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Title:
COATED ABRASIVE DISC AND METHODS OF MAKING AND USING THE SAME
Document Type and Number:
WIPO Patent Application WO/2019/102331
Kind Code:
A1
Abstract:
A coated abrasive disc includes a disc backing having an outer circumference. An abrasive layer is disposed on the disc backing. The abrasive layer comprises triangular abrasive platelets secured to a major surface of the disc backing by at least one binder material. The triangular abrasive platelets are outwardly disposed at regularly-spaced points along a spiral pattern extending outwardly toward the outer circumference. Each triangular abrasive platelet has respective top and bottom surfaces connected to each other, and separated by, three sidewalls. On a respective basis, one sidewall of at least 90 percent of the triangular abrasive platelets is disposed facing and proximate to the disc backing, and at least 70 percent of the triangular abrasive platelets are disposed in a recurring sequential orientation having an oscillating Z-axis rotational orientation of the first respective sidewall relative to the tangents to the spiral pattern at regularly-spaced points. Methods of making and using the coated abrasive disc are also disclosed.

Inventors:
HANSCHEN, Thomas P. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
KEIPERT, Steven J. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
ECKEL, Joseph B. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
NIENABER, Aaron K. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
SPRING, Erin D. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
MOEGENBURG, Brant A. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
MOORE, Eric M. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
NELSON, Thomas J. (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
Application Number:
IB2018/059065
Publication Date:
May 31, 2019
Filing Date:
November 16, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
3M INNOVATIVE PROPERTIES COMPANY (3M Center, Post Office Box 33427Saint Paul, Minnesota, 55133-3427, US)
International Classes:
B24D3/00; B24D3/28; B24D11/02; C09K3/14
Foreign References:
US20170225299A12017-08-10
US20130344786A12013-12-26
US20170252898A12017-09-07
US9457453B22016-10-04
US20160289521A12016-10-06
Attorney, Agent or Firm:
WRIGHT, Bradford B. , et al. (3M Center, Office of Intellectual Property CounselPost Office Box 3342, Saint Paul Minnesota, 55133-3427, US)
Download PDF:
Claims:
What is claimed is:

1. A coated abrasive disc comprising:

a disc backing having an outer circumference;

an abrasive layer disposed on the disc backing, wherein the abrasive layer comprises triangular abrasive platelets secured to a major surface of the disc backing by at least one binder material, wherein the triangular abrasive platelets are outwardly disposed at regularly-spaced points along a spiral pattern extending outwardly toward the outer circumference,

wherein each one of site triangular abrasive platelets has respective top and bottom surfaces connected to each other, and separated by, three sidewalls,

wherein, on a respective basis, one sidewall of at least 90 percent of die triangular abrasive platelets is disposed facing and proximate to the disc backing, and

wherein at least 70 percent of the triangular abrasive platelets are disposed in a recurring sequential orientation having:

i) a first triangular abrasive platelet with a first respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the first respective sidewall is longitudinally outwardly oriented at an angle of -10 to -40 degrees relative to the tangent to the spiral pattern at a first one of the regularly -spaced poi nts ;

ii) a second triangular abrasive platelet with a second respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the second respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a second one of tire regularl -spaced points;

iii) a third triangular abrasive platelet with a third respective sidewall facing tire disc backing, wherein the Z-axis rotational orientation of the third respective sidewall is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to the spiral pattern at a third one of the regularly-spaced points; and

iv) a fourth triangular abrasive platelet with a fourth respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the fourth respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a fourth one of the regularly-spaced points.

2. The abrasive disc of claim 1, wherein the triangular abrasive platelets have an average thickness, wherein the spiral pattern comprises a spiral pattern, and wherein the arithmetic spiral pattern lias a pitch that is 1 to 3 times the average thickness of the triangular abrasive platelets.

3. The abrasive disc of claim 1, wherein the abrasive layer further comprises crushed abrasive or non-abrasive particles.

7

4. The abrasive disc of claim 1, wherein the disc backing comprises vulcanized fiber.

5. The abrasive disc of claim 1, wherein the abrasive layer comprises a make layer and a size layer disposed over the make layer and the triangular abrasive platelets.

6. The abrasive disc of claim 1, wherein the triangular abrasive platelets comprise alpha alumina.

7. A method of abrading, the method comprising frictionaliy contacting a portion of the abrasive layer of a coated abrasive disc according to any one of claims 1 to 8 with a substrate, and moving at least one of the substrate and die abrasive disc relative to Site other to abrade the substrate.

8. The method of claim 7, wherein the substrate comprises carbon steel, and wherein the abrasive layer contacts the carbon steel.

9. A method of making a coated abrasive disc, the method comprising:

disposing a curable make layer precursor on a major surface of a disc backing;

embedding triangular abrasive platelets into the curable make layer precursor, wherein the triangular abrasive platelets are outwardly disposed at regularly -spaced points along a spiral pattern extending outwardly toward the outer circumference,

wherein each one of the triangular abrasive platelets has respective top and bottom surfaces connected to each oilier, and separated by, three sidewalls,

wherein, on a respective basis, one sidewall of at least 90 percent of tire triangular abrasive platelets is disposed lacing and proximate to the disc backing, and

wherein at least 70 percent of the triangular abrasive platelets are disposed in a recurring sequential orientation having:

i) a first triangular abrasive platelet with a first respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the first respective sidewall is longitudinally’ outwardly oriented at an angle of -10 to -40 degrees relative to the tangent to the spiral pattern at a first one of the regularly-spaced points;

ii) a second triangular abrasive platelet with a second respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the second respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to die spiral pattern at a second one of the regularly-spaced points;

iii) a third triangular abrasive platelet with a third respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the third respective sidewall is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to the spiral patern at a third one of the regularly-spaced points; and

iv) a fourth triangular abrasive platelet with a fourth respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the fourth respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a fourth one of the regularly-spaced points;

at least partially curing the curable make layer precursor to provide a make layer;

disposing a curable size layer precursor over the make layer and triangular abrasive platelets; and at least partially curing the curable size layer precursor to provide a size layer.

10. The method of claim 9, wherein the triangular abrasive platelets have an average thickness, wherein the spiral pattern comprises a spiral pattern, and wherein the arithmetic spiral pattern lias a pitch that is 1 to 3 times the average thickness of the triangular abrasive platelets. 11. The method of claim 9, wTserein the abrasive layer further comprises crushed abrasive or nonabrasive particles.

12. The method of claim 9, wherein the disc backing comprises vulcanized fiber. 13. The method of claim 9, wherein the triangular abrasive platelets comprise alpha alumina.

Description:
COATED ABRASIVE DISC AND METHODS OF MAKING AND USING THE SAME

TECHNICAL FIELD

The present disclosure broadly relates to coated abrasive discs, methods of making them, and methods of using them.

BACKGROUND

Coated abrasive discs made from triangular abrasive platelets are useful for abrading, finishing, or grinding a wide variety of materials and surfaces in the manufacturing of goods. In particular, high- pressure off-hand grinding of high carbon steel by off-hand abrading with a handheld right-angle grinder is an important application for coated abrasive discs. In view of Site above, there continues to be a need for improving the cost, performance, and/or life of the coated abrasive discs.

