CA1291760C

CA1291760C - Aromatic iodonium complex salt photoinitiators

Info

Publication number: CA1291760C
Application number: CA000224450A
Authority: CA
Inventors: George H. Smith
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1974-05-08
Filing date: 1975-04-11
Publication date: 1991-11-05
Anticipated expiration: 2008-11-05

Abstract

ABSTRACT

Photopolymerizable compositions which comprlse cationically polymerizable organic material and photo-sensitive aromatic iodonium salt of a halogen-contain-ing complex ion are described as are coated substrates and methods for bonding materials together using such compositions.

Description

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.

:

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 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 ~91'76(~

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 ~::

, ~ ~ :
, . ~

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 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-~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 R C O

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 ~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 ~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 ~?,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.

~.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.

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~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.

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~ ?,91760 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.

~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.

~.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.

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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.

Claims

1. A photopolymerizable composition comprising:
(a) an organic material which is cationically polymeriz-able; 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 salt photoinitiator of the formula X-wherein Ar1 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; ?=O;
?=O; O=?=O; R-? where R is hydrogen, lower alkyl or acyl; a carbon-to-carbon bond; or R1-?-R2 where R1 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 Ar1 and Ar2; and X- is a halogen-containing complex anion selected from the group consisting of tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexachloroantimonate and hexafluoroantimonate.

2. A photopolymerizable composition in accordance with claim 1, wherein said organic material has an epoxy function-ality of at least 1.

3. A photopolymerizable composition in accordance with claim 2, wherein said organic material is selected from the group consisting of epichlorohydrins, alkylene oxides, alkenyl oxides, glycidyl esters, glycidyl ethers, epoxy novolaks, co-polymers of acrylic acid esters of glycidol and copolymerizable vinyl compounds, and polyurethane polyepoxides.

4. A photopolymerizable composition in accordance with claim 1, wherein said Ar1 and Ar2 are selected from the group consisting of phenyl and lower alkyl substituted phenyl groups.

5. A photopolymerizable composition in accordance with claim 1, wherein said Ar1 and Ar2 groups are selected from the group consisting of thienyl and substituted thienyl groups.

6. A photopolymerizable composition in accordance with claim 4, wherein n is zero.

7. A photopolymerizable composition in accordance with claim 5, wherein n is zero.

8. A photopolymerizable composition in accordance with claim 4, wherein Ar1 and Ar2 are alkylphenyl groups.

9. A photopolymerizable composition in accordance with claim 1, wherein said halogen-containing complex anion is selected from the group consisting of tetrafluoroborate, hexa-fluorophosphate, and hexafluoroantimonate.

10. A photopolymerizable composition in accordance with claim 1, wherein said photoinitiator is present in an amount of about 1 to 7 parts by weight per 100 parts by weight of said organic compound.

11. A photopolymerizable composition in accordance with claim 1 further containing about 0.01 to 1 part by weight of sensitizing dye per part by weight of photoinitiator.

12. A process for obtaining a cured coating comprising:
(a) applying a thin layer of the composition of claim 1 to a substrate, and (b) exposing said layer to actinic radiation or electron beam irradiation.

13. A substrate bearing at thin layer of the composition of claim 1 which has been cured in situ.

14. A photopolymerizable composition 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 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 X-wherein Ar1 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; ?=O;
?=O; O=?=O; R-? where R is hydrogen, lower alkyl or acyl; a carbon-to-carbon bond; or R1-?-R2 where R1 and R2 are selected from the group consisting of hydrogen, an alkyl radical having 1 to 4 carbon atoms; and n is zero or 1, such that when n is zero there is no bond between Ar1 and Ar2; and X- is a halogen-containing complex anion selected from the group consisting of tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexachloroantimonate and hexafluoroantimonate.

15. A process for bonding a radiation-transparent sub-strate to a second substrate comprising:
(a) disposing a layer 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 said layer insoluble.

16. An aromatic iodonium complex salt of the formula X-wherein Ar1 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; ?=O;
?=O; O=?=O; R-? where R is hydrogen, lower alkyl or acyl; a carbon-to-carbon bond; or R1-?-R2 where R1 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 Ar1 and Ar2; and wherein X- is a halogen-containing complex anion selected from the group con-sisting of hexafluorophosphate, hexafluoroarsenate, and hexa-fluoroantimonate.

17. An aromatic iodonium complex salt in accordance with claim 16, wherein X is hexafluorophosphate.

18. An aromatic iodonium complex salt in accordance with claim 16, wherein X is hexafluoroantimonate.

19. An aromatic iodonium complex salt in accordance with claim 16, wherein X is hexafluoroarsenate.

20. A photopolymerizable composition in accordance with claim 1 further containing up to 50% by volume of a filler.

21. A photopolymerisable composition comprising (a) a cationically polymerizable organic material, and (b) an aromatic iodonium complex salt photoinitiator of the formula [R-I+-R1] X-where R and R1 are phenyl optionally substituted by one or more substituents selected from halogen, nitro, hydroxyl, carboxyl, anilino or N-alkylanilino groups, ester groups, sulfo ester groups, amido groups, carbamyl groups, sulfamyl groups, alkoxy groups, aryl groups, alkyl groups, aryloxy groups alkyl-sulfonyl, arylsulfonyl groups, perfluoroalkyl groups and perfluoroalkylsulfonyl groups, and X- is BF4-, PF6-, AsF6- or SbF6-.

22. The iodonium salt of claim 16, having the formula where M is selected from the class consisting of P, As and Sb.