Patent ID: 8449967

Claim:
A composite element which has the following layer structure: (i) a thickness of from 2 to 20 mm of metal, (ii) a thickness of from 10 to 300 mm of plastic, and (iii) a thickness of from 2 to 20 mm of metal, where (i) and/or (iii) have an opening having a length, width, and height wherein said opening is sealed across said length and said width with a filling material having a melting point below 250° C. and comprising an organic compound and/or a plastic, and where the opening opens when a pressure difference between (ii) and the other, outward-facing, side of (i) and/or (iii) is at least 10 bar, and the higher pressure is present in (ii) or the opening opens in response to and dissipating gases from (ii), wherein the plastic of layer (ii) is further defined as a polyurethane comprising the reaction product of: A. a polyphenylpolymethylene polyisocyanate, B. a methylene diphenyldiisocyanate, and C. a mixture of; (i) a first polyether polyalcohol having an average functionality of from 1.9 to 3.2 and an average molecular weight of from 2,500 to 8,000 g/mol and present in an amount of from 40 to 98 parts by weight per 100 parts by weight of the mixture, (ii) a second polyether polyalcohol having an average functionality of from 1.9 to 3.2 and an average molecular weight of from 150 to 399 g/mol and present in an amount of from 1 to 30 parts by weight per 100 parts by weight of the mixture, and (iii) a diol having from 2 to 14 carbon atoms and present in an amount of from 1 to 30 parts by weight per 100 parts by weight of the mixture.