CA1285395C - Coated abrasive having radiation curable binder - Google Patents

Abstract

ABSTRACT
This invention relates to coated abrasive products, and, in particular, to coated abrasive products having a radiation-curable binder.
Radiation-curable coated abrasives heretofore known exhibit the shortcoming of poor adhesion of abrasive granules to the backing because the binder does not cure in areas where the granules screen out radiation, unless high dosages of ionizing radiation are employed. High dosages of radiation can adversely affect the backing. The poor adhesion of the abrasive granules results in a large loss of abrasive granules, i.e. "shelling", from the backing upon flexing and grinding. Attempts to improve the adhesion of the abrasive granules by curing by ionizing radiation, e.g., electron beam, through the backside of the backing often leads to degradation of the backing.
This invention provides a coated abrasive product and a process for producing same. The coated abrasive product comprises a backing, a make coat, and a size coat, and may contain an optional saturant coat, an optional presize coat, an optional backsize coat, or any combination of said optional coats, in which at least one coat is formed from a composition curable by electromagnetic radiation comprising:
(A) a curable portion containing both ethylenically unsaturated groups and 1,2-epoxide groups, which groups can be in the same compound or in different compounds, and (B) a photoinitiator portion.
The photoinitiator portion activates both free-radical and cationic curing mechanisms. The use of the radiation curable composition of this invention overcomes the problem of poor adhesion of abrasive granules resulting from incomplete cure of the binder by combining a cationic curing mechanism with a free-radical curing mechanism.

Description

i3~5 41367 CAN lA
COATED ABR~SIVE HA~ING
RADIAl'ION Cl)BABLE BINDER

BACKGROUND OF THE INVENTION
This invention relates to caated abrasive products, and, ln particular, to coated abrasive products having a radiation curable binder.
Coated abrasives generally compriss a backing 10 and abraslve granules ~upported there~y and adhered thereto. The backing may be paper, cloth, poIymeric, film, vulcanized fiber, etc. or a combination of two or more of these materials. The abrasive granules may be formed of flint, garnet, aluminum oxide, alumina-zircon.ia, 15 diamond, silicon carbide, etc. Binders for the purpose of adhering the granules to the backing include phenolic resins, hide glue, varnish, epoxy resins, urea-formaldehyde resins, and polyurethane resini. -The coated abrasive may employ a "make" coat of -~0 resinous binder material which is uti}ized to secure the ends of the abrasive granules onto the backing as the granules are oriented and a "size" coat o ~esino~s binder material oYer the make coat which provides for firm adherent bonding of the abrasive qranules. The size coat 25 resin may be of the same material as the make coat resin or it may be o~ a different resinous material.
In the manufacture of conventional coated abrasives, the make coat resinous binder is first applied to the backing, the abrasive granules are then applied, 30 the make coat is partially cured, the size coat resinous binder is then applied, and finally, the construction is fully cured. Generally, thermally curable binders provide coated abrasives having excellent properties, e.g. heat resistance, Thermally curable binders include phenolic 35 resins, epoxy resins, and alkyd resins. With backings formed of polyester or cellulose, however, curing temperatures are limited to a maximum of about ~30C. At ~.~85~

this tempera~ure, cure times are sufficiently long to necessitate the use of festoon curing areas. Festoon curing areas are disadvantageous in that they result in formation of defects at the suspension rods, inconsistent cure due to temperature variations in the larg0 fes~oon ovens, sagging of the binder, and shifting of abrasive granules. Further~ore, festoon curing areas require large amounts of space and large amounts o energy.
Accordingly, it would be desirable to develop a resin that 10 does not require a great deal of heat to effect cure.
Radiation curable resins are known in the art.
Ofenlegungsschrift 1,956,810 discloses the use of radiation for the curing of unsaturated polyester resins, acid hardenable urea resins, and other synthetic resins, lS especially in mixtures with styrene as binder for abrasives. U.S. Patent No. 4,047,903 discloses a radiation curable binder comprising a resin prepared by at least partial reaction of ~a) epoxy cesins having at least 2 epoxy groups, e.g. from diphenylolpropane and 20 epichlorohydrin, with l~) unsaturated monocarboxylic acids, and ~c) optionally polycarboxylic acid anhydride.
U.S~ Patent No. 4,457,766 discloses the use of acrylated epoxy resins, which are desiqnated therein "epoxy acrylates", such as the diacrylate esters of bisphen~l 25 epoxy resins, as a radiation curable binder for coated abrasives.
The coated abrasives described in the foregoing patents exhibit the shortcoming of poor adhesion of abrasive granules to the backing because the binder does 30 not cure in areas where the granules screen out radiation, unless high dosages of ionizing radiation are employed.
~igh dosages of radiation can adversely affect the backing. The poor adhesion of the abrasive granules results in a large loss of abrasive granules, i.e.
35 "shelling", from the backing upon flexing and grinding.
Attempts to improve the adhesion of the abrasive granules by curing by ionizing radiation, e.g., electron beam, 3~
--3~

through the backside of the backing often leads to degradation of the backing.

SUMMARY OF THE INVENTION
This invention involves a coated abrasive product and a process for producing this abrasive product.
The coated abrasive product comprises a backing, a make coat, a layer of abrasive grains, a size coat, and, optionally, a saturant coat, or a presi~e coat, or a 10 backsize coat, or any combination of these optional coats, wherein at least one coat is formed from a composition curable by electromagnetic radiation. Surprisingly, this radiation curable composition is curable by electromagnetic radiation even in areas where abrasive 15 granules screen out radiation. The use of the radiation curable composition of this invention overcomes the problem of poor adhesion of abrasive granules resulting from incomplete cure of the binder by combining a cationic curi~g mechanism with a free-radical curing mechanism.
20 Another significant advantage of this invention is that the radiation curable binder can be cured relatively quickly to ~irmly anchor the deposited abrasive granules.
When a heat curable phenolic resin is used as the binder for the make coat, its relatively long curing time 25 provides ample opportunity for the abrasive granules to shift from their orientation at deposition.
The radiation curable somposition suitable for use in this invention comprises a resin portion comprising ethylenically-unsaturated groups and 1,2-epoxide groups, 30 and a photoinitiator portion, in an amount sufficient to cure the radiation curable composition, comprising at least one polymerization photoinitiator selected from the group consisting of:
(1) salts having an onium cation and a 35 halogen-containing complex anion of a metal or metalloid, e.g., diphenyliodonium hexafluoroantimonate, and (2~ a mixture of (a) at least one salt ha~ing an organometallic complex cation and a halogen-containing complex anion of a metal or metalloid, e.g., (n5-cyclopentadienyl)tricarbonyliron(1+~
hexafluoroantimonate, and (b) at least one free-radical 5 polymerization initiator.
It is generally preferred to use a free-radical polymerization initiator in conjunction with the photoinitiator salts of the aforementioned group (1).
Optionally, the photoinitiator can also contain one or 10 more thermally activated cationic or free-radical initiators. In addition, the photoinitiator can optionally contain photosensitizers to sensitize the composition to visible light.
Preferably, the curable portion is selected from 15 the group consisting of:
(A) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, (B) at least one ethylenically-unsaturated compound and at least one compou~d containing at least one 1~2-epoxide group, (C) at least one bi~eactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, and at least one ethylenically-unsaturated compound, (D) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, and at least one compound containing at least one 1,2-epoxide group, and (E) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, 3~ at least one ethylenically-unsaturated compound, and at least one compound containing at least one 1,2-epoxide group.

~28~3~S

It is within the scope of the present invention to utilize various combinations of radiation curable resin systems with conventional heat curable resin systems. For instance, the backsize coat of a cloth substrate could be - 5 formed using radiation curable resin, and then the make and size coats formed utilizing conventional heat curable resin systems. xn another case, the make coat may be formed by a radiation curable resin; while the size coat may be of a conventional heat curable resin. Thus, the radiation 10 curing resin systems of the present invention are compatible with, and may be utilized in various combinations with conventional heat curable resins.

E~RIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates in cross-section a coated abrasive on a cloth backing material.
FIG. 2 illustrates in cross-section a coated abrasive on a paper backing material.

DETAILED DESCRXPTION
Coated abrasives that may be produced by the resin systems of the invention are illustrated in FIGS. 1 and 2. As illustrated in FIG. 1, the coated abrasive generally indicated as 10 is cloth backed. Cloth 12 has 25 been treated with an optional backsize coat 14 and an optional presize coat 16. Overlaying the presize coat is a make coat 18 in which are embedded abrasive granules 20 such as silicon carbide or aluminum oxide. A siæe coat 22 has been placed over the make coat 18 and the abrasive 30 granules 20. There is no cleac line of demarcation between the backsize coat and the presize coat which meet in the interior of the cloth backing which is saturated as much as possible with the resins of these coats.
In FIG. 2 there is illustrated a coated abrasive 35 generally indicated as 30 which is formed on a paper backing 32. Paper backing is treated with a backsize coat 34 and presize coat 36. The presize coat is overcoated S;b~S

with a make coat 38 in which are embedded abrasive ~ranules 40. The abrasive granules 40 and ~ake coat 38 are overcoated with a size coat 42 which aids in holding the abrasive granules 40 onto the bac~ing during utilization and further may contain cutting aids.
As used herein the term, "electromagnetic radiation" means non-particulat2 radiation having a wavelenqth within the range af 200 to 700 nanometers.
"Bireactive compounds" are those which contain at least one 10 ethylenically-unsaturated group and at least one 1,2-epoxide group.
Ethylenically-unsaturated compounds that can be used in the polymerizable mixture of this invention include monomeric or polymeric compounds that contain atoms of 15 carbon, hydrogen, and oxygen, and optionally, nitrogen and the halogens. Oxygen and nitrogen atoms are general~y present in ether, ester, urethane, amide, and urea groups.
The compounds preferably have a molecular weight of less than about 4000 and are preferably ssters Oe aliphatic 20 monohydeoxy and polyhydroxy group-containing compounds and unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like. Representative examples of preferred ethylenically-unsaturated compounds include 25 methyl methacrylate, ethyl methacrylate, styrene, divinylben~ene, vinyl toluene, ethylene glycol diacrylate and methacrylate, hexanediol diacrylate, triethylene glycol diacrylate and methacrylate, trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol 30 triacrylate and methacrylate, pentaerythritol tetraacrylate and methacrylate, dipentaerythritol pentaacrylate, sorbitol triacrylate, sorbital hexaacrylate, bisphenol A diacrylate, and ethoxylated bisphenol A diacrylate. Other examples of ethylenically-unsaturated compounds include ethylene glycol 35 diitaconate, 1,4-butanediol diitaconate, propylene glycol dicrotonate, dimethyl maleate, and the liks. Other ethylenically-unsaturated compounds include monoallyl, polyallyl, and polymethallyl esters and amides of carboxylic acids, such as diallyl phthalate, diallyl adipate and, N,N-diallyladipamide. Still other nitrogen-containing compounds include tris(2-acryloyl-5 oxyethyl~isocyanurate, 1,3,5-tri(2-methacryloxyethyl)-s-triazine, acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, and N-vinylpiperidone. It is preferred that the ethylenically unsaturated compounds be acrylic compounds because of their ready availability and high speed of cure.
Polymeric ethylenically-unsaturated compounds that can be used include the reaction products of acrylic or methacrylic acid or an isocyanato-alkyl acrylate or methacrylate with a polymeric polyether or polyester 15 polyol. Repre~entative examples of polymeric polyols include the polyoxyalkylene polyols, i.e., the diols, triols, and tetrols, the polyester diols, triols, and tetrols formed by the reaction of organic dicarhoxylic acids with polyhydric alcohols, and the polylactone diols, 20 triols, and tetrols. Examples of polymeric polyols that are commerically available incl~de polyoxyethylene diols, triols and tetrols, such as the CarbowaxR polyols available from Union Carbide, the polyoxytetramethylenediols, such as PolymegR polyols available from Quaker Oats Company, the 25 polyester polyols such as the ~ultronR
poly(ethyleneadipate)polyols available from Mobay Chemical Company, the polycaprolactone polyols such as the PCP
polyols available from Union Carbide, and the urethane acrylates such as "C-9504" available from ARCO Chemical~.
The 1,2-epoxide group-containing compounds that can be used in the polymerizable mixture of this invention have an oxirane ring, i.e., --C-- C~
\ /

3 ~ 5 and the compound is polymerizable by ring opening. Such materials, broadly called epoxides, include monomeric epoxy compounds and polymeric epoxides, and may vary greatly in the nature of their backbones and substituent groups. For S example, the backbone may be of any type and substituent groups thereon can be any group free of an active hydrogen atom which is reactive with an oxirane rin~ at room temperature. RepresentatiYe examples of acceptable substituent groups include halogens, ester groups, ether lQ groups, sulfonate groups, siloxane groups, nitro groups, and phosphate groups. The molecular weight of the epoxy-containing materials can vary from about 60 to about 4000, and preferably range from about 100 to about 600.
Mixtures of various epoxy-containing materials can be used 15 in the compositions of this invention.
Epoxy-containing materials that are particularly useful in the practice of this invention incl~de glycidyl ether monomers of the formula R'(OCH2C ~ f H2)m where R/ is alkyl or aryl and m is an integer of l to 6, inclusive. Representative examples of these are the glycidyl ethers of polyhydric phenols obtained by reacting 30 a polyhydric phenol with an excess of a chlorohydrin, such as epichlorohydrin. Specific examples of such materials include 2,2-bis[4-(2,3-epoxypropoxy)phenyl~propane (diglycidyl ether of bisphenol A) and commercially '~` ava~lable materi~ls under the trade designations "Epon 35 828", "Epon 1004", and "Epon 1010~ available f ~ m Shell Chemical Co. r "DER-33~', "DER-332" and "DER-334", available from Dow Chemical Co., ~lame retardant epoxy resins ~e.g.

;~ Trc~c~e ~mc~f ~

g i "DER-580", a brominated bisphenol type epoxy resin available from Dow Chemical Co.), glycidyl ethers of phenol-formaldehyde novolac (e.g., "DEN-431~ and "DEN-42 ~
available from Dow Che~ical Co.), and resorcinol diglycidyl S ether (e.g., "Kapoxite", available from Koppers Company, Inc.). Additional examples of epoxides of this type that can be used in the practice of this invention are described in U.S. Patent No. 3,018,262, incorporated herein by reference, and in Lee and Neville, "Handbook of Epoxy Resins", McGraw-Hill Book Co., New York ~1967~.
Commercially available epoxy-containing materials use~ul in this invention include cycloaliphatic epoxide monomers such as the epoxycyclohexanecarboxylates, typified by 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxy-lS late (e.g. "ERL-422 ~ from Vnion Carbide Corp.), 3,4-epoxy-2-methylcyclohexylmsthyl 3,4 epoxy-2-methylcyclohexanecarboxylate, bis~3,4-cpoxy-6-methyIcyclohexylmethyl) adipate, 3,4-epoxy-6-~ethylcyclohexylmethyl 3,q-epoxy-6-20 metbylcyclohexanecarboxylate ~e.g., "ERL-4201' from Union Carbide Corp.), vinylcyclohexene dioxide (e.g., "ERL 4206"
fro~ Union Carblde Corp.), his~2,3-epoxycyclopentyl~ ether (e.g., "ERL-0400~ from Union Carbide Corp.). Other useful epoxides of this nature are disclosed in U.S. Patent No.
3,177,099.
Additional commercially available epoxy-containing materials that can be used in the practice of this invention include octadecyl oxide, epichlorohydrin, styrene oxide, glycidol, butyl glycidyl ether, glycidyl 30 acrylate and methacryla~e, epoxy modifi~ polypropylene glycol (e.g., "ERL-4050' and "ERL-4052", available from Union Carbid~ Corp.j, epoxidized polybutadiene ~e.g., "Oxison 2001 , available from FMC Corp.), silicone resi~s containing epoxy functionality, and copolymers of acrylic 35 acid esters of glycidol, such as glycidyl acrylate and glycidyl methacrylate, with one or more copolymerizable vinyl compounds, such as methyl methacrylate, vinyl --10-- .

chloride, and styrene. Examples of such copolymers are 1:1 styrene: glycidyl methacrylate, 1:1 methyl methacrylate:glycidyl acrylate, and 62.5:24:13.5 methyl methacrylate:ethyl acrylate:glycidyl methacrylate.
The polymeric epoxides include linear polymers having terminal epoxy groups (e.g. a diglycidyl ether of a polyoxyalkylene glycol), polymers having skeletal oxirane units le.g. polybutadiene polyepoxide), and polymers having pendent epoxy groups (e.g. a glycidyl methacrylate polymer 10 or copolymer). The epoxides may be isolated, individual 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 15 material by the total number of epoxy molecules present.
~ ireactive compounds can be made by introducing at least one ethylenically-unsaturated group into a compound that already contains one or more 1,2-epoxide group, or, conversely, by introducing at least one 20 1,2-epoxide group into a compound that already contains one or more ethylenically-unsaturated group.
The bireactive compounds can be prepared by the reaction of a compound having at least two epoxide groups with a stoichiometric deficiency, based on epoxide content, 25 of a compound containing both an ethylenically-unsaturated group and a group having an active hydrogen, such as the carboxyl (-COOH), hydroxyl~-O~), mercapto~-SH), or amidol-CN~2) group. This method of preparation generally 30 yields DO m~re than fifty percent of the bireactive compound. ~hus, reaction of one mole of a diepoxide and one mole of acrylic acid would yield a product, cansisting of 50 mole percent of an epoxy acrylate compound having both an acrylic group and an epoxy group, 25 mole percent 35 of a diacrylate, and 25 mole percent o unchanged diepoxide on a statistical basis. With lesser or greater amounts of acrylic acid, there would be obtained lesser or greater - 3~S~S

