CA1064637A - Method of preparing gelled polymeric microparticles, product produced thereby, and compositions containing the same - Google Patents

Abstract

ABSTRACT

Crosslinked acrylic polymer microparticles having a particle size of from 0.1 to 10 microns are produced in relatively high con-centrations by a method comprising the free radical addition copolymeri-zation of at least one ethylenically-unsaturated monomer with an alpha, beta-ethylenically unsaturated monocarboxylic acid and a crosslinking monomer selected from the group consisting of epoxy group-containing compounds, or a mixture of alkylenimine and organoalkoxysilane in the presence of a dispersion stabilizer and a dispersing liquid in which the cross-linked polymer particles are insoluble.
These crosslinked polymeric microparticles can be blended with various resins to produce compositions having improved application characteristics as well as other desirable properties.

Description

1~646~7' This application is directed to polyurethane coating compositions containing microgel particles whereas divisional application S.N.3 2/,Z6g filed ~ 7~ is directed to polyester coating compositions containing microgel particles and divisional application S.N. 298,122 filed 3 March 1978 is directed to the microgel particles and the preparation of them.
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Background of the Invention Methods of preparing crosslinked polymeric microparticles commonly referred to as microgel particles are known in the art. One ~- `
such method is disclosed in commonly-assigned Canadian Patent 1,035,486 issued 25 July 1978 of Roger M. Christenson et al. In this method, a ~ -non-aqueous polymer dispersion is prepared by polymerizing an ethyleni-cally-unsaturated monomer containing hydroxyl groups in the presence of (1) a dispersingliquid which is a solvent for the monomer but in which the resultant polymer is insoluble and (2) a dispersion stabili~er. `~
the resultant non-aqueous .', ' ' ' ~,. ' .

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polymerdispersion produced by this method consists of major pro-portion of uncrosslinked polymer particles and a minor proportion (e.g., lO percent by weight or less) of crosslinked polymer particles (i.e~, microgel particles). Accordingly, in this method, it is necessary to separate the microgel particles from the uncrosslinked polymer particles. This is accomplished by the addition to the dis-persion of an active solvent for the uncrosslinked polymer particles, thereby converting the dispersion to essentially a solution, but for the presence of the insoluble microgel particles. The microgel particles are then separated from the bulk of the polymer by conven-tional means such as centrifuging, filtering, and the like.
The above process, wh~le advantageous in some respects, has seve~al serious- disadvantages. Thus, as will be apparent, the micro-gel particles are an incidental by-product of the non-aqueous disper-sion process and therefore the yield is relatively low (e.g. 5 to lO
percent by weight or lessl. Mareover, because of this factor, it is necessary to separate the microgel pa:rticles from a dispersion which - contains a major proportion of uncrosslinked polymer particles by dissolving the uncrossli:nked polymer particles with an active solvent.
Still another method for producing microgel particles is disclosed in British Patent No. 967,051 to sullitt et al, dated August 19, 1964. In this method, microgel particles are prepared by ~; forming an aqueous emulsion of monoethylenic unsaturated monomer and a crosslinking monomer containing at least two ethylenic double bonds, heating the emulsion to a ternperature of about 40 to 100C. until the reaction is substantially complete to yield a microgel and during the reaction adding an agent to inhibit the formation of high molecu-lar ~' .
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weight substantially uncrosslinked material. The inhibiting agent as disclosed in Bullitt et al can be an active solvent for the monomers or a chain transfer agent. This method has several disadvantages.
Thus, the method utilizes conventional emulsion polymerization tech-niques requiring careful control of the process to prevent settling and the like. ~urther, the use of crosslinking monomers containing at least ~ ~
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2 ethylenic double bonds (e.g., divinyl and diacrylate monomers) has ~
:-been found to lead to flocculation problems in relatively high solidslevel ti.e. 40 percent by weight or higher) microgel particle dispersions.
Finally, this method requires the additional step of adding a water-imrniscible solvent or chain transfer agent to the reaction mixture. ~ -The method of the present invention overcomes essentially all of ; ~.. ~'.': - :
the disadvantages of the prior art. Thus, the present invention provides a method of producing crosslinked acrylic polymer microparticles of from 0.1 to 10 microns particle size in relatively high concentrations ~i.e.
solids levels of 20 to 60 percent by weight) by a process which comprises the free radical addition copolymerization of from about 0.5 to 15 percent of an alpha, beta-ethylenically unsaturated monocarboxylic acid with from about 70 to 99 percent of at least one other ethylenically unsaturated monomer and from about 0.5 to 15 percent of a crosslinking nomer selected from the group consisting of (1) epoxy group~

- containing compounds, (2) a mixture of alkylenimine and organoalkoxy-:.: . .:
~ ~ silane, wherein l a O said epoxy group-containing compound is monoepoxide compound which additionally contains ethylenia unsaturation, b. said organoalkoxysilane is selected from the group con~
sisting of acrylatoalkoxysilane, methacrylatoalkoxysilane and vinylalkoxysilane, and ,-c. said monomerpercentages are based on the weight of monomers used in the copolyrneri7ation process, :

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in the presence of hydrocarbon dispersing liquid which is a solvent for the polymerizable monomers but a non-solvent for the resultant polymer, and polymeric dispersion stabilizer containing at least two segments of which one segment i5 solvated by said dispersing liquid and a second segment is of different polarity than said first segment and is relatively insoluble in said dispersing liquid, wherein the reaction is carried out at elevated temperature such that the dispersion polymer first forms and then is crosslinked. Usually the temperature of reaction should be between about 50 C and 150 C.
The crosslinked acrylic polymer microparticles resulting from the method of this invention can be blended with resins such as ~.
polyurethanes, " ; ~
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31 ~64637 polyesters and the like to produce coating compositions having improved application characteristics and other desirable properties.

Vescription of the Preferred Embodiments The preferred alpha, beta-ethylenically unsaturated mono-carboxylic acids employed in the process of this invention are acrylic and methacrylic acid. Ilowever, other ethylenically unsaturated carboxylic -acids such as ethacrylic acid, crotonic acid, and half esters of maleic and fumaric acids may also be used. In the half esters, one of the carboxyl groups is esterified with an alcohol, the identity of which is not significant so long as it does not prevent polymerization or preclude the desired utilization of the product. Butyl hydrogen maleate and ethyl hydrogen fumarate are examples.
From about 0.5 to about 15.0 percent by~weight of such acid monomers based on the weight of monomer solids ~_*_~ employed in the process of the invention. -Various other ethylenically unsaturated monomers may be co-polymerized with the acid monomer and crosslinking monomers in the process of this invention. Although essentially any copolymerizable ethylenic monomer may be utilized, depending upon the properties desired the preferred ethylenically-unsaturated monomers are the alkyl esters of acrylic or methacrylic acid, particularly those having from about 1 to about 4 carbon atoms in the alkyl group. Illustrative of such com-pounds are the alkyl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate and the alkyl methacrylates, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate and ~ -butyl methacrylate. Other ethylenically unsaturated monomers whlch ~ 4 ~
: ' ': ' 1~64~37 may advantageously be employed include, for example, the vinyl aromatic hydrocarbons, such as styrene, alpha-methyl styrene, vinyl toluene, unsaturated esters of organic and inorganic acids, such as vinyl acetate, vinyl chloride and the like, and the unsaturated nitriles, such as acrylonitrile, methacrylonitrile, ethacrylonitrile, and the ; like. From about 70 percent to about 99 percent by weight of such ethylenically unsaturated monomers, based on the weight of monomer solids is utilized.
As indicated above, the crosslinking monomers employed in the process of tha invention are selected from the group consisting of epoxy group-containing compounds, or a mixture of alkylenimine and organo-alkoxysilane.

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~064637 The epoxy group-containing compounds which may be utilized in the practice of the invention are monoepoxide compounds which add-itionally contain ethylenic unsaturation. Illustrative of such com-pounds are, for example, glycidyl acrylate and glycidyl methacrylate.
Various alkylenimines can be utilized in the practice of the invention including substituted alkylenimines. The preferred class of such amines are those of the formula:

R R R
,2 ,6 ,3 lQ Rl - C - (CH ~ C R4 N

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where Rl, R2, R3, R4 and R5 are each hydrogen; alkyl, such as methyl,~
ethyl, propyl or the like, having, for example, up to about 20 carbon atoms; aryl, such as phenyl or the like; aralkyl, such as tolyl, xylyl or the like; or aralkyl~ such as benzyl, phenethyl or the like. R6 in the above formula is hydrogen or a lower alkyl radical usually having not more than about 6 carbon atoms, and n ::, is an integer from 0 to 1.
It is intended that the groups designated by the above formula include substituted radicals of the classes indicated where the substituent groups do not adversely affect the basic na-ture of the imine in the reaction. Such substituents can include the groups such as cyano, halo, amino, hydroxy, alkoxy, carbalkoxy . . ~, !
- and nitrile. The substituted groups may thus be cyanoalkyl, halo- -alkyl, aminoalkyl, hydroxyalkyl , alkoxyalkyl, carbalkoxyalkyl4 and similar substituted derivatives of aryl, alkaryl and aralkyl groups where present.

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~: ' ~06~i37 number of specific examples of alkylenimines within the ~ class described are as follows:

; Ethylenimine (aziridine) 1,2-propylenimine (2-methyl aæiridine) 1,3-propylenimine (azetidine) 1,2-dodecylenimine (2-decyl aziridine) l,l-dimethyl ethylanimine (2,2-dimethyl aziridine) Phenyl ethylenimine (2-phenyl aziridine) ; : Benzyl ethylenimine (2-phenylmethyl aziridine) . Hydroxyethyl ethylenimine (2-(2-hydroxyethyl)aziridine) Aminoethyl ethylenimine (2-(2~aminoethyl)aziridine) 2-methyl propylen-lmine (2-methyl azetidine)

3-chloropropyl ethylenimine (2-(3-chloropropyl)aziridine) Methoxyethyl ethylenimine (2-(2-methoxyethyl)aziridine) Dodecyl aziridinyl formate (dodecyl l-aziridinyl carboxylate) N-ethyl ethylenimine (l-ethy:L aziridine) ~ N-(2-aminoethyl)ethylenimine (1-(2-aminoethyl)aziridine) -~ N-tphenethyl)ethylenimine (1-(2-phenylethyl)aziridine . N-(2-hydroxyethyl)ethylenimine (1-(2-hydroxyethyl)aziridine) N-(cyanoethyl)ethylenimine (l-cyanoethyl aziridine) : N-phenyl ethylenimine (l-phenyl aæiridine) N-(p-chlorophenyl)ethylenimine (1-(4-chlorophenyl)aziridinej Because of their availability and because they have been found to be among the most effective, the preferred imines are hydroxyalkyl-substituted alkylenimines, such as N-hydroxyethyl ethylenimine and N- -hydroxyethyl propylenimine.

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~6~64~37 Organoalkoxysilane monomers which are employed in the prac-tice of this invention are the acrylatoalkoxysilanes, methacrylato-alkoxysilanes and the vinylalkoxysilanes. Illustrative of such com-pounds are acryloxypropyltrimethoxysilane, gamma-methacryloxypropyl-trimethoxysilane~, gamma-methacryloxypropyltriethoxysilane, gamma-methacryloxypropyl-tris(2-methoxyethoxy) silane, vinyltriméthoxy-silane, vinyltriethoxysilane, vinyl-tris(2-methoxyethoxy) silane and the like. Of these organoalkoxysilanes, gamma-methacryloxypropyl-trimethoxysilane is especia:]ly preferred.
lQ The proportion of such crosslinking monomers employed in the process of the invention may range fro~ 0.5 percent to 15 percent by weight.
The ethylenically-unsaturated monomer, acid monomer and cross-linking monomer are polymerized in a dispersing liquid which solubilizes the monomers but in which the resulting polymers are es-sentially not soluble and form dispersed polymer particles. The non-solvent is a hydrocarbon medium consisting essentially of liquid ali-phatic hydrocarbons. A pure aliphatic hydrocarbon or a mixture of two or more may be employed. To the extent that any particular poly-mer produced is mostly insoluble in the hydrocarbon medium resulting,the essentially aliphatic hydrocarbon may be modified by the incorpor-ation of other solvent mater~als such as aromatic or naphthenic hydro-carbons, and in certa~n instances the amount of such non-aliphatic . .
component may attain as high as 49 percent by weight of the entire liqu~d medium. However, the liquid medium preferably consists essen- ;~
tially of aliphatic hydr~carbons and, in general, the compositions of the present invention contain less than 25 percent by ~eight based on the weight of the liquid medium of an aromatic hydrocarbon and often none at all at this stage.
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' ' ' . . ' ~' . ' ' , ' '. . ' ,' ' ~, ;' , ~6~37 It is essential that the hydrocarbon be of liquid character, but it may have a wide boiling range from a minimum of about 30C. (in which case high pressures may be needed in the polymerization) to a maximum which may be as high as 300C. For most purposes, the boiling point should be from about 50C. up to about 235C.
Examples of non-solvents useful herein are pentane, hexane, heptane, octanc, mixtures of tho same, and the like.
Ordinarily, the polymerizable composition of monomers and non-solvent should contain from about 30 to about 80 percent by weight of the non-solvent. It is understood, however, that the monomeric ;~ -solution need contain only that amount of non-solvent necessary to solubilize the monomers and maintain the resulting polymers in a dis~
persed state after polymerization.
The monomers are polymerized in the presence of a dispersion stabilizer. The dispersion stabilizer employed in producing the micro- -particles of the invention is a compound, usually polymeric, which contains at least two segments of which one segment is solvated by the dispersing liquid and a second segment is of different polarity ;~ than the first segment and is relatively insoluble (compared to the first segment) in the dispersing liquid. Although such compounds have been used in the past to prepare dispersions of polymer, in those instances it has been considered necessary that the polymer produced be ungelled, film-forming and soluble in certain solvents.
Included among such dispersion stabilizers are polyacrylates and polymethacrylates, such as poly(lauryl)methacrylate and poly(2-ethyl- -hexyl acrylate); diene polymers and copolymers such as polybutadiene and degraded rubbers; aminoplast resins, particularly highly naphtha-tolerant compounds such as melamine-formaldehyde resins etherified r 9 1~6463~
with highe~ alcohols (e.g., alcohols having 4 to 12 carbon atoms), for example, butanol, hexanol, 2-ethylhexanol, etc., and other aminoplasts of similar characteristics such as certain resins based on urea, benzo-guanamine, and the like, and various copolymers designed to have the desired characteristics, for example, polyethylene vinyl acetate co- -polymers.
The presently preferred dispersion stabilizers used in this invention are graft copolymers comprising two types of polymer components of which one segment is solvated by the aliphatic hydrocarbon solvent and is usually not associated with polymerized particles of the poly- -merizable ethylenically-unsaturated monomer and the second type is an anchor polymer of different polarity from the first type and being relatively non-solvatable by the aliphatic hydrocarbon solvent and capable oE anchoring with the polymerized particles of the ethylenically msaturated monomer, said anchor polymer containing pendant groups capable of copolymerizing with ethylen:Lcally-unsaturated monomers.
The preferred dispersion stabilizers are comprised of two segments. The first segment (A) comprises the reaction product of (l) a long-cllain hydrocarbon molecule which is solvatable by the dispersing liquid and contains a terminal reactive group and (2) an ethylenically-unsaturated compound which is copolymerizable with the ethylenically unsatùrated monomer to be polymerized and which contains a functional group capable of reacting with the-terminal reactive group of the long-chain hydrocarbon molecule (1).
Generally, the solvatable segment (A) is a monofunctional polymeric material of molecular weight of about 300 to about 3,000.
These polymers may be made, for example, by condensation reaction producing a polyester or polyether. The most convenient monomers to .

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:~064~37 use are hydroxy acids or lactones which form hydroxy acid polymers.
For example, a hydroxy fatty acid such as 12-hydroxystearic acid may be polymerized to form a non-polar component solvatable by such non-polar organic liquids as aliphatic and aromatic hydrocarbons. The polyhydroxy stearic acid may then be reacted with a compound which is copolymerizable with the acrylic monomer to be polymerized, such as glycidyl acrylate or glycidyl methacrylate. The glycidyl group would react with the carboxyl groups oE the polyhydroxy stearic acid and the polymer segment (Aj would be rormed.
Somewhat more complex, but still useful, polyesters may be ~-made by reacting diacids with diols. For example, 1,12~dodecanediol may be reacted with sebacic acid or its diacid chloride to form a component solvatable by aliphatic hydrocarbons.
The preferred polymeric segment (A) of the dispersion stabilizer is formed by reacting poly-(12-hydroxystearic acid) with glycidyl meth~
acrylate.
The second polymeric segment (B) of the dispersion stabilizer -;
is of polarity different from the first segment (A) and, as such, is relatively non-solvated by the dispersing liquid and is associated with ,~
or capable of anchoring onto the acrylic polymeric particles formed by the polymerization and contains a pendant group which is copolymerizable with the acrylic monomer. This anchor segment (B) provides around the polymerized particles a layer of the stabilizer. ~he solvated polymer segment (A) which extends outwardly from the surface of the particles provides a solvated barrier which sterically stabilizes the polymerized particles in dis~ersed form.
The anchor segment (B) may comprise copolymers of (1) compounds which are readily associated with the acrylic monomer to be polymerized ' -- 11 -- `

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,-such as acrylic or methacrylic esters, such as methyl acrylate, methyl methacry]ate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, octyl methacrylate, and the like, with (2) compounds which contain groups copolymerizable with the acrylic monomer to be polymerized and which contain groups which are reactive with the polymeric segment (~), such as glycidyl-containing acrylates and methacrylates, such as glycidyl acrylate and glycidyl methacrylate.
These copolymers are further reacted with polymerizable ethylenically-unsaturated acids, such as acrylic acid, methacrylic acid, 3-butenoic acid, crotonic acid, itaconic acid, and others mentioned previously -`~
which contain pendant groups which are copolymerizable with the acrylic monomer. ~-.~ The preferred polymeric segment (B) is a terpolymer of methyl methacrylate, glycidyl methacrylate, and methacrylic acid.
The segments (~) and (B) are usually combined entities, the segment (A) being attached to the backbone of the graft copolymer and .
the segment (B) being carried in or on the backbone.
, ~ The monomer solution containing the stabilizer preferably con-tains from about 1 to about 25 percent by weight of the stabilizer.
I The polymeri7ation may be carried out in a conventional -~ manner, utilizing heat and/or catalysts and varying solvents and techniques.
; ; Generally, a free radical catalyst such as cumene hydroperoxide, benzoyl peroxide or slmllar peroxygen compound, or an azo compound such as azo-bisisobutyronitrile is employed.
; The resultant non-aqueous acrylic dispersion consists ess- -entially of microgel particles (i.e., crosslinked polymer particles) dispersed therein. These particles have particle sizes ranging from ` 0.1 to 10 microns. Depending upon the original concentration of 10646;~7 monomer soli~s, non-aqueous dispersions consisting essentially of the microgel particles can be produced by the process at relatively high concentrations. The term "relatively high concentration" as employed herein refers to the solids level of the non-aqueous dispersion. Thus, the process of this invention permits the production of non-aqueous dispersions of microgel particles having solids contents of from 20 to 60 percent by weight or even higher.
; As mentioned above, the gelled polymeric microparticles pre- ~ `
pared by the process, can be blended with various resins such as poly-urethanes, polyesters and the like to produce coating compositions having improved application characteristics and other desirable properties.
Thus, by blending these gelled polymeric microparticles in appropriate quantities with resins of the above type, coating compositions can be obtained which upon application exhibit improved film build, metallic pattern control and flow control. Moreover, these improved character- -istics can be obtained without adverse:ly affecting the gloss of films formed from the resultant coating compositions. A particularly sig-nificant impro~ement obtained when these gelled polymeric microparticles are included in a coating composition is as indicated in the area of film build, particularly the film build of compositions utilized as -topcoat materials in the automotive industry. Heretofore, most commercial topcoat compositions for use in the automotive industry when spray applied often required at least three spray coats to obtain films having the desired thiclcness. By including an appropriate quantity of the gelled polymeric microparticles produced in this invention in such topcoat compositions, the same thickness can be obtained in two spray coats.
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: , ~L~6~637 Polyurethane coa-ting compositions having the improved application characteristics and cther desirable properties can be obtained by blending the crosslinked acrylic polymer microparcicles with an isocyanate modified resin containing hydroxyl groups, formed by reacting a polyhydric material with an organic polyisocyanate, and, if desired, curing agents and other additives.
The polyhydric material preferably contains a polymeric polyol such as a polyether polyol, a polyester polyol, or an acrylic polyol. The polymeric polyol should be predominantly llnear (that is, lQ absence of crosslinks) to avoid gelling of the resultant polymeric product and should have a molecular weight of between 500 and S000.
As examples of polyether polyols, any suitable polyalkylene ether polyol may be used lncluding those which have the following structural formula:
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R ~-_ n m where R is hydrogen or lower alkyl and n is typically from 2 to 6 and ` m is from 2 to lO0 or even higher. Included are poly(oxytetramethyl-ene) glycols, poly(oxyethylene)glycols, poly(oxytrimethylene)glycols, : .
poly(oxypentamethylene)glycols, polypropylene glycols, etc. Also use-ful are polyether polyols formed from the oxyalkylatlon of various polyols, for example, glycols such as ethylene glycol, l,6-hexanediol and the like, or higher polyols, such as trimethylol propane, trimeth- ~;
ylolethane, pentaerythritol and the like. Polyols of~higher function-.~
ality which can be utilized as indicated can be made, for instance, by oxyalkylation of compounds as sorbitol or sucrose.
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6~637 ~lso suitable are polyhydric polythioether such as, for example, the condensation product of thioglycol or the reaction product of a polyhydric alcohol with tllioglycolic or any other suitable glycol.
Polyester polyols can also be used as a polymeric polyol component in making the polyurethane resin. Such polyester polyols can be prepared by the polyesterification of organic polycarboxylic acids or anhydrides thereof with organic polyols. Usually, the poly-carboxylic acids and polyols are aliphatic or aromatic dibasic acids and diols, although a minor amount, i.e., up to about 25 mole percent of polyols and polybasic acids having a functionality of 3 or more, can be used. However, the use of higher functionality polybasic acids and polyols must be carefully controlled 50 as to avoid gelling in the resultant polymeric product. Diols which are usually employed in making the polyester include alkylene glycols, such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol and neo- -pentyl glycol and other glycols such as hydrogenated Bisphenol A, cyclohexane dimethanol, caprolactone diol (for example, the reaction product of caprolactone and ethylene glycol), hydroxyalkylated bis- w phenols, polyether glycols, for example, poly(oxytetramethylene)glycol and the like. However, other diols of various types and, as indicated, -polyols of higher functionality can also be utilized, including for ~-~
example, trimethylol propane, trimethylol ethane, pentaerythritol, and the like, as well as higher molecular weight polyols such as those produced by oxyalkylating low molecular weight polyols.
Tl~e acid component of the polyester consists primarily of monomeric carboxylic acids or anhydrides having 2 to 14 carbon atoms per molecule. The acid should have an average functionality of at .

i4637 least about 1.9; the acid component in most instances contains at least 75 mole percent of dicarboxylic acids or anhydrides. The functionality of the acid component is based upon considerations similar to those discussed above in connection with the alcohol component, the total functionality of the system being kept in mind.
Among the acids which are useful are phthalic acid, iso-phthalic acid, terephthalic acid, tetrahydrophthalic acid, hexa-hydrophthalic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, glutaric acid, chlorendic acid, tetrachlorophthalic acid, and other dicar~oxylic acids of varying types. The polyester may include minor amounts of monobasic acid, such as benzoic acid, and there may also be employed higher polycarboxylic acids such as trimellitic acid and tricarballylic acid (where acids are referred to above, it is understood that the anhydrides of those acids which form anhydrides can be used in place of the acid). It is preferred that the polyester include an aliphatic dicarboxylic acid as at least part of the acid component.
The polyester polyols useful herein also include polyester amide polyols,~and polyhydric compounds having polyester structures but not formed from the reaction of an alcohol and an acid. Examples -of this latter type include the so-called lactone polyesters, such as polycaprolactone polyols, as described in U.S. Patent 3,169,945 to Hostettler et al.
Besides polyether and polyester polyols, useful polyols in-clude hydroxyl-containing interpolymers of ethylenically unsaturated -monomers. Examples of such interpolymers are the so-called acrylic polyols, which include interpolymers of a hydroxyalkyl ester of an ethylenically unsaturated carboxylic acid and one or more copolymerizable ethylenically unsaturated compounds.

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The preferred interpolymers are those containing hydroxy groups clerived ~rom monoacrylates or methacrylates of a diol such as hydroxyalkyl acrylates and methacrylates. Examples include acrylic acid and metllacrylic acid esters of ethylene glycol and 1,2-propylene glycol sucll as hydroxyethyl acrylate and methacrylate and hydroxy- -propyl methacrylate as well as polyethylene glycol monoacrylate and `
polycaprolactone diol or polyol monoacrylate. Hydroxybutyl acrylate, hydroxyoctyl methacrylate, and the like are further examples of the hydroxyalkyl esters of the interpolymer. Also useful are the hydroxy-containing esters of such unsaturated acids as maleic acid, fumaric acid, itaconic acid, and the like. The hydroxyalkyl ester is inter-polymerized with any ethylenically unsaturated compound copolymerizable with the ester, the polymerization taking place through the ethylenically unsaturated linkages; acrylic monomers and vinyl aromatic hydrocarbon monomers are often utilized. Functional monomers, such as acrylamide, N-alkoxyalkyl acrylamides and masked or blocked ethylenically unsaturated isocyanates may also be used.
~` One particularly preferred class of acrylic polyols comprises interpolymers of hydroxyethyl acrylate or methacrylate, one or more ;~
lower alkyl acrylates and, if desired, an unsaturated nitrile and an N-alkoxymethyl acrylamide.
Besides polymeric polyols, low molecular weight polyols, that is those having molecular weights up to 250, can be employed as part or all of the polyhydric material. The low molecular ueight polyols include diols, triols and higher alcohols. Such materials include allphatic polyols particularly alkylene polyols containing from about 2 to 15 carbon atoms. Examples include ethylene glycol, 1,2-propanediol, ` 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,3 pentanediol; cycloaliphatic 16~6~63~7 polyols such as 1,2-cyclohexanediol, 1,2-bis(hydroxymethyl)cyclohexane and cyclohexane dimethanol. Examples of triols and higher alcohols include trimethylol propane, trimethylol ethane, glycerol and pen-taerythritol. Also useful are polyols containing ether linkages such as diethylene glycol, and triethylene glycol.
To produce optimunl coatings, the overall functionality per unit weight of the reaction system should be controlled. Preferably, there should not be present more than about one gram-mole of acids and/or alcohols having a functionality of 3 or more, per 500 grams of the total weight of these compounds. By "functionality" is meant the number of reactive hydroxyl and carboxyl groups per molecule, with anhydride groups being considered as equivalent to two carboxyl groups.
It can be noted that certain compounds contain both hydroxyl and car-boxyl groups; examples are 6-hydroxyhexanoic acid, 8-hydroxyoctanoic acid, tartaric acid, etc.
The organic polyisocyanate which is reacted with the poly-hydric material as described is essentially any polyisocyanate, e.g., hydrocarbon polyisocyanates or substituted hydrocarbon diisocyanates.
Many such organic polyisocyanates are known in the art, including p-phenylene diisocyanate, biphenyl diisocyanate, toluene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 1,4-tetramethylene diiso-cyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexane-1,6-diisocy-anate, methylene bis(phenyl isocyanate), lysine diisocyanate, bis(iso-cyanatoethyl)fumarate, isophorone diisocyanate and methyl cyclohexyl diisocyanate. There can also be employed isocyanate-terminated adducts of diols, such as ethylene glycol, 1,4-butylene glycol, polyalkylene glycols, etc. These are formed by reacting more than one mole of a diisocyanate, such as those mentioned, with one mole of a diol to .

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~Q64i637 form a longer chain diisocyanate. Alternatively, the diol can be addecl along with the diisocyanate.
While diisocyanates are preferred, higher polyisocyanates can be utiliæed as part of the organic polyisocyanate. Examples are 1,2,4-ben~ene triisocyanate and polymethylene polyphenyl isocyanate.
It is preferred to employ an aliphatic diisocyanate, since it has been found that these provide better color stability in the finished coating. Examples include bis(isocyanatocyclohexyl)methane, 1,4-butylene diisocyanate and methylcyclohexyl diisocyanate. The ~ `~
proportions of the diisocyanate and the polyhydric material are chosen so as to provide a hydroxyl-containing product. This can be accomplished by utili~ing a less than stoichiometric amount of polyisocyanate, i.e., less than one isocyanate group per hydroxyl group in the polyhydric material. Higher (e.g., stoichiometric or excess) isocyanate levels can be present if the reaction is terminated at the desired stage, as by addition of a compound which reacts with the residual isocyanate groups, water, alcohols and amines are examples of such compounds.
- In one especially desirable embodiment, a polyfunctional alcohol is used to terminate the reaction at the desired stage (determined `
by the viscosity), thereby also contributing residual hydroxyl groups.
Particularly desirable for such purposes are aminoalcohols, such as ethanolamine, diethanolamine and the like, since the amino groups preferentially react with the isocyanate groups present. Polyols, such as ethylene glycol, trimethylolpropane and hydroxyl-terminated poly-esters, can also be employed in this manner.
While the ratios of the components of the polyhydric material the polyisocyanate and any terminating or blocking agent can be varied, it will be noted by those skilled in the art that the amounts should - 19 - .

' ~064~i37 be chosen so as to avoid gellation and to produce an ungelled, urethane reaction procluct containing hydroxyl groups. The hydroxyl value of the urethane reaction product should be at least 10 and preferably 20 to 200.
The urethane reaction product as described above, can optionally be mixed with a curing agent, along with the gelled polymeric micro-particles, to provide the coating composition. Other additive materials such as polymeric polyols of low glass transition temperature (which can be added before, during or after the reaction to form the urethane reaction product) can also be employed.
; The curing agent, when one is used, can be, for example, an aminoplast resin, i.e., an aldehyde condensation product of melamine, urea, benzoguanamine or a similar compound; products obtained from the reaction of formaldehyde with melamine5 urea or benzoguanamine are most common and are preferred herein. The aminoplast resins utilized contain methylol or similar alkylol groups, and in most instances at least a portion of these alkylol groups are etherified by a reaction with an alcohol, such as methanol, butanol, 2-ethylhexanol, or the :- .
like.
Other curing agents include phenolic resins formed by the condensation of an aldehyde and a phenol. A common phenolic resin is phenolformaldehyde resin.
Any blocked or masked organic polyisocyanate may also be used as the curing agent herein. The conventional organic polyiso-cyanates, as described above, which are blocked with a volatile alcohol, gamma-caprolactam, ketoximes or the like, so that they will be unblocked at temperatures above 100C. may be used. Masked poly-isocyanates, as is known in the art, are not derived from isocyanates, ... . . . .. . . . . . . . .
-~, . . . .
- . , . ., ~, .. : . . .

~- ~06~63~
but do produce isocyanate groups upon heating at elevated tempera-tures. ~xamples of useful maskeil polyisocyanates include diaminimides ~e-g-, (CH3)3-N-N-C-(CH2)4-C-N-N-(CH3_3~ adiponitrile dicarbonate, and the like.
The curing agent may comprise up to about 60 percent by weight of the coating composition and in many cases preferably com-prises from about 4 to about 50 percent by weight of the coating com- `-position.
The polyurethane coating compositions are prepared by blending the crosslinked acrylic polymer microparticles to solutions or dispersions of the above-described urethane reaction products. The solvents employed in forming such solutions and dispersions are well ~;
known and may be any of those conventionally employed in the polyur-ethane coatings art. Accordingly, any solvent or solvent mixture in which the urethane reaction product and aminoplast resin are compat-ible and soluble and~or dispersible to the desired extent may be utilized~ When water is desired to be utilized as the solvent medium, it is often preferable to include in the urethane reaction product salt groups- which impart the desired clegree of solubility or dispers-~ 20 ibil~ty in water.
; In most cases, the overall polyurethane coating composi-tion may contain from about 30 percent to about 90 percent by weight of the urethane reaction product, from about 0 percent to about 50 percent by weight of curing agent, and from about 2 percent to`about 5Q percent by weight, preferably 2 to 20 percent by weight of the crosslinked acrylic polymer microparticles. Where it is desired to include a polymeric polyol, from about 2 to about 20 percent by weight : .
may be employed. As will be understood, when a polymeric polyol is ~`

included in the composition the amo~nt of urethane reaction product .
:, ,' ' ~':''' and curing agent will be xeduced ~ccoxclingly, generally on a 1:1 basls .

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-1~64637 Polyester coating compositions havin~ improved application characteristics and other desirable properties can be obtained by crossl~ 7cr~ c ~70/~
~J blending ~lle ~e~_~Y~t~*~}e microparticles with an oil-modified or oil-free polyester resin, an aminoplast resin and if desired, other additives.
The term "oil-modified polyester" as used throughout this specification refers to resins produced by reacting a polyfunctional ` alcohol, i~e-, a polyol, a polyEunctional acid (or acid anhydride) and an oil or oil fatty acid. These resins are variously referred to in the art as oil-modified polyesters or oil-modified alkyds. -A wide variety of such oil-modified polyesters may be employed in forming the coating compositions. Thus, oil-modified polyester resins having molecular weigbts ranging from about 1,000 to about 10,000 may be utili~ed in the compositions of this invention.
Polyols which may be utili~ed in preparing the oil-modified polyester resins are preferably polyol~; having from 3 to 10 hydroxyl~
groups or diols or a mixture of a polyol and a diol.
, Typical polyols having 3 or more hydroxyl groups which may be employed include trimethylol propane, trimethylol ethanej pentaery~
thritol, dipentaerythritol, glycerin, sorbitol, mannitol, hexanetriol ~ -and the like. A wide variety of diols may be employed. Typical of the many diols which may be employed are alkylene glycols, such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol and neopentyl glycol and other glycols such as hydrogenated Bisphenol A, cyclohexane dimethanol, caprolactone ancl ethylene glycol, hydroxy-alkylated bisphenols, polyether glycols, for example, poly(oxytetra-methylene)glycol and the like.
The oil modified polyester resin will also contain a poly-Eunctional acid constituent, preferably an aromatic dicarboxylic acid ,- -~, . ~-.

such as phthalic acid, isophthalic acid, terephthalic acid, tetrahydro-phthalic acid, hexahydrophthalic acid, and the like, or a saturated aliphatic dicarboxylic acid such as succinic, glutaric, adipic, pimelic, suberic, a~elaic, brassic, dodecandoic and the like. The oil-modified polyester resin may also advantageously contain a minor amount of a monobasic acid constituent such as ben~oic acid, a substituted ben~oic acid or a similar monobasic aromatic acid. In addition, there may also be employed higher polycarboxylic acids such as trimellitic acid and tricarballylic acid (where acids are referred to above, it is understood that the anhydrides of those acids which form anhydrides can be used in place of the acid). It is preferred that the oil-modified polyester contain an aliphatic dicarboxylic acid as at least part of the acid component.
The oil employed in preparing the oil-modified polyester can be a non-drying saturated oil such as coconut oil, cottonseed oilJ
peanut oil, olive oil and the like, or a drying or semi-drying oil, such as linseed oil, tall oil, soya oil, safflower oil, perilla oil, tung oil, oiticica oi], poppyseed oil, sunflower oil, dehydrated castor oil, herring oil, menhadan oil, sardine oil and the like. The '~
above oils can be used per se or in the form of an oil fatty acid.
The oil-modified polyester resin is produced by methods well known in the polyester resin art employing conventional techniques and procedures. Thos, for example, the oil-modified polyester can readily be prepared by the simple interaction of a mixture of a polyfunctional alcohol (i.e., polyol or diol or mixture thereof), a polyfunctional acid (or acid anhydride) and an oil or oil fatty acid.
Where the oil per se is employed, it becomes necessary as is well known in the art, to first convert the oil to a mono- or diglyceride by ' :~ :

., .

~06~637 alcoholysis with glycerol before adding the acid or acid anhydride and esterifying.
As will be recogni~ed, the type and amounts of the various components which make up the oil-modified polyester resin can be varied widely, depending upon the physical characteristics desired in the resin. Thus, the oil-modified polyester can be prepared in such a manner that it exhibits both carboxyl and hydroxyl functionality or substantially only carboxyl functionality or essentially no functionality at all. The term "functionality" as used herein refers to the number of reactive hydroxyl and carboxyl groups per molecule, with anhydride groups being considered as equivalent to two carboxyl groups. It will be noted that certain compounds contain both hydroxyl and carboxyl .. . .
~ groups, e.g., 6-hydroxyhexanoic acid, 8-hydroxyoctanoic acid, tartaric ; acid, etc.
, .
; The preferred oil-modified polyester resins employed in these compositions are those having substantial hydroxyl functionality so that crosslinking with aminoplast resins may be readily accomplished.
As is well known in the art, hydroxyl functional polyester resins~may ~ be readily prepared by reacting an excess of the polyfunctional alcohol `~ constituent with the polyEunctional acid constituent. Thé preferred :
oil-modified polyester resins employed in these compositions have hydroxyl values ranging from about 10 to about 200, more preferably from 40 to 120 and acid values ranging from about 0.1 to about~ 50, .
more preferably from 2 to 20.
As will be evident, lt may in certain cases be desirable to -~
fornl salt groups in the above-described oil-modified polyesters for purposes of water dispersibility. In that event, it may be desirable to include a somewhat higher proportion of acid constituent in the polyester.

106~637 As indicated, the resin component of the compositions of this invention may alternatively be an oil-free polyester resin. A
wide variety of such oil-free polyester resins may be utilized in the compositions of the present invention. Thus, virtually any oil-free polyester resin prepared by the polyesterification of organic poly-carboxylic acids or anhydrides thereof with organic polyols utilized heretofore in the coatings industry may be utilized in the compositions of the invention. The preferred oil-free polyester resins are those having molecular weights ranging from 1,000 to 10,000.
The oil-free polyester produced can be prepared from those polyols utilized in the preparation of conventional polyesters. Such polyols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, neopentyl glycol, trimethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, trimethylolethane, tr:Lmethylolpropane, tetramethylene glycol, 2,3-dihydroxybutane, 1,4-dihydroxybutane, 1,4-dihydroxy-2-ethyl butane, 1,6-dihydroxyhexane, 1,3-dihydroxyoctane, 2,10-dihydroxy-decane, 1,4-dihydroxycyclohexane, 2,2-diethylpropanediol-1,3, 2,2-diethylbutanediol-1,3, 4,5-dihydroxynonane, pentamethylene glycol, heptamethylene glycol, decamethylene glycoI, butene-2-diol-1,4, 2,7-dihydroxy-n-hexane-4, 2-ethylhexanediol-1,3, glycerol, 1,2,6-hexanetriol, pentaerythritol, sorbitol, mannitol, methyl glycoside, 2,2-bis(hydroxy-ethylphenyl)propane, 2,2-bis(betahydroxypropoxyphenyl)propane, 2-hydroxyethylhydroxyacetate~ l,l-bis(hydroxymethyl)nitroethane, and tile like. Additionally, polyether polyols may be utilized, such as for example, poly(oxyethylene)-glycol, poly(oxytetramethylene)glycol, poly(oxypentanethylene)glycol and the like.
Particularly useful polyols include diols and triols. Gen-erally, the diol component includes glycols of the Eormula IIO(CH2) OH

.. : . : :

~ ~0~637 :;:
:,wherein n equals 2 to 10, glycols of the formulas HO(CH2CH20)nH and IIO[CII(Cl-l3)C~l20] ll in which n equals 1 to 10, such as ethylene glycol, diethylene glycol, and the like, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, N-methyl and N-ethyl diethanolamines. Others include 4,4'-methylenebis-cyclohexanol, 4,~s'-isopropylidene-biscyclohexanol and various xylene-diols, hydroxymethylphenylethyl alcohols, hydroxymethylphenylpropanols, phenylenediethanols, phenylenedipropanols, and heterocyclic diols such as 1,4-piperazine diethanol and the like. Some of the preferred diols include 2-methyl-2-ethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 1,6-hexanediol and 2,2-dimethyl-3-hydroxypropyl, 2,2-dil~ethyl-3-hydroxy-propionate and the like. The preferred triols (trifunctional polyols) are trimethylolpropane; trimethylolethane, 1,2,3-propanetriol, 1,2,4-'!
butanetriol; 1,2,6-hexanetriol, and the like.
A wide variety of polycarboxylic acids can be reacted with -the above-described polyols to form the oil-free polyester resins.
Virtually any of the polycarboxylic aclds conventionally employed in oil-free polyester resins may be employed. Thus, acids such as maleic, fumaric, itaconic, propionic, citraconic, isobutyric, trans-crotonic, mesaconic, acetylene dicarboxylic, aconitric, alpha-methyl itaconic, -alpha, alpha dimethyl itaconic, oxalic, malonicj succinic, adipic, glutaric, brassic, dodecandoic, sebacic, 2-methylsuccinic, pimelic, 2,3-dimethyl succinic, suberic, hexyl succinic, aæelaic, 3,3-diethyl glutaric, 3,3-dimethyl gIutaric, 2,2-dimethyl glutaric, 2,2-dimethyl succinic, phthalic, isophthalic, terephthalic, tetrahydrophthalic, exahy(lrophtllalic, trimellitic, tricarballylic, and the like may be utilized. Anhydrides of these acids, where they exist, can be employed and are encompassed by the term "polycarboxylic acid".

, :

:

: . . . ., ~
,': ' ' ' , . . . .

~6~37 The preferred polycarboxylic acids which can be util-ized in preparing the oil-free polyester resin component of these composi~ions are the aromatic dicarboxylic acids such as phthalic, isophthalic,terephthalic, tetrahydrophthalic, hexahydrophthalic and ` the like, or the saturated aliphatic dicarboxylic acids such as succinic, glutaric, adipic, pimelic, suberic, azelaic, brassic, dode- -candoic, and the like.
As in the case of the oil-modified polyesters, the oil-free polyester resins employed in the coating compositions are prefer-ably those having hydroxyl functionality. Thus, the oil-free poly-ester resin may have hydroxyl values ranging from about 10 to about 200, and acid values ranging from about 0.1 to about 50.
As indicated above, the improved polyester coating com-positions are prepared by the addition of aminoplast resins (described above) crosslinking agents and crosslinked acrylic polymer micropartic-les to solutions or dispersions of the above described oil-modified or oil-free polyester resins.
The aminoplast crosslinking agent may comprise up to about 60 percent by weight of the polyester coating composition and, in many cases, preferably compr;ses from about 4 to about 50 percent by weight of the coating composition.
In most cases, the overall composition may contain from about 30 percent to about 90 percent by weight of the oil-modified or .
oil-free polyester resi`n, from about 4 percent to about 60 percent by `-weight of the aminoplast crosslinking agent, and from about 2 percent to about 50 percent by weight, preferably 2 to 20 percent by weight of the crosslinked acrylic polymer microparticles.
The polyurethane and polyester coating compositions des-cribed above may also contain other ingedients such as catalysts, .~ .

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6~637 pl~sticizers .

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~C~641i37 fillers, pigments and the like. This invention is particularly useful in ~hc cleposition of films con~alning metallic flake pigments such as aluminum, nickel, stainless steel, or the like, as the pattern control of the resulting film is excellent.
The compositions are quite useful as coatings on substrates.
The compositions are applied to the substrate and baked at 150F. to 350F. for about 5 to about 60 minutes to cure the coating on the substrate. The coatings may be applied by any conventional means such as spray coating, dip coating, roll coating, and the like. The pre-ferred method is spray coating as the compositions containing cross- -linking polymeric microparticles can be applied with good deposition, efficiency and rapid film build.
~ ny substrate such as paper, metal, wood, paperboard, plastic, foam, extruded rubber, and the like may be coated with these compositions.
The following examples are submitted for the purpose of further illustrating the nature of the present invention and should not be interpreted as a limitation on the scope thereof. All parts and percentages in the examples as well as throughout the specification are by weight unless otherwise indicated.

To a 5-liter flask equipped with an up and over condenser, agitator, thermometer, and heating mantle was charged 1900 grams of Napoleum~30 (a medium boiling naphtha from Kerr-McGee Company) 950 grams of hexane, and 950 grams of heptane. The mixture was heated to reflux (about 85C.) and then 200 grams of methyl methacrylate;

34 grams of a dispersion stabilizer comprising a 50.3 percent solids solution of 45.4 percent methyl methacrylate, 4.2 percent glycidyl ~ Tr~d~

1~641637 methacrylate, 0.9 percent methacrylic acid9 and 49.5 percent of a reaction product of 89.2 percent poly-12-hydroxystearic acid and 10.8 percent glycidyl methacrylate in a solvent solution comprising 52.1 percent butyl acetate, 40.0 percent VM&P naphtha, and 7.9 percent toluene, and 14.3 grams of azobisisobutyronitrile were added. After this addition was complete, reflux was continued for about 20 minutes and then over a 3-hour period was added 4060 grams methyl methacrylate, 226 grams of gamma-methacryloxypropyltrimethoxysilane, 595 grams of the above dispersion stabilizer, 34.0 grams of methacrylic acid, 34.0 grams of 2-hydroxyethyl ethylenimine, 18.0 grams of azobisisobutyronitrile ~ -and 18 grams of p-octyl mercaptan. After this addition, reflux was -continued for another 1.5 hours and the mixture was then cooled and filtered.
The resultant polymeric dispersion consisting essentially of crosslinked polymer particles (i.e., microgel particles) had a total solids content determined at 150C. of 54.5 percent by weight.

'' :
To a 5-liter flask equipped with an up and over condenser, agitator, thermometer and heating mantle were charged 1250 grams of heptane, 540 grams of Isopar H (a mixed aliphatic hydrocarbon having an initial boiling point of 350F. and a dry point of 371F.with 90 percent distilling between 353-357F., available from Humble Oil and Refining Company), 50 grams of methyl methacrylate, lO grams of the dispersion stabilizer of Example 1 and 4 grams of azobisisobutyronitrile.

