CA1286430C - Hydroxyl functional graft copolymers - Google Patents

Abstract

ABSTRACT
A liquid, hydroxyl functional graft copolymer is prepared by the vinyl addition polymerization of a vinyl monomer component comprising at least a portion of a carboxyl functional vinyl monomer in the presence of a polymer containing epoxy groups. The graft copolymer is especially useful in formulating clear coating compositions which exhibit excellent sag resistance without the necessity for externally added rheology control agent.

Description

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~YDROXYL FUNCTIONAL GRAFT COPOLYMERS

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In recent yeflrs there has been a growing trend towards the development of coating compositions having a reduced volatile organic content. One approach to achieving this goal has been to move toward high solids compositions which are formulated from low molecular weight polymers. High solids compositions such as these, however, generally require a rheology control agent such as, for example, microgel in order to minimize sag and provide metallic pigment pattern control where such pigments are utilized. The presence of rheology control agents can be disadvantageous since quite often they detract from the clarity of clear coating compositions by imparting a hazy or yellowish cast to the fllm. ~oreover, the gloss i5 often reduced since the rheology control agents lend a flat appearance to the cured film.
There is a need, therefore, for a way to prepare high solids coating compositions which can be formulated into "water-like" clear coating compositions whlch exhibLt good gloss, sag resistance, and metallic pigment pattern control without the necesRity oE externally added rheology control agents.
Summary of the Invention In accordance wlth the present invention, there is provided an ungelled, hydroxyl functional graft copolymer prepared by the vinyl addition polymerlzatLon oE a vinyl monomer component comprising at least a portion oE a carboxyl functional vinyl monomer in the presence of a polymer containing epoxy groups.
Also provided is a coating composition prepared from the liquid hydroxyl functional graft copolymer which has good sag resistance and metallic pigment pa~tern control.
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Detailed Desc iption of the Invention - The ungelled, hydroxyl functional graft copolymer of the present invention is prepared by the free radical initiated vinyl addition polymerization of a vinyl monomer component. The 5 polymerization is conduc~ed in the presence of a polymer containing epoxy groups. Either the polymer containing epoxy groups or the vinyl monomer component can con~ain hydroxyl functionality, so long as at least one of them does. Preferably both the vinyl monomer component and the polymer containing epoxy groups are hydroxyl functional.
It should be understood that by the term "~mgelled" is meant that the graft copolymer is soluble in a suitable solvent with essentially no insoluble fraction. Examples of suitable solvents include tetrahydrofuran, acetone, xylene and other similar common organic solvents. A gelled material is a three dimensional 15 crosslinked matrix which cannot be dissolved in common organic solvents and whose molecular weight by gel permeation chromatography cannot be determined. In addition, it is believed that the presence of gelled material interferes with the rheology of a polymeric product resulting in poor atomization during spray application and poor flow 20 in coating applications.
Moreover, by "hydroxyl functional" is meant predominantly that hydroxyl functionality which comes from the hydroxyl functional vinyl monomers of the vinyl. monomer component. There is also some minor proportion which is generated from the reaction of epoxy groups 25 with carboxyl groups.
The vinyl monomer component comprises at least a portion of a carboxyl functional vinyl monomer. Moreover, it is preferred that the vinyl monomer component is free of epoxy group containing vinyl monomers. Examples of suitable carboxyl functional vinyl monomers 30 include acrylic acid, methacrylic acid and monoesters of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, for example, mono(hydroxyethyl) and mono(hydroxypropyl) esters of maleic acid. The balance of the vinyl monomer component can include a variety of other vinyl monomers which contain polymeri~able 35 vinyl unsaturation. For example, hydroxyl functional vinyl monomers such as 2~hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, ~L2~

