Document 7R1pyaqg7vrG45z3GR2OnXJRB

,9 488,889 5 and light trucks, particularly when they may fie In the form of finely divided dust-llke particles or operated under severe conditions, and which em so-called dispersed discrete particles composed of bodies as a friction-controlling agent finely di the materials heretofore employed for this pur vided dust-like particles which resist heat decom pose, while at the same time being free from the position and heat depolymerization and excessive 6 aforesaid and other objectionable characteristics softening and loss of friction stability resulting of harsh abrasive materials. from such decomposition, and which are also More speclficalhCwe have ascertained that fric highly resistant to carbonization at the high tem tion elements embodying as a friction-controllings' peratures to which such friction elements are sub or friction-stabilizing ingredient finely divided jected in use. 10 dust-llke particles composed essentially of one An additional object of the present invention or more vulcanlzable synthetic rubber elasto is to afford a new and Improved friction element, prenes or so-called synthetic rubbers of the buta and method of making the same, employing finely diene-acrylonitrile copolymer type, compounded divided particles of a synthetic rubber-like elasto- with a relatively low sulphur content, are highly prene of the butadiene-acrylonitrile copolymer 15 resistant to heatdecoznpositlon and heat depoly type as a friction-controlling or friction-stabiliz merization and.carbonization even at the high ing Ingredient therein and in which the desired temperatures to which heavy duty friction ele degree of hardness and heat resistance and re ments are subjected In use upon heavy duty lated properties and characteristics which It may trucks and buses and the like. Moreover, we be desired to Impart to said finely divided par ticles, and( to a friction element containing said 20 have ascertained that friction elements embody ing the finely divided dust-llke materials which particles, may be readily controlled and varied by have been found useful and advantageous as fric employing in the making of said finely divided tion-controlling agents In the practice of the particles a butadiene-acrylonitrile copolymer con present invention do not tend to form a relatively taining a selected and predetermined percentage of acrylonitrile as a component of the copolymer 25 high percentage of benzol-extractable material upon being subjected to relatively high braking material. temperatures and hence do not tend to exhibit A further object of the present Invention, an cillary to the immediately preceding object, is to the consequent loss of fnctlon stability which is exhibited by friction elements embodying the afford a new and improved friction element, and 30 finely divided dust-llke materials which have been method of making the same, containing as a employed heretofore. as friction-controlling friction-controlling or friction-stabilizing ingre agents in friction elements, but retain substan dient finely divided particles of a synthetic rub tially their original friction stability and other ber-like elastoprene of the butadiene-acrylonitrile desirable characteristics. copolymer type and which particles possess im 35 Hence, It will be seen that the present inven proved properties and characteristics as com tion is primarily concerned with friction ele pared to finely divided particles of vulcanized ments containing as a friction-controlling In soft scrap rubber including markedly superior gredient finely divided particles or dust-llke ma heat resistance and the additional desirable ad terials composed essentially of one or more vul vantage which resides in the fact that the degree 40 canlzable synthetic vulcanized rubbery butadi of such increased or superior heat resistance pos ene-acrylonitrile copolymer elastoprenes, com sessed by the new friction-stabilizing particles pounded with a low sulphur content, and which may be predetermined and controlled and varied may be subjected to severe service conditions by employing in the making of said new friction- without exhibiting objectionable heat decompo stabilizing particles a butadiene-acrylonitrile co 45 sition or heat depolymerization and softening or polymer containing a selected and predetermined carbonization resulting from or incidental to the percentage of acrylonitrile, thus enabling friction high temperatures and severe service conditions elements containing said friction-stabilizing par to which friction elements are frequently sub ticles to be readily adapted or adjusted to par jected in use, and as may occur In the use of ticular and varying requirements and uses. 50 friction elements embodying as a friction-con Other and further objects of the present inven trolling ingredient therein the finely divided par tion will be apparent from the following descrip ticles or dust-like materials heretofore employed tion and claims and from the accompanying for this purpose while being, at the same time, drawings. substantially free from the objectionable char In the drawings,' 55 acteristics of the harsh finely divided abrasive Figs. 1 and 2 are graphs illustrating certain materials which have been employed heretofore properties or characteristics of finely divided as friction-controlling Ingredients in friction ele particles composed of materials heretofore em ments. - ',, ployed as friction-controlling ingredients in fric The class of finely divided particles or dust-llke tion elements and illustrating comparable prop erties or characteristics of the friction-controlling 60 materials which may be employed as friction controlling or friction-stabilizing agents In fric materials which are employed In the practice of tion elements, in the practice of the present In the present invention. vention, is that class of vulcanlzable synthetic We have found, among other things, that rubbery elastoprenes or so-called synthetic rub friction elements embodying as friction-control 65 bers which are essentially copolymers of the bu ling or friction-stabilizing agents finely divided tadiene-acrylonitrile type and which are exem dust-like materials or so-called dispersed discrete plified by, but not limited to, the disclosure of particles composed essentially of certain vulcan- United States Letters Patent No. 1,973,000, grant Izable synthetic rubbery elastoprenes or so-called ed September 11,1934. synthetic rubbers, which are referred to herein 70 We have found that such materials have de after, overcome or are substantially free from the sirable properties as friction-controlling agents foregoing and other difficulties and objectionable in friction elements in the practice of the pres features which have been experienced heretofore ent invention Including resistance to heat decom in the use of friction elements embodying fric position and heat depolymerization and soften tion-controlling or friction-stabilizing materials 76 ing, as well as resistance to carbonization, under