JP3354906B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition having excellent weather resistance, and more particularly to an aqueous coating composition having excellent gloss retention, yellowing resistance, water resistance and solvent resistance over a long period of time. The present invention relates to an aqueous coating composition capable of forming a film having excellent adhesion to various paint resins and being widely applicable to various aqueous paints.

[0002]

2. Description of the Related Art In the field of architectural coatings, a water-based coating for a top coat using a resin having excellent weather resistance, such as a silicone-based or fluorine-based resin, in order to meet the needs of users to protect the long-term appearance of buildings. Is developing and market development is also progressing.

[0003] On the other hand, an aqueous coating composition using a relatively general-purpose (meth) acrylic resin and having excellent weather resistance is disclosed in Japanese Patent Application Laid-Open No. H06-26,026.
No. 37574 discloses an aqueous coating composition using a copolymer emulsion of a polymerizable monomer having a cycloalkyl group and a polymerizable monomer having a sterically hindered piperidinyl group. It is described that it exhibits excellent weather resistance.

Further, Japanese Patent Publication No. 3-46506 discloses that
It is described that weather resistance can be improved by adding a hindered phenol-based antioxidant and a benzotriazole-based ultraviolet absorber to a coating resin containing butyl methacrylate as an essential component.

[0005]

SUMMARY OF THE INVENTION However, Patent 2
When using a water-based paint described in JP-A-637574 for the top coat, when a base coat or an intermediate paint is applied for the purpose of imparting substrate protection or improving water permeability, it is conventionally generally used. Intermediate coatings and primer coatings have a problem that they tend to peel off due to lack of adhesion to the waterborne coatings for topcoats. However, there is a problem that an intermediate coating or a primer must be used.

In addition, the coating composition described in Japanese Patent Publication No. 3-46506 bleeds out of the coating film with the lapse of time when the additives are blended, so that it is difficult to maintain the weather resistance for a long period of time. Further, since the additive is hard to dissolve in water which is a main medium of the water-based paint, in order to uniformly disperse in the paint, a dispersant or the like is added and the additive is dispersed in water in advance. It is necessary to adopt a technique, the production method is complicated, and there is a problem in the stability of the produced paint.

Further, when an acrylic water-based paint is applied on a paint film coated with a fluorine-based paint for the purpose of repair or the like, the paint film of the acrylic water-based paint has an adhesive property to the paint film of the fluorine-based paint. However, there is a problem that peeling is apt to occur when direct recoating is performed.

The present invention has been made in order to solve the above-mentioned problems, and has no bleed-out in a coating film, has excellent weather resistance, and has an acrylic, silicone, fluorine, etc. It is an object of the present invention to provide an aqueous coating composition capable of forming a paint film having good adhesion to a film formed by various paints.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies with the aim of solving the above problems, and have found that an aqueous coating composition containing a copolymer obtained from a monomer having a specific structure has been obtained. The formed film has excellent weather resistance and has been found to have good adhesion to films formed with various paints, and has completed the present invention.

That is, the present invention relates to an ethylenically unsaturated monomer (a) represented by the following general formula (I): 5 to 80% by mass.
And CH ₂ ＣＲCR 1 —COO—C (CH ₃ ) ₃ (I) (R 1 represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms.) An ethylenic compound represented by the following general formula (II) 0.1 to 10% by mass of a saturated monomer (b);

[0011]

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(R2 represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, X represents an oxygen atom or an imino group, and Y represents a hydrogen atom or a hydrocarbon substituent having 1 to 20 carbon atoms.) Ethylenically unsaturated carboxylic acid Acid monomer (c) 0.1 to 10
% By mass and other ethylenically unsaturated monomers (d)
The present invention relates to an aqueous coating composition containing a copolymer (A) obtained by polymerizing 94.8% by mass.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The copolymer (A), which is the main component of the aqueous coating composition of the present invention, comprises an ethylenically unsaturated monomer (a) represented by the above general formula (I) Polymerizing an ethylenically unsaturated monomer (b) represented by the formula (II), an ethylenically unsaturated carboxylic acid monomer (c) and, if necessary, another ethylenically unsaturated monomer (d) And is composed of repeating units derived from each monomer unit.

