PACKAGING LAMINATE FOR A PACKAGING CONTAINER, AS WELL AS A PACKAGING CONTAINER PRODUCED FROM THE PACKAGING LAMINATE

Abstract

A packaging laminate for a retortable packaging container which comprises a paper or paperboard layer and outer, liquid-tight, heat-resistant layers of plastic on both sides of the paper or paperboard layer. Between the paper or paperboard layer and the outer plastic layer, the packaging laminate has at least one additional layer of a material possessing tightness properties vis-à-vis gases. In order to improve the preconditions for providing the packaging laminate with decorative artwork of printing ink with good print quality, the paper or paperboard layer has, on its one side, a printable coating of pigment and binder or adhesive, and on its other side a coating of starch.

Description

TECHNICAL FIELD

The present invention relates to a packaging laminate for a packaging container provided with decorative artwork and being of the type which is produced from a prefabricated, flat folded packaging blank of the packaging laminate, in that the packaging blank is first raised to an open, tubular container carton whose one end is sealed by fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar bottom closure, whereafter the container carton provided with the bottom is filled with a food and the other end of the filled container carton is sealed by an additional fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar top closure, the packaging laminate comprising a paper or paperboard layer whose one side has a printable coating of pigment and binder or adhesive in contact with the paper or paperboard layer and decorative artwork of printing ink applied directly on the printable coating by means of suitable printing technology.

The present invention also relates to a packaging container of the type which, after filling and sealing, is to be subjected to a shelf-life-extending heat treatment in a retort with steam as heat medium, the packaging container being produced from a prefabricated, flat folded packaging blank of the packaging laminate in that the packaging blank is first raised to an open, tubular container carton whose one end is sealed by fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar bottom closure, whereafter the container carton, provided with a bottom, is filled with a food and the other end of the filled container carton is sealed by an additional fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar top closure.

BACKGROUND ART

A packaging laminate as well as a packaging container of the type described above are known from, for example, International Patent Application number PCT/SE2011/050978. The prior art packaging laminate has a rigid, but foldable layer of paper or paperboard and outer, liquid-tight, heat-resistant layers of plastic on both sides of the paper or paperboard layer. Between the paper or paperboard layer and one of the outer, liquid-tight plastic layers, the prior art packaging laminate has at least one additional layer possessing tightness properties vis-à-vis gases, in particular oxygen gas. One preferred example of such a material possessing tightness properties vis-à-vis gases is an aluminium foil, Alifoil, which moreover possesses the advantage that it makes for thermosealing of the packaging laminate by so-called induction thermosealing which is a both rapid, simple and efficient sealing technology.

As a rule, a paper surface has a coarse as well as uneven surface profile which makes it difficult to print direct on the paper or paperboard surface with sufficiently uniform print quality. In order to counteract this difficulty, the surface of the paper or paperboard layer on the side intended for printing is therefore provided with a printable coating of pigment and binder or adhesive which renders the coarse paper or paperboard surface sufficiently even and smooth to be able to be printed with good print quality.

A packaging laminate of the prior art type is produced from a web of paper or paperboard which, on its one side, has a printable coating of pigment and binder or adhesive in contact with the surface of the web. The web is unwound from a magazine reel and led through a printing station in which the web, on its coated side, is provided with the desired decorative artwork of printing ink which is printed on the printable coating of pigment and adhesive or binder.

From the printing station, the paper or paperboard web provided with decorative artwork is led further to a lamination station in which the other or uncoated side of the web is provided with a layer of a material possessing tightness properties vis-à-vis gases, e.g. an aluminium foil, Alifoil, which is laminated to the paper or paperboard web.

From the lamination station, the laminated web is led finally to a coating station in which the web is coated with outer, heat-resistant layers of plastic which are extruded on both sides of the web, whereafter the web is rolled up for further handling and use.

