Method for manufacturing a macroporous material, macroporous material, vacuum insulation material, and outdoor equipment

Abstract

This invention provides a method for producing a macroporous polysiloxane that has sufficient mechanical strength, low manufacturing costs, and low environmental impact. [Solution] A method for producing a polysiloxane macroporous body, comprising: preparing a composition containing methyltrialkoxysilane, an aprotic polar solvent, and water; gelling the composition to form a gel; and drying the gel. In the composition, the ratio (S / W) of the mass of the aprotic polar solvent to the mass (W) of the water is 0.48 to 0.70, and the content of the methyltrialkoxysilane is 30.0% to 41.0% by mass.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a macroporous material, a macroporous material, a vacuum insulation material, and outdoor equipment. [Background technology]

[0002] Monolithic porous materials of methylsilsesquioxane (MSQ) possess properties such as heat insulation and water repellency, and are expected to be applied to high-performance thermal insulation materials. For example, Non-Patent Document 1 reports the preparation of a macroporous material with macropores using organosilicon alkoxide (MTMS: methyltrimethoxysilane) as a raw material via a sol-gel method. Because water is necessary to efficiently carry out the hydrolysis and polycondensation reactions during synthesis, and because the MSQ after the reaction is highly hydrophobic, surfactants are used as phase separation control agents to successfully form a porous structure.

[0003] Furthermore, research on aerogels with nanostructures is also actively being conducted as MSQ monolithic porous materials (for example, Patent Document 1). Similar to macroporous materials, a sol-gel method using surfactants (phase separation control agents) is used for the preparation of aerogels.

[0004] Furthermore, the present inventors have reported a core-shell type MSQ monolithic porous material (macroporous material) using ceramic particles (e.g., boehmite nanofibers) as a core material (for example, Non-Patent Literature 2). Non-Patent Literature 2 describes how to control the structure of the MSQ monolithic porous material using nanofibers, and how to manufacture the macroporous material by the sol-gel method without using surfactants. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] WO2005 / 110919 [Non-patent literature]

[0006] [Non-Patent Document 1] Journal of the Ceramic Society of Japan 123 [9] 770-778 2015

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The surfactants used in the production methods of Non-Patent Document 1 (macroporous bodies) and Patent Document 1 (aerogels) become impurities after synthesis, and thus need to be removed from the porous bodies by washing with solvent exchange. Since the diffusivity of liquids in the porous bodies is poor, the washing and removal operations take time, and there was room for improvement in terms of cost and environmental load. In the case of monolithic porous bodies, as the scale increases, the diffusion from the center becomes slower, so the removal of surfactants can be an obstacle to scale-up. In addition, aerogels having a nanostructure (for example, Patent Document 1) also had the problem of insufficient mechanical strength (brittleness).

[0008] On the other hand, the production method of the core-shell type MSQ monolithic porous body disclosed in Non-Patent Document 2 does not use a surfactant, so the removal operation of the surfactant does not occur. In addition, the obtained monolithic porous body has sufficient mechanical strength. However, since nanofibers such as boehmite are hydrophilic, it is difficult to completely remove moisture from the porous bodies containing them. Therefore, for example, when trying to use a porous body containing boehmite or the like as a vacuum insulation material, there was a risk that the degassing process in a vacuum would become complicated. For this reason, the development of a production method for monolithic porous bodies with an approach different from that of Non-Patent Document 2 has been desired.

[0009] An object of the present invention is to solve the above problems. That is, the present invention provides a method for producing a macroporous body of polysiloxane that can produce a porous body having sufficient mechanical strength and has low production cost and environmental load.

Means for Solving the Problems

[0010] As a result of diligent research to achieve the above objectives, the inventors of the present invention have found that the above objectives can be achieved with the following configuration.

[0011] [1] According to the first aspect, a method for producing a macroporous polysiloxane, A composition containing methyltrialkoxysilane, an aprotic polar solvent, and water is prepared, and then gelled to form a gel. The process includes drying the gel, In the above composition, The ratio (S / W) of the mass (S) of the aprotic polar solvent to the mass (W) of the water is 0.48 to 0.70. A method for producing a macroporous material is provided, wherein the methyltrialkoxysilane content is 30.0% to 41.0% by mass. [2] The aprotic polar solvent may include at least one selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP). [3] The aprotic polar solvent may be N,N-dimethylformamide (DMF). [4] The methyltrialkoxysilane may be at least one selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, and methyltributoxysilane. [5] The methyltrialkoxysilane may be methyltrimethoxysilane. [6] The composition may not contain a surfactant. [7] The methyltrialkoxysilane may be present in an amount of 70 mol% or more relative to the total amount of alkoxysilane contained in the composition. [8] In the polysiloxane, the proportion of polymethylsilsesquioxane structures may be 70 mol% or more. [9] The alkoxysilane contained in the composition may consist solely of the methyltrialkoxysilane.

[10] The polysiloxane may consist solely of polymethylsilsesquioxane.

[11] The ratio (S / W) may be 0.50 to 0.65.

[12] In the composition, the content of the methyltrialkoxysilane may be 32.0% by mass to 40.0% by mass.

[13] In the above composition, the content of the aprotic polar solvent may be 20.0% by mass to 27.0% by mass.

[14] In the composition, the water content may be 38.0% by mass to 44.0% by mass.

[15] According to a second embodiment, a macroporous polysiloxane comprising a polymethylsilsesquioxane structure, A macroporous material is provided in which, when uniaxially compressed to a strain of 25%, the remaining compression set after unloading is 3% or less.

