Note: Descriptions are shown in the official language in which they were submitted.
3~
BACKGROU~nD OF THE INVENTION
Thiæ invention relate~ to an lmproved proce~ ror
applying aqueou~ coatlng composition~ and in parti¢ular
t~ an improved proces~ ~or the appli¢ation o~ thermo-
setting acrylic enamel coating compoæition~ to prov~de
finiæhe~ having a unifoFm appearance.
Thermosetting acrylic en~mels are well known in
the ~rt as ~hown by Fraizer et al, U.S. Patent 2,681,897,
i~su~d 3une 22, 1954; Vasta, U.S~ Patent 3,338,~60, is~ued
Augu~t 29, 1967; Fi~k et al., U.S, P~tent 3,365,414,
i~sued ~anuary 23, 1968; Vasta, U.S. Patent 3~6 æ ,651,
ls~ued November 23, 1971; Parker, U.S. Patent 3,637,546,
issued January 25, 1972. These enamels are æolvent based
sy~tems and the spray application of the~e enamel~ has
not posed a problem~ However, aqueou~ ba~ed acryl~c
enamels as lllu~trated by Ta~t, U.S. Patent 3,661,827,
is~ued May 9, 1972, prsvide problem~ ln drying Or the
rinish during and a~ter applicst~on. If the appllcation i3
on a very humid day, the paint doee not dry and run8
12 and 8ag~, and conversely~ on very hot, dry days, the paint
dries exce~sively as it is sprayed onto the panel, thereby
giving a poor appearance. Also, variation~ ln the
humidity whlch do not cau~e di~iculties in drying
cAuse change~ in the appearance o~ the paint ~ilm.
In particular, paints containing metallic flakeæ, such
as aluminum ~lakes, the appearance change~ æubstantially
under varying humidity conditionæ.
m e improved procegs o~ thiæ invention provides
~or in~tial drying condition~ in which the air iæ
3~ .
~06~, 7,~
under controlled temperature and humidity conditions
which re~ults in ~inishe~ that consistently have an
excellent and uniform appearance without using conven-
tional air condltioning, i.~., cooling of the air to
reduce temperature and humidity.
SUMMARY OF T~E INVENTION
m e improved proce~s o~ this invention is
directed to the application o~ an aqueous paint to a ~ub-
strate by air spraying the paint wlth a ~pray gun
utllizing atomizing air at a ~low rate of about 5-40
cubic feet per minute and at an air presæure o~ 30-95
pounds per square inch at the spra~ gun and a paint flow
rate o~ 5-30 ounces per minute to form air atomized
paint which then 18 applied to the sub~trate and subse-
quently baked at 75 to 200 C. to ~orm a ~ini~h on the
sub~trate,
the improvement used therewith comprises spray-
ing the atomized paint in an atmo~phere that is controlled
at a temperature o~ about 15-40C. and at ~uch a relative
humidity that the air ha~ a driving force value in the
range o~ 0.002 to 0.004 humidity units which is const~ntly
maintained at a set value within this range, thereby
providing a uni~orm atmosphere for initially drying the
aqueous paint during ~praying to form a finish that has
a uni~orm appear~nce after being baked.
BRIEF DESCRIPTION OF '~ DRAWING
The Flgure illu~trates a schematic diagram
for automatically ad~usting the temperature and humidity
of air in a paint spray booth.
~ ~774
DESCRIPTION OF THE INVENTION
In a conventional process ~or apply~ng aqueou~
paints to a sub~trate by air Epr~ying the paint, a spray
gun i8 utillzed which atomize~ the paint to a fine spray
to apply the paint to a ~ub~trate. Generally, the atomiz-
lng air is utilized at a flow rate of 5-40 cubic Peet
per minute and under a pressure o~ 30 to 95 pounds per
~quare inch at the spray gun. The flow rate o~ palnt
passing through the gun i8 about 5-30 ounce~ per minute.
m e sprAy gun form~ a unirorm cone of air atomized
paint which 1~ applied to the substrate and ~ubsequently
the ~ubstrate i~ baked at about 75-200nC. to provide a
high quality ~inish. One pre~erred baking cycle for
aqueous thermosetting acrylic enamels comprlsing a pre-
bake ak about 75-95C. for about 5-30 minutes and then
a final bake at about 125-200C. to ~orm the flnish.
The resulting ~iniBh i8 about 0.5-3.5 mils in thickne~s
and prePerably, 1.0-2.5 mils in thickness. Generally,
the~e ~lnishes can be rubbed or po113hed in accordance
with conventional technique~ to improve
glOB8 .
