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A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through the porous partition walls to remove particulates from the exhaust gas, the predetermined flow paths among the flow paths being seal

A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through the porous partition walls to remove particulates from the exhaust gas, the predetermined flow paths among the flow paths being sealed at their ends, a catalyst being carried by the porous partition walls, the porous partition walls having a porosity of 60-75% and an average pore diameter of 15-25 μm when measured according to a mercury penetration method, and the maximum of a slope S n of a cumulative pore volume curve of the porous partition walls relative to a pore diameter obtained at an n-th measurement point being 0.7 or more, the S n being represented by the following formula (1): S n =−( V n −V n−1 )/[log D n −log ( D n−1 )]  (1), n is a pore diameter (μm) at an n-th measurement point, D n−1 is a pore diameter (μm) at an (n−1)-th measurement point, V n is a cumulative pore volume (cm 3 /g) at an n-th measurement point, and V n−1 is a cumulative pore volume (cm 3 /g) at an (n−1)-th measurement point.

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1. A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through said porous partition walls to remove particulates from said exhaust gas, the predetermined flow paths among said flow paths bein

1. A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through said porous partition walls to remove particulates from said exhaust gas, the predetermined flow paths among said flow paths being sealed at their ends, said porous partition walls having a porosity of 60-75% and an average pore diameter of 15-25 μm when measured according to a mercury penetration method, and the maximum of a slope S n of a cumulative pore volume curve of said porous partition walls relative to a pore diameter obtained at an n-th measurement point being 0.7 or more, said S n being represented by the following formula (1): S n =−( V n −V n−1 )/[log D n −log ( D n−1 )]  (1),wherein D n is a pore diameter (μm) at an n-th measurement point, D n−1 is a pore diameter (μm) at an (n−1)-th measurement point, V n is a cumulative pore volume (cm 3 /g) at an n-th measurement point, and V n−1 is a cumulative pore volume (cm 3 /g) at an (n−1)-th measurement point. 2. The ceramic honeycomb filter according to claim 1, wherein the maximum of the slope S n of the cumulative pore volume curve of said porous partition walls is 0.9 or more. 3. The ceramic honeycomb filter according to claim 1, wherein said porous partition walls have a porosity of 65-70%. 4. The ceramic honeycomb filter according to claim 1, wherein said porous partition walls have an average pore diameter of 18-22 μm. 5. The ceramic honeycomb filter according to claim 1, wherein said ceramic honeycomb structure is made of a porous ceramic having a main component chemical composition substantially comprising 42-56% by mass of SiO 2 , 30-45% by mass of Al 2 O 3 , and 12-16% by mass of MgO, a main component of its crystal phase being cordierite. 6. A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through said porous partition walls to remove particulates from said exhaust gas, the predetermined flow paths among said flow paths being sealed at their ends, flow paths near its outer peripheral wall being sealed by sealers at both ends, the length of said sealers from a filter end surface being 8.2% or less of the total length of said filter, and said flow paths having both ends sealed existing within a range of a radial length corresponding to 5 times the partition wall pitch at maximum from the outer periphery toward the center of said filter. 7. The ceramic honeycomb filter according to claim 1, wherein flow paths near its outer peripheral wall are sealed by sealers at both ends, the length of said sealers from a filter end surface is 8.2% or less of the total length of said filter, and said flow paths having both ends sealed exist within a range of a radial length corresponding to 5 times the partition wall pitch at maximum from the outer periphery toward the center of said filter. 8. A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through said porous partition walls to remove particulates from said exhaust gas, the predetermined flow paths among said flow paths being sealed at their ends, a pitch of said porous partition walls being 2.54 mm or less, at least some of said sealers sealing flow paths except for those near its outer periphery wall projecting from the end surfaces of said partition walls by 0.01-5 mm in a flow path direction. 9. The ceramic honeycomb filter according to claim 1, wherein a pitch of said porous partition walls is 2.54 mm or less, and at least some of said sealers sealing flow paths except for those near its outer periphery wall projecting from the end surfaces of said partition walls by 0.01-5 mm in a flow path direction. 1 0. The ceramic honeycomb filter according to claim 7, wherein a pitch of said porous partition walls is 2.54 mm or less, and at least some of said sealers sealing flow paths except for those near its outer periphery wall projecting from the end surfaces of said partition walls by 0.01-5 mm in a flow path direction. 11. A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through said porous partition walls to remove particulates from said exhaust gas, the predetermined flow paths among said flow paths being sealed at their ends, a catalyst being carried by said porous partition walls, said porous partition walls having a porosity of 60-75% and an average pore diameter of 15-25 μm when measured according to a mercury penetration method, and the maximum of a slope S n of a cumulative pore volume curve of said porous partition walls relative to a pore diameter obtained at an n-th measurement point being 0.7 or more, said S n being represented by the following formula (1): S n =−( V n −V n−1 )/[log D n −log ( D n−1 )]  (1),wherein D n is a pore diameter (μm) at an n-th measurement point, D n−1 is a pore diameter (μm) at an (n−1)-th measurement point, V n is a cumulative pore volume (cm 3 /g) at an n-th measurement point, and V n−1 is a cumulative pore volume (cm 3 /g) at an (n−1)-th measurement point. 12. The ceramic honeycomb filter according to claim 11, wherein flow paths near its outer peripheral wall are sealed by sealers at both ends, the length of said sealers from a filter end surface is 8.2% or less of the total length of said filter, and said flow paths having both ends sealed exist within a range of a radial length corresponding to 5 times the partition wall pitch at maximum from the outer periphery toward the center of said filter. 13. The ceramic honeycomb filter according to claim 11, wherein a pitch of said porous partition walls is 2.54 mm or less, and at least some of said sealers sealing flow paths except for those near its outer periphery wall projecting from the end surfaces of said partition walls by 0.01-5 mm in a flow path direction. 14. The ceramic honeycomb filter according to claim 12, wherein a pitch of said porous partition walls is 2.54 mm or less, and at least some of said sealers sealing flow paths except for those near its outer periphery wall projecting from the end surfaces of said partition walls by 0.01-5 mm in a flow path direction.