JP3386143B2 - Resin-coated aluminum alloy plate for can lid - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin-coated aluminum alloy plate used as a can lid. More specifically, the present invention relates to a resin-coated aluminum alloy plate for a canopy having excellent coating adhesion and corrosion resistance.

BACKGROUND ART In recent years, as a material for cans, the conventional material in which a metal plate is formed into a can and then painted is replaced with a material in which the metal plate is pre-coated with a resin and formed into a can in consideration of environmental protection. Is progressing. The metal plate coated with a resin in advance is widely applied to a member for a can body, in particular, but it is also attempted to be applied as a material for a can lid as shown below.

For example, an aluminum material for a can described in JP-A-2-86433 is obtained by thermocompression-bonding a modified polyolefin resin as an adhesive layer and a polyolefin resin layer to a chromate-treated aluminum plate material at the time of opening the lid. Enamel feathering is less likely to occur. In addition, Japanese Patent Laid-Open No. 3-
Aluminum alloy composite material for can lids described in Japanese Patent No. 258534 is an aluminum alloy plate that has been subjected to a base treatment such as phosphoric acid chromate treatment, and an olefin resin film is attached using an olefin adhesive, and a score processing portion It is intended to prevent reduction in plate thickness.

Further, the can lid material made of a thermoplastic resin-coated steel sheet described in JP-A-6-312234 is obtained by scoring a plated steel sheet or a surface-treated steel sheet subjected to chemical conversion treatment such as chromate treatment, and then heat-treating the polyester resin or the like. It is coated with a plastic resin to improve the corrosion resistance of the scored portion. Further, the thermoplastic resin laminate lid described in JP-A-8-224628 is a tin-plated steel sheet plated with chromate, a nickel-plated steel sheet, a tin / nickel-plated steel sheet nickel-plated and then tin-plated, or metallic chromium and chromium. A crystalline saturated polyester resin film is laminated on an electrolytic chromic acid-treated steel sheet having a two-layer film of hydrated oxide formed thereon.

The aluminum material for cans described in JP-A-2-86433 and the aluminum alloy composite material for can lids described in JP-A-3-258534 are aluminum alloy plates coated with a chemical conversion coating such as a phosphoric acid chromate coating. Although a resin film such as an olefin resin film is laminated on, the adhesiveness between the metal substrate and the resin film, especially the processing adhesiveness, is sufficient compared with the case where the resin film is laminated on the above electrolytic chromic acid treated steel sheet. Instead, when extremely severe processing such as rivet processing is performed, the resin film may peel off.

On the other hand, the thermoplastic resin-coated steel sheet described in JP-A-6-312234 and the thermoplastic resin laminate lid described in JP-A-8-224628 are can lid materials using a steel sheet as a substrate, and an aluminum alloy sheet is used. Compared with a can lid material used as a substrate, it has excellent processing adhesion to a resin film, but has a difficulty in opening the lid, and its use is limited, and it is not widely used at present.

The present invention is to provide a resin-coated aluminum alloy plate for a can lid having excellent coating adhesion and corrosion resistance of the coated resin film, and a can lid manufactured using the resin-coated aluminum alloy plate for the can lid. To do.

DISCLOSURE OF THE INVENTION The resin-coated aluminum alloy plate for a can lid of the present invention has a film formed by silane treatment using a silane coupling on at least the surface of the aluminum alloy plate which is the inner surface of the can lid, and has a resin formed thereon. It is characterized by coating.

Further, the resin-coated aluminum alloy plate for a can lid of the present invention is formed by subjecting at least the inner surface of the can lid to a surface treatment film obtained by subjecting the surface to a silane treatment using a silane coupling agent. It is characterized in that it has a film and is further coated with a resin.

The surface treatment film of the resin-coated aluminum alloy plate is preferably a phosphoric acid chromate treatment film, a zirconium-based treatment film, or an alumite treatment film.

And it is desirable that the coating resin is a thermoplastic resin. The can lid of the present invention is characterized by using the above resin-coated aluminum alloy plate for a can lid.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to subject at least the inner surface of a can lid of an aluminum alloy plate to a silane treatment using a silane coupling agent, or a phosphoric acid chromate treatment, or a zirconium-based treatment. Alternatively, it is subjected to an alumite treatment and further subjected to the above-mentioned silane treatment, and then coated with a thermoplastic resin to obtain a resin lid-coated aluminum alloy plate for a can lid. It is preferable that the outer surface of the can lid is also coated with the above thermoplastic resin after forming any one of the above surface-treated coatings. Further, the present invention provides a can lid by pressing the resin-coated aluminum alloy plate for a can lid thus obtained.

