Method for producing a gel particle dispersion

Abstract

To provide a method with which it is possible to efficiently obtain a gel particle dispersion in which a residual amount of a solvent used for a gel manufacturing and an amount of a by-product in a gelled product are reduced.SOLUTION: A method for manufacturing a gel particle dispersion includes subjecting a gel slurry to cross-flow filtration.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing a gel particle dispersion. More specifically, this invention relates to a method for producing a gel particle dispersion that can efficiently reduce the amount of residual solvent and by-products used during gel production. [Background technology]

[0002] Gels are used in a variety of fields. For example, gels of silicon compounds have functional properties such as thermal insulation, low dielectric constant, and low refractive index, and are used in various applications such as optical and electronic materials. When using such gels, methods are known, such as preparing a paint containing pulverized gels and a solvent, coating it onto a substrate, and drying it to form a film made of the gel.

[0003] Various methods have been known to date for producing materials using such gels. For example, Patent Document 1 describes a method for manufacturing a gel in which a gel material is gelled in a gel manufacturing solvent, the solvent in the gel is replaced with another solvent, the solvent replacement process is divided into multiple solvent replacement steps, and in the solvent replacement steps, a solvent with lower hydrophilicity is used in the later steps than in the earlier steps, thereby enabling the production of a void structure film with a low residual amount of gel manufacturing solvent in the gel and a high void ratio.

[0004] Furthermore, Patent Document 2 describes a method for producing a silica aerogel film, which includes the steps of dispersing organically modified silica in a solvent and forming a film with a dispersion containing organically modified silica, wherein the method involves dispersing the organically modified silica in a ketone-based solvent in the dispersion step to produce an organically modified silica aerogel film having excellent hydrophobicity. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-100100 [Patent Document 2] Japanese Patent Publication No. 2006-151800 [Overview of the project] [Problems that the invention aims to solve]

[0006] When using gels in this way, a gel particle dispersion is used, which is obtained by dispersing the gel in a solvent. However, the gel contains the solvent used during gel production and by-products such as methanol generated during gel production. If a gel particle dispersion is prepared using a gel that still contains the solvent, catalyst, and by-products used during gel production, problems may arise, such as the gel not being able to fully exhibit its function. Therefore, it is necessary to minimize the amount of residual solvent, catalyst, and by-products used during gel production. However, conventional methods have not been able to efficiently reduce these amounts.

[0007] This invention has been made in view of the above-mentioned circumstances, and aims to provide a method for efficiently obtaining a gel particle dispersion in which the amount of residual solvent and by-products used during gel production in the gel is reduced. [Means for solving the problem]

[0008] The inventors of the present invention investigated various methods for producing gel particle dispersions and found that by filtering the gel slurry in a cross-flow manner, the amount of residual solvent used during gel production and the amount of by-products in the gel can be efficiently reduced, thus completing the present invention.

[0009] The present invention provides the following embodiments of the invention. [1] A method for producing a gel particle dispersion, the method comprising a step of cross-flow filtering a gel slurry. [2] The method for producing a gel particle dispersion according to [1] above, characterized in that the filtration pressure in the cross-flow filtration step is 0.05 to 1.0 MPa. [3] The method for producing a gel particle dispersion according to [1] or [2] above, wherein a treatment temperature in the cross-flow filtration step is 10 to 100°C. [4] The method for producing a gel particle dispersion according to any one of [1] to [3] above, wherein a linear velocity of a circulating liquid in the cross-flow filtration step is 0.5 to 5.0 m / sec. [5] The method for producing a gel particle dispersion according to any one of [1] to [4] above, wherein solvent substitution is performed in the cross-flow filtration step. [6] The method for producing a gel particle dispersion according to any one of [1] to [5] above, wherein the gel slurry is an aged stirred gel slurry obtained by stirring and aging a gel before the cross-flow filtration step. [7] The method for producing a gel particle dispersion according to [6] above, wherein the stirring and aging is a step of stirring the gel at 10 to 80°C for 1 to 40 hours. [8] The method for producing a gel particle dispersion according to any one of [1] to [7] above, wherein the gel particle dispersion is an organosilicon compound gel particle dispersion. [9] The method for producing a gel particle dispersion according to [8] above, wherein the organosilicon compound is a siloxane compound.

[10] The method for producing a gel particle dispersion according to any one of [1] to [9] above, further comprising a pulverization step. Effects of the Invention

[0010] The method for producing a gel particle dispersion of the present invention can efficiently obtain a gel particle dispersion in which the residual amount of a solvent used in gel production and the amount of by-products are reduced. Mode for Carrying Out the Invention

[0011] The present invention is described in detail below. Furthermore, combinations of two or more individual preferred embodiments of the present invention described below are also preferred embodiments of the present invention.

