JPH0977509A - Formation of independent gel film by sol-gel method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an independent gel film having smoothness, denseness and uniform thickness without the need of high temp. treatment. SOLUTION: A sol obtained by hydrolyzing and condensation polymerizing a starting material containing an organoalkoxy silane is spread on a supporting aq. solution insoluble in the sol to make a gel. The independent gel film consisting essentially of an organopolysiloxane, in which the net-work unit of a three dimensional network structure is expressed by Rn SiO(4-n)/2 (where, R is an organic group selected from groups of methyl, ethyl, n-propyl, isopropyl, phenyl and a vinyl and (n) is 0<n<=1.7), is obtained by using organotrialkoxy silane alone or with a tetraalkoxysilane and/or diorganoalkoxy silane in combination as the starting material.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an independent film using a sol-gel method, and in particular to an independent film for which it is difficult to form a thin film directly on a substrate or where surface smoothness is required. It relates to a forming method.

2. Description of the Related Art Dip coat method and spin coat method are often used as a method for forming a film using the sol-gel method. The glass and ceramic coating thin film has a film thickness limit of about 1.5 μm. When trying to achieve a film thickness greater than that, cracks,
It is known that problems such as peeling occur. Therefore, a method of repeating coating and firing is used to increase the film thickness. In addition, a method of forming a film by forming a film on a substrate and peeling the thin film from the substrate has been disclosed (Japanese Patent Laid-Open No. 63-171670, Japanese Patent Laid-Open No. 1-220620).
No. 1). Also, a method for producing a silica gel thick film at the interface between a silicon alkoxide-containing organic solution and a basic water solvent has been disclosed (Japanese Patent Laid-Open No. 4-362033). In addition, mercury, which has a large specific gravity, and tristearin,
A method in which a sol obtained from a metal alkoxide is spread on an organic liquid such as dibromoethane to form a gel thick film and used as a glass plate (JP-A-61-2336620, JP-A-6-236620).
No. 2-70237), a method in which a similar sol is spread on an aqueous solution to obtain a gel thin film, which is used as a glass thin film (JP-A-51).
(JP-A-34219) is also published. However, such a film is porous and needs to be heat-treated at a high temperature of 1000 ° C. or higher in order to make it non-porous, and there is a problem of warpage or cracking due to shrinkage. In addition, since mercury and dibromoethane supporting liquids are harmful and tristearin and the like are not liquid at room temperature, there is a problem in operation, and the sol obtained from metal alkoxides is supported even when developed in an aqueous solution. When contacted with an aqueous solution, it rapidly gels, so the thickness is 10 μm.
There was a problem that only a thin film up to a certain degree could be produced.
Therefore, in the present invention, a sol obtained by a hydrolysis / polycondensation reaction is spread on the free surface of a supporting aqueous solution in which the sol of an organic group-containing polysiloxane is insoluble and gelled, so that high temperature heat treatment is not required, and a smooth surface is obtained. It is an object of the present invention to provide a method for forming a uniform and dense thick film.

SUMMARY OF THE INVENTION The present invention is an independent gel characterized in that a sol obtained by hydrolyzing and polycondensing a starting material containing an organoalkoxysilane is spread on a supporting aqueous solution in which the sol is insoluble. The present invention relates to a method for forming a film. In particular, the formula: R _n SiO
A network constituent unit represented by _{(4-n) / 2} (0 <n ≦ 1.7) (R is an organic group selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a phenyl group, and a vinyl group) Relates to a method for forming an independent film mainly composed of polysiloxanes which are repeatedly bonded to form a three-dimensional network structure, and has the formula: R _n Si (OR ′) _4-n (n = 0, 1,
2) Alkoxysilanes or organoalkoxysilanes (R 'is a lower alkyl group such as a methyl group, an ethyl group, a propyl group) are used as a main starting material.

According to the present invention, a siloxane bond is obtained by forming a siloxane bond by hydrolysis, dehydration and dealcoholization condensation of the above-mentioned alkoxysilane or organoalkoxysilane, but a sol solution is obtained in order to increase the insolubility of the sol in a supporting aqueous solution. It is important to control the reaction state and the content of the organic group (R). Further, as the polymerization proceeds, the affinity between the sol and the supporting aqueous solution decreases, so it is preferable to develop the sol on the supporting aqueous solution to which alcohol, amine, surfactant, etc. have been added. Further, the density of the supporting aqueous solution is adjusted in order to form a uniform film on the supporting aqueous solution. By the method described above, the sol is uniformly spread on the supporting aqueous solution and further gelled to obtain a transparent, smooth and dense independent thick film.

