JP2002256209A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous coating composition forming a film having excellent properties at a normal temperature under a forced drying condition, having excellent coating stability. SOLUTION: This aqueous coating composition comprises (A) a water dispersion of an acrylic modified epoxy resin obtained by making an acrylic modified epoxy resin having 30-90 acid value obtained by polymerizing a radically polymerizable unsaturated monomer mixture containing 20-95 wt.% of an acidic group-containing ethylenic unsaturated monomer in the presence of a bisphenol A type epoxy resin having 1,000-30,000 number-average molecular weight into a water dispersion in the weight ratio of the bisphenol A type epoxy resin to the unsaturated monomer mixture of 75/25 to 95/5, (B) a water dispersion of a modified bisphenol A type epoxy resin having 30-70 acid value, containing 20-50 wt.% unsaturated fatty acid component and a pigment and has the weight ratio of the resin content of the component (A) to the component (B) of 20/80-80/20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based coating composition, and more particularly to a water-based coating composition which exhibits excellent performance under normal temperature to forced drying conditions.

[0002]

2. Description of the Related Art It has been desired to make aqueous paints for automotive parts used under conditions of forced drying from room temperature. Considering the coating properties such as adhesion and water / corrosion resistance, it seems that the use of a modified epoxy resin is suitable for this aqueous conversion. It is already known to use a modified epoxy resin for aqueous conversion, and JP-A-2000-86972 discloses that
It discloses the use of an acrylic-modified epoxy resin to make a paint composition for exterior coating of cans water-based. However, the aqueous coating composition disclosed herein is a thermosetting material containing a curing agent such as an amino resin, and when used under forced drying conditions from room temperature, obtains the required performance. Can not do.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-based coating composition which can provide a coating film having excellent properties under conditions of forced drying from room temperature and also has excellent coating stability. .

[0004]

The aqueous coating composition of the present invention comprises, in the presence of (A) a bisphenol A type epoxy resin having a number average molecular weight of 1,000 to 30,000 (a-1), an ethylenically unsaturated group containing an acidic group. 20 to 95 monomers
An aqueous solution of an acrylic-modified epoxy resin having an acid value of 30 to 90 obtained by polymerizing a radical polymerizable unsaturated monomer mixture (a-2) containing the bisphenol A type epoxy resin (a -1) and the weight ratio of the unsaturated monomer mixture (a-2) is 75/25 to 95.
/ 5 aqueous dispersion of an acrylic-modified epoxy resin,
(B) an acid value of 30 to 70 and an unsaturated fatty acid component of 2
An aqueous dispersion of a modified bisphenol A type epoxy resin (A) and an aqueous dispersion of a modified bisphenol A type epoxy resin (B) containing a water dispersion of a modified bisphenol A type epoxy resin containing 0 to 50% by weight, and a pigment. Is 20/80 to 80/20. Here, the crosslinking efficiency of the initiator used for the polymerization may be 28% or more. The aqueous dispersion (B) of the modified bisphenol A type epoxy resin has a number average molecular weight of 1,000 to 30,000.
After reacting the unsaturated fatty acid with the bisphenol A type epoxy resin (b-1), a radical polymerizable unsaturated monomer mixture (b-2) containing an acidic group-containing ethylenically unsaturated monomer is polymerized. Even if the obtained resin is made to be aqueous, or the aqueous dispersion (B) of the modified bisphenol A type epoxy resin has a number average molecular weight of 1
A radical polymerizable unsaturated monomer mixture (b-) containing an acidic group-containing ethylenically unsaturated monomer and a macromonomer modified with the above unsaturated fatty acid in the presence of 2,000 to 30,000 bisphenol A type epoxy resin (b-1);
The resin obtained by polymerizing 2 ′) may be aqueous. Here, the bisphenol A type epoxy resin (b-
The ratio of 1) can be 15 to 70% by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION (A) Acrylic-modified epoxy resin
Aqueous Dispersion of Acrylic Modified Epoxy Resin Aqueous Dispersion (A) contained in the aqueous coating composition of the present invention contains 20 to 95% by weight of an acidic group-containing ethylenically unsaturated monomer in the presence of a bisphenol A type epoxy resin. % Of a radical-polymerizable unsaturated monomer mixture polymerized to make the resin aqueous.

The above bisphenol A type epoxy resin comprises:
It can be obtained by condensing a halogen-substituted bisphenol A with epichlorohydrin or β-methylepihalohydrin. The bisphenol A type epoxy resin preferably has a number average molecular weight of 1,000 to 30,000. When the number average molecular weight is less than 1000, sufficient paint stability cannot be obtained due to low resin stability. On the other hand, when it exceeds 30,000, it is difficult to make the aqueous solution. The bisphenol A type epoxy resin can be used as a mixture of two or more.

As such an epoxy resin, a commercially available epoxy resin can be used, for example, Epicoat 1007, Epicoat 1010 (both manufactured by Yuka Shell Epoxy);
Epotote YD-017, Epotote YD-019, Epotote YD-020H, Epotote YDF2004,
Phenotote YP-50S, Epotote YD-128,
Epototo YD-014U (all manufactured by Toto Kasei)
Is mentioned.

The radically polymerizable unsaturated monomer mixture (a-2) which is polymerized in the presence of the epoxy resin (a-1) contains 20 to 95% by weight of an acidic group-containing ethylenically unsaturated monomer. I have. When the amount is less than 20% by weight, a stable aqueous coating composition cannot be obtained, and when the amount is more than 95% by weight, the water resistance of the obtained coating film decreases. This acidic group-containing ethylenically unsaturated monomer imparts an acidic group to the acrylic-modified epoxy resin, and neutralizes at least a part of the acidic group to make the acrylic-modified epoxy resin aqueous. it can. In addition, it is preferable that the acid value of this radical polymerizable unsaturated monomer mixture (a-2) shows 30-90.

The acidic group-containing ethylenically unsaturated monomer is not particularly limited as long as it has a carboxyl group, a sulfonic acid group or a phosphoric acid group as the acidic group. Such acidic group-containing ethylenically unsaturated monomers include:
For example, a carboxylic acid or dicarboxylic acid-containing ethylenically unsaturated monomer such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; or a dicarboxylic acid monoester such as ethyl maleate, butyl maleate, ethyl itaconate, and butyl itaconate Acrylamide t-butylsulfonic acid, 2-acrylamide-2-methylsulfonic acid, acrylic acid 3-sulfonylpropyl ester,
Sulfonic acid group-containing ethylenically unsaturated monomers such as methacrylic acid 3-sulfonylpropyl ester and itaconic acid bis (3-sulfonylpropyl) ester; acid phosphooxyethyl acrylate, acid phosphooxyethyl methacrylate, acid phosphoxypropyl methacrylate and acid phosphonate Phosphoric acid group-containing ethylenically unsaturated monomers such as xyl-3-chloropropyl methacrylate; and mixtures thereof. Among them, those having 6 or less carbon atoms in the molecule are preferable. If it exceeds 6, the aqueous solution may not be sufficiently converted. Particularly preferred are methacrylic acid and acrylic acid.

The radically polymerizable unsaturated monomer mixture (a-2) contains other ethylenically unsaturated monomers in addition to the acidic group-containing ethylenically unsaturated monomers.
The unsaturated monomer is not particularly limited as long as it is a vinyl monomer which coexists with the above-mentioned acidic group-containing ethylenically unsaturated monomer and does not adversely affect the properties of the aqueous dispersion (A) of the acrylic-modified epoxy resin. Such other ethylenic monomers include, for example, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, N Alkyl ester monomers of α, β-ethylenically unsaturated aliphatic carboxylic acids such as N, N-dimethylaminoethyl acrylate; glycidyl of α, β-ethylenically unsaturated aliphatic carboxylic acids such as glycidyl acrylate and glycidyl methacrylate Ester monomers; vinyl esters of saturated aliphatic carboxylic acids such as vinyl acetate and vinyl propionate; and styrene monomers such as styrene, α-methylstyrene and vinyltoluene. As other ethylenic monomers, those having a hydroxyl group introduced therein may be used, and 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, methacrylic acid Alkyl ester monomers of α, β-ethylenically unsaturated aliphatic carboxylic acids having a hydroxyl group, such as 4-hydroxybutyl acid or a reaction product of 2-hydroxyethyl methacrylate with ε-caprolactone, can be used. Further, the other ethylenic monomer may be an ethylenically unsaturated monomer having an amide group, particularly preferably having 12 or less carbon atoms in the molecule. When the number of carbon atoms in the molecule exceeds 12, hydrophilicity is not sufficiently imparted to the obtained acrylic-modified epoxy resin. Specific examples of the ethylenically unsaturated monomer (2) having such an amide group include acrylamide, methacrylamide, N-methylolacrylamide, N-methoxybutylacrylamide, diacetoneacrylamide, N, N-dimethylaminopropylacrylamide and the like. Is mentioned.

The acrylic-modified epoxy resin is obtained by polymerizing the radically polymerizable unsaturated monomer mixture (a-2) in the presence of the epoxy resin (a-1). An initiator is used for the above polymerization. In the above polymerization, first, an initiator acts on a monomer in the monomer mixture (a-2) to generate a monomer radical, and at the same time, hydrogen is abstracted from a methine or methylene group in the epoxy resin (a-1). Occurs. Further, it is considered that the radicals generated by the hydrogen abstraction are recombined with each other, so that a dimer is formed first, and finally, an acryl-modified epoxy resin is obtained. For this reason, various initiators can be used, but the crosslinking efficiency is 2
It is preferable to use one having 8% or more. Here, the “crosslinking efficiency” of the initiator is defined by the molar amount of the dimer generated per mole of the initiator to be added, and is expressed as a percentage. When the crosslinking efficiency of the initiator is less than 28%, grafting does not occur between the epoxy resin (a-1) and each monomer in the radically polymerizable unsaturated monomer mixture (a-2), and acrylic modification is performed. There is a possibility that hydrophilicity cannot be sufficiently imparted to the epoxy resin. Such initiators include, for example, benzoyl peroxide, t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxytrimethylhexanoate,
t-octyl peroxybenzoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxystearyl carbonate, t-amyl perbenzoate, dicumyl peroxide, t-butyl cumyl peroxide, dimethyldi-t-butylhexane, bis ( t
-Butylperoxyisopropyl) benzene, di-t-
Organic peroxides such as butyl peroxide and dimethyl-di-t-butylhexyne are included.

