WATER-BLOWN RIGID FOAMS WITH IMPROVED MECHANICAL PROPERTIES AT LOW TEMPERATURES

摘要

The present invention relates to a process for preparing a reaction mixture comprising (a) an isocyanate, (b) a compound having a group reactive with isocyanate, (c) a blowing agent comprising water, (d) a catalyst, and optionally A rigid polyurethane foam obtainable by applying a reaction mixture to a reinforcing material and curing the reaction mixture, wherein the isocyanate (a) has a viscosity at 25 of not more than 500 mPas, and has a group reactive with the isocyanate (B1) having a functionality of at least 4 and a viscosity at 25 DEG C of less than 10000 mPas (b1), a functionality of less than 3.5 and a viscosity at 25 DEG C of less than 600 mPas (b2) (B3) having a viscosity at 25 DEG C of not more than 2000 mPas, a chain extender (b4) comprising at least 30% of a secondary OH group, and optionally a crosslinking agent (b5) . The invention relates to a process for the preparation of the rigid polyurethane foam and to the use of a rigid polyurethane foam for the isolation of a liquefied natural gas tank.