TECHNICAL FIELD

The present invention relates to a porous material, a honeycomb structure, and a method of producing a porous material. More specifically, the present invention relates to a high-strength porous material, a high-strength honeycomb structure, and a method of producing the porous material.

BACKGROUND ART

Porous materials with a plurality of pores, in which an aggregate such as silicon carbide particles (SiC particles) is bound together with a binding material as an oxide phase such as cordierite, have excellent properties such as high thermal shock resistance. These porous materials are used to form honeycomb structures that include a plurality of cells partitioned off and formed by partition walls, and these honeycomb structures are used as catalyst carriers or diesel particulate filters (DPFs) in various applications such as processing for purifying exhaust gases (see Japanese Patent Nos. 4111439 and 4227347, for example).

The Japanese Patent No. 5478259 discloses a silicon carbide porous body that contains silicon carbide particles as an aggregate and an oxide as a binding material and in which the amount of the added oxide to the surface area of the silicon carbide particles is greater than or equal to 0.5 g/m2and less than 3.0 g/m2, and the oxide contains Si elements and Sr. Japanese Patent Application Laid-Open (Translation of PCT Application) No. 2016-523800 describes that a formed ceramic substance used as a support for catalysts desirably retains a low sodium content in order to maintain high catalytic activity.

In recent years, some applications have demanded large-sized catalyst carriers or DPFs using the above-described porous materials. Thus, large-sized honeycomb structures are produced, which have large honeycomb diameters and long axial lengths (honeycomb lengths). On the other hand, honeycomb structures other than large-sized honeycomb structures are also produced, such as those having complicated cell structures in order to improve functionality and performance, and those having thin partition walls that partition off and form cells in order to suppress pressure loss.

These honeycomb structures are subjected to heavy thermal loads or dynamic loads during use. Hence, the honeycomb structures formed of the porous materials are required to have adequate strength (mechanical strength) for dynamic loads, in addition to high thermal shock resistance.

SUMMARY OF INVENTION

The present invention is intended for a porous material, and it is an object of the present invention to increase the mechanical strength of the porous material.

A porous material according to the present invention includes an aggregate, and a binding material that binds the aggregate together in a state where pores are formed. The porous material contains 0.1 to 10.0 mass % of an MgO component, 0.5 to 25.0 mass % of an Al2O3component, and 5.0 to 45.0 mass % of an SiO2component with respect to a mass of the porous material as a whole, and further contains 0.01 to 5.5 mass % of an Sr component in terms of SrO.

Another porous material according to the present invention includes an aggregate, and a binding material that binds the aggregate together in a state where pores are formed. The binding material contains 5.0 to 15.0 mass % of an MgO component, 30.0 to 60.0 mass % of an Al2O3component, and 30.0 to 55.0 mass % of an SiO2component with respect to a mass of the binding material as a whole, and further contains 0.3 to 15.0 mass % of an Sr component in terms of SrO.

According to the present invention, it is possible to increase the mechanical strength of the porous material.

In a preferred embodiment of the present invention, the binding material contains 50 mass % or more of cordierite with respect to a mass of the binding material as a whole.

In another preferred embodiment of the present invention, the ratio of the mass of the binding material to the mass of the porous material as a whole is in a range of 8 to 40 mass %.

In another preferred embodiment of the present invention, an alkali metal component is contained in the porous material, and a ratio of a mass of the alkali metal component in terms of an oxide is less than 0.1 mass % of the porous material as a whole.

For example, the porous material contains Na or K as the alkali metal component.

In another preferred embodiment of the present invention, the aggregate contains SiC particles as particle bodies.

In this case, it is preferable that the aggregate further contains oxide films that are formed on surfaces of the particle bodies, and more preferably, the oxide films contain cristobalite. The oxide films have a thickness of, for example, 0.3 to 5.0 μm.

Preferably, at least part of the Sr component contained in the binding material exists as SrAl2Si2O8. The ratio of the mass of the SrAl2Si2O8to the mass of the porous material as a whole is in a range of 0.1 to 10.0 mass %.

It is preferable that a representative value for an angle at which an edge of the binding material in a cross-section of the porous material rises with respect to a direction tangent to the edge at a position at which curvature is locally a maximum is greater than 0 degrees and less than or equal to 25 degrees.

The present invention is also intended for a honeycomb structure. The honeycomb structure according to the present invention is a tubular member made of the porous material described above and having an interior partitioned into a plurality of cells by partition walls.

The present invention is also intended for a method of producing a porous material. A method of producing a porous material according to the present invention includes a) obtaining a compact by molding a mixture of an aggregate raw material, a raw material of binding material, and a pore forming material, and b) obtaining a porous material by firing the compact, the porous material being a fired compact. The porous material contains 0.1 to 10.0 mass % of an MgO component, 0.5 to 25.0 mass % of an Al2O3component, and 5.0 to 45.0 mass % of an SiO2component with respect to a mass of the porous material as a whole, and further contains 0.01 to 5.5 mass % of an Sr component in terms of SrO.

Another method of producing a porous material according to the present invention includes a) obtaining a compact by molding a mixture of an aggregate raw material, a raw material of binding material, and a pore forming material, and b) obtaining a porous material by firing the compact, the porous material being a fired compact. A binding material of the porous material contains 5.0 to 15.0 mass % of an MgO component, 30.0 to 60.0 mass % of an Al2O3component, and 30.0 to 55.0 mass % of an SiO2component with respect to a mass of the binding material as a whole, and further contains 0.3 to 15.0 mass % of an Sr component in terms of SrO.

Preferably, the method of producing a porous material further includes c) subjecting the porous material to oxidation treatment, and the aggregate raw material contains SiC particles. The temperature of the oxidation treatment in the operation c) is in a range of, for example, 1200 to 1350° C.

These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