The weight ratio of the epoxy resin (a-1) to the unsaturated monomer mixture (a-2) for obtaining the acrylic-modified epoxy resin is in the range of 75/25 to 95/5. Here, if the weight ratio is less than 75/25,
The water resistance and rust resistance of the resulting coating film are reduced. 95 /
If it exceeds 5, sufficient water dispersibility cannot be imparted.

The acid value of the acrylic-modified epoxy resin thus obtained is in the range of 30 to 90. If it is less than 30, the water dispersibility is not sufficient, and if it exceeds 90, the water resistance of the obtained coating film is reduced. The number average molecular weight is 2000
It is preferably in the range of ３５35,000.

The acrylic-modified epoxy resin is made aqueous by neutralizing at least a part of the acidic groups with a basic substance. Although various substances can be used as the basic substance used for the neutralization, it is particularly preferable to use organic amines. Examples of such organic amines include amine compounds such as ammonia, tributylamine, triethylamine, monoethanolamine, dimethylethanolamine, methylethanolamine, morpholine, and N-methylmorpholine. The amount of the basic substance used for the neutralization is an amount such that the acrylic-modified epoxy resin can be dispersed in water, for example,
The amount may be equivalent to 30 to 200% of the acidic group equivalent.

The above-mentioned aqueous conversion can be carried out simultaneously with the above-mentioned neutralization. For example, a method of adding a basic substance and water to the above-mentioned acrylic-modified epoxy resin, or the above-mentioned acrylic-modified epoxy resin in water containing a basic substance can be used. You can take the method of adding. After completion of the aqueous conversion, it is preferable to distill off the solvent contained in the system under reduced pressure. Thus, an aqueous dispersion (A) of an acrylic-modified epoxy resin can be obtained. In consideration of stability, the pH of the aqueous dispersion (A) is preferably 6.0 to 9.5, and the average particle diameter is preferably 500 nm or less.

(B) Modified bisphenol A type epoxy tree
Aqueous Dispersion of Fat The aqueous dispersion (B) of the modified bisphenol A type epoxy resin contained in the aqueous coating composition of the present invention has an acid value of 30.
To 70, and contains 20 to 50% by weight of an unsaturated fatty acid component. If the acid value is less than 30, water dispersibility is not sufficient, and if it exceeds 70, the water resistance of the obtained coating film is reduced. The preferred range of the acid value is 35 to 60. On the other hand, when the unsaturated fatty acid component is less than 20% by weight, the pigment dispersibility decreases, and when it exceeds 50% by weight, the coating film drying property decreases. As described later, the modified bisphenol A type epoxy resin before being made aqueous has a number average molecular weight of 1,000.
~ 30000 bisphenol A type epoxy resin (b-
The content of the unsaturated fatty acid component, which is obtained by modifying 1), means the proportion of the unsaturated fatty acid in the raw materials used for producing the modified bisphenol A type epoxy resin. Similarly, the ratio of the bisphenol A type epoxy resin (b-1) in the raw material is 1%.
It is preferably from 5 to 70% by weight. If the content is less than 15% by weight, the water resistance and the salt spray resistance of the obtained coating film decrease,
If it exceeds 70% by weight, the stability of the paint will be reduced. Further, the number average molecular weight is preferably in the range of 2,000 to 35,000. The modified bisphenol A type epoxy resin may be used as a mixture of two or more.

There are two methods for producing the modified bisphenol A type epoxy resin. As a first method, a bisphenol A type epoxy resin (b-1) having a number average molecular weight of 1,000 to 30,000 is reacted with an unsaturated fatty acid, and then a radical polymerizable resin containing an acidic group-containing ethylenically unsaturated monomer is produced. Unsaturated monomer mixture (b
-2). In this case, a reaction and polymerization are performed as the modification, and the raw material is a radical polymerizable unsaturated monomer containing a bisphenol A type epoxy resin (b-1), an unsaturated fatty acid, and an ethylenically unsaturated monomer having an acidic group. There are three types of mixture (b-2).

The same bisphenol A type epoxy resin (a-1) as the bisphenol A type epoxy resin (b-1) having a number average molecular weight of 1,000 to 30,000 can be used. In addition, it may be the same as the bisphenol A type epoxy resin (a-1) or may be different.

In the first method, an unsaturated fatty acid is first reacted with the bisphenol A type epoxy resin (b-1). The reaction can be performed by a method well known to those skilled in the art. As the unsaturated fatty acids, soybean oil fatty acids,
Tall oil fatty acids, linseed oil fatty acids, dehydrated castor oil fatty acids, and the like can be used. This unsaturated fatty acid component
In the above-mentioned raw materials used for producing the modified bisphenol A type epoxy resin, an amount of 20 to 50% by weight is used.

