Aqueous branched polymer dispersant for hydrophobic materials

A waterbased dispersion useful for forming aqueous coating compositions containing dispersed hydrophobic material, an aqueous carrier and a branched polymer dispersant (binder); PA1 the branched polymer has a weight average molecular weight of about 5,000-100,000 and contains 20-80% by weight of a hydrophilic backbone and correspondingly 80-20% by weight of macromonomer side chains; wherein the backbone is of polymerized ethylenically unsaturated monomers and 2-30% by weight, based on the weight of the backbone of polymerized ethylenically unsaturated monomers having an acid-functional group; and wherein at least 10% of the acid-functional groups are neutralized with an amine or an inorganic base and is hydrophilic in comparison to the side chains; and PA1 the side chains are of macromonomers of polymerized ethylenically unsaturated monomers that are polymerized into the backbone via an ethylenically unsaturated group and the macromonomers have a weight average molecular weight of about 1,000-30,000 and wherein the weight ratio of hydrophobic material to binder is about 1/100-200/100.

TECHNICAL FIELD 
This invention relates to improved waterborne dispersions containing an 
aqueous branched polymer dispersant and a dispersed hydrophobic material. 
BACKGROUND OF THE INVENTION 
Waterborne coating compositions are widely used to coat automobiles and 
trucks since these compositions have substantially reduced VOC (volatile 
organic content) and meet with stringent pollution regulations. Typically, 
these coating contain a latex as the main film forming component, a 
crosslinking agent, and other non-latex resins, additives and pigments. 
The latex to keep it dispersed in an aqueous medium can contain 
surfactant, and/or the latex polymer contains anionic or cationic groups 
which when formed into a salt with an acid used for cationic groups or a 
base used for anionic groups. The presence of surfactant, cationic or 
anionic constituents in a finished formed from such a coating composition 
cause defects such as water spotting, poor resistance to humidity and 
increase acid etching caused by acid rain and the finish has poor 
resistance to exterior weathering. To improve such defects in a coating, 
hydrophobic constituents can be added to the coating composition such as 
hydrophobic melamine crosslinking resins and hydrophobic polymers. 
However, these hydrophobic constituents are very difficult to disperse in 
an aqueous medium. 
Water dispersible polymers that are used as dispersants for pigments and 
used to form pigment dispersions for formulating waterborne coating 
compositions are known in the art and may be considered as a dispersant 
for such hydrophobic materials. U.S. Pat. No. 5,231,131, issued Jul. 27, 
1993 to Chu et al shows aqueous graft polymer pigment dispersants in which 
the side chains of the graft copolymer contain carboxyl groups that are 
neutralized with an inorganic base or an amine. While these graft 
copolymers are used as dispersants for pigments, relatively large amounts 
of polymerized ethylenically unsaturated acid monomers are present in the 
side chains of the graft copolymer to provide water dispersibility but the 
presence of these acid groups in the graft copolymer makes a coating 
formed with such a copolymer sensitive to water and would not be suitable 
for dispersing hydrophobic materials in a coating. 
A polymer dispersant is needed that will adequately disperse hydrophobic 
components used in coating compositions such as crosslinking agents like 
melamine crosslinking agents, hydrophobic polymers like acrylic polymers 
and polyesters and mixtures of such components and the polymeric 
dispersant contains relatively small amounts of polymerized acid monomers. 
When dispersion of such a polymer is formulated into a waterborne coating 
composition, a finish is formed that is free from the undesirable effects 
of exposure to water and weathering. 
SUMMARY OF THE INVENTION 
A waterbased dispersion useful for forming aqueous coating compositions 
containing dispersed hydrophobic material, an aqueous carrier and a 
branched polymer dispersant (binder); 
the branched polymer has a weight average molecular weight of about 
5,000-100,000 and contains 20-80% by weight of a hydrophilic backbone and 
correspondingly 80-20% by weight of macromonomer side chains; wherein the 
backbone of the branched polymer is of polymerized ethylenically 
unsaturated monomers and 2-30% by weight, based on the weight of the 
backbone of polymerized ethylenically unsaturated monomers having an acid- 
functional group; and wherein at least 10% of the acid-functional groups 
are neutralized with an amine or an inorganic base and is hydrophilic in 
comparison to the side chains; and 
the side chains are of macromonomers of polymerized ethylenically 
unsaturated monomers that are polymerized into the backbone via an 
ethylenically unsaturated group and the macromonomers have a weight 
average molecular weight of about 1,000-30,000 and wherein the weight 
ratio of hydrophobic material to binder is about 1/100-200/100. 
