ABRASIVE ARTICLE CONTAINING AN INORGANIC PHOSPHATE

BACKGROUND OF THE INVENTION

10 Field of the Invention

This invention relates to abrasive products comprising abrasive particles, binder, and an inorganic phosphate grinding aid, and to methods of making and using same The grinding aid may be an alkali metal metaphosphate, an alkaline earth metal metaphosphate, or a Group IIIA metal orthophosphate These abrasive

Is products include bonded abiasives, coated abiasives, and nonwoven abrasives

Description of the Related Art In the competitive and economically significant field of abrasive products, a continuing desire exists to i educe manufacturing costs and mciease performance of

20 such pioducts in efforts to seek and acquire competitive edge

Abiasive pioducts aie generally known having abrasne panicles adherently bonded to a sheet-like backing Foi example, it is known to coat in slurry form, a dispersion of abiasive particles in a liquid oi semi-liquid binder upon the surface of a sheet-form substrate, and then cuiing the binder to anchor the coating as a single

2s layer to the substrate Alteinativelv, anothei known approach is to generally stratify the giains and bindei into separate layers that are serially formed upon the sheet-foim substrate, such as in coated abrasive articles, in such a as to basicallv segregate the abiasive grains as a paniculate monolayer sandwiched between underlying and ovei laying bindei layers More specifically, coated products typrcalK a backing substrate, abrasive grams, and a bonding system which operates to hold the abrasive grains to the backing In a typical coated abiasive pioduct, the backing is first coated with a layer of adhesive, commonly lefeπed to as a "make coat", and then the abiasive giains are applied to the adhesive coating The application of the

T abrasive giains to the make coat invokes electrostatic deposition oi a mechanical

-I-

process which maximizes the probability that the individual abrasive particles are positioned with their 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 abrasive grains to the backin After curing or setting the make coat, a second layer of adhesive, commonly referred to as a "size coat", is applied over the surface of the 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 In 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 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 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 paniculate filler as an adjuvant Typically, the binder will comprise between 40 to 70 percent by weight paniculate filler The addition of the filler either increases the toughness and hardness of the 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 paniculate 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 paniculate 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 ) deciease the lnction between the abiasive giains and the workpiece being abiaded, and/or (2) prevent the abiasive grams fioin "capping", l e prevent metal particles fiom becoming welded to the tops of the abiasive grains, and/or (1) decrease the inteiface temperature between the abiasive grains and the workpiece, and/or (4) decrease the lequired grinding force

Grinding aids can be especially effective in abrading stainless steel, exotic metal alloys slow to oxidize and so ioith In some instances, a coated abrasive product containing a gi indmg aid in the bindei can abiade up to 100% more stainless steel than a coi responding coated abiasive product in which the binder is devoid of a giinding aid The leason, in theory, being that the activity of grinding metal by abrasive articles produces freshly formed hot, and uncontaminated metal surfaces If the newly fonned uncontaminated metal surface is not rapidly "contaminated", metal will tiansfei and adhere to the abιasι\e particle stιrface(s) causing "capping" which decreases gniidmg peiformance One puipose and function of grinding aids is to prevent capping b\ rapidly contaminating the freshly formed metal surface Gimdrng aids aie normally incorporated into the bond resιn(s) of the abiasive article Grinding aids (active fillers) can be classified as physically active oi chemically active Cryolite, sodium chlonde, and potassium tetrafluoioborate are known physicallv active grinding aids that melt between 500 and l,000°C which can form thin films on heshl\ formed metal Chemically active grinding aids include non p\ιιte, polyvmyl chlonde, and pol\vιnyhdene chlonde which decompose when heated foimmg chemicals that lapidly leact with the freshly formed metal surface

Also, combinations of gi Hiding aids in abi sive articles (grinding wheels) may produce more than a cumulative giinding 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, 2,811,410, 2919777, 3,246970, and \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 2,949,15 I and 2,952,529

Another type of gi inding aid enhancement is described in U S Patent No 5,441 ,549 (Helmin) w hei em the gr inding aid effect of potassium tetrafluoroborate is enhanced by the addition of specific thei moplastics Othei descnptions of grinding aids include U S Pat No 2,2 16, 135 (Rainiei ), which teaches a gi inding wheel having as a grinding aid an anhydi ous, water-soluble non-oxidizing rnoiganic alkali or alkaline earth metal salts whose melting points aie within the t ange of 700 to 1200°C These materials include sodium chlonde, potassium chloride, anhydrous sodium carbonate, sodium sulfate, potassium sulfate, lithium sulfate, sodium pyrophosphate, potassium pyi ophosphate, calcium chlonde, calcium bromide magnesium sulfate, barium chlonde, bai ium bi omide magnesium chlonde magnesium br omide or strontium chlonde

U Pat No 2,243,049 (Kistlei ), which teaches an abr asive body (grinding wheels) containing finely div ided sti ongly acidic or potentially acidic inorganic compounds Acid sulfates, phosphates or pyi ophosphates ai e satisfactory, as are the ammonium, sodium, potassium, calcium, oi barium salts theieof Phosphorus pentoxide is also possible The gi inding aid constitutes about 7% of the bond When used on metal woi k s i faces, the gi inding aid reduces loading and increases the gi ain efficiency 40 to 100% U S Pat No 2 690,385 (Richlin), which teaches a metal cleaning cloth or felt impregnated with abi asiv e, sodium bisulfate and a humectant Substitutes for the sodium bisulfate include ammonium chlonde, ammonium phosphate, aluminum chlonde, antimonious chloride, potassium bisulfate, oxalic acid, phosphoric acid and tartaπc acid U S Pat No 3,030 198 (Kibbe), which discloses a gi inding 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 pi eferable to also include potassium aluminum fluoride in the grinding wheel

U S Pat No 3 770 40 1 (Sheets et al ), which descnbes an abrasive body (grinding wheel) compnsed of gnt-sized particles of alumina or silicon carbide held together by a watei -insoluble aluminum phosphate bonding matr ix

U S Pat No 5.096,983 (Geiber ), which teaches the use of up to 5 0% of a 5 water soluble salt such as sodium phosphate to r etard the l oom temperature and eventual hardening of phenolic resole l esins which are mixed with magnesium oxide with or without an ester functional hai dening agent

U Pat No 5, 1 16,392 (Selgi ad et al ), which teaches a grinding aid having the foi mula uM i ^• M ₂ ^• wHal ^• xChal ^• zPh, where M | is a pure metal or io mixtui e of alkali metal alkaline earth metal and/oi Al, M ₂ is a pure metal or mixture of Zn, Mn Fe except f i Fe as chlonde Hal is a puie halogen or mixture of F, CI, Br, I, Chal is chalcogenides, O and/oi S Ph is phosphate or moi e highly condensed phosphates of the formula P,O whei e r = I to 10, prefei ably 1 to 2 s = 4 to 20, preferably 4 to 7, and u \ , w, x oi z = 0 to 95%

15 U S Pat No 4 770 671 (Moni oe et al ) descnbes adding var ious types of grinding aids onto the sui face of alpha-alumina-based ceramic abrasive grits in coated abrasives In one example. Monroe et al describe K ₂ H O ₄ as a grinding aid

Also, commonly assigned U S Pat Appln Senal No 08/214,394, filed March 16 1994, descnbes abrasive articles having a peπphei al (outennost) coating

20 comprised of grinding aid par ticles and a bindei where the grinding aid particles are mdividuallv coated with an inert h\ dι ophobιc, hv di ocarbon-containing substance, such as a fatty acid 01 fatty acid salt The individuallv-coated gi inding aid particles also may be incorpor ated into erodible gi inding aid agglomei ates, with a binder to adhere the grinding aid particles togethei , and these agglomerates can be

25 incorporated into the make, size and/01 supersize coats of a coated abrasive Although a numbei of examples of gi inding aid particles ai e disclosed in U S Appln Senal No 08/2 14,394, alkali metal 01 alkaline earth metal phosphates are not named

Commonly assigned U S Pat Appln Serial No 0S 4\874 (Ho et al ),

^" Ui filed on even date with the pi esent application, descnbes coated abrasive articles having an abrasive grain la\ eι formed on a make coat, which, in turn, is coated with

a size coat oi a size coat and a supei size coat, w hei e the abi sive gi ain layer is comprised of abrasiv e gi ins and composite gi ains which contain inoi anic nonabrasive particles bonded togethei by a metal salt of a fatty acid or colloidal silica, or combinations thei eof Commonly assigned U S Pat Appln Senal No 08/386,887 (Gagliardi et al ) relates to abrasive articles, and in particular to abrasive articles comprising a combination of grinding aids In particular, the Gagliardi et al application relates to abrasive articles compnsing a combination of potassium teti afluoroborate and a halogenated polymer in a bindei , as well as abrasive articles comprising a combination of potassium tetr tlui oboi te in halogenated binder

Titanium alloys, in particular such as designed foi aei ospace applications, are extremely difficult to gnnd, even with conventional grinding aids Although the high sti ength of these alloys is a maι,oι cause of pooi gi mdabilitv , chemical adhesion of the titanium to the abi asive gi ain is also thought a factor conti ibutmg to poor abrasive perfor mance These difficulties have been alleviated somewhat by use of certain gi inding fluids, such as coolants oi lubncants, used to flood the grinding interface between the abi asive article and woi kpiece Matenals used as grinding fluids for titanium include soluble cutting oils such as highly chlorinated cutting oils and buftei ed inoiganic tπpotassium phosphate solutions, the iattei of which being described by I S Hong et al , "Coated abi asive machining of titanium alloys with inorganic phosphate solutions", Ti ans ASLE 14 ( 1971 ) pages 8- 1 1 Additionally, a compaiativ e study of gr inding aid lubncants in olving the use of among four inoiganic salts NaN0 ₂ KN0 ₂ , Na PUj, and K-.POj, is descπbed by Caldwell et al , "Grinding a titanium alloy with coated abiasives " ASME Paper 58-SA-44, June 1958 Although widely used in buffered solutions, the tπpotassium phosphate salts have proven difficult to incorpoi te into l esin-bonded svstems due to then hygioscopic natur e

A v ariety of "phosphates" exist as salts of acids of phosphorus The conventional nomenclatui e and associated chemical formulae of sevei al common anions for these salts include the following orthophosphate = PO

monohydrogen orthophosphate = HPCλf ^" dihydrogen orthophosphate = H ₂ PO ₄ ^" metaphosphate = PO , ^" pyrophosphate = P2O7 ^4" This terminology is applicable for purposes of this application

SUMMARY OF THE INVENTION

The present invention provides abrasive articles having improved abrading efficacy and performance by containing an inorganic phosphate. The term "inorganic phosphate," as used herein, refers to an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and/or a Group IIIA metal orthophosphate. 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) an inorganic phosphate selected from the group consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Group Til A metal orthophosphate.

In one aspect of the invention, the presence of an alkali metal metaphosphate or an alkaline earth metal metaphosphate in an abrasive article has been discovered to increase abrading efficacy and performance of the abrasive article. For purposes of this invention, alkali metals are comprised of the Periodic Table Group IA (i.e., Na, K, Li, Rb, Cs, and Fr). Alkaline earth metals are comprised of the Periodic Table Group 11 A (i.e.. Be, Mg, Ca, Sr, Ba and Ra), all exhibiting the oxidation state, +2 Ther efore, inorganic metaphosphate compounds within the scope of this invention can be generally represented by the formula M (PO?) _N , where the metal atom M is selected from among the Periodic Table Group I A, or Group II A, and x and y will have values that provide an electrically neutral compound between the particular M ^' ion(s) and the metaphosphate ion(s) (i.e. PO;, ^" ). M is the same type of metal atom for any given inorganic phosphate compound of the subject formula In yet another aspect of the invention, the presence of a Group IIIA metal orthophosphate in an abrasive article has been discovered to increase abrading

efficacy and performance of a coated abrasive article, especially in titanium grinding, when added to a peripheral coating of a coated abrasive, as compared to conventional fillers such as calcium carbonate. For purposes of this invention, a Group IIIA metal means a metal selected from the Periodic Table Group IIIA (i.e., Al, B, Ga, In, and Tl) By "orthophosphate", it is meant the anion having the formula P0 ^'

In another 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 particles of an inorganic phosphate To illustrate, the pi esent invention relates to a coated abrasive article comprising a substrate having a plurality of abrasive particles adherently bonded thereto by a binder, and a peripheral coating layer comprising a plurality of particles which comprise an inorganic phosphate, wherein said inorganic phosphate is selected from the group consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Group IIIA metal orthophosphate; and a coated abrasive article comprising a cured abrasive slurry coating comprising a plurality of abrasive grains; a plurality of particles comprising an inorganic phosphate selected from the group consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Group II IA metal orthophosphate; and a binder. More particularly, in this aspect, the inorganic phosphate can be advantageously used in a peripheral coating layer of a coated abi asive article or slurry-coated abrasive article. For purposes of this application, a "peripheral coating layer" means the outermost coating, i e the coating having an exposed and uncoated major surface, as disposed on the working side of a coated or slurry- coated abrasive article construction The "working side" of the coated abrasive article being a side of the construction where the abrasive grains are adherently bonded to the backin The per ipheral coating generally is a size coat (without an overlaying supersize coat), a supersize coat, or an abrasive slurry coating, 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 not.

In the instance of the peripheral coating also constituting an abrasive slurry coating, the abrasive particles are co-dispersed with the inorganic phosphate particles in a liquid or semi-liquid binder precursor and the resulting dispersion cast or coated upon the substrate, and then the binder precursor is cured, and the resulting coiningled abrasive particle and grinding aid-containing hardened coating is left exposed and uncoated on its outer major surface. The abrasive slurry in this regard can be formed into a single thickness layer, or alternatively, the abrasive slurry can be shaped before completing hardening of the binder medium to impart a surface topography therein including three-dimensional geometric shapes to provide a stnictured abrasive

The peripheral coating includes a binder, preferably a thermoset binder or resin, which serves as the continuous phase or medium by which the grinding aid particles, and any other dispersed additives and/or abrasive particles, are attached within and bound into the laye 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 The term "thermoplastic resin" means a polymer material that is solid, that is possesses significant elasticity at room temperature and turns into a viscous liquid-like material at some higher temperature, the change being reversible Also, the term "dispersed", or variants of this term, as used herein, does not necessarily denote a uniform distribution of the inorganic phosphate- containing grinding aid throughout the resinous binder of the peripheral coating, although uniform dispersions of such are contemplated in this invention.

A peripheral coating containing the inorganic phosphate grinding aid erodes during the abrading process so that fresh grinding aid is introduced to and replenished at the abrading interface. The peripheral coating may contain other non-abrasive additives to manage the erodability of the grinding aids in the peripheral coating The peripheral coating preferred for this invention contains an epoxy binder and water insoluble sodium metaphosphate as grinding aid. It is to be understood that the abrasive article of the invention includes not only coated abrasive articles and abrasive slurry-coated abrasives, but also bonded

abrasives, and nonwoven abrasives Bonded abiasives compnse a shaped mass of abrasive particles adheied togethei with a bindei which can be oiganic, metallic or vitrified which, in the piesent invention, would also include a dispersion in the binder of the inoiganic phosphate gi inding aid Thus, a bonded abrasive article of the present invention can compnse a shaped mass, wherein said shaped mass compnses a plurality of abrasi e particles and an inoiganic phosphate selected from the group consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Gioup III . metal orthophosphate, adhered together with a bindei The bonded abi sive can be molded and shaped into a wide variety of useful giinding shapes beloie completely cuiing the bindei, such as including a giinding wheel shape oi a conical shape A nonwoven abiasive of the invention involves dispeision of the inorganic metaphosphate grinding aid in a binder along with abrasive gi ms adheied to the fibei of a lofty, open nonwoven web The inorganic phosphate giinding aid can be added to a binder of an abrasive article as indi idual particles oi in agglomei te foim where, in the latter form, individual particles of the fillet aie bound togethei with an agglomerate binder, such as a theimosettmg resinous bindei The agglomei ates if used, should be erodible By "eiodible' , it is meant that the agglomerate has the ability to break down in a controlled mannei toi example by fiactuie due to mechanical stress and/or by dissolving fully oi in part undei wet giinding conditions "Wet" means grinding conditions wheie a vvatei spray oi flood is used One prefeired binder for such agglomei ates is a metal salt of tatty acid, such as zinc stearate Theiefore, the present invention relates to an eiodible giinding aid agglomeiate comprising (a) a plurality of particles compiising an inoiganic phosphate, said inoiganic phosphate being selected from the group consisting of an inoiganic phosphate selected from the group consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate and a Gioup IIIA metal orthophosphate, and (b) a binder adhering said inorganic phosphate particles together

The inoiganic phosphate is contained in an amount effective to increase the amount of woikpiece suiface removed by grinding a woikpiece such as a titanium workpiece with an abiasive article of the invention as compaied to the use of the

same abrasive article construction except as devoid of the inorganic metal phosphate constituent

Other advantages, in addition to the grinding enhancement, attributable to the use of an inorganic phosphate additive in an abrasive article include ( 1 ) its excellent rheology in both aqueous phenolic and aqueous epoxy systems, allowing its incorporation into either size and/or supersize coats; and (2) ease to incorporate into an abrasive article

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 panicles in said first binder resin precursor,

(c) at least partially curing said first binder resin precursor to form a make coat; (d) applying, over said make coat and said plurality of abrasive particles, a second binder resin precursor and an inorganic phosphate selected from the group consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Group IIIA metal orthophosphate; and

(e) curing said second binder resin precursor to form a peripheral coating, and completely curing said lu st binder resin precurso

In yet 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 to form a make coat;

(d) applying, over said make coat and said plurality of abrasive particles, a second binder resin precursor; and (e) at least partially curing said second binder resin precursor to form a size coat.