This conventional spray application process pro-
vides adequate finishes under ideal drying conditions,
for example, 25C. and 50% relati~e humidity. However,
problems arlse under high humidity conditions, ~or example,
relative humidity of 90% and above allo~æ the aqueou~
finish to dry at a very ~low rate and aæ a result, the
~lnish has a poor appearance caused by sagging and
-- 4 --
running o~ the paint and also a color di~erence is
often noted, and conversely under low relative humidity
conditions such as 0-10% relative humidity, the atomized
paint dries excessively while being ~prayed onto the
sub~trate and results in a gritty finish which has a
poor appearance and also poor phy~ical properties. Even
under condition~ which are conducive to drying, the
~inish produced from the aqueouæ paint has a di~ferent
hue or shade and surrace texture at various levels of
relative humldity; in paxticular, this i8 most pronounced
with paint containing metall~c ~lake pigments.
me improved process of this invention economi-
cally provides a controlled air atmosphere for the
initlal drying of the finish which reæults ln the uni~orm
drying o~ the finish which is extremely important ~or the
appearance of this finish. Thi~ is accomplished by
controlling the air atmosphere at about 15-40C. and at
such a relative humldity that the ~ir has a driving
~orce ~alue in the range of 0.002 to 0.004 which is
constantly mainta~n~d at a set value within this range.
Pre~erably, the air has a driving force value o~ 0.003
humidity units.
The driving force value of the air is the
humidity of the air corresponding to the adiabatlc sat-
uration temperature expre~sed in pounds of water per
pound o~ dry air less the humidity o~ the ambient air also
exprea~ed in pounds of water per pound o~ dry air. mese
humidity values are determlned with a standard humidity-
temperature chart, ~or example~ shown in John H. Perry's
Chemical Engineer~s Handbook, 4th Edition (McGra~ Hill
Chemical Engineering Series)~
774
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~(~6977'4
me humidlty of amblent air at a low relative
humidity may be ad~usted by the addition of ~team or water
or both. By proper choice o~ amount o~ ~team and water, the
air temperature can be ad~u$ted. Ir the tem~erature o~ the
ambient air ls exceptionally high and the relative humidity
low, water may ~e sprayed into the air to incre&se the
humidity and also to lower the air temperature. If the
ambient humid~t~ is high, the air can be heated to ~uch a
temperature that the de~ired driving ~orce ~or dryin~ of
the palnt i~ achieve~.
The spray proce~æ can be further controlled by
heating the atomlzlng air from 40 to 150C. whi~h, o~
cour~e, heats the paint on atomi~ation and enhanceæ the
drying~ This technlque i~ particularly useful under high
relative humid~ty condition~ and increaæe~ the rate o~
drying o~ the paint during application thereby eliminating
aagglng and running o~ the paint.
The novel process of this invention is particularly
advantageous in that it allows for a uniform spray applica-
tion o~ the aqueous based paints under all type~ o~ relativehumidity condition and does not require the manu~acturer
to completely alr condition a spray area. mi~ technique
reduce~ a manufacturer~s initial costs and manu~acturing
costs since air conditioning equipment is not required. It
ls ~ubstantially more economical to heat or humidi~y or heat
and humldify the air in the ~pray zone to control the evapora-
tion than to air condition the entire spray area to a prescribed
temperature and humidity. me novel process is particularly
useful in the ~pray zones where the paint i8 applied by
automatic machines.
16~69~4
Convention~l air conditioning brings air to a
fixed ~et of temperature and humidity conditions and u~e~
one or a combination of the following ~tep~ heating, cooling,
humidification and dehumidification to achieve these condi-
tions and a~ pointed out i~ an expen~ive proceEs. me
proce~s o~ this invention only uses heat and humidification
and does not attempt to maintain const~nt temperature and
humidity conditions as does air conditioning. The procesæ
of this invention maintains a constant dri~ing force value
~o that the evaporation rate of the palnt belng sprayed
remains at the æame level to provide finl~he~ with a
unl~orm appearance.
me figure illuætrate~ one practical syætem for
controlling the temperature and humidity of the air fed
into the controlled spray ~one of a spray booth. Out~ide
air is pa~sed through a water 3crubber to remove dust
particles and clean the air. The air is next pasæed
through a ~ilter to remove any residual particles. A
temperature indicator ~nd a relative hum~dity indicator
are posltloned in the air llne which are electrically
connected to a computer controller which monitors the
~lgnal from the two indicators. The air paæses through
a heater and through a humidifier which are electrlcally
or pneumatlcally couplea to the computer controller and
controlled by the computer controller.
me heater i~ a conventional heat exchanger
wherein the air is passed over a heated æurface.
Steam or hot water or another fluld can be u~ed in the
heat exchanger and the fluid flow is controlled by a
valve that i~ electrically coupled to and controlled
by the computer controller.
1()6~774
The humidifier can utilize a water spray or
steam to increase the water content in ~he air. The
humidifier is coupled to and controlled by the computer
controller.
The air is then passed onto the portion of the
spray booth ~hat is being automatically controlled. The
air passes over a second set of temperature and humidity
indicators electrically coupled to the computer controller~
The computer controller receives the signals from khe temp-
erature and humidity indicators and utilizes the data to
control the heater and humidifier.