DETAILED DESCRIPTION OF THE INVENTION 
The novel dispersion of this invention of a hydrophobic material dispersed 
by the branched polymer is stable and in general is non flocculated or 
agglomerated and is compatible with a variety of polymeric film forming 
binders that are conventionally used in waterborne coating compositions 
and in particular compatible with acrylic polymers that are used in 
waterborne coatings. The branched polymer dispersant upon curing of the 
coating composition into which it has been incorporated reacts with other 
film forming components of the coating composition and becomes part of the 
film and does not cause deterioration of the film upon weathering as may 
occur if it remained an unreacted component of the film. Also, since the 
branched polymer is an excellent dispersant, the ratio of polymer to 
hydrophobic component being dispersed is less than used with conventional 
dispersants. Further, the branched polymers allow for the use of higher 
molecular weight polymers that have a lower viscosity in comparison to 
linear polymers of the same composition that have the same molecular 
weight. The acid content of the backbone of the branch polymer can readily 
be adjusted to maximize dispersion properties of the polymer without 
increasing molecular weight and not detract from the performance 
properties of a coating composition into which a dispersion of this 
polymer has been incorporated. Finishes of aqueous coatings formulated 
with dispersions containing these branched polymers are hard, water and 
humidity resistant. 
The branched polymer used to formulate the dispersion of this invention is 
prepared from a macromonomer which forms the side chains of the branched 
polymer and comprises polymerized alpha-beta ethylenically unsaturated 
monomers and has one terminal ethylenically unsaturated moiety and has a 
weight average molecular weight (MW) of 1,000-30,000, preferably 6,000 to 
15,000. About 20-80% (by weight), preferably 30-70%, of the macromonomer 
is copolymerized with 80-20%, preferably 70-30%, of a blend of other 
alpha, beta-ethylenically unsaturated monomers which form the backbone of 
the branched polymer, at least 2%, preferably 2-30% by weight, most 
preferably 3-15%, of the alpha, beta ethylenically unsaturated monomers of 
the backbone have carboxylic acid functionality, to form a branched 
polymer with a MW of 5,000-100,000, preferably 5,000-40,000, which after 
neutralizing with an amine or other neutralizing agent can be dispersed in 
water. 
All molecular weights herein are determined by GPC (gel permeation 
chromatography) using a polystyrene standard. 
It has been found that improved aqueous or waterborne coating compositions 
are obtained by using these branched polymers as dispersants for 
hydrophobic materials such as certain crosslinking agents and hydrophobic 
polymers. These coating compositions also contain a film forming binder 
usually an acrylic polymer. Such compositions have the advantage of 
providing excellent coating properties desirable for automotive finishes. 
The side chains of the branched polymer are hydrophobic relative to the 
backbone and therefore contain less than 1% by weight, preferably 
essentially zero percent by weight, based on the weight of the branched 
polymer, of polymerized ethylenically unsaturated acid-functional monomers 
which are listed hereinafter. The side chains contain polymerized 
hydrophobic monomers such as alkyl methacrylates and acrylates, 
cycloaliphatic methacrylates and acrylates and aryl methacrylates and 
acrylates and styrene as are listed hereinafter and also may contain up to 
30% by weight, based on the weight of the branched polymer, of polymerized 
ethylenically unsaturated non-hydrophobic monomers which may contain 
functional groups. 
Examples of such monomers are hydroxy ethyl acrylate, hydroxy ethyl 
methacrylate, acrylamide, nitro phenol acrylate, nitro phenol 
methacrylate, phthalimido methyl acrylate, phthalmido methacrylate, 
acryloamido propane sulfonic acid, and mixtures thereof. 
The acrylic macromonomer may be prepared using a free radical initiator in 
a solvent with a Co (II) or Co (III) chelate chain transfer agent. 
The backbone of the branched polymer contains at least 2 percent by weight 
of an acid functional (neutralized) monomer as, e.g., acrylic acid, 
methacrylic acid, maleic acid, itaconic acid and the like. Methacrylic and 
acrylic acid are preferred. Other acids that can be used are ethylenically 
unsaturated sulfonic, sulfinic, phosphoric or phosphonic acid and esters 
thereof; typically, styrene sulfonic acid, acrylamido methyl propane 
sulfonic acid, vinyl phosphonic or phosphoric acid and its esters and the 
like also can be used. 
The backbone of the branched polymer preferably contains 2-30% by weight 
methacrylic acid or acrylic acid and preferably, 3 to 15% by weight and 
has a MW of 1,000-70,000. The acid functional groups on the branched 
polymer are neutralized with an inorganic base or an amine. The backbone 
is thus relatively hydrophilic in comparison to the side chains and the 
branched polymer keeps the hydrophobic constituents well dispersed in the 
resulting coating composition. Of course, relative hydrophobicity or 
hydrophilicity of the backbone and side chains of the branched polymer 
could be further adjusted by varying the percent of acid and/or hydroxy 
functional monomers versus more hydrophobic monomers such as 2-ethyl hexyl 
methacrylate. 
