Abstract: An alkaline-catalyzed process for preparing poly-2-pyrrolidone characterized by the step of treating the polypyrrolidone reaction product mixture with an acid to prevent polymer agglomeration and prevent base-catalyzed polymer degradation. In another embodiment, unreacted poly-2-pyrrolidone is recovered by washing the acid-treated polymer reaction product mixture with water and the resulting wash water recovered, treated with further acid, and then subjected to a two-stage evaporation process. Poly-2-pyrrolidone is known as nylon 4, and can be shaped into filaments and various molded articles.

Abstract: 2-Pyrrolidone is continuously polymerized to a high-molecular-weight particulate product by the stirred polymerization of the carbonated alkaline polymerizate. The polymerizate is prepared by contacting an aqueous hydroxide with excess 2-pyrrolidone, maintaining the resultant alkaline mixture at an elevated temperature for sufficient time to reduce the 2-pyrrolidone dimer content of the mixture to within the desired limits, dehydrating the alkaline mixture to reduce the water content to within the desired limits, and contacting the alkaline mixture with carbon dioxide to form the carbonated alkaline polymerizate. The paste of particular polypyrrolidone and liquid polymerizate is continuously withdrawn from the reactor, neutralized with aqueous acid and washed with warm water.

Abstract: A catalyst solution for the anionic polymerization of 2-pyrrolidone is produced by contacting an alkali metal hydroxide and excess 2-pyrrolidone. The catalyst solution is dehydrated under stripping conditions.

Abstract: A two-stage evaporative method for recovering polymerizable 2-pyrrolidone from alkaline aqueous solutions such as those obtained by washing the catalyst from an incompletely reacted polypyrrolidone polymerizate, includes the steps of neutralizing the base with mineral acid, removing most of the water in an initial reduced pressure evaporation and recovering the pyrrolidone from a salt/pyrrolidone slurry by vaporization under reduced pressure.