WO2019102312A1

WO2019102312A1 - Abrasive article

Info

Publication number: WO2019102312A1
Application number: PCT/IB2018/058971
Authority: WO
Inventors: Aaron K. NIENABER; Thomas J. Nelson; Dwight D. Erickson
Original assignee: 3M Innovative Properties Company
Priority date: 2017-11-27
Filing date: 2018-11-14
Publication date: 2019-05-31
Also published as: US20200353594A1

Abstract

An abrasive article having a backing layer having a first major surface opposing a second major surface and a plurality of apertures extending from the first major surface to the second major surface. A plurality of abrasive particles having a first end with a smaller dimension than a second end and at least some of the plurality of abrasive particles located in at least some of the plurality of apertures such that the first end of the abrasive particle passes through an individual aperture and extends above the second major surface and the second end of the abrasive particle will not pass through the individual aperture. A binder coating applied to the plurality of abrasive particles retaining them in the backing layer.

Description

ABRASIVE ARTICLE

BACKGROUND

Abrasive particles and abrasive articles made from the abrasive particles are useful for abrading, finishing, or grinding a wide variety of materials and surfaces in the manufacturing of goods. As such, there continues to be a need for improving the cost, performance, or life of the abrasive particle and/or the abrasive article.

Triangular shaped abrasive particles and abrasive articles using the triangular shaped abrasive particles are disclosed in U.S. patents 5,201,916 to Berg; 5,366,523 to Rowenhorst; and 5,984,988 to Berg all herein incorporated by reference. In one embodiment, the abrasive particles’ shape comprised an equilateral triangle. Triangular shaped abrasive particles are useful in manufacturing abrasive articles having enhanced cut rates.

SUMMARY

In a coated abrasive article (e.g., sandpaper), the backing, in one embodiment, is a relatively dense planar substrate. A make layer precursor or make coat containing a first binder material precursor is applied to the backing, and then abrasive particles are partially embedded into the make layer precursor. In some embodiments, the formed abrasive particles, which have a shape selected for a sanding or grinding application, are embedded in the make layer precursor with a preferred orientation. Suitable techniques for orienting the particles include, for example, electrostatic coating or mechanical placement techniques.

The make layer precursor is then at least partially cured to retain the abrasive particles. A size layer precursor or size coat containing a second binder material precursor is overlaid on the at least partially cured make layer precursor and the abrasive particles. The size layer precursor, and the make layer precursor can then be further cured if needed to form a coated abrasive article.

Desirably, when using formed or shaped abrasive particles, they should remain in their orientation embedded in the binder material precursor until the binder precursor material has been sufficiently cured to fix them in place. Maintaining the preferred particle orientation can be difficult when the binder precursor material is viscous or fluid such that the formed abrasive particles may tip over by gravity. Alternatively, if the binder precursor material is sufficiently hard such that the formed abrasive particles do not adhere well to the binder precursor material they may again tip over due to gravity.

Maintaining preferred upright particle orientation is especially problematic as the size and weight of the formed or shaped abrasive particle becomes larger.

The inventors have discovered that by making a plurality of apertures in the backing, the abrasive particles can be located at least partially within the apertures such that the abrasive particles extend above the surface of the backing forming a grinding layer on one side of the backing. A binder precursor material can then be applied to the backing and the abrasive particles to lock the abrasive particles to the apertured backing. In one embodiment, when the apertures pass through the backing, the binder precursor can be applied to either the front of the backing where the abrasive particles protrude, the rear of the backing where the abrasive particles are too large to pass through the apertures, or to both surfaces. This not only retains the exact placement of the abrasive particles within the backing since they are locked within the apertures, it also substantially retains the vertical orientation of the shaped abrasive particles and prevents them from tipping over in the conventional process of electrostatic coating.

Hence, in one embodiment the invention resides in an abrasive article having a backing layer having a first major surface opposing a second major surface and a plurality of apertures extending from the first major surface to the second major surface. A plurality of abrasive particles having a first end with a smaller dimension than a second end and at least some of the plurality of abrasive particles located in at least some of the plurality of apertures such that the first end of the abrasive particle passes through an individual aperture and extends above the second major surface and the second end of the abrasive particle will not pass through the individual aperture. A binder coating applied to the plurality of abrasive particles retaining them in the backing layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 illustrates one embodiment for making the abrasive article and the abrasive article.

FIG. 2 illustrates a triangular shaped abrasive particle and an apertured backing.

FIG. 3 illustrates one embodiment for coating the abrasive article. DEFINITIONS

As used herein, forms of the words "comprise", "have", and "include" are legally equivalent and open-ended. Therefore, additional non-recited elements, functions, steps or limitations may be present in addition to the recited elements, functions, steps, or limitations.

As used herein, the term "abrasive dispersion" means an alpha alumina precursor that can be converted into alpha alumina that is introduced into a mold cavity. The composition is referred to as an abrasive dispersion until sufficient volatile components are removed to bring solidification of the abrasive dispersion.

As used herein“formed ceramic abrasive particle” means a ceramic abrasive particle having at least a partially replicated shape. Non-limiting processes to make formed abrasive particles include shaping the precursor abrasive particle in a mold having a predetermined shape, extruding the precursor abrasive particle through an orifice having a predetermined shape, printing the precursor abrasive particle though an opening in a printing screen having a predetermined shape, or embossing the precursor abrasive particle into a predetermined shape or pattern. Formed abrasive particles are monolithic and do not use a binder holding together a plurality of abrasive particles that are compacted and formed into an agglomerate. Non-limiting examples of formed ceramic abrasive particles include shaped abrasive particles formed by a screen, such as triangular plates as disclosed in U.S. patent numbers RE 35,570; 5,201,916, and 5,984,998; or extruded elongated ceramic rods/filaments often having a circular cross section produced by Saint-Gobain Abrasives an example of which is disclosed in U.S. patent number 5,372,620. Formed abrasive particle as used herein excludes randomly sized abrasive particles obtained by a mechanical crushing operation.

As used herein, the term "precursor shaped abrasive particle" means the unsintered particle produced by removing a sufficient amount of the volatile component from the abrasive dispersion, when it is in the mold cavity, to form a solidified body that can be removed from the mold cavity and substantially retain its molded shape in subsequent processing operations.

As used herein, the term“shaped abrasive particle”, means a ceramic abrasive particle with at least a portion of the abrasive particle having a predetermined shape that is replicated from a mold cavity used to form the shaped precursor abrasive particle. Except in the case of abrasive shards (e.g. as described in U.S. patent publication US 2009/0169816, the shaped abrasive particle will generally have a predetermined geometric shape that substantially replicates the mold cavity that was used to form the shaped abrasive particle. Shaped abrasive particles are monolithic and do not use a binder holding together a plurality of abrasive particles that are compacted and formed into an

agglomerate. Shaped abrasive particle as used herein excludes randomly sized abrasive particles obtained by a mechanical crushing operation.

As used herein,“z-direction rotational orientation” refers to the particle’s angular rotation about a z-axis passing through the particle and through the backing at a 90 degree angle to the backing when the particle is attached to the backing by a make layer.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2, a backing 100 has a first major surface 110 and a second major surface 120. A plurality of apertures 130 are located in the backing. In one embodiment, the plurality of apertures 130 extend from the first major surface 110 through the backing to the second major surface 120 and the plurality of apertures are through holes. In other embodiments when the backing is thicker and/or more rigid, the plurality of apertures 130 can be blind holes located in either the first major surface 110 or in the second major surface 120.

A plurality of abrasive particles 150 are at least partially located in the apertures.

