JP2012162636A - Water dispersion, and aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water dispersion which is excellent in storage stability, exhibits no generation of foaming and can provide a coating film whose finishing is good, and an aqueous coating composition in which the water dispersion is dispersed.SOLUTION: The water dispersion contains a specific dispersing resin (A) and benzoin or a derivative thereof (B) dispersed in an aqueous medium, wherein the benzoin or the derivative thereof (B) is contained in 0.1 to 400 pts.mass in 100 pts.mass of the solid content of the dispersing resin (A). The dispersing resin (A) is a resin obtained by radical polymerization reacting a mixture of 3 to 98 mass% of a radical polymerizable unsaturated monomer (a1) having a polyoxyalkeylene chain, 2 to 97 mass% of a nitrogen-containing radical polymerizable unsaturated monomer (a2), 0 to 20 mass% of a carboxyl group-containing radical polymerizable unsaturated monomer (a3), and 0 to 95 mass% of other radical polymerizable unsaturated monomers (a4), with respect to the total mass of the constituting monomers.

Description

  The present invention relates to an aqueous dispersion excellent in storage stability, and further relates to an aqueous coating composition that can provide a coating film with good finish without occurrence of cracks using the aqueous dispersion.

  Conventionally, the outer plate portion of an automobile body is usually covered with a multilayer coating film formed from an undercoat paint, an intermediate coat paint, and a top coat paint by a cationic electrodeposition paint for the purpose of providing corrosion prevention and aesthetics.

On the other hand, paints using organic solvents have been the mainstream of conventional paints, but due to concerns about health and environmental impact, volatile organic compounds are also used in automotive paints (for example, intermediate paints and colored base paints). Reduction (lower VOC) is required, and water-based paints are becoming mainstream.
However, a coating film made of a water-based paint is likely to cause so-called “bumps” due to water boiling during curing, and this phenomenon may be observed in a film thickness of 15 to 40 μm, which causes a decrease in finish. Yes.

Conventionally, Patent Document 1 discloses a water-based intermediate coating material containing a polyester resin, a water-based amino resin, and a polyether polyol as a main component and an alkyl etherified benzoin.
Patent Document 2 discloses a polyester resin, an aqueous amino resin, and a linear low molecular weight polyester having an acid value of 10 to 100 mgKOH / g, a hydroxyl value of 20 to 300 mgKOH / g, and a number average molecular weight of 800 to 10,000. An aqueous intermediate coating composition containing a diol as a main component and an alkyl etherified benzoin is disclosed.

  In addition, Patent Document 3 discloses a three-coat one-bake in which an intermediate coating, a base coating, and a clear coating are sequentially applied to the surface of an object to be coated by a wet-on-wet method and then baked to cure each coating film. In the method of forming a coating film, a method is disclosed in which benzoin or a benzoin derivative and a vinyl polymer are added to at least one of the intermediate coating, base coating, and clear coating. Further, in Production Example 1, benzoin is blended as it is in the paint, as 0.4 part of benzoin is blended with disper stirring with respect to the midcoat and an intermediate coat is obtained.

  However, since the benzoin is not sufficiently dispersed under the production conditions of the water-based coating compositions described in Patent Documents 1 to 3, the finish of the coating film such as unevenness and rough skin may be impaired. Further, since the added benzoin is not sufficiently compatible with the resin component, the effect on the armpit may not be sufficient.

JP-A-4-41572 JP-A-4-93374 JP 2002-113414 A

  An object of the present invention is to provide an aqueous dispersion having excellent storage stability. Another object of the present invention is to provide an aqueous coating composition that can provide a coating film that has excellent coating stability, does not generate cracks, and has good finish.

  The present inventors are an aqueous dispersion in which a specific dispersing resin (A) and a benzoin or benzoin derivative (B) are dispersed in an aqueous medium, and the solid content of the dispersing resin (A) is 100 mass. By using an aqueous dispersion containing 0.1 to 400 parts by mass of benzoin or a benzoin derivative (B) per part, the inventors have found that the above object can be achieved, and have completed the present invention.

That is, the present invention
1. The dispersion resin (A) having the following characteristics and the benzoin or benzoin derivative (B) are dispersed in an aqueous medium, and the benzoin or An aqueous dispersion containing 0.1 to 400 parts by mass of the benzoin derivative (B),
Dispersing resin (A): 3 to 98% by mass of a radically polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain and a nitrogen-containing radically polymerizable unsaturated monomer with respect to the total mass of constituent monomers 2 to 97% by mass of the monomer (a2), 0 to 20% by mass of the carboxyl group-containing radical polymerizable unsaturated monomer (a3), and 0 to 95% of the other radical polymerizable unsaturated monomer (a4). 1. Resin obtained by radical polymerization reaction of a mass% mixture The aqueous dispersion according to 1, wherein the aqueous dispersion contains less than 20 parts by mass of the amine compound (C) per 100 parts by mass of the solid content of the resin for dispersion (A).
3. The aqueous dispersion according to 1 or 2, wherein the aqueous dispersion contains less than 100 parts by mass of a surfactant per 100 parts by mass of the solid content of the dispersing resin (A),
4). An aqueous coating composition containing the hydroxyl group and carboxyl group-containing resin (D), the curing agent (E), and the aqueous dispersion according to any one of items 1 to 3,
5. 5. The aqueous coating composition according to item 4, containing 0.1 to 50 parts by mass of the solid content of the aqueous dispersion with respect to 100 parts by mass of the total solid contents of the hydroxyl group and carboxyl group-containing resin (D) and the curing agent (E). ,
6). 6. The aqueous coating composition according to item 4 or 5, which is an intermediate coating or colored base coating for automobiles,
The present invention relates to a coated article obtained by coating the aqueous coating composition according to any one of 7.4 to 6.

  The aqueous dispersion of the present invention is excellent in storage stability even under severe conditions such as being heated to 40 ° C. or higher and then stored at 5 ° C. or lower. Furthermore, since the benzoin or the benzoin derivative in the aqueous coating composition containing the aqueous dispersion does not cause aggregation or the like, a coating film having excellent finish can be obtained. In addition, it is possible to improve the limit film thickness at the time of painting.

  When the aqueous coating composition of the present invention is used in an aqueous intermediate coating or colored base coating for automobiles, a multilayer coating film having excellent finish without causing coating film defects such as armpits and bumps on the coating film. Obtainable. As a result, in the painting line, it is possible to reduce labor and cost for repairing coating film defects as well as preheating performed as a countermeasure against armpits, thereby contributing to energy saving.

The aqueous dispersion and aqueous coating composition of the present invention will be described in detail.
[Water dispersion]
An aqueous dispersion in which a dispersion resin (A) and a benzoin or benzoin derivative (B) are dispersed in an aqueous medium.

Resin for dispersion (A)
The dispersing resin (A) comprises a radically polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain and a nitrogen-containing radically polymerizable unsaturated monomer (a2) with respect to the total of the constituent monomers. , A resin obtained by radical polymerization reaction of a carboxyl group-containing radical polymerizable unsaturated monomer (a3) and another radical polymerizable unsaturated monomer (a4).

Radical polymerizable unsaturated monomer having a polyoxyalkylene chain (a1)
The radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain (hereinafter sometimes abbreviated as “radical polymerizable unsaturated monomer (a1)”), for example, (meth) acrylic acid and An esterified product of mono- or polyalkylene or a monoether derivative thereof,
Those represented by the following general formula (1) are included.

(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom, a C1-C20 alkyl group, an aryl group (for example, a phenyl group) or an aralkyl (preferably a benzyl group), and m represents 2 is an integer of 2 to 5, and n is an integer of 1 to 20.)

