Alumina-silica-based fiber, ceramic fiber, ceramic fiber complex, retaining seal material, production method thereof, and alumina fiber complex production method

Abstract

An object of the present invention is to provide a manufacturing method by which alumina-silica based fibers excellent in mechanical strength can be readily and securely obtained, and the present invention obtains precursor fibers as a material by using an alumina-silica based fiber spinning stock solution for use in an inorganic salt method. Next, the precursor fibers are heated under an environment which makes it difficult to carry out an oxidizing reaction on the carbon component contained in the precursor fibers. Thus, the precursor fibers are sintered to obtain alumina-silica based fibers.

1 . An alumina-silica based fiber which presents a blackish color.  
     
     
         2 . An alumina-silica based fiber which presents a blackish color derived from a carbon component.  
     
     
         3 . An alumina-silica based fiber which has a residual carbon content of 1% by weight or more, presents a blackish color derived from its residual carbon component, and has a fiber tensile strength of 1.2 GPa or more, a fiber bending strength of 1.0 GPa or more and a fracture toughness of 0.8 MN/m 3/2  or more.  
     
     
         4 . A manufacturing method of alumina-silica based fibers, comprising: a spinning step of obtaining precursor fibers by using a spinning stock solution of the alumina-silica based fibers for an inorganic salt method as a material; and a firing step of heating said precursor fibers under an environment which makes it difficult to carry out an oxidizing reaction on the carbon component contained in said precursor fibers, thereby sintering said precursor fibers.  
     
     
         5 . The manufacturing method of alumina-silica based fibers according to  claim 4 , wherein 
 said precursor fiber is heated at a temperature of 1000 to 1300° C. under a nitrogen atmosphere.    
     
     
         6 . The manufacturing method of alumina-silica based fibers according to  claim 4  or  5 , wherein 
 the carbon component contained in said precursor fiber is derived from an organic polymer added to said spinning stock solution of the alumina-silica based fiber as a fiber-drawing property applying agent.  
 
     
     
         7 . A holding seal material which has the alumina-silica based fibers, according to any of  claims 1  to  3 , aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body.  
     
     
         8 . The holding seal material according to  claim 7 , 
 wherein said ceramic body includes a catalyst carrier, and said holding seal material is used as a holding seal material for a catalyst converter.    
     
     
         9 . A holding seal material which has a fiber aggregation of alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 a crystallization rate in a portion on a first face side is different from that in a portion on a second face side.    
     
     
         10 . A holding seal material which has a fiber aggregation of alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 a crystallization rate is gradually increased from a first face side toward a second face side.    
     
     
         11 . The holding seal material according to  claim 10 , comprising a sheet of fiber aggregation, wherein 
 the crystallization rate of the fiber aggregation is gradually increased from the first face side toward the second face side.    
     
     
         12 . The holding seal material according to any of  claims 9  to  11 , wherein 
 the difference between the crystallization rates in the portion on the first face side and that in the portion on the second face side is 3% by weight or more.  
 
     
     
         13 . The holding seal material according to any of  claims 9  to  11 , wherein 
 the crystallization rate in the portion on the first face side is 0 to 1% by weight, and the crystallization rate in the portion on the second face side is 1 to 10% by weight.  
 
     
     
         14 . The holding seal material according to any of  claims 9  to  13 , wherein 
 said ceramic body includes a catalyst carrier, and said holding seal material is used as a holding seal material for a catalyst converter.  
 
     
     
         15 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 a crystallization rate is made different depending on portions.    
     
     
         16 . The holding seal material according to  claim 15 , wherein 
 said ceramic body includes a catalyst carrier, and said holding seal material is used as a holding seal material for a catalyst converter.    
     
     
         17 . A manufacturing method of the holding seal material according to any of  claims 9  to  14 , comprising: 
 a spinning step of obtaining precursor fibers by using a spinning stock solution of ceramic fibers as material;  
 a laminating step of laminating said precursor fibers to form a mat-shaped fiber aggregation; and  
 a firing step of sintering said fiber aggregation so as to provide a difference between a firing temperature on a first face side and that on a second face side.  
 
     
     
         18 . The manufacturing method of a holding seal material according to  claim 17 , wherein 
 the difference between said firing temperatures is set to 100° C. or more.    
     
