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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a novel polyester coating composition
characterized by having a lower solvent requirement for attaining a
coating viscosity, improved physical properties, and a better cure
response than polyester resin compositions currently available.
Oil-modified alkyd (polyester) resins have long been used in the paint
industry, and generally are prepared by the reaction of polybasic organic
acids, polyhydric alcohols and unsaturated fatty acids. The "oil length"
of an oil modified alkyd resin may be defined as the weight percent of the
resin contributed by the aliphatic, "fatty" chains of the fatty acids. As
pointed out in U.S. Pat. No. 4,111,871 (Aritomi), the oil length of an
alkyd resin is important to the physical properties of the paint or
coating which the resin forms. Oil length affects solubility, hardness,
gloss, color preserving ability, weather resistance, hardening time and
storage life of the paints made from alkyd resins. Increasing the oil
length is reported in U.S. Pat. No. 4,111,871 to enhance the flexibility
of the resulting film, to increase its solubility in organic solvents, and
to decrease film hardness. Reduction in oil length is said to enhance
gloss and color preserving ability of the film.
The above-mentioned U.S. Pat. No. 4,111,871 describes a resin composition
which comprises an oil-modified alkyd resin and an acrylate or
methacrylate monoester of an alcohol. The resulting resin composition is a
liquid and is said to be usable without the addition of solvent. Of
importance, the oil length of the oil-modified alkyd resin must
necessarily be at least 40% to avoid inferior waterproofness of the
initial film coating. Aritomi U.S. Pat. No. 4,147,675 shows the use of
oil-modified alkyd resins when combined with sorbic, crotonic or
2(beta-furyl) acrylic acids.
U.S. Pat. Nos. 4,224,202 and 4,225,473 (Heiberger) refer to high-solids
coating compositions containing an unsaturated fatty acid alkyd resin, an
alkyl dimethacrylate or trimethacrylate monomer, a protected cobalt oxime
catalyst, a polar solvent and a peroxide. The oil length of the alkyd
resin disclosed in these references exceeds 40%.
U.S. Pat. No. 4,014,830 (Rumfield) discusses an acrylate or methacrylate
modified alkyd resin or epoxy ester which contains a small amount (up to
10% by weight) of an acrylate or methacrylate ester of a polyol and which
is characterized by rapid drying.
Commercially available alkyd resin coating compositions which have
excellent physical properties and cure responses commonly are quite
viscous and accordingly require, for proper coating, a substantial amount
of solvent such as methyl propyl ketone, xylene or butyl acetate, and such
resin compositions commonly have volatile organic contents ("VOC"),
primarily due to organic solvents, of 3.5 lbs./gallon (420 g/l) and above.
Alkyd coating compositions which require less solvent to attain a coating
viscosity generally suffer from poorer physical properties and poorer cure
responses.
Conventional and high solids industrial alkyd resins may have oil lengths
on the order of 20 to 50% and commonly must be dissolved in aromatic and
oxygenated solvents to be used as air dried paints or oven cured paints.
Difficulty has been experienced in achieving high solids coatings that have
the low viscosities necessary for industrial applications. A major factor
involves the molecular weight of the alkyd resin. Generally speaking,
increasing the molecular weight of an alkyd resin generally improves
physical characteristics of a coating made from the resin and decreases
the coating drying time; that is, the time required for the coating to dry
sufficiently so that it can be handled without damage. However, increasing
the molecular weight also increases the amount of solvent needed to
achieve a viscosity appropriate for coating applications. The amount of
solvent that is needed to provide the desired coating viscosity may be
reduced by increasing the oil length of the alkyd. However increasing the
oil length increases the drying time.
It would be highly desirable to prepare alkyd resin coating compositions
which have relatively low solvent concentrations and which yet exhibit
good coating properties and excellent physical and cure response
properties.