  Specific examples of such radical polymerizable unsaturated monomer (a1) include diethylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, dipropylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, Propylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene (meth) acrylate, ethoxyethylene (meth) acrylate, butoxyethylene (meth) acrylate, hexyloxyethylene (meth) acrylate, ethoxypropylene (meth) acrylate, Ethoxydiethylene (meth) acrylate, butoxydiethylene (meth) acrylate, dodecyloxydiethylene (meth) acrylate, phenoxy dip Pyrene (meth) acrylate, benzyloxy (meth) acrylate, and the like. These may be used alone or in combination. The weight average molecular weight of the radically polymerizable unsaturated monomer (a1) is generally 100 to 5,000, preferably 150 to 1,500.

  In the present specification, the weight average molecular weight is a value obtained by converting the retention time (retention capacity) measured by gel permeation chromatography using tetrahydrofuran as a solvent, based on the weight average molecular weight of polystyrene. The number average molecular weight is a value obtained by calculation from the weight average molecular weight.

Nitrogen-containing radically polymerizable unsaturated monomer (a2)
Examples of the nitrogen-containing radical polymerizable unsaturated monomer (a2) include an unsaturated monomer (1) having a nitrogen-containing heterocyclic ring and a nitrogen-containing derivative (2) of (meth) acrylic acid. Specifically, the unsaturated monomer (1) having a nitrogen-containing heterocyclic ring includes a monomer in which a monocyclic or polycyclic heterocyclic ring containing 1 to 3 ring nitrogen atoms is bonded to a vinyl group. In particular, the following monomers may be mentioned.

(I) Vinylpyrrolidones: For example, 1-vinyl-2-pyrrolidone, 1-vinyl-3-pyrrolidone and the like.
(Ii) Vinylpyridines; for example, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine and the like.
(Iii) Vinylimidazoles; for example, 1-vinylimidazole, 1-vinyl-2-methylimidazole and the like.
(Iv) Vinylcarbazoles; for example, N-vinylcarbazole.
(V) Vinylquinolines; for example, 2-vinylquinoline.
(Vi) Vinyl piperidines; for example, 3-vinyl piperidine, N-methyl-3-vinyl piperidine and the like.
(Vii) N- (meth) acryloylpyridine and the like. Among the above vinyl monomers having a nitrogen-containing heterocycle, preferred are vinylpyrrolidones, vinylimidazoles and vinylcarbazoles.
On the other hand, the nitrogen-containing derivative (2) of (meth) acrylic acid includes N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, Nt-butylaminoethyl (meth). Acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N-propylaminoethyl (meth) acrylate, N-butylaminoethyl (meth) acrylate and the like are included. .

  Also, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-butyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide N, N-dipropyl (meth) acrylamide, N-methylol (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethylaminopropyl acrylamide and the like are included. . The nitrogen-containing radically polymerizable unsaturated monomer (a2) described above can be used alone or in combination of two or more.

Carboxyl group-containing radical polymerizable unsaturated monomer (a3)
Examples of the carboxyl group-containing radical polymerizable unsaturated monomer (a3) include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxylethyl (meth) acrylate, 2- Carboxypropyl (meth) acrylate etc. are mentioned, These can be used individually or in combination of 2 or more types, respectively.

Other radical polymerizable unsaturated monomer (a4)
The other radical polymerizable unsaturated monomer (a4) includes a radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain, a nitrogen-containing radical polymerizable unsaturated monomer (a2), and a carboxyl group-containing It is a radically polymerizable unsaturated monomer other than the radically polymerizable unsaturated monomer (a3), and is not particularly limited and can be widely selected depending on the desired coating film performance.
For example, (a) esters of acrylic acid or methacrylic acid: for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, methyl methacrylate, Ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate, etc .; (b) vinyl aromatic compounds: for example, styrene, α-methylstyrene, vinyl toluene, p -Chlorstyrene; (c) Polyolefin compounds: for example, butadiene, isoprene, chloroprene; (d) hydroxyl group-containing unsaturated monomers: for example, hydroxyethyl (meth) acrylate, hydroxypropyl (me ) Acrylate and other hydroxyl groups such as Plaxel FM1, Plaxel FM2, Plaxel FM3, Plaxel FA1, Plaxel FA2, Plaxel FA3 (above, Daicel Chemical Industries, trade name, caprolactone-modified (meth) acrylic acid hydroxy esters) Unsaturated monomer and the like; (e) Others: acrylonitrile, methacrylonitrile, methyl isopropenyl ketone, vinyl acetate, and the like.
These other radical unsaturated monomers (a4) may be used alone or in combination of two or more.

  The dispersing resin (A) is composed of the above-mentioned radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain, nitrogen-containing radical polymerizable unsaturated monomer (a2), and carboxyl group-containing radical polymerizable. The unsaturated monomer (a3) and other radically polymerizable unsaturated monomer (a4) are subjected to a radical polymerization method known per se, for example, in the presence of a polymerization initiator, an inert gas such as nitrogen gas It can be produced by radical copolymerization in an organic solvent at a temperature of 50 ° C. to 300 ° C., preferably 60 ° C. to 250 ° C. in an atmosphere for 1 hour to 24 hours, preferably 2 hours to 10 hours. .

The use ratio of each polymerizable unsaturated monomer at that time is a radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain, a nitrogen-containing radical polymerizable unsaturated monomer (a2) and a carboxyl group. Based on the total amount of the containing radical polymerizable unsaturated monomer (a3) and the other radical polymerizable unsaturated monomer (a4), it can be as follows.
Radical polymerizable unsaturated monomer having a polyoxyalkylene chain (a1): 3-98% by mass, preferably 10-85% by mass, nitrogen-containing radical polymerizable unsaturated monomer (a2): 2-97% by mass %, Preferably 3 to 90% by weight, carboxyl group-containing radical polymerizable unsaturated monomer (a3): 0 to 20% by weight, preferably 2 to 18% by weight, other radical polymerizable unsaturated monomers ( a4) is 0 to 95% by mass, preferably 5 to 83% by mass.

  Examples of the polymerization initiator include benzoyl peroxide, di-tert-butyl hydroperoxide, azobisdimethylvaleronitrile, azobisisobutyronitrile, and the like. Examples of organic solvents that can be used for the radical polymerization reaction include aromatic hydrocarbon solvents such as toluene and xylene; ketone solvents such as methyl isobutyl ketone and cyclohexanone; n-butanol, ethyl cellosolve, butyl cellosolve, methoxypropanol, Examples include alcohol solvents such as diethylene glycol monobutyl ether. These organic solvents can be used alone or in combination of two or more. The dispersion resin (A) thus obtained has a weight average molecular weight of 500 to 150,000, preferably 1,000 to 60,000. The acid value is 0 to 60 mgKOH / g, preferably 1 to 50 mgKOH / g, and the amine value is 0 to 80 mgKOH / g, preferably 1 to 60 mgKOH / g.

Benzoin or benzoin derivatives (B)
Specific examples of benzoin or a benzoin derivative (B) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, benzoin n-hexyl ether, benzoin Examples thereof include n-octyl ether. Among these, benzoin and benzoin ethyl ether are preferred from the viewpoint of industrial availability and paint stability.

The amount of the benzoin or benzoin derivative (B) used is 0.1 to 400 parts by weight, preferably 10 to 300 parts by weight of the benzoin or benzoin derivative (B) per 100 parts by weight of the solid content of the dispersion resin (A). Part, more preferably 50 to 250 parts by weight. Outside this range, the dispersibility of the benzoin or benzoin derivative decreases, which is not preferable.
The aqueous dispersion of the present invention comprises a dispersion resin (A), benzoin or a benzoin derivative (B), and, if necessary, at least one amine compound selected from an alicyclic amino compound and an amino alcohol ( C), a surfactant, a thickener, an organic solvent, a surface preparation agent and the like can be added and dispersed.

