A benzoxazole sulfenamide accelerator: Synthesis, structure, property, and implication in rubber vulcanization mechanism

Abstract

A benzoxazole sulfenamide and its related zinc compound were synthesized and characterized, which are shown to be useful accelerators for sulfur vulcanization. In comparison with the benzothiazole accelerator, the benzoxazole sulfenamide revealed nearly no reversion, an improved feature that is desirable for tire industry. Through the synthesis of the zinc complex 9, which was assumed to be an accelerator-activator for vulcanization, the study aimed to shed some light on the vulcanization mechanism. The crystal structure of the zinc complex 9 showed that two benzoxazole-2-thiol ligands were attached to the zinc center in different isomeric forms, with one in the thio form (linked via sulfur atom) while the other in thio-keto form (linked via nitrogen atom). Lack of the vulcanization accelerator activity from 9 led to the assumption that the sulfurating species might be zinc complexes containing only one benzoxazole-2-thiol ligand.

Advances in S–N bond formation via electrochemistry: a green route utilizing diverse sulfur and nitrogen sources

“…Synthesized sulfenamide 2-mercapto benzothiazoles (MBTs) are widely used as rubber vulcanization accelerators. 53,54…”

“…Synthesized sulfenamide 2-mercapto benzothiazoles (MBTs) are widely used as rubber vulcanization accelerators. 53,54 Although primary and secondary aliphatic amines were tolerated well and smoothly converted to the cross-coupling product, it required ten equivalents of amine which shows poor atom economy. The transformation of hindered secondary amine was inhibited due to the steric effect and gave the products in low yields (3e-3f ).…”

Aceleradores do tipo mercapto-benzotiazol e mercapto-piridil - parte II: modelagem molecular e a estimativa da termodinâmica e do equilíbrio químico na vulcanização de NR e SBR

“…Dando continuidade à investigação, neste novo manuscrito o objetivo é gerar parâmetros termodinâmicos e de equilíbrio químico hipotéticos, mediante modelagem molecular, para as possíveis reações que ocorrem durante a vulcanização, conforme sugerem Rong et al (2014). Os parâmetros estimados serão novamente empregados para a geração de modelos de regressão tomando-se o tempo de cura prematura como variável a ser prevista.…”

Flowing scalable production of sulfenamides by active site-tuned lacunary polyoxometalate foams

“…23,24 For instance, N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N-tert-butyl-2-benzothiazolesulfenamide (TBBS), and 2-(morpholinothio)benzothiazole (MBS) have been widely applied as rubber-vulcanization accelerators and plasticizers in the rubber industry. 25,26 Among these accelerators, CBS as the most widely used accelerator in rubber vulcanization has the advantages of scorch resistance and a fast vulcanization speed. 27 Conventional methods to produce CBS mainly involve the direct oxidative coupling of thiols and amines derivatives.…”