(f) applying, over said size coat, a thud binder lesin precursor and an inorganic phosphate selected fiom the gioup consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Gioup IIIA metal orthophosphate, and (g) curing said thud bindei lesin piecuisor to foim a penpheral coating, and completely curing said fust and second binder lesin precui ors

In a different aspect of the invention, there is a method of making a slurry- coated abrasive article comprising the steps of

(a) applying a coating to a substrate, the coating comprising a binder resin piecui oi a plurality of abiasi e particles, and an inoiganic phosphate selected from the gioup consisting of an alkali metal metaphosphate an alkaline earth metal metaphosphate and a Group IIIA metal orthophosphate and

(b) cuiing said bindei lesin piecursoi

The present invention in another aspect relates to a method of using the abrasive articles of the invention to gnnd titanium, composing

(a) piovidmg an abiasive article compiismg an inorganic phosphate selected fiom the gioup consisting of an alkali metal metaphosphate, an alkaline earth metal metaphosphate, and a Group IIIA metal orthophosphate in a penpheial coating layei theieof, and a wor piece compnsing titanium, (b) f ctionallv engaging said penpheral coating layer of said abrasive article with a suiface of said workpiece, and

(c) mo ing at least one of said abiasive article and said workpiece relative to each effective to i educe the surface of said workpiece

The incoiporation of an inorganic phosphate into a penpheial coating of an abrasive article, in paiticulai endows the abrasive article with an unexpected abrading efficiency when compared to a similai abrasive containing conventional nonabrasive filleis foi penpheial coatings, without unduly increasing cost

DETAILED DESCRIPTION OF THE INVENTION The coated and slui y-coated abiasive pioducts of the present invention generally include conventional backings and binders foi the coatings, as modified to

contain an inorganic phosphate grinding additive As will be shown abrasive pioducts of this invention have been found to demonstiate high peitormance in abrading workpieces pieferably metal workpreces such as titanium

The coated abrasive pioducts ot this invention can make use of backings, make coats, abrasive grains size coats supersize coats, and optional adjuvants, such as giinding aids filleis and other additives which aie known oi conventional in making coated abiasive pioducts such materials oi substances and their forms and use aie described, foi example in Kirk-Othmei loc cit, p 17-37, McKetta, J J , Cunningham W A Encyclopedia of Chemical Processing and Design. Marcel Dekker Ine p 1-19 and said U S Pat Nos 5011512 and 5078753

The backing used as a base oi substrate foi abrasive pioducts of this invention generally will be made ot a sheet oi film ot a material that is compatible with the make coat oi abiasi e slimy coat and other elements or components of the abiasive pioduct and that is capable ot maintaining its integnty during tabi ication and use ot the abiasne pioduct Examples of backing matenals aie papei, fiber, polymenc film woven and nonwoven tabnc oi cloth and vulcanized fibre Specific weights tensile stiengths and chaiactei istics of some of such backings are set forth on p 4 of the McKetta and Cunningham text loc cit Still othei examples of backings include U S Patent No 5316812 and Euiopean Patent Application No 0619769 The backing may also contain a treatment oi tieatments to seal the backing foi example, to make them vateipioof and modify physical pioperties thereof Also lefeience is made to U S Pat No 5,011512 describing specific, woven polyestei cloth backings ot certain weights and saturated with a calcium carbonate-filled latex/phenolic lesin coating (useful also as a make coat) The backing mav also have an attachment means on its back sin face to secure the resulting coated abrasiv to a support pad or back-up pad This attachment means can be a piessure sensiti e adhesive oi a loop fabnc foi a hook and loop attachment Alternatively theie may be a mtei meshing 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 oi fnctional coating Examples of such coatings

include an inorganic paniculate (e g , calcium cai bonate oi quartz) dispersed in an adhesive

The bindei used to bind the inorganic phosphate component in a peripheral coating of an abrasive article, such as a size, supei size, or abi asive slurry coat, (also referred to as a "penphei al coating binder") generally will be l esmous binder or adhesive The resinous adhesive generally will be selected such that it has the suitable properties necessary foi an abi asive article binder Examples of typical resinous adhesives useful in this invention include thermosetting lesins or thermoplastic resins The penphei al coating binder may be the same as or different from the binder adhering the abi asi e particles

Suitable examples of thermosetting resins foi use in this invention include, for example, phenolic l esins, aminoplast resins having pendant ,β-unsaturated carbonyl gi ups, urethane lesins, epoxy resins, ethylenicallv -unsatutated resins, acrylated isocyanurate l esins, ui ea-toi maldehyde resins, isocya urate resins, acrylated urethane l esins, acrylated epoxy l esins, bismaleimide resins, fluorene modified epoxy r esins, waxes, and mixtur es thei eof These binders may also be useful to bond the abrasive gi ains together to foi m a bonded abi asive, or bond the abrasive grains to a backing to from a coated abiasive

Phenolic l esins ai e widely used abi asiv e article bindei s because of their thermal properties, availability , cost and ease of handling Thei e ai e two types of phenolic l esins, l esole and novolac, and they can be used in this invention Resole phenolic l esins hav e a molai nitio of toi maldehyde to phenol, of greater than or equal to 1 1 , typically between I 5 1 0 to 3 0 0 Novolac resins have a molar ratio of formaldehyde to phenol of less than to one to one Examples of commeicially-available phenolic resins include those available from Occidental Chemical Corp , Tonawanda, NY, under the ti ade designations "Durez," and "Varcum", those available fi om Monsanto Co , St Louis, MO, under the trade designation "Resmox ^" , and those a ailable fiom Ashland Chemical Ine , Columbus, OH, under the tiade designations "Aiofene" and "Arotap" The aminoplast l esins which can be used as binder in the make, size and supersize coats have at least one pendant α,β-unsaturated caibonyl group per

molecule oi ohgomei These matenals are fui thei descnbed in U S Pat Nos 4,903,440 and 5,236 472

Epoxy resins useful as bindei in make, size oi supei size coats have an oxirane ring and are polymenzed by the ring opening Such epoxide resins include monomenc epoxy l esins and polymenc epoxy resins These l esins can vary greatly in the nature of their backbones and substituent gi oups Foi example, the backbone may be of any type noi mally associated with epoxy l esins and substituent groups thereon can be any gi oup ti ee ot an active hydi ogen atom that is l eactive with an oxirane ring at l oom tempei ature Repi esentative examples of acceptable substituent groups include halogens, estei gi oups, ether gi oups, sulfonate groups, siloxane gi oups, nrti o gi oups and phosphate groups Examples of some preferred epoxy lesins include 2 2-bιs[4-(2,3-epoxγ- pι opoxy)phenyl]pι opane (diglycidyl ethei of bisphenol) and matenals comniei cially available fi om Shell Chemical Co , Houston, TX under the ti de designations "Epon 828," "Epon 1004," and "Epon 100 IF' and fi om Dow Chemical Co , Midland , MI, under the trade designations "DER 33 I " DER 332. ^" and "DER 334" Aqueous emulsions of the diglycidyl ether of bisphenol A have fi om about ^0 to 90 wt % solids pi eferably 50 to 70 wt % solids and further comprise a nonionic emulsifiei An emulsion meeting this description is available fi om Shell Chemical Co , Louisville, KY, under the trade designation "CMD 35201 " Such aqueous epoxy emulsions ai e described as binder for grinding aids in EP 486308 (Lee et al ) Other suitable epoxy resins include glycidy ethei s of phenol toi maldehyde novolac (e g , available fi om Dow Chemical Co , undei the tiade designations ' DEN 43 1 " and "DEN 438")

Ethylenically-unsatui ated resins which can be used in the make, size or supersize coats include both monomei ic and polymeric compounds that contain atoms of cai bon, hydi ogen and oxygen and optionally, nitrogen and the halogens Oxygen or nitrogen atoms or both ai e generally pi esent in ethei , ester, urethane, amide, and ui ea groups The ethylenically-unsaturated compounds pi eferably have a molecular weight of less than about 4,000 and aie preferably esters made fi om the reaction of compounds containing aliphatic monohydioxy gi oups or aliphatic polyhydroxy groups and unsaturated caiboxylic acids, such as acrylic acid.

