Method for producing porous composite material, and porous composite material

Abstract

To provide a method for producing a porous composite material, capable of easily obtaining a porous composite material containing a silica aerogel and a porous resin.SOLUTION: There is provided a method for producing a porous composite material containing a silica aerogel and a porous resin, the method including: a preparation step of preparing a homogeneous phase containing an organic solvent, a polysiloxane precursor, an organic polymer, and water; a condensation precipitation step of subjecting the homogeneous phase to a condensation step of condensing a part or all of the polysiloxane precursor to obtain polysiloxane particles and a precipitation step of precipitating the organic polymer by a phase separation method to obtain a porous resin, to obtain a precipitate containing the polysiloxane particles and the porous resin; and a drying step of drying the precipitate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a porous composite material, and to a porous composite material. [Background technology]

[0002] Silica aerogel is lightweight and has excellent thermal insulation properties, making it a promising material for practical use. However, silica aerogel has the drawback of being extremely brittle when used alone. Therefore, composite materials made from silica aerogel and organic polymers are being investigated.

[0003] For example, Patent Document 1 proposes a method for producing an inorganic-polymer composite molded product by decompressing a homogeneous phase containing a supercritical fluid, a metal compound such as tetramethoxysilane, and a polymer to foam the polymer, phase-separating the supercritical fluid and the metal compound within the foam cells that are formed, and decomposing the metal compound to fill the cells of the foamed polymer with a metal oxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4915845 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method for manufacturing inorganic-polymer composite molded bodies described in Patent Document 1, a supercritical fluid is used instead of a solvent, allowing the fluid to be removed without generating a liquid-gas interface (supercritical drying). This is thought to make it possible to avoid deformation due to interfacial tension and its effect on the microstructure.

[0006] However, the manufacturing method using supercritical drying as in Patent Document 1 has the problem that the operation procedure is complicated, and there is also the problem that the manufacturing cost increases when supercritical drying is performed.

[0007] Furthermore, the molded body obtained by the method of Patent Document 1 has a structure different from that of a single silica aerogel, and has the problem of being inferior in properties compared to a single silica aerogel.

[0008] Therefore, an object of the present invention is to provide a method for producing a porous composite material that can easily produce a porous composite material containing silica aerogel and a porous resin. Another object of the present invention is to provide a porous composite material having a predetermined structure. [Means for solving the problem]

[0009] The present inventors have conducted extensive research with the aim of solving the above-mentioned problems, and have newly discovered that the above-mentioned problems can be solved by subjecting a homogeneous phase containing an organic solvent, a polysiloxane precursor, an organic polymer, and water to a predetermined process to obtain a precipitate containing polysiloxane particles and a porous resin, and then drying the precipitate, thereby completing the present invention.

[0010] That is, the present invention aims to advantageously solve the above-mentioned problems, and [1] the present invention is a method for producing a porous composite material containing silica aerogel and a porous resin, the method comprising: a preparation step of preparing a homogeneous phase containing an organic solvent, a polysiloxane precursor, an organic polymer, and water; a condensation step of condensing part or all of the polysiloxane precursor from the homogeneous phase to obtain polysiloxane particles; and a precipitation step of precipitating the organic polymer by a phase separation method to obtain a porous resin, thereby obtaining a precipitate containing the polysiloxane particles and the porous resin.; and a drying step of drying the precipitate. The above-described production method makes it possible to easily obtain a porous composite material containing silica aerogel and a porous resin.

[0011] [2] In the method for producing a porous and composite material according to [1] above, the mass ratio of the organic polymer to the polysiloxane precursor is preferably 0.1 or more and 2.0 or less. When the mass ratio of the organic polymer to the polysiloxane precursor is equal to or greater than the above lower limit, the structure of the resulting porous composite material can be made closer to a silica aerogel structure. Furthermore, when the mass ratio of the organic polymer to the polysiloxane precursor is within the above range, the apparent density of the resulting porous composite material is low, and the properties can approach those of a single silica aerogel.

[0012] [3] In the method for producing a porous composite material according to [1] or [2] above, the phase separation method is preferably a thermally induced phase separation method. If the phase separation method is a thermally induced phase separation method, a porous composite material containing silica aerogel and a porous resin can be more easily obtained.

[0013] [4] In the method for producing a porous composite material according to any one of [1] to [3] above, the organic solvent and the organic polymer are preferably a combination of an alcohol and a poly(meth)acrylic acid alkyl ester, or a combination of a sulfur-containing solvent and a nitrile group-containing polymer. When the organic solvent and the organic polymer are used in the above combination, a porous composite material containing silica aerogel and a porous resin can be more easily obtained.

[0014] [5] In the method for producing a porous composite material according to any one of [1] to [3] above, the organic solvent and the organic polymer are preferably a combination of ethanol and polymethyl methacrylate, or a combination of dimethyl sulfoxide and polyacrylonitrile. When the organic solvent and the organic polymer are used in the above combination, a porous composite material containing silica aerogel and a porous resin can be more easily obtained.

[0015] Another object of the present invention is to advantageously solve the above-mentioned problems, and [6] the present invention is a porous composite material comprising silica aerogel and a porous resin, wherein the porous resin has an interconnected pore structure, and silica aerogel in which polysiloxane particles are strung together like a pearl necklace is present in the interconnected pores of the porous resin. A porous composite material having the above structure can exhibit properties similar to those of a single silica aerogel. In this specification, the term "pearl necklace-like" means that the polysiloxane particles are three-dimensionally linked together to form a shape resembling a pearl necklace. In this specification, the term "communicating pore structure" refers to a structure that constitutes part of a porous resin, in which a plurality of fine pores are formed from the surface toward the inside of a porous composite material, and in which the pores do not exist independently of each other but are interconnected (connected) to each other.

[0016] [7] In the porous composite material of [6] above, the content of polysiloxane particles in the porous composite material is preferably 15% by mass or more and 35% by mass or less. If the content of the polysiloxane particles in the porous composite material is within the above range, the properties can approach those of a single silica aerogel. In this specification, the content of polysiloxane particles in the porous and composite material can be measured according to the method described in the examples.

[0017] [8] In the porous composite material of the above [6] or [7], the porous resin is preferably composed of a poly(meth)acrylic acid alkyl ester or a nitrile group-containing polymer. If the porous resin is made of a poly(meth)acrylic acid alkyl ester or a nitrile group-containing polymer, the properties can approach those of a single silica aerogel.

[0018] [9] In the porous composite material of the above [6] or [7], the porous resin is preferably composed of polymethyl methacrylate or polyacrylonitrile. If the porous resin is made of polymethyl methacrylate or polyacrylonitrile, the properties can approach those of a single silica aerogel. [Effects of the Invention]

[0019] According to the present invention, a method for producing a porous composite material can be provided that can easily produce a porous composite material containing silica aerogel and a porous resin. Furthermore, according to the present invention, a porous composite material having a predetermined structure can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail.

[0021] (Method of manufacturing porous composite material) The method for producing a porous composite material of the present invention (hereinafter sometimes simply referred to as the "production method") includes: a preparation step of preparing a homogeneous phase containing an organic solvent, a polysiloxane precursor, an organic polymer, and water; a condensation step of subjecting the homogeneous phase to a condensation step of condensing part or all of the polysiloxane precursor to obtain polysiloxane particles; and a precipitation step of precipitating the organic polymer by a phase separation method to obtain a porous resin, thereby obtaining a precipitate containing polysiloxane particles and a porous resin. Finally, a drying step of drying the precipitate. According to the above-described production method, a porous composite material containing silica aerogel and a porous resin (hereinafter, sometimes simply referred to as "porous composite material") can be easily obtained. Furthermore, the porous composite material obtained by the above-described production method can have a high porosity in the porous resin, which allows the content of polysiloxane particles to be increased, and as a result, can exhibit properties similar to those of a single silica aerogel. Furthermore, the porous composite material obtained by the above-described production method can effectively retain its shape because the silica aerogel and the porous resin are intricately entangled in the porous composite material. The manufacturing method of the present invention can provide the porous and composite material of the present invention described below.

[0022] In addition to the above-mentioned preparation step, condensation-precipitation step, and drying step, the production method of the present invention may optionally include a washing step in which the precipitate obtained in the condensation-precipitation step is washed with a washing solvent, and a solvent substitution step in which the solvent such as the washing solvent contained in the precipitate after the washing step is replaced with another solvent (hereinafter, may be referred to as a "substitution solvent").

[0023] <Preparation process> In the preparation step, a homogeneous phase containing an organic solvent, a polysiloxane precursor, an organic polymer, and water is prepared. Note that components other than the organic solvent, the polysiloxane precursor, the organic polymer, and water (hereinafter, sometimes referred to as "other components") may be optionally added to the homogeneous phase.

