A plastic bag comprises first and second panels each having a top, a bottom, and first and second opposing sides. The first and second panels are joined to each other along their respective bottoms, their respective first opposing sides, and their respective second opposing sides. The plastic bag includes a zipper having a male and female track.
The male track includes a male profile and a first fin, in which the first fin is affixed to the first panel in proximity to the top of said first panel. The female track includes a female profile and a second fin, in which the second fin is affixed to the second panel in proximity to the top of said second panel. The male and female profiles having complementary cross-sections.
The inventive fins comprise a first resin and, optionally, a second resin which, along with the fins seals, are able to withstand greater forces and more adverse conditions. At least one of the fins comprises a first resin having a polydispersity of about 1 to about 4, a melt index of about 0.2 to about 20, and a melt flow ratio of about 12 to about 35. The second resin, if used, may either be coextruded or blended with the first resin.
The use of plastic bags is increasingly more common in the marketplace. A factor affecting their acceptance and range of application, however, is the strength and reliability of the bags and the seals.
Plastic bags are in widespread use in a varied and diverse number of household and commercial applications. The primary advantage of plastic bags is their ease of opening and resealing. The plastic bag includes first and second opposing body panels fixedly connected to each other along a pair of sides and a bottom, in which the bottom extends between the pair of sides. The plastic bag includes a fastener, such as a zipper, extending along a mouth formed opposite the bottom of the plastic bag. The zipper includes a male track and a female track. The male track includes a male profile and a first depending fin or flange extending downward from the male profile. Likewise, the female track includes a female profile and a second depending fin or flange extending downward from the female profile. The first and second fins may be extruded separately from the body panels and then thermally fused to inner surfaces of the respective first and second body panels.
The male and female tracks may be rolled or pressed into their interlocking arrangement so as to securely close the bag by one of two means. First, the tracks are rolled or pressed together at one end by a user and then sequentially fitted together along the length of the zipper by the user running a finger along the length of the zipper on each side of the tracks. Alternatively, some bags employ a plastic slider that rides along the tracks of the zipper. If the slider is pulled in one direction, the bag is sealed shut; if the slider is pulled in the opposite direction, the bag is reopened.
Plastic bags with a zipper-type closure mechanism typically have at least two types of seals. One type of seal ("side seal") seals a first body panel to a second opposing body panel along the sides of the plastic bag. A second type of seal ("fin seal") is created when a plastic fin is used to attach the zipper-type closure mechanism to the body panels. Since the popularity of these bags has placed increased demands on the tasks they are asked to perform, a need exists for bags having fin seals that are able to withstand increased forces and more adverse conditions.
According to one embodiment of the present invention, a zippered plastic bag has first and second panels, a zipper and a slider. The zipper includes a male and female track. The male track includes a male profile and a first fin portion. The first fin portion is affixed to the first panel in proximity to the top of the first panel. The female track includes a female profile and a second fin portion. The second fin portion is affixed to the second panel in proximity to the top of the second panel. The male and female profiles have complementary cross-sections.
The first and second zipper fin portions are attached. At least one of the fin portions is made from a first resin which is prepared in the presence of a single site catalyst and a second resin. The first resin has a polydispersity of from about 2 to about 3, a melt index of from about 0.2 to about 20 g/10 min., and a melt flow ratio of from about 12 to about 35. The second resin is a low density polyethylene. At least one of the fin portions comprises from about 5 to about 50 wt. % of the first resin, and from about 50 to about 95 wt. % of the second resin.
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