JPH0541726B2 - - Google Patents

Description

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

BACKGROUND TECHNIQUE Conventionally, commonly used alumina ceramic fibers are obtained by the so-called melt fiberization method, in which blended raw materials containing aluminum oxide, silicon oxide, etc. are melted and then fiberized. Although it is not impossible to use the fiber obtained from this process as it is, generally speaking, the raw cotton made of this fiber is made to have a high bulk density (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 and subjecting it to needle punching, as well as methods such as treating raw cotton with a fiber treatment agent in advance, or interposing a reinforcing nonwoven fabric between layered aggregates. Improvement methods are known. 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 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. .

Problems to be Solved by the Invention Ceramic fibers obtained by the precursor fiberization method are different from fibers produced by the melt fiberization method, and when attempting to make a blanket from the ceramic fibers obtained by the precursor fiberization method, no entanglement of fibers can be obtained with the raw cotton as it is. Even if treated with a fiber treatment agent, it was not possible to improve fiber entanglement and increase the bulk density of raw cotton to 0.1 g/cm ³ or higher, and until now it was thought that it was impossible to manufacture high bulk density blankets from alumina ceramic fibers. It's here.

Means for Solving the Problem In view of the above circumstances, the inventors of the present invention have conducted intensive studies on making ceramic fibers into blankets obtained by a precursor fiberization method using aluminum salt as a raw material, and have found that the final product in the fiberization process is Breaking away from the conventional technical common sense of processing raw cotton made of fired fibers, and applying needle punching to the fibers before they become the final product, that is, raw cotton made of unfired fibers, it is possible to It has been found that the degree of entanglement of the fibers is greater than when the treated fibers are treated with a fiber treatment agent and subjected to needle punching treatment, and a good blanket can be obtained without causing any problems even after firing. Furthermore, the present inventors have found that if a non-aqueous fiber treatment agent is added to raw unfired fibers, followed by needle punching treatment, and then firing, the entanglement is further improved and a high-strength and good blanket can be obtained. I found out.

The present invention was completed based on this unexpected finding, and its purpose is to provide an industrially advantageous manufacturing method for blankets using ceramic fibers obtained by a precursor fiberization method using aluminum salt as a raw material. It is about providing. Therefore, this purpose was to accumulate unfired ceramic fibers obtained by a precursor fiberization method using aluminum salt as a raw material, add a non-aqueous fiber treatment agent, perform needle punching treatment, and then sinter the fibers. However, this can be easily achieved by removing the fiber treatment agent.

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.

Precursor fiberization methods are known. To produce alumina ceramic fiber using this method,
After an organoaluminum compound, aluminum oxychloride, or other aluminum salt is fiberized in the presence or absence of a suitable organic thickener, the volatile portion or volatile components are removed by firing to obtain a ceramic fiber. In the present invention, an unfired ceramic fiber obtained by a precursor fiberization method using an aluminum salt as a raw material is used. As a precursor fiberization method using aluminum salt as a raw material, aluminum formate, aluminum acetate, aluminum oxychloride, etc. are used. (Tokuko Showa 47-
33021, JP-A-48-75823) 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 stock solution, and if this ratio is too large, the solution will become unstable and there is a risk that aluminum hydroxide gel will precipitate. .

Silica sol is preferred as the silicon compound, but
Water-soluble silicon compounds such as tetraethylene 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 65:35. 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 silicon compound is too large, excess silica (SiO ₂ ) is produced in addition to mullite (3Al ₂ O ₃ .2SiO ₂ ), resulting in a 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 various 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 become droplets 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 will not be fully drawn, the fiber diameter will become too thick, and the H ₂ O content, Cl content, organic polymers, etc. in the precursor fibers will cause thermal decomposition. Due to volatilization, 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 purpose is to take advantage of its flexibility to perform needle punching.
Therefore, if thermal decomposition occurs as described above, the effects of the present invention will not be achieved. Also, from this point of view, it is preferable to use a spinning dope containing an organic thickener such as polyvinyl alcohol.

By accumulating the precursor fibers thus obtained, adding a non-aqueous fiber treatment agent thereto, subjecting them to needle punching treatment, and then firing, a good blanket with an improved degree of entanglement can be obtained.

