478 



THE INDIA RUBBER WORLD 



[July 1, 1912, 



Progress in Artificial Rubber Production. 



GERMAN scientists have expressed the hope that success 

 in the production of artilicial ruhber will be attained 

 more quickly than was the case with artificial indigo. 

 In dealing with the subject in "Kunststoffe," Herr Rassfeld 

 (certified engineer) remarks that while it is as yet too early 

 to cast a very favorable horoscope for artificial rubber, the 

 numerous patents appHed for and granted since the beginning 

 of 1911, and the most recent literature on the subject illus- 

 trate how energetically work is being carried on ; further show- 

 ing that from a technical point of view we are a good way 

 nearer the solution of the problem. Those who a year ago 

 regarded competition l)etween artificial and natural rubber as 

 •excluded from consideration, are now forced to admit that 

 as the work now stands, artificial rubber if not (as was the 

 case with indigo) conquering the world, will be in a position 

 to exercise influence towards a reduction of the price of rubber. 



JiEPOLYMERIZ.'VTION AND POLYMERIZATION. 



While Tilden and Harries had demonstrated with regard to 

 natural rubber, that the hydro-carbon molecule of rubber is de- 

 composed by depolymerization into isoprene, it would seem that 

 at about the same time methods were discovered by which the 

 polymerization of the isoprene molecule into the rubber mole- 

 cule was effected. For this purpose several new methods have 

 been discovered during the past year. In tliis way the question 

 of polymerization offers less difficulty, the main question still 

 being : Will it be possible to produce at a sufficiently low price 

 the isoprene and kindred basic substances necessary for poly- 

 merization? The determination and recognition of the fact that 

 these kindred (or in chemical terms homologous) substances 

 are transformed by polymerization into substances homologous 

 to rubber, may be regarded as discoveries of the highest im- 

 portance. Herr Rassfeld adds that, without being too optimistic, 

 we may regard these homologous substances with particularly 

 hopeful anticipations. It is regarded as possible that these "rub- 

 bet homologues" will be found to possess quahties rendering ar- 

 tificial rubber specially valuable. 



PRODUCTION OF ISOPRENE AND KINDRED SUBSTANCES. 



The production of isoprene and kindred substances is prin- 

 cipally effected in two forms : 



1. The reduction into isoprene of natural products containing 

 the isoprene molecule. 



2. The building up of the isoprene molecule from the start, by 

 so transforming easily accessible products, that isoprene or its 

 homologous substances may be obtained by division. 



Hitherto the technical extraction of isoprene from natural 

 products (such as turpentine) did not promise well, on account 

 of the unsatisfactory yield, which Tilden had estimated at a 

 maxiirium of 10 per cent.* Efforts have therefore naturally been 

 directed to finding methods for increasing the yield. While 

 formerly the vapors of oil of turpentine were conducted through 

 pipes at a temperature of about 600° C. (1.112° F. ) for the pur- 

 pose of separating the hydro-carbon molecule from the turpen- 

 tine, much better yields are now obtained by working at sub- 

 pressure instead of ordinary pressure. Silberrad, it is added, 

 conducts the oil of turpentine vapors at sub-pressure, through 

 pipes heated to 450°-750° C. (842°-l,382° F.) the yield being 

 25-50 per cent, instead of 2-3 per cent., as by the old method, 

 the low yield of which was due to the re-polymerization of the 

 isoprene. 



Still better results are claimed for two similar, yet independ- 

 ent, processes of Staudinger and Klewer, and of Harries. These 

 inventors effect the decomposition of the oil of turpentine 

 vapors — not by conducting them through heated pipes, but by 



*See India Rubber World, September 1, 1911. p. 463. 



means of metal wires, brought to a red heat by an electric cur- 

 rent. Herr Rassfeld calls special attention to the fact that the 

 yield obtained by this method is 60 per cent, or more. W'hile 

 Harries works with atmospheric pressure, the other experts 

 named likewise use the vacuum system. 



In the decomposition of turpentine vapors into isoprene, as 

 one part of turpentine gives two parts of isoprene an increase 

 of volume takes place. In other words, the pressure is increased 



On the other hand the temperature depends upon the pressure. 

 If the latter is artificially reduced (by working at sub-pressure) 

 the vapors are rarefied and the temperature of decomposition 

 sinks. As the polymerization of isoprene depends upon the tem- 

 perature, a higher yield is in this manner produced ; owing to 

 the reduced formation of antagonistic agents. 



Heinemann starts with the same object in view, of attaining 

 decomposition at the lowest possible temperature. Only he 

 uses the catalytic properties of finely divided copper or silver. 

 Therefore, either he conducts the oil of turpentine vapors over 

 these metals, finely divided, or he rllows the decomposition to 

 take place in copper or silver vessels. This inventor claims 

 that decomposition is attained at 450° to 480°- C. (842° to 896° 

 F.), and that the yield amounts to as much as 50 per cent. 



SUBSTITUTES FOR OIL OF TURPENTINE. 



In both of the two forms already referred to, for the pro- 

 duction of isoprene, progress has been recorded. 



As oil of turpentine is relatively high in price, efforts have 

 been made to use for obtaining isoprene the resinous residues 

 of the extraction of that oil. It is added that the diflferent copals 

 (such as Manila and Borneo copals), and above all the resins 

 which result from the purification of rubber, are suitable for the 

 extraction of isoprene, by vacuum distillation at 250°-450° C. 

 482° -842° F.). 



BUILDING UP ISOPRENE. 



Particularly as to the second form of isoprene production 

 (that of building up the isoprene molecule) has progress been 

 made during the past year. The most important point is that 

 up-building methods have been discovered, which are not so 

 complicated as to involve their technical impracticability ; in fact, 

 methods which are not interesting solely from a scientific point 

 of view. 



Specially prominent in this connection are the Elberfeld 

 Farben Fabriken, formerly F. Bayer & Co., whose chemists have 

 discovered a number of processes leading more or less easily to 

 the desired end. Thus Dr. F. Hoffman and his colleagues have 

 been using as a basic material para-cresole, obtained from coal- 

 tar and wood-tar, and which is derived from toluol, in the same 

 way as phenole (carbolic acid) is derived from benzole. 



In the search for shorter methods, it has been found possible 

 to obtain isoprene derivate from zyklo-hexanole. It is 

 remarked that coal-tar, which in the fullest sense of the word 

 is a gold mine, w'ill apparently present us with artificial rubber. 

 Further basic materials for isoprene are furnished by wood 

 spirit and pyroxylic acid, in the form of formaldehyde and 

 acetone. Fusel oils, contained in crude alcohol, are another 

 source of isoprene. 



Finally Herr Rassfeld remarks: "Even if artificial rubber will 

 never supersede the natural article, we are justified in hoping 

 that the German chemical industry will succeed in placing upon 

 the market, a rubber which will, on the one hand, help to regu- 

 late prices, and on the other will render our rubber manufac- 

 turing industry more independent of foreign supplies." 



This contribution to the technical literature regarding arti- 

 ficial rubber will doubtless be found of interest. 



