Note: Descriptions are shown in the official language in which they were submitted.
F.N. 911,515
i291760
~_.
This invention relates to photopolymerizable
compositions. More particularly, this invention relates
to compositions which comprise an organic, cationically
polymerizable material and an aromatic iodonium complex
salt as photoinitiator and which can be cured by expo-
sure to actinic radiation or electron beam irradiation.
Although photopolymerizable epoxy compositions
comprising epoxy resin materials and photosensitizers
have been desired for some time, those which have pre-
viously been proposed suffer from one or more drawbacks.Thus, in U.S. Patent 3,074,869 there are disclosed photo-
sensitive epoxy composition~ containing a nitrosoamine as
photosensitizer. Compositions of this type require
relatively long exposure to a high intensity light source
to produce complete polymerization.
In U.S. Patents 3,205,157 and 3,708,296, there
are disclosed photosensitive epoxy compositions contain-
ing respectively aryldiazonium salts and aryldiazonium
salts of halogen-containing complex anions. Such composi-
tions have limited usefulness because they have poorthermal stabllity, because their spectral response is
limited to the ultraviolet region of the spectrum, and
because nitrogen is evolved during photopolymerization
causing pinholes and bubbles in heavy coatings of the
composition.
~: ff
1~91760
When these known aryldiazonium salts are used to
induce polymerization of oxetanes, or mixtures of
oxetanes with epoxy resins, e.g., as described in U.S.
Patent 3,835,003, the same types of problems are encoun-
5 tered. Although several patents describe various tech-
niques for stabilizing mixtures of diazonium salts and
epoxides, such techniques are not satisfactory for several
reasons. For example, the increase in stability which
is obtained is measured only in days. Also, the addition
of stabilizers contaminates the compositions with non-
reactive material which softens the resulting product
and also reduces the rate of photocure. See, e.g., U.S.
Patents 3,711,390; 3,711,931; 3,816,278; 3,816,280;
3,816,281; 3,817,850; and 3,817,845.
In U.S. Patent 3,450,613 there is described
another photopolymerizable epoxy composition comprising
the reaction product of an epoxy resin prepolymer and an
ethylenically unsaturated organic acid, a photosensitizer,
and optionally polyfunctional acids or bases. This compo-
20 sition on exposure to ultraviolet light gels by reason
of the photoinduced polymerization of the ethylenically
unsaturated portion of the reaction product. Completion
of the cure of the composition is effected by heating to
bring about reaction of the epoxy resin portlon of the
25 composition. Such compositions as this have limited
usefulness because of the requirement of both light
and heat to effect complete polymerization of the
composition. The composition furthermore is oxygen
sensitive and has poor thermal stability.
- 2 -
:
l~J91760
The present invention provides novel photopoly-
merizable compositions, comprising cationically poly-
merizable materials and a photoinitiator, which are
sensitive throughout the ultraviolet and visible spectral
regions, i.e., wavelengths from about 300 to 700 milli-
microns, and which may be photocured by exposure for
relatively short periods of time to radlation within this
range of wavelengths or by exposure to electron beam
irradiation. The invention also provides novel complex
salt photoinitiators.
In accordance with the present invention there
are provided photopolymerizable compositions which are
readily photocured by exposure to actinic radiation or
electron beam comprising an organlc material which is
cationically polymerlzable and certain photosensitive
aromatic iodonium comple~ salts as photoinitiator and,
optionally, a sensitizer for said photoinitiator. The
photopolymerizable compositions of the invention are
sensitive throughout the ultraviolet and visible
spectral regions and photocure rapdily, without use of
heat, to polymers having desirable properties. For example,
the epoxy compositions cure to polymers which possess in-
herent superior toughness; abrasion resistance; adhesion
to metal, glass, plastic, wood and other sur~aces; and
resistance to chemical attack. The compositions of the
invention are one-part, stable compositions haYing very
good shelf life and good thermal stability. Consequently,
the compositions can be used under conditions o~ high
temperature. Mixtures o~ oxetanes, vlnyl ethers or lactones
1~91~0
60557-1980
with epoxy-containinq materials make p~otopolymerizable compo-
sitions having very desirable properties which can be varied,
as desired, to fit any particular application.
