Plastic and nonmetallic article shaping or treating: processes – Utilizing heat releasable stress to reshape solid workpiece
Patent
1983-09-09
1985-12-10
Thurlow, Jeffery
Plastic and nonmetallic article shaping or treating: processes
Utilizing heat releasable stress to reshape solid workpiece
156 69, 156 85, 156203, 15624413, 15624419, 264515, 264544, 264249, 264314, 425389, 425393, B29C 112
Patent
active
045578885
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the manufacture of a packing container from a web or a plane sheet or blank of a heat-shrinkable material comprising a laminate of orientation-stretched polyester, which has at least one surface coating of glycol-modified polyester (so-called PETG), the said web or sheet being formed to a tube in the first place in that two opposite edge zones of the web or sheet are joined together, and that thereafter parts of the tube formed are heated so that the material for the purpose of forming is made to shrink. The invention also relates to an arrangement for the realization of the method and to packing containers manufactured in accordance with the method.
It is known in the technology of packaging that bottlelike packing containers can be manufactured by the plastic deforming of packing material in the form of a web or a blank. This is done e.g. by blowing of plastic bottles, but also by the shrink-forming of a previously orientation-stretched plastic material, which after heating is made to shrink over a mandrel. It has long been desirable to manufacture such containers with a gas-barrier layer, which is necessary if the contents are pressurized or sensitive to oxygen gas. One example of such a product is beer, which has to have a packing material, which does not give admission to oxygen gas from the atmosphere as this would have a detrimental effect on the quality of the beer, and which neither lets out the carbon dioxide in the beer package.
It is known that for this purpose plastic material can be used, which is formed by blowing or deep-drawing, and in this connection both acrylonitrile material, e.g. a material which is marketed under the trade mark BAREX, has been used, but also polyester material. The acrylonitrile material has the advantage that it has relatively good gas-tightness characteristics, but it has on the other hand inferior pressure, absorbing characteristics and is subject to a constant deformation, so-called creep, when it is exposed to pressure. Polyester material for its part has very good pressure-absorbing characteristics, especially if it is orientation-stretched, whilst in return the gas-tightness is inferior.
It is well known that aluminium foil has very good gas barrier properties even if the aluminium foil is extremely thin (5 .mu.m or less). However, the problem has been to create a plastic deformable laminate comprising aluminium foil. Up to now this has been impossible, owing to the fact that an aluminium foil will rupture when it is stretched already when the stretching only is a few per cent and this means that laminate comprising aluminium foil can not be blown or deep drawn in a normal way. A laminate, which is containing a combination of aluminium foil and orientation stretched polyester should be an ideal packaging material, for instance beer, provided the laminate can be formed to a container or bottle. Up to now it has not been possible to use aluminium foil as a gas barrier in a container, which has been produced by plastic deforming of a material, but the present invention is giving a teaching about a method and a device for producing such packaging containers, which characterizing features appear from the enclosed patent claims.
An embodiment of the method and device in accordance with the invention will in the following be described with references to the enclosed schematic drawing, in which:
FIG. 1 is showing an enlarged cross-section of an orientation stretched packaging laminate,
FIGS. 2, 3 and 4 are showing how a laminate, in accordance with FIG. 1 in the form of a web or a sheet, is folded into a tube by joining the longitudinal edges of the web or sheet in an overlap joint. The figures are showing the overlap joint in an enlarged cross-section.
FIG. 2 is showing a conventional overlap joint,
FIG. 3 is showing an overlap joint, in which the aluminium foil layer has been cut out along one of the web edges, and
FIG. 4 is showing an overlap joint with cut-out parts in the aluminium foil layer and with an intermediate
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Nilsson Erling I.
Rausing Anders R.
Tetra Pak Developpement SA
Thurlow Jeffery
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