Curable Organic Resin Compositions and Foaming Method

The present invention relates to curable organic resin compositions -which employ a diaryliodonium-redox catalyst system of copper salt and as corbic acid. More particularly, the present invention relates to organic resin foam and method of foaming.

As shown in my copending application RD-10257, filed con¬ currently herewith, aromatic iodonium salts can be employed in combination -with organic acids or copper salts to facilitate the heat cure of various organic materials, such as epoxy resins. I have also found that valuable results also can be achieved if reducing agents such as thiophenol are used in combination with aryl onium salts to facilitate the thermal cure of epoxy resins. Surprisingly, in the absence of such cocatalysts, the heat cure of cationically polymerizable organic materials, such as epoxy resins, with an aromatic iodonium salt can require temperatures exceeding 200 C over an extended period of time. I have now discovered that if a diaryliodonium salt of the formula,

^(I) ι αυ _a (R ^x ) _b i] m ^" ,

is employed with a redox catalyst comprising a mixture of copper salt and as corbic acid or derivative thereof in combination with a cationically polymerizable material, such as an epoxy resin, the cure of the organic material can be achieved without the use of external heat, where R is a monovalent aromatic organic radical, R is a divalent aromatic organic radical, Y is a non-nucleophilic anion defined below, a is a whole number equal to 0 or 2, b is a whole number equal to 0 or 1. In instances where an organic sol¬ vent is utilized in combination with a cationically curable organic

resin and the above described diaryliodonium salt-redox catalyst curing system, an organic foam can be generated as the result of exothermic heat of reaction.

There is provided by the present invention, curable com- positions comprising

(A) a cationically polymerizable organic resin, and

(B) 1% to 35% by weight of the curable composition of a catalyst consisting es sentially of

(i) a diaryliodonium salt of formula (I), (ii) 0. 5 part to 10 parts, per part of

(i), of copper salt and (iii) 0. 5 part to 10 parts, per part of (i) of a member selected from the class consisting of ascorbic acid, an ascorbic acid derivative and mixture thereof.

Anions included by Y of formula (I) are, for example,

MQ , where M is a metal or metalloid, Q is a halogen radical and d d is an integer having a value of from about 4-6 inclusive. Besides epoxy resins, formula (I) iodonium salts also have been found to be useful in curing cyclic ethers, lactones, lactams and cyclic acetals, where the iodinium salts also can have non-nucleophilic counterions such as per chlorate, CF,SO, ~ and C, H .SO,~. Again, the cation-

3 3 6 4 3 ically polymerizable material is a phenol -formaldehyde resin, urea -formaldehyde or melamine -formaldehyde resin, Y of formula (I) also can include in addition to MQ , and the other non-nucleophilic d counterions previously recited, halide counterions such as Cl, Br,

F and I as well as nitrate, phosphate.

Radicals included by R of formula (I) can be the same or different aromatic carbocyclic or heterocyclic radicals having from

6 to 20 carbon atoms, which can be substituted with from 1 to 4 monovalent radicals selected from C . _{n 0} . al oxy, phenyl,

(l-o)

chlorophenyl, nitrophenyl, methoxyphenyl, pyridyl, etc. Radicals included by R are divalent radicals such as

0 0

R' etc., Z can be -0- , -S-, -S- , -S-, -(CH.,0)-, -C- , -N- , ii ■ -i n

0

R is C... ₀ . a yl or C., ,_,, aryl and n is an integer equal to 1-8 (l-o) (D-13) inclusive. Metal or metalloids included by M of formula (I) are transition metals such as Sb, Fe, Sn, Bi, Al, Ga, In, Tx, Zr, Sc,

V, Cr, Mn, Cs, rare earth elements such as the lanthanides, for example, Cd, Pr, Nd, actinides, such as Th, Pa, TJ, Np, and metalloids such as B, P, As, etc. Complex anions included by

MQ ^" ~ ^e ' are, for example BF,~, PF ~, AsF ^" , SbF ~, FeCl. , d ^ 6 6 6 4

SnCl, ^" , SbCl ~ BiCl =.. 6 6 5

Halonium salts included by formula (I) are, for example,

There is also provided by the present invention a foaming method which comprises (I) agitating a curable composition com¬ prising