In one embodiment, the plurality of abrasive particles has a first end 160 with at least one smaller dimension 165 than a second end 170. At least some of the plurality of abrasive particles 150 located in at least some of the plurality of apertures 130 such that the first end 160 of the abrasive particle passes through an individual aperture and extends above the second major surface 120. The apertures are sized such that the second end 170 of the abrasive particle does not pass through the individual aperture due to the difference in the dimension 165 between the first end and the second end. Thus, the abrasive particles 150 can be tapered, stepped, discontinuous, have a projection, or other feature that allows a portion of the abrasive particle 150 to pass through the aperture 130 while another portion is retained by the aperture due to the smaller dimension 165 of the first end when compared to the second end. In various embodiments, formed abrasive particles, shaped abrasive particles, agglomerates, or even crushed abrasive particles that are elongated and tapered can be used. A suitable precursor binder material 180 is then applied to either the first major surface 110 and the second ends 170, the second major surface 120 and the first ends 160, or to both surfaces and ends of the abrasive particles to adhere and secure the abrasive particles 150 to the backing 100. After application of the binder, the material is cured and/or dried to firmly lock the abrasive particles 150 in the apertures 130.

In a conventional coated abrasive article, a make coat is applied to the backing and abrasive particles are then applied to the make coat where they become attached while the make coat is at least partially cured. A size coat is then applied over the abrasive particles. Then the make coat and the size coat are fully cured to secure the abrasive particles to the backing. Even still, pull out or grit loss can occur under high grinding loads when the abrasive particles are shelled or pulled out from the abrasive layer in use. Because the abrasive particles in the present invention, in one embodiment, cannot completely pass through the apertures (due to the at least one dimensional difference 165 between the first and second ends in relation to the size of the aperture), the abrasive articles are

mechanically locked to the backing and grit loss or shelling can be reduced as the abrasive particles must physically tear their way through the backing to be pulled out.

Another feature of the present invention is that the abrasive particles can be applied to the backing layer prior to it being coated with a make coat or a binder precursor material. This can reduce the manufacturing complexity and make it easier to recycle the extra abrasive particles that do not land within an aperture for a subsequent application to the backing. Furthermore, in some embodiments the abrasive particles are not obscured or buried in the resin since the binder material is on the back surface (110) and not on the abrasive layer side (120). Hence the abrasive particle can be completely used down to the backing without interference from the binder material.

Another feature of the present invention, is to use differently sized apertures and/or abrasive particles such that the first ends 160 extend to differing heights from the first major surface 120. Thus,“fresh” abrasive particles can be provided such that as grinding progresses new abrasive particles come into contact with the workpiece. Since the height of the abrasive particle above the first major surface 120 can be controlled by the aperture’s size and how far it allows the first end 160 to protrude, the heights of the abrasive particles can be easily varied even though they may all be approximately the same size. For example, three different aperture holes sizes could be punched or laser cut into the backing when using the same sized equilaterally triangle, and the abrasive layer would have three different heights for the first end 160 of the abrasive particles. A convention make coat process would result in the abrasive layer having a uniform height for the first ends 160.

Another feature of the invention, is that because the abrasive particles are secured in the apertures they have a precisely fixed orientation both in the X and Y plane of the backing and with regard to their z-direction rotational orientation. The density, individual placement and orientation of the aperture uniquely controls the same features of the abrasive particles. Creating a pattern in the abrasive layer is as simple as creating that pattern in the plurality of apertures and then filling them up with protruding abrasive particles.

Another feature of the inventions, is that manufacturing costs can be reduced since an additional binder layer such as a size coat can be eliminated in some embodiments. In some embodiments, a single binder layer covering the first major surface 110 and the second ends 170 is all that is required to form the coated abrasive article.

The various components of the abrasive article will be discussed in further detail in the following sections. The coated abrasive article with an apertured backing may be in the form of sheets, discs, belts, pads, or rolls. In some embodiments, the backing should be sufficiently flexible to allow the coated abrasive article to be formed into a loop to make an abrasive belt that can be run on suitable grinding equipment.

Apertured Backing

Suitable backings include polymeric films, metal foils, woven fabrics, knitted fabrics, paper, vulcanized fiber, nonwovens, foams, screens, laminates, netting, thin tissue layer, and combinations thereof. Thinner backing materials can be reinforced through the application of thicker binder coatings on either the first major surface 110, the second major surface 120, or both surfaces. Maximum thickness of the backing material is controlled by the height of the abrasive particles since at least part of the particle should extend above the second major surface 120. Suitable backings can have a thickness of approximately 10-40 mils.

