WO1995027012A1

WO1995027012A1 - Non-aqueous dispersions of carboxylic acid-functional polymeric microparticles used for flow control in polyepoxide-polyacid based coating compositions

Info

Publication number: WO1995027012A1
Application number: PCT/US1995/004054
Authority: WO
Inventors: Suryya K. Das; Soner Kilic; Dennis A. Simpson; Michael A. Pinchok, Jr.; James R. Christenson
Original assignee: Ppg Industries, Inc.
Priority date: 1994-04-04
Filing date: 1995-03-30
Publication date: 1995-10-12
Also published as: AU2236295A

Abstract

Polyepoxide-polyacid based coating compositions contain dispersions of carboxylic acid-functional polymeric microparticles for controlling sag and metallic flake orientation. The carboxylic acid-functional polymeric microparticles can be synthesized by a variety of methods, and can optionally be cross-linked.

Description

NON-AQUEOUS DISPERSIONS OF CARBOXYLIC
ACID-FUNCTIONAL POLYMERIC MICROPARTICLES USED FOR
FLOW CONTROL IN POLYEPOXIDE-POLYACID BASED COATING
COMPOSITIONS
Background of the Invention
The present invention relates to dispersions of carboxylic acid-functional polymeric microparticles and to their use in coating compositions for control of sagging and for metallic flake orientation. More specifically, this invention relates to the use of said dispersions in acid-cured epoxy coating compositions.

Dispersions of carboxylic acid-functional polymeric microparticles have shown practical utility: they significantly modify the rheological and physical properties of coating compositions to which they are added. These materials improve the spraying efficiency of the coating compositions, enabling complete coverage in fewer passes of the spray gun. They also provide high film build without pinholing or popping, and improve the sag resistance of the applied coating. Further, they improve the pigment pattern control of coating compositions that contain large pigment particles such as aluminum flake or mica. This property is especially relevant to the formulation of highsolids spray-applied coating compositions, which tend to exhibit more pronounced sagging and flow control problems than low- or medium-solids coating compositions.

Dispersions of carboxylic acid-functional polymeric microparticles are known in the art. They can be prepared by several methods. The book entitled DISPERSION
POLYMERIZATION IN ORGANIC MEDIA, edited by K. E. J. Barrett, John Wiley and
Sons, 1975 describes the synthesis of various polymeric microparticles by non-aqueous dispersion techniques, for example polymerization in non-aqueous media using grafting dispersants.

Various other references describe the preparation of dispersions of carboxylic acid-functional polymeric microparticles in aqueous media by emulsion polymerization techniques. For example, Patent Nos. 4,290,932 and 4,377,661 describe materials prepared by these techniques. These references disclose polymeric microparticles which can contain high levels of carboxylic acid functionality, for example, up to 90 percent by weight of acid functional monomers.

Acid-cured epoxy coating compositions are also known in the art. These can be one-package or two-package systems, as described in U.S. Patent Nos. 5,196,485 and 4,650,718, respectively. While particulate materials such as silica have been added to such coatings to improve sag resistance, these materials typically affect gloss and distinctness of image of the coating. Therefore, it is desirable to improve sag resistance in such coatings without compromising appearance properties.

Summarv of the Invention
In accordance with the present invention, there is provided a coating composition comprising a film-forming polyepoxide polymeric resin; a polyacid curing agent; and particular stable, organic, colloidal dispersions of carboxylic acid-functional polymeric microparticles prepared by one of three synthesis routes disclosed herein.

These include dispersion polymerization in polar non-aqueous medium, aqueous emulsion polymerization with subsequent transfer to non-aqueous medium, and dispersion polymerization in non-polar, non-aqueous medium. The monomers from which the carboxylic acid functional microparticles are polymerized vary in accordance with the particular synthesis route employed.

A particularly advantageous type of dispersion of carboxylic acidfunctional polymeric microparticles are those comprising polymers prepared by dispersion polymerization in polar, non-aqueous medium of the following monomer composition:
50 to 100 percent by weight of acrylic acid, methacrylic acid, betacarboxyethyl acrylate, 2-hydroxyethyl acrylate, acrylonitrile, or mixtures thereof;
0 to 15 percent (preferably 0 to 5 percent) by weight of one or more other vinyl monomer; and
0 to 50 percent (preferably 5 to 20 percent) by weight of a crosslinker.

The percentages above are based on total weight of monomers in the polymerization. The crosslinker may be present during the polymerization of the vinyl monomers or it may be introduced at a subsequent step. The polymers are dispersed in a non-aqueous polar medium comprising solvent selected from the group consisting of esters, ketones, and mixtures thereof. The non-aqueous polar medium is adapted to retard hydrogen bonding of the monomers in the vinyl monomer component and to dissolve the polymeric acrylic dispersant. The microparticles are stabilized in a dispersed state by the inclusion of a polymeric acrylic dispersant free of polymerizable unsaturation.

Detailed Description
The coating compositions of the present invention comprise a polyepoxide resin; a polyacid curing agent; and an organic colloidal dispersion comprising carboxylic acidfunctional polymeric microparticles stably dispersed in a non-aqueous medium that can be either polar or non-polar. By "stable" is meant that the polar polymeric microparticles do not settle or precipitate upon standing.

As used herein, the term "polar" describes substances that contain polar groups such as hydroxyl groups; carboxyl or other acid groups; carbonyl groups; ether groups; ester groups; amide groups; amino groups; halogenated hydrocarbon groups; or other such polar groups. Conversely, the term "non-polar" describes substances that are essentially free of polar groups such as those mentioned above.

The organic colloidal dispersions of carboxylic acid-functional polymeric microparticles can be prepared by any of the methods described in the art; or preferably by the methods described herein. This method (referred to hereafter as Synthetic Route
I) involves a non-aqueous dispersion polymerization proceeding in a non-aqueous polar medium, and is capable of producing materials with very high levels of carboxylic acid functionality. By "very high", it is meant that the theoretical acid value of the carboxylic acid-functional polymeric microparticles produced by this method can be as much as about 780. Calculations yielding theoretical acid value are well understood by those skilled in the art of polymer synthesis and will not be discussed in detail here.

An alternative method (referred to hereafter as Synthetic Route II) involves emulsion polymerization proceeding in an aqueous polar medium and a transfer step in which the emulsion polymerization reaction product is transferred to a non-aqueous medium. The method is more completely described in US 5,212,273 which is incorporated by reference herein. The method disclosed in US 5,212,273, was used to prepare non-functional polymeric microparticles which were preferably dispersed in ester solvents, however the method can be used to produce materials with intermediate levels of carboxylic acid functionality dispersed in a variety of solvents. The specific manner of preparation for the present invention is fully detailed below.

By "intermediate", it is meant that the theoretical acid value of the carboxylic acid-functional polymeric microparticles produced by this method can be as much as about 400.

Another alternative method (referred to hereafter as Synthetic Route III) involves a non-aqueous dispersion polymerization proceeding in a non-aqueous, non-polar medium, and is capable of producing materials with elevated levels of carboxylic acid functionality. By "elevated", is meant that the theoretical acid value of the carboxylic acid-functional polymeric microparticles produced by this method can be as much as about 60.

Dispersions of carboxylic acid-functional polymeric microparticles can be prepared at various levels of carboxylic acid functionality via these three synthetic routes.

For the purposes of the claimed coating compositions, the theoretical acid value of the carboxylic acid-functional polymeric microparticles should be at least 10. To optimize the effect produced when the dispersions are added to the claimed acid-cured epoxy coating compositions, higher levels of acid functionality are desirable.

The specific mixture of monomers chosen to prepare the carboxylic acidfunctional polymeric microparticles is, in part, determined by the synthetic route that is employed. Generally, though, the carboxylic acid-functional polymeric microparticles can be prepared from the following mixture of materials in the indicated proportions:
1) about 1 percent to about 100 percent by weight of a carboxylic acid
functional vinyl monomer or mixture of such monomers;
2) up to about 99 percent by weight of hydroxyl-functional vinyl monomers,
nitrile functional vinyl monomers, or mixtures thereof;
3) up to about 97.5 percent by weight of a non-functional vinyl monomer or
mixture of such monomers; and
4) up to about 50 percent by weight of a crosslinker; wherein the total amount of the aforesaid components is equal to 100 percent.

Synthetic Route I
As mentioned, above, the synthesis of dispersions of carboxylic acid-functional polymeric microparticles via non-aqueous dispersion polymerization proceeding in a non-aqueous polar medium is denoted here as Synthetic Route I.

The organic colloidal dispersions prepared by Synthetic Route I comprise carboxylic acid-functional polymeric microparticles stably dispersed in a non-aqueous medium with a polymeric acrylic dispersant free of polymerizable unsaturation. The polymeric microparticles are insoluble in the non-aqueous medium used for polymerization while the polymeric acrylic dispersant is soluble in the non-aqueous medium. Because the polymerization is conducted directly in a non-aqueous medium, it is not necessary to dry the polar polymeric microparticles and transfer them to a different medium, although this is possible.

Carboxylic acid-functional polymeric microparticles prepared via Synthetic
Route I are prepared in a non-aqueous polar medium from:
1) about 1 percent to about 100 percent by weight of carboxylic acid
functional vinyl monomers;
2) up to about 99 percent by weight of hydroxyl-functional vinyl monomers
or nitrile functional;
3) up to about 15 percent by weight of non-functional vinyl monomers; and
4) up to about 50 percent by weight of crosslinker; wherein the total amount of the aforesaid components is equal to 100 percent. The resulting polymeric microparticles generally have a theoretical acid value of up to about 780 preferably from 10 to about 780.

Preferably, the carboxylic acid-functional polymeric microparticles of Synthetic
Route I are prepared from a vinyl monomer component comprising at least a major portion of, that is at least about 50 percent by weight of, acrylic acid; methacrylic acid; beta-carboxyethyl acrylate, acrylonitrile, 2-hydroxyethyl acrylate; or mixtures thereof; the percentage based on the total weight of monomers in the vinyl monomer component.

The monomers are chosen such that they are soluble in the non-aqueous polar medium in which polymerization is conducted, while the resulting polymer is insoluble.

More preferably, the vinyl monomer component is entirely comprised of the polar functional vinyl monomers listed above or mixtures thereof; however, non-functional vinyl monomers or functional vinyl monomers other than those listed above may be present if the solubility conditions are met. Examples include non-functional vinyl monomers such as methyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, and the like; and functional vinyl monomers such as hydroxyl functional monomers, glycidyl functional monomers, amino functional monomers and the like; well known to those skilled in the art, or mixtures thereof.

If present at all, the amount of these monomers, should be limited to levels which will not destabilize the microparticle dispersion, preferably to levels no higher than about 15 percent by weight, based on the total weight of monomers in the vinyl monomer component.

In a particularly preferred embodiment, the polar polymeric microparticles are prepared entirely from acrylic acid such that the resulting polymeric microparticles have a theoretical acid value of about 780.

Typically, polymerization of the monomers used to prepare the polymeric microparticles is initiated by free radical initiators that are soluble in the non-aqueous polar medium. Examples include peroxy initiators such as benzoyl peroxide, lauroyl peroxide, or tert-butylperoxy-2-ethyl-hexanoate (tert-butylperoctoate); or azo initiators such as 2,2'-azobis (2,4-dimethylpentane nitrile) or 2,2'-azobis (2-methylbutane nitrile)
The azo initiators are preferred.

Polymerization of the monomers used to prepare the polymeric microparticles is usually conducted at reflux temperature to prevent oxygen from inhibiting the polymerization reaction. Reflux temperature typically falls in the range of from about 60"C to about 200"C, and more commonly falls in the range of from about 70"C to about 140"C, depending on the boiling point of the solvents comprising the non-aqueous medium in which the microparticles are prepared.

The polymeric acrylic dispersant is free of polymerizable unsaturation. It is theorized that the dispersant is adsorbed onto the surfaces of the polar polymeric microparticles, and stabilizes them in the dispersed state by steric forces. It is further theorized that no grafting or chemical bonding between the dispersant and the polar polymeric microparticles is necessary for stabilization of the dispersion.

The polymeric acrylic dispersant can be prepared from a variety of vinyl monomers including non-functional vinyl monomers; hydroxyl-functional vinyl monomers; glycidyl-functional vinyl monomers; amino-functional vinyl monomers; silane-functional vinyl monomers; N-alkoxyalkyl functional vinyl monomers; or mixtures thereof.

Examples of suitable non-functional vinyl monomers include methyl methacrylate; methyl acrylate; n-butyl methacrylate; n-butyl acrylate; styrene; and the like. Examples of suitable hydroxyl-functional vinyl monomers include 2-hydroxyethyl methacrylate; 2-hydroxyethyl acrylate; 2-hydroxypropyl methacrylate; 2-hydroxypropyl acrylate; and the like. Examples of suitable glycidyl-functional vinyl monomers include glycidyl methacrylate; glycidyl acrylate; allyl glycidyl ether; and the like. Examples of suitable amino-functional vinyl monomers include N,N'-dimethylaminoethyl methacrylate; N-tert-butyl aminoethyl methacrylate; and the like. Examples of suitable silane-functional vinyl monomers include vinyl alkoxy, acrylato-alkoxy, and methacrylato-alkoxy silanes such as vinyl trimethoxy silane; gamma-methacryloxypropyl trimethoxy silane; and the like.

Examples of suitable N-alkoxyalkyl functional vinyl monomers include N-butoxymethyl acrylamide; N-isobutoxymethyl acrylamide; and the like.

A particularly preferred polymeric acrylic dispersant is prepared from about 40 percent glycidyl methacrylate; about 30 percent n-butyl methacrylate; and about 30 percent methyl methacrylate, the percentages based on the weight of monomers used to prepare the dispersant.

Typically, polymerization of the monomers used to prepare the polymeric acrylic dispersant requires free radical initiators. These must be soluble in the non-aqueous polar medium. Examples include the peroxy and azo initiators described above. The azo initiators are particularly preferred here also.

The polymeric acrylic dispersant is typically prepared by solution polymerization techniques. As with preparation of the microparticles, polymerization of the monomers used to prepare the polymeric acrylic dispersant is also conducted at reflux temperature to prevent oxygen from inhibiting the polymerization reaction. Reflux temperature typically falls in the ranges described above in connection with preparation of the microparticles.

The polymeric acrylic dispersant typically has a number-average molecular weight of from about 500 to about 100,000, preferably from about 1,000 to about 30,000 and more preferably from about 2,000 to about 10,000, as determined by gel permeation chromatography using polystyrene as a standard. The dispersant is typically prepared at a solids content of from about 20 percent to about 80 percent, preferably from about 50 percent to about 60 percent by weight, based on the total weight of the polymeric acrylic dispersant, as determined at 11 00C for one hour.

The polymeric acrylic dispersant is typically present in the dispersion of polar polymeric microparticles at levels of from about 2 percent to about 90 percent, preferably from about 10 percent to about 75 percent and more preferably from about 20 percent to about 30 percent, the percentage based on the weight of the solids of the dispersion.

The non-aqueous medium in which the dispersion polymerization proceeds is one that is adapted to retard hydrogen bonding of the monomers in the vinyl monomer component described above. Further, the medium is chosen such that the vinyl monomer component described above is dissolved while the resulting particulate polymer is not.

Additionally, the non-aqueous medium is chosen such that it dissolves the polymeric acrylic dispersant.

The non-aqueous medium is comprised of polar organic solvents. Typically these are ester or ketone solvents or mixtures thereof; preferably, the medium is comprised of ethyl acetate or a mixture of ethyl acetate and another suitable ester solvent. Other suitable ester solvents include n-butyl acetate, n-hexyl acetate, and mixtures thereof.

Examples of suitable ketone solvents include methyl ethyl ketone; methyl isobutyl ketone; and mixtures thereof. Mixtures of ester and ketone solvents can also be used. For example, in one embodiment, a mixture of ethyl acetate and methyl ethyl ketone is used as the non-aqueous medium.

The carboxylic acid-functional polymeric microparticles prepared by Synthetic
Route I can be crosslinked or uncrosslinked. Dispersions of crosslinked polar polymeric microparticles are generally preferred to dispersions of uncrosslinked polar polymeric microparticles because uncrosslinked materials are more likely to swell or dissolve in the organic solvents that are commonly found in many of the coating compositions to which the dispersions are subsequently added. However, in one embodiment, the polar polymeric microparticles of the dispersion are uncrosslinked.

When a crosslinker is used, the crosslinker type and level are usually chosen based on the functional groups present in the polar polymeric microparticles. For example, polyepoxide crosslinkers such as 3,4-epoxy cyclohexylmethyl-3,4-epoxy cyclohexane carboxylate, bis(3,4-epoxy cyclohexylmethyl) adipate, 1,3,5-triglycidyl isocyanurate and pentaerythritol tetra(2-glycidyloxycarbonyl cyclohexane carboxylate) are preferred when the polar polymeric microparticles contain mostly carboxylic acid functionality.

When the polar polymeric microparticles contain mostly hydroxyl functionality, polyisocyanate or polyanhydride crosslinkers are preferred. The polyisocyanate crosslinkers are particularly preferred.

Examples of suitable polyisocyanate crosslinkers include aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate or m-phenylene diisocyanate; aliphatic diisocyanates such as hexamethylene diisocyanate or tetramethylxylene diisocyanate; cycloalkylene diisocyanates such as 1 ,4-cyclohexane diisocyanate or isophorone diisocyanate; tri- or tetra-isocyanates such as triphenylmethane-4,4',4"-triisocyanate or 4,4'-dimethyl diphenylmethane-2,2',5,5'-tetraisocyanate; polymerized polyisocyanates such as tolylene diisocyanate dimers and trimers; and the like. Isophorone diisocyanate is preferred. Examples of suitable polyanhydride crosslinkers include monomeric species such as isoprene disuccinyl anhydride or pyromellitic dianhydride.

Typically, crosslinking is conducted in a separate synthetic step after the carboxylic acid-functional polymeric microparticles have been prepared. However, one can add the crosslinker with the vinyl monomer component provided the solubility conditions are met. More specifically, the crosslinker is chosen such that it is soluble in the non-aqueous medium in which polymerization is conducted. Further, the crosslinker is chosen such that the polymerization reaction produces a crosslinked polar polymeric microparticle that is insoluble in the non-aqueous medium in which the polymerization is conducted.

This is typically accomplished by choosing crosslinkers comprising polyfunctional vinyl monomers, for example, ethylene glycol dimethacrylate, divinyl benzene, pentaerythritol triacrylate, and the like. However, excessive amounts of these types of crosslinkers can lead to flocculation; therefore polyisocyanates or epoxides are preferred crosslinkers.

Generally, crosslinkers bearing different coreactive functional groups are not mixed. However, it will be appreciated by those skilled in the art that mixtures of such crosslinkers can be prepared and used provided the functional groups are appropriately modified to permit mixture. As mentioned above, the crosslinker can be used in amounts up to 50 percent by weight based on the total weight of the components used in preparing the microparticle, preferably from about 5 to about 20 percent by weight.

Polar polymeric microparticles prepared by Synthetic Route I can be transferred to a non-aqueous medium different from that in which the microparticles are prepared.

This is more readily accomplished when the microparticles have been crosslinked since flocculation and swelling are less likely to occur. Although transfer of uncrosslinked microparticles is not preferred, the medium into which the dispersion of uncrosslinked microparticles is transferred, is chosen such that it will not destabilize the dispersion by causing flocculation, nor swell the polar polymeric microparticles. In other words, the medium into which the dispersion of uncrosslinked microparticles is transferred must be a "poor" solvent for the microparticles but a "good" solvent for the polymeric acrylic dispersant; that is, it is chosen such that it will not dissolve the polar polymeric microparticles but will dissolve the polymeric acrylic dispersant.

Examples of solvents to which the crosslinked microparticle dispersions can be transferred include alcohols such as ethanol, isopropanol, n-butanol, n-propanol, and the like; esters such as n-butyl acetate, n-hexyl acetate, pentyl propionate, and the like; ethers such as the monoethyl, monobutyl and monohexyl ethers of ethylene glycol, and the like; ketones such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and the like; aromatic hydrocarbons such as xylene, or toluene, and the like; and mixtures thereof. Although a variety of solvents are offered as examples, solvents that are relatively much more or much less polar than the polar polymeric microparticles are not preferred. With these materials, transfer becomes difficult because of potential problems with destabilization of the dispersion and swelling of the microparticles.

Particularly preferred solvents into which crosslinked polar polymeric microparticles can be transferred are n-propanol, butyl acetate and ethyl-3-ethoxy propionate.

Transfer to a different medium can be achieved by a variety of methods, for example, by spray-drying, freeze-drying, coagulation, or centrifugation followed by redispersion in the new medium. Preferably, transfer to a different medium is accomplished by adding a new organic solvent to the dispersion then removing the unwanted solvent by distillation. All of these methods are well understood by those skilled in the art and will not be discussed in detail here.

The dispersions of polar polymeric microparticles can contain various other optional ingredients such as cosolvents, catalysts, or surfactants, though preferably, these are absent.

Synthetic Route II
The synthesis of dispersions of carboxylic acid-functional polymeric microparticles via emulsion polymerization proceeding in an aqueous medium is denoted here as Synthetic Route II.

Carboxylic acid-functional polymeric microparticles prepared via Synthetic
Route II are prepared in an aqueous medium from:
1) about 1 percent to about 50 percent by weight of carboxylic acid
functional vinyl monomers;
2) up to about 49 percent by weight of hydroxyl-functional vinyl monomers
or nitrile functional vinyl monomers or mixtures thereof;
3) up to about 94 percent by weight of non-functional vinyl monomers; and
4) about 5 percent to about 50 percent by weight of crosslinker; provided the total amount of components 1) and 2) described above does not exceed about 50 percent by weight; and wherein the total amount of components described above is equal to 100 percent. The resulting polymeric microparticles generally have a theoretical acid value of from about 10 to about 400.

Examples of carboxylic acid-functional vinyl monomers that can be used include acrylic acid or methacrylic acid and the like; and mixtures thereof.

Examples of hydroxyl-functional vinyl monomers that can be used include 2hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2hydroxypropyl methacrylate and the like; and mixtures thereof.

Examples of the non-functional vinyl monomers that can be used include esters of organic carboxylic acids such as acrylic acid or methacrylic acid, for example, esters of alkyl acrylates and alkyl methacrylates containing from 1 to 18, preferably 1 to 6 carbon atoms in the alkyl group. Most preferably, the non-functional vinyl monomers used are acrylic monomers, examples of which include methyl acrylate; n-butyl acrylate; methyl methacrylate; n-butyl methacrylate; and the like.

Also, polymerizable ethylenically unsaturated aromatic monomers such as styrene and alkyl-substituted styrenes having 1 to 4 carbon atoms in the alkyl group can be used as the non-functional vinyl monomer. Examples include alpha-methylstyrene; ethyl vinyl benzene; vinyl toluene; and the like.

Other examples of non-functional vinyl monomers include the alpha-olefins such as ethylene and propylene; vinyl esters of organic carboxylic acids such as vinyl acetate and vinyl propionate and diene compounds such as butadiene and isoprene, and the like.

The microparticles prepared by this synthetic method are generally crosslinked with from about 5 to about 50 percent of a suitable crosslinker, the percentage based on the sum of the total weight of all monomeric components and the weight of the crosslinker (as noted above).

Suitable crosslinkers include polyethylenically unsaturated monomers having at least two ethylenically unsaturated bonds in the molecule. Examples of such monomers are esters of a polyhydric alcohol and an ethylenically unsaturated monocarboxylic acid; esters of an ethylenically unsaturated monoalcohol and a polycarboxylic acid and an aromatic compound having at least two vinyl substituents; or an ester of a polyhydric alcohol with an ethylenically unsaturated mono-carboxylic acid such as the polyacrylate or polymethacrylate ester of an alkylene polyol having two to three hydroxyl groups and in which the alkylene group contains two to eight carbon atoms.

Preferably, crosslinkers are difunctional vinyl monomers, and more preferably, difunctional acrylic monomers. Examples include the glycol diacrylates and dimethacrylates, specifically, ethylene glycol diacrylate; ethylene glycol dimethacrylate; neopentyl glycol diacrylate; neopentyl glycol dimethacrylate; and the like. Other examples include di-, tri- or tetrafunctional vinyl monomers such as tetraethylene glycol dimethacrylate; 1,6,-hexanediol diacrylate; 1,6,-hexanediol dimethacrylate; pentaerythritol diacrylate; pentaerythritol dimethacrylate; trimethylolpropane triacrylate; trimethylolpropane trimethacrylate; pentaerythritol tetramethylacrylate; triallylisocyanurate; diallylphthalate; divinylbenzene; and the like. Ethylene glycol dimethacrylate is a particularly preferred crosslinker.

Crosslinkers can also be of the polyisocyanate type. Examples include the aromatic diisocyanates; aliphatic diisocyanates; cycloalkylene diisocyanates; tri- or tetraisocyanates; and polymerized polyisocyanates all of which have been exemplified in connection with synthetic Route I, above.

Alternatively, crosslinkers can be epoxy-functional vinyl monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, N-glycidyl acrylamide, vinyl cyclohexane monoepoxide, and the like.

Similar to Synthetic Route I, mixtures of crosslinkers bearing different coreactive functional groups are generally not used unless appropriately modified to permit mixture.

In a preferred embodiment, the crosslinked microparticle is prepared from about 18 percent methyl methacrylate, about 18 percent n-butylacrylate, about 21 percent styrene, about 29 percent ethylene glycol dimethacrylate and about 14 percent methyl methacrylate. Typically, polymerization is initiated with free-radical initiators.

Preferably, a persulfate initiator such as ammonium, sodium or potassium persulfate is used; alternatively, a perphosphate initiator such as potassium perphosphate; or a peroxy initiator such as t-butyl-hydroperoxide, cumene hydroperoxide or, simply, hydrogen peroxide can be used.

The amount of initiator required is usually from about 0.1 to about 5 percent, preferably from about 0.2 to about 3 percent by weight, the percentage based on the total weight of the polymerizable monomers.

Polymerization is typically conducted in the presence of a surfactant. Among the surfactants that can be used are anionic, cationic and non-ionic surfactants, including mixtures of anionic and non-ionic or mixtures of cationic and non-ionic surfactants.

Water-soluble anionic surfactants are generally preferred. Examples of such anionic surfactants include alkali metal and ammonium salts of long chain alkyl sulfates, sulfonates and sulfosuccinates; alkali metal and ammonium phosphate esters and alkali metal and ammonium alkyl phenoxy polyethoxysulfates, sulfonates or phosphates in which the alkyl group contains from about 4 to about 18 carbon atoms and the oxyethylene units range from about 6 to about 60. Specific examples include sodium lauryl sulfate, sodium cetyl sulfate and ammonium nonylphenoxy (polyethoxy)6 60 sulfonate.

Examples of cationic surfactants include quaternary ammonium salts such as tetramethyl ammonium chloride and ethylene oxide condensates of cocoamines.

Examples of non-ionic surfactants include alkylphenoxy polyethoxy ethanols having alkyl groups of from about 4 to about 18 carbon atoms and from about 6 to about 60 or more oxyethylene units such as octylphenoxy polyethoxy ethanol, nonylphenoxy (polyethoxy)6 60 ethanol and dodecylphenoxy (polyethoxy)6 60 ethanol. Also, ethylene oxide derivatives of long chain acids such as lauric and oleic acid can be used as can ethylene oxide condensates of long chain alcohols such as octyl, decyl, lauryl or cetyl alcohol.

