JP2005314518A - Matte electrodeposition coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anionic type matte electrodeposition coating composition having a low contamination property and excellent in coated film properties, finishing appearance and a coating operation property. <P>SOLUTION: The anionic type matte electrodeposition coating composition excellent in low contamination property comprises (A) 100 pts.wt. vinyl copolymer having a carboxy group, a hydroxy group and a crosslinking functional group, (B) 30-100 pts.wt. amino resin and (C) 0.5-40 pts.wt. tetraethoxysilane and/or its partially hydrolysed and condensed product. In the coating composition, the coated film obtained by electrodeposition coating has ≤70° contact angle of the coated film with water when the film is allowed to stand within 240 hr in an atmosphere of ≥98% relative humidity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an anionic matte electrodeposition coating composition, and a coating film obtained from the coating exhibits characteristics excellent in contamination.

  Conventionally, anodized aluminum materials are light and strong, and are excellent in corrosion resistance. Therefore, they are widely used in building materials such as window frames, doors, and exteriors of buildings and houses. An anionic electrodeposition coating with a single coat and good finish is generally used for coating an aluminum material. Of these, matte-type paints tend to be preferred, and as anionic matte electrodeposition paints, melamine is obtained by mixing a water-borne acrylic resin containing a carboxyl group and a hydroxyl group with a melamine resin cross-linking agent and dispersing in water. A curable electrodeposition coating is typical.

  However, in recent years, the needs for aluminum building materials have diversified, and as one of them, there is a need to wash away contaminants adhering to the coating film by rain or the like to maintain the aesthetics of aluminum building materials for a long period of time. In order for the contaminants adhering to the coating film to be washed away due to rain or the like, the water contact angle of the coating film is preferably smaller than 70 degrees. Since the angle is 80 degrees or more, it cannot be expected that contaminants will be washed away due to rainfall or the like.

  In the solvent-based paint, for example, in Japanese Patent No. 2869443 (Patent Document 1), an organosilicate and / or a condensate thereof is blended with an organic solvent-based paint composition containing a hydroxyl group-containing fluororesin and an amino resin crosslinking agent. An organosilicate and / or condensation thereof to a coating composition (Claim 1) and an organic solvent-based coating composition containing a hydroxyl group-containing fluororesin and / or a hydroxyl group-containing acrylic resin and a (blocked) polyisocyanate compound crosslinking agent. A coating composition (Claim 2) formed by blending a product is disclosed, and cured coatings obtained from these coating compositions are treated with an acid, resulting in a water contact angle of 70 degrees or less. The coating film is said to be a stain-resistant coating film (having good stain resistance).

  However, although the above method can be applied to an organic solvent-based paint composition, as described later, it cannot be applied to an anionic electrodeposition paint composition that is a water-based paint. It was not possible to obtain a good anionic matte electrodeposition coating film having a low contamination of 70 degrees or less.

On the other hand, a water-based paint is obtained by dispersing organosilicate and / or a condensate thereof, a vinyl copolymer having an alkoxysilyl group, and a melamine resin in water in JP-A-11-315254 (Patent Document 2). An aqueous matte coating composition containing an aqueous dispersion is disclosed, and it is said that a coating film having high hardness and excellent scratch resistance can be obtained by blending an organosilicate and / or a condensate thereof. As will be described later, there is no description about reduction of water contact angle or contamination.
Japanese Patent No. 2869443 JP-A-11-315254

  Therefore, the present invention has low contamination and is excellent in coating film performance such as weather resistance, chemical resistance, solvent resistance, hardness, and the finished appearance of the coating film, coating workability, coating stability, etc. An object of the present invention is to provide an anionic matte electrodeposition coating composition.

