JPS6175818A - Production of alumina fiber - Google Patents

Abstract

PURPOSE:An aqueous liquid composed of basic aluminum chloride, colloidal silica, and an organic binder is combined with a specific organic additive, then extruded into fibers and roasted to produced the titled fibers with high mechanical properties and heat resistance easily at a low cost. CONSTITUTION:At first, an aqueous liquid which is composed of (A) basic aluminum chloride, (B) colloidal silica and (C) an organic binder such as PVA is combined with (D) a compound which is composed of carbon, hydrogen and oxygen atoms, has 2 hydroxyls and is soluble in water with neutral chain, or can form a chain organic compound in the aqueous liquid, preferably ethylene glycol. Then, the resultant aqueous liquid is converted into fibers and the fiber precursor is roasted to give the objective fibers. The weight ratio of components A:B:C:D is preferably (80-98):(20-2):(3-10):(3-10).

Description

[Detailed description of the invention] "Industrial application field" The present invention uses basic aluminum chloride as a raw material.

Fire-resistant AS (
The present invention relates to a method for producing alumina fibers that can stably produce alumina fibers.

``Prior Art'' Inorganic oxide fibers such as alumina fibers can be used as heat or sound insulation, fillers such as plastics, films, reinforcements or tensile and abrasion strength reinforcements or carbonization produced from heat engines. It is used as a catalyst or catalyst carrier for hydrogen exhaust gas, and in many other applications that take advantage of its fire resistance.

Therefore, many proposals have been made as a method for producing the same.
A method of obtaining metal oxide fibers by heating and converting them into metal oxides (Japanese Patent Publication No. 45-9896).

(2) After evaporating and concentrating a solution of a reaction mixture consisting of a sol of a refractory inorganic oxide such as alumina sol or silica sol and a water-soluble fiber-forming organic polymer, it is formed into a fiber shape and heated and fired. A method for producing fire-resistant inorganic oxide fibers (Japanese Patent Publication No. 47-37215).

Quina (3) by molding an aqueous solution containing a water-soluble metal compound and a water-soluble polysilona-polyoxyalkylene copolymer into a desired shape, drying it to make it solid, and then heating it. Method for producing a solid composition consisting of a homogeneous mixture of metal oxide and silica (Japanese Patent Publication No. 57
-44626), (4) Add lactic acid to a mixed solution of basic aluminum chloride solution and colloidal silica, heat concentrate, then spin, dry and heat-treat the spun fibers to produce polycrystalline oxide fibers. There is a method (Japanese Patent Publication No. 54-23727).

"Problems to be Solved by the Invention" However, in these methods, method (1) is difficult to produce a fibrous molded product because the spinning solution does not contain a siliceous substance when alumina fibers are produced by this method. The crystal growth rate of alumina is slow when heated to high temperatures, making it unsuitable for obtaining high-temperature refractory polycrystalline fibers with good mechanical strength. In method (2), although fire-resistant fibers can be obtained, they are porous and cannot have sufficient mechanical strength. Method (3) uses expensive organic polysiloxane, resulting in extremely high production costs.

In method (4), since an acid is added to the basic aluminum chloride solution, insoluble salts are precipitated and spinning is often difficult, and the spinning solution does not contain a binder for fiber formation. Therefore, there was a problem that it was difficult to maintain the shape of the spun fibers.

Note that the mechanical strength of alumina fibers is generally

α-
It is strongest when the temperature is just before the formation of coarse grain crystals such as alumina (for example, 1200°C), but α
-Temperature at which alumina etc. are produced in large quantities (e.g. 1300
℃ or higher), it tends to be weaker. On the other hand, the heat resistance properties of alumina fibers are generally good when the final heating temperature is higher than the temperature at which α-alumina and the like are produced;
It tends to get worse at low temperatures where alumina etc. do not form. Alumina fibers that are resistant to high temperatures must have both sufficient mechanical strength and sufficient heat resistance, and to achieve this, the above-mentioned contradictory tendencies must be overcome.