The amount of surfactant can vary, but generally is not more than about 15 percent. More preferably, the amount is from about 2 to about 10 percent, and most preferably from about 4 to about 7 percent by weight based on the total weight of polymerizable ethylenically unsaturated monomers.

Polymerization is usually conducted at temperatures below about 90"C, preferably in the range of from about 25"C to about 80"C, although slightly lower or higher temperatures can be used.

Carboxylic acid-functional polymeric microparticles produced by Synthetic
Route II are, by definition, dispersed in aqueous media. They must be dehydrated by one of a variety of methods before they can be stably dispersed in an organic medium.

Transfer to an organic medium can be achieved by the variety of methods described above in Synthetic Route I, for example, by azeotropic distillation followed by inversion into the organic medium. As mentioned above, all of these methods are well appreciated by those skilled in the art.

The medium into which the dispersion is transferred is chosen such that it is sufficiently polar to avoid destabilization of the dispersion of polymeric microparticles by flocculation, nor swell the polymeric microparticles. Examples of solvents to which the crosslinked microparticle dispersions can be transferred include all of those described above in connection with Synthetic Route I. Relatively polar and relatively non-polar solvents are not preferred because transfer becomes difficult, leading to problems of destabilization and swelling ofthe carboxylic acid-functional microparticles. The alcoholic solvents are preferred with n-butanol being particularly preferred or a mixture of n-butanol and n-butylacetate.

Synthetic Route III
The synthesis of dispersions of carboxylic acid-functional polymeric microparticles via non-aqueous dispersion proceeding in a non-aqueous, non-polar medium is denoted here as Synthetic Route Ill. When Synthetic Route III is employed, the carboxylic acid-functional polymeric microparticles in a non-aqueous nonpolar medium from:
1) about 2 percent to about 15 percent by weight of carboxylic acid
functional vinyl monomers;
2) up to about 25 percent by weight of hydroxyl-functional vinyl monomers
or nitrile functional vinyl monomers or mixtures thereof;
3) about 50 to about 97.5 percent by weight of non-functional vinyl
monomers; and
4) from about 0.5 percent to about 10 percent by weight of an epoxy
functional vinyl monomer as crosslinker; wherein the total amount of the four components described above is equal to 100 percent.

The resulting polymeric microparticles generally have a theoretical acid value of from about 10 to about 60.

When employing Synthetic Route III, carboxylic acid-functional vinyl monomers are polymerized in the presence of epoxy-functional vinyl monomers as crosslinkers such that there is a molar excess of the carboxylic acid-functional vinyl monomer. A polymeric chain, containing carboxylic acid and/or epoxy functional groups is formed initially. Subsequently, the epoxy functional groups react with the carboxylic acid groups to form a crosslinked polymeric microparticle. A non-functional vinyl monomer component is also present. Preferably, hydroxyl-functional and nitrile functional monomers are absent.

The monomers are chosen such that they are soluble in the non-aqueous, non polar medium while the resulting polymer is insoluble.

Examples of suitable carboxylic acid-functional vinyl monomer include acrylic acid; methacrylic acid; beta-carboxyethylacrylate; and the like. Mixtures of the above carboxylic acid-functional monomers can be used as well.

Examples of suitable crosslinking epoxy-functional vinyl monomers include glycidyl methacrylate; glycidyl acrylate; allyl glycidyl ether; N-glycidyl acrylamide, vinyl cyclohexane monoepoxide, and the like. Mixtures of the above crosslinkers can be used as well.

Examples of suitable non-functional vinyl monomers include methyl methacrylate; methyl acrylate; n-butyl methacrylate; n-butyl acrylate; and the like.

Mixtures of the above non-functional vinyl monomers can be used as well.

Typically, polymerization is initiated with free-radical initiators. Preferably, an azo type initiator such as 2,2-azobis (2-methylbutanenitrile) is used. Alternatively, a peroxy initiator such as lauryl peroxide, benzoyl peroxide or t-butyl peroctoate can be used.

The amount of initiator required is usually from about 0.1 to about 5 percent, preferably from about 0.2 to about 3 percent by weight, based on the total weight of the polymerizable monomers.

Polymerization proceeds in the presence of an amphipathic stabilizer added at a level of from about 5 percent to about 98 percent, the percentage based on the total weight of all monomers present. By amphipathic, it is meant that the stabilizer is a socalled "comb-type" stabilizer, that is, a stabilizer comprising a lyophobic backbone and numerous lyophillic side chains; or, alternatively, a lyophillic backbone and numerous lyophobic side chains. Typically, it is a block or graft polymer such as those described in
U.S. Patent No. 4,220,679, column 8, which is incorporated by reference herein.

Specifically, the amphipathic stabilizer can be a polymer comprising an acrylic backbone derived mainly from methyl methacrylate and numerous side chains composed of poly (12-hydroxy-stearic acid).

Polymerization is usually conducted at the reflux temperature of the solvent or solvent mixture, typically from about 95O5C to about 1 00O5C temperature, although slightly lower or higher temperatures can be used.

Typically, a catalyst is added along with the monomer feed to accelerate the crosslinking reaction between the epoxy and carboxylic acid groups during the formation of the crosslinked particle, although this is optional. Suitable catalysts include tertiary amine compounds such as triethylamine or dimethylethylamine. A preferred catalyst for the reaction is cocodimethylamine commercially available from Armak Chemicals as
ARMEEN DMCD.

The polymerization is conducted in a non-aqueous non-polar medium. The medium is chosen such that the monomer component described above is dissolved while the resulting microparticulate polymer is not. Additionally, the non-aqueous medium is chosen such that it dissolves the amphipathic stabilizer. In other words, the medium chosen must be a "poor" solvent for the microparticles but a "good" solvent for the amphipath ic stabilizer.

Typically, the non-aqueous, non-polar medium consists primarily of an aliphatic hydrocarbon solvent, an aromatic hydrocarbon solvent, or mixtures thereof. These materials are "poor" solvents for most polymers. However, they are generally also "poor" solvents for the film forming polymers used in formulating the coating compositions to which the dispersions of carboxylic acid-functional polymeric microparticles are subsequently added.

Examples of solvents that can be used as the non-aqueous, non-polar medium include alkane or cycloalkane compounds containing from 1 to about 15 carbon atoms.

Specific examples of suitable solvents include hexane, heptane, octane, decane, and the like. Mixtures of these solvents can be used as well. Although, individual solvents may have boiling points higher than the preferred polymerization temperature, described above, it should be understood these solvents can be-blended with lower boiling solvents resulting in a mixture having an appropriate reflux temperature.

Carboxylic acid-functional polymeric microparticles produced by Synthetic
Route III are prepared directly in non-aqueous, non-polar media. Transfer to a different organic medium is usually problematic, and hence not preferred, since there are limited media that will not destabilize the dispersion.

Regardless of the synthetic route employed, the carboxylic acid-functional polymeric microparticles produced in accordance with the present invention are of colloidal dimensions, that is, from about 0.001 to about 5 microns (10 to 50,000
Angstroms) in diameter, preferably, from about 0.05 to about 0.5 microns (500 to 5000
Angstroms) in diameter. The particle size can be measured by light scattering techniques, for example, with a particle size analyzer such as the Coulter N4 instrument, commercially available from Coulter.

Also regardless of the synthetic route employed, the dispersions that are produced are typically prepared at a solids content of from about 15 percent to about 75 percent, preferably from about 25 percent to about 50 percent by weight, based on the total weight of the dispersion.

Coating Compositions
The organic colloidal dispersions of carboxylic acid-functional polymeric microparticles prepared by any of the three synthetic routes described above are easily incorporated into the claimed coating compositions with agitation. In accordance with the present invention, the dispersions are added to acid-cured epoxy resin based coating compositions in an amount effective to inhibit sagging. Typically, this is accomplished at a level of from about 1 percent to about 80 percent by weight, preferably from about 2 to about 70 percent by weight, more preferably from about 2 to about 25 percent by weight, the percentages based on the total weight of solids present in the coating composition.

The use of these dispersions is particularly desirable in coating compositions that contain flake pigments, particularly aluminum flake or mica, in that they help to orient the pigment properly in the film, resulting in a lustrous shiny appearance with excellent flop, distinctness of image and high gloss. "Flop" describes the visual change in brightness or lightness of a metallic coating with a change in viewing angle, that is, a change from 180 to 90 degrees. The use of the dispersions is particularly advantageous in that sagging of the applied coating is inhibited while the excellent appearance properties of the coating are not compromised.

The claimed coating compositions can be one-package or two package systems, as described in U.S. Patent Nos. 5,196,485 and 4,650,718, respectively. In accordance with the present invention, a one-package composition is preferred. This composition is further characterized in that it is substantially free of basic esterification catalyst, it has a cured softening point of above about 20"C and a minimum solids content of about 40 percent by weight.

Besides the dispersions of carboxylic-acid functional polymeric microparticles prepared as described above, the claimed coating compositions comprise a polyepoxide resin as film former and a polyacid curing agent. Optionally, the coating composition can further comprise up to about 30 percent by weight of an aminoplast resin.

Although any of the conventionally known polyepoxide resins can be used in the claimed coating compositions, the preferred one-package compositions contain a polyepoxide resin with a high level of epoxy functionality, and a correspondingly low epoxide equivalent weight. More specifically, the polyepoxide resin has an epoxide equivalent weight on resin solids of less than about 600, more preferably less than about 400, and most preferably less than about 300. The polyepoxide resin also preferably has a relatively low molecular weight. More specifically, the polyepoxide resin has a weight average molecular weight of less than about 20,000, more preferably less than about 10,000 and most preferably less than about 5000, as determined by gel permeation chromatography using polystyrene standard as a standard.

Among the polyepoxides that can be used are epoxy-functional acrylic polymers, epoxy condensation polymers such as polyglycidyl ethers of alcohols and phenols, polyglycidyl esters of polycarboxylic acids, certain polyepoxide monomers and oligomers and mixtures thereof. Epoxy-functional acrylic polymers prepared from methacrylate and styrene monomers are preferred.

Examples of the epoxy-containing acrylic polymers include copolymers of an ethylenically unsaturated monomer having at least one epoxy group; and at least one polymerizable ethylenically unsaturated monomer that is free of epoxy groups. Examples of ethylenically unsaturated monomers containing epoxy groups are those containing 1,2 epoxy groups and include glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether.

Ethylenically unsaturated monomers that do not contain epoxy groups can also be used. Specific examples include alkyl esters of acrylic and methacrylic acid containing from 1 to about 20 carbon atoms in the alkyl group such as methyl methacrylate and nbutyl acrylate; vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl and vinylidine halides such as vinyl chloride and vinylidine fluoride; and vinyl esters such as vinyl acetate.

The epoxy group-containing ethylenically unsaturated monomer is preferably used in an amount of from about 20 to about 90 percent, more preferably from bout 30 to about 70 percent by weight of the total monomers used in preparing the epoxy-containing acrylic polymer. Of the remaining polymerizable ethylenically unsaturated monomers, preferably from about 10 to about 80 percent, preferably from about 30 to about 70 percent by weight of the total monomers are the alkyl esters of acrylic and methacrylic acid.

The epoxy condensation polymers used are polyepoxides, that is, those having a 1,2-epoxy equivalency greater than 1, preferably up to about 5.0. Useful examples of such epoxides are polyglycidyl esters from the reaction polycarboxylic acids with epihalohydrin such as epichlorohydrin. The polycarboxylic acid can be formed by any method known in the art, and in particular, by the reaction of aliphatic alcohols with an anhydride, and in particular, diols and higher functionality alcohols. For example, trimethylol propane of pentaerythritol can be reacted with hexahydrophthalic anhydride to produce a polycarboxylic acid that is then reacted with epichlorohydrin to produce a polyglydicyl ester.

Further examples of such epoxides are polyglycidyl ethers of polyhydric phenols and of aliphatic alcohols. These polyepoxides can be produced by etherification of the polyhydric phenol or aliphatic alcohol with an epihalohydrin such as epichlorohydrin in the presence of alkali.

Examples of suitable polyphenols are 2,2-bis (4-hydroxyphenyl) propane (Bisphenol A) and 1 ,1-bis-(4-hydroxyphenyl)ethane. Examples of suitable aliphatic alcohols are ethylene glycol, diethylene glycol, pentaerythritol, trimethylol propane, 1,2 propylene glycol and 1,4-butylene glycol. Also, cycloaliphatic polyols such as 1,2 cyclohexanediol, 1 ,4-cyclohexanediol, 1,4-cyclo-hexane dimethanol, 1,2bis(hydroxymethyl) cyclohexane and hydrogenated Bisphenol A can also be used.

Besides the epoxy-containing polymer described above, certain polyepoxide monomers and oligomers can also be used. Examples of these materials are described in
U.S. Patent No.4,102,942 in column 3, lines 1-16, which is incorporated by reference herein. These materials are aliphatic polyepoxides, as are the epoxy-containing acrylic polymers. The epoxy-containing acrylic polymers are generally preferred because they result in products that have the best combination of coating properties.

The polyepoxide is present in the film-forming composition in amounts of about 10 percent to about 90 percent by weight, preferably from about 40 percent to about 70 percent by weight, the percentages based on the total weight of resin solids.

The composition of the present invention further includes a polyacid component having a high average acid functionality. More specifically, the polyacid curing agent of the present invention on average contains greater than two acid groups per molecule, more preferably three or more, and most preferably four or more, such acid groups. These acid groups can react with the polyepoxide to form a coating that is crosslinked, as indicated by the coating's resistance to organic solvent.

Mixtures of polyacid curing agents in which difunctional curing agents are mixed with tri- or higher functionality polyacid curing agents are suitable for the purposes of the present invention. Mixtures of polyacid curing agents including up to about 50 percent of a difunctional curing agent with a trifunctional curing agent are also suitable. Higher percentages of difunctional material can also be useful.