(C) a cationically polymerizable organic material,

(D) 1% to 35% by weight of the curable composition of a mixture of formula (I),

(iv) a diaryliodonium salt of formula (I), (v) 0. 5 part to 10 parts, per part of (iv), of a copper salt and (vi) 0. 5 part to 10 parts, per part of (iv), of a member selected from ascorbic acid, an ascorbic acid derivative, and mixtures thereof,

(E) 1% to 30% by weight of (C), (D) & (E) of a volatile inert organic solvent, and (2) thereafter allowing the ingredients of the resulting mixture to react resulting in the production of exothermic heat and the simultaneous vaporization of the organic solvent and the cure of the cationically curable organic resin.

Copper I and II salts included by the redox system of the

present invention are, for example, carboxylic acid and mineral acid copper salts such as Cu(II) citrate Cu(II) formate, Cu(II) acetate, Cu(II) stearate, Cu(II) oleate, Cu(II) carbonate; Cu(I) bromide, Cu(I) chloride, Cu(II) nitrate, Cu(II) sulfonate, Cu(II) gluconate. As cor - bic acid and its derivatives which can be employed in combination with the copper salts include, for example, ascorboyl palmitate, as- corboyl oleate, as corboyl acetate.

The diaryliodonium salts of formula (I) and methods for making the are shown in Crivello U. S. patent 3, 981, 897. Additional methods for making such diaryliodonium salts are shown by F. M. Beringer, R. A. Falk, M. Kar al, J. Lillien, G. Masullo, M. Mausner, E. Sommer, J. Am. Chem. Soc. , 81_342 (1958) and I. Mason, Nature, 139, 150 (1937); I. Mason and E. Race, J. Am. Chem. Soc , 1718 (1937). Included by the cationically polymerizable materials which can be employed in the curable compositions of the present invention are, for example, epoxy resins which include any monomeric, dimeric or oligomeric or polymeric epoxy material containing one or a plur¬ ality of epoxy functional gro ups. For example, those resins which result from the reaction of bis -phenol- A (4, 4' -isopropylidenediphenol) and epichlorohydrin, or by the reaction of low molecular weight phenol-formaldehyde resins (Novolak resins ) with epichlorohydrin, can be used alone or in combination with an epoxy containing compound as a reactive diluent . Such diluents as phenyl glycidyl ether, 4-vinyl- cyclohexene dioxide, limonene dioxide, 1, 2-cyclohexene oxide, glycidyl acrylate, glycidyl methacrylate, styrene oxide, allyl glycidyl ether, may be added as viscosity modifying agents .

In addition, the range of these compounds can be extended to include polymeric materials containing terminal or pendant epoxy groups . Examples of these compounds are vinyl copolymers con¬ taining glycidyl acrylate or methacrylate as one of the comonomers . Other classes of epoxy containing polymers amenable to cure using

_OΛ-_Γ; _

^{' '}

the above catalysts are epoxy -siloxane resins, epoxy -polyu ethanes and epoxy -polyesters . Such polymers usually have epoxy functional groups at the ends of their chains. Epoxy -siloxane resins and method for making are more particularly shown by E. P. Plueddemann and G. Fanger, J. Am. Chem. Soc. 8JL 632- 5 (1959). As described in the literature, epoxy resins can also be modified in a number of standard ways such as reactions with amines, carboxylic acids , thiols, phenols alcohols, etc. , as shown in U. S. patents 2, 935, 488; 3, 235, 620, 3, 369, 055; 3, 379, 653; 3, 398, 211; 3, 403, 199; 3, 563, 850; 3, 567, 797; 3, 677, 995. Further examples of epoxy resins which can be used are shown in the Encyclopedia of Polymer Science and Technology, Vol. 6, 1967, Inters cience Publishers, New York, pp 209 -271.

