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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to a coating composition for flexible substrates and
in particular to a coating composition that is used to repair finishes on
flexible substrates.
The automotive and truck manufacturing industry now is utilizing bumpers of
flexible material, flexible filler panels located between the bumper and
the chassis, flexible exterior trim parts such as side moldings and other
energy and impact absorbing parts to reduce damage in the event of a minor
impact or a collision. These parts are coated with finishes that have
excellent adherence to the substrate, are flexible and are highly durable.
Hick, U.S. Pat. No. 3,841,895 issued Oct. 15, 1974, shows these types of
finishes. Repair of these flexible finishes has been particularly
troublesome since a repair paint must have good adhesion to the flexible
substrate and to the flexible finish and must dry and cure rapidly to a
high quality finish which is durable, weatherable, and flexible. Sheppard,
U.S. Pat. No. 3,829,397, issued Aug. 13, 1974, is directed to such a
repair finish and while it is of high quality for most uses, the
flexibility of the resulting finish requires improvement. Conventional
repair finishes designed for rigid substrates are shown in Miller, U.S.
Pat. No. 3,789,037, issued Jan. 29, 1974; Miller, U.S. Pat. No. 3,844,993,
issued Oct. 29, 1974; and Miller, U.S. Pat. No. 3,753,935, issued Aug.
21, 1973; but are not acceptable for repairing finishes on flexible
substrates due to inadequate flexibility of the resulting finish.
SUMMARY OF THE INVENTION
The coating composition of this invention comprises 5-60% by weight of a
film forming binder and 40-95% by weight of an organic solvent for the
binder; wherein the binder consists essentially of about
A. 20-90% by weight of an acrylic polymer containing hydroxyl groups and
other adhesion promoting groups or a mixture of acrylic polymers each
containing adhesion promoting groups and the acrylic polymer has a weight
average molecular weight of about 5,000-80,000 determined by gel
permeation chromatography;
B. 5-40% by weight of a hydroxy terminated ester or a hydroxy terminated
polyester; and
C. 5-75% by weight of an organic polyisocyanate;
Wherein a dried film about 2 mils thick of the composition on a flexible
hydrocarbon rubber substrate can withstand a 360.degree. mandrel bend test
at 5.degree. C. without cracking of the film or loss of adhesion of the
film to the substrate.
DESCRIPTION OF THE INVENTION
The coating composition is used to repair finishes on all types of flexible
substrates used on automobiles and trucks and the resulting finish has
excellent adhesion to these substrates, good flexibility, weatherability
and durability. The composition after application can be dried at ambient
temperatures to a tack-free finish in about 30-100 minutes and is
essentially fully cured in about 24 hours. The finish can be baked at low
temperatures, such as 50.degree.-140.degree. C. for about 5 to 10 minutes,
to enhance drying and curing of the finish.
The coating composition of this invention contains about 5-60% by weight of
the film-forming binder and about 95-40% by weight of an organic solvent
for the binder. The composition can contain a 0.1-50% by weight pigment,
but can be unpigmented and utilized as a clear composition.
In determining the flexibility of the composition by the mandrel bend test,
a film of the composition is sprayed onto a sanded or roughened flexible
hydrocarbon rubber substrate and dried for about 24 hours at 25.degree. C.
or for about 20 minutes at 65.degree. C. to give a film on the substrate
about 2 mils thick. The resulted coated substrate is cooled to about
5.degree. C. and then the coated substrate is bent 360.degree. over a
one-inch steel mandrel with the rubber substrate being the side that is
placed next to the mandrel. The film them is examined for cracking and
loss of adhesion of the film to the substrate. If no cracking, chipping,
flaking, or loss of adhesion is noted, the composition passed the test and
is acceptable. Even if only slight cracking or loss of adhesion is noted,
the composition is not acceptable.
The acrylic polymer used in the coating composition contains hydroxyl
groups and other adhesion promoting groups, such as carboxyl groups,
groups from primary, secondary, or tertiary amines, oxazoline ester
groups, and the like.
The acrylic polymer has a weight average molecular weight of about
5,000-80,000, but usually has a weight average molecular weight of about
15,000-40,000. The molecular weight is determined by gel permeation
chromatography.
