METHOD FOR MANUFACTURING GAS PERMEABLE PACKAGE MATERIALS AND GAS PERMEABLE PACKAGING MATERIALS OBTAINABLE THEREBY

摘要

A method of manufacturing a gas permeable packaging material, which comprises the steps of forming a laminate composed of an outer plastic film and a gas permeable inner sheet with a first heat-sealable layer interposed therebetween, perforating the laminate with a number of micro-pores, which extend from the outer film side to at least the inner sheet, heat-sealing a second heat-sealable film with or without a number of small-pores to the inner sheet, and, if the second heat-sealable film is of no porous, forming a number of small-pores in the second heat-sealable film, a pore ratio of the second heat-sealable film being greater than that of the outer film.