conductivity, high mechanical strength . From such a viewpoint, in the formula (C), R ^1C includes an alkyl group having 1 to 6 carbons, an alkoxy group having 1 to 6 carbons, and the like. Examples of the alkyl group or alkoxy group include: Methyl, methoxy, ethoxy, etc. In formula (C), R ^2C and R ^3C each independently include an alkoxy group having 1 to 6 carbon atoms. Examples of the alkoxy group include a methoxy group and an ethoxy group. In the formula (C), x and y may be 2 to 30, but may be 5 to 20.

As the polysiloxane compound having a structure represented by the general formula (C), a commercially available product can be used, and for example, KC-89, KR-515, KR-500, and X-40-9225 (both Shin-Etsu can be used) (Manufactured by Chemical Industry Co., Ltd.), SR-2402, AY42-163, US-SG2403 (all manufactured by Toray Dow-corning Co., Ltd.), XC96-B0446, XR31-B1410 (all are Momentive from Japan) (Manufactured by contract company Momentive Performance Materials Japan), Ethyl Silicate 28, Ethyl Silicate 40, Methyl Silicate 51, Methyl Silicate ) 53A (both manufactured by Colcoat Co., Ltd.) and so on.

In addition, alkoxy groups are hydrolyzed, so a polysiloxane compound having an alkoxy group may exist as a hydrolysate in a sol, and a polysiloxane compound having an alkoxy group and its hydrolysate may also be mixed together. . In addition, in the polysiloxane compound having an alkoxy group, the alkoxy group in the molecule may be entirely hydrolyzed or partially hydrolyzed.

These polysiloxane compounds having a hydrolyzable functional group or a condensable functional group and the hydrolysates of the polysiloxane compounds having a hydrolyzable functional group may be used alone or as a mixture of two or more.

When producing the aerogel of this embodiment, as the silicon compound having a hydrolyzable functional group or a condensable functional group, a silicon compound other than the polysiloxane compound can be used. That is, the silicon compound-containing sol may be contained in addition to or in place of the polysiloxane compound group, and the silicon compound-containing sol may contain a compound selected from the group having hydrolyzability At least one of the group consisting of a silicon compound (other than a polysiloxane compound) having a functional group or a condensing functional group, and a hydrolysate of the silicon compound having a hydrolyzable functional group (hereinafter, referred to as "silicon as appropriate" Compound Group "). The number of silicon in the molecule in the silicon compound can be set to 1 or 2.

The silicon compound having a hydrolyzable functional group in the molecule is not particularly limited, and examples thereof include alkyl silicon alkoxides. From the viewpoint of improving water resistance, the number of hydrolyzable functional groups of the alkyl alkoxide can be three or less. Examples of such alkoxyalkyl silicon include monoalkyltrialkoxysilane, monoalkyldialkoxysilane, dialkyldialkoxysilane, monoalkylmonoalkoxysilane, and Alkyl monoalkoxysilanes, trialkyl monoalkoxysilanes, and the like, specifically, methyltrimethoxysilane, methyldimethoxysilane, dimethyldiethoxysilane, and dimethyldisilane Methoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, etc. Here, examples of the hydrolyzable functional group include alkoxy groups such as a methoxy group and an ethoxy group.

The silicon compound having a condensable functional group is not particularly limited, and examples thereof include silane tetraol, methylsilane triol, dimethylsilanediol, phenylsilanetriol, phenylmethylsilanediol, and diphenyl. Silanediol, n-propylsilanetriol, hexylsilyltriol, octylsilyltriol, decylsilyltriol, trifluoropropylsilyltriol, etc.

The silicon compound having a hydrolyzable functional group or a condensable functional group may further have the reactive group (a functional group not equivalent to the hydrolyzable functional group and the condensable functional group) different from the hydrolyzable functional group and the condensable functional group. ).

As the silicon compound having three or less hydrolyzable functional groups and having a reactive group, vinyl trimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidyloxy can also be used. Propylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-propenyloxy Propyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2- (Aminoethyl) -3-aminopropylmethyldimethoxysilane and the like.

In addition, as the silicon compound having a condensable functional group and a reactive group, vinyl silanetriol, 3-glycidoxypropylsilyltriol, 3-glycidoxypropylmethylsilane can also be used. Diol, 3-methacryloxypropylsilyltriol, 3-methacryloxypropylmethylsilanediol, 3-propenyloxypropylsilyltriol, 3-mercaptopropyl Silanetriol, 3-mercaptopropylmethylsilanediol, N-phenyl-3-aminopropylsilanetriol, N-2- (aminoethyl) -3-aminopropylmethylsilane Diols, etc.

Further, a silicon compound having three or less hydrolyzable functional groups at the molecular end, that is, a ditrimethoxysilylmethane, a ditrimethoxysilylethane, a ditrimethoxysilylhexane, an ethyl group, or the like can also be used. Trimethoxysilane, vinyltrimethoxysilane, etc.

The silicon compound (other than a polysiloxane compound) having a hydrolyzable functional group or a condensable functional group, and a hydrolysate of the silicon compound having a hydrolyzable functional group may be used alone or as a mixture of two or more.

By using the silicon compound (other than the polysiloxane compound), a structure represented by the following general formula (4) to general formula (6) can be introduced into the aerogel skeleton. The aerogel of this embodiment may have any one of these structures alone or two or more of them.

[Chemical 9]

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

[Chemical 10]

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

[Chemical 11]

In the formula (6), R ¹² represents an alkylene group. Here, examples of the alkylene group include an alkylene group having 1 to 10 carbon atoms, and examples of the alkylene group include an ethylene group and a hexyl group.

(Fourth Aspect) From the viewpoint of further strengthening and toughening and further achieving excellent thermal insulation and flexibility, the aerogel of this embodiment may further contain silica particles in addition to the aerogel component. . An aerogel containing an aerogel component and silica particles may be referred to as an aerogel composite. Although an aerogel composite is composed of an aerogel component and silica particles, it is believed that the aerogel composite has an aerogel-like cluster structure and a three-dimensionally fine porous structure.

