| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of a defective void part like bubbles and a flow pattern in an upper part layer by floating a float having smaller apparent specific gravity than a polymerizable lactam on the lactam cast in a mold and polymerizing the lactam in the absence of oxygen. SOLUTION: Immediately after a lactam liquid being cast into a mold 5, the lid of the mold is opened, and a float 10 nearly of the same length with that of the mold 5 is floated on the polymerizable lactam. The lid is closed, the mold 5 is put in an oven of 100-210 deg.C to polymerize the lactam. The float 10 is used to shut off air from the lactam cast in the mold 5 so that it is non- gas-permeable and has at least smaller apparent specific gravity than the lactam. |
