Patent Application
20220018027
The present invention relates to a metal coloring solution for chemical conversion treatment and a method for coloring a metal.
Conventionally, in coloring of various metals, in particular aluminum or an aluminum alloy, it is known to adsorb a dye onto an anodized coating or an anodic oxidation coating in order to obtain a yellowish to brownish color tone.
For example, Patent Literature 1 discloses a method for electrolytically coloring aluminum and an aluminum alloy, comprising forming a coating structure capable of electrolytic coloring, from a colored coating formed on a base surface of aluminum or the aluminum alloy due to electrolytic coloring or spontaneous coloring; and then carrying out electrolytic coloring to superimpose the colors to obtain a coating having a new color tone. It also discloses that according to such a structure, it is possible to provide an electrolytic coloring method that can obtain various color tones including various intermediate colors, which would not otherwise be obtained by the conventional electrolytic coloring method.
However, conventionally, in order to color the metal surface into a yellowish to brownish color tone, it is necessary to use alumite, for example, if the metal to be colored is aluminum or an aluminum alloy. That is, in order to color the metal surface into a yellowish to brownish color tone it is necessary to use a metal having an oxide film on the surface, so that there are many treatment steps. Therefore, there is a need for improvement of treatment efficiency.
Further, Patent Literature 2 discloses a treatment agent for coloring a surface of aluminum or an aluminum alloy into gold color. However, there are still room for further research and development in order to color a metal surface into a yellowish to brownish color tone by a chemical conversion treatment.
In view of such problems, an object of the present invention is to provide a metal coloring solution for chemical conversion treatment and a method for coloring a metal, which can color a metal surface into a yellowish to brownish color tone with good treatment efficiency.
As a result of intensive studies to solve the above problems, the present inventors have found that a metal surface can be colored into a yellowish to brownish color tone with good treatment efficiency by carrying out a treatment with a metal coloring solution for chemical conversion treatment containing permanganic acid or a salt thereof, and one or both of an inorganic acid and a salt thereof, and a condensed phosphate.
In an aspect, the present invention completed on the basis of the above findings relates to a metal coloring solution for chemical conversion treatment, comprising: permanganic acid or a salt thereof; one or both of an inorganic acid and a salt thereof; and a condensed phosphate.
In an embodiment of the metal coloring solution for chemical conversion treatment according to the present invention, the permanganic acid or the salt thereof is permanganic acid, sodium permanganate, potassium permanganate, zinc permanganate, magnesium permanganate, calcium permanganate, ammonium permanganate, or a combination thereof.
In another embodiment of the metal coloring solution for chemical conversion treatment according to the present invention, the inorganic acid and the salt thereof are phosphoric acid, sulfuric acid, nitric acid, carbonic acid, hydrochloric acid, and salts thereof, or combinations thereof.
In yet another embodiment of the metal coloring for chemical conversion treatment according to the present invention, the condensed phosphate is potassium pyrophosphate, sodium tripolyphosphate, or a combination thereof.
In still another embodiment, the metal coloring solution for chemical conversion treatment according to the present invention contains 0.5 to 50 g/L of the permanganic acid or the salt thereof.
In still another embodiment, the metal coloring solution for chemical conversion treatment according to the present invention contains 0.5 to 100 g/L of the inorganic acid and the salt thereof.
In still another embodiment, the metal coloring solution for chemical conversion treatment according to the present invention contains 1 to 150 g/L of the condensed phosphate.
In yet another embodiment, the metal coloring solution for chemical conversion treatment according to the present invention further comprises an oxo acid or a salt thereof.
In still another embodiment of the metal coloring solution for chemical conversion treatment according to the present invention, the oxo acid or the salt thereof is perchloric acid, chloric acid, chlorous acid, hypochlorous acid, bromic acid, boric acid, or a salt thereof, or a combination thereof.
In still another embodiment, the metal coloring solution for chemical conversion treatment according to the present invention contains 0.5 to 100 g/L of the oxo acid or the salt thereof.
In yet another embodiment of the metal coloring solution for chemical conversion according to the present invention, the metal to be treated is at least one selected from the group consisting of aluminum, aluminum alloys, copper, copper alloys, iron, iron alloys, zinc, zinc alloys, magnesium, and magnesium alloys.
In another aspect, the present invention relates to a method for coloring a metal, comprising a step of coloring the metal by a chemical conversion treatment using the metal coloring solution for chemical conversion treatment according to the present invention.
In one embodiment of the method for coloring the metal according to the present invention, the step of coloring the metal by the chemical conversion treatment comprises immersing the metal in the metal coloring solution for chemical conversion treatment at a temperature of 10° C. to 80° C. for 30 seconds to 20 minutes to color the metal.
According to the present invention, it is to provide a metal coloring solution for chemical conversion treatment and a method for coloring a metal, which can color a metal surface into a yellowish to brownish color tone with good treatment efficiency.
Hereinafter, embodiments of a metal coloring solution for chemical conversion treatment and a method for coloring a metal according to the present invention will be described. However, the present invention is not limited to the embodiments, and various changes, modifications, and improvements may be added without departing from the scope of the present invention, based on knowledge of those skilled in the art.
A metal coloring solution for chemical conversion treatment according to an embodiment of the present invention contains permanganic acid or a salt thereof, and one or both of an inorganic acid and a salt thereof, and a condensed phosphate. By using the metal coloring solution for chemical conversion treatment containing permanganic acid or the salt thereof, and one or both of the inorganic acid and the salt thereof, and the condensed phosphate, a coating (colored coating) can be formed on the metal surface simply by immersing a metal to be treated in metal coloring solution for chemical conversion treatment, whereby the metal surface can be colored into a yellowish to brownish color tone. Therefore, when the metal surface is colored into the yellowish to brownish color tone, there is no need to form an oxide film on the surface of the metal, and there is no need to color the metal by electrolysis, and an improved treatment efficiency can be achieved. Further, according to the metal coloring solution for chemical conversion treatment according to an embodiment of the present invention, adhesion of the coating (colored coating) formed on the metal surface is also improved.
A metal whose surface is to be colored with the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention (a metal to be treated) includes at least one selected from the group consisting of aluminum, aluminum alloys, copper, copper alloys, iron, iron alloys, zinc, zinc alloys, magnesium, and magnesium alloys. The metal to be treated may be the metal itself, or for example, a plating of the metal formed on a surface of a metal substrate such as an iron-based material or an iron-based component.
Examples of permanganic acid or the salt thereof that can be used include permanganic acid, sodium permanganate, potassium permanganate, zinc permanganate, magnesium permanganate, calcium permanganate, ammonium permanganate, or a combination thereof. Further, as the permanganic acid or the salt thereof, sodium permanganate and potassium permanganate are more preferable.
The content of permanganic acid or the salt thereof in the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention can be, for example, from 0.5 to 50 g/L, although it depends on types of metals to be treated and a degree of a yellowish to brownish color tone. Basically, a lower content of the permanganic acid or the salt thereof can allow the metal surface to be colored into a lighter yellowish to darker yellowish color tone. Further, a higher content of the permanganic acid or the salt thereof can allow the metal surface to be colored into a lighter brownish to darker brownish color tone. The content of permanganic acid or the salt thereof is more preferably from 1 to 30 g/L, and more preferably from 2 to 20 g/L.
As will be described later, the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention may contain an oxo acid or a salt thereof. However, for a metal coloring solution for chemical conversion treatment that does not contain these components, the surface of the metal such as aluminum or an aluminum alloy can be colored into a yellowish to brownish color tone that can provide further improved aesthetic appearance.
The inorganic acid and the salt thereof in the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention are preferably phosphoric acid, sulfuric acid, nitric acid, carbonic acid, hydrochloric acid, and salts thereof, or combinations thereof. The salts of phosphoric acid, sulfuric acid, nitric acid, carbonic acid, and hydrochloric acid that can be used include metal salts or ammonium salts of those acids. Further, as the inorganic acid and the salt thereof, trisodium phosphate, nitric acid, copper nitrate and zinc chloride are more preferable.
The content of the inorganic acid and the salt thereof in the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention can be, for example, from 0.5 to 100 g/L, although it depends on types of metals to be treated and a coloring degree of a yellowish to brownish color tone. Basically, a lower content of the inorganic acid and the salt thereof can allow the metal surface to be colored into a lighter yellowish to darker yellowish color tone. Further, a higher content of the inorganic acid and the salt thereof can allow the metal surface to be colored into a lighter brownish to darker brownish color tone. The content of the inorganic acid and the salt thereof is more preferably from 1 to 30 g/L, and more preferably 2 to 20 g/L.
The condensed phosphate is preferably potassium pyrophosphate, sodium tripolyphosphate, or a combination thereof. The content of the condensed phosphate can be, for example, from 1 to 150 g/L, although it depends on types of metals to be treated and a coloring degree of a yellowish to brownish color tone. Basically, a lower content of the condensed phosphate can the metal surface to be colored into a lighter yellowish to darker yellowish color tone. Further, a higher content of the condensed phosphate can allow the metal surface to be colored into a lighter brownish to darker brownish color tone. The content of the condensed phosphate is more preferably from 3 to 50 g/L, and more preferably from 4 to 40 g/L.
The metal coloring solution for chemical conversion treatment according to the embodiment of the present invention may further contain an oxo acid or a salt thereof. Even if the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention contains the oxo acid or salt thereof, the surface of the above metal to be treated can be colored into a yellowish to brownish color tone with good treatment efficiency. Further, the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention contains the oxo acid or the salt thereof, so that the surface of metal such as copper, copper alloys, iron, iron alloys, zinc, and zinc alloys can be colored into a yellowish to brownish color tone that can provide more improved aesthetic appearance.
The oxo acid or the salt thereof may preferably be perchloric acid, chloric acid, chlorous acid, hypochlorous acid, bromic acid, boric acid, or salts thereof, or combinations thereof. The salts of perchloric acid, chloric acid, chlorous acid, hypochlorous acid, bromic acid, and boric acid that can be used include metal salts or ammonium salts of those acids.
The total content of the oxo acid or salt thereof in the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention can be from 0.5 to 100 g/L. Basically, as the total content of the oxo acid or the salt thereof is lower, the surface of the metal can be colored into a lighter yellowish to darker yellowish color tone. Further, as the total content of the oxo acid or the salt thereof is higher, the surface of the metal can be colored into a lighter brownish to darker brownish color tone. The total content of the oxo acid or the salt thereof is more preferably from 1 to 50 g/L, and even more preferably from 10 to 30 g/L.
The metal coloring solution for chemical conversion treatment according to the embodiment of the present invention may be a mixture of the various components as described above and an aqueous medium. The aqueous medium refers to a medium containing water as a main component. Examples of the aqueous medium include a medium containing water as a main component and an organic solvent such as an alcohol miscible with water. During the preparation of the metal coloring solution for chemical conversion treatment according to an embodiment of the present invention, during storage of the metal coloring solution for chemical conversion treatment, or after coloring of the surface of the metal, the aqueous medium may optionally contain various components that advantageously act to improve any property of the colored surface of the metal, or various components that do not substantially inhibit the effects of the present invention. Specific examples of these components include pH adjusting agents, storage stabilizers and the like.
Next, a method for coloring a metal according to an embodiment of the present invention will be described in detail. First, a bath is prepared that contains the metal coloring solution for chemical conversion treatment according to the embodiment of the present invention. The metal to be treated is then immersed in the metal coloring solution for chemical conversion treatment while controlling a temperature of the metal coloring solution for chemical conversion treatment in the bath. After a certain period of time, the metal to be treated is pulled up from the bath to obtain a metal having a surface colored into a yellowish to brownish color tone. Thus, according to the method for coloring the metal according to the embodiment of the present invention, only immersion of the metal to be treated in the metal coloring solution for chemical conversion treatment can allow the surface of the metal to be colored into the yellowish to brownish color tone. Therefore, when coloring the surface of the metal, it is not necessary to form an oxide film on the surface of the metal, and it is not necessary to perform coloring by electrolysis, thereby improving the treatment efficiency.
Further, in the method for coloring the metal according to the embodiment of the present invention, the surface of the metal to be treated may be colored, for example by bringing the metal coloring solution for chemical conversion treatment into contact with the surface of the metal, for example in a spraying step of the metal coloring solution for chemical conversion treatment, in addition to the immersion of the metal to be treated in the metal coloring solution for chemical conversion treatment.
A treatment temperature with the metal coloring solution for chemical conversion treatment is preferably in a range of from 10 to 80° C., and more preferably in a range of from 10 to 60° C., and even more preferably in a range of from 30 to 60° C. When the treatment temperature is 10° C. or more, a reaction velocity of the surface treatment increases, and when the treatment temperature is 80° C. or less, a decrease in a liquid level of the metal coloring solution for chemical conversion treatment due to evaporation can be suppressed.
A treatment time with the metal coloring solution for chemical conversion treatment is preferably in a range of from 30 seconds to 20 minutes, and more preferably in a range of from 1 minute to 20 minutes, and even more preferably in a range of from 1 minute to 10 minutes. Basically, as the treatment time is shorter, the surface of the metal can be colored into a lighter yellowish to darker yellowish color tone. Further, as the treatment time is longer, the surface of the metal can be colored into a lighter brownish to darker brownish color tone.
When carrying out the metal surface treatment, the metal to be treated can be previously degreased, activated, or surface-adjusted to improve the appearance, corrosion resistance of the metal to be treated and reactivity of the metal to be treated with the metal coloring solution for chemical conversion treatment.
After the metal surface treatment, a post-treatment may be carried out with coating agents containing one or more selected from the group consisting of silicon, a resin and a wax. These coating agents are not particularly limited as long as they do not affect the desired color tone on the surface of the metal, and include coating agents containing resins such as acrylic resins, olefin resins, alkyd resins, urea resins, epoxy resins, melamine resins, fluororesins, polyethylene, polyvinyl chloride, polystyrene, polypropylene, methacrylic resins, phenolic resins, polyester resins, polyurethane, polyamide, and polycarbonate, and silicates, colloidal silica or the like. The concentration of those resins is preferably from 0.01 to 800 g/L, although the appropriate concentration varies depending on the type of resins. Specific examples of the coating agents include Cosmer Coat (trade name; from Kansai Paint Co., Ltd.); High Seal 272 (trade name; from NIPPON HYOMEN KAGAKU KABUSHIKI KAISHA); Stron JS Coat (trade name; NIPPON HYOMEN KAGAKU KABUSHIKI KAISHA); Triner TR-170 (trade name; NIPPON HYOMEN KAGAKU KABUSHIKI KAISHA); Finigard (trade name; from Coventya) and the like. Specific examples of acrylic resins include Hirotite (trade name; Hitachi Chemical Co., Ltd.) and Alloset (trade name; Nippon Shokubai Co., Ltd.). Specific examples of the olefin resins include FLO-THENE (trade name; SUMITOMO SEIKA CHEMICALS CO., LTD.); PES (trade name; Nippon Unicar Co., Ltd.); CHEMIPEARL (trade name; Mitsui Chemicals, Inc.); and SUNFINE (trade name; Asahi Kasei Corporation) and the like.
The metal coloring solution for chemical conversion treatment according to the embodiment of the present invention can be used for the purpose of coloring the metal surface into a desired color, imparting a desired aesthetic appearance, or imparting distinctiveness, or the like. As a form of the metal to be treated, any form can be used, and there is no particular limitation. For example, decorative articles, fastening members such as buttons and fasteners, parts for vehicles, and the like can be used. The shape of the metal to be treated is not limited, and any shape can be used.
Hereinafter, while Examples of the present invention will be described, these Examples are provided for better understanding of the present invention, and are not intended to limit the present invention.
JIS A5052 (aluminum-magnesium alloy), A2017 (aluminum-copper alloy) and ADC12 (aluminum die-cast) were prepared as specimens (metal pieces to be treated), and the surfaces of the specimens were degreased and washed with water in this order.
A bath containing each metal coloring solution for chemical conversion treatment having each solution composition as shown in Tables 1 to 6 and 8 were prepared. Pure water was used as an aqueous medium of the metal coloring solution for chemical conversion treatment.
Subsequently, each specimen was immersed in the metal coloring solution for chemical conversion treatment while controlling the metal coloring solution for chemical conversion treatment in the bath at each temperature as shown in Tables 1 to 6 and 8. After immersion for each time as shown in Tables 1 to 6 and 8, each specimen was taken out. The surface of each specimen was washed with water and then dried.
In Examples 90 and 91, each specimen after forming a coating (a colored coating) by immersion were washed with water, subjected to a coating treatment, and dried. For the coating treatment in Example 90, Stron JS Coat (a coating agent from NIPPON HYOMEN KAGAKU KABUSHIKI KAISHA) was used, and for the coating treatment in Example 91, TR-170 (a coating agent from NIPPON HYOMEN KAGAKU KABUSHIKI KAISHA) was used.
JIS C2600P (brass) and C1100P (pure copper) were prepared as specimens (metal pieces to be treated), and the surfaces of the specimens were degreased and washed with water in this order.
A bath containing each metal coloring solution for chemical conversion treatment having each solution composition as shown in Table 7 was prepared. Pure water was used as an aqueous medium of the metal coloring solution for chemical conversion treatment.
Subsequently, each specimen was immersed in the metal coloring solution for chemical conversion treatment while controlling the metal coloring solution for chemical conversion treatment in the bath at each temperature as shown in Table 7. After immersion for each time as shown in Table 7, each specimen was taken out. Subsequently, the surface of each specimen was washed with water and then dried.
