Note: Descriptions are shown in the official language in which they were submitted.
~ 181 RD 11,717
The present invention relates to certain
triarylsulfonium salts having chemically combined sulfur
or oxygen containing monovalent polyaryl radicals and
photocurable compositions containing such triarylsulfonium
salts.
Prior to the present invention, as shown by
Crivello in U.S. Patent No. 4,058,401 issued November 15, 1977,
U.S. Patent No. 4,069,055 issued January 17, 1978 and
U.S. Patent No. 4,161,478 issued July 17, 1979, epoxy resins
and other cationically polymerizable organic materials were
rapidly cured under ultraviolet light with various
aryl sulfonium salts. Although valuable results were
achieved by the use of such photocurable compositions
and photoinitiators, the cure of the cationically poly-
merizable organic material to a tack-free state was
generally effective only to a thickness of up to about
10-15 mils within a period of up to about 60 seconds.
Experience has shown that in certain applications, such as
for use in encapsulation of electronic components, or
for use in protective coatings, deep section curing of
various cationically polymerizable organic materials, that
is, a cure of at least 20 mils, is often required. As
a result, the use of triarylsulfonium salt photoinitiators
has been somewhat restricted.
The present invention is based on the discovery
that photoinitiators having the formula
~k .
112~181 RD 11, 717
(1) [(R)a (Rl)b (R )C S] [Y]
have been found effective for the deep section cure of a
wide variety of cationically polymerizable organic materials,
such as epoxy resins, phenolformaldehyde resins, vinyl ethers,
episulfides, cyclic amines, etc., under either ultraviolet light
or visible light when used in combination with certain organic
sensitizers as described hereinafter, where R in formula (1)
is a monovalent organic radical having the formula
R3 (X)~ 4 -
\ ( Z ~ /
Rl is a monovalent C(6 13) aromatic radical, R is a divalent
C(6 20) aromatic radical, R3 is a monovalent or divalent C(6 13
aromatic radical, R4 is a divalent or trivalent C(6 13)
aromatic radical, X is -S- or -0-, Y is a non-nucleophilic
anion defined more particularly below, Z is a divalent radical
selected from
0 0
R " " e
-N-, -0-, -S-, -S-, -S- and --~CH2 ~ , and R iS a C(1-13)
organic radical, a is an integer equal to 1 to 3 inclusive, b
is an integer equal to 0 to 2 inclusive, c is an integer equal
to 0 or 1, and the sum of a + b + 2c is equal to 3, d i8 equal
to 0 when R3 is monovalent and R4 is divalent, and d is equal
to 1 when R3 is divalent and R4 is trivalent, and e is an integer
equal to 1 to 4 inclusive. In addition, it has been found
that the cure of the aforementioned cationically polymerizable
organic materials is substantially faster when utilizing the
l~Z0~8~ RD 11,717
photoinitiators of formula (1) as compared to the
photoinitiators of the prior art.
Some of the non-nucleophilic anions shown by Y
of formula (1) are, for example, MQn, where M is a metal or
metalloid, Q is a halogen radical and n has a value of 4-6
inclusive, where MQn is preferably MF6, such as PF6 , SbF6-
and AsF6 . In addition, Y also can include perchlorate,
CF3SO3 , C6H4SO3 , Cl , Br , F , I , nitrate, phosphate,
CF3CO2 , FPO4 , etc.
There is provided by the present invention
photocurable compositions comprising
(A) a cationically polymerizable organic material
and
(B) an effective amount of photoinitiator of
formula (1).
Radicals included by R of formula (1) are, for
example,
<~S~ , ~0~,
~ O~ , etc-,
derivatives of such radicals, substituted with 1-4, C(l 8)
alkyl, or alkoxy radicals, such as the corresponding methyl,
methoxy, ethyl, propyl, butoxy, etc., halogen radicals, for
example, chlorine, bromine or fluorine, etc. Radicals
included within R are more particularly phenyl, tolyl,
xylyl, naphthyl, anthryl. Radicals included by R are, for
example,
l~ZO18~ RD 11,717
~Z~
where Z is as previously defined.