The novel process of this invention can be
utilized with a variety of aqueous based paints to improve
the drying and appearance of the finish. Preferably, the
novel process is utilized with aqueous thermosetting acrylic
coating compositions and in particular thermosetting acrylic
coating compositions in which the film-forming consituents
comprise
(1) an acrylic polymer selected ~rom the
group consisting of (A) a polymer of (a) at least
one of styrene and methyl methacrylate, (b) at least
one of an alkyl acrylate and an alkyl methacrylate,
where the alkyl group has 2-12 carbon atoms, and (c)
an ~,~ unsaturated carboxylic acidg and (B) a poly-
mer of (a), (b) and (c) and at least one of a hydroxy
alkyl acrylate and a hydroxy methacrylate; and
(2) a ~ater-soluble or water-dispersible cross-
linking agent.
,~ ,
~.,
106~7~4
One use~ul aqueous thermosetting acrylic
enamel contains the ~ollowing ~ilm-form~ng constituent~:
(1) 60-90% by weight of an acrylic
polymer o~
(a) 20-60% by weight of methyl
methacrylate or ætyrene or a mixture
of methyl methacrylate and ætyrene,
(b) 20-40% by weight o~ an &lXyl group
having 2-12 carbon atoms in the alkyl
group or an alkyl methacrylate having
4-12 carbon atom~ in the alkyl group;
(c) ~-20% by weight of an ~,~-
ethylenically unæaturated carboxylic
acid such as acrylic acid, methacrylic
acid or itaconie acid; and
(2) 10-40% by weight o~ a water dispersible
or water-soluble cro~æ-linking resin ~uch as
an alkylated melamine ~ormaldehyde reæin having
1-4 carbon atom~ in the alkyl group,
the compo~ition contains ~uf~icient baæic compound to
provide a pH o~ about 6-10.
One pre~erred aqueous thermosetting acrylic
enamel coatlng compoæition utilized with the proce~s o~
this lnvention compriæes 10-60% by ~eight of film-~orming
conætituents, where-in the ~ilm-~orming conætituents con-
3ist eæsentially o~
(1) 60-90% by ~eight, based on the weight o~ the
film-~o~min~ constituent~, o~ ~n acrylic polymer
having a uniformlty factor o~ at lea~t 75% which
consistæ essentiplly o~
- 10 ~
~6g77~ ~
(a) 20-50~ by weight, based on the
weight of the acrylic polymer,- of a hard
constituent which is either methyl meth-
acrylate, or a blend of methyl methacrylate
and styrene wherein the styrene comprises
up to 40% by weight of the acrylic polymer;
(b) 20-40~ by weight, based on the
weight of the acrylic polymer, of a soft
acrylic constituent that is either an
alkyl acrylate having 2-12 carbon atoms
in the alkyl group, an alkyl methacrylate
. having ~-12 carbon atoms in the alkyl
group, or a mixture of the above alkyl
acrylate and alkyl methacrylate;
(c) 4-20% by weight, based on the
weight of the acrylic polymer, of a hydroxy-
containing constituent which is either a
hydroxyalkyl methacrylate or a hydroxyalkyl
acrylate or a mixture thereof in which the
? alkyl groups have 2-4 carbon atoms~
(d~ 4-20% by weight, based on the weight
of the acrylic polyrner of ~,~ -unsaturated
carboxylic acid;
wherein the polymer has a carboxyl to
hydroxyl ratio of 1:0.2 to 1:1.8 and an acid
number of about 35-150 and a weight average
molecular weight of 5,000-80,000; and
(2) 10-40~ by weight, based on the welght of the
fi~n-formlng constltuent, o~ a water dispersible or
water soluble cross-linking resin, preferably an
~069774
alkylated melamine formaldehyde resin ha~ing 1-4
carbon atoms in the alkyl group; and
the composltion contains su~ficient water-soluble
am~ne to provide ~ pH of about 6-9.
The aforementioned coating composition is usually
p~gmented and contains about 0.1-40~o by weight of pigment,
but preferably, about 0.1-30~ by weight of pigment. In
particular, the composit~on can contain metallic flake
pigments such as aluminum ~lake in amounts of 0.1-~.0
by weight. A variety of conventional pigments are
utilized in the aforementioned compositions, such as
metallic oxide, for example, titanium dioxide, iron
oxide, zinc oxide and the like, metal hydroxides, metal
powders, chromates, sulphates, carbonates, car~on black,
silicate~ talc, phthalocyanine blues and greens, indanthrone
pigments and other organic pigments and dyes.
The water-dispersible or water-soluble cross-
lin~ing resin in the aforementioned enamel preferably is
an all~ylated melamine formaldehyde resin which is com-
? patible with the acrylic polymer used in the enamel.Preferably, the enamel contains 65_85% by weight of the
acrylic resin and 35-15% by weight of an alkylated
melamine formaldehyde resin, and more preferably, about
70% by weight of the acrylic polymer is used in combina-
tion with about 30~ by weight of an alkylated melal~ine
formaldehyde resin.
Preferably, the alkylated melamine formaldehyde
resins used in the aforementioned enamel have 1-4 carbon
atoms in the alkyl group and are prepared by conventional
techniques in which an alcohol, such as methanol, ethanol,
- 1069774
propanol, isopropanol, butanol is reacted with the melamine
formaldehyde resin. The melamine formaldehyde resin is
reacted with isopropanol and is another use~ul resin.