     
         19 . The manufacturing method of a holding seal material according to  claim 17 , wherein 
 the firing temperature on the first face side is set to 800 to 1100° C., and the firing temperature on the second face side is set to 1100 to 1400° C.    
     
     
         20 . A catalyst converter comprising: a catalyst carrier; a cylinder-shaped metal shell covering the outer circumference of the catalyst carrier; and a holding seal material placed in a gap between these elements, and having alumina-silica based fibers aggregated into a mat shape as a constituent element, wherein 
 said holding seal material is placed in said gap in such a state that a first face side having a relatively small crystallization rate is made in contact with said metal shell, and a second face side having a relatively large crystallization rate is made in contact with said catalyst carrier.    
     
     
         21 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 said alumina-silica based fiber has a non-circular shape in its cross-section.    
     
     
         22 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 said alumina-silica based fiber has a deformed shape in its cross-section.    
     
     
         23 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 said alumina-silica based fiber has a flat shape in its cross-section.    
     
     
         24 . The holding seal material according to any of  claims 21  to  23 , wherein 
 said alumina-silica based fiber has a substantially elliptical or cocoon shape in its cross-section.  
 
     
     
         25 . The holding seal material according to  claim 21  or  22 , wherein 
 said alumina-silica based fiber is a hollow fiber.  
 
     
     
         26 . The holding seal material according to any of  claims 21  to  25 , wherein 
 said ceramic body includes a catalyst carrier, and said holding seal material is used as a holding seal material for a catalyst converter.  
 
     
     
         27 . A manufacturing method of alumina-silica based fibers used in the holding seal material according to any of  claims 21  to  26 , comprising: a spinning step of obtaining precursor fibers by discharging a spinning stock solution containing a solution of aluminum salt water, silica sol and an organic polymer through a nozzle; and a firing step of heating and sintering said precursor fibers, wherein 
 dried hot air is blown to said precursor fibers immediately after having been discharged from the discharging section of said nozzle having a non-circular shape in its cross-section.  
 
     
     
         28 . The manufacturing method of alumina-silica based fibers according to  claim 27 , wherein 
 said dried hot air is blown in a forward direction with respect to the discharging direction of said precursor fiber.    
     
     
         29 . The manufacturing method of alumina-silica based fibers according to  claim 27  or  28 , wherein 
 a water-soluble plasticizer is preliminarily added to said spinning stock solution.  
 
     
     
         30 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 the dispersion of fiber diameter in said alumina-silica based fiber is within ±3 μm.    
     
     
         31 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 the dispersion of fiber length in said alumina-silica based fiber is within ±4 mm.    
     
     
         32 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 the dispersion of fiber diameter in said alumina-silica based fiber is within ±3 μm, and the dispersion of fiber length in said alumina-silica based fiber is within ±4 mm.    
     
     
         33 . The holding seal material according to any of  claims 30  to  32 , wherein the content of shots is 3% by weight or less.  
     
     
         34 . A holding seal material which has alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 the average fiber diameter of said alumina-silica based fiber is 5 to 15 μm, the dispersion of fiber diameter therein is within ±3 μm, the average fiber length thereof is 5 to 20 mm, the dispersion of fiber length therein is within ±4 mm, and no shots are contained therein.    
     
     
         35 . The holding seal material according to any of  claims 30  to  34 , wherein 
 said ceramic body includes a catalyst carrier, and said holding seal material is used as a holding seal material for a catalyst converter.  
 
     
     
         36 . A manufacturing method of the holding seal material according to any of  claims 30  to  35 , comprising: 
 a spinning step of obtaining long precursor fibers by continuously discharging a spinning stock solution containing a solution of aluminum salt water, silica sol and an organic polymer through a nozzle;  
 a cutting step of chopping said long fibers into a predetermined length to obtain short fibers;  
 a molding step of allowing said short fibers to aggregate three-dimensionally, thereby forming into a mat-shaped fiber aggregation; and  
 a firing step of heating and sintering said mat-shaped fiber aggregation.  
 
     
     
         37 . A holding seal material which has ceramic fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein 
 said ceramic fibers are partially bonded to each other by a ceramic adhesive.    
     
     
         38 . The holding seal material according to  claim 37 , wherein 
 said ceramic adhesive comprises a substance which constitutes said ceramic fiber.    
     
