Polymerization of 2-pyrrolidone with alkali metal pyrrolidonates and certain quaternary ammonium salts

摘要

There is disclosed the use of certain quaternary ammonium sulfates and bisulfates as polymerization accelerators in the polymerization of 2-pyrrolidone employing alkali metal pyrrolidonates as primary catalysts together with CO2, SO2 or MoO3 as activators. Methods for recycling both the unchanged monomer and the accelerator are disclosed. The structural formula for the operable quaternary ammonium salts is: <IMAGE> wherein R1, R2, R3 and R4 are alkyl, aryl and aralkyl radicals, including mixtures thereof, and n is 1 or 2 depending on the valence of X, and X is a bisulfate or sulfate. In addition to accelerating the rate of polymerization these substances also act as color suppressors when SO2 is used as the activator. For this purpose X in the above formula may also be a halide. Less than 0.01 mol per mol of alkali metal pyrrolidonate is needed in this use. Cesium or rubidium pyrrolidonates are also disclosed as color suppressors when using SO2 as the activator. A method of forming anhydrous solutions of quaternary ammonium salts in 2-pyrrolidone is also disclosed.