AU593282B2

AU593282B2 - An aqueous coating composition

Info

Publication number: AU593282B2
Application number: AU62693/86A
Authority: AU
Inventors: Shinichi Ishikura; Teruaki Kuwajima; Hiroshi Miwa; Hideyoshi Noda
Original assignee: Nippon Paint Co Ltd
Current assignee: Nippon Paint Co Ltd
Priority date: 1986-02-05
Filing date: 1986-09-12
Publication date: 1990-02-08
Anticipated expiration: 2006-09-12
Also published as: GB2187465A; GB8622582D0; AU6269386A; GB2187465B; DE3632617A1; CA1324224C

Description

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COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION FOR OFFICE USE Form Short Title: 6 /l6 Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: 593282 dL C10" 1 4; 11 i. t 25 0 09 t t*i t cc 4I rt t:~ C 1 C c c TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: NIPPON PAINT CO., LTD.

1-2, Oyodokita 2-chome, Oyodo-ku, OSAKA-SHI, JAPAN Teruaki Kuwajima Hiroshi Miwa Hideyoshi Noda and Shinichi Ishikura GRIFFITH HASSEL FRAZER 71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: AN AQUEOUS COATING COMPOSITION The following statement is a full description of this invention, including the best method of performing it known to me/us:- 7273A:rk 1 -r I 1 The present invention relates to an aqueous coating composition which is useful as a top coat.

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 inventors had formerly found that by the selective use S"

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V t a 4 r r C 1A- 4' r 7 of a particular water soluble resin which will fulfil the requirements that the water tolerance, expressed in terms of water dilution multiplicand of the resin for the solution 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 26 point typed letter in printed matter is read through the said beaker, is 4 or more, o o 10 and the surface tension calculated for a 1% w/w aqueous solution is 51 dyne/cm or less, it is possible to formulate o oe* 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 c ,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 i developed to obtain the better quality powders to be compouil-ed with a water soluble resin since then. In facts, Scertain improvements have been attained with these products /i -7-n h -u dflrc\QZ -2in 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 Ia,(-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 r and that when a water soluble radical initiator was selected, said initiator was likewise remained at the end I 15 portions of the polymer chain, giving undesired effect on 1 film properties, too. Thus, an additional improvement has *been longed for.

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.

S The present invention seeks to mitigate the aforementioned problems by providing a high quality, aqueous coating composition which has, enhanced storage stability, application characteristics and film properties (including water resistance and the like) and i -3i

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L. A T i q 1 1 'lot 1. -U1U-~ which has far improved gloss and smoothness,and which is particularly useful as a top coat for automobile bodies and other articles.

Accordingly, the present invention provides an aqueous coating composition comprising as resinous vehicle a mixture of an aqueous, resin particles containing composition obtained by polymerizing at least one a,P-ethylenically unsaturated monomer in an aqueous medium and in the presence of an aqueous resin and an organic initiator, the solid weight ratio of said aqueous resin to said monomer being between 35:65 and 95:5, and an aqueous resin having a water tolerance of 4 or Smore and a surface tension for a 1% w/w aqueous resin 6 15 solution of 51 dyne/cm or less, *o a the solid weight ratio of said resin particles to the o total of said aqueous resin and aqueous resin being *o between 70:30 and 1:99.

As the aqueous resin any of the members 0Gi 0e 0 00 f 0 0 0; isr 0cr 4,, eLI S4 customarily used in a coating 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 aqueous resins as well as the aqueous resins hereinafter mentioned, are not necessarily completely soluble in water, but rather, they may be either partially soluble or partially dispersible in water. Therefore, the expression i "aqueous resin" as used herein denotes both completely and partially water soluble resins together with water reducible .o 15 or dilutable resins.

Similarly, the expression "aqueous coating" as used herein denotes both completely and partially water soluble coatings together with water reducible or dilutable coatings, and the expression "aqueous medium" as used herein denotes a medium composed principally of water.

As already mentioned, the present resin particles are prepared by the polymerization of a,p-ethylenically I unsaturated monomer(s) in an aqueous medium and in the presence of a comparatively large amount of said aqueous resin in place of a surfactant or emulsifier as used in j 25 a conventional emulsion polymerization.

I At this time, the solid weight ratio of said aqueous resin to said monomer is determined in a range of 35:65 to 95:5. This is because, if the amount of said aqueous resin 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 customarily used in the preparation of acryl resins may be satisfactorily used, each in singularily or combination of two or more. Examples of these monomers are as follows.

1) carboxyl containing monomer: for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid and the like, S2) hydroxyl containing monomer: 4, for example, 2-hydroxyethyl acrylate, hydroxypropyl o, e acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl S, methacrylater hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, methallyl alcohol and the like, Se 3) nitrogen containing alkyl (meth) acrylates: It for example, dimethyl aminoethyl acrylate, dimethyl aminoethyl methacrylate and the like, 4) polymerizable amides: for example, acrylamide, methacrylamide and the like, 4 OA 5) polymerizable nitriles: '.444.

for example, acrylonitrile, methacrylonitrile and the like, 6) alkyl acrylates and alkyl methacrylates: for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethyl hexyl acrylate and the like, 7) polymerizable aromatic compounds: -6- 7 ~r-au~ran~

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for example, styrene,c dt-methyl styrene, vinyl toluene, t-butyl styrene and the like, 8) c1-olefins: for example, ethylene, propylene and the like, 9) vinyl compounds: for example, vinyl acetate, vinyl propionate and the like, diene compounds: for example, butadiene, isoprene and the like.