Hereinafter, the present invention will be described in detail. First, the aluminum alloy plate used in the present invention is not particularly limited as long as it is an aluminum alloy plate that can be formed into a can lid as an object of the present invention, but from the viewpoint of cost and forming processability, Plate thickness widely used in forming 0.20 to 0.35
A 5000 series aluminum alloy plate of mm is preferable. In the present invention, the aluminum alloy plate is premised on being molded in a state of being covered with a thermoplastic resin film or the like, so that the moldability, the surface treatment property such as the surface chemical conversion treatment, and the coating film to be coated. It may be selected in consideration of the processing adhesion and the like.

Next, the surface treatment method of the aluminum alloy plate of the present invention will be described. First, the aluminum alloy plate is subjected to the following pretreatments including degreasing treatment, alkali treatment, and pickling. In the degreasing treatment, a commercially available degreasing agent is used to remove oil adhering to the surface of the aluminum alloy plate. The temperature of the treatment liquid is preferably in the range of 30 to 90 ° C, 40 to 80
The range of ° C is more preferable. As a treatment method, the aluminum alloy plate is immersed in the treatment liquid, or the treatment liquid is sprayed on the aluminum alloy plate. A treatment time of 1 to 30 seconds is sufficient, and a range of 3 to 15 seconds is more preferable.

Then, it is washed with water and alkali-treated. Alkali treatment is an alkali metal or ammonium hydroxide, carbonate,
An aqueous solution containing one or more compounds of bicarbonate, phosphate, silicate, and borate as a main component is used. In the alkali treatment, the oxide film formed on the surface of the aluminum alloy plate is removed. In some cases, the surface of the aluminum alloy plate may be etched. The concentration of the alkaline aqueous solution used is preferably in the range of 1 to 20%, more preferably in the range of 2 to 10%. The temperature of the treatment liquid is preferably 30 to 80 ° C, more preferably 40 to 60 ° C. As a treatment method, the aluminum alloy plate is immersed in the treatment liquid, or the treatment liquid is sprayed on the aluminum alloy plate. Processing time of 1 to 20 seconds is enough, and 3
The range of up to 10 seconds is more preferable.

Then, it is washed with water and pickled. For pickling, an aqueous solution whose main component is one or more inorganic acids of sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid is used. The pickling is performed to remove the smut formed on the surface of the aluminum alloy plate by the alkali treatment, but in some cases, fine holes may be simultaneously formed on the surface of the aluminum alloy plate.
The aqueous solution concentration of the acid used is preferably in the range of 1 to 10%, 1
The range of up to 5% is more preferable. The temperature of the treatment liquid is preferably room temperature to 60 ° C, more preferably room temperature to 40 ° C. As a treatment method, the aluminum alloy plate is dipped in an aqueous solution of acid, or the aqueous solution of acid is sprayed on the aluminum alloy plate. A processing time of 1-10 seconds is sufficient,
The range of 1 to 5 seconds is more preferable. With the above, the preprocessing is completed.

After performing the above-mentioned pretreatment, this treatment is performed. In the present invention, any one of silane treatment using a silane coupling agent, further silane treatment after phosphoric acid chromate treatment, further silane treatment after zirconium treatment, and further silane treatment after alumite treatment is performed. First, the silane treatment will be described. In the silane treatment of the present invention, a commercially available silane coupling agent is diluted with a solvent, coated on an aluminum alloy plate and dried. Although water alone can be used as the solvent, it is preferable to use a mixed solvent of ethanol and water. For example, the mixing ratio of water and ethanol is water: ethanol = 1: 4 to 4: 1, preferably 1 :.
Good results are obtained with a mixed solvent of 2 to 2: 1. When the mixing ratio of ethanol to water is more than 1: 4, the silane coupling agent is sufficiently and uniformly dispersed in the mixed solution, but ethanol is expensive and is not advantageous in cost. On the other hand, when the mixing ratio is less than 4: 1, the silane coupling agent is not sufficiently uniformly dispersed in the mixed solution, and it takes a long time to dry after being applied on the surface of the aluminum alloy. The concentration of the silane coupling agent is preferably in the range of 0.5 to 20%, more preferably 1 to 10% with respect to the mixed solution. If it is less than 0.5%, the coating state after drying tends to be non-uniform, and sufficient adhesion cannot be obtained. If it exceeds 20%, the effect of improving the adhesion is saturated, which is not advantageous in terms of cost. The temperature of the treatment liquid is preferably room temperature to 60 ° C, more preferably room temperature to 40 ° C. As a treatment method, after immersing the aluminum alloy plate in the treatment liquid, the excess liquid is squeezed by a roll and then dried. Immersion time is 1-15
Seconds are sufficient, and a range of 3 to 10 seconds is more preferable. The treatment amount is preferably 0.3 to 30 mg / m ² as silicon.
The range of up to 10 mg / m ² is more preferred.

