The alkali‐catalyzed polymerization of caprolactam

Publisher Website
Google Scholar
Abstract
An attempt has been made to combine the advantages of the rapid, base‐catalyzed addition polymerization of caprolactam with the more stable molecular weight distribution given by the much slower polycondensation process. This aim has been achieved by polymerizing the monomer in the presence of sodium hydroxide or carbonate and, at a later stage, introducing a small amount of a second agent which promotes hydrolysis or segment interchange reactions and which thus accelerates the chain length re‐distribution of the polymer. The polymerization and molecular weight re‐equilibration steps can be conveniently conducted as two distinct, consecutive batch processes or can be operated on a continuous basis. The practical, industrial significance of these results is discussed. Suitable agents promoting the re‐distribution reactions include water, 6.6 nylon salt, aminocaproic acid, acetic acid, and n‐butyl alcohol. All experiments were carried out at 250°C. under a nitrogen atmosphere and the course of the reaction was followed by measurement of the rate of change of the water‐soluble content of the polymer, and of its end group concentrations, solution viscosity and, in part, turbidity titrations of the water‐extracted products. An observation incidental to the main aim of this work was that the polycaproamide, after washing with water, contained an excess of free amine end groups over carboxyl terminal units. No chain branching was detectable from solution viscosity or infrared spectral investigations, and the polymer was free from sodium. Similar end group effects have been previously described by Dutch and German workers.

This publication has 5 references indexed in Scilit: