Acid cleaning agent for aluminum-based metal materials and cleaning method for aluminum-based metal materials

Abstract

To provide: a coating composition which makes it possible to form a lower-gloss high-strength matte coating film; and a coating film produced from the coating composition.SOLUTION: An acidic cleaning agent contains phosphoric acid ions, sulfuric acid ions and ferric ions, wherein the phosphoric acid ions are the main component and the ratio of the concentration of the phosphoric acid ions to the concentration of the ferric ions falls within a specified range. More specifically, the concentration of the phosphoric acid ions is 15 to 26 g / L, the concentration of the phosphoric acid ions is adjusted to a value higher than the concentration of the sulfuric acid ions, and the ratio of the concentration of the phosphoric acid ions to the concentration of the ferric ions is 35:1 to 180:1.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an acidic cleaning agent for aluminum-based metallic materials and a cleaning method for aluminum-based metallic materials, and more particularly to an acidic cleaning agent for aluminum-based metallic materials which has good desmutting properties even when cleaning at low temperatures and can suppress the occurrence of brown spots even when chemical conversion treatment is omitted, and a cleaning method for aluminum-based metallic materials using said cleaning agent. [Background technology]

[0002] Aluminum-based metal materials made from aluminum or aluminum alloys generally have aluminum oxides, oil, etc. on their surfaces. Furthermore, aluminum cans such as beverage cans, which are manufactured by a drawing process called drawing and ironing (hereinafter referred to as DI processing), have aluminum powder (hereinafter referred to as smut) that is generated by shaving during drawing and lubricating oil adhering to their surfaces.

[0003] Generally, aluminum cans such as beverage cans are used after a chemical conversion coating is formed by a chemical conversion treatment and then a paint coating is formed by a painting treatment. In order to form a strong chemical conversion coating and a paint coating, it is necessary to thoroughly remove aluminum oxide, oil, smut, and the like present on the surface and clean the surface.

[0004] Generally, a method for cleaning the surface of aluminum-based metal materials includes treatment with an acidic cleaner that moderately etches and cleans the surface. Conventionally, hydrofluoric acid-based cleaners have been used as acidic cleaners, but in recent years, fluorine-free cleaners have come to be used from the viewpoint of environmental protection.

[0005] As such a fluorine-free cleaning agent, an acidic cleaning aqueous solution for aluminum-based metal materials has been proposed, which contains predetermined amounts of at least one selected from inorganic acids, bromide ions, and oxidized metal ions (see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-113189 Summary of the Invention [Problem to be solved by the invention]

[0007] However, ferric ions (Fe 3+ ) and metavanadate ion (VO 3- However, acidic cleaning agents containing oxidized metal ions such as fluorine-containing fluoride must be treated at a high temperature of 70 to 80° C. in order to ensure etching ability, which makes them less economical.

[0008] As described above, aluminum cans such as beverage cans are subjected to a process of forming a chemical conversion coating by carrying out a chemical conversion treatment after cleaning the surface with an acidic cleaning agent. If a chemical conversion coating is not formed, when the washing water is dried, the washing water reacts with aluminum to form aluminum hydroxide, and the affected area appears brown, resulting in so-called brown spots.

[0009] If a coating could be formed on the aluminum-based metal material at the same time as cleaning the surface with an acidic cleaning agent, it would be possible to omit the chemical conversion treatment process for forming the chemical conversion coating. If the chemical conversion treatment process could be omitted, it would be possible to move directly to the painting process after cleaning, and the economic effect of omitting the process would be very large. However, such a cleaning agent has not been proposed so far.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide an acidic cleaning agent for aluminum-based metallic materials and a cleaning method for aluminum-based metallic materials which have good desmutting properties even when cleaning at low temperatures and can suppress the occurrence of brown spots even when chemical conversion treatment is omitted. [Means for solving the problem]

[0011] The present inventors conducted extensive research to solve the above problems, and discovered that, in an acidic cleaning agent containing phosphate ions, sulfate ions, and ferric ions, if phosphate ions are the main component and the concentration ratio of phosphate ions to ferric ions is within a specific range, the surface of an aluminum-based metal material can be sufficiently cleaned even at a low treatment temperature, and a phosphorus-based film can be formed, thereby solving the above problems and completing the present invention.

