Epoxy resin compositions

The present invention provides a coating composition comprising one or more curable resins which contain, among the resins, free acrylic moieties and free or reacted epoxy moieties, and a ketone blocked polyamine type curing agent, the ingredients being chosen to provide in the coating after curing, more than 50% by weight of cured epoxy groups and less than 50% by weight of cured acrylic groups.

The present invention relates to curable epoxy resin compositions suitable 
for use as coatings and adhesives. 
Epoxy coating compositions usually contain solid or semi-solid epoxy resins 
in an organic solvent. When the solvent has evaporated, a solid or near 
solid residue forms a film even before significant reaction with the 
hardener takes place. 
There is an increasing need to reduce the amount of organic solvents used 
in such coatings and produce what is referred to a low Volatile Organic 
Content (V.O.C). 
The amount of V.O.C. is desirably reduced to 20% of the total or less. To 
achieve viscosities low enough for application by a spray gun it is 
necessary to use liquid epoxy resins instead of the solid or semi-solid 
type. This means that a rapid reaction is needed in order to render the 
liquid resins solid shortly after the solvent has evaporated. 
We have now found that this can be achieved by incorporating into the 
composition an acrylic resin and a certain type of latent curing agent for 
both the acrylic and epoxy resins. 
Accordingly the present invention provides a coating composition comprising 
one or more curable resins which contain, among the resins, free acrylic 
moieties and free or reacted epoxy moieties, and a ketone blocked 
polyamine type curing agent, the ingredients being chosen to provide in 
the coating after curing, more than 50% by weight of cured epoxy groups 
and less than 50% by weight of cured acrylic groups. 
Ketone blocked polyamines (sometimes called ketimines) are produced by 
condensing amines with ketones to produce alkylnitrilo (1-alkyl) 
alkylidyne compounds. 
For example, 2 moles of ketone reacted with diethylenetriamine. 
##STR1## 
yield a compound in which both primary amines are blocked. In this case, 
as there is still a reactive hydrogen present, reaction of the imine with 
1 mole of phenyl glycidyl ether eliminates the active hydrogen on the 
secondary amine: 
##STR2## 
Such a compound, when incorporated into the composition has low reactivity. 
However, because of hydrolytic instability of the double bond in these 
compounds, hydrolysis occurs with moisture from the air once the 
composition is applied, and the regenerated primary amines provide cure. 
The ketone which is regenerated diffuses to the surface and evaporates. 
The regenerated amine reacts very rapidly with the acrylic resin, even at 
ambient temperatures. This causes rapid solidification of the film, 
thereby holding the film in position while the epoxy resin is cured by the 
amine. 
The curing agent may be derived from a polyamine having from 2 to 6 amino 
groups, preferably from 3 to 5 amino groups. The ketone blocking group may 
be derived from a ketone of the formula R.sub.1 R.sub.2 C.dbd.O where 
R.sub.1 and R.sub.2 are, independently, alkyl groups having from 1 to 15 
carbon atoms, preferably from 1 to 4 carbon atoms. 
Suitable epoxides include polyglycidyl esters, polyglycidyl ethers, and 
cycloaliphatic epoxides. 
Epoxides which may be employed are preferably those containing, on average, 
more than one group of formula 
##STR3## 
directly attached to an atom or atoms of oxygen or nitrogen, where R.sup.1 
denotes a hydrogen atom or a methyl group. 
As examples of such epoxides may be mentioned polyglycidyl and 
poly(beta-methylglycidyl) esters obtainable by reaction of a compound 
containing two or more carboxylic acid groups per molecule with 
epichlorohydrin, glycerol dichlorohydrin, or beta-methylepichlorohydrin in 
the presence of an alkali. Such polyglycidyl esters may be derived from 
aliphatic polycarboxylic acids, e.g. oxalic acid, succinic acid, glutaric 
acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 
or dimerised or trimerised linoleic acid; from cycloaliphatic 
polycarboxylic acids such as tetrahydrophthalic acid, 
4-methyltetrahydrophthalic acid, hexahydrophthalic acid, and 
4-methylhexahydrophthalic acid; and from aromatic polycarboxylic acids 
such as phthalic acid, isophthalic acid, and terephthalic acid. 