According to one aspect of the present invention
there is provided a photopolymerizable composition comprising:
(a) an organic material which is cationically polymerizable;
and (b) about 0.5 to 30 parts by weight, per 100 parts by
weight of said organic material, of an aromatic iodonium com-
plex ~alt photoinitiator of the formula
~ 1 X-
Ar2
wherein Arl and Ar2 are aromatic groups having 4 to 20 carbon
atoms and are selected from the group consisting of phenyl,
thienyl, furanyl, and pyrazol-4-yl groups; Z is selected from
the group ccnsisting of an oxygen atom; a sulfur atom: I=
C=0: 0=S-0; R-N where R is hydrogen, lower alkyl or acyl; a
carbon-to-carbon bond; or Rl-C-R2 where Rl and R2 are selected
from the group consisting of hydrogen, an alkyl radical having
1 to 4 carbon atoms, and an alkenyl radical having 2 to 4
carbon atom~; and n is zero or 1~ such that when n is zero
there i8 no bond between Arl and Ar2: and X~ i8 a halogen-
containing complex anion selected from the group consisting of
~: tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate,
hexachloroantimonate and hexafluoroantimonate.
; According to another aspect of the present invention
there is provided a photopolymerizable compo~ition comprising
an admixture of: (a) 80 to 100 parts by weight of diglycidyl
ether of Bisphenol A, (b) up to 20 parts by weight of a phenyl
- 4 -
~91'76(~
60557-1980
glycidyl ether, (c) up to 10 parts by weight of a solvent
carrier, (d) up to about 1 part by weight of a sensitizing dye,
(e) 0.5 to 20 parts by weight of an aromatic iodonium complex
salt photoinitiator of the formula
( Z ) n = r X~
wherein Arl and Ar2 are aromatic groups having 4 to 20 carbon
atoms and are selected from the group consisting of phenyl,
thienyl, furanyl, and pyrazol-4-yl groups; z is selected from
the group consisting of an oxygen atom; a sulfur atom; S=0;
C=0; 0=S=0; R-N where R is hydrogen, lower alkyl or acyl; a
carbon-to-carbon bond; or Rl-C-R2 where Rl and R2 are ~elected
from the group consisting of hydrogen, an alkyl radica~l having
1 to 4 carbon atoms; and n is zero or 1, such that when n is
zero there is no bond between Arl and Ar2; and X~ is a halogen-
containing aomplex anion selected from the group consisting of
tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate,
hexachloroantimonate and hexafluoroantimonate.
According to a ~urther aspect of the present inven-
tion there is provided a process for bonding a radiation-
transparent substrate to a second substrate comprising:
;~ ~a) disposing a l.ayer of the composition of claim 1 between
said substrates and in contact therewith; and (b) exposing said
layer to actinic radiation or electron beam irradiation through
said radiation-transparent substrate in an amount and for a
time sufficient to render ~aid layer insoluble.
'
- 4a -
~91760 60S57-1980
According to another aspect of the pre~ent invention
there i~ pxovided an aromatic iodonium complex ~alt o~ the
~ormula
~ )n = ~ X~
wherein Arl and Ar2 are aromatic group~ havin~ 4 to 20 carbon
atoms and are selected fro~ the group con~i~ting o~ phenyl,
thienyl, furanyl, and pyrazol-4-yl group~; Z i8 ~elected from
the group consisting of an oxygen a~o~; a sul~ur ato~ O;
I~; osl~o; R-l where R i~ hydrogen, lower alk~l or acyl; a
carbon-to-carbon bond; or Rl-l-R2 where Rl and R2 are selected
from the group con~i~ting of hydrogen, an alkyl radical having
l to 4 carbon atoms, and an alkenyl ~adical havin~ 2 to 4
carbon atoms; and n i8 ze~o or 1, such that when n i8 zero
there i8 no bond between Arl and Ar2; and whor~in X~ i~ a
halogen-containing complex anion ~lected ~ro~ the group con-
~isting of hexafluoropho~phate, hexa1uoroar~enate, and hexa-
fluoroanti~onat-.
A pre~erred iodonium salt has the for~ula
. ``~
I+ MF6-
: where M i9 selected fro~ the clas~ consisting of P, As and Sb.
~ According to a further aspect of the present inven-
,
tion there i~ provided a photopolymerisable composition
comprising
:' ~ . ' ' .
: -4b-
,
j~ .
,
1 ~ 9 ~7 6 0 60557-1980
(a) a cationically polymerizable organic material, and
(b) an aromatic iodonium complex salt photoinitiator of the
formula
[R-I+-Rl] X-
where R and Rl are phenyl or substituted phenyl, and X~ is
BF4 , PF6 , AsF6- or SbF6-.