Next, a radical polymerizable unsaturated monomer mixture containing an acidic group-containing ethylenically unsaturated monomer (b-
By polymerizing 2), a modified bisphenol A type epoxy resin is obtained. This unsaturated monomer mixture (b
The amount of the acidic group-containing ethylenically unsaturated monomer in -2) is set so that the resulting modified bisphenol A type epoxy resin has an acid value of 30 to 70. The description of the other unsaturated monomer mixture (b-2) and the polymerization is described in the radical polymerizable unsaturated monomer mixture (a-
The description given for the polymerization of 2) is applied as it is. The modified bisphenol A type epoxy resin obtainable by the first production method is commercially available, for example, Arolon 11, Arolone 21 (both manufactured by Nippon Shokubai Co., Ltd.), Watersol CD540, Watersol EFD5501, and Watersol EFD5501. Zol BM100
0 (all manufactured by Dainippon Ink and Chemicals, Inc.).

In the second method for producing the modified bisphenol A type epoxy resin, the number average molecular weight is from 1,000 to 3,000.
A radical polymerizable unsaturated monomer mixture (b-2 ′) containing an acidic group-containing ethylenically unsaturated monomer and a macromonomer modified with an unsaturated fatty acid in the presence of a bisphenol A type epoxy resin (b-1). It is to be polymerized. In this case, polymerization is performed as the modification, and the raw material is bisphenol A type epoxy resin (b-
1) A radical polymerizable unsaturated monomer mixture containing an unsaturated fatty acid, a raw material monomer of the macromonomer, and an acidic group-containing ethylenically unsaturated monomer excluding the macromonomer modified with the unsaturated fatty acid. Here, as for the components other than the macromonomer modified with the unsaturated fatty acid and the polymerization, those already described above are applied as they are or in accordance therewith. Therefore, the macromonomer modified with the unsaturated fatty acid will be described below.

The macromonomer modified with the unsaturated fatty acid is obtained by reacting the unsaturated fatty acid with an acrylic monomer having an epoxy group such as glycidyl methacrylate in a ratio of a carboxyl group to an epoxy group of 1: 1. Can be obtained by The macromonomer modified with the unsaturated fatty acid is contained in the radically polymerizable unsaturated monomer mixture (b-2 ′). Its content is 20-90% by weight, preferably 30-80% by weight. If the amount is less than 20% by weight, the salt spray resistance of the coating film decreases, and if it exceeds 90% by weight, the drying property of the coating film decreases. As described above, the macromonomer modified with the unsaturated fatty acid such that the unsaturated fatty acid component is 20 to 50% by weight in the raw material used for producing the modified bisphenol A type epoxy resin. Must be set at the same time. The modified bisphenol A type epoxy resin thus obtained is neutralized with a basic substance and made aqueous. As for the neutralization, aqueous conversion and desolvation, the description of the aqueous dispersion (A) of the acrylic-modified epoxy resin is applied as it is. For example, it is obtained in a mixture of a predetermined amount of an organic amine and water. The modified bisphenol A type epoxy resin thus obtained is added, and the contained solvent is distilled off under reduced pressure to obtain an intended aqueous dispersion (B) of the modified bisphenol A type epoxy resin. This aqueous dispersion (B) has a pH of 6.0 to 6.0, similarly to the aqueous dispersion (A).
9.5, the average particle diameter is preferably 500 nm or less.

Aqueous coating composition The aqueous coating composition of the present invention contains the aqueous dispersion (A) of the acrylic-modified epoxy resin, the aqueous dispersion (B) of the modified bisphenol A type epoxy resin, and a pigment. The weight ratio of the resin solid content of the aqueous dispersion (A) of the acrylic-modified epoxy resin and the aqueous dispersion (B) of the modified bisphenol A-type epoxy resin is 20/80 to 80/20. 2
If it is less than 0/80, the drying property of the coating film will be reduced, and if it is more than 80/20, the stability of the coating will be reduced. Preferably, 40 /
60 to 60/40.

The aqueous coating composition of the present invention contains a pigment. The pigment is not particularly limited. For example, phosphorus extenders such as barium sulfate, talc, calcium carbonate, barium sulfate, and the like as extender pigments; Molybdate anticorrosive pigments, molybdate anticorrosive pigments, phosphate anticorrosive pigments and the like can be mentioned. In addition to these, ordinary coloring pigments can also be used. The content of the pigment in the aqueous coating composition is 40 to 55 in PWC (weight ratio of the pigment to the total solid content in the coating).
%. If it is less than 40%, the rust prevention of the coating film is insufficient, and if it exceeds 55%, the stability as a coating decreases.

The aqueous coating composition of the present invention preferably contains a dryer. This drier acts as an oxidation polymerization catalyst for unsaturated fatty acid components contained in the aqueous coating composition of the present invention. Known dryers can be used as the dryer, and examples thereof include metal salts such as cobalt naphthenate, zinc naphthenate, and lead naphthenate. When a dryer is included, its content is preferably 0.02 to 0.5% by weight based on the resin solid content. If it is less than 0.02% by weight, curing does not proceed sufficiently, and if it exceeds 0.5% by weight, no effect on the increment is recognized.

