JPH0478733B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to silica, which has excellent heat resistance and is used as a heat-resistant material, and also has excellent strength and is used as a reinforcing material for plastics, metals, cement, etc. This invention relates to a method for producing alumina fibers or membranes.

[Conventional technology]

The method for producing silica-alumina fibers is to utilize the slurry method, inorganic salt method, sol method, etc., which are conventionally known as methods for producing alumina fibers, and add a colloid of silica component to the alumina component liquid used in these methods. A common method is to mix an aqueous suspension. There is also a method of mixing silicate polyester or polysilicate ester into the alumina component liquid using a precursor polymer method known as a method for producing inorganic fibers. In either method, a spinning solution containing a silica component and an alumina component is spun and sintered to obtain silica-alumina fibers. And silica with uniform thickness and excellent strength.
In order to stably obtain alumina fibers, it is necessary for the spinning solution to be spun uniformly and stably, and this is largely influenced by the viscosity, spinnability, uniformity, and stability of the spinning solution. It is important that such a spinning solution with excellent spinnability can be easily produced. However, in the method using the slurry method, the spinning solution of the slurry method, that is, the alumina component liquid, is a so-called heterogeneous system, and the particle size, amount, and dispersion state of the solid particles contained therein have a subtle influence on the spinnability.
Furthermore, when a colloidal suspension of a silica component is added, there is a problem in that it becomes even more difficult to control spinnability. In the method using the inorganic salt method, the viscosity of the spinning solution is controlled by the amount of water-soluble organic polymer contained in the alumina component liquid of the inorganic salt method. Addition of a liquid causes aggregation and gelation of colloids, which not only deteriorates the stability of the spinning solution but also reduces the strength of the silica-alumina fibers. In methods using the sol method, the alumina component liquid itself in the sol method tends to precipitate or rapidly increase in viscosity at the stage of concentrating to form a spinning solution, and this tends to result in a colloidal suspension of the silica component. There is a problem that the addition of liquid will further promote the problem. Further, in the method using the precursor polymer method, although it is possible to obtain a uniform spinning solution, there is a problem in that it is difficult to control the manufacturing process for obtaining the spinning solution.

[Problem to be solved by the invention]

The present invention was made in order to solve the above-mentioned problems, and it is possible to easily obtain a spinning solution with excellent uniformity, stability, and spinnability, and to use silica-alumina having a uniform thickness and excellent strength. The object of the present invention is to provide a manufacturing method by which fibers or a silica-alumina film having uniform thickness and excellent strength can be stably obtained.

[Means to solve the problem]

As a result of repeated research in order to obtain a spinning solution that solves the above-mentioned problems, the present inventors have discovered that aluminum alkoxide or aluminum carboxylate is dissolved as an alumina component in an aqueous solution of citric acid or tartaric acid, while silane alkoxide is dissolved in an aqueous solution of citric acid or tartaric acid. Use hydrochloric acid or ammonia as a catalyst and dissolve it in a sufficient amount of water to create an alumina component solution and a silica component solution (however, if aluminum carboxylate is used as the alumina component, the silica component solution should be dissolved in hydrochloric acid). (limited to those used as a catalyst)
By mixing and concentrating, uniformity, stability,
It has been found that a spinning solution with excellent spinnability can be easily obtained.

The present invention was made based on this knowledge, and involves dissolving aluminum alkoxide in an aqueous solution of citric acid or tartaric acid, dissolving silane aracoxide in water using hydrochloric acid or ammonia as a catalyst, and mixing both solutions. , a method for producing a silica-alumina fiber or membrane product, which comprises obtaining a viscous liquid by concentrating it, forming the viscous liquid into a fiber or membrane shape and sintering it, and aluminum carboxylate. is dissolved in an aqueous solution of citric acid or tartaric acid, and silane alkoxide is dissolved in water using hydrochloric acid as a catalyst. Both solutions are mixed and concentrated to obtain a viscous liquid. Silica characterized by being molded into and sintered.
A method for producing alumina fibers or membranes.

[Effect]

According to the method of the present invention described above, a viscous liquid with excellent uniformity, stability, and spinnability can be easily obtained, and the viscous liquid can therefore be stably and uniformly discharged from a spinning nozzle or a slit nozzle. By sintering the discharged fibers or films, it is possible to obtain stable, uniform, and strong silica-alumina fibers or films.

