CA1224928A - Coated abrasive containing epoxy binder and method of producing the same - Google Patents

Abstract

Coated Abrasive Containing Epoxy Binder and Method of Producing the Same Abstract An epoxy resin latently curable composition including a novel curing agent comprising the liquid salt of a substituted pentafluoroantimonic acid and an aromatic amine selected from the group consisting of aniline and a hindered amine has a desirably long pot life yet cures rapidly with heating to a cured composition. A novel coated abrasive product is provided which includes the cured resin as a binder.

Description

~2~

Technical Field ~
This invention relates to coated abrasive produc~s l-aving an epoxy resin binder which holds and supports abrasive granules on a backing sheet. In another aspect, the invention relates to a method of making such a coated abrasive product employing liquid epoxy resin and a novel curing agent therefore.

Background Art .
Coated abrasives or coated abrasive products generally comprise a flexible backing upon which an adhesive binder holds and supports a coating of abrasive granules. The backing may be paper, cloth, film, vulcanized fiber, etc.
or a combination of one or more of these ma~erials. The abrasive granules may be formed of flint, garnet, aluminum oxide, alumina:zirconia, diamond, silicon carbide, etc.
Popular present day binders are phenolic resins, hide glue and varnish. Besides phenolic resins, hide glue and varnish, other known resinous binder materials employed in the preparation of coated abrasive products include epoxy resins, ureaform~ldehyde and polyurethane resins.
The coated abrasive may employ a "make" coat o~
resinous binder material which is utilized to secure the ends of the abrasive granules onto the sheet as the granules are oriented and a "Size" coat of resinous binder material over the make coat which provides for firm adherent bonding of the abrasive granules to the sheet. The size coating may be the sa~e as the maJce coating or of differen~ rc~inou~
material.

.r The popular presen~ly used binders for coated abrasives have many disadvantages. Hide glue make coatlngs are generally re~uired to be applied hot (about 150F) and must be cooled below their gel ~emperature before another coat can be applied. Hide glue size coatings are also generally applied hot, requiring drying times on the order of 30 minutes to 2 hours at 100 - 135E~. Hide glue is also water-soluble and may result in removal of the abrasive granules upon exposure to moisture. Varnish make coatings generally require cure or drying times of about 8 hours at about 195F. Phenolic size coatings require at least 2 hours to cure at 195 F. Phenolic coatings are also usually pre-cured for at least one hour.
While epoxy resins appear to be good candidates for the binder material of a coated abrasive product, and some have been used for this purpose, the abrasive products employing epoxy resin binders have not been satisfactory because of deficiencies in the coating process, mainly because of curing time.
Epoxy resins are monomers or prepolymers that further react with curing agents to yield high-performance thermo-setting plastics. They have gained wide acceptance in pro--tective coatings and electrical and structural applications because of their exceptional combination of properties such as toughness, adhesion, chemical resistance, and superior electrical properties.
Epoxy resins are characterized by the presence of a 3-member cyclic ether group commonly referred to as an epoxy, 1,2-epoxide, or oxirane group. The epoxy resins are commonly cured, or caused to harden, by the addition o~ a curing or hardening agent. Curing agents commonly used to convert epoxy resins to thermosets include anhydrides, amines, polyamides, Lewis acids, and others. Many curing agents begin to react immediately, or after a short period of time, even at room ~emperature or lower temperatures.
This requires that the epoxy resin and the curing agent be stored separately and only mixed immediately before use.
This is extremely inconvenien-t in some cases and also leads to waste if part or all of the mixture cannot be used in time.
While various attempts have been made to prolong the cure time or "pot life" of cura~le epoxy resin compositions, they have met with limited success. The preferred curing agents, Lewis acids, cannot be used where appreciable pot life of the composition is required. Because of the rapidity with which the Lewis acid brings about curing of the epoxy resin compositions, various attempts have been made to modify the Lewis acid in order to prolong the cure time or pot life o~ the composition. One method of accomplishing this result has called-for the formation of a complex of the Lewis acid with a nucleophilic reagent such as an ether, alcohol, amine or the like. It has been generally found, however, that any increase in pot life of epoxy compositions containing the modified version of the Lewis acid results in a corresponding sacrifice of cure time and/or physical characteristics of the resultant cured resin.
Various references disclosing the preparation and/or use of curing agents for epoxy resins and/or other curable compositions are discussed below.
Harris (U.S. Pat. No. 3,542,828) discloses hexafluoro-antimonate amine catalys~s useful in cationic polymerization of vinyl ether. Harris reacts fluoroantimonic acid or its alkaline salt with amines such as aniline, diphenylamine, triphenylamine, me~hylamine, diethylamine, trimethylamine, nonylamin,e, trichlorophenylamine, ~ritolylamine and the like to produce his catalyst. Experimentation has shown that the Harris catalyst does not appreciably increase the pot life of epoxy resin compositions to produce a room temperature latent composition which cures rapidly with heating. In fact, some epoxy resin compositions catalyzed with ~he Harris catalyst have ~een found to cure rapidly as low as OC .
White et al (U.S. Pat. No. 3,565,861) discloses amine complexes of phosphorous pentafluoride, arsenic penta-fluoride, or antimony pentafluoride with a primary acylic aliphatic amine ~o provide latent curing agents for epoxy resins. This patent points out that amines having the NH2 z~
group attached directly to an unsubstitu~ed aromatic ring form complexes which function as rapid curing agents but are not sufficiently stable to be latent curing agents.
Udding et al (U.S. Pat. No. 3,879,312) discloses a process for the preparatioll of polyester polyols by cationic polymerization of or~anic cyclic ethers using hydroxyl ammonium hexafluoroantimonate catalysts. Such catalysts have been found not to provide an appreciably long pot life for epoxy resin compositions and have been found to cause such epoxy compositions to cure at relatively low temperatures, even as low as 36C.
Buck et al (U.K. Pat. Spec. No. 963,058) discloses room temperature storable mixtures of epoxy resin and a curing agent provided by the amine salt of hydrofluoroboric acid.
Any amine appears to be suitable including primary, secondary, tertiary aliphatic or aromatic amine, hetero-cyclicamine, or alicyclic amine, with or without nuclear or side-chain substituents, although ~he aromatic amines are designated as preferred, because of curing temperature considerations.
While certain of the modi~ied catalysts or curing agents known in the prior art have been somewhat successful in prolonging the cure time or pot life of a curable epoxy composition, few are known to applicant to provide a significant increase in pot life which, for example, permits s~orage of -the mixture of epoxy resin composition and curing agent for a matter of days at room temperature yet provides rapid cure at an elevated curin~ temperature.

Disclosure of the Invention .
In accordance with the present invention, an improved coated abrasive employing epoxy resin binder is provlded.
~Binding is accomplished by the use of a one-part latent, room-temperature stable epoxy resin-catalyst system which is curable to epoxy binder. The curable epoxy resin contains a novel modified Bronsted acid catalyst sys~em or curing agent. The catalyst and the curable epoxy resin are described in prior copending application Serial No. 616,438, 5~
filed May 31, 1984, now Patent No. 4,503,211~
The curing agent comprises a liquid sal~ of a substi-tuted pentafluoroantimonic acid and an aromatic amine selected from the group consisting of aniline and hindered amine. The mole ratio of substitu~ed pentafluoroantimonic acid to aromatic amine is in the rang~ of 1:1.05 to 1:4. The substituted pentafluoroantimonic acid has the formula H Sb~5X, wherein X is halogen, hydroxy, or -OR. "OR" is the residue of an aliphatic or aromatic alcohol preferably 19having a molecular weight of 32 to 100, oon, or more, and a primary or secondary hydroxyl functionality of at least 1, preferably at least 2. The most preferred alcohol is diethy-lene glycol, i.e., making the -OR group 2-(2-hydroxyethoxy)-ethoxy.
15In ~he preferred curing agent, the hindered amine has the general formula ~ <

wherein Rl and R2 are independently hydrogen, primary or secondary lower alkyl group having 1-6 carbon atoms, or benzyl;
R3, R4, and R5 are independently hydrogen, an electron donating group, benzyl, or at least one of R3 and R4 is joined together with R5 to form a benzo group;
provided that, if no benzo group is present in the hindered amine, at least one of Rl~ R2, R3, and R4 is an alkyl group or an 0 electron donating group; and i R3, R4 and one of Rl or R2 is hydrogen, the other of Rl or R2 is an alkyl group having at least 2 carbon atoms.
~f the curing agen~ is used to cure cycloaliphatic epoxide material, at least one of Rl or R2 is preferably lower alkyl of 1 to 6 carbon atoms and at least one of R
or R4 is an electron donating group.

- 6 ~ ~2~9~
Suitable electron donating groups include a hydroxyl group, branched straight chain or cylic alkyl or alkoxy groups having up to 18 carbon atoms and amine groups.
The coated abrasive products according to the present invention are characterized by having at least a make coating or a size coating of epoxy resin binder. This binder coating contains residual curing agent derived from substi-tuted pentafluoroantimonic acid and an aromatic amine selec~ed from the group consisting of aniline and hindered 0 amine.
The invention also provides an improved method of making coated abrasive products. The improved method has the s~eps of:
(1) uniformly coating a backing sheet with a make coat of a first resinous material in liquid form;

(2) depositing a plurality of abrasive granules uniformly over the surface of the make coat of the first resinous material;

(3) curing the first resinous material to adherently bond the granules to the backing sheet surface;

(4) coating over the make coat and the granules with a size coat of a second resinous materiali and

(5) curing the resultant coated product until the second resinous material is solid.
The improvement comprises employing, as at least one of the first or the second resinous binder material, a latent, stable curable composition. The curable composition comprises:
(A) epoxy resin composition having a 1,2-epoxy equivalency greater than onei and (B) a curing agent in an amount sufficient to cure the composition of heating comprising substituted pentafluoroantimonic acid having the general formula H SbF5X wherein X is halogen, a hydroxy, or an OR group wherein OR is the residue of an aliphatic or aromatic alocholi and aromatic amine seleoted from the group consisting of aniline and hindered amine. The mole ratio of the su~sti-tuted pentafluoroantimonic acid to aromatic amine is in the ~ange of 1:1.05 to 1:4. ~ ~
The following de~initions are provided ~or terms used in the present application:
The term "pot life" or "pot stability" means the time taken for a composition to increase ten-fold in viscosity.
The term "latent" or "latently curable" means an appreciable delay in the cure time or a relatively long po~
life or pot stability, preferably 5 days or more.
The term "hindered aromatic amine" means an aromatic compound having an amine nitrogen attached directly to an aromatic group and at least one alkyl group attached to the nitrogen or to a carbon alpha to the carbon atom to which the amino group is attached.

Detailed De iptlon The the~mally curable resin compositions of the present invention comprise epoxy resin having an epoxide function-ality of at least one. The thermally curable resin compo-sition may also include up to one hydroxyl equivalent per epoxy equivalent of an aliphatic alcohol having a hydroxyl functionality of at least one, co-reactive, cationically polymerizable, ethylenically unsaturated monomer, and other additi~e ingredients conventional in ~ormulating curable compositions of this type.
Examples of aromatic amines useful in preparing the curing agent o~ the present invention include the ~ollowing:
2-methylaniline, 2-isopropylaniline, 2-propylaniline, 2-hexylaniline, 2,4-dimethylaniline, 2,5-dimethylaniline, 2,6-dimethylaniline, 2,6-diethylaniline, N,2,6-triethyl-aniline, N-methyl-2,6-diethylaniline, N,N,2~trimethyl-aniline~ N,N,2,6-tetramethylaniline, 2,6-dipropylaniline, 2,6-diisobu~ylaniline, 2,6-di-n-butylaniline, 2,6-di-n-pentylaniline, N,N,diethyl-2-n-butylaniline 2,4,6-triethyl-aniline, N,N dimethyl-2,6-diethylaniline, 2,3,4,5,6-penta-methylaniline, l-naphthylamine, 2-methoxyaniline, 2,4-di-methoxyaniline, 2-methoxy-N-methylaniline, N-propylaniline, N-n-hexylaniline, N-sec-butylaniline, N-benzylaniline, N,N,2-trimethylaniline, 2-ethyl-6-sec-butylaniline, m-phenylenediamine, p-phenylenediamine, 2,6-diethyl-m-- 8 ~ 2~

phenylene-diamine.
.
The curing agent for use in the curable compositions of the invention are Bronsted acid salts of hindered amines that are prepared by the addition of 1.05 to ~.0 moles of hindered amine to one mole of suhstituted pentafluoroanti-monic acid. The addition is conveniently carried out in a low boiling solvent such as diethyl ether or sulfur dioxide.
The substituted antimonic acids are prepared by the addition of one mole of antimony pentafluoride in sulfur dioxide or other .suitable solvent to one mole of hydrogen halide, such as HF, HCl, HBr or HI, or water to form hexafluoroantimonic acid, chloropentafluoroantimonic acid, bromopentafluoro-antimonic acid, iodopentafluoroantimonic acid, or hydroxy-pentafluoroantiomonic acid, respectively. Because of the exothermic nature of these reactions, care should be taken to avoid splattering.
The hindered amine salt, in which X is OR, is the most preferred modified Bronsted acid. It is prepared by mixing one molar equivalent of antimony pentafluoride with one or more molar equivalents of an alcohol that is liquid at the reaction temperature. Conveniently, the curing agent is prepared by the addition of one part by weight of antimony pentafluoride to one to ten parts by weight of alcohol followed by the addition of 1~05 to 4.0 moles of hindered aromatic amine. In this method, alcohol used in excess of one mole per mole of antimony pentafluoride performs as solvent during the preparation of the hindered amine salt which, by reason of its hydroxy group, reacts with an epoxide group in the epoxy resin composition. In place of the solvent alcohol (i.e., alcohol in excess of an equiva-lent of antimony pentafluoride) other electron donating solvents such as die-thyl ether, diglyme, and sulfur dioxide may be used.
Alcohols having a hydroxyl functionali-ty of at least one may be used in the present invention as elther a co-reactant and solvent in the preparation of the liquid salt of a substi~uted pentafluoroantimonic acid with hindered amine or as an optional component of the curable _ 9 epoxy resin composition. Such alcohols may be any aliphatic or aromatic alcohol or a li~uid mixture ~f one or more solid alcohols with one or more liquid alcohols.
Representative examples of suitable aliphatic alcohols having a hydroxyl functionality of one include alkanols, monoalkyl ethers of polyoxyalkylene glycols, monoalkyl ethers of alkylene glycols, and others known to the art.
Representative examples of suitable mon~meric aliphatic alcohols having a hydroxyl functionality greater than one include alkylene glycols (e.g., 1,2-ethanediol, 1,3-propane-diol, 1,4-butanediol, 2-ethyl-1,6-hexanediol, bis(hydroxy-methyl)cyclohexane, l,l~-dihydroxyoctadecane, 3-chloro-1,2-propanediol)~ polyhydroxyalkanes (e.g., glycerine, tri-methylolethane, pentaerythrltol, sorbitol) and other poly-lS hydroxy compounds such as N,N bis(hydroxyethyl)benzamide,2-butyne-1,4-diol, 4,4'-bis(hydroxymethyl)diphenylsulfone, castor oil, etc.
Representative examples of suitable glycols include .... poly~xyethylene and polyoxypropylene glycols and triols having molecular weights from about 106 to about 10,000 corresponding to equivalent weight of 53 to 5,000 for the diols or 70 to 3,300 for triols; polytetramethylene glycols of varying molecular weight; copolymers o~ hydroxypropyl and hydroxyethyl acrylates and methacrylates with other free radical-polymerizable monomers such as acrylate esters, vinyl halides, or styrene; copolymers containing pendent hydroxy groups formed by hydrolysis or partial hydrolysis o~ vinyl ace~a~e copolym~r~, pol~vinylacetal resins containing pendent hydroxy groups; modified cellulose ~olymers such as hydroxyethylated and hydroxypropylated cellulose; hydroxy-terminated poly sters and hydroxy-terminated polytactones; and hydroxy-texminated polyalka-dienes. Especially preferred are di,tri-, and tetraethylene glycol.
Useful commercially available aliphatic alcohols include glycols commercially available under the registered trademark "Polymeg" (available from Quaker Oats Company) lncluding, for example, polytetramethylene ether glycols such as "Polymeg" 650, 10~0 and 2~00; glycols coi~lercially available under the trade designation "Pep" (available from Wyandotte Chemicals Corporation) including polyoxyalkylene tetrols having secondary hydroxyl groups such as "Pep" 450, 550 and 650; polyols available under the commercial desig-nation "PCP" (available from Union Carbide) including poly-caprol.actone polyols such as "PCP" 0200, 0210, 0230, 0240, 0300; aliphatic polyester diols available under the trade-mark "Paraplex U-148" (available from Rohm and Haas);
saturated polyester polyols available under the registered trademark "Multron" (available from Mobay Chemical Co.) such as "Multron" R-2, R-12A, R-16, R-18, R-38, R-68 and R-74;
hydroxypropyla~ed cellulose having an equivalent weight of approximately 100 available under the trademark "Klucel E"
(available from Hercules Inc.); and cellulose acetate butyrate ester having a hydroxyl equivalent weight of approximately 400 "Alcohol Soluble Butyrate" (available from Eastman Kodak).
. Representation examples of suitable aromatic alcohols include phenols such as phenol, cardinol, m-cresol, 2-methyl-5-isopropylphenol (carvacrol), 3-methyl-6-tert-butylphenol, 2,4-dimethyl-6-tert-butyl phenol, guaiacol, m-, o-, and p-chlorophenol.
The amount of alcohol used in the compositions of the invention depends upon factors such as compatibility of the hydroxyl-containing material with the epoxide, the equiva-lent weight and functionality of the hydroxy-containing material, the physical properties desired in the final cured compositions, the desired speed of cure, etc.
Generally speaking, with increasing amounts of alcohol in the composition, the cured product exhibits improved impact resistance, adhesion ko substrates, flexibility, and decreased shrinkage duriny curing, and correspondingly there is a gradual decrease in hardness, tensile strength and solvent-resistance.
Although both mono-functional and poly-functional hydroxy-con~aining materials provi~e desirable results in the compositions of the invention, use of the poly-functional hydroxy-containing materials is highly preferred 22~9%~3 ~or a majority of applications, although the mono-functional hydroxy-containing materials are particularly effective in providing low viscosity, solvent-free coating compositions.
When using hydroxyl~containing organic materials having a functionality significantly less ~han 2 (e.g., to 1 to 1.5), amounts greater than about 0 2 equivalent of hydroxyl per equivalent of epoxy tend to pro~ide cured compositions which are generally low in internal strength and tensile strength and are susceptible to solvent attack, and consequently may be unsuitable for some applications. This tendency becomes increasingly more apparent with increasing equivalent weight of the hydroxy-containing material. Accordingly, when using mono-functional hydroxy materials it is preferred that the equivalent weight thereo~ be no greater than about 250.
When poly-functional, hydroxy-containing organic material is used, an amount having up to one equivalent of hydroxy, preferably 0.2 to 0.5 equivalents of hydroxy per equivalent of epoxy can be used. Generally speaking, the higher the hydroxyl equivalent weight the more effective such material is in imparting a given degree of toughness and 1exibility to the cured epoxy resin composition.
Mixtures of hydroxyl-containing materials may be used, when desired. For example, one may use mixtures o~ two or more poly-functlonal hydroxy materials, one or more mono-functional hydroxy materials with poly-functional hydroxy materials etc.
The epoxide group containing materials that can be used in the curable composition of the invention are well known.
They can be any organic compound having at least one oxirane ring, i.e., -~-~-that is polymerizable by ring opening. Such materials may be monomeric or polymeric and aliphatic, cycloaliphatic, or heterocyclic but are prefer-ably aromatic. These materials generally have, on the average, at least 1.5 polymeri~able epoxy groups per molecule (preferably two or more epoxy groups per molecule).
The polymeric epoxides include linear polymers having terminal epoxy groups (e.gO, a diglycidyl ether of a poly-:L2 ~ 492~
oxyalkylene glycol), polymers having skeletal oxirane units(e.g., polybutadiene polyepoxy), and polymers having pendent epoxy groups (e.g., a glycidyl methacrylate polymer or copolymer). The epoxides may be pure compounds but are generally mixtures containing one, two, or more epoxy groups per molecule. The "average" number of epoxy groups per molecule is determined by dividing the total number of epoxy groups in the epoxy-containing material by the total number of epoxy molecules present.
These epoxy group-containing materials may vary from low molecular weight materials up to 100,000 or more.
Mixture of various epoxy group-containing materials may be used in the compositions of this invention.
Useful epoxy-containing materials include those which contain cyclohexene oxide ~roups such as the epoxycyclo-hexane carboxylate, typified by 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclo-hexylmethyl 3,4-epoxy-2-methylcyclohexane carboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipateO For a more detailed list of useful epoxides of this nature, reference is made to the U.S. Patent No. 3,117,099, incorporated herein by reference.
Further epoxy-containing materials which are particu-larly useful in the practice of this invention include glycidyl ether monomers of the formula X'(OCH2-CH-5H2)n wherein R' is alkyl but preferably is aryl and n is an interger of 1 to 6. Examples are glycidyl ethers of poly-hydric 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-epoxypropoxyphenol)-propane). Further examples of epoxides of this type which can be used in the practice of this invention are described in ~.S. Patent No. 3,018,262, incorporated herein by re~erellce and in "llandbook of Epoxy Resins" by Lee and Neville, McGraw-Hill Book Co., New York (1967).
Typical examples of preferred aromatic glycidyl ethers are the diglycidyl ethers of bisphenol A-epichlorohydrin .

- 13 ~2~9~8 resins include:
"Epon" 562 ("Epon" :is a trademark product of Shell Chemical Company) which is an uncured epoxy (liquid) having an epoxide equivalent weight (number of grams of resin containing one gram equivalent of epoxide) of 140 to 165 and an average molecular weighk of 300;
"Epon" 815 which is an uncured epoxy (liquid) having an epoxide equivalent weight of 175 to 210 and an average molecular weight of 340 to 400;
"Epon" 820 which is an uncured epoxy (liquid) having an epoxide equivalent weight of 175 to 210 and an average molecular weight of 350 to 400;
"Epon" 828 which is an uncured epoxy (liquid) having an epoxide equivalent of about 190 and an average molecular weight of 350 to 400;
"~pon" 834 which is an uncured epoxy (liquid) having an ~poxide equivalent weight 225 to 290 and an average molecular weight of 450;
"DER" 331 ("DER" is a trademark product of Dow Chemical Company) which is an epoxy resin having an epoxide equiva-lent weight of 182 to 190 and a viscoslty of 10,000 to 16,000 cps;
"Epon" 1310 which is understood to be the condensation product of l,1,2,2-tetrabis (4-hydroxyphenyl) ethane and epichlorochydrin having an average of about three glycidl ether groups in the molecule;
"Epon" 812 is a liquid glycerol polyglycidyl ether resin marketed by Shell Chemical Company having a 3 max.
Gardener color, 1.0 to 1.7 poises viscosity at 25 C, and l40 to 160 epoxy e~quivalent weight, as noted in Modern Plastics Encyclopedia, 1965, Vol. 42. No. la, p. 206, New York, N.Y., McGraw-Hill, Inc. (September 1964);
"Epon" 826 is a liquid bisphenol A-diglycidyl e~her resin marketed by Shell Chemical- Company having a 2 max.
Gardener color, 65 to 95 poises viscosity a~ 25C., and 180 to 188 epoxy equivalent weight, as noted in Modern Plastics Encyclopedia, 1965, Vol. ~2, No. la, p. 206, New York, N.Y., McGraw-Hill, Inc. (September 1964);

"Araldite" 6004 is a ~iquid bisphenol A-diglycidyl ether resin marketed by Ciba Products Company having a 185 epoxy equivalent weigh-t, and 5,000 to 6,000 centipoises of viscosity at 25C as disclosed in ~.S. Patent No. 2,633,458;
and "ERL" 2772 is a liquid bisphenol A-diglycidyl ether resin marketed by Union Carbide Plastics Division having a 7,000 to 9,000 centipoise viscosity at 25C and 175 to 185 epoxy equivalent weight. Also see Example 1 of U.S. Pat. No.
2,506,486, issued May ~, 1950 (Howard L. Bender et al) entitled "Thermosetting Resin From a Diphenol and a Diglycidyl Ether of a Diphenol."
Still other aromatic glycidyl ethers that may be used are the reaction products of epichlorohydrin with polyhydric phenols including resorcinol, catechol, hydroquinone, phloroglucinol and ~he polynuclear phenols including p,p-dihydroxydibenzyl, p,p-dihydroxydiphenyl, p,p'dihydroxy-phenyl sulfone, p,p'dihydroxybenzophenone, 2,2'dihydroxy-l,l'-dinaphthylemethane, and the 2,2'; 2,3'; 2,4; 3,3';
3,4'; and 4,4' isomers of dihydroxydiphenylmethane, dihydroxydiphenyldimethylmethane, dihydroxy-diphenylethylmethylmethane, dihydrodiphenylmethylpropyl-methane, dihydroxydiphenylethylphenylmethane, dihydroxy-diphenylpropylphenylmethane, dihydroxydiphenylbutylphenyl-methane, dihydroxydiphenyltolymethane, dihydroxydiphenyl-~olylmethylmethane, dihydroxydiphenyldicyclohexylmethane, dihydroxydiphenylcyclohexane, poly-hydric phenolic formal-dehyde condensation products, and the like. Preferred poly-glycidyl polyethers are those which contain as reactive groups only epoxy groups and hydroxyl groups. Where the aromatic glycidyl ether has a melting point above 30C, it is desirable that the epoxy resin composition also contain material having a hydroxyl group or material having co-reactive ethylenic unsaturation or both so that the mixture has a melting point below about 30C.
Co-reactive cationically polymerizable monomers which, as mentioned above, are an optional component with the epoxy material that may be used in the compositions of this ~rc~e ~ r~