Further examples are polyglycidyl and poly(beta-methylglycidyl)ethers 
obtainable by reaction of a compound containing at least two free 
alcoholic hydroxyl and/or phenolic hydroxyl groups per molecule with the 
appropriate epichlorohydrin under alkaline conditions or, alternatively, 
in the presence of an acidic catalyst and subsequent treatment with 
alkali. These ethers may be made from acrylic alcohols such as ethylene 
glycol, diethylene glycol, and higher poly(oxyethylene) glycols, 
propane-1,2-diol and poly(oxypropylene)glycols, propane-1,3-diol, 
butane-1,4-diol, poly(oxytetramethylene)glycols, pentane-1,5diol, 
hexane-1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylol-propane, 
pentaerythritol, sorbitol, and polyepichlorohydrins; from cycloaliphatic 
alcohols such as resorcitol, quinitol, bis(4-hydroxycylohexyl)methane, 
2,2-bis(4-hydroxycyclohexyl)propane, and 
1-1-bis(hydroxymethyl)cyclohex-3-ene; and from alcohols having aromatic 
nuclei, such as 2,4-(dihydroxymethyl)benzene. They may also be made from 
mononuclear phenols, such as resorcinol and hydroquinone, and from 
polynuclear phenols, such as bis(4hydroxyphenyl)methane, 
4,4'-dihydroxydiphenyl, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 
2,2-bis(4hydroxyphenyl)-propane, 
2,2-bis(3,5dibromo-4-hydroxyphenyl)propane, and novolaks formed from 
aldehydes such as formaldehyde, acetaldehyde, chloral, and furfuraldehyde, 
vith phenols such as phenol itself, and phenol substituted in the ring by 
chlorine atoms or by alkyl groups each containing up to nine carbon atoms, 
such as 4chlorophenol, 2-methylphenol, and 4-tert-butylphenol. 
Epoxides in which some or all of the epoxide groups are not terminal may 
also be employed, such as vinylcyclohexane dioxide, limonene dioxide, 
dicyclopentadiene dioxide, 4-oxatetracyclo [6,2.1.0.sup.2,7.0.sup.3,5 ] 
undec-9-yl glycidyl ether, the 
bis(4-oxatetracyclo[6.2.1.0.sup.2,7.0.sup.3,5 ] undec-9-yl ether or 
ethylene glycol, 3-4-epoxycylohexylmethyl 3', 4'-epoxycyclohexane 
carboxylate and its 6,6.sup.1 dimethyl derivative, the 
bis(3,4-epoxycyclohexane-carboxylate) of ethylene glycol, 
3-(3,4-epoxycyclohexyl)-8.9-epoxy-2,4-dioxaspire[5,5]undecane, and 
epoxidised butadienes or copolymers of butadiene with ethylentic compounds 
such as styrene and vinyl acetate. 
Epoxide resin having the 1,2-epoxide groups attached to different kinds of 
hetero atoms may be employed, e.g. the glycidyl ether-glycidyl ester of 
salicyclic acid. If desired, a mixture of epoxide resins may be used. 
Preferred epoxides are polyglycidyl esters, polyglycidyl ethers of 
2,2-bis(4-hydroxyphenyl)propane, of bis(4-hydroxyphenol)-methane or of a 
novolak formed from formaldehyde and phenol, or phenol substituted in the 
ring by one chlorine atom or by one alkyl hydrocarbon group containing 
from one to nine carbon atoms, and having a 1,2-epoxide content of at 
least 0.5 equivalent per kilogram, and 3,4-epoxycyclohexylmethyl 3', 
4'-epoxycyclohexane carboxylate. 
Suitable acrylic resins include compounds in containing at least two groups 
of formula 
EQU CH.sub.2 .dbd.CR.sup.3 --COO-- (II) 
where R.sup.3 represents a hydrogen or chlorine atom, or a methyl or ethyl 
group. 
Sutable est having at least two groups of formula (II) include esters, 
especially acryfates and methacylates, of aliphaic, cycoaeliphatic, 
alicyclyaliphatic, araliphatic or heterocyclyialiphatic polyhydric 
alcohols, especially diols and briols; polyhydroxy-, particularly 
dihydroxy-, carboxyfic acid; polyhydroxy-, particularly dihydroxy-, 
alkylamines; and polyhydroxy-, particularly dihydroxy-, alkylnitriles. 
Acrylic ester-urethanes and -ureides may also be used. Such esters are, in 
general, commercially available, and any that are not may be prepared by 
known methods. 