From a flat folded, tubular blank of the prior art packaging laminate, a finished packaging container of the type described by way of introduction is produced in the following manner. The flat-folded blank is first raised to an open packaging carton whose one end (e.g. the bottom end) is sealed by fold forming and thermosealing of the corresponding foldable bottom panels of the packaging carton. The packaging carton, provided with a bottom, is filled with the relevant food, whereafter the other end of the packaging carton (in this example the top end) is sealed by an additional fold forming and thermosealing operation of the corresponding foldable top panels of the packaging carton. The thus filled and sealed packaging container is thereafter ready to be subjected to a shelf-life-extending heat treatment in a retort with steam as the heat medium.

Retortable packaging containers, of which one well-known commercial package is sold under the name Tetra Recart, has many valuable advantages, not least for the consumer. They are mechanically strong and configurationally stable, at the same time as they are both easy to open and otherwise convenient to use. Moreover, they have the advantage over, for example, traditional conserve cans of metal and plastic that, after emptying, they may readily be compressed to but minimum space saving flat sheets by simple flattening.

With the known packaging laminate it nevertheless not seldom happens that problems with uneven print quality occur in connection with printing of the pigment-coated paper or paperboard web. Problems of this type may in many cases be attributed to fibre dust which is released from the freely exposed fibre surface of the paper or paperboard web (i.e. non-pigment coated) and transferred to the pigment coated surface in connection with the pigment coated paper or paperboard web being wound up onto a magazine reel. When the magazine reel is subsequently unwound for printing and conversion into finished packaging laminate, released fibre dust thus accompanies the laminate adhering to the pigment coating of the paper or paperboard web into the printing station and thus impedes printing direct on the printable coating.

There is thus still a need for an improved packaging laminate, without consequential dust-related problems which are associated with the prior art technology.

OBJECTS OF THE INVENTION

One object of the present invention is therefore to realise a packaging laminate of the type described by way of introduction, without those problems and drawbacks which are associated with the prior art packaging laminate.

A further object of the present invention is to realise a packaging container produced from the packaging laminate which, after filling and sealing, is to be subjected to a shelf-life-extending heat treatment in a retort using steam as heat medium.

BRIEF OUTLINE OF THE INVENTION

According to one aspect of the present invention, there will thus be realised a packaging laminate for a packaging container provided with decorative artwork and produced from a prefabricated, flat folded packaging blank of the packaging laminate, in that the packaging blank is first raised to an open tubular container carton whose one end is sealed by fold forming and thermosealing of the corresponding foldable end panels of the container carton for the formation of a liquid-tight, substantially planar bottom closure, whereafter the container carton provided with the bottom is filled with a food, and the other end of the filled container carton is sealed by an additional fold forming and thermosealing of the corresponding foldable end panels of the container carton for the formation of a liquid-tight, substantially planar top closure, the packaging laminate comprising a paper or paperboard layer whose one side has a printable coating of pigment and adhesive or binder in contact with the paper or paperboard layer, with a decorative artwork of printing ink applied by suitable printing technology direct on the printable coating. The packaging laminate is characterised in that the other, or non-pigment coated side of the paper or paperboard layer has a coating of starch in contact with the paper or paperboard layer.

By providing a paper or paperboard web, whose one side is coated with a printable coating of pigment and binder or adhesive, with an additional coating of starch on the other, or non-pigment coated side of the paper or paperboard web, the thus double-sided coated paper or paperboard web may be wound up directly after production in a paper machine without the risk of releasing fibre dust and problems associated therewith in later printing of the web.

The coating of starch may be made extremely thin and in practice is of a thickness of 1-5 g/m², preferably 3 g/m².

According to one practical embodiment of the packaging laminate according to the present invention, the printable coating on the one side of the paper or paperboard layer comprises a combination of pigment and adhesive or binder, as well as at least one further substance capable of modifying the rheological properties of the coating. Examples of such printable coatings are those which are described and disclosed in International Patent Application PCT/SE2011/050978.

