JP2012005916A - Method for manufacturing aluminum alloy-coated plate for can lid, and aluminum alloy-coated plate for can lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy-coated plate for a can lid which does not cause the defective appearances such as a blister defect and a dent defect, and has a coating film excellent in coating performances such as film adhesion and corrosion resistance, and to provide a method for manufacturing the aluminum alloy-coated plate for the can lid.SOLUTION: The method for manufacturing the aluminum alloy-coated plate for the can lid includes: a heating and drying process for drying an aluminum alloy plate to which a reaction type chemical conversion treatment has been applied for at least one second at an atmospheric temperature of 100-150°C; a cooling process for cooling the aluminum alloy plate after drying to a temperature of 60°C or less, spending ten seconds or more; and a film formation process for forming the coating film on a surface of the aluminum alloy plate by applying an aqueous coating material to the surface of the aluminum alloy plate after cooling, and baking the aqueous coating material to the surface of the aluminum alloy plate.

Description

  The present invention relates to a method for producing an aluminum alloy coated plate for can lids and an aluminum alloy coated plate for can lids.

  In general, an aluminum alloy coated plate is manufactured by a coil coating method in which a coating material is continuously applied to a coiled aluminum alloy strip and the coating material is baked on a metal surface. According to this coil coating method, it is possible to manufacture aluminum alloy coated plates with high production efficiency, so materials that can produce a large amount of industrial demand, such as can lid materials, building materials, and home appliance outer plates. Widely used in

  Conventionally, as a coating applied to an aluminum alloy strip, a solvent-based coating using an organic solvent as a solvent has been used because of excellent coating performance such as coating adhesion and corrosion resistance. However, solvent-based paints require expensive equipment for protecting and maintaining the work environment during painting and for treating exhaust gases containing organic harmful substances generated during drying. From the viewpoint, water-based paints containing water as a main component are being used instead of solvent-based paints.

  Also in aluminum alloy coated plates as materials for can lids, the switch from conventional solvent-based paints to water-based paints is steadily progressing due to the increase in regulations and public opinion on environmental problems. However, water-based paints are inferior in film performance such as film adhesion and corrosion resistance as compared with solvent-based paints. Therefore, in an aluminum alloy coated plate for can lids for beverage cans containing an acidic solution such as a carbonic acid-containing acidic liquid or fruit juice liquid, it is necessary to increase the thickness of the coating film in order to improve corrosion resistance. With such thickening of the water-based paint (coating film), the appearance defect of the blistering defect of the coating film called “Awa” or “Waki”, and the dent-like defect in which the metal substrate is exposed on the surface, The problem that coating film defects such as coating film peeling are likely to occur has been pointed out.

  As a method of manufacturing an aluminum alloy coated plate for can lids by a coil coating method using a water-based paint that is harmless to the environment, the surface of the aluminum alloy plate after pretreatment such as chemical conversion treatment is 150 ° C. A method is known in which the surface is dried and stabilized by heating as described above, and after cooling to 100 ° C. or lower, a water-based paint is applied. According to this method, although the adhesion of the coating film is reduced, the flowability of the water-based paint on the surface of the aluminum alloy plate is ensured to prevent the blistering defect of the coating film and to have an excellent appearance. It has been reported that a coated plate can be obtained (see, for example, Patent Document 1).

In addition, in the method for producing an aluminum alloy coated plate for can lids, which is similarly water-based and has a relatively thick coating (coating amount 40 to 200 mg / dm ² ), the coating is continuously baked after coating. When carrying out the process, the temperature rise rate of the aluminum alloy plate is adjusted to 5 to 120 ° C./second, so that the can lid does not have poor coating such as poor appearance even when using a water-based paint that requires a thick coating. It has been reported that an aluminum alloy coated plate can be obtained (for example, see Patent Document 2).

