A METHOD OF PRODUCING A PACKAGING LAMINATE PROVIDED

WITH DECORATIVE ARTWORK

TECHNICAL FBELD

The present invention relates to a method of producing a packaging laminate provided with decorative artwork and comprising a layer of paper or paperboard and a film serving as decorative artwork carrier, in which method the film serving as decorative artwork carrier is laminated onto a web of paper or paperboard with the aid of an adhesive which is applied between the film and the web, whereafter the web is led further for at least one additional working operation on the web. Such a method is previously known from SE 503 218.

BACKGROUND ART Within packaging technology, use is often made of packages of single-use disposal nature for packing and transporting liquid foods. A very large group of these so-called single-use disposable packages is produced from a packaging laminate Gømpr-ising layers of- paper and plastic. When -the -food which is to be packed is a particularly oxygen gas-sensitive food, such as juice, the packaging laminate may be supplemented with at least one additional layer of a material possessing the requisite tightness properties vis-a-vis oxygen gas, e.g. an aluminium foil (Alifoil).

Such single-use disposable packages are most generally produced with the aid of packing and Filling machines of the type which, from a web or from prefabricated sheets of the packaging laminate both form, fill and seal finished packages. From, for example, a web, packages are produced in that the web is first reformed into a tube by both of the longitudinal edges of the web being folded towards and sealed to one another in a longitudinal overlap joint. The tube is filled with the relevant food contents and is divided into continuous cushion-shaped packaging units by repeated compression and transverse sealing of the tube. The packaging units are separated from one another by repeated incisions or cuts in the transverse sealing zones and are given the desired geometric outer configuration, normally parallelepipedic, by an additional fold forming- and sealing operation. In order to facilitate fold forming of the packaging laminate and at the same time ensure that packages with straight well-defined or calibrated edges and desired geometric configuration and outer shape are obtained when the sheet- or web-shaped packaging laminate is reformed into packages, the packaging laminate is most generally provided with a suitable pattern of lines (so-called crease lines) facilitating the folding operation, along which lines the packaging laminate may readily be folded to the desired package form. The appearance of the packages may be improved and further enhanced by also providing the packaging laminate with an attractive unique pattern of printing ink (decorative artwork) which may also be used for the ready distinguishing of packages from a given supplier from corresponding packages from one or more other competing suppliers of the same food. In order not to unnecessarily worsen or jeopardize the appearance of the finished package, the pattern of printing ink (decorative artwork) and crease lines of the packaging laminate must be in register with one another at the same time as the packaging laminate must not at any time during the fold forming into packages be incorrectly folded or be folded outside these crease lines.

A packaging laminate comprising a core layer of paper or paperboard and a film serving as decorative artwork carrier for such well-decorated, well-fbrffied packages may be produced using, for example, the method disclosed in the above mentioned Patent Specification SE 503 218. A film serving as decorative artwork carrier is unwound from a magazine reel at the same time as a web of paper or paperboard is unwound from a corresponding magazine reel. The film is converged with the one side of the web and laminated thereto with the aid of an adhesive which is extruded between the film and the web. The film and the web are thereafter led further for at least one additional working operation on the web.

A film lamination of the type and using the means described in SE 503 218 is a both time-consuming and energy-consuming process which presupposes that the film-coated web is produced each time in excessively large volumes in order for the method according to that invention to be able to be carried into effect at an economically viable level. Production of a film-coated web in greater quantities than that which is actually needed unavoidably entails that large surplus quantities must thus be stored and kept in large capital-tied stores from the time of production and until the actual occasion of use.

The large energy consumption in the prior art method is at least partly attributable to the fact that the film lamination is put into effect with adhesives which under normal pressure and temperature conditions are in solid form and must therefore be first heated to melting point before being able to be extruded. The high energy consumption may also to some degree be attributed to the fact that an extruder device is per se a constructionally large and robust device which requires the supply of large quantities of thermal energy so as to heat up the entire equipment to the requisite operational temperature for melting and extruding the adhesive.