Amine compound (C)
Good dispersion stability can be obtained by adding the amine compound (C) to the aqueous dispersion of the present invention. Specifically, the amine compound (C) is triethylamine, diethylaminopropylamine, di-n-dibutylamine, di-i-dibutylamine, diisopropylamine, di-n-propylamine, tri-n-propylamine, monobutylamine. Aliphatic amino compounds such as N-octylamine, cyclic amino compounds such as N, N-dimethylbenzylamine; monoethanolamine, ethylaminoethanol, dimethylethanolamine, N-methaneethanolamine, Nn-butylethanol And amino alcohols such as amine, 2-diethylaminoethanol, dimethylamino-2-propanol, isopropylaminoethanol, 2-amino-2-methylpropanol, and dodecylbenzenesulfonic acid diisopropanolamine salt. Among these amine compounds (C), amino alcohol is particularly preferable.

  The amine compound (C) has a boiling point, 80 to 180 ° C, preferably 100 to 160 ° C, and a molecular weight of 60 to 460, preferably 75 to 145. The amine compound (C) is used in an amount of less than 20 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the solid content of the dispersion resin (A). It is also desirable in order to mitigate the occurrence of scumming due to the aggregation of the resin or the like when the aqueous dispersion of the present invention is blended during the production of the paint.

  The reason for this is that by mixing the amine compound (C) in the aqueous dispersion, the dispersion resin (A) and the benzoin or benzoin derivative (B) become more stable, and the benzoin or benzoin derivative (B ) We think that we can alleviate the aggregation of comrades.

Surfactant The surfactant that can be added as necessary may be any of nonionic, anionic, cationic, or zwitterionic. When a nonionic surfactant is used, the HLB is 8 or more, preferably about 10 to about 20. The HLB is an abbreviation for Hydrophile-Lipophile Balance showing the balance between the hydrophilic group and the lipophilic group in the molecule. In this specification, HLB is determined by the following method. When the emulsifier is a polyhydric alcohol and a fatty acid ester, the formula of HLB = 20 (1-S / A), when it is difficult to obtain a clear saponification value, the formula of HLB = (E + P) / 5, hydrophilic group When it contains only a polyoxyethylene group, it calculated | required by the formula of HLB = E / 5. In the above formulas, S represents the saponification value of the ester, A represents the acid value of the fatty acid, P represents the polyhydric alcohol weight distribution, and E represents the weight distribution of the oxyethylene group.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyalkylene alkylphenol ether, polyoxyalkylene alkyl ester, sorbitan alkyl ester, polyoxyalkylene sorbitan alkyl ester polyoxyalkylene glycol, Alkyl polyglucosides, polyoxyethylene derivatives, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, alkylalkanolamides and the like can be mentioned.

Examples of the anionic surfactant include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, and alkyl phosphates. Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts. Examples of the zwitterionic surfactant include alkylbedine.
The use ratio of the surfactant is such that the surfactant is less than 100 parts by mass, preferably 1 to 50 parts by mass with respect to 100 parts by mass of the solid content of the dispersion resin (A), and the coating performance such as water resistance is improved. It is also desirable not to reduce it.

  The water dispersion is produced by using, for example, a shaker, a ball mill, a pebble mill, a sand mill, a planetary ball mill, a homogenizer or the like as a dispersing means, and an average particle diameter is 20 μm or less, preferably 0.1 to 10 μm, more preferably 1 to 1. It is preferable to disperse so as to have an average particle diameter of 7 μm in order to be excellent in coating stability and resistance to peeling when added to an aqueous coating composition. The “average particle size” was measured using UPA-EX250 (trade name, particle size distribution measuring device, dynamic light scattering method / laser Doppler method (UPA method) manufactured by Nikkiso Co., Ltd.). Next, an aqueous coating composition using the aqueous dispersion will be described.

[Water-based paint composition]
The content of the aqueous dispersion in the aqueous coating composition of the present invention is such that the solid content of the aqueous dispersion is 100 parts by mass in total of the solid content of the following hydroxyl group- and carboxyl group-containing resin (D) and curing agent (E). The content of 0.1 to 50 parts by weight, preferably 1 to 40 parts by weight, and more preferably 2 to 35 parts by weight is intended to improve the stability and resistance of the water-based coating composition. Is necessary.

Hydroxyl and carboxyl group-containing resin (D)
Examples of the hydroxyl group and carboxyl group-containing resin include a polyester resin, an acrylic resin, a polyether resin, a polycarbonate resin, and a polyurethane resin.
In particular, the hydroxyl group and carboxyl group-containing resin is preferably a hydroxyl group and carboxyl group-containing polyester resin, a hydroxyl group and carboxyl group-containing acrylic resin, or the like. These hydroxyl group and carboxyl group-containing resins can be used singly or in combination of two or more. The hydroxyl group- and carboxyl group-containing polyester resin can be synthesized by an ordinary method, for example, by an esterification reaction between a polybasic acid and a polyhydric alcohol.
The polybasic acid is a compound having two or more carboxyl groups in one molecule. Examples of the polybasic acid include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid. Examples thereof include acid and pyromellitic acid. In addition, anhydrides of these polybasic acids can also be used.

  The polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 2,2-diethyl-1. , 3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxypivalic acid neopentyl glycol ester, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl Diols such as -1,5-pentanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A; trivalent or higher polyols such as trimethylolpropane, trimethylolethane, glycerin, pentaerythritol; 2,2 -Dimethylolpropionic acid, 2,2- Methylol butanoic acid, 2,2-dimethylol pentanoic acid, 2,2-dimethylol-hexanoic acid, and the like hydroxycarboxylic acids, such as 2,2-dimethylol octanoic acid.

  Further, a monoepoxy compound such as an α-olefin epoxide such as propylene oxide and butylene oxide, and a glycidyl ester of a highly branched saturated fatty acid may be introduced into the polyester resin by reacting with a carboxyl group in the polyester resin. A commercially available product can be used as the glycidyl ester of the highly branched saturated fatty acid. Examples of commercially available products include “Cardura E10P” (trade name, manufactured by HEXION Specialty Chemicals, Inc., a glycidyl ester of a synthetic highly branched saturated fatty acid).

  The hydroxyl value of the hydroxyl group- and carboxyl group-containing polyester resin is in the range of 50 to 200 mgKOH / g, and preferably in the range of 80 to 150 mgKOH / g. The acid value of the hydroxyl group- and carboxyl group-containing polyester resin is in the range of 5 to 100 mgKOH / g, preferably in the range of 20 to 70 mgKOH / g. The number average molecular weight of the hydroxyl group- and carboxyl group-containing polyester resin is preferably 250 to 4,000, more preferably 300 to 3,500, and still more preferably 300 to 3,000. The hydroxyl group and carboxyl group-containing polyester resin may be an alkyd resin or a urethane-modified polyester resin.

Hydroxyl group and carboxyl group-containing acrylic resin The hydroxyl group and carboxyl group-containing acrylic resin can be synthesized according to a conventional method, for example, by copolymerizing a radical polymerizable monomer. As the hydroxyl group- and carboxyl group-containing acrylic resin, it is preferable to use a resin synthesized by a solution polymerization method. As the organic solvent used for this polymerization reaction, for example, it is preferable to use a hydrophilic organic solvent such as a propylene glycol type or a dipropylene glycol type.

  As the radical polymerizable monomer, known ones can be used. For example, a hydroxyl group-containing radical polymerizable monomer, a carboxyl group-containing radical polymerizable monomer, and other radical polymerizable monomers can be used. Can do. In the present specification, “(meth) acrylate” means “acrylate or methacrylate”.

