JP5095932B2 - Resin-coated aluminum plate and method for producing the same - Google Patents

Description

  The present invention relates to a resin-coated aluminum plate obtained by coating a resin paint or laminating a resin film on at least one surface of a base material made of an aluminum plate or an aluminum alloy plate, and in particular, after a molding process such as press molding. The present invention relates to an aluminum alloy plate for can lids having excellent film adhesion.

  Aluminum plates or aluminum alloy plates are lightweight, have appropriate mechanical properties, and have excellent aesthetics, moldability, corrosion resistance, etc., so they can be used in various containers, structural materials, machine parts, etc. Widely used. In particular, a molding process in which a coil-shaped aluminum alloy plate is continuously supplied to a press machine is excellent in productivity, and is therefore widely used in the above applications.

  The aluminum plate or aluminum alloy plate for the above uses is coated with a resin paint or laminated with a resin film on its surface to further improve corrosion resistance and elution resistance, improve appearance, and prevent scratches. Often done. In this case, the aluminum plate or the aluminum alloy plate is generally subjected to some surface treatment (for example, phosphate chromate, chromate chromate, zirconium phosphate, etc.). In the case of an aluminum can lid, a so-called pre-coating method is often employed in which an aluminum plate or an aluminum alloy plate as a material is subjected to a base treatment and a resin coating and then molded.

  The precoat type can lid aluminum plate or aluminum alloy plate is required to have resin adhesion so that the resin does not peel off during molding and corrosion resistance that does not erode even when exposed to a corrosive atmosphere. For this reason, many methods have been proposed for improving the background processing methods by devising them.

  For example, in Patent Document 1, in a resin-coated aluminum material in which a resin film is provided on an aluminum material, a chemical film P2 having good adhesion to aluminum is provided on the aluminum material 1, and the chemical film P2 is formed on the chemical film P2. There is disclosed a resin-coated aluminum material excellent in workability, in which a chemical conversion film Q3 is provided that adheres well to both the film P2 and the resin film 4, and the resin film 4 is provided thereon.

Patent Document 2 discloses a surface-treated aluminum alloy composite plate for a can having a core material layer and a skin material layer, wherein a film is laminated on at least one of the outer surface of the core material layer and the skin material layer. The material layer is made of pure aluminum having an Al purity of 99.7% by weight or more. On the outer surfaces of the skin material layer and the core material layer, the flat portion is less than 90%, the surface area is 2 cm ² or more per 1 cm square, and from the flat portion. Surface-treated aluminum alloy for cans, provided with a phosphoric acid chromate-treated film roughened so as to have a recess having a depth of 0.05 to 0.5 μm, and the film laminated on the phosphoric acid chromate-treated film A composite plate is disclosed.

Furthermore, Patent Document 3 discloses that both surfaces of an aluminum alloy plate are subjected to a phosphoric acid chromate treatment with a coating amount of 3 to 50 mg / m ² as chromium, or a zirconium system with a coating amount of 3 to 30 mg / m ² as zirconium. A surface treatment film is formed by performing a treatment, and a silane coupling agent is added to the mixed solvent of water: ethanol = 1: 4 to 4: 1, and the concentration of the silane coupling agent with respect to the mixed solvent. Is immersed in a treatment solution diluted to 0.5 to 20% to form a film formed by silane treatment with a film amount of 0.3 to 30 mg / m ² as silicon, and polyethylene terephthalate is further formed thereon. Copolymer polyesters mainly composed of ethylene terephthalate units, polyesters mainly composed of butylene terephthalate units, or composite resins blended with these. The aluminum alloy plate directly by heating and melting a resin consisting of or displacement extruding a resin film, a resin layer having a thickness 5~300μm resin-coated aluminum alloy sheet for can lid formed by laminating the coating is disclosed.
JP 2001-295066 A Japanese Patent No. 3229511 Japanese Patent No. 3386143