[16] In a third embodiment, a vacuum insulation material is provided which includes the macroporous body of the second embodiment.

[17] In a fourth aspect, an outdoor installation is provided which includes the macroporous body of the second aspect. [Effects of the Invention]

[0012] The present invention provides a method for producing a macroporous polysiloxane, which allows for the production of a porous material with low manufacturing costs and environmental impact, and possesses sufficient mechanical strength. [Brief explanation of the drawing]

[0013] [Figure 1] This is a flowchart illustrating the method for producing the polysiloxane macroporous material according to this embodiment. [Figure 2] This graph shows the relationship between strain and axial pressure during a uniaxial compression test of sample 2 prepared in the example. [Figure 3]This is a triangular diagram showing the mass ratios of N,N-dimethylformamide (DMF), water (H2O), and methyltrimethoxysilane (MTMS) in the compositions of samples 1 to 23 prepared in the examples. [Figure 4] This is a scanning electron microscope (SEM) image of sample 2 prepared in the example. [Figure 5] This graph shows the relationship between strain and axial pressure during a uniaxial compression test of sample 24 prepared in the example. [Modes for carrying out the invention]

[0014] The present invention will now be described in detail. The following descriptions of constituent elements may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, numerical ranges represented by "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits.

[0015] <Definitions of terms used herein> A "monolithic porous material" refers to a porous material that has a network of interconnected rod-shaped skeletons (mainly composed of polysiloxane), in which the voids of the co-continuous structure are partitioned by this skeleton. "Co-continuous structure" refers to a state in which, when the cross-section of a material is observed with a scanning electron microscope, the skeletal phase, which is mainly composed of polysiloxane, and the voids are continuous and intertwined in three dimensions. A "macroporous material" refers to a monolithic porous material in which voids form macropores, and which possesses a microstructure on the submicrometer scale (submicron order). Macroporous materials are distinct from aerogels, which have a nanostructure. According to the IUPAC definition, "macropore" refers to a pore with a diameter (pore size) of 50 nm or larger. "Polysilsesquioxane" is a siloxane-based compound whose main chain skeleton consists of Si-O bonds, [(RSiO 1.5It is a network polymer represented by the chemical formula )n] (where R is a monovalent organic functional group such as an alkyl group), and is a hydrolysis condensate of a trifunctional alkoxysilane. It is sometimes simply referred to as "silsesquioxane".

[0016] [Method for producing macroporous polysiloxanes] As shown in Figure 1, the present invention's method for producing a polysiloxane macroporous material (hereinafter also referred to as "this production method") comprises preparing a composition containing methyltrialkoxysilane (MTAS), an aprotic polar solvent, and water, and forming a gel by gelling the composition (step S1), and drying the formed gel (step S2). In the composition, the ratio of the mass of the aprotic polar solvent (S) to the mass of water (W) (S / W) is 0.48 to 0.70, and the content of methyltrialkoxysilane is 30.0% to 41.0% by mass.

[0017] The synthesis of silicone-backed monoliths proceeds via a so-called sol-gel reaction. Therefore, a composition containing a polyfunctional alkoxysilane (silicon alkoxide) with hydrolyzable groups is prepared, and the polycondensate of the hydrolysis products of the alkoxysilane, i.e., the polysiloxane which forms the gel's backbone phase, is sequentially increased within this composition. At this time, the phase separation occurring between the backbone phase and the solution phase containing unreacted alkoxysilane, etc., is adjusted to be viscoelastic phase separation, thereby forming a co-continuous structure in which the backbone phase and the solution phase each have a continuous three-dimensional network structure and are intertwined with each other. Conventionally, surfactants (phase separation control agents) have been considered indispensable for controlling phase separation in the production of silicone-backed monoliths.

[0018] The inventors of this invention, disregarding the above-mentioned common technical knowledge, diligently continued their research and, after trying a vast number of compositions, finally discovered that by using methyltrialkoxysilane (MTAS) as the main component of the monomer alkoxysilane, and by setting the concentration of MTAS within a predetermined range (for example, 30.0% to 41.0% by mass) and the ratio of water (W) to aprotic polar solvent (S) within a predetermined range (for example, mass ratio S / W = 0.48 to 0.70), the phase separation behavior can be controlled, viscoelastic phase separation can be induced, and a macroporous polysiloxane can be obtained. This discovery led to the completion of the present invention. The method for producing this macroporous polysiloxane is described in detail below.

[0019] (1) Step S1: Preparation of composition and gelation (sol-gel step) The composition of this embodiment comprises methyltrialkoxysilane (MTAS), an aprotic polar solvent, and water.

[0020] <Methyltrialkoxysilane:MTAS> The methyltrialkoxysilane used in this manufacturing method is a trifunctional alkoxysilane, and R 1 When is an alkyl group, formula 1: CH3-Si-(OR 1 )3 is a compound represented by (multiple R in the molecule) 1 They may be the same or different, but it is preferable that they be the same.

[0021] R 1 The alkyl group may be linear, branched, or cyclic, but a linear or branched alkyl group is preferred in that it provides better effects of the present invention. R 1 The number of carbon atoms is not particularly limited, but 1 to 10 is preferred, and 1 to 4 is more preferred, because the alcohol produced by hydrolysis condensation has better hydrophilicity.