[0012] That is, the present invention provides an pickling agent for aluminum-based metallic materials containing phosphate ions, sulfate ions and ferric ions, wherein the concentration of the phosphate ions is 13 to 26 g / L, the concentration of the phosphate ions is greater than the concentration of the sulfate ions, and the concentration ratio of the phosphate ions to the ferric ions is 35:1 to 180:1.

[0013] The concentration of the sulfate ions may be 0.25 to 1.25 g / L.

[0014] The concentration of the ferric ions may be 0.1 to 0.5 g / L.

[0015] The concentration ratio of the phosphate ions to the sulfate ions may be 10:1 to 75:1.

[0016] It may further contain a surfactant.

[0017] The concentration of the surfactant may be 0.5 to 3.0 g / L.

[0018] It may further contain an organic sulfonic acid.

[0019] Another aspect of the present invention is a method for cleaning an aluminum-based metallic material, comprising a cleaning step of bringing the above-mentioned acidic cleaning agent for aluminum-based metallic materials into contact with the surface of the aluminum-based metallic material at a liquid temperature of 40 to 70°C to clean the surface of the aluminum-based metallic material.

[0020] The contact time may be from 15 to 60 seconds. Effect of the Invention

[0021] The acidic cleaning agent for aluminum-based metallic materials of the present invention has a good desmutting property even when the aluminum-based metallic materials are cleaned at low temperatures, and can suppress the occurrence of brown spots even when chemical conversion treatment is omitted after cleaning. Therefore, it has a great economic value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described, however, the present invention is not limited to the following embodiment.

[0023] <Acidic cleaner for aluminum-based metal materials> The pickling agent for aluminum-based metallic materials of the present invention contains phosphate ions, sulfate ions, and ferric ions as essential components, and has phosphate ions as the main component, with the concentration ratio of the phosphate ions to the ferric ions being within a specific range.

[0024] [Phosphate ion] The phosphate ion (PO 4 3- ) is the main component of the acid cleaning agent for aluminum-based metal materials.

[0025] The pickling agent for aluminum-based metallic materials of the present invention contains phosphate ions, sulfate ions, and ferric ions as essential components, with the concentration of phosphate ions being greater than the concentration of sulfate ions.

[0026] Since the main component is phosphate ion, it is possible to form a phosphorus-based film on the surface of the aluminum-based metal material cleaned with the acidic cleaning agent of the present invention. By covering the surface of the aluminum-based metal material with a phosphorus-based film, it is possible to suppress exposure of aluminum and to suppress brown spots caused by reaction with the washing water.

[0027] Therefore, the pickling agent for aluminum-based metallic materials of the present invention makes it possible to omit the step of forming a chemical conversion coating by chemical conversion treatment, which has been conventionally performed, and after cleaning, the process can be directly transferred to painting treatment to form a coating film. Therefore, in the field of beverage cans, etc., the omission of the step can greatly contribute to the economic effect.

[0028] The concentration of phosphate ions is 13 to 26 g / L, preferably 18 to 23 g / L, and particularly preferably 18 to 20 g / L.

[0029] If the phosphate ion concentration is less than 15 g / L, the effects of removing smut and suppressing brown spots will be insufficient, while if the phosphate ion concentration is more than 26 g / L, excessive matte will be removed, hindering the formation of a phosphorus-based film that has the effect of suppressing brown spots.

[0030] Furthermore, the concentration ratio of phosphate ions to ferric ions is from 35:1 to 180:1, preferably from 90:1 to 115:1, and particularly preferably from 90:1 to 100:1.

[0031] If the concentration ratio of phosphate ions to ferric ions is outside the range of 35:1 to 180:1, the effects of removing smut and suppressing brown spots will be insufficient.

[0032] The concentration ratio of phosphate ions to sulfate ions is preferably from 10:1 to 75:1, more preferably from 30:1 to 52:1, and particularly preferably from 36:1 to 40:1.

[0033] If the concentration ratio of phosphate ions to sulfate ions is outside the range of 10:1 to 75:1, the effects of removing smut and suppressing brown spots will be insufficient.

