190 



THE INDIA RUBBER WORLD 



[January 1, 1917. 



A Brief Review of the Organic Accelerators. 



The following summary represents an effort to classify the principal nitrogen-bearing accelerators in a logical manner, and to 

 record conciselv thcxr characteristics and efficacy as described by H. Ditiiwr and translated into French for "Le Caoutchouc & la 

 Cutla-l'crcha" by Georges Noyer; Andrew H. King in "Metallurgical and Chemical Enginee 

 Rubber Journal"; and others. 



ecring" ; S. J. Peachey in "The India 



WHATEVER may be the future of synthetic rubber, the 

 investigations in connection with it led to the discovery 

 of organic accelerators, which have revolutionized several 

 lines of rubber manufacture. It was found that synthetic rubber 

 could not be vulcanized without the presence of certain organic 

 catalyzers to facilitate the union of rubber and rubber-like sub- 

 stances with sulphur, and when all natural rubber was substi- 

 tuted the increased rapidity of vulcanization was truly remark- 

 able. The difficulty, as for a time with plantation rubbers, 

 appears to have been the absence of certain so-called impurities 

 found evenly distributed throughout Para rubber coagulated by 

 the Amazon method. These natural catalyzers of rubber latex 

 are believed to be decomposition products and related to the 

 proteins. It is certain that all organic accelerators yet known 

 are nitrogen-bearing and many have amino groups, so that the 

 function of nitrogen appears to be important. 



Manufacturers who had been using the old, well-known mineral 

 accelerators began to experiment with these new organic 

 catalyzers and found that they could double their output without 

 expensive increase of steam pressure or danger of impairing 

 the product by high temperature. Those engaged in the pro- 

 duction of cheap molded goods discovered that by employing 

 both high temperatures and catalyzers their increased output 

 would take care of overhead as never before. 



While this most important recent developi;.cnt in rubber 

 chemistry is still in its infancy, there is already considerable 

 generalization and a goodly amount of definite facts on v/hich 

 to build. It is thought that, unlike the mineral accelerators 

 which undergo no chemical change during vulcanization, an 

 organic catalyzer unites with one of the reacting substances and 

 forms an unstable compound which then reacts with the other 

 substance. Meanwhile the catalyzer is set free and the entire 

 process is repeated. From a mechanical standpoint a catalyzer 

 is most conveniently mixed when a solid capable of being very 

 finely pulverized. A high boiling point is essential to prevent 

 vaporizing during vulcanization and consequent spongy appear- 

 ance, known as "blowing." 



The following list includes the most important organic acceler- 

 ators now in use : » 

 Carbon bisulphide addition products with 



Aniline 



Dipenylthiourea or thiocarbanilide 



Diniethylaniline 



Tetrahydropyrrole 



Dimethylamine 



B8 Dimethyl .r methyl trimethylene amme 

 Ammonium compounds 



.Ammonium borate 



■Mdehyde ammonia_ 



Quaternary ammonium bases 

 Amino compounds 



Accelerene or paranitroso dimethylaniline 



Para-phenylenediamine 



Tetramyth'ylenediamine 



Hexamethylene-tetramine or hexamethyleneamme or tor- 

 min 



Sodium amide 



Naphthvlenediamine 



Q0 Dirnethyl A trimethyleneimine 



Trimethyleneamine 



Benzylamine 



Nitrosodimethylaniline 

 Piperidine and derivatives 



Piperidine or aminopentane 



Methyl piperidine 



Quinoline and derivatives 



Quinoline 



Quinoline sulpliate or quinoline sulphonic acid . 



Hydroxy quinoline 



Quinosol 



Oxiquinoline 



O-xiquinoline sulphonic acid 



Oxiquinoline sulphide 

 Miscellaneous 



Anthraquinone 



Antipyrine 



Naphthylamine 



Urea derivatives 



Anilides 



Formanilide 

 Thioformanilide 

 Several of these accelerators are covered by patents and can- 

 not be bought of the concerns manufacturing them until a license 

 for their use has been obtained from the patent owners. Applica- 

 tions for such licenses should be addressed to Dr. Hugo Schweit- 

 zer, of the Synthetic Patents Co., 115 Hudson street. New York 

 City. Prices will be quoted to license holders. The catalyzers 

 in question are piperidine and methyl piperidine, tetramethylene- 

 diamine, hexamethyl-tetramine, thiocarbanilide, and aniline hy- 

 drochloride. The first three of these are not made in the United 

 States at present. 



CARBON BISULPHIDE .'\r>DITION PRODUCTS. 



With Aniline: Diphenylthiourea, or thiocarbanilide, 

 ^.-^NH, CHs 



c=s 



~-~\NH, CeHs 



is one of the earliest known organic accelerators. It takes the 

 form of large colorless tablets melting at 154 degrees C, and is 

 a very efficient catalyzer, particularly for quick-curing stocks 

 because it does its work at the very beginning of vulcanization. 

 The proportions used vary from yi to 3 per cent. 



IVith Dimethylaniline: Cited by Ditmar and King. 



IVith Tetrahydropyrrole: (CHj),NH. Known as pyrrolidin 

 in Germany. Cited by Ditmar and King. 



With Dimethylamine: This substance, 

 /^N (CH3). 



c = s 



^■^^N (CH,), 



gives an active addition product. With Para, 100 per cent sul- 

 phur and the addition of 1 per cent of the compound of carbon 

 bisulphide and dimethylamine vulcanization takes place com- 

 pletely with IS minutes' cure at 135 degrees C. (German patent 

 269,512.) 



With BR Dimethyl x methyl trimethylene amine: Cited by 



Ditmar. 



.\MMONlUM COMPOUNDS. 



Ammonium borate: This has a noticeable eflfect on the cure, 

 but the fact is only of scientific interest, according to Ditmaj. 



Aldehyde ammonia: CH, CH (OH) NH,. This very satis- 

 factory catalyzer is readily soluble in water, sparingly soluble in 

 alcohol and almost insoluble in ether. It melts between 70 and 

 80 degrees C. and sublimes without decomposition at 100 de- 

 grees C. Its efficacy as an accelerator, according to King, may 

 be seen in the fact that 100 parts Para, 10 parts sulphur, and 1 

 part aldehyde ammonia will cure in 30 minutes at 45 pounds 

 steam pressure, 140 degrees C. (Ditmar says 1 hour at 3 atmos- 



