KR20190013755A - Method of forming cured electrodeposited coating - Google Patents

Abstract

An object of the present invention is to provide a method for forming a cured electrodeposited coating film having a gloss-adjusted property, such as a low-gloss coating film or a matte coating film having a low mirror-surface gloss. The present invention relates to a method of forming a cured electrodeposition coating film, which comprises: an electrodeposition coating step of immersing a substrate in an anion electrodeposition coating composition to form an electrodeposited coating film; and a step of curing the electrodeposition coating film formed in the coating step, Wherein the anionic electrodeposition coating composition comprises an acrylic resin (A), a curing agent (B), an aqueous dispersion type of gloss control agent (C) and a curing catalyst (D) Is a water dispersion of one or more waxes selected from the group consisting of natural waxes and polyolefin waxes and the wax constituting the water dispersible gloss control agent (C) has a softening point (T _m ) of 100 ° C or higher The solid content of the aqueous dispersion type gloss control agent (C) contained in the anionic electrodeposition coating composition is in the range of 0.91 to 1.10, and the solid content of the resin solid component 100 And 6 to 20 parts by mass with respect to ryangbu, the coating viscosity at 50 ℃ of the electrodeposition coating film formed in the electrodeposition coating process is provided a method, in the range of · s 10,000~100,000Pa.

Description

Method of forming cured electrodeposited coating

The present invention relates to a method for forming a cured electrodeposited coating film using an anion electrodeposition coating composition.

Electrodeposition coating is a coating method performed by immersing a substrate in an electrodeposition coating composition and applying a voltage. This method is widely used as a method of applying undercoats of various objects because it can be painted even to a detail even if it has a complicated shape and can be painted automatically and continuously. As this electrodeposition coating composition, there are two kinds of electrodeposition coating composition and anion electrodeposition coating composition. The cationic electrodeposition coating composition can generally form a cured electrodeposition coating film having better rust resistance and corrosion resistance. On the other hand, for an aluminum material, an anion electrodeposition composition is often used. This is because, in the case of the aluminum material, excellent corrosion resistance can be imparted to an aluminum material by first forming an anodic oxidation coating (an alumite coating) by an anodic oxidation treatment and then performing an anion electrodeposition coating using an anion electrodeposition composition Because.

In the anion electrodeposition coating, for example, in the case of painting an aluminum chassis, a low-gloss coating film or a matte coating film having a low mirror-surface gloss is generally provided with a calm visual impression, , A demand for a coating method capable of forming such a coating film is increasing.

As a matte anionic electrodeposition coating composition, for example, Japanese Patent Application Laid-Open No. 2002-188044 (patent document 1) discloses a multi-stage emulsion polymerization using a polymerizable unsaturated monomer in the presence of an acrylic resin (I), water and an emulsifier (II) containing an alkoxysilyl group-containing polymerizable unsaturated monomer as the polymerizable unsaturated monomer in a proportion of 5 to 40% by weight based on the total weight of monomers used in multiple stages, Wherein the mixing ratio of the acrylic resin (I), the alkoxysilyl group-containing emulsion polymer (II) and the crosslinking agent (III) is 20% or more based on the sum of the resin solids of the resin (I) (II) is contained in an amount of 5 to 40% by weight, and (III) is contained in an amount of 20 to 60% by weight based on the total weight of the composition. Japanese Unexamined Patent Publication (Kokai) No. 2005-307161 (Patent Document 2) discloses an emulsion polymer produced by emulsion polymerization in a multistage manner using a polymerizable unsaturated monomer in the presence of water and an emulsifier, wherein the polymerizable unsaturated monomer is an alkoxysilyl group Shell emulsion (A), an acrylic resin (B) and a curing agent (C), which comprises a core / shell type emulsion (A) containing a polymerizable unsaturated monomer in a proportion of 1 to 40% . However, the cured electrodeposition coating film obtained by these anionic electrodeposition coating compositions largely fluctuates depending on the coating condition and / or the shape of the coated object, and there is a problem in that so-called gloss unevenness is caused.

JP-A-5-039445 (Patent Document 3) discloses a method for forming a matte coating film by electrodepositing a matte electrodeposition coating composition by diluting, wherein the matte electrodeposition coating composition comprises (A) a water- (B) 5 to 60% by weight of a water-soluble or water-dispersible acrylic copolymer resin having alkoxysilyl groups, and (C) 20 to 60% by weight of a cross-linking agent. A method of forming a coating film is described (claim 1). In the matte electrodeposition coating composition of Patent Document 3, the water-soluble or water-dispersible acrylic copolymer resin (B1) having alkoxysilyl content is crosslinked to become an insoluble gel structure, and the insoluble gel particles have a matte effect The method of the present invention is different from that of the method of the present invention.

Japanese Patent Application Laid-Open No. 8-113735 (Patent Document 4) discloses a process for producing a water-soluble or water-dispersible vinyl-based copolymer (A) having a carboxyl group and a hydroxyl group in the side chain, (B) an alkoxysilyl-containing ester monomer of an alpha, beta -ethylenically unsaturated carboxylic acid, (c) a monomer mixture (B) of a monomer containing a copolymerizable vinyl group having no carboxyl group, (E) is added to a copolymer (D) obtained by copolymerizing a polyamide resin (A), and then the wax (F) is mixed and partially neutralized with an organic amine, followed by adding water to form an emulsion (Claim 1). However, in the matte-cured electrodeposition coating film obtained by using the resin composition for electrodeposition coating obtained by this production method, the gloss of the resulting cured electrodeposition coating film greatly changes depending on the heating curing temperature, and a cured electrodeposition coating film of desired gloss is obtained .

However, in recent years, it has been demanded to lower the heat curing temperature in forming a coating film by further request for reduction of environmental load such as energy saving and CO ₂ emission reduction. On the other hand, by lowering the heat curing temperature, the crosslinking density of the resulting cured electrodeposition coating film is lowered, and the physical properties of the coating film such as coating film hardness or corrosion resistance may be lowered.

Japanese Patent Laid-Open No. 2002-188044 Japanese Patent Application Laid-Open No. 2005-307161 Japanese Patent Application Laid-Open No. 5-039445 Japanese Patent Laid-Open No. 8-113735

An object of the present invention is to provide a method of forming a cured electrodeposited coating film having a gloss-adjusted state, such as a low-gloss coating film or a matte coating film having a low mirror-surface gloss.

In order to solve the above problems, the present invention provides the following aspects.

