Process for producing cemented and skinned ceramic honeycomb structures
Organic polymer particles are provided in a cement composition that is used to apply a skin to a ceramic honeycomb, or to bond the ceramic honeycomb to another honeycomb or another material. The presence of the organic polymer particles reduces the penetration of the cement composition through porous walls of the honeycomb. In this way, less blocking of the honeycomb cells is seen, and the reduction in thermal shock performance that is often seen when cement compositions are applied to ceramic honeycombs is reduced.
1. A method for applying a cementitous layer onto a porous ceramic honeycomb structure, comprising the steps of (a) applying a cement composition to at least one porous surface of a ceramic honeycomb containing multiple axially-extending cells defined by intersecting porous walls and (b) firing the honeycomb and cement composition, wherein the cement composition comprises at least one inorganic binder, at least one inorganic filler, a carrier fluid and organic polymer particles having a size from about 10 nanometers to 250 nanometers dispersed in the carrier fluid.
2. The method of claim 1 , wherein the cement composition contains from 0.5 to 85% by weight of the organic polymer particles.
3. The method of claim 2 , wherein the cement composition contains from 1 to 5% by weight of the organic polymer particles.
4. The method of claim 2 , wherein the organic polymer particles are provided in the form of a latex.
5. The method of claim 4 , wherein the latex is the product of an emulsion polymerization.
6. The method of claim 4 , wherein the latex has a pH of at least 7.
7. The method of claim 6 , wherein the latex has a pH of from 8 to 9.5.
8. The method of claim 2 , wherein the organic polymer particles have a size of at least 25 nanometers.
9. The method of claim 1 , wherein the organic polymer particles have a size of 25 to 250 nanometers.
10. The method of claim 1 , wherein the inorganic binder includes colloidal silica, colloidal alumina or a mixture thereof.
11. The method of claim 1 , wherein the carrier fluid includes water, an alcohol or a mixture thereof.
12. The method of claim 1 , wherein the cement layer forms a peripheral skin on the ceramic honeycomb.
13. The method of claim 1 , wherein the cement layer adheres a ceramic honeycomb to another ceramic honeycomb.
14. The method of claim 1 wherein the firing step is performed at a temperature of from 800° C. to 1500° C.