Pollution control device and mat for mounting a pollution control element

Abstract

A mat for mounting a pollution control element (e.g., a catalytic converter and diesel particulate filter, etc.) that maintains support holding strength without impairing elasticity even when exposed to high temperatures in excess of 800° C. for long periods of time, and a pollution control device that includes such a mat. The mat comprises at least two layers, an alumina fiber layer and a ceramic fiber layer, that are formed into a single sheet without the use of an auxiliary bonding means.

1 . A mat for mounting a pollution control element in a pollution control device, said mat comprising at least an alumina fiber layer and a ceramic fiber layer, wherein the weight ratio of said alumina fiber layer to said ceramic fiber layer is 3:11-11:3 and said mat maintains holding strength even when exposed to high temperatures in excess of 800° C. for long periods of time.  
   
   
       2 . The mat according to  claim 1 , wherein said alumina fiber layer and said ceramic fiber layer form a single sheet without the use of an auxiliary bonding means.  
   
   
       3 . The mat according to  claim 1 , wherein the ceramic fibers that compose the ceramic fiber layer are annealed at a temperature of 700-1200° C.  
   
   
       4 . The mat according to  claim 1 , wherein the alumina fiber layer contains crystalline alumina fibers formed from a mixture containing alumina and silica, and the alumina content of that fiber is 50 wt % or more.  
   
   
       5 . The mat according to  claim 1 , wherein the ceramic fiber layer contains ceramic fibers formed from a mixture containing alumina and silica, and the silica content of that fiber is 45 wt % or more.  
   
   
       6 . The mat according to  claim 1 , wherein the alumina fiber layer and ceramic fiber layer are formed into a single sheet by preparing a slurry containing alumina fibers and a slurry containing ceramic fibers, adhering either of the slurries to a permeable substrate and partially dehydrating the adhered slurry to form a first layer, and then adhering the other slurry to the first layer and partially dehydrating that slurry to form a second layer.  
   
   
       7 . The mat according to  claim 1 , wherein said mat is for mounting a catalyst support in a catalytic converter.  
   
   
       8 . The mat according to  claim 1 , wherein neither said layer includes an expanding material.  
   
   
       9 . The mat according to  claim 1 , wherein said mat maintains its holding strength even when exposed to high temperatures in excess of 800° C. for 10 years as determined by extrapolation.  
   
   
       10 . A pollution control device comprising: 
 a housing;    a pollution control element mounted in said housing; and    a mat disposed between said housing and said pollution control element so as to mount said pollution control element in said housing, said mat comprising at least two layers, an alumina fiber layer and a ceramic fiber layer,    wherein the weight ratio of said alumina fiber layer to said ceramic fiber layer is 3:11-11:3 and said mat maintains holding strength even when exposed to high temperatures in excess of 800° C. for long periods of time.    
   
   
       11 . The pollution control device according to  claim 10 , wherein said alumina fiber layer and said ceramic fiber layer form a single sheet without the use of an auxiliary bonding means.  
   
   
       12 . The pollution control device according to  claim 10 , wherein the ceramic fibers that compose the ceramic fiber layer are annealed at a temperature of 700-1200° C.  
   
   
       13 . The pollution control device according to  claim 10 , wherein the alumina fiber layer contains crystalline alumina fibers formed from a mixture containing alumina and silica, and the alumina content of that fiber is 50 wt % or more.  
   
   
       14 . The pollution control device according to  claim 10 , wherein the ceramic fiber layer contains ceramic fibers formed from a mixture containing alumina and silica, and the silica content of that fiber is 45 wt % or more.  
   
   
       15 . The pollution control device according to  claim 10 , wherein the alumina fiber layer and ceramic fiber layer are formed into a single sheet by preparing a slurry containing alumina fibers and a slurry containing ceramic fibers, adhering either of the slurries to a permeable substrate and partially dehydrating the adhered slurry to form a first layer, and then adhering the other slurry to the first layer and partially dehydrating that slurry to form a second layer.  
   
   
       16 . The pollution control device according to  claim 10 , wherein neither said layer includes an expanding material.  
   
   
       17 . The pollution control device according to  claim 10 , wherein said mat maintains its holding strength even when exposed to high temperatures in excess of 800° C. for 10 years as determined by extrapolation.  
   
   
       18 . The pollution control device according to  claim 10 , wherein said pollution control device is a catalytic converter.  
   
   
       19 . The pollution control device according to  claim 10  in combination with an engine exhaust.  
   
   
       20 . The pollution control device according to  claim 10  in combination with an engine.