Method for producing low-density gel body

Abstract

To provide a low-density gel body having high strength when compressed and high visible light transmittance and a production method of a low-density gel body.SOLUTION: A low-density gel body contains a polysiloxane chain and an organic polymer chain and has a three-dimensional network structure. The low-density gel body has a density of 0.3 g / cm3 or less, a pore size of 10 nm or more and 40 nm or less, and a skeleton diameter of 3 nm or more and 10 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention , low The present invention relates to a method for producing a high density gel body. [Background technology]

[0002] As described in Patent Documents 1 and 2, low-density gel bodies containing polysiloxane chains and organic polymer chains and having a three-dimensional network structure are known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 039541 [Patent Document 2] International Publication No. 2007 / 010949 Summary of the Invention [Problem to be solved by the invention]

[0004] In some cases, the low-density gel body described above is required to have high strength when compressed and high visible light transmittance. [Means for solving the problem]

[0005] The low-density gel body that solves the above problems is a low-density gel body that contains polysiloxane chains and organic polymer chains and has a three-dimensional network structure, and has a density of 0.3 g / cm 3 The pore diameter is within the range of 10 nm or more and 40 nm or less, and the skeleton diameter is within the range of 3 nm or more and 10 nm or less.

[0006] The low-density gel body may have a strength of 2 MPa or more when compressed by 50%. In the low-density gel body, the pore diameter may be 25 nm or less, and the skeletal diameter may be 7 nm or less.

[0007] The method for producing a low-density gel body is a method for producing a low-density gel body as described above, and comprises an organic polymer preparation step, a hydrolysis step, a dispersion step, and a gel preparation step. The organic polymer preparation step is a step of preparing an organic polymer having an organic polymer chain by radically polymerizing a first alkoxide having a radically polymerizable group. The hydrolysis step is a step of hydrolyzing the alkoxide by adding an acid to a mixed liquid containing the organic polymer and a second alkoxide that can be polymerized only by siloxane bonds. The dispersion step is a step of dispersing the components in the mixed liquid by mixing a surfactant consisting of an amphiphilic substance other than alcohol with the mixed liquid before the gel preparation step. The gel preparation step is a step of preparing a gel by adding a base to the mixed liquid after the hydrolysis step.

[0008] In the above-mentioned method for producing a low-density gel body, the surfactant may contain a polyoxyethylene-polyoxypropylene block copolymer. In the above-described method for producing a low-density gel body, the organic polymer preparation step may be carried out using a monomer liquid containing the first alkoxide and the second alkoxide. [Effects of the Invention]

[0009] According to the present invention, it is possible to increase the strength during compression and also increase the visible light transmittance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing an example of the molecular structure of a low-density gel body. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a low-density gel body and a method for producing a low-density gel body will be described below. <Low density gel body> The low-density gel body of this embodiment contains polysiloxane chains and organic polymer chains and has a three-dimensional network structure. The low-density gel body has a skeleton containing polysiloxane chains and organic polymer chains, and pores.

[0012] The polysiloxane chain is composed of two or more siloxane bonds (-Si-O-). A hydrogen atom, a hydroxyl group, a methyl group, or the like may be bonded to the silicon atom of the polysiloxane chain. The organic polymer chain is obtained from a radically polymerizable monomer. The organic polymer chain is, for example, an acrylic chain formed by polymerizing a methacrylic acid ester or an acrylic acid ester, and has an ester bond in the side chain.

[0013] The skeleton including the polysiloxane chain and the organic polymer chain has a structure in which the polysiloxane chain and the organic polymer chain are covalently bonded to each other at silicon atoms of the polysiloxane chain as bonding points. The skeleton including the polysiloxane chain and the organic polymer chain has a structure in which the polysiloxane chain and the organic polymer chain are covalently bonded to each other at multiple positions on both chains at silicon atoms of the polysiloxane chain as bonding points.

