2.2. Synthesis of resins
Fatty acid technique with solvent process was employed to synthesize the alkyd resins. The reactionwas carried out in 2-l fournecked flask equipped with a variable speed stirrer, a thermometer, nitrogen gas inlet tube and condenser. A Dean and Stark apparatus was used to remove the water of reaction azeotropically. Concept alkyds have been synthesized according to the following protocol:
• Fatty acids, PE and/or DPE, phthalic anhydride, benzoic acid (as chain terminator), hypophosphorous acid and xylene (4% on raw materials) were charged.
• Heating started. Temperature was raised at the rate of 4 ◦C/min up to 160 ◦C.
• Further the temperature was raised to 240±5 ◦C at 1◦C/min increase and maintained until the final acid number of