Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Patent
1998-01-26
1999-09-07
Acquah, Samuel A.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
528275, 528298, 528302, 528308, 5283086, 528502, 525444, 524731, 428 357, 428333, 428338, B32B 712, C08F 2000, C08G 6302
Patent
active
059485256
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a biaxially stretched polyester film for forming containers. More particularly, it relates to a biaxially stretched polyester film that is excellent in formability, impact resistance and taste property and that is suitable for containers and, especially, metallic cans, to be produced by a forming process.
BACKGROUND ART
It has been widely practiced, for the purpose of preventing corrosion, to coat the internal surface and external surface of a metallic can with a material obtained by dissolving or dispersing in a solvent a thermosetting resin of various types, such as epoxy-based resin, phenol-based resin or the like, and thereby cover the metal surfaces. However, such a method of covering with a thermosetting resin has unfavorable problems such as the time consuming process of drying the coating material, a reduction in productivity, environmental pollution due to a large amount of the organic solvent, and the like.
As a method for solving these problems, there is a method that laminates a film on a material of a metallic can, that is, a steel sheet or an aluminum sheet, or one of these metallic sheets that has been surface-treated in a manner such as plating or the like. If a film-laminated metallic sheet is drawn or ironed to produce metallic cans, the film is required to have the following properties: such as a pinhole after the forming process. metallic can. of the metallic can or should cause degradation of the flavor of the content of the metallic by a substance dissolved from the film (hereinafter, referred to as "taste property").
Many proposals have been made to meet these requirements. For example, Japanese patent application laid-open No. Sho 64-22530 discloses a polyester film having specific density and face orientation coefficient; Japanese patent application laid-open No. Hei 2-57339 discloses a copolymerized polyester Film having specific crystallinity; and Japanese patent application laid-open No. Hei No. 6-218895, Japanese patent application laid-open No. Hei 6-107815, etc., disclose a polyester film coplymerized with an isophthalic acid component containing specific particles, or the like. However, these proposals cannot satisfy all the various requirements as stated above, and cannot be said to be at sufficiently satisfying levels especially in applications where both a high level formability and an excellent taste property after retorting are required.
An object of the present invention is to solve the aforementioned problems of the conventional art and to provide a biaxially stretched polyester film for forming containers that is excellent in formability, heat resistance and taste property and, more particularly, that is suitable for metallic cans produced by a forming process and having an excellent taste property.
DISCLOSURE OF THE INVENTION
The present invention is a result of finding that a polyester film obtained by copolymerizing or blending an ethylene terephthalate unit and an ethylene naphthalate unit and controlling the film structure at a high level is a film that is not only excellent in laminate characteristics but also excellent in the formability during high speed forming and good in taste property especially after retorting.
BEST MODE FOR CARRYING OUT THE INVENTION
The biaxially stretched polyester film for forming containers of the present invention is a film which is formed from a polyester substantially consisting of an ethylene terephthalate unit and an ethylene naphthalate unit and whose refractive index in the direction of thickness of the film is 1.5 or greater.
The "polyester substantially consisting of an ethylene terephthalate unit and ethylene naphthalate unit" herein means a polyester that contains substantially no repetition unit, especially, ethylene isophthalate unit, other than the ethylene terephthalate and the ethylene naphthalate unit.
That is, the use of a polyester that contains substantially no isophthalic acid component is a feature of the present invention. The polyester composition of
REFERENCES:
patent: 3683060 (1972-08-01), Tanabe et al.
patent: 5106681 (1992-04-01), Endo et al.
patent: 5337174 (1994-08-01), Wada et al.
patent: 5698309 (1997-12-01), Dallmann et al.
patent: 5783120 (1998-07-01), Ouderkirk et al.
Abe Koichi
Kimura Masahiro
Kojima Hiroji
Takahashi Kohzo
Acquah Samuel A.
Miller Austin R.
Toray Industries Inc.
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