In one preferred embodiments, the branched polymer contains overall 
(including both backbone and macromonomer arms) about 0 to 40, preferably 
5 to 40, and more preferably 10 to 30, percent of hydroxy functional 
acrylic monomers as, e.g., 2-hydroxyethyl acrylate, 2-hydroxyethyl 
methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 
2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate and the like. These 
hydroxy groups can be used for crosslinking in addition to the acid 
groups. Hydroxy groups are not necessary when acid groups are the only 
crosslinking functionality on the copolymer. Hydroxy groups are necessary 
when the cross-linking agent of the coating composition is a melamine or a 
blocked polyisocyanate. 
As indicated earlier, the branched polymer comprises macromonomer side 
chains attached to a polymeric backbone. Each macromonomer ideally 
contains a single terminal ethylenically unsaturated group which is 
polymerized into the backbone of the branched polymer and typically 
contains polymerized monomers of styrene, esters and/or nitriles and/or 
amides of methacrylic or acrylic acid or mixtures of these monomers. 
Other polymerized ethylenically unsaturated monomers can be present in the 
macromonomer and backbone, for example (but not limited to), acrylic and 
methacrylic acid esters of straight-chain or branched monoalcohols of 1 to 
20 carbon atoms. Alkyl acrylates and methacrylates having 1-12 carbons in 
the alkyl group can be used such as methyl acrylate, ethyl acrylate, 
propyl acrylate, isopropyl acrylate, butyl acrylate, pentyl acrylate, 
hexyl acrylate, 2-ethyl hexyl acrylate, nonyl acrylate, lauryl acrylate, 
methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl 
methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, 
2-ethyl hexyl methacrylate, nonyl methacrylate, lauryl methacrylate and 
the like can be used. Cycloaliphatic acrylates methacrylates can be used 
such as trimethylcyclohexyl acrylate, t-butyl cyclohexyl acrylate, 
cyclohexyl methacrylate, isobornyl methacrylate, 2-ethylhexyl 
methacrylate, and the like. Aryl acrylates and methacrylates such as 
benzyl acrylate and benzyl methacrylate also can be used. 
Ethylenically unsaturated monomers containing hydroxy functionality include 
hydroxy alkyl acrylates and hydroxy alkyl methacrylates, wherein the alkyl 
has 1 to 12 carbon atoms. Suitable monomers include hydroxy ethyl 
acrylate, hydroxy propyl acrylate, hydroxy isopropyl acrylate, hydroxy 
butyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate, 
hydroxy isopropyl methacrylate, hydroxy butyl methacrylate, and the like, 
and mixtures thereof. 
Suitable other olefinically unsaturated comonomers include: acrylamide and 
methacrylamide and derivatives as alkoxy methyl (meth) acrylamide 
monomers, such as methacrylamide, N-isobutoxymethyl methacrylamide, and 
N-methylol methacrylamide; maleic, itaconic and fumaric anhydride and its 
half and diesters; vinyl aromatics such as styrene, alpha methyl styrene 
and vinyl toluene; and polyethylene glycol monoacrylates and 
monomethacrylates. 
The above monomers also can be used in the backbone of the branched 
polymer. 
The branched polymer may be prepared by polymerizing ethylenically 
unsaturated monomers in the presence of macromonomers each having a 
terminal ethylene unsaturation. The resulting branched polymer can be 
envisioned as being composed of a backbone having a plurality of 
macromonomer "arms" attached thereto. 
In the present composition, both the macromonomer arms and the backbone may 
have reactive functionality capable of reacting with a crosslinking 
compound or polymer, although it is optional to have such reactive 
functionality only or essentially only or substantially only on the 
backbone. 
It is to be understood that the backbone or macromonomers referred to as 
having functionality may be part of a mixture of macromonomers of which a 
portion do not have any functionality or variable amounts of 
functionality. It is also understood that, in preparing any backbone or 
macromonomers, there is a normal distribution of functionality. 
To ensure that the resulting macromonomer only has one terminal 
ethylenically unsaturated group which will polymerize with the backbone 
monomers to form the branched polymer, the macromonomer is polymerized by 
using a catalytic chain transfer agent. Typically, in the first step of 
the process for preparing the macromonomer, the monomers are blended with 
an inert organic solvent which is water miscible or water dispersible and 
a cobalt chain transfer agent and heated usually to the reflux temperature 
of the reaction mixture. In subsequent steps additional monomers and 
cobalt catalyst and conventional polymerization catalyst are added and 
polymerization is continued until a macromonomer is formed of the desired 
molecular weight. 
Preferred cobalt chain transfer agents or catalysts are described in U.S. 
Pat. No. 4,680,352 to Janowicz et al and U.S. Pat. No. 4,722,984 to 
Janowicz. Most preferred are pentacyanocobaltate (II), 
diaquabis(borondifluorodimethyl-glyoximato) cobaltate(II) and 
diaquabis(borondifluorophenyl glyoximato) cobaltate (II). Cobalt (III) 
versions of these catalysts are also preferred. Typically these chain 
transfer agents are used at concentrations of about 5-1000 ppm based on 
the monomers used. 