As mentioned above, the aromatic iodonium complex
salt photoinitiator suitable for use in the compositions of the
invention can be defined by the formula
~1 )n>~ X~
wherein Arl and Ar2 are the same or different aromatic groups
having 4 to 20 carbon atoms and are selected from the group
consisting of phenyl, thienyl, furanyl, and pyrazol-4-yl
groups; Z is selected from the group consisting of an oxygen
atom; a sulfur atom; S=0; C=0; 0=1=0; R-~ where R i8 hydrogen,
lower alkyl or acyl (such as acetyl, benzoyl, etc.); a carbon-
to-carbon bond; or Rl-C-R2 where Rl and R2 are selected from
the group consisting of hydrogen, an alkyl radical having 1 to
4 carbon atoms, and an alkenyl radical having 2 to 4 carbon
atoms; and n is zero or 1, such that when n is zero there is no
bond between ~rl and Ar2; and X~ is a halogen-containing com-
plex anion selected from the group consisting of tetrafluoro-
borate, hexfluorophosphate, hexafluoroarsenate, hexachloroanti-
monate and hexafluoroantiomonate.
The aromatic iodonium cations are stable and are well
known and recognized in the art. See for example, United
States Patents 3,565,906; 3,712,920: 3,759,989:
;~
~91~60
and 3~7~3~187; F. Beringer, et al., Diaryllodonium Salts
IX, J. Am. Chem. Soc. 81, 342-51 (1959) and F. Beringer,
et al., Diaryliodonium Salts XXIII, J. Chem. Soc. ly64,
4l~2-51; F. Beringer, et al., Iodonium Salts Containing
lieterocyclic Iodine, J. Org. Chem. 30, 1141-8 (1965).
Representative Arl and Ar2 groups are aromatic
groups having 4 to 20 carbon atoms selected rrom phenyl,
thienyl, ruranyl, and pyrazolyl groups. These aromatic
groups may optionally have one or more fused benzo rings
(e.g., naphthyl and the like; benzothienyl, dibenzothienyl~
benzofuranyl, dibenzoruranyl; etc.). Such aromatic
groups may also be substituted, if desired, by one or
more of the following groups: halogen, n~tro, hydroxyl,
carboxyl, anilino or N-alkylanilino groups, ester groups
(e.g., alkoxycarboxyl such as methoxycarbonyl and
ethoxycarbonyl, phenoxycarbonyl), sulfo ester groups
(e.g., alkoxysulfonyl such as methoxysulfonyl and
butoxysulfonyl, phenoxysulfonyl, and the like), amido
groups (e.g., acetamido, butyramido, ethylsulfonamido,
and the like), carbamyl groups (e.g., carbamyl, N-
alkylcarbamyl, N-phenylcarbamyl, and the like), sulfamyl
groups (e.g., sulfamyl, N-alkylsulamyl, N,N-dialkyl-
sulfamyl, N-phenylsul~amyl, and the like), alkoxy groups
(e.g., methoxy, ethoxy, butoxy, and the like), aryl groups
(e.g., phenyl), alkyl groups (e.g., methyl, ethyl, butyl,
and the like), aryloxy groups (e.g., phenoxy) alkyl-
sulfonyl (e.g., methylsulfonyl, ethylsulfonyl, and the
like), arylsulfonyl groups (e.g., phenylsulfonyl groups),
perfluoroalkyl groups (e.g., tri~luoromethyl, perfluoro-
ethyl, and the like), and perfluoroalkylsulfonyl groups
;:
~ - 5 -
:
~ .
9~760
(e.~, trifluoromethylsul~onyl, perfluorobutylsulfonyl,
and the like).
Suitable examples of the aromatic iodonium
complex salt photoinitiators include:
diphenyliodonium tetrafluoroborate
di(4-methylphenyl)iodonium tetrafluoroborate
phenyl-4-methylphenyliodonium tetrafluoroborate
di(4-heptylphenyl)iodonium tetrafluoroborate
di(3-nitrophenyl)iodonium hexafluorophosphate
di(4-chlorophenyl)iodonium hexafluorophosphate
di(naphthyl)iodonium tetra~luoroborate
di(4-trifluoromethylphenyl)iodonium tetrafluoro-
borate
dlphenyliodonium hexafluorophosphate
di(4-methylphenyl)iodonium hexafluorophosphate
diphenyliodonium hexafluoroarsenate
di(4-phenoxyphenyl)iodonium tetrafluoroborate
phenyl-2-thienyliodonium hexa~luorophosphate
~ 3,5-dimethylpyrazolyl-4-phenyliodonium hexa-
: 20 fluorophosphate
diphenyl~odonium hexachloroantimonate
: diphenyliodonium hexafluoroantimonate
2,2'-diphenyliodonlum tetrafluoroborate
~ di(2,4-dichlorophenyl)iodonium hexafluorophosphate
:~: 25 di(4-bromophenyl)iodonium hexafluorophosphate
di(4-methoxyphenyl)iodonium hexafluorophosphate
di~3-carboxyphenyl)iodonium hexafluorophosphate
di(3-methoxycarbonylphenyl)iodonium hexafluoro-
, ,
phosphate
~::
- 6 -
,
~ ~ :
, . ~
1;~91~60
di(3-methoxysulfonylphenyl)iodonium hexafluoro-
phosphate
di(4-acetamidophenyl)iodonium hexarluorophosphate
di(2-benzothienyl)iodonium hexafluorophosphate
Of the aromatic iodonium complex salts which are
suitable for use in the compositions of the invention the
preferred salts are the diaryliodonium hexafluorophos-
phate such as diphenyliodonium hexafluorophosphate. These
salts are preferred because, in general, they are more
thermally stable, promote faster reaction, and are more
soluble in inert organic solvents than are other aromatic
iodonium salts of complex ions.
