Friction material composition and friction material

Abstract

A friction material composition including a fiber base material, a friction modifier and a binder. A content of copper in the friction material composition is 0.5% by mass or less. The friction material composition includes a partially graphitized coke and muscovite. A friction material is formed by molding the friction material composition.

Claims

1. A friction material composition comprising a fiber base material, a friction modifier and a binder, wherein a content of copper in the friction material composition is 0.5% by mass or less and the friction material composition comprises a partially graphitized coke and muscovite, wherein the content of the partially graphitized coke is from 3% by mass to 8% by mass based on the whole amount of the friction material composition and a content of the muscovite is from 1% by mass to 6% by mass based on the whole amount of the friction material composition.

2. The friction material composition according to claim 1, wherein the binder is from 7% by mass to 12% by mass of a whole amount of the friction material composition.

3. The friction material composition according to claim 1, wherein an average particle diameter of the partially graphitized coke is from 0.1 mm to 1.0 mm.

4. The friction material composition according to claim 1, wherein an average particle diameter of the muscovite is from 5 m to 50 m.

5. The friction material composition according to claim 1, wherein the friction modifier comprises 0.5% by mass to 3% by mass of zinc powder.

6. The friction material composition according to claim 5, wherein the zinc powder has an average particle diameter of 2 m to 20 m.

7. A friction material formed by molding the friction material composition as described in claim 1.

Description

EXAMPLES

(1) The present invention is described more specifically below by referring to Examples, but the scope of the present invention is not limited only to these Examples.

Examples 1 to 7 and Comparative Examples 1 to 4

Preparation of Friction Material

(2) The blending materials shown in Tables 1 and 2 were collectively put in a mixer, followed by mixing. Thereafter, each of the obtained mixtures was processed through steps of preforming (1), thermoforming (2), heating and grinding (3), etc., thereby preparing a friction material (brake pad).

(3) (1) Preforming

(4) The mixture above was put in the mold for preforming press, followed by forming at room temperature under 20 MPa for 10 seconds, thereby preparing a preformed article.

(5) (2) Thermoforming

(6) This preformed article was put in a thermoforming mold, and a metal plate (pressure plate: P/P) previously coated with an adhesive was laminated thereon, followed by thermocompression-forming at 150 C. under 45 MPa for 5 minutes.

(7) (3) After this thermocompression-formed body was heat-treated at 250 C. for 3 hours, grinding was performed so as to have a predetermined thickness of 17.0 mm, and coating was performed, thereby obtaining a friction material (brake pad).

(8) <Friction Material Evaluation Test>

(9) Using the prepared frictions materials of Examples 1 to 7 and Comparative Examples 1 to 4, evaluation of rotor attack, measurement of compression deformation amount (compression strain), evaluation of pedal feeling, friction performance (effect performance) test, wear performance test, and squeal test were performed. The results obtained are also shown in Tables 1 and 2. In the following, the base material indicates the conventional friction material containing copper (Comparative Example 2).

(10) (1) Evaluation of Rotor Attack

(11) The brake pad was processed into a test piece of 20 mm30 mm and pressed against a rotor at 60 km/h and a pressure of 0.02 MPa for 40 hours and thereafter, the wear amount of the rotor was checked and evaluated according to the following evaluation criteria:

(12) [Evaluation Criteria]

(13) A: Base material+less than 5%

(14) B: Base material+5% or more and less than 10%

(15) C: Base material+10% or more

(16) (2) Measurement of Compression Deformation Amount (Compression Strain)

(17) In conformity with JIS D4413, the compression deformation amount (compression strain) (mm) when applying a load of 2 MPa, 4 MPa, 6 MPa, 8 MPa and 10 MPa was measured, respectively.

(18) (3) Evaluation of Pedal Feeling

(19) By using the measurement result of compression strain in the evaluation of 4 MPa in the measurement of compression deformation amount (compression strain) above, the pedal feeling was evaluated according to the following evaluation criteria:

(20) [Evaluation Criteria]

(21) A: The variation from base material is within 30%.

(22) B: The variation from base material is more than 30% and less than 35%.

(23) C: The variation from base material is 35% or more.

(24) (4) Friction Performance Test (Effect Test)

(25) The test was performed in conformity with JASO C406, and the performance was evaluated according to the following evaluation criteria:

(26) [Evaluation Criteria]

(27) A: 0.400.03

(28) B: More than 0.34 and less than 0.37

(29) C: 0.34 or less

(30) (5) Friction Performance Test

(31) The test was performed in conformity with JASO C427, and the performance was evaluated according to the following evaluation criteria:

(32) [Evaluation Criteria]

(33) A: Base material+less than 5%

(34) B: Base material+5% or more and less than 10%

(35) C: Base material+10% or more

(36) (6) Squeal Test

(37) The number of occurrences of squeal noise of 70 dB or more during 1,000 braking events at 100 C. in the wear test was counted and evaluated according to the following evaluation criteria:

(38) [Evaluation Criteria]