Other acrylic polymers which are useful in the composition have a relative
viscosity of about 1.03 to 1.30 measured at 25.degree. C. on a 0.5%
polymer solids solution using dichloroethylene as the solvent.
These acrylic polymers are prepared by conventional polymerization
techniques in which the monomers, solvents, and polymerization catalysts
are charged into a reaction vessel and the reaction mixture is heated to
about 50.degree.-200.degree. C. and reacted from about 1 to 6 hours to
form a polymer having the aformentioned viscosity range.
The following are typical of polymerization catalysts which can be used to
prepare these acrylic polymers such as azo, bis-isobutyronitrile,
azo-bis-(.alpha.,.gamma.-dimethylvaleronitrile), benzoyl peroxide,
t-butylperoxypivalate, di-tertiary-butyl peroxide and the like.
The following are typically useful solvents that can be used to prepare the
acrylic polymers or can be subsequently used to dilute the polymer
composition in the preparation of a coating composition: acetone, 2-nitro
propane, methyl ethyl ketone, amyl alcohol, ethylene glycol monoethyl
ether acetate, ethyl acetate, ethyl alchohol, isopropanol, ethylene
dichloride, diacetone alcohol, diisobutyl ketone, cyclohexanone, amyl
acetate, ethylene glycol monobutyl ether, furfural, petroleum naphtha,
toluene, xylene, substituted benzene, benzene, substituted toluene,
hexane, aromatic hydrocarbons, high boiling petroleum naphthas, high
solvency petroleum hydrocarbons, diethyl ether, methyl amyl acetate,
butanol and the like.
One acrylic polymer useful in this invention is of 20-40% by weight of
methyl methacrylate, 40-74% by weight of an alkyl methacrylate having 2-12
carbon atoms in the alkyl group or an alkyl acrylate having 1-12 carbon
atoms in the alkyl group or a mixture of these acrylates and
methacrylates, 5-15% by weight of a hydroxyalkyl methacrylate or a
hydroxyalkyl acrylate each having 2-4 carbon atoms in the alkyl group or a
mixture thereof, and 1-15% by weight of an alkyl amino alkyl methacrylate
or acrylate.
Typical alkyl acrylates or alkyl methacrylates that can be utilized in
preparing this copolymer are ethyl acrylate, propyl acrylate, butyl
acrylate, isobutyl acrylate, hexyl acrylate, 2 ethylhexyl acrylate, nonyl
acrylate, pentyl acrylate, lauryl acrylate, ethyl methacrylate, propyl
methacrylate, butyl methacrylate, isobutyl methacrylate, hexyl
methacrylate, 2 ethylhexyl methacrylate, octylmethacrylate, nonyl
methacrylate, pentyl methacrylate and lauryl methacrylate.
Typical hydroxy alkyl acrylates and methacrylates that can be used to
prepare this acrylic polymer are hydroxy ethylacrylate, hydroxy
propylacrylate, hydroxy butylacrylate, hydroxy ethylmethacrylate, hydroxy
propylmethacrylate, and hydroxy
Typical alkyl amino alkyl methacrylates and acrylates that are used are of
the formula
##STR1##
where R.sup.1 is either hydrogen or methyl, R.sup.2 is an aliphatic
hydrocarbon group having 1-6 carbon atoms, R.sup.3 and R.sup.4 are either
hydrogen or an aliphatic saturated hydrocarbon group having 1-6 carbon
atoms.
Typical compounds are as follows: dimethyl amino ethyl methacrylate,
diethyl amino ethyl methacrylate, dipropyl amino ethyl methacrylate,
methyl ethyl amino ethyl methacrylate, butyl amino ethyl methacrylate,
tertiary butyl amino ethyl methacrylate, diethyl amino propyl
methacrylate, diethyl amino butyl methacrylate, diethyl amino pentyl
methacrylate, diethyl amino hexyl methacrylate, dimethyl amino ethyl
acrylate, methyl ethyl amino ethyl acrylate, and the like. Diethylamino
ethyl methacrylate and tertiary butyl amino ethyl methacrylate are
preferred since these compounds provide finishes with excellent adhesion.
Optionally, about 0.1-5% by weight of an ethylenically unsaturated
carboxylic acid can be used in the aforementioned acrylic polymer.
