Shaped abrasive particles

Abstract

This disclosure discloses a mold for preparing abrasive particles. The mold includes a surface and a plurality of cavities extending downward from the surface. Each cavity includes: a particle-shaped portion having a polygonal shape; and a fracture portion connected to the particle-shaped portion. The fracture portion is configured to fracture from the particle-shaped portion during a stress event, thereby obtaining abrasive particles with a fractured shape.

Description

Background Art

[0001] Abrasive grains and abrasive articles comprising abrasive grains can be used to grind, polish or grind a variety of materials and surfaces during product manufacturing.Therefore, there is always a need to improve the cost, performance or life of abrasive grains or abrasive articles. Summary of the Invention

[0002] A mold for producing abrasive particles is provided. The mold includes a surface and a plurality of cavities extending downward from the surface. Each cavity includes a particle-shaped portion having a polygonal shape and a fracture portion connected to the particle-shaped portion. The fracture portion is configured to break from the particle-shaped portion during a stress event, thereby producing an abrasive particle having a fractured shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The drawings illustrate generally by way of example, but not limitation, of the various embodiments discussed in this document.

[0004] Figure 1 are abrasive articles in which embodiments of the present invention may be used.

[0005] Figure 2A and Figure 2B is an illustrative diagram for aligning shaped abrasive particles on a coated abrasive article according to one embodiment of the present invention.

[0006] Figure 3 is a graph showing the effect of a magnetic field on abrasive particles.

[0007] Figure 4 is a diagrammatic representation of a hypothetical abrasive particle.

[0008] Figures 5A to 5E A torque graph of shaped abrasive particles according to one embodiment of the present invention is shown.

[0009] Figure 6 Components of shaped abrasive particles according to embodiments of the present invention are shown.

[0010] Figures 7A to 7J A view showing shaped abrasive particles according to one embodiment of the present invention is shown.

[0011] Figure 8 A method of making a coated abrasive article according to one embodiment of the present invention is shown.

[0012] Figure 9 A method of using a coated abrasive article according to one embodiment of the present invention is shown.

[0013] 10A to 10DAbrasive grains are shown as part of an abrasive article.

[0014] Figure 11 Fractured abrasive particles according to an embodiment of the present invention are shown.

[0015] Figure 12A and Figure 12B An abrasive tool for fracturing abrasive grains according to an embodiment of the present invention is shown.

[0016] Figure 13 Components of fractured shaped abrasive particles according to embodiments of the present invention are shown.

[0017] Figure 14 A method of preparing fractured abrasive grains according to an embodiment of the present invention is shown.

[0018] 15A to 15D Additional shapes of abrasive particles according to embodiments herein are shown.

[0019] 16-17 illustrate mold cavity shapes used to prepare abrasive grains as discussed in the Examples. DETAILED DESCRIPTION

[0020] Throughout this document, values ​​expressed in a range format should be interpreted in a flexible manner to include not only the values ​​explicitly listed as the limits of the range but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly listed. For example, the range "about 0.1% to about 5%" or "about 0.1% to 5%" should be interpreted to include not only about 0.1% to about 5%, but also individual values ​​(e.g., 1%, 2%, 3%, and 4%) and subranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. Unless otherwise indicated, the expression "about X to Y" has the same meaning as "about X to about Y." Similarly, unless otherwise indicated, the expression "about X, Y, or about Z" has the same meaning as "about X, about Y, or about Z."

[0021] In this document, unless the context clearly indicates otherwise, the terms "a", "an", or "the" are used to include one or more than one. Unless otherwise indicated, the term "or" is used to refer to a non-exclusive "or". The expression "at least one of A and B" has the same meaning as "A, B, or A and B". In addition, it should be understood that the words or terms used herein and not otherwise defined are for illustrative purposes only and are not limiting. Any use of section headings is intended to facilitate understanding of the document and should not be construed as limiting; information related to a section heading may appear within or outside that particular section.

[0022] In the methods described herein, unless a time or sequence of operations is explicitly enumerated, the various actions may be performed in any order without departing from the principles of the invention. Furthermore, specified actions may be performed simultaneously unless explicit claim language implies that they should be performed separately. For example, performing a claimed act of X and performing a claimed act of Y may be performed simultaneously in a single operation, and the resulting process would fall within the literal scope of the claimed process.

[0023] As used herein, the term "about" can allow for a degree of variability in a value or range, such as within 10%, within 5%, or within 1% of the stated value or limit of the stated range, and includes the specifically recited value or range.

[0024] As used herein, the term "substantially" refers to a majority or majority, such as 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%.

[0025] As used herein, term " shaped abrasive grain " means that at least a portion of abrasive grain has a predetermined shape, and this predetermined shape is copied by the die cavity for forming shaped precursor abrasive grain. Except in the case of abrasive fragments (for example, as described in U.S. Patent Application Publication No. 2009 / 0169816 and 2009 / 0165394), shaped abrasive grain will generally have the predetermined geometry that has roughly copied the die cavity for forming shaped abrasive grain. As used herein, shaped abrasive grain does not include the abrasive grain obtained by mechanical crushing operation. Suitable examples of the geometric shape with at least one top include polygonal (including equilateral, equiangular, star-shaped, regular and irregular polygons), lens-shaped, half-moon-shaped, circular, semicircular, elliptical, circular sector, circular segment, teardrop-shaped and hypocycloid (for example, superelliptical).

[0026] The term "ferrimagnetic" refers to a material that exhibits ferrimagnetism. Ferrimagnetism is a type of permanent magnetism that occurs in solids in which the magnetic fields associated with individual atoms spontaneously align themselves, some parallel, or in the same direction (as in ferromagnetism), while others are roughly antiparallel, or paired in opposite directions (as in antiferromagnetism). The magnetic behavior of single crystals of ferrimagnetic materials can be attributed to the parallel alignment; the dilution effect of these atoms in the antiparallel arrangement keeps the magnetic strength of these materials generally less than that of pure ferromagnetic solids such as metallic iron. Ferrimagnetism occurs primarily in magnetic oxides called ferrites. The spontaneous alignment that produces ferrimagnetism is completely destroyed above a temperature called the Curie point (a characteristic of every ferrimagnetic material). When the temperature of the material drops below the Curie point, ferrimagnetism is restored.

[0027] The term "ferromagnetic" refers to a material that exhibits ferromagnetism. Ferromagnetism is a physical phenomenon in which certain uncharged materials strongly attract other materials. Compared to other substances, ferromagnetic materials are easily magnetized, and in strong magnetic fields, the magnetization approaches a well-defined limit called saturation. When the field is applied and then removed, the magnetization does not return to its initial value. This phenomenon is known as hysteresis. When heated to a certain temperature called the Curie point (which is usually different for each substance), ferromagnetic materials lose their inherent properties and are no longer magnetic; however, they become ferromagnetic again when cooled.

[0028] The terms "magnetic" and "magnetized" mean ferromagnetic or ferrimagnetic at 20°C, or capable of being made so, unless otherwise indicated. Preferably, the magnetizable layer according to the present disclosure has or can be made so by exposure to an applied magnetic field.

[0029] The term "magnetic field" refers to a magnetic field that is not generated by any celestial body or bodies (e.g., the Earth or the Sun). Generally speaking, the magnetic field used in the practice of the present disclosure has a magnetic field strength of at least about 10 Gauss (1 mT), preferably at least about 100 Gauss (10 mT), and more preferably at least about 1000 Gauss (0.1 T) in the region of the magnetizable abrasive particles.

[0030] The term "magnetizable" means capable of being magnetized or already in a magnetized state.

[0031] For the purposes of the present invention, geometric shapes are also intended to include regular or irregular polygons or star shapes, wherein one or more sides (peripheral portions of a face) may be arcuate (either facing inward or facing outward, with the first alternative being preferred). Thus, for the purposes of the present invention, triangular shapes also include three-sided polygons wherein one or more sides (peripheral portions of a face) may be arcuate. The second side surface may include (and preferably is) a second face. The second face may have an edge of the second geometric shape.

[0032] For purposes of the present invention, shaped abrasive grains also include abrasive grains that for example have faces with different shapes on the different faces of the abrasive grains. Some embodiments include shaped abrasive grains with opposite sides that have different shapes. Different shapes can include the difference in the surface area of ​​for example two opposite sides, or the different polygonal shapes of two opposite sides.

[0033] The shaped abrasive particles are typically selected to have side lengths in the range of 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 can be used.

[0034] The shaped abrasive particles may have a "sharp portion", which is used herein to describe a sharp point or sharp edge of an abrasive article. The sharp portion can be defined using a radius of curvature, which in the present disclosure is understood to be the radius of the arc of the curve that most closely approximates the point at which the sharp point is formed. For a sharp edge, the radius of curvature is understood to be the radius of curvature of the profile of the edge on a plane perpendicular to the tangent direction of the edge. In addition, the radius of curvature is the radius of the circle that best fits the average value of the normal section or measured section along the length of the sharp edge. The smaller the radius of curvature, the sharper the sharp portion of the abrasive particle. Shaped abrasive particles having a sharp portion are defined in U.S. Provisional Patent Application Serial No. 62 / 877,443, filed on July 23, 2019, which is hereby incorporated by reference.

