June 1, 1915.] 



THE INDIA RUBBER WORLD 



493 



What the Rubber Chemists Are Doing. 



RESEARCH in Rubber Recovery. F Kirchhof, in the "Kol- 

 loid-Zeitschrift," vol. IS, pp. 126-131 (1914), recounts a 

 series of experiments demonstrating the possibility of 

 recovering rubber from its tetrabromide, basing his conclusions 

 on Harries' octadiene formula for rubber 



Vulcanization Accelerators. R. Ditmar, in "Gummi- 

 Zeitung," vol. J 1 ', pp. 424-426 (1915), discusses the efficiency of 



ihi- class of materials, including the old-time reliable litharge, 

 although no mention is made of lime. It is stated that positive 

 materials have always been used to increase the speed and de- 

 crease the temperature of vulcanization; also, to overcome vul- 

 canization retarders or negative materials, such as oil substi- 

 tutes, .'spied of vulcanization, up to a certain point, is propor- 

 tional to lb' increase of amount ol accelerator. Beyond this 

 point, in some instances, the added substance acts negatively and 



retards. In general, accelerators must he used m small quan- 

 tity, as otherwise the quality of the product is injuriously af- 

 fected. 



Acting together in a compound, accelerators produce an in- 

 ■ ii i-e oi speed greater than would be indicated by th< sum of 



the mdnidu.il reactions. Litharge accelerates because of the 

 heat of reaction resulting between it and hydrogen sulphide, or, 



rding to equallj good authority, to the heat liberated in 



forming lead sulphate and lead sulphide from litharge and free 

 sulphur in the compound. Magnesium oxide is almost as widely 

 used as litharge. Iron oxide frequently helps in compounds 

 containing brown substitute. Manganese and copper oxides 

 should be avoided, owing to their deteriorating action on the 

 rubber. 



The use as accelerators has been patented, including piperidine 

 and its homologues, certain amines, urea derivatives, carbon bi- 

 sulphide addition products and all organic bases having relatively 

 large amounts of dissociation constituents. The latter group act 

 as accelerators irrespective of constitution. Organic and inor- 

 ganic compounds of ammonia may also be used. For the com- 

 plete list of available accelerators given by Ditmar, the original 

 article should be consulted. 



V \i I >\ es for Coloring Rubber Goods. R. Ditmar, in "Gumrii- 

 Zeitung," vol. 29, pp. 85-87 (1914), reports the successful use of 

 organic coloring agents in the manufacture of colored rubber 



- Is, Of a hundred different dyes tried, in white, soft and 



hard rubber mixes, about one-third of the dyes gave good colors, 

 which withstood vulcanization. More delicate shades were ob- 

 tained than with the ordinary inorganic colors. 



Analytic Method for Sulphur in Rubber, reported by R. 

 Gaunt, in "Analyst," vol. 40, pp. 9-10 (1915). The method of 

 determining sulphur by burning in oxygen and absorbing the 

 s « I has not been applied to rubber because of the formation of 

 volatile decomposition products, which may escape combustion 

 or form explosive mixtures with oxygen. The following method 

 obviates this difficulty: The rubber (0.2 to 0.3 gram), contained 

 in a small hard glass tube closed at one end, is placed in a 

 combustion tube. 30-5 cm. long, drawn out at the rear and 

 fitted into a small flask, which is connected with another 

 flask by a small tube. In each flask is placed 25 c.c. of 20 vol- 

 ume hydrogen peroxide. A loose plug of platinized asbestos is 

 placed in the rear of the combustion tube, in front of the con- 

 striction. Dry oxygen is led through the tube, and the mouth 

 of the inner tube containing the rubber is heated by a burner, 

 the rubber is then gently heated by another burner until 

 melting and decomposition begin. The gas evolved ignites 

 at the month of the containing tube and burns with a smokeless 

 flame, if care be taken. The gaseous products are usually de- 

 stroyed in about 30 minutes, and the residual mass is then heated 



more strongly until completely burned, any carbon deposits be- 

 ing burned awaj al the same time by moving the burner. The 

 sulphuric acid formed in the peroxide solution may be titrated 

 with a standard alkali, oi pitation, after decomposing the 



oi peroxide by boiling with hydrochloric acid. Blank 

 determinations must be made on the peroxide. In the ease of 

 rubbers high in mineral matters, sulphates in the residual ash 

 should i; determined Hie results repot el agree with 



those obtained bj th< i iriu method. 



ii BBER FROM CRUDE OIL. 

 It is reported that a Russian chemi I has recently been able 

 to ecun from crude petroleum oi the Baku oil fields a yield of 

 20 per cent, of adipic acid, the material being derived from 

 in fraction boiling between 208 and 223 degrei I enheit. 

 It is known that adipii acid is convertible, through its own amide, 

 into butadiene. The discovery of an abundant supply of adipic 

 acid is thus of great importance as a source from which to ob- 

 tain synthetic rubber, since butadiene is simply converted into 

 caoutchouc. California petroleum contains markedly similar 

 tractions to those found in the oils from the Baku region, on 

 sequentbj there is a pn spec! of manufacturing rubber syn- 

 theticallj on the Pacific coast. In fact, the matter is said to be 

 under experiment at present with that object in view. 

 PATENTED I; I ITMENT OF RUBBER. 



Preserving Rubber Inner Tubes with mixture of glycerol 

 and corn syrup, in equal parts, applied as a surface coating. 



Accelerating Vulcanization by the addition of one per cent, 

 of piperidine or one of its derivatives before heating with a vul- 

 canizing agent in the usual manner. 



Separating Vl Li v\i/in Rubber from Fabric by soaking the 

 rubber-coated material in certain hydrocarbons of the Dutch 

 East Indus, especially rich in saturated hydrocarbons of the 

 cyclic and alicyclic series. Contact in the cold causes the vul- 

 canized rubber to swell in time, losing its elastic propertv and 

 changing into a colloidal mass. In this state the rubber is readily 

 separable from the fabric and may then be regenerated by means 

 suitable to its nature. 



CONDENSITE-RUBBER MIXTURES SUITABLE FOR ELECTRIC INSU- 

 LATION Cables. Halogen substitution products of naphthalene 

 are found to facilitate the mixing and combination of sulphur 

 and rubber in the vulcanizing process, and they remain in the 

 vulcanized product as a solid solution with modifying properties. 

 The materials bind well and are but slightly inflammable. Hard 

 rubber mixtures by this process are said to he less brittle than 

 ordinary, even at low temperatures. 



Impregnating Material with Rubber. — Reclaimed or regen- 

 erated rubber is adapted for impregnating fabrics by reduction 

 to emulsions with solvent and water. If emulsions containing 

 only regenerated rubber are used, the coated material must be 

 dried before vulcanization. 



Improving Low-Grade Crude Rubbers. The material is 

 treated direct or after solution or softening with one or more 

 alkali metals or their alloys — hydroxides or alcoholates in the 

 dry form at temperatures not exceeding 212 degrees Fahrenheit. 

 Regenerated rubber mav also be treated in the same way. The 

 rubber to be improved is intimately mixed on rolls in the pro- 

 portion of 100 parts rubber with 5 parts of sodium, raising the 

 temperature of the rolls to about 150 degrees to 160 degrees 

 Fahrenheit. In a few minutes the mass begins to acquire the 

 properties of high-grade rubber, not adhering to the rolls and 

 working readily. The material is sheeted thin and allowed to 

 remain for 24 hours at about 150 degrees. The sodium can be 

 ered after the operation is completed. 



