Note: Descriptions are shown in the official language in which they were submitted.
~2~ 4
TITLE
~ligh Solids Color Coat Containing
Alcohol Soluble Cellulose Acetate Butyrate
BACKGROUND OF THE INVENTION
5This invention is related to a color coat/
clear coat finish oE high solids coating compositions,
in particular, to mottle and strike-in resistant high
solids color coat compositions containing as a rheology
control additive an alcohol soluble cellulose acetate
butyrate-
Conventional enamel coating composltions of ahigh molecular weight acrylic polymer and melamine cross-
linking resin are well known in the art as shown by
Vasta U.S, Patent 3,622,651, issued November 23, 1971;
Hick U.S. Patent 3,841,895, issued October 15, 1974;
Parter U.S. Patent 3,674,734, issued July 4, 1972; and
Parker U.S. Patent 3,637,546, issued January 25l 1972.
These patents illustrate high quality coating composi-
tions. However, these compositions have a relatively
low solids content to provide for good application
properties and good properties of the resulting dried
finish. To utilize these compositions in areas which
have strict air pollution regulations, pollution abate-
ment equipment is required. This equipment is expensive
and increases capital investment of a plant and is
costly to operate. Attempts to reduce the solvent con-
tent of these conventional compositions generally have
been unsuccessful.
Color coat/clear coat finishes have been
developed in recent years as a topcoat system for auto-
mobiles and other industrial articles which give appear
ance superior to conventional "unifinish" enamels. Color
~æ~ls~
coat/clear enamels are two-layer finishes consist-
ing of a pigmented basecoat overcoated with a trans
parent clearO The clear is usually applied to the wet
basecoat after a short solvent flash period, and the
color coat/clear coat coating is then baked to cure both
layers simultaneously. The clear coat imparts a smooth-
ness, depth and clarity to the color coat/clear coat
enamel which cannot be obtained in a "unifinish" enamel
contai.ning pigment throughout its thickness. The
superior appearance of color coat/clear coat enamels is
especially pronounced in metallic finishes containing
aluminum flake, because this relatively large pigment
tends to reduce the surface smoothness and gloss of con-
ventional enamels whereas in color coat/clear coat
enamels t.he metallic basecoat is overcoated with a
smooth clear.
Formulation of acceptable color coat/clear
coat coatings requires the solution of two problems
peculiar to these finishes. A problem in metallic base-
coats is the pronounced tendency of aluminum flakes, atthe high concentrations needed for hiding at the 0.5-1
mil dry film thickness used, to assume different
orientations in the cured basecoat film depending on
film thickness and application conditions, resulting in
large scale mottling, a blotchy appearance~ and an un-
acceptable variation of brightness and color with color
coat film thickness. A problem in both metalli.c and
solid color coat/clear coat finishes is the tendency
of solvents from the clear coat applied over the wet
basecoat to diffuse into the basecoat and remobilize
the pigments in it, resulting in mottling of metallic
f$~
basecoats and color change in both metallic and solid
color basecoats. This phenomenon is referred to as
"strike-in" of the clear.
These problems have been overcome in low
solids acrylic/melamine and polyester/melamine color
coats by incorporating a high molecular weight cellulose
acetate butyrate, of a type conventionally used in
finishes for metallic flake control, into the basecoat
binder, as exemplified in an article by K. Walker titled
"Wet-On-Wet Coatings" in Polymers Paint and Colour
Journalr October 17, 1979. However, because of the high
molecular weight of the cellulose acetate butyrate em-
ployed, these basecoats must be spray-applied at very
low solids contents in the range of 12-15 weight percent.
In an effort to obtain high solids color coat/-
clear coat coating compositions that meet current or
anticipated air pollution regulations and can be applied
by conventional spraying techni~ues, the molecular
weight of the acrylic polymer used in these compositions
was reduced substantially, resulting in a reduction in
the basecoat solvent content. These higher solids color
coat/clear coat enamels had much poorer mottle resist-
ance and color uniformity, which could not be corrected
by addition of the aforementioned high molecular weiqht
cellulose acetate butyrate resins to the basecoat with-
out reducing its spray solids content to unacceptably
low levels.
There is a need for high solids color coating
compositions that provide a low viscosity under typical
spraying conditions when the coatinq compositions are
applied and provide a substantially increased viscosity
after application to prevent mottling and color varia-
tions. High solids color coat compositions containing
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rheology control additives of this invention have sueh
properties and have an overall appearance acceptable for
exterior finishes of automobilies and trucks and other
industrial articles.
_ MARY OF THE INVENTION
An acrylic color coat enamel coating
composition has now been developed having about 25-50%
by weight of a binder of film-forming constituents and
50-75% by weight of a volatile organie solvent carrier
at spray viscosity and containing in addition about
2-150% by weight, based on the weight of the binder, of
pigment; the binder having about 20-70% by weight ,
based on the weight of the binder, of an acrylic polymer
containing reactive hydroxyl groups, carboxyl groups,
amide groups, or any mixture of such groups, about 0.4-%
by weight, based on the weight of the binder, of a
hydroxy-terminated polyester urethane resinl about
25=40% by weight~ based on the weight of the binder, of
any alkylated melamine formaldehyde erosslinking agent
and about 4-20% by weight, based on the weight of the
binder, or a rheology eontrol agent which consists
essentially of an aleohol soluble eellulose aeetate
butyrate having a butyryl eontent of about 45-50% by
weight, a hydroxyl eontent of about 4-5% by weight and a
viscosity of about 0.2-0.4 seeond.
DESCRIPTION OF THE INVENTION
It has now been found that aleohol soluble
eellulose aeetate butyrate is an effeetive rheology eon-
trol agent in high solids eolor eoat/elear coat eoat-
ings. When added to the base eolor eoat, the rheologycontrol agent of this inven-tion permits coatings of
uniform color to be applied over a broader range of film
thicknesses and application conditions (greater appli-
cation latitude) and gives freedom from resolubilization
of the color coat by the clear coat ~strike-in) causing
,~
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pigments to become mobile again and change the color of
the coatins. The rheology control a~ent of this inven-
tion is especially ~ffective as aluminum 1ake control
agent in metallic color coats where, in addition to the
above-mentioned advantages, it prevents color nonuni-
formities known as mottling and gives high metallic
brightness.
The high solids color coat coating composition
of this invention has a binder content of film-forming
constituents of about 25-50% by weight. Preferably, the
composition has a binder content of about 28-45~. The
composition contains about 50-75% by weight of a vola-
tile organic sol~ent carrier which generally is a sol-
vent Eor the binder. The binder contains 4-20% by
weight of a rheology control agent. The composition
contains about 2-150% by weight of pigment based on the
weight of the binder.
