Mat, holding sealing material, method for producing mat, and exhaust gas purifying apparatus

1. 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.

2. The method for producing a mat according to claim 1 ,

wherein the first and second needles each include a finely tapered tip and barbs.

3. The method for producing a mat according to claim 1 ,

wherein in the piercing of the sheet, a minimum distance between one needle piercing point and a nearest needle piercing point to the one needle piercing point is from about 1 mm to about 10 mm.

4. The method for producing a mat according to claim 1 ,

wherein in the piercing of the sheet, a diameter of each of the needle piercing points is from about 0.1 mm to about 2 mm.

5. An exhaust gas purifying apparatus comprising:

an exhaust gas treating body;

a casing accommodating the exhaust gas treating body; and

a holding sealing material disposed between the exhaust gas treating body and the casing and holding the exhaust gas treating body, the holding sealing material comprising a mat produced by a method 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, the first and second main faces and the first and second side faces being each 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.

6. The exhaust gas purifying apparatus according to claim 5 ,

wherein the exhaust gas treating body includes a catalyst.