JPH0722695B2 - Alkoxide hydrolysis sol and / or gel and method for preparing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrolyzed sol and / or gel of an alkoxide that can be used for producing a ceramic coating film, ceramic fiber and the like, and a method for preparing the same.

[Prior Art] A technique of forming a ceramic into a coating film, a molded article such as a fiber by a sol-gel method using an alkoxide as a starting material has been known. In such a sol-gel method, when a ceramic is formed into a coating film, a hydrolysis sol and / or gel of an alkoxide is applied to the surface of an object and then heated. Further, when the ceramic is formed into a fibrous shape, it is produced by spinning a hydrolyzed sol and / or gel of an alkoxide in the same manner as in the case of using an organic polymer and then heating it.

[Problems to be Solved by the Invention] However, for example, Journal of Ceramic Industry, 92 , 242-247 (198
As reported in 4), the hydrolysis sol and / or gel of alkoxide increases its viscosity with time due to polymerization. In order to carry out the above-mentioned coating and spinning, it is necessary that the hydrolyzed sol and / or gel is in an appropriate viscosity range, and if the hydrolyzed sol and / or gel viscosity increases with time. However, it can be used only while the viscosity is within a predetermined range, and there is a problem that the pot life is limited. Therefore, the hydrolyzed sol and / or gel must be used within a limited time, which is a great limitation in terms of the manufacturing process. When the viscosity increases with time, the viscosity at the time of molding is different between the one molded at the beginning of the manufacturing process and the one molded at the end of the manufacturing process. There was also the problem of different diameters.

The present invention has been made to solve the above problems, and an object of the present invention is to suppress the increase of viscosity with time and to stabilize the viscosity of an alkoxide hydrolysis sol and / or gel and a method for preparing the same. To provide.

[Means and Action for Solving Problems] The alkoxide hydrolysis sol and / or gel according to the first invention of this application is characterized by containing an organic ammonium salt as a viscosity stabilizer. In this application, the organic ammonium salt refers to a quaternary ammonium salt represented by the general formula R ₄ N ⁺ X ⁻ . Here, R represents a hydrocarbon group such as alkyl and aryl, and X ⁻ represents an anion. In the general formula, R ₄ is simply represented, but the hydrocarbon groups bonded to one nitrogen may be different hydrocarbon groups. Preferably, R is an alkyl group and X ^- is a halide ion.

A second invention of this application is a method for preparing a hydrolyzed sol and / or gel of an alkoxide, which comprises hydrolyzing an alkoxide, polymerizing the hydrolyzate to a predetermined viscosity, and then adding an organic ammonium salt. The feature is that it is added. In this invention, the organic ammonium salt is the same as in the above invention.

A third invention of this application is a method for preparing a hydrolyzed sol and / or gel of an alkoxide, which is characterized in that a predetermined amount of an organic ammonium salt is added to the alkoxide and then the hydrolysis is carried out. Also in this invention,
The organic ammonium salt is the same as in the above 2 invention.

The alkoxide hydrolysis sol and / or gel forms a structure such as HOSiO ₂ nOH (in the case of alkoxide silane) in the solution, and the OH groups at the terminals are dehydrated and condensed with each other to proceed with the polymerization. When an organic ammonium salt is added to a solution of such a hydrolysis sol and / or gel, the end of the hydrolysis sol and / or gel is
The OH group is protected like O ^- N ⁺ R ₄ . Therefore, the OH groups that contribute to the polymerization are reduced, and the subsequent polymerization is suppressed.

The first invention of this application includes such an organic ammonium salt as a viscosity stabilizer, whereby the terminal OH group in the hydrolysis sol and / or gel is protected by the organic ammonium salt and polymerization is suppressed. There is. Therefore, there is almost no increase in viscosity with time, and long-term use and storage are possible.

The second invention of this application is to add an organic ammonium salt at the stage when the hydrolyzate of the alkoxide is increased to a predetermined viscosity to suppress the subsequent polymerization,
It is to prepare a hydrolyzed sol and / or gel showing a stable viscosity depending on the application.

The third invention of this application is that an organic ammonium salt is added to an alkoxide in a predetermined amount in advance, and the organic ammonium salt is allowed to act on a hydrolyzed sol and / or gel produced by hydrolysis. And suppresses the polymerization. By adjusting the amount of the organic ammonium salt added in advance, a hydrolyzed sol and / or gel stabilized at a desired viscosity can be obtained. That is, if the addition amount of the organic ammonium salt is increased, a relatively low viscosity is obtained, and if the addition amount of the organic ammonium salt is reduced, a relatively high viscosity is obtained.

