Composition and method for making ceramic filters

Abstract

The channel-plugging of porous ceramic honeycombs to provide wall flow filter bodies therefrom is carried out using water-based cements comprising ceramic powders and soluble alkali metal silicates; the cements form durable plugs that are resistant to thermal and chemical damage upon drying and without firing.

1 . A cement composition for plugging a ceramic honeycomb consisting of a plastically shapeable blend comprising a ceramic powder, a water-soluble alkali metal silicate, and water.  
     
     
         2 . A cement composition in accordance with  claim 1  wherein the blend is essentially free of ceramic reinforcing fibers.  
     
     
         3 . A cement composition in accordance with  claim 1  wherein the alkali metal silicate is potassium silicate.  
     
     
         4 . A cement in accordance with  claim 1  wherein the ceramic powder consists essentially one or more powders selected from the group consisting of cordierite, silicon carbide, silicon nitride, aluminum titanate, clay, talc, alumina, and mixtures thereof.  
     
     
         5 . A cement in accordance with  claim 1  wherein the blend consists essentially of ceramic powder and an alkali metal silicate solution.  
     
     
         6 . A method for selectively plugging channels of a ceramic honeycomb comprising: introducing into the channels a plastically shapeable cement composition comprising a blend of a ceramic powder, a water-soluble alkali metal silicate, and water; and drying the cement composition to form solid plugs.  
     
     
         7 . A method in accordance with  claim 6  wherein the blend is essentially free of ceramic reinforcing fibers.  
     
     
         8 . A method in accordance with  claim 6  wherein the alkali metal silicate is potassium silicate.  
     
     
         9 . A method in accordance with  claim 6  wherein the ceramic powder consists essentially one or more powders selected from the group consisting of cordierite, silicon carbide, silicon nitride, aluminum titanate, clay, talc, alumina, and mixtures thereof.  
     
     
         10 . A method in accordance with  claim 6  wherein the blend consists essentially of ceramic powder and an alkali metal silicate solution.