... .
The mixture was heated to reflux (about 103C.) and held for about 30 minutes. Then over a period of about 3 hours were added I288 grams of ~ T~a~ ~o ~

1~6~1f;37 methyl metllacrylate, 70 grams of glycidyl methacrylate, 42 grams of methacrylic acid, 4.2 grams of Armeen D~ICD ~dimethyl cocoamine, available from ~rmour Chemical Company), 200 grams of the dispersion stabiliæer of Example 1, 14 grams of octyl mercaptan and 5.6 grams of azobisisobutyronitrile. After this addition was completed, reflu~ -was continued for an additional 30 minutes and then an additional 2.8 grams of azobisisobutyronitrile were added. Reflux was then continued for another one hour and the mixture was then cooled and filtered.
The resul~ant polymeric dispersion consisting essentially of crosslinked polymer particles (i.e.. , microgel particles) had a total ~ _ ~ ?
solids content determined at 150~C. of 44.9 percent by weight.
The following Examples illustrate coating compositions pre-pared by bl.ending the gelled polymeric microparticles with polyester and polyurethane resins and other additives.

This example illustrates the preparation of gelled polymeric microparticles for use in polyurethane coating compositions.
To a 5-liter flask equipped with an up and over condenser, agitator, thermometer and heating mantIe was charged 1900 grams of Napoleum~ 0, 950 grams of hexane, and 950 grams of heptane. The mixture was heated to reflux (about 85C.) and then 200 grams of methyl methacrylate; 34 grams of a dispersion stabilizer comprising a 50.3 percent solids solution ~f 45.4 percent methyl methacrylate,

4.2 percent glycidyl methacrylate, 0.9 percent methacrylic acid, and 49.5 percent of a reaction product of 89.2 percent poly-12-hydroxy- -stearic acid and 10.8 percent glycidyl methacrylate in a solvent e ~t~ -1064~7 solution comprising 52.1 percent butyl acetate, 40.0 percent V~I~P
naphtha, and 7.9 percent toluene, and 14.3 grams of azobisisobutyro-nitrile were added. AEter this addition was complete, reflux was continued for about 20 minutes and then over a 3-hour period was added 4060 grams methyl methacrylate, 226 grams of gamma-methacryloxypropyl-trimethoxysilane, 595 grams of the above dispersion stabilizer, 34.0 grams of methacrylic acid, 34.0 grams of 2-hydroxyethyl ethylenimine, 18.0 grams of azobisisobutyronitrile and 18 grams of p-octyl mercaptan.
After this addition, reflux was continued for another 1.5 hours and the mixture was then cooled and filtered. ~-The resultant polymeric dispersion consisting essentially of crosslinked polymer particles (i.e.~ microgel particles) had a total solids content determined at 150C. of 54.5 percent by weight.
The above dispersion was then spray dried to produce a finely divided powder. This powder was then dispersed in an aliphatic hydrocarbon solvent at a 1:1 ratio for use in the examples below.

' :

- .
This example illustrates the preparation of a urethane reaction product of the polyurethane coating composition.
; The following were charged to a reaction vessel:

Parts by Weight Neopentyl glycol 126.9 Trimethylolpropane 22.1 Adipic acid 72.3 Isophthalic acid 123.2 ~.

: , . , ~069~637 Tllis n~ixture was heated to 200C. for 30 minutes and then at 220C. until the resin hacl a Gardner-Holdt viscosity of F (60 per-cent solids in methyl ethyl ketone), an acid value of about 10 and a hydroxyl value of about 100. This polyester polyol was then mixed with the following: -arts by Weight Polyester polyol 70 ~lethyl ethyl ketone 35 Methane-bis(cyclohexyl isocyanate) -(Mobay D-244) 7.13 This m:Lxture was heated at 150C. for 20 hours and then ;~ cooled to 120F. for 3 more hours. There were then added 22 parts of ~ n-butanol and 0.3 part of ethanolamine. The product had a Gardner-Holdt viscosity of Zl-z2~ a non-volatile sollds content of about 60 percent and an acid value of 3.7.
.. .

This example illustrates the preparation of a pigmented ~ ~ GrSS I i t~k~
polyurethane coating composition to which the ~ 1 polymeri~ed microparticles are added to form the lmproved conditions.
A titanium dioxide pigmented polyurethane coating composition was first formulated using the urethane reaction product of Example 4 by blending the following:

Parts by Weight - Urethane reaction product of Example 4 204.90 Butylated melamine formaldehyde resin 100.80 .

, ,, i .... . . . . . . .

~6~3'7 Parts by Weight C~B* solution 4.2 Pigment paste 396.70 Tinuvin 828 (ultraviolet absorber) 8.5 Cellosolve acetate 18.70 Isobutyl alcohol 30.90 Santowhite~ 8.5 p-Toluene sulfonic acid 2.80 Isobutyl acetate 216.0 Diethanolamine 1.0 ~tha~ k) ~20 percent solution of 1/2 second cellulose acetate butyrate in 80/20 toluene/ethanol .~
The pigment paste employed was ground in a solution of a polyester made from 131 parts of neopentyl glycol, 141 parts of sebacic acid, 174 parts of isophthalic acid, 93.6 parts of trimethylolpropane, :
and 8.5 parts hydroxyethyl ethylenimine; the paste was produced by mixlng the following:

Parts by Weight Polyester (60 percent solids in a 90:10 mixture of xylene and butyl Cellosolv~ 91.80 ~ Poly(oxytetramethylene)glycol 26.20 . TiO2 223.30 ; Diacetone alcohol 8.90 Methyl ethyl ketone 26.60 Isobutyl acetate 8.9 This mixture was ground in a ball mill until the particles had a fineness oE 7.5 Hegman.

~ T~de ~ k . ., , . ~ ~

~L~)64637 The polyurethane coatin~ composition thus obtained served as a control composition for the examples below and also as the base r~s~/l'~ ~
composition to which the-g~e~ polymeric microparticles were added.

A polyurethane coating composition was prepared as in Example 5 except thac the titanium dioxide pigment was replaced by aluminum flake pigment at a level of 3 percent by weight. The compo-sition also was utilized both as a control composition and as the cros~basic composition to which the ~11A~ polymeric microparticles were add~d.
'' These examples illustrate the improvement in properties croSs ll~ecl--obtained by adding the gcll~ polymeric microparticles to polyurethane coating compositions.

Parts~by Weight ` Example 1 (control)Example 2 :
Polyurethane of Example S 200.0 200.0 Gelled polymeric micro-particles of Example 3 -- 8.0 Total 200.0 208.0 The above compositions were sprayed onto a panel, flashed - for 2 minutes at room temperature, at which time another coat was applied and flashed for 5 minutes at room temperature and then baked ~ -at 250F. for 30 minutes to cure.

.

3~

The film build of Example 1 (no crosslinked polymeric micro-particles) was 1.20 mils wilile the film build of Example 2 (8 parts crosslinked polymeric microparticles) was 1.70 mils. The flow control - of Example 2 was excellent compared to fair for the Eilm of Example 1.

cr~s s I I n k~( These examples further illustrate the effect of the ge~h~
polymeric microparticles on the properties of polyurethane coating compositions.
' Parts by Weight Example 3 (control) Example 4 Polyurethane of Example 6 200.0 200.0 Gelled polymeric micro-particles of Example 8 -- 8.0 Total 200.0 208.0 These compositions were sprayed onto panels, utili~ing the same procedure as in Examples 1 and 2. The film build of Example 3 ~ ~

` (the control) was 1.3 mils while the film build of example 4 was 1.9 -, .
mils. The pattern control of Example 3 was fair while that of Example - 4 was excellent.
:. , '~ ' ' , .

,~
c~ ss l;Y~k~
This example illustrates the preparation of a gol~ed poly-~ nlcrc,~ ~ ;cl~ Smeric mi~r{~p~rticl-c~ Eor use in polyester coating compositions.
To a 5-liter flask equipped with an up and over condenser, agitator, thermometer and heating mantle were charged 1250 grams of ~'' ' . . ~ .. ...

