Heat curable compositions

Diaryliodonium salts have been found to be effective thermal initiators for the polymerization of a variety of cationically polymerizable materials including epoxides, cyclic ethers, phenol formaldehyde resins, etc., when used in combination with various cocatalysts. Among the cocatalysts which have been found to be effective are, for example, copper chelates and mixtures of such copper chelates with various reducing agents such as ascorbic acid, tin.sup.+2 salts, etc.

BACKGROUND OF THE INVENTION 
The present invention relates to the use of diaryliodonium salts in 
combination with certain copper chelates or mixtures thereof with certain 
reducing agents as cocatalysts for the heat cure of a variety of 
cationically polymerizable organic materials. 
As shown in my U.S. Pat. No. 4,173,551, assigned to the same assignee as 
the present invention, diaryliodonium salts and copper salts or mixtures 
of copper salts and organic acids have been found to be useful for 
effecting the polymerization of a variety of cationically polymerizable 
organic materials. In my above-identified copending application Ser. No. 
58,318, valuable results were achieved when aromatic iodonium salts were 
utilized in combination with various reducing agents to effect the low 
temperature cure of a variety of organic polymerizable materials. I have 
found that copper chelates, or mixtures of such copper chelates and 
reducing agents when used at effective levels, will also initiate to a 
surprising degree the cationic cure of a variety of organic materials when 
used in combination with diaryliodonium salts. 
STATEMENT OF THE INVENTION 
There is provided by the present invention, curable compositions comprising 
(A) a cationically polymerizable organic material, (B) a diaryliodonium 
salt and (C) a member selected from a copper chelate and a mixture of a 
copper chelate and a reducing agent. 
The diarylidonium salts which can be utilized in the practice of the 
invention are shown as follows: 
EQU [(R).sub.a (R.sup.1).sub.b I].sup.+ [Y].sup.-, (1) 
where R is a C.sub.(6-13) aromatic hydrocarbon radical, R.sup.1 is a 
divalent aromatic organic radical, and Y is an anion, a is equal to 0 or 
2, b is equal to 0 or 1 and the sum of a+b is equal to 1 or 2. Preferably, 
Y is an MQ.sub.d anion where M is a metal or metalloid, Q is a halogen 
radical and d is an integer equal to 4-6. Y also can be a counterion ion 
such as perchlorate, CF.sub.3 SO.sub.3.sup.-, C.sub.6 H.sub.5 
SO.sub.3.sup.-, Cl.sup.-, Br.sup.-, F, nitrate, phosphate, etc. 
Radicals included within R of formula (1) 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 of formula (1) are divalent radicals 
such as 
##STR1## 
where Z is selected from --O--, --S--, 
##STR2## 
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 formula (1) are transition metals 
such as Sb, Fe, Sn, Bi, Al, Ga, 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, 
Sb, etc. Complex anions included by MQ.sub.d are, for example, 
BF.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-, SbF.sub.6.sup.-, 
FeCl.sub.4.sup.-, SnCl.sub.6.sup.-, SbCl.sub.6.sup.-, BiCl.sub.5.sup.--, 
etc. 
Some of the diaryliodonium salts which can be used in the practice of the 
invention are as follows: 
##STR3## 
Copper chelates which can be used in the practice of the invention are 
shown in Cotton and Wilkinson, Advanced Inorganic Chemistry, 3rd Edition, 
Interscience Publishers, New York, 1972, pages 905 to 922. Copper chelates 
which are preferred, are those compounds which can be readily incorporated 
or dispersed in the cationically polymerizable material, as defined 
hereinafter, for example, an epoxide resin, or by an in situ reaction, or 
in a carrier solvent. Additional reference is made to the definition of 
chelate in Kirk-Othmer, Encyclopedia of Chemical Technology 3rd Edition, 
Vol. 5, pp. 339-367 (1979) John Wiley and Sons, New York. 
