Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
2002-02-22
2004-04-27
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S034900, C428S035200
Reexamination Certificate
active
06726968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to packaging films. More particularly, the invention pertains case ready packaging films having good antifog performance that are suitable for use in meat packaging.
2. Description of the Related Art
Containers have long been used to store perishable foods, such as meats, fruits and vegetables, prior to sale in the marketplace to consumers. Maximizing the time in which the food remains preserved in the containers minimizes the amount of spoilage.
The environment around which the food is preserved is an important factor in the preservation process. It is important that the food is maintained at an adequate temperature, while also controlling the molecular and chemical content of the gases surrounding the food. By providing an appropriate gas content to the environment surrounding the food, the food can be better preserved when maintained at the proper temperature or even when it is exposed to variations in temperature. This gives the food producer some assurance that the food will be in an acceptable condition when it reaches the consumer. Preferred modified atmosphere packaging systems for foods, including raw meats, exposes these foods to extremely low levels of oxygen because it is well known that the freshness of meat can be preserved longer under anaerobic conditions than under aerobic conditions. Maintaining low levels of oxygen minimizes the growth and multiplication of aerobic bacteria. Additionally, modified atmosphere packaging can involve high levels of oxygen (80%) combined with nitrogen and/or carbon dioxide. The gases in these combinations do not favor bacterial growth but allow the raw meat to maintain a preferred red color that is acceptable to the consumer.
It is also important that the packaging exhibit good resistance to the formation of condensation inside the package on a surface of the film. This is known in the art as an antifog property. Multilayered films for modified atmosphere packaging having such antifog properties are well known and are commonly used when packaging food products having a high moisture content, such as fresh meats, and when it is important for the product to be clearly visible to the consumer. For example, U.S. Pat. No. 5,766,772 describes multi-layer heat-shrinkable films endowed with antifog properties having a different structure from this invention.
To produce a film exhibiting this antifog property, an antifog component is typically blended with or coated onto a sealant film such as a polyethylene film. This antifog-polyethylene component then forms a part of a multilayered packaging film, such as a nylon packaging film, that may also incorporate an oxygen barrier polymer layer such as ethylene vinyl alcohol. However, one significant problem associated with such known multilayered films having this antifog component is that the antifog component tends to be drawn toward polar materials, such as nylon, and away from the non-polar polyethylene. This is particularly a problem when the film is rolled up after manufacture such that the antifog layer or antifog containing polyethylene layer is brought into direct contact with an adjacent nylon layer. This causes the antifog component to migrate out of its existing polyethylene layer and into the nylon layer, compromising the performance of the nylon layer as well as degrading the antifog property of the film. Therefore, it would be desirable to have a multilayered packaging film having good antifog performance and having an antifog component which does not migrate into adjacent nylon layers when stored. The present invention provides such a solution to this need.
SUMMARY OF THE INVENTION
The invention provides a multilayered film comprising:
a) a nylon film having first and second surfaces;
b) a sealant film, positioned on the first surface of the nylon film, either directly on the first surface of the nylon film or via an intermediate adhesive;
c) an antifog composition contained within at least part of the sealant film or coated on a surface of the sealant film opposite the nylon film; and
d) a protective film applied onto the second surface of the nylon film.
The invention also provides a multilayered film comprising:
a) a first nylon layer having first and second surfaces;
b) an ethylene vinyl alcohol layer positioned on the first surface of the nylon layer;
c) a second nylon layer positioned on a surface of the ethylene vinyl alcohol layer opposite the first nylon layer;
d) a polyethylene sealant film, positioned on a surface of the second nylon layer which is opposite to the ethylene vinyl alcohol layer;
e) an antifog composition contained within the sealant film or coated on a surface of the sealant film which is opposite the second nylon layer; and
f) a polyurethane protective film applied on the second surface of the first nylon film.
The invention further provides a process for forming a multilayered film comprising:
a) positioning a sealant film onto a first surface of a nylon film, wherein the sealant film has an antifog composition which is either incorporated therein or coated on a surface of the sealant film opposite the nylon film; and
b) applying a protective film onto a second surface of the nylon film.
The invention still further provides a food package which comprises a container having an open portion and a multilayered film sealing the open portion, which multilayered film comprises:
a) a nylon film having first and second surfaces;
b) a sealant film, positioned on the first surface of the nylon film, either directly on the first surface of the nylon film or via an intermediate adhesive;
c) an antifog composition contained within at least part of the sealant film or coated on a surface of the sealant film opposite the nylon film; and
d) a protective film applied onto the second surface of the nylon film; the multilayered film being positioned such that the protective film is away from the open portion of the container.
The invention therefore provides a desirable multilayered packaging film having good antifog performance and having an antifog component which does not migrate into adjacent nylon layers when stored.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention provides a multilayered packaging film having good antifog properties wherein the antifog composition does not migrate into adjacent polar film layers. In the production of a multilayered film according to the invention, a nylon film having first and second surfaces is positioned on a surface of a sealant film, either directly on the first surface of the nylon film or via an intermediate adhesive layer. An antifog composition is contained within at least part of the sealant film or coated on a surface of the sealant film that is opposite to the nylon film, i.e. a surface different than the surface to which the nylon film is attached. A protective film is also applied onto the second surface of the nylon film opposite the sealant film. This film exhibits good, permanent antifog properties and avoids migration of the antifog composition out of the sealant film.
Nylons are conventionally used in the art of multilayered packaging films. Suitable nylons within the scope of the invention non-exclusively include homopolymers or copolymers selected from aliphatic polyamides and aliphatic/aromatic polyamides having a molecular weight of from about 10,000 to about 100,000. General procedures useful for the preparation of polyamides are well known to the art. Such include the reaction products of diacids with diamines. Useful diacids for making polyamides include dicarboxylic acids which are represented by the general formula
HOOC—Z—COOH
wherein Z is representative of a divalent aliphatic radical containing at least 2 carbon atoms, such as adipic acid, sebacic acid, octadecanedioic acid, pimelic acid, suberic acid, azelaic acid, dodecanedioic acid, and glutaric acid. The dicarboxylic acids may be aliphatic acids, or aromatic acids such as isophthalic acid and terephthalic acid. Suitable diamines for making polyamides inclu
Criss Roger H.
Honeywell International , Inc.
Nordmeyer Patricia L.
Pyon Harold
Szigeti Virginia
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