Notes

In the coating of plastic onto aluminum foil or other metal foil it has been found that the coating can happen by means of a traditional extrusion process which implies the extrusion of a melted plastic mass underneath excessive pressure via a slim, slotlike opening to form a skinny movie which is precipitated onto the metal foil layer, whereupon the metallic foil coated with the plastic materials is introduced between compressive rollers, which at the identical time have a cooling impact. It is type of attainable in itself to supply by this methodology a comparatively good adhesion between the coated plastic layer and the metal foil layer, which, furthermore, could be combined prematurely with the mentioned base paper layer, however in such a case the extrusion of plastic materials must be carried out at a really high temperature, that is to say at a temperature which on the extrusion of polyethylene exceeds 300° C. At this comparatively excessive temperature the plastic materials is exposed to a floor oxidation which unfortunately has the outcome that the plastic layer can not be heat-sealed as easily as if it had not been oxidized. As it's crucial that the within layer of the packing laminate must be heat-sealable, since in any other case tight packages cannot be obtained, it is necessary within the coating of the plastic material onto the metal foil layer to use an extrusion temperature which is so low that the plastic materials isn't oxidized. Approximately and in biscuit production line of the extrusion temperature a selection of outdoors components should be taken under consideration, corresponding to e.g., the plastic high quality, the room temperature, the speed of extrusion and so forth.
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 issues a technique for the manufacture of laminated packing material containing a minimal of one layer of a metallic foil, e.g., aluminum foil, and a layer of plastic material utilized to the mentioned metallic foil. The invention additionally concerns an apparatus for the realization 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, regularly comprise a layer of a steel foil, particularly aluminum foil, which lends the packing laminate superb tightness traits against gases and moreover gives very efficient light protection.
The packing laminate of the type involved right here moreover frequently comprises a base layer of some sort, particularly paper of carton, and likewise linings of thermoplastic material, which linings on the one hand are intended to protect the completed packages from moisture and wetness, then again have the item of constructing the packing laminate heat-sealable and finally have the thing of joining together the fabric layer introduced into the laminate. The facet of the packing laminate which might be turned toward the within of the completed package deal 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 fastened to a supporting paper layer with the help of an intermediate thermoplastic coat of e.g., polyethylene. Finally, the surface of the packing laminate, that's to say the facet of the packing laminate which will kind the skin of the package deal, shall be supplied with a thermoplastic coat of e.g., polyethylene, which has as its object the safety of the bottom layer of paper and the prevention of the absorption of moisture by the said layer. It could additionally be acceptable in certain circumstances to heat the metal foil layer to a temperature which appreciably exceeds 100° C., e.g., 150° - 200° C., but to forestall on this case the plastic layer from melting down it could be acceptable to apply a cooling gas, e.g., a chilly air in opposition to the surface of the plastic layer three. Naturally it's potential inside the framework of the idea of the invention to rearrange the coils, by the use of which the electromagnetic field is generated, in another method than that proven here, however sensible experiments have advised that the embodiment described right here is very suitable, a minimal of in the treatment of comparatively flexible materials webs. It may after all be applicable typically to chill the coil windings, that is to say the bars 6 which can readily be accomplished by offering the bars 6 with bores through which a cooling liquid can be made to circulate.
As talked about 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 in the completed package deal could delaminate and thus in principle type a plastic bag inside the package deal which is free from the metallic foil layer. This in fact is not desirable, however it should be the thing to obtain a non-oxidized internal plastic layer as properly as good adhesion between plastic layer and steel foil, and to find a way to achieve this it was necessary to simply accept a compromise between sealability and lamination energy and accordingly the lamination temperature had to be adjusted and maintained very precisely, which may cause great difficulties. The invention is characterized additional in that the gadget for the execution of the stated second operational stage consists of certainly one of a number of coils ideally organized in a single plane, that are connectable to a source of present which may 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 steel foil net. Furthermore a pair of compression rollers cooperating with one another is marked 4 and a pair of guide rollers 5. A excessive frequency present source is designated 9 and the feed strains from the supply of current 9 to the bars 6 are marked 8.
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