The aqueous coating composition of the present invention may contain, in addition to the above components, additives generally used for coatings. Examples of these include a pigment dispersant, a surface conditioner, and an antifoaming agent.

[0027] The coating method and drying conditions of the coating composition of the present invention are not particularly limited, and generally well-known ones can be applied. Also,
Although the coating composition of the present invention can be used for various applications,
In particular, since excellent performance is exhibited under conditions of drying from room temperature to forced drying, it is effective to use these drying conditions, for example, as a paint for automobile parts. In addition, forced drying usually means heating at about 80 ° C.,
For example, heating to about 150 ° C. may be performed.

[0028]

EXAMPLES Production Example 1 Water content of acrylic-modified epoxy resin
Production of powder 1 In a reactor equipped with a heating device, a stirrer and a reflux condenser,
45 parts by weight of phenothote YP-50S (Toto Kasei Co., Ltd., number average molecular weight 14000), Epotote YD-020H
(Toto Kasei Co., Ltd., number average molecular weight 8,000, epoxy equivalent 5000) 45 parts by weight were charged, and butyl carbitol 1 was added.
5 parts by weight, methyl isobutyl ketone 30 parts by weight and methoxypropanol 60 parts by weight,
The temperature was raised to and maintained at 20 ° C., and the bisphenol A type epoxy resin was dissolved. The temperature was lowered to 110 ° C., and a monomer mixture comprising 8 parts by weight of methacrylic acid, 1 part by weight of ethyl acrylate, 1 part by weight of styrene and 10 parts by weight of methyl isobutyl ketone was dropped from the dropping funnel over 2 hours.
At the same time, a solution of 1 part by weight of benzoyl peroxide dissolved in 20 parts by weight of methyl isobutyl ketone was dropped from another dropping funnel over 2 hours. 30 minutes after dropping
Keep at 10 ° C, then add benzoyl peroxide 0.1
A solution in which 2 parts by weight of methyl isobutyl ketone was dissolved was added dropwise over 30 minutes, and then kept at 110 ° C. for another 3 hours to obtain an acrylic-modified epoxy resin. The resin thus obtained had a non-volatile content of 41.8% and an acid value of solids of 57 mg KOH /
g, number average molecular weight 8300. Further, when the temperature of the acrylic-modified epoxy resin was lowered to 60 ° C., 197 parts by weight of deionized water and dimethylethanolamine were added.
A solution of 28 parts by weight was added dropwise over 2 hours. After dropping,
Keep at 60 ° C for 30 minutes, then remove the solvent under reduced pressure,
An aqueous dispersion of an acrylic-modified epoxy resin was obtained. The aqueous dispersion of the resulting acrylic-modified epoxy resin has a nonvolatile content of 3
4.5%, solid content acid value 55 mg KOH / g, pH 7.5
4. The average particle diameter was 280 nm.

Production Example 2 Water of acrylic-modified epoxy resin
Production of Dispersion Part 2 In a reactor equipped with a heating device, a stirrer and a reflux condenser,
90 parts by weight of Epototo YD-020H (manufactured by Toto Kasei Co., Ltd., number average molecular weight: 8,000, epoxy equivalent: 5000) are charged, 15 parts by weight of butyl carbitol, 30 parts by weight of methyl isobutyl ketone, and 60 parts by weight of methoxypropanol are added and stirred. The temperature is raised to 115 ° C. and held,
The bisphenol A type epoxy resin was dissolved. 110 ° C
Then, a monomer mixture comprising 8 parts by weight of methacrylic acid, 1 part by weight of ethyl acrylate, 1 part by weight of styrene and 10 parts by weight of methyl isobutyl ketone was dropped from the dropping funnel over 2 hours. At the same time, a solution of 1 part by weight of benzoyl peroxide dissolved in 20 parts by weight of methyl isobutyl ketone was dropped from another dropping funnel over 2 hours. After completion of the dropping, the solution was kept at 110 ° C. for 30 minutes, then a solution in which 0.1 part by weight of benzoyl peroxide was dissolved in 2 parts by weight of methyl isobutyl ketone was added dropwise over 30 minutes, and then kept at 110 ° C. for another 3 hours. A resin was obtained. The nonvolatile content of the obtained resin is 41.5%,
Solid content acid value 55 mgKOH / g, number average molecular weight 6700
Met. Furthermore, this acrylic-modified epoxy resin is
The temperature was lowered to 0 ° C., and a solution of 197 parts by weight of deionized water and 8.28 parts by weight of dimethylethanolamine was added dropwise over 2 hours. After completion of the dropwise addition, the temperature was maintained at 60 ° C. for 30 minutes, and then the solvent was removed under reduced pressure to obtain an aqueous dispersion of an acrylic-modified epoxy resin. The aqueous dispersion of the obtained acrylic-modified epoxy resin has a nonvolatile content of 34.9% and an acid value of solids of 54 mg KOH.
/ G, pH 7.49, and average particle size 270 nm.