Examples of usable binder or adhesive for the printable coating are selected from the group essentially comprising styrene butadiene latex, methyl metacrylate butadiene latex, polyacrylate latex, styrene acryl latex, polyvinyl acetate, polyvinyl alcohol, polysaccharides, starch, protein and combinations thereof.

Examples of usable substances capable of modifying the viscosity of each respective coating are selected from the group essentially comprising protein, polysaccharides, carboxy methyl cellulose (CMC), hydroxy ethyl cellulose (HEC), alkali soluble acrylic polymer emulsion (ASE), hydrofobically modified alkali soluble acrylic polymer (HASE), polyurethane (PU), polyvinyl alcohol (PVOH) and starch.

Examples of usable pigment for both of the above mentioned surface coatings are selected from the group essentially comprising layered silicate mineral, hydratised magnesium silicate, calcium carbonate, titanium dioxide and kaolin.

According to one practical embodiment of the packaging material according to the invention, at least 50% of the pigment in the printable coating is calcium carbonate, while both the binder or adhesive and the above mentioned rheology modifier comprise an acrylic copolymer.

In particular, the printable coating in the packaging material according to the present invention may contain:

• • an adhesive or binder of a styrene acrylic copolymer in an amount of 10-20%, calculated on the weight of the composition;
  • pigment of layered silicate mineral clay and calcium carbonate in an amount of 80-90%, calculated on the weight of the composition; and
  • a substance capable of modifying the rheological properties of the coating (“rheology modifier”) in a quantity of 0.1-1%, calculated on the weight of the composition.

The coating of starch has, as has already been mentioned, a thickness or coating quantity of less than 10 g/m², preferably approx. 5 g/m², and the printable coating has a corresponding thickness or coating quantity of 15-20 g/m², preferably 20 g/m².

In order to protect the moisture and liquid-sensitive paper or paperboard layer against penetration of moisture and liquid, the packaging laminate according to the present invention has outer, liquid-tight layers of plastic which moreover should be sufficiently heat resistant to withstand such temperatures to which a packaging container produced from the packaging laminate is to be subjected when the closed packaging container, together with its filled contents, is heat treated in a retort with steam as heat medium. Examples of usable plastics for the outer, heat-resistant layers may be selected from the group essentially comprising high density polyethylene, linear low density polyethylene, polypropylene and polyester.

The packaging laminate according to the present invention may be supplemented with at least one further layer of a material possessing superior tightness properties vis-à-vis gases, in particular oxygen gas. Examples of materials possessing desirable gas tightness properties may be so-called barrier polymers, such as, for example, ethylene vinyl alcohol copolymer and polyamide. Preferably however, this layer consists of an aluminium foil, Alifoil, which renders the packaging laminate thermosealable by so-called induction thermosealing which is a both rapid and efficient sealing technology.

According to another aspect of the present invention, there will be realised a packaging container which, after filling and sealing by thermosealing is, for purposes of extending its shelf-life, to be subjected to a heat treatment under pressure with steam as heat medium in a retort.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will now be described in greater detail hereinbelow, with reference to the accompanying Drawings. In the accompanying Drawings:

FIG. 1 is a schematic cross section of a packaging laminate according to one embodiment of the present invention;

FIG. 2 schematically illustrates a method of producing the illustrated packaging laminate according to FIG. 1; and

FIG. 3 is a perspective view of a packaging container produced by fold forming and thermosealing of a packaging laminate according to the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 thus schematically illustrates a cross section of a packaging laminate according to a first embodiment of the present invention. In the illustrated example, the packaging laminate 10 has a layer 11 of paper or paperboard and outer, liquid-tight, heat-resistant layers 12 and 13, respectively, of plastic on both sides of the paper or paperboard layer 11. Between the paper or paperboard layer 11 and one of the two outer, liquid-tight plastic layers 13, the packaging laminate 10 moreover has a layer 14 of a material possessing tightness properties vis-à-vis gases, in particular oxygen gas, which is laminated to the paper or paperboard layer 11 by the intermediary of a lamination layer 15.