As a part of said d,A-ethylenically unsaturated monomers, one may use a crosslinking monomer having 2 or more tc S* 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, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane dtriacrylate, 1,1,1-trishydroxymethylethane dimethacrylate, 1,1,1-trishydroxymethylethane dtrimethacrylate, S1,1,1-trishydroxymethylprethopane trimethacrylate, 1,l,l-trishydroxymethylpropane dtiacrylate, 1,1,1-trishydroxymethyl propane dimethacrylate, 1,1,1-trishydroxymethyl propane dtrimethacrylate, 1,1, -trishydroxyme thyl propane trime thacrylate triallyl cyanurate, triallyl isocyanurate, triallyl 10 trimellitate, diallyl terephthalate, diallyl phthalate, o. o divinyl benzene 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 wa r 1 resin and at that time, an organic initiator may advantageously be used.

As the organic initiator, use can be made of such members as I Idiacyl peroxides acetyl peroxide, lauroyl peroxide, benzoyl peroxide and the like), hydroperoxides cumene hydroperoxide and the like), alkyl peroxides di-tbutyl peroxide, t-butyl peroxy 2-ethyl hexanoate, t-butyl perpiperate, t-butyl perbenzoate and the like), azo Cr,..

compounds 2,2-azobis isobutyronitrile and the like), disulfides tetramethyl thiuram disulfide and the like), and sulfinic acids p-toluene sulfinic acid and the like).

Among them, particular preference is givent to a water

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4 nsoluble organic initiator as azobis isobutyronitrile, 0 1 7 (C"4r i -8- 00A "il -r-v t V u i 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 is prepared by a method wherein- c,4/-ethylenically unsaturated monomers are polymerized in a mixture of water and an organic solvent and in the presence of a large quantity of aqueous resin and. a water insoluble organic initiator, and thus obtained composition is compounded with an aqueous resin hereinafcer mentioned, a particularly useful aqueous coating composition can be obtained, which is less foaming, hardly give pinholes, less sagging and capable of resulting a coating with higher gloss and far improved smoothness. Therefore, in a preferred embodiment of the a.

invention, the aqueous composition is prepared in a a reaction medium comprising water and an appropriate amount of a common organic solvent customarily used in the 0o 20 preparation of solvent type coating composition.

Thus, in the present invention, it is essential that an aaueous composition containing resin particles be prepared a by the polymerization of at least one d,4-ethylenically e4 unsaturated monomer in an aqueous medium optionally blended a a with an organic solvent and in the presence of a large quantity of an aqueous resin and in the presence of an organic initiator, preferably a water insoluble organic 12'ii ii rr, NTo -9- 1

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i 1~ j 71 0 0 *000 -Q 00 00 0 0 00 0c i 0o 0 00r a initiator. In this aqueous composition, thew-at--K=cE-te resin 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 W le resin used.

Since the aqueous composition does not include any of the undesired water-soluble by-products, ionic substances and other impurities, and the Ftezzs-o1ube 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.

The inventors have also found that when o,f-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 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 containing solvent encapsulated resin particles obtained by the polymerization of a mixture of at least one o,3- 0 0 0 too, 0 I' 00 1010; 0 it Os i 0 0t

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-v A~ nc '~'NrO~ 10 ethylenically unsaturated monomer and at least one hydrophobic solvent in an aqueous medium and in the presence ofj-a .s -sF lble resin 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,/3-ethylenically unsaturated monomer and a hydrophobic resin or both hydrophobic resin and hydrophobic organic solvent, in an aqueous medium and in the presence of =-NdiL sae resin and an organic initiator.

0o f In the abovesaid embodiment, as the hydrophobic solvent, any of the organic solvents having solubility in 20°C water of ea«* 10 weight or less may be satisfactorily used, providing o having an optimum evaporation rate and boiling point seeing from the view point of application characteristics of the coating composition. Examples of such organic solvents are heptane, hexane, n-octane, iso-octane, decane, ligroin, kerosine, toluene, xylene, naphthalene, isobutanol, nbutanol, 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 S- 11 Ll~l_ i. i ill__ l III--II_ XYU~~ 1131~-.-- #9 #9 91 9 9 #9 #9 46 9o 4 9*p 9 I #9 immiscible nature. By the 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 va *ed in a wider range.

It is, however, generally determined in 80:20 to 3:97, preferably 60:40 to 10:90, on weight basis. This is because 10 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 significant 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 stages, and hence considerable improvements in application characteristics and coating appearance and especially smoothness can be attained therewith.

d,,/-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 4 t 4 4 t I4 994' 4 4e 12

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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 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 1-70:99-30, preferably 5-50:95-50, on "I 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 0 coating cannot be attained therewith.

t t toC 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 13r A; obtained. Both of the hydrophobic resin and hydrophobic solvent are effective for the improvement in smoothness of the coating. When a phdrophobic melamine resin is used, yield value of the coating composition is markedly increased and hence, a sag resistance is greatly improved. The presence of a hydrophobic solvent in the resin particles is effective in the control of viscosity of coating composition at the coating and baking stages, 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 aqueous resin having a water tolerance of 4 or more and a surface tension for 1% w/w aqueous varnish of o 15 51 dyne/cm or less.