The copolymer (A) used in the aqueous coating composition of the present invention has a total monomer amount of 10% at the time of polymerization from the viewpoint of stain resistance and adhesion to a coating film formed of various coatings.
When the amount is 0% by mass, the amount of the ethylenically unsaturated monomer (a) represented by the general formula (I) needs to be 5% by mass or more, and preferably 10% by mass or more. Further, from the viewpoint of the flexibility of the coating film, the content of the ethylenically unsaturated monomer (a) represented by the general formula (I) needs to be 80% by mass or less, and 70% by mass or less. Is preferred. Examples of the ethylenically unsaturated monomer (a) represented by the general formula (I) include tertiary butyl (meth) acrylate.

Further, the copolymer (A) used in the aqueous coating composition of the present invention has a general formula (A) in which the total amount of monomers at the time of polymerization is 100% by mass from the viewpoint of the weather resistance of the coating. II)
It is necessary that the amount of the ethylenically unsaturated monomer (b) represented by the formula (b) is 0.1% by mass or more, and more preferably 0.5% by mass or more. Further, from the viewpoint of the water resistance of the coating film, the amount of the ethylenically unsaturated monomer (b) represented by the general formula (II) needs to be 10% by mass or less, and may be 6% by mass or less. preferable.

As the piperidyl group-containing ethylenically unsaturated monomer (b) represented by the general formula (II), those having an ultraviolet ray stabilizing function can be used.
(Meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-
2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-
1,2,2,6,6-pentamethylpiperidine, 4-cyano-4- (meth) acryloyloxy-2,2,6
6-tetramethylpiperidine and the like, each of which may be used alone or in combination of two or more.

The copolymer (A) used in the aqueous coating composition of the present invention, when the total amount of the monomers at the time of polymerization is 100% by mass, the ethylenically unsaturated carboxylic acid monomer (c) ) Needs to be 0.1 to 10% by mass,
It is preferably from 2 to 10% by mass, more preferably from 2 to 8% by mass.

Ethylenically unsaturated carboxylic acid monomer (c)
Is 0.1% by mass or more, the dispersion stability of the aqueous coating composition is improved, and when the aqueous coating composition of the present invention is colored by adding a pigment, it is possible to avoid a problem that aggregates are generated. Can be. 10 ethylenically unsaturated carboxylic acid monomers
When the content is not more than mass%, the dispersion stability can be maintained without lowering the water resistance of the coating film obtained using the aqueous coating composition.

The ethylenically unsaturated carboxylic acid monomer (c) used in the aqueous coating composition of the present invention includes (meth) acrylic acid, itaconic acid, citraconic acid, maleic acid, monomethyl maleate, and maleic acid. Monobutyl, monomethyl itaconate, monobutyl itaconate, vinylbenzoic acid, monohydroxyethyl oxalate (meth) acrylate and the like can be mentioned.

Further, as the ethylenically unsaturated carboxylic acid monomer unit (c), a compound represented by the following general formula (III) is preferable. By using an ethylenically unsaturated carboxylic acid monomer having such a structure, excellent adhesion to a metal substrate or the like can be provided. _{CH 2 = CR3-COO-R4} -O-C (O) -R5-COOH (III) (R3 is a hydrogen atom or an alkyl group having a carbon number of 1 to 2, R
4 is a linear or branched alkylene group having 1 to 12 carbon atoms, and R5 is a linear or branched hydrocarbon substituent having 2 to 15 carbon atoms or a hydrocarbon substituent having a cyclic structure. )

As the ethylenically unsaturated carboxylic acid monomer (c) represented by the general formula (III), monohydroxyethyl tetrahydrophthalate (meth) acrylate, monohydroxypropyl tetrahydrophthalate (meth) acrylate, 5 -Methyl-1,2-cyclohexanedicarboxylic acid monohydroxyethyl (meth) acrylate, phthalic acid monohydroxyethyl (meth) acrylate, monohydroxypropyl phthalate (meth) acrylate,
Monohydroxypropyl (meth) acrylate maleate, monohydroxyethyl (meth) acrylate maleate, monohydroxybutyl (meth) acrylate tetrahydrophthalate and the like can be mentioned.

The amount (mass percentage) of the other ethylenically unsaturated monomer (d) used is such that the sum of the mass percentages of the monomers (a) to (c) becomes 100% by mass. Can be In addition, the copolymer (A) is the monomer (a),
It may be obtained by polymerizing only (b) and (c).

Other ethylenically unsaturated monomers (d) include methyl (meth) acrylate, ethyl (meth)
Acrylate, n-butyl (meth) acrylate, i-
Butyl (meth) acrylate, cyclohexyl (meth)
Acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate and the like, alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms, 2-hydroxyethyl (meth) acrylate, Hydroxyalkyl (meth) acrylates such as 2-hydroxypropyl (meth) acrylate, glycol di (meth) acrylates such as ethylene glycol di (meth) acrylate and butylene glycol di (meth) acrylate, and dimethylaminoethyl (meth) acrylate Alkylamino (meth) acrylate, dimethylaminoethyl (meth) acrylate methyl chloride salt, allyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycidyl (meth ) Acrylate, styrene, alpha-
Examples include aromatic vinyl compounds such as methylstyrene and p-methylstyrene, vinyl acetate, vinyl propionate, (meth) acrylonitrile, benzyl (meth) acrylate, acrylamide, and diacetone acrylamide.

The copolymer (A) constituting the aqueous coating composition of the present invention has a calculated glass transition temperature (Tg) determined by the Fox equation from the viewpoint of the non-adhesiveness and stain resistance of the obtained coating film. ) Is preferably -20 ° C or higher,
-10 ° C or higher is more preferable. Further, the temperature is preferably 70 ° C. or less from the viewpoint of crack resistance in a cooling / heating cycle test.
C. or lower is more preferable.

The Fox equation is the following relational equation regarding the glass transition temperature of the copolymer.

1 / Tg = Σ (Wi / Tgi) (Wi is the mass fraction of monomer i, and Tgi is the Tg of the homopolymer of monomer i.)

The aqueous coating composition of the present invention contains 0.1 to 10 surfactants per 100 parts by mass of the copolymer (A).
Those added in the range of parts by mass are preferred. Such an aqueous coating composition is preferably prepared by obtaining a copolymer (A) by an emulsion polymerization method in the presence of a surfactant having the above content. The presence of the surfactant in an amount of 0.1 part by mass or more improves the storage stability of the aqueous coating composition, and also improves the stability during polymerization when emulsion polymerization is performed in the presence of the surfactant. By adjusting the surfactant content to 10 parts by mass or less, it is possible to maintain the stability at the time of compounding into a coating composition, the stability over time, and the like without impairing the water resistance.

Examples of the surfactant used in the present invention include known anionic, cationic, and nonionic surfactants, and further, a polymer emulsifier, and an ethylenically unsaturated bond in the surfactant component. A so-called reactive emulsifier having the following formula can also be used.

The copolymer (A) constituting the aqueous coating composition of the present invention is obtained by polymerizing the monomers (a) to (d) by a known solution polymerization method, suspension polymerization method, or emulsion polymerization method. However, the copolymer (A) which is in the form of an emulsion by emulsion polymerization is preferred from the viewpoint of various physical properties such as storage stability, hardness and stain resistance of the aqueous coating composition.

In order to obtain the emulsion used in the present invention by emulsion polymerization, a method in which a monomer mixture is fed into a polymerization system in the presence of an emulsifier and polymerization is carried out with a water-soluble initiator, or an organic peroxide is used. A known method such as a method in which polymerization is carried out using a redox initiator obtained by combining a product with a reducing agent such as sodium thiosulfate can be used.

The method of supplying the monomer into the polymerization system is as follows.
A conventionally known technique can be used.

The emulsion obtained by the emulsion polymerization method can be prepared by adding a basic compound after polymerization to adjust the pH of the system from a neutral range to a weak alkalinity, that is, a pH range of about 6.5 to 10.0. Stability can be improved.

Examples of the basic compound to be added include ammonia, triethylamine, propylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, and 1-amino-2-amine. Propanol, 2-amino-1-propanol, 3-amino-1-
Examples thereof include propanol, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine, aminobenzyl alcohol, morpholine, sodium hydroxide, and potassium hydroxide.

When adjusting the molecular weight of the copolymer (A), n-dodecyl mercaptan, t
-It can be adjusted by using a chain transfer agent such as dodecyl mercaptan or α-methylstyrene dimer.

The aqueous coating composition of the present invention containing the copolymer (A) thus obtained as a main component has various pigments, antifoaming agents, A pigment dispersant, a slip agent, a preservative, a plasticizer and the like can be added and used. As a coating method when forming a coating on the surface of various materials using the aqueous coating composition of the present invention, spray coating, roller coating,
A conventionally known method such as a bar coating method, an air knife coating method, a brush coating method, and a dipping method can be appropriately selected and used.

When the aqueous coating composition of the present invention is used as a coating material, a sufficiently formed film can be obtained by drying at room temperature to about 120 ° C. for about 10 minutes to 1 hour.

[0037]

The present invention will be described below in detail with reference to examples.

The weather resistance, adhesion, water resistance and storage stability were evaluated by the following methods.

(1) Weather resistance test Taipaque R-930 (sulfuric acid method titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) 196.3 g, OROTAN SG (pigment dispersant manufactured by Rohm & Haas Co.) 2.1 g, Surfynol DF-58 ( Air Products, Antifoaming agent) 0.08
g, propylene glycol 29.4 g, deionized water 3
After sufficiently mixing 4.3 g and 1.8 g of a 28% aqueous ammonia solution, glass beads were added, the pigment was dispersed with a high-speed disperser for 30 minutes, and then the glass beads were filtered off with a 300 mesh nylon gauze. Mill base.

Next, the aqueous coating composition (emulsion) 1
55 g of the above-mentioned mill base for evaluation, 6.4 g of Kyowanol M (plasticizer manufactured by Kyowa Hakko Co., Ltd.), and RHEOLATE 350 (RH) with respect to 20 g (solid content: 45% by mass).
1.5 g of a thickener (manufactured by EOX Corporation) were added in order, and the mixture was sufficiently stirred, and then adjusted by adding deionized water using a Ford cup # 4 so as to be about 100 to 140 seconds.

Thereafter, filtration was again performed using a 300 mesh nylon gauze to prepare a white enamel aqueous paint for a weather resistance test.

This water-based paint was applied to a zinc phosphate-treated steel sheet of 150 mm × 70 mm using a bar coater # 40.
After setting for 30 minutes in an environment of 65 ° C. × 65% Rh, drying was performed in a dryer at 80 ° C. for 1 hour to prepare a coated plate for a weather resistance test.

A polyester tape was stuck on the painted surface of the painted plate to prevent water droplets and the like from being applied during the weather resistance test from adhering to places other than the painted surface.

Thereafter, the irradiance was 30 W / m ² , the irradiation temperature was 70 ° C., the wet temperature was 50 ° C., and the cycle was set to 12 hours (irradiation time: 8 hours, wet time: 4 hours) manufactured by Suga Test Instruments Co., Ltd. Dew panel light control weather meter DPWL-5
A weather resistance test was carried out using the retention of 60 ° gloss after 00 hours as an index.

(2) Adhesion test: The aqueous coating composition (acrylic emulsion) contained 20% by mass (vs. solids) of butylcellosolve as a plasticizer, and 3 RHEOLATE 350 manufactured by RHEOX as a thickener.
% By mass (based on solid content), and after thorough stirring, 30
Filtration was performed using a 0 mesh nylon gauze.

This blended acrylic emulsion is
A mortar plate conforming to IS A 6910 is coated so that the wet film thickness is 30 μm, and the setting is performed in an environment of 20 ° C. × 65% Rh for 30 minutes, followed by drying in a dryer at 80 ° C. for 1 hour. Was.

After completely cooling the coated plate to room temperature, a fluorine-based emulsion Lumiflon FE manufactured by Asahi Glass Co., Ltd.
-4000, a cold-crosslinkable one-pack type acrylic emulsion produced according to the following Production Example 1 and Production Example 2 and the same blend as the above-mentioned acrylic emulsion were respectively prepared so as to have a wet film thickness of 30 μm. A mortar plate on which the acrylic emulsion was completely coated was applied, set in an environment of 20 ° C. × 65% Rh for 30 minutes, and then dried in a dryer at 80 ° C. for 1 hour.