Suitable acrylic esters include those of formula 
##STR4## 
where R.sup.3 is as hereinbefore defined, R.sup.5 denotes H, --CH.sub.3, 
--C.sub.2 H.sub.5, --CH.sub.2 OH, or 
##STR5## 
R.sup.4 denotes H, OH, or 
##STR6## 
x is an integer of from 1 to 8, b is an integer of from 1 to 20, and 
c is zero or 1. 
Among compounds of formula (III), those where x is from 1 to 4,b is from 1 
to 5 and R.sup.3 denote a hydrogen atom or a methyl group are preferred. 
Specific examples of such compound are the diacylates and dimethac a of 
ethylene glycol, propylene glycol, butane-1,4-diol, diethylene glycol, 
dipropylene glycol, triethylene glycol, bipropylene glycol, tetraethylene 
glycol and tetrapropylene glycol. 
Other suitable acrylic esters are of formula: 
##STR7## 
where b, c, R.sup.3 and R.sup.4 have the meanings assigned above, d is 
zero or a positive integer, provided that c and d are not both zero, 
e is 2, 3, or 4, and 
R.sup.6 denotes an organic radical of valency e linked through a carbon 
atoms or carbon atoms thereof to the indicated b oxygen atoms. 
Preferred among compounds of formula (IV) are those where b, c and d are 
each 1, R.sup.3 is a hydrogen atom or methyl group and R.sup.6 is a 
hydrocarbon residue of an aliphatic polyhydric alcohol having from 2 to 6 
carbon atoms, such as a pentaerythrityl group. A specific example of such 
compounds is pentaerythrityl tetrakis (dimethylene glycol acrylate). 
Still other suitable esters are urethane acrylates and ureide acrylates of 
formula: 
##STR8## 
where R.sup.3 has the meaning assigned above, 
R.sup.9 denotes a divalent aliphatic, cycloaliphabc, aromatic, or 
araliphatic group, bound through 
a carbon atom or carbon atoms thereof of the indicate --O-- atom and --X-- 
atom or group, 
X denotes --O--, --NH--, or --N(alkyl)--, in which the alkyl radical has 
from 1 to 8 carbon atoms, 
g is an integer of at least 2 and at most 6, and 
R.sup.10 denotes a g-valent cycloaliphatic, aromatic, or araliphatic group 
bound through a carbon atoms or carbon atoms thereof to the indicate NH 
groups. 
Preferably R.sup.9 denotes a divalent aliphatic group of 2 to 6 carbon 
atoms and R.sup.10 denotes one of the following: 
a divalent aliphatic group of 2 to 10 carbon atoms, such as a group of 
formula 
--(CH.sub.2).sub.6 --, CH.sub.2 C(CH.sub.3).sub.2 CH.sub.2 
CH(CH.sub.3)(CH.sub.2)--, or 
--CH.sub.2 CH(CH.sub.3)CH.sub.2 C(CH.sub.3).sub.2 CH.sub.2).sub.2 --; or 
a phenylene group, optionally substituted by a methyl group or a chlorine 
atom; a naphthylene group; a group of formula 
--C.sub.6 H.sub.4 C.sub.6 H.sub.4 --, C.sub.6 H.sub.4 CH.sub.2 C.sub.6 
H.sub.4 --, or --C.sub.6 H.sub.4 C(CH.sub.3).sub.2 C.sub.6 H.sub.4 --; 
or a mononuclear alkylcycloalkylene or alkylcycloalkylalkylene group of 
from 6 to 10 carbon atoms, such as a methylcyclohex-2, 4-ylene, 
methylcyclohex-2,6-ylene, or 1,3,3-trimethylcyclohex-5-ylenemethyl group. 
Specific examples of compounds of formula (V) are 2,4- and 
2,6-(bis(2-acryloyloxyethoxycarbonamido)toluene and the corresponding 
methacryloyloxy compounds. 
Further suitable acrylic esters are those of formula 
##STR9## 
where R.sup.3 has the meaning assigned above, 
R.sup.11 denotes CH.sub.3 --, C.sub.2 H.sub.5 --, --CH.sub.2 OH or CH.sub.2 
.dbd.C(R.sup.3)COOCH.sub.2 --, and 
R.sup.12 denotes --CH.sub.2 OH or --CH.sub.2 OOC--C(R.sub.3).dbd.CH.sub.2, 
especially 1,1,1-trimethylolpropane triacrylate, pentaerythritol 
tetra-acrylate and the corresponding methacrylates. 
