CA1260185A - Laser irradiated catalytic complexes as low temperature curing agents for organic resins - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A room temperature curable composition is made by admixing an organic resin with a catalytic complex formed by irradiation of a mixture of carboxylic acid anhydride and a carbon containing cyclic compound containing an electron deficient component, or admixing the organic resin with a carboxylic acid anhydride and laser irradiating the mixture in-situ.

Description

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LASER IRRADIATED CATALYTIC COMPLEXES
AS LOW TEMPERATURE CURING AGENTS
FOR ORGANIC RESINS

sACKGROUND OF THE INVENTION

Carboxylic acid anhydride curing agents have been found to be useful with epoxy resins for high voltage insulating applications. Usually the addition of an accelerator is required to give reasonable gel times at elevated temperatures, but at room temperature, even with high concentrations of accelerators, very slow gel times are experienced. Considerable effort has been devoted in recent years to devéloping improved room temperature curing agents for epoxy-anhydride resins.
Smith et al., in U.S. Patent 4,020,017, used minor amounts of organotin compounds, such as -triphenyl-tin chloride, to form apparent complexes with reactive epoxide diluents for use as additives for cycloaliphatic and 15 ~ glycidyl ester epoxy resins, to provide resinous electrical insulating compositions wi-thout using acid anhydrides.
These compositions, however, required at least 120C curing temperatures. In a later improvement, Smith et al., in :: :

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U.S~ Patent 4,273,91~ dlscovered a low temperature, fast curinq epoxy insulating composition which consists of an epoxy resin a~d a carboxylic acid anhydride complex. The anhydride ~omplex was made by the low temperature reaction of a selected Lewis acid catalyst, such as antimony pentachloride, titanium tetrachloride, boron trifluoride, tin tetra chloride, or triphenyl tin chloride, with a carboxylic acid anhydride. There, the catalyst and anhy-dride were simply pre-reacted at a reacting mass tempera-ture of from 10C to about 45C. The complex allowedsubstantially complete cure of the epoxy resin at 25C in about 48 hours~
-Von Brachel et al. in U.S. Patent 3,499,077 utilized a peroxide initiated, non-irradiated, free-radical chain reaction of maleic anhydride and straight chained polyalkylene ethers, at from about 80C to 160C, to provide addition products, noting that the literature showed successful reaction of maleic anhydride with tetrahydrofuran, but not dioxane, in the presence of radical initiators. These addition products were found useful as raw materials for lacquers, and as surface active anhydride components in the production of polyesters.
These addition products were usually reacted at from 100C
to about 130C with epoxies and the like.
What is needed is a room temperature curable resin system or catalytic curing agent which will also have extended shelf life, -and wh~ch will help provide good electrical insulatiny properties to the resins it cures.
SUMMARY OF THE INVENTION
The above problems have been solved and the above needs met, most broadly, by admixing an epoxy resin or vinyl resin with a selected carboxylic acid anhydride and irradiating the mixture with a laser having a wavelength range of from about 2,000 Angstrom units to about 3,900 Angstrom units, most preerably an Argon ion laser operated in the region of about 3,600 Angstrom units. This provides an in-situ, two component, laser curable composition. In a .