amounts of the diacrylate and the diepoxide but in each, a lesser amount of the epoxy acrylate.
Specifically, bireactive compounds are the reaction product of an aromatic, alkyl, cycloalkyl, or alkaryl compound havin~ n 1,2~epoxy groups ~in which n is a number having a value of 2 to 10 or more) with 0.2 n to 0.9 n equivalents of ethylenically-unsaturated compoun~ having an active hydro~en group.
Preferred bireactive compounds are those contained in the reaction products of an acrylic acid (the term "an acrylic acid" is used generically to inclu~e acrylic acid, methacrylic acid, and ~-chloroacrylic acid) with a cycloalkyl, aryl, or alkaryl polyepoxy compound having n 1,2-epoxy groups wherein n is defined hereinabove.
15 Examples o~ such preferred hireactive compounds are those contained in the reaction products of O . 4 to 0.6 weight equiva~ents of an acrylic acid and one mole of diglycidyl ether of bisphenol A ~DGEsA), polyglycidyl ether of phenol-ormaldehyde novolac, polyglycidyl ether of 20 cresol-formaldehyde novolac, diglycidyl terephthalate, triglycidyl ester of trimellitic ~cid, dicyclopentadiene dioxide, vinylcylohexene dioxide, bis-(2,3-epoxycyrlopentyl)ether, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, and 2S bis(3,4-epoxy-6-methylcyclohexyl)methyl adipate.
The photoinitiators of group (1), i.e., salts of an onium cation and a halogen-containing complex anion of a metal or metalloid are adducts of (1) an aromatic organoatomic cation of a Periodic Group VA, VIA, or VIIA
30 atom, recently given the notation of Groups 15, 16, and 17 in Chem. ~ Eng. News. Vol. 63, No. 5, 26 (Feb. 4, 1985), particularly phosphorous, antimony, sulfur, nitrogen, chlorine, and iodine atoms, and (2~ an anion. The Group 15, 16 or 17 atom from which the salt derives its name 35 (e.g., phosphorus in phosphonium, sulfur in sulfonium, iodine in iodonium, etc.) is referred to hereafter as the nominative atom. The term "aromatic", as used in the description of the groups on the photoinitiator means an aro~atic ring which can be carbocyclic or a 5-, 6- or 7-membered heterocyclic ring wherein the ring atoms comprise carbon and one or more atoms selected from the 5 group consisting of N, S, O, and Se atoms so attached to the nominative atoms that the aromatic ring is at least as electron withdrawing as phenyl. For example, ~ C-CH2-, phenacyl, would be a useful 10 aromatic group, because it is at least as electron withdrawing as phenyl, but benzyl, ~ -C~2 ~~ would not be useful because of instability of the compound thereof. Representative examples of 15 aro~atic rings are phenyl, naphthyl, thienyl, pyranyl, ~uranyl, and pyrazolyl, eithec substituted or unsubstituted.
The onium salt photoinitiators useful in the practice of this present invention can be represented by 20 the formula:
Rn A~ X

(' ~l)a wherein R represents an aromatic group at least as electron withdrawing as phenyl;
Rl represents either an aromatic group or a straight chain, ~ranched, or cyclic alkyl or alkenyl group having, for example, 1 to 19 carbon atoms;
A represents an atom of the Periodic ~roup 15, 16, oc 17;
n represents a positive integer having a value of at least 2 ~preferably 2) up to the valence of A plus one;
a represents zero or a positive integer of up to the valence of A plus one; and ~8S39~ .

X represents a halogen containing complex anion of a metal or metalloid.
U.S. Paten~ Nos. 4l026,705, 4,032,673, 4,069,054, 4,I36,102 and 4,173,476, all of which are incorporated herein S by reference, show the use of certain onium compounds as cationic polymerization catalysts for specific monomers such as organo~ilicon cyclics, vinyl resins,- cyclic ethers, cyclic esters, cyclic sulfides, epoxy resins, phenolic resins, polyamines, lactones, styrene, urea/formaldehyde resins, and 10 melamine/for~aldehyde resins.
The organo groups may also b~ directly linked one to another via a covalent bond, a methylene group, a -~-group, an -SO2- group, an oxygen atum, a sulfur atom, or the 15 like. One or more of the organo groups can share two atoms in a condensed ring system.
Representative examples of onium salts that are useful in the practice o the present invention include:
A. onium salts having as nominative atom a 20 Pe~iodic Group 15 cation: diphenylmethylammon-um tetrafluoroborate, tetraphenylphosphonium hexafluorophosphate, (4-bromophenyl)triphenylphosphonium hexafluorophosphate, tetraphenylarsonium tetrafluoroborate, tetraphenylammonium hexafluorophosphate, 25 di(1-naphthyl)dimethylammonium tetrafluorobcrate, tri-(3-thienyl)methylammonium tetrafluoroborate, and diphenacyldimethylammonium hexafluorophosphate. ~hese and other onium salts and the preparation thereof are diselosed in 8elgium Patent No. ~28,668.
~. Onium salts having as nominative atom a Periodic Group 16 cation: triphenylsulfonium hexafluoroantimonate, 4-chlorophenyldiphenylsulfonium tetrafluoroborate, 4-chlorophenyldiphenylsulfoniu~
hexafluorophosphate, triphenyltelluronium 35 pentachlorobismuthate, and triphenylselenonium hexafluoroantimonate. These and other onium salts having as nominative atom a Periodic Group 16 cation and the ~.2~353~9~

preparation thereof are disclosed in Belgium Pat. Nos. 828,670 and 833,472 and U.S. Patent No. 4,256,825.
C. Onium salts having as nominative atom a Periodic Group 17 cation: diphenyliodonium hexa1uorophosphate, 4-chloro-phenylphenyliodonium hexafluoroantimonate, diphenyliodonium hexa-fluoroar 5 enate, 4-trifluoro,nethylphenylphenyliodoniu~ te-trafluoro-borate, di(4-methoxyphenyl)iodonium hexafluoroarsenate, 4-methyl-phenylphenyliodonium tetrafluoroborate, diphenylbromoniu~ hexa-fluorophosphate, and 2,2'~biphenyliodonium hexafluorophosphate.
These and other haloniu~ salts and the preparation thereof are disclosed in Belgium Pat. No. 828,669 and U.S. Patent No. 4,256,828.
Photoinitiator salts having an organometallic complex cation and a halogen containing complex anion of a metal or metal-loid are salts in which the cation is capable of adding an inter-mediate strength nucleopl~ile (e.g. triphenylphosphine) or, upon photolysis, is capable of liberating at leas-t one coordin~tion site. The metal of the organometallic complex cation can be selected fro~ elements of Periodic Groups IVB, VB, VIB, VIIB, and 20 VIIIB, recently given the notation of Groups 4, 5, 6, 7, 8, 9, and 10 by Chem. & Eng. News, supra. Examples o such ionic salts and the preparation thereof are disclosed in European Patent Application No. 83307~02.0, published May 30, 1984.
Preferred salts for use in the practice of this inven-tion can be represented by the formula:
[(L9)(LlO)(Mf)]+qYn wherein Mf represents a metal selected -from the group consist-ing of Cr, Mo, W, Mn, Re, Fe, and Co;
L9 represents 1 or 2 ~ -electron-contributing ligands that can be the same or different, said '~.

;3~3~

ligands being selected from substituted and unsubstituted n3-allyl, n5-cyclopentadienyl, and ~7-cycloheptatrienyl and ~6-aromatic compounds selected from ~6-benzene compounds and compounds having 2 to 4 fused rings, each capable of contributing 3 to 8 ~electrons to the valence shell of Mf;
L10 represents none or 1 to 3 ligands that can be the same oe different said ligands contributing an even number of a-electrons and selected from carbon monoxide or nitrosonium;
q represents an integer having a value of 1 or 2, the residual electrical charge of the complex cation;
Y represents a halogen-containing complex anion selected from the ~roup consisting o~ AsF6, SbF6 and S~F~OH, and n represents an integer ha~ing a ~aluc D 1 or 2, the num~er o~ compl~x anions required to neutralize the ~harge q on the complex cation;
with the proviso that the total electronic charge contributed to Mf by L9 and L10 plus ionic charge on metal M results in a net residual positive charge of q to the complex.
~epresentative examples of salts of organometallic complex cations useful in the practice of the present invention include the followinq:
(~5-cyclopentadienyl)tricarbonyllron~l+) hexafluorophosphate (n6-mesitylenej~n5-cyclopentadienyl)iron~1+) hexafluoroantimonate (~5-cyclopentadienyl)carbonylbis~triphenylstibine)iron(1~) hexa~luorophosphate (n5-methylcyclopentadienyl)dicarbonylnitrososylmanganese~l+) hexafluoroantimonate 5 ~n5-cyclopentadienyl)tetracarbonylmoly~denum(1+) hexafluorophosphate ~5-cyclopentadienyl)dicarbonylmethylisonitrileiron(1+) hexafluoroarsenate bis(n6-benzene)chromium(1~) hexafluoroantimonate bis(~6-hexamethylbenzene)cobalt(2+) hexafluoroantimonate bis(n6-mesitylene)iron(2~) bis(hexafluoroantimonate).
Other examples of salts of organometallic complex S cations useful in the practice o this invention are described in the above-mentioned patent application U.S.S.N.
443,660.
The salts of group ~2) photoinitiators require the use of a free-radical polymerization initator. It is 10 preferred to use a free-radical polymerization initiator with the salts of qeoup ~l) photoinitiators Representative examples of free-radical generating compounds that can be activated by thermal energy or by light energy are organic peroxides, azo compounds, quinones, 15 benzophenones, nitroso compounds, acyl halides, aryl halides, hydrazones, mercapto compounds, pyrylium compounds, triarylimidazoles, bisimidazoles, chloroalkyltriazines, benzoin ethe~s, benzil ketals, thioxanthones, and acetophenone derivatives. Additional reference to free-20 radical photoinitiator systems for ethylenically-unsaturated compounds are included in U.S~ Patent No. 3,887,450 (e.g., col 4) and U.S. Patent No. 3,8g5,949 (e.g., col.7). Other desirable photoinitiators are chloroalkyltriazines as disclosed in U.S. Patent No. 3,775,113. Another good 25 reference to free-~adical photoinitiator systems is J. Kosar, Li~ht-Sensitive Systems, J. Wiley and Sons, Inc. (1965), especially Chapter ~.
A radiation curable composition that has been found to be useful in the present invention is that described in 30 U.S. Patent 4,156,035. Although it is asserted that this composition is useful for providing photoresists, and, as such, would not be expected to be curable in the absence of direct exposure to electromagnetic radiation, it has been discovered that, in the case of coated abrasives, this 35 composition can be sufficiently cured by electromagnetic radiation even in areas where abrasive granules screen out radiation to firmly secure abrasive granules to the backing.