Further, the following methods are known as methods for producing an aluminum alloy coated plate for can lids, which also uses a water-based paint and has a relatively thick coating film. According to this method, the surface of the aluminum alloy plate subjected to the chromate treatment has a solid content of 20 to 40 mass (weight)%, an organic solvent amount of 10 to 30 mass%, the balance is made of an aqueous medium, and the surface tension is low. An aqueous paint having a weight of 26 to 29 mN / m is applied so that the weight after drying is 90 to 150 mg / dm ² . In the subsequent baking and drying step, the temperature of the aluminum alloy plate is set to 100 ° C. or less for 5 seconds after the start of baking drying, and 150 ° C. or less for 5 to 10 seconds. This is a method of baking and drying the surface of According to this method, it has been reported that a coating film excellent in corrosion resistance and coating surface properties can be obtained (see, for example, Patent Document 3).

  Furthermore, the following are known as a manufacturing method of the aluminum alloy coating plate for can lids which similarly used the water-based coating material. According to this method, 5 to 40 mass% of resin, 5 to 20 mass% of solvent, and 40 to 90 mass% of water are contained with respect to 100 mass% of water-based paint, respectively. An aqueous paint having a solvent component content of 2 mass% or less and a highly volatile component having a boiling point of less than 50 ° C. is substantially 0 mass%. This water-based paint is applied to an aluminum alloy plate, and after the start of baking of the coating film, baking is performed so that the surface of the aluminum alloy plate becomes 200 to 280 ° C. after 15 to 45 seconds, thereby suppressing the occurrence of foam defects. To do. According to this method, it has been reported that an aluminum alloy coated plate for can lids having a coating film excellent in coating performance such as corrosion resistance can be obtained (for example, see Patent Document 4).

Japanese Patent Laid-Open No. 11-290774 JP 11-319705 A JP 2002-219405 A JP 2007-126549 A

  However, according to the method for producing an aluminum alloy coated plate for can lids using any of the water-based paints described above, when coating is continuously performed from the chemical conversion treatment step, there is no appearance defect such as a blister defect or a dent defect, In addition, it has not been possible to stably obtain an aluminum alloy coated plate for can lids that satisfies coating film performance such as coating film adhesion and corrosion resistance.

  The present invention has been made in view of such problems, and there are no appearance defects such as blistering defects and dent defects, and the coating film is excellent in coating film performance such as coating film adhesion and corrosion resistance. It aims at providing the manufacturing method of the aluminum alloy coating plate for can lids which has these, and the aluminum alloy coating plate for can lids.

In order to achieve the above object, a method for producing an aluminum alloy coated plate for a can lid according to the first aspect of the present invention,
A drying step of drying the aluminum alloy plate subjected to the reactive chemical conversion treatment at an ambient temperature of 100 to 150 ° C. for 1 second or more;
A cooling step of cooling the aluminum alloy plate after the heat drying to a temperature of 60 ° C. or less over a time of 10 seconds or more;
A coating film forming step of forming a coating film on the surface of the aluminum alloy plate by applying an aqueous coating material to the surface of the aluminum alloy plate after cooling, and further baking the aqueous coating material on the surface of the aluminum alloy plate; Having
It is characterized by that.

  In the coating film forming step, the temperature of the aluminum alloy plate is increased to 230 to 280 ° C. over a period of 20 to 60 seconds after the start of baking of the water-based paint onto the surface of the aluminum alloy plate, and the temperature is increased. In this case, the time until the temperature of the aluminum alloy plate reaches 100 ° C. is 10 seconds or more, and the rate of temperature increase until the temperature of the aluminum alloy plate reaches 100 ° C. to 200 ° C. is 20 ° C./second or less. It is preferable to do.

Coating film formed on the surface of the aluminum alloy plate in the coating film forming step, it is preferable that the dry weight is 30~160mg / dm ^2.

An aluminum alloy coated plate for can lids according to the second aspect of the present invention is an aluminum alloy coated plate in the method for producing an aluminum alloy coated plate for can lids according to the first aspect of the present invention. The time until the temperature of the aluminum alloy plate reaches 100 ° C. is increased to 230-280 ° C. over a period of 20 to 60 seconds after the start of baking of the water-based paint onto the surface of the aluminum alloy plate. For 10 seconds or more, and the rate of temperature rise until the temperature of the aluminum alloy plate reaches from 100 ° C. to 200 ° C. is set to 20 ° C./second or less, and is formed on the surface of the aluminum alloy plate in the coating film forming step. The coating film is an aluminum alloy coated plate for can lids produced by setting the dry weight to 30 to 160 mg / dm ^2, and is present on the surface of the coating film The number of bulged defects having a diameter of 50 μm or more is 1 piece / cm ² or less, and there is no dent-like defect in which the aluminum alloy plate as a substrate is exposed on the surface of the coated plate.
It is characterized by that.