[0035] Figure 1 1 is an abrasive article in which embodiments of the present invention can be used. In one embodiment, the coated abrasive article 100 includes a plurality of shaped abrasive particles 110 adhered to a backing 122. The cutting direction of the abrasive particles 110 is indicated by arrow 120. The abrasive particles are arranged on the backing 102 so that the cutting face 130 of each abrasive article is exposed to grind the surface. In some embodiments, as shown by parallel lines 150, at least a majority of the cutting faces 130 are aligned parallel to each other. In some embodiments, at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%, or at least about 90%, or at least about 95%, or substantially all of the cutting faces 130 are aligned relative to each other. In addition, at least a majority of the abrasive particle bases of the abrasive particles are also aligned relative to each other, as shown by reference numeral 140. In one embodiment, the abrasive particle bases are aligned perpendicular to the web direction, as shown by parallel lines 150. In some embodiments, at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%, or at least about 90%, or at least about 95%, or substantially all of the bases are aligned relative to each other.

[0036] The orientation of abrasive grains is particularly important for the efficacy of abrasive articles. For example, shaped abrasive grains can have sharp tips or sharp edges that should be oriented away from the backing material. As discussed in more detail below, sharp edges can have preferred grinding orientations and can have different grinding properties, depending on whether the cutting surface is leading or trailing during the grinding operation. The orientation of abrasive grains in coated abrasive articles generally has an impact on grinding properties. In the case of precise shaping of abrasive grains (for example, precisely shaped as triangular flakes or conical particles), this orientation effect may be particularly important, as described in U.S. Patent Application Publication No. 2013 / 0344786A1 (Keipert), which is incorporated herein by reference.

[0037] For several reasons, the orientation and alignment of the particles 110 are advantageous. The particles described herein can have sharp cutting edges along the cutting face. Orienting such particles so that the cutting face is perpendicular to the web direction allows the abrasive article to have a sustained and higher cutting rate. Specifically, a 90° orientation relative to the web direction can help reduce wear-out by enabling the shaped abrasive particles to more easily subsequently break after they have already broken.

[0038] A solution is needed that can align the shaped particles generally perpendicular to the web direction while orienting the sharp edges or tips of the abrasive particles away from the backing, e.g. Figure 1 As shown. The solution should also be able to orient the precisely shaped abrasive particles with a forward to backward tilt to achieve the desired rake angle. The rake angle is described in more detail in the commonly owned provisional patent application serial number 62 / 754,225 filed on November 1, 2018, which is incorporated herein by reference. In some embodiments, the shaped particles are shaped so that all or substantially all are oriented so that the cutting edges face in the same direction. The shaped abrasive particles described herein have improved orientation control, allowing more particles to be in the desired orientation and oriented relative to each other.

[0039] In addition to providing orientation benefits, in some embodiments, the particles designed herein include portions designed to break apart during manufacturing or during the first grinding operation. Due to limitations in mold design and release agent use, complete breakage can produce sharper tips or edges than can be achieved by molding alone. Furthermore, the sharp edges or tips formed by breakage during the manufacturing process can reduce or eliminate the need for high precision in manufacturing master tools, thereby increasing manufacturing speed, tooling options, and reducing costs.

[0040] Figure 2A and Figure 2B is a schematic diagram for aligning shaped abrasive particles on a coated abrasive article according to one embodiment of the present invention. Figure 2A A system 200 is shown for aligning magnetically responsive abrasive particles on a backing using a magnetic field. Preferred orientation of the shaped abrasive particles 250 can be achieved using shaped abrasive particles that include at least some magnetic material and exposing them to a magnetic field. The shaped abrasive particles can include magnetic material in their composition, can be coated with a layer of magnetic material, or both.

[0041] The magnetically responsive shaped abrasive particles can be randomly arranged or deposited on the backing 210. The shaped abrasive particles 250 can then be exposed to a magnetic field 230 in a manner that orients the shaped abrasive particles 250. Once properly oriented, the shaped abrasive particles 250 can be adhered to the backing 210 with a resin binder called a make coat. Optionally, additional layers, such as a size coat, can also be applied. As a result of this process, the individual shaped abrasive particles 250 are positioned on the backing 210 such that the abrasive particles 250 are parallel to each other and have cutting faces facing in the downweb direction 214.

[0042] Figure 2A A backing 210 is shown receiving abrasive particles 250 from a hopper 275. The backing 210 may have a make coat or make coat precursor (not shown) disposed thereon. The backing 210 moves along a web path 212 in a downweb direction 214 (e.g., machine direction). The backing 210 has a crossweb direction (not shown) that is perpendicular to the downweb direction 214. The magnetizable particles 250 fall through a portion of an applied magnetic field 230 onto the backing 210. At least some of the magnetizable particles 250 are abrasive particles having shapes described in further detail herein that cause them to experience a net magnetic moment when exposed to the magnetic field 230. Although Figure 2A and Figure 2B Triangular prisms are shown as examples in FIG. 2 , but it is expressly contemplated that other shapes described herein may better respond to the magnetic field 230 such that they are more easily aligned in a desired direction relative to the web and each other.

[0043] The magnetizable particles 250 are primarily deposited onto the backing 210 after traveling down the downwardly inclined dispensing surface 240, which is fed from a hopper 275. The backing 210 is handled by various web handling components 280, such as rollers, conveyor belts, feed rollers, and take-up rollers.

[0044] The shape of the magnetizable particles 250 affects how and whether each particle 250 will align when exposed to the magnetic field 230. Some of the factors that affect the orientation of the particles during manufacturing are: the size of the particles, the shape of the particles, the strength of the magnetic field, the type of magnetic material on the particles, the composition of the primer layer, the line speed and other manufacturing processes. As described in more detail in co-pending application 62 / 924,956 filed on October 23, 2019 (which is incorporated herein by reference), different shapes of magnetizable particles will experience different magnetic moments when exposed to a magnetic field that can cause them to "stand up" or "lie flat" on the backing 212. In addition to the standing or lying torque, there is also a torque that rotates the particles about the z-axis and orients the cutting surface. For example, Figure 2A and Figure 2BShown in FIG. 2 are particles 250, 292 that are "standing" on edge so that both the polygonal face and the cutting face 254 are perpendicular to the web.

[0045] It is desirable to have magnetizable particles 250 with shapes that orient them in the Z direction so that the cutting faces 254 are oriented in the downweb direction 214 and the cutting faces 254 of other particles are parallel to each other.

[0046] Generally, the applied magnetic field used in the practice of the present disclosure has a field strength of at least about 10 Gauss (1 mT), at least about 100 Gauss (10 mT), or at least about 1000 Gauss (0.1 T) in the region of the magnetizable particles that is affected (e.g., attracted and / or oriented), but this is not required.

[0047] The magnetic elements 202 and 204 are positioned so that the magnetic particles 250 are subjected to the force 230 of the magnetic field before the particles 250 also contact the backing 210. In one embodiment, the magnetic particles 250 are not subjected to the magnetic force 230 substantially before contacting the backing 210. In embodiments where the magnetic particles 250 are dispensed without being affected by a magnetic field, the particles 250 have a tendency to fall on the largest surface and be in a random orientation. When a magnetic field 230 is subsequently applied by the magnetic elements 202 and 204, the magnetic particles 250 will "stand up" so that the thickness 293 contacts the backing 210, so that the cut faces 254 are aligned in the downweb direction, and so that the particles 250 are substantially parallel to each other. In one embodiment, the magnetic particles 250 contact the backing 210 prior to applying a primer layer or primer precursor.

[0048] The applied magnetic field can be provided by, for example, one or more permanent magnets and / or electromagnets or a combination of magnets and ferromagnetic components. Suitable permanent magnets include rare earth magnets. The applied magnetic field can be static or variable (e.g., oscillating). The upper magnetic element and / or lower magnetic element (202, 204), each having a north pole (N) and a south pole (S), can be monolithic, or they can be composed of, for example, multiple component magnets and / or magnetizable bodies. If composed of multiple magnets, the multiple magnets in a given magnetic component can be connected and / or aligned together (e.g., at least approximately parallel) with respect to the magnetic field lines that are closest to each other of their component magnets. Magnets 202 and 204 can be held in place by one or more retainers (not shown). Although stainless steel 304 or equivalent materials are suitable for holding magnets 202 and 204 in place due to their low magnetic properties, magnetizable materials can also be used. Mild steel brackets can support the stainless steel retainers. However, the application of the magnetic field is not intended to be limited to the illustrated arrangement. In some embodiments, a yoke is also contemplated that connects magnet 202 and magnet 204. Additionally, in some embodiments, a Halbach magnet array may be suitable.

[0049] The downwardly inclined dispensing surface 240 can be inclined at any suitable angle, provided that the magnetizable particles can travel downward along the surface and be dispensed onto the web. Suitable angles can range from 15 to 60 degrees, although other angles can also be used. In some cases, it may be desirable to vibrate the downwardly inclined dispensing surface to facilitate particle movement.

