Receptacles – Closures – With closure opening arrangements for means
Patent
1989-06-09
1990-04-17
Fidei, David T.
Receptacles
Closures
With closure opening arrangements for means
220269, 220458, 428 358, B65D 1734
Patent
active
049172603
DESCRIPTION:
BRIEF SUMMARY
FIELD
This invention relates to metal can ends with plastics closures.
BACKGROUND
In our British Patent Specifications Nos. 2180520A and 2180521A, we have described metal can ends, having a central panel with an aperture therein and a one-piece tear-open plastics closure of a polyolefin material (e.g., polypropylene or polyethylene) moulded, e.g. by injection moulding, on to the central panel, the plastics closure comprising a plug part filling the aperture, a rim surrounding the aperture on both upper and under sides of the central panel and a pull tab joined laterally to the plug part and lying against the upper side of the central panel, the can end being provided on its under side with a coating of a similar material to that of the closure to facilitate bonding.
It would be advantageous to provide the upper side of the can end with a similar coating to protect the metal from corrosion and from the effects of double seaming the can end to a can body, but this is not practicable since the pull tab and the rim surrounding the aperture on the upper side of the can end would then bond to the can end during the moulding process and it would be impossible to lift the tab and open the closure.
It is known to apply coatings of polymers of differing characteristics to opposite sides of a metal sheet in separate sequential lamination steps, but the different thermal conditions required have previously made it impossible to achieve simultaneous lamination of different polymers having the desired characteristics for the present application.
In our copening British Patent Application No. 8724237 of 15th October 1987 we have described how simultaneous thermal lamination of films of different polymers to opposite sides of a metal sheet can be achieved by matching the softening characteristics of the different polymers.
SUMMARY
According to the present invention, there is provided a metal can end having a central panel with an aperture therein and a one-piece tear-open closure of a polymeric material moulded on to the central panel, the plastics closure comprising a plug part filling the aperture, a rim surrounding the aperture at least on the under side of the central panel and a pull tab joined laterally to the plug part and lying against the upper side of the central panel, wherein the can end is provided on its under side with a coating of a polymeric material bonded to the polymeric material of the rim of the closure and is provided on its upper side with a coating whose outer surface is of a different polymeric material chosen so as not to bond with the polymeric material of the closure but to be capable of being laminated in film form to the metal simultaneously with the polymeric material of the coating on the under side, and to protect the metal of the can end from corrosion and from the effects of double seaming the can end to a can body.
The can ends can thus be made from metal sheet which has been simultaneously laminated with films of the two different polymeric materials to form the coatings on the under side and the upper side, with a considerable resultant saving in costs as compared with sequential lamination, and with the realisation of the desired protection of the metal of the can end and non-adhesion to the closure, permitting easy opening.
In the description which follows, relating to the embodiments of the invention which employ a composite polyester or polyolefin based film as the coating on the upper side of the can end, that coating will be referred to as A, while the film which forms the coating on the under side will be referred to as B.
The closure may be of a polyolefin or a polyamide and the coating (B) on the under side may be a single layer film of a bonding resin which is an acid-modified polyolefin resin containing carboxyl or anhydride groups.
Preferably the closure is of a polyolefin or a polyamide and the coating (B) on the under side is a composite film comprising an inner layer (B1) of a bonding resin which is an acid-modified polyolefin resin containing carboxyl or anhydr
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Heyes Peter J.
Middleton Nicholas J.
CMB Packaging (UK) Limited
Fidei David T.
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