Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Patent
1998-05-22
2000-06-06
Thibodeau, Paul
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
428220, 428458, 428480, B32B 702, B32B 1508, B32B 2706, B32B 2736
Patent
active
060715995
DESCRIPTION:
BRIEF SUMMARY
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a polyester film to be laminated onto metal plate and molded. More specifically, it relates to a polyester film to be laminated onto metal plate and molded, which exhibits excellent moldability when a metal plate onto which the film is laminated and subjected to the deep-drawing or the like in a can-making process and which can give metal cans, such as drink cans and food cans, having excellent impact resistance, heat resistance, retort resistance and taste and flavor retention properties.
Metal cans are generally coated on interior and exterior surfaces thereof to be prevented from corrosion. Recently, the development of methods for obtaining corrosion resistance without using an organic solvent has been promoted to simplify production process, improve sanitation and prevent pollution. As one of the methods, coating of a metal can 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 on a plate of a metal such as tin, tin-free steel or aluminum and then drawing the laminated metal plate. A polyolefin film or polyamide film has been tried as this thermoplastic resin film but could not satisfy all requirements for moldability, heat resistance, flavor retention property and impact resistance.
On the other hand, a polyester film, particularly a polyethylene terephthalate film attracts much attention as a film having well-balanced properties and there have been made some proposals based on the polyethylene terephthalate film.
Japanese Laid-open patent application publications 56-10451 and 1-192546 disclose a can making material formed by laminating a biaxially oriented polyethylene terephthalate film onto a metal plate via a low-melting polyester adhesive layer.
Although this biaxially oriented polyethylene terephthalate film has excellent heat resistance and flavor retention property, its moldability is unsatisfactory with the result that the film is whitened (generation of fine cracks) and ruptured when it is subjected to a can making process which inevitably invites large deformation.
Japanese Laid-open patent application publications 1-192545 and 2-57339 disclose a can-making material formed by laminating an amorphous or extremely low crystalline aromatic polyester film onto a metal plate. Since this can making material comprises an amorphous or extremely low crystalline aromatic polyester film, it is good in moldability but inferior in flavor retention property, and is liable to be embrittled during the post-treatment such as printing or retort sterilization after can-making or during a long-term preservation, and may be changed into a film that easily cracks by an externally exerted impact.
Japanese Laid-open patent application publication 64-22530 discloses a can making material formed by laminating a heat set biaxially oriented polyethylene terephthalate film that has been heat set at a low degree of orientation, onto a metal plate. This film is intended to achieve effects in a domain intermediate area between the above two different types of films but does not yet attain the low orientation applicable to the can-making process. Even if it can be processed in a domain with a small degree of deformation, it is easily embrittled by subsequent printing and retort treatment for sterilizing the contents of a can and may be degraded into a film which easily cracks by an impact exerted from the outside of the can, like the above amorphous and extremely low crystalline film.
U.S. Pat. No. 4,362,775 discloses a polyester film heat-bonded metal plate formed by heat bonding a biaxially oriented polyester film (C) to a metal plate, using an adhesive, the adhesive being a polyblend comprising 5 to 80% by weight of at least one high melting point polyester having a melting point of at least 200.degree. C., and 20 to 95% by weight of at least one low melting point polyester having a melting point of at least 100.degree. C.
Japanese Laid-open patent applicat
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Hasegawa Tetsuya
Kimura Manabu
Kosuge Masahiko
Kubo Koji
Murooka Hirofumi
Teijin Limited
Thibodeau Paul
Zacharia Ramsey
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