Novel coating systems comprising high solids content blends of epoxy prepolymers and a catalyst complex comprising a complex iodonium salt, a copper salt, and a tin salt and a conventional pigment. The compositions cure rapidly to highly chemically resistant, tough coatings.

BACKGROUND OF THE INVENTION 
In Watt, U.S. Pat. No. 3,936,557, are described blends of epoxide materials 
which, although essentially free of volatile solvents, are liquid and 
tractable for coating and related applications. The blends comprise epoxy 
prepolymers of the type glycidyl-bisphenol-A resins, epoxidized novolaks, 
polyglycidyl ethers, and alicyclic diepoxides, blended with 
bis(epoxycycloalkyl) esters. The compositions include a cationic 
polymerization initiator, in particular a radiation sensitive catalyst 
precursor, such as an aromatic diazonium salt of a complex halogenide. In 
use, the compositions are coated on a substrate, followed by the 
application of energy, through heating or through irradiation, to effect 
substantial polymerization of the epoxidic materials of the coating. A 
related, relevant disclosure is Schlesinger, U.S. Pat. No. 3,703,296. In 
Crivello and Schroeter, U.S. Pat. No. 4,026,705, it is disclosed that 
certain radiation sensitive diaryl iodonium complex salts, such as 
diphenyliodonium hexafluoroboate, can be incorporated into epoxy resins to 
produce one package radiation curable compositions. Related teachings are 
found in Barton, U.S. Pat. No. 4,090,936. Such catalyst systems are more 
stable than the complex diazonium compounds. In Crivello, U.S. Pat. No. 
4,173,551, diaryliodonium salts are disclosed to be effective thermal 
initiators for polymerization of epoxides, when used in combination with 
various co-catalysts, such as copper salts. All of the foregoing patents 
are incorporated herein by reference. 
It has now been found possible to formulate epoxide coatings, using such 
technology if a novel and judicious choice is made of the type of epoxy 
compound used, the catalyst employed, a solvent-free environment and 
suitable pigment loadings. With the new coatings, no need of thinner 
reduction to application viscosity is necessary--application can be made 
surprisingly easily at solids contents approaching 90 percent by weight. 
The coatings can be formulated, in general, with any conventional pigment 
and, if a tin salt is used, unique advantages in terms of room temperature 
cure rate will result. It is a principal object to provide the finisher 
with the option to totally eliminate the need for organic solvents. If the 
finisher still needs a solvent, the composition can still function with 
less than 10 percent by weight--which is well within Environmental 
Protection Agency regulations. As mentioned, it is remarkable that all 
these features are achieved at application viscosity, permitting the 
finisher to apply extremely heavy films with ease. In addition, as has 
also been discovered, the embodiments using tin catalyst will cure at room 
temperature. These unique and versatile coatings depend on the presence in 
the composition of the epoxide, the complex catalyst, the copper salt 
co-catalyst and the pigment and such is the subject matter of this 
invention. 
DESCRIPTION OF THE INVENTION 
According to the present invention there are provided pigmented, high 
solids curable compositions comprising 
(a) an epoxidic prepolymer blend comprising 
(i) a diglycidyl ether of cyclohexanedimethanol 
(ii) a diglycidyl ether of bis-phenol-A; 
(iii) a polyepoxidized phenol or cresol novolak; 
(iv) a polyglycidyl ether of a polyhydric alcohol; 
(v) an epoxidic ester having two epoxycycloalkyl groups; or 
(vi) a mixture of any of the foregoing; and 
(b) from 0.5 to 35 parts by weight per 100 parts by weight of (a) and (b) 
combined of a catalyst comprising 
(i) a diaryliodonium salt of the formula 
EQU [(R).sub.a (R.sup.1).sub.b I].sub.c.sup.+ [MQ.sub.d ].sup.-(d-e) 
wherein R is a monovalent organic radical, R.sup.1 is a divalent aromatic 
organic radical, M is a metal or metalloid, Q is a halogen radical, a is a 
whole number equal to 0 or 2, b is a whole number equal to 0 or 1 and the 
sum of a+b is equal to 2 or the valence of I, c=d-e, e equals the valence 
of M and is an integer equal to 2-7 inclusive and d&gt;e and is an integer 
having a value up to 8; and 
(ii) from 0.01 parts to 10 parts, per part of (i), of a copper salt; and 
(c) from 10 to 100 parts by weight, per 100 parts by weight of (a) and (b) 
of a pigment. 
In preferred features, there will also be included (d) stannous octoate. 
With respect to the ingredients, the diglycidyl ether of 
cyclohexanedimethanol (a)(i) has the formula: 
##STR1## 
It can be made in conventional ways, e.g., by the reaction of 
epichlorohydrin with 1,4-cyclohexanedimethanol. It also is commercially 
available, e.g., from Wilmington Chemical Co., under the tradename Heloxy 
MK-107. 
In preferred blends, components will be, e.g., 
(a)(ii) the well known reaction product of epichlorohydrin and a diphenolic 
compound, e.g., bisphenol-A. This is a viscous liquid resin, available 
from a number of sources, e.g., EPON 828, a product of Shell Chemical Co.; 
(a)(iii) a polyepoxidized phenol or cresol novolac, such as the well-known 
products having average molecular weights in the vicinity of 1000, and 
epoxy equivalent weights in the range of 160 to 200, frequently about 
170-180, and commercially available, e.g., from Dow Chemical Co. under the 
tradename D.E.N. 438; 
(a)(iv) a polyglycidyl ether of a polyhydric alcohol, such as the 
diglycidyl ether of 1,4-butanediol; the diglycidyl ether of diethylene 
glycol; the triglicydyl ether of glycerol, and the like. The 
first-mentioned is commercially available, e.g., from Ciba-Geigy under the 
tradename Araldite RD-2; or 
(a)(v) as examples of epoxidic esters having two epoxycycloalkyl groups, 
there can be mentioned 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane 
carboxylate and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, available 
from Union Carbide Co. under the respective tradenames ERL 4221 and 4289, 
the former being available as well from Ciba-Geigy under the tradename 
CY-179. In preferred features, blends of epoxides will comprise from about 
15 to 90% by weight of epoxide (a)(i) and about 85 to 10% by weight of one 
or more of the other enumerated epoxides. 
In the diaryliodonium component of the catalyst, radicals embraced by R can 
be the same or different aromatic carbocyclic radicals having from 6 to 20 
carbon atoms, which can be substituted with from 1 to 4 monovalent 
radicals selected from C.sub.(1-8) alkoxy, C.sub.(1-8) ; alkyl, nitro, 
chloro, etc. R is more particularly, phenyl, chlorophenyl, nitrophenyl, 
methoxyphenyl, pyridyl, etc. Radicals included by R.sup.1 are divalent 
radicals such as 
##STR2## 
where Z is selected from 
##STR3## 
R.sup.2 is C.sub.(1-8) alkyl or C.sub.(6-13) aryl, and n is an integer 
equal to 1-8 inclusive. 
Metals or metalloids included by M of formulas above are transition metals 
such as Sb, Fe, Sn, Bi, Al, Gaa, In, Ti, Zr, Sc, V, Cr, Mn, Cs, rare earth 
elements such as the lanthanides, for example, Cd, Pr, Nd, etc. actinides, 
such as Th, Pa, U, Np, etc., and metalloids, such as B, P, As, etc. 
Complex anions included by MQ.sub.d.sup.-(d-e) are, for example 
BR.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-, SbF.sub.6.sup.-, 
FeCl.sub.4.sup.=, SnCl.sub.6.sup.-, BiCl.sub.5.sup.=, etc. 
Iodonium salts included by the above formulas are, for example: 
##STR4## 
The preferred iodoium salt is diphenyl-iodonium hexafluoroarsenate. 
