Coating compositions
Quick-drying, solvent-based coating compositions, which are curable by UV-A radiation and contain at least one amorphous polyurethane with a glass transition temperature of from 35° C. to 100° C., the proportion by weight of soft groups in said amorphous polyurethane being less than 30 wt. %. The compositions are prepared by mixing all of the components that are free of isocyanate groups, and mixing in the components that contain free isocyanate groups just before application to a substrate.
1 . Coating compositions which are curable by UV-A radiation and contain at least one amorphous polyurethane with a glass transition temperature of from 35° C. to 100° C., the proportion by weight of soft groups in said amorphous polyurethane being less than 30 wt. %.
2 . Coating compositions according to claim 1 , comprising the following as other components:
A1) at least one photoinitiator,
A2) optionally at least one compound which has at least one isocyanate-reactive group and optionally contains one or more functional groups that undergo a polymerization reaction with ethylenically unsaturated compounds under the action of actinic radiation,
A3) optionally polyisocyanates which optionally contain one or more functional groups that undergo a polymerization reaction with ethylenically unsaturated compounds under the action of actinic radiation,
A4) optionally compounds which carry functional groups that undergo a polymerization reaction with ethylenically unsaturated compounds under the action of actinic radiation, and which have neither isocyanate groups nor isocyanate-reactive groups,
A5) optionally catalysts and
A6) optionally auxiliary substances and additives, at least one of components A2) to A4) and/or the amorphous polyurethane containing one or more functional groups that undergo a polymerization reaction with ethylenically unsaturated compounds under the action of actinic radiation.
3 . Coating compositions according to claim 1 , wherein the amorphous polyurethanes have a glass transition temperature of 40 to 76° C.
4 . Coating compositions according to claim 1 , wherein the amorphous polyurethanes have a glass transition temperature of 40 to 52° C.
5 . Coating compositions according to claim 1 , wherein the amorphous polyurethanes have a linear molecular structure.
6 . Coating compositions according to claim 1 , wherein in addition to photochemical crosslinking, the compositions are curable by an additional crosslinking mechanism which proceeds at temperatures below 60° C. within eight hours to a sufficient degree of completion that even the non-irradiated coating cures until dry to handle.
7 . Coating compositions according to claim 6 , wherein the additional crosslinking mechanism is based on the isocyanate-hydroxyl reaction or the reaction of isocyanate with aminic components, or on both types of reaction simultaneously.
8 . A process for the preparation of coating compositions according to claim 1 , comprising mixing all of the components that are free of isocyanate groups, and mixing in the components that contain free isocyanate groups just before application to a substrate.
9 . A method of repairing lacquering comprising applying the composition according to claim 1 to a lacquered object.
10 . Large objects lacquered with the composition of claim 1 .
11 . The large objects according to claim 10 , wherein the large objects are selected from motor vehicles, aeroplanes, ships and railway vehicles.
12 . Substrates coated with at least one layer obtained from the coating compositions according to claim 1 .
13 . Coating compositions according to claim 1 , wherein the auxiliary substances and additives A6) are selected from the group consisting of light stabilizers, antioxidants, fillers, antisettling agents, defoaming agents, wetting agents, flow control agents, reactive thinners, plasticizers, catalysts, solvents, thickeners, pigments, dyestuffs, flatting agents and combinations thereof.
14 . Coating compositions according to claim 2 , wherein the amorphous polyurethanes have a glass transition temperature of 40 to 76° C.
15 . Coating compositions according to claim 2 , wherein the amorphous polyurethanes have a glass transition temperature of 40 to 52° C.
16 . Coating compositions according to claim 2 , wherein the amorphous polyurethanes have a linear molecular structure.
17 . Coating compositions according to claim 2 , wherein in addition to photochemical crosslinking, the compositions are curable by an additional crosslinking mechanism which proceeds at temperatures below 60° C. within eight hours to a sufficient degree of completion that even the non-irradiated coating cures until dry to handle.
18 . Large objects lacquered with the composition of claim 2 .
19 . The large objects according to claim 18 , wherein the large objects are selected from motor vehicles, aeroplanes, ships and railway vehicles.
20 . Substrates coated with at least one layer obtained from the coating compositions according to claim 2.