[0012] The present invention relates to a method for producing a gel particle dispersion, wherein the production method comprises a step of subjecting a gel slurry to cross-flow filtration. By performing cross-flow filtration on the gel slurry, the residual amount of the solvent used in gel production (solvent for gel production) in the gel and the amount of by-products can be efficiently reduced.

[0013] (Cross-flow filtration step) In the cross-flow filtration, the liquid flows parallel to the filtration surface, and filtration is performed in a mode where the flow of the feed liquid and the filtrate are orthogonal to each other. There is no particular limitation as long as it is such a cross-flow filtration method, and the filtration can be performed by a known method. In cross-flow filtration, efficient filtration can be achieved by circulating the liquid to be filtered to bring it into contact with the filtration membrane. Therefore, by using the gel slurry as a circulating liquid and performing continuous cross-flow filtration, the residual amount of the solvent for gel production contained in the gel slurry and the amount of by-products can be efficiently reduced.

[0014] The filtration membrane used in the cross-flow filtration is not particularly limited, and filtration membranes made of known materials such as polysulfone, polyacrylonitrile, polyethylene, tetrafluoroethylene, polypropylene, polyethersulfone, aluminum oxide, zirconium oxide, titanium oxide, stainless steel, glass, ceramics, and metal mesh can be used. Among these, filtration membranes made of ceramics are preferred in terms of high corrosion resistance, high heat resistance, and high strength.

[0015] The pore size of the filtration membrane may be appropriately selected depending on the size of the gel, but is preferably 0.005 to 10 µm, more preferably 0.01 to 5 µm, and even more preferably 0.05 to 3 µm.

[0016] Commercially available products may be used as the filtration membrane. Examples of filtration membranes that can be used in the present invention include ceramic membrane filters manufactured by NGK Insulators, Ltd., ceramic filters manufactured by Noritake Co., Ltd., and ceramic membrane filters manufactured by Pall Corporation Japan.

[0017] The filtration pressure for the above cross-flow filtration is preferably 0.05 to 1.0 MPa. The filtration pressure mentioned above is the pressure difference between the flow passage side and the filtration side of the filtration membrane. If there is a pressure difference between the inlet and outlet of the flow passage of the filtration membrane, the flow passage side pressure can be calculated using the following formula. Flow channel side pressure (MPa) = (Flow channel inlet pressure (MPa) + Flow channel outlet pressure (MPa)) / 2 When the filtration pressure is within the above range, efficient filtration can be achieved. The above filtration pressure is more preferably 0.06 to 0.8 MPa, and even more preferably 0.08 to 0.5 MPa.

[0018] The processing temperature for the above cross-flow filtration is preferably 10 to 100°C. Filtration can be performed efficiently within this processing temperature range. The processing temperature is preferably 80°C or lower, and more preferably 60°C or lower, in terms of suppressing thermal degradation of the gel and reducing heating costs. Furthermore, it is preferably 10°C or higher, and more preferably 20°C or higher, in terms of suppressing viscosity increase of the gel solution and reducing cooling costs.

[0019] The linear velocity of the circulating fluid in the above cross-flow filtration is preferably 0.5 to 5.0 m / sec. Here, the linear velocity is calculated by the following formula. Linear velocity of circulating fluid (m / sec) = Flow velocity of circulating fluid (m 3 / sec) / filtration membrane flow path inlet area (m 2 ) Furthermore, if the filtration membrane has multiple flow channels, or if multiple filtration membranes are used, the linear velocity of the circulating fluid within the filtration membrane flow channels shall be the average linear velocity of the circulating fluid relative to the total cross-sectional area of ​​all flow channels. When the linear velocity of the circulating fluid is within the above range, filtration can be performed efficiently. A higher linear velocity of the circulating fluid is more effective in removing gel deposited on the surface of the filter membrane, reducing filtration resistance and increasing the filtration speed, so a linear velocity of 1.0 m / sec or higher is more preferable. On the other hand, if the linear velocity is too high, the circulation pump will need to have excessive capacity, which is disadvantageous from an economic standpoint (capital investment and running costs), and the pressure loss between the inlet and outlet of the filter membrane flow path will increase with the linear velocity, increasing the possibility of the filter membrane being damaged, so a linear velocity of 4.0 m / sec or lower is more preferable.

[0020] In the method for producing a gel particle dispersion of the present invention, it is preferable to perform solvent replacement in the cross-flow filtration step described above. By performing solvent replacement, the amount of residual solvent for gel production and the amount of by-products can be efficiently reduced, and at the same time, a gel particle dispersion containing a solvent appropriate to the purpose and application can be produced. Conventionally, for example, bulk gels were divided into chunks, and solvent replacement was performed by decantation, bringing the divided gels into contact with a solvent. However, in order to achieve sufficient solvent replacement using this method, it was necessary to repeat decantation several times using multiple types of solvents as needed, which presented problems such as being time-consuming and requiring an increased amount of solvent. In the cross-flow filtration process described above, solvent replacement can reduce the amount of solvent used and shorten the time required, thereby reducing the amount of residual solvent and by-products for gel production, and enabling the efficient production of a gel particle dispersion containing the target solvent. Furthermore, in this invention, the filtrate can be easily recovered.

