Abstract: A method of producing printed containers for retortable material comprising subjecting the outer surfaces of sheets or container of polyolefin to a flame treatment to produce a wet index of 45 dyne/cm or higher and then printing the outer surfaces. The polyolefin used comprises an olefin polymer compound comprising a mixture of (a) 100 parts by weight of a crystalline propylene polymer having a melt flow index of 0.1-100 g/10 min and (b) 3.0-30 parts by weight of an ethylene polymer having a density of 0.925-0.975 g/cc and a melt index of 0.1-20 g/10 min; or an olefin polymer compound comprising a mixture of (a) 100 parts by weight of a crystalline propylene polymer having a melt flow index of 0.1-100 g/10min, (b) 3.0-30 parts by weight of an ethylene polymer having a density of 0.925-0.975 g/cc and a melt flow index of 0.1-20 g/10 min, and (c) 2.0-25 parts by weight of an ethylene-propylene copolymer rubber having a Mooney viscosity (ML 1+4.multidot.100.degree. C.

Abstract: A method of preforming a cover for a can. The cover is formed from a planar base having a metallic barrier layer and resin layers on either side thereof. The base is first premolded to have a flat bottom recess, a cylindrical sidewall, and preferably an upper flap portion. In the premolding the base is stretched no more than by a factor of 1.8. Then a resin is injection molded over the premolded base to form either a uniform bottom cover or a top cover with a tab.

Abstract: A can comprising a barrel, an upper lid and a lower lid bonded to the barrel. Both the upper and lower lids comprise a gas liquid impermeable barrier layer, preferably aluminum foil, and resin layers heat fused to both sides thereof. Another resin layer is bonded to the exterior of the lids, with the upper lids having a tab and score to be perforated by the tab built into the resin layer. According to the invention, the yield strength of the top lid is made greater than that of the lower lid to prevent breaking of the score if the can is dropped. The differential strength may be accomplished by making the barrier layer of the top lid greater than that of the bottom lid.