[0014] Figure 1 shows a schematic representation of a portion of the molecular structure of a polymer obtained from methacryloxypropyltrimethoxysilane (MPTMS) and methyltrimethoxysilane (MTMS). MPTMS is a radically polymerizable monomer that contains a methacryl group as the radically polymerizable group. Furthermore, the silicon atoms of the polymer generated from MPTMS and the silicon atoms of MTMS serve as bonding points, allowing the formation of a three-dimensional network structure of a low-density gel body.

[0015] The density of the low-density gel is 0.3 g / cm 3 The density of the low-density gel body is within the range of 0.3 g / cm 3 In the following cases, the low-density gel body can be prevented from breaking when it is compressed and deformed. The lower limit of the density of the low-density gel body is not particularly limited. The lower limit of the density of the low-density gel body is, for example, 0.05 g / cm. 3 It may be 0.16 g / cm or more. 3It may be more than that.

[0016] The pore size of the low-density gel body is in the range of 10 nm or more and 40 nm or less. When the pore size of the low-density gel body is 10 nm or more, it is possible to suppress breakage of the low-density gel body when it is compressed and deformed. When the pore size of the low-density gel body is 40 nm or less, it is possible to increase the visible light transmittance of the low-density gel body. It is preferable that the pore size of the low-density gel body is 25 nm or less.

[0017] The skeletal diameter of the low-density gel body is in the range of 3 nm or more and 10 nm or less. When the skeletal diameter of the low-density gel body is 3 nm or more, the strength of the low-density gel body can be increased when it is compressed and deformed. When the skeletal diameter of the low-density gel body is 10 nm or less, the visible light transmittance of the low-density gel body can be increased. The skeletal diameter of the low-density gel body is preferably 7 nm or less.

[0018] The strength of the low-density gel when compressed to 50% is preferably 2 MPa or more. The visible light transmittance of the low-density gel measured at a wavelength of 550 nm and a thickness of 10 mm is preferably 60% or more, and more preferably 70% or more.

[0019] The low-density gel body has a pore structure finer than the mean free path of gas molecules, and therefore the contribution of gas thermal conduction due to collisions between gas molecules and solid thermal conduction is low due to its low skeletal fraction. Therefore, the thermal conductivity of the low-density gel body is kept low. Furthermore, the low-density gel body has high visible light transmittance and compressive strength. Therefore, the low-density gel body of this embodiment can be suitably used, for example, as a heat insulating layer for double-glazing.

[0020] <Method of manufacturing low-density gel body> Next, a method for producing the low-density gel body will be described. The method for producing a low-density gel body includes an organic polymer preparation step, a hydrolysis step, a dispersion step, and a gel preparation step.

[0021] The organic polymer preparation step is a step of preparing an organic polymer having an organic polymer chain by radically polymerizing a first alkoxide (A1) having a radical polymerizable group. As the first alkoxide (A1), for example, methacryloxypropyltrimethoxysilane can be suitably used.

[0022] In the organic polymer preparation step, a polymerization solution containing a first alkoxide (A1) having a radical polymerizable group and water is used. The content of the first alkoxide (A1) having a radical polymerizable group in the polymerization solution is preferably, for example, 1% by volume or more and 20% by volume or less.

[0023] In the organic polymer preparation step, for example, azobisisobutyronitrile (AIBN) can be used as a radical polymerization initiator. The radical polymerization initiator is preferably blended in an amount of, for example, 0.01 mol or more and 0.1 mol or less per 1 mol of the first alkoxide (A1).

[0024] The hydrolysis step is a step of hydrolyzing the alkoxide by adding an acid to a mixed solution containing an organic polymer and a second alkoxide (A2). Unlike the first alkoxide (A1), the second alkoxide (A2) is an alkoxide that can be polymerized only through siloxane bonds. Examples of the second alkoxide (A2) include tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS), and dimethyldimethoxysilane (DMDMS). The second alkoxide (A2) preferably contains MTMS. The acid used in the hydrolysis step is preferably a strong acid such as nitric acid. The strong acid is preferably an aqueous solution of a strong acid, for example, in the range of 5 mM to 10 mM. The amount of the aqueous solution of the strong acid added is, for example, about 1 mL per 1 mL of the mixed solution.