[0050] The downwardly inclined dispensing surface may be constructed of any dimensionally stable material, which may be a non-magnetizable material. Examples include: metals, such as aluminum; wood; and plastics.

[0051] Once the magnetizable particles are applied to the backing 210, the make layer precursor is at least partially cured at a curing station (not shown) to securely hold the magnetizable particles in place. In some embodiments, additional magnetizable particles and / or non-magnetizable particles (e.g., filler abrasive particles and / or grinding aid particles) may be applied to the make layer precursor prior to curing.

[0052] In the case of a coated abrasive article, the curable binder precursor comprises a make coat precursor, and the magnetizable particles comprise magnetizable abrasive particles. A size coat precursor may be applied to the at least partially cured make coat precursor and the magnetizable abrasive particles, but this is not required. If a size coat precursor is present, the size coat precursor is at least partially cured at a second curing station, and the at least partially cured make coat precursor is optionally further cured. In some embodiments, a top coat is disposed on the at least partially cured size coat precursor.

[0053] Figure 2B A schematic diagram of a system 290 for aligning magnetically responsive particles on a backing is shown. Figure 2B A simple example is shown of a single particle 292 on a backing 294. The backing 294 is moved in the coating direction as indicated by arrow 295. As shown, magnetic elements 296, 297 generate a magnetic field 298 that acts on the particle 292.

[0054] Magnetic elements 296, 297 are positioned on opposite sides of the coated web and are offset relative to the coated web direction 295. In one embodiment, as Figure 2B As shown, the first magnetic element 296 encountered by the particle 292 is located below the backing 294, while the second magnetic element 297 is located above the backing 294. However, in another embodiment, the particle 292 first experiences the magnetic element located above the backing and the second magnetic element located below the backing. Other suitable configurations are also possible.

[0055] Figure 33 is a diagram showing the effect of a magnetic field on abrasive particles. Abrasive particles 300 are magnetically responsive abrasive particles, including, for example, a magnetically responsive coating (not shown). Figure 3 5 and 7 ). For ease of understanding, abrasive particles 300 are shown as rectangular prisms. However, similar principles will apply to abrasive particles with other shapes, such as those described in FIG. 5 and FIG. 7 .

[0056] The abrasive particles 300 have a length 330, a width 340, and a thickness 350. When dropped onto a backing, the abrasive particles 300 tend to land in position 310, as shown, with the maximum surface area in contact with the backing. However, when a magnetic field 360 is applied, the torque experienced by the abrasive particles 300 causes the maximum dimension to align with the direction of the magnetic field, into a second position 320.

[0057] Figure 4 4 is a diagrammatic representation of a hypothetical abrasive particle having equal height 420 and length 410, each having width 422 and width 412, respectively. The entire particle has a thickness 430. As described in greater detail in co-pending application 62 / 924,956, filed on October 23, 2019, by varying width 422, width 412, and thickness 430, the behavior of particle 400 can be altered as the net magnetic moment experienced is varied. When exposed to a perpendicular magnetic field, this L-shaped particle will experience a net magnetic moment with contributions from the base and axis.

[0058] Figure 1 2 illustrate triangular abrasive particles that may be used in constructing abrasive articles, such as coated abrasive articles, nonwoven abrasive articles, bonded abrasive articles, or other abrasive articles. However, it may be difficult to orient the triangular abrasive particles so that they "stand" in thickness with the cutting faces facing the same direction. However, as Figure 3 As can be appreciated from FIG. 5 , by adding one or more sacrificial portions to a particle, the magnetic moment experienced by the triangular particle can be altered.

[0059] Figures 5A to 5E A torque diagram of shaped abrasive particles according to one embodiment of the present invention is shown. Figures 5A to 5E The particles are responsive to magnetic fields, for example, comprising magnetically responsive materials or coatings of magnetically responsive materials. Figures 5A to 5E The particles were modeled as thin sheets of steel with a thickness of 1 / 4 unit length and various contours. The particles were positioned in a uniform magnetic field of 0.17 Tesla. Modeling and simulations were performed using Finite Element Method Magnetics (Version 4.2, http: / / www.femm.info). Figure 5A A depiction 510 of a rod-shaped particle having a length 502 of 1 unit and a width 504 of 0.1 units is shown. Figures 5B to 5E shows additional profiles and the resulting relative torque, which is relative to Figure 5A The rod is normalized so that the rod is subjected to a reference torque normalized to 1.0. The torque analysis of FIG5 does not directly consider the torque that forces the particles to "stand up", but rather analyzes the torque used to align the particles parallel to each other and with the cutting surface facing the down-web direction (e.g., Figure 1 2). Shapes that produce higher torques may be preferred to achieve better alignment, especially when the particles are exposed to adhesives or viscous fluids, and in situations where it may be desirable to use less magnetic material per particle. Figure 5B Shown is a depiction 520 of a right triangle shaped abrasive particle having a hypotenuse having a length of 1 unit 522. Triangle 522 is subjected to a relative torque of 0.545.

[0060] Figures 5C to 5E A triangular abrasive particle is shown with a sacrificial portion added to either end of the hypotenuse. In one embodiment, the sacrificial portion is in line with the side of the triangle that is not the hypotenuse. In one embodiment, the sacrificial portion is coplanar with respect to the triangular portion of the shaped abrasive particle. However, it is expressly contemplated that other positions of the sacrificial portion(s) are possible, such as those in line with the hypotenuse, or positioned so that they are not in line with any side. Figures 5C to 5E , each of the sacrificial portions has a width of 0.05 units, and the sacrificial portions have the same thickness as the triangular portion of the shaped abrasive particle.

[0061] Figure 5C A depiction 530 of a particle is shown having a hypotenuse having a length 532 of 1 unit and a first sacrificial portion 536 and a second sacrificial portion 538, each having a length of 0.15 units. Particle 530 experiences a relative magnetic moment of 0.859.

[0062] Figure 5D A depiction 530 of a particle is shown having a hypotenuse having a length 542 and a first sacrificial portion 546 and a second sacrificial portion 548. Sacrificial portion 546 and sacrificial portion 548 each have a length of 0.25 units. Particle 540 experiences a relative magnetic moment of 1.021, which is higher than rod 510.

[0063] Figure 5E A depiction 550 of a particle is shown having a hypotenuse having a length 552 and a first sacrificial portion 556 and a second sacrificial portion 558. Sacrificial portion 556 and sacrificial portion 558 each have a length of 0.35 units. Particle 550 experiences a relative magnetic moment of 1.170, which is higher than rod 510.

[0064] Figures 5A to 5E The sacrificial portion is shown as being symmetrical about the hypotenuse of the triangular particle. However, it is expressly contemplated that asymmetric sacrificial portions may also be used. A symmetrical design may be useful in that it does not matter which side, other than the hypotenuse, contacts the backing - due to the symmetry of the particle, the profile of the particle on the backing will be the same either way. However, for particle shapes where a specific "standing" orientation is desired, an asymmetric sacrificial portion or portions may be used to align the preferred cutting face perpendicular to the backing and parallel to the preferred cutting faces of the other particles.

[0065] In addition to altering the net magnetic moment of the shaped abrasive particles, the addition of the sacrificial portion can provide structural and performance benefits over similar shaped abrasive particles without the sacrificial portion. For example, as discussed in more detail below, Figure 10B and Figure 10D As shown, the sacrificial portion 1064 connected to the base surface 1062 can provide additional surface area for embedding in the make coat 1020. In addition, due to the geometry of the cutting face, the sacrificial portion 1068 will break at the breaking point when exposed to the working surface, resulting in a sharp edge 1078.

[0066] Figure 6 The component of shaped abrasive grain is shown.Shaped abrasive grain 600 has accurate engineering shape 610.Shape 610 comprises regular portion 612 and sacrificial portion 640.Regular portion 612 can be similar to rod-shaped 614, circle 616, polygon 622 or another shape.As in regular portion 612, term rule refers to the repeated shape seen in a plurality of abrasive grains 600 in abrasive article.Rule can comprise regular shape, such as regular polygonal shape, or it can comprise other shape, such as star-shaped, crescent-shaped or other irregular shape.In some embodiments, sacrificial portion 640 refers to a part for abrasive grain 600, and it breaks during or before the first grinding operation of abrasive article and does not provide any grinding effect to workpiece basically.In some embodiments, sacrificial portion 640 keeps being connected with regular portion 612 during grinding operation, but does not contribute to the grinding effect of abrasive grain 600 basically.

[0067] The sacrificial portion 640 may also be defined to last less than the full useful life of the article. For example, if the abrasive article is intended to last 100 hours of use, the sacrificial portion 640 lasts less than 100 hours of use. For example, the sacrificial portion 640 may last less than 10% of the useful life of the abrasive article, or less than 5%, or less than 4%, or less than 3%, or less than 2%, or less than 1%, or less than 0.5%, or less than 0.1%, or less than 0.01%.

[0068] The sacrificial portion 640 may have a shape, and may be a rod shape 642, or a polygonal shape 644, such as Figures 5C to 5EThe sacrificial portion 640 may be straight or may have a curvature 646. The sacrificial portion 640 may also have other defining features 648.

[0069] Although Figure 6 A single sacrificial portion 640 is shown in FIG, but it is expressly contemplated that a pair of sacrificial portions 640 may exist, such as Figures 5C to 5E 6. However, in some embodiments, there may be even more sacrificial portions 640, such as 3, 4, 5, or more sacrificial portions. In some embodiments, at least one sacrificial portion 640 is positioned such that it is planar 620 with at least a portion of the regular portion 612. However, in some embodiments, at least one sacrificial portion 640 is not planar 630 with the regular portion 612.

[0070] The shape 610 may include one or more cutting faces 632 that are intended to be angled away from the coated abrasive article backing so that the cutting faces 632 interact with the work surface during the grinding operation. The shape 610 may also include one or more base faces 634 that are intended to be directly connected to the abrasive article backing or embedded in a make resin.

[0071] The shaped abrasive particles are formed from a material 650. In one embodiment, the material 650 can be a ceramic material. The material 650 can be an aluminum oxide based material 652 or a zirconium oxide based material 654 or another material 656. Although Figure 6 6. Although not shown, it is expressly contemplated that material 650 may be a doped material, as described herein. Material 650 may be a continuous material 658 comprising a single material or a substantial blend of multiple materials. For example, material 650 may also include discrete portions 662 that may, for example, be more doped, formed of different materials, or comprise a blend of different materials. Additionally, material 650 may include one or more phases 664 of different materials.

[0072] In some embodiments, the shaped abrasive particles 600 can further include a magnetically responsive element 670. The magnetically responsive element 670 can include a magnetic coating applied prior to firing 672 of the particle, as described in U.S. Provisional Nos. 62 / 914,778, filed October 14, 2019, 62 / 875,700, filed July 18, 2019, and 62 / 924,956, filed October 23, 2019, or applied after firing, as described in PCT Patent Application Publications WO 2018 / 080703 (Nelson et al.), WO 2018 / 080756 (Eckel et al.), WO 2018 / 080704 (Eckel et al.), WO 2018 / 080705 (Adefris et al.), WO 2018 / 080706 (Adefris et al.), and WO 2018 / 080707 (Eckel et al.). 765 (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.). In some embodiments, the magnetically responsive element 670 can be part of the material 650 or can be another treatment of the abrasive grains 600 such that the abrasive grains 600 respond to an applied magnetic field. However, in other embodiments, a magnetic coating is not required, as particles herein having certain shapes may be self-aligned or electrostatically aligned.

[0073] Figures 7A to 7J A view showing shaped abrasive particles according to one embodiment of the present invention is shown.

[0074] Although many embodiments herein describe particle portions for orientation purposes, they may also provide other benefits. For example, the curved sacrificial portion may not be able to fully retract into the mold due to the mold shape, and in some embodiments will partially or completely rupture. Due to the limitations of mold design and release agent use, complete rupture can produce sharper tips or edges than can be achieved by molding alone. In addition, the sharp edges or tips formed by rupture during the manufacturing process can reduce or eliminate the need for high precision when manufacturing master mold tools, thereby increasing manufacturing speed, tool manufacturing options and reducing costs.

[0075] Figure 7AA spherical particle 700 is shown having a first sacrificial portion 702 and a second sacrificial portion 704. Spherical or nearly spherical particles are particularly difficult to orient. For example, if the particle has a preferred fracture orientation, orientation of the spherical particle may be desired. The first sacrificial portion 702 and the second sacrificial portion 704 may be of similar size or of different sizes, depending on the desired orientation of the particle 700. The first sacrificial portion 702 and the second sacrificial portion 704 may also each have a length between 10% and 100% of the diameter of the particle 700. Figure 7A In the embodiment of the present invention, the sacrificial portion 702 and the sacrificial portion 704 are each positioned perpendicular to the surface of the particle 700, but it is clearly contemplated that either or both of the sacrificial portions 702 and 704 may be positioned at another angle relative to the surface of the particle 700.

[0076] Figure 7B A rod-shaped particle 705 is shown having a single sacrificial portion 706. However, while a single sacrificial portion 706 is shown at the first end of the rod 705, it is expressly contemplated that another sacrificial portion may be positioned at the second end of the rod 705 or along the length of the rod. The sacrificial portion 706 is shown at an angle to the axis defined by the length of the rod 705. However, it is expressly contemplated that the sacrificial portion 706 may be co-linear with the rod 705 and may be a portion that extends beyond the size coat and / or top coat far enough so that it breaks apart during the first abrading operation. The sacrificial portion 706 may allow the rod 705 to be perpendicular to the backing of the coated abrasive article so that it is connected to the backing directly or through a make coat.

[0077] Figure 7C A particle 710 is shown having a first sacrificial portion 711 and a second sacrificial portion 712. Figure 7C As shown, in some embodiments, sacrificial portion 711 and sacrificial portion 712 are similarly shaped such that both include wedge-shaped edges. However, in other embodiments, either or both of sacrificial portion 711 and sacrificial portion 712 may be rod-shaped.

[0078] Figure 7D Particle 715 is shown having a first sacrificial portion 716 and a second sacrificial portion 717. Figure 7D As shown, both sacrificial portion 716 and sacrificial portion 717 are rectangular in shape. However, it is expressly contemplated that either or both of sacrificial portions 716, 717 may be cylindrical or another suitable shape. Additionally, while sacrificial portions 716, 717 are shown as being coplanar with the triangular portion of particle 715, it is expressly contemplated that either or both of sacrificial portions 716, 717 may not be coplanar with the triangular portion. In some embodiments, sacrificial portions 716, 717 may be cylindrical or another suitable shape. Figure 7D715 are shown as being collinear with the non-hypotenuse side of particle 715. However, either or both of sacrificial portions 716, 717 may not be collinear with either or both of the non-hypotenuse sides of particle 715. Additionally, while sacrificial portions 716, 717 are shown as being positioned at the first and second ends of the hypotenuse side of particle 715, it is expressly contemplated that they may be positioned at other suitable locations.

[0079] Figure 7E Particle 720 is shown having a first sacrificial portion 721 and a second sacrificial portion 722. Similar to particle 715, particle 720 has sacrificial portions 721 and 722 positioned at the first and second ends of the hypotenuse. However, first sacrificial portion 721 and second sacrificial portion 722 have a curvature. The curvature can be imparted through a molding process or through a firing process. In one embodiment, while first sacrificial portion 721 and second sacrificial portion 722 are shown as being located at either end of the hypotenuse, it is expressly contemplated that they may be located in other suitable locations.

[0080] Figure 7E The curvature of the sacrificial portions 721, 722 in the particle also has the added effect that during the particle drying process the portions 721, 722 will not be able to shrink and will break, leaving the generally triangular particle 720 with sharp edges at two corners.

[0081] Figures 7B to 7E An embodiment is shown in which the sacrificial portion is coplanar with the regular portion of the abrasive grain. However, in some embodiments, such as Figures 7F to 7I The sacrificial portions may not be coplanar as those shown in FIG.

[0082] Figure 7F An embodiment is shown having a particle 725 and a sacrificial portion 726 with a face angled away from the particle 725. The sacrificial portion 726 can be positioned at an angle such that it acts as a "holder" for the particle 725, such that the cutting edge 727 is angled relative to the backing of the coated abrasive article. In one embodiment, the cutting edge 727 can be parallel to the backing, or can be angled.

[0083] Figure 7G A particle 730 is shown having a sacrificial portion 731. In one embodiment, the sacrificial portion 731 is shown as being angled relative to the triangular faces of the particle 730. However, in another embodiment, the sacrificial portion 731 can be coplanar with the triangular faces.

[0084] Figure 7H and Figure 7IParticle 735 and particle 740 are shown having sacrificial portions 736 and 741, respectively. Sacrificial portions 736 and 741 are attached to the sides of particles 735 and 701 and are configured to be attached to the backing of a coated abrasive article. While a single sacrificial portion is shown for each of particles 735 and 740, it is expressly contemplated that additional sacrificial portions may be present.

[0085] Figure 7J A particle 745 having an equilateral triangle shape is shown. The particle 745 has three sacrificial portions 746, each extending from a vertex of the equilateral triangle shape.

[0086] Although Figures 7D to 7J A right triangle or an equilateral triangle is shown, but it is clearly contemplated that other polygonal shapes can be used as the base of abrasive particles. For example, another triangular shape, such as a scalene triangle, an isosceles triangle, an equilateral triangle, an acute angle or an obtuse angle triangle, can also be used as the theoretical polygonal shape of abrasive particles, with defects designed to similarly affect the net magnetic moment on the particle. In addition, a parallelogram, a rectangle, a square or other quadrilateral shapes can also be used as the theoretical polygonal base of abrasive particles. Other polygons can also be suitable, including five-star shapes like a star and a pentagon. In addition, shapes with curved sides (such as a crescent) can also be suitable. Other shapes can also be suitable, like a cross.

