SYNTHESIS OF HIGH-MOLECULAR-WEIGHT NYLON-6 BY ANIONIC-POLYMERIZATION OF EPSILON-CAPROLACTAM

To obtain high molecular weight nylon 6, the anionic polymerization of epsilon-caprolactam was investigated in terms of water content in mon omer and concentration of catalyst (Grignard reagent; ethyl magnesium bromide) and chain initiator (monofunctional; N-acetyl-epsilon-caprola ctam or bifunctional; N,N'-adipoyl-bis-epsilon-caprolactam). The weigh t average molecular weight, M(w) = 7.0 x 10(5) (the intrinsic viscosit y; [eta] = 11.2) was obtained using the monofunctional chain initiator , and M(w) = 9.5 x 10(5) ([eta] = 14.1) was found using the bifunction al chain initiator under the following conditions: water content, 0.01 3 mol%; concentration of catalyst, 0.1 mol%; concentration of chain in itiator, 0.03 mol% (monofunctional), 0.015 mol% (bifunctional); polyme rization temperature, 150 degrees C. In the present study, the molecul ar weight of the polymer is governed by quantities of active molecular chains. Since water mainly terminates the propagation of molecular ch ains, minimizing water content in epsilon-caprolactam is indispensable to maximizing the molecular weight of the polymer.