The backing has a plurality of apertures as previously discussed. The backing may be a continuous sheet with the apertures die cut, punched or laser cut through the backing. Alternatively, the backing may be in the form of a woven screen or netting material. A suitable netting-like extendable scrim for the backing is disclosed in WO2018/063962 and herein incorporated by reference in its entirety. In one embodiment, the netting-like extendable scrim had at least two elongate strands periodically joined together at bond regions to form an array or apertures between the strands. The apertures can have a first minimum dimension and at least some of the bond regions are flexible. The scrim is extendable along at least one direction into an extended scrim and the apertures increase in size to a second minimum dimension that is larger than the first minimum dimension.

The plurality of apertures 130 are desirably arranged into a pattern versus randomly located. The pattern geometry and abrasive particle density can be selected based on the cutting performance desired, direction and travel of the coated abrasive article and/or the workpiece relative to each other, material of the workpiece, and the shape of the abrasive particle. Suitable patterns are disclosed in US 2013/0344786 herein incorporated by reference. In the‘786 patent application, Figures 2-5 show various suitable patterns that are discussed in paragraphs [0047] to [0058], which figures and paragraphs are specifically referenced and incorporated herein by reference. The abrasive particles may be arranged in concentric circumferential circles, linearly in parallel lines parallel to the longitudinal axis, linearly in parallel lines parallel to the transverse axis, radially in lines radiating outward from a point, or rotated at an angle such as 45 degrees to the direction of the disc’s or belt’s travel, or in a crosshatch or parquet pattern. Other suitable patterns include spiral wherein the abrasive particles are disposed at regularly-spaced points along an arithmetic spiral pattern extending outwardly from a center of the disc towards outer circumference. A double parquet where a first set of two abrasive particles are disposed parallel to each other, a second set of two abrasive particles are disposed parallel to each other, and the first set and the second set are disposed at approximately ninety degrees to each other. A saw tooth spiral pattern wherein the abrasive particles are disposed at regularly-spaced points along an arithmetic spiral and wherein a z-axis rotational orientation pivots a sequence of three abrasive particles alternately such that a face of the first abrasive particle is at a positive angle to the tangent line of the spiral, the same face of the second abrasive particle is then parallel to the tangent line, and then the same face of the third abrasive particle is at a negative angle to the tangent line where upon the pattern for each of the next three abrasive particles repeats itself again as best seen in FIGS. 1B and 4B of U.S. Provisional application no. 62/589,248, filed November 21, 2017, attorney docket number 79831US002. These patterns are disclosed in US patent applications having attorney docket numbers: 79447US002 entitled Coated Abrasive Disc and Methods of Making and Using the Same filed on November 21, 2017 U.S. application no. 62/589,193); 79691US002 entitled Coated Abrasive Disc and Methods of Making and Using the Same filed on November 21, 2017 U.S. application no. 62/589,186;

79692US002 entitled Coated Abrasive Disc and Methods of Making and Using the Same filed on November 21, 2017 (U.S. application no. 62/589,164); and 79831US002 entitled Coated Abrasive Disc and Methods of Making and Using the Same filed on November 21, 2017 (U.S. application no. 62/589,248) all of which are herein incorporated by reference.

The apertures may be square, rectangular, round, oval, trapezoid, or other suitable geometric shape. In one embodiment, rectangular apertures were used that contained triangular shaped abrasive particles similar to those shown in FIG. 2. The rectangle was sized such that at least 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95 percent of the triangle’s height, h, projected above the first major surface 120 of the apertured backing.

In another embodiment, a rectangular aperture was used having a width, w, and thickness, t, as illustrated in FIG. 2. A triangular shaped abrasive particle having a width, w, of the second end 170 and a thickness, t, was positioned in the apertures. The width, w, of the second end of the abrasive particle is at least 10 percent greater than the width, w, of the aperture 130. In some embodiments, the width, w, of the base of the abrasive particle is no more than 40 percent greater than the width, w, of the aperture. In some

embodiments, the plurality of particles comprises triangular particles having a base dimension of X in width and the plurality of apertures comprise a rectangular shape having a width dimension of 0.6X to 0.90X. In some embodiments, the base dimension is 1.5 mm and the aperture width dimension ranges from 0.9 mm to 1.35 mm.