After the evaluation coated plate in which the fluorine emulsion and the acrylic emulsion were coated on this acrylic emulsion coating was cooled to room temperature, the cutter knife was applied only to the coating film of the upper fluorine emulsion and the acrylic emulsion. Then, 100 squares of 2 mm square were formed, and then the cellophane tape peeling test was performed three times at the same location. After performing the peeling test three times, the cells that were not peeled were counted. The numerical value of the adhesion evaluation in Table 2 is the ratio of the area that has not been peeled off (the ratio of the area that has not been peeled to 100 cells).
It is.

(3) Water resistance test 20% by mass (based on solid content) of butyl cellosolve as a plasticizer and RHEOLATE 350 manufactured by RHEOX as a thickener were added to the aqueous coating composition (acrylic emulsion).
% By mass (based on solid content), and after sufficiently stirring, 300
Filtration was performed with a mesh nylon gauze.

This blended acrylic emulsion is treated with J
A mortar plate conforming to IS A 6910 is coated so that the wet film thickness is 30 μm, and the setting is performed in an environment of 20 ° C. × 65% Rh for 30 minutes, followed by drying in a dryer at 80 ° C. for 1 hour. Was.

After completely cooling the coated plate to room temperature, a fluorine-based emulsion Lumiflon FE manufactured by Asahi Glass Co., Ltd.
-4000, a cold-crosslinkable one-pack type acrylic emulsion produced according to the following Production Example 1 and Production Example 2 and the same blend as the above-mentioned acrylic emulsion were respectively prepared so as to have a wet film thickness of 30 μm. A mortar plate on which the acrylic emulsion was completely coated was applied, set in an environment of 20 ° C. × 65% Rh for 30 minutes, and then dried in a dryer at 80 ° C. for 1 hour.

A coated plate for evaluation, in which a fluorine-based emulsion and an acrylic-based emulsion were applied on this acrylic-based emulsion coating, was cooled to room temperature, and then cooled to 20 ° C.
The coated plate was immersed in pure water for 120 hours, and superiority was determined based on the following criteria based on the state of the gloss immediately after lifting.

◎: No gloss was observed, and the initial appearance was maintained.

(4) Storage stability test The storage stability was measured by immersing in a constant temperature water bath at 40 ° C. for 168 hours, and after one month at room temperature, measuring the viscosity and pH and observing the condition. Was evaluated.

◎: No aggregates were generated, and the change in pH was less than 0.5 and the change in viscosity was less than 5% of the initial value. ：: The change in pH was less than 1.0 and the change in viscosity was less than 1.0. Less than 10% of the initial value ×: Aggregates, gelation, etc. occurred and could not be used as a coating material

(5) Overall Evaluation The overall evaluation was performed according to the following criteria.

◎: Gloss retention of 90% or more, adhesion to a film formed of various paints of 90 or more, no problem with water resistance and storage stability (○ or more) ○: Gloss retention of 80% or more, various paints Adhesion to coating film of 90 or more, no problem with water resistance and storage stability (○ or more) ×: Gloss retention, adhesion, and storage stability were below any of the above criteria

(Production Example 1) 60 parts by mass of deionized water was charged into a polymerization vessel equipped with a stirrer, a cooler, and a thermometer, and the internal temperature was raised to 60 ° C.

Thereafter, 12 parts by mass of methyl methacrylate, 22 parts by mass of tert-butyl methacrylate, 23 parts by mass of styrene, and 3 parts of 2-ethylhexyl acrylate
6 parts by mass, 3 parts by mass of diacetone acrylamide, 4 parts by mass of Acryester HH (manufactured by Mitsubishi Rayon Co., Ltd.), 6 parts of Sannole NP-2030 (manufactured by Lion Corporation) and 40 parts of deionized water are sufficiently mixed. 10 at 5000 rpm
The mixture was stirred at high speed for 1 minute to prepare a pre-emulsion in a uniform emulsified state (hereinafter abbreviated as “PE liquid”).

5 parts by weight of the prepared PE solution was put into a polymerization vessel, and the internal temperature of the polymerization vessel was raised to 75 ° C. When the internal temperature was stabilized, 0.2 parts by weight of sodium persulfate was added to deionized water. Dissolved in 5 parts by mass and sodium bisulfite 0.1%
One part by mass dissolved in 5 parts by mass of deionized water was added and left for 1 hour.

