Notes

In the coating of plastic onto aluminum foil or different steel foil it has been discovered that the coating can happen by the use of a standard extrusion course of which implies the extrusion of a melted plastic mass underneath high stress by way of a slender, slotlike opening to kind a skinny movie which is precipitated onto the metallic foil layer, whereupon the steel foil coated with the plastic materials is introduced between compressive rollers, which at the same time have a cooling effect. It is kind of potential in itself to produce by this methodology a relatively good adhesion between the coated plastic layer and the metallic foil layer, which, furthermore, may be mixed prematurely with the stated base paper layer, but in such a case the extrusion of plastic material has to be carried out at a very excessive temperature, that's to say at a temperature which at the extrusion of polyethylene exceeds 300° C. At biscuit production line is exposed to a surface oxidation which sadly has the outcome that the plastic layer can now not 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 in any other case tight packages can't be obtained, it is essential within the coating of the plastic material onto the steel foil layer to make use of 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 exterior factors have to be taken under consideration, such as 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 implies that the plastic layer within the finished bundle could delaminate and thus in precept form a plastic bag inside the bundle which is free from the steel foil layer. This after all just isn't desirable, but it have to be the object to obtain a non-oxidized internal plastic layer as nicely as good adhesion between plastic layer and metallic foil, and so as to achieve this it was necessary to just accept a compromise between sealability and lamination energy and accordingly the lamination temperature had to be adjusted and maintained very accurately, which can trigger nice difficulties. The invention is characterised further in that the device for the execution of the mentioned second operational stage consists of certainly one of several coils preferably organized in a single plane, which are connectable to a supply of current 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 steel foil layer or a steel foil web. Furthermore a pair of compression rollers cooperating with each other is marked four and a pair of information rollers 5. A high frequency current supply is designated 9 and the feed traces from the source of present 9 to the bars 6 are marked 8.
The packing laminate of the sort involved right here furthermore incessantly includes a base layer of some type, in particular paper of carton, and likewise linings of thermoplastic material, which linings on the one hand are meant to protect the finished packages from moisture and wetness, on the opposite hand have the item of making the packing laminate heat-sealable and eventually have the object of joining together the material layer introduced into the laminate. The aspect of the packing laminate which shall be turned towards the inside of the finished bundle is generally covered with a layer of thermoplastic materials, e.g., polyethylene, and the material layer following that is normally constituted of a metal foil layer which then in its flip is fixed to a supporting paper layer with the help of an intermediate thermoplastic coat of e.g., polyethylene. Finally, the outside of the packing laminate, that is to say the side of the packing laminate which is in a position to form the surface of the package deal, might 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 mentioned layer. It may be acceptable in sure cases 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 may be applicable to use a cooling gasoline, e.g., a chilly air towards the skin of the plastic layer 3. Naturally it is possible throughout the framework of the idea of the invention to rearrange the coils, by means of which the electromagnetic field is generated, in some other manner than that shown right here, but sensible experiments have suggested that the embodiment described right here is especially appropriate, a minimum of in the remedy of relatively flexible material webs. It could in fact be appropriate typically to chill the coil windings, that is to say the bars 6 which might readily be done by providing the bars 6 with bores by way of which a cooling liquid can be made to flow into.
Finally a second pair of compression rollers is designated 10 and a magazine roller for the finished packing material is designated 11. The present invention considerations a technique 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 metal foil. The invention additionally concerns an equipment for the realization of the strategy for the manufacture of laminated packing material. Modern packages, that are manufactured from an internet of packing laminate or from sheet of laminated material, regularly comprise a layer of a metal foil, particularly aluminum foil, which lends the packing laminate very good tightness characteristics towards gases and moreover provides very efficient mild protection.
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