Extrusion coating compositions and method

A method of coating an aluminum substrate comprising:

• (a) heating the aluminum substrate to a temperature of about 120.degree. C. to about 250.degree. C. to provide a preheated aluminum substrate;
• (b) heating a solid, thermoplastic coating composition to a temperature of about 180.degree. C. to about 240.degree. C. to melt the coating composition and provide a molten coating composition, said coating composition comprising:
• (i) about 50% to about 95%, by total weight of the composition, of a polyester having a weight average molecular weight of about 10,000 to about 35,000, a glass transition temperature of about -30.degree. C. to about 120.degree. C., a melt viscosity of about 75 to about 150 Pa.s at 240.degree. C., a melt flow index of about 20 to about 200 g/10 min at 200.degree. C., and a softening point of about 120.degree. C. to about 200.degree. C., and
• (ii) about 5% to about 15%, by total weight of the composition, of an epoxy modifying resin having an epoxy equivalent weight of about 500 to about 3,000;
• (c) extruding the molten coating composition onto a surface of the preheated aluminum substrate to provide a layer of molten coating composition about one to about 40 microns thick on the preheated aluminum substrate and provide a coated aluminum substrate;
• and
• (d) allowing the coated aluminum substrate to cool.

A method of coating a metal substrate comprising:

• (a) heating the metal substrate to a temperature of about 120.degree. C. to about 250.degree. C. to provide a preheated metal substrate;
• (b) heating a solid, thermoplastic coating composition to a temperature of about 180.degree. C. to about 240.degree. C. to melt the coating composition and provide a molten coating composition, said coating composition comprising:
• (i) about 50% to about 95%, by total weight of the composition, of a polyester having a weight average molecular weight of about 10,000 to about 35,000, a glass transition temperature of about -20.degree. C. to about 25.degree. C., a melt viscosity of about 70 to about 80 Pa.s at 240.degree. C., a melt flow index of about 70 to about 80 g/10 min at 200.degree. C., and a softening point of about 170.degree. C. to about 180.degree. C., and
• (ii) about 5% to about 15%, by total weight of the composition, of an epoxy modifying resin having an epoxy equivalent weight of about 500 to about 3,000;
• (c) extruding the molten coating composition onto a surface of the preheated metal substrate to provide a layer of molten coating composition about one to about 40 microns thick on the preheated metal substrate and provide a coated metal substrate;
• and
• (d) allowing the coated metal substrate to cool.

A method of coating a metal substrate comprising:

• (a) heating the metal substrate to a temperature of about 120.degree. C. to about 250.degree. C. to provide a preheated metal substrate;
• (b) heating a solid, thermoplastic coating composition to a temperature of about 180.degree. C. to about 240.degree. C. to melt the coating composition and provide a molten coating composition, said coating composition having a melt flow index of about 65 to about 95 g/10 minutes at 200.degree. C. and a melting peak of about 155.degree. C. to about 170.degree. C., as determined by differential scanning calorimetry, and said coating composition comprising:
• (i) about 50% to about 95%, by total weight of the composition, of a blend of polyesters, each polyester having a weight average molecular weight of about 10,000 to about 35,000, a glass transition temperature of about 20.degree. C. to about 25.degree. C., a melt viscosity of about 35 to about 80 Pa.s at 240.degree. C., a melt flow index of about 70 to about 120 g/10 min at 200.degree. C., and a softening point of about 140.degree. C. to about 180.degree. C., and
• (ii) about 5% to about 15%, by total weight of the composition, of an epoxy modifying resin having an epoxy equivalent weight of about 500 to about 3,000;
• (c) extruding the molten coating composition onto a surface of the preheated metal substrate to provide a layer of molten coating composition about one to about 40 microns thick on the preheated metal substrate and provide a coated metal substrate;
• and
• (d) allowing the coated metal substrate to cool.