US20230061952A1

US20230061952A1 - Coated abrasive articles

Info

Publication number: US20230061952A1
Application number: US17/759,727
Authority: US
Inventors: Daniel M. Lentz; Geoffrey I. Wilson; Thomas J. Nelson; Blake R. Rustad; Junting LI; Willam S. Maher; Gregory S. Mueller
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2020-01-31
Filing date: 2021-01-25
Publication date: 2023-03-02
Also published as: WO2021152444A1; EP4096867A1

Abstract

An abrasive article is presented that includes a first set of shaped abrasive particles with a majority of the first set of shaped abrasive particles are oriented with respect to a backing in a first orientation. The abrasive article also includes a second set of shaped abrasive particles with a majority of the second set of shaped abrasive particles are oriented with respect to the backing in a second orientation, and wherein the second orientation differs from the first orientation. The first and second set of shaped abrasive particles are embedded within a coating layer on the baking.

Description

BACKGROUND

Coated abrasive articles containing shaped abrasive grains are useful for shaping, finishing, or grinding a wide variety of materials and surfaces such as wood, metals (e.g., especially non-ferrous metals such as aluminum that tend to clog grinding wheels), and flash.
Coated abrasive articles having rotationally aligned triangular abrasive particles are disclosed in U.S. Pat. No. 9,776,302 (Keipert). The coated abrasive articles have a plurality of triangular abrasive particles each having a surface feature. The plurality of triangular abrasive particles is attached to a flexible backing by a make coat comprising a resinous adhesive forming an abrasive layer. There continues to be a need for improving the cost, performance, and/or life of coated abrasive articles.

SUMMARY

An abrasive article is presented that includes a first set of shaped abrasive particles with a majority of the first set of shaped abrasive particles are oriented with respect to a backing in a first orientation. The abrasive article also includes a second set of shaped abrasive particles with a majority of the second set of shaped abrasive particles are oriented with respect to the backing in a second orientation, and wherein the second orientation differs from the first orientation. The first and second set of shaped abrasive particles are embedded within a coating layer on the baking.
At least some abrasive articles presented herein provide greater cutting performance over the use life.
The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. It is to be understood, therefore, that the following description should not be read in a manner that would unduly limit the scope of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top-down schematic of an exemplary coated abrasive article.

FIG. 2 is a schematic cross-sectional view of an exemplary coated abrasive article.

FIG. 3 is an image of a coated abrasive disc after some wear.

FIG. 4 is a schematic cross-sectional view of a coated abrasive article in accordance with embodiments described herein.

FIG. 5 illustrates a method of manufacturing a coated abrasive article in accordance with embodiments described herein.

FIG. 6 is a schematic cross-sectional view of an abrasive article deposition process for a coated abrasive article.

FIG. 7 is a top down schematic of a coated abrasive article accordance with embodiments described herein.

FIGS. 8A and 8B illustrated close up views of coated abrasive articles.

FIGS. 9-10 illustrate data discussed in the Examples included herein.