After 1 hour, the remaining PE solution and 0.2 parts by weight of sodium persulfate were dissolved in 10 parts by weight of deionized water, and 0.1 part by weight of sodium bisulfite was added to 10 parts by weight of deionized water. The melted solution was cooled to 75 ° C.
The mixture was added dropwise to the polymerization vessel over 3 hours while maintaining the temperature at 0 ° C. After completion of the addition, the internal temperature was maintained at 80 ° C for 2 hours to complete the reaction. After the reaction was completed, cooling was performed, the emulsion was taken out, and a 28% aqueous ammonia solution was added so that the pH of the emulsion was between 7.5 and 10.

Thereafter, 1.5 parts by mass of adipic dihydrazide was added to obtain an acrylic emulsion of Production Example 1.

The obtained acrylic emulsion of Production Example 1 had a solid content of 45.2% by mass, a pH of 8.9, and a viscosity of 6
It was 0 mPa · s.

(Production Example 2) The same procedure as in Production Example 1 was carried out except that the monomer composition was changed to 42 parts by mass of methyl methacrylate, 36 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of cyclohexyl methacrylate, and 2 parts by mass of methacrylic acid. The polymerization was carried out by a suitable method to obtain an acrylic emulsion of Production Example 2.

After completion of the reaction, cooling was carried out, the emulsion was taken out, and a 28% aqueous ammonia solution was added so that the pH of the emulsion was between 7.5 and 10.

The obtained acrylic emulsion of Production Example 2 had a solid content of 44.8% by mass, a pH of 8.8, and a viscosity of 5
It was 3 mPa · s.

Example 1 A polymerization vessel equipped with a stirrer, a cooler and a thermometer was charged with 60 parts by mass of deionized water, and the internal temperature was raised to 60 ° C.

Thereafter, 100 parts by mass of the monomer mixture having the composition shown in Table 1 below, a surfactant and deionized water were sufficiently mixed, and the mixture was stirred at 5,000 rpm for 10 minutes at a high speed to obtain a pre-emulsion in a uniform emulsified state. (Hereinafter “PE
Liquid).

5 parts by weight of the prepared PE solution were put into a polymerization vessel, and the internal temperature of the polymerization vessel was raised to 75 ° C., and when the internal temperature was stabilized, 0.2 parts by weight of sodium persulfate was added to deionized water. Dissolved in 5 parts by mass and sodium bisulfite 0.1%
One part by mass dissolved in 5 parts by mass of deionized water was added and left for 1 hour.

After 1 hour, the remainder of the PE solution and 0.2 parts by weight of sodium persulfate dissolved in 10 parts by weight of deionized water, and 0.1 part by weight of sodium bisulfite were added to 10 parts by weight of deionized water. The melted solution was cooled to 75 ° C.
The mixture was added dropwise to the polymerization vessel over 3 hours while maintaining the temperature at 0 ° C. After completion of the addition, the internal temperature was maintained at 80 ° C for 2 hours to complete the reaction. After the reaction was completed, cooling was performed, the emulsion was taken out, and a 28% aqueous ammonia solution was added so that the pH of the emulsion was between 7.5 and 10.

The obtained acrylic emulsion of the present invention had the solid content (heating residue), pH and viscosity as shown in Table 2 below.

The results of the weather resistance test, adhesion test, water resistance test, and storage stability test were as shown in Table 2 below.

Examples 2 to 6 Emulsions having the compositions shown in Table 1 below were prepared in the same manner as in Example 1. The solid content, pH, and viscosity of the obtained acrylic emulsion of the present invention were as shown in Table 2 below.

The results of the weather resistance test, adhesion test, water resistance test and storage stability test were as shown in Table 2 below.

Comparative Examples 1 to 8 Emulsions having the compositions shown in Table 1 below were prepared in the same manner as in Example 1. The solid content, pH, and viscosity of the obtained acrylic emulsion were as shown in Table 2 below.

In Comparative Example 5, however, the solid content of the emulsion having the composition shown in Table 1 was compared with ADK STAB LX-332 manufactured by Asahi Denka Co., Ltd. (containing no polymerizable unsaturated double bond, (A piperidyl group-containing compound having a function) was added in an outer proportion of 2% by mass in terms of an active ingredient to obtain an aqueous coating composition.

The results of the weather resistance test, adhesion test, water resistance test, and storage stability test were as shown in Table 2 below. However, in Comparative Example 2, performance was not evaluated because cracks occurred in the coating film during setting after coating.