  According to the present invention, it is possible to obtain an aluminum alloy coated plate for a can lid which has no appearance defect such as a bulge-like defect or a dent-like defect, and which has a coating film excellent in coating film performance such as coating film adhesion and corrosion resistance. Can do.

It is a figure which shows one step of the feathering test method using the aluminum alloy coating board (resin coating aluminum material) for can lids. It is a figure which shows one step of the feathering test method following FIG. FIG. 3 is a diagram illustrating one step of the feathering test method following FIG. 2. FIG. 4 is a diagram illustrating one step of the feathering test method following FIG. 3.

  Hereinafter, the manufacturing method of the aluminum alloy coating plate for can lids and the aluminum alloy coating plate for can lids which concern on embodiment of this invention are demonstrated. Here, the reason why the use is set for “for can lid” and the aluminum alloy coated plate is that the aluminum alloy coated plate manufactured in the embodiment of the present invention is used as a lid member of a beverage can. The “aluminum alloy plate” in the present specification is a general term for a metal plate or an alloy plate mainly composed of aluminum metal, and is a concept including not only a so-called aluminum alloy plate material but also a pure aluminum plate material. is there.

  A pure aluminum material or an aluminum alloy material is used for the aluminum alloy plate according to the present embodiment. Here, 5000 series alloy, for example, 5021, 5052, 5182 etc. is used suitably for an aluminum alloy material.

In the present embodiment, a water-based paint is applied to the surface of the aluminum alloy plate subjected to the reactive chemical conversion treatment by a roll coater, and the water-based paint is baked on the surface of the aluminum alloy plate, thereby coating the surface of the alloy plate. Form.
As this reactive chemical conversion treatment, for example, a conventional chemical conversion treatment method, that is, a phosphate chromate treatment, a zirconium phosphate treatment, a titanium phosphate treatment, a zirconium oxide treatment and the like can be employed without particular limitation.

  Hereinafter, the manufacturing method of the aluminum alloy coating plate for can lids is demonstrated in detail. The manufacturing method of the aluminum alloy coating plate for can lids of this embodiment has an alkali degreasing process, a chemical conversion treatment process, a drying process, a cooling process, and a coating film formation process.

A. Alkaline degreasing treatment step The aluminum base material is preferably subjected to an alkaline degreasing treatment as a pretreatment for the chemical conversion treatment. Such an alkaline degreasing process can apply the degreasing liquid and degreasing method based on a prior art as it is. The alkaline degreasing solution is a solution in which an alkaline degreasing agent is dissolved or dispersed in a solvent such as water at a concentration of 0.5 to 2.0% by weight, for example, and has a pH of about 9 to 13 having etching properties. Used. The alkaline degreasing agent preferably contains an alkali builder, a surfactant, a chelating agent and the like.

  Examples of alkali builders include alkali metal carbonates such as Na carbonate and K carbonate; alkali metal hydroxides such as caustic Na; alkali metal phosphates such as Na phosphate and Na hydrogen phosphate; alkali metals such as Na silicate Silicates or the like; or a mixture thereof is used.

  Surfactants include polyoxyethylene surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers having a HLB (hydrophilic / lipophilic ratio) of about 8 to 11, and higher alcohol surfactants. Etc. are used. As the chelating agent, EDTA · 2Na salt, naphthylamine, or the like is used.

As for the etching amount of the aluminum base-material surface by an alkali degreasing process, about 60-300 mg / m < ² > is preferable. The amount of the oxide film formed on the aluminum base material by rolling is about 2 to 20 nm, and the thickness is not uniform. In order to completely remove this, and to completely remove contaminants such as residual rolling oil and aluminum wear powder on the surface of the substrate, it is desirable that the etching amount is 60 mg / m ² or more. However, if the etching amount exceeds 300 mg / m ² , not only the effect of removing the oxide film is not improved, but also sludge generation is accelerated, which is not preferable.