[0021] The solvent substitution described above may be a direct substitution from the gel manufacturing solvent to the target solvent, or it may be a multi-step substitution. In particular, from the viewpoint of manufacturing efficiency, it is preferable to perform the solvent substitution in a single step.

[0022] When performing solvent replacement by the cross-flow filtration method described above, a mixture containing the gel slurry and the replacement solvent will be used as the circulating solution. When cross-flow filtering the mixture containing the above-mentioned gel slurry and substitution solvent, the gel slurry and substitution solvent may be mixed beforehand and then cross-flow filtered, or the substitution solvent may be added to the gel slurry while cross-flow filtering is performed and the mixture is mixed.

[0023] The solvents used for gel production are not particularly limited and include known solvents commonly used in gel production, such as aprotic polar solvents like dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), dimethylformamide (DMF), γ-butyllactone (GBL), acetonitrile (AN), acetone, and ethylene glycol monoethyl ether (EGEE); alcoholic solvents like methanol, ethanol, isopropyl alcohol, isobutyl alcohol, and n-butyl alcohol; and protic polar solvents like water. In particular, as the solvent for manufacturing the gel, aprotic polar solvents are preferred in terms of ensuring the stability and transparency of the primary particles of the gel, with N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), γ-butyllactone (GBL), and N,N-dimethylacetamide (DMAc) being more preferred, and dimethyl sulfoxide being even more preferred. The above-mentioned solvents for gel production may be used individually or in combination of two or more types.

[0024] Furthermore, if water is used as the solvent for gel production, an emulsifier may be added. Examples of the emulsifiers mentioned above include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, and polymer emulsifiers. Among these, anionic emulsifiers are preferred in terms of gel stability. The emulsifiers mentioned above may be used individually or in combination of two or more.

[0025] The amount of emulsifier added is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of silicon compound.

[0026] The above-mentioned substitution solvent is not particularly limited and can be appropriately selected according to the purpose and application of the gel particle dispersion. Specifically, examples include alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, n-butanol, 2-butanol, isobutyl alcohol, pentyl alcohol, ethylene glycol, diethylene glycol, and glycerin; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether-based solvents such as diethyl ether, tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, diethylene glycol ethyl ether, and anisole; ester-based solvents such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; cellosolve-based solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; and aromatic hydrocarbons such as benzene and toluene. Among these, alcohol-based solvents are preferred because they easily maintain the transparency of the gel. The above substitution solvents may be used individually or in combination of two or more.

[0027] When performing the above solvent substitution in multiple stages, for example, if the solvent for gel production is less hydrophilic than the substitution solvent, the solvent substitution may be performed by sequentially using solvents with higher hydrophilicity than the solvent used in the previous stage, starting with the solvent with lower hydrophilicity. Alternatively, if the solvent for gel production is more hydrophilic than the substitution solvent, the solvent substitution may be performed by sequentially using solvents with lower hydrophilicity than the solvent used in the previous stage, starting with the solvent with higher hydrophilicity. Substituting solvents with significantly different hydrophilicity levels may lead to poor substitution due to phase separation or a decrease in gel stability, so it is preferable to perform the substitution in order of similar hydrophilicity. In particular, the method of performing solvent substitution by sequentially using solvents with lower hydrophilicity than the solvent used in the previous stage, starting with the solvent with higher hydrophilicity, is preferred. Furthermore, the solvent substitution described above may involve substituting a low-boiling point solvent with a high-boiling point solvent, or vice versa.

[0028] The above multi-stage process is not particularly limited, but since a large number of stages reduces manufacturing efficiency, it is preferable to perform the process in 1 to 4 stages, and more preferably in 1 to 3 stages.

[0029] The amount of substitution solvent used in the above cross-flow filtration is not particularly limited as long as it is sufficient to adequately replace the target solvent. However, since the amount of substitution solvent used can be reduced compared to conventional methods, it is preferably 100 to 5000 parts by mass, more preferably 300 to 4000 parts by mass, and even more preferably 500 to 3000 parts by mass per 100 parts by mass of the above gel slurry.

[0030] The gel slurry used for the cross-flow filtration described above is a dispersion in which solid gel is dispersed in a gel-making solvent. In this invention, the dispersion containing the gel-making solvent before the cross-flow filtration process is referred to as "gel slurry." The gel dispersion after the cross-flow filtration process is referred to as "gel particle dispersion." If solvent replacement is performed in the cross-flow filtration process, the "gel particle dispersion" is a dispersion in which the gel is dispersed in the replacement solvent.

[0031] The shape of the gel contained in the above gel slurry is not particularly limited and may be spherical, non-spherical, or amorphous.

