JP2003055598A - Water-based coating material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based coating material composition which can form coating films having excellent weather resistance, hot water resistance and smoothness. SOLUTION: This water-based coating material composition is characterized by comprising (A) the aqueous solution of an alkali-soluble or alkali-swelling copolymer obtained from (a) a UV light-absorbing monomer, (b) an ethylenic unsaturated carboxylic acid monomer, and (c) an ethylenic unsaturated monomer capable of being copolymerized with the monomers (a) and (b), and (B) the aqueous suspension of a copolymer obtained from an ethylenic unsaturated monomer and having an average particle diameter of 70 to 350 nm, in the aqueous solution (A) : aqueous emulsion(B) weight ratio (converted into solid contents) of (0.5 to 25:100).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous coating composition which is excellent in weather resistance, hot water resistance and the like and forms a coating film having good smoothness.

[0002]

2. Description of the Related Art In recent years, water-based paints have been widely used as paints for coating building materials from the viewpoint of environmental problems and resource saving. Weather resistance has come to be required. As the coating having improved weather resistance, for example, as described in Japanese Patent No. 2637574, a copolymer obtained from an ethylenic monomer containing cyclohexyl (meth) acrylate and a UV stable monomer is used. Aqueous emulsion paints using an emulsion resin as a binder, and as described in Japanese Patent No. 3056427, an acrylic silicone emulsion resin introduced at the time of polymerization of a specific silane compound and an ultraviolet absorber, an aqueous emulsion paint containing a Is being developed. However, many emulsion paints such as these water-based emulsion paints having good weather resistance have poor smoothness, that is, the leveling property of the paint at the time of painting is poor, and the formed coating film has wrinkles, blemishes, and cracks. However, there was a problem that checking and the like were likely to occur. Therefore, a method of adding a thickener to an emulsion paint to improve smoothness has been widely adopted. However, although the thickener has the effect of improving the smoothness, there is a problem that the coating performance, particularly water resistance and weather resistance is adversely affected as the amount of the thickener added increases.

[0003]

The present invention has been made against the background of such problems of the prior art, and forms a coating film excellent in weather resistance, water resistance, etc. and smoothness. It is an object of the present invention to provide a water-based coating composition that

[0004]

Means for Solving the Problems The inventors of the present invention have made extensive studies to achieve the above-mentioned object, and as a result,
The inventors have found that the above-mentioned problems can be achieved without fail and have reached the present invention. According to the present invention, the following aqueous coating composition is provided: UV absorbing monomer (a), ethylenically unsaturated carboxylic acid monomer (b) and said monomers (a), (b). An ethylenic liquid having an average particle diameter of 70 to 350 nm and an aqueous solution (A) of an alkali-soluble or alkali-swellable copolymer obtained from another ethylenically unsaturated monomer (c) copolymerizable with An aqueous emulsion (B) of a copolymer obtained from an unsaturated monomer is included, and the mass ratio (solid content conversion) of the aqueous liquid (A) and the aqueous emulsion (B) is (0.5 to 25). : 100).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The aqueous liquid (A), which is a constituent of the aqueous coating composition of the present invention, comprises an ultraviolet absorbing monomer (a), an ethylenically unsaturated carboxylic acid monomer (b), the monomer (a),
It is an aqueous solution of an alkali-soluble or alkali-swellable copolymer obtained from another ethylenically unsaturated monomer (c) copolymerizable with (b) and having a pH of 7 to 10.
The ultraviolet absorbing monomer (a) is basically a benzophenone, benzotriazole or triazine-based monomer having at least one ethylenically unsaturated double bond in one molecule, and Specifically, for example, 2-hydroxy-4-acryloxybenzophenone, 2-hydroxy-4-methacryloxybenzophenone, 2-hydroxy-5-acryloxybenzophenone, 2-hydroxy-5-acryloxybenzophenone, 2-hydroxy. -4- (acryloxy-ethoxy) benzophenone, 2
-Hydroxy-4- (methacryloxy-ethoxy) benzophenone, 2-hydroxy-4- (methacryloxydiethoxy) benzophenone, 2-hydroxy-4-
(Acryloxy-triethoxy) benzophenone, 2-
(2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole (manufactured by Otsuka Chemical Co., Ltd.,
Product name: RUVA-93), 2- (2'-hydroxy-
5'-methacryloxyethyl-3-tert-butylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methacryloxypropyl-3-ter.
t-Butylphenyl) -5-chloro-2H-benzotriazole, 3-methacryloyl-2-hydroxypropyl-3- [3 '-(2''-benzotriazoyl) -4-
Hydroxy-5-tert-butyl] phenyl propionate (Nippon Ciba Geigy Ltd., product name: CGL-1)
04), triazine-based monomers and the like described in JP-A-8-193180 are typical examples. Only one type of these monomers may be used, or two or more types may be appropriately mixed and used. Specific examples of the ethylenically unsaturated carboxylic acid monomer (b) include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, monoethyl maleate and monoethyl itaconate. Is a typical example.

