Adhesion-promoting primer compositions for polyolefin substrates

A solvent-based primer composition comprising:

• about 5 to about 10 weight percent of a modified polyolefin having an acid number ranging from about 20 to about 60 and a number average molecular weight ranging from about 4,000 to about 10,000 comprising an amorphous polyolefin selected from the group consisting of polypropylene copolymers, polypropylene terpolymer and mixtures thereof, wherein the amorphous polyolefin contains about 80 to about 90 mole percent propylene, the polyolefin being chemically modified with one or more unsaturated carboxylic acids selected from the group consisting of acids, esters and anhydrides;
• and
• about 85 to about 95 weight percent of a solvent selected from the group consisting of ester solvents, ketone solvents, aliphatic solvents, aromatic solvents and mixtures thereof.

A method of improving the adherence of paint to a substrate comprising the steps of:

• applying a solvent-based primer composition to a substrate,
• wherein the primer composition comprises about 0.5 to about 40 weight percent of a modified polyolefin having a number average molecular weight ranging from about 1,000 to 15,000 comprising an amorphous polyolefin selected from polypropylene homopolymers, copolymers, terpolymers and mixtures thereof, wherein the propylene copolymers and terpolymers contain about 1 to about 99 mole percent ethylene, 1-butene, 1-pentene, and 1-hexene, the amorphous polyolefin being chemically modified with one or more unsaturated carboxylic acids selected from the group consisting of acids, esters and anhydrides, and a solvent selected from the group consisting of ester solvents, ketone solvents, aliphatic solvents, aromatic solvents and mixtures thereof.