Radiation curing of powder coatings on wood
AssigneeHerberts Powder Coatings, Inc.
InventorsKevin M. Biller, Ben A. Mac Fadden
Life of this patent
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Abstract
Powder coatings are described which are curable by means of exposure to radiation, typically ultraviolet radiation, and the electrostatic deposition thereof onto substrates of wood or similar materials. Free radical curing coatings are described using specific chemical formulations of acrylourethane resins, unsaturated polyester resins and mixtures thereof in combination with morpholino, phenol, phosphine and ketal photoinitiators. Electrostatic application onto wooden substrates involves grounding of the substrate, electrostatic deposition and, typically, heating the substrate to flow the coating into a smooth finish prior to radiation curing. Moisture and humidity controls may also be used to improve the electrostatic coating process.
Claims23
A method for coating a substrate comprising the steps of:
- a) depositing onto said substrate a powder coating comprising;
- i) a radiation curable resin mixture comprising a mixture of acrylourethane resin and an unsaturated polyester resin wherein the polyester resin is chosen from the group consisting of maleate containing resins and fumarate containing resins, and, ii) a photoinitiator chosen from the group consisting of morpholino containing photoinitiators, phenol containing photoinitiators, ketal containing photoinitiators, and phosphine containing photoinitiators, wherein said photoinitiator comprises from approximately 0.8% to approximately 7.5% of the total weight of said radiation curable resin mixture, and, iii) a plasticizer in sufficient quantity to cause the flow temperature of said powder to be less than approximately 200 degrees Fahrenheit;
- b) heating said coated substrate to a temperature of approximately 185 to 200 degrees Fahrenheit for sufficient time for said coating to coalesce into a substantially continuous coating on said substrate;
- and,
- c) exposing said coating to uv radiation for sufficient time to cure said coating.
A method for applying a powder coating to a wooden substrate comprising the steps of:
- a) electrically grounding said wooden substrate;
- b) electrostatically charging a powder coating comprising;
- i) a radiation curable resin mixture comprising a mixture of acrylourethane resin and an unsaturated polyester resin wherein the polyester resin is chosen from the group consisting of maleate containing resins and fumarate containing resins, and, ii) a photoinitiator chosen from the group consisting of morpholino containing photoinitiators, phenol containing photoinitiators, ketal containing photoinitiators, and phosphine containing photoinitiators, wherein said photoinitiator comprises from approximately 0.8% to approximately 7.5% of the total weight of said radiation curable resin mixture, and, iii) a plasticizer in sufficient quantity to cause the flow temperature of said powder to be less than approximately 200 degrees Fahrenheit;
- c) directing said electrostatically charged powder onto said substrate until substantially all of said substrate requiring coating is coated with said powder;
- and,
- d) curing said powder coating, forming thereby a continuous coating on said substrate.
Dependencies are inferred from the claim text.