The macromonomer is preferably formed in a solvent or solvent blend using a 
free radical initiator and a Co (II) or (III) chelate chain transfer 
agent. Examples of solvents are aromatics, aliphatics, ketones, glycol 
ethers, acetates, alcohols as, e.g., methyl ethyl ketone, isopropyl 
alcohol, n-butyl glycol ether, n-butyl diethylene glycol ether, propylene 
glycol methyl ether acetate, propylene glycol methyl ether, and N-butanol. 
Peroxy- and azo-initiators (0.5-5% weight, based on the weight of the 
monomer) can be used in the synthesis of the macromonomers in the presence 
of 2-5,000 ppm (on total monomer) or Co (II) chelate in the temperature 
range between 70.degree.-160.degree. C., more preferably azo-type 
initiators as, e.g., 2,2'-azobis (2,4 dimethylpentane nitrile), 
2,2'-azobis (2-methylpropane nitrile), 2,2'-azobis (2-methylbutane 
nitrile), 1,1'-azo (cyclohexane carbonitrile) and 4,4'-azobis 
(4-cyanopentanoic) acid. 
After the macromonomer is formed as described above, solvent is optionally 
stripped off and the backbone monomers are added to the macromonomer along 
with additional solvent and polymerization catalyst. Any of the 
aforementioned azo-type catalysts can be used as can other suitable 
catalysts such as peroxides and hydroperoxides. Typical of such catalysts 
are di-tertiarybutyl peroxide, di-cumyl peroxide, tertiary amyl peroxide, 
cumene hydroperoxide, di(n-propyl) peroxydicarbonate, peresters such as 
amyl peroxyacetate and the like. Commercially available peroxy type 
initiators include, e.g., t-butyl peroxide or Triganox.RTM. B from AKZO, 
t-butyl peracetate or Triganox.RTM. FC50 from AKZO, t-butyl perbenzoate or 
Triganox.RTM. C from AKZO, and t-butyl perpivalate or Triganox.RTM. 25 
C-75 from AKZO. 
Polymerization is continued at or below the reflux temperature of the 
reaction mixture until a branched polymer is formed of the desired 
molecular weight. 
Typical solvents that can be used to form the macromonomer or the branched 
polymer are ketones such as methyl ethyl ketone, isobutyl ketone, ethyl 
amyl ketone, acetone, alcohols such as methanol, ethanol, isopropanol, 
esters such as ethyl acetate, glycols such as ethylene glycol, propylene 
glycol, ethers such as tetrahydrofuran, ethylene glycol mono butyl ether 
and the like. 
In the synthesis of the macromonomer and/or the branched polymer small 
amounts of difunctional alpha-beta unsaturated compounds can be used as, 
e.g., ethylene glycol dimethacrylate or hexane diol diacrylate. 
After the branched polymer is formed, it is neutralized with an amine or an 
inorganic base such as ammonium hydroxide or sodium hydroxide and then 
water is added to form a dispersion. Typical amines that can be used 
include AMP (2-amino-2-methyl-1-propanol), dimethyl-AMP, amino methyl 
propanol, amino ethyl propanol, dimethyl ethanol amine, triethylamine and 
the like. One preferred amine is amino methyl propanol and the preferred 
inorganic base is ammonium hydroxide. 
The conversion into a water dispersion may be accomplished preferably by 
stripping our 30 to 60% of the solvent followed by admixing with an 
organic amine or ammonia and diluting with water, or by admixing with a 
solution of water and amine after the solvent stripping. Alternatively, 
the branched polymer solution, after stripping, can be stirred slowly into 
a solution of water and the amine. The degree of neutralization of the 
dispersion can be from 10 to 150% of the total amount of acid groups, 
preferably from 40-100%. The final pH of the dispersion can accordingly be 
about 4-10, preferably 7-9. The solvents can be stripped-off eventually 
afterwards. 
The overall branched polymer water borne dispersion should be characterized 
by an acid value of from 5 to about 150 (mg KOH/g resin solids), more 
preferably from 10 to about 70 and still more preferably from 15 to about 
35, and an hydroxyl number of about 0 to about 250 (mg KOH/g resin 
solids), more preferably 5 from 40 to 150. 
Particularly useful branched polymers include the following: 
a branched polymer having a backbone of polymerized acrylate or 
methacrylate monomers, styrene monomers, methacrylic or acrylic acid 
monomers, and hydroxy-functional acrylate or methacrylate monomers, and 
side chains of a macromonomer having a weight average molecular weight of 
about 2,000-30,000 and containing about 50% by weight, based on the weight 
of the backbone, of polymerized alkyl methacrylate or acrylate monomers, 
hydroxy-functional acrylate or methacrylate monomers and 2-30 % by weight, 
based on the weight of the backbone, of polymerized methacrylic acid or 
acrylic acid. 
a branched polymer having the above backbone of side chains comprising 
polymerized methyl methacrylate, butyl acrylate, methacrylic acid, 
styrene, and hydroxyethyl acrylate. 
a branched polymer having the above backbone and macromonomers comprising 
polymerized 2-ethylhexyl acrylate, butyl methacrylate, and hydroxyethyl 
methacrylate. 
a branched polymer having the above backbone and macromonomers of isobutyl 
methacrylate, 2 ethyl hexyl methacrylate and hydroxy ethyl methacrylate. 