[0034] The source of phosphate ions contained in the acidic cleaning agent for aluminum-based metallic materials of the present invention is not particularly limited as long as it can be ionized in the cleaning agent to generate phosphate ions. Examples of the source of phosphate ions include phosphoric acid, phosphonic acid, pyrophosphoric acid, and metaphosphoric acid. In the present invention, the substance serving as the source of phosphate ions may be used alone or in combination of two or more kinds.

[0035] Among these, phosphoric acid is preferred because it is widely used industrially and is also used as a food additive. Phosphoric acid also functions as an etching accelerator.

[0036] [Sulfate ion] The sulfate ion contained as an essential component in the pickling agent for aluminum-based metallic materials of the present invention functions as an etching accelerator.

[0037] The concentration of sulfate ions is preferably 0.25 to 1.25 g / L, and more preferably 0.5 to 1.25 g / L.

[0038] If the concentration of sulfate ions is less than 0.25 g / L, the etching rate decreases and the effect of removing smut becomes insufficient, whereas if the concentration of sulfate ions is more than 1.25 g / L, no further effect on etching is observed, which is economically disadvantageous.

[0039] The source of sulfate ions contained in the acidic cleaning agent for aluminum-based metal materials of the present invention is not particularly limited as long as it can be ionized in the cleaning agent to generate sulfate ions. For example, sulfuric acid or its salts (iron sulfate, aluminum sulfate, calcium sulfate, sodium sulfate, etc.) can be mentioned. In the present invention, the substance that is the source of sulfate ions may be used not only as one type but also as a combination of two or more types.

[0040] For example, when ferric sulfate is supplied as a source of ferric ions, which are an essential component of the pickling agent for aluminum-based metallic materials of the present invention, sulfate ions are ionized together with the ferric ions. In the present invention, the concentration of sulfate ions contained in the pickling agent can be adjusted by combining another sulfate ion source with ferric sulfate.

[0041] As the source of sulfate ions, sulfuric acid is particularly preferred because it is widely used industrially and is economically efficient.

[0042] [Ferric ion] The ferric ion contained as an essential component in the pickling agent for aluminum-based metallic materials of the present invention functions as an etching accelerator.

[0043] Normally, the etching reaction of aluminum-based metals in acidic cleaning agents is such that aluminum is converted into aluminum ions (Al 3+ ) in the anode reaction, and H + is reduced to 1 / 2H 2 This is the cathodic reaction. Therefore, the presence of ferric ions (Fe 3+ ) is present, this Fe 3+ Fe 2+ The anode reaction in which H is reduced to + This occurs simultaneously with the reduction of , promoting the aluminum etching reaction.

[0044] The concentration of ferric ions is preferably 0.1 to 0.5 g / L, and more preferably 0.2 to 0.5 g / L.

[0045] If the concentration of ferric ions is less than 0.1 g / L, the etching rate decreases and the effect of removing smut becomes insufficient, whereas if the concentration of ferric ions is more than 0.5 g / L, no further effect on etching is observed, which is economically disadvantageous.

[0046] The source of the ferric ions contained in the pickling agent for aluminum-based metallic materials of the present invention is not particularly limited as long as it can be ionized in the cleaning agent to generate ferric ions.

[0047] Among these, since it is preferable to supply the ferric ion as a water-soluble salt such as sulfate or nitrate, it is preferable that the ferric ion is supplied as ferric sulfate or ferric nitrate. When supplied as ferric sulfate, sulfate ions ionize together with the ferric ion, and when supplied as ferric nitrate, nitrate ions ionize together with the ferric ion.

[0048] As the etching reaction proceeds, the amount of ferrous ions (Fe 2+ As the concentration of ferrous iron increases, the oxidation-reduction potential (ORP) drops (also known as the aging of the cleaning agent), and the etching-promoting effect on the aluminum surface disappears. Therefore, an oxidizing agent that controls the ORP can be added from the beginning or at any time to oxidize the ferrous ions to ferric ions.

[0049] [Other ingredients] The pickling agent for aluminum-based metallic materials of the present invention may contain other components, such as surfactants and organic sulfonic acids, in addition to the essential components of phosphate ions, sulfate ions, and ferric ions.

[0050] (Surfactant) Surfactants are primarily used to remove oil and fat components that have adhered to the surface of aluminum-based metal materials, and in particular, to remove lubricants from aluminum cans after DI processing.

[0051] In addition, the surfactant prevents the removed oil and lubricant components from floating in the cleaning agent. If oil and lubricant components float in the cleaning agent, they may be re-adsorbed onto the surface of the aluminum-based metal material, but this can be avoided by adding a surfactant.

[0052] The type of surfactant is not particularly limited, and any of nonionic, cationic, anionic, and amphoteric surfactants can be used. Among them, nonionic surfactants are preferred, and for example, ethoxylated alkylphenols, hydrogen carbonate derivatives, abietic acid derivatives, primary ethoxylated alcohols, modified polyethoxylated alcohols, etc. are preferably used.

[0053] The concentration of the surfactant is preferably from 0.5 to 3.0 g / L, more preferably from 1.0 to 2.5 g / L, and particularly preferably from 1.5 to 2.0 g / L.

[0054] If the surfactant concentration is less than 0.5 g / L, cleaning performance, especially degreasing performance, decreases, while if the surfactant concentration is more than 3.0 g / L, foaming occurs in the detergent, making cleaning difficult and placing a strain on wastewater treatment.

[0055] (Organic Sulfonic Acid) The organic sulfonic acid is added mainly to provide a sufficient etching effect even under low temperature conditions.

[0056] The organic sulfonic acid has a structure represented by the following formula (1): [C1] R-SO 3 H (1) (In the formula, R represents a methyl group or a substituted alkyl group having 1 to 9 carbon atoms and at least one hydroxyl group.)

[0057] The substituted alkyl group in the above formula (1) is not limited to a straight chain, but may be a branched chain. Specific examples of the above organic sulfonic acid include HSO 3 -CH 3 In addition, HSO 3 -CH 2 OH, HSO 3 -CH 2 CH 2 OH, HSO 3 -CH 2 CH 2 CH 2 OH, HSO 3 -CH 2 CH(OH)CH 2 OH, etc. The organic sulfonic acids may be used alone or in combination of two or more kinds.

[0058] The content of the organic sulfonic acid is preferably 0.01 g / L to 0.2 g / L. If the content is less than 0.01 g / L, the effect is insufficient, and if the content exceeds 0.2 g / L, no further effect is observed, which is economically disadvantageous.

[0059] <Cleaning method for aluminum-based metal materials> The method for cleaning aluminum-based metallic materials of the present invention includes a cleaning step in which the above-mentioned pickling agent for aluminum-based metallic materials of the present invention is brought into contact with the surface of an aluminum-based metallic material at a liquid temperature of 50 to 60° C. As long as the method includes the cleaning step, it may include any other steps.

[0060] The method for contacting the aluminum-based metal material with the acidic cleaner is not particularly limited, and any method known in the art can be appropriately selected, such as a spray method or an immersion method.

[0061] In the cleaning method for aluminum-based metallic materials of the present invention, the acidic cleaning agent is used at a liquid temperature of 40 to 70° C. That is, cleaning can be performed at a lower temperature compared to conventional cleaning methods. The treatment temperature is more preferably 40 to 60° C., and most preferably 40 to 50° C.

[0062] The time for which the aluminum-based metallic material is in contact with the acidic cleaning agent is not particularly limited as long as it is a time that allows sufficient etching and allows a uniform phosphorus-based coating to be formed on the surface of the aluminum-based metallic material, and can be appropriately set depending on the treatment temperature.

[0063] For example, when the acidic cleaning agent is used at a liquid temperature of 50 to 60° C., the contact time is preferably 15 to 60 seconds, more preferably 25 to 45 seconds, and most preferably 25 to 45 seconds. EXAMPLES

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. However, Examples 3 to 6 are reference examples.

[0065] <Material> The materials used in the examples and comparative examples are shown below. [Phosphate ion source] Phosphoric acid (Coop Chemical Company, product name: 75% phosphoric acid) [Sulfate ion source] Sulfuric acid (Mitsubishi Materials Corporation, product name: dilute sulfuric acid) [Ferric ion source] Ferric sulfate (manufactured by Jujo Synthetic Chemical Laboratory, product name: Ferric sulfate liquid) [Organic sulfonic acids] Methanesulfonic acid (manufactured by BASF Japan, product name: Lutropur MSA) [Surfactants] Polyoxyalkylene ether (ADEKA Corporation, product name: Adekanol LG294)

[0066] <Examples 1 to 16 and Comparative Examples 1 to 20> [Preparation of coating composition] The materials were mixed to the concentrations shown in Tables 1 and 2 to prepare pickling agents for aluminum-based metallic materials of Examples and Comparative Examples.

