JPH0329731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a porous gel molded body,
In particular, the present invention relates to a method for producing a porous gel molded body, which is characterized in that a water-insoluble organic binder solution is used when a porous gel is produced by hydrolyzing a metal alcoholate.

In recent years, in order to improve the quality of industrial materials, the management and adjustment of raw materials has become stricter, and particularly high-purity raw materials have come to be used. On the other hand, as various energy issues have come to the fore, research into improving efficiency and reviewing the manufacturing methods of industrial materials has become popular. Under these circumstances, metal alcoholates are being used in ceramics and electronics because they have particularly high purity as a raw material for glass synthesis using a solution method, and furthermore, they can be synthesized at relatively low temperatures and have the potential to save energy. It has come to be in the spotlight in the field of

Low-temperature synthesis of glass uses metal alcoholates as starting materials, and when they are hydrolyzed under appropriate conditions, a three-dimensional condensation reaction progresses, growing into macromolecules and forming gels. By heating and dehydrating this gel, a product similar to oxide glass obtained by high-temperature melting method can be obtained. Conventionally, when a metal alcoholate is hydrolyzed to form a gel, a large volumetric contraction occurs and the gel is fragmented, making it difficult to obtain a gel with a certain shape. Therefore, although much research has been conducted in this area, it is limited to forming a film that is difficult to peel off on a certain substrate, and there is still no method to produce gel molded bodies with good dimensional stability without fragmentation. Not served. In view of the current situation, the inventors of the present invention have made efforts to study and have found a method for producing a gel molded body that does not become fragmented, has good dimensional stability, and has porosity that is very easy to handle.

That is, the present invention relates to a method for producing a porous gel molded body characterized by using a water-insoluble organic binder solution when hydrolyzing a metal alcoholate to produce a porous gel. This method significantly improves the stability and handling of the porous gel obtained by hydrolyzing a metal alcoholate without fragmenting it.

To explain the present invention in detail below, the metal alcoholate of the general formula M(OR)n used in the present invention is M
is a metal to metalloid of Groups 1 to 4 in the periodic table, R
is an alkyl group having 4 or less carbon atoms, and n is an integer of 1 to 4, such as sodium methoxide, lithium ethoxide, potassium ethoxide, calcium ethoxide, magnesium ethoxide, strontium budoxide,
Barium propoxide, aluminum isopropoxide, aluminum butoxide, boron methoxide, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraethyl titanate, tetrabutyl titanate, tetraisopropyl titanate, diethyl dibutyl titanate, Examples include germanium isopropoxide and zirconium tertiary amylooxide, but are not particularly limited to these. The above-mentioned metal alcoholates can be used alone or in combination, and are not particularly limited. Furthermore, the above-mentioned metal alcoholates can be used in the form of monomers to multimers just before gelation, and can be used depending on the purpose.

Hydrolysis of the metal alcoholate is not particularly limited and can be carried out by any known method, but in order to obtain a uniform gel at an appropriate hydrolysis rate, it is desirable to use a multimeric metal alcoholate. The organic binder used in the present invention moderately controls the hydrolysis rate of the metal alcoholate, improves the uniformity of the gel produced, prevents the gel from fragmenting, and further stabilizes the shape of the porous gel molded body. In particular, water-insoluble organic binders are used for the purpose of significantly improving properties, and specific examples include cellulose acetate, cellulose acetate derivatives, polyvinyl chloride, vinyl chloride copolymers, polyacrylonitrile, acrylonitrile copolymers, Examples include polyurethane, nylon, etc., and these organic binders can be used alone or in combination and are not particularly limited, but they are all used in the form of a solution dissolved in the organic solvent described below. The concentration of the organic binder can be appropriately adjusted depending on the type of metal alcoholate used and the degree of hydrolysis, and is not particularly limited.

The solvent used in the present invention needs to dissolve both the metal alcoholate hydrolyzate and the organic binder, and specifically includes lower alcohols such as methanol and ethanol, hexane, benzene,
Hydrocarbons such as toluene and cyclohexane, halogenated hydrocarbons such as chloroform and carbon tetrachloride, as well as dimethylformamide, dimethylacetamide, tetramethylurea, dimethylsulfoxide, acetonitrile, ethylene carbonate, tetramethylsulfone, and hexane. Examples include methylphosphoramide, but are not particularly limited to these. The above-mentioned solvents can be used alone or in combination, and are not particularly limited, and can be appropriately selected depending on the type of metal alcoholate and organic binder used.

The method for molding the solution containing the metal alcoholate hydrolyzate and organic binder of the present invention is not particularly limited, and various known methods can be used. For example, it can be formed into fibers and films by known thread spinning and film forming methods. Thus, the porous gel molded body obtained through hydrolysis of metal alcoholate maintains a continuous phase, has a large specific surface area, has good morphological stability without being fragmented, and is very easy to handle. It is easy to use and can be used as is or after being subjected to appropriate post-treatment depending on the application.

As detailed above, when metal alcoholate is hydrolyzed, when no organic binder is added, the resulting gel is fragmented, opaque, discontinuous, and difficult to handle; however, the method of the present invention is extremely useful. It is possible to provide a material with good shape stability and easy handling.

The present invention will be specifically explained below with reference to Examples.

Example 1 A solution prepared by dissolving 45 parts of tetraethyl silicate tetramer in 205 parts of a mixed solvent of chloroform/methanol at room temperature and a solution prepared by dissolving 5 parts of cellulose acetate in 95 parts of the same solvent mentioned above were mixed at room temperature and homogenized. A solution was obtained. This solution was slowly stirred for 24 hours in an atmosphere of 70% relative humidity and 25°C to promote hydrolysis, and then casted onto a uniform flat substrate and slowly desolvented to a thickness of approximately
20μm, tensile strength 35Kg/ ^mm2 , specific surface area ^300m2 /
A colorless, transparent, and highly flexible film having the following properties was obtained. On the other hand, when the film was molded in the same manner as described above without adding cellulose acetate, the film fragmented on the substrate, making it impossible to obtain a film with a constant shape.

Example 2 After uniformly mixing a solution of 90 parts of tetrabutyl titanate hexamer dissolved in 240 parts of dimethylformamide and a solution of 10 parts of polyacrylonitrile (average molecular weight approximately 100,000) dissolved in 90 parts of dimethylformamide. Approximately 24°C under an atmosphere of 40% relative humidity and 250°C
After slowly stirring for some time to allow hydrolysis to proceed,
Wet spinning was performed using a known method to obtain transparent, flexible continuous fibers having a diameter of about 5 denier, a strength of 1.5 g/denier, an elongation of 3.5%, and a specific surface area of 350 m ² /g. On the other hand, when molded in the same manner as described above without adding polyacrylonitrile, it contracted significantly during drying and was further divided into smaller pieces, making it impossible to obtain a molded product with good shape control.

Claims (1)

[Claims] 1 Metal alcoholate represented by the formula M(OR)n (M is a metal to semimetal of Groups 1 to 4 of the periodic table, R is an alkyl group having 4 or less carbon atoms, and n is an integer of 1 to 4) 1. A method for producing a porous gel molded body, characterized in that a water-insoluble organic binder and an organic solvent are used when hydrolyzing to produce a porous gel.