Packaging bag with self-closeable outflow port, and method of manufacturing the packaging bag

A pouch, comprising:

• a self-closable pouring spout defined by a boundary area between heat-sealed parts and a non-heat sealed part, said non-heat sealed part forming a pouring spout passage,
• a metering chamber that communicates with said self-closable pouring spout, and
• a handle provided in the lower part of said self-closable pouring spout and adapted to be removable by cutting or tearing,
• wherein when said self-closable pouring spout is in a closed state, no gap is present between inside surfaces of plastic films contacting each other at a non-heat sealed side of said boundary area,
• wherein the pouch is produced by a process comprising heat sealing said plastic films while uniformly pressing said plastic films in the boundary area between said heat sealed parts and said non-heat sealed part,
• wherein said plastic films are heat-sealed by pressing and heating using a heat sealing head equipped with heating pressing members in regions corresponding to said heat-sealed parts and a cooling member in a region corresponding to said non-heat-sealed part,
• wherein said cooling member is disposed between said heating pressing members, and
• wherein said cooling member pressurizes said plastic films to form said non-heat sealed part wherein when said self-closable pouring spout is in an open state, in a portion of said self-closable pouring spout from said boundary area to a point that is separated from said boundary area by a distance equivalent to the thickness of one of said plastic films, each of said plastic films have a cross-sectional shape which is a rectilinear shape or a convex shape with respect to an interior of said pouring spout passage, and
• wherein when said self-closable pouring spout is in the open state, an angle of greater than 0 degrees but less than or equal to 20 degrees or less is formed by tangent lines of said inside surfaces of said plastic films, said tangent lines passing through said boundary area.