Next, the process of performing the silane treatment after the phosphoric acid chromate treatment will be described. For the phosphoric acid chromate treatment, a commercially available phosphoric acid chromate treatment liquid is used, and dipping treatment or spray treatment is performed. The temperature of the processing solution is room temperature to 80
The range of 0 ° C is preferable, and the range of room temperature to 60 ° C is more preferable. A treatment time of 1 to 10 seconds is sufficient, and a range of 1 to 5 seconds is more preferable. Coating amount is preferably in a range of from 3 to 50 mg / m ² as chromium, the range of 5 to 30 mg / m ² is more preferable.
When the coating amount of chromium is less than 3 mg / m ² , there is almost no effect on the improvement of adhesion, and when it exceeds 50 mg / m ² , the adhesion amount increases and the coating becomes uneven locally, resulting in poor adhesion. The appearance becomes dark brown, which is not preferable. After the phosphoric acid chromate treatment, the above silane treatment is performed.

Next, the treatment of further performing the silane treatment after the zirconium treatment will be described. As the zirconium-based material, a commercially available zirconium-based processing liquid is used and subjected to dipping treatment or spraying treatment. The temperature of the treatment liquid is preferably room temperature to 60 ° C, more preferably room temperature to 45 ° C. A treatment time of 3 to 40 seconds is sufficient, and a range of 10 to 30 seconds is more preferable. Coating amount is preferably in a range of from 3 to 30 mg / m ² on a zirconium, a range of 7~15mg / m ² is more preferable. After the zirconium-based treatment, the above-mentioned silane treatment is performed.

Next, the process of further performing the silane treatment after performing the alumite treatment will be described. The alumite treatment carried out in the present invention is different from the alumite treatment for obtaining a thick film which does not require processability which is usually carried out after the molding process, and the film coated on the alumite treatment layer is What is required is a film that has excellent adhesion even when subjected to severe molding and that can obtain a thin processed film that can be continuously processed in a short time. As an alumite treatment that satisfies this requirement, the method of anodic oxidation by direct current electrolysis in an acid solution is most preferable. In the method using an alkaline solution, it takes a long time to wash and remove the alkaline solution remaining on the surface of the aluminum alloy plate after the treatment, and the adhesion of the film coated thereon is not sufficient. Further, the AC electrolysis method requires a long time to form an alumite film and is not suitable for high-speed treatment. As one aspect of the alumite treatment of the present invention, a solution obtained by adding borax to an aqueous boric acid solution is used as the acid solution. The concentration of boric acid is preferably in the range of 5 to 100 g / l. When it is less than 5 g / l, the conductivity of the treatment liquid is low, the treatment current density cannot be increased, and it takes a long time to form a treatment film having a predetermined thickness, which is not preferable. On the other hand, 10
If it exceeds 0 g / l, the amount that adheres to the aluminum alloy plate and is carried out of the treatment tank during continuous treatment increases, which is not advantageous in terms of cost. It is preferable to add borax at a concentration of 1 to 10 g / l to this boric acid solution because the treatment bath is stabilized. The bath temperature is preferably in the range of room temperature to 60 ° C. The anode current density is preferably in the range of 2.5~50A / dm ^2, a range of 3~20A / dm ² is more preferable. When the anode current density is less than 2.5 A / dm ² , it takes a long time to form a film, which is not preferable in terms of productivity.
Also, it is difficult to form a uniform thin film. On the other hand, 50A / dm ²
If it exceeds, the electrolysis voltage becomes too high and uneven appearance such as burning is likely to occur, and it is difficult to form a uniform thin film. The time required for electrolysis is 0.1 to 10 seconds, and a sufficiently thick film can be obtained. After the alumite treatment, the above silane treatment is performed.