Additional examples of the cationically polymerizable mat¬ erials are, for example, vinyl organic monomers, vinyl organic pre- polymers, cyclic organic ethers, cyclic organic esters, cyclic organi sulfides, organo silicon cyclics, etc. There are included,, for exampl styrene, vinyl acetamide, - -methyl styrene, isobutyl vinylether, n-octyl vinylether, acrolein, 1, l _r diphenylethylene, ^β -pinene ; vinyl arenes such as 4-vinyl biphenyl, 1-vinyl pyrene, 2-vinyl fluorene, acenaphthalene, 1 and 2-vinyl naphthalene; 9 -vinyl carbazole, vinyl pyrrolidone, 3- methyl -1-butene; vinyl cycloaliphatics such as vinyl - cyclohexane, vinyl cyclopropane, 1-phenylvinylcyclopropane; dienes such as isolbutylene, isoprene, butadiene, 1, 4-pentadiene.

Some of the vinyl organic prepoly ers which can be us ed to make the polymerizable compositions of the present invention are, for example CH =CH-0-(CH ₂ -CH ₂ 0) -CH^CH-, where m is a posi¬ tive integer having a value up to about 1000 or higher; multi¬ functional vinylether s, such as 1, 2, 3 -propane trivinyl ether, pre¬ polymers having the formula,

_0A.PI

5 WWiiPPOO

and low molecular weight polybutadiene having a vis cosity of from 200 to 10, 000 centipoises at 25 C. Products resulting from the cure of such compositions can be us ed as potting resins , cros slinked coat¬ ings , printing inks and other applications typical of thermos etting or network resins .

A further category of the organic materials which can be used to make the polymerizable compositions are cyclic ethers which are convertible to thermoplastics . Included by such cyclic ehters are, for example, oxetanes such as 3, 3 -bis chloromethyl- oxetane alkox oxetanes as shown by Schroeter U. S. Patent 3, 673, 216, assigned to the same as signee as the pres ent invention; oxolanes such as tetrahydrofuran, oxepanes, oxygen containing spiro compounds , trioxane, dioxolane.

In addition to cyclic ethers, there are also included cyclic esters such as β - lactones , for example, propiolactone, cyclic amines, such a 1, 3, 3 -trimethylazetidine and organosilicone cyclics , for example, materials included by the

R ₂ S iO

where R" can be the s ame or different monovalent organic radicals such as methyl or phenyl and q is an integer equal to 3 to 8 inclusive. An example of an organosilicon cyclic is hexamethyl trisiloxane, octamethyl tetrasiloxane, etc. The products made in accordance with the pres ent invention are high molecular weight oils and gums .

_., O. Pl ^v - ^: --° -

Included by the thermosetting organic condensation resins of formaldehyde which can be used in the practice of the present in¬ vention are, for example, urea type resins, such as

[CH ₂ ^« N-CONH ₂ ] _χ . H ₂ 0

[ CH ₂ =NC0 H ₂ ] _χ CH ₃ C00H

[CH ₂ --NC0NHCH ₂ NHC0NHCH ₂ 0H] ;

phenol -formaldehyde type resins, such as

where r and s are integers having a value of 1 or greater;

In addition, there can be used melamine thiourea resins , melamine, or urea aldehyde resins, cresol-formaldehyde resins and combinations with other car boxy, hydroxyl, a ino and mercapto con¬ taining resins, such as polyesters, alkyds and polysulfides . In particular instances , depending upon the compatability of the halonium salt with the organic material, the halonium salt can be dissolved or dispersed in an organic solvent such an nitro methane, acetonitrile, methylene chloride, etc. , prior to its incorporation into the organic material. Experience has shown that the proportion of halonium salt to organic material can vary widely inasmuch as the salt is substantially inert, unles s activated. Effective results can be achieved, for example, if a proportion of at least 0. 1% by weight of halonium salt is employed, based on the weight of polymer¬ izable composition. Higher or lower amounts can be used, however, depending upon factors such as the nature of organic material, and polymerization time desired.