[0087] The shape of each face of abrasive grain can be controlled in part by the length that changes height, width or diameter.Though every limit can have any suitable length, every limit generally speaking can have in the scope of about 0.01mm to about 10mm, about 0.03mm to about 5mm, be less than, equal to or greater than about 0.01mm, 0.05mm, 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm or the length of about 10mm.

[0088] Shaped abrasive particles can be used in coated abrasive articles (e.g., Figure 1 The backing may have any desired degree of flexibility. The backing may comprise any suitable material. For example, the backing may comprise a polymer film, a metal foil, a woven fabric, a knitted fabric, a paper, a vulcanized fiber, a nonwoven, a foam, a screen, a laminate, or a combination thereof. The backing may also comprise various additives. Examples of suitable additives include colorants, processing aids, reinforcing fibers, heat stabilizers, UV stabilizers, and antioxidants. Examples of useful fillers include clay, calcium carbonate, glass beads, talc, clay, mica, wood chips, and carbon black.

[0089] At least some of the particles described herein can be characterized as having two portions, a cutting portion and a base portion. The cutting portion and the base portion are connected and can be imagined as forming two sides of a triangle. The cutting portion and the base portion can be connected at a 90° angle, or can be connected so that the particle has a controlled rake angle between -60° and 60°.

[0090] In some embodiments, the cutting portion and the base portion have similar shapes so that either can be used as the cutting portion or the base portion. The base portion is designed to be parallel to the backing and fixed to the backing. When the base portion is fixed to the backing, the cutting portion will be angled with respect to the backing at any angle between 30° and 129°.

[0091] The ratio of the height of the cutting portion to the maximum thickness is between 1.5 and 20. The ratio of the length of the base portion to the average width of the base portion is between 2 and 10. The width of the cutting edge is between 10% and 1000% of the height of the cutting edge.

[0092] It is envisioned that the particles described herein are all responsive to magnetic fields. For example, the particles may include a magnetic material or may have a magnetic coating applied before or after firing. When exposed to a suitable magnetic field, the magnetic response causes the particles to align in a preferred arrangement. The particles are designed to withstand a magnetic moment greater than the gravity on the particles, thereby causing the particles to "stand up" and the base edge to face the backing. The aspect ratio of the cutting portion and the base portion needs to be within a certain range so that the particles are aligned in a 90 ° orientation and stand vertically.

[0093] Figure 8 A method of making a coated abrasive article according to one embodiment of the present invention is shown. Figure 8 The method can be applied to form any of the particles described in Figures 5 or 7. Such methods are also applicable to forming particles of other shapes. In addition, although method 800 is described as a continuous set of steps, it is clearly contemplated that for some applications, the steps described below can occur in a different order. For example, steps 830, 840, and 850 can occur in a different order depending on, for example, the particles, binder, or coating composition.

[0094] In block 810, abrasive grains are formed. In one embodiment, the abrasive grains may be formed from a magnetic material such that they are magnetically responsive.

[0095] In step 810, abrasive grains are formed into a shape that experiences a net magnetic moment that, when exposed to a magnetic field, orients the grains so that the majority of the cutting faces of the abrasive grains are aligned with one another. Additionally, the grains are aligned so that the majority of their bases are in contact with or directly bondable to a backing material.

[0096] While many of the embodiments described herein contemplate particles having parallel surfaces, other shapes are expressly contemplated. Additionally, while cutting edges are described, it is contemplated that in some embodiments a cutting tip may be present.

[0097] The abrasive particles can be formed from a variety of suitable materials or combinations of materials. For example, the shaped abrasive particles can comprise a ceramic material or a polymer material. Useful ceramic materials include, for example, fused alumina, heat-treated alumina, white fused alumina, ceramic alumina materials (such as those commercially available from 3M Company, St. Paul, Minnesota, USA as 3M CERAMIC ABRASIVE GRAIN), alpha-alumina, zirconia, stabilized zirconia, mullite, zirconia-toughened alumina, spinel, aluminosilicates (e.g., mullite, cordierite), perovskites, silicon carbide, silicon nitride, titanium carbide, titanium nitride, aluminum carbide, aluminum nitride, zirconium carbide, zirconium nitride, iron carbide, aluminum oxynitride, silicon aluminum oxynitride, aluminum titanate, tungsten carbide, tungsten nitride, steatite, diamond, cubic boron nitride, sol-gel derived ceramics (e.g., alumina ceramics doped with additives), silica (e.g., quartz, glass beads, glass bubbles, and glass fibers), etc., or combinations thereof. Examples of sol-gel derived comminuted ceramic particles can be found in U.S. Patents 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.). Modifying additives can be used to enhance certain desired properties of the abrasive or to improve the efficiency of a subsequent sintering step. Modifying additives or precursors to modifying additives can be in the form of soluble salts, typically water-soluble salts. They are typically composed of metal-containing compounds and can be precursors to oxides of magnesium, zinc, iron, silicon, cobalt, nickel, zirconium, hafnium, chromium, calcium, strontium, yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium, cerium, dysprosium, erbium, titanium, and mixtures thereof. The specific concentrations of these additives that may be present in the abrasive dispersion can vary according to the requirements of those skilled in the art. Further details regarding methods of making sol-gel derived abrasive particles can be found, for example, in U.S. Patents 4,314,827 (Leitheiser), 5,152,917 (Pieper et al.), 5,213,591 (Celikkaya 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. Published Patent Applications 2009 / 0165394A1 (Culler et al.) and 2009 / 0169816A1 (Erickson et al.).

[0098] The shaped abrasive grains comprising polymeric material can be characterized as soft abrasive grains.Soft shaped abrasive grains can comprise the combination of any suitable material or material.For example, soft shaped abrasive grains can comprise the reaction product of the polymerizable mixture comprising one or more polymerizable resins.These one or more polymerizable resins are selected from phenolic resin, urea-formaldehyde resin, urethane resin, melamine resin, epoxy resin, bismaleimide resin, vinyl ether resin, aminoplast resin (it can comprise side chain α, β unsaturated carbonyl), acrylate resin, acrylated isocyanurate resin, isocyanurate resin, acrylated polyurethane resin, acrylic modified epoxy resin, alkyl resin, polyester resin, drying oil or their mixture.Polymerizable mixture can comprise additional components, such as plasticizer, acid catalyst, crosslinking agent, surfactant, soft abrasive, pigment, catalyst and antibacterial agent.

[0099] Where multiple components are present in the polymerizable mixture, the components may comprise any suitable weight percentage of the mixture. For example, the polymerizable resin may be in the range of about 35% to about 99.9% by weight, about 40% to about 95% by weight of the polymerizable mixture, or may be less than, equal to, or greater than about 35%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, 107%, 108%, 109%, 110%, 111%, 112%, 113%, 114%, 115%, 116%, 117%, 118%, 119%, 120%, 121%, 122%, 123%, 124%, 125%, 126%, 127%, 128%, 129%, 130%, 131%, 132%, 133%, 134%, 135%, 13 %, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or about 99.9% by weight.

[0100] If present, the crosslinking agent can range from about 2% to about 60%, from about 5% to about 10% by weight of the polymerizable mixture, or can be less than, equal to, or greater than about 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or about 15% by weight. Examples of suitable crosslinking agents include those available under the tradename CYMEL 303LF from Allnex USA Inc., Alpharetta, Georgia, USA; or CYMEL 385 from Allnex USA Inc., Alpharetta, Georgia, USA.

[0101] If present, the mild abrasive can range from about 5% to about 65%, from about 10% to about 20% by weight of the polymerizable mixture, or can be less than, equal to, or greater than about 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 100%, 110%, 111 %, 0%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, or about 65% by weight. Examples of suitable mild abrasives include the mild abrasive available from Imerys Talc America, Inc., Three Forks, Montana, USA, under the trade designation MINSTRON 353 TALC; the mild abrasive available from USG Corporation, Chicago, Illinois, USA, under the trade designation USG TERRA ALBA NO. 1 CALCIUM SULFATE; recycled glass (grit 40-70) available from ESCA Industries, Ltd., Hatfield, Pennsylvania, USA, silica, calcite, nepheline, syenite, calcium carbonate, or mixtures thereof.

[0102] If present, the plasticizer can be in the range of about 5% to about 40% by weight, about 10% to about 15% by weight of the polymerizable mixture, or less than, equal to, or greater than about 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% by weight of the polymerizable mixture. Examples of suitable plasticizers include acrylic resins or styrene butadiene resins. Examples of acrylic resins include those available under the tradename RHOPLEX GL-618 from Dow Chemical Company, Midland, Michigan, USA; HYCAR 2679 from The Lubrizol Corporation, Wickliffe, Ohio, USA; HYCAR 26796 from The Lubrizol Corporation, Wickliffe, Ohio, USA; ARCOL LG-650, a polyether polyol available from The Dow Chemical Company, Midland, Michigan, USA; or HYCAR 26315 from The Lubrizol Corporation, Wickliffe, Ohio, USA. Examples of styrene butadiene resins include those available under the tradename ROVENE 5900 from Mallard Creek Polymers, Inc., Charlotte, North Carolina, USA.

