Method for manufacturing organic-inorganic hybrid aerogels

Abstract

This invention provides a method for producing an organic-inorganic hybrid aerogel, in which a low-density organic-inorganic hybrid aerogel (dry gel) can be obtained by properly treating a wet gel using means other than washing. [Solution] A method for producing an organic-inorganic hybrid aerogel having a skeleton with a network structure of Si-O-Si bonds, wherein the -C bond portion of the Si-C bond, in which C is bonded to at least a portion of the Si constituting the Si-O-Si bond, is present at least inside the skeleton, the method comprising a neutralization step of neutralizing an organic-inorganic hybrid wet gel obtained by a sol-gel method.

Description

[Technical Field]

[0001] This invention relates to a method for producing organic-inorganic hybrid aerogels. [Background technology]

[0002] Aerogels have a mesoscale, uniform porous structure, high porosity (typically over 90%), and low bulk density (0.004-0.500 g / cm³). 3 ), it is a material that has extremely low thermal conductivity (20 mW / mK or less).

[0003] Silica aerogel, a representative aerogel containing Si, has low thermal conductivity, low dielectric constant, and high specific surface area, making it suitable for various applications such as thermal insulation, insulating materials, and adsorbents. Silica aerogel has a framework composed of amorphous silica (SiO2), and generally has a three-dimensional network structure consisting of Si-O-Si bonds.

[0004] Silica aerogels are generally produced by the sol-gel method. In the sol-gel method, for example, a sol is obtained by hydrolyzing a monomer solution of a silane compound, and then this sol is subjected to a condensation reaction to obtain a wet gel (condensed compound) having a microstructure that forms the basis of pores with small diameters. Next, the wet gel is dried to obtain an aerogel (dried gel) having a large number of fine pores. A manufacturing method for silica aerogels by the sol-gel method is disclosed, for example, in Patent Document 1.

[0005] Furthermore, while silica aerogels often undergo hydrophobic treatment on the surface of their microstructure for stabilization, a key characteristic is the presence of a large number of uncondensed silanol groups (Si-OH) in the internal structure, which consists of Si-O-Si bonds. Due to its structure, silica aerogels are very brittle and easily broken, and consequently, the silanol groups remaining inside the framework become exposed, leading to performance degradation due to moisture absorption.

[0006] In response to the problems of silica aerogels, organic-inorganic hybrid aerogels have attracted attention as aerogels developed to address these issues. Here, organic-inorganic hybrid aerogels consist of a skeleton with a network structure of Si-O-Si bonds, where at least some of the Si atoms constituting the Si-O-Si bonds are bonded to C, and the -C bond portion of these Si-C bonds exists at least within the skeleton. Here, "within the skeleton" refers to the interior of the three-dimensional structure when three or more Si-O-Si bonds constituting the skeleton are sterically bonded. Furthermore, "-C bond portion" refers to the non-Si portion of the Si-C bond.

[0007] An example of this organic-inorganic hybrid aerogel is polymethylsilsesquioxane (PMSQ) aerogel, which is obtained by hydrolysis and polycondensation of methyltrimethoxysilane (MTMS), a trifunctional silane compound having a methyl group as an organic substituent.

[0008] Organic-inorganic hybrid aerogels, like silica aerogels, possess properties such as low thermal conductivity, low dielectric constant, and high specific surface area. Furthermore, compared to silica aerogels, organic-inorganic hybrid aerogels generally have a lower crosslinking density and significantly fewer residual silanol groups during manufacturing. As a result, organic-inorganic hybrid aerogels have advantages over silica aerogels, such as superior mechanical flexibility, higher fracture resistance, and less performance degradation due to moisture absorption.

[0009] A manufacturing method for producing an organic-inorganic hybrid aerogel by the sol-gel method is disclosed, for example, in Patent Document 2. Specifically, Patent Document 2 discloses a process of (a) performing in one step a reaction for generating a sol using a silicon compound and a surfactant and a reaction for gelling the sol, and (b) drying the gel formed by the step (a). A manufacturing method for an alkylsiloxane aerogel including these steps is disclosed. Further, in the examples of Patent Document 2, it is disclosed that a solvent substitution treatment (washing treatment) of immersing a wet gel in methanol is performed multiple times for a total of 72 hours, and then a drying treatment is carried out.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] In aerogels such as organic-inorganic hybrid aerogels, many properties such as high heat insulation properties and low dielectric properties are manifested based on the fact that the porosity is very high and the microstructure has a pore diameter of 100 nm or less. Therefore, aerogels are generally preferably of low density.

[0012] The density of aerogels (dry gels) tends to increase if additives such as polycondensation catalysts and surfactants used during the preparation of the wet gel remain in the pores of the wet gel. This is thought to be because the pores irreversibly contract or collapse due to the attractive interactions of impurities remaining in the pores, and this tendency is more pronounced the finer the porous structure of the gel. To obtain a low-density aerogel, solvent replacement treatment (washing treatment) is generally performed to reduce the concentration of additives remaining in the pores of the wet gel. However, aerogels have very small pores, and diffusion of substances does not occur easily. Therefore, washing treatment is usually carried out using a large amount of solvent over a long period of time, ranging from several hours to tens of hours.

[0013] However, the cleaning process, which involves using large amounts of solvent and taking a long time, has been a factor in increasing the manufacturing cost of aerogels. On the other hand, if the amount of solvent or cleaning time is reduced in the cleaning process, the cleaning process becomes insufficient, and the density of the aerogel (dry gel) tends to increase. In other words, if the cleaning process is insufficient, it becomes impossible to manufacture a low-density aerogel with good performance, or a defective product with increased density is produced, resulting in a poor yield. Organic-inorganic hybrid aerogels exhibit mechanical flexibility due to their lower crosslinking density, but their elasticity tends to decrease, and density increases due to shrinkage and pore breakdown are likely to occur during the manufacturing process, making this problem particularly pronounced.

[0014] Therefore, there is a need for a method to produce low-density organic-inorganic hybrid aerogels (dry gels), particularly those with very fine porous structures, from wet gels using methods other than washing. However, no such method has been known to date.

[0015] This invention has been made in view of the above circumstances, and aims to provide a method for producing an organic-inorganic hybrid aerogel (dry gel) by properly treating a wet gel using means other than washing. [Means for solving the problem]

[0016] To achieve the above objective, the gist of the present invention is as follows.

[0017] (1) A method for producing an organic-inorganic hybrid aerogel having a skeleton with a network structure of Si-O-Si bonds, wherein the -C bond portion of the Si-C bond, in which C is bonded to at least a portion of the Si constituting the Si-O-Si bond, is present at least inside the skeleton, A method for producing an organic-inorganic hybrid aerogel, characterized by including a neutralization step of neutralizing an organic-inorganic hybrid wet gel obtained by the sol-gel method.

[0018] (2) The wetted gel is a basic organic-inorganic hybrid wetted gel, The method for producing an organic-inorganic hybrid aerogel according to (1) above, characterized in that the neutralization step is to neutralize the basic organic-inorganic hybrid wet gel with an acid.

[0019] (3) The organic-inorganic hybrid aerogel is a bulk material, and the density of the bulk material is 0.3 g / cm³. 3 A method for producing an organic-inorganic hybrid aerogel as described in (1) or (2) above, characterized in that the pore size peak by the BJH method is 100 nm or less.

[0020] (4) The organic-inorganic hybrid aerogel is in the form of granules or powder and has a tap density of 0.2 g / cm³ 3 A method for producing an organic-inorganic hybrid aerogel according to (1) or (2) above, characterized in that the pore size peak by the BJH method is 100 nm or less.

[0021] (5) Before the neutralization step, A sol generation step involves generating an organic-inorganic hybrid sol by performing at least one of hydrolysis and polycondensation on a silane compound containing at least an alkylalkoxysilane, A wet gel formation step of generating an organic-inorganic hybrid wet gel from the sol in the presence of a basic catalyst, A method for producing an organic-inorganic hybrid aerogel according to (1) or (2) above, further comprising the above.

[0022] (6) The method for producing an organic-inorganic hybrid aerogel according to (1) or (2) above, characterized in that the neutralization treatment in the neutralization step involves adding a neutralizing agent in an amount of 0.5 molar equivalents or more relative to hydrogen ions or hydroxide ions in the wet gel.

[0023] (7) A sol generation step to produce an organic-inorganic hybrid sol by performing at least one of hydrolysis and polycondensation on a silane compound containing an alkylalkoxysilane having at least a Si-CH3 bond, A wet gel generation step in which an organic-inorganic hybrid wet gel is generated from the organic-inorganic hybrid sol by a sol-gel reaction, A method for producing an organic-inorganic hybrid aerogel according to (1) or (2) above, further comprising the above. [Effects of the Invention]

[0024] According to the present invention, a method for producing an organic-inorganic hybrid aerogel (dry gel) is provided, which involves properly treating an organic-inorganic hybrid wet gel using means other than washing, thereby obtaining a low-density organic-inorganic hybrid aerogel (dry gel) having a fine porous structure. This significantly reduces the amount of solvent used compared to conventional methods, leading to cost reduction. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described in detail below.

[0026] [Method for manufacturing organic-inorganic hybrid aerogels] The present invention provides a method for producing an organic-inorganic hybrid aerogel, which consists of a skeleton having a network structure of Si-O-Si bonds, and in which at least a portion of the Si constituting the Si-O-Si bonds is bonded to C, the -C bond portion of the Si-C bond is present at least inside the skeleton.