Still further suitable acrylic esters are those of formula 
##STR10## 
where R.sup.3 has the meaning assigned above, 
R.sup.13 denotes --H, --CH.sub.3 or --CH.sub.2 Cl, and 
R.sup.14 denotes a tetravalent residue, containing up to 20 carbon atoms 
and one or more carbocyclic rings, of a tetracarboxylic acid after removal 
of four carboxyl groups, each indicate pair of groups 
--COOCH(R.sup.13)CH.sub.2 OOCC(R.sup.3).dbd.CH.sub.2 and --COOH being 
directly linked to adjacent carbon atoms. 
Preferably, R.sup.3 and R.sup.13 are --H or --CH.sub.3 and R.sup.14 is the 
residue of an aromatic tetracarboxylic acid having one or two benzene 
rings, especially pyromellitic acid or benzophenone-3, 3', 
4,4'-tetracarboxylic acid. 
Examples of compounds in which epoxy groups are at least partially reacted 
with acidic groups in an acrylic resin are those of the formula: 
##STR11## 
where c and e have the meanings previously assigned, R.sup.7 denotes --H 
or --CH.sub.3, and 
R.sup.8 denotes an organic radical of valency e, linked through a carbon 
atom thereof other than the carbon atom of a carbonyl group. 
More particularly, when c is zero, R.sup.8 may denote the residue, 
containing from 1 to 60 carbon atoms, of an alcohol or phenol having e 
hydroxyl groups. 
R.sup.8 may thus represent an aromatic, araliphatic, alkaromatic, 
cycloaliphatic, heterocyclic, or heterocycloaliphatic group, such as an 
aromatic group containing only one benzene ring, optionally substituted by 
chlorine, bromine or an alkyl group of from 1 to 9 carbon atoms, or an 
aromatic group comprising a chain of two to four benzene rings, optionally 
interrupted by ether oxygen atoms, aliphatic hydrocarbon groups of 1 to 4 
carbon atoms, or sulphone groups, each benzene ring being optionally 
substituted by chloride, bromine or an alkyl group of from 1 to 9 carbon 
atoms, or a saturated or unsaturated, straight or branched-chain aliphatic 
group, which may contain ether oxygen linkages and which may be 
substituted by hydroxyl groups, especially a saturated or 
monoethylenically unsaturated straight chain aliphatic hydrocarbon group 
of from 1 to 8 carbon atoms. 
Specific examples of such groups are the aromatic groups of the 
formulae--C.sub.6 H.sub.4 C(CH.sub.3).sub.2 C.sub.6 H.sub.4 --, in which 
case e is 2, and --C.sub.6 H.sub.4 (CH.sub.2 C.sub.6 H.sub.3 --).sub.f 
--CH.sub.2 C.sub.6 H.sub.4 --where f is 1 or 2, in which case e is 3 or 4, 
and the aliphatic groups of formula --CH.sub.2 CHCH.sub.2 -- or CH.sub.2 
CH(CH.sub.2).sub.3 CH.sub.2 --, in which case e is 3, or of formula 
--(CH.sub.2).sub.4 --, --CH.sub.2 CH.dbd.CHCH.sub.2 --, CH.sub.2 CH.sub.2 
OCH.sub.2 CH.sub.2 --, or --(CH.sub.2 CH.sub.2 O).sub.2 CH.sub.2 CH.sub.2 
--, in which case e is 2. 
When c is 1, R.sup.8 may represent the r esidue, containing from 1 to 60 
carbon atoms, of an acid having e carboxyl groups, preferably a saturated 
or ethylenically unsaturated, straight chain or branched aliphatic 
hydrocarbon group of from 1 to 20 carbon atoms, which may be substituted 
by chlorine atoms and which may be interrupted by ether oxygen atoms 
and/or by carbonyloxy (--COO--) groups, or a saturated or ethylenically 
unsaturated cycloaliphatic or aliphatic-cydoaliphatic hydrocarbon group of 
at least 4 carbon atoms, which may be substituted by chlorine a toms, or 
an aromatic hydrocarbon group of from 6 to 12 carbon atoms which may be 
substituted by chlorine or bromine atoms. 
