Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1996-02-01
2000-01-25
Thibodeau, Paul
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
428457, 428458, 428461, 428463, 428212, 156311, 156321, 264544, 220450, 220454, B29D 2200
Patent
active
060175990
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
This invention concerns laminated sheet and a manufacturing method for it. This invention especially concerns a laminated sheet for beverage or food cans and an efficient manufacturing method therefor. The laminated sheet includes a thermoplastic the resin film and metallic substrate.
BACKGROUND TECHNOLOGY
A two piece can which consists of the can body combined with the bottom lid is used for the manufacture of a food can or beverage can. Those cans are formed from a metal substrate such as a cold rolled steel sheet, an aluminum sheet or tinplate. Those cans are usually coated with various resin coatings in order to prevent the metal from being dissolved into the contents of the can and to improve its corrosion resistance and durability.
The above-mentioned two-piece can is occasionally formed by means of drawing the laminated sheet which is produced by laminating the resin film to the metal substrate. Such laminated sheet should endure the drawing, the pressing or the stretching processing.
Therefore, the laminated sheet is conventionally produced by a method of laminating the resin film without using adhesive (Japanese patent Application No. TOKU-KOU-SHO 60-47103) or by a method of laminating a polyester film which is coated with epoxy resin together with curing agent, etc. (e.g. Japanese Application NO. TOKU-KOU-SHO 63-13829 or No. TOKU-KAI-HEI 1-249331).
One of the requirements is denting resistance in the drawn and formed can. There must be impact resistance of the film and also resistance to cracking of the film when the can is dented.
We have previously proposed to use the steel sheet covered with bi-axially oriented or un-oriented polyester resin film which has a specified intrinsic viscosity as a material of the laminated can (Japanese Patent Application No. TOKU-KAI-HEI 4-224936).
Above-mentioned bi-axially oriented polyester resin film improves the strength and the denting resistance because the crystalline structure is highly oriented (the molecule is highly oriented). However, such a polyester film does not have enough adhesion to the metal substrate. Therefore it peels off easily during drawing process or ironing (e.g. pressing) process.
In order to solve such problems, the resin film is laminated to the metal substrate which is heated in advance. As a result, the crystal orientation of the film on the side of the oriented film in contact with the metal substrate decreases to some degree. And, adhesion and bonding improve.
So this is a method of giving the inclination in the direction of thickness of the film concerning crystal orientation. However, the denting resistance of the can decreases when crystal orientation of the film decreases too much and it causes a problem concerning the durability of the can.
In order to improve adhesion, it has been proposed that the film of laminated sheet be partially heated, especially for the high adhesion required part, just before the drawing process (Japanese patent application No.TOKU-KAI-HEI 4-118121). However, it is difficult to control and maintain the film temperature within the range from the glass transition temperature to the temperature of re-crystallization.
SUMMARY OF INVENTION
This invention relates to a laminated sheet for a metal can, which laminated sheet has excellent denting resistance and adhesion to the can, and the method of manufacturing the laminate.
The laminated sheet according to the present invention improves denting resistance of the part of the can where considerable denting is likely to occur such as the can bottom, etc., and also improves the adhesion of the film to the metal substrate in the other parts of the laminate.
Furthermore, that laminated sheet can be simply formed into cans and the damage at the time of circulation is small and durability is high.
BRIEF EXPLANATION OF DRAWING
FIG. 1 is a projected drawing which shows one example of the laminated sheet of the present invention.
FIG. 2(a) is an magnified cross section of the laminated sheet and
FIG. 2(b) is an expanded cross section w
REFERENCES:
patent: 3898358 (1975-08-01), Ryan et al.
patent: 4276347 (1981-06-01), Shimada
patent: 4943780 (1990-07-01), Redding
patent: 5059460 (1991-10-01), Heyes et al.
patent: 5112695 (1992-05-01), Watanabe et al.
patent: 5204181 (1993-04-01), Suzuki et al.
patent: 5330605 (1994-07-01), Tanaka et al.
patent: 5384354 (1995-01-01), Hasegawa et al.
patent: 5582319 (1996-12-01), Heyes et al.
Iketaka Satoshi
Sakamoto Yoshiki
Tanaka Atsuo
Yasunaka Kenji
Tarazano D. Lawrence
Thibodeau Paul
Toyo Kohan Co. Ltd.
LandOfFree
Laminated sheet and manufacturing method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laminated sheet and manufacturing method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laminated sheet and manufacturing method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2314314