PURPOSE: To mold a hollow molding having a uniform thickness and a high impact strength in a short time by charging ω-lactam, anion polymer catalyst and activator in molds, and setting, to polymerize the m in a rotary molding machine, a temperature in the molds to a specific temperature range.
CONSTITUTION: ω-lactam, anion polymer catalyst and activator are cast in molds at 150-300°C of an inner surface temperature of the molds, and polymerized in a rotary molding machine. The catalyst and the activator to be used bay be know, and the activator is particularly preferably compound represented by a formula I. In the formula, R1 is bivalent organic group, R2, R3 are hydrogen, at least one type of group selected from 1-11C alkyl group, 4-15C cycloalkyl group, 6-15C aryl group. X and X' are acyl group selected from formula II, and n and n' are integer of 3-11. 50wt.% or more of a raw material to be cast in the molds is preferably in a powder or flake state having a diameter or a longest length of 0.05-20mm.
ONISHI KOJI
IWAMOTO MASAAKI
