CA2182580A1

CA2182580A1 - Abrasive article, a method of making same, and a method of using same for finishing

Info

Publication number: CA2182580A1
Application number: CA002182580A
Authority: CA
Inventors: Timothy L. Hoopman; Scott R. Culler
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1994-02-22
Filing date: 1995-01-27
Publication date: 1995-08-24
Also published as: EP0745020B1; JPH09509106A; WO1995022436A1; US5681217A; KR970701118A; JP3874790B2; DE69511068T2; EP0745020A1; BR9506932A; AU686335B2; AU1735595A; DE69511068D1

Abstract

An abrasive article (11) having sheet-like structure including a major surface (11, 25) extending within an imaginary plane (111) with a plurality of individual three-dimensional abrasive composites (15, 21) deployed in fixed positions thereto in an ar-ray, each of the composites (15, 21) has abrasive particles (16) dispersed in a binder (17) and has a substantially precise shape and a distal end (D), where another imagi-nary plane (114) extends parallel to and is spaced from the first imaginary plane (111) and intersects the lowest distal end (D') among the composites (15, 21), wherein any imaginary line drawn within the latter-mentioned imaginary plane (114) in the di-rection(s) of intended use intersect at least one cross section among the abrasive com-posites (15, 21) in the array. The invention also relates to methods for manufacturing such an abrasive article and its usage to re-fine a work surface.

Description

WO9~22436 2 ~ ~25~O r ".)~. J~ g ABRASIVE ARTICLE, A MET~OD OF MAE~IG SAME, AND
A METHOD OF USING SAME FOR l'lNl~iHlNG
This invention relates to an abrasive article having a sheet-like structure 5 having a major surface having deployed thereon a plurality of abrasive composites having precise shapes which are positioned on the major surface m a prescribed pattern. The mvention also relates to methods of making same and using such an abrasive article to reduce a surface finish.
In general, abrasive articles employ a plurality of abrasive particles which 10 are bonded together as a unitary structure (e.g., a grinding wheel) or bondedseparately to a common backing (e.g., a coated abrasive article). While these types of abrasive articles have been utilized to abrade and finish wu~ e~ for many years, problems remain in the field.
For instance, one persistent problem ~,UIIfiUll~ the abrasive mdustry arises 15 from the generally mverse ., ' ', associated between the cut rate (i.e., the amount of workpiece removed for a given time interval) and the finish that is imparted by the abrasive article on the workpiece surface. That is, it is difficult to design an abrasive article that affords a relatively high rate of cut while imparting a relatively fine surface finish on the workpiece being

2 o abraded. This explains the presence of a wide range of abrasive products in the market usmg coarse grit (i.e., relatively large particle size of abrasive partides) to fine grit (i.e., relatively small particle size of abrasive particles). The use of these differently grit-sized abrasive products m a separate and sequential manner cam provide some measure of success in ultimately achieving both a high cut and a fime 2 5 finish, but the practice can be ~ ' and time consuming. Naturally, a single abrasive article which " 'S, would provide both high cut rate and fine finish would be more convenient and highly desired in the industry.
In addition to these goals, it has also been desired m the abrasive industry to provide an abrasive article which imparts a consistent surface finish m the

3 0 workpiece while lessening or preventing scribing. Scribing refers to the occurrence of ~ ' unwanted grooves in the workpiece surface which results m an increase in surface roughmess units (Ra). In many instances, scribing is not desired.

woss/22436 2 1 8 2 ~ 8 0 Pcr/usgs/ollsg Ra is the arithmetic average of the scratch depth. Typically, the grooves, when they occur, extend in the surface of the workpiece in a direction tracking the relative motion of the abrasive article vis-à-vis the workpiece surface.
More specificaUy, U.S. Patent No. 2,115,897 (Wooddell et al.) teaches an 5 abrasive article having a backing and attached thereto by an adhesive are a plurality of blocks of bonded abrasive material. These bonded abrasive blocks can be adhesively secured to the backing in a specified pattern.
U.S. Patent l~o. 2,242,877 (Albertson) teaches a method of making a CO~ ~d abrasive disc. The method involves embedding abrasive particles in a l O binder layer that is coated on a fibrous backing. Then, a mold die is used to impart a molded pattern or contour into the thickness of binder and particle layer under heat and pressure to form a CC)~ n ~ abrasive disc. The molded surface of the abrasive disc has a specified working surface pattern which is the inverse of the profile of the molding die.
U.S. Patent ~o. 2,755,607 (Haywood) teaches a coated abrasive in which there are land and groove abrasive portions, which can form, for example, an overall rectlinear or serpentine pattern. An adhesive coat is applied to the front surface of a backing and this adhesive coat is then combed to create peaks and valleys to pattern the surface of the adhesive coat. Haywood 2 0 discloses that each of the lands and grooves formed in the adhesive coat by such a combing procedure preferably have the same width and thickness, but that they may be varied. Next the abrasive grains are distributed uniformly in the lands and grooveS of the previously pattemed adhesive coat followed by ' ' '' of the adhesive coat. The abrasive particles used in Haywood are individual grains which 2 5 are not used in slurry fomm with other grains in a binder. Therefore, the individual abrasive gr~uns have irregular non-precise shapes.
U.S. Patent No. 3,048,482 (Hurst) discloses an abrasive article comprising a backing, a bond system and abrasive granules that are secured to ~he backing by the bond system. The abrasive granules are a composite of abrasive glains and a binder 0 which is separate from the bond system. The abrasive gr~mules are three and are preferably pyrarnidal in shape. To make this abrasive article, the abrasive granules are first made via a molding process. Next, a backing is w095122436 2 1 825~o PCTIUS95/01159 placed in a mold, followed by the bond system and the abrasive granules. The mold has patternized cavities therein which results in the abrasive granules having aspecified pattern on the backing.
U.S. Patent No. 3,605,349 (Anthon) pertains to a lapping type abrasive 5 arLicle. The binder and the abrasive grain are mixed together and then sprayed onto the backing through a grid. The presence of the grid results in a patterned abrasiw coating.
Great Britain Patent Application No. 2,094,824 (Moore) pertains to a patterned lapping film. The abrasive slurry is prepared and the slur y is applied 10 through a mask to form discrete islands. Next, the resin or binder is cured. The mask can be a silk screen, stencil, wire, or a mesh.
U.S. Patent No. 4,644,703 (Kaczmarek et al.) concerns a lapping abrasive article comprising a backing and an abrasive coating adhered to the backing. Theabrasive coating further comprises a suspension of lapping size abrasive grains and a 15 binder cured by free radical pGI~ ~aliOll. The abrasive coating can be shaped into a pattem by a lUlU~laVIII~ roll.
U.S. Patent No. 4,773,920 (Chasman et al.) concerns a lapping abrasive article comprising a backing and an abrasive coating adhered to the backing. Theabrasive coating comprises a suspension of lapping size abrasive grains and a binder 2 0 cured by free radical ~Gl~ The abrasive coating can be shaped into a pattern by a luL~;lavult; roll.
U.S. Patent No. 4,930,266 (Calhoun et al.) teaches a patterned abrasive sheeting in which the abrasive granules are strongly bonded and lie ' "~, in a plane at a p,~ ' ~t ' lateral spacing. In this invention the abrasive granules are 2 5 applied via a . g technique so that each granule is essentiaily u~di~klu~
applied to tile abrasive backing. This results in an abrasive sheeting having a precisely controlled spacing of the abrasive granules.
U.S. Patent No. S,014,468 (Ravipati et al.) pertains to a lapping film intended for ophthalmic ~ The lapping film comprises a pattemed 3 0 surface coating of abrasive grains dispersed in a radiation cured adhesive binder.
The pattemed surface coating bas a pluraiity of discrete raised three ~' ' fomlations having widths which diminish in the direction away from the backing.

woss/22436 2 1 82580 F~~ fvll59 To make the patterned surface, an abrasive slurry is applied to a rotograwre roll to provide a shapes surface which is then removed from the roll surface and then the radiation curable resin is cured.
U.S Patent No. 5,015,266 (Yamamoto) pertauls to an abrasive sheet by unifomlly coating an abrasive adhesive slurry over an embossed sheet. The resulting abrasive coating has high and low abrasive portions formed by the surface tension ofthe slurry, ~.u.l~ to the u.~ , ofthe base sheet.
U.S.PatentNo. 5,107,620(Mucci)teachesamethûdofprûvidinga patterned surface on a substrate by abrading with a coated abrasive containing aplurality ûf precisely shaped abrasive Cf~mroeitpe The abrasive composites are in a non-random array and the abrasive composites comprise a plurality of abrasive grains dispersed in a binder.
U.S. Patent No. 5,152,917 (Pieper et al.) discloses a coated abrasive article that provides both a relatively high rate of cut and a relatively fine surface finish on the workpiece surface. The structured abrasive of Pieper et al. involves precisely shaped abrasive composites that are bonded to a backing in a regular pattem. The Col~ t~ ~ of the profile of the abrasive composites provided by the abra~eive structure of Pieper et al., among other things, helps provide a consistent surface finish in the worked eurface.
2 0 Japanese Laid-Open Patent Application No. 63-235942 published March 23, 1990 teaches a method of a m~ng a lapping film having a specified pattem. An abrasive slurry is coated into a network of ;- ~f . .~ Ul ;. '-- - in a tool. A backing is then applied over the tool and the binder in the abrasive slurry is cured. Next, the resulting coated abrasive is removed from the tool. The binder can be cured by 2 5 radiation energy or thermai ener8Y
Japanese Laid-Open Patent Application No. 4-159084 pubGshed June 2, 1992 teaches a method of making a lapping tape. An abrasive slurry comprising abrasive grains and an electron beam curable resin is applied to the surface of an intaglio roll or indentation plate having a network of; 1- .,li.l;....~ Then, the 3 0 abrasive slurry is exposed to an electron beam which cures the binder and the resulting lapping tape is removed from the roll.