Typically useful acids are acrylic acid, methacrylic acid, itaconic acid,
maleic acid, itaconic acid, ethacrylic acid and the like. Either
methacrylic acid or acrylic acid is usually used.
One preferred acrylic polymer which gives a high quality finish that has
good adhesion is of methyl methacrylate, butyl acrylate, hydroxy
ethylacrylate, and tertiary butyl amino ethyl methacrylate.
Another useful acrylic polymer is of 20-44% by weight of methyl
methacrylate, 50-70% by weight of an alkyl acrylate having 2-12 carbon
atoms in the alkyl group or an alkyl methacrylate having 6-12 carbon atoms
in the alkyl group, or a mixture of these acrylates and methacrylates,
5-20% by weight of a hydroxy alkyl acrylate or methacrylate or a mixture
thereof each having 2-4 carbon atoms in the alkyl group and 1-20% by
weight of an .alpha.,.beta. ethylenically unsaturated carboxylic acid.
Any of the aforementioned alkyl acrylates and methacrylates, hydroxy alkyl
acrylates and methacrylates and acids can be used to prepare the above
acrylic polymer.
One acrylic polymer which has good adhesion and flexibility of the above
type is of methyl methacrylate, butyl acrylate, hydroxyethyl acrylate and
acrylic acid.
Generally, the coating composition is pigmented. The pigments are
introduced into the coating composition by first forming a mill base with
a compatible dispersing resin, such as one of the aforementioned acrylic
polymers, by conventional sand grinding, attritor grinding, or ball mill
techniques, and then the mill base is blended with the film-forming binder
as shown in the Examples.
The following are examples of the great variety of pigments which are used
in the coating composition: metallic oxides, preferably titanium dioxide,
zinc oxide, and the like, metal hydroxides, metal flakes, such as aluminum
flake, bronze flake, "Afflair" pigments, i.e., mica-coated with titanium
dioxide, metal powders, chromates, such as lead chromate, sulfides,
sulfates, carbonates, carbon black, silica, talc, china clay, iron blues,
organic reds, organic maroons, and other organic pigments.
One useful dispersing resin is an acrylic vinyl oxazoline ester polymer of
40-70% by weight of methyl methacrylate, 5-25% by weight of an alkyl
methacrylate having 2-12 carbon atoms in the alkyl group or an alkyl
acrylate having 1-12 carbon atoms in the alkyl group or a mixture of these
methacrylates and acrylates, 1-10% by weight of acrylonitrile and 15-35%
by weight of a vinyl oxazoline ester of drying oil fatty acids.
Any of the aforementioned alkyl acrylates and alkyl methacrylates can be
used to prepare this polymer.
The oxazoline ester used in the polymer is polymerized into the polymer
backbone and is of the following formula:
##STR2##
wherein R.sup.5 is a hydrocarbon group having 2-20 carbon atoms,
R.sup.6 is either hydrogen or an alkyl group having 1-4 carbon atoms,
R.sup.7 and R.sup.8 are either hydrogen or an alkyl group having 1-4 carbon
atoms or
##STR3##
R.sup.9 is a hydrocarbon group having 3-21 carbon atoms. Preferably,
R.sup.5 and R.sup.9 are unsaturated aliphatic hydrocarbon groups which are
from drying oil fatty acids and R.sup.6 is hydrogen. Typical drying oil
fatty acids that are used to prepare the above oxazoline esters are
linseed oil fatty acids, tall oil fatty acids and dehydrated castor oil
fatty acids.
The oxazoline esters can be made according to Purcell U.S. Pat. No.
3,248,397, issued Apr. 26, 1966. One preferred compound of this type is a
reaction product of 1 mol of tris-(hydroxymethyl)-amino methane and 3 mols
of tall oil fatty acids which is subsequently reacted with formaldehyde.
This compound is currently sold under the trademark "Chemacoil TA-100".
One acrylic-vinyl oxazoline ester polymer is of methyl methacrylate, ethyl
acrylate, acrylonitrile and a vinyl oxazoline ester of tall oil fatty
acids.
