JPS6246589B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates generally to composition-type railway friction materials, and more particularly to such materials characterized by the use of synthetic fibers and the absence of asbestos and lead. Most of the composite railway friction materials currently in use contain asbestos and lead. An example of this type of material is described in Spokes et al., US Pat. No. 3,168,487. Some environmental scientists have warned that the use of lead in friction materials can cause problems. As a result, a demand has arisen for lead-free friction materials. Some examples of lead-free friction material compositions include U.S. Pat. No. 3,492,262 to Griffith and No. 3,959,194 to Adelman. The former of these patents describes compositions that are lead-free and contain up to 16.5% by weight asbestos fibers, while the latter describes several compositions that are lead-free and contain up to 11.1% by weight asbestos fibers. More recently, some environmental scientists have pointed out that the use of asbestos fibers in friction materials can cause problems. Therefore, it is desirable to exclude asbestos and lead from the friction material composition. Although U.S. Pat. No. 3,959,149 describes some examples of using cellulose fibers in the range of 3.5-8.0% by weight as a replacement for asbestos, this patent is not directed to the removal of asbestos in friction materials. Asbestos has traditionally been used in friction materials because of its high heat resistance, strength, and low cost. As other types of fibers are significantly more expensive than asbestos, it is uneconomical to directly replace asbestos with other fibers, and there are no known fibers that have all of the desirable properties of asbestos. It is difficult because it is not. It is known to use high content carbon or graphite fibers in aircraft friction materials as described in Nitz, US Pat. No. 3,552,533. The use of glass fibers in friction materials has been described in several patents. Barnett, U.S. Pat. No. 3,743,069, relates to a clutch plate consisting almost entirely of a bundle of continuous glass filaments. U.S. Pat. No. 3,627,606 to Bentz describes a glass filament reinforced cloth clutch face impregnated with a lead (Resurge) containing bonding agent.
U.S. Pat. No. 3,713,934 to Morton describes a clutch face made of glass and asbestos. None of these friction materials are suitable for use in railway brake shoes because they are too expensive and/or contain lead or asbestos. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lead-free, asbestos-free, and high coefficient of friction friction material composition that contains synthetic fibers but is characterized by a low fiber content and a low wear rate. AA for brake shoe from compositions with non-asbestos fibers, including low content of synthetic fibers
The applicant has discovered that it is possible to manufacture a railway brake shoe that meets R.R. (American Railroad Association) standards. The friction material according to the invention is from 0.5 to 0.5 by weight.
11.0% non-asbestos fibers, including at least 0.5% synthetic fibers, and 66-81% fillers and 14-21% organic binders. A preferred embodiment of this friction material composition for railroad vehicle use includes 2.7-3.5% synthetic fiber, 74-82% filler, and 16-19% organic binder. The criteria for suitability of a friction material composition for use in railway vehicle brake shoes is that the friction material can pass the standards set forth in AAR Inspection Regulations M-926-72, revised on February 13, 1973. It depends on whether or not. The relevant dynamometer performance test standards required by this AAR inspection rule include: 1 Instantaneous braking force in a 45-minute dynamometer drag test: Drag Braking force Heavy load 400 lb/min Light load 300 lb/min 2 Static friction coefficient Average of 9 tests - 0.38 min 3 90, 70, at light and heavy brake load
Stopping distances from 50, 30, 10 m/h (all stopping distances must be within their respective tolerances). 4 Abrasion loss: Drag test (total) - up to 0.60 cubic inches Test stops (series total) - up to 1.20 cubic inches As used herein, the term "synthetic fiber" refers to fibers made from materials that do not naturally exist in fibrous form. and includes glass, polyester and kaowool. Here, "kao wool" refers to a ceramic fiber derived from the raw material of kaolin, which is a natural, highly pure, alumina-silica fireclay. The term "synthetic fiber" excludes all forms of cellulose that naturally exist in fibrous form, although they can be processed into different fibrous states (eg, rayon). Some example compositions used a single synthetic fiber, while other examples used a combination of several types of synthetic fibers. Another example composition used a mixture of synthetic and cellulose fibers. All compositions were asbestos and lead free. Examples of organic binders used include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), modified phenolic resin, and cashew resin. Here, the term "modified phenolic resin" refers to a mixture of an unmodified phenolic resin and a cashew resin, or a reaction product thereof. Sulfur, zinc oxide, and hexamethylenetetramine were used as curing agents for this organic binder. A number of fillers were used in various combinations to provide the required low wear rate, hardness and high coefficient of friction.
