High throughput manufacture of polyurethane foam layers

Process for making polyurethane foam layer, said process comprising at least the following steps:

• (i) at least one mixing step in which one or more polyurethane prepolymer(s) comprising an isocyanate-capped polyol or an isocyanate-capped polyurethane is/are mixed or brought in contact, with each other, and with water, in a mixing or contact zone, wherein said polyurethane prepolymer derive(s) from a reaction between a polyol, and a diisocyanate compound selected from the group consisting of hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), and isophorone diisocyanate (IPDI), or any mixture thereof;
• (ii) at least one layer forming step in which the mixture from step (i) is applied onto a moving substrate to form a layer and to begin the curing process on the substrate;
• (iii) at least one transporting step during which the foam layer on the substrate from step (ii) is a least partly moved along a production line, during which step the polyurethane prepolymer or precursor thereof in the foam layer at least partly cures, and the thickness of the layer increases due to foaming;
• (iv) at least one step of accelerated curing, which occurs at a predetermined point in time after conclusion of step (ii) and, correspondingly, at a predetermined location along the production line, wherein curing is accelerated by subjecting the foam as moving on the substrate to radiation heating,
• wherein said “predetermined point” in time in step (iv) is reached 2 to 10 minutes after the beginning of step (iii), or
• wherein said “predetermined point” in time in step (iv) is reached once a given volume segment of the foam layer has reached a degree of curing of from 50% to 90%.