WO1997014535A1 - Abrasive article containing an inorganic metal orthophosphate - Google Patents

Abstract

An abrasive article, and methods of making and using same, containing an inorganic metal orthophosphate salt. The abrasive article including a coated abrasive article having a size or supersize coating layer containing an alkali metal or alkaline earth metal orthophosphate salt devoid of hydrogen. The inventive abrasive article reduces the grinding energy required while improving abrading efficiency in some cases.

Description

ABRASIVE ARTICLE CONTAINING AN INORGANIC METAL

ORTHOPHOSPHATE

BACKGROUND OF THE INVENTION

Field ofthe Invention This invention relates to abrasive products comprising abrasive particles, binder, and an inorganic metal orthophosphate salt, and to methods of making and using same These abrasive products include bonded abrasives, coated abrasives, and nonwoven abrasives

Description of the Related Art In the competitive and economically significant field of abrasive products, a continuing desire exists to reduce manufacturing costs and increase performance of such products in efforts to seek and acquire competitive edge

Abrasive products are generally known having abrasive particles adherently bonded to a sheet-like backing It is generally known to stratify the abrasive grains and binders into separate layers that are serially formed upon a sheet-form substrate, such as in coated abrasive articles, in such a way as to basically segregate the abrasive grains as a particulate monolayer sandwiched between underlying and overlaying binder layers

More specifically, coated abrasive products typically have a backing substrate, abrasive grains, and a bonding system which operates to hold the abrasive grains to the backing In a typical coated abrasive product, the backing is first coated with a layer of adhesive, commonly referred to as a "make coat", and then the abrasive grains are applied to the adhesive coating The application ofthe abrasive grains to the make coat involves electrostatic deposition or a mechanical process which maximizes the probability that the individual abrasive particles are positioned with its major axis oriented perpendicular to the backing surface As so applied, the abrasive particles optimally are at least partially embedded in the make coat The resulting adhesive/abrasive grain layer is then generally solidified or set (such as by a series of drying or curing ovens) sufficient to retain the adhesion of abrasive grains to the backing After curing or setting the make coat, a second layer of adhesive, commonly referred to as a "size coat", is applied over the surface ofthe make coat and abrasive particles, and, upon setting, it further supports the particles and enhances the anchorage of the particles to the backing Optionally, a "supersize" coat, which may contain grinding aids, can be applied over the cured size coat ln any event, once the size coat and supersize coat, if used, has been cured, the resulting coated abrasive product can be converted into a variety of convenient forms such as sheets, rolls, belts, and discs As an optional supersize enhancement, to mitigate any anticipated loading or clogging of the abrasive product with swarf (i e , debris liberated from the workpiece during the abrading operation), a coating of anti-stick stearate also can be applied as supersize over the exterior of the abrasive coating, once formed, as suggested in Kirk- Othmer Encyclopedia of Chemical Technology Fourth Ed , Vol 1 , (p 29)

In many abrasive articles the binder includes a particulate filler as an adjuvant Typically, the binder will comprise between 40 to 70 percent by weight particulate filler The addition ofthe filler either increases the toughness and hardness ofthe binder and/or reduces the cost of the finished article, e g , by decreasing the amount of binder required The filler is typically an inorganic particulate material, generally having a particle size less than about 40 micrometers Examples of common fillers in the abrasive industry include calcium carbonate, calcium oxide, calcium metasilicate, alumina trihydrate, silica, kaolin, quartz, and glass

There exists a subclass of fillers, referred to as grinding aids, cutting aids, or generically as "active fillers" An active filler is typically a particulate material the addition of which to the binder has a significant affect on the chemical and physical processes of abrading which leads to improved performance It is believed that active fillers will either (1 ) decrease the friction between the abrasive grains and the workpiece being abraded, and/or (2) prevent the abrasive grains from "capping", i.e. prevent metal particles from becoming welded to the tops of the abrasive grains, and/or (3) decrease the interface temperature between the abrasive grains and the workpiece, and/or (4) decrease the required grinding force

Grinding aids can be especially effective in abrading stainless steel, exotic metal alloys, titanium, metals slow to oxidize, and so forth In some instances, a coated abrasive product containing a grinding aid in the binder can abrade up to 100% more stainless steel than a corresponding coated abrasive product in which the binder is devoid ofa grinding aid The reason, in theory, being that the activity of grinding metal by abrasive articles produces freshly formed, hot, and uncontaminated metal surfaces If the newly formed, uncontaminated metal surface is not rapidly "contaminated", metal will transfer and adhere to the abrasive particle surface(s) causing "capping" which decreases grinding performance One purpose and function of grinding aids is to prevent capping by rapidly contaminating the freshly formed metal surface Grinding aids are normally incorporated into the bond resin(s) ofthe abrasive article Grinding aids (active fillers) can be classified as physically active or chemically active Cryolite, sodium chloride, and potassium tetrafluoroborate are known physically active grinding aids that melt between 500 and 1,000°C which can form thin films on freshly formed metal Chemically active grinding aids include iron pyrite, polyvinyl chloride, and polyvinylidene chloride which decompose when heated forming chemicals that rapidly react with the freshly formed metal surface

Also, combinations of grinding aids in abrasive articles (grinding wheels) may produce more than a cumulative grinding effect U S patents describing use of the combination of a sulfide salt and an alkali metal salt include U S Patent Nos 2,408,319, 2,81 1 ,430, 2,939,777, 3,246,970, and 5,061,295 Other patents that combine an inorganic salt containing fluorine, e g cryolite, and a salt such as ammonium chloride include U S Patent Nos 2,949,351 and 2,952,529

Another type of grinding aid enhancement is described in U S Patent no 5,441,549 (Helmin) wherein the grinding aid effect of potassium tetrafluoroborate is enhanced by the addition of specific thermoplastics Other descriptions of grinding aids include

U S Pat No 2,216, 135 (Rainier), which teaches a grinding wheel having as a grinding aid an anhydrous, water-soluble non oxidizing inorganic alkali or alkaline earth metal salts whose melting points are within the range of 700 to 1200°C These materials include sodium chloride, potassium chloride, anhydrous sodium carbonate, sodium sulfate, potassium sulfate, lithium sulfate, sodium pyrophosphate, potassium pyrophosphate, calcium chloride, calcium bromide, magnesium sulfate, barium chloride, barium bromide, magnesium chloride, magnesium bromide or strontium chloride U S Pat No 2,243,049 (Kistler), which teaches an abrasive body (grinding wheels) containing finely divided strongly acidic or potentially acidic inorganic compounds Acid sulfates, phosphates or pyrophosphates are satisfactory, as are the ammonium, sodium, potassium, calcium, or barium salts thereof Phosphorus pentoxide is also possible The grinding aid constitutes about 7% ofthe bond When used on metal work surfaces, the grinding aid reduces loading and increases the grain efficiency 40 to 100%

U S Pat No 3,502,453 (Baratto) discloses abrasive articles containing hollow spherules filled with lubricant, which spherules rupture during grinding to release the lubricant In one example, Baratto discloses a formulation molded into a wheel for titanium snagging, where the formulation includes silicon carbide, bonding resin, trisodium phosphate, and encapsulated lubricant

U S Pat No 2,690,385 (Richlin), which teaches a metal cleaning cloth or felt impregnated with abrasive, sodium bisulfate and a humectant Substitutes for the sodium bisulfate include ammonium chloride, ammonium phosphate, aluminum chloride, antimonious chloride, potassium bisulfate, oxalic acid, phosphoric acid and tartaric acid

U S Pat No 3,030, 198 (Kibbe), which discloses a grinding wheel containing potassium hexafluorophosphate as a grinding aid

U S Pat No 3,032,404 (Douglass et al ), which discloses a grinding wheel containing as a grinding aid finely divided solid heavy metal phosphide It is preferable to also include potassium aluminum fluoride in the grinding wheel U S Pat No 3,770,401 (Sheets et al ), which describes an abrasive body (grinding wheel) comprised of grit-sized particles of alumina or silicon carbide held together by a water-insoluble aluminum phosphate bonding matrix

