Notes

In the coating of plastic onto aluminum foil or other metal foil it has been found that the coating can take place by means of a normal extrusion course of which means the extrusion of a melted plastic mass underneath high strain through a narrow, slotlike opening to kind a skinny movie which is precipitated onto the metal foil layer, whereupon the steel foil coated with the plastic material is launched between compressive rollers, which on the similar time have a cooling effect. It is quite possible in itself to produce by this method a relatively good adhesion between the coated plastic layer and the metallic foil layer, which, moreover, can be combined in advance with the stated base paper layer, but in such a case the extrusion of plastic material needs to be carried out at a very excessive temperature, that is to say at a temperature which on the extrusion of polyethylene exceeds 300° C. At Snack food extruder machine is exposed to a floor oxidation which sadly has the outcome that the plastic layer can no longer be heat-sealed as easily as if it had not been oxidized. As it is crucial that the within layer of the packing laminate should be heat-sealable, since in any other case tight packages can't be obtained, it's needed within the coating of the plastic materials onto the metallic foil layer to use an extrusion temperature which is so low that the plastic materials is not oxidized. Approximately and within the alternative of the extrusion temperature a number of outside elements have to be taken into account, corresponding to e.g., the plastic quality, the room temperature, the speed of extrusion and so on.
Finally a second pair of compression rollers is designated 10 and a magazine curler for the completed packing materials is designated 11. The present invention concerns a technique for the manufacture of laminated packing materials containing at least one layer of a metal foil, e.g., aluminum foil, and a layer of plastic materials applied to the stated metallic foil. The invention also issues an apparatus for the realization of the tactic for the manufacture of laminated packing materials. Modern packages, that are manufactured from an online of packing laminate or from sheet of laminated materials, regularly comprise a layer of a metal foil, particularly aluminum foil, which lends the packing laminate superb tightness characteristics towards gases and furthermore provides very effective light safety.
As talked about above, a worse adhesion is obtained between plastic layer and metallic foil layer if the extrusion temperature is low, which implies that the plastic layer within the completed package may delaminate and thus in principle form a plastic bag contained in the package deal which is free from the metallic foil layer. This in fact is not fascinating, nevertheless it should be the item to acquire a non-oxidized inner plastic layer in addition to good adhesion between plastic layer and steel foil, and so as to obtain this it was essential to accept a compromise between sealability and lamination power and accordingly the lamination temperature had to be adjusted and maintained very precisely, which may trigger great difficulties. The invention is characterised further in that the device for the execution of the said second operational stage consists of certainly one of a number of coils preferably arranged in one plane, which are connectable to a supply of present which can deliver an a.c. In the FIGURE numeral 1 refers to a laminate web the upward turned layer of which consists of a steel foil layer or a metallic foil web. Furthermore a pair of compression rollers cooperating with one another is marked 4 and a pair of guide rollers 5. A excessive frequency present supply is designated 9 and the feed strains from the source of present 9 to the bars 6 are marked 8.
The packing laminate of the type involved here moreover incessantly includes a base layer of some kind, particularly paper of carton, and likewise linings of thermoplastic materials, which linings on the one hand are intended to guard the completed packages from moisture and wetness, then again have the thing of making the packing laminate heat-sealable and eventually have the item of joining together the fabric layer launched into the laminate. The side of the packing laminate which will be turned toward the inside of the completed package deal is mostly coated with a layer of thermoplastic materials, e.g., polyethylene, and the fabric layer following this is usually constituted of a metallic foil layer which then in its turn is fixed to a supporting paper layer with the assistance of an intermediate thermoplastic coat of e.g., polyethylene. Finally, the surface of the packing laminate, that is to say the facet of the packing laminate which is able to kind the outside of the package, shall be supplied with a thermoplastic coat of e.g., polyethylene, which has as its object the safety of the base layer of paper and the prevention of the absorption of moisture by the stated layer. It may be applicable in sure instances to heat the steel foil layer to a temperature which appreciably exceeds 100° C., e.g., 150° - 200° C., but to stop in this case the plastic layer from melting down it may be appropriate to apply a cooling gas, e.g., a chilly air towards the surface of the plastic layer three. Naturally it's possible inside the framework of the idea of the invention to arrange the coils, by the use of which the electromagnetic field is generated, in another method than that proven here, but practical experiments have instructed that the embodiment described right here is especially appropriate, no much less than in the remedy of comparatively flexible materials webs. It may in fact be appropriate generally to cool the coil windings, that's to say the bars 6 which may readily be done by offering the bars 6 with bores by way of which a cooling liquid may be made to flow into.
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