SUMMARY OF THE INVENTION
We have found that polyester (e.g., alkyd) resin coating compositions
having reduced solvent requirement and excellent physical and cure
properties can be obtained by blending together from about 15% to about
85% (preferably about 50%-80%) by weight, based upon the weight of the
blend, of a fatty acid-modified polyester resin having an oil length of
not greater than about 27%, and from about 85% to about 15% (preferably
about 20-50%) by weight of an addition-polymerizable monomer or oligomer
characterized by vinyl unsaturation and capable of undergoing addition
polymerization under free radical initiating conditions.
In another embodiment, an alkyd resin coating composition is provided that
comprises a blend of from about 15% to about 85% (preferably about
50%-80%) by weight, based upon the weight of the blend, of a fatty
acid-modified polyester resin having an oil length not greater than about
35% and the resin being substantially free of pendant groups providing
alpha-beta ethylenic unsaturation; and from about 85% to about 15%
(preferably about 20%-50%) by weight, based on the weight of the blend, of
a monomer or oligomer having vinyl unsaturation and capable of undergoing
addition polymerization under free radical-initiating conditions.
In yet another embodiment, a one-part coating composition is provided that
comprises a blend of from about 15% to about 85% (preferably about
50%-80%) by weight, based on the weight of the blend, of a fatty
acid-modified polyester resin having hydroxyl functionality; from about
85% to about 15% (preferably about 20%-50%) by weight, based on the weight
of the blend, of a monomer or oligomer having vinyl unsaturation and
capable of undergoing addition polymerization under free
radical-initiating conditions; and an effective quantity of free-radical
initiator to initiate addition polymerization of said monomer or oligomer,
the initiator comprising a room temperature stable azo free radical
initiator, or a room temperature stable peroxide initiator or both. The
free radical initiator may, as desired, contain drying agents and
particularly complexed drying agents. Particularly preferred is an
initiator comprising a room temperature stable azo free radical initiator
and one or more complexed drying agents.
Although the resulting resin compositions can be used with as much solvent
as is needed, the solvent concentrations needed to provide coating
compositions of appropriate viscosity are exceptionally low. Yet, the
physical properties of coatings resulting from the compositions are
surprisingly good and the cure response of such compositions is similarly
unexpectedly good.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The fatty acid-modified polyester (e.g., alkyd) resins useful in the
present invention have oil lengths of not greater than about 35% and
preferably in the range of about 15%-30%. Most preferably, the oil lengths
of the alkyd resins are in the range of about 20%-27%. The alkyd resins
are generally the reaction products of polybasic acids, polyhydric
alcohols, and fatty acids which may be unsaturated. The polybasic acids
suitable for use in preparation of the alkyd resin constituent are
aromatic, aliphatic and alicyclic saturated and unsaturated polybasic
acids, and include such acids as phthalic acid, adipic acid, isophthalic
acid, terephthalic acid, maleic acid, trimellitic acid, tetrahydrophthalic
acid, sebacic acid, napthalic acid, chlorendic acid, heptanedioic acid and
succinic acid. Preferred acids include phthalic, isophthalic and maleic
acids.
Polyhydric alcohol components are those which can react with the carboxyl
groups of polybasic acids in an esterification reaction and which have at
least two hydroxyl groups. Examples of suitable alcohols include ethylene
glycol, diethylene glycol, glycerin, pentaerythritol, trimethylol ethane,
trimethylol propane, neopentyl glycol, propylene glycol, sorbitol,
dipropylene glycol, 1,6-hexanediol, 1,3-butylene glycol, dipentaerythritol
and triethylene glycol. The preferred polyols are trimethanol ethane,
pentaerythritol, neopentyl glycol and propylene glycol.
The fatty acid modifying agent desirably, but not necessarily, is partially
unsaturated, and may be supplied as an acid or as an oil containing the
acid. The reactive fatty acids have at least one unsaturated site.