- 15 ~
invention are any of the cationally polymeriza~le ethylenic-ally unsaturated monomers, preferably having up to 12 carbon atoms and optionally up to two atoms of oxygen and nitrogen.
Examples of such cati.onically polymerizable monomer include aliphatlc olefins s~lch as isobutylene, isoamylene, butadiene and isoprene; cycloolefin.s sllch as dipentene (limonene) arornati.c olefins such as styrene, ~-methy~styrene, t-butystyrene, ~-chlorostyrene, l-vinylnaphthalene and 2-vinylnaphthalene; vi.nyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-pentyl vinyl ether, dodecyl vinyl ether, and divinyl ether; vinyl ketones, such as methyl vi.nyl ketonc and hydroxy methyl vi.nyl ke~.one, vi.nyl hetero-cyclics such a.s N~vinyl-2-pyrrolidinone and N-isopropenyl-2-pyrroli.d.inone. The preferred cat.ionical]y polymerizab.le monomers are the olef.i.ns, most preferably styrene and dipentene.
There can be used in the curable composition up to about two parts, preferably 0.1 to 0.5 parts, by weight of ethyl.eni.cally unsaturated monomer per part of epoxy material.
The composit.ions are made by mixing in any order the epoxy material and the curing agent described above and, when used, the alcohol and cationically polymerizable monomers. It, however, is preferable to add the curing agent to the alcohol and add this mixture to the epoxy material that may contain the cationicall.y polymeri~.able monomers.
The amount of curing agent ne~ded to cure the curable composition is preferably no more than that amount needed for this purpose. Effective curing has bef-rl observed when ~he curable composition contains curing agent which resul-ts in an antimony concentra-tion of about 2 to about 500 milli-moles per kilogram total weight of curable composition.
Excessive concentrations of curing agent are preferably avoided since they are wast.eful but not harmful to the result desi.red.
The conventional components going to form the coated abrasive product of the invention will be selected from those typically used in this art. The backing, as previously -16- ~
mentioned, may be formed of paper, cloth, vulcanized fiber, film or any other backing mat~rial known for this use. The abrasive granules may be of any conventional grade utilized in the formation of coated abrasives and may be formed of flint, garnet, aluminum oxide, alumina:zirconia, diamond and silicon carbide, etc., or mixtures thereof. The frequency of the abrasive granules on the sheet will also be conventional. The abrasive granule may be oriented or may be applied to the backing without orientation, depending upon the requirement: of the particular coated abrasive product. Eit:her the make coat or ~he size coat of t:he coat:ed abrasive product may be formed of a resinous material known for t:his use, the remaininq coat:, of course, being formed of epoxy according to the invention. Both the make and size coat: may be formed of epoxy.
The use of epoxy hinder for coaled abrasives according to the present invention avoids many of the problems which plague binders gener~lly used in coated abr~sives. Epoxy does not require prolonged heating and/or dwell t:imes before subsequent: co~tings may be applied to make coatings. ~nlike glue, epoxy is unaffected by moisturen In fact, coat:ed abrasive product:s having epoxy as a binder perform well under wet grinding conditions. Unlike varnish, epoxy may be applied wit:h little or no solvent: and may be cured in a much short:er processing t:ime. Varnish softens during wet: grinding while the epc)xy is not: delet:eriously affected. Curing of epoxy is accomplished much more rapidly then phenolic resin.
The coated abrasive product. oE the invention may also include such modifications as are known in this art. For example, a back coating such as pressure-sensitive adhesive may be applied t:o t:he backing and various supersizes may be applied to the abrasive surface, such as zinc st:earate t:o prevent abrasive loading, and others.

-17- ~2~28 EXAMPLES
- The invention will be further and more specifically illustrated by the following nonlimiting examples, wherein all parts are by weight unless otherwise specified.
Examples 1-75 disclose examples of resin binder systems and Examples 76-77 disclose examples of coated abrasive products.
In certain of the Examples there is given the results of "Lap Shear Test". The Lap Shear Test is ASTM Standard Method No. D 1002-2 of Test for Strength Properties of Rdhesives in Shear by Tension ~oading Metal-to-Metal with the following modifications:
1. The adherends (or test panels) were 2024 T3 bar aluminum sheet 1.60 ~n (63 mils) thick x 102 mm (4.0 in) wide x 178 ~n (7.0 in) longi 2. The adherends were prepared with an "FPL etch" (i.e., immersed in a sulfuric acid-chromic acid bath), rinsed with tap water, and dried;
3. The components of the adhesive were weighed, then mixed by hand for two minutes until homogeneous;
4. The laminated panels were prepared by spreading adhesive at a thickness of about 0.81 mm (32 mils) onto one adherend over an area of about 75 nun (3 in) x 175 mm (6 in), leaving an uncoated area of about 50 mm (2 in) x 75 mm (3 in) and using as spacers glass -thread of about O.1 mm in diameter that was placed in the adhesive; and 5. Thc a~hercnds were held in place by a short strip of tape placed about the sides of the overlap.

Tefi L Procedure The assembled test panels were stacked on a smooth horizontal surface in an oven preheated to the test temperature in the following order: 1) two laminated panels, 2) two 100 ~n x 200 metal plates weighing about 4.5 kg each, 3) two lapped panels, and 4) one 100 mm x 200 metal plate weighing about 4.5 kg., the metal plates having been preheated to the test temperature. The metal plates were used to apply pressure to the bonds. Below, above, and between the test panels, strlps of cardboard were placed to .,, insure even distribution o:E pressure on the test panels and release paper was used to prevent the panels from being bonded one to the other by adhesive tha~ might be pressed from each assembly. The assembled stacks were left in the oven for one hour, t.hen removed from the oven and a]lowed to cool.

