Ceramic honeycomb filter and its production method
A ceramic honeycomb filter comprising a ceramic honeycomb structure having pluralities of flow paths partitioned by porous cordierite cell walls, and plugs formed in predetermined flow paths of the ceramic honeycomb structure; the plugs being formed by ceramic particles and an amorphous oxide matrix existing between the ceramic particles; in a cross section of the plugs, an area ratio A 1 of the amorphous oxide matrix in a longitudinal range of ⅓×t from one end, and an area ratio A 2 of the amorphous oxide matrix in a longitudinal range of ⅓×t from the other end meeting the relation of ½≤A 1 /A 2 ≤2, wherein t represents the length of the plug in a direction perpendicular to the longitudinal direction of the plug.
1. A method for producing a ceramic honeycomb filter comprising a ceramic honeycomb structure having pluralities of flow paths partitioned by porous cell walls made of a material comprising cordierite as a main crystal, and plugs formed in predetermined flow paths of said ceramic honeycomb structure; comprising
charging a plugging material comprising at least 100 parts by mass of ceramic particles, 5-20 parts by mass on a solid basis of colloidal oxide and 1.5-4 parts by mass of a binder into the predetermined flow paths of said ceramic honeycomb structure, and drying said plugging material by microwave heating or high-frequency dielectric heating to form said plugs;
said ceramic particles having a particle size distribution at least a first peak and a second peak lower than said first peak, said first peak being in a particle size range of 100-200 μm, and said second peak being in a particle size range of 10-30 μm.
2. The method for producing a ceramic honeycomb filter according to claim 1 , wherein after said plugging material is charged into the predetermined flow paths of said ceramic honeycomb structure, and before said microwave heating or high-frequency dielectric heating is conducted, an end surface of said ceramic honeycomb structure on the side that said plugging material is charged is preheated at 30-80° C. for 1-10 minutes with a heat-conducting means contacted.
3. The method for producing a ceramic honeycomb filter according to claim 1 , wherein said ceramic particles comprise 20-50% by mass of first ceramic particles having an average particle size of 90-200 μm, and 50-80% by mass of second ceramic particles having an average particle size of 5-30 μm.
4. The method for producing a ceramic honeycomb filter according to claim 1 , wherein said microwave heating is conducted by irradiating microwave with power of 1-30 W/g per a unit mass of said plugging material for 1-20 minutes.
5. The method for producing a ceramic honeycomb filter according to claim 1 , wherein said high-frequency dielectric heating is conducted by applying a high-frequency electric field with power of 1-20 W/g per a unit mass of said plugging material at a distance of 1-15 mm between an end surface of said ceramic honeycomb structure and a high-frequency electrode, for 1-5 minutes.
6. The method for producing a ceramic honeycomb filter according to claim 1 , wherein said colloidal oxide is colloidal silica.
7. The method for producing a ceramic honeycomb filter according to claim 1 , wherein said ceramic particles are based on cordierite.
8. The method for producing a ceramic honeycomb filter according to claim 1 , wherein said plugs are formed without sintering.