3 51,153C
preferred embodiment, the above problems have been solved by admixing an organic resin, such as an epoxy resin or a vinyl resin, with a catalytic complex produced by irradiat-ing a mixture of: (a) a selected carboxylic acid anhy-dride, and (b) a carbon containing cyclic stabilizingcompound containing an electron deficient element, such as sulfur or preferably oxygen and their mixtures, selected from the group consisting of tetrahydrofuran, dioxane, trioxane, and sulfolane, and their mixtures. The weight ratio of (carboxylic acid anhydride): (carbon containing cyclic compound) is from about (1):~0.8 to 2). In both cure reactions, no free radical U.V. photGinitiators are used or desired, no additional curing ayents are needed, and the temperature is kept below about 40C during irradiation.
In the preferred three component system, the catalytic complex, when added in a weight ratio of (resin):(catalytic complex) of from about (1):(0.2 to 1), will effect substantially complete cure at 25C in from about 60 hours to 144 hours. The irradiation in the preferred three component system is within the wavelength range of from about 2,000 to about 5,200 Angstrom units.
The irradiation is effective only when both the selected carboxylic acid anhydride and the selected carbon contain-ing cyclic compound are mixed together, the irradiation of the mixed product solution producing an active species which is responsible for initiating resin polymerization at room temperature.
The in-situ resin system, using only epoxy resin plus selected anhydride, is particularly useful to coat flat surfaces haviny patte~rned conductive circuitry, where only the resin covering the metal pattern is laser irradi-ated to cause cure, after which the rest of the resin can be washed off with solvent or the like, to Ieave an insu-lated conductiny metal pattern on the flat surface, whichmay be a printed circuit board of some type. This does require sophisticated laser technology, however. In the : :
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4 51,153C -preferred resin system, the resins incorporating the catalytic complexes can be used to impregnate electrical coll insulation, to encapsulate electrical articles, to act as an insulating adhesive for polyurethane and other type articles, to act as a low viscosity room temperature curable resin, and the like. Both of these complex catalyzed resins can be especially useful when insuLating temperature sensitive materials that might be melted by application of heat, or, as in certain semiconductors, which might change their characteristics upon heating.
Also, these complex catalyzed resins can ba used where heating the resin to cure it would also unduly cause expansion of the wires or other components that are being bonded or insulated.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, reference may be made to the preferred embodiments, exem-plary of the invention, shown in the accompanying drawings, in which:
Fig. 1 shows one type of apparatus that can be used to produce the catalytic complexes used in this invention;
Fig. 2 shows a wrapped, resin-impregnated coil made with the preferred resinous composition of this ~5 invention; and Fig. 3 shows an encapsulated electrical article made with the preferred resinous composition of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The first sections of this description will deal with the preferred three component, curable system, which includes a carbon containing cyclic stabilizer which is mixed with anhydride and irradiated before addition to the resin; with later sections dealing with the two component system, which is appropriately applied to a substrate and irradiated in-sltu.

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It has been found that selected carbon containing cyclic compounds, containing an electron deficient element, can effectively interact and complex with selected carbox-ylic acid anhydrides, through irradiation in the radiation wavelength range of from about 2,000 Angstrom units to about 5,200 Angstrom units, preferably in the ultraviolet portion of that range, i.e., from about 2,000 to about 3,900 Angstr~.l units. Laser irradiat;on, for example ~ith an Argon laser at about 3,600 Angstrom units, is a very concentrated and energy efficient substitute for common ultraviolet (U.V.) lamp sources, and allows the reaction to proceed at about 25C without coo~ing.
When a laser is used, 10 to 90 minutes irradia-tion will provide an effective amount of reactive species to cure organic resins. When a 250 to 500 U.V. watt lamp is used, 30 to 120 minutes will provide an effective amount of reactive species to cure organic resins, but the react-ing mixture must be surrounded by a refrigeration means, so that the heat of the U.V. lamp doesn't cause undue evapora-tion. In all cases, the temperature must be kept below about 40C, to prevent evaporation of reactants, for example, maleic anhydride has a sublimation temperature of about 52C and tetrahydrofuran has a boiling point of about 60C. These complexes formed by irradiatlon are reactive species that are particularly effective in curing epoxy, vinyl, polyester, and other organic resin systems, at temperatures below about 30C, with no ionic contamination of the cured resin.
The useful carbon containing cyclic stabilizing compounds for these complexes contain one or more sulfur and/or oxygen, preferably oxygen, electron deficient elements or components, where the electron deficient element or component need not be present in the rin~
structure. Particularly useful compounds of this type 3S include sulfolane, trioxane, and preferably dioxane (1,4-dioxane) and tetrahydrofuran, whose respective chemi-cal structures are shown below:
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O O , O O O
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S H2CI fH2 H2CI C~H2 H2C CH2 ~ O / , H2C\ / 2 C-C

H2 C ~CH2 CH2 0 Usef~ll carboxylic acid anhydrides for these complexes include a class of carboxylic acid a~hydrides having the chemical formula:
C ~o R'C~ \

RC
~ C~o where R and R' = H, CH3, C2H5, Cl, Br or I, for example, R' can = Cl and R can = CH3.
Use of a higher alkyl than C2H5 as R or R' will slow the irradiation reaction with the carbon containing cyclic compound. The most preferred carboxylic acid anhydrides are those where R - H and R' = CH3, and where R
and R' = H, i.e., citraconic anhydride, and preferably maleic anhydride, respectively:
C~ ~
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CH3~C \ HC
ll O, 11 ~