Suitable fatty acids include linoleic acid, linolenic acid, oleic acid,
eleosteric acid, and stearic acid. Generally, useful fatty acids will have
molecular weights in the range of about 140 to about 300.
Fatty acids used in the manufacture of alkyds may be derived from
biological oils. Oils commonly used in the manufacture of alkyds include
tung oil, oiticica oil, dehydrated castor oil, fish oil, linseed oil,
safflower oil, soya oil, tall oil acids, cottonseed oil and coconut oil.
Particularly useful oils are soya oil and tall oil, which consist of
mixtures of suitable fatty acids.
Soya oil, for example, contains about 25% oleic, 51% linoleic, and 9%
linolenic acids. The remaining 15% soya fatty acids are saturated. Tall
oil comprises about 46% oleic, 41% linoleic, and 3% linolenic acids. The
remaining 8% tall oil fatty acids are saturated.
As is well known, alkyds are the reaction products of the esterification
reaction between polyols, fatty acid(s) and polybasic acid(s). The typical
esterification procedure involves charging these three components to a
reaction vessel and reacting at a temperature of around
400.degree.-500.degree. F. Xylene is typically used at 3 to 10% level as a
refluxing medium to azeotrope off water from the reaction vessel, the
xylene being returned to the reaction vessel. The reaction is considered
complete when a certain acid number is reached, e.g., from about 0 to
about 55. The acid number is based on the degree of ester bond formation
desired. Typically, the alkyd is cooked to 95% or better completed
reactions between the three components.
The alkyd usable for the present invention should have an oil length of 15%
to 35%, preferably 15-30% and most preferably in the range of about 20% to
about 27%. If the oil length is less than 15%, surface cure of the film is
poor, resulting in inferior water and chemical resistance and slower
drying. If the oil length is over 35%, the hardness of the film decreases,
resulting in an initially soft film that is easily damaged when handled.
Any monomer or oligomer which is addition polymerizable and which has vinyl
unsaturation can be employed in the invention. However, monomers or
oligomers having molecular weights not less than about 200 are preferred.
Monomers having molecular weights less than 200 are acceptable, but tend
to be somewhat volatile resulting in odor and solids loss by evaporation.
Acrylate and methacrylate monomers and oligomers are preferred.
Appropriate vinyl monomers and oligomers include acrylates, methacrylates,
allyl-functional compounds, alpha olefins, vinyl ethers, vinyl benzenes
and acrylamides, and epoxy and urethane oligomers. Acrylates are typified
by isooctyl acrylate, isobornyl acrylate, stearyl acrylate, n-lauryl
acrylate, cyclohexyl acrylate, 2-ethoxyethoxyethyl acrylate,
2-phenoxyethyl acrylate, isodecyl acrylate, 1,4-butanediol diacrylate,
1,3-butandiol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol
diacrylate, neopentylglycol diacrylate, triethylene glycol diacrylate,
tripropylene glycol diacrylate, ethoxylated Bisphenol A diacrylate,
trimethylol propane triacrylate, pentaerythritol triacrylate, ethoxylated
trimethylol propane triacrylate, propoxylated trimethylol propane
triacrylate. The preferred acrylates are stearyl acrylate, tripropylene
glycol diacrylate, ethoxylated Bisphenol A diacrylate and trimethylol
propane triacrylate. Acrylate oligomers common to the ultraviolet-electron
beam industry are also desirable and are the reaction products of an
acrylic acid with hydroxyl functional oligomers such as epoxies,
polyesters and polyether polyols. Acrylate oligomers also desirable are
the reaction products of hydroxy functional acrylates such as hydroxy
ethyl acrylate with isocyanate functional monomers and oligomers such as
toluene diisocyanate. Methacrylates are exemplified by cyclohexyl
methacrylate, n-hexyl methacrylate, 2-ethoxyethyl methacrylate, isodecyl
methacrylate, lauryl methacrylate, stearyl methacrylate, 2-phenoxyethyl
methacrylate, isobornyl methacrylate, triethylene glycol dimethacrylate,
tetraethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate,
1,4-butanediol dimethacrylate, 1,6-hexanedioldiacrylate, neopentyl glycol
dimethacrylate, ethoxylated Bisphenol A dimethacrylate, trimethylol
propane trimethacrylate. The preferred methacrylates are 1,6-hexanediol
dimethacrylate, stearyl methacrylate, ethoxylated Bisphenol A
dimethacrylate and trimethylol propane trimethacrylate. Other methacrylate
monomers and oligomers are the reaction products of (meth)acrylic acid
with hydroxyl functional monomers and oligomers such as epoxies,
polyesters and polyether polyols. Methacrylate oligomers also desirable
are the reaction products of hydroxy functional methacrylates such as
hydroxy ethyl acrylate with isocyanate functional monomers and oligomers
such as toluene diisocyanate. Typical allyl functional monomers and
oligomers are diallyl phthalate, diallyl maleate and allyl methacrylate.