The rheology or flake control agent is an
alcohol soluble butyrate, a grade of cellulose acetate
butyrate (Eastman CAB-533-0.4), hereinafter referred to
- as ASB. ASB has a butyryl content of about ~15-5G% by
weight, a hydroxyl content of about 4-5% by weight and viscosity
vf about 0.2-0.4 second measured accordir.g to ~STM
Method D-1343 in the solution described as Formula ~,
ASTM Method D-817. In order to maximize the sollds
content and minimize the solvent content of the color
coat enamels, it is preferred to use ASB having a vis-
cosity of about a . 2-0.3 second. Because of its high
hydroxyl content, ASB crosslinks with the melamine
resin when the coaling is haked, forming an integral
part of the binder.
The solubility properties of ASB are markedly
different from those of normal finishes grades of cellu-
lose acetate butyrate. ASB forms low viscosity solu-
tions in low molecular weight alcohols, ketones and
glycol ethers, and in blends of aromatic hydrocarbonswith minor amounts of ethanol but yields extremely high
viscosity solutions in slow solvents such as methyl
n-amyl ketone, a principal slow solvent in basecoat
enamel. Its solubility properties differ markedly from
those of normal finishes grac1es of cellulose acetate
butyrate, such as Eastman's CAB-381-0.5 and CAB-531-1,
as shoen by the following comparison of solution
viscosities:
lO ASB Solution Viscosity of Viscosity of
~SB Viscosity 15% CAB-387-0.5 15% CAB-531-1
SolventConc'n Centipoises Solution, Cps. Solution, CpS.
Methanol 15% 52 Insoluble Insoluble
Ethanol 15% 205 Insoluble Insoluble
Methyl ethyl
ketone 15% 138 80 170
~thylene glycol
monoethyl
ether 15% 235 700 950
n-Butyl acetate 10% >100,000 272 585
Methyl n-amyl
ketone 10%>100,000 267 577
Toluene -Insoluble Gel Insoluble
Toluene/95%
ethanol
(80/20 blend) 15%130 90 150
It is desirable to formulate color coat
enamels in a blend of volatile, strong solvents for ASB
with a slower evaporating, poor solvents for ASB to
obtain low viscosity and high spray so]ids and rapid
set-up after application. When fast strong ASB solvents
evaporate rapidly on application of the color coat, ASB
forms a viscous solution in slow poor solvents and
"gels" the color coat. This allows the color coat to
remain fluid and few seconds after application to obtain
flow-out.
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but then sets up -the colol coat rapidly to prevent
further differential movement of al.uminum flakes in
metallic colors. If no slower evaporating, stong ASB
solvents are present in the clear coatp AS~ in the color
coat prevents strike-in of solvents from the clear coat
into the wet basecoat which can resul~ in remobilization
of aluminum flake and other pigments. ASB is
conveniently introduced as a 30% solution in 1:1 by
weight ethanol/methyl n-amyl ketone or 1:1 by weight
ethanol/methyl ethyl ketone.
The advantages of high solids color coat
coating compositions that contain the rheology control
additive are as follows: the composition can be sprayed
on vertical surfaces without sagging and running on the
substrate to which it was applied; the resulting finish
has excellent gloss and image definition (smoothness);
when metallic flakes are used in the composition, the
flakes are more properly oriented and :more uniformly
dispersed in the finish with an improved brightness and
~ with less or no evidence of mottli.ng caused by
differential orientation of the metallic flakes.
The principal binder of the composition is an
acrylic polymer having carboxyl, hydroxyl or amide
groups, a weight average molecular weight of about
2500-25,000 and a glass transition temperature of about
-20C to +25C.
Typically useful acrylic polymers contain
alkyl methacrylate, alkyl acrylate, hydroxyalkyl
acrylate, hydroxyalkyl methacylate and can contain
styrene, acrylic acid or methacrylic acid. Amide
monomers such as methyacrylamide and acrylamide can be
used; glycidyl monomers such as glycidyl acrylate or
glycidyl methacrylate can also be used.
9~
Preferred acrylic po]ymers are of an alkyl
methacrylate that has 1-18 carbon atoms in the alkyl
9L'OUp, an alkyl acrylate that has 1-18 carbon atoms in
the alkyl group and a hydroxyalkyl acrylate or a
hydroxyalkyl methacrylate each having 2-4 carbon atoms
in the hydroxyalkyl group. To form an acrylic polymer
which has a hydroxyl content of about 2-6% by weight, a
sufficient amount of the aforementioned hydroxyalkyl
acrylate or methacrylate is utilized. The polymer also
can contain small amounts of ethylenically unsaturated
carboxylic acid, such as acrylic acid, methacrylic acid,
itaconic acid, in amounts of about 0.1-5% by weight.
Typical alkyl methacrylates and acrylates that
can be used to prepare the acrylic polymers are: methyl
methyacrylate, ethyl methacrylatel butyl methacrylate,
hexyl methacrylate, 2-ethylhexyl methacrylate, nonyl
methacrylate, lauryl methacrylate, stearyl methacrylate,
cyclohexyl methacrylate, isodecyl methacrylate, propyl
methacrylate, phenyl methaerylate, isobornyl methacry-
late, methyl aerylate, ethyl aerylate, propyl aerylate,isopropyl aerylate, butyl aerylate, isobutyl aerylate,
hexyl aerylate, 2-ethylhexyl aerylate, nonyl aerylate,
lauryl aerylate, stearyl acrylate, eyelohexyl aerylate,
isodecyl aerylate, phenyl aerylate~ isobornyl aerylate,
and the like.
Adhesion promoting monomers ean also be used
in the aerylie polymers sueh as diethyl aminoethyl
methaerylate, tertiary butyl aminoethyl methaerylate,
3-(2-methaeryloxy ethyl)-2,2-spiro eyelohexyl
oxazolidene and the like.
Typical hydroxyalkyl aerylates and methaery-
lates which can be used to prepare the acrylic polymers
7~P~
are: 2-hydroxyethyl acrylate, hydroxypropyl acrylate,
4-hydroxybutyl acrylate, 2-hydroxyethyl methacylate,
hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate,
and the like.
The acrylic polymers can contain about 0Ol-30%
by weight of other constituents such as acrylonitrile,
methacrylonitrile, acrylamide and methacrylamide,
styrene or substituted styrene such as methyl styrene.
The acrylic polymers utilized in the coating
composition are prepared by solution polymerization in
which the monomers are blended with solvent,
polymerization initiator and, optionally, a chain
transfer agent, and heated to about 75-lOSC for 1-6
hours to form a polymer that preferably has a weight
average molecular weight of about 2500-25,000, a
hydroxyl content of 2-6~ by weight and a glass
transition temperature of about -20C to +25C.
The weight average molecular weight of the
acrylic polymers is determined by gel permeation chroma-
tography using polymethylmethacrylate or polystyrene as
a standard.
The glass transition temperature of the poly-
mers is determined by differential scanning calorimetry
or is calculated.
One technique that is successfully used in
preparing the acrylic polymers is a pro~rammed addition
of monomers, solvents, initiator solution and optionally
a chain transfer agent into a polymerization vessel at a
given rate. Optionally, the polymers can be terminated
with the chain transfer agent at the desired low
molecular weight. Also, if required, after the poly-
merization is completed, solvents can be stripped off -to
increase the polymer solids content of the resulting
polymer solution.
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Typical solvents which are used to prepare the
acrylic polymer are the following: toluene, n-butyl
acetate, methyl ethyl ketone/ methyl n-amyl ketone, n-
butyl alcohol/ ethylene glycol monoethyl ether acetate,
and other aliphatic, cyloaliphatic and aromatic hydro-
carbons, esters, ethers, ketones and alcohols.
About 0.1-4% by weight, based on the weiqht of
the monomers, of the polymerization initiator is used to
prepare the acrylic polymer. Typlcal initiators are:
azobisisobut~ronitrile, azobis(gamma-dimethyl
valeronitrile), benzoyl peroxide, t-butyl peracetate,
di-ti-butyl peroxide and the like.
A chain transfer agent can be used to control
the molecular weight of the acrylic polymer. Typical
chain transfer agents are 2--mercaptoethanol, dodecyl
mercaptan, benzene thioethanol, mercaptosuccinic acid,
butyl mercaptan, mercaptopropionic acid and the like.
When a transfer agent is used, the resulting acrylic
polymer contains about 0.1-10% by weight of the chain
transfer agent.
Useful acrylic polymers for the preferred
composition contain 50-90% by weight of an alkyl methac-
rylate or an alkyl acrylate each having 1-12 carbon
atoms in the alkyl groups or a mixture thereof, and
10-50% by weight of a hydroxyalkyl acrylate or a hydroxy-
alkyl methacrylate each having 2-4 carbon atoms in the
alkyl group or a mixture thereof. These polymers can
contain up to 30~ by weight of styrene which replaces a
portion of the alkyl methacrylate or alkyl acrylate.
Also these polymers can contain up to 5% by weight of an
ethylenically unsaturated carboxylic acid.
An alkylated melamine formaldehyde crosslink-
ing agent is used in the composition. The alkylated
~a2~L27e~4
melami~e formaldehyde resin used generally has 1-4 car-
bon atoms in the alkyl group. The resin is prepared by
conventional techniques in which an alcohol such as
methanol, ethanol, propanol, isopropanol, butanol, iso-
butanol and the like is reacted with a melamine formalde-
hyde resin. The resin can be fully alkylated and sub-
stantially monomeric or partially alkylated and poly-
meric. One preferred resin which gives a high quality
finish is a fully alkylated methoxy/butoxymethyl mela-
mine (Monsanto Resimene~ 755). Another useful resin isa low temperatur~ cure, high solids, partially methy-
lated, polymeric melamine formaldehyde resin (~onsanto
Resimene~ 717). When a fully alkylated melamine is used,
the compo~itlon contains about 0.1-2.0% by weight, based
on the weight of the binder, of a strong acid catalyst.
When a polymeric melamine is used, the main film-forming
polymer contains about 2-5% of a carboxylic acid to
catalyze the curing reaction.
The composition may contain hydroxy-terminated
polyester urethanes to improve flow-out of the color
coat and, consequently, smoothness of the clear applied
over it. These polyurethanes can be incorporated for
the additional purpose of increasing the flexibility of
the color coat so that it can be applied to flexible
substrates such as fascia materials under a flexible
clear and will withstand bending of the coated fascia
material at low temperatures without cracking. The
composition may contain up to 40% by weight, based on
the total binder, of polyurethane which replaces a por-
tion of the acrylic resin. One polyurethane used inthese compositions is prepared by reacting 75 parts by
weight of polycaprolactonediol ha~ing a number average
molecular weight of 830 and 2 parts by weight of 2,2-
bis(hydroxymethyl) propionic acid with 30 parts by
7~
weight of methylenebis(cyclohexylisocyanate) in xylene/
ethyl acetate solution and has a number average
molecular weight of about 7,000 as determined by gel
permeation chromatography using polymethyl methacrylate
as standard.
Also, in addition to the above constituents,
plasticlzers in the amount of 0.1-10% by weight, based
on the weight of ~he binder, can be used in the composi
tion. Plasticizers that can be used are, for example,
butyl benzyl phthalate, dibutyl phthalate, triphenyl
phosphate, 2-ethylhexyl benzyl phthalate, dicyclohexyl
phthalatel diallyl phthalate, dibenzyl phthalate, fatty
acid esters of pentaerythritol, poly-(propylene adipate)
dibenzoate, diethylene glycol dibenzoate, tetrabutyl~
thiodisuccinate, butylphthalylbutyl glycolate, acetyl-
tributyl citrate, dibenzyl sebacate, tricresyl phos-
phate, toluene N-ethyl sulfonamide, and di-2-ethylhexyl
phthalate.
An acid catalyst solution can be added to the
composition to increase the rate of crosslinking of the
composition on curing. Generally, about 0.1-2% by
weight, based on the weight of the binder, of acid
catalyst is used. For example, phosphoric acid or an
alkyl acid phosphate in which the alkyl group has 1-12
carbon atoms can be utilized for this purpose. Typical
alkyl acid phosphates are methyl acid phosphate, ethyl
acid phosphate, octyl acid phosphate, phenyl acid phos-
phate, and the like. An alkyl sulfonic acid or an aryl
sulfonic acid can be used such a methane sulfonic acid,
para-toluene sulfonic acid or dodecylbenzene sulfonic
acid.
To prevent viscosity increase and gelation
"in the can" of the compositions containing a strong
12
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13
acid catalyst, the acid catalyst must be fully
neutralized with an amine which will volatilize or
decompose at the baking temperature of the coating.
Examples of such amines are n-propylamine and alkyl
oxazolidines. A preferred neutralizing amine is
4,4-dimethyloxazolidine.
The color coat composition contains pigments
in a pigment-to-binder ratio of about 2/100 to 150/100.
These pigments can be introduced into the composition by
first forming a mill base with the acrylic polymer
utilized in the composition or with other compatible
polymers or polymeric dispersants by conventional
techni~ues, such as sand grinding, ball milling,
attritor grinding, two roll milling to disperse the
pigments. The mill base is blended with the film-
forming constituents as shown in the following Examples.
Any of the conventional pigments used in the
coating compositions can be utilized in this composition
such as the following: metallic oxides, such as
titanium dioxide, zinc oxide, iron oxide and the like,
metal hydroxides, metal flakes such as aluminum flake,
chromates, such as lead chromate, sulfides, sulfates,
carbonates, carbon black, silica, talc, china clay,
phthalocyanine blues and greens, organo reds, organo
maroons and other organic dyes, organic pigments and
lakes.
The volatile organic solvent carrier in which
the high solids color coat enamel composition of the
invention is dissolved should contain at least one fast
evaporating, strong solvent for AS~ such as methanol,
ethanol, acetone and methyl ethyl ketone in order to
maximize the spray solids at spray viscosity. A combi-
nation of methanol with one or both of ethanol and
methyl ethyl ketone ranging from about 30% to about 60~
by weight o~ the total solvents present in the enamel at
13
~%~ ;J94
spray viscosity is generally used. The color coat
enamel should also contain at least one slower evapor-
ating poor solvent or solvent mixture for ASB in order
to allow the ASB to set up the color coat as soon as the
volatile, strong ASB solvents have evaporated. Examples
of such poor solvents are methyl n-amyl ketone, n-butyl
acetate, ethylene glycol monobutyl ether acetate, and an
approximately equivolume blend of ethylene glycol mono-
ethyl ether acetate with diisobutyl ketone. The color
coat enamel may also contain minor amounts, up to 20% of
total solvents, of a medium evaporating, good ASB sol-
vent to promote flow-out of the color coat and smooth-
ness of the color coat/clear coat finish. Examples of
such solvents are ethylene glycol monomethyl ether and
propylene glycol monomethyl ether. The color coat
enamel should contain a minimum of and preferably no
slow evaporating, good solvents for ASB which would
prevent the ASB from setting up the color coat by
forming a relatively low viscosity solution of it.
Examples of such undesirable solvents are diacetone
alcohol, ethylene glycol monobutyl ether and diethylene
glycol monoethyl ether. Minor amounts of non-solvents
for ASB, such as aromatic and aliphatic hydrocarbons,
may be incorporated in the color coat enamel without
interfering with the desired rheological effect of the
ASB.
Any suitable clear coat composition can be
applied over the color coat enamel of this invention pro-
vided it contains no substantial amount of slower evapo-
rating, strong ASB solvents which can stri~e into thecolor coat and provided it adheres firmly to the color
coat layer after cure. To obtain good outdoor durabili-
ty, clear coat enamels based on acrylic/melamine binders
are preferred for use over rigid substrates like steel
and rigid plastics. Over flexible substrates like RIM,
14
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the clear binder may comprise a hydroxy-terminated poly-
ester urethane resin in combination with a hydroxy-
functional acrylic ~r polyester resin and a melamine
crosslinker.
Optionally, the color coat can contain about
0.1-10% by weight, based on the weight of the binder of
the color coat, of an ultraviolet light absorber.
Another option is that the color coat and the clear
coat each can contain about 0.1-10% by weight, based on
the weight of the binder of the coat, of an ultraviolet
light absorber. Also, the color coat or the clear coat
can contain about 0~1-5% by weight, based on the weight
of the binder, of a hindered amine light stabilizer.
When a hindered amine light stabilizer is used, the
ratio of ultraviole~ light absorber to hindered amine
light stabilizer is about 1:1 to about 5:1.
Preferred, to lorm a durable finish, the color
coat contains about 1-2~ by weight of an ultraviolet
light absorber and about 1% of a hindered amine light
stabilizer and the clear coat contains about 2-5% of
an ultraviolet light absorber and about 1% of a hindered
amine light stabilizer.
The coating compositions of this invention can
be applied over a variety of substrates, such as metal;
wood, glass, plastics, and the like, by any suitable
spray application method, such as conventional spraying,
electrostatic spraying, or spraying from electrostatic
high speed rotary atomizers, e.g., turbobells, and the
like. The viscosity of the composi~ions can be adjusted
for any of these methods by adding solvents if necessary.
Generally, the composition is utilized at a high solids
content which keeps air pollution at a minimum.
~2'79~
16
The clear coat is usually applied to the wet
color coat after a solvent flash period of 1 5 minutes,
but the color coat may be dried or cured partially or
completely by baking before applying the clear. One
technique that is used to insure that there will be no
popping or cratering of the coating is to allow the
sol~ents to flash off for about 1-5 minutes before a
second coating ~s sprayed on or otherwise applied, then
waiting for about 2-10 minutes before baking the coating
to allow additional solvents to flash off.
The color coat/clear coat coatings are baked
at relatively low temperatures of about 70-150C for
about 15 minutes to 2 hours. The resulting coating is
about 1-5 mils thick but for most uses a 2-3 mil thick
~5 coating is used. Generally, the color coat is about
0.4-1.6 mils thick and preferably 0.6-1.4 mils thick,
and the clear coat is about 0.6-4.0 mils thick and
preferably 1.5-2.0 mils thick.
The resulting coating has good gloss, appear-
ance and adhesion to substrates of all types. Thesecharacteristics make the compositior. particularly use-
ful as a finish for automobiles, trucks and other out-
door equipment.
The following examples illustrate the inven-
tion. All parts, percentages and ratios are on a weight~asis unless otherwise indicated. Molecular weights
are determined by gel permeation chromatography.
EXAMP~E 1
An acrylic polymer solution was prepared as
follows. A 5 liter round bottom flask equipped with a
thermometer, stirrer, reflux condenser, two addition
funnels, and a heating mantle was charged with 960 grams
of methyl n-amyl ketone. The following premixed solu-
tions were charged to the addition funnels:
16
2~4
Grams
Monomer ~ixture
Methyl methacrylate 600
Butyl acrylate 800
2-~ydroxyethyl acrylate 600
Total 2000
Initiator Solution
Methyl n-amyl ketone 120
t-Butyl peracetate (75% solids
in mineral spirits) 80
Total 200
The flask charge was heated to reflux. Addl-
tion of the monomer mixture and initiator solution was
then started simultaneously. The monomer mixture was
added linearly over 240 minutes and the initiator solu-
tion was added linearly over 260 minutes. The reaction
mixture was maintained at reflux during the addition
period and for an additional 30 minutes after addition of
the initiator solution was complete. The resulting
polymer solution was cooled. It had a solids content
of 64.0~.
The polymer was a methyl methacrylate~butyl
ac~ylate/2-hydroxyethyl acrylate copolymer in a weight
ratio of 30/40/30. The polymer had a weight average
molecular weight (Mw) of 5300 and nad a calculated glass
transition temperature (Tg) of -9C.
The following aluminum flake mill base was
prepared:
Grams
Non-leafing, acid spot resistant,
medium particle size aluminum flake
paste (64% solids in mineral spirits) 293.0
Methyl n-amyl ketone 105~5
Acrylic polymer solution (prepared
abo~-e) 351.5
:~L2~
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The above ingredients we~e vi~orously stirr2d
together for 2 hours to form a homog~neous dispersion of
the aluminum flake~O The mill base contained 25~ o~
pigment and 30% of acrylic p~lymer.
The following light bl~le meta].lic color coat
enamels were prepared:
Grams
Color Coat A Color Coat B
Ingredients Containing ASB Without ASB
Portion 1
Acrylic polymer solution
(prepared above) 196.3 154.7
Polyurethane solution consisting of
62.5% of hydroxy-terminated poly-
ester urethane (condensation
product of 75.16 parts of poly-
caprolactonediol of number average
molecular weight of 830, 1.94 parts
of 2,2-bis(hydroxymethyl)propionic
acid and 22.90 parts of methylene-
bis(cyclohexylisocyanate) having a
number average molecular weight of
about 7,000),24.2% of xylene and
13.3% of ethyl acetate 144.0 76.8
Indanthrone blue mill base consisting
of 12.0% of indanthrone blue pigment,
48.0% of a styrene/methyl methacry-
late/butyl acrylate/2-hydroxyethyl
acrylate (15/15/40/30 weight ratio)
copolymer having a ~w of about
6,000, and 40.0% of methyl n-amyl
ketone and prepared by grinding in
a Schold mill 60.5 32.2
Phthalocyanine blue mill base consist-
ing of 18.2% of copper phthalocyanine
blue pigment, 21.5% of the copolymer
present in the above mill base, 2.8%
of an A-B dispersant (methyl methacry-
late/butyl methacrylate 50/50 weight
ratio copolymer terminated with the
mercaptoethanol and reacted with the
biuret of hexamethylenediisocyanate
and capped with ammonia), 55.3% of
methyl n-amyl ketone and 2.2% of
toluene and prepared by grinding in a
steel mill with diagonal steel media 8.6 4.6
18
27~4
19
Black mill base consisting of 11.7%
of high color furnace type carbon
black pigment, 11~7% of the copoly-
mer present in the above mill base,
11.7% of the A-B dispersant present
in the above mill base, 55O4% of
methyl n-amyl ketone and 9.5% of
toluene and prepared by grinding in
a steel mill with diagonal steel
media 2.0 1.1
Ultraviolet light absorber solution
of a substituted benzotriazole
(Tinuvin~ 328) in xylene (30%
solids) 20.0 10.7
Hindered amine light stabilizer
(Tinuvin~ 079) solution in xylene
(40% solids) 15.0 3.0
Portion 2
Aluminum flake mill base (prepared
above) 275.8147.1
Portion 3
Methyoxy/butoxymethyl melamine
(Resimene~755) 210.0112.0
ASB solution consisting of 30% of
alcohol soluble cellulose acetate
butyrate (Eastman CAB-533-0.4) hav-
ing a viscosity of 0~25 second,
35% of toluene-denatured anhydrous
ethyl alcohol, and 35% of methyl
n-amyl ketone 200.0
Toluene denatured anhydrous ethyl
alcohol 70.2 64.3
Portion 4
Catalyst solution consisting of 28.57%
a Cycat~ 600 dodecylbenzenesulfonic
acid solution in isopropanol (70%
solids, 12.76% of Amine CS-1135
4,4 dimethyloxazolidine solution in
water (78% active), and 58.67% of
methanol 24.0 12.8
Methanol 44.1 23.5
Portion 5
Thinner consisting of 25% of toluene-
denatured anhydrous ethyl alcohol,
25% of butyl acetate, 25% of propy-
lene glycol monomethyl ether and
25% of methyl n-amyl ketone 520.099.3
19
~2~271~4
Portion 1 was charged to a mixing vesse], and
thoroughly blended. Portion 2 was added and stirred in
for 30 minutes. Portions 3 and 4 were then added in
turn and each stirred in for 30 minutes. Finally, the
color coat enamels were reduced to a spray viscosity of
22 seconds in a No. 2 Fisher viscosity cut with Portion
5 and filtered through a fine paint strainer.
Following are compositional data on the re-
sulting color coat enamels:
10 Color Coat A Color ~oat B
Acrylic polymer/polyurethane/ 38~9/],4.6/ 48.6/14.6/
melamine formaldehyde resin/ 34.0/9.7/ 34.0/0/0.8/
ASB/dodecylbenzene sul~onic 0.8/1.0/1.0 I.0/1.0
acid/ultraviolet light
absorber/hindered amine light
stabiliæer binder ratio
Pigment/binder ratio 12.6/100 12.6/100
Calculated solids content 38~8~ 49.6%
The following high solids clear coat enamel was
Prepared:
Grams
Portion 1
Acrylic polymer solution of a styrene/
methyl methacrylate/butyl acrylate/
2-hydroxyethyl acrylate (15/36/32/
17 weight ratio) copolymer having a
~w of 15,000 (65.1% solid in methyl
n-amyl ketone) 1997.0
Methoxy/butoxymethyl melamine 588.8
Ultraviolet light absorber solution of
a substituted benzotriazole (Tinuvin~
328) in xylene (30% solids) 200.0
Hindered amine light stabilizer (Tinuvin~
079) solution in xyler,e (40~ solids) 50.0
Silicone solution of an orqanofunctional
silicone (Baysilone~ Fluid OL) in
xylene (10% solids) 1.7
~ ,,
~Z~IZ~94
Portion 2
Silica mill base consisting of 8~93%
of a hydrophobic fumed silica
(Aerosil~ R-972), 49.60% of methoxy/
buto~ymethyl melamine (Resimene~ 755)
and 41.47% of xylene and prepared by
sancl grinding 224.0
Portion 3
-
Catalyst solution (described under
Portion 4 of above color coat compo-
sitions) 80.0
10 Methanol 84.8
Portion 4
-
Silica bridging agent solution of poly-
~inyl pyrrolidone of weight average
molecular weight of about 40,000
~PVP-K-30) in methanol (10% solids) 5.0
Portion 5
Aromatic hydrocarbon solvent boiling
at 150-190C (Aromatic 100)782.3
Portion 1 was charged to a mixing vessel and
thoroughly blended. Portions 2 and 3 were added in
turn and stirred in for 10 minutes each. Portion 4 was
added and stirred in for 30 minutes. Finally, the
clear coat enamel was reduced to a spray viscosity of
45 seconds in a No. 2 Fisher cup with Portion 5 and
filtered through a milk filter.
The resulting clear coat enamel has an acrylic
polymer/melamine formaldehyde resin/dodecylbenzene
sulfonic acid/ultraviolet light absorber/hindered amine
light stabilizer binder ratio of 62.0/33.3/0.8/2.9/1.0,
a silica/binder ratio of 1.0/100 and a calculated solids
content of 52.7%.
Each of the color coat enamels in combination
with the clear coat enamel was sprayed onto 20 gauge
phosphatized steel panels primed first with an electro-
deposition primer and then with a high solids polyester/
melamine type primer-surfacer. The color coat enamel
~L21Zl~9~
22
and the clear coat enamel were applied from separate
De ~ilbiss Model J~,A-502*pressure feed spray guns each
equipped with an FX fluid tip having an orIfice of
0,0425 inch and with a No. 797 air cap. The color coat
5 and clear coat enamels were delivered to the spray guns
from separate pressure tanks at controlled flow rates.
The atomizing air pressure was 70 psi at the base of the
color coat gun and 60 psi at the base of the clear coat
gun.
The color coat/clear coat coating compositions
were applied by means of a Spraymation~ automatic panel
spray machine. The color coat and clear coat spray guns
were mounted side-by-side on a reciprocation arm travel-
ling horizontally at a speed of about 764 inches/minute.
The panels were mounted vertically at a distance of 13
inches from the tips of the spray guns on a panel rack
which moved vertically from a low to a high position in
six 4-inch increments between passes of the spray gun
across the pa~els to "index" the panels during the appli-
cation of each coat of paint. The color coat enamelwas applied in two coats with a 1 minute solvent flash
period between coats. The panels were then dried on
the rack for 2 minutes and the clear coat was applied in
two coats with a 1 minute solvent flash period between
coats. The panels were then dried in a horizontal posi-
tion for about 8 minutes, prebaked 15 minutes at 82C
and baked 30 minutes at 131C.
The propexties of the two color coat/clear
coat finishes are compared below. The "distinctness of
image" was determined b~T means of a Hunter Lab Dori-Gon
Meter D47-6~and is a measure of film smoothness, with
higher values representing smoother films having a more
mirror-like reflectance. The "head-on brightness" and
*denotes trade mark
~27~1~
23
"metallic index" (also called "flake orier~tation index")
were measured with a special goniophotometer called
Object-Modulated Reflectometer~ ~OMR~ and described in
Troy U.S. Patent 4,359,504 issued November 16, 1982.
The head-on brightness was the lightness calculated from
the reflectance measured at an angle of 5 from the
normal and was a measure of the metallic lightness of
the coating when viewed head-on. The metallic index
was explained in U.SO 4,359,504 and was a measure of the
metallic glamour or degree of two-tone of the coating.
For a given color coat pigmentation higher values of
both of these metallic appearance properties result from
better Elake orientation and represent a more desirable
appearance than lower values.
15 Color Coat A/ Color Coat B/
Clear Coat Clear Coat
Properties Finish Finish
Thickness, mils:
Color coat 0.77 0.74
Clear coat 1.8 1.8
20 Gloss measured at 20~ 93 76
Distinctness of image 82 42
Head-on brightness 110 69
Metallic index 60 32
Mottling Slight Definite
25 Tukon hardness, Knoop7.9 6.4
The color coat/clear coat finish prepared
from color coat A containing ASB had greatly superior
gloss, distinctness of image, head-on brightness, metal-
lic index and freedom from mottling than the comparable
finish prepared from color coat B con-aining no ASB.
Additional coatings were sprayed from the
color coat A enamel with the clear coat enamel under
the conditions described above at different col~r coat
and clear coat film thicknesses and had the following
properties:
~271~
2~
Thin Intermediate Thick
Property Coatinq Coating _ Coating
Thickness t mils:
Color coat 0.53 0.71 1.04
Clear coat 1.7 1.8 2.2
Gloss measured at 2Q93 95 94
Distinctness of image 81 84 84
Head-on brightness 111 112 113
Metallic index 60 61 61
10 Mottling None None None
The above coatings prepared from color coat A
had consistent and excellent appearance properties o~er
a wide range of color coat film thicknesses at least as
great as that encountered in commercial application of
this type of finish.
EX~MPLE 2
An acryllc polymer solution was prepared as
follows. A 12 liter round bottom flas}; equipped with
a thermometer, stirrer, distillation head with reflux
condenser, two addition funnels, and a heating mantle
was charged wlth 3093 grams of methyl n-amyl ketone.
The following premixed solutions were charged to the
addition funnels:
Grams
25 Monomer Mi~ture
Styrene 750
~ethyl methacrylate 750
Butyl acrylate 2000
2-Hydroxyethyl acrylate 1500
Total 5000
Initiator Solution
Methyl n-amyl ketone 333
t-Butyl peracetate (75~ solids in
mineral spirits) 167
Total 500
2~
The flask charge was heated to reflux.
Addition of the monomer mixture and initiator solution
was then started simultaneously. The monomer mix-ture
was added linearly over 225 minutes and the initiator
solution was added linearly over 240 minutes. The
reaction mixture was maintained at reflux during the
addition period and for an additional 30 minutes after
addition of -the initiator solution was complete. About
1762 grams of volatiles, consisting principalLy of
methyl n-amyl ketone, was then distilled off and the
~olution in the flask was cooled. The resul~in~ polymer
solution has a solids content of about 75~,
The polymer was a styrene/methyl methacrylate/-
butyl acrylate/2-hydroxyethyl acrylate copolymer in a
weight ratio of 15/15/40/30. The polymer had a Mw of
about 6,000 and a calculated Tg of -9C.
The following aluminum flake mill base was
prepared:
Grams
Portion 1
Acrylic polymer solution ~prepared above) 2780
Ultraviolet light absorber solution of a
substituted benzotriazole (Tinuvin~
328) in xylene (30~ solids) 632
25 Hindered amine light stabilizer (Tinuvin~
079) solution in xylene (40% solids) 237
Portion 2
Non-leafinq, acid spot resistant, medium
particle size aluminum flake paste
(64% solids in mineral spirits) 1851
Portion 1 was charged to a mixing vessel and
thoroughly blended. Portion 2 was added, and the mix-
ture was stirred vigorously to form a homogeneous dis-
persion of the aluminum flakes. The mill base contained
21.5490 of pigment, 37.9% of acrylic polymer, 3.45% of
ultraviolet light absorber, and 1.72% of hindered light
absorber.
,'
7'~4
26
The following dark blue metallic color coat
enamel was prepared:
Grams
Portion 1
~lue mill base consisting of 12.0% of
copper phthalocyanine blue pigment
(green shade), 48.0% of the acrylic
polymer prepared above and 40.0% of
methyl n-amyl ketone and prepared by
grinding in a Schold mill 284h.4
Black mill base (described under Por-
tion 1 of Example 1 color coat compo-
sitions) 373.8
White mill base consisting of 70.0% of
rutile titanium dioxide pigment, 10.0%
of the acrylic polymer prepared above,
and 20.0% of methyl n-amyl ketone and
prepared by sand grinding 37.2
Aluminum flake mill base (~repared above) 179.7
Acrylic polymer solution (prepared above) 246.3
Ultraviolet light absorber solution of
a substituted benzotriazole (Tinuvin~
328) in xylene (30~ solids) 179.1
Hindered amine li~ht stabilizer (Tinuvin~
079) solution in xylene (40% solids) 67.5
Portion 2
-
Methoxy/butoxymethyl melamine
(Resimene~ 755) 1140.0
ASs solution (described under Portion 3
of Example 1 color coat compositions) 500.0
Toluene denatured anhydrous ethyl alcohol 550.2
Portion 3
Amine solution consisting of 25.64% of
Amine CS-1135~ 4,4-dimethyyloxazolidine
solution in water (78% active) and
74O36% of methanol 44.7
Catalyst solution consisting of 17.8% of
p-toluenesulfonic acid, 12.5% of Amine
CS-1135~, and 69.7% of methanol60.6
Methanol 198.0
26
~ Z~ ~J~9
Portion 4
Thinner consisting of 25% of toluene-
denatured anhydrous ethyl alcohol, 25%
of propylene qlycol monomethyl ether,
and 50% of xylene 940.0
Portion 1 was charged to a mixing vessel and
thoroughly blended. Portion 2 was added and stirred
in for 15 minutes. Portion 3 was then added and stirred
in for 30 minutes. The color coat enamel was reduced
to a stray viscosity of 35 seconds in a No. 2 Fisher
cut with Portion 5 and filtered through a fine paint
strainer. The resulting color coat enamel had an
acrylic polymer/melamine formaldehyde resin/~SB/p-
toluenesulfonic acid/ultraviolet light absorber/hindered
amine light stabilizer binder ratio of 55.15/36.76/4.8~/
0.35/1.93/0.97, a pigment/binder ratio of 14.5/100 and a
calculated solids content at 48.2%.