The fillers used were cast iron grit, kyanite, cashewite particles, red iron oxide (hematite), black iron oxide, powdered alumina, graphite, barite, coke, kaolin, cryolite,
It was carbon black and zinc dust. An illustrative example of a composition that has been formulated and tested is given below as Composition A.
- Indicated by R. The composition of raw materials is expressed in weight percentages. In addition, hexamethylenetetramine was used as a curing agent in all of the above compositions A to R. Further, the resin used in all of the above compositions A to R was a commercially available cashew resin. Composition A Weight % glass fiber 3.02 Organic binder 18.63 Rubber 15.74 Resin 2.89 Curing agent 1.64 Filler 76.71 Iron grit 12.11 Kyanite 12.11 Powdered alumina 0.27 Black iron oxide 8.46 Barite 21.21 Coke 22.55 Composition B Weight % glass fiber 2.91 Organic bonds Agent 17.25 Rubber 14.47 Resin 2.78 Hardener 1.62 Filler 78.22 Iron grit 23.37 Kyanite 11.68 Powdered alumina 0.26 Graphite 7.90 Barite 20.42 Coke 11.68 Cryolite 2.91 Composition C wt% Glass fiber 1.61 Organic bond Agent 16.98 Rubber 12.03 Resin 4.95 Hardener 1.54 Filler 79.85 Iron grit 24.54 Kyanite 13.99 Powdered alumina 0.48 Graphite 3.92 Barite 17.11 Coke 14.99 Cryolite 4.82 Composition D Weight % glass fiber 1.62 Organic binder 17.18 Rubber 14.59 Resin 2.59 Hardeners 3.08 Fillers 78.13 Iron grit 24.75 Kyanite 14.11 Powdered alumina 0.26 Graphite 7.65 Barite 16.22 Coke 15.12 Composition E weight% polyester fiber 0.71 Organic binder 18.93 Rubber 10.98 Resin 7.95 Hardener 1.24 Filler 79.11 Iron grit 13. 36 Kyanite 20.60 Powdered Alumina 0.53 Graphite 8.73 Barite 19.10 Coke 11.44 Cryolite 5.35 Composition Fwt% Glass fiber 3.20 Organic binder 19.74 Rubber 16.68 Resin 3.06 Hardener 1.74 Filler 75.32 Kyanite 12.84 Hematite 16.04 Cashew particles 1.28 Powdered alumina 0.28 Graph Aite 6.40 Barite 22.44 Coke 16.04 Composition G weight % Glass fiber 2.87 Organic binder 17.69 Rubber 14.95 Resin 2.74 Hardener 1.56 Filler 77.90 Iron grit 23.02 Kyanite 11.51 Powdered alumina 0.26 Graphite 5.74 Barite 20.12 Coke 14.38 Cryolite 2.87 Composition H weight% fiber 3.59 Glass 3.06 Cellulose 0.53 Organic binder 17.81 Rubber 6.64 Resin 11.17 Hardener 2.39 Filler 76.22 Graphite 6.99 Barite 13.87 Coke 7.31 Kaolin 3.62 Powdered alumina 0.53 Iron grit 22.37 Kyanite 13. 17 Hematite 8.36 Composition J weight% fiber 2.16 Glass 1.45 Cellulose 0.71 Organic binder 17.82 Rubber 15.06 Resin 2.76 Hardener 1.57 Filler 78.45 Kyanite 11.59 Powdered alumina 0.26 Iron grit 23.19 Graphite 5.78 Barite 20.26 Coke 14.48 Cryolite 2.89 Composition L weight% fiber 3.32 Cellulose 0.50 Polyester 0.33 Kao wool 2.49 Organic binder 19.57 Rubber 2.95 Resin 16.62 Hardener 2.65 Filler 74.48 Iron grit 31.08 Kyanite 12.44 Graphite 6.70 Barite 15.56 Coke 4.98 Powdered alumina 0.50 Kaolin 3.22 Composition M weight% glass fiber 3.24 Organic binders 16.97 Rubber 9.46 Resin 7.51 Hardener 1.17 Filler 78.64 Iron grit 24.71 Kyanite 14.09 Powdered alumina 1.01 Graphite 1.98 Barite 16.81 Coke 10.26 Cryolite 4.86 Carbon black 4.92 Composition N wt% glass fiber 3.19 