CA1324224C - Aqueous coating composition particularly useful as a top coat for automobile bodies - Google Patents

Abstract

Abstract of the disclosure An aqueous coating composition comprising, as resinous vehicle, (1) and aqueous composition containing resin particles obtained by polymerizing at least one .alpha.,.beta.-ethylenically unsaturated monomer in an aqueous medium and in the presence of an aqueous resin (A) with the help of an organic initiator, and (2) an aqueous resin (B) having a water tolerance of 4 or more and a surface tension of 1%
aqueous resin varnish of 51 dyne/cm or less, the solid weight ratio of said resin particles to the total aqueous resins (A)+(B) being 70-1:30-99. The coating composition is excellent in storage stability and application characteristics and is capable of resulting a coating with excellent film properties, and hence is particularly useful as a top coat for automobile bodies and the like.

Description

The present invention relates to an aqueous coating composition which is useful as a top coat. More specifically, the invention concerns an aqueous coating composition comprising as resinous vehicle (a), an aqueous S resin particles containing composition obtained by the polymerization of ~ ethylenically unsaturated monomer(s) in an aqueous medium and in the presence of a larger amount of a water soluble resin, and (b) a particular water soluble resin, which is excellent in storage stability and application characteristics and is capable of resulting a coating with excellent film properties and especially improved gloss and smoothness, and hence is specifically useful as a top coat for automobile bodies and the like.

lS An aqueous coating composition is generally inferior to a ' solvent type composition in durability and water resistance of the formed coating and since it is unable to get a ~ composition with a higher non-volatile content, application -~ characteristics are rather poor. Even if an amount of water insoluble resin powders are compounded with said aqueous composition with the hope for increasing the non-volatile content thereof, viscosity of the compounded system is inevitably increased therewith and hence, a practical coating composition cannot be obtained.

The lnventors had formerly found that by the selective use , .

of a particular water soluble resin which will fulfil the requirements that ~he water tolerance, expressed in terms o~
water dilution multiplicand of the resin for the solu~ion incapable of reading out the defined type in the test wherein 5g of aqueous varnish having a common viscosity usually employed in the manufacture of a coating composition ; are correctly weighed in a 100 ml beaker, diluted with an increasing amount of deionized water, and a No. 1 type (26 point type) i9 read through the said beaker, is 4 or more, and the surface tension calculated for a 1~ w/w aqueous solution is 51 dyne/cm or less, it is possible to formulate an aqueous coating composition comprising said water soluble resin and water insoluble resin powders uniformly dispersed therein having a wider solid weight ratio of 98:2 to 45:55, without the fear of undesired increase in viscosity of the system, and it is thus able to increase the resinous content of a coating composition and have the composition with excellent application characteristics, as well as the improved dispersion stability and film properties. On the basis of these findings, a patent application was filed, which is now publicly opened as Japanese Patent Application Kokai No. 15567/83. Though the resinous powders used in that invention were prepared by pulverizing a solidified resin and shieving the same, various technique have been developed to obtain the better quality powders to be compounded with a water soluble resin since then. In facts, certain improvements have been attained with these products i - .

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in respect of application characteristics and storage stability of the coating composition and film properties including gloss and smoothness, of the formed coating.
However, in most of the heretofore proposed processes, the water insoluble resin powders were advantageously prepared by an emulsion polymerization of ~ ethylenically unsaturated - monomer(s) in an aqueous medium containing a surfactant or emulsifier and in the presence of a polymerization initiator, and therefore, it was unavoidable that the surfactant used was always remained on the surfaces of the formed particles, giving undesired effect on the film properties and especially on water resistance of the film and that when a water soluble radical initiator was selected, said initiator was likewise , remained at the end portions of the polymer chain, giving $ 15 undesired effect on film properties, too. Thus, an I additional improvement has been longed for.

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J Moreover, with an increasing demand for high-grade articles, an aqueous type, top-coat composition capable of resulting a coating with far improved gloss and smoothness has been required, especially in an automobile and an electric appliance industries.

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i According to the invention, there i8 provided an aqueous coating composition comprising as resinous vehicle, (1) an aqueous, resin particles containing composition obtained by polymerizing at least one a,~-ethylenically S unsaturated monomer in an aqueous medium and in the presenceof a water soluble resin (A) with the help of an organic initiator, in which the solid weight ratio ôf said water soluble resin to said monomer i8 35-95:65-5, and . (2) a water soluble resin (B) having a water tolerance of 4 or more and a surface tension for a 1% w/w aqueous resin . solution of 51 dyne/cm or less, `~. the solid weight ratio of said resin particles to the total of said water soluble resins (A) and (B) being 70-1:30-99.
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The present aqueous, resin particles containing composition should be prepared by the polymerization of at least one a,~-ethylenically unsaturated monomer in an aqueous medium and in the presence of a water soluble resin (A), with the help of an organic initiator. The solid weight ratio of said water ~: 20 soluble resin to said monomer should be in a range of 35:65 ~: to 95:5.

As the water soluble resin (A), any of the members .

, customar~ly used in a coatlng composition area may be satisfactorily used, including polyester resin, alkyd resin, - acryl resin, acryl modified polyester resin, acryl modified alkyd resin and the like. Since they have, in general, an amount of acidic groups as carboxyl group, they are neutralized with a basic material so that solubility is given to them.
However, in the present invention, the water soluble resins (A~, as well as the water soluble resins (B) hereinafter mentioned, do not absolutely necessary be of fully soluble type and they may be of partly soluble and partly dispersible type. Therefore, the term "water soluble resin"
as used herein denotes either of water soluble resin and water reducible or dilutable resin.
As already mentioned, the present resin particles are prepared by the polymerization of d,~-ethylenically unsaturated monomer(s) in an aqueous medium and in the presence of a comparatively large amount of said water soluble resin ~A) in place of a surfactant or emulsifier as used in a conventional emulsion polymerization.
At this time, the solid weight ratio of said water soluble resin (A) to said monomer is determined in a range of 35:65 to 95:5. This is because, if the amount of said water soluble resin (A) is less than 35 wt% of the total of said resin and monomers, it is very hard to obtain a stable aqueous composition containing the resin particles and if the amount of said monomer is less than 5 wt~, it is unable to carry out an emulsion polymerization smoothly and effectively.
As the d,~-ethylenically unsaturated monomer, any of the members cu~tomarily u~ed in the preparation o~ acryl resin9 may be satisfaetorily used, each in singularily or combination of two or more. Examples of these monomers are as follows.
1) carboxyl containing monomer:
for example, aerylic acid, methacrylie acid, erotonie aeid, `~ 10 itaconic acid, maleic acid, fumaric aeid and the like, . , 2) hydroxyl containing monomer:
for example, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl 15 methacrylate, allyl alcohol, methallyl alcohol and the like, 3) nitrogen containin~ alkyl ~meth) acrylates:
for example, dimethyl aminoethyl acrylate, dimethyl aminoethyl methacrylate and the like, 4) polymerizable amides:
20 Eor example, acrylamide, methacrylamide and the like, 5) polymerizable nitriles: -for example, acrylonitrile, methacrylonitrile and the like, ~ 6) alkyl acrylates and alkyl methacrylates:
3 for example, methyl acrylate, methyl methacrylate, ethyl ~ 25 acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl 3~ methacrylate, 2-ethyl hexyl acrylate and tha like, 3 - 7) polymerizable aromatic compounds:

~ , ' ' , -' ` 1 324224 for example, ~tyrene, d-methyl styrene, vinyl toluene, t-butyl styrene and the like, 8) d-olefins:
for example, ethylene, propylene and the like, 9) vinyl compounds:
for example, vinyl acetate, vinyl propionate and the like, 10) diene compounds:
for example, butadiene, isoprene and the like.
As a part of said ~,~-ethylenically unsaturated monomers, one may use a crosslinking monomer having 2 or more radically polymerizable, ethylenic bonds per molecule.
Examples of such crosslinking monomers are polymerizable unsaturated monocarboxylic acid esters of polyhydric alcohols, polymerizable unsaturated alcohol esters of polycarboxylic acids, and aromatic compounds substituted with 2 or more vinyl groups and the like, including ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylol propane triacrylate, trimethylol propane trimethacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, glycerol diacrylate, glycerol allyloxy dimethacrylate, ~~ ~

l,l,l-trishydroxymethylethane diacrylate, l,l,l-trishydroxymethylethane triacrylate, l,l,l-trishydroxymethylethane dimethacrylate.
l,l,l-trishydroxymethylethane trimethacrylate, 5 l,l,l-trishydroxymethylpropane diacrylate, l,l,l-trishydroxymethyl propane triacrylate, l,l,l-trishydroxymethyl propane dimethacrylate, l,l,l-trishydroxymethyl propane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl 10 trimellitate, diallyl terephthalate, diallyl phthalate, divinyl benæene and the like. By using such a crosslinking monomer, particles of crosslinked copolymer can be obtained.
The abovesaid monomers are polymerized in an aqueous medium and in the presence of a water soluble resin (A) and at that :1 15 time, an organic initiator may advantageously be-used.
s As the oryanic initiator, use can be made of such members as diacyl peroxides (e.g. acetyl peroxide, lauroyl peroxide, benzoyl peroxide and the like), hydroperoxides (e.g. cumene hydroperoxide and the like), alkyl peroxides (e.g. di-t-20 butyl peroxide, t-butyl peroxy 2-ethyl hexanoate, t-butyl ! perpiperate, t-butyl perbenzoate and the like), azo compounds (e.g. 2,2-azobis isobutyronitrile and the like), disulfides (e.g. tetramethyl thiuram disulfide and the like), and sulfinic acids (e.g. p-toluene sulfinic acid and 25 the like).
Among them, particular preference is givent to a water insoluble organic initiator as azobis isobutyronitrile, ,, .

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benzoyl peroxide, di-t-butyl-peroxide, cumene hydroperoxide and the like.
Usually, water is used as a reaction medium, but in a more preferable embodiment of the invention, a mixture of water and an organic solvent is selectively used. The inventors have found that when an aqueous composition (l) is prepared by a method wherein ~,a-ethylenically unsaturated monomers are polymerized in a mixture of water and an organic solvent and in the presence of a large quantity of water soluble resin (A) and a water insoluble organic initiator, and thus obtained composition (l) is compounded with a water soluble resin (B) hereinafter mentioned, a particularly useful aqueous coating composition can be obtained, which is less foaming, hardly give pinholes, less sagginy and capable of resulting a coating with higher gloss and far improved ~moothness. Therefore, in a preferred embodiment of the invention, the aqueous composition (l) is prepared in a reaction medium comprising water and an appropriate amount of a common organic solvent customarily used in the preparation of solvent type coating composition.
Thus, in the present invention, it is essential that an aqueous composition containing resin particles be prepared by the polymerization of at least one d,R-ethylenically unsaturated monomer in an aqueous medium optionally blended - 25 with an organic solvent and in the presence of a large quantity of a water soluble resin (A) and in the presence of an organic initiator, preferably a water insoluble organic _ g _ , initiator. In this aqueous composition, the water soluble resin (A) is physically adsorped on or bound with the resin particles and the particles are stably dispersed in the medium by the high molecular effect of the water soluble resin (A) used.
Since the aqueous composition does not include any of the undesired water-soluble by-products, ionic substances and other impurities, and the water soluble resin per se is useful as a binder resin, there are no undesired effects on the properties of the formed coating mainly due to the emulsifier or surfactant usually presented in a conventional coating composition.
he inventors have also found that when ~,~-ethylenically unsaturated monomer(s) is (are) used in the form of mixture with at least one hydrophobic solvent or with at least one hydrophobic solvent and at least one hydrophobic resin, hydrophobic solvent and/or hydrophobic resin encapsulated resin particles can be obtained and far improved coating composition can be formulated with thus obtained aqueous composition and an aqueous resin (B) hereinafter defined.
At this time, outstanding improvements are realized in respect of application characteristics of the coating composition and gloss and smoothness of the formed coating.
Therefore, in a particularly preferred embodiment of the present invention, use is made of an aqueous composition containiny solvent encapsulated resin particles obtained by the polymerization of a mixture of at least one ~