Abrasive Particles

The plurality of abrasive particle, in one embodiment, have a first end 160 with a smaller dimension 165 in either its width or thickness or both than a second end 170. At least some of the plurality of abrasive particles 150 are located in at least some of the plurality of apertures 130 such that the first end 160 of the abrasive particle passes through an individual aperture and extends above the second major surface 120 and the second end 170 of the abrasive particle will not pass through the individual aperture. Thus, the abrasive particles can be tapered, stepped, discontinuous, have a projection, or other feature that allows a portion of the abrasive particle to pass through the aperture while another portion is retained by the aperture. In various embodiments, formed abrasive particles, shaped abrasive particles, agglomerates, or even crushed abrasive particles that are elongated and tapered can be used.

In one embodiment, a triangular shaped abrasive particle with a sloping sidewall is used. The first end 160 of the triangular shaped abrasive particle is one of the three vertexes and the second end 170 is the opposing base. The width (165) of the vertex is significantly smaller than the width (165) of the base while the thickness of each is substantially the same. Triangular shaped abrasive particles with a sloping sidewall are disclosed in US patent number 8,142,531 entitled Shaped Abrasive Particles with a sloping sidewall filed on December 17, 2008 and herein incorporated by reference. The material from which the shaped abrasive particle with a sloping sidewall is made comprises a ceramic and specifically in one embodiment alpha alumina. Alpha alumina particles can be made from a dispersion of aluminum oxide monohydrate that is gelled, molded to shape, dried to retain the shape, calcined, and then sintered. The shaped abrasive particle’s shape is retained without the need for a binder to form an agglomerate comprising abrasive particles in a binder that are then compacted or manipulated into a shaped structure.

In general, the shaped abrasive particles with a sloping sidewall comprise thin bodies having a first face, and a second face and having a thickness t. The first face and the second face are connected to each other by at least one sloping sidewall. In some embodiments, more than one sloping sidewall can be present and the slope or angle for each sloping sidewall may be the same as shown or different.

In some embodiments, the first face is substantially planar, the second face is substantially planar, or both faces are substantially planar. Alternatively, the faces could be concave or convex as discussed in more detail in U.S. patent publication 2010/0151195 entitled“Dish-Shaped Abrasive Particles With A Recessed Surface”, filed on December 17, 2008. Additionally, an opening or aperture through the faces could be present as discussed in more detail in U.S. patent publication 2010/0151201 entitled“Shaped Abrasive Particles With An Opening, filed on December 17, 2008. Both disclosures herein incorporated by reference.

In one embodiment, the first face and the second face are substantially parallel to each other. In other embodiments, the first face and second face can be nonparallel such that one face is sloped with respect to the other face and imaginary lines tangent to each face would intersect at a point. The sloping sidewall of the shaped abrasive particle with a sloping sidewall can vary and it generally forms the perimeter of the first face and the second face. In one embodiment, the perimeter of the first face and second face is selected to be a geometric shape, and the first face and the second face are selected to have the same geometric shape, although, they differ in size with one face being larger than the other face. In one embodiment, the perimeter of first face and the perimeter of the second face was a triangular shape. In some embodiments, an equilateral triangular particle is used.

A draft angle a between the second face and the sloping sidewall of the shaped abrasive particle can be varied to change the relative sizes of each face. In various embodiments of the invention, the draft angle a can be between about 90 degrees to about 130 degrees, or between about 95 degrees to about 130 degrees, or between about 95 degrees to about 125 degrees, or between about 95 degrees to about 120 degrees, or between about 95 degrees to about 115 degrees, or between about 95 degrees to about 110 degrees, or between about 95 degrees to about 105 degrees, or between about 95 degrees to about 100 degrees. As discussed in U.S. patent number 8,142,531 entitled“Shaped Abrasive Particles With A Sloping Sidewall” filed on December 17, 2008, specific ranges for the draft angle a have been found to produce surprising increases in the grinding performance of coated abrasive articles made from the shaped abrasive particles with a sloping sidewall.