ARTICLE 34 AM~:NI~ ~2 3 8 2 5 8 0 1 g. sep. lgg~
United States Patent No. 5,437,754 filed 13 January 1992 (Calhoun), which is commonly assigned to the owner of the present application, teaches a method of making an abrasive article. An abrasive slurry is coated into recesses of an embossed substrate. The resulting construction is laminated to a backing and the5 binder in the abrasive slurry is cured. The embossed substrate is removed and the abrasive slurry adheres to the backing.
U.S. Patent No. 5,219,462 (Bruxvoort et al.) teaches a method for making an abrasive article. An abrasive slurry is coated ~u~allLi~lly only into the recesses of an embossed backing. The abrasive slurry comprises a bindeF, abrasive grains 10 and an expanding agent. After coatin~, the binder is cured and the expanding agent is activated.. This causes the slurry to expand above the surface of the embossed backing. The lateral spacing between precisley spaced individual abrasive composites is not necessarily the same, but are spaced as desired for the particular ~rF~ ti~n For instance, Bruxvoort et al. exemplifies this type of àll allg~ as 15 being a disc application, where there is described a ~JIU~ ,ly higher density of abrasive composites as one proceeds radially from the center of the disc.
United States Patent No. 5,435,816 filed 30 December 1993 (Spurgeon et al.), which is commonly assigned to the owner of the present application, teaches a method of making an abrasive article. In one aspect of this patent application, an 2 0 abrasive slurrv is coated into recesses of an embossed substrate. Radiation energy is transmitted through the embossed substrate and into the abrasive slurry to cure the binder.
United States patent application No. 08/067,708 filed 26 May 1993 (Mucci et al.), which is commonly assigned to the owner of the present ~rp~ir~tion~ teaches 2 5 a method of polishing a workpiece with a structured abrasive. The structuredabrasive comprises a plurality of precisely shaped abrasive composites bonded to a backing. During polishing, the structured abrasive oscillates.
Although some of the abrasive articles made according to the ~ patents, viz. Pieper et al., rnight provide an abrasive article yielding 3 0 both high rate of cut and relatively fine finish, it has been observed thae scribing can occur in surfaces worked by some prior art abrasive articles when the abrasive articles are used. For instance, many abrasive articles have directional limitations AMEI\IDE3 SIIEET

WO 9s~2436 2 18 2 5 8 0 r~l,L~ IIS9 insofar as how the articles are to be oriented relative to the work surface to be }educed, i.e., some articles cannot be used, ~ . If used improperly by accident or neglect, e.g., if such an abrasiYe article is not properly aligned with the surface to be worked by the operator, these abrasiYe articles, among other things, 5 can cause scribing irl the worked surface.
U.S. Patent application No. 081120,300 filed 13 September 1993 (Hoopman et al.) describes one successful approach to solYing the scribing problem in terms of proYiding ~ ,; ,el.7 ' 1, ' abrasiYe ~f~mrr~ C, such as p,Yramidal shapes, in anarray in which the shapes are not all identical and the spacing is not identical along 10 the distal ends of the çrmroCitpc U.S. Patent application no. 08/120,297 (Gagliardi et al.) describes a coated abrasiYe article with ridges of abrasive material arranged at a nonzero angle to the machine direction, which produces a helical pattern.
~ ile the aboYe-mentioned Hoopman et al. and Gagliardi et al. ilLlluvaliu 15 represent effectiYe solutions to scribing, it can be understood that the abrasiYe industr,Y would be interested in ~f .~ ? other alternate proposals for proYiding a Yersatile high-cut rate, fine finish abrasiYe article which is resistant to inadYertent scribing and adaptable to a wider range of abrasive conditions.
The present invention proYides an abrasive article which has a high cut rate 2 0 yet imparts a relatiYely fine surface finish Y~ithout scribing the workpiece. In general, the inYention pertains to an abrasiYe article haYing sheet-like structure including a major surface extending within an imaginary plane with a plurality of individual three-~' ' abrasiYe composites deployed in fixed positions thereto in an array, each of the composites comprise abrasiYe particles dispersed in a binder 25 and haYe a ~ precise shape and a distal end, where another imaginary plane extends parallel to and is spaced from the first imaginar,Y plane and intersects the lowest distal end(s) among the cr mr-.cit-~C wherein traces of any imaginary line drawn within the latter-mentioned imaginary plane in the direction(s) of intended use intersect at least one cross-section among the abrasiYe composites in the array 30 Iying in the latter-mentioned imaginary plane.
For purposes of this inYention, the following terms haYe the meaning as indicated:

~ wog~,22436 2 1 ~ 2 5 8~ T~ 59 "imaginary line" is a line extending indefinitely in the either direction of extent of the hine;
"intersects" meams a hne or plane touches a cross-section of the composite.
This "cross-section" will essentially be a point if the; ~ occurs at a distal 5 end or outermost ternlinus of an abrasive composite. For example, if the planeparallel to the major surface slices the composites at their outermost height, such as the outer end of rounded or conical portions, the plame will be virtuaUy tangential to the distal end and the therewith will be a cross-section that is essentially a point. An imaginary line also intersects such a distal end at such a point.
10 Alternatively, the term "intersects" also means an imaginary line touching a cross-sectional slice of am abrasive composite having more significamt tWo-~surface area in the sense that, in a plan top view of the abrasive article, the traces of the line at least touch the perimeter of the outer profile of a cross-sectional slice cut by the plane parallel to the major surface plame, such as in a tangential manner15 thereto, or the Ime extends across the perimeter of the cross-section at a first location to enter and cross an interior area of the cross-section and departs therefrom at a second location along the perimeter;
"precise-shape", and the like, as used herein in describing the abrasive ,.. , refers to abrasive composites having a shape that has been formed by 2 0 curing the curable binder of a flowable mixture of abrasive particles and curable binder while the mixture is both being borne on a backing and filling a cavity on the surface of a production tool to provide a "precise shape" in the abrasive composite formed. Thus, the "precise shape" of the abrasive composite has essentially the same g ' shape as the cavity from which it is formed. Further, the precise 2 5 shape of the abrasive composite is defined by relatively smooth-surfaced sides. As small bubble recesses may occur in the outer surface areas of the composite shapes during fabrication, the shapes may be "~ ," precise in some instances;
although the overall three-.' ' shape of the composites are still clearly discernible despite these slight . ' , if occuring;
3 0 "boundary", as used herein to define the abrasive . , , meams the exposed surfaces and edges of each abrasive composite that delimit and define the actual three-l' ' shape of each abrasiw composite.

wo 95~22436 PCI/[JS95/01159 These distinct and discernible boundaries are readily visible and clear when a cross-section of the abrasive article of the invention is examined under a u~.ùpc such as a scanrling electron llfi.,l u ~up~. The distinct and discernible boundaries of each abrasive composite form the cross-sectional outlines and contours of the 5 precise shapes of the present invention. These boundaries separate amd distinguish one ind&vidual abrasive composite from another. By c.. ~ in an abrasive composite that does not have a precise shape, the boundaries and edges are not definitive, e.g., where the abrasive composite sags before completion of its curing;
"dimension", as used in connection with defining the abrasive .
10 means a measure of spatial extent such as an edge length of a side surface or height of the shape associated with an abrasive composite or, ' ~ , the "dimension" can mean a measure of an angle of inclination of a side surface extending from the backing;
~g. "" ,. ~ shape" means a three- ' ' gf.. .~ I shape;
"rounded", as used to define a geometry of the shape of the abrasive composites or a portion thereof, means a three- ' ' dome-like or . ' ' shape; amd "adjacent composite" or "adjacent . . ", or the &ke, means at least two n~ V composites which lack any intervening abrasive composite 2 o structure located on a direct line 1ll~. el,~,.. .
In one c..~ - ' ofthe invention, where the abrasive article of the invention is intended for usage as an endless belt form intended primarily for one basic direction of motion, i.e., a machine direction, it is enough to prevent scribing where thecomposites are so arranged to preclude the ability to draw any imaginary line in the 25 machine direction of the belt in a plane parallel to the major surface of the abrasive article that intersects the distal end nearest the major surface among the r ' , which does not intersect at least one cross-section of any abrasive composite among the array Iying in such a plane. This ' " of the invention is also ~ u~ for discrete sheet 3 0 forms of the abrasive article.
On the other hand, it is expected that there would be instances where the n. ,.. ;l .;.. ~ abrasive article of the invention is . , ' ' for IllulL;dil~ iullal wo ss/22436 2 ~ 8 2 5 8 0 ~1",~ 59 usage capabiiity where there should be no restridions on the orientation of the composite array vis-à-vis the work surface in any of a , ' ~ pluraiity of machine directions. Accordulgiy, in another "~ - ' of the mvention, the abrasive composites are arbitrariiy positioned to provide the ability to draw 5 imaginary iines in any of a pluraiity of mtended machine directions within a plane extendmg paraliel to the major surface of the abrasive article that intersects the distai end nearest the mdjor surface among the ~ . , which wiii mtersect at least one cross-section of any abrasive composite among the array in such a plDe.
The latter .~lll' " is especiaily needed and convenient in the use of abrasive l 0 articles presented in discrete (nonendless) sheet form where it may represent a great nuisance to the operator if fastidious care would be required to orient the array of composites borne on an abrasive article in a specific limited manner reiative to the workpiece before and during fi ictionai, ,, " l}.~ .. However, this is aiso applicable to a belt form of the abrasive article.
In one further ~ ~ - " of the abrasive article of the invention, the individuai abrasive composites have a ~ shape selected from the group of . . . l,; -I shapes consisting of a fi usto-conicai shape (truncated cone), a frusto-conicai shape (truncated cone) hA..fl.ld~ at its distai end m a rounded or dome shape, a frusto-conicai shape (truncated cone) i ~ at its distai end in a 2 0 second smalier conicai shape, cubic, prismatic, conicai, cylindricai, dogbone, pyraTnidai, and truncated pyrarnidai.
One useful composite shape is a complex shape having two basic portions including: (l) a frusto-conicai shape portion, which is attached to amd projectsoutwardly from the major surface of the abrasive article, and (2) another portion 2 5 ti]at is a rounded or I . ' ' shape located at the outer end of the composite member on top of the frusto-conicai portion. By "frusto-conicai", it is meant a f~ustum sbape as a truncated part of a conicai solid defined between two paraliel plames cutting the soiid, viz. the section between the base of the composite shape in contact with the major surface of the abrasive article and a plane parailel to the 3 0 base. Generaily, the two cutting planes are p.,~ i;Cul~ to the centrai axis of the cone; aithough some slight tilt of these planes is aiso; , ' J to form a tiited truncated cone structure. Aiso, the cross-sections of the truncated cone cam be g woss/22436 21 82580 r~ S9 circular or elliptical. The rounded shape can be contoured convexly outwardly from the bulk of the frusto-conicai portion of the composite or7 ' .~ , concaved towards the base into the bulk of the frusto-conicai portion.
It has been discovered that the force per unit area and hence cut rate is more 5 urJiformiy maintained after such rounded tips start to wear and the frusto-conicai portion of the abrasive composites become the wori~ing surfaces. The frusto-conicai shape is thought to experience a decreased rate of change m force per unit area during grinding due to the relatively steep inciining sidewails forming the shape of the ~ . , such as truncated cones. The provision of an abrnsive article l o employing the complex abrasive composite shapes having a frusto-conicai portion and a rounded tip or di$ai end is considered to represent another 1 ' of the invention.
Aiso, the individuai shapes of the abrasive composites can be so grouped together in subarrays where each such subarray of composites prevents the ability to 15 to draw imaginary iines in any intended machine direction(s) within a piane extending parailel to the major surface of the abrasive article that intersects the distai end neare$ the major surface among the composites in each subarray, whichwiii intersect at lea$ one cross-section of any abrasive composite in the given subarray in such a plane. By replicating these subarrays across tbe entirety of the 2 o major surface of the abrasive article, the, ~4U;I I ' of the invention can be satisfied without the necessity of arbitrarily fixing the location of ever~v individual composite in the array over the entire abrasive article. This approach provides a pseudo-random technique for achieving the objectives of the invention. However, the various subarrays mu$ be arranged in proximity to each other so as not to leave 2 5 rectiiinear pathways between the different subarrays that extend in the direction(s) of use intended for the abrasive article. Mosaic patterns are preferred where each subarray of composites defines an area having a perimeter and the respective areas of adjacent subarrays can be inset or overlap somewhat reiative to each other. As a , no clear pathways are created in the direction of intended usage 3 0 between adjacent subarrays arranged in this manner.
For instamce, herring bone, cro.,s ' ' i, and dogbone subarray A ~ I A ~1~" .. ~t~ of the abrasive composites can be used in this regard. A "herring 2 ~ 82580 WO 95/22436 l'CTlUS95101159 bone" pattern comprises rows of short, slanted parailel lines of abrasive composite materiai as seen in a plan view, with the direction of the slant aiternating row by row. A "cros~ ~ ' "' pattern has subsets of severai parailel iines of abrasive composite material as seen m a plan view which closely approach ~ ,uLuly but do not touch other such subsets. A "dogbone" pattern comprises individuai members of abrasive composite materiai where each are generaily .~ ~ ' aiong its l - ngit-- ' ' axis but having eniarged ends as seen in a plan view, where these members are arranged ~ ,uL ly in close ~ proximity to each other in the patterrl. Further, the herring bone, cross ' ' l, and dogbone 0 A~ can be formed by a~ L~ locating together individual composites each having upstanding shapes from the major surface of the abrasive article, with or without rounded tips or end portions.
In another further ' ' of the abrasive article of the present inventio4 each abrasiYe composite has a distai end (outermost terminai end) spaced from the base surface and each distai end extends to r ' "~ the same distarlce to the same imaginary plane which is spaced from and paraiiel to the base surface.
For example, in one . ~ ~ ' t, the abrasive composites have the saine height vaiue measured from the base surface to distai end in a range of from about 50 .t~ toabout 1020 2 0 In yet another further . ' ' of the abrasive article of the inventio4 abrasive composites are fixed on the major surface in a density of about lO0 to about lO,000 abrasive . '~..ll2.
In another .. l.. ~.i .. l ofthe invention there is a method for making the aforesaid abrasive article of the invention comprising the steps of:
2 5 (a) preparing an abrasive slurry wherein the abrasive slurry comprises a pluraiity of abrasive particles dispersed m a binder precursor;
(b) providing (i) a bacicing having a front major surface with a machine direction axis and a pair of opposite side edges, each of the side edgesbeing parailel to the rnachine direction axis and each side edge being ~
3 0 witbin a second and third imaginary plane each of wbich extends p~ ,L~,u6l to the front surface, and ~li) a production tool having a major surface bounded by paraliel opposing side edges and a pluraiity of cavities each defined by a walied wo s5/22436 8 r~l~iJ~ 59 ~!
recess having an opening at the major surface, wherein each cavity comprises a precise shape defined by distinct and discernible boundaries which include specific ' , whereby any imaginary line drawn to traverse said major surface in a direction paraUel to the opposing side edges of the production tool intersects at 5 least one cavity opening among the cavities of the array;
(c) providing a means to apply the abrasive slurry into a plurality of the cavities of the production tool;
(d) contacting the front major surface of the backing with the production tool such that the abrasive slurry wets the front major surface of the 1 0 backing;
(e) solidifying the binder precursor to form a binder, whereupon the abrasive slurry is converted into a plurality of abrasive composites bonded to the backing; and (f) separating the production tool from the front major surface after 15 solidifying to provide a plurality of individual three- ' ' abrasive composites attached in arl array to the front major surface, where the composites are so arranged to preclude the ability to draw any imaginary line in the machine direction of the article in a plane parallel to the major surface of the abrasive article that intersects the composite distal end(s) nearest the major surface among the 2 o cnmrr~cit~c~ which does not intersect at least one cross-section of any abrasive composite among the array Iying in such a plane.
In another ~ ' of the invention, the abrasive article described herein is used in a method to reduce the surface of a workpiece, having the steps of:
(a) bringing into frictional contact a workpiece surface and one of the 25 aforesaid abrasive articles ofthe invention; and (b) moving at least one of the abrasive article or the workpiece surface relative to the other such that the surface finish of the workpiece surface is reduced.
Other features, advantages, arid 1~1DLi u.,Liu.,.. of the invention will be better understood from the following description of figLires and the preferred l - -' ,o~l;"
3 0 of the present invention.
Fig. I is an en'iarged perspective top view ICi~lCD~ilLilli~ one, 1: ' of an abrasive article of this invention. 12 I~ w095/22436 21 82580 r~ J~l1S9 Fig. 2 is an eniarged end sectional view of an ilustrative abrasive article of the invention showing different shapes of composites of the invention.
Fig. 3 is a Scanning Electron M;.,~u~wy~. (SEM) ~ yl~ taken at - 100 ~ of the top surface of an abrasive article of the invention made by 5 the General Procedure for Making the Abrasive Article described hereinafter.
Fig. 4 is a SE~i ~ v . ' taken at 25 ~ ';-- in a plan view of an abrasive article of Figure 3 showing the spacing of the ~ . ~
Fig.'s 5 and 6 represent iiiustrative top views of various ~Ul v of dogbone-shaped composites in an array of the invention.
Fig.'s 7 and 8 1~.7y~,~Li~ represent illustrative top views of a cross-hatched and a herring bone lv of composites in arrays of the mvention.
Fig. 9 is a side schematic view showing an apparatus used to make an abrasive article according to this invention.
l 5 Fig. 10 is an end view m the direction 10-10 shown in Fig. 1.
Fig. 11 is a cut view, in smaller overall scale somewhat, of the abrasive aTticle of Fig. 10 showing cross-sections, by shading, of the slices of the abrasive composites Iying within an imaginary plane spaced from the major surface.
The abrasive article of the invention exhibits a high rate of cut while 2 0 imparting a relatively level, fine surface finish on the workpiece being abraded and does not readily scribe the workpiece. In the present invention, it is believed that the variation in the spacing between adjacent ylv ;..~ ' . d abrasive composites disrupts and/or prevents vibrational resonance from developing to thus provide ahigh cut-rate, fine finish with decreased chatter incidence in addition to decreased 25 scribing.
Referring to Figure 1, an iilustrative top y~ y~ ~ live~ view is shown of an abrasive article I of the invention of the . ~ ' where the abrasive composites are so arranged in the array to preclude the ability to draw any imaginary iine in the machine direction of the article within a plane extending parailel to the major 3 0 surface of the abrasive article that intersects the distai end nearest the major surface among the ~ ----r " , which does not intersect at least one cross-section of anyabrasive composite among the array Iying m such a plane.

