Friction material composition
Provided is a friction material composition capable of giving friction materials which, although low in copper or copper-alloy content, have excellent fade resistance at high temperature and give a satisfactory pedal feeling during braking. The friction material composition has a binder, a fibrous base material, an inorganic filler, and an organic filler, and contains no copper or has a copper content of 0.5 mass or less. The inorganic filler contains two γ-alumina powders, i.e., a first γ-alumina powder, which has a median diameter (D 50 ) of 0.8-60 μm, and a second γ-alumina powder, which has a median diameter (D 50 ) of 80-400 μm.
1. A friction material composition, comprising: a binder; a fibrous base material; an inorganic filler; and an organic filler, and containing no copper or having a copper content of 0.5 mass % or less,
wherein the inorganic filler comprises two γ-alumina powders of a first γ-alumina powder having a median diameter (D 50 ) of 0.8-60 μm, and a second γ-alumina powder having a median diameter (D 50 ) of 80-400 μm, and
wherein the first γ-alumina powder contains a fraction classified to a particle diameter of 0.8 to 60 μm at a ratio of 50 volume % or more, and the second γ-alumina powder contains a fraction classified to a particle diameter of 80 to 400 μm at a ratio of 50 volume % or more.
2. The friction material composition as set forth in claim 1 , wherein a content of the first γ-alumina powder is 0.5 to 3.0 volume % and a content of the second γ-alumina powder is 0.5 to 2.0 volume %.
3. The friction material composition as set forth in claim 1 , wherein a difference in the median diameter (D 50 ) between the first γ-alumina powder and the second γ-alumina powder is 139 to 305 μm.
4. The friction material composition as set forth in claim 1 , wherein the content of a fraction of γ-alumina classified to a particle diameter of 0.8 to 60 μm is 0.25 to 3.0 volume % of the friction material composition, and the content of a fraction of γ-alumina classified to a particle diameter of 80 to 400 μm is 0.25 to 2.0 volume % of the friction material composition.
5. The friction material composition as set forth in claim 1 , wherein the ratio of a fraction classified to a particle diameter of 0.8 to 60 μm is 10 to 90 volume % and the ratio of a fraction classified to a particle diameter of 80 to 400 μm is 10 to 90 volume %, to the total amount of the γ-alumina powders contained in the friction material composition.
6. The friction material composition as set forth in claim 1 , wherein the ratio of a fraction of γ-alumina having a particle diameter exceeding 60 μm and less than 80 mμ is 20 volume % or less to the total amount of the γ-alumina powders contained in the friction material composition.
7. A friction material produced by a process comprising molding the friction material composition as set forth in claim 1 .
8. The friction material composition, comprising: a binder; a fibrous base material; an inorganic filler; and an organic filler, and containing no copper or having a copper content of 0.5 mass % or less,
wherein the inorganic filler comprises two γ-alumina powders of a first γ-alumina powder having a median diameter (D 50 ) of 0.8-60 μm, and a second γ-alumina powder having a median diameter (D 50 ) of 80-400 μm, and
wherein the ratio of a fraction of γ-alumina having a particle diameter exceeding 60 μm and less than 80 mμ is 20 volume % or less to the total amount of the γ-alumina powders contained in the friction material composition.
9. The friction material composition as set forth in claim 8 , wherein a content of the first γ-alumina powder is 0.5 to 3.0 volume % and a content of the second γ-alumina powder is 0.5 to 2.0 volume %.
10. The friction material composition as set forth in claim 8 , wherein a difference in the median diameter (D 50 ) between the first γ-alumina powder and the second γ-alumina powder is 139 to 305 μm.
11. The friction material composition as set forth in claim 8 , wherein the content of a fraction of γ-alumina classified to a particle diameter of 0.8 to 60 μm is 0.25 to 3.0 volume % of the friction material composition, and the content of a fraction of γ-alumina classified to a particle diameter of 80 to 400 μm is 0.25 to 2.0 volume % of the friction material composition.
12. The friction material composition as set forth in claim 8 , wherein the ratio of a fraction classified to a particle diameter of 0.8 to 60 μm is 10 to 90 volume % and the ratio of a fraction classified to a particle diameter of 80 to 400 μm is 10 to 90 volume %, to the total amount of the γ-alumina powders contained in the friction material composition.
13. A friction material produced by a process comprising molding the friction material composition as set forth in claim 8 .