"Means for Solving the Problem" The present inventors have repeatedly researched a method using basic aluminum chloride, colloidal silica, and an organic binder.
First, in order to prepare an aqueous liquid that is a mixed solution of these, at least a part of the constituent components of the aqueous liquid is dried in advance, and this dried product is dissolved in water or an aqueous solution in which the remaining components are dissolved. We have proposed a method of preparing an aqueous solution for spinning by dissolving it (Japanese Patent Applications 154937/1982 and 84157/1989), but we have also proposed a method of preparing an aqueous solution for spinning by dissolving it (Japanese Patent Applications 154937/1984 and 84157/1989), but we also developed a method for preparing an aqueous solution for spinning by dissolving it. In order to obtain a means to stably produce superior alumina fibers at low cost, we measured the mixer disintegration rate as an index of mechanical strength and the hot load linear shrinkage rate as an index of heat resistance properties. As a result of examining the relationship with the physical properties of the alumina fiber, the mechanical strength of the alumina fiber is
As the volume of micropores in the range of 5 to 0.1 μm (hereinafter referred to as macropore volume) becomes smaller, the strength increases.
This is because if there are many micropores of 0.015 μm or more in the fiber, cracks are likely to occur when an external force is applied to the fiber, but even if there are some micropores of 0.015 μm or less, the external force It was found that the growth of cracks caused by this process was not significant. In addition, when the final heating temperature of the fiber is relatively high, a large amount of coarse crystals such as α-alumina are likely to be generated, and as a result, macropores are likely to be generated at the grain boundaries.
It has been found that the macropore volume generally increases. moreover.

In order to keep the macropore volume small regardless of the final heating temperature, a siliceous material such as colloidal silica can be added to the spinning stock solution to heat the fiber precursor to high temperatures and form α-alumina crystals. At the same time when the formation begins, fine crystals of mullite are formed at the α-alumina grain boundaries and α-
This has a favorable effect because it suppresses the growth of alumina crystals.

In the conventional method using colloidal silica, colloidal silica is insufficiently dispersed in the spinning stock solution.
By adding a specific organic compound, it was recognized that the growth of α-alumina crystals was not sufficiently suppressed, the macropore volume was large, and therefore only fibers with weak mechanical strength were obtained.

The present invention was made based on the discovery that the volume of macropores in the resulting fibers can be made extremely small even when heated at such high temperatures that α-alumina is produced in large numbers. That is, the present invention provides a method for producing alumina fibers by heating and firing a fiber precursor obtained by fiberizing an aqueous liquid material consisting of basic aluminum chloride, colloidal silica, and an organic binder. A water-soluble and neutral chain organic compound composed of carbon-hydrogen and oxygen and having two hydroxyl groups in one molecule, or a compound capable of producing the chain organic compound in the above aqueous liquid. This is a method for producing alumina fiber containing at least one compound.

The basic aluminum chloride used in the present invention may have a basicity of 50 or more, particularly a basicity of 82 to 82.
84% is preferred.

The colloidal silica may be one that can be dispersed in water, and in particular, one that has been treated to be stably dispersed in an acidic solution (for example, Cataloid SN manufactured by Catalysts & Chemicals Co., Ltd.) is suitable. Examples of the organic binder include commonly used nonionic water-soluble fiber-forming organic polymers, such as polyvinyl alcohol, polyoxyethylene, and polyvinylpyrrolidone.

Furthermore, a water-soluble and neutral chain organic compound composed of carbon-hydrogen and oxygen and having two hydroxyl groups in one molecule, or a compound capable of producing the chain organic compound in an aqueous liquid (hereinafter referred to as organic Examples of additives include ethylene glycol, α-propylene glycol,
Examples include β-propylene glycol, 1,3-butylene glycol, 1,4-phthylene gelicol, 2,3-butylene glycol, 1,2-butylene oxide, and imbutylene oxide, but considering the price, α- Propylene glycol, ethylene glycol and the like are preferred.

That is, basic aluminum chloride, colloidal silica, polyvinyl alcohol, and various organic additives are blended in a ratio of +AItos:sto,:polyvinyl alcohol:organic additive = 95:5:5:5, and water is added. In addition, an aqueous liquid was prepared, formed into a fiber under certain conditions, heated to a maximum heating temperature of 1300°C, and the macropore volumes of the various alumina fibers obtained were determined.
Shown in the table. In addition, the results obtained in the same manner when no organic additive was added and when an organic compound other than the organic additive in the present invention was added are also shown. In addition, the macropore volume (r
nlA9) is a mercury porosimeter model 65 manufactured by Carlo Erba.
．． The volume of micropores of 0.015 to 0.1 μm was measured and calculated as the volume (mJ) of the micropore range per 1 measurement sample.