[0022] Examples of linear or branched alkyl groups having 1 to 10 carbon atoms include: methyl group (1 carbon atom); ethyl group (2 carbon atoms); propyl group, isopropyl group (3 carbon atoms); butyl group, isobutyl group, tert-butyl group, sec-butyl group (4 carbon atoms); pentyl group (5 carbon atoms), 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1,1-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group; hexyl group (6 carbon atoms), 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 1,4-dimethylbutyl group, 2,3-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, 1-ethyl-2-methylpropyl group, 1 ,1,2-trimethylpropyl group; heptyl group with 7 carbon atoms, 1-methylhexyl group, 2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1,1-dimethylpentyl group, 2,2-dimethylpentyl group, 3,3-dimethylpentyl group, 4,4-dimethylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, 1-ethylpentyl group, 2-ethylpentyl group, 3-ethylpentyl group, 1,2,2-trimethylbutyl group, 1,1,2-trimethylbutyl group, 1,3,3-trimethylbutyl group, 1,1,3-trimethylbutyl group, 2,2,3-trimethylbutyl group, 2,3,3-trimethylbutyl group;Octyl group with 8 carbon atoms, 1-methylheptyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 6-methylheptyl group, 1-ethylhexyl group, 2-ethylhexyl group, 3-ethylhexyl group, 4-ethylhexyl group, 1-propylpentyl group, 2-propylpentyl group, 1,1-dimethylhexyl group, 2,2-dimethylhexyl group, 3,3-dimethylhexyl group, 4,4-dimethylhexyl group, 5,5-dimethylhexyl group, 3-ethyl-3- Methylpentyl group, 1,1-diethylbutyl group, 2,2-diethylbutyl group, 1,1,2,2-tetramethylbutyl group, 1,1,3,3-tetramethylbutyl group, 2,2,3,3-tetramethylbutyl group, 1,1-dimethyl-2-ethylbutyl group; 9-carbon nonyl group, 2-methyloctyl group, 3-methyloctyl group, 4-methyloctyl group, 2,2-dimethylheptyl group, 2,3-dimethylheptyl group, 2,4-dimethylheptyl group, 2,6-dimethylheptyl group, 3,3-dimethylheptyl group , 3,4-dimethylheptyl group, 3,5-dimethylheptyl group, 4,4-dimethylheptyl group, 3-ethylheptyl group, 4-ethylheptyl group, 2,2,3-trimethylhexyl group, 2,2,4-trimethylhexyl group, 2,2,5-trimethylhexyl group, 2,3,3-trimethylhexyl group, 2,3,4-trimethylhexyl group, 2,3,5-trimethylhexyl group, 2,4,4-trimethylhexyl group, 3,3,4-trimethylhexyl group, 2-methyl-3-ethylhexyl group, 3-methyl-3- Examples include ethylhexyl group, 3-ethyl-4-methylhexyl group, 3-ethyl-5-methylhexyl group, 2,2,3,3-tetramethylpentyl group, 2,2,3,4-tetramethylpentyl group, 2,2,4,4-tetramethylpentyl group, 2,3,3,4-tetramethylpentyl group, 2,2-dimethyl-3-ethylpentyl group, 2,3-dimethyl-3-ethylpentyl group, 2,4-dimethyl-3-ethylpentyl group, 3,3-diethylpentyl group; decyl groups and isodecyl groups with 10 carbon atoms; etc.

[0023] Examples of cyclic alkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups. Examples of cyclic alkenyl groups include cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cyclohexadienyl, cycloheptenyl, cycloheptadienyl, cyclooctenyl, and cyclooctadienyl groups. Examples of cyclic alkynyl groups include cycloalkenyl, cyclooctinyl, cyclononinyl, cyclodecinyl, and cyclodecadienyl groups.

[0024] Examples of MTAS include methyltrimethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, methyltriisopropoxysilane, and methyltributoxysilane, with methyltrimethoxysilane (MTMS) being preferred.

[0025] MTAS may consist of only one type or a mixture of two or more types.

[0026] The MTAS content in the composition is 30.0% to 41.0% by mass, preferably 32.0% to 40.0% by mass. If the MTAS content is below the lower limit of the above range, it becomes difficult to produce the macroporous material itself. Similarly, if it exceeds the upper limit of the above range, it also becomes difficult to produce the macroporous material, and even if it can be produced, there is a risk that sufficient thermal insulation properties (low thermal conductivity) cannot be obtained.

[0027] In the composition of this embodiment, the main component of the alkoxysilane (monomer component) is MTAS, which facilitates the formation of a random structure (network structure) in the polysiloxane. The alkoxysilane contained in the composition may consist solely of MTAS. In this case, the resulting polysiloxane consists solely of polymethylsilsesquioxane.

[0028] On the other hand, within the scope where the effects of the present invention can be achieved, an alkoxysilane (monomer component) other than MTAS may be contained. For example, with respect to the total amount of alkoxysilane contained in the composition, MTAS is preferably 70 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more. In this case, in the obtained polysiloxane, the ratio of the polymethylsilsesquioxane structure can be 70 mol% or more, 90 mol% or more, or 95 mol% or more. The silsesquioxane structure of the present embodiment has a random structure, thereby forming a macroscopic structure and having a handleable strength.

[0029] <Alkoxysilane other than MTAS> Examples of the alkoxysilane (monomer component) other than MTAS include trifunctional organotrialkoxysilane (3AS) other than MTAS, tetrafunctional tetraalkoxysilane (4AS), difunctional organodialkoxysilane (2AS), and monofunctional organomonoalkoxysilane (1AS). Each silane will be described below.