In order to solve the above problems, the present inventors have conducted extensive studies on a paint modifying component capable of reducing the water contact angle of the coating film, and as a result, tetraethoxysilane and / or its partial hydrolysis condensate have excellent effects. The present invention has been completed.
That is, the present invention relates to (A) 100 parts by weight of a vinyl copolymer having a carboxyl group, a hydroxyl group, and a cross-linking functional group, and (B) 30 to 100 parts by weight of an amino resin and (C) tetraethoxysilane. And / or an anionic matte electrodeposition coating composition containing 0.5 to 40 parts by weight of a partially hydrolyzed condensate thereof, the coating film obtained by electrodeposition coating having a relative humidity of 98% It is an anionic matte electrodeposition coating composition excellent in low contamination, in which the water contact angle of the coating film becomes 70 degrees or less when left in the above atmosphere for 240 hours or less.

By applying the anionic matte electrodeposition coating material and electrodeposition coating method of the present invention, it has become possible to provide a coating film that is excellent in coating film appearance and coating film performance and particularly excellent in low contamination. .
Moreover, as a use, it is suitable for the coating especially for improving the designability of an aluminum raw material.

Below, the electrodeposition coating material of this invention is demonstrated in detail.
[(A) Vinyl copolymer]
The vinyl copolymer (A) used in the present invention is composed of an α, β-ethylenically unsaturated carboxylic acid monomer, a hydroxyl group-containing α, β-ethylenically unsaturated monomer, and a crosslinking functional group-containing α, β. -Copolymerized with ethylenically unsaturated monomer and other α, β-ethylenically unsaturated monomer.

  The α, β-ethylenically unsaturated carboxylic acid monomer imparts water dispersibility and electrophoretic properties to the vinyl copolymer. Illustrative examples include acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid and the like. These 1 type (s) or 2 or more types can be mixed and used.

  The α, β-ethylenically unsaturated carboxylic acid monomer has an acid value in the vinyl copolymer of preferably 10 to 150 mg KOH / g solid, more preferably 20 to 100 mg KOH / g solid. used. If the acid value of the vinyl copolymer is less than 10, sufficient water dispersion stability is difficult to obtain, and if it exceeds 150, the electrophoretic properties and coating film deposition properties deteriorate, and the water resistance and alkali resistance of the coating materials also deteriorate. To do.

  The hydroxyl group-containing α, β-ethylenically unsaturated monomer reacts with an amino resin to impart curability when the coating film is baked. For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, polyethylene glycol mono Examples include acrylate, polyethylene glycol monomethacrylate, dipropylene glycol monoacrylate, dipropylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, and lactone-modified products thereof. Can be used.

  Such a hydroxyl group-containing α, β-ethylenically unsaturated monomer preferably has a hydroxyl value in the vinyl copolymer of 20 to 200 mg KOH / g solid, more preferably 40 to 160 mg KOH / g solid. Used in range. When the hydroxyl value is less than 20, sufficient curability cannot be ensured, and when it exceeds 200, the coating film becomes brittle, water resistance is lowered, and sufficient performance is hardly obtained.

  The cross-linked functional group-containing α, β-ethylenically unsaturated monomer is one that partially crosslinks the vinyl copolymer in the paint to form a microgel and impart matte performance. Examples include acetoacetoxyethyl acrylate, acetoacetoxyethyl methacrylate, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, β -Methyl-substituted glycidyl acrylate, β-methyl-substituted glycidyl methacrylate and the like can be mentioned. After water dispersion by the method described later, a microgel is formed in the dispersed particles to reduce gloss. An acetoacetoxy group-containing unsaturated monomer and an alkoxysilyl group-containing monomer can be preferably used. Also, for acetoacetoxyethyl acrylate and acetoacetoxyethyl methacrylate, the use of formaldehyde together promotes the formation of microgels. It is preferable to use formaldehyde in combination.

  Furthermore, for other α, β-ethylenically unsaturated monomers, alkyl esters of acrylic acid or methacrylic acid, or other vinyl monomers and amide monomers can be used. Specific examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl. Acrylic acid such as methacrylate, t-butyl acrylate, t-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate or the like Methacrylic acid Alkyl ester, styrene, α-methylstyrene, vinyl toluene, vinyl acetate, acrylonitrile, methacrylonitrile and other vinyl monomers, acrylamide, methacrylamide, methylol acrylamide, methylol methacrylamide, methoxymethyl acrylamide, n-butoxymethyl acrylamide, Examples thereof include amide monomers such as diacetone acrylamide and diacetone methacrylamide. These may be used alone or in combination of two or more.

