Radiation-curable whipped foams
The present invention relates to a process for the production of radiation-cured foams, characterized in that the radiation-cured foams are produced by 1) foaming of an aqueous composition A), 2) thermal drying of the foam produced from step 1), 3) curing of the foam by actinic radiation, the radiation-curable aqueous compositions A), the radiation-cured foams produced by the process according to the invention and the use of the radiation-cured foams for coating substrates.
1. A process for producing radiation-cured foams comprising
1) foaming an aqueous composition A) comprising
A1) one or more radiation-curable aqueous binders comprising polyurethane (meth)acrylates (i);
A2) one or more thickeners; and
A3) one or more foam stabilizers,
wherein the foaming is carried out by introducing a blowing agent selected from the group consisting of air and inert gas, in an amount sufficient to obtain a foam density of from 200 to 1,000 g/L;
2) thermal drying of the foam produced from step 1);
2a) embossing the foam produced from step 2); and
3) curing of the foam by actinic radiation;
wherein 2) and 3) are optionally repeated one or more times, and
wherein the foam produced by 1) foaming of the aqueous composition A) has a foam density of from 200 to 1,000 g/L prior to 2) thermal drying of the foam produced from 1) and has a foam density of from 50 to 600 g/L after 2) thermal drying of the foam produced from 1).
2. The process of claim 1 , wherein the polyurethane (meth)acrylates (i) are prepared from at least
A1.1) one or more compounds with at least one group which is reactive towards isocyanate and at least one unsaturated group which can undergo free radical polymerization;
A1.2) one or more monomeric and/or polymeric compounds which differ from A1.1);
A1.3) one or more compounds with at least one group which is reactive towards isocyanate and additionally at least one group having a hydrophilizing action; and
A1.4) one or more organic polyisocyanates.
3. The process of claim 2 , wherein a component A1.5) which differs from A1.1) to A1.3) and has at least one amine function is present in the composition from which said polyurethane (meth)acrylates (i) are prepared.
4. The process of claim 2 , wherein component A1) comprises polyurethane (meth)acrylates (i) and component (ii), a reactive diluent with at least one group which can undergo free radical polymerization.
5. The process of claim 1 , wherein the content of radiation-curable unsaturated groups of component A1) is between 0.3 and 6.0 mol/kg, based on the sum of the parts by weight of the non-aqueous constituents of component A1).
6. The process of claim 1 , wherein 2) thermal drying of the foam produced from 1) is carried out at 25 to 150° C.
7. A radiation-cured foam produced by the process of claim 1 .
8. A substrate coated with the radiation-cured foam of claim 7 .