Also, urea formaldehyde resins can also be used as cross-
linking agents,
The acryl~c polymer used in the a~orementioned
enamel coating composition is partially soluble and
partially dispersed in the aqueous medium. Abou-t 30_50~ by
weight of the acrylic polymer is dispersed and has a particle
size of about 0.01-0.10 micron and preferably about 0.02-
o.o6 micron and the residual 50-70% by weight o~ the
acrylic polymer is soluble and dissolved in the aqueous
medium. To obtain water-solubility and dispersibility,
the acrylic polymer preferably has a carboxyl to hydroxyl
ratio of 1:0.2 to 1:1.8, which is the molar ratio of
carboxyl groups to hydroxyl groups of polymer.
The acrylic polymer used in the aforementioned
enamel composition has a uniformity factor of at least
75% and preferably 80-95%. The uniformity factor is
the percent o~ polymer in which the constituents are
in plus or minus 15% of the average amount given for
the polymer. For example, if the average composition
of the acrylic polymer is 54% methyl methacrylate, 34%
butyl acrylate, 6% 2-hydroxyethyl acrylate and 6~ acrylic
acid; 75% o~ the polymer will be within plus or minus
- 15~ of these average values or 54$ plus or minus 8%
methyl methacrylate, 34~ plus or minus 5~0 butyl acrylate,
6 plus or minus 0.9~ 2-hydroxyethyl acrylate and 6 plus
or mlnus 0.9~ acrylic acid.
1~69774
The acrylic polymer utilized in the above com-
position i~ prepared by a programmed addition of the
monomers, polymerization catalysts ~ld solvents. This
progra~med addi-tion process is an attempt to form polymer
at all stages of the polymerization process ~hich is
essentially the same as the predetermined composition~
and results in a polymer composition upon completion of
the process ~Ihich has a uni~ormity factor o~ at least
75~. This process allows ~or high percentage conversion
of monomers to polymer and also provides a polymer having
a relatively uniform molecular weight. These polymers,
when used in the novel composition of this invention,
provide hlgh quality finishes.
Conventional polymerization processes, such as
batch polymerization, commonly used in the art, provide
polymers with a wide range of composi~ions and molecular
weights which are not suitable for the novel coating
compositlon of this invention.
me above programmed addition polymerization
process is based on a computer program which uses known
polymerization e~uations and activity ratios of monomers
to determine the monorner addition rates and ratios and
polymer polymerization temperatures and t~nes. This
forms a polymer that has a uni~orm composition through-
out. The above programmed addition procedure can be based
on a computer program which uses a pol~nerization equation
in which the polymerization values of the monomers are
used. In general, the progra~ned polymeriza-tion pro-
cedure comprises an initial charge of monomers and
~069774
solvents which are heated to the reflux temperature in
the polymerlzation vessel, then at given intervals
monomers and polymer~zation initiator are charged into
the vessel while maintaining a re*lux temperature accord-
ing to the programmed polymerization procedure~ Throughout
the polymeriæation reaction, the polymer being formed has
a uniformity factor of at least 75~. In general, the
polymerization is conducted at about 75-125C. over a
2-4 hour period to ~orm a polymer that has a weight
average molecular weight of about 5,ooo-80,000, and
preferably, about 10,000-50,000 determined by gel per-
meation chromo-tographyO The polymer has an acid number
of about 35-150, pre~erably about 35-80.
Water-miscible solvents are used in the
polymerization process to prepare the acrylic polymer,
such as isopropanol n-propyl alcohol, 2-ethylhexanol,
diacetone alcohol and other alcohols, acetone, acetyl
acetone, ethylene glycol monoethylether, ethylene glycol
monobutyl ether and ethylene glycol monomethyl ether
~0 acetate. Minor amounts of sol~ents of limited water
solubility can be used, such as methylethyl ketone,
ethylene glycol monoethyl ether acetate. The novel com-
position can contain up to about 20~ by weight of water-
miscible solvent but preferably contains 5~15~ by weight
of solvent. If desired, the novel composition may be
made solvent free.
106~774
About 0.1-4% by welght, based on -the weight o~
the monomer used to prepare the acrylic polymer,o~ the
polymerization catalyst is utilized, Typical catalysts
are azo-bis-isobutyronitrile, azo-bis~ ~-dimethYl-
valeronitrile), benzoyl peroxide, t-butyl peroxypivalate,
t~butgl peracetate and the like. Chain transfer agents,
~ - such as lauryl mercaptan are also used~
The acrylic polymer contains 20-60~ by weight
of a~hard constituent which can be methyl methacrylate
or a mixture of methyl methacrylate and styrene; up to
40% by weight of the polymer can be styrene. The acrylic
polymer can contain 5 to 30~ by weight of styrene in
combination with 15 to 30% by weight of methyl methacrylate.
Preferably, the polymer contains about 52-57~ by ~Jeight
of methyl methacrylate.
