Document M4g64bE9r68Y8x6KyE4e4X6L9

,8 498,880 78 the high temperatures experienced In the severe which are referred to above and which X have usage of such friction elements, while still pos found to be useful as friction-controlling or fric sessing a substantial 'degree or amount of resili tion-stabilizing agents in friction elements, in the ency and even after prolonged and severe usage practice of the present invention, may be illus and exposure to the high temperatures inciden 6 trated as follows (J. L E. C., vol. 34, No. 2, pp. tal thereto. Moreover, resiliency in such finely 245-251, and News edition. Am. Chem. Soc., 19, divided and dispersed particles is of particular 750 (1941), and revision, Chem. and Eng. News, significance, in that it enables the finely divided VOL 20, No. 8, April 25, 1942, pp. 536, 537, 538): particles which are employed as friction-con HHHH HH 1" H H HEHH*1 trolling agents in friction elements to compen 10 H0=0--C=H0 + H0=0k ------ * L--HC-CiN-----HC--0=0--HC--1I sate for such loss of friction stability and de crease in coefficient of friction which might otherwise occur if it were not for the resiliency Batsdtene + BcrylonitrOe or vinyl cyanide which is inherent in the finely divided or dust particles composed essentially of one or more 15 Product: "Perbtxnan" "Buna N" synthetic vulcanizable rubbery elastoprenes of the butadiene-acrylonitrile copolymer type which are "Hycar OR" or -* "Hycar Ninone B" (Goodrich) "Chexoigom" ("X" or *T') (Goodyear) employed as friction controlling agents in Mo * "Bianco" (Standard Oil of New Jersey) tion elements in the practice of the present in It will be understood In connection with the vention; 20 general type of synthesis or copolymerization il While a certain degree or amount of resiliency lustrated above that certain of the materials is inherent in the finely divided particles of soft which are employed in or are necessary in such scrap rubber, and in the finely divided particles syntheses, including the emulsifying, wetting, of heat polymerized drying oils and, to a some modifying and catalytic agents which are em what greater degree in the particles of cashew 25 ployed-in the synthesis of the above mentioned nut shell liquid polymer, which have been em butadiene-acrylonitrile copolymer type synthetic ployed heretofore in friction .elements as friction- rubber-like elastoprenes, are trade secrets, al controlling agents, such resiliency as is possessed though all of these materials are known to be by these materials is present therein only in the essentially copolymers of the butadiene-acrylo earlier stages of the use of such materials in fric 30 nitrile type. tion elements and the resiliency of such materials All of the synthetic elastoprenes or so-called is substantially lost or decreased either by heat synthetic rubbers referred to above, and which decomposition or carbonization of such materials are known to be useful as friction-controlling or incidental to the use thereof as friction-control friction-stabilizing materials, in the practice of ling agents in friction elements, as referred to 35 the present invention, are currently available hereinbefore. upon the market in commercial quantities, un Other types of synthetic elastoprenes or so- der the trade names referred to. called synthetic rubbers are, of course, known, It will be seen, therefore, from the foregoing -and among these are those of the butadiene-sty description, and from the disclosures referred rene copolymer type which are exemplified by 40 to therein, that the present invention is primarily the disclosure of United States Letters Patent concerned with friction elements containing or No. 1,938,731, granted December 12,1933, and the ganic bonding agents and which friction elements non-vulcanizable chloro-butadiene or chloro- contain as an ingredient thereof a friction-con prene type of polymers, which have been referred trolling agent in the form of dust-like materials to above, and which are known as "Neoprene," 45 or so-called finely divided dispersed discrete par "Duprene," and the like. ticles composed essentially of one or more vul We have found, however, that finely divided or canizable synthetic rubber-like elastoprenes or dust-like particles composed essentially of syn so-called synthetic rubbers of the character ob thetic elastoprenes of the butadiene-styrene co tained by copolymerization (under conditions and polymer type, as well as those of the chloro-buta 60 in the presence of other materials, such, for ex diene type, do not possess or impart to friction ample, as those which are disclosed in Patent No. elements the desirable characteristics, including 1,973,000) of an unsaturated dlolefinlc or butadi friction stability, and resistance to heat decom ene hydrocarbon of the type position and carbonization, which are imparted to friction elements by finely divided particles 55 HH composed essentially of synthetic elastoprenes of c=c--c=d) the butadiene-acrylonitrile copolymer type com pounded with a relatively low sulphur content, as in the practice of the present invention. The where x represents either hydrogen or an alkyl present invention is, therefore, primarily con cerned with friction elements embodying as fric 60 group, type and a compound (an acrylonitrile) of the tion-controlling or friction-stabilizing agents H therein finely divided dust-like materials or so- i=o--C=N called dispersed discrete particles composed es sentially of vulcanizable synthetic rubber-like 05 ik elastoprenes or so-called synthetic rubbers of the butadiene-acrylonitrile copolymer type, com where R represents either hydrogen, as in acrylic add nitrile, per se, or an alky] group, as in metha- pounded with preferably from about five percent cryllc acid nitrile, to form a synthetic rubber-like to about ten percent, by weight, of sulphur, and high molecular wdght elastoprene of the butadi to which more specific reference will now be 70 ene-acrylonitrile copolymer type, followed by made. compounding the product thus obtained with a The relationship of the monomer components relatively low percentage of sulphur and which and the general type of synthesis of the copolymer is preferably not substantially less than five per nuclei of the group of class of vulcanizable syn cent nor substantially more than ten percent, thetic elastoprenes or so-called synthetic rubbers 75 by weight, of the copolymer, and then finely