U S Pat No 5,096,983 (Gerber), which teaches the use of up to 5 0% of a 5 water soluble salt such as sodium phosphate to retard the room temperature and eventual hardening of phenolic resole resins which are mixed with magnesium oxide with or without an ester functional hardening agent

U.S Pat No 5, 1 16,392 (Selgrad et al ), which teaches a grinding aid having the formula uM,^# M₂* wHal* xChal'zPh, where Mi is a pure metal or i o mixture of alkali metal, alkaline earth metal and/or Al, M₂ is a pure metal or mixture of Zn, Mn, Fe except for Fe as chloride, Hal is a pure halogen or mixture of F, Cl, Br, I, Chal is chalcogenides, O and/or S, Ph is phosphate or more highly condensed phosphates of the formula P,O where r = I to 10, preferablv 1 to 2, s = 4 to 20, preferably 4 to 7, and u, v, w, x or z = 0 to 95%

15 Also, commonly assigned U S Pat Appln Serial No 08/214,394, filed

March 16, 1994, describes abrasive articles having a peripheral (outermost) coating comprised of grinding aid particles and a binder, where the grinding aid particles are individually coated with an inert, hydrophobic, hydrocarbon-containing substance. For coated abrasive articles, the peripheral coating is stated to refer to either the 0 size or supersize coat that is the outermost coating on the abrasive surface ofthe article The individually-coated grinding aid particles also may be incorporated into erodible grinding aid agglomerates, with a binder to adhere the grinding aid particles together, and these agglomerates can be incorporated into the make, size and/or supersize coats of a coated abrasive Although a number of examples of 5 grinding aid particles are disclosed in U S Appln Serial No 08/214,394, alkali or alkaline earth metal phosphates are not named

Commonly assigned U S Pat Appln Serial No 08/545,984 (Harmer et al.), filed on even date with the present application, describes abrasive articles having an alkali or alkaline earth metal metaphosphate, such as sodium metaphosphate, in the 0 peripheral coating layer, and methods of making these abrasive articles, as well as a method of using them to grind titanium Commonly assigned U S Pat Appln Serial No 08/545,874 (Ho et al.), filed on even date with the present application, describes coated abrasive articles having an abrasive grain layer formed in a make coat, which, in turn, is coated with a size coat or a size coat and a super size coat, where the abrasive grain layer is 5 comprised of abrasive grains and nonabrasive composite grains which contain inorganic nonabrasive particles bonded together by a metal salt of a fatty acid or colloidal silica, or combinations thereof

Titanium alloys, in particular, such as those designed for aerospace applications and other applications where high strength to weight ratios are i o desirable, are extremely difficult to grind, even with conventional grinding aids. Although the high strength of these alloys is a major cause of poor grindability, chemical adhesion of the titanium to the abrasive grain is also thought a factor contributing to poor abrasive performance These difficulties can be alleviated somewhat by use of certain grinding fluids, such as coolants or lubricants, used to

15 flood the grinding interface between the abrasive article and workpiece Materials used as grinding fluids for titanium include soluble cutting oils such as highly chlorinated cutting oils and buffered inorganic tripotassium phosphate solutions, the latter of which being described by I S Hong et al , "Coated abrasive machining of titanium alloys with inorganic phosphate solutions". Trans ASLE, 14 ( 1971 ), pages

20 8- 1 1 Additionally, a comparative study of grinding aid lubricants involving the use of among four inorganic salts NaN0₂, KN0₂, Na-,P0 , and K;P0₄, is described by Caldwell et al , "Grinding a titanium alloy with coated abrasives," ASME Paper 58- SA-44, June, 1958 Although widely used in buffered solutions, the tripotassium phosphate salts have proven difficult to incorporate into resin-bonded systems due

25 to their hygroscopic nature

U S Pat No 4,770,671 (Monroe et al ) describes adding various types of grinding aids onto the suiface of alpha-alumina-based ceramic abrasive grits in coated abrasives In one example, Monroe et al describe K₂HP0₄ as a grinding aid. A variety of "phosphates" exist as salts of acids of phosphorus The

30 conventional nomenclature and associated chemical formulae of several common anions for these salts include the following orthophosphate = P0₄ ^" monohydrogen orthophosphate = HPO₄ ^"2 dihydrogen orthophosphate = H₂PO₄ ^"' metaphosphate = POi^"' pyrophosphate = P₂0?^"4

This terminology is applicable for purposes of this application

SUMMARY OF THE INVENTION

The present invention relates to abrasive articles containing an alkali or alkaline earth metal orthophosphate salt, which, in some abrading applications, require less energy to grind metal surfaces such as titanium while providing useful and even improved abrading efficiency The alkali metal or alkaline earth metal orthophosphate salt is a compound devoid of hydrogen atoms Thus, the present invention relates to an abrasive article comprising (a) a plurality of abrasive particles, (b) at least one binder to which said plurality of abrasive particles are adhered, and (c) a peripheral surface, said peripheral surface containing an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of an alkali metal orthophosphate salt and an alkaline earth metal orthophosphate salt.

In one aspect, the present invention provides coated abrasive articles having improved abrading efficacy and performance by containing an alkali metal or alkaline earth metal orthophosphate salt devoid of hydrogen in a peripheral coating layer thereof

In a further aspect of this invention, there is a coated abrasive article including a substrate having abrasive grains adherently bonded thereto by at least one binding material, and a peripheral coating layer comprising an alkali metal or alkaline earth metal orthophosphate salt devoid of hydrogen

Suitable inorganic alkali or alkaline earth metal orthophosphates devoid of hydrogen include those having high melting points such as tripotassium (ortho)phosphate (K₃P0₄)(m p 1340°C), trisodium (ortho)phosphate (Na₃PO ), or tribarium di(ortho)phosphate (Ba-,(P0₄) ) (m.p 1670°C), or combinations thereof. For purposes of this application, a "peripheral surface" means the outermost surface of an abrasive article, which represents the surface for contacting and abrading a workpiece In the context of coated abrasive articles, a "peripheral coating" or "peripheral coating layer" is the outermost coating of a coated abrasive article, i.e. the coating having an exposed and uncoated major surface, as disposed on the working side of a coated abrasive article construction The "working side" of the coated abrasive being a side of the construction where the abrasive grains are adherently bonded to the backing The peripheral coating generally is a size coat, or a supersize coat, with the proviso that the layer in all cases represents the outermost layer of the abrasive article construction and is left uncoated by any other separate coating whether it is derived from the same composition or a different composition

The peripheral coating layer containing the alkali metal or alkaline earth metal orthophosphate of the inventive abrasive article includes a binder, preferably a thermoset binder or resin, which serves as the continuous phase or medium by which the inorganic phosphate, and any other dispersed additives, are attached within and bound into the layer The term "thermoset" resin, as used herein, means a cured resin that has been exposed to an energy source (e g , heat and/or radiation) sufficient to make the resin incapable of flowing The term "thermosetting" means an uncured thermoset resin Also, the term "dispersed", or variants of this term, as used herein, does not necessarily denote a uniform distribution ofthe alkali metal or alkaline earth metal orthophosphate salt throughout the resinous binder ofthe coating layer, although uniform dispersions of such are contemplated in this invention In one preferred mode ofthe invention, a peripheral coating layer ofthe coated abrasive article of this invention containing the alkali metal or alkaline earth metal orthophosphate salt includes a binder that is an epoxy binder, an acrylic binder, or a phenolic binder The preferred binder materials in this regard include a diglycidyl ether of bisphenol A epoxy resin and an amine-functional acrylic polymer Another advantage, in addition to reduction of energy required for grinding, attributable to the usage of the alkali metal or alkaline earth metal orthophosphate salt in a peripheral coating layer of an abrasive article includes avoiding the potential of halogens being liberated as from halogen-containing grinding aids. In another aspect, the invention provides a method for making a coated abrasive article, comprising the steps of:

(a) applying a first binder resin precursor to a substrate;

(b) at least partially embedding a plurality of abrasive particles in said first binder resin precursor; (c) at least partially curing said first binder resin precursor;

(d) applying a second binder resin precursor over said at least partially cured first binder resin precursor and said plurality of abrasive particles;

(e) at least partially curing said second binder precursor resin precursor; (f) applying a third binder resin precursor and an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of an alkali metal orthophosphate and an alkaline earth metal orthophosphate; and

(g) completely curing said first, second and third binder precursor resin precursors. The third binder coating can be an aqueous-based system, such as with an acrylic/latex binder-based system, or a non-aqueous organic solvent based system, such as a xylene solvent-based epoxy binder system. Non-aqueous solvent-based systems are preferred. The present inventors have developed methods to successfully incorporate K₃PO₄ into binder systems of coated abrasive peripheral layers in manners effective to overcome and avoid the problems arising from the hygroscopic propensities of K₃PO₄

The present invention, in another aspect, relates to a method of using the coated abrasive articles of the invention to grind titanium. Therefore, in one aspect the present invention relates to a method of using a coated abrasive article to grind titanium, comprising: (a) providing a coated abrasive article comprising a plurality of abrasive particles, a binder to which said abrasive particles are adhered, and a peripheral coating layer containing an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of alkali metal orthophosphate salt and alkaline earth metal orthophosphate salt, and a workpiece comprising titanium;

(b) frictionally engaging said peripheral coating layer with a surface of said workpiece; and

(c) moving at least one of said coated abrasive article and said workpiece relative to each effective to reduce the surface of said workpiece The coated abrasive articles of this invention are used in dry grinding operations without water flooding as the water may dissolve the alkali metal or alkaline earth metal orthophosphate-containing coating

The incorporation of the alkali metal orthophosphate salt in a coating layer of the coated abrasive article of the present invention endows the coated abrasive article with an unexpected abrading efficiency when compared to a similar abrasive containing conventional grinding aids and fillers.

In yet another aspect of the invention, the abrasive article is a bonded abrasive comprising a shaped mass of the abrasive particles and the alkali metal or alkaline earth metal orthophosphate adhered together with a binder, which can be an organic, metallic or vitrified binder. By way of example, the shaped mass can be in the foπn of a grinding wheel or a conical shape Thus, the present invention relates to a bonded abrasive article comprising a shaped mass having a peripheral surface, wherein said shaped mass comprises a plurality of abrasive particles and an inorganic phosphate salt adhered together by a thermosetting binder, said inorganic phosphate salt being devoid of hydrogen and selected from the group consisting of an alkali metal orthophosphate salt or an alkaline earth metal orthophosphate salt.

In another aspect of the invention, abrasive particles are provided as erodible abrasive agglomerates where the alkali metal or alkaline earth metal orthophosphate and abrasive grains are adhered together with a binder. The term "erodible", as used herein, means that the agglomerate has the ability to break down in a controlled manner, for example, by fracture due to mechanical stress. Thus, the present invention relates to an erodible grinding aid agglomerate comprising a plurality of particles of an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of alkali metal orthophosphate salt and alkaline earth metal orthophosphate salt, and a binder that adheres said inorganic metal phosphate salt particles together

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The coated abrasive products ofthe present invention generally include conventional backings and binders for the coatings, and a peripheral coating layer containing an alkali metal or alkaline earth orthophosphate salt devoid of hydrogen As will be shown, coated abiasive products of this invention have been found to demonstrate high performance in abrading workpieces such as titanium The terminology "alkali metal", as used herein, refers to the Group IA metallic elements ofthe Periodic Table, viz , lithium, sodium, potassium, rubidium, cesium, and francium Examples of alkali metal orthophosphates useful in the invention include tripotassium phosphate and trisodium phosphate The terminology "alkaline earth metal", as used herein, refers to the Group IIA metallic elements, ofthe Periodic Table, viz , beryllium, magnesium, calcium, strontium, barium, and radium An example of an alkaline earth metal orthophosphate useful in the invention is tribarium di(ortho)phosphate The alkali metal and alkaline earth metal orthophosphates used in this invention preferably are compounds devoid of hydrogen atoms

The coated abrasive products of this invention can make use of backings, make coats, abrasive grains, size coats, supersize coats, and optional adjuvants, such as grinding aids, fillers, and other additives, which are known or conventional in making coated abrasive products, such materials or substances and their forms and use are described, for example, in Kirk-Othmer. loc cit. p 17-37, McKetta, J J , Cunningham, W A , Encyclopedia of Chemical Processing and Design, Marcel Dekker, Inc , p 1-19, and said U S Pat Nos. 5,01 1,512 and 5,078,753 The backing used as a base or substrate for the abrasive product of this invention generally will be made ofa sheet or film ofa material that is compatible with the make coat or abrasive slurry coat and other elements or components of the abrasive product and that is capable of maintaining its integrity during fabrication and use of the abrasive product Examples of backing materials are paper, fiber, polymeric film, woven and nonwoven fabric or cloth, and vulcanized fibre Specific weights, tensile strengths, and characteristics of some of such backings are set forth on p 4 of the McKetta and Cunningham text, |oc_ cit_ The backing may also contain a treatment or treatments to seal the backing, for example, to make them waterproof, and modify physical properties thereof Still other examples of useful backings include U S Patent No 5,3 16,812 and European Patent Publication No. 0 619 769 Also, reference is made to U S Pat No 5,01 1, 12 describing specific, woven, polyester cloth backings of certain weights and saturated with a calcium carbonate-filled latex/phenolic resin coating (useful also as a make coat) The backing may also have an attachment means on its back surface to secure the resulting coated abrasive to a support pad or back-up pad This attachment means can be a pressure sensitive adhesive or a loop fabric for a hook and loop attachment Alternatively, there may be a intermeshing attachment system as described in the said U S Pat No 5,201 , 101 The back side of the abrasive article may also contain a slip resistant or frictional coating Examples of such coatings include an inorganic particulate (e g , calcium carbonate or quartz) dispersed in an adhesive

The binder used in the coated abrasive, such as a make, size or supersize coat, generally will be formed from a resinous binder or adhesive This binder can also serve to bind the alkali or alkaline earth metal orthophosphate grinding aid to the coated abrasive Additionally, the binder may serve to bond both the abrasive particles and the grinding aid particles to the backing The resinous adhesive generally will be selected such that it has the suitable properties necessary for an abrasive article binder Examples of typical resinous adhesives useful in this invention include thermosetting resins, such as phenolic resins, aminoplast resins having pendant a,b-unsaturated carbonyl groups, urethane resins, epoxy resins, ethylenically-unsaturated resins, acrylated isocyanurate resins, urea-formaldehyde resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy resins, bismaleimide resins, fluorene modified epoxy resins, and mixtures thereof

Epoxy resins useful as binders have an oxirane ring and are polymerized by the ring opening Such epoxide resins include monomeric epoxy resins and polymeric epoxy resins These resins can vary greatly in the nature of their backbones and substituent groups For example, the backbone may be of any type normally associated with epoxy resins and substituent groups thereon can be any group free of an active hydrogen atom that is reactive with an oxirane ring at room temperature Representative examples of acceptable substituent groups include halogens, ester groups, ether groups, sulfonate groups, siloxane groups, nitro groups and phosphate groups Examples of some preferred epoxy resins include 2,2-bis[4-(2,3-epoxy- propoxy)phenyl]propane (diglycidyl ether of bisphenol) and resins which are commercially available from Shell Chemical Co , Houston, TX, under the trade designations "Epon 828", "Epon 1004", and "Epon 1001F", and from Dow Chemical Co , Midland, MI, under the trade designations "DER 331", "DER 332", and "DER 334" The mixing ratio of phosphate salt grinding aid to binder for the epoxy binder system based on solids weight is I 10 to 5 1 0, preferably I 5 1 0 to 4 0 1 0, and more preferably 2 0 1 0 to 3 0 I 0 Aqueous emulsions o the diglycidyl ether of bisphenol A have from about 50 to 90 wt % solids, preferably 50 to 70 wt % solids, and further comprise a nonionic emulsifier An emulsion meeting this description is available from Shell Chemical Co , Louisville, KY, under the trade designation "CMD 35201" Such aqueous epoxy emulsions are described as binder for grinding aids in EP 486308(Lee et al ) Other suitable epoxy resins include glycidyl ethers of phenol formaldehyde novolac (which are available from Dow Chemical Co , Midland, MI, under the trade designations

"DEN 431" and "DEN 438")

Phenolic resins are widely used in abrasive article binders because of their thermal properties, availability, cost and ease of handling There are two types of phenolic resins, resole and novolac, and they can be used in this invention Resole phenolic resins have a molar ratio of formaldehyde to phenol, of greater than or equal to 1 1 , typically between 1 5 1 0 to 3 0 1 0 Novolac resins have a molar ratio of formaldehyde to phenol of less than one to one. Examples of phenolic resins include those commercially available from Occidental Chemical Corp., Tonawanda, NY, under the trade designations "Durez" and "Varcum"; from Monsanto Co., St. Louis, MO, under the trade designation "Resinox"; and from Ashland Chemical Inc., Columbus, OH, under the trade designations "Arofene" and "Arotap". Care must be taken with phenolic resins due to the water associated with phenolic resins and the hygroscopic nature of phosphate salts.

The aminoplast resins which can be used as binders have at least one pendant , β-unsaturated carbonyl group per molecule or oligomer. These materials are further described in U.S Pat. Nos. 4,903,440 and 5,236,472

Ethylenically-unsaturated resins which can be used in this invention include both monomeric and polymeric compounds that contain atoms of carbon, hydrogen and oxygen, and optionally, nitrogen and the halogens Oxygen or nitrogen atoms or both are generally present in ether, ester, urethane, amide, and urea groups. The ethylenically-unsaturated compounds preferably have a molecular weight of less than about 4,000 and are preferably esters made from the reaction of compounds containing aliphatic monohydroxy groups or aliphatic polyhydroxy groups and unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and the like. Representative examples of ethylenically-unsaturated resins include those made by polymerizing methyl methacrylate, ethyl methacrylate, styrene, divinylbenzene, vinyl toluene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, hexanediol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, or pentaerythritol tetramethacrylate, and mixtures thereof Other ethylenically-unsaturated resins include those of polymerized monoallyl, polyallyl, and polymethallyl esters and amides of carboxylic acids, such as diallyl phthalate, diallyl adipate, and N,N-diallyladipamide Still other polymerizable nitrogen-containing compounds include tris(2-acryloxyethyl)isocyanurate, l ,3,5-tri(2-methacryl-oxyethyl)-s-triazine, acrylamide, methylacrylamide, N-methylacrylamide, N,N-dimethyl-acrylamide, N-vinylpyrrolidone, and N-vinylpiperidone

Acrylated urethanes are diacrylate esters of hydroxy terminated isocyanate extended polyesters or polyethers Examples of acrylated urethanes which can be used in the make coats o the present invention include those commercially available from Radcure Specialties, Inc . Atlanta, GA, under the trade designations, "UVITHANE 782", "CMD 6600", "CMD 8400", and "CMD 8805". Acrylated epoxies which can be used in the make coats are diacrylate esters of epoxy resins, such as the diacrylate esters of bisphenol A epoxy resin Examples of acrylated epoxies include those available from Radcure Specialties, Inc , Atlanta, GA, under the trade designations, "CMD 3500", "CMD 3600", and "CMD 3700"

Bismaleimide resins which also can be used as binder are further described in U.S Pat No 5,3 14,513 (Miller et l )

The binder for the alkali or alkaline earth metal orthophosphate salt grinding aid particles should be selected such that it is compatible with the orthophosphate salt In general, certain orthophosphate salts (e g , K PO ) are hygroscopic and pH may be a significant factor When the K-,PO₄ tends to absorb too much water, this then results in a non-homogenous binder that can be difficult to process Thus, care should be taken to select the proper binder such that the orthophosphate salt is compatible which will result in a uniform binder that is easy to process

The bond system of the abrasive article, viz any ofthe make coat, size coat, or supersize coat, and the like, as applicable, also can contain adjuvants with the primary component thereof, i e , the binder precursor optional additives, such as, for example, fillers (including grinding aids), fibers, lubricants, wetting agents, thixotropic materials, surfactants, pigments, dyes, antistatic agents, coupling agents, plasticizers, and suspending agents The amounts of these materials are selected to provide the properties desired

For example, although not required, other grinding aids, in addition to the alkali metal or alkaline earth metal orthophosphate present in the peripheral coating layer, can be used in the coated abrasive articles ofthe invention, if desired A grinding aid is defined as particulate material that the addition of which has a significant effect on the chemical and physical processes of abrading which results in improved performance In general, the addition of a grinding aid increases the useful life of the coated abrasive Grinding aids encompass a wide variety of different materials and can be inorganic or organic based Examples of chemical groups of grinding aids include waxes, organic halide compounds, halide salts and metals and their alloys The organic halide compounds will typically break down during abrading and release a halogen acid or a gaseous halide compound Examples of such materials include chlorinated waxes like tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride Examples of halide salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride Examples of metals include, tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium Other miscellaneous grinding aids include sulfur, organic sulfur compounds, graphite and metallic sulfides It is also within the scope of this invention to use a combination of different grinding aids The above mentioned examples of grinding aids is meant to be a representative listing of grinding aids, and it is not meant to encompass all grinding aids usable

As another optional adjuvant for the make and/or size coats, a coupling agent can provide an association bridge between the binder precursor and the

particles or abrasive particles Examples of coupling agents include silanes, titanates, and zircoaluminates, and their manner of use for this function is described, for example, in U S Pat No 4,871 ,376 (DeWald). The abrasive bond preferably contains from about 0 01 to 3 wt % coupling agent.

Since K-,PO₄, in particular, as the inorganic orthophosphate coating layer additive ofthe present invention, is difficult to incorporate into resin-bonded systems due to its hygroscopic nature, the present invention embodies improved techniques for incorporating K-,P0₄ into a binder K-,P0₄ has the common names of tripotassium phosphate or tertiary potassium (ortho)phosphate The physical nature of K₃PO is that it is colorless, rhombic, and deliquescent When a water-soluble solid, such as K-,P0₄, acquires sufficient water of hydration it will dissolve in the water and form a solution Anhydrous forms of K~,PO4 are commercially available, for example fiom Aldπch Chemical Cυ , Milwaukee, W isconsin However, upon exposure to moisture such as air moistui e the K-.P0₄ takes on watei of hydration as explained above

One impr oved technique discovered by the present inventors for incorporating K P0 into a binder involves an aqueous system where the tripotassium phosphate is incoi poi ated into an acrylic/latex binder system The general procedure involves heating an excess of K ,PO₄ ιn watei , decanting off the solute, and cooling to give a solution

Then the solution of K-P0₄ is blended with an acrylic resin latex at approximately 100m tempei ature (about 25°C) 111 a ratio, bv weight of about 1 10 to about 5 1 , respectiveK On a diy weight/weight basis the ratio of K-,P0 to acrylic latex solids used in a coating genet ally should be about 2 3 to about 3 2, preferably about 5 4 5 If the mixing l atio of K ,P0₄ to aci \ lie latex becomes too large, the formulation can become difficult to coat and insufficient acrylic resm might be present to fully covei the K P0₄ to pievent it from picking up air moisture when pat t of the coated abrasiv e article On the othei hand if the weight ratio of K-,PO₄ to acrylic latex becomes too small, the amount of K PO₄ becomes inadequate to provide the desn ed grinding benefit The optimal mixing ratio of K-,P0 to acrv lic latex can be detei mined empiπcally in a sti aightfoi ward manner with above guidance An acι\ lιc latex should be chosen which does not salt out

