Alkyd resin processing fatty acid method

There are two main methods for preparation of alkyd resins. In the first one, called the fatty acid process, a free fatty acid is coesterified directly with the dibasic acid and the polyol at 200-240 °C. The reaction may be carried out without a solvent by first heating in an inert atmosphere. At the end, an inert gas may be blown into the resin from the bottom of the reaction kettle to remove water and unreacted materials. As a modification of this, a small quantity of a solvent may be used to remove water of esterification continuously by azeotropic distillation with the aid of moisture traps. 

Alkyd resins cannot be prepared by simply heating a mixture of oil, polyol and dibasic acid. Because of the preferential reaction of the polyol and acid, a heterogeneous mixture of polyester and oil is obtained which has no value as a surface coating vehicle. There are two main methods whereby useful resins are prepared commercially, namely the fatty acid process and the alcoholysis process (often called the monoglyceride process). 

As indicated earlier, materials based on a structure of this type are brittle and of little practical use however, the incorporation of fatty acid residues into such a structure leads to highly successful surface coating vehicles. The detailed structure of the latter materials depends on the method of preparation. In the fatty acid process (Section 10.5.4.1.), the polyol, dibasic acid and fatty acids react simultaneously and it has been shown [8] that the primary hydroxy groups of glycerol react more readily with phthalic carboxy groups than with fatty acids whilst the reverse applies to the secondary hydroxy groups. It is to be expected, therefore, that in an alkyd resin prepared by the fatty acid process the following type of structure would predominate ... 

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