The acrylic polymer contains 20-40~ by weight
of a soft acrylic constituent which is either an alkyl
acrylate that has 2-12 carbon atoms in the alkyl group,
an alkyl methacrylate ha~ing 4-12 carbon atoms in the
alkyl group or a mixture o~ these two constituents.
P~eferably, the scrylic polymer contains 28 Oo 38S by
- lG -
.
1069774
weight o~ the soft ac~ylic constituent, preferably, an
alkyl acrylate having 2-8 carbon atoms in the alkyl
group. The following are typical soft acrylic monomers
which can be utilized: ethyl acrylate, propyl acrylate,
isopropyl acrylate, butyl acrylate, isobutyl acrylate,
- hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,
nonyl acrylate, laul~l acrylate and the like, butyl meth-
acrylate, isobutyl methacrylate, pentyl methacrylate,
hexyl methacr~late, octyl methacrylate, 2-ethylhexyl
methacrylate, decyl methacrylate, lauryl methacrylate
and the like~ Butyl acrylate is the pre~erred so~t.
acrylic constituent since it forms a high quality
polymer that has excellent physical propertiesO
The acrylic polymer contains 4-20~o by weight
of a hydroxy containing constituent such as a hydroxy
alkyl acrylate or a hydroxy alkyl methacrylate or a mix-
ture of these two compounds. Preferably, the polymer
contains about 5-10~ o~ the hydroxyl contai.ning con~
stituent. These constituents contain 2-4 carbon atoms
.
1 ~ .
1069774
in the al~yl groups and are, for example, hydroxyethyl
acrylate, hydroxybutyl acrylate, hydroxyethyl meth-
acrylate, hydroxypropyl methacrylate and hydroxybutyl
methacrylate,
me acrylic polymer also contains 4-20~ by
weight, based on the weight of the acrylic polymer, of
an ~ unsaturated carboxylic acid. Typically useful
acida are acrylic acid, methacrylic acid, crotonic acid,
itaconic acid, propyl acrylic acid, and the like. Prefer-
ably, acrylic acid and methacrylic acid are used in amountsof 4-10~ by weight since these acids form high quality
polymers.
One preferred acrylic polymer used in this in-
vention contains 50-60% by weight of methyl methacrylate,
30-40% by weight of a soft acrylic constituent, prefer-
ably butyl acrylate, 5-10~ by weight oP the hydroxy-
containing constituent, preferably hydroxyethyl acrylate
or hydroxypropyl methacrylate, and 4-12% by weight of
acrylic acid, methacrylic acid, or itaconic acid. These
preferred acryllc polymers have a weight a~erage molecular
weight of about 10,000-50,000, an acid number of about
35-100 and a carboxyl to hydroxyl ratio of about 1:1.03
to 1:1,5.
Another particularly useful acryllc polymer
which gives a high quality finish contains about 28-32%
by weight o~ styrene, 22-26~ by weight of methyl meth-
acrylate, 30-35% by weight of butyl acrylate, 7-9~ by
weight of hydroxy ethyl acrylate and 4-6% by weight o~
1069774
acrylic acid ~ld has an acid number of about 30 to 50,
a carboxyl to hydroxyl ratio of 1:0.4 to 1:1.5 and a weight
average molecular weight oP about 10,00o-5o~ooo.
To form the aqueous dispersion, the acrylic
polymer is at least partially neutralized with a water-
- soluble amine and then dispersed in water. Typical water-
soluble amines that can be used are primary amines~ secondary
amines, tertiary amines, polyamines and hydroxyamines, such
as ethanol~mine, diethanolamine, triethanolamine, n-methyl-
ethanolamine~ N,N-diethylethanolamine, N-aminoethanolamine,
N-methyldiethanolamine, monoisopropanol~L;ne, diisopropanol-
amineS triisopropanolamine, hydroxyamine, butanolamine,
hexanolamine, methyl diethanolamine, N,N-diethylamino-
ethylamine, ethylene diamine, diethylene triamine, di-
ethylene tetramine, hexamethylene tetramine, triethylamine
and the like. The acrylic polymer is usually 50-60~
neutralized and can be 100% neutralized, Neutralization
of 50-60% is preferred since this degree of neutralization
forms an aqueous dispersion which permits enamel ~ormula-
tion at high solids. The pH of the resulting aqueouscoating composltion is generally adjusted to a pH of
6-9, preferably 7.1-7~5.
The novel process of this invention can be
utilized to apply the paints over a variety o~ substrates
such as metal, wood, glass, steel, iron, plastics, and
the like. Preferably~ the novel process is utilized for
applying aqueous coatings over primed metal substrates.
Typical al~yd primers and epo~y primers pi~mented with
iron oxide, carbon black, titanium dioxide are used.
-- 1~
~069774
The primer can be applied on the metal by electro-
deposition or can be applied by conventional spray or
dipplng techniques. The process can be utilized to pro-
vide coatings directly over galvanized steel to ~orm a
durable flnish.