3~2~5;39~

A sufficient amount of polymerization photoinitiator must be used to cure the composition. Generally, t'ne total amount of photoinitiator in the radiation curable composition of the present invention can range fro~ a concentration of 0.05 to 10, preferably 0.1 to 5, parts by weight per 100 parts by weight of total composition. ~hen a mixture of cationic polymerization initiators and free-radical polymerization initiators is used, the mi~ture comprises about 5 to 50 percent, preferably 15 to 30 per-cent, by weight of cationic polymerization initiator, and 95 to 50 percent, preferably 85 to 70 percent, by weight of free-radical polymerization initiator.
The photoinitiator salts useEul in the radiation curable compositions of this invention are themselves generally photo-sensitive in the ultraviolet portion of the electromagnetic spec-trum, i.e., about 200 to 400 nm. It is within the scope of this invention to include spectral sensitizers, i.e., compounds that extend the sensitivity of the photoinitiator salts into the visible range of th~ spectrum (up to about 700 nm). Spectral sensitizers that can be used are known in the art and include polycyclic compounds such as the polyarylenes, polyarylpolyenes, 2,5-diphenyl-isobenzofurans, 2,5-diarylcyclopentadienes, diaryl-furans, diarylthiofurans, diarylpyrrols, polyarylphenylenes, cou-marins, and polyaryl-2-pyrazolines.
Examples of preferred spectral sensitizers are: 9,10-diethoxyanthracene, perylene, 2-isopropylthioxanthone, pheno-thiazines, 1,1,4,4-tetraphenyl-1,3-butadiene, 1,3-diphenyl-2-pyrazoline, 1,3-diphenylisobenzofuran, 7-dimethylamine-4-trifluoromethylcoumarin, Setoflavin T (C.I. No. 49005), Acridine Red (C.I. No. 45000), and Acridine Orange (~I. No. 46055). Other spectral sensitizers that can be used are described in U.S. Patent Nos. 3,729,313, 4,026,705, and 4,307,177. If a spectral sensi-tizer is used, about 0.001 to 0.2 part of spectral sensitizer is used per part by weight of polymerization photoinitiator.

'~I

~ z~
. -18-The thermally acti~ated cationic polymerization initiators that can optionally be used in the composition of the present invention are generally salts or complexes of Lewis acids and Bronsted acids, such as hydrofluoric acid, boron trifluoride, antimony pentafluoride, hexafluoroantimonic acid, and the like, with an amine. If a Lewis acid or sronsted acid were used alone as the cationic polymerization initiator of a cationically polymeriæable material, the resin composition would have a pot life entirely too short to be useful in the preparation of coated abrasives. By the addition of an amine to the Lewis acid, particularly an aliphatic amine, such as ethylenediamine or morpholine, a salt or complex of the Lewis acid and amine is formed and the properties of the Lewis acid modified so that the pot life of the resin composition containing the salt or complex will be lengthened~ By application of heat to the resin composition, the modified Lewis acid is thermally activated and the polymerization of the resin co~positi.on initiated. Examples of modified or latent Lewis acid 20 initiators that can be used in the resin system of the invention are the amine complexes of phosphorous pentafluoride, the primary aliphatic amine complexes with antimony pentafluoride as are disclosed in U.S. Patent No.
3,565,861, the hydroxyl ammoniu~ hexafluoroantimonate 25 disclosed in U.S. Patent No. 3,B79,312, and the amine salts of hydrofluoroboric acid disclosed in U.K. Pat. Spec. No.
963,058.
Preferred thermally activated cationic initiators for use in the resin composition of the present invention are 30 the modified Bronsted acid curing agent disclosed in U.S.
.Patent No. 4,503,211. This initiator comprises a liquid salt formed from a substituted pentafluoroantimonic acid and aniline or a hindered aromatic amine, such as 2-methylaniline and 2-isopropylaniline. The substituted pentafluoroantimonic 35 acid has the formula HSbF5X, wherein X represents halogen, hydroxy, or the residue of an aliphatic or aromatic alcohol, p~eerably diethylene glycol.

~.2~353~

--19-- .

The resin composition of the present invention can contain fillers, lubricants, and minor amounts of other additives such as su~factants, pigments, and suspending agents. The amounts of the~e materials are selected to give the properties desired.
The fillers can be selected from any filler material which does not adversely affect the characteristics o~ the resin composition. Preferred fillers include calcium carbonate, calcium oxide, aluminum sulfate, aluminum $0 trihydrate, barium sulfate, cryolite, magnesia, kaolin, quart~, and glass. Fillers that function as cutting aids are cryolite, potassium fluoroborate, feldspar, and sulfur. The fillers can be used in amounts up to about 250 parts, preferably from about 30 to about 150 parts, per 100 parts of 15 polymerizable composition while retaining good fl~xibility and toughness of the cured resin composition.
The radiation curable resin composition useful in the practice of the present invention can be prepared by mixing the curable portion and the photoinitiator portion.
20 If the curable portion comprises more than one type of compound, these compounds can be added to the mixture in any order. It is preferred that there be present in the composition at least 0.2 equivalent of ethylenically-unsaturated, preferably acrylic, groups present 25 in ethylenically-unsaturated compounds or bireactive compounds and at least 0.05 equivalent of 1,2-epoxide groups present in 1,2 epoxide group-containing co~pounds or bireactive compounds for each 100 grams of total composition.
~he backing, as previously mentioned, can be paper, 30 cloth, vulcanized fiber, film, or any other backing material known for this use. The radiation curable composition can be used to treat the backing material, e.g., cloth, paper, or plastic sheeting, to saturate or provide a back or front coat thereta, to provide a make coat to which abrasive granules 35 are initially anchored, or to provide a size or reinforcing coat for tenaciously holding the abrasive granules to the backing material. 'rhe abrasive granules can be of any ;3~

conventional grade of mineral utiliæed in the formation of coated abrasives, including natural or synthetic materials such as, for example, ~lint, garnet, aluminum oxide, alumina:zirconia, diamond and silicon carbide, and ceramic S minerals sush as modified aluminum oxide, available as Cubitron from Minnesota Mining and Manufacturing Company, and mixtures thereof. The abrasive layer may further include non-abrasive diluent particles. The frequency of the abrasive granules on the sheet will also be conventional.
10 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.
In another embodiment of the present invention, abrasive granules can be adhered to the backing by means of a 15 single binder coat of the radiation curable resin composition described herein. In this embodiment, it is preferred that the abrasive granules be no larger than gcade 220.
The radiation curable resin co~position for coated abr~sives according to the present inventian cure~ rapidly, 20 i.e. less than 5 minutes; consequently, prolonged heating and dwell times ~efore subsequent coating, are avoided. Unlike glue and phenolic resin co~positions, the resin composition of th~ present invention is relatively unaf~ected by moisture. Unlike varnish, the resin composition of the 25 invention can be applied with little or no solvent. This characteristic renders the composition particularly useful for preparing the make coat, because the rapid cure insures that the orientation of the abrasive granules will not shift as the make coat is being cured.
The coated abrasive product of the present invention may also include such modifications as are known in this art. For example, a back coating such as a pressure-sensitive adhesive may be applied to the backing and various supersizes may be applied to the abrasive surface.
35 For example, zinc stearate can be used to prevent abrasive loading.