HC ~ C / ~o Other carboxylic acid anhydrides, such as hexa-hydrophthalic anhydride, succinic anhydride, and dodecenyl succinic anhydride, are not effective to provide catalytic reactiv species. The~ double bond opposite the central, ~ :
single bonded oxygen, appears to be of critical importance in providing ~catalytic reactive species with the above described carbocyclic compounds during irradiation. The :~ : ~: :
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carboc~clic com~ounds act as a solvent for the selected acid anhydrides which are usually in solid form. The useful weight range of (selected carboxylic acid anhydride):(selected carbon containing cyclic compound~ is from about (1):(0.8 to 2). ~ess than o.a part/l part acid anhydride, a solution will not result. Over 2 parts/l part acid anhydride, the complex may not form.
Usually, the selected acid anhydride is added the selected liquid carbon containing cyclic compound, acting as solvent, and mixed, at about 25C to 30C, until a solution results. At this point there is no interaction between the two ingredients other than solution formation, i.e., the product of the mixture contains no complexes- or reactive species. Then a source o ultraviolet light irradiation, such as a bank of U.V. lamps or, for example, an Argon ion laser beam, which provides concentrated radiation and fast interaction, is directed into the solution. Fig. 1 of the Drawings, shows the use of a coherent CR-18 Argon ion laser to produce useful complexes for curing resins. In Fig. 1, mirrors 1 reflect laser beam 2, from laser source 3, through convex lens 4 into monomer solution 5 in contact with magnetic stirrer means 6 and having optional nitrogen bubbler means 7.
Upon irradiation of the solution, within the wavelength range of from about 2,000 Angstrom units to ~ about 5,200 Angstrom units, and preferably from about 2,000 ; Angstrom units to about 3,900 Angstrom units, a complex forms. Although applicants are not to be held to any particular theory, using the interaction between maleic anhydride and dioxane as an example, the possible reactions that, it is thought, might occur include:

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C~O
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O I + I
\ / 2 \ C /
0~ (I) ,,0 ~ (II) ~0 .HC fH2 H2C~ ,~CH2 : O
(III) As shown in the previously described reactions, it i5 believed that argon ion laser action on the product :solution admixture of maleic anhydride and dioxane in step (A) produces a singlet excited species which goes to triplet excited state via step (B). The triplet excimer thus produced reacts with another maleic anhydride unit in : the g-ound state (step C) and produces a reactive charge :: :

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transfer complex (after step C). This charge transfer complex then abstracts a hydrogen atom from dioxane. This results in a color change between step (C) and step (D) indicating the presence of catalytic complexes consisting essentially of reactive species such a.s cation (I), radical anion (II) and a free radical (III) containing only an electron as a reactive component. The catalytic com~lexes are capable of initiating a cationic polymerization in epoxies and a free radical polymerization in vinyl mono-mers. In addition to the reactive species shown, someunreacted carbon containing cyclic compound, i.e., dioxane is thought to remain. No deliberate heating is used, care being taken to react only up to about 40C, with no cata-lysts, or initiators being present, the reaction proceeding solely due to irradiation effects.
Epoxy resins are the most preferred resins used with the catalytic complexes previously described. One type of epoxy resin which may be used as the base resin in the invention, or used in combination with, for example, a cycloaliphatic epoxy, is a bisphenol type obtainable by reacting epichlorohydrin with a dihydric phenol in an alkaline medium at about 50C, using 1 to 2 or more moles of epichlorohydrin per mole of dihydric phenol. The heating is continued for several hours to effect the reaction and the product is then washed free of salt and base. The product, instead of being a single simple compound, is generally a complex mixture of glycidyl polyethers, but the principal product may be represented by the chemical structural formula:
O
CH2-C~-cH2 O(R-o-cH2-cHOH-cH2-o)n~R-o-cH2-c~-cH2 where n is an integer of the series, O, 1, 2, 3..., and R
represents the divalent hydrocarbon radical of the dihydric phenol. Typically R is:

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to provide a diglycidyl ether of bisphenol A type epoxy resin or ~ H ~
to provide a diglycidyl ether of bisphenol F type epoxy resin.
The ~ sphenol epoxy resins used in the invention have a 1, 2 epoxy equivalency greater than one. They will generally be diepoxides. By the epoxy equivalency, refer-ence is made to th average number of 1, 2 epoxy groups, CH2 \ C -- -contained in the average molecule of the glycidylether.
Other epoxy resins that are useful in this invention include polyglycidylethers of a novolac. The polyglycidylethers of a novolac suitable for use in accor-dance with this invention are prepared by reacting anepihalohydrin with phenol formaldehyde condensates. While the bisphenol-based resins contain a maximum of two epoxy groups per molecule, the epoxy novolacs may contain as many as seven or more epoxy groups per molecule. In addition to phenol, alkyl-substituted phenols such as o-cresol may be used as a starting point for the production of epoxy novolac resins.
Other useful epoxy resins include glycidyl esters, hydantoin epoxy resins, cycloaliphatic epoxy resins and diglycidyl ethers of aliphatic diols. Of these latter four varieties of epoxies, cycloaliphatic epoxies are particularly useful, used alone or blended with-the other epoxy types. The cycloaliphatic type epoxy resins that can be employed as the resin ingredient in the invention are selected from nonglycidyl ether epoxy resins containing more than one 1,2 epoxy group per molecule. These are general~ly prepared by epoxidizing unsaturated aromatic hydrocarbon compounds, such as cyclo-olefins, using hydro-- carbon compounds, such as cyclo-olefins, using hydrogen :: :
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peroxide or peracids such as peracetic acid and perbenzoic acid. The organic peracids are generally prepared by reacting hydrogen peroxide with either carboxylic acids, acid chlorides ketones to give the compound R-COOOH.
Examples of cycloaliphatic epoxy resins ~ould include: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (containing two epoxide groups which are part of ring structures, and an ester linkage); ~ nyl cyclo-hexene dioxide (containing two epoxide groups, one of which is part of a ring structure); 3,4-epoxy-6-methyl-cyclohexyl methyl-3,4-epoxy-6-methylcyclohexane carboxy late and dicyclopentadiene. All of these epoxy resins are well known in the art, and reference can be made to U~S.
Patent 4,273,914 for additional details in their produc-tion.
Other useful resins that can be used with thecatalytic complexes previously described include, prefera-bly, vinyl monomers, such as, styrene, 4-methoxy styrene, vinyl toluene, methyl methacrylate, methyl vinyl ketone, 1,1 diphenyl ethylene and the like, and their mixtures.
Unsaturated polyester resins should also work. Both of these classes of resins are well known in the art.
Natural oil extenders, such as epoxidized linseed or soy bean oils, octyl epoxy tallate and reactive plasti-cizers such as the conventional phthalates and phosphatesmay also be used in small amounts, up to about 50 parts per 100 parts of resin to provide increased flexibility.
Thixotropic agents, such as SiO2 and pigments, such as TiO2, may ba used as aids in fluidizing the composition or enhancing the color tones of the cured resins.
Similarly, various inorganic particulate fillers, such as silica, quartz, mica, chopped glass, beryllium aluminum silicate, lithium aluminum silicate and mixtures thereof, in average particle sizes from about 10 microns to about 100 microns, may be employed in amounts up to about ; lOO parts per 100 parts of resin, to improve electrical properties of the resin formulation, to lo~Jer costs, and to : ~ :

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provide thick casting or pasting compositi.ons. Photoini-tiators are neither requir~d nor desired, since they can provide an impurity element in the composition.
Regarding the broad two component, in-situ composition, irradiation must be in the ultraviolet range of from about 2,000 to about 3,900 Angstrom units, prefera-bly from about 3,300 Angstrom units to about 3,900 Angstrom units, most preferably, an Argon ion laser, or a suitable eximer laser, operated in the region of about 3,600 Ang-strom units. Ultraviolet (U.V.) lamp sources were notfound to be practical in this in-situ embodiment, since they required almost 2,000 times more energy to cure this resin system than a laser. When a laser is used, 1 to 45 minutes laser irradiation will usually produce an efective amount of reactive species to cause gellation and eventual cure of the resin system at 25C. In all cases, the temperature must be kept below about 40C, to prevent evaporation of maleic or other anhydride.
In this in-situ embodiment, carbon containing cyclic compounds are not used. The useful carboxylic acid anhydrides are those described previously with the most preferred being citraconic anhydride and maleic anhydride.
Other carboxylic acid anhydrides, such as hexahydrophthalic anhydride, succinic anhydride, and dodecenyl succinic anhydride are not effective to provide catalytic reactive species. Useful epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins and cycloali-phatic type epoxy reslns, all described previously in detail. Included within the useful epoxy resins is the diglycidyl ether of an aliphatic diol, such as neopentyl glycol (DGENPG), and cyclohexene oxide, having the respec tlve structures:
O CH O
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13 51,153C
A very preferred cycloaliphatic epoxy is 3,4-epoxy cyclohexymethyl (3,4 epoxy) cyclohexane carboxylate. Other useful resins include vinyl monomers, such as, styrene, 4-methoxy styrene, vinyl toluene, methyl methacrylate, methyl vinyl ketone, 1,1 diphenyl ethylene and the like.
Epoxy resins are the most preferred resins. Oil extenders and fillers described previously may also be added to the com~osition. U.V. photoinitiators are neither need-1 nor desirable, since they may add ionic impurities to the resin, and are excluded.
The epoxy or vinyl resin are mixed together, at under 40C, in the weight ratio of (resin):(anhydride) of from about (1):(0.1 to 1) with (1):(0.2 to O.S) preferred, to form a solution. Use of less than about 0.10 part per 1 part epoxy or vinyl will result in very long gel times. At this point no catalytic complex is formed. Upon irradia-tion of the solution, within the wavelength range of from about 2,000 Angstrom units to about 3,900 Angstrom units, prefarably using an Argon ion laser, a complex forms which causes direct cure of the epoxy or vinyl resin. Although applicants are not to be held to any particular theory, using the interaction between maleic anhydride and cyclohexene dioxide as an example, the possible reactions that, it is thought might occur i~clude:

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L~~o~ c c;

As shown, it is believed that the Argon ion laser action in step (A) produces a singlet excited species which :~ :goes to triplet excited stage via step (B). This, in turn, ~: :: 5 proceeds to charge transfer complex (IV) via step (C). In ~ the initial stages of polymerization, during step (D), : polyether linkage (V) is probable. This suggests that the electron donor: cyclohexene oxide undergoes a cationic polymer:ization in the presence of a counteranion-radical.
:~ lO At longer irradiation times the maleic anhydride adduct of a polyether is formed via step (E). A color change from ::: ~

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clear to yellow or oranye indicates formation of charge transfer complex (IV).
Referring now to Fig. 2, a closed full coil 10 is shown which can be used in an electric motor or the like.
The coil comprises an end portion comprlsing a tangent 12, a connecting loop 14 and another tan~ent 16 with bar leads 18 extending therefrom. Slot portions 20 and 22 of the coil which som imes are hot pressed to precure the resin and to form them to predetermined shape and size are connected to the tangents 12 and 16, respectively. These slot portions are connected to other tangents 24 and 26 connected through another loop 28.
In the case of a motor, generally the entire motor containing the coils would be placed in an impreg-nating bath containing a low viscosity version o the resinof this invention, and vacuum impregnated. Thereafter, the impregnated motor could be removed from the impregnating tank, drained, and air dried for about 100 hours.
Eig. 3 shows an insulated electrical member such as a coil 30, which has conductors 32, potted or encapsu-lated in a thick, cured, insulating casting 34, the casting being the reslno~s composition of this invention applied to the mem~er in a casting or pasting operation and cured at room temperature.
The resin of this invention can be used to adhesively bond coils together or adhesively bond plastic articles, such as polyurethane or other plastic mountings to a variety of flat or tubular structures, without the use of heat for curing. With filler added, the composition can be used as a thick paste to coat a variety o articles.
The in-situ composition of this invention can be used to selectively insulate patterned areas of a substrate or patterned conductors on a substrate.

Three catalyic complexes were made and used as a curing agent and then used with epoxy resin, to illustrate ; the preferred three component system. In a 40 ml. glass ' ., .

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beaker, 0.0~ mole (1.96 grams) of maleic anhydride (MAH) and 2.0 ml. (1.78 grams) of tetrahydrofuran (THF) were added and well mixed with a magnetic stirrer. Into another 40 ml. glass beaker, 0.02 mole of maleic anhydride (MAH) and 2.0 ml. (2.07 grams) of dioxane (DOX) were added and well mixed with a magnetic stirrer. Into a third 40 ml.
gl~ss beaker, 0.02 mole of maleic anhydride (MAH) and 2.0 m_. (2.52 grams) of sulfolane (SOL) were added ~nd well mixed with a magnetic stirrer. At this point a simple solution occurred with no color change or apparent reac-tion. The solution temperature was ~5C. An argon ion laser beam was directed into each beaker separately with the help of reflecting mirrors, as shown in Fig. 1 of the Drawings. An optional flow of Nitrogen gas was bubbled through the solutions. The temperature of the solution was maintained at 25C during irradiation.
The laser was a coherent radiation CR-18 USG
Argon ion laser, tunable over a number of discr te wave-lengths. The laser was operated in the re~ion of about 20 3,600 Angstrom Units at a power level of 1.3 watts. The irradiation was continued for 30 minutes during which the colorless MAH/~HF solution turned to deep red and the colorless MAH/DOX solution turned to yellow-red, indicating some interaction between the MAH and the THF, and the MAH
and the DOX.
The development of the color in the beakers was followed spectrophotometrically. No absorption was ob-served in the visible region until these mixture solutions were irradiated with argon ion laser. In case of maleic anhydride/tetrahydrofuran and maleic anhydride/dioxane systems, charge transfer complexes, having an absorption maxima at 4,480 Angstrom Units were formed. Maleic anhydride/sulfolane showed an absorption maxima at 4,000 Angstrom Units. ~he UV-visible spectrum of maleic anhydride/tetrahydrofuran shows a linear increase in the concentration of the charge transfer complex with the :rradlation time~ A~ similar behavior was observed in 17 51,153C
maleic anhydride~dioxane and maleic anhydride~sulfolane.
The colored complexes formed in all these systems can be closely related to the active species, which would initiate the polymerization of epoxies or vinyl monomers.
One gram of each compLex was then added separate-ly at 25C to 2.0 grams of 3,4-epoxy cyclohexylmethyl (3,4 epoxy) cyclohexane carboxylate, a cycloaliphatic epoxy resin having an epoxy equivalent weight of 133 and a viscosity at 25C of from 350 cps. to 450 cps. (sold commercially by Union Carbide Corp. under the tradename of ERL-4221), and one gram of MAH/THF was also added at 25C
to 2.0 grams of a diylycidyl ether of neopentyl glycol, a low visco~sity epoxy resin of the diglycidyl ether of- an aliphatic dlol type, having a viscosity at 25C of from 5 cps. to 100 cps. (sold commercially by Ciba Geigy Co.
under the tradename XU-193). The gel time at 25C and cure time at 25C for these four resin systems were then record-ed as set forth in TABLE 1 below:

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As can be seen, epoxy resins can be catalyzed and cured at 25C using the complexes of this invention.
Cycloaliphatic epoxy resins such as ERL-4221 show excellent results, curing at 25C in Sample 1 within 3 days, noting, that in some instances, BF3 catalyzed epoxies may require 12 to 18 hours cure at 75C to cure. The XU-193 required a substantial cure time, but it must be remembered that it is an extremel- lo~ vi~cosity epoxy resin. Cure time of bisphenol A and other type epoxies could be improved by blending with cycloaliphatic epoxies. Eleckrical proper ties of the ERL-4221 epoxy were determined and compared to ERL-4221, catalyzed by a mixture of 3 wt% BF3 and methyl ethyl amine (MEA~ and a 3 wt% addition of triphenyl tin chloride (TPTCL). The results are set forth in TABLE 2 below:

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The higher the resistivity and breakdown strength the better the insulating effect. As can be seen, break dcwn strength of the catalytic complex, Samples 1 and 3, is very good and resistivity i5 adequate. Samples 5 and 6 do not show much detrimental effect of halide since only minor amounts were used. However, even such minor amo~nts were used. However, even such minor amounts could attack elec:rical c aponents of the apparatus beiny insulate~ or bonded.
In order to determine if irradiation time of the catalytic complex would lower cure time of the resin system, cyclohexene oxide, 0 = 0, which is an epoxy model, was used as a base resin for MAH/THF complexes.
Here 0.02 mole (1.96 grams) of MAH and 2.0 ml. (1.78 grams) of THF were irradiated at 25C as previously described for 15, 30, and 40 minutes usiny different resin:catalytic complex weiyht ratios. The results of gel and cure times at 25C are set forth in TABLE 3 below:
_ TABLE 3 ~ ___________ Wt. ratio cyclohexene oxide Irradiation Gel Time Cure Time Sample :MAH/THF Timehours hours

6 1:0.25 30 min.4.5 hr.15 hrs.

7 1:0.50 30 minØ2 hr.8 hrs.

8 1:0.50 20 min.6 hr. 18 hrs.

9 1:0.50 40 minØ1 hr.6 hrs.¦
As can be seen, a 40 minute irradiation time lowered cure time substantially over a 30 minute irradia-tion time, and so the cure times of TABLE 1 should also belowered if more irradiation time is used to produce strony-er complexes. The cure times of TABLE 1 should also be lowered if the weight ratio of resin:complex is raised to l:0.75 or possibly l:l.