[0027] (Organic-inorganic hybrid aerogel) <Skeletal structure> The organic-inorganic hybrid aerogel is an aerogel having a skeleton with a network structure of Si-O-Si bonds, in which the -C bond portion of the Si-C bond, where C is bonded to at least some of the Si constituting the Si-O-Si bond, exists at least inside the skeleton. The network structure is, for example, a three-dimensional network structure.

[0028] Organic-inorganic hybrid aerogels are characterized by having Si-C bonds, which are organic components, in their framework, and that Si-C bonds exist not only on the surface of the framework but also inside the framework. In this invention, "inside the framework" refers to the interior of the three-dimensional space formed by the bonding of multiple frameworks. In this invention, "Si-C bonds exist inside the framework" means that at least a portion of the Si-C bonds are present inside the framework. Silica aerogels may contain organic components on the framework surface due to hydrophobic treatment, but the Si-O-Si network inside the framework does not contain organic components such as Si-C bonds, and has a rigid, inflexible framework derived from silica (SiO2). In contrast, organic-inorganic hybrid aerogels have Si-C bonds as organic components even inside the framework, and due to the reduced crosslinking density of the Si-O-Si network structure and the physical properties derived from the organic components, their framework is highly flexible.

[0029] If we define the constituent units of the molecular structure that makes up the skeleton as follows: a Q unit is formed when one Si atom is bonded to four O atoms; a T unit is formed when one Si atom is bonded to three O atoms; a D unit is formed when one Si atom is bonded to two O atoms; and an M unit is formed when one Si atom is bonded to one O atom, then the Si-O-Si network structure consists of any combination of Q, T, D, and M units. In organic-inorganic hybrid aerogels, the Si-O-Si network structure contains at least one of the T, D, and M units. Note that Si-C bonds are included within these T, D, and M units.

[0030] The framework of an organic-inorganic hybrid aerogel may have bonds other than Si-O-Si bonds in a network structure as bonds that form its network structure. Here, "network structure" refers to a structure in which long-distance structures are formed by crosslinking, and does not include uncrosslinked side-chain structures such as Si-CH3. Examples of such bonds other than Si-O-Si bonds include CC bonds, C=C bonds, CN bonds, imide bonds, amide bonds, Al-O-Al bonds, Fe-O-Fe bonds, etc. In organic-inorganic hybrid aerogels, shrinkage and pore collapse are less likely to occur during the manufacturing process and after drying, and the gel can exist as a low-density structure after drying. This is largely due to the formation of stable and strong Si-O-Si bonds. Therefore, the framework of an organic-inorganic hybrid aerogel preferably contains 30% or more by mass, more preferably 50% or more by mass, and even more preferably 70% or more by mass of Si-O-Si bonds to form stable and strong Si-O-Si bonds. Here, the mass ratio of Si-O-Si bonds in the organic-inorganic hybrid aerogel skeleton is the ratio of the total mass of Si and O constituting the Si-O-Si bonds to the total mass of the skeleton.

[0031] Examples of carbon-containing groups that constitute Si-C bonds include non-crosslinking groups such as methyl, ethyl, vinyl, propyl, isopropyl, allyl, butyl, aminopropyl, and phenyl groups; polyvinyl groups; polyallyl groups; and crosslinking groups such as ethylene crosslinking groups (Si-CH2-CH2-Si), ethenylene crosslinking groups (Si-CH=CH-Si), and hexylene crosslinking groups (Si-(CH2)6-Si). Of these, methyl groups are particularly preferred because they easily form a dense structure while reducing the crosslinking density of the network from the viewpoint of steric hindrance, and it is easy to obtain a flexible and strong low-density aerogel even with a fine porous structure.

[0032] The carbon-containing groups that constitute the Si-C bond consist of one or more types.

[0033] The amount of carbon-containing groups constituting the Si-C bond is not particularly limited, but in order for the organic-inorganic hybrid aerogel to have better flexibility and durability despite its low density, the amount of C relative to Si should be, for example, 10% or more, preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more.

[0034] The shape of the skeleton in the porous structure of organic-inorganic hybrid aerogels is not particularly limited and can be, for example, particle-linked, fibrous, columnar, sheet-like, etc. The skeleton shape may consist of one type or a combination of two or more types.

[0035] The size of the skeleton is, for example, an average thickness of 1 nm to 200 nm. However, as the size of the aerogel skeleton increases, problems such as a decrease in thermal insulation due to the increase in pore diameter and a decrease in specific surface area arise. For this reason, in order for an organic-inorganic hybrid aerogel to have sufficient thermal insulation and sufficient adsorption properties, the upper limit of the average thickness of the skeleton is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less.

[0036] <shape> The form of the organic-inorganic hybrid aerogel is not particularly limited and includes, for example, granules, powders, and bulk materials. Here, granules refer to powders with large particle sizes. Bulk materials refer to materials in a lump-like form. Examples of bulk materials include plates and columns. In the present invention, granules refer to materials that are granular in form, have a particle size for which measuring bulk density is difficult and for which measuring density by tapping density is preferable, and do not fall under the definition of powder described later. Specifically, granules refer to materials that are granular in form, have a particle size of 1 mm or less, and do not fall under the definition of powder described later. For this reason, in the present invention, even if a material is granular, particles with a particle size exceeding 1 mm are defined as bulk materials. Furthermore, even if a material is granular in form and has a particle size of 1 mm or less, if it falls under the definition of powder described later, it is defined as powder. Furthermore, as described later, bulk materials, granulated materials, and powders may be measured using both bulk density and tap density if measurable. However, it is preferable to evaluate the density of bulk materials primarily using bulk density, and granulated materials and powders primarily using tap density.

[0037] Granular organic-inorganic hybrid aerogels can be obtained, for example, by coarsely grinding a bulk organic-inorganic hybrid aerogel using a known grinder.

[0038] If the organic-inorganic hybrid aerogel is in granular form, the particle size of the granules is classified to a particle size of 1 mm or less, for example, 0.1 to 1 mm.

[0039] When the organic-inorganic hybrid aerogel is in powder form, the particle size of the powder is classified to, for example, less than 0.1 mm. Also, the average particle size D of the powder is... 50 For example, this is between 0.01 μm and less than 0.1 mm.

[0040] Organic-inorganic hybrid aerogels can form composites with other materials. Examples of such materials include fiber-based materials such as glass wool and nonwoven fabrics, cellulose nanofibers, and hollow silica particles. In this case, the aerogel portion extracted from the composite corresponds to the organic-inorganic hybrid aerogel.

[0041] <Pore> Organic-inorganic hybrid aerogels have pores, which are spaces formed between the framework.

[0042] The pores are not particularly limited, but their average pore diameter is, for example, between 1 nm and 200 nm. Here, the average pore diameter is the average inner diameter of a tube, assuming the pores are approximated to be tubular.

[0043] The lower limit of the average pore diameter is not particularly limited and may be, for example, 1 nm or more, or 5 nm or more. The upper limit of the average pore diameter is not particularly limited, but for example, it is 200 nm or less. In order for the organic-inorganic hybrid aerogel to have a low thermal conductivity suitable as an insulating material, it is preferably 100 nm or less, more preferably 85 nm or less, and even more preferably 70 nm or less.

[0044] Since the pores of organic-inorganic hybrid aerogels are typically distributed over a wide range from nanometers to micrometers, evaluation based on pore size distribution is preferred. The pore size distribution can be determined, for example, by calculation using the BJH method from nitrogen adsorption isotherms. In this case, the pore size peak obtained by the BJH method is, for example, 100 nm or less, preferably 80 nm or less, and more preferably 60 nm or less. It is preferable for the pore size peak to be within the above range because, for example, the thermal conductivity tends to be low.

[0045] <Porosity> The porosity of the organic-inorganic hybrid aerogel, that is, the ratio of the pore volume of the pores in the total volume of the aerogel, is not particularly limited, but for example, it is 70% or more, and may be 75% or more, 80% or more, 85% or more, or 90% or more. In order for the organic-inorganic hybrid aerogel to have a sufficiently low thermal conductivity and a sufficiently low dielectric constant, the porosity of the organic-inorganic hybrid aerogel is preferably 80% or more.

[0046] <Density> The density (bulk density) of the organic-inorganic hybrid aerogel as a bulk body is, for example, 0.5 g / cm 3 or less. Here, the bulk density of the organic-inorganic hybrid aerogel can be obtained by calculating weight / volume from its weight and volume values. As the volume value, for example, a numerical value obtained by the rapeseed displacement method can be used. When the bulk density of the organic-inorganic hybrid aerogel is preferably 0.4 g / cm 3 or less, more preferably 0.3 g / cm 3 or less, the organic-inorganic hybrid aerogel is likely to have good heat insulation properties, high porosity, etc.

[0047] Note that when the size of the aerogel becomes small, such as a granular body with a particle size of 1 mm or less or a powder, it is difficult to know the exact volume value, so the evaluation of the bulk density is usually difficult. Therefore, in the present invention, for the density of the granular body or powder of the organic-inorganic hybrid aerogel, it is evaluated by the tap density. The tap density of the organic-inorganic hybrid aerogel is, for example, 0.4 g / cm 3 or less. When the tap density of the granular body or powder of the organic-inorganic hybrid aerogel is preferably 0.3 g / cm 3 or less, more preferably 0.2 g / cm 3 or less, the granular body or powder of the organic-inorganic hybrid aerogel is likely to have good heat insulation properties, high porosity, etc.

