Non-blistering thick film coating compositions and method for providing non-blistering thick film coatings on metal surfaces

A non-blistering, thick film primer coating composition, which comprises an organic solvent solution of:

• (a) from about 40 wt. % to about 92 wt. % of total resins solids of a hydroxy-functional polyester resin;
• (b) from about 0 wt. % to about 15 wt. % of total resin solids of a thermosetting acrylic resin;
• (c) from about 3 wt. % to about 15 ,wt. % of total resin solids of a hydroxy-terminal polybutadiene resin selected from the group of a hydroxy-terminal polybutadiene resin and a hydroxy-terminal epoxidized polybutadiene resin, or mixtures thereof;
• (d) from about 3 wt. % to about 20 wt. % of total resin solids of a blocked isocyanate crosslinker comprising at least one dimethyl pyrazole blocked isocyanate;
• (e) from about 1 wt. % to about 10 wt. % of total resin solids of an aminoplast crosslinker comprising at least one melamine-formaldehyde condensate;
• (f) from about 0.05 wt. % to about 0.7 wt. % of total resin solids of a catalyst;
• and,
• (g) a pigment.

A method of protecting a metal substrate with a composite protective coating, which comprises:

• (a) applying an organic solvent solution of a non-blistering, thick film primer coating composition to a metal substrate to form a first primer layer, said primer coating composition comprising:
• (i) from about 40 wt. % to about 92 wt. % of total resins solids of a hydroxy-functional polyester resin;
• (ii) from about 0 wt. % to about 15 wt. % of total resin solids of a thermosetting acrylic resin;
• (iii) from about 3 wt. % to about 15 wt. % of total resin solids of a hydroxy-terminal polybutadiene resin, a hydroxy-terminal epoxidized polybutadiene resin, or mixtures thereof;
• (iv) from about 3 wt. % to about 20 wt. % of total resin solids of blocked isocyanate crosslinker;
• (v) from about 1 wt. % to about 10 wt. % of total resin solids of an aminoplast crosslinker;
• (vi) from about 0.05 wt. % to about 0.7 wt. % of total resin solids of a catalyst;
• and,
• (vii) a pigment;
• (b) heat curing said first primer layer on said metal substrate;
• (c) over coating said primer layer with a top coating composition to form a second top coat layer, said top coating composition selected from the group of a fluorocarbon polymer, a silicone polyester, and a polyester;
• and,
• (d) heat curing said second top coat layer on said primer layer to form a composite coated metal substrate.