  However, such conventional techniques have the following problems. That is, depending on the contents filled in the can, the resin coating film may be made thicker with emphasis on corrosion resistance and barrier properties. In this case, internal stress of the resin coating film during processing is likely to accumulate. Become. If the internal stress exceeds the resin adhesion, the resin coating film may be peeled off. In particular, when a retort treatment is applied after processing, this tendency is remarkable, and even if the adhesion improving techniques represented by the above Patent Documents 1 to 3 are used, peeling of the resin coating film is not necessarily solved. There wasn't. In addition, Patent Documents 1 and 3 need to perform different chemical conversion treatments twice, and Patent Document 2 inevitably increases costs due to the addition of processes, such as the necessity of a material cladding process. In view of the above problems, there has been a demand for a cheaper and simpler means for improving resin adhesion.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have formed a resin after molding processing when an aluminum hydrate oxide exceeding a predetermined amount is formed in the chemical conversion film in the pretreatment step of chemical conversion treatment. The present inventors have found that the adhesiveness is remarkably lowered, and found a pretreatment method for suppressing such aluminum hydrated oxide below the predetermined amount, thereby completing the present invention.

According to a second aspect of the present invention, as shown in claim 1, a step of subjecting at least one surface of a substrate made of an aluminum plate or an aluminum alloy plate to an alkaline degreasing treatment, a step of washing the alkaline degreasing treatment surface, And a step of forming a resin coating film on the surface of the chemical conversion treatment. A method for producing a resin-coated aluminum plate for a can lid, wherein the cleaning treatment step is performed on the surface of the alkaline degreasing treatment. the method comprising spraying a 30 to 80 ° C. of the cleaning liquid, a spray injection amount is 3 to 50 per second l / ^{m 2,} and spraying pressure are 1.0~3.5kgf / cm ^2, washed A method for producing a resin-coated aluminum plate for a can lid, wherein the pH in the vicinity of the surface of the aluminum substrate is lowered to 8 or less within 3 seconds after the start .

According to a second aspect of the present invention, in the first aspect, the base material made of the aluminum alloy plate is a 5000 series alloy. Further, the present invention provides, in claim 3, in claim 1 or 2, wherein the cleaning liquid is a complex-forming substance having a stability constant K _A with aluminum ions (Al ³⁺ ) of log K _A ≧ 15 to 0.05 to 0.00. The content was 5 mol / liter.

  Since the characteristic of the chemical conversion film used for the resin-coated aluminum plate according to the present invention is remarkably improved as compared with the prior art, high resin adhesion after molding of the aluminum can lid can be ensured. In addition, since the conventional chemical conversion treatment process can be used as it is, it is possible to provide a resin-coated aluminum plate that is simple in manufacturing process and inexpensive in manufacturing cost. Such a manufacturing method is extremely industrially. Useful.

  The resin-coated aluminum plate according to the first aspect of the present invention is the production method according to the second aspect of the present invention, that is, the surface of the aluminum substrate is subjected to alkali degreasing treatment, and then the alkali degreasing surface is sprayed under predetermined conditions. It is obtained by subjecting the surface of the cleaning treatment to a chemical conversion treatment to form a chemical conversion film, and finally forming a resin coating film on the chemical conversion film. Hereinafter, the present invention will be described in detail.

A. Aluminum base material As the base material of the resin-coated aluminum plate used in the present invention, a pure aluminum material and an aluminum alloy material are used, and can be appropriately selected according to the application and required characteristics. As the aluminum alloy material, 1000 series, 3000 series, 5000 series, and the like are used. For can lids, it is preferable to use a 5000 series alloy excellent in strength and moldability.
In the present invention, the term “aluminum” is intended to include both pure aluminum and aluminum alloys, and the term “aluminum substrate” is intended to include both pure aluminum substrates and aluminum alloy substrates. The term “aluminum plate” is intended to include both pure aluminum plates and aluminum alloy plates.
In the present invention, an aluminum material is used as the base material. However, other base materials such as metals, alloys, ceramics, and plastics other than aluminum can be used.

B. Aluminum hydrate oxide content and adhesion in the conversion coating Chemical conversion coatings obtained by conventional chemical conversion treatment, especially inorganic reaction type conversion coatings typified by phosphate chromate, etc. On the other hand, it is hard and brittle, but has a problem in processing adhesion. Specifically, when subjected to strong processing such as overhang molding or rivet processing, the chemical conversion film cannot follow the deformation of the material, and a crack is generated in the chemical conversion film. There was a problem that the resin coating film peeled off. In particular, when retorting is performed after molding, there is a problem that moisture enters the cracks of the chemical conversion film, and the resin coating film is more easily peeled off from the chemical conversion film.