The acid functionality is preferably carboxylic acid, although acids such as phosphorus-based acid can be used. Preferably, the polyacid curing agent is a carboxylic acid terminated material having, on average, greater than two carboxylic acid groups per molecule. The polyacid curing agents that can be used include carboxylic acid groupcontaining polymers such as acrylic polymers, polyester and polyurethanes; oligomers such as ester group-containing oligomers and monomers.

Preferred polyacid curing agents are ester group-containing oligomers. Examples include half-esters formed from reacting polyols and 1,2-acid anhydrides or acid functional polyesters derived from polyols and polyacids or anhydrides. The half-esters are generally preferred.

The half-ester is obtained by reaction between a polyol and a 1,2-acid anhydride under conditions sufficient to ring-open the anhydride forming the half-ester with substantially no polyesterification occurring. By this, it is meant that less than 10 percent, and preferably less than 5 percent by weight high molecular weight polyester is formed.

Such reaction products are of relatively low molecular weight with narrow molecular weight distributions and low viscosity.

Among the polyols that can be used are simple polyols, that is, those containing from about 2 to about 20 carbon atoms, preferably from about 2 to about 10 carbon atoms. Specific examples include pentaerythritol, trimethylol propane, trimethylol ethane, 1,2,6-hexanetriol, glycerin, trishydroxyethyl isocyanurate, dimethylol propionic acid, ethylene glycol, neopentyl glycol, diethylene glycol, and the like.

Oligomeric polyols and polymeric polyols such as polyester polyols, polyurethane polyols and acrylic polyols can be used as well. Specific examples include the reaction products of diacids and triols, for example, the reaction product of trimethylol propane and adipic acid; or the reaction product of polycarboxylic acids or anhydrides thereof and organic polyols or epoxides. The acid component of the polyester consists primarily of monomeric carboxylic acids or anhydrides having from about 2 to about 18 carbon atoms per molecule. Among the acids that are useful are phthalic acid, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, maleic acid, glutaric acid, and the like. The polyols used in such reactions include trimethylol propane, the alkylene glycols, or other glycols such as hydrogenated Bisphenol A, and the like.

Polyester polyols formed from polylactone-type polyesters can also be employed.

Polyurethane polyols such as polyester-urethane polyols that are formed from reacting an organic polyisocyanate with a polyester polyol can be used as well.

Among the anhydrides that can be used in the formation of the desired polyesters are those which, exclusive of the carbon atoms and the anhydride moiety, contain from about 2 to about 30 carbon atoms. Examples include aliphatic, olefinic, and aromatic anhydrides. Specific examples include succinic anhydride, methylsuccinic anhydride, dodecyl succinic anhydride, phthalic anhydride, maleic anhydride and the like.

The polyacid curing agent is present in the crosslinkable composition in amounts of about 10 percent to about 90 percent, preferably of from about 25 percent to about 75 percent by weight, based on the total weight of resin solids.

In a preferred embodiment, the coating composition is substantially free of any basic esterification catalyst. Although the absence of catalyst has a negative effect on cure of the composition, it is beneficial because it provides for a stable composition and is also beneficial in reducing or eliminating cure inhibition between layers in a colorplus-clear formulation when the basecoat contains an acid catalyzed resinous binder.

More specifically, in a preferred embodiment, the composition of the present invention has no or only small amounts of basic esterification catalyst such that the composition is stable for a time sufficient to allow formulation of the composition as a single-component composition.

The present invention further optionally includes an aminoplast resin for improved resistance to water spotting. Typically, when present, the aminoplast resin of the present invention is present in the composition in amounts up to about 30 percent by weight, more preferably up to about 20 percent by weight, and most preferably up to about 15 percent by weight.

Aminoplast resins are condensation products of amines or amides with aldehydes. Examples of suitable amines or amides are melamines, benzoguanamines, ureas or similar compounds. Suitable aminoplast resins are commercially available from
CYTEC Industries under the trademark CYMEL and from Monsanto Chemical Company under the trademark RESIMENE. A preferred aminoplast resin is methylated melamineformaldehyde condensate.

Alternatively, optionally, an anhydride copolymer such as that prepared from 1octene, maleic anhydride and ethanol can be used in conjunction with the polyacid curing agent to facilitate cure and modify physical properties of the cured film such as hardness and water resistance
The present composition can also include other optional ingredients, such as plasticizers, anti-oxidants, UV light absorbers, surfactants, flow control agents, thixotropic agents, anti-gassing agents, organic co-solvents, catalysts, and epoxy crosslinkers. These components can constitute up to about 40 percent by weight of the coating solids.

Where the coating composition of the present invention is used as a one-coat system or as the basecoat in a color-plus-clear system, the composition will also include pigments. These can be flake pigments, for example, aluminum flake or mica; or they can be pigments of the conventional type, for example inorganic pigments such as titanium dioxide, carbon black, iron oxide, or lead chromate; organic pigments such as phthalocyanine blue and green, or perrindo maroon; fillers, flatteners or extenders such as china clay, barytes, silicas or bentonites; or mixtures thereof.

In general, the pigments are incorporated into the coating composition in amounts of from about 0.5 percent to about 80 percent by weight based on the weight of coating solids. Flake pigments are employed in amounts of from about 0.5 percent to about 25 percent by weight based on the weight of coating solids.

Where the coating composition of the present invention is used as a topcoat in a color-plus-clear system, the film-forming composition of the basecoat can be any of the compositions useful in coating applications, particularly automotive applications.

The coating compositions of the present invention can be applied any of the various substrates to which they adhere. Specific examples of suitable substrates include wood, metals, glass, cloth, plastic, foam, elastomeric substrates, and the like. The compositions can be applied by conventional means including brushing, dipping, flow coating, spraying and the like, but preferably, they are applied by spraying. The usual spray techniques and equipment for air-spraying or electrostatic spraying can be used.

The coating composition of the present invention is applied to the substrate to a uniform thickness from about 0.25 mils to about 5.0 mils, preferably from about 0.5 mils to about 2.0 mills. Once the coating composition is applied, film formation can be achieved with heating. Typically, a baking schedule of from about 5 minutes to about 60 minutes, preferably of from about 20 minutes to about 40 minutes at from about 1 000C to about 200 C is required.

The compositions of the present invention can be applied as a one-coat system; or as the basecoat or the topcoat or both in a color-plus-clear system. Typically, the claimed coating composition is used as a clear topcoat to be applied over a pigmented basecoat.

When used in a color-plus-clear system, first the pigmented basecoat is applied to a uniform film thickness of from about 0.25 mils to about 1.5 mils. It is then "flashed," that is, it is left to stand at temperatures ranging from the ambient temperature to about 80" C for about 10 seconds to about 30 minutes or longer before another coating composition is applied to it. Then, typically, a clear topcoating composition is applied over the coated substrate in one or more coats to a uniform film thickness from about 1.0 mils to about 5.0 mils. The substrate is then flashed again and finally baked until the film is cured, typically from about 20 minutes to about 40 minutes at from about 1 000C to about 2000 C to produce the coated article of the present invention.

Illustrating the invention are the following examples that, however, are not to be considered as limiting the invention to their details. All parts and percentages in the examples as well as throughout the specification are by weight unless otherwise indicated.

EXAMPLES
The following examples illustrate the synthesis of carboxylic acid functional polymeric microparticles and their use in acid-cured epoxy coating compositions.

Examples A-C illustrate the synthesis of carboxylic acid functional polymeric microparticles in accordance with the present invention. Examples D-E illustrate the synthesis of polymeric microparticles having an acid value of less than 5 in accordance with the prior art. Examples 1-6 illustrate the synthesis of various polymers used to prepare the acid-cured epoxy coating compositions of the present invention.

Examples I-XII illustrate the preparatidn of various acid-cured epoxy coating compositions. Three different formulations are presented. Examples I-III represent one formulation, examples IV - VIII represent a different formulation, and Examples IX - XII represent a third formulation. Each of the three formulations was prepared at least two ways:
1) Each formulation was prepared using carboxylic acid functional
polymeric microparticles in accordance with the present invention; and
2) Each formulation was prepared using fumed silica as a conventional flow
control agent.

Additionally, comparative examples showing coating compositions prepared using nonfunctional polymeric microparticles as flow control agents or using no flow control agent were also included. These comparative examples also represent the prior art. Tables 1-3 show the results of various tests comparing the coating compositions of
Examples I-XIl.

In all the examples, the particle size of the polymeric microparticles is reported in
Angstroms, and was determined using a Coulter N4 particle size analyzer, commercially available from Coulter. The particle size of fumed silica dispersions was determined using a Hegman grind gauge. Number-average molecular weight and weight-average molecular weight were determined by Gel Permeation Chromatology (GPC), using polystyrene as a standard. Weight percent solids were determined at 1100C for one hour. Weight percent water was determined by the Karl-Fisher titration method.

Viscosity was measured with a Brookfield viscometer, model RTV commercially available from Brookfield Engineering Labs, Inc. Alternatively viscosity was measured with a Gardner-Holdt bubble tube, commercially available from Gardner.

Experimentally determined acid values were measured by titration with 0.1 methanolic potassium hydroxide.

NON-AQUEOUS DISPERSIONS OF POLYMERIC MICROPARTICLES
The following examples show the preparation of non-aqueous dispersions of polymeric microparticles.

EXAMPLE A
A non-aqueous dispersion of acid functional polymeric microparticles was prepared according to Synthetic Route I as follows:
First, a glycidyl-functional polymeric acrylic dispersant was prepared. An initial charge of 750 grams of ethyl acetate was heated to reflux temperature in a reaction vessel suitable for acrylic solution polymerization. A mixture of 750.0 grams of ethyl acetate, 800.0 grams of glycidyl methacrylate, 600.0 grams of n-butyl methacrylate, 600.0 grams of methyl methacrylate and 100.0 grams of 2,2'-azobis(2-methylbutane) nitrile, (commercially available from E.I du Pont de Nemours and Company as VAZO-67), was added in a substantially continuous manner over a period of 5 hours while maintaining the reaction mixture at reflux temperature.

At the completion of the addition, the reaction mixture was held for 3 hours at reflux temperature to complete the polymerization. The resultant acrylic polymer was cooled and filtered. The polymer had 61.4 weight percent solids.

To prepare the non-aqueous dispersion, an initial charge of 44.5 grams of the glycidyl functional polymeric acrylic dispersant prepared above and 281.3 grams of ethyl acetate was heated to reflux temperature in a reaction vessel suitable for dispersion polymerization. A mixture of 27.3 grams of ethyl acetate, 82.0 grams of acrylic acid and 1.6 grams of tert-butylperoctoate (commercially available from Atochem at 50% active material in odorless mineral spirits as Lupersol(g) PMS) was added in a substantially continuous manner over a period of 3 hours while maintaining the reaction mixture at reflux temperature. At the completion of the addition, the reaction mixture was held for about 2 hours at reflux temperature to complete the polymerization. The reaction product was cooled and filtered to yield a stable dispersion at 24.5 weight percent solids.

The theoretical acid value of this material was about 585 based on polymer solids.

EXAMPLE B
The following example shows the preparation of a non-aqueous dispersion of carboxylic acid functional polymeric microparticles according to Synthetic Route II:
Ingredients Parts by Weight
Initial Charge
Deionized water 609.60 ALIPAL-CO4361 2.85
Feed 1
Methyl methacrylate 6.20 n-Butyl acrylate 6.60
Feed 2
Deionized water 4.80
Feed 3
Deionized water 4.00
Ammonium persulfate 0.80
Feed 4
Deionized water 2.40
Feed 52
Styrene 62.80
Methyl methacrylate 46.20 n-Butyl acrylate 46.20
Ethyleneglycol dimethacrylate 86.50
Methacrylic acid 42.60 ALIPAL-CO436 22.10
Deionized water 178.0
Feed 6
Deionized water 96.80
Ammonium persulfate 1.12
Sodium tetraborate decahydrate 0.15
Feed 7
Deionized water 14.40
Feed 8
Deionized water 11.80
Feed 9 n-Butanol 800.00
I Ammonium salt of ethoxylated nonyl phenol

sulfate commercially
available from Rhone-Poulenc, Inc.

2 Feed 5 was pre-emulsified by adding the vinyl monomers to an agitated
solution of the ALIPAL-CO436 and the deionized water.

The initial charge was heated to 830C with agitation under a nitrogen blanket in a reaction vessel suitable for aqueous emulsion polymerization and azeotropic distillation at low pressure. Feeds 1 and 2 were added to the reaction vessel and the reaction mixture was held for 5 minutes at 820C. Feeds 3 and 4 were then added, and the reaction mixture was held at 820C for 30 minutes. Next, the pre-emulsified monomer mixture (Feed 5) and Feed 6 were added to the reaction mixture simultaneously over a 3-hour period while maintaining the reaction mixture at about 820C. At the completion of this addition, the addition funnels were rinsed with Feeds 7 and 8, and the reaction mixture was held for 2 hours at 820C to complete the polymerization.

Finally, Feed 9 was added to the reaction vessel and the reaction mixture was agitated for 30 minutes to invert the aqueous emulsion into organic diluent. The agitation was stopped and the mixture was held for phase separation. The clear aqueous layer that formed at the bottom of the vessel (about 600 grams) was drained out. The reaction mixture was dehydrated by azeotropic distillation at low pressure. The reaction product was cooled and filtered to yield a stable, bluish colored dispersion at 25.2 weight percent solids, 1.7 weight percent water, with a particle size of 768 Angstroms and a viscosity of 1 12 centipoise, measured with a &num;2 spindle at 50 RPM. The theoretical acid value of this material was 94 based on polymer solids.