, ethylenically unsaturated monomer and at least one hydrophobic solvent in an aqueous medium and in the presence of a water soluble resin (A) and an organic initiator~ or an aqueous composition containing hydrophobic resin encapsulated resin particles obtained by the polymerization of a mixture of at least one d,~-ethylenically unsaturated monomer and a hydrophobic resin or both hydrophobic resin and hydrophobic organic solvent, in an aqueous medium and in the presence of a water soluble resin ~A) and an organic initiator.
In the abovesaid embodiment, as the hydrophobic solvent, any of the organic solvents having solubility in 20C water of . lO weight % or less may be satisfactorily used, providing ~` having an optimum evaporation rate and boiling point seeing from the view point of application characteristics of the coating composition. Examples of such oryanic solvents are heptane, hexane, n-octane, iso-octane, decane, ligroin, kerosine, toluene, xylene, naphthalene, isobutanol, n-butanol, n-hexanol, methyl-n-butyl ketone, butyl acetate, Solvesso 150 (trademark, Esso Petroleum~ and other aliphatic or aromatic hydrocarbons, petroleum cuts, alcohols, esters, ketones and the like.
As already stated, the reaction medium may be water alone or a mixture of water and an organic solvent. The latter solvent may be of the same or different type from the abovesaid hydrophobic organic solvent to be encapsulated in the resin particles, and it may be of water miscible or ,!, ,J
~ ~ -- 1 1 -- ' .~ t `-' ` 1 324224 immiscible natUre. ~y th~ inclusion of said solvent in a reaction medium, it is possible to obtain an aqueous coating composition which is low in foaming, hardly form pinholes and is excellent in gloss, smoothness and sag resistance.
When a mixture of hydrophobic solvent and polymerizable monomer(s) is used, the mixing rate of said solvent and monomer(s) may be varied in a wider range.
It is, however, generally determined in 80:20 to 3:Y7, preferably 60:40 to 10:90, on weight basis. This is because if the solvent to be encapsulated is more than 80 wt ~, there is a tendency that stability of the coating composition be lowered and if the solvent is less than 3~, there is no slgnificant improvement in smoothness of the coating.
As already stated, inclusion of a hydrophobic solvent in the resin particles is effective for the control of viscosity of the coating composition at the application and the baking stayes, and hence considerable improvements in application characteristics and coating appearance and especially smoothness can be attained therewith.
ethylenically unsaturated monomers may also be used in the form of mixture with a hydrophobic resin or a combination of hydrophobic resin and hydrophobic solvent, to obtain the hydrophobic resin encapsulated resin particles.
In this particular embodiment, any of the known hydrophobic resins may be satisfactorily used provided that they are insoluble in water. Examples of such resins are an alkyd resin, a polyester resin, an acryl resin, an acryl modified alkyd resin, an acryl modi~ied polyester resin, an epoxy resin, an aminoplast resin, a polyether resin, a petroleum resin, a silicone resin, a polyurethane resin, a fluorine plastic, a cellulosic resin and the like.
The hydrophobic solvents are the same members as stated hereinbefore.
The mixing ratio of said hydrophobic resin and polymerizable monomer(s~ may be varied in a considerable range. It is, however, determined in 1-7~:99-30, preferably 5-50:95-50, on weight basis. This is because if the amount of said hydrophobic resin is too large, there is a tendency that stability of the resin particles in an aqueous composition be lowered and if the amount of the hydrophobic resin is too small, the desired effect of improvement in smoothness of coating cannot be attained therewith.
The inventors have now found that inclusion of hydrophobic resin or a combination of hydrophobic resin and hydrophobic solvent in resin particles is very effective for the improvements in coating appearance and especially smoothness and gloss, and in application characteristics and sag resistance of the coating composition.
That is, the presence of hydrophobic resin in the resin ~- particles may contribute to the formation of coating wherein comparatively small size of aggregates of resin particles , are stably and uniformly distributed in a water soluble resin phase, for which a highly glossy coating can be , .

obtained. ~oth of the hydrophobic resin and hydrophobic solvent are effectivè for the improvement in smoothness of the coating. When a phdrophobic melamine resin i5 us-ed, yield value of the coating composition is markedly increased and hence, a sag resistance is yreatly improved. The presence of a hydrophobic solvent in the resin particles i9 effective in the control of viscosity of coating composition at the coating and baking stayes, which may attribute to the ~ ' marked improvement in application characteristics such as pinholing and smoothness of coating.
In the present invention, thus obtained aqueous composition ` containing resin particles is compounded with a particular water soluble resin ~B) having a water tolerance of 4 or 1 more and a surface tension for 1~ w/w aqueous varnish of 51 J~ 15 dyne/cm or less, which is minutely stated in Japanese Patent Application Kokai No. 15567/83.
That is, the water soluble resin (B) must fulfil the ~ requirements:
¦ (1) that the water tolerance, expressed in terms of the 20 water dilution multiplicand of the water soluble resin for the solution incapable of reading out the defined type in the test wherein 59 of aqueous varnish having a common viscosity usually employed In the manufacture of a coating composition are correctly weighed in a 100 ml beaker, diluted with an increasing amount of deionized water, and a No. 1 type (26 point type) is read through the said beaker, is 4 or more, and r ~ 1 4 ~

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(2) that the Sur~ace tension o~ the solution obtained by dissolving the abovesaid aqueous varnish with deionized water to 1 wt% solid content, is 51 dyne/cm or less.
Any of the known water soluble resins customarily used in a water soluble type coating composition may be satisfactorily used providing fulfilliny the requirements stated hereinabove, and examples of such resins are an alkyd resin, a polyester resin, maleic oil, maleic polyalkadiene, and epoxy resin, an acrylic resin, a urethane resin, an aminoplast resin and the like.
However, in the present invention, the solid wei~ht ratio of the abovementioned resin particles to the total of said water soluble resins (A) and (~) should be in a range of 70:30 to 1:99, preferabl~ 60:40 to 1:99.
This is because, if the amount of water soluble resin is too low, it will cause deterioration of the dispersion stability of the resln powders and will damage the leveling properties of the coated film and if the amount of water soluble resin is too high, it will cause an excessive increase in the viscosity of the composition and give rise to a decrease in water resistance of the coated film.
However, in the abovementioned compounding ratio, there is no undesired increase in the viscosity of the composition.
Therefore, in the present invention, it is possible to increase the solid content of an aqueous coating composition and obtain the product which is excellent in application characteristics and storage stability and capable of ,, .