2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate. Also useful are acrylamlde; an N-methylol- acrylamide such as the reaction product of acrylamide with formaldehyde; N-butoxymethyl acrylamide; ter~iarybutylaminoethyl 5 methacrylate; sulfoethyl methacrylate; and alkyl acrylates and methacrylates which contain from 1 to 18 carbon atoms, preferably 1 to ~ carbon atoms in the alkyl portion such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl ~meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 10 2-ethylhexyl methacrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isodecyl (meth)acrylate and isobornyl (meth)acrylate.
Also useful are styrene, para-methyl styrene, alpha-methyl styrene, acrylonitrile, methacrylonitrile and vinyl ethers such as vinyl acetate or vinyl versatate. Mixtures of the aforesaid monomers can 15 also be utilized if desired.
In one preferred embodiment of the present invention, the vinyl monomer component contains hydroxyl functionality, therefore, it will contain some proportion of hydroxyl functional vinyl monomer or mixture of monomers, examples of which have been detailed above.
The amount of carboxyl functional vinyl monomer in the vinyl monomer component generally ranges from about 1.5 percent by weight to about 15 percent by weight, the percentages based on the total weight of the vinyl monomer component. Usually, the amount of carboxyl functional vinyl monomer ranges from about 1.5 percent by weight to 25 about 10 percent by weight, preferably from abo~lt 1.5 percent by weight to about 4 percent by weight and more preferably from about 2.5 percent by weight to about 3 percent by weight.
The polymer containing epoxy groups is preferably an epoxy functional acrylate whlch is prepared by the vlnyl addition 30 polymerlzatlon of a vinyl monomer component containlng at least a portlon of an epoxy functional vlnyl monomer such as glycldyl acrylate, glycldyl methacrylate, or allyl glycldyl ether. The balance of the vlnyl monomers can be selected from those detailed above. In one preferred embodlment of the present lnvention the polymer 35 containing epoxy groups also contains hydroxyl functionality;
therefore, lt wlll contaln some proportion of moleties derived from hydroxyl functlonal vlnyl monomers.

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The amount of epoxy functional vinyl monomer present in the polymer containing epoxy groups generally ranges from about 3 percent by weight to about 30 percent by weight, the percentages be:Lng basecl on the total weight oE the monomers utilized in the preparation of the 5 polymer containing epoxy groups. Usually the amount of epoxy functional vinyl monomer ranges from about 3 percent by weight to about 20 percent by weigh~, preferably from about 3 percent by weight to about 10 percent by weight and more preferably from about 4 percent by weight to about 8 percent by weight.
The polymer containing epoxy groups generally has a number average molecular weight determined by gel permeation chromatography using a polystyrene standard ranging from about 1000 to about 50,000 preferably 1000 to 5000 and more preferably 2000 to 3000.
The grafting reaction for the preparation of the claimed 15 hydroxyl functlonal graft copolymer occurs by the condensation reaction between the carboxyl groups of the vinyl monomer component and the epoxy groups in the backbone polymer containing epoxy groups.
The ratio of epoxy groups of the backbone polymer to the carboxyl groups in the vinyl monomer component is generally withln the range 20 from 1:0.5 to 0.5:1.
The vinyl addition polymerization reaction to prepare the graft copolymer is usually conducted at a temperature within the range of about 125C to about 200C, preferably 140C to 160C. There is generally present a free radical initiator which is selected from a 25 wide variety of materials. Suitable types of materials include peroxides, hydroperoxides and azo initiators. Examples of these types of initiators include di--tertiarybutyl peroxide, di-cumylperoxide;
amyl peroxyacetate; cumenehydroperoxide; 2,5 dimethyl-2,5-bis(tertiarybutylperoxy) hexane; hexyne-3-tertiarybutyl 30 cumylperoxide; tertiaryamyl peroxide; 2,5-dihydroperoxy 2,5-dimethyl hexane, di(n-propyl) peroxydicarbonate, and 2,2'-azobis(2,4-dlmethyl-4-methoxy-valeronitrile).
The amount of initiator can very widely although usually it is present in an amount ranging from about 3 percent to about 8 35 percent, the percentage based on the total weight of the vinyl monomer component. Generally, there is also present during the vinyl addition polymerization a solvent which assists in ma:Lntaining the preferred reaction temperature. Examples of these solvents include methyl amyl ketone, aromatic petroleum distillates, 2 ethylhexyl acetate, and hlgh boiling ester solvents such as those commercially available from Exxon 5 Chemical Corporation under the trademark designations EXTATE 600 and EXTATE 700.
The graft copolymers of the present invention are use~ul as film-forming vehicles in the preparation of high solids coating composltions such as, for example, clear coating compositions useful 10 in automotive applications. The resultant coating compositions have low volatile organic content, generally to a maximum of 3.50 pounds/gallon, preferably to a maximum of 3.1 pounds/gallon, and the cured films exhibit good physical properties. The claimed graft copolymers usually have a peak molecular weight as determined by GPC
15 using a polystyrene standard ranging from about 4,000 to about 20,000, preferably from about 6,000 to about 12,000. One very important advantage of the claimed graft copolymers is that coating compositions formulated from them exhibit excellent gloss, sag resistance and metallic pigment pattern control without the necessity of adding 20 external rheology control agents. In addition, particularly in the clear coating compositions, the compositions exhibit exceptional clarity. As has been discussed previously, clear coating compositions containing externally added rheology control agent~ often have a hazy appearance or yellowish cast. Of course, it should be understood 25 that, if desired, externally added rheology control agents also can be added.
In preparing the coating compositions of the present invention the gra~t copolymer is usually combined with a curing agent which is capable of reacting with the hyclroxyl functionality which :Ls 30 present on the graft copo:Lymer.
Examples of suitable curing agents are aminoplast, phenoplast and polyisocyanate curing agents, including blocked isocyanates. Typically, a cure promoting catalyst is utilized in conjunction with an aminoplast curing agent, for example, acid 35 catalysts and blocked acid catalysts such as para-toluenesulfonic acid, di-nonylnapthalene disulfonic acid, and the amine blocked forms of both of these.

