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AssigneeE. I. Du Pont de Nemours and Company
InventorsCarmen Flosbach, Thomas Fey, Eva Frigge
Estimating the term…
Dual cure coating compositions having a resin solids content of 40 to 80 wt. %, said resin solids content consisting of (a) 30 to 90 wt. % of at least one hydroxy-functional polyester urethane having olefinic double bonds, (b) 0 to 60 wt. % of at least one binder other than the polyester urethane (a) and/or at least one reactive diluent, and (c) 10 to 50 wt. % of at least one cross-linking agent for hydroxy-functional components (a) and optionally (b), wherein the at least one polyester urethane (a) has a number average molecular mass of 1000 to 5000 and a hydroxyl value of 80 to 250 mg KOH/g, contains olefinic double bonds corresponding to an olefinic double bond equivalent weight of 250 to 2000 and is obtainable by the reaction, which proceeds with consumption of all isocyanate groups, of a component (a1) containing at least one isocyanate group and at least one olefinic double bond with a non-aromatic polyester polyol (a2) having a calculated molecular mass of 600 to 1400, an acid value of 0 to 30 mg KOH/g and a hydroxyl value of 250 to 600 mg KOH/g at a calculated hydroxyl functionality of 4.5 to 10, and wherein the sum of weight percentages of components (a) to (c) is 100 wt. %.
Dual cure coating compositions having a resin solids content of 40 to 80 wt. %, said resin solids content consisting of
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Polyurethanes having carbon-to-carbon unsaturated bonds: having terminal carbon-to-carbon unsaturated bonds
By baking: multistage baking
With unsaturated compounds having only one group containing active hydrogen: with esters of acrylic or alkylacrylic acid having only one group…
By baking: after-treatment
Term end not estimated
The invention relates to dual cure coating compositions and to a process for the production of multilayer coatings using the dual cure coating compositions, in particular for the production of outer clear coats or top coats of multilayer coatings.
In relation to the present invention, the term “dual cure coating composition” means a coating composition that is curable by free-radical polymerization on UV irradiation and additionally by thermally induced polyaddition and/or polycondensation with the participation of hydroxyl groups.
U.S. Pat. No. 4,212,901, for example, discloses dual cure coating compositions based on polyester polyols esterified with (meth)acrylic acid which are curable by free-radical polymerization of olefinic double bonds on UV irradiation and additional polyisocyanate curing agents.
773 g of trimethylolpropane, 604 g of hexahydrophthalic anhydride and 231 g of dimer fatty acid (commercial name Empol® 1008 from Cognis) were combined with 60 g of xylene and heated to a maximum of 230° C. Esterification was continued, with removal of water, until an acid value of 5 mg KOH/g was obtained. After cooling to 125° C., a solids content of 79.5 wt. % was established with 322 g of butyl acetate.
The polyester polyol had an OH value of 324 mg KOH/g, a calculated hydroxyl functionality of 5.6 and a calculated molecular mass of 980.
398 g of HDI isocyanurate (Tolonate® HDT from Rhodia), 1.2 g of methylhydroquinone, 1 g of dibutyltin dilaurate solution (10%) and 100 g of butyl acetate were mixed and heated to 60° C. 207 g of pentaerythritol triacrylate in 147 g of pentaerythritol tetraacrylate were added in such a manner that the temperature did not exceed 80° C. Once the solution had reached an NCO value of 6.7%, 81 g of hydroxyethyl acrylate were apportioned in such a manner that the temperature did not exceed 80° C. Rinsing was performed with 100 g of butyl acetate. Once the solution had reached an NCO value of 2.8%, 833 g of the polyester polyol (a2) from Example 1 were added. The reaction mixture was maintained at 80° C. until an NCO value was no longer detectable. The mixture was then thinned with butyl acetate to yield a resin solution with a solids content of 73.1 wt. %.