Reactions of Accelerators during Vulcanization. II—A Theory of Accelerators Based on the Formation of Polysulfides during Vulcanization.

Abstract

give up their sulfur to the rubber. The formation of thiozonides is illustrated by the following equation: 2R-NH2 + 4S -> R-NH-S-S-S-NH-R + H2S By this scheme, the true accelerator is produced together with hydrogen sulfide by the reaction of the amine and sulfur. Such an explanation necessarily

Reactions of Benzylamine with Sulfur

“…[13]. Second, since benzyl- absence of benzylamine (alternatively and equally good, equilibrium [7] may lie fairly far to theleft). Equations 7 and 8 may consequently be combined combining eqs.…”

“…Aniline, for example, shows an accelerating effect on the rate of vulcanization of natural rubbers (6)(7)(8). Mercaptans, unreactive toward elemental sulfur at low temperatures, readily evolve hydrogen sulfide in the presence of butylamine (9, 10) providing a convenient route to alkyl disulfides.…”

“…Equations 4 to 8 are consequently proposed to account for the benzylamine-sulfur system1 where [6] is base catalyzed and [7] is catalyzed by sulfide ion. The latter point seems justified since only small amounts of N-benzylidene benzylamine and ammonia were produced from benzylidenirnine tetrasulfide and benzylamine in the presence of lead(I1) oxide, a sulfide ion scavenger.…”

“…7 appears to be fairly common in sulfur-amine reactions (20,21). Since benzylamine polysulfides are produced in [7], all steps will be repeated until all the sulfur is converted to benzylammonium polysulfides or all the benzylamine is converted to N-benzylidene benzylamine and ammonia. The proposed scheme is obviously complex with benzylamine polysulfides and benzylidenirnine polysulfides involved in a cyclical catalytic sense.…”

“…4 through 8 to eliminate all to eliminate benzylidenimine (twice [8] added to intermediates. Benzylamine polysulfides may be [7]) to give [15]. Finally, it should be noted that eliminated by adding eq.…”