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Description  |
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The present invention relates to epoxy resin compositions which can be
cured by exposure to radiant energy.
Epoxy resins have generally been employed in a variety of applications
requiring high performance materials. Cure of an epoxy resin can generally
be achieved by two package systems based on the incorporation into the
resin of active amine containing compounds or carboxylic acid anhydrides.
These systems require thorough mixing of the ingredients; in addition,
cure time can be several hours.
Another catalyst which can be used to cure epoxy resins as "one package"
systems is based on the employment of a Lewis Acid catalyst in the form of
an amine complex such as boron trifluoride-monoethyl amine. The Lewis Acid
is released on heating; cure takes place within 1 to 8 hours and can
require a temperature of 160.degree. C. and higher. As a result, these one
package epoxy compositions cannot be employed to coat heat sensitive
devices such as delicate electronic components. Nor can epoxy monomers
having low boiling points be used due to the resulting losses to
evaporation during cure.
As shown by Schlesinger, U.S. Pat. No. 3,703,296, certain photosensitive
aromatic diazonium salts can be employed to cure epoxy resins. When
photolyzed, these aromatic diazonium salts are capable of releasing, in
situ, a Lewis Acid catalyst which can initiate the rapid polymerization of
the epoxy resin. However, even though these one package epoxy resin
mixtures can provide fast curing compositions, a stabilizer must be used
to minimize cure in the dark during storage of these mixtures. Despite
these measures, gellation of the mixture can occur even in the absence of
light. In addition, nitrogen is released during UV-cure, which can result
in film imperfections. Diazonium salts are generally thermally unstable,
rendering the use of such materials hazardous because of the possibility
of run-away decomposition.
The present invention is based on the discovery that radiation sensitive
aromatic onium salts of Group VIa elements, such as
##STR1##
can be incorporated in epoxy resins to provide one package radiation
curable compositions which do not require a stabilizer to minimize cure at
ambient temperatures during the shelf period, and are free of all of the
aforementioned disadvantages of the aromatic diazonium salt compositions.
Included by the aromatic Group VIa onium salts which can be used to make
the curable compositions of the invention are compounds of the formula,
[(R).sub.a (R.sup.1).sub.b (R.sup.2).sub.c X] .sub.d.sup.+ [MQ.sub.e
].sup.-(e-f)
where R is a monovalent aromatic organic radical, R.sup.1 is a monovalent
organic aliphatic radical selected from alkyl, cycloalkyl and subtituted
alkyl, R.sup.2 is a polyvalent organic radical forming a heterocyclic or
fused ring structure selected from aliphatic radicals and aromatic
radicals, X is a Group VIa element selected from sulfur, selenium and
tellurium, M is a metal or metalloid, Q is a halogen radical, a is a whole
number equal to 0 to 3 inclusive, b is a whole number equal to 0 to 2
inclusive, c is a whole number equal to 0 or 1, where the sum of a + b + c
is a value equal to 3 or the valence of X,
d=e-f
f=valence of M and is an integer equal to from 2 to 7 inclusive
e is > f and is an integer having a value up to 8.
Radicals included by R are, for example, C.sub.(6-13) aromatic hydrocarbon
radicals such as phenyl, tolyl, napthyl, anthryl, and such radicals
substituted with up to 1 to 4 monovalent radicals such as C.sub.(1-8)
alkoxy, C.sub.(1-8) alkyl, nitro, chloro, hydroxy, etc.; arylacyl radicals
such as benzyl, phenylacyl, etc.; aromatic heterocyclic radicals such as
pyridyl, furfuryl, etc. R.sup.1 radicals include C.sub.(1-8) alkyl, such
as methyl, ethyl, etc., substituted alkyl such as --C.sub.2 H.sub.4
OCH.sub.3, --CH.sub.2 COOC.sub.2 H.sub.5, --CH.sub.2 COCH.sub.3, etc.
R.sup.2 radicals include such structures as:
##STR2##
Complex anions included by MQ.sub.e.sup.-(e-f) of formula I 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.=,
AlF.sub.6.sup.-3, GaCl.sub.4.sup.-, InF.sub.4.sup.-, TiF.sub.6.sup.=,
ZrF.sub.6.sup.-, etc., where M is a transition metal such as Sb, Fe, Sn,
Bi, Al, Ga, Tn, Ti, Zr, Sc, V, Cr, Mn, Cs, rare earth elements such as the
lanthanides, for example, Ce, Pr, Nd, etc., actinides, such as Th, Pa, U,
Np, etc. and metalloids such as B, P, As, etc.
Group VIa onium salts included by Formula I are, for example,
##STR3##
There is provided by the present invention curable epoxy compositions
comprising,
(A) an epoxy resin polymerizable to a higher molecular weight state
selected from epoxy monomer, epoxy prepolymer, oxirane containing organic
polymer and mixtures thereof, and
(B) an effective amount of a radiation sensitive aromatic Group VIa onium
salt capable of effecting the cure of (A) by release of a Lewis Acid
catalyst when exposed to radiant energy. Group VIa onium salts of formula
I are well known and can be made by the procedure shown in J. W. Knapczyk
and W. E. McEwen, J. Am. Chem. Soc., 91 145, (1969); A. L. Maycock and G.
A. Berchtold, J. Org. Chem. 35, No. 8, 2532 (1970); H. M. Pitt, U.S. Pat.
No. 2,807,648, E. Goethals and P. De Radzetzky, Bul. Soc. Chim. Bleg., 73
546 (1964); H. M. Leicester and F. W. Bergstrom, J. Am. Chem. Soc., 51
3587 (1929), etc.
The term "epoxy resin" as utilized in the description of the curable
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 phenol-formaldehyde resins
(Novolak resins) 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 epoxy-siloxane
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.
Plueddemann and G. Fanger, J. Am. Chem. Soc. 81 632-5 (1959). As described
in the literature, epoxy resins can also be modified in a number of
standard ways such as reactions 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; 3,563,850; 3,567,797;
3,677,995; etc. Further examples of epoxy resins which can be used are
shown in the Encyclopedia of Polymer Science and Technology, Vol. 6, 1967,
Interscience Publishers, New York, pp 209-271.
The curable compositions of the present invention can be made by blending
the epoxy resin, which hereinafter will signify epoxy monomer, epoxy
prepolymer, epoxy polymer or mixture thereof, with an effective amount of
the Group VIa onium salt or "onium salt". The resulting curable
composition which can be in the form of a varnish having a viscosity of
from 1 centipoise to 100,000 centipoises at 25.degree. C. or a free
flowing powder, can be applied to a variety of substrates by conventional
means and cured to the tackfree state within 1 second or less to 10
minutes or more.
Depending upon the compatability of the onium salt with the epoxy resin,
the Group VIa onium salt can be dissolved or dispersed therein along with
an organic solvent such as nitromethane, acetonitrile, etc., prior to its
incorporation. In instances where the epoxy resin is a solid,
incorporation of the onium salt can be achieved by dry milling or by melt
mixing the resin whereby the onium salt is incorporated.
It has been found that the onium salt also can be generated in situ in the
presence of the epoxy resin if desired. For example, an onium salt of the
formula,
(R).sub.a (R.sup.1).sub.b (R.sup.2).sub.c X.sup.+ Q'.sup.-,
where R, R.sup.1, R.sup.2, X, a, b and c are as previously defined, and Q'
is an anion such as Cl.sup.-, Br.sup.-, I.sup.-, F.sup.-, HSO.sub.4.sup.-,
NO.sub.3.sup.-, etc., can be separately or simultaneously introduced into
the epoxy resin with a Lewis Acid salt of the formula
M'[MQ]
where M' is a metal cation, such as Na.sup.+, K.sup.+, Ca.sup.++,
Mg.sup.++, Fe.sup.++, Ni.sup.++, Co.sup.++, Zn.sup.++, etc. and organic
cations such as ammonium, pyridinium, etc., and where [MQ] is defined in
formula I above.
Experience has shown that the proportion of onium salt to epoxy resin can
vary widely inasmuch as the salt is substantially inert, unless activated.
Effective results can be achieved if a proportion of from 0.1% to 15% by
weight of onium salt is employed, based on the weight of curable
composition.
The curable compositions may contain inactive ingredients such as inorganic
fillers, dyes, pigments, extenders, viscosity control agents, process
aids, UV-screens, etc. in amounts of up to 100 parts of filler per 100
parts of epoxy resin. The curable compositions can be applied to such
substrates as metal, rubber, plastic, molded parts or 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, photoresists, wire insulation, textile coatings, laminates,
impregnated tapes, printing plates, etc.
Cure of the curable composition can be achieved by activating the onium
salt to provide the release of the Lewis Acid catalyst. Activation of the
onium salt can be achieved by heating the composition at a temperature in
the range of from 150.degree. C. to 250.degree. C. Preferably cure can be
achieved by exposing the curable composition to radiant energy such as
electron beam or ultraviolet light. Electron beam cure can be effected at
an accelerator voltage of from about 100 to 1,000 KV. Cure of the
compositions is preferably achieved by the use of UV irradiation having a
wavelength of from 1849 A to 4000 A and an intensity of at least
5,000-80,000 microwatts per cm.sup.2. The lamp systems used to generate
such radiation can consist of ultraviolet lamps such as from 1 to 50
discharge lamps, for example, xenon, metallic halide, metallic arc, such
as a low, medium or high pressure mercury vapor discharge lamp, etc.
having an operating pressure of from a few millimeters to about 10
atmospheres, etc., can be employed. The lamps can include envelopes
capable of transmitting light of a wavelength of from about 1849 A to 4000
A, and preferably 2400 A to 4000 A. The lamp envelope can consist of
quartz, such as Spectrocil, or Pyrex, etc. Typical lamps which can be
employed for providing ultraviolet radiation are, for example, medium
pressure mercury arcs, such as the GE H3T7 arc and the Hanovia 450 W arc
lamp. The cures may be carried out with a combination of various lamps,
some or all of which can operate in an inert atmosphere. When using UV
lamps, the irradiation flux on the substrate can be at least 0.01 watts
per square inch to effect cure of the organic resin within 1 to 20 seconds
and permit the cure to be carried on continuously as, for example, in the
curing of epoxy-coated steel strip to be taken up at a rate of from 100 to
600 feet per minute. The strip can be cut to a predetermined width for use
as transformer laminates, etc. A combination of heat and light may be used
to cure reactive compositions. Such a combination of heat and light may
serve to reduce the overall cure time.
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
A curable composition was prepared by forming a mixture of 0.2 part of
triphenylsulfonium tetrafluoroborate dissolved in acetonitrile and 5 parts
of 4-vinyl-cyclohexene dioxide. A 2 mil film was drawn on a glass plate
and exposed to ultraviolet irradiation from a GE H3T7 lamp at a distance
of from 6 inches. The resin had cured to a hard film within 30 seconds.
The film was found to be insoluble in dipolar aprotic solvents and it
could not be scratched with a fingernail.
A portion of the above curable composition having a viscosity at 25.degree.
C. of about 6 centipoises was allowed to stand under average daylight
conditions for four months in a transparent container. It was found that
the viscosity remained substantially the same.
A portion of the curable composition was applied onto a steel strip. The
treated steel surface was eposxed 15 seconds to the ultraviolet radiation
of an H3T7 lamp at a distance of 2 inches. A clear, tack-free film was
formed which showed no signs of bubbles or other imperfections.
The above treated strip was then immersed in 10C hydrocarbon oil for 48
hours at 120.degree. C. to determine its hydrolytic stability in
accordance with IFT test ASTM D971-50 Interfacial Tension of Oil Against
Water shown on page 322 of the 1970 Annual Book of ASTM Standards, part 17
(November). The initial reading of the oil was about 39.0 dynes/cm. After
the test the oil showed an interfacial tension reading of 38. In order to
pass, a reading of at least 30 is required.
EXAMPLE 2
An 80:20 mixture of an epoxy novolak resin, an epoxy equivalent weight of
173 and 4-vinylcyclohexene dioxide was sensitized with 3% by weight of
triphenylsulfonium hexafluoroantimonate. This solution was used to
impregnate glass cloth. Two 6 in .times. 6 in squares of the cloth were
then stacked together and cured to form a laminate by irradiating the
cloth for 1 minute on each side using a GE H3T7 lamp at a distance of six
inches. The stiff laminate was integrally bonded and could be used for
circuit boards.
EXAMPLE 3
Triphenylselenonium chloride was prepared according to the procedure of H.
M. Leicester and F. W. Bergstrom, J. Am. Chem. Soc., 51 3587 (1929)
starting with diphenyl selenide. The corresponding fluoroborate,
hexafluoroarsenate and hexafluoroantimonate salts were prepared by adding
sodium hexafluoroarsenate, sodium tetrafluoroborate or potassium
hexafluoroantimonate to an aqueous solution of triphenylselenonium
chloride. The products were white crystalline solids which were dried in
vacuo.
Three percent solutions of the above salts in 4-vinylcyclohexene dioxide
were cured as 2 mil films at a distance of six inches from a GE H3T7 lamp.