This example illustrates the preparation of a hindered amine Bronsted acid salt curing agent according to the present invention.
Into a 100 ml 3-neck flask equipped with a stirrer, addition funnel, thermometer, and apparatus for exclusion of atmospheric moisture was placed 21.7 g (0.2 mole) diethy~ene glycol (DEG) that had been dried by passage -through molecular seives. (In subsequent preparations, it was found that drying wa~ unnecessary) The flask was fitted wit.h an ice water bath and the conten-ts cooled to about 5C. To the cooled contents was added dropwise over a 10 minute period via the addition funnel, while stirring the mixture, 21.7 (0.1 mole) g of antimony pentafluoride. During the addition, the temperature rose to about 62C~ The m.ix~ure was coo:Led ~o 25C and there was then added 3ropwise 16.4 g (O.ll mole) 2,6-diethylaniline (DEA) over a period of lO minutes, causing the temperature to rise to about 50C. There was obtained a dark greenish-yellow fluid having about 1.1 mole of hindered aromatic amine per mole of antimonic acid. This product was designated curing agent "A".
Carbon-~3 NMI~ s~ectra on a sample of curing agent "~"
showed minor absorption peaks at 65.8 ppm and 72.7 ppm and major absorption peaks at 62.0 ppm and 72.4 ppm~ The two minor peaks are unchanged from the absorption peaks of coordinated diethylene glycol-antimony pentafluoride in the absence of DE~. Absorption peaks, typical of an aromatic amine salt were a].so seen at 129.3(C-1), l37.4~C-2~, ~27.9(C-3,5), and 130.4 ppm. This data indicates a salt ~19 ~

having the formula ~ ~ NH3 -F5SbO(CH2CH2O)2H

Infrared spec~rum of a sample of the reaction fluid showed broad bands in the 2,500 to 3,500 cm region and a band at 2,570 cm 1 supporting further the presence of a salt of the above formula.

Into a mixture of 80 g "Epon" 828 ~a trademark product of Shell Chemical Company which is an uncured gl.ycidyl ether of bisphenol A having an epoxide-equivalent weight of about 190 and an average molecular weight of 350 to 400) and 20 g diethylene glycol was added 7.3 g (containing 0.01 mole antimonic acid, 0.011 mole hindered amine and 0.02 mole of aliphatic alcohol) of curing agent "A". A ten gram portion of the mixture gelled in 6 seconds on heating at 150C.
Lap shear was determined on laminated panels that had been heated at 120/C for one hour to cure the adhesive composition. A lap shear of 3000 psi (20.7 MPa*) was o~served.
A portion of the mixture was stored at 25C. Viscosity increased from 1.,000 centipoise ~o 10,000 centipoise in 5 days.

These examples illustrate the effect o~ varying the ratio of hindered aromatic amine to antimony in substituted pentafluoroantimonic sal.ts on the characteristics of epoxy resin compositions.
A stoclc solution containing one part ant.imony pen~a-Eluoride to one part by weight of diethylene glycol was prepared as described :in Example 1. To 4.2 g, containing 0.01 mole of substituted pentafluoroant:illlollic acid, was added 0.009 to 0.031 mole of 2,6-diethylanil.ine and 20 g diethylene glycol. The mixture was thoroughly mixed and 80 g of "Epon" 828 stirred into it. The pot life, gel time, and *Megapascal lap shear strength of each composition was deterrnined and is recorded in Table I below.
_ TABLE I
Ex. Ratio Pot Life(C)Gel Time Lap Shear(b) 5 No. (a) Days Sec. at 150C MPa ~ _ . . _ . . . _ _ .
3 0.9 0.25 1 24.2 4 1.0 2 ~ 25.0 1.1 5 6 2~.2

6 1.6 7 10 17.9 10 7 2.0 10 25 20.7 8 2.6 11 40 1~.9 9 3.1 13 100 15.9 (a) ratio of moles of hindered amine to mole of subs~ituted pentafluoroantimonic acid (b) determined on laminated panels cured at 120C
(c) time for viscosity to increase 10-fold.

It is to be observed in Table I that at amine to substituted pentafluoroantimonic acid ratios of 1.0 or less there result~ a ~apid gel time and exce]lent lap shear, but an undesirably short pot life of less than 1 day. At ratios Or 1 .l to 3.1l l:he pot life is 5 days or lon~er, ge~ times are 100 seconds or shorter a~ld lap shear i6 15.9 t~ 20.7 MPa. At ratios o~ about 4.0, g~l times rise rapidly and lap shear decreases rapidly indicating increasingly poorer curing of the compositions.

EX~MPLES 10-25 These examples illustrate compositions in which aniline and various hindered aromatic amines are used in the prepar-ation of the curing agent of the invention.
Compositions were prepared as described in Examples 3-9 wit:h t:he exception that, in p~ace of 0.009 t:o 0.031 mo]e of 2,6-~icthylarliline, ~:here was used 0.02 mo~e o~ varjous hindered aromatic amines as shown in Table II below providing a molar ra-tio of hindered aromatic amine to substituted pentafluoroantimonic acid o~ two.

TABLE II
Ex. Pot Life Gel Timetd) Lap Shear No. Ilindered Amine (days)(sec.) (MPa) .. . .. _ . . _ . .. . _ lO Aniline 5 20 20.7 11 N-methylaniline 6 140 14.5 12 N,N-dimethylaniline l5 180 (e) 13 2-methylaniline 10 50 20.7 14 2,6-dimethylaniline 9 60 17.2 ~o 15 2,6-diethylanlline 10 25 20.7 16 2-methyl-6-propyl-aniline 10 50 19.3 17 2-ethyl-6-propyl-aniline 10 30 17.4 18 2-ethyl-6-~ec-butyl-aniline ~0 35 15.2 1~ 2-me~hoxyaniline 16 150 20.0 N-propylaniline ~ 30 20.0 21 N-sec-~utylaniline 30 50 17.9 22 N,N-diethylaniline >60 180 (e) 23 N,Nr2-trimethylaniline > 60 lO0 13.8 24 N,N-diethyJ-2,5 dimethylaniline >60 90 9.7 l-(dimethylamino)-naphthaline 30 18.6 26 2-isopropy]ani]ine 7 20 17.2 27 2,6-di.ethyl-m-phenylene-diarnlne 10 2S 24.]
28 p-phenylenediamine 10 50 20.0 29 2,3-dimet:hylani]inel] 55 20.7 2,6-diisopropylaniline lO 30 17.9 3] 2,4,6-trimet:hylaniline 15 120 21.4 32 4-methoxyaniline 12 130 19.3 33 2,4-dimethoxyaniline>lO 60 20.0 34 2~6-diet:hyl-N-methylaniline lO 25 20.7 2,6-diethyl-N,N-dimethyl-aniline 7 15 13.8 (e) t:he composition does not cur~

By inspection ol. Table II, aniline and a number of hindered amines are shown to provide compositions having long pot life but rapid cure. Examples 12 and 22 with N,N-di.methylaniline and diethylaniline show long pot life an-l long gel tlme at: 150C and also do no~. cure sat:is-factori~y.

