Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1993-09-15
1995-01-24
Szekely, Peter
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524425, 524440, 524493, 524605, 525444, 525446, 525448, 428458, C08L 6702, C08K 326, C08K 334, C08K 308
Patent
active
053843541
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INDUSTRIAL UTILIZATION
The present invention relates to a polyester film for lamination onto a metal sheet for processing of said metal sheet as well as to use of said film. More particularly, the present invention relates to a polyester film which shows excellent molding-processability when it is laminated onto a metal sheet and the laminated metal sheet is made into a can by deep drawing or the like and which is suitable for production of a metal can (e.g. a can for drinks, a can for foods) having excellent heat resistance, impact resistance and flavor-retaining property, as well as to use of said film.
PRIOR ART
Metal cans are generally coated at the inner and outer surfaces for the prevention of said surfaces from corrosion. Recently, methods of achieving rust prevention without coating of any organic solvent have been developed for the purposes of the simplification of the processes employed, the improvement in sanitary aspect, the elimination of environmental pollution, etc. and, as one of such methods, it has been attempted to coat a metal sheet with a thermoplastic resin film. Namely, a number of researches are under way on a method of laminating a thermoplastic resin film onto a metal sheet of, for example, tinplate, tin-free steel, aluminum or the like and then making the laminated metal sheet into a can by deep drawing or the like. As the thermoplastic resin film, use of polyolefin films and polyamide films has been tried, but these films cannot satisfy all of the molding-processability and the heat resistance and flavor-retaining properties of manufactured can.
On the other hand, a polyester film, particularly a film formed from a polyethylene terephthalate or a copolyethylene terephthalate, is drawing attention because of its balanced properties, and a number of proposals are made of using them as the base film. Such proposals are, for example, as follows. is laminated onto a metal via an adhesive layer of a non-oriented or low-melting polyester and the laminated metal is used as a can material (Japanese Laid-Open Patent Publication No. 10,451/1981 and Japanese Laid-Open Patent Publication No. 192,546/1989). polyester film is laminated onto a metal sheet and the laminated metal sheet is used as the can material (Japanese Laid-Open Patent Publication No. 192,545/1989 and Japanese Laid-Open Patent Publication No. 57,339/1990). which has a low degree of orientation and which has been thermoset is laminated onto a metal sheet and the laminated metal is used as the can material (Japanese Laid-Open Patent Publication No. 22,530/1989). orientation coefficient, heat shrinkage and density is laminated onto a metal sheet and the laminated metal sheet is used as the can material (Japanese Laid-Open Patent Publication No. 86,729/1991, Japanese Laid-Open Patent Publication No. 110,124/1991 or EP-A-0415383). index and containing a lubricant of a particular particle diameter is used onto a metal sheet and the laminated metal sheet is used as the can material (EP-A-0472240).
It has been revealed, however, that the conventional techniques according to the above proposals could not provide films having sufficient properties and each has the following problems.
In the above (1), the biaxially oriented polyethylene terephthalate film has excellent heat resistance and flavor-retaining property but is not sufficient in molding-processability. Therefore, when the laminated metal is subjected to can-making processing which inevitably invites large deformation, there occurs the whiting (formation of fine cracks) and rupture of film.
In the above (2), since the film used is an amorphous or very low crystalline aromatic polyester film, it is good in molding-processability. However, the film is inferior in flavor-retaining property and is apt to become brittle during the post treatment such as printing after can-making, retort sterilization and during prolonged storage, and hence, has fear of becoming a film quality which cracks easily by externally exerted impact.
In the above (3), the film is intended to a
REFERENCES:
patent: 4362775 (1982-12-01), Yabe et al.
patent: 4761327 (1988-08-01), Hamono et al.
patent: 4801640 (1989-01-01), Dallmann et al.
Asai Takeo
Hasegawa Kinji
Murakami Yoji
Szekely Peter
Teijin Limited
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