[0024] The method for preparing the homogeneous phase is not particularly limited, and examples thereof include (1) a method in which the components are mixed in any order to prepare a homogeneous phase, (2) a method in which an aqueous solution containing an organic solvent is first prepared, and a polysiloxane precursor and an organic polymer are added to the aqueous solution and dissolved together to prepare a homogeneous phase, and (3) a method in which an aqueous solution containing an organic solvent is first prepared, and one of the polysiloxane precursor and the organic polymer is dissolved in the aqueous solution, and then the other is dissolved to prepare a homogeneous phase, etc. Among these, method (3) is preferred because it allows for efficient production of a homogeneous phase, and it is more preferred to prepare an aqueous solution containing an organic solvent, dissolve the organic polymer in the aqueous solution, and then dissolve the polysiloxane precursor.

[0025] The dissolution temperature of the polysiloxane precursor and the organic polymer when preparing the homogeneous phase is not particularly limited as long as it is a temperature at which a homogeneous phase can be maintained, but is preferably 40°C or higher, more preferably 55°C or higher, and is preferably 100°C or lower, more preferably 90°C or lower. If the dissolution temperature is within the above range, a porous composite material can be obtained more easily.

[0026] <<Polysiloxane precursor>> The polysiloxane precursor is not particularly limited as long as it forms polysiloxane particles and can obtain a uniform phase, but examples include alkoxysilane compounds such as tetramethoxysilane and tetraethoxysilane; oligomers obtained by partially hydrolyzing alkoxysilane compounds such as tetramethoxysilane and tetraethoxysilane; and organoalkoxysilane compounds such as methyltrimethoxysilane and phenyltrimoxysilane. These may be used alone or in combination of two or more in any ratio. Among these, alkoxysilane compounds are preferred as the polysiloxane precursor, as they can more easily produce porous composite materials, and tetramethoxysilane is more preferred.

[0027] The content of the polysiloxane precursor in the homogeneous phase is preferably 4% by mass or more, more preferably 5% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less. When the content of the polysiloxane precursor in the homogeneous phase is equal to or higher than the lower limit, the condensation of the polysiloxane precursor can proceed efficiently in the condensation step. On the other hand, if the content of the polysiloxane precursor in the homogeneous phase is equal to or less than the upper limit, the production cost can be effectively reduced.

[0028] <<Organic polymers>> The organic polymer is not particularly limited as long as it forms a porous resin and a uniform phase, but examples thereof include poly(meth)acrylic acid alkyl esters such as polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, and polyethyl methacrylate; nitrile group-containing polymers such as polyacrylonitrile and polymethacrylonitrile; polylactide; and lactide-ε-caprolactone copolymers. These may be used alone or in any combination of two or more in any ratio. Among these, the organic polymer is preferably a poly(meth)acrylic acid alkyl ester or a nitrile group-containing polymer. The poly(meth)acrylic acid alkyl ester is preferably polymethyl methacrylate, and the nitrile group-containing polymer is preferably acrylonitrile. In this specification, "poly(meth)acrylic" means polyacrylic and / or polymethacrylic.

[0029] The content of the organic polymer in the homogeneous phase is preferably 1% by mass or more, more preferably 4% by mass or more, particularly preferably 6% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less. When the content of the organic polymer in the homogeneous phase is equal to or greater than the above lower limit, the organic polymer can be efficiently precipitated in the precipitation step. On the other hand, if the content of the organic polymer in the homogeneous phase is equal to or less than the upper limit, the organic polymer becomes more easily soluble in the organic solvent, and the production process can be made more efficient.

[0030] Here, the mass ratio of the organic polymer to the polysiloxane precursor in the homogeneous phase is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.7 or more, and is preferably 2.0 or less, more preferably 1.8 or less, and particularly preferably 1.5 or less. When the mass ratio of the organic polymer to the polysiloxane precursor is equal to or greater than the above lower limit, the structure of the resulting porous composite material can be made closer to a silica aerogel structure. Furthermore, when the mass ratio of the organic polymer to the polysiloxane precursor is within the above range, the apparent density of the resulting porous composite material is low, and the properties can approach those of a single silica aerogel.

[0031] <<Organic solvents>> The organic solvent is not particularly limited as long as it can provide a homogeneous phase, and examples thereof include alcohols such as methanol and ethanol, sulfur-containing solvents such as dimethyl sulfoxide and sulfolane, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, etc. These may be used alone or in combination of two or more in any ratio. The organic solvent is preferably an alcohol or a sulfur-containing solvent, with ethanol being preferred as the alcohol and dimethyl sulfoxide being preferred as the sulfur-containing solvent.