  The alkaline degreasing treatment is performed, for example, by spraying an alkali degreasing solution at 50 to 80 ° C. onto the aluminum substrate for 1 to 20 seconds, or applying an aluminum substrate to the alkali degreasing solution at 50 to 90 ° C. for 10 to 60 seconds. A dipping method is employed.

  After completion of the alkaline degreasing treatment, it is preferable to immediately perform washing with water. This is for preventing contamination of the subsequent processing liquid and removing alkali components, surfactants, reaction residues and the like on the surface of the aluminum substrate. In this water washing step, for example, a method of spraying ion-exchanged water or industrial water onto the aluminum substrate surface for 1 to 20 seconds is employed.

  After the rinsing step is completed, it is desirable to immediately move to the chemical conversion treatment step, which is the next step, before the aluminum substrate surface is dried. This is because once the surface of the aluminum substrate is dried, an aluminum natural oxide film is formed immediately. By forming such an aluminum natural oxide film, the reaction rate of forming a phosphate chromate film is reduced or non-uniform. As a result, a uniform phosphate chromate film is not formed over the entire aluminum substrate surface.

  Moreover, after completion | finish of a water washing process, you may give an acid washing | cleaning and water washing before the chemical conversion treatment process which is the next process. By this acid cleaning step, MgO present on the surface of the aluminum substrate can be removed. As the acid cleaning, for example, a method of spraying 2-5 mass% dilute sulfuric acid onto an aluminum substrate at 30-60 ° C. for 1-30 seconds or immersing the aluminum substrate for 10-60 seconds can be employed. After the completion of the acid cleaning, it is preferable to immediately perform washing with water in the same manner as after the alkaline degreasing treatment.

B. Chemical conversion process Here, the case where a phosphoric acid chromate process is performed as a reactive chemical conversion process is demonstrated. Of the phosphoric acid chromate treatment performed based on the prior art, the temperature of the treatment liquid is 30 to 60 ° C., the hydrofluoric acid concentration in the treatment liquid is 500 to 3000 ppm, and the Cr ⁶⁺ concentration (A) and the phosphoric acid concentration ( Processing conditions for controlling the ratio A / B of B) to 0.03 to 0.7 can be employed.

In addition, about the adhesion amount of a phosphoric acid chromate film | membrane converted to metal Cr, it is 5-50 mg / m < ² >, In the range which maintains the said conditions about a process liquid, Cr component density | concentration and hydrofluoric acid density | concentration in a process liquid In addition, it can be easily achieved by appropriately setting the treatment liquid temperature and the treatment time.

By the way, when the deterioration of the phosphoric acid chromate treatment solution proceeds, Cr ³⁺ ions increase in the treatment solution. It is desirable to manage Cr ³⁺ ions in a range as low as possible. Specifically, it is desirable to control the abundance ratio of Cr ³⁺ ions to all Cr ions to be less than 50%. This is because Cr ⁶⁺ ions are mainly involved in the phosphate chromate formation reaction, but Cr ³⁺ has an extremely fast deposition rate on the surface of the aluminum substrate, and therefore partially heterogeneous when Cr ³⁺ is present in a certain amount or more. A phosphate chromate film is easily formed. And when the abundance ratio of Cr ³⁺ ions with respect to all Cr ions exceeds 50%, the above heterogeneity appears more remarkably. Note that the density control of Cr ⁶⁺ ions and Cr ³⁺ ions, performs various online analysis, the replacement of part or all of the processing liquid if desired be carried by performing appropriate.

  It is preferable to immediately perform washing with water after the above chemical conversion treatment. This is to remove the chemical conversion treating agent component, reaction residue and the like on the surface of the aluminum substrate. In this water washing step, for example, a method of spraying ion-exchanged water or industrial water on the surface of the aluminum substrate for 1 to 20 seconds is employed. In addition, it is desirable to use ion-exchanged water for finishing the washing process in order to suppress the adhesion of impurities to the aluminum base material surface. Further, the washing water may be heated to promote drying.

