| 摘要 |
PROBLEM TO BE SOLVED: To efficiently obtain a self-supporting bag with excellent impact resistance and self-supporting properties and with no generation of pinholes and wrinkles and without generating leakage by welding a flat square-shaped bottom part forming sheet on a bottom open face so as to form a heat seal part on its peripheral edge. SOLUTION: On one opening part of a cylindrical bag main body 10 whose both ends are opened, each arbitrary point on facing folded lines is made a base point and a folded line from the base point to one end of the bag main body 10 is turned back to the side face side of the bag main body to form a square-shaped opening face 25 of the bottom part. On the other hand, a square-shaped flat bottom part forming sheet 30 is prepd. and this bottom part forming sheet 30 and a bottom part opening face 25 are laminated. A hot plate is pushed on the peripheries of the bottom part forming sheet 30 and the bottom part opening face 25 under laminated condition like this so as to perform so- called four sides sealing to heat-fuse the peripheral edge of the opening part of the bag main body 10 and the bottom part forming sheet 30. |
