Optimal analysis of the effects of process conditions on the yield of alkyd resins from castor and soybean seed oils using response surface methodology

Abstract

This research studied the optimization of the production of alkyd resin from dehydrated castor oil (Ricinus communis) and soybean oil (Glycine max) respectively. The natural content of iodine in soybean oil was sufficient for producing drying alkyd resin while refined castor oil has low iodine content; hence it was severely dehydrated at high temperature to increase its iodine value from 83 to 130, which made it suitable for alkyd resin production. Nine different samples of medium oil alkyd resins of 50% oil length were synthesized from each oil at different reaction conditions using monoglyceride method, which involved mixing of appropriate amount of each oil with glycerol via alcoholysis, followed by the addition of phthalic anhydride via esterification. The acid value was observed to decrease with time during the esterification process and this decrease was a measure of alkyd resin production. The outcomes of the standardization of the soybean and castor oil modified resins through coating analyses revealed that both have desirable commercial attributes in terms of chemical resistance, set to touch, solubility in solvent media and drying time though at any given similar production conditions, soybean oil modified resins have better qualities due to their lower acid values. The kinetic studies carried out indicated that only first order and second order kinetics fitted into the experiment data. Time, temperature and phthalic anhydride dosage were the three independent factors studied and optimized using Composite Rotatable Design (CCRD) of Response Surface Methodology (RSM) while the response was percentage conversion. The suggested model and the process variables were significant as depicted by their p-values. The model validation showed that the optimal conversions, 87.3% and 76.7%, obtained for soybean and castor oil modified resins respectively, at a reaction temperature of 247.5 °C, reaction time of 155.3mins and 46.2 g of phthalic anhydride conformed wholly with the actual conversions, 84.7% and 75.2%, obtained respectively at the same conditions. Therefore, it can be deduced that soybean oil modified resins have better yield and offered more desirable features.

Keywords

• Alkyd resin
• Castor oil (ricinus communis)
• Soybean oil (glycine max)
• Process conditions
• Optimization