A wet friction material includes a base including a matrix of fibers and filler particles embedded in the matrix of fibers; a binder embedded in an interior of the base; and a quaternary ammonium salt containing coating on an outer surface of the base. The quaternary ammonium salt containing coating can include a quaternary ammonium salt and a solution binder.

A phenol resin for a wet friction material of the invention contains a resol-type phenol resin having, in one molecule, a structural unit A which is derived from a phenol compound having one phenolic hydroxyl group and a structural unit B which is derived from a polyfunctional phenol compound having two phenolic hydroxyl groups.

A method for manufacturing a friction material containing a friction modifier, a fibrous material and a binder as raw materials is provided. The method includes a step of mixing and agitating the raw materials by low frequency acoustic agitation. A content of the fibrous material in the friction material may be 1 mass % or more and 50 mass % or less. The content of the fibrous material in the friction material may be 3 mass % or more and 40 mass % or less.

Disclosed is a wet friction member for use in a wet clutch that can achieve an increased coefficient of static friction (μs) between it and a counterpart surface in frictional contact with it. The wet friction member includes base paper that is formed using a fiber base material and a filler, and a binder for curing the base paper. The filler includes rubber particles made of at least one kind of highly lipophilic rubber material. The rubber particles contains carbon black for reinforcement.

A wet friction material includes a base including a matrix of fibers and filler particles embedded in the matrix of fibers; a binder embedded in an interior of the base; and a quaternary ammonium salt containing coating on an outer surface of the base. The quaternary ammonium salt containing coating can include a quaternary ammonium salt and a solution binder

The wet friction member 1 of the invention includes a core plate 2 formed in a flat ring shape, a friction part 3 arranged in a ring shape. The friction part 3 has segment pieces including rectangular shaped G.sub.1 to G.sub.4: G.sub.1 in which a lower right corner of rectangular piece is notched; G.sub.2 in which an upper left corner of rectangular piece is notched; G.sub.3 in which an upper right corner of rectangular piece is notched; G.sub.4 in which a lower left corner of rectangular piece is notched. The friction part 3 has arrangements T.sub.1 and T.sub.2: T.sub.1 in which G.sub.1 and G.sub.2 are arranged in a manner a right side of G.sub.1 and a left side of G.sub.2 face each other; T.sub.2 in which G.sub.3 and G.sub.4 are arranged in a manner a right side of the G.sub.3 and a left side of G.sub.4 face each other.

A wet running friction lining includes a plastic matrix, which contains at least one filler. The wet running friction lining contains bentonite as a filler.

A method of making a wet friction material includes joining filler particles and fibers together and forming a base; coating an outer surface of the base with a quaternary ammonium salt containing solution; and drying the quaternary ammonium salt containing solution to form a quaternary ammonium salt containing coating on the outer surface of the base.

The invention relates to a method for improving braking performance of a microporous friction material under wet conditions. A hydrophobic agent is added into the components for preparing microporous friction material. The microporous friction material is prepared from the following raw materials in percentage by weight: 10%-20% of nano-silica modified phenolic resin, 4%-14% of butadiene-styrene rubber, 5%-15% of glass fiber, 2%-11% of aramid pulp, 4%-15% of aluminum borate whisker, 4%-10% of hydrophobic agent and 3%-8% of calcium silicate, 1%-8% of artificial graphite, 2%-8% of coke, 2%-7% of mica, 5%-10% of cryolite and 4%-10% of diatomite.

A method for producing a wet-running friction paper includes providing a fiber portion with a fiber, providing a filler portion with a filler, providing a binder portion with a phenol-resin-based binder, dissolving the binder portion to form a phenolate, and processing the fiber portion, the filler portion and the phenolate in a paper production process to form the wet-running friction paper.