Any other suitable formed or shaped abrasives particle can be used. Other suitable shapes are a tetrahedron, a tapered rod, a tapered elongated geometric shape, triangles with a concave curvilinear side, or intersecting plate abrasive particles.

Binder Coating

The binder coating to secure the abrasive particles comprises a resinous adhesive. The resinous adhesive applied to either the first major surface or to the second major surface or both can be the same as or different from each other. Examples of resinous adhesives that are suitable for these coats include phenolic resins, epoxy resins, urea- formaldehyde resins, acrylate resins, aminoplast resins, melamine resins, acrylated epoxy resins, urethane resins and combinations thereof. In addition to the resinous adhesive, may further comprise additives that are known in the art, such as, for example, fillers, grinding aids, wetting agents, surfactants, dyes, pigments, coupling agents, adhesion promoters, and combinations thereof. Examples of fillers include calcium carbonate, silica, talc, clay, calcium metasilicate, dolomite, aluminum sulfate and combinations thereof.

A grinding aid can be applied to the coated abrasive article. A grinding aid is defined as particulate material, the addition of which has a significant effect on the chemical and physical processes of abrading, thereby resulting in improved performance. Grinding aids encompass a wide variety of different materials and can be inorganic or organic. Examples of chemical groups of grinding aids include waxes, organic halide compounds, halide salts, and metals and their alloys. The organic halide compounds will typically break down during abrading and release a halogen acid or a gaseous halide compound. Examples of such materials include chlorinated waxes, such as

tetrachloronaphthalene, pentachloronaphthalene; and polyvinyl chloride. Examples of halide salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluorob orate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride. Examples of metals include tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium. Other grinding aids include sulfur, organic sulfur compounds, graphite, and metallic sulfides. It is also within the scope of this invention to use a combination of different grinding aids; in some instances, this may produce a synergistic effect. In one embodiment, the grinding aid was cryolite or potassium tetrafluoroborate. The amount of such additives can be adjusted to give desired properties.

It is also within the scope of this invention to utilize a supersize coating applied to the second major surface. The supersize coating typically contains a binder and a grinding aid. The binders can be formed from such materials as phenolic resins, acrylate resins, epoxy resins, urea-formaldehyde resins, melamine resins, urethane resins, and

combinations thereof.

In order that the invention described herein can be more fully understood, the following examples are set forth. It should be understood that these examples are for illustrative purposes only, and are not to be construed as limiting this invention in any manner.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure. Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.

Unless stated otherwise, all other reagents were obtained, or are available from fine chemical vendors such as Sigma-Aldrich Company, St. Louis, Missouri, or may be synthesized by known methods.

Unit Abbreviations used in the Examples:

°C: degrees Centigrade

cm: centimeter

g: gram

g/m²: grams per square meter

mm: millimeter

Abrasive Particles Used in the Examples:

AP1 : Shaped abrasive particles were prepared according to the disclosure of U.S. Patent 8,142,531 (Adefris et al.). The shaped abrasive particles were prepared by molding alumina sol gel in equilateral triangle-shaped polypropylene mold cavities. After drying and firing, the resulting shaped abrasive particles were about 1.5 mm (side length) x 0.3 mm (thickness), with a draft angle approximately 98 degrees.

EXAMPLE 1

A 7-inch (l7.8-cm) diameter x 0.83-mm thick vulcanized fiber web (obtained as DYNOS VULCANIZED FIBER, from DYNOS GmbH, Troisdorf, Germany) was used as a fiber disc backing. The fiber disc backing was processed through a laser cutting machine to achieve a spiral hole pattern throughout a disc. The hole pattern began at an inner diameter of 89 mm and spiraled to the outer edge of the disc at a pitch of 25 revolutions per inch with a hole spacing of 2 mm. Each hole was primarily rectangular in shape with dimensions of 1.3 mm by 0.58 mm. The longer of the rectangular dimensions tangentially followed the direction of the spiral.