  The preferred weight average molecular weight of the vinyl copolymer is 10,000 to 100,000, more preferably 20,000 to 70,000. When the weight average molecular weight is 10,000 or less, the coating film durability is not sufficiently obtained. When the weight average molecular weight is 100,000 or more, the water dispersibility is lowered, and the handleability of the coating becomes poor.

  The vinyl copolymer as described above is obtained by polymerizing each of the above monomers by a known method such as solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Polymerization is preferred, and the reaction temperature is usually 40 to 170 ° C.

  Reaction solvents include n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol, propyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono It is preferable to use a hydrophilic solvent such as butyl ether. Moreover, as a polymerization initiator, well-known things, such as an organic peroxide, an azo compound, ammonium persulfate, potassium persulfate, can be used.

[(B) amino resin]
Examples of the (B) amino resin used in the present invention include conventionally known melamine resins, benzoguanamine resins, urea resins, and the like. Among them, preferred is alkoxylation of at least a part of methylol group with a lower alcohol. In the alkyl etherified methylol melamine resin, as the lower alcohol, one or more of methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like can be used. Moreover, even if it is 1 type of melamine resin and 2 or more types of melamine resins are combined, there is no problem.

  Examples of alkyl etherified methylol melamine resins include Cymel 266, 232, 235, 238, 236 manufactured by Mitsui Cytec Co., Ltd., My Coat 506, 508, 548, Sumimar M-66B manufactured by Sumitomo Chemical Co., Ltd. ( Nicalak MX-40, MX-45, etc. manufactured by Sanwa Chemical Co., Ltd. are not limited thereto.

  A preferred range of the amount of the (B) amino resin used in the present invention is 30 to 100 parts by weight with respect to 100 parts by weight of the (A) vinyl copolymer. If the amount is less than this range, the coating film is insufficiently crosslinked, resulting in a decrease in hardness, mechanical properties, solvent resistance, chemical resistance, and the like. On the other hand, when the amount exceeds 100 parts by weight, the affinity with the vinyl copolymer becomes insufficient, the stability of the aqueous dispersion is poor, the dispersion particle size is not uniform, the water washability after electrodeposition, the water repellency phenomenon. In addition, problems such as uneven gloss of the coating film and opacification occur, and an excessive amino resin remains as a plasticizer without being cured.

[(C) tetraethoxysilane and / or its partial hydrolysis condensate]
(C) Tetraethoxysilane and / or its partially hydrolyzed condensate (hereinafter referred to as ethyl silicate) used in the present invention reduces the water contact angle of the coating film and imparts low contamination to the coating film. It is.
The coating film obtained by the electrodeposition coating according to the present invention has a water contact angle of 70 degrees or less when left for 240 hours in an atmosphere having a relative humidity of 98% or more. The water contact angle of the coating film in the present invention is the contact angle of water droplets when a drop of deionized water is dropped on the horizontal coating film surface and held at 23 ° C. for 30 seconds. Have been proposed. For example, a contact angle measuring device LCD-400S manufactured by Kyowa Chemical Co., Ltd. can be applied as a measuring instrument. Regarding the standing time, it is preferable that the water contact angle of the coating film is 70 degrees or less in a short standing time because the period until the effect of low contamination is realized in actual use is shortened, and the standing time is longer than 240 hours. However, when the water contact angle of the coating film does not become 70 degrees or less, the period until the effect of low contamination is manifested in actual use becomes long and is not practical.

  The reason why ethyl silicate is effective as a coating modifying component capable of reducing the water contact angle of the coating film in the anionic matte electrodeposition coating composition of the present invention will be described below.