[0048] When an organic-inorganic hybrid aerogel possesses typical aerogel properties such as high thermal insulation (low thermal conductivity) and low dielectric constant, it is usually required to have a low density (for example, a bulk density of 0.3 g / cm³). 3 Below; if tap density is 0.2 g / cm³ 3 The following are preferred: the organic-inorganic hybrid aerogel has a small pore size (for example, a pore size peak of 100 nm or less by the BJH method). Such low-density organic-inorganic hybrid aerogels with small pore sizes have a very dilute structure consisting of a minute porous structure. For this reason, low-density organic-inorganic hybrid aerogels with small pore sizes are much more susceptible to shrinkage and pore damage during the manufacturing process compared to aerogels with relatively large pore sizes or high-density (more dense) aerogels. Consequently, in conventional manufacturing methods for low-density organic-inorganic hybrid aerogels with small pore sizes, performance degradation due to increased density was easily achieved unless processes such as washing and drying were carried out more carefully and cautiously. In contrast, the manufacturing method of the present invention was completed based on the discovery that even such delicate organic-inorganic hybrid aerogels with small pore sizes can be easily made low-density by incorporating a neutralization step, thereby easily obtaining low-density organic-inorganic hybrid aerogels with small pore sizes.

[0049] The present invention relates to a method for producing an organic-inorganic hybrid aerogel, which involves using an organic-inorganic hybrid wet gel obtained by the sol-gel method. Here, an organic-inorganic hybrid wet gel refers to a wet gel from which an "organic-inorganic hybrid aerogel" is obtained by drying. Specifically, an organic-inorganic hybrid wet gel refers to a wet gel consisting of a skeleton with a network structure of Si-O-Si bonds, where at least a portion of the Si constituting the Si-O-Si bonds is bonded to C, and where the -C bond portion of the Si-C bond is present at least inside the skeleton. Specifically, the present invention relates to a method for producing an organic-inorganic hybrid aerogel, which includes a neutralization step of neutralizing the organic-inorganic hybrid wet gel obtained by the sol-gel method.

[0050] In the method for producing the organic-inorganic hybrid aerogel of the present invention, steps other than the neutralization step are not particularly limited. However, from the viewpoint of ease of production and the quality of the resulting aerogel, the method described below is preferred for producing the organic-inorganic hybrid aerogel of the present invention.

[0051] An example of a preferred method for producing the organic-inorganic hybrid aerogel of the present invention includes the following steps: a sol formation step, a wet gel formation step, a neutralization step, and a drying step. The sol formation step is a step of producing an organic-inorganic hybrid sol containing a dispersed phase having Si-O-Si bonds and Si-C bonds in which C is bonded to at least a portion of the Si constituting the Si-O-Si bonds. The wet gel formation step is a step of producing an organic-inorganic hybrid wet gel. The neutralization step is a step of neutralizing at least a portion of the organic-inorganic hybrid wet gel with an acidic or basic substance. The drying step is a step of drying the organic-inorganic hybrid wet gel that has been neutralized. The preferred method for producing the organic-inorganic hybrid aerogel of the present invention is not particularly limited to steps other than the sol formation step, the wet gel formation step, the neutralization step, and the drying step, as long as the aforementioned organic-inorganic hybrid aerogel can be produced. The preferred method for producing the organic-inorganic hybrid aerogel of the present invention may optionally include, for example, a washing step for washing the organic-inorganic hybrid wet gel, a mixing step with a fiber material, etc. The following provides a detailed explanation of each step.

[0052] (Sol formation process) The sol formation process involves generating a sol using a silicon compound, which is the main raw material for the organic-inorganic hybrid wetted gel. The sol formation process is performed before the neutralization process.

[0053] More specifically, the sol formation process is a process of generating an organic-inorganic hybrid sol containing a dispersed phase comprising Si-O-Si bonds and Si-C bonds, in which at least some of the Si constituting the Si-O-Si bonds are bonded to C. If the polymerization reaction of the dispersed phase in the sol generated in this process is continued, a sol-gel transition occurs, and an organic-inorganic hybrid wet gel can be obtained.

[0054] The sol can be produced by using a silicon compound containing a silane compound having an organic substituent as a precursor of the dispersed phase, and appropriately hydrolyzing and polycondensing the silicon compound in a dispersion medium consisting of at least one of water and an organic solvent. Alternatively, the sol can be produced, for example, by subjecting the silane compound to at least one of hydrolysis and polycondensation.

[0055] Examples of silicon compounds that can be used include alkali metal silicates such as potassium silicate and sodium silicate; and silane compounds such as alkoxysilanes, chlorosilanes, and silazanes. Of these, silane compounds are preferred from the viewpoint of stability, ease of reaction control, and ease of manufacture, and alkoxysilanes are particularly preferred.

[0056] The silicon compound can be used alone or in combination of two or more. The dispersed phase in the organic-inorganic hybrid sol is equipped with Si-C bonds. Therefore, in order to prepare a dispersed phase equipped with Si-C bonds, it is preferable to use at least a silane compound having Si-C bonds as a raw material for the dispersed phase, and more preferably to use an alkoxysilane having Si-C bonds. In addition, in order to produce a low-density, flexible organic-inorganic hybrid aerogel, it is even more preferable to use an alkylalkoxysilane, and particularly preferable to use an alkoxysilane having a methyl group (Si-CH3).

[0057] The sol generation step is preferable because it is easier to obtain an organic-inorganic hybrid sol by subjecting a silane compound containing at least an alkylalkoxysilane to at least one of hydrolysis and polycondensation.

[0058] The sol generation step is a step of generating an organic-inorganic hybrid sol by subjecting a silane compound containing an alkylalkoxysilane having at least a Si-CH3 bond to at least one of hydrolysis and polycondensation. This is preferable because, in the subsequent wet gel generation step, a sol-gel reaction easily yields an organic-inorganic hybrid wet gel with small pore size, low density, and flexibility, and after drying, an organic-inorganic hybrid aerogel with low density, small pore size, and excellent handling properties is easily obtained.

[0059] <Silane compounds> More specifically, examples of silane compounds used to produce the aforementioned organic-inorganic hybrid sol include chlorosilanes such as chlorotrimethylsilane, dichlorodimethylsilane, dichlorodiethylsilane, dichlorodipropylsilane, trichloromethylsilane, trichloroethylsilane, and trichloropropylsilane; hexamethyldisilazane; and monofunctional silane compounds, difunctional silane compounds, trifunctional silane compounds, and tetrafunctional silane compounds. Here, an n-functional silane compound means a silane compound in which n oxygen atoms are bonded to one Si atom. To obtain an organic-inorganic hybrid aerogel with suitable properties, it is preferable to use a difunctional silane compound, a trifunctional silane compound, or a tetrafunctional silane compound.

[0060] As the bifunctional silane compound, for example, dialkoxysilanes and diacetoxysilanes can be used, and dialkoxysilanes with 1 to 9 carbon atoms in the alkoxy group can be preferably used. Examples of dialkoxysilanes with 1 to 9 carbon atoms in the alkoxy group include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diisobutyldimethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, 1,2-bis(methyldiethoxysilyl)ethane, 1,2-bis(methyldiethoxysilyl)ethylene, etc. Of these, dimethyldimethoxysilane (DMDMS) and dimethyldiethoxysilane (DMDES), which have a methyl group, can be particularly preferably used because the reaction can be controlled relatively easily and they are easy to handle, and they can form a dense structure while moderately reducing the crosslinking density of the network.

[0061] As trifunctional silane compounds, for example, trialkoxysilanes and triacetoxysilanes can be used, and trialkoxysilanes with 1 to 9 carbon atoms in the alkoxy group can be preferably used. Examples of trialkoxysilanes with 1 to 9 carbon atoms in the alkoxy group include methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, phenyltrimethoxysilane, 1,2-bis(trimethoxysilyl)ethane, 1,2-bis(triethoxysilyl)ethylene, 1,6-bis(trimethoxysilyl)hexane, etc. Of these, methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES), which have methyl groups, are particularly suitable for use because they are relatively easy to control and handle, and they can form a dense structure while moderately reducing the crosslinking density of the network.

[0062] As tetrafunctional silane compounds, for example, tetraalkoxysilanes and tetraacetoxysilanes can be used, and tetraalkoxysilanes with 1 to 9 carbon atoms in the alkoxy group are preferably used. Examples of tetraalkoxysilanes with 1 to 9 carbon atoms in the alkoxy group include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, etc. Of these, tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS) are particularly preferred because they are relatively easy to control and handle, and they readily form a uniform network when copolymerized with other silicon compounds.

[0063] In the sol generation process, it is also possible to use oligomers and polymers that are formed by the polymerization of multiple silane compounds, either as a silane compound or in addition to a silane compound. Examples of such oligomers and polymers include poly(dimethylsiloxane), hydroxy-terminated, which is a hydrolysis condensate of DMDMS; poly(vinylmethyldimethoxysilane), which is obtained by radical polymerization of vinylmethyldimethoxysilane; and methyl silicate oligomers and ethyl silicate oligomers, which are hydrolysis condensates of tetramethoxysilane and tetraethoxysilane.

[0064] The dispersed precursor may, if necessary, contain compounds other than silicon compounds. Examples of such compounds other than silicon compounds include aluminum chloride, aluminum nitrate, iron chloride, iron nitrate, zinc chloride, zinc nitrate, etc. However, the Si-O-Si bond obtained from the reaction of the silicon compound is important for the formation of organic-inorganic hybrid gels. For this reason, the dispersed precursor contains, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, of the silicon compound.