w095/22436 2 1 82580 PCT/US95101159 In Figure 1, a major front surface 11 is shown having a pair of opposite side edges 12 and 13, and a machine direction axis 14 extending parallel to the direction of said side edges, amd a plurality of abrasive composites 15 fixed to at least the front major surface 11 of the backing. Each abrasive composite has a discernibleprecise shape defined by a discernible boundary 18. As the coated abrasive article is being used to abrade a surface, the composite breaks down revealing unused abrasive particles. Composite "s" is a shortest composite in the array while composites "t" are relatively taller thereto. For illustrative purposes, in Figure 1, as well as Figures 10 and 11, a ~ . portion of the array is shown in enlarged views, but not the entire array across the lateral width direction of the abrasive article.
Figure 10 shows an end view of the abrasive article of Figure I along the direction 10-10. The front major surface 11 lies in a first imaginary plane 111 extending parallel to backing 26, and the side edges 12, 13 of the abrasive article lie within second imaginar~v plane l l2 and third imaginary plane l l3, 1~ 4, which extend p~; ' ' to plane 111. The fourth imaginary plane 114 extends parallel to and is spaced from the first imaginary plane 111 (major wrface 11) on the side of the article bearing the . ~ ~~ The fourth plane 114 cuts through a cross-section of the abrasive composites 15 at sites 150, including composite(s) "s"
2 o having distal end D' nearest the major surface 11 in vertical height, and taller composites "t". More than one composite can have the same height S with a distalend D' located nearest said major surface 11. For example, although not shown inFigure 10, all of the composites can be formed with height S in this invention.
The abrasive composites 15 each comprise a plurality of abrasive particles 2 5 16 dispersed in the binder 17, such as shown in the composites "s" and "t". The abrasive composites 15 are "individual" in the sense that their distal ends, i.e. the terminus of each composite located vertically furthest from the major surface of the backing, are free from each other, i.e., are spaced amd not ;IlIC.~ ' with any adjacent çr,mrrlcit,.c Flgure 11 is a cut plan view ofthe abrasive article of Figure 1, at the surface of imagr~Iary plane 114, in somewhat reduced scale, to show a larger portion of the array of çf~rçcit~c The cross-sections of the abrasive composites which are cut or /~ Wo s~/22436 2 1 8 2 5 8 0 ~ sg siiced by piane 114 are indicated as the shaded portions 101 while the profile of the base side of the abrasive composites that are in contact with major surface 11 are indicated as portions 102. It is un~P~-od that plane 114 is drav~n at a spacing S
from the major surface 11 e~iuai to the shortest verticai height S of the , 5 i.e., composite(s) "s", where the cross-section(s) of the shortest composite(s) "s"
siiced by plane 114 essentiaily become a point(s).
In any event, no imaginary iines, such as 12A, 12B 12C, 12D, 12E or 12F
and so forth, can be drawn aiong exposed piane 114 parailel to the machine direction axis 14 without ;, .l ,. !~_. l; ,, at least one cross-sectionai portion 101 of the 10 abrasive composites Iying in plane 114 oriented as def ned above.
The shape of the individuai abrasive composites in the ~ o~' of the mvention relatmg to truncated conicai shapes with domes is shown in the SEM
llG~lu~ U~I~ in Figure 3 at 100 times " ~ " These composites are made by the Generai Procedure for Making the Abrasive Article described 15 hereinafter. The density of the composites over the surface area is about 775 - r ' /S'I''a' t; centimeter amd the shapes have a height of about 160 u..._t.,. ~.
As shown in Figure 4, a top view of the abrasive composites in Figure 3 at 25 times ~ ~ , the composites are positioned on the major surface in an 2 0 array such that the abrasive composites are not aiigned on the major surface to form rectiiinear columns or ridges of abrasive materiai. In Figure 4, the darkened centers represent the largest cross-sectionai profile of the rounded tip and the white circles represent the greatest outward extent of the base of the shapes.
It cam be understood that where the abrasive article is intended to be 25 adaptable to abrading in more than one machine direction, that the compositeswould be so arranged in an array to preclude the ability to draw am imagina~y Gne in any and ail of the intended directions of use without ;..~ a cross-section of at least one composite Iying in a piane paraliel to major surface 11 and spaced at composite height S.
3 0 While the invention was ~ l rd above by use of an array of frusto-conicai abrasive shapes have domed ends, other arrays and shapes of abrasive composites aiso are . ' ' witbin the scope of the invention. For instance, a wo ss/22436 2 ~ 8 2 5 8 0 r~ sg "dogbone" array of composites of the invention can be used which comprises individuai members of abrasive composite materiai where each are generaily rectamguiar aiong its l ' ' axis but having eniarged ends as seen in a pian view, where these members are arranged ~ i;.,ul~ in close 5 proximitv to each otiler in the pattern. Figures 5 and 6 show exempiary dogbone pattems with patterns of abrasive composite materiai 51 and 61, .~,..I,.,~,li~.,l~. A
"cros~ ~ ' "' pattern has subsets of severai paraiiel iines of abrasive composite materiai as seen in a plan view which closely approach ~ ,ul~uly but do not touch other such subsets. Figure 7 shows an exemplary c}oss-hatched pattern of the 10 invention with a pattem of abrasive composite materiai 71. The invention aiso ,1 theuseofcompositearraysinthe~.r.--r;~,..i.l;...~ofaherring-bone pattern, such as depicted in Figure 8, with a pattern of abrasive composite materiai 81. While the abrasive materiai segments in Figure 8 are shown as ~~ each other at ~ , a ninety degree angle, the segments of abrasive materiai in the herring bone pattern can approach each other at a wide range of angies. It will be understood that these patterns shown in any of Figures 5, 6, 7 amd 8 can be replicated as subarrays so as to provide an array which covers the entire surface area of the abrasive article.
Backin~
2 0 A baci~ing can be ~,Oll . . l~, used in this invention to provide a surface for deploying the abrasive composites thereon, wherein such a backing has a front and back surface and can be any ,u..~, ' abrasive backing. Examples of such include polymeric fiim, primed polymeric fiim, cloth including a dry cloth (greige cloth), paper, vulcanized fiber, nonwovens, and ' thereof. The backing 2 5 optionaily may be a reinforced l h- . .~ ~p~ backing, or an endless belt such as described, for example, in PCT Publication WO/93/12911 published 8 July 1993 (Benedict et ai.). The backing may aiso contain a treatment or treatments to seai the backing and/or modify some physicai properties of the backing. These treatments are well icnown in the art.
3 0 The backing may aiso ilave 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 wo ss/22436 2 1 8 2 5 8 0 PCT/US95/Oll!i9 and loop s~ttarl~pnt Alternatively, there may be a ' ~ attachment system, such as described, for example, in the U.S. Patent No. 5,201,101 (Rouser et al.).
The back side of the abrasive article may also contain a slip resistant or - frictional coating. An example of such a coating include ~ containing an 5 irlorganic particulate (e.g., calcium carbonate or quartz) dispersed in an adhesive.
An antistatic coating comprising materials such as carbon black or vanadium oxide also may be included in the abrasive article, if desired.
Abrasive ComPosite a. Abrasive Particles The abrasive particles typically have a particle size ranging from about 0.1 to lO00 ~ t~ , usually between about 0.1 to 400 l~f~ u~ .t~ , preferably between 0.1 to 100 llfi~ It is preferred that the abrasive particles have a Mohs' hardness of at least about 8, more preferably above 9. Examples of such abrasive particles include fused aluminum oxide (which includes brown aluminum oxide, heat treated aluminum oxide, and white aluminum oxide), ceramic aluminum oxide, green silicon carbide, silicon carbide, chromia, alumina zirconia, diamond, iron oxide7 ceria, cubic boron nitride, boron carbide, garnet, and thereo 2 0 The term abrasive particles also ~ , when single abrasive particles are bonded together to form an abrasive l~' Suitable abrasive for this invention are further described in U.S. Patent Nos. 4,311,489 (Kressner); 4,652,275 (Bloecher et al.) and 4,799,939 (Bloecher et al.).
It is also within the scope of this invention to have a surface coating on the 2 5 abrasive particles. The surface coating may have many different functions. In some instances the surface coatings increase adhesion to the binder, alter the abrading rl ;~1;. .~ of the abrasive particle, and the Gke. Examples of surface coatings include coupling agents, halide salts, metal oxides including silica, refractory metal nitrides, refractory metal carbides, and the like.
3 0 In the abrasive composite there may also be diluent particles. The particlesize of these diluent particles may be on the same order of magnitude as the wo gsl22436 2 1 8 2 5 8 0 PCINS95101159 ~
abrasive particles. Examples of such diiuent particles include gypsum, marble, hmestone, f int, siiica, glass bubbles, giass beads, aiurninum silicate, amd the like.
b. Binder The abrasive particles are dispersed in am orgaluc birlder to form the abrasive 5 composite. The organic bmder can be a Ih . l, - ,pl ~ ;. . binder, however, it is preferably a i' ~ binder. The binder is formed from a binder precursor.
During the r ' t: of the abrasive article, the i' ,, binder precursor is exposed to an energy source which aids in the initiation of the pul.~ ...~i~Liu,. or curing process Examples of energy sources include thermai energy and radiation 10 energy which includes electron beam, ultraviolet light, and visible iight. After this pol~....,.i~Liu.. process, the binder precursor is converted into a solidified binder.
Aiternatively for a l h. ~ . binder precursor, durirlg the ...~uluL~,Lu.~; of the abrasive article the ll.- ,.-- ,~l ll- binder precursor is cooled to a degree that results in ~ ~r '' ofthebinderprecursor. Upon ' ~ '' ofthebinderprecursor, the abrasive composite is formed.
The bmder m the abrasive composite is generaily aiso responsible for adhering the abrasive composite ~o the front surface of the baci~ing. However, it some instances there may be an additionai adhesive layer between the front surface of the baci~ing and the abrasive composite.
2 0 There are two main classes of ' " resirls, ' curable and addition pGI~ ' resins. The preferred binder precursors are addition pUIylll~ ,;i resin because they are readily cured by exposure to radiation energy.
Addition pGI~ i~.i resins can polymerize through a cationic mechanism or a free radicai ' Dependmg upon the energy source that is utilized and the 2 5 binder precursor chemistry, a curing agent, initiator, or cataiyst is sometimes preferred to help initiate the pûl~ .i~Liùil.
Examples of typicai binders precursors mclude phenolic resins, urea-'` ' ' ' ,~i~, resins, melamine c~ resins, acrylated urethanes, acrylated epoxies, ~Li~ r- ~ ~, aminoplast derivatives having pendant I ~ carbonyl groups, ;Sb~a~lul~le derivatives having at least one pendant acrylate group, isocyanate derivatives having at least one pendant wo 95/22436 2 1 8 2 5 8 0 P~ 1159 acrylate group, vinyl ethers, epoxy resins, and mixtures and ~ thereo The term acrylate; A acrylates and I~ LI~
Phenolic resins are widely used in abrasive article binders because of their - thermai propérties, avaiiabiiity, and cost. There are t vo types of phenolic resins, 5 resole and novoiac. Resole phenolic resins have a molar ratio of '` ' ' ', du to phenol greater than or eciuai to one to one, typicaily bet veen 1.5:1.0 to 3.0:1Ø
Novolac resins have a molar ratio of ' ' ' ', du to phenol of less than one to one. Examples of , ~ available phenoiic resins include those known by the i ' "DUREZ" and "VARCUM" from Occidentai Chemicais Corp.;
10 "RESlNOX" from Monsanto; "AEROFENE" from Ashiand Chemicai Co. and "AEROTAP" from Ashiand Chemicai Company.
Acrylated urethanes are diacryiate esters of hydroxy terminated NCO
extended polyesters or polyethers. Examples of ~ , available acrylated uretilanes include "UVITHANE 782", available from Morton Thiokol Chemicai, and ~CMD 6600", "C~iD 8400", and "CMi~ 8805", available from Radcure Speciaities.
Acrylated epoxies are diacrylate esters of epoxy resins, such as the diacrylate esters of bisphenol A epoxy resin. Examples of; I '1~ avaiiable ucrylated epoxies include "CMi~ 3500", "CMi~ 3600", ai-d "CMi~ 3700", available 2 o from Radcure Sr EL~ , I ' resins include both monomeric and polymeric ... ~ .I.v.., ,.I~ that contain atoms of carbon, hydroge4 and oxygen, and optionaily, nitrogen and the haiogens. Oxygen or rlitrogen atoms or both are generaily present in ether, ester, urethane, amide, and urea groups. ElilJ' "~
2 5 -~ .j.U. . . I~ preferably have a molecular weight of less than about 4,000 and are preferably esters made from the reaction of c. - ~ cont_ining aiiphatic IIUllVllJJlU~y groups or aiiphatic i;vl;il~i.u~y groups and . ~ rd carboxylic acids, such as ucryiic acid, ' ~ acid, itaconic ucid, crotonic acid, isocrotonicacid, maieic acid, and the iike. R~ ., examples of acrylate resins include 3 0 methyl ' yl_i~, ethyl 1~ ' styrene, J;~ ,Ib~ ...6, vinyl toluene, ethylene giycol diacrylate, ethylene giycol 1..~ .." hexanediol diacrylate, triethylene giycol diacrylate, trimethylol propane triacrylate, giycerol triacrylate, wo95122436 2 1 82580 ~ 59 pentaery-thritol triacrylate. ~ ,.y~hlilul l~ la~ta ~ .y~ ùl y' ' and p.,.,~.yl~ ul Le~ y~ Other c~ rA
resins mclude monoallyl, polyallyl, and ~ esters and amides of carboxylic wids, such as diallyl phthalate, diallyl adipate, amd N,N-diallyl adipamide.
5 Still other nitrogen containing: . ' include tris(2-acryloyl oxyethyl)-i~u~
1,3,5-tri(2 ~ ylu~ yl)-s-triazine, acrylamide, ' ,' ~' ', N ..._~lylc.~,ly' '~, N,N-dimethyl acrylamide, N ....,1~ ' ' , and N .:...,~ r ; The aminoplast resins have at least one pendamt alpha, bet~ ' carbonyl group per molecule or oligomer. These ' carbonyl groups can be acrylate, Il~ ,l y' , or acrylamide type groups. Examples of such materials includeN-l~y,l.u~ yl -acrylamide, N,N'-u~y,' ' ~ .,~bi~ ,lylolllhl~ ortho and para a~ ' ' phenol, a~,ly' ' ' ~' I phenolic novolac, amd 15 . ' thereof. Examples of these materials are set forth in U.S. Patent No.

