Document NEGdL2b8EV4VdMBD78wjZNkLQ

United States Patent Office 3,210,303 Patented Oct. 5, 1965 ABEX-078.30 12 at 10,000 p.s.i. at 305 F., while Walker in an applica 3,210,303 tion filed in 1940 -which matured as U.S. Patent 2,369,502 RESIN BONDED FRICTION COMPOSITION suggested a resin bonded friction material pressed at PRODUCT AND METHOD 3500 p^j. and cured. To my knowledge these composi Robert W. Biggs, Shaker Heights, Ohio, assignor, by , tions have not been found useful for passenger car brake mesne assignments, to American Brake Shoe Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Sept. 26,1960, Ser. No. 58,577 5 Claims. (Cl. 260--19) 0 linings. By contrast, I have found that an improved friction composition product particularly useful for passenger car brake linings may be made by using a high pressure com My invention generally relates to improvements in resin 10 pacted -low temperature low pressure cured mix compris bonded fnrtion material and has particularly significance ing powdered iron as a base, synthetic resin as a bond, in connection with a pressed and bonded material which and a very high graphite content, for example 23% by is predominantly metallic and useful as a friction facing weight powdered graphite. Other additives useful for cer adapted to engage a relatively movable metallic element tain purposes are later described herein. for vehicular use. 15 Good results have been obtained using 68% powdered I find that friction materials used for facings in brakes, iron, 23% powdered graphite, 9% powdered synthetic clutches, automatic transmissions and the like, must be resin such as phenol formaldehyde thermosetting resin. selected and compounded with many factors in mind The iron is substantially pure (preferably) and dry, if customer acceptance and satisfactory operation are to and dry artificial graphite is preferred. Particle size of be assured. These factors include high coefficient of fric- 20 all the materials was found to be important to give good tion, low wear of the facing and of the surface which it compact strength, a mix comprising iron powder having engages, absence of "fading" (by winch is meant a de a majority passing through a 20 mesh screen (Tyler crease of coefficient of friction, for example, due to a rapid Standard) and remaining on an 80 mesh screen, graphite succession of high speed engagements), quietness of opera powder having a majority passing through a 40 mesh tion of the material, freedom from "grabbing" and erratic 25 screen and remaining on an 80 mesh screen, and the operation, strength of the facing against ruptures, and resin being either a liquid (for example sprayed on the relatively low cost of the materials and of their com metal particles) or a powder for example 90% through a pounding. 325 mesh screen, giving good compact strength. Particularly for passenger car brake and clutch ap The ingredients are first mixed as in a blender. As plications, there has long been a search for a satisfactory SB little as 55% iron (by weight) may be used, as will later friction material. For many years various formulations be apparent from adding maximal quantities of the other for predominantly metallic faction facings made from ingredients. As much as 90% iron may be used, as will powders have been used for heavy duty applications such be apparent from adding maximal quantities of the other as in trucks, busses, military vehicles, airplanes, and in dustrial machinery, but such facings have not heretofore met all of the economic and other requirements for a satisfactory friction material for many pleasure car ap 35 necessary ingredients. The graphite should be at least 5% (to prevent high wear) and not more than 30% (from a structural strength plications. standpoint and also in order to not affect friction proper It is an object of my invention to provide a novel ties adversely). Preferably the graphite range (by weight friction material which satisfies requirements set out above. 40 of the mix) is 13 to 25%, most desirably 22 to 24%, Other objects and advantages will become apparent and although 18% may be most desirable in special cases the invention may be better understood from considera one of which is described hereinafter. tion of the following description. To some extent the resin itself acts like graphite to Typical of a predominantly metallic friction facing as prevent excessive wear, but the total of the two com heretofore known is that described and claimed in U.S. 45 ponents together should be at least 10% of the mix and Patent No. 2,863,211 issued December 9, 1958 on an ' preferably 15%. application filed by Samnel K. Wellman in 1955 and which For the resin, the thermosetting phenol formaldehyde contains one