[0032] The number-average particle size of the gel particles contained in the above gel slurry is preferably 0.2 to 300 μm. When the number-average particle size is within the above range, the gel particles do not clog the pores of the filtration membrane or permeate through the filtration membrane, allowing for efficient cross-flow filtration. The number-average particle size is more preferably 0.5 to 200 μm, and even more preferably 1 to 100 μm. The above number-average particle diameter can be determined using a laser diffraction particle size distribution analyzer, and specifically, it can be determined by the method described in the examples below.

[0033] The solid content concentration of the gel slurry is not particularly limited, but is preferably 0.5 to 20% by mass, more preferably 0.8 to 10% by mass, and even more preferably 1 to 5% by mass, from the viewpoint of achieving better cross-flow filtration efficiency.

[0034] The gel slurry is not particularly limited, and includes dispersions of known gelled materials. Among these, organosilicon compound gel slurry is preferably mentioned. An organosilicon compound gel slurry, which is a preferred embodiment of the present invention, is described below.

[0035] (Organosilicon Compound Gel Slurry) The organosilicon compound gel slurry is a dispersion in which an organosilicon compound gel is dispersed in a solvent for gel production. The organosilicon compound gel slurry can be produced by hydrolyzing a silicon compound, and condensing and aging the hydrolyzate.

[0036] (1) Hydrolysis of Silicon Compound Hydrolysis of the silicon compound can be performed by mixing the silicon compound with a solvent for gel production, water, and an acid catalyst. The hydrolysis may be performed while stirring the mixture.

[0037] Examples of the silicon compound include compounds represented by the following formula (1). (R 1 ) 4-a Si(OR 2 ) a (1) (wherein R 1 and R 2 are the same or different and each represents a hydrogen atom or a hydrocarbon group. A plurality of R 1 and R 2 may each be the same as or different from each other. a represents an integer of 1 to 4.)

[0038] The above R 1and R 2 The hydrocarbon group represented by may be linear, branched, or cyclic, and may be saturated or unsaturated hydrocarbon groups. In particular, the hydrocarbon group is preferably linear or branched, and more preferably linear.

[0039] The saturated hydrocarbon group mentioned above is preferably an aliphatic hydrocarbon group. Examples of the above-mentioned aliphatic hydrocarbon groups include linear alkyl groups such as methyl, ethyl, propyl, and butyl groups; branched alkyl groups such as isopropyl and isobutyl groups; and cycloalkyl groups such as cyclohexyl groups.

[0040] Examples of the above-mentioned unsaturated hydrocarbon groups include linear alkenyl groups such as vinyl, n-propenyl, 1-butenyl, 2-butenyl, and 1-pentenyl groups; branched alkenyl groups such as isopropenyl groups; aromatic hydrocarbon groups such as aryl groups such as phenyl, tolyl, and xylyl groups, and aralkyl groups such as benzyl and phenethyl groups.

[0041] The number of carbon atoms in the hydrocarbon group is preferably 1 to 6, more preferably 1 to 3, even more preferably 1 to 2, and even more preferably 1.

[0042] In particular, the above R 1 From the viewpoint of membrane strength and the stability of primary particles within the gel, it is preferably an aliphatic hydrocarbon group, more preferably an aliphatic hydrocarbon group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0043] The above R 2 It is preferably a hydrogen atom or an aliphatic hydrocarbon group, more preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms, and even more preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 2 carbon atoms.

[0044] In formula (1) above, a represents an integer from 1 to 4, preferably from 2 to 4, and more preferably from 2 to 3. In formula (1) above, when a is 1, it is a "monofunctional" silicon compound; when a is 2, it is a "bifunctional" silicon compound; and when a is 3, it is a "trifunctional" silicon compound. In particular, the silicon compound described above is preferably 2- to 4-functional, and more preferably trifunctional, in that it has high film strength and can maintain flexibility.

[0045] Specific examples of silicon compounds represented by formula (1) above include, for example, tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane; alkyltrialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane; alkyldialkoxysilanes such as dimethyldimethoxysilane and dimethyldiethoxysilane; and arylalkoxysilanes such as phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane. Among these, alkylalkoxysilanes are preferred because they have high film strength and maintain flexibility, and alkyltrialkoxysilanes are preferred.

[0046] The silicon compounds described above may be used individually or in combination of two or more.

[0047] As solvents for the production of the above-mentioned gel, those listed above are suitable, but among them, aprotic polar solvents are preferred in terms of ensuring the stability and transparency of the primary particles of the organosilicon compound gel. N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), γ-butyllactone (GBL), and N,N-dimethylacetamide (DMAc) are more preferred, and dimethyl sulfoxide is even more preferred.

[0048] The amount of the above-mentioned gel manufacturing solvent added is not particularly limited, but for example, it is preferably 100 to 2000 parts by mass, more preferably 200 to 1800 parts by mass, and even more preferably 300 to 1600 parts by mass, per 100 parts by mass of the silicon compound.