  Examples of the hydroxyl group-containing radical polymerizable monomer include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and ε-caprolactone modification. Tetrahydrofurfuryl (meth) acrylate, ε-caprolactone modified hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- Examples thereof include hydroxy-3-butoxypropyl (meth) acrylate and monohydroxyethyl (meth) acrylate phthalate.

  Examples of the carboxyl group-containing radical polymerizable monomer include acrylic acid and methacrylic acid.

  Examples of other radical polymerizable monomers include styrene, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meta ) Acrylate, cyclohexenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (Meth) acrylate, p-cumylphenol ethylene oxide modified (meth) acrylate, N-methylol (meth) acrylamide, N-butoxy (meth) acrylami , It may be mentioned acryloyl morpholine, dimethylaminoethyl (meth) acrylate, N- vinyl-2-pyrrolidone, and the like γ- acryloyloxy propyl trimethoxysilane.

The hydroxyl value of the hydroxyl group- and carboxyl group-containing acrylic resin is in the range of 10 to 200 mgKOH / g, and preferably in the range of 60 to 180 mgKOH / g.
The acid value of the hydroxyl group- and carboxyl group-containing acrylic resin is in the range of 10 to 100 mgKOH / g, preferably in the range of 25 to 60 mgKOH / g.

  The number average molecular weight of the hydroxyl group- and carboxyl group-containing acrylic resin is preferably 1,000 to 4,000, and more preferably 1,000 to 3,000. The hydroxyl group- and carboxyl group-containing acrylic resin may be a urethane-modified acrylic resin.

Curing agent (E)
On the other hand, as the curing agent, melamine resin, blocked polyisocyanate compound, non-blocked polyisocyanate, etc. can be used, but are not limited to these, and melamine resin and blocked polyisocyanate from the viewpoint of curability and coating film performance. Compounds are preferred.

The melamine resin melamine resins, specifically, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentaerythritol melamine, methylol melamine, such as hexamethylol melamine, alkyl etherified product or condensate of these methylol melamine; melamine And the condensates of alkyl ethers. The alkyl etherification of methylolmelamine can be carried out by a known method using monoalcohol such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, 2-ethylhexyl alcohol and the like.

  A commercial item can be used as a melamine resin. Commercially available product names include, for example, “Cymel 303”, “Cymel 323”, “Cymel 325”, “Cymel 327”, “Cymel 350”, “Cymel 370”, and “Cymel 380” manufactured by Nippon Cytec Industries. "Cymel 385", "Cymel 212", "Cymel 251", "Cymel 254", "My Coat 776"; "Resimin 735", "Resimin 740", "Resimin 741", "Resimin 745" manufactured by Monsanto , “RESIMIN 746”, “RESIMIN 747”; “SUMIMAL M55”, “SUMIMAL M30W”, “SUMIMAL M50W” manufactured by Sumitomo Chemical; “Uban 20SB”, “Uban 20SE-60”, “Uban” manufactured by Mitsui Chemicals, Inc. 28-60 "and the like.

  The melamine resin preferably has a triazine mononuclear content of 35% by mass or more, more preferably 40% by mass or more, and still more preferably 45% by mass or more. Further, from the viewpoint of excellent storage stability of the coating composition, smoothness of the coating film, etc., a methylated melamine resin having a methoxy group / butoxy group molar ratio of about 100/0 to 60/40 mol%, a ratio of methoxy group A high methyl / butyl mixed etherified melamine resin is preferred. In the methyl / butyl mixed etherified melamine resin, the molar ratio of methoxy group / butoxy group is more preferably about 100/0 to 70/30 mol%.

  As a particularly preferred melamine resin, a methylated melamine resin having a triazine mononuclear content of 35% by mass or more and a methoxy group / butoxy group molar ratio of 100/0 to 70/30 mol%, methyl / butyl mixed Mention may be made of etherified melamine resins.

  A commercial item can be used as this melamine resin. Commercially available product names include, for example, “Cymel 325”, “Cymel 327”, “Cymel 350”, “Cymel 212”, “Cymel 251”, “My Coat 212”, “My Coat” manufactured by Nippon Cytec Industries, Ltd. 776 "and the like. A melamine resin can be used individually by 1 type or in mixture of 2 or more types.

  When a melamine resin is used as the curing agent (E), sulfonic acids such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid; salts of these acids and amines are used as catalysts. be able to.

Block Polyisocyanate Compound A block polyisocyanate compound is a compound in which all isocyanate groups of a polyisocyanate compound having two or more free isocyanate groups in one molecule are blocked with a blocking agent.

  As the polyisocyanate compound and the blocking agent, the polyisocyanate compound and the free isocyanate group which are compounds having two or more free isocyanate groups not blocked in one molecule exemplified in the description of the urethane-modified polyester resin are blocked. A blocking agent which is a compound to be used can be used.

  Moreover, the hydroxycarboxylic acid which has 1 or more hydroxyl group and 1 or more carboxyl group in 1 molecule as a blocking agent can be used. Examples of the hydroxycarboxylic acid include hydroxypivalic acid and dimethylolpropionic acid. The blocked polyisocyanate compound blocked with a hydroxycarboxylic acid has a carboxyl group derived from the raw material hydroxycarboxylic acid, and is preferable from the viewpoint of good water dispersibility based on the hydrophilicity of the carboxyl group. . Reaction of a polyisocyanate compound and a blocking agent can be performed by a well-known method.

  The number average molecular weight of the block polyisocyanate compound is preferably 250 to 4,000, more preferably 300 to 3,000, and still more preferably 300 to 2,500.

  In the aqueous coating composition of the present invention, the ratio of the hydroxyl group and carboxyl group-containing resin (D) to the curing agent (E) is 50 to 50 hydroxyl group and carboxyl group-containing resin based on the total solid content of 100 parts by mass. 90 mass parts, Preferably it is 60-85 mass parts, and a hardening | curing agent is 10-50 mass parts, Preferably it is 15-40 mass parts.

  Moreover, a well-known pigment component can be used for an aqueous coating composition as needed. Examples of such pigments include colored pigments such as titanium dioxide, zinc white, carbon black, phthalocyanine blue, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, selenium pigments, and perylene pigments. An extender pigment such as clay, kaolin, barita, barium sulfate, talc, barium carbonate, calcium carbonate, silica, and alumina white; and a bright pigment such as aluminum flake and mica flake.

The blending ratio of these pigment components is preferably 2 to 200 parts by weight, more preferably 30 to 170 parts by weight, based on 100 parts by weight in total of the hydroxyl group and carboxyl group-containing resin (D) and the curing agent (E). 50-150 mass parts is still more preferable.
Among the above pigment components, such a thin and flat scale having a thickness of 0.1 to 2 μm, more preferably 0.2 to 1.5 μm and a longitudinal dimension of 1 to 100 μm, preferably 2 to 20 μm. There are flat pigments in shape. Specific examples include talc, aluminum flakes, mica flakes, and the like.

  The content of such a flat pigment is 2 to 30 parts by mass, preferably 5 to 20 parts by mass with respect to 100 parts by mass in total of the hydroxyl and carboxyl group-containing resin (D) and the curing agent (E). It is desirable. When the particles are contained within this range, the smoothness of the coating film can be improved by the effect that the particles are oriented in parallel to the coating film surface.

  In the aqueous coating composition of the present invention, if necessary, an organic solvent, a dispersant, a thickener, an antisettling agent, a catalyst for promoting urethanization reaction (for example, an organic tin compound), a hydroxyl group of the base resin, and A catalyst for promoting reaction with the melamine resin (for example, an acid catalyst), an antifoaming agent, a rust preventive agent, an ultraviolet absorber, a surface conditioner, and the like can be appropriately blended.