An aerogel containing an aerogel component and silica particles can be referred to as a dried gel of a wet gel which is a condensate of a sol containing the above-mentioned selected from the group consisting of a hydrolyzable functional group or a condensable functional group. At least one of the group consisting of a silicon compound and a hydrolysate of a silicon compound having a hydrolyzable functional group, and silicon dioxide particles. Therefore, the description about the first aspect to the third aspect is also applicable to the aerogel of this embodiment.

The silica particles can be used without particular limitation, and examples thereof include amorphous silica particles. Examples of the amorphous silica particles include fused silica particles, fumed silica particles, and colloidal silica particles. Among these, colloidal silica particles have high monodispersity and are easily inhibited from agglomerating in the sol. The silica particles may be silica particles having a hollow structure, a porous structure, or the like.

The shape of the silica particles is not particularly limited, and examples thereof include a spherical shape, a cocoon shape, and an association type. Among these, by using spherical particles as the silica particles, aggregation in the sol is easily suppressed. From the viewpoint of easily providing an aerogel with moderate strength and flexibility, and easily obtaining an aerogel having excellent shrinkage resistance during drying, the average primary particle diameter of the silica particles may be 1 nm or more, or may be 5 nm or more, or 20 nm or more. From the viewpoint that it is easy to suppress the solid heat conduction of the silicon dioxide particles and to easily obtain an aerogel with excellent thermal insulation properties, the average primary particle diameter of the silicon dioxide particles may be 500 nm or less, or 300 nm or less, or may be Below 100 nm. From these viewpoints, the average primary particle diameter of the silicon dioxide particles may be 1 nm to 500 nm, 5 nm to 300 nm, or 20 nm to 100 nm.

In this embodiment, the average particle diameter of the aerogel component and the average primary particle diameter of the silica particles can be directly performed on the aerogel by using a scanning electron microscope (hereinafter abbreviated as "SEM (scanning electron microscope)"). Obtained. The "diameter" herein refers to a diameter when a cross section of a particle exposed in a cross section of an aerogel is regarded as a circle. The "diameter when the cross section is regarded as a circle" is the diameter of the perfect circle when the area of the cross section is replaced with a perfect circle of the same area. When calculating the average particle diameter, the diameter of a circle was calculated for 100 particles, and the average value was taken.

The average particle diameter of the silicon dioxide particles can also be measured from the raw materials. For example, the biaxial average primary particle diameter is calculated from the result of observation of arbitrary 20 particles by SEM as follows. In other words, if colloidal silica particles having a solid content concentration of about 5% to 40% by mass and dispersed in water are taken as an example, crystals with pattern wiring are immersed in a dispersion of colloidal silica particles. After the wafer obtained by circular cutting into a 2 cm square was obtained for about 30 seconds, the wafer was rinsed with pure water for about 30 seconds, and then subjected to nitrogen blow drying. Thereafter, the wafer was placed on a sample stage for SEM observation, an acceleration voltage of 10 kV was applied, and the silica particles were observed at a magnification of 100,000 times, and an image was taken. Twenty silica particles were arbitrarily selected from the obtained image, and the average value of the particle diameters of these particles was taken as the average particle diameter.

From the viewpoint of easily obtaining an aerogel having excellent shrinkage resistance, the number of silanol groups per 1 g of the silica particles may be 10 × 10 ¹⁸ particles / g or more, or 50 × 10 ¹⁸ particles / g or more. Or it may be 100 × 10 ¹⁸ pieces / g or more. From the viewpoint of easily obtaining a homogeneous aerogel, the number of silanol groups per 1 g of the silica particles may be 1,000 × 10 ¹⁸ particles / g or less, or 800 × 10 ¹⁸ particles / g or less, or may be 700 × 10 ¹⁸ pieces / g or less. From these viewpoints, the number of silanol groups per 1 g of the silica particles may be 10 × 10 ¹⁸ particles / g to 1000 × 10 ¹⁸ particles / g, or 50 × 10 ¹⁸ particles / g to 800 × 10. ¹⁸ / g, or may be 100 × 10 ¹⁸ / g to 700 × 10 ¹⁸ / g.

From the viewpoint that it is easier to obtain good reactivity, the content of the polysiloxane compound group (having a hydrolyzable functional group or a condensable functional group) contained in the sol relative to 100 parts by mass of the total amount of the sol The sum of the content of the polysiloxane compound and the content of the hydrolysate of the polysiloxane compound having a hydrolyzable functional group may be 5 parts by mass or more, or 10 parts by mass or more. From the viewpoint that it is easier to obtain good compatibility, the content of the group of polysiloxane compounds contained in the sol may be 50 parts by mass or less with respect to 100 parts by mass of the total amount of the sol. 30 parts by mass or less. From these viewpoints, the content of the polysiloxane compound group contained in the sol may be 5 to 50 parts by mass, or 10 to parts by mass, with respect to 100 parts by mass of the total amount of the sol. 30 parts by mass.

When the sol contains a silicon compound (except a polysiloxane compound), the silicon compound group (has hydrolyzability) with respect to 100 parts by mass of the total amount of the sol from the viewpoint that it is easier to obtain good reactivity. The sum of the content of the silicon compound of the functional group or the condensable functional group and the content of the hydrolysate of the silicon compound having a hydrolyzable functional group may be 5 parts by mass or more, or 10 parts by mass or more. From the viewpoint that it is easier to obtain good compatibility, the content of the group of silicon compounds contained in the sol may be 50 parts by mass or less, or 30 parts by mass with respect to 100 parts by mass of the total amount of the sol. the following. From these viewpoints, the content of the silicon compound group contained in the sol may be 5 to 50 parts by mass, or 10 to 30 parts by mass.

In the case where the sol includes the polysiloxane compound group and the silicon compound group, the content of the polysiloxane compound group and the content of the silicon compound group are more likely to obtain good compatibility. The ratio may be 1: 0.5 or more, or 1: 1 or more. From the viewpoint of making it easier to suppress the shrinkage of the gel, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1: 4 or less, or may be 1: 2 or less. From these viewpoints, the ratio of the content of the polysiloxane compound group to the content of the silicon compound group may be 1: 0.5 to 1: 4, or may be 1: 1 to 1: 2.