The branched polymer is used as a dispersing resin to form an aqueous 
dispersion of a wide variety of hydrophobic materials that are commonly 
used in waterborne coating compositions. Typical hydrophobic materials 
include hydrophobic melamine resins, hydrophobic polyesters, hydrophobic 
acrylic polymers, hydrophobic polyurethanes, blocked organic 
polyisocyanates and mixtures of any of the above. 
Typical hydrophobic melamines include partially or fully alkylated melamine 
formaldehyde resins having 1-4 carbon atoms in the alkylated group and 
that can be monomeric or polymeric having a degree of polymerization of 
about 1-3. 
Typical alcohols that are used to alkylate these melamines are methanol, 
ethanol, propanol, butanol, isobutanol and the like. Typical commercially 
available melamine resins are as follows: "Cymel" 373, "Cymel" 385, 
"Resimine" 745, BM 7512 from Monsanto Corporation, HM 2608 from Monsanto 
Corporation, and BM 9539 from Monsanto Corporation. 
Typical hydrophobic acrylic resins comprise polymers of alkyl methacrylates 
and acrylate, hydroxy alkyl acrylates and methacrylates and styrene such 
as a polymer of styrene, butyl methacrylate, butyl acrylate and hydroxy 
propyl acrylate. 
Typical hydrophobic polyester resins are the esterification product of an 
aromatic dicarboxylic acid or an anhydride thereof and a polyol such as a 
polyester of phthalic anhydride, isophathalic acid, neopentyl glycol and 
trimethylol propane. 
Typical blocked organic polyisocyanates that can be used are aliphatic 
polyisocyanates, aromatic polyisocyanate, cycloaliphatic polyisocyanates 
blocked with alcohols, ketimines, oximes and the like. 
Typical hydrophobic polyurethanes include hydrophobic polyesters reacted 
with a polyisocyanate, hydrophobic acrylic polymers having reactive 
hydroxyl groups reacted with a polyisocyanate. 
Cellulose acetate butyrate polymers such as CAB's from Eastman Chemical 
Company can be dispersed in aqueous compositions with the branched polymer 
and formulated into a waterborne coating composition. 
The preferred method for forming the waterborne dispersion of this 
invention is to add with agitation the hydrophobic material to be 
dispersed to a solvent solution of the branched polymer before it is 
neutralized and dispersed in water and the neutralizing agent of amine or 
base is added with agitation. Water then is added and mixed in to form the 
aqueous dispersion. The resulting dispersion has a yield stress of about 
0-1,000 Pa (Pascals), a low (20 sec-1) shear viscosity of about 100-10,000 
m Pas (milli Pascal seconds) and a high shear (1000 sec-1) viscosity of 
about 10-1,000 m Pas measured on a Rotvfisco viscometer. 
An alternative method for forming the water borne dispersion of this 
invention is to neutralized the branched polymer with amine or base and 
add water with constant agitation and the hydrophobic material to be 
dispersed to form a dispersion. 
Waterborne coatings in which the dispersions of the present invention are 
used may optionally contain a latex of an acrylic-based polymer. These 
latexes are stable dispersions in water, typically as a dispersed latex 
polymer has an average particle size diameter of 10 nm to 1 micron, 
preferably 20 to 400 nm. These coating compositions contain about 10-70%, 
more typically 15-50% by weight of binder, and about 30-90%, more 
typically 50-85% by weight, of an aqueous carrier. The carrier is at least 
50% water, preferably 75 to 95% water. Suitable waterborne coatings are 
prepared by blending other useful components in accordance with normal 
paint formulation techniques. 
To form a coating composition which will crosslink under elevated baking 
temperatures of about 60.degree.-180.degree. C. for abut 5-60 minutes, 
about 10 to 40%, preferably 15 to 30% by weight, based on the weight of 
the binder, of a water-soluble water dispersible alkylated melamine 
formaldehyde crosslinking agent having 1-4 carbon atoms on the alkylated 
group can be used or a dispersion of a hydrophobic alkylated melamine 
formaldehyde resin of this invention can be used. These crosslinking 
agents are generally partially alkylated melamine formaldehyde compounds 
and may be monomeric or polymeric as described above. 
These coating compositions containing a melamine crosslinking agent 
preferably contain about 0.1 to 1.0%, based on the weight of a binder, of 
a strong acid catalyst or a salt thereof to lower curing temperatures and 
time. Paratoluene sulfonic acid is a preferred catalyst or its ammonium 
salt. Other catalysts that can be used are dodecyl benzene sulfonic acid, 
phosphoric acid and amine or ammonium salts of these acids. 
