JPS62156299A - Corrosion preventive treatment of can cap - Google Patents

Abstract

PURPOSE:To coat the end face at the cut end of an aperture with a resin compsn. coated layer and to make easy and inexpensive corrosion preventive treatment of a can cap by hermetically closing the aperture of the can cap formed by blanking a surface coated metallic base material with a tearable sealing piece then subjecting the material to an electrodeposition painting treatment. CONSTITUTION:A laminated material formed by providing an outside protective layer 3 consisting of lacquer, etc. on one face of the metallic base material 2 consisting of Al, steel, etc. and a thermoadhesive resin layer 4 on the other face is blanked and the blanked aperture 5 is hermetically closed by thermal adhesion 7 of the tearable sealing piece 5 thereto from the outside surface side, by which the can cap 1 is formed. The above-mentioned can cap 1 is then subjected to the electrodeposition painting treatment using a wafer soluble acryl/melamine resin compsn., etc., as an electrodeposition paint to coat the cut end face at the peripheral edge of the above-mentioned aperture 5 with the electrodeposition resin compsn. coated layer 10. The thickness of the coated layer 10 is specified preferably to a 5-50mu range. The can cap of high quality which obviates the feathering in the stage of opening the seal and is free from corrosion is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a can lid, particularly a can lid formed by punching from a laminated material having a resin layer formed on both sides of a metal substrate, and sealed with a peel-off sealing piece. The present invention relates to a method for anticorrosion treatment of an easy-open can lid having one opening for extracting contents.

Prior Art This type of metal can lid is generally made of a metal lid made of thin plate or foil of aluminum (including aluminum alloys), tinplate, steel, etc., and coated with a lacquer, such as a phenolic epoxy-based lacquer, on one side of the outside of the metal lid. It is formed by punching out a laminated material, which is provided with an outer protective layer coated with lacquer, and a heat-adhesive resin layer made of ionomer, polyamide, EVA, etc. is provided on the other inner surface. In many cases, an opening such as an extraction hole or an air hole is cut out in a part of the top surface of the can lid, at a position slightly closer to the periphery than the center, and this is covered with a cutout on the outside surface and on the lid side surface. A sealing piece having substantially the same structure as the above-mentioned laminate material and provided with thermal adhesive properties is attached to the periphery of the opening by thermal bonding and removable.

However, the can lid configured as described above has an essential drawback of poor resistance to contents. In other words, if the contents that are corrosive to the metal material that makes up the lid are packaged, the cut surface where the metal base material around the opening such as the extraction port is exposed will be directly corroded by the contents. Being exposed to the environment not only caused damage to itself, but also its contents could be spoiled by its corrosion products. For this reason, although the above-mentioned can lid is the simplest in structure, can be easily sealed, and is advantageous in terms of cost, it is not suitable for packaging corrosive contents. There was a drawback that it could not be used suitably.

The following two methods have been proposed to solve this corrosion problem.

One method is to apply plastisol to the inner surface of an opening sealed with a sealing piece of a can lid, dry it, and cover the entire lower surface of the opening with a layer of plastisol, as shown in Japanese Patent Application Laid-Open No. 57-194948. Another method is to separately bond a synthetic resin film to the inner surface of the can lid to cover the entire surface.

However, when using the former conventional method, the process of applying plastisol and the pretreatment process to ensure its youthfulness are relatively time-consuming, and the application and drying process is relatively time-consuming. The disadvantage is that the equipment is large and costs are high, including equipment costs. In addition, even in the latter method, the work of attaching a separate film to the inner surface of the can lid is troublesome, and the material cost is low.
There was a concern that both processing and equipment costs would be high. Furthermore, when using any of the above-mentioned conventional methods, when the sealing piece is peeled off to open the seal, a so-called feathering phenomenon in which the resin coating material becomes stringy from the opening end surface tends to occur.
There was a problem in that the opening could not be maintained beautifully.

The present invention aims to provide a method for anticorrosion treatment of can lids that can solve these problems.

Means for Solving the Problems The object of the present invention is to form a desired electrodeposition coating on the cut end surface of the opening of a can lid by an electrodeposition coating method.

That is, the present invention is formed by punching out a laminated material in which an outer protective layer is provided on one side of a metal base material and a heat-adhesive resin layer is provided on the other side, and at least one extraction port is formed. The treatment target is a can lid which has a cut-out opening and is sealed from the outside by thermal bonding with a 1.1 mirror piece that can be peeled off from the opening, and by applying electrodeposition coating treatment to the can lid. , the gist of the invention is a method for anticorrosion treatment of can lids, characterized in that the cut surface of the periphery of the opening is coated with a coating layer of an electrodeposited resin composition.

This will be further explained below based on the attached drawings.

As shown in Fig. 2, the lid material constituting the can lid (1) consists of a metal base material (2) made of a thin plate or foil of aluminum, tinplate, steel, etc., and a metal base material (2) coated or laminated on one of its outer surfaces. A laminated material consisting of an outer protective layer (3) made of lacquer or other resin film, and a heat-adhesive resin layer (4) laminated on the other inner surface of the same metal base material (1). It is. The above heat-adhesive resin layer (4
) is usually formed by adhering a thermoplastic film made of, for example, ionomer, polyamide, EVA, etc.

The can lid (1) is formed by punching out the laminated lid material described above, and has an opening (5), which usually constitutes one drinking spout or extraction hole, located slightly closer to the periphery than the center.
) or perforated.