[0065] The silicon compound contained in the dispersed precursor preferably contains 30 mol% or more, more preferably 50 mol% or more, and even more preferably 80 mol% or more of the silane compound in order to obtain an organic-inorganic hybrid aerogel with suitable properties.

[0066] <Solvent> In the sol formation process, at least one of water and an organic solvent can be used as the dispersion medium for the organic-inorganic hybrid sol. Here, the water and organic solvent may be added or produced by the reaction of the compound. In particular, water can be preferably used because the water, which is the dispersion medium, is also used in the reaction of the silane compound, thereby increasing the efficiency of organic-inorganic hybrid gel formation.

[0067] The amount of water added is not particularly limited, as it depends on the type of silane compound used, but it is, for example, 0.1 mol or more, preferably 0.3 mol or more, and more preferably 0.5 mol or more, per mol of silane compound. The amount of water added is, for example, 100 mol or less, preferably 75 mol or less, and more preferably 50 mol or less, per mol of silane compound.

[0068] Examples of organic solvents that can be used include alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 1-butanol, 2-butanol, and t-butanol; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, acetone, methyl ethyl ketone, and dimethyl sulfoxide; and aprotic nonpolar solvents such as n-hexane, n-heptane, toluene, and 1,3,5-trimethylbenzene. Of these, alcohols are preferred in light of their ease of drying and high ability to form pore structures suitable for organic-inorganic hybrid aerogels.

[0069] Dispersion media for organic-inorganic hybrid sols include, for example, those produced during the hydrolysis and polycondensation reactions of silicon compounds. Examples of such dispersion media include methanol and water, which are produced by the hydrolysis and polycondensation reactions of methyltrimethoxysilane.

[0070] The solvent can be used alone or in combination of two or more. In this invention, a solvent consisting of water and alcohol is particularly suitable because it can make the porous structure of the organic-inorganic hybrid aerogel finer, strengthen the gel skeleton, and tend to result in a lower density after drying.

[0071] The amount of solvent added as a dispersion medium is a factor that affects the density of the gel after drying. The amount of solvent required to produce an aerogel with a desired density varies depending on the type and combination of precursors used in the dispersed phase. Therefore, the amount of solvent added as a dispersion medium is not particularly limited, but from the viewpoint of reducing the density of the aerogel, it is, for example, 100 mol or less, preferably 75 mol or less, more preferably 50 mol or less, and 5 mol or more, preferably 7 mol or more, more preferably 10 mol or more, and even more preferably 15 mol or more, per 1 mol of the total amount of precursor compounds in the dispersed phase.

[0072] <Catalyst> In the sol formation process, a catalyst can be added to the raw materials containing the silicon compound to produce an organic-inorganic hybrid sol. In particular, since silicon compounds are easily subjected to hydrolysis and polycondensation reactions under acidic or basic conditions, it is preferable to add at least one of an acid and a base as a catalyst. Generally, a base catalyst is preferably used during the polycondensation reaction.

[0073] Examples of acid catalysts include inorganic acids, organic acids, and acidic salts. Examples of base catalysts include inorganic bases, organic bases, and basic salts.

[0074] Among these, inorganic acids such as hydrochloric acid, sulfuric acid, sulfurous acid, nitric acid, hydrofluoric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, bromate, chloric acid, chlorous acid, and hypochlorous acid can be used. Organic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, adipic acid, and azelaic acid can be used. Acidic salts such as acidic aluminum phosphate, acidic magnesium phosphate, and acidic zinc phosphate can be used.

[0075] Examples of base catalysts include ammonium compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and ammonium hydroxide; thermally hydrolyzable base catalyst sources such as urea and formamide; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; basic sodium phosphate salts such as sodium metaphosphate, sodium pyrophosphate, and sodium polyphosphate; allylamine, diallylamine, triallylamine, isopropylamine, diisopropylamine, ethylamine, diethylamine, and triethylamine. Aliphatic amines such as methylamine, 2-ethylhexylamine, 3-ethoxypropylamine, diisobutylamine, 3-(diethylamino)propylamine, di-2-ethylhexylamine, 3-(dibutylamino)propylamine, tetramethylethylenediamine, t-butylamine, sec-butylamine, propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, 3-methoxyamine, dimethylethanolamine, methyldiethanolamine, diethanolamine, triethanolamine, etc.; nitrogen-containing heterocyclic compounds; etc. can be used. Examples of nitrogen-containing heterocyclic compounds include morpholines such as morpholine, N-methylmorpholine, and 2-methylmorpholine and their derivatives; piperazine and its derivatives; piperidine and its derivatives; imidazole and its derivatives, etc.

[0076] In this invention, the use of organic acids, organic bases, and ammonium compounds is preferable because they are less likely to remain in the organic-inorganic hybrid aerogel after drying due to volatilization, decomposition, and other effects during the drying process of the organic-inorganic hybrid wet gel.

[0077] Acid and base catalysts can be used individually or in combination of two or more.

[0078] There are no particular restrictions on the method of using the catalyst. When producing an organic-inorganic hybrid sol using a silane compound, it is preferable to use the catalyst in the following ways, for example: a method in which an acid is first added to perform hydrolysis, and then a base is added to promote the polycondensation reaction and produce the sol; a method in which the silane compound, solvent, and base are mixed at once to produce the sol; a method in which a compound that can decompose to produce a base, such as urea, is introduced into the system, and after hydrolysis by adding an acid, the polycondensation reaction is accelerated by generating a base by heating or other methods to produce the sol; etc. It is preferable to use the catalyst in these ways. The catalyst added in this step can also be used directly in the subsequent wet gel production step.

[0079] The concentrations of the acid and base catalysts are, for example, 0.0001 mol / L to 0.1 mol / L, preferably 0.0005 mol / L to 0.05 mol / L, and more preferably 0.001 mol / L to 0.01 mol / L.

[0080] <Additives> To form a microstructure suitable for bringing out the various properties of organic-inorganic hybrid aerogels, additives can be used as needed in the manufacturing process before gelation. Suitable additives often include hydrophobic polymers of silicon compounds that can constitute the framework of the organic-inorganic hybrid aerogel, and surfactants, which are used to improve affinity with hydrophilic solvents, particularly water, and to suppress the progression of phase separation. The surfactants contribute to the formation of the pore structure of the organic-inorganic hybrid aerogel in the wet gel formation process described later.

[0081] As the surfactant, either an ionic surfactant or a nonionic surfactant can be used. One type of surfactant or a combination of two or more types can be used.

[0082] Examples of ionic surfactants used in the present invention include cationic surfactants, anionic surfactants, and amphoteric surfactants. Examples of cationic surfactants used in the present invention include n-hexadecyltrimethylammonium chloride and cetyltrimethylammonium bromide. Examples of anionic surfactants used in the present invention include sodium lauryl sulfate and sodium dodecylbenzenesulfonate. Examples of amphoteric surfactants used in the present invention include lauryldimethylaminoacetic acid betaine, cocamidopropyl betaine, and acyl glutamic acid.

[0083] Examples of nonionic surfactants used in the present invention include polyoxyethylene alkyl ethers, polyoxyethylene nonylphenyl ethers, and block copolymers of polyoxyethylene and polyoxypropylene.

[0084] The amount of surfactant added is not particularly limited, as it depends on the type and mixing ratio of the silicon compound and the type of surfactant. However, for example, it is 0.001 to 100 parts by mass, preferably 0.01 to 90 parts by mass, and more preferably 0.1 to 80 parts by mass, per 100 parts by mass of the total amount of silicon compound.

[0085] <Solu formation conditions> The conditions for forming organic-inorganic hybrid sols are not particularly limited, as the preferred conditions vary depending on the type and combination of compounds used. However, generally, stirring or heating is preferred to promote a uniform reaction and improve the reaction rate.

[0086] (Wet gel formation process) The wet gel generation process is a process of obtaining an organic-inorganic hybrid wet gel by the sol-gel method. Specifically, the wet gel generation process is often performed consecutively from the sol generation process. It involves further polymerization of the generated organic-inorganic hybrid sol to produce an organic-inorganic hybrid wet gel through sol-gel transition, and then, if necessary, maturation to improve the strength of the organic-inorganic hybrid wet gel, thereby producing an organic-inorganic hybrid wet gel with strength suitable for drying.

[0087] The wet gel generation step is preferable because it is easier to obtain an organic-inorganic hybrid wet gel with excellent mechanical properties suitable for drying, if it is a step of generating an organic-inorganic hybrid wet gel from the sol in the presence of a basic catalyst. Furthermore, the wet gel generation step is preferable because it is easier to obtain an organic-inorganic hybrid wet gel from the organic-inorganic hybrid sol by a sol-gel reaction, if it is a step of generating an organic-inorganic hybrid sol by performing a sol generation step, in which a silane compound containing an alkylalkoxysilane having at least a Si-CH3 bond, on which at least one of hydrolysis and polycondensation is performed on the silane compound, if it is a step of generating an organic-inorganic hybrid sol by a sol-gel reaction, if it is an organic-inorganic hybrid wet gel with small pore size and a uniform microstructure, and if it is easier to obtain an organic-inorganic hybrid aerogel that has a microstructure similar to that of the wet gel even after drying.