Other ethylenically unsaturated monomers (c) copolymerizable with the above-mentioned monomers (a) and (b) include various ethylenic unsaturated monomers which have been conventionally used in vinyl resins for coatings. Although unsaturated monomers can be used, specifically,
For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, 2 -Ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, α-chloroethyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, methoxyethyl (meth) (Meth) acrylate monomers such as acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate; styrene and methyl styrene Emissions, chlorostyrene,
Styrene-based monomers such as methoxystyrene; 2-hydroxyethyl (meth) acrylate, 2 (3) -hydroxypropyl (meth) acrylate, 4-hydroxybutyl acrylate, allyl alcohol polyhydric alcohol mono (meth) acrylic acid. Hydroxyl group-containing monomers such as esters; amide group-containing monomers such as (meth) acrylamide and maleinamide; 2-aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, 3-aminopropyl (meth ) Acrylate, 2-butylaminoethyl (meth) acrylate, an amino group-containing monomer such as vinylpyridine; glycidyl (meth) acrylate, allyl glycidyl ether, an epoxy compound having two or more glycidyl groups, and an active hydrogen atom. Have ethylenic fatigue Epoxy group-containing monomer or oligomer obtained by reaction with monomer; other N-methylol acrylamide having N-methylol group, vinyl acetate, vinyl chloride, ethylene, butadiene, acrylonitrile, dialkyl fumarate Etc. are mentioned as typical ones. These monomers are, of course, 1
Only one kind may be used, or two or more kinds may be appropriately mixed and used.

Further, in place of a part of the monomer (c), divinylbenzene, divinyl adipate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, 1,4-butylene glycol di (meth)
Acrylate, 1,3-butyl di (meth) acrylate, trimethylolethane tri (meth) acrylate,
Monomers having two or more polymerizable unsaturated double bonds such as trimethylolpropane tri (meth) acrylate, dipentaerythrityl tri (meth) acrylate, diallyl phthalate, triazyl dicyanurate, and tetraallyloxyethane ( Preference is given to using c ′).

Further, instead of a part of the monomer (c),
Acrolein, diacetone (meth) acrylamide,
Formyl styrene, (meth) acryloxyalkyl propanal, diacetone (meth) acrylate, acetonyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate-acetylacetate, butanediol-1,4 -Acrylate-Acetyl acrylate, vinyl ethyl ketone, vinyl isobutyl ketone, or other carbonyl group-containing monomer (c ") is used, and the amount is 0.1 to 1 relative to the amount of the carbonyl group of the monomer (c"). It is preferably used in combination with the compound (C) having two or more hydrazide groups in one molecule corresponding to an amount of 0.0 equivalents of hydrazide groups. The ratio of the monomer (a), the monomer (b) and the monomer (c) constituting the copolymer is 1 to 40, respectively.
% By mass, 10 to 50% by mass, 10 to 89% by mass, preferably 3 to 20% by mass, 20 to 45% by mass and 35 to 77% by mass, respectively. When the content of the ultraviolet absorbing monomer (a) is less than 1% by mass, the effect of improving the weather resistance of the resulting coating film is small, and when it exceeds 40% by mass, the stability during polymerization is improved. Alternatively, the stability of the aqueous liquid (A) tends to decrease.