     
         39 . The holding seal material according to  claim 37 , wherein 
 said ceramic fibers are alumina-silica based fibers, and said ceramic adhesive has alumina as a main component.    
     
     
         40 . The holding seal material according to any of  claims 37  to  39 , wherein 
 1 to 8% by weight of said ceramic adhesive is contained therein.  
 
     
     
         41 . The holding seal material according to any of  claims 37  to  40 , wherein 
 said ceramic body includes a catalyst carrier, and said holding seal material is used as a holding seal material for a catalyst converter.  
 
     
     
         42 . A manufacturing method of the holding seal material according to any of  claims 37  to  41 , comprising: 
 a spinning step of obtaining precursor fibers by using a spinning stock solution of ceramic fibers as a material;  
 a firing step of heating and sintering said precursor fibers;  
 a molding step of allowing thus obtained ceramic fibers to aggregate three-dimensionally, thereby forming into a mat-shaped aggregation; and  
 bonding step of bonding the ceramic fibers forming said aggregation by using a ceramic adhesive.  
 
     
     
         43 . The manufacturing method of a holding seal material according to  claim 42 , wherein 
 in said bonding step, after the material solution of said ceramic adhesive has been supplied between the ceramic fibers forming said aggregation, said aggregation is heated to sinter specific components in said material solution so as to be formed into ceramics.    
     
     
         44 . The manufacturing method of a holding seal material according to  claim 42 , wherein 
 in said bonding step, after said aggregation has been impregnated with a water-soluble metal solution, which is said material solution, having a low viscosity, said aggregation is dried and heated so that the metal component in said solution is sintered to be formed into ceramics.    
     
     
         45 . The manufacturing method of a holding seal material according to  claim 44 , wherein 
 said water-soluble metal solution is supplied by an amount of 1 to 10% by weight of said aggregation.    
     
     
         46 . The manufacturing method of a holding seal material according to any of  claims 43  to  45 , wherein 
 said spinning stock solution of the ceramic fibers is a spinning stock solution of alumina-silica based fibers prepared by using an inorganic salt method, and said water-soluble metal solution is a water solution containing aluminum ions.  
 
     
     
         47 . A manufacturing method of the holding seal material according to any of  claims 37  to  41 , comprising: 
 a spinning step of obtaining precursor fibers by using a spinning stock solution of ceramic fibers as a material;  
 a molding step of allowing said precusor fibers to aggregate three-dimensionally, thereby forming into a mat-shaped aggregation;  
 a liquid substance supplying step of allowing a liquid substance capable of being a ceramic adhesive later to adhere to portions at which said precursor fibers forming said aggregation are overlapped adjacent to each other; and  
 a firing step of heating said aggregation to sinter said precursor fibers and said liquid substance.  
 
     
     
         48 . The manufacturing method of a holding seal material according to  claim 47 , wherein 
 in said liquid substance supplying step, the aggregation including said precursor fibers of alumina-silica based fibers is put in a highly moistened environment with high moisture.    
     
     
         49 . The manufacturing method of a holding seal material according to  claim 47 , wherein 
 in said liquid substance supplying step, a non-aqueous liquid substance containing an inorganic element contained in said alumina-silica based fiber is atomized and supplied to the aggregation including the precursor fibers of the alumina-silica based fibers.    
     
     
         50 . The manufacturing method of a holding seal material according to any of  claims 47  to  49 , wherein 
 a cutting step of chopping the long fibers of said precursor fibers into a predetermined length to obtain short fibers is carried out between said spinning step and said molding step.  
 
     
     
         51 . A ceramic fiber aggregation wherein 
 three-dimensionally aggregated ceramic fibers are partially bonded to each other by a ceramic adhesive.    
     
     
         52 . A ceramic fiber aggregation comprising ceramic fibers having a branched structure.  
     
     
         53 . A ceramic fiber having a branched structure.  
     
     
         54 . A manufacturing method of an alumina fiber aggregation, comprising: 
 a spinning step of obtaining a continuous long-fiber precursor by using an alumina fiber stock solution used in an inorganic salt method as a material;    a chopping step of cutting said continuous long-fiber precursor into short-fiber precursors;    a mat preparing step of preparing a mat-shaped short fiber precursor by using thus obtained said short-fiber precursor; and    a firing step of firing said mat-shaped short fiber precursor to manufacture an alumina fiber aggregation.