The preferred aqueous acrylic enamel c~n be
applied dlrectly over the primed metal su~strates ~th-
out the use of an intermediate sealer coat. However,
a sealer coat can be used to provide a finish with
excellent adhesion and smoothnessO These sealers may
be water based or solvent based. One typ cally use~ul
sealer composition is disclosed in Rohrbacher, U.S. Patent
3,509,086, issued ~pril 28, 1970.
Finishes applied by the novel process of this
invention are characterized by a glossy, smooth and even
finish that has a uni~orm appearance, that has excellent
water spot resistance, craze resistance, good durability
and weatherability and gloss retention and excellent
gasoline resistance. These characteristics of the finish
applled by the no~el process Or this invention makes the
process particularly attractive for applying the exterior
finishes on automob~le and truck bodies.
The following Examples illustrate the invention.
The parts and percentages are by weight unless otherwise
specl~ied.
- 20 -
~069774
EXAMPLE 1
A coating composition is prepared by first
forming the following acrylic polymer dispcrsicn:
Parts By
Wei~,ht
- Portlon 1
Methy] methacrylate monomer 17.080
Butyl acrylate monomer 19.130
2-Ethyl hexyl acrylate monomer 2.720
Acrylic acid monomer 1.150
Isopropanol 6.140
Ethylene glycol rnonobutyl ether9.680
Lauryl mercaptan 0.294
Portion 2
Benzoyl peroxide 0.672
Methylethyl ketone 1.580
Ethylene glycol monomethyl ether acetate 1.580
Ethylene glycol monobutyl ether 2.360
Portion 3
-
Methyl methacrylate monomer 24.530
Butyl acrylate mono~.er 11.520
2-Hydroxyethyl acrylate 3.910
Acrylic acid 2.090
Benzoyl peroxlde 0.906
I~opropyl alcohol 3.ooo
Ethylene glycol monobutyl ether9.800
Portion 4
Methyl methacrylate monomer 25.720
Butyl acrylate 12.080
2-Hydroxyethyl acrylate monomer4.ogo
3 Acrylic acid monomer 2.200
_ 21 -
16~6977~
Parts By
~ei~ht_
Portion 4 (Continued)
Benzoyl peroxide 1.248
Isopropanol 4.120
Ethylene glycol monobutyl ether 13.150
Portion 5
Ethyl methacrylate 9.570
Butyl acrylate 4.490
2-Hydroxyethyl acrylate 1~520
Acrylic acid monomer 0.820
10 Benzoyl peroxlde 0.440
Isopropanol 1.460
Ethylene glycol monobutyl ether 4.760
Portion 6
Diethylethanolamine 7.900
Demineral~zed water 101.300
Portion 7
Demineralized water 169.090
Total 492.100
Portion 1 is charged into a reaction veæsel
equipped with a stirrer, a heating mantle and a reflux
condenser and then heated to the reflux temperature which is
about 160C. Portion 2 i8 premixed and then added and then
Portion 3 is premixed and added at a uniform rate over a 20-
minute period, while maintaining the reaction mixture at ita
reflu~ temperature. Portion ~ is premixed and added at a
uniform rate over a 60-~nuts period while the reaction mlxture
is maintained at its re~lux temperature. Portion 5 i~ premixed
- 22 -
~9~4
and added at a uni~orm rate over a 100-minute period, then
the reaction mixtur~ i~ malntained at ~ts reflux tempera-
ture ~or an additional 1/2 hour. Portion 6 i~ premixed ana
then added to the resction m~ture and then Portion 7 i8
added to the reaction mixture and the reaction mixture i8
cooled to room temperature and filtered to remove any
coagulum.
The resultlng polymer dispersion ha~ a 34% polymer
solid~ content in which the particle size is about 0.02-0.06
microns. The polymer has a relative visc06ity o~ 1.16
measured at 25C~ in dimethyl formamide at about 0.5% polymer
solids and has ~n acid number of about 33 to 35 and a
carbo~yl to hydroxyl ratio o~ 1 to 1.5. The polymer ha~ the
rollo~ing composition: methyl methacrylate/butyl acrylate/
2-hydroxyethyl acrylate/acrylic acid in a weight ratlo o~
about 54.2/33.1~8.4/4.3 and uni~ormity factor Or about
75-85%-
A phthalocyanine blue mill base iB prepared as~ollows:
Part~ By
Weight
Portion 1
Hexa(metho~ymethyl) melami~e 546
I~opropanol 630
Portion 2
_
Phthalocyanine blue pigment 210
Portion 3
Hexa(methoxymethyl) melamine 285
I~opropanol 426
~otal 2~97
- 23 -
1~)69774
Portion 1 is mixed with Portion 2 over a 30
minute period and then Portion 3 is added and the constituents
are mixed for 30 minutes. The resulting composition is passed
through a standard sand mill and ground two passes to provide
a uniform mill base.
A blue mill base is prepared as follows:
Parts By
Wei~ht
Portion 1
Hexa(methoxymethyl) melamine 78
Isopropanol go
Portion 2
MONASTRAL* blue pigment 30
Portion 3
Hexa(methoxymethyl) melamine 41
Isopropanol 61
Total 300
Portion 1 is mixe~ with Portion 2 over a 30-minute
period and then Portion 3 is added and the constituents are
mixed for 30 minutes. The resulting composition is passed
through a standard sand-mill and ground for two passes to
provide a uniform blue mill base.