As shown in FIG. 1, this opening (5) is sealed by a sealing piece (6) that covers the can lid (1) from the outside. This sealing piece (6) is also made of a laminated material in which an outer protective layer and a thermoadhesive resin layer are laminated on both sides of a base material such as aluminum foil, and the opening is sealed by heat sealing. It is thermally bonded to the peripheral edge of portion (5) with a width of about 1 to 2 mm. (7) shows this thermal bonding part,
(6a) shows a flap portion that serves as a knob when peeling off the sealing piece (6).

In the can lid (1) produced as described above, without the treatment according to the present invention, the cut surface is exposed as it is at the periphery of the opening (5), so there is no possibility of corrosion occurring at the cutout. Have a misunderstanding.

Therefore, in the present invention, the above-mentioned molded can lid is treated and subjected to an electrodeposition coating process using an electrodeposition coating apparatus (A) as schematically shown in FIG. In the same figure, (7) is a treatment tank containing an electrodeposition paint (8) made of a resin composition, (
9) is an electrode, and (10) is a transfer route for the can lid (1) to be treated.

Using the coating device (A), the cut surface of the outer periphery of the can lid (1) is coated with the electrode by applying a DC voltage from the electrode (7) while rolling the can lid (1) on the path (9). Then, the paint (8) is electrodeposited on the cut surface of the periphery of the opening (5), and an electrodeposited resin composition coating layer (10) of a required thickness is formed thereon. After that, wash it with water and heat it at 180-230°C1
It is preferably heated and cured at around 200°C.

As the electrodeposition paint used here, for example, a water-soluble acrylic-melamine resin composition, an epoxy polyamino resin composition, an alkyd-polyester-acrylic copolymer, etc. are used after adjusting the pH.

The thickness of the coating (10) is preferably in the range of about 5 to 50 microns. That is, if the thickness is less than 5μ, it is difficult to obtain a sufficient effect in improving corrosion resistance, and if the thickness exceeds 50μ, it is disadvantageous from an economic point of view.

Note that the sealing piece (6) may be attached to the can lid (1) after the above-mentioned electrodeposition coating process, but in order to protect the coating layer (10), the sealing piece (6) may be attached by heat bonding in advance before the process. It is preferable to have it installed.

Effects of the Invention According to the present invention, in a can lid that is formed by punching from a laminated material containing a metal base material as described above and has a cutout opening serving as at least one drinking spout, the cut surface of the periphery of the opening Since the coating layer of the resin composition is formed on the surface of the container, it is possible to provide sealed packaging cans for packaging beverages containing CO2, etc., and other contents that cause corrosion of metals, for example, by imparting resistance to the contents. It can also be suitably used as can lids for aluminum cans, tin cans, composite cans, and the like.

Of course, the easy-open function of the sealing piece is not impaired, and there is no risk of the aforementioned feathering phenomenon occurring when the seal is opened. In addition, the formation of the coating layer is as follows:
Since this is applied by means of electrodeposition coating, the work process is simple and efficient, and since the coating film can be formed only on the necessary areas, the amount of resin material consumed is extremely small, reducing costs. Can be measured. In addition, because it uses electrodeposition coating, it is possible to simultaneously repair defects such as pinholes that may occur in the lid material, which not only prevents corrosion around the opening but also prevents corrosion from occurring from other defective areas. It becomes possible to provide high-quality can lids that are free from fear.

Example A daily drinking opening formed by punching out a laminated material having a protective layer made of a lacquer coating on one side of a base material made of aluminum foil and a heat-adhesive resin layer made of polyamide resin on the other side. After a sealing piece was attached in advance to the can lid, the exposed metal part, that is, the cut surface around the opening, was repaired and painted under the following electrolytic conditions.

The electrolytic conditions were as follows: an acrylic water-soluble paint containing water-soluble acrylic resin, melamine resin, solubilizer, etc. was used as the electrodeposition paint, and the solid content was adjusted to 7% and the pH was adjusted to 8°0, and the liquid temperature was 20°C.
℃ and a coating voltage of 200 V for 2 minutes. Thereafter, it was washed with water and heat-cured at 200° C. for 5 minutes.

By the above coating operation, a resin coating layer with a thickness of 13 μm could be formed on the cut surface. Therefore, this treated can lid has corrosion resistance for the contents and can be suitably used for packaging cans for various foods and drinks.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a can lid treated according to the present invention;
FIG. 2 is a sectional view of a laminated material used as a material for the can lid, and FIG. 3 is a schematic diagram showing the state of processing by an electrodeposition coating device. (A)...electrodeposition coating device, (1)...can lid, (2)
...Metal lid material, (3)...Outer surface protective layer, (4)...
・Thermoadhesive resin layer, (5)...opening, (6)...
Sealing piece, (10)...Resin composition coating layer. Above Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A cutout opening formed by punching out a laminated material having an outer protective layer provided on one side of a metal base material and a thermoadhesive resin layer provided on the other side, and forming at least one extraction port, etc. The processing target is a can lid in which the opening is sealed by thermal bonding from the outside with a removable sealing piece, and by applying electrodeposition coating to the can lid, the periphery of the opening is sealed. 1. A method for anticorrosion treatment of can lids, which comprises coating the cut surface of a can lid with a coating layer of an electrodeposited resin composition. (2) The method for anticorrosion treatment of can lids according to claim 1, wherein the thickness of the electrodeposited resin composition layer is in the range of 5 to 50 μm.