[Examples] Hereinafter, the invention of this application will be described with reference to specific examples.

Example 1 tetra t- butoxysilane _{[(t-C 4 H 9} O) 4 Si] 5g,
0.31 g of water [H ₂ O], 9.83 mg of nitric acid [HNO ₃ ] and 95 cc of isopropanol [i-C ₃ H ₇ OH] were added and hydrolyzed. After stirring this hydrolyzed sol for 1 hour at 80 ° C., 1.8 g of tetrabutylammonium bromide [(C ₄ H ₉ ) ₄ N ⁺ Br ⁻ ] was added. After the addition, the viscosity was measured every predetermined time using an Ostwald viscometer (measurement temperature 25 ° C. ± 0.1 ° C.).
The measurement was performed by changing the concentration within the range of 2 to 10 g / dl to calculate the intrinsic viscosity. The intrinsic viscosity at each time is shown in Table 1. The hydrolyzed sol did not gel even after 60 days.

When this hydrolyzed sol was spin-coated on quartz glass, the viscosity did not exceed 0.04 even after a long time had passed.

Example 2 To 5 g of tetra-t-butoxysilane, 1.5 g of tetrabutylammonium bromide was added in advance, and then 0.31 g of water and 95 cc of isopropanol were added and hydrolyzed. The intrinsic viscosity of the obtained hydrolyzed sol was measured in the same manner as in Example 1. The measurement results are also shown in Table 1.

Comparative Example Tetra t-butoxysilane 5g, water 0.31g, nitric acid 9.83mg
And 95 cc of isopropanol were added for hydrolysis. The intrinsic viscosity of this hydrolyzed sol was measured in the same manner as in Example 1. The hydrolyzed sol gelled after 70 days.

As is clear from the results shown in Table 1, the hydrolyzed sols obtained in Examples 1 and 2 showed almost no increase in viscosity with time, and were hydrolyzed sols having a stabilized viscosity. On the other hand, the hydrolyzed sol of Comparative Example not containing tetrabutylammonium bromide as the organic ammonium salt increases in viscosity with the passage of time and completely gels after 70 days and cannot be used for applications such as spin coating. It became a state.

Although the embodiment of the hydrolyzed sol has been described above, the present invention can be applied to a gel. It can also be applied to a mixed state of sol and gel.

In addition, in the series of inventions of this application, the organic ammonium salt contained in the hydrolyzed sol and / or gel is evaporated or decomposed by heating after molding into a molded article such as a coating film. Therefore, the polymerization proceeds further after heating,
It can be made into ceramics.

The alkoxide to which the series of inventions of this application is applied is not limited to tetra-t-butoxysilane shown in the examples, and includes all alkoxides that form a hydrolyzed sol and / or gel by the sol-gel method. .

[Effects of the Invention] As described above, the alkoxide hydrolysis sol and / or gel according to the invention of this application is used with a limited pot life as in the prior art, because the viscosity hardly increases with time. No need. Furthermore, since the viscosity is stable, it has an advantage that the thickness of the coating film produced and the diameter of the fibers are uniform.

Further, according to the preparation method of the invention of this application, the hydrolyzed sol and / or gel can be prepared to have a desired viscosity. It can be / or a gel.

Claims (6)

[Claims] 1. A hydrolyzed sol and / or gel of an alkoxide, which comprises an organic ammonium salt as a viscosity stabilizer. 2. The alkoxide hydrolysis sol and / or gel according to claim 1, wherein the organic ammonium salt is a tetraalkylammonium halide. 3. Preparation of hydrolyzed sol and / or gel of alkoxide, which comprises hydrolyzing an alkoxide, polymerizing the hydrolyzate to a predetermined viscosity, and then adding an organic ammonium salt. Method. 4. The method for preparing a hydrolyzed sol and / or gel of an alkoxide according to claim 3, wherein the organic ammonium salt is a tetraalkylammonium halide. 5. A method of adding a predetermined amount of an organic ammonium salt to an alkoxide, followed by hydrolysis.
Method for preparing hydrolysis sol and / or gel of alkoxide. 6. An alkoxide hydrolyzed sol according to claim 5, wherein the organic ammonium salt is a tetraalkylammonium halide, and / or
Or a method of preparing the gel.