[0049] The water mentioned above is not particularly limited and may be any type of water, such as distilled water, deionized water, or pure water. The amount of water added is not particularly limited, but for example, it is preferably 50 to 1000 parts by mass, more preferably 60 to 900 parts by mass, and even more preferably 80 to 800 parts by mass, per 100 parts by mass of silicon compound.

[0050] Examples of the acid catalysts mentioned above include hydrochloric acid, oxalic acid, and sulfuric acid. The amount of the above-mentioned acid catalyst added is not particularly limited, but for example, it is preferably 0.01 to 1.0 parts by mass, more preferably 0.02 to 0.5 parts by mass, and even more preferably 0.03 to 0.3 parts by mass per 100 parts by mass of the silicon compound.

[0051] The temperature of the above hydrolysis reaction is preferably 10 to 60°C, more preferably 15 to 50°C, and even more preferably 20 to 40°C. The reaction time is preferably 0.1 to 40 hours, more preferably 0.2 to 20 hours, and even more preferably 0.5 to 10 hours.

[0052] The above silicon compound hydrolysis step results in the "(OR)" in formula (1) representing the above silicon compound. 2 ) a " is "(OH) a A hydrolyzed product is generated, which is a result of this process.

[0053] (2) Condensation and maturation of hydrolyzed products The condensation and maturation of the hydrolysate can be carried out by mixing a base catalyst with the hydrolysate obtained by the above hydrolysis. Furthermore, a gel-making solvent or water may be added when mixing with the base catalyst. The hydrolysate undergoes dehydration condensation, and a cross-linking reaction proceeds through maturation, producing a gel-like silicon compound.

[0054] Examples of the above-mentioned base catalysts include ammonia, potassium hydroxide, and sodium hydroxide. The amount of the above-mentioned base catalyst added is preferably 1 to 500 parts by mass, more preferably 5 to 200 parts by mass, and even more preferably 10 to 100 parts by mass, per 100 parts by mass of the silicon compound.

[0055] The temperature for the above condensation and maturation reaction is preferably 10 to 80°C, more preferably 15 to 70°C, and even more preferably 20 to 60°C. The reaction time is preferably 1 to 40 hours, more preferably 2 to 35 hours, and even more preferably 3 to 30 hours.

[0056] The above condensation and maturation reaction produces a gel-like silicon compound. Preferably, the gel-like silicon compound is a compound having siloxane bonds (Si-O-Si bonds). In the present invention, compounds having such siloxane bonds are referred to as "organosilicon compounds" or "organosilicon compound gels." The above-mentioned gel slurry preferably contains such an organosilicon compound gel.

[0057] The above organosilicon compound is preferably a siloxane compound. As described above, the siloxane compound is a compound having a siloxane bond, and the siloxane skeleton, which is the main skeleton that requires the siloxane bond, is (SiO m ) n It can be expressed as follows.

[0058] The siloxane skeleton described above may be, for example, linear (linear or branched), ladder-like, reticular, annular, cage-like, cubic, random, or the like. The siloxane compound described above is preferably a polysilsesquioxane.

[0059] An organosilicon compound gel slurry can be obtained by the above method. In the production method of the present invention, when the above organosilicon compound gel slurry is used as the gel slurry, an organosilicon compound gel particle dispersion can be obtained as the gel particle dispersion.

[0060] (ripening process) Furthermore, as described above, by maturing the gel slurry, gelation proceeds sufficiently, and a gel slurry containing a large amount of the desired gel can be obtained. For this reason, it is preferable that the manufacturing method of the present invention includes a maturation step before the cross-flow filtration step.

[0061] The temperature of the above maturation process is preferably 10 to 80°C, more preferably 15 to 70°C, and even more preferably 20 to 60°C.

[0062] The duration of the above maturation process is preferably 1 to 40 hours, more preferably 2 to 30 hours, and even more preferably 3 to 25 hours.

[0063] The above maturation process can be carried out by standing, but it is preferable to carry it out by stirring. That is, the manufacturing method of the present invention preferably further includes a step of stirring and maturing the gel slurry before the above cross-flow filtration step. In this invention, a matured gel slurry is referred to as "matured gel slurry," and a gel slurry that has been stirred and matured is referred to as "stirred and matured gel slurry." Therefore, it is preferable that the gel slurry used in the cross-flow filtration process is a stirred and matured gel slurry obtained by stirring and matured the gel before the cross-flow filtration process.

[0064] The above-mentioned stirring and aging process involves aging the gel while stirring it, and more specifically, it is preferable to stir the gel at 10-80°C for 1-40 hours. In gel production, if only normal aging is performed, a bulk gel containing solvent is produced. However, by aging while stirring, the temperature is applied uniformly to the gel, resulting in better gel aging and the progress of the crosslinking reaction, making it easier to form a gel that maintains a network while having voids. In addition, a gel slurry containing coarsely ground gel is produced, and by subjecting such coarsely ground, stirring-aged gel slurry to cross-flow filtration, the contact area between the gel and the substitution solvent increases, allowing for more efficient substitution. Furthermore, the viscosity of the stirring-aged gel slurry decreases, making it easier to handle.

