January l; 1921 



THE INDIA RUBBER WORLD 



237 



PREPARATION OF BALATA 



Balata is a non-vulcaiiizable gum of the gutta varietj- derived 

 from the "bully" or "bullet" tree, Mimusops balata. It is found 

 in several South American countries, particularly in the Guianas 

 and Venezuela. Crude balata as received comes in the form of 

 blocks or sheets. Both forms contain such impurities as wood, 

 sand and moisture which must be removed by washing. Balata 

 sheets contain 10 to IS per cent of moisture and the blocks from 



with rolls of equal speed, in which it is rolled out into thin 

 sheets preparatory to the next operation. In the illustration it 

 will be seen that the sheeting mill, like the washer, is provided 

 with a pan mounted on rails, serving the same purpose. 



Before compounding and making the solution it is essential, 

 as in rubber working, that all moisture be eliminated from the 

 gum. The clean sheets are, therefore, taken from the shecter 

 direct to an oven or drying stove, Fjg. S. This is a chamber 



-■^ 



Fig. C. Strip Cuttinc Machine 



Fig. 10. Overhead Open Drying and Cooling 

 Apparatus 



Fir. 



Inprecnatinr Uachine 



Fig. 11. Cloth Slitting Machine 



Fi^. '?• Solution Mixing Machine 



Horizontal Drying Uachine 





Fig. 12. Rolling Uachine 



Da'-id Bridge ^r Co., l.imitcu 



30 to 35 per cent. The removal of the impurities is effected by 

 a method resembling that used in cleaning wild rubber. 



The stiff crtide gum is lirst put through a slicing machine, 

 Fig. 1, which reduces it to convenient form for the next opera- 

 tion of softening it in tanks of boiling water heated by sleam. 

 Under this treatment the gum becomes very soft and plastic, 

 permitting the inclosed foreign matters to be readily brought to 

 the surface and removed by the subsequent cleaning operations. 



The first of these is washing in a specially adapted machine, 

 substantially in effect a Hollander or so-called paper engine, Fig. 

 2. This consists of a large tank with a central vertical portion 

 and at the side, on one end, a heavy revolving cylinder provided 

 with knife edges working shear-like with a fixed cutting edge 

 under water, past which the softened balata passes with the cur- 

 rent of water set in motion by the wheel mentioned 



The balata is mechanically fed to the revolving cutters of this 

 machine by a special roller feed and after cutting it is delivered 

 into the tank below, where it is subjected to agitation in warm 

 water, so that the wood and other impurities are separated. The 

 light-gravity material floats away on the surface while the sand 

 and earth sink to the bottom. 



The partly cleaned gum is taken next to a washing mill. Fig. 3, 

 resembling that commonly used for crude rubber. It differs by 

 having under it instead of a screen or mill pan a portable tank- 

 like pan mounted on a truck that runs on a track. This affords 

 a bath of warm water for retaining the balata in a workable 

 state of plasticity. The washer mill rolls are corrugated and 

 have a differential speed for tearing apart the gum. while an 

 overhead supply of water descends and washes out the im- 

 purities brought to the surface by the milling. 



Having been thoroughly freed of foreign matters in the wash- 

 ing mill the balata passes next to a sheeting machine, Fig. 4, 



provided with shelving to receive the stock, and operates by a 

 fan-actuated system of .ventilation in which air at suitable tem- 

 perature is drawn in at one side and expelled moisture-laden from 

 the other. The thoroughly dry sheets are prepared for solution 

 and compounding by passing through the strip-cutting machine, 

 Fig. 6, in which they are reduced to thin strips to render the 

 gum more readily soluble. 



The solution-mixing machine. Fig. 7, consists of a vertical 

 steam-jacketed power churn. The clean, dry, thin balata strips 

 are placed in the mixer with the solvent and fillers, which may 

 include sitch materials as regenerated balata, oxides, carbonates, 

 resins and coloring matters. In the mixer the process of solu- 

 tion is effected by paddles rotating in opposite directions, while 

 tlie materials are maintained at about 90 degrees F. by steam 

 circulation in the outer jacket. When ready for use the charge 

 is received in an open tank car placed under the mixer which is 

 discharged through a quick-opening gate-valve. 



.\\. this point in the manufacture of balata belting comes the 

 process of impregnation of the duck employed. 



IMPREGNATION BY SOLUTION 



English and American practices differ from tlic French in the 

 method used for applying the balata to the fabric. The English 

 and American processes deal directly with the compounded solu- 

 tion from the mi.xer in a machine of the type illustrated in Fig. 8, 

 which shows an end view. The arrangement consists of two pairs 

 of pressure rollers, through one pair of which the dry duck to 

 be impregnated is passed down into the prepared balata solution 

 contained in a V-shaped truck tank run under the machine. The 

 entire structure of the duck is thus filled with the gum prepara- 

 tion and the excess is removed by the second pair of pressure 

 rollers and returns to the tank. 



The solvent which saturates the impregnated fabric is ex- 