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A solvent is also typically utilized, in mirl:Lmal amolmts, to facili~ate formulation and applicat~on of the coating compos:ltions oE
the present invention. An organic solvent is utilized which is compatible with the components of the compositions. The amounts of 5 graft copolymer9 curing agent, and catalyst will, of course, vary widely depending upon many fac~ors, among them the specific components of the composition and the intended use of the composition. The curing agents mentioned above are described more fully below.
Aminoplast condensates are obtained from the reaction of 10 formaldehyde with an amine or an amide. The most common amines or amides are melamine, urea or benzoguanamine, and are preferred.
However, condensates with other amines and amides can be employed, for example, aldehyde condensates or triazines, triazoles, guanidines, guanamines and alkyl and aryl di-substituted deriva~ives of such 15 compounds including alkyl and aryl-substituted ureas and alkyl and aryl-substituted melamines and benzoguanamines. Some examples of such compounds are N,N-dimethylurea, N-phenylurea, dicyandiamide, formoguanamine, acetoguanamine, 6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole, triaminopyrimidine, 20 2,6-triethyltriamine-1,3-S-triazine and the like.
While the aldehyde employed is most often formaldehyde, other aldehydes such as acetaldehyde, crotonaldehyde, benzaldehyde and furfural may be used.
The aminoplast contains methylol or similar alkylol groups 25 and preferably at least a portion of these alkylol groups are etherified by reaction wlth an alcohol to provide organic solvent-soluble resins. Any monohydric alcohol can be employed for this purpose including such alcohols as methanol, ethanol, butanol and hexano].
Preferably, the aminoplasts which are used are melamine, urea- or benzoguanamine-formaldehyde condensates etherified ~ith an alcohol containing 1 to ~ carbon atoms such as methanol, ethanol, butanol or mixtures thereof.
Polyisocyanates and blocked polyisocyanates may also be used 35 as curing agents. Examples oE suitable polyisocyanates include monomeric polyisocyanates such as toluene diisocyanate and ~l,4~-methylene-bis- (cyclohexyllsocyanate), isophorone cllLsocyanate ancl NCO-prepolymers s-ch as the reaction proclucts of monomerlc poly:Lsocyanate such as those mentioned above w:Lth polyester or polyetller polyols. Particularly useful isocyanates are isophorone 5 diisocyanate and the biuret from 1,6 hexamethyl ~e diisocyanate commercially available from Bayer as DESMODUR N. The polyisocyanate may optionally be blocked. Examples of suitable blocking agents are those materials wh:Lch would unblock at elevated temperatures such as lower aliphatic alcohols such as methanol, oximes such as methyl ethyl 10 ketone oxime, and lactams such as epsilon-caprolactam. Blocked isocyanates can be used to form stable one-package systems.
Polyfunctional isocyanates with free isocyanate groups can be used to form two-package room temperature curable systems. In these systems, the product ancl isocyanate curing agent are mixed ;just prior to their 15 application.
The phenolic resins which may be used as curing agents herein are formed by the condensation of an aldehyde and a phenol.
The most used aldehyde is formaldehyde, although other aldehydes, such as acetaldehyde, can also be employed. Methylene-releasing and 20 aldehyde-releasing agents such as paraformaldehyde and hexamethylene tetramlne, can be utilized as the aldehyde agent :Lf desired. Various phenols can be used; for instance, the phenol employed can be phenol per se, a cresol, or a substituted phenol in which a hydrocarbon radical having either a straight chain, a branched chain or a cyclic 25 structure is substituted for a hydrogen :Ln the aromatic ring.
Mixtures of phenols are also often employed. Some specific examples of phenols utilized to produce these resins include p-phenylphenol, p-tert-butylphenoL, p-tert-amylphenol, cyclopentylphenol and unsatl1rated hyclrocarbon substituted pilenols, such as monobutenyl 30 phenols containing a butenyl group in ortho, meta or para position, and where the double bond occurs ln varlous posit~ons in the hydrocarboll chain. ~ common phenolic resin is phenol Eormaldehyde, In addition, the composieLons of the present invention may contain a variety of other optional ingredients, including pigments, 35 fillers, plastici~ers, antloxidants, surfactants and flow control agents.