resultiny the coating with excellent ~ilm properties, gloss and smoothness.
The reasons why the present coating composition can give a coatiny which is far superior to the heretofore proposed ' 5 a~ueous coating compositions in respect of glos9 and smoothness have not been fully understood at the moment, but . the followiny miyht have a close connection therewith.
That is, since a particular water soluble resin (B) is selected and compounded with the aforesaid resin particles, ' 10 the particles are floated on the surface layer of the water soluble resin varnish and a uniform coating is easily obtained therefrom.
The present coating composition is, therefore, particularly useful as a top coat in an automobile or other industries where a higher level of gloss, e.g. 80 or more of 20 gloss, or smoothness of the coating is required.
The present coating composition may be used as a clear coating composition as desired, and however, in most applications, it is used as a color lacquer. In that case, coloring matter, crosslinking agent and other additives, 3 including antisagging agent, antiflooding agent, q anticratering agent, surface conditioner, antioxidant, light stabilizer, UV absorber, antisettle agent and the like, may !3 be added thereto.
The coating composition can be applied, as it is or after being diluted with water, in a conventional way, e.g.
spraying, dipping, brushing or the like, and dried or baked ~' .
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at an elevated temperature to yive the coating with excellent properties as hereinbe~ore stated.
The invention shall be now more fully explained in the following Examples. Unless otherwise being stated, all parts and % are by weight.
Synthetic Example 1 Preparation of water soluble resin varnish-l Into a 1 liter flask fitted with a stirrer, a thermoregulator and a condenser, were placed 76 parts of ethyleneglycol monobutyl ether, added with 61 parts of a monomer mixture comprising 45 parts of styrene, 63 parts of methyl methacrylate, 48 parts of 2-hydroxyethyl methacrylate, 117 parts of n-butyl acrylate, 27 parts of methacryl acid, 3 parts of lauryl mercaptane, and 3 parts of , ,- 15 azobisiisobutyronitrile and the combined mixture was heated under stirring to 120C. Thereafter, the remaining 245 parts of the abovesaid monomer mixture were dropwise added in 3 hours and then the mixture was stirred for 1 hour.
Next, 28 parts of dimethyl ethanolamine and 200 parts of deionized water were added to obtain an agueous acrylic resin varnish having a non-volatile content of 50%. Number average molecular weight of the contained resin was 6000.
Synthetic Example 2 Preparation of water soluble resin varnish-2 Into a 2 liter glass reactor fitted with a stirrer, a thermoregulator, and a decanter, were placed 69 parts of trimsthylol propane, 297 parts of neopentyl glycol, 91 parts f l~.~drogenated bisphenol A, 201 parts of tetrahydrophthalic acid, 155 parts of trimellitic anh~dride, and 10 parts of xylene and the mixture temperature was raised under stirring condition. The reaction was continued, while maintaining the temperature at 180 to 210C and removing the formed water from the reaction mixture, for 5 hours to obtain a polyester resin having an acid value of 55, a hydroxyl value of 100 and a nulnber average molecular weight of 1500. Then, 183 parts of ethyleneglycol monobutyl ether and 82 parts of dimethyl ethanol amine were added and the combined mixture . was diluted with 851 parts of deionized water to obtain an aqueous varni~h having a non-volatile content of 45~.
Synthetic Example 3 Preparation of resin particles containiny composition-l Into a 1 liter reaction vessel fitted with a stirrer, a thermoregulator and a condenser, were placed 320 parts of the water soluble resin varnish-l obtained in Synthetic Example 1, 3U0 parts of deionized water and 20 parts of butyl diglycol and the mixture was heated, under stirring, to 85 C. To this, a monomer solution of 40 parts of styrene, 40 parts of methyl methacrylate, 60 parts of 2-ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, and 4.0 parts of t-butyl peroxy 2-ethyl hexanate was dropwise added in 2 hours and thereafter, the realction was continued, under stirring, for additional 2 hours to obtain an aqueous composition containing resin particles whose non-volatile content was 40.0%.

Synthetic Example 4 nto the similar reaction vessel as used in Synthetic Example 3, were placed 356 parts of the water soluble resin varnish-2 obtained in Synthetic Example 2, 264 parts of ` 5 deionized water and 20 parts of butyl diylycol and themixture was heated, under stirring, to 85C. Thereafter, the same monomer solution as used in Synthetic Example 3 `~ were added and reacted as in Synthetic Example 3 to obtain `~ an aqueous composition containing resin particles, whose '? 10 non-volatile content was 4~.1%.
~ . Synthetic Example 5 7 Preparation of resin particles containing composition-3 Into the similar reaction vessel as used in Synthetic ~? Example 3, were placed 576 parts of the water soluble resin 15 varnish-l obtained in Synthetic Example 1 and 192 parts of . deionized water and the temperature was raised, under stirring, to 85-C. Next, a monomer solution of 3 parts of styrene, 8 parts of methyl methacrylate, 14 parts of 2-ethyl hexyl acrylate, 2 parts of 2-hydroxyethyl methacrylate and 20 0.4 part of azobisisobutyronitrile was dropwise added in 2 ? hours and the combined mixture was reacted, under stirring, : for 2 hours, to obtain an aqueous composition containing resin particles, whose non-volatile content was 40.0~.
Synthetic Example 6 i 25 Preparation of resin particles containing composition-4 Followiny the procedures of Synthetic Example 3, 256 parts of the water soluble resin varnish-l, 322 parts of deionized . .

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water and 30 parts of butyl diglycol were placed in a reactor, the mixture was, under stirring, heated to 85C, a . monomer solution consisting o~ 48 parts of styrene, 48 parts i of methyl methacrylate, 80 parts o 2-ethyl hexyl acrylate, 16 parts of 2-hydroxyethyl methacrylate and 2 parts of azobisisobutyronitrile was dropwise added in 2 hours and the combined mixture was reacted, under stirring, for 2 hours, to obtain an aqueous composition containing resin particles.
Synthetic Example 7 Preparation of resin particles containing composition-5 The same procedures as stated in Synthetic Example 3 were repeated excepting substituting the following for the monomer solution of Synthetic Example 3.
styrene 40 parts , 15 methyl methacrylate 40 1 2-ethyl hexyl acrylate 60 2-hydroxyethyl methacrylate 15 ethyleneglycol dimethacrylate 5 azobisisobutyronitrile 2 An aqueous composition containing resin particles and having a non-volatile content of 40.1% was obtained.
Synthetic Example 8 Preparation of resin particles containing composition-6 (comparative composition) Following the procedures of Synthetic Example 3, 128 parts of the water soluble resin varnish-l, 400 parts of deionized water and 16 parts of butyl diglycol were placed in a .. . .
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` 1 324224 ; reactor, the mixture was heated, under stirring, to 85C, a monomer solution consiqting of 64 parts of styrene, 64 parts , .
of methyl methacrylate, 100 parts of 2-ethyl hexyl acrylate, ~8 parts of 2-hydroxyethyl methacrylate and 3 parts of azobisisobutyronitrile was dropwise added in 2 hours and the ¦ combined mixture was reacted, under stirring, for 2 hours, to obtain an aqueous composition containing resin particles, whose non-volatile content was 40~.
(Outside of the invention, because the weight ratio of water 10 soluble resin (solid) to monomers is 20:80.) Synthetic Example 9 ' Preparation of comparative resin particles-l Into a 2 liter glass made reaction vessel fitted with a ~ stirrer, a thermoregulator, and a condenser, were placed ;~ 15 1100 parts of deionized water, which was then heated to 80C. To this, an aqueous solution of 6 parts of ammonium persulfate in 100 parts of deionized water and 5 parts of a monomer solution of 210 parts of methyl methacrylate, 75 parts of 2-ethyl hexyl acrylate and 15 partæ of n-dodecyl 20 mercaptane were dropwise added, under stirring, and thereafter, stirring was continued for 5 minutes. Then, the ~ remaining parts, i.e. 259 parts~ of the monomer solution 7 were dropwise added under stirring, and after stirring for 15 minutes, an aqueous solution of 1 part of ammonium 25 persulfate in 10 parts of deionized water was added and the ' reaction was continued for 1 hour to obtain a seed emulsion . having a non-volatile content of 20~.
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Into the simllar reaction vessel as used in the preparation of said se~d emulsion, were plac~d 300 parts of deionized water and 25 parts of said seed emulsion, and the mixture was heated to 80C. To this, an aqueous solution of 0.1 part of ammonium persulfate in 20 parts of deionized water was added, under gtirring, and then a pre-emulsion of 360 : parts of methyl methacrylate, lOS parts of 2-ethyl hexyl acrylate, 35 parts of 2-hydroxyethyl acrylate, 5 parts of n-dodecyl mercaptane, 200 parts of deionized water, 0.4 part of sodium dodecyl benzene sulfonate and 0.8 part of ammonium persulfate was dropwise added in 2 hours. After completion of said addition, the mixture was stirred for 30 minutes, added with an aqueous solution of 0.2 part of ammonium persulfate in 20 parts of deionized water and further stirred for l hour. Thus obtained emulsion had a non-3 volatile content of 48.5%, and the resin particles separated from the emulsion had an average diameter (measured by electron microscope) of 0.7~. The maximum grain diameter was 1.4~ and number average molecular weight of the resin was ~800.
Synthetic Example lO
Preparation of comparative resin particles-2 Into the similar reaction vessel as used in Synthetic Example 9, were placed 700 parts of deionized water and 10 parts of sodium dodecyl benzene sulfonate and the temperature was raised to 80C. To this, under stirring, 4.5 parts of ammonium persulfate were added and then a ~. .