A violet mill base is prepared as follows:
* denotes trade mark
- 24 -
~, ,,
377~
Parts By
Weight
Portion 1
Hexa(methoxymethyl) melamine 13.6
Isopropanol 45.1
Portion 2
MONASTRAL violet pigment 7.o
Portion 3
Hexa(methoxymethyl)melamine 7.6
Isopropanol 26.7
Total 100.0
Portions 1 and 2 are blended together and then
mixed for 30 minutes and then Portion 3 is added and the
composition is mixed for an additional 15 minutes. The
resulting composition is then ground two passes in a standard
sand-grinding mill to form a uniform mill base.
A phthalocyanine green-yellow mill is formed as
~ollows:
Parts By
Weight
Portion 1
Hexa~methoxymethyl) melamine 78
Isopropanol go
Portion 2
Phthalocyanine green-yellow pigment 30
Portion 3
Hexa(methoxymethyl) melamine 41
Isopropanol 61
Total 300
- 25 -
.~
1069774
Portion 1 is blended with Portion 2 in a mlxing
vessel for 30 minutes and then Portion 3 ls added and
blended to an additional 15 mlnutes. The resultlng
composition is then ground two passes in a standard sand-
grinding mill to form a uniform mill base.
An aluminum flake mill base is prepared as
~ollo~s:
Parts By
Weight
10 Aluminum flake 1.71
Hexa(methox~nethyl) melamine 5-75
Isopropanol 11.05
- - Total 18.51
The above constituents are thoroughly blended
together for 30 minutes to form a uniform dispersion.
A paint composition is prepared by blending
together the followlng ingredients: -
Parts By
20 Portion l Weight
Phthalocyanine Blue mill base
(prepared 2.bove) 6.35
Blue mill base (prepared above) 0.20
Violet mill base (prepared above) 0,70
Phthalocyanine green-yellow mill base (prepared
above) 0.45
Aluminum flake mill base (prepared above) 11.05
Portion 2
= ~
Hexa(methoxymethyl) melamine 20.40
Portion 3
Acrylic polymer dlspersion (prepared above) 272.40
- 2~, -
parts By
Weight
Portlon 4
Deionized ~ater 18.00
Port~on 5
Butyl acrylate/acrylic acid copolymer
solution - (80% polymer solid~ in alcohol
o~ an 85/15 butyl acrylate/acrylic
acid copolymer) 3~30
Silicone anti-cratering agent solut~on
(10% low molecul~r weight ~ilicon
re~in ln water) 3.35
10 Deionized water 31.00
Total367.10
Portion 1 i~ charged in a mi~1ng veæsel and
thoroughl~ blended together and then Portion 2 i~ added
then blended with Portion 1 and Portion~ 3~ 4 and 5 are
added consecutively w~th blending after e&ch addition. me
resulting composition haæ a 30 second vi~cosity uæing a
No. 2 Fi~her cup and a total solids content o~ 28.1%.
A Bink~ 62-~ spray gun is used with a 63 PB cap,
palnt ~low rate 16 ounces per minute, atomizing air
pre~sure 70 p~. All spraying i8 done wlth an Eclipæe
automatic machine with an index speed æet at 900 inches
per minute travel. Four coats of paint are applied wlth
two spra~ passes for each coat and with a two minute ~la~h
time between coatæ. The gun ls po~itloned 14 inches ~rom
the panel. The panel~ are 4" x 6" of phosphatized steel
primed with a 1.5 mil iron oxide pigmented alkyd resin
primer. After application~ each of the panels is baked
for 15 minutes at 85C. and then 45 minutes at 150C.
- 27 -
~069774
Panels are sprayed under the following
conditions:
- 28 -
:10~9t~74
Q !~ ~d
O
3 ~ ~
~D I'
~' ~
,'~ ~ ~ r~) ~ ~3
o ~rl ~ I~ I~ ~D
o o o o o ~
C~ Q Q Q Q ~d
C~
Co ~ ~ ~ 3
~n ~ o .
a ~a ~ x
o o o o o
o o o o o P~ o ~s
o o o o o ~ ~ C
~ 1-- 0 I-- r~ ~
-~ ~ Co O -1 3
J
Co ~ ~
O r~) ~ ~3
Q o o I (D
~ Q Q
O . ~ C~
Cl . 03
C~ .
~ ~
~n ~d ~_
~a ~ ~a ~ ' x P.
tD ~
~ 1~-
o o o
o o o I C o ~s
r~) ~ ~ ~
~ 0~
P ~ ~ u~ C~ Q Q ~ p
O ~ O O o ~ ~
O :~ 3 a~ O O O (D (D
R, 1'- 3 cq ~ Q~ Q~ P~ 1--
~n ~. 1~.