Included by the triarylsulfonium salts of
formula (1), are compounds having the formula,
_ __ _ ,
112~181 RD 11, 717
.+~ ~ +~ _ '
PF6, 5 5 A5F6
S AsF6 , ~52~ S AsF6
SbF6 ' ~5{~5~5
~> _ ' +~)
<~5~ 5l?6~- ~5 SbF6
~; ~'$
O----~ S AsF6 ~ (~ ~ 5 PF6
RD 11,717
~ PF6 , etc-
The triarylsulfonium salts of formula (1) can
be made by procedures related to methods shown in our U.S.
Patent No. 4,238,619 issued December 9, 1980 and assigned
to the same assignee as the present invention. A diaryl-
thioether can be reacted with a diaryliodonium salt in
the presence of a copper (II) catalyst as shown by the
following
R S R + [(R )2 I ] [MQn ] ( )> [(R)2 R S ] [MQn ]
where R, Rl, M, Q and n are as previously defined. An
additional method is based on the use of AlC13. U.S.
Patent No. 2,807,648 issued September 24, 1957 to Pitt
shows a direct Friedel Crafts condensation of an aromatic
hydrocarbon using AlC13. A method which can be used to
make some of the photoinitiators of formula (1) is based
on the use of sulfur monochloride and chlorine as follows:
4 ~ + 2S2C12 + 2C1 3~ ~ ~ - ~ Cl + 5HCl.
~OJ
The above triarylsulfonium salt can be converted t~~'the
preferred photoinitiators of formula (1) where Y is MQ or
MF6 by a metathesis using an alkali metal MQn or MF6 salts
` l~Z0~81 RD 11,717
such as KMQn, KMF6~ NaMF6~ etc.
Organic polymerizable materials which can be
utiliæed in the photocurable compositions of the present
invention include epoxy resins such as monomeric, dimeric or
oligomeric of polymeric epoxy materials containing one or a
plurality of epoxy functional groups. For example, those
resins which result from the reaction of bisphenol-A
t4,4'-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. Epoxysiloxane resins and method for making
are more particularly shown by E. P. Plueddemann 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. PatenLs Nos.
2,935,488 - issued May 3, 1960 - Phillips et al; 3,235,620 -
issued February 15, 1966 - Phillips et al; 3,369,055 - issued
llZ0181
RD 11,717
February 13, 1968 - Salyer et al; 3,379,653 - issued
April 23, 1968 - Ernst et al; 3,398,211 - issued August 20,
1968 - Ramos; 3,403,199 - issued September 24, 1968 - Ramos;
3,563,840 - issued February 16, 1971 - Stine; 3,567,797 -
issued March 2, 1971 - Mango et al; 3,677,995 - issued
July 18, 1972 - Earing; 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 resins, etc.
In addition, there can be used melamine thiourea
resins, melamine, or urea aldehyde resins, cresol-formaldehyde
resins and combinations with other carboxy, hydroxyl, 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, CH2=CH-O-(CH2-CH2O)n,-CH=CH2,
where n' is a positive integer having a value up to about
lOOQ or higher, multi-functional vinylethers, such as
1,2,3-propane trivinylether, trimethylolpropane
trivinylether, prepolymers having the formula,
~ CH~ , and
n
CH=CH 2
11~181 RD 11,717
low molecular weight polybutadiene having a viscosity of from
200 to lO,nO0 centipoises at 25C, 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
U.S. Patent No. 3,673,216 - issued June 27, 1972 - Schroeter,
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 - lactones, for example, propiolactone,
cyclic amines, such as 1, 3, 3-trimethyl-azetidine and
A organosilicon~cyclics, for example, materials included by the
formula,
4 R"Si
m
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.
The photocurable compositions of the present
invention can be made by blending the cationically polymerizable
organic material with an effective amount such as from 0.1%
to 15~ by weight of the photocurable composition of the
triarylsulfonium salt of formula (1~.