C. Drying step After the reactive chemical conversion treatment, drying is performed to remove the washing water adhering to the surface of the aluminum alloy plate. In this drying step, heating of the aluminum alloy plate is not necessarily required, and a removal method using air such as air drying or air blow may be used. However, in the present embodiment, as an example, a coil coating method that is continuously performed from pretreatment to painting is adopted, and therefore it is necessary to perform drying in a short time in order to improve productivity. . Insufficient drying is not preferable because moisture remaining on the surface of the alloy plate becomes a gas when the coating film is baked and causes defective appearance such as blistering defects and dent defects.

  Therefore, it is necessary to perform sufficient drying before applying the water-based paint to the surface of the aluminum alloy plate. Here, if the surface temperature of the alloy plate is too high, the hydrate in the chemical conversion film will be dehydrated and the adhesion will be reduced. Therefore, as a result of diligent search, it was found that a good dry state can be obtained by performing heat drying at an ambient temperature of 100 to 150 ° C. for a time of 1 second or longer. If the atmospheric temperature is less than 100 ° C., it is necessary to lengthen the drying time, and it is difficult to obtain a good dry state with a continuous coating facility such as a coil coating method employed in this embodiment. On the other hand, if the atmospheric temperature exceeds 150 ° C., the temperature of the aluminum alloy plate becomes too high, and as described above, the hydrate in the chemical conversion film is dehydrated, and the problem of poor adhesion occurs. Absent. Further, the drying time is required to be at least 1 second in order to remove the washing water on the alloy plate almost completely. If the drying time is less than 1 second, a good dry state cannot be obtained. Furthermore, the drying time is desirably 20 seconds or less. If the drying time is too long, the productivity is lowered and the continuous coating equipment is enlarged. As a drying method in this case, hot air drying using an electric furnace, a gas furnace or the like is preferably used.

D. Cooling step After the surface of the aluminum alloy plate is dried, the aluminum alloy plate is cooled to a temperature of 60 ° C. or lower over a period of 10 seconds or longer. As described above, the cooling to a temperature of 60 ° C. or lower is because when the temperature of the alloy plate surface exceeds 60 ° C. after cooling, the coating after the water-based coating is applied is dried too quickly, and the water on the surface of the alloy plate is increased. This is because the fluidity of the paint is hindered and a uniform coating surface cannot be obtained. From such a viewpoint, it is preferable that the aluminum alloy plate is cooled to about 20 ° C. at room temperature. In addition, it is necessary to spend 10 seconds or more for the cooling here. In the case of less than 10 seconds, the moisture present on the surface of the aluminum alloy plate cannot be completely evaporated, and bulge defects and dent defects are likely to occur. From such a viewpoint, the cooling is preferably performed for 15 seconds or longer. Here, the cooling to 60 ° C. or lower is preferably natural cooling. If natural cooling is difficult due to the configuration of the continuous coating equipment, a cooling device can be provided separately.

E. Coating film forming process After the aluminum alloy plate is cooled, a water coat is applied to the surface of the alloy plate with a roll coater, and the applied aqueous paint is baked onto the surface of the alloy plate to form a coating film on the surface. .

  The water-based paint used here constitutes a dispersion system composed of a resin component and an organic solvent as a dispersoid, and water as a dispersion medium. Here, as the resin component, it is preferable to use at least one resin selected from the group consisting of an epoxy resin, an acrylic resin, a phenol resin, and a polyester resin. As the organic solvent, isobutyl alcohol, diethylene glycol monobutyl ether, propylene glycol monopropyl ether, ethylene glycol monobutyl ether, 3-methyl-3-methoxybutanol and the like can be used.

  In this coating film forming step, the time until the temperature of the aluminum alloy plate reaches 100 ° C. is 10 seconds when the temperature of the aluminum alloy plate is raised to 230-280 ° C. over 20-60 seconds after the start of baking. The temperature increase rate until the temperature of the aluminum alloy plate reaches 100 ° C. to 200 ° C. is preferably 20 ° C./second or less.

  Thus, when baking a water-based coating material on the surface of an aluminum alloy plate, it is preferable that the highest reached temperature (PMT) of an alloy plate shall be 230-280 degreeC. Here, if the maximum temperature reached is less than 230 ° C., baking may be insufficient. On the other hand, if it exceeds 280 ° C., overbaking will occur, and sufficient coating performance cannot be obtained.