monomer mixture oE 36~ parts of methyl methacrylate, 105 parts of ethyl hexyl acrylate, 35 part~ o~ hydroxyethyl acrylate and 1~ parts of n-dodecyl mercaptane was dropwise added in 2 hours. After elapsiny 15 minutes from the completion of said addition, an aqueous solution of 0.5 part of ammonium persul~ate in 50 parts o~ deionized water was added and the reaction was further continued, under stirring, for 1 hour. Thus obtained emulsion had a non-volatile content of 40% and the average grain diameter of the resin particles separated from the said emulsion was 0.19 ~, and number average molecular weight of the resin was ~200.
Synthetic Example 11 Preparation of comparative resin particles-3 Into the similar reaction vessel as used in Synthetic xample 9, were placed 900 parts of deionized water, 1.5 parts of Metrose 60 SH-50 ~methyl cellulose, trade mark, Shinetsu Kagaku Co.), 216 parts of methyl methacrylate, 63 parts of 2-ethyl hexyl acrylate, 21 parts of 2-hydroxyethyl acrylate, 6 parts of n-dodecyl mercaptane, and 6 parts of azobisisobutyronitrile, and the mixture was reacted, under stirring (rotation speed 250 rpm), at 65C for 7 hours.
Thus obtained suspension was filtered through 20U mesh wire net to obtain pearl particles having 20 to 600~ diameters, which was then pulverized in a ball mill for 24 hours to obtain resin microparticles having an average diameter of 18 and the maximum grain diameter of 45~. Number average , .

' 1 324224 molecular weight of the resin was 76~0.
Example 1 nto a 5~ cc stainless steel beaker, were placed lO.part~
of the water soluble resin varnish 3 shown in the following ; 5 Table 1, 1160 parts of the re~in particles containing composition-l obtained in Synthetic Example 3, and 15 parts of hexamethoxymethylol melamine and the mixture was stirred well to obtain a clear coating composition.
This composition was flow-coated on a glass plate and heat-~` 10 treated at 120~C for 20 minutes to obtain a clear coating,, which had a smooth surface and showed no change even after'~ dipping in a top water for 24 hours. The abovesaid composition was diluted with water to a Ford Cup #4 viscosity of 30 seconds and then spray-coated on a test 15 plate. The maximum film thickness showing no sayging in this test was 43~.
Comparative Example 1 A comparative clear coating composition was prepared as in xample 1, usiny 100 parts of the water soluble resin 20 varnish 3 and 15 parts of hexamethoxymethylol melamine, and diluted with water and spray-coated. The maximum film thickness showing no sagging with this coating composition ~ was less than 15 ~.
g The characteristics of the water soluble resins ~B) used in this and subsequent Examples and Comparative Examples are shown below.

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.

.: Examples 2 to 9 (Preparation of pigment paste) Into a 1.5 liter stainless steel vessel with a closed~cover, were placed 36 parts of the water soluble resin varnish 3, 5 320 parts of Rutile type titanium dioxide and 60 part-q of deionized water and the mixture was, after being predispersed in a stirrer with 500 cc of glass beads, dispersed well in a paint conditioner for 2 hours to obtain a pigment paste-l.
10 ~nother pigment paste-2 was prepared in a same way, by substituting the water soluble resin varnish-4 for the abovesaid varnish-3.
(Preparation of coating composition) Into a stainless steel vessel, the materials shown in the ~- 15 following Table 2 were placed in and the mixture was stirred well in a stirrer at a room temperature to obtain the . respective coating composition of Examples 2 to 9.

';
s 25 ., ; - 26 -:

:.
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, ~` 'C

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T , R, a ~i ~1 .'' ~, COmpAratiVe ~xamples 2 to 8 ; Using the same procedures as stated in Examples 2 to 9, but substitutiny the following materials for those of Examples 2 to 9, comparative coating compositions were prepared.

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:~ 20 .
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' ' ' ~ ` 1 324224 ach of tl~e coating compositions o~ Examples 2 to 9 and Comparative Examples 2 to 8 was diluted with deionized water to a Ford Cup #4 ViSc09ity of 30 seconds and the diluted composition was spray-coated on a steel plate. After : 5 setting for 5 minuteg, the coating was baked at 150C for 15 minutes to obtain a crosslinked coating.
~ The maximum film thickness showing no pinholes and the i maximum film thickness showiny no sagging were determined for the respective composition, and gloss value and smoothness of thus obtained coating were evaluated.
Evaluation standards are as follows: -f Application characteristics:
,. . Mark film thickness showing film thickness showing `f no pinholes (Jlm) no sagging (l1m) 3 15 ~ more than 50 more than 50 more than 40 to 50 more than 40 to 50 more than 30 to 40 more than 30 to 40 X 30 or less 30 or less gloss:
Mark 60 gloss 20 gloss ~ more than 93 more than 85 O more than 90 to 93 more than 75 to 85 A more than 80 to 90 more than 65 to 75 80 or less 65 or less 25 Smoothness: -excellent good no good ~ ' 1324224 ~, .