[One]

A method for forming a cured electrodeposited coating film,

An electrodeposition coating step of immersing a substrate in an anionic electrodeposition coating composition and applying a voltage to form an electrodeposited coating film, and

A heat curing step of forming a cured electrodeposited coating film by thermally curing the electrodeposited coating film formed in the electrodeposition coating step

/ RTI >

Wherein the anionic electrodeposition coating composition comprises an acrylic resin (A), a curing agent (B), an aqueous dispersion type gloss control agent (C) and a curing catalyst (D)

The aqueous dispersion type gloss adjuster (C) is an aqueous dispersion of one or more waxes selected from the group consisting of natural wax and polyolefin wax,

The wax constituting the aqueous dispersion type gloss adjuster (C) preferably has a softening point (T _m ) of 100 ° C or higher and a density of 0.91 to 1.10,

The solid content of the aqueous dispersion type gloss control agent (C) contained in the anionic electrodeposition coating composition is 6 to 20 parts by mass based on 100 parts by mass of the resin solid content of the anion electrodeposition coating composition,

Wherein the electrodeposition coating film formed in the electrodeposition coating step has a coating film viscosity at 50 캜 within a range of 10,000 to 100,000 Pa · s,

Way.

[2]

Wherein the heating temperature (T _h ) in the heat curing step is 110 to ₁₆₀ 캜.

[3]

Wherein the softening point (T _m ) is in the range of 100 to 140 캜.

[4]

Wherein the electrodeposition coating film formed in the electrodeposition coating step has a coating film viscosity at 80 캜 within a range of 1,000 to 10,000 Pa · s.

[5]

The acrylic resin (A) is an acrylic resin having a carboxyl group and a hydroxyl group,

Wherein the curing agent (B) is one or more selected from the group consisting of an amino resin and a block isocyanate compound,

Gt;

[6]

Wherein the difference (DELTA T) between the softening point (T _m ) and the heating temperature (T _h ) is not less than 10 ° C and not more than 50 ° C, and T _h > T _m .

[7]

Wherein the cured electrodeposition coating film formed by the forming method has a 60 占 specular gloss of 70 or less.

On the other hand, in the present specification, the uncured electrodeposition coating film before heat curing is referred to as an " electrodeposition coating film ", and the coated film after heat curing is referred to as a " cured electrodeposition coating film "

According to the method of the present invention, it is possible to obtain a cured electrodeposited coating film whose gloss is adjusted, such as a low-gloss coating film having low mirror-surface gloss or a matte coating film. By the method of the present invention, it is possible to obtain a cured electrodeposited coating film having excellent finish appearance without gloss unevenness such as change in gloss due to a change in the heat curing temperature. In the method of the present invention, a cured electrodeposited coating film having good hardness can be obtained even when the electrodeposited coating film is formed and then heat cured under low temperature curing conditions.

The method for forming a cured electrodeposition coating film of the present invention comprises the steps of:

An electrodeposition coating step of immersing a substrate in an anionic electrodeposition coating composition and applying a voltage to form an electrodeposited coating film, and

A heat curing step of forming a cured electrodeposited coating film by thermally curing the electrodeposited coating film formed in the electrodeposition coating step

. Hereinafter, the method of the present invention will be described in detail.

Object

The substrate to be used in the forming method of the present invention is not particularly limited as long as it is a substrate having conductivity. Examples of the substrate include metallic materials such as iron, stainless steel, aluminum, copper, zinc, tin and alloys thereof, molded products of these metallic materials, and conductive plastics and surface treated products thereof. The metal material may be a substrate on which a plating treatment has been performed. Suitable substrates for the present invention include iron substrates such as iron and stainless steel, and aluminum substrates such as aluminum and aluminum alloys.

Anionic electrodeposition coating composition

The anionic electrodeposition coating composition of the present invention comprises an acrylic resin (A), a curing agent (B), an aqueous dispersion type of gloss control agent (C) and a curing catalyst (D).

Acrylic resin (A)

The acrylic resin (A) contained in the anionic electrodeposition coating composition is a film-forming resin. The acrylic resin (A) is preferably an acrylic resin having a carboxyl group and a hydroxyl group. Examples of such an acrylic resin (A) include a carboxyl group-containing radical polymerizable unsaturated monomer (a-1) and a hydroxyl group-containing radical polymerizable unsaturated monomer (a-2), and further, And an acrylic resin obtained by radical polymerization of these monomers using the unsaturated monomer (a-3).

The carboxyl group-containing radical polymerizable unsaturated monomer (a-1) is a compound having at least one carboxyl group and at least one polymerizable unsaturated bond in one molecule. Examples of the carboxyl group-containing radical polymerizable unsaturated monomer (a-1) include (meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, maleic acid monoester, itaconic acid monoester, (Meth) acrylic monomers containing a vinyl polymerizable α, β-unsaturated fatty acid, caprolactone-modified carboxyl group, and mixtures thereof, and the like. As the carboxyl group-containing radical polymerizable unsaturated monomer (a-1), at least one member selected from the group consisting of acrylic acid and methacrylic acid is preferably used.

In the present specification, (meth) acrylic acid represents acrylic acid or methacrylic acid.

The hydroxyl-containing radical polymerizable unsaturated monomer (a-2) is a compound having at least one hydroxyl group and at least one polymerizable unsaturated bond in one molecule. Examples of the hydroxyl group-containing radical polymerizable unsaturated monomer (a-2) include (meth) acrylate such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and hydroxybutyl Alkyls; (Meth) acrylic acid (poly) alkylene glycols such as (meth) acrylic acid (poly) ethylene glycol and (meth) acrylic acid (poly) propylene glycol; And a copolymer of these hydroxyl group-containing acrylic monomers and at least one monomer selected from the group consisting of? -Propiolactone, dimethylpropiolactone, butyrolactone,? -Valerolactone,? -Caprolactone,? -Caprylolactone,? -Laurolactone, Lactones, and lactone compounds such as? -Caprolactone. Examples of such reactants include commercially available products such as Flaccel FM1 (trade name, product name, caprolactone-modified (meth) acrylic acid hydroxy esters), Flaxel FM2 FM3 (co-worker), Flaxel FA1 (co-worker), Flaxel FA2 (co-worker), Flaxel FA3 (co-worker).

The other radically polymerizable unsaturated monomer (a-3) is a monomer other than the carboxyl group-containing radically polymerizable unsaturated monomer (a-1) and the hydroxyl group-containing radically polymerizable unsaturated monomer (a-2) Radically polymerizable unsaturated bonds. Examples of other radically polymerizable unsaturated monomer (a-3) include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, ) C _1-8 alkyl ester or C _3-8 cycloalkyl ester of (meth) acrylic acid such as 2-ethylhexyl acrylate, octyl (meth) acrylate, lauryl (meth) acrylate and cyclohexyl (meth) acrylate; Aromatic polymerizable monomers such as styrene,? -Methylstyrene, and vinyltoluene; (Meth) acrylamide and derivatives thereof such as (meth) acrylic acid amide, N-butoxymethyl (meth) acrylamide and N-methylol (meth) acrylamide; (Meth) acrylonitrile compounds; (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, vinyltrimethoxysilane, etc. An alkoxysilyl group-containing polymerizable monomer; And the like.