Some of the copper chelates which are included within the scope of the 
present invention are, for example, copper acetyl acetonate, copper 
salicylate, CuI(C.sub.6 H.sub.5).sub.3 P, CuI(C.sub.2 H.sub.5 O).sub.3 P, 
CuCl.sub.2 C.sub.2 H.sub.8 N.sub.2, 
##STR4## 
The term reducing agent as used in the present invention includes any 
organic or inorganic compound or polymer capable of lowering or reducing 
the charge of the hetero atom of the diaryliodonium salt. There are 
included, for example, ascorbic acid and its derivatives, such as 
ascorboyl palmitate, ascorboyl oleate, ascorboyl acetate, etc.; tin 
(Sn.sup.+2) compounds also can be used, for example, Sn.sup.+2 carboxylic 
acid salts, e.g., stannous octoate, stannous stearate, stannous laurate, 
stannous citrate, stannous oxalate, stannous benzoate, etc. Among organic 
compounds there are included .alpha.-hydroxy compounds, for example, 
ketones such as acyloins and benzoins, 
##STR5## 
There are also included iron (Fe.sup.+2) compounds, for example, ferrocene, 
FeBr.sub.2, FeCl.sub.2, etc; reducing sugars, such as glucose, fructose, 
galactose; etc., phenols, for example, thiophenol, etc.; silanes, for 
example, Si(H).sub.c (R.sup.2).sub.d compounds, where R.sup.2 is defined 
above, c is an integer having a value of 1 to 4 inclusive, d is a whole 
number equal to 0 to 3, and the sum of c+d=4; SiH containing 
organosiloxane, etc. 
In addition to ascorbic acid and .alpha.-hydroxy ketones, other activated 
.alpha.-hydroxy compounds which can be used with copper chelates as 
defined above, are included by the following 
##STR6## 
where R.sup.3 is a C.sub.(1-20) alkyl radical, or C.sub.(6-20) aryl 
radical and X is a monovalent radical selected from the class of nitro, 
halo, sulfone, CO.sub.2 R.sup.4, cyano, 
##STR7## 
--CCl.sub.3 and CHCl.sub.2, where R.sup.4 is selected from hydrogen and 
R.sup.3. 
The term cationically polymerizable organic material includes epoxy resins, 
thermosetting organic polyorganic condensation resins of formaldehyde, 
vinyl organic prepolymers, cyclic ethers, organo silicon cyclics, etc. 
The term "epoxy resin" as utilized in the description of the cationically 
polymerizable compositions of the present invention, includes any 
monomeric, dimeric or oligomeric or polymeric epoxy material containing 
one or a plurality of epoxy functional groups. For example, those resins 
which result from the reaction of bisphenol-A 
(4,4'-isopropylidenediphenol) and epichlorohydrin, or by the reaction of 
low molecular weight phenolformaldehyde resin (Novolak resin) with 
epichlorohydrin, can be used alone or in combination with an epoxy 
containing compound as a reactive diluent. Such diluents as phenyl 
glycidyl ether, 4-vinylcyclohexene dioxide, limonene dioxide, 
1,2-cyclohexene oxide, glycidyl acrylate, glycidyl methacrylate, styrene 
oxide, allyl glycidyl ether, etc., may be added as viscosity modifying 
agents. 
In addition, the range of these compounds can be extended to include 
polymeric materials containing terminal or pendant epoxy groups. Examples 
of these compounds are vinyl copolymers containing glycidyl acrylate or 
methacrylate as one of the comonomers. Other classes of epoxy containing 
polymers amenable to cure using the above catalysts are epoxysiloxane 
resins, epoxy-polyurethanes and epoxy-polyesters. Such polymers usually 
have epoxy functional groups at the ends of their chains. Epoxy-siloxane 
resins and method for making are more particularly shown by E. P. 
Pluedemann and G. Fanger, J. Am. Chem. Soc., 80 632-5 (1959). As described 
in the literature, epoxy resins can also be modified in a number of 
standard ways such as reaction with amines, carboxylic acids, thiols, 
phenols, alcohols, etc., as shown in U.S. Pat. Nos. 2,935,488; 3,235,620; 
3,369,055; 3,379,653; 3,398,211; 3,403,199; 3,563,840; 3,567,797; 
3,677,995; etc. Further coreactants which can be used with epoxy resins 
are hydroxy terminated flexibilizers such as hydroxy terminated 
polyesters, shown in the Encyclopedia of Polymer Science and Technology, 
Vol. 6, 1967, Interscience Publishers, New York, pp. 209,271 and 
particularly p. 238. 
Included by the thermosetting organic condensation resins of formaldehyde 
which can be used in the practice of the present invention are, for 
example, urea type resins, phenol-formaldehyde type resin. 
In addition, there can be used melamine thiourea resins, melamine, or urea 
aldehyde resins, cresole-formaldehyde resins and combinations with other 
carboxy, hydroxy, amino and mercapto containing resins, such as 
polyesters, alkyds and polysulfides. 