Coated abrasive articles having rotationally aligned triangular abrasive platelets are disclosed in U. S. Pat. No. 9,776,302 (Keipert). The coated abrasive articles have a plurality of triangular abrasive platelets each having a surface fea ture. The plurality of triangular abrasive platelets is attached to a flexible backing by a make coat comprising a resinous adhesive forming an abrasive layer. The surface features have a specified z-direction rotational orientation that occurs more frequently in the abrasive layer than would occur by a random z-direction rotational orientation of the surface feature.

SUMMARY

In one aspect, the present disclosure pro vides a coated abrasive disc comprising:

a disc backing having an outer circumference;

an abrasive layer disposed on the disc backing, wherein the abrasive layer comprises triangular abrasive platelets secured to a major surface of tire disc backing by at least one binder material, wherein the triangular abrasive platelets are outwardly disposed at regularly -spaced points along a spiral pattern extending outwardly toward the outer circumference,

wherein each one of the triangular abrasive platelets has respective top and bottom surfaces connected to each other, and separated by, three sidewalls,

wherein, on a respective basis, one sidewall of at least 90 percent of the triangular abrasive platelets is disposed facing and proximate to the disc backing, and

wherein at least 70 percent of the triangular abrasive platelets are disposed in a recurring sequential orientation having:

i) a first triangular abrasive platelet with a first respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the first respective sidewall is longitudinally outwardly oriented at an angle of -10 to -40 degrees relative to the tangent to the spiral pattern at a first one of the regularly-spaced points; ii) a second triangular abrasive platelet with a second respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the second respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a second one of the regularly -spaced points;

iii) a third triangular abrasive platelet with a third respective sidewall lacing tire disc backing, wherein the Z-axis rotational orientation of tire third respective sidewall is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to the spiral pattern at a third one of the regularly-spaced points; and

iv) a fourth triangular abrasive platelet with a fourth respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the fourth respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a fourth one of the regularly-spaced points.

Advantageously, coated abrasive discs according to tire present disclosure are useful for high- pressure off-hand abrading of high carbon steel, where they exhibit superior performance as compared to previous similar discs.

Accordingly, in a second aspect, the present disclosure provides a method of abrading a workpiece, the method comprising frictionaliy contacting a portion of the abrasive layer of a coated abrasive disc according to the present disclosure with a workpiece, and moving at least one of the workpiece and the coated abrasive disc relative to the other to abrade the workpiece.

In a third aspect, the present disclosure provides a method of making a coated abrasive disc, the method comprising:

disposing a curable make layer precursor on a major surface of a disc backing;

embedding triangular abrasive platelets into the curable make layer precursor, wherein the triangular abrasive platelets are outwardly disposed at regularly -spaced points along an spiral pattern extending outwardly toward tire outer circumference,

wherein each one of the triangular abrasive platelets has respective top and bottom surfaces connected to each other, and separated by, three sidewalls,

wherein, on a respective basis, one sidewnll of at least 90 percent of the triangular abrasive platelets is disposed facing and proximate to the disc backing, and

wherein at least 70 percent of the triangular abrasive platelets are disposed in a recurring sequential orientation having:

i) a first triangular abrasive platelet with a first respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the first respective sidewall is longitudinally outwardly oriented at an angle of -10 to -40 degrees relative to the tangent to the spiral pattern at a first one of tire regularly-spaced points;

ii) a second triangular abrasive platelet with a second respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the second respective sidewull is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a second one of the regularly-spaced points; iii) a third triangular abrasive platelet with a third respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the third respective sidewall is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to the spiral patern at a third one of the regularly-spaced points; and iv) a fourth triangular abrasive platelet with a fourth respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the fourth respective side wall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a fourth one of the regularly-spaced points;

at least partially curing the curable make layer precursor to provide a make layer;

disposing a curable size layer precursor over die make layer and triangular abrasive platelets; and at least partially curing the curable size layer precursor to provide a size layer.

As used herein:

The term "mild steel" refers to a carbon-based steel alloy containing less than about 0.25 percent by weight of carbon.

The term "offhand abrading” means abrading where the operator manually urges the disc/wheel against a workpiece or vice versa.

The term "proximate" means very near or next to (e.g., contacting or embedded in a binder layer contacting).

The term "spiral" refers to a spiral which is planar. In some preferred embodiments, the spiral may be an arithmetic spiral, also known as an "Archimedean spiral". An arithmetic spiral has the property that any ray from die origin intersects successive turnings of tire spiral in points with a constant separation distance.

The term "workpiece" refers to a thing being abraded.

As used herein, the term "triangular abrasive platelet", means a ceramic abrasive particle with at least a portion of die abrasive particle having a predetermined shape that is replicated from a mold cavi ty used to form the shaped precursor abrasive particle. Except in the case of abrasive shards (e.g , as described in U S. Pat. Appl Publ. 2009/0169816 A1 (Erickson et a!.), the triangular abrasive platelet wall generally have a predetermined geometric shape that substantially replicates the mold cavity that was used to form the triangular abrasive platelet. Triangular abrasive platelet as used herein excludes randomly sized abrasive particles obtained by a mechanical crushing operation.

As used herein, "Z-axis rotational orientation" refers to the angular rotation, about a Z-axis perpendicular to the major surface of the disc backing, of the longitudinal dimension the triangular abrasive platelet sidewall that most faces die disc backing.

Features and advan tages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view' of exemplar}' coated abrasive disc 100 FIG. 1 A is an enlarged view of region 1 A in FIG. I.

FIG. IB is an enlarged view of region IB in FIG. 1 A.

FIG. 1C is a schematic cross-sectional view' of coated abrasive disc 100 taken along line 1C-1C in FIG. IB.

FIG. 2A is a schematic top view of exemplary triangular abrasive platelet 130a.

FIG. 2B is a schematic perspective view of exemplary triangular abrasive platelet 130a.

FIG. 3 A is a schematic top view of exemplary triangular abrasive platelet 330.

FIG. 3B is a schematic side view of exemplary triangular abrasive platelet 330b.

FIG. 4 is a schematic top view of a production tool 400 useful for making coated abrasive disc

100

FIG. 4A is an enlarged view 7 of region 4A in FIG. 4.

FIG. 4B is and enlarged view of region 4B in FIG. 4A.

FIG. 4C is an enlarged schematic cross-sectional view of production tool 400 taken along line 4C-4C m FIG. 4B.

FIG. 4D is an enlarged schematic cross-sectional view of production tool 400 taken along line 4D-4D in FIG. 4B.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

FIG. 1 show's an exemplary coated abrasive disc 100 according to the present disclosure, wherein triangular abrasive platelets 130 are secured at precise locations and Z-axis orientations to a disc backing 110

Referring now to FIGS. l A and IB, abrasive layer 120 disposed on a major surface 1 15 of disc backing 110. Abrasive layer 120 comprises triangular abrasive platelets 130 secured to major surface 115 of disc backing 110 by at least one binder material 140 (shown as make layer 132 and size layer 134). Triangular abrasive platelets 130 are disposed at regularly-spaced points 132 along an arithmetic spiral pattern 134 extending radially outward toward outer circumference 140. On a respective basis, one sidewall of at least 90 percent of the triangular abrasive platelets 130 is disposed facing and proximate to the disc backing.

At least 70 percent of the triangular abrasive platelets 130 are disposed in a recurring sequential orientation that includes four regularly spaced sequential triangular platelets 130.

