Ceramic honeycomb structure and its production method
A ceramic honeycomb structure having pluralities of flow paths partitioned by porous cell walls; (a) the cell walls having porosity of 50-60%; and (b) in a pore diameter distribution in the cell walls measured by mercury porosimetry, (i) pore diameters at cumulative pore volumes corresponding to particular percentages of the total pore volume being within specific ranges and having specific relationships; and (ii) the difference between 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 its production method.
1. A method for producing a ceramic honeycomb structure comprising the steps of extrusion-molding a moldable material comprising a ceramic material and hollow resin particles as a pore-forming material to 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;
said pore-forming material having a median particle diameter D50 of 20-53 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 50-75 μm, a particle diameter D95 at a cumulative volume corresponding to 95% of the total volume being 60-90 μm, and D50/(D90-D10) being 0.85-1.30, in a curve of a cumulative volume to a particle diameter;
said ceramic material comprising 15-25% by mass of silica, 40-43% by mass of talc, and 15-30% by mass of alumina, per 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, 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, and D20<D80, in a curve of a cumulative volume to a particle diameter;
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 3-6 μm, and D90 of 20 μm or less, the percentage of particles having diameters of 25 μm or more being 0.4% or less by mass.
2. The method for producing a ceramic honeycomb structure according to claim 1 , wherein said moldable material comprises 3.5-8% by mass of said pore-forming material per 100% by mass of said ceramic material.