Notes

Finally a second pair of compression rollers is designated 10 and a magazine curler for the finished packing materials is designated 11. The current invention concerns a method 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 applied to the said steel foil. The invention also considerations an equipment for the realization of the strategy for the manufacture of laminated packing materials. Modern packages, that are manufactured from an online of packing laminate or from sheet of laminated material, frequently comprise a layer of a metal foil, specifically aluminum foil, which lends the packing laminate superb tightness characteristics against gases and moreover gives very effective mild safety.
In the coating of plastic onto aluminum foil or other steel foil it has been discovered that the coating can happen by the use of a standard extrusion process which suggests the extrusion of a melted plastic mass underneath high strain through a narrow, slotlike opening to form a skinny film which is precipitated onto the metallic foil layer, whereupon the metallic foil coated with the plastic material is launched between compressive rollers, which on the similar time have a cooling impact. It is quite possible in itself to provide by this method a relatively good adhesion between the coated plastic layer and the metal foil layer, which, furthermore, could be mixed upfront with the stated base paper layer, but in such a case the extrusion of plastic materials needs to be carried out at a really high temperature, that's to say at a temperature which at the extrusion of polyethylene exceeds 300° C. At this comparatively excessive temperature the plastic materials is uncovered to a surface oxidation which sadly has the end result that the plastic layer can now not be heat-sealed as simply as if it had not been oxidized. As it's crucial that the inside layer of the packing laminate should be heat-sealable, since otherwise tight packages cannot be obtained, it's needed in the coating of the plastic materials onto the steel foil layer to use an extrusion temperature which is so low that the plastic materials just isn't oxidized. Approximately and within the choice of the extrusion temperature numerous outside elements should be taken under consideration, corresponding to e.g., the plastic high quality, the room temperature, the rate of extrusion and so forth.
As talked about above, a worse adhesion is obtained between plastic layer and metal foil layer if the extrusion temperature is low, which suggests that the plastic layer within the finished bundle could delaminate and thus in principle form a plastic bag inside the package deal which is free from the metallic foil layer. This of course isn't desirable, however it must be the object to acquire a non-oxidized internal plastic layer in addition to good adhesion between plastic layer and steel foil, and in order to obtain this it was essential to merely accept a compromise between sealability and lamination strength and accordingly the lamination temperature needed to be adjusted and maintained very precisely, which can cause nice difficulties. The invention is characterized additional in that the system for the execution of the mentioned second operational stage consists of certainly one of a quantity of coils ideally organized in a single plane, which are connectable to a supply of present which can deliver an a.c. In the FIGURE numeral 1 refers to a laminate internet the upward turned layer of which consists of a steel foil layer or a metallic foil internet. Furthermore a pair of compression rollers cooperating with one another is marked four and a pair of guide rollers 5. automatic biscuit production line is designated 9 and the feed traces from the supply of present 9 to the bars 6 are marked eight.
The packing laminate of the sort concerned here furthermore regularly comprises a base layer of some type, in particular paper of carton, and likewise linings of thermoplastic materials, which linings on the one hand are supposed to guard the completed packages from moisture and wetness, however have the thing of making the packing laminate heat-sealable and at last have the object of joining together the fabric layer launched into the laminate. The facet of the packing laminate which shall be turned towards the within of the finished bundle is generally coated 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 turn is mounted to a supporting paper layer with the assistance of an intermediate thermoplastic coat of e.g., polyethylene. Finally, the skin of the packing laminate, that is to say the aspect of the packing laminate which will type the outside of the package deal, might be provided 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 said layer. It could also be acceptable in sure cases to warmth the steel foil layer to a temperature which appreciably exceeds 100° C., e.g., 150° - 200° C., however to stop on this case the plastic layer from melting down it might be acceptable to use a cooling fuel, e.g., a cold air in opposition to the skin of the plastic layer three. Naturally it's attainable throughout the framework of the idea of the invention to rearrange the coils, via which the electromagnetic area is generated, in some other method than that shown right here, but sensible experiments have instructed that the embodiment described right here is very suitable, a minimum of within the remedy of relatively versatile material webs. It might in fact be acceptable sometimes to cool the coil windings, that is to say the bars 6 which can readily be carried out by providing the bars 6 with bores through which a cooling liquid may be made to flow into.
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