That is, the aqueous resin must fulfil the requirements: that the water tolerance, expressed in terms of the water dilution multiplicand of the aqueous resin for the solution incapable of reading out the defined type in the test wherein 5g of aqueous varnish having a common viscosity usually employed (solid content 30%) in the manufacture of a €coating composition are correctly weighed in a 100 ml beaker, diluted with an increasing amount of deionized 25 water, and a 26 point typed letter in printed matter is read through the said beaker, is 4 or more, and 0360s/as 14 A

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3 I _c 44 0e o 00 that the surface tension of 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 jw ol-h!e resins customarily used in an (vaz sa~a le type coating composition may be satisfactorily used providing fulfilling 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 weight ratio of the abovementioned resin particles to the total of said Jcnn 4,=,blie resins and should be in a range of 70:30 to 1:99, preferably 60:40 to 1:99.

This is because, if the amount of at e soubl resin is too low, it will cause deterioration of the dispersion stability of the resin powders and will damage the leveling properties of the coated film and if the amount of\W .bl 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 f- -15 4a .4 1 0 44 0 0 4444 04* i~ resulting the coating with excellent film properties, gloss and smoothness.

The reasons why the present coating composition can give a coating which is far superior to the heretofore proposed aqueous coating compositions in respect of gloss and smoothness have not been fully understood at the moment, but the following might have a close connection therewith.

That is,. since a particular o e resin is selected and compounded with the aforesaid.resin particles, the particles are floated on the surface layer of the-wter ~ulubteresin 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, including antisagging agent, antiflooding agent, anticratering agent, surface conditioner, antioxidant, light stabilizer, UV absorber, antisettle agent and the like, may be added thereto.

The coating composition can be applied, as it is or after 4 being diluted with water, in a conventional way, e.g.

spraying, dipping, brushing or the like, and dried or baked 16- i. LCC- dA

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at an elevated temperature to give the coating with excellent properties as hereinbefore 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 ja=t- resin varnish-1 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 methicryl acid, 3 parts of lauryl mercaptane, and 3 parts of azobisiisobutyronitrile and the combined mixture was heated under stirring to 120°C. 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 20 deionized water were added to obtain an aqueous 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 a-t ol; resin varnish-2 Into a 2 liter glass reactor fitted with a stirrer, a thermoregulator, and a decanter, were placed 69 parts of trimethylol propane, 297 parts of neopentyl glycol, 91 parts 11 t e s v. eL I S r I r, r CC\rZL 17 -'251 of hydrogenated bisphenol A, 201 parts of tetrahydrophthalic acid, 155 parts of trimellitic anhydride, 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 210°C 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 number 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 varnish having a non-volatile content of Synthetic Example 3 S' Preparation of resin particles containing composition-1 Into a 1 liter reaction vessel fitted with a stirrer, a 3 thermoregulator and a condenser, were placed 320 parts of I the$.LI.il resin varnish-1 obtained in Synthetic we Example 1, 300 parts of deionized water and 20 parts of butyl diglycol and the mixture was heated, under stirring, to 85 0 C. To this, a monomer solution of 40 parts of S styrene, 40 parts of methyl methacrylate, 60 parts of 2- 4" t} Iethyl hexyl acrylate, 20 parts of 2-hydroxyethyl Smethacrylate, and 4.0 parts of t-butyl peroxy 2-ethyl hexanate was dropwise added in 2 hours and thereafter, the reaction was continued, under stirring, for additional 2 hours to obtain an aqueous composition containing resin particles whose non-volatile content was 40.0%.

18 Synthetic Example 4 Into the similar reaction vessel as used in Synthetic Example 3, were placed 356 parts of the:t.L sluble resin varnish-2 obtained in Synthetic Example 2, 264 parts of deionized water and 20 parts of butyl diglycol and the mixture was heated, under stirring, to 85"C. 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 non-volatile content was 40.1%.

Synthetic Example Sot Preparation of resin particles containing composition-3 Into the similar reaction vessel as used in Synthetic 0 Example 3, were placed 576 parts of the' wa 1 gi resin varnish-1 obtained in Synthetic Example 1 and 192 parts of deionized water and the temperature was raised, under stirring, to 85 0 C. Next, a monomer solution of 8 p~rts of styrene, 8 parts of methyl methacrylate, 14 pa? of 2-ethyl hexyl acrylate, 2 parts of 2-hydroxyethyl methacrylate and 0.4 part of azobisisobutyronitrile was dropwise added in 2 S" hours and the combined mixture was reacted, under stirring, S* for 2 hours, to obtain an aqueous composition containing resin particles, whose non-volatile content was 40.0%.

Synthetic Example 6 Preparation of resin particles containing composition-4 Following the procedures of Synthetic Example 3, 256 parts of the,. resin varnish-1, 322 parts of deionized S- 19 "WTSr *W i water and 30 parts of butyl diglycol were placed in a reactor, the mixture was, under stirring, heated to 85"C, a monomer solution consisting of 48 parts of styrene, 48 parts of methyl methacrylate, 80 parts of 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 The same procedures as stated in Synthetic Example 3 were 0 0 repeated excepting substituting the following for the 0 monomer solution of Synthetic Example 3.

