JuLv 1, 19191 



THE INDIA RUBBER WORLD 



557 



RECLAIMING HARD RUBBER. 



By Haticock Haskms. 



SuFT RUBBER ill its great variety of forms as scrap, trim- 

 mings, and worn out articles, has been reclaimed, recovered 

 jr regenerated almost from the time of Goodyear. Hard rub- 

 oer scrap, however, for a long time was neglected, first because 

 it was mechanically difficult, and second because none of the 

 common acid or alkali processes were adapted or, rather, needed 

 in its reclamation. It therefore happened that while old boots 

 and shoes, belting, hose, and tires were collected, and a huge 

 business built up on their recovery, hard rubber scrap was not 

 sought for. 



Hard rubber scrap comes in a great variety of shapes. Worn 

 out battery jars, bases for truck tires, electrical sheets and rods, 

 valves, druggists' and surgical fittings, etc., etc. Before pro- 

 ceeding to a discussion of the methods of turning hard rubber 

 scrap into dust, a word concerning the use of this dust is in 

 order. 



Hard rubber dust is not desulphurized or devulcanized. Nor 

 is this necessary, for the sulphur contained in it is in no sense 

 a handicap. Indeed it is useful for revulcanization. The dust 

 is simply added as if it were so much whiting and under 

 pressure and heat it continues to be hard rubber but shaped 

 and pressed into solid form. 



For illustration take one of the well-known "dust com- 

 pounds." It is: 5 pounds of Para rubber, 20 pounds of hard 

 rubber dust, S pounds of sulphur, and 3 pounds of substitute. 



Of course, this is only one of hundreds, some containing much 

 dust, some little, some calling for substitute and some for vege- 

 table oil. 



In soft rubber, hard rubber dust is of no use at all, but in 

 hard rubber it is of prime importance, especially for electrical, 

 physical or chemical purposes, or when it is to be made into 

 objects demanding a high degree of polish. 



In all of the above the dust must contain neither metal parts 

 nor grit, and the best hard rubber scrap should be used, as it 

 contains the highest percentage of rubber and no fillers such 

 as chalk. The scrap should therefore be sorted by experienced 

 hands before be- 

 ing ground. The 

 best results are 

 obtained with 

 powerful, short- 

 built mills pro- 

 vided with 

 smooth, not 

 ribbed, rollers. 

 Regardless of the 

 grinding system 

 resorted to, the 

 operation always 

 results in the 

 rollers of the 

 grinders giving 

 ofif more or less 

 metallic powder. 

 To pass through 

 various sieves the hard rul 

 them is magnetic, does not 

 particles pass through sieves 



Day's Dust Grinder. 

 ler dust obtained, eve 



d, even if one of 

 all impurities. Sand or grit 

 Washing hard rubber dust means 

 the loss of much of the valuable material; further, the drying 

 of the washed dust requires much care and time, and there is 

 always the risk that sufficient humidity will remain to increase 

 the porosity of the finished product. 



The best method of removing impurities is probably to use a 

 combination of ventilators and sieves in a dust-tight room. The 



following is a description of one of these fanning installations 

 in a room ten feet high and fifty feet long, the ceiling, walls 

 and floor zinc covered. In the room are two longitudinal par- 

 titions, reaching from the ceiling to the floor. At the point 

 where the hard rubber dust enters, there is a sieve, with a 

 wooden frame covered with zinc, the sieve running on iron 

 rollers along 

 an iron track. 

 It is provided 

 at the bottom 

 with small 

 openings for 

 the rubber 

 dust. As the 

 dust leaves 

 the sieve it is 

 caught by a 

 fan which 

 disperses it 

 throng hout 

 the rooin. The 

 h e a V y par- 

 ticles such as 

 metal and 



sand, 



dialely fall. 



The Sturtevant Mill. 

 rublier dust is blown farther along, where it settles. 

 The room has two observation windows, through which it can 

 be ascertained that the dust has settled, it also has an air-tight 

 door through which the workman enters to remove the dust, 

 and finally it has a half-dozen slatted windows through which 

 the air forced into the room by fans can escape. It does not 

 take much experience in operating this dust room to discover 

 where the finer dust deposits. Several qualities of hard rubber 

 dust can be obtained simultaneously. Rubber dust not suffi- 

 ciently fine can be reground and no dust is lost. The room 

 described has been in use for a number of years, works almost 

 automatically, and gives good results. 



SECOND PAN-AMERICAN COMMERCIAL CONFERENCE. 



This congress of 1,181 delegates representing the official, un- 

 official, commercial, financial and business life of all of the 

 American republics, held in Washington, D. C, June 2 to 6, 

 inclusive, under the auspices of the Pan .'American Union, was 

 the most successful series of meetings of their kind ever held 

 on this continent. Never before has such a conference been 

 so comprehensive in topics discussed, so fair to all the countries 

 participating, nor so productive of practical results. 



.\mong the principal results of benefit to Latin Ainerica which 

 will be early outgrowths of the conference are better steamship 

 facilities, extensive railway, highway and hotel construction ; 

 improved commercial methods and regulations ; extension of 

 banking connections, ample loans and credit facilities ; safeguard- 

 ing patents, trade-marks and copyrights ; extension and simpli- 

 fication of the parcel post and improvement of news and cable 

 service ; similarity of consular office administration, invoices 

 and fees ; revision and permanency of tariffs, insurance and 

 packing; encouragement of vocational training for Pan .Amer- 

 ican trade ; and arrangements for holding the Second Pan 

 Ainerican Financial Congress in Washington in January, 1920. 



The complete proceedings, which will be the most up-to-date 

 handbook on Pan .'\merican commerce yet published, are being 

 printed and ran be obtained on application to the director gen- 

 era! of the Pan .\merican Union, Washington, D. C. 



War Savincs Stamps— Build 

 ur own success. 



.•\meric. 



prosperity 



