Patent ID: 8574334

Claim:
A method for producing a mat, comprising: preparing a sheet including inorganic fibrous substance precursors intertwined with each other, a first main face, a second main face opposite to the first main face, a first side face, and a second side face opposite to the first side face, each of the first and second main faces and the first and second side faces being defined by the inorganic fibrous substance precursors; piercing the sheet with first needles to form first intertwined portion precursors in such a manner that the first needles intersect with a first virtual straight line at a first angle of less than about 90° when viewed from the first side face to the second side face, the first virtual straight line being defined along a direction perpendicular to a thickness direction of the sheet; piercing the sheet with second needles to form second intertwined portion precursors in such a manner that the second needles intersect with the first virtual straight line at a second angle of more than about 90° and intersect with second virtual straight lines at a third angle when viewed from the first side face to the second side face, the second virtual straight lines being respectively defined along the first intertwined portion precursors; and firing the sheet to convert the inorganic fibrous substance precursors into inorganic fibrous substances after the sheet is pierced with the first and second needles.