The preferred allyl functional compound is diallyl phthalate.
Alpha olefins include C.sub.8, C.sub.10, C.sub.12, C.sub.14, C.sub.16, and
C.sub.18 alpha olefins, which are generally straight-chained hydrocarbons
with one vinyl unsaturation in the alpha position. The preferred alpha
olefin is the C.sub.18 alpha olefin 1-octadecene. Vinyl ethers are
typified by diethylene glycol divinyl ether and decyl vinyl ether, and
vinyl benzenes by styrene, divinyl benzene, and vinyl toluene. Acrylamides
are exemplified by N,N-dimethyl acrylamide and preferably are acrylamide
functional melamine resins such as those manufactured by Monsanto Inc.
under the designations AM-300 and AM-325.
It will be understood, of course, that the alkyd resins which are employed
in the invention may be produced from one or a mixture of fatty acids, and
polyhydric alcohols. Moreover, the coating composition of the invention
may include one or more alkyd resins and one or more vinyl monomers or
oligomers, selections from among the various resins and monomers or
oligomers being dependent at least in part upon the ultimate properties
that the coating composition is desired to exhibit. Free radical
initiators which may be blended into the resin compositions of the
invention include various well known peroxides and azo compounds. Typical
peroxides include benzoyl peroxide, methylethylketone peroxide,
2,4-pentanedione peroxide, di(2-ethyl-hexyl) peroxydicarbonate, di-t-butyl
peroxide and t-butyl hydroperoxide.
Azo compounds which are quite stable at room temperature and which
decompose when heated to form free radicals include 2,2-azo bis
(2,4-dimethylpentanenitrile), 2.2-azo bis (2-methylbutanenitrile), and
2,2-azo bis (2-methylpropanenitrile).
In one embodiment, the invention provides a coating composition package
having two parts, one part comprising the blend of the alkyd resin and the
vinylically unsaturated monomers or oligomers, and the other part
comprising a free radical initiator preferably but not necessarily carried
in a solvent solution. If metal driers such as those described below are
employed, it is desirable to include the drier in one part of the package
and a peroxide catalyst, if this is used, in the second part of the
package. Thus, one part of the package may include an alkyd resin, a vinyl
monomer or oligomer and a metal drier and the other part may include an
organic peroxide. Less desirably, the one part may include the alkyd, the
vinyl compound and a peroxide catalyst and the other part may include a
metal drier.
In another embodiment, the composition of the invention may be provided as
a one-part blend containing the alkyd resin and vinyl monomer or oligomer,
the blend including a peroxide catalyst, a peroxide catalyst with
complexed metal driers an azo catalyst which exhibits room temperature
stability or, most preferred, an azo catalyst and a metal drier. It has
been found that the azo catalysts work remarkably well in compositions of
the invention in that they store well at room temperature in the presence
of the composition without significant reaction or deterioration over a
period of, e.g., 21 days, but decompose readily at elevated temperatures
to catalyze addition polymerization of the vinyl monomer or oligomer.