(coagulate) upon addition of the phosphate solution Exemplars' of a usable acrylic latex is an amine functional acrylic polymer having 46% solids with the trade designation "XA5 ] 07", 01 dx. aen lie latex having the trade designation "A5 102", both commeicially available fiom Zeneca Division of ICI America, Wilmington, MA

To accomplish the blending of the K ,P0 and acrylic latex, K-,PO₄ should be added slowlv with light mixing, 01 , alternatively, under vigoi ous mixing conditions, to the acrvlic latex until the weight of K,P0₄ is about 20% of the weight of the acrylic resin latex At this point the remainder o the K,P0₄ can be added rapidly with mixing to the acrylic latex at anv rate, even all at once For the slow addition at light mixing conditions, the K ,P0 addition to the acrylic latex genei lly should be spi ead ov ei about 1 5 minutes with substantially a constant l ate of addition until the weight of K,P0₄ is about 20% of the weight of the acrylic resin latex At this point the remainder of the K PO can be added rapidly with mixing to the latex at any rate, even all at once

For the alternative approach using vigorous mixing conditions, such mixing conditions can be achieved by use of high shear mixing, such as with an air mixer For example, such high shear mixing can involve a two inch stainless steel blade rotating at least at 360 l pm in the mixtui e of contents contained in a container When using vigoi ous mixing conditions, the addition l ate is substantially uniform and at a rate where the weight of K PO4 reaches about 20% o the weight of the acrylic i esm latex mixing ratio in about 10 to 1 seconds At this point, the remaindei ot the k POi can be added tapidlv with mixing to the latex at any rate, even all at once Othei

ants optionally can be added as well to the coating formulation such as fillei (e g CaCO ) colorants (such as i ed iron oxide), and so forth

After complete addition o the inorganic phosphate to the aci ylic latex resin, the mixture can be coated upon a coated abrasive article by coating techniques such as roll coatmg or spra\ coating The 1 ol I coater can be a single roll coater, e g a coating t oll of 60 Shoi e A dui ometei with a metal back-up 1 oil foi ming a nip with a soft opposing roll Drying ot the coating containing the inotganic phosphate and acrylic latex bindei can be accomplished by an di ymg overnight at room temperature or oven drying at 60°C foi about 1 5 to 3 hours Drying of the coating is deemed complete when the coating is not wet to the touch and has "skmned- over", typically where the div weight of the coating becomes about 25% the original wet weight o the coating The dned layei , as incoi oi ated into a coated abrasive, such as a peπphei l coating is used in a dry grinding s stem because water will destroy (dissolve) the coating

Another technique o the invention for successfully incorporating K,PO₄ into a coating binder involv es the addition of the K,P0₄ solid particles to a non- aqueous (anhydi ous) 01 game solvent-based epoxy resin system ln this technique, the epoxy resin first is dissolved in an anhydrous oiganic solvent in a ratio generally of about 1 2 to about I 4, l espectivelv , on a weight basis, pi eferably approximately 1 3 Usable solvent mcludes a xylene-containing aromatic hydrocarbon blend solvent, such as that having the trade designation "AROMATIC 100", commercially available from Worum Chemical Co , Saint Paul, Minnesota The epoxy resin preferably is a diglvcidyl ethei of bisphenol A epoxy resm coatable from an anhydrous organic solvent An epoxy resin of this type includes those having the trade designation "EPON 828", ha ing an epoxy equivalent weight ranged from about 185 to about 1 5, which is commercially available from Shell Chemical Co , Houston, Texas Optionally, a conventional inorganic anhydrous thickener is added to the mixture, such as colloidal oi fumed silica, to maintain a total coating mixture viscosity in the range of about 2 ^00 to 5.000 cps, as measui ed on a Brookfield viscometei having a #2 spindle and t un at 6 i pm at loom tempei ature (about 25°C) The silica thickenei includes colloidal fumed silicas such as that having the trade designation "Cab-O-Sil M-5" (40 to 100 mici ometers in diametei ), commercially a ailable fiom Cabot Corp Tuscola, Illinois Also, an amine curative for the epoxy should be added, which pi eferably is not an acidic curative to avoid reaction with the inorganic phosphate An example of a useful amme curative in this regard is a polyamide cuπng agent, commercially available fi om Henkel Corp , Cincinnati, Ohio, undei the ti ade designation "VERSAMID 125" Other adjuvants optionally can be added as well coloi ants (such as red n on oxide), filler (e g , CaCO-,), and so forth

The alkali metal oi alkaline earth metal orthophosphate, e g , K5PO , is added to the premixtui e of anhydi ous 01 game solvent and the epoxy l esin at vigorous mixing conditions such as mixing conditions achieved by use of high shear mixing, such as with an air mixei The K5PO₄ het e, unlike in the acrylic latex system described herein, is not ti eated to acquire more watei of hydration before addition to the organic solvent and epoxy resin, and prefei ably is in anhydrous form, such as commeicialls available, foi example, from Aldπch Chemical Co , Milwaukee, Wisconsin The K ,P0₄ generally is used in a particle diameter in the range of from about 30 to about 200 mici ometers If the K .PO4 is too large in particle sizing, it can be cr ushed using a high speed blendei foi a few seconds to satisfy this genei al range The high sheai mixing can involv e a two inch stainless steel blade l otatmg at least at 360 rpm in the mixtui e contents as contained in a container ln this embodiment, there is no need to slowly add the inorganic phosphate to the lesin foi a portion of the addition period ln fact, it is preferable to add the inorganic phosphate into the resin and solvent at once to avoid any additional watei pick-up by the -,P0₄ The i atio of K,P0 to epoxy resin generally is about 4 I to about 6 I l espcctiv ely on a weight basis

An example of usable lot initiation of K P0₄ and the epoxy resin/anhydrous organic sol ent svstem includes about 25 to 30% anhydrous oiganic solvent such as xylene and/oi othei ai omatic hydrocai bons, about I to 2% colloidal or fumed silica thickenei , about 8 to 12% epoxy i esin such as a diglycidy l ethei of bisphenol A epoxy resm about 6 to 8% epoxy i esin cui ative such as a polyamide cuπng agent, about 45 to % K ,P0₄ and the balance being optional adjuv ants such as 2 to 3% colorant (e g iron oxide), all percentages being by weight These types of formulations tend to have a pot life of about 3 to 4 hours at l oom temperature The percentage of K, 0₄ genet ally lepresents between about ^0% to 85% of the mixture on a solids basis At lowet amounts of K P0 , additional thickenei may be required to maintain a total coating mixtui e viscosity in the desired range of about 2,500 to 5 000 cps as measui ed on a Bt ookfield v iscometei having a #2 spindle and am at 6 i pm at l oom tempei atui e ( about 25°C)

The K O and epoxy i esin foi mulation, as combined can be coated upon a coated abrasive article by coating techniques such as roll coating or spray coating The t oll coater can be a single roll coatei , e g a coating roll of 60 Shore A durometei with a metal back-up 1 oil, forming a nip with a soft opposing roll

Drying of the coating containing the inorganic phosphate and epoxy resin binder can be accomplished by oven cuπng at I OOT for about 2 5 hout s These drying/curing conditions are also dependent upon the chemistry of the bindei The dned layer, as incorporated into a coated abrasive, such as a peripheral coating is used in a dry grinding system because watei will destroy (dissolve) the coating The abrasive particles to be used in this invention typically have a particle size ranging from about 0 I to I >0ϋ miciometeis, usually between about 01 to 500 micrometeis It is piefeπed that the abiasive particles have a Mohs' hardness of at least about 8, more pieferably above 9 Examples of such abrasive particles include fused aluminum oxide (which mcludes brown aluminum oxide, heat treated aluminum oxide, and white aluminum oxide), ceramic aluminum oxide, green silicon carbide, silicon caibide chromia, alumina zirconia, diamond, iron oxide, ceπa, cubic boron nitride, boron carbide, gainet, and combinations thereof