Some of the vinyl organic prepolymers which can be used to make the 
polymerizable compositions of the present invention are, for example, 
CH.sub.2 .dbd.CH--O--(CH.sub.2 --CH.sub.2 O).sub.n' --CH.dbd.CH.sub.2, 
where n' is a positive integer having a value up to about 1000 or higher; 
multifunctional vinylethers, such as 1,2,3-propane trivinylether, 
trimethylolpropane trivinylether, prepolymers having the formula, 
##STR8## 
low molecular weight polybutadiene having a viscosity of from 200 to 
10,000 centipoises at 25.degree. C., etc. Products resulting from the cure 
of such compositions can be used as printing inks and other applications 
typical of thermosetting resins. 
A further category of the organic materials which can be used to make the 
polymerizable compositions are cyclic ethers which are convertible to 
thermoplastics. Included by such cyclic ethers are, for example, oxetanes 
such as 3,3-bis-chloromethyloxetane, alkoxyoxetanes as shown by Schroeter 
U.S. Pat. No. 3,673,216, assigned to the same assignee as the present 
invention; oxolanes such as tetrahydrofuran, oxepanes, oxygen containing 
spiro compounds, trioxane, dioxolane, etc. 
In addition to cyclic ethers there are also included cyclic esters such as 
.alpha.-lactones, for example propiolactone, cyclic amines, such as 
1,3,3-trimethyl-azetidine and organo-silicone cyclics, for example, 
materials included by the formula, 
##STR9## 
where R" can be the same or different monovalent organic radical such as 
methyl or phenyl and m is an integer equal to 3 to 8 inclusive. An example 
of an organosilicone cyclic is hexamethyl trisiloxane, octamethyl 
tetrasiloxane, etc. The products made in accordance with the present 
invention are high molecular weight oils and gums. 
In the practice of the present invention, the heat curable compositions can 
be made by blending the cationically polymerizable material, the 
diaryliodonium salt and the copper chelate. In instances where a low 
temperature cure of the cationically polymerizable material is desired, a 
reducing agent can be utilized in combination with the diaryliodonium salt 
and copper chelate. 
Effective results have been achieved if there is employed by weight from 
0.01% to 20% of the diaryliodonium salt, based on the weight of 
diaryliodonium salt and cationically polymerizable organic material. The 
weight of the copper chelate can vary between about 0.01 to 10 parts of 
copper chelate, per part of diaryliodonium salt. In instances where the 
reducing agent is employed, there can be used from 0.05 to 20 parts of 
reducing agent per part of the diaryliodonium salt. Overall, when the 
total parts of diaryliodonium salt, copper chelate and optionally reducing 
agent are considered together as the catalyst for the cationically 
polymerizable organic material, there can be used from 1% to about 35% of 
catalyst based on the combined weight of cationically polymerizable 
material and catalyst. 
The resulting curable compositions can be in the form of a varnish having a 
viscosity of from 1 to 100,000 centipoises at 25.degree. C. or a 
free-flowing powder, depending upon the nature of the cationically 
polymerizable organic material. The curable compositions can be applied to 
a variety of substrates by conventional means and cured to the tack-free 
state within 0.5 to 20 minutes depending upon the temperature employed. 
In certain instances, an organic solvent, such as nitromethane, 
acetonitrile, can be used to facilitate the mixing of various ingredients. 
The diaryliodonium salts can be formed in situ if desired. In addition, 
the curable compositions may contain inactive ingredients, such as silica, 
talc, clay, glass fibers, extenders, hydrated alumina, carbon fibers, 
process aids, etc., in amounts of up to 500 parts of filler per 100 parts 
of cationically polymerizable organic material. The curable compositions 
can be applied to such substrates as metal, rubber, plastic, molded parts 
of films, paper, wood, glass, cloth, concrete, ceramic, etc. 
Some of the applications in which the curable compositions of the present 
invention can be used are, for example, protective, decorative and 
insulating coatings, potting compounds, printing inks, sealants, 
adhesives, molding compounds, wire insulation, textile coatings, 
laminates, impregnated tapes, varnishes, reaction injection molding, 
pultrusion, filiment winding, etc.

In order that those skilled in the art will be better able to practice the 
invention, the following examples are given by way of illustration and not 
by way of limitation. All parts are by weight. 
EXAMPLE 1 
Heat curable compositions were prepared by adding 0.5% by weight of various 
copper nitrogen chelates to a 2% by weight solution of diphenyliodonium 
hexafluoroarsenate and Epon 828 (a diglycidal ether of bisphenol-A). A 
mixture was also prepared free of the copper nitrogen chelate. The 
diphenyliodonium salt was utilized as a 50% solution in propylene 
carbonate. The heat curable compositions were placed in a forced air oven 
at 100.degree. C. to determine the time required for gelling the mixture. 