metallic powder (iron) and one non-metal- resins known under the trademarks "Durez 13848" (ther lic powder (graphite) with the iron in such quantity mosetting phenol formaldehyde retin of two-step type) and (e.g., about 80% by weight) as to provide a substantially 50 "Bakelite BRP 8880" (modified phenolic resin of two- continuous network or matrix and the graphite in such quantity (e.g., at least 15% of the mix by weight) as to form a continuous film upon mating engagement with another part, in that mix iron was used as the base ma step type) have given excellent results. So, also, have the thermosetting polyester resins, for example, that known under the trademark "Atlac Grade 363E" (poly terial both to provide strength and to act as a friction 55 ester alkyd retin). Moreover, the thermosetting mel producing agent and graphite in excess of 15% was amines, for example, the one known under the trade mark added for its lubricating properties and to reduce wear. "CYMEL 405" melamine resin. See U.S. Patent 2,260, According to the then prevailing art these materials are 239), can also be used. powdered, then measured by weight and mixed as in a Strength and also hardness of the faction composition blender, then cold compacted under a pressure on the 6( is apt to change with increase of resin content above order of 12.5 tons per square inch, and then sintered at about 15% by weight of the mix and I have found that 1800" F. while under a pressure of 250 p s.i. strength decreases with decrease of resin-content in the One Elerath, in his U.S. Patent 2,110,571 filed in 1936, lower ranges below 9% especially below 7% and more suggested a resin bonded friction lining one step molded particularly below 5%. SCF-ABEX-0960 3,210,303 34 Strength of the final friction product is affected by com Other material (for lower wear): pacting pressure. Using a two step process with a high pressure during initial compacting, but with the applica tion of a lower pressure during curing reduces the out lay for capital equipment (by eliminating high pressure processing equipment in a furnace). This is not essen tial (except for one aspect of the invention which relates Fe67.8 Graphite 5 Resin 9 Stearic acid 0.2 Percent 23 to cost reduction) and the high initial pressure may be the final pressure (during curing) but I have found that it is essential to have same high pressure compacting, by which 'I mean a pressure greater than 9 TSI (18,000 10 While resin bonded friction facings have long been known, they have heretofore not been entirely satisfactory from the standpoint of wear, noise and frictional charac p.sx), more particularly greater than 10 TSI (20,000 p.sx), and most desirably more than 18 TSI (36,000 teristics. To a lesser extent the same has been true of the sintered (at about 1800 F.) predominantly metallic p-si.) in order to give a proper article particularly as regards transverse rupture strength which is an important consideration in the manufacture of friction -facings. 15 mixes which have had further disadvantages due to high cost of processing. Also heretofore the sintered metallics have often shown too much coeffident of friction build-up Those in the art recognize that transverse rupture or (e.g, increase with decreasing speed during one stop) matrix strength is a good indication of how well the ma terial will stand up in service without deteriorating or crumbling or otherwise failing structurally during use, and field tests have indicated that at least 4,000 p.s.i. and prior resin bonded mixes, most always containing a material such as asbestos, have shown the opposite, that is too much "fade" in coeffident of friction during one 20 or many stops. I have found that the way to get the best transverse rupture strength is necessary to prevent fracture charcteristics of both is not to combine lead or zinc or of friction facings in severe service. For a mix in ac copper or other metal with asbestos, but to combine iron cordance with the present invention this transverse rup and more than 13% graphite with a resin bonding agent ture strength requirement is satisfied by using a relatively high compacting pressure as compared to the prior art, and then bond and cure the same with such pressure and 25 temperature processing as has been described. This gives that is, above 10 TSI, or most desirably above 18 TSI, improved friction characteristics plus a substantial saving and this high pressure permits the friction article to have in cost in manufacturing techniques so as to overcome a high content of graphite (to reduce wear) or of other the prior prindpal drawback of high cost and lack of friction tailoring agent and still be within minimum 30 stability of friction level. When used for passenger