In the present invention, when a thermoplastic resin is coated on the aluminum alloy plate subjected to the above surface treatment, the thermoplastic resin to be coated is polyethylene, polypropylene,
One of polyester, polyamide, polycarbonate, polyvinyl chloride, polyvinylidene chloride, acrylic resin,
Examples thereof include a copolymer resin of two or more kinds, or a composite resin in which two or more kinds are blended. Polyester is particularly preferable for the present invention, and polyethylene terephthalate, a copolymerized polyester mainly composed of ethylene terephthalate units, a polyester mainly composed of butylene terephthalate units, and a film composed of a composite resin in which these are blended are applicable, and It is more preferable to use a biaxially oriented film of resin. Further, when impact processability is required, a film made of a composite resin obtained by blending the above polyester with bisphenol A polycarbonate, or a two-layer film having the above composite resin as an upper layer and the above polyester as a lower layer, Further or preferably, a three-layer film having the above polyester as an upper layer and a lower layer and the above bisphenol A polycarbonate as an intermediate layer is used.

The thickness of the above-mentioned thermoplastic resin layer should be selected based on the required characteristics, but in general, the range of 5 to 300 µm is preferable, and the range of 10 to 250 µm is more preferable.
When the thickness is less than 5 μm, the coating work on the aluminum alloy plate becomes extremely difficult, and pinholes are apt to occur after coating or after molding, and sufficient corrosion resistance cannot be obtained. On the other hand, when it exceeds 300 μm, it is not advantageous in terms of cost as compared with a film coated with paint.

If necessary, additives such as a stabilizer, an antioxidant, an antistatic agent, a pigment, a lubricant and a corrosion inhibitor may be added to the above thermoplastic resin.

Adhesion of the above thermoplastic resin to the aluminum alloy plate, if the adhesion after particularly severe processing is not sufficient, or if the thermoplastic resin layer alone cannot secure sufficient corrosion resistance, from the thermosetting resin An adhesive such as, for example, an epoxy-phenolic adhesive is applied to an aluminum alloy plate and then coated with a thermoplastic resin, or the adhesive is previously applied to the adhesive surface of the thermoplastic resin to be coated with the aluminum alloy plate. Alternatively, the aluminum alloy plate may be coated.

The thermoplastic resin is an extrusion method in which the resin is heated and melted and directly extruded and laminated on the aluminum alloy plate, or a biaxially oriented film of the thermoplastic resin is brought into contact with an aluminum alloy plate heated to a temperature equal to or higher than the melting point of the resin. The coating can be performed by any of the film laminating methods in which both are sandwiched by a pair of rolls and laminated.

  Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example) Both surfaces of an aluminum alloy plate (JIS5052) having a plate thickness of 0.26 mm were subjected to degreasing treatment, alkali treatment and pickling pretreatment under the conditions shown below. After that, surface treatment was performed under the conditions shown in Tables 1 to 7.

[Pretreatment conditions] ・ Degreasing treatment Commercially available degreasing agent heated to 80 ° C (Surf Cleaner 32
The aluminum alloy was immersed in a 3% by weight aqueous solution of 2N-8 (manufactured by Nippon Paint Co., Ltd.) for 15 seconds, washed with water, and then dried.

・ Alkaline treatment In a 5% aqueous sodium hydroxide solution heated to 50 ° C,
The degreased aluminum alloy plate was dipped for 10 seconds, washed with water, and then dried.

-Pickling The aluminum alloy plate subjected to the alkali treatment was dipped in 1% sulfuric acid at room temperature for 3 seconds, washed with water, and then dried.

24 aluminum alloy plates that have been subjected to these surface treatments
Heat to 0 ° C and apply polyethylene terephthalate 8 on both sides.
A film obtained by biaxially stretching a copolymerized polyester consisting of 8 mol% and polyethylene isophthalate 12 mol% and heat-setting (the surface which will be the inner surface of the can lid after being molded into the can lid described later: thickness 25 μm, can The surface that will be the outer surface of the lid: thickness 15 μm) is brought into contact at the same time, the film and the aluminum alloy plate are sandwiched by a pair of rolls to be laminated, immediately immersed in water and rapidly cooled,
It was then dried.

The polyester film-coated aluminum alloy plate obtained as described above was evaluated by the test methods shown below. The evaluation results are shown in Tables 8-9.

