Patent ID: 8293374

Claim:
A liquid mixture comprising a) 1,3-bis(pyrrolidon-1-yl)butane and b) at least one compound of the formula I in which Q is CH 2 —Z, CH 2 —CH 2 —Z or CHZ—C 1 -C 4 -alkyl, n is 0, 1, 2 or 3, and the Z radicals are C 1 -C 20 -alkylcarbonyloxy, carboxy, C 1 -C 20 -alkyloxycarbonyl, C 2 -C 4 -hydroxyalkyloxycarbonyl, di(C 1 -C 4 -alkyl)amino-C 2 -C 4 -alkyloxycarbonyl or tri(C 1 -C 4 -al-kyl)ammonium-C 2 -C 4 -alkyloxycarbonyl.