〔Example〕

As the aluminum oxide in the present invention, those whose organic residue is a methoxy group, an ethoxy group, a normal propoxy group, an isopropoxy group, a normal butoxy group, a secondary butoxy group, or a tertiary butoxy group are used. Further, as the aluminum carboxylate, those whose organic residue is formyloxy group or acetyloxy group are used. An aluminum organic compound, which is a raw material for alumina, is dissolved in an aqueous solution of citric acid or tartaric acid using distilled water with a molar number 20 to 50 times the molar number of the aluminum organic compound. When the alumina component is aluminum alkoxide, the amount of citric acid or tartaric acid at this time is preferably at least 1 mole based on the aluminum contained therein.
1.2 to 1.5 times the mole is appropriate, and if the alumina component is aluminum carboxylate, preferably 0.6 times or more the mole of aluminum contained therein.
Approximately 0.75 times the molar amount is appropriate. If the amount of citric acid or tartaric acid is less than 1 times the mole or 0.6 times the above-mentioned mole, precipitation or turbidity will occur during the subsequent concentration and the system will likely not be homogeneous, and it may be difficult to obtain sufficient viscosity for stable spinning. It becomes difficult.

As the silane alkoxide, those having an organic residue such as a methoxy group or an ethoxy group are used.
Silane alkoxide, which is a raw material for such silica, is dissolved in a sufficient amount of water, preferably distilled water with a mole number 50 times or more that of the silane alkoxide. If the amount of water is as small as, for example, about 20 times the mole, gelation will occur during this dissolution stage and the alumina component will not dissolve when mixed with the alumina component solution. The suitable amount of hydrochloric acid or ammonia as a catalyst for dissolving silane alkoxide in water is about 0.01 to 0.1 times the number of moles of silane alkoxide; if the amount is too large, it will not only not be useful for dissolving silane alkoxide, but also increase the viscosity necessary for spinning. and adversely affect solidification after spinning. Note that ammonia cannot be used when the alumina component solution is an aluminum carboxylate solution because it causes cloudiness when concentrating the mixture with the silane alkoxide solution.

When mixing alumina component solution and silica component solution, the molar ratio of alumina and silica is 95:5 to 25:75.
It is preferable to use a mixing ratio within the range of .
If the proportion of silica is increased beyond this range, the resulting liquid will have poor spinnability even if it is mixed and concentrated.On the other hand, if the proportion of alumina is increased, fibers or membranes with excellent strength will be obtained. It becomes difficult. In addition,
From the point of view of obtaining heat-resistant materials, alumina is 50%
It is preferable to set the mixing ratio to 60% or more. Further, this mixing or the dissolution of the alumina component and the silica component before this is performed at room temperature or, for rapid operation, at a temperature of up to about 90° C. while stirring. In addition, a small amount of lithium, beryllium, boron, sodium, potassium, magnesium, titanium,
One or more of chromium, manganese, yttrium, zirconium, tantalum, phosphorus, tungsten, etc. may be added in the form of an organometallic compound, carbonate, inorganic acid salt, or the like. This addition may be performed not only during or after mixing, but also when preparing a solution of the alumina component or silica component.

Concentration of the mixed solution is carried out in an open system by heating it to 100° C. or higher until a viscous state suitable for spinning is obtained. The viscous liquid obtained thereby has fluidity suitable for spinning at 70 to 80°C, but when left at room temperature, it gradually increases in viscosity and eventually solidifies. This solidification phenomenon becomes more noticeable in a dry atmosphere.

Therefore, the resulting viscous liquid can be formed into a continuous fiber or film by extruding it from a spinning nozzle or slit into a dry atmosphere below room temperature at a temperature of 70-80°C. Moisture is removed from this molded product in a dry atmosphere, and then the molded product is exposed to air.
When fired at a temperature of 500 to 800°C, organic components in the molded product are decomposed and removed. Next, the molded product is heated to 1200~1400
By sintering at °C, a silica-alumina fiber or film with excellent uniformity and strength can be obtained. If the process from extrusion through a nozzle to sintering is performed continuously, continuous fibers or continuous membranes can be obtained. Moreover, ultrafine silica-alumina short fibers can be obtained by extruding the viscous liquid through a spinning nozzle having a wide discharge hole and blowing it away with flame. In this case, the above-mentioned water removal, firing, and sintering were performed at the same time.

