Method for on-mold coating molded articles with a coating powder as a liquid gel coat replacement
First Claim
1. A method for on-mold coating a molded article in an open plastic mold, comprising:
- a) providing a thermosetting unsaturated polyester coating powder composition which consists essentially of an unsaturated polyester resin containing active hydrogen atoms and having a melt viscosity at 175°
C. of between 3,750 and 4,750 centipoise, a copolymerizable cross-linking prepolymer, and a thermal initiator, with the proviso that the composition is essentially free of a copolymerizable cross-linking monomer;
b) applying said coating powder composition, which becomes the outer skin of the molded article, onto a shape-imparting mold surface;
c) heating said powder coated mold surface to a temperature sufficient to flow and coalesce the coating powder into a substantially continuous coating film and effect cure, with the temperature being below the mold deformation temperature;
d) applying a fill resin, which constitutes the bulk of the molded article, onto said cured powder coating and allowing the cure of the fill resin to advance sufficiently until said powder coating film and fill resin are integral; and
, e) releasing said finished coated article from said mold.
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Accused Products
Abstract
Method for on-mold surface coating fiberglass-reinforced molded articles during their manufacture with environmentally friendly and physiologically safe thermosetting unsaturated polyester on-mold coating powders which serve as replacements for liquid gel coats. The thermosetting coating powders employed are adapted to cure at low temperatures to avoid causing thermal damage to the heat sensitive plastic molds which must be reused over and over again, and to cure in the presence of atmospheric oxygen to enable over coating with liquid fill resins and fiberglass, which constitute the bulk of the finished article, without having the fill resins bleed through the powder coating film and detrimentally affect the overall quality of the surface finish.
81 Citations
11 Claims
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1. A method for on-mold coating a molded article in an open plastic mold, comprising:
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a) providing a thermosetting unsaturated polyester coating powder composition which consists essentially of an unsaturated polyester resin containing active hydrogen atoms and having a melt viscosity at 175°
C. of between 3,750 and 4,750 centipoise, a copolymerizable cross-linking prepolymer, and a thermal initiator, with the proviso that the composition is essentially free of a copolymerizable cross-linking monomer;
b) applying said coating powder composition, which becomes the outer skin of the molded article, onto a shape-imparting mold surface;
c) heating said powder coated mold surface to a temperature sufficient to flow and coalesce the coating powder into a substantially continuous coating film and effect cure, with the temperature being below the mold deformation temperature;
d) applying a fill resin, which constitutes the bulk of the molded article, onto said cured powder coating and allowing the cure of the fill resin to advance sufficiently until said powder coating film and fill resin are integral; and
,e) releasing said finished coated article from said mold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification