Chemical conversion treatment agent for aluminum can, aluminum can provided with chemical conversion coating film, and surface treatment method for aluminum can

Abstract

The present invention addresses the problem of providing a chemical conversion treatment agent for forming a coating film on a surface of an aluminum can, the coating film being excellent in corrosion resistance during retort sterilization treatment, paint adhesion, and slipperiness for improving transportability during manufacturing of an aluminum DI can.　The problem is solved by a chemical conversion treatment agent for an aluminum can, the chemical conversion treatment agent comprising (A) an ion of a metal element selected from zirconium, titanium, and hafnium, (B) a phosphorus-containing ion including a phosphate ion and / or a phosphite ion, (C) a fluoride ion, and (D) a water-soluble resin, wherein the water-soluble resin (D) contains a resin represented by formula (1) and / or formula (2). (In formula (1) and formula (2): X represents at least one selected from the constituent unit group consisting of hydroxyethyl acrylamide, diallylamine, allylamine, acrylic acid, acrylonitrile, ethylene, ethylene glycol, propylene glycol, glycerin, and ethylene oxide; n and m each represent a number average polymerization degree; and the ratio n:m is 0:100 to 80:20.

Description

Chemical conversion treatment agent for aluminum cans, aluminum cans with chemical conversion coating, and method for treating the surface of aluminum cans

[0001] The present invention relates to a novel chemical conversion treatment agent for aluminum cans, an aluminum can provided with a chemical conversion coating, and a method for treating the surface of an aluminum can.

[0002] Surface treatment solutions for aluminum-containing metal materials, i.e., metal materials made of aluminum or aluminum alloys, can be broadly divided into chromate types and non-chromate types, and currently, zirconium-based non-chromate type surface treatment solutions are mainly used for the surface treatment of aluminum DI (Drawing and Ironing) cans.

[0003] In aluminum DI cans, the exterior bottom surface is generally not painted after a zirconium-based non-chromate surface treatment is performed. Furthermore, in recent years, improvements in sterilization technology have led to aluminum DI cans being filled with beverages that require retort sterilization. For example, Patent Document 1 discloses a retort sterilization method in which sterilization and cooling are performed consecutively. If the corrosion resistance of a zirconium-based non-chromate surface treatment is insufficient, the exterior will discolor to white. Therefore, the surface treatment film must have corrosion resistance that can withstand retort sterilization.

[0004] Furthermore, in the can manufacturing process, the high coefficient of friction on the outer surface of the can causes poor sliding on the surface of the can when the can is transported, which can lead to the can tipping over. Therefore, there is a need to reduce the coefficient of static friction on the outer surface of the can without affecting the adhesion of the paint or ink applied to the can.

[0005] As a technique for improving lubricity, for example, Patent Document 2 proposes a surface treatment agent for metal cans containing a water-soluble organic substance selected from phosphate esters, alcohols, mono- or poly-valent fatty acids, fatty acid derivatives, and mixtures thereof. Similarly, as a technique for improving lubricity and corrosion resistance, Patent Document 3 proposes an aqueous solution having a pH of 1.8 to 4.0, containing phosphate ions, a water-soluble Zr compound and / or Ti compound, a fluoride, and a water-soluble polyamide having a tertiary amine group and / or a polyalkylene group.

[0006] As another method for improving the problems of corrosion resistance and slipperiness, Patent Document 4 proposes a surface treatment composition for aluminum-containing metal materials containing predetermined amounts of phosphate ions, condensed phosphate ions, and a water-soluble polymer having a bisphenol skeleton. Also, as another method for improving the corrosion resistance and slipperiness, Patent Document 5 proposes an aluminum-containing metal material composition containing predetermined amounts of phosphate ions, a water-soluble zirconium compound and / or titanium compound, a fluoride, and a water-soluble polymer having a bisphenol A skeleton.

[0007] JP-A-53-038642, JP-A-64-85292, JP-A-7-331276, JP-A-7-278836, JP-A-9-031404

[0008] However, in recent years, with the increase in production line speeds, higher-temperature water (around 125°C) comes into contact with aluminum DI cans during sterilization, so even coatings that can prevent the above-mentioned white discoloration lack corrosion resistance, resulting in a black discoloration of the exterior. Therefore, the technologies described in the aforementioned Patent Documents 2 and 3 also lack sufficient corrosion resistance in a retort sterilization environment. Furthermore, the technology described in Patent Document 4 contains condensed phosphoric acid as an essential component, which gradually decomposes in an acidic solution, preventing the stable formation of a coating. Furthermore, the technology described in Patent Document 5 contains endocrine disrupting substances and has problems with insufficient corrosion resistance in a continuous retort sterilization environment.

[0009] The present invention has been made to solve the above-mentioned problems of the prior art, and specifically provides a chemical conversion treatment agent for aluminum cans which, when applied to aluminum-containing metal materials, particularly aluminum DI cans, is capable of forming a coating on the surface that is excellent in whitening resistance during retort sterilization treatment, blackening resistance during immersion retort sterilization treatment, and paint adhesion, and which also has excellent lubricity for transport during the production of aluminum DI cans, providing a satisfactory overall result.

[0010] The present inventors have conducted extensive research into means for solving the above-mentioned problems of the prior art, and as a result have found that a chemical conversion treatment agent containing ions (A) containing a metal element selected from zirconium, titanium, and hafnium, phosphorus-containing ions (B) including phosphate ions and / or phosphite ions, fluoride ions (C), and a predetermined water-soluble resin (D) can form a chemical conversion coating that is excellent in whitening resistance during retort sterilization, blackening resistance during immersion retort sterilization, paint adhesion, and slip properties, thereby completing the present invention.

[0011] The present invention includes the following: [1] A chemical conversion treatment agent for aluminum cans, comprising ions (A) containing a metal element selected from zirconium, titanium, and hafnium, phosphorus-containing ions (B) containing phosphate ions and / or phosphite ions, fluoride ions (C), and a water-soluble resin (D), wherein the water-soluble resin (D) contains a resin represented by the following formula (1) and / or (2): [In the above formulas (1) and (2), X represents at least one selected from the group consisting of structural units of hydroxyethylacrylamide, diallylamine, allylamine, acrylic acid, acrylonitrile, ethylene, ethylene glycol, propylene glycol, glycerin, and ethylene oxide, and n and m represent number average degrees of polymerization, with n:m being 0:100 to 80:20.] [2] The chemical conversion treatment agent according to [1], wherein the weight average molecular weight of the water-soluble resin (D) is 500 or more and 100,000 or less; [3] The chemical conversion treatment agent according to [1] or [2], which contains 10 to 1,000 ppm of the ions (A) calculated as metal; [4] An aluminum can provided with a chemical conversion coating formed by the chemical conversion treatment agent according to any one of [1] to [3]; [5] A surface treatment method for an aluminum can, comprising the steps of: bringing an aluminum can into contact with the chemical conversion treatment agent according to any one of [1] to [3], washing the aluminum can that has been contacted with the chemical conversion treatment agent with water, and drying the washed aluminum can.

[0012] The chemical conversion treatment agent of the present invention can form a chemical conversion coating on the surface of an aluminum can that is resistant to whitening during retort sterilization, resistant to blackening during immersion retort sterilization, and has excellent paint adhesion and slip resistance that improves transportability during the production of aluminum DI cans.

[0013] The present invention will be described in detail below. One embodiment of the present invention is a chemical conversion treatment agent for aluminum cans, which contains (A) ions containing a metal element selected from zirconium, titanium, and hafnium, (B) phosphorus-containing ions including phosphate ions and / or phosphite ions, (C) fluoride ions, and (D) a predetermined water-soluble resin.

[0014] <Ions (A) Containing a Metal Element> The chemical conversion treatment agent according to this embodiment contains ions (A) (hereinafter also simply referred to as ions (A)) containing a metal element selected from zirconium, titanium, and hafnium. The ions (A) are a chemical conversion coating-forming component that improves the corrosion resistance and abrasion resistance of the substrate and can also enhance adhesion to the coating. Examples of the ions (A) include metal ions of zirconium, titanium, or hafnium; complex ions containing zirconium, titanium, or hafnium; and oxide ions of zirconium, titanium, or hafnium. One or more of these ions may be contained in the chemical conversion treatment agent.

[0015] The concentration of the ion (A) in the chemical conversion treatment agent is not particularly limited, but from the viewpoint of reactivity with the surface of an aluminum can, the metal-equivalent mass concentration is preferably 10 ppm or more, more preferably 20 ppm or more, and is preferably 1000 ppm or less, more preferably 500 ppm or less. When two or more types of ions (A) are contained, the mass concentration means the total of these ions.

[0016] The source of ions (A) is not particularly limited as long as it is a compound that can provide ions (A) when mixed with an aqueous medium. Examples of sources of zirconium-containing ions include hexafluorozirconic acid, zirconium nitrate, zirconium oxynitrate, ammonium zirconium nitrate, zirconyl acetate, zirconyl lactate, zirconyl nitrate, zirconium carbonate, zirconium hydroxide, and zirconium oxide. Examples of sources of titanium-containing ions include hexafluorotitanic acid, titanium nitrate, titanium oxynitrate, ammonium titanium nitrate, titanyl nitrate, titanium hydroxide, titanium oxide, and ammonium titanium fluoride. Examples of sources of hafnium-containing ions include hafnium trifluoromethanesulfonate, hexafluorohafnic acid, hafnium nitrate, and hafnium oxide. When these can take the form of a salt, the salt may also be used. These sources may be used alone or in combination of two or more. From the viewpoint of film-forming ability, the source of ions (A) is preferably hexafluorozirconic acid, hexafluorotitanic acid, hexafluorohafnic acid, or salts thereof.

[0017] <Phosphorus-Containing Ions (B)> The chemical conversion treatment agent according to this embodiment contains phosphorus-containing ions (B) (hereinafter also simply referred to as ions (B)) including phosphate ions and / or phosphite ions. The ions (B) are a chemical conversion coating-forming component, and contribute to improving the corrosion resistance and retort resistance of the substrate. The ions (B) may include ions such as hypophosphite ions, polyphosphate ions, and phosphonate ions in addition to phosphate ions and / or phosphite ions. One or more types of ions (B) may be contained in the chemical conversion treatment agent.

[0018] The concentration of the ion (B) in the chemical conversion treatment agent is not particularly limited, but from the viewpoint of reactivity with the surface of an aluminum can, the phosphorus-equivalent mass concentration is preferably 10 ppm or more, more preferably 20 ppm or more, and also preferably 3000 ppm or less, more preferably 1000 ppm or less, and even more preferably 400 ppm or less. When two or more types of ion (B) are contained, the mass concentration means the total of these.

[0019] The source of phosphorus-containing ions (B) is not particularly limited as long as it is a compound that can provide ions (B) when mixed with an aqueous medium. Both inorganic and organic phosphorus compounds can be used, including inorganic phosphoric acid, organic phosphoric acid, and salts thereof (e.g., metal salts such as alkali metal salts and alkaline earth metal salts, ammonium salts, etc.). Specific examples include phosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, and salts thereof. Examples include phosphoric acid, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium phosphate, calcium phosphate; phosphorous acid, disodium hydrogen phosphite; hypophosphorous acid, sodium hypophosphite, ammonium hypophosphite; tripolyphosphate, tetraphosphoric acid, sodium tripolyphosphate, sodium tetrapolyphosphate, etc., but are not limited thereto. These sources of phosphorus-containing ions (B) may be used alone or in combination of two or more.

[0020] <Fluoride ions (C)> The chemical conversion treatment agent according to this embodiment contains fluoride ions (C) (hereinafter also simply referred to as ions (C)). The ions (C) serve as an etching agent for the substrate. The concentration of the ions (C) in the chemical conversion treatment agent is not particularly limited, but is preferably 30 ppm or more, more preferably 50 ppm or more, in terms of fluorine equivalent mass concentration, from the viewpoint of reactivity with the surface of an aluminum can, and is preferably 1500 ppm or less, more preferably 1000 ppm or less, and even more preferably 600 ppm or less, from the viewpoint of obtaining a good appearance.

[0021] The source of fluoride ions (C) is not particularly limited as long as it is a compound (hereinafter also referred to as a fluorine-containing compound) that can provide ions (C) when mixed with an aqueous medium. Examples of fluorine-containing compounds include fluorides such as hydrofluoric acid, ammonium fluoride, fluoroboric acid, ammonium hydrogen fluoride, sodium fluoride, potassium fluoride, and sodium hydrogen fluoride; and complex fluorides such as hydrosilicic acid, zinc hydrosilicic acid, manganese hydrosilicic acid, magnesium hydrosilicic acid, nickel hydrosilicic acid, iron hydrosilicic acid, calcium hydrosilicic acid, hexafluorozirconate, hexafluorotitanate, and hexafluorohafnate, but are not limited thereto. These sources of fluoride ions (C) may be used alone or in combination of two or more. Hexafluorozirconic acid, hexafluorotitanic acid, hexafluorohafnic acid, etc. also correspond to sources of ions (A) and contribute to the concentrations of ions (A) and ions (C), respectively.

[0022] <Water-soluble resin (D)> The chemical conversion treatment agent according to this embodiment contains a predetermined water-soluble resin (D) (hereinafter also simply referred to as resin (D)). The resin (D) is represented by the following formula (1) and / or the following formula (2).

[0023] In the above formulas (1) and (2), X represents at least one selected from the group consisting of hydroxyethyl acrylamide, diallylamine, allylamine, acrylic acid, acrylonitrile, ethylene, ethylene glycol, propylene glycol, glycerin, and ethylene oxide structural units, and n and m represent the number average degree of polymerization, with n:m being 0:100 to 80:20. It is believed that the chemical conversion treatment agent according to this embodiment is capable of forming a chemical conversion coating that is excellent in adhesion to metal substrates and corrosion resistance in a retort sterilization environment due to the action of the amide group contained in the resin (D). The chemical conversion treatment agent may contain only one type of resin (D), or two or more types.

[0024] Resin (D) is not particularly limited as long as it contains the above structural units and has the above number average degree of polymerization, but from the viewpoint of retort resistance, n:m is preferably 0:100 to 80:20, more preferably 0:100 to 60:40, and even more preferably 0:100 to 20:80.

[0025] Resin (D) preferably has 0.01 moles or more of primary amide groups per 100 g of resin, more preferably 0.1 moles or more, and even more preferably 0.15 moles or more.

[0026] The mass concentration of the resin (D) in the chemical conversion treatment agent is preferably 20 ppm or more, more preferably 50 ppm or more, from the viewpoint of forming a coating with good retort resistance with the resin solids, and is preferably 5000 ppm or less, more preferably 3000 ppm or less, from the viewpoint of film-forming properties.

[0027] From the viewpoint of forming a film with good retort resistance, the resin (D) preferably has a weight average molecular weight of 500 or more, more preferably 5,000 or more, and from the viewpoint of film-forming properties, the weight average molecular weight is preferably 100,000 or less, more preferably 50,000 or less.

[0028] <Mass Ratio of Resin (D) / Ions (A)> In the chemical conversion treatment agent, the mass ratio of Resin (D) / Ions (A) is preferably 0.1 or more, more preferably 1.0 or more, from the viewpoint of retort resistance, and is preferably 50 or less, more preferably 30 or less.

[0029] <Aqueous Medium> The chemical conversion treatment agent according to this embodiment may contain an aqueous medium. The aqueous medium is not particularly limited as long as it is water or a mixture of water and a water-miscible organic solvent (containing 50% or more by volume of water based on the volume of the aqueous medium). The water-miscible organic solvent is not particularly limited as long as it is miscible with water, and examples thereof include ketone-based solvents such as acetone and methyl ethyl ketone; amide-based solvents such as N,N'-dimethylformamide and dimethylacetamide; alcohol-based solvents such as methanol, ethanol, and isopropanol; ether-based solvents such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether; and pyrrolidone-based solvents such as 1-methyl-2-pyrrolidone and 1-ethyl-2-pyrrolidone. One of these water-miscible organic solvents may be mixed with water, or two or more may be mixed with water.

[0030] <Other Components> In addition to the above components, the chemical conversion treatment agent according to this embodiment may contain additives that are commonly used in chemical conversion treatment agents as other components, as needed. Examples of other components include a metal ion source other than the ion (A), a silicon-containing compound, a water-soluble or water-dispersible resin other than the water-soluble resin (D), a chelating agent, a surfactant, a pH adjuster, and the like. Only one of these other components may be blended, or two or more may be blended. These other components may be blended within a range that does not impair the effects of the present invention.

[0031] <Source of Metal Ions Other Than Ions (A)> Examples of sources of metal ions other than ions (A) that can be blended into the chemical conversion treatment agent according to this embodiment include, but are not limited to, compounds that can supply ions containing metal elements such as zinc, magnesium, calcium, aluminum, manganese, iron, cobalt, and copper. Only one type of source of metal ions other than ions (A) may be blended, or two or more types may be blended.

[0032] <Silicon-containing compound> Examples of silicon-containing compounds that can be incorporated into the chemical conversion treatment agent according to this embodiment include silica, water-dispersible silica, alkali metal or alkaline earth metal silicates, alkyl silicate esters, silane coupling agents, etc. Specific examples include potassium silicate, sodium silicate, silicic acid dimer, silicic acid oligomer, colloidal silica, tetramethoxysilane, methyltrimethoxysilane, tetraethoxysilane, glycidoxypropyltriethoxysilane, aminopropyltriethoxysilane, epoxycyclohexylethyltrimethoxysilane, etc., but are not limited thereto. Only one type of silicon-containing compound may be incorporated, or two or more types may be incorporated.

[0033] <Water-soluble resin or water-dispersible resin other than the water-soluble resin (D)> Examples of water-soluble resins or water-dispersible resins other than the water-soluble resin (D) that can be blended in the chemical conversion treatment agent according to this embodiment include, but are not limited to, urethane resins, acrylic resins, epoxy resins, phenolic resins, amine resins, etc. One type of water-soluble resin or water-dispersible resin other than the water-soluble resin (D) may be blended alone, or two or more types may be blended.

[0034] <Chelating Agent> Examples of chelating agents that can be incorporated into the chemical conversion treatment agent according to this embodiment include, but are not limited to, citric acid, gluconic acid, oxalic acid, organic phosphonic acid, etc. Addition of a chelating agent can improve instability of the treatment solution caused by metal ions such as copper ions and manganese ions, which are ions of eluted alloy components.

[0035] <Surfactant> Examples of surfactants that can be blended in the chemical conversion treatment agent according to this embodiment include nonionic surfactants and ionic surfactants such as cationic, anionic and amphoteric surfactants.

[0036] <pH of Chemical Conversion Treatment Agent> The pH of the chemical conversion treatment agent according to this embodiment is not particularly limited, but the pH value at the temperature when the agent is brought into contact with the surface of an aluminum can is preferably 1.5 or more, more preferably 2.0 or more, and preferably 6.0 or less, and more preferably 5.0 or less, at 25°C. Within the above pH range, a good coating can be obtained through appropriate etching. The pH can be measured using a commercially available pH meter. The pH of the chemical conversion treatment agent can be adjusted using, but is not limited to, acids such as phosphoric acid, nitric acid, hydrochloric acid, hydrofluoric acid, and organic acids, and alkalis such as sodium hydroxide, sodium carbonate, ammonium hydroxide, and amines as pH adjusters. One or more pH adjusters may be used.

[0037] <Method for producing chemical conversion treatment agent> The chemical conversion treatment agent according to this embodiment can be produced by blending predetermined amounts of a source of ions (A), a source of phosphorus-containing ions (B), a source of fluoride ions (C), and a predetermined water-soluble resin (D) as raw materials into an aqueous medium.

[0038] <Method of forming chemical conversion coating> The surface treatment of the metal with the chemical conversion treatment agent is not particularly limited, and can be carried out by bringing the chemical conversion treatment agent into contact with the surface of the aluminum can or on the surface thereof under normal treatment conditions. The chemical conversion treatment method is not particularly limited, and examples thereof include a dipping method, a spraying method, and a roll coating method.

[0039] The treatment temperature in the chemical conversion treatment is not particularly limited as long as the desired chemical conversion coating is obtained, but is preferably 30° C. or higher, more preferably 35° C. or higher, and is preferably 70° C. or lower, more preferably 60° C. or lower. The chemical conversion time in the chemical conversion treatment is not particularly limited as long as the desired chemical conversion coating is obtained, but is preferably in the range of 5 to 200 seconds. The lower limit is more preferably 10 seconds, and the upper limit is more preferably 100 seconds.

