Notes

The packing laminate of the sort concerned right here moreover regularly comprises a base layer of some type, specifically paper of carton, and also linings of thermoplastic material, which linings on the one hand are meant to guard the finished packages from moisture and wetness, on the opposite hand have the thing of making the packing laminate heat-sealable and eventually have the object of becoming a member of together the material layer launched into the laminate. The side of the packing laminate which might be turned towards the inside of the completed bundle is generally coated with a layer of thermoplastic material, e.g., polyethylene, and the material layer following that is normally constituted of a metal 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 outside of the packing laminate, that is to say the side of the packing laminate which will kind the surface of the bundle, will be provided with a thermoplastic coat of e.g., polyethylene, which has as its object the protection of the bottom layer of paper and the prevention of the absorption of moisture by the stated layer. It could also be appropriate in sure cases to warmth the metal foil layer to a temperature which appreciably exceeds 100° C., e.g., 150° - 200° C., however to forestall on this case the plastic layer from melting down it might be applicable to apply a cooling fuel, e.g., a chilly air towards the outside of the plastic layer 3. Naturally it's potential inside the framework of the idea of the invention to arrange the coils, via which the electromagnetic area is generated, in some other manner than that shown here, but sensible experiments have suggested that the embodiment described here is particularly appropriate, no much less than within the remedy of relatively versatile materials webs. It may after all be acceptable sometimes to chill the coil windings, that's to say the bars 6 which may readily be accomplished by offering the bars 6 with bores via which a cooling liquid may be made to flow into.
Finally Snack food extruder machine of compression rollers is designated 10 and a magazine curler for the completed packing material is designated 11. The present invention considerations a technique for the manufacture of laminated packing materials containing no much less than one layer of a metal foil, e.g., aluminum foil, and a layer of plastic material utilized to the mentioned steel foil. The invention additionally concerns an apparatus for the realization of the method for the manufacture of laminated packing material. Modern packages, that are manufactured from an online of packing laminate or from sheet of laminated material, regularly comprise a layer of a metallic foil, specifically aluminum foil, which lends the packing laminate excellent tightness traits against gases and moreover provides very efficient mild safety.
As mentioned above, a worse adhesion is obtained between plastic layer and steel foil layer if the extrusion temperature is low, which means that the plastic layer in the completed package deal may delaminate and thus in precept type a plastic bag contained in the package deal which is free from the metallic foil layer. This in fact isn't desirable, nevertheless it must be the object to obtain a non-oxidized inner plastic layer in addition to good adhesion between plastic layer and metallic foil, and in order to achieve this it was essential to accept a compromise between sealability and lamination power and accordingly the lamination temperature had to be adjusted and maintained very accurately, which may cause great difficulties. The invention is characterized additional in that the gadget for the execution of the mentioned second operational stage consists of considered one of several coils ideally arranged in a single airplane, which are connectable to a source of current which can ship an a.c. In the FIGURE numeral 1 refers to a laminate web the upward turned layer of which consists of a metal foil layer or a metal foil net. Furthermore a pair of compression rollers cooperating with each other is marked four and a pair of guide rollers 5. A high frequency present supply is designated 9 and the feed lines from the source of current 9 to the bars 6 are marked 8.
In the coating of plastic onto aluminum foil or other metallic foil it has been found that the coating can happen by the use of a standard extrusion course of which means the extrusion of a melted plastic mass underneath high pressure through a slender, slotlike opening to type a skinny 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 identical time have a cooling impact. It is type of attainable in itself to produce by this technique a relatively good adhesion between the coated plastic layer and the metal foil layer, which, furthermore, could be mixed in advance with the stated base paper layer, however in such a case the extrusion of plastic materials must be carried out at a really excessive temperature, that is to say at a temperature which on the extrusion of polyethylene exceeds 300° C. At this relatively high temperature the plastic material is uncovered to a floor oxidation which unfortunately has the end 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 in any other case tight packages cannot be obtained, it is needed 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 within the alternative of the extrusion temperature a variety of exterior elements have to be taken into account, such as e.g., the plastic quality, the room temperature, the rate of extrusion etc.
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