The preparation method of the aqueous coating composition of this invention is not limited, For example, it can carry out by the method (1)-method (4) described below.
Method (1): hydroxyl group and carboxyl group-containing resin (D), curing agent (E), aqueous dispersion and optionally other additives are combined together, mixed thoroughly and added with neutralizing agent and dispersed. A method of blending a pigment dispersion paste into the obtained emulsion.
Method (2): Obtained by neutralizing the hydroxyl group- and carboxyl group-containing resin (D) in advance, combining the curing agent (E), the aqueous dispersion, and optionally other additives, thoroughly mixing and dispersing. A method of blending a pigment dispersion paste into an emulsion.
Method (3): A water dispersion, a pigment component and a catalyst, other additives and water are added and dispersed to prepare a pigment dispersion paste, and the pigment dispersion paste is mixed with a hydroxyl group- and carboxyl group-containing resin (D), a curing agent. A method of blending (E) and optionally other additives together, mixing well, adding a neutralizing agent, and dispersing the resulting aqueous dispersion.
Method (4): The method of mix | blending an aqueous dispersion in the aqueous coating composition produced previously is mentioned.

  Examples of the neutralizing agent include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and barium hydroxide; ammonia; ethylamine, propylamine, Primary monoamine compounds such as butylamine, benzylamine, monoethanolamine, neopentanolamine, 2-aminopropanol, 3-aminopropanol; diethylamine, diethanolamine, di-n-propanolamine, di-iso-propanolamine, N -Secondary monoamine compounds such as methylethanolamine and N-ethylethanolamine; dimethylethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine, dimethylaminoethane And tertiary monoamine compounds such as diol; polyamine compounds such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, and methylaminopropylamine. Of these, primary monoamine compounds, secondary monoamine compounds, tertiary monoamine compounds, and polymonoamine compounds are preferably used.

  The aqueous coating composition of the present invention is usually diluted with deionized water as necessary when coating, for example, Ford Cup No. 4 is measured at 20 ° C., and the viscosity is preferably adjusted to 30 to 120 seconds, more preferably 35 to 90 seconds. In this case, the solid content concentration is preferably 35 to 65% by mass, and more preferably 40 to 60% by mass.

The aqueous coating composition of the present invention can be applied by a known method, for example, air spray, airless spray, rotary atomization coating or the like. Electrostatic application can also be applied during painting.
The coating film thickness is not particularly limited, but usually 10 to 45 μm, preferably 20 to 40 μm is suitable for a cured coating film. The coating film can be cured by heating at 110 to 180 ° C., preferably 130 to 170 ° C. for 10 to 40 minutes.
The aqueous coating composition of the present invention described above can form a coating film having excellent coating stability, excellent resistance to cracking, and excellent finish.

  The material to be coated with the water-based coating composition is not particularly limited, and examples thereof include various automobile bodies such as automobiles and motorcycles, home appliances, steel furniture, kitchen appliances, and the like. Also, cold-rolled steel sheets, galvanized steel sheets, zinc alloy-plated steel sheets, stainless steel sheets, tin-plated steel sheets, etc., metal substrates such as aluminum plates, aluminum alloy plates, plastic substrates, etc. May be. Moreover, as a to-be-coated object, surface treatments, such as a phosphate process and a chromate process, may be given to the metal surface of the said vehicle body or a metal base material.

  The aqueous coating composition of the present invention is an intermediate coating or top coating for automotive coatings in a method of forming a coating film by forming an electrodeposition coating film, an intermediate coating film, and then a top coating film on the object to be coated. Useful as a colored base paint.

  In the above coating film forming method, when the aqueous coating composition of the present invention is used, the crack generation limit film thickness is usually 2 μm or more, preferably compared to the aqueous coating composition to which no aqueous dispersion is added. Can be improved by 3 μm or more, more preferably 4 μm or more.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited thereby. “Parts” and “%” indicate “parts by mass” and “% by mass”.

Production and Production Example 1 of Dispersing Resin 1 production (for example)
In a reaction vessel, 300 parts of ethylene glycol monobutyl ether was added and heated to 120 ° C. Next, two types of “mixture 1” and “mixture 2” in the proportions shown below were dropped into the reaction vessel separately over about 2 hours. The reaction was performed under nitrogen injection.
"Mixture 1"
Bremer PE-350 (Note 1) 113 parts N-vinylpyrrolidone 40 parts Acrylic acid 11 parts Methyl methacrylate 86 parts
"Mixture 2"
18 parts of azobisdimethylvaleronitrile 50 parts of ethylene glycol monobutyl ether Next, the above mixture was added dropwise while stirring the reaction solution while maintaining the reaction temperature at 120 ° C. One hour after the completion of the dropping, 2.5 parts of azobisisobutyronitrile was added to the reaction vessel, and after another 2 hours, 2.5 parts of azobisisobutyronitrile was added to the reaction solution, and then kept at 120 ° C. for 2 hours. The reaction solution was added as it was, and then the reaction was carried out for 2 hours while maintaining at 120 ° C. After completion of the reaction, unreacted monomers and ethylene glycol monobutyl ether were distilled under reduced pressure to obtain a copolymer solution having an acid value of 36.5 mgKOH / g. Further, this copolymer was neutralized with triethylamine (one equivalent neutralization), and water was added to add a dispersant No. 40 having a solid content of 40%. 1 was obtained.
(Note 1) Bremer PE-350: manufactured by NOF Corporation, trade name, equivalent to a radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain.

Production Example 2 Dispersant No. Production of 2 (for Examples)
In a reaction vessel, 200 parts of ethylene glycol monobutyl ether was added and heated to 120 ° C. Next, two types of “mixture 1” and “mixture 2” in the proportions shown below were dropped into the reaction vessel separately over about 2 hours. The reaction was performed under nitrogen injection.
"Mixture 1"
Methyl methacrylate 50 parts N-butyl acrylate 20 parts Hydroxyethyl acrylate 5 parts Blemmer PE-100 (Note 2) 20 parts Dimethylaminoethyl methacrylate 5 parts
"Mixture 2"
18 parts of azobisdimethylvaleronitrile 50 parts of ethylene glycol monobutyl ether Next, the above mixture was added dropwise while stirring the reaction solution while maintaining the reaction temperature at 120 ° C. One hour after the completion of the dropping, 2.5 parts of azobisisobutyronitrile was added to the reaction vessel, and after another 2 hours, 2.5 parts of azobisisobutyronitrile was added to the reaction solution, and then kept at 120 ° C. for 2 hours. The reaction solution was added as it was, and then the reaction was carried out for 2 hours while maintaining at 120 ° C. After completion of the reaction, unreacted monomers and ethylene glycol monobutyl ether were distilled under reduced pressure to obtain a copolymer solution having an amine value of 17.7 mgKOH / g. Further, this copolymer was neutralized with triethylamine (one equivalent neutralization), and water was added to add a dispersant No. 40 having a solid content of 40%. 2 was obtained.
(Note 2) Bremer PE-100: manufactured by NOF Corporation, trade name, equivalent to a radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain.