The following cure times were observed:
______________________________________
Salt Cure Time
______________________________________
(C.sub.6 H.sub.5).sub.3 Se .sup.+ BF.sub.4.sup.-
10 sec.
(C.sub.6 H.sub.5).sub.3 Se .sup.+ AsF.sub.6.sup.-
5 sec.
(C.sub.6 H.sub.5).sub.3 Se .sup.+ SbF.sub.6.sup.-
3 sec.
______________________________________
EXAMPLE 4
There were added three parts phenacyl tetramethylene sulfonium
hexafluoroarsenate to a 70:30 mixture of bisphenol-A-diglycidyl ether and
4-vinylcyclohexene dioxide. The catalyzed mixture of epoxides was then
used to impregnate a 1 inch wide glass fabric tape. After winding one
layer onto a 5" .times. 2" diameter cylinder, the impregnated tape was
cured while rotating the wound cylinder under a GE H3T7 lamp. The total
exposure time to UV light was 5 minutes. At the end of this time the tape
was fully cured into the shape of a rigid cylinder. The wound cylinder
could then be used as a spool for winding wire to make transformer coils.
EXAMPLE 5
A mixture was prepared consisting of 14.5 g (0.25 mole) glycidyl allyl
ether, 10 mg t-butylcatechol, and three drops of chloroplatinic acid in
octyl alcohol. The reaction mixture was heated to 50.degree. C. in a water
bath and then 13.0 g of a polydimethyl siloxane resin containing 0.89% by
weight Si-H groups was added dropwise by means of a dropping funnel.
Immediate exothermic reaction took place with the temperature rising to
65.degree. C. Reaction proceeded smoothly at this temperature giving a
clear fluid resin.
Three parts by weight of triphenylsulfonium fluoroborate dissolved in a
small amount of acetonitrile was added to 97 parts of the above silicone
epoxy resin. A 2 mil film of the sensitized resin was drawn on a glass
plate and then exposed to UV light from a GE H3T7 lamp at a distance of
six inches. The film was tack-free within 15 to 20 seconds. A small amount
of silica was added to the sensitized resin to produce a thixotropic
mixture and the resin cured as described previously. A tough, rubbery
coating resulted. These UV cured epoxy-siloxanes are useful as sealants
and caulks.
EXAMPLE 6
There were added 3 parts S-phenyldibenzothiophenium fluoroborate to 97
parts 4-vinylcyclohexene dioxide. This mixture was spread on a glass plate
as a 2 mil film and exposed to irradiation from a GE H3T7 lamp at a
distance of six inches. One minute exposure was required to fully cure the
film to a hard, scratch resistant state.
EXAMPLE 7
A 3% solution of phenacyl tetramethylene sulfonium hexafluoroarsenate in
40:60 mixture of 4-vinylcyclohexene dioxide and an epoxy novolak having an
epoxy equivalent weight of 206 were knife coated onto a steel plate to a
thickness of 3 mil. A mask was placed over the film and the entire
assembly irradiated for 1 minute. The mask was removed and the film was
washed with i-propanol. The unexposed portions of the film were washed
away having a clear sharp negative image of the mask.
EXAMPLE 8
There were added 6 parts of a 50% aqueous solution of triphenylsulfonium
chloride and 2.1 parts of NaAsF.sub.6 to 97 parts of an 80:20 mixture of
bisphenol-A-diglycidyl ether and 4-vinylcyclohexene dioxide. The reaction
mixture was agitated by stirring for one-half hour and then allowed to
settle. An aliquot of the resin was taken and spread onto a glass plate
using a draw knife with a 3 ml aperture. A tack-free film formed within 15
seconds after exposure to an H3T7 lamp at a distance of six inches. The
film was hard and clear.
Resistors were potted in the above resin by dipping the resistor into the
sensitized resin and then curing it by rotating the resistor for 30
seconds beneath the ultraviolet lamp.
EXAMPLE 9
An equimolar mixture of diphenyliodonium fluoroborate and thioxanthene was
heated at 200.degree. C. for 3 hours. After recrystallization from
methylene chloride-diethyl ether, there was obtained an 80% yield of
product having a.m.p. of 168.degree.-169.degree. C. Based on method of
preparation the product was S-phenylthioxanthene fluoroborate. A hard
clear scratch resistant 1 mil coating was obtained, when a 3% solution of
the above onium compound in limonene dioxide was knife coated onto a
polystyrene sheet and exposed to UV irradiation from a 450 W Hanovia
medium pressure mercury arc at a distance of 3 inches.
