Seubkber 1, 1914.] 



THE INDIA RUBBER WORLD 



651 



Zeitschrift," which was noted in this journal lor May, 1914, it 

 was shown that the nitrogenous constituents had much influence 

 and the resinous constituents little intluence on vulcanization. 



Clayton Beadle and H. P. Stevens separated the protein mat- 

 ter which contained the nitrogen from smoked sheet. ("India 

 Rubber Journal," 1912, pp. 554-604; Abstracts in "Journal 

 Society Chemical Industry," 1912, pp. 999 and 1099.) Then they 

 vulcanized the nitrogenous part and the nitrogen free part and 

 the original sheet. It was found that the part of the rubber 

 with high nitrogen contents vulcanized more rapidly and com- 

 bined with more sulphur than the original sheet, and that the 

 nitrogen free part combined with the least. The strength and 

 resiliency of the nitrogen containing part was the greatest, the 

 original sheet being less, and the nitrogen extracted part was the 

 weakest. To assure themselves that the solution in benzine was 

 not the cause of the difference, they analyzed and cured four 

 samples as follows : 



1st, the original sheet untreated in any way. 



2nd, an original sheet swelled in benzine. 



3rd, the lower half of solution containing nitrogen and coloring 

 matter. 



4th, upper part free from nitrogen. 



The nitrogen contents were as follows : Xo. 1 — 0.47 per cent. ; 

 No. 2 — 0.46 per cent. ; No. 3 — 0.84 per cent., and Xo. 4 — 0.07 per 

 cent. /These were mi.xed witli 7 per cent, sulphur and cured for 

 threejtiours at the steam pressure given below, with the following 

 results ; 



Per Cent. 

 No. 1 No. 2 No. 3 Xo. 4 

 3 hours' cure at 35 lbs., comh'd sulphur. 2.5 2.3 3.2 0.9 

 3 hours' cure at 45 lbs., comh'd sulphur. 4.6 4.1 5.2 0.8 

 3 hours' cure at 55 lbs., comb'd sulphur. 6.4 3.6 



3 hours' cure at 65 lbs., comb'd sulphur. 6.6 6.1 



The tensile strengths and elongations of the cured samples 

 were as follows : 



Three hours' cure at 35 lbs pressure. 



No. 1 No. 2 Xo. 3 Xo. 4 



Tensile strength 59 53 75 13 



Elongation 910 950 840 710 



Three hours' cure at 45 lbs. pressure. 



Tensile strength 100 100 95 33 



Elongation 740 780 600 1 140 



Three hours' cure at 55 lbs. pressure. 



Tensile strength 50 . . . . 41 



Elongation 470 . . . . 960 



Three hours' cure at 65 lbs. pressure. 



Tensile strength 40 . . 30 



Elongation 380 . . . . 400 



The resins were about the same in all samples. 



The tensile strength is calculated in proportion to 100, taken 

 as the best result. 



In calculating the tensile strengths, those found for samples 

 Nos. 1 and 2, at three hours' cure at 45 pounds pressure, were 

 taken as 100, as these were the best results obtained from any of 

 the specimens. 



The above tables conclusively show the influence of the nitro- 

 gen compounds in hastening the cure and combining more sul- 

 phur in the same time, and they show how the lack of the nitro- 

 genous constituent results in lack of cure, and a resulting poor 

 tensile strength and elongation. 



Turning from the natural constituents of rubber, it may be well 

 to inquire whether nitrogenous comiKiunds may be added to rub- 

 ber to act as hasteners of vulcanization or to give improved 

 products. 



In tlie "Gummi Zeitung," No. 28. p. 731, it is shown that albu- 

 men added to rubber increases the speed of vulcanization. 



In the French patent to the Xylos Rubber Co., No. 466,243, 

 scrap rubber is heated with caustic soda and a small quantity 

 of an aromatic amino compound ; for example, aniline, which 

 acts as a catalyst to unite the free and combined sulphur with the 

 alkali. 



In the German patent No. 265,221 of 1912, and English patent 

 No. 11,530, 1913, Beyer & Co. claim a "process of facilitating 

 the vulcanization of natural or artihcial caoutchouc," in which 

 piperidine or its homologues are added to the vulcanizing masses. 

 .\s an example, where Para rubber and 10 per cent, sulphur — to 

 which '/< per cent, piperidine has been added — are vulcanized at 

 135 degrees C. for 15 minutes, a completely vulcanized product 

 containing 3.5 combined sulphur is claimed as a result. It is 

 stated that without the use of the piperidine the same result 

 would require an hour. 



The same party, in German patent No. 266,618, uses piperidine 

 or its homologues for producing hard rubber by adding 25 per 

 cent, sulphur. In No. 266.619 they claim the use of derivatives 

 or salts of piperidine. In No. 268,947 aliphatic amines, with open 

 or closed chains and their derivatives, are said to be equally suit- 

 able with the above, and are claimed as also the addition prod- 

 uct of carbon bi-sulphide and dimethylamine. In No. 269,512 it 

 is claimed that with Para and 100 per cent, sulphur, and the 

 addition of 1 per cent, of the compound of carbon bisulphide 

 and dimethylamine, vulcanization takes place completely with 15 

 minutes' cure at 135 degrees C. In a previous patent, aniline 

 was claimed for this object. Nearly all the agents above men- 

 tioned are basic organic nitrogen compounds and of the amino 

 group; and these numerous instances of their use with rubber 

 lead to the conclusion that amines in general have some hasten- 

 ing influence on the vulcanization of rubber. 



In the German patent No. 273,744, of 1913. J. Ephraim im- 

 proves synthetic, sticky or impure caoutchouc by adding from yi 

 per cent, to 10 per cent, sulphur, and enumerates various other 

 reagents, among them being napthyl amine, and then heating at 

 140 degrees C. for one and a half hour. The heating is sup- 

 posed to stop before the characteristic vulcanization takes place. 

 It is claimed that this greatly improves caoutchouc. 



In the German patent Xo. 273,482, of 1912, to W. Esch, the 

 patentee incorporates a paste of albumen and lime with rubber 

 and then smokes or tans it to improrve its quality. 



The piperidine product mentioned in the German patent No. 

 265,221 and English patent Xo. 11,530, of 1913, has appeared on 

 the English market under the name of "Bayer Patent Accelera- 

 tor," and it is claimed that the addition of a very small percentage 

 to any rubber mixing accelerates vulcanization so that it can be 

 carried out in from one-quarter to one-sixth the usual time. 

 Samples were exhibited at the recent exhibition in London, and 

 it is said to have been extensively taken up in France. 



A consideration of the above references showing the use of 

 organic nitrogen, usually in the forms of amines or like com- 

 pounds, indicates that this form of nitrogen has some catalytic 

 influence in hastening the combination of rubber and sulphur, 

 and also has some influence in polymerizing the rubber itself. 

 The field seems to be yet open for research as to the best re- 

 agent to apply from the wide variety available and the best 

 methods of ajiplying. 



With the use of large quantities of plantation rubbers, which 

 are known to be deficient in both proteins and other nitrogen com- 

 pounds, and which are recognized as being much slower in vul- 

 canization than Para, it would seem that it is desirable to de- 

 termine on some substance like the above which will act as a 

 hastener. Aside from any technically improved results which 

 are to be anticipated, it is evident that any hastening of the 

 process of vulcanization will result in great economies in manu- 

 facture. 



Replete with information for rubber manufacturers — Mr. 

 Pearson's "Crude Rubber and Compounding Ingredients." 