[0025] The organic polymer preparation step is preferably carried out using a monomer liquid containing a first alkoxide (A1) and a second alkoxide (A2). In the monomer liquid, the content of the first alkoxide (A1) is preferably, for example, in the range of 1% by volume or more and 30% by volume or less, when the total amount of the first alkoxide (A1) and the second alkoxide (A2) is taken as 100% by volume.

[0026] The content of the organic polymer in the mixed solution after the hydrolysis step is, for example, preferably in the range of 20% to 50% by volume, more preferably in the range of 30% to 50% by volume. When the content of the organic polymer in the mixed solution is 50% by volume or less, the density of the low-density gel can be further reduced. On the other hand, when the content of the organic polymer in the mixed solution is 20% by volume or more, the pore size can be prevented from becoming excessively small.

[0027] The dispersion step is a step in which a surfactant consisting of an amphipathic substance other than alcohol is mixed with the mixture before the gel preparation step to disperse the components in the mixture. The dispersion step may be performed on the mixture before the hydrolysis step or on the mixture after the hydrolysis step. By performing the dispersion step, it becomes easier to keep the skeletal diameter of the low-density gel body small.

[0028] The surfactant used in the dispersion process is composed of an amphiphilic substance other than alcohol. Examples of surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Among surfactants, nonionic surfactants are preferred. More preferably, the surfactant contains a polyoxyethylene-polyoxypropylene block copolymer, which is a type of nonionic surfactant.

[0029] The content of the surfactant in the mixed liquid is, for example, in the range of 1% by mass or more and 70% by mass or less. The gel preparation step is a step of preparing a gel by adding a base to the mixture obtained after the hydrolysis step. In the gel preparation step, silicon atoms in the organic polymer obtained from the first alkoxide (A1) are further condensed with polysiloxane chains obtained by condensation of the second alkoxide (A2), thereby obtaining a low-density gel body.

[0030] The base used in the gel preparation step is preferably a strong base, more preferably a quaternary ammonium hydroxide, and even more preferably tetramethylammonium hydroxide (TMAOH). The base is preferably an aqueous TMAOH solution with a concentration of, for example, 10 mM to 500 mM.

[0031] The gel obtained in the gel preparation step is preferably aged for about 24 hours, and then the solvent is replaced with, for example, isopropanol. The method for drying the gel is not particularly limited. The gel is preferably dried by supercritical drying using a supercritical drying device.

[0032] Next, the operation and effects of this embodiment will be described. (1) The low-density gel body contains polysiloxane chains and organic polymer chains and has a three-dimensional network structure. The density of the low-density gel body is 0.3 g / cm. 3 The pore diameter of the low-density gel body is within the range of 10 nm or more and 40 nm or less. The skeletal diameter of the low-density gel body is within the range of 3 nm or more and 10 nm or less.

[0033] As described above, when the pore diameter of the low-density gel body is 10 nm or more, the strength during compression can be increased. When the pore diameter of the low-density gel body is 40 nm or less, the visible light transmittance can be increased. When the skeletal diameter of the low-density gel body is 3 nm or more, the strength during compression can be increased. When the skeletal diameter of the low-density gel body is 10 nm or less, the visible light transmittance can be increased. Therefore, it is possible to increase the strength during compression and also increase the visible light transmittance.

[0034] (2) The pore size of the low-density gel body is preferably 25 nm or less, and the skeletal diameter is preferably 7 nm or less. In this case, for example, it becomes possible to maintain the strength of the low-density gel body at 50% compression to 2 MPa or more, and to increase the visible light transmittance measured at a wavelength of 550 nm and a thickness of 10 mm to 70% or more.