~6~30 The compositions can be applied by any conventional method including hrushlng, dipping, flow coating, etc., but typically they are applied by spraying. Also, the compositions can be applied over a variety of substrates lncluding wood, metals, and glass.
The followiIIg examples are illustrative of the invention and are not intended to limit it to their details.
Example I
This Example illustrates the preparation of a liquid, ungelled hydroxyl functional graft copolymer according to the present 10 invention.

Part A
Preparation of Acrylic Polymer Containing Epoxy Groups Parts by Weight Charge Ingredients (grams) 1~
I AROMATIC-100 366.80 20 II styrene 205.80 butyl acrylate 195.30 butyl methacrylate 181.30 hydroxypropyl acrylate 68.60 glycidyl methacrylate 26.04 III AROMATIC-100 2 7.50 amyl peroxyacetate 67.60 IV AROMATIC-100 35,00 V AROMATIC-100 21.00 (l) This solvent was an aromatic petroleum distillate commescially available from Exxon.
35 (2) Available from Pennwalt Corp. as a 6 percent solution in ISOPAR
K. (ISOPAR K is a trademark of Exxon.) A suitably equipped reactor vessel was charged with (I) and heated to reflux. Charges (II) and (III) were added together 40 continuously over a three hour period. When the addition was completed, Charges (IV) and (V) were added and the reaction mixture was held at reflux temperature for four hours. Finally, the reaction mixture was allowed to cool to room temperature. The resultant epoxy . ', . ~ .

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flmctional acryllc polyrner had a peak molecular weight oE 4499 as determined by gel permeation chroma~ography (GPC) using a polystyrene standard; a total solids content of 60.5 percent determined at 110C
for one nour; a Gardner viscosity of D and an acld value of 1.2.
S Part B
Preparation of Ungelled H _roxyl Functional GraEt Copol~mer Parts by Weight Charge Ingredients (~rams) I Epoxy-functional acrylic polymer 11/~.9 of Part A
AROMATIC-100 344.4 15 II methyl methacrylate 10.2 styrene 201.6 butyl acrylate 200.9 butyl methacrylate 190.4 hydroxypropyl acrylate 776.3 acrylic acid 31.8 III amyl peroxyaceta-te 141.1 AROMATIC-100 13.4 25 IV AROMATIC-100 35.0 V AROMATIC-100 21.0 VI butyl aeetate 266.5 A suitably equipped reactor vessel was charged wlth (I) and heated to reflux. Charges (II) and (III) were then added together continuously over a period of three hours. During the course of the addition L5.3 grams of solvent was removed by azeotropic distillation 35 in order to maintain the temperature above 150C. After the additlon was completed, Charges ~IV) and (V) were added and the reactlon mixture was held at reflux temperature for a four hour period.
Finally, the reaetion mixture was allowed to cool to room temperature and Charge (VI) was added to reduee the viseoslty. The resultant 40 procluct had a peak moleeular weight of 8929 as determined by GPC using a polystyrene standard; a Gardner viscosity of X-; a total solids content of 65 percent at 110C for one hour and an acid value of 1 to 2.