The fiber disc backing with the patterned holes was filled with AP1 by method of providing an excess of AP1 onto major surface 1 and gently shaking the disc back and forth until substantially all of the holes had a mineral AP1 with a tip protruding through the disc to major surface 2 which would in future serve as the cutting surface. The resultant add-on weight of AP1 was 8.3g.

The backing was held in the position with the first major surface facing upward while a urethane resin, obtained under trade designation ALBERDINGK U 6150 from Alberdingk Boley, Greensboro, North Carolina, was applied by means of a spray nozzle at a total weight of 6g ± .5 g. The sample was placed into the oven for a time of 20 minutes at 82 °C.

The disc was removed from the oven and inverted such that the second major surface was facing upwards. A conventional cryolite-containing phenolic size resin was rolled onto disc by a hand roller at a weight of 8 g with a variation of ± .5 g. The sample was placed into the oven and cured (45 minutes at 70°C, followed by 45 minutes at 90°C followed by 16 hours at l05°C).

COMPARATIVE EXAMPLE A

A 7-inch (l7.8-cm) 982C 36+ fiber disc, obtained as 982C grade 36+ from 3M Company, Saint Paul, Minnesota, was used. The 982C 36+ fiber disc utilized

approximately 16 g of AP1 grain.

Performance Test

The abrasive discs were tested using the following procedure. Seven-inch (17.8- cm) diameter abrasive discs for evaluation were attached to a rotary grinder fitted with a 7- inch (17.8 cm) ribbed disc pad face plate (“051144” EXTRA HARD RED RIBBED, obtained from 3M Company). The grinder was then activated and urged against an end face of a 0.75 ^c 0.75 inch (1.9 ^c 1.9 cm) pre-weighed 1045 steel bar under a load of 9 pounds (4.1 kilograms). The resulting rotational speed of the grinder under this load and against this workpiece was 5000 rpm. The workpiece was abraded under these conditions for a total of twenty (20) 20-second grinding intervals (passes). Following each 20-second interval, the workpiece was allowed to cool to room temperature and weighed to determine the cut of the abrasive operation. Test results were reported in Table 1 as the incremental cut for each interval and the total cut removed. TABLE 1

EMODIMENTS OF THE INVENTION

Various embodiments of the invention can be provided as follows.

Embodiment 1. An abrasive article comprising:

a backing layer having a first major surface opposing a second major surface and a plurality of apertures extending from the first major surface to the second major surface; a plurality of abrasive particles having a first end with a smaller dimension than a second end;

at least some of the plurality of abrasive particles located in at least some of the plurality of apertures such that the first end of the abrasive particle passes through an individual aperture and extends above the second major surface and the second end of the abrasive particle will not pass through the individual aperture; and

a binder coating applied to the plurality of abrasive particles retaining them in the backing layer. Embodiment 2. The abrasive article of embodiment 1 wherein for a majority of the plurality of apertures only one abrasive particle resides in an individual aperture.

Embodiment 3. The abrasive article of claim 1 wherein more than one individual abrasive particle resides in an individual aperture.

Embodiment 4. The abrasive article of any preceding embodiment wherein the plurality of abrasive particles comprise formed abrasive particles.

Embodiment 5. The abrasive article of embodiment 4 wherein the plurality of abrasive particles compromise a triangular shape and a vertex of the triangle comprises the first end and extends above the second major surface and a base of the triangle comprises the second end and extends above the first major surface.

Embodiment 6. The abrasive article of embodiment 5 where a width dimension of the base is at least 10% greater than a width dimension of the apertures and the width dimension of the base is no more than 40% greater than the width dimension of the apertures.

Embodiment 7. The abrasive article of any preceding embodiment wherein the plurality of apertures comprise a shape selected from the group consisting of rectangular, oval, square, circle, and trapezoid.