methacrylic acid, itaconic acid, ci otonic acid, isoci otonic acid, maleic acid, and the like Repi esentative examples ot ethv lenically-unsaturated i esins include those made by polymerizing methyl methaciylate, ethyl methacrylate, styi ene, divinylbenzene, vinyl toluene, ethvlene glvcol diacrvlate, ethylene glycol dimethacrylate, hexanediol diacrylate, tnethylene glvcol diaciΥlate, ti imethvloipropane tnacrylate, glycerol tnacrylate, pentaerythπtol tnacrylate, pentaerythπtol trimethacrylate, pentaerythntol teti aacrylate oi pentaerythπtol tetramethaci ylate, and mixtures thereof

Othei ethylenicallv -unsaturated i esins include those of polymenzed monoallyl, polyallyl and polymethallyl esters and amides ot cai boxylic acids, such as diallyl phthalate, dially l adipate, and N,N-dιally ladιpamιde Still other polymei izable niti ogen-contaming compounds include tι ιs(2-acryl- oxyethyl )ιsocyanurate, I 3 5-tι ι-(2-methacryl-oxvethvl)-s-tι ιazιne acrylanude, methylaci lamide K-methylacrylanude, N,N-dιmethyl-acry lamιde, N-vιnvlpvrι olιdone and \-v mylpipei idone

Aciylated m ethanes ai e diaciy late esters of hydi oxy ter minated isocyanate extended polyesters oi polyethei s Examples of commercially-available acrylated ui ethanes which can be used in the make, size and supersize coats include those available from Radcuie Specialties lnc Atlanta, GA, undei the tiade designations "UVITHANE 782 ' ' CMD 6600," 'CMD 8400 " and ' CMD 8805" Acrylated epoxies which can be used are diacrvlate esters of epoxy i esins, such as the diacrylate estei s of bisphenol A epoxv lesin Examples of aciylated epoxies include those commei ciallv available fi om Radcui e Specialties lnc , Atlanta, GA, under the trade designations "CMD 3500," "CMD 3600," and "CMD 3700" Bismaleimide resins which also can be used in the make, size or supersize coats ai e furthei described in U S Pat No 5,3 14, 13 (Millei et al )

Suitable thei moplastic i esins foi use in this invention to bind the alkali metal or alkaline earth metal metaphosphate in a penphei al coating of a coated abrasive article include halogenated polymei s Examples of halogenated polymers useful in this invention include polyvmyl halides (e g polyv inyl chlonde) and copolymers thereof, and poly inylidene halides such as disclosed in U S Pat No 3,616,580,

highly chlorinated paraffin waxes such as those disclosed in U S Pat No 3676,092 completely chloi mated hydiocaibon iesins such as those disclosed in US Pat No 3784,365 and fluoiocaibons such as polytetiatluoroethylene and polytπfluoiochloioethvlene as disclosed in U S Pat No 3869834 The more preferred halogenated polymers aie polyvinyl chlonde, a vinyl cliloiide/vinyl acetate copolymei and polwinylidene chlonde

An example of a useful polyvinyl chloride is commeicially-available under the trade designation "GEON I03EPF-76", which can be obtained from the Specialty Polvmers & C hemicals of B F Goodnch of C leveland Ohio An example of a useful vinyl cliloiide/vinyl acetate copolymei is commeicially available from Occidental Chemical Coip Dallas TX under the tiade designation "OXY- 0565"

Pietened halogenated polymei s are solids having an average particle size of between 1 micrometeis and 150 micrometers and more pieferably between 10 miciometeis and 100 miciometeis The polymei particles can be round, or can be another selected shape

The halogenated polymei bind i such as polyvinyl chloride or a copolymer thereof, preteiably is used in latex foim oi is plasticized An example of polyvinyl chlonde latex is that commeicially available fiom B F Goodnch, Cleveland, OH undei the trade designation GEON660-XI4' In addition, a pi eferred abrasive article includes a penpheial coating compnsing the inorganic phosphate, a plasticized polyvinvlchlonde and a thermosetting bindei Useful thermosetting binders include epoxy bindeis, phenolic binders, melamme foimaldehyde binders, acrylate bindeis, and latex bindeis, such as those described above Plasticized matenals oi plastisols" are stable, pourable, cream-like dispeisions of resin powders e g , polyvinyl chlonde, in a plasticizer Paste systems of polyvinyl chloride resins aie formulated so that the plasticizer wets the lesin particle at room temperature but only very slowly penetiates and solvates the lesin Upon heating, the paste systems fuse to piovide a well plasticized resin Plasticizeis suitable for polyvinyl chloride genei ally aie low viscosity, organic estei tor example, dioctyl phthalate dι-2-ethylhexyl phthalate, diisononyl phthalate and tnphenyl or diphenyl

alkyl phosphate, and generally are 100% solids systems Examples of such plasticizers useful for forming a plastisol with the halogenated polymer, such as polyvinyl chloride, include, for example, a diisononyl phthalate plasticizer, commercially available from Exxon Chemical Co., Houston, TX, and a diphenyl alkyl phosphate plasticizer, commercially available from Monsanto Co., St. Louis, MO, under the trade designation "Santicizer 14 1 ". These systems generally do not require an organic solvent and the total cure or fusion time is very short since no volatile solvents have to be removed prior to curing or fusion.

The types of abrasive particles or grains useful in this invention include aluminum oxide, diamond like carbon, fused alumina zirconia. titanium diboride, chromia, iron oxide, silica, tin oxide, garnet, ceria, flint, diamond, silicon carbide, cubic boron nitride (CBN), boron carbide, and the like The term aluminum oxide includes alumina, heat treated alumina, and sintered alumina, such as sol-gel alpha alumina-based abrasive grain Alpha aluminum-based ceramic materials useful to this invention include those abrasive grains such as disclosed in U.S. Patent nos 4,3 14,827; 4,5 18,397; 4,574,003; 4,623,364; 4,744,802; 4,770,67 I ; 4,88 1 ,95 1 , 5,0 I 1 ,508; 5,291 ,591 ; 5,201 ,916; and 5,304,3.3 1 ; and European Patent Application No. 228,856 Examples of fused alumina zirconia include abrasive grains such as disclosed in U.S. Pat. Nos. 3,78 1.408 and 3,893,826

The abrasive grains to be used in this invention typically have an average particle size ranging from about 0. 1 to 1 500 micrometers, usually between about 0. 1 to 750 micrometers It is preferred that the abrasive particles have a Mohs' hardness of at least about 8, more preferably above 9 The term abrasive grains also encompasses single abrasive particles bonded together to form an abrasive agglomerate Abrasive agglomerates are described in U. S Pat Nos. 4,3 1 1 ,489; 4,652,275; and 4,799.939.

It is also within the scope of this invention to have a surface 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 of the abrasive grain or particle Examples of surface coatings

include coupling agents, halide salts metal oxides such as silica, refi actory metal nitrides, and l efi actoiv metal carbides

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

A prefei red inoi ganic metaphosphate for use in this inv ention is sodium metaphosphate (i e , NaPO,), a ciystalline matenal, that is also l efen ed to in the field as "phosphate glass" oi "Maddi elf s salt" These terms ar e used interchangeably in this application to denominate NaPO Sodium metaphosphate is essentially water insoluble Compatibility with aqueous epoxy oi phenolic resins can be enhanced by coupling agents and/oi wetting agents A coupling agent can provide an association budge between the bindei pi ec sor and the inorganic metaphosphate, filler particles, and/oi abrasive particles Examples of coupling agents include silanes, titanates and zii coaluminates, and then manner of use for this function is descnbed, for example in U S Pat No 4,871 ,376 (DeWald) The abi asive bond pretei ablv contains fi om about 0 01 to 3 wt % coupling agent One system used to enhance i heology foi these l esin/phosphate glass systems is an equal parts mixtui e of a titanate available fiom Kennch Petrochemicals, lnc , Bayonne, N l, undei the ti ade designation "LICA 38", and nonyl-phenoxypoly(ethylene-oxy)ethanol available fr om Rhone-Poulenc, lnc , Cranbury, NJ, under the ti ade designation "IGEPAL CO-660' An aqueous slurry of an insoluble sodium metaphosphate can be tieated with 0 625 parts of a LICA 38/IGEPAL CO-660 mixtui e per 100 parts of the phosphate glass This treatment is applied in-situ pπoi to the addition of othei components of the foi initiation such as thermosettable resin piecursoi , red n on oxide fillei , and so forth Subsequently, this formulation is applied as a penphei al coating layei

The filler may also contain a coupling agent Examples of such coupling agents suitable for this inv ention include oiganosilanes. zii coaluminates, and titanates

