Method and Device for Sealing

Abstract

The present invention refers to a method for sealing a first packaging material laminate (10) to a second packaging laminate (12), at least the first laminate (10) comprising at least one layer of magnetizable particles and a sealable layer (34). The method is characterized in facing the sealable layer (34) towards the second laminate (12), providing an alternating magnetic field to the laminates in a sealing zone, thereby generating magnetic hysteresis losses in the laminate (10) comprising the magnetizable particles, which losses create heat substantially melting the sealable layer (34) in the sealing zone, and applying a sealing pressure to the first and second laminate (10, 12), which pressure causes the first and second laminate (10, 12) to be pressed together in the sealing zone, thereby sealing the laminates (10, 12) to each other. The invention also relates to a device for carrying out the method.

Description

THE FIELD OF INVENTION[0001]The present invention refers to a method and a device for magnetic hysteresis sealing of a packaging material laminate comprising at least one layer comprising magnetizable particles.BACKGROUND OF THE INVENTION[0002]In the international patent publication WO 03 / 095198, which is hereby incorporated by reference, a packaging material laminate is described which comprises at least one layer comprising magnetizable particles. The laminate is of the type used for manufacturing of for example liquid food packages, and generally comprises a layer of paper or carton, layers of plastic and barriers, such as for example oxygen barriers. One of the outer layers is normally a sealable layer of a thermoplastic material which is used when sealing one laminate to another. Using thermoplastic layers is known in the art and will not be further described herein.[0003]The magnetizable particles can for example be magnetite, Fe3O4 and have a mean size of about 0.5 μm. Other ...

AI Technical Summary

Benefits of technology

[0012]An object of the invention has been to find an efficient and practical way of using magnetic hysteresis for sealing packaging material laminates in a high speed packaging machine. Another object is to achieve a sealing technique by which overheating of the packaging material laminates is prevented.

Problems solved by technology

These objects have been achieved by a method comprising providing an alternating magnetic field to the laminates in a sealing zone, thereby generating magnetic hysteresis losses in the laminate comprising the magnetizable particles, which losses create heat substantially melting the sealable layer in the sealing zone, and applying a sealing pressure to the first and second laminate, which pressure causes the first and second laminate to be pressed together in the sealing zone, thereby sealing the laminates to each other.

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