[0032] The content of the organic solvent in the homogeneous phase is preferably 20% by mass or more, more preferably 30% by mass or more, and is preferably 85% by mass or less, more preferably 80% by mass or less, and particularly preferably 70% by mass or less. When the content of the organic solvent in the homogeneous phase is equal to or higher than the lower limit, the organic polymer can be efficiently dissolved. On the other hand, if the content of the organic solvent in the homogeneous phase is equal to or less than the upper limit, the precipitation of the organic polymer in the precipitation step will be rapid, and productivity can be improved.

[0033] When preparing a homogeneous phase by the above method (2) or (3), the content of the organic solvent in the aqueous solution is not particularly limited as long as it is a content that allows a homogeneous phase to be maintained, but is preferably 50% by volume or more, more preferably 75% by volume or more, and more preferably 95% by volume or less, and more preferably 85% by volume or less. When the content of the organic solvent in the aqueous solution is within the above range, a porous composite material can be more easily obtained.

[0034] <Other ingredients> Other ingredients that may optionally be added to the homogeneous phase include, for example, flame retardants, dyes, and the like.

[0035] <<Combination of organic solvent and organic polymer>> In one embodiment, a combination of an alcohol and a poly(alkyl (meth)acrylate) is preferred, and a combination of ethanol and polymethyl methacrylate is more preferred, because a porous composite material can be more easily obtained from the organic solvent and the organic polymer.

[0036] In another embodiment, a combination of a sulfur-containing solvent and a nitrile group-containing polymer is preferred, and a combination of dimethyl sulfoxide and polyacrylonitrile is more preferred, since a porous composite material can be more easily obtained from the organic solvent and the organic polymer.

[0037] <<Solid concentration of homogeneous phase>> The solid content concentration of the homogeneous phase is preferably 5% by mass or more, more preferably 8% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less. When the solid content of the homogeneous phase is within the above range, a porous composite material can be obtained more easily, and the structure of the obtained porous composite material can be made closer to a silica aerogel structure.

[0038] <Condensation precipitation process> In the condensation precipitation step, the homogeneous phase prepared in the preparation step is subjected to a condensation step in which part or all of the polysiloxane precursor is condensed to obtain polysiloxane particles, and a precipitation step in which an organic polymer is precipitated by a phase separation method to obtain a porous resin, thereby obtaining a precipitate containing polysiloxane particles and a porous resin. The precipitate obtained by the condensation precipitation step has a desired porous interior and maintains the porous state, so that it can be dried without supercritical drying in the subsequent drying step. The condensation precipitation step may optionally include a gel formation step in which the solution after the condensation step is left for a predetermined period of time to obtain a wet gel body, and a crushing step in which the gel body obtained in the gel formation step is crushed.

[0039] Here, in the condensation-precipitation step, the order of the condensation step and the precipitation step is not particularly limited, and the condensation step may be performed after the precipitation step, or the condensation step may be performed after the precipitation step, or the condensation step and the precipitation step may be performed simultaneously. However, it is preferable to perform the condensation step after the precipitation step, as this makes it easier to obtain a porous composite material.

[0040] Hereinafter, the condensation-precipitation step will be described by taking as an example a condensation-precipitation step in which a precipitation step is carried out after a condensation step, but the condensation-precipitation step in the production method of the present invention is not limited to this.

[0041] <<Condensation process>> In the condensation step, a part or all of the polysiloxane precursor contained in the homogeneous phase is condensed to obtain polysiloxane particles.

[0042] The condensation of the polysiloxane precursor is not particularly limited as long as polysiloxane particles can be obtained, and can be carried out by adding a catalyst to a homogeneous phase. Examples of the catalyst include base catalysts such as aqueous ammonia, urea, and amines; and acid catalysts such as hydrochloric acid, acetic acid, and oxalic acid. These may be used alone or in combination of two or more in any ratio. Among these, the base catalyst is preferred, and aqueous ammonia is more preferred.

[0043] The amount of catalyst added to the homogeneous phase is preferably 0.05 mmol or more, more preferably 0.01 mmol or more, and is preferably 0.3 mmol or less, more preferably 0.2 mmol or less, per mol of the polysiloxane precursor. When the amount of catalyst added to the homogeneous phase is within the above range, the structure of the resulting porous composite material can be made closer to a silica aerogel structure.

[0044] The condensation time of the polysiloxane precursor is preferably 1 minute or more, more preferably 5 minutes or more, and is preferably 20 minutes or less, more preferably 15 minutes or less. When the condensation time of the polysiloxane precursor is equal to or greater than the above lower limit, the amount of unreacted polysiloxane precursor can be effectively suppressed. On the other hand, if the condensation time of the polysiloxane precursor is equal to or less than the upper limit, the productivity of the porous and composite material can be improved. The condensation time means the time from the completion of the addition of the catalyst to the homogeneous phase until the start of the formation of a gel body, which will be described later, or the time until the start of the precipitation step, which will be described later.

