Extruded porous substrate and products using the same

Abstract

A highly porous substrate is provided using an extrusion system. More particularly, the present invention enables the production of a highly porous substrate. Depending on the particular mixture, the present invention enables substrate porosities of about 60% to about 90%, and enables advantages at other porosities, as well. The extrusion system enables the use of a wide variety of fibers and additives, and is adaptable to a wide variety of operating environments and applications. Fibers, which have an aspect ratio greater than 1, are selected according to substrate requirements, and are typically mixed with binders, pore-formers, extrusion aids, and fluid to form a homogeneous extrudable mass. The homogeneous mass is extruded into a green substrate. The more volatile material is preferentially removed from the green substrate, which allows the fibers to form interconnected networks. As the curing process continues, fiber to fiber bonds are formed to produce a structure having a substantially open pore network. The resulting porous substrate is useful in many applications, for example, as a substrate for a filter or catalyst host, or catalytic converter.

1 . A porous ceramic substrate: 
 having a porosity in the range of about 60% to about 85%;    having a structure formed of bonded ceramic fibers and    the substrate produced by an extrusion process comprising: 
 mixing ceramic-material fiber with additives and a fluid to form an extrudable mixture;  
 extruding the extrudable mixture into a green substrate; and  
 curing the green substrate into the porous substrate.  
   
     
     
         2 . The porous ceramic substrate according to  claim 1 , further comprising sintered, crystal, or glass bonds between fibers.  
     
     
         3 . The porous ceramic substrate according to  claim 1 , wherein the cured porous ceramic substrate consists essentially of ceramic fibers.  
     
     
         4 . The porous ceramic substrate according to  claim 1 , wherein the cured porous ceramic substrate consists essentially of an open-pore network of ceramic fibers.  
     
     
         5 . The porous ceramic substrate according to  claim 1 , wherein the cured porous ceramic substrate has a pore-network such that substantial all pores are interconnected.  
     
     
         6 . A porous substrate having a porosity in the range of about 60% to about 90% and having a structure formed of bonded inorganic fibers, the substrate produced by an extrusion process comprising: 
 mixing an inorganic fiber with additives and a fluid to form an extrudable mixture;    extruding the extrudable mixture into a green substrate; and    curing the green substrate into the porous substrate.    
     
     
         7 . The porous substrate according to  claim 6 , wherein the curing step generates fiber-to-fiber bonds that form the structure.  
     
     
         8 . The porous substrate according to  claim 6 , wherein the bonds are formed by sintering or by formation of glass, glass-ceramic or ceramic bonds.  
     
     
         9 . The porous substrate according to  claim 6 , wherein the curing step generates fiber-to-fiber bonds that form an open pore network.  
     
     
         10 . The porous substrate according to  claim 6 , wherein the inorganic fibers have a distributed aspect ratio with a mode in the range of 3 to 1000.  
     
     
         11 . The porous substrate according to  claim 6 , wherein the inorganic fibers are selected from Table 1 of  FIG. 6 .  
     
     
         12 . The porous substrate according to  claim 6 , wherein the cured substrate has a detectable residue from burning off the additives.  
     
     
         13 . The porous substrate according to  claim 6 , wherein at least some fiber-to-fiber contacts do not form bonds.  
     
     
         14 . The porous substrate according to  claim 6 , wherein substantially all of the fiber-to-fiber contacts form bonds.  
     
     
         15 . The porous substrate according to  claim 6 , further including a first substrate section having a first porosity, and a second substrate section having a second porosity.  
     
     
         16 . The porous substrate according to  claim 6 , further including a first substrate section having a first density, and a second substrate section having a second density.  
     
     
         17 . The porous substrate according to  claim 6 , further including a first substrate section bonding using a first type of fiber-to-fiber bond, and a second substrate section using a second type of fiber-to-fiber bond.  
     
     
         18 . The porous substrate according to  claim 6 , wherein the inorganic fibers include crystalline, amorphous, glass, or ceramic materials.  
     
     
         19 . The porous substrate according to  claim 6 , wherein the inorganic fibers are metal fibers, metal-alloy or ceramic fibers.  
     
     
         20 . The porous substrate according to  claim 6 , wherein the extrudable mixture further comprises organic fibers.  
     
     
         21 . A porous substrate with about 40% to about 75% porosity having been extruded from an extrudable mixture that did not comprise any functionally effective pore former component.  
     
     
         22 . An extruded porous substrate consisting essentially of bonded fibers.  
     
     
         23 . The substrate according to  claim 22  wherein the fibers consist essentially of ceramic fibers.  
     
     
         24 . The substrate according to  claim 23 , further including solid state, crystalline, or glass bonds between ceramic fibers.  
     
     
         25 . The substrate according to  claim 24  wherein the bonded ceramic fibers form an open pore network.  
     
     
         26 . The porous substrate according to  claim 23 , wherein the ceramic fibers have a distributed aspect ratio with a mode in the range of 3 to 1000.  
     
     
         27 . The porous substrate according to  claim 23 , wherein the ceramic fibers are selected from Table 1 of  FIG. 6 .  
     
     
         28 . The porous substrate according to  claim 22 , further including parallel inlet and outlet channels in a honeycomb pattern.  
     
     
         29 . The porous substrate according to  claim 22 , further including parallel inlet and outlet channels, and the inlet channels are larger than the outlet channels.  
     
     
         30 . The porous substrate according to  claim 22 , wherein the porous substrate is a block having random channels.  
     
     
         31 . A filter product, comprising: 
 an extruded substrate having an open pore network formed by bonded fibers;    a housing for holding the substrate;    an inlet for receiving a fluid and an outlet for providing a filtered fluid.    
     
     
         32 . The filter product according to  claim 31 , wherein the fluid is an exhaust gas or a liquid.  
     
     
         33 . The filter product according to  claim 31 , wherein the filter product is a vehicle air filter, a vehicle exhaust filter, or a vehicle cabin filter.  
     
     
         34 . The filter product according to  claim 31 , further comprising a catalyst disposed on the extruded substrate.  
     
     
         35 . A catalytic converter product, comprising: 
 an extruded substrate having an open pore network formed by bonded fibers;    a catalyst disposed on the extruded substrate;    a housing for holding the substrate;    an inlet for receiving a fluid and an outlet for providing a filtered fluid.    
     
     
         36 . The catalytic converter product according to  claim 35 , wherein the fluid is an exhaust gas or a liquid.  
     
     
         37 . The catalytic converter product according to  claim 35 , wherein the filter product is a vehicle air filter, a vehicle exhaust filter, or a vehicle cabin filter.  
     
     
         38 . The catalytic converter product according to  claim 35 , further comprising a catalyst disposed on the extruded substrate.