[0030] The trifunctional organotrialkoxysilane (3AS) other than MTAS is a compound in which the methyl group in Formula 1 representing MTAS described above is replaced with another organic functional group (for example, an alkyl group). That is, when R 11 is an organic functional group, it is a compound represented by Formula 11: R 11 -Si-(OR 1 )3 (R 11 and the plurality of R 1 in the molecule may be the same or different, but it is preferable that the plurality of R 1 are the same. However, R 11 is not a methyl group). In Formula 11, examples of R 11 and R 1 are the same as those of R 1 described above, and the preferred embodiments are also the same. Examples of the trifunctional organotrialkoxysilane (3AS) other than MTAS include vinyltrimethoxysilane, vinyltriethoxysilane, and the like.

[0031] The tetrafunctional tetraalkoxysilane (4AS) is R 2 When is an organic functional group (e.g., an alkyl group), formula 2: Si-(OR 2 ) is a compound represented by 4 (there are multiple R in the molecule) 2 (They may be the same or different, but it is preferable that they be the same). Note that R 2 The alkyl group is the R mentioned above. 1 Examples of alkyl groups similar to those mentioned above, and the preferred form, are also similar. Examples of 4AS include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and tetrakis(2-ethylhexyloxy)silane, with tetramethoxysilane being preferred in terms of ease of reaction control and cost.

[0032] The bifunctional organodialkoxysilane (2AS) is R 3 and R 31 When R is an organic functional group (for example, an alkyl group), then formula 3:(R 31 )2-Si-(OR 3 )2 is a compound represented by (there are multiple R in the molecule) 31 , and R 3 They may be the same or different, but there are multiple R 3 (It is preferable that they are the same). Note that R 3 and R 31 The alkyl group is the R mentioned above. 1 Examples of alkyl groups similar to those mentioned above are also available, and the preferred form is the same. 31 The group is preferably a methyl group. Examples of 2AS include dimethyldimethoxysilane and diethoxydimethylsilane, with dimethyldimethoxysilane being preferred.

[0033] Monofunctional organomonoalkoxysilanes (1AS) are R 4 and R 41 When R is an organic functional group (e.g., an alkyl group), then formula 4:(R 41 )3-Si-OR 4 It is a compound represented by (multiple R in the molecule) 41 , and R4 (They may be the same or different).

[0034] Note, R 41 , and R 4 The alkyl group is R 1 Examples of alkyl groups similar to those mentioned above are also available, and the preferred form is the same. 41 It is preferable that it be a methyl group.

[0035] Examples of 1AS include trimethylmethoxysilane and ethoxytrimethylsilane, with trimethylmethoxysilane being preferred.

[0036] The polysiloxane obtained in this embodiment is preferably a condensate of alkoxysilanes in which all alkyl groups bonded to silicon (Si) are methyl groups. That is, if it contains alkoxysilanes other than MTAS, in formulas 11 and 2 to 4, R 11 , R 21 , R 31 , R 41 It is preferable that it be a methyl group.

[0037] When using alkoxysilanes (monomer components) other than MTAS, the alkoxysilanes other than MTAS may consist of only one type or a mixture of two or more types.

[0038] <Water and aprotic polar solvents> The aprotic polar solvent used in this manufacturing method is not particularly limited, but N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP) are preferred, with N,N-dimethylformamide (DMF) being more preferred, in that they provide better effects of the present invention. The protic polar solvent may consist of only one type or a mixture of two or more types.

[0039] The water used in this manufacturing method is not particularly limited, and for example, pure water, deionized water, RO water, etc., can be used.

[0040] In the composition of this embodiment, the ratio (S / W) of the mass of the aprotic polar solvent to the mass (W) of water is (S / W) = 0.48 to 0.70, preferably (S / W) = 0.50 to 0.65. By keeping the ratio (S / W) within this range, the phase separation of the composition of this embodiment can be sufficiently controlled even without containing a surfactant, and a macroporous body with sufficient mechanical strength can be produced. Because the phase separation of the composition can be sufficiently controlled, for example, there is no need to add a core material (such as nanofibers of boehmite) to the composition as reported in Non-Patent Document 2.

[0041] The content of the aprotic polar solvent and the water in the composition of this embodiment are not particularly limited as long as the ratio (S / W) is within the above range. For example, the content of the protic polar solvent in the composition may be 20.0% to 27.0% by mass, and the content of water may be 38.0% to 44.0% by mass.

[0042] The total content of water and aprotic polar solvent in the composition is not particularly limited and may be the remainder after excluding the MTAS mentioned above and other components (optional components) described later. The total content of water and aprotic polar solvent may be, for example, 59.0% to 70.0% by mass.

[0043] <Other ingredients> The composition may consist only of monomer components such as MTAS, an aprotic polar solvent, and water, or it may contain other components within the range that achieves the effects of the present invention. Examples of other components include acids and bases. On the other hand, the composition does not have to contain a surfactant that functions as a phase separation control agent. It also does not have to contain materials that can serve as the core material of a porous body (for example, ceramic particles disclosed in Patent Document 2). In the solid content of the composition, the alkoxysilane (monomer component) such as MTAS may be, for example, 90% by mass or more, 95% by mass or more, or 100% by mass. Details of the other ingredients are described below.

[0044] (i) Acid The composition preferably contains an acid. The acid hydrolyzes the alkoxysilane and catalyzes the curing reaction. When the alkoxysilane is hydrolyzed in the system and hydrolysis products are formed, polycondensation reactions occur sequentially. Hydrolysis by acid produces H3O + It proceeds electrophilically by H3O. + The alkoxy group's oxygen atom is attacked, producing -Si-OH and an alcohol. This reaction is characterized by its lack of steric hindrance, allowing hydrolysis and polycondensation to proceed sequentially, and easily synthesizing linear polysiloxanes.