0 styrene 40 parts methyl methacrylate 2-ethyl hexyl acrylate 2-hydroxyethyl methacrylate ethyleneglycol dimethacrylate 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 (k s bl resin varnish-1, 400 parts of deionized water and 16 parts of butyl diglycol were placed in a 20 reactor, the mixture was heated, under stirring, to 85°C, a monomer solution consisting of 64 parts of styrene, 64 parts of methyl methacrylate, 100 parts of 2-ethyl hexyl acrylate, 28 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 (Outside of the invention, because the weight ratio of water soluble resin (solid) to monomers is 20:80.) Synthetic Example 9 oo Preparation of comparative resin particles-i Into a 2 liter glass made reaction vessel fitted with a o* stirrer, a thermoregulator, and a condenser, were placed 1100 parts of deionized water, which was then heated to 80"C. To this, an aqueous solution of 6 parts of ammonium Spersulfate in 100 parts of deionized water and 5 parts of a monomer solution of 210 parts of methyl methacrylate, parts of 2-ethyl hexyl acrylate and 15 parts of n-dodecyl 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 were dropwise added under stirring, and after stirring for minutes, an aqueous solution of 1 part of ammonium persulfate in 10 parts of deionived water was added and the reaction was continued for 1 hour to obtain a seed emulsion having a non-volatile content of 21 Into the similar reaction vessel as used in the preparation of said seed emulsion, were placed 300 parts of deionized water and 25 parts of said seed emulsion, and the mixture was heated to 80 0 C. To this, an aqueous solution of 0.1 part of ammonium persulfate in 20 parts of deionized water was added, under stirring, and then a pre-emulsion of 360 parts of methyl methacrylate, 105 parts of 2-ethyl hexyl acrylate, 35 parts of 2-hydroxyethyl acrylate, 5 parts of ndodecyl mercaptane, 200 parts of deionized water, 0.4 part of sodium dodecyl benzene sulfonate and 0.8 part of ammonium 4, 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 1 hour. Thus obtained emulsion had a nonvolatile content of 48.5%, and the resin particles separated from the emulsion had an average diameter (measured by electron microscope) of The maximum grain diameter I was 1.4/ and number average molecular weight of the resin was 9800.

Synthetic Example Preparation of comparative resin particles-2 Into the similar reaction vessel as used in Synthetic Example 9, were placed 700 parts cf deionized water and parts of sodium dodecyl benzene sulfonate and the temperature was raised to 80 0 C. To this, under stirring, parts of ammonium persulfate were added and then a 22 monomer mixture of 360 parts of methyl methacrylate, 105 parts of ethyl hexyl acrylate, 35 parts of hydroxyethyl acrylate and 10 parts of n-dodecyl mercaptane was dropwise added in 2 hours. After elapsing 15 minutes from the completion of said addition, an aqueous solution of 0.5 part of ammonium persulfate in 50 parts of deionized water was added and the reaction was further continued, under stirring, for 1 hour. Thus obtained emulsion had a nonvolatile content of 40% and the average grain diameter of the resin particles separated from the said emulsion was 0.19au, and number average molecular weight of the resin was 8200.

Synthetic Example 11 Preparation of comparative resin particles-3 Into the similar reaction vessel as used in Synthetic Example 9, were placed 900 parts of deionized water, parts of Metrose 60 SH-50 (methyl cellulose, trade mark, Shinetsu Kagaku 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 65"C for 7 hours.

Thus obtained suspension was filtered through 200 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 45A,. Number average 23 0- molecular weight of the resin was 7600.

Example 1 Into a 500 cc stainless steel beaker, were placed 10 parts of the p_-tIts h.e resin varnish 3 shown in the following Table 1, 1160 parts of the resin particles containing composition-1 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 heattreated at 120"C for 20 minutes to obtain a clear coating, S, which had a smooth surface and showed no change even after dipping in a top water for 24 hours. The abovesaid ot composition was diluted with water to a Ford Cup #4 8 viscosity of 30 seconds and then spray-coated on a test 15 plate. The maximum film thickness showing no sagging in this test was 43A..

Comparative Example 1 A comparative clear coating composition was prepared as in Example 1, using 100 parts of the wea e Ad resin varnish 3 and 15 parts of hexamethoxymethylol melamine, and 4. diluted with water and spray-coated. The maximum film thickness showing no sagging with this coating composition was less than The characteristics of thef lal resins used in this arid subs:equent Examples and Comparative Examples are shown below.

24 j-- Table 1 aqueous composition water surface acid 110 resin No. tolerance tension value value dyne/cm 3 acrylic resin 10( 42 70 60 4 polyester resin 5 49 15 100 acrylic resin 2 54 15 60 (for Comp.Ex.) neutra- non-volatile Molecular lization content weight 100 40 8200 100 45 1480 100 25 4500 Water tolerance: 5 g of aqueous resin varnish were weighed in a 100 ml beaker, diluted with an increasing amount of deionized water and No. 1 type was read through the beaker.

.Water tolerance was a measure of water dilution limit for the aqueous resin and expressed as the water dilution factor at the stage when No. 1 type can no longer be correctly read through the beaker.

