The invention is an epoxy resin coating composition. The composition comprises: PA0 1. a bisphenol A resin, and PA0 2. an acrylate ester, reacted with a mixture of PA0 3. a polyether polyamine of the formula: PA1 a. NH.sub.2 CH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2 PA1 wherein x ranges from 2 to 6, or PA1 b. ##STR1## wherein x+y+z ranges from 4 to 6; and 4. piperazine. The weather resistant formulations cure rapidly to form attractive blemish-free, blush-free coatings.

This application is also related to a patent application Ser. No. 
07/092,855, now U.S. Pat. No. 4,766,186 filed on even date titled Epoxy 
Adhesive to K. B. Sellstrom and H. G. Waddill. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to rapid curing, blemish-free epoxy coatings. 
2. Description of Other Relevant Materials in the Field 
Epoxy resins constitute a broad class of polymeric materials having a wide 
range of physical characteristics. The resins are characterized by epoxide 
groups which are cured by reaction with catalysts or curing agents to 
provide cured epoxy resin compositions with certain desirable properties. 
U.S. Pat. No. 4,051,195 to W. F. McWhorter teaches curable epoxy resin 
compositions comprising (1) a blend of an epoxide resin and a polyacrylate 
or polymethacrylate ester of a polyol wherein the ester contains more than 
one terminal acrylate or methacrylate and (2) an aliphatic polyamine 
curing agent. The weight ratio of epoxide resin: ester is 100:5 to 
100:100. The aliphatic polyamine is incorporated into the resin 
composition in a specified amount. The epoxy resin compositions are said 
to cure rapidly even at low temperature and are useful as coatings and 
adhesives. 
U.S. Pat. No. 4,528,345 to H. G. Waddill teaches a method for making 
weather-resistant epoxy coatings. The method comprises prereacting a 
cycloaliphatic diepoxide resin with aminoethylpiperazine or a mixture of 
aminoethylpiperazine and polyoxyalkylenepolyamine in an amount which is 
balanced to give the maximum level of primary amine reaction without 
yielding an excessively viscous reaction product. The prereacted product 
is reacted with a curing amount of a polyoxyalkylene polyamine and an 
accelerator. 
U.S. Pat. No. 3,875,072 to H. G. Waddill teaches an accelerator for curing 
epoxy resins. The accelerator comprises piperazine and an alkanolamine in 
a weight ratio of 1:8 to 1:1. A number of alkanolamines are taught. U.S. 
Pat. No. 4,195,153 to H. G. Waddill teaches an epoxy resin curing 
accelerator comprising a mixture of N-aminoethylpiperazine (AEP) and 
triethanolamine (TEA). U.S. Pat. No. 4,189,564 to H. G. Waddill teaches a 
non-crystallizing accelerator for curing epoxy resins. The accelerator 
comprises a mixture of 10 to 20% piperazine, 5 to 10% 
N-aminoethylpiperazine and 65 to 80% triethanolamine. The accelerator is 
sold commercially as Accelerator 399 by Texaco Chemical Co. The 
accelerator is said to be synergistic for accelerating the curing of a 
polyglycidyl ether of a polyhydric phenol cured with a polyoxyalkylene 
polyamine at ambient or elevated temperatures. Such amines include 
polyoxypropylene diamines of the formula: 
EQU NH.sub.2 CH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2 
wherein x ranges from 2 to 40. Such amines also include polyoxypropylene 
triamines of the formula: 
##STR2## 
wherein R is a lower alkyl and x+y+z ranges from 3 to 40. 
These diamines and triamines may be synthesized according to U.S. Pat. No. 
3,654,370 to E. L. Yeakey which teaches a method comprising a nickel, 
copper and chromium catalyst for aminating polyols. 
U.S. Pat. No. 3,236,895 to J. M. Lee and J. C. Winfrey and U.S. Pat. No. 
3,462,393 to Legler are pioneer patents. They describe a series of amine 
compounds which are solids or liquids and having utility particularly in 
curing epoxy resins. The amine compounds have the general formula: 
##STR3## 
wherein R's ae selectively defined as hydrogen, alkyl radicals and 
alkylene oxide radicals and x and m are defined integers. 
SUMMARY OF THE INVENTION 
The invention is an epoxy resin coating composition. The epoxy component 
comprises a mixture of an aromatic vicinal polyepoxide containing at least 
1.8 reactive 1,2-epoxy groups per molecule and an acrylate ester in a 
weight ratio of 2:1 to 10:1. The curative component comprises a curing 
amount of a polyether polyamine. The curative additionally comprises a 
piperazine accelerator in molar equivalence with the acrylate ester. 
