Mav 1, 1921 



THE INDIA RUBBER WORLD 



573 



phide accelerator. The ammonia condensation products of otlier 

 alipathic aldehydes behave in a similar manner. 



/)-Phenylenediamine is an accelerator that is much more active 

 than would be assumed from its basicity. At curing tempera- 

 tures, this accelerator reacts with sulphur to form large amounts 

 of ammonia and hydrogen sulphide together with certain weaker 

 bases. If the reaction be carried out under a cold reflux, the 

 condenser will frequently become clogged with the white solid 

 compounds of ammonia and hydrogen sulphide which are described 

 by Roscoe and Schorlemmer. The action of p-phenylenediaminc 

 in the cure is entirely that of a hydrogen sulphide polysulphide 

 accelerator. 



The three above-mentioned accelerators are not dependent on 

 the rubber resins or proteins for their supply of hydrogen sulphide, 

 since this is one of their sulphur reaction products. It is to be 

 expected that these accelerators will function in a deresinated or 

 a synthetic rubber, and the Bayer patents state that this is true. 

 It is also known that piperidine will cure in a nitrogen-free rubber. 

 Here we have a strong base acting apparently without the aid of 

 hydrogen sulphide. Pipendine, however, reacts with sulphur at 

 temperatures lower than those used in vulcanization, with the 

 formation of hydrogen sulphide. Both the sulphur reaction 

 product and the unchanged piperidine may then use this hydrogen 

 sulphide to form polysulphides with sulphur. 



INORGANIC ACCELEEATOES 



Inorganic accelerators that function in the cure by the removal 

 of hydrogen sulphide the writers choose to term "secondary accel- 

 erators," while those that function in the same manner as the 

 organic polysulphide accelerators may be classed with them as 

 "primary accelerators.'' A third class consists of those com- 

 pounds that are both primary and secondary accelerators. 



I. Secondary Accelerators. Litharge, zinc, oxide, etc., seem 

 to act no further than to form the corresponding sulphides, in 

 connection with hydrogen sulphide polysulphides. 



II. Primary Accelerators. To this class belong the 

 sulphides and hydrosulphides of the alkali and alkaline-earth 

 metals. 



III. Accelerators That Are Both Primary and Secondary. 

 Inorganic oxides and hydroxides function first as secondary ac- 

 celerators forming sulphides or hydrosulphides which then take up 

 sulphur and act as primary accelerators. Such accelerators are 

 sodium and calcium hydroxides, magnesium oxide and basic car- 

 bonate, etc. 



Secondary accelerators are believed to function as aids to 

 organic polysulphides by breaking them up into colloidal sulphur 

 and the original nitrogen base. This may be illustrated by the 

 decolorization of polysulphide solutions by litharge or zinc oxide. 

 Ferric oxide does not act as a secondary accelerator, and neither 

 does it readily decompose the polysulphide solutions. The solu- 

 bility of organic accelerators in sulphur and rubber gives them 

 much more intimate contact with hydrogen sulphide at the time 

 of its formation than is the case with the comparatively large 

 particles of litharge or zinc oxide. Hydrogen sulphide is there- 

 fore available for the formation of organic polysulphides before 

 being taken up by the secondary accelerators. The decomposition 

 of a polysulphide by a secondary accelerator regenerates the free 

 base, which with more hydrogen sulphide and sulphur re-forms 

 the polysulphide. Secondary accelerators do not act as true 

 catalysts ; once formed into sulphides they do not react again with 

 hydrogen sulphide. 



SUMMARY 



1. .\11 organic accelerators are believed to function through 

 the formation of some type of polysulphide. 



2. Organic bases and compounds that form bases during vul- 

 canization are believed to form polysulphides through the aid of 

 hydrogen sulphide. These are termed "hydrogen sulphide poly- 

 sulphide accelerators." 



3. Thioureas, dithiocarbamates, thiurams, and niercaptan com- 

 pounds are believed to form polysulphides directly, or by first 



forming disulphides, and are termed "carbo-sulphydryl polysul- 

 phide accelerators." 



4. It is proposed that the function of such compounds as 

 litharge and zinc oxide may lie in the decomposition of polysul- 

 phides into colloidal sulphur and amines. 



5. Such inorganic compounds as sodium hydroxide, calcium 

 hydroxide and magnesium oxide arc believed to function as 

 "primary accelerators" through the formation of inorganic poly- 

 sulphides. 



BENZOL POISONING IN RUBBER FACTORIES 



That rubber manufacturers are eager to safeguard tlie 

 health of their employes is evidenced in the exhaustive 

 study being made by experts into the causes and prevention of 

 the occupational diseases that have been incidental to the rubber 

 industry. Typical of such valuable research work is the investi- 

 gation recently made by Dr. Robert S. Quinby, of the Hood 

 Rubber Co., of Watertown, Massachusetts, as to the manner 

 in which benzol poisoning is occasioned, the best treatment for 

 those affected by the noxious vapor, and the surest means for 

 overcoming any menace to health from this source. 



According to the report of the State Board of Labor and In- 

 dustries of Massachusetts, five workers died within three years 

 from the toxic action of benzol used in rubber works, but dur- 

 ing the past year and a half there have been no deaths from this 

 cause, the gratifying change for the better being due mainly to 

 the fact that the use of benzol had been practically discontinued 

 and that comparatively harmless rubber solvents have been sub- 

 stituted. 



Dr. Quinby's inquiry has revealed the fact that most of the cases 

 of ppisoning in the rubber industry have been due to the use 

 of pure benzol, rather than commercial benzol. The latter boils at 

 or over 100 degrees C, while the former distills at 80.5 degrees C. 

 Tests indicated that the toxicity of pure benzol is much greater 

 than that of the commercial article, as the amount of vapor given 

 off and breathed by operatives is larger with the benzol having a 

 lower boiling point. Oddly enough, the vigorous, deep-breathing 

 workers were more affected than those of apparently less phy- 

 sical resistance. Females appear to be more susceptible to the 

 fumes than males. Hot, humid weather, in which such a solvent 

 was more volatile, increased the susceptibility of workers to the 

 toxic action. In a general sense those affected show symptoms 

 closely resembling indications of pernicious anemia. Poisoning 

 by benzol is usually due to breathing the fumes, but, like aniline, 

 it may also be absorbed through the skin. 



As a prophylactic measure, it is suggested that whenever pos- 

 sible benzol should be replaced with solvent naphtha, xylol, toluol, 

 carbon tetrachloride, or xylol compound. Where benzol must 

 be used, it is advised that ample ventilation be provided, that all 

 benzol operations be carried on in closed containers, and provi- 

 sion made for the filling of containers by gravity from storage 

 tanks, or by other mechanical means. Examination of workers 

 exposed to benzol fumes should be made at least once a month, 

 especially to determine the condition of the blood (diminution of 

 white blood cells being a characteristic symptom of poisoning), 

 and none with heart or kidney disease should be permitted to be 

 exposed to the vapor of benzol. 



TIRE BUILDERS AFFLICTED 



All of the five cases referred to occured in the tire-building 

 department of a rubber works, where benzol had been used in 

 a cement and where it was customary to wipe tires with a cloth 

 saturated with benzol prior to vulcanization. The process was 

 repeated about every half hour, or about eighteen times in an 

 8-hour day. In the case of one m.an who succumbed to the poison, 

 it is stated that he was thirty-three years old, had been working 

 eight years in a rubber factory, and that he had not been working 

 long in the tire-building department to which he had been trans- 



