SE528260C2 - Packaging laminate and packaging container - Google Patents

Abstract

A packaging laminate (10, 20) for a packaging container for a food product, which packaging laminate (10, 20) comprises a bulk layer (11), outer heat sealable layers (12, 13), and an electrically conductive layer (14) that according to the invention is comprised of an intrinsically conductive polymer. The invention also relates to a packaging container formed from such a packaging laminate.

Description

20 25 30 528 260 stable, processable, manufacturable on a large scale and suitable for use in connection with food products.

WO 031063548 relates to a means for heating materials comprising (a) at least a number of electrically non-conductive receivers, and (b) at least a number of electrically conductive receivers in a polymer or ceramic matrix. In one aspect, the electrically conductive receivers may consist of particles of a conductive polymer per se.

Conductive polymers in themselves (ICP) are a type of polymeric material that has been under development for some time but which in recent years has been improved to allow electrically conductive properties that in some cases can compete with electrically conductive materials consisting of metal. The Nobel Prize in Chemistry in 2000 was awarded for the discovery and development of such conductive polymers. Conductive polymers are currently used in, for example, antistatic photographic films, batteries, transistors, display units and EMI and RFI protection devices for eyepieces, but, as far as the present inventors know, they are not used today in packaging linerins and packaging containers for food products. ICP is sometimes referred to as conductive polymers, organic metals, synthetic metals and so on.

BRIEF DESCRIPTION OF THE INVENTION The object of the present invention is to provide a packaging linerinate and a packaging container by means of which the above-mentioned problems are mitigated or eliminated.

In particular, the object of the present invention is to provide an aluminum-free packaging laminate which nevertheless allows inductive heat sealing of the laminate while at the same time providing a packaging container formed from such a laminate.

These and other objects are achieved by means of a packaging laminate according to the preamble of the description in which the electrically conductive layer consists of a polymer conductive per se.

With the development of the present invention, it has surprisingly been shown that conductive polymers per se can be used to achieve inductive heat sealing in an aluminum-free packaging laminate consisting of outer heat sealable layers. Positive tests have been made in which strong and durable seals have been produced in such a laminate.

The present invention also relates to a packaging container for a food product, preferably a liquid or liquid food product, wherein said packaging container is formed and sealed from a packaging laminate according to the invention. In the high-speed, continuous packaging processes that are well known for Tetra Brik® type cartons, a web of packaging laminate is continuously formed in a tube filled with contents and sealed to form cushion-shaped packaging containers by a simultaneous heat sealing and cutting operation. The cushion-shaped packaging container is then normally folded into a parallelepipedic packaging container. However, any other type of packaging container for food products formed from a packaging laxinate which allows heat sealing by inductive heating is also conceivable as a packaging container with a container body consisting of such a laminate and a plastic top, for example.

DETAILED DESCRIPTION OF THE INVENTION According to one aspect of the present invention, the electrically conductive layer consists essentially of a homogeneous layer formed from the conductive polymer itself. However, minor amounts of additives such as additives to promote bonding may be allowed in the electrically conductive layer. Typically, the electrically conductive layer of a per se conductive polymer may comprise up to 10% by weight at most, preferably 5% by weight at most and even more preferably 3% by weight at most of one or more such additives, such additive (s) er) preferably consists of non-conductive materials.

According to an embodiment of the invention, the electrically conductive layer consists of a continuous layer extending through the entire laminate. According to a further preferred embodiment of the invention, however, the electrically conductive layer is arranged only in sealing areas of the packaging laminate. This can be achieved because it is technically possible to apply the electrically conductive layer only at positions of the larnate which are to be sealed to each other when the laminate is formed into a packaging container, in other words in sealing areas. This is also advantageous because it reduces the amount of inherently conductive polymer required, and said inherently conductive polymer does not contribute to the barrier functions of the laminate (unlike the aluminum foil layer commonly used today).

