Barrier compositions and articles made therefrom

Abstract

Improved oxygen barrier and oxygen absorbing compositions and structures comprising blends of xylylene group-containing polyamides and cobalt octoate and xylylene group-containing polyamides, polyesters and cobalt octoate are disclosed and claimed. These blends have superior barrier properties and clarity obtained by controlling the degree of orientation and the amount of cobalt. These novel blends are used as single layers and as the core layer in multiple layer films, structures and articles. When used in multiple layer structures, the adjacent layers are comprised of polyesters and/or polyamides. The structures made from the blends of the present invention have a clarity that is superior to structures previously known in the art.

Description

[0001] This application is a continuation-in-part of application Ser. No. 07 / 472,400, filed Jan. 31, 1990, entitled “Improved Barrier Composition and Articles Made Therefrom”, incorporated herein by reference. The present invention relates to further improvements in the composition and articles of application Ser. No. 07 / 472,400. [0002] A continuation-in-part application Ser. No. 07 / 761,490 entitled “Improved Barrier Composition and Articles Made Therefrom”, was filed on Sep. 18, 1991 as a continuation of application Ser. No. 07 / 472,400. Application Ser. No. 07 / 761,490 is incorporated herein by reference.BACKGROUND OF THE INVENTION [0003] Many products, particularly food products are sensitive to the presence of oxygen and / or the loss or absorption of water. These products are susceptible to deterioration, when packaged, due to oxygen and / or moisture absorption or loss through the wall of the package. Attempts to solve the problem have led to the widespread use of oxygen barriers an...

AI Technical Summary

Problems solved by technology

These products are susceptible to deterioration, when packaged, due to oxygen and / or moisture absorption or loss through the wall of the package.

A problem with conventional barrier materials is that due to their high cost or their unstable structural characteristics or other weaknesses, it is difficult to fabricate commercial packaging solely out of barrier materials.

For instance, EVOH, while having superior oxygen barrier properties, suffers moisture problems because of the many hydroxyl groups in the polymer.

Other barrier materials are so expensive that to manufacture structures solely from those barriers would be cost prohibitive.

Although multilayer structures containing a barrier layer may be cheaper and stronger than a single layer of barrier materials, such structures are more complicated to manufacture than single-layered ones.

In addition, multilayer structures comprised of layers of a variety of different materials may be opposed in some instances on environmental grounds, they may be more difficult to recycle since it is often difficult and expensive to separate the layers.

In addition, reducing the thickness of the barrier layer in a multilayer structure can reduce the barrier properties of the film.

These structures have the same barrier properties of prior art barriers but at lower cost due to a decrease in the amount of expensive barrier material used.

While PET has a number of valuable properties in packaging, it does not have as good a gas barrier property as is frequently required or desired in many applications.

For example, although PET has good carbon dioxide barrier properties for soft drinks, it has not been found useful in packaging such products as beer because beer rapidly loses its flavor due to oxygen migration into the bottle.

Similar problems are encountered with citrus products, tomato based products and aseptically packed meat.

A packaging material with physical properties similar to PET is polyethylene naphthalate (PEN) which is 3-20 times more effective as a barrier but is considerably more expensive.

However, multilayer structures employing polyester, such as PET, Frequently have adhesion problems between the polyester and the barrier layer which frequently leads to delamination over time.

Kushida indicates that amounts of xylylene group-containing polyamide resin greater than 30% by weight causes the container to become a laminated foil structure which is susceptible to exfoliation between the foil layers of the container.

Such conditions impose severe stresses on the packages.

When sterilizing conditions are required, however, most of these packages fail to survive the processing.

Typically, problems are encountered with excessive weakening or failure of the heat seals about the periphery of She pouch.

Also certain weaknesses or separations may develop between the layers in the multiple layer sheet structure.

In addition, the high humidity experienced during the sterilizing process can change the chemical or structural properties of some materials.

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