To prevent cracks in the can hight direction due to an impact from occurring, and improve the dent resistance by a method wherein a large number of dot-form protruding parts are formed on one part or the whole surface of a side wall resin layer on the internal surface of the can, and they are made orientation-relaxing parts.
A seamless can 1 is formed by drawing and bending-straightening or additionally ironing a thermoplastic resin-metal laminate, and consists of a bottom part 2 and a side wall part 3. When desired, a flange part 5 is formed with a neck part 4, at the upper end of the side wall part 3. The side wall part 3 consists of a metal base body 6 and an internal surface thermoplastic resin layer 7. On one part or the whole surface of the can internal surface side wall resin layer 7, a large number of dot-form protruding parts are provided. For the formation, a re-draw-molding or iron-molding at the final state is performed in such a manner that a punch on which a large number of dot-form recessed parts are formed, and the internal surface resin layer 7 of the laminate are engaged, and the shape of the dot-form recessed part is transferred to the internal surface resin layer 7. the formed large number of dot-form protruding parts impart a disturbance, i.e., an orientation-releasing part, to the molecular orientation as the whole body of the resin layer 7, and by this disturbance, even when an impact is applied, the resin layer 7 is prevented from cracking.
SATO NOBUYUKI
KOBAYASHI TOMOSANE
KOBAYASHI AKIRA
IMAZU KATSUHIRO