Embodiment 8. The abrasive article of any preceding embodiment wherein the plurality of apertures are arranged in a pattern selected form the group consisting of spiral, linear, double parquet, and sawtooth.

Embodiment 9. The abrasive article of any preceding embodiment wherein the backing comprises a thickness of between 10 to 40 mils.

Embodiment 10. The abrasive article of any preceding embodiment wherein the plurality of particles comprise triangular particles having a base dimension of X in width and the plurality of apertures comprise a rectangular shape having a width dimension of 0.6X to 0.90X.

Embodiment 11. The abrasive article of any preceding embodiment wherein the binder is applied to the second ends of the abrasive particles and the second major surface.

Embodiment 12. A method of making an abrasive article comprising:

forming a backing layer having a first major surface opposing a second major surface and a plurality of apertures extending from the first major surface to the second major surface; providing a plurality of abrasive particles having a first end with a smaller dimension than a second end;

positioning at least some of the plurality of abrasive particles in at least some of the plurality of apertures such that the first end of the abrasive particle passes through an individual aperture and extends above the second major surface and the second end of the abrasive particle will not pass through the individual aperture; and

applying a binder coating applied to the plurality of abrasive particles retaining them in the backing layer.

Embodiment 13. The method of embodiment 12 wherein the backing layer does not have a binder coating applied to it prior to applying the abrasive particles.

Embodiment 14. The method of embodiment 13 wherein the binder coating is applied to the second ends of the abrasive particles and the first major surface.

Embodiment 15. The method of embodiment 14 further comprising the step of bringing the first ends of the abrasive particles into contact with a workpiece and inducing relative motion between the workpiece and the first ends to abrade the workpiece.

Persons of ordinary skill in the art may appreciate that various changes and modifications may be made to the invention described above without deviating from the inventive concept. Thus, the scope of the present invention should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.

Claims

What is claimed is:

1. An abrasive article comprising:

a binder coating applied to the plurality of abrasive particles retaining them in the backing layer.

2. The abrasive article of claim 1 wherein for a majority of the plurality of apertures only one abrasive particle resides in an individual aperture.

3. The abrasive article of claim 1 wherein more than one individual abrasive particle resides in an individual aperture.

4. The abrasive article of any preceding claim wherein the plurality of abrasive particles comprise formed abrasive particles.

5. The abrasive article of claim 4 wherein the plurality of abrasive particles compromise a triangular shape and a vertex of the triangle comprises the first end and extends above the second major surface and a base of the triangle comprises the second end and extends above the first major surface.

6. The abrasive article of claim 5 where a width dimension of the base is at least 10% greater than a width dimension of the apertures and the width dimension of the base is no more than 40% greater than the width dimension of the apertures.

7. The abrasive article of any preceding claim wherein the plurality of apertures comprise a shape selected from the group consisting of rectangular, oval, square, circle, and trapezoid.

8. The abrasive article of any preceding claim wherein the plurality of apertures are arranged in a pattern selected form the group consisting of spiral, linear, double parquet, and sawtooth.

9. The abrasive article of any preceding claim wherein the backing comprises a thickness of between 10 to 40 mils.

10. The abrasive article of any preceding claim wherein the plurality of particles comprise triangular particles having a base dimension of X in width and the plurality of apertures comprise a rectangular shape having a width dimension of 0.6X to 0.90X.

11. The abrasive article of any preceding claim wherein the binder is applied to the second ends of the abrasive particles and the second major surface.

12. A method of making an abrasive article comprising:

forming a backing layer having a first major surface opposing a second major surface and a plurality of apertures extending from the first major surface to the second major surface;

providing a plurality of abrasive particles having a first end with a smaller dimension than a second end;

13. The method of claim 12 wherein the backing layer does not have a binder coating applied to it prior to applying the abrasive particles.

14. The method of claim 13 wherein the binder coating is applied to the second ends of the abrasive particles and the first major surface.

15. The method of claim 14 further comprising the step of bringing the first ends of the abrasive particles into contact with a workpiece and inducing relative motion between the workpiece and the first ends to abrade the workpiece.