EXAMPLE 10
There were added 2.6 parts phenacyltetramethylene sulfonium bromide to a
mixture of 95 parts of 4-vinylcyclohexene dioxide containing 2.2 parts of
NaAsF.sub.6. The solution was placed in a dark bottle and rolled on a ball
mill for 8 hours. After the salts were removed by filtration, the solution
was coated onto a 3 in .times. 6 in steel panel and cured as in Example 1.
A hard coating was obtained after 15 seconds exposure which could not be
removed by rubbing the coating with acetone.
EXAMPLE 11
There were dissolved two parts of triphenylsulfonium hexafluoroantimonate
into a 40:60 mixture of dicyclopentadiene dioxide and glycidyl acrylate.
Following the procedure of example 1, a hard crosslinked 1 mil coating was
obtained after a 15 second exposure to ultraviolet light.
EXAMPLE 12
There were added four parts of triphenylsulfonium hexafluoroarsenate to 100
parts of a blend of equal parts of 4-vinylcyclohexene dioxide and
(3,4-epoxycyclohexyl)methyl-3,4-epoxycyclohexanecarboxylate. An aliquot of
the resulting sensitized resin was spread onto a polycarbonate sheet using
a draw-down blade to give a 0.5 mil film. The film was cured as described
in Example 1 for 10 seconds resulting in a clear hard mar resistant and
solvent resistant coating.
EXAMPLE 13
A mixture of 50 parts bispheol-A-diglycidyl ether and 50 parts
(3,4-epoxycyclohexyl)methyl-3,4-epoxycyclohexanecarboxylate was stirred
until homogeneous. There was then added 3 arts of triphenylsulfonium
hexafluoroantimonate to the solution. It was mixed until the sensitizer
had dissolved. A portion of the above solution was coated onto a steel
plate using a 0.2 mil drawbar. The plate was then exposed to a GE H3T7
lamp at a distance of six inches for 5 seconds. A hard cured adherent film
formed on the steel.
EXAMPLE 14
A blend of epoxy resins consisting of 50 parts 4-vinylcyclohexene dioxide,
40 parts of novolak-epoxy resin having an epoxy equivalent weight of
172-178 and 10 parts n-octylglycidyl ether were thoroughly mixed together.
A 100 part aliquot was removed to which was added 1 part of
triphenylsulfonium hexafluoroarsenate. The resulting mixture was stirred
until the onium salt had dissolved. When the above mixture was coated onto
a 3 in .times. 6 in steel panel and exposed to a 450 watt medium pressure
mercury arc lamp at a distance of 3 inches, a glossy, dry coating was
obtained in 2 seconds. The coating withstood attack by hot boiling water
for four hours. It could not be removed by rubbing with acetone.
EXAMPLE 15
There was added 10 parts of a solid multifunctional aromatic glycidyl ether
having an epoxy equivalent weight of 210-240 to 40 parts of limonene
dioxide. The mixture was combined with 1 part of phenacyltetramethylene
sulfonium hexafluoroarsenate and stirred at 50.degree. C. for 0.5 hour to
produce a homogeneous solution. When the mixture was coated onto glass
using a 0.5 mil drawbar, and irradiated for 5 seconds at a distance of 3
inches from a GE H3T7 mercury arc lamp having an intensity of 200
watts/sq. inch., a hard cured film was produced.
EXAMPLE 16
There was added 0.2 part of triphenylsulfonium hexafluoroantimonate in 2
parts of 4-vinylcyclohexene dioxide to 10 parts of an epoxidized butadiene
resin. After mixing the components thoroughly, the mixture was applied to
a one-sixteenth inch thick glass plate to a 1 mil thickness. Another plate
of glass was placed on top of the first and the assembly was exposed to a
GE H3T7 medium pressure mercury arc lamp having an intensity of 200
watts/sq. inch at a distance of three inches. The total exposure time was
30 seconds. The glass plates were permanently bonded together. Based on
characteristics of the glass laminate, a similar procedure can be used to
make a shatterproof windshield for automobiles.
