JPS6158423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a metal oxide molded article, particularly a method for producing metal oxide fibers by a wet process.

Silica and alumina fibers themselves, or by carbonizing or nitriding them, are becoming widely used as various high-temperature insulation materials and reinforcing materials for high-temperature materials.

The biggest technical challenge with this type of material is how to form it into a fibrous shape, and various attempts have been proposed. For example, fibers have been made by polymerizing or isomerizing metal organic compounds such as silicon and aluminum as raw materials.

However, in all of these conventional methods,
First, metal-organic compounds are expensive, and the solvents, catalysts, stabilizers, etc. required for polymerization and isomerization are special and expensive, and the operations are complicated, so it is not always possible to produce them industrially. It was hard to say that there were many things.

In view of the above, the present invention was developed as a result of various studies and examinations for the purpose of eliminating the above-mentioned drawbacks of conventional methods and industrially advantageously producing metal oxide molded bodies, especially fibers. It has been discovered that the above object can be achieved by using a metal compound, a solvent, and a fiberizing agent.

Thus, the present invention involves mixing and dissolving a silicon alkoxide and a viscosity-imparting agent in a solvent containing a small amount of acid or alkali that volatilizes when heated to obtain a viscous solution, and forming the solution into a desired shape. It is an object of the present invention to provide a method for producing a metal oxide molded article having characteristics.

Examples of the viscosity imparting agent include cellulose acetate, polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose, etc., and one or more of these can be used as appropriate.

Examples of acids or alkalis that volatilize upon heating include aqueous solutions of inorganic acids such as hydrochloric acid, nitric acid, carbonic acid, and boric acid, and examples of alkalis include ammonia and various amines.

Further, as the solvent, acetone, water, methylene chloride, dimethylformamide, etc. can be appropriately selected and used.

The appropriate amount of the viscosity imparting agent to be used is about 0.1 to 10.0 in weight ratio to the commonly used silicon alkoxide.

If the amount used is less than the above range, it will be difficult to mold it into the desired shape, and conversely, if it exceeds the above range, the amount used will simply increase.
None of these methods are preferable because no further effect can be expected.

Among these ranges, it is particularly preferable to adopt a weight ratio of about 0.5 to 2.0 with respect to the silicon alkoxide, since molded bodies of desired shapes can be produced industrially advantageously.

In addition, the amount of acid or alkali that is volatilized by heating when used with a solvent varies somewhat depending on the acid or alkali used and the type of solvent, but generally it is about 1 x 10 ^-3 to 1.0 mol/based on the solvent. It is appropriate to adopt it.

If the amount used is less than the above range, the reaction will not substantially proceed and the proportion of silicon oxide produced will be low; on the other hand, if the amount exceeds the above range, the reaction will proceed before the molded product is formed. Both are undesirable because they cause problems in giving the shape.

And within these ranges, 5×
It is particularly preferable to use about 10 ^-3 to 0.1 mol/mole, since moldability is good and a desired shape can be easily obtained.

The amount of the acid- or alkali-containing solvent to be used is generally about 1.0 to 10.0 by weight relative to the silicon alkoxide.

If the amount used is less than the above range, the reaction will not substantially proceed and the production rate of silicon oxide will be low.On the other hand, if the amount used exceeds the above range, excess heat will be generated when the solvent is removed by heating. None of these methods are preferable because they require energy.

Among these ranges, it is particularly preferable to use a weight ratio of about 2.0 to 7.0 to the silicon alkoxide because moldability is good and unnecessary thermal energy is not consumed.

The viscous solution thus obtained is molded into the desired shape. For example, it can be made into a thread by methods such as dry spinning, wet spinning, and centrifugal spinning to form fibers, or into a film by methods such as roll molding and extrusion molding.

The temperature of the viscous solution during such molding is preferably about 10 to 80°C from the viewpoint of moldability and physical properties of the product obtained, and the viscosity at this time is approximately 0.01 to 1000 poise. preferable.

The obtained moldings are preferably dried and then calcined in an oxidizing atmosphere at approximately 200-1800°C, so that the final product can also be obtained as an oxide or in any desired manner, e.g. with carbon. By heating the molded body to 200 to 2200°C in a non-oxidizing atmosphere, the molded body can be converted into a composition other than an oxide, such as a carbide.

It goes without saying that in the present invention, other components such as viscosity modifiers, molding aids, sintering aids, etc. may be added to the composition as desired, as long as they do not impede the object of the present invention.

Next, the present invention will be explained by examples.

