| 摘要 |
A reclosable bag is formed of a first wall and a second wall of a polymeric sheet material joined to form an enclosure with a mouth defined by the wall edges. The bag has a closure for selectively opening and sealing the mouth. The closure includes a first and a second mutually interlocking profile, each of which extends along and is bonded to the internal surface of its respective first and second wall. The first and second mutually interlocking profiles are extruded from a first polymeric resin material, and have a web portion which is bonded to the wall. Coextruded onto the web portions, or applied to the web portions following the extrusion of the strips, is at least one rib of a second polymeric resin material which includes an ultraviolet-light-excitable tracer material. The second polymeric resin material has a lower melting point than the first polymeric resin material, and is used to bond the profiles to the sheet material of the walls. Before such bonding, the ribs appear as discrete lines under ultraviolet light. After a complete bonding, the ribs disappear and are replaced by a smeared brightening of the region between the profiles and the sheet material of the walls. The appearance of ribs after bonding indicates an unsuccessful bonding operation that could possibly lead to an increase in the occurrence of leaking packages.
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