The term "abrasive particles" or "abrasives grains" also encompasses single abrasive particles bonded together to form an abrasive agglomerate Abrasive agglomeiates are described in U S Pat Nos 4,311,489, 4,652,275, and 4,799,939 In some instances it is piefeired that the agglomerate grains be the same size or about the same size as the abiasive grams

Examples of ceiamic aluminum oxide abiasive gia s include those disclosed in U S Pat Nos 4314827 4 18,397,4,574,003,4,623,364,4,744,802,

4,770,671,4.881,951, 5,011,508, 5,291,591, 5,201,916, and 5,304,331, and EP publication 228,8^6 Examples of fused alumina zirconia abiasive grains mclude those disclosed in U S Pat Nos 3,781,408 and 3,893,826

It is also within the scope of this invention to have a suiface coating on the abrasive grains The surface coating may have many different functions In some instances the surface coatings increase adhesion to the binder or alter the abrading characteristics o the abiasive giam oi particle Examples of suiface coatings include coupling agents, halide salts, metal oxides such as silica refiactory metal nitrides, and letiactory metal carbides It is within the scope of this invention to have (1) coated agglomerate grains along side of abrasive gi s (I e . agglomerate grains are between abrasive grains), (2) agglomeiate grains coated undei eath abrasive grains, (3) agglomerate grains coated over abrasive giains, and (4) combinations thereof

The abrasive giains of this invention also can embrace abrasive particles mixed or agglomerated with each othei or diluent particles The particle size of these diluent particles preferably is on the same order of magnitude as the abrasive grains or particles Examples of such diluent par ticles include gypsum marble, limestone, flint, silica grinding aids glass bubbles, glass beads aluminum silicate,

The manipulativ e steps o the pi ocess foi making the coated abrasive articles of the invention can be essentially the same as those cui i ently practiced in the art Coated abrasiv es genei lly consist of a backing abrasive gi ains, and at least one binder to hold the abi asive giains to the backing The backing typically is saturated with a satin ant coat pi ecursor by any conventional technique such as dip coating, roll coatmg, powdei coating, or hot melt coating Foi purposes of making the coated abrasive article of this invention not only the satin ant coat precursor, but also the backsize coat pi ecui soi the presize coat precui soi , the make coat precui sor, the size coat precui sor, and the supersize pi ecui soi , are each fully cured, or at least either dned or partially cui ed after application to an extent such that the coating is dry to the touch before the next coat is applied Attei the last coat is applied, and if necessary the r emaining partially cui ed coats ai e fully cured

After the satui ant coat is applied the backsize oi presize coat precursors are applied by any conventional technique such as spray coating roll coating, die coating, powdei coating hot melt coating or knife coating The coated abrasive then comprises providing on the satin ated and sized backing a first bond system, commonly r eferred to as the make coat on the front side ot the backing The make coat is applied in a liquid or flowable form to the fi ont side of the backing Then, abrasive particles are at least partially embedded into the make resin by conventional projection techniques such as by a electrostatic coating process, before the make coat is partially dned oi cured The make coat is then partially dried or cured and a second bond system is applied over the make coated abrasive particles commonly refened to as a size coating The size coat is applied in a liquid or flowable form over the abrasive gi ains and make coat The size coat, and if still necessaiy, the make coat are then fully cured Notably if a thermoplastic resin is used alone foi any bond s stem the thei moplastic i esin can be dried in order to solidify Thus foi the pm pose of this application, the tei cin e' l efers to the polymenzation, gelling oi drying pi ocedure necessary to convert a binder precursor

ι ? into a binder Therefoi e, ' at least partially cuπng" refers to at least partially polymerizing gelling oi drying a bindei precursoi

The make and size coats can be applied by any numbei of techniques such as roll coating, spray coating curtain coating, and the like In some instances, a third 5 coating or a supei size coat is applied over the size coat by conventional techniques The make, size, and supei size coats can be cured either by drying or the exposure to an eneigy soui ce such as thei mal energy, oi l adiation eneigy including electron beam ultraviolet light and visible light The choice ofthe energy source will depend upon the particulai chemistry of the l esmous adhesiv e General methods for io making the coated abi asive articles of this invention aie descnbed in U S Patents 4,734, 104 and 4,737, 163

The abiasive pi oducts of the pi esent invention are not limited as to the types of workpiece that can be abi aded thei ewith By "abrading" the term as used herein generally can mean any of grinding, polishing, finishing, and the like The i s workpiece surfaces made of wood, metal, metal alloy, plastic cei amic, stone, and the like, can be abi aded bv the coated abrasive pioducts of the present invention The abrasive products of this invention are particularly well-suited for difficult to abrade metal grinding opei ations especially titanium gnnding

Also the coated abi asiv e pi oducts of the present invention can be readily

20 converted into vanous geometπc shapes to suit the contemplated application, such as disci ete sheets, disc toi ms endless belt forms conical forms, and so forth, depending on the particulai abrading operation envisioned

While a coated abrasive ar ticle embodiment of the mv ention has been described in detail hei em foi illustr ative purposes, the invention also encompasses 5 other types of abi asive articles such as a bonded abrasive article, and abrasive articles using abrasive agglomer ates and nonwoven abrasive articles, each of which contam an inorganic alkali oi alkaline earth metal orthophosphate in a surface region thereof The bonded abrasive ar ticles comprise a shaped mass of the abrasive particles and an alkali metal or alkaline earth metal orthophosphate adhered 0 together with a bindei which can be an oiganic, metallic or vitrified binder By way of example, the shaped mass can be in the forms o a grinding wheel or a conical shape. ln another aspect of the invention, abrasive particles are used in an abrasive article, such as a coated abrasive, in the form of erodible abrasive agglomerates where composite abrasive panicles are formed of alkali metal or alkaline earth metal orthophosphate and abrasive grains adhered together with a binder. Known methods, such as described in U.S. Patent Nos. 4,3 1 1 ,489, 4,652,275, 4,799,939, can be used to make the bonded abrasives and erodible agglomerates of this invention with the modification of adding the inorganic metal orthophosphate. Thermosetting binders, such as those described supra, are prefen ed for adhering the inorganic metal orthophosphate grinding aid particles together in the agglomerates. The alkali metal or alkaline earth metal orthophosphate, and/or as included in erodible agglomerates, also can be incorporated into lofty, open nonwoven abrasive articles, such as those prepared according to the teachings of U.S. Pat. Nos. 2,958,593, 4,991 ,362, and 5,025,596. In general, nonwoven abrasives include open, lofty, three-dimensional webs of organic fibers bonded together at points where they contact by an abi asive binder These webs may be roll coated, spray coated, or coated by other means with binder precursor compositions including the alkali or alkaline earth metal orthophosphate, and/or agglomerates including same, and subsequently subjected to conditions sufficient to cure the resin. In the following examples, objects and advantages of this invention are further illustrated by various embodiments thereof but the details of those examples should not be construed to unduly limit this inventio All parts and percentages therein are by weight unless otherwise indicated.