  The inventors of the present invention conducted a cross-sectional observation of the chemical conversion film after intensive processing with a TEM (transmission electron microscope) or the like. Found out that it would occur. For this reason, it was found that when a force in the vertical direction is applied to the resin coating film, the resin coating film easily peels from the crack portion.

As a result of various investigations on the cause of the occurrence of such cracks, in the resin-coated aluminum plate, when the aluminum hydrated oxide contained in the chemical conversion film after forming the resin coating film is 100 mg / m ² or less, It was found that cracks hardly occur. If the aluminum hydrated oxide contained in the chemical conversion film is 100 mg / m ² or less, the resin coating film continues to adhere to the aluminum base material even when a strong vertical processing force is applied to the resin coating film. Therefore, high adhesion can be maintained even after strong processing.

This is because when the content of the aluminum hydrated oxide in the chemical conversion film of the resin-coated aluminum plate is 100 mg / m ² or less, the network structure of the chemical conversion film molecules is regularly formed without interposing the aluminum hydrated oxide. This is probably because a strong chemical conversion film is formed. On the other hand, when the content of the aluminum hydrate oxide exceeds 100 mg / m ² , a hard and brittle network structure is formed in which the aluminum hydrate oxide molecules intervene in the network structure of the chemical conversion film molecules. As a result, it is considered that parallel cracks occur in the chemical conversion film during strong processing, resulting in a decrease in adhesion.

  By the way, most of the aluminum hydrated oxides which are problematic in the above are formed at the stage of pretreatment prior to chemical conversion treatment. In general, as a pretreatment for the chemical conversion treatment, a degreasing / etching process using an alkaline degreasing agent is performed, and the rolling oil, wear powder, oxide film, and the like on the surface of the aluminum plate are removed. And it turned out that most aluminum hydrated oxide is produced | generated in the washing | cleaning process after completion | finish of this alkali degreasing process, and such aluminum hydrated oxide is taken in in a chemical conversion film during chemical conversion treatment. Therefore, the aluminum hydrated oxide contained in the chemical conversion film can be reduced by suppressing the formation of the aluminum hydrated oxide in the cleaning treatment step.

C. Alkaline degreasing process The alkali degreasing process can apply the degreasing liquid and the 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 includes an alkali builder, a surfactant, a chelating agent, and the like. As such an alkaline degreasing agent, for example, trade name “SC-EC370” manufactured by Nippon Paint Co., Ltd. can be used.

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.
As surfactants, polyoxyethylene surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers having a HLB (hydrophilic-lipophilic ratio) = 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. Since the amount of the oxide film on the aluminum base material produced by rolling is in the range of several tens to several hundreds mg / m ² , the oxide film removal is insufficient when the etching amount is less than 60 mg / m ² , and the etching amount is 300 mg / m 2. Exceeding ² is not preferable because not only the effect of removing the oxide film is not improved, but also sludge generation is accelerated.

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

D. Cleaning process A cleaning process is performed following the alkali degreasing process. As described above, the pH of the alkaline degreasing agent is 9 or higher, and the pH in the vicinity of the surface of the aluminum substrate immediately after completion of the alkaline degreasing is naturally 9 or higher. At this point, aluminum is only dissolved in the degreasing liquid remaining on the substrate surface. However, when the cleaning process is started and the cleaning water comes into contact with the surface of the aluminum substrate, the pH in the vicinity of the surface of the aluminum substrate becomes a weak alkaline region of 8-9. The solubility of aluminum at such a weak alkaline pH is very low. Therefore, when the cleaning treatment is started and the pH in the vicinity of the surface of the aluminum substrate is lowered to a weak alkali of 8-9, aluminum dissolved in a state of pH 9 or higher is precipitated as aluminum hydrated oxide. The aluminum hydrated oxide thus deposited forms a new hydrated oxide layer on the surface of the aluminum substrate. This hydrated oxide layer is incorporated into the chemical conversion film in the chemical conversion treatment step, and as a result, the resin adhesion after processing of the resin-coated aluminum plate is lowered. Therefore, in order to prevent the formation of the aluminum hydrated oxide layer, it is necessary to lower the pH in the vicinity of the surface of the aluminum substrate to 8 or less in the water washing treatment step.

