132 



THE INDIA RUBBER WORLD 



[December 1, 1914. 



for a long time. It is. therefore, worth while considering these 

 as solvents — particularly what are known as "Wood Turpen- 

 tines" made from the de; usually have a very 

 disagreeable odor, and this is fatal to theii ■ n they ap- 

 pear in the finished goods liki and varnishes, but where 

 they are removed their odor can be tolerated in the workrooms 

 with proper mechanical Pine oil is also made from 

 me lime as turpentine, and is a less volatile com- 

 pound. Both of these oils will dissolve rubber better than 

 petroleum naphthas and as well as coal tar products, and the 

 volatility i f turpentine is just right for many purposes. 



ETHER. 



This is an excellent solvent, but nearlj as volatile and dan- 

 gerous as carbon bi-sulphide. It has only a faint, pleasant odor. 

 It is rather expensive, selling at 18 cents per pound, but as it is 

 made from denatured alcohol, its price may be reduced in the 

 future. 



TIIF. NON INFLAMMABLE SOLVENTS. 



I lure is a large number of non-inflammable rubber solvents 

 which are in nearly all cases compounds of chlorine with the 

 hydrocarbons. Among them may be mentioned: Carbon tetra- 

 chloride, chloroform, di-chlor-methane, tri-chlor ethane andtetra- 

 chlor-ethane. The chlor-ethylenes have also come on the mar- 

 ket. These are as follows : Di-chlorethylene, boiling point 55 

 C; tri-chlorethylene, boiling point 88 C, or 190 F.; tetra-chlore- 

 thvlene, boiling point. 121 C, or 249 F., and specific gravity of 

 1 :60. All the above are made in Europe and were until recently 

 sold at about 7 cents per pound. The last one mentioned is, 

 however, made as a by-product in the United Stati - when making 

 carbon tetra-chloride. 



CARBON TETRA-CHLORIDE. 



This is the most available non-inflammable solvent, the price 

 recently having been 6.5 cents per pound. It is now much higher. 

 but as it is made in this country, it will probably soon be again 

 available. This solvent is used as a fire extinguisher, and with 

 60 per cent, tetra-chloride and 40 per cent, naphtha the mixed 

 solvent will not explode or burn. 



Other uninflammable solvents which may soon come into use 

 are "Dutch liquid," or ethyl chloride, Cdl.CL. with a specific 

 gravity of 1.25 and boiling point of 84 degs C. and propylene 

 chloride, CiHeCU, the specific gravity of which is 1.165 and the 

 boiling point of which is 97 degs. C. Their manufacture has been 

 begun in this country. 



\\ ere it not for the price at which the chlorinated compounds 

 are held, these would be universally used on account of the 

 lessened risk in using them, compared with the hydrocarbons 

 themselves, but they will never, perhaps, be brought down to a 

 comparative price. When, however, the solvents can be in large 

 part recovered, as is sometimes possible, then the additional 

 price for the uninflammable solvents will not prohibit their use, 

 particularly in those places where, as in a large city or in a large 

 factory, any tire would endanger a very large amount of property. 



(iTIIER SOLVENTS. 



There are othi of rubber among the essential oils and 



balsams and oleo resins. On account of the price, however, these 

 are seldom used, though some were formerly used in rubber 

 mixings to make them adhesive; for example. Canada Balsam 

 and Oregon Balsam d Venice turpentine. These are all 



exudations of trees of the pine family. 



Of the basic chemical bodies which are oils nitro-benzol may be 

 mentioned. It has been n^^-il a ent for vulcanized rubber 



in analysis, though C. O. Weber preferred the nitro-toluol. 

 Pyridine is also a basic body which will dissolve rubber, but 

 Kenneth MacKenzie pointed out (Journal of Industrial and En- 

 gineering Chemistry, 1909, p. 361) that pyridine is liable to be 

 contaminated by the hydrate which boils at ''4 5 degrees C. which 



does not dissolve rubber, but the pure pyridine which boils at 

 115 degrees C. with a specific gravity of .98 will dissolve crude 

 rubber. C. O. Weber uses pyridine to separate asphalts, tars, etc., 

 from the vulcanized rubber in analytical work. It might be a 

 good accelerator, but its smell is almost unendurable. 



Sulphur chloride, though not strictly a rubbet solvent, is used 

 for the cold cure. It has been described in Pearson's "Crude 

 Rubber and ( ompounding Ingredients" and is familiar to all in 

 the rubber trade. 



In general those liquids which dissolve in water and not in oils 

 are not solvents of rubber, but some of them are used for 

 various purposes in the rubber industry. Methyl or wood alcohol 

 will not dissolve rubber, but will dissolve resins to some extent. 

 Ethyl or grain alcohol will dissolve most rubber resins better 

 than wood alcohol, though the latter will dissolve shellac better, 

 and most varnish gums can be dissolved better in these alcohols, 

 if not raw. than after heating. 



The higher alcohols, such as fusel oil, together with their esters 

 such as amyl-acetate, will dissolve rubber quite perceptibly, but 

 they are of no importance in the rubber industry though of great 

 importance in the celluloid and like industries. Amyl-acetate is 

 almost necessary in all nitrocellulose solutions to get a proper 

 protective coating which is of the proper glassy consistency. 

 Acetone is a better rubber resin solvent than the alcohols, but 

 methyl and ethylacetati an ^t ill better solvents, in fact the best 

 which will not dissolve the rubber at the same time. Many rubber 

 solvents have not been mentioned as they are rather rare chemi- 

 cals or oils of such high price that they are of no practical 

 interest. 



COAL TAR PRODUCTS FOR THE RUBBER TRADE. 



I TIE ramifications of the rubber trade call for a wide variety 

 of coal tar products. It might be well to consider the list 

 of materials that are demanded by the manufacturers of various 

 rubber goods : 



Benzol, which boils at the lowest point of all the coal tar dis- 

 tillates, is made in five grades. 



Benzol Pure is made water-white and refined so that 100 

 per cent, of it will distil within a 2-deg. C. range of the boiling 

 point, 82 degs. C, and has a gravity of approximately .880. 

 This material is crystallizable at freezing temperatures. 

 It carries little in the way of impurities and a very 

 small amount of higher boiling homologues. It is used 

 chiefly in cements where speed of evaporation is required. It 

 is also used as a carrier for sulphur chloride, sometimes alone, 

 and at others mixed 50 per cent, with carbon tetra-chloride. 

 There is a small percentage of sulphur compounds in the way of 

 impurities, and certain sources of crude will yield a small amount 

 of carbon-bisulphide in the resultant benzol. Of late there has 

 been a demand for benzol free from these compounds. 



100 Per Cent. Benzol is water-white and refined to a similar 

 degree as the preceding, except that higher boiling homologues 

 are present in sufficient quantity to elevate the boiling point so 

 that 100 per cent, will distil at 100 degs. C. It is used in about 

 the same way as pure benzol. 



90 Per Cent Benzol is the grade that is used most by the 

 trade. This material is water-white, of good odor and very 

 strong in solvent power. It is fast in evaporation and will cut 

 rubber, rosin, gum, etc.. with considerable speed. This enters 

 into a wide variety of cements, particularly pure Para. It has 

 been used for "wiping off" in tire building, but as a usual thing 

 the low cost of petroleum products precludes this. 



50 Per Cent. Benzol is similar to the preceding grades, but 

 slower in evaporation because the boiling point is now elevated 

 so that only 50 per cent, will distil at 100 degs. C. It is seldom 

 used in the trade except in a few special cements where a cer- 

 tain drying time is required. 