In the resulting composition, when an acrylicvinyl oxazoline ester polymer
is used as a dispersing resin, the acrylic polymer constituent of the
composition is a mixture of about 1-50% by weight of an acrylic-vinyl
oxazoline ester polymer and 50-99% by weight of one of the aforementioned
acrylic polymers.
The hydroxy terminated ester used in the composition of this invention is
an ester of a dicarboxylic acid and a polyol or an ester of a polyol and a
hydroxy terminated monocarboxylic acid. One useful ester is of a bis
primary diol of 2-22 carbon atoms and a hydroxy terminated monocarboxylic
acid. One preferred ester which gives a high quality product is
2,2-dimethyl-1,3-hydroxy-propyl-2,2-dimethyl-1,3-hydroxypropionate.
A hydroxy terminated polyester can also be used which is the esterification
product of a glycol or polyol and a dicarboxylic acid or a mixture of
dicarboxylic acids or alkyl esters of dicarboxylic acids. In the latter, a
polyester is formed by an ester interchange reaction. These polyesters
have a wieght average molecular weight of about 300-6,000 determined by
gel permeation chromatography.
Typical glycols and polyols that can be used to prepare these polyesters
are ethylene glycol, propylene glycol, butanediol, neopentyl glycol,
diethylene glycol, and the like.
Typical acids that can be used as oxalic acid, malonic acid, succinic acid,
glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and the
like. Mixtures of these acids can also be used. Lower alkyl esters such as
the methyl esters of these acids can be used.
One useful hydroxy terminated polyester is the esterification product of
neopentyl glycol and mixed methyl esters of succinic acid, glutaric acid
and adipic acid. This polyester has a weight average molecular weight of
about 300-1,500.
The polyisocyanate used in this invention is preferably added to the other
constituents of the coating composition and blended therewith only a short
time before the composition is used. For best results, it is preferable to
add the polyisocyanate in a solution. The polyisocyanate solution is of
about 2-75% by weight of a polyisocyanate dissolved in a solvent or a
blend of solvents for the polyisocyanate that are compatible with the
coating composition. Any of the aforementioned solvents can be used.
Typical aliphatic polyisocyanates and cycloaliphatic diisocyanates that can
be used are:
ethylene diisocyanate,
propylene-1,2-diisocyanate,
tetramethylene diisocyanate,
hexamethylene diisocyanate,
decamethylene diisocyanate,
cyclohexylene-1,2-diisocyanate,
methylene-bis-(4-cyclohexylisocyanate),
ethylene-bis-(4-cyclohexylisocyanate),
propylene-bis-(4-cyclohexylisocyanate), and the like.
The preferred polyisocyanate used in this invention has the formula:
##STR4##
wherein R.sup.1 is an alkyl group having 1-12 carbon atoms. One preferred
polyisocyanate is the biuret of hexamethylene diisocyanate that has the
above structural formula in which R.sup.1 is a saturated straight chain
hydrocarbon group having 6 carbon atoms. These biurets are prepared
according to the process described in Mayer et al. U.S. Pat. No.
3,245,941, issued Apr. 12, 1966.
In addition to the above constituents of the filmforming binder, the
composition can contain from about 0.5 to 15% by weight, based on the
weight of the binder, of an alkyd resin. These alkyd resins are of the
typical type which are the esterification product of a drying oil fatty
acid, such as chinawood oil, linseed oil, soya oil, tall oil and
dehydrated castor oil fatty acids, a polyhydric alcohol, a dicarboxylic
acid or anhydride and an aromatic monocarboxylic acid.
Typical polyhydric alcohols that can be used to prepare the alkyd resin
used in this invention are glycerine, pentaerythritol, trimethylol ethane,
trimethylol propane, glycols, such as ethylene glycol, propylene glycol,
butane diol, pentane diol and the like.
Typical dicarboxylic acids or anhydrides can be used to prepare the alkyd
resin are phthalic acid, phthalic anhydride, isophthalic acid,
terephthalic acid, maleic acid, fumaric acid, and the like. Typical
monocarboxylic aromatic acids are benzoic acid, paratertiary butylbenzoic
acid, phenol acetic acid, triethyl benzoic acid, and the like.