Test Procedure I

The coated abrasive material made by the examples herein were converted into 203 cm by 7.6 cm continuous belts and were installed on a Thompson Type C 12 grinding machine The effective cutting area of the abrasive belt was 2.54 cm by 203 cm The workpiece abraded by these belts was titanium, 2.54 cm width by 17.78 cm length by 10.2 cm height Abrading was conducted along the 2 54 cm by 1778 face The woikpiece was preweighed and then mounted on a reciprocating table The speed of the abiasi e belt was 610 suiface metei pei minute The table speed, at which the woi piece tiaveised, was 6 I meteis pei minute The downfeed mcrement ofthe abiasive belt wasO 0025 to 00127 cm/pass of the workpiece The process used was conventional suiface gnnding wheiein the woikpiece was reciprocated beneath the rotating abiasive belt with incremental downfeeding between each pass This grinding was earned out dry However as the workpiece exited the grinding lnteiface on each pass, it was flooded with watei to cool it followed by a blast of cool an to dry the workpiece before re-entiy into the grinding interface Each belt was used until it shelled Then the woi piece was reweighed, and the diffeience between the initial weight and the final weight repiesenting the total cut ot the belt Shelling is the prematuie release of the abiasive particles, shelling generally marks the end ot the useful life of the belt and can be detected on that basis Specific energy E was etei mined foi some of the examples Specific energy E is the amount of eneigy lequiied to iemove a unit volume of material (I e , I/mm ) A bettei pei forming coated abrasive will have lower specific energies of grinding E_v is calculated by multiplying the cutting foice (tangential grinding force) by the belt speed and then dividing by the material iemoval rate

Materials

The materials indicated in the examples herein have following meanings

Epoxy resins BPAW a composition containing a diglycidyl ether of bisphenol A epoxy resin coatable from water containing approximately 60% solids and 40% water This composition having the trade designation "CMD 35201" was commercially obtained from Shell Chemical C o , Louisville Kentucky This composition also contained a nonionic emulsifiei The epoxy equivalent weight ranged from about 600 to about 700

2 BPAS a composition containing a diglycidyl ether of bisphenol A epoxy resin coatable from an organic solvent This composition, having the trade designation "EPON 828", was commercially obtained from Shell Chemical Co., Houston, TX

Acrylic binder

ACR amine functional acrylic polymer having 46% solids in water, having the trade designation "XA5 107", w as commercially obtained from Zeneca Division of ICI America, Wilmington, MA

Phenolic resin

RPI a resole phenolic resin with 75% solids (non-volatile)

Curing agents

EMI 2-ethvl-4-meth l imidazole This curing agent, having the trade designation "EMI-24", was commercially obtained from Air Products, Allentown, PA

PA a polyamide curing agent, having the trade designation "Versamid 125", was commercially obtained from Henkel Corporation, Cincinnati, OH

Grinding Aids

KBF 98% pure micropulverized potassium tetrafluoroborate. in which a 95% fraction by weight passes through a 325 mesh screen and a 100% fraction by weight passes through a 200 mesh screen

PVC. polyvinyl chloride which had the trade designation "GEON 103EPF-76", was commercially obtained from the Specialty Polymers &. Chemicals Div of B.F Goodrich of Cleveland, OH

K-,P0₄ anhydrous tripotassium (ortho)phosphate. was commercially obtained from Aldrich Chemical Co . Milwaukee, WI Na-,Pθ tiisodium (oιtho)phosphate tnbasic dodecahvdiate was commeicially obtained fiom EM Science Gibbstovvn Nl

Ba-,(Pθ₄)j tπbaπum dι(ortho)phosphate, was commercially obtained from Alpha Inorganics Inc Beverly MA

Additives

IO iron oxide

Thixotropic Thickener

CAB M5 colloidal silica having the tiade designation "C ab-0-Sιl iV ", was commeicially obtained fiom Cabot Coip Tuscola, IL

Dispersing agent AOT a dispeising agent, i e sodium dioctyl sulfosuccinate, having the trade designation "Aeiosol OT" was commeicially obtained from Rohm & Haas Company, Philadelphia PA

Solvent WC100 an aromatic hydiocaibon solvent, having the trade designation

"AROMATIC 100' was commeicially obtamed fiom W'oium Chemical Co , St Paul, MN

HP a mixture of 85% 2-methoxy piopanol and I 5% H₂0 commercially obtained from Wouim Chemical Co St Paul, MN

General Procedure for Making Coated Abrasives (Belts)

For the following examples, coated abiasive belts vveie made as follows The backing of each coated abiasive was a Y weight woven polyester cloth which had a four over one weave Each backing was saturated with a latex/phenolic resin and then placed in an oven to initially cure this resin Next a calcium caibonate- filled latex/phenolic resin pretreatment coating was applied to the back side of each backing Each coated backing was heated to approximately 120°C and maintained at this temperature until the resin had cured to a tack-free state Finally, a pretreatment coating of latex/phenolic resin was applied to the front side of each coated backing and each coated backing was heated to approximately 120°C and maintained at this temperature until the resin had precured to a tack-free state. Each backing made by this procedure was completely pretreated and was ready to receive a make coat

A coatable mixture f r producing a make coat for each coated backing was prepared by mixing 69 parts of 70% solids phenolic resin (48 parts phenolic resin), 52 parts non-agglomerated calcium carbonate filler (dry weight basis), and an adequate amount of a solution comprised of 90 parts water/ 10 pails ethylene glycol monoethyl ether to form a make coat in each case which was 84% solids This coatable mixture was applied to the backing with a wet coating weight of 194 g/m . The make coat w s applied in each case via a knife coating technique.

Next, grade 60 (ANSI standard B74. 1 8 average particles size of 286 micrometers) silicon carbide abrasive particles w ere electrostatically coated onto the uncured make coat with a weight of 527 g/m² Then the resulting constructions received a precure of 3 hours at 100° A 82% solids coatable mixture suitable for forming a size coat was then applied over the abrasive particles/make coat construction via two-roll coater. A 82% solids coatable mixture suitable for forming a size coat consisting of 32% RPI, 50.2% CRY, 1 5% IO. and 16 3% HP, was then applied over the abrasive particles/make coat construction via a two-roll coater The wet size coating weight in each case was about 350 g/ιτf The resulting coated abrasives received a thermal cure of 30 minutes at 88°C follow ed by 12 hours at 100°C

Where indicated in the following examples, a supersize coat was then applied Where applied, the supersize coat was applied by roll coating followed by curing at 100°C for 90 minutes. Specific details of the supersize compositions are provided below in the procedure for each abrasive example Aftei ther mal cin e, the coated abrasives wer e single flexed (i e , passed over a roller at an angle of 90°C to allow a controlled ci ackmg of the make coat, the size coat, and any super size coat), then converted into 7 6 cm by 203 cm coated abrasive belts

EXAMPLE I and COMPARATIVE EXAMPLE A

The coated abi sives for Example 1 and Comparative Example A were made accoiding to the General Pi ocedui e for Making Coated Abi asives These examples compared the abr ading characteristics of coated abrasive articles of this invention including an alkali metal phosphate salt, viz , tripotassium phosphate, in the supersize vei sus a compar ative example using a conventional grinding aid, viz , potassium teti afluoroboi ate, in the supei size Comparative Example A was supersize at a coating l ate of 193 g/nr with the composition as follows 29 2% BPAW, 035% EMI. 53 3 KBF₄. 14 1 % water, 0 75% AOT, and 2 3% IO

Example I was supei ized with the following composition using a weight of 193 g/m² 29 2% BPAW 0 35% EMI, 53 3% K ,P0₄»7H₂0, 14 1 % water, 0 75% AOT, and 2 3% 10

The Test Procedui e I was utilized to test these examples and the performance t esults ai e tabulated in Table 1

Table

This example serv es to illusti ate that not all grades of coated abrasives and/or grinding conditions will be improved on gnnding titanium with the additions of K-.PO4 in a watei -based epoxv supei size EXAMPLE 2 and COMPARATIVE EXAMPLES B-D

The coated abiasi es foi Example 2 and Compaiative Examples B-D were made accoiding to the General Pi ceduie for Making Coated Abrasives except the make coat was applied at a coatmg weight of 130 g/m² (wet) giade 80 silicon carbide was applied to the make coat at 340 g/nr, and the size coat was applied at 250 g/m² (wet) A wax foimulation, either alone or with a gnnding aid indicated herein, in cooled solidified form was applied peripherally to the abrasive belt during grinding The Compaiative Example B was a contiol having no wax formulation peripheral coating applied Compaiative Example C was peripherally coated with a stick compnsed of CALWAX 2 2-B wax alone Comparative Example D was made by peπphei lly coating the abr sive belt with a wax stick foimed by mixing equal parts bv weight of KBF₄ gnnding aid and polyv yl chlonde (PVC) with CALWAX 2^2-B Example 2 was made by peripherally coating the abrasive belt with a wax stick formed by mixing K,POj with CALWAX 2^2-B The abrasive belts weie tested accoiding to Test Procedure I