[0045] The acid may be an inorganic or organic acid. Examples of inorganic acids include hydrochloric acid and sulfuric acid. Examples of organic acids include formic acid, acetic acid, propionic acid, oxalic acid, and citric acid. Acetic acid is preferred because it allows for easier control of the hydrolysis reaction.

[0046] The acid content in the composition is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 5 to 2000 mmol per liter of water in the composition, and more preferably 100 to 1000 mmol.

[0047] (ii) base The composition preferably contains a base. The base hydrolyzes the alkoxysilane and catalyzes the curing reaction. Hydrolysis by a base involves OH - It proceeds nucleophilically by OH. - It directly attacks silicon atoms, RO - This reaction generates (where R is an organic group). Although this reaction is initially slow due to steric hindrance, once it starts, the steric hindrance is reduced and the reaction proceeds rapidly. As a result, the number of hydroxyl groups contributing to polycondensation increases, making it easier to synthesize branched polysiloxanes.

[0048] The base is not particularly limited, but examples include alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, and lithium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide, strontium hydroxide, and barium hydroxide; alkali metal carbonates such as potassium carbonate and sodium carbonate; ammonia; and amines such as monomethylamine, dimethylamine, triethylamine, monoethylamine, diethylamine, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine.

[0049] Furthermore, any substance that produces a basic substance through a decomposition reaction may also be used. Examples of such substances include urea and hexamine, but among these, urea is preferred because it has high solubility and volatility in water and is easy to remove.

[0050] The base content in the composition is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 5 to 2000 mmol, and preferably 100 to 1000 mmol, per liter of water in the composition.

[0051] (iii) Surfactants The composition preferably does not contain surfactants. In conventional methods for producing porous polysiloxanes using the sol-gel method, surfactants were used as phase separation control agents, but in the production method of this embodiment, phase separation control is possible without the use of surfactants. By not including surfactants, the surfactant removal step is unnecessary. This reduces manufacturing costs and environmental impact, and also facilitates scale-up.

[0052] The statement that a composition does not contain surfactants means, for example, that the amount of surfactant per mole of methyltrialkoxysilane (MTAS) is less than 0.001 moles, preferably 0.0001 moles or less, and more preferably 0.00001 moles or less.

[0053] Surfactants can be categorized as cationic, anionic, amphoteric, or nonionic.

[0054] Examples of anionic surfactants include hexylbenzenesulfonic acid, octylbenzenesulfonic acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, cetylbenzenesulfonic acid, myristylbenzenesulfonic acid, lauryl sulfate, polyoxyethylene lauryl sulfate, dodecenesulfonic acid, tetradecenesulfonic acid, hexadecenesulfonic acid, hydroxydodecanesulfonic acid, hydroxytetradecanesulfonic acid, hydroxyhexadecanesulfonic acid, as well as their sodium salts, potassium salts, ammonium salts, and triethanolamine salts.

[0055] Examples of cationic surfactants include octyltrimethylammonium hydroxide, lauryltrimethylammonium hydroxide, stearyltrimethylammonium hydroxide, dioctyldimethylammonium hydroxide, distearyldimethylammonium hydroxide, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, dicocoyldimethylammonium chloride, distearyldimethylammonium chloride, benzalkonium chloride, and stearyldimethylbenzylammonium chloride.

[0056] Examples of nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene hydrogenated castor oil, polyoxyethylene sorbitol fatty acid esters, polyethylene glycol, polypropylene glycol, and diethylene glycol.

[0057] Examples of amphoteric surfactants include amino acid-type and betaine-type surfactants.

[0058] <Preparation of composition and gelation (sol-gel process)> The macroporous polysiloxane of this embodiment includes a step (sol-gel step) in which a gel composed of a skeletal phase and a solution phase is formed by simultaneously performing hydrolysis of methyltrialkoxysilane (MTAS), polycondensation of the hydrolysis product, and phase separation of the polycondensate (polysiloxane) obtained by polycondensation from a solution system containing unreacted MTAS and hydrolysis products, using a composition obtained by mixing the components already described.

[0059] The skeletal phase of the formed gel is rich in polycondensates of the hydrolysis products of the alkoxysilane. The solution phase is rich in the solvent of the above composition, and the content of the polycondensates in the solution phase is relatively small compared to the content in the skeletal phase. Phase separation is a phase separation that proceeds simultaneously with the hydrolysis of the alkoxysilane and the polycondensation of the hydrolysis products, and is typically viscoelastic phase separation. The skeletal phase and solution phase resulting from this phase separation process each have a continuous three-dimensional network structure and are intertwined with one another.

[0060] The gel has a co-continuous structure of a skeletal phase and a solution phase. Furthermore, the polymer constituting the skeletal phase is a polysiloxane having a network of siloxane bonds (-Si-O-Si-) formed by polycondensation of the hydrolysis products of the alkoxysilane by a sol-gel reaction. In other words, the gel formed in the gelation process is a polysiloxane gel.

[0061] The sol-gel process proceeds by mixing the components to prepare the composition. The composition may be heated at this time. The heating conditions are not particularly limited, but generally 40°C to 100°C is preferred, and the heating time is preferably 2 hours to 48 hours.

[0062] (2) Step S2: Drying of the gel (drying step) The gel obtained by the sol-gel process is a wet polysiloxane gel. The drying process involves drying this wet gel to obtain a macroporous polysiloxane body. There are no particular restrictions on the drying method, but examples include holding it at room temperature to 120°C for 1 to 24 hours.