~12018~
RV 11,717
In certain instances, an organic solvent, such as
acetone, nitromethane and 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 insulations, textile coatings,
laminates, impregnated tapes, varnishes, 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
A mixture of 19.6 parts of 86% potassium
hydroxide, 33 parts of thiophenol and about 120 parts of
dimethylacetamide was heated at a temperature of 120C with
stirring to effect the removal of water. After about 6.5
parts of water was collected, there was added to the resulting
mixture 26.3 parts of para-dibromobenzene and the mixture was
heated to reflux. After 6 hours at reflux the reaction
mixture was allowed to cool and 300 parts of water was added.
There was obtained a tan colored solid which was filtered
-- 10 --
~ 81 RD 11,717
and washed with water several times. The product wa~ then
dried. There was obtained 34.7 parts of 1,
4-dithiophenoxybenzene based on method of preparation.
A mixture of 7.35 parts of the above disulfide,
11.75 parts of diphenyliodonium hexafluoroarsenate and 0.2
part of copper benzoate was heated for 3 hours at 120C.
The resulting reaction mixture was washed several times with
about 50 part portions of diethylether and the remaining solid
was recrystalized from 95% ethanol. There was obtained a 45%
yield of a very light tan crystalline product having a melting
point of 69-75 and the following elemental analysis:
Calculated %C, 51.3; %H, 3.50; %S, 11.43. Found %C, 51.21;
%H, 3.59; %S, 11.37. Based on method of preparation there
was obtained a triarylsulfonium salt having the formula,
~S~S AsF6
A 3~ solution of the above photoinitiator was
prepared in 4-vinylcyclohexene dioxide. A similar solution
was prepared for triphenylsulfonium hexafluoroarsenate.
The respective solutions were then measured for tack-free time
using a GE H3T7 mercury arc lamp at a distance of 6 inches
from the substrate which consisted of the respective epoxy
formulas applied as a 1 mil film onto a glass slide. The
photoinitiator of the present invention had a tack-free time
of less than 1 second while the triphenylsulfonium
hexafluoroarsenate mixture had a tack-free time of about
5 seconds.
EXAMPLE 2
Chlorine was introduced into a mixture of 37.2
~ RD 11,717
parts of dipllenylsulfide and 13.34 parts of aluminum
chloride to a total of 9.5 parts of chlorine was added with
stirring. The reaction mixture was poured onto 500 parts of
ice to effect the decomposition of the aluminum chloride
complex. There was obtained a white semi-solid which was
washed twice with 200 part portions of hot water. There was
then added to the resulting washed residue, 27.8 parts of
potassium hexafluoroarsenate and 500 parts of hot water and
the mixture was stirred at a temperature of 30C for 1 hour.
There was obtained an orange oil which separated and which
was recovered by decanting the aqueous solution. It was
purified by washing with water several times and finally with
anhydrous ethyl ether. The resulting product was then dried
under reduced pressure at 60C for 16 hours. The product was
then recrystallized from 95% ethanol. There was obtained a
31% yield of a triarylsulfonium salt having a melting point of
77-87C. Based on method of preparation, the salt had the
following formula:
~ S ~}-St' AsF6
EXAMpLE 3
-
Three percent solutions were prepared consisting of
3, 4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexanecarboxylate
and triphenylsulfonium hexafluoroarsenate (Prior art~ and the
photoinitiator of the present invention as shown by Example 2.
Films of increasing thickness were drawn onto glass plates
and cured for one minute using a G.E. H3T7 medium pressure
mercury arc lamp at a distance of 6 inches from the films.
The thickest film which could be cured down to the glass to a
- 12 -
~ 181 RD 11,717
non-tacky state using the aforementioned photoinitiators is
shown as follows:
Photoinitiator Max. Thickness
Prior Art 10-15 mils
Example 2 50 mils
The above results show that the photocurable
compositions of the present invention containing a photo-
initiator within the scope of formula (1) cured to a thickness
more than 4 times that of the photocurable composition of
the prior art.