Insoluble phosphate glass-latty acid salt paniculate can be made by mixing the phosphate glass with an aqueous dispersion of a fatty acid salt This mixture is thoroughly mixed and watei added as necessary to facilitate dispersion of the materials Then, ammonium hydi oxide is added until this mixtuie gels The gelled mass is dned at about 80 to I 00°C, ci ushed, and screened to the desired size

The inoiganic phosphate gi inding aid filler of the invention, as used in coated oi slut ry-coated abi asives, generally is incoi poi ated into a penpheral coating being a size oi supei ize coat oi an abi sive slui ry, as applicable, in an amount of 10 to 90 wt %, and pi efer ably 20 to 70 wt %, of the total coating weight (wet basis), and the penphei l coating bindei genei ally is included in an amount of between 10 and 40 wt %, preferably between 1 5 and 35 wt % based on total coating weight (wet basis) of the size supersize, or abi asive slurry The mixing ratio, by dry weight (solids) of phosphate glass additive to penpheral coating bindei in the penphei l coating layei is about I 0 75 to about 2 25 1 lespectively, for this invention

The inorganic phosphate grinding aid panicles genei ally have an average particle size of between 1 and I 50 mici ometei , and prefei ably between 5 and 100 micrometei s, oi e prefei bly 5 to 50 micrometei s

Binders used to bind and consolidate a plurality of the inorganic phosphate particles used in the agglomerate foi m thei eof include fatty acid metal salts, silica, and the thei mosetting i esins discussed above The fatty acid is, in general, a long straight oi substantially sti aight-chain hydi ocaibon including a carboxylic acid group and at least 8 carbon atoms, pi etei ably 8 to 20 carbon atoms The fatty acid can be saturated oi unsaturated If the tatty acid is saturated, its salt can be repi esented by the formula CH-,(CH ) θ ₂ M, where x can be between 6 and 18 and the metal atom M can be selected fi om the group consisting of zinc, calcium, lithium, aluminum, nickel lead, banum and the like If x is 16, then a stearate salt is formed, likewise if x is 14 a palmitate salt is foi med, if x is 6, an octanoate salt is

formed The fatty acid can also be unsaturated, as in the case of a undecylenate salt, Steanc acid is the piefened fatty acid A mixtuie of fatty acids can be used, such as that commonly encounteied in cunently-available comnieicia! sources of "steanc acid"

The softening points of the above-described fatty acid salts aie greater than 100°C It is piefened in this invention to use metal salts of a fatty acid that have a high softening point Dunng abiadmg applications a considerable amount of heat can be generated This heat may soften the loading-resistant coating to the point that the perfoimance ot the coated abiasive is substantially i educed and may cause the coating to smear on the workpiece being abraded Metal steaiates have a softening point in the lange of 110-212°C

The metal salt ot a fatty acid is in general insoluble in water and spanngly soluble in oiganic solvents such as ketones, estei s, alcohols, and mixtures thereof Howevei, if an appiopiiate suifactant is employed, the metal salt of a fatty acid can be rendered dispersible in watei It is prefened to use watei as the solvent instead of organic solvents to minimize the environmental concerns associated with solvent removal In general, the amount of the suifactant contained is between 001 to 10 wt % of the total tot initiation of phosphate salt paniculate metal salt of fatty acid, and suifactant that is to be used to make the agglomei te Typical examples of surfactants which can be used aie polvoxethylene alkylphenolether, sodium alkylsulfate polyoxyethylene alkylestci, polyoxyethylene alkvlether polyhydπc alcoholesteis polyhydπc esteretheis, sulfonates, oi sulfosuccinates The surfactant can be added dnectly to the agglomei ate-foimtng formulation oi the metal salt of the fatty acid can be pietieated with the suifactant and then added to the formulation

The agglomeiate composite paniculate giains with the inorganic phosphate salts can be piepaied by stilting or otherwise mixing a dispetsion of the inorganic phosphate salt particles, e g , NaPO,, in an aqueous solution or dispeision of the binder therefor, e g , zinc steaiate Zn(Cι H,,θ ₂ ), gelling the lesulting mixture of particulate and bindei, drying such mixtuie, and giinding, ciushing, or otherwise

pulverizing oi shaping and classifying the resulting dry solid to toi ni a composite paniculate oi grain pi oduct

Colloidal silica oi silica sol ai e also useful as bindei for the inorganic phosphate particulates foi making the agglomei ate form thei eof These sols are stable dispersions of amoi phous silica particles in water Commeicial products contain silica particles with diametei s of about 3- 100 nm and specific surface areas of 50-270 nr/g, with silica contents of 1 5-50 w t % They contain small amounts (< 1 wt %) of stabilizei s, most commonly sodium ions Then pH should be above 7 to maintain the negative charges on the silica particles that pt event aggregation This surface charge is neuti ahzed by soluble salts that ionize and form a double layer around the silica suiface, which then allows aggregation therefoi e, sols are only stable at low salt concenti ation

Also the fatty acid metal bindei s and colloidal silica binders of the invention can be combined and used together as a bindei toi the agglomei ate The agglomei ates of the inoiganic metaphosphates particles genei ally have an average size of between 20 and 750 micrometers, moie pi efei ably between 100 and 700 mici ometei s In some instances it is preferred that the agglomerate grains be the same size or about the same size as the abrasive grains

It is w ithin the scope of this inv ention to have ( I ) coated agglomerate grains along side of abrasive, (2) agglomei ate gi ains coated undei neath abi asive grains, (3 ) agglomei ate grains coated ovet abi asive giains, and (4) combinations thereof

The agglomerate gi ains including the inoiganic phosphate generally comprise 5 to 90 wt % phosphate salt paniculate and 10 to 95 wt % binder, and preferably 10 to 80 wt % phosphate salt paniculate and 20 to 90 wt % binder The phosphate salt-containing agglomei ates composite gi ains can further comprise optional additi es, such as, foi example, fillers (including grinding aids), fiber s, lubricants, wetting agents, thixoti opic materials, surfactants, pigments, dyes, antistatic agents, coupling agents, plasticizei , and suspending agents The amounts of these materials aie selected to pi o ide the properties desned It is also within the scope of this invention to incoi porate inorganic phosphate into both an agglomerate admixed into a penphei l coating and also

directly with the main bindei of a penpheral coating In eithei instance, the particle size prefeπ ed is 30 microns oi less

The bond system of the coated abi asive article, viz any of the make coat, size coat, abi asive slim y coat, or supersize coat, and the like, as applicable, also can contain such adiuvants with the primary component thereof i e , the binder precursoi

Foi example although not r equit ed, grinding aids, in addition to the phosphate salt in the penpheial coating, can be used in the coated and slurry-coated abrasive articles of the invention, if desn ed A gr inding aid is defined as a participate material that the addition of which has a significant effect on the chemical and physical pi ocesses of abi dmg which results in improved per for mance In gener al, the addition of a grinding aid inci eases the useful lite of the coated abrasive Gi inding aids encompass a w ide vanety of diflei ent matenals and can be inorganic oi organic based Examples of chemical gi oups ot gi inding aids include waxes, oi game halide compounds, halide salts and metals and their alloys The organic halide compounds will typically break down dunng abi ading and r elease a halogen acid or a gaseous halide compound Examples of such mater ials include chlorinated waxes like teti chloi onaphthalene, pentachloi onaphthalene, and polyvinyl chlonde Examples of halide salts include sodium chlonde, potassium crvolite, sodium cryolite ammonium ci yolite, potassium teti fluoi oborate, sodium tetrafluoroboi ate silicon fluoi ides, potassium chloride, magnesium chloride Examples of metals include, tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium Other miscellaneous gi inding aids include sulfui , organic sulfur compounds, gi aphite and metallic sulfides It is also within the scope of this invention to use a combination of diflei ent gi inding aids The above mentioned examples of grinding aids are meant to be a repi esentative showing of grinding aids, and they are not meant to encompass all gi inding aids usable in the pi esent invention

Examples of antistatic agents which can be lncorpoi ated into the make, size, supersize, oi abi asive slui v coatings are gi aphite, cai bon black vanadium oxide,

and humectants. These antistatic agents are described, for example, in U.S. Pat. Nos. 5,0 1 ,294; 5, 137,542, and 5,203,884.