  In order to lower the pH in the vicinity of the surface of the aluminum substrate after completion of the alkali degreasing treatment step to 8 or less in the cleaning treatment step, a method of supplying a large amount of cleaning liquid at a predetermined temperature onto the aluminum substrate at a stretch is adopted. . Specifically, a method in which the cleaning liquid is sprayed onto the surface of the aluminum substrate is preferably used.

The spray injection conditions are preferably a spray injection amount of 3 to 50 liters / m ² per second and a spray injection pressure of 1.0 to 3.5 kgf / cm ² . When the spray amount of the cleaning liquid is less than 3 liters / m ² per second or when the spray spray pressure is less than 1.0 kgf / cm ² , the pH in the vicinity of the aluminum substrate surface cannot be rapidly reduced to 8 or less. As a result, formation of new aluminum hydrated oxide is promoted, which is not preferable. On the other hand, even if the spraying amount of the cleaning liquid exceeds 50 liters / m ² , the effect of lowering the pH is saturated, and the production cost increases as much water is consumed, which is not preferable. Further, when the spray injection pressure exceeds 3.5 kgf / cm ² , it is not preferable because not only the effect of lowering the pH is saturated but also strengthening of piping and the like to withstand high pressure is required, which is uneconomical.

  In addition, although a dip (immersion) method is also mentioned as a cleaning treatment method, since the pH lowering rate on the aluminum base material becomes slow, a rapid pH lowering effect as in the spray injection method cannot be obtained. However, by using an immersion bath equipped with a stirrer, or using a flowing water type immersion bath, it is possible to promote the dissolution and diffusion of the alkaline component in the cleaning liquid on the alkaline degreasing surface of the aluminum substrate, thereby spraying. It is possible to obtain a rapid pH lowering effect as in the method.

  About the temperature of a washing | cleaning liquid, it selects in the range of 30-80 degreeC. This is because if a cleaning solution exceeding 80 ° C. comes into contact with a fresh aluminum substrate surface that has undergone the degreasing / etching process, the aluminum and water react with each other to generate a new pseudoboehmite-like aluminum hydrated oxide, which is inappropriate. Further, when the temperature of the cleaning liquid is less than 30 ° C., a sufficient degreasing rate or etching rate cannot be obtained. When the temperature is lower than 30 ° C., the dissolution rate of the degreasing agent is slow, the pH change becomes slow, and the temperature of the aluminum base material is lowered to cause precipitation of aluminum dissolved in the degreasing agent.

  The cleaning liquid only needs to have a water quality that is conventionally used as industrial water. That is, although distilled water or pure water (deionized water) is preferably used, soft water or industrial water having an electric conductivity of 20 mS / m or less can also be used.

By stability constant log K _A and Al ³⁺ is used a cleaning solution containing 0.05 to 0.5 mol / liter of complex forming substance is 15 or more, aluminum hydrous oxide than with the distilled water Formation can be greatly suppressed. In other words, such a cleaning solution can trap Al ³⁺ ions on the surface of the aluminum base as a complex in the cleaning process, thereby exhibiting an effect of preventing precipitation and precipitation of aluminum hydrated oxide. Because it does. Such complexed products with Al ³⁺ include EDTA (ethylenediaminetetraacetic acid), CyDTA (cyclohexane-1,2-diaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraminehexaacetic acid), etc. Examples include organic coordination substances such as chelating reagents and citric acid. The added concentration of these substances is preferably 0.05 to 0.5 mol / liter. This is because if it is less than 0.05 mol / liter, the effect of sufficiently preventing the precipitation and precipitation of the aluminum hydrated oxide by forming a complex with Al ³⁺ cannot be obtained. On the other hand, even if it exceeds 0.5 mol / liter, the effect of precipitation / precipitation of the aluminum hydrated oxide is saturated, so that it is disadvantageous in terms of cost only by using a large amount.