[0063] The present manufacturing method may include other steps not described above, as long as they do not impair the effects of the present invention. For example, other steps include heating and dehydrating the polysiloxane macroporous material. The heating temperature is not particularly limited, but it is preferably above 200°C. If silanol (Si-OH) remains in the polysiloxane macroporous material, it can be dehydrated by heating.

[0064] [Polysiloxane macroporous materials] The polysiloxane macroporous material produced by the manufacturing method described above has a co-continuous structure of a polysiloxane-based skeleton and macropores. The polysiloxane constituting the skeleton includes a polymethylsilsesquioxane structure formed by hydrolysis of MTAS and polycondensation of the hydrolysis products. In other words, it is a monolithic macroporous member of a silicone composition in which the skeleton is formed by viscoelastic phase separation accompanying the polycondensation reaction of MTAS in the above composition.

[0065] The polysiloxane in the macroporous material may consist solely of polymethylsilsesquioxane (PMSQ), or it may contain polysiloxane structures other than PMSQ, within the range that achieves the effects of the present invention. For example, in the polysiloxane in the macroporous material, the proportion of PMSQ structures is preferably 70 mol% or more, 90 mol% or more, or 95 mol% or more. The PMSQ structure in this embodiment has a random structure (network structure), thereby forming a macroscopic structure and providing strength that allows for handling. Examples of polysiloxane structures other than PMSQ include the hydrolysis condensate structures of alkoxysilanes other than MTAS used in the porous material manufacturing method described above.

[0066] Furthermore, the proportion (mol%) of PMSQ structures in the polysiloxane within the macroporous material is approximately the same as the proportion (mol%) of methyltrialkoxysilane (MTAS) in the total amount of alkoxysilane contained in the composition used to produce the macroporous material. Additionally, the proportion (mol%) of PMSQ structures in the polysiloxane within the macroporous material can be determined, for example, by analyzing the macroporous material using solid-state DD / MAS 29Si-NMR analysis (DD: dipole decoupling, MAS: magic angle spinning, NMR: nuclear magnetic resonance).

[0067] The macroporous material of this embodiment does not need to contain a core material (for example, ceramic particles disclosed in Non-Patent Literature 2). By not including hydrophilic materials such as boehmite, the hydrophobicity of the porous material can be increased. In the macroporous material, the polysiloxane content may be 90% by mass or more, 95% by mass or more, or 98% by mass, and the macroporous material may be composed solely of the polysiloxane.

[0068] The above-mentioned polysiloxane macroporous material undergoes a sol-gel reaction combined with a phase separation process, forming macropores with a co-continuous structure with the framework, and thus possessing macropores of uniform diameter. This structure is completely different from the structure of a porous material obtained through a foaming process with a foaming agent (in such a porous material, numerous independent pores are formed by foaming).

[0069] The average pore size of macropores in a porous material is, for example, 500 nm to 1 μm. The average pore size of a porous material can be determined, for example, by image analysis of electron microscope observations. The bulk density of a porous material is not particularly limited, but 0.50 g / cm³ is a reasonable value. -3 The following is preferable: 0.40 g / cm³ -3 The following is more preferable: 0.30 g / cm² -3 The following is even more preferable. The lower limit is not particularly limited, but generally it is 0.05 g / cm³. -3 The above is preferable. Furthermore, the bulk density of the porous material is 0.20 g / cm³. -3 ~0.45 gcm -3 It can be to a certain extent.

[0070] The average skeletal diameter of the macroporous material is 10 nm to 20 μm, preferably 50 nm to 10 μm, more preferably 100 nm to 3 μm, and even more preferably 200 nm to 2 μm. By keeping the average skeletal diameter within the above range, the macroporous material of this embodiment can obtain sufficient mechanical strength. The average skeletal diameter can be determined by image analysis of electron microscope observations, for example, by the arithmetic mean of the skeletal diameters at any 10 locations.

[0071] The macroporous material possesses excellent heat resistance and excellent heat insulation properties. While there are no particular limitations on its thermal conductivity, a thermal conductivity of 0.05 W / (m·K) or less at 20°C (at atmospheric pressure, in air) is preferred. There are no particular lower limits, but generally, 0.03 W / (m·K) or more is preferred. The above thermal conductivity is measured by the method described in the examples below.

[0072] In this embodiment, when the macroporous material is subjected to uniaxial compression up to a strain of 25% (i.e., when the height of the macroporous material in the axial pressure direction is 75% of its height before compression), the remaining compression set after unloading is preferably 3% or less, and more preferably 0%. A macroporous material with such high viscoelasticity is resistant to collapse due to external stress and can be said to have high mechanical strength.

[0073] The macroporous material of this embodiment preferably has high thermal insulation properties and high light reflectivity. The macroporous material preferably has a high total light reflectivity of, for example, 80% or more, 95% or more, or 98% or more for light in a wide range of wavelengths from 300 nm to 1100 nm.

[0074] [Applications of macroporous polysiloxanes] The macroporous polysiloxane material of this embodiment is lightweight due to its porous structure and possesses excellent thermal insulation, superior mechanical properties (high viscoelasticity), and high light reflectivity. Furthermore, as described above, it can be manufactured using a simple method with few manufacturing steps, making it easy to scale up and enabling the production of large products at low cost. Therefore, the macroporous polysiloxane material of this embodiment can be applied to a variety of products, including thermal insulation materials.