When the amount of the ethylenically unsaturated carboxylic acid monomer (b) is less than 10% by mass, the pH is 7 to 1.
Alkali-soluble or alkali-swellable in an aqueous solution of 0 is unlikely to occur, the stability of the aqueous solution (A) is lowered, and the smoothness improving effect of the obtained coating film is small. If it exceeds, the water resistance of the obtained coating film tends to be lowered.

In the present invention, the monomer (c ') having two or more polymerizable unsaturated double bonds described above is used in place of part of the monomer (c) component. , The viscoelasticity of the paint is improved, the smoothness of the resulting coating film,
It is desirable because it improves hot water resistance and blocking resistance. The monomer (c ') is used in the copolymer in an amount of 0.1 to 10% by mass, preferably 1 to 7% by mass, but when it is excessive, the stability of the aqueous liquid (A) decreases. Is not preferred. Further, in the present invention, the above-mentioned monomer (c ″) having a carbonyl group is used (in this case,
It is desirable because it improves the blocking resistance of the coating film obtained by using the compound (C) having a hydrazide group described later together). The monomer (c ″) is used in the copolymer,
It is preferable to use 0.5 to 10% by mass, preferably 1 to 7% by mass, but if it is excessive, the water resistance of the coating film deteriorates, which is not preferable.

Next, a method for producing the aqueous liquid (A) will be described. In producing the aqueous liquid (A), the monomers (a) to
As the copolymerization method (c), a conventionally known solution polymerization method, emulsion polymerization method, or the like can be adopted. In the solution polymerization method, the monomer mixture is usually added at a temperature of 70 to 150 ° C. in a hydrophilic organic solvent in the presence of a polymerization initiator and, if necessary, a chain transfer agent for controlling the molecular weight. After the reaction, the hydrophilic organic solvent is removed under reduced pressure as required, water is added to produce an aqueous liquid (A). For the reaction, a batch charging method of monomers, a monomer dropping method, or the like can be adopted.

As the above-mentioned polymerization initiator, an oil-soluble one is adopted, and specifically, azo such as 2,2'-azobisisobutyronitrile or 2,2-azobis (4-dimethylvaleronitrile) is used. Systematic compounds; benzoyl peroxide, cumene hydroperoxide, and other peroxides. Specific examples of the chain transfer agent include n-dodecyl mercaptan, mercaptoacetic acid, mercaptoethanol, and mercaptopropionic acid ester.
As the hydrophilic organic solvent, specifically, hydrophilic organic solvents such as isopropyl alcohol, n-butanol, isobutyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, etc. Is mentioned.

The pH of the aqueous liquid (A) must be adjusted to 7 to 10, preferably 8 to 9 with an alkaline substance in order to have stability. The pH is 7
If the amount is less than, the alkali solubilization and swelling of the copolymer will be insufficient and the stability will be deteriorated, and the viscosity of the aqueous coating composition will be insufficient and the smoothness of the resulting coating film will be improved. This is not preferable because the effect is reduced. On the other hand, conversely, p
When H exceeds 10, the water resistance of the resulting coating film is deteriorated, which is not preferable.

As the alkaline substance having a pH within the above range, neutralizing agents which have been conventionally used in water-based paints can be used without any particular limitation. Specifically, monoethanolamine, dimethylamine, Representative examples include organic amines such as triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, and ammonia. The neutralizing agent is preferably added in advance to the hydrophilic organic solvent, or after the reaction, before or after water is added, or simultaneously with water. It is also possible to add the neutralizing agent after mixing the aqueous liquid (A) and the aqueous emulsion (B) described below.