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

Throughout this document, values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “about 0.1% to about 5%” or “about 0.1% to 5%” should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “about X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.
In this document, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.
In the methods described herein, the acts can be carried out in any order without departing from the principles of the disclosure, except when a temporal or operational sequence is explicitly recited. Furthermore, specified acts can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed act of doing X and a claimed act of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.
The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range, and includes the exact stated value or range.
The term “substantially” as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%.
As used herein, the term “shaped abrasive particle,” means an 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. Pat. Application Publication Nos. 2009/0169816 and 2009/0165394), 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 particle as used herein excludes abrasive particles obtained by a mechanical crushing operation. Suitable examples for geometric shapes having at least one vertex include polygons (including equilateral, equiangular, star-shaped, regular and irregular polygons), lens- shapes, lune-shapes, circular shapes, semicircular shapes, oval shapes, circular sectors, circular segments, drop-shapes and hypocycloids (for example super elliptical shapes).
For the purposes of this invention, geometric shapes are also intended to include regular or irregular polygons or stars wherein one or more edges (parts of the perimeter of the face) can be arcuate (either of towards the inside or towards the outside, with the first alternative being preferred). Hence, for the purposes of this invention, triangular shapes also include three- sided polygons wherein one or more of the edges (parts of the perimeter of the face) can be arcuate. The second side may include (and preferably is) a second face. The second face may have a perimeter of a second geometric shape.
For the purposes of this invention, shaped abrasive particles also include abrasive particles comprising faces with different shapes, for example on different faces of the abrasive particle. Some embodiments include shaped abrasive particles with different shaped opposing sides. The different shapes may include, for example, differences in surface area of two opposing sides, or different polygonal shapes of two opposing sides.
The shaped abrasive particles are typically selected to have an edge length in a range of from 0.001 mm to 26 mm, more typically 0.1 mm to 10 mm, and more typically 0.5 mm to 5 mm, although other lengths may also be used.
The shaped abrasive particle may have a “sharp portion” which is used herein to describe either a sharp tip or a sharp edge of an abrasive article. The sharp portion may be defined using a radius of curvature, which is understood in this disclosure, for a sharp point, to be the radius of a circular arc which best approximates the curve at that point. For a sharp edge, the radius of curvature is understood to be the radius of the curvature of the profile of the edge on the plane perpendicular to the tangent direction of the edge. Further, the radius of curvature is the radius of a circle which best fits a normal section, or an average of sections measured, along the length of the sharp edge. The smaller a radius of curvature, the sharper the sharp portion of the abrasive particle. Shaped abrasive particles with sharp portions are defined in U.S. Provisional Pat. Application Ser. No. 62/877,443, filed on Jul. 23, 2019, which is hereby incorporated by reference.
In the instance that the abrasive particles are precisely-shaped (e.g., into triangular platelets or conical particles), this effect of orientation can be especially important as discussed in U.S. Pat. Appl. Publ. No. 2013/0344786 A1 (Keipert), incorporated by reference herein. As used herein, the term “alignment” is used to refer to a relative position of an abrasive particle on a backing, while the term “orientation” refers to a rotational position of the abrasive particle at the aligned position. For example, a triangle-shaped particle may have a “tip up” orientation or a “tip down” orientation with respect to the backing.
As used herein, the term shaped abrasive particle refers to a monolithic abrasive particle. As shown, shaped abrasive particle is free of a binder and is not an agglomeration of abrasive particles held together by a binder or other adhesive material.
FIGS. 1 and 2 show an exemplary coated abrasive disc 100 according to the present disclosure, wherein shaped abrasive particles 130 are secured at precise locations and Z-axis rotational orientations to a backing 110. In one embodiment, shaped abrasive particles 130 are triangular prism shaped particles that appear rectangular when viewed from above.
Generally, a coated abrasive article 100 includes a plurality of abrasive particles embedded within a make coat that secures the particles to a backing. The backing may be formed from any known flexible coated abrasive backing, for example. Suitable materials for the backing include polymeric films, metal foils, woven fabrics, knitted fabrics, paper, nonwovens, foams, screens, laminates, combinations thereof, and treated versions thereof.
The abrasive particles 130 may be embedded within an abrasive layer, which can include multilayer construction having make 120 and size layers 140. Coated abrasive articles according to the present disclosure may include additional layers such as, for example, an optional supersize layer that is superimposed on the 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.
Make layer 120 can be formed by coating a curable make layer precursor onto a major surface of backing 110. The make layer precursor may include, for example, glue, phenolic resin, aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, free-radically polymerizable polyfunctional (meth)acrylate (e.g., aminoplast resin having pendant α,β-unsaturated groups, acrylated urethane, acrylated epoxy, acrylated isocyanurate), epoxy resin (including bis-maleimide and fluorene-modified epoxy resins), isocyanurate resin, and mixtures thereof. Of these, phenolic resins are preferred.
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 catalysts, 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 VARCUM (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., PHENOLITE 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 intended use(s), type(s) of abrasive particles, and nature of the coated abrasive article 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 particles are applied to and embedded in the make layer precursor. The triangular abrasive particles are applied nominally according to a predetermined pattern and Z-axis rotational orientation onto the make layer precursor. Using known orientation methods, such as electrostatic or magnetic orientation, it is possible to orient the abrasive particles with respect to the backing in order to improve performance of the particles.
FIG. 3 illustrates an image of a coated abrasive disc after some wear. Disc 200 has multiple rows 202 of abrasive particles embedded within a make coat 204 on backing 206. As abrasive article 200 is used in an abrading operation, shelling, or unintended removal, of abrasive particles occurs, as noted in the comparison of section 220, which still has abrasive particles substantially intact, with section 210, which has experienced significant shelling and, in some cases, complete removal of the make coat, exposing backing 206. However, while disc 200 appears to be unusable for further abrading operations, because of the experienced wear in area 210, the disc still has some abrasive life remaining in area 220. Uneven wear can result for a variety of factors, such as the different velocity experienced by abrasive particles in each of sections 210 and 220 during rotation.
It is desired to engineer an abrasive article, such as disc 200, that experiences wear more evenly across its diameter, and even circumferential wear. This may increase overall abrading performance of an abrasive article, as well as increase an experienced abrading performance as users are more likely to continue using the abrasive article.
FIG. 4 is a schematic cross-sectional view of a coated abrasive article in accordance with embodiments described herein. An abrasive article 300 includes a backing 310, to which a make coat 320 is applied. Abrasive particles 330 and 340 are embedded within make coat 320.
The use of precision shaped abrasive grain in abrasive articles has often focused on orienting abrasive particles such that a sharp tip is oriented toward a workpiece during an abrading operation. For this reason, many previous attempts at designing abrasive articles have focused on increasing a percentage of abrasive particles 330 with a base edge 334 embedded within a make coat 320 such that an opposing corner 332 can abrade a workpiece.
Surprisingly, it has been found that a wear life of an abrasive article 300 can be increased by orienting a second set of abrasive particles 340 with a different orientation than particles 330. As illustrated in FIG. 4 , particles 340 have an orientation opposite those of particles 330. Particles 340 are generally oriented such that a base edge 344 will engage a workpiece and an opposing tip 342 will embed in a make coat. Surprisingly, it was found that the addition of some particles 340 to an abrasive article 300, with a majority of particles being in orientation 330, increased the wear life of abrasive article 300 without significant reduction in abrasive performance. While the majority of abrasive particles are embedded in an abrading orientation (e.g., in a “tip up” position for a triangular shaped abrasive particle), if a portion of the abrasive particles are embedded in a stabilizing orientation (e.g. in a “tip down” position), the wear life of the abrasive article improved. In some embodiments, abrasive articles are, therefore, purposefully embedded in an orientation other the abrading orientation. For example, at least 0.5% of the abrasive particles are in a non-abrading orientation, in one embodiment. In another embodiment, at least 1%, or at least 2%, or at least 3%, or at least 4%, or at least 5%, or at least 6%, or at least 7%, or at least 8%, or at least 9%, or at least 10%, or at least 11%, or at least 12%, or at least 13%, or at least 14%, or at least 15%, or at least 16%, or at least 17%, or at least 18%, or at least 19%, or at least 20%, or at least 21%, or at least 22%, or at least 23%, or at least 24%, or at least 25%. In some embodiment, up to 30%, 35%, or 40% of abrasive particles are in a non-abrading orientation.
While FIGS. 1-3 describe coated abrasive particles with triangular shaped abrasive particles, it is expressly contemplated that other shapes are possible. For example, rod shaped particles may be present in either or both of the first and second orientations on the abrasive article backing. Additionally, other polygonal prism shapes are also possible, in other embodiments. Further, other shapes such as trapezoids, pyramids, cones or truncated pyramids or cones are also contemplated.
FIG. 4 illustrates one embodiment where particles 340 are concentrated along the outer edge of a radius of abrasive article 300. However, it is expressly contemplated that, in some embodiments, particles 340 are spread across the entire diameter of abrasive article 300. Additionally, while particles 340 are illustrated as filling completely the spaces between rows of particles 330, it is expressly contemplated that in some embodiments, particles 340 are present at a lower density than particles 330 in a given area of coated abrasive article.
FIG. 5 illustrates a method of manufacturing a coated abrasive article in accordance with embodiments described herein. Method 400 may be used, for example, to make any of the coated abrasive articles discussed herein. However, it can also be used to make other suitable coated abrasive articles.
In block 410, a backing is provided. The backing may have a pre-treatment prior to the coating process, as indicated in block 402. Pre-treatments may help increase adhesion, reduce shelling, or reduce static, for example. The provided backing may also be untreated, however, as indicated in block 406. The backing may also have other features, as indicated in block 408. For example, the backing may be flexible or stiff, and may be made from any suitable woven or nonwoven material.
In block 420, a make coat is provided. The make coat is typically provided in an uncured form such that deposited abrasive particles can embed. The make coat can be deposited on the backing in any number of suitable manners including, for example, spray coating, roll-coating, etc.
In block 430, a first set of abrasive particles are embedded within the make coat. The first set of abrasive particles are precision shaped abrasive particles. The first set of abrasive particles may be triangular prisms, as indicated in block 412, rod shaped, as indicated in block 414, another polygonal shaped prism, as indicated in block 416, or another suitable shape 418. The first set of abrasive particles may be deposited and oriented on the backing using any suitable method, such as using electrostatic alignment, as indicated in block 422, which orients the particles in an X-Y direction, but not in a Z direction. Alternatively, the first set of abrasive particles may be deposited and oriented using magnetic alignment, as indicated in block 424. For example, the abrasive particles may include a magnetically responsive element or coating such that the particles, when exposed to a magnetic field, will orient in a desired orientation. For example, in one embodiment the particles orient such that corresponding faces of nearby particles are parallel to one another, and such that a sharp tip or edge is facing away from the backing. Alignment of abrasive particles may be accomplished using electrostatic coating or magnetic coating, as described in PCT Pat. Appl. Publ. Nos. WO2018/080703 (Nelson et al.), WO2018/080756 (Eckel et al.), WO2018/080704 (Eckel et al.), WO2018/080705 (Adefris et al.), WO2018/080765 (Nelson et al.), WO2018/080784 (Eckel et al.), WO2018/136271 (Eckel et al.), WO2018/134732 (Nienaber et al.), WO2018/080755 (Martinez et al.), WO2018/080799 (Nienaber et al.), WO2018/136269 (Nienaber et al.), WO2018/136268 (Jesme et al.), WO2019/207415 (Nienaber et al.), WO2019/207417 (Eckel et al.), WO2019/207416 (Nienaber et al.), and U.S. Provisional Nos. 62/914,778 filed on Oct. 14, 2019 and 62/875,700 filed Jul. 18, 2019, and 62/924,956, filed Oct. 23, 2019.
In some embodiments, the abrasive particles are magnetically responsive. In one embodiment, making particles magnetically responsive includes coating non-magnetically responsive particles with a magnetically responsive coating. However, in another embodiment, the particles are formed with magnetically responsive material, for example as recited in co-owned provisional patent U.S. 62/914778, filed on Oct. 14, 2019. At least one magnetic material may be included within or coated to shaped abrasive particle. Examples of magnetic materials include iron; cobalt; nickel; various alloys of nickel and iron marketed as Permalloy in various grades; various alloys of iron, nickel and cobalt marketed as Fernico, Kovar, FerNiCo I, or FerNiCo II; various alloys of iron, aluminum, nickel, cobalt, and sometimes also copper and/or titanium marketed as Alnico in various grades; alloys of iron, silicon, and aluminum (about 85:9:6 by weight) marketed as Sendust alloy; Heusler alloys (e.g., Cu2MnSn); manganese bismuthide (also known as Bismanol); rare earth magnetizable materials such as gadolinium, dysprosium, holmium, europium oxide, alloys of neodymium, iron and boron (e.g., Nd2Fe14B), and alloys of samarium and cobalt (e.g., SmCo5); MnSb; MnOFe2O3; Y3Fe5O12; CrO2; MnAs; ferrites such as ferrite, magnetite; zinc ferrite; nickel ferrite; cobalt ferrite, magnesium ferrite, barium ferrite, and strontium ferrite; yttrium iron garnet; and combinations of the foregoing. In some embodiments, the magnetizable material is an alloy containing 8 to 12 weight percent aluminum, 15 to 26 wt% nickel, 5 to 24 wt% cobalt, up to 6 wt% copper, up to 1 % titanium, wherein the balance of material to add up to 100 wt% is iron. In some other embodiments, a magnetizable coating can be deposited on an abrasive particle 100 using a vapor deposition technique such as, for example, physical vapor deposition (PVD) including magnetron sputtering. Including these magnetizable materials can allow shaped abrasive particle to be responsive a magnetic field. Any of shaped abrasive particles can include the same material or include different materials.