EXAMPLE 4
Additional photocurable compositions were prepared
utilizing the photoinitiators of Example 2 and cyclohexene
oxide as a cationic polymerizable organic material. The
solution contained 0.021 mols of photoinitiator per liter of
cyclohexene oxide. Aliquots of these photocurable mixtures
(3 ml) were irradiated under sealed conditions using a
Hano~ia 450 medium pressure mercury arc lamp. The aliquots
were withdrawn periodically, quenched at various times and the
polymer isolated by precipitation in methanol. The resulting
photocured products were recovered by filtering and drying the
polymer overnight at 60 C in vacuo. The polymer was weighed
to determine the percent conversion. The following table
shows the results obtained, where the values are expressed in
percent conversion:
- TABLE II
Irradiation Photoinit. Photoinit.
Time (prior art) (Example 2)
0.5 8 32
30 1 min. 14 41
2 min. 18 49
4 min. 34 64
- 13 -
~1~0~8~ RD 11,717
table II cont'd.
6 min. 49 69
8 min. 55 77
EXAMPLE 5
The procedure of example 4 was repeated except
that in place of the cyclohexene oxide there was utilized
2-chloroethylvinylether. Four ml aliquots of the mixture
were irradiated in accordance with the procedure of Example
4 to provide the following percent conversion values:
TABLE III
Irradiation Photoinit. Photoinit.
Time (prior art) (Example 2
15 sec. 0 17
30 sec. 0 43
60 sec. 0 87
300 sec. 0 87
2100 sec. 2 87
The above results sho~ that the photoinitiators
of the present invention are superior to the photoinitiator
of the prior art.
EXAMPLE 6
The procedure of Example 4 was repeated except
that in the place of the cyclohexene oxide there was utilized
trioxane and methylene chloride. Solutions were prepared
containing 1.386 x lO lmol of trioxane and 1.386 x 10 4mol
of photoin~tiator. The mixtures were then irradiated in
accordance with the procedure of Example 5 resulting in the
following percent conversion values.
- 14 -
1~8~ RD 11,717
TABLE IV
Irradiation Photoinit. Photoinit.
Time (prior art) (Example 2)
30 sec. 9
60 sec. 0 86
120 sec. 0 78
240 sec. 60 85
EXAMPLE 7
One percent solutions were prepared consisting of
diethyleneglycol divinyl ether and triphenylsulfonium
hexafluoroarsenate and the photoinitiator of the present
invention as shown by Example 2. Ten grams of each of the
above mixtures were poured into identical 2 in. diameter cups
and irradiated for 5 seconds at a distance of 23 cm from a
GE H3T7 medium pressure mercury arc lamp. The solid polymer
was remoyed from the cups, washed with acetone to remove
unreacted divinyl ether and then dried. The respective weights
of the dry polymers were proportional to the thickness of cure
in the samples.
Photoinitiator Weight (grams~
Prior Art 0.89
Example 2 2.33
The above results show that the photocurable
compositions of the present invention containing a
photoinitiator within the scope of formula (l) cured to a
thickness of more than 2.6 times that of the prior art. On a
molar basis, the compounds of the present invention were 3.2
times more efficient than the prior art.
EXAMPLE 8
Two percent solutions were prepared consisting of
Methylon 75201, a phenol-formaldehyde resol of the formula,
- 15 -
~lZ0~8~
RD 11,717
O-CH2-CH=CH O-CH -CH=CH2
HOH2C ~ CH2 ~CH20H
CH20H CH20H
and triphenylsulfonium hexafluoroarsenate (prior art) and
the photoinitiator of the present invention as shown by
Example 2. The two solutions were spread as 3 mil films
onto glass plates and exposed to W light at a distance of
6 inches from a GE H3T7 mercury arc lamp. The resin film
containing the photoinitiator of the present invention
re~uired 1.5 minutes to become tack-free whereas the film
containing the photoinitiator of the prior art requixed
5.5 minutes irradiation under the same conditions.