[0067] Specifically, the materials were mixed and stirred in industrial water to the concentrations shown in Tables 1 and 2. In this case, the activator was added last after the materials were mixed. After the preparation of the acidic cleaning agent for aluminum-based metal materials, the temperature was raised to the specified processing conditions.

[0068] [Processing of aluminum-based metal materials] A lidless container with lubricating oil and smut attached was prepared by DI machining of an aluminum plate made of alloy 3104. The lidless container was sprayed with the acidic cleaner for aluminum-based metal materials obtained in the examples and comparative examples under the treatment conditions shown in Tables 1 and 2.

[0069] It was then washed with tap water for 15 seconds, followed by a spray rinse with deionized water for 5 seconds, and dried at 195° C. for 3 minutes.

[0070] <Evaluation> After drying, the following evaluations were carried out for each of the resulting containers.

[0071] [Anti-smut properties] After drying, a transparent adhesive tape was attached to the inner surface of the container, which was then peeled off and attached to a white mount. Similarly, a tape that had not been peeled off was attached to the white mount. The whiteness of the tape-attached surface was then compared between the tape that had been peeled off and the tape that had not been peeled off. Specifically, the degree of contamination (the presence or absence of adhesions, or blackening) of the tape-attached surface was evaluated on the following 10-point scale. 5. No contamination 4.5 Contamination that is difficult to detect with the naked eye 4 Trace contamination 3.5 Slight contamination 3. Minor contamination 2.5 Contamination less than 2 points 2. Moderate pollution 1.5 Less than 1 point contamination 1. Massive pollution 0 No adhesion or contamination on the entire surface

[0072] [Whether or not brown spots occur] 5.0 mL of industrial water was dropped onto the center of the bottom (dome part) of the treated can with a dropper, and the can was dried in a hot air drying oven at 195°C for 3 minutes, after which the percentage of the cans that had discolored was visually confirmed. The evaluation criteria are as follows. The number of cans that were evaluated was 100, and the percentage of the cans that had discolored was confirmed. 4 No occurrence 3. Less than 1.0% of cases occurred 2. Less than 5.0% of cases occurred 1. Occurrence of 5.0% or more of the number of transactions

[0073] [Table 1]

[0074] [Table 2]

Claims

1. An acidic cleaning agent for aluminum-based metallic materials, comprising phosphate ions, sulfate ions, and ferric ions, The concentration of the phosphate ions is 18 to 20 g / L; the concentration of the phosphate ions is greater than the concentration of the sulfate ions; The concentration ratio of the phosphate ions to the ferric ions is 35:1 to 180:

1. Acidic cleaning agent for aluminum-based metal materials.

2. 2. The pickling agent for aluminum-based metallic materials according to claim 1, wherein the concentration of the sulfate ions is 0.25 to 1.25 g / L.

3. 3. The pickling agent for aluminum-based metallic materials according to claim 1, wherein the concentration of the ferric ions is 0.1 to 0.5 g / L.

4. 4. The pickling agent for aluminum-based metallic materials according to claim 1, wherein a concentration ratio of the phosphate ions to the sulfate ions is from 10:1 to 75:

1.

5. The pickling agent for aluminum-based metallic materials according to claim 1 , further comprising a surfactant.

6. 6. The pickling agent for aluminum-based metallic materials according to claim 5, wherein the concentration of the surfactant is 0.5 to 3.0 g / L.

7. The pickling agent for aluminum-based metallic materials according to claim 1 , further comprising an organic sulfonic acid.

8. A method for cleaning an aluminum-based metallic material, comprising a cleaning step of contacting the surface of an aluminum-based metallic material with the pickling agent for aluminum-based metallic materials according to any one of claims 1 to 7 at a liquid temperature of 40 to 70°C to clean the surface of the aluminum-based metallic material.

9. 9. The method for cleaning an aluminum-based metallic material according to claim 8, wherein the contact time is from 15 to 60 seconds.

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