Liquid polyester resin: A vehicle for coil coating

摘要

Liquid polyester resins of molecular weight 1000-3000 having terminating carboxy groups were prepared using diethylene glycol and maleic anhydride. Low molecular weight liquid polyester (100% NVM) was found to have the viscosity as low as 10 poise. 1% concentration of hexamine as curing agent was found to be sufficient to give hard dry film within 1 minute at 200°C stoving temperature. Various coil coating compositions were prepared using these liquid polyester resins and 1% hexamine along with colored pigments. The coatings were stoved at 200°C and evaluated for their film properties. The coatings exhibited excellent film properties with scratch hardness more than 2000 gms and 6H pencil hardness, excellent flexibility (OT), excellent resistance to solvents, water and chemicals. They also showed excellent MEK double rub resistance for 100 times, 100% adhesion and excellent impact resistance. The coil coating compositions did not need any primer.