JPH0241595B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the gloss of an electrodeposited product. With regard to clear-coated aluminum satsushi and other electrodeposition-coated products, due to the recent diversification of the hobbies of general consumers, there are now not only glossy ones, but also matte ones, as well as various matte ones. There is a growing demand for something with a certain degree of quality. Some of the methods proposed as matting methods to meet these demands include, for example, the use of electrodeposition coating containing a matting pigment such as silicon oxide, but this method causes the matting pigment to settle or regenerate. Not only does the coating have poor stability due to agglomeration, but it is also difficult to obtain a coated product with stable gloss without gloss spots, and the alkali resistance of the coating film is also poor. It is also known to use a matte paint containing a resin with poor compatibility instead of a matte pigment, but this method has drawbacks such as poor stability over time and poor water washability, such that gloss spots are likely to appear. Furthermore, it is also known to obtain a matte coating film by immersing a coated object coated with a glossy coating in an aqueous solution of an inorganic acid, an organic acid or a salt, and then baking it to dry.
With this method, a sufficient matting effect cannot be obtained because the dipping treatment solution is washed away by water washing (even without washing, gloss spots may occur due to drops of the chemical solution from the hanger or dripping of the chemical solution when lifting). (occurs). Another method for matting electrodeposited materials is the method of JP-A-Sho.
There is a method related to No. 54-85628. In this method, the electrodeposited coating is energized in an aqueous salt solution, but gloss spots are likely to occur and the specular reflectance at 60° is 40.
There are disadvantages such as difficulty in obtaining the following gloss. Further, the above matting method has the disadvantage that it is difficult to adjust the degree of matting, and it is difficult to match the taste of general consumers. The present inventors have determined that the voltage (hereinafter referred to as
The pulsation rate of the DC conversion voltage (referred to as "DC conversion voltage") is selected within a certain range, and the coating film electrodeposited at this pulsation rate is immersed in an acid aqueous solution in an uncured state, a voltage is applied, and then baked to harden. It has been found that excellent coatings with no defects are obtained, yet by varying the pulsation rate or acid concentration, articles with any degree of matteness can be produced. That is, the gist of the present invention is to provide a method for matting an electrodeposited coating film, in which an uncured coated object after electrodeposition coating is immersed in an acid aqueous solution, a voltage is applied using the coated object as an anode, and then cured by baking. The method consists in controlling the matting of the coating film by selecting the pulsation rate during electrodeposition coating. The pulsation rate of the DC converted voltage used in the present invention is given by the following formula in the voltage of a current converted from commercial AC, for example, three-phase AC to DC, that is, three-phase half-wave or three-phase full-wave DC voltage: Pulsation rate = Maximum voltage - Minimum voltage / Average voltage x 100 If this pulsation rate is selected within the range of 10 to 140%, various degrees of matteness can be obtained. In other words, if you want to increase the degree of matteness, reduce the pulsation rate during electrodeposition,
If it is desired to reduce the degree of matting, the pulsation rate during electrodeposition may be increased. Therefore, the lower the pulsation rate, the lower the gloss, and the higher the pulsation rate, the higher the gloss. For electrodeposition, conventional electrodeposition paints are used, such as acrylic resin-melamine resin mixed clear paint, epoxy resin-melamine resin mixed clear paint, urea resin-melamine resin mixed clear paint, alkyd resin-melamine resin mixed clear paint. This is carried out by a conventional method using an anionic electrodeposition paint such as (particularly preferred is an acrylic resin-melamine resin mixed clear paint). The conditions for electrodeposition are within the range of commonly used conditions. However, the average voltage used is in the range of 2 to 300 volts, and its pulsation rate satisfies the above-mentioned conditions. Preferably it is 50-250 volts. The acid used in the present invention may be an inorganic acid such as sulfuric acid, nitric acid, phosphoric acid, or an organic acid such as an organic sulfonic acid. Preferred is an organic sulfonic acid. Examples of organic sulfonic acids include methanesulfonic acid,
Aliphatic sulfonic acids such as ethanesulfonic acid and 1,2-ethanedisulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenesulfonic acid,
Dodecylbenzenesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, 1-naphthylamine-4-sulfonic acid, 1-naphthylamine-2-sulfonic acid, naphtholsulfonic acid, naphtholdisulfonic acid, phenol-2,4-disulfone Acid, o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, p-bromobenzenesulfonic acid, 1,8-dioxy-3,6-naphthalenesulfonic acid, 1,2
-dioxy-7-anthraquinone sulfonic acid, p
-diazobenzenesulfonic acid, p-chlorobenzenesulfonic acid, o-xylene-4-sulfonic acid,
1-anthraquinonesulfonic acid, o-aminobenzenesulfonic acid, sulfosalicylic acid, p-toluenesulfonic acid, m-toluenesulfonic acid, 5,
Examples include aromatic sulfonic acids such as 5'-indigo disulfonic acid and cresol sulfonic acid,