The aromatic iodonium complex salts may be
prepared by metathesis of corresponding aromatic iodonlum
simple salts (such as, for example, the diphenyliodonium
bisulfate) in accordance with the teachings of Beringer,
et al., J. Am. Chem. Soc. 81, 342 (1959). Thus, for
example, the complex salt diphenyliodonium tetrafluoro-
bora~e is prepared by the addition at 60C. of an aqueous
solution containing 29.2 g. (150 millimoles) silver
fluoroborate, 2 g. fluoroboric acid, and 0.5 g. phos-
phorous acid in about 30 ml. of water to a solution of
44 g. (139 millimoles) of diphenyliodonium chloride. The
silver halide that precipitates is filtered off and the
filtrate concentrated to yield diphenyliodonium fluoro-
borate which may be purified by recrystallizatlon.
The aromatic iodonium simple salts may be pre-
pared in accordance with Beringer,et al., above, by
various methods including (1) coupling of two aromatic
- 7 -
1~,91760
compounds with iodyl sulfate in sulfuric a~id, (2) coupling
of two aromatic compounds with an iodate in acetic acid-
acetic anhydride-sulfuric acid, (3) coupling of two
aromatic compounds with an iodine acylate in the presence
'; of an acid, and (4) condensation of an iodoso compound,
an iodoso diacetate, or an iodoxy compound with another
aromatic compound in the presence of an acid. Diphenyl-
iodonium bisulfate is prepared by method (3), for example,
by the addition over a period of eight hours at below
5C. of a mixture of 35 ml. of conc. sulfuric acid and
50 ml. of acetic anhydride to a well-stirred mixture of
55.5 ml. of benzene, 50 ml. of acetic anhydride, and
53.5 g. of potassium iodate. The mixture is stirred
for an additional four hours at O-5C. and at room
temperature for 4~ hours and treated with 300 ml. of
diethyl ether. On concentrating, crude dlphenyliodonium
bisul~ate precipitates. lf desired, it may be purified
by recrystallization.
Epoxy-containing material useful in the compo-
sitions of the invention are any organic compounds having
an oxirane ring polymerizable by ring opening. Such
materials, broadly called epoxides, include monomeric
epoxy compounds and epoxides of the polymerlc type and
can be ~liphatic, cycloaliphatic, aromatic or heterocyclic.
These materials generally have at least one polymerizable
epoxy group per molecule (preferably two or more epoxy
groups per moleoule) and, in the polymeric type there
are many pendent epoxy groups (e.g., a glycidyl meth-
acrylate polymer could have several thousand pendent
epoxy groups per average molecular weight).
. .
1;291760
These epoxy-containing materials may vary from
low molecular weight monomeric materials to high molecular
weight polymers and may vary greatly in the nature of
their backbone and substituent groups. For example, the
backbone may be of any type and substituent groups
thereon can be any group not having an active hydrogen
atom which is reactive with an oxirane ring. Illustrative
of permissible substituent groups include halogens,
ester groups, ethers, sulfonate groups, siloxane groups,
nitro groups, amide groups, nitrile groups, phosphate
groups, etc. The molecular weight o~ the epoxy-contain-
ing materials may vary from 58 to about 100,000 or more.
Mixtures of various epoxy-containing materials can also
be used in the compositions of this invention.
Such epoxy-containing materials are well known
and include such epoxides as epichlorohydrins, e.g.,
epichlorohydrin; alkylene oxides, e.g., propylene oxide,
styrene oxide; alkenyl oxides, e.g., butadiene oxide;
glycidyl esters, e.g., ethyl glycidate; glycidyl-type
epoxy resins, e.g~, the diglycidyl ethers of Bisphenol
A and of novolak resins, such as described in "Handbook
o~ Epoxy Resins" by Lee and Neville, McGraw-Hill Book
Co., New York (1967).