Although the dispersion of this invention is aqueous, a solvent can be 
utilized, preferably in minimal amounts, to facilitate formulation and 
application of the coating compositions formulated with these dispersions. 
An organic solvent is utilized which is compatible with the components of 
the composition. 
In addition, coating composition utilizing the dispersion of the present 
invention may contain a variety of other optional ingredients, including 
pigments, fillers, plasticizers, antioxidants, surfactants and flow 
control agents. 
Typical pigments that are used are metallic oxides such as titanium 
dioxide, iron oxides of various colors, zinc oxide, carbon black, filler 
pigments such as talc, china clay, barytes, carbonates, silicates and a 
wide variety of organic colored pigments such as quinacridones, copper 
phthalocyanines, perylenes, azo pigments, indanthrone blues, carbazoles 
such as carbazole violet, isoindolinones, isoindolones, thioindigo reds, 
benzmilazolinones, and metallic flake pigments such as aluminum flake, 
nickel flake, pearlescent pigments and the like. 
To improve weatherability of a finish formed from such coating 
compositions, an ultraviolet light stabilizer or a combination of 
ultraviolet light stabilizers can be added in the amount of about 0.1-5% 
by weight, based on the weight of the binder. The stabilizer may be added 
for example to a dispersion of this invention containing hydrophobic 
material or may be added directly to the coating composition or to pigment 
dispersions used to formulate the coating composition. Such stabilizers 
include ultraviolet light absorbers, screeners, quenchers, and specific 
hindered amine light stabilizers. Also, an anitoxidant can be added, in 
the about 0.1-5% by weight, based on the weight of the binder. 
Typical ultraviolet light stabilizers that are useful include 
benzophenones, triazoles, triazines, benzoates, hindered amines and 
mixtures thereof Specific examples of ultraviolet stabilizers are 
disclosed in U.S. Pat. No. 4,591,533, the entire disclosure of which is 
incorporated herein by reference. 
Such coating composition may also include conventional formulation 
additives such as flow control agents, for example, "Resiflow" S 
(polybutylacrylate), BYK 320 and 325 (high molecular weight 
polyacrylates); rheology control agents, such as fumed silica and 
thickeners such as the Acrylsol.RTM. copolymers from Rohm & Haas. 
Coating compositions formulated with the dispersion of this invention have 
excellent adhesion to a variety of metallic or non-metallic substrates, 
such as previously painted substrates, cold rolled steel, phosphatized 
steel, and steel coated with conventional primers by electrodeposition. 
These coating composition can be used to coat plastic substrates such as 
polyester reinforced fiberglass, reaction injection-molded urethanes and 
partially crystalline polyamides. These coating compositions may be used a 
pigmented monocoats, as clear coats, as the pigmented base coat of a clear 
coat/base coat or as both the clear coat and the base coat. 
Coating compositions formulated with the dispersion of this invention can 
be applied by conventional techniques such as spraying, electrostatic 
spraying, dipping, brushing, flowcoating and the like. The preferred 
techniques are spraying and electrostatic spraying. In OEM applications, 
the composition is typically baked at 100.degree.-150.degree. C. for about 
15-30 minutes to form a coating about 0.1-3.0 mils thick. When the 
composition is used as a clearcoat, it is applied over the color coat 
which may be dried to a tack-free state and cured or preferably flash 
dried for a short period before the clearcoat is applied. The color 
coat/clearcoat finish is then baked as mentioned above to provide a dried 
and cured finish. The present invention is also applicable to non-baking 
refinish systems, as will be readily appreciated by those skilled in the 
art. 
It is customary to apply a clear topcoat over a basecoat by means of a 
"wet-on-wet" application, i.e., the topcoat is applied to the basecoat 
without curing or completely drying the basecoat. The coated substrate is 
then heated for a predetermined time period to allow simultaneous curing 
of the base and clear coats. 
The following Examples illustrate the invention. All parts and percentages 
are on a weight basis unless otherwise indicated. All molecular weights 
disclosed herein are determined by GPC (gel permeation chromatography) 
using a polystyrene standard.

EXAMPLE 1 
A branched polymer was prepared by first preparing a macromonomer and then 
polymerizing the macromonomer with monomers that form the backbone of the 
branched polymer. A dispersion was then prepared from the branched 
polymer. 