(39) A: 70 dB or more, less than 5%

(40) B: 70 dB or more, 5% or more and less than 15%

(41) C: 70 dB or more, 15% or more

(42) TABLE-US-00001 TABLE 1 (Content: % by mass) Example 1 2 3 4 5 6 7 Blending Phenol resin 10 10 10 10 10 10 10 composition Rubber dust 4 4 4 4 4 4 4 Cashew dust 4 4 4 4 4 4 4 Barium sulfate 14 16 12 11 14 11.5 10.5 Calcium carbonate 2 2 2 2 2 2 2 Calcium hydroxide 3 3 3 3 3 3 3 Potassium titanate 17 17 17 17 17 17 17 Tin sulfide 3 3 3 3 3 3 3 Mica Phlogopite 0 0 0 0 0 0 0 Muscovite 3 1 5 6 3 3 3 Zirconium silicate 6 6 6 6 6 6 6 Iron oxide 12 12 12 12 12 12 12 Aramid pulp 4 4 4 4 4 4 4 Graphite 10 10 10 10 10 10 10 Petroleum coke 0.5 0.5 0.5 0.5 3 0.5 0.5 Elastic coke 4.5 4.5 4.5 4.5 2 7 8 Biosoluble ceramic fiber 2 2 2 2 2 2 2 Zinc 1 1 1 1 1 1 1 Electrolytic copper powder 0 0 0 0 0 0 0 Total 100 100 100 100 100 100 100 Physical Compression 2 MPa 0.030 0.030 0.030 0.030 0.023 0.030 0.037 properties strain 4 MPa 0.070 0.070 0.070 0.070 0.07 0.080 0.088 (mm) 6 MPa 0.100 0.100 0.100 0.100 0.09 0.120 0.130 8 MPa 0.130 0.130 0.130 0.130 0.12 0.150 0.160 10 MPa 0.150 0.150 0.150 0.150 0.14 0.170 0.187 Friction Pedal feeling A A A A A A A properties Rotor attack A A A B A A A Squeal A A A B A A A Effect () 50 km/h A A A A A A A 100 km/h A A A A A A A 130 km/h A B A A A A B Wear 100 C. A A A A A A A 200 C. A A A A A A A 300 C. A A A A A A A 400 C. A A A A A A A

(43) TABLE-US-00002 TABLE 2 (Content: % by mass) Comparative Example 1 2 3 4 Blending Phenol resin 10 10 10 10 composition Rubber dust 4 4 4 4 Cashew dust 4 4 4 4 Barium sulfate 14 9 17 14 Calcium carbonate 2 2 2 2 Calcium hydroxide 3 3 3 3 Potassium titanate 17 17 17 17 Tin sulfide 3 3 3 3 Mica Phlogopite 3 3 0 0 Muscovite 0 0 0 3 Zirconium silicate 6 6 6 6 Iron oxide 12 12 12 12 Aramid pulp 4 4 4 4 Graphite 10 10 10 10 Petroleum coke 5 5 0.5 5 Elastic coke 0 0 4.5 0 Biosoluble ceramic fiber 2 2 2 2 Zinc 1 1 1 1 Electrolytic copper powder 0 5 0 0 Total 100 100 100 100 Physical Compression 2 MPa 0.020 0.030 0.030 0.020 properties strain 4 MPa 0.060 0.070 0.070 0.060 (mm) 6 MPa 0.080 0.100 0.100 0.080 8 MPa 0.100 0.130 0.130 0.110 10 MPa 0.120 0.150 0.150 0.130 Friction Pedal feeling A A A A properties Rotor attack A A A A Squeal C A A C Effect () 50 km/h A A A A 100 km/h B A B A 130 km/h C A C B Wear 100 C. A A A A 200 C. A A A A 300 C. B A A A 400 C. C A A A

(44) In Table 1, in Examples 1 to 7 using partially graphitized coke (elastic coke) and muscovite as the blending material in a copper-free friction material, Examples 1 to 4 are the case where the blending amount of muscovite in the friction material was changed, and Examples 5 to 7 are the case where the amount of partially graphitized coke added was changed.

(45) It has been found from the results in Tables 1 and 2 that based on the friction material having added thereto copper, the friction material of Examples 1 to 7 where both of muscovite and partially graphitized coke were added can achieve performances comparable to those of the friction material containing 5% by mass of copper (Comparative Example 2). However, the friction material where at least one of muscovite and graphitized coke was not added (Comparative Examples 1, 3 and 4) cannot satisfy the evaluation items of squeal, effect and wear.

(46) While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2013-234269 filed on Nov. 12, 2013, the contents of which are incorporated herein by way of reference.

INDUSTRIAL APPLICABILITY

(47) The friction material in the present invention, in which both of partially graphitized coke and muscovite, i.e., hard mica, are blended each in an appropriate amount as part of the friction modifier in the raw material of the friction material, can ensure wear resistance at high temperature as a copper-free friction material and adjust the balance with noise resistance while keeping a high friction coefficient (effect) and therefore, the friction material is expected to have a demand in particular as an industrial machine or a friction material fitting to a wide range of vehicle types such as railroad vehicle, cargo vehicle and passenger car, more specifically, as an ecologically-minded product for a brake pad, a brake lining or a clutch facing to be used in the applications above.