When silicon dioxide particles are contained in the sol, it is easy to provide an aerogel with a moderate strength, and it is easy to obtain an aerogel having excellent shrinkage resistance during drying, with respect to 100 of the total amount of the sol. The content of the silicon dioxide particles may be 1 part by mass or more, or 4 parts by mass or more. From the viewpoint of easily suppressing the solid heat conduction of the silicon dioxide particles and easily obtaining an aerogel having excellent thermal insulation properties, the content of the silicon dioxide particles may be 20 parts by mass or less based on 100 parts by mass of the total amount of the sol. It is 15 parts by mass or less. From these viewpoints, the content of the silica particles may be 1 to 20 parts by mass, or 4 to 15 parts by mass with respect to 100 parts by mass of the total amount of the sol.

<Aerogel particles> The aerogel particles of this embodiment can be obtained by pulverizing a bulk aerogel as described later.

The specific surface area of the aerogel particles is 350 m ² / g or less. Thereby, a dispersion liquid in which aerogel particles are preferably dispersed can be prepared. Therefore, aerogel particles having a specific surface area of 350 m ² / g or less may be referred to as aerogel particles for dispersion preparation. From this viewpoint, the specific surface area may be 300 m ² / g or less, 250 m ² / g or less, or 150 m ² / g or less. The lower limit of the specific surface area of the aerogel particles is not particularly limited, and can be set to about 30 m ² / g from the viewpoint of suppressing aggregation in the dispersion and improving the filling rate. As a method of adjusting the specific surface area of aerogel particles, various methods are considered, and examples thereof include adjusting the amount of an aerogel component having a bridge portion structure represented by the general formula (2), and adjusting the amount of silica particles.

The specific surface area can be measured by the BET method. As the measuring device, a gas adsorption amount measuring device (manufactured by a contract company of Quantachrome Instruments Japan, Autosorb-iQ (Autosorb is a registered trademark)) can be used.

The average particle diameter D50 of the aerogel particles can be set to 1 μm to 1000 μm, but it can also be 3 μm to 700 μm, 5 μm to 500 μm, 10 μm to 100 μm, or 10 μm ～ 50 μm. When the average particle diameter D50 of the aerogel particles is 1 μm or more, it is easy to obtain aerogel particles having excellent dispersibility and handling properties. On the other hand, when the average particle diameter D50 is 1,000 μm or less, it is easy to obtain aerogel particles having excellent dispersibility. The average particle diameter of the aerogel particles can be appropriately adjusted by a pulverization method and pulverization conditions, a method of sieving, and classification.

The average particle diameter D50 of the aerogel particles can be measured by a laser diffraction / scattering method. For example, aerogel particles are added to a solvent (ethanol) so that the content of the aerogel particles becomes 0.05% by mass to 5% by mass, and then agitated with a 50 W ultrasonic homogenizer for 15 to 30 minutes to perform aerogel particles. Of scattered. Thereafter, about 10 mL of the dispersion was injected into a laser diffraction / scattering type particle size distribution measurement device, and the particle diameter was measured at 25 ° C. with a refractive index of 1.3 and an absorption of 0. Then, the particle diameter at 50% (volume basis) of the cumulative value in this particle size distribution is taken as the average particle diameter D50. As the measuring device, for example, Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name) can be used.

<The manufacturing method of aerogel particles> The manufacturing method of an aerogel particle is not specifically limited, For example, it can manufacture by the following method.

The aerogel particles of this embodiment can be produced by a manufacturing method mainly including the following steps: a sol generation step; a wet gel generation step, gelling the sol obtained in the sol generation step, and then aging to obtain wetness Gelation; washing and solvent replacement steps, washing and (optionally) solvent replacement of the wet gel obtained in the wet gel generation step; drying step, drying of the washing and solvent replacement wet gel; and pulverization In the step, the aerogel obtained by drying is pulverized.

In addition, it can also be manufactured by a manufacturing method mainly including the following steps: a sol generation step; a wet gel generation step; a wet gel pulverization step, pulverizing the wet gel obtained in the wet gel generation step; washing and solvent A replacement step; and a drying step.

The size of the obtained aerogel particles can be further made uniform by sieving, classification, and the like. Dispersibility can be improved by adjusting the particle size. The term “sol” refers to a state before a gelation reaction occurs, and in this embodiment means a state in which the silicon compound and optionally silica particles are dissolved or dispersed in a solvent. The moist gel refers to a gel solid in a wet state that does not have fluidity although it contains a liquid medium.

(Sol generation step) The sol generation step is a step of mixing a silicon compound and optionally silica particles (also a solvent containing silica particles) and subjecting them to a hydrolysis reaction to generate a sol. In this step, in order to promote the hydrolysis reaction, an acid catalyst may be further added to the solvent. In addition, as shown in Japanese Patent No. 5250900, a surfactant, a thermally hydrolyzable compound, or the like may be added to the solvent. Furthermore, for the purpose of suppressing heat ray radiation and the like, components such as carbon graphite, aluminum compounds, magnesium compounds, silver compounds, and titanium compounds may be added to the solvent.

As the solvent, for example, water or a mixed solution of water and alcohol can be used. Examples of the alcohol include methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and third butanol. Among these, in terms of reducing the interfacial tension with the gel wall, examples of the alcohol having a low surface tension and a low boiling point include methanol, ethanol, and 2-propanol. These can be used alone or in combination of two or more.

For example, when using alcohol as a solvent, the amount of alcohol can be set to 4 mol to 8 mol relative to the total amount of the silicon compound group and the polysiloxane compound group, but it can also be 4 mol. ∼6.5, or alternatively 4.5 mol ~ 6 mol. By setting the amount of alcohol to 4 mol or more, it is easier to obtain good compatibility, and by setting it to 8 mol or less, it is easier to suppress gel shrinkage.