According to a further aspect of the invention, the inherently conductive polymer is selected from the group consisting of polyaniline, polypyrrole, polythiophene, polyethyldioxytiophene, poly (p-phenylene vinylene), polyacetylene, polydiacetylene, polyphenylene sulfide, polythienylene vinylene and polyvinyl chloride. Preferably doped. the inherently conductive polymer to enhance its conductivity. However, the just mentioned examples of in themselves conductive polymers should only be seen as viable examples today. As development in the field of conductive polymers progresses, new types or improved versions of already existing types of conductive polymers will surely be found and such polymers will then also form part of the present invention. According to a further aspect of the invention, the inherently conductive polymer used can be defined by its electrical conductivity. Accordingly, it should have an electrical conductivity of at least 1 S / cm, preferably at least 102 S / cm, even more preferably at least 104 S / cm and most preferably at least 106 s / cm.

It is difficult to define the thickness required of the electrically conductive layer of the conductive polymer itself because the desired thickness may vary depending on the type of polymer and application. However, a thickness of 10 μm at most, preferably 5 μm at most and even more preferably 2 μm at most and most preferably 1 μm at most is expected to be sufficient.

The electrically conductive layer of the conductive polymer itself can occupy any suitable position within the packaging laminate taken over the cross section of the packaging laminate. According to one aspect of the present invention, it is bonded to the core layer by means of a laminating layer. Such a lamination layer may be a known type of (usually polyiner) barrier layer (other than aluminum), preferably a gas banner layer or a combination of barrier layers.

Alternatively, adhesive layers are arranged between the core layer, optional barrier layers and the electrically conductive layer of the conductive polymer itself. It is suitable if the electrically conductive layer of the conductive polymer itself is arranged adjacent to the inner sealing layer of the laminate, but it is also conceivable for one or more of the barrier layers and / or adhesive layers to be arranged therebetween.

According to a further aspect of the invention, it is preferred that the core layer consists of a paper or cardboard core layer. However, it is also conceivable that it may be a polymer layer. In the case of a polymer core layer, it is also possible to obtain a transparent, optionally colored packaging laminate which is sealable by means of inductive heat sealing.

The inner and outer heat-sealable layers suitably comprise a thermoplastic in the group consisting of polyethylene, preferably metallocene polyethylene, and polypropylene. For example, the use of polypropylene-based heat-sealable layers is conceivable in the case of autoclavable packaging containers.

The utilization of metallocene polyethylene is of particular interest in the innermost heat-sealable layer, i.e. the layer which will face the food contents of the packaging container formed from the packaging laminate.

COMPILATION OF DRAWING FIGURES The present invention will be described in more detail below with reference to a preferred embodiment and with reference to the accompanying drawings where: Fig. 1 basic packaging larninate according to the invention. shows a cross section of the structure of a preferred Fig. 2 shows a cross section of an alternative embodiment of a packaging laminate according to the invention.

DETAILED DESCRIPTION OF DRAWING FIGURES AND EMBODIMENTS Fig. 1 schematically shows a preferred basic concept for a packaging laminate according to the invention. The packaging laminate 10 has a rigid but foldable base or core layer 11 of cardboard or paperboard as well as an outer, liquid-tight and heat-sealable layer 13 and an inner, liquid-tight and heat-sealable layer 12 on each respective side of the core layer 11. The inner the layer 12 will form the inside of the packaging container which is formed from the packaging laminate and preferably consists of metallocene polyethylene.

The packaging laminate 10 further has an electrically conductive layer 14 of a conductive polymer disposed between the core layer 11 and the inner, liquid-tight layer 12. The electrically conductive layer 14 is suitably laminated to the core layer 11 by an intermediate laminate layer 15 of a pewter material such as a polyethylene or polypropylene based material, for example. A surface activation treatment, such as corona, breastfeeding or plasma treatment and / or adhesive layers, is optionally used to enhance bonding of the electrically conductive layer 14 of a per se conductive polymer to the core layer 11 and / or to the inner heat sealable layer 12.

In the embodiment of the packaging larynx 20 shown in Fig. 2, it is schematically shown that a specifically dedicated banner layer 16, preferably a gas barrier layer, may be present between the core layer 11 and the electrically conductive layer 14 of a per se conductive polymer. However, it is also conceivable (but not shown) that the banner layer 16 is arranged between the electrically conductive layer 14 of a conductive polymer itself and the inner heat sealable layer 12. The gas barrier layer 16 may be formed from any known gas barrier material except aluminum foil, such as ethylene vinyl alcohol copolymers, polyvinyl alcohols Other.

Adhesive layers or lamination layers (not shown) may be included in the packaging laminate as needed.