  The baking time here is preferably 20 to 60 seconds. If the baking time is less than 20 seconds, the rate of temperature rise from the temperature of the aluminum alloy plate immediately after application of the water-based paint to a predetermined baking temperature in the range of 230 to 280 ° C. becomes too fast, “Waki” that is a trace of moisture bumping easily occurs. On the other hand, if the baking time exceeds 60 seconds, the baking time becomes too long, and the productivity is lowered particularly in high-speed coating. Moreover, in this baking process, it is preferable that time until the temperature of an aluminum alloy plate reaches 100 degreeC is 10 second or more. When the temperature of the aluminum alloy plate is reached to 100 ° C. in less than 10 seconds, the fluidity of the water-based paint on the surface of the aluminum alloy plate is hindered, and dents and streaks are likely to occur. Furthermore, it is preferable that the rate of temperature increase until the temperature of the aluminum alloy plate reaches 100 ° C. to 200 ° C. is 20 ° C./second or less. When the rate of temperature rise exceeds 20 ° C./second, bumping of moisture and solvent components in the paint occurs, and blistering defects are likely to occur.

In the coating film forming step, the coating film formed on the surface of the aluminum alloy plate is preferably dry coating weight is formed to have a 30~160mg / dm ^2. If it is less than 30 mg / dm ² , the corrosion resistance is insufficient. On the other hand, if it exceeds 160 mg / dm ² , the workability of the aluminum alloy plate is reduced and the coating film breakage when opening the can lid is poor. Become. In addition, the cost is increased, which is not preferable.

In the aluminum alloy coated plate obtained by the production method of the embodiment of the present invention, the number of blister defects having a diameter of 50 μm or more present on the coating film surface is 1 piece / cm ² or less. Further, there is no dent-like defect such that the aluminum alloy plate is exposed on the surface of the coated plate. Here, when there are 2 / cm ² or more bulged defects having a diameter of 50 μm or more, or when there are dent defects such that the aluminum alloy plate as a substrate is exposed on the surface of the coated plate, This is not preferable because it affects the coating performance such as corrosion resistance. Further, even if there are ² or more blisters / cm ² , the coating film performance is not affected when the diameter of each defect is less than 50 μm.

  According to the method for producing an aluminum alloy coated plate for can lids according to the present embodiment, appearance defects such as blistering defects and dent defects do not occur, and coating film performance such as coating film adhesion and corrosion resistance is also achieved. An aluminum alloy coated plate for can lids having a coating film having an excellent coating film, and a method for producing an aluminum alloy coated plate for can lids can be provided.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to Examples, Comparative Examples, and Reference Examples. The technical idea of the present invention is not limited to these examples.

(Examples 1-13, Comparative Examples 1-4, Reference Examples 1-4)
In each example, each comparative example, and each reference example, a plate-like JIS A5182-H19 alloy (plate thickness 0.25 mm) was used as the aluminum alloy plate. A degreasing treatment was performed on both surfaces of the aluminum alloy plate using a commercially available alkaline degreasing solution (manufactured by Nippon Paint Co., Ltd., Surf Cleaner 420N-2) as a pretreatment. Thereafter, a commercially available phosphoric acid chromate solution (manufactured by Nippon Paint Co., Ltd., Alsurf 48 and Alsurf 408) was subjected to a chemical conversion treatment of 20 mg / m ^{2 in} terms of metal Cr as the amount of phosphate chromate film (chemical conversion film). Thereafter, the aluminum alloy plate was washed with water.

Thereafter, the aluminum alloy plate was dried at the atmospheric temperature (° C.) and the drying time (second) shown in Table 1, and the alloy plate was cooled at the cooling time (second) and the plate temperature (° C.) after cooling shown in Table 1. . Furthermore, the water-based paint shown in Table 1 was applied to the surface of the aluminum alloy plate using a roll coater so that the coating amount shown in Table 1 was obtained. Then, the gas oven heating method at the maximum attained temperature (PMT) (° C.), baking time (second), 100 ° C. arrival time (second), and 100 ° C. to 200 ° C. heating rate (° C./second) shown in Table 1. The coating film was dried and baked in a drying oven to obtain an aluminum alloy coated plate. The coating amount (mg / dm ² ) of the water-based paint here was measured by a coating mass test method using sulfuric acid film removal. Specifically, a 100 mm × 100 mm aluminum alloy coated plate is immersed in concentrated sulfuric acid to dissolve the coating film on the surface, and the coating amount as the dry weight of the coating film is obtained from the difference in weight before and after the dissolution. It was. In each example, each comparative example, and each reference example, the obtained aluminum alloy coated plate was evaluated for blister defects, dent defects, corrosion resistance, adhesion, and openability (feathering test) by the methods described later. did. The evaluation results are shown in Table 1.

