Notes

The packing laminate of the kind involved here furthermore frequently contains a base layer of some type, in particular paper of carton, and in addition linings of thermoplastic materials, which linings on the one hand are intended to protect the finished packages from moisture and wetness, then again have the thing of constructing the packing laminate heat-sealable and at last have the object of joining collectively the material layer introduced into the laminate. The facet of the packing laminate which will be turned toward the within of the completed bundle is usually coated with a layer of thermoplastic material, e.g., polyethylene, and the fabric layer following that is usually constituted of a steel foil layer which then in its turn is mounted to a supporting paper layer with the help of an intermediate thermoplastic coat of e.g., polyethylene. Finally, the skin of the packing laminate, that's to say the facet of the packing laminate which will type the surface of the bundle, 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 stated 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 acceptable to apply a cooling gasoline, e.g., a cold air towards the outside of the plastic layer 3. Naturally it is possible within the framework of the concept of the invention to rearrange the coils, by the use of which the electromagnetic subject is generated, in some other manner than that shown right here, but sensible experiments have advised that the embodiment described here is particularly appropriate, a minimal of in the therapy of relatively flexible material webs. It might of course be applicable typically 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 could be made to circulate.
Finally a second pair of compression rollers is designated 10 and a magazine roller for the finished packing material is designated eleven. The present invention issues a technique for the manufacture of laminated packing material containing a minimum of one layer of a metallic foil, e.g., aluminum foil, and a layer of plastic material utilized to the said metallic foil. Snack Food Extruder concerns an apparatus for the belief 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 material, regularly comprise a layer of a metal foil, specifically aluminum foil, which lends the packing laminate superb tightness characteristics in opposition to gases and moreover provides very efficient light protection.
In the coating of plastic onto aluminum foil or other metal foil it has been discovered that the coating can happen by the use of a normal extrusion process which implies the extrusion of a melted plastic mass beneath high stress via a narrow, slotlike opening to form a thin film which is precipitated onto the metallic foil layer, whereupon the metallic foil coated with the plastic materials is launched between compressive rollers, which on the identical time have a cooling impact. It is type of potential in itself to supply by this method a relatively good adhesion between the coated plastic layer and the metal foil layer, which, moreover, can be combined in advance with the said base paper layer, however in such a case the extrusion of plastic material needs to 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 material is exposed to a floor oxidation which unfortunately has the outcome that the plastic layer can now not be heat-sealed as simply as if it had not been oxidized. As it is crucial that the inside layer of the packing laminate ought to be heat-sealable, since otherwise tight packages can't be obtained, it's essential in the coating of the plastic materials onto the metal foil layer to make use of an extrusion temperature which is so low that the plastic material isn't oxidized. Approximately and within the choice of the extrusion temperature a number of outdoors factors need to be taken into consideration, corresponding to e.g., the plastic high quality, the room temperature, the speed of extrusion etc.
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 package could delaminate and thus in precept kind a plastic bag inside the package deal which is free from the metal foil layer. This in fact just isn't desirable, however it should be the thing to obtain a non-oxidized internal plastic layer as nicely as good adhesion between plastic layer and steel foil, and to find a way to obtain this it was essential to simply accept a compromise between sealability and lamination power and accordingly the lamination temperature needed to be adjusted and maintained very precisely, which may trigger great difficulties. The invention is characterised further in that the gadget for the execution of the said second operational stage consists of certainly one of several coils ideally organized in a single airplane, which are connectable to a supply of present which may ship an a.c. In the FIGURE numeral 1 refers to a laminate web the upward turned layer of which consists of a metallic foil layer or a metal foil net. Furthermore a pair of compression rollers cooperating with one another is marked four and a pair of guide rollers 5. A high frequency current source is designated 9 and the feed strains from the supply of present 9 to the bars 6 are marked 8.
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