Enzymatic synthesis of low molecular weight polyols from methylesters of ricinoleic acid

In this work the catalytic efficiency of immobilized Candida antarctica lipase B (Novozym 435) for the transesterification reaction of methylesters of hydroxyfunctional fatty acids and low molecular weight di- and polyols was studied. The starting raw materials for the preparation of model samples were methylesters of ricinoleic acid and growing centers of 1,3-propanediol, trimethylolpropane and sorbitol. The reaction was catalyzed with 5 and 10 wt. % of the enzyme and carried out at 65°C in bulk and pressure reduced to 250 mbar in order to remove methanol as a side condensation product. The reaction was studied by molecular weight distribution development within 12 h period using gel permeation chromatography. The results showed that Novozyme 435 preferably catalyses condensation of primary hydroxyl groups of low molecular weight di- and polyols while reaction of secondary hydroxyl groups of methylesters of ricinoleic acid is suppressed. The selective catalytic efficiency of Novozyme 435 allowed the synthesis of star branched low molecular weight polyols terminated with secondary hydroxyl groups. This is not possible using conventional condensation catalysts and high reaction temperatures over 200°C leading to production of high molecular weight polyester polyols.

Financial support for the presented work by Ministry of Industry and Trade of the Czech Republic (project number 2A-2TP1/135) is gratefully acknowledged.