JPS60209016A - Preparation of composite ceramic fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fibers useful as a heat insulating material for high temperature, by blending non-crystalline ceramic fiber consisting essentially of alumina and silica with a precursor of crystalline ceramic fiber by a specific method, calcining the blend. CONSTITUTION:Melt consisting essentially of alumina and silica is extruded from a thin hole nozzle into a thin stream, and high-speed air current is sprayed through a nozzle on it. On the other hand, one or more of aluminum, zirconium, and magnesium are blended with a water-soluble organic polymer, and, if necessary, a silicon compound, to prepare a viscous aqueous solution of precursor. The aqueous solution of precursor is introduced into the high-speed air current, made into fibers, and blended with the noncrystalline ceramic fibers consisting essentially of alumina and silica, to give the a fiber aggregate. The aggregate is successively calcined at 650-1,250 deg.C, to give composite ceramic fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing composite ceramic fibers suitable for use as high-temperature heat insulating materials, and its purpose is to produce composite ceramic fibers that are made of amorphous ceramic fibers and crystalline ceramic fibers. Aluminosilicate material is used as the lining of various industrial furnaces by efficiently mixing and intertwining with ceramic am to provide a high-performance and inexpensive heat insulating material that maintains low shrinkage and high strength even at high temperatures. Ceramic fibers are used in various forms.

However, the main component of this ceramic fiber is 40 to 70%.
Since it is an amorphous fiber containing 30 to 60% by weight of 8 ioz by weight, the fiber has high strength, but at high temperatures, significant shrinkage occurs due to precipitation of crystals.

Furthermore, although crystalline ceramic fibers having an M2O3 component of 70% by weight or more have a small shrinkage at high temperatures, the fibers are brittle, so even when used as a molded article, they lack strength and have poor durability.

Therefore, in order to maintain high strength and low shrinkage even at high temperatures, amorphous ceramic fiber and crystalline ceramic #
BACKGROUND ART A laminated fiber composite made of a mixture of i-fibers, fine crystals, etc. has been proposed in the past.

For example, Japanese Patent Application Laid-Open No. 55-71684 proposes a method of producing a molded body by dispersing and mixing amorphous ceramic fibers and crystalline ramic fibers in water, and filtering the mixture by suction. However, with this method, since the fibrous materials are layered on top of each other, the intertwining of the fibers is restricted in two-dimensional directions, and shrinkage cannot be suppressed sufficiently. The effect of mixing fibers is lost.

Mata, Japanese Patent Application Laid-Open No. 57-47972, discloses a ceramic M fiber in which a refractory oxide is introduced during the production of Ceramic A/minosilicate fiber to form an oxide coating on the surface of the Ceramic fiber. A method for making the composite is described.

However, this method relates to a method for manufacturing a composite consisting of ceramic fibers and a refractory oxide, and is not intended to improve the intertwining of fibers as in the present invention. The entire fiber cannot be sufficiently covered with oxide particles, and the shrinkage rate at high temperatures cannot be reduced.

As described above, in the conventional method for manufacturing ceramic fiber composites, it is not possible to manufacture ceramic fiber composites in which Ia miscellaneous particles are sufficiently intertwined with each other in three dimensions and can maintain low shrinkage rate and high strength even at high temperatures. could not.

The present invention is a composite ceramic IP having a structure in which amorphous ceramic fibers and crystalline ceramic fibers are three-dimensionally intertwined, and which can maintain low shrinkage and high strength even at high temperatures.
The purpose is to provide four fibers. That is, in the present invention, a molten material mainly composed of alumina and silica is made into a thin stream through a fine-hole nozzle, and a high-speed air stream is blown onto the thin stream to produce an amorphous medium ramic fiber mainly composed of alumina and silica. At this time, a viscous aqueous solution prepared by adding one or more water-soluble metal compounds of aluminum, zirconium, and magnesium, a water-soluble organic polymer, and, if necessary, a silicon compound, is introduced into the high-speed air flow. #I fiber aggregate, which is a mixture of the precursor fibers and amorphous ceramic fibers mainly composed of alumina and silica, is fired at a temperature range of 650 to 1250°C. The present invention provides a method for manufacturing a composite ceramic fiber.

The present invention will be explained in detail below.

A method for obtaining a low shrinkage rate by mixing amorphous ceramic fibers and crystalline ceramic fibers is known. However, since the mixing method is carried out through dispersion in water, the fibers are mixed during mixing. The II fibers are cut short and the intertwining of the II fibers becomes insufficient. Additionally, extra heat is required for drying, which increases cost. Furthermore, as a means for sufficiently mixing two or more types of fibers without shortening the fibers, there is known a means for dispersing the fibers in an air stream, such as that used when blending organic fibers.