The emulsion polymerization method is carried out in the presence of an emulsifier and a polymerization initiator, and if necessary, a chain transfer agent, an emulsion stabilizer, etc.
The aqueous mixture (A) is produced by reacting the monomer mixture in water at a temperature of usually 60 to 90 ° C. As described above, the reaction may be a batch charging method of a monomer, a monomer dropping method, a multi-step emulsion polymerization method of adding a monomer several times, a seed method, or the like. Further, a pre-emulsion dropping method in which a preliminarily emulsified mixture of water, an emulsifier and a monomer mixture is dropped can be employed.

Specific examples of the emulsifiers include fatty acid salts such as sodium lauryl sulfate, higher alcohol sulfuric acid ester salts, alkylbenzene sulfonic acid salts such as sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether sulfates, and polyoxy salts. Nonyl phenyl ether sulfonate ammonium, polyoxyethylene-polyoxypropylene glycol ether sulfate, having a sulfonic acid group or a sulfuric acid ester group and a polymerizable carbon-carbon unsaturated double bond in the molecule, so-called reactive emulsifier, etc. Anionic surfactant; polyoxyethylene alkyl ether, polyoxyethylene nonylphenyl ether, sorbitan fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block Polymer, or a nonionic surfactant such as a reactive nonionic surfactant having a carbon-carbon unsaturated double bond polymerizable with the above-mentioned skeleton in the molecule; alkylamine salt, quaternary ammonium salt, etc. Cationic surfactants; (modified) polyvinyl alcohol and the like. Among them, anionic and nonionic ones are preferably used.

Preferable examples of the polymerization initiator include potassium persulfate, persulfates such as ammonium persulfate, and peroxides such as hydrogen peroxide and t-butyl hydroperoxide. In the redox reaction in which a polymerization initiator is combined with a reducing agent such as L-ascorbic acid, sodium thiosulfate, and ferrous sulfate, it is 30 to 7
The emulsion polymerization reaction is possible even at 0 ° C. Further, a polymerization accelerator such as copper sulfate can also be used. The aqueous liquid obtained by the emulsion polymerization method is adjusted to pH 7 to 10 in the same manner as in the solution polymerization method to obtain an aqueous liquid (A). The aqueous emulsion (B) which is a constituent component of the present invention is an emulsion which is a main component of the aqueous coating composition of the present invention, which is produced by a known method including the emulsion polymerization method described above.

With respect to the types of monomers to be emulsion-polymerized, the above-mentioned monomers (a), (b) and (c) can be used without particular limitation, and further 4- (meth) ) Acroyloxy-2,2,6,6-tetramethylpiperidine and 4-
(Meth) acryloylamino-2,2,6,6-tetramethylpiperazine, 4- (meth) acroyloxy-
1,2,2,6,6-pentamethylpiperidine, 4-
(Meth) acryloylamino-1,2,2,6,6-pentamethylpiperazine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperazine, 4-crotonoylamino- 2,2,6,6-tetramethylpiperazine, 1- (meth) acryloyl-4-
(Meth) acryloylamino-2,2,6,6-tetramethylpiperazine, 1- (meth) acryloyl-4-cyano- (meth) acryloylamino-2,2,6,6-
UV stable monomers such as polymerizable hindered amine compounds such as tetramethylpiperazine and 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine can also be used.

However, the aqueous emulsion (B) is a copolymer obtained from an ethylenically unsaturated monomer having an average particle size in the dynamic light scattering method of 70 to 350 nm, preferably 80 to 200 nm. Must be an aqueous emulsion of When the average particle size is less than 70 nm, the viscosity of the system after mixing with the aqueous liquid (A) becomes extremely high, which makes it difficult to handle as a coating composition, while when it exceeds 350 nm, It is not preferable because the water resistance of the coating film deteriorates. Further, the aqueous emulsion (B) is preferably adjusted to a pH of about 7 to 9 with a neutralizing agent, like the aqueous liquid (A).

