Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1999-10-28
2001-04-10
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S216000, C428S336000, C428S457000, C428S458000, C428S480000, C428S690000, C428S690000, C428S910000, C156S244240, C264S290200
Reexamination Certificate
active
06214440
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a coextruded, biaxially oriented polyester film which, after metalization, has low oxygen permeation and good adhesion to the metalization, and which is composed of at least one base layer B and, applied to this base layer, at least one layer A, where this layer A has a defined number of elevations and a copolyester coating. The invention further relates to the use of the film and to a process for its production.
BACKGROUND OF THE INVENTION
Food and drink packaging frequently requires a high level of barrier action with respect to gases, water vapor and flavors (meaning low permeability or low permeation). A process frequently used to produce packaging of this type involves treating the plastic films used by metalization or high-vacuum deposition with aluminum.
Metalized films have good barrier properties. Therefore, these films are used in particular to pack foods and other consumable items for which long storage or transport times pose a risk that, if the barrier is inadequate, the packaged foods may spoil, become rancid or lose flavor. This applies, for example, to coffee, snacks containing fats (nuts, chips, etc.), and to drinks containing carbon dioxide (in pouches).
Where polyester films with a metalized aluminum layer are to be used as a packaging material, they are generally a constituent of a composite film with two or more layers (laminate). The inner side (i.e., the side facing the contents) of the bags is sealed, and the sealable layer is generally composed of polyethylene or polypropylene. A typical structure here for the film composite is as follows: polyester layer/aluminum layer/adhesive layer/sealable layer.
For a laminate thickness of from about 50 to 150 &mgr;m, the thickness of the metal layer is only from 10 to 80 nm. Although this functional layer is very thin, it is sufficient to give adequate protection from light and to achieve very good barrier properties.
Detailed results of studies ofthe effect of substrate surface on barrier properties in polyester films can be found in the dissertation by H. Utz (Munich Technical University 1995: “Barriereeigenschaften aluminiumbedampfter Kunststoffolien” (Barrier properties of aluminum-metalized plastic films).
EP 0 144 878 describes a polyester film which, in order to improve adhesion to the metalized layer, has a polyester coating which is applied to the film during the production process in the form of an aqueous dispersion. A disadvantage here is that polyester coating leads to a marked deterioration in the barrier effectiveness of the metalized film.
However, for many applications it is desirable to provide a film which has both good barrier properties and also good adhesion capability with respect to the metalization.
SUMMARY OF THE INVENTION
It was therefore an object of the present invention to provide a coextruded, biaxially oriented polyester film which, after metalization, has a high level of oxygen barrier properties and of adhesion to the metalization. In addition, the film is to have good optical properties and good processing performance. In summary, the object was to provide a film with the following combination of features:
low oxygen permeation of the polyester film after metalization
high adhesion between the polyester film and the metalization
high gloss and low haze
low coefficients of friction (no blocking of the film with itself).
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Davis Richard Lee
Hellmann Joerg
Peiffer Herbert
Chen Vivian
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Mitsubishi Polyester Film GmbH
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