The Application Of Sorbitol In The Preparation Of Alkyd Resin

Alkyd resins are the most versatile coating binders and mainly synthesized by thepolycondensation of polyols, polybasic acids and fatty acids (or triglycerides). Glycerol,pentaerythritol and trimethylol are the main polyols used for the preparation of alkydresins. Sorbitol is a type of polyol containing six hydroxyl groups and considered as apotential raw material for the manufacture of alkyd resins since it is a cheap andrenewable resource and has many similar properties to glycerol. In this paper, a series ofalkyd resins are prepared with sorbitol, and the film properties of the alkyd varnishesare determined.(1) Three kinds of alkyd resins having fatty acid content (OLf) of42%(SAR1),52%(SAR2) and62%(SAR3) are prepared with70wt%sorbitol aqueous solution,phthalic anhydride and soya bean fatty acid using fatty method. The kinetics on thesynthesis of alkyd resins is investigated, and a second-order rate law relates only to theinitial and latter stages of the reactions. The molecular weight and polydispersity indexof the three alkyd resins are determined by GPC，and the obtained molecular weight iscompared with the theoretical calculated values. Varnish of the three alkyd resins isprepared with driers, and the drying performance, physical and chemical film propertiesare determined and compared with that of standard alkyd resin varnish.(2) Basic alkyd resin of42%fatty acid content is prepared from70wt%sorbitolaqueous solution, phthalic anhydride, soya bean fatty acid and benzoic acid. Chlorine ispassed into the basic alkyd resin at room temperature and three kind of chlorinatedalkyd resins with different chlorination degree are synthesized by changing the reactiontime. The changes of iodine value and reaction temperature with reaction time and theeffect of solvents on the viscosity of chlorinated alkyd resins are studied. The dryingperformance, physical and chemical film properties of the chlorinated alkyd resinvarnish are determined, the effects of drier on them are investigated.(3) The modified alkyd resin with42%fatty acid content is synthesized by mixedpolyols (70wt%sorbitol aqueous solution mixed with equivalent pentaerythritol),phthalic anhydride, maleic anhydride, soya bean fatty acid and benzoic acid. The dryingperformance, physical and chemical film properties of the modified alkyd resin varnishare determined.