In the aqueous coating composition of the present invention, the mass ratio of the above-mentioned aqueous liquid (A) and aqueous emulsion (B) in terms of solid content is (0.5 to 25: 100), preferably,
It contains a mixture of (5 to 20: 100). The aqueous emulsion (B) of the aqueous liquid (A)
If the amount is less than the above range, the effect of simultaneously improving the smoothness and the weather resistance of the obtained coating film cannot be obtained, while if it is excessive, the water resistance of the obtained coating film decreases, which is not preferable.

When the aqueous liquid (A) is a copolymer using an ethylenically unsaturated monomer (c ″) having a carbonyl group instead of a part of the monomer (c) component, The compound (C) having at least two or more hydrazide groups in one molecule is used in combination, whereby a coating film having excellent blocking resistance is obtained. The amount of the compound (C) is the same as that of the monomer ( c ") relative to the amount of carbonyl group, 0.1 to 1.0
An amount corresponding to an equivalent amount of hydrazide group is suitable. Examples of the compound (C) include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, citric acid trihydric acid, citric acid, and the like. 1,2,4-benzene trihydrazide, thiocarbodihydrazide and the like can be mentioned. In particular, carbohydrazide, adipic acid dihydrazide, and succinic acid dihydrazide are preferable from the viewpoint of dispersibility in emulsion and water resistance. The compound (C) is usually added to the aqueous liquid (A), but may be added to the mixture of the aqueous liquid (A) and the aqueous emulsion (B).

The aqueous coating composition of the present invention comprises the above-mentioned aqueous liquid (A), an aqueous emulsion (B), and optionally a compound having a hydrazide group (C). Various additives such as film aids, dispersants, thickeners, defoamers, UV absorbers, light stabilizers, anti-microscopic agents, preservatives, freeze stabilizers, extender pigments, coloring pigments, anti-rust pigments, etc. It is a mixture of pigments and the like. It should be noted that the dispersant and the thickener should be added in the minimum necessary amount in view of the compatibility with the aqueous liquid (A). The aqueous coating composition of the present invention thus obtained, various inorganic materials, metal materials,
Applicable to wood materials, plastic materials, etc., natural drying,
Alternatively, by forced drying at a temperature of 100 ° C. or lower, a coating film having good smoothness and excellent weather resistance and water resistance can be formed.

[0023]

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

(Aqueous liquid A-1) In a 4-neck separable flask equipped with a stirrer, a thermometer, a condenser and a dropping device, 2- (2'-hydroxy-5'-methacryloxyethylphenyl)- 2H-benzotriazole [RUVA
93 (manufactured by Otsuka Chemical Co., Ltd.)] (a) 14 parts, methacrylic acid (b) 112 parts, ethyl acrylate (c) 154 parts 10% amount of a monomer mixture and ion-exchanged water 6
After charging 46 parts and 4 parts of sodium lauryl sulfate [Emar 10 Needle (manufactured by Kao Corporation)], the temperature inside the flask was raised to 80 ° C. while displacing the inside of the flask by 10%.
Add 15 parts of ammonium persulfate aqueous solution, 80 ° C, 30
Let react for minutes. Then, the remaining monomer mixture (90% content) was continuously added dropwise over 2 hours while maintaining 80 ° C. 1% ammonium persulfate aqueous solution 2
0 part was added dropwise over 30 minutes, and the mixture was aged at 80 ° C. for 2 hours while stirring, and then cooled to 30 ° C. Next, ion-exchanged water and 25% ammonia water are added to add PH8.
0, an aqueous solution (A-1) of an alkali-soluble copolymer having a nonvolatile content of 20% was obtained.

(Aqueous liquids A-2 to A-4 and A'-1) Aqueous liquid A-1 was prepared, except that the total amount of the monomers was not changed and the monomer composition was changed to the distribution shown in Tables 1 and 2. In the same manner as in the production method, an aqueous solution having a non-volatile content of 20% and having a pH of 8.0 (A-2 to
4 and A'-1) were obtained. The aqueous liquids A-3 and A-
For 4, the 28.0% aqueous solution of adipic acid dihydrazide was used as the hydrazide compound corresponding to diacetone acrylamide (DAAM) as the monomer (c ″) component.
Added in parts.