Further preferred compounds where c is 1 are those in which R.sup.8 
represents a saturated or ethylenically unsaturated straight chain or 
branched aliphatic hydrocarbon group of from 1 to 8 carbon atoms, 
optionally substituted by a hydroxyl group, or a saturated or 
ethylenically unsaturated straight chain or branched aliphatic hydrocarbon 
group of from 4 to 50 carbon atoms and interrupted in the chain by 
carbonyloxy groups, or a saturated or ethylenically unsaturated monocyclic 
or bicyclic cycloaliphatic hydrocarbon group of 6 to 8 carbon atoms, or an 
ethylenically unsaturated cycloaliphatic-aliphatic hydrocarbon group of 
from 10 to 51 carbon atoms, or a mononuclear aromatic hydrocarbon group of 
from 6 to 8 carbon atoms. Specific examples of these residues of 
carboxylic acid are those of formula --CH.sub.2 CH.sub.2 --, CH.dbd.CH--, 
and --C.sub.6 H.sub.4 --where e is 2. 
R.sub.8 may also contain one or more epoxy groups of the formula (I) above. 
Specific examples of suitable compounds of formula (VIII) are epoxy 
acrylates such as 1,4bis(2-hydroxy-3(acryloyloxy)propoxy)butane, 
poly(2-hydroxy-3-(acryloyloxy)propyl)ethers of bis(4-hydroxyphenyl)methane 
(bisphenol F), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and 
phenol-formaldehyde novolaks, bis(2-hydroxy-3-acryloyloxypropyl) adipate 
and the methacryloyloxy analogues of these compounds. 
The compounds of formula (VIII) may be prepared, for example, by reacting 
an acrylic or methacrylic acid with the appropriate amount of epoxy resin 
to give either a fully acrylated epoxy resin product or a dual functional 
material which contains both acrylic groups and epoxy groups. 
When an epoxy acrylate or a dual functional material is used, it may 
replace all or part of the epoxy resin and/or acrylic resin. 
Preferably the ingredients of the coating composition are chosen to 
provide, in the coating after curing, 51 to 95% by weight of cured epoxy 
groups, preferably 51 to 80% by weight. The remainder of the cured groups 
are from the acrylic groups. 
It should be noted that some of the cured epoxy groups may come from the 
curing agent if one is used which has had any reactive hydrogen reacted 
with a glycidyl ether. 
Thus the coating composition may contain an acrylic resin plus an epoxy 
resin; an acrylated epoxy resin with or without an epoxy resin; or a dual 
functional material with or without another epoxy resin. 
Sufficient curing agent is used to react with both the acrylic moieties and 
any free epoxy moieties. Actual amounts needed vary according to the 
specific compounds used. 
If the viscosity of the composition is too high to enable it to be sprayed, 
an organic solvent may be added. Suitable solvents include hydrocarbons, 
especially aromatic hydrocarbons such as xylene, and alcohols, for example 
butanol.

The invention is illustrated by the following Examples. 
EXAMPLES 1 to 3 
Formulations are made up using a liquid epoxy resin based on bisphenol A. 
Acrylic esters used are an epoxy acrylate sold under the Tradename UVU 100 
by Croda or a urethane acrylate sold under the Tradename Ebercryl 220 by 
Radcure/UCB. A 4:1 mixture of xylene acid n-butanol is used as solvent. 
The curing agent is a ketone blocked polyamine sold under the Tradename 
Hardener LC 283 by Ciba-Geigy. The amounts used are shown in Table 1 in 
parts by weight. 
TABLE 1 
______________________________________ 
Example 1 2 3 
______________________________________ 
Epoxy resin 
100 100 100 
UVU 100 30 -- -- 
Ebecryl 220 -- 30 50 
LC 283 56.5 62.7 75.25 
Solvent 21.1 22.2 26.7 
______________________________________ 
Each formulation is sprayable and rapidly forms a solid film. 
EXAMPLE 4 
A formulation is made up of 80 parts by weight of an epoxy diacrylate 
formed from acrylic acid and the diglycidyl either of bisphenol A; 20 
parts by weight of a 4:1 mixture of xylene and n-butanol; and 33 parts by 
weight of hardener LC 283. 
The formulation is sprayable and gives a re-coat time of 3-4 hours at 
20.degree. C. and 3-5 hours at 5.degree. C. The coating is rub resistant 
to methyl ethyl ketone after 16 hours.