[0045] The condensation temperature of the polysiloxane precursor is usually 23°C or higher and 80°C or lower.

[0046] <<Gel body formation process>> In the optional gel formation step, the solution after the condensation step is left to stand for a predetermined time to obtain a wet gel. By including the gel body forming step in the condensation precipitation step, the polysiloxane precursor can be sufficiently condensed to efficiently obtain polysiloxane particles.

[0047] The standing time in the gel forming step is preferably 0.1 hour or more, more preferably 0.5 hour or more, and is preferably 24 hours or less, more preferably 12 hours or less. When the standing time in the gel body forming step is equal to or longer than the above lower limit, the amount of unreacted polysiloxane precursor can be effectively suppressed. On the other hand, if the standing time in the gel body forming step is equal to or less than the upper limit, the productivity of the porous and composite material can be improved. The above-mentioned standing time means the time from when the formation of the gel body starts until the start of an optional crushing step described later, or the time until the start of a precipitation step described later.

[0048] The temperature at which the mixture is left standing in the gel forming step is usually 23°C or higher and 80°C or lower.

[0049] <<Crushing process>> In the optional crushing step, the gel body obtained in the gel body forming step is crushed. By including a crushing step in the condensation-precipitation step, the apparent density of the resulting porous and composite material is reduced, and the properties can be made closer to those of a single silica aerogel. The method for crushing the gel body is not particularly limited, and may be carried out automatically using a stirrer or the like, or manually using a rod or the like.

[0050] In the disintegration step, the viscosity may be adjusted by adding the above-mentioned organic solvent or an aqueous solution containing an organic solvent to the gel body, thereby enabling the gel body to be disintegrated efficiently. The amount of the organic solvent or the aqueous solution containing the organic solvent used can be adjusted appropriately according to the desired viscosity.

[0051] In the crushing step, the gel body may be heated to suppress precipitation of the organic polymer, thereby enabling the gel body to be crushed efficiently. The heating temperature is not particularly limited as long as it is a temperature that can suppress precipitation of the organic polymer, but is preferably 40°C or higher, more preferably 50°C or higher, and is preferably 70°C or lower, and more preferably 65°C or lower.

[0052] <<Precipitation process>> In the precipitation step, an organic polymer is precipitated by a phase separation method to obtain a porous resin. When the condensation-precipitation step is performed after the condensation step, a precipitate containing polysiloxane particles and a porous resin can be obtained by the precipitation step. The precipitate is usually in a wet state.

[0053] In the precipitation step, the phase separation method is not particularly limited as long as it can precipitate an organic polymer to obtain a porous resin. However, a thermally induced phase separation method, i.e., a method in which a solution or gel containing an organic polymer is cooled to precipitate a porous resin, is preferred because it makes it easier to obtain a porous composite material.

[0054] When a thermally induced phase separation method is used in the precipitation step, the cooling temperature is not particularly limited as long as it is a cooling temperature at which the structure of the porous resin is solidified and is equal to or lower than the crystallization temperature (crystalline polymer) or glass transition temperature (amorphous polymer) of the organic polymer, but is preferably equal to or higher than -40°C, more preferably equal to or higher than -30°C, and is preferably equal to or lower than 0°C, and more preferably equal to or lower than -10°C. When the cooling temperature is equal to or higher than the lower limit, freezing of the organic solvent and water can be suppressed, and the productivity of the porous and composite material can be improved. On the other hand, if the cooling temperature is equal to or lower than the upper limit, the porous resin can be efficiently precipitated.

[0055] When a thermally induced phase separation method is used in the precipitation step, the cooling time is usually 5 minutes or more and 3 hours or less.

[0056] <Cleaning process> In the optional washing step, the precipitate obtained in the condensation precipitation step is washed with a washing solvent, which effectively removes unreacted polysiloxane precursors and the like.

[0057] As the washing solvent, a solvent that is a poor solvent for the porous resin and a good solvent for water can be used, and for example, the solvents listed in the above section "organic solvent" can be used.

[0058] The temperature of the washing solvent when washing the precipitate is usually −40° C. or higher and 0° C. or lower.

[0059] <Solvent substitution process> In the optional solvent substitution step, the cleaning solvent or other solvent contained in the precipitate after the cleaning step is substituted with a substitution solvent. This allows the precipitate to be efficiently dried in the drying step described below. Furthermore, damage to the precipitate, such as cracking, can be effectively prevented.