As the method of radical copolymerization reaction of the monomers (a-1), (a-2) and (a-3), solution polymerization methods and emulsion polymerization methods commonly used in the art can be used. In the preparation of the acrylic resin (A)

The content of the carboxyl group-containing radical polymerizable unsaturated monomer (a-1) is preferably 3 to 30% by mass, more preferably 4 to 20% by mass,

The amount of the hydroxyl-containing radical polymerizable unsaturated monomer (a-2) is preferably 3 to 40% by mass, more preferably 5 to 30% by mass with respect to the total mass of the monomers,

Is preferably 30 to 90% by mass, more preferably 40 to 85% by mass, based on the total mass of the monomers, of the other radical polymerizable unsaturated monomer (a-3)

Is preferably used within a range of < RTI ID = 0.0 >

The acrylic resin (A) preferably has an acid value of 15 to 150 mgKOH / g, more preferably 40 to 80 mgKOH / g. When the acid value of the acrylic resin (A) is 15 mgKOH / g or more, the water dispersibility of the resin becomes high, and a uniform paint can be produced. When it is 150 mgKOH / g or less, there is an advantage such that the corrosion resistance and acid resistance of the cured coating film are increased.

The acrylic resin (A) preferably has a hydroxyl value of 30 to 200 mgKOH / g, more preferably 50 to 150 mgKOH / g. When the hydroxyl value of the acrylic resin (A) is 30 mgKOH / g or more, the curing reaction sufficiently occurs, and the original coating film performance is obtained. Further, when it is 200 mgKOH / g or less, unreacted hydroxyl groups do not remain in the coating film, and corrosion resistance and acid resistance are not lowered.

In the present specification, the acid value and the hydroxyl value indicate the solid acid value and the hydroxyl value of the solid content, respectively, and can be measured by the method described in JIS K 0070.

The acrylic resin (A) preferably has a weight average molecular weight (Mw) of 5,000 to 100,000, more preferably 10,000 to 50,000. When the weight average molecular weight (Mw) of the acrylic resin (A) is 5000 or more, the coating film performance such as corrosion resistance and acid resistance is advantageously increased. When it is 100,000 or less, there is an advantage that the electrophotographic coating film has a high flow property and a cured electrodeposited coating film having a good coating film appearance can be obtained.

In the present specification, the weight average molecular weight (Mw) is a polystyrene reduced value measured by gel permeation chromatography (GPC).

In the anionic electrodeposition coating composition of the present invention, the acrylic resin (A) is obtained by neutralizing a carboxyl group with a basic substance (for example, triethylamine, dimethylethanolamine, ammonia, etc.) Is preferably used as the resin. In the neutralization of such an acrylic resin (A), the neutralization ratio is preferably 30 to 100%, more preferably 50 to 80%. When the neutralization ratio is in the above range, the acrylic resin (A) can be well dispersed in the anionic electrodeposition coating composition.

In the anionic electrodeposition coating composition of the present invention, the content of the acrylic resin (A) is preferably 50 to 80% by mass based on 100% by mass of the total resin solid content of the acrylic resin (A) and the curing agent (B) desirable. When it is 50 mass% or more, the chemical resistance and corrosion resistance such as acid resistance and alkali resistance are improved. When the content is 80 mass% or less, the electrodeposition coating film is sufficiently cured, and desired coating film performance is obtained.

The coating composition of the present invention may contain other coating film forming resin as needed other than the acrylic resin (A). Examples of other coating film forming resins include polyester resins, urethane resins, epoxy resins, butadiene resins, phenol resins, and xylene resins. From the viewpoint of improving the corrosion resistance of the cured electrodeposition coating film, an epoxy resin is preferable. The content of such another film-forming resin is preferably less than 20 mass%, more preferably less than 10 mass%, based on the solid content of the resin contained in the coating composition.

The curing agent (B)

The anionic electrodeposition coating composition of the present invention contains a curing agent (B). The curing agent (B) is preferably one or more selected from the group consisting of an amino resin and a block isocyanate compound.

The amino resin is obtained by modifying a condensate of an amino compound such as melamine, urea, benzoguanamine and the like with an aldehyde compound such as formaldehyde or acetaldehyde using a lower alcohol such as methanol, ethanol, propanol or butanol Lt; / RTI > As specific examples of such amino resins, there may be mentioned, for example, a mixture of a fully alkyl type methyl / butyl mixed esterified melamine resin, a methylol modified methyl / butyl mixed esterified melamine resin, an imino type mixed methyl / butyl mixed esterified melamine resin, Methylated melamine resins, and imino modified methylated melamine resins.

As the amino resin, a commercially available product may be used. Commercially available products include, for example, methyl methacrylate / methyl methacrylate copolymers such as Cymel 232, Cymel 232S, Cymel 235, Cymel 236, Cymel 238, Cymel 266, Cymel 267, Cymel 285, Suzy; Butyl melamine resin in a methylol group type methyl / butyl mixture such as Cymel 272; Butyl methacrylate resin such as Cymel 202, Cymel 207, Cymel 212, Cymel 253, Cymel 254 and the like; Methylated melamine resins such as Cymel 300, Cymel 301, Cymel 303, and Cymel 350; Imino type methylated melamine resins (such as those manufactured by Allenex Japan) such as Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 254, Cymel 253, Cymel 212 and Cymel 1128, (Manufactured by Mitsui Chemicals, butyl ethereal melamine resin), and the like.

As the block isocyanate compound, the following 1) to 3);

1) alicyclic diisocyanates such as trimethylene diisocyanate and hexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate;

2) bifunctional or higher polyisocyanates obtained by reacting the above diisocyanates with polyhydric alcohols such as ethylene glycol, trimethylol propane and pentol,

3) an isocyanurate bond-containing trifunctional isocyanate obtained by reacting 3 mol of the diisocyanates of the above 1);

Is suitably used as a block isocyanate compound obtained by reacting a block agent with at least one member selected from the group consisting of

Examples of the blocking agent include monovalent alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenol carbinol and methylphenyl carbinol; Cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono-2-ethylhexyl ether; Polyether terminal diol such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycolphenol; Diols such as ethylene glycol, propylene glycol and 1,4-butanediol, and polyester-type polyols obtained from dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid and sebacic acid Terminal polyols; Para-tert-butylphenol, and cresol; Oximes such as dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, methyl amyl ketoxime, and cyclohexanone oxime; And lactams represented by? -Caprolactam and? -Butyrolactam are preferably used.

Specific examples of commercially available products of the polyisocyanate compound include Baiduur VPLS2186 (manufactured by Sumika Bayer Eletenzhen) and the like.

As the curing agent (B), a mixture of the amino resin and the block isocyanate compound may be used. As the curing agent (B), an amino resin is more preferably used because the effect of the present invention can be effectively obtained.

In the anionic electrodeposition coating composition of the present invention, the content of the curing agent (B) is preferably 20 to 50% by mass based on 100% by mass of the total resin solid content of the acrylic resin (A) and the curing agent (B) Do. When it is 20% by mass or more, the curing reaction proceeds sufficiently, and desired coating film performance is obtained. When it is 50 mass% or less, the adhesion and flexibility of the coating film are enhanced.

Water-dispersible polish regulator (C)

The anionic electrodeposition coating composition of the present invention includes an aqueous dispersion type of gloss control agent (C). The water-dispersible gloss-adjusting agent (C) is an aqueous dispersion of one or more waxes selected from the group consisting of natural waxes and polyolefin waxes. The wax has a softening point (T _m ) of 100 ° C or higher and a density of 0.91 to 1.10.

Specific examples of the natural waxes include waxes, carnauba waxes, petroleum-based microcrystalline waxes, paraffin waxes, mineral waxes, and the like. Specific examples of the polyolefin wax include polyolefin waxes such as polyethylene, polypropylene, polyethylene oxide, oxidized polypropylene, chlorinated polyethylene, and chlorinated polypropylene.

As an example of a method of preparing the water dispersion of the wax, for example,

A method in which the wax is dissolved in a hydrophilic organic solvent and then mechanically dispersed in an aqueous solvent,

A method of dispersing the wax in an aqueous solvent using a surfactant or a polymer emulsifier, and

A method of reacting the wax with an?,? - unsaturated carboxylic acid to introduce a carboxyl group and then neutralizing the introduced carboxyl group with an organic amine or an inorganic base to emulsify and disperse the resulting compound in an aqueous solvent

And the like.

In these preparation methods, it is preferable to use polyethylene, polypropylene, polyethylene oxide, oxidized polypropylene or the like as the wax.

In the present invention, a wax having a softening point (T _m ) of 100 캜 or higher is used as the wax constituting the aqueous dispersion type gloss adjuster (C). If the softening point (T _m) of the aqueous dispersion type wax constituting the gloss-adjusting agent (C) is less than 100 ℃ is, a sufficient luster-adjusting effect can not be obtained. Further, there is a problem that gloss unevenness occurs in the cured electrodeposition coating film. Dispersed in water glossy softening point (T _m) of the wax constituting the controlling agent (C) is preferably within a range of 100~140 ℃.

The softening point of the wax constituting the aqueous dispersion type gloss-adjusting agent (C) (T _m) is dispersed in water in the solid state prior to dispersing the wax constituting the gloss-adjusting agent (C) may, measure the temperature at the time of softening by heating And the like. Measurement of the water dispersion type glossy softening point (T _m) of the wax constituting the controlling agent (C) is, specifically, for use in the preparation of the aqueous dispersion type gloss-adjusting agent (C), can by means of the wax in the dispersed state before, JIS K 2207, which is incorporated herein by reference. In the above measurement, it is also possible to use the water dispersion type gloss control agent (C) in which the aqueous medium is evaporated and the wax becomes solid state instead of the solid state before the wax constituting the water dispersion type gloss control agent (C) have.

In the present invention, the wax constituting the aqueous dispersion type gloss adjuster (C) has a density in the range of 0.91 to 1.10. It is preferable that the density of the wax constituting the aqueous dispersion type of the gloss adjusting agent (C) is in the range of 0.92 to 1.05. When the density of the wax constituting the water dispersible type gloss adjuster (C) is out of the above range, there is a possibility that the appearance of the cured coating film may be problematic in the resulting cured electrodeposition coating film.

The density of the wax constituting the water dispersible type gloss adjuster (C) can be measured by a method in accordance with JIS K 7112.

It is preferable that the aqueous dispersion type gloss adjuster (C) is an anion dispersion type. When the aqueous dispersion type of gloss control agent (C) is an anion dispersion type, there is an advantage that the paint stability of the resulting anionic electrodeposition coating composition is improved.

A commercially available product may be used as the water-dispersible type gloss-adjusting agent (C). As a commercial product, for example, HI-DISPER ^(trademark) series of Climate Cell ^Co. , AQUACER ^(trademark) series and AQUAMAT ^(trademark) series of Big Chemie Japan, Chemie Pearl W ^(trademark) series of Mitsui Chemicals, And the erotic base ^(trademark) series made by the manufacturer.

In the present invention, the solid content of the aqueous dispersion type gloss control agent (C) contained in the anionic electrodeposition coating composition is 6 to 20 parts by mass based on 100 parts by mass of the resin solid content of the anionic electrodeposition coating composition. The solid content of the water-dispersible gloss-regulating agent (C) is preferably 7 to 20 parts by mass, more preferably 10 to 15 parts by mass. When the solids content of the water dispersible type gloss control agent (C) exceeds 20 parts by mass, the hardness of the resulting cured electrodeposition coating film may be lowered. Further, when the solids content of the water dispersible type gloss control agent (C) is less than 6 parts by mass, sufficient gloss control effect can not be obtained.

As used herein, the term "resin solid content of the anionic electrodeposition coating composition" refers to the resin solid content of the coating film forming resin contained in the electrodeposition coating composition, and specifically refers to a resin solid content of an acrylic resin (A), a curing agent (B) Refers to the resin solid content of the other coating film forming resin.

The curing catalyst (D)

The anionic electrodeposition coating composition of the present invention comprises a curing catalyst (D). Examples of the curing catalyst (D) include n-butyl benzene sulfonic acid, amyl benzene sulfonic acid, octyl benzene sulfonic acid, dodecyl benzene sulfonic acid, octadecyl benzene sulfonic acid, dibutyl benzene sulfonic acid, Sulfonic acid catalysts such as sulfonic acid, p-toluenesulfonic acid, dodecylnaphthalenesulfonic acid, dynonylnaphthalenesulfonic acid, and dynonylnaphthalenedisulfonic acid; and amine halides of these sulfonic acid catalysts; Tin compound catalysts such as dioctyltin dilaurate, dioctyltin dibenzoate, and dibutyltin dibenzoate; And the like.

As the curing catalyst (D), it is more preferable to use the above-mentioned sulfonic acid catalyst, and it is more preferable to use the above-mentioned sulfonic acid catalyst as the curing catalyst (D) It is more preferable to use one or more selected from the group consisting of In the anionic electrodeposition coating composition of the present invention, by using such a curing catalyst (D), the heating temperature in the heat curing step is set to, for example, 100 to 160 캜, preferably 110 to 160 캜 The temperature can be set at a comparatively low temperature. Further, there is an advantage that a cured electrodeposited coating film having excellent performance such as scratch resistance can be formed even if the heating temperature in the heat curing step is a relatively low temperature heating condition as described above.

The amount of the curing catalyst (D) contained in the anionic electrodeposition coating composition is preferably 0.05 to 10 parts by mass as a solid content of the curing catalyst (D) based on 100 parts by mass of the total solid content of the acrylic resin (A) and the crosslinking agent (B) More preferably from 0.1 to 5 parts by mass, and most preferably from 0.2 to 4 parts by mass. When used in the above range, a cured electrodeposited coating film having excellent performance such as scratch resistance can be formed.

Other components

The anionic electrodeposition coating composition of the present invention is a water-based coating composition and contains water as a main solvent. On the other hand, the anionic electrodeposition coating composition of the present invention may contain an organic solvent if necessary. Specific examples of the organic solvent include alcohols such as methanol, isopropanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol and methoxypropanol, ethylene glycol monobutyl ether, propylene Ethers such as glycerol monobutyl ether and diethylene glycol monobutyl ether, ketones such as acetyl acetone, esters such as ethylene glycol monoethyl ether acetate, and hexane. These organic solvents may be used alone or in combination of two or more. However, from the viewpoint of regulation of VOC emission, the amount of the organic solvent is preferably as small as possible.

The anionic electrodeposition coating composition of the present invention may contain a colorant, a pigment, a film forming auxiliary, a drying retarding auxiliary, a viscosity adjusting agent, an antiseptic, an antiseptic, an antiseptic, a defoaming agent, a light stabilizer (for example, An amine-based light stabilizer, etc.), an antioxidant, an ultraviolet absorber, a pH adjuster, and other additives known in the art.

The anionic electrodeposition coating composition of the present invention may contain a pigment as required. The pigment is not particularly limited, and examples thereof include extender pigments such as barium sulfate, talc, calcium carbonate and barium sulfate; Rust inhibitive pigments such as phosphorous acid salt-based antirust pigments such as zinc molybdate zinc oxide, zinc molybdate zinc oxide, zinc molybdate zinc oxide and calcium molybdate dehydrogenate; and rust inhibitive pigments such as molybdate salt based antirust pigments and phosphate based antirust pigments; And coloring pigments commonly used in the field of paints; And the like.

Anionic pigment dispersion paste

When the pigment is contained in the anionic electrodeposition coating composition, it is preferable to prepare the pigment in the form of a pigment dispersion paste in advance from the viewpoint of ease of dispersion of the pigment. The anionic pigment dispersion paste can be prepared by dispersing the pigment in an anionic pigment dispersion resin.

As the anionic pigment dispersing resin, for example, a modified acrylic resin prepared by using acrylic acid ester, acrylic acid and azonitrile compound can be used.

The anionic pigment dispersion paste may be prepared by mixing an anionic pigment dispersing resin, a pigment, an aqueous medium and, if necessary, a neutralizing base, and then mixing the pigment with a ball mill or a sand mill until the particle diameter of the pigment in the mixture becomes a predetermined uniform particle diameter. And dispersing them using a commonly used dispersing device such as a mill or a grind mill.

As the neutralizing base, for example, ammonia; Organic amines such as diethylamine, ethylethanolamine, diethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, diethylenetriamine and triethylamine; Basic compounds such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; And the like. Generally, the anionic pigment dispersion paste is prepared at a solid content of 35 to 70% by mass, preferably 40 to 65% by mass.

As an anionic pigment dispersion paste, a commercially available anionic coloring paste may be used. Examples of commercially available products include WAJ-AAT-907 Black, WAJ-AAT-825 Violet, WAJ-AAT-731 Blue (manufactured by Toyobo Co., Ltd.), Emarkol NS Oaker 4622 .

Preparation of anionic electrodeposition coating composition

The anionic electrodeposition coating composition of the present invention can be obtained by mixing the acrylic resin (A), the curing agent (B), the water dispersible gloss control agent (C), the curing catalyst (D) And dispersing it in a medium. The aqueous medium is water, or a mixture of water and the above organic solvent. As the water, it is preferable to use ion exchange water. The neutralizing base may be used here if necessary.

The amount of the neutralizing base is preferably used in an amount sufficient to neutralize at least 30%, preferably 50 to 120%, of the anionic group (carboxyl group) of the coating film forming resin such as the acrylic resin (A). Further, the pH of the anionic electrodeposition coating composition may be adjusted using a neutralized base. The pH of the anionic electrodeposition coating composition is preferably 7.0 to 9.0, more preferably 7.0 to 8.5.

Formation of cured electrodeposited coating

The method of the present invention comprises the steps of:

An electrodeposition coating step of immersing a substrate in an anionic electrodeposition coating composition and applying a voltage to form an electrodeposited coating film, and

A heat curing step of forming a cured electrodeposited coating film by thermally curing the electrodeposited coating film formed in the electrodeposition coating step

.

In this method, the anodic electrodeposition coating composition is used, and the electrodeposition coating film formed in the electrodeposition coating step has a coating film viscosity at 50 ° C in the range of 10,000 to 100,000 Pa · s, It is possible to obtain a cured electrodeposited coating film whose gloss is adjusted such as a low-gloss coating film or a matte coating film having a low mirror-surface glossiness, which does not involve a problem such as gloss difference caused by the surface gloss or bad matte effect.

The electrodeposition coating of the anionic electrodeposition coating composition is carried out by immersing the substrate in an anion electrodeposition coating composition using the substrate as an anode and then applying a voltage of usually 1 to 400 V between the substrate and the negative electrode. The coating temperature of the anionic electrodeposition coating composition in electrodeposition coating is preferably 10 to 45 캜, more preferably 15 to 30 캜. The time for applying the voltage can be arbitrarily selected in accordance with electrodeposition coating conditions, and can be, for example, 30 seconds to 5 minutes. By applying a voltage, an electrodeposited coating film is formed on the surface of the substrate. The formed electrodeposition coating film may be washed with water if necessary.

In the method of the present invention, the electrodeposition coating film formed in the electrodeposition coating step has a coating film viscosity at 50 ° C within a range of 10,000 to 100,000 Pa · s. When the coating film viscosity at 50 ° C of the electrodeposition coating film is within the above range, the aqueous dispersion type gloss control agent (C) contained in the anion electrodeposition coating composition of the present invention exerts a satisfactory gloss control function, The gloss of the electrodeposition coating film can be designed in a low range (60 ° specular gloss is 70 or less).

In the present invention, the reason why the viscosity of the electrodeposition coating film is measured at 50 캜 is as follows. The electrodeposition coating film is a coating film deposited on the surface of the substrate by application of a voltage. The electrodeposited coating is generally designed to have a higher viscosity (high Tg). Therefore, when the viscosity of the electrodeposition coating film is measured at a temperature of a general electrodeposition bath (for example, 30 ° C), the measurement is sometimes impossible because the viscosity is very high. For this reason, it is difficult to measure the coating film viscosity of the electrodeposition coating film at 30 占 폚. On the other hand, the precipitated electrodeposited coating film is thermally flowed by heating, and the viscosity once decreased. By further heating, the coating film forming resin such as the acrylic resin (A) and the curing agent (B) contained in the electrodeposited coating film undergoes a crosslinking reaction, and the viscosity of the coating film rapidly increases. As a result, the electrodeposition coating film is cured to become a cured electrodeposition coating film. That is, the viscosity of the electrodeposition coating film is once lowered by heating, and then the viscosity is increased.

Further, in the electrodeposition coating, the vicinity of the workpiece rises to about 40 to 50 占 폚 due to the occurrence of the line heat. That is, the viscosity measurement at 50 ° C can be said to be a state in which the physical properties at the time of deposition of the electrodeposited coating film are reproduced. From the above, the temperature of 50 占 폚 is a temperature which is a preferable temperature for measuring the viscosity of the coating film from the above properties of the electrodeposition coating composition, and a temperature at which no crosslinking of the coating film forming resin occurs, that is, a property at the time of precipitation of the uncured electrodeposition coating film I think it is suitable temperature.

When the coating viscosity of the electrodeposition coating film at 50 ° C is less than 10,000 Pa · s, the deposited electrodeposited coating film has an improved thermal flow property, so that the gloss of the resulting cured electrodeposition coating film is increased. On the other hand, when the coating film viscosity of the electrodeposition coating film at 50 캜 exceeds 100,000 Pa · s, the appearance of the cured coating film becomes poor due to the reduced flowability of the resulting electrodeposition coating film.

In the present invention, it is more preferable that the electrodeposition coating film formed in the electrodeposition coating step has a coating film viscosity at 80 ° C in the range of 1,000 to 10,000 Pa · s. When the coating viscosity of the electrodeposition coating film at 80 캜 is within the above range, the finished appearance of the cured electrodeposition coating film can be made uniform while designing the obtained cured electrodeposition coating film in a low range. The temperature of 80 占 폚 is a temperature immediately before the curing reaction of the acrylic resin (A) and the curing agent (B) contained in the electrodeposition coating film is started. When the viscosity of the electrodeposition coating film at such a temperature condition is within the above-mentioned range, the flowability of the electrodeposition coating film due to heating does not excessively increase and formation of a cured electrodeposition coating film with low glossiness becomes possible , And it is also possible to avoid defective appearance of the cured electrodeposition coating film.

The coating film viscosity at 50 캜 and the coating film viscosity at 80 캜 of the electrodeposition coating film can be measured as follows. First, electrodeposition coating is performed on the substrate for 180 seconds so as to have a film thickness of about 20 占 퐉 to form an electrodeposited coating film, which is then washed with water to remove the excess electrodeposition coating composition. Subsequently, after removing excess moisture adhering to the surface of the electrodeposition coating film, the coating film is immediately taken out without drying, and a sample is prepared. The viscosity of the thus-obtained sample is measured using a dynamic viscoelasticity measuring apparatus, whereby the viscosity of the coating film at 50 ° C and 80 ° C can be measured.

By heating the electrodeposition coating film formed in the coating step, the electrodeposition coating film is cured to obtain a cured electrodeposition coating film (heat curing step). In the method of the present invention, it is preferable that the heating temperature (T _h ) in the heat curing step is 110 to ₁₆₀ 캜.

The difference? T between the softening point (T _m ) and the heating temperature (T _h ) is more preferably from 10 ° C to 50 ° C. With respect to the softening point (T _m ) and the heating temperature (T _h )

T _h > T _m ,

Softening point (T _m) and a heating temperature (T _h) of the difference ΔT is more than 10 ℃ below 50 ℃

Is more preferable.

It is more preferable that the above-mentioned? T is 10 占 폚 or more and 30 占 폚 or less.

The difference between the heating temperature (T _h ) in the heat hardening step and the softening point (T _m ) of the wax constituting the water dispersible type gloss adjuster (C) is within a suitable range and the gloss of the resulting cured electrodeposited coating film The degree of gloss uniformity can be satisfactorily designed in a low range (60 ° specular gloss is 70 or less), and the occurrence of gloss unevenness can be suppressed.

The heating time of the electrodeposition coating film can be appropriately selected depending on the size of the substrate and the heating temperature (T _h ). The heating time is, for example, 5 to 60 minutes, preferably 10 to 30 minutes.

The film thickness of the cured electrodeposition coating film formed in the method of the present invention is preferably 5 to 30 m, more preferably 10 to 25 m.

It is more preferable that the cured electrodeposition coating film formed by the method of the present invention has a 60 占 specular gloss of 70 or less. The 60 占 specular glossiness is an index commonly referred to as a 60 占 gloss (Gs (60 占). The surface of the coating film is irradiated with light from a light source at an incident angle of 60 degrees to measure the specularly reflected light flux? Gs (60 占 = ψs / os × 100 (%)], which is expressed by a ratio of the specularly reflected light flux ψos of the glass surface having the refractive index n = 1.567 under the condition, It is the value measured by the method. The 60 占 specular gloss can be measured using a gloss meter such as Uni-Gross 60 (manufactured by Konica Minolta).

By the method of the present invention, it is possible to form a cured electrodeposited coating film adjusted to a low gloss without causing occurrence of gloss unevenness. The technical effect of such include, but are not bound by theory, and control the anionic electrodeposition the aqueous dispersion type glossy softening point (T _m) of the wax constituting the controlling agent (C) contained in the coating composition, and in 50 ℃ the electrodeposited coating By controlling the viscosity of the coating film to a specific range, it is possible to control the change in the state of the coating film that occurs during heating and curing of the electrodeposition coating film, thereby suppressing the occurrence of gloss unevenness in the formation of a cured electrodeposition coating film having low glossiness It is thought that it is possible to do.

In the method of the present invention, the heating temperature in the heat curing step is, for example, in the range of 100 to 160 DEG C, which is lower than that in the ordinary heat curing step in electrodeposition coating, There is an advantage that a coating film having sufficient coating film hardness can be formed. Thereby, there is an advantage that the environmental load can be reduced in the coating step.

Example

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "part" and "%" are based on mass unless otherwise noted.

