JPH0138901B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a ceramic fiber blanket. Ceramic fibers, such as alumina ceramic fibers, have excellent fire resistance and are used as various fire-resistant heat insulating materials.

Conventionally, commonly used alumina ceramic fibers are produced by melting raw materials containing aluminum oxide, silicon oxide, etc., and then turning them into fibers.
It was obtained by the so-called melt fiberization method. Although it is not impossible to use the fiber obtained from this process as it is, it is generally necessary to make the original made of this fiber into a high bulk density material (for example, around 0.1 g/cm ³ ). bulk density)
However, in order to make it an easy-to-handle material, it is processed into blankets by needle punching, or it is dispersed in water with an inorganic binder and then dehydrated under pressure and processed into felts and boards. .

Blanket manufacturing methods include stacking raw cotton as it is in layers and subjecting it to needle punching treatment, as well as treating the raw cotton with a fiber treatment agent in advance, or interposing a reinforcing nonwoven fabric between the layered aggregates. Improved methods have been obtained. These improvement methods are used to increase bulk density and strength because ceramic fibers themselves are relatively hard, and if needle punching is applied as is, the fibers will not entangle sufficiently. It is something.

In recent years, ceramic fibers obtained by the so-called precursor fiberization method have been attracting attention, especially as ceramic fibers for high temperatures. In this method, a fiber precursor solution of an inorganic compound, for example, in the case of an alumina-based ceramic fiber, a solution of aluminum oxychloride, etc. is turned into fibers and then fired to remove volatile components to obtain a ceramic fiber. . However, the ceramic fibers obtained by the precursor fiberization method are different from the fibers obtained by the melt fiberization method, and when trying to make a blanket from the ceramic fibers, no fiber entanglement can be obtained with the raw cotton as it is, and it is necessary to treat it with a fiber treatment agent. However, it is not possible to improve the intertwining of fibers and make the bulk density of raw cotton 0.1 g/cm ³ or more, and on the contrary, the use of fiber treatment agents increases costs.

In view of the above-mentioned circumstances, the present inventors have conducted intensive studies on making ceramic fibers obtained by the precursor fiberization method into blankets. Breaking away from the conventional technical common sense of processing and applying needle punching to the fiber before it becomes the final product, that is, the raw cotton of unfired fiber, the result is the same or even better than that obtained by applying a fiber treatment agent. It was discovered that a good blanket can be obtained even after the entanglement is developed, and even after firing, a good blanket can be obtained, and the present invention has been achieved.

The present invention was completed based on this unexpected finding, and its purpose is to provide an industrially advantageous method for manufacturing blankets using ceramic fibers obtained by the precursor fiberization method. . Accordingly, this object can be easily achieved by stacking unfired ceramic fibers obtained by the precursor fiberization method in a layered manner, subjecting the fibers to a needle punching treatment, and then firing them.

The present invention will be explained in detail below.

The ceramic fiber used in the method of the present invention is produced by a precursor fiberization method.

The precursor fiberization method is a method in which an organometallic compound or metal oxyhalide is made into fibers in the presence or absence of an appropriate organic thickener, and then volatile parts or volatile components are removed by firing. In the invention method, unfired ceramic fibers obtained by various methods can be used, but usually, unfired ceramic fibers obtained by fiberizing a spinning stock solution containing aluminum oxychloride and a silicon compound are used. It will be done.

The method for producing an aluminum oxychloride solution is known, and can be easily produced, for example, by dissolving metallic aluminum in hydrochloric acid or an aqueous aluminum chloride solution. Al/Cl of aluminum oxychloride
The atomic ratio of is usually 1.2 to 2.0, preferably 1.6 to 1.9. If this ratio is too small, it will be difficult to obtain a solution with an appropriate aluminum concentration as a spinning dope, while if this ratio is too large, the solution will become unstable and there is a risk that an aluminum hydroxide gel will precipitate.