  The vinyl copolymer of the present invention forms a microgel having a partially cross-linked structure in the paint, and the movement in the coating film before curing is compared with the vinyl copolymer not forming the microgel. Is suppressed. Therefore, methyl silicate having good compatibility with the vinyl copolymer cannot be diffused into the coating film and distributed at a high concentration on the coating film surface. In combination with the vinyl copolymer of the present invention, it is achieved only in ethyl silicate that is not very compatible with a high concentration distribution on the coating film surface.

  In Japanese Patent No. 2869443 (Patent Document 1), in both methyl silicate and ethyl silicate, they are distributed at a high concentration on the surface of the coating film. This is because a vinyl copolymer that does not form and is easy to move in the coating film before curing is used.

  The coating obtained by the electrodeposition coating of the present invention is not very good in compatibility with the vinyl copolymer in the present invention, so that the ethyl silicate easily migrates to the coating surface due to the repulsive action of intermolecular force. However, it is highly distributed on the surface of the coating film as compared with the inside of the coating film. Furthermore, since the reactivity of ethyl silicate to water is not so high, a considerable amount of ethoxysilyl groups remain in ethyl silicate distributed at a high concentration on the surface of the coating film, and this ethoxysilyl group has a relative humidity of 98% or more. It is considered that the water contact angle of the coating film becomes 70 degrees or less by being hydrolyzed only by being left in the atmosphere and becoming a highly hydrophilic silanol group.

  On the other hand, methyl silicate and / or its partially hydrolyzed condensate (hereinafter referred to as methyl silicate) is highly reactive to water, so that most methoxysilyl groups are hydrolyzed in the paint before forming a coating film. It causes a decomposition reaction, becomes more hydrophilic than before hydrolysis, and has good compatibility with the vinyl copolymer in the present invention, so that it cannot be distributed at a high concentration on the coating film surface.

  That is, in the coating film obtained in the present invention, ethyl silicate is distributed at a high concentration on the coating film surface, the ethoxysilyl group remains in the ethylsilicate, and the hydrolysis of the remaining ethoxysilyl group proceeds, Whereas the water contact angle is 70 degrees or less, the coating obtained using methyl silicate is not highly concentrated on the surface of the coating and the methoxysilyl group hardly remains, so hydrolysis proceeds. Without, the water contact angle of the coating film cannot be less than 70 degrees.

  In Japanese Patent Application Laid-Open No. 11-315254 (Patent Document 2), an aqueous gloss containing an aqueous dispersion obtained by dispersing an organosilicate and / or a condensate thereof, a vinyl copolymer having an alkoxysilyl group, and a melamine resin in water. An erase coating composition has been disclosed, and it is said that a coating film having high hardness and excellent scratch resistance can be obtained. In the examples, only organosilicates and / or those using methyl silicate as the condensate thereof are exemplified, and the description of contamination and the measurement results of water contact angle and evaluation of contamination are described in the examples. Not. Methyl silicate is highly reactive to water, and therefore, most of the methoxysilyl groups disappear due to hydrolysis reaction in the paint, hydrolysis during the baking process, and condensation reaction, resulting in a highly condensed product. Japanese Patent Application Laid-Open No. 11-315254 (Patent Document 2) is an invention that obtains a high-hardness coating film by utilizing the high reactivity of methyl silicate, and is completely different from the present invention.

  Propyl silicate and butyl silicate are lower in reactivity to water than ethyl silicate. In this respect, propoxysilyl groups and butoxysilyl groups can remain in the coating film, but the reaction Due to its low nature, hydrolysis of propoxysilyl groups and butoxysilyl groups does not proceed as much as ethyl silicate when left in an atmosphere with a relative humidity of 98% or more, and the water contact angle of the coating does not become 70 degrees or less.

  Examples of the (C) ethyl silicate of the present invention are: normal ethyl silicate, silicate 40, silicate 45, silicate 48 manufactured by Tama Chemical Co., Ltd., ethyl silicate 28, ethyl silicate 40, ethyl silicate 48 manufactured by Colcoat Co., Ltd. However, it is not limited to these.