Metal salt drying agents such as cobalt naphthenate, cobalt octoate, and
manganese naphthenate aid in the decomposition of organic peroxides by
acting as reducing agents. The metal driers also increase the oxidative
cure of the alkyd portion of the composition. Other metal driers that also
beneficially affect the overall cure of the composition include zinc
naphthenate, calcium octoate, lead octoate, zirconium octoate, rare earth
naphthenates and potassium octoate. It is understood that various metals
may be complexed with various organic acids to yield metal driers which
will affect the cure of the composition, and metal driers are well known
in the field.
The organic peroxides are typically used at 0.3 to 3 parts by weight based
on resin solids of the alkyd and vinyl compound(s). The metal driers are
typically used at about 0.01 to about 0.5 parts by weight (of metal) based
on resin solids of the alkyd and vinyl compound(s). Moreover, the cure of
the composition may be completed with any one of various organic peroxides
or azo compounds, including metal driers to aid in the cure of the
composition as desired.
The coating composition may include pigments such as medium chrome yellow,
titanium dioxide, yellow iron oxide and various other pigments as required
for the appropriate color and hiding qualities. Various solvents,
flow/surface modifying agents, dispersing aids, stabilizers and the like
may be utilized to prepare coating compositions. The coating compositions
may be formulated, for example, to cure when forced dried at temperatures
up to 190.degree. F. (88.degree. C.) or to require baking at temperatures
above 190.degree. F., with the appropriate coatings composition including
a desired free radical source and metal drier(s) to control the curing
characteristics.
The following non-limiting examples are provided for illustrative purposes
only. Unless otherwise indicated, parts are given by weight.
EXAMPLE 1
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Preparation of Oil Modified Alkyd Resin
Raw Materials Parts
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Refined Soya Oil 130
Pentaerythritol 78
Trimethylol ethane
37
Phthalic Anhydride
138
Benzoic Acid 54
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The ingredients were mixed with 4% xylene as a reflux solvent and heated
with agitation under nitrogen gas to 480.degree. F. (249.degree. C.). The
reaction mixture was held at that temperature until about 24 parts of
water were removed and an acid value of 5-10 was obtained. The resulting
polyester alkyd resin was then reduced with xylene to a solids content of
50% by weight and a Gardner-Holdt viscosity of X-Y.
EXAMPLE 2
The alkyd of Example 1 is made into the following coating by combining
parts A and B, as follows:
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PART A (Grind portion)
Alkyd of Example 1 100
Aromatic 100 20
Dispersing Aid.sup.(1) 3
Titanium Dioxide 200
Bentone SA-38.sup.(2) 3
Part A Total 326
PART B (Let down portion)
Alkyd of Example 1 270.5
Trimethyolpropane 39
Trimethacrylate.sup.(3) ("TMPTMA")
C-14 diol diacrylate.sup.(4)
39
Xylene 30
N-Butyl Alcohol 9.9
Hydroquinone 0.1
Cobalt octoate (12%) 0.6
Manganese octoate (6%) 1.2
Dimethyl aniline 2.0
10% SF-69.sup.(5) 1.0
Part B Total 393.3
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.sup.(1) Disperse Ayd DA1, Daniel Products Co.
.sup.(2) Hectorite Organoclay; NC Chemicals
.sup.(3) SR 350, Sartomer Co.
.sup.(4) Chemlink 2000, Sartomer Co.
.sup.(5) Silicone Oil, General Electric
The white paint was catalyzed with methyl ethyl ketone peroxide (DDM-9,
8.9% Active Oxygen, Pennwalt Corporation) at 0.5% by weight based on paint
solids, and was coated upon a metal substrate and cured for 40 minutes at
160.degree. F. (71.1.degree. C.) to an initial pencil hardness of 3B.
After 24 hours at room temperature, the pencil hardness increased to B.