略語対照）ＰＭＴ：最高到達温度、
Ep-Acr：エポキシアクリル樹脂系水性塗料、
PlyEst：ポリエステル系樹脂水性塗料、
Ep-Phe：エポキシフェノール樹脂系水性塗料、

Abbreviation control) PMT: Maximum temperature reached,
Ep-Acr: Epoxy acrylic resin water-based paint
PlyEst: Polyester resin water-based paint
Ep-Phe: Epoxy phenol resin water-based paint

(Bulging defect)
The surface of the aluminum alloy coated plate after baking of the coating film was observed with an optical microscope at a magnification of 50 times, and the number of bulged defects having a diameter of 50 μm or more per 1 cm ^{2 of the} coated surface was measured. The case where the generated number was 1 or less was evaluated as pass (◯), and the case where 2 or more were generated was evaluated as reject (x).

(Dented defect)
The surface of the aluminum alloy coated plate after the coating is baked is observed at a magnification of 100 with a backscattered electron image with an acceleration voltage of 20 keV, and the substrate is observed white so that the aluminum alloy plate as a substrate is exposed on the surface of the coated plate. The number of dent-like defects generated per 1 cm ^{2 of the} painted surface was measured. The case where the generated number was 0 was evaluated as pass (◯), and the case where the number was 1 or more was evaluated as reject (x).

[Corrosion resistance]
A sample juice (0.5 wt% NaCl + 1 wt% citric acid aqueous solution) obtained by masking the periphery of a test piece cut out from an aluminum alloy coated plate after baking of the coating film using a polyester tape so that the evaluation area becomes 100 mm × 100 mm ) And kept at 70 ° C. for 72 hours. The subsequent corrosion state was observed with an optical microscope. As a result, it was evaluated by visual observation that a sample in which corrosion was not observed passed (◯) and a sample in which corrosion was found rejected (x).

[Adhesion]
Nylon film (manufactured by Daicel Finechem, Daiamide 7000 (model number), film thickness 30 μm) is sandwiched between two 5 mm x 150 mm test plates cut out from the aluminum alloy coated plate after baking of the coating film, and further using a hot press A test piece was prepared by pressure bonding at 210 ° C. for 30 seconds. About this test piece, the peeling strength when peeling at a speed of 200 mm / min was measured with a tensile tester. As a result, a peel strength of 1.5 kgf / 5 mm or more is acceptable (◎), 1.0 kgf / 5 mm or more and less than 1.5 kgf / 5 mm is acceptable (◯), and 0.5 kgf / 5 mm or more and less than 1.0 kgf / 5 mm is unacceptable. Pass (△) and less than 0.5 kgf / 5 mm were evaluated as fail (x).

[Openness (feathering test)]
Openness was evaluated by a feathering test. Specifically, as shown in FIG. 1, a pair of left and right cuts 2 a (upper end) with a spacing interval of 50 mm from one side to the inside of a test piece 1 (100 mm × 100 mm) of an aluminum alloy coated plate after baking of the coating film A straight notch 2a) in which the angle of the bent portion of 10 mm is 150 ° inward and the length of the straight portion below the bent portion is 66 mm was formed. Next, as shown in FIG. 2, the rectangular cut portion 2 formed between the pair of cuts 2a, 2a was bent to the surface opposite to the evaluation surface (the surface corresponding to the outer surface of the can lid). . In the bent state, it was immersed in boiling water at 100 ° C. for 30 minutes. Thereafter, the notch 2 is pulled upward (in the “pull” direction) at a speed of 200 mm / min with a tensile tester, and the notch 2 is torn from the main body of the test piece as shown in FIG. Formed. As shown in FIG. 4, the tear film 3 remained with the coating film 4 peeled off from the evaluation surface (the surface corresponding to the inner surface of the can lid). Referring to FIG. 4, the maximum value Wmax of the width (height) of the remaining coating film 4 is measured, and the case where the maximum value Wmax is less than 0.2 mm is acceptable (◎), 0.2 mm or more and 0.0. The case of less than 5 mm was evaluated as pass (◯), the case of 0.5 mm or more and less than 1.0 mm was rejected (Δ), and the case of 1.0 mm or more was evaluated as reject (x).