Other useful epoxy-containing materials which
can be used in this invention are those which contain one
or more cyclohexene oxide groups such as the epoxycyclo-
hexanecarboxylates, typi~ied by 3,4-epoxycyclohexylmethyl-
3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclo-
hexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate,
_ g _
1~9176~
and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate.
A more detailed list of well known useful epoxides o~
this nature 1s described in U.S. Patent 3,117,099.
Further epoxy-containing materials which are
5 particularly useful in the practice of this invention
include glycidyl ether monomers of the formula
RtOCH2-CH--CH2)n
where R is alkyl or aryl and n is an integer of 1 to 6.
10 Examples are the glycidyl ethers of polyhydric phenols
obtained by reacting a polyhydric phenol with an excess
of chlorohydrin such as epichlorohydrin (e.g., the
diglycidyl ether of 2,2-bis-(2,3-epoxy propoxyphenol)-
propane). Further examples of epoxides of this type
15 which can be u~ed in the practlce of thls invention
are de~cribed ln U.S. Patent 3,018,262.
There are a host of commercially available
epoxy-containing materials which can be used in this
invention. In particular, epoxides which are readily
20 available include propylene oxide, epichlorohydrin, styrene
oxide, vinyl cyclohexene oxide, glycidol, ~;lycidyl-
methacrylate, diglycidyl ether of Blsphenol A (e.g.,
those available under the trade designations "Epon 828"
(R) from Shell Chemical Co., "DER-331" (R),"DER-332" (R),
25 and 'bER-334" (R), from Dow Chemical Co.), vinylcyclo-
; ~ hexene dioxide ~e.g., t'ERL-4206" (R) from Union Carbide
Corp.), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene
carboxylate (e.g., "ERL-4221" ~R) from Un~on Carbide Corp.),
3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methyl-
-- 10 --
~rAde fru~k
l~t91760
cyclohexene carboxylate (e.g.~ "ERL-4201" (R) from Union
Carbide Corp.), bis(3,4-epoxy-6-methylcyclohexylmethyl)
adipate (e.g., "ERL-4289" (R) from Union Carbide Corp.),
bis(2,3-epoxy~cyclopentyl) ether (e.g., "ERL-o400" (R)
from Union Carbide Corp.), aliphatic epoxy modified
with polypropylene glycol (e.g., "ERL-4050" (R) and
"ERL-4052" tR) from Union Carbide Corp.), dipentene
dioxide (e.g., "ERL-4269" (R) from Union Carbide Corp.),
epoxidized polybutadiene (e.g., "Oxiron 200 ~ (R) from
FMC Corp.), silicone resin containing epoxy functionallty,
flame retardant epoxy resins (e.g., "DER-580" (R), a
brominated bisphenol type epoxy resin available from
Dow Chemical Co.), 1,4-butanediol diglycidyl ether
(e.g., "Araldite RD-2" (R) from Ciba-Geigy), poly-
~lycidyl ether of phenolformaldehyde novolak (e.g.,"DEN-431" (R) and "DEN-438" (R) from Dow Chemical Co.),
and resorcinol diglycidyl ether (e.g., "Kopoxite'l (R)
from Koppers Company, Inc.).
Still other epoxy-containing materials are
copolymers of acrylic acid esters of glycidol such as
glycidylacrylate and glycidylmethacrylate with one or
more copolymerizable vinyl compounds. Examples o~ such
copolymers are 1:1 styrene-glycidylmethacrylate, 1:1
methylmethacrylate-glycidylacrylate and a 62.5:24:13.5
methylmethacrylate-ethyl acrylate-glycidyl-methacrylate.
Still other epoxy-containing materials are the
polyurethane polyepoxides which are ob~ained by reacting
an organic polyisocyanate with a triol or a mixture of
a triol and diol to form an isocyanate-terminated
de ~Rrk
1~9~60
polyurethane prepolymer and reacting the prepolymer with
a hydroxy aliphatic epoxide compound. Further examples of
epoxy-containing material o~ this type which can be used
in the practice of this invention are described in U.S.
Patent 3,445,436.
Other organic materials which can be cationically
polymerized in accordance with this invention include
well known classes of cationically polymerizable materials
such as oxetanes, alkylvinyl ethers, lactones, and the
llke. The useful oxetanes include those represented by
the formula
73 14
R6 - I 1 5
R C O
R8
3, R4, R5, R6, R7, and R8 are selected from the
group consisting of hydrogen, alkyl, haloalkyl, alkoxy,
aryloxy, aryl, or acyloxy, where halogen substituents
are preferably chloro, fluoro, bromo, and iodo. The
useful alkylvinyl ethers include those represented by
the formula (H2C=CH-O)n-R where n is an integer of l to
4 and R is alkyl, aralkyl, or other organic material
(whether polymeric or a simple low molecular weight
radical) which is free of basic groups (such as primary
or secondary amino g~oups) which are more basic than
triphenylamine. Useful lactones are those well known
in the art.
