CA1103384A - Composition railroad friction material with synthetic fiber content - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE: Composition railroad friction materials having low wear rates are characterized by the use of synthetic fiber and by the absence of lead and as-bestos. These friction materials are particularly suit-able for use in railroad brake shoes and contain, by approximate weight, 0.5-11% non-asbestos fiber, of which at least 0.5% is synthetic fiber, 66-81% filler and 14-21% organic binder.

Description

` This invention relates generally to composition type railroad friction materials and, more particularly, to such materials which feature the use of synthetic fibers and the absence of asbestos and lead.

BACKGROU~D OF THE INVENTION
Most of the composition type railroad friction materials in use today include asbestos and lead. An ex-ample of this type of material is shown in U.S. Patent No.
3,168,4~7 - Spokes et al. Some environmentalists have warned of possible problems caused by the use of lead in friction materials. As a result, d~mand has developed for a lead-free friction material. xamples of some com-position friction materials which exclude lead are U.S, Patents Nos. 3,492,262 - Griffith and 3,959,1~4 - Adelman.
The former patent discloses a composition which has no lead and includes up to 16.5~ by weight asbestos fiber, while the latter patent discloses some compositions which delete lead and have up to 11.1% by weight asbestos fiber.
2Q More recently, certain environmentalists have pointed out that possible problems may be cause~ by the use of asbestos fiber in friction materials. Thus, it may be desirable to eliminate asbestos as well as lead from composition fxiction ~terials, U,S. Patent No.
3,g59,194 has scme examples which utilize cellulosic fiber in a range of 3.5-8.0~ by weight as a substitute for as-bestos, although the patent is not concerned with elimina-ting asbestos in friction materials.
As~estos has traditionally been used in frictlon 3Q materials because of its high heat resistance and strength ~nd its low cost. A direct substitution of cther types _]

11~)3384 of fiber for asbestos is expensive, since other fibers cost much more than asbestos, and difficuit, since no known fiber combines all of the desirable qualities of asbestos noted above. It is known to use high-content carbonized or graphitized fibers in aircraft friction ma.erials, as shown in U.S. Patent No. 3,552,533 - Nitz. The use of glass fiber in friction materials is disclosed in several patents. U.S. Patent No. 3,743,069 - Barnett relates a clutch facing consisting almost entirely of hundles o~ continuous glass fil~ments. U.S. Patent No.
3,627,606 - Bentz teaches a glass-filament- reinforced fabric clutch facing impregnated with ~ cement containing lead (litharge), U.S. Patent No. 3,713,934 - Morton dis-closes a clutch facing composed of glass and asbestos.
None of these friction materials would be suitable for railroad brake shoe use, since they are either too ex-pensive and/or conta~n lead or asbestos.
It is, ~herefore, an object of this invention to provide lead-free, asbestos-free, high coef~icient of ~riction, composition friction materials which feature a low fiber content including synthetic fiber and low wear rates.

SU~ARY OF THE INVENTION
. . _ . . _ I have discovered that railro~d brake shoes that meet A.A.R. ~Association of American Railroads) standards for ~rake shoes can be made from compositions ha~ing a low, non-asbestos fiber content which includes synthetic fiber.

The friction materials according to this invention comprise, by weight, 0.5-11.0% non-asbestos fiber, including at least 0 5% synthetic ~iber, 66-81~ filler and 14-21% org~nic binder. A preferred embodiment of this composition friction material for railroad car use contains 2.7-3.5%
synthetic fiber, 74-82% filler and 16-19% organic binder.

DETAILED DESCRIPTION O~ THE INVENTION
The criterion for suitability of a composition friction material for railroad car brake shoe use is the ability of the friction material to pass the standards set forth in the A.A.R. Specification M-926-72, February 13, 1973 Revision. Some of the pertinent dynamometer performance test criteria called for in this A.A,R. Speci-fication are as follows:

1. Instantaneous Retardinq Force During 45 Minute Dynamometer Drag Test:
Drag Retar ~ ~orce Heavy load 400 lbs. min.
Light load 300 lbs. min.

2~ Static Coefficient of Friction:
9 Test Average - .38 min.

3. Stop Distances From 90, 70, 50, 30, 10 mph Under Light and Heavy Brake Shoe Loads (all stop dis-tances must be within varying tolerances).