The fiber treatment agent used in the present invention is preferably an ester of a higher fatty acid such as lauric acid, palmitic acid, or stearic acid diluted approximately 10 times with a solvent such as n-heptane or mineral oil.
When using an aqueous solvent, the precursor fibers dissolve,
This is not preferable because the fiber shape cannot be maintained.
Furthermore, it is necessary to use a fiber treatment agent that does not form hartz after firing. The fiber treatment agent can be added by spraying it onto the raw cotton of unfired fibers, etc.
A method of uniform distribution is adopted.

Fiber treatment agent is 0.5-1.5wt for precursor fiber
%, preferably 0.7 to 0.8 wt%. If the addition ratio is smaller than this range, it will not be possible to sufficiently improve the entanglement of the fibers, and if it exceeds this range, no noticeable effect will be seen in improving the entanglement of the fibers, resulting in stickiness of the unfired fibers. It takes a large amount of heat energy and time during firing,
It's not economical.

By appropriately selecting the number of needle punching from 1 to 50 times/cm ³ , a blanket with a desired bulk density can be obtained ^. In order to obtain this, it is preferable to perform needle punching 5 to 10 times/cm ³ . The bulk density of the blanket is usually 0.05~
Although it is appropriately selected from the range of 0.2, it is preferably 0.08 to 0.12 when used at high temperatures of 1000°C or higher. The needle-punched blanket is then fired at a high temperature of 500°C or higher to maintain the intertwining between the fibers even after the organic polymer and fiber treatment agent are burned out, resulting in alumina fibers having the desired bulk density and tensile strength. It can be used as a blanket. Firing is done at 500℃ according to the usual method.
Above, it is preferably carried out at 1200 to 1300°C.
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. 1400 again
When heated above ℃, crystal grain growth progresses and the strength of the resulting fiber decreases.

According to the present invention, a blanket of crystalline alumina fibers can be easily produced without any special treatment after firing by subjecting the fibers to needle punching before firing. Furthermore, by adding a nonaqueous fiber treatment agent before the needle punching treatment, it is possible to obtain a high bulk density, high strength blanket with further improved fiber entanglement. 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 70g/, 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℃ under reduced pressure to obtain a spinning stock solution (viscosity
27 poise and alumina content of 26.5 wt%), and was spun using a blowing method to obtain raw fibers. The approximate bulk density of this material was 0.05 g/cm ³ . After collecting this in layers, palmitic acid ester (C ₁₅ H ₃₁ COOC ₈ H ₁₇ ) diluted 10 times with n-heptane was used as a fiber treatment agent for raw fibers.
Spray uniformly at a ratio of 0.7wt% and use a needle punching machine (needle spacing 15-23mm: 220 needles)
Punching was performed 6 to 7 times/cm ³ to obtain a blanket.

This was then calcined in air at 1260°C for 1 hour. This blanket had a bulk density of 0.10 g/cm ³ and a vertical peel strength of 1.0 g/cm ³ .

Comparative Example 1 The raw fibers obtained by the method of Example 1 were collected in layers and subjected to the same needle punching treatment as in Example 1 without using a fiber treatment agent to obtain a blanket. This was then calcined in air at 1260°C for 1 hour. This blanket had a bulk density of 0.10 g/cm ³ and a vertical peel strength of 0.6 g/cm ³ .

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 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 0.05 g/cm ³ and a vertical peel strength of 0.2.
g/ ^cm3 .

Comparative Example 3 The raw fiber obtained by the method of Example 1 was heated to 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 had a bulk density of 0.09 g/cm ³ and a vertical peel strength of 0.5 g/cm ³ .

Claims (1)

[Scope of Claims] 1. Unfired ceramic fibers obtained by a precursor fiberization method using aluminum salt as a raw material are assembled, a non-aqueous fiber treatment agent is added thereto, a needle punching treatment is performed, and the fibers are then fired. ,that time,
A method for producing a ceramic fiber blanket, which comprises removing a fiber treatment agent. 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 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 65:35.
The method described in section.