The cleaning processing time is appropriately set depending on the configuration of the production line, but is preferably 2 seconds or longer. When the cleaning treatment time is less than 2 seconds, the surfactant contained in the degreasing agent remains without being removed, which may contaminate the chemical conversion treatment solution used in the chemical conversion treatment step. In order to remove the surfactant more reliably, the washing time is preferably 4 seconds or longer.
On the other hand, the upper limit of the cleaning treatment time is not particularly limited, but it is preferably 30 seconds or less in consideration of the configuration of the production line and the operation speed of the production line. If the cleaning processing time exceeds 30 seconds, a very long cleaning processing line is required or the operation speed of the cleaning processing line needs to be extremely reduced, resulting in a decrease in productivity. is there.

  By the way, the formation of the aluminum hydrated oxide layer on the aluminum substrate surface is promoted as the time during which the pH in the vicinity of the surface of the aluminum substrate exceeds 8 after the completion of the alkaline degreasing process becomes longer. . When the formation of the aluminum hydrated oxide layer is promoted, a large amount of aluminum hydrated oxide accumulates, and a large amount of cleaning liquid and a long time are required to remove this. Therefore, when the alkaline degreasing treatment step is completed, it is desirable to reduce the pH in the vicinity of the surface of the aluminum base to 8 or less as quickly as possible. Specifically, the formation promotion of the aluminum hydrated oxide layer can be suppressed by rapidly lowering the pH in the vicinity of the surface of the aluminum substrate to 8 or less within 3 seconds after the end of the alkaline degreasing treatment step. It is preferable to start the cleaning process simultaneously with the end of the alkaline degreasing process and to lower the pH to 8 or less within 3 seconds after the start.

E. The chemical conversion treatment is performed following the chemical conversion treatment cleaning step. As the chemical conversion treatment, a conventional chemical conversion treatment method, that is, a reactive chemical conversion treatment such as a phosphoric acid chromate treatment, a zirconium phosphate treatment, or a titanium phosphate treatment can be employed. Since formation of aluminum hydrated oxide can be suppressed in the above-described cleaning treatment step, the amount of aluminum hydrated oxide taken into the chemical conversion film can be 100 mg / m ² or less. As a result, it is possible to obtain a resin-coated aluminum plate having excellent adhesion of the resin-coated film after molding.

F. Resin Coating Film Formation Process A resin coating film is formed following the chemical conversion treatment process described above. In the resin coating film forming step, resin coating is applied, a resin coating film is formed by baking, or a resin film is formed by lamination.

Examples of resin coatings include general resins such as epoxy resins, epoxy / acrylic resins, polyester resins, vinyl chloride resins, epoxy / urea resins, and epoxy / phenol resins, such as aqueous solvents such as water or cyclohexanone, butyl cellosolve, etc. A resin paint dissolved or dispersed in an organic solvent is used. Moreover, the baking conditions of the applied resin paint are 150 to 300 ° C. and 10 to 60 seconds.
Examples of the resin film used for laminating include a polyester film such as polyethylene terephthalate; a polyolefin film such as polyethylene and polypropylene; a polyamide film such as nylon. Moreover, the lamination conditions of a resin film are 150-300 degreeC.
The resin-coated aluminum plate produced in this way is excellent in the adhesion of the resin-coated film even after molding such as press molding. Therefore, the aluminum can lid molded by strong processing is suitably manufactured by the resin-coated aluminum plate according to the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples and comparative examples.

