US Patent 7309725 Fiber base material for wet friction material

A fibrous base material giving a wet frictional material used for clutch, differential gear, brake, etc. of cars, industrial machines, etc. having an excellent durability where plastic deformation of fiber and deterioration by acidic decomposition products of lubricant additives do not take place is provided. A fibrous base material for wet frictional materials which comprises a fiber component, a friction adjusting material and a filler, said fiber component containing 5 to 50% by weight of a homoacrylonitrile fiber where modulus of elasticity at 180° C. is not less than 10 cN/dtex and shrinking rate at 200° C. is within 5% and/or a homoacrylonitrile fiber in a pulp form prepared by fibrillation of said homoacrylonitrile fiber.