April 1, 1S?1 



THE INDIA RUBBER WORLD 



487 



Solvents and Thinners Used in the Rubber Industry' i 



By Frederic Dannerlh, Ph.D. 



A Study of Specifications, Technical Properties, and Methods of Testing, Volatile Organic Solvents 



IN THE RUBBER INDUSTRY the use of thinners, or volatile sol- 

 vents is a primary requirement in the process of spreading, in 

 the vapor vulcanization of rubberized and rubber-coated 

 fabrics, in the preparation of dipping solutions which contain sul- 

 phur chloride, and in the preparation of cements used in connec- 

 tion with many different "building-up" processes, .^s examples 

 of these built-up articles, we have such druggists' sundries as 

 hot water bottles and fountain syringes; raincoats and rubber 

 footwear; power transmission belting and rubber hose. Solvents 

 are also used for the purpose of cleaning surfaces before rubber 

 or rubber compounds arc applied. These "wiping liquids" are 

 used in the manufacture of auto tires, as well as rubber-covered 

 rolls. 



SPECIFICATIONS 



In writing specifications for volatile solvents or thinners, it is 

 desirable and necessarj' to taKC into consideration the effect which 

 the operator seeks to attain — the effect of the solvent on rubber 

 and rubber compounds, as well as the effect of the solvent on the 

 workers. The questions which the buyer and the factory superin- 

 tendent must therefore keep in mind are these : 



1. Is it non-to.xic? Will it injure the worker either externally 

 or internally? Will it shorten his life? 



2. Is it non-corrosive? Will it attack any cans, tanks or drums 

 in which it may be stored or transported? 



3. Has it the proper "speed of evaporation"? Will it evaporate 

 before it has accomplished its purpose, or will it remain as an 

 oily deposit after it has done its work? 



4. Has it a definite boiling point, or is it a mixture of various 

 solvent liquids which boil at different temperatures? 



5. Does it contain any "high-boiling residues" such as are con- 

 tained in raw petroleum before it is refined ? If the solvent is 

 to be used as a wiping fluid this is an important consideration 

 because any grease or oil content would interfere with the ad- 

 hesion of the rubber compound. 



6. Is it non-inflammable? This factor will, of course, affect the 

 fire risk and determine the amount of insurance premium de- 

 manded by the insurance companies. Solvents having a very low 

 "flash point" will, as a rule, be prohibited by the authorities, and, 

 on the other hand, they will generally be found to be unsuited 

 for use in any of the operations mentioned above. 



7. Is it odorless? Foul smelling liquids and those which irri- 



^Tliis article may not be reprinted without permission of the author who 

 reserves all publication rights. 



tate the membranes of the eye and nose will interfere with the 

 erticicncy of most workmen. For that reason an odorless liquid 

 would be preferred to those having a foul, pungent, irritant, caus- 

 tic, disgusting, offensive or other unpleasant odor. 



8. What is the solvent or the swelling power which it possesses 

 for rubber? If a cubic inch of fine Para rubber is immersed in 

 the solvent for 60 minutes, what change in size, shape or condi- 

 tion is noticeable ? 



9. What is the price of the solvent or thinner per gallon in 

 original packages, F. O. B. your factory? 



GLOSSARY 



G.ASoLiNE. The refining processes of the petroleum industry 

 consist for the most part of washing and distilling. The crude 

 oil is then, one might say, analyzed on an industrial scale into its 

 component parts. And this is possible because each part boils at 

 a different temperature, just as we find that a teaspoonful of 

 ether and a teaspoonful of water will not evaporate with equal 

 rapidity. 



The type of gasoline or light naphtha used in the preparation 

 of cements and dough for rubberizing is preferably not heavier 

 than 0.730 specific gravity, with a boiling point of SO degrees to ISO 

 degrees C. (122 to 30O degrees F.). Municipal fire laws usually 

 require the user of gasoline to bury the storage tanks so far be- 

 low ground level as to keep the tank cool and prevent the access 

 of flames or electricity. Workmen should remember that the 

 vapors of gasoline are heavy and are therefore more dense near 

 the floor, that the sense of smell tires very quickly, and for that 

 reason they may suddenly find themselves overcome by the vapors 

 unless proper ventilation has been provided. The matter of cor- 

 rect and active ventilation is then one of the principal safeguards 

 which must be adopted wherever this solvent is stored or used 

 or evaporated. 



Coal-tar Benzene. This is a refined oil obtained from the 

 light oil of coal-tar by fractional distillation. It boils at a con- 

 stant temperature of 81 degrees C. (=: 177 degrees F.) and con- 

 tains no high boiling oils, such as is the case with gasoline or 

 petroleum naphtha. Some factory superintendents claim that it 

 is undesirable because it evaporates all at one temperature. In 

 1902 Carl Otto Weber e.xpressed the opinion that "for most prac- 

 tical purposes the use of a homogeneous solvent having a con- 

 stant boiling point, results in solutions or doughs which dry from 

 the surface. This yields harsh and rough coatings, and in the 



T.\ble Showing Properties of the Principal Volatile Organic Solvents 



Specific 

 Solvents Gravity 



Gasoline 65° Bi 0.718 



Benzene pure 0.880 



Benzene 90% 0.870 



Coal-tar naphtha, 160° 0.860 



Turpentine 0.870 



Acetone 0.800 



Methanol. 95% 0.817 



Denat. (?rain alcohol, 190 proof. 0.P16 



Butyl alcohol 0.815 



Fusel oil refined 0.820 



Carbon disulphide 1.292 



Carbon tetrachloride 1.630 



Tri-chlor-ethylenc 1.470 



retra-cblor-ethane 1 ,600 



Water 1.000 