~L~6q~637 heptane, 540 grams of Isopar 11 (a mixed aliphatic hydrocarbon having an initial boiling point of 350F. and a dry point of 371F. with 90 percent distilling between 353-357F., available from Humble Oil and Refining Company), 50 grams of methyl methacrylate, 10 grams of a dispersion stabilizer comprising a 50.3 percent solids solution of 45.4 percent methyl methacrylate, 4.2 percent glycidyl methacrylate, 0.9 percent methacrylic acid, and 49.5 percent of a reaction product of 89.2 percent poly-12-hydroxystearic acid and 10.8 percent glycidyl methacrylate in a solvent mixture comprising 52.1 percent butyl acetate, 40.0 percent VM&P naphtha, and 7.9 percent toluene, and 4 grams of azobisisobutyronitrile. The mixture was hPated to reflux (about 103C.) and held for about 30 minutes. Then over a period of about 3 hours were 1288 grams of methyl methacrylate, 70 grams of glycidyl methacry-late, 42 grams of methacrylic acid, 4.2 grams of Armeen DMCD (dimethyl ~
cocamine, available from Armour Chemical Company), 200 grams of the - -above dispersion stabilizer, 14 grams of octyl mercaptan and 5.6 grams of azobisisobutyronitrile. After this addition was completed, reflux was continued for an additional 30 minutes and then an additional 2.8 grams of azobisisobutyronitrile were added. Reflux was then continued for another one hour and the mixture was then cooled and flltered.
The resultant polymeric dispersion consisting essentially of crosslinked polymeric microparticles had a total solids content~de-termined at 150C. of 44.9 percent by weight.
: .
~,~
E~AMPLES 12-13 ~ : :
L~i erOss~
These examples illustrate the effect of adding the ~ h~
polymeric microparticles of Example 11 to an oil-modified polyester.
In these examples, a control composition comprising an aluminum pigmented `' ': ` ' ' `', . , ` ' ' ` ~ ~ ' ~ ' :L06~63~

oi].-modified pol.yester coating composition (Example 12) and a test composition (~xample 13) having substantially the same composition except that it contained approximately 10 percent by weight solids c~c~ ss, , ~ked~
of the go].lod polymeric microparticles of Example 11 were prepared using standard polyester coating composition mixing procedures.

The compositions had the following formulations:

Parts by Wei~ht Ingredients Example No. 12Example No. 13 .
Oil-modified polyester resin ( ) 125.0 110.0 Pigment paste (2) 10.0 10.0 Butylated melamine formaldehyde 41.0 41.0 Xylene 30.0 75.0 Crc~
Cellcd polymeric microparticle dispersion of Example 11 -- ~~

Total 206.0 258.0 .'~ ' . ''.
~; ( )A 60 percent solids solution of an oil-modified .~ polyester resin having a hydroxyl value of 76, ~ an acid value of 9, and a Gardner-Holdt viscosity .. ~ of V-X, prepa~ed by reacting a monomer mixture consisting of 33.8 percent coconut oil, 38.3 `;~ percent phthalic anhydride, 2.4 percent tertiary . ~ butyl benzoic acid, 21.6 percent pentaerythritol and 20.9 percent trimethylolethane in a solvent mixture consisting of 91 percent xylene and 9 percent n-butanol.
. ~ : , .

.;~ ( )A pigment paste consisting of 23.7 percent aluminum -~ flake, 5.9 percent phthalocyanine blue, 16.2 per-~ cent methyl-1-12-hydroxystearate, 27.1 percent VM&P
:~ naphtha and 27.1 percent methyl ethyl ketone. The paste was prepared in conventional manner by grinding on a ball mill until the particles had a fineness of ~ 7.5 Hegman.
'`': ~ ' : The above compositions were reduced to 40 percent total solids with xylene and sprayed onto metal substrates. Example 12, the control ., :

:' , ~ 41637 somposition, showed poor metallic pattern control whlle Example 13, the composition containing the crosslinked polymeric microparticles showed excellent metallic pattern control.
E.~AMPLES 14-15 ~ -These examples illustrate the effect of adding the cross-linkedpolymeric microparticles to an oil-free polyester resin coating composition. In these examples, a control composition comprising an aluminum pigmented oil-free polyester coating composition (Example 14)~ ;
and a test composition (Example 15) having substantially the same composition except that it contained approximately 10 percent by weight solids of the crosslinked polymeric microparticles of Example 11, were prepared utilizing standard polyester coating composition ~ -mixing procedures. The compositions had the following formulations: ;

Parts by Weight Ingredients ; Example No. 3 Example No. 4 ` Oil-free polyester resin(l) 125.0 108.0 Pigment paste of Examples 12 and 13 10.0 10.0 ~`~
Methylolated melamine formaldehyde 31.0 31.0 Gelled po~eric microparticle , ~ disp~rsion of Example 11 -- 22.0 ` ~ 1 percent SF1023*(anti-cratering agent)(2)4.0 4.0 :~ , ;` p-toluene sulfonic acid 2.0 2.0 Methyl-n-butyl ketone 86.0 81.0 Total258.0 258.0 .,, ' :

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1~6~637 (1) A 60 percent solids solution of an oil-free polyester resin having a hydroxyl value of 74, an acid value of 4 and a Gardner-Holdt viscosity of R prepared by reacting a monomer mixture consisting of 28.6, 1,6-hexanediol, 19.6 percent adipic acidl 33.4 percent isophthalic acid, 18.0 percent trimethylolpropane and 0.4 percent hydroxy-ethyl ethylenimine in a solvent mixture consisting of 82.0 percent methyl n-butyl ketone and 18.0 percent toluene.
( )A 1 percent solution of silicone in toluene available from the General Electric Corporation.
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- ~ The above compositions were reduced 50 percent by volume to - ? spray using a solvent mixture consisting of 75 percent xylene, 10 ~ percent n-butanol and 15 percent Cellosolve acetate and sprayed onto : . * u'`
; ~ metal substrates. Example 14, the control composition, showed poor -: r'~
~ ~ metallic pattern control while Example 15, the composition containing ~, cross \ ;I~k6~
j the ~ e~ polymeric microparticles, showed excellent metallic pattern control.
~`` According to the provisions of the Patent Statutes there is described above the invention and what are now considered to be its best embodiments. However, within the scope of the appended claims, it is to be understood that the~invention can be practlced otherwise '~ than as specificaIly described.
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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a polyurethane coating composition comprising an ungelled hydroxyl-containing urethane reaction product of an organic polyiso-cyanate and a polyhydric material having a hydroxyl value of at least 10, the improvement which comprises the addition thereto of from about 2 percent to about 50 percent by weight of crosslinked acrylic polymer microparticles having a particle size of from 0.1 to 10 microns formed by the free radical addition copolymerization of from about 0.5 to 15 percent of alpha, beta-ethylenically unsaturated monocarboxylic acid, from about 70 to 99 percent of at least one other copolymerizable monoethylenically unsaturated monomer and from about 0.5 to 15 percent of crosslinking monomer selected from the group consisting of (1) epoxy group-containing compound and (2) a mixture of alkylenimine and organo-alkoxysilane, wherein:
a. said epoxy group-containing compound is monoepoxide compound which additionally contains ethylenic unsaturation, b. said organo alkoxysilane is selected from the group con-sisting of acrylatoalkoxysilane, methacrylatoalkoxysilane and vinylalkoxysilane, and c. said monomer percentages are based on the weight of monomers used in the copolymerization process, in the presence of hydrocarbon dispersing liquid which is a solvent for the polymerizable monomers but a non-solvent for the resultant polymer, and polymeric dispersion stabilizer containing at least two segments of which one segment is solvated by said dispersing liquid and a second segment is of different polarity than said first segment and is relatively insoluble in said dispersing liquid, wherein the reaction is carried out at elevated temperature such that the dispersion polymer first forms and then is crosslinked.

2. The composition of claim 1 wherein said polyhydric material contains a polymeric polyol.

3. The composition of claim 2 wherein said polymeric polyol is selected from the group consisting of polyester polyols, polyether polyols and acrylic polyols.

4. The composition of claim 1 wherein said polyhydric material contains a total of not more than one gram-mole of compounds having a functionality of 3 or more per 500 grams of polyhydric material.

5. The composition of claim 1 wherein the organic polyisocyanate is a hydrocarbon polyisocyanate or substituted hydrocarbon diisocyanate.