[0088] Here, the process until the sol loses its fluidity can be considered a sol formation process, and the process after the fluidity is lost due to the sol-gel transition (gelation occurs), followed by maturation as needed to improve the strength of the organic-inorganic hybrid wet gel until it reaches a sufficient level, can be considered a wet gel formation process.

[0089] The method for producing an organic-inorganic hybrid wet gel in the wet gel production step is not particularly limited, but for example, it can be produced by applying a predetermined amount of energy to the organic-inorganic hybrid sol produced in the sol production step over a predetermined period of time.

[0090] As the predetermined energy added in the wet gel formation process, for example, thermal energy can be used. As a method of adding thermal energy, for example, heating can be used. The heating temperature is, for example, 25°C (room temperature) to 160°C. In order to sufficiently increase the degree of polymerization of the gel and improve the strength of the resulting organic-inorganic hybrid aerogel, the heating temperature is generally preferably 40°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher.

[0091] The time for applying the predetermined energy is not particularly limited, as the reactivity varies depending on the type and combination of precursors, but for example, it ranges from 0.01 hours to 7 days.

[0092] In the wet gel formation process, the use of a catalyst is preferred to promote the polymerization reaction within the system. The catalyst may be the same one added during the organic-inorganic hybrid sol formation process, or it may be newly added or added during this wet gel formation process.

[0093] Furthermore, when generating an organic-inorganic hybrid wetted gel using the formation of Si-O-Si bonds as the main reaction of the polymerization reaction, it is preferable to use an acid or base catalyst, as in the sol formation step, and it is particularly preferable to use a base catalyst.

[0094] <Aging process> In the wet gel formation process, it is preferable to mature the organic-inorganic hybrid wet gel after gelation by sol-gel transition. Maturement is carried out, for example, by applying a predetermined amount of energy for a predetermined period of time, similar to the gelation process.

[0095] As the predetermined energy added during the maturation process, for example, thermal energy can be used. As a method of adding thermal energy, for example, heating can be used. The heating temperature is, for example, 25°C (room temperature) to 160°C, and in order to sufficiently increase the degree of polymerization of the gel and improve the strength of the resulting organic-inorganic hybrid aerogel, it is generally preferable to use a temperature of 40°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher.

[0096] In the maturation process, the time for which the predetermined energy is applied is not particularly limited, as the reactivity varies depending on the type and combination of precursors, but for example, it is between 0.01 hours and 7 days.

[0097] Organic-inorganic hybrid wetted gels, for example, are formed in which solvents such as water and organic solvents are retained in the pores formed between the frameworks of organic-inorganic hybrid aerogels. These solvents may contain unwanted components such as catalysts (acids, bases, etc.), surfactants, and reaction byproducts used throughout the process from sol formation to wetted gel formation.

[0098] Furthermore, when a basic polycondensation catalyst is used as the polycondensation catalyst, the organic-inorganic hybrid wetted gel tends to become a basic organic-inorganic hybrid wetted gel.

[0099] (neutralization process) The neutralization step is a process of neutralizing the organic-inorganic hybrid wet gel obtained by the sol-gel method.

[0100] The neutralization process specifically involves continuing the neutralization treatment on an organic-inorganic hybrid wetted gel using a neutralizing agent for a predetermined period of time. In this invention, the "treatment time in the process of continuing the neutralization treatment for a predetermined period of time" is also simply referred to as the "neutralization time."

[0101] This neutralization process is defined as reacting at least some of the hydrogen ions or hydroxide ions in an organic-inorganic hybrid wetted gel with a neutralizing agent. In other words, it is not necessarily required that all of the hydrogen ions or hydroxide ions in the organic-inorganic hybrid wetted gel be reacted (complete neutralization); if a neutralizing agent is added so that at least some of them are neutralized (partial neutralization), it can be considered a neutralization process.

[0102] If the organic-inorganic hybrid wetted gel is a basic organic-inorganic hybrid wetted gel, the neutralizing agent is an acid. In this case, the neutralization step is, for example, a step of neutralizing the basic organic-inorganic hybrid wetted gel with an acid. On the other hand, if the organic-inorganic hybrid wetted gel is an acidic organic-inorganic hybrid wetted gel, the neutralizing agent is a base. In this case, the neutralization step is, for example, a step of neutralizing the acidic organic-inorganic hybrid wetted gel with a base. In the present invention, the step of neutralizing the basic organic-inorganic hybrid wetted gel with an acid is more preferable because the effect of reducing density is more pronounced. The neutralization process will be described in detail below, using the case of neutralizing a basic organic-inorganic hybrid wetted gel with an acid as an example.

[0103] When the organic-inorganic hybrid wetted gel is a basic organic-inorganic hybrid wetted gel, the neutralizing agent can be an acid such as an organic acid, an inorganic acid, or an acidic salt. The acid can be used alone or in combination of two or more types.

[0104] Examples of organic acids include carboxylic acids such as acetic acid, formic acid, citric acid, oxalic acid, lactic acid, tartaric acid, and malic acid; and sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, and benzenesulfonic acid. Examples of inorganic acids include hydrochloric acid, nitric acid, nitrite, sulfuric acid, sulfurous acid, phosphoric acid, and boric acid. Examples of acidic salts include acidic aluminum phosphate, acidic magnesium phosphate, and acidic zinc phosphate.

[0105] For the purpose of reducing the density of organic-inorganic hybrid aerogels after drying, there are no particular restrictions on the type of acid used. However, if inorganic acids or acidic salts are used as neutralizing agents, for example, there is a possibility that components derived from the neutralizing agent may remain as impurities in the pores of the gel after drying. To minimize the residue of such impurities, organic acids can be suitably used because they are less likely to remain due to volatilization and decomposition during the drying process, and carboxylic acids in particular can be suitably used.

[0106] In the neutralization step, the neutralization treatment involves adding a neutralizing agent in an amount of, for example, 0.05 molar equivalents or more, preferably 0.5 molar equivalents or more, more preferably 0.8 molar equivalents or more, and even more preferably 1 molar equivalent or more, relative to the hydrogen ions or hydroxide ions in the organic-inorganic hybrid wetted gel.

[0107] Here, the addition of the neutralizing agent is carried out as follows: First, the ion with the larger total charge (LC ion) among the hydrogen ions and hydroxide ions present in the organic-inorganic hybrid wetted gel is determined, and the total charge of the LC ions in the organic-inorganic hybrid wetted gel (C LC First, calculate the charge (Coulomb). Second, determine the neutralizing agent (OC neutralizing agent) that generates ions with the opposite charge to these LC ions. Third, use this OC neutralizing agent to determine the total charge (Coulomb) of the LC ions in the organic-inorganic hybrid wetted gel. LC For example, add 0.05 molar equivalents or more relative to (Coulomb). Here, "0.05 molar equivalents or more" means "the total amount of ion charge (C) generated by the OC neutralizer in the organic-inorganic hybrid wetted gel." OC (Coulomb)) is the total charge of LC ions in an organic-inorganic hybrid wetted gel (C LC This means it is "more than 0.05 times (Coulomb)".

[0108] For example, if the LC ions are hydroxide ions, the total charge of the LC ions in the organic-inorganic hybrid wetted gel is C LCWhen (Coulomb) is 1 mole and the OC neutralizing agent is acetic acid, "the amount of neutralizing agent added is 0.05 molar equivalent or more" means "adding 0.05 moles of acetic acid." Also, in the above case, if the OC neutralizing agent is oxalic acid, for example, "the amount of neutralizing agent added is 0.05 molar equivalent or more" means "adding 0.025 moles of oxalic acid."

[0109] Furthermore, the amounts of hydrogen ions and hydroxide ions depend on the degree of ionization of the acid and base added to the system and are affected by the solvent and additives, so strictly speaking, the C of the LC ions is not precisely measured. LC It is difficult to calculate this. Therefore, in this invention, for the sake of simplification and generalization, the acids and bases added to the system, regardless of type, are assumed to completely ionize, and the LC ions are determined by desk calculations, C LC The calculation of the ions and the amount of OC neutralizing agent to be added shall be determined. For the sake of simplicity and generalization, the ions generated by the OC neutralizing agent shall also be calculated on paper assuming complete ionization, and the values ​​obtained from this calculation shall be followed.

[0110] If the organic-inorganic hybrid wetted gel is a basic organic-inorganic hybrid wetted gel, the amount of acid used as a neutralizing agent should be, for example, 0.05 molar equivalents or more, preferably 0.5 molar equivalents or more, more preferably 0.8 molar equivalents or more, and even more preferably 1 molar equivalent or more, relative to the hydroxide ion concentration of the organic-inorganic hybrid wetted gel.

[0111] When the equivalent amount of acid used as a neutralizing agent is above a certain value, the density of the resulting organic-inorganic hybrid aerogel (dry gel) tends to decrease, and the effect of decreasing the density of the dry gel becomes easier to control.

[0112] As will be discussed later, based on the reaction mechanism presumed to occur in the neutralization process, when neutralizing a basic organic-inorganic hybrid wetted gel with acid, the upper limit of the equivalent amount of acid used as a neutralizing agent is considered to be much larger and is not particularly limited. However, if the amount is too excessive, the neutralization process may not proceed further and may become uneconomical. Therefore, for example, it should be 500 equivalents or less, preferably 300 equivalents or less, and more preferably 100 equivalents or less.

[0113] To control the decrease in density of the dried gel, for example, a calibration curve showing the relationship between the equivalent amount of added acid and the density of the resulting dried gel can be created in advance, and the density of the resulting dried gel can be controlled by controlling the equivalent amount of added acid based on this calibration curve.