The hardness was measured per ASTM D-3363-74 and run at a dry film
thickness (DFT) of 0.0015 inches (0.038 mm). The reported hardness is the
pencil gouge hardness. The cured film also had excellent early water spot
resistance where a 1-inch diameter drop of water was placed on the cured
film immediately after the panel was removed from the oven. The hardness
and water resistance properties were compared to a similar coating made
with the same resin but replacing the acrylate and methacrylate with alkyd
on a solids basis.
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Initial 24-Hour Initial Water
Coating Hardness Hardness Resistance
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Alkyd <6B 5B Lost Gloss
Example 2 3B B No Effect
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EXAMPLE 3
A yellow high solids paint was made using a urethane acrylate oligomer.
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Raw Materials Parts
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PART A (Grind portion)
Duramac 2707.sup.(1) 120
Disperse Ayd DA-1 20
Aromatic 100 100
Aromatic 150 20
Bentone SA-38 2
MPA 1078-X.sup.(2) 2
Medium Chrome Yellow 415
Molybdate Orange 6
Titanium Dioxide 9
Yellow Iron Oxide 26
PART B (Let down
Duramac 2707 240
TMPTMA 60
C-14 diol Diacrylate 60
Chempol 19-4883 oligomer.sup.(3)
60
Butyl cellosolve acetate 50
Aromatic 100 25
Cobalt octoate (12%) 1.0
Manganese octoate (6%) 2.0
N-Butyl alcohol 21
Hydroquinone 0.4
Methyl Ethyl Ketoxime 0.8
10% SF-69 2.0
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.sup.(1) 26% oil length alkyd; McWhorter
.sup.(2) Rheologic Additive; NL Chemicals
.sup.(3) Urethane Acrylate oligomer; Radcure Inc.
The volatile organic content (VOC) of the paint of Example 3 was measured
as 3.15 lbs/gal. (377 g/l) by ASTM test D-3960-81. The paint, catalyzed
with MEK peroxide (DDM-9) at a weight concentration of 0.35% based on the
total paint, was coated on metal panels to a dry film thickness of 0.0015
inches (0.038 mm) and cured for 40 minutes at 140.degree. F. (60.degree.
C.). The resulting coating was characterized by a pencil hardness of HB.
The paint of Example 3 exhibited superior properties of hardness and
resistance to various liquids when compared to a similar control paint not
containing acrylates, as shown in the following Table 1:
TABLE 1
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Initial Twenty-Four Hour Resistance.sup.(1) to
Coat- Hard- Water Anit- Unleaded
Diesel
ing ness Resistance
freeze.sup.(2)
Gasoline
Fuel
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Ex. 3 HB No Effect No Effect
No Effect
Slight
Discolor-
ation
Con- 6B Loss of Loss of Blistering,
Severe
trol Gloss Gloss Loss of Discolor-
Gloss ation
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.sup.(1) Two-hour spot test on panels coated, cured and aged for 24 hours
.sup.(2) 50% ethylene glycol antifreeze, 50% water
EXAMPLE 4
Vinyl Compound Comparisons
Various paints were made using the following formula:
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Raw Materials Parts
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Grind Portion (Part A)
Duramac 2633.sup.(1) 95
Disperse Ayd DA-1 3
Aromatic 100 45
SA-38 3
Titanium Dioxide 306
Part A Total 452
Let down portion (Part B)
Duramac 2633 407.5
Candidate Vinyl 130
Compound(s) (see Table 2)
Cobalt Octoate (12% Co) 2.1
Manganese Octoate (6% Mn) 2.1
Hydroquinone 0.2
N-Butyl Alcohol 20
Aromatic 100 100
SF-69 0.2
662.1
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.sup.(1) 35% oil length alkyd; McWhorter
The paints were subjected to pencil hardness, water spot resistance and
resistance to xylene. Results are reported in Table 2.