Surface tension: An aqueous resin varnish was diluted with deionized water to obtain a 1% w/w aqueous solution. Surface tension was determined with this solution by using a tensiometer (CB-VP type tensiometer, manufactured by Kyowa Kagaku K.K).

I B 4u- 4.c *0 S C 4, i- 4' 4.4.4.

U r EU4 4, 4' 4 Examples 2 to 9 (Preparation of pigment raste) Into a 1.5 liter stairle:,s steel vessel with a closed cover, were placed 36 parts of theI ate.- soluble resin varnish 3, 320 parts of Rutile type titanium dioxide and 60 parts of deionized watei- 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-1.

Another pigment paste-2 was prepared in a same way, by substituting the I l"b-le resin varnish-4 for the abovesaid varnish-3.

(Preparation of coating composition) Into a stainless steel vessel, the materials shown in the following Table 2 were placed in and the mixture was stirred well in a stirrer at a room temperature to obtain the S. respective coating composition of Examples 2 to 9.

Vr -26- 1 1 1 1 1 l 1 r 2 1 1 1 1 1 1 1 1 1 i 1 ^v ~w f w w Each of the coating compositions obtained in Examples 10 to rr -:o Table 2 Example piginerul paste 1 2 2 133 3 133 4 133 133 6 133 7 133 8 133 9 133 queous resin varntish 3 4 52 52 65 70 52 52 142 5 resin particles cotitainiiig compos itiomi 1 2 3 4 150 150 125 125 160 15 14 14 19 14 0 14 12 1 t: I I.j .1 -a *r r C. so 4* 4' 4' ar a 4 a i j 4; a' i *Y r U 'i

S

4 U Comparative Examples 2 to.8 ,,Using the same procedures as stated in Examples 2 to 9, but substituting the following materials for those of Examples 2 to 9, comparative coating compositions were prepared.

ta w S 4 44,4 4 4'

S

e,*t 44 4' t 4' 44' 4.4' '4 4' 4' 4 4' 4' 4' t b 28 4 V. '4 A7 Comparative pigment Example paste 3 133 3 133 4 133 133 6 133 7 133 aquLe Otts resin MB Varnish ,3 5 'table 3 Comparative resin particles 1 2 3 resin particles containing composition 1 3 6 250 250 125 140 140 14U At-ter the preparatin of 'coating composition, the resin particles had been coagulated.

rd L m, 0 U) -Hi 4-4 rH Qro o rs4 (a 4 P f vw E! 9 t #00 9 0 '0 i~iSt~ 0 ~i 0 00 0. ~4 S.t it tI t. C C. C.

C. C. U C. C.

'.4 Each of the coating compositions of Examples 2 to 9 and Comparative Examples 2 to 8 was diluted with deionized water to a Ford Cup #4 viscosity of 30 seconds and the diluted composition was spray-coated on a steel plate. After setting for 5 minutes, the coating was baked at 150 0 C for minutes to obtain a crosslinked coating.

The maximum film thickness showing no pinholes and the maximum film thickness showing no sagging were determined for the respective composition, and gloss value and smoothness of thus obtained coating were evaluated.

Evaluation standards are as follows: Application characteristics: Mark film thickness showing film thickness showing no pinholes no sagging (,am) more than 50 more than 0 more than 40 to 50 more than 40 to A more than 30 to 40 more than 30 to X 30 or less 30 or less 4 4, 4 41* i 44 4 44i 44 44 *4.

4i 4 415 gloss: Mark 0

A

X

Smoothness: 60° gloss more than 93 more than 90 to 93 more than 80 to 90 80 or less 200 gloss more than more than 75 to more than 65 to 65 or less excellent good no good 30 -t h.

i 1 ti; ff~ Table 4 Example 2 3 4 6 7 8 9 Comp. Ex.

coating appearance 600 gloss 200 gloss 0 0 0 0 A A 0 0 owo0 smoothness excellent nogo goo no good pinhole resistance 0 0 0D x sagging resistance 0 0

A

I

C.,

4>

I

I'

$x I r.l-iyrrr; r r- i, .z *i 9 9 9 9 4* 9.

*i I

I

#4 4 b 44 4 Synthetic Example 12 Preparation of resin particles containing composition-7 Into a 1 liter reaction vessel fitted with a stirrer, a thermoregulator and a condenser, were placed 320 parts of the wate uble resin varnish-i obtained in Synthetic Example 1, 300 parts of deionized water and 20 parts of butyl diglycol and the mixture was heated under stirring to To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, 2 parts of azobisisobutyronitrile and 100 parts of xylene was dropwise added in 2 hours, and the mixture was stirred for additional 2 hours to obtain a composition containing resin particles and having a nonvolatile content of 35.5%.

Synthetic Example 13 Preparation of resin particles containing composition-8 Into a similar reaction vessel aL used in Synthetic Example 12, were placed 356 parts of thek""_ er soluble resin varnish 2 obtained in Synthetic Example 2, 264 parts of deionized water and 20 parts of butyl diglycol and the mixture was heated, under stirring, to To this, the same monomer solution as used in Synthetic 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 S- 32 ii t *9 i i 4i :Irii Preparation of resin particles containing composition-9 Using the same procedures of Synthetic Example 12, 576 parts of the resin varnish 1 and 192 parts of deionized water were placed in a reactor and heated, under stirring, to 85°C. To this, a monomer solution consisting of 8 parts of styrene, 8 parts of methyl methacrylate, 14 parts of 2-ethyl hexyl acrylate, 2 parts of 2-hydroxyethyl methacrylate, 0.4 part of azobisisobutyronitrile and parts of xylene was dropwise added in 2 hours and the reaction was continued for additional 2 hours to obtain a Scomposition containing resin particles and having a nonvolatile content of 36.3%.

