Laminated polyester film to be laminated onto metal plate

Details Laminated polyester film to be laminated onto metal plate Laminated polyester film to be laminated onto metal plate

1996-03-15

1998-09-29

Chen, Vivian

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

428141, 428216, 428323, 428480, 2065246, B32B 102, B32B 1508, B32B 2708, B32B 2736

Patent

active

058143858

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a laminated polyester film for use as a film to be laminated onto a metal plate. More particularly, the present invention relates to a laminated polyester film to be laminated onto a metal late, which exhibits excellent moldability when laminated onto a metal plate and subjected to can fabrication by drawing or the like, which has good winding property, and which can be used for production of metal cans (e.g. cans for beverages and cans for foods) having excellent heat resistance, retort sterilization resistance, flavor and taste-retaining property, impact resistance, etc.
2. Description of the Related Art
Metal cans are generally coated at the inner and outer surfaces for the prevention of said surfaces from corrosion. Recently, methods for acquiring rust prevention without using an organic solvent have been developed for the purpose of achieving the simplification of the process employed, the improvement in hygiene aspect, the elimination of environmental pollution, etc. and, as one such method, it has been tried to coat the inner and outer surfaces of metal plate with a thermoplastic resin film. That is, researches have been pushed forward on a method of laminating a thermoplastic resin film onto a metal plate such as tin-plated steel plate, tin-free steel plate, aluminum plate or the like and then fabricating the laminated metal plate into a can by drawing or the like. Polyolefin films and polyamide films have been attempted to use as the thermoplastic resin film, but these films do not always satisfy all of moldability, heat resistance, flavor-retaining property and impact resistance.
Meanwhile, polyester films, particularly a polyethylene terephthalate film has drawn attention on the balanced properties, and there were made various proposals of using them as a base film. Such proposals are as follows. a metal plate via an adhesive layer of a low-melting polyester, and the laminated metal plate is used as a material for can (Japanese Laid-Open Patent Application No. 56-10451 and Japanese Laid-Open Patent Application No. 1-192546). laminated onto a metal plate, and the laminated metal plate is used as a material for can (Japanese Laid-Open Patent Application No. 1-192545 and Japanese Laid-Open Patent Application No. 2-57339). a low orientation is laminated onto a metal plate, and the laminated metal plate is used as a material for can (Japanese Laid-Open Patent Application No. 64-22530).
The study by the present inventors has revealed, however, that any of the above proposals fails to provide cans of sufficient properties and each involves the following problems.
In the above (A), the biaxially oriented polyethylene terephthalate film has excellent heat resistance and flavor-retaining property but has insufficient moldability. Therefore, when the laminated metal plate is subjected to can fabrication which inevitably invites large deformation, there occur whitening (generation of microcracks) and rupture of film.
In the above (B), the film used is an amorphous or very low crystalline aromatic polyester film and accordingly, has good moldability. However, the film is inferior in flavor-retaining property, is liable to embrittle easily by the post-treatment such as printing and retort sterilization after can fabrication, or during a long-termed storage; and may deteriorate to a film which tends to crack easily when an external impact is applied thereto.
In the above (C), the film is intended to have effects in a region between the above (A) and (B). The film, however, can not attain a low orientation to such a extent that it can be used in can fabrication; even if fabricable in the region with small deformation, the film has the same problems as the film of the above (B). That is, the film tends to embrittle easily by the post-treatment (such as printing and retort treatment for sterilization of can contents) after can fabrication, and may deteriorate to a film which cracks easily when an external impact is applied the

REFERENCES:
patent: 4362775 (1982-12-01), Yabe et al.
patent: 5059470 (1991-10-01), Fukuda et al.
Database WPI, Week 9431, Derwent Publ., Ltd., Abstract of Jap. Laid-Open Pat. Publ. No. 6-182953 (Jul. 5, 1994).

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