The first triangular abrasive platelet 130a has a first respective sidewall 136a lacing the disc backing 110. The Z-axis rotational orientation 138 of the first respective sidewall is longitudinally outwardly oriented at an angle of -10 to -40 degrees relative to the tangent 150 to the spiral pattern 134 at a first point 132. For clarity, the determination of Z-axis orientation is shown only for triangular abrasive platelet 130a. Z-axis orientation is determined in an analogous maimer for the remaining three triangular abrasive platelets.

The second triangular abrasive platelet 130b has a second respective sidewall facing the disc backing, wherein the Z-axis ro tational orientation of the second respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a second point 132b.

The third triangular abrasive platelet 130c has with a third respective sidewall facing the disc backing, wherein tire Z-axis rotational orientation of the third respective sidewall is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to tire spiral pattern at a third point 132c.

The fourth triangular abrasive platelet 130d has a fourth respective sidewall facing the disc- backing, wherein the Z-axis rotational orientation of the fourth respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral patern at a fourth point 132d.

As used herein, the horizontal Z-axis rotational direction is considered to be Q degrees relative to a tangent at a point on the spiral pattern if its Z-axis projection onto the arithmetic spiral pattern 140 (which is planar) intersects the tangent line at an angle of Q degrees. For collinear and parallel configurations Q = 0 degrees.

In this regard, the horizontal Z-axis rotational direction is considered to be within 10 degrees of the tangent at a point on tire spiral pattern if its Z-axis projection onto the arithmetic spiral pattern 140 (which is planar) intersects the tangent line at an angle of 10 degrees or less

Referring now to FIGS. 2A and 2B, each triangular abrasive platelet 130 has respective top and bottom surfaces (132, 134) connected to each other, and separated by, three sidewalls (136).

FIGS. 3A and 3B show another embodiment of a useful triangular abrasive platelets 330, triangular abrasive platelet 330 has respective top and bottom surfaces (332, 334) connected to each other, and separated by, three sloping sidewalls (336).

The disc backing may comprise any known coated abrasive backing, for example. In some embodiments, the disc backing comprises a continuous uninterrupted disc, while in others it may have a central arbor hole for mounting. Likewise, the disc backing may be fiat or it may have a depressed central hub, for example, a Type 27 depressed center disc. The disc backing may be rigid, semi-rigid, or flexible. In some embodiments, the backing has a mechanical fastener, or adhesive fastener securely attached to a major surface opposite Site abrasive layer. Suitable materials for the substrate include polymeric films, metal foils, woven fabrics, knitted fabrics, paper, vulcanized fiber, nonwovens, foams, screens, laminates, combinations thereof, and treated versions thereof. For off-hand grinding applications where stiffness and cost are concerns, vulcanized fiber backings are typically preferred. For applications 3 where stiffness of the backing is desired a flexible backing may also be used by affixing it to a rigid backup pad mounted to the grinding tool.

The disc backing is generally circular and preferably roiationaliy symmetric around its center. Preferably it has a circular perimeter, but it may have additional features along the perimeter such as. for example, in the case of a scalloped perimeter.

The abrasive layer may comprise a single binder layer having abrasive particles retained therein, or more typically, a multilay er construction having make and size layers. Coated abrasive discs according to the present disclosure may include additional layers such as, for example, an optional supersize layer that is superimposed on die abrasive layer, or a backing antistatic treatment layer may also be included, if desired. Exemplary suitable binders can be prepared from thermally curable resins, radiation-curable resins, and combinations thereof.

The make layer can be formed by coating a curable make layer precursor onto a major surface of the backing. The make layer precursor may comprise, for example, glue, phenolic resin, aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, iree-radically polymerizable polyfunctional (meth)acrylate (e.g., aminoplast resin having pendant a,b-unsaturated groups, acrylated urethane, acrylated epoxy, aciylated isocyanurate), epoxy resin (including bis-maleimide and fluorene- modified epoxy resins), isocyanurate resin, and mixtures thereof. Of these, phenolic resins are preferred, especially when used in combination with a vulcanized fiber backing.

Phenolic resins are generally formed by condensation of phenol and formaldehyde, and are usually categorized as resole or novolac phenolic resins. Novolac phenolic resins are acid-catalyzed and have a molar ratio of formaldehyde to phenol of less than 1 :1. Resole (also resol) phenolic resins can be catalyzed by alkaline catal sts, and the molar ratio of formaldehyde to phenol is greater than or equal to one, typically between 1.0 and 3.0, thus presenting pendant methylol groups. Alkaline catalysts suitable for catalyzing the reaction between aldehyde and phenolic components of resole phenolic resins include sodium hydroxide, barium hydroxide, potassium hydroxide, calcium hydroxide, organic amines, and sodium carbonate, all as solutions of the catalyst dissolved in water.

Resole phenolic resins are typically coated as a solution with water and/or organic solvent (e.g., alcohol). Typically, the solution includes about 70 percent to about 85 percent solids by weight, although other concentrations may be used. If the solids content is very low, then more energy is required to remove the water and/or solvent. If the solids content is very high, then the viscosity of the resulting phenolic resin is too high which typically leads to processing problems.

Phenolic resins are well-known and readily available from commercial sources. Examples of commercially available resole phenolic resins useful in practice of the present disclosure include those marketed by Durez Corporation under the trade designation VARCIJM (e.g., 29217, 29306, 29318,

29338, 29353); those marketed by Ashland Chemical Co. of Bartow, Florida under the trade designation AEROFENE (e.g., AEROFENE 295); and those marketed by Kangnam Chemical Company Ltd. of Seoul, South Korea under the trade designation PHENOLITE (e.g., PHENOLTTE TD-2207). The make layer precursor may be applied by any known coating method for applying a make layer to a backing such as, for example, including roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, and spray coating.

The basis weight of the make layer utilized may depend, for example, on the in tended use(s), type(s) of abrasive particles, and nature of the coated abrasive disc being prepared, but typically will be in the range of from 1, 2, 5, 10, or 15 grams per square meter (gsm) to 20, 25, 100, 200, 300, 400, or even 600 gsm. The make layer may be applied by any known coating method for applying a make layer (e.g., a make coat) to a backing, including, for example, roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, and spray coating.

Once the make layer precursor is coated on the backing, the triangular abrasive platelets are applied to and embedded in the make layer precursor. The triangular abrasive platelets are applied nominally according to a predetermined pattern and Z-axis rotational orientation onto the make layer precursor.

The triangular abrasive platelets are outwardly disposed from the disc backing (i.e., they extend away from the disc backing). As used herein the term "outwardly disposed" means that the triangular abrasive platelets extend away from the disc backing, typically forming a dihedral angle of from 45 to 90 degrees, preferably from 60 to 90 degrees, and more preferably from 75 to 90 degrees, relative to the nearest surface of the backing.

In some preferred embodiments, the spacing between the respective points on the spiral pattern is from 1.0 to 3 times, more preferably 1.2 to 2 times, and even more preferably 1.2 to 1.7 times the average length of the sidewalls of tire triangular abrasive platelets that are facing the fiber disc backing, although other spacings may also be used.

In some embodiments, the triangular abrasive platelets are shaped as thin triangular prisms, hile in other embodiments, the triangular abrasive platelets are shaped as truncated triangular pyramids (preferably with a taper angle of about 8 degrees). The triangular abrasive platelets may have different side lengths, but are preferably equilateral on their largest face.

The triangular abrasive platelets have sufficient hardness to function as abrasive particles in abrading processes. Preferably, the triangular abrasive platelets have a Mohs hardness of at least 4, at least 5, at least 6, at least 7, or even at least 8. Preferably, they comprise alpha alumina.