Production Example 3 Dispersant No. Production of 3 (for comparative example)
In a reaction vessel, 60 parts of ethylene glycol monobutyl ether was added and heated to 120 ° C. Next, two types of “mixture 1” and “mixture 2” in the proportions shown below were dropped into the reaction vessel separately over about 2 hours. The reaction was performed under nitrogen injection.
"Mixture 1"
2-hydroxyethyl acrylate 13 parts 2- (methacryloyloxy) ethyltrimethylammonium chloride 5 parts 2-ethylhexyl acrylate 20 parts methyl methacrylate 31 parts n-butyl acrylate 20 parts styrene 5 parts methacrylic acid 6 parts
"Mixture 2"
Azobisdimethylvaleronitrile 2 parts Propylene glycol monomethyl ether 35 parts Next, the above mixture was added dropwise while stirring the reaction solution while keeping the reaction temperature at 120 ° C. One hour after the completion of the dropping, 2.5 parts of azobisisobutyronitrile was added to the reaction vessel, and after another 2 hours, 2.5 parts of azobisisobutyronitrile was added to the reaction solution, and then kept at 120 ° C. for 2 hours. The reaction solution was added as it was, and then the reaction was carried out for 2 hours while maintaining at 120 ° C. After completion of the reaction, unreacted monomer and ethylene glycol monobutyl ether were distilled under reduced pressure to obtain a copolymer solution having an acid value of 39 mgKOH / g. Further, this copolymer was neutralized with triethylamine (one equivalent neutralization), and water was added to add a dispersant No. 40 having a solid content of 40%. 3 was obtained.

Production Example 4 Dispersant No. 4 (for comparative example)
To a four-necked flask equipped with a stirrer, a thermometer, and a nitrogen gas introduction tube, 58 parts of ethylene glycol monobutyl ether was added and the temperature was raised to 117 ° C. in a nitrogen stream. After reaching 117 ° C., 10 parts RMA-450M (Note 3), 19 parts methyl methacrylate, 22 parts n-butyl methacrylate, 40 parts isobornyl acrylate, 5 parts hydroxyethyl acrylate, 4 parts acrylic acid, and A mixture of 0.3 parts of azobisisobutyronitrile was added dropwise over 3 hours. The monomer tank was washed with 11.5 parts of ethylene glycol monobutyl ether and united with the reaction solution. After completion of the dropwise addition of the monomer, the mixture was further reacted for 30 minutes, and then a solution composed of 0.5 part of 2,2′-azobis (2,4-dimethylvaleronitrile) and 11.5 parts of ethylene glycol monobutyl ether was added over 1 hour. The mixture was added dropwise and stirred for another 30 minutes, and then cooled to 70 ° C. to obtain a copolymer having an acid value of 31 mgKOH / g. The obtained copolymer was neutralized with triethylamine (1 equivalent neutralization), and water was added to add a dispersant No. 40 having a solid content of 40%. 4 was obtained.
(Note 3) RMA-450M: manufactured by Nippon Emulsifier Co., Ltd., trade name, equivalent to radical polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain.
Production of aqueous dispersion Example 1
Add the dispersant No. to the shaker. 1 was mixed with 25 parts (solid content 10 parts), benzoin 20 parts (solid content 20 parts) and water 21.7 parts, and the mixture was dispersed for 3 hours. 1 was obtained. Water dispersion No. The average particle size of 1 was 12 μm.

Examples 2-9, Comparative Examples 1-3
A water dispersion No. 1 was prepared in the same manner as in Example 1 except that the blending contents shown in Table 1 were used. 2-No. 12 was obtained. The average particle size of each aqueous dispersion is also shown in the table.

(Note 4) AMP-95: manufactured by Dow Chemical Co., Ltd., trade name, 2-amino-2-methylpropanol (Note 5) Amino alcohol MMA: Japanese emulsifier, trade name, N-ethylethanolamine
(Note 6) Neugen TDX-50: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name, polyoxyalkylene tridecyl ether, nonionic surfactant.

Test of water dispersion (Note 7) Storage stability: 500 g of each water dispersion was placed in a glass bottle with a lid and stored at 40 ° C. for 40 days. The state after storage was observed and evaluated based on the following criteria.
◎ immediately returns to the state before storage upon stirring, and ◯ indicates no problem, and the pigment settles to form a cake layer, and returns to the state before storage when stirring for less than 1 hour.
In Δ, the pigment settles and a cake layer is observed, and if it is stirred for 1 to 5 hours or more, it returns to the state before storage.
In x, the pigment settles and a cake layer is observed, and even if stirring is performed for more than 5 hours, the aggregated pigment remains in the pigment dispersion paste.

Production of pigment dispersion paste Production Example 5 Pigment dispersion paste No. 5 Example 1
Put 142.5 parts deionized water in a stainless steel container and stir with a disper. Efka 4550 (Note 8) 24.0 parts (solid content 12 parts), talc (Note 10) 10 parts, titanium white (Note 11) 80 parts 30 parts after adding 1 part of carbon black (Note 12) to the mixture, the mixture was dispersed with a shaker for 5 hours. 1 was obtained.

Production Examples 6 to 8 Pigment dispersion paste No. 2-No. Production Example 4 No. 4 was prepared in the same manner as in Production Example 5 except that the blending contents shown in Table 3 were used. 2-No. 4 was obtained.

(Note 8) Efka4550: Trade name, manufactured by BASF, Dispersant (Note 9) DISPER BYK-190: Trade name, manufactured by Big Chemie, Dispersant (Note 10) Talc: MICRO ACE S-3, manufactured by Nippon Talc, Thickness 0.3-0.9 μm, longitudinal dimension 5-10 μm
(Note 11) Titanium white: JR-805, manufactured by Teica, rutile titanium white (Note 12) Carbon black: Carbon MA-100, manufactured by Mitsubishi Chemical Corporation.

Production Example 9 Production of hydroxyl and carboxyl group-containing polyester resin In a four-necked flask equipped with a heating device, a stirring device, a thermometer, a reflux condenser, and a water separator,
28.0 parts of phthalic anhydride, 25.7 parts of adipic acid, 26.4 neopentyl glycol
Part, 22.9 parts of trimethylolpropane were charged. Next, after heating the content from 160 ° C. to 230 ° C. over 3 hours, the content is maintained at 230 ° C., and the condensed water produced is distilled off by a water separator, so that the acid value becomes 3 mgKOH / g or less. The reaction was continued until
Next, 6.69 parts of trimellitic anhydride was added to the product, neutralized by adding an equivalent amount of N-dimethylethanolamine to the carboxyl group, and then deionized water was gradually added. By aqueous dispersion, an aqueous dispersion of a hydroxyl group- and carboxyl group-containing polyester resin having a solid content of 40% was obtained. The obtained hydroxyl group and carboxyl group-containing polyester resin had a hydroxyl value of 137 mgKOH / g, an acid value of 40 mgKOH / g, and a number average molecular weight of 2,000.

Production of water-based paint Example 10
In 257.5 parts (solid content 103 parts) of the pigment dispersion paste obtained in Production Example 5, the aqueous dispersion No. obtained in Example 1 was added. 1 6.7 parts (solid content 3.0 parts), 407.5% of the hydroxyl group- and carboxyl group-containing polyester resin obtained in Production Example 9 (solid content 75 parts), Cymel 325 (Note 13) 31 3 parts (25 parts solids) with stirring with a disper, dimethylethanolamine and deionized water were added, and the viscosity was adjusted to Ford Cup No. 4 for 30 seconds (20 ° C). 1 was obtained.
(Note 13) Cymel 325: manufactured by Mitsui Cytec Co., Ltd., trade name, imino group-containing methoxy-modified melamine resin, number average molecular weight 1,000, solid content 80%.

Examples 11-19
Except for the formulation shown in Table 4, aqueous paint No. 1 was prepared in the same manner as in Example 10. 2-No. 10 was obtained.

Comparative Examples 4-8
Except for the composition shown in Table 5, water-based paint No. 1 was prepared in the same manner as in Example 7. 11-No. 15 was obtained.