Optionally, plasticizers in amounts from about 0.5 to 20% by weight, based
on the weight of binder, can be added in addition to the above
constituents to the composition. Plasticizers that can be used are castor
oil, blown castor oil, benzylbutyl phthalate, dibutyl phthalate, triphenyl
phosphate, 2-ethylhexylbenzyl phthalate, dicyclohexyl phthalate, diallyl
phthalate, dibenzyl phthalate, butylcyclohexyl phthalate, mixed benzoic
acid and fatty oil acid esters of pentaerythritol,
poly(propyleneadipate)dibenzoate, diethylene glycol dibenzoate,
tetrabutylthiodisuccinate, butyl phthalyl butyl glycolate, acetyltributyl
citrate, dibenzyl sebacate, tricresyl phosphate, toluene ethyl
sulfonamide, the di-2-ethylhexyl ester of hexamethylene diphthalate,
di(methylcyclohexyl)phthalate. One preferred plasticizer of this group is
benzyl butyl phthalate, since it forms a coating with excellent balance of
properties.
Small amounts of about 0.1-2.0%, based on the weight of the binder of
conventional metallic driers can be used in the coating composition, such
as lead naphthenate, manganese naphthenate, cobalt naphthenate, lead
tallate, nickel salts, such as nickel octoate, alkyl tin dilaurates such
as dibutyl tin dilaurate and the like.
From about 0.1 to 1% by weight, based on the weight of the binder, in
addition to the other binder constituents of ultraviolet light absorbers
can be added to the coating composition. Typical ultraviolet light
absorbers are substituted benzophenone derivatives, such as 2,4-dihydroxy
benzophenone, a polymeric reaction product of
orthohydroxybenzophenone/formaldehyde/phenol, dibenzoate of diphenylol
propane, nonyl phenyl benzoate, 2,4-dihydroxyacetophenone, substituted
benzotriazoles, such as 2-(2'-hydroxy-5'-methyl phenyl)benzotriazole, and
the like.
Also in addition to the above binder constituents, about 0.5 to 10% by
weight, based on the weight of the binder, of cellulose acetate butyrate
can be used in the coating composition. The cellulose acetate butyrate
generally has a butyryl content of about 30-55% by weight and a viscosity
of 0.1-6 seconds determined at 25.degree. C. according to ASTM-D-1343-56.
The coating compositions of this invention can be applied to a substrate by
any of the usual application methods, such as spraying, electrostatic
spraying, dipping, brushing, flow coating and the like. The viscosity of
the composition can be adjusted for any of these methods by varying the
solvents. These coatings can be air dried or baked at a relatively low
temperature. The resulting coating is about 0.1-5 mils thick, preferably
1-3 mills thick, and has good gloss. The coating composition of the
invention does not yellow noticeably on baking and gives a hard, flexible,
durable, scratch-resistant, gasoline-resistant, weather-resistant,
alkali-resistant, glossy coating which is suitable as a repair finish for
flexible substrates used on automobile and truck bodies.
Typical examples of flexible substrates which are currently used on
automobiles and trucks to which the coating composition can be applied are
flexible hydrocarbon rubbers such as EPDM (terpolymers of ethylene,
propylene and diene), butyl rubber, styrene-butadiene rubber,
polybutadiene rubber, polyisoprene rubber, urethane rubbers, "Hytrel"
rubbers, polyester rubbers, injection molded polyester urethane rubbers,
elastoplastic microcellular urethane foams, ABS rubbers (terpolymers of
acrylonitrile, butadiene and styrene). Also, the composition can be
applied to polyvinyl chloride substrates. The coating composition can be
used as a repair finish as well as an original finish. The composition can
also be used as a finish over a variety of conventional substrates, such
as wood, metals, such as aluminum and steel, polymer reinforced fiber
glass, plastics, and the like.
The following Examples illustrate the invention. All quantities shown are
on a weight basis unless otherwise indicated.