Example 1 30 g of cellulose acetate (manufactured by Kodatsu, acetyl group content 39.8%, viscosity (ASTM) 3 sec.) was dissolved in a mixed solution consisting of 120 ml of acetone and 7.5 ml of a 0.15N-HCl aqueous solution, and ethyl silicate was added to the solution. (Genuine Chemical
30 ml of Chemical Co., Ltd.) was added to make a homogeneous solution. This was placed in a container equipped with a 60 μm nozzle at the tip, pressurized with nitrogen gas, the raw material liquid was jetted out from the nozzle tip, and was wound up at a speed of 90 m/min while drying with hot air. The obtained fibers have an average diameter of 20μ
It was a continuous fiber.

This fiber was heat-treated at 800° C. for 2 hours in a nitrogen atmosphere to obtain a black fiber. After further heat-treating this at 1350℃ for 3 hours in an argon atmosphere, 2050℃
When the temperature was raised to ℃ and fired for 30 minutes, silicon carbide fibers were obtained.

Example 2 The same raw material preparation and yarn spinning as in Example 1 were carried out to obtain continuous fibers with a flat diameter of 20 μm. This is heated to 800℃ in the air.
The carbon was removed by heat treatment for 3 hours.
Fibers made of SiO ₂ were obtained. Specific surface area is 160m ² /g
It was hot.

Example 3 A mixture of the raw materials described in Example 1 and 2.6 g of triethyl borate (manufactured by Tokyo Kasei Co., Ltd.) was used as a raw material solution for yarn spinning to obtain continuous fibers with an average diameter of 20 μm. This was subjected to the same heat treatment as in Example 1 to obtain silicon carbide fibers.

Example 4 Continuous fibers obtained by preparing raw materials and spinning in the same manner as in Example 3 were heat treated in air at 500°C for 3 hours to remove carbon produced from cellulose acetate, and then further heated at 900°C for 2 hours. By processing time,
Fibers made of SiO ₂ and B ₂ O ₃ were obtained. The specific surface area of this product was 2.0 m ² /g.

Example 5 Example 3 was placed on a glass plate measuring 20 cm x 20 cm.
10 g of the raw material solution described above was spread using a glass rod to form a homogeneous film. After air-drying the glass plate on which this film was placed for 24 hours, the peeled film was subjected to the same heat treatment as in Example 1, and a film-shaped silicon carbide sintered body was obtained.

Example 6 Silicon carbide fibers were obtained in the same manner as in Example 3 except that 120 ml of methylene chloride was used instead of acetone.

Example 7 100 g of polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd., degree of polymerization approximately 1000) was dissolved in 200 ml of a 0.15N-HCl aqueous solution, and 100 g of ethyl silicate and 10 g of trimethyl borate were added thereto. This liquid was kept at 70°C and stirred for 10 minutes to obtain a homogeneous solution. When this solution was used for spinning yarn in the same manner as in Example 1, the average diameter was 20 μm.
Continuous fibers were obtained. This fiber was subjected to the same heat treatment as in Example 1 to obtain silicon carbide fiber.

Example 8 30 g of polyacrylonitrile was dissolved in a mixed solvent consisting of 150 ml of dimethylformamide and 20 ml of a 0.15N-HCl aqueous solution, and 120 g of ethyl silicate and 10 g of trimethyl borate were added to make a homogeneous solution. Continuous fibers were obtained by charging this into a container equipped with a 60 μm nozzle at the tip and spouting the raw material solution into water from the nozzle tip. This fiber was subjected to the same heat treatment as in Example 1 to obtain silicon carbide fiber.

Claims (1)

[Claims] 1. A silicon alkoxide and at least one viscosity imparting agent selected from cellulose acetate, polyvinyl alcohol, polyacrylonitrile, and carboxymethylcellulose are mixed in a solvent containing a small amount of acid or alkali that volatilizes when heated. 1. A method for producing a metal oxide molded article, which comprises mixing and dissolving to obtain a viscous solution, molding the solution into a desired shape, carbonizing the solution, and then heat-treating it to remove carbon. 2. The method according to claim 1, wherein the acid volatilized by heating is hydrochloric acid, nitric acid, carbonic acid, acetic acid, or boric acid. 3. The method according to claim 1, wherein the alkali volatilized by heating is ammonia or amines. 4. The method of claim 1, wherein the solvent is acetone, water, methylene chloride, or dimethylformamide. 5. The method according to claim 1, wherein the amount of the acid or alkali that volatilizes when heated is contained in the solvent is 1 x 10 ^-3 to 1.0 mol/.