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~ le II
This Example is similar to Rxample II, above, wlth the axception that the initiator was ditertiarybutyl peroxide.
Part A
Preparation of Acrylic Polymer Containing Epoxy Groups Parts by Weight Charge Ingredients (grams) .
10 I AROMATIC-100 2934.4 II styrene 1646.4 butyl acrylate 1563.2 butyl methacrylate 1450.4 hydroxypropyl acrylate 548.8 glycidyl methacrylate 273.6 III ARO~ATIC-100 268.8 ditertiarybutyl peroxide273.6 IV AROMATIC-100 280.0 V AROMATIC-100 168.0 25 A suitably equipped reactor vessel was charged with (I) and heated to reflux. Charge (II) was then added at a rate of 31.7 stroke while Charge (III) was added at a rate of 210 grams over 3 hours~
When the addition was completed, Charges (IV) and (V) were added and the reaction mixture held at reflux for four hours. The reaction 30 mixture was then allowed to cool to room temperature. The resultant epoxy functional acrylic polymer had a peak molecular weight of 5303 as determined by GPC using a polystyrene standard; a total s~lids content of 63.1 percent at 110~C for one hour; a Gardner viscosity of Q and an acid value of zero.

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Part B
Preparation of Ungelled, Hydroxyl_Funct-10nal Graft Copolymer Parts by Weight Char$e Ingredients (Prams) I Epoxy-functional acrylic polymer 1175.8 of Part A
AROMATIC-100 3~4.4 II methyl methacrylate 10.2 styrene 201.6 butyl acrylate 200.9 butyl methacrylate 190.4 hydroxy propyl acrylate 776.3 acrylic acid 31.8 III AROMATIC-100 70.0 ditertiarybutyl peroxide 70.7 IV AROMATIC-100 35.0 V AROMATIC-100 21.0 VI butyl acetate 258.0 A suitably equipped reactor vessel was charged with (I) and heated to reflux. Charges (II) and (III~ were then added together 30 continuously over a three hour period. When the addition was completed, Charges (IV) and (V) were added and the reaction mixture was held at reflux for four hours. Finally the reaction mixture was allowed to cool to room temperature and reduced in viscosity with the addition of Charge (VI). The resultant product had a total solids 35 content oE 63.9 percent at 110C Eor one hour, a Gardner viscosity of Z-7; and an acid value of 8.~.
Example III
This Example illustrates the preparation and evaluation of a clear coating composition utilizing the hydroxyl functional graft ~.
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copolymer of Example II, above, as a film former. This coating composition was compared to a control coating composition Eormulated without the graft copolymer.
The control coating composition was identical to the coating 5 composition set out below with the exceptions that instead of the graft copolymer of Example II, the film-former was the acrylic polymer of Part A of Example II. Also utilized was an externally added rheology control agent in the form of microgel as described in U.S.
Patent 4,147,688, Example II. The amount of microgel which was added 10 was 4.5 grams (2 percent based on 100 grams of resin solids.) In addition, xylene was utilized inseead of butyl acetate.

Parts by Weight Ingredients (grams)_ hydroxy functional graft copolymer of 70.50 Example II utilizing 5 percent glycidyl methacrylate monomer TINUVIN 328 ~ 3.00 20 butyl acetate 30.00 CYMEL 1130 50.00 blocked acid catalyst 2.50 polybutylacrylate6 0.75 methanol 6.00 25 butyl acetate 25.00 (3) This benzotriazole ultraviolet light stabilizer is commercially available from Ciba-Giegy Corp.

(4) This 50 percent methylated, 50 percent butylated melamine-formaldehyde condensate is commerclally available from American Cyanamid.

(5) This blocked acid caealyst was a diisopropanolamine blocked dinonylnapthalene disulfonic acid.