Hereinafter, further specific examples of the present invention will be shown.

Example 1 22.0 g of aluminum isopropoxide was dissolved in an aqueous solution of 28.8 g of citric acid dissolved in 100 ml of distilled water to obtain a transparent and uniform alumina component liquid. Further, 6.94 g of tetraethoxysilane was dissolved in 100 ml of distilled water in which 0.5 g of hydrochloric acid had been dissolved to obtain a transparent and uniform silica component liquid. Mix both liquids and make 100 in open system.
℃ and concentrated until the viscosity was 30-50 boids. The resulting viscous liquid is colorless and transparent, and its viscosity gradually increases as it is allowed to cool. This viscous liquid was extruded from a spinning nozzle at 70 to 80°C into a dry atmosphere at room temperature to obtain a fibrous molded product with a diameter of 5 to 100 μm. This molded product was dried at 100°C overnight, then treated at 800°C for 2 hours, and then heated and sintered at 1300°C for 10 hours to obtain silica-alumina long fibers.

Example 2 37.8 g of basic aluminum acetate was dissolved in an aqueous solution of 22.5 g of tartaric acid dissolved in 100 ml of distilled water to obtain a transparent and uniform alumina component liquid. This alumina component liquid and the silica component liquid obtained in Example 1 were mixed to obtain silica-alumina long fibers in the same manner as in Example 1.

Example 3 5.61 g of tetraethoxysilane was dissolved in 100 ml of distilled water in which 0.1 g of ammonia was dissolved to obtain a transparent and uniform silica component liquid. This silica component liquid and the alumina component liquid obtained in Example 1 were mixed to obtain silica-alumina long fibers in the same manner as in Example 1.

Example 4 37.8 g of basic aluminum acetate was dissolved in an aqueous solution of 28.8 g of citric acid dissolved in 100 ml of distilled water to obtain a transparent and uniform alumina component liquid. Further, 1.84 g of tetraethoxysilane was dissolved in 100 ml of distilled water in which 0.4 g of hydrochloric acid had been dissolved to obtain a transparent and uniform silica component liquid. Both solutions were mixed to obtain silica-alumina long fibers in the same manner as in Example 1.

Example 5 22.0 g of aluminum isopropoxide was dissolved in an aqueous solution containing 22.5 g of tartaric acid dissolved in 100 ml of distilled water to obtain a transparent and uniform alumina component liquid. This alumina component liquid and the silica component liquid obtained in Example 4 were mixed to obtain silica-alumina long fibers in the same manner as in Example 1.

Example 6 The alumina component liquid obtained in Example 5 and the silica component liquid obtained in Example 3 were mixed to obtain silica-alumina long fibers in the same manner as in Example 1.

In all of the above examples, spinning was carried out stably, and the obtained silica-alumina fibers were excellent in uniformity and strength.

〔Effect of the invention〕

According to the method of the present invention, it is possible to easily obtain a viscous liquid containing a silica component and an alumina component that has excellent stringability, uniformity, and good spinnability, and furthermore,
Both the silica component and the alumina component are organic compounds, and because they are dissolved in an organic acid aqueous solution and a catalytic amount of hydrochloric acid or ammonia aqueous solution, there is a risk of harmful gas generation or impurity contamination during the manufacturing process. It is possible to obtain a silica-alumina fiber or film-like product with almost no droplets, and therefore has high purity, excellent uniformity, and strength.

Claims (1)

[Claims] 1. A viscous liquid is obtained by dissolving aluminum alkoxide in an aqueous solution of citric acid or tartaric acid, dissolving silane alkoxide in water using hydrochloric acid or ammonia as a catalyst, and mixing and concentrating both solutions. . A method for producing a silica-alumina fiber or film, which comprises forming the viscous liquid into a fiber or film and sintering it. 2 Dissolve aluminum carboxylate in an aqueous solution of citric acid or tartaric acid, dissolve silane alkoxide in water using hydrochloric acid as a catalyst, mix and concentrate both solutions to obtain a viscous liquid, and convert the viscous liquid into fibers. 1. A method for producing silica-alumina fibers or membranes, the method comprising forming and sintering silica-alumina fibers or membranes. 3 The molar ratio of silica and alumina is 5:95 to 75:25
A method for producing a silica-alumina fiber or membrane material according to claim 1 or 2, which falls within the scope of claim 1 or 2.