[0035] (3) The method for producing a low-density gel body includes an organic polymer preparation step, a hydrolysis step, a dispersion step, and a gel preparation step. The organic polymer preparation step is a step of preparing an organic polymer having an organic polymer chain by radically polymerizing a first alkoxide having a radically polymerizable group. The hydrolysis step is a step of hydrolyzing the alkoxide by adding an acid to a mixed solution containing an organic polymer and a second alkoxide that can be polymerized only through siloxane bonds. The dispersion step is a step of dispersing the components in the mixed solution by mixing a surfactant made of an amphiphilic substance other than alcohol with the mixed solution before the gel preparation step. The gel preparation step is a step of preparing a gel by adding a base to the mixed solution after the hydrolysis step.

[0036] According to this method, a low-density gel body having the density, pore size, and skeletal size within the above ranges can be easily produced. (4) In the method for producing a low-density gel body, the surfactant used in the dispersion step preferably contains a polyoxyethylene-polyoxypropylene block copolymer, which makes it easier to produce a low-density gel body having the density, pore size, and skeleton size within the above ranges.

[0037] (5) In the method for producing a low-density gel body, the organic polymer preparation step is preferably carried out using a monomer liquid containing the first alkoxide (A1) and the second alkoxide (A2). In this case, gelation of the organic polymer obtained from the first alkoxide (A1) due to a side reaction can be suppressed. More specifically, it is believed that the second alkoxide (A2) serves as a reaction solvent for the radical polymerization reaction of the first alkoxide (A1), thereby dispersing the organic polymer formed from the first alkoxide (A1), and thus suppressing the gelation reaction of the organic polymer. [Example]

[0038] Next, examples and comparative examples will be described. Example 1 <Organic polymer preparation process> As the first alkoxide (A1), methacryloxypropyltrimethoxysilane (MPTMS) represented by the following structural formula (1) was prepared. Also, as the second alkoxide (A2), methyltrimethoxysilane (MTMS) represented by the following structural formula (2) was prepared.

[0039] [ka] First, 2.0 mL of MPTMS and 8.0 mL of MTMS were placed in a screw cap bottle.

[0040] Azobisisobutyronitrile (AIBN) was added to the screw cap vial so that the amount was 0.05 mol per 1 mol of MPTMS, and the screw cap vial was then sealed. The components in the screw cap vial were mixed using a stirrer. After confirming that the AIBN had dissolved, the screw cap vial was placed in an oven at 70°C. After heating in the oven for 24 hours, the screw cap vial was removed from the oven and allowed to cool slowly to room temperature. This resulted in the preparation of a mixed solution containing an organic polymer having an organic polymer chain and a second alkoxide (A2).

[0041] The organic polymer having an organic polymer chain is represented by the following structural formula (3).

[0042] [ka] The column "Content of first alkoxide" in Table 1 shows the content of the first alkoxide (A1) when the total amount of the first alkoxide (A1) and the second alkoxide (A2) is taken as 100% by volume.

[0043] <Hydrolysis process> 1.0 mL of the above mixture was placed in a screw cap vial with a stirrer tip, and 1.0 mL of 5 mM nitric acid aqueous solution (HNO3aq) was added while stirring the mixture. At this time, HNO3aq was added in 0.2 mL increments every 2 minutes, and stirring was continued for 12 minutes from the start of HNO3aq addition to prepare a uniform sol.

[0044] The hydrolysate of the organic polymer is represented by the following structural formula (4): The hydrolysate of MTMS is represented by the following structural formula (5):

[0045] [ka] <Dispersion process> Next, 0.8 g of surfactant (B1) was added to the sol obtained in the hydrolysis step and stirred for another 3 minutes. The screw cap bottle was then immersed in an ice bath and stirred for 10 minutes to cool the sol.

[0046] The surfactant (B1) is a nonionic surfactant (manufactured by Sigma-Aldrich, trade name: Pluronic L-64, polyoxypropylene chain molecular weight: 1750, ethylene oxide content: 40% by mass). This nonionic surfactant is a polyoxyethylene-polyoxypropylene block copolymer.

