Holding seal material for catalytic converter and method of manufacturing the holding and seal material

Abstract

A holding and sealing material ( 1 ) for a catalytic converter is disposed between a cylindrical catalyst carrier ( 3 ) and a metal shell ( 2 ) covering the outer periphery of the catalyst carrier ( 3 ). The holding and sealing material ( 1 ) comprises a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 10 wt % or less, and the fiber aggregate is subjected to a needle punch treatment. Owing to the improved holding and sealing material, a catalytic converter having excellent durability and assemblage and having extremely low pollution characteristics is provided.

1 . A holding and sealing material ( 1 ) disposed between a catalyst carrier ( 3 ) and a metal shell ( 2 ) covering the catalyst carrier, the holding and sealing material ( 1 ) comprising a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 10 wt % or less, and the fiber aggregate having been subjected to a needle punch treatment.  
     
     
         2 . A holding and sealing material ( 1 ) disposed between a catalyst carrier ( 3 ) and a metal shell ( 2 ) covering the catalyst carrier, the holding and sealing material ( 1 ) comprising a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 0.5 to 4 wt %, and the fiber aggregate having been subjected to a needle punch treatment.  
     
     
         3 . The holding and sealing material according to  claim 1  or  2 , wherein said alumina-silica based ceramic fibers have a chemical composition with the alumina content being 68 wt % to 83 wt % and the silica content being 17 wt % to 32 wt %.  
     
     
         4 . The holding and sealing material according to any one of  claims 1  to  3 , wherein the seal material disposed between the catalyst carrier ( 3 ) and the metal shell ( 2 ) generates a contact pressure of 0.02 MPa or more.  
     
     
         5 . The holding and sealing material according to any one of  claims 1  to  4 , wherein the abundance density of said needle punch spots is from 10 to 500 spots per 100 cm 2 .  
     
     
         6 . A holding and sealing material ( 1 ) disposed between a catalyst carrier ( 3 ) and a metal shell ( 2 ) covering the catalyst carrier, the holding and sealing material comprising a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 10% or less, with some of said ceramic fibers intertwined in the direction of thickness of said fiber aggregate.  
     
     
         7 . A method for manufacturing a holding and sealing material ( 1 ) for a catalytic converter disposed between a catalyst carrier ( 3 ) and a metal shell ( 2 ) covering the catalyst carrier, the method comprises the steps of: 
 performing fiber spinning using as a raw material an aqueous solution composed of a mixture of an aluminum salt, a silica sol and an organic polymer to prepare alumina-silica based ceramic fibers;    stacking the alumina-silica based ceramic fibers to prepare a fiber aggregate:    subjecting said fiber aggregate to a needle punch treatment; and    baking said fiber aggregate subjected to the needle punch treatment to prepare a holding and sealing material ( 1 ) comprising a fiber aggregate having a mullite crystal content of 10 wt % or less.    
     
     
         8 . The method for manufacturing a holding and sealing material according to  claim 7 , wherein the baking temperature in said baking step is 1100° C. to 1300° C.  
     
     
         9 . The method for manufacturing a holding and sealing material according to  claim 8 , wherein the baking time in said baking step is 1 to 60 minutes.  
     
     
         10 . A catalytic converter ( 5 ) comprising: 
 a catalyst carrier ( 3 );    a metal shell ( 2 ) covering said catalyst carrier; and    a holding and sealing material ( 1 ) disposed between the catalyst carrier ( 3 ) and the metal shell ( 2 ), the holding and sealing material ( 1 ) including a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 10 wt % or less, and the fiber aggregate having been subjected to a needle punch treatment.    
     
     
         11 . A catalytic converter ( 5 ) comprising: 
 a catalyst carrier ( 3 );    a metal shell ( 2 ) covering said catalyst carrier; and    a holding and sealing material ( 1 ) disposed between the catalyst carrier ( 3 ) and the metal shell ( 2 ), the holding and sealing material ( 1 ) including a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 0.5 to 4 wt %, and the fiber aggregate having been subjected to a needle punch treatment.    
     
     
         12 . The catalytic converter according to  claim 10  or  11 , wherein said alumina-silica based ceramic fibers have a chemical composition with the alumina content being 68 wt % to 83 wt % and the silica content being 17 wt % to 32 wt %.  
     
     
         13 . The catalytic converter according to any one of  claims 10  to  12 , wherein contact pressure generated in the seal material disposed between the catalyst carrier ( 3 ) and the metal shell ( 2 ) is 0.02 MPa or more.  
     
     
         14 . The catalytic converter according to any one of  claims 10  to  13 , wherein the abundance density of said needle punch spots is 10 to 500 spots per 100 cm 2 .  
     
     
         15 . A catalytic converter ( 5 ) comprising: 
 a catalyst carrier ( 3 );    a metal shell ( 2 ) covering said catalyst carrier; and    a holding and sealing material ( 1 ) disposed between the catalyst carrier ( 3 ) and the metal shell ( 2 ), said holding and sealing material including a fiber aggregate mainly comprised of alumina-silica based ceramic fibers having a mullite crystal content of 10% or less, with some of said ceramic fibers intertwined in the direction of thickness of said fiber aggregate.