[0114] The neutralization time is, for example, 10 minutes or more, preferably 1 hour or more, and more preferably 3 hours or more.

[0115] There is no particular upper limit to the neutralization time. However, if the neutralization time exceeds a certain period, the neutralization process may not proceed further and may become uneconomical. For example, it should be 7 days or less, preferably 5 days or less, and more preferably 3 days or less.

[0116] Furthermore, in organic-inorganic hybrid wetted gels, it is presumed that the completion of the neutralization of the entire solvent held in the pores formed between the organic-inorganic hybrid aerogel skeletons is due to the addition of a certain amount or more of a neutralizing agent and a neutralization period of a certain duration or longer. The above values ​​for the amount of acid added and the neutralization time were set based on the results of examples, etc., and are thought to reflect the presumed mechanism described above.

[0117] The temperature of the organic-inorganic hybrid wetted gel during the neutralization treatment is not particularly limited, and is, for example, between 10°C and 300°C. However, in order to increase the diffusion of the neutralizing agent and the rate of the neutralization reaction, it is considered preferable to carry out the neutralization treatment at a temperature above a certain level. The temperature of the organic-inorganic hybrid wetted gel during the neutralization treatment is, for example, preferably 25°C (room temperature) or higher, more preferably 40°C or higher, and even more preferably 60°C or higher.

[0118] The neutralization process yields an organic-inorganic hybrid wet gel (post-neutralization wet gel) suitable for obtaining a low-density organic-inorganic hybrid aerogel (dry gel). The post-neutralization wet gel is a precursor to the organic-inorganic hybrid aerogel (dry gel) obtained by further drying.

[0119] The neutralized wet gel, like the organic-inorganic hybrid wet gel obtained in the wet gel generation process, retains solvents such as water from a basic aqueous solution and organic solvents in the pores formed between the organic-inorganic hybrid aerogel skeletons. However, it is presumed that the organic-inorganic hybrid aerogel skeletons contained in the neutralized wet gel have a structure that allows for the production of a lower-density organic-inorganic hybrid aerogel (dry gel) compared to the organic-inorganic hybrid aerogel skeletons contained in conventional wet gels obtained without the neutralization process.

[0120] The reason why the organic-inorganic hybrid aerogel skeleton contained in the neutralized wet gel is presumed to have a structure that yields a low-density organic-inorganic hybrid aerogel (dry gel) is as follows:

[0121] As mentioned above, organic-inorganic hybrid wet gels are formed primarily by the development of a network structure through the formation of Si-O-Si bonds. The pores formed between the frameworks of the organic-inorganic hybrid wet gel hold solvents such as water and organic solvents, and these solvents may contain unwanted components such as acids, surfactants, polycondensation catalysts, and reaction by-products used as raw materials. When an organic-inorganic hybrid wet gel in equilibrium is subjected to washing or drying treatments, it is presumed that the reverse reaction of the polycondensation reaction (decomposition reaction of the polycondensate) occurs during the process due to changes in the surrounding environment, polycondensation catalysts, surfactants, etc. in the pores. It is then presumed that when this reverse reaction occurs, at least some of the Si-O-Si bonds in the framework of the organic-inorganic hybrid aerogel decompose, reducing the strength of the gel framework from its original level, and making the resulting organic-inorganic hybrid aerogel (dry gel) more prone to high density.

[0122] In contrast, the neutralization step of the present invention is presumed to suppress the reverse reaction (decomposition reaction) of the polycondensation reaction by neutralizing the organic-inorganic hybrid wet gel. Furthermore, it is presumed that by suppressing this reverse reaction, the decomposition of Si-O-Si bonds in the backbone of the organic-inorganic hybrid aerogel is suppressed, resulting in a lower density of the resulting organic-inorganic hybrid aerogel (dry gel).

[0123] In other words, it is presumed that the essential effect of the neutralization step in the present invention is to suppress the decomposition reaction (reverse reaction) of Si-O-Si bonds that may occur in the manufacturing process of organic-inorganic hybrid aerogels through neutralization treatment, thereby preventing an unnecessary decrease in the strength of the gel skeleton and creating a state in which the density of the aerogel after drying is easily reduced.

[0124] In this invention, when the neutralization step involves neutralizing a basic organic-inorganic hybrid wet gel with an acid, a significant decrease in density of the aerogel after drying tends to occur. This is thought to be a result of the fact that the decomposition of Si-O-Si bonds generally occurs more easily under basic conditions and less easily under acidic conditions.

[0125] Furthermore, organic-inorganic hybrid aerogels generally have superior mechanical flexibility and thus higher fracture resistance compared to silica aerogels. Therefore, it is presumed that one reason why a low-density organic-inorganic hybrid aerogel (dry gel) can be obtained in the manufacturing method of the present invention is that the target material processed in the neutralization step is an organic-inorganic hybrid aerogel (dry gel) that has superior mechanical flexibility compared to silica aerogels.

[0126] Incidentally, in conventional aerogel manufacturing methods, solvent washing of the wet gel has been performed to obtain aerogel with low density (dry gel).

[0127] The neutralization step of the present invention is similar in action to the solvent washing in conventional aerogel manufacturing methods in that it yields a low-density organic-inorganic hybrid aerogel (dry gel). However, it is presumed that the mechanism of the neutralization step of the present invention and the solvent washing in conventional aerogel manufacturing methods differ in that the neutralization step of the present invention suppresses the decomposition of the Si-O-Si bond in the backbone of the organic-inorganic hybrid aerogel (dry gel) based on the suppression of the reverse reaction (decomposition reaction) of the polycondensation reaction described above.

[0128] In other words, conventional methods fail to completely suppress the decomposition of Si-O-Si bonds due to the reverse reaction, resulting in a decrease in the strength of the gel skeleton from what should have been achieved. Unless unwanted components in the pores are removed as much as possible through washing, the aerogel easily shrinks after drying, and its density tends to increase. However, by performing the neutralization treatment in the present invention, the decomposition of Si-O-Si bonds is suppressed, allowing the strength of the gel skeleton to approach its original strength. It is presumed that the density decreases even without completely removing unwanted components in the pores, or without removing them to the same extent as in conventional methods.

[0129] <Solvent> In the neutralization step, a solvent may be added to the organic-inorganic hybrid wetted gel along with the neutralizing agent. Specifically, for example, if the neutralizing agent is an acid, the solvent may be added to the organic-inorganic hybrid wetted gel before, during, or simultaneously with the addition of the acid in the neutralization step.

[0130] The solvent added in the neutralization process is primarily used to prevent drying of the organic-inorganic hybrid wet gel and to promote the movement of the neutralizing agent. For this reason, it is preferable to add the solvent before or simultaneously with the addition of the neutralizing agent.

[0131] The solvent added in the neutralization step includes the same solvents used in solvent washing of organic-inorganic hybrid wet gels in conventional aerogel manufacturing methods. However, the solvent added in this invention along with the neutralizing agent is added primarily to prevent drying of the organic-inorganic hybrid wet gel and to promote the movement of the neutralizing agent, and is not an essential substance, thus differing in its action from solvent washing.

[0132] Examples of solvents added in the neutralization step include alcohol, water, N,N-dimethylformamide, n-hexane, and n-heptane. As the alcohol, those similar to the organic solvents used in the sol formation step are preferably used.

[0133] The amount of solvent added is not particularly limited, but for example, 10 to 1000 parts by mass, preferably 30 to 500 parts by mass, and more preferably 50 to 300 parts by mass, per 100 parts by mass of the organic-inorganic hybrid wetted gel.

[0134] Furthermore, if the solvent added at this stage has a cleaning effect, it not only promotes the movement of the neutralizing agent but also reduces the concentration of unwanted components in the organic-inorganic hybrid wetted gel (cleaning effect). Therefore, to further reduce the density of the aerogel after drying, it is considered better to add a larger amount of solvent at this stage. However, this dilutes the concentration of the neutralizing agent, which may lead to problems such as the effectiveness of the neutralization treatment becoming unclear, or the need to increase the absolute amount of neutralizing agent added to maintain the effectiveness of the neutralization treatment, which would be uneconomical.

[0135] (Washing process) The method for producing the organic-inorganic hybrid aerogel of the present invention may optionally include a washing step for washing the organic-inorganic hybrid wet gel. For example, the washing step may be a solvent washing step of the wet gel. The washing step can be introduced when it is desired to reduce the concentration of impurities in the pores that cannot be completely removed by neutralization treatment, or when it is desired to replace the solvent in the pores of the organic-inorganic hybrid wet gel with another solvent, etc.

[0136] When a washing process is performed, it can be done before or after the neutralization process. If the washing process is performed before the neutralization process, the organic-inorganic hybrid wetted gel to be washed is usually the organic-inorganic hybrid wetted gel after the wetted gel generation process. If the washing process is performed after the neutralization process, the organic-inorganic hybrid wetted gel to be washed is usually the post-neutralization wetted gel.

[0137] Furthermore, if the washing performed before the neutralization process is excessive, it may become economically undesirable, and the density reduction effect of the neutralization process may be diminished. Therefore, to maximize the effectiveness of the neutralization treatment, it is preferable to perform the washing process as much as possible after the neutralization process.

[0138] The solvent used in the solvent washing process is not particularly limited; for example, the solvent added as needed in the neutralization step or water can be used. Furthermore, the time, temperature, and pressure conditions of the solvent washing process are not particularly limited.