Synthetic Example Preparation of resin particles containing Using the same procedures of Synthetic Example 12, 320 parts of the(ae 2.lubIe resin varnish 1, 322 parts of deionized water and 20 parts of butyl diglycol were: placed in a reactor and the mixture was heated, under stirring, to S To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2ethyl 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 was further continued for 2 hours to obtain a composition (10) containing resin particles. A non-volatile content of S this composition was 38.4%.

Synthetic Example 16 rr0 f 2 p 33 .J of 0.2 part of ammonium persulfate in 20 parts of deionized _i I+J +1 Preparation of resin particles containing composition-11 Using the same procedures of Synthetic Example 12, 150 parts of the t jb e resin varnish 1 and 150 parts of deionized water were placed in a reactor and heated, under stirring, to 85 0 C. To this, a monomer solution consisting of 40 parts of styrene, 30 parts of methyl methacrylate, parts of 2-ethyl hexyl acrylate, 10 parts of 2-hydroxyethyl methacrylate, 1.5 parts of azobisisobutyronitrile and parts of xylene was dropwise added in 2 hours and the reaction was further continued, under stirring, for 2 hours to obtain a composition (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 i Using the same procedures of Synthetic Example 12, 320 parts

C

r of thef atk- no]h'e resin varnish 1, 400 parts of deionized .water and 20 parts of butyl diglycol were placed in a t reactor and the mixture was heated, under stirring, to To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, and 2 parts of azobisisobutyronitrile was dropwise added in 2 hours and the reaction was continued, under stirring, for additional 2 hours to obtain a composition (12) containing resin particles. The nonvolatile content of the composition was' 35.5%.

34 I 1 t !t ~~1i 7 Synthetic Example 18 Preparation of comparative resin particles-4 Into a 2 liter glass reaction vessel fitted with a stirrer, a thermoregulator, and a condenser, were placed 1100 parts of deionized water and the temperature was raised to 80 0

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 210 parts of methyl methacrylate, 75 parts of 2-ethyl hexyl acrylate and parts of n-dodecyl mercaptane were added and the combined mixture was stirred for 5 minutes. Thereafter, the e*4 remaining 259 parts of said monomer mixture were dropwise t 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 e, mixture was further stirred and reacted for 1 hour to obtain a seed emulsion having a non-volatile content of S Into a similar reaction vessel as used herein, were placed 300 parts of deionized water and 25 parts of the aforesaid Iseed emulsion, and the mixture was heated to To this, an aqueous solution of 0.1 part of ammonium persulfate and 20 parts of deionized water was added and i 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 35 k i i S.t~44~rrtr persulfate and 180 parts of xylene was dropwise added in 2 hours. After 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.A, (by electromicroscopic determination) and the maximum grain diameter was The number average molecular weight of the resin was S 9800.

Examples 10 to Into a stainless steel vessel, the materials shown in the following Table 5 were placed and stirred will at a room temperature to obtain the respective coating compositions of Examples 10 to 36

S

i 1 1 1 s e l l y .6 l, 1 l L 3 1 1 r 1

F.

Table Example pigmeiit paste *aqi re 1 2 3 52 25 11 52 12 52 5 13 52 2U 14 52 75 52 5 aqueous resin and p hexainethoxy inethylolme] .100 US sin (B3) 4 resin particles containing composition 7 8 9 10 11 I-IF 85 22 05 12 100 85 12 20 12 03 igmen t .amine resin Q~ 1-

I

4~ 4* 2*4 44 44 ~44 4 Comparative Examples 9 to 11 Using the same procedures of Example 10, but using the materials shown in the following Table 6, comparative coating compositions were prepared.

I

rable 6 Comparative pigment paste aqlucous Example resin varnish (13) _1 3 5 9 52 25 resin particles (4) obtained in Synthetic Ex. 10 4 resin particles containing comipos I t ion 7 12 52 5U liAft 52 63 37 hexamethoxy inethyloimelamine resin after the preparation of coating composition, tile resin particles contained were agglomerated and separated in the composition.

MF 0'

I

Ir 11 Each of the coating compositions obtained in Examples 10 to 15 and Comparative Examples 9 to 11 was diluted with deionized water to a Ford Cup #4 viscosity of 30 seconds, and the diluted composition was spray-coated onto a steel plate, and after setting for 5 minutes, baked at 150"C for minues to obtain a cured coating. The gloss value, and smoothness of the coating and time stability of the respective coating composition were evaluated and the results were shown in Table 7.