Examples of the acid catalyst include inorganic acids such as hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, sulfurous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromic acid, chloric acid, chlorous acid, and hypochlorous acid; acidic aluminum phosphate Acidic phosphates, such as acidic magnesium phosphate, acidic zinc phosphate; organic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, azelaic acid, etc. . Among these, as an acid catalyst which further improves the water resistance of the obtained aerogel, an organic carboxylic acid is mentioned. Examples of the organic carboxylic acid include acetic acid, but may be formic acid, propionic acid, oxalic acid, malonic acid, and the like. These can be used alone or in combination of two or more.

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

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

As the surfactant, a nonionic surfactant, an ionic surfactant, or the like can be used. These can be used alone or in combination of two or more.

As the nonionic surfactant, for example, a compound containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly containing an alkyl group, a compound containing a hydrophilic portion such as polyoxypropylene, and the like can be used. Examples of the compound containing a hydrophilic portion such as polyoxyethylene and a hydrophobic portion mainly containing an alkyl group include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene alkyl ether. Examples of the compound containing a hydrophilic portion such as polyoxypropylene include a polyoxypropylene alkyl ether, a block copolymer of polyoxyethylene and polyoxypropylene, and the like.

Examples of the ionic surfactant include a cationic surfactant, an anionic surfactant, and a diionic surfactant. Examples of the cationic surfactant include cetyltrimethylammonium bromide and cetyltrimethylammonium chloride. Examples of the anionic surfactant include sodium dodecylsulfonate. Examples of the diionic surfactant include amino acid-based surfactants, betaine-based surfactants, and amine oxide-based surfactants. Examples of the amino acid-based surfactants include amidinoglutamic acid and the like. Examples of the betaine-based surfactant include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, and the like. Examples of the amine oxide-based surfactant include lauryl dimethylamine oxide.

It is thought that these surfactants play a role in the wet gel formation step described later to reduce the difference in chemical affinity between the solvent in the reaction system and the grown siloxane polymer, and to suppress phase separation.

The amount of the surfactant added is also affected by the type of the surfactant or the type and amount of the silicon compound. For example, it can be set to 1 mass based on 100 parts by mass of the total of the polysiloxane compound group and the silicon compound group. Parts to 100 parts by mass. The added amount may be 5 to 60 parts by mass.

It is believed that the thermally hydrolyzable compound generates an alkali catalyst by thermal hydrolysis, and makes the reaction solution alkaline to promote the sol-gel reaction in the wet gel generation step described later. Therefore, the thermally hydrolyzable compound is not particularly limited as long as it can make the reaction solution basic after hydrolysis, and examples thereof include urea; formamidine, N-methylformamide, and N, N- Acid amines such as dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, and cyclic nitrogen compounds such as hexamethylenetetramine. Among these, urea is easy to obtain the said promotion effect.

The addition amount of the thermally hydrolyzable compound 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, in the case where urea is used as the thermally hydrolyzable compound, the added amount may be 1 to 200 parts by mass based on 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group. The added amount may be 2 to 150 parts by mass. By setting the addition amount to 1 part by mass or more, it is easier to obtain good reactivity, and by setting the amount to 200 parts by mass or less, it is easier to suppress the precipitation of crystals and the decrease in gel density.

The hydrolysis in the sol-generating step is also affected by the types and amounts of silicon compounds, silicon dioxide particles, acid catalysts, and surfactants in the mixed solution. 24 hours, or 5 minutes to 8 hours in a temperature environment of 50 ° C to 60 ° C. Thereby, the hydrolyzable functional group in a silicon compound is fully hydrolyzed, and the hydrolyzate of a silicon compound can be obtained more reliably.

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

(Wet Gel Generation Step) The wet gel generation step is a step of gelling the sol obtained in the sol generation step and then curing to obtain a wet gel. In this step, an alkali catalyst may be used in order to promote gelation.

Examples of the alkali catalyst include carbonates such as calcium carbonate, potassium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, ammonium carbonate, copper (II) carbonate, iron (II) carbonate, and silver (I) carbonate. ; Bicarbonates such as calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, ammonium bicarbonate, etc .; alkali hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide; ammonium hydroxide, fluoride Ammonium compounds such as ammonium, ammonium chloride, and ammonium bromide; basic sodium phosphates such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropyl Methylamine, diisopropylamine, ethylamine, diethylamine, triethylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3- (diethylamine) Methylamino) propylamine, di-2-ethylhexylamine, 3- (dibutylamino) propylamine, tetramethylethylenediamine, third butylamine, second butylamine, propyl Methylamine, 3- (methylamino) propylamine, 3- (dimethylamino) propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine Other aliphatic amines; morpholine, N-methyl? , Methyl morpholine, piperazine and nitrogen-containing cyclic compounds such as derivatives, piperidine and derivatives thereof, imidazole and derivatives thereof. Among these, ammonium hydroxide (aqueous ammonia) is excellent in terms of high volatility and difficulty in remaining in the aerogel particles after drying, so that it is difficult to impair water resistance, and in terms of economy. The alkali catalyst may be used alone or in combination of two or more.

By using an alkali catalyst, the dehydration condensation reaction or dealcoholization condensation reaction of the silicon compound and the silicon dioxide particles in the sol can be promoted, and the sol can be gelled in a shorter time. In addition, a wet gel with higher strength (rigidity) can be obtained by this. In particular, ammonia has high volatility and is difficult to remain in aerogel particles. Therefore, by using ammonia as an alkali catalyst, aerogel particles having more excellent water resistance can be obtained.

The addition amount of the alkali catalyst may be 0.5 parts by mass to 5 parts by mass with respect to 100 parts by mass of the total amount of the polysiloxane compound group and the silicon compound group, but may be 1 to 4 parts by mass. By setting it to 0.5 parts by mass or more, gelation can be performed in a shorter period of time, and by setting it to 5 parts by mass or less, a decrease in water resistance can be further suppressed.