The following high solids clear coat enamel was
prepared:
Grams
POrtion 1
-
Acrylic polymer solution (prepared above) 3200.0
Silica mill base (described in Portion 2
of Exam~le 1 clear coat composition) 896.0
Methoxy/butoxymethyl melamine
(Resimene~ 755) 1155.5
Portion 2
Ultraviole~ light absorber solution of a
substituted benzotriazole (Tinuvin~
328) in xylene (30% solids) 400.0
Hindered amine light stabilizer (Tinuvin~
079) solution in xylene (40% solids) 100.0
Silicone solution (1% solids in xylene
of 100 centistroke silicone fluid) 60.0
Portion 3
Amine solution (described in Portion 4
of above color coat composition)62.8
27
,~ ,,
lZ~'7~L
28
Catalyst solution (described in Portion
4 of above color coat composltion) 80.8
Methanol 198~9
Portion 4
5 Polyvinyl pyrrolldone solution (described
in Portion 4 of Example 1 clear coat
composition) 20,0
Portion _
Xylene 703.8
Portlon 1 was charged to a mixing vessel and
thoroughly blended. Portions 2 and 3 were added in turn
and stirred in until homogeneous. Portion 4 was then
added and stirred in for 30 minutes. The clear coat
enamel was reduced to a spray viscosity of 45 seconds
in a No~ 2 Fisher cup with Portion 5 and filtered
through a milk filter.
The resulting clear coat enamel had an acrylic/
polymer/melamine formaldehyde resin/p-toluenesulfonic
acid/ultraviolet light absorber/hindered amine light
stabilizer binder ratio of 57.49/38.33/0.35/2.87/0.96,
a silica/binder ratio of 1.9/100 and a calculated solids
content of 61.9~.
The above color coat enamel and the above
clear coat enamel were sprayed consecutively onto a
20 gauge phosphatized steel panel primed with an alkyd
resin type dip primer. The application, solvent flash-
ing and baking conditions were similar to those in
Example 1. The resultlng dark blue metallic color coat/
clear coat flnish was free of mottling and had an at-
tractive, uniform appearance. The coating had a color
coat thickness of 0.8 mil, a clear coat thickness of
1.5 mils, a gloss measured at 20 of 89 and a distinct-
ness of image of 78.
7~
29
EXAMP1E 3
An acrylic polymer solution was prepared as
follows-
Grams5 Portion 1
Ethylene glycol monoethyl ether acetate 1180
n-Butyl alcohol 230
Aromatic hydrocarbon solvent boiling
at 150-l90~C (~romatic 100) 1920
Total3330
Monomer Mixtu~e
Methyl methacrylate 2150
Butyl acrylate 2050
2-Hydroxyethyl acrylate 850
15 Acrylic acid 210
Total 5260
In _ ator
Di-t~rt-butyl peroxide 157
Portion 1 was charged into a 1- llter round
bottom flask equipped with a thermometer, stirrer, re-
flux condenser, two addition funnels, and a heating
mantle. The monomer mixture was premixed and charged
to one of the addition funnels and the initiator was
charged to the other addition funnel. The flask charge
was heated to re lux. Addition of the monomer mixture
and the initiator was then started simultaneously, and
both were added continuously and linearly over a period
of 4 hours. The reaction mixture was maintained a-t re-
flux during the addi.ion period and then ~or an addi-
tional 4 hours. The resulting polymer solution wascooled. It had a solids content of about 6i%.
The polymer was a methyl methacrylate/butyl
acrylate/2-hydroxyethyl acrylate/acrylic acid copolymer
in a weight ratio of 41/39/16/4. The polymer had a Mw
of about 18,000 and a calculated Tg of 5C.
29
~Z~Z~94
3~
A composite mill base was prepared by charg-
a one-half gallon steel mill containing 925 cc of
diagonal steel media with the followiny ingre~ients:
Grams
Acrylic polymer solution (prepared above) 507.3
Nickel octoate solution in xylene
(66% solids) 5.5
Xylene 235.6
n-Butvl acetate 58.9
10 Rutile titanium dloxide pigment 17.3
High color furnace type carbon black
pigment 13.8
Quinacridone pigment (Monastral~ Violet
RT-887-D) 56.8
Total895.2
The mill was placed on rolls to grind for 64
ho-~rs. The resulting .~ill base was fluld and contained
well dispersed pigments. It was filtered off from the
grinding media. The mill base had a solids content of
44.8% and contained 9.8% of pigments.
The following light blue metallic color coat
enamel was prepared:
Grams
Port
Acrylic polymer solution (prepared above) 1268.4
25 Ultraviolet light absorber solution of a
substituted benzotriazole (Tinuvin~
328) in xylene (30% solids)93.5
Bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)
decanedioate hindered amine light sta-
bilizer (Tinuvin~ 292) ~8.0
30 Toluene 148.4
Silicone solution of an organofunctional
silicone (Baysilone~ Fluid OL) in xylene
(10% solids) 1.4
121Z7'9~
Portion 2
Blue mill base consisting of 18.0% of
copper phthalocyanine blue pi~gment,
40~0% of the acrylic polymer solution
prepared above, 2.0% of a solution (55%
solids in toluene) of the A-B dispersant
described under Portion 1 of Example 1,
30.0% of methyl n-amyl ketone, and 10.0%
of xylene and prepared by grinding in a
steel mill with diagonal steel media 335.5
Composite mill base (prepared above) 340.5
Portion 3
Polyurethane solution described under
Portion 1 of Example 1 662.0
Portion 4
Bright, non-leafing, acid spot resistant,
medium particle size aluminum flake
paste (65.5% solids in mineral spirits) 370.0
Di_i50butyl ketone 146.8
Portion 5
ASB solution consisting of 30% of alcohol
soluble cellulose acetate butyrate
(Eastman CAB-553-0.4) having a viscosity
of 0.25 second, 35% of toluene-denatured
absolute ethyi alcohol, and 35~ of
methyl ethyl ketone 1399.0
High solids, polymeric, methylated mela-
mine-formaldehyde resin, 85% solids in
n-butanol (Resimene~ 717) llC0.9
Methanol 249.5
25 Methyl ethyl ketone 256.1
Portion 6
Thinner consisting of 50~ vf methyl ethyl
ketone, 25~ of ethylene glycol mono-
ethyl ether, and 25% of ethylene glycol
monobutyl ether acetate 3890
30 Portion 1 was charged to a mixing vessel and
thoroughly blended. Portions 2 and 3 were added in turn
and each stirred in for 10 minutes. Portion 4 was then
added and stirred in vigorously for 1 hour to disperse
~21,~,7'94
the aluminum flakes. Portion 5 was added and ~tirred
in ~or , hour. The color coat enamel was reduced to a
spray viscosity of 22 seconds in a No. 2 Fisher cup with
Porti.on 6 and fIltered through a fine paint strainer.