  The preferred range of the amount of the (C) ethyl silicate used in the present invention is 0.5 to 40 parts by weight with respect to 100 parts by weight of the (A) vinyl copolymer. When it is less than this range, the contact angle of water does not become 70 degrees or less, and low contamination is not sufficiently obtained. On the other hand, if it exceeds 40 parts by weight, the stability of the paint deteriorates, which is not preferable. A more preferred range is 1 to 30 parts by weight.

  The matte electrodeposition paint of the present invention is prepared by mixing a vinyl copolymer (A), an amino resin (B), and ethyl silicate (C) with stirring at 40 to 100 ° C., and a base such as an organic amine or an inorganic base. After neutralizing with a chemical substance, it is a general method to carry out emulsification dispersion by stirring and mixing with deionized water at 20 to 80 ° C. Further, if necessary, a warming reaction is carried out, or deionized water or diluted with deionized water partially containing a hydrophilic solvent is used for electrodeposition coating.

  The aforementioned basic substance is a substance for neutralizing at least a part of the carboxyl group of the vinyl copolymer (A) to be dispersed in water. For example, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine Alkylamines such as triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, tributylamine, alkanolamines such as diethanolamine, diisopropanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethylenediamine , Propylenediamine, diethylenetriamine, alkyleneethylenes such as triethylenetetramine, ammonia, ethyleneimine, pyrrolidine, piperidine Piperazine, morpholine, sodium hydroxide and potassium hydroxide. The neutralization rate with such a basic substance is suitably 30 to 120%, but particularly 50 to 100% is preferable because water dispersibility is good and gloss unevenness does not occur.

In addition, the electrodeposition coating material may be further used with an additive such as a surfactant such as a curing catalyst, an antifoaming agent, and a leveling agent, if necessary.
The technique of the present invention can also be applied to a colored type electrodeposition paint in combination with a pigment.

[Electrodeposition coating method]
In the case of carrying out electrodeposition coating, the solid content concentration of the coating is suitably 4 to 20% by weight. If it is lower than 4% by weight, it takes a long time to obtain the required coating thickness. If it exceeds 20% by weight, the bath liquid becomes unstable and the amount of paint taken out of the coating system is large. It becomes a problem in gender.

  As for the coating method, electrodeposition is performed using the object to be coated as an anode. The coating voltage is 30 to 350 V, preferably 50 to 300 V, and the energization time is 0.5 to 7 minutes, preferably 1 to 5 minutes. is there. The higher the voltage, the shorter the energization time, and conversely, the lower the voltage, the longer the energization time. The painting voltage can be applied either by applying a set voltage simultaneously with energization or by gradually increasing the set voltage to the set voltage. The electrodeposition-coated object is washed with water if necessary, and then heated at 150 to 200 ° C. for 15 to 60 minutes to obtain a final coating film. The coating thickness is preferably 5 to 30 μm.

The material of the object to be coated to which the electrodeposition coating method of the present invention is applied is not particularly limited as long as it has conductivity, but is suitable for a material using aluminum or an aluminum alloy.
Moreover, the obtained coating film is excellent in appearance such as smoothness and uniformity, and also in performance such as mechanical properties, solvent resistance, chemical resistance, and weather resistance.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In addition, the compounding quantity in a table | surface represents a weight part unless there is special description.