The gelation of the sol in the wet gel generation step can be performed in a closed container in a manner that the solvent and the alkali catalyst are not volatile. The gelation temperature may be 30 ° C to 90 ° C, but may be 40 ° C to 80 ° C. By setting the gelation temperature to 30 ° C or higher, gelation can be performed in a shorter period of time, and a wet gel with higher strength (rigidity) can be obtained. In addition, by setting the gelation temperature to 90 ° C. or lower, volatilization of a solvent (especially an alcohol) is easily suppressed, and thus gelation can be performed while suppressing volume shrinkage.

The aging in the wet gel generation step can be performed in a closed container in a manner that the solvent and the alkali catalyst are not volatile. By aging, the binding of the components constituting the wet gel is strengthened, and as a result, a wet gel having high strength (rigidity) sufficient to suppress shrinkage during drying can be obtained. The aging temperature may be 30 ° C to 90 ° C, but may be 40 ° C to 80 ° C. By setting the curing temperature to 30 ° C or higher, a wet gel with higher strength (rigidity) can be obtained. By setting the curing temperature to 90 ° C or lower, the volatilization of the solvent (especially alcohol) can be easily suppressed, so it can be suppressed at the same time Gelation occurs while shrinking the volume.

In addition, since it is difficult to discriminate the gelation end time of the sol in many cases, the gelation of the sol and the subsequent aging may be continuously performed in a series of operations.

The gelation time and aging time can be appropriately set according to the gelation temperature and the aging temperature. Compared with the case where the sol does not contain silica particles, the gelation time can be shortened especially when the silica is contained in the sol. The reason is speculated that the silanol group or reactive group of the silicon compound in the sol forms a hydrogen bond or a chemical bond with the silanol group of the silicon dioxide particle. The gelation time may be 10 minutes to 120 minutes, but may be 20 minutes to 90 minutes. By setting the gelation time to 10 minutes or more, it is easy to obtain a homogeneous wet gel. By setting the gelation time to 120 minutes or less, the cleaning and solvent replacement steps to the drying steps described later can be simplified. In addition, as a whole step of gelation and aging, the total time of the gelation time and the aging time may be set to 4 hours to 480 hours, but may be 6 hours to 120 hours. By setting the total of the gelation time and the aging time to 4 hours or more, a wet gel with higher strength (rigidity) can be obtained, and by setting it to 480 hours or less, it is easier to maintain the effect of aging.

In order to reduce the density of the obtained aerogel particles or increase the average pore diameter, it is also possible to increase the gelation temperature and the maturation temperature within the range, or to extend the gelation time and the maturation time within the range. Total time. In addition, in order to increase the density of the obtained aerogel particles or reduce the average pore diameter, the gelation temperature and the aging temperature may be reduced within the range, or the gelation time and the aging time may be shortened within the range. The total time of time.

(Wet gel pulverizing step) When the wet gel pulverizing step is performed, the wet gel obtained in the wet gel generating step is pulverized. The pulverization can be performed, for example, by putting a wet gel into a Henschel mixer or performing a wet gel generation step in the mixer, and setting the mixer under moderate conditions (speed and time). Next operation. In addition, more simply, it can be performed by putting a wet gel in a sealable container or performing a wet gel generation step in a sealable container, and shaking with an appropriate time using an oscillation device such as a vibrator. In addition, the particle size of the wet gel may be adjusted using a jet mill, a roll mill, a bead mill, or the like as necessary.

(Washing and solvent replacement step) The washing and solvent replacement step is a step having a step of washing the wet gel obtained by the wet gel generation step or the wet gel pulverization step (washing step); and A step (solvent replacement step) of replacing the cleaning solution in the wet gel with a solvent suitable for drying conditions (the drying step described later). The cleaning and solvent replacement steps may be performed without the step of cleaning the wet gel, and only the solvent replacement step may be performed. However, impurities such as unreacted substances and by-products in the wet gel can be reduced, and the purity can be improved. From the viewpoint of high aerogel particles, the wet gel can also be washed.

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

As the organic solvent, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, 1,2-dimethoxyethane, acetonitrile, hexane, Various organic solvents such as toluene, diethyl ether, chloroform, ethyl acetate, tetrahydrofuran, dichloromethane, N, N-dimethylformamide, dimethylmethane, acetic acid and formic acid. The organic solvents may be used alone or as a mixture of two or more.

In the solvent replacement step described later, in order to suppress shrinkage of the gel caused by drying, a solvent having a low surface tension can be used. However, low surface tension solvents generally have very low mutual solubility with water. Therefore, when a low surface tension solvent is used in the solvent replacement step, examples of the organic solvent used in the cleaning step include a hydrophilic organic solvent having high mutual solubility with respect to both water and a low surface tension solvent. Furthermore, the hydrophilic organic solvent used in the washing step can perform a pre-replacement function for performing the solvent replacement step. Among the organic solvents, examples of the hydrophilic organic solvent include methanol, ethanol, 2-propanol, acetone, and methyl ethyl ketone. Furthermore, methanol, ethanol, and methyl ethyl ketone are excellent in terms of economic efficiency.

The amount of water or organic solvent used in the washing step may be an amount sufficient to replace and clean the solvent in the wet gel. This amount can be set to 3 to 10 times the capacity of the wet gel. It can be repeatedly washed until the moisture content in the wet gel after washing becomes 10% by mass or less with respect to the mass of the silica.