0u 4 44 0o t #4 *r 4 4 U

I

b( 1

I

4 Sl SI I 40 1 i 11-,.]j Table 7 Example 10 11 12 13 14 Comp. Ex. 9 10 coating appearance 600 gloss 200 gloss smoothness excellent 0 0 0 A no good A Xgood time. stabi lity excellent excellent good no good 00 00 0 0 0 0090 9* Oq 0* 0 0 0000 00 0 0# *0 9 0900 I~t f t O t 41 Synthetic Example 19 Preparation of hydrophobic resin varnish Into a 1 liter reaction vessel fitted with a stirrer, a thermoregulator and a condenser, were placed 25 parts of xylene and the temperature was raised, under stirring, to 125 0 C. To this, a monomer solution consisting of 30 parts of styrene, 15 parts of methyl methacrylate, 40 parts of 2ethyl hexyl methacryalte, 15 parts of 2-hydroxyethyl methacrylate and 4 parts of azobisisobutyronitrile was dropwise added in 2 hours and thereafter, the combined mixture was stirred for 2 hours to obtain an acrylic, 9t* hydrophobic resin varnish having a non-volatile content of 80%. The number average molecular weight of the formed resin was 5000.

15 Synthetic Example Prepartion of hydrophobic resin encapsulated resin Sparticles containing composition-13 Into a 1 liter reaction vessel fitted with a stirrer, a thermoregulator and a condenser, were placed 320 parts of the 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 85*C. To this, a monomer solution consisting of 50 parts of styrene, 50 parts of methyl methacrylate, 40 parts of 2ethyl hexyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, 2 parts of azobisisobutyronitrile and 60 parts of the hydrophobic resin varnish obtained in Synthetic 42 T h -I Example 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%.

Synthetic Example 21 Preparation of hydrophobic resin encapsulated resin particles containing composition-14 Using the same procedures as stated in Synthetic Example 356 parts of the aqueous resin varnish 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 85 0 C. 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 containing hydrophobic resin encapsulated resin particles. The non-volatile content of the composition was 42.6%.

Synthetic Example 22 Preparation of hydrophobic resin encapsulated resin 20 particles containing As in Synthetic Example 20, 320 parts of the aqueous resin varnish-i, 300 parts of deionized water and 20 parts of butyl diglycol were placed in a reactor and the mixture was heated, under stirring, to 85 0 C. 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 azobisisobutyronitrile and 20 parts of hexamethoxy methylol melamine 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%.

I

1~ 43 i Synthetic Example 23 Preparation of hydrophobic resin encapsulated resin particles containing composition-16 As in Synthetic Example 20, 320 parts of the aqueous resin varnish 1, 400 parts of deionized water and 10 parts of butyl diglycol were placed in a reactor and the mixture 9 9 t A V t 43A

H

i I was heated, under stirring, to 85"C. To this, a monomer solution consisting of 75 parts of styrene, 75 parts of methyl methacrylate, 60 parts of 2-ethyl hexyl methacrylate, parts of 2-hydroxyethyl methacrylate, 3 parts of azobisisobutyronitrile and 24 parts of Epicoat 1001 (Shell Chemical) 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%.

Synthetic Example 24 Preparation of comparative resin particles containing composition-17 o• As in Synthetic Example 20, 320 parts of the emwa©=©ble resin varnish 1, 400 parts of deionized water and 20 parts 15 of butyl diglycol were placed in a reactor and the mixture was heated, under stirring, to 85°C. To this, a monomer a 4 solution consisting of 50 parts of styrene, 50 parts of 0 methyl methacrylate, 40 parts of 2-ethyl hexyl acrylate, 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 composition containing resin particles. The non-volatile content of the composition was 35.5%.

Synthetic Example Preparation of comparative resin particles Into a 2 liter glass reaction vessel fitted with a stirrer, a thermoregulator and a condenser, were placed 1100 parts of -44deionized water and the content was heated, under stirring, to 80 0 C. To this, an aqueous solution of 6 parts of ammonium persulfate in 100 parts of deionized water and parts of the monomer mixture of 210 parts of methyl additional 15 minutes.

0" 0 Thereafter, an aqueous solution of 1 part of ammonium persulfate in 10 parts of deionized water was added and the S mixture was reacted, under stirring, for 1 hour to obtain a seed emulsion having a non-volatile content of Into a simmilar reaction vessel as stated hereinabove, were placed 300 parts of deionized water and 25 parts of the abovesaid seed emulsion, and the temperature was raised to To this, an aqueous solution of 0.1 part of ammonium persulfate in 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, parts of 2-hydroxyethyl methacrylate, 5 parts of ndodecy mercaptane, 200 parts of deionized water, 0.4 part of sodium dodecyl benzene sulfonate, 0.8 part of ammonium persulfate and 150 parts of the hydrophobic r esin varnishe obtained in Synthetic Example 19 was dropwise added in 2 hours. After stirring for 30 minutes, an aqueous solution 45 k 1 1 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 particles. The non-volatile content of the emulsion was 41.2%. The resin particles were separated from thus obtained emulsion. By an electron microscopic examination, it was found that the average grain diameter of said particles was 0.7,and the maximum grain diameter was 1.4AL.

j The number average molecular weight of the resin was 9800.