4,903,440 (Larson et al.) and U.S. Patent No. 5,236,472 (Kirk et al.).
T~ y - ~ derivatives having at least one pendant acrylate group and isocyanate derivatives having at least one pendant acrylate group are further described, for = ple, in U.S. Patent 4,652,274 (13oettcher et al.). The preferred 2 0 iSu~.ula~t: material is a triacrylate of tris(hydroxy ethyl) i~u~yallula~e~
Epoxy resins have an oxirane and are ~GI~.._,iL..,.:l by the ring opening.
Such epoxide resins include monomeric epoxy resms and oligomeric epoxy resins.
Examples of some preferred epoxy resins include 2,2-bis[4-(2~3-~ y~JI U~JU~y)~JIl~.,: propane] (diglycidyl ether of bisphenol A) and 2 5 , "~ available materials under the trade designation "EPON 828", "EPON
1004", and "EPON IQOIF" available from Shell Chemical Co., "DER-331", "DER-332", and ~DER-334" available from Dow Chemical Co. Other suitable epoxy resins include glycidyl ethers of phenol r ~ r~ novolac (e g., "DEN-43 1 " and "DEN-428" available from Dow Chemical Co.).
3 0 The epûxy resins of the invention can polymerize via a cationic mechanism with the addition of an appropriate cationic curing agent. Cationic curing agents generate an acid source to initiate the pG4 " of an epoxy resin. These 2 1 ~2580 WO 95122436 I ~ U.,,~ lS9 cationic curing agents can include a salt having an onium cation and a halogen containing a complex anion of a metal or metaLloid. Other cationic curing agentsinclude a salt having an ulL " complex cation and a halogen containing complex anion of a metal or metalloid which are further described in U.S. Patent 4,751,138 (Tumey et al.)(column 6, line 65 to column 9, line 45). Another example is an ~ll, " salt and an onium salt is described in U.S. Patent 4,985,340 (Paiazotto) (column 4 line 65 to column 14 line 50); European Patent Ai r~' "
306,161 and 306,162. Stiii other cationic curing agents include an ionic salt of an ~.~, "' complex in which the metal is selected from the elements of Periodic Group IVB, VB, VIB, VriB and VriIB which is described in European Patent Application 109,851.
Regarding free radical curable resins, in some instances it is preferred that the abrasive slurry further comprise a free radical curing agent. However in thecase of an electron beam energy source, the curing agent is not always required because the electron beam itself generates free radicals.
Examples of free radical thermal initiators include peroxides, e.g., benzoyl peroxide, azo ~ . ', L --r' , and quinones. For either ultraviolet or visible light energ,v source, this curing agent is sometimes referred to as a l ' . Examples of initiators, that when exposed to ultraviolet light 2 0 generate a free radical source, inciude but are not limited to those selected from the group consisting of orgarlic peroxides, azo r ~, quinoneS, 1,.
nitroso ~ r ~, acryl haiides, ~J~ilU~uilC5, mercapto ~ .u~ , pyrylium ', ~li4~1,~' ' ' ' , I ' ' ' ' ' , ~,lliuluaii~yi ' ' , benzoin ethers, benzii ketais, i' ' , and r' ~ derivatives, and mixtures thereof.
2 5 Ex4mples of initiators that when exposed to visible radiation generate a free radicai source, can be found in U.S. Patent No. 4,735,632 (Oxman et ai.), entitled Coated Abrasive Binder Containing Temary ~ System. The preferred initiator for use with visible light is " iRGACURE 369" . , "~ available from Ciba Geigv Corporation.
3 0 The weight ratios between the abrasive particles and binder can range between 5 to 95 parts abrasive particles to 5 to 95 parts binder; more typicaily, 50 to 90 parts abrasive particles and 10 to 50 parts binder.

