January i, 1903.] 



THE INDIA RUBBER WORLD 



113 



REGENERATION OF OLD RUBBER AND WASTE RUBBER.* 



By L. Edgar Andes. 



UNDER the name of "old rubber" are included all the 

 rubber articles of any kind whatsoever, which have 

 been in use and can no longer serve their purpose, and 

 hence are to be discarded and destroyed. While these 

 almost worthless waste products, for such they must be desig- 

 nated, did not serve, twenty years ago, any other purpose than 

 to be burned up, a number of uses have since been found for 

 them, and their value varies, according to condition and purity, 

 from I to 6 marks per kilogram [= li to 65 cents per pound], 

 so that the collecting and sorting pays tolerably well. The 

 utilization of the products is not such that they are subjected 

 directly to a regeneration process, but rather they are used in 

 the cleaned and reduced state for intermixing. The manufac- 

 turing waste proper, such as unvulcanized rubber, the so-called 

 clippings, etc., however, because they are of good quality, are 

 generally used in the manufacture in place of the cheap kinds 

 of crude rubber ; they are not resinous, rather elastic, and do not 

 become porous as soon as inferior crude rubber, besides which 

 the washing and attendant losses are avoided. The natural 

 colored clippings have a higher value than the colored ones, 

 which latter cannot be employed for all purposes ; but they are 

 not frequently met with, as they are generally worked up again 

 in the factories. 



The main bulk of the scrap rubber, however, results from 

 vulcanized rubber and from hard rubber, the former being dis- 

 tinguished as follows: (i) Scrap with fillings, and (2) scrap 

 without fillings. These in turn are divided into floating and 

 non-floating — /. e., with or without weighting or other admix- 

 tures. 



The following are counted among scrap with filling: Play- 

 ing balls, usually with a hard and fissured inside rubber layer 

 caused by ammonia, which have to be boiled out very carefully • 

 balls from surgical instruments, atomizers, etc., as well as all 

 the various gray and red rubber articles used in surgery ; also, 

 toys, dolls, pump valves, pressed plates, centrifugal pjids, rub- 

 ber hose, discs, bandsaw covers, bicycle and other tires, roller 

 coverings, etc. 



Among the items of waste of this kind of inferior value are ; 

 Plates and other technical articles, rubber erasers, irrigator 

 tubing, rings of every description, oil valves, etc. Further- 

 more, there are scraps from rain coats, whose linings of fabric 

 are pulled ofl mechanically or destroyed by acids ; and old rub- 

 ber shoes, which, especially in America, are valued as an admix- 

 ture. Rubber lined linen and cotton hose, vulcanized and un- 

 vulcanized, and rubber coated asbestos fabric scrap, freed from 

 wires and brass tissues, are also readily sold. 



To accomplish a rational utilization, the floating scrap and 

 such as sink only after remaining in the water for some time, 

 has to be separated in this case; also the different colors, 

 which are assorted into gray and variegated. The floating 

 scrap without filling — that is, such as contain only crude rub- 

 ber and sulphur — has a specific gravity from 0.99 to i.o; but 

 there are also floating scraps which are mixed with rubber sub- 

 stitutes or with boiled out floating waste. Among the floating 

 scraps are hose and rings of every description, valves, roller 

 coverings, boundary straps. Para products, billiard cushions, 

 thread waste from rubber weaving, etc. 



* Translated for The India Rubber World, from Nueste Erjin.iungin und 

 Er/ahrungtn^ Vienna. XXIX-6 ilyoa), pp. 243-245. 



The floating waste must be elastic and must, drawn out to a 

 certain length, re-assume its former condition, and not bend 

 or be brittle. Among the semi-floating waste are pneumatic 

 covers pulled off from the layer of fabric, nipples, gloves, sur- 

 gical patent rubber goods, rubber dress shields, imitation pat- 

 ent plates, and articles made from them. The value of this 

 waste is less because the quality suffers through the chlorine in 

 vulcanizing and, in the case of patent rubber, admixtures of 

 artificial rubber are frequent. The specific gravity of the semi 

 floating scrap is i.o to i.io as the maximum ; if lying for a long 

 time in water the scrap becomes spongy, soft, or sticky, and 

 then sinks to the bottom. 



The hard rubber scrap furnishes a large contingent, but, 

 owing to the foreign admixtures (pumice stone, chalk, mag- 

 nesia, soapstone, talcum, and heavy spar) it is of inferior value. 

 Scraps from electrotechnical factories and electrical works are 

 of good quality, have a smooth, not rough, black fracture, are 

 glossy, can be pulverized, and, if used along with other rubber, 

 are susceptible of a polish. 



For the purpose of utilization, the hard rubber scrap is first 

 broken up by means of a rolling balls grinding mill and then, 

 for further reduction, conveyed to the disintegrator. The pro- 

 duct of the latter is finely ground by means of rollers and 

 sifted ; then the coarser particles are again treated, and finally 

 the fine product of the grinding is blown into a dust chamber, 

 where it deposits in different degrees of fineness, owing to its 

 varying gravity, and is freed from adhering iron particles by 

 means of magnet apparatus. The waste of the various assort- 

 ings is chiefly used in the Caoutchouc industry, for insulating 

 substances, in the varnish manufacture, in the production of 

 emery discs, etc., and the treatment to which they are sub- 

 jected after the assorting and mechanical cleaning is mainly 

 that of removing the adhering and absorbed acids, the salts 

 etc., and the separation of free sulphur. The scrap is generally 

 washed for some time, under great pressure, with caustic soda 

 lye or hydrochloric and sulphuric acids, respectively, and then 

 treated further with clean water. The object is the removal of 

 the free sulphur, while the bound sulphur remains in the mass. 



Although the cleansing of vulcanized Caoutchouc by com- 

 plete removal of the sulphur has been repeatedly tried and a 

 number of patents have latterly been taken out for such pro- 

 cesses, success has not yet been achieved in performing the 

 desulphuration in a really rational manner. 



By the reclaiming process of Dr. Wimmer a rubber is said 

 to be obtained which is free from all odor and possesses the 

 entire elasticity of the former article. Ground or finely cut 

 old rubber reduced as finely as possible is heated with about 

 the same weight of castor oil to a temperature of 180" C, to 

 at most 210° C.,t until dissolved. After cooling, this solution 

 is poured with constant stirring into double the volume of 90 

 per cent, spirit. The rubber dissolved in the oil will then 

 separate in the form of a tough mass, while the castor oil re- 

 mains dissolved in the alcohol. The liquid is separated from 

 the rubber .and the latter is repeatedly washed with a small 

 quantity of frQsh spirit. As the rubber still contains plenty of 

 spirit, it is washed with warm water to which some soda lye is 

 added and finally with pure water. 



Hudson Marks, of Akron, subjects rubbed up or reduced 



t =356^ F. and 410° F. 