JIS ZDC2 (zinc die-cast) and a zinc plating material were prepared as specimens (metal pieces to be treated), and the surfaces of the specimens were degreased and washed with water in this order. The zinc plating material was obtained by forming a zincate zinc plating having a thickness of 8 μm onto a base material of JIS SPCC (rolled steel sheet) as defined in the JIS standard. Further, 9000 ABS from NIPPON HYOMEN KAGAKU KABUSHIKI KAISHA was used as a brightener for the zincate zinc plating.
A bath was then prepared that contained each metal coloring solution for chemical conversion treatment having each solution composition as shown in Table 7. Pure water was used as an aqueous medium of the metal coloring solution for chemical conversion treatment.
Subsequently, each specimen was immersed in the metal coloring solution for chemical conversion treatment while controlling the metal coloring solution for chemical conversion treatment in the bath at each temperature as shown in Table 7. After immersion for each time as shown in Table 7, each specimen was taken out. Subsequently, the surface of each specimen was washed with water and then dried.
JIS SPCC (rolled steel sheet) was prepared as a specimen (a metal piece to be treated), and the surface of the specimen was sequentially degreased and washed with water.
A bath was then prepared that contained each metal coloring solution for chemical conversion treatment having each solution composition as shown in Table 7. Pure water was used as an aqueous medium of the metal coloring solution for chemical conversion treatment.
Subsequently, each specimen was immersed in the metal coloring solution for chemical conversion treatment while controlling the metal coloring solution for chemical conversion treatment in the bath at each temperature as shown in Table 7. After immersion for each time as shown in Table 7, each specimen was taken out. Subsequently, the surface of each specimen was washed with water and then dried.
JIS AZ31 (magnesium-zinc alloy) was prepared as a specimen (metal pieces to be treated), and the surface of the specimen was degreased and then washed with water.
Subsequently, a bath was prepared that contained a metal coloring solution for chemical conversion treatment having a solution composition as shown in Table 7. Pure water was used as an aqueous medium of the metal coloring solution for chemical conversion treatment.
Subsequently, the specimen was immersed in the metal coloring solution for chemical conversion treatment while controlling the metal coloring solution for chemical conversion treatment in the bath at the temperature as shown in Table 7. After immersion for the time shown in Table 7, the specimen was taken out. Subsequently, the surface of the specimen was washed with water and then dried.
Metals as shown in Table 9 were prepared as specimens (metal pieces to be treated), and the surfaces of the specimens were sequentially degreased and washed with water.
A bath was then prepared that contained each metal coloring solution for chemical conversion treatment having each composition as shown in Table 9. Pure water was used as an aqueous medium of the metal coloring solution for chemical conversion treatment.
Next, each specimen was immersed in the metal coloring solution for chemical conversion treatment while controlling the temperature of the metal coloring solution for chemical conversion treatment in the bath at each temperature as shown in Table 9. After immersion for each time as shown in Table 9, each specimen was taken out. Subsequently, the surface of each specimen was washed with water and then dried.
The specimens prepared in Examples 1 to 91 and Comparative Examples 1 to 4 were evaluated for a color tone and adhesion, as follows:
The color tone of the surface of each specimen was visually evaluated. The evaluation criteria are shown below:
A cutting of 10×10 squares (100 squares in total) was created in the surface of each specimen with a cutter, and a number of squares was counted in which the colored coating did not peel off when a cellophane tape (registered trademark) was affixed and released. The size of one square was 1 mm×1 mm in length×width.
In each table, the ratio is shown by (a number of squares where the colored coating did not peel off)/100, which indicates that as the number of squares where the colored coating did not peel off is larger, the adhesion of the colored coating is higher.
Tables 1 to 9 show test conditions and evaluation results for Examples 1 to 91 and Comparative Examples 1 to 4.
It was confirmed from the above results that according to the metal coloring solution for chemical conversion treatment containing permanganic acid or the salt thereof, and one or both of the inorganic acid and the salt thereof, and condensed phosphate as in Examples 1 to 91, the surface of the metal could be colored into the yellowish to brownish color tone with good treatment efficiency.
On the other hand, it was confirmed that the metal surface could not be colored into the yellowish to brownish color tone unless the metal coloring solution for chemical conversion treatment contained permanganic acid or the salt thereof, and one or both of the inorganic acid and the salt thereof, and condensed phosphate, as can be seen from Comparative Examples 1 to 4.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-116562 | Jul 2020 | JP | national |