woss/22436 2 ~ 82~8~ P~ S9 c. Additives The abrasive slurry can further comprise optionai additives, such as, for example, fiiier-c (including grinding aids), fibers, lubricants, wetting agents,5 thixotropic materiais, surfactants, pigments, dyes, antistatic agents, coupiing agents, pl~ ~iri7Prc and suspending agents. The amounts of these materiais are selected to provide tile properties desired. The use of these can affect the erodability of the abrasive composite. In some instances an additive is purposely added to maice the abrasive composite more erodable, thereby expelling dulied abrasive particles and 10 exposing new abrasive particles.
Examples of useful fiiiers for this invention include: metai carbonates, such as caicium carbonate materiais including chaik, caicite, marl, travertine, marble, iimestone, caicium magnesium carbonate; sodium carborlate; r~S~gr l'Cill~ carbonate;
siiica materiais, such as quartz, giass beads, glass bubbles and giass fibers; siiicates, 15 such as taic, clays, -' , feldspar, mica7 caicium siiicate, caicium , sodium ' - ' , sodium siiicate; metai suifates, such as caicium suifate, barium suifate, sodium suifate, aiun~inum sodium suifate, aiumirlum suifate;
gypsum; ~.. ' , wood flour; aiuminum trihydrate; carbon black; metai oxides, such as caicium oxide, iime, aiuminum oxide, titanium oxide; and metai sulfites,2 0 such as caicium suifite.
The term filler aiso . . materiais that are icnown in the abrasive industry as grinding aids. A grinding aid is deflned as particulate materiai that the addition of which has a significant effect on the chemicai and physicai processes of abradirlg which results in improved ~. '` Examples of chemicai groups of 2 5 grinding aids include waxes, organic haiide cl~rs~ c, haiide saits and metais and their alioys. The organic haiide rl~mroll~ ~c will typicaily breaic down during abrading and release a haiogen acid or a gaseous haiide compound. Examples of such materiais include chiorinated waxes l ' lell ' ' , . ' ' .lliUI~ . ' " ' , and polyvinyl chioride. Examples of haiide saits include 3 0 sodium chioride, potassium.cryoiite, sodium cryolite, ammonium cryoiite, potassium d[iu~Jlubo~ie, sodium t~,LlaLiuoluiJ~ e~ siiicon fuorides, potassium chioride, magnesium chioride. Examples of metais include, tin, lead, bismuth, cobait, wo ss/22436 r~ 59 antimony,.cadmium~ iron, and titanium. Other ~ grinding aids include suhfur, organic sulfur cu---r ', graphite, and metallic suh~ides.
Examples of antistatic agents include graphite, carbon black, vanadium oxide, l and the Gke. These antistatic agents are dGsclosed in U.S. Patent

5 Nos. 5,061,294 (Harmer et al.); 5,137,542 (Buchanan et al.), and 5,203,884 (Buchanan et al.).
A couphng agent can provide an association bridge between the binder precursor and the filler particles or abrasive particles. Examples of coupGng agents include silanes, titanates, and ~.l ' The abrasive slurry preferably 1 û contains anywhere from about 0.01 to 3% by weight coupGng agent.
An example of a suspending agent is an amorphous silica particle having a surface area less than 150 meters s.~u~J~ that is ~ available from DeGussa Corp., under the trade name "OX-50".
15 Abrasive ComPosite ShaDe Each individual abrasive composite has a precise shape associated with it.
The precise shape is delimited by a distinct and discernible boundary, these terms being defined 1.~ b~ ._. These di$inct and discernible boundaries are readily visible and clear when the abrasiYe article of the invention is examined under a2 0 ..f.~,. v .w,v~i such as a scanning electron u ,~,vl.~" e.g., as shown in Figure 3 . The distinct and discernible boundaries of each abrasive composite form the outhne or contour of the precise shapes of the present invention. These boundaries separate and distinguish one indGvidual abrasive composite from another.
In rnmr~iC"n, in an abrasive composite that does not have a precise shape, 25 the boundaries and edges are not definitive, e.g., where the abrasive composite sags before completion of its curing. Thus, the expression "l~lt~G.~ , shaped", or the Gke, as used herein in describing the abrasive rnmrn~ c~ also refers to abrasive composites having a shape that has been formed by curing or at least partially curing, or drying or partially drying, the curable binder of a flowable mixture of 3 0 abrasive particles and curable binder while the mixture is both being borne on a backing and filling a cavity on the surface of a production tool. Such a precisely wo 9sl22436 2 1 8 2 ~ 8 0 PCI/IJS9~/01159 shaped abrasive composite would thus have precisely the same c.~ shape as that of the cavity.
A pluraiity of such composites provide three-l'' ' ' shapes that project outward from the surface of the bacicing in an inverse pattern to that presented by 5 the production tool. Each composite is defirled by a weii-defined boumdary or perimeter, the base portion of the boundary being the interface with the bacicing to which the precisely shaped composite is adhered. The remaining portion of the boundary is defined as the inverse shape of the cavity m the surface of the production tool in which the composite is cu}ed. The entire outer surface of the10 composite is confined, either by the bacicing or by the cavity, during its formation.
Suitable methods and techniques for forming ~ d composites are disciosed, for example, in U.S. Patent No. 5,152,917 (Pieper et ai.).
An array of protrusions can be formed in a surface of a master tool, such as by match roii engraving, from which is produced a production tool having an array 15 of cavity shapes wbich is the inverse shape of the 1~" ' ' ' array of abrasive composite shapes, which, in turn, can receive and mold an abrasive slurry described herein.
A f exible plastic production tooling aiso can be formed from the master as disclosed, for ample, in U.S. Patent No. 5,1~2,917 (Pieper et ai.). As a result, the 2 0 plastic production tooling has a surface which includes ' ' ' hAving the mverse sllape of the abrasive composites to be formed therewith. Exemplary techniques for malcing the array of abrasive composites will be described in greater detaii h~ ' ' ' ...
, the production tool could be formed directly by laser abiation 5 of recesses into a metal or plastic surface where the recesses have shapes counter-r " ,, to the ultirnate abrasive composite shapes. This metai or plastic surface, as contoured by the laser, can be used to shape an abrasive slurry into the desired array of abrasive composite shapes. The recesses in the production tool shape the abrasive slur~y until it cures and soiidifies to a point where it can hold the 0 shape and be separated from the production tool.
The abrasive composite shape of this invention can be any convenient shape.
The shape can be a three-~'' ' ' geometric shape such as a frusto-conical

6 PCT/US9~/Oll!i9 (truncated cone-flat top), a frusto-conical shape with a rounded, ~ . ' ' or domed outer end, a frusto-conical shape (truncated cone) i 3 at its outer end m a second smaller conical shape, cubic, prismatic (e.g., triangular, ' ' 1, hexagonal, and so forth), conical, cylindrical, pyrarnidal, truncated 5 pyramidal (fiat top), and the lilce. The ,5. ~ shape of adjacent abrasive composites can be varied, e.g. frusto-conical next to truncated pyramidal. Thesegeomtric shapes rnay have a cross sectional shape of a circle, triamgle, square,diamond, pentagon, hexagon, oval, octagon and other polygons.
In one . ' '~ of the invention, the shapes of the abrasive composites 10 all are provided with the same total height value, measured from the backing, m a rangeoffromabout50~ ,lu.l.~,tt.0toaboutlO20ll.i~,.u.l..,t~,l0.Inthissituation, the plane drawn parallel to the major surface of the backing will intersect all the abrasive composites in points at their distal ends or cross-sectional slices for all spacings of the plane equal to or less than, l~op~ the total height value of ther - I ~Iowever, it is possible to vary the heights of the abrasive .
In that situation, the plane drawn parallel to the major surface of the backing at a height spacing therefrom which is equal to or less than the shortest height value of the composites will intersect the composites taller than the shortest composite(s) m cross-sections instead of essentially at points, as shown in Figure l O. It is desired 2 0 tbat the plane l 14 drawn parallel to the major surface is at a height equal to or, ' ~,ly, at a height equal to or less than the shortest composite(s), to properlydeflne the invention.
It is also within the scope of the invention to employ an array of abrasive composites having varying diameters at their base sides.
In general there are at least 5 individual abrasive rnmrocitPc per square centimeter. In some instances, there may be at least about lOû individual abrasive __ r loUUal~ centimeter. More preferably, there are provided about 500 to 10,000 abrasive ~ /SU,~ centimeter. There is no operational upper limit on the density of the abrasive ~ , although, from a practical standpoint, at 3 0 some point it may not be possible to increase the cavity density and/or form precisely shaped cavities in the surface of the production tooling used to make the array of abrasive cnmrnCitpc As for the lower limit, enough composites must be 2 1 82~80 wo 9~22436 ~ J,.,r ~1159 utilized to form an array which satisfies the aforestated overarching . , ~ of the mvention amd provides adequate grinding action Regarding the, ~ of the abrasive composites per se, and referring to Figure I fo} illustrative purposes, the abrasive composite 15 has a boumdary 18.
The boundary or boundaries associated with the shape result in one abrasive composite ~ from an adjacent abrasive composite 19. Although not shown in Figure 1, the base portions of the abrasive composites m the array can abutt with or be joined to an adjacent abrasive composite.
Referring to Figure 2, the abrasive article of the invention comprises a l o backing 26 and several superposed layers bearing a plurality of abrasive composites 21. Again, the abrasive composites each comprise a plurality of abrasive particles that are dispersed in a bmder. The abrasive composites 21 typically are bonded to a major surface 25 of a contmuous land layer 27 of the abrasive composite materialextending beneath and between the abrasive cr~mrf~ C Thus it is preferred that the bacl~ng be 1~ covered with the abrasive composites and lands, i.e., the bacl~ng is not exposed. The abrasive composites amd land 27 are formed at the same time from the same abrasive slurry when deposited upon a backing with production tools and techniques described herein. As a result, the three~
abrasive composite structures 21 merge into the common monolithic base layer or 2 0 land 27 at their lower edges forming fillets 29 therewith. Thus, the major surface of the land 27 (amd abrasive article 20) is coplanar with the outer exposed surface area of land 27 extending between the three- ' ' abrasive composites 21.
Heights of the çomrr.r;~c, as indicated herein, are measured relative to this major surface. The land generally has a vertical thickness above the backing 26 (or 2 5 backing 26 plus primer layer 24) of no greater than 50%, preferably between I to 25%1 the vertical height H of the abrasive, . Typically, the tbickness of the land 27 will be less than about 10 llfi.,l~ where the height H of the abrasive composites is between 50 to 1020 llfi~,l~J..._,~,.~.
As depicted in Figure 2 for illustrative purposes, the abrasive composites A, 3 0 B and C of abrasive article 20 represent various geometric shapes within the scope of the invention, in an end view. Each shape includes a frusto-conical (truncated conical) shape portion 28 attached at its lower end 22 to a major surface 25.