However, compared to organic fibers, crystalline ceramic fibers have a higher elastic modulus and so-called high rigidity, so they are weak against bending force and tend to break easily. Under the force of air turbulence, the long parts break and become short, and they coagulate together into granules, which no longer exhibit the characteristics of fibers.

The inventors of the present invention have conducted intensive research on methods that can achieve sufficient entanglement using a method other than the wet method (hereinafter referred to as the dry method), and have found that if the crystalline ceramic fibers are given flexibility, This is a new finding that sufficient entanglement can be generated even when

Generally, crystalline ceramic fibers are made by extruding, centrifuging, spraying, stretching, etc. a viscous aqueous solution made by dissolving a metal compound and an organic polymer in water, which are converted into metal oxides by firing. It is made by firing the precursor fiber obtained by Since the precursor fiber contains an organic polymer, it has excellent flexibility, but has poor strength and must be handled with care.

Therefore, it was predicted that if this precursor fiber could be utilized effectively, it would be possible to achieve mixing by a dry method.

However, as mentioned above, the strength of the precursor fibers is poor, so simply dispersing the amorphous ceramic fibers and the precursor fibers in an air stream will cause the precursor fibers to be cut into short lengths, which may not be sufficient. There wasn't.

Therefore, as a result of various studies on methods of dispersing amorphous ceramic fibers and precursor fibers in an air flow, we found that when making amorphous ceramic fibers by spraying them into a trickle of melt mainly composed of alumina and silica. It has been found that it is most effective to introduce an aqueous solution of a precursor fiber spinning dope into the high-speed air stream used to produce precursor m-fibers simultaneously with the production of amorphous ceramic fibers. That is, according to the method described above, it was possible to obtain a fiber aggregate in which amorphous ceramic fibers and relatively long precursor fibers were mixed in a three-dimensionally sufficiently intertwined state.

As a means of introducing the aqueous solution of the precursor fiber spinning dope into the high-speed airflow, for example, another nozzle disposed near the nozzle that blows a high-speed airflow of air into a trickle of melt mainly composed of alumina and silica can be used. There is a method of press-fitting through. The amount of the aqueous solution of the precursor fiber spinning dope can be determined in accordance with the production rate of the amorphous ceramic fibers based on the blending ratio of the desired amorphous ceramic fibers and the crystalline ceramic fibers produced by firing the precursor fibers. can. Furthermore, it is possible to change the thickness and length of the precursor fiber by changing the discharge speed of the aqueous solution of the precursor am spinning dope depending on the speed and amount of the high-speed airflow.

The aqueous solution of the precursor fiber spinning stock solution is a viscous aqueous solution prepared by dissolving one or more water-soluble metal compounds of aluminum, zirconium, and magnesium and a water-soluble organic polymer in water, or if necessary, the above-mentioned viscous solution. This is an aqueous solution in which a silicon compound is dissolved and dispersed in an aqueous solution. The water-soluble metal compound of aluminum includes aluminum chloride,
Basic aluminum chloride, basic acid Al E: v7
aluminum, basic aluminum acetate, basic aluminum lactate, etc., and it is particularly preferable to use one or more of aluminum chloride, basic aluminum chloride, and basic aluminum lactate.

Examples of the water-soluble metal compounds of zirconium include zirconium chloride, basic zirconium chloride, basic zirconium formate, basic zirconium acetate, and basic zirconium nitrate. Examples of the water-soluble metal compound of magnesium include magnesium chloride. In addition, water-soluble organic polymers include polyvinyl acetate, polyvinyl alcohol, polyethylene oxide, polyethylene glyfur, and polyacrylamide, and in particular, one or more of polyvinyl alcohol, polyethylene oxide, and polyacrylamide is used. It is preferable that Examples of the silicon compound include colloidal silica. In particular, as the aqueous solution of the precursor fiber spinning stock solution introduced into the high-speed airflow, any one or two of aluminum chloride, basic aluminum chloride, and basic aluminum M may be used.
A viscous material made by dissolving and dispersing in water one or more water-soluble aluminum compounds, one or more water-soluble organic polymers of polyvinyl acyfur, polyethylene oxide, and polyacrylamide, and colloidal silica. Aqueous solutions are preferred. Further, the aqueous solution of the precursor fiber spinning dope is preferably a viscous aqueous solution having a viscosity within the range of 10 to 1000 poise. - Next, a fiber aggregate in which the amorphous ceramic fibers mainly composed of alumina and silica obtained as described above and the precursor fibers are mixed in a three-dimensionally sufficiently intertwined state is heated to contain oxygen. Atmosphere, e.g. 650-1250℃ in air
Fire at a temperature within the range of . This firing burns out the organic polymer constituting the precursor fibers, decomposes and oxidizes the aluminum, zirconylam, magnesium compounds, and silicon compounds into oxides, converting the precursor II fibers into substantially crystalline ceramics. l1I4 Make it sloppy. The reason for limiting the firing temperature to within the range of 650 to 1250°C is
Temperatures below 650°C do not substantially convert the precursor fibers into crystalline ceramic fibers, while temperatures below 1250°C
This is because the thermal deterioration of the amorphous ceramic fiber becomes significant at temperatures exceeding 100 mL.

