Abstract: Described herein are processes for producing a polyurethane foam by mixing the following: (a) polymeric MDI with less than 40% by weight content of difunctional MDI and an aliphatic halogenated hydrocarbon compound (d1) composed of 2 to 5 carbon atoms and of at least one hydrogen atom and of at least one fluorine and/or chlorine atom, where the compound (d1) includes at least one carbon-carbon double bond, to give an isocyanate component (A), and reacting with a polyol component (b) to give the polyurethane foam. Also described herein is a polyurethane foam obtainable by said process.

Abstract: The present invention is directed to the use of a composite comprising a layer (L1) selected from the group of polyurethane layers, polyisocyanurat layers and polyurea layers as a landfill liner as well as a process for preparing a composite landfill liner comprising a layer (L1) selected from the group of polyurethane layers, polyisocyanurat layers and polyurea layers, the process comprising the step of applying a reaction mixture which is suitable to form a product selected from the group of polyurethane, polyisocyanurat and polyurea products onto a surface. Furthermore, the present invention is directed to a composite comprising a layer (L1) selected from the group of polyurethane layers, polyisocyanurat layers and polyurea layers, a primer layer on one surface of layer (L1), and a protective layer (L2) selected from the group of mortar layers or elastomer layers on the surface of the primer layer.