Friction material and method for manufacturing the same

Abstract

Using a friction material composition comprising: a fiber; a friction adjusting material; a binding material; and an uncrosslinked rubber being solid at normal temperature (25° C.), a friction material is obtained, wherein an ambient compressibility in a piston-pressing direction is 2% or less at normal temperature (25° C.) and at 4 MPa, and a tan δ value in a sliding direction at −20° C. to 50° C. is 0.05 or larger. Thereby, a friction material which has high damping properties and acceptable brake noise, which can prevent a decrease in responsiveness when brakes are applied, and prevent a decrease in the feeling of effectiveness associated therewith, and which can suppress a decrease in the fuel efficiency and an increase in abrasion caused by the dragging occurring when the friction material is brought into contact with a brake rotor; and a method for producing the friction material, can be provided.

1 . A friction material obtainable by molding a friction material composition comprising: a fiber; a friction adjusting material; a binding material; and an uncrosslinked rubber being solid at normal temperature (25° C.),
 wherein an ambient compressibility is 2% or less when the friction material is compressed in a piston-pressing direction at normal temperature (25° C.) and at 4 MPa, and 
 a tan δ value in a sliding direction at −20° C. to 50° C. is 0.05 or larger. 
 
     
     
         2 . The friction material according to  claim 1 ,
 wherein a proportion of the uncrosslinked rubber is within the range of 0.5% to 10% by mass relative to the total amount of the friction material composition,   the fiber includes one kind, or two or more kinds selected from the group consisting of a metal fiber, an inorganic fiber and an organic fiber, a proportion of the metal fiber is 8% by mass or less relative to the total amount of the friction material composition, and   a proportion of an organic filler material in the friction adjusting material is 1% by mass or less relative to the total amount of the friction material composition.   
     
     
         3 . The friction material according to  claim 2 ,
 wherein the fiber includes metal fiber.   
     
     
         4 . The friction material according to  claim 2 ,
 wherein the fiber includes metal fiber in a proportion of 5% by mass or less relative to the total amount of the friction material composition.   
     
     
         5 . The friction material according to  claim 2 ,
 wherein an amount of the fiber is in a range of 1% to 50% by mass relative to the total amount of the friction material composition.   
     
     
         6 . The friction material according to  claim 2 ,
 wherein an amount of the fiber is in a range of 2% to 40% by mass relative to the total amount of the friction material composition.   
     
     
         7 . The friction material according to  claim 1 ,
 wherein an amount of the fiber is in a range of 1% to 50% by mass relative to the total amount of the friction material composition.   
     
     
         8 . The friction material according to  claim 1 ,
 wherein an amount of the fiber is in a range of 2% to 40% by mass relative to the total amount of the friction material composition.   
     
     
         9 . The friction material according to  claim 1 ,
 wherein the friction adjusting material comprises an inorganic filler material selected from the group consisting of zirconia, alumina, silica, barium sulfate, calcium carbonate, mica, potassium titanate, graphite, antimony trioxide, and antimony disulfide.   
     
     
         10 . The friction material according to  claim 1 ,
 wherein the friction adjusting material comprises an organic filler material comprises cashew dust.   
     
     
         11 . The friction material according to  claim 1 ,
 wherein the friction adjusting material comprises an organic filler material in a proportion of 1% by mass or less.   
     
     
         12 . The friction material according to  claim 1 ,
 wherein the friction adjusting material comprises an organic filler material in a proportion of 0.5% by mass or less.   
     
     
         13 . The friction material according to  claim 1 ,
 wherein an amount of the friction adjusting material is in a range of 35% to 95% by mass relative to the total amount of the friction material composition.   
     
     
         14 . The friction material according to  claim 1 ,
 wherein an amount of the friction adjusting material is in a range of 50% to 80% by mass relative to the total amount of the friction material composition.   
     
     
         15 . The friction material according to  claim 1 ,
 wherein the friction material is produced by a method comprising:   a mixing step of mixing a friction material composition comprising fiber, friction adjusting material, binding material, and uncrosslinked rubber at a proportion of 0.5% to 5% by mass relative to the total amount of the friction material composition to obtain a mixture;   a molding step of heat and press-molding the obtained mixture in a pressing direction to yield a molded product under conditions at which the binding material reacts and the uncrosslinked rubber flows perpendicularly to the pressing direction; and   a heat-treating step of heat-treating the molded product to cure the binding material in the molded product.   
     
     
         16 . The friction material according to  claim 15 , wherein, in the mixing step, the uncrosslinked rubber is mixed with all materials of the friction material composition other than the uncrosslinked rubber. 
     
     
         17 . The friction material according to  claim 15 , wherein, in the mixing step, the uncrosslinked rubber is mixed with a portion of materials of the friction material composition other than the uncrosslinked rubber, and then a mixed material is further mixed with a remaining material of the friction material composition. 
     
     
         18 . The friction material according to  claim 15 , wherein, in the molding step, the heat and press-molding is conducted at a temperature of 130° C. to 200° C. 
     
     
         19 . The friction material according to  claim 15 , wherein, in the molding step, the heat and press-molding is conducted at a molding pressure of 5 MPa to 40 MPa. 
     
     
         20 . The friction material according to  claim 15 , wherein, in the molding step, the heat and press-molding is conducted at a temperature of 130° C. to 200° C. and a molding pressure of 5 MPa to 40 MPa, for a molding time of 1 minute to 10 minutes.