[0103] If present, the acid catalyst can range from 1% to about 20%, from about 5% to about 10%, or can be less than, equal to, or greater than about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or about 20% by weight of the polymerizable mixture. Examples of suitable acid catalysts include aluminum chloride solution or ammonium chloride solution.

[0104] If present, the surfactant may range from about 0.001% to about 15%, about 5% to about 10% by weight of the polymerizable mixture, or may be less than, equal to, or greater than about 0.001%, 0.01%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or about 15% by weight of the polymerizable mixture. Examples of suitable surfactants include those available under the trade designation GEMTEX SC-85-P from Innospec Performance Chemicals, Salisbury, North Carolina, USA; DYNOL 604 from Air Products and Chemicals, Inc., Allentown, Pennsylvania, USA; ACRYSOL RM-8W from The Dow Chemical Company, Midland, Michigan, USA; or XIAMETER AFE 1520 from The Dow Chemical Company, Midland, Michigan, USA.

[0105] If present, the antimicrobial agent can be in the range of 0.5 wt % to about 20 wt %, about 10 wt % to about 15 wt % of the polymerizable mixture, or can be less than, equal to, or greater than about 0.5 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt % or about 20 wt %. The example of a suitable antimicrobial agent includes zinc pyrithione.

[0106] If present, the pigment may range from about 0.1% to about 10%, about 3% to about 5% by weight of the polymerizable mixture, or may be less than, equal to, or greater than about 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% by weight of the polymerizable mixture. Examples of suitable pigments include pigment dispersions available under the tradename SUNSPERSE BLUE 15 from Sun Chemical Corporation, Parsippany, New Jersey, USA; pigment dispersions available under the tradename SUNSPERSE VIOLET 23 from Sun Chemical Corporation, Parsippany, New Jersey, USA; pigment dispersions available under the tradename SUN BLACK from Sun Chemical Corporation, Parsippany, New Jersey, USA; or pigment dispersions available under the tradename BLUE PIGMENT B2G from Clariant Ltd., Charlotte, North Carolina, USA.

[0107] The shaped abrasive particles are monolithic abrasive particles. As shown, the shaped abrasive particles do not contain a binder and are not agglomerates of abrasive particles held together by a binder or other adhesive material.

[0108] The shaped abrasive particles can be formed in many suitable ways, for example, the shaped abrasive particles can be prepared according to a multi-operation method. The method can be performed using any material or precursor dispersion material. In short, for embodiments in which the shaped abrasive particles are monolithic ceramic particles, the method may include the following operations: preparing a seeded or seedless precursor dispersion that can be converted into a counterpart (e.g., a boehmite sol-gel that can be converted into alpha alumina); filling one or more mold cavities having the desired shape of the shaped abrasive particles with the precursor dispersion; drying the precursor dispersion to form precursor shaped abrasive particles; removing the precursor shaped abrasive particles from the mold cavity; calcining the precursor shaped abrasive particles to form calcined precursor shaped abrasive particles; and then sintering the calcined precursor shaped abrasive particles to form shaped abrasive particles. This method will now be described in more detail in the context of shaped abrasive particles containing alpha-alumina. In other embodiments, the mold cavity can be filled with melamine to form melamine shaped abrasive particles.

[0109] The method may include providing a seeded or seedless precursor dispersion capable of being converted into a ceramic. In the example of adding seeds to the precursor, the precursor may introduce a seed iron oxide (e.g., FeO). The precursor dispersion may include a liquid as a volatile component. In one example, the volatile component is water. The dispersion may include enough liquid to make the viscosity of the dispersion low enough to fill the mold cavity and replicate the mold surface, but the amount of liquid cannot be too much because it will cause the cost of subsequently removing the liquid from the mold cavity to be too high. In one example, the precursor dispersion includes 2% to 90% by weight of particles capable of being converted into ceramics, such as monohydrated aluminum oxide (boehmite) particles, and at least 10% by weight, or 50% to 70% by weight, or 50% to 60% by weight of volatile components, such as water. Conversely, in some embodiments, the precursor dispersion includes 30% to 50% by weight or 40% to 50% by weight of solids.

[0110] Examples of suitable precursor dispersions include zirconium oxide sols, vanadium oxide sols, ceria sols, aluminum oxide sols, and combinations thereof. Suitable aluminum oxide dispersions include, for example, boehmite dispersions and other aluminum oxide hydrate dispersions. Boehmite can be prepared by known techniques or can be commercially obtained. Examples of commercially available boehmite include products sold under the trade names "DISPERAL" and "DISPAL," both from Sasol North America, Inc., or under the trade name "HIQ-40," from BASF. These monohydrated aluminum oxides are relatively pure; that is, they contain relatively little, if any, other hydrate phases besides the monohydrate and have a high surface area.

[0111] The physical properties of the resulting shaped abrasive particles can generally depend on the types of materials used in the precursor dispersion.As used herein, a "gel" is a three-dimensional network of solids dispersed in a liquid.

[0112] The precursor dispersion can comprise a modifying additive or a precursor of a modifying additive. The modifying additive can be used to enhance certain desired characteristics of the abrasive grain, or to improve the efficiency of subsequent sintering steps. The modifying additive or the precursor of the modifying additive can be in the form of a soluble salt, such as a water-soluble salt. They can comprise a metal-containing compound, and can be a precursor of an oxide of magnesium, zinc, iron, silicon, cobalt, nickel, zirconium, hafnium, chromium, yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium, cerium, dysprosium, erbium, titanium, and a mixture thereof. The specific concentrations of these additives that can be present in the precursor dispersion can vary.

[0113] The introduction of a modifying additive or a modifying additive precursor can cause the precursor dispersion to gel. The precursor dispersion can also be gelled by heating for a period of time to reduce the liquid content of the dispersion by evaporation. The precursor dispersion can also contain a nucleating agent. Nucleating agents suitable for use in the present disclosure can include fine particles of alpha alumina, alpha iron oxide, or its precursors, titanium dioxide and titanates, chromium oxide, or any other substance that nucleates the conversion. If a nucleating agent is used, it should be present in an amount sufficient to convert the alpha alumina.

[0114] Peptizing agent can be added in the precursor dispersion to prepare more stable hydrosol or colloidal precursor dispersion.Suitable peptizing agent is monoprotic acid or acidic compound, such as acetic acid, hydrochloric acid, formic acid and nitric acid.Also can use polyprotic acid, but they may make the precursor dispersion rapid gelling, thereby make to be difficult to it and handle or be difficult to introduce additional component.The boehmite of some commercial source comprises the acid titer (for example, formic acid or nitric acid that absorbs) that helps to form stable precursor dispersion.

[0115] The precursor dispersion can be formed by any suitable means; for example, in the case of a sol-gel alumina precursor, it can be formed by simply mixing alumina monohydrate with water containing a peptizing agent, or by forming a slurry of alumina monohydrate to which a peptizing agent is added.

[0116] Defoamers or other suitable chemicals may be added to reduce the tendency to form bubbles or entrap air during mixing. Other chemicals such as wetting agents, alcohols, or coupling agents may be added if desired.

[0117] Further operations may include providing a mold having at least one mold cavity, or a plurality of cavities formed in at least one major surface of the mold. In some examples, the mold is formed as a production tool, which can be, for example, a belt, a sheet, a continuous fiber web, a coating roller such as a rotary gravure roller, a sleeve mounted on a coating roller, or a die. In one example, the production tool may comprise a polymeric material. Examples of suitable polymeric materials include thermoplastics such as polyesters, polycarbonates, poly(ethersulfone), poly(methyl methacrylate), polyurethanes, polyvinyl chloride, polyolefins, polystyrene, polypropylene, polyethylene, or combinations thereof, or thermosetting materials. In one example, the entire mold is made of a polymeric material or a thermoplastic material. In another example, the surface of the mold that contacts the precursor dispersion when the precursor dispersion is dried (such as the surface of the plurality of cavities) comprises a polymeric material or a thermoplastic material, and the remaining portions of the mold can be made of other materials. For example, a suitable polymer coating can be applied to a metal mold to change its surface tension properties.

[0118] Polymer or thermoplastic production tools can be replicated from a metal master tool. The master tool can have the reverse pattern desired for the production tool. The master tool can be made in the same manner as the production tool. In one example, the master tool is made of metal (e.g., nickel) and is diamond turned. In one example, the master tool is formed at least in part using a stereolithography technique. The polymer sheet material can be heated together with the master tool so that the master tool pattern is embossed on the polymer material by pressing the two together. The polymer or thermoplastic material can also be extruded or cast onto the master tool and then pressed. The thermoplastic material is cooled to harden, thereby producing the production tool. If a thermoplastic production tool is used, care should be taken not to generate too much heat, which can deform the thermoplastic production tool, thereby limiting its lifespan.