EXAMPLE 1
A clear composition is formed by thoroughly blending together the following
constituents:
______________________________________
Parts by
Weight
______________________________________
Ester Diol (2,2-dimethyl-1,3-hydroxy
propyl-2,2-dimethyl-1,3-hydroxy proprionate)
65.99
Acrylic Polymer Solution (55% solids of
a polymer of methyl methacrylate/butylacrylate/
hydroxyethylacrylate/tertiary butyl amino
ethyl methacrylate in weight ratio of 28/60/
10/2 and having a weight average molecular
weight of about 28,000 determined by gel
permeation chromatography and having a
Gardner Holdt viscosity of about V-X and
measured at 25.degree. C. and the above solids in a
solvent blend of toluene/butyl acetate/methyl
ethylketone/xylene) 329.62
Blown Castor Oil 15.35
Dibutyl tin dilaurate solution
52.18
(2.7% solids in ethyl acetate)
Butyl acetate 108.19
Toluene 112.08
Methyl ethyl ketone 79.80
Silicone resin solution 3.07
(.2% resin solids in xylene)
Total 767.00
______________________________________
A cellulose acetate butyrate/acrylic polymer clear composition is prepared
by thoroughly blending together the following constituents:
______________________________________
Parts by
Weight
______________________________________
Porton 1
Acetone 15.34
Isopropanol 12.94
Toluene 7.58
Portion 2
Cellulose Acetate Butyrate 13.45
(having a 38% butyryl content and a
2 second viscosity)
Portion 3
Silicone Resin Solution 0.22
(described above)
Butyl cyclohexyl phthalate 1.49
Portion 4
Toluene 4.43
Acrylic-vinyl oxazoline ester polymer
25.22
solution (48% polymer solids in organic
solvent mixture of a polymer of methyl
methacrylate/ethyl acrylate/acrylonitrile/vinyl
oxazoline ester of tall oil fatty acids in a
weight ratio of 55/15/5/25 and having a
relative viscosity of 1.1199 measured at
25.degree. C. on a 0.5% solids in dichloroethylene
and having Gardner Holdt viscosity of about
W measured at 25.degree. C. and the above solids.
Acetone 19.33
Total 100.00
______________________________________
Portion 1 is charged into a mixing vessel and mixed for five minutes.
Portion 2 is slowly added and mixed until Portion 2 is dissolved. Portion
3 is then added and mixed for 30 minutes and then portion 4 is added and
mixed for an additional 30 minutes.
A white mill base is prepared as follows:
______________________________________
Parts by
Weight
______________________________________
Portion 1
White Acrylic Dispersion (67% solids of
89.28
titanium dioxide pigment dispersed with
an acrylic-vinyl oxazoline ester polymer
described above, in organic solvents and
having a pigment/binder ratio of 636/100)
Portion 2
Bentone Pigment Dispersion (25.7% solids
166.46
of Bentone 34 pigment dispersed with an
acrylic-vinyl oxazoline ester polymer
described above in organic solvents and
having a pigment to binder ratio of
45.2/100)
Methyl methacrylate/butyl acrylate copoly-
325.45
mer solution (40% polymer solids in which
the copolymer 82% methyl methacrylate and
18% butyl acrylate in an organic solvent
mixture and having a Gardner Holdt viscosity
at 25.degree. C of W-Y)
Acrylic-vinyl oxazoline ester polymer solution
142.90
(described above)
Toluene 81.46
Silicone resin solution (described above)
1.89
Portion 3
Toluene 16.56
Total 824.00
______________________________________
Portion 1 is charged into a mixer and then the mixer is started and
ingredients of portion 2 are added in the order shown and the mixing is
continued for one hour and then portion 3 is added with mixing. The
resulting mill base has a pigment to binder ratio of 22/100 where the
binder is the film forming polymeric material in the mill base.
A maroon mill base is prepared as follows:
______________________________________
Parts by
Weight
______________________________________
Portion 1
Red Pigment Dispersion (33.6% solids of
530.85
thio fast red lake dispersed with the
acrylic vinyl oxazoline ester polymer
described above, in organic solvents having
a pigment to binder ratio of about 50/100)
Portion 2
Acrylic-vinyl oxazoline ester polymer
282.15
solution (described above)
Silicone resin solution (described above)
2.00
Total 815.00
______________________________________
Portion 1 is charged into a mixer and the mixer is started and then portion
2 is added and mixed for one hour. The resulting mill base has a pigment
to binder ratio of about 25/100.
