Biaxially oriented polyester film to be laminated onto a metal p

Details Biaxially oriented polyester film to be laminated onto a metal p Biaxially oriented polyester film to be laminated onto a metal p

1998-06-10

2000-07-11

Chen, Vivian

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

428339, 428458, 428480, 428910, 1563082, 264299, 528302, 528308, 5283081, 5283086, 5283087, B32B 2736, B32B 3104

Patent

active

060869895

DESCRIPTION:

BRIEF SUMMARY
TECHNOLOGICAL FIELD

This invention relates to a polyester film to be laminated onto a metal plate and molded. More specifically, it relates to a polyester film to be laminated onto a metal plate and molded, which exhibits excellent moldability when a metal plate onto which the film is laminated is deep-drawn to make a can and which can give cans, such as drink cans and food cans, having excellent heat resistance, retort resistance, flavor retention properties, impact resistance and corrosion resistance.


BACKGROUND ART

Metal cans are generally coated on interior and exterior surfaces thereof to be protected from corrosion. Recently, the development of methods for obtaining corrosion resistance without using an organic solvent has been promoted for the purpose to simplify production process, improve sanitation and prevent pollution. As one of such methods, coating of a metal can with a thermoplastic resin film has been attempted.
That is, studies on a method for making cans by laminating a thermoplastic resin film onto a metal plate such as tinplate, tin-free steel or aluminum and then drawing the laminated metal plate are under way.
It is becoming clear that a copolyester film is suitable for use as this thermoplastic resin film in view of moldability, heat resistance, impact resistance and flavor retention properties. However, the polyester film does not always exhibit sufficient taste and flavor retention properties when a can coated therewith contains a drink of which very delicate taste is important, such as green tea, or mineral water which must be tasteless and unflavored, and changes in flavor and taste are detected.
Japanese Laid-open (Kokai) patent application No. 6-116376 proposes a polyester film to be laminated onto a metal plate and molded, which comprises a copolyester containing alkali metal elements and germanium element in specific amounts and has improved flavor retention properties. This film exhibits excellent taste and flavor retention properties when the container with the content is not heated, like the case of a cold pack system, but the film does not always obtain sufficient taste and flavor retention properties when the container with the content undergoes heat treatment, like the case of a retort treatment.
Japanese Laid-open (Kokai) patent application No. 8-231690 proposes a copolyester film comprising terephthalic acid as a main acid component and 1,4-cyclohexanedimethanol and ethylene glycol in a specific proportion range as diol components. Although this film has been proposed to obtain flavor retention properties for contents which require a retort treatment, it cannot obtain sufficient can making properties due to its low heat resistance.
It is an object of the present invention to provide a polyester film to be laminated onto ametal plate and molded, which has overcome the defects of conventional technology and has improved flavor retention properties for contents, particularly taste and flavor retention properties after a retort treatment, while retaining excellent moldability, heat resistance and impact resistance of a copolyester film.
Other objects and advantages of the present invention will become clear from the following description.


BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows a DSC chart.


DISCLOSURE OF THE INVENTION

According to the present invention, firstly, the above objects and advantages of the present invention can be attained by a biaxially oriented polyester film to be laminated onto a metal plate and molded, amount of 82 to 100 mol % and 2,6-naphthalenedicarboxylic acid or a combination of 2,6-naphthalenedicarboxylic acid and other dicarboxylic acid(s) in an amount of 0 to 18 mol %, based on the whole dicarboxylic acid component and (b) ethylene glycol in an amount of 82 to 100 mol % and cyclohexanedimethanol or a combination of cyclohexanedimethanol and other diols in an amount of 0 to 18 mol %, based on the whole diol component, and having (c) a glass transition temperature of 78.degree. C. or higher and (d) a melting point in a range of 210 to 25

REFERENCES:
Abstract XP002122391 (JP 05 155991), Database WPI, Section Ch, Week 199329.
Abstract XP002122392 (JP 05 320377), Database WPIU, Section Ch, Week 199402 .

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