As illustrated schematically in FIG. 1, the paper or paperboard layer 11 has, on its one side, a printable coating 16 of pigment and adhesive or binder in contact with the surface of the subjacent paper or paperboard layer 11. As was mentioned earlier, the printable coating 16 also includes a substance capable of modifying the rheological properties of the coating 16.

It will further be apparent from FIG. 1 that the paper or paperboard layer 11 has, on its other side, a coating 17 of starch in contact with the paper or paperboard layer 11.

Usable examples of pigment for the printable coating 16 are, as has been mentioned earlier, selected from the group essentially comprising layered silicate mineral, hydratised magnesium silicate, calcium carbonate, titanium dioxide and kaolin.

Examples of usable binders or adhesives for the printable coating 16 are selected from the group essentially comprising styrene butadiene latex, methyl metacrylate butadiene latex, polyacrylate latex, styrene acryl latex, polyvinyl acetate, polyvinyl alcohol, polysaccharides, starch, protein and combinations thereof.

Examples of usable substances capable of modifying the rheological properties of the printable coating 16 are selected from among the group essentially comprising protein, polysaccharides, carboxy methyl cellulose (CMC), hydroxy ethyl cellulose (HEC), alkali soluble acrylic polymer emulsion (ASE), hydrofobically modified alkali soluble acrylic polymer (HASE), polyurethane (PU), polyvinyl alcohol (PVOH) and starch.

In the illustrated embodiment of the packaging material 10 according to the present invention, at least 50% of the pigment in the printable coating 16 is calcium carbonate, while both the adhesive or binder and the substance capable of modifying the rheological properties of the coating comprise an acrylic copolymer.

The coating 17 of starch has, as was previously mentioned, a thickness or coating quantity of less than 10 g/m², preferably less than 5 g/m², such as for example 3 g/m², while the printable coating 16 has a corresponding thickness or coating quantity of 15-30 g/m², preferably 20 g/m².

In order not to conceal decorative artwork of printing ink printed on the printable coating 16 (schematically illustrated at reference numeral 18), the outer, liquid-tight, heat-resistant plastic layer 12 of the packaging material 10 should be transparent, so that the printed decorative artwork 18 is clearly visible on visual inspection of the decorated packaging laminate 10.

Examples of usable transparent plastics for the outer, liquid-tight, heat-resistant layer 12 may be selected from the group essentially comprising high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP) and polyester (PET).

Usable plastics for the outer, liquid-tight, heat-resistant layer 13 may also be selected from among the same group as the plastics mentioned for the outer, liquid-tight, heat-resistant layer 12, i.e. from the group essentially comprising high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP) and polyester (PET).

Examples of materials possessing gas tightness properties for the layer 14 may be so-called barrier polymers such as, for example, ethylene vinyl alcohol copolymer and polyamide. Preferably however, the layer 14 is an aluminium foil, Alifoil, which renders the packaging laminate 10 thermosealable by so-called induction thermosealing, which is a both rapid, simple and efficient sealing technology.

The illustrated packaging laminate in FIG. 1 is produced using, for example, the method which is schematically illustrated in FIG. 2. A web 20 of paper whose both sides are coated with a surface coating of pigment and binder or adhesive as described in greater detail in connection with FIGS. 1 and 2, is unwound from a magazine reel 21. The paper web 20 is led through a printing station at A where the paper web 20 is provided with the desired decorative artwork of printing ink which, by a suitable printing technology, is printed direct on the surface of one of the two above mentioned coatings of pigment and binder or adhesive.

From the printing station A, the paper web 20 thus provided with decorative artwork is led via bending rollers 22-25 to a lamination station B where an aluminium foil 26 is converged with and laminated to the non-decorated side of the paper web by means of a lamination layer 27 which is extruded between the web 20 and the foil 26 in connection with these together being led through the nip between two lamination rollers 28.