[0065] The stirring method is not particularly limited as long as it can stir the material to a certain particle size, and known stirring methods using a stirrer with stirring blades are examples.

[0066] The temperature for the stirring and aging process described above is more preferably 20 to 65°C. The stirring time during the above stirring and maturation process is more preferably 3 to 25 hours.

[0067] (Grinding process) The method for producing a gel particle dispersion of the present invention may further include a grinding step. By including a step of grinding the gel, the particle size of the gel particles can be adjusted, the amount of residual solvent for gel production and by-products can be reduced more efficiently, and the desired gel particle dispersion can be produced efficiently.

[0068] The above grinding process may be performed before the cross-flow filtration process, after the cross-flow filtration process, or before or after the cross-flow filtration process. In other words, after grinding the (stirred) matured gel slurry, the ground gel slurry may be cross-flow filtered, or the gel particle dispersion after cross-flow filtering may be ground, or both may be performed. In particular, it is preferable to perform the grinding step after the stirring and maturation step and before the cross-flow filtration step, as this allows for a more efficient cross-flow filtration process.

[0069] The above grinding process may be carried out in a solvent. The solvent used for grinding may be the same solvent as the gel manufacturing solvent or substitution solvent described above, or a mixture thereof. Alternatively, these solvents may be added as appropriate before grinding.

[0070] The above-mentioned grinding method is not particularly limited as long as it can grind the gel particles to the desired particle size. Examples include known grinding methods such as emulsifying and dispersing machines such as homomixers, milders, ultrasonic homogenizers, and high-speed rotary homogenizers, and media grinders such as ball mills, bead mills, and sand mills. Among these, homomixers and milders are preferred.

[0071] After the grinding process described above, known and commonly performed processes such as concentration, purification, and washing may be carried out.

[0072] The number-average particle diameter of the gel particles in the gel particle dispersion obtained by the manufacturing method of the present invention can be appropriately selected depending on the purpose and application of the gel particle dispersion, but is preferably 0.2 to 300 μm, more preferably 0.5 to 200 μm, and even more preferably 1 to 100 μm. The above-mentioned number-average particle diameter can be determined by the same method as described above.

[0073] The viscosity of the above gel particle dispersion is preferably 10 to 10,000 mPa·s, more preferably 15 to 5,000 mPa·s, and even more preferably 20 to 2,000 mPa·s. The viscosity described above can be determined by the method described in the examples below.

[0074] The solid content concentration of the above gel particle dispersion is not particularly limited, but is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 0.5 to 10% by mass.

[0075] The amount of gel manufacturing solvent remaining in the above gel particle dispersion is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 1,000 ppm or less, even more preferably 500 ppm or less, and particularly preferably 200 ppm or less. The amount of solvent remaining can be determined by the method described in the examples below.

[0076] The residual methanol content in the above gel particle dispersion is preferably 10,000 ppm or less. Methanol is produced as a by-product when the above organosilicon compound is synthesized. Therefore, the gel slurry contains methanol as a by-product, but the production method of the present invention can efficiently reduce the residual methanol content. The remaining amount of methanol is more preferably 5000 ppm or less, and even more preferably 1000 ppm or less. The remaining amount of methanol can be determined by the method described in the examples below.

[0077] The above-mentioned gel particle dispersion can be used for a variety of applications depending on the properties of the gel. For example, if the gel particle dispersion is an organosilicon compound gel particle dispersion, it can be suitably used as a composition for forming a heat insulating film, a composition for forming a low dielectric constant film, or a composition for forming a low refractive index film.

[0078] Furthermore, the gel composition may include the above-mentioned gel particle dispersion. The above gel composition may contain other additives, such as catalysts, depending on its purpose and application.

[0079] As described above, the method for producing a gel particle dispersion of the present invention can efficiently reduce the amount of residual solvent for gel production. [Examples]

[0080] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "percent mass".

[0081] The various evaluation methods used in this embodiment are as follows.

[0082] <Remaining DMSO amount, remaining methanol amount> Approximately 1 g of gel slurry and 0.1 g of diethylene glycol diethyl ether as an internal standard were mixed with 1 g of acetonitrile. The mixture was filtered, and the amount of dimethyl sulfoxide in the filtrate was determined by a calibration curve (internal standard) using gas chromatography. The gas chromatography conditions were as follows: Equipment: GC-2014 (manufactured by Shimadzu Corporation) Column: DB-WAX (manufactured by Agilent Technologies, column length: 30m, column inner diameter: 0.25mm, capillary inner film thickness: 0.25μm) Carrier gas: Helium Column temperature: Hold at 50°C for 5 minutes, increase temperature at 10°C / min, hold at 240°C for 6 minutes. Inlet temperature: 280℃ Detector temperature: 320°C (FID) Detected substances and retention times: methanol (2 min), diethylene glycol diethyl ether (12 min), dimethyl sulfoxide (14 min)

[0083] <Viscosity> An E-type viscometer (Toki Sangyo Co., Ltd.: TV-20L, low viscosity range: 1°34'×R24 rotor or high viscosity range: 3°×R9.7 rotor) was used to perform measurements at a temperature of 25°C and a rotation speed of 5 rpm. The value taken 2.5 minutes after the start of measurement was adopted.