[0119] The cavity can be accessed from an opening in either the top or bottom surface of the mold. In some examples, the cavity can extend through the entire thickness of the mold. Alternatively, the cavity can extend only a portion of the thickness of the mold. In one example, the top surface is generally parallel to the bottom surface of the mold, wherein the cavity has a generally uniform depth. At least one side of the mold, i.e., the side in which the cavity is formed, can remain exposed to the ambient atmosphere during the step of removing volatile components.

[0120] The cavities have a specific three-dimensional shape to produce shaped abrasive particles. The depth dimension is equal to the vertical distance from the top surface to the lowest point on the bottom surface. The depth of a given cavity can be uniform or can vary along its length and / or width. The cavities of a given mold can have the same shape or different shapes.

[0121] Another operation involves filling the cavity in the mold with the precursor dispersion (e.g., by conventional techniques). In some examples, a knife-roll coater or a vacuum slot die coater can be used. If necessary, a release agent can be used to assist in removing the particles from the mold. Examples of release agents include oils (such as peanut oil or mineral oil, fish oil), silicones, polytetrafluoroethylene, zinc stearate, and graphite. Generally, a release agent such as peanut oil in a liquid such as water or alcohol is applied to the surface of the production mold in contact with the precursor dispersion so that when demolding is required, there is about 0.1 mg / in per unit area of ​​the mold. 2 (0.6mg / cm 2 ) to about 3.0 mg / in 2 (20mg / cm 2 ), or about 0.1 mg / in 2 (0.6mg / cm 2 ) to about 5.0 mg / in 2 (30mg / cm 2) release agent. In some embodiments, the top surface of the mold is coated with the precursor dispersion. The precursor dispersion can be pumped onto the top surface.

[0122] In another operation, a scraper or leveling rod can be used to completely press the precursor dispersion into the cavity of the mold. The remaining portion of the precursor dispersion that did not enter the cavity can be removed from the top surface of the mold and recycled. In some examples, a small portion of the precursor dispersion can remain on the top surface, and in other examples, the top surface is substantially free of the dispersion. The pressure applied by the scraper or leveling rod can be less than 100 psi (0.6 MPa), or less than 50 psi (0.3 MPa), or even less than 10 psi (60 kPa). In some examples, the exposed surface of the precursor dispersion does not extend substantially beyond the top surface.

[0123] In those instances where it is desired to use the exposed surfaces of the cavities to form flat surfaces of shaped ceramic abrasive particles, it may be necessary to overfill the cavities (eg, using a micronozzle array) and allow the precursor dispersion to dry slowly.

[0124] Another operation involves removing volatile components to dry the dispersion. Volatile components can be removed by a rapid evaporation rate. In some examples, the removal of volatile components by evaporation is performed at a temperature above the boiling point of the volatile components. The upper limit of the drying temperature generally depends on the material from which the mold is made. In the case of a polypropylene mold, the temperature should be below the melting point of the plastic. In one example, for an aqueous dispersion containing about 40% to 50% solids and a polypropylene mold, the drying temperature can be from about 90°C to about 165°C, or from about 105°C to about 150°C, or from about 105°C to about 120°C. Higher temperatures can result in improved production speeds, but can also result in degradation of the polypropylene mold, thereby limiting its useful life as a mold.

[0125] During drying, the precursor dispersion shrinks, typically resulting in retraction from the cavity walls. For example, if the cavity has planar walls, the resulting shaped abrasive particles may often have at least three concave major sides. It has now been discovered that by concavely shaping the cavity walls (thereby increasing the cavity volume), shaped abrasive particles having at least three substantially planar major sides can be obtained. The degree of retraction generally depends on the solids content of the precursor dispersion.

[0126] In addition, as compared to Figure 7EAs described, some particle shapes as herein described are designed to utilize the retraction of particle precursor.For example, the curved sacrificial portion will not be able to retract in the mold due to the mold shape, and in some embodiments will be partially or completely broken.Due to the restriction that mold design and release agent use, complete breaking can produce than can realize by molding more sharp tip or edge alone.In addition, during the manufacturing process, the sharp edge or tip formed by breaking can reduce or eliminate when making master mold tool to high precision needs, thereby increase manufacturing speed, tool manufacturing option and reduce cost.

[0127] An additional operation involves removing the resulting precursor shaped abrasive particles from the mold cavity. The precursor shaped abrasive precursors can be removed from the cavity by using the following processes on the mold, alone or in combination: gravity, vibration, ultrasonic vibration, vacuum, or pressurized air to remove the particles from the mold cavity.

[0128] The precursor shaped abrasive particles can be further dried outside the mold. If the precursor dispersion is dried to the desired degree in the mold, this additional drying step is not necessary. However, in some cases, it may be economical to employ this additional drying step to minimize the residence time of the precursor dispersion in the mold. The precursor shaped abrasive particles will be dried at a temperature of 50° C. to 160° C., or 120° C. to 150° C., for 10 minutes to 480 minutes, or 120 minutes to 400 minutes.

[0129] Another operation involves calcining the precursor shaped abrasive particles. During calcination, substantially all volatile materials are removed, and the various components present in the precursor dispersion are converted to metal oxides. The precursor shaped abrasive particles are typically heated to a temperature of 400°C to 800°C and maintained within this temperature range until free water and more than 90% by weight of any bound volatile materials are removed. In an optional step, it may be desirable to introduce modifying additives by impregnation. Water-soluble salts can be introduced by injecting them into the pores of the calcined precursor shaped abrasive particles. The precursor shaped abrasive particles are then pre-calcined again.

[0130] An additional operation may involve sintering the calcined precursor shaped abrasive particles to form abrasive particles. However, in some examples where the precursor comprises a rare earth metal, sintering may not be necessary. Prior to sintering, the calcined precursor shaped abrasive particles are not fully densified and therefore lack the hardness required for use as shaped abrasive particles. Sintering is performed by heating the calcined precursor shaped abrasive particles to a temperature of 1000° C. to 1650° C. The length of time that the calcined precursor shaped abrasive particles can be exposed to the sintering temperature to achieve this degree of conversion depends on a variety of factors, but five seconds to 48 hours is possible.

[0131] In another embodiment, the duration of the sintering step ranges from one minute to 90 minutes.After sintering, the shaped abrasive particles 14 can have a Vickers hardness of 10 GPa (gigapascals), 16 GPa, 18 GPa, 20 GPa, or greater.

[0132] The method can be modified using additional operations such as rapidly heating the material from the calcining temperature to the sintering temperature and centrifuging the precursor dispersion to remove sludge and / or waste. Furthermore, the method can be modified by combining two or more of these method steps if desired.

[0133] In order to form soft shaped abrasive particles, the polymerizable mixture described herein can be deposited in a cavity. The cavity can have a shape corresponding to the negative stamp of the desired shaped abrasive particles. After the cavity is filled to the desired degree, the polymerizable mixture is cured in the cavity. Curing can occur at room temperature (e.g., about 25°C) or at any temperature above room temperature. Curing can also be achieved by exposing the polymerizable mixture to an electromagnetic radiation source or an ultraviolet radiation source.

[0134] The shaped abrasive particles can be individually sized according to designated nominal grades recognized by the abrasives industry. Recognized grading standards in the abrasives industry include those promulgated by ANSI (American National Standards Institute), FEPA (European Federation of Abrasive Manufacturers), and JIS (Japanese Industrial Standards). 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 numbers include F4, F5, F6, F7, F8, F10, F12, F14, F16, F18, 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 numbers 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 JIS10,000.

[0135] Any of the surfaces of the shaped abrasive particles can include surface features such as a generally planar surface; a generally planar surface having a triangular, rectangular, hexagonal, or other polygonal perimeter; a concave surface; a convex surface; a hole; a ridge; a line or lines; a protrusion; a point; or a depression. The surface features can be selected to change the cutting rate, reduce the wear of the formed abrasive particles, or change the final finish of the abrasive article. In addition, the shaped abrasive particles 300 can adopt a combination of the above-mentioned shape elements (e.g., convex side faces, concave side faces, irregular side faces, and flat side faces).

[0136] The shaped abrasive particles may have at least one sidewall, which may be a slanted sidewall. In some embodiments, there may be more than one (e.g., two or three) slanted sidewalls, and the inclination or angle of each slanted sidewall may be the same or different. In other embodiments, the sidewall may be minimized for particles where the first and second faces taper to a thin edge or point where they meet without a sidewall. The slanted sidewall may also be defined by a radius R (e.g., as in U.S. Patent Application No. 2010 / 0151196). Figure 5B ). The radius R of each of the side walls may vary.

[0137] Specific examples of shaped particles having ridges include roof-shaped particles, such as those described in WO 2011 / 068714. Figure 4 A to Figure 4 The particles shown in C. Preferred roof-shaped particles include particles having a hip roof or a hip roof shape (a type of roof in which any side wall facets present slope downwardly from a ridgeline to a first side). A hip roof generally does not include vertical side walls or facets.

