Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1999-02-04
2001-05-29
Pezzuto, Helen L. (Department: 1713)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S307300, C428S315500, C428S315900, C428S318400, C428S319300
Reexamination Certificate
active
06238783
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a manufacturing method and a manufacturing apparatus of a thermoplastic resin laminated aluminum alloy sheet mainly used for can stocks. More in detail, it relates to a thermoplastic resin laminated aluminum alloy sheet of which at least one side is covered with a thermoplastic resin, having excellent formability, adhesion after forming, corrosion resistance, impact resistance and retainability of flabor. Therefore, it is suitable not only for common use such as can lid or drawn can, but also for drawn and compression formed can, drawn and stretch-formed can, drawn, stretch-formed and further compression formed can which require extremely excellent formability, adhesion after forming and adhesion after retort treatment. And it further relates to a manufacturing method and a manufacturing apparatus of the thermoplastic resin laminated aluminum alloy sheet.
BACKGROUND TECHNIQUE
An aluminum alloy sheet laminated with a thermoplastic resin, for example polyester resin, has already been used for the manufacture of can lids and so on. However, when adhesion of the laminated thermoplastic resin layer to the aluminum alloy sheet is not sufficient, there are some cases where the thermoplastic resin layer peels off during forming and corrosion is generated at the portion where adhesion of the laminated thermoplastic resin layer is not sufficient. The adhesion is affected by formability of the aluminum alloy sheet and characteristics of the thermoplastic resin to be laminated thereto, and it is particularly affected by the surface roughness of the aluminum alloy sheet. For this reason, several surface pre-treatments mentioned below have been so far given to an aluminum alloy sheet in order to improve the adhesion of a thermoplastic resin layer or a coating layer to the aluminum alloy sheet.
(1) Chemical treatment of an aluminum alloy sheet in a phosphate solution or in a chromate solution
(2) Coating a thermosetting resin primer on one surface of a thermoplastic resin film or on an aluminum alloy sheet
(3) Forming an anodic oxide film having 5 to 60% of an occupied area rate by micro pores of 2000 angstrom or more of diameter and 5 &mgr;m or less of depth on an aluminum alloy sheet using a solution including chromic acid (Laid Open Japanese Patent No. Hei 3-44496)
(4) Forming an oxide film having 20 angstrom or more of thickness by heating an aluminum alloy sheet for 2 hours or more at the temperature of 250 to 650° C. in the atmosphere after cleansing (Laid Open Japanese Patent No. Hei 6-272015)
(5) Forming an oxide film having 500 to 5000 angstrom of thickness and branched micro pores by electrolytically treating in an alkali solution using alternate wave-form current after cleansing (Laid Open Japanese Patent No. Hei 6-267638)
In the aforementioned chemical treatment (1) in a phosphate solution or in a chromate solution, phosphate, chromate or fluoride is mainly used in the treating solution, and the formed film by the chemical treatment has an effect on the improvement of adhesion of coating film. Therefore, it is generally used. But when the thus chemically treated aluminum alloy sheet covered with a coating or laminated with a thermoplastic resin is formed by a more severe than usual forming, which is the objective of the present invention, the coating or the laminated thermoplastic resin tends to peel off, which is not favorable. Coating a primer for adhesion according to treatment (2) is not favorable from the viewpoint of an increase in cost for coating of primer as well as the productivity because it requires another process for baking. It also requires an exhauster for organic solvent. Forming an anodic oxide film (3) having specified micro pores using chromate solution is not favorable from the viewpoint of productivity because it takes long time to form the anodic oxide film and there is a tendency of peeling off of the thermoplastic resin layer when the laminate is heavily formed. Forming an oxide film (4) by heating in the atmosphere for a long time is not favorable since the thermoplastic resin layer peels off when the laminate is heavily formed as with the case of (3), and this prior technique is also unfavorable from the viewpoint of productivity because it takes a long time to form the oxide film. Forming an oxide film (5) having 500 to 5000 of thickness by electrolytically treating in an alkali solution using alternate wave-form current can be practiced continuously in a short duration of electrolysis and has some effect on the adhesion after forming of the laminated resin film; however, it does not give sufficient adhesion after forming since the laminated resin film peels off when the laminate is heavily formed as drawn, stretch-formed and further pressed.
As mentioned above, the lamination of a thermoplastic resin on aluminum alloy sheet that is surface-treated using conventional surface-treating manner can not be successfully used for adhesion therebetween after heavy forming, which is the objective of the present invention, since the laminated thermoplastic resin layer peels off when the laminate is heavily formed as drawn, stretch-formed and further pressed.
The technical problems to be solved by the present invention is to produce a thermoplastic resin laminated aluminum alloy sheet having excellent adhesion after forming in such a manner that the laminated thermoplastic resin does not peel off even when the laminate is deep-drawn, stretch-formed and further pressed to shape, that is superior to a laminate in which resin film is laminated on the conventionally surface-treated aluminum alloy sheet, and to obtain excellent adhesion after sterilization. The technical problems to be solved by the present invention are is also to produce a manufacturing method and a manufacturing apparatus thereof which can produce the laminate at low cost and high production speed.
DISCLOSURE OF INVENTION
A thermoplastic resin laminated aluminum alloy sheet of the present invention is characterized in that a thermoplastic resin is laminated on at least one side of an aluminum alloy sheet in which the specific surface area is increased by electrolytical treatment in a chromate solution so that the increasing rate of the specific surface is in the range of 7 to 45%.
It is characterized in that an aluminum alloy sheet is favorably treated in an alkali solution and followed by being treated in acid solution so that the increasing rate of the specific surface on the surface of the alloy sheet is in the range of 3 to 30%, and wherein the so-treated sheet is electrolytically treated in the chromate solution, and after that a thermoplastic resin is laminated on at least one side of the thus surface treated aluminum alloy sheet. It is favorable that in such a thermoplastic resin laminated aluminum alloy sheet micro pores are formed on the surface of the aluminum alloy sheet after the treatment in alkali solution and in acid solution, in which the diameter of the micro pores is in the range of 50 to 3000 nm, the maximum depth is 1000 nm or less, and the occupied area rate by the micro pores is in the range of 10 to 95%. It is further favorable that the average diameter of the micro pores is in the range of 200 to 900 nm, the depth of such micro pores is half or less than the diameter, and the pores are formed along the thickness direction from the surface of the aluminum alloy sheet.
Further, it is favorable that the thermoplastic resin is polyethylene terephthalate, copolyester resin mainly composed of ethylene terephthalate unit, polyester resin mainly composed of butylene terephthalate unit, blended resin of these resins or multi-layered composite resin of these resins.
Furthermore, it is also preferable that the thermoplastic resin to be laminated is a multi-layered resin composed of an upper layer and a lower layer of polyester resin and an intermediate layer of a blended resin consisting of polyester resin blended with bis-phenol A polycarbonate or bis-phenol A polycarbonate.
The manufacturing method of a thermoplastic resin laminated a
Komai Masao
Kunishige Fumio
Shimizu Keiichi
Tanabe Jun-ichi
Taniguchi Ayumu
Browdy & Neimark
Pezzuto Helen L.
Toyo Kohan Co. Ltd.
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