Notes

The packing laminate of the type concerned right here furthermore frequently includes a base layer of some type, particularly paper of carton, and also linings of thermoplastic materials, which linings on the one hand are meant to protect the finished packages from moisture and wetness, however have the thing of creating the packing laminate heat-sealable and at last have the item of joining together the material layer launched into the laminate. The aspect of the packing laminate which will be turned toward the within of the completed package is generally covered with a layer of thermoplastic materials, e.g., polyethylene, and the material layer following this is often constituted of a steel foil layer which then in its flip is mounted 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 is to say the facet of the packing laminate which will type the surface of the package, might be provided with a thermoplastic coat of e.g., polyethylene, which has as its object the protection of the base layer of paper and the prevention of the absorption of moisture by the mentioned layer. It could additionally be acceptable in certain circumstances to warmth the metallic foil layer to a temperature which appreciably exceeds 100° C., e.g., 150° - 200° C., but to prevent on this case the plastic layer from melting down it may be acceptable to apply a cooling gas, e.g., a cold air towards the outside 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 another method than that shown right here, however practical experiments have suggested that the embodiment described here is very appropriate, a minimal of within the therapy of comparatively flexible materials webs. It may in fact be acceptable sometimes to chill the coil windings, that is to say the bars 6 which may readily be carried out by offering the bars 6 with bores by way of which a cooling liquid can be made to circulate.
Finally a second pair of compression rollers is designated 10 and a journal curler for the completed packing materials is designated eleven. The current invention issues a way for the manufacture of laminated packing material containing at least one layer of a metal foil, e.g., aluminum foil, and a layer of plastic material utilized to the said metal foil. The invention additionally concerns an apparatus for the realization of the method for the manufacture of laminated packing materials. Modern packages, which are manufactured from a web of packing laminate or from sheet of laminated material, regularly comprise a layer of a steel foil, in particular aluminum foil, which lends the packing laminate superb tightness traits in opposition to gases and moreover provides very efficient mild protection.
In the coating of plastic onto aluminum foil or other steel foil it has been discovered that the coating can take place by the use of a traditional extrusion course of which suggests the extrusion of a melted plastic mass beneath high stress via a slim, slotlike opening to form a thin movie which is precipitated onto the steel foil layer, whereupon the steel foil coated with the plastic materials is launched between compressive rollers, which at the similar time have a cooling impact. Snack food extruder machine is type of attainable in itself to provide by this technique a comparatively good adhesion between the coated plastic layer and the metal foil layer, which, furthermore, may be mixed in advance with the mentioned base paper layer, but in such a case the extrusion of plastic material needs to be carried out at a really excessive temperature, that's to say at a temperature which on the extrusion of polyethylene exceeds 300° C. At this relatively high temperature the plastic material is exposed to a floor oxidation which sadly has the result that the plastic layer can no longer be heat-sealed as easily as if it had not been oxidized. As it's imperative that the within layer of the packing laminate ought to be heat-sealable, since otherwise tight packages cannot be obtained, it's needed in the coating of the plastic material onto the metal foil layer to use an extrusion temperature which is so low that the plastic material just isn't oxidized. Approximately and in the choice of the extrusion temperature a number of outdoors elements should be taken under consideration, corresponding to e.g., the plastic quality, the room temperature, the rate of extrusion and so forth.
As mentioned above, a worse adhesion is obtained between plastic layer and metal foil layer if the extrusion temperature is low, which implies that the plastic layer within the finished package deal could delaminate and thus in principle kind a plastic bag contained in the package which is free from the metal foil layer. This in fact isn't fascinating, but it have to be the item to obtain a non-oxidized internal plastic layer in addition to good adhesion between plastic layer and metal foil, and so as to achieve this it was necessary to accept a compromise between sealability and lamination energy and accordingly the lamination temperature needed to be adjusted and maintained very accurately, which can trigger nice difficulties. The invention is characterised additional in that the system for the execution of the mentioned second operational stage consists of certainly one of a number of coils preferably arranged in one aircraft, that are connectable to a source of current which might deliver an a.c. In the FIGURE numeral 1 refers to a laminate internet the upward turned layer of which consists of a metal foil layer or a metal foil web. Furthermore a pair of compression rollers cooperating with one another is marked 4 and a pair of information rollers 5. A excessive frequency current supply is designated 9 and the feed lines from the source of current 9 to the bars 6 are marked 8.
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