Crashed abrasive or non-abrasive particles may be included in the abrasive layer between the abrasive elements and/or abrasive platelets, preferably in sufficient quantity to form a closed coat (i.e., substantially the maximum possible number of abrasive particles of nominal specified grade(s) that can be retained in the abrasive layer).

Examples of suitable abrasive particles include: fused aluminum oxide; heat-treated aluminum oxide; white fused aluminum oxide; ceramic aluminum oxide materials such as those commercially available under the trade designation 3M CERAMIC ABRASIVE GRAIN from 3M Company, St. Paul, MN; brown aluminum oxide; blue aluminum oxide; silicon carbide (including green silicon carbide); titanium diboride; boron carbide; tungsten carbide; garnet; titanium carbide; diamond; cubic boron nitride; garnet; fused alumina zirconia; iron oxide; chromia; zirconia; titania; tin oxide; quartz; feldspar; flint; emery; sol-gel-derived abrasive particles; and combinations thereof. Of these, molded sol-gel derived alpha alumina triangular abrasive platelets are preferred in many embodiments. Abrasive material that cannot be processed by a sol-gel route may be molded with a temporary' or permanent binder to form shaped precursor particles which are then sintered to form triangular abrasive platelets, for example, as described in U. S. Pat. Appln. Publ. No. 2016/0068729 A1 (Erickson et al).

Examples of sol-gel-derived abrasive particles and methods for their preparation can be found in U. S. Pat. Nos. 4,314,827 (Leitheiser et al); 4,623,364 (Cottringer et al.); 4,744,802 (Sehwabel),

4,770,671 (Monroe et al); and 4,881,951 (Monroe et al. ). It is also contemplated that the abrasive particles could comprise abrasive agglomerates such, for example, as those described in U. S. Pat. Nos. 4,652,275 (Bloecher et al.) or 4,799,939 (Bloecher et al.). In some embodiments, the triangular abrasive platelets may be surface-treated with a coupling agent (e.g., an organo silane coupling agent) or other physical treatment (e.g., iron oxide or titanium oxide) to enhance adhesion of the abrasive particles to the binder (e.g., make and/or size layer). The abrasive particles may be treated before combining them with the corresponding binder precursor, or they may be surface treated in situ by including a coupling agent to the binder.

Preferably, the triangular abrasive platelets comprise ceramic abrasive particles such as, for example, sol-gel-derived polycrystalline alpha alumina particles. Triangular abrasive platelets composed of crystallites of alpha alumina, magnesium alumina spinel, and a rare earth hexagonal aluminate may be prepared using sol-gel precursor alpha alumina particles according to methods described in, for example, U. S. Pat. No. 5,213,591 (Celikkaya et al.) and U. S. Pat. Appln. Publ. Nos. 2009/0165394 Al (Culler et al.) and 2009/0169816 Al (Erickson et al).

Alpha alumina-based triangular abrasive platelets can be made according to well-known multistep processes. Briefly, the method comprises tire steps of making either a seeded or non-seeded sol- gel alpha alumina precursor dispersion that can be converted into alpha alumina; filling one or more mold cavities having the desired outer shape of the triangular abrasive platelet with the sol-gel, drying the sol- gel to form precursor triangular abrasive platelets; removing the precursor triangular abrasive platelets from the mold cavities; calcining the precursor triangular abrasive platelets to form calcined, precursor triangular abrasive platelets, and then sintering the calcined, precursor triangular abrasive platelets to form triangular abrasive platelets. The process will now be described in greater detail.

Further details concerning methods of making so 1-gel -derived abrasive particles can be found in, for example, U. S. Pat. Nos. 4,314,827 (Leitheiser); 5,152,917 (Pieper et al.); 5,435,816 (Spurgeon et al); 5,672,097 (Hoopman et al.); 5,946,991 (Hoopman et al.); 5,975,987 (Hoopman et al.); and 6,129,540 (Hoopman et al.); and in U. S. Publ. Pat. Appln. No. 2009/0165394 Al (Culler et al.).

The triangular abrasive platelets may include a single kind of triangular abrasive platelets or a blend of two or more sizes and/or compositions of triangular abrasive platelets. In some preferred embodiments, the triangular abrasive plateiets are precisely-shaped in that individual triangular abrasive platelets will have a shape that is essentially the shape of the portion of the cavity of a mold or production tool in which the particle precursor was dried, prior to optional calcining and sintering.

Triangular abrasive platelets used in the present disclosure can typically be made using tools (i.e., molds) cut using precision machining, which provides higher feature definition than other fabrication alternatives such as, for example, stamping or punching. Typically, the cavities in the tool surface have planar faces that meet along sharp edges, and form the sides and top of a truncated pyramid. The resultant triangular abrasive platelets have a respective nominal average shape that corresponds to the shape of cavities (e.g., truncated pyramid) in die tool surface; however, variations (e.g., random variations) from the nominal average shape may occur during manufacture, and triangular abrasive platelets exhibiting such variations are included within die definition of triangular abrasive platelets as used herein.

In some embodiments, die base and the top of the triangular abrasive platelets are substantially parallel, resulting in prismatic or truncated pyramidal shapes, although this is not a requirement. In some embodiments, the sides of a truncated trigonal pyramid have equal dimensions and form dihedral angles with the base of about 82 degrees. However, it will be recognized that other dihedral angles (including 90 degrees) may also be used. For example, the dihedral angle between the base and each of the sides may independently range from 45 to 90 degrees, typically 70 to 90 degrees, more typically 75 to 85 degrees.

As used herein in referring to triangular abrasive platelets, the term "length” refers to the maximum dimension of a triangular abrasive platelet. "Width" refers to the maximum dimension of the triangular abrasive platelet that is perpendicular to the length. The terms "thickness" or "height" refer to tire dimension of the triangular abrasive platelet that is perpendicular to tire length and width.

Examples of sol-gel-derived triangular alpha alumina (i.e., ceramic) abrasive particles can be found in U. S. Pat. Nos. 5,201,916 (Berg); 5,366,523 (Rowenhorst (Re 35,570)); and 5,984,988 (Berg). Details concerning such abrasive particles and methods for their preparation can be found, for example, in U. S. Pat. Nos. 8, 142,531 (Adefris et al.); 8,142,891 (Culler ei al); and 8,142,532 (Erickson et at.); and in U. S. Pat. Appl. Publ. Nos. 2012/0227333 (Adefris et al.); 2013/0040537 (Schwabel et al); and

2013/0125477 (Adefris).

The triangular abrasive platelets are typically selected to have a length in a range of from 1 micron to 15000 microns, more typically 10 microns to about 10000 microns, and still more typically from 150 to 2600 microns, although other lengths may also be used.

Triangular abrasive platelets are typically selected to have a width in a range of from 0.1 micron to 3500 microns, more typically 100 microns to 3000 microns, and more typically 100 microns to 2600 microns, although other lengths may also be used.

Triangular abrasive plateiets are typically selected to have a thickness in a range of from 0.1 micron to 1600 microns, more typically from I micron to 1200 microns, although other thicknesses may be used. In some embodiments, triangular abrasive platelets may have an aspect ratio (length to thickness) of at least 2, 3, 4, 5, 6, or more.