EXAMPLE 17
There were added with stirring 89 parts of aluminum chloride in small
portions to a solution of 122 parts of 2,6-xylenol in 505.12 parts of
carbon disulfide maintained at 10.degree. C. To the resulting greenish
solution were added 79.5 parts of thionyl chloride in a dropwise fashion
maintaining the temperature between 10 and 15.degree. C. A black
precipitate and solution was obtained which was stirred for an additional
2 hours and then poured onto 1000 parts of ice containing about 50 parts
of concentrated HCl. This mixture was placed on a steam bath to remove
CS.sub.2 and to decompose the complex. A tan solid was obtained which was
filtered, washed with water and dried.
To a solution of 21.5 parts of the above crude product in about 117 parts
of hot absolute ethanol were added 11.4 parts of KAsF.sub.6 and 10 parts
of water. The reaction mixture was stirred and more water was added to
effect the precipitation of product. The product was filtered, washed with
water and dried. A material was obtained having a m.p. of
245.degree.-251.degree. C. Based on method of preparation and elemental
analysis for C.sub.24 H.sub.27 O.sub.3 SAsF.sub.6. Calc: % C, 49.3; % H,
4.62; % S, 5.48. Found: % C, 49.4; % H, 4.59; % S, 5.55, the product was
tris-3,5-dimethyl-4-hydroxyphenyl sulfonium hexafluoroarsenate.
A three percent solution of the above onium salt was made with
4-vinylcyclohexene dioxide. Cure of the solution was effected by
irradiating a 2 mil film on glass according to the procedure described in
Example 3. A hard mar-resistant coating was obtained after 5 seconds of
irradiation.
EXAMPLE 18
Three parts of triphenylsulfonium hexafluoroantimonate were ground to a
fine powder. The powder was intimately mixed with 97 parts Reichhold
Epotuf.RTM. 37-834 powder coating resin by tumbling these together for 30
minutes. The powder was then electrostatically sprayed onto 3 in .times. 6
in steel panels to form approximately a 2 mil coating using a GEMA model
171 spray gun. Subsequently, the samples were heated briefly to
150.degree. C. to fuse the powder and then exposed while hot to a GE H3T7
medium pressure mercury arc lamp at a distance of 3 inches. Cured samples
were obtained after a 15 second irradiation. The cured films were adherent
and mar resistant.
EXAMPLE 19
Triphenacyl hexafluoroarsenate was added to a mixture of 67% by weight of a
novolak-epoxy resin having an epoxy equivalent weight of 172-178, 33%
4-vinylcyclohexene dioxide and 0.5% of a surface active agent. The
resulting mixture contained about 1% by weight of the onium salt. A
coating was applied as a 0.1 mil film to 3 in .times. 6 in steel plates
and cured for 20 seconds at a distance of 4 inches from a GE H3T7 medium
pressure mercury arc lamp. Some panels were subsequently immersed for 5
hours at room temperature in methylene chloride. Other panels were
immersed for 4 hours in acetone. In all cases, no visible signs of solvent
attack of the coatings were observed. The same were then baked for 1 hour
at 160.degree. C. Tests were run separately in boiling 50% KOH solution
for 30 minutes and in boiling distilled water for 4 hours. Again, no
visible degradation of the coatings was observed.
EXAMPLE 20
Mixtures of triphenylsulfonium hexafluoroarsenate in 4-vinylcyclohexene
dioxide having a concentration of 0 to 10% onium salt, were thermally aged
at 25.degree. C. and 55.degree. C. The viscosities of the mixtures were
measured over a two-week period (336 hrs.). The following results were
recorded at 25.degree. C.:
______________________________________
Viscosity Viscosity at
Concentration (%)
Start (cps) 336 hr (cps)
______________________________________
0 6.06 6.06
1 6.26 6.34
3 6.90 6.90
5 7.65 7.59
10 9.80 9.71
______________________________________
at 55.degree. C.:
______________________________________
Viscosity Viscosity at
Concentration (%)
Start (cps) 336 hr (cps)
______________________________________
0 6.06 6.06
1 6.42 6.37
3 6.91 6.93
5 7.65 7.67
10 9.75 9.71
______________________________________
Within experimental error, the above results show that there is essentially
no viscosity change over the period the sensitizer was tested at a
temperature range of 25.degree. C. to 55.degree. C.
Although the above samples are limited to only a few of the very many
curable compositions and uses thereof which are included within the scope
of the present invention, it should be understood that the present
invention is intended to cover a much broader class of curable
compositions and uses thereof. Those skilled in the art would also know
that the curable compositions also cover the use of onium polymers
containing Group VIa onium functionality as part of the polymer backbone
or in the pendant position.
* * * * *
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