Iodonium salts of the type used herein can be made by the procedure in 
Crivello, U.S. Pat. No. 3,981,897, incorporated herein by reference, 
wherein contact between an aryl halonium bisulfate and the corresponding 
hexafluoro acid or salt can be effected under aqueous conditions. 
Copper salts which can be used as component (b)(ii) include, for example, 
Cu(I) salts such as copper halides, e.g., Cu(I) chloride, etc., Cu(II) 
salts such as CU(II) benzoate, Cu(II) acetate, Cu(II) stearate, Cu(II) 
gluconate, Cu(II) citrate, etc. Copper(II) naphthenate is preferred. 
Suitable tin salt co-catalysts are stannous salts of carboxylic acids of 
the formula 
##STR5## 
where R.sup.3 is a monovalent organic radical selected from C.sub.(1-18) 
alkyl and C.sub.(6-13) aryl. Illustrative organic acids are acetic acid, 
2-ethylhexanoic acid, hexanoic acid, oleic acid, stearic acid, palmitic 
acid, benzoic acid, salicylic acid, and the like. Preferably the tin salt 
will be stannous octoate. 
The epoxidic resins can be used alone or in combination with reactive 
diluents, in known ways. For example, such diluents include phenyl 
glycidyl ether, 4-vinylcyclohexene dioxide, limonene dioxide, 
1,2-cyclohexene oxide, glycidyl acrylate, glycidyl methacrylate, styrene 
oxide, allyl glycidyl ether, etc. Other compounds can also be included, 
e.g., epoxysiloxane resins, epoxypolymethanes and epoxypolyesters. Other 
conventional modifiers include amines, carboxylic acids, thiols, phenols, 
alcohols, etc. Flexibilizers such as hydroxy-terminated polyesters can 
also be used. 
The pigment component (c) can vary widely. Any conventional pigment can be 
used at conventional levels, e.g., 10-200 parts per 100 parts of 
composition. Preferably the pigment/binder ratio will be from 1:1 to 1:5 
and especially preferably it will be about 1:2. Suitable pigments include 
titanium dioxide, lamp black, red iron oxide, mixtures thereof, and the 
like. Titanium dioxide is preferred. 
Conventional paint making techniques can be used to make the compositions 
of this invention. These techniques are well known to those skilled in 
this art. For example, the pigment, epoxy prepolymer and a very small 
amount of solvent, e.g., cyclohexanone, can be milled or ground, e.g., in 
a Cowles mixer to produce a master grind containing, e.g., 55 to 65 wt. % 
pigment, 25-35 wt. % of epoxidic prepolymer; and a solids content of from 
about 80 to about 98 wt. %, preferably from 85 to 95 wt. %. Separately, a 
catalyst solution is prepared from a solvent, e.g., methyl ethyl ketone, 
the iodonium salt, e.g., diphenyliodonium hexafluoroarsenate, and the 
copper co-catalyst, e.g., 6% copper naphthanate. Suitable such solutions 
comprise about 60 to 80wt. % solvent, 2 to 10 wt. % copper salt and 15-40 
wt. % of iodonium salt. Then the final composition is formulated by 
providing formulations with additional epoxide, the master grind, the 
catalyst solution, and optional stannous salt. The final pigment binder 
ratio is for example about 1:2 and a useful viscosity is 20 to 60 seconds 
in a Zahn #2 cup. This can be readily achieved, for example, by blending 
50 parts of epoxide, e.g., a cycloaliphatic epoxide, e.g., Union Carbide's 
ERL-4221, or a BPA-type epoxy, such as Shell Chemicals EPON 828. If 
stannous octoate is present, the compositions should be freshly prepared 
because the pot life is generally less than one hour. The pot life can be 
greatly increased by excluding the stannous octoate. 
