740 



THE INDIA RUBBER WORLD 



JuLV 1, 1921 



Hartjens varied the conditions o{ manufacture in order to 

 Irace the origin of tlicse spots or patches and came to the con- 

 clusion that they could be connected with the use of sulphite and 

 bisulphite of soda, or a combination of both. Small amounts of 

 these chemicals seldom produce spots, but larger proportions may 

 produce very dark and distinct spots. 



It is, therefore, possible that these dark spots are in some way 

 connected with mould growth and also with the use of sulphite 

 and bisulphite in sheet manufacture. There are insufficient data 

 to explain what the connection may be. Possibly the dark parts 

 retain more moisture than the light and are therefore more prone 

 to develop mould. In any case, the observations call for an 

 investigation of the effect of sulphite and bisulphite on the liability 

 of smoked sheet to go mouldy. 



Sodium sulphite is used in only very small quantities to keep 

 the late.x fluid, but bisulphite is sometimes used in larger quantities 

 to keep the sheet light in color, owing to the marked objection to 

 so-called "oversmoked" sheet. If found that the use of bisulphite 

 tends to cause mould it would probably be better to risk the 

 sheet being dark in color. 



It is known that bisulphite hinders the drying of crepe rubber, 

 that is to say, rubber so treated tends to retain moisture, and what 

 is true of crepe is probably true of sheet. Sheet which tends to 

 retain moisture, even if thoroughly smoked, will lend to take up 

 moisture again at the first favorable opportunity, and the more 

 moisture present, the greater the liability to mould. Hence there 

 are already definite reasons for thinking that sodium bisulphite inay 

 cause mould to develop in smoked sheet, especially in transit. 



The effect of bisulphite is probably aggravated by the circum- 

 stance that so much of it is of very poor quality. It is quite like- 

 ly that the sodium sulphite and other impurities are as responsible 

 for the retention of water as the bisulphite itself, and where pos- 

 sibly large quantities of poor quality material have to be added to 

 produce the necessary effect on the color, it is easily realized that 

 the quality of the rubber and resistance to mould are impaired. 



The Rubber Growers' Association recommendations for the 

 treatment of latex and the curing of sheet rubber state that 

 5odium bisulphite should not be used for the preparation of sheet 

 rubber. 



STORAGE OF PLANTATION RUBBER 



Henry P. Stevens, consulting chemist to the Rubber Growers' 

 Association, has recently reported on the storage of plantation 

 rubber, of which the following conveys the principal points. 



Plantation rubber does not deteriorate rapidly but is remarkably 

 stable and little altered after long storage, provided certain ele- 

 mentary precautions be taken. The most important of these is 

 protection from direct sunlight. Fluctuations of temperature have 

 practically no effect on rubljer and it is doubtful whether even 

 tropical temperatures cause any appreciable deterioration. 



In London, laboratory-stored samples of properly prepared 

 rubber dating back ten years and more have in no instance shown 

 any marked signs of deterioration. At the most, the surface be- 

 comes very slightly adhesive. This is by no means the case gen- 

 ■erally and many samples of rubber made eight and ten years ago 

 cannot be distinguished from rubber made yesterday. 



The peculiar property of rubber to freeze at moderately low 

 temperatures may have given rise to the assumption that the 

 rubber had perished on keeping. Such is not the cause, and if 

 gently warmed at temperature under that of boiling water, rubber 

 soon becomes flexible, elastic and translucent as originally. 



When stored raw rubbers are broken down, mixed and vulcan- 

 ized, they behave in normal manner. Any differences shown do 

 not appear to be greater than in fresh samples recently imported. 

 No diflference in vulcanizing properties could be detected in this 

 same smoked sheet, the first half of which was testetl in England 

 a year previous to the second half which was retained in the East 

 for a year before importation for test. Old samples of plantation 



rubber vulcanized in comparison with current samples of the same 

 rubber showed only such small variations as would be found with 

 fresh consignments. 



It is evident from the foregoing that deterioration need not take 

 place when ordinary pale crepe or smoked sheet rubber is stored 

 for long periods under suitable conditions. 



Fewer data are available as regards the lower grades, but it is 

 probable that these will keep satisfactorily if properly cleaned and 

 dried. But rubber which contains an appreciable proportion of 

 organic impurity and is exposed to conditions under which putre- 

 faction sets in, will rapidly deteriorate. 



"XLO" ACCELERATOR 



"XLO" is the trade designation of a recently perfected vulcani- 

 zation accelerator from which excellent results have been obtained. 

 It is specially recommended for automobile tire stocks, inner tubes 

 and high-class mechanical goods. It is magnesiated di-phenylguan- 

 adine in the constant proportions of one-third of the former to 

 two-thirds of the latter. From one-quarter to three-quarters of 

 one per cent of the rubber content of a mixing are the recom- 

 mended proportions of this accelerator to be used in practical 

 work. 



CHEMICAL PATENTS 



THE UNITED STATES 



TIRE Filling Composition co.mprising the following ingredi- 

 ents and proportions : vegetable oil 74 per cent ; magnesium 

 oxide 2.2 per cent; ultramarine 2.2 per cent; litharge 2.2 per cent; 

 oakum 1.9 per cent; chloride of sulphur 17.5 per cent. — John A. 

 Schmidtke, Calgary, Alberta, Canada. United States patent No. 

 1,376,973. 



H.'\logenated Rubber Comtound, the molecul.\r structure 

 of which includes more than two halogen atoms ana an atom of a 

 vulcanizing agent — Clayton W. Bedford and William J. Kelly, 

 assignors to The Goodyear Tire & Rubber Co., all of ."Xkron, 

 Ohio. United States patent No. 1,377,152. 



Rubber-Like Material Process, comprising macerating 

 heating and extracting the fleshy parts of cactus, adding a cataly- 

 zer containing a mineral acid radical, concentrating the juice, 

 adding a solution of Para rubber, linseed oil, and a mixture of 

 asphaltum and sulphur and boiling, drying and oxidizing the 

 resultant mass. — John C. Wichmann, Los Angeles, California, 

 United States patent No. 1,379,149. 



Rubber-Like M.\terial Process, co.mprising macerating the 

 fleshy parts of the yucca plant, heating it above the boiling point of 

 water, extracting the juice to which is added a catalyzer consisting 

 of a mixture of sodium tungstate, concentrating the juice, adding 

 a solution of Para rubber, linseed oil and a molten solution of 

 asphalt and sulphur, boiling the mixture under agitation, drying 

 and oxidizing the resultant mass. — John C. Wichmann, Los An- 

 geles, California. United States patent No. 1,379,150. 



the dominion of canada 



Acceleration of Vulcaniz.\tion produced by the use of 

 alkylated, dialyated or methylated dithiocarbamic acid. — The Mich- 

 igan Chemical Co., Bay City, Michigan, assignee of Stuart B. 

 Molony, Wellesley Hills, Massachusetts, U. S. A. Canadian patent 

 No. 211,926. 



.Acceleration of Vulcanization by the use of an alkylated, 

 methylated or mono-methyl dithiocarbamate of a metal. The 

 Michigan Chemical Co., Bay City, Michigan, assignee of Stuart 

 B. Molony, Wellesley Hills, Massachusetts, and Yasujuro Nikaido, 

 Bay City, Michigan, both in U. S. A. Canadian patent No. 

 211,927. 



-Acceleration of VuLCANiZArroN by the use of the methyl- 

 ester of iihcnyl dithiocarbamic acid; the metallic salts of pheny- 

 lated dithiocarbamic acid ; or the metallic salts of phenyl dithio- 

 carbamic acid. — The Michigan Chemical Co., assignee of Stuart 