C
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i~

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;

Synthetic Example 12 Preuaration of resin particles containing composition-7 Into a 1 liter reaction vessel fitted with a stirrer,,a thermoreyulator and a condenser, were placed 320 parts of the water soluble resin varnish-l obtained in Synthetic Example 1, 300 parts of deionized water and 20 parts of butyl diglycol and the mixture was heated under Stirring to 85C. To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2-ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, 2 parts of azobisisobutyronitrile and lO0 parts of xylene was dropwise added in 2 hours, and the ` mixture was stirred Por additional 2 hours to obtain a : composition containing resin particles and having a non-... .
`~ 15 volatile content of 35.53.
Synthetic Example 13 Preparation of resin particles containing composition-8 Into a similar reaction vessel as used in Synthetic Example 12, were placed 356 parts of the water soluble resin varnish 20 2 obtained in Synthetic Example 2, 264 parts of deionized . water and 2U parts of butyl diylycol and the mixture was heated, under stirring, to 85C.
To this, the same monomer solution as used in Synthetic s Example 12 was dropwise added in 2 hours and the mixture was further stirred for 2 hours to obtain a composition (8) containing resin particles.
Synthetic Example 14 - ` 1 324224 Pre~aration of resin particles containing composition-9 using the same procedureg of Synthetic Example 12, 576 parts of the water soluble resin varnish 1 and 192 part~ of~
deionized water were placed ln a reactor and heated, under stirring, to 85C. To this, a monomer solution consistiny 1 of U parts of styrene, 8 parts of methyl methacrylate, 14 `.3 parts of 2-ethyl hexyl acrylate, 2 parts of 2-hydroxyethyl methacrylate, 0.4 part of azobisisobutyronitrile and 80 parts of xylene was dropwise added in 2 hours and the reaction was continued for additional 2 hours to obtain a Composition ~9) containiny resin particles and having a non-~ volatile content of 36.3%.
:~ Synthetic Example 15 Preparation of resin particles containing composition-10 ~`- 15 Using the same procedures of Synthetic Example 12, 320 parts ~ of the water soluble resin varnish 1, 322 parts of deionized `~ water and 20 parts of butyl diglycol were placed in a `i reactor and the mixture was heated, under stirriny, to 85C.
To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2-ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, 3 parts of azobisisobutyronitrile and 10 parts of isophorone was dropwise added in 2 hours and the reaction .3 was further continued for 2 hours to obtain a composition (10) containing resin particles. A non-volatile content of this composition was 38.4~.
3 Synthetic Example 16 ~3 ~ - 33 -.~ , , -` ~ ` 1 324224 Pre~aration of resin particles containiny composition-ll Usin~ the same procedures of Synthetic Example 12, 150 parts of the water soluble resin varnish 1 and 150 parts of-deionized water were placed in a reactor and heated, under stirring, to 8SC. To this, a monomer solution consisting of 40 parts oE styrene, 30 parts of methyl methacrylate, 50 parts of 2-ethyl hexyl acrylate, 1~ partS of 2-hydroxyethyl methacrylate, 1.5 parts of azobisisobutyronitrile and 20 parts of xylene was dropwise added in 2 hours and the .r 10 reaction was Eurther continued, under stirring, for 2 hours to obtain a compo9ition (11) containing resin particles.
The non-volatile content of the composition was 45.5~.
synthetic Example 17 Preparation of comparative resin particles containing composition-12 / Using the same procedures of Synthetic Example 12, 320 parts J of the water soluble resin varnish 1, 400 parts of deionized , water and 20 parts of butyl diylycol were placed in a reactor and the mixture was heated, under stirring, to 85C.
20 To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2-ethyl hexyl acrylate, Z0 parts of 2-hydroxyethyl r methacrylate, and 2 parts of azobisisobutyronitrile was dropwise added in 2 hours and the reaction was continued, 25 under stirring, for additional 2 hours to obtain a composition (12) containing resin particles. The non-- volatile content of the composition was 35.5%.

,: .
,,~ ~ . , ~' - ` 1 324224 Synthetic Example 18 Preparation of comparative resin particles-4 Into a 2 liter glass reactlon vessel fitted with a stirrer, a thermoregulator, and a condenser, were placed 1100 parts of deionized water and the temperature was raised to 80-C.
To this, an aqueous solution of 6 parts of ammonium persulfate and 100 parts of deionized water and 5 parts of a monomer mixture consisting of 21U parts of methyl methacrylate, 75 parts of 2-ethyl hexyl acrylate and 15 parts of n-dodecyl mercaptane were added and the combined mixture was stirred for 5 minutes. Thereafter, the remaining 25~ parts of said monomer mixture were dropwise added to the reactor in 1 hour. After completion of said addition, the mixture was stirred for additional 15 minutes, added with an aqueous solution of 1 part of ammonium persulfate and 10 parts of deionized water, and the combined mixture was further stirred and reacted for 1 hour to obtain a seed emulsion having a non-volatile content of 20%.
Into a similar reaction vessel as used herein, were placed 20 300 parts of deionized water and 25 parts of the aforesaid seed emulsion, and the mixture was heated to 80-C.
To this, an aqueous solution of 0.1 part of ammonium persulfate and 20 parts of deionized water was added and then a pre-emulsion consisting of 155 parts of styrene, 155 parts of methyl methacrylate~ 125 parts of 2-ethyl hexyl acrylate, 65 parts of 2-hydroxyethyl methacrylate, 0.4 part of sodium n-dodecylbenzene sulfonate, 0.8 part of ammonium persulfate and 180 p~rts of xylene was dropwise added in 2 hours. AEter completion of said addition, stirring was continued for 30 minutes and at this stage, an aqueous solution of 0.2 part of ammonium persulfate and 20 parts of deionized water was added and the combined mixture was further stirred and reacted for 1 hour to obtain an emulsion having a non-volatile content of 41.2%. The mean diameter of the resin particles contained was 0.7~1 (by electromicro-scopic determination) and the maximum grain diameter was lO 0.4 ~. The number average molecular weight of the resin was 9800.
Examples 10 to 15 Into a stainless steel vessel, the materials shown in the ~, following Table 5 were placed and stirred will at a room 1 15 temperature to obtain the respective coating compositions of 3 ~xamples 10 to 15.

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: Comparative Examples 9 to 11 Using the same procedures of Example 10, but usin~ the materials shown in the following Table 6, comparative.
coatlng compositlon= were prepared.

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. .

. -; . .
.. , Each of tlle coating compositions obtained in Examples 10 to 15 and Comparatlve Examples 9 to 11 was diluted with deionized water to a ~ord Cup #4 viscosity of 30 secohds, and the diluted composition was spray-coated onto a steel plate, and a~ter setting for 5 minutes, baked at 150C Por 15 minues to obtain a cured coating. The glo~s value, and smoothness of the coating and time stability of the respective coating composition were evaluated and the results were shown in Table 7.

. 10 ' 15 ' .