[Production of vinyl copolymer (A)]
Production Example 1 (Production of vinyl copolymer resin liquid A1)
A four-necked flask equipped with a stirrer, reflux condenser, and thermometer was charged with 40 parts of isopropyl alcohol and 10 parts of propylene glycol-t-butyl ether, and kept at the reflux temperature. 16 parts of n-butyl acrylate, methyl methacrylate 30 parts, 8 parts 2-ethylhexyl methacrylate, 10 parts styrene, 23 parts 2-hydroxyethyl acrylate, 7 parts acrylic acid, 6 parts acetoacetoxyethyl methacrylate, and 1 part azobisisobutyronitrile are added dropwise over 3 hours. did. After completion of dropping, the mixture is kept at 87 ° C. for 1 hour, 1 part of azobisisobutyronitrile is added, and further kept at the same temperature for 2 hours, acid value 55 mgKOH / g solid content, hydroxyl value 111 mgKOH / g solid content, weight A vinyl copolymer resin liquid A1 having an average molecular weight of about 45,000 was obtained.
Production Example 2 (Production of vinyl copolymer resin liquid A2)
A four-necked flask equipped with a stirrer, reflux condenser, and thermometer was charged with 40 parts of isopropyl alcohol and 10 parts of propylene glycol-t-butyl ether, and kept at the reflux temperature. 20 parts of n-butyl acrylate and methyl methacrylate A mixture of 34 parts, 8 parts 2-ethylhexyl methacrylate, 10 parts styrene, 20 parts 2-hydroxyethyl acrylate, 7 parts acrylic acid, 1 part γ-methacryloxypropyltrimethoxysilane, and 1 part azobisisobutyronitrile. It was dripped in 3 hours. After completion of dropping, the mixture is kept at 87 ° C. for 1 hour, 1 part of azobisisobutyronitrile is added, and further kept at the same temperature for 2 hours, acid value 55 mgKOH / g solid content, hydroxyl value 97 mgKOH / g solid content, weight A vinyl copolymer resin liquid A2 having an average molecular weight of about 47,000 was obtained.

[Production of dispersion resin liquids D1 to D12]
According to the composition shown in Table 1 and Table 2, (1) to (9) are charged into a four-necked flask equipped with a stirrer, reflux condenser, and thermometer, and stirred and mixed at 60 ° C. for 2 hours. ) Was added, and (11) was gradually added to emulsify. Further, (12) was added (dispersion resin liquids D2 and D4 were not added), and the mixture was kept at 50 ° C. for 4 hours to carry out a microgelation reaction. After keeping the temperature, (13) was added to each to obtain dispersed resin liquids D1 to D12.
Further, the dispersion resin liquids D7 to D12 are for comparative examples. When D7 does not contain ethyl silicate (C), D8 is when ethyl silicate exceeds 40 parts by weight, D9 and D10 are methyl silicate, D11 is In the case of propyl silicate, D12 is the case of butyl silicate.

Used raw material Cymel 238: Mixed ether type melamine resin ethyl silicate manufactured by Nippon Cytec Co., Ltd. 40: Ethyl silicate manufactured by Colcoat Co., Ltd.
Average pentamer SiO ₂ min 40%
Ethyl silicate 48: Ethyl silicate manufactured by Colcoat Co., Ltd.
Average 10-mer SiO ₂ min 48%
MS51: Methyl silicate manufactured by Mitsubishi Chemical Corporation
Average pentamer SiO ₂ min 51%
MS56S: Methyl silicate manufactured by Mitsubishi Chemical Corporation
Average 10-mer SiO ₂ min 58%
Propyl silicate: Tama Chemical Industry Co., Ltd. Butyl silicate: Tama Chemical Industry Co., Ltd.

[Production of electrodeposition paints E1 to E12]
After adding deionized water to the dispersion resin liquids D1 to D12 to adjust the solid content to 10%, triethylamine is added to adjust the pH to 8.0, and the corresponding electrodeposition paints E1 to E12 are added. Obtained.

[Electrodeposition coating and coating film performance evaluation]
The electrodeposition paints obtained above (Examples 1 to 6 are the respective electrodeposition paints E1 to E6, and Comparative Examples 1 to 6 are the respective electrodeposition paints E7 to E12) are placed in a vinyl chloride bath, The cathode was a SUS304 steel plate, an alumite treatment (alumite film thickness = 9 μm) was applied to a 6063S aluminum alloy plate, and electrodeposition coating was performed using an aluminum material washed with hot water by a conventional method as an anode (coating material). The specific conditions for the electrodeposition coating were as follows: the bath temperature was 22 ° C., the distance between the electrodes was 12 cm, and the electrode ratio (+/−) 2/1. After completion, it was washed and subsequently baked at 185 ° C. for 30 minutes. The performance of the obtained coating film was evaluated, and the results are shown in Tables 3 and 4.