539~i The following, non-limiting examples will further illustrate this invention. Unless otherwise noted, all parts and percentages are in terms of weight. In the following examples, the trademarks and suppliers of the following compounds were as follows:

3g ;39~

COMPOUND TRADEMARK

pentaerythritol triacrylate . . . ."SR-444", ARCO Chemicals diglycidyl ether of bisphenol A . ."Epon 828", Shell Chemical Co.
quartz filler . . . . . . . . . . ."I~SIL AlOE", Illinois Mineral Co.
diglycidyl ether of 1,4-butanediol. . . . . . . . . . ."Araldite RD-2", Ciba-Geigy butyl glycidyl ether. . . . . . . ."Araldite RD-1", Ciba-Geigy triphenylsulfonium hexa-fluorophosphate in y-butyrolactone . . . . . . . . ."FX-512", Minnesota Mining and Manufacturing Co.
2,2-dimethoxy-1,2-diphenyl-1-ethanone. . . . . . . . . . . ."Irgacure 651'1, Ciba-Geigy 2-isopropylthioxanthone . . . . . ."2-ITX", Aceto Chemical Co.
ethoxylated bisphenol A
diacrylate. . . . . . . . . . ."SR-349", ARCO Chemicals ~0 1,6-hexanediol diacrylate . . . . ."SR-238", ARCO Chemicals trimethylolpropane triacrylate. . ."SR-351", ARCO Chemicals a C14-C15 linear aliphatic diacrylate. . . . . , . . . . ."C-2000", ARCO Chemicals an aliphatic urethane acrylate. . ."C-9504", ARCO Chemicals cycloaliphatic epoxide . . . . . ."Cyracure 6110", Union Carbide cycloaliphatic epoxi~e . . . . . ."Cyracure 6100", Union Carbide epoxy-based flexibili~ing agent . ."Cyracure 6379", Union Carbide triacrylate ester of tris-(hydroxyethyl)isocyanurate . ."SR-368", ARCO Chemicals neopeneyl glycol diglycidyl ether "Heloxy WC-68", Uilmington Chemical Corp.
resorcinol diglycidyl ether . . . ."Denacol EX-201", Nagase Chemical Co.
1,4-bis~hydroKymethyl)cyclohexane diglycidyl ether. . . . . . . ."Heloxy UR-107", ~ilmington Chemical Corp.
urea-for~aldehyde . . . . . . . ."Varc~m 404B", Reichhold Chemicals, Inc.
cresyl glycidyl ether . . . . . . ."Araldite DY023", Ciba-Geigy , 395i Example 1 This example illustrates the preparation of coated abrasives utilizing the electromagnetic radiation curable resin composition o~ the present invention.
sacking material of vulcanized fiber (30 mil) was primed by brush coating with a composition consisting of (a) 100 parts by weight of the reaction product of one mole of diglycidyl ether of 1,4-butanediol, with one mole of acrylic lO acid, hereinafter Bireactive No. 1, lb) 1.3 parts of diphenyliodonium hexafluorophosphate, ancl 0.13 parts of 9,10-diethoxyanthracene. The coating weight was 1.2 g/m2 (0.29 grains/24 sq. in.) The primed backing was cured in air in an RPC Processor Model #QC1202 ANIR (from PPG, Inc.~ at 30 15 cm/sec (60 ft/min) with two standard medium pressure mercury lamps operating at 40 watts per centimeter (100 watts per inch). The lamps were located at a distance of abGut 9.5 cm from the backing.
The backing bearing the cured primer was then brush 20 coated with composition UV-1, a compo~ition consisting of:
55 parts pentaerythritol triacrylate 40 parts the reaction product of one mole of diglycidyl ether of bisphenol A with one mole of acrylic acid lhereinafter Bireacti~e No. 2) 5 parts butyl glycidyl ether as a reactive diluent 100 parts quartz filler 0.46 part o 60~ solution of triphenylsulfonium hexa~luorophosphate in r-butyrolactone 1.50 parts 2,2-dimethoxy-1,2-diphenyl-1-ethanane 30 The coating weight was 280 9/m2 ~67 grains/24 sq. in.~
This "make" coated pr~med backing was then dcop coated with 739 g/m2 ~180 grains/24 s~. in.) of Grade 50 A12O3 mineral and the "make" coat cured by fouc passes at 30 cm/sec in air in the RPC Processor with two la~ps at 120 35 watts per centimeter.

OYer the mineral and curPd "make" coats was brush coated composition UV-2, a CQmpOSitiOn consisting of ., 3.~3~5 40 parts pentaerythritol triacrylate 30 parts Bireactive No. 2 30 parts N-vinyl-2-pyrrolidone ~hereinafter NVP) available from GAF
S 100 parts quartz filler 0.46 part of 60~ solution of triphenylsulfonium hexafluorophosphate in r-butyrolactone 1.50 parts 2,2-dimethoxy-1,2-diphenyl-1 ethanone ~he coating weight was 293 g/m2. ~he sized construction 10 was heated to 100C by means of an infrared heater and cured in air by six passes through the RPC Processor at 30 cm/sec with two lamps set at 120 watts per centimeter. The cured article was cut to form 23 cm diameter abrasive discs, the performances of which were determined in 15 acco~dance with the following procedure. The discs were installed in a slide action testing machine. The work piece was 1018 steel at a loading pressure, at the grinding interace, of 0.70 ~g/cm2. The average weights in grams for initial, final and total cuts are shown in Table I.
Com~rative Examele A
This example illustrates a conventional method of making abrasive sheet material.
Vulcanized fiber backin~ was coated with 25 conventional phenol-formaldehyde resole resin make coat at a coating weight of 280 g/m2. The phenolic ~ake coat was then drop coated with 740 g/m2 of grade 50 ~12O3 mineral.
The make coat was then partially cured by heatin~ in an oven at 88C for four hours. The construction was then 30 size coated with the same phenol-formaldehyde resole resin used for the make coat at a coating weight of 220 g/m2.
The abrasive coated construction was then thermally cured by heating in an oven at 88C for 12 hours. The cured conventional abrasive sheet material was cut into 23 cm 35 abrasive discs, the abrasive performance of which was determined according to procedures described in Example 1.
The average weights in grams for the initial, final, and total cuts are shown in Table ~.

i3~3~

Example 2 The procedure of Example 1 was repeated with the exception that as size coat the composition uV-3 was u~ed in place of the composition UV-2. The composition UV-3 consisted of:
10 parts pentaerythritol triacrylate 50 parts of an experimental diacrylated epoxy resin from Celanese Speciality Resins 40 parts NVP
150 parts calcium carbonate 3 parts 2,2-dimethoxy-1,2-diphenyl-1-ethanone The cured article was cut to form 23 cm diameter abcasive discs, the performances of which were determined in 15 accordance with the procedure described in Example 1. The average weights in grams for initial, final, and total cuts are shown in Table 1.

xample 3 ~his example illustrates the use of conventional make coat and the radiation curable size coat of the present invention in the preparation of abrasive shePting.
Vulcanized fiber backing was coated with phenolic resin, drop coated with mineral, and cured as described in 25 Comparative Example A. The construction was then size coated with composition uv-2 and cured as described in Example 1. The cured construction was cut into 23 cm diameter abrasive discs, the performance of which was determined according to procedures described in Example 1.
30 The a~erage weights in grams ~or initial, final and total cut~ are shown in Table I.

Example 4 This example illustrates the use of the 35 radiation curable make coat of this invention and a conventional phenolic resin for the size coat in the preparation of abrasive sheeting.

r ~ g ~26-The procedure of Example 1 was repeated using in place of size coat composition UV-2 the phenolic size coat as described in ~omparative Example A. The coating weight was 230 g/m2. The cured construction was cut into 23 cm S abrasive discs, the performance of which was determined according to procedures described in Example 1. The average weights for initial, final and total cuts are shown in Table I.

TABLE I
Abrasive cutting performance ~g) Example Make coat Size coat Initial F _ Total 1 UV-l UV-2 24.1 2.3 109 2 UV-l UV-3 22.8 1.4 110 3 Phenolic UV-2 22.9 3.6 143 4 UV-1 Phenolic 26.7 3.1 135 A* Phenolic Phenolic 20.4 2.9 115 ~Comparative example which was cured for 16 hours at 88 C.
It can he seen from Table I that when electromagnetic radiation cured coats are used in the preparation of abrasive discs, the abrasive performance is about equivalent to that of conventionally prepared abrasive 25 discs. Yet, the preparation is accomplished without the need for the long heating period used for curing of resin compositions used in the preparation of conventional abrasive discs.