Another optional adjuvant for the make, size and/or supersize binder precursors are modifying particles which have the effect of lowering the binder precursor viscosity and reduce the rate of sedimentation of abrasive and/or filler particles in the binder precursors Modifying particles are described in U.S. Patent No. 5,368, 1 (Culler). Preferred modifying particles include silica particles such as those available from the Degussa Corp., Ridgefield Park, NJ, under the trade designations "OX-50 ^" , "R-8 12", and "P-820", the first being an amorphous silica having an average particle size of 40 millimiciOmeters and surface area of 50 m ² /g, the second being a hydrophobic fumed silica having an average particle size of 7 millimiciOmeters and surface area of 260 m ^" /g, and the third being a precipitated silica having an average particle size of 15 millimiciOmeters and surface area of 100 tτr/g. The modifying particle generally is an inorganic particulate of relatively small particle size, prefei ably having an average particle size less than about 100 millimicrometers, more preferably less than about 50 millimiciOmeters. Modifying particles are preferably present in the slurries and binder precursor dispersions from about 0 01 dry weight percent to about 30 dry weight percent, more preferably from about 0 05 to about 10 weight percent, and most preferably from about 0.5 to about 5 weight percent

The manipulativ e steps of the process for making a coated abrasive articles of the invention can be essentially the same as those currently practiced in the art. Coated abrasives generally consist of a backing, abrasive grains, and at least one binder to hold the abrasive gi ains to the backin In general, the coated abrasive comprises a backing having a first bond system, commonly referred to as the make coat present on the front side of the backin At least partially embedded into the make resin are the abrasive particles Over the make coated abrasive particles is a second bond system, commonly referred to as a size coat. In some instances, a third coating or a supersize coat comprises the grinding aid and a binder. Methods of making the coated abrasive is described in US Patents 4,734, 104 and 4,737, 163.

To make the coated abrasive of the invention, the make coat is applied in a liquid or flowable form to the front side of the backing Next, a plurality of abrasive grains are projected, preferably by electrostatic coating, into the make coat. The resulting constniction is at least partially cured Notably, if a thermoplastic resin is used alone for any bond system, the thermoplastic resin can be dried in order to solidify Thus, for the purpose of this application, the term "cure" refers to the polymerization, gelling, or drying procedure necessary to convert a binder precursor into a binder. Therefore, "at least partially curing" refers to at least partially polymerizing, gelling, or drying a binder precursor. Then, the size coat is applied in a liquid or flowable form over the abrasive grains/make coat The size coat, and if necessary, the make coat are fully cured. The make and size coats can be applied by any number of techniques such as roll coating, spray coating, curtain coating, and the like An optional supersize coat containing resin binder can be further coated upon the size coat to reinforce the abrasive panicle retention, if desired The make and size coats can be cured either by drying or by exposure to an energy source such as thermal energy, or radiation energy including electron beam, ultraviolet light and visible light The choice of the energy source will depend upon the particular chemistry of the resinous adhesive. In any event, the peripheral (outermost) coating of the coated abrasive article construction, whether it is the size or supersize, must contain the phosphate salt additive

The abrasive article of the invention involving forming an abrasive slurry coat as the peripheral coat itself can be made by the steps of mixing a resinous binder precursor, the phosphate salt additive, and any other adjuvants, and then coating the resulting dispersion upon a substrate, followed by curing the binder to harden the coating. The abrasive slimy coat can take the form of a single thickness coating.

Alternatively, the abrasive slurry, before curing the binder, can be shaped to form a so-called "structured abrasive article" meaning an abrasive article wherein a plurality of shaped abrasive composites (binder plus abrasive particles, inorganic phosphate, and other additives distributed in the binder) are formed in the surface

topography of the abrasive slurry Slurry-shaping tooling equipment and modes of operation thereof can be used to shape the abrasive slurry in this regard, for example, such as those described in U. S Pat. No 5, 152,9 1 7 (Pieper et al ), and U.S. Pat No 5,435,8 16 (Spurgeon et al ). In a stnictured abrasive of this invention, abrasive composites are shaped, preferably precisely shaped, and comprise a plurality of abrasive particles, a binder, and the alkali metal or alkaline earth metal phosphate additive The abrasive particles usable in abrasive composites of a stnictured abrasive of this invention are as described above Suitable binders include cured binder precursors which include acrylate monomer(s), acrylated epoxies, aciylated isocyanates, acrylated isocyanurates, aciylated urethanes, and combinations thereof such as those described above

The precisely shaped composites may have the following shapes: pyramids, truncated pyramids, cones, ridges, or truncated cones, preferably pyramids One general method for making a structured abrasive article of this invention involves introducing an abi asive slurry comprising a binder precursor, abrasive particles, and the inorganic phosphate onto a production tool, wherein the production tool has a specified pattern

The binder precursor is then at least partially gelled or cured, before the intermediate article is removed from the outer surface of the production tool, to form a structured coated abrasive article, which is then removed from the production tool.

If the production tool is made from a transparent material, e.g., a polypropylene or polyethylene thermoplastic, then either visible or ultraviolet light can be transmitted through the production tool and into the abrasive slurry to cure the binder precursor. This step is further described in U. S. Pat. No. 5,435,816 (Spurgeon et al. ) Alternatively, if the backing is transparent to visible or ultraviolet light, visible or ultraviolet light can be transmitted through the backing to cure the binder precursor By at least partially curing on the production tool, the abrasive composite has a precise shape and predetermined pattern However, the production tool can

be removed befoi e a pi ease shape has been achieved resulting in an abrasive composite that does not have a pi ease shape The binder pi ecursoi can be further cured off the production tool

The phi ase production tool" as used herein means an article containing cavities or openings thei em For example, the production tool may be a cylinder, a flexible web, oi an endless belt A backing is inti oduced onto the outer surface of the production tool aftei the cavities have been filled so that the abi asive slurry contained in the cavities wets one ma|or surface of the backing to form an intermediate article The bindei pi ecui sor is then at least partially cuied oi gelled, before removing the intei mediate article from the outei sui ace of the production tool Alternatively the abrasive shiny can be introduced onto the backing so that the abi asiv e slui ry wets one ma|oι sui face of the backing to form an intermediate article The intennediate article is then intioduced to a production tool having a specified pattern The production tool can be a belt, a sheet, a continuous sheet or web, a coating roll, a sleev e mounted on a coating roll oi die The outer surface of the production tool can be smooth oi have a surface topography oi pattern The pattern will generally consist of a plui a ty of cavities or features The i esultmg abrasiv e particle will hav e the nivei se of the pattern fi om the pi oduction tool These cavities can have any geometnc shape such as a l ectangle, semicircle circle, triangle square hexagon pyi amid octagon, etc The cavities can be present in a dot-like pattern oi continuous rows, oi the ca ities can butt up against one another

The production tool can be made from metal or be made from a thermoplastic matenal The metal tool can be fabneated by any conventional technique such as engraving, hobbing, electrofoi ming, diamond turning and the like The following description outlines a general procedui e for making a thermoplastic production tool A mastei tool is first pi ovided If a pattern is desired in the production tool then the master tool should also have the inverse of the pattern for the pi oduction tool The master tool is pi efei ably made out of metal, e g , nickel The metal mastei tool can be fabneated by any conventional technique such as engiaving, hobbing, electroformmg, diamond turning, etc The

thermoplastic material is then heated optionally along with the master tool so that the thermoplastic material is embossed with the master tool pattern After the embossing, the thermoplastic material is cooled to solidify

A peripheral coating comprising a bindei and an inorganic phosphate optionally can be at least partially coated over the abrasive composites. For example, if the abrasive composite is in the shape of a truncated pyramid, the peripheral coating could be coated on the tops of the truncated pyramid.

Another use of the inorganic phosphate in this invention is its inclusion in ei odible agglomerates or bonded abrasives, such as those generally described in U. S. Pat. Nos 4,3 1 1 ,489, 4,652,275, and 4,799,939,

The inorganic phosphate, and/or as included in eiodible agglomerates, also can be incorporated into lofty, open nonwoven abrasives, such as those prepared according to the teachings of U. S Pat . Nos. 2,958,593, 4.9 1 .362. and U. S. Pat. No 5,025,59 In general, nonwoven abrasives include open, lofty, three- dimensional webs of organic fibers bonded together at points where they contact by an abrasive binder These webs may be roll coated, spray coated, or coated by other means with binder precursor compositions including the inorganic phosphate grinding aid particles, and/or erodible agglomerates including same, and subsequently subjected to conditions sufficient to cure the resin A general procedure for making a nonwoven abrasive incorporating the inorganic phosphate includes mixing together binder precursor, abrasive particles, the inorganic phosphate( and/or ei odible grinding aid agglomerates including the combination), and other optional additives or supplemental binder (such as a PVC plastisol) to form a homogeneous mixtui e. This mixture is then sprayed or coated into a fibrous, lofty, nonwoven substrate The binder precursor is then cured to form the nonwoven abrasive

The abrasive products of the present invention are not limited as to the types of workpiece that can be abraded therewith. By "abrading", the term as used herein generally can mean any of grinding, polishing, finishing, and the like The workpiece surfaces made of wood, metal, metal alloy, plastic, ceramic, stone, and the like, can be abraded by the coated abrasive products of the present invention.