Surface coatings on the triangular abrasive platelets may be used to improve the adhesion between the triangular abrasive platelets and a binder in abrasive discs, or can be used to aid in electrostatic deposition of the triangular abrasive platelets in one embodiment, surface coatings as described in U S. Pat. No 5,352,254 (Celikkaya) in an amount of 0 1 to 2 percent surface coating to triangular abrasive platelet weight may be used. Such surface coatings are described in U. S. Pat. Nos. 5,213,591 (Celikkaya et al); 5,011,508 (Wald et a!.); 1,910,444 (Nicholson); 3,041,156 (Rowse et al. ); 5,009,675 (Kunz et al); 5,085,671 (Martin et al); 4,997,461 (Markhoff-Matheny et al.); and 5,042,991 (Kunz et al.). Additionally, the surface coating may prevent the triangular abrasive platelet from capping. Capping is Site term to describe the phenomenon where metal particles from the workpiece being abraded become welded to tire tops of the triangular abrasive platelets. Surface coatings to perform the above functions are known to those of skill in the art.

The abrasive particles may be independently sized according to an abrasives industry' recognized specified nominal grade. Exemplary abrasive industry' recognized grading standards include those promulgated by ANSI (American National Standards Institute), FEPA (Federation of European Producers of Abrasives), and IIS (Japanese Industrial Standard). ANSI grade designations (i.e , specified nominal grades) include, for example: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 46, ANSI 54, ANSI 60, ANSI 70, ANSI 80, ANSI 90, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600. FEPA grade designations include F4, F5, F6, F7, F8, F10, F12, F14, F16, F16, F20, F22, F24, F30, F36, F40, F46, F54, F60, F70, F80, F90, FI 00, F120, F150, F180, F220, F230, F240, F280, F320, F360, F400, F500, F600, F800,

F1000, F1200, FI 500, and F2000. JIS grade designations include JIS8, JIS12, JIS16, JIS24, JIS36, JIS46, J1S54, JIS60, J1S80, JIS100, JIS150, JIS 180, JIS220, JIS240, JIS280, J1S320, J1S360, JIS400, J1S600, 118800, J1S1000, 1181500, JIS2500, JIS4000, JIS6000, J1S8000, and J1S10000. According to one embodiment of the present disclosure, the average diameter of the abrasive particles may be within a range of from 260 to 1400 microns in accordance with FEP A grades F60 to F24.

Alternatively, the abrasive particles can be graded to a nominal screened grade using U. S.A. Standard Test Sieves conforming to ASTM E-l l "Standard Specification for Wire Cloth and Sieves for Testing Purposes". ASTM E-l 1 prescribes the requirements for the design and construction of testing sieves using a medium of woven wire cloth mounted in a frame for the classification of materials according to a designated particle size. A typical designation may be represented as -18+20 meaning that lire abrasive particles pass through a test sieve meeting ASTM E-l 1 specifications for the number 18 sieve and are retained on a test sieve meeting ASTM E-l 1 specifications for the number 20 sieve. In one embodiment, the abrasive particles have a particle size such that most of the particles pass through an 18 mesh test sieve and can be retained on a 20, 25, 30, 35, 40, 45, or 50 mesh test sieve. In various embodiments, the abrasive particles can have a nominal screened grade of: -18+20, -20/+25, -25+40, - 40+35, -35+40, 5 -40+45, -45+50, -50+60, -60+70, -70/+80, -80+100, -100+120, -120+140, -140+170, - 170+200, -200+230, -230+270, -270+325, -325+400, -400+450, -450+500, or -500+635. Alternatively, a custom mesh size can he used such as -90+100.

The spiral pattern can be characterized by its pitch (i.e., the regular separation between lines of the spiral while traveling radially outward from the real or theoretical center of the spiral in some preferred embodiments, the spiral pitch is an arithmetic spiral having a pitch of from 1.0 to 3 times, more preferably 1.2 to 2.5 times, and even more preferably 1.2 to 2 times the thickness of the triangular abrasive platelets, although this is not a requirement. Likewise, in some preferred embodiments, the regularly-spaced interval is from 1 to 3 times, more preferably from 1.2 to 2 times, and even more preferably 1.2 to 1.5 times the length of the triangular abrasive platelets, although this is not a requirement.

Coated abrasive discs according to the present disclosure can be made by a method in which the triangular abrasive platelets are precisely placed and oriented. The method generally involves the steps of filling the cavities in a production tool each writh one or more triangular abrasive platelets (typically one or two), aligning the filled production tool and a make layer precursor-coated backing for transfer of the triangular abrasive platelets to the make layer precursor, transferring the abrasive particles from the cavities onto the make layer precursor-coated backing, and removing the production tool from the aligned position. Thereafter, the make layer precursor is at least partially cured (typically to a sufficient degree that the triangular abrasive platelets are securely adhered to the backing), a size layer precursor is then applied over the make layer precursor and abrasive particles, and at least partially cured to provide the coated abrasive disc. The process, which may be batch or continuous, can be practiced by hand or automated, e.g., using robotic equipment. It is not required to perforin all steps or perform them in consecutive order, but they can be performed in tire order listed or additional steps performed in between.

The triangular abrasive platelets can be placed in the desired Z-axis rotational orientation formed by first placing them in appropriately shaped cavities in a dispensing surface of a production tool arranged to have a complementary spiral pattern.

An exemplary production tool 400 for making the coated abrasive disc 100 shown in FIGS. 1 and 1 A— 1 C, formed by casting a thermoplastic sheet, is shown in FIG 4. Referring now to FIG. 4, production tool 400 has a dispensing surface 410 comprising a spiral pattern 430 of cavities 420 sized and shaped to receive the triangular abrasive platelets. Cavities 42.0 are Z-axis rotationally aligned so that when filled with triangular abrasive platelets that when they are subsequently transferred the form the desired corresponding arithmetic spiral pattern and Z-axis rotational orientation in the resultant coated abrasive disc.

Once most, or all, of the cavities are filled with the desired number of triangular abrasive platelets the dispensing surface is brought into close proximity or contact with the make layer precursor layer on the disc backing thereby embedding and transferring the triangular abrasive platelets from the production tool to the make layer precursor while nominally maintaining horizontal orientation. Of course, some unintended loss of orientation may occur, but it should generally be manageable within the ±10 degree or less tolerance.

in some embodiments, the depth of the cavities in the production tool is selected such that the triangular abrasive platelets fit entirely within the cavities. In some preferred embodiments, the triangular abrasive platelets extend slightly beyond the openings of the cavities. In tins way, they can be transferred to the make layer precursor by direct contact with reduced chance of resin transfer to the to the production tool. In some preferred embodiments, the center of mass for each triangular abrasive platelet resides within a respective cavity of the production tool when the triangular abrasive platelet is fully inserted into tire cavity. If the depth of the cavities becomes too short, with die triangular abrasive platelet’s center of mass being located outside of tire cavity, the triangular abrasive platelets are not readily retained within die cavities and may jump back out as die production tool is used in the apparatus.

In order to fill die cavities in tire production tool, an excess of die triangular abrasive platelets is preferably applied to the dispensing surface of the production tool such that more triangular abrasive platelets are provided than the number of cavities. An excess of triangular abrasive platelets, which means that there are more triangular abrasive platelets present per unit length of the production tool than cavities present, helps to ensure that most cavities within the production tool are eventually filled with a triangular abrasive platelet as the triangular abrasive platelets accumulate onto the dispensing surface and are moved about either due to gravity or other mechanically applied forces to translate them into a cavity. Since the bearing area and spacing of the abrasive particles is often designed into the production tooling for the specific grinding application, it is generally desirable to not have too much variability in the number of unfilled cavities.