An aluminum flake mill base is prepared as follows:
______________________________________
Parts by
Weight
______________________________________
Portion 1
Acrylic-vinyl oxazoline ester polymer solu-
427.35
tion (described above)
Aluminum Flake Paste (65% medium particle
85.18
size aluminum flake in mineral spirits)
Portion 2
Acrylic-vinyl oxazoline ester polymer solution
228.51
(described above)
Toluene 75.43
Silicone resin solution (described above)
2.22
Portion 3
Toluene 14.31
Total 833.00
______________________________________
Portion 1 is charged into a mixer and mixed for four hours. The
constituents of portion 2 are added in the order shown and then mixed for
one hour. Portion 3 is added with mixing. An aluminum flake mill base is
formed having a pigment to binder ratio of 17.5/100.
A blue mill base is prepared as follows:
______________________________________
Parts by
Weight
______________________________________
Portion 1
Blue pigment dispersion (33% solids of a
674.68
copper phthalocyanine blue pigment dispersed
with the above described acrylic-vinyl oxazoline
ester polymer in an organic solvent mixture and
having a pigment to binder ratio of about 58/100)
Portion 2
Acrylic-vinyl oxazoline ester polymer solution
122.22
(described above)
Silicon resin solution (described above)
1.77
Portion 3
Toluene 7.33
Total 806.00
______________________________________
Portion 1 is charged into a mixer and then the mixer is started and portion
2 is added and mixed one hour then portion 3 is added with mixing. The
resulting mill base has pigment to binder ratio of about 40/100.
A black mill base is prepared as follows:
______________________________________
Parts by
Weight
______________________________________
Portion 1
Black Pigment Dispersion (31% solids of a
418.26
peptized carbon black pigment dispersed with
the above acrylic vinyl oxazoline ester poly-
mer in an organic solvent mixture and having
a pigment to binder ratio of about 30/100)
Portion 2
Bentone Pigment Dispersion (described above)
124.89
Acrylic-vinyl oxazoline ester polymer solution
247.15
(described above)
Silicon resin solution (described above)
2.70
Total 793.00
______________________________________
Portion 1 is charged into a mixer and the mixer is started and then portion
2 is added and mixed one hour. The resulting mill base has a pigment to
binder ratio of about 12/100.
A composite mill base is prepared as follows:
______________________________________
Parts by
Weight
______________________________________
Black mill base (prepared above)
4.0
White mill base (prepared above)
7.0
Maroon mill base (prepared above)
19.0
Blue mill base (prepared above)
39.0
Aluminum flake mill base (prepared above)
139.0
Total 208.0
______________________________________
The above mill bases are thoroughly blended together to form a composite
mill base.
A pigmented coating composition is prepared by thoroughly blending together
the following:
______________________________________
Parts by
Weight
______________________________________
Composite mill base (prepared above)
208.0
Clear composition (prepared above)
790.0
Cellulose Acetate Butyrate/Acrylic Polymer
Clear composition (prepared above)
858.0
Total 1856.0
______________________________________
A pigmented acrylic enamel is prepared by blending together the following:
______________________________________
Parts by
Weight
______________________________________
Pigmented coating composition (prepared
214.5
above)
Isocyanate Solution (43.8% solids of the biuret
54.0
of hexamethylene diisocyanate in ethyl acetate)
Total 268.5
______________________________________
The above enamel is reduced to a spray viscosity of a No. 2 cup Zahn
viscosity of 25-35 seconds using the following solvent mixture:
acetone/methanol/isopropanol/ethylene glycol monoethyl ether
acetate/toluene in a weight ratio of 10/3/12/2.6/66.4.
The enamel is then sprayed onto flexible "Nordel" rubber panels primed with
an acrylic polymer crosslinked with an alkylated melamine formaldehyde
resin and top coated with a flexible acrylic enamel. The top coat is
lightly sanded before the enamel is applied. The resulting finish is dried
for 24 hours at about 25.degree. C. giving a 2-mil thick finish that is
tacky-free and has a good appearance and good gloss. The finish has
excellent flexibility as shown by the mandrel bend test in which the
finish did not crack, chip, or peel. In the mandrel bend test, the panel
is bent around a one-inch mandrel with the unfinished side of the panel
placed next to the mandrel. During the test, the panel is at 5.degree. C.
The finish has excellent weatherability and retained its flexibility e | | |