The magnetic coating may be a continuous coating, for example that coats an entire abrasive particle, or at least coats an entire surface of an abrasive particle. In another embodiment, a continuous coating refers to a coating present with no uncoated portions on the coated surface. In one embodiment, the coating is a unitary coating - formed of a single layer of magnetic material and not as discrete magnetic particulates. In one embodiment, the magnetic coating is provided on an abrasive particle while the particle is still in a mold cavity, such that the magnetic coating directly contacts an abrasive particle precursor surface. In one embodiment, the thickness of the magnetic coating is at most equal to, or preferably less than, a thickness of the abrasive particle. In one embodiment, the magnetic coating is not more than about 20 wt.% of the final particle, or not more than about 10 wt.% of the final particle, or not more than 5 wt.% of the final particle.
Magnetically aligning the abrasive particles with respect to each other generally requires two steps. First, providing the magnetizable abrasive particles described herein on a substrate having a major surface. Second, applying a magnetic field to the magnetizable abrasive particles such that a majority of the magnetizable abrasive particles are oriented substantially perpendicular to the major surface. Without application of a magnetic field, the resultant magnetizable abrasive particles may not have a magnetic moment, and the constituent abrasive particles, or magnetizable abrasive particles may be randomly oriented. However, when a sufficient magnetic field is applied the magnetizable abrasive particles will tend to align with the magnetic field. In favored embodiments, the ceramic particles have a major axis (e.g. aspect ratio of 2) and the major axis aligns parallel to the magnetic field. Preferably, a majority or even all of the magnetizable abrasive particles will have magnetic moments that are aligned substantially parallel to one another. As described above, abrasive particles described herein may have more than one magnetic moment, and will align with a net magnetic torque.
The magnetic field can be supplied by any external magnet (e.g., a permanent magnet or an electromagnet) or set of magnets. In some embodiments, the magnetic field typically ranges from 0.5 to 1.5 kOe. Preferably, the magnetic field is substantially uniform on the scale of individual magnetizable abrasive particles.
For production of abrasive articles, a magnetic field can optionally be used to place and/or orient the magnetizable abrasive particles prior to curing a binder (e.g., vitreous or organic) precursor to produce the abrasive article. The magnetic field may be substantially uniform over the magnetizable abrasive particles before they are fixed in position in the binder or continuous over the entire, or it may be uneven, or even effectively separated into discrete sections. Typically, the orientation of the magnetic field is configured to achieve alignment of the magnetizable abrasive particles according to a predetermined orientation, for example such that abrasive particles are parallel to each other and have cutting faces facing in a downweb direction.
Examples of magnetic field configurations and apparatuses for generating them are described in U. S. Pat. No. 8,262,758 (Gao) and U. S. Pat. Nos. 2,370,636 (Carlton), 2,857,879 (Johnson), 3,625,666 (James), 4,008,055 (Phaal), 5,181,939 (Neff), and British (G. B.) Pat. No. 1 477 767 (Edenville Engineering Works Limited).
In another embodiment, the abrasive particles are oriented and placed using a tool, as illustrated in block 426. In some embodiments, patterned drop coating can be achieved using an alignment tool by methods analogous to that described in PCT Pat. Appl. Publ. Nos. 2016/205133 (Wilson et al.), 2016/205267 (Wilson et al.), 2017/007703 (Wilson et al.), 2017/007714 (Liu et al.). The method generally involves the steps of filling the cavities in a production tool each with one or more triangular abrasive particles (typically one or two), aligning the filled production tool and a make layer precursor-coated backing for transfer of the triangular abrasive particles 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 particles 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 belt. 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 perform all steps or perform them in consecutive order, but they can be performed in the order listed or additional steps performed in between. The triangular abrasive particles 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 rectangular grid pattern, or other suitable pattern based on the shape of the abrasive particles.
Transfer coating using a tool having patterned cavities can be analogous to that described in U.S. Pat. Appln. Publ. No. 2016/0311081 A1 (Culler et al.). In some embodiments, abrasive particles can be applied onto the make layer through a patterned mesh or sieve.
In block 440, a second set of abrasive particles are embedded within the make coat. The second set of abrasive particles are also precision shaped abrasive particles, in one embodiment. The second set of abrasive particles may be triangular prisms, as indicated in block 432, rod shaped, as indicated in block 434, another polygonal shaped prism, as indicated in block 436, or another suitable shape, as indicated in block 438. The second set of abrasive particles may be deposited and oriented on the backing using any suitable method, such as using electrostatic alignment, as indicated in block 432, or using magnetic alignment, as indicated in block 434, or oriented and placed using an alignment tool, as illustrated in block 446. Additionally, the second set of abrasive particles may be placed with some randomness, as indicated in block 448, such that an average density of second abrasive particles are present, but alignment is not precise. Other alignment and orientation methods are also expressly contemplated, as indicated in block 449.
First and second particle sets may be the same shape, for example triangles 412 and triangles 432, or may be different shapes, such as triangles 412 and rods 434, for example. Other shapes and combinations are also expressly contemplated.
First and second particle sets may be the same size, in one embodiment. In another embodiment, first and second particle sets are different sizes. For example, the second particle set may include smaller particles that more easily fit between placed particles of the first particle set.
Additionally, while FIG. 5 illustrates placement of a first and second set of particles, it is expressly contemplated that a third set of particles may also be present and used to create 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). In some embodiments the third particle set includes crushed particles. The third particle set may include crushed particles that are smaller than the first and / or second particle sets. The third particle set may be randomly deposited to fill in gaps between the first and second sets of particles.
The first and second sets of abrasive particles may be embedded within the make coat and aligned using the same, or different deposition methods. For example, since the first abrasive particles are oriented and aligned with the intention of performing an abrading operation, they may be precisely aligned, for example using an alignment tool or using magnetic alignment methods. The second set of abrasive particles may be placed, in some embodiments, using a less precise method, such as electrostatic alignment or drop coating. In other embodiments, the first and second sets of abrasive particles are oriented using the same method. For example, an alignment tool may allow for simultaneous placement of the first and second sets of abrasive particles. Alternatively, each of a first and second tool, with different cavity arrangements can be used to place the particles.
Examples of suitable abrasive particles for first and / or second sets of 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 abrasive particles 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 shaped abrasive particles, 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 (Schwabel), 4,770,671 (Monroe et al.); and 4,881,951 (Monroe et al.). It is also contemplated that the abrasive particles could include 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, first and / or abrasive particles may be surface-treated with a coupling agent (e.g., an organosilane 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, first and / or second abrasive particles are ceramic abrasive particles such as, for example, sol-gel-derived polycrystalline alpha alumina particles. Abrasive particles 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 A1 (Culler et al.) and 2009/0169816 A1 (Erickson et al.).
Alpha alumina-based triangular abrasive particles can be made according to well-known multistep processes. Briefly, the method includes the 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 abrasive particle with the sol-gel, drying the sol-gel to form precursor triangular abrasive particles; removing the precursor abrasive particles from the mold cavities; calcining the precursor abrasive particles to form calcined, precursor abrasive particles, and then sintering the calcined, precursor abrasive particles to form the first and / or second set of abrasive particles. The process will now be described in greater detail.
Further details concerning methods of making sol-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 A1 (Culler et al.).
Examples of slurry derived alpha alumina abrasive particles can be found in WO 2014/070468, published on May 8, 2014. Slurry derived particles may be formed from a powder precursor, such as alumina oxide powder. The slurry process may be advantageous for larger particles that can be difficult to make using sol-gel techniques.
The abrasive particles may undergo a sintering process, such as the process described in U.S. Pat. 10400146, issued on Sep. 3, 2019, for example. However, other processing techniques are expressly contemplated.
Ultra-fine grain shaped grains may be formed using techniques described in U.S. PAP 2019/0233693, published on Aug. 1, 2019, or in WO 2018023177, published on Dec. 20, 2018, or in WO 2018/207145, published on Nov. 15, 2018.
Softer shaped grain particles, with Mohs hardness’ between 2.0 and 5.0, that can be used for non-scratch applications, can be made according to methods described in WO 2019/215539, published on Nov. 14, 2019.
In some preferred embodiments, the abrasive particles are precisely-shaped in that individual abrasive particles 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.
Abrasive particles 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.
The shaped abrasive particles can have at least one sidewall, which may be a sloping sidewall. In some embodiments, more than one (for example two or three) sloping sidewall can be present and the slope or angle for each sloping sidewall may be the same or different. In other embodiments, the sidewall can be minimized for particles where the first and the second faces taper to a thin edge or point where they meet instead of having a sidewall. The sloping sidewall can also be defined by a radius, R (as illustrated in FIG. 5B of US Patent Application No. 2010/0151196). The radius, R, can be varied for each of the sidewalls.
Specific examples of shaped particles having a ridge line include roof-shaped particles, for example particles as illustrated, in FIGS. 4A to 4C of WO 2011/068714. Preferred, roof-shaped particles include particles having the shape of a hip roof, or hipped roof (a type of roof wherein any sidewalls facets present slope downwards from the ridge line to the first side. A hipped roof typically does not include vertical sidewall(s) or facet(s)).
Methods for making shaped abrasive particles having at least one sloping sidewall are for example described in US Pat. Application Publication No. 2009/0165394.
Shaped abrasive particles can also include a plurality of ridges on their surfaces. The plurality of grooves (or ridges) can be formed by a plurality of ridges (or grooves) in the bottom surface of a mold cavity that have been found to make it easier to remove the precursor shaped abrasive particles from the mold.
The plurality of grooves (or ridges) is not particularly limited and can, for example, include parallel lines which may or may not extend completely across the side. Preferably, the parallel lines intersect with the perimeter along a first edge at a 90° angle. The cross-sectional geometry of a groove or ridge can be a truncated triangle, triangle, or other geometry as further discussed in the following. In various embodiments of the invention, the depth, of the plurality of grooves can be between about 1 micrometer to about 400 micrometers.
According to another embodiment the plurality of grooves include a cross hatch pattern of intersecting parallel lines which may or may not extend completely across the face. In various embodiments, the cross hatch pattern can use intersecting parallel or non-parallel lines, various percent spacing between the lines, arcuate intersecting lines, or various cross-sectional geometries of the grooves. In other embodiments the number of ridges (or grooves) in the bottom surface of each mold cavity can be between 1 and about 100, or between 2 to about 50, or between about 4 to about 25 and thus form a corresponding number of grooves (or ridges) in the shaped abrasive particles.
Methods for making shaped abrasive particles having grooves on at least one side are for example described in US Pat. Application Publication No. 2010/0146867.
The shaped abrasive particles may also have one or more notches on one of the faces of the abrasive particle, as described in PCT Application Ser. No. IB2019/060861, filed on Dec. 16, 2019.
Shaped abrasive particles can have an opening (preferably one extending or passing through the first and second side). Methods for making shaped abrasive particles having an opening are for example described in US Pat. Application Publication No. 2010/0151201 and 2009/0165394.
Shaped abrasive particles can also have at least one recessed (or concave) face or facet; at least one face or facet which is shaped outwardly (or convex). Methods for making dish-shaped abrasive particles are for example described in US Pat. Application Publication Nos. 2010/0151195 and 2009/0165394. Additionally, shaped abrasive particles may also have a multifaceted surface as described in U.S. Pat. 10,150,900, issued on Dec. 11, 2018.
Shaped abrasive particles can also have at least one fractured surface. Methods for making shaped abrasive particles with at least one fractured surface are for example described in US Pat. Application Publication Nos. 2009/0169816 and 2009/0165394.
Shaped abrasive particles can also have a cavity. Shaped abrasive particles may also include an aperture, such as that described in U.S. Pat. 8,142,532, issued on Mar. 27, 2012, herein incorporated by reference.
Shaped abrasive particles can also have a low roundness factor. Methods for making shaped abrasive particles with low Roundness Factor are for example described in US Pat. Application Publication No. 2010/0319269.