In the practice of the invention, the curable compositions can be made by effecting contact between the diaryliodonium salt, the cationically polymerizable organic resin and the redox system of the copper salt and the ascorbic acid or as corbic acid derivative. In certain situations, a volatile organic solvent als o can be utilized in combination with the aforementioned ingredients to produce a foam, based on the vaporization of the organic solvent due to the generation of exther ic heat of reaction while the cationically polymerizable organic resin is curing.

It has been found that contact between the various ingred¬ ients of the curable mixture of the present invention can be effected if the diaryliodonium salt is contacted with the redox catalyst in the presence of the cationically polymerizable organic material. For example, the diaryliodonium salt can be combined with an epoxy resin to produce a stable mixture while the redox catalyst can separately be employed in combination with an epoxy resin which also has infinite shelf stability. In instances where a foam is desired, a volatile organic solvent can be combined with either of the afore - mentioned stable mixtures or can be introduced separately during the mixing of the respective mixtures. Suitable volatile organic solvents which can be employed to produce rigid or flexible foams in the practice of the present invention are, for example, acetone, hexane, trichlorofluoromethane, n-pentane 2 -methylhexane, dichloro- methane, 1, 1, 2-trichlorotrifluoroethane, methyl alcohol, ethyl alcohol and methyl ethyl ketone. In addition to such volatile solvents, there are also included thermally unstable compounds such as ethylene car¬ bonate, ammonium nitrite, benzoyl peroxide, cyclohexanone peroxide, methyl ethyl ketone peroxide, 2, 2' -azobis (2-methylpropionitrile), azobisforma ide, etc.

The foamable mixture can be injection molded into suitable recptacles, such as refrigerator doors and the like to provide for the production of insulating foams . Thorough mixing of the ingredients has been found to facilitate the production of a uniform foam which can be achieved by the erαployment of a mechanical stirrer or agita¬ tor, as generally utilized in the art.

In instances -where a flexible foam is desired, the above described epoxy resin can be combined with pol caprolactones or any hydroxy terminated polyester to render the foams made in ac¬ cordance with the present invention more flexible. Typical hydroxy terminated polycaprotactones are Niax pol ols, manufactured by the Union Carbide Corporation. There can be utilized from 1 to 60 parts

of the hydroxy terminated polyester per part of the epoxy resin and preferably from 1 to 50 parts. Included by the hydroxy terminated polyesters which can be employed in the practice of the pres ent in¬ vention to flexibilize cured epoxy resin films or foams are compounds of the formula,

CH ₃ 0 0

H- -0- CH ₂ -C-CH ₂ -0-C - CH ₂ - - C- — OH , CH ₃ ^C

where t is an integer having an average value of from 1 to 100. As previously indicated, the curable compositions of the present invention also can be used in coating applications and in the production of rigid or flexible films . In addition to the cationically • polymerizable organic resin which includes any of the aforementioned epoxy resins, as well as the organic cyclics as previously defined, as well as additives , such as caprolactones for flexibilizing the films and foams made therefrom, there also can be combined with such ingred¬ ients fillers in a proportion by weight of from 0 to 500 parts of such filler per 100 parts of the cationically polmerizable organic resin. Suitable fillers include, for example, talc, alumina fibers mica, barium sul ate, titanium dioxide.

In addition, the above curable compositions may include additives to enhance surface properties and to control foam cell size. Among such additives are polyalkylene oxide surfactants and silicone fluids . In order that those skilled in the art will be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation. All parts are by weight. Example 1. There was added a mixture of copper salt and as corbic

acid in n-butanol to a 3% solution of diphenyliodoniu hexafluoro- arsenate in 3, 4-epox cyclohexylmethyl-3', 4-epαxycyclohexanecar- boxylate. A series of mixtures were made following the procedure using various copper compounds to produce mixtures having an average of from 1-3% by weight of the copper salt and from 0. 5 to 3% by weight of ascorbic acid, based on the weight of the mixture. The cure time (sec) was recorded which represented the time for the respective mixtures to harden when examined in 4 dram vials. The following results were obtained where the percent shown is based on the weight % of the ingredient in the mixture:

Copper II Compound Ascorbic Acid Cure Time T (7,) WT (7.) (sec)

- No Cure

3 No Cure ^' Copper benzoate (3) - No Cure

Copper benzoate (3) 3 380

Copper benzoate ( 1) .05 120

Copper benzoate (1) 1 <60

Copper s tearate ( 1) 1 60-120 Copper acetate (3) 3 30

Copper formate (3) 3 30

Copper benzoate ( 1) 2 <30

The above results show the need for copper salts and the ascorbic acid to achieve a cure of the epoxy resin and the effect on the cure time when the weight percent of the respective ingredient is varied at ambient conditions. Example 2.

