BACKGROUND ART In the packaging industry, use has long been made of packages of a single-use nature, so-called single-use disposable packages, for packing and transporting products such as, for example, liquid foods.

A major group of these single-use disposable packages is produced by thermoforming of a plastic laminate with a rigidifying core layer of a thermoformable plastic and an outer layer (the inside layer in a finished packaging container) of a likewise thermoformable plastic essentially consisting of polyethylene or polypropylene possessing superior properties such as, for instance, liquid barrier and flavour barrier properties vis-à-vis the packed food product.

Another major group of single-use disposable packages is produced from a laminate packaging material comprising a core layer of paper or paperboard and outer, liquid-tight coatings of plastic on both sides of the core layer, normally consisting of a low density polyethylene (LDPE).

The composition of such packaging laminates is intended to impart to the packed product the best possible protection, at the same time as making the package both easy to produce and easy to handle. A rigid core layer imparts to the package good mechanical configurational stability such that the package can be distributed in a simple, rational manner and be conveniently handled. An inside layer of, for example, LDPE has well- documented superior properties for direct contact with food products, and also superior thermosealing properties, at the same time as outer coatings of LDPE effectively protect a liquid-absorbing fibre core layer against penetration of moisture and liquid which would otherwise rapidly weaken

and destroy the core layer and thereby make the package itself sloppy and impossible to handle.

In order to supplement such a packaging laminate with barrier properties against light or gases, it is known in the art to provide different types of barrier layers between the core layer and the one outer plastic coating of the packaging material, such as, for example, an aluminium foil (Alifoil) or a layer of a polymer possessing superior gas barrier properties.

Such polymers are, for example, ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVOH), polyamides, polyvinylidene chloride (PVDC) and polyesters such as, for example, polyethylene terephthalate (PET).

Packaging containers from such a laminated packaging material are produced by means of thermoforming or fold-forming, respectively.

Thermoforming is a method known to persons skilled in the art, which implies that an intermittently running web of the packaging laminate is heated in one section and thereafter formed by means of cooperating forming tools into packaging containers, such as beakers, trays or the like.

Fold-forming generally takes place such that a running crease-lined packaging material web is reformed into a tube by the longitudinal edges of the web being united to one another, whereafter the tube is filled with the intended contents and sealed along repeated, narrow, transverse sealing zones. The thus--sealed-off packaging units containing their contents are separated from the tube by means of incisions in the transverse sealing zones and are formed by folding along the crease lines to the desired geometric configuration However, depending upon what type of food product that is to be packed, such conventional packaging containers with an inside layer substantially consisting of polyethylene or polypropylene are often difficult to empty because the product tends to adhere to the inside walls of the packaging container. This problem is particularly manifest in the packing of solid or semi-solid food products such as, for example, various types of cheese.

Japanese Patent Application JP-A-07062163 (Tonen Kagaku KK) describes packaging containers for the packing of puddings, jellies and tofu- like products, these packaging containers being produced by injection moulding of a mixture of an ethylene propylene copolymer and additives

such as antioxidants, calcium stearate and glycerin monostearate (GMS). The packages may then readily be emptied without being deformed.

Japanese Patent Specification JP-B-53088339 (Nippon Petrochemicals Co. Ltd.) describes similar packaging containers for jelly-like food products, these being manufactured from a mixture of LDPE and additives of 250 ppm oleamide and 250 ppm monostearine (GMS). Given that the additives migrate to the surface of the packaging container, the packed product is prevented from adhering to the surfaces of the packaging container.

Japanese Patent Specification JP-B-01025776 (Tokan Kogyo KK) describes similar packaging containers possessing good emptying properties, so-called "release properties" for packing jelly-like food products.

The packaging containers are produced by injection moulding of a mixture of 50-95 parts by weight of polypropylene, 5-50 parts by weight of LDPE, 0.05-0.35 parts by weight of "stearic acid monoglyceride" (GMS) and 0.03- 0.07 parts by weight of stearamide.

The above summarised Japanese publications describe different combinations of additives for achieving the desired effect, i.e. superior release properties vis-à-vis viscous food products, but not that GMS may be employed as the sole additive in an inside layer of polyethylene or polypropylene in a laminated packaging material, the packaging material comprising both an inside layer of a material possessing superior release- and thermosealing properties, and a rigidifying core layer of another material. The known publications prescribe complex and expensively uneconomical additive compositions and are not aimed at packaging containers produced by means of thermoforming or fold-forming, respectively. Nor do they disclose anything about the release properties of the prior art packages in respect of packed cheese.