The evaluation method of the coated plate is as follows.
(1) Gloss value: 60 ° specular reflectance [%] was measured with a gloss meter.
(2) Pencil hardness: JIS K-5600-5-4 scratch hardness (conforms to the pencil method. Cohesive failure determination.)
(3) Cross-cut adhesion: Judged by a method according to JIS K-5600-5-6 adhesion (cross-cut method). The numerical value of the result is the number of grids remaining without peeling in 100 grids.
(4) Alkali resistance: The surface of the coating was observed after being immersed in a 0.5% aqueous sodium hydroxide solution at 20 ° C. for 120 hours.
(5) Acid resistance: The coated surface state was observed after immersion in a 5% sulfuric acid aqueous solution at 20 ° C. for 120 hours.
(6) Silicon concentration ratio (surface / inside): Ratio of silicon concentration on the coating film surface and silicon concentration in the coating film after polishing the coating film, measured by XPS (X-ray photoelectron spectroscopy).
(7) Water contact angle (after baking): The water contact angle of the coated plate is measured with a contact angle measuring device LCD-400S manufactured by Kyowa Chemical Co., Ltd.
(8) Water contact angle (after 120 hours): After leaving the coated plate in an atmosphere with a relative humidity of 98% for 120 hours, the water contact angle was measured in the same manner as in (7).
(9) Water contact angle (after 240 hours): After leaving the coated plate in an atmosphere with a relative humidity of 98% for 240 hours, the water contact angle was measured in the same manner as in (7).
(10) Contamination: After leaving the coated plate in an atmosphere with a relative humidity of 98% for 5 days, the following contamination test was conducted.
Compliant with the accelerated pollution assessment method proposed by the Ministry of Construction, Public Works Research Institute.
The contaminated liquid is a dispersion of water / carbon = 95/5.
About 3 cc of contaminated liquid is dropped on the painted plate and dried at 60 ° C for 1 hour.
After drying, wash with water and dry at 60 ° C. for 10 minutes without wiping.
The L value of the test part and the non-test part is measured, and | ΔL | is calculated.
In case of | ΔL | <3
In the case of | ΔL |> 3, the contamination property was poor and x was determined. (11) Paint stability: The electrodeposition paint was adjusted to 30 ° C. and kept under stirring for 4 weeks.
Compare electrodeposition results before and after holding.
○ when there is almost no difference in coating film appearance and gloss
When there was a difference in the appearance and gloss of the coating film, it was marked as x.

Claims (4)

  (A) 30 parts by weight to 100 parts by weight of (B) amino resin and (C) tetraethoxysilane and / or part thereof with respect to 100 parts by weight of vinyl copolymer having a carboxyl group, a hydroxyl group, and a cross-linking functional group An anionic matte electrodeposition coating composition containing 0.5 to 40 parts by weight of hydrolyzed condensate, and the coating film obtained by electrodeposition coating has an atmosphere with a relative humidity of 98% or more. An anionic matte electrodeposition coating composition that is excellent in low-contamination property, with a water contact angle of the coating film of 70 degrees or less when left for 240 hours or less.   The anionic matte electrodeposition coating composition according to claim 1, wherein the vinyl copolymer (A) has an acid value of 10 to 150 mg KOH / g solid and a hydroxyl value of 20 to 200 mg KOH / g solid.   The anionic matte electrodeposition coating composition according to claim 1 or 2, wherein the cross-linking functional group is an acetoacetyl group. The anionic matte electrodeposition coating composition according to claim 1 or 2, wherein the cross-linking functional group is an alkoxysilyl group.