P~
o
O p~ . (D
- 29 _
106977~
EXAMPLE 2
A coating composition is prepared as follows:
Parts By
Weight
Portion 1
~ . _
Acrylic polymer dispersion (solids
- content of 70~ and the polymer has a
relative viscosity of about 1.09
measured at 25 in dimethyl formamide
and about 0.5% polymer solids and an
acid-number of about 47 and a carboxyl
to hydroxyl ratio of 1 to o.58 and is
of the follo~ing composition:
methyl methacrylate/butyl acrylate/
2-hydroxyethyl acrylate/acrylic acid
in a weight ratio of about 54/34.2/
5.7/6.1 and has a uniformity factor
of about 75-85~) 200
- Portion 2
Diethylaminoethanolamine 14
Portion 3
Deionized water 318
Portion 4
Hexa(methoxymethyl)melamine) 60
Total 592
Portion 1 is charged into a mixing vessel and then
Portion 2 is added and blended with Portion 1. Portion 3 is
then slowly added with constant agitation. After Portion 3
is added, all of Portion 4 is then added and mixed in. The
resulting coating composition has a solids content of
about 33~ and a spray viscosity of about 30 seconds using
a No. 2 Parlin cup.
- 30 -
106~774
The above prepared coating composition is
applied as in Example 1 using the ~dentical spraying and
baking procedures and the same primed steel panels under
the same ambient air and controlled air conditions. The
results of the application are very similar to the
results of Exarnple 1. The panels sprayed under uncontolled
conditions exhibited running and sagging.
EXAMPLE 3
A coating composition is prepared by blending
the following ingredients:
Parts By
Weight
Portion 1
Acrylic polymer dispersion (solids
content of 71% and the polymer has a
relative viscosity of 1.096 measured
at 25C. in dimethyl formamide at about
0.5% polymer solids, an acid number of
about 93 to 94 and a carboxyl to hydroxyl
ratio of 1 to 0.31 and is of the
following composition: methyl methacrylate/
butyl acrylate/hydroxyethyl acrylate/
acrylic acid - 53.8/28.2/6.0/12.0 and has
a uniformity factor of about 75-85%.) 200
Portion 2
Diethylaminoethanolamine 15
Portion 3
Deionized water 318
Portion 4
~exa(methoxymethyl) melamine 60
Total 593
- 31 -
3~
Portion 1 is charged into a mixing vessel and
then Portion 2 is added with constant agitation and then
Portion 3 is slowly added to the reaction mixture and after
Portion 3 has been added, Portion 4 is added and blended
with the reaction mixture. The resulting composition has
a 33% polymer solids content and a spray viscosity of 30
seconds measured in a No. 2 Parlin cup.
The above prepared coating composition is applied
as in Example 1 using the identical spraying and baking
procedures and the same primed steel panels under the same
ambient air and controlled air conditions. The results of
the application are very similar to the results o~ Example
1. The panels sprayed under controlled conditions have a
good appearance while the panel sprayed under uncontrolled
conditions exhibited running and sagging.
EXAMPLE 4
A paint composition is prepared by blending
together the following ingredients:
Parts By
Weight
Portion 1
Mill base (described in Example 1) 6-35
MONASTRAL blue mill base (prepared in
Example 1) 0.20
MONASTRAL violet mill base (prepared
in Example 1) 0.70
Phthalocyanine green-yellow mill base
(prepared in Example 1) 0.45
Aluminum flake mill base (prepared in
Example 1) 11.05
,~,
, .
1069774 Parts By
Wei~ht
Po_tion 2
Hexa(methoxymethyl) melamine 20.40
Portion 3
.
- Acrylic polymer dispersion (polymer
solids content of 26~ by weight and
the polymer has a relative viscosity of
about 1.15 measured at 25C. in di-
methyl formamide solvent at about 0.5~polymer solids) an acid number of about
46 to 47 and a carboxyl to hydroxyl
ratio of 1 to 0. 62 and the polyrner is of
the composition: methy]. methacrylate/
butyl acrylate/2-hydroxyethy]. acrylate/
acrylic acid in a weight ratio of about
54/34/6/6 and has a uni-formity factor
of about 75-85%) 272.40
Portion 4
Deionized water 18.00
Portion 5
Butyl acrylate/acrylic acid copolymer
solution (described in Example 1) 3.30
Anti-cratering solution (10~ silîcone
solution) 3. 35
Deionized water 31.00
Total 367.20
Portion 1 is charged into a mixing vessel and
thoroughly blended together and then Portion 2 is added
and blended and then Portion 3 is added and the consti-
tuents are thoroughly blended together. Portion 4 is added
and blended with the mixture and then Portion 5 is added
and thoroughly blended with.the mixture. The resutling
paint composition has a 28~ solids content and a spray
viscosity of 31 seconds using a No. 2 Zahn cup.
- 33 ~
1069774
The above prepared coating composition is
applied as in Example 1 using the identica] spraying and
baking procedures and the same primed steel panels under
the same ambient air and controlled air conditions. The
results of the application are very similar to the
results o~ Example 1. The panels sprayed under controlled
conditions have a good appearance while the panel sprayed
under uncontrolled conditions exhibited running and sagging.
_ 3~ _
