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Twist-wrap film and use thereof as packaging film

Twist-wrap film and use thereof as packaging film description/claims

This application is a continuation application of U.S. patent application Ser. No. 11/667,830, of the same title, having a §371 date of May 16, 2007, which was a National Phase Patent Application based on International Patent Application No. PCT/EP2005/012370, filed Nov. 18, 2005 (International Patent Publication No. WO 2006/058621 A1, published Jun. 8, 2006) which, in turn, was based upon priority Austrian Patent Application Serial No. A 2001/2004, filed Nov. 29, 2004. The priorities of the foregoing applications are hereby claimed and their disclosures incorporated herein by reference.

The invention relates to a twist-wrap film that can be produced by co-extrusion of several plastic layers as well as use thereof as packaging film.

For packaging sweets, such as candy, but also confectionery, it is known to use so-called twist-wrap films, whereby these films are to have a good dead fold, i.e., low shape recovery, good rigidity as well as transparency. These twist-wrap films are used for twist-wrap packagings (twist packagings), whereby the packing process is carried out so that the twist-wrap film is wrapped around the material to be packaged, the latter is laterally cut to length in sleeve form, and then the side ends are rotated so that the contents are protected from contaminants.

A packaging film that is suitable for the twist-wrapping consists of, for example, cellophane. The latter is characterized by transparency as well as high rigidity. Its production, however, is often labor-intensive and complicated.

Alternatives in this respect were found in the provision of polypropylene films; however, the latter have an unsatisfactory dead fold. This means that the packaging ends, i.e., the twisted ends, tend to fold back into their original form.

A switch was subsequently made to find suitable additives that improve the shape recovery of the twist-wrap packaging. In this case, the properties of so-called cycloolefin copolymers (COC) were used that are produced, for example, by polymerization of ethylene with norborane with the aid of metallic catalysts. Owing to the molecular structure thereof, cycloolefin copolymers are more rigid than low density polyethylene (LDPE) that is known in the art. By use of these cycloolefin copolymers in the form of polymer blends, the rigidity of the originally proposed twist packaging materials based on polyethylene or polypropylene could therefore be increased. In this connection, sets of solutions are disclosed in EP-A-920 989, DE-A1-195 36 043 as well as in JP-A-11077924. Another possibility of increasing the rigidity of the materials for twist packagings was used according to JP-A-10166529 to the effect that an adhesive layer is provided between a polypropylene film and a film that consists of cycloolefin copolymers. Although the rigidity desired for twist-packaging materials could obviously be increased by provision of COC blends or by adhesives, these measures, on the one hand, are relatively complex by the precise indication of the mixing ratios in the polymer blends and, on the other hand, by use of an additional intermediate layer in the form of an adhesive in the production of twist-wrap films (twist-packaging materials).

Here, the invention is intended to correct this.

According to the invention, a twist-wrap film of the initially-mentioned type is proposed, which is characterized in that a) one or more plastic layer(s) of partially crystalline polyolefin(s) that is/are uniform in its (their) structure, and b) at least one additional plastic layer, uniform in its structure, consists of amorphous cycloolefin copolymer, whereby the plastic layers a) and b) are in direct contact with one another.

Additional advantageous configurations of the twist-wrap film according to the invention are disclosed according to subclaims.

In addition, the invention relates to the use of a multilayer plastic film, produced by co-extrusion, that consists of a) one or more plastic layer(s) of partially crystalline polyolefin(s) that is (are) uniform in its (their) structure, and b) at least one plastic layer, uniform in its structure, of amorphous cycloolefin copolymer, whereby the plastic layers a) and b) are in direct contact with one another, as packaging film for twist packagings.

Other configurations of the use according to the invention are disclosed according to subclaims.

The invention is explained in more detail below based on FIGS. 1 to 3 as well as based on embodiments. In this case, FIG. 1 shows a possible embodiment of the twist-wrap film according to the invention based on a three-layer structure 1, while FIG. 2 shows a twist-wrap film according to the invention that is based on a five-layer structure 2. Another possible embodiment of the twist-wrap film according to the invention is shown in FIG. 3, and here also a five-layer structure 3 is present, but with an arrangement of the layers to one another that is different to FIG. 2.

The twist-wrap film according to the invention, as it is shown, for example, according to FIGS. 1 to 3, can now be produced as follows:

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