472 



THE INDIA RUBBER WORLD 



[June 1, 1914. 



Rubber Cement and Some of Its Uses. 



Ox Li of the important and constantly increasing uses of rub- 

 ber is in the form of cement, and many and varied are 

 the arts, trades and occupations in which this form of 

 adhesive has become practically indispensable. 



Rubber cement may be divided into two classes, namely : 

 a simple solution of the gum which by the evaporation of 

 the solvent leaves a thin layer of the rubber between the parts 

 to be stuck together ; and a compound cement, which, after 

 being applied and the pieces stuck together, is vulcanized, and 

 to a certain extent becomes incorporated as a part of the 

 article so formed. The tirst is used very largely in the manu- 

 facture of leather goods, such as boots and shoes, bags, pocket- 

 books and similar articles. Tlie compound cements are mainly 

 used in the various rubber industries, such as waterproof 

 clothing manufacture, the druggists' sundry business and in 

 automobile tire work. 



The manufacture of those cements used in the production of 

 leather footwear is a comparatively simple matter. The cement 

 is a solution of gum in naphtha, and while there is no secret in 

 its composition, every manufacturer has his own formula as 

 to the proportion of gum to the solvent, and also the kind and 

 quality of the various rubl)crs which enter into his various 

 grades. 



Naphtha is used as the solvent in preference to gasolene or 

 benzine, because of the higher volatility of the former, and the 

 oiliness of the latter. Gasolene wo/ld evaporate too quickly 

 for most purposes where the cement is used, while benzine is 



Goodyear Twin Sole-Laying Machine. 



too heavy and holds sufficient grease to detract from the 



adhesiveness of the rubber. 



The finest qualities of rubber cement are made from Knapsack 

 Para, while in some grades a 



large proportion of Massai is 



used, and in the cheaper grades 



lower cost gums, even down 



to Pontianak. A cement manu- 

 facturer can furnish rubber 



cement at almost any figure 



a customer desires, the price 



bein,g practically determined by 



the quality and quantity of the 



gum used. One manufacturer 



quotes for his best cement one 



dollar a gallon, but another's 



best sells in quantity at $1.50, 



while a leading rubber heel 



manufacturer quotes $2.50 per 



gallon for his best cement for 



attaching rubber heels to leather 



shoes. From these prices the 



scale runs down to almost any 

 amount a customer cares to 



pay, some such preparatiins 1)6- 



ing quoted as low as thirty cents. 



The manufacture 

 of such cement is 

 very simple. The 

 crude rubber is cut 

 in small pieces, 

 softened by hot 

 water, and run 

 through the wash- 

 ing rolls in the 

 usual manner, then 

 sheeted and hung 

 in lofts until 

 thoroughly dry. It 

 is then ready for 

 dissolving in naph- 

 tha. The proper 



quantities of rubber and naphtha are placed in a "muddler," an 

 iron tank having a capacity of about ten barrels. This tank 

 has a central revolving shaft, furnished with projecting arms, 

 while similar arms fastened to the inner surface of the tank en- 

 mesh those on the shaft and by constant stirring facilitate the 

 solution of the gum; and a steam jacket over the lower half 

 of the tank serves to further hasten the process. When the 

 gum has entirely dissolved the cement is ready for drawing ofif 

 into cans or other air-tight containers, for delivery to customers. 

 Simple as this process is, it requires care and experience, 

 while the admixture of the various qualities of gum requires a 

 knowledge of their individual properties and also of their prices 

 current, where cement must be manufactured at certain prescribed 

 prices. For many purposes such cement is entirely satisfactory, 

 but in some of the arts it is required that it be practically 

 colorless in order that it may not stain in any way the materials 

 on which it is used during its application. In this case some 

 manufacturers prepare a quality of their cement from the pure 

 Ceylon or East Indian Pale Crepe which makes a handsome 

 article, not exactly clear but beautifully opalescent, and which 

 leaves no stain upon white canvas or delicate shades of leather. 

 Then, there is a condition that requires a cement which 



Star Chaxxei. Ce.menting Machine. 