Organic binder 16.90 Rubber 14.35 Resin 2.55 Hardened Agent 1.60 Filler 78.31 Iron grit 24.34 Kyanite 13.88 Powdered alumina 0.26 Graphite 7.78 Barite 17.16 Coke 10.11 Cryolite 4.78 Composition O wt% glass fiber 6.21 Organic binder 16.99 Rubber 4.92 Resin 12.07 Curing 3.79 Fillers 73.01 Iron grit 31.12 Kyanite 12.46 Graphite 6.63 Barite 12.12 Coke 7.62 Zinc dust 3.06 Composition P weight% fiber 6.85 Glass 6.34 Cellulose 0.51 Organic binder 17.36 Rubber 5.02 Resin 12.34 Hardening agent 2.40 Filler 73.40 Iron Grit 31.75 Kyanite 12.71 Graphite 6.85 Barite 13.89 Coke 5.08 Zinc dust 3.12 Composition R wt% fiber 9.56 Glass 3.18 Cellulose 6.38 Organic binder 18.32 Rubber 10.21 Resin 8.11 Hardener 4.51 Filler 67.61 Iron grit 26.67 Kyanite 15.21 Barite 6.38 Coat 11.17 Powdered alumina 1.08 Carbon black 7.10 These The performance of the friction material composition according to AAR standards is shown below. Here, P indicates pass and F indicates fail.

【table】

Table: All of the above compositions passed the AAR performance specifications in all respects except Composition A, which exhibited a slightly lower coefficient of friction. Composition L exhibited a relatively high wear rate, but within AAR specifications. From the above test results, various synthetic fibers alone,
or in combination with other synthetic fibers, or in combination with cellulosic fibers, it has been found that friction materials made from compositions containing the same meet stringent AAR specifications and exhibit low wear rates. The best wear rates were shown by compositions A, B, C, G, N (which contain 1.61-3.19% of a single synthetic fiber) and J (which contains a fiber mixture of synthetic and cellulose fibers). ). Overall fiber content ranged from 0.71% polyester (Composition E) to 9.56% glass and cellulose (Composition R). Binder content is 16.90
% (composition N) to 19.74% (composition F), while the filler content was 67.51% (composition R).
to 79.85% (composition C). The amount and type of curing agent depends primarily on the amount and composition of organic binder used. In summary, the use of various synthetic fibers, alone or in combination, or in combination with cellulose fibers, at relatively low contents, results in friction material compositions suitable for railway applications without the use of lead or asbestos. The applicant has discovered that this can be done by prescription.

Claims (1)

[Scope of Claims] 1. (1) about 0.5-11% by weight of fibers, of which at least 0.5% is synthetic fibers, (2) about 66-81% by weight of filler, and (3) An asbestos- and lead-free railway friction material composition comprising about 14 to 21% by weight of an organic binder comprising rubber and modified phenolic resin or cashew resin, wherein the fibers are glass fibers, cellulose , polyester fibers, and cao wool fibers; the synthetic fibers are selected from the group consisting of glass fibers, polyester fibers, and cao wool fibers; , black iron oxide, powdered alumina, graphite, barite,
A composition selected from the group consisting of coke, kaolin, cryolite, carbon black and zinc dust.