~; Table 7 coating appearance time stability s 60 ~loss 20 yloss smoothness ~5 Example 10 ~ ~ excellent excellent `` 12 ~5 13 , 15 ~ O ~ ~
~, Comp. Ex. 9 O ~ no good excellent ~ X good good no good ~' ' , .

' .

1 3242~4 ~ynthetic Example 19 Preparation of hydrophobic resin varnish Into a 1 liter reaction vessel fitted with a stirrer~ a ! thermoregulator and a condenser, were ulaced 25 part~ of xylene and the temperature was raised, un~er stirrin~, to 125C. To this, a monomer solution consisting of 30 parts of styrene, 15 parts of methyl methacrylate, 40 parts of 2-ethyl hexyl methacryalte, 15 parts of 2-hydroxyethyl methacrylate and 4 parts o azobisisobutyronitrile was 1~ dropwise added in 2 hours and thereafter, the combined mixture was stirred for 2 hours to obtain an acrylic, hydrophobic resin varnish having a non-volatile content of 80~. The number averaye molecular weight of the formed resin was 5000.
Synthetic Example 20 Prepartion of hydrophobic resin encapsulated resin particles containing composition-13 Into a 1 liter reaction vessel fitted with a stirrer, a thermoreyulator and a condenser, were placed 320 parts of the water soluble resin varnish 1 obtained in Synthetic Example 1, 300 parts of deionized water and 20 parts of butyl diglycol, and the mixture was heated, under stirring, to 85C. To this, a monomer solution consisting of 5U parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2-ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl - methacrylate, 2 parts of azobisisobutyronitrile and 60 parts of the hydrophobic resin varnish obtained in Synthetic .,~ .. .... _ ,.. ..... .. . .. , ,... ... _. . .. ..

, ~ ^' 1 324224 ;;
xample 19 was dropwise added in 2 hours and the combined mixture was stirred for 2 hours to obtain a composition , containing hydrophobic resin encapsulated resin particles.
The non-volatile content of the composition was 42.6%.
.~ 5 Synthetic Example 21 Preparation of hydrophobic resin encapsulated resin particles containing composition-14 Using the same procedures as stated in Synthetic 10 Example 20, 356 parts of the water soluble resin varnish 3 obtained in Synthetic Example 2, 264 parts of deionized water and 20 parts of butyl diglycol were placed in a reactor and the mixture was heated to 85C. Then, the similar monomer solution as used in Synthetic Example 19 was dropwise added in 2 hours and the combined mixture was stirred for 2 hours to obtain a composition containin~ -hydrophobic resin encapsulated resin particles. The non-volatile content of the composition was 42.6%.
:J
Synthetic Example 22 Preparation of hydrophobic resin encapsulated resin particles containing composition-15 As in Synthetic Example 20, 320 parts of the water soluble resin varnish-l, 300 parts of deionized water and 20 parts of butyl diglycol were placed in a reactor and the mixture was heated, under stirring, to 85C. Then a monomer solution consisting of 8 parts of styrene, 8 parts of methyl methacrylate, 10 parts of 2-ethyl hexyl methacrylate, 6 parts of 2-hydroxyethyl methacrylate, 1.5 parts of azobi-sisobutyronitrile and 20 parts of hexamethoxy methylol mela-mine resin was dropwise added in 2 hours and the combined mixture was stirred for 2 hours to obtain a composition containing hydrophobic resin encapsulated resin particles.
The non-volatile content of the composition was 49.0%.

, . ~

- Synthetic Example 23 `~ Preparation of hydrophobic resin encapsulated resin ;`( particles containing composition-16 ~' As in Synthetic Example 20, 320 parts of the water soluble resin varnish l, 400 parts of deionized water and 10 parts of butyl diglycol were placed in a reactor and the ` mixture .~
', 10 ~, `~;
'~ 1 5 .
~ 25 `

~ 30 Y, à 35 43a -', ~,. . . .

.

~` ` 1 324224 was heatQd, under s~irrlng, to 85C. To this, a monomer solution consistiny of 75 yarts of styrene, 75 parts of methyl methacrylate, 60 parts of 2-ethyl hexyl metha~rylate, 30 ~arts of 2-hydroxyethyl methacrylate, 3 parts of azobisisobutyronitrile and 24 parts of Epicoat lU~l ~Shell Chemical) was dropwise added in 2 hours and the combined mixture was stirred for 2 hours to obtain a composition containiny hydrophobic resin encapsulated resin particles.
The non-volatile content of the composition was 42.6~.
Synthetic Example 24 Preparation of comparative resin particles containing composition-17 As in Synthetlc Example 2U, 320 parts of the water soluble resln varnish l, 400 parts of deionized water and 20 parts of butyl diglycol were placed in a reactor and the mixture ; was heated, under stirring, to 85C. To thisr a monomer J solution consisting of 5U parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2-ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, and 2 parts of azobisisobutyronitrile was dropwise added in 2 hours and the combined mixture was stirred for 2 hours to obtain a 3 composition containing resin particles. The non-volatile content of the composition was 35.5%.
J, Synthetic Example 25 Preparation of comparative resin particles 5 Into a 2 liter glass reaction vessel fitted with a stirrer, a thermoregulator and a condenser, were placed llO0 parts of ` ~ 1 324224 deionized water and the content was heated, under stirring, ~ to 80C. To this, an aqueous solution of 6 parts of ; ammonium persulfate in 100 parts of deionized water and 5 ` parts of the monomer mixture of 210 parts of methyl methacrylate, 75 parts of ~-ethyl hexyl acrylate and 15 3 parts of n-dodecyl mercaptane were added, under stirring, ;` and the combined mixture was stirred for 5 minutes. While u stirring, the rsmaininy 259 parts of the monomer mixture ; were dropwise added and the combined mixture was stirred for !. 10 additional 15 minutes.
Thereafter, an aqueous solution of 1 part of ammonium persulEate in 10 parts of deionized water was added and the mixture was reacted, under stirring, for 1 hour to obtain a seed emulsion haviny a non-volatile content of 20%.
~`~ 15 Into a similar reaction vessel as stated hereinabove, were r~ placed 300 parts of deionized water and 25 parts of the t abovesaid seed emulsion, and the temperature was raised to `A 80C. To this, an aqueous solution of 0.1 part of ammonium peræulfate in 2U parts of deionized water was added and then a pre-emulsion consisting of 155 parts of styrene, 155 parts of methyl methacrylate, 125 parts of 2-ethyl hexyl acrylate, 65 parts of 2-hydroxyethyl methacrylate, 5 parts of n-dodecyl mercaptane, 200 parts of deionized water, 0.4 part of sodium dodecyl benzene sulfonate, 0.8 part of ammonium r; 25 persulfate and 15U parts of the hydrophobic resin varnish obtained in Synthetic Example 19 was dropwise added in 2 -i hours. After stirring for 30 minutes, an aqueous solution ,~., , ~

.