Conventional coating methods, e.g., brush, spray, dip, flow, etc. can be 
used. In general, thicknesses of 3-4.0 mils. of paint will give excellent 
combination of protection, life and economy. The coatings are curable at 
room temperature, especially if stannous salts are included, and also they 
are bakeable at elevated temperatures, e.g., for 5 to 20 minutes at 
300.degree.-500.degree. C. They are corrosion resistant, flexible and 
suprisingly resistant to strong solvents, such as methyl ethyl ketone and 
dimethyl formamide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following examples illustrate the practice of the present invention. 
The claims should not be limited to them in any manner whatsoever. 
EXAMPLE 1 
A master grind is prepared in a Cowles mixer from the following: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
bis-glycidyl ether of 
cyclohexane dimethanol.sup.a 
887 
pigment, titanium dioxide 
260 
wetting agent.sup.b 
10 
cyclohexanone 140 
______________________________________ 
.sup.a Heloxy MK107, Wilmington Chemical Co. 
.sup.b AntiTerra U, bykMallinckrodt Co. 
The pigment comprises 57.48 wt. %, epoxy 28.97 wt. %, and the solids 
content is 86.79 wt. %. 
A catalyst solution is prepared from the following: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
methyl ethyl ketone 74 
diphenyliodonium hexafluoro-. -arsenate 
20 
copper naphthanate 6 
______________________________________ 
The following coating composition is prepared: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
bis-glycidyl ether of bisphenol- 
A and small amount of copper 
stearate.sup.c 50 
master grind (above) 
50 
xylene 5 
catalyst solution (above) 
1.3 
stannous octoate 1.2 
______________________________________ 
.sup.c General Electric Co. Arnox 3110 
The intimate blend has a viscosity of 40 seconds in a Zahn #2 cup, a 
pigment/binder ratio of 1:2, and a solids content of 88 wt. %. 
It is coated onto a cleaned and treated metal panel and cured for 5 minutes 
at 400.degree. F. The thickness of the coating is 3-4.0 mils., the pencil 
hardness is 6H; it withstands 200 methyl ethyl ketone rubs; the reverse 
impact is 5 in.lbs. and after 72 hours of soaking in dimethylformamide, 
there is only a very, very slight softening effect. 
EXAMPLE 2 
The following coating composition is prepared: 
______________________________________ 
Components Parts by Weight 
______________________________________ 
3,4-epoxycyclohexylmethyl 
3,4-epoxycyclohexane carboxylate.sup.a 
50 
master grind (Example 1) 
50 
catalyst solution (Example 1) 
7 
stannous octoate 1.4 
______________________________________ 
.sup.a Union Carbide ERL4221 
The intimate blend has a viscosity of 26 seconds in a Zahn #2 cup, a 
pigment/binder ratio of 1:2, and a solids content of 88 wt. %. 
It is coated onto a cleaned and treated metal panel and cured for 5 minutes 
at 400.degree. F. The thickness of the coating is 3-4.0 mils., the pencil 
hardness is 7H; it withstands 200 methyl ethyl ketone rubs; the reverse 
impact is 0 in. lbs. and after 72 hrs. of soaking in dimethyl formamide 
there is no adverse effect whatsoever. Example 2 is coated on cold rolled 
steel (untreated) and cured for 5 minutes at 400.degree. F. This system 
goes 1200 hours in the 5% salt fog cabinet without blistering or creeping. 
This is outstanding. 
The foregoing examples demonstrate that cycloaliphatic and BPA-type 
epoxies, pigmented and catalyzed with diaryliodonium complex salts, and 
copper salts produce extremely useful coatings. These coatings are 
formulated to be easily applied at solids contents approaching 90% by 
weight with viscosities less than 40 seconds Zahn #2. These coatings are 
seen to exhibit great resistance to strong solvents, like methyl ethyl 
ketone and dimethyl formamide. These coatings also yield basically the 
same properties when force cured as low as 195.degree. F. or air dry. The 
degree of cure is directly related to the addition of stannous octoate 
when curing at low temperatures. 
Many variations will suggest themselves to those skilled in this art. All 
such obvious variations are within the full intended scope of the appended 
claims.