An optionai resinous presize coat 24, such as a phenolic-latex blend7 càn be applied to the backing 26 prior to forming the abrasive composites therein as means to modify some physical property of the bacicing including improving adhesion between the abrasive composites and the backing. The truncated cone portion 28 of 5 the composites has a ~ub~L~u~Li~lly ~yl~lul~ l tapering down in cross-sectional area towards the outer second geometrical portion 23 of the composite shape; portions23 and 28 being divided by imaginary line 28'. The outer portion 23 of the composite shape A is shown as a convexiy rounded or hPmicphP~ shape in Figure 2.
The overall shape of composite A can be ~ .,L~ d as a so-ca~led "gumdrop'' shape. In oné embodiment of the invention, alrthe abrasive compositeshave the overail ~C~mPtn~l shape of composite A. Composite B shows another l~mhn~iimPnt where the rounded portion 23 is concave as shown by hidden hatched iine 23 '. Composite C is a truncated cone ~. "l ,o. l " ~r . ,1 of the invention having no 15 rounded tip. For instance, composites of shape A can be formed by methods described herein, and then the outer rounded portions of the abrasive article can be ground off(dressed) to leave truncated flat topped cones.
The angle a of the side wails of the truncated cone portion 21 is defined as the angle between the sidewails and the major surface 25. Angie a can be in a range 20 between about 30~ to 90~ in each o~composites A, B, and C. Lower a values candecrease grinding p~ru~ llce as the three- ~ l shape of the composite is more flattened. Where a closely approaches or becomes gOc, the lower portions 28of the shapes will change from truncated cones to a post-like shape~ In one moreparticular ~...I,o i;...~..i, a values of 65~ to 75~ are employed. Aiso, the height h2 of 2 5 the truncated conicai portion generaiiy wili represent about 5û-95% of the overaii verticai height H of the shape where a rounded portion 23 having verticai height h, is provided in composites A and B. In one particular Pmho~iimPnt the height h2 can represent about 80% of the overaii H of Composites A or B.
Again, it is to be understood that the rounded shape of the outer end portion 3 0 23 of the composites can be eiiminated to leave a flat top truncated cone, or contoured inwardly (concavely) into the bulk of the frusto-conicai portion as a depression to form an overail volcano-like shape as an altemative to being shaped ANiE~il)ED S'iEET

convexly outwardly from the bulk of the frusto-corlical portion of the compositeThe concave indentation can be formed during the master tool process such as described herein.
Although it is ordinarily acceptable to use convexly rounded distal ends in the practice of the invention, there are instances . . ' ' where it may be desired for the tips of the composite to break off more quickly to provide an increased initial cutting ability. In those instances, the concavely or inwardly shaped distal ends may be helpful. The width and height of the composite shapes can be adjusted to provide the desired cut rate. In general, this array of abrasive composites results in an abrasive article that has a relatively high rate of cut, a long life, but also results in a relatively fine surface finish on the workpiece being abraded with minimized scribing. Additionally, with this number of abrasive composites there is a relatively low unit rorce per each abrasive composite. In some instances, this can result in better, more consistent, breakdown of the abrasive composite.It is also within the scope of this invention to have a ~ . . .1 .; ., ~ ;.~, . of abrasive composites bonded to a backing in which some of adjacent abrasive composites abutt, while other adjacent abrasive composites have open spaces between them aslong as the ~ C4U;ICI~A_.IL is met with respect to no line being drawable through the array of composites in a direction(s) of intended use of the abrasive 2 o article in service within an imaginary plane spaced parallel to the major surface that intersects the shortest distai end of the: -t,^ , that does not intersect at lenst one cross-section of the abrasive composites in such an imaginary plane.
Method of Mnkin~ the Abrnsive Article 2 5 Although additional detnils will be described later herein on the methods of making the abrasive article of the invention, in general, the first step in making the abrasive article is to prepare an abrasive slurry. The abrasive slurry is made by combining together by any suitable mixing technique the binder precursor, the abrnsive particles, and the optional additives. Examples of mixing techniques 3 0 include low shear and high shear mixing, with high she~tr mixing being preferred.
Ultrasonic energy may also be utilized in c~, i - - ~ ;. ~ with the mixing step to lower the abrasive slurry viscosity. Typically, the abrasive particles are graduaily added .

wo ss/22436 2 1 8 2 5 8 0 PCTNS95/oll~9 into the bmder precursor. The amount of air bubbles in the abrasive siurry can be minimized by puiiing a vacuum during the mixing step, for example, by employing ' methods and equipment.
- In some instances it is preferred to heat, generaily in the range of 30 to 5 70C, the abrasive slurry to lower the viscosity. It is important the abrasive slurry have a rheology that coats weil and in wkich the abrasive particles and other fiiiers do not settie.
If a i' ,, binder precursor is employed, the energy source for curing the binder precursor can be thermai energy or radiation energy depending 10 upon the binder precursor chemistry. If a Ih ' '~ binder precursor is employed the Ih .. ,...,~ l;.. is cooled such that it becomes solidified and theabrasive composite is formed. Other more detailed aspects of the method(s) to mai~e the abrasive article of the invention wili be described k~
r,.- Tool The production tool contains a pluraiity of cavities. These cavities are essentiaily the inverse shape of the abrasive composite desired and are responsible for generating the shape of the abrasive . . The dimensions of tke cavities are selected to provide the desired skape and dimensions of the abrasive 2 0 . . If the skape or dimensions of the cavities are not properly fabricated,the resulting production tool will not provide the desired dimensions for the abrasive The cavities can be present in a dotlike pattern with spaces between adjacent cavities, such as shown in Figure 4, or the cavities can abutt against one another at 2 5 tkeir mouth portions; aithough the cavities must be configured such that the distai ends of the composites formed from the cavities must be free and " .. .. ~. 1 to each in this mvention.
The protiuction tool cam be a belt, a sheet, a continuous sheet or web, a coating roii such as a IU~U~IV~ roll, a sleeve mounted on a coating roii, or 3 0 stampmg die. The production tool can be composed of metal, ~e.g., nickel), metai aiioys (e.g., nickel ailoys), plastic (e.g., pol~.u~ ,..l, an acrylic plastic~, or any other COI~ formable materiai.

wo 9sl22~36 2 ~ 8 2 5 8 0 PCTIUS95/011~9 The 1~.... ,1,l 1;- production tool can be made by replication offa metai master roii tQol. The metai master roll will have a surface lop~ y that is the inverse pattem desired for the production tool. The metai master can be made by icnown matched roll engraving process techniques, i~nurling, and diamond tuming.5 In the event of use of a metai master roll, a 1~ l; sheet materiai can be heated and optionaily along with the metai master such that the ~
materiai is embossed with the surface pattem presented by the metai master by pressmg the two surfaces together. The Ih~ o~ cam aiso be extruded or cast onto to tlle metai master. The 1' r ~ " ~ materiai is cooled to soiidify and 10 produce the production tool. Examples of preferred ~ pl ~ . production tool materiais inciude polyester, p~l~bulld~s, polyvinyl chioride, PUIYIJIUIUYI~
POIJ~ J~ and ~ ' thereof.
If a 11,.... "~pl ---l ;.. production tool is utilized, then care must be tai~en not to generate excessive heat, p~ L;.,ulcl.ly during the solidifying or curing of the binder precursor in the abrasive slurry step, that may distort the 11.. ~.~ .1 ;~ production tool.
The production tooi aiso can be cast by extruding polymeric resin onto the drum and passing the cxtrudant between a nip roll and the drum, and then cooiingthe extrudant to fomm a production tool in sheet fomm having an array of cavities 2 0 fommed on the surface thereof in mverse cu. . .~1.., 1 ~ to the surface protrusions presented by the master tool. This process can be conducted ~ , to produce a polymeric tool of any desired length.
In an aitemate aspect of the invention, the abrasive composites can be fommed in a production tool, such as described herein, where the composites are 2 5 iiberated from the production tool cavities as individual composite shapes, and tilese loose composite shapes deposited upon and are bonded to a bacicing via a binder layer.
I~ner~ Sources When the abrasive slurry comprises a i' ,, binder precursor, the 3 0 binder precursor is cured or pul~ . This pcl~ is generaiiy initiated upon exposure to an energy source. Examples of energy sources include themlai energy and radiation energy. The amount of energy depends upon severai factors _ _ _ _ _ . , ... . .. _ . _ . . . . . .