Useful photopolymerizable compositions of this
- 12 -
~91760
invention also include mixtures of two or more organic
materials capable o~ cationic polymerization in combinà-
tion with an aromatic iodonium complex salt photoinitiator.
For example, it may be desirable to adjust the viscosity,
coatability, or final cured properties of a photopoly-
merizable epoxy composition by including therein some
amount of an oxetane, alkylvinyl ether or lactone, and
vice-versa.
The photopolymerizable compositions of the
invention can be used as adhesives, caulking and sealing
compounds, casting and molding compounds, potting and
encapsulating compounds, impregnating and coating compounds,
etc., depending on the particular organic material and
aromatic iodonium complex salt used. The photopolymeri-
zable composition can be used as a one-component cured-
in-place composition.
If desired, one may include in the photopoly-
merizable compositlons various conventional non-basic
fillers (e.g., silica, talc, glass bubbles, clays,powdered
metal such as aluminum, zinc oxide, etc.) up to about
50% by volume or more, viscosity modifiers, plasticizers,
anhydrides, rubbers, tackifying agents, pigments, and
so forth.
The photopolymerizable compositions are parti-
cularly suitable in a variety of applications in thefield of graphic arts due to their superior abrasion-
resistance and adhesion to rigid, resilient and flexible
substrates such as metal, plastic, rubber, glass, paper,
wood, and ceramics; their excellent resistance to most
~91~60
solvents and chemicals; and their capability of forming
high resolution images. Among such uses are in making
acid- and alkali-resist images for chemical milling,
gravure images, off~et plates, flexographic printing,
screenless lithography, printing plates, stencil
making, microimages for printed circuitry, microimages
for information storage, decorations of paper, glass, and
metal surfaces, and light-cured coatings. m e composi-
tions may also be used to impregnate substrates such as
glass cloth and the like to obtain a shelf-stable
product which is useful in many manufacturing and re-
pairing processes where a curable liquid composition is
not convenient to use.
The photopolymerization of the compositions
of the invention occurs on exposure of the compositions
to any source of radiation emitting actinlc radiation
at a wavelength within the ultraviolet and vlsible
spectral regions. Suitable sources of radiatlon include
mercury, xenon, carbon arc and tungsten filament lamps,
sunlight, etc. Exposures may be from less than about l
second to lO minutes or more depending upon the amounts
and particular epoxy materials and aromatic lodonium
complex salts being utilized and depending upon the
radiation source and distance from the source and the
thickness o~ the coating to be cured. The compositions
may also be polymerized by exposure to electron beam
irradiation. Generally speaking the dosage necessary
is from less than l megarad to lOO megarad or more.
One of the ma~or advantages with using electron beam
- 14 _
1~,91760
curing is that highly pigmented compositions can be
effectively cured at a faster rate than by mere exposure
to actinic radiation.
While not desiring to be bound by theory, the
photopolymerization apparently takes place by reason
of the photoinduced degradation o~ the aromatic lodonium
complex salt with the production of a Lewis acid which
catalyzes the polymerization of the organic material.
The curing is a triggered reaction, i.e., once the de-
gradation of the aromatic iodonium complex salt has beeninitiated by exposure to a radiation source, the curing
reaction proceeds and will continue even after the
radiation source is removed. The use of thermal energy
during or after exposure to a radiation source will
greatly accelerate the curing reaction.
The aromatic iodonium complex salts useful in
the photopolymerizable compositions of the invention
are of themselves photosensitive only in the ultraviolet.
They, however, are sensitized to the near ultraviolet
and the visible range of the spectrum by sensitizers
for known photolyzable organic halogen compounds
as described in U.S. Patent 3,729,313. Illustrative
sensitizers are found in the following categories:
aromatic amines, aminoketones, and colored aromatic poly-
cyclic hydrocarbons. The use of basic amino compoundsis avoided since such compounds tend to slow the
polymerization of the organic material by reacting with
the Lewis acid generated by the photoinitiator.