Examples 16 to Into a stainless steel vessel, the materials shown in the following Table 8 were placed in and the mixture was stirred well in a stirrer at a room temperature to obtain the respective coating composition of Examples 16 to 46 .17, Table 13 Example pigmet paste 1 2 aueC o us resin (13) varnish 3 4 resin particles m 1 containinig comuposition 13 14 15 16 liexaiethylol inelainine a C S @0S

-K

I i r" _s Comparative Examples 12 to 14 Using the same procedures as stated in Examples 16 to but substituting the following materials for those of Examples 16 to 20, comparative coating compositions were prepared.

a l* 48 48 b, Table 9 Comnp. Ex. pigment paste 12 52 13 52 1411 52 a queo0us resin (13) varnish 3 5 Comparative resin particles 13 resin particles (5) obtained in Synth. Ex. 1.1 F 12 12 1 u 1 14 After the preparation of coating composition, the resin particles contained were agglomerated and separated.

*4.

*A p j~ Ii

U

r r.

1'

M

Each of the coating compositions of Examples 16 to 20 and Comparative Examples 12 to 14 was diluted with deionized water to a Ford Cup #4 viscosity of 30 seconds and the diluted composition was spray-coated on a steel plate.

After setting for 5 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 showing no sagging were determined for the respective composition, and gloss value and smoothness of thus obtained coating were evaluated. The results are shown in Table a 9 99 9 4 *1r *01

IL

1 a ~R"1 i; 50

T

4 2 Table coating appearance 600 gloss 20* gloss smoothness Example 16 ©©excellent 170 180 19 ©0 Comp. Ex. 12 0A no good 13 A good 14 time stability excellent excellent good no good 04 *4 0 0 4, 0994 6 99 99 4 0 #4 9, 4 6*41 9* 4 6 4 9 *1 6 *4 4 9 4 .4.4 4 *4 I 4 *444 4 44 .44 4 4~ 51

Claims

1. An aqueous coating composition comprising as resinous vehicle a mixture of an aqueous composition containing resin particles obtained by polymerizing at least one a,3-ethylenically unsaturated monomer in an aqueous medium and in the presence of an aqueous resin and an organic initiator, the solid weight ratio of said aqueous resin to said monomer being between 35:65 and 95:5 and an aqueous resin 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 resin and aqueous resin (B) being between 70:30 and 1:99.

2. A composition according to claim 1, wherein the aqueous resin and the aqueous resin are similarly or differently selected from the group consisting of a polyester resin, an alkyd resin, an acryl resin, an acryl modified polyester resin, an acryl modified alkyd resin.

3. 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 S" 25 azo compound, a disulfide and a sulfinic acid.

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

5. A composition according to claim 1, wherein the a3,P-ethylenically unsaturated monomer includes a S* 30 crosslinking monomer having in its molecule at least 2 S, radically polymerizable, ethylenically unsaturated bondings. 4 3 4 t 52 1 i ik 4

6. An aqueous coating composition comprising as resinous vehicle a mixture of an aqueous composition containing solvent encapsulated resin particles obtained by polymerizing a mixture of at least one a,P-ethylenically unsaturated monomer and at least one hydrophobic solvent in an aqueous medium and in the presence of an aqueous resin and an organic initiator, the solid weight ratio of said aqueous resin to the monomer being between 35:65 and 95:5, and an aqueous resin 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 resin and aqueous resin (B) being between 70:30 and 1:99.

7. A composition according to claim 6, wherein the weight ratio of said hydrophobic solvent to 'Ca,-ethylenically unsaturated monomer is between 80:20 and 3:97. 20

8. A composition according to claim 6, wherein the aqueous resin and the aqueous resin are similarly or differently selected from the group consisting of a polyester resin, an alkyd resin, an acryl resin, an acryl Smodified polyester resin, an acryl modified alkyd resin. S 25

9. A composition according to claim 6, 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.

S 53 O S q' S A composition according to claim 6, wherein the aqueous medium contains an organic solvent.

11. A composition according to claim 6, wherein the a,P-ethylenically unsaturated monomer includes a crosslinking monomer having in its molecule at least 2 radically polymerizable, ethylenically unsaturated bondings.

12. An aqueous coating composition comprising as resinous vehicle a mixture of an aqueous composition containing hydrophobic resin encapsulated resin particles obtained by polymerizing a mixture of at least one a,j-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 an organic initiator, the solid weight ratio of said aqueous resin to the monomer being between 35:65 and 95:5, and an aqueous resin 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 resin and aqueous resin (B) being between 70:30 and 1:99.

13. A composition according to claim 12, wherein the aqueous resin and the aqueous resin are similarly or differently selected from the group consisting of a polyester resin, an alkyd resin, an acryl resin, an acryl Smodified polyester resin, an acryl modified alkyd resin. t 1 *54 i. e 'iS 1 r

14. A composition according to claim 12, wherein the organic initiator is selected from the group consisting of a diacy1 peroxide, a hydroperoxide, an alkyl peroxide, an azo compound, a disulfide and a sulfinic acid.

15. A composition according to claim 12, 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.

16. A composition according to claim 12, wherein the aqueous medium contains an organic solvent.

17. A composition according to claim 12, wherein the a,-ethylenically unsaturated monomer includes a crosslinking monomer having in its molecule at least 2 radically polymerizable, ethylenically unsaturated bondings.

18. A composition according to claim 12, wherein the solid weight ratio of said hydrophobic resin to said unsaturated monomer is between 1:99 and 70:30.

19. An aqueous coating composition substantially as herein described with reference to any one of the Examples. Dated 4th day of September 1989 NIPPON PAINT CO., LTD. By their Patent Attorney GRIFFITH HACK CO. 55 e' eZ i o \-a