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INDIA RUBBER WORLD. 



[September 1, 1912. 



The History of Synthetic Rubber 



IN dealing with the history of synthetic rubber production, Dr. 

 Fritz Frank, of Berlin, in a special communication to The 

 India Rubber World, has recalled the various raw materials 

 and chemical processes hitherto employed for that purpose. He 

 remarks at the outset that his idea has been to make his state- 

 ments intelligible to the non-professional reader, while the use of 

 chemical and technical expressions could not be entirely avoided. 



ISOPRENE. 



As it is known, the basic material of synthetic rubber is, in the 

 first place, a carbo-hydrate, isoprene, which was first obtained 

 from rubber itself by Williams in 1860. Within the last three 

 years it has been found that not only isoprene itself, but also its 

 kindred carbo-hydrates, which have two double linkages, give 

 the same or analogous reactions, and can therefore, by chemical 

 and physical means, be transformed into rubber substances. 



Bouchardat (in 1879) was probably the first to obtain from 

 isoprene a body like rubber. Tilden was then, at a later date, the 

 first to define the formula of the constitution of isoprene, being 

 likewise the first to produce these carbo-hydrates from a basic 

 material other than rubber. He obtained the desired result, by 

 conducting oil of turpentine vapors through red-hot pipes, trans- 

 forming these artificial products into a substance of the nature 

 of rubber. 



Other workers upon the above-named carbo-hydrate, which 

 forms an extremely volatile and mobile substance (boiling at 38 

 degrees Cent.), were Gladziatzky, Ipatie v. Wittorf and a number 

 of other noted chemists ; those of more recent date including 

 Kondakow, Euler, Blaise and Courtot. All these reseaches had, 

 however, only purely scientific importance. Neither the above- 

 named scientists, nor others unnamed, succeeded in obtaining 

 real rubber from this carbo-hydrate and its homologues. 



In consequence Tilden, the genial English scientist, declared 

 on the occasion of the First International Rubber Exposition of 

 1908, in London, that the attempt to obtain rubber in this way 

 would have to be finally abandoned. His expressions of that time 

 must, in Dr. Frank's opinion, be regarded as having been justified ; 

 the results obtained by him and Williams not having been re- 

 produced by any other scientists in subsequent experiments. Even 

 Kondakow, who now claims to have really made rubber from 

 butadiene carbo-hydrates, following up the work of Tilden, did 

 not, in Dr. Frank's opinion, actually do so. According to the 

 descriptions given, the preparations obtained by him displayed 

 either too low or too high a stage of polymerization, too large a 

 molecule being in the latter case formed by combination. His 

 first product was therefore still soluble in alcohol, while his 

 specially solidified material was no longer soluble in benzine, 

 benzole or other rubber solvents. 



RESEARCHES OF HARRIES AND HOFMANN. 



Meanwhile, Harries, of Kiel, the German scientist, had been 

 able to give a very probable interpretation of the formula of 

 genuine rubber, characterizing the basic carbo-hydrate as 

 dimethylcyclooktadiene. From his researches it appeared in the 

 highest degree probable that success would yet attend the effort 

 to build up rubber from isoprene, or from products of a similar 

 nature to this carbo-hydrate. 



WMle Harries was still engaged with his investigations the 

 Bayer Factory of Elberfeld (ope of the leading chemical establish- 

 ments) had occupied itself with this question. It started from the 

 principle that the matter should rest on a purely scientific basis, 

 and had first of all produced by synthetic means chemically pure 

 isoprene. 



It was Hofmann (the director), in conjunction with Coutelle, 



who was able to solve this question in the factory named. He 

 employed a product of relatively low value, resulting from coal- 

 tar distillation (/i-kresole) as a basic material, transforming it 

 into isoprene by a complicated process. From this material (after 

 a large number of experiments with negative results) he finally 

 succeeded in obtainirg a rubber product, which he submitted in 

 1909 to one of the leading German rubber factories, where it was 

 worked up into rubber goods. 



This first artificial rubber, produced on a manufacturing scale, 

 was made from isoprene, by exposing the latter for a long time 

 in closed tubes to the influence of light, and later on to light and 

 heat (by polymerization). The product thus obtained not only 

 acted like rubber when being manipulated, but from a scientific 

 point of view was distinctly recognizable as rubber. This process 

 is patented, and is the basis of an extremely large number of 

 patents applied for and granted in all countries, numbering up- 

 wards of 130, according to Dr. Frank's published lists. 



ENGLISH RESEARCHES. 



About the same time similar results were obtained by the in- 

 dependent researches of scientists residing in England. Of these. 

 Dr. Frank refers to Heinemann, Wolteneck, Silberrad and others ; 

 adding that a certain credit is due to Heinemann, who built up 

 his processes upon purely speculative work. Up to the present it 

 is, however, not known which of them is capable of development 

 upon an extensive technical scale. 



Important features of the researches of the English and German 

 scientists referred to, are the processes for obtaining an increased 

 yield of isoprene from oil of turpentine : thereby considerably re- 

 ducing the temperatures of reaction, as well as the pressures. 

 These resulted through working in a space with diluted air, through 

 the use of metals acting catalytically, through the dilution of the 

 oil vapors exposed to the influences named, through indifferent 

 gases and through other means. Of predominating importance 

 are the processes elaborated by Harries, Gottlob, and Staudinger, 

 based on conducting the vapors of oil of turpentine and other 

 terpene carbo-hydrates (with or without dilution with indifferent 

 gases, etc.) over a wire brought by electricity to a state of in- 

 candescence; the products of decomposition thus resulting being 

 immediately caught up. For this purpose an "isoprene lamp" is 

 used. 



While this process is of considerable technical importance, it is, 

 however, still founded upon a terpene carbo-hydrate as a basic 

 material. The last-named substances are, like rubber, vegetable 

 products, being thus, in a technical sense, only available to a 

 limited extent. 



It is different with processes based on the employment of 

 acetylene, acetone, alcohol, starch and similar materials. But the 

 yields obtained by these processes. Dr. Frank adds, are as yet 

 so small that their technical prospects can only be regarded as 

 limited. But, it is remarked, should the labors of Fernbach, 

 Perkins and Ramsay succeed in causing the fermentation of 

 starch and sugar in such a manner that amy! — and butyl — alcohol 

 will be the main products, the matter would present a different 

 aspect. Ehrlich of Breslau had already influenced fermentation 

 in the direction of forming amyl-alcohol (German patent 177.174), 

 but technical difficulties have prevented the carrying out of this 

 scientifically important work. 



OTHER SYNTHETIC PROCESSES. 



Some other processes.^arc; refer/ed to by Dr. Frank as having 

 more favorable prospects from a technical standpoint, for the 

 future production of artificial rubber. These are based on the 