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

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

Examples of the low surface tension solvent include solvents having a surface tension of 20 mN / m or less at 20 ° C. The surface tension may be 25 mN / m or less, or may be 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), and 3-methylpentane. Aliphatic hydrocarbons such as alkane (18.1), 2-methylhexane (19.3), cyclopentane (22.6), cyclohexane (25.2), 1-pentene (16.0); benzene (28.9), toluene (28.5 ), M-xylene (28.7), para-xylene (28.3) and other aromatic hydrocarbons; dichloromethane (27.9), chloroform (27.2), carbon tetrachloride (26.9), 1-chloropropane (21.8), 2 -Halogenated hydrocarbons such as chloropropane (18.1); diethyl ether (17.1), propyl ether (20.5), isopropyl ether (17.7), butyl ether (20.8), 1,2-dimethoxyethane (24.6), etc. Ethers; ketones such as acetone (23.3), methyl ethyl ketone (24.6), methylpropyl ketone (25.1), diethyl ketone (25.3); methyl acetate (24.8), ethyl acetate (23.8) , Propyl acetate (24.3), isopropyl acetate (21.2), isobutyl acetate (23.7), ethyl butyrate (24.6) and other esters (the brackets indicate the surface tension at 20 ° C, the unit is [mN / m]). Among these, aliphatic hydrocarbons (hexane, heptane, etc.) have low surface tension and are excellent in working environment. Among these, by using a hydrophilic organic solvent such as acetone, methyl ethyl ketone, or 1,2-dimethoxyethane, the organic solvent can also be used as the organic solvent in the cleaning step. Among these, a solvent having a boiling point of 100 ° C. or lower at normal pressure may be used in terms of easier drying in a drying step described later. The solvents may be used alone or in combination of two or more.

The amount of the solvent used in the solvent replacement step may be an amount sufficient to replace the solvent in the wet gel after washing. This amount can be set to 3 to 10 times the capacity of the wet gel.

The temperature environment in the solvent replacement step can be set to a temperature lower than the boiling point of the solvent used in the replacement. For example, when heptane is used, the temperature can be set to about 30 ° C to 60 ° C.

When the silica particles are contained in the gel, the solvent replacement step is not necessary. The estimated mechanism is as follows. That is, the silicon dioxide particles function as a support for a three-dimensional mesh-like skeleton, and 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 supplied to the drying step without replacing the solvent used for washing. In this way, by using silicon dioxide particles, the cleaning and solvent replacement steps to the drying step can be simplified.

(Drying step) In the drying step, the wet gel that has been washed and (if necessary) replaced with a solvent is dried as described above. Thereby, an aerogel (aerogel block or aerogel particle) can be obtained. That is, an aerogel obtained by drying a wet gel produced from the sol can be obtained.

The method of drying is not particularly limited, and known atmospheric pressure drying, supercritical drying, or freeze drying can be used. Among these methods, normal-pressure drying or supercritical drying can be used from the viewpoint of easily producing a low-density aerogel. In addition, from the viewpoint that production can be performed at low cost, atmospheric pressure drying can be used. In this embodiment, the normal pressure means 0.1 MPa (atmospheric pressure).

Aerogels can be obtained by drying the wet gel that has been washed and (if necessary) replaced with a solvent at a temperature below the critical point of the solvent used in the drying and at atmospheric pressure. The drying temperature varies depending on the type of the solvent to be replaced (the solvent used for cleaning without solvent replacement), but in view of the existence of drying, especially at high temperatures, the evaporation rate of the solvent is accelerated, resulting in a large gel. In the case of cracking, the temperature can be set to 20 ° C to 150 ° C. The drying temperature may be 60 ° C to 120 ° C. The drying time varies depending on the capacity of the wet gel and the drying temperature, and it can be set to 4 to 120 hours. In addition, the case where the drying is accelerated by applying a pressure less than the critical point in a range not hindering productivity is also included in the normal-pressure drying.

In addition, aerogels can also be obtained by supercritical drying the wet gel that has been washed and (if necessary) replaced with a solvent. Supercritical drying can be performed by a known method. The method of performing supercritical drying includes, for example, 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, a method of performing supercritical drying includes a method of immersing a wet gel in liquefied carbon dioxide under conditions of, for example, 20 ° C to 25 ° C and about 5 MPa to 20 MPa, thereby containing the wet gel All or a part of the solvent is replaced with carbon dioxide whose critical point is lower than the solvent, and then the carbon dioxide is removed alone, or a mixture of carbon dioxide and the solvent is removed.

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

(Grinding step) Without performing the wet gel pulverizing step, the aerogel (aerogel block) obtained by drying is pulverized to obtain aerogel particles. For example, it can be performed by putting aerogel into a jet mill, a roll mill, a bead mill, a hammer mill, and the like, and operating at a moderate rotation speed and time.

<Dispersion liquid> The dispersion liquid contains aerogel particles having a specific surface area of 350 m ² / g or less, and a dispersion medium. The dispersion liquid may be one obtained by dispersing the aerogel particles in a dispersion medium. The pores of the aerogel particles in the dispersion may be filled with a dispersion medium.

Examples of the dispersion medium include organic solvents. The organic solvent is not particularly limited as long as it can disperse the aerogel particles, and examples thereof include aromatics such as toluene, xylene, mesitylene, cumene, and p-cymene. Hydrocarbons; aliphatic hydrocarbons such as hexane, heptane, pentane; ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane; methanol, ethanol, isopropanol, butanol, ethylene glycol, propylene glycol, etc. Alcohols; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone; methyl acetate, ethyl acetate, butyl acetate And other esters; N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, and other amines. Among these, from the viewpoints of volatility and boiling point, alcohols and ketones can be used, and particularly alcohols can be preferably used. Alcohols and ketones are easy to mix with water, water-based resins, etc., so they are also preferred when used in combination with these ingredients.

From the viewpoints of dispersibility, the filling amount of the aerogel particles, and the viscosity of the dispersion liquid, the content of the aerogel particles in the dispersion liquid may be set to 0.1% by mass to 30% by mass, but may also be 1% by mass to 25% by mass.

Such a dispersion liquid may also be referred to as a coating liquid. The coating liquid containing the aerogel particles and the dispersion medium is applied to the object, and then the dispersion medium is volatilized and removed to form a coating film containing the aerogel particles on the object. In the preparation of the coating liquid, from the viewpoint of improving the film-forming properties and thermal insulation properties of the coating film, an adhesive component, a fibrous component, and the like may be further added. [Example]

Next, the present invention is further described in detail by the following examples, but these examples do not limit the present invention.