A further drawback inherent in the prior art method is that it is associated with excessively large material losses every time the extruder device is to be started, since the extruder device not only consumes adhesive but also a corresponding quantity of paper or paperboard as recipient of the extruded adhesive throughout the entire running-in period. Corresponding losses of adhesive and paper or paperboard moreover occur every time it is necessary to correct defects or errors in the process during ongoing operation.

OBJECTS OF THE INVENTION One object of the present invention is therefore to realise a method of producing a packaging laminate provided with decorative artwork of the type described by way of introduction, without the consequential problems and drawbacks of the type associated with the prior art technology.

A further object of the present invention is to realise a method of producing a packaging laminate including a paper or paperboard layer and a film serving as decorative artwork carrier, in which method the film is laminated to a paper or paperboard web using an adhesive which is applied between the film and the web employing application equipment which neither requires excessive consumption of energy and/or excessive time losses to achieve stable conditions for the application process.

Yet a further object of the present invention is to realise such a method which is suitable for the production of a film-coated web also in small or limited quantities. SOLUTION

These and other objects and advantages will be attained according to the present invention in that the method described by way of introduction has been given the characterising features set forth in the characterising clause of appended Claim 1. Advantageous and expedient embodiments of the method according to the present invention have further been given the characterising features as set forth in the appended subclaims.

BRIEF SUMMARY OF THE INVENTION According to the present invention, there will thus be realised a method of producing a packaging laminate including a paper or paperboard layer and a film serving as decorative artwork carrier, in which method the film is laminated to a paper or paperboard web by means of an adhesive which is applied between the film and the web. The method is characterised in that the film is laminated to the paper or paperboard web by means of an adhesive which is liqueform already at normal room temperature.

An adhesive which is liqueform already at room temperature requires no extra supply of thermal energy for melting prior to application on the web, but is in suitable form for application right from the outset. One further advantage is that the application of the adhesive, as well as the corresponding advancement of the paper or paperboard web, may rapidly be discontinued and kept stationary on every occasion when it is time to correct errors or defects in the process, without adhesive and/or lengths of the paper or paperboard web thus being used up unnecessarily in connection with such corrections. Examples of adhesives which may be employed in the method according to the present invention may be selected from the group essentially comprising radiation curable adhesives, i.e. adhesives which after application may rapidly be set and cured by means of exposure to radiation from a suitable radiation source. One particularly preferred such adhesive is, according to the invention, an electron radiation curable adhesive which, already in extremely slight application quantities, realises an efficient bonding between the film and the web. Yet a further advantage inherent in such an electron radiation curable adhesive is that it makes for an efficient lamination with requisite bonding strength also at extremely high web advancement speeds. Adhesives possessing the capability to cure and set on exposure to electron radiation are normally acrylate based and are also commercially available.

According to one preferred embodiment of the method according to the invention, the web is led without stay-time after the film lamination to a printing operation where the film-coated web is provided with a recurring pattern of printing ink (decorative artwork) which is printed direct on the film-coated side of the web by a suitable printing operation. Use is preferably made as printing ink of a similarly radiation curable printing ink, preferably an electron radiation curable printing ink. In yet a further embodiment of the method according to the present invention, the web is led without stay-time after the printing operation to a subsequent creasing operation where the web provided with decorative artwork is provided with a recurring pattern of fold-facilitating material weakening portions (crease lines) in register with the recurring pattern of printing ink by means of a creasing operation.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The present invention will be described in greater detail hereinbelow with reference to the accompanying Drawing. The accompanying Drawing schematically illustrates how a packaging laminate provided with decorative artwork and comprising a layer of paper or paperboard and a film serving as decorative artwork carrier may be produced using the method according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

A web 1 of paper or paperboard is unwound from a magazine reel 2 and a film 3 is unwound from a corresponding magazine reel 4. The film 3 and the web 1 are converged to one another and led together through the nip between two rotary rollers 5, 6 in order under pressure to laminate the film 3 to the web 1 by means of an adhesive which is applied by means of an applicator 7 between the film 3 and the web 1 in conjunction with or before the passage through the roller nip. The film 3 may, according to the present invention, be a thin paper film, but is preferably a prefabricated film of plastic. Examples of plastic films which may be employed in the method according to the present invention are oriented films of polypropylene, polyethylene terephthalate and polyethylene.