[0075] One example of an applied product is vacuum insulated panel (VIP). Vacuum insulated panels are made by wrapping a core material with a gas barrier film (outer material), sealing it in a vacuum, and minimizing heat conduction by gas. Vacuum insulated panels have recently been widely used in refrigerators, natural refrigerant heat pump water heaters (EcoCute), vending machines, and houses. The macroporous material of this embodiment has high thermal insulation properties, is lightweight, and can be easily scaled up, making it suitable as a core material for vacuum insulated panels. Furthermore, the macroporous material of this embodiment does not require the inclusion of hydrophilic fillers such as boehmite. Therefore, it has high hydrophobicity and also has the advantage of allowing for efficient degassing (including dehydration) in a vacuum during the manufacturing of vacuum insulated panels.

[0076] Other applications include outdoor equipment. Outdoor equipment refers to, for example, electrically and / or mechanically driven equipment, and the macroporous material of this embodiment can be used as housings, boxes, covers, cabinets, etc., for such equipment. The macroporous material of this embodiment, which has high mechanical strength (has viscoelastic properties and is resistant to collapse due to external stress), is suitable for equipment housings and covers. Furthermore, because it has high thermal insulation and light reflectivity, it can protect outdoor equipment from changes in outside temperature and sunlight. Moreover, since the macroporous material of this embodiment is composed of polysiloxane, unlike metal covers, it transmits electromagnetic waves without blocking them. For this reason, it can also be used in outdoor equipment that transmits and receives electromagnetic waves. Outdoor equipment is not particularly limited, but examples include outdoor units for air conditioners, natural refrigerant heat pump water heaters (EcoCute), vending machines, mobile phone base station equipment, outdoor Wi-Fi router units, surveillance cameras, junction boxes (current collection panels), control panels, distribution panels equipped with wiring equipment and measuring instruments for solar power generation systems, and charging equipment for electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs). [Examples]

[0077] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the examples shown below.

[0078] [Samples 1-23] Samples 1 to 23 were prepared using the predetermined volumes (mL) of raw materials shown in Table 1. Specifically, first, at room temperature, N,N-dimethylformamide (DMF) was mixed with 1 M aqueous acetic acid solution and methyltrimethoxysilane (MTMS) and stirred for 30 minutes. Then, 1 M aqueous ammonia was added and stirred for 1 minute to obtain a composition (sol). The obtained sol was sealed in a PFA (perfluoroalkoxyalkane) container and left to stand in an 80°C oven for 12 hours to gel and age. The obtained gel was removed from the mold (PFA container) and immersed in isopropyl alcohol (IPA) for 24 hours to wash away the solvent and unreacted substances. Finally, evaporation drying was performed to obtain the target product (sample).

[0079] Table 1 shows the volume of the raw materials for each sample, along with the mass of the constituent materials of the composition (DMF, water (H2O), and MTMS). The masses of DMF and MTMS were determined by multiplying the volume of each raw material (DMF and MTMS) by its specific gravity. The mass of water was determined by multiplying the total volume of the acetic acid solution and ammonia solution by its specific gravity (1.0). Table 2 shows the composition ratio (mass ratio) of the compositions used to prepare each sample, and the solvent mass ratio (DMF / H2O) in the compositions.

[0080] [evaluation] (Evaluation 1) Visual observation of the sample Samples 1-23 were observed visually, and evaluated according to the following evaluation criteria to determine whether a homogeneous macroporous material was obtained (Evaluation Result: A) or not (Evaluation Result: B). The results are shown in Table 2.

[0081] <Evaluation Criteria for Rating 1> A: A sample (40 mm in diameter, 10 mm in height) was obtained that was free of cracks and had almost no powder fallout. B: Samples were obtained that showed cracking or produced a large amount of powder shedding.

[0082] (Evaluation 2) Uniaxial compression test (compression set measurement) For the samples that received an A rating in Evaluation 1, the following uniaxial compression test was performed. Each sample was cut with a razor blade and processed to a size of approximately 10 mm x 10 mm x 8 mm. A 500 N load cell was attached to a small benchtop testing machine (Shimadzu Corporation, EZ-SX), and each processed sample was uniaxially compressed at a speed of 1 mm / min at room temperature until the strain reached 25% (until the sample height of approximately 10 mm became approximately 7.5 mm). After the axial load was removed and 1 minute had passed, the remaining strain (compression set, residual strain) was measured. Each sample was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.

[0083] <Evaluation Criteria for Evaluation Level 2> A: The compression set of the sample after the uniaxial compression test was 3% or less. B: The sample fractured during compression in the uniaxial compression test, or the compression set of the sample after the uniaxial compression test exceeded 3%.

[0084] Figure 2 shows the relationship between strain and stress during the test for sample 2. In the hysteresis curve in Figure 2, the upper curve is the curve under load, and the lower curve is the curve after unloading. The compression set of sample 2 was 0%.

[0085] Furthermore, Figure 3 shows the mass ratios of DMF, H2O, and MTMS in the compositions used to prepare each sample, as shown in a triangular diagram. In the triangular diagram, samples 1-3 are shown as black circles, and samples 4-23 are shown as white circles.

[0086] [Table 1]

[0087] [Table 2]

[0088] As shown in Table 2 and Figure 3, samples 1 to 3, in the compositions used for production, with a solvent mass ratio (S / W) = (DMF / H2O) of 0.48 to 0.70 and an MTMS content of 30.0% to 41.0% by mass, were homogeneous macroporous materials (Evaluation 1 result: A), and the compression set after uniaxial compression testing was small (Evaluation 2 result: A). Scanning electron microscope (SEM) observation of samples 1 to 3 confirmed that samples 1 to 3 were macroporous materials from the SEM images. A representative SEM image of sample 2 is shown in Figure 4. From the above, it was confirmed that by keeping the composition of the composition used in manufacturing within a specific range, a macroporous material with sufficient mechanical strength (possessing viscoelasticity and being resistant to fracture by external stress) can be obtained without using surfactants. In samples 1 to 3, the DMF content in the composition was 20.0 to 27.0% by mass, and the water content was 38.0% to 44.0% by mass.

[0089] On the other hand, in the compositions used for manufacturing, samples 4 to 23, in which the solvent mass ratio (S / W) = (DMF / H2O) was outside the range of 0.48 to 0.70, or the MTMS content was outside the range of 30.0% to 41.0% by mass, were either not homogeneous macroporous materials (Evaluation 1 result: B) or were destroyed during compression in the uniaxial compression test (Evaluation 2 result: B).

[0090] (2) Measurement of thermal conductivity The thermal conductivity was measured using a NETZSCH HFM446Lambda small thermometer, following the thermal flow metering method (ASTM C518) as described below. The temperature of the upper plate was set to 25°C (high temperature side) and the lower plate to 15°C (low temperature side). Sample 2 (110mm × 110mm × 10mm) was sandwiched between these two plates, and the thermal conductivity was measured while applying compressive stress. The test was conducted at 20°C, which is the intermediate temperature between the upper and lower plates. The thermal conductivity of sample 2 was 0.042 Wm². -1 K -1 That was the case.

[0091] [Sample 24] Sample 24 was prepared in the same manner as Sample 2 described above, except that N-methyl-2-pyrrolidone (NMP) was used instead of DMF. Specifically, the composition used to prepare Sample 24 was a mixture of NMP: 3.5 mL, 1 M aqueous acetic acid: 2.0 mL, 1 M aqueous ammonia: 4.0 mL, and MTMS: 5.0 mL. The MTMS content in the composition was 33.0% by mass, and the mass ratio (NMP / water) = 0.60.

[0092] The above evaluations 1 and 2 were performed on sample 24. As a result, sample 24 was found to be a homogeneous macroporous material (Evaluation 1 result: A), and the compression set after the uniaxial compression test was small (Evaluation 2 result: A). Figure 5 shows the relationship between strain and axial pressure during the uniaxial compression test of sample 24. In the hysteresis curve in Figure 5, the upper curve is the curve under load, and the lower curve is the curve after unloading. The compression set of sample 24 was 0%. Based on the above, it was confirmed that sample 24, which used NMP instead of DMF, is a macroporous material with sufficient mechanical strength (possesses viscoelasticity and is resistant to fracture by external stress). [Industrial applicability]

[0093] The present invention provides a method for producing a polysiloxane macroporous material that is cost-effective, environmentally friendly, and possesses sufficient mechanical strength. The macroporous material produced by this invention can be widely used in applications such as thermal insulation materials.

Claims

1. A method for producing a macroporous polysiloxane, A composition containing methyltrialkoxysilane, an aprotic polar solvent, and water is prepared, and then gelled to form a gel. The process includes drying the gel, In the above composition, The ratio (S / W) of the mass (S) of the aprotic polar solvent to the mass (W) of the water is 0.48 to 0.

70. A method for producing a macroporous material, wherein the content of the methyltrialkoxysilane is 30.0% by mass to 41.0% by mass.

2. The method for producing a macroporous material according to claim 1, wherein the aprotic polar solvent comprises at least one selected from the group consisting of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP).

3. The method for producing a macroporous material according to claim 1 or 2, wherein the aprotic polar solvent is N,N-dimethylformamide (DMF).

4. A method for producing a macroporous material according to any one of claims 1 to 3, wherein the methyltrialkoxysilane is at least one selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, and methyltributoxysilane.

5. The method for producing a macroporous material according to claim 4, wherein the methyltrialkoxysilane is methyltrimethoxysilane.

6. A method for producing a macroporous body according to any one of claims 1 to 5, wherein the composition does not contain a surfactant.

7. A method for producing a macroporous material according to any one of claims 1 to 6, wherein the methyltrialkoxysilane is present in the composition in an amount of 70 mol% or more relative to the total amount of alkoxysilane contained in the composition.

8. The method for producing a macroporous body according to claim 7, wherein the proportion of polymethylsilsesquioxane structures in the polysiloxane is 70 mol% or more.

9. The method for producing a macroporous material according to claim 7, wherein the alkoxysilane contained in the composition consists solely of the methyltrialkoxysilane.

10. The method for producing a macroporous body according to claim 9, wherein the polysiloxane is composed solely of polymethylsilsesquioxane.

11. A method for producing a macroporous body according to any one of claims 1 to 10, wherein the ratio (S / W) is 0.50 to 0.

65.

12. A method for producing a macroporous body according to any one of claims 1 to 11, wherein the content of the methyltrialkoxysilane in the composition is 32.0% by mass to 40.0% by mass.

13. A method for producing a macroporous body according to any one of claims 1 to 12, wherein the content of the aprotic polar solvent in the composition is 20.0% by mass to 27.0% by mass.

14. A method for producing a macroporous body according to any one of claims 1 to 13, wherein the water content in the composition is 38.0% by mass to 44.0% by mass.

15. A macroporous polysiloxane containing a polymethylsilsesquioxane structure, A macroporous material in which, when uniaxially compressed to a strain of 25%, the remaining compression set after unloading is 3% or less.

16. A vacuum insulation material comprising a macroporous body as described in claim 15.

17. Outdoor equipment comprising the macroporous body described in claim 15.

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