[0060] The replacement solvent may be a poor solvent for the porous resin and have a lower surface tension than the washing solvent, such as an alkane such as n-hexane or n-heptane. Of these, n-heptane is preferred.

[0061] <Drying process> In the drying step, the precipitate obtained in the condensation precipitation step, the optional washing step, or the optional solvent substitution step is dried. In the production method of the present invention, the interior of the precipitate is in a desired porous state, and drying is possible while maintaining the porous state, so drying is possible without performing supercritical drying. Therefore, supercritical drying is usually not performed in the drying step in the production method of the present invention.

[0062] The drying temperature of the precipitate is not particularly limited as long as it can remove the solvent contained in the precipitate (organic solvent, water, washing solvent, replacement solvent, etc.), but is usually 20°C or higher and 40°C or lower.

[0063] The drying time for the precipitate is not particularly limited as long as the solvent contained in the precipitate can be removed, but is usually 2 hours or more and 24 hours or less.

[0064] (Porous composite material) The porous composite material of the present invention comprises a silica aerogel and a porous resin, and the porous resin has an interconnected pore structure, and silica aerogel in which polysiloxane particles are strung together like a pearl necklace is present in the interconnected pores of the porous resin. In a porous composite material having the above structure, the porous resin can have a high porosity, which allows the content of polysiloxane particles to be increased, and as a result, the material can exhibit properties similar to those of a single silica aerogel. Furthermore, the porous composite material having the above-described structure can effectively maintain its shape because the silica aerogel and the porous resin are intricately entangled in the porous composite material. The porous and composite material of the present invention can be obtained by the above-mentioned production method of the present invention.

[0065] <Porous resin> As the polymer constituting the porous resin, the polymers listed in the above section "organic polymer" and the like can be used. Here, the porous resin is preferably composed of a poly(meth)acrylic acid alkyl ester or a nitrile group-containing polymer, since this allows the properties to approach those of a single silica aerogel. The poly(meth)acrylic acid alkyl ester is preferably polymethyl methacrylate, and the nitrile group-containing polymer is preferably acrylonitrile.

[0066] The content of the porous resin in the porous composite material is preferably 50% by mass or more, more preferably 85% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less. If the content of the porous resin in the porous composite material is within the above range, the properties can approach those of a single silica aerogel.

[0067] <Polysiloxane particles> As the polysiloxane constituting the polysiloxane particles, a condensate (condensation product) of the compounds listed in the above section "Polysiloxane precursor" can be used. Here, the polysiloxane particles are preferably composed of a condensate of an alkoxysilane compound, and more preferably composed of a condensate of tetramethoxysilane, since this allows the polysiloxane particles to have properties similar to those of a single silica aerogel.

[0068] The content of polysiloxane particles in the porous composite material is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less. If the content of the polysiloxane particles in the porous composite material is within the above range, the properties can approach those of a single silica aerogel.

[0069] <Apparent density of porous composite material> The apparent density of the porous composite material is 0.7 g / cm 3 It is preferable that the concentration is 0.6 g / cm or less. 3 More preferably, it is 0.3 g / cm or less. 3 More preferably, it is 0.2 g / cm or less. 3 Even more preferably, the following: If the apparent density of the porous composite material is equal to or less than the upper limit, the properties can approach those of a single silica aerogel. On the other hand, the apparent density of the porous composite material is, for example, 0.05 g / cm 3 or more, and 0.1 g / cm 3 More than 0.15g / cm 3 More than that is fine. In this specification, the apparent density of the porous and composite material can be measured according to the method described in the Examples. [Example]

[0070] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, the content ratio of polysiloxane particles or silica particles, apparent density, silica aerogel structure, and shape retention upon drying were measured or confirmed.

[0071] <Measurement of the content of polysiloxane particles or silica particles> The content of polysiloxane particles or silica particles in the porous and composite materials obtained in the examples and comparative examples was measured using a differential scanning calorimeter ("STA7200" manufactured by Hitachi High-Tech Science). Specifically, a sample cut from the porous composite material was placed in an aluminum container made specifically for the instrument, and heated to 500°C under conditions of a nitrogen gas flow rate of 20 mL / min and 20°C / min, to obtain a TG curve. The residual weight rate at 500°C was calculated using the analysis software provided with the instrument, and this calculated value was taken as the content rate of polysiloxane particles or silica particles.