. .
- These examples illustrate the effect of various concent:rations of catalyst: syst:em on the characteristics of curcd epoxy res.in composit:ion.
~ ca~a~yst: system was prepared by adding t:o 42 g of the st.ock solut:.ion described in Example 3-9, cont:aining 0.~ mo] e of substitut;ed pent:afluoroantimonic acid and 30 g (0.2 mole) oE 2,6-diet:hy].ailili.ne. Then, in separa~e containers containing 8U g "Epon" 828 and 20 g diethylene glycol, were added 1.8 g, 0.7 g, and 0.2 g of the curing agent containing 2.5 x 10 3, 1 x 10 3 and 3 x 10 4 mole of substituted penta-fluoroantimonic acid, respectively. Tlle pot ].ife, ge~. time and lap shear were determined for each composit:ion and t:hey are recorded in Table III below. The composition of Example 2 con~aining the same curing agent: with 0.01 mole of substituted pentafluoroantimonic acid is also included in 'rable III for compari.son.

TABLE III
Curing Lap Shear Ex. Agent Pot Life Gel Time Temp. of cuOe N~. (grams) (days) (sec.) 93~C _ 120 C
2 7.2 10 25 - 20.7 36 ~.8 13 20 23.5 25.5 30 37 0.7 15 25 21.4 26.2 38 0.2 1.9 110 no cure 16.6 It is apparent from Table III that the curing agents of the invention are effective in providing long pot life, rapid gelling and good cure in concentrations as low as 3 x 10 4 mo~e of substit.uted pentafluoroantiomonic acid salt per 100 grams of reaction composition.

, ~
These examp~es illustrate use of various catalysts systems for the cu.ring cycloaliphatic epoxy material--diet:hylene glycol mixtures.
Compositions were prepared by adding 0.01 mole of the amines listed below in Table IV and 2.1 9 port:ions of the ant:imony pent:a~luoride-diethylene glycol stock so]ut:ion described in Examples 3-9 (containing 0.005 mole of substi-tu~ed pentafluoroantimonic acid) to 20 g diethylene glycol and thoroughly mixing. To this mixture was then added 80 g "ERI" 4221 (t:he commercial designation of a product of Union C~rbide Corp. for 3,4-epoxycyclohexylmethyl 3,4-epoxycyclo-hexanecarbo~ylat:e). The pot life and lap shear strength of each composit:ion was det:ermined and is recorded in Table IV.
TABLE IV
Æx. Pot Life~C) Lap Shear( No. Aromatic Amine (days) (MPa) ............. ~ line ~~ ~~ 0.08 (f) ~ ~~
40 2,6-dimethylaniline 0.04 (f) 41 2,6-diisopropy~aniline 0.04 (f) 42 2,6-di-sec-butylaniline (f) 43 N-propylaniline 0.04 (f) 44 N-sec-butylaniline 0.08 (f) 45 N,N-dimethylaniline 0.01 (f) 46 N,N-dimethylaniline 0.7 20.0 47 N,N-d.imethy]-2-methylaniline 0.8 18.6 48 N,N-diet.hy~
methylaniline 4.0 ll.0 49 N,N-diethyl-2,5-dimethylaniline 10 20.0 50 N-methyl-2,6-diethyl-aniline 7 18 51 2,4-dimethy~arliline 1.3 (b) cure one hour at 1 (c) at 25C
(f) not determined because of very short pot life 2~

. EXAMPLES _ -63 These examples ill.ustrate the use of several alcohols u~seful in preparing the curing agent of the present invention.
Stock solutlons containing antimony pentafluoride and separately the various alcohols were prepared as described in Example 1. To each of these stock solutions were added l.0 to 1.1 moles of 2,6-diethylaniline per mole of antimony pentafluoride. The various curing agents thus prepared were t:horoughly mixed into 80 g of "Epon" 828 and 17 g of dipentene and evaluated for pot life and gel time as shown in Table V.

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These examples illustrate compositions in which various epoxy resins are cured with the curing agent of the present invention.
A stock solution containing one part antimony penta-f J uoride to one part by weight of diethylene glycol was prepared as described in Example I. To -this stock solut:ion was added 1.0 to 2.0 moles of 2,6-diethylaniline per mole of antimony pentaEluoride. These various curing agents were ~0 thoroughly mixed into 80 g of epoxy resin and 17 g of dipentene and evaluated for pot ~ife and gel times as shown in ~l'able VI.

TA~r~E VI
.

Gel Time Ex. Epoxy Moles(a) Amine~SbF (b) at 150C Pot Life 15 No- Resin Catalyst mole ratio(sec.)(days) ... .. .. _ . _ . . .
64 Epon 82~3 0.005 1.0 - C 0 04 ~pon 828 0.005 1.1 6 3 66 Epon 828 0.004 2.0 26 23 67 D.E.~. 332(C) 0.005 1.0 - ~ 0 04 20 68 D.E.R. 332 0.005 1.1 6 3 69 1) . 1~ . 332 0.004 2.0 20 20 Epon 871(d) 0.005 1.0 13 ~ 1 71 Epon 871 0.005 1.1 18 22 72 Epon 871 0.004 2.0 38 >41 25 73 D.E.N. 431(e) 0.005 1.0 ~ ~ 0 04 74 D.E.N. 431 0.005 1.1 6 D.E.N. 431 0.004 2.0 18 17 . _ (a) Moles of substituted pentafluoroantimonic acid per 80 g epoxy resin and 17 g dipentene mixture.
30(b) Rat-io of moles of 2,6-diethylaniline to mole oE subst:ituted pent:aEluoroantimonic acid.
~c) "D.~.R." 332 is a virt:ually pure liquid bisphenol ~-digly-cidyl et:her resin market:ed by the Dow Chemical Company and having an epoxy equiv~lenl: weight of ~72-176.