Preparation of the macromonomer 
A macromonomer of 5% IBMA (isobutyl methacrylate), 20% HEMA (hydroxyethyl 
methacrylate), and 75% 2EHMA (2-ethyl hexyl methacrylate), for use in a 
preparing a branched polymer was prepared as follows: to a 2-liter flask 
fitted with an agitator, condenser, heating mantle, nitrogen inlet, 
thermocouple and an addition port was added 15.25 g of IBMA monomer, 
228.94 g of 2-EHMA monomer, 61.07 g of HEMA monomer and 251.3 g of 
propylene glycol monomethyl ether. The mixture was agitated and heated to 
reflux (128.degree.-135.degree. C.) under nitrogen. To this was then 
added, as a shot, a pre-mix of a solution of 0.5 g of Vazo.RTM. 88 
initiator 1,1 azobis(cyanocyclohexane)!. 13.8 g of propylene glycol 
monomethyl ether and 26.1 g of a 0.17% solution of bis(boron difluoro 
diphenyl glyoximato) cobaltate(II) in ethyl acetate. This was followed by 
the addition of a pre-mix of a solution of 22.87 g of IBMA monomer, 343.42 
g of 2-EHMA monomer, 91.61 g of HEMA monomer, 2 g of Vazo.RTM. 88 
initiator, 10.0 g of ethyl acetate, 70.6 g of propylene glycol monomethyl 
ether over 240 minutes while maintaining a reflux temperature. 
(116.degree.-122.degree. C). Following a 30 min. hold period, a pre-mixed 
solution of 0.4 g of Vazo.RTM. 88 initiator, 4.95 g of ethyl acetate and 
18 g of propylene glycol monomethyl ether was added over 60 mins. while 
maintaining reflux. The batch was then held at reflux for an additional 60 
mins. at which time a mixture of 0.3 g of t-butyl peroctoate and 33.35 g 
of ethyl acetate were added as a single add and then the reaction mixture 
was cooled. The macromonomer thus prepared has a number average molecular 
weight of 5322 and a weight average molecular weight of about 7627 as 
determined by GPC, weight solids are 61.9% and Gardner viscosity of U. The 
percent terminal vinyl unsaturation is greater than 95 as determined by 
thermogravimetric analysis. 
Preparation of branched polymer 
To a 2-liter flask fitted with an agitator, condenser, heating mantle, 
nitrogen inlet, thermocouple and an addition port was added 305.01 g of 
the macromonomer prepared above and 296.06 g of propylene glycol 
monomethyl ether and the temperature raised to reflux 
(110.degree.-115.degree. C.) under nitrogen. This was followed by the 
addition of a premixed solution of 122.98 g of methyl methacrylate monomer 
(MMA), 91.1 g of styrene monomer (STY), 91.1 g of hydroxy ethyl acrylate 
monomer (HEA), 118.42 g of butyl acrylate monomer (BA), 31.88 g 
methacrylic acid monomer (MAA), 8.2 g t-butyl peracetate and 86.54 g butyl 
acetate over 180 minutes holding temperature at reflux and then cooling 
the reaction mixture to room temperature. The branched polymer has a 
number average molecular weight of 14,710 and a weight average molecular 
weight of 37,190. Weight solids are 53.3% and Gardner viscosity is Y. The 
ration of backbone to macromonomer arms is about 60/40. The composition of 
the backbone is MMA/STY/BA/BEA/MAA in the weight ratio of 27/20/26/20/7. 
Preparation of waterborne dispersion of branched polymer and hydrophobic 
melamine 
To a 2-liter flask fitted with an agitator, condenser, heating mantle, 
nitrogen inlet, thermocouple and an addition port was added 500 g of 
branched polymer prepared above and the temperature raised to distill 133 
g of solvent. The batch was cooled to less than 50.degree. C. at which 
time a 41.95 g of a 30% solution of ammonia in water was added to 
neutralize the acid functionality of the branch polymer. The batch was 
agitated for 10 mins. at which time 124.06 g. of a butylated melamine 
resin (BM 7512 from Monsanto Corp.) and 1.5 g heptane were added and the 
mixture was agitate for 15 minutes. At this time 588.28 g deionized water 
was slowly added over 60 minutes with good agitation and the resulting 
dispersion was cooled to room temperature. A white, stable dispersion of 
the branched polymer and butylated melamine was obtained having a total 
weight solids 35% (24.5% branched polymer and 10.5% butylated melamine), 
Gardner viscosity A, pH 8.31 and a particle size of 140 nanometers as 
determined by quasi electric light scattering. No phase separation of the 
butylated melamine was noted on standing at room temperature over 30 days. 
EXAMPLE 2 
Another waterborne dispersion of the branched polymer of Example 1 but with 
a different butylated melamine was prepared. 133.93 g of hydrophobic 
butylated melamine (HM 2608 from Monsanto) was used. A white, stable 
dispersion of the branched polymer and butylated melamine was obtained 
having a total weight solids 35% (24.5% branched polymer and 10.5% 
butylated melamine), Gardner viscosity A, pH 8.31 and a particle size of 
45 nanometers as determined by quasi electric light scattering. No phase 
separation of the butylated melamine was noted on standing at room 
temperature over 30 days. 
