Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1998-06-04
2002-07-16
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S213000, C428S220000, C428S323000, C428S331000, C428S458000, C428S480000
Reexamination Certificate
active
06420010
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Technical Field
This invention relates to a white laminated polyester film for metallic plate lamination work, more particularly, relates to a white laminated polyester film for metallic plate lamination work having excellent workability and hiding effect in the case of laminating to a metallic plate and forming the laminate to a metallic can having the film at the outer surface of the can and causing little abrasion of rolls for the manufacture of the film.
2. Background Arts
Metallic cans are generally coated on the inner and outer surfaces to prevent the corrosion of the metal. Coating with a thermoplastic resin film is recently attempted as a means for imparting the metallic can with rustproofness without using organic solvent for the simplification of process, improvement in hygiene, prevention of environmental pollution, etc.
Namely, the investigation is in progress to laminate a thermoplastic resin film to a metallic plate such as tinned sheet iron, tinfree steel or aluminum and manufacture a can by the drawing, etc., of the laminated plate.
Polyolefin films and polyamide films were attempted as the above thermoplastic resin film, however, these films did not satisfy the required workability, heat-resistance and aromaproofness at the same time.
Polyester films, especially polyethylene terephthalate films are attracting attention owing to the balanced characteristics, and several proposals have been made based on the film.
For example, there are the following proposals.
(1) A method to laminate a biaxially oriented polyethylene terephthalate film to a metallic plate and use the laminate as a can-manufacturing-material (Japanese Patent TOKKAISHO 56-10451 and TOKKAIHEI 1-192546),
(2) A method to laminate an amorphous or an extremely low-crystalline aromatic polyester film to a metallic plate and use the laminate as a can-manufacturing material (Japanese Patent TOKKAIHEI 1-192545 and TOKKAIHEI 2-57339) and
(3) A method to laminate a heat-set biaxially oriented polyethylene terephthalate film having low orientation degree to a metallic plate and use the laminate as a can-manufacturing material (Japanese Patent TOKKAISHO 64-22530).
However, these methods have failed in getting sufficiently satisfiable results and revealed the following problems.
In the method (1), the biaxially oriented polyethylene terephthalate film has excellent heat-resistance and aromaproofness, however, the workability is insufficient to generate microscopic cracks and, in extreme cases, cause the breakage of the film in the case of can-manufacturing work accompanying a large deformation.
The method (2) uses an amorphous or extremely low-crystalline aromatic polyester film having good workability but poor aromaproofness and liable to cause the embrittlement by the post-heat treatment such as printing, retort-sterilization, etc., after the manufacture of a can or by the storage over a long period to form a film easily breakable by the external shock.
The method (3) aims at the development of the effect in a region between the methods (1) and (2), however, it is not yet successful to get a film having sufficiently low orientation applicable to the manufacture of a can.
Metallic cans are generally printed on the outer surface, and the print is applied after undercoating the surface with a white coating for light-shielding. The undercoating with a white coating can be omitted by using a light-shielding white film as the thermoplastic resin film to be laminated to the metallic plate, however, the white film produced by adding white pigment to the films of the methods (1), (2) and (3) cannot solve the demerits of each method.
Further, a white film containing titanium oxide at high concentration for improving the hiding effect is brittle to deteriorate the film-forming property by the frequent film breakage in drawing and causes the problem of the abrasion of rolls used in the film-forming process.
Various methods have been proposed to improve the above-mentioned workability, aromaproofness and heat-resistance of the film.
Followings are example of these methods.
(4) A method to use a copolyester having a melting point falling within a specific range as the can-manufacturing material (Japanese Patent TOKKAIHEI 5-339391) and
(5) A method to use a laminated film composed of two layers having different contents of white pigment (Japanese Patent TOKKAIHEI 6-39981).
Although the use of the method (4) or (5) is effective for improving the workability, aromaproofness and heat-resistance, the problem of the roll abrasion remains unsolved and a film having satisfactory characteristics in the film-forming process and the working of a metallic can is not yet attainable.
Problems to be Solved by the Invention
The object of the present invention is to provide a white laminated polyester film for metallic plate lamination work having excellent workability, aromaproofness and heat-resistance and causing little abrasion of rolls.
Means for Solving the Problems
According to the present invention, the above object and advantages of the present invention can be achieved first by a white laminated polyester film for metallic plate lamination work consisting of a laminated film comprising a layer (layer A) composed of a copolyester A and a layer (layer B) composed of a copolyester B, wherein
(I) (i) the copolyester A contains 0 to 15% by weight of rutile titanium oxide having an average particle diameter of from 0.1 to 0.5 &mgr;m and has a melting point of from 210 to 245° C., (ii) the copolyester B contains 10 to 50% by weight of rutile titanium oxide having an average particle diameter of from 0.1 to 0.5 &mgr;m and has a melting point of from 210 to 245° C. and an intrinsic viscosity of the polymer part of from 0.46 to 0.66,
(II) the intrinsic viscosity (&eegr;
A
) of the polymer part of copolyester A and the intrinsic viscosity (&eegr;
B
) of the polymer part of the copolyester B satisfy the following relationship:
|&eegr;
A
−&eegr;
B
|<0.15, and
(III) the ratio of the apparent density (&rgr;). to the calculated density (&rgr;
0
) of the whole laminated film (&rgr;/&rgr;
0
) satisfies the following formula:
0.65≦&rgr;/&rgr;
0
≦1.00
wherein
ρ
0
=
100
ρ
t
∑
i
=
1
n
(
Xi
ρ
i
W
i
(
ρ
i
-
ρ
t
)
+
100
ρ
t
)
∑
i
=
1
n
X
i
in the above formula,
&rgr;: apparent density (g/cm
3
) of the whole laminated film:
&rgr;
0
: calculated density (g/cm
3
) of the whole laminated film:
&rgr;
i
: density (g/cm
3
) of the polymer part of each copolyester:
&rgr;
t
: density (g/cm
3
) of rutile titanium oxide:
X
i
: thickness (&mgr;m) of each layer:
W
i
: concentration (wt. %) of rutile titanium oxide in each copolyester:
n: number of copolyester layers.
Secondly, the object and advantages of the present invention can be achieved by a white laminated polyester film for metallic plate lamination work consisting of a laminated film (which may be abbreviated hereinafter as a second laminated film) produced by laminating a layer (layer A) composed of a copolyester A and a layer (layer C) composed of a copolyester C to both surfaces of a layer (layer B) composed of a copolyester B, provided that
(i) the copolyester A contains 0 to 10% by weight of rutile titanium oxide having an average particle diameter of from 0.1 to 0.5 &mgr;m and 0.01 to 0.1% by weight of silicon dioxide particles having an average particle diameter of from 0.6 to 2.0 9 &mgr;m and has a melting point of from 210 to 245° C. and an intrinsic viscosity of the polymer part of from 0.46 to 0.66,
(ii) the copolyester B contains 120 to 50% by weight of rutile titanium oxide having an average particle diameter of from 0.1 to 0.5 &mgr;m and has a melting point of from 210 to 245° C. and an intrinsic viscosity of the polymer part of from 0.46 to 0.66 and
(iii) the copolyester C contains 0 to 10% by weight of rutile titanium oxide having an average particle diameter of from 0.1 to 0.54 &mgr;m and 0.01 to 0.1% by w
Hasegawa Tetsuya
Kubo Koji
Murooka Hirofumi
Yoshida Tetsuo
Sughrue & Mion, PLLC
Teijin Limited
Thibodeau Paul
Zacharia Ramsey
LandOfFree
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