(d) "Epon" 87l is a liquid diglycidyl ester of linoleic dimer acid resin marketed by the Shell Chemical Company and having an epoxy equivalent weight of 390 470.
(e) "D.E.N." 431 is an epoxy novalac resin marketed by the Dow Chemica] Company having an epoxy equivOlent weight of 172-179 and a viscosity of 1100-1700 cps at 52 C.
~.X~MPT.E~ 7f,-77 _, . . . . _ A coated abras.ive paper backiny ~"~" weight paper 130 pollnds per 480 sheet ream or 220 g/m2) was coated wit:h a mixture of 90 part.s epoxy resin (available under t:he t:rade de~ignat:ion "Epor)" 328), 7 parts dipentene and 3 parts of curing agent: "A" of Example l to provide a coating weight:
before dryi.ng o~ 2h grains per 4-inch by 6-.inch segment:
(about: ll0 grams l~er sq. met:er). Grade 36 (average parl:.icle size 653 micromet:ers) aluminum oxide mineral was electro-st.atically deposit:ed upon the freshly coa~ed surface to provide an abrasive coating weight of 120 grains per 4-inch by 6-inch segment (about 500 grams per sq. meter). The resinous coating was then cured in a forced air oven with a first: zone heated at 265F (129C) with a 40 second residence time t.herein, a second zone heated at 300F (~49 C) with a 40 second residence time therein and a third zone heated a~ 285F (141C) with a 40 second residence t:ime therein. Thereafter a size coat:ing comprised of a mixture of 81 parts epoxy resin ("Epon" 828), l6 part:s dipentene and 3 part.s o;E curing agent A" of Example 1 was applied to t:he abrasive covered surface of the cured composite to provide a coating weight before drying oE 32.5 grains per 30 4-inch by 6-incll sec~merl~ (about 135 grams per sq. meter).
The size coating was cured at 250F (121C) for 4 minutes.

Following the procedure of Example 76, another coated abrasive product, i.dentified herein as Example 77, was 35 prepared. The spec:ifications of Example 77 are set forth in -Table VII.

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Test samples of Examp1es 76-77 were cut and installed in a Schiefer testing machine for evaluat.ion of abrasiveness.
ese samples were compared to commercially available control coated abrasive samples of the same abrasive grade S available from the Minnesota Mining and ManuFacturing Company nnder t.l)e t:rademark "Product:ion Paper" glue bond abrasive paper. ~xample 76 was test:ed on "Plexiglas"
acrylat.e resin workpieces while Example 77 was tesLed on "Plexiglas" acrylate resi.n, wood (maple) and a commercial ~)olyest:er body E.i.llcr compound. ~esult:s o~ t:hese t.est.s are shown below in Table VIII and reported relative to controls.

TABLE VIII

Ex. Relative Abrasiveness (~) No. "PlexigLas" Wood (maple) Body Filler _ _ ~ _ . . . . _ .............. _ _ ~- 77 125 131 148

Claims (14)

_30_ THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a coated abrasive product including abrasive granules which are supported on and adherently bonded to at least one major surface of a backing sheet by a make coating of a first resinous binder material and a size coating of a second resinous binder material, tile improvement comprising at least one of the said resinous materials being epoxy resin, said epoxy resin characterized by comprising cured epoxy resin and residual curing agent derived from substituted penta-fluoroantimonic acid and an aromatic amine selected from the group consisting of aniline and hindered amine.

2. The abrasive product of claim 1 wherein said backing sheet is formed of paper, film, fiber, or woven cloth.

3. The abrasive product of claim 1 wherein said abrasive granules are selected from the group consisting of flint, garnet, aluminum oxide, alumina:zirconia, diamond, and silicon carbide.

4. In a coated abrasive product including abrasive granules which are supported on and adherently bonded to at least one major surface of a backing sheet by a resinous binder material, the improvement comprising epoxy resin as the resinous binder material, said epoxy resin being characterized by comprising cured epoxy resin and residual curing agent derived from substituted pentafluoroantimonic acid and an aromatic amine selected from the group consisting of aniline and hindered amine.

5. In a method of making coated abrasive products having the steps of (1) uniformly coating a backing sheet with a make coat of a first resinous material in liquid form;

(2) depositing a plurality of abrasive granules uniformly over the surface of said make coat of first resinous material;
(3) curing said first resinous material to adherently bond said granules to said backing sheet surface;
(4) coating over said make coat and said granules with a size coat of a second resinous material;
and (5) curing the resultant coated product until said second resinous material is solid, the improvement comprising employing, as at least one of said first or said second resinous binder materials, a latent room-temperature stable, curable system comprised of (A) epoxy resin composition having a 1,2-epoxy equivalency greater than one; and (B) a curing agent in an amount sufficient to cure said composition on heating comprising (1) substituted pentafluoroantimonic acid having the general formula H+SbF5X-wherein X is halogen, a hydroxy, or an OR group wherein OR is the residue of an aliphatic or aromatic alcohol; and (2) an aromatic amine selected from the group consisting of aniline; and hindered amine the mole ratio of said substituted penta-fluoroantimonic acid to aromatic amine being in the range of 1:05 to 1:4.

6. The method of claim 5 wherein said hindered amine has the general formula wherein:
R1 and R2 are independently hydrogen, primary or secondary lower alkyl group having 1-6 carbon atoms, or benzyl;
R3, R4, and R5 are independently hydrogen, an electron donating group, benzyl, or at least one of R3 and R4 is joined together with R5 to form a benzo group; provided that, if no benzo group is present in said hindered amine, at least one of R1, R2, R3, and R4 is an alkyl group or an electron donating group; and if R3, R4 and one of R1 or R2 is hydrogen, the other R1 or R2 is an alkyl group having at least 2 carbon atoms.

7. The method of claim 5 wherein said OR group is 2-(2-hydroxyethoxy)ethoxy.

8. The method of claim 5 wherein said OR group is the residue of an aliphatic alcohol having a molecular weight of at least 32 and a primary or secondary hydroxyl functionality of at least 1.

9. The method of claim 5 wherein said alcohol is selected from the group consisting of ethylene glycol, diethy-lene glycol and triethylene glycol.

10. The method of claim 5 wherein said hindered amine is selected from the group consisting of N-methyl-2,-6-diethylaniline, 2,6-dimethylaniline, 2,6-diethyl-aniline, N-sec butylaniline N,N-diethyl-2,5-dimethyl aniline and N,N-diethyl-2-methylaniline.

11. The method of claim 5 wherein said A also includes up to one hydroxyl equivalent per epoxy equivalent of an alcohol having a functionality of at least one.

12. The method of claim 5 wherein said A also includes coreactive cationically polymerizable ethylenically unsaturated monomer.

13. The method of claim 12 wherein said cationically polymerizable ethylenically unsaturated monomer is selected from the group consisting of styrene, t-butyl styrene, dipentene, and indene.

14. The method of claim 5 wherein said curing agent is contained in a concentration which results in a concentration of 2 to 500 millimoles of antimony per kilogram total weight of curable composition.