Preferred Embodiment In the method for forming an independent gel film of polysiloxane represented by the above formula: R _n SiO _{(4-n) / 2} (0 <n ≦ 1.7), tetraethoxysilane ( TEOS),
Tetraalkoxysilane such as tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS),
A mixture of trialkoxysilanes such as methyltriethoxysilane (MTES), ethyltrimethoxysilane (ETMS) and phenyltriethoxysilane (PhTES), dialkoxysilanes such as dimethyldiethoxysilane (DMDE) and diphenyldimethoxysilane (DPhDM). Can be used. Further, trialkoxysilane may be used alone. Formula: R _n SiO _{(4-n) / 2} (0 <
In n ≦ 1.7), n ≦ 1.7 means that when n exceeds 1.7, it becomes difficult to form a three-dimensional network structure.
This is because it is difficult to obtain a uniform gel film. In addition, 0.2 ≦
More preferably, n ≦ 1.6. When n ≧ 0.2, the sol becomes more difficult to mix with the supporting aqueous solution, and a film having higher transparency can be obtained. By setting n ≦ 1.6, a film with higher strength can be obtained.

For the above raw materials, 1.4 ≦ H ₂ O / Si ≦ 4.0
It is desirable to add water so as to have a (molar ratio) and carry out the hydrolysis / polycondensation reaction. When H ₂ O / Si <1.4 (molar ratio), unreacted alkoxy groups remain and the strength of the independent film is apt to deteriorate. On the other hand, when H ₂ O / Si> 4.0 (molar ratio), when a large amount of organoalkoxysilane is contained, phase separation easily occurs and it becomes difficult to obtain an optically uniform gel film. When the tetraalkoxysilane is contained in a large amount, the sol easily migrates to the supporting liquid layer, which makes it difficult to obtain a film. The amount of water added is 1.4 ≦ H ₂ O / Si ≦ 2.5
(Mole ratio) is more preferable.

The pH of the reaction solution is preferably 7.0 or less as an initial value immediately after preparation of the reaction solution. Under the condition of pH> 7.0,
It is difficult for the desired reaction to proceed. It is more preferable to add an acid catalyst to make the initial pH of the reaction solution 5.0 or less in order to accelerate the reaction. The acid catalyst used is not particularly limited, and inorganic acid catalysts such as nitric acid and hydrochloric acid and organic acid catalysts such as acetic acid are used according to a conventional method.

Further, when a large amount of methyltrialkoxysilane is used as a raw material, in order to suppress crystal precipitation,
As described in Japanese Patent Application No. 6-332515, it is preferable to add a soluble metal chelate compound to this raw material.
When a metal chelate compound is not used, Japanese Patent Application No. 6-8
As described in 7497, complicated operations such as dividing the addition of water into two stages are required.

As the chelate compound satisfying the above conditions, metal chelates of β-diketones (compounds having 1,3-dioxopropylenes), metal chelates of macrocyclic polyether compounds, and o, o'-dihydroxy aromatic azo compounds. Examples thereof include compound metal chelates, metal chelates of o-salicylidene aminophenol and its derivatives, and the like. The type of metal ion is not particularly limited, but it is necessary to select one having a large complex formation constant with the ligand. As a specific example, tris (acetylacetonato) aluminum (I
II), tris (ethylacetoacetato) aluminum (III), tris (diethylmalonato) aluminum (III), bis (acetylacetonato) copper (II),
Tetrakis (acetylacetonato) zirconium (I
V), tris (acetylacetonato) chromium (II
I), tris (acetylacetonato) cobalt (II
I) and β-diketone metal chelates such as titanium (II) acetylacetonate ((CH ₃ COCHCOCH ₃ ) ₂ TiO), β-diketone metal chelates of rare earth metals, and 18-crown-6-potassium chelate compounds Macrocyclic polyether compound metal chelate such as salt, 12-crown-4-lithium chelate compound salt, 15-crown-5-sodium chelate compound salt, o, o ′
-Metal chelates of aluminum, cobalt, copper, titanium, etc. of dihydroxyazobenzene, metal chelates of o-salicylidene aminophenolato copper (II), o-salicylidene aminophenolato aluminum (III), and the like. it can. It is considered that these metal chelate compounds interact with silanol to control the polymerization reaction. Regarding the amount of addition, depending on the effect, it is 0.001 relative to methyltrialkoxysilane.
It is preferably added in the range of ˜5 mol%. 0.001
If it is less than mol%, it is difficult to obtain the effect of suppressing crystal precipitation.
On the contrary, if it is added in an amount of more than 5 mol%, a chelate compound may be precipitated or the properties of the gel may be affected. The metal chelate compound may be prepared by adding a ligand component and a metal component separately to the reaction system and chelating in situ. The addition amount of the metal chelate compound is more preferably 0.01 to 1 mol% with respect to methyltrialkoxysilane.