Silica sol is preferred as the silicon compound, but
Water-soluble silicon compounds such as tetraethyl silicate and water-soluble siloxane derivatives are also used. These silicon compounds also change into silica during the firing process of the precursor fibers, and have the effect of suppressing alumina from becoming α-alumina and suppressing crystal growth of alumina.

The ratio of aluminum oxychloride and silicon compound in the spinning dope is converted to the ratio of Al ₂ O ₃ and SiO ₂ as follows:
It is preferably in the range of 99:1 to 72:28. When the amount of the silicon compound is less than this range, the alumina constituting the fiber is likely to be converted into α-alumina, and the alumina particles are likely to become coarse, causing the fiber to become brittle. On the other hand, if the amount of the silicon compound is too large, silica (SiO ₂ ) is produced in addition to mullite (3Al ₂ O ₃ .2SiO ₂ ), resulting in a significant decrease in heat resistance.

Preferably, an organic polymer is present in the spinning dope. Although it is possible to carry out the present invention using a spinning stock solution obtained by simply adding a silicon compound to an aqueous aluminum oxychloride solution and concentrating it to a predetermined concentration, the presence of an organic polymer in the spinning stock solution may cause problems in spinning properties. will improve. Examples of organic polymers include natural or synthetic polymeric compounds capable of forming fibers, such as acetated starch, hydroxyethyl starch,
Soluble derivatives of starch and cellulose such as methylcellulose and carboxymethylcellulose, and water-soluble synthetic polymer compounds such as polyvinyl alcohol, polyethylene glycol, and polyacrylamide are used. When selecting the organic polymer, care must be taken to ensure that the spinning stock solution does not become cloudy or precipitate. The organic polymer is added to the spinning dope so that it has an optimum viscosity for the spinning method applied, but usually it may be added so that the viscosity of the spinning dope is 1 to 1000 poise.

The spinning dope is prepared by adding a silicon compound and an organic polymer to an aqueous aluminum oxychloride solution and concentrating the solution to a predetermined aluminum concentration. If desired, the silicon compound and organic polymer may be added to the solution during or after concentration. In particular, organic polymers may cause foaming during concentration, and in such cases it is preferable to add the organic polymer after concentration.

As the spinning method, any known method such as an extrusion method, a stretching method, a blowing method, a centrifugation method, etc. can be adopted. For example, when using the blow-out method, 5
0.1 to 0.5 mm of spinning dope adjusted to ~100 poise
Spinning is carried out by extrusion into a high-speed air stream through φ pores. The extruded spinning stock solution is heated to 200℃
Stretching in an air stream preferably at 0 to 100°C,
It is dried to become a precursor fiber. This method requires that the precursor fibers be sufficiently dried before being collected from the air stream. If drying is insufficient, the collected precursor fibers may adhere to each other or droplets may drop due to elastic recovery, resulting in shots.

Therefore, if necessary, heated air may be used to promote evaporation of the solvent within a range that does not cause foaming.

On the other hand, if the drying is too strong, the precursor fibers may not be fully drawn, the fiber diameter may become too thick, or the H ₂ O content, Cl content, organic polymers, etc. in the precursor fibers may be subject to thermal decomposition. Since the fibers are raised and volatilized, the fibers lack flexibility and become unsuitable for the needle punching treatment described below. That is, the method of the present invention is characterized by subjecting an unfired ceramic fiber to a needle punching treatment. The needle punching process was carried out by taking advantage of its flexibility, so it is unlikely that thermal decomposition occurred as described above.
The effects of the present invention will not be realized. Also, from this point of view, it is preferable to use a spinning dope containing an organic thickener such as polyvinyl alcohol.