Particularly preferred are dinonylnaphthalenesulfonic acid and dinonylnaphthalene disulfonic acid. These acids are used alone or as a mixture of two or more in the form of an aqueous solution of usually 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight. Usually, a base such as ammonia or an amine such as diethylamine, triethylamine, dimethylethanolamine, triethanolamine, morpholine, aniline, amylamine, isobutylamine, isopropylamine is added to the acid aqueous solution to adjust the pH to 1.0 to 12, preferably 3. Adjust to ~10 and use. If desired, a water-soluble organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl cellosolve, butyl cellosolve, carbitol, acetone, or a mixed solvent of two or more of these may be added to the acid aqueous solution whose pH has been adjusted to 1.0 to 12. It may be added (usually 0.1 to 10% by weight, preferably 0.5 to 5% by weight) to effectively prevent the occurrence of gloss spots on the painted object. Addition of a water-soluble organic solvent is preferable, especially when the coated article is subjected to a cleaning treatment before being baked and dried, since it improves compatibility with the cleaning solution and more effectively prevents the occurrence of glossy spots. The base material used in the method of the present invention is aluminum,
Aluminum alloy, iron, iron alloy, magnesium alloy, copper, copper alloy, etc., and preferably aluminum and aluminum alloy. After electrodepositing these substrates using a power source capable of producing the above-mentioned pulsation rate, the uncured coating film is immersed in the acid aqueous solution prepared as described above, and the coated material is used as an anode. A voltage is applied between the counter electrode and the opposite electrode. The temperature of the acid aqueous solution is usually 15 to 25°C. The current used when applying voltage while immersed in an acid aqueous solution is generally direct current, but alternating current, pulsed current,
Alternatively, a good matte finish can be obtained by using a pulsating flow. The applied voltage and application time are the pulsation rate during electrodeposition,
For example, in the case of direct current, a voltage of usually 10 to 250 volts, preferably 50 to 250 volts, is applied for 0.5 to 15 minutes, depending on the degree of matte finish, the temperature and concentration of the acid aqueous solution, and is not limited to this. Apply for 1-5 minutes. The coated object subjected to voltage application treatment by acid immersion is taken out of the immersion liquid and subjected to heat curing treatment either as it is or after being washed. Tap water, pure water, UF can be used as a cleaning solution for painted objects.
Examples include liquid (ultrafiltration liquid), RO filtration (reverse osmosis liquid), and an aqueous solution containing a surfactant. The heat curing conditions for the painted object depend on the type of electrodeposition paint, alumite, coloring liquid, etc., and are not particularly limited, but are usually cured at 150 to 200°C for 15 to 40 minutes.
Preferably, the temperature is 170-190°C for 20-30 minutes. According to the method of the present invention, by appropriately selecting the pulsation rate during electrodeposition, the temperature and concentration of the acid aqueous solution, the applied voltage of the acid aqueous solution, the current application time, etc., good coating film properties such as hardness and durability can be obtained. Any uniform matte coating surface with no gloss spots can be obtained while maintaining alkalinity, scratch resistance, etc. In particular, by keeping the concentration, temperature, and other conditions of the acid aqueous solution constant (changing these conditions has the disadvantage of interfering with operation), by selecting the pulsation rate, it is easy to obtain an appropriate matte coating surface (usually,
A matte painted surface with a gloss level of approximately 5 to 90% at 60°C specular reflectance can be obtained. Furthermore, according to the method of the present invention, there is no need to worry about paint stability as in the case of matte paints, etc.
There is no need to operate processing equipment such as UF equipment or RO equipment, or deneutralization agents using ion exchange, and the concentration of the processing liquid is low, which not only lowers operating costs but also reduces the cost compared to when using matte paint. The above-mentioned problems associated with conventional matting methods are all solved, such as sufficient coating film performance even under low heat curing conditions. Although the method of the present invention can be applied to all electrodeposited objects, it is particularly suitable for matting aluminum sash. This will be explained below using examples. Examples 1 to 6 Power Mite 3000 (acrylic resin-melamine resin mixed anionic electrodeposition paint manufactured by Nippon Paint Co., Ltd.) was coated in an electrodeposition solution (liquid temperature 21°C) diluted with pure water to a heating residue of 10% by weight. Coating [Aluminum plate and aluminum alloy plate obtained according to JISH9500 (70
mm After electrodeposition for a minute, the coated article was pulled out and washed by immersion in tap water. The resulting electrodeposition coating was immersed in an uncured state in a 0.05% by weight aqueous solution of dinonylnaphthalenedisulfonic acid (adjusted to pH 7-8 with triethylamine) at 20°C, and this was used as an anode at an average voltage of 150 volts.
After applying a DC voltage for 2.5 minutes, it was pulled up, washed with tap water, and then baked and dried at 170°C for 30 minutes. Table 1 shows the properties of the obtained matte coating film. 【table】

Claims (1)

[Scope of Claims] 1. A method for matting an electrodeposited film by immersing an uncured coated object in an acid aqueous solution after electrodeposition coating, applying a voltage using the coated object as an anode, and then curing by baking. A method of controlling the matting of the coating film by selecting the pulsation rate of the DC conversion voltage during electrodeposition coating. 2. The method according to item 1, wherein the pulsation rate of the DC conversion voltage is selected from 10 to 140%. 3. The method according to item 1, wherein the acid is an organic sulfonic acid. 4. The method according to item 1, wherein the acid is dinonylnaphthalene sulfonic acid.