(Aqueous Emulsion B-1) In a 4-neck separable flask equipped with a stirrer, a thermometer, a cooling tube and a dropping device, 220 parts of ion-exchanged water, 2.5 parts of sodium hydrogen carbonate and polyoxyethylene were added. 1.5 parts of alkylphenylsulfate ammonium salt [Hitenol N-08 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)] was charged, and the temperature was raised to 80 ° C. while displacing the inside of the flask with nitrogen, and then 2 parts of potassium persulfate. 50 parts of styrene, 265 parts of methyl methacrylate, 175 parts of 2-ethylhexyl acrylate, 10 parts of methacrylic acid, 6 parts of Hitenol N-08, and 250 parts of ion-exchanged water, which have been mixed by stirring in advance in a separate container. The monomer emulsion was continuously added dropwise over 3 hours. Subsequently, 20 parts of a 1% ammonium persulfate aqueous solution was added dropwise over 30 minutes, and the mixture was aged at 80 ° C. for 2 hours with continuous stirring, and then aged.
Cooled to 0 ° C. Next, 50% dimethylethanolamine, ion-exchanged water at pH 8.0 and solid content concentration of 50
% Aqueous emulsion (B-1) was obtained. The average particle size of the obtained copolymer emulsion particles was 125 n.
m [Particle size analyzer based on dynamic light scattering method [MICROTRAC MOD
EL: 9340-UPA (manufactured by Nikkiso Co., Ltd.)].

(Aqueous emulsion B-2) 230 parts of methyl methacrylate, 125 parts of 2-ethylhexyl acrylate, 12 parts of cyclohexyl methacrylate were used as monomers.
5 parts, methacrylic acid 10 parts, 1,2,2,6,6-pentamethyl-piperidyl methacrylate 10 parts, except that the production method of the aqueous emulsion (B-1) was changed to pH 8.0, solid. An aqueous emulsion (B-2) having a concentration of 50% was obtained. The average particle size of the obtained copolymer emulsion particles was 131 nm.

(Aqueous emulsion B′-1) Stirrer ,
In a 4-neck separable flask equipped with a thermometer, a cooling tube and a dropping device, 550 parts of ion-exchanged water, 2 parts of sodium thiosulfate, 0.08 part of copper sulfate and Hitenol N-08 were placed.
After charging 5 parts and 5 parts of sodium lauryl sulfate and heating the inside of the flask to 70 ° C. while replacing the inside of the flask with nitrogen,
2 parts of potassium persulfate was added, and 50 parts of styrene and methyl methacrylate 265 were mixed by stirring in a separate container in advance.
Part, 175 parts of 2-ethylhexyl acrylate, and 10 parts of methacrylic acid were continuously added dropwise over 1.5 hours. Subsequently, 20 parts of a 1% ammonium persulfate aqueous solution was added dropwise over 30 minutes, and the mixture was aged at 80 ° C. for 2 hours while stirring, and cooled to 30 ° C. Then 5
PH with 0% dimethylethanolamine and deionized water
Aqueous emulsion (B'-8.0, solid concentration 40%, 8.0)
1) was obtained. The average particle size of the obtained copolymer emulsion particles was 56 nm.

(Aqueous Emulsion B′-2) 0.2 parts of Hitenol N-08 initially charged in a separable flask is charged.
Parts, except that the amount of Hitenol N-08 charged in the monomer emulsion is changed to 9.8 parts, in the same manner as in the production method of the aqueous emulsion B-1, pH 8.0, solid content concentration 50%.
Aqueous emulsion (B'-2) of was obtained. The average particle size of the obtained copolymer emulsion particles was 390 n.
It was m.