The following example shows the preparation of a non-aqueous dispersion of carboxylic acid functional polymeric microparticles according to Synthetic Route III:
Ingredients Parts by Weight
Initial Charge
n-Heptane 1,023.3
Isopar E1 137.7 Feedl
Amphipathic stabilizer2 81.6
Methyl methacrylate 42.0
VAZO-67 3.6
Isopar E 150.6
Feed 2
Methyl methacrylate 252.6
Glycidyl methacrylate 14.7
Methacrylic acid 27.6
n-Octyl mercaptan 3.0
Amphipathic stabilizer 103.8
VAZO-67 1.2
N,N-Dimethylcocoamine 0.9
n-Heptane 168.9
Isopar E 72.3
Feed 3 n-Heptane 10.5
Isopar E 4.2 A A blend of synthetic aliphatic hydrocarbons commercially available from
EXXON Chemical Company.

2 The amphipathic stabilizer was prepared by inter-polymerizing 45.4 weight
percent methyl methacrylate, 4.2 weight percent glycidyl methacrylate,
0.9 weight percent methacrylic acid, and 49.5 weight percent of a methacrylate
terminated polyester as follows: The polyester was prepared from 89.2 percent
12-hydroxystearic acid, 10.8 percent glycidyl methacrylate at 83.5 percent
solids in a mixture of 80 percent toluene and 20 percent VM & Naphtha.

The resulting polymer was reduced to 40 weight percent solids with a blend of
68.5 weight percent n-butyl acetate, 26.4 weight percent of an aliphatic and
aromatic hydrocarbon mixture, commercially available from Unocal as
Unocal Blend 2324, and 5.1 weight percent toluene.

The initial charge was heated to reflux temperature with agitation in a reaction vessel suitable for dispersion polymerization. Feed I was added to the reaction vessel over 10 minutes and the reaction mixture was held for 1 hour at reflux temperature. Feed
2 was added in a substantially continuous manner over a period of 3 hours while
maintaining the reaction mixture at reflux temperature. At the completion of Feed 2, the
addition funnel was rinsed with Feed 3 and the reaction mixture was held for 1 hour at
reflux temperature to complete the polymerization. The reaction product was cooled and
filtered to yield a stable dispersion at 19.0 weight percent solids. The theoretical acid
value of this material was about 30 based on solids assuming complete reaction of all
methacrylic acid monomer.

COMPARATIVE EXAMPLE D
The following example shows the preparation of a non-aqueous dispersion of
non-functional polymeric microparticles in accordance with U.S. Pat. No. 5,212,273.

Ingredients Parts by Weight
Initial Charge
Deionized water 2,460.1
ALIPAL-CO436 17.1
Feed 1
Methyl methacrylate 37.4
n-Butyl acrylate 40.2
Feed 2
Deionized water 28.7
Feed 3
Deionized water 24.0
Ammonium persulfate 4.9
Feed 4
Deionized water 14.4
Feed 51
Styrene 518.3
Methyl methacrylate 259.8
n-Butyl acrylate 259.8
Ethyleneglycol dimethacrylate 688.8
ALIPAL-CO436 133.9
Deionized water 1,082.5
Feed 6
Deionized water 317.1
Ammonium persulfate 3.4
Sodium tetraborate decahydrate 0.8
Feed 7
Deionized water 71.9
Feed 8
Deionized water 86.2
Feed 9
EXXATE-6002 Feed9 4,500.0
Feed 5 was pre-emulsified by adding the vinyl monomers to an agitated
solution of the ALIPAL-C0436 and the deionized water.

2 Hexyl acetate, commercially available from Exxon Chemical
Company.

The initial charge was heated to 800C with agitation under a nitrogen blanket in a reaction vessel suitable for aqueous emulsion polymerization and azeotropic distillation at low pressure. Feeds 1 and 2 were added to the reaction vessel and the reaction mixture was held for 5 minutes at 800C. Feeds 3 and 4 were then added, and the reaction mixture was held at 800C for 30 minutes. Next, the pre-emulsified monomer mixture (Feed 5) and Feed 6 were added to the reaction mixture simultaneously over a 3-hour period while maintaining the reaction mixture at about 800C. At the completion of this addition, the addition funnels were rinsed with Feeds 7 and 8, and the reaction mixture was held for 4 hours at 800C to complete the polymerization.

Finally, Feed 9 was added to the reaction vessel and the reaction mixture was agitated for 30 minutes to invert the aqueous emulsion into organic diluent. The reaction mixture was dehydrated by azeotropic distillation at 400-580C and 95-140 mm Hg pressure. The reaction product was cooled and filtered to yield a stable bluish colored dispersion. About 300 parts of EXXATE 600 was used to adjust to about 30 weight percent solids. This material had 0.223 weight percent water, with a particle size of 1060 Angstroms and viscosity of 12.4 centipoise, measured with a #1 spindle at 20 RPM. The theoretical acid value of this material was zero.

EXAMPLE E
(COMPARATIVE)
The following example shows the preparation of a non-aqueous dispersion of nonfunctional polymeric microparticles, in accordance with U.S. Pat. No. 4,147,688:
Ingredients Parts by Weight
Initial Charge n-Heptane 4,464.4
Isopar E 597.4
Feed 1
Amphipathic stabilizer1 717.4
Methyl methacrylate 368.9
VAZO-67 31.2
Isopar E 1,298.5
Feed 2
Methyl methacrylate 9,531.1
Glycidyl methacrylate 515.0
Methacrylic acid 387.0 n-Octyl mercaptan 107.0
Amphipathic stabilizer 1,822.6
VAZO-67 41.8
N,N-Dimethylcocoamine 30.0 n-Heptane 4,465.8
Isopar E 1,903.4
Feed 3 n-Heptane 360.0
Isopar E 149.3 1 Same as Note 2, Example C.

The initial charge was heated to reflux temperature with agitation in a reaction vessel suitable for dispersion polymerization. Feed 1 was added to the reaction vessel and the reaction mixture was held for 30 minutes at reflux temperature. The Feed 2 was added in a substantially continuous manner over a period of 3 hours while maintaining the reaction mixture at reflux temperature. At the completion of Feed 2, the addition funnel was rinsed with Feed 3, and the reaction mixture was held for 30 minutes at reflux temperature to complete the polymerization. The reaction product was cooled and filtered to yield a stable dispersion at 44 weight percent solids and a viscosity of 21 centipoise, measured with a &num;4 spindle at 100 RPM. The theoretical acid value of this material was about 3 based on solids assuming complete reaction of all methacrylic acid monomers.

EPOXY AND ACID CONTAINING POLYMERS
The following examples show the preparation of various epoxy functional acrylic polymers and polyacid curing agents.

EXAMPLE 1
The following example shows the preparation of an epoxy functional acrylic polymer:
Ingredients Weight in grams Charger
Xylene 1 186.1
Ethyl 3-ethoxypropionate 572.9 Chare2
Glycidyl methacrylate 1200.0
Methyl methacrylate 11.7 n-Butyl methacrylate 350.1
Styrene 81.7
Alpha-methyl styrene dimer 23.2
Ethyl 3-ethoxypropionate 10.0
Charge3
LUPERSOL 555-M602 200.0
Ethyl 3-ethoxypropionate 110.0
Charge4
Methyl methacrylate 8.3 n-Butyl methacrylate 250.1
Styrene 58.3
Alpha-methyl styrene dimer 16.6
Ethyl 3-ethoxypropionate 10.0 Charge t-Butyl perbenzoate 20.0
Ethyl 3-ethoxypropionate 15.0 Charge6 t-Butyl perbenzoate 20.0
Ethyl 3 -ethoxypropionate 13.7 Charge7 t-Butyl perbenzoate 20.0
Ethyl 3-ethoxypropionate 15.0 1 EKTAPRO

EEP solvent from Eastman Chemicals 2 t-amyl peracetate (60%) in odorless mineral spirits available from
Atochem
Charge 1 was heated in a suitable reactor to reflux. Charge 2 and Charge 3 were added simultaneously to the reaction vessel over a period of about 4 hours then Charge 4 was added over a period of 30 minutes while maintaining the reaction at reflux. At the completion of the additions, the reaction mixture was held at reflux for one hour, cooled to 1 300C then Charge 5 was added over a period of 1 hour. The reaction was then held for 30 minutes at reflux. Charge 6 was added over a period of 1 hour and the reaction was held for another 30 minutes at 1300 C. Then Charge 7 was added over a period of 1 hour and the reaction was heid-at 1300C for two hours.

The reaction mixture was then cooled to room temperature. The resultant epoxy containing acrylic polymer had a total solids content of about 64.5 percent and a weight average molecular weight of about 2800. The theoretical epoxy equivalent weight based on solids was 237.

EXAMPLE 2
The following example shows the preparation of an epoxy functional acrylic polymer:
Ingredients Weight in Grams
Initial Charge Ethyl-3 -ethoxypropionate 353.1
Xylene 891.0
Feed I
Glycidyl methacrylate 2,532.9
Styrene 107.9
Methyl methacrylate 107.9 n-Butyl methacrylate 3,284.8
Feed 2
LUPERSOL 555-M60 724.1 Ethyl-3 -ethoxypropionate 363.0
Feed 3
Methyl methacrylate 36.9
Styrene 36.9 n-Butyl methacrylate 1,133.1
Feed 4 Ethyl-3 -ethoxypropionate 40.0
Feed 5 Ethyl-3 -ethoxypropionate 80.1
Feed 6 t-Butyl perbenzoate 217.9
Ethyl-3-ethoxypropionate 29.9
Feed 7
Ethyl-3 -ethoxypropionate 51.0
The initial charge was heated to reflux temperature in a suitable reactor and held for five minutes.

The materials in Feed 2 were preblended together and added to the reactor in a continuous manner over 4 hours. The materials in Feed 1 were preblended together. Fifteen minutes after the start of Feed 2, Feed 1 was added to the reactor in a continuous manner over 2-1/2 hours through a separate addition funnel while maintaining the reaction at reflux temperature. After the addition of Feed 1, Feed 3 was added to the reactor over 30 minutes. After the completion of Feed 2, Feed 4 was added to the reactor. At the completion of Feed 4, Feed 5 was added to the reactor. At the completion of Feed 5, the reaction was held at reflux for 1 hour, then cooled to about 265-270"F (129 to 1320C). Then, Feed 6 was divided into (3) equal portions. Each portion was added to the reactor sequentially over one hour, with a 30 minute hold between portions.

The reaction was maintained at about 265-270"F (129 to 1320C) throughout the addition of
Feed 6.

At the completion of Feed 6, Feed 7 was added to rinse the addition funnel, and the reaction was held at about 265-270 F (129 to 1320C) for 2 hours. Additional Ethyl-3ethoxypropionate was used to adjust the solids. The reaction prodsuct was then cooled and filtered to yield a material at 74 weight percent solids with a weight-averagae molecular weight of about 2800. The theoretical epoxy equivalent weight based on solids was 410.

EXAMPLE 3
The following examples show the preparation of a polyacid curing agent which is a polyacid half-ester of di-trimethylolpropane and methylhexahydrophthalic anhydride.

Ingredients Weight in Grams
Di-trimethylolpropane 1,584.8 Methylhexahydrophthal ic anhydride 4,120.7
Methyl isobutyl ketone 569.2 n-Propanol 2,117.7
The di-trimethylolpropane and 559.2 grams of methyl isobutyl ketone were charged to a reaction vessel and heated under a nitrogen atmosphere to 11 50C. The methylhexahydrophthalic anhydride was added over a period of 2 hours at 11 50C. The remainder of the methyl isobutyl ketone was added as a rinse. The reaction was held at 11 50C for 4 hours. The reaction mixture was then cooled to 100 C, and the n-propanol was added. The reaction mixture was then heated to 1050C held and held for 30 minutes and then cooled to room temperature.

The resultant product had a solids content of 72.3 percent and an acid value of 163.

EXAMPLE 4
The following example shows the preparation of a polyacid curing agent which is a polyacid half-ester of trimethylolpropane, methylhexahydro-phthalic anhydride and hexahydrophthal ic anhydride.

Ingredients Weight in grams
Charge 1
Trimethylolpropane 134.1
Hexahydrophthalic anhydride 151.1
Methyl isobutyl ketone 244.0
Charge 2
Methylhexahydrophthalic anhydride 352.5
Methyl isobutyl ketone 20.0
Charge 3
Ethyl alcohol 9.3
Charge 1 was placed into a suitable reactor and heated under a nitrogen atmosphere to 11 50C. Charge 2 was added over 1 to 2 hours, the reaction mixture was held at 1 15"C for 4 hours, and then cooled to 100"C followed by the addition of Charge 3. The reaction mixture was then heated to 1050C, held for 30 minutes, and then cooled to room temperature. The reaction mixture had a solids content of 69.5 percent and an acid value of 189.5.

EXAMPLE 5
The following example shows the preparation of polyacid curing agent which is a polyacid half-ester of pentaerythritol and methylhexahydro-phthalic anhydride:
Ingredients Weight in Grams
Pentaerythritol 136.16
Methylhexahydrophthalic anhydride 659.30 n-Amyl propionate 187.17 n-Propanol 187.17
The pentaerythritol and 177.17 grams of n-amyl propionate were charged to a reaction vessel and heated under a nitrogen atmosphere to 1250C. The methylhexahydrophthalic anhydride was added over a period of2 hours at 1250C. At the completion of the addition, the addition funnel was rinsed with the remainder of the namyl propionate. The reaction was cooled and was held at 1150 for 4 hours. The reaction mixture was then cooled again to. 1000C, and the N-propanol was added.

Next, the reaction mixture was heated to 105"C and held for 30 minutes. Finally, the reaction mixture was cooled to room temperature to yield a product at 68 weight percent solids and an experimentally determined acid value of 180.

EXAMPLE 6
The following example shows the preparation of a l-octene/maleic anhydride/ethanol copolymer.

