1. Field of the Invention
The present invention pertains to the attachment of zippers to film substrates of various compositions and adhesive formulations, in the manufacture of reclosable packages and bags.
2. Description of the Prior Art
In the manufacture of reclosable packages and bags, it is known that sealants on polyethylene base zipper flanges are different types of polyethylene copolymers with low to medium affinity to polypropylene film substrates, thereby resulting in the formation of weak bonds. These weak bonds are the result of high affinity between the polyethylene base resin of the zipper flange and the ethylene-based copolymers used as a sealant.
As has been recognized in the packaging tests disclosed in application Ser. No. 11/728,413, entitled “Hot Melt Adhesive Systems for Zipper Assemblies on Large Bag Constructions of Various Substrates”, filed on Mar. 26, 2007, it is imperative that packaging be designed which can withstand extreme conditions which may occur routinely in the manufacture, shipping, storage, sale and use of consumer products.
It is therefore an object of the present invention to improve the sealing strength between polyethylene zipper flanges or other zipper components and polypropylene package or bag walls.
This and other objects are attained by provided a coating which adheres or sticks to the polypropylene. The coating is coextruded as a sealant on the zipper flanges. The coating, when heat sealed or glued to the polypropylene film, creates a very strong bond. More specifically, the coextruded sealant provides an even distribution of polypropylene and polyethylene in the zipper sealant layer to ensure excellent bonds across the zipper base material, the coextruded layer and the polypropylene film substrates.
Additionally, embodiments including a polypropylene zipper attached to a polypropylene substrate are disclosed.
Further objects and advantages of the invention will become apparent from the following description and from the accompanying drawings, wherein:
Referring now to the drawings in detail, wherein like numerals refer to like elements throughout the several views, one sees that
As shown in
The coextruded blend which forms layer 400 may include a metallocene ethylene-based plastomer homogeneously blended with a low ethylene content propylene plastomer or an ethylene/propylene plastomer resin. The specific plastomers chosen would vary with the application, with a broad range of equivalents being apparent to one of ordinary skill in the art after review of this disclosure.
The results of the embodiments of this invention have been exceptional. For example, without using an embodiment of the present invention, for a polyethylene zipper with a coextruded blend of ethylene based metallocene with an ethylene/propylene copolymer plastomer sealed to various polypropylene substrates, T-peel strengths in the range of 1.6 to 2.1 pounds per inch were typical results. However, by using similar polypropylene substrates, additionally with various APAO hot melt adhesives as described above, T-peel strengths in the range of 14.7 to 15.1 pounds per inch were typical results. Typically, T-peel strengths in the range of at least 7.0 pounds per inch are sought.
Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.
This application claims priority under 35 U.S.C. §119(e) from provisional application Ser. No. 61/057,601, filed on May 30, 2008, entitled “Sealant on Polyethylene Zipper for Polypropylene Film Substrates/Polypropylene Zipper for Polypropylene Bag”, the contents of which are hereby incorporated by reference.
Number | Date | Country | |
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61057601 | May 2008 | US |