| http://www.w3.org/ns/prov#value | - For the preparation of polyester polyols, organic, for example aromatic and preferably aliphatic polycarboxylic acids and/or derivatives and polyvalent alcohols can be polycondensed without a catalyst or preferably in the presence of esterification catalyst, advantageously in an atmosphere of inert gas, for example nitrogen, carbon monoxide, helium, argon and others, in melt at temperatures of 150
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