4. Wear Loss:
Drag Tests (total) - 0.60 in3 max.
Test Stops (total per sequence) - 1.20 in3 max.

As used herei~, the term "synthetic fiberU means fiber made from a substance which does not naturally occur in a fibrous state and includes glass, polyester and kao-wuol. The term "synthetic fiberU ex dudes All forms of cellulose, which naturally occurs in a fibrous state, but also which can~be processed into a different fibrous form (e.g., rayon). Some example mixes used a single type of synthetic fiber, while others used several types of syn-thetic fibers in combination. Other example mixes con-tained a mixture of synthetic and cellulose fibers. All mixes were totally free of asbestos and lead.
Organic binders, such as styrene butadiene rubber (SB~), nitrile butadiene rubber (NBR) and modified phenolic and cashew resins were used, Curing agents for the organic binders included sulfur, zinc oxide and hexamethy-lene tetramine.
A number of filler materials were used in vary-ing combina~ions to produce the necessary low wear rate, haxdness and high coefficient of friction. The fillers used were cast iron grit, kyanite, cashew nut particles, red iron oxide (hematite), black iron oxide, powdered alumin~, graphite, barytes, coke, kaolin, cryclite, carbon black and zinc powder.
Examples of the mixes formulated and tested are shown below and denoted Mixes A-R. The compositions of ingredients are expressed in weight percentages:

MIX A
Weight %
Glass Fiber 3.02 Organic Binder 18.63 rubber 15.74 resin 2.89 Curative Agents 1.64 Filler Materials 76.71 iron grit 12.11 kyanite 12.11 powdered alumina 0.27 black iron oxide 8.46 barytes 21.21 coke 22.55 MIX B
Weiqht %
Glass Fiber 2.91 Organic Binder 17.25 rubber 14.47 resin 2.78 Curative Agents 1.62 Filler Materials 78.22 iron grit 23.37 kyanite 11.68 powdered alumina 0.26 graphite 7.90 barytes 20.42 coke 11.68 cryolite 2.91 ~33384 MIX C
Weight Glass Fiber 1.61 Organic Binder 16.98 rubber 12.03 resin 4.95 Curative Agents 1.54 Filler Materials 79.85 iron grit 24.54 kyanite 13.99 powdered alumina 0.48 graphite 3.92 barytes 17.11 coke . 14.99 cryolite 4.82 MIX D
Weight Glass Fiber 1.62 Or~anic 8inder 17.18 rubber 14.59 resin 2.59 Curative Agents 3.08 Filler Materials 78.13 iron grit 24.75 kyanite 14.11 powdered alu~ina 0,26 graphite 7.65 barytes 16.22 coke 15.12 MIX E
Weiqht %
Polyester Fiber 0.71 Organic Binder 18.93 rubber 10.98 resin 7.95 Curative Agents 1.24 Filler Materials 79.11 iron grit 13.36 kyanite 20.60 : powdered alumina 0.53 graphite 8.73 barytes 19.10 coke 11.44 cryolite 5.35 MIX F
Weight %
Glass Fiber 3.20 Organic Binder 19.74 rubber 16,68 resin 3.06 Curative Agents 1.74 Filler Materials 75.32 kyanite 12.84 hematite 16.04 cashew particles 1.28 powdered alumina 0.28 graphite 6.40 barytes 22.44 coke 16.04 i~iL6)3384 MIX G
Weight Glass Fiber 2,87 Organic Binder 17.69 rubber 14.95 resin 2.74 Curative Agents 1.56 Filler Materials 77.90 iron grit 23.02 kyanite 11.51 powdered alumina 0.26 graphite 5,74 barytes 20.12 coke 14.38 cryolite 2.87 MIX H
Weight %
Fiber 3~59 glass 3.06 cellulose 0.53 Organic Binder 17.81 rubber 6.64 resin 11.17 Curati~e Agents 2.39 Filler Materials 76.22 graphite 6.99 barytes 13.87 coke 7.31 kaolin 3.62 powdered alumina0.53 iron grit 22.37 kyanite 13.17 hematite 8.36 il~)3384 MIX J
Weight Fi~er 2.16 glass 1.45 cellulose 0.71 Organic Binder 17.82 rubber 15.06 resin 2.76 Curative Agents 1.57 Filler Materials 78.45 kyanite 11.59 powdered alumina0.26 iron grit 23.19 graphite 5~78 barytes 20.26 coke 14.48 cryolite 2.89 MIX L
Weiqht %
Fiber 3.32 cellulose 0.50 polyester 0.33 kaowool 2.49 Organic Binder 19.57 rubber 2.99 resin 16.62 Curative Agents 2.65 Filler Materials 74.48 iron grit 31.08 kyanite 12.44 graphite 6.70 barytes 15.56 coke 4.98 powdered alumina0.50 kaolin 3.22 MIX M
Weight %
Glass Fiber 3.24 Organic Binder 16.97 rubber 9.46 resin 7.51 Curative Agents 1.17 Filler Materials 78.64 iron grit 24.71 kyanite 14.09 powdered alumina1.01 graphite 1.98 barytes 16.81 coke 10.26 cryolite 4.86 carbon black 4.92 lg~;~3~4 MIX N
Weiqht %
Glass Fiber 3.19 Organic Binder 16.90 rubber 14.35 resin 2.55 Curative Agents 1.60 Filler Materials 78.31 iron grit 24.34 kyanite 13.88 powdered alumina0.26 graphite 7.78 barytes 17.16 coke 10.11 cryolite 4.78 MIX O
Weight %
Glass Fiber 6.21 Organic Binder 16.99 rubber 4.92 resin 12.07 Curative Agents 3.79 Filler Materials 73.01 iron grit 31.12 kyanite 12.46 graphite 6.63 barytes 12.12 coke 7.62 zinc powder 3.06 -il~;)33B4 MIX P
Weiqht %
Fiber 6.85 glass 6.34 cellulose 0.51 Organic Binder 17.36 rubber 5.02 resin 12.34 Curative Agents 2,40 Filler Materials 73.40 iron grit 31.75 kyanite 12.71 graphite 6.85 barytes 13.89 coke 5.08 zinc powder 3.12 _ 14 _ ~33~34 MIX R
W ignt %
Fiber 9.56 glass 3.18 cellulose 6.38 Organic Binder 18.32 rubber 10.21 resin 8.11 Cura~ive Agents 4.51 Filler Materials 67.61 iron grit 26.67 kyanite 15.21 barytes 6.38 coke 11.17 powdered alumina 1.08 carbon black 7.10 The performance of these composition friction materials against the A.A.R. standards is shown below, where P = passed test and F = failed test:

1~33~4 TEST RESULTS - EX~MPLE MIXES
Static Wear Loss (in3) Drag Tests Stop Distances Coeff. of Light Heavy Light Heavy Mix Friction Drag/Stops Drag Drag ~SL BSL
A .347 .16/.33 P P P P
B .514 .09/.33 P P P P
C .570 .11/.26 P P P P
D .480 .23/.56 P P P P
E .390 .17/.57 P P P P
~ .563 .33/.18 P P P P
G .515 .11/.33 P P P P
H .397 .23/.56 P P P P
J .597 .10/.32 P P P P

L .494 .17/1.03 P P P P
M .457 .15/.59 P P P P
N .544 .12/.31 P P P P
O
p All of the above mixes passed all of the A.A.R.
performance tests, with the exception of Mix A ~
which exhibited slightly low coefficients of friction.
Mix L showed a relatively high weax rate, although within the A~A.R. standards.
It can be seen from the above test results that friction materials made from compositions including various synthetic fibers alone, in combination with other synthetic fiber, or in combination with cellulose fiber can meet rigorous A.A.R. standards and exhibit low wear rates.
The best wear rates were ex~ibited by Mixes A, B, C, G

~ ;33~ ~

and N, which contained from 1.61-3.19% of a single syn-thetic fiber, and by Mix J which contained a low total content fiber mixture of synthetic and cellulose fibers.
Overall fiber content ranged from 0.71% poly-ester (Mix E) to 9.56% glass and cellulose (Mix R), ~inder content ranged from 16~90% (Mix N) to 19~74% (Mix F), while filler content was from 67.61% (Mix R) to 79.85%
. (Mix C). The amount and type of curative agents is mainly dependent on the amount and composition of the organic binder used.
In summation, I have discovered that composition friction materials suitable for railroad use can be formu-lated, without the use of lead or asbestos, by using a relatively low content of various synthetic fibers alone, in combinations, or in combination with cellulose fiber.

~0 _

Claims (16)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 0.5-11% fiber, of which at least 0.5% is synthetic fiber, 66-81% filler and 14-21% organic binder.

2. The friction material of claim 1, wherein the fiber content includes at least 1% glass fiber.

3. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 1.5-10% fiber, of which at least 0.5% is synthetic fiber and at least 0.4% is cellulose fiber, 66-80% filler and 14-21% organic binder.

4. The friction material of claim 3, wherein the fiber content includes at least 1.5% glass fiber.

5. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 5-10% fiber, of which at least 2.5% is synthetic fiber and at least 2.5% is cellulose fiber, 72-79% filler and 14-19% organic binder.

6. The friction material of claim 5, wherein the synthetic fiber is glass fiber.

7. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 2-5% fiber, of which at least 1% is synthetic fiber and at least 0.5% is cellulose fiber, 72-82% filler and 14-21% organic binder.

8. The friction material of claim 7, wherein the synthetic fiber is glass fiber.

9. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 0.5-7% synthetic fiber, 72-81% filler and 15-21% organic binder.

10. The friction material of claim 9, wherein the synthetic fiber is glass fiber.

11. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 0.5-2% synthetic fiber, 74-82% filler and 15-22% organic binder.

12. The friction material of claim 11, wherein the synthetic fiber is polyester fiber.

13. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 1.4-3.5% synthetic fiber, 74-82% filler and 16-21%
organic binder.

14. The friction material of claim 13, wherein the synthetic fiber is glass fiber.

15. An asbestos-free and lead-free composition friction material, comprising approximately, by weight, 2.7-3.5% synthetic fiber, 74-82% filler and 16-19%
organic binder.

16. The friction material of claim 15, wherein the synthetic fiber is glass fiber.