EXAMPLE 9
The previous example was repeated except the
phenolformaldehyde was replaced with a silicone resin having
the following formula,
(CH30)3Si-CH2-CH ~
After 10 seconds irradiation, the sample containing the
photoinitiator of Example 2 was tack-free and could not
be removed by rubbing with acetone. On the other hand,
the sample containing the triphenylsulfonium salt was soft
and readily removed by acetone.
EXAMPLE 10
The above example was repeated in which the resin
employed had the following molecular structure: (A-187
Union Carbide Corp.)
/\
CH2-cH-cH2-o-cH2-cH2-cH2-si(OcH3)3
- 16 -
`` ~120181
RD 11,717
Seventy-five seconds irradiation were necessary to produce
a tack-free 3 mil film using the photoinitiator of the
prior art, while only 30 seconds were required to give a
tack-free film with the photoinitiator of the present
invention.
EXAMPLE 11
Three percent solutions in cycloaliphatic epoxy
resin ERL 4221 of photoinitiators of the formulas,
~ 6 5~3 PF6- and ~ S ~ S+ pF6
were applied onto glass substrates and cured in accordance
with Example 7. After washing the resulting cured films
with acetone and allowing them to dry the films were weighed.
The photoinitiator of the present invention was found to
provide a film twice as thick as that of the prior art.
EXAMPLE 12
A three percent solution of the photoinitiator of
Example 2 in 3, 4-epoxycyclohexylmethyl-3', 4'-
epoxycyclohexane carboxylate was prepared. The sample was
divided into equal portions and Q.5% by weight perylene was
added to one of the solutions. The samples were exposed to
visible light from a GE H3T7 lamp fitted with a filter to
remove all ultraviolet light at wavelengths below 390 nm.
The sample containing the perylene dye sensitizer cured
within 30 seconds, while the sample free of dye remained
uncured even after 5 minutes irradiation. This example
demonstrates the use of dye sensitizers in combination with
the photoinitiators of the present invention to provide
visible light curable compositions.
- 17 -
- ~lZ0~8~
RD 11,717
EXAMPLE 13
A mixture was stirred for 18 hours at room
temperature consisting of 11.2 parts (0.02 mole) of diphenyl-
4-thiophenoxyphenyl sulfonium hexafluoroarsenate, 20 parts
o glacial acetic acid, and about 4 parts of 30% hydrogen
peroxide. The mixture was then poured into 200 parts of
distilled water. A crude product was obtained which was
washed with water and then with anhydrous ethyl ether.
Based on elemental analysis, spectroscopic analysis and
method of preparation, the product had the following
structure:
~ SO~ S AsF6
A three percent solution of the above photoinitiator in
4-vinylcyclohexene dioxide cured to a tack-free film when
irradiated with a GE H3T7 lamp at a distance of 10 inches.
EXAMPLE 14
There was added 11.2 parts (0.02 mole~ of the
sulfonium salt of Example 2 in about 15 parts of acetone.
There was then added, 2 parts of 30% hydrogen peroxide,
slowly with cooling. The solution was allowed to stir
overnight and then poured into 200 parts of water. An oil
was obtained which solidified on washing with water followed
by anhydrous ethyl ether. The product which was obtained
after drying overnight in vacuo had a melting point of 70-74F
and by elemental analysis, and spectroscopic analysis as
well as by method of preparation had the following
structure:
- 18 -
~ ~Oifl~ RD 11,717
~ 3--SO ~ S+ AsF6
~>
A three percent solution of the above photoinitiator in
4-vinyl-cyclohexene dioxide cured as a film as described
in the previous example had a tack-free time of seconds.
Although the above examples are directed to only
a few of the very many variables which can be used in the
practice of the present invention, it should be understood
that the present invention is broadly directed to W curable
compositions, certain triarylsulfonium salts included within
formula (1) and methods or making such materials. As
utilized in the definition of the present invention, the
expression "effective amount" when applied to the
triarylsulfonium salt is that amount required for cure of the
organic material. It has been found 0~1% to 15% by weight
of triarylsulfonium salt, based on the weight of
photocurable composition can be used.
- 13 -
