Foamed and stretched plastic containers and method of producing the same

A method of producing a foamed and stretched plastic container by forming a preform of a shape having a mouth portion and a forming portion continuous to the mouth portion by injection-molding a mold cavity with a molten polymer, transferring said preform taken out from the mold cavity to the step of stretch-forming, and stretch-forming the forming portion of said preform, wherein;

• said molten polymer is a melt in which an inert gas is dissolved an inert gas;
• the metal mold forming said mold cavity is a metal mold of which a portion corresponding to said mouth portion has a cooling capability larger than that of a portion corresponding to said forming portion;
• said mold cavity is injection-filled with said molten polymer while applying a pressure thereto to hold a high pressure in said mold cavity so that the foaming does not take place;
• said mouth portion is forcibly cooled by said metal mold so that the foaming does not take place even after the pressure is released;
• said forming portion is weakly cooled by said metal mold so that the foaming takes place starting from the central portion of the container wall due to the temperature of the resin after the pressure has been released;
• and
• the preform taken out from said metal mold is transferred to said step of stretching and is stretch-formed while the central portion of the container wall of said forming portion is still being maintained at a stretch-formable temperature.