<Example 1> Aqueous emulsion (B-1)
100 parts of ethylene glycol monobutyl ether 5
Parts, 25 parts of the aqueous liquid (A-1) and 1 part of the defoaming agent were added and stirred, and then ion-exchanged water was added to prepare an aqueous coating composition having a nonvolatile content of 34%.

<Examples 2 to 6 and Comparative Examples 1 to 5> As shown in Tables 1 and 2, except that the combination of the aqueous liquid (A) and the aqueous emulsion (B) and the mixing ratio thereof are changed.
An aqueous coating composition was obtained in the same manner as in Example 1. The nonvolatile content of these water-based coating compositions is 34
Adjusted to%. The abbreviations of the monomer raw materials shown in Tables 1 and 2 have the following meanings. ST: Styrene MMA: Methyl methacrylate 2EHA: 2-Ethylhexyl acrylate CHMA: Cyclohexyl methacrylate EA: Ethyl acrylate MAA: Methacrylic acid BGDA: 1,4-Butylene glycol diacrylate RUVA93: 2- (2'-hydroxy-5'-methacryloxy) Ethylphenyl) -2H-benzotriazole DAAM: diacetone acrylamide LA82: 1,2,2,6,6-pentamethyl-piperidyl methacrylate Aqueous coating compositions obtained in Examples 1-6 and Comparative Examples 1-5. Each test of the smoothness, weather resistance and hot water resistance of the coating film was conducted, and the results are shown in the lower row of Tables 1 and 2. The test method and evaluation were performed according to the following methods.

<Smoothness of coating film> Each aqueous coating composition was applied onto a glass plate with a 6 mil and a 10 mil applicator,
After forced drying at 100 ° C. for 5 minutes, the appearance of the coating film was visually evaluated. Criteria ⊚: Both 6 mil and 10 mil coatings are smooth with no wrinkles (distortion) on the coating surface. ◯: With 6 mil coating, there were no wrinkles (strains) on the surface of the coating film, and the surface was smooth, but with 10 mil coating, wrinkles occurred only partly. ×: Wrinkles (distortion) were generated on the coating film surface in both 6 mil and 10 mil coating.

<Weather resistance> A test plate prepared with a 6-mil applicator in the same manner as the coating smoothness test was used to measure the gloss retention of the coating film after 3000 hours of sunshine weatherometer (gloss after test / before test / pre-test). The gloss was evaluated. Judgment Criteria : Gloss retention rate is 90% or more. ◯: Gloss retention rate is 80% or more and less than 90%. Δ: Gloss retention rate is 60% or more and less than 80%. X: Gloss retention rate is less than 60%.

<Warm water resistance> A test plate prepared with a 6-mil applicator in the same manner as the coating film smoothness test was heated at 50 ° C.
Immersed in warm water for 24 hours, visually judge the appearance of the coating film immediately after taking it out from the warm water, and leave it at room temperature for 24 hours.
After drying, the appearance of the coating film was visually judged. Judgment Criteria ⊚: Little whitening of the coating film, and the original clear coating film is completely recovered after drying. ◯: Little whitening of the coating film, and almost 2-3 hours after drying, the original clear coating film was recovered. Δ: Some whitening of the coating film was observed, it was a little cloudy even after drying for 24 hours, and recovered to a clear coating film after 48 hours. X: Significant abnormality of the coating film such as whitening and blistering was observed, and almost never recovered even after drying.

<Blocking resistance> A test plate prepared with a 6-mil applicator in the same manner as the coating film smoothness test was placed on a hot plate heated to 50 ° C. Next, place a gauze on the surface of the coating film, and further place a 500 g weight preheated to 50 ° C. on it, 0.5 kg
A load of / cm ² was applied for 1 hour. Then, after cooling to room temperature, the gauze was slowly peeled off, and the peeling resistance and the trace of the gauze at that time were visually judged. Evaluation Criteria ⊚: Gauze fell naturally, and almost no trace of gauze remained on the coating film. ◯: Gauze does not fall naturally, but almost no trace of gauze remains on the coating film. Δ: The gauze does not fall naturally, but it can be peeled off with a little force, and some traces of gauze remain. X: A part of the coating film was peeled off when the gauze was peeled off, and the traces of the gauze remained clearly.