Since the unfired precursor fiber is amorphous and highly flexible, it is collected in layers in this state and then subjected to needle punching.
Most of the fibers can be intertwined with each other without cutting them. By appropriately selecting the number of needle punching from the range of 1 to 30 times/cm ² , ^a blanket with a desired bulk density can be obtained. Needle punching is 5 to get
It is preferable to carry out ~10 times/ ^cm3 . The blanket made of the unfired fiber obtained in this way is then fired at a high temperature of 500°C or higher to
Even after the organic polymer is burnt off, the intertwining between the fibers is maintained as is, making it possible to obtain an alumina fiber blanket having the desired bulk density and tensile strength. Firing is carried out according to the usual method at 500℃ or higher, preferably at 1200℃ or higher.
It is carried out at 1300℃. At temperatures below 500°C, the alumina fibers of the blanket obtained have low strength and are brittle, and furthermore, the reheating shrinkage rate at 1400°C is large, making them unsuitable for practical use. Furthermore, when heated to 1400°C or higher, crystal grain growth progresses and the strength of the resulting fiber decreases.

According to the present invention, by needle punching the fibers before firing, it is possible to easily produce a crystalline alumina fiber blanket without any special treatment after firing. Further, the ceramic fiber blanket obtained by the method of the present invention has better heat resistance than the ceramic fiber blanket obtained by the melt fiberization method, and is useful as a fireproof material.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 Aluminum oxychloride aqueous solution (aluminum content 70 g/, Al/Cl (atomic ratio) = 1.8) 1,
35 g of a 20% silica sol solution and 278 g of a 5% aqueous polyvinyl alcohol solution were added and mixed. This mixed solution was concentrated at 50° C. under reduced pressure to obtain a spinning stock solution (viscosity: 27 poise, alumina content: 26.5 wt%), which was then spun using a blowing method to obtain raw fibers. The approximate bulk density of this material was 0.05 g/cm ³ . This is collected into layers and needle punching machine (needle spacing 15 to 23
A blanket was obtained by punching 9 to 7 times/cm ² using a needle (mm; 220 needles). Then heat this to 1260℃
It was baked in air for 1 hour. This blanket had a bulk density of 0.10 g/cm ³ and a tensile strength of 1.2 Kg/cm ² .

Comparative Example 1 The raw fiber obtained by the method of Example 1 was heated to 1260°C.
Alumina fibers were obtained by firing in air for hours. Thereafter, the cotton was collected in the same manner as in Example 1 and subjected to needle punching treatment to obtain a blanket. This blanket has a bulk density of 0.05g/cm ³ and a tensile strength of 0.6Kg/cm ²
It was hot.

Comparative Example 2 The raw fiber obtained by the method of Example 1 was heated at 1260°C.
Alumina fibers were obtained by firing in air for an hour. This was impregnated with a fiber treatment agent consisting of a water emulsion of 1200 parts of H ₂ O, 5 parts of kerosene, and 1 part of fatty acid amine acetate, subjected to the same needle punching treatment as in Example 1, and then dried to obtain a blanket. This blanket has a bulk density of 0.09g/cm ³ and a tensile strength of
It was 1.0Kg/ ^cm2 .

Claims (1)

[Scope of Claims] 1. A method for manufacturing a ceramic fiber blanket, which comprises stacking unfired ceramic fibers obtained by a precursor fiberization method in a layer, subjecting the layers to needle punching, and then firing. 2. The method according to claim 1, wherein the ceramic fiber is obtained by fiberizing a spinning dope containing aluminum oxychloride and a silicon compound. 3. The method according to claim 1, wherein the ceramic fiber is obtained by fiberizing a spinning dope containing aluminum oxychloride, a silicon compound, and an organic polymer. 4 The ratio of aluminum to silicon in the spinning stock solution is
Claim 2, characterized in that the ratio of Al ₂ O ₃ to SiO ₂ is in the range of 99:1 to 72:28.
or the method described in paragraph 3. 5. The method according to any one of claims 1 to 4, wherein the needle punching treatment is performed at a rate of 1 to 30 times/cm ² . 6. The method according to any one of claims 1 to 5, wherein the ceramic fiber is obtained by fiberizing a spinning dope at an ambient temperature of 200° C. or lower.