EXAMPLE 3 
A third waterborne dispersion of the branched polymer of Example 1 and a 
different butylated melamine was prepared. 110.92 g of hydrophobic 
butylated melamine (BM 9539 from Monsanto) was used. A white, stable 
dispersion of the branched polymer and butylated melamine was obtained 
having a total weight solids 35% (24.5% branched polymer and 10.5% 
butylated melamine), Gardner viscosity A1D, pH 8.2 and a particle size of 
116 nanometers as determined by quasi electric light scattering. No phase 
separation of the butylated melamine was noted on standing at room 
temperature over 30 days. 
EXAMPLE 4 
Preparation of a branched polymer 
To a 5-liter flask fitted with an agitator, condenser, heating mantle, 
nitrogen inlet, thermocouple and an addition port was added 1762.0 g of 
macromonomer from Example 1 above, 237.96 g of hexanol and the temperature 
raised to 99.degree.-101.degree. C. under nitrogen. This was followed by 
the addition of a premixed solution of 392.8 g of MMA, 224.5 g of STY, 
168.3 g HEA, 224.5 g of BA, 112.2 g MAA, 12.4 g of Vazo.RTM.88 initiator, 
145.9 g of propylene glycol monomethyl ether and 145.9 g of butyl acetate 
over 120 min. holding the temperature at 99.degree.-101.degree. C. This 
was followed by a hold period of 60 min. at which time the temperature was 
reduced to 90.degree. C. over a 30 minute period and the reaction mixture 
was held at this temperature of an additional 270 minutes and cooled to 
room temperature. The number average molecular weight of the branched 
polymer was 9080 and the weight average molecular weight was 17800. The 
weight solids are 64.4% and the Gardner viscosity is Z.sub.2. The 
composition of the backbone is MMA/STY/HEA/BA/MAA in the weight ratio of 
20 35/20/15/20/10 and the weight ratio of backbone to macromonomer about 
40/60. 
Preparation of waterborne dispersion of branched polymer and a water 
immiscible polyester 
To a 2-liter flask fitted with an agitator, condenser, heating mantle, 
nitrogen inlet, thermocouple and an addition port was added 300 g of 
branched polymer prepared above and the temperature raised to distill 58.3 
g of solvent. The batch was cooled to less than 80.degree. C. at which 
time a 7.96 g of dimethyl ethanol amine and 15.0 g water were added to 
neutralize the acid functionality of the branch polymer. The batch was 
agitated for 15 mins. at which time 118.4 g. of a polyester of a 
composition of (in equivalents) phthalic anhydride (0.528)/isophthalic 
acid (0.471)/neopentyl glycol (0.819)/trimethylol propane (0.057)/MPDIOL 
(0.236) diol from Arco Chemical. The polyester was a 69.8% solids solution 
in methyl amyl ketone and the polyester has a hydroxyl number of 58, and a 
number average molecular weight of 2115 and a weight average molecular 
weight of 5066. After the polyester was added the composition was agitated 
for 15 minutes and then 840.1 g deionized water was slowly added over a 30 
minute period with good agitation and the dispersion was cooled to room 
temperature. A white, stable dispersion of the branched polymer and the 
polyester was obtained having a total weight solids 25% (17.5% branched 
polymer and 7.5% polyester), Gardner viscosity A3, pH 8.6 and a particle 
size of 260 nanometers as determined by quasi electric light scattering. 
No phase separation of the polyester was noted on standing at room 
temperature over 30 days. 
EXAMPLE 5 
Preparation of waterborne dispersion of branched polymer and a water 
immiscible acrylic polymer 
To a 2-liter flask fitted with an agitator, condenser, heating mantle, 
nitrogen inlet, thermocouple and an addition port was added 300 g of 
branched polymer prepared above Example 12 and the temperature raised to 
distill 58.3 g of solvent. The batch was cooled to less than 80.degree. C. 
at which time a 7.96 g of dimethyl ethanol amine and 15.0 g water were 
added to neutralize the acid functionality of the branch polymer. The 
batch was agitated for 15 mins. at which time 118.4 g. of an acrylic 
polymer of a composition of styrene/butyl methacrylatelbutyl 
acrylate/hydroxy propyl acrylate (weight ratio of 15/30/17/38), 70% solids 
in Solvesso.TM. (Shell Chemical) and the acrylic polymer has a number 
average molecular weight 2300 and weight average molecular weight 6220 was 
added and the mixture agitated for 15 minutes. and then 840.1 deionized 
water was slowly added over a 30 minute period with good agitation and the 
dispersion was cooled to room temperature. A white, stable dispersion of 
the branched polymer and the acrylic polymer was obtained having a total 
weight solids 25% (17.5% branched polymer and 7.5% polyester), Gardner 
viscosity A3, pH 8.68 and a particle size of 133 nanometers as determined 
by quasi electric light scattering. No phase separation of the acrylic 
polymer was noted on standing at room temperature over 30 days. 
Various modifications, alterations, additions or substitutions of the 
components of the compositions of this invention will be apparent to those 
skilled in the art without departing from the scope and spirit of this 
invention. This invention is not limited to the illustrative embodiments 
set forth herein, but rather the invention is defined by the following 
claims.