Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1991-12-03
1995-02-14
Lesmes, George F.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428507, 428515, 428913, 428 352, 252 90, B32B 2714, B32B 2708, C11D 1700
Patent
active
053894251
DESCRIPTION:
BRIEF SUMMARY
This invention concerns water soluble or water dispersible packaging materials.
Water soluble and water dispersible packaging materials have been proposed hitherto, in particular for packaging materials which are themselves to be dissolved and/or dispersed in water. Thus it has been proposed to package soaps or detergents in water soluble polymeric films, for example polyvinyl alcohol films, or in paper containers bonded by a water soluble adhesive. Hitherto proposed polyvinyl alcohol films often have the disadvantage that they start to dissolve when handled with wet hands. Furthermore, substances present in the packaged materials can inhibit dissolution of the polyvinyl alcohol and therefore defeat the object of having a soluble film. Thus borate ion-containing materials tend to cause gelling of polyvinyl alcohol which inhibits its dissolution. It has been proposed in European Patent Specification 79712, for example, to incorporate certain polyols such as sorbitol in the polyvinyl alcohol to reduce this undesirable gelling effect, but it doesn't address the problem of softening and/or partial dissolution on handling. Dispersible paper containers suffer from the disadvantage that the paper itself remains and has to be physically removed for example from a load of washing in a washing machine. Such paper containers have proved to be unacceptable to consumers.
An alternative approach to these problems described in GB 2109706A is to make containers for such products from a base film of an at least partially water-soluble plastics material carrying on one surface a protective layer of particles of polytetrafluoroethylene, the layer of particles preventing the packaged product from contacting the water-soluble plastics material, for example of polyvinyl alcohol. Such containers are complicated to produce as areas of the film where heat seals are to be formed should not have a layer of polytetrafluoroethylene thereon.
According to the present invention there is provided a water soluble or water dispersible polymeric film comprising a layer of a first polymer resistant to dissolution and/or softening on handling with wet hands, and a layer of a second polymer resistant to insolubilization in water by perborate ions.
Although films of the present invention can consist of the two specified layers, it is generally preferred to incorporate a layer of an at least cold water soluble polymer between the said first and second layers. This has a number of advantages, for example the choice of materials for the first and second layers is generally wider when such a third layer is present, and these third layers also often serve to impart improved mechanical properties to the films.
The first polymer layer should be of a polymeric material which imparts to the film resistance to dissolution and/or softening on handling the film with wet hands. Preferred polymeric materials for the purpose include nitrocellulose, polyvinylidene chloride and polyvinyl alcohol having low solubility at ambient temperature, when the polymeric materials such as nitrocellulose or polyvinylidene chloride are used, they preferably form an incoherent layer so that when it is intended to cause dissolution or dispersion of the film in water, the water can reach the layer or layers underneath. Such layers can be produced by known methods, for example gravure printing.
Layers of polyvinyl alcohol used for the first layer should have only low solubility at ambient temperature. The precise temperature at which solubility occurs is generally not critical. However, it is generally preferred that the polymer layer doesn't feel sticky on normal handling, for example when a container of a washing powder produced from a film of the present invention is placed in a washing machine using wet hands. It is generally preferred that this should be so for a period of about two minutes. The polyvinyl alcohol should, however, be sufficiently soluble that the film will dissolve and/or disperse at a desired elevated temperature at which the contents of a container made of
REFERENCES:
patent: 3623659 (1971-11-01), Malerson
patent: 3762454 (1973-10-01), Wilkins, Jr.
patent: 4348293 (1982-09-01), Clarke et al.
patent: 4797211 (1989-01-01), Gueldenzopf
Holloway Andrew
Platt David N.
Courtaulds Packaging Limited
Lesmes George F.
Shelborne Kathryne E.
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