Patent Application
20060003123
The invention relates to a process for manufacturing a packaging material having at least two films or foils that are bonded together by means of at least one adhesive to make up a multi-layer laminate, whereby the adhesive layer/layers is/are cured. Also within the scope of the invention is a pouch-type form of packaging made from the laminate.
Laminates for manufacturing pouch-type forms of packaging for snacks such as e.g. crisps or crackers are made today by laminating a printed oriented poly-propylene (oPP)-film to a metallised. oPP-film. Thereby, the metallised oPP-film is printed on using a counter-printing process and laminated to an oPP-film which is coated with a solvent-free or solvent-based polyurethane (PUR)-adhesive.
The solvent-free process of manufacture is environmental-friendly, however, requires a longer curing time. The metallised oPP-film is adhesively bonded to a printed oPP-film coated with a solvent-free polyurethane-adhesive. The final structure is oPP-film/adhesive/oPP-film. After the subsequent curing over an interval of several days, the laminate can be cut to size and dispatched to the customers. The time required from receipt of the order to the delivery of the final product i.e. the throughput time, depends essentially on the time required for curing the PUR-adhesive.
The object of the present invention is to provide a process of the kind mentioned at the start, by means of which The time for curing the adhesive necessary for lamination—and thereby the throughput time—can be reduced in comparison with conventional laminate manufacture.
That objective is achieved by way of the invention in that the—at least one—adhesive layer is of an adhesive that can be cured by an electron beam and the laminated is radiated with an electron beam in order to cure the adhesive.
The radiation curing using an electron beam takes place within a fraction of a second as the laminate is passed through a radiation station, whereby essentially, the final bond strength is achieved—without any additional curing time—when the laminate emerges from the radiation station and is coiled.
The advantage of laminate manufacture using electron-beam-curable adhesive lies not only in a substantially reduced throughput time, but also in a reduction of solvent emissions when solvent-based adhesives can be replaced by electron-beam-curable adhesives.
A preferred laminate exhibits two films or foils and an adhesive layer which is made of art electron-beam-curable adhesive.
The adhesive layers of an electron-beam-curable adhesive are preferably cured at a voltage of 50 to 125 kV, in particular 70 to 100 kV, using an electron beam directed at the surface of the laminate delivering a radiation dose amounting to 10 to 50 kGy, preferably 20 to 40 kGy.
A preferred laminate has the following structure: oPP-film/printing/adhesive layer of an electron-beam-curable adhesive/oPP-film.
A further preferred laminate exhibits the following structure: oPP-film/printing/adhesive layer of an electron-beam-curable adhesive/barrier layer/oPP-film.
The barrier layer serving as a barrier to gases, vapours and moisture is e.g. a layer of ceramic materials such as silicon oxide, aluminium oxide or aluminium nitride deposited on the substrate film as a thin layer, e.g. in the region of 10 to 500 nm thick, in vacuum. Examples of other barrier layers are metallic layers e.g. of aluminium.
In the present case metallising is in particular a suitable means for providing the plastic film and therefore the packaging film with barrier properties which hinder the penetration of fluids, gases, vapours, water vapour, aromas or substances that smell. A preferred form of metallising is that of aluminium deposited on the oPP-film e.g. by sputtering or deposition in vacuum to a thickness about 10 nm to about 2 μm.
Preferred as electron-beam-curing adhesive is an acrylic-based adhesive.
The acrylic-based adhesive may contain monomers, oligomers or mixtures of monomers and oligomers as the basis. Examples of monomers are mono-, di- and multifunctional acrylates such as phosphoric-acid-ester-acrylates, hydroxy-acrylates, carboxy-acrylates, amino-acrylates, acrylic acid, and acrylic amide. Examples of oligomers are epoxy acrylates, urethane acrylates, polyester acrylates, silicon-acrylates and silane-acrylates. The monomers and oligomers mentioned are commercially available or can be manufactured using routine methods. The term “acrylate” (or “acryl”) used here also includes “methacrylate” (or “methylacryl”), whereby the acrylates are preferred.
The laminate manufactured according to the process of the invention is particularly suitable for manufacturing pouch-type forms of packaging, in particular pouch-type forms of packaging for snack-type foodstuffs.
Further advantages, features and details of the invention are revealed in the following description of preferred exemplified embodiments and with the aid of the drawings which show schematically in:
Shown in
The packaging film 10 with the completely cured adhesive layer 13 can be divided immediately on the spool 24 into conventional, commercial widths using a cutting device.
It is self-evident that in the bonding of the films or foils in the described lamination process the adhesive can also be deposited on the other film or foil than those selected in the examples.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04405407.0 | Jul 2004 | EP | regional |