car strength requirements. brake linings, the product of the invention has proved Strength of the final friction product is also affected better than prior sintered material in build-up and in by the time length and temperature and pressure of cure. cost Also it has proved better than the prior art asbestos 350 F. for 60 minutes, and 400-450 F. (depending on containing linings in improving wear, noise, fade and resin used) for 60 seconds, were found to be optimum 35 other operating characteristics (while equal thereto in combinations for curing. Temperatures in excess of 650 cost). F. (way below usual sintering temperatures such as 1800 While I have described a particular embodiment, vari F.) result in decomposition of the plastic. Satisfactory ous modifications may obviously be made without de pressure during curing was found from 100 to 650 p.sj, parting from the true spirit and scope of the present but, of course, only if there was a prior high initial pres 40 invention as defined in the accompanying claims taken sure. While the iron, high graphite and resin mix alone is satisfactory in some instances (e.g, for brakes on one with all reasonable equivalents. I claim: United States make of car where the brakes are so large 1. Friction facing composition product for brakes, that lower frictional values are used), in other instances 45 clutches, automatic transmissions, and the like having low a higher coefficient of friction is desired and is obtained wear, low fade and high structural strength and com by adding a percentage of an abrasive grit such as silica prising a pressed and resin bonded mixture substantially or, preferably, a higher melting point refractory, most free of asbestos and essentially consisting of 55% to 90% desirably 4% zircon (ZrSiO*) or 0.8% alumina (A]2Oj). iron, 5% to 30% graphite, and more than 6% up to Another desirable additive is 0.2% stearic acid useful 50 about 15% cured thermosetting phenol formaldehyde to prevent mold sticking. resin bonding agent. A preferred composition for a friction facing in accord 2. Friction composition product for brakes, dutches, ance with the present invention is: automatic transmissions and the like characterized by low Powdered iron63.8 Percent wear and high structural strength and consisting essen 55 tially of pressed and bonded mixture of 60% to 80% Powdered graphite 23 iron, 13% to 25% graphite, 7% to 15% cured thermo Powdered phenol formaldehyde resin-------------------- 9 setting phenol formaldeyhde resin. Stearic add--------------------------------------------------------- 0.2 3. A bonded and cured friction facing composition Z1S1O4---------------------------------------------------------------- 4 60 product having low wear and high structural strength ini In the art sometimes it is desired to use different co- tially consisting essentially of about 68% powdered iron, effident of friction materials in the same application, for about 23% powdered graphite, about 9% powdered ther example with one material in end segments of a brake mosetting phenol formaldehyde resin, up to about 4% shoe and the other material used as a center segment, or ingredient of the group consisting of zircon, silica and with the different materials on different shoes contacting 65 alumina. the same brake drum. For such use two preferred mixes 4. A high coefficient of friction material characterized in accordance with my invention are: by low wear and high structural strength comprising a One material (for high coefficient of friction): bonded and cured mixture initially consisting essentially Percent 70 of about 72% powdered iron, about 18% powdered graphite, about 9% powdered thermosetting phenol form Graphite 18 Resin 9 AljOs------------------------------------------------------------------- 0.8 Stearic acid0.2 aldehyde resin, about 0.8% alumina, and about 0.2% stearic acid. 5. A friction material which is characterized by high 75 strength and low wear comprising a bonded and cured ? 3,210,303 56 mixture initially consisting essentially of about 66% 2,162,600 6/39 Ball51--298 to 68% iron, about 23% grapbite, about 9% thennoset- 2,369,502 2/45 Walker. ting phenol formaldehyde resin, about 0.2% stearic acid, 2,686,140 8/54 De Gaugue260--38 and 0% to about 1.5% friction producing agent in the 2,881,065 4/59 Reuter51--298 form of an abrasive grit. 5 2,910,449 10/59 Evans260--38 2,978,850 4/61 Gleaszer_______________ 51--298 References Cited by the Examiner 3,062,633 11/62 Coes-----------------------------51--298 UNITED STATES PATENTS LEON J. BERCOVlIZ, Primary Examiner. 1,969,041 8/34 Seabury et al------------------- 260--38 10 ALPHONSO D. SULLIVAN, MILTON STERMAN, 2,159,935 5/39 Sanders------------------------- 260--38 Examiners.