Many other variations of the packaging laminate are conceivable, all of which have the common feature that they have a polymer or cardboard chain layer, an electrically conductive layer of a per se conductive polymer and outwardly wetting surfaces of a heat-sealable polymer.

The electrically conductive layer 14 of a conductive polymer is suitably applied by dispersion, using any known dispersion telmic. It can optionally be coated on a carrier sheet which is then laminated in the packaging laminate. It is also conceivable, and preferred, that the electrically conductive layer 14 of a per se conductive polymer be arranged only in sealing areas of the packaging laminate. 10 15 20 528 260 EXAMPLES Two packaging laminates of the basic concept were heat sealed by inductive heating. A reference packaging larnate with an aluminum foil layer instead of the electrically conductive layer of a per se conductive polymer was also tested. Table 1 indicates the frequency tested for as shown in fi g. 1 induction protection equipment and sealing times needed to achieve a strong and durable seal. As can be seen, the known use of aluminum foil gave the shortest sealing times, but above all the test showed that it was possible to achieve acceptable seals within a reasonable time even when using an electrically conductive layer of a per se conductive polymer instead of the aluminum foil layer. With further optimization, sealing times and other sealing conditions will be improved for the electrically conductive layer of a per se conductive polymer.

Table 1 1.8 MHz Baytron P1 0.9 sec PANIZ 0.7 sec Aluminum foil <0.02 sec 1) Baytron P = poly (3,4-ethylenedioxytiophene) - (poly (styrene sulfonic acid)) 2) PANI = polyaniline-dodecylbenzenesulfonic acid In conclusion, it should be noted that the present invention described above with particular reference to the accompanying drawings is not limited to these embodiments described and shown for illustrative purposes only, and that modifications and changes apparent to those skilled in the art are possible without departing from the spirit of the invention. this is described in the appended claims.

Claims (1)

A package packaging laminate (10, 20) for a packaging container for a food product, said packaging laminate (10, 20) comprising a core layer (11), outer heat sealable layer (12, 13) and an electrically conductive layer. (14), characterized in that said electrically conductive layer (14) consists of a polymer conductive per se. Packaging laminate according to claim 1, characterized in that said electrically conductive layer (14) of a per se conductive polymer comprises up to 10% by weight at most, preferably 5% by weight at most and even more preferably 3% by weight at most of one or more additives. wherein said additive (s) preferably consists of non-conductive material. Packaging laminate according to claim 1 or 2, characterized in that said electrically conductive layer (14) consists of a substantially homogeneous layer of said inherently conductive polymer. Packaging laminate according to any one of the preceding claims, characterized in that said electrically conductive layer (14) is arranged only in sealing areas of the packaging laminate. Packaging larninate according to any one of the preceding claims, characterized in that said conductive polymer is selected from the group consisting of polyaniline, polypyrrole, polythiophene, polyethylene dioxithiophene, poly (p-phenylene vinylene), polyacetylene, polydiacetylene, polyphenylenesylvinylene polyvinyl and polyvinyl doped. Packaging laminate according to any one of the preceding claims, characterized in that said inherently conductive polymer has an electrical conductivity of at least 1 S / cm, preferably at least 102 S / cm, even more preferably at least 104 S / cm and most preferably at least 106 S / cm. Packaging laminate according to any one of the preceding claims, characterized in that said electrically conductive layer (14) has a thickness of 10 μm at most, preferably 5 μm at most, even more preferably 2 um most and most preferably 1 hour at most. Packaging laminate according to any one of the preceding claims, characterized in that the meshed electrically conductive layer (14) is bonded to said core layer (11) by means of a laminating layer (15). Packaging laminate according to one of the preceding claims, characterized in that said core layer (1 l) consists of a paper or cardboard core layer. Packaging laminate according to any one of claims 1-8, characterized in that said core layer (11) consists of a polymer layer. Packaging laxinate according to any one of the preceding claims, characterized in that said heat-sealable layer (12, 13) comprises a thermoplastic in the group consisting of polyethylene, preferably metallocene polyethylene, and polypropylene. Packaging laminate according to one of the preceding claims, characterized in that it also comprises at least one gas barrier layer (16). Packaging containers formed and heat sealed from a packaging laminate (10, 20) according to any one of claims 1-12.