Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-09-19
2001-10-30
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S035700, C428S035800, C428S212000, C428S457000, C428S458000, C428S480000, C428S910000
Reexamination Certificate
active
06309720
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyester laminate film to be laminated on a metal material for food cans and beverage cans for soft drinks, beer and the like, a metal plate that has been laminated with said film and a film-laminated metal container obtained by forming said plate. More particularly, the present invention relates to a polyester laminate film particularly suitable for inner and outer walls of a two-piece can, a metal plate that has been laminated with this film and a film-laminated metal container obtained by forming said plate.
BACKGROUND OF THE INVENTION
In a known method for the prevention of corrosion, a thermoplastic film is laminated on the inner wall and outer wall of a metal can. For example, Japanese Patent Unexamined Publication No. 7-227946 discloses a polyester film to be laminated on a metal material for food cans. This polyester film is superior in scratch resistance, and a metal plate laminated with this film (hereinafer to be referred to as a film-laminated metal plate) is free of degradation of a product value due to the occurrence of scratches on the film surface in, for example, a can manufacture step comprising forming a metal plate into a cylindrical shape and seaming lids on the upper and lower openings of this cylinder, when the film-laminated metal plate is delivered or subjected to seaming.
The above-mentioned polyester film is superior in resistance to seaming and associated with less elution of oligomer from the film during heat treatment such as retorting applied after can manufacture and packing food therein. Consequently, this film serves well as a film to be applied to the inner wall of a metal container.
Cans for soft drinks include a so-called three-piece can wherein lids are set on the upper and lower openings of a cylinder formed using a metal plate, and a so-called two-piece can wherein a metal plate is drawn deep to form a container part and a lid is seamed onto the upper opening of this container part.
In the case of a three-piece can, a film-laminated metal plate is formed into a cylindrical shape, but in the case of a two-piece can, a film-laminated metal plate undergoes a draw-wipe forming.
Consequently, the film to be laminated on a metal plate that is used to make a two-piece can is required to have superior moldability that allows the film to be molded following the shape change of the metal plate. At the same time, the film is required to show superior adhesion to the metal plate. When the film has insufficient moldability or poor adhesion to the metal plate, the film may come off from the metal plate (i.e., delamination) or the film may be broken during manufacture of the container part of a two-piece can.
A film-laminated metal plate is formed into the container part of a two-piece can by repeated ascending and descending of a punch used for drawing. Therefore, the film constituting the inner wall of the container is required to be easily releasable from the punch.
Moreover, the film constituting the outer wall of the container is required to be free of whitening or precipitation of oligomer due to heat treatment for retorting or printing, which is applied after can manufacture including drawing and wiping.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a polyester laminate film superior in adhesion to a metal plate, moldability, releasing property, resistance to heat treatment and strength, that can be applied as a laminate film for a metal plate to be used for manufacture of two-piece cans; a metal plate that has been laminated with this film; and a film-laminated metal container obtained by forming this metal plate.
The present invention provides two aspects as represented by the following (1)-(8) and (9)-(16).
(1) A polyester laminate film comprising plural polyester layers, which comprises one surface layer comprising a polyester and a lubricant having an average particle size of 1-3 &mgr;m in a proportion of 1-5 wt % and the other surface layer comprising a polyester, wherein 5-15 mol % of the entire acid component is a dimer acid component, the polyester laminate film having a crystallization peak temperature of 80-120° C. under temperature rise of the film.
(2) The polyester laminate film of (1) above, which has been biaxially oriented.
(3) A film-laminated metal plate comprising a metal plate and the polyester laminate film of (1) or (2) above laminated on the metal plate in such a manner that said other surface layer of the film is in contact with the metal plate.
(4) The film-laminated metal plate of (3) above, wherein the film is obtained by rapid cooling after heat treatment, so that the film is substantially noncrystalline and unoriented.
(5) A film-laminated metal container comprising a metal container and the polyester laminate film of (1) or (2) above, said film being laminated on the inner wall of the metal container in such a manner that said other surface layer of the film is in contact with the metal container.
(6) A film-laminated metal container obtained by forming the film-laminated metal plate of (3) or (4) above in such a manner that the film constitutes an inner wall of the film-laminated metal container.
(7) The film-laminated metal container of (5) or (6) above, wherein the film is obtained by rapid cooling after heat treatment, so that the film is substantial noncrystalline and unoriented.
(8) The film-laminated metal container of any of (5)-(7) above, which is a two-piece can.
(9) A polyester laminate film comprising plural polyester layers, which comprises one polyester surface layer having a melting peak temperature of 200-260° C. and a crystallization peak temperature of 60-100° C. under temperature rise of the layer, and the other polyester surface layer having a melting peak temperature of 180-240° C. and a crystallization peak temperature of 60-100° C. under temperature rise of the layer, wherein the melting peak temperature of said one polyester surface layer is higher by 5-25° C. than the melting peak temperature of said other polyester surface layer.
(10) The polyester laminate film of (9) above, which has been biaxially oriented.
(11) A film-laminated metal plate comprising a metal plate and the polyester laminate film of (9) or (10) above laminated on the metal plate in such a manner that said other surface layer of the film is in contact with the metal plate.
(12) The film-laminated metal plate of (11) above, wherein the film is obtained by rapid cooling after heat treatment, so that the film is substantially noncrystalline and unoriented.
(13) A film-laminated metal container comprising a metal container and the polyester laminate film of (9) or (10) above, said film being laminated on the outer wall of the metal container in such a manner that said other surface layer of the film is in contact with the metal container.
(14) A film-laminated metal container obtained by forming the film-laminated metal plate of (11) or (12) above in such a manner that the film constitutes an outer wall of the film-laminated metal container.
(15) The film-laminated metal container of (13) or (14) above, wherein the film is obtained by rapid cooling after heat treatment, so that the film is substantial noncrystalline and unoriented.
(16) The film-laminated metal container of any of (13)-(15) above, which is a two-piece can.
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment of the present invention is described in detail in the following.
The polyester laminate film of the present invention comprises the following specific polyester layers constituting the surface layers.
The polyester layer on one side of the inventive polyester laminate film (hereinafter this polyester layer is to be briefly referred to as polyester layer A) is explained in the following. This layer is not brought into contact with the metal plate.
The polyester layer A is made from a polyester composition A containing a polyester and a lubricant having an average particle size of 1-3 &mgr;m in a proportion of 1-5 wt %. When compared to the
Igushi Hideki
Nagano Hiroshi
Oko Tsutomu
Shimizu Hideki
Chen Vivian
Morrison & Foerster / LLP
Toyo Boseki Kabushiki Kaisha
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