Table 1 All of the alumina fibers obtained when using the organic additives used in the present invention have significantly small macropore volumes. The reason for this is not clear, but it is a result of the dispersibility of colloidal silica in aqueous liquids being improved by the action of organic additives.

This is presumed to be because crystal growth of α-alumina was suppressed. No good results were obtained when organic compounds other than those used in the present invention were added. This is thought to be because monovalent pulcols such as ethyl alcohol generally have a low boiling point and rapidly vaporize when the fiber precursor is heated, increasing the macropore volume in the fiber precursor. Also, with trihydric or higher alcohols such as glycerin.

It is believed that it itself has poor dispersion in aqueous liquids and does not improve the dispersibility of colloidal silica.

Furthermore, in organic compounds such as tartaric acid, which has two hydroxyl groups, but at the same time a carphokyfur group.

This results in the deterioration of the dissolved stability of components in aqueous liquids and the precipitation of insoluble salts such as alumina gel.

It is difficult to form it into a fibrous form.

The addition and blending ratio of each raw material in the present invention is 2 weight ratio,
A1.0 Coni S 10s: Binder: Organic additive;
It is preferable to mix the organic additive in a ratio of 80 to 98:20 to 2:3 to 10:3 to 10, and the organic additive is one in which at least one type of compound is added, and several types of compounds are appropriately selected and combined. They can be added together. In this case, it is sufficient to add the combined amount within the above range.
The proportions of each compound in the combination may be arbitrary.

However, when using an organic compound that produces the chain organic compound in an aqueous liquid, it is added so that the amount of the chain organic compound produced is equal to the blending ratio.

A known method such as a blowing method, an extrusion method, a centrifugation method, etc. can be used to obtain a fiber precursor by forming the aqueous liquid material thus obtained into a fiber shape.

The heating atmosphere for converting the obtained fiber precursor into alumina fibers may be an oxidizing atmosphere (2) and usually air is used. What is the final temperature of heating?

Although it varies depending on the required physical properties of the fiber, if heat resistance is important, the temperature is preferably 1200°C or higher.

It is preferable to maintain the temperature at that temperature for about 0.5 to 1 hour.

In this way, Altos so ~98%t
Alumina fibers having a composition range of Slow 2 Q to 2 Q can be obtained.

"Effects of the Invention" In the present invention, specific organic additives are added to an aqueous liquid material consisting of basic aluminum chloride, colloidal silica, and an organic binder, which is then spun and heated and fired.
0.80~98%) SiQt is the most effective for producing alumina fibers with a composition range of 20~2Q.
Al*Qs-S joy-based fibers with a SiO content of 2% or less or more than 20%, or Almost 5
It can be used in the production of fibers containing other metal oxides in addition to ift, and can easily and inexpensively produce alumina fibers with excellent mechanical properties and heat resistance properties, and has excellent effects. is recognized.

Next, two embodiments of the present invention will be described.

Example 1 Basic aluminum chloride with basicity of 83.3%, colloidal silica (manufactured by Catalysts Kasei Kogyo Co., Ltd., trade name Cataloid SN)
An aqueous liquid was prepared by blending polyvinyl alcohol and ethylene glycol in a ratio of 95:5:5:5. The polyvinyl alcohol used was a 10% aqueous solution.

The viscosity of this was adjusted and the centrifugal spinning method was used to create a diameter of approximately 3 μm.
A fibrous precursor was formed and held at 1300° C. for 1 hour to produce alumina fibers.

After dispersing 0.5 g of the obtained fiber in 5 ml of water, a mixer (MX-120S manufactured by Matsushita Electric Co., Ltd.)
After running for 30 seconds, solid-liquid separation was carried out, the solid content was dried, and classified using a 40-mesh standard sieve, and the amount passing through the sieve was weighed, and the weight of the 40-mesh passing through the sieve was calculated as a percentage of the weight of the original sample. The sample was filled into a heat-resistant cylindrical container at a packing density of 0.1 g/i, and a load was placed on the sample to give a pressure of 13.7 g/CI/L.