Manufacturing example 1 Acrylic  Preparation of Resin (A)

700 parts of isopropyl alcohol was placed in a 2 L reaction vessel equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer connected to a temperature regulator, and the mixture was heated to 80 DEG C under a nitrogen atmosphere. 324 parts of methyl methacrylate (MMA), 140 parts of butyl acrylate (nBA), 105 parts of styrene (St), 84 parts of hydroxyethyl methacrylate (HEMA), 49 parts of acrylic acid (AA) And 7 parts of azoisobutyronitrile was added dropwise at a constant rate over 3 hours and then maintained at 80 DEG C for 2 hours to obtain an acrylic resin having an acid value of 55 mg KOH / g, a hydroxyl value of 52 mg KOH / g and a weight average molecular weight of 30,000 To obtain a resin (A).

Example 1 anion  Preparation of electrodeposition coating composition

, 328 parts of the acrylic resin (A) prepared in Preparation Example 1 (solid content concentration 50%), 86 parts of Cymel 235 (a product of Alnex Japan, solid content concentration 100%) as a curing agent (B) , 3.75 parts of the dynonylnaphthalenesulfonic acid (curing catalyst (D)) in the amounts shown in the following table and 71.4 parts of the aqueous dispersion type of gloss-adjusting agent (C) of the kind and amount described in the following table were added and mixed. The obtained mixture was diluted to a solid content of 10% by using ion-exchanged water to obtain an anionic electrodeposition coating composition.

The amount of the aqueous dispersion type of gloss-adjusting agent (C) described in the following table is the solid content part by mass of 100 parts by mass of the total resin solids of the acrylic resin (A) and the curing agent (B)

Formation of hardened electrodeposited coating

A SUS430 plate as a substrate was immersed in the anodic electrodeposition coating composition obtained above, and a direct current voltage of 80 to 200 V was applied for 2.5 minutes to electrodeposition the coating so that the cured film thickness became 20 占 퐉 to prepare an electrodeposition coating film. Three of these paintings were made.

The coated plate having the electrodeposited coating, in the preparation of the anionic electrodeposition coating composition using the aqueous dispersion type gloss 10 ℃ from the softening point (T _m) of the controlling agent (C), 30 ℃ and 50 ℃ high heating temperature (each 145 ℃, 165 ℃, 185 DEG C) for 30 minutes, respectively, to obtain a coated plate having a cured electrodeposited coating film.

Example 2 and Comparative Examples 1 to 5

An anion electrodeposition coating composition was prepared in the same manner as in Example 1 except that the kind and amount of the aqueous dispersion type gloss control agent (C) and the amount of the curing catalyst (D) were changed as shown in the following table in the preparation of the anionic electrodeposition coating composition It was prepared.

Using the obtained anion electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a coated plate having a cured electrodeposited coating film.

Comparative Example 6

An anion electrodeposition coating composition was prepared in the same manner as in Example 2, except that the aqueous dispersion type gloss control agent (C) was not used in the preparation of the anionic electrodeposition coating composition.

Using the obtained anodic electrodeposition coating composition, electrodeposition coating was carried out in the same manner as in Example 1, and baking was carried out at 120 캜, 140 캜 and 160 캜 for 30 minutes, respectively, to obtain a coated plate having a cured electrodeposited coating film.

Evaluation was carried out by the following standards using the coating plates obtained by the above-mentioned Examples and Comparative Examples. The evaluation results are shown in the following table.

Measurement of the electrodeposited coating viscosity at 50 ° C and 80 ° C of the electrodeposited coating film

Using the anionic electrodeposition coating composition obtained in the above Examples and Comparative Examples, electrodeposition coating was performed on the substrate for 180 seconds so as to have a film thickness of about 20 μm to form an electrodeposited coating film, which was then washed with water to remove the excess electrodeposition coating composition. Subsequently, after the moisture was removed, the coating film was immediately taken out without drying, and a sample was prepared. The sample thus obtained was subjected to frequency-dependent measurement of dynamic viscoelasticity under the conditions of a deformation of 0.5 deg and a frequency of 0.02 Hz by using a rotating dynamic viscoelasticity measuring instrument, Rheosol G-3000 (manufactured by UBM Co., Ltd.). The prepared sample was set and the measurement temperature was maintained at 50 캜. After the start of the measurement, the viscosity of the coating film was measured when the electrodeposition coating film was uniformly spread in the cone plate. The coating film viscosity at 80 캜 was measured in the same manner as above except that the measurement temperature was changed.

Evaluation of gloss change by heating temperature change

Measurement of 60 ° specular gloss and evaluation of gloss

The 60 degree mirror polish of the coated plate thus obtained was measured using Uni-Gross 60 (manufactured by Konica Minolta).

The case where the 60 占 specular glossiness was 70 or less was evaluated as "? &Quot; because it was adjusted to the low gloss range, and the case of exceeding 70 was evaluated as " X "

Caused by heating temperature change Polished  car

The 60 ° mirror surface glossiness of each of the coating plates heated and cured at the above heating temperatures was compared and the minimum value was subtracted from the maximum value of the mirror surface gloss of 60 ° and the difference in glossiness was calculated. I appreciated.

?: The difference in glossiness is 20 or less

X: Difference in glossiness exceeds 20

It can be judged that the larger the value of this difference is, the more likely a change in gloss depending on the change in heating temperature is likely to occur. When the difference in glossiness exceeds 20, the difference in glossiness can be clearly recognized even in the visual evaluation.

When the gloss change depending on the change of the heating temperature is likely to occur, for example, when a large-sized substrate or an electrodeposition coating film provided on a substrate having a different thickness is heated and cured, There is a problem that gloss unevenness occurs.

Appearance evaluation

The cured electrodeposition coating film obtained by heating at the softening point + 30 占 폚 of the aqueous dispersion type gloss control agent (C) was visually evaluated based on the following criteria.

○: The coating film appearance defects such as agitation marks are not recognized

X: defective appearance of coating film such as agitating mark is recognized

Stirring mark: Defective appearance of the coating film, which is recognized as a stripe mark on the cured electrodeposited coating film, which is thought to originate from the stirring of the electrodeposition coating composition at the time of forming the electrodeposition coating film.

Evaluation of horizontal appearance unevenness

Using the electrodeposition coating composition described in each of the Examples and Comparative Examples, the electrodeposition coating was carried out by placing the base material in a horizontal state in the electrodeposition coating composition in an uncrosslinked half-state. The obtained electrodeposition coating film was cured by heating at a softening point of the aqueous dispersion type gloss control agent (C) + 30 占 폚 for 30 minutes. The outer appearance of the obtained coating film after baking was visually observed, and the difference in appearance of the upper and lower surfaces was visually evaluated by the following criteria.

&Amp; cir &: No difference was recognized by visual observation, and the appearance was judged to be good.

X: Since the degree of mattiness of the upper and lower surfaces is recognized as being different by visual observation, it is judged that the appearance is defective.

