294 



THE INDIA RUBBER WORLD 



[March 1. 1916. 



THE HUNTER DRY KILN— A COMPARISON. 



\ ROOM for drying is a very important adjunct in the manu- 

 facture of rubber goods that in these days of competition 

 and close prices are generally sold under a guarantee. It is well 

 known that the materials, which make up the compounded rubber, 

 must be intelligently prepared in order to produce reliable goods. 



Many of the modtrn drying systems are highly inefficient and 

 unsatisfactory because of the time and space required or the in- 

 ferior quality of the stock after being dried. That the old dry- 

 ing principles are wrong is claimed by the Hunter Dry Kiln 

 Co., Indianapolis, Indiana, in the following description and com- 

 parative tests of the Hunter process and dry kiln : 



The kiln is constructed to bring about a rapid circulation of 

 conditioned air by purely natural means, thus eliminating the 

 possibility of mechanical disorder and lack of uniformity of 

 conditions in the drying room. These conditions are automat- 

 ically controlled, thereby making every day a perfect drying day 

 regardless of atmospheric irregularities. 



An ordinary dry room, perhaps, 85 feet long and 17 feet wide, 



with forced air circulating and condensing system, has a capacity 



of 14,000 pounds of dry rubber each 7 to 14 days, according 



to the moisture content of the crude material. 



THE HUNTER DRV KILN. 



A Hunter dry kiln is 18 feet wide and 35 feet long, inside 

 measurement, and has a capacity of 15,120 pounds of rubber 

 each twenty-four hours. This time allows from 6 to 9 hours for 

 emptying and re-tilling the room, the actual drying time being 

 from 15 to 18 hours. 



In order to arrive at a figure whereby the efficiency of the 

 two systems may be compared, space, quantity and time must 

 be taken into consideration. The ratio of efficiency will be in- 

 versely proportional to the product of the figures representing 

 space, quantity and time of each system. Substituting the mini- 

 mum time (7 days) of the dry room, and the maximum time 

 (24 hours) of the dry kiln, the efficiency factor is: 

 Dry Kiln 15.7 



Dry Room 1 



Disregarding space and simply considering the possible capac- 

 ity of each system under existing conditions, the output of the 

 kiln is 7.5 times that of the dry room. 



COMPARATIVE RUBBER DRYING TESTS. 

 The following comparative tests on washed and compounded 

 stocks show interesting diiTerences in favor of the dry kiln : 



A batch of rubber was washed, careful attention being given 

 to insure uniformity of mixing on the mills. Of the resultant 

 crepe sheet, one-half was dried in the regular dry room, and 

 the other half was placed in the Hunter dry kiln. After drying, 

 test batches were mixed from each of the samples, checks being 

 kept on each one. The following data were the results obtained : 

 PREPARATION OF SAMPLES. 



Drv Kiln 15 hours Moisture 079 percent. 



Dry Room 184 hours Moisture 28 per cent. 



GREEN TESTS. 



Cure at 



Break. Stretch. 40 Pounds. 



Pounds. Inches. Efficiency. Hours. 



Dry Kiln 1,325 6.56 8,692 2'A 



Dry Room 1,275 6.12 7,802 2J^ 



Dry Kiln 1,562 6.56 10,246.72 2% 



Dry Room 1,526 6.43 9,805.75 2^ 



AGED TESTS. 

 Samples of above cures were aged in circulating dry heated 

 air for three hours at 235 degs F. 



Cure at 

 Break. Stretch. 40 Pounds. 



Pounds. Inches. Efficiency. Hours. 



Dry Kiln 762 5.75 4,381.5 2'/, 



Dry Room 525 4.75 2,493.75 2'A 



Dry Kiln 1,075. 5.91 6,245.75 2Vi 



Dry Room 637.5 5.12 3,264 2^4 



Moisture. Sulphur Mix. Oil Mix. 



Per Cent. Efficiency. Eflficiency, 



Dry Kiln 21 1,510 1.720 



Dry Room 59 1,350 1,375 



Dry Kiln 30 1,675 1,800 



Dry Room 43 1,410 1,290 



DRYING PONTIAN.\(. 

 When Pontianac is washed and milled in one-fourth inch 

 sheets, it presents a dense, dough-like mass, .-^fter hanging 

 these sheets in the dry room at 96 degrees F. for ten days, the 

 stock presents a hard, brittle external crust of a creamy white 

 color, and is apparently dry, but contains from I'/i to 4^ per 

 cent moisture by test. The material is shown to contain 1.44- 

 per cent of moisture after twenty-one days under the above 

 conditions, and becomes so crumbly that it is difficult to handle. 

 However, when placed in the dry kiln, Pontianac is dried from 

 0.75 per cent to 1 per cent moisture in 38 hours, and from 0.3- 

 per cent to 0.5 per cent in 48 hours. This material is then a. 

 brown colored, flexible mass, which is slightly tacky, is easy to 

 handle and not injurious to the stock in which it is used. 



DRYING COMPOUNDING INGREDIENTS. 



Zinc, lithopone, whiting and barytes are dried in from 24 to 90 

 hours by placing the barrels in the kiln in an upright position 

 and permitting a circulation of air on all sides. These com- 

 pounds, especially zinc, and lithopone, after being thus dried, do 

 not form in sticky lumps which are hard to pulverize, but 

 powder very readily through the sieve, and seldom cake oa 

 the mixing rolls. 



DRYING CEMENTED SURFACES. 



Two to three hours, depending largely upon weather condi- 

 tions, are required to dry the cement on inner tube splices and 

 valve bases. In the dry kiln this operation is accomplished per- 

 fectly in 25 ininutes. Life is apparently given to the cement 

 by this process, and tight, firm splices are the result. 



In the construction of double operation motorcycle casings, it 

 has been the custom to paint a heavy coating of cement on a 

 carcass, and a .period of from three to five hours was required 

 before the cement was sufficiently dry to permit of the applica- 

 tion of the tread. By the Hunter process, however, the carcass 

 is ready for the application of the tread after one hour in the 

 dry kiln, and this period can be shortened if necessary. 



.Ml of the above data was taken under actual working con- 

 ditions. 



THE AMSTERDAM CHUDE RUBBER MARKET IN 1914. 



Official industrial and commercial reports of the Netherlands- 

 for 1914 have recently been published. They contain interesting 

 facts relating to the effect of the war on the .Amsterdam crude 

 rubber market during the first five months of the war. 



The year 1914 opened very favorably for the Amsterdam 

 rubber market; business was active and the number of buyers- 

 increasing. War came early in August and, from then on, very 

 little crude rubber was received. That which arrived was sold 

 without the usual sorting, sampling and careful examination, 

 thereby preventing the levying of the usual taxes, as it was im- 

 possible to determine values regarding which no indications were 

 available. 



Prices increased with a bound. Hevca rubber was especially- 

 sought for and brouglit prices as high as 7 florins per half kilo- 

 gram [$2.55 per pound], which was about equal to the highest 

 prices paid in 1910, during the rubber boom. 



Shipments which arrived after the stocks included in the 

 auction of July 29, amounted to 499.956 kilograms [1,099.903 

 pounds], of which 418,924 kilograms [921,633 pounds] were 

 Hcvea; 61,543 kilograms [135,395 pounds], plantation Ficus; 8,255, 

 kilograms [18.161 pounds], CastiUoa: 1,384 kilograms [3.045 

 pounds], Manihot and 9,850 kilograms [21,670 pounds] of various 

 kinds of forest rubber. 