Preferably, a majority of tire cavities in die dispensing surface are filled with a triangular abrasive platelet disposed in an individual cavity such that the sides of the cavity and platelet are at least approximately parallel. This can be accomplished by shaping the cavities slightly larger than the triangular abrasive platelets (or multiple thereof). To facilitate filling and release it may be desirable that the cavities have inwardly sloping sidewalls with increasing depth and/or have vacuum openings at the bottoms of the cavities, wherein the vacuum opening lead to a vacuum source. It is desirable to transfer the triangular abrasive platelets onto the make layer precursor-coated backing such that they stand up or are erectly applied. Therefore, the cavity shape is designed to hold the triangular abrasive platelet erectly.

In various embodiments, at least 60, 70, 80, 90, or 95 percent of the cavities in the dispensing surface contain a triangular abrasive platelet. In some embodiments, gravity can be used to fill the cavities. In other embodiments, the production tool can be inverted and vacuum applied to hold the triangular· abrasive platelets in the cavities. The triangular abrasive platelets can be applied by spray, fluidized bed (air or vibration), or electrostatic coating, for example. Removal of excess triangular abrasive platelets would be done by gravity as any abrasive particles not retained would fall back down. The triangular abrasive platelets can thereafter be transferred to the make layer precursor-coated disc backing by removing vacuum. As mentioned above, excess triangular abrasive platelets may be supplied than cavities such that some will remain on the dispensing surface after the desired number of cavities have been filled. These excess triangular abrasive platelets can often be blown, wiped, or otherwise removed from the dispensing surface. For example, a vacuum or other force could be applied to hold the triangular abrasive platelets in the cavities and the dispensing surface inverted to clear it of the remaining fraction of the excess triangular abrasive platelets.

After substantially all the cavities in the dispensing surface of the production tool are filled with the triangular abrasive platelets, the dispensing surface of the production tool is brought into proximity with the make layer precursor.

In preferred embodiments, the production tool is formed of a thermoplastic polymer such as, for example, polyethylene, polypropylene, polyester, or polycarbonate from a metal master tool. Fabrication methods of production tools, and of master tooling used in their manufacture, can be found in, for example, U. S. Pat. Nos. 5,152,917 (Pieper et al); 5,435,816 (Spurgeon et al); 5,672,097 (Hoopman et al.); 5,946,991 (Hoopman et al); 5,975,987 (Hoopman et a ); and 6,129,540 (Hoopman et al.); and lJ. S. Pat. Appl. Publ. Nos. 2013/0344786 Al (Keipert) and 2016/031 1084 A l (Culler et al.).

In some preferred embodiments, the production fool is manufactured using 3-D printing techniques.

Once the triangular abrasive platelets have been embedded in the make layer precursor, it is at least partially cured in order to preserve orientation of the mineral during application of the size layer precursor. Typically, this involves B-staging the make layer precursor, but more advanced cures may also be used if desired. B-staging may be accomplished, for example, using heat and/or light and/or use of a curative, depending on the nature of the make layer precursor selected.

Next, tire size layer precursor is applied over the at least partially cured make layer precursor and triangular abrasive platelets. The size layer can be formed by coating a curable size layer precursor onto a major surface of tire backing. The size layer precursor may comprise, for example, glue, phenolic resin, aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, free-radically polymerizable polyfunctional (meth)aciylate (e.g., aminoplast resin having pendant a,b-unsaturated groups, acrylated urethane, aciylated epoxy, aciylated isocyanurate), epoxy resin (including bis- maleimide and fluorene-modified epoxy resins), isocy anurate resin, and mixtures thereof. If phenolic resin is used to form the make layer, it is likewise preferably used to form the size layer. The size layer precursor may be applied by any known coating method for applying a size layer to a backing, including roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, spray coating, and the like. If desired, a presize layer precursor or make layer precursor according to the present disclosure may be also used as the size layer precursor.

The basis weight of the size layer wall also necessarily vary depending on the intended use(s), type(s) of abrasive particles, and nature of the coated abrasive disc being prepared, but generally wall be in the range of from 1 or 5 gsm to 300, 400, or even 500 gsm, or more. The size layer precursor may be applied by any known coating method for applying a size layer precursor (e.g., a size coat) to a backing including, for example, roll coating, extrusion die coating, curtain coating, and spray coating.

Once applied, the size layer precursor, and typically the partially cured make layer precursor, are sufficiently cured to provide a usable coated abrasive disc. In general, this curing step involves thermal energy, although other forms of energy such as, for example, radiation curing may also be used. Useful forms of thermal energy include, for example, heat and infrared radiation. Exemplary' sources of thermal energy include ovens (e.g., festoon ovens), heated rolls, hot airblowers, infrared lamps, and combinations thereof.

In addition to other components, binder precursors, if present, in the make layer precursor and/or presize layer precursor of coated abrasive discs according to the present disclosure may optionally contain catalysts (e.g., thermally activated catalysts or photocatalysts), free-radical initiators (e.g., thermal initiators or photoinitiators), curing agents to facilitate cure. Such catalysts (e.g., thermally activated catalysts or photocatalysts), free-radical initiators (e.g., thermal initiators or photoinitiators), and/or curing agents may be of any type known for use in coated abrasive discs including, for example, those described herein.

In addition to other components, the make and size layer precursors may further contain optional additives, for example, to modify performance and/or appearance. Exemplary' additives include grinding aids, fillers, plasticizers, wetting agents, surfactants, pigments, coupling agents, fibers, lubricants, thixotropic materials, antistatic agents, suspending agents, and/or dyes.

Exemplary grinding aids, which may be organic or inorganic, include waxes, halogenated organic compounds such as chlorinated waxes like tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride; halide salts such as sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium teirafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride; and metals and their alloys such as tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium. Examples of other grinding aids include sulfur, organic sulfur compounds, graphite, and metallic sulfides A combination of different grinding aids can be used.

Exemplary' antistatic agents include electrically conductive material such as vanadium pentoxide (e.g., dispersed in a sulfonated polyester), humeefants, carbon black and/or graphite in a binder.

Examples of useful fillers for this disclosure include silica such as quartz, glass beads, glass bubbles and glass fibers; silicates such as talc, clays, (montmoriJlonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate; metal sulfates such as calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate; gypsum; vemticulite; wood flour; aluminum trihydrate; carbon black; aluminum oxide; titanium dioxide; cryolite; chiolite; and metal sulfites such as calcium sulfite.

Optionally a supersize layer may be applied to at least a portion of the size layer. If present, the supersize typically includes grinding aids and/or anti-loading materials. The optional supersize layer may- serve to prevent or reduce the accumulation of swarf (the material abraded from a workpiece) between abrasive particles, which can dramatically reduce the cutting ability of the coated abrasive disc. Useful supersize layers ty pically include a grinding aid (e.g., potassium tefrafluoroborate), metal salts of fatty acids (e.g., zinc stearate or calcium stearate), salts of phosphate esters (e.g., potassium behenyl phosphate), phosphate esters, urea-formaldehyde resins, mineral oils, crosslinked silanes, crossiinked silicones, and/or fluorochemicals. U seful supersize materials are further described, for example, in U. S. Pat. No. 5,556,437 (Lee ef af). Typically, the amount of grinding aid incorporated into coated abrasive products is about 50 to about 400 gsm, more typically about 80 to about 300 gsm. The supersize may contain a binder such as for example, those used to prepare the size or make layer, but it need not have any binder.

