Selection of stabilizer and coagulant for natural rubber latex colloidal system during diimide catalytic hydrogenation at semi pilot scale reaction

Abstract

Hydrogénation of natural rubber latex improves its thermal properties such as thermal oxidative resistance. Hydrogenation converts unsaturated C double bond into saturated C single bond on natural rubber molecular chains without being followed by chain scissioning. The hydrogenated natural rubber is considered can substitute synthetic rubber such as chloroprene rubber, EPDM, and butyl rubber in the manufacture of outdoor rubber based product. The optimized hydrogenation require natural rubber latex colloidal system remains in the liquid phase during the reaction, however it should be easily coagulated at the end of hydrogenation to reach high yield of reaction. The aim of the research was to study the effect of latex colloidal stabilizer system and coagulant to the natural rubber hydrogenation efficiency. Insitu catalytic hydrogenation of natural rubber latex by diimide compound was run at semi pilot scale at capacity 2.5 kg latex concentrated/batch. The diimide was generated from oxidation of hydrazine hydrate with hydrogen peroxide. The hydrogenation used strong base and surfactant stabilizer type. While, organic acid and inorganic salt were selected as coagulant. The best of stabilizer and coagulant were determined based on qualitative analysis such as FTIR spectra, stability of natural rubber latex colloidal system during the reaction and visual characteristic of hydrogenated natural rubber. The result showed that anionic surfactant could ensure the colloidal natural rubber latex remains in liquid phase during hydrogenation which was indicated by the absence of latex coagulation and decrease possibility of side reaction. Further, organic acid was selected as the best coagulant for hydrogenated natural rubber latex. It was characterized by clear-coloured serum, and hard-non sticky hydrogenated natural rubber sheet.