The two components are reacted and cured to form an attractive coating free 
of surface blush and blemishes. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The invention is an improvement in U.S. Pat. No. 4,051,195 to W. R. 
McWhorter, incorporated herein by reference. 
An improved epoxy formulation has been developed which cures rapidly to 
form attractive, blemish-free, blush-free coatings. The formulation 
comprises a blend of an aromatic-containing epoxy resin and an acrylate 
ester, cured with a mixture of polyether polyamine and a reactive amine 
accelerator derived from piperazine. 
It has been found that the addition of piperazine to an acrylate 
ester-epoxy resin system comprising aromatics, shortened drying time and 
promoted rapid curing of the epoxy resin with the selected polyether 
polyamines demonstrated in the Example. 
The vicinal polyepoxide containing compositions which may be cured with the 
products of the invention are aromatic organic materials having an average 
of at least 1.8 reactive 1,2-epoxy groups per molecule. These polyepoxide 
materials can be monomeric or polymeric, mono-aromatic or heterocyclic, 
and may be substituted if desired with other substituents besides the 
epoxy groups, e.g., hydroxyl groups, ether radicals, aromatic halogen 
atoms and the like. These vicinal polyepoxide containing compounds 
typically are of an epoxy equivalent weight of 150 to 250. Preferably the 
base resin, which has an epoxide equivalent weight of from 175 to 195, is 
derived from condensing epichlorohydrin with 2,2-bis(p-hydroxyphenyl 
propane) to form 2,2-bis[p-2,3 epoxy propoxy)phenyl]propane, a derivative 
of bisphenol A. 
Preferred polyepoxides are those of glycidyl ethers prepared by epoxidizing 
the corresponding allyl ethers or reacting, by known procedures, a molar 
excess of epichlorohydrin and an aromatic polyhydroxy compound, i.e., 
isopropylidene bisphenol, novolac, resorcinol, etc. The epoxy derivatives 
of methylene or isopropylidene bisphenols are especially preferred. 
A widely used class of polyepoxides which are useful according to the 
instant invention includes the resinous epoxy polyethers obtained by 
reacting an epihalohydrin, such as epichlorohydrin, and the like, with 
either a polyhydric phenol or a polyhydric alcohol. Typicaklly the epoxy 
resins have an average of at least 1.8 reactive, 1,2-epoxy groups per 
molecule. An illustrative, but by no means exhaustive, listing of suitable 
dihydric phenols includes 4,4'-isopropylidene bisphenol, 
2,4'-dihydroxydiphenylethyl methane, 3,3'-dihydroxydiphenyldiethylmethane, 
3,4'-dihydroxydiphenylmethylpropylmethane, 
2,3'-dihydroxydiphenylethylphenylmethane, 
4,4'-dihydroxydiphenylpropylphenylmethane, 
4,4'-dihydroxydiphenylbutylphenylmethane, 
2,2'-dihydroxydiphenylditolylmethane, 
4,4'-dihydroxydiphenyltolylmethylmethane and the like. Other polyhydric 
phenols which may also be co-reacted with an epihalohydrin to provide 
these epoxy polyethers are such compounds as resorcinol, hydroquinone, 
substituted hydroquinones, e.g., methylhydroquinone, and the like. 
Among the polyhydric alcohols which can be co-reacted with an epihalohydrin 
to provide these resinous epoxy polyethers are such compounds as ethylene 
glycol, propylene glycols, butylene glycols, pentane diols, 
bis(4-hydroxycyclohexyl)dimethylmethane, 1,4-dimethylolbenzene, glycerol, 
1,2,6-hexanetriol, trimethylolpropane, mannitol sorbitol, erythritol, 
pentaerythritol, their dimers, trimers and higher polymers, e.g., 
polyethylene glycols, polypropylene glycols, triglycerol, 
dipentaerythritol and the like, polyallyl alcohol, polyhydric thioethers, 
such as 2,2'-, 3,3'-tetrahydroxydipropylsulfide and the like, mercapto 
alcohols such as monothioglycerol, dithioglycerol and the like, polyhydric 
alcohol partial esters, such as monostearin, pentaerythritol monoacetate 
and the like, and halogenated polyhydric alcohols such as the 
monochlorohydrins of glycerol, sorbitol, pentaerythritol and the like. 
