An investigation on synthesis of alkyd resin with sorbitol

• Three kinds of alkyd resins were synthesized using sorbitol.
• The initial and later stage of the reaction followed a second-order rate law.
• The average molecular weight were measured and theoretically calculated.
• The film properties of the synthesized resins were determined.

Sorbitol, as an abundant, cheap and renewable resource, is considered as a potential raw material for the manufacture of alkyd resin. In this study, the kinetics on preparation of alkyd resin using phthalic anhydride, sorbitol and soya bean fatty acid as raw materials is investigated. Three kinds of sorbitol based alkyd resins (SAR) samples having fatty acid content (OLf) of 42% (SAR1), 52% (SAR2) and 62% (SAR3) were prepared with phthalic anhydride, sorbitol aqueous solution and soya bean fatty acid using fatty acid method. Kinetic studies showed that the initial and latter stages of the reaction follow a second-order rate law. The second-order rate constants were found to be of the order of 10−5 g/mg KOH/min. Molecular weight and polydispersity index were determined by GPC and end-group analysis. The number average molecular weight of the alkyd resins ranged from 1435 to 1626 and the weight average molecular weight ranged from 3041 to 3648. A large polydispersity index was found in a range from 2.12 to 2.24. The varnish of alkyd resin SAR1 containing 50% 200# solvent gasoline and 1.25% cobalt naphthenate (drying agent) by weight dried faster than the others. The physical and chemical film properties of the sorbitol based alkyd resins were determined and compared with standard alkyd resins. The results showed that the performance of alkyd resin having fatty acid contents (OLf) of 42% (SAR1) was almost the same as the standard alkyd resins. It could be a choice binder for alkyd resin paint and helpful to reduce production cost.

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