Heated at a temperature increase rate of 200°C/hr to 1400°C and 1
Hold at 600'C for 2 hours and calculate the shrinkage rate using the 9th order formula to obtain the hot load linear shrinkage rate, Carlo Erb
a Measure the pore distribution with a mercury porosimeter model 65.

The macropore volume (diameter 0.015 to 0.1
The volume m//9) of micropores of μm was determined. Second result
Shown in the table. As shown in Table 2, according to the method of the present invention, extremely excellent alumina fibers with small macropore volume, low mixer collapse rate, and low linear shrinkage under hot load can be produced. I know what I'm getting.

Examples 2 to 4 Fiber precursors were obtained in the same manner as in Example 1 using β-propylene glycol as an organic additive.

In the same manner as in Example 1, alumina fibers were produced by heating and firing at 1250° C. (Example 2), 1275° C. (Example 3), and 1300° C. (Example 4) for 1 hour, respectively. The same tests as in Example 1 were conducted on each of the obtained fibers. The results are shown in Table 2.

Example 5 H using β-propylene glycol as an organic additive
AltQl a 5lot: Binder: Organic additive = 90
Alumina fibers were prepared in the same manner as in Example 1 by maintaining the final heating temperature of 1250° C. for 1 hour.

Various tests were conducted on the obtained fibers in the same manner as in Example 1. The results are shown in Table 2.

Example 6 Except for using β-propylene glycol as the organic additive,
Alumina fibers were produced in the same manner as in Example 1, and various tests were conducted in the same manner as in Example 1.

The results are shown in Table 2.

Example 7 Alumina fibers were produced in the same manner as in Example 1, except that 2,3-butylene glycol was used as the organic additive, and various tests were conducted in the same manner as in Example 1.

Example 8 Except that the organic additive was imbutylene oxide and the blending ratio of each raw material was 95:5:5.

Alumina fibers were produced in the same manner as in Example 1.

Various tests were conducted in the same manner as in Example 1. The results are shown in Table 2.

Example 9 Alumina fibers were produced in the same manner as in Example 1, except that a mixture of ethylene glycol and β-propylene glycol at a ratio of 3:2 was used as the organic additive. Various tests were conducted in the same manner. Second result
Shown in the table.

Example 10 Example 1 except that a mixture of ethylene glycol and inbutylene oxide in a ratio of 4=1 was used as the organic additive, and the blending ratio of each raw material was 95:5:5:5.
Alumina fibers were produced in the same manner as in Example 1, and various tests were conducted in the same manner as in Example 1. The results are shown in Table 2.

Example 11 As organic additives, ethylene glycol, β-propylene glycol, and 2,3-butylene glycol were mixed in 3:
Alumina fibers were produced in the same manner as in Example 1, except that they were mixed at a ratio of 1:1, and various tests were conducted in the same manner as in Example 1. The results are shown in Table 2.

Comparative Examples 1-2 No organic additives were used and the mixing ratio of each raw material was 95:5:5
The final heating temperature was set to 1300° in the same manner as in Example 1.
C (Comparative Example L) Alumina fibers were produced at 1275°C (Comparative Example 2) in the same manner as in Example 1. Various tests were conducted on the obtained fibers in the same manner as in Example 1. Shown in the table.

Comparative Example 3 Alumina fibers were produced in the same manner as in Example 1, except that no organic additives were used, the mixing ratio of each raw material was 9°:10nia, and the final heating temperature was 1250°C. Various tests were conducted in the same manner as in 1.

The results are shown in Table 2.

Claims (1)

[Claims] 1) In a method for producing alumina fibers by heating and firing a fiber precursor obtained by fiberizing an aqueous liquid material consisting of basic aluminum chloride, colloidal silica, and an organic binder, carbon-hydrogen is added to the aqueous liquid material. and at least one type of water-soluble and neutral chain organic compound composed of oxygen and having two hydroxyl groups in one molecule, or a compound capable of producing the chain organic compound in the aqueous liquid. A method for producing alumina fiber, characterized by containing a compound.