Thixotropic agent that can be activated using actinic radiation, a method for its production and the use thereof

A process for preparing a thixotropic agent comprising urea crystals, comprising

• reacting at least one of a primary amine, a secondary amine, and water with at least one polyisocyanate in a liquid organic medium comprising at least one compound comprising at least one activatable functional groups per molecule, said each activatable functional group comprising at least one bond that can be activated with actinic radiation, wherein the urea crystals have a particle size distribution such that 80% of the urea crystals are smaller than 2μm, and the at least one bond comprises carbon-carbon double bonds that are present in at least one of a (meth)acrylate group, an ethacrylate group, a crotonate group, a cinnamate group, a vinyl ether group, a vinyl ester group, a dicyclopentadienyl group, a norbornenyl group, an isoprenyl group, an isopropenyl group, an allyl group, a butenyl group, a dicyclopentadienyl ether group, a norbornenyl ether group, an isoprenyl ether group, an isopropenyl ether group, an ally ether group, a butenyl ether group, a dicyclopentadienyl ester group, a norbornenyl ester group, an isoprenyl ether group, an isopropenyl ether group, an ally ether group, and a butenyl ester group.