[Processing adhesion of resin coating] Width 20m from polyester resin coated aluminum alloy plate
A strip-shaped test piece with a length of 100 mm and a length of 100 mm was cut out, and one end in the length direction was bent 180 ° at 3 mmR so that the side that would become the inner surface of the can lid was the outside. The peeling condition of the polyester resin in the processed portion was visually evaluated.

[Corrosion resistance] The processed part of the above-mentioned test material was immersed for 30 days in a saline solution of 38 ° C whose pH was adjusted to 3.0 with citric acid and sodium citrate, and the corrosion state was visually evaluated.

  The evaluation results are shown in Tables 8-9.

Sample Nos. 1 to 21 (Examples) are the case of the film-coated plate obtained by coating the surface-treated aluminum alloy plate of the present invention with the polyester film, and all of them show excellent work adhesion and excellent corrosion resistance. . On the other hand, sample numbers 22 to 35
(Comparative Example) is a case of a film-coated plate obtained by coating a polyester film on a conventional aluminum alloy plate subjected to surface treatment, and none of them has the processing adhesion and corrosion resistance of the resin film of the present invention.

INDUSTRIAL APPLICABILITY The present invention has a can formed by coating a resin on a surface of at least an inner surface of a can lid of an aluminum alloy plate, the coating having a silane treatment using a silane coupling. A resin-coated aluminum alloy plate for the lid, or a film formed by phosphoric acid chromate treatment, zirconium-based treatment, or alumite treatment is formed, and a silane-treated film is formed on top of this, and a resin is further formed on it. It is a resin-coated aluminum alloy plate for a can lid formed by coating, and has excellent process adhesion of the resin even after being formed into a can lid, and exhibits excellent corrosion resistance.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI C25D 11/18 C25D 11/18 A (56) Reference JP-A-4-66173 (JP, A) JP-A-63-149387 ( JP, A-61-52369 (JP, A) -JP-A-7-266496 (JP, A) JP-A-8-27563 (JP, A) JP-A-62-52045 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B32B 15/08 C23C 22/00-22/86

Claims (3)

(57) [Claims] 1. An aluminum alloy plate is subjected to phosphoric acid chromate treatment with a coating amount of chromium of 3 to 50 mg / m ^{2 on} both sides, or with a coating amount of zirconium of 3
A surface treatment film is formed by applying a zirconium-based treatment of up to 30 mg / m ² and a silane coupling agent is added on it, water: ethanol = 1:
In a mixed solvent of 4 to 4: 1, the coating amount is 0.3 to 30 mg / m ² as silicon by immersing in a treatment solution diluted so that the concentration of the silane coupling agent is 0.5 to 20% with respect to the mixed solvent. Which is a silane-treated film, on which polyethylene terephthalate, a copolymerized polyester mainly composed of ethylene terephthalate units, a polyester mainly composed of butylene terephthalate units, or a composite resin in which these are blended is formed. A resin-coated aluminum alloy plate for a can lid, comprising a resin layer having a thickness of 5 to 300 μm laminated and coated by heat-melting a resin composed of (3) and extruding the resin film directly onto an aluminum alloy plate. ^2. A phosphorous chromate treatment with a coating amount of chromium of 3 to 50 mg / m ² is applied to both surfaces of an aluminum alloy plate, or a coating amount of zirconium is 3 to 50 mg / m ^2.
A surface treatment film is formed by applying a zirconium-based treatment of up to 30 mg / m ² and a silane coupling agent is added on it, water: ethanol = 1:
In a mixed solvent of 4 to 4: 1, the coating amount is 0.3 to 30 mg / m ² as silicon by immersing in a treatment solution diluted so that the concentration of the silane coupling agent is 0.5 to 20% with respect to the mixed solvent. A silane-treated film to form a film, on which polyethylene terephthalate, a copolymerized polyester mainly composed of ethylene terephthalate units, a polyester mainly composed of butylene terephthalate units, or a composite resin in which these are blended is formed. A resin for a can lid, characterized in that the resin film is brought into contact with an aluminum alloy plate heated to a temperature higher than the melting point of the resin and is sandwiched by a pair of rolls, and a resin layer having a thickness of 5 to 300 μm is laminated and covered. Coated aluminum alloy plate. 3. A can lid manufactured using the resin-coated aluminum alloy plate for a can lid according to claim 1 or 2.