Example 1
As the aluminum substrate, a 5182-H38 alloy plate having a thickness of 0.25 mm was used. First, an alkaline degreasing solution in which an alkaline degreasing agent “SC-EC370 (Nippon Paint)” was dissolved in water as a solvent was prepared. The concentration of the alkaline degreasing agent in the alkaline degreasing solution was 2.0% by weight. An alkali degreasing solution having a temperature of 70 ° C. was sprayed on both surfaces of the aluminum substrate at a spray spraying pressure of 1.5 kgf / cm ² and a spray spraying time of 5 seconds. The etching amount of the aluminum substrate was about 150 mg / m ² .
Simultaneously with the end of the alkaline degreasing treatment, the spray spray amount per second is 3.3 liters / m ² , the spray spray pressure is 1.1 kgf / cm ^2, and the spray spray time is 5 seconds. Was sprayed onto the alkali degreasing treatment surfaces on both sides of the aluminum substrate to wash the aluminum degreased aluminum substrate.
Next, both surfaces of the cleaned aluminum base material were subjected to a phosphoric acid chromate treatment (chromium adhesion amount 20 mg / m ² ) based on a conventional chemical conversion treatment method. A paint was applied (coating amount 12 g / m ² , baking temperature 250 ° C., baking time 30 seconds), and an aqueous acrylic modified epoxy resin coating film was formed as a resin coating film to prepare a resin-coated aluminum plate.

  On the other hand, separately from the production of the resin-coated aluminum plate as described above, the pH of the alkaline degreasing surface after 3 seconds from the end of the alkaline degreasing treatment step was measured using an aluminum base material having the same material and dimensions. First, an alkali degreasing treatment was performed on the aluminum base material under the same conditions as in the production of the resin-coated aluminum plate. Subsequently, the aluminum substrate was washed under the same conditions as in the production of the resin-coated aluminum plate except that the spraying time was 3 seconds. Next, the pH of the cleaning surface was measured with a pH test paper.

Examples 2-7
In Example 2, a resin-coated aluminum plate was produced in the same manner as in Example 1 except that deionized water having a temperature of 32 ° C. was used as the cleaning liquid, and the pH was measured. In Example 3, a resin-coated aluminum plate was prepared in the same manner as in Example 1 except that deionized water having a temperature of 77 ° C. was used as the cleaning liquid, and the pH was measured. In Example 4, resin-coated aluminum was used in the same manner as in Example 1 except that deionized water having a temperature of 51 ° C. was used as the cleaning liquid and zirconium phosphate treatment (zirconium deposition amount: 10 mg / m ² ) was performed as the chemical conversion treatment. A plate was prepared and the pH was measured. In Example 5, a resin-coated aluminum plate was produced in the same manner as in Example 1 except that a commercially available polyethylene terephthalate film was laminated (film thickness: 10 μm, laminating temperature: 200 ° C.) as the resin-coated film. And the pH was measured. In Example 6, a resin-coated aluminum plate was prepared in the same manner as in Example 1 except that an EDTA aqueous solution (0.07 mol / liter) at a temperature of 50 ° C. was used as the cleaning liquid, and the pH was measured. In Example 7, a resin-coated aluminum plate was prepared in the same manner as in Example 1 except that an aqueous citric acid solution (0.07 mol / liter) at a temperature of 50 ° C. was used as the cleaning liquid, and the pH was measured.

Comparative Examples 1-4
In Comparative Example 1, a resin-coated aluminum plate was produced in the same manner as in Example 1 except that the spray spray amount in the water washing treatment was 2.1 liter / m ² per ^second, and the pH was measured. In Comparative Example 2, a resin-coated aluminum plate was produced in the same manner as in Example 1 except that the spray spray pressure in the water washing treatment was 0.9 kgf / cm ^2, and the pH was measured. In Comparative Example 3, a resin-coated aluminum plate was prepared in the same manner as in Example 1 except that deionized water having a temperature of 26 ° C. was used as the cleaning liquid, and the pH was measured. In Comparative Example 4, a resin-coated aluminum plate was prepared in the same manner as in Example 1 except that deionized water having a temperature of 83 ° C. was used as the cleaning liquid, and the pH was measured.

Comparative Example 5
In Comparative Example 5, the resin was washed in the same manner as in Example 1 except that the aluminum base material subjected to alkaline degreasing treatment was immersed for 5 seconds in a 60 liter water tank filled with deionized water at a temperature of 50 ° C. A coated aluminum plate was produced. In the pH measurement of the cleaning surface, the aluminum base material subjected to alkaline degreasing treatment was taken out for 3 seconds in a 60 liter water tank filled with deionized water at a temperature of 50 ° C., and the pH of the cleaning surface was measured by pH test. Measured with paper.

  Table 1 shows the production conditions of the resin-coated aluminum plates produced in Examples 1-7 and Comparative Examples 1-5.