着色ベース塗料の製造
製造例１０ アクリル樹脂エマルション（ＡＣ）の製造
温度計、サーモスタット、撹拌器、還流冷却器、窒素導入管および滴下装置を備えた反応容器に脱イオン水１３０部、アクアロンＫＨ−１０（注１４）０．５２部を仕込み、窒素気流中で撹拌混合し、８０℃に昇温した。
次いで下記の単量体乳化物（１）のうちの全量の１％量および６％過硫酸アンモニウム水溶液５．３部を反応容器内に導入し８０℃で１５分間保持した。その後、残りの単量体乳化物（１）を３時間かけて、同温度に保持した反応容器内に滴下した。滴下終了後、１時間熟成を行なった。
次いで、下記の単量体乳化物（２）を１時間かけて滴下した。１時間熟成した後、５％ジメチルエタノールアミン水溶液４０部を反応容器に徐々に加えながら３０℃まで冷却し、１００メッシュのナイロンクロスで濾過することにより、固形分濃度３０％のアクリル樹脂エマルション（ＡＣ）を得た。得られたアクリル樹脂は、酸価が３３ｍｇＫＯＨ／ｇ、水酸基価が２５ｍｇＫＯＨ／ｇであった。
（注１４）アクアロンＫＨ−１０：ポリオキシエチレンアルキルエーテル硫酸塩エステルアンモニウム塩、第一工業製薬株式会社製、有効成分９７％。
単量体乳化物（１）：脱イオン水４２部／アクアロンＫＨ−１０ ０．７２部／メチレンビスアクリルアミド２．１部／スチレン２．８部／メチルメタクリレート１６．１部／エチルアクリレート２８部／ｎ−ブチルアクリレート２１部の乳化物
単量体乳化物（２）：脱イオン水１８部／アクアロンＫＨ−１０ ０．３１部／過硫酸アンモニウム０．０３部／メタクリル酸５．１部／２−ヒドロキシエチルアクリレート５．１部／スチレン３部／メチルメタクリレート６部／エチルアクリレート１．８部／ｎ−ブチルアクリレート９部の乳化物。

Production Production Example 10 of Colored Base Paint Manufacture of Acrylic Resin Emulsion (AC) 130 parts of deionized water, Aqualon KH-10 in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device (Note 14) 0.52 part was charged, stirred and mixed in a nitrogen stream, and heated to 80 ° C.
Next, 1% of the total amount of the following monomer emulsion (1) and 5.3 parts of a 6% aqueous solution of ammonium persulfate were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion (1) was dripped in reaction container kept at the same temperature over 3 hours. After completion of the dropping, aging was performed for 1 hour.
Subsequently, the following monomer emulsion (2) was dripped over 1 hour. After aging for 1 hour, 40 parts of a 5% dimethylethanolamine aqueous solution was gradually added to the reaction vessel, cooled to 30 ° C., and filtered through a 100 mesh nylon cloth to obtain an acrylic resin emulsion (AC ) The obtained acrylic resin had an acid value of 33 mgKOH / g and a hydroxyl value of 25 mgKOH / g.
(Note 14) Aqualon KH-10: polyoxyethylene alkyl ether sulfate ester ammonium salt, Daiichi Kogyo Seiyaku Co., Ltd., active ingredient 97%.
Monomer emulsion (1): 42 parts of deionized water / 0.72 part of Aqualon KH-10 / 2.1 parts of methylenebisacrylamide / 2.8 parts of styrene / 16.1 parts of methyl methacrylate / 28 parts of ethyl acrylate / Emulsion of n-butyl acrylate 21 parts Monomer emulsion (2): Deionized water 18 parts / Aqualon KH-10 0.31 part / Ammonium persulfate 0.03 part / Methacrylic acid 5.1 part / 2-hydroxy Emulsion of ethyl acrylate 5.1 parts / styrene 3 parts / methyl methacrylate 6 parts / ethyl acrylate 1.8 parts / n-butyl acrylate 9 parts.

Production Example 11 Production of polyester resin solution (PE2) In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and water separator, 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, anhydrous hexahydro First, 126 parts of phthalic acid and 120 parts of adipic acid were charged, and the temperature was raised between 160 ° C. and 230 ° C. over 3 hours, followed by condensation reaction at 230 ° C. for 4 hours. Next, in order to add a carboxyl group to the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was further added, reacted at 170 ° C. for 30 minutes, and then diluted with 2-ethyl-1-hexanol. A polyester resin solution (PE2) having a solid content concentration of 70% was obtained. The obtained polyester resin had an acid value of 46 mgKOH / g, a hydroxyl value of 150 mgKOH / g, and a weight average molecular weight of 6,400.

Production Example 12 Production Example of Brilliant Pigment Dispersion Liquid (P1) In a stirring and mixing container, 19 parts of aluminum pigment paste (trade name “GX-180A” manufactured by Asahi Kasei Metals Co., Ltd., metal content 74%), 2-ethyl- A glittering pigment dispersion (P1) was obtained by uniformly mixing 35 parts of 1-hexanol, 8 parts of a phosphate group-containing resin solution (Note 15) and 0.2 part of 2- (dimethylamino) ethanol.
(Note 15) Phosphate group-containing resin solution: 25 parts of styrene / 27.5 parts of n-butyl methacrylate / branched higher alkyl acrylate (trade name “Isostearyl Acrylate” manufactured by Osaka Organic Chemical Industries, Ltd.) 20 parts / 4-hydroxy Phosphoric acid with a solid content concentration of 50% obtained by reacting 7.5 parts of butyl acrylate / 15 parts of polymerizable monomer solution containing phosphoric acid group (Note 16) /22.5 parts of 2-methacryloyloxyethyl acid phosphate Group-containing resin solution. The acid value due to the phosphate group of the phosphate group-containing resin was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight average molecular weight was 10,000.
(Note 16) Phosphoric acid group-containing polymerizable monomer solution: phosphoric acid group containing 50% solid content obtained by reacting 57.5 parts monobutyl phosphoric acid / 42.5 parts glycidyl methacrylate in an organic solvent Polymerizable monomer solution.

Example 20 Colored base paint no. 1 100 parts of the acrylic resin emulsion (AC) obtained in Production Example 10, 57 parts of the polyester resin solution (PE2) obtained in Production Example 11, 62 parts of the glitter pigment dispersion (P1) obtained in Production Example 12, and 37.5 parts of Cymel 325 (Note 13) were mixed uniformly, and further a polyacrylic acid thickener (trade name “Primal ASE-60”, manufactured by Rohm and Haas Co.), the aqueous dispersion obtained in Example 1. No. 1 was mixed with 20.1 parts (9.0 parts solid content), 2-ethyl-1-hexanol and deionized water were added, and a colored base paint No. 1 having a paint solid content of 25% was added. 1 was obtained.

Comparative Example 9 Colored base paint No. Production of 2 100 parts of the acrylic resin emulsion (AC) obtained in Production Example 10, 57 parts of the polyester resin solution (PE2) obtained in Production Example 11, 62 parts of the glitter pigment dispersion (P1) obtained in Production Example 12, and 37.5 parts of Cymel 325 (imino group-containing methylated melamine resin, trade name, manufactured by Nippon Cytec Co., Ltd., solid content 80%) were mixed uniformly, and a polyacrylic acid thickener (trade name “Primal ASE- 60 "Rohm and Haas Co.), 10 parts 2-ethyl-1-hexanol, and deionized water were added to give a colored base paint no. 2 was obtained.
Tables 6 and 7 show the results of preparing the following test plates using the water-based paints of the above Examples and Comparative Examples, and subjecting them to the tests according to the evaluation criteria.