The abrasive products of this invention are particularly well-suited for metal grinding operations, especially titanium grinding

Also, the abiasive pioducts of the present invention can be leadily converted into various geometnc shapes to suit the contemplated application, such as discrete sheets, disc forms, endless belt foims, conical foims, and so forth, depending on the particulai abrading opeiation envisioned The abiasive articles can be flexed and/or humidified prior to use

In the following examples, objects and advantages of this invention are further illustrated by vaiious embodiments thereof but the details of those examples should not be construed to unduly limit this invention All parts and peicentages therein are bv weight unless othei wise indicated

EXAMPLES

In the examples eithei of two difleient Abiasive Efficiency Test Procedures, I or II, weie used to evaluate coated abiasive pioducts (belts oi discs) described in the examples The abiasive testing pioceduies and methods foi making the belts and discs will first be descnbed

Abrasive Efficiency Test Pioceduie I Fibie discs of coated abiasive pioducts, each disc having a diameter of

178 cm, with a 22 cm diameter center hole and backing thickness of 076 mm, were installed on a swing-aim testing machine The fibre discs weie first conventionally flexed to contiollably bieak the haid bonding iesins, mounted on a beveled aluminum back-up pad, and used to gnnd the edge of a titanium disc woikpiece Each disc was dnven at 1710 rpm while the portion of the disc overlaying the beveled edge of the back-up pad contacted with workpiece at 40 kg pressure, unless indicated otherwise in the following examples Each disc was used to grind the same woi piece foi a total of 8 minutes or 10 minutes as indicated in the following examples the workpiece was preweighed and then weighed after every 1 minute of grinding

Abrasive Efficiency Test Procedure 11

The abrasive product to be evaluated was converted into two 7.6 cm x 335 cm endless abrasive belts which were tested on a constant-load surface grinder. Two belt samples from each example abrasive product were tested A pre-weighed, titanium workpiece, approximately 2 5 cm x 5 cm x 18 cm, was mounted in a holder, positioned vertically, with the 2 5 cm x 1 8 cm face confronting an approximately 36 cm diameter, 60 Shore A durometer serrated rubber, contact wheel and one-on-one lands over which entrained the coated abrasive belt. The workpiece was then reciprocated vertically through a 18 cm path at the rate of 20 cycles per minute, while a spring-loaded plunger urged the workpiece against the belt with a load of I I 0 kg as the belt was driven at about 2.050 m per minute. After 1 5 seconds of grinding time had elapsed, the workpiece holder assembly was removed and reweighed, and the amount of stock abrasively removed from the workpiece was calculated bv subtracting the weight thereof after abrading from the original weight Then a new, pre-weighed workpiece and holder were mounted on the equipment. The cut results reported in the tables below for Test Procedure II are an average value of the two belt samples thereof tested for each example The experimental error on this test was about +/- 10% The total cut is a measure of the total amount of titanium removed dunng the test The test was deemed ended after three (3 ) minutes of grinding

For purposes of Test Procedures 1 and I I described herein, in general, the initial cut is the amount of the workpiece removed upon completion of the first prescribed interval of grinding; the final cut is the amount of workpiece removed in the last interval of grinding; and the total cut is the total amount of workpiece removed over the entire grinding procedure for the subject workpiece.

MATERIALS DESCRI PTION :

The following materials and descriptions thereof are used in the examples.

Epoxy Resins

BPAW a composition containing a diglycidyl ethei of bisphenol A epoxy lesin coatable from water containing appioximately 60% solids and 40% water This composition which had the trade designation "CMD 35201' was purchased from Shell Chemical Co Louisville, KY This composition also contained a nonionic emulsifiei The epoxy equivalent weight ranged from about 600 to about 700

EPR A composition containing a diglycidyl ethei of bisphenol A epoxy resin coatable fiom an oiganic solvent This composition which had the trade designation "EPON 828" was puichased fiom the Shell hemical C ompany,

Houston TX The epoxy equivalent weight ranged fiom about 185 to about 195

Phenolic Resin

RP1 a resole phenolic lesin with 75% solids (non-volatile)

APR an acidified resole phenolic resin formulation consisting of 963% resole phenolic resin 34% PTSA (defined elsewhere heiein), and 03% AlCl, solution (defined elsewheie heiein)

Radintion Curnhle Resin Components & Additives

MSCA gamma-methacryloxyptopyltπmethoxvsilane, known undei the trade designation "A- 174", ft oni Union C ai bide Chemicals and Plastics Co , Danbury, CT

ASP amoiphous silica particles having an aveiage suiface aiea of 50 m /g, and average particle size of 40 millimicrometeis, commercially available from Degussa Corp , Ridgefield Pai , NI, under the tiade designation "OX-50"

TATHEIC tnacrylate of tns(hydιoxyethyl) isocyanurate

TMPTA tnmethvlol ptopane tnaciylate

PH 1 . 2,2-dimethoxy- 1 -2-diphenyl- 1 -ethanone, commercially available from Ciba Geigy Corp , Hawthorne, NY, under the trade designation "I GACURE 65 1 ".

Plasticizers

S- 141 ; a diphenyl alkyl phosphate plasticizer, commercially available from Monsanto Co., St Louis, MO, under the trade designation "Santicizer 141 ".

DiNP: diisononyl phthalate plasticizer, commercially available from Exxon Chemical Co , Houston. TX

Thermoplastic

OXY-0565 a vinyl chloride'viny I acetate copolymer commercially available from Occidental Chemical Corp Dallas. TX, under the trade designation "OXY-0565".

Curing Agents/Catalysts

EMI : 2-ethyl-4-ιnethyl imidazole This curing agent, which had the designation

"EMI-24", was commercially available from Air Products, AUentown, PA.

SbLAC . a complexed, latent Lew is Acid made by dissolving SbF ₅ in diethylene glycol followed by forming a complex with an equivalent excess of 2,6-diethyl aniline

PTSA: 65% para-toluene sulfonic acid in water

AlCL: 28% aluminum chloride in water

Grinding Aids

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

AIPO4 aluminum phosphate

Ca(H ₂ P0 ₄ ) ₂ calcium dihydrogen phosphate

PhG Phosphate glass, 1 e , sodium metaphosphate (NaPO , a water insoluble crystalline particulate. commeicially available fiom Sigma Chemical Co , St Louis, MO

Na-,A1F,, cryolite (tπsodium hexatluoioaluminate)

Additives

10 red non oxide

HP a mixtuie of 85% 2-methoxy piopanol and I 5% HiO commercially available from Worum Chemical Co , St Paul, MN

Dispersing Agent

AOT a dispersing agent (sodium dioctyl sulfosucαnate), which had the trade designation "Aeiosol OT" was commeicially available fiom Rohm and Haas Company. Philadelphia, PA

Filler

CaCO-, calcium carbonate

In the following examples, vanous abrasive articles of the invention are described General piocedures for making these abiasive pioducts will first be described

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General Procedure for Making Coated Abrasives Discs

A coated abiasive disc was piepaied according to the following procedure A 076 mm thick vulcanized fibie backing having a 22 cm diameter center hole was coated with a calcium caibonate-filled resole phenolic resin comprising 69 parts resole phenolic resin (70 wt % solids) 52 parts non-agglomeiated CaCO^, (dry weight basis) and enough of a solution of 90 parts wateι/10 parts ethylene glycol monoethyl ether to foim a make coat having 83 wt % total nonvolatile solid content The wet coating weight ot the make coat was appioxiniately 161 g/m ² Grade 36 (ave diametei appioxiniately 650 mtciometers) silicon cai bide abrasive grains weie electrostatically coated onto the make coat at a weight of approximately 695 g/m The lesulting abiasive article was piecuied foi 150 minutes at 93°C A size composition was applied ovei the abi sive grains and the make coat at an aveiage weight ot appi xiniately 605 g/m- to toim a size coat prior to testing Unless indicated othei wise in the examples below, the size coat consisted ol 32% RP1, 517% CaCO, and 163% HP The resulting product was cuied foi 115 houis at 93 ^C C Aftei this step, the coated abiasive discs were flexed and humidified at 45% RH foi one week

General Procedure for Making Structured Coated Abrasive Articles The abiasive articles employing sluines ot the invention weie made generally in accoi dance with assignee's U S Patent No 5435816 (Spurgeon et al ) Fust a sluirv was prepared by thoroughly mixing 223 parts by weight binder resin composition (70/30/1 of TMPTA/TATHEIC7PH1 ), 08 % ASP, 1 1% MSCA 587% abrasive giains (of the type indicated in the examples) and 171% inorganic filler (of the type indicated in the example) The slum, used in preparing abrasive pioduct was coated into a pioduction tool with a i ndom pitch pattern The height of this pattern was 14 mιl(35o micrometers) This pattern was the same pattern as descnbed in the examples of U S Pat Appln Sei No 08/120,300 (corresponding to PCT Publ No 95/07797, published Maich 23, 1995) The production tool was made fiom polypiopylene