[0047] <Gel preparation process> Next, 0.6 mL of a 100 mM aqueous solution of tetramethylammonium hydroxide (TMAOHaq) was added to the sol obtained in the dispersion step, followed by stirring for 3 minutes. The stirrer tip was then removed from the screw cap, and the screw cap was then sealed. The screw cap was left standing at room temperature for 1 hour to gel the sol. The gel was then aged by leaving the screw cap in an oven at 60°C for 96 hours. The screw cap was removed from the oven, and the gel was immersed in water in a wide-mouth bottle. The wide-mouth bottle was then sealed and left standing in an oven at 60°C for 24 hours. The water in the wide-mouth bottle was replaced with a mixed solvent (water volume: isopropanol (IPA) volume = 1:1), and the bottle was then sealed and left standing in an oven at 60°C for 8 hours. The mixed solvent in the wide-mouth bottle was then replaced with IPA, and the bottle was then sealed and left standing in an oven at 60°C for 8 hours, performing a solvent exchange procedure. This solvent exchange procedure was repeated five times to obtain a gel in which the solvent had been exchanged with IPA. This gel was then dried in a supercritical dryer at 80°C and 14 MPa to obtain a low-density gel.

[0048] Example 2 As shown in Table 1, in Example 2, a low-density gel was obtained in the same manner as in Example 1, except that the amount of surfactant (B1) added in the dispersion step was changed.

[0049] Example 3 As shown in Table 1, in Example 3, a low-density gel body was obtained in the same manner as in Example 1, except that the amount of MPTMS blended in the polymer solution preparation step was changed.

[0050] Example 4 As shown in Table 1, in Example 4, a low-density gel body was obtained in the same manner as in Example 1, except that the amount of polymer solution used in the hydrolysis step was changed.

[0051] Example 5 As shown in Table 1, in Example 5, a low-density gel was obtained in the same manner as in Example 1, except that the surfactant (B1) used in the dispersion step was changed to surfactant (B2).

[0052] The surfactant (B2) is a nonionic surfactant (manufactured by Sigma-Aldrich, trade name: Pluronic L-44, molecular weight of polyoxypropylene chain: 1200, ethylene oxide content: 40% by mass). This nonionic surfactant is a polyoxyethylene-polyoxypropylene block copolymer.

[0053] (Comparative Example 1) As shown in Table 2, in Comparative Example 1, a low-density gel body was obtained in the same manner as in Example 1, except that the amount of surfactant (B1) added in the dispersion step was changed.

[0054] (Comparative Example 2) As shown in Table 2, in Comparative Example 2, a low-density gel body was obtained in the same manner as in Example 1, except that the polymer solution preparation step was omitted and the polymer solution was changed to MTMS.

[0055] (Comparative Example 3) As shown in Table 2, in Comparative Example 3, a low-density gel body was obtained in the same manner as in Example 1, except that the amount of polymer solution used in the hydrolysis step was changed.

[0056] Comparative Example 4 As shown in Table 2, in Comparative Example 4, a low-density gel was obtained in the same manner as in Example 1, except that the surfactant (B1) used in the dispersion step was not added and 0.8 g of isopropanol (IPA) was added.

[0057] [Table 1]

[0058] [Table 2] (Physical properties of low-density gel bodies) <density> The bulk density of the low-density gel body of each example was measured by a volume displacement method (Micromeritics, trade name: GeoPyc1360). The results are shown in the "Density" column in Tables 3 and 4.

[0059] <Pore diameter> The peak pore size of the low-density gel was measured by nitrogen adsorption analysis. A nitrogen adsorption analyzer (Microtrack-Bell, trade name: BELSORP-mini) was used for this measurement. The peak pore size was determined from the adsorption branch using the Barrett-Joyner-Halenda (BJH) method. The peak pore size was measured three times and the average value was calculated.

[0060] The low-density gel samples for each example were prepared as follows: First, the low-density gel was crushed to a size of several millimeters to obtain gel powder. Next, approximately 30 mg of the obtained gel powder was placed in a cell and degassed under vacuum at 80°C for 24 hours. The results are shown in the "Pore diameter" column in Tables 3 and 4.