As is evident from Table 2, the aqueous coating composition of this example has excellent water resistance and storage stability, as well as excellent weather resistance and adhesion to paint films obtained from various paints.

On the other hand, when the copolymer does not have an ethylenically unsaturated monomer unit having a specific structure as in a comparative example, when the copolymer does not fall within a specific composition range,
Those that do not contain a specific amount of unsaturated carboxylic acid monomer units have inferior weather resistance and adhesion, or lack various stability required as an emulsion, and at the stage of blending a plasticizer or the like. It could not be used for coating applications due to generation of aggregates.

If the calculated Tg is not within the range of the specific calculated Tg, if the Tg is too high, cracks occur in the film at the stage when the acrylic emulsion is applied and dried, and conversely, the Tg is too low. In such a case, there was a problem that dirt easily adhered and the appearance of the coating film was spoiled.

[0081]

[Table 1]

TBMA: tertiary butyl methacrylate tBA: tertiary butyl acrylate LA-82: 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (trade name: ADK STAB LA)
-82, manufactured by Asahi Denka Co., Ltd.) LA-87: 2,2,6,6-tetramethyl-4-piperidyl methacrylate (trade name: ADK STAB LA-8)
MAA: methacrylic acid HH: 2-methacryloyloxyethyl hexahydrophthalate nBMA: normal butyl methacrylate 2EHMA: 2-ethylhexyl methacrylate 2EHA: 2-ethylhexyl acrylate CHMA: cyclohexyl methacrylate MMA: methyl methacrylate DAA : Diacetone acrylamide Liponox NC-200: Nonionic emulsifier manufactured by Lion Corporation Liponox NC-300: Nonionic emulsifier manufactured by Lion Corporation Adecaria Soap NE-40: Reactive nonionic emulsifier manufactured by Asahi Denka Co., Ltd.

[0083]

[Table 2]

[0084]

As is apparent from the above description, according to the present invention, there are no bleed-out substances from the coating film, and while having excellent weather resistance, various types of acrylic, silicon, fluorine, etc. An aqueous coating having good adhesion to a paint film formed by a paint can be provided, which is extremely useful industrially.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takaaki Ito 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Inside Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Yukihiro Ikegami 4-chome Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture No. 1-60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Kazuhiko Hotta 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory (56) References JP2 JP-A-10-265636 (JP, A) JP-A-8-188694 (JP, A) JP-A-10-176016 (JP, A) JP-A 8-283615 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C09D 1/00-10/00 C09D 101/00-201/10

Claims (4)

(57) [Claims] 1. An ethylenically unsaturated monomer (a) represented by the following general formula (I): 5 to 80% by mass, and CH ₂ ＣＲCR1-COO-C (CH ₃ ) ₃ (I) (R1 Represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms.) 0.1 to 10% by mass of an ethylenically unsaturated monomer (b) represented by the following general formula (II): (R2 is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, X
Represents an oxygen atom or an imino group, and Y represents a hydrogen atom or a hydrocarbon substituent having 1 to 20 carbon atoms. ) Ethylenically unsaturated carboxylic acid monomer (c) 0.1 to 10
An aqueous coating composition comprising a copolymer (A) obtained by polymerizing 0 to 94.8% by mass of another ethylenically unsaturated monomer (d) in an amount of 0 to 9% by mass. 2. The calculated glass transition temperature (Tg) of the copolymer (A) obtained from the Fox equation is -20 ° C. or higher.
The aqueous coating composition according to claim 1, wherein the temperature is 0 ° C or lower. 3. The aqueous coating composition according to claim 1, wherein the surfactant is added in an amount of 0.1 to 10 parts by mass based on 100 parts by mass of the copolymer (A). object. 4. The aqueous coating composition according to claim 1, wherein the ethylenically unsaturated carboxylic acid monomer (c) is a compound represented by the following general formula (III). . _{CH 2 = CR3-COO-R4} -O-C (O) -R5-COOH (III) (R3 is a hydrogen atom or an alkyl group having a carbon number of 1 to 2, R
4 is a linear or branched alkylene group having 1 to 12 carbon atoms, and R5 is a linear or branched hydrocarbon substituent having 2 to 15 carbon atoms or a hydrocarbon substituent having a cyclic structure. )