Next a I-vveiglu layon cloth was piessed against the pioduction tool by means of a lollei so that the sluiiv wetted the tiont suiface of the cloth This J-weight layon backing had a dned phenolic/latex presize

Ultraviolet light was then tiansmitted thiough the polypropylene tool and into the slurry The ultiaviolet light initiated the polymerization of the radiation curable resin contained in the slurry lesulting in the slurry being transformed into an abrasive composite, with the abiasive composite being adheied to the cloth backing The ultiaviolet light souices used were two Fusion Systems "D" bulbs, which operated at 600 watts/in (236 watts/cm) of bulb width Finally, the cloth/ abrasive composite oi stiuctuied abiasive was sepaiated fiom the polypropylene production tool, providing a coated abiasive article

Example 1 and Comparative Examples A-E

The coated abiasives foi Example I and Compaiative Examples A-E were made accoiding to the Geneial Pioceduie foi Making Coated Abiasives Discs

These examples compaie the abiadmg characteiistics of a coated abrasive article of this invention using phosphate glass in a supeisize penpheial coating as compared to other grinding aids and a contiol using no supeisize After cure of the make and size coats, supersizes were applied as shown in Table I with the following composition 292% BPAW 035% EMI, 533% of the supeisize filler as indicated, 141% watei, 075% AOT, 23% IO (all peicentages by wt ) Table 1 also indicates the total wt % solids and coaling late foi the vanous supersizes examined The phosphate supersizes weie furthei diluted with water to decrease viscosity and enhance coatabihty Aftei standaid cine of the supersized discs, the discs containing Caιo(Pθ ) _f ,(OH) ₂ had noticeable ciacks Follo ing flexing and humidifying of these supei sized discs, the discs were tested foi giinding peiformance using Test Pioceduie I and the lesults ate displa ed in Table 2 The initial, final and total cuts (ovei 8 minutes) aie leported in Table 2 in grams (g) The % of Comp Ex C value in Table 2 is based on the total cut value of the given example lelative to the total cut value foi Compaiative Example C

Table 2

The disc of Example 1 with the phosphate glass-containing supeisize performed 143% ot discs without supeisize (i e Compaiative Example C), and was superior to all the grinding aids of Compaiative Examples A B D and E It is to be noted that ompaiative Example A with AIP0 ₄ is "compaiative" in the limited sense as lelative to a piefened embodiment ot the invention as exemplified by Example I Inclusion ot Cnoup IIIA metal oithophosphates in a peripheral coating of a coated abrasive article is withm the scope of anothei aspect of the invention

Example 2 and Comparative Examples F-H

The coated abiasives foi Example 2 and Compaiative Examples F-H were made accoiding to the Geneial Pioceduie foi Making Coated Abiasives Discs except the size coat was applied in a wet late indicated in Table 3 and the size formulations each weie 50 g RP1 plus the fillei in the amount indicated in Table 3, the mixture being diluted to 44 wt % solids Compaiative Example H using CaCO^ filler was designated the contiol tor this series ot examples No supei ize was applied so that the size coat lepiesented the penpheral coat of the coated abrasive The type ot fillei added to the size coat is indicated in Table 3

After final cin e ( no supersize), flexing, and humidifieation of these discs, Test Procedure 1 was used to test the discs f r grinding performance and the results are displayed in Table 4 The initial, final, and total cuts (over 10 minutes) are reported in Table 4 in grams (g) The % of Comp Ex H value in Table 4 is based on the total cut value of the given example relative to the total cut value of Comp Ex H

precoated with minei al oil

Table 4

The disc of Example 2 with phosphate glass in the phenolic size performed 144% of the disc with CaCO-. filler in the phenolic size (i e , Comp Ex H) while the disc w ith cryolite (Na;AlF,,) in the phenolic size (Comp Ex G) only performed 122% of Comp Ex H The remarks made supra relative to Comparative Example A are similarly applicable to Comparative Example F

Examples 3-4 and Comparative Examples l-K The following examples were conducted to examine the use of phosphate glass in plastisol-based supersize coats The discs were made according to the General Procedure for Making the Coated Abrasives Discs, except that grade 50 (ave diameter approximately 430 micrometers) SiC was used as the abrasive grains.

Preparation of Plastisols

Into a Hobart or Kitchen Aid "bread dough mixer" was placed 2 10 parts plasticizer (either DiNP or S- 14 1 ) With stirring was added 280 parts OXY-0565. After 20 to 30 minutes of stirring, the mix was ready for the addition of further additives (e g inorganic filler, stabilizer, curable resin, and so forth). This gave 100% solids with viscosities varying broadly. Plastisols used for supersizing in Comparative Example K and Examples 3-4 had the specific formulations shown in Table 5 Comparative Example I had no supersize applied to the size coat Comparative Example .1 had an aqueous epoxy supersize f i mulation applied at 4.0 g/m ² comprising 29 2% BP.AW, 0 3 S EMI, 53 3% KBF ₄ , 14 1 % water, 0 75% AOT, and 2 3% 10 (all percentages by w t )

Supersizing of discs

The supersize formulations, if any, were brushed over the cured size on discs, and cured at 90 to 100°C Test Procedure 1 was used to test grinding performance and the results are displayed in Table 6 The initial, final, and total cuts (over 10 minutes) are reported in Table 6 in grams (g) The % of Comp. Ex. I value in Table 6 is based on the total cut value of the given example relative to the total cut value of Comp Ex I

Table 5

Comparative Example K had a wet coating rate of 6 7 g/m ^" . Example 3 had a wet coating rate of 7 I g/nr, and Example 4 had a wet coating rate of 5 0 n m

Table 6

The results summarized in Table 6 show that plastisols can be formulated with phosphate glass to perform relatively well as grinding aid supersizes on coated abrasives

Example 5 and Comparative Example L

The coated abrasives for Example 5 and Comparative Example L were made according to the General Pi ocedui e for Making Coated Abrasives Discs except that the make coat was applied at a rate of 95 g/nr, Cirade 100 SiC was applied to the make at a rate of 323 g/nr, and the size was applied at a rate of 242 g/nr Comparati e Example L had no supersize, while Example 5 had a supersize foi initiation applied comprising 46 wt % PhG and 54 wt % APR applied at a wet rate of about 488 g/nr Following flexing and humidifying of these discs, the disc Test Procedure 1 as used to test the discs for grinding performance and the results ai e displayed in Table 7 The initial, final, and total cuts (over 10 minutes) ai e reported in Table 7 in grams (g) The % of Comp Ex L were based on total cut of the given example relative to the total cut of Comparative Example L

Table 7

The discs of Example 5 with phosphate glass in the phenolic supersize penpheial coat perfoi ed 1 5% of the discs of Comparative Example L lacking such a supeisize coat

Examples 6-7 and Comparativ Example M

The use of phosphate glass was also investigated in a structuied abrasive article The slurry composition foi Example 6 had this composition 327% parts binder resin composition (70301 of TMPTA/TATHE1C/PH I) 07% ASP, 15% MSCA, 504% Giade 180 SiC, and 147% PhG (all percentages by wt ) The slurry composition foi Example 7 had this composition 313% parts bindei resin composition (7030 I ot TMP1 A/1 AT I IE1C7PH I ), 08% ASP 16% MSCA, 555% Giade 180 SiC and 1 8% bone ash (1 e an ash composed pnncipally of Caιo(P0 ₄ ),(OH) ) (all peicentages by wt ) The stiuctuied coated abrasive article of each ot Example 6 and Example 7 was made by the General Proceduie for Making Stiuctuied Abiasive Articles No additional coatings were applied to the abrasive slunv coating Compaiative Example M was a Giade 150, J weight, cloth belt, commercially available fi m Minnesota Mining & Manufacturing Co , St Paul, MN, under the trade designation ' Tn-M-tte Resinbond" The abrasive belts were tested on titanium undei constant i te conditions accoidtng to Test Procedure II The results ate summaii/ed in Table 8 with the cut values ieported in giams (g) and compaied to the total cut value of Comparative Example M

The structuied abiasive of Example 6 containing the phosphate glass in the abrasive slurry penphei l coating was not only fully opei ble but outperformed the compaiative commeicial pioduct ot Compaiative Example M Example 7

containing bone ash as the inorganic phosphate additive also outperformed Comparative Example M

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 and spirit of this invention