.
- ~ ' , .

:`;
of 0.2 part of ammonium persulfate in 20 parts of deionized water was added and the combined mixture was reacted under stirring for 1 hour to obtain an emulsion containing~resin articles. The non-volatile content of the emulsion was S 41.2%. l'he resin particles were separated from thus obtained emulsion. ~y an electron microscopic examination, it was ound that the averaye grain diameter of said ~articles was 0.7~ and the maximum grain diameter was 1.4~.
The number averaye molecular weiyht of the resin was 9800.
. 10 Examples 16 to 20 ~ Into a stainless steel vessel, the materials shown in the ;~ followiny Table 8 were placed in and the mixture was stirredwell in a stirrer at a room temperature to obtain the respective coating composition of Examples 16 to 20.

~' ~ 20 ~' 3~

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`` `~ ` 1 324224 Comparative Examples 12 to 14 Using the same procedureg as stated in Examples 16 to 20, - but substitutiny the following materials for those o~
Examples 16 to 20, comparative coating compositions were prepared.

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., 15 .~

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. - 48 .i ~ -,. .

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`` ` ` 1 324224 Each of the coating compositions of Examples 16 to 20 and Comparative Examules 12 to 14 was diluted with deionized water to a Ford Cup #4 viscosity of 3~ seconds and the diluted composition was spray-coated on a steel plate.
After setting for S minutes, the coating was baked at 150-C
for 15 minutes to obtain a crosslinked coating. The maximum film thickness showing no pinholes and the maximum film thickness showiny no sagginy were determined for the respective composition, and gloss value and smoothness of thus obtained coatiny were evaluated. The results are shown in Table 10.

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Table 10 coatiny appearance time stability 60 gloss 20 gloss smoothness Example 16 ~ ) excellentexcellent O 1` 1`
1' 20 .
? comp. Ex. 12 O ~ no yood excellent 13 ~ X good good 14 ~ o good 1 .
,.~

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Claims (15)

1. An aqueous coating composition comprising as resinous vehicle (1) an aqueous composition containing resin particles obtained by polymerizing at least one .alpha.,.beta.-ethylenically unsaturated monomer in an aqueous medium and in the presence of an aqueous resin (A) with the help of an organic initiator, in which the solid weight ratio of said aqueous resin to said monomer is 35-95:65-5, and (2) an aqueous resin (B) having a water tolerance of 4 or more and a surface tension for a 1 % w/w aqueous resin solution of 51 dyne/cm or less, the solid weight ratio of said resin particles to the total of said aqueous resins (A) and (B) being 70-1:30-99, wherein the aqueous resins (A) and (B) each is selected from the group consisting of a polyester resin, an alkyd resin, an acryl resin, an acryl modified polyester resin and an acryl modified alkyd resin.

2. A composition according to claim 1, wherein the organic initiator is selected from the group consisting of a diacyl peroxide, a hydroperoxide, an alkyl peroxide, an azo compound, a disulfide, and a sulfinic acid.

3. A composition according to claim 1, wherein the aqueous medium contains an organic solvent.

4. A composition according to claim 1, wherein the .alpha.,.beta.-ethylenically unsaturated monomer includes a crosslinking monomer having in its molecule at least 2 radically polymerizable, ethylenically unsaturated bondings.

5. An aqueous coating composition comprising as resinous vehicle (1) an aqueous composition containing solvent encapsulated resin particles obtained by polymerizing a mixture of at least one .alpha.,.beta.-ethylenically unsaturated monomer and at least one hydrophobic solvent in an aqueous medium and in the presence of an aqueous resin (A) with the help of an organic initiator, in which the weight ratio of said aqueous resin solid to the monomer is 35-95:65-5, and (2) an aqueous resin (B) having a water tolerance of 4 or more and a surface tension for 1 % w/w aqueous resin solution of 51 dyne/cm or less, the solid weight ratio of said resin particles to the total of said aqueous resins (A) and (B) being 70-1:30-99, wherein the aqueous resins (A) and (B) each is selected from the group consisting of a polyester resin, an alkyd resin, an acryl resin, and acryl modified polyester resin and an acryl modified alkyd resin.

6. A composition according to claim 5, wherein the weight ratio of said hydrophobic solvent to .alpha.,.beta.-ethylenically unsaturated monomer is 80-3:20-97.

7. A composition according to claim 5, wherein the organic initiator is selected from the group consisting of a diacyl peroxide, a hydroperoxide, an alkyl peroxide, an azo compound, a disulfide, and a sulfinic acid.

8. A composition according to claim 5, wherein the aqueous medium contains an organic solvent.

9. A composition according to claim 5, wherein the .alpha.,.beta.-ethylenically unsaturated monomer includes a crosslinking monomer having in its molecule at least 2 radically polymerizable, ethylenically unsaturated bondings.

10. An aqueous coating composition comprising as resinous vehicle (1) an aqueous composition containing hydrophobic resin encapsulated resin particles obtained by polymerizing a mixture of at least one .alpha.,.beta.-ethylenically unsaturated monomer and a hydrophobic resin or both hydrophobic resin and hydrophobic organic solvent, in an aqueous medium and in the presence of an aqueous resin (A), with the help of an organic initiator, the weight ratio of said aqueous resin solid to the monomer being 35-95:65-5, and (2) an aqueous resin (B) having a water tolerance of 4 or more and a surface tension for 1 % w/w aqueous resin solution of 51 dyne/cm or less, the solid weight ratio of said resin particles to the total of said aqueous resins (A) and (B) being 70-1:30-99, wherein the aqueous resins (A) and (B) each is selected from the group consisting of a polyester resin, and alkyd resin, an acryl resin, an acryl modified polyester resin and an acryl modified alkyd resin.

11. A composition according to claim 10, wherein the organic initiator is selected from the group consisting of a diacyl peroxide, a hydroperoxide, an alkyl peroxide, an azo compound, a disulfide, and a sulfinic acid.

12. A composition according to claim 10, wherein the hydrophobic resin is selected from the group consisting of an alkyd resin, a polyester resin, an acryl resin, an acryl modified alkyd resin, an acryl modified polyester resin, an epoxy resin, an aminoplast resin, a polyether resin, a petroleum resin, a silicon resin, a polyurethane resin, a fluorinated resin, and a cellulose series resin.

13. A composition according to claim 10, wherein the aqueous medium contains an organic solvent.

14. A composition according to claim 10, wherein the ethylenically unsaturated monomer includes a crosslinking monomer having in its molecule at least 2 radically polymerizable, ethylenically unsaturated bondings.

15. A composition according to claim 10, wherein the solid weight ratio of said hydrophobic resin to said unsaturated monomer is 1/99 to 70/30.