[0040] The surface of the aluminum can may be subjected to pretreatments such as degreasing and water washing before being chemically treated with the chemical conversion treatment agent. A post-chemical water washing treatment may also be performed after the chemical conversion treatment. The degreasing treatment is performed to remove oil and dirt adhering to the surface of the aluminum can. It is typically performed by spraying a known acidic or alkaline degreaser at 40 to 80°C for 10 to 120 seconds. If desired, a preliminary degreasing treatment may be performed before the degreasing treatment. The post-degreasing water washing treatment is performed by spraying a large amount of water one or more times to wash away the degreaser after the degreasing treatment. The post-chemical water washing treatment is performed one or more times to avoid adversely affecting adhesion, corrosion resistance, etc., after various subsequent coatings. In this case, it is appropriate to perform the final water washing with pure water. This post-chemical water washing treatment may be performed by either spray water washing or immersion water washing, or a combination of these methods. After the above-mentioned post-chemical washing treatment, the plate may be dried as required according to a known method, and then various coatings may be applied.

[0041] The aluminum-containing metal material forming the aluminum can is not particularly limited and includes materials made of aluminum and aluminum-containing alloys such as aluminum-manganese alloys, aluminum-magnesium alloys, and aluminum-silicon alloys, such as plates, bars, pipes, and wires. Examples include 3000 series aluminum alloys, 5000 series aluminum alloys, and 6000 series aluminum alloys. There are no limitations on the size or shape of this metal material. The aluminum can is preferably an aluminum DI (Drawing and Ironing) can.

[0042] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0043] Evaluation Method (1) Whitening Resistance (Retort 1) With regard to the corrosion resistance (retort resistance) of aluminum DI cans, 350 mL of deionized water was filled into aluminum DI cans produced by the methods of Examples 1-22 and Comparative Examples 1-5 below, and the cans were exposed to steam at 125°C for 30 minutes with the bottoms facing downwards, and the degree of discoloration (whitening) after exposure was evaluated visually according to the following evaluation criteria: S: No whitening on either the outside or inside of the can. A: No whitening on the outside of the can, but slight whitening on the inside. B: Whitening on part of the outside of the can, and whitening on the inside as well. C: Whitening over the entire surface of the can. (2) Blackening Resistance (Retort 2) With regard to the corrosion resistance (retort resistance) of aluminum DI cans, aluminum DI cans produced by the methods of Examples 1-22 and Comparative Examples 1-5 below were immersed in deionized water and heated at 125°C for 30 minutes, and the degree of discoloration (blackening) after heating was visually evaluated according to the following evaluation criteria: S: No blackening on either the outside or inside of the can. A: No blackening on the outside of the can, but slight blackening on the inside. B: Blackening on part of the outside of the can, and blackening on the inside as well. C: Blackening over the entire surface of the can. (3) Paint Adhesion Paint adhesion of aluminum DI cans was tested as follows. An epoxyurea-based can coating was applied to the surface of aluminum DI cans prepared according to the methods of Examples 1-22 and Comparative Examples 1-5 below, with a coating thickness of 5 to 7 μm. The cans were then baked at 215°C for 4 minutes. These cans were then cut into 5 x 150 mm strips and thermocompressed with a polyamide film to form test specimens. These specimens were then peeled using a 180° peel test, and the peel strength was evaluated. Higher peel strength indicates better paint adhesion; generally, a peel strength of 4.0 kgf / 5 mm width or greater is considered satisfactory for practical use. (4) Slipperiness Slipperiness was evaluated by measuring the static friction coefficient of the can exterior. Specifically, three aluminum DI cans prepared according to the methods of Examples 1-22 and Comparative Examples 1-5 below were stacked in a bale shape and tilted at a rate of 3 degrees per second. The friction angle θ was measured when the cans began to slide. The static friction coefficient μ was calculated using the equation: static friction coefficient μ = tan θ. The lower the static friction coefficient, the better the slipperiness, and generally, a static friction coefficient of 1.0 or less is considered to be satisfactory.

[0044] Example 1: An aluminum DI can prepared by DI processing an aluminum alloy plate (A3004) was degreased with an 8% aqueous solution of an acidic degreaser (trademark: Palclean 501, manufactured by Nippon Parkerizing Co., Ltd.) by spraying at 75°C for 60 seconds, then rinsed and cleaned with tap water. The cleaned surface was sprayed with chemical conversion treatment agent 1 having the following composition at 40°C for 10 seconds. The can was then rinsed with tap water and further sprayed with deionized water having a resistivity of 3,000,000 Ωcm or more for 10 seconds, after which it was dried in a hot air oven at 200°C for 2 minutes. The whitening resistance, blackening resistance, adhesion, and slipperiness of the aluminum DI can were then measured and evaluated using the methods (1) to (4) described above. The evaluation results are shown in Table 2.