First, a prepolymer was prepared. An initial charge of 230.7 grams of l-ocetene was heated to a reflux temperature of about 1200C in a reaction vessel fitted with a condenser, thermometer, nitrogen sparging inlet and agitator. Then, 67.3 grams of benzoyl peroxide (commercially available at 78 percent active material in water from
Pennwalt Corporation as LUCIDOL 78) was added over a period of two hours followed by 3.4 grams of n-butyl acetate as a funnel rinse. Beginning ten minutes after the start of this addition, a separate mixture of 100.9 grams of maleic anhydride and 242.2 grams of n-butyl acetate was added over a period of 1.5 hours. A final feed of 3.4 grams of butyl acetate was then added as a rinse. After the completion of the additions, the reaction mixture was held at reflux temperature for one hour.

Then, the reaction mixture was heated to about 128"C under 5 percent nitrogen sparge and the solvent was removed by distillation, until a Gardner-Holdt viscosity of Z was attained. The reaction product was a l-octene/maleic anhydride copolymer at 75.9 weight percent solids, with a numberaverage molecular weight of 1,061 and a weight average molecular weight of 2,731.

To produce the final copolymer, to an initial charge of 3050.6 grams of the prepolymer prepared above, a mixture of 25 grams of denatured ethanol and 1.8 grams of n,n-dimethylethanolamine was added. The addition funnel was rinsed with an additional 25 grams of denatured ethanol and 677.4 grams of ethanol was added continuously over 20 minutes. The exotherm was limited to 175"F(79"C) by adjusting the addition rate of the ethanol. After the addition was complete, the reaction was held until a temperature of 180"C was reached. Then the reaction was heated to about 68"C and held until a constant acid value was reached (about 3 hours). Finally, remaining ethanol was removed by distillation until a Gardner-Holdt viscosity of U+ to W was reached. The product was cooled and filtered.

Coating Compositions
The following examples show the preparation of unpigmented (clear) film forming coating compositions containing the non-aqueous dispersion of polymeric microparticles described in Examples A-E. The coating compositions were evaluated for sag resistance and appearance. The results of these evaluations are shown below in
Tables I-III.

EXAMPLE I
The following example shows the preparation of a coating composition using the carboxylic acid functional microparticles of Example A. This example illustrates the use of carboxylic acid functional polymeric microparticles prepared via Synthetic Route I:
Ingredients Parts by Weight Resin Solids n-Amyl propionate 20.00
Dipropylene glycol 6.10
TINUVIN 328 2.65 2.65
TINUVIN 1232 0.35 0.35
Poly(n-butyl acrylate)3 0.83 0.50
MULTIFLOW4 0.06 0.03
Polymeric microparticles 15.62 4.00 of Example A
Epoxy-functional acrylic polymer 52.32 32.96 of Example 1
Epoxy-functional acrylic polymer 24.86 18.40 of Example 2
Polyacid curing agent 46.68 31.74 of Example 5
I-Octene/maleic anhydride/ 14.65 10.25 ethanol copolymer of Example 6
Isostearic acid 2.80 2.80 1 2-(2'-Hydroxy-3',5'-ditert-amylphenyl) benzotriazole UV light stabilizer 2 commercially available from Ciba-Geigy

Corp.

B is( 1 -octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate hindered
amine light stabilizer commercially available from Ciba-Geigy Corporation 3 Commercially available from Ciba-Geigy Corporation.

A A copolymer of ethyl acrylate and 2-ethylhexyl acrylate commercially
available from Monsanto Company.

All the ingredients were added to a mixing tank sequentially under agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 23.7 seconds with 3.8 grams xylene for application. The resultant coating composition contained 54.4 weight percent solids.

EXAMPLE II
(COMPARATIVE)
The following example shows the preparation of a coating composition using fumed silica as a flow control agent. This is a comparative example illustrating the prior art.

Ingredients Parts by Weight Resin Solids n-Amyl propionate 14.50
Dipropylene glycol 6.10
Ethanol 5.50
TINUVIN 328 2.65 2.65
TINUVIN 123 0.35 0.35
Poly(n-butyl acrylate) 0.83 0.50
MULTIFLOW 006 0.03
Epoxy functional acrylic polymer 50.00 31.50 of Example 1
Epoxy functional acrylic polymer 23.78 17.60 of Example 2
Polyacid curing agent 47.79 32.50 of Example 5
I-Octene/maleic anhydride/ 15.00 10.50 ethanol copolymer of Example 6
Isostearic acid 2.80 2.80
Fumed silica dispersion1 15.00 5.25 1
The fumed silica dispersion was made by grinding 64.9 grams of
fumed silica (commercially available from Degussa Corp.

AEROSIL R812) 405.7 grams of the polyacid curing agent of
Example 4, and 340.8 grams of n-amyl alcohol on a dispersion mill filled
with ceramic media until a Hegman reading of 7.5 was reached. Finally,
the dispersion was filtered through a mesh strainer to remove the grind media.

All the ingredients were added sequentially to a mixing tank with agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 23.8 seconds with 11.85 grams of xylene for application. The resultant formulated coating composition contained 53.4 weight percent solids.

EXAMPLE III
(COMPARATIVE)
The following example shows the preparation of a coating composition with no flow control agent. This is a comparative example illustrating the performance of acidcured epoxy coating compositions without polymeric microparticles:
Ingredients Parts by Weight Resin Solids n-Amyl propionate 14.50
Dipropylene glycol 6.10
Ethanol 5.50
TINUVIN 328 2.65 2.65
TINUVIN 123 0.35 0.35
Poly (n-butyl acrylate) 0.83 0.50
MULTIFLOW 0.06 0.03
Epoxy functional acrylic polymer 50.00 31.50 of Example 1
Epoxy functional acrylic polymer 23.78 17.60 of Example 2
Polyacid curing agent 47.79 32.50 of Example 5
I-Octene/maleic anhydride/ 15.00 10.50 ethanol copolymer of Example 6
Isostearic acid 2.80 2.80
Polyacid curing agent 7.50 5.25 of Example 4
All the ingredients were added to a mixing tank sequentially with agitation.

The coating composition was reduced to a No. 4 Ford cup viscosity of 23.2 seconds with 16.4 grams xylene for application. The resultant coating composition contained 53.6 weight percent solids.

EXAMPLE IV
The following example shows the preparation of a coating composition using the carboxylic acid functional polymeric microparticles of Example B. The example illustrates the use of carboxylic acid functional polymeric microparticles prepared via
Synthetic Route II. In this example, the carboxylic acid functional polymeric microparticles were used at a level of 6% by weight, the percentage based on the weight of solids in the coating composition:

:
Ingredients Parts by Weight Resin Solids
Ethyl 3-ethoxypropionate 20.02 n-Propanol 5.61
Polymeric microparticles 25.32 6.38 of Example B
TINUVIN 328 2.66 2.66
TINUVIN 2921 0.35 0.35
MULTIFLOW 1.00 0.50
Epoxy functional acrylic polymer 52.77 33.25 of Example 1
Epoxy functional acrylic polymer 24.71 18.29 of Example 2
Polyacid curing agent 55.82 39.91
Example 3
I-Octene/maleic anhydride/ 12.22 8.55 ethanol copolymer of Example 6 1 Bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate hindered amine stabilizer,
commercially available from Ciba-Geigy Corporation.

All the ingredients were added to a mixing tank sequentially with agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 23: 1 seconds with 11.0 grams of ethyl 3-ethoxypropionate for application. The resultant coating composition contained 52.0 weight percent solids.

EXAMPLE V
The following example shows the preparation of a coating composition containing a higher level of the carboxylic acid functional polymeric microparticles used in Example IV. In this example, the carboxylic acid functional polymeric microparticles were at a level of 12% by weight, based on the weight of solids in the coating composition:
Ingredients Parts by Weight Resin Solids
Ethyl 3-ethoxypropionate 10.00 n-Propanol 5.61
Polymeric microparticles 54.09 13.63 of Example B
TINUVIN 328 2.66 2.66
TINUVIN 292 0.35 0.35
MULTIFLOW 1.00 0.50
Epoxy functional acrylic polymer 52.77 33.25 of Example 1
Epoxy functional acrylic polymer 24.71 18.29 of Example 2
Polyacid curing agent 55.82 39.91
Example 3
I-Octene/maleic anhydride/ 12.22 8.55 ethanol copolymer of Example 6
All the ingredients were added to a mixing tank sequentially under agitation.

The coating composition was reduced to a No. 4 Ford cup viscosity of 24.2 seconds with 9.6 grams of ethyl 3-ethoxypropionate for application. The resultant coating composition contained 51.2 weight percent solids.

EXAMPLE VI
(COMPARATIVE)
The following example shows the preparation of a coating composition using the non-functional polymeric microparticles of Example D. This Ba comparative example illustrating the use of non-functional polymeric microparticles prepared via Synthetic
Route II. In this example, the non-functional polymeric microparticles were added at a level of 6 percent by weight, based on the weight of solids in the coating composition:

:
Ingredients Parts by Weight Resin Solids
Ethyl 3-ethoxypropionate 20.02 n-Propanol 5.61
Polymeric microparticles 20.71 6.38 of Comparative Example D
TINUVIN 328 2.66 2.66
TINUVIN 292 0.35 0.35
MULTIFLOW 1.00 0.50
Epoxy functional acrylic polymer 52.77 33.25 of Example 1
Epoxy functional acrylic polymer 24.71 18.29 of Example 2
Polyacid curing agent 55.82 39.91
Example 3
I-Octene/maleic anhydride/ 12.22 8.55 ethanol copolymer of Example 6
All the ingredients were added to a mixing tank sequentially with agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 24.2 seconds with 9.6 grams of ethyl 3-ethoxypropionate for application. The resultant coating composition contained 53.5 weight percent solids.

EXAMPLE VII
(COMPARATIVE)
The following example shows the preparation of a coating composition containing a higher level of the non-functional polymeric microparticles used in Example
VI. In this example, the non-functional polymeric microparticles were added at a level of 12% by weight, based on the weight of solids on the coating composition:
Ingredients Parts by Weight Resin Solids
Ethyl 3-ethoxypropionate 10.00 n-Propanol 5.61
Polymeric microparticles 44.25 13.63 of Comparative Example D
TINUVIN 328 2.66 2.66
TINUVIN 292 0.35 0.35
MULTIFLOW 1.00 0.50
Epoxy functional acrylic polymer 52.77 33.25 of Example 1
Epoxy functional acrylic polymer 24.71 18.29 of Example 2
Polyacid curing agent 55.82 39.91
Example 3
I-Octene/maleic anhydride/ 12.22 8.55 ethanol copolymer of Example 6
All the ingredients were added to a mixing tank sequentially within agitation.

The coating composition was reduced to a No. 4 Ford cup viscosity of 24.4 seconds with 8.4 grams of ethyl 3-ethoxypropionate for application. The resultant coating composition contained 53.8 weight percent solids.

EXAMPLE VIII
(COMPARATIVE)
The following example shows the preparation of a coating composition using fumed silica as a flow control agent. This is a comparative example illustrating the prior art:
Ingredients Parts by Weight Resin Solids
Ethyl 3-ethoxypropionate 20.12 n-Propanol 5.64
TINUVIN 328 2.66 2.66
TINUVIN 292 0.35 0.35
MULTIFLOW 1.00 0.50
Epoxy functional acrylic polymer 53.03 33.41 of Example 1
Epoxy functional acrylic polymer 24.83 18.37 of Example 2
Polyacid curing agent 50.83 36.34
Example 3
I-Octene/maleic anhydride/ 12.28 8.60 ethanol copolymer of Example 6
Fumed silica dispersion of 9.36 3.28
Footnote 1 in Example II
All the ingredients were added to a mixing tank sequentially with agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 24.3 seconds with 16.2 grams of ethyl 3-ethoxypropionate for application.

The resultant coating composition contained 53.1 weight percent solids.

EXAMPLE IX
The following example shows the preparation of a coating composition using the carboxylic acid functional polymeric microparticles of Example C. This example illustrates the use of carboxylic acid functional polymeric microparticles prepared via
Synthetic Route III:
Ingredients Parts by Weight Resin Solids n-Amyl propionate 17.34
Dipropylene glycol 3.61
Ethanol 2.61 n-Amyl alcohol 5.57
TINUVIN 328 2.54 2.54
TINUVIN 123 0.35 0.35 Poly(n-butyl acrylate) 0.83 0.50
MULTIFLOW 0.20 o.io
Polymeric microparticles 26.32 5.00 of Example C l-Octene/maleic anhydride/ 10.77 7.54 ethanol copolymer of Example 6
Epoxy functional acrylic polymer 48.40 30.49 of Example 1
Epoxy functional acrylic polymer 23.03 17.04 of Example 2
Polyacid curing agent 8.75 6.12
Example 4
Polyacid curing agent 45.63 31.03
Example 5
Isostearic acid 2.78 2.78
All the ingredients were

added to a mixing tank sequentially with agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 24.3 seconds with 3.0 grams of xylene for application. The resultant coating composition contained 51.3 weight percent solids.

EXAMPLE
(COMPARATIVE)
The following example shows the preparation of a coating composition using the non-functional polymeric microparticles of Example E. This is a comparative example illustrating the use of non-functional polymeric microparticles prepared via Synthetic
Route III:

:
Ingredients Parts by Weight Resin Solids n-Amyl propionate 17.34
Dipropylene glycol 3.61
Ethanol 2.61 n-Amyl alcohol 5.57
TINUVIN 328 2.54 2.54
TINUVIN 123 0.35 0.35
Poly(n-butyl acrylate) 0.83 0.50
MULTIFLOW 0.20 0.10
Polymeric microparticles 11.36 5.00 of Comparative Example E l-Octene/maleic anhydride/ 10.84 7.59 ethanol copolymer of Example 6
Epoxy functional acrylic polymer 47.95 30.21 of Example 1
Epoxy functional acrylic polymer 22.87 16.92 of Example 2
Polyacid curing agent 8.97 6.28
Example 4
Polyacid curing agent 45.91 31.22
Example 5
Isostearic acid 2.78 2.78
All the ingredients were added to a mixing tank sequentially with agitation. The coating composition was reduced to No. 4 Ford cup viscosity of 24.7 seconds with 12.8 grams of xylene for application. The resultant coating composition contained 52.7 weight percent solids.