As shown in Table 1, Examples 1 to 13 all showed good results in all evaluation items (bulging defects, dent defects, corrosion resistance, adhesion, and openability).
On the other hand, each comparative example and each reference example were rejected for the reasons described below. In Comparative Example 1, the atmosphere temperature at the time of drying after the chemical conversion treatment was low at less than 100 ° C., the aluminum alloy plate surface was insufficiently dried, blistering defects and dent defects were generated, and the corrosion resistance was insufficient. Further, in Comparative Example 2, the atmosphere temperature during drying after the chemical conversion treatment was too high exceeding 150 ° C., so that the coating film adhesion and the openability were inferior, and the cooling was insufficient, and blistering defects were frequently generated. did. Moreover, in Comparative Example 3, the drying time was as short as less than 1 second, the surface of the aluminum alloy plate was insufficiently dried, swelling defects and dent defects were generated, and the corrosion resistance was insufficient. In Comparative Example 4, the cooling time was as short as less than 10 seconds, moisture remained on the aluminum alloy plate surface, and dent defects occurred frequently. Moreover, since the comparative example 5 was inadequately cooled, the blister-like defect occurred frequently. Further, in Reference Example 1, the initial temperature increase rate (100 ° C. arrival time) in coating film baking after coating of the paint became too fast, less than 10 seconds, and thus blister defects were frequently generated. Further, in Reference Example 2, the temperature increase rate from 100 ° C. in baking after coating of the paint became too high exceeding 20 ° C./second, and thus the blister defects could not be suppressed. Further, in Reference Example 3, since the coating amount was as small as less than 30 mg / dm ² , the corrosion resistance was insufficient. Furthermore, in Reference Example 4, since the coating amount was too thick exceeding 160 mg / dm ² , blistering defects were likely to occur, and the opening property was inferior.

  Various embodiments and examples can be made without departing from the broad spirit and scope of the present invention. The above-described embodiments and examples are for explaining the present invention and do not limit the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Test piece of aluminum alloy coating plate (resin-coated aluminum material) for can lid 2 Cut part 2a Cut 3 Tear part 4 Coating film

Claims (4)

A drying step of drying the aluminum alloy plate subjected to the reactive chemical conversion treatment at an ambient temperature of 100 to 150 ° C. for 1 second or more;
A cooling step of cooling the aluminum alloy plate after the heat drying to a temperature of 60 ° C. or less over a time of 10 seconds or more;
A coating film forming step of forming a coating film on the surface of the aluminum alloy plate by applying an aqueous coating material to the surface of the aluminum alloy plate after cooling, and further baking the aqueous coating material on the surface of the aluminum alloy plate; Having
A method for producing an aluminum alloy coated plate for can lids.   In the coating film forming step, the temperature of the aluminum alloy plate is increased to 230 to 280 ° C. over a period of 20 to 60 seconds after the start of baking of the water-based paint onto the surface of the aluminum alloy plate, and the temperature is increased. In this case, the time until the temperature of the aluminum alloy plate reaches 100 ° C. is 10 seconds or more, and the rate of temperature increase until the temperature of the aluminum alloy plate reaches 100 ° C. to 200 ° C. is 20 ° C./second or less. The manufacturing method of the aluminum alloy coating plate for can lids of Claim 1 characterized by the above-mentioned. The coating film formed on the surface of the aluminum alloy plate in the coating film forming step has a dry weight of 30 to 160 mg / dm ² . Production method. An aluminum alloy coated plate for a can lid produced by the production method according to claim 3, wherein the number of blisters having a diameter of 50 μm or more present on the surface of the coating film is 1 piece / cm ² or less, and An aluminum alloy coated plate for a can lid, characterized in that a certain aluminum alloy plate does not have a dent-like defect exposed on the surface of the coated plate.

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