Abstract: A filter reinforcing material is disclosed that does not cause peeling or pleat adhesion at the time of pleating, is excellent in pleating, and has high stiffness. A filter reinforcing material includes a bonding layer comprising a thermal bonded nonwoven including thermal bondable short fibers, and a reinforcing layer comprising a nonwoven including high-melting fibers having a higher melting point than a melting point of the thermal bondable short fibers having the lowest melting point in the bonding layer by 30° C. or more. Further, the bonding layer preferably comprises two or more kinds of thermal bondable short fibers with a fineness difference of more than or equal to 5 dtex.

Abstract: It is provided that a pre-air-filter, for an internal combustion engine, which allows stiffness to be assured even when the weight is reduced, which also has excellent dust holding properties, and which has an excellent resistance to entry of water. A pre-air-filter for an internal combustion engine (1) contains a nonwoven fabric comprising a first fiber having a melting point of not lower than 80° C. and not higher than 200° C., a second fiber having a melting point of higher than the melting point of the first fiber by not less than 30° C., being crimped, and having a hollow structure, entanglement of the first fiber and the second fiber by needle punching, and fusion of partly or entirely melted first fiber and the second fiber. This pre-air-filter (1) is installed at an air-inlet-side of a main-air-filter (2).

Abstract: A nonwoven fabric for a filter excellent in cleaning efficiency and trapped matter retention volume is constructed by two or more different kinds of fibrous layers placed one over the other. The nonwoven fabric has an average pore size from 30 ?m inclusive to 60 ?m inclusive and a total pore area at 0.011 cm2/cm2 or more with respect to an entire surface of the nonwoven fabric. The average pore size is calculated according to a bubble point method as defined in ASTM F-316-80 with use of a Coulter Porometer II.

Abstract: A filter for an air cleaner is produced by impregnating a fiber web composed of one or more layers with a liquid binder in the form of solution, suspension, or emulsion. The impregnated fiber web is dried such that the solvent or dispersing medium on one side evaporates faster then that on the other side. As the result, more binder is deposited on one side than on the other side; in other words, a gradient of binder distribution is formed. The thus-produced filter has such a structure that the voids among fibers continuously change across the thickness, while fibers are bonded together by the binder. The filter thus produced can collect more dust than a conventional one.