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It was found that the catalytic curing activity of the complexes remained stabl.e for about 4 months. The pot life of the resin system into which the complexes are incorporated are, naturally, only about 12 hours at 25C.
In addition to polymerizing epoxies, these catalytic complexes were successfully used to initiate polymerization in vinyl monomers such as styrene, p-methoxy styrene and 1,1 diphenyl ethylene. Hence .hese catalytic complexes can be used to polymerize a wide variety of monomers at room temperature without exposing the epoxy or vinyl resin itself to radiation, or exposing the electrical components bonded or insulated with the complexed resins to excesses of halide-action.
EXAM~LE 2 Eight, clear, in-situ polymerizable co~positions were made with maleic anhydride and an epoxy resin, and gelled using the CR-18 USG Argon ion laser o~ Example l, operated in the region of about 3,600 Angstrom units at 1.2 watts. The Argon ion laser was directed into the sample as shown in Fig. 1 with help of reflecting mirrors. A con-stant flow of N2 was bubbled through the solution. The irradiation was continued until the magnetic stirrer stopped stirring and the composition gelled. Table 4 illustrates the results:
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__ _ ~ _ W . Ratio Maleic Laser Epoxy Anhydride IrradiAtion Color After S~pleResin (~AH) Time Gel Time Irratiation __ _ ~ _ __ 10Cyclohexene 1:0.253.3 min. 3.3 ~in. Yellow 11Cyclohexene 1:0.502.5 min. 2.5 min. Yellow -oxide 12ERL-4221 1:0.36 16 ~in. 16 min. Orange 13ERL-4221 1:0.17 30 min. 30 ~in. Or;nge-14ERL-4221 1:0.10 47 min. 47 min. OrangP-Yellow 15DGENPG 1:0.46 25 min. 25 min. OR~ndge' 16DGENPG 1:0.31 41 min. 41 min. Orsnge-20 . 17DGENPG 1:0.23 62 min. j62 min. Red At the point of gellation there was polymeriza-Sion of the composition. After an additional 3 to 5 minutes, the cyclohexene oxide cured at 25~C. After an additional 20 to 60 minutes, the ERL-4221 completely cured at 25C, with the DGENPG taking somewhat longer.

,

Claims (29)

WE CLAIM

1. A stable catalytic complex consisting essential-ly of: a cation (I), a radical anion (II) and a free radical (III), wherein (I) and (II) are a cation and radical anion of a carboxylic acid anhydride having the formula:

where R and R' = H, CH3, C2H5, Cl, Br or I, and (III) is a free radical of a carbon containing cyclic compound contain-ing an electron deficient element selected from the group consisting of sulfur, oxygen, and mixtures thereof.

2. The catalytic complex of claim 1, wherein the carboxylic acid anhydride is maleic anhydride and the carbon containing cyclic compound does not contain carbon to carbon double bonds.

3. The catalytic complex of claim 1, wherein the carbon containing cyclic compound is selected from the group consisting of sulfolane, trioxane, dioxane, and tetrahydro-furan.

4. The catalytic complex of claim 2, wherein the carbon containing cyclic compound is selected from the group consisting of sulfolane, trioxane, dioxane, and tetrahydro-furan.

5. The catalytic complex of claim 2, wherein the carbon containing cyclic compound is dioxane.

6. The catalytic-complex of claim 2, wherein the carbon containing cyclic compound is tetrahydrofuran.

7. The catalytic complex of claim 1, in a solvent.

8. The catalytic complex of claim 7, wherein the solvent is a carbon containing cyclic compound.

9. The catalytic complex of claim 8, wherein the solvent is selected from the group consisting of sulfolane, trioxane, dioxane, and tetrahydrofuran.

10. A stable reactive complex containing reactive species, useful for catalyzing curable organic resins, con-sisting essentially of the irradiated product of the mixture:
(a) a carboxylic acid anhydride having the chemical formula:

where R and R' = H, CH3, C2H5, Cl, Br or I, and (b) a carbon containing cyclic compound selected from the group consisting of tetrahydrofuran, dioxane, tri-oxane, sulfolane, and mixtures thereof; where the weight ratio of (carboxylic acid anhydride): (carbon containing cyclic compound) is from about (1): (0.8 to 2) allowing interaction of carbon containing cyclic compound (b) with carboxylic acid anhydride (a) and formation of a reactive complex between (b) and (a) during irradiation, and, where irradiation includes the wavelength range of from about 2,000 Angstrom units to about 5,200 Angstrom units.

11. The reactive complex of claim 10, where the carboxylic acid anhydride is maleic anhydride, the complex is formed by irradiation at a temperature below about 40 C,and the irradiation is by a laser operating in the region between 2,000 Angstrom units and 3,900 Angstrom units.

