Zinc(II)-Catalyzed Disproportionation in Rubber: The mechanism of Sulfur Vulcanization Revisited
摘要:
AbstractModel studies have shown that cross‐link precursors, that is, intermediates in the sulfur vulcanization of rubber, are transformed into cross‐links by a nonsymmetric but regioselective disproportionation mechanism. Thus, two equivalents of the crosslink precursor of the type RSSX are transformed into XSX and the actual cross‐link RSSSR. Exchange of sulfur atoms is a prerequisite. A mechanism involving an SNi′ reaction with an allylic moiety, suggested in the literature, has not been observed. The disproportionation reaction is catalyzed by rubber‐soluble zinc‐dithiocarbamate complexes, an important class of vulcanization accelerators. By virtue of ligand‐functional‐group exchange reactions these complexes serve to transport and exchange sulfur atoms.
在2,3-二甲基丁-2-烯(C 6 H 12)的硫磺硫化反应中,在S 8,ZnO和有机促进剂的存在下,形成中间产物,该中间产物由与硫结合的烯烃构成促进剂片段:C 6 H 11 -S n -S(S)CNMe 2,其中n 0;描述了2,3-二甲基丁-2-烯-1-基二甲基三硫代过氨基甲酸[C 6 H 11 –SS–S(S)CNMe 2 ]的分离表征和硫化活性。