To prevent a powder from flying up when the powder is filled, and prevent an environmental contamination from occurring due to the swirl up of the powder by forming a large number of protuberance form openings which have air permeability and protrude to the inside, in a packaging bag in which a power of activated charcoal, iron powder, paulownia ash, zeolite, a highly moisture-absorbent polymer or the like is filled.
When a perforated film 17 having protuberance form openings 16 is manufactured, a resin film 13 is placed on a porous cylinder 12 made of a metal on which a large number of openings 11 are provided, and after heating the resin film 13 to a temperature of the resin softening point or higher, the resin film 13 is vacuumized by a negative pressure from the rear surface side of the porous cylinder 12 made of the metal, and the resin film 13 at the opening sections is sucked to the rear surface side of the porous cylinder 12 made of the metal. Also, on such a perforated film 17, a paper, a fabric or a perforated film 18 on which fine pores are formed, is affixed and laminated, and a composite sheet 28 of a two layer or three layer structure is formed. By this constitution, the strength is improved, and a powder is prevented from leaking out, and at the same time, the air permeability can be increased/decreased depending on a purpose.
HATA ISAO
EZAKI MOTOYUKI
MINAZU HIROSHI
YAMAZAKI TATSUO
JOBAN SANGYO KK
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