The laminated paper web 20 is thereafter led further by the intermediary of an additional bending roller 29 to a coating station C where the web 20 is coated with outer, liquid-tight, heat-resistant coatings 30 and 31 which are extruded on both sides of the web 20 when the web 20 is led through the nip between two coating rollers 32.

From the coating station C, the laminated paper web 20 is thereafter led further for rolling up onto a magazine reel 33 for further processing and use.

As was mentioned earlier, packaging containers may be produced from the packaging laminate according to the present invention being of the type which, after filling and sealing, are to be subjected to a shelf-life-extending heat treatment in a retort with steam as the heat medium. One example of such a retortable packaging container is schematically illustrated in FIG. 3. The illustrated packaging container 300 is a substantially parallelepipedic package of the known packaging type which occurs on the market under the trade name Tetra Recart.

The packaging container 300 is produced from a prefabricated, flat folded packaging blank of the packaging laminate in that the packaging blank is first raised to an open tubular container carton. The one end of the container carton is sealed by fold forming and thermosealing o the corresponding end panels of the container carton for the formation of a liquid-tight substantially planar bottom closure. The container carton thus provided with a bottom is filled with the relevant food, whereafter the other end of the filled container carton is sealed by a further fold forming and sealing operation of the corresponding end panels of the container carton for the formation of a liquid-tight, substantially planar top closure 301, as illustrated in FIG. 3.

Claims

1. A packaging laminate for a packaging container provided with decorative artwork and produced from a prefabricated, flat folded packaging blank of the packaging laminate, in that the packaging blank is first raised to an open, tubular container carton whose one end is sealed by fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar bottom closure, whereafter the container carton provided with the bottom is filled with a food and the other end of the thus filled container carton is sealed by an additional fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar top closure, the packaging laminate including a paper or paperboard layer whose one side has a printable coating of pigment and binder or adhesive in contact with the paper or paperboard layer with decorative artwork of printing ink applied by a suitable printing technology on the printable coating, wherein the other side of the paper or paperboard layer has a coating of starch in contact with the paper or paperboard layer.

2. The packaging laminate as claimed in claim 1, wherein the coating of starch is of a thickness or coating quantity of less than 10 g/m2.

3. The packaging laminate as claimed in claim 1, further comprising outer, liquid-tight, heat-resistant layers of plastic on both sides of the paper or paperboard layer.

4. The packaging laminate as claimed in claim 3, wherein the outer, liquid-tight plastic layers are selected from the group essentially comprising high density polyethylene, linear low density polyethylene, polypropylene and polyester.

5. The packaging laminate as claimed in claim 1, further comprising a layer of a material possessing tightness properties vis-à-vis gases.

6. The packaging laminate as claimed in claim 5, wherein the layer possessing gas tightness properties is an aluminium foil.

7. A parallelepipedic packaging container of the type which, after filling and sealing, is to be subjected to a shelf-life-extending heat treatment in a retort with steam as heat medium, the packaging container being produced from a prefabricated, flat folded packaging blank of a packaging laminate as claimed in claim 1, in that the packaging blank is first raised to an open, tubular container carton whose one end is sealed by fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar bottom closure, whereafter the container carton, provided with the bottom, is filled with a food and the other end of the thus filled container carton is sealed by an additional fold forming and thermosealing of the corresponding foldable end panels of the container carton, for the formation of a liquid-tight, substantially planar top closure.

8. The packaging laminate as claimed in claim 1, wherein the coating of starch is of a thickness or coating quantity of less than 5 g/m2.

9. The packaging laminate as claimed in claim 1, wherein the coating of starch is of a thickness or coating quantity of 3 g/m2.

10. The packaging laminate as claimed in claim 1, further comprising a layer of a material possessing tightness properties vis-à-vis oxygen gas.