The amount of aromatic iodonium complex salt
- 15 -
~J91760
that may be employed in the compositions of the invention
is from about 0.5 to 30 parts per 100 parts of organlc
material and preferably from about 1 to 7 parts per 100
parts of organic material. For those compositions where-
in a sensitizer is used to make the composition sensitiveto radiation in the visible range, about 0.01 to 1.0
parts and preferably about 0.1 to 1.0 parts by weight
of sensitizer per part of aromatic iodonium complex
salt may be employed.
m e photopolymerizable compositions of the in-
vention are prepared by simply admixing, under "safe
light" conditions, the aromatic iodonium complex salt
and the sensitizer, when used,with the organic material.
Suitable inert solvents may be employed if desired when
effecting this mixture. Examples of suitable solvents
are acetone, acetonitrile, methanol and includes any
solvent which does not react appreciably with the
organic material, the aromatic iodonium complex salt or
the sensitizer. A liquid organic material to be poly-
merized may be used as a solvent for another liquid orsolid organic material to be polymerized. A solvent,
however, is generally used only to aid in providing a
suitable viscosity to the composition for purposes of
coating. Solventless compositions can be prepared
by simply dissolving the aromatic iodonium complex
salt and sensitizer in the organic material with or
without the use of mild heating.
In the following examples which will serve to
illustrate the present invention, all parts are parts
- 16 -
~?,9~760
by wei~t and all percentages are given as percentages by
weight~ unless otherwise indicated.
Examples 1-6
In separate examples the various amounts of
5 diphenyliodonium hexafluorophosphate (designated ~2IPF6)
shown in Table I were added to 5 parts of "DER-331" (R)
(a diglycidyl ether of Bisphenol A available from Dow
Chemical Co. having an epoxy equivalency of about 190)
and well mixed at about 50C. Each portion was then
wire rod coated at 2.3 mils (0.006 cm.) thick onto a
2 mil (0.005 cm.) polyester film. Samples of the coat-
ing were then exposed to a 275 watt General Electric RS
(R) sunlamp at a distance of 5 inches (12.7 cm.). The
time required for the surface of the coating to become
15 tack-free is listed in Table I.
Table I
Example 1 2 3 4 5 6
~2IPF6 (Parts) 0.05 0.10 0.15 0.20 0.25 0.30
Tack-Free
(Seconds) 120 90 80 60 25 25
-
It may be observed by inspection of Table I that
the time required ~or the epoxy composition to become tack-
free decreases from 120 seconds at 1% concentration of
diaryllodonium complex salt to 25 seconds at 5% of the salt.
25 Increase of the salt concentration to 6% does not further
decrease the tack time because at 6%, the solubility of
the salt in "DER-331" (R) has been exceeded.
-- 17 --
~.9176Q
Examples 7~1~
In separate examples, coatingswere prepared as
in Examples 1-6 from photopolymerizable compositions con-
taining the various epoxy materials and the various
5 amounts o~ the various aromatic iodonium complex salts
shown in Table II, the coatings then being exposed to
a General Electric sunlamp at 5 inches (12.7 cm.) or to
a General Electric "H3T7" (R) mercury lamp at 7 inches
(17.8 cm.). The time required ~or the sur~ace of the
coating to become tack-free is also reported in Table II.
Table II
Parts By Tack-
Weight Free
Epoxy Iodonium Complex Exposure Cure
15 Exam~le Material Complex Salt Salt Unit (Sec.
7 *"DER-334" ~2IPF6(a) 6 Sunlamp25
8 *"DER-334" ~2IBF4(b) 6 H3T7 (R) 60
9 DER-334 ~2IBF4 4 H3T7 (R) 90
*"DER-334" ~2IPF6 2 H3T7 (R) 60
; 20 11 *"ERL-4221" ~2IPF6 4 H3T7 (R) 90
~ 12 *llERL-422~ 2IBF4 4 H3T7 (R) 180
; 13 Phenyl ~2IPF6 4 H3T7 (R) 180
Glycidyl
Ether
14 *"Epon-828" ~2ISbF6(C) 2 H3T7 (R) 60
*"DER-331" (CH3-~)2IPF6(d) 6 Sunlamp 40
16 *"Epon-828" ~2ISbF6 5 Sunlamp10
* Designates trademark identification.
- 18 -
::
, ~
~29~7~i0
(a) diphenyliodonium hexafluorophosphate
(b) diphenyliodonium tetrafluoroborate
(c) diphenyliodonium hexafluoroantimonate
(d) ditolyliodonium hexafluorophosphate
Examples 17-23
Photopolymerizable compositions were prepared
and coated as described in Examples 1-6 using the epoxy-
containing materials, aromatic iodonium complex salt,
and sensitizing dye (wt. % based on wt. Or complex salt)
shown in Table III. The time required for the surface
Or the coating of each composition to become tack-free
is presented in Table III.