The results aie summarized in Table II

Table II

SAMPLE PERIPHERAL TOTAL CUT (g) SPECIFIC COATING ENERGY (E_s) (Joules/mm²)

Comp Ex B None 42 715

Comp Ex C Wax alone 291 934

Comp Ex D W KBF4/PVC 677 371

Example 2 WWK.PO4 744 355

The coated abiasive belt of Example 2 demonstrated the highest total cut values, and lowest specific energy values, 1 e the lowest energy required for grinding EXAMPLES 3-4 and COMPAR ATIVE EXAMPLE E

The coated abi asiv es for Examples 3-4 and Compai ative Example E were made according to the Genei al Pr ocedur e for Making Coated Abi asives except the make coat was applied at a coating weight of 233 g/m" (wet), gi ade 40 silicon carbide was applied to the make coat at 909 g/m², the size coat was applied at 465 g/m" (wet), and the supei size coats had the following details An aqueous supersize was applied at a wet coating weight of 348 g/m² to the coated abrasive belt of Comparative Example E having a composition identical to the supersize for Comparative Example A The supersize for Example 3 was the same as that of Comparative Example E except the gnnding aid additive was K~,P0₄ Example 4 had a supei size of the following composition 1 1 2% BPAS, 7 5% PA, 50 4% K,P0 , 28 0% WC 100, 2 9% IO Test Procedure I was used to test the performance of these examples and the results are summanzed in Table III

The coated abi asiv e belts of Examples 3-4 demonstr ated higher total cut values, and significantly lovvei specific energy values, I e lower energy was required for grinding, as compar ed to Compaiative Example E using conventional KBF₄ supersize gnnding aid

EXAMPLES 5-8 and COMPARATIVE EXAMPLE F

The coated abiasives foi Examples 5-8 and Comparativ e Example F were made according to the Genei al Pi ocedui e for Making Coaled Abrasives except the make coat was applied at a coating weight of 200 g/m^" (wet), grade 100 silicon carbide was applied to the make coat at 402 g/m², the size coat was applied at 230 g/m² (wet), and a supei size coat w as applied at 21 5 g/nr The supersize for Comparative Example F had the same composition as the supersize composition to that of Comparative Example A The supersize for Example 5 w as the same as that of Example 4 For Example 6, the supersize composition was 50% ACR 50% K^P0₄ The supersize composition of Example 7 was 50% ACR/50% Ba^(P0₄)₂, and the supersize composition of Example 8 was 50% ACR/50% Na-,P0₄»H₂O Test Procedure 1 was used to test the performance of these examples and the results are summarized in Table IV

EXAMPLES 9- 13 and COMPARATIVE EXAMPLES G-H

The coated abrasives for Examples 9- 13 and Comparative Examples G and H were made according to the Genei al Procedure for Making Coated Abrasives except the make coat was applied at a coating weight of 1 1 7 g/m" (wet, grade 100 silicon carbide was applied to the make coat at 242 g/m², the size coat was applied at 150 g/m² (wet), and a supersize coat was applied at 130 g/m²

The supersize coats of Examples 9- 12 and Comparative Example G used the following composition I I 2% BPAS, 7 5% PA, 50 4% of the grinding aid(s) in the weight % ratio indicated in Table V, 28 0% WC 100, 2 9% 10 Comparative Example H was the same as Comparative Example G except it omitted the grinding aid component Test Procedure 1 was used to test the performance of these examples and the results are summaπzed in Table V Table V

SAMPLE GRINDING AI D TOTAL SPECIFIC ENERGY (E_s) BF4 K O₄ CUT (g) (Joules/mm¹)

Comp Ex G 100/0 298 109

Ex 9 75/25 386 88

Ex. 10 50/50 284 75

Ex 1 1 25/75 276 1 1 1

Ex 12 0/ 100 384 56

Comp Ex. H None 19 1 34

EXAMPLES 13- 14 and COMPARATIVE EXAMPLE 1

The coated abrasives for Examples 13- 14 and Comparative Example I were made accoi ding to the General Procedure for Making Coated Abrasives except the make coat was applied at a coating weight of 142 g/m^" (wet), grade 100 silicon carbide was applied to the make coat at 602 g/m^"; the size coat was applied at 130 g/m² ( wet); and a supersize composition for Comparative Example G. The supersize composition of Example 1 was the same as that of Example 9. The supersize composition of Example 14 was the same as that of Example 12. Test Procedure I was used to test the performance of these examples and the results are summarized in Table VI

Table VI

SAM PLE GRIN DI NG AI D TOTAL SPECIFIC ENERGY (E_s) KBF4/K,PO₄ CUT (g) (Joules/mm³)

Comp. Ex 1 100/0 162 123

Ex 1 3 75/25 188 90

Ex. 14 0/ 1 0 270 66

Various modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing description without departing from the scope of spirit of this invention

Claims

What is claimed is

1 An abiasive article compnsing

(a) a pluia ty of abiasive particles

(b) at least one binder to which said pluiahty of abiasive particles are adhered, and

(c) a peripheral suiface, said peπpheial surface containing an inorganic metal phosphate salt devoid of hydrogen selected tiom the group consisting of an alkali metal orthophosphate salt and an alkaline earth metal orthophosphate salt

2 A coated abiasive article comprising a substrate having a plurality of abrasive particles adheiently bonded theieto by a binding matenal, and a peripheral coating laver compnsing an moiganic metal phosphate salt devoid of hydrogen selected tiom the gioup consisting ol ΛX. alkali metal orthophosphate salt and an alkaline earth metal orthophosphate salt

3 The coated abrasive article of claim 2, wherein said peripheral coating layer is selected fiom the gioup consisting ofa size coat and a supersize coat

4 The coated abrasive article of claim 2 wheiem said penpheral coating layei further comprises a bindei

5 The coated abiasive article of claim 4, wheiein said binder is selected from the group consisting of epoxy lesms and acrylic resins

6 The coated abi sive article ot claim 2 wherein said inorganic metal phosphate salt is selected tiom the group consisting of tnpotassium orthophosphate, trisodium orthophosphate and tπbaπum dι(ortho)phosphate

7 An erodible grinding aid agglomerate comprising a plurality of particles of an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of alkali metal orthophosphate salt and alkaline earth metal orthophosphate salt, and a binder that adheres said inorganic metal phosphate salt particles together

8. A method for making a coated abrasive article, comprising the steps of:

(a) applying a first binder resin precursor to a substrate; (b) at least partially embedding a plurality of abrasive particles in said first binder resin precursor,

(c) at least partially curing said first binder resin precursor;

(d) applying a second binder resin precursor over said at least partially cured first binder resin precursor and said plurality of abrasive particles; (e) at least partially curing said second binder precursor resin precursor,

(f) applying a third binder resin precursor and an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of an alkali metal orthophosphate and an alkaline earth metal orthophosphate, and (g) completely curing said first, second and third binder precursor resin precursors

9. A method of using a coated abrasive article to grind titanium, comprising: (a) providing a coated abrasive article comprising a plurality of abrasive particles, a binder to which said abrasive particles are adhered, and a peripheral coating layer containing an inorganic metal phosphate salt devoid of hydrogen selected from the group consisting of alkali metal orthophosphate salt and alkaline earth metal orthophosphate salt, and a workpiece comprising titanium; (b) frictionally engaging said peripheral coating layer with a surface of said workpiece; and

3 M (c) mov mg at least one of said coated abi asive article and said wor kpiece i elative to each effective to 1 educe the surface of said woi kpiece

10 A bonded abi asiv e article comprising a shaped mass having a peripheral suiface, w hei ein said shaped mass comprises a plui ahty of abrasive particles and an inoi ganic phosphate salt adher ed together by a thermosetting binder, said inoiganic phosphate salt being devoid of hydrogen and selected from the group consisting of an alkali metal orthophosphate salt 01 an alkaline earth metal orthophosphate salt