Radiation-curable coating for thermoplastic substrates
AssigneeGeneral Electric Company
InventorStuart R. Kerr, III
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Abstract
A novel radiation curable coating composition for thermoplastic substrates contains a polyfunctional acrylic monomer, a mono-, di- or trifunctional acrylic monomer, a thermoplastic or elastomeric polymer and a photoinitiator. The coatings can be cured to hard, abrasion resistant coatings, yet retain a significant degree of residual unsaturation. The residual unsaturation and the thermoplastic or elastomeric polymer provide excellent adhesion between the coating and topcoats.
Claims24
A radiation curable coating composition for a thermoplastic substrate, which comprises:
- (a) a polyfunctional acrylic monomer having a degree of functionality of at least about 4;
- (b) a mono-, di-, or trifunctional acrylic monomer;
- (c) an acrylic monomer-soluble, acrylic polymer compatible thermoplastic polymer, having a molecular weight greater than about 2000;
- and
- (d) a polymerization initiation amount of a polymerization initiator;
- wherein the polyfunctional acrylic monomer is used at a concentration sufficient to impart a topcoat-binding degree of surface unsaturation to the cured coating when cured to a hard, durable coating, wherein the thermoplastic polymer is in a surface-plasticizing amount, wherein the concentration of the polyfunctional acrylate ranges from about 5 to about 50% by wt. of the composition, the concentration of the thermoplastic polymer ranges from about 1 to about 30% by wt. of the composition, and the concentration of the mono- or difunctional acrylate ranges from about 10 to about 94% by wt. of the composition, exclusive of the polymerization initiator, wherein said initiator is employed in an amount ranging from about 0.01% to about 10% by wt. of the composition, and wherein the relative proportions of the polyfunctional acrylate, the mono-, di- or trifunctional acrylate and the thermoplastic polymer are controlled such that, upon curing, the surface of the coating has a degree of unsaturation of from about 5% to about 50%.
A process for coating a thermoplastic article which comprises the steps of (i) applying a thin coating of a composition comprising:
- (a) a polyfunctional acrylic monomer having a degree of functionality of at least about 4;
- (b) a mono-, di- or trifunctional acrylic monomer;
- (c) an acrylic monomer-soluble, acrylic polymer compatible thermoplastic polymer, having a molecular weight greater than about 2000;
- and
- (d) a polymerization initiation amount of a polymerization initiator;
- wherein the polyfunctional acrylic monomer is used at a concentration sufficient to impart a topcoat-binding degree of surface unsaturation to the cured coating when cured to a hard, durable coating, wherein the thermoplastic polymer is in a surface-plasticizing amount, wherein the concentration of the polyfunctional acrylate ranges from about 5 to about 50% by wt. of the composition, the concentration of the thermoplastic polymer ranges from about 1 to about 30% by wt. of the composition, and the concentration of the mono-, di- or trifunctional acrylate ranges from about 10 to about 94% by wt. of the composition, exclusive of the polymerization initiator, wherein said initiator is employed in an amount ranging from about 0.01% to about 10% by wt. of the composition, and (ii) curing the coating from an amount of radiation sufficient to form a hard, durable coating, yet leave a topcoat binding surface unsaturation, wherein the residual unsaturation of the cured coating ranges from about 5% to about 50% and (iii) curing the coating with radiation.
The process of claim 16, wherein the mono-, di- or trifunctional acrylic monomer is selected from the group consisting of C.sub.1 -C.sub.6 alkylacrylates, C.sub.3 -C.sub.8 cycloakylacrylates, C.sub.1 -C.sub.6 alkylene di- or triacrylates, C.sub.3 -C.sub.8 cycloalkylene di- or triacrylates;
- polyether di- or triacrylates, wherein the polyether group containing from 2 to about 6 carbon atoms, and mixtures thereof, wherein each of the above mono-, di- or trifunctional acrylates may optionally be substituted with one or more halogen atoms, hydroxy groups, C.sub.2 -C.sub.4 lower alkoxy groups, amino groups or carbonyls.
A radiation curable coating composition for a thermoplastic substrate, which consists essentially of:
- (a) a polyfunctional acrylic monomer having a degree of functionality of at least about 4;
- (b) a mono-, di-, or trifunctional acrylic monomer;
- (c) an acrylic monomer-soluble, acrylic polymer compatible thermoplastic polymer, having a molecular weight greater than about 2000;
- and
- (d) a polymerization initation amount of a polymerization initiator;
- wherein the polyfunctional acrylic monomer is used at a concentration sufficient to impart a topcoat-binding degree of surface unsaturation to the cured coating when cured to a hard, durable coating, wherein the thermoplastic polymer is in a surface-plasticizing amount, wherein the concentration of the polyfunctional acrylate ranges from about 5 to about 50% by wt. of the composition, the concentration of the thermoplastic polymer ranges from about 1 to about 30% by wt. of the composition, and the concentration of the mono- or difunctional acrylate ranges from about 10 to about 94% by wt. of the composition, exclusive of the polymerization initiator, wherein said initiator is employed in an amount ranging from about 0.01% to about 10% by wt. of the composition, and wherein the relative proportions of the polyfunctional acrylate, the mono-, di- or trifunctional acrylate and the thermoplastic polymer are controlled such that, upon curing, the surface of the coating has a degree of unsaturation of from about 5% to about 50%.
Dependencies are inferred from the claim text.