Shaped abrasive particles may have a second vertex on a second side, as described in U.S. 9,447,311, issued on Sep. 16, 2016. Methods for making abrasive particles wherein the second side is a vertex (for example, dual tapered abrasive particles) or a ridge line (for example, roof shaped particles) are for example described in U.S. PAP 2012/022733, published on Sep. 13, 2012.
Shaped abrasive particles may be formed to have sharp tips, such as those described in U.S. PAP 2019/0233693, published on Aug. 1, 2019, or in U.S. Provisional Application with Serial No. 62/877443, filed on Jul. 23, 2019.
Shaped abrasive particles may also be formed to include a rake angle, such as those described in WO 2019/207423, published on Oct. 31, 2019, or in WO 2019/207417, published on Oct. 31, 2019, or in PCT Application Ser. No. IB 2019/059112, filed on Oct. 24, 2019.
Shaped abrasive particles may also be formed to have a precision shaped portion and a non-shaped portion, such as a crushed portion, as described in U.S. Provisional Pat. Application 62/833865, filed on Apr. 15, 2019.
Shaped abrasive particles can also have a combination of one or more of shape features discussed herein, including a sloping sidewall, a groove, a recess, a facet, a fractured surface, a cavity, more than one vertex, sharp edges, a non-shaped portion, a notch, a rake angle and / or a low roundness factor.
As used herein in referring to triangular abrasive particles, the term “length” refers to the maximum dimension of a triangular abrasive particle. “Width” refers to the maximum dimension of the triangular abrasive particle that is perpendicular to the length. The terms “thickness” or “height” refer to the dimension of the triangular abrasive particle that is perpendicular to the length and width. For abrasive particles with shapes other than triangles, length refers to a longest dimension, and width refers to the maximum dimension perpendicular to the length, while thickness refers to a dimension perpendicular to both the length and width.
The shaped abrasive particles may have an elongated shape, such as that described in U.S. PAP 2019/0106362, published on Apr. 11, 2019, or in WO 2019/069157, published on Apr. 11, 2019. The elongate shape may be triangular-prism shaped, rod-shaped, or otherwise including one or more vertices along the perimeter.
The shaped abrasive particles may have a variable cross-sectional area along a length of the particle, such as those described in U. S. PAP 2019/0249051. For example, the shaped abrasive particles may be dogbone shaped, or otherwise have a cross sectional area that varies from a first end to a second end.
The shaped abrasive particles may have a tetrahedron shape, such as those described in WO 2018/207145, published on Nov. 15, 2018, or those of U.S. Pat. No. 9,573,250, issued on Feb. 21, 2017.
The shaped abrasive particles may also have a concave or convex portion, or may be defined as having one or more acute interior angles, such as those described in U.S. 10,301,518, issued on May 28, 2019.
The shaped abrasive particles may also include shape-on-shape particles, such as a plate on plate shaped particle as described in 8,728,185, issued on May 20, 2014.
The shaped abrasive particles may also include shaped abrasive particles that have an irregular polygonal shape, as described in U.S. Provisional Pat. Application 62/924956, filed on Oct. 23, 2019.
The shaped abrasive particles may also be shaped to be self-standing abrasive particles, such that cutting portions are more likely to embed in a make coat, for example, in an orientation away from the backing, such as those described in PCT Application with Ser. No. IB 2019/060457, filed on Dec. 4, 2019.
The first and / or second sets of abrasive particles 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.
The first set of abrasive particles 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.
Abrasive particles are typically selected to have a thickness in a range of from 0.1 micron to 1600 microns, more typically from 1 micron to 1200 microns, although other thicknesses may be used. In some embodiments, Abrasive particles may have an aspect ratio (length to thickness) of at least 2, 3, 4, 5, 6, or more.
Surface coatings either of the first and / or second abrasive particles may be used to improve the adhesion between abrasive particles and a binder in abrasive articles, or can be used to aid in electrostatic deposition of the abrasive particles. 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 abrasive particle 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 al.); 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 abrasive particle from capping. Capping is the term to describe the phenomenon where metal particles from the workpiece being abraded become welded to the tops of the abrasive particles. 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 JIS (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, F20, F22, F24, F30, F36, F40, F46, F54, F60, F70, F80, F90, F100, F120, F150, F180, F220, F230, F240, F280, F320, F360, F400, F500, F600, F800, F1000, F1200, F1500, and F2000. JIS grade designations include JIS8, JIS12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS600, JIS800, JIS1000, JIS1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS10000. 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 FEPA 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-11 “Standard Specification for Wire Cloth and Sieves for Testing Purposes”. ASTM E-11 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 the abrasive particles pass through a test sieve meeting ASTM E-11 specifications for the number 18 sieve and are retained on a test sieve meeting ASTM E-11 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+30, -30+35, -35+40, -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 be used such as -90+100.
Once the first and second abrasive particles 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.
In block 450, a size coat is applied over the embedded particles. The size layer precursor is applied over the at least partially cured make layer precursor and triangular abrasive particles. The size layer can be formed by coating a curable size layer precursor onto a major surface of the backing. The size layer precursor may include for example, glue, phenolic resin, aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, free-radically polymerizable polyfunctional (meth)acrylate (e.g., aminoplast resin having pendant a,β-unsaturated groups, acrylated urethane, acrylated epoxy, acrylated isocyanurate), epoxy resin (including bis-maleimide and fluorene-modified epoxy resins), isocyanurate 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 will also necessarily vary depending on the intended use(s), type(s) of abrasive particles, and nature of the coated abrasive belt being prepared, but generally will 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 article. 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 air blowers, 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 belts 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 belts 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 tetrafluoroborate, 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), humectants, 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, (montmorillonite) 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; vermiculite; wood flour; aluminum trihydrate; carbon black; aluminum oxide; titanium dioxide; cryolite; chiolite; and metal sulfites such as calcium sulfite.
Additionally, in some embodiments, in block 460, a supersize coat is applied over the size coat. The supersize coat may include fillers, grinding aids, lubricants, or suitable other materials.
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 belt. Useful supersize layers typically include a grinding aid (e.g., potassium tetrafluoroborate), 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, crosslinked silicones, and/or fluorochemicals. Useful supersize materials are further described, for example, in U. S. Pat. No. 5,556,437 (Lee et al.). 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 the construction of coated abrasive articles comprising an abrasive layer secured to a backing, wherein the abrasive layer includes 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).
FIG. 6 is a schematic cross-sectional view of an abrasive article deposition process for a coated abrasive article. An abrasive article 500 includes a backing 510 to which a make coat precursor 520 has been applied. A first set of abrasive particles 530 are embedded in make coat 520 such that a long base edge 534 is coupled to backing 510 and a tip 532 faces away from the backing. However, while triangles are illustrated in FIG. 6 , other shapes are also expressly contemplated. For example, tetrahedrons could also be placed with a bottom face coupled to backing 510 and a tip facing away from backing 510. Other shaped abrasive grains can also be suitably deposited onto backing 510.
A second set of abrasive grains 540 are illustrated in FIG. 6 during a deposition phase. However, while abrasive grains 540 are illustrated in their post orientation and alignment positions, it is expressly contemplated that, in some embodiments, at least some alignment occurs after particles 540 are placed. Particles 540 are illustrated as having an opposite orientation to particles 530, with a long edge 542 facing away from backing 510 and a tip 544 facing backing 510. From an abrading standpoint, the presence of long edge 542 facing away from backing 510 is generally not desired because edge 542 of particle 540 generally does not offer as much abrading efficacy as tip 544.
Surprisingly, it was found, as discussed in greater detail in the Examples herein, that having a portion of abrasive particle in the 540 orientation resulted in better overall wear performance of an abrasive article. As illustrated by the ratio 550, in some embodiments a majority of abrasive particles are present in a primary orientation 530. In some embodiments, the percentage of abrasive particles present in orientation 540 is as low as 1%. The percentage of abrasive particles in second orientation may be higher, in some embodiments, for example, 2%, 3%, 4%, 5%, 8%, 10%, 15%, or even 20%, as illustrated in FIG. 6 . However, as described in the Examples in greater detail, increasing the percentage of particles in the secondary orientation higher does result in a decrease in abrading efficacy of abrasive article 500.
FIG. 7 is a top down schematic of a coated abrasive article accordance with embodiments described herein. While FIG. 6 illustrates an embodiment where a second set of abrasive particles are precisely shaped with respect to the first set of abrasive particles, FIG. 7 illustrates an article 700 with row of abrasive particles on a backing 710. Within the rows are two types of abrasive particles, a primary set of abrasive particles 720, which are in an abrading orientation and a secondary set of abrasive particles 730 are present in a secondary orientation. The second orientation may be opposite the abrading orientation, as illustrated in FIG. 6 , in some embodiments. However, in other embodiments, the secondary orientation may include secondary abrasive particles oriented at an angle with respect to primary abrasive particles.
FIGS. 8A and 8B illustrated close up views of coated abrasive articles. As illustrated in FIG. 8A, a coated abrasive particle 800, prior to size and supersize coating application, includes rows 812 of abrasive particles 810 with spacings 814 in between adjacent particles. Rows 812 have spacings 816 in between. As illustrated in FIG. 8A, a second set of particles 820 has been deposited such that particles 820 generally have a different orientation with respect to particles 810. Many particles 820 have landed in spacings 816 between rows 812 of particles 810 with a long edge facing away from the backing. Particles 820 may have an angle with respect to a backing (e.g. not standing perpendicular to backing), may be at an angle with respect to particles 810 (e.g. having a face that is not parallel to particles 810 in rows 812). While some particles 820, as illustrated in FIG. 8B, may have an orientation with a face substantially parallel to the backing, the majority of particles 820 are oriented such that a tip generally faces the backing and an edge generally faces away from the backing. A third set of particles 830 may also be present to create a closed coat. As illustrated in FIGS. 8A and 8B, the third set of particles 830 includes crushed particles of a smaller grade than either first or second particles 810, 820, respectively.
Examples of workpiece materials include metal, metal alloys, steel, steel alloys, aluminum, exotic metal alloys, ceramics, glass, wood, wood-like materials, composites, painted surfaces, plastics, reinforced plastics, stone, and/or combinations thereof. The workpiece may be flat or have a shape or contour associated with it. Exemplary workpieces include metal components, plastic components, particleboard, camshafts, crankshafts, furniture, and turbine blades.
An abrasive article is presented. The abrasive article includes a first set of shaped abrasive particles. A majority of the first set of shaped abrasive particles are oriented with respect to a backing in a first orientation. The abrasive article includes a second set of shaped abrasive particles. A majority of the second set of shaped abrasive particles are oriented with respect to the backing in a second orientation. The second orientation differs from the first orientation. The first and second set of shaped abrasive particles are embedded within a make coat layer on the backing.
The article may be implemented such that each of the first set of shaped abrasive particles includes a base portion and an abrading portion. The base portion is embedded within the make coat layer and the abrading portion faces away from the backing.
The article may be implemented such that some of the second set of shaped abrasive particles are oriented at least 90° with respect to the majority of the first set of shaped abrasive particles.
The article may be implemented such that the majority of the second set of shaped abrasive particles are oriented up to 180° with respect to the majority of the first set of shaped abrasive particles.
The article may be implemented such that it further includes a third set of abrasive particles forming a closed coat on the backing.
The article may be implemented such that the first set of shaped abrasive particles are oriented with respect to each other, such that faces of adjacent abrasive particles are parallel.
The article may be implemented such that the first set of shaped abrasive particles are more than 60% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 0.5% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 1% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 2% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 5% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 10% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 15% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are at least 20% by weight of the first and second sets of shaped abrasive particles.
The article may be implemented such that the second set of shaped abrasive particles are 25% by weight or less of the first and second sets of shaped abrasive particles.
The article may be implemented such that one of the first and second sets of abrasive particles are magnetically responsive.
The article may be implemented such that the abrasive article is an abrasive belt or an abrasive disc.
The article may be implemented such that the first set of shaped abrasive particles are rods, tetrahedrons, right angle triangular prisms, isosceles triangular prisms, equilateral triangular prisms, scalene triangular prisms, trapezoidal prisms, crescents, stars, cubes, dual tapered, or shape-on-shape.
The article may be implemented such that the second set of shaped abrasive particles are rods, tetrahedrons, right angle triangular prisms, isosceles triangular prisms, equilateral triangular prisms, scalene triangular prisms, trapezoidal prisms, crescents, stars, cubes, dual-tapered, shape-on-shape, or agglomerates.