wo ss/22436 2 1 8 2 5 8 0 PCI/US95/011~9 such as the binder precursor chemistry, the dimensions of the abrasive slurry, the amount and type of abrasive particles and the amount and type of the optional additives. For thermal energy, the t~ Lul~; can range from about 30 to 150C, generally between 40 to 120C. The time can range from about 5 minutes to over 5 24 hours. The radiation energy sources include electron beam, ultraviolet light, or visible light. Electron beam radiation, which is also known as ionizing radiation, can be used at an energy level of about 0.1 to about 10 Mrad, preferably at an energy level of about I to about 10 Mrad. Ultraviolet radiation refers to non-particulate radiation having a ~a~ '' within the range of about 200 to about 400 , preferably within the range of about 250 to 400 .~
lt is preferred that 300 to 600 Wattrmch (120-240 Watt/cm) ultraviolet lights are used. Vlsible radiation refers to non-patticulate radiation having a ~a~
within the range of about 400 to about 800 ~, preferably in the range of about 400 to about 550 ~. It is preferred that 300 to 600 Watt/inch (120-240 Watt/cm) visible lights are used.
One method to make the abrasive article of the invention is illustrated in Figure 9. Backing 41 leaves an unwind station 42 and at the same time the production tool 46 leaves an unwind station 45. Cavities (not depicted) formed in the upper surface of production tool 46 are coated and filled vith an abrasive slurty 2 0 by means of coating station 44. Alternatively, coating station 44 can be relocated to deposit the slurty on backing 41 mstead of the production tool before reaching drum 43 and the same enwmg steps are followed as used for coating the productiontooling as described below. Either way, it is possible to heat, by means not shown, the abrasive slurry and/or subject the slurry to ultrasonics prior to coating to lower 2 5 tbe viscosity. The coating station can be any ~Oll. . ' convenient coating meatls such as drop die coater, knife coater, curtain coater, vacuum die coater or a die coater. During coating the formation of air bubbles should be minimized. Onesuitable coating technique uses a vacuum die coater, which can be of a known type wch as described, for example, in U.S. Patent Nos. 3,594,g65; 4,959,265 and 3 0 5,077,O70. After the production tool is coated, the backing and the abrasive slurry are brought into contact by any means such that the abrasive slurry wets the front wrface of the backing. In Figure 9, the abrasive slurry is brought into contact with woss/22436 2 1 8 2 ~ 8 ~ PCT/US95101159 the baci~ing by means of contact nip roll 47, and contact nip roll 47 forces theresuiting ~,o~ lu~.liu.. against support drum 43.
Next, any convenient form of energy 4~ is transmitted into the abrasive slurry that is adetiuate to at least partiaily cure the binder precursor. The term partiai cure is meant that the binder precursor is i~VI~ ~i to such a state that the abrasive siurry does not flow from an inverted test tube. The binder precursor can be fuliy cured once it is removed from the production tool by any energy source.The production tool is rewound on mandrel 49 so that the production tool can be reused again. Additionaily, abrasive article 120 is wound on mandrel 121. If thebinder precursor is not fully cured, the binder precursor can then be fully cured by either tir~e and/or exposure to an energy source. Other guide rolls are used where convenient and are desigrlated rolls 40.
Relative to this first method, it is preferred that the binder precursor is cured by radiation energy. The radiation energy can be transmitted through a transparent production tool or transparent backing to radiate the abrasive siurry where the production tooi or backing does not all~n c~,;~ly absorb the radiation energy.
Additionaily, the radiation energy source should not ~ degrade tile production tool. It is preferred to use a Ih . ""~ ;. . production tool and ultraviolet or visible light.
2 0 As mentioned above, in a variation of this first method, the abrasive slurry can be coated onto the baci~ing and not into the cavities of the production tool. The abrasive slurry coated baci~ing is then brought into contact with the production tool such that the abrasive slurry flows into the cavities of the production tool. The remaining steps to maiie the abrasive article are the same as detaiied above.
2 5 There is aiso a second method for making the abrasive article. The production tool is provided in the outer surface of a drum, e.g., as a sleeve which is secured around the .,;., '` ~ e of a drum in separate sheet form (e.g., as a heat-shrunk rlickel form) in any convenient manner. A backing leaves an unwind station and the abrasive siurry is coated into the cavities of the production tool by means of 3 0 the coating station. The abrasive slur y can be coated onto the backing by any technique such as drop die coater, roll coater, knife coater, curtain coater, vacuum die coater, or a die coater. Alterrlatively, the abrasive slurry can be coated into the . .

wo gs/22436 2 1 8 2 5 8 0 . ~ sg cavities of the production tool. Again, it is possible to heat the abrasive slurry andlor subject the slurry to ultrasonics prior to coating to lower the viscosity.
During coating the formation of air bubbles should be minimized. Then, the backing and the production tool containing the abrasive slurry are brought into 5 contact by a nip roii such that the abrasive slurry wets the front surface of the backing. Next, the binder precursor in the abrasive slurry is at least partialiy cured by exposure to an energy source sufficient such that the abrasive slurry is converted to an abrasive composite that holds its shape and is bonded or adhered to the backing. The resulting abrasive article is stripped and removed from the production 10 tool at nip roiis and wound onto a rewind station. In this method, the energy source can be thermai energy or radiation energy. If the energy source is either ultraviolet Gght or visible Gght, the backing should be transparent to ultraviolet or visible light.
An examp~e of such a backing is polyester backing.
After the abrasive article is made7 it can be fiexed and/or humidified prior to 15 converting. The abrasive article can be converted into any desired form such as a cone, endless belt, sheet, disc, etc. before the abrasive article is put into service.
Method of Refinin~ a Work~iece Surrsce Another ....~ of this invention pertains to a method of refining a 2 0 workpiece surface. This method involves bringing into fi ictionai contact the abrasive article of this invention with a workpiece. The term refine means that a portion of the workpiece is abraded away by tbe abraqive article. Additionaily, the surface finish associated with the workpiece surface is reduced after this refining process. One typical surface finish l..~.~ is Ra; Ra is the arithmetic surface 2 5 firlish generaily measured in I ' or IIU-,I U~ . The surface finish can be measured by a I~IUIilUIII~.t~,l, such as that avaiiable under the trade tipr~ nnr, or Surtronic.
WorkrJiece 3 0 Tbe workpiece can be any type of materiai such as metal, metai aiioy, exotic metal aiioyl ceramic, giass, wood, wood like materiai, ~n~roCitpq~ painted surface, plastic, reinforced plastic, stone, and ~ ' thereo The workpiece may be wo 95/22436 2 1 8 2 5 8 0 PCTNS95/01159 flat or may have a shape or contour associated with it. Examples of W~Jli p;~.ces include giass ophthaimic lenses, plastic ophthaimic lenses, glass television screens, metai automotive: . plastic ~ r ', particle board, carn shafts, crarlk shaf~s, furniture, turbine blades, painted automotive: , magnetic 5 media, and the iike.
Depending upon the ~j ' , the force at the abrading interface can range from about 0 1 kg to over I 000 kg. Generaily this range is between I kg to 500 kg of force at the abrading interface. Aiso depending upon the ~
there may be a hquid present during abrading. This iiquid can be water andlor an10 organic compound. Examples of typicai organic . ' inciude lubricamts, oiis, emulsified organic ~mrol-~ ;c, cutting fluids, soaps, or the iike. These liquids may aiso contain other additives such as defoamers, degreasers, corrosion inbibitors, or the like.
The abrasive article of the invention can be used by hand or used in 15 .,. ,. ~ .(,., with a machine. At least one or both of the abrasive article and the woricpiece is moved relative to the other in frictionai contact. The abrasive article can be converted mto a belt, tape rolls, disc, sheet, and the iike. ~or belt . . ' the two free ends of an abrasive sheet are joined together and a spiice is formed. It is aiso within the scope of this invention to use a spliceless belt.
2 0 Generaily the endless abrasive belt traverses over at least one idler roll and a platen or contact wheel. The hardness of the platen or contact wheel is adjusted to obtain the desired rate of cut and workpiece surface finish. The abrasive belt speed ranges anywhere from about 150 to 5000 meters per minute, generally between 500 to 3000 meters per minute. Again this belt speed depends upon the desired cut rate 2 5 and surface finish. The belt dimensions can range from about 5 mm to I meter wide and firom about 5 cm to 10 meters long. Abrasive tapes are continuous lengths ofthe abrasive article. They can range in width firom about I mm to I meter, generaily between S mm to 25 cm. The abrasive tapes are usually unwound, traverse over a support pad that forces the tape against the workpiece and then rewound. The 3 0 abrasive tapes can be: 'y feed tblough the abrading interface or can be indexed. The abrasive disc, which also includes what is known in the abrasive art as "daisies", can range from about 50 mm to I meter in diameter. Typicaily abrasive34 ~ w0 95/22436 2 1 8 2 5 8 0 ~ sg discs are secured to a back-up pad by an attachment means These abrasive discs can rotate between 100 to 20,000 revolutions per minute, typicaiiy between 1,000to 15,000 revolutions per minute.
The features and advantages of the present invention will be further 5 iliustrated by the foiiowing nu,, l- ,, examples. Ali parts, p~., ,, , ratios, arld the hke, in the examples are by weight uniess otherwise indicateci.
.
F. ' ' Procedure The foiiowing alb~ are used ~LI~ _' 10TMPTA: trimethylol propane triacrylate;
PH2: 2-benzyl-2-N,N-~' ' ~' -r ~ -butanone~ available from Ciba Geigy Corp. under the trade ~ _ "IRGACURE 369", ASF: amorphous siiica filler, .,ul. .l~l "~ available from DeGussa under thetrade ' _ "OX-50";
FAO: fused heat treated aiuminum o~de;
SCA: siiane coupling agent; 3 .. ~ UAy-ylUy,'.lUI.. ,;l~U~ ' , "~ availab!e from Union Carbide under the trade ' _ "A-174";
KBF4: potassium ~ell~[iuvlulJul~e.
General Procedure ~or Makino the Abrasive Article An abrasive slurry was prepared that contained 22 parts TMPTA, 0.2 part PH2, û.9 part ASF, 17 parts KBF4, 0.9 part SCA and 59 parts of grade P-320 FAO. The slur~y was mixed for 20 minutes at 1200 rpm using a high shear mixer.
The production tool was a continuous web made from a transparent pcl~l,l uy~ sheet materiai .,ul.ull~ v avaiiable from Exxon under the trade .' _ "POLYPRO 3445". The pro.duction tool was embossed offof a krlurled master roli by d;~ a ribbon of the pGI~yluy~ in a molten state 3 0 downward between the nip formed by the master tool and a smooth-surfaced back-up roii, and then cooled to retain the surface contour imparted from the master tool.

w095122436 2 1 82580 p~usgs/0ll~9 The master tool was made by known mateh roll engraving teehniques. A roll tool having recesses therein ~,UII~ '' ,, in shape to the desired truncated coneshapes in the abrasive eomposites was rolled over the top of a steel roll or drum eovered with a wax resist. The ~ r~ on the roll ~ool eontacted and 5 displaced wax on the dtum rnto the areas Cu~ to the reeesses of the match roll. As the drum is rotated through an eteh bath, the portions of the drum where wax was displaced were ~,.u~.,..~ etched away tbrough each rotation of the drum to ultimately form a struetured surface on the drum comprising an array of individual ~,.u~ The struetured surface on the drum is eonversely 10 replicated in a surface of a production tool, which, rn turn, was used to shape an abrasive slurry into abrasive composites having shapes ~.ull~-r ' ~ tû those UI ~ Il ~. . n 11~ -~ left rn the surface of the master drum tool.
In general, the production tool, as made from the master tool, contained an array of cavities that were inverted frusto-conieal shapes having about 100 15 ..f..,.u....,.~. high truneated cones as lower portions and about 60 ...h,.u.,.~,t~.. high conve~dy rounded domes as upper portions, and the three- " ' cavity shapes had a eonstant overall depth of about 160 u...~
The pattern is premised on a repeating mosaic pattern of composite subarrays where no line eould be drawn in the machine direetion on the surface of 2 0 the abrasive belt without; ~ g the cross-section of least one composite in aplane extending parallel to the major surface and ~ the shortest distal end of the ~t~r. eit~ such as shown in Figure 4.
The abræive article wæ made by a method and nl . i ~, ,. - - -l generally depicted in Figure 9. This process was a wntinuous process that operated at about 25 15.25 /~ . The baeking was a J weight rayon backing that eontained a dried I~L~A/, ' ' presize eoating to seal the backing. The abrasive slurry was knife-eo~tted onto the production tool at 15.2 meterslmin (50 fpm) with a 76 Ull~t~,~ knife gap (3 mil) without vacuum and about a 15 cm wide coating area onto the produetion tool. The nip pressure, such as exerted by roll 47 in Figure 9, 3 0 between the produetion tool and the backing was about 3. I x IO Pa. The enerQy source was two v;~il,l~ !iVht lamps, each which eontained a V-bulb made by Fusion Systems, Co., which operated at 600 Wattsrmch (240 wo ss/22436 2 1 8 2 5 8 0 PCT/U595/oll~s Watt/cm). The partially cured slurry released very well from the production tool.
A~er partially curing the abrasive slurry, the resulting coated abrasive was thermally cured for 12 hours at 240F (11 6C) to final cure the phenolic presize of the - backing. There were about 775 abrasive Çrl~rO~;fPc per square centimeter formed 5 on the surface of the backing having heights of about 160 u~.~,t~
Test Procedure I
The coated abrasive article was converted into 7.6 cm by 335 cm endless belt Gnd tested on a constant load surface grinder. A pre-weighed, 304 stainless10 steel workpiece CI~IJIUIUIIIG~ / 2.5 cm by 5 cm by 18 cm was mounted in a holder.
The workpiece was positioned vertically, with the 2.5 cm by 18 cm face facing anG~ / 36 cm diameter 65 Shore A durometer serrated ruWer contact wheel with one on one lands over which was entrained the coated abrasive belt. The workpiece was then lt~ ,l . ' vertically through an 18 cm path at the rate of 2015 cycles per minute, while a spring loaded plunger urged the workpiece against the belt with a load of 4.5 kg (10 lbs) as the belt was driven at a surface speed of about 1400 meters per minute. Afler thirty seconds elapsed grinding time, the workpiece holder assembly was removed Gnd re-weighed, the amount of stock removed calculated by subtracting the abraded weight from the original weight, and a new, 2 0 pre-weighed workpiece and holder were mounted on the equipment.
Additionally, the surface finish Ra and the Rz of the workpiece was also measured Gnd these procedures will be described below. The test endpoint was when the amount of steel removed in the sixty second interval was less than one third the value of the steel removed in the first sixty seconds of grinding a control 2 5 belt or until the workpiece burned, i.e., became discolored.
Ra is a common meaSure of roughness used in the abrasives industry. Ra is defmed as the arithmetic mean of the departures of the roughness profile from the meGn hne. Ra was measured with a ~,.uLlu...~,i~ probe, which was a diamond tipped stylus, at three locations and the Grithmetic mean was calculated as the 3 0 average of these three . l In general, the lower the Ra value was, the smoother or finer the workpiece surface finish. The results were recorded in llli~lUll~ The ,UlUfilUIII~ . used was a Perthen M4P.
3~