[0139] (drying process) The drying process is performed after the neutralization process and involves drying the organic-inorganic hybrid wet gel (post-neutralization wet gel).

[0140] The drying pressure is not particularly limited, but for example, it is set to a vacuum of ~1100 hPa.

[0141] Furthermore, the drying pressure can be set to, for example, less than the critical pressure of the solvent used in the drying process of the neutralized wet gel. Here, the solvent used in the drying process of the neutralized wet gel refers to the solvent held by the neutralized wet gel being dried.

[0142] The drying temperature is not particularly limited, but is, for example, 20 to 350°C, preferably 60 to 300°C.

[0143] Furthermore, the drying temperature can be set below the critical temperature of the solvent used for drying the neutralized wet gel.

[0144] The pressure and temperature of the drying process can be set below the critical pressure and critical temperature of the solvent used for drying the neutralized wet gel, i.e., below the critical point.

[0145] The drying time is not particularly limited, but for example, it is 0.1 to 100 hours, preferably 0.3 to 50 hours.

[0146] (effect) According to the present invention, a method for producing an organic-inorganic hybrid aerogel (dry gel) can be obtained by properly treating an organic-inorganic hybrid wet gel using means other than washing.

[0147] Furthermore, according to the present invention, it becomes possible to control the density of the resulting organic-inorganic hybrid aerogel (dry gel) by controlling the neutralization treatment conditions in the neutralization process, for example, by controlling the amount of acid added.

[0148] The organic-inorganic hybrid aerogel produced by the present invention can be suitably used as an insulating material in cryogenic containers, space applications, construction, automotive, home appliances, semiconductors, industrial equipment, and the like. In addition to its use as an insulating material, the organic-inorganic hybrid aerogel produced by the present invention can also be used for applications such as water repellency, sound absorption, vibration damping, low dielectric properties, and catalyst support. [Examples]

[0149] Next, examples will be described to further clarify the effects of the present invention, but the present invention is not limited to these examples.

[0150] [Synthesis Example 1] 1.34 parts by mass of tetramethoxysilane, 3.58 parts by mass of methyltrimethoxysilane, and 1.25 parts by mass of 0.005 mol / L acetic acid were mixed and stirred for 2 hours to allow hydrolysis to proceed. Then, 9.5 parts by mass of methanol as a solvent and 0.10 parts by mass of 25% aqueous solution of tetramethylammonium hydroxide as a polycondensation catalyst were added and stirred for 1 minute. The resulting sol was transferred to an autoclave container and allowed to stand in a 120°C constant temperature bath for 12 hours to gel and mature. This yielded an organic-inorganic hybrid wet gel (sample No. A1). Multiple organic-inorganic hybrid wet gels (sample No. A1) were prepared.

[0151] [Synthesis Example 2] An organic-inorganic hybrid wetted gel was prepared in the same manner as in Synthesis Example 1, except that 9.43 parts by mass of 2-propanol were used instead of methanol as the solvent. This yielded an organic-inorganic hybrid wetted gel (Sample No. A2). Multiple organic-inorganic hybrid wetted gels (Sample No. A2) were prepared.

[0152] [Synthesis Example 3] 4.73 parts by mass of methyltrimethoxysilane and 1.30 parts by mass of 0.005 mol / L acetic acid were mixed and stirred for 2 hours to allow hydrolysis to proceed. Then, 9.5 parts by mass of methanol as a solvent and 0.10 parts by mass of 25% aqueous tetramethylammonium hydroxide solution as a polycondensation catalyst were added and stirred for 1 minute. The resulting sol was transferred to an autoclave container and allowed to stand in a 120°C constant temperature bath for 12 hours to gel and mature. This yielded an organic-inorganic hybrid wet gel (sample No. A3). Multiple organic-inorganic hybrid wet gels (sample No. A3) were prepared.

[0153] [Synthesis Example 4] 1.07 parts by mass of tetramethoxysilane, 3.35 parts by mass of methyltrimethoxysilane, 0.42 parts by mass of dimethyldimethoxysilane, and 1.25 parts by mass of 0.005 mol / L acetic acid were mixed and stirred for 2 hours to allow hydrolysis to proceed. Then, 9.5 parts by mass of methanol as a solvent and 0.10 parts by mass of 25% aqueous solution of tetramethylammonium hydroxide as a polycondensation catalyst were added and stirred for 1 minute. The resulting sol was transferred to an autoclave container and allowed to stand in a 120°C bath for 12 hours to gel and mature. This yielded an organic-inorganic hybrid wet gel (sample No. A4). Multiple organic-inorganic hybrid wet gels (sample No. A4) were prepared.

[0154] [Synthesis Example 5] 0.534 parts by mass of tetramethoxysilane, 4.30 parts by mass of methyltrimethoxysilane, 10 parts by mass of 0.005 mol / L acetic acid, and 0.20 parts by mass of n-hexadecyltrimethylammonium chloride (CTAC) as a surfactant were mixed and stirred for 30 minutes to allow hydrolysis to proceed. Subsequently, 0.10 parts by mass of 14 mass% aqueous ammonia was added as a polycondensation catalyst and stirred for 1 minute. The resulting sol was transferred to an autoclave container and allowed to stand in a 90°C constant temperature bath for 48 hours to gel and mature. This yielded an organic-inorganic hybrid wet gel (sample No. A5). Multiple organic-inorganic hybrid wet gels (sample No. A5) were prepared. Table 1 shows the raw materials used in synthesis examples 1 to 5.

[0155] [Table 1]

[0156] [Example 1] 14.7 parts by mass of methanol were added to the organic-inorganic hybrid wet gel (Sample No. A1) prepared in Synthesis Example 1. Further, 0.011 parts by mass of glacial acetic acid were added, and neutralization was carried out at 60°C for 8 hours. The organic-inorganic hybrid wet gel after neutralization was collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B11). The bulk density of the obtained dried gel was 0.263 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.160 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 28 nm. The bulk density of the dry gel was calculated by measuring its weight and volume. The volume was measured using Geopyc from Micromerities. The tap density of the granular dry gel was measured as follows: First, the granular dry gel was poured into a screw-cap tube with an inner diameter of 31.5 mm and its mass was measured. Next, the exposed surface of the dry gel filled in the screw-cap tube was tapped 200 times. The reason for using 200 taps was that the height of the filled dry gel remained unchanged after fewer than 200 taps. Furthermore, the height of the exposed surface of the dry gel after 200 taps was measured to determine the volume of the filled dry gel, and the tap density of the dry gel was calculated using this volume and the weight mentioned above. The pore size peak of the dried gel was determined by applying the BJH method to the adsorption isotherm obtained from nitrogen adsorption / desorption measurements. The measurements were performed using a BELSORP-max from Microtrac-Bell Co., Ltd. The sample used for measurement was dried at 200°C for 1 hour before measurement. In the following examples and reference examples, the bulk density of the dried gel, the tap density of the granular dried gel, and the pore size peaks were measured using the BJH method in the same manner as in Example 1.

[0157] [Example 2] 14.7 parts by mass of methanol were added to the organic-inorganic hybrid wet gel (Sample No. A1) prepared in Synthesis Example 1. Further, 0.021 parts by mass of glacial acetic acid were added, and neutralization was carried out at 60°C for 8 hours. The organic-inorganic hybrid wet gel after neutralization was collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B12). The bulk density of the obtained dried gel was 0.123 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0741 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 53 nm.

[0158] [Example 3] 14.7 parts by mass of methanol were added to the organic-inorganic hybrid wet gel (Sample No. A1) prepared in Synthesis Example 1. Further, 0.084 parts by mass of glacial acetic acid were added, and neutralization treatment was carried out at 60°C for 8 hours. The organic-inorganic hybrid wet gel after neutralization was collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B13). The bulk density of the obtained dried gel was 0.118 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0711 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 55 nm.

[0159] [Example 4] The organic-inorganic hybrid wet gel (Sample No. A1) prepared in Synthesis Example 1 was neutralized by adding 0.021 parts by mass of glacial acetic acid and neutralizing it at 60°C for 8 hours. The organic-inorganic hybrid wet gel after neutralization was collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B14). The bulk density of the obtained dried gel was 0.138 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0831 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 51 nm.

[0160] [Example 5] 14.7 parts by mass of methanol were added to the organic-inorganic hybrid wet gel (Sample No. A1) prepared in Synthesis Example 1. Further, 0.028 parts by mass of 35-37 mass% hydrochloric acid were added, and neutralization was carried out at 60°C for 8 hours. The organic-inorganic hybrid wet gel after neutralization was collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B15). The bulk density of the obtained dried gel was 0.137 g / cm³. 3This dried gel was further pulverized and classified to a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0844 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 51 nm.

[0161] [Reference example 1] The organic-inorganic hybrid wet gel (Sample No. A1) prepared in Synthesis Example 1 was washed with 14.7 parts by mass of methanol at 60°C for 8 hours. The organic-inorganic hybrid wet gel was then collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B16). The bulk density of the obtained dried gel was 0.290 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.175 g / cm³. 3 That was the case.

[0162] [Example 6] To the organic-inorganic hybrid wet gel (Sample No. A2) prepared in Synthesis Example 2, 14.8 parts by mass of 2-propanol and 0.021 parts by mass of glacial acetic acid were added, and neutralization treatment was carried out at 60°C for 8 hours. Subsequently, the organic-inorganic hybrid wet gel was recovered and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B21). The bulk density of the obtained dried gel was 0.138 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0832 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 47 nm.