Production Example 3 Water of acrylic-modified epoxy resin
Production of Dispersion Part 3 In a reactor equipped with a heating device, a stirrer and a reflux condenser,
90 parts by weight of Epototo YD-020H (manufactured by Toto Kasei Co., Ltd., number average molecular weight: 8,000, epoxy equivalent: 5000) are charged, and 15 parts by weight of butyl carbitol, 30 parts by weight of methyl isobutyl ketone, and 60 parts by weight of methoxypropanol are added and stirred. The temperature was raised to and maintained at 115 ° C. to dissolve the epoxy resin. The temperature was lowered to 110 ° C., and a monomer mixture consisting of 6 parts by weight of methacrylic acid, 2 parts by weight of ethyl acrylate, 2 parts by weight of styrene and 10 parts by weight of methyl isobutyl ketone was dropped from the dropping funnel over 2 hours.
At the same time, a solution of 1 part by weight of benzoyl peroxide dissolved in 20 parts by weight of methyl isobutyl ketone was dropped from another dropping funnel over 2 hours. 30 minutes after dropping
Keep at 10 ° C, then add benzoyl peroxide 0.1
A solution in which 2 parts by weight of methyl isobutyl ketone was dissolved was added dropwise over 30 minutes, and then kept at 110 ° C. for another 3 hours to obtain an acrylic-modified epoxy resin. The resin thus obtained had a nonvolatile content of 41.7% and an acid value of 43 mg KOH / solid.
g, number average molecular weight was 6,800. Further, the temperature of the acrylic-modified epoxy resin was lowered to 60 ° C., and a solution of 197 parts by weight of deionized water and 6.21 parts by weight of dimethylethanolamine was added dropwise over 2 hours. After completion of the dropwise addition, the temperature was maintained at 60 ° C. for 30 minutes, and then the solvent was removed under reduced pressure to obtain an aqueous dispersion of an acrylic-modified epoxy resin. The nonvolatile content of the aqueous dispersion of the obtained acrylic-modified epoxy resin is 34.5%,
The acid value of the solid component was 42 mgKOH / g, the pH was 7.39, and the average particle size was 230 nm.

Production Example 4 Water of acrylic-modified epoxy resin
Production of Dispersion 4 A water dispersion 3b of an acrylic-modified epoxy resin was prepared in the same manner as in Production Example 3 except that 7.05 parts by weight of triethylamine was used instead of dimethylethanolamine.
I got The aqueous dispersion of the obtained acrylic-modified epoxy resin has a nonvolatile content of 35.2% and an acid value of solids of 41 mgKOH /
g, pH 7.30 and average particle diameter 160 nm.

Production Example 5 Modified bisphenol A type epoxy
Preparation of aqueous dispersion of silicone resin <Production of macromonomer modified with unsaturated fatty acid> In a reactor equipped with a heating device, a stirrer and a reflux condenser, 51.9 parts by weight of soybean oil fatty acid, hydroquinone monomethyl ether 0.1 , 0.2 parts by weight of tetra-n-butylphosphonium bromide and 4.7 parts by weight of dipropylene glycol monomethyl ether, and stirred.
The temperature was raised to ° C. Then, glycidyl methacrylate 2
When 7.9 parts by weight and 1.2 parts by weight of dipropylene glycol monomethyl ether were added, the temperature rose to 170 ° C. due to the exothermic reaction. After stirring at 170 ° C. for 30 minutes, the mixture was cooled to obtain a nonvolatile content of 78.5% by weight.
A fatty acid-modified macromonomer having an acid value of 0.4 and Gardner viscosity B was obtained. <Production of modified bisphenol A type epoxy resin> Epototo YD-020H (Toto Kasei Co., Ltd., number average molecular weight 800
0, epoxy equivalent 5000), 40 parts by weight, butyl carbitol 15 parts by weight, methyl isobutyl ketone 3
0 parts by weight and 51.5 parts by weight of methoxypropanol were added, the temperature was raised to 115 ° C. while stirring, and the bisphenol A type epoxy resin was dissolved. The temperature was lowered to 110 ° C., and a monomer mixture consisting of 8 parts by weight of methacrylic acid, 38.5 parts by weight of the above fatty acid-modified macromonomer, 2 parts by weight of styrene, 20 parts by weight of ethyl acrylate and 10 parts by weight of methyl isobutyl ketone was added dropwise to the funnel. For 2 hours. At the same time, a solution of 1 part by weight of benzoyl peroxide dissolved in 20 parts by weight of methyl isobutyl ketone was dropped from another dropping funnel over 2 hours. After completion of the dropwise addition, the solution was kept at 110 ° C. for 30 minutes, and then a solution in which 0.1 part by weight of benzoyl peroxide was dissolved in 2 parts by weight of methyl isobutyl ketone was added dropwise over 30 minutes.
While maintaining the temperature at 110 ° C. for a time, a modified bisphenol A type epoxy resin was obtained. The obtained resin had a nonvolatile content of 42.2%, an acid value of solid content of 54.0 mgKOH / g, and a number average molecular weight of 540.
It was 0. <Aqueous conversion of modified bisphenol A type epoxy resin> The obtained modified bisphenol A type epoxy resin was cooled to 60 ° C, and a solution of 197 parts by weight of deionized water and 8.28 parts by weight of dimethylethanolamine was added in 2 hours. It was dropped. After completion of the dropwise addition, the temperature was maintained at 60 ° C. for 30 minutes, and then the solvent was removed under reduced pressure to obtain an aqueous dispersion of a modified bisphenol A type epoxy resin. The aqueous dispersion of the modified bisphenol A type epoxy resin thus obtained has a nonvolatile content of 35.5% and an acid value of 5 for the solid content.
4.5 mg KOH / g, pH 7.42, average particle size 35
It was 0 nm.