The article may be implemented such that first set of shaped abrasive particles and the second set of shaped abrasive particles are the same shape.
The article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are different shapes.
The article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are substantially the same size.
The article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are different sizes.
The article may be implemented such that the coating layer is a make coat layer.
The article may be implemented such that the coating layer is a size coat.
The article may be implemented such that the coating layer is a supersize coat.
The article may be implemented such that the backing is a woven or nonwoven article.
The article may be implemented such that the second set of particles are within 10% of an average tip height for the first set of particles.
The article may be implemented such that the second set of particles are within 15% of an average tip height for the first set of particles.
The article may be implemented such that the second set of particles are within 20% of an average tip height for the first set of particles.
The article may be implemented such that the second set of particles are within 25% of an average tip height for the first set of particles.
A method of making a coated abrasive article is presented. The method includes coating a backing with a coating precursor layer. The method also includes embedding a first set of abrasive particles within the make coat precursor. A majority of the first set of abrasive particles have a first orientation with respect to the backing and are oriented such that faces of adjacent particles are parallel to each other. The method also includes embedding a second set of abrasive particles within the coating precursor layer. A majority of the second set of abrasive particles have a second orientation with respect to the backing. The method also includes curing the coating precursor layer.
The method may be implemented such that the coating precursor layer is a make coat. The method may also include applying a size coat over at least one of the first and second sets of abrasive particles.
The method may be implemented such that the coating precursor layer is a size coat. The method also includes applying a make coat to the backing.
The method may be implemented such that the first set of abrasive particles are embedded within the make coat. The second set of abrasive particles are embedded within the size coat.
The method may be implemented such that the coating precursor layer is a supersize coat. The method may also include applying a make coat and a size coat to the backing.
The method may be implemented such that the coated abrasive article is an abrasive disc or an abrasive belt.
The method may also include embedding a third set of abrasive particles within the make coat precursor.
The method may be implemented such that the third set of abrasive particles are smaller than the first or second set of abrasive particles.
The method may be implemented such that the third set of abrasive particles are crushed abrasive particles.
The method may also include filling an alignment tool with the first set of abrasive particles such that a plurality of cavities within the alignment tool receive one of the first set of abrasive particles, and positioning the alignment tool such that each of the first set of abrasive particles move out of the plurality of cavities and embed within the make coat.
The method may be implemented such that the first set of abrasive particles are magnetically responsive. Embedding the first set of abrasive particles within the make coat precursor may include exposing the first set of abrasive particles to a magnetic field such that the first set of abrasive particles move into the first orientation.
The method may be implemented such that the second set of abrasive particles are magnetically responsive. Embedding the second set of abrasive particles within the make coat precursor may include exposing the second set of abrasive particles to a magnetic field such that the second set of abrasive particles move into the first orientation.
The method may be implemented such that embedding the second set of abrasive particles within the make coat precursor includes exposing the second set of abrasive particles to an electrostatic field such that the second set of abrasive particles move into the second orientation.
The method may be implemented such that embedding the second set of abrasive particles within the make coat precursor includes drop coating the second set of abrasive particles. The first orientation may include the first set of abrasive particles aligned in rows on the backing. The second orientation may include each of the second set of abrasive particles embedding into the make coat in a space between a first row and a second row of the first set of abrasive particles.
The method may be implemented such that the first set of abrasive particles are shaped as one of: triangular prisms, rods, tetrahedrons, crescents, stars, cubes, rectangular prisms, or another regular polygonal prism.
The method may be implemented such that the second set of abrasive particles are shaped as one of: triangular prisms, rods, tetrahedrons, crescents, stars, cubes, rectangular prisms, or another regular polygonal prism.
The method may be implemented such that the first and second sets of abrasive particles are the same shape.
The method may be implemented such that the first and second sets of abrasive particles are different shapes.
The method may be implemented such that the first set of abrasive particles include a first size, the second set of abrasive particles include a second size. The first and second sizes are the same.
The method may be implemented such that the first set of abrasive particles are a first size, the second set of abrasive particles are a second size, and the first and second sizes are different.
An abrasive article is presented that includes a backing and a coating layer applied to the backing. The abrasive article includes a first set of shaped abrasive particles, each of the first set of shaped abrasive particles having a first base edge and a first cutting portion. The first set of shaped abrasive particles are in a first orientation with the first base edge embedded within the coating layer and the first cutting portion oriented away from the backing. The abrasive article includes a second set of shaped abrasive particles, each of the second set of shaped abrasive particles having a second base edge and a second cutting portion. The second set of shaped abrasive particles are in a second orientation with the second cutting portion embedded within the coating layer and the first base edge facing away from the backing.
The abrasive article may be implemented such that the first orientation includes the first set of abrasive particles aligned such that faces of adjacent particles are substantially parallel.
The abrasive article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are the same shape.
The abrasive article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are different shapes.
The abrasive article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are substantially the same size.
The abrasive article may be implemented such that the first set of shaped abrasive particles and the second set of shaped abrasive particles are different sizes.
The abrasive article may be implemented such that it includes a third set of abrasive particles that are smaller than the first set of shaped abrasive particles.
The abrasive article may be implemented such that the third set of abrasive particles are crushed abrasive particles.
The abrasive article may be implemented such that the cutting portion includes a cutting tip or a cutting edge.
The abrasive article may be implemented such that the first set of shaped abrasive particles are more than 60% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 0.5% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 1% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 2% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 5% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 10% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 15% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are at least 20% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles are 25% by weight or less of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that one of the first and second sets of abrasive particles are magnetically responsive.
The abrasive article may be implemented such that the abrasive article is an abrasive belt or an abrasive disc.
The abrasive article may be implemented such that the coating layer is a make coat layer.
The abrasive article may be implemented such that the coating layer includes a make coat layer and a size coat layer and the first set of shaped abrasive particles are embedded within the make coat layer.
The abrasive article may be implemented such that the second set of shaped abrasive particles are embedded within the size coat layer.
An abrasive article is presented that includes a backing and a make coat layer adhered to the backing. The abrasive article also includes a first set of abrasive particles embedded within the make coat layer. Each of the first set of abrasive particles has a first axis of rotation extending from a first base, and each of the first set of abrasive particles are orientated such that the first base is embedded within the make coat layer. The abrasive article also includes a second coat layer applied over the embedded first set of abrasive particles. The abrasive article also includes a second set of abrasive particles embedded within the make coat layer or second coat layer. Each of the second set of abrasive particles has a second axis of rotation extending from a second base. Each of the second set of abrasive particles are oriented such that the second base faces away from the backing.
The abrasive article may be implemented such that the first set of abrasive particles has a cutting edge, and the axis of rotation is defined by a line extending through the cutting edge and the base.
The abrasive article may be implemented such that each of the first set of abrasive particles are aligned such that adjacent bases are substantially parallel.
The abrasive article may be implemented such that each of the first set of abrasive particles are aligned such that adjacent axes of rotations are parallel.
The abrasive article may be implemented such that second bases of adjacent particles at oriented at an angle with respect to each other.
The abrasive article may be implemented such that the first set of abrasive particles are arranged in rows on the backing with a particle spacing between adjacent particles and a row spacing between adjacent rows.
The abrasive article may be implemented such that the second set of abrasive particles are embedded within the make coat layer or size coat layer such that a majority are embedded in the row spacings.
The abrasive article may be implemented such that it includes a third set of abrasive particles forming a closed coat.
The abrasive article may be implemented such that the coat layer is a size coat.
The abrasive article may be implemented such that it also includes a supersize coat.
The abrasive article may be implemented such that the coat layer is the supersize coat.
The abrasive article may be implemented such that the first and second sets of abrasive particles are shaped abrasive particles. The shape of each of the first and second sets of abrasive articles are selected from the group consisting of: triangular prisms, trapezoidal prisms, tetrahedrons, crescents, stars, rectangular prisms, or rods.
The abrasive article may be implemented such that the first set of shaped abrasive particles is more than 60% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 0.5% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 1% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 2% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 5% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 10% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 15% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 20% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is 25% by weight or less of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the first and second sets of shaped abrasive particles are the same size.
The abrasive article may be implemented such that the first and second sets of shaped abrasive particles are different sizes.
The abrasive article may be implemented such that one of the first and second sets of abrasive particles are magnetically responsive.
The abrasive article may be implemented such that the abrasive article is an abrasive belt or an abrasive disc.
An abrasive article is presented that includes a backing, a make coat layer, and a plurality of shaped abrasive particles embedded within the make coat layer. The plurality of shaped abrasive particles include a first plurality of shaped abrasive particles in a primary orientation. The primary orientation is an abrading orientation such that the first plurality of shaped abrasive particles are oriented with a cutting portion facing away from the backing. The plurality of shaped abrasive particles also include a second plurality of shaped abrasive particles in a secondary orientation. The secondary orientation is a stabilizing orientation such that the second plurality of shaped abrasive particles are oriented with a cutting portion facing toward the backing.
The abrasive article may be implemented such that the primary orientation is at least 60% of the plurality of shaped abrasive particles by weight and wherein the secondary orientation is between 0.5% and 25% of the plurality of shaped abrasive particles by weight.
The abrasive article may be implemented such that the first plurality of shaped abrasive particles are aligned with respect to each other.
The abrasive article may be implemented such that aligned includes corresponding faces of a first shaped abrasive particle and a second shaped abrasive particle being parallel.
The abrasive article may be implemented such that the first and second plurality of particles are the same shape.
The abrasive article may be implemented such that the first and second plurality of particles are different shapes.
The abrasive article may be implemented such that the first and second plurality of particles are the same size.
The abrasive article may be implemented such that the first and second plurality of particles are different sizes.
The abrasive article may be implemented such that the first plurality of shaped abrasive particles each have a base, and the bases of adjacent shaped abrasive particles are substantially parallel.
The abrasive article may be implemented such that the shape of each of the first and second sets of abrasive articles are selected from the group consisting of: triangular prisms, trapezoidal prisms, tetrahedrons, crescents, stars, rectangular prisms, or rods.
The abrasive article may be implemented such that the first set of shaped abrasive particles is more than 60% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 0.5% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 1% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 2% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 5% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 10% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 15% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is at least 20% by weight of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that the second set of shaped abrasive particles is 25% by weight or less of the first and second sets of shaped abrasive particles.
The abrasive article may be implemented such that one of the first and second sets of abrasive particles are magnetically responsive.
The abrasive article may be implemented such that the abrasive article is an abrasive belt or an abrasive disc.
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

