Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1998-06-29
2000-07-11
Thibodeau, Paul
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428220, 428323, 428458, 428910, B32B 516, B32B 1508, B32B 2736
Patent
active
06086978&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNIQUE
The present 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 is excellent in retort resistance and taste retainability and is suitable for the production of a metal can such as a drink can or a food can.
BACKGROUND TECHNOLOGY
Metal cans are generally coated on interior and exterior surfaces thereof for prevention of corrosion. Recently, there has been promoted the development of methods for obtaining corrosion resistance without using an organic solvent for the purpose of simplifying production process, improving sanitation and preventing pollution. As one of the methods, coating of a metal can surface with a thermoplastic resin film has been attempted. That is, studies are under way on a method for making cans by laminating a thermoplastic resin film onto a plate of metal such as tin, tin-free steel, aluminum or the like and then, drawing the laminated metal plate. Although a polyolefin film or polyamide film has been tested as this thermoplastic resin film, neither of them satisfies all the requirements consisting of moldability, heat resistance, odor retainability and impact resistance.
In the prior art, a polyester film, particularly a polyethylene terephthalate film is paid much attention as a film having well-balanced properties and there have been made some proposals based on this film. However, polyethylene terephthalate films involve such a problem that moldability is poor when heat resistance and odor retainability are excellent, while odor retainability and retort resistance are poor when moldability is excellent. It has been becoming clear that a copolyester film is excellent in moldability, heat resistance, retort resistance and odor retainability and is suitable for making cans (see Japanese Laid-Open Patent Application 3-86729).
However, it has also been becoming clear that when this copolyester film is used in a drink can or food can, it has a problem in that it spoils the taste of the contents of the can due to its insufficient taste retainability.
Meanwhile, Japanese Laid-Open Patent Application 6-263893 discloses a polyester film to be laminated onto a metal plate, which contains 0.01 to 1 wt % of diethylene glycol to improve impact resistance and enumerates homopolymers and copolymers of polyethylene naphthalate as the polyester.
Japanese Laid-Open Patent Application 6-116486 discloses a copolyester film to be laminated onto a metal plate, which contains 0.05 to 20 wt % of polyoxyalkylene glycol (including diethylene glycol) to improve flavor-retention property and enumerates homopolymers and copolymers of polyethylene naphthalate as the polyester.
Japanese Laid-Open Patent Application 7-82391 discloses a biaxially oriented polyester film to be laminated onto a metal plate and molded, which is composed of a copolyester comprising 80 to 95 mol % of 2,6-naphthalenedicarboxylic acid and 5 to 20 mol % of an aliphatic dicarboxylic acid represented by the following formula: as a main glycol component, the copolyester having an intrinsic viscosity of 0.5 to 0.7 and containing a lubricant having an average particle diameter of 2.5 .mu.m or less.
It is an object of the present invention to provide a polyester film to be laminated onto a metal plate and molded, which has more excellent odor retainability and good retort resistance while retaining excellent properties of a conventional polyester film such as moldability, heat resistance, odor retainability and impact resistance.
Other objects and advantages of the present invention will become apparent from the following description.
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 (may be referred to as "the first polyester film of the present invention" hereinafter): 2,6-naphthalenedicarboxylic acid in an amount of 80 to 100 mol %, an
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Hasegawa Kinji
Kubo Koji
Murooka Hirofumi
Teijin Limited
Thibodeau Paul
Zacharia Ramsey
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