Studies on the Synthesis of Polyoxyethylene Sorbitan Fatty Acid Esters. I.

Abstract

From the analytical data of commercial polyoxyethylene (POE) sorbitan fatty acid esters, Tweens (ATLAS POWDER Co., USA), author studied the constitutions of sorbitan fatty acid esters used as raw material and amount of ethyleneoxide (EO) added.Based on these results, various POE sorbitan fatty acid esters were synthesized. Addition-polymerization of EO was performed in an autoclave, whereby reaction temperature was optimum at about 130140°C. As the catalyst of polymerization, CH3ONa, remained in the raw sorbitan fatty acid esters as the catalyst of esterification, was satisfactory without further addition of new catalyst.Analytical figures of sorbitan fatty acid esters used as the raw material and amount of EO added (expressed as “times by weight” of raw sorbitan fatty acid esters) were as follows : sorbitan monolaurate with saponification value (S.V.) 160 and hydroxyl value (OH.V.) 360 as the analytical result, 2.5 times of EO; sorbitan monopalmitate (S.V. 150, OH.V. 270), 2.1 times EO; sorbitan monostearate (S.V. 145150, OH.V. 260270), 2.1 and 0.5 times EO; sorbitan tristearate (S.V. 175180, OH.V. 90100), equal weight of EO; sorbitan monooleate (S.V. 150, OH.V. 220230), 2.2 and 0.5 times of EO; sorbitan trioleate (S.V. 175180, OH.V. 80), equal weight of EO. Reaction products obtained were nearly equal to the analytical data of Tween 20, 40, 60, 61, 65, 80, 81 and 85 respectively.