Measurement of pencil hardness

The pencil hardness of the coating film was measured in accordance with JIS K 5600-5-4 using a cured electrodeposition coating film obtained by heating at a softening point + 30 占 폚 of the aqueous dispersion type gloss control agent (C). Specifically, a pencil (for scratching hardness test of Japan Paint Inspection Association, manufactured by Mitsubishi Nippon Paint Co., Ltd.) was pushed and moved on the surface of the cured electrodeposition coating film so that the scratch angle was 45 °, and the presence or absence of scratches by the core of the pencil was visually observed did.

For example, in the case of a test using a pencil of H, it was judged that H was abnormal when no scratch occurred. When the occurrence of a slight depression in one test in five tests was recognized, it was judged to be H. Then, in the case where there were two or more occurrences during the five tests and there was a recess, it was judged to be less than H, and the evaluation of lowering by one level was carried out in the same manner.

When the pencil hardness is less than F, it can be judged that the hardness and scratch resistance are inferior.

The aqueous dispersion type of gloss control agent (C) used in the above Examples and Comparative Examples is as follows.

(C1) of Example 1, Comparative Examples 3 and 4: Big Chemie Japan Co. AQUAMAT 208 (solid concentration (NV) = 35%, softening point (T _m) = 135 ℃, density = 1.00)

(C2 = 20%, _Tm = 105 占 폚, density = 0.93)

(C3 = 25%, _Tm = 80 deg. C, density = 0.93). Comparative Example 1:

(C4) Comparative Example 2: Chemipearl WP-100 (NV = 40%, _Tm = 148 占 폚, density = 0.90) manufactured by Mitsui Chemicals,

(C5) Comparative Example 5: Big Chemie Japan Co. AQUACER 531 (non-ionic wax _{emulsion, NV = 45%, T m} = 130 ℃, density = 0.98)

As shown in the above evaluation results, it was confirmed that in the formation of the cured electrodeposition coating film using the anionic electrodeposition coating composition obtained by the examples, the change in the gloss caused by the change in heating temperature was small and the coating film appearance defect was not accompanied .

Comparative Example 1 is an experimental example in which the softening point (T _m ) of the wax constituting the aqueous dispersion type gloss control agent (C) is lower than 100 캜. In this case, the gloss of the resulting cured electrodeposition coating film was increased as a whole, and the difference in glossiness caused by the heating temperature change was increased. Furthermore, there is a problem that the hardness of the cured electrodeposited coating film is lowered.

Comparative Example 2 is an experimental example in which the density of the wax constituting the water dispersible type gloss adjuster (C) is less than 0.91. In this case, the difference in gloss caused by the change in heating temperature was large. Further, occurrence of horizontal uneven appearance was confirmed. This is because the density of the wax constituting the water-dispersible type gloss-adjusting agent (C) is low, so that the water-dispersible type gloss-adjusting agent (C) is not well dispersed in the anionic electrodeposition coating composition, and in the electrodeposition coating step and the heat- (C) in the electrodeposition coating film and the cured electrodeposited coating film were not uniformly present on the upper and lower surfaces of the substrate.

Comparative Example 3 is an experimental example in which the amount of the aqueous dispersion type of gloss control agent (C) is small. In this case, the gloss of the resulting cured electrodeposition coating film was increased as a whole, and the difference in glossiness caused by the heating temperature change was increased. Furthermore, uneven appearance of the coating film was confirmed.

Comparative Example 4 is an experimental example in which the amount of the aqueous dispersion type of gloss control agent (C) is large. In this case, the gloss value was lowered while the difference in glossiness caused by the heating temperature change was larger. Furthermore, there is a problem that the hardness of the cured electrodeposited coating film is lowered.

Comparative Example 5 is an experimental example in which the coating film viscosity of the electrodeposition coating film at 50 캜 is less than 10,000. In this case, the difference in gloss caused by the change in heating temperature was large.

Comparative Example 6 is an experimental example which does not include the aqueous dispersion type of gloss control agent (C). In this case, the gloss of the cured electrodeposited coating film was very high.

According to the method of the present invention, it is possible to form a cured electrodeposited coating film whose gloss has been adjusted, such as a low-gloss coating film or a matte coating film having a low mirror-surface glossiness, without involving glossy unevenness There is an advantage. In the method of the present invention, furthermore, there is an advantage that a cured electrodeposited coating film having good hardness can be obtained even when the electrodeposited coating film is formed and then heat cured under low temperature curing conditions.

Claims (7)

A method for forming a cured electrodeposited coating film,
An electrodeposition coating step of immersing a substrate in an anionic electrodeposition coating composition and applying a voltage to form an electrodeposited coating film, and
A heat curing step of forming a cured electrodeposited coating film by thermally curing the electrodeposited coating film formed in the electrodeposition coating step
/ RTI >
Wherein the anionic electrodeposition coating composition comprises an acrylic resin (A), a curing agent (B), an aqueous dispersion type gloss control agent (C) and a curing catalyst (D)
The aqueous dispersion type gloss adjuster (C) is an aqueous dispersion of one or more waxes selected from the group consisting of natural wax and polyolefin wax,
The wax constituting the aqueous dispersion type gloss adjuster (C) preferably has a softening point (T _m ) of 100 ° C or higher and a density of 0.91 to 1.10,
The solid content of the aqueous dispersion type gloss control agent (C) contained in the anionic electrodeposition coating composition is 6 to 20 parts by mass based on 100 parts by mass of the resin solid content of the anion electrodeposition coating composition,
Wherein the electrodeposition coating film formed in the electrodeposition coating step has a coating film viscosity at 50 캜 within a range of 10,000 to 100,000 Pa · s,
Way. The method according to claim 1,
Wherein the heating temperature (T _h ) in the heat hardening step is 110 to ₁₆₀占 폚. 3. The method according to claim 1 or 2,
Wherein the softening point (T _m ) is in the range of 100 to 140 캜. 4. The method according to any one of claims 1 to 3,
Wherein the electrodeposited coating film formed in the electrodeposition coating step has a coating film viscosity at 80 ° C in a range of 1,000 to 10,000 Pa · s. 5. The method according to any one of claims 1 to 4,
The acrylic resin (A) is an acrylic resin having a carboxyl group and a hydroxyl group,
Wherein the curing agent (B) is one or more selected from the group consisting of an amino resin and a block isocyanate compound,
Way. 6. The method according to any one of claims 1 to 5,
Wherein the difference (DELTA T) between the softening point (T _m ) and the heating temperature (T _h ) is not less than 10 ° C. and not more than 50 ° C., and T _h > T _m . 7. The method according to any one of claims 1 to 6,
Wherein the cured electrodeposition coating film formed by the forming method has a 60 占 specular gloss of 70 or less.