Examples of the present invention will be described below along with comparative examples.

A mixture of 45% by weight alumina and 55% silica sand was melted and discharged through a pore, and the discharge stream was blown with high pressure air through a nozzle at a velocity close to the speed of sound.

On the other hand, a basic aqueous aluminum chloride solution or a basic aqueous zirconium chloride solution, a 4% by weight aqueous solution of one or more of polyvinyl alcohol, polyethylene oxide, and polycyclylamide, and if necessary, froidal chloride and magnesium chloride are added. After mixing, an aqueous precursor solution was prepared so as to have a viscosity of 30 voices by concentration. The precursor aqueous solution prepared in this manner is introduced into the aforementioned high-pressure air flow and fiberized to produce a mat-like composite ceramic m-fiber consisting of amorphous ceramic fibers and crystalline ceramic fiber precursors. did. This complex was then heated to 800″C.
The precursor fibers were converted into crystalline fibers by passing through a furnace heated to

In addition, crystalline ceramic fibers obtained by previously fiberizing the aqueous precursor solution and amorphous ceramic fibers having the above composition are dispersed in water, vacuum-sucked, molded, and dried to form a mat-like composite. It was produced by a wet method and used as a comparative example of the present invention.

Table 1 shows the compositions and sizes of test pieces used to measure the tensile strength and linear shrinkage percentage of composites according to Examples and Comparative Examples of the present invention.

Figure 1 shows the tensile strength values in the longitudinal direction of the test specimens fired for 24 hours at each temperature, and similarly, Figure 2 shows the values of the bending strength in the thickness direction, with the solid line for Examples and the broken line for Comparative Examples. 1 shown. Here, the bending strength was compared by fixing both ends of the test piece and bending it at regular intervals, and calculating the number of bends until the center part split and was cut off.

In addition, Figure 3 shows the values of the linear shrinkage percentage in the length direction of the test pieces fired for 24 hours at each temperature, and similarly, Figure 4 shows the values of the linear shrinkage percentage in the thickness direction. is indicated by a broken line.

The tensile strength was measured using a tensile strength tester manufactured by Shimadzu Corporation, with a tensile speed of 10□ and a grip interval of 60 f.
It was measured as l.

From the results shown in Figures 1 to 4, it is clear that the Examples maintain high strength and low shrinkage, especially at high temperatures, compared to the Comparative Examples, and the improvement in the thickness direction is remarkable. It can be seen that the fibers are efficiently intertwined three-dimensionally.

As shown in Table 1, according to the manufacturing method of the present invention, composite ceramic fibers that can maintain high strength and low shrinkage even at high temperatures can be manufactured easily and at low cost.

[Brief explanation of the drawing]

゛Figure 1 is a graph comparing the tensile strength of the example of the present invention with the comparative example, Figure 2 is the flexural strength, Figure 3 and Figure 4 are the graphs of the heating linear shrinkage ratio of the example of the present invention and the comparative example. It is a graph shown about. Patent applicant IBIDEN Co., Ltd. Representative Jun Taga Partially υo l1oo tzoo 1joo tqoυ1
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Claims (1)

[Claims] 1. Amorphous ceramic m-fibers mainly composed of alumina and silica are formed by forming a molten material mainly composed of alumina and silica into a thin stream through a fine-hole nozzle, and blowing a high-speed air stream onto the thin stream. When producing a viscous material, a water-soluble metal compound of one or more of aluminum, zirfnium, and magnesium, a water-soluble organic polymer, and optionally a silicon compound are added to the high-speed air stream. A viscous aqueous solution is introduced to obtain precursor fibers, and a fiber aggregate consisting of a mixture of the precursor fibers and amorphous ceramic fibers mainly composed of alumina and silica is produced at 650.
A method for producing a composite ceramic fiber, characterized by firing at a temperature range of 1260°C. 2. The viscous aqueous solution introduced into the high-speed airflow contains one or more water-soluble aluminum compounds such as aluminum chloride, basic aluminum chloride, and basic aluminum lactate, and polyvinyl alcohol, polyethylene oxide, and polyacrylamide. 2. The method according to claim 1, wherein the aqueous solution comprises one or more water-soluble organic polymers and colloidal silica. 3. The viscosity of the viscous aqueous solution introduced into the high-speed airflow is 10
3. The manufacturing method according to claim 1, wherein the poise is within the range of 1000 to 1000 poise.