EXAMPLE XI
(COMPARATIVE)
The following example shows the preparation of a coating composition using fumed silica as a flow control agent. This is a comparative example illustrating the prior art:
Ingredients Parts by Weight Resin Solids n-Amyl propionate 17.34
Dipropylene glycol 3.61
Ethanol 2.61 n-Amyl alcohol 5.57
TINUVIN 328 2.54 2.54
TINUVIN 123 0.35 0.35
Poly(n-butyl acrylate) 0.83 0.50
MULTIFLOW 0.20 0.10 I-Octene/maleic anhydride/ 11.44 8.01 ethanol copolymer of Example 6
Epoxy functional acrylic polymer 50.61 31.88 of Example 1
Epoxy functional acrylic polymer 24.14 17.86 of Example 2
Polyacid curing agent 5.42 3.79
Example 4
Polyacid curing agent 48.47 32.96
Example 5
Isostearic acid 2.78 2.78
Fumed silica dispersion1 10.71 2.72 1 The fumed silica dispersion was made by grinding 114.8 grams of
fumed silica (commercially available from Degussa

Corporation as
AEROSIL R812), 302.5 grams of the polyacid curing agent of Example 4,
and 402.6 grams of n-amyl alcohol in a laboratory dispersion mill, filled
with ceramic media until a Hegman reading of 7.5 was reached. Finally,
thedispersion was filtered through a mesh strainer to remove the
grind media.

All the ingredients were added to a mixing tank sequentially with agitation. The coating composition was reduced to a No. 4 Ford cup viscosity of 23.9 seconds with 15.1 grams of xylene for application. The resultant coating composition contained 52.0 weight percent solids.

EXAMPLE XII
(COMPARATIVE)
The following example shows the preparation of a coating composition with no flow control agent. This is a comparative example illustrating the performance of an acid-cured epoxy coating composition prepared without polymeric microparticles:
Ingredients Parts by Weight Resin Solids n-Amyl propionate 17.34
Dipropylene glycol 3.61
Ethanol 2.61 n-Amyl alcohol 5.57
TINUVIN 328 2.54 2.54
TINUVIN 123 0.35 0.35
Poly(n-butyl acrylate) 0.83 0.50
MULTIFLOW 0.20 0.10
I-Octene/maleic anhydride/ 11.44 8.01 ethanol copolymer of Example 6
Epoxy functional acrylic polymer 50.61 31.88 of Example 1
Epoxy functional acrylic polymer 24.14 17.86 of Example 2
Polyacid curing agent 9.30 6.51
Example 4
Polyacid curing agent 48.47 32.96
Example 5
Isostearic acid 2.78 2.78
All the ingredients were added to a mixing tank sequentially with agitation.

The coating composition was reduced to a No. 4 Ford cup viscosity of 24.1 seconds with 17.55 grams of xylene for application. The resultant coating composition contained 52.4 weight percent solids.

Phvsical Testing
The unpigmented coating compositions of Examples I-XII were used as the topcoat in a color-plus-clear system. All the coating compositions were applied over a pigmented basecoat and electrocoated steel. The pigmented basecoat used with the coating compositions of Examples I-VIII was a silver metallic basecoat, commercially available from PPG Industries, Inc. as NHU-34744. The pigmented basecoat used with the coating compositions of Examples IX-XII was a black basecoat commercially available from PPG Industries, Inc. as NHU-95 17.

To evaluate the appearance of the color-plus-clear systems, the coating compositions were spray-applied to electrocoated steel test panels at 750F (24"C). The basecoat to be used was applied in two passes, with a 90 second flash between coats.

After the second coat of basecoat was applied, the test panels were flashed again for five minutes, then the unpigmented coating composition to be evaluated was applied in two passes, with a 90 second flash between coats. The resulting composite coating was again flashed for 15 minutes at ambient temperature, then heat-cured at 2850F (140"C) for 30 minutes. One test panel was cured on the horizontal position, and another was cured on the vertical position.

The composite coatings were evaluated for dry film thickness, 20 gloss and distinctness of image. Dry film thickness was measured with a permascope, commercially available from Fisher. 20 gloss was measured with a 200 gloss meter, commercially available from Gardner Instrument Company. Distinctness of image was measured with a Dori-gon Meter D-47-6, commercially available from Hunter
Laboratories.

To evaluate the sag resistance of the color-plus-clear system, the test panel that was to be cured in the vertical position was drilled with a 1/4-inch diameter hold before the basecoat was applied to it. The length of the sag from the bottom of the hole was measured on millimeters.

The results of the physical testing described above are reported in Tables 1-3, below:
TABLE 1. Properties of Clear Coatings of Examples l-III.

Clear Drv Film Thickness DOI SAG
Coat Basecoat Clearcoat Hor. Ver. mm.

Ex.I 0.71 1.79 72 73 17 Ex.II 0.72 1.73 65 71 14 Ex.III 0.76 1.77 67 68 25
TABLE 2. Properties of Clear Coatings of Examples IV-VIII.

Clear DFT ¯ GLOSS DOI SAG
Coat BC CC Ver. Hor. Ver. Hor. mm.

Ex.IV 0.85 2.03 92 91 70 76 14
Ex.V 0.83 1.83 90 92 43 66 0
Ex.VI 0.78 2.04 92 92 74 81 38
Ex.VII 0.89 1.88 89 93 70 83 18
Ex.VIII 0.86 1.99 88 89 46 76 23
TABLE 3. Properties of Clear Coatings of Examples IX-XII.

Clear . Drv Film Thickness DOI SAG
Coat Basecoat Clearcoat Hor. Ver. mm.

Ex.IX 0.69 1.69 76 70 5
Ex.X 0.69 1.58 83 91 5
Ex.XI 0.63 1.62 89 92 15
Ex.XII 0.67 1.56 89 88 7
EXAMPLES 7- 14
The Examples 7 - 14 are additional examples of the preparation of functional and non-functional polymeric acrylic dispersants in various solvents by the same solution polymerization technique that was described in Example A. These dispersions are used in Synthetic Route I for producing polymeric microparticle dispersions.

The figures in Table 4 represent the weight percent of each component, excluding initiator, used to prepare the polymeric acrylic dispersants, based on the total weight of all monomers present. The amount of initiator is presented as weight percent based on the total weight of monomers present.
EMI51.1

<tb>

GMA4
<tb> INGREDIENT <SEP> EXAMPLE
<tb> <SEP> 7 <SEP> 8 <SEP> 9 <SEP> 10 <SEP> 11 <SEP> 12 <SEP> 13 <SEP> 14
<tb> MMAÚ <SEP> 45.0 <SEP> 50.0 <SEP> 20.0 <SEP> 50.0 <SEP> 50.0 <SEP> 40.0 <SEP> 42.5 <SEP> 45.0
<tb> BAê <SEP> 45.0 <SEP> 50.0 <SEP> 20.0 <SEP> 50.0 <SEP> 50.0 <SEP> 45.0
<tb> BMA <SEP> 40.0 <SEP> 42.5
<tb> GMA4 <SEP> 60.0
<tb> HPMA <SEP> 10.0 <SEP> ¯¯ <SEP> <SEP> 10.0
<tb> AA <SEP> 15.0 <SEP>
<tb> DMAEMA <SEP> / <SEP> <SEP> 20.0
<tb> <SEP> Initiator
<tb> VAZO-67 <SEP> 5.0 <SEP> 5.0 <SEP> 5.0 <SEP> 5.0 <SEP> 5.0 <SEP> 5.0 <SEP> 5.0
<tb> LUPERSOL <SEP> 1.5
<tb> PMS8
<tb> Solvent <SEP> EtAc <SEP> <SEP> BuAc <SEP> | <SEP> EtAc <SEP> MEK <SEP> MIBK <SEP> EtAc <SEP> EtAc <SEP> EtAc
<tb> Weight%Solids <SEP> 58.5 <SEP> 55.8 <SEP> 59.2 <SEP> 58.4

<SEP> 56.1 <SEP> 59.7 <SEP> 60.9 <SEP> 55.1
<tb> Mn10 <SEP> 8,988 <SEP> 3,452 <SEP> 7,182 <SEP> 6,091 <SEP> 3,880 <SEP> 6,679 <SEP> 7,906 <SEP> N/A
<tb> 1Methyl methacrylate 2n-Butyl acrylate 3n-Butyl methacrylate 4Glycidyl methacrylate 52-Hydroxypropyl methacrylate 6Acrylic acid 7N,N-Dimethylaminoethyl methacrylate 8tert-Butylperoxy-2-ethylhexanoate (tert-butylperoctoate), at 50% active material in
odorless mineral spirits, commercially available from Atochem.

9EtAc is ethyl acetate; BuAc is n-butyl acetate; MEK is methylethyl ketone; and MIBK
is methyl isobutyl ketone.

I ONumber-average molecular weight.

1 1The number-average molecular weight of this material was not determined.

EXAMPLE 15
(COMPARATIVE)
The following example shows the preparation of a non-functional polymeric acrylic dispersant similar to that of Example 8, but in which the solvent was replaced with toluene. This is a comparative example showing the preparation of a polymeric acrylic dispersant in a medium that is unsuitable for the non-aqueous dispersion polymerization that is subsequently conducted.

The following initial charge and feed were used in the preparation.

INGREDIENT GRAMS
Initial Charge
Toluene 375.0
Feed
Toluene 350.0
n-Butyl Acrylate 500.0
Methyl Methacrylate 500.0
VAZO-67 50.0
The resultant acrylic polymer was cooled and filtered to yield a resin at 57.2 weight percent solids with a number-average molecular weight of 4,004.

The following Examples F through Q show the preparation of dispersions of uncrosslinked polar polymeric microparticles using the various functional and nonfunctional polymeric acrylic dispersants prepared above in Examples 7 - 14 (Synthetic
Route I).

EXAMPLE F
The following example shows the preparation of carboxylic acidfunctional polar polymeric microparticles dispersed in ethyl acetate in the presence of the glycidyl-functional polymeric acrylic dispersant of Example A above.

INGREDIENT GRAMS
Initial Charge
Polymeric Acrylic Dispersant of Example 1 246.7
Ethyl Acetate 1559.4
Feed
Ethyl Acetate 151.4
Acrylic Acid 454.5
LUPERSOL PMS 18.2
The initial charge was heated to reflux temperature with agitation in a reaction vessel suitable for dispersion polymerization. Five weight percent of the feed was added to the reaction mixture at a fast rate, and the reaction mixture was held at reflux temperature for an additional 30 minutes for seed particle formation. The remainder of the feed was added in a substantially continuous manner over a period of three hours while maintaining the reaction mixture at reflux temperature. At the completion of the feed, the reaction mixture was held for about two hours at reflux temperature to complete the polymerization.

The reaction product was cooled and filtered to yield a stable dispersion at 26.9 weight percent solids with a particle size of 3630 Â.

EXAMPLES G - Q
The following examples show the preparation of dispersions of uncrosslinked polar polymeric microparticles using the method of Example F. The figures in the following table represent the weight percent of each component, excluding initiator, used to prepare the dispersions. The amount of initiator is presented as weight percent based on the total weight of monomers present.

EXAMPLE
INGREDIENT G H J K L M N O P Q
DISPERSANT
EMI53.1

<tb> Polymeric <SEP> Acrylic <SEP> 25.0 <SEP> 25.0
<tb> Dispersant <SEP> of <SEP> Ex. <SEP> 7
<tb> Polymeric <SEP> Acrylic <SEP> 25.0
<tb> Dispersant <SEP> of <SEP> Ex. <SEP> 8
<tb> Polymeric <SEP> Acrylic <SEP> 25.0 <SEP> 62.5
<tb> Dispersant <SEP> of <SEP> Ex. <SEP> 9
<tb> <SEP> Polymeric <SEP> Acrylic <SEP> 25.0
<tb> Dispersant <SEP> of <SEP> Ex <SEP> 10 <SEP>
<tb> <SEP> Polymeric <SEP> Acrylic <SEP> 25.0
<tb> Dispersant <SEP> of <SEP> Ex. <SEP> I <SEP> I <SEP>
<tb> Polymeric <SEP> Acrylic <SEP> 25.0
<tb> <SEP> Dispersant <SEP> of <SEP> Ex.

<SEP> 13
<tb> Polymeric <SEP> Acrylic <SEP> 46.9
<tb> Dispersant <SEP> of <SEP> Ex. <SEP> 14
<tb> Polymeric <SEP> Acrylic <SEP> 25.0
<tb> Dispersant <SEP> Prepared
<tb> According <SEP> to <SEP> the
<tb> Method <SEP> of <SEP> Ex.131 <SEP>
<tb> MICROPARTICLES
<tb> AA <SEP> 75.0 <SEP> 3.8 <SEP> 3.8 <SEP> 37.5 <SEP> 35.6
<tb> HEA <SEP> 75.0 <SEP> 71.2 <SEP> 71.2 <SEP> 37.5 <SEP> 75.0 <SEP> 35.6
<tb> MAA <SEP> 53.1
<tb> Beta-CEA <SEP> 45.0 <SEP> 37.5 <SEP>
<tb> ACN <SEP> 30.0
<tb> BA6 <SEP> 3.8
<tb> INITIATOR
<tb> lVAZO-67 <SEP> 2.0 <SEP> 12.0 <SEP> 11.0
<tb> <SEP> LUPERSOL <SEP> PMS <SEP> 3.0 <SEP> 3.0 <SEP> 3.0 <SEP> 3.0 <SEP> 3.0 <SEP> | <SEP>

3.0
<tb>
EMI54.1

<tb> VAZO-52 <SEP> / <SEP> = <SEP> Buck <SEP> <SEP> Etc <SEP> <SEP> 2.0
<tb> Solvent <SEP> EtAc <SEP> BuAc <SEP> EtAc <SEP> EtAc <SEP> MEK <SEP> MIBK <SEP> EtAc <SEP> EtAc <SEP> EtAc <SEP> EtAc
<tb> Weight <SEP> % <SEP> Solids <SEP> 1 <SEP> 24.1 <SEP> 51.4 <SEP> 50.3 <SEP> 52.5 <SEP> 52.9 <SEP> 51.4 <SEP> 25.3 <SEP> 30.1 <SEP> 49.4 <SEP> 25.2
<tb> <SEP> Particle <SEP> Size <SEP> ( ) <SEP> 3310 <SEP> 13900 <SEP> 4900 <SEP> 2970 <SEP> 4140
<tb> 1A polymeric acrylic dispersant was prepared as described in Example 13, but the
dispersant was diluted to 45.4 weight % solids with ethyl acetate after polymerization was completed.

