THE INDIA RUBBER WORLD 



[August 1, 1916. 



FATENT REGISTRY. 



Tlie Diet also decided that the terms of 



of the Japanese (Government shall be e 



ten years, but the duration of patents w 



years. 



"New Idea Registry" 

 ctended from six to 

 ill continue to be 20 



THE ILCKEN-DOWN COAGULATION PROCESS. 



I.\ the March, 1916, 



Prkssure Co.XGL-I.ATlXC T;\ 



jsue of The India Kubhek World, a brief 

 description was given of the Ilcken-Down method of coagu- 

 lation. Since this process was introduced last October, several 

 improvements have been made. One factory has been working 

 this process for some months, and others are now beginning to 

 use it. Some of the leading estates on the Peninsula have or- 

 dered tanks, to test the process on a large scale. 



I'.rieHy described, the improved process is as follows : 



^___ The fresh late.x is strained 



into a tank, whence it runs 

 into a second tank fitted with 

 a stirrer and a cover, where 

 it receives one-tenth of an 

 ounce of glycerine to every 

 gallon of latex, and is thor- 

 oughly stirred. As soon as 

 the latex has coagulated, 

 which will occur in from six 

 to eight hours, and is visible 

 by a soft, spongy clot having 

 formed containing nearly all 

 the serum, a mixture com- 

 posed of any of the follow- 

 ing agents : A — alcohol and 

 B — petroleum-benzine, or A 

 — alcohol and B — gasolene, is 

 forced into the tank by 

 means of an injector fitted 

 at the base, and envelops the 

 soft coagulum. It is found 

 that good qualities of de- 

 naturated or methylated spirit 

 and benzine give most sat- 

 isfactory results. 



The time taken to trans- 

 form the latex depends on the nature of the latex. The purer 

 and the richer the latex, the quicker will it be transformed into 

 a soft clot by the action of the glycerine, in which will be 

 developed a certain bacterium called "Sorbose" bacterium, trans- 

 forming the glycerine into dioxyacetone and the dioxyacetone 

 fermenting the enzyme action into ethylalcohol and carbon diox- 

 ide. On a large scale it is recommended that engine power be 

 used for stirring for about 

 five minutes. When stirring 

 is completed, the stirring ap- 

 paratus is removed from the 

 tank, which is then covered. 



When this clot is formed, 

 the mixture of methylated 

 .spirit and benzine is gradu- 

 ally athled to the latex, until 

 a quantity of not less than 

 2 ounces per gallon of latex 

 has been injected round the 

 clot, thoroughly enveloping 

 it. 



Complete precipitation of 

 the coagulum will have taken 

 place and the serum is suf- 

 ficiently clear in aliout 12 

 hours. The serum is run otT 

 and the hard coagulum may 

 then lie removed from the 

 tank and made into slabs or 

 creped. 



.-\fter removing the rubber 

 from the tank a certain 

 amount of pure rubber in the 

 form of fine flour (less than 

 one per mil of the dry rubber weight) will be found in the tank. 

 This should be poured into a clean cylindrical receptacle with tap 

 at bottom and treated by separation in the ordinary way. The 

 flour floats on top, and the serum is run off. 



S-l -JHV 



Flrifving Tai. 



It should be borne in mind that all delay that may arise from 

 time of tapping to collecting and treating the latex with glycerine 

 afifects its coagulation. Therefore, to insure the best results the 

 collection and treatment with glycerine should be done ex- 

 peditiously, the spongy clot frequently forming in 6 hours. 



For small estates zinc or earthenware column-shaped tanks 

 about 6 inches diameter and 18 inches high, to treat 1 to Ij^ 

 gallons of latex, each, can be used. For these small tanks an 

 injector is not necessary. The mixture is merely poured on 

 the coagulum, and the tank is turned round by the hands in a 

 circular direction from left to right and from right to left, thus 

 insuring complete envelopment of the coagulum by the mixture. 



NITRE CAKE IN RUBBER RECLAIMING. 



\ LMOST every type of rubber scrap is today treated for re- 

 *^ covery. These types are generally divided into three gen- 

 eral classes, fabric free, fabric bearing and ebonite. 



Fabric bearing material includes such scrap as belting, hose, 

 overshoes and auto tires. Preliminary to depolymerization and 

 softening all fabric must be destroyed and removed. The fabric 

 is usually cotton and is by various reagents changed into such 

 a form that it may be removed by washing with water. The 

 three principal methods of accomplishing this are the mechanical, 

 the alkali and the acid. In the first method, which is now little 

 used, the scrap is very finely ground and the fluffy fibre blown 

 away. The second, the alkali method, consists in heating ground 

 scrap with alkaline solution to destroy the fibre. The third is 

 the acid process. In this the ground scrap is treated with a hot 

 solution of sulphuric acid varying in strength from IS per cent 

 to 30 per cent, according to the character of the scrap and the 

 fineness to which it has been ground. 



As a result the cellulose of the fabric is charred and can be 

 removed by the'thorough washing. This washed scrap, free from 

 fabric, is then ready for the depolymerization and softening. 



Sulphuric acid is no inconsiderable cost factor in rubber re- 

 claiming and the increase in prices following the outbreak of the 

 war has been keenly felt by the rubber reclaimer. Naturally, 

 an acid substitute has been eagerly sought. In the manufacture 

 of nitric acid by the treatment of sodium nitrate with sulpuric 

 acid, there is produced a secondary product termed nitre cake, 

 and this has proved in many industries the solution of the 

 acid problem. 



Nitre cake is a fused salt made up chiefly of sodium acid 

 sulphate. It is readily soluble in hot water and has an average 

 acidity of 32 per cent in terms of sulphuric acid. That is, three 

 pounds of nitre cake approximately equal one pound of 66" acid. 

 The chemical action of a nitre cake solution is practically the 

 same as that of sulphuric acid solution, though it does not have 

 the tendency of acid to char or burn organic matter. Nitre cake 

 is shipped in lump form, either in bulk or barrels. Being a solid, 

 its handling does not present the difficulties of handling acid, 

 especially in carboys. 



The substitution of nitre cake for acid in defiberizing rubiier 

 scrap is dependent upon the character of the scrap and the degree 

 of fineness to which the scrap is ground or cracked, the strength 

 of the acid solution licing governed chiefly by this factor. A 

 hot saturated solution of nitre cake is approximately equal iii 

 strength to an 18 per cent acid solution and a cold solution to 

 a IS per cent solution. Where a stronger solution is necessary 

 it is prepared by dissolving nitre cake in dilute acid. This 

 effects a partial substitution of nitre cake for acid. The method 

 of treatment with a nitre cake solution is the same as with acid 

 and the results the same, except as to the lack of tlie charring 

 tendency where the nitre cake solution is used. 



The grades of scrap treated and the variation in the method 

 of treatment are so wide that it is really necessary for the re- 

 claimer to make an actual trial to determine the applicability of 

 this material to his needs. Certainly, it has merit for it is. al- 

 ready being successfully used on a large scale. 