The adhesive is, as was previously mentioned, a radiation curable adhesive, preferably an electron radiation curable adhesive which is in liquid or semi-liquid form already at ambient temperature and which, as a result, requires no extra supply of thermal energy for melting. Such electron radiation curable adhesives are commercially available from among others Ashland, USA and Sun Chemical, USA. A large group of these commercial adhesives is cured at a radiation intensity of approx. 26-28 kGy. The adhesive employed may, according to the present invention, be applied on the paper or paperboard web 1, but is preferably applied on the plastic film 3, since the surface of the film is smooth in comparison with the relatively rough or coarse paper or paperboard surface and as a result makes for application of an adhesive layer with a relatively uniform thickness. The application of the radiation curable adhesive, preferably the electron radiation curable adhesive, may be put into effect according to the invention using any suitable means whatever in the art. Preferably, the adhesive is applied by a suitable pressure method employing conventional compression rollers.

After the passage through the roller nip at the rollers 5, 6, the thus film-coated web 1 is led further to an electron radiation gun 8 (EB gun) where the web is led through the electron radiation field aimed by the EB gun 8 at the web 1 for at least partial curing of the applied adhesive between the film 3 and the web 1. Preferably, the EB gun is installed such that the emitted electron radiation is aimed at the film- coated side of the web 1, since the radiation will thereby have a shorter and quicker path in to the adhesive than if the radiation were to be aimed against the paper or paperboard side of the web.

According to the present invention, the web 1 is led without stay-time further to a printing station at A where the film 3 serving as decorative artwork carrier is provided with a recurring pattern of one or more printing inks which are printed in sequence after one another on the free surface of the film. When a plurality of printing inks is employed, it is of course important that these be printed in register with one another in order to obtain and maintain good print quality throughout the entire printing operation. In the illustrated embodiment, use is made of four printing presses 9-12 in order to print four different printing inks in direct sequence after one another, but the number of printing inks may vary and is determined in each individual case by the desired appearance and colour composition of the final decorative artwork.

Nor is the choice of printing ink critical to the present invention. Preferably however, printing inks are selected which, like the adhesive, are electron radiation curable in order to make for curing of both adhesive and printing ink or printing inks in one and the same curing operation using one and the same electron radiation source (EB gun).

From the printing operation at A, the film-coated web 1 provided with decorative artwork is led without stay-time direct to an additional electron radiation gun 13 (EB gun) where the web is led through the electron radiation field aimed by the EB gun 13 at the web 1 for complete curing of the at least partly cured adhesive between the film 3 and the web 1 and simultaneous curing of the printing ink or inks applied at the printing station A.

When the packaging laminate which has been produced using the method according to the present invention has a relatively rigid layer of paper or paperboard, the packaging laminate may, as has already been mentioned, be provided with a pattern of fold-facilitating material weakening portions (crease lines). From the EB gun 13, the thus cured web 1 is led without stay-time directly further to a creasing station at B where the web is thus provided with the desired pattern of such crease lines by means of a suitable creasing operation. As has previously been explained, both the patterns of printing ink or printing inks and the crease lines must be applied in register with one another in order not unnecessarily to destroy or disrupt the preconditions for producing well-decorated, well-formed packages from the thus produced packaging laminate.

From the creasing station B, the thus decorated and creased web of packaging laminate is wound up on a magazine reel 14 for further handling, such as for example lamination of one or more additional layers and/or other working operations to the web known in the art, for example trimming, cutting etc. INDUSTRIAL APPLICATION

Using the method according to the present invention, a packaging laminate is produced for well-decorated, well-formed packaging containers of the type produced by fold forming and thermal sealing of the packaging laminate. The present invention should not be considered as restricted to that described above and shown on the Drawing, any modifications being conceivable without departing from the scope of the appended Claims.