Comparative Production Example Comparative acrylic-modified epoxy
Production reactor for water dispersion of resin
YD-020H (Toto Kasei Co., Ltd., number average molecular weight 800
0, epoxy equivalent 5000), 70 parts by weight, butyl carbitol 15 parts by weight, methyl isobutyl ketone 3
0 parts by weight and 60 parts by weight of methoxypropanol were added, and the temperature was raised to 115 ° C. while stirring and maintained to dissolve the bisphenol A type epoxy resin. The temperature was lowered to 110 ° C., and a monomer mixture consisting of 6 parts by weight of methacrylic acid, 12 parts by weight of ethyl acrylate, 12 parts by weight of styrene, and 10 parts by weight of methyl isobutyl ketone was dropped from the dropping funnel into the flask.
It was dropped over time. At the same time, a solution of 1 part by weight of benzoyl peroxide dissolved in 20 parts by weight of methyl isobutyl ketone was dropped from another dropping funnel over 2 hours. After completion of the dropping, the solution was kept at 110 ° C. for 30 minutes, then a solution in which 0.1 part by weight of benzoyl peroxide was dissolved in 2 parts by weight of methyl isobutyl ketone was added dropwise over 30 minutes, and then kept at 110 ° C. for another 3 hours. A modified epoxy resin was obtained. The nonvolatile content of the obtained resin is 42.7%,
Solid content acid value 46 mgKOH / g, number average molecular weight 6700
Met. Furthermore, this acrylic-modified epoxy resin is
The temperature was lowered to 0 ° C., and a solution of 197 parts by weight of deionized water and 7.05 parts by weight of triethylamine was added dropwise over 2 hours. After completion of the dropwise addition, the temperature was maintained at 60 ° C. for 30 minutes, and then the solvent was removed under reduced pressure to obtain a water dispersion of a comparative acrylic-modified epoxy resin. The aqueous dispersion of the comparative acrylic-modified epoxy resin obtained had a nonvolatile content of 36.4% and an acid value of solids of 37 mgK.
OH / g, pH 8.29, average particle diameter 360 nm.

Example 1 To 30 parts by weight of the aqueous dispersion of the acrylic-modified epoxy resin obtained in Production Example 1 and 25 parts by weight of the aqueous dispersion of the modified bisphenol A-type epoxy resin obtained in Production Example 5,
8 parts by weight of barium sulfate, 8 parts by weight of talc, 5.5 parts by weight of aluminum phosphomolybdate, 1.5 parts by weight of Mitsubishi Carbon Black MA-100 (manufactured by Mitsubishi Carbon Corporation), DI
0.5 parts by weight of CNATE 3111 (5% cobalt naphthenate, manufactured by Dainippon Ink and Chemicals, Inc.), Dispalon 50
1 (a surface conditioner manufactured by Kusumoto Kasei Co., Ltd.) and 7.5 parts by weight of ion-exchanged water were added, and stirred with a disper to obtain an aqueous coating composition.

Examples 2 to 4 and Comparative Examples 1 to 3 Except that the types and amounts of the aqueous dispersions of the acrylic modified epoxy resin and the aqueous dispersions of the modified bisphenol A type epoxy resin were changed to those shown in Table 1, respectively. Example 1
In the same manner as in the above, an aqueous coating composition was obtained. In Table 1, Arolone 11 and Arolone 21 are each an aqueous dispersion of a modified bisphenol A type epoxy resin having an acid value of 40 and a number average molecular weight of 5,000 to 6000 manufactured by Nippon Shokubai Co., Ltd. High molecular weight, low in unsaturated fatty acid component. As other special numerical values, Allolone 11 has a pH of 8.5 to 9.5, a non-volatile content of 40%, and a viscosity of 500 to 4000 cps.
8.0 to 9.0, nonvolatile content 37%, viscosity 100 to 200
0 cps. On the other hand, water sol EFD5501
Is an aqueous dispersion of a modified bisphenol A type epoxy resin having an acid value of 33 to 38 and a number average molecular weight of about 5,000 manufactured by Dainippon Ink and Chemicals, pH 8.0 to 9.5, nonvolatile content of 35%, viscosity 100 to 1000 cps.

Evaluation of aqueous coating compositions The aqueous coating compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated by the tests described below.
The results are summarized in Table 1.