[0072] <Measurement of apparent density> The apparent density of the porous composite material obtained in each of the examples and comparative examples was determined by measuring the mass of the porous composite material using an electronic balance and dividing the mass by the volume of the porous composite material. When comparing porous composite materials with the same content of polysiloxane particles or silica particles, the lower the apparent density of the porous composite material, the closer its properties are to those of a single silica aerogel.

[0073] <Confirmation of silica aerogel structure> The silica aerogel structure of the porous composite materials obtained in the examples and comparative examples was confirmed using a field emission scanning electron microscope (JEOL Ltd., JSM-7800F). Specifically, a measurement sample was prepared by coating the surface of the porous composite material with osmium using an osmium coater using a field emission scanning electron microscope. The structure of the obtained measurement sample was observed at magnifications of 10,000 to 50,000 times and evaluated according to the following criteria. A: Has an overall silica aerogel structure. B: Does not have a silica aerogel structure.

[0074] <Confirmation of shape retention after drying> The state of the materials in the drying process of the Examples and Comparative Examples was checked and evaluated according to the following criteria. A: The material was lumpy after drying and retained its shape before drying. B: The material was lumpy after drying, but was unable to retain its shape before drying. C: Cracks appeared during drying and the material crumbled after drying.

[0075] Example 1 <Preparation process> 0.625 g of polymethyl methacrylate (PMMA) as an organic polymer was dissolved in 6 mL of 80% by volume ethanol aqueous solution at 60° C. Next, 0.64 g of tetramethoxysilane (Tokyo Ohka Kogyo Co., Ltd.) as a polysiloxane precursor was added to the resulting solution to obtain a homogeneous solution (homogeneous phase).

[0076] <Condensation precipitation process> To the homogeneous solution obtained in the preparation step, 0.354 mL (6.1 mmol in terms of ammonia) of 1.73 M aqueous ammonia (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added little by little, and the mixture was left standing for 10 minutes after the addition was completed (condensation step). After 10 minutes, the solution was cooled to -20°C for 15 minutes to obtain a wet precipitate (precipitation step).

[0077] <Cleaning process> The precipitate obtained in the condensation precipitation step was washed with ethanol at -20°C.

[0078] <Solvent substitution process> The solvent of the precipitate after the washing step was simply replaced from ethanol to heptane using n-heptane at -20°C.

[0079] <Drying process> The precipitate after the solvent substitution step was dried at room temperature to obtain a porous composite material. The obtained porous composite material was used to measure the content ratio of polysiloxane particles or silica particles, measure the apparent density, confirm shape retention upon drying, and confirm the silica aerogel structure. The results are shown in Table 1.

[0080] Example 2 Except for carrying out the condensation-precipitation step in the following manner, various operations, confirmations, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0081] <Condensation precipitation process> To the homogeneous solution obtained in the preparation step, 0.354 mL of 1.73 M aqueous ammonia (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added little by little (condensation step). Next, the solution after the addition of aqueous ammonia was left to stand for 60 minutes to obtain a wet gel (gel formation step). The solution was then cooled at -20°C for 15 minutes to obtain a wet precipitate (precipitation step).

[0082] Example 3 Except for changing the amount of 80% by volume aqueous ethanol solution used in the preparation step from 6 mL to 9 mL and carrying out the condensation precipitation step in the following manner, various operations, confirmations, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0083] <Condensation precipitation process> To the homogeneous solution obtained in the preparation step, 0.354 mL of 1.73 M aqueous ammonia (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added little by little (condensation step). Next, the solution after the addition of aqueous ammonia was left to stand for 60 minutes to obtain a wet gel (gel formation step). Next, the obtained wet gel was crushed, and 3 mL of 80% by volume aqueous ethanol solution was added to adjust the viscosity. The mixture was heated to 60°C and stirred to prevent the precipitation of polymethyl methacrylate (crushing step). The mixture was cooled to -20°C for 15 minutes to obtain a wet precipitate (precipitation step).

[0084] Example 4 In the preparation step, 0.625 g of polymethyl methacrylate (PMMA) was changed to 0.625 g of polyacrylonitrile (PAN), and 6 mL of 80% by volume ethanol aqueous solution was changed to 10.3 mL of 10% by volume dimethyl sulfoxide aqueous solution. Except for this, various operations, confirmations, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0085] Example 5 Except for changing the amount of polymethyl methacrylate (PMMA) used in the preparation step from 0.625 g to 0.15 g, various operations, confirmations, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0086] Example 6 In the preparation step, the amount of polymethyl methacrylate (PMMA) used was changed from 0.625 g to 1.00 g, and the amount of 80% by volume aqueous ethanol solution used was changed from 6 mL to 10 mL, except that various operations, confirmations, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0087] (Comparative Example 1) Except for not adding tetramethoxysilane in the preparation step and not adding aqueous ammonia in the condensation precipitation step, various operations were carried out in the same manner as in Example 1, and shape retention upon drying was confirmed. The results are shown in Table 1. Note that, since no polysiloxane precursor was added, confirmation of the silica aerogel structure was not carried out.

