Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Reexamination Certificate
1999-10-12
2003-03-18
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
C428S035700, C428S036700, C428S423500, C428S424700, C428S424800, C428S474900, C428S515000, C428S520000
Reexamination Certificate
active
06534137
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an article comprising a multilayer film suitable for packaging end use, especially a multilayer film suitable for use in the packaging of relatively hard, granular bulk products, such as dry pet food. The multilayer film can be a laminate of two components wherein the first component comprises at least three film layers, and a second component has an oxygen barrier layer. The exposed first component surface is heat-sealable to both itself (end sealable) and the second component surface (lap sealable) while the exposed second component surface is heat-sealable to itself (gusset seal) as well to first component (lap sealable). The article preferably comprises a heat seal of the film to itself or another film. The external surface of the article comprises a film layer which can be free of anti-block and slip additives to improve stackability of the articles. The present invention also relates to packaged products in which the package comprises the article of the invention.
BACKGROUND OF THE INVENTION
For some time various products have been packaged in packages which comprise paper alone or paper in combination with a thermoplastic film. Such packaging has typically included a plurality of paper layers, with a relatively thin, flexible plastic film adhered to the inside paper layer, the film serving as a moisture and grease barrier. The paper provides the package with an exterior surface which is highly printable, as well as a stiffness which provides the packaging article, which is, for example, a gusseted bag, with an ability to be self-supporting and to provide the package with overall aesthetic qualities which consumers perceive as being desirable. Such paper packaging has been used in a variety of applications, particularly gusseted bags which are used in the packaging of dry granular material such as pet food, livestock feed, sugar, coffee, cookies, cereals, baking products such as cake mixes, crackers, chips, powdered milk, charcoal, cement, fertilizer, lime, pesticides, etc. The packaging can also be used to package cheese, in grated, ground, and/or block form.
More recently, paper-free plastic film packaging materials have been used for the packaging of a such products as pet food, etc. In order to obtain a desirable performance level, i.e., in terms of impact strength and toughness, such packaging films have contained relatively large quantities of polymers which are recognized.for their toughness and impact resistance, such as polyamide, polyester, and polyacrylonitrile. However, these polymers are also relatively expensive. It would be desirable if a comparably tough, impact-resistant package could be made from less expensive polymers. Moreover, it would also be desirable to provide packaging which provides a high O
2
-barrier layer to increase the shelf-life of the product. In addition, in such plastic packaging, particularly in the packaging of hard, granular bulk products such as dry pet food, it has-been found that “dimples” tend to form in the plastic, thereby creating a rough, dimpled appearance in the outside of the package. It would be desirable to provide packaging which avoids this “dimpling” effect. Finally, it would be desirable to provide such packaging which is also relatively stiff, e.g., capable of providing a self-supporting gusseted bag.
In the case of the packaging of food in paper packaging, particularly pet food, it has heretofore been desirable to mix antioxidant into the food product, otherwise the food tends to lose metabolizable energy, exhibit decreased acceptability, including undesirable odors and flavors, protein degradation, and the development of health hazards in .the consuming animal. Thus, without antioxidant present, food packaged in paper packaging exhibits reduced shelf life and/or reduced product quality. It would be desirable to provide a type of packaging which requires less antioxidant, or even no antioxidant, to be mixed with a food product within the package, without the detrimental effects associated with the oxidation of the food product. In this manner, the expense of providing the antioxidant as well as the mixing of the antioxidant with the food product, are both reduced or avoided, while maintaining a good shelf life for the packaged food product.
U.S. Pat. No. 5,846,620 to Compton discloses a high strength bag which is made from a self-sealing heat-shrinkable film comprising at least three layers, e.g., LLDPE/EVA/LLDPE. U.S. Pat. Nos. 4,765,857 and 4,755,403 to Ferguson also disclose such multilayer films.
PCT Application WO98/22282, published May 28, 1998 discloses tough and impact resistant bags which are substitutes for paper packaging while being made for the most part from less expensive polymers. The bags are made by laminating a three film layer first component (inside bag surface) to a second component (outside bag surface) containing at least a fourth film layer, e.g., a non-self-sealing blown monolayer film such as high density polyethylene, as substitutes for paper packaging. However, such bags have been difficult to form seals with second component surfaces, requiring offset printing and laminating steps to create an edge lip of first component which extends beyond the second component to permit better lap sealing by allowing first component overlap of a first component surface. Although this construction provides for both inside/outside and outside/outside seals, the extra steps result in added manufacturing expense. Moreover, while large bags require good stackability on a pallet, the second component film employed requires slip and antiblock additives for processing, resulting in a slippery outer surface of the bag, hindering stackability. Moreover, embodiments which employ heat-shrinkable, unblown or solid state oriented second component equivalent barrier film (Examples 1 to 4) exhibit reduced interply adhesion which results in weak gusset seal in the bags. Finally, difficulty in maintaining repeat length of the bag arises when temperatures encountered during processing,. e.g., during ink drying and laminating adhesive drying, result in unintended shrinkage.
Accordingly, it would be useful to provide plastic bags which are sufficiently inexpensive to compete with paper-containing packages while providing a high quality appearance and feel to the consumer. Such articles would comprise a multilayer film having excellent optics and improved ink adhesion for appearance, high coefficient of friction (COF) on its outer surface for stackability of packages made with such film, strong interply adhesion to promote both gusset sealing and lap sealing for bag strength, as well as reduced shrinking tendency at processing temperatures of 110° to 150° F. to maintain repeat length during manufacture.
SUMMARY OF THE INVENTION
The present invention is directed to a multilayer film as well as an article which is suitable for packaging end-use and which comprises a multilayer film. The majority of the multilayer film is made from relatively inexpensive polymers. Nevertheless, it has been found that the multilayer film can be provided with toughness and impact resistance characteristics which are adequate for the packaging of various products, including dry pet food. Moreover, it has been found that the multilayer film can be provided with toughness and impact resistance characteristics which are comparable to, or even superior to, plastic packaging materials which comprising higher amounts of more expensive polymers such as nylon, polyester, and polyacrylonitrile.
In addition, the multilayer film in the article of the present invention comprises an O
2
-barrier layer which increases the shelf life of, for example, a packaged food product therein. The presence of the O
2
-barrier layer reduces or eliminates the need to add antioxidants, etc. to a food product, such as pet food, to prevent the oxidative rancidity, off-flavors, and off-odors of the packaged food product. The multilayer film also can be provided with a stiffness which, if the multilayer film is convert
Cryovac Inc.
Hurley Jr. Rupert B.
Nolan Sandra M.
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