S The resulting color coat enamel had an acrylic polymer/
polyurethane/melami~e formaldehyde resin/ASB/ultraviolet
light absorber/hindered amine light stabilizer binder
ratio of 35/15/33/15/1/lr a pigment/binder ratio of
12/100 and a calculated solids content of 30.5%.
10 The following clear coat enamel was prepared:
Grams
Portion _
Substituted benzotriazole ultraviolet
liqht absorber (Tinuvin~ 328) 61.3
Hindered amine light stabilizer (Tinuvin~
144) 20.6
Aromatic hydrocarbon solvent boiling at
150-1903C (Aromatic 100) 253.2
Acrylic polymer solution of a styrene~
methyl methacrylate/butyl acrylate/2-
hydroxyethyl acrylate/acrylic acid
(15/28/30~'25/2 weight ratio)copolymer
having a Mw of about 20,000 (65~ solids
in methyl n-amyl ketone) 1969.6
Portion 2
_
Polymeric, butylated melamine-formaldehyde
resin, 58% solids in 32/12 n-butanol/
xylene (Luwipal~ 012/58) 721.1
Polymeric, methylated melamine-formaldehyde
resin, 80~ solids in isobutanol
(Cymel~ 325) 540.8
Silicone solution (1% solids in xylene
of 100 centistoke silicone fluid) 8.6
30 Methanol 18.0
Portion 3
Aromatic hydrocarbon solvent boiling at
150-190C (Aromatic 100) 1750
~L21~7~4
Portion 1 was charged to a mixing vessel and
thoroughly hlended. Portion 2 was added and stirred in
for 30 minutes. The clear coat ena~el was reduced to a
spray vlscosity of 35 seconds in a No. 2 Fisher cup with
Portion 3 and filtered thrcugh a milk filter. The re-
sulting clear coat enamel had an acrylic polymer/bu~y-
lated melamine ormaldehyde resin/methylated melamine
formaldehyde resin/ultraviolet light absorber/hindered
amine liyht stabilizer binder ratio of 58.1/18.8/19~4/
2.8/o.s and a calculated solids content of 41.7~.
The above color coat enamel and the above
clear coat enamel were sprayed consecutively onto 20
~auge phosphatized steel panels primed as in Example 1.
The application, solvent flashing ~nd baking conditions
were the same as in Example 1, except that the recipro-
cating arm carrying the spray guns was run at 1400 inches/
minute, the solvent flash period between the color coat
and the clear coat was3 minutes, and the gun-to-panel
distance and atomizing air pressure were varie~ as
follows in order to determine the appearance uniformity
of the finish under an extreme range of application
conditions:
9" Panel - The color coat was applied at a gun-to-
panel distance of 9 inches usir.g an
atomizing air pressure of 55 psi in order
to give a coarse spray and a wet, thick
color coat film.
12" Panel - The color coat was applied at a gun-to-
panel distance of 12 inches using an
atomizing air pressure of 65 psi, repre-
senting average application conditions.
15" Panel - The color coat was applied at a gun-to-
panel distance of 15 inches using an
atomizing air pressure of 75 psi in order
to give a fine spray and a dry, thin
color coat film.
~lZ79~
34
The clear coat was applied in an identical man-
mer to all three panels using a gun-to-panel distance
of 1~ inches and an atomizing air pressure of 65 psi,
representing average application conditions.
The properties of the three color coat/clear
coat panels were as follows:
Property 9" Panel 12" Panel 15" Panel
Thickness r mils:
Color coat 1.0 0.80.5
Clear coat 1. 7 1. 71. 7
Gloss measured at 20 94 94 94
Distinctness of image 91 86 88
Head-on brightness 84 85 84
Metallic index 61 61 61
15 MOttllng None NoneNone
This light blue metallic color coat/clear
coat finish showed a uniform metallic appearance and
freedom from mottling when applied under an extreme
range of application conditions. It, therefore, had
excellent ap~ ation latitude.
EXAMæLE 4
The following white color coat enamel was
prepared:
Grams
POrtion 1
Xylene 138.4
Substituted benzotriazole ultraviolet
light absorber (Tinuvin~ 328~13.3
Bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)
decanedioate hindered amine light
stabilizer (Tinuvin~ 292) 13.3
Silicone solution of an organofunctional
silicone (Baysilone~ Fluid OL) in
xylene (10~ solids) 1.0
Acrylic polymer solution (prepared in
Example 3) 91.0
34
7~
Portion 2
-
ASB soluti~n (described under Portion 3
of Example l color coat) 217.7
Polyurethane soluticn (described under
Portion l of Example l color coat) 833.6
High solids, polymeric, methylated
melamine-formaldehyde resin, 85% sollds
in n-butanol (Resimene~ 717) 515.7
Methyl n-amyl ketone 423.7
Methanol 160.7
10 Denatured anhydrous ethyl alcohol 211.2
Portion 3
__
White mill base described under Portion 1
of Example 2 2054.8
Portîon 4
Catalyst solution consisting of 42% of
phenyl acid phosphate and 58~ of
n-butanol 17.9
Ethylene glycol monoethyl ether acetate 252.2
Methyl isobut~l ketone 54.3
Portion 5
20 Ethylene glycol monoethyl ether acetate 380
Portion l was charged to a mixing vessel and
thoroughly blended. Portlons 2, 3, and 4 were added
ln turn and each stirred in for 30 minutes. The color
coat enamel was recuced to a spray viscosity of 32
seconds in a No. 2 Fisher cup and filtered through a
fine paint strainer. The resulting color coat enamel
had a low molecular weight acrylic polymer/higher
molecular weight acrylic poly~er/polyurethane/melamine
formaldehyde resin/ASB~phenyl acid phosphate/ ultra-
violet light absorber/hindered amine light stabilizer~)inder ratio of 1~.7/40.0/32.7/5.0/0.6/l.0/l.0, a
pigment/binder ratio of 109/lO0 and a calculated solids
content of 51.3%.
f79~
36
The above color coat enamel and the clear
coat enamel prepared in E~amPle 3 were sprayed consecu-
tively onto a 20 gauge phosphatized steel panel primed
as in Example 1. The application, solvent flashing and
baking conditions w~re similar to those in Example 1.
T~e resulting wh~te color coat/clear coat finish had
a color coat thickness of about 1.4 mils, a clear coat
thickness of about 1.8 mils, a gloss measured at 20
of about 95, a distinctness of image of about 90 and
a Tukon hardness of about 5 Knoop. It had a uniform
color free of any clear coat strike-in effects.
