Holding material for catalytic converter and method for producing the same

Abstract

A holding material for a catalytic converter is interposed in a gap between a catalyst carrier and a metal casing receiving the catalyst carrier. The holding material includes a mat including alumina fiber and mullite fiber, wherein the alumina fiber and the mullite fiber are unitarily collected to form the holding material having a predetermined thickness.

What is claimed is:  
     
         1 . A holding material for a catalytic converter, interposed in a gap between a catalyst carrier and a metal casing receiving the catalyst carrier, comprising: 
 a mat including alumina fiber and mullite fiber,    wherein the alumina fiber and the mullite fiber are unitarily collected to form the holding material having a predetermined thickness.    
     
     
         2 . The holding material according to  claim 1 , 
 wherein a first portion of the mat is a alumina fiber mat including alumina fiber and collected into a first thickness, and    wherein a second portion of the mat is a mullite fiber mat including mullite fiber and collected into a second thickness, and    wherein the alumina fiber mat is disposed on the mullite fiber mat to form a laminate and disposed on a side where the alumina fiber mat comes into contact with the catalyst carrier.    
     
     
         3 . The holding material according to  claim 2 , 
 wherein the laminate is shaped like a cylinder so that the alumina fiber mat is located on an inner side while the mullite fiber mat is located on an outer side.    
     
     
         4 . The holding material according to  claim 1 , 
 wherein the mat is a mixture of alumina fiber and mullite fiber collected into a shape having the predetermined thickness.    
     
     
         5 . The holding material according to  claim 4 , 
 wherein the mixture of alumina fiber and mullite fiber is molded into a shape corresponding to a contour shape of the catalyst carrier.    
     
     
         6 . The holding material according to  claim 4 , 
 wherein a mixture ratio of alumina fiber to mullite fiber is selected to be in a range of from 10:90 to 90:10.    
     
     
         7 . The holding material according to  claim 4 , 
 wherein at least one of the alumina fiber and the mullite fiber is partially replaced by at least one member selected from the group consisting of silica-alumina fiber, silica fiber, glass fiber, rock wool and biodegradable fiber.    
     
     
         8 . A method of producing a holding material for a catalytic converter, interposed in a gap between a catalyst carrier and a metal casing receiving the catalyst carrier, said method comprising the steps of: 
 preparing a first slurry including alunima fiber and a first organic binder;    preparing a second slurry containing mullite fiber and a second organic binder;    molding the first slurry by suction dehydration;    drying the first slurry to obtain an alumina fiber mat after molding the first slurry;    applying the second slurry on a surface of the alumina fiber mat after drying the first slurry;    molding the second slurry by suction dehydration to obtain a laminate of the alumina fiber mat and a mullite fiber mat;    drying the laminate.    
     
     
         9 . A method of producing a holding material for a catalytic converter, interposed in a gap between a catalyst carrier and a metal casing receiving the catalyst carrier, said method comprising the steps of: 
 forming a molding having one of a flat shape and a shape corresponding to a contour shape of the catalyst carrier by sucking and dehydrating an aqueous slurry including alumina fiber and mullite fiber; and    drying the molding.