[0045] Chemical conversion treatment agent 1 Zr ions (A): 100 ppm P ions (B): 100 ppm F ions (C): 175 ppm Water-soluble resin 1 (D): 500 ppm The raw material was 40% hydrofluoric zirconium acid (H ２ ZrF ６ ), 75% phosphoric acid (H ３ P.O. ４ ), 55% hydrofluoric acid (HF), and water-soluble resin 1 were used. Water-soluble resin 1 is a water-soluble resin represented by the above formula (1), where X = diallylamine, n:m = 50:50, weight-average molecular weight = 10,000, and the number of moles of primary amide groups per 100 g of resin is 0.60. The chemical conversion treatment agent was adjusted to a pH of 2.5 using nitric acid.

[0046] Examples 2-19, Comparative Examples 1-3 The chemical conversion treatment agents of Examples 2-19 and Comparative Examples 1-3 were prepared to the ion concentrations and pHs shown in Table 1 using the components other than the water-soluble resin as listed in Chemical Conversion Treatment Agent 1. The water-soluble resin was prepared using the water-soluble resin shown in Table 1. The treatment object, treatment method, and evaluation method were the same as in Example 1. The evaluation results are shown in Table 2.

[0047] Examples 20-22 The chemical conversion treatment agents of Examples 20-22 were prepared to the ion concentrations and pHs shown in Table 1, using the components described in Chemical Conversion Treatment Agent 1 except for ions (A) or ions (B). Ions (A) were prepared using hydrofluoric titanic acid as a Ti ion source, hafnium trifluoromethanesulfonate as a Hf ion source, and ions (B) were prepared using phosphorous acid as a phosphite ion source, and the ion concentrations were shown in Table 1. The treatment object, treatment method, and evaluation method were the same as in Example 1. The evaluation results are shown in Table 2.

[0048] Comparative Example 4 An aluminum DI can was treated by the method described in Example 1 of JP-A-7-331276. Thereafter, the whitening resistance, blackening resistance, adhesion, and slipperiness of this aluminum DI can were evaluated by the same methods. The evaluation results are shown in Table 2.

[0049] Comparative Example 5: An aluminum DI can was treated by the method described in Example 1 of JP-A-9-031404. Thereafter, the whitening resistance, blackening resistance, adhesion, and slipperiness of this aluminum DI can were evaluated by the same methods. The evaluation results are shown in Table 2.

[0050]

[0051]

[0052] As is clear from the results in Table 2, the chemical conversion treated aluminum cans obtained using the chemical conversion treatment agents of Examples 1 to 22 were all excellent in corrosion resistance, paint adhesion, and lubricity. On the other hand, the performance of the chemical conversion treated aluminum cans obtained using the chemical conversion treatment agents of Comparative Examples 1 to 5 was poor, particularly in terms of blackening resistance (retort).

[0053] Although the present invention will be described in detail with reference to specific examples, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

Claims

1. A chemical conversion treatment agent for aluminum cans, comprising: ions (A) containing a metal element selected from zirconium, titanium, and hafnium; phosphorus-containing ions (B) containing phosphate ions and / or phosphite ions; fluoride ions (C); and a water-soluble resin (D), wherein the water-soluble resin (D) contains a resin represented by the following formula (1) and / or (2): [In the above formulas (1) and (2), X represents at least one selected from the group consisting of structural units of hydroxyethylacrylamide, diallylamine, allylamine, acrylic acid, acrylonitrile, ethylene, ethylene glycol, propylene glycol, glycerin, and ethylene oxide, and n and m represent number average degrees of polymerization, with n:m being 0:100 to 80:20.] 2. The chemical conversion treatment agent according to claim 1, wherein the water-soluble resin (D) has a weight average molecular weight of 500 or more and 100,000 or less.

3. The chemical conversion treatment agent according to claim 1, which contains 10 to 1,000 ppm of said ions (A) calculated as metal.

4. An aluminum can provided with a chemical conversion coating formed using the chemical conversion treatment agent according to any one of claims 1 to 3.

5. A method for treating the surface of an aluminum can, comprising the steps of: bringing an aluminum can into contact with the chemical conversion treatment agent according to any one of claims 1 to 3; rinsing the aluminum can that has been contacted with the chemical conversion treatment agent; and drying the aluminum can that has been washed with water.

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