322 



THE INDIA RUBBER WORLD 



|M <kch 1, 1915. 



A Review of Recent Progress in Rubber Chemistry II. 



Contributed. 



The author of this paper, a well known rubber chemist, submitted it, not as in any way a descriptive article, but merely as an 

 index of progress during the last tivo years. To elaborate it and make it a readable article would necessitate the use of many 

 hundreds of pages. 



I I VGl'I.A I [I IN. ( 



W I'M 11, (Chimie Industrie, 1913, p. 142) has patented the 

 # use of carbonic acid, hydrochloric acid, etc., for coagu- 

 lating, .mil 1 1 tin rich Coloseus (.The India Rubber 

 World, January, 1915, p. 197) has received a Brazilian patent for 

 coagulating latex by use of alkalies followed by use of iron or 

 similar heavy metal salts. I.. C. Davidson uses soap, oils and for- 

 maldehyde, and also creosote, for coagulating latex (The India 

 Rubber World, December, 1914, p. 130). 



In German patent No. 260,916, H. Klopstock claims the use of 

 a compound of selenium or tellurium with a halogen for vul- 

 canizing. Rape oil thus treated is said to form a tactice. This 

 is evidently a cold vulcanization. 



IMPROVING RUBBER BY TREATING THE RAW PRODUCT. 



Several attempts have been made lately to improve the lower 

 . - of rubber by treating the product in various ways with 

 chemicals before vulcanization. D. Spence in United States 

 patent No. 1,112,938, assigned to the Diamond Rubber Co., has 

 claimed the use of metallic sodium or alkaline salts for im- 

 proving low grade or synthetic rubbers. (The India Rubber 

 World, November, 1914, p. 67.) H. O. Chute has received United 

 States patent No. 1,051,987 for process of treating rubber which 

 claims the maceration of crude rubber with pyroligneous acid 

 containing the oily products of wood distillation. The object 

 is to creosote the rubber, as is done by the Brazilian system of 

 smoking. 



J. E. Ephraim, in German patent No. 273,774, adds a little sul- 

 phur and vulcanizes slightly. He may also add a little nitrogenous 

 substance. 



A. Heim, in British Patent No. 1S.506 of 1912 (The India 

 Rubber World, February, 1914. p. 224), uses methyl acetate to 

 dissolve out depolymerized rubber from that which is polymer- 

 ized. Debauge, in French Patent No. 424,457, purifies rubber by 

 dissolving it and precipitating the caoutchouc. 



Heineman (German patent No. 276,678) claims a process of 

 separating sterling caoutchouc from depolymerized caoutchouc, 

 in synthetic rubber. 



VULCANIZING. 



\.xelrod had announced that continued milling affects the af- 

 finity of rubber for sulphur. Spence and Ward ("Chemische 

 Industrie," Vol. 11, p. 274) show that milling does not affect 

 the affinity for sulphur, for by taking two samples and milling 

 one for one and one-half hours, while the other was lightly 

 worked, the amount of combined sulphur was the same in both 

 after like treatment in the cure, but the physical properties of 

 the two samples were different, as the long-milled sample was 

 much weaker. These authors have described ("Chemical Ab- 

 ts," April, 1913, p. 271) an experimental vulcanizer by 

 means of which exact experimental conditions can be obtained. 

 These same authors (The India Rubber World, April, 1913, p. 

 340) have written on the chemistry of rubber and theory of 

 vulcanization. 



F. Ahrens (The India Rubber World, October, 1914, p. 18) 

 claims that vulcanization is a reversible reaction and proves il 

 by analyzing an old sample which contained less combined sul- 

 phur than it did when new. 



In the report of Gross Lichterfelde (The India Rubber World. 

 February, 1914, p. 267) Hinrichsen and Kindscher contributed 



their theorj of vulcanization. In cold vulcanization they find 

 that CioHtsSiCl] is the final product ("Journal of the Society of 

 Chemical Industry," 1913, p. 544). 



A. 0. Bourne experimented ("India Rubber Journal," 1913, p. 

 120) on vulcanizing and testing the product physically, and de- 

 duced laws for increase of temperature and time as applied to 

 vulcanization. No chemical tests were made to confirm this. 



i ). Kausch ("Kunststoffe," Xo. 18, 1912, p. 363) has compiled 

 a list of all British patents on vulcanization, granted before 1912. 



Hinrichsen ("Journal of the Society of Chemical Industry." 

 p. 544, 1913) found that the limits of sulphur which could be 

 combined with rubber in a cumene solution were at about 32 

 per cent. 



SULPHUR IX VULCANIZATION. 



1 he role that sulphur plays in vulcanization has lately been a 

 matter of some dispute. It is well known that sulphur com- 

 bines with rubber in widely varying amounts, ranging from J/J 

 pet cent, as reported by Heilbronner in cements vulcanized by 

 the ultra-violet rays (The India Rubber World, December, 1914, 

 p. 130, to 32 per cent., as long ago announced by C. O. Weber),. 

 shown bj Hinrichsen and just referred to. In each case it ap- 

 pears that perfect vulcanization has taken place if vulcanization 

 be defined as that change in rubber which gives it useful qualities, 

 though the vulcanized rubbers are not vulcanized to the same 

 degree, and differ widely in their physical characteristics. 



H. Loewen ("Zeitschrift Analytischer Chimie." Vol. 25, p. 

 1553) has reviewed the material on which Ostwald based his 

 absorption theory for sulphur in rubber. He thinks the fact that 

 rubber forms a whole series of vulcanized products, the end 

 members of which are not definite chemical compounds, is just 

 as strong as argument for the chemical as for the absorption 

 theory of vulcanization. In his opinion Ostwald overlooked the 

 fact that in forming bromine and nitrosite derivatives sulphur 

 goes to the derivative, i. e.. is chemically hound to the molecule. 

 E. Stein ("Gummi Zeitung," Vol. 27, p. 623) criticizes the above 

 and believes the solution method is the only one by which to 

 study the phenomena of vulcanization, Loewen (Ibid.) takes ex- 

 ception to the above and Stern replies. Spence ( "Gummi Zeitung," 

 Vol. 27. p. 1646) also criticizes Loewen's paper and his inter- 

 pretation of facts. 



Later ("Gummi Zeitung,'*' Vol. 27, p. 1301, and India Rubber 

 World, December. 1913) Loewen experimented by observing 

 rubber and sulphur under a microscope while heated to a vulcan- 

 izing temperature, and when cooling he found that the rubber 

 formed a clear solution with sulphur when hot, and on cooling 

 the sulphur separated out in globules, changing to crystalline 

 sulphur on further cooling. This, he thinks, proves that sulphur 

 is not dissolved in the colloidal state. He thinks the absorption 

 theory of vulcanization should be dropped. 



H. Skellon (India Rubber World, December, 1913) experi- 

 mented on the migration of sulphur by placing a sheet of rub- 

 ber containing 40 per cent, sulphur over one without sulphur 

 and then submitting them to vulcanizing temperature. He found 

 that the sheet free from sulphur had absorbed and combined 

 with about 10 per cent, sulphur. ("Kolloid Zeitschrift," 1914. p. 

 96.) He deduces from this experiment ("India Rubber Journal," 

 1913, p. 723) that sulphur is soluble in polyprene sulphide, 

 C,TI,„S : . F. Kirchoff ("Kolloid Zeitschrift," 1914, p, 35) 

 thinks sulphur is only a catalyzer. Hinrichsen ("Journal 



