Method for increasing polyamide viscosity

A process for increasing the viscosity of synthetic linear polyamides comprises subjecting polyamide-forming reactants of the type which are capable of forming polyamides having recurring carbonamide groups as an integral part of the polymer chain, which groups are separated by at least two carbon atoms to a condensation reaction by heat treatment at a temperature in the range of from 180 DEG C. to 300 DEG C., permitting the reaction to reach at least 95% completion, and thereafter introducing into the reaction mass a polycarbonate having a molecular weight in excess of 5,000 and in an amount of 0.1 to 10% of the weight of the polyamide to be formed. Many polyamides and polycarbonates of conventional types are specified. In the examples, modified polyamides are made from:-(II) to (VI) hexamethylene diammonium adipate and 2:2-bis(4-hydroxyphenyl) propane polycarbonate and (VII) hexamethylene diammonium adipate and a resorcinol polycarbonate. U.S.A. Specifications 2,071,250, 2,071,253 and 2,071,948 are referred to.