Exploring the efficacy of tin-free catalysts in alkyd resin synthesis
摘要
Organotin compounds are widely used as catalysts for the esterification and transesterification reactions in the production of polyesters and alkyd resins. However, they have been classified as toxic and harmful to humans as well as aquatic animals and plants. Hence, there is a need to find catalysts which are environment friendly, sustainable and shall have similar catalytic activity as that of organotin catalysts. Present research work deals with the investigation of tin-free catalysts based on zinc and titanium metals in the synthesis of alkyd resin for coating applications. For this purpose, four catalysts namely zinc acetate, zinc sulfate, titanium lactate (Tytan AQ33) and titanium complex (Tyzor TE) were screened and studied. Various concentrations of catalysts were attempted, i.e., 0.02 wt%, 0.05 wt% and 0.1 wt% and progress of the reaction was monitored by evaluating viscosity and acid value at periodic intervals. To optimize catalyst concentration and catalytic activity, resin characteristics were compared with the resin synthesized using conventional tin catalyst namely dibutyltin oxide (DBTO). It was observed that zinc-based catalysts exhibited better catalytic activity as compared to titanium-based catalysts as drop in acid value was much faster in the former case. Furthermore, zinc sulfate proved to be excellent catalyst among all the non-tin alternatives and demonstrated similar catalytic activity as that of DBTO. In addition, clear resin systems were also evaluated for performance properties and structure property relationships have been established.