The following results were obtained: 
TABLE I 
______________________________________ 
Copper Chelate Gel Time (min) 
______________________________________ 
None &gt;165 
[(NC.sub.4 H.sub.9).sub.4 N].sub.2 CuCl.sub.4 
10 
##STR10## 10 
##STR11## 20 
______________________________________ 
The above results show that the copper nitrogen chelates of the present 
invention accelerate the cure of the epoxy resin to a surprising degree. 
EXAMPLE 2 
Example 1 was repeated, except that in place of the diphenyliodonium 
hexafluoroarsenate there was employed diphenyliodonium 
hexafluorophosphate. The following results were obtained: 
TABLE II 
______________________________________ 
Copper Chelate Gel Time (min) 
______________________________________ 
None &gt;240 
[(n-C.sub.4 H.sub.9).sub.4 N].sub.2 CuCl.sub.4 
9 
##STR12## 15 
##STR13## 32 
______________________________________ 
EXAMPLE 3 
Example 1 was repeated, except that biscycloaliphatic epoxide 
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate (ERL 4221, of 
the Union Carbide Corporation) was employed as the epoxy resin. The 
following results were obtained: 
TABLE III 
______________________________________ 
Copper Chelate Gel Time (min) 
______________________________________ 
None &gt;360 
[(n-C.sub.4 H.sub.9).sub.4 N].sub.2 CuCl.sub.4 
10 
##STR14## 10 
##STR15## 10 
______________________________________ 
EXAMPLE 4 
There was added 91 parts of the epoxy resin of Example 3, 6 parts of 50% 
solution of diphenyliodonium hexafluoroarsenate in propylene carbonate and 
3 parts of stannous octoate. The resulting mixture was vigorously stirred 
and divided into 10 part aliquots to which various copper compounds were 
added respectively in 0.1 part amounts. The resulting mixtures were then 
stirred and allowed to rest under atmospheric conditions. Table IV shows 
the gel time obtained in minutes which were obtained from each of the 
mixtures containing a particular copper compound: 
TABLE IV 
______________________________________ 
Copper Compound Gel Time (min) 
______________________________________ 
copper naphthenate 
0.8 
copper benzoate 15.5 
copper salicylate 12.4 
copper acetylacetonate 
16.4 
copper stearate 47.5 
______________________________________ 
The above results show that the effectiveness of copper chelates as redox 
catalysts as compared to copper salts. 
EXAMPLE 5 
A stock solution composed of 96 parts Epon 828 and 4 parts of a 50% 
solution of (C.sub.6 H.sub.5).sub.2 I.sup.+ AsF.sub.6.sup.- in propylene 
carbonate was prepared. To 10 ml aliquots, there was added 0.5 g (0.5 
parts) each of the copper compounds shown below. The gel times were 
measured in a forced air oven at 100.degree. C. 
______________________________________ 
Compound Cure Time (min) 
______________________________________ 
copper benzoate 28 
copper stearate 48 
copper (II) chloride &gt;70 
##STR16## 10 
______________________________________ 
The above results further show the surprising results obtained with copper 
chelates as cocatalysts as compared to copper salts. 
EXAMPLE 6 
A solution composed of 98 parts diethyleneglycol divinylether and 4 parts 
of a 50% solution of (C.sub.6 H.sub.5).sub.2 I.sup.+ PF.sub.6.sup.- in 
propylene carbonate was divided into 10 gram aliquots and the gel times at 
100.degree. C. were measured. 
______________________________________ 
Compound Cure Time (min) 
______________________________________ 
(n-Bu.sub.4 N).sub.2 CuCl.sub.4 
2.5 
##STR17## 2.5 
copper stearate 3.5 
##STR18## 5.5 
None &gt;9 
______________________________________ 
Although the above results are directed to only a few of the very many 
variables within the scope of the present invention, it should be 
understood that the present invention is directed to a much broader class 
of heat curable compositions comprising a much broader variety of 
cationically polymerizable organic materials as previously set forth in 
the specification as well as a broader variety of diaryliodonium salts and 
copper chelates. These results establish that copper chelates utilized in 
the practice of the present invention offer significant improvements over 
a variety of copper salts when utilized in combination with diaryliodonium 
salts with or without a reducing agent to effect the cure of a variety of 
cationically polymerizable organic materials.