Preparation of test plate 1 (Waki resistance, water-based paint composition)
Through the following steps 1 to 4, “test plate A” for evaluating the resistance to cracking was obtained.
Step 1: Cold rolled steel sheet (15 cm × 45 cm) subjected to Palbond # 3020 (manufactured by Nihon Parkerizing Co., Ltd., trade name, zinc phosphate treatment) is added to ELECRON GT-10LF (manufactured by Kansai Paint Co., Ltd., trade name, cationic electricity) Electrodeposition coating), and an electrodeposition coating plate having a film thickness of 20 μm was obtained.
Step 2: Next, each water-based paint No. obtained in Examples and Comparative Examples was used. 1-No. 15 is applied to the coated plate obtained in step 1 in a horizontal state so that the film thickness is 20 to 60 μm, and left in a booth atmosphere (23 ° C., relative humidity 67%) for 2 minutes and 30 seconds, Thereafter, it was pre-dried at 80 ° C. for 3 minutes. Next, it was allowed to cool so as to give the atmosphere of a painting booth.
Step 3: Further, a water-based metallic base coat WBC713T (trade name, acrylic / melamine resin-based paint manufactured by Kansai Paint Co., Ltd.) is applied to a film thickness of 15 μm, and the booth atmosphere (23 ° C., relative humidity 67%) is 1 minute. It was left for 30 seconds and then pre-dried at 80 ° C. for 3 minutes.
Step 4: Next, KINO # 1200TW clear (trade name, acid / epoxy curable acrylic resin-based clear paint manufactured by Kansai Paint Co., Ltd.) was applied to the uncured coating surface to a film thickness of 35 μm, and the booth atmosphere (23 ° C., The sample was allowed to stand at a relative humidity of 67% for 5 minutes, and then heat-cured at 140 ° C. for 20 minutes to obtain “Test plate A”.

Test plate creation 2 (Waki resistance, colored base paint)
Through the following steps 1 to 4, “test plate B” for evaluating the resistance to cracking was obtained.
Step 1: Same as Step 1 in Test Plate Preparation 1.
Step 2: Next, using WP-305 (trade name, polyester resin / melamine resin curable aqueous intermediate coating) manufactured by Kansai Paint Co., Ltd., the coating plate obtained in Step 1 has a thickness of 35 μm. In a horizontal state, it was left in a booth atmosphere (23 ° C., relative humidity 67%) for 2 minutes and 30 seconds, and then pre-dried at 80 ° C. for 3 minutes. Next, it was allowed to cool so as to give the atmosphere of a painting booth.
Step 3: Furthermore, a colored base paint No. 1 or colored base paint No. 1 2
The film was applied in an inclined manner in a horizontal state so as to have a film thickness of 10 to 40 μm, left in a booth atmosphere (23 ° C., relative humidity 67%) for 1 minute 30 seconds, and then pre-dried at 80 ° C. for 3 minutes.
Step 4: “Test plate B” was obtained in the same manner as in step 4 in Test plate preparation 1.

Preparation of test plate 3 (Finish after storage of paint, water-based paint composition)
Step 1: Same as Step 1 in Test Plate Preparation 1.
Step 2: Next, the water-based paint no. 1-No. 15 was coated to a film thickness of 35 μm, left in a booth atmosphere (23 ° C., relative humidity 67%) for 2 minutes and 30 seconds, and then pre-dried at 80 ° C. for 3 minutes. Next, it was allowed to cool so as to give the atmosphere of a painting booth.
Step 3: Furthermore, an aqueous metallic base coat WBC-713T (trade name, acrylic / melamine resin-based paint manufactured by Kansai Paint Co., Ltd.) is applied to a film thickness of 15 μm in a booth atmosphere (23 ° C., relative humidity 67%). It was allowed to stand for 1 minute and 30 seconds, and then pre-dried at 80 ° C. for 3 minutes.
Step 4: “Test plate C” was obtained in the same manner as in step 4 in Test plate preparation 1.

Test plate preparation 4 (finish after paint storage, colored base paint)
Step 1: Same as Step 1 in Test Plate Preparation 1.
Step 2: Next, WP-305 (trade name, polyester resin / melamine resin cured aqueous intermediate coating) manufactured by Kansai Paint Co., Ltd. is applied to the coated plate obtained in Step 1 so that the film thickness becomes 35 μm. , Left in a booth atmosphere (23 ° C., relative humidity 67%) for 2 minutes and 30 seconds, and then pre-dried at 80 ° C. for 3 minutes. Next, it was allowed to cool so as to give the atmosphere of a painting booth.
Step 3: Furthermore, a colored base paint No. 1 or colored base paint No. 1 2
Was coated in a film thickness of 15 μm, left in a booth atmosphere (23 ° C., relative humidity 67%) for 1 minute 30 seconds, and then pre-dried at 80 ° C. for 3 minutes.
Step 4: “Test plate D” was obtained in the same manner as in Step 4 in Test plate preparation 1.

(Note 17) Storage stability:
Each water-based paint No. obtained in Examples and Comparative Examples was used. 1-No. 15 and the colored base paint No. 1 and colored base paint No. 1 2, 1,000 g was put into a glass bottle with a lid, stored at 40 ° C. for 5 days, and further observed at 5 ° C. for 2 days, and evaluated based on the following criteria.
◎: No settling of the paint, and immediately after stirring at 20 ° C, it returns to the state before storage. No problem: ○ Although the settling of the paint is slightly observed, it is stirred for less than 1 hour at 20 ° C (room temperature). Return to the state before storage.
In Δ, the paint settles and a cake layer is seen, and if it is stirred at 20 ° C. (room temperature) for 1 to 5 hours, it returns to the state before storage.
In x, the paint settles and a cake layer is seen, and even if stirring is carried out at 20 ° C. for more than 5 hours, cohesive spots remain.

(Note 18) Waki resistance:
In the test plate obtained from the test plate A of “Test plate creation 1”, the water-based paint No. 1 was used. 1-No. Fifteen armature limit film thicknesses were measured. In the test plate obtained in the test plate B of “Test plate creation 2”, the colored base paint No. 1-No. 2 was measured.

(Note 19) Finishability after storage of paint:
The test plate C of the “test plate preparation 3” and the test plate D obtained according to the “test plate preparation 4” were visually evaluated according to the following evaluation contents.
◎: Good with no problem ○: Slightly uneven skin but no problem △: At least one occurrence of rough or rough skin is observed ×: At least one of rough or rough skin is marked

  The present invention is suitable for coating industrial products because it can provide a coating film with excellent cracking properties.

Claims (7)

The dispersion resin (A) having the following characteristics and the benzoin or benzoin derivative (B) are dispersed in an aqueous medium, and the benzoin or An aqueous dispersion containing 0.1 to 400 parts by mass of a benzoin derivative (B).
Dispersing resin (A): 3 to 98% by mass of a radically polymerizable unsaturated monomer (a1) having a polyoxyalkylene chain and a nitrogen-containing radically polymerizable unsaturated monomer with respect to the total mass of constituent monomers 2 to 97% by mass of the monomer (a2), 0 to 20% by mass of the carboxyl group-containing radical polymerizable unsaturated monomer (a3), and 0 to 95% of the other radical polymerizable unsaturated monomer (a4). Resin obtained by radical polymerization reaction of mass% mixture The aqueous dispersion according to claim 1, wherein the aqueous dispersion contains less than 20 parts by mass of the amine compound (C) per 100 parts by mass of the solid content of the dispersing resin (A). The aqueous dispersion according to claim 1 or 2, wherein the aqueous dispersion contains less than 100 parts by mass of a surfactant per 100 parts by mass of the solid content of the dispersing resin (A). A water-based coating composition containing the hydroxyl group and carboxyl group-containing resin (D), the curing agent (E), and the water dispersion according to any one of claims 1 to 3. The water-based paint composition according to claim 4, wherein the solid content of the aqueous dispersion is 0.1 to 50 parts by mass with respect to 100 parts by mass of the total solids of the hydroxyl group and carboxyl group-containing resin (D) and the curing agent (E). object. The water-based paint composition according to claim 4 or 5, which is an intermediate paint or a colored base paint for automobiles. A coated article obtained by coating the aqueous coating composition according to any one of claims 4 to 6.