OBJECTS OF THE INVENTION One object of the present invention is thus to obviate the drawbacks inherent in the packages described by way of introduction and to realise a novel and improved packaging laminate in respect of the prior art technique for producing packaging containers which are either thermoformed or fold- formed, respectively.

A further object of the present invention is to realise a simple, and cost effective thermosealable packaging laminate for producing packaging

containers possessing superior release properties vis-à-vis solid and semi- solid food products, without the employment of a plurality of different additives.

Yet a further object of the present invention is to realise a packaging laminate for producing packaging containers possessing superior barrier properties against gases, in particular oxygen gas, and also superior release properties vis-à-vis solid and semi-solid food products.

Still a further object of the present invention is to realise a thermoformable packaging laminate for producing packaging containers possessing superior release properties vis-à-vis solid and semi-solid food products, and also superior gas barrier properties.

Yet a further object of the present invention is to realise a packaging container produced from the packaging laminate and possessing superior gas barrier properties and also release properties vis-à-vis solid and semi- solid food products.

A particular object of the present invention is to realise a thermoformed or fold-formed packaging container possessing superior release properties for cheese.

SOLUTION These and other objects are attained in that a packaging laminate of the type described by way of introduction has been given the characterizing feature as disclosed in appended Claim 1. Preferred embodiments of the packaging laminate according to the present invention are further apparent from appended subclaims 2 to 9. In addition, the present invention realises a thermoformed or fold-formed packaging container according to appended Claims 10 and 11, respectively.

OUTLINE OF THE INVENTION The rigidifying core layer according to the present invention may consist of a thermoformable plastic or a paper/paperboard material of suitable packaging quality. Thermoformable plastics suitable for a core layer according to the present invention are, for instance, selected from a group essentially comprising polystyrene, polypropylene, high density polyethylene (HDPE), polyethylene terephthalate (PET), mineral-filled co- or homopolymers of olefin monomers and mixtures of these plastics.

Preferably, a thermoformable core layer is selected from polystyrene or polypropylene.

The outer layer consists substantially of a polymer selected from a group essentially comprising polyethylene, polypropylene, ethylene propylene copolymers and mixtures of these polymers. Preferably, the outer layer consists of a homopolymer of polyethylene or polypropylene and most preferably of low density polyethylene (LDPE).

Glycerol monostearate (GMS) is added as friction-reducing additive to the above-mentioned polyethylene or polypropylene homopolymers, copolymers or mixtures of these polymers, before coating of the core layer in order to achieve improved so-called "release properties", on emptying of the packed food product. GMS is added in a minor quantity depending upon the adhesion and friction properties of the packed food product. Preferably, GMS is added in an amount of approximately 0.1-3 weight per cent, more preferably approximately 0.5-2.5 weight per cent, and most preferably approximately 0.5-2 weight per cent of the total quantity of polymer.

Experimental trials have shown that excellent release properties for most types of food products are achieved with a quantity of added GMS of approximately 0.5-2 weight per cent. For foods displaying a lesser tendency to adhere to the inside of the package, smaller quantities of GMS will also function satisfactorily, but at least approximately 0.1 weight per cent.

Optimum release properties for most packed foods such as, for example cheese will be attained using a quantity of added GMS of approximately 0.5- 2 weight per cent.

In order to obtain a packaging container possessing superior barrier properties against light and gases, and in particular oxygen gas, the packaging laminate may be provided with a layer of a polymer material possessing superior oxygen gas barrier properties, such as, for example ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVOH), polyamides, polyvinylidine chloride (PVDC) or polyesters of the type polyethylene terephthalate (PET).

Alternatively, such a gas and/or light barrier layer may consist of a metal or metal oxide. Examples of such metals or metal oxides are aluminium, aluminium oxide or silica oxide (SiOx where x may vary between 1.8 and 2.2). A thin layer of metal or metal oxide may be applied by means of deposition techniques well known to a person skilled in the art

(such as vacuum deposition), or in the form of a foil, for example Alifoil. Gas barrier layers of metal or metal oxides are well-suited as gas barrier layers in fold-formed packaging containers, but however not for packaging laminates which, on reforming into packaging containers, are to be thermoformed.

In order to achieve a well-integrated packaging laminate possessing superior adhesion or bonding strength between the different component layers, one or more adhesion layers including an adhesive polymer may be disposed therebetween. Examples of such adhesive polymers are copolymers of olefins and (meth)acrylic acid, maleic acid anhydride- modified polyolefins and so-called ionomers.

