July 1, 1911.] 



THE INDIA RUBBER WORLD 



371 



Recent Developments in Rubber Deresination. 



DV H. O CHUTE, CH. E. 



IX the June issue of this journal there is a reference by your 

 English corrcsiiondent to an article on deresination found in 

 the February and March issues of Lc dwutchuuc et la (lulla 

 Percha, by A, Chaplet and H. Rousset. A review of that article 

 is here given, but attention is called to a series of articles on 

 deresination by the writer which appeared in the May, June 

 and July issues of The Ixdi.^ Rubber World for' 1909. As these 

 articles covered many of the subjects of the article under review 

 they will be compared with the statements of the foreign authors. 



The articles begin in the February 15 issue of Lc Caoutchouc 

 et la Gutla Percha, and the authors there point out that resins of 

 various kinds are always associated with crude rubbers, and 

 some tables and analyses of the amounts of resins are given, 

 showing a wide range of resin contents, from 2 per cent, or 

 3 per cent, in Para to 46.9 per cent, in Borneo. 



It is stated, however, that with more than 2 per cent, or 3 per 

 cent, of resin it becomes impossible to conveniently work the 

 rubbers. Of course it is well known that in the United States 

 rubbers are habitually worked with far greater resin contents 

 without difficulty. 



The resins are said to produce cracks and render the product 

 heterogeneous. The statement is made on the authority of 

 Hanriot (Revue Generate des Sciences, 1909), that wdiile Para, 

 Ceylon Para and Manitoba rubbers contain only a small per- 

 centage of resin, some pasty and sticky rubbers like Palembang, 

 Sumatra Jelutong and Flake .-Xccra contain resin in quantity 

 ranging from 80 per cent, to 100 per cent, of the dry substance, 

 and some contain 50 per cent, water. This is pretty well known. 

 A table of the optical indices of the rubber resins is given, but 

 it does not seem important or new. 



Dead Borneo or Jelutong is said to contain from 10 per cent, 

 to 20 per cent, of rubber, which can be extracted, of good quality. 

 It is remarked that the resin contents of various rubbers from 

 the same province show wide variations, no doubt due to the 

 different methods of preparation of the latex. 



A table is given showing one sample of crude Para with 

 63 per cent, rubber, 2.1 per cent, resin and 34.6 per cent, insoluble. 

 Xo rubbers are mentioned as containing more than 10 per cent, 

 resin except a Xew Guinea sample with 20 per cent, and Dead 

 Borneo with 46.9 per cent, resin. 



A discussion of the nature of resins is entered into, but it is 

 stated that little is known of them. A table of the saponification 

 values of the resins states that the resin of Para is 15 per cent, 

 non-saponifiable ; while Congo is 56.6 per cent., Ceylon 20.8 per 

 cent., guayule 78.2 per cent., and Dead Borneo 100 per cent, or 

 totally unsaponifiable. 



Resin solvents are discussed with the general conclusion that 

 acetone is the best, for it dissolves some things out of rubber 

 that alcohol will not touch, besides it will dissolve a larger 

 quantity. 



Pyridine is stated to be a resin solvent but not a rubber 

 solvent, and soda and potash have been employed in large 

 quantities. 



Mixed solvents, one of which is a rubber solvent and the other 

 a resin solvent which precipitates the rubber, are also discussed 

 and methods employing them shown, but it is concluded that 

 any solution of the rubber breaks up the complex structure and 

 weakens it or destroys the "nerve," and therefore solvents which 

 attack the resins only, give the best product. The rubbers from 

 mixed solvents were more soft and sticky. Moreover, oils or 

 rubber solvents will not attack rubber till quite dry, while 

 acetone will first take out the water and then remove the resin. 



In concluding the first article the authors say : "It is estab- 

 lished practically that when rubber is well deresinated it is of 

 excellent quality. Marckwald Bros., and Licbschutz (Gummi 

 Zcituitg, 1S07) made a series of trials of rubbers before and 

 after deresination (made in the works of the Rheinische Gummi 

 Werke), and concluded that the special smell of the crude gum 

 disappeared, that the rubber thus treated was not sticky and in 

 consequence it was easier to mix ; in fine, that the resistance 

 increased 50 per cent, or more." 



The subject is continued in the issue of March 15 of the 

 journal, and under the head of "Industrial Proceedings" there 

 are given outlines of a number of processes. These may be 

 divided as follows : 



First — Those which depend on the action of an alkali on the 

 resins for purification. 



Second — Those which use a mixed solvent which at high tem- 

 peratures is a solvent for rubber, but at lower temperatures at- 

 tacks preferably the resin. 



Third — Those processes which use a rubber solvent for dis- 

 solving both rubber and resin and then precipitate out the resin 

 by use of another resin solvent which will separate the rubber. 



Fourth — Those which use a solvent for resin only without at 

 any time dissolving or affecting the rubber. 



Fifth — Those processes which first extract resin then later 

 extract the rubber from woody matter such as guayule by 

 naphtha. 



Sixth — Those which use a rubber solvent in limited quantity 

 to swell the rubber only and then extract with a resin solvent. 



Seventh — Those which have some special mechanical devices 

 for stirring or holding or treating the rubber. 



There are no examples given of the first class except it is 

 noted that lately it was found that a washing with alkali after 

 deresination removed some albuminoids and oxydases which 

 would otherwise turn it black and oxydize it. 



As the type of the second method is cited the English patent 

 to Combanaire et de la Fresnaye Xo. 22,758 of 1901. This is 

 particularly suitable for gutta, and the picture shows a rather 

 crude extraction apparatus with petroleum naphtha which at 

 certain heats dissolves gutta resins. 



The French patent Xo. 375,118 to Societe Beige, de Raffinage 

 du Caoutchouc heats solvent to 60° C. 



Wiklman, in French patent X'o. 366,704, found that if rubber 

 was dissolved in a solvent like chloroform at 60° C, and alcohol 

 little by little was added, that rubbers of different qualities and 

 values were precipitated at different times. 



As the third type there is cited the German patent to Gratz, 

 February, 1906. where the mass is treated with benzine, turpen- 

 tine, carbon bisulphide or gasoline. This dissolves the rubber; 

 they then add methyl, ethyl or aniyl alcohol and precipitate the 

 rubber and the alcohols dissolve the resins. 



For very poor rubbers like pontianak, Dybowski (Procede de 

 r.-lsia Caoutchouc Co.) recommends ether and carbon bisulphide, 

 then a treatment with acetone or alcohol. The rubber granu- 

 lates at end of the work and thus separates itself from the 

 alcohol which is not lost, there being no cavities in the rubber, 



As an example of the fourth type the French patent to Grak, 

 Xo. 363,340 (1908), is cited as using aniline to dissolve the resins 

 only, without affecting the rubber. 



.•\s an example of the fifth class there is cited the French patent 

 to Foelsing, Xo. 368,958 (1906), wherein only acetone is used to 

 dissolve resins without dissolving the rubber. This is said to 

 produce refined rubber with better "nerve" than when the rubber 