[0084] <Solid content> The solid content was measured using the following method. 1. The aluminum tray was weighed accurately. 2. The sample to be measured for solid content was placed on a precisely weighed aluminum pan and weighed accurately. 3. Place the aluminum tray containing the sample accurately weighed in step 2 onto a hot plate heated to 180°C for 1 hour. 4.1 hours later, the aluminum tray and the components to be measured for solid content were removed from the hot plate and allowed to cool. 5. After cooling, the aluminum tray and the sample (after drying) to be measured for solid content were accurately weighed. 6. Using the weight measured above, the solid content was calculated using the following formula. Solids content (%) = (Weight obtained using the precision scale in 5 above (g) - Weight of the aluminum pan obtained using the precision scale in 1 above (g)) / (Weight obtained using the precision scale in 2 above (g) - Weight of the aluminum pan obtained using the precision scale in 1 above (g)) × 100

[0085] <Average particle size by number of particles> The number-average particle size was determined using a laser diffraction particle size analyzer (Malvern's "Mastersizer 3000"), which was prepared by diluting the gel particle dispersion 3 to 10 times with isobutyl alcohol as the measurement sample.

[0086] (Example 1) In a four-necked flask equipped with a condenser, thermometer, and dropping spout, 208 parts of dimethyl sulfoxide, 23 parts of deionized water, and 100 parts of methyltrimethoxysilane (trade name KBM-13: manufactured by Shin-Etsu Chemical Co., Ltd.) were charged, and the internal temperature was adjusted to 30°C while stirring with a Three-One Motor (manufactured by Shinto Kagaku Co., Ltd.). While continuing to stir the mixture, 53 parts of 0.015 M oxalic acid aqueous solution were added dropwise through the dropping spout, and the mixture was held at 30°C for 45 minutes to hydrolyze the methyltrimethoxysilane. To the resulting hydrolyzed solution, a mixture of 1335 parts of dimethyl sulfoxide, 210 parts of deionized water, and 58 parts of 25% ammonia aqueous solution was added, and the mixture was held at 40°C for 20 hours while continuing to stir, allowing for stirring and maturation to occur, resulting in gelation.

[0087] 100 parts of the obtained gel slurry (solid content 3.6% by mass) were mixed with 100 parts of isobutyl alcohol and ground in a Primix MARK II 2.5 homomixer at 25°C and 8000 rpm for 5 minutes to obtain a stirred and matured gel slurry containing gel particles with a number average particle size of 76.8 μm. The obtained stirred and matured gel slurry was then filtered through a filter with a channel diameter of 3 mm, a length of 250 mm, 7 holes, a pore size of 0.1 μm, and a filtration area of ​​0.016 m². 2 The material was placed in a cross-flow filtration apparatus equipped with a ceramic precision filtration membrane (manufactured by NGK Insulators, Inc.), and 1900 parts of isobutyl alcohol were continuously added under conditions of filtration pressure of 0.1 MPa, processing temperature of 40°C, and circulating fluid linear velocity of 3 m / s. After solvent replacement for 11.5 hours, a concentration treatment was performed to obtain an isobutyl alcohol-substituted gel particle dispersion with a solid content of 3.18% by mass and a number-average particle size of 37.0 μm. The resulting gel particle dispersion had a residual DMSO content of 54 ppm, a residual methanol content of 2 ppm, and a viscosity of 95.9 mPa·s.

[0088] (Example 2) In a four-necked flask equipped with a condenser, thermometer, and dropping spout, 208 parts of dimethyl sulfoxide, 23 parts of deionized water, and 100 parts of methyltrimethoxysilane (trade name KBM-13: manufactured by Shin-Etsu Chemical Co., Ltd.) were charged, and the internal temperature was adjusted to 30°C while stirring with a Three-One Motor (manufactured by Shinto Kagaku Co., Ltd.). While continuing to stir the heated mixture, 53 parts of 0.015 M oxalic acid aqueous solution were added dropwise through the dropping spout, and the mixture was held at 30°C for 45 minutes to hydrolyze the methyltrimethoxysilane. To the resulting hydrolyzed solution, a mixture of 918 parts of dimethyl sulfoxide, 121 parts of deionized water, and 58 parts of 25% ammonia aqueous solution was added, and stirring was stopped. The mixture was then held at 40°C for 20 hours to induce gelation.