Examples 5-8 These examples illustrate the use of various diluent monomers in the electromagnetic radiation curable compositions of the present invention.
The procedure of Example 1 was repeated using as 35 backing spun polyester cloth having a 4/1 weave and a weight of 270 9/m2 in place of the vulcanized fi~er. The polyester cloth was saturated with a composition of ~5 par~s of an ~ 3539~

acrylated epoxy resin ("Celrad 3500" from CPlanese), 5 parts of NVP, 10 parts of pentaerythritol triacrylate, and 1.5 parts of 2,2-dimethoxy-1,2-diphenyl-1-ethanone. The coating weight was 146 g/m2.
The satura~ed cloth was cured by four passes at 30 cm/sec in air in the RPC Processor having four standard medium pressure mercury lamps set at 120 watts/cm. The lamps were located a~ a distance of about 9.5 cm from the backing.
The cured saturated cloth was backsized with a co~position comprising 75 parts "Celrad 3500" resin, 15 parts NVP, 10 parts pentaerythritol triacrylate, 100 parts of calcium carbonate, and 1.0 part of free-radical initiator ("Irgacure 651"). The coating weight was 63 g/m2. The backsize was cured under the same conditions as was the saturant except 15 that a nitrogen atmosphere was used instead of air. The primed, backsized polyester backing was coated by means of knife coating with composition UV-1 at a coat wei~ht of 151 g/m2, electrostatically coated with 377 g/m2 of grade 80 A12O3 mineral, and cured in air using four passes at 7.5 20 cm/sec under a Fusion Model F450 lamp operated at 120 watts/cm. The lamps were located at a distance of about 7.6 cm from the backing. In Example 5, the cured make coated and mineral coated sheet ~aterial was size coated with composition UV-1. In Examples 6, 7 and 8, the butyl glycidyl 25 ether diluent of composition UV-1 was replaced with equivalent weight percentages of the diluents styrene, cresyl glycidyl ether, and NVP, respectively, and size coated at the coating weights shown in Table II. Included in each composition was a latent thermal cationic polymerization 30 initiator, designated SbF5 DEA DEG, the adduct of antimony pentafluoride with 2,6-diethylaniline and diethylene glycol (1.0 part). Each coating was cured under the same conditions as used to cure the make coat. Each cured abrasive coated construction was cut into strips and converted to endless 35 belts that were subjected to belt grinding tests on 1018 steel at 1.06 kg/cm2 (15 lb/in2) loading pressure. The abrasive perfor~ance of each belt is shown in Table II.

~ ~8~3~

TABLE I I
S i z~
Reactive coat Abrasive cutting performance (g) Example diluent t~/m2) Initial Final Total butyl glycidyl ether 611 37 19 491 6 styrene 311 39 1~ 486 7 cresyl glycidyl ether 352 39 18 473 8 NVP 289 . 38 19 490 Examples 5-8 show that effective grinding performance was obtained not only with ethylenically unsaturated monomers, styrene [Example 6) and NVP ~Example 8) lS but also with epoxy monomers, butyl glycidyl ether ( xample 5~ and cresyl glycidyl ether ~Example 7).

Examples 9-10 These examples compare the grinding performance of 20 abrasive materials prepared using radiation curable compositions UV-4 and VV-5. Composition UV-4 contained both epoxy and acrylic groups in different molecules and composition UV-5 contained epoxy and acrylic groups in the same molecule.
Composition W -4 contained the following ingredients:
55 parts pentaerythritol triacrylate 20 parts diglycidyl ether of bisphenol A
20 parts diacrylate of diglycidyl ether o bisphenol A
5 parts butyl glycidyl ether l.S parts 2,2-dimethoxy-1,2-diphenyl-1-ethanone 0.58 part diphenyliodonium hexafluorophosphate 0.058 part 2-isopropylthioxanthone 100 parts quartz filler Composition W-5 contained the same ingredients as 3.~8S39~;i composition uv-4 except that 20 parts of diglycidyl ether of ~isphenol A and 20 parts of the diacrylate of diglycidyl ether of bisphenol A were replaced with 40 parts of ~ireactive No. 2.
One portion of the polyester cloth primed and backsized as described in Examples 5-8 was coated by means of knife coating with comp~sition UV-4 (Exa~ple 9) as make coat, at a coating weight o 172 g/m2, coated electrostatically with grade 50 A12O3 at a coating weight of 456 g/m2, and cured using four passes under a Fusion Model F450 lamp in air. The lamps were located at a distance of about 7.6 cm from the backing. Composition UV-4 was coated over the make coat and abrasive coat, by means of roll coater, at a coating weight of 368 g~m2 as size coat, and cured under the same conditions as used for curing the make coat. Another portion of the polyester cloth primed and backsized as described in Examples 5-8 was coated by means of knifP coating with composition UV~ xample 10) at a coating weight of 159 g/m2, coated electrostatically with grade 50 A12O3 at a 20 coating weight of 456 g/m2, cured using four passes under a Fusion lamp in air~ Composition UV-5 was coated over the make coat and abrasive coat, by means of roll coater, at a coating weight of 318 g/m2 as size coat, and cured under the same conditions as used for curing the make coat.
~ach abra~ive coated construction was cut into strips and converted to endless belts that were subjected to belt grinding tests on 4150 steel at 1.76 kg/cm2 loading pressure. The results obtained are shown in Table III.

TABLE III

Abrasive cutting performance (g) ExampleInitial Final Total 3.~3S39~

The results of ~xamples 9 and 10 show that essentially the same cutting capability is obtained with abrasive belts prepared usinq make coat and size coat having acrylic and epoxy groups in either the same or in different S molecules.
Example I1 - This example illustrates the use of aliphatic bireactive material in addition to aromatic bireactive material in abrasive constructions. Composition W-6 contain~d the following ingredients:
2~ parts ethoxylated bisphenol A diacrylate 12.5 parts pentaerythritol triacrylate 50 parts Bireactive No. 2 12.5 parts Bireactive No. 1 0.8 part diphenyliodonium hexafluorophosphate 0.08 part 9,10-die~hoxyanthracene 0.92 part 2,2-dimethoxy-1,2-diphenyl-1-ethanone C weight paper was coated by means of knife coating at a thickness of 0.025 mm to form the make coat, 20 electrostatically coated with grade 180 SiC at a coating weight of 121 gjm2, and radiation cured by g passes through the RPC ~rocessor at 30 cm/sec in air with two standard medium pressure mercury lamps set at 120 watts/cm. The lamps were located at a distance of about 9.5 cm from the backing.
25 A size coat of composition UV-6 was then coated over the make coat and abrasive coat by roll coater at 50 ~/m2 and radiation cured under the same conditions as used for curing the make coat, except curing was conducted under nitrogen instead of air.
The cured coated abrasive sheet was cut into samples, which were installed in a Schieffer testing machine for evaluation. These samples were compared to commercially ,;~ available coated abrasive ~amples of the same abrasive grade ,~ c~ ("Tri-M-ite WetorDry Paper available from Minnesota Mining 35 and ~anufacturing Company). The work piece was made of "Plexiqla~' acrylate and the results are shown in Table IV.

_ 3 1 _ TABLE IV

Example ~m~un ~f~ 9 Control -2.09 11 1.99 Exam~les 12=17 El~ctromagnetic radiation curable compositions as shown in Table V were prepared by mixing the listed ingredients in the amounts indi~ated.

TABLE V
Radiation curable composition (parts by weight) 15 ~ onents UV-7 UV-8 W -9 UV-10 UV-11 UV-12 W -13 UV-14 Pentaerythritol triacrylate 25 25 -- 12.5 -- 12.5 -- --1,6~Hexanediol diacrylate 25 25 -- 25 -- ~5 -- --20 Ethoxylated bisphenol A diacrylate -- ~ 62.5 -- 6~5 -- --Trimethylolpropane triacrylate -- -- 10 ~ ~- 10 --A C14 C15 n a aliphatic di~crylate -- -- 20 ~ -- 40 25 An aliphatic urethane acrylate. -- -- 3S --Dipentene - -- -- -- 17 -- -- --~0 Cycloaliphatic epoxide(a) __ __ 35 -- -~ ~~ lO 50 autyl glycidyl ether -- -- -- -- -- -- 35 --Epoxy-based flexibilizing agent -- -- -- -- -- -- -- 25 Diglycidyl ether of bisphenol A 50 50 -~ 0 -- -- --~i~8~

TABLE V ~cont.) Radiation curable composition tparts by weight) 5 Components UV-7 UV-8 UV-9 UV-10 UV-ll UV-12 UV-13 UV-14 Diphenyliodonium hexafluorophos-phate 3.0 0.76 3.0 -- -- -- 3.0 3.0 2-Isopropylthioxan-thone 0.3 0.076 0.3 ~ - 0.3 0.3 2,2-Dimethoxy-1, 2-diphenyl-1-ethanone -- 0.88 -- 1.8 SbF5.DEA.DEG( ) -- -- -- -- 3.0 -- -- --15 FC 431~C) 0.1 ~- -- -- --Trimethylolpropane -~ - -- - 5 --~; = Union Carbide Corp.
(b~ ~he adduct of antlmony pentafluoride with 2,6-diethylaniline and diethylene glycol (c) Fluorocarbon sur~actant from Minnesota Mining and Manufacturing Co.