[0088] (Comparative Example 2) Various operations, confirmations, and measurements were carried out in the same manner as in Example 1, except that in the preparation step, polymethyl methacrylate (PMMA) was not used, and 0.64 g of tetramethoxysilane (manufactured by Tokyo Ohka Kogyo Co., Ltd.) as a polysiloxane precursor was added to 6 mL of an 80% by volume aqueous ethanol solution to obtain a homogeneous solution (homogeneous phase). The results are shown in Table 1. Because the material did not retain its shape after drying, measurement of the apparent density and confirmation of the silica aerogel structure were not carried out.

[0089] (Comparative Example 3) In the preparation step, 0.625 mL of tetramethoxysilane as a polysiloxane precursor was replaced with 0.64 g of particulate colloidal silica (organosilica sol IPA-ST, manufactured by Nissan Chemical Industries, Ltd.), which is a silicon oxide, to obtain a heterogeneous solution (heterogeneous phase). Except for this, various operations, confirmations, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0090] In addition, in Table 1, "PMMA" indicates polymethyl methacrylate; "PAN" indicates polyacrylonitrile; "TMA" indicates tetramethoxysilane; "DMSO aqueous solution" refers to an aqueous solution of dimethyl sulfoxide, "Organic polymer / polysiloxane precursor or silicon oxide (mass ratio)" refers to the mass ratio of the organic polymer to the polysiloxane precursor or silicon oxide.

[0091] [Table 1]

[0092] As is clear from Table 1, the manufacturing methods of Examples 1 to 6 enable porous composite materials containing silica aerogel and porous resin to be easily obtained without supercritical drying, because the porous composite materials retain their shape after drying. Furthermore, as is clear from Table 1, the porous and composite materials of Examples 1 to 6 have a predetermined silica aerogel structure. [Industrial Applicability]

[0093] According to the present invention, a method for producing a porous composite material can be provided that can easily produce a porous composite material containing silica aerogel and a porous resin. Furthermore, according to the present invention, a porous composite material having a predetermined structure can be provided.

Claims

1. A method for producing a porous composite material containing silica aerogel and a porous resin, comprising: a preparing step of preparing a homogeneous phase including an organic solvent, a polysiloxane precursor, an organic polymer, and water; a condensation-precipitation step in which the homogeneous phase is subjected to a condensation step in which a part or all of the polysiloxane precursor is condensed to obtain polysiloxane particles, and a precipitation step in which the organic polymer is precipitated by a phase separation method to obtain a porous resin, thereby obtaining a precipitate containing the polysiloxane particles and the porous resin; a drying step of drying the precipitate; A method for producing a porous composite material, comprising:

2. The method for producing a porous and composite material according to claim 1 , wherein a mass ratio of the organic polymer to the polysiloxane precursor is 0.1 or more and 2.0 or less.

3. The method for producing a porous and composite material according to claim 1 , wherein the phase separation method is a thermally induced phase separation method.

4. The method for producing a porous and composite material according to any one of claims 1 to 3, wherein the organic solvent and the organic polymer are a combination of an alcohol and a poly(meth)acrylic acid alkyl ester, or a combination of a sulfur-containing solvent and a nitrile group-containing polymer.

5. The method for producing a porous and composite material according to any one of claims 1 to 3, wherein the organic solvent and the organic polymer are a combination of ethanol and polymethyl methacrylate, or a combination of dimethyl sulfoxide and polyacrylonitrile.

6. A porous composite material comprising silica aerogel and a porous resin, the porous resin has a continuous pore structure, A porous composite material, wherein a silica aerogel in which polysiloxane particles are strung together like a pearl necklace is present in the interconnected pores of the porous resin.

7. The porous and composite material according to claim 6, wherein the content of the polysiloxane particles in the porous and composite material is 15% by mass or more and 35% by mass or less.

8. 8. The porous and composite material according to claim 6, wherein the porous resin is composed of a poly(meth)acrylic acid alkyl ester or a nitrile group-containing polymer.

9. 8. The porous and composite material according to claim 6, wherein the porous resin is composed of polymethyl methacrylate or polyacrylonitrile.

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