Further details concerning coated abrasive articles (e.g., coated abrasive discs) comprising an abrasive layer secured to a fabric backing, wherein the abrasive layer comprises abrasive particles and make, size, and optional supersize layers are well known, and may be found, for example, in U. S. Pat. Nos. 4,734,104 (Broberg); 4,737,163 (Larkey); 5,203,884 (Buchanan et al); 5,152,917 (Pieper et al); 5,378,251 (Culler et al); 5,417,726 (Stout et al); 5,436,063 (Follett et al); 5,496,386 (Broberg et al); 5,609,706 (Benedict et al); 5,520,711 (Helmin); 5,954,844 (Law' et al); 5,961 674 (Gagliardi et al); 4,751,138 (Bange et al.); 5,766,277 (DeVoe et al); 6,077,601 (DeVoe et al.); 6,228,133 (Thurber et al); and No. 5,975,988 (Christianson)

Coated abrasive discs according to the present disclosure are useful for abrading a w'orkpiece; for example, by off-hand abrading with a handheld right-angle grinder. Preferred workpieces include welding beads (e.g., especially mild steel welds), flash, gates, and risers off castings.

SELECT EMBODIMENTS OF THE PRESENT DISCLOSURE

In a first aspect, the present disclosure provides a coated abrasive disc comprising:

a disc backing having an outer circumference;

an abrasive layer disposed on the disc backing, wherein the abrasive layer comprises triangular abrasive platelets secured to a major surface of the disc backing by at least one binder material, wherein the triangular abrasive platelets are outwardly disposed at regularly-spaced points along a spiral pattern extending outwardly toward the outer circumference,

wherein each one of the triangular abrasive platelets has respective top and bottom surfaces connected to each other, and separated by, three sidewalls,

wherein, on a respective basis, one sidewall of at least 90 percent of the triangular abrasive platelets is disposed facing and proximate to the disc backing, and

wherein at least 70 percent (preferably at least 80 percent, more preferably at least 90 percent, and more preferably 95 percent) of the triangular abrasive platelets are disposed in a recurring sequential orientation having:

i) a first triangular abrasive platelet with a first respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the first respective sidewall is longitudinally outwardly oriented at an angle of -10 to -40 degrees relative to the tangent to the spiral pattern at a first one of the regularly -spaced points;

ii) a second triangular abrasive platelet with a second respective sidewall facing the disc backing, wherein the Z-axis ro tational orientation of the second respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to tire spiral pattern at a second one of the regularly -spaced points;

iii) a third triangular abrasive platelet with a third respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the third respective sidewall is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to the spiral pattern at a third one of the regularly-spaced points; and

iv) a fourth triangular abrasive platelet with a fourth respective sidewull facing the disc backing, wherein the Z-axis rotational orientation of the fourth respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral patern at a fourth one of the regularly-spaced points.

In a second embodiment, wherein the triangular abrasive platelets Slave an average thickness, wherein the spiral pattern comprises a spiral pattern, and wherein the arithmetic spiral pattern lias a pitch that is 1 to 3 times the average thickness of the triangular abrasive platelets.

In a third embodiment, the present disclosure provides a coated abrasive disc according to the first or second embodiment, wherein the abrasive layer further comprises crushed abrasive or nonabrasive particles.

In a fourth embodiment, the present disclosure provides a coated abrasive disc according to any one of the first to third embodiments, wherein the disc backing comprises vulcanized fiber.

In a fifth embodiment, the present disclosure provides a coated abrasive disc according to any one of the first to fourth embodiments, wherein the abrasive layer comprises a make layer and a size layer disposed over the make layer and the triangular abrasive platelets.

In a sixth embodiment, the present disclosure provides a coated abrasive disc according to any one of the first to fifth embodiments, wherein the triangular abrasive platelets comprise alpha alumina.

In a seventh embodiment, the present disclosure provides a method of abrading a workpiece, the method comprising frictionaily contacting a portion of the abrasive layer of a coated abrasive disc according to any one of the first to sixth embodiments with the workpiece, and moving at least one of the workpiece and the coated abrasive disc relative to the other to abrade the workpiece.

In an eighth embodiment, the present disclosure provides a method of abrading a wwkpiece according to the seventh embodiment, wherein the substrate comprises high carbon steel, and wherein the abrasive layer contacts tire high carbon steel.

In a ninth embodiment, the present disclosure provides a method of making a coated abrasive disc, tire method comprising:

disposing a curable make layer precursor on a major surface of a disc backing; embedding triangular abrasive platelets into the curable make layer precursor, wherein the triangular abrasive platelets are outwardly disposed at regularly -spaced points along a spiral pattern extending outwardly toward the outer circumference,

wherein each one of the triangular abrasive platelets has respective top and bottom surfaces connected to each other, and separated by, three sidewalls,

wherein, on a respective basis, one sidewall of at least 90 percent of the triangular abrasive platelets is disposed facing and proximate to the disc backing, and

wherein at least 70 percent (preferably at least 80 percent, more preferably at least 90 percent, and more preferably 95 percent) of the triangular abrasive platelets are disposed in a recurring sequential orientation having:

i) a first triangular abrasive platelet with a first respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the first respective sidewali is longitudinally outwardly oriented at an angle of -10 to -40 degrees relative to the tangent to the spiral pattern at a first one of the regularly-spaced points;

ii) a second triangular abrasive platelet with a second respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the second respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral pattern at a second one of the regularly-spaced points;

iii) a third triangular abrasive platelet with a third respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the third respective sidewali is longitudinally outwardly oriented at an angle of +10 to +40 degrees relative to the tangent to the spiral pattern at a third one of the regularly -spaced points; and iv) a fourth triangular abrasive platelet with a fourth respective sidewall facing the disc backing, wherein the Z-axis rotational orientation of the fourth respective sidewall is longitudinally outwardly oriented at an angle of -15 to +15 degrees relative to the tangent to the spiral patern at a fourth one of the regularly-spaced points;

at least partially curing the curable make layer precursor to provide a make layer;

disposing a curable size layer precursor over the make layer and triangular abrasive platelets; and at least partially curing the curable size layer precursor to provide a size layer.

In a tenth embodiment, the present disclosure provides a method according to the ninth embodiment, wherein the triangular abrasive platelets have an average thickness, wherein the spiral pattern comprises a spiral pattern, and wherein the arithmetic spiral pattern has a pitch that is 1 to 3 times Hie average thickness of tire triangular abrasive platelets.

In an eleventh embodiment, the present disclosure provides a method according to the ninth or tenth embodiment, wherein the abrasive layer further comprises crashed abrasive or non-abrasive particles. In a twelfth embodiment, the present disclosure provides a method according to any one of the ninfli to eleventh embodiments, wherein tire disc backing comprises vulcanized fiber.

in a thirteenth embodiment, the present disclosure provides a method according to any one of the Hindi to twelfth embodiments, wherein die triangular abrasive platelets comprise alpha alumina.

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.