  In the production process of the resin-coated aluminum plates of Examples 1 to 7 and Comparative Examples 1 to 5, the amount of aluminum hydrated oxide formed on the surface of the aluminum base material after the water washing treatment step, contained in the chemical conversion film after the chemical conversion treatment step Table 2 shows the amount of aluminum hydrated oxide and the amount of aluminum hydrated oxide contained in the chemical conversion film after the resin coating film forming step. Further, Table 2 also shows the pH of the cleaning surface.

The amount of aluminum hydrated oxide was measured by a simple quantitative operation using FT-IR (Fourier transform infrared spectrophotometer). That is, calibration of the amount of aluminum hydrated oxide by the absorptance of Al-OH vibration (peak appearing in the vicinity of 600 to 800 cm ^- 1; the peak position varies depending on the type of chemical conversion film) by polarization reflection method (p-wave) FT-IR By creating a line, the amount of aluminum hydrated oxide was determined simply, rapidly and non-destructively.
Regarding the amount of aluminum hydrated oxide contained in the chemical conversion film after the resin coating film forming step, the prepared resin-coated aluminum plate is immersed in concentrated sulfuric acid at room temperature (25 ° C.) for 2 minutes, and then washed in running water. Thus, the resin coating film was removed from the resin-coated aluminum plate, and the amount of aluminum hydrated oxide contained in the chemical conversion film was measured.

Since the conditions of the cleaning treatment steps of Examples 1 to 7 satisfy the cleaning treatment requirements shown in claim 2, the chemical conversion treatment step is performed after the water washing treatment step regardless of the type of chemical conversion film and the type of the resin coating film. Most of the amount of aluminum hydrated oxide after and after the resin coating film forming step was 100 mg / m ² or less (only after the water washing treatment step of Example 3 exceeded 100 mg / m ² ). In particular, when the EDTA aqueous solution is used as the cleaning solution (Example 6) and when the citric acid aqueous solution is used (Example 7), the effect of suppressing the formation of the aluminum hydrated oxide is extremely large.
The amount of aluminum hydrated oxide decreases in the order after the water washing treatment process, after the chemical conversion treatment process, and after the resin coating film formation process. This is due to the aluminum hydration oxidation in the chemical conversion treatment process and the resin coating film formation process. This is probably because part of the product is decomposed or reduced. In addition, the amount of aluminum hydrated oxide prescribed | regulated to Claim 1 is a thing after a resin coating film formation process.

In contrast, in Comparative Example 1, the amount of spray in the water washing treatment process was too small, and in Comparative Example 2, the spray spray pressure in the water washing treatment process was too low, so after the water washing treatment process, after the chemical conversion treatment process, and the resin coating film The amount of aluminum hydrated oxide after the forming step exceeded 100 mg / m ^{2 in} all cases. In Comparative Example 3, since the temperature of the cleaning liquid was too low, and in Comparative Example 4, the temperature of the cleaning liquid was too high, and pseudoboehmite was generated. Therefore, the amount of aluminum hydrated oxide exceeded 100 mg / m ² . In Comparative Example 5, since the dip-type water washing treatment was performed, the pH decrease in the vicinity of the surface of the aluminum base material was slow, and a large amount of aluminum hydrated oxide was formed.

Moreover, in all of Examples 1 to 7, the pH of the alkaline degreasing surface after 3 seconds from the end of the alkaline degreasing treatment step was 8 or less. In these examples, in the cleaning process, a method of spraying a large amount of cleaning liquid at a predetermined temperature onto the surface of the aluminum base material at a stretch was adopted, and the pH of the alkaline degreasing surface could be rapidly lowered.
In contrast, in Comparative Examples 1 to 3, the spraying conditions were not appropriate, and in Comparative Example 5, the dip-type water washing treatment was performed. It was over.
In Comparative Example 4, the pH of the alkaline degreasing surface after 3 seconds from the end of the alkaline degreasing treatment step was 8 or less. This is because the alkaline component remaining on the surface of the base material was not used because of the high temperature cleaning liquid. It is thought that it was dissolved in the cleaning solution.