TABLE 2
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Initial 1-Hour Xylene Double
Candidate Example
Pencil Water Spot
Double Rubs
Vinyl Compound(s)
Hardness Resistance
to Failure
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a. Control, Duramac
6B Ring 10
2633 Alkyd Formation
b. 1-Octadecene.sup.(1)
6B Slight Ring
17
Formation
c. 50% 1-Octadecene,
5B No Effect
70
50% TMPTMA
d. Diallyl Phthalate.sup.(2)
6B Slight Ring
17
Formation
e. 50% Diallyl 4B No Effect
73
Phthalate
50% TMPTMA
f. Diethylene Glycol
4B No Effect
27
Divinyl.sup.(3) Ether
(DGDE)
g. 50% DGDE, 2B No Effect
200+
50% TMPTMA
h. Vinyl Terminated
6B No Effect
56
Butadiene Resin.sup.(4)
("VTBN")
i. 50% VTBN, 6B No Effect
200+
50% TMPTMA
j. Acrylamide 4B No Effect
94
AM-300.sup.(5)
k. 50% AM-300, 3B No Effect
200+
50% TMPTMA
l. Acrylated Epoxy
2B No Effect
200+
Celrad 3800
m. 50% Celrad 3800.sup.(6)
B No Effect
200+
50% TMPTMA
n. 50% TMPTMA 2B No Effect
150
50% Duramac-2633
o. TMPTMA B Cuts No Effect
200+
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.sup.(1) 1-Octadecene (C18 alpha olefin); Ethyl Corporation
.sup.(2) Diallyl Phthalate; FMC Corporation
.sup.(3) Diethylene Glycol Divinyl Ether; GAF Corporation
.sup.(4) Vinyl Terminated Butadiene Resin, 1300 .times. 22 Hycar Resin; B
F. Goodrich
.sup.(5) AM-300; Monsanto Company
.sup.(6) Celrad 3800; Celanese Corporation
The paint specimens were catalyzed with 0.4% by weight of MEK peroxide
(DDM-9) , were coated upon steel panels to a dry film thickness of 1.5
mils (0.038 mm), and were tested after curing at 40 minutes at 180.degree.
F. The 1-hour water spot resistance test requires a 1-inch diameter drop
of water to be placed on the cured film within 15 minutes of panel removal
from the oven, and the panel is examined one hour later. The xylene double
rubs test tests early chemical resistance; a cloth saturated with xylene
is manually rubbed across the panel until the paint film is rubbed off.
EXAMPLES 5-8
Single Package Coatings
The paint of Example 3 was prepared, excluding the cobalt octoate and
manganese octoate driers. To this paint may be added the following curing
agents to produce stable, one-package coating compositions:
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Example 5 Vazo 67 (2,2' -azobis
(2-methylbutanenitrile))
Example 6 Vazo 67 (0.4% by weight), 12% cobalt
octoate (0.08% by weight), and 6%
manganese octoate (0.16% by weight)
Example 7 MEK Peroxide (DDM-9) 0.4% by weight
Example 8 MEK peroxide (DDM-9) at 0.4% by weight,
12% cobalt octoate at 0.08% by weight
based on the weight of paint, and 6%
manganese octoate at 0.16% by weight of
paint. The drier solutions are complexed
with 0.24% methyl ethyl ketoxime by weight
before addition to the paint.
______________________________________
The coatings of Examples 6 and 8 were coated on metal panels and cured for
40 minutes at 230.degree. F. (110.degree. C.) to a pencil hardness of HB,
and the coatings of Examples 5 and 7, similarly coated, were cured for 20
minutes at 300.degree. F. (149.degree. C.) to a pencil hardness of 2B.
The single package coatings of Examples 5 and 8 did not significantly
change after aging at room temperature for three weeks.
While a preferred embodiment of the present invention has been described,
it should be understood that various changes, adaptations and
modifications may be made therein without departing from the spirit of the
invention and the scope of the appended claims.
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