Abrasive constructions wece prepared using compositions 25 UV-7 through UV-9 as make coats and compositions W -10 through W -14 as size coats.
The make coat and mineral coat were applied and cured in the same manner as in Example 11. The size coat was applied at a coating weiqht of 38 g/m2. Size coats of 30 compositions UV-10, UV-13, and UV-14 were cured with a RPC
Processor #QC1202 ANIR, at 30 cm/sec. with 4 passes, with two standard medium pressure mercury lamps set at 120 watts/cm, under a nitrogen atmosphere. The lamps were located at a distance of about 9.5 cm from the backing.
35 The size coat of composition UV-12 was cured by electron beam at 12.5 cm/sec., 5 Mrad, and 230 ~eV. The size coat of composition UV-11 was thermally cured at 150C for 5 minutes.

~ 2~3~

The samples were tested in a Schieffer testing machine in the same manner as in Example 11. The results are shown in Table VI.

TABLE VI

ExampleMake coat Size coat Amount o~ cut (~) 12 UV-7 UV-12 1 . 936 13 VV-7 UV-10 1.880 14 UV-7 UV-ll 1 . 874 UV-8 UV-10 1 . 638 16 UV-9 UV-13 1.648 17 UV-9 UV-14 2 . 005 XAMPLES 18~20 Radiation curable compo~itions as shown in Table VII were prepared by mixing the listed ingredients in the amounts indicated.

~9~ 9~

TABLE VII
Radiation curable composition (parts by weight) Pentaerythritol triacrylate 55 65 60 Triacrylate ester of tr s-(hydroxyethyl)isocyanurate10 2thoxylated bisphenol A
diacrylate -- 33 --Cycloaliphatic epoxide(a) 25 -~ __ Neopentylglycol diglycidyl ether 10 -- --Resorcinol diglycidyl ether -- -- 30 15 1~4-~is(hydroxymethyl) cyclohexane diglycidyl ether ~ 10 N-Vinyl-2-pyrcolidone -- 5 --Quartz 43 . - -~
20 Cryolite __122 122 Diphenyliodonium hexafl~orophosphate 0.60 -- 0.60 2-Isopropylthioxanthone 0.060 -- 0.060 2,2-Dimethoxy-1,2-diphenyl-1-ethanone 1.50 2.0 1.50 .
~a) "Cyracure 6100", Union Carbide Corp.

Abrasive constructions were prepared using Xayon 30 Jeans Cloth that was saturated with phenolic latex resin and cured by heating in an oven at 88C for 10 hours.
Composition UV-15, as a make coat, was knife coated onto the backing at a loading of 84 g/m2, then 326 g/m2 of grade P120 A12O3 mineral was coated onto the make coat, and the coating 35 cured by four passes in air at 7.5 cm/sec under a Fusion Model F450 lamp operated at 120 watts/cm. The lamps were located at a distance of about 6.3 cm from the backing.

;i3~

Composition UV-16, as a size coat, was roll coated onto a first portion of the mineral coated construction at a c~ating weight of 212 g/m2 and cured under the same conditions used to cure the make coat (Example 18~. A second portion of the mineral coated construction was roll coated with UV-17 composition and cured under the same conditions as was the size coat of Example 13 ~Sxample 19). A third p~rtion of the ~ineral coated construction was roll coated with cryolite filled phenol-formaldehyde resole resin at a coating weight of 176 g/m2 and cured by heating in an oven at 88C for 10 hours (Example 20).
Comparative Example a Phenol-formaldehyde resole resin was coated onto phenolic latex saturated Rayon Jeans backinq at a weight of 100 g/m . Grade P120 Al2O3 mineral was electrostatically coated thereon at a weight of 326 g/m2. The resin was partially cured by heat in an oven for 1 1/2 hours at 88C.
Cryolite filled phenol-formaldehyde resin size coat wa~
applied over the make coat and mineral coat and cured in the same manner as in Comparative Example ~.
Each cured coated abrasive construction was cut into strips and converted to endless belts tha~ were subjected to the belt grinding tests using 1018 steel at a loading pressure at the grinding interface of 0.70 kg/cm2.
25 The performance of each belt is shown in Table VIII.

TABLE VIII
, . _ Ab}asive cutting performance (~) 30 Example Make coat Size coat Initial Final Total 18 UV-15 UV-l~ 39 18 505 UV-15 Phenolic 33 15 415 B* PhenolicPhenolic 26 12 330 *Comparative example which was cured with heat and no electromagnetic radiation.

3.~ 3~5 Examples 18~20 show that abrasive articles having excellent abrasive performance can be prepared using phenolic resin-containing substrates when the electromagnetic 5 radiation curable compositions of the present invention are used as the make coat. The size coat can be a radiation cured composition containing epoxy and acrylic groups or it can be a phenolic resin, and the abrasive construction will still provide high quality cutting performance.
Examples 21-.27 ~ brasive sheeting having a cloth backing was prepared as follows. Spun polyester cloth! as described in Examples 5-8, was saturated with radiation curable lS composition UV-18 having the composition shown in Table IX
and c~red in air at 20 cm/sec using an RPC Processor #QC1202 ANIR having the first lamp set at 80 watts/cm and the second lamp set at 40 watts/~m. The lamps were located at a distance o~ about 9.5 cm from the backing. The 20 saturated cloth was then presized with UV-18 j cured, and then the backside of the cloth cured, the curing carried out under the same conditions as used to cure the saturant.
The cured saturated cloth backing was labeled l'I". In a similar manner, spun polyester cloth was saturated, 25 presized, and backsized with UV-19, the composition of which is also show~ in Table IX. Each curing step was carried out at lS cm/sec rather than the 20 cm/sec used for backing 'II". The saturated cloth backing obtained was labeled "II".

TABLE IX
Radiation curable composition (parts by weight) In~redient UV-18 UV-19 5 Diglycidyl ether of bisphenol A 50 --~ireactive No. 2 -- 75 Ethoxylated bisphenol A
diacrylate 25 --10 N-vinyl-2-pyrrolidone 15 15 Pentaerythritol triacrylate 10 10 Diphenyliodonium hexafluorophosphate 1.25 --60% solution of triphenyl-sulfonium hexafluorophosphate in y-butyrolactone -- 1O25 2-Isopropylthioxanthone 0.~25 --2,2-Dimethoxy-1,2-d.iphenyl-1-ethanone 1.0 1.0 Curable compositions UV-20 to UV-27 as shown in Table X were prep~red by mixing the listed ingredients in the amounts indicated.

~5 3~

TABLE X
Radiation curable composition (parts by weight) W-20 UV-2~ UV-22 W-23 UV-24 UV-25 UV-26 W-27 5 Resorcinol diglycidyl 15 15 -- -- -- -- -- --ether Bireactive No. 2 -- -- 17.5 17.5 17.5 17.5 -- --Triacrylate ester of ~ris(hydroxyethyl~
10 iqo~yanurate -- -- -- -- -- - 25 --Trimethylolpropane triacrylate -- -- -- -- -- -- 25 --Urea-formaldehyde -- -- -- -- -- -- -- 66 Pentaerythritol triacrylate 30 30 22.5 22.5 22.5 22.5 -- --Cycloaliphatic epoxide~a) 2.52.5 -- -- -- -- -- --N-vinyl-2-pyrrolidone 2.52.5 -- -- -- -- -- --20 Styrene -- -- 10 10 10 10 -- --Water -- -- -- -- -- -- -- 4-7 Diphenyliodoniu~ .
hexafluoropho~phate 0.33 1.5 -- -- -- -- -- --2-Isopropylthio-xanthone 0.033 0.15 -- -- -- -- -- --2,2-Dimethoxy-1,2-diphenyl-1-ethanone 0.75 -- 0.75 0.75 0.75 0.75 0~75 --lC13 ~~ -- -~ -- -- __ __ 4 3 30 ~uartz 50 50 50 -- -- -- -- --CaC0~ -- -- -- 50 -- -- 50 --aS04 ~~ ~- -- -- 50 50 -- __ Feldspar -- -- -- -- -- -- -- 25 SbF5- DEA- DEG -- -- ~- -- -- 0 . 5 -- --35 60% solution of tri-phenylsulfonium hexa-fluoropho~phate in r-butyrolactone -- __ 0.25 0.25 0.25 0.25 -- --(a) "Cyracure 6100", Union Carbide Corp.

8~39~

Radiation curable composition W-20 was then knife coated, as a make coat, onto treated cloth backing II
for use in Examples 21-24 at a coating weight of 200 g/m2.
Grade 40 silicon carbide mineral was electrostatically coated at a coating weight of 495 g/m2. The make coat was then cured by 4 passes in air through a Fusion Model F450 lamp at 7.5 cm~sec. The lamp was set at 120 watts/cm. The lamps were located at a distance of about 6.3 cm from the backing. Compositions UV-22, UV-23, UV-24, UV~25, and UV-27 were then roll coated onto portions of the ~ured construction at a weight of 450 g/m2. Size coats formed of compositions W -22 through UV-25 were cured under the same conditions used to cure the make coat. The size coat formed of composition UV-27 was thermally cured for 10 15 minutes at 37C and 20 minutes at 60C. The samples for Examples 25-27 were prepared in the same manner as the samples for ~xamples 21-24, using treated cloth backing I
and the compositions shown in Table XI.