(Example 1) 100.0 parts by mass of PL-2L (manufactured by Fuso Chemical Industry Co., Ltd.) as a raw material containing silicon dioxide particles, 80.0 parts by mass of water, and 0.5 parts by mass of an acid catalyst Acetic acid, 1.0 part by mass of cetyltrimethylammonium bromide (manufactured by Wako Pure Chemical Industries, Ltd.) as a cationic surfactant, and 150.0 parts by mass of urea as a thermally hydrolyzable compound were mixed, and 60.0 parts by mass of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KBM-13) and 20.0 parts by mass of dimethyldimethoxysilane (Shin-Etsu Chemical Industry Co., Ltd.) as silicon compounds were added thereto. Co., Ltd., product name: KBM-22), 20.0 parts by mass of a two-terminal difunctional alkoxy-modified polysiloxane compound having a structure represented by the general formula (B) (hereinafter referred to as "poly The siloxane compound A ") was reacted at 25 ° C for 2 hours to obtain a sol. The obtained sol was gelatinized at 60 ° C, and then matured at 60 ° C for 48 hours to obtain a wet gel 1.

The "polysiloxane compound A" was synthesized as follows. First, in a 1-liter three-necked flask including a stirrer, a thermometer, and a Daimler cooling tube, 100.0 parts by mass of dimethylpolysiloxane XC96-723 (Momentive, Japan) Performance Materials Japan) (manufactured by the contract company, product name), 181.3 parts by mass of methyltrimethoxysilane and 0.50 parts by mass of third butylamine were mixed and reacted at 30 ° C for 5 hours. Thereafter, the reaction liquid was heated under reduced pressure of 1.3 kPa at 140 ° C for 2 hours to remove volatile components, thereby obtaining a di-functional alkoxy-modified polysiloxane compound (polysiloxane compound at both ends). A).

After that, the obtained wet gel 1 was transferred to a plastic bottle and sealed, and then was used an Extreme Mill (manufactured by AS ONE Co., Ltd., MX-1000XTS) at 27,000 rpm The powder was pulverized for 10 minutes to obtain a particulate wet gel. The obtained particulate wet gel was immersed in 2500.0 parts by mass of methanol, and washed at 25 ° C. for 24 hours. This washing operation was performed a total of 3 times while changing to new methanol. Next, the washed particulate wet gel was immersed in 2500.0 parts by mass of heptane as a low surface tension solvent, and the solvent was replaced at 25 ° C. for 24 hours. This solvent replacement operation was performed a total of 3 times while changing to new heptane. The washed and solvent-replaced particulate wet gel was dried under normal pressure at 40 ° C for 96 hours, and then further dried at 150 ° C for 2 hours. Finally, it was applied to a sieve (manufactured by Tokyo Screen Co., Ltd., with a hole diameter of 45 μm and a wire diameter of 32 μm) to obtain a structure represented by the general formula (3), general formula (4), and general formula (5). Of aerogel particles 1. The average particle diameter D50 of the aerogel particles 1 was 24.3 μm. The measurement method is as follows.

The content of the aerogel particles was added to ethanol so that the content of the aerogel particles became 0.5% by mass, and then a 50 W ultrasonic homogenizer was used to shake them for 20 minutes to prepare a dispersion. 10 mL of the obtained dispersion was poured into Microtrac MT3000 (manufactured by Nikkiso Co., Ltd., product name), and the particle diameter was measured at 25 ° C. with a refractive index of 1.3 and an absorption of 0. Then, the particle diameter at 50% (volume basis) of the cumulative value in the obtained particle size distribution was set as the average particle diameter D50.

(Example 2) 100.0 parts by mass of PL-2L, 60.0 parts by mass of water, 0.10 parts by mass of acetic acid, 20.0 parts by mass of cetyltrimethylammonium bromide, and 60.0 parts by mass of methyltrimethoxysilane were added. , 20.0 parts by mass of dimethyldimethoxysilane, and 20.0 parts by mass of the polysiloxane compound A were reacted at 25 ° C. for 2 hours to obtain a sol. 40.0 parts by mass of a 5% strength sodium carbonate aqueous solution as an alkali catalyst was added to the obtained sol, and gelation was performed at 60 ° C, followed by aging at 80 ° C for 24 hours to obtain wet gel 2. Thereafter, using the obtained wet gel 2, it was performed in the same manner as in Example 1 to obtain aerogel particles 2 having a structure represented by the general formula (3), general formula (4), and general formula (5). . The average particle diameter D50 of the aerogel particles 2 was 14.2 μm.

(Example 3) 30.0 parts by mass of XR31-B1410 (manufactured by Momentive Performance Materials Japan) as a polysiloxane compound, 15.0 parts by mass of dimethyldimethoxysilane, 100.0 parts by mass of 2-propanol, 20.0 parts by mass of water, and 0.05 parts by mass of acetic acid were reacted at 25 ° C for 4 hours to obtain a sol. 40.0 parts by mass of a 5% strength ammonium carbonate aqueous solution as an alkali catalyst was added to the obtained sol, and gelation was performed at 60 ° C, followed by aging at 60 ° C for 72 hours to obtain a wet gel 3. Then, using the obtained wet gel 3, it carried out similarly to Example 1, and obtained the aerogel particle 3 which has a structure represented by the said General formula (4) and General formula (5) at least. The average particle diameter D50 of the aerogel particles 3 was 19.7 μm.

(Comparative Example 1) To 10 parts by mass of water glass (manufactured by Fuji Chemical Co., Ltd .: SiO ₂ ; 8.0 wt%, 2Na ₂ O ･ 3SiO ₂ ･ mH ₂ O) was added 20 parts by mass of an H-type ion exchange resin ( Sumika Chemtex Co., Ltd., Duolite C20), and stirred until the pH of the solution became 1.5. Next, after the ion exchange resin was separated by filtration, 400 parts by mass of ammonia water (manufactured by Kanto Chemical Co., Ltd., special grade, 1 mol / L) was added to adjust the pH to 4.0. This was gelatinized at room temperature for 20 minutes, and then matured at 50 ° C for 24 hours to obtain a wet gel.

