Ceramic honeycomb structure and its production method
A ceramic honeycomb structure including large numbers of flow paths partitioned by porous cell walls; (a) the cell walls having porosity of 55-65%; and (b) in a pore diameter distribution in the cell walls measured by mercury porosimetry, (i) a pore diameter at a cumulative pore volume corresponding to specific percentages of the total pore volume being within specific ranges and satisfying specific relationships; (ii) the difference of a logarithm of the pore diameter at a cumulative pore volume corresponding to 20% of the total pore volume and a logarithm of the pore diameter at 80% being 0.39 or less; and (iii) the volume of pores of more than 100 μm being 0.05 cm 3 /g or less.
1. A method for producing a ceramic honeycomb structure comprising the steps of extruding a moldable material comprising a ceramic material, and a pore-forming material constituted by hollow resin particles, to form a predetermined green body, and drying and sintering said green body;
said moldable material comprising 3-9% by mass of said pore-forming material per 100% by mass of said ceramic material;
in a curve of a cumulative volume to a particle diameter in said pore-forming material, a median particle diameter D50 being 35-53 μm, a particle diameter D5 at a cumulative volume corresponding to 5% of the total volume being 12-27 μm, a particle diameter D10 at a cumulative volume corresponding to 10% of the total volume being 15-30 μm, a particle diameter D90 at a cumulative volume corresponding to 90% of the total volume being 58-75 μm, a particle diameter D95 at a cumulative volume corresponding to 95% of the total volume being 65-85 μm, and D50/(D90−D10) being 0.85-1.30;
said ceramic material comprising 15-25% by mass of silica, 40-43% by mass of talc, and 15-30% by mass of alumina, based on 100% by mass of said ceramic material;
said silica having a median particle diameter D50 of 15-30 μm, D10 of 10-20 μm, and D90 of 40-60 μm, the percentage of particles having diameters of 5 μm or less being 1% or less by mass, the percentage of particles having diameters of 10 μm or less being 3% or less by mass, the percentage of particles having diameters of 100 μm or more being 3% or less by mass, and the percentage of particles having diameters of 200 μm or more being 1% or less by mass, and a particle diameter distribution deviation SD [=log(D80)−log(D20)] being 0.4 or less, wherein D20 represents a particle diameter at a cumulative volume corresponding to 20% of the total volume, D80 represents a particle diameter at a cumulative volume corresponding to 80% of the total volume, in a curve of a cumulative volume to a particle diameter, and D20<D80;
said talc having a median particle diameter D50 of 5-15 μm, D10 of 10 μm or less, and D90 of 25 μm or more; and
said alumina having a median particle diameter D50 of 3-10 μm, and D90 of 60 μm or less.
2. The method for producing a ceramic honeycomb structure according to claim 1 , wherein said moldable material comprises 4-8% by mass of said pore-forming material per 100% by mass of said ceramic material.