- 19 -
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Example 24
Solution of 20 grams "DER-331" (R), 1.0 gram
diphenyli~donium hexafluorophosphate, and 0.1 gram
2-ethyl-9, 10-dimethoxyanthracene was coated at 30.0
mils (0.076 cm.) thick on 2 mil (0.005 cm.) thick polyester
rilm. After exposure of the coated film for 5 minutes
at 5 inches (12.7 cm.) from a General Electric sunlamp,
a hard cure~ sample was obtained, the coating being firm-
ly bonded to the film. The cured sample was completely
transparent and contained no bubbles. Unexposed portions
of the coating can be washed away with acetone leaving
a sharp, clearly defined image area.
Example 25
A solution was prepared containing 5 grams of
a 5% solution of a 1:1 styrene-glycidylmethacrylate co-
polymer in acetone, 0.01 gram of diphenyliodonium hexa-
fluorophosphate, and 0.005 gram 2-ethyl-9,10-dimethoxy-
anthracene. It was coated on 2 mil (0.005 cm.) thick
polyester film at a wet thickness of 2.3 mils (0.006
cm.) and air dired. A sample was exposed to a General
Electric H3T7 (R) lamp at 7 inches (17.8 cm.) distance
through a r2 photographic step tablet for 3 minutes and
dipped in acetone to remove the unexposed areas. Seven
steps of polymerized material remained.
Example 26
As another example of the utility of the compo-
sitions described herein a photopolymerizable varnish is
prepared which is useful for coating fishing rod windings.
- 21 -
~2917~i0
The composition is prepared with the following ingredients:
Parts
"DER-334" (R) (a diglycidyl ether
of Bisphenol A)100
Phenyl glycidyl ether 10
Diphenyliodonium hexafluorophosphate 2
2-Ethyl-9,10-dimethoxyanthracene0.1
The "DER-334" (R) and phenyl glycidyl ether are
mixed with gentle heating while the diphenyl iodonium
complex salt and sensitizer are added thereto with stir-
ring. A clear photopolymerizable solution is obtained.
The photopolymerizable solution is coated onto
the nylon thread windings of a fishing rod guide. The
thread had been previously heated to about 50C. so that
the solutlon would saturate rapidly into the windings
when applied thereto with a brush. The impregnated
windings are then exposed to a 275 watt sunlamp at a
distance of about 7.5 centimeters for about two minutes,
the fishing rod being rotated slowly during exposure.
After exposure in the manner described a second applica-
tion of photopolymerizable solution to the windings is
made, followed by exposure to a sunlamp to cure the
coating. A smooth, varnished winding with high gloss
and durability is obtained.
This technique for coating windings on fishing
rods is much faster and simpler than with conventional
techniques wherein solvent-based lacquers and varnishes
are used.
- 22 -
~.9~760
Examples 27-33
Various organic materials (in an amount of 3
grams) were added separately to separate solutions con-
taining diphenyliodonium hexafluorophosphate (0~15 grams)
and 2-ethyl-9,10-dimethoxyanthracene (0.02 gram) in
1-2 grams of methylene chloride. The resulting solutions,
in separate vials, were each exposed to a General Electric
sunlamp (275 watts) at a distance of 5 inches. The
following results were obtained:
10 Example Exposure
No. Organic Material Time Result
27 HO(CH2)40CH CH2 15 seconds gellation*
28 diethyleneglycoldivinyl 5 seconds vigorous
ether exothermic
polymeriza-
tion
29 chloroethylvinyl ether 30 seconds gellation*
NHco2(cH2)4ocH CH2 60 seconds insoluble
~ NHCO2(cH2)40cH CH2 formed
; CH3
31 ~ SO N C O 90 seconds solid
2 \ / \ / polymer
CH2~ CH2 formation
32 ~ -valeroiactone 120 seconds polymer
formation
33 caprolactone 120 seconds polymer
formation
*Upon standing, solid polymers were formed in
: less than 24 hours.
1;?,917fi~
Examples 34-35
Two solutions were prepared containing the follow-
ing ingredients in the parts by weight shown:
Ingredients Example 34 Example 35
Epoxy resin ("DER-331" (R)) 5.0 5.0
acetone 2.0 2.0
diphenyliodonium hexafluorophosplate --- 0.25
The two solutions were coated on separate samples
of polyester film using a #10 wire rod and then dried
to leave a tacky coating 0.7 mil (17 microns) thick. Each
sample was exposed to electron beam apparatus of 100
kilovolts and 2.5 milliamps at a distance of 0.75 inch.
A 10 megarad dosage did not cause any noticeable effect
in Example 34, but a 3 megarad dosage was sufficient
to cure the composition of Example 35 to a tack-free state.
- 24 -