On the other hand, when a large amount of tetraalkoxysilane is used as the raw material, it is preferable to add alcohol in order to obtain a uniform sol.

The sol prepared by the above method is spread on the supporting aqueous solution, and the density of the supporting aqueous solution is adjusted by dissolving the water-soluble inorganic metal salt in water so that the gel film remains on the liquid surface until it is sufficiently solidified. The density of the supporting aqueous solution is 1.05 g / c
It is preferably m ³ or more. By using such an aqueous solution as a supporting liquid, hydrolysis and polycondensation of unreacted alkoxy groups in the gel film can be promoted, and a gel film having a stronger network can be formed, and the produced alcohol can be removed. It can also be efficiently removed from the gel film. Further, in order to adjust the affinity with the sol and the surface tension, a polar organic solvent such as alcohol or amine or a surfactant may be added to the supporting liquid.

With respect to the sol liquid, the initial starting material has a low polarity, water is consumed as the reaction proceeds, the silanol groups of the oligomer increase, and alcohol is formed, so that the polarity of the solvent is convenient for dissolving the oligomer. It becomes a value. As the polymerization proceeds further, the polarity of the oligomer decreases. Therefore, it is important to adjust the solubility of the oligomer in water so that the oligomer does not migrate to the supporting aqueous solution layer in the sol developed on the supporting aqueous solution. That is, it is necessary to adjust the content of organic groups and the concentration of alcohol and control the degree of polymerization. It is preferable to use a sol having a viscosity of 5 × 10 ⁻³ Pas or more until gelation. If the viscosity is lower than this, there are many low-molecular compounds containing a large amount of silanol, and they are easily dissolved in the supporting aqueous solution. On the other hand, regarding the supporting aqueous solution,
In a sol starting from a raw material containing a large amount of organoalkoxysilane, as the polymerization proceeds, the affinity with the supporting aqueous solution becomes small and it becomes difficult to develop.Therefore, a water-soluble organic solvent such as alcohol is added to the supporting aqueous solution to improve the affinity. Adjust sex. When there are many organic groups, the water-soluble organic solvent such as alcohol in the supporting aqueous solution is preferably 30 vol% or less. If there is more than this, the sol will dissolve in the supporting liquid layer,
It becomes difficult to form a film. In the case of a sol starting from a raw material containing a large amount of tetraalkoxysilane, the water-soluble organic solvent content is preferably 10 vol% or less so that the sol does not dissolve in the supporting liquid layer. Specifically, after a certain reaction time has elapsed, the concentration of the organic solvent in the supporting aqueous solution may be changed to select the supporting aqueous solution composition in which the sol easily develops.

Since the film obtained by the method of the present invention is formed on the free surface which is the liquid surface, a transparent independent film having a high surface smoothness can be prepared. Further, the thickness of the independent gel film can be easily controlled by changing the container size and the amount of sol to be spread.

The starting materials are Al, Zr, Ti and G.
By adding an alkoxide such as e or B, a multi-component independent gel film can be formed. It is also possible to add a polymerizable sol of different composition onto the membrane to bring about a compositional distribution and to obtain an independent composite membrane.

Example 1 Methyltriethoxysilane (Shin-Etsu Chemical Co., Ltd., LS-18)
90, hereinafter MTES), distilled water was added so that the molar ratio of distilled water and MTES was 1.25: 1. As 10 wt% water in distilled water, 0.1N nitric acid was used as a catalyst. Initially it is in a two-phase state, but if stirring is continued at room temperature, it will become uniform as the hydrolysis / polycondensation reaction proceeds,
It became transparent within 10 minutes. After leaving it in a sealed state at room temperature for 2 days, the alcohol produced by the reaction was evaporated by a 70% theoretical evaporator to obtain an oligomer. Furthermore, 0.1 mol% of tris (acetylacetonato) aluminum (III) (hereinafter Al (A
cAc) ₃ ) was added and kept at 50 ° C. for 30 minutes,
0.5 mol of distilled water was added per mol of MTES.
Continue stirring in a sealed state until a uniform solution is obtained, then
It was left still at 15 ° C for 15 hours. The density of the obtained sol is 1.01
It was g / cm ³ and the viscosity was 13 × 10 ⁻³ Pas. This sol was treated with NaCl having a density of 1.125 g / cm ³ .
A tray (20 x 30c) containing 500 ml of the supporting aqueous solution.
3 ml was added dropwise to m) and uniformly spread. The mixture was allowed to stand at room temperature for 3 days to obtain a transparent gel film having a thickness of about 50 μm.