In the following examples, fibre disc samples were made in the same way by hand using the specified minerals and alignment tools, including a circular plastic transfer tool consisting of a rectangular array of triangular cavities, having geometries such as those described in FIGS. 4A-4C of PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al.). A make resin consisting of 49% resole phenolic resin (obtained as GP 8339 R-23 155B from Georgia Pacific Chemicals, Atlanta, Ga.), 41% calcium metasilicate (obtained as WOLLASTOCOAT from NYCO Company, Willsboro, N.Y) , and 10% water was used, along with a size resin consisting of 38% resole phenolic resin, 60% cryolite (Solvay Fluorides, LLC, Houston, Tex.), and 2% red iron oxide pigment. Discs were cured using a ramp up at 6 °/minute with stops at 70° for 45 minutes, 90° for 45 minutes, and 105° for 3 hours after make application or 16 hours after size application. Discs were then ramped down to room temperature at 6 °/min. After curing, discs were flexed in 2 perpendicular directions and left to condition in a humidity-controlled room for at least 3 days.
The discs were tested using either an automated test or an offhand beveling test. For the automated testing, a consistent torque control (set up at 3.4 amps) method was used. For each test, a 1018-14 steel bar measuring 1-inch (2.54-cm) by 1-inch (2.54-cm) was used as the test substrate (workpiece) with the surface to be abraded. The disc sample (7-inch (17.8-cm)) diameter disc with ⅞-inch (2.22-cm) diameter center hole) was installed on a disc grinder together with a 7-inch Extra Hard Red Ribbed back-up pad (available from 3M Company, St. Paul, Minnesota). The disc was run at 5000 revolutions per minute (rpm). The workpiece was pressed into the disc and moved from near-center (about 6.35 cm from the center) to the edge for four passes, and then near the end of the grind time it was swung back and forth quickly against the edge of the disc. This grinding process took 15 seconds, which was defined as one cycle. The workpiece was then cooled and tested again. The cut (the weight loss of the workpiece after an individual cycle) and the cumulative cut (the cumulative weight loss of the workpiece) in grams was recorded after each cycle. The end point of the test was 40% of maximum cut, or 100 or 300 cycles as specified in a given example. In the offhand testing, a right angle tool with an identical Extra Hard Red Ribbed back-up pad was used to grind a roughly 45° angle bevel onto a ¾” thick sheet of 1018 carbon steel alternately with flattening said bevel back out. A single cycle involves repeating this pattern back and forth for 1 minute. Testing was done for 10 cycles, or until a disc no longer was functional.