A study was made with a mixture of an epoxy resin con¬ taining 1% by weight of copper benzoate and 3% by weight of ascorbic

acid to determine whether cure time would be affected by varying the type of diaryliodonium salt used. The redox catalyst was added as a suspension in ethylene glycol to the epoxy resin of Example 1 which contained 3% by weight of diaryliodonium salt. The following results were obtained:

Diaryliodonium Salt Cure Time ( s ec)

The above results show that the structure of the nion and the cation of the diaryliodonium salt had a significant effect on the epoxy resin cure time at ambient conditions. Example 3.

The procedure of Example 1 was repeated, except that 1% by weight of ascorboyl palmitate in 0. 3% by weight n-butanol, based

on the weight of the resulting curable composition, was used in place of ascorbic acid. It was found that the resulting composition cured within 3 -4 minutes without the us e of external heat under atmos pheric conditions. Example 4.

There was added 0. 1 part of copper benzoate and 0. 2 part of ascorbic acid in combination with 0. 6 part of acetone to a mixture with stirring consisting of 6 parts of 3, 4-epoxycyclohexlmethyl-3 ^r , 4' - epoxycyclohexane carboxylate and 0. 2 part of diphenyliodoniu hexa- fluo roar senate. The mixture was stirred vigorously and then allowed to stand in a small container. After about 150 seconds , the mixture foamed and filled the container. There was obtained a rigid foam having a density of approximately 0. 05 g/cc. The foam was suitable as a thermal insulator for a refrigerator. The above procedure was repeated, except that Freon 11 was used in place of acetone. A foam was formed similar to the foam, obtained using acetone. Example 5.

A mixture of 6 parts of 3, 4-epoxycyclohexylmethyl-3 ' , 4 ¹ - epoxycyclohexanecarboxylate and 3 parts of polycaprolactone,

PCP0300, a product of the Union Carbide Corporation, was mixed with 0. 2 part of diphenyliodonium hexafluoroarsenate, 0. 1 part of copper benzoate, 0. 2 part of ascorbic acid and 0. 6 part of acetone. The mixture was vigorously stirred in a small glass container approx imately 1/3 filled. In approximately 150 seconds the reaction mixture foamed and filled the container and then overflowed the container. The resulting foam was found to be flexible, based on the fact that it could be flexed at 180 without being permanently set. The density of the foam was approximately the same as in Example 4. Example 6.

There was added to a .1. 5% solution of diphenyliodonium hexafluoroarsenate in 2-chloroethylvinyl ether, 0. 5% of copper

benzoate and 0. 5% of as corbic acid. A vigorous reaction occurred within 3 minutes. The reaction mixture was then poured into methanol after standing an additional 15 minutes. There was obtained a 61. 3% yeild of polychloroethylvinyl ether after the resulting product was washed in methanol and dryed.

The above procedure was repeated, except that tri ethyl- eneoxide was used in place of 2 -chloroethylvinyl ether and the re¬ action was performed at 0 C. A 41. 4% yield of polytrimethyle e oxide was obtained. Example 7.

There was added 0. 3 part of copper benzoate and 0. 3 part of ascorbic acid suspended in ethylene glycol to 9. 4 parts of an acid reactive resole phenol formaldehyde based resin having allylic ether functional groups (Methylon 11 of the General Electric Company). The mixture was stirred thoroughly and poured into a shallow aluminum cup. After 30 minutes, the phenol formaldehyde resin was found to have cured to a hard rigid solid.

^' "