The packaging laminate according to the present invention is suitably reformed by means of thermoforming or by means of fold-forming, respectively, and thermosealing which are both methods well known to a person skilled in the art, into packaging containers possessing superior release properties vis-à-vis solid and semi-solid food products, such as, for example cheese, jellies and puddings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The present invention will now be described in greater detail hereinbelow, with reference to the accompanying Drawings, in which: Fig. 1 schematically shows a cross section through a laminated packaging material 10 according to the present invention; Fig. 2 schematically shows a cross section through a laminated packaging material 20 according to the present invention; Fig. 3 schematically shows a cross section through a laminated packaging material 30 according to the present invention; Fig. 4 schematically illustrates the production of a thermoformed packaging container according to the present invention; and Fig. 5 schematically illustrates a fold-formed packaging container according to the present invention DESCRIPTION OF PREFERRED EMBODIMENTS It should be observed that the specifically selected laminate structures and packaging containers in the accompanying Figures merely constitute examples among many other alternatives conceivable to a person skilled in the art, and that different modifications and variations may be made by

adding further material layers with or without interjacent adhesive or lamination layers for the purpose of satisfying the requirements of best possible product protection, without departing from the inventive concept as this is defined in the appended Claims.

Referring to the Drawings, Fig. 1 thus schematically illustrates a cross section of a packaging laminate according to the present invention carrying the generic reference numeral 10.

The core layer 11 consists of thermoformable polypropylene or polystyrene. The polypropylene may be filled, i.e. mixed with a mineral in particulate form, such as, for example chalk, talcum, mica or clay. An adjacent laminated layer 12 which forms the inside layer in a packaging container produced from the packaging laminate, consists of polyethylene or polypropylene, preferably LDPE, and GMS in a quantity of approximately 0.5-2 weight per cent. The inside layer is preferably applied on the core layer by means of extrusion. The packaging laminate 10 may be thermoformed into packaging containers of different types, such as beakers, cups, trays etc.

Fig. 2 shows a similar packaging laminate 20, in which the core layer 21 and the inside layer 22 are of the same type as in Fig. 1 and which, moreover, includes a gas barrier layer 23 of EVOH which has been laminated to adjacent layers by the intermediary of the adhesive layer 24 of an adhesion-promoting polymer. The packaging laminate 20 may be reformed into packaging containers by means of thermoforming.

Fig. 3 shows a packaging laminate 30 with a core layer 31 of paper or paperboard, with outer layers 32 and 33 of LDPE. The layer 32 forms the inside layer in a packaging container produced from the packaging laminate and moreover includes a minor quantity of GMS, preferably approximately 0.5-2 weight per cent. In order to achieve improved adhesion between the inside layer 32 and the core layer 31, an adhesion layer 34 of an adhesive polymer may be applied between the two layers. The layer 32 is preferably applied by means of extrusion. The packaging laminate 30 is reformed by means of fold formation into packaging containers possessing superior release properties vis-à-vis food products.

Fig. 4 schematically illustrates how thermoformed packaging containers are produced in that a packaging laminate web is unrolled from a magazine reel and is heated at a) to a sufficiently elevated temperature in order, with the aid of forming tools and compressed air devices at b) to

reform local portions into beakers, trays or the like, at c). The cooling formed packaging containers c) may be separated from the running web before or after filling at d), whereafter a lid is applied at e) and the filled and finished package is stored or distributed. The thermoformed packaging containers c) may also be separated from one another and stored or transported to another site before filling at d) with food product.

The lid of such a packaging container may consist of materials well known to a person skilled in the art. For example, a lid for a packaging container according to the present invention has an inside layer of LDPE, or some other thermosealable thermoplastic in order to make for thermosealing between the beaker/tray and the lid. Particularly wdl functioning lids for a packaging container of a packaging laminate 20 according to the present invention is produced separately and consists, for example of a core layer of PET or polypropylene and an inside layer of LDPE, with an interjacent oxygen gas barrier layer of SiOx, EVOH or PVOH.

Fig. 5 shows one example of a fold-formed and thermosealed packaging container of the Tetra Bring) type. Other fold-formed packaging containers may also be produced from the packaging laminate according to the invention, such as, for example tetrahedron or gable-top shaped packaging containers (Tetra Classics or Tetra Rest)) Thus, it will be apparent from the foregoing description that the present invention, in a simple manner and using simple means, satisfies the established objects and realises an efficient packaging laminate for producing packaging containers possessing superior release properties vis- à-vis solid and semi-solid food products. Further, the present invention realises a thermosealable packaging laminate possessing superior gas barrier and release properties for reforming into packaging containers by thermoforming or fold-forming, respectively.

Finally, the present invention realises thermoformed or fold-formed packaging containers, respectively, possessing - where applicable - superior barrier properties vis-à-vis oxygen gas, and also superior release properties vis-à-vis solid and semi-solid food products, in particular cheese.