22-Hydroxyethyl acrylate 3Methacrylic acid 4Beta-Carboxyethylacrylate 5Acrylonitrile 6n-Butyl Acrylate 72,2'-Azobis(2,4-dimethylvaleronitrile), commercially available from E.I. duPont de
Nemours & Company.

EXAMPLE R
(COMPARATIVE)
The following example shows the preparation of acid- and hydroxylfunctional polar polymeric microparticles dispersed in toluene in the presence of the nonfunctional dispersant of Example 15, above. This is a comparative example showing the preparation of a dispersion in an unsuitable medium.

INGREDIENT GRAMS
Initial Charge
Polymeric Acrylic Dispersant of 206.6
Example 15
Toluene 361.2
Feed A
Acrylic Acid 18.1
LUPERSOL PMS 0.7
Feed B
2-Hydroxyethyl Acrylate 343.5
LUPERSOL PMS 13.7
Toluene 34.8
The initial charge was heated to reflux temperature with agitation¯ in a reaction vessel suitable for dispersion polymerization. Feed A was added to the reaction mixture at a fast rate and the reaction mixture was held at reflux temperature for 30 minutes for seed particle formation. Feed B was added in a substantially continuous manner over a period of three hours while maintaining the reaction mixture at reflux temperature. At the completion of Feed B, the reaction mixture was held for about two hours at reflux temperature to complete the polymerization. The reaction product settled out immediately after agitation ceased and did not yield a stable dispersion.

The following Examples S through U show the preparation of additional examples of dispersions of crosslinked polar polymeric microparticles in accordance with
Synthetic Route I.

EXAMPLE S
The following example shows the preparation of a dispersion of carboxylic acid-functional polar polymeric microparticles that were crosslinked with a polyepoxide crosslinker.

INGREDIENT GRAMS
Initial Charge
Dispersion of Example H 300.0
ARALDITEB PT 8101 15.24 11 ,3,5-Triglycidyl isocyanurate, commercially available from Ciba-Geigy Corporation
The initial charge was heated to reflux temperature with agitation in a reaction vessel suitable for dispersion polymerization and held at that temperature until the epoxy equivalent weight was greater than 100,000. About 31/2 hours were required to reach that epoxy equivalent weight. The reaction product was cooled to yield a stable dispersion at 55.4 weight percent solids. The particle size of this material was not determined.

EXAMPLE T
The following example shows the preparation of a dispersion of hydroxyl-functional polar polymeric microparticles that were crosslinked with an isocyanate crosslinker.

INGREDIENT GRAMS
Initial Charge
Dispersion of Example P 300.0
Dibutyltin Dilaurate 1.6
Feed A
Isophorone Diisocyanate 5.3
Feed B
n-Butyl Acetate 225.0
The initial charge was heated to reflux temperature in a vessel suitable for hydroxyl-isocyanate reaction. Feed A was added over 15 minutes at reflux temperature and the reaction mixture was held at reflux until the isocyanate groups were consumed, as detected by infrared spectrophotometry. About 1 l/2 hours were required to react the isocyanate groups with the hydroxyl groups. Feed B was subsequently added to the reaction mixture, and then 225.0 grams of the solvent mixture was removed by distillation.

The final temperature was 117"C. The reaction product was cooled to yield a stable dispersion at 51 weight percent solids with a particle size of 4,430 .

EXAMPLE U
The following example shows the preparation of a dispersion of crosslinked carboxylic acid- and hydroxyl-functional polar polymeric microparticles in which the crosslinker comprises a polyfunctional vinyl comonomer. The example further shows how crosslinking can be conducted without the need for a separate synthetic step after the polar polymeric microparticles have been prepared. In this example, the crosslinker was added with the vinyl monomer component.

INGREDIENT GRAMS
Initial Charge
Polymeric Acrylic Dispersant
Prepared According to the 121.2
Method of Example 131
Ethyl Acetate 469.6
Feed
Ethyl Acetate 122.5
Acrylic Acid 78.4
2-Hydroxyethyl Acrylate 78.4
Ethylene Glycol Dimethacrylate 8.3
VAZO-67 1.7 1A polymeric acrylic dispersant was prepared as described in Example 13, but the dispersant was diluted to 45.4 weight % solids with ethyl acetate after polymerization was completed.

The initial charge was heated to reflux temperature with agitation in a vessel suitable for dispersion polymerization. Five weight percent of the feed was added to the reaction mixture at a fast rate, and the reaction mixture was held at reflux temperature for 30 minutes for seed particle formation. Then the remainder of the feed was added in a substantially continuous manner over a period of three hours while maintaining the reaction mixture at reflux temperature. At the completion of the Feed, the reaction mixture was held for about two hours at reflux temperature to complete the polymerization. The reaction product was cooled and filtered to yield a stable dispersion at 26.2 weight percent solids with a particle size of 3220 .

Claims

We claim: 1. A coating composition comprising: (A) a film-forming polymeric polyepoxide resin having a 1,2-epoxy equivalency greater than 1; (B) a polyacid curing agent; and (C) an organic colloidal dispersion comprising carboxylic acid-functional polymeric microparticles having a particle size of 0.001 to 5 microns, having a theoretical acid value of at least 10, and being selected from the group consisting of: (I) a microparticle dispersion prepared by non-aqueous dispersion polymerization, in the presence of a polymeric acrylic dispersant which is substantially free of polymerizable unsaturation, in non-aqueous polar medium, of:

: (i) 1 to 100 percent by weight of a carboxylic acid-functional vinyl monomer, or mixtures thereof; (ii) 0 to 99 percent by weight of a material selected from the group consisting of hydroxyl-functional vinyl monomers, nitrile functional vinyl monomers, and mixtures thereof; (iii) 0 to 15 percent by weight of non-functional vinyl monomers or mixtures thereof;

and (iv) 0 to 50 percent by weight of crosslinker; (II) a microparticle dispersion prepared by aqueous emulsion polymerization of: (i) 1 to 50 percent by weight of a carboxylic acid-functional vinyl monomer, or mixtures thereof; (ii) 0 to 49 percent by weight of'a material selected from the group consisting of hydroxyl-functional vinyl monomers, nitrile functional vinyl monomers, and-mixtures thereof; (iii) 0 to 94 percent by weight of non-functional vinyl monomers or mixtures thereof; and (iv) 5 to 50 percent by weight of crosslinker; and subsequent transfer of the dispersion to non-aqueous medium;

and (III) a microparticle dispersion prepared by non-aqueous polymerization in non-polar medium of: (i) 2 to 15 percent by weight of a carboxylic acid-functional vinyl 'monomer, or mixtures thereof; (ii) 0 to 25 percent by weight of a material selected from the group consisting of hydroxyl-functional vinyl monomers, nitrile functional vinyl monomers, and mixtures thereof; (iii) 50 to 97.5 percent by weight of non-functional vinyl monomers or mixtures thereof; and (iv) 0.5 to 10 percent by weight of crosslinker.

2. The composition of claim 1 wherein the polymeric acrylic dispersant has a number-average molecular weight of from about 500 to about 100,000.

3. The composition of claim 1 wherein the polymeric acrylic dispersant is present at a level of from about 2 percent to about 90 percent, the percentage based on the weight of the solids of the dispersion.

4. The composition of claim 1 wherein the non-aqueous polar medium comprises an ester solvent which is ethyl acetate.

5. The composition of claim 1 wherein the carboxylic acidfunctional polymeric microparticles are crosslinked with a polyepoxide crosslinker.

6. The composition of claim 1 wherein the carboxylic acidfunctional polymeric microparticle dispersion is of type (I) and is the polymerization product of a monomer mixture including at least 50% of a total of the monomers of (i) and (ii), and the non-aqueous medium for the dispersion polymerization is selected from the group consisting of esters, ketones, and mixtures thereof.

7. The composition of claim 6 wherein the monomer mixture from which the microparticles is made contains no more than 5 percent of the non-functional monomers of (iii).

8. The composition of claim 6 wherein the non-aqueous dispersion polymerization medium comprises ethyl acetate.

9. The composition of claim 6 wherein the carboxylic vinyl monomer component (i) consists essentially of acrylic acid.

10. The composition of claim 6 wherein the polymeric acrylic dispersant comprises 10 to 50 percent of the solids weight of the microparticle dispersion.

11. The composition of claim 10 wherein the polymeric acrylic dispersant is prepared from glycidyl methacrylate, n-butyl methacrylate, and methyl methacrylate.

12. The composition of claim 6 wherein the carboxylic acidfunctional polymeric microparticles are transferred after dispersion polymerization to an organic medium selected from the group consisting of alcohols; esters; ethers; ketones; aromatic hydrocarbons; and mixtures thereof..

13. The composition of claim 1 wherein the carboxylic acidfunctional polymeric microparticles are prepared from 100 percent acrylic acid; are stabilized with a polymeric acrylic dispersant prepared from about 40 percent glycidyl methacrylate, about 30 percent n-butyl methacrylate and about 30 percent methyl methacrylate, the percentages based on the weight of monomers used to prepare the dispersant; and dispersed in a non-aqueous polar medium comprising an ester solvent which is ethyl acetate.

14. The composition of claim 2 wherein the crosslinked carboxylic acid-functional polymeric microparticles are of type (II) and are prepared by emulsion polymerization in an aqueous medium in the presence of a surfactant and are inverted into a non-aqueous medium.

15. The composition of claim 14 wherein the crosslinked carboxylic acid-functional polymeric microparticles have a theoretical acid value of from about 10 to about 400.

16. The composition of claim 14 wherein the carboxylic acidfunctional polymeric microparticles are crosslinked with a difunctional vinyl monomer.

17. The composition of claim 16 wherein the difunctional vinyl monomer is ethylene glycol dimethacrylate.

18. The composition of claim 14 wherein the surfactant is present at a level of from about 4 percent to about 7 percent, the percentage based on the total weight of the vinyl monomers.

19. The composition of claim 1 wherein the crosslinked carboxylic acid-functional polymeric microparticles are of type (III) and are prepared by nonaqueous dispersion polymerization of a carboxylic acid-functional vinyl monomer in the presence of an epoxy-functional vinyl crosslinker such that there is a molar excess of the carboxylic acid-functional vinyl monomer; said polymerization proceeding in a nonaqueous, non-polar medium in the presence of an amphipathic stabilizer.

20. The composition of claim 19 wherein the crosslinked carboxylic acid-functional polymeric microparticles have a theoretical acid value of from about 10 to about 60.

21. The composition of claim 19 wherein the amphipathic stabilizer is present at a level of from about 5 percent to about 98 percent, the percentage based on the weight of the monomers.

22. The composition of claim 1 wherein the coating composition is substantially free of basic esterification catalyst; has a cured softening point of about 20"C or higher; and a minimum solids content of about 40 percent by weight.

23. The composition of claim 1 further comprising up to 30 percent by weight of an aminoplast resin.

24. The composition of claim 1 wherein the polyepoxide resin (A) comprises a copolymer of at least one monoethylenically unsaturated monomer having at least one epoxy group and at least one monoethylenically unsaturated monomer that is free of epoxy groups.

25. The composition of claim 1 wherein the polyepoxide resin (A) comprises an epoxy-functional acrylic polymer prepared from monomers including methacrylate monomers and styrene.

26. The composition of claim 1 wherein the polyacid curing agent (B) is a carboxylic acid-terminated material having an average of greater than two carboxylic acid groups per molecule.

27. The composition of claim 1 wherein the composition contains an aluminum or mica flake pigment.

28. The composition of claim 1 wherein the composition is formulated as a clear coating substantially free of pigment.

29. An organic colloidal dispersion comprising: (a) polar polymeric microparticles prepared by non-aqueous dispersion polymerization of, on a weight basis of total monomers and crosslinkers: (i) 50 to 100 percent of vinyl monomers selected from the group consisting of acrylic acid, methacrylic acid, beta-carboxyethylacrylate, 2 hydroxyethyl acrylate, acrylonitrile, or mixtures thereof; (ii) 0 to 15 percent vinyl monomers other than those in (i); and (iii) 0 to 50 percent crosslinkers; (b) stabilized in a dispersed state with a polymeric acrylic dispersant free of polymerizable unsaturation;

and (c) dispersed during polymerization in a non-aqueous polar medium comprising solvent selected from the group consisting of esters, ketones, and mixtures thereof adapted to retard hydrogen bonding of the monomers in the vinyl monomer component and to dissolve the polymeric acrylic dispersant.

30. The dispersion of claim 29 wherein the polymeric microparticles comprise no more than 5 percent of the monomers of(ii).

31. The dispersion of claim 29 wherein the polar polymeric microparticles have a particle size of from 0.01 microns to 2 microns.

32. The dispersion of claim 29 wherein the polar polymeric microparticles have a theoretical acid value from 10 to 780.

33. The dispersion of claim 29 wherein the vinyl monomer (i) consists essentially of acrylic acid.

34. The dispersion of claim 29 wherein the polymeric acrylic dispersant is prepared from glycidyl methacrylate, n-butyl methacrylate, and methyl methacrylate.