Compositions for applying to ceramic honeycomb bodies
Disclosed are compositions for applying to honeycomb bodies. The compositions can be used as plugging mixtures for forming a ceramic wall flow filter. Alternatively, the compositions can be used to form skin coatings on exterior portions of a honeycomb body. The disclosed compositions include an inorganic powder batch composition, an organic binder, a liquid vehicle, and a rheology modifier. The compositions exhibit improved rheological properties, including an increased yield strength and reduced viscosity under shear, which, among various embodiments, can enable the manufacture of sintered phase end plugs having reduced levels of dimple and pinhole formations in the final dried and fired end plugs as well as end plugs having relatively uniform and desired depths. Also disclosed are methods for forming end plugged ceramic wall flow filters from the plugging mixtures disclosed herein.
1. A method for manufacturing a porous ceramic wall flow filter, comprising the steps of:
providing an already fired ceramic honeycomb structure defining a plurality of cell channels bounded by porous channel walls that extend longitudinally from an upstream inlet end to a downstream outlet end;
selectively plugging an end of at least one predetermined channel with a plugging mixture which exhibits a capillary viscosity less than 8000 Pa-s when measured at a shear rate of 10/sec to form a honeycomb body; and
heating the end plugged honeycomb body at a temperature of at least 50° C. for a period of time sufficient to at least substantially remove the liquid vehicle from the plugging mixture; and then
firing the selectively plugged honeycomb body to a peak plug firing temperature of at least 400° C., the peak plug firing temperature being lower than a peak firing temperature of the already fired ceramic honeycomb structure, effective to set or cure the plugging material in the at least one selectively plugged channel;
wherein the plugging mixture also exhibits an inclined plane flow rate less than 60mm/8min when measured at an angle of 60 degrees; and
wherein the plugging mixture comprises: an inorganic batch composition; a binder; a liquid vehicle; and a rheology modifier selected from the group consisting of an oil, a non-ionic surfactant, and combinations thereof; and
wherein the rheology modifer comprises a polyethylene glycol 200 dioleate.
2. The method of claim 1 , wherein the rheology modifier comprises an oil.
3. The method of claim 1 , wherein the rheology modifier comprises peanut oil, soybean oil, or vegetable oil.
4. The method of claim 1 , wherein the inorganic batch composition comprises cordierite.
5. The method of claim 4 , wherein the cordierite comprises a blend of a first powdered cordierite having a median particle size in the range of from 35 μm to 45 μm and a second powdered cordierite having a median particle size in the range of from 10 μm to 20 μm.
6. The method of claim 4 , wherein the inorganic batch further comprises a borosilicate glass.
7. The method of claim 1 , wherein the binder component comprises colloidal silica, colloidal alumina, or a combination thereof.
8. The method of claim 1 , wherein the inorganic batch composition is an aluminum titanate forming batch composition, comprising an alumina source, a silica source, and a titania source.
9. The method of claim 1 , wherein the inorganic batch composition is a cordierite forming batch composition, comprising a magnesium oxide source; an alumina source; and a silica source.
10. The method of claim 1 , wherein the rheology modifier is present as a super addition in an amount in the range of from 0.1 weight percent to 15 weight percent relative to the inorganic batch composition.
11. The method of claim 1 wherein the firing results in the formation of a sintered phase ceramic plug in the at least one selectively plugged channel.
12. The method of claim 1 wherein the plugging material has a depth of 5 to 10 mm.
13. A method for manufacturing a porous ceramic wall flow filter, comprising the steps of:
providing an already fired ceramic honeycomb structure defining a plurality of cell channels bounded by porous channel walls that extend longitudinally from an upstream inlet end to a downstream outlet end;
selectively plugging an end of at least one predetermined channel with a plugging mixture which exhibits a capillary viscosity less than 8000 Pa·s when measured at a shear rate of 10/sec to form a honeycomb body; and
heating the end plugged honeycomb body at a temperature of at least 50° C. for a period of time sufficient to at least substantially remove the liquid vehicle from the plugging mixture; and then
firing the selectively plugged honeycomb body to a peak plug firing temperature of at least 400° C., the peak plug firing temperature being lower than a peak firing temperature of the already fired ceramic honeycomb structure, effective to set or cure the plugging material in the at least one selectively plugged channel;
wherein the plugging mixture also exhibits an inclined plane flow rate less than 60mm/8min when measured at an angle of 60 degrees; and
wherein the plugging mixture comprises: an inorganic batch composition; a binder; a liquid vehicle; and a rheology modifier comprising a polyethylene glycol 200 dioleate.
14. The method of claim 13 , wherein the inorganic batch composition comprises cordierite.
15. The method of claim 14 , wherein the cordierite comprises a blend of a first powdered cordierite having a median particle size in the range of from 35 μm to 45 μm and a second powdered cordierite having a median particle size in the range of from 10 μm to 20 μm.
16. A method for manufacturing a porous ceramic wall flow filter, comprising the steps of:
providing an already fired ceramic honeycomb structure defining a plurality of cell channels bounded by porous channel walls that extend longitudinally from an upstream inlet end to a downstream outlet end;
selectively plugging an end of at least one predetermined channel with a plugging mixture which exhibits a capillary viscosity less than 8000 Pa·s when measured at a shear rate of 10/sec to form a honeycomb body; and
heating the end plugged honeycomb body at a temperature of at least 50° C. for a period of time sufficient to at least substantially remove the liquid vehicle from the plugging mixture; and then
firing the selectively plugged honeycomb body to a peak plug firing temperature of at least 400° C., the peak plug firing temperature being lower than a peak firing temperature of the already fired ceramic honeycomb structure, effective to set or cure the plugging material in the at least one selectively plugged channel;
wherein the plugging mixture also exhibits an inclined plane flow rate less than 60mm/8min when measured at an angle of 60 degrees; and
wherein the plugging mixture comprises: an inorganic batch composition; a binder; a liquid vehicle; and a rheology modifier selected from the group consisting of an oil, a non-ionic surfactant, and combinations thereof, wherein the inorganic batch composition comprises cordierite comprising a blend of a first powdered cordierite having a median particle size in the range of from 35 μm to 45 μm and a second powdered cordierite having a median particle size in the range of from 10 μm to 20 μm; and wherein the rheology modifier comprises a polyethylene glycol 200 dioleate.
17. The method of claim 16 , wherein the rheology modifier comprises an oil.