Production of new soy-based polyols by enzyme hydrolysis of bodied soybean oil

Abstract

Polyols are one of the predominate reactants in polyurethane synthesis. Soy-based polyols are potentially low-cost materials in plastic and polymer industrials for decades. However, the performance of most commercial soy-based polyols is limited by their low molecular weights (low hydroxy equivalent weights), low alcohol reactivity due to the prominence of secondary moieties, and limited control on crystalline behavior due to large non-functional branches on the soy-based polyols. The objective of this investigation was to produce new soy-based polyols from enzyme hydrolysis. Soy-based polyols were synthesized by a two-step process consisting of heat bodying soybean oil followed by enzyme hydrolysis of bodied soybean oil. Possible advantages of this approach include the production of primary alcohol moieties, reduction of saturated fatty acid moieties, control of hydroxy equivalent weights, and elimination of organic co-reagents. Several commercial enzymes were investigated for removing saturated fatty acids and imparting the hydroxy functional groups in order to produce the better soy-based polyols. The lipase from Candida rugosa significantly hydrolyzed palmitic acid and was recommended to be used to produce the soy-based polyols. Burkholderia cepacia, Aspergillus niger, Mucor javanicus, and Rhizomucor miehei lipases showed some significance in the hydrolysis against palmitic acid and against stearic acid for some reaction conditions. The soy-based polyols were produced with a hydroxy number of about 50 mg KOH/g after only 3 h of the simple hydrolysis reaction by lipase C. rugosa. Higher hydroxy numbers could be obtained with the longer reaction time. However, polyol yield was reduced and undesirable acid residue was increased when the percent hydrolysis increased.