The obtained wet gel was immersed in 2500.0 parts by mass of ethanol and washed at 50 ° C for 24 hours. This washing operation was performed a total of 3 times while changing to new methanol. Next, the washed wet gel was immersed in 2500.0 parts by mass of n-hexane as a low surface tension solvent, and the solvent was replaced at 50 ° C for 24 hours. This solvent replacement operation was performed a total of 3 times while changing to new n-hexane. Thereafter, trimethylchlorosilane was added to the hexane solution in an amount of 0.05 parts by mass based on 1 part by mass of the wet gel, and the wet gel was subjected to hydrophobic treatment at 50 ° C for 24 hours. Then, the wet gel was immersed again in 2500.0 parts by mass of n-hexane, and the solvent was replaced at 50 ° C for 24 hours. The wet gel with solvent replacement was transferred to a plastic bottle and sealed, and then pulverized at 27,000 rpm for 10 minutes using an extreme mill (manufactured by AS ONE Co., Ltd., MX-1000XTS). A granular wet gel was obtained.

The obtained particulate wet gel was dried at normal pressure at 40 ° C for 96 hours, and then further dried at 150 ° C for 2 hours. Finally, it was applied to a sieve (manufactured by Tokyo Screen Co., Ltd., having a pore diameter of 45 μm and a wire diameter of 32 μm) to obtain aerogel particles 4. The average particle diameter D50 of the aerogel particles 4 was 21.5 μm.

(Comparative Example 2) The solution of No. 3 sodium silicate was diluted and adjusted to a concentration of SiO ₂ : 80 g / L and Na ₂ O: 27 g / L. The diluted sodium silicate solution was passed through a strongly acidic cation exchange resin IR120B (manufactured by Rohm & Haas Co., Ltd., product name) to obtain 100 parts by mass of silica sol. The silica sol had a pH of 2.8.

While stirring the silica sol, 0.1% ammonia water was added dropwise to adjust the pH of the silica sol to 5.5. The silica sol gelled after a few minutes. The container in which the gel was put was kept at 50 ° C. for 12 hours, thereby being aged, to obtain a wet gel. Thereafter, the obtained wet gel was immersed in 2500.0 parts by mass of ethanol, and washed at 50 ° C. for 24 hours. This washing operation was performed a total of 3 times while changing to new methanol. Next, the washed wet gel was immersed in 2500.0 parts by mass of n-hexane as a low surface tension solvent, and the solvent was replaced at 50 ° C for 24 hours. This solvent replacement operation was performed a total of 3 times while changing to new n-hexane. Thereafter, dimethyldichlorosilane was added to the hexane solution in an amount of 0.12 parts by mass based on 1 part by mass of the wet gel, and the wet gel was subjected to hydrophobic treatment at 50 ° C for 24 hours. Then, the wet gel was immersed again in 2500.0 parts by mass of n-hexane, and the solvent was replaced at 50 ° C for 24 hours. The wet gel with solvent replacement was transferred to a plastic bottle and sealed, and then pulverized at 27,000 rpm for 10 minutes using an extreme mill (manufactured by AS ONE Co., Ltd., MX-1000XTS). A granular wet gel was obtained. The obtained particulate wet gel was dried at normal pressure at 40 ° C for 96 hours, and then further dried at 150 ° C for 2 hours. Finally, it was applied to a sieve (manufactured by Tokyo Screen Co., Ltd., having a pore diameter of 45 μm and a wire diameter of 32 μm) to obtain aerogel particles 5. The average particle diameter D50 of the aerogel particles 5 was 17.3 μm.

(Comparative Example 3) As the aerogel particles 6, JIOS AeroVa (registered trademark, manufactured by JIOS AEROGEL CORPORATION, product name) was prepared. The average particle diameter D50 of the aerogel particles 6 was 8.7 μm.

The aerogel particles obtained in the examples and comparative examples were measured and evaluated as follows. The evaluation results are shown in Table 1.

(Specific Surface Area Measurement) The BET specific surface area of the aerogel particles was measured using a gas adsorption amount measuring device (Autosorb-iQ (Autosorb is a registered trademark) manufactured by a contract company of Quantachrome Instruments Japan).

(Dispersibility evaluation) 4 g of 2-propanol as a dispersion medium was placed in a 9 mL spiral tube, and 1 g of aerogel particles were put therein, and stirred for 30 seconds using a vortex mixer to prepare a dispersion liquid. The agitated dispersion was visually observed, and the dispersibility of the aerogel particles was evaluated. A case where the aerogel particles were well dispersed and fluidity in the dispersion liquid was set as A evaluation, and a case where the aerogel particles were agglomerated without being dispersed and agglomerated and had no fluidity in the dispersion liquid was set as B evaluation.

[Table 1]

(Other evaluations) The aerogel particles of Example 1 were used to prepare a coating liquid, and the film-forming properties, adhesion properties, and thermal insulation properties of the obtained coating films were evaluated. First, 10 g of aerogel particles, 1 g of chopped strand glass CS 3DE-256 (manufactured by Nittobo Industries Ltd., product name), and carboxymethyl cellulose were added to 50 g of isopropyl alcohol. 1 g of ammonium (manufactured by Wako Pure Chemical Industries, Ltd.) was stirred at 300 rpm for 10 minutes using a three-in-one motor. Then, 50 g of water was added, and it stirred at 300 rpm for 10 minutes, and prepared the coating liquid. This coating liquid was applied on a 12 μm aluminum foil using a metal pressure spoon so that the thickness became 1 mm, and dried at 120 ° C. for 1 hour to obtain a coating film.

The obtained coating film had a good appearance without cracks. Moreover, even if the aluminum foil as a base material was stood upright, peeling of a coating film was not observed. Furthermore, the thermal insulation of the coating film was evaluated by the steady-state method. As a result, the thermal conductivity was sufficiently low (0.035 W / m · K).

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Claims (4)

A dispersion liquid comprising: aerogel particles having a specific surface area of 350 m ² / g or less; and a dispersion medium. The dispersion liquid according to item 1 of the patent application scope, wherein the dispersion medium comprises an organic solvent. An aerogel particle having a specific surface area of 350 m ² / g or less. The aerogel particles according to item 3 of the patent application scope, which are used for preparing a dispersion.