[0036]

[Table 1]

[0037]

[Table 2] As apparent from Tables 1 and 2, Examples 1 to 6 of the present invention
The water-based coating composition (1) had good balance between the smoothness, weather resistance, warm water resistance and blocking resistance of the coating film.

However, the ultraviolet absorbing monomer (a)
Comparative Example 1 using the aqueous liquid (A′-1) that does not use
It was inferior in weather resistance. Also, without using the aqueous liquid (A),
Comparative Example 2 using the conventional emulsion (B-2) having high weather resistance as the aqueous emulsion (B) was inferior in the smoothness of the coating film. Further, Comparative Example 3 in which the amount of the aqueous liquid (A) was excessive was excellent in smoothness of the coating film, but inferior in hot water resistance. In Comparative Example 4 using the aqueous emulsion (B'-1) having an average particle diameter of 56 nm, the effect of adding the aqueous liquid (A) was not obtained, and the smoothness of the coating film was poor. On the contrary, in Comparative Example 5 using the aqueous emulsion (B′-2) having an average particle diameter of 390 nm, the coating film was excellent in smoothness, but the coating film was significantly inferior in hot water resistance.

[0039]

The water-based coating composition of the present invention has excellent weather resistance and
It forms a coating film with excellent hot water resistance and good smoothness.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroharu Sasaki             7-1414 Shimonagata, Nishinasuno Town, Nasu District, Tochigi Prefecture             46 (72) Inventor Hiroaki Omoto             8-15 Asahi-cho, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture             Ji heim 205 F-term (reference) 4J038 CA021 CA022 CB031 CB032                       CC021 CC022 CC091 CC092                       CF031 CF032 CG141 CG142                       CG161 CG162 CG171 CG172                       CH031 CH032 CH041 CH042                       CH131 CH132 CH171 CH172                       CH191 CH192 CH201 CH202                       GA06 GA09 JB17 KA03 MA08                       MA10 NA01 NA03 NA04 PB05

Claims (4)

[Claims] 1. An ultraviolet absorbing monomer (a), an ethylenically unsaturated carboxylic acid monomer (b) and the monomer (a),
It has an aqueous solution (A) of an alkali-soluble or alkali-swellable copolymer obtained from other ethylenically unsaturated monomer (c) copolymerizable with (b), and has an average particle diameter of 70 to 350 nm. , A water-soluble emulsion (B) of a copolymer obtained from an ethylenically unsaturated monomer, and the mass ratio (solid content conversion) of the water-based liquid (A) and the water-based emulsion (B) is (0). 0.5 to 25: 100). 2. The aqueous liquid (A) comprises 1 to 40 mass% of the ultraviolet absorbing monomer (a), 10 to 50 mass% of the ethylenically unsaturated carboxylic acid monomer (b), and 10 to 89% by mass of the other ethylenically unsaturated monomer (c)
The aqueous coating composition according to claim 1, which is an aqueous liquid of a copolymer consisting of: 3. The ethylenically unsaturated monomer wherein the aqueous liquid (A) has two or more polymerizable unsaturated double bonds in place of part of the ethylenically unsaturated monomer (c). (C ′) is an aqueous liquid of a copolymer containing 0.1 to 10% by mass,
The aqueous coating composition according to claim 1 or 2. 4. The aqueous liquid (A) contains 0.5 parts of an ethylenically unsaturated monomer (c ″) having a carbonyl group instead of 1 part of the ethylenically unsaturated monomer (c). 10 to 10% by mass, and having 2 or more hydrazide groups in one molecule corresponding to the amount of hydrazide groups of 0.1 to 1.0 equivalent to the amount of carbonyl groups of the monomer (c ″). The water-based coating composition according to claim 1 or 2, containing the compound (C).