[0138] The shaped abrasive particles may have one or more shape features selected from the group consisting of: an opening (preferably an opening extending through the first side and the second side); at least one recessed (or concave) face or facet; at least one face or facet that is outwardly shaped (or convex); at least one side comprising a plurality of grooves; at least one fractured surface; a cavity having a low roundness coefficient; or a combination of one or more of the shape features.

[0139] The shaped abrasive particles 300 may also include a plurality of ridges on their surface. The plurality of grooves (or ridges) may be formed by a plurality of ridges (or grooves) in the bottom surface of the mold cavity, which have been found to make it easier to remove the shaped abrasive particle precursors from the mold.

[0140] A plurality of grooves (or ridges) are not specifically limited and can, for example, comprise parallel lines which may extend completely or incompletely through the entire side. Preferably, the parallel lines intersect with the periphery at a 90 ° angle along the first edge. The cross-sectional geometry of the grooves or ridges can be a truncated triangle, a triangle or other geometric shapes, as further discussed below. In various embodiments of the present invention, the depth of a plurality of grooves can be between approximately 1 micron and approximately 400 microns.

[0141] In another embodiment, a plurality of grooves include a crosshatch pattern of intersecting parallel lines, which may extend completely or incompletely through the entire face. In various embodiments, the crosshatch pattern may include parallel lines or non-parallel lines, various lines intersecting with a percentage spacing, an arcuate crosshatch, or various cross-sectional geometries of the groove. In other embodiments, the quantity of the ridge (or groove) in the bottom surface of each die cavity may be between 1 and approximately 100, or between 2 to approximately 50, or between approximately 4 to approximately 25, thereby forming the groove (or ridge) of corresponding number in the formed abrasive grain.

[0142] Methods for preparing shaped abrasive particles having at least one inclined sidewall are described, for example, in U.S. Patent Application Publication No. 2009 / 0165394. Methods for preparing shaped abrasive particles having openings are described, for example, in U.S. Patent Application Publication Nos. 2010 / 0151201 and 2009 / 0165394. Methods for preparing shaped abrasive particles having grooves on at least one side are described, for example, in U.S. Patent Application Publication No. 2010 / 0146867. Methods for preparing dish-shaped abrasive particles are described, for example, in U.S. Patent Application Publication Nos. 2010 / 0151195 and 2009 / 0165394. Methods for preparing shaped abrasive particles with a low roundness coefficient are described, for example, in U.S. Patent Application Publication No. 2010 / 0319269. Methods for preparing shaped abrasive particles having at least one fractured surface are described, for example, in U.S. Patent Application Publication Nos. 2009 / 0169816 and 2009 / 0165394. Methods for preparing abrasive particles in which the second side comprises a vertex (eg, a double-wedge-shaped abrasive particle) or a ridge line (eg, a roof-shaped particle) are described, for example, in WO 2011 / 068714.

[0143] In block 820, the abrasive particles are rendered magnetically responsive. In one embodiment, rendering the particles magnetically responsive comprises coating non-magnetically responsive particles with a magnetically responsive coating. However, in another embodiment, the particles are formed of a magnetically responsive material such that steps 810 and 820 are performed substantially simultaneously, for example as described in commonly owned U.S. Provisional Patent No. 62 / 914,778, filed October 14, 2019.

[0144] In addition to the materials already described, at least one magnetic material may be included in or coated onto the shaped abrasive particles. Examples of magnetic materials include iron; cobalt; nickel; various alloys of nickel and iron sold as various grades of Permalloy; various alloys of iron, nickel, and cobalt sold as Fernico, Kovar, Fernico I, or Fernico II; various alloys of iron, aluminum, nickel, cobalt, and sometimes copper and / or titanium sold as various grades of Alnico; alloys of iron, silicon, and aluminum (about 85:9:6 by weight) sold as FeAlSi; Heusler alloys (e.g., Cu2MnSn); manganese bismuth (also known as Bismanol); rare earth magnetizable materials such as alloys of gadolinium, dysprosium, holmium, europium oxide, neodymium, iron, and boron (e.g., Nd2Fe 14 B) and alloys of samarium and cobalt (e.g., SmCo5); MnSb; MnOFe2O3; Y3Fe5O 12 ; CrO 2 ; MnAs ; ferrites, such as ferrite, magnetite ; zinc ferrite ; nickel ferrite ; cobalt ferrite, magnesium ferrite, barium ferrite, and strontium ferrite ; yttrium iron garnet ; and combinations thereof. In some embodiments, the magnetizable material is an alloy containing 8 to 12 weight percent aluminum, 15 to 26 weight percent nickel, 5 to 24 weight percent cobalt, up to 6 weight percent copper, and up to 1 weight percent titanium, with the balance of the material totaling 100 weight percent being iron. In some other embodiments, the magnetizable coating can be deposited on the abrasive grains 100 using vapor deposition techniques such as, for example, physical vapor deposition (PVD), including magnetron sputtering.

[0145] The inclusion of these magnetizable materials can make the shaped abrasive particles responsive to a magnetic field.Any of the shaped abrasive particles can comprise the same material or comprise different materials.

[0146] The magnetic coating can be a continuous coating, for example coating the entire abrasive particle, or coating at least one entire surface of the abrasive particle. In another embodiment, a continuous coating refers to a coating in which there are no uncoated portions on the coated surface. In one embodiment, the coating is an integral coating formed from a single layer of magnetic material, rather than as discrete magnetic particles. In one embodiment, the magnetic coating is provided on the abrasive particle while the abrasive particle is still in the mold cavity, such that the magnetic coating is in direct contact with the surface of the abrasive particle precursor. In one embodiment, the thickness of the magnetic coating is at most equal to or preferably less than the thickness of the abrasive particle. In one embodiment, the magnetic coating does not exceed about 20% by weight of the final particle, or does not exceed about 10% by weight of the final particle, or does not exceed 5% by weight of the final particle.

[0147] In block 830, the particles are positioned relative to one another on the backing. Aligning the abrasive particles relative to one another generally requires two steps. First, the magnetizable abrasive particles described herein are provided on a substrate having a major surface. Second, a magnetic field is applied to the magnetizable abrasive particles such that a majority of the magnetizable abrasive particles are oriented approximately perpendicular to the major surface.

[0148] In the absence of an applied magnetic field, the resulting 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 advantageous embodiments, the ceramic particles have a major axis (e.g., an aspect ratio of 2) and the major axis is aligned parallel to the magnetic field. Preferably, most or even all of the magnetizable abrasive particles will have magnetic moments that are aligned approximately parallel to each other. As described above, the abrasive particles described herein may have more than one magnetic moment and will be aligned with the net magnetic moment.

[0149] The magnetic field can be provided by any external magnet (e.g., a permanent magnet or an electromagnet) or a magnet group. In some embodiments, the magnetic field is typically in the range of 0.5 to 1.5 kOe. Preferably, the magnetic field is substantially uniform over the scale of a single magnetizable abrasive particle.

[0150] For the production of abrasive articles, a magnetic field can optionally be used to position and / or orient the magnetizable abrasive particles prior to curing a binder (e.g., glassy or organic) precursor to produce the abrasive article. The magnetic field can be substantially uniform across the magnetizable abrasive particles before they are fixed in place in the binder or continuous throughout the binder, or the magnetic field can be non-uniform or even effectively separated into discrete portions. Typically, the orientation of the magnetic field is configured to achieve alignment of the magnetizable abrasive particles according to a predetermined orientation.

[0151] As a result of this process, the individual shaped abrasive particles are positioned on the backing such that the abrasive particles are parallel to each other and have cutting faces facing in the downweb direction.

[0152] Examples of magnetic field configurations and apparatus for generating magnetic fields 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 UK Patent No. 1 477 767 (Edenville Engineering Works Limited).

[0153] In block 840, the particles are adhered to a backing.Any abrasive article, such as an abrasive belt or disc, may include a make layer to adhere the shaped abrasive particles or a blend of shaped and crushed abrasive particles to a backing.

[0154] Figure 8 Block 430 and block 440 are shown as two separate steps. However, it is expressly contemplated that in some embodiments, placement and alignment occur simultaneously, for example by exposing the particles to a magnetic field during placement.

[0155] In frame 850, apply other coating, such as double size coating or top size coating.Abrasive article can also comprise the double size coating that shaped abrasive grain is adhered to the base coat.Base coat, double size coating or the two can comprise any suitable resin, such as phenolic resin, epoxy resin, urea-formaldehyde resin, acrylate resin, amino plastic resin, melamine formaldehyde resin, acrylic modified epoxy resin, urethane resin or their mixture.In addition, base coat, double size coating or the two can comprise filler, grinding aid, wetting agent, surfactant, dye, pigment, coupling agent, tackifier or their mixture.The example of filler can comprise calcium carbonate, silicon dioxide, talcum, clay, calcium metasilicate, dolomite, aluminum sulfate or their mixture.In some embodiments, need curing step between the application of coating.For example, before applying double size coating, can at least partially solidify base coat.

[0156] Figure 9 A method of using an abrasive article according to one embodiment of the present invention is shown. Method 910 can be used to abrade a variety of different workpieces. While in contact, one of the abrasive article and the workpiece is moved relative to each