[0089] 100 parts of isobutyl alcohol were added to 100 parts of the obtained gel, and the mixture was ground in a Primix MARK II 2.5 homomixer at 25°C and 13,000 rpm for 1 minute to obtain a matured gel slurry containing gel particles with a number-average particle size of 75.7 μm. The obtained matured gel slurry was then filtered through a channel with a diameter of 3 mm, a length of 250 mm, 7 holes, a pore size of 0.1 μm, and a filtration area of ​​0.016 m².2 The material was placed in a cross-flow filtration apparatus equipped with a ceramic precision filtration membrane (manufactured by NGK Insulators, Inc.), and 1900 parts of isobutyl alcohol were continuously added under the conditions of a filtration pressure of 0.1 MPa, a processing temperature of 33°C, and a circulating fluid linear velocity of 2 m / s. After solvent replacement for 9.7 hours, a concentration treatment was performed to obtain an isobutyl alcohol-substituted gel particle dispersion with a solid content of 3.11% by mass and a number-average particle size of 65.4 μm. The resulting gel particle dispersion had a residual DMSO content of 64 ppm, a residual methanol content of 10 ppm, and a viscosity of 4250 mPa·s.

[0090] (Comparative Example 1) In a four-necked flask equipped with a condenser, thermometer, and dropping port, 232 parts of dimethyl sulfoxide and 100 parts of methyltrimethoxysilane (trade name KBM-13: manufactured by Shin-Etsu Chemical Co., Ltd.) were charged, and the internal temperature was adjusted to 30°C while stirring with a Three-One Motor (manufactured by Shinto Kagaku Co., Ltd.). While continuing to stir the heated mixture, 53 parts of 0.01 M oxalic acid aqueous solution were added dropwise through the dropping port, and the mixture was held at 30°C for 45 minutes to hydrolyze the methyltrimethoxysilane. To the resulting hydrolyzed solution, a mixture of 812 parts of dimethyl sulfoxide, 21 parts of ion-exchanged water, and 40 parts of 28% ammonia aqueous solution was added, and stirring was stopped. The mixture was held at 40°C for 20 hours to induce gelation. The resulting gel was crushed into cubes with a long side of 1-3 cm, and 100 parts of gel were immersed in 800 parts of water, and the mixture was slowly stirred at room temperature for 1 hour to allow only the water to circulate. After 1 hour, the water was replaced with an equal amount of water, and the mixture was stirred for another 3 hours. After that, the water was replaced again, and the mixture was heated at 60°C for 3 hours with slow stirring. Then, the water was replaced with 400 parts isopropyl alcohol, and the mixture was heated at 60°C for 6 hours with stirring. Finally, the isopropyl alcohol was replaced with 100 parts isobutyl alcohol, and the mixture was heated at 60°C for 6 hours to replace the solvent in the gel with isobutyl alcohol, thereby obtaining an isobutyl alcohol-substituted gel particle dispersion. The remaining DMSO content of the obtained gel was 180 ppm, and the remaining methanol content was 12 ppm.

[0091] From the above results, it can be seen that in the example, an isobutyl alcohol-substituted gel particle dispersion with a lower amount of residual DMSO and methanol (a by-product) was obtained with a shorter solvent substitution time compared to the comparative example. From this, it can be seen that the method for producing the gel particle dispersion in the example is able to produce a gel particle dispersion with a reduced amount of residual solvent and by-products used during gel production in the gelled product very efficiently.

Claims

1. A method for producing a gel particle dispersion, The manufacturing method includes a step of cross-flow filtering the gel slurry, The gel slurry is a stirred and aged gel slurry obtained by aging the gel while stirring it before the cross-flow filtration step. The process includes a grinding step, which is performed after the stirring and aging step to obtain a stirred and aged gel slurry, and before the step of cross-flow filtering the stirred and aged gel slurry. A method for producing a gel particle dispersion characterized by the following:

2. The method for producing a gel particle dispersion according to claim 1, characterized in that the filtration pressure in the cross-flow filtration step is 0.05 to 1.0 MPa.

3. The method for producing a gel particle dispersion according to claim 1 or 2, characterized in that the processing temperature in the cross-flow filtration step is 10 to 100°C.

4. The method for producing a gel particle dispersion according to claim 1 or 2, characterized in that the linear velocity of the circulating liquid in the cross-flow filtration step is 0.5 to 5.0 m / second.

5. A method for producing a gel particle dispersion according to claim 1 or 2, characterized in that solvent replacement is performed in the cross-flow filtration step.

6. The method for producing a gel particle dispersion according to claim 1, characterized in that the stirring and aging process involves stirring the gel at 10 to 80°C for 1 to 40 hours.

7. The method for producing a gel particle dispersion according to claim 1 or 2, characterized in that the gel particle dispersion is an organosilicon compound gel particle dispersion.

8. The method for producing a gel particle dispersion according to claim 7, characterized in that the organosilicon compound is a siloxane compound.