Example 1

Shaped abrasive particles were prepared according to the disclosure of U.S. Pat No. 8,142,531 (Adefris et al.). The shaped abrasive particles were prepared by molding alumina sol gel in equilateral triangle-shaped polypropylene mold cavities of side length 0.11 inch (2.794 mm) and a mold depth of 0.037 inch (0.931 mm).
The shaped abrasive particles were patterned on fibre discs using a circular plastic transfer tool consisting of a rectangular array of triangular cavities, having geometries such as those described in FIGS. 4A-4C of PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al.) at densities of 344 and 384 grains/in². Subsequently, the discs were backfilled with 50 grit garnet, or with electrostatically coated shaped grain of a lower aspect ratio (with additional 50 garnet as a final backfill). Sample details are shown in Table 1.

Table 1

Sample formulation details for Example 1
Sample	Shaped Grain Patterning Density (grains/in2)	Make (g)	Mineral (g)	Shaped grain Backfill (g)	50 garnet backfill (g)	Size (g)
1	344	4.3	14.4		13.6	13.7
2	384	4.4	16.8		12.2	14.3
3	344	4.3	14.4	3.5	10.7	14.2

Offhand bevel testing as described above was performed to evaluate these three samples, as well as 982C and 782C controls. Results are shown in FIGS. 9A and 9B. The experimental samples, in general, are shown to have similar performance by virtue of their identical mineral and similar pattern density. However, differences can be seen when considering weight loss and grams cut/grams weight lost. In this case, Sample 3, with electrostatically coated shaped grain, is found to have the lowest weight loss and highest grams cut/grams weight lost of the experimental samples. This is also seen observationally, in that Sample 3 is the only of the experimental samples to not have bare backing visible at some location on the disc following this relatively high pressure testing. FIG. 9C reinforces the idea that this improvement in disc survivability is due to the upside down particles, showing that Sample 3 has about 14 upside down grains/in². The other two samples shown have 0.2 g and 1.5 g shaped grain electrostatically coated, respectively, representing levels of 1.5%, 11%, and 25% w/w of the second grain relative to the patterned shaped grain. Corresponding samples were also tested via the above described automated method, where even the low 1.5% electrostatically coated addition is seen to have very low weight loss at similar cut values.

Table 2

Automated testing results for three different levels of electrostatically coated shaped grain backfill onto patterned lower aspect ratio shaped grain
No.	Material	Initial Cut (g)	Max Cut	Total Cut (g), Cycle 100	Weight Loss
4	0.2 g shaped grain backfill	20.85	28.86	2443	1.04
5	1.5 g shaped grain backfill	21.44	30.06	2511	1.38
6	3.6 g shaped grain backfill	21.61	27.6	2216	1.14

Example 2

Shaped abrasive particles were prepared according to the disclosure of U.S. Pat No. 8,142,531 (Adefris et al.). The shaped abrasive particles were prepared by molding alumina sol gel in equilateral triangle-shaped polypropylene mold cavities of side length 0.11 inch (2.794 mm) and a mold depth of 0.028 inch (0.711 mm).
The shaped abrasive particles were patterned on a fibre disc using a circular plastic transfer tool consisting of a rectangular array of triangular cavities, having geometries such as those described in FIGS. 4A-4C of PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al.). The overall cavity densities were 160 cavities per square inch (24.8 cavities /cm²), 264 cavities per square inch (40.9 cavities /cm²), and 304 cavities per square inch (47.1 cavities/cm²). Subsequently, the same shaped grain were electrostatically coated as backfill. The percentage of electrostatically coated shaped grains to precisely placed shaped grains ranged from 20% to 250%, with total mineral weights ranging from 9.3 to 16.8 g/disc. Additional 40 grit aluminum oxide (AO) backfill was added to some discs that were 12 g/disc total mineral weight or less.
Automated testing results are tabulated in Table 3. The 304 grains/in² samples had the highest total cut, but also very high weight loss. In general, weight loss was high for these samples across the board and there was no clear performance differentiation with these relatively high shaped grain backfill weights. One clear trend was that the addition of further backfill in the form of 40 AO improved life, as seen by the higher g cut/g weight loss ratio in identical pairs of samples with and without this additional backfill. Peak counts and number of upside down particles are shown in FIGS. 10A and 10B. Both measures correlated roughly to the total shaped grain mineral coat weight, though not linearly and not predictably.

Table 3

Example 2 formulation and automated test data
No.	Shaped Grain Patterning Density (grains/in2).	Make (g)	Miner. (g)	Shaped Grain Backfill (g)	AO Backfill (g)	Size (g)	% Weight shaped backfill	Total Cut (g)	Max Cut (g)	Total Cycles	Weight Loss
A
	160	4.2	4.6	11.6	0	15.8	252	3055	34.2	133	14.3
B	160	4.2	4.3	12.5	0	14.1	291	1892	31.4	76	16.8
C	160	4,4	4.1	7.3	13.1	14.8	178	3662	35.0	165	4.6
D	160	4.3	4.6	7.3	0	14.2	159	5089	35.5	236	7.8
E	160	4.2	4.2	5.1	9.9	14.4	121	2718	33.7	131	5.3
F	160	4.2	4.7	4.9	9.7	14.5	104	3310	35.7	151	4.7
G	264	4.3	8.2	8.4	0	15.1	102	6668	33.2	300	12.5
H	264	4.2	8.4	8.8	0	14	105	2913	33.1	117	15.4
I	264	4.3	8.3	4	8.2	14	48	4182	37.3	186	5.9
J	264	4.2	8.2	4.1	0	14.2	50	1279	38.2	42	6.0
K	264	4.3	7.8	1.7	8.4	14.2	22	3174	35.2	145	3.6
L	264	4.2	8.4	2	8.9	14	24	4292	37.2	186	3.6
M	304	4.2	10	6.9	0	14.3	69	6360	34.7	300	9.6
N	304	4.3	9.6	6.6	0	14.7	69	6165	35.2	300	11.7
O	304	4.2	9.9	2	8.2	15.2	20	4992	34.7	242	3.9
P	304	4.3	10	2.2	0	14.1	22	4262	40.8	177	5.7