12. A method of making a stable reactive complex containing reactive species, useful for catalyzing curable organic resins, comprising the steps:
(a) admixing a carboxylic acid anhydride having the chemical formula:

where R and R' = H, CH3, C2H5, C1, Br or I, and a carbon con-taining cyclic compound selected from the group consisting of tetrahydrofuran, dioxane, trioxane, sulfolane, and mixtures thereof; and (b) irradiating said admixture with radiation which includes the wavelength range of from about 2,000 Angstrom units to about 5,200 Angstrom units, where the weight ratio of (carboxylic acid anhydride):(carbon containing cyclic compound) is from about (1):(0.8 to 2) allowing interaction of carbon containing cyclic compound with carboxylic acid anhyd-ride and formation of a reactive complex between carbon con-taining cyclic compound and carboxylic acid anhydride during irradiation.

13. A curable composition comprising the mixture:
(1) an organic resin selected from the group consist-ing of epoxy resin and unsaturated polyester resin; and (2) a stable reactive complex containing reactive species, formed by irradiation induced interaction between:

(a) a carboxylic acid anhydride having the chemical formula:

where R and R' = H, CH3, C2H5, Cl, Br or I, and (b) a carbon containing cyclic compound selected from the group consisting of tetrahydrofuran, dioxane, triox-ane, sulfolane, and mixtures thereof, where the weight ratio of (carboxylic acid anhydride):(carbon containing cyclic com-pound) is from about (1):(0.8 to 2) allowing interaction of carbon containing cyclic compound (b) with carboxylic acid anhydride (a), and the irradiation has a wavelength effective to form a reactive complex between (b) and (a).

14. The curable composition of claim 13, where the carboxylic acid anhydride is selected from the group consist-ing of citraconic anhydride and maleic anhydride.

15. The curable composition of claim 13, where the carboxylic acid anhydride is maleic anhydride and the carbon containing cyclic compound is selected from the group consist-ing of tetrahydrofuran, dioxane, and mixtures thereof.

16. The curable composition of claim 13, where the organic resin contains cycloaliphatic epoxy resin.

17. The curable composition of claim 13, where the composition also contains filler particles.

18. The curable composition of claim 13, where the reactive complex is formed by radiation including the wave-length range of from about 2,000 Angstrom units to about 5,200 Angstrom units.

19. The curable composition of claim 13, where the weight ratio of (organic resin):(reactive complex) is from about (1):(0.2 to 1).

20. The composition of claim 13, insulating an electrical article.

21. A curable composition comprising the mixture:
(A) an organic resin; and (B) a stable reactive complex consisting essential-ly of the irradiated product of the mixture:
(a) a carboxylic acid anhydride having the chemical formula:

where R and R' = H, CH3, C2H5, Cl, Br or I, and (b) a carbon containing cyclic compound selected from the group consisting of tetrahydrofuran, dioxane, triox-ane, sulfolane and mixtures thereof; where the weight ratio of (carboxylic acid anhydride):(carbon containing cyclic compound) is from about (1):(0.8 to 2) allowing interaction of carbon containing cyclic compound (b) with carboxylic acid anhydride (a) and formation of a reactive complex between (b) and (a) during irradiation, and where the irradiation includes the wavelength range of from about 2,000 Angstrom units to about 5,200 Angstrom units.

22. The composition of claim 21, where the organic resin is selected from the group consisting of epoxy resin and unsaturated polyester resin, and the weight ratio of resin:reactive complex) is from about (1):(0.2 to 1).

23. The curable composition of claim 21, where the carboxylic acid anhydride is maleic anhydride, the reactive complex is formed by irradiation at a temperature below about 40 C, the irradiation is with a laser, and the reactive com-plex consists essentially of reactive species.

24. A curable composition comprising the irradiated product of the mixture:
(1) an epoxy resin, and (2) a carboxylic acid anhydride having the chemical formula:

where R and R' = H, CH3 C2H5, Cl, Br or I; where the weight ratio of (epoxy resin):(anhydride) is from about (1):(0.1 to 1), and the radiation includes the wavelength range of from about 2,000 Angstrom units to about 3,900 Angstrom units.

25. The composition of claim 24,where the resin is a cycloaliphatic epoxy resin and the anhydride is selected from the group consisting of citraconic anhydride and maleic anhy-dride.

26. The composition of claim 24, applied over patterned conductive circuitry to insulate said circuitry.

27. The curable composition of claim 13, where the organic resin is selected from the group consisting of cycloa-liphatic epoxy resin, bisphenol A epoxy resin, and mixtures thereof.

28. The curable composition of claim 21, where the organic resin is selected from the group consisting of cyclo-aliphatic epoxy resin, bisphenol A epoxy resin, and mixtures thereof.

29. The curable composition of claim 24, where the epoxy resin is selected from the group consisting of cyclo-aliphatic epoxy resin, bisphenol A epoxy resin, and mixtures thereof.