A process for production of a bag having linear ribs.

摘要

A process for production of a bag having linear ribs (7) uses an apparatus for forming linear ribs which comprises a plate mold (71) having linear protrusions on both faces thereof and upper (72) and lower (73) female molds placed at both sides of the mold, having penetrated linear cavities at positions corresponding to those of the linear protrusions and capable of opening and closing as desired. Multi-layer resin films are inserted between the plate mold and the female molds. The molds are heated and pressed to each other to prepare multi-layer resin films having linear ribs. A bag is produced using the multi-layer resin film having linear ribs thus prepared. Ribs convex to the outside can be formed on the multi-layer film comprising a layer of a resin having a low melting point at the inside and a layer of a resin having a high melting point at an outer side thereof. The self-supporting bag produced by the process has a higher stiffness.