Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-06-29
2001-10-30
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S549000, C525S285000
Reexamination Certificate
active
06310134
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to adhesion-promoting primer compositions for use on polyolefin substrates. More particularly, the invention relates to solvent-based primer compositions containing an amorphous polyolefin being chemically modified with one or more unsaturated carboxylic acids, as well as, their corresponding acid anhydrides thereof and having a number average molecular weight ranging from about 1,000 to 15,000.
BACKGROUND OF THE INVENTION
Molded plastic parts are widely used in automobiles, trucks, household appliances, toys and the like. Frequently these plastic parts are made from polyolefins such as polyethylene, ethylene copolymers, polypropylene, propylene copolymers, and polyolefin blends. One such blend is thermoplastic olefin (TPO), which is rubber-modified polypropylene. Frequently, these plastic parts have to be painted in order to match the color of painted metal parts which are also present in the automobiles, appliances, or toys. Generally, paints do not adhere well to these plastic parts due to their wax-like surface and their chemical inertness.
One approach to improving the adherence of paint to polyolefins is to use an adhesion promoting composition as a separate primer coating between the polyolefin substrate and the paint. The primer coating adheres adequately to both the polyolefin and the paint and thereby creates a unitary three component structure with the paint as the outer portion of the structure. Alternatively, an adhesion promoting primer composition may be added directly to the paint as a “stir in” adhesion promoter.
Certain carboxylate modified polyolefins have been found to be useful as adhesion promoting primers. Generally, these modified polyolefins have been formulated into solvent-based and water-based adhesion promoting primer compositions. The surface of the part is “primed” by application of the adhesion promoting primer composition and the solvent or water is allowed to evaporate. The surface so primed is then readily coated with any of a variety of different coating compositions to provide a strongly adherent and durable coating.
Conventionally, adhesion promoting primer compositions have been formulated with polyolefins which have been modified with unsaturated carboxylic acids or acid anhydrides. In some instances, such as in U.S. Pat. Nos. 3,579,485, 4,070,421 and 4,954,573, carboxylic acid modified polyolefins have themselves been chlorinated to further improve their primer properties. Chlorinated polyolefins, however, can be expensive to produce and their toughness and durability depends upon the amount of chlorination provided, which can vary. Additionally, some chlorinated polyolefins exhibit only limited solubility in anything other than aromatic or chlorinated solvents. Additionally, the presence of chlorine in the chlorinated polyolefin may pose environmental concerns as to the recyclability and disposal of the chlorine coated materials.
Another approach that has been taken for coating polyolefins involves primer compositions containing carboxylate modified polyolefins which are solubilized in an organic solvent. For example, U.S. Pat. No. 4,299,754 and Canadian Patent 835,910 disclose the coating of polyolefins with compositions containing carboxylate modified polyolefins which may be solubilized in a solvent, such as an aromatic or aliphatic hydrocarbon or a chlorinated hydrocarbon. Unfortunately, such compositions have not always proven effective for coating molded plastic parts.
Other primer-based compositions have attempted to avoid the use of solvents in forming modified polyolefin primer compositions. Typically such compositions are water-based primer coating compositions which require the addition of an emulsification agent, such as a nonionic or anionic surfactant. While such primers may be suitable for certain applications, water-based primers generally suffer from water-sensitivity problems. For example, water-based compositions typically exhibit poor adhesion when immersed in 40 ° C. water or subjected to high temperatures with high humidity.
Thus, there exists a need for a primer composition having a modified polyolefin which exhibits good solubility in non-aromatic solvents and which provides suitable adhesion of paints to polyolefin substrates.
SUMMARY OF THE INVENTION
The invention solves the problems arising from previous primer compositions. The invention provides superior levels of paint adhesion to polyolefin surfaces, and improved durability and resistance to water and gasoline as well as thermal shock. Another benefit is the ease in which conventional additives may be added to the primer compositions of the invention.
The primer compositions of the invention generally are solvent-based. Primer compositions of the invention contain a solvent selected from the group consisting of ester solvents, ketone solvents, aliphatic solvents, aromatic solvents and mixtures thereof, and about 0.5 to 40 weight percent of modified polyolefin. The modified polyolefin comprises an amorphous polyolefin which has been chemically modified with one or more unsaturated carboxylic acid or acid anhydrides thereof. The amorphous polyolefin is formed from a polyolefin, including, but not limited to polypropylene homopolymers, copolymers and terpolymers and ethylene copolymers and terpolymers. Generally, the amorphous propylene copolymers and terpolymers of the invention contain ethylene, 1-butene, 1-pentene, or 1-hexene in amounts ranging from about 1 to about 99 mole percent. Similarly, amorphous ethylene, 1-butene, 1-pentene and 1-hexene copolymers and terpolymers of the invention contain about 1 to about 99 mole percent ethylene, 1-butene, 1-pentene or 1-hexene. The modified polyolefin has a number average molecular weight which may range from about 1,000 to 15,000. As mentioned above, the primer compositions of the invention are capable of significantly improving the adhesion of paints to polyolefin surfaces.
DESCRIPTION OF THE INVENTION
The invention provides solvent-based primer compositions which improve the adhesion of paint to polyolefin surfaces. In particular, the primer compositions of the invention are capable of improved durability and resistance to water, gasoline and thermal shock. Furthermore, the primer compositions of the invention can be formulated to exhibit better adhesion for both urethane and melamine topcoats.
The invention relates to solvent-based primer compositions. One component of the primer composition is a chemically-modified amorphous polyolefin. The amorphous polyolefin is preferably a propylene homopolymer, copolymer or terpolymer and is chemically modified with one or more unsaturated carboxylic acids, preferably selected from the group consisting of acids, esters, and anhydrides. The chemically modified polyolefin generally has a number average molecular weight ranging from 1,000 to 15,000. The modified polyolefin may be dispersed in an ester, ketone aliphatic or aromatic solvent to form a solvent-based primer composition. The solvent-based primer composition may contain other conventional ingredients or components to provide the desired aesthetic or functional effects.
A solvent-based primer composition of this invention is useful as a primer for coating substrates of olefin polymer molded articles and applying adhesives or varnishes to various substrates. Furthermore, the primer composition may be used in ink formulations and may be used in a foil stamping process where the primer composition aids the adhesion of foil to a substrate such as polypropylene. A preferred use of the solvent-based primer composition of the invention is as a primer for coating the surfaces of olefin polymer molded articles. For example, a primer composition of the invention may be used with a variety of plastic surfaces or parts made from polyolefins such as polyethylene, ethylene copolymers, polypropylene, propylene copolymers, and polyolefin blends with other polymers (e.g., thermoplastic olefin (TPO), a rubber-modified polypropylene). The primer compositions may also be used to promote
Callahan Michael Alan
McConnell Richard Leon
Templeton Lisa Kay
Williams Kevin Alan
Allen Rose M.
Eastman Chemical Company
Gwinnell Harry J.
Lipman Bernard
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