(6) This was a flow control agent and anticratering additive.
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The coating compo~sltlon having a resin solids content of 53.2 percant was prepared by combinlng the ingredients together with mild agitation. It was applled to a steel panel coated with UNI-PRIME~ coating composition ~commercially available from PPG
5 Industries, Inc., as ED 3150). This primed panel was base coated at a dry film thickness of 0.57 mll with a coating composition commercially available from PPG Industries, Inc., as UBC 9021. The basecoat was flashed for two minutes and then the clear coating composition detailed above was applied at a dry film thickness of 1.5 mil and then 10 baked for 25 minutes at 285F (141C). The control clear coating composition was applied to a control panel and evaluated in identical fashion. The panels were evaluated for appearance (clarity) of the cured film, 20 gloss (horizontal/vertical) as well as distinctness of image (DOI) and the amount of sag.
The appearance of the film (clarity) was determined by visual inspection.
Gloss was measured with a glossmeter at 20.
Sag was determined after the panels were baked. The panels were positioned horizontally in a rack at a 4~ angle and the amount 20 of sag from the edge of the panel was measured in centimeters.
DOI was measured with a "C-box" which is commercially available from I R Company. To measure DOI a series of C's of different sizes are projected onto the surface of the film being evaluated. Each size of C is given a numerical rating between O and 25 100 with O indicating that the film has no reflective clarity to the opening part of the C and 100 indicating that the film has maximum reflective clarity to the opening part of the C. The values in between indicate varying degrees of clarity.
The results are set out below.

3~9 Resin 20 Gloss DOI Appearance Coating Solids Horizontal Horizontal SAG of Composition (percent) /Vertical /Vertical (CM) Film _ Graft 53.2 96 / 98.2 45 / 40 0 water~ e copolymer clear Control 56.2 99 / 99 60 / 50 0 .yellowish cast The above results illustrate that the coating compositions of the present invention formula~ed with the claimed graft copolymers exhibit excellent water~like film clarity, good gloss, DOI and sag 15 resistance, comparable to the control, without the necessity of externally added rheology control agents. The control composition utilizing an externally added rheology control agent had poor film clarity since the film had a yellowish cast, although the other properties were comparable to the composition utilizing the graft 20 copolymer.

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Claims (16)

1. An ungelled, hydroxyl functional graft copolymer prepared by the vinyl addition polymerization of a vinyl monomer component comprising at least a portion of a carboxyl functional vinyl monomer in the presence of a polymer containing epoxy groups.

2. The ungelled graft copolymer of claim 1 wherein the vinyl monomer component contains hydroxyl functionality.

3. The ungelled graft copolymer of claim 1 wherein the polymer containing epoxy groups contains hydroxyl functionality.

4. The ungelled graft copolymer of claim 1 wherein both the polymer containing epoxy groups and the vinyl monomer component contain hydroxyl functionality.

5. The ungelled graft copolymer of claim 4 wherein the vinyl monomer component comprises a hydroxyl functional vinyl monomer selected from 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.

6. The ungelled graft copolymer of claim 1 wherein the carboxyl functional vinyl monomer of the vinyl monomer component is selected from acrylic acid, methacrylic acid, a monoester of maleic acid, and a monoester of fumaric acid.

7. The ungelled graft copolymer of claim 1 wherein the polymer containing epoxy groups is an acrylic polymer.

8. An ungelled hydroxyl functional graft copolymer prepared by the vinyl addition polymerization of a vinyl monomer component comprising at least a portion of both a hydroxyl functional vinyl monomer and a carboxyl functional vinyl monomer in the presence of an acrylic polymer containing epoxy groups.

9. The ungelled graft copolymer of claim 8 wherein the ratio of epoxide groups in the acrylic polymer to the carboxyl groups in the vinyl monomer component is within the range of from 1:0.5 to 0.5:1.

10. A coating composition comprising an ungelled, hydroxyl functional graft copolymer prepared by the vinyl addition polymerization of a vinyl monomer component comprising at least a portion of a carboxyl functional vinyl monomer in the presence of a polymer containing epoxy groups; and a curing agent adapted to cure the hydroxyl functional graft copolymer.

11. The coating composition of claim 10 wherein the vinyl monomer component contains hydroxyl functionality.

12. The coating composition of claim 10 wherein the polymer containing epoxy groups contains hydroxyl functionality.

13. The coating composition of claim 10 wherein both the polymer containing epoxy groups and the vinyl monomer component contain hydroxyl functionality.

14. The coating composition of claim 10 wherein the curing agent is selected from aminoplasts, phenoplasts and polyisocyanates.

15. The coating composition of claim 10 wherein the composition is a high solids coating composition.

16. The coating composition of claim 10 wherein it is essentially free of externally added rheology control agents.