Process for the production of polyurethane sandwich elements

A process for the continuous production of polyurethane sandwich elements comprising an upper outer layer, a lower outer layer and a layer of cellular polyurethane lying in between and which is firmly bonded to the outer layers, said process comprising:

• a) continuously conveying the two outer layers in the longitudinal direction such that a gap extending in the longitudinal direction of the outer layers is formed between the outer layers,
• b) applying the polyurethane reaction mixture pro rata from a position above the upper side of the lower outer layer and onto the upper side of the lower outer layer, and from a position below the under-side of the upper outer layer and onto the under-side of the upper outer layer,
• c) feeding the outer layers with the polyurethane reaction mixture into a shaping zone in which the thickness of the polyurethane sandwich element is established and in which the polyurethane reaction mixture reacts,
• and
• d) removing the resultant polyurethane sandwich element off the conveying means,
• wherein the ratio of the material flow of the polyurethane reaction mixture applied to the upper outer layer to the material flow of the polyurethane reaction mixture applied to the lower outer layer is between 0.001:1 and 0.2:1.