<Dryness of coating film> The aqueous coating composition was diluted with ion-exchanged water, and then spray-coated on an SPC steel sheet to a thickness of about 25 µm. Thereafter, drying was carried out by heating at 80 ° C. for 20 minutes, and the coating film immediately after that was evaluated for touch dryness according to the following criteria. ◎: No stickiness at all ○: Very slight stickiness △: Trace after fingerprint ×: Sticky

<Water Resistance> The aqueous coating composition was diluted with ion-exchanged water, and then spray-coated on an SPC steel sheet to a thickness of about 25 μm. Thereafter, drying was performed by heating at 80 ° C. for 25 minutes to obtain a test plate. After immersing this test plate in warm water of 40 ° C. for 240 hours, JIS K 5400 8.
According to 5.2, the grid (1 mm x 1 mm square 100
A tape peeling test was performed, and the number of squares remaining without peeling out of 100 squares was counted. At the same time, the occurrence of blisters was visually evaluated according to the following criteria. ◎: No blister generated at all ○: Very slight blister generated Δ: Slight blister generated ×: Many blisters generated

<Salt water spray resistance> A test plate prepared in the same manner as in the water resistance evaluation was subjected to salt water spray for 240 hours in accordance with JIS Z 2371, and the test plate after spraying was subjected to the maximum rust width from the edge. A certain edge rust width (mm) was measured. 0.5 mm or less is a pass.

<Paint Stability> The aqueous paint composition was stored at 40 ° C. for one month, and the condition of the paint after storage was visually evaluated.

[0041]

[Table 1]

With the aqueous coating composition of the present invention, good results were obtained in any of the test items. On the other hand, in Comparative Example 1, since the amount of the bisphenol A type epoxy resin in the acryl-modified epoxy resin was small, sufficient water resistance and salt spray resistance were not obtained. Comparative Example 2
In Comparative Example 3, the coating film drying property was not sufficient because the weight ratio of the acrylic-modified epoxy resin was small, whereas in Comparative Example 3, the coating stability was not sufficient because the weight ratio of the modified bisphenol A type epoxy resin was small.

[0043]

The aqueous coating composition of the present invention contains an aqueous dispersion of an acrylic-modified epoxy resin and a modified bisphenol A-type epoxy resin, and a coating film having excellent properties can be obtained from room temperature under forced drying conditions. As well as excellent paint stability. This is presumably because the acrylic-modified epoxy resin contributes to the improvement of coating film drying property, water resistance and salt spray resistance, and the modified bisphenol A-type epoxy resin contributes to paint stability. The water-based coating composition of the present invention has the characteristics described above, and is therefore useful as a coating for automobile parts.

Continued on the front page F term (reference) 4J038 CG121 CG122 CH171 CH172 DB371 DB372 DB451 DB452 GA06 JA66 KA03 MA08 MA14 NA23 NA26 PA17 PA18 PB07

Claims (5)

[Claims] (A) a number average molecular weight of 1,000 to 30,000
In the presence of the bisphenol A type epoxy resin (a-1), 20
An acid value of 30 to 90 obtained by polymerizing a radical polymerizable unsaturated monomer mixture (a-2) containing from 95 to 95% by weight.
Wherein the weight ratio of the bisphenol A type epoxy resin (a-1) to the unsaturated monomer mixture (a-2) is 75/25.
Aqueous dispersion of an acrylic modified epoxy resin having an acid value of 30 to 70, and an aqueous dispersion of a modified bisphenol A type epoxy resin having an acid value of 30 to 70 and an unsaturated fatty acid component of 20 to 50% by weight, Wherein the weight ratio of the resin solid content of the aqueous dispersion (A) of the acrylic-modified epoxy resin and the aqueous dispersion (B) of the modified bisphenol A-type epoxy resin is 20/80 to 80/20. Paint composition. 2. The aqueous coating composition according to claim 1, wherein the crosslinking efficiency of the initiator used for the polymerization is 28% or more. 3. The aqueous dispersion (B) of the modified bisphenol A type epoxy resin has a number average molecular weight of 1,000 to 3,000.
After reacting the unsaturated fatty acid with the bisphenol A type epoxy resin (b-1) of No. 0, a radical polymerizable unsaturated monomer mixture (b-2) containing an acidic group-containing ethylenically unsaturated monomer is polymerized. The aqueous coating composition according to claim 1 or 2, wherein the resin obtained by the above method is aqueous. 4. An aqueous dispersion (B) of the modified bisphenol A type epoxy resin has a number average molecular weight of 1,000 to 3,000.
A radical polymerizable unsaturated monomer mixture (b-2 ′) containing an acidic group-containing ethylenically unsaturated monomer and a macromonomer modified with the unsaturated fatty acid in the presence of a bisphenol A type epoxy resin (b-1) The aqueous coating composition according to claim 1 or 2, wherein the resin obtained by polymerizing is aqueous. 5. The aqueous coating composition according to claim 3, wherein the proportion of the bisphenol A type epoxy resin (b-1) in the raw materials used for the reaction and / or polymerization is 15 to 70% by weight.