[0163] [Reference example 2] The organic-inorganic hybrid wet gel (Sample No. A2) prepared in Synthesis Example 2 was treated with 14.8 parts by mass of 2-propanol and washed at 60°C for 8 hours. The organic-inorganic hybrid wet gel was then collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B22). The bulk density of the obtained dried gel was 0.286 g / cm³. 3 This dried gel was further pulverized and classified to a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.173 g / cm³. 3 That was the case. Table 3 shows the treatment and tap density of the dried gel carried out in Reference Example 2. Table 3 also shows the treatment and tap density of the dried gel carried out in Reference Examples 3 to 5 and Examples 6 to 9 described later.

[0164] [Example 7] To the organic-inorganic hybrid wet gel (Sample No. A3) prepared in Synthesis Example 3, 16.6 parts by mass of methanol and 0.021 parts by mass of glacial acetic acid were added, and neutralization treatment was carried out at 60°C for 8 hours. Subsequently, the organic-inorganic hybrid wet gel was recovered and dried at 100°C for 3 hours to obtain a dried gel (Sample No. B31). The bulk density of the obtained dried gel was 0.152 g / cm³. 3 This dried gel was further pulverized and classified to a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0850 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 92 nm.

[0165] [Reference example 3] The organic-inorganic hybrid wet gel (Sample No. A3) prepared in Synthesis Example 3 was washed with 16.6 parts by mass of methanol at 60°C for 8 hours. The organic-inorganic hybrid wet gel was then collected and dried at 100°C for 3 hours to obtain a dried gel (Sample No. B32). The bulk density of the obtained dried gel was 0.163 g / cm³. 3This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0985 g / cm³. 3 That was the case.

[0166] [Example 8] To the organic-inorganic hybrid wet gel (Sample No. A4) prepared in Synthesis Example 4, 14.7 parts by mass of methanol and 0.021 parts by mass of glacial acetic acid were added, and neutralization treatment was carried out at 60°C for 8 hours. Subsequently, the organic-inorganic hybrid wet gel was recovered and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B41). The bulk density of the obtained dried gel was 0.106 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0683 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 53 nm.

[0167] [Reference example 4] The organic-inorganic hybrid wet gel (Sample No. A4) prepared in Synthesis Example 4 was washed with 14.7 parts by mass of methanol at 60°C for 8 hours. The organic-inorganic hybrid and wet gels were then collected and dried at 250°C for 1 hour to obtain a dried gel (Sample No. B42). The bulk density of the obtained dried gel was 0.248 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.150 g / cm³. 3 That was the case.

[0168] [Example 9] To the organic-inorganic hybrid wet gel (Sample No. A5) prepared in Synthesis Example 5, 10 parts by mass of water were added, and the gel was washed at 60°C for 8 hours. The washing solution was then discarded, and 0.084 parts by mass of glacial acetic acid was added, followed by neutralization at 60°C for 8 hours. Next, 30 parts by mass of methanol was added, and the gel was washed again at 60°C for 8 hours. Finally, the gel was dried at 120°C under reduced pressure of 50 hPa for 30 minutes to obtain a dried gel (Sample No. B51). The bulk density of the obtained dried gel was 0.165 g / cm³. 3 This dried gel was further pulverized and classified to obtain a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.0987 g / cm³. 3 Furthermore, the pore size peak obtained by the BJH method was 93 nm.

[0169] [Reference example 5] The organic-inorganic hybrid wet gel (Sample No. A5) prepared in Synthesis Example 5 was washed with 10 parts by mass of water at 60°C for 8 hours. The washing solution was then replaced with 30 parts by mass of methanol, and the gel was washed again at 60°C for 8 hours. Finally, the gel was dried at 120°C under reduced pressure of 50 hPa for 30 minutes to obtain a dried gel (Sample No. B52). The bulk density of the obtained dried gel was 0.225 g / cm³. 3 This dried gel was further pulverized and classified to a particle size of 500-1000 μm. This yielded a granular dried gel. The tap density of the granular dried gel was 0.136 g / cm³. 3 That was the case. Tables 2 and 3 show the treatments performed in Examples 1 to 9 and Reference Examples 1 to 5, as well as the tap density of the dried gel.

[0170] [Table 2]

[0171] [Table 3]

[0172] Tables 2 and 3 show that the density (bulk density and tap density) of the dried gels from Examples 1-5 and 6-9, which were neutralized without washing, was lower than that of the dried gels from Reference Examples 1 and 2-5, which underwent the same pre-drying treatment (similar to the neutralization treatment except that no neutralizing agent was used) for the same duration as the neutralization treatment. Furthermore, it was found that all the dried gels obtained in the examples had a fine pore structure with a pore size peak of 100 nm as measured by the BJH method. Therefore, it was found that even when neutralization is performed instead of washing, it is possible to reduce the density of the dried gel, and a fine, dilute porous material can be obtained.

[0173] Furthermore, a comparison of Examples 1-3 revealed that Example 2, which had a larger amount of neutralizing agent added, had a lower density of dried gel than Example 1. In addition, Example 3, which had the largest amount of neutralizing agent added, only had a slightly lower density of dried gel compared to Example 2, indicating that the amount of neutralizing agent added saturates above a certain value, and adding more does not further decrease the density.

[0174] Furthermore, a comparison of Example 2 and Example 4 revealed that the presence or absence of solvent addition during the neutralization treatment had virtually no effect on the density of the dried gel. Therefore, it is presumed that the solvent added during the neutralization treatment has a different effect than that of the washing treatment.

[0175] Furthermore, a comparison between Example 2 and Example 5 revealed that the type of neutralization treatment had virtually no effect on the density of the dried gel.

[0176] Furthermore, Tables 2 and 3 show that, regardless of the starting composition of the gel (precursor composition ratio, solvent composition, presence or absence of surfactant, type of catalyst, etc.), a low-density organic-inorganic hybrid aerogel can be obtained by performing a neutralization treatment without washing.

[0177] Furthermore, Tables 2 and 3 show that, regardless of the temperature and pressure conditions during drying, a lower density dry gel can be obtained by performing a neutralization treatment instead of a washing treatment.

[0178] A comparison of Example 9 and Reference Example 5 revealed that adding a neutralization treatment to the washing treatment results in a lower density dried gel than when no neutralization treatment is performed. In other words, even if a partial washing treatment is included, the neutralization treatment has the effect of reducing the density of the dried gel (regardless of whether or not a washing treatment step is performed, the neutralization treatment has the effect of reducing the density of the dried gel).

[0179] (Effects inferred from neutralization treatment) The organic-inorganic hybrid aerogel produced by the present invention has a skeleton comprising a network structure of Si-O-Si bonds, and has a structure in which the -C bond portion of the Si-C bond, in which C is bonded to at least a portion of the Si constituting the Si-O-Si bond, is located at least inside the skeleton. The neutralization treatment is presumed to suppress the decomposition of Si-O-Si bonds formed in the organic-inorganic hybrid wet gel. Therefore, it is presumed that the manufacturing method according to the present invention will increase the mechanical strength of the skeleton of the dry gel (organic-inorganic hybrid aerogel) and yield a dry gel with low density.

Claims

1. A method for producing an organic-inorganic hybrid aerogel having a skeleton with a network structure of Si-O-Si bonds, wherein the -C bond portion of the Si-C bond, in which C is bonded to at least a portion of the Si constituting the Si-O-Si bond, is present at least inside the skeleton, A method for producing an organic-inorganic hybrid aerogel, characterized by including a neutralization step of neutralizing an organic-inorganic hybrid wet gel obtained by the sol-gel method.

2. The aforementioned wet gel is a basic organic-inorganic hybrid wet gel. The method for producing an organic-inorganic hybrid aerogel according to claim 1, characterized in that the neutralization step involves neutralizing the basic organic-inorganic hybrid wet gel with an acid.

3. The aforementioned organic-inorganic hybrid aerogel is a bulk material, and the density of the bulk material is 0.3 g / cm³. ３ A method for producing an organic-inorganic hybrid aerogel according to claim 1 or 2, characterized in that the pore size peak obtained by the BJH method is 100 nm or less.

4. The aforementioned organic-inorganic hybrid aerogel is in the form of granules or powder, and has a tap density of 0.2 g / cm³. ３ A method for producing an organic-inorganic hybrid aerogel according to claim 1 or 2, characterized in that the pore size peak obtained by the BJH method is 100 nm or less.

5. Prior to the neutralization step, A sol generation step involves generating an organic-inorganic hybrid sol by performing at least one of hydrolysis and polycondensation on a silane compound containing at least an alkylalkoxysilane, A wet gel formation step in which an organic-inorganic hybrid wet gel is produced from the sol in the presence of a basic catalyst, A method for producing an organic-inorganic hybrid aerogel according to claim 1 or 2, further comprising:

6. The method for producing an organic-inorganic hybrid aerogel according to claim 1 or 2, characterized in that the neutralization treatment in the neutralization step involves adding a neutralizing agent in an amount of 0.5 molar equivalents or more relative to hydrogen ions or hydroxide ions in the wet gel.

7. At least Si-CH ３ A sol generation step involves producing an organic-inorganic hybrid sol by performing at least one of hydrolysis and polycondensation on a silane compound containing an alkylalkoxysilane having a bond, A wet gel generation step in which an organic-inorganic hybrid wet gel is generated from the organic-inorganic hybrid sol by a sol-gel reaction, A method for producing an organic-inorganic hybrid aerogel according to claim 1 or 2, further comprising:

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