Example 2 The sol of Example 1 was treated with NaC having a density of 1.125 g / cm ³ .
A tray (20 × 30) containing a mixed solution of 450 ml of aqueous solution and 50 ml of ethanol (density: 1.11 g / cm ³ ).
cm). The mixture was allowed to stand at room temperature for 3 days to obtain a transparent gel film having a thickness of about 50 μm.

Comparative Example 1 3 ml of the sol of Example 1 was dropped on a tray (20 × 30 cm) containing 500 ml of ion-exchanged water. Due to the low density of the supporting liquid, it precipitated in the form of drops on the bottom and became a granular gel.

Comparative Example 2 The sol of Example 1 was treated with NaC having a density of 1.125 g / cm ³ .
3 ml was dropped onto a tray (20 × 30 cm) containing a mixed solution of 330 ml of 1 l aqueous solution and 170 ml of ethanol. The sol dissolved in the supporting liquid, and no film was obtained.

Example 3 Distilled water was added to MTES so that the molar ratio of distilled water and MTES was 1.25: 1. As 10 wt% water in distilled water, 0.1N nitric acid was used as a catalyst. After becoming homogeneous, the mixture was allowed to stand in a sealed state at room temperature for 2 days, and then the alcohol produced by the reaction was evaporated by an evaporator at 80% of the theoretical value. Next, 0.1 mol% of A with respect to MTES
1 (AcAc) ₃ and 0.5 mol of water per mol of MTES were added, and the mixture was stirred at 50 ° C. for 30 minutes in a sealed state to obtain a solution A. Next, tetraethoxysilane (hereinafter TEO
S), ethanol and water were mixed at a ratio (molar ratio) of 1: 2: 1.5. As 10 wt% water in distilled water, 0.1N nitric acid was used as a catalyst. After reacting in a sealed state at room temperature for 2 days, 3 mol of ethanol was evaporated from the solution with respect to 1 mol of TEOS by an evaporator to obtain a solution B. The obtained solution A and solution B are MTES: TEOS =
Mix 1: 1. After reacting in a sealed state for 30 minutes, 1 mol of water was added per 1 mol of TEOS in the mixed solution, and the liquid was kept in a sealed state at 40 ° C. for 20 hours. The obtained sol had a density of 1.02 g / cm ³ and a viscosity of 13 × 10 ⁻³ Pas. This sol was added to a NaCl supporting aqueous solution having a density of 1.125 g / cm ³ 500
3 ml was dropped on a tray (20 × 30 cm) containing ml and uniformly spread. Immediate gelation occurred and a transparent gel film having a thickness of about 60 μm was obtained.

Example 4 Distilled water was added to MTES so that the molar ratio of distilled water and MTES was 1.25: 1. As 10 wt% water in distilled water, 0.1N nitric acid was used as a catalyst. After becoming homogeneous, the mixture was allowed to stand in a sealed state at room temperature for 2 days, and then the alcohol produced by the reaction was evaporated by an evaporator at 80% of the theoretical value. Next, dimethyldiethoxysilane (hereinafter DMDE), Al (AcAc) _3, and water were mixed with MTES: D.
MDE: Al (AcAc) ₃ : H ₂ O = 1: 1: 0.0
It was added so as to be 01: 2.5 (molar ratio). The mixture was stirred in a sealed state at 50 ° C. for about 10 minutes and then kept at 40 ° C. for 45 hours. The density of the obtained sol is 0.96 g / cm ^3.
And the viscosity was 8 × 10 ⁻³ Pas. 50 g of this sol was added to a NaCl supporting aqueous solution having a density of 1.125 g / cm ^3.
3 ml was dropped on a tray (20 × 30 cm) containing 0 ml and uniformly spread. Gelation occurred in one week, and a transparent gel film having a thickness of about 50 μm was obtained.

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Claims (5)

[Claims] 1. A self-supporting gel film, characterized in that a sol obtained by hydrolyzing and polycondensing a starting material containing an organoalkoxysilane is spread on a supporting aqueous solution in which the sol is insoluble and gelled. Forming method. 2. A supporting aqueous solution in which the sol is insoluble has a density of 1.05.
The method for forming an independent gel film according to claim 1, which is an aqueous solution of g / cm ³ or more. 3. A sol which has a viscosity of 5 × 10 ⁻³ Pas or more at room temperature and which has not gelled yet is used.
Alternatively, the method for forming an independent gel film according to the item 2. 4. The volume fraction of the water-soluble organic solvent contained in the supporting aqueous solution is 30% or less.
4. The method for forming an independent gel film according to any one of 3 to 3. 5. The formula: R _n SiO _{(4-n) / 2} (0 <n ≦ 1.
7) (R is an organic group selected from a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a phenyl group, and a vinyl group) is repeatedly bonded so as to form a three-dimensional network structure. The method for forming an independent gel film according to any one of claims 1 to 4, wherein said polysiloxane is a main component.