Notes

The packing laminate of the kind involved here furthermore incessantly includes a base layer of some sort, particularly paper of carton, and likewise linings of thermoplastic material, which linings on the one hand are meant to guard the finished packages from moisture and wetness, then again have the item of constructing the packing laminate heat-sealable and eventually have the item of joining collectively the fabric layer introduced into the laminate. The side of the packing laminate which will be turned toward the inside of the completed bundle is usually covered with a layer of thermoplastic material, e.g., polyethylene, and the fabric layer following this is often constituted of a steel foil layer which then in its flip is fixed to a supporting paper layer with the assistance of an intermediate thermoplastic coat of e.g., polyethylene. Finally, the outside of the packing laminate, that's to say the facet of the packing laminate which will kind the skin of the bundle, 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 mentioned layer. It could additionally be applicable in certain circumstances to heat the metallic foil layer to a temperature which appreciably exceeds 100° C., e.g., 150° - 200° C., however to stop in this case the plastic layer from melting down it may be applicable to use a cooling gasoline, e.g., a chilly air against the skin of the plastic layer 3. Naturally it is attainable within the framework of the idea of the invention to rearrange the coils, by means of which the electromagnetic field is generated, in some other method than that proven right here, but sensible experiments have suggested that the embodiment described here is very appropriate, no much less than in the treatment of comparatively versatile material webs. It could after all be appropriate sometimes to cool the coil windings, that's to say the bars 6 which might readily be done by providing the bars 6 with bores via which a cooling liquid may be made to flow into.
Finally a second pair of compression rollers is designated 10 and a journal roller for the completed packing material is designated 11. The present invention considerations 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 material applied to the said steel foil. The invention also issues an equipment for the conclusion of the tactic for the manufacture of laminated packing material. Modern packages, that are manufactured from an online of packing laminate or from sheet of laminated materials, frequently comprise a layer of a metallic foil, in particular aluminum foil, which lends the packing laminate very good tightness characteristics against gases and moreover provides very efficient mild protection.
As talked about above, a worse adhesion is obtained between plastic layer and metallic foil layer if the extrusion temperature is low, which suggests that the plastic layer within the finished package could delaminate and thus in precept form a plastic bag contained in the package which is free from the steel foil layer. This of course isn't desirable, however it have to be the object to obtain a non-oxidized inner plastic layer in addition to good adhesion between plastic layer and metal foil, and to be able to obtain this it was needed to simply accept a compromise between sealability and lamination power and accordingly the lamination temperature needed to be adjusted and maintained very accurately, which may cause great difficulties. The invention is characterised additional in that the gadget for the execution of the mentioned second operational stage consists of considered one of several coils ideally arranged in one aircraft, which are connectable to a supply of current which can deliver an a.c. In the FIGURE numeral 1 refers to a laminate net the upward turned layer of which consists of a metal foil layer or a steel foil internet. Furthermore a pair of compression rollers cooperating with each other is marked four and a pair of information rollers 5. A excessive frequency current source is designated 9 and the feed lines from the source of current 9 to the bars 6 are marked eight.
In the coating of plastic onto aluminum foil or other steel foil it has been found that the coating can take place via a normal extrusion course of which means the extrusion of a melted plastic mass beneath excessive strain by way of a narrow, slotlike opening to form a skinny movie which is precipitated onto the steel foil layer, whereupon the metallic foil coated with the plastic material is launched between compressive rollers, which at the identical time have a cooling impact. It is sort of possible in itself to produce by this method a comparatively good adhesion between the coated plastic layer and the metal foil layer, which, moreover, could be combined in advance with the said base paper layer, but in such a case the extrusion of plastic material has to be carried out at a very high temperature, that is to say at a temperature which at the extrusion of polyethylene exceeds 300° C. At this relatively high temperature the plastic materials is uncovered to a surface oxidation which sadly has the result that the plastic layer can no longer be heat-sealed as simply as if it had not been oxidized. As Snack food extruder machine that the within layer of the packing laminate ought to be heat-sealable, since in any other case tight packages can't be obtained, it is necessary within the coating of the plastic materials onto the metal 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 components need to be taken under consideration, corresponding to e.g., the plastic high quality, the room temperature, the rate of extrusion and so forth.
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