EXAMPLES

Unless odierwise noted, all parts, percentages, ratios, etc. in die Examples and tire rest of the specification are by weight. Unless otherwise noted, all reagents were obtained, or are available from chemical vendors such as, for example, Sigma-Aldrich Company, St. Louis, Missouri, or may be synthesized by known methods. Abrasive particles used in the Examples are reported in Table 1, below. TABLE 1

EXAMPLE 1

A 7 -inch (178-nun) circular plastic transfer tool consisting of a continuous arithmetic spiral of triangular· cavities, having geometries such as those described in PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al), was prepared by 3-D printing. The spiral extended from the disc edge to within 1 inch

(2.54 cm) of tire disc center. The spiral pitch was approximately 0.059 inches (1.49 mm). The centers of the cavities were regularly spaced along the length of the spiral at intervals of approximately 0.087 inches (2.21 mm). The angular orientation of the long axis of each cavity relative to the spiral path varied sequentially along the spiral path. The repeat pattern relative to the spiral path was 0 degrees, + 45 degrees, 0 degrees, -45 degrees and so on as shown in FIGS. 4 and 4A-4D. The total number of cavities on tire tool was approximately 5600. The transfer tool was treated with a molybdenum sulfide spray lubricant (obtained under the trade designation MOLYCOAT from the Dow' Coming Corporation, Midland Michigan) to assist abrasive grain release.

An excess of abrasive grain API was applied to the surface of the transfer tool having the cavity openings and the tooling was shaken from side to side by hand. The transfer tooling cavities were soon filled with API grains held in a vertex down and base up orientation and aligned along the cavity long axis. Additional API was applied and the process repeated until greater titan 95 percent of tire transfer tooling cavities were filled by API grain. Excess grain was removed from Site surface of the transfer tool leaving only the grains contained within the cavities.

A make resin was prepared by mixing 49 parts of resole phenolic resin (based-cataly zed condensate from 1.5: 1 to 2.1:1 molar ratio of formaldehyde :phenol), 41 parts of calcium carbonate (HUBERCARB, Huber Engineered Materials, Quincy, Illinois) and 10 parts of water. 3.7 +/- 0.1 grams of make resin was applied via a brush to a 7-inch (17.8-cm) diameter x 0.83 mm thick vulcanized fiber web (DYNOS VULCANIZED FIBER, DYNOS GmbH, Troisdorf, Germany) having a 0.875-inch (2.22-em) center hole.

The API filled transfer tool was placed cavity side up on a 7-inch by 7-inch (18-cm X 18-cm) square wooden board. The make resin coated surface of the vulcanized fiber disc was brought into contact with the filled transfer tool and another 7-inch by 7-inch (18 cm x 18 cm) square wooden board was placed on top. The resulting assembly w'as inverted w'hile being held in rigid contact and gently tapped to dislodge the API grains from the transfer tool so as to fall base first onto the make resin surface. The vulcanized fiber disc backing was then allowed to fall away from the now' substantially grain-free transfer tool resulting in an API coated vulcanized fiber disc replicating the transfer tooling patern.

A drop-coated filler grain consisting of AP2 was applied in excess to the wet make resin and agitated until the entire exposed make resin surface was filled to capacity with AP2. The disc was inverted to remove excess AP2. The amount of AP2 addition w'as 15.0 +/- 0.1 grams.

The make resin was partially cured in an oven by heating for 45 minutes at 70°C, followed by 45 minutes at 90°C, followed by 3 hours at 105°C. The disc was then coated with 1 1.5 +/- 0.2 grams of a conventional ctyo lite -containing phenolic size resin and cured for 45 minutes at 70°C, followed by 45 minutes at 90°C, followed by 16 hours at !05°C. EXAMPLE 1 was used to grind AISI 1018 mild steel using Grinding Test Method A. AISI 1018 mild steel has the composition, on a weight basis: 0.18 percent carbon, 0.6-0.9 percent manganese, 0.04 percent (max) phosphorus, 0.05 percent (max) of sulfur. and 98.81-99.26 percent iron. Grinding performance results are reported in Table 2. The resultant disc had shaped abrasive particles arranged according to the patern shown in FIG. 1.

EXAMPLE 2

EXAMPLE 2 was prepared generally by the method of EXAMPLE 1 with the exception as follows. The make resin weight was 3.7 +/- 0.1 grams. AP2 drop coated secondary grain was used in the amount of 16.3 +/- 0.2 grams. Size resin weight was 11.9 +/- 0.2 grams. The final 105°C size cure sequence was reduced from 16 to 3 hours after which an additional KBF 4 supersize coating was applied at a weight of 9 4 grams. Final cure was 45 minutes at 70°C, followed by 45 minutes at 90°C, followed by 12 hours at 105°C. EXAMPLE 2 was used to grind 304 stainless steel using Grinding Test Method B.

Grinding performance results are reported in Table 3.

COMPARATIVE EXAMPLE A

COMPARATIVE EXAMPLE A was prepared generally by die method of EXAMPLE 1 with the exception that die cavities of the circular plastic transfer tool had all cavity long axes at zero degrees deviation relative to die spiral padi, lacking tire sequential change in orientation of die EXAMPLE 1 transfer tool. The cavity dimensions, pitch, spacing and total number of cavities was otherwise identical to the transfer tool of EXAMPLE 1. COMPARATIVE EXAMPLE A was used to grind 1018 mild steel using Grinding Test Method A. Grinding performance results are reported in Table 2.

COMPARATIVE EXAMPLE B

COMPARATIVE EXAMPLE B was prepared generally by the method of COMPARATIVE EXAMPLE A with the exception as follows. The make resin weight was 3.7 +/- 0.1 grains. AP2 drop coated secondary' grain was used in the amount of 15.3 +/- 0.2 grams. Size resin weight was 11.7 +/- 0.1 grams. The final 105°C size cure sequence was reduced from 16 to 3 hours after which an additional KBF 4 supersize coating was applied at a weight of 9.5 grams. Final cure was 45 minutes at 70°C, followed by 45 minutes at 90°C, followed by 12 hours at 05°C. COMPARATIVE EXAMPLE B was used to grind 304 stainless steel using Grinding Test Method B. Grinding performance results are reported in Table 3.

GRINDING TEST METHOD A

The grinding performance of the various discs was evaluated by grinding 1018 mild carbon steel using the following procedure. Seven-inch (17.8 cm) diameter abrasive disks for e valuation were attached to a drive motor running at a constant rotational speed of 5000 rpm and 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 activated and urged against an end face of a 1 x 1 in (2,54 x 2.54 cm) preweighed 1018 steel bar under a controlled force. The workpiece was abraded under these conditions for 13-second grinding intervals (passes). Following each 13-second interval, the workpiece was cooled to room temperature and weighed to determine the cut of the abrasive operation. The test end point was determined when the cut fell below 15 grains per cycle. Test results were reported as the incremental cut (gtoycle) for each interval and the total stock removed (g). METHOD B

The grinding performance of the various discs was evaluated by grinding 304 stainless steel using die following procedure. Seven-inch (17.8-cm) diameter abrasive disks for evaluation were attached to a drive motor running at a constant rotational speed of 5000 rpm and 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 activated and urged against an end face of a 1 x 1 in (2.54 x 2.54 cm) pre-weighed 304 stainless steel bar under a controlled force. The workpiece was abraded under these conditions for 13-second grinding intervals (passes). Following each 13-second interval, the workpiece was cooled to room temperature and weighed to determine the cut of the abrasive operation. The test end point was determined when the cut fell below 10 grams per cycle. Test results were reported as the incremental cut (g/cycle) for each interval and the total stock removed (g).

Results reported in Table 2 (below') were obtained according to the Grinding Test, Method A.

TABLE 2

Results reported in Table 3 (below) were obtained according to the Grinding Test, Method B.

TABLE 3

All cited references, patents, and patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in die preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.