Comparative_Example C
Conventional calcium carbonate filled phenol-formaldehyde resole resin was knife-coated onto phenolic latex treated polyester cloth backing II to form a make coat. Grade 40 silicon carbide mineral was 25 electrostatically coated onto the make coat at a weight of 495 g/m . The resin was partially cured by heat in an oven for 1 1/2 hours at 88C. Calcium carbonate filled phenol formaldehyde resin size coat was applied over the make coat and mineral coat and cured in the same manner as in 30 Comparative Example A.
Each cured coated abrasive sheet from Examples 21-27 and Comparative Example C was cut into strips and converted to endless belts, which were then subjected to belt grinding tests using pressboard at loadiny pressure, 35 at the qrinding interface, of 0.70 kg/cm2. The results of the grinding tests are shown in Table XI.

TABLE XI
Abrasive cuttin~ performance ~) Exam~ Backin~ Make coat Size coat Initial Final Total 23 II uV-20 UV-24 978 666 4623 I UV-20 UV-2~ S99 619 4079 C*PhenolicPhenolicPhenolic 1069 903 5496 ~Comparative example cured with heat only and no electromagnetic 15 radiation.
... .
Examples 21-27 show that abrasive articles having excellent abrasive performance can be prepared on cloth backing when the compositions of this invention are us~d as 20 make coat and curing is carried out with electromagnetic radiation. The cutting capability of the abrasive sheets prepared in accordance with this invention compares favorably with the cutting capability of the conventionally prepared abrasive sheeting which was cured by heating in an 25 oven at 88C for 13 1/2 hours.
Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention 30 is not to be unduly limited to the illustrated embodiment set forth herein.

Claims (19)

1. A coated abrasive product comprising a backing, a make coat, a layer of abrasive grains, and a size coat, wherein at least one of the make coat and size coat is formed from a composition curable by electromagnetic radiation comprising ethylenically-unsaturated groups and 1,2-epoxide groups, and a photoinitiator portion, in an amount sufficient to cure the composition, comprising at least one polymerization photoinitiator selected from the group consisting of (1) salts having an onium cation and a halogen-containing anion of a metal or metalloid, and (2) a mixture of (a) at least one salt having an organometallic complex cation and a halogen-containing complex anion of a metal or metalloid, and (b) at least one free-radical polymerization initiator.

2. The product of claim 1 wherein the ethylenically-unsaturated groups are provided by esters of aliphatic hydroxy group-containing compounds and unsaturated carboxylic acids.

3. The product of claim 2 wherein said ethylenically-unsaturated groups are provided by an ester of acrylic or methacrylic acid.

4. The product of claim 1 wherein the ethylenically unsaturated groups are provided by compounds selected from the group consisting of ethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, diacrylate of bisphenol A, ethoxylated diacrylate of bisphenol A, aliphatic urethane acrylate, and N-vinyl-2-pyrrolidone.

5. The product of claim 1 wherein the 1,2-epoxide groups are provided by compounds selected from the group consisting of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane-carboxylate, 3,4-epoxy-2-methylcyclohexylmethyl 3,4-epoxy-2-methylcyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, 2,2-bis[4-(2,3-epoxypropoxy)phenyl])propane, butyl glycidyl ether, neopentylglycol diglycidyl ether, and resorcinol diglycidyl ether.

6. The product of claim 1 wherein the ethylenically-unsaturated groups and 1,2-epoxide groups are provided by bireactive compounds which are the reaction pcoduct of compounds having at least two 1,2- epoxide groups with a stoichiometric deficiency of an ethylenically-unsaturated compound that contains active hydrogen.

7. The product of claim 6 wherein said bireactive compounds are the reaction product of 0.4 to 0.6 weight equivalents of acrylic acid and one mole of a member selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of 1,4-butanediol, polyglycidyl ether of phenol-formaldehyde novolac, polyglycidyl ether of cresol-formaldehyde navolac, diglycidyl terephthalate, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane-carboxylate, and bis(3,4-epoxy-6-methylcyclohexyl)methyl adipate.

8. The product of claim 1 further containing a latent thermally activated polymerization initiator.

9. The product of claim 1 wherein said composition comprises at least about 0.2 equivalent of ethylenically-unsaturated group and at least about 0.05 equivalent of 1,2-epoxide group per 100 grams of composition.

10. The coated abrasive product of claim 1 wherein the total amount of photoinitiator ranges from about 0.05 to about 10 parts by weight of said radiation curable composition.

11. The coated abrasive product of claim 1 wherein at least one of said make coat and said size coat is formed from a phenolic resin.

12. A coated abrasive product comprising a backing, a make coat, a layer of abrasive grains, and a size coat, wherein at least one of the make coat and size coat is formed from a composition curable by electromagnetic radiation comprising (1) a curable portion selected from the group consisting of:
(A) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, (B) at least one ethylenically-unsaturated compound and at least one compound containing at least one 1,2-epoxide group, (C) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, and at least one ethylenically-unsaturated compound, (D) at least one bireactive compound containing at least one ethyienically-unsaturated group and at least one 1,2-epoxide group, and at least one compound containing at least one 1,2-epoxide group, and (E) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, at least one ethylenically-unsaturated compound, and at least one compound containing at least one 1,2-epoxide group, (2) a photoinitiator portion, in an amount sufficient to cure the composition, comprising at least one polymerization photoinitiator selected from the group consisting of:
(a) salts having an onium cation and a halogen-containing complex anion of a metal or metalloid, and (b) a mixture of (a) at least one salt having an organometallic complex anion of a metal or metalloid and (b) at least one free radical polymerization initiator.

13. A coated abrasive product comprising a backing, a make coat, a layer of abrasive grains, and a size coat, wherein said backing has at least one of a saturant coat, a presize coat, or a backsize coat, wherein at least one of said saturant coat, said presize coat, or said backsize coat is formed from a composition curable by electromagnetic radiation comprising ethylenically-unsaturated groups and 1,2-epoxide groups and a photoinitiator portion, in an amount sufficient to cure the composition, comprising at least one polymerization photoinitiator selected from the group consisting of (1) salts having an onium cation and a halogen-containing anion of a metal or metalloid, and (2) a mixture of (a) at least one salt having an organometallic complex cation and a halogen-containing complex anion of a metal or metalloid, and (b) at least one free-radical polymerization initiator.

14. A coated abrasive product comprising a backing, a make coat, a layer of abrasive grains, and a size coat, wherein said backing has at least one of a saturant coat, a presize coat, or a backsize coat, wherein at least one of said saturant coat, said presize coat, or said backsize coat is formed from a composition curable by electromagnetic radiation comprising (1) a curable portion selected from the group consisting of:
(A) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, (B) at least one ethylenically-unsaturated compound and at least one compound containing at least one 1,2-epoxide group, (C) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, and at least one ethylenically-unsaturated compound, (D) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, and at least one compound containing at least one 1,2-epoxide group, and (E) at least one bireactive compound containing at least one ethylenically-unsaturated group and at least one 1,2-epoxide group, at least one ethylenically-unsaturated compound, and at least one compound containing at least one 1,2-epoxide group, (2) a photoinitiator portion, in an amount sufficient to cure composition, comprising at least one polymerization photoinitiator selected from the group consisting of:

(a) salts having an onium cation and a halogen-containing complex anion of a metal or metalloid, and (b) a mixture of (a) at least one salt having an organometallic complex anion of a metal or metalloid and (b) at least one free-radical polymerization initiator.

15. The coated abrasive product of claim 13 wherein the total amount of photoinitiator ranges from about 0.05 to about 10 parts by weight of said radiation curable composition.

16. The coated abrasive product of claim 13 wherein at least one of said make coat and said size coat is formed from a phenolic resin.

17. A coated abrasive product comprising abrasive granules which are supported on and adherently bonded to at least one major surface of a backing by a resinous binder material, said resinous binder material formed from a composition curable by electromagnetic radiation comprising ethylenically-unsaturated groups and 1,2-epoxide groups, and a photoinitiator portion, in an amount sufficient to cure the composition, comprising at least one polymerization photoinitiator selected from the group consisting of (1) salts having an onium cation and a halogen-containing anion of a metal or metalloid, and (2) a mixture of (a) at least one salt having an organometallic complex cation and a halogen-containing complex anion of a metal or metalloid, and (b) at least one free-radical polymerization initiator.

18. Method of preparing the coated abrasive product of claim 1 comprising the steps of (1) providing a backing, (2) applying a make coat over said backing, (3) applying a layer of abrasive grains over said make coat, (4) applying a size coat over said layer of abrasive grains, (5) curing at least one of said make coat or said size coat by means of electromagnetic radiation.

19. Method of preparing the coated abrasive product of claim 13 comprising the steps of (1) providing a backing having at least one of a saturant coat, a presize coat, or a backsize coat, (2) curing at least one of said saturant coat, presize coat, or backsize coat by means of electromagnetic radiation, (3) applying a make coat over said backing, (4) applying a layer of abrasive grains over said make coat, (5) applying a size coat over said layer of abrasive grains, (6) curing said make coat and said size coat.