A method for continuous production of an endless string of polyurethane reactive plastic material including, a) conveying the reactive components to a mixer in a metered manner, b) mixing the reactive components into a reactive mixture, c) subsequently discharging the reactive mixture and d) coating a first sheet section made from a plane, flexible material which is conveyed continuously in a transporting direction with the reactive mixture. Further including: e) guiding the first sheet section across a guiding element, which has a concave section and a flat section which follows the concave section in the transporting direction; f) feeding two lateral sheet sections to the first sheet section, wherein the feeding occurs into the two lateral end sections of the first sheet section; g) merging the two lateral sheet sections and the first sheet section so that a bowl-shaped structure is formed for reception of the reactive mixture.