  Next, bending workability and lid moldability were measured as evaluations regarding the adhesion of the resin-coated film in the resin-coated aluminum plates produced in Examples 1 to 7 and Comparative Examples 1 to 5. The results are shown in Table 3.

The bendability and lid moldability of the resin-coated aluminum plate were evaluated as follows.
Bending Workability The resin-coated aluminum plate produced as described above was cut into a strip shape of 3 cm wide × 10 cm long with respect to the rolling line, and subjected to 180 ° bending (2T bending) at the center. Next, after performing a retort process at 125 ° C. for 30 minutes, the energization current (enamel lator value, ERV) of the 2T bent portion was measured. The meanings of the judgment symbols in Table 3 are as follows, ◎ and ○ are acceptable, and Δ × and × are unacceptable. The number of samples tested in each example was 10.
A: Indicates that the energization current (ERV) is less than 0.5 mA.
◯: Indicates that the energization current (ERV) is 0.5 mA or more and less than 1.0 mA.
Δ ×: Indicates that the energization current (ERV) is 1.0 mA or more and less than 2.7 mA.
X: Indicates that the energization current (ERV) is 2.7 mA or more.

Formability of the lid The resin-coated aluminum plate produced as described above is formed into a full-form shell having an outer diameter of 2 × 6/10 inch diameter (206 diameter) by a shell press, and then subjected to a three-stage overhanging process by a conversion press. A rivet portion having an outer diameter of 3.0 mm was formed at the center of the shell. Subsequently, after retorting at 125 ° C. for 30 minutes, the sample was immersed in an acetone-copper sulfate solution for 5 minutes to count the number of black spots (with a diameter of 0.5 mm or more being counted) based on coating film peeling. . The number of samples tested in each example was three.

The meanings of the judgment symbols in Table 3 are as follows, ◎ and ○ are acceptable, and Δ × and × are unacceptable.
A: The number of black spots is 0-2.
○: The number of black spots is 3 to 5.
Δ: Indicates that the number of black spots is 6 to 10.
X: Indicates that the number of black spots exceeds 10.

  In Examples 1-7, the determination of bending workability and lid moldability was both acceptable. In particular, Examples 1 and 4 to 7 were extremely excellent in both bending workability and lid moldability. Thus, it was confirmed that the resin-coated aluminum plate produced in each example has high adhesion of the resin-coated film. In addition, it turned out that bending workability and lid moldability correspond to the amount of aluminum hydrated oxide after the water washing treatment step shown in Table 2, after the chemical conversion treatment step, and after the resin coating film forming step. That is, it was confirmed that the smaller the amount of the aluminum hydrated oxide, the better the bending workability and the lid moldability. On the other hand, in Comparative Examples 1-5, the determination of bending workability and lid moldability was unacceptable.

  In the resin-coated aluminum plate, by reducing the content of the aluminum hydrated oxide in the chemical conversion film, high adhesion of the resin-coated film after molding of an aluminum can lid or the like is achieved.

Claims (3)

A step of subjecting at least one surface of a substrate made of an aluminum plate or an aluminum alloy plate to an alkaline degreasing treatment, a step of washing the alkaline degreased surface, a step of subjecting the washed surface to chemical conversion, and a resin on the chemical conversion treated surface Forming a coating film, and a method for producing a resin-coated aluminum plate for can lids,
The cleaning treatment step includes spraying a cleaning liquid of 30 to 80 ° C. onto the alkaline degreasing surface, the spray injection amount is 3 to 50 liters / m ² per second, and the spray injection pressure is 1. A method for producing a resin-coated aluminum plate for a can lid, wherein the pH is 0 to 3.5 kgf / cm ² and the pH in the vicinity of the surface of the aluminum substrate is lowered to 8 or less within 3 seconds after the start of cleaning.   The manufacturing method of the resin-coated aluminum plate for can lids of Claim 1 whose base material consisting of the said aluminum alloy plate is 5000 series alloy. The can lid according to claim 1 or 2, wherein the cleaning liquid contains 0.05 to 0.5 mol / liter of a complex-forming substance having a stability constant K _A with aluminum ions (Al ³⁺ ) of log K _A ≧ 15. For producing a resin-coated aluminum plate.