Another class of polymeric polyepoxides which can be cured by the products 
of the invention in accordance with the present invention includes the 
epoxy novolac resins obtained by reacting, preferably in the presence of a 
basic catalyst, e.g., sodium or potassium hydroxide, an epihalohydrin, 
such as epichlorohydrin, with the resinous condensate of an aldehyde, 
e.g., formaldehyde, and either a monohydric phenol, e.g., phenol itself, 
or a polyhydric phenol. Further details concerning the nature and 
preparation of these epoxy novolac resins can be obtained in Lee, H. and 
Neville, K., Handbook of Epoxy Resins, McGraw Hill Book Co., New York, 
1967. 
It will be appreciated by those skilled in the art that the polyepoxide 
compositions which are useful according to the practice of the present 
invention are not limited to those containing the above described 
polyepoxides, but that these polyepoxides are to be considered merely as 
being representative of the class of polyepoxides as a whole. 
The acrylate esters useful in this invention are those esters which contain 
more than one terminal acrylate or methacrylate group. These esters 
include the acrylic and methacrylic acid esters of aliphatic polyhydric 
alcohols such as, for example, the di- and polyacrylates and the di- and 
polymethacrylates of alkylene glycols, alkoxylene glycols, alicyclic 
glycols and higher polyols, such as ethylene glycol, triethylene glycol, 
tetraethylene glycol, tetramethylene glycol, hexanediol, 
trimethylolethane, trimethylolpropane, pentaerythrtiol, dipentaerythritol, 
tripentaerythritol and the like, or mixtures of these with each other or 
with their partially esterified analogs. 
Typical compounds include but are not limited to trimethylolpropane 
triacrylate, trimethylolethane triacrylate, trimethylolpropane 
trimethacrylate, trimethylolethane trimethacrylate, tetramethylene glycol 
dimethacrylate, ethylene glycol dimethyacrylate, triethylene glycol 
dimethacrylate, pentaerythritol triacrylate, pentaerythritol 
tetraacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 
dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and the 
like. Particularly preferred esters are 1,6-hexanediol diacrylate, 
trimethylolpropane triacrylate, pentaerythritol triacrylate, and 
pentaerythritol tetraacrylate. 
The procedures for preparing these acrylate and methacrylate esters of 
epoxide resins is described in U.S. Pat. No. 3,377,406 incorporated by 
reference. 
The acrylate or methacrylate esters are blended with the polyepoxide resin 
in the weight ratio of about 5 to about 100 parts of ester for each 100 
parts of resin. 
Of the amine curing agents known to be effective in curing a vicinal epoxy 
resin, preferred curing agents in accordance with the instant invention 
are the polyoxyalkylene containing amine compounds. A preferred class of 
polyoxyalkylene polyamines is of the formula: 
##STR4## 
wherein X is hydrogen, methyl or ethyl radical; R is the nucleus of an 
oxyalkylation susceptible polyhydric alcohol containing 2 to 12 carbon 
atoms and 2 to 8 hydroxyl groups; n is a number ranging from 1 to about 15 
and r is a number ranging from 2 to 4. 
The most preferred polyoxyalkylene polyamines are a polyoxypropylene 
diamine having a molecular weight of about 230 or a triamine of molecular 
weight about 400. These products are available under the tradename 
JEFFAMINE.RTM. D-230 and JEFFAMINE.RTM. T-403 from Texaco Chemical Co. 
Their use as curing agents is described in U.S. Pat. No. 4,189,564. 
JEFFAMINE.RTM. D-230 is represented by the formula: 
EQU H.sub.2 NCH(CH.sub.3)CH.sub.2 -[OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2 
wherein x averages 2.6. 
JEFFAMINE.RTM. T-403 is represented by the formula: 
##STR5## 
wherein x+y+z averages 5.3. 
The reactive amine accelerators of the instant invention are piperazine 
compounds which are described, for example, in U.S. Pat. No. 3,875,072 and 
U.S. Pat. No. 4,528,345 to Waddill incorporated herein by reference. The 
preferred accelerator is piperazine itself. N-aminoethylpiperazine is also 
shown in the Example to produce good coatings. 
The piperazine compound is incorporated in an amount which will ensure a 
maximum level of primary amine reaction but give a reaction product which 
is not too viscous to handle. The greater the ratio of accelerator to 
acrylate ester, the less primary amine is reacted. However, a large excess 
of epoxy resin will result in a very viscous product or even a gel which 
is undesirable. However, excess piperazine compound is undesirable because 
of extraneous reactions. Accordingly, the instant coatings are formulated 
with piperazine compound in an approximate equivalence with the acrylate 
ester.