Rz is a common measure of roughness used in the abrasive industry. Rz is deSned as the Ten Point Roughness Height which is the average of the five greatest vertical peak-to-valley height differences within one cutofflength. Rz is measured with the same equipment as the Ra value. The results are recorded m ~.
5 In general, the lower the Rz, the smoother the firlish.
EXAMPLI~S
E~amPle 1 To ~1, ., - ."~m. 1~ the w~ and ad~a~ ~u~ effects of the abrasive articles ..,~ , of the invention, two sarnples of abrasive articles were both 10 ~llal~ura~luuod according to the "General Procedure for making the Abrasive Article"
described herein to provide Samples A and B The abrasive articles were tested according to Test Procedure I and the test results are ~r' in Table IA for Sample A results and Table ~B for Sample B results.
Three I~ a ~UI~ were taken for each of Ra amd Rz for each workpiece 15 being refimed by Sample A and B at several incipient and later times of interest during grinding, and the average value of these ~ aSUI~ are indicated in Tables IA and IB, I.,;.~ . The grinding time is in&cated in and the cut rate is quantified in grams that were abraded away for the period between each indicated time and the immediate prior tirne.

.
.
T:lble IA
Time Cut Ra~ Ra2 R~ Ra(ave) Rz~ R~2 Rl~ R~(aYe) 00:30 3.1 24 25 28 25.7 213 201 227 213.7 01:00 5.3 39 36 47 40.7 298 280 304 294.0 02:00 17.3 39 44 44 42.3 299 292 307 299.3 03:00 16.5 04:00 14.0 05:00 12.4 06:00 1 1.4 07:00 9.8 08:00 8.9 09:00 7.3 10:00 7.6 11:00 6.9 12:00 6.6 13:00 6.2 14:00 5.7 15:00 5.4 16:00 4 9 17:00 5.0 18:00 4.9 19:00 4.7 20:00 4.6 21:00 4.2 22:00 4.4 23:00 3 9 24:00 3.1 14 17 19 167 114 137 128 126.3 184.6 (total cut) 3 9 ~ c' Table lB
Time Cut Ra~ ve) Rz~ ve~
00:30 3.5 24 28 24 25.3 188 220 199 202.3 01:00 5.3 27 25 34 28.7 234 198 219 217.0 02:00 16.0 44 54 40 46.0 325 372 327 341.3 03:00 15.8 04:00 13.8 05:00 12.4 06:00 1 1.3 07:00 9.6 08:00 8.6 09:00 8.0 10:00 7.7 I I :00 . 7.0 12:00 6.7 13:00 6.6 14:00 5.9 15:00 5.8 16:00 5.7 17:00 5.0 18:00 4.8 19:00 4.6 20:00 4.6 21:00 4.3 22:00 4.2 23 :00 4.0 24:00 3.8 24 14 17 18.3 179 120 154 151.0 184.7 (total cut) .i.

The above results show that the abrasive articles of the present invention olla~ d high cut and provided fine finish and without any scribing grooves being observed in the finished surface of the steel workpiece. Although the initial cut of the inventive abrasive article was not aggressive at 4. 5 kg of pressure7 as soon as the rounded tips of the composites began to wear away within about 2 minutes the cut rate became excellent to provide a total cut of about 185 grams at 24 minutes.
l~arnple 2 An abrasive article was manufactured according to the "General Procedure for making the Abrasive Article" described hereul, and the same as used in Example 1, to provide Sample C. However, the abrasive article of Sample C was tested according to Test Procedure I except at about 9 kg of pressure and the test results are ~" " " " -,, rfi in Table 2. Three ...~.~u. ~ La were taken for each of Ra and Rz for each workpiece being refined by Sample C at several incipient and a later time of interest during grinding, and the average values thereof are indicated in Table 2.
The grinding time is indicated in Ill~ Cc~ C and the cut rate is quantified in grams that were abraded away for the period between each indicatedtime and the immediate prior time.
Table 2 Tirne Cut Ral Ra2 Ra3 Ra(ave) R~l RZ2 E~ (ave) 00:30 25.8 34 36 31 33.7 254 288 218 253.3 01:00 24.5 34 31 29 31.3 æ7 273 232 244 0 02:00 2Q0 25 23 26 24.5 lg7 176 220 197.7 03:00 16.0 04:00 13.1 05:00 11.2 06:00 10.8 121.4 (tota~ cut) .. , ., .. _ ~

Ihe results show that at 9 kg of initial pressure, the tips of the composites began to cut immediately and a total cut of about 171 grams was achieved within only about 6 minutes.
Various mnrlifi(~tinnc and alterations of this invention will become apparent 5 to those skilled in the art without departing from the scope and spirit of this.
invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

I .

41a

Claims

CLAIMS:

1. An abrasive article (1), characterized by a sheet-like structure including:
(a) a major surface (11, 25) extending within a first imaginary plane (111) with a plurality of individual three-dimensional abrasive composites (15, 21) deployed in fixed positions thereto to form an array on said major surface (11, 25), each of said composites (15, 21) comprising abrasive particles (16) dispersed in a binder (17) and having a substantially precise shape and a distal end (D) spacedfrom said major surface (11, 25), and wherein said plurality of composites each include cross-sections coplanar and parallel to said first imaginary plane (111) and include at least one composite(s) having a distal end (D') spaced nearest to said major surface (11, 25), as measured in a direction perpendicular to said first imaginary plane (111);
(b) wherein a second imaginary plane extends parallel to and is spaced from said first imaginary plane that intersects said nearest distal end, wherein any imaginary line drawn within said second imaginary plane intersects at least one said cross-section among said abrasive composites in said array.

2. The abrasive article of claim 1, wherein said composites (15, 21) have a geometrical shape having a first portion (28) in contact with a major surface (11, 25) of said sheet-like structure and a second portion (23) as an outer end,where said first portion comprises a frusto-conical shape and said second portion comprises a rounded shape.

3 . The abrasive article of claim 1, wherein each of said distal ends (D) are free from contact with any other said distal ends of said plurality of composites (15, 21).

4. The abrasive article of claim 1, wherein each said distal end (D) of said composites (15, 21) is vertically spaced from said major surface (11, 25) adistance (H) of about 50 micrometers to about 1020 micrometers.

5. The abrasive article of claim 1, wherein each said distal end (D) of said composites (15, 21) is vertically spaced substantially the same distance (H) from said major surface (11, 25).

6. The abrasive article of claim 1, wherein said abrasive composites (15, 21) are fixed on said major surface (11, 25) in a density of about 100 to about 10,000 abrasive composites/cm2.

7. An abrasive article (1) comprising a sheet-like structure including a major surface (11, 25) with a plurality of individual three-dimensional abrasivecomposites (15, 21) deployed in fixed positions thereto, each of said composites(15, 21) comprising abrasive particles (16) dispersed in a binder (17) and having a substantially precise shape, wherein said composites (15, 21) have a three-dimensional geometrical shape comprising a frusto-conical shape (28) in contact with said major surface (11, 25) and a rounded shape as a distal end (23).

8. A method for manufacturing an abrasive article according to claim 1, characterized by the steps of:
(a) preparing an abrasive slurry wherein the abrasive slurry comprises a plurality of abrasive particles dispersed in a binder precursor;
(b) providing (i) a backing (26, 41) having a front major surface with a machine direction axis (14) and a pair of opposite side edges (12, 13), each said side edge being parallel to said machine direction axis (14) and each side edge being respectively within a second and third imaginary plane (112, 113) each of which extends perpendicular to said front surface, and (ii) a production tool (46) having a major surface bounded by parallel opposing side edges and a plurality of cavities each defined by a walled recess baving an opening at said major surface, whereineach cavity comprises a precise shape defined by a distinct and discernible boundary which includes specific dimensions, whereby any imaginary line drawn to traversesaid major surface of said production tool in a direction parallel to said opposing side edges of said production tool intersects at least one cavity opening among said cavities of said array, (c) providing a means to apply said abrasive slurry into and at least filling a plurality of said cavities of said production tool (46);
(d) contacting said front major surface of said backing (26, 41) with said production tool (46) such that the abrasive slurry wets said front major surface;
(e) solidifying the binder precursor to form a binder, whereupon solidification the abrasive slurry is converted into a plurality of abrasive composites;
and (f) separating said production tool (46) from said from major surface after said solidifying to provide a plurality of individual three-dimensional abrasive composites (15, 21) attached in an array to said backing (26, 41) on a major surface (11, 25) thereof extending within a first imaginary plane (111), each of said composites (15, 21) comprising abrasive particles (16) dispersed in a binder (17) and having a substantially precise shape and a distal end (D) spaced from said major surface (11, 25), and wherein said plurality of composites (15, 21) each includecross-sections coplanar and parallel to said major surface (11, 25) and include at least one composite(s) having a distal end (D') spaced nearest to said major surface (11, 25), as measured in a direction perpendicular to said first imaginary plane(111), and wherein a fourth imaginary plane (114) extends parallel to and is spaced from said first imaginary plane (111) that intersects said nearest distal end (D'), wherein any imaginary line drawn within said fourth imaginary plane (114) in a direction parallel to said machine direction axis (14) and between said second and third imaginary planes (112, 113) intersects at least one said cross-section among said abrasive composites (15, 21) in said array.