Example 3

Shaped abrasive particles were prepared according to the disclosure of U.S. Pat No. 8,142,531 (Adefris et al.). The shaped abrasive particles were prepared by molding alumina sol gel in equilateral triangle-shaped polypropylene mold cavities of side length 0.11 inch (2.794 mm) and a mold depth of 0.037 inch (0.931 mm) were patterned on a fibre disc using a circular plastic transfer tool consisting of a rectangular array of triangular cavities, having geometries such as those described in FIGS. 4A-4C of PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al.) at a density of 384 grains/in². Subsequently, equilateral triangle shaped grains of height about 762 microns were electrostatically coated as backfill. The backfill was electrostatically coated at 12.5%, 25%, and 35% of total patterned mineral weight, for total mineral weights of about 17.2 g, 19.4 g, and 21.6 g. Additional 50 garnet backfill was added to all discs.
Automated testing results are tabulated in Table 4. 25% (4 g 762 micron equilateral triangle backfill) seems to be a tipping point for performance, as total cut begins to decrease and weight loss increases going to 35%. 12.5% (2 g of backfill) does not see the benefit of as much reinforcement, and thus has higher weight loss. Although its initial cut and total at cycle 100 are higher than the others, this is expected with a more open mineral coat. This 12.5% sample would not be expected to hold up as well in higher pressure testing as the 25% and 35% samples due to the higher weight loss.

Table 4

Automated testing results of three levels of electrostatically coated shaped grain backfill of smaller height
No.	Backfill (g)	Initial	Initial (7-10)	Max Cycle	Max Cut	Cycle	100	Total Cyc100	In. Wt	Fin. Wt	Slope	Wt loss
A
	2	22.55	126.3	9	34.1	23.3	2770	68.95	66.26	-0.119	2.69
B	4	21.17	122.7	4	35.4	22.5	2684	70.73	69.21	-0.134	1.52
C	6	23.21	116.3	6	30.8	24.7	2608	72.38	70.57	-0.064	1.81

Example 4

Shaped abrasive particles were prepared according to the disclosure of U.S. Pat No. 8,142,531 (Adefris et al.). The shaped abrasive particles were prepared by molding alumina sol gel in equilateral triangle-shaped polypropylene mold cavities of side length 0.11 inch (2.794 mm) and a mold depth of 0.037 inch (0.931 mm). These grains were patterned on a fibre disc a circular plastic transfer tool consisting of a rectangular array of triangular cavities, having geometries such as those described in FIGS. 4A-4C of PCT Pat. Publ. No. WO 2015/100018 A1 (Adefris et al.) at densities of 160 and 304 grains/in². Subsequently, equilateral triangle shaped grains of height about 762 microns were electrostatically coated as backfill. The backfill was electrostatically coated at 10-110% of total patterned mineral weight, for total mineral weights of about 18.6 g for the 304 grains/in² density, and about 9.6 g for the 160 grains/in² density.
Automated testing results for Example 4 are shown in Table 5. The two 304 grains/in² discs have moderate weight loss and total cut values, indicating some degree of reinforcement from the ~110% w/w smaller shaped grains coated, relative to the patterned mineral. However, the ~100% w/w addition of grains to the 160 linear samples is insufficient to overcome this very low mineral coating weight, thus leading to high weight loss.

Table 5

Formulation and automated test results for Example 4
No	Shaped Grain Patterning Density (grains/in2)	Mak e (g)	Miner al (g)	Backfi 11 (g)	Size (g)	Initial Cut (g)	Weigh t loss (g)	Total Cycle s	Total Cut (g)
A	304	4.6	8.8	9.6	18. 4	28.5	2.82	203	4699
B	304	4.5	8.8	9.9	19	28.1	2.74	150	3427
C	160	3.3	6	6.1	12. 1	32.7	9.82	149	3570
D	160	3.5	5.9	6.2	13. 9	33.5	7.56	300	6599

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 the 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.

Claims

1. An abrasive article comprising:

a first set of shaped abrasive particles, wherein a majority of the first set of shaped abrasive particles are oriented with respect to a backing in a first orientation;

a second set of shaped abrasive particles, wherein a majority of the second set of shaped abrasive particles are oriented with respect to the backing in a second orientation, and wherein the second orientation differs from the first orientation; and

wherein the first and second set of shaped abrasive particles are embedded within a make coat layer on the backing.

2. The abrasive article of claim 1, wherein each of the first set of shaped abrasive particles includes a base portion and an abrading portion, and wherein the base portion is embedded within the make coat layer and the abrading portion faces away from the backing.

3. The abrasive article of claim 1, wherein some of the second set of shaped abrasive particles are oriented at least 90° with respect to the majority of the first set of shaped abrasive particles.

4. The abrasive article of claim 1, wherein the majority of the second set of shaped abrasive particles are oriented up to 180° with respect to the majority of the first set of shaped abrasive particles.

5. The abrasive article of claim 1, and further comprising a third set of abrasive particles forming a closed coat on the backing.

6. The abrasive article claim 1, wherein the first set of shaped abrasive particles are oriented with respect to each other, such that faces of adjacent abrasive particles are parallel.

7. The abrasive article of claim 6, wherein the second set of shaped abrasive particles is at least 5% by weight of the first and second sets of shaped abrasive particles.

8. The abrasive article of claim 1, wherein one of the first and second sets of abrasive particles are magnetically responsive.

9. The abrasive article of claim 1, wherein the first set of shaped abrasive particles comprise:

a shape selected from the group consisting of: rods, tetrahedrons, right angle triangular prisms, isosceles triangular prisms, equilateral triangular prisms, scalene triangular prisms, trapezoidal prisms, crescents, stars, cubes, dual tapered, irregular polygonal faces, shape-on-shape, variable cross-sectional area; or

a feature selected from the group consisting of: a sloping sidewall, a groove, a recess, a facet, a fractured surface, a cavity, more than one vertex, sharp edges, a non-shaped portion, a notch, a rake angle and / or a low roundness factor.

10. A method of making a coated abrasive article, the method comprising:

coating a backing with a coating precursor layer;

embedding a first set of abrasive particles within the make coat precursor, wherein a majority of the first set of abrasive particles have a first orientation with respect to the backing and are oriented such that faces of adjacent particles are parallel to each other;

embedding a second set of abrasive particles within the coating precursor layer, wherein a majority of the second set of abrasive particles have a second orientation with respect to the backing; and

curing the coating precursor layer.

11. The method of claim 10, wherein the coating precursor layer is a make coat, and wherein the method also comprises applying a size coat over at least one of the first and second sets of abrasive particles.

12. The method of claim 10, wherein the coating precursor layer is a size coat, and wherein the method also includes applying a make coat to the backing.

13. The method of claim 12, wherein the first set of abrasive particles are embedded within the make coat, and wherein the second set of abrasive particles are embedded within the size coat.

14. The method of claim 10, and further comprising embedding a third set of abrasive particles within the make coat precursor.

15. The method of claim 14, and wherein the third set of abrasive particles are crushed abrasive particles.

16. The method of claim 10, and further comprising:

filling an alignment tool with the first set of abrasive particles such that a plurality of cavities within the alignment tool receive one of the first set of abrasive particles; and

positioning the alignment tool such that each of the first set of abrasive particles move out of the plurality of cavities and embed within the make coat.

17. The method of claim 10, wherein the first set of abrasive particles are magnetically responsive, and wherein embedding the first set of abrasive particles within the make coat precursor comprises exposing the first set of abrasive particles to a magnetic field such that the first set of abrasive particles move into the first orientation.

18. The method of claim 10, wherein embedding the second set of abrasive particles within the make coat precursor comprises drop coating the second set of abrasive particles, wherein the first orientation comprises the first set of abrasive particles aligned in rows on the backing, and wherein the second orientation comprises each of the second set of abrasive particles embedding into the make coat in a space between a first row and a second row of the first set of abrasive particles.

19. The method of claim 10, wherein the first set of abrasive particles are shaped as one of: triangular prisms, rods, tetrahedrons, crescents, stars, cubes, rectangular prisms, or another regular polygonal prism.

20. An abrasive article comprising:

a backing;

a coating layer applied to the backing;

a first set of shaped abrasive particles, each of the first set of shaped abrasive particles comprising a first base edge and a first cutting portion, wherein the first set of shaped abrasive particles are in a first orientation comprising the first base edge embedded within the coating layer and the first cutting portion oriented away from the backing; and

a second set of shaped abrasive particles, each of the second set of shaped abrasive particles comprising a second base edge and a second cutting portion, wherein the second set of shaped abrasive particles are in a second orientation comprising the second cutting portion embedded within the coating layer and the first base edge facing away from the backing.

21-37. (canceled)