[0061] <Bone diameter> The skeletal diameter of the low-density gel body was measured using a field emission transmission electron microscope (FE-TEM, manufactured by JEOL Ltd., product name: JEM-2200FS). First, three images were obtained by imaging three different positions on the measurement sample using the FE-TEM. For each image, the skeletal diameter of three isolated skeletal points was measured. The skeletal diameter was calculated from the ratio with the scale bar in the image. The average skeletal diameter of a total of nine points measured from each image was calculated. The results are shown in the "Skeletal Diameter" column in Tables 3 and 4.

[0062] (Strength and elastic modulus at 50% compression) The strength and modulus of elasticity of the low-density gel at 50% compression were measured using a compression / tensile tester (Shimadzu Corporation, product name: EZGraph). Measurement samples were obtained by cutting 9.5 mm diameter rod-shaped gels into 10 mm lengths. These samples were compressed longitudinally at a compression rate of 0.5 mm / s until they reached 50% compressive strain, at which point the strength was measured. The modulus of elasticity was calculated from strains within a test force range of 10 to 20 N. Measurements of the strength and modulus of elasticity of the low-density gel at 50% compression were performed on three samples, and the average values ​​were calculated. The results are shown in the "Strength at 50% Compression" and "Modulus of Elasticity" columns in Tables 3 and 4. If a sample broke before reaching 50% compressive strain, the "Broken" column is displayed.

[0063] (Visible light transmittance) The visible light transmittance of the low-density gel body was measured using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-670). The thickness of the measurement sample was 10 mm, and the wavelength of visible light was 550 nm. The results are shown in the "Visible Light Transmittance" column in Tables 3 and 4.

[0064] [Table 3]

[0065] [Table 4] The strength of the low-density gel bodies of Examples 1 to 5 when compressed to 50% was 2 MPa or more. In contrast, the low-density gel bodies of Comparative Examples 1, 3, and 4 were unable to withstand the 50% compression strain and were destroyed. The strength of the low-density gel body of Comparative Example 2 when compressed to 50% was less than 2 MPa.

[0066] Furthermore, the visible light transmittance of the low-density gel bodies of Examples 1 to 5 was 60% or more, indicating that the low-density gel bodies of Examples 1 to 5 had good visible light transmittance. In particular, the visible light transmittance of Examples 1, 3 to 5 was 70% or more, indicating that the low-density gel bodies of Examples 1, 3 to 5 had excellent visible light transmittance.

Claims

1. A method for producing a low-density gel body having a three-dimensional network structure, comprising: a polysiloxane chain and an organic polymer chain; The low-density gel body is The density is in the range of more than 0 g / cm 3 and not more than 0.3 g / cm 3 , The pore diameter is in the range of 10 nm or more and 40 nm or less, The skeletal diameter is in the range of 3 nm or more and 10 nm or less, The manufacturing method includes: The method comprises an organic polymer preparation step, a hydrolysis step, a dispersion step, and a gel preparation step, The organic polymer preparation step includes: a step of radically polymerizing a first alkoxide having a radical polymerizable group to prepare an organic polymer having the organic polymer chain; the hydrolysis step is a step of hydrolyzing the alkoxide by adding an acid to a mixed solution containing the organic polymer and a second alkoxide polymerizable only through a siloxane bond; the dispersion step is a step of dispersing components in the mixed solution by mixing a surfactant made of an amphipathic substance other than alcohol with the mixed solution before the gel preparation step, The method for producing a low-density gel body, wherein the gel preparation step is a step of preparing a gel by adding a base to the mixed liquid after the hydrolysis step.

2. A method for producing a low-density gel body as described in claim 1, wherein the low-density gel body has a strength of 2 MPa or more when compressed by 50%.

3. A method for producing a low-density gel body as described in claim 1 or claim 2, wherein the low-density gel body has a pore diameter of 25 nm or less and a skeletal diameter of 7 nm or less.

4. The method for producing a low-density gel body according to claim 1 , wherein the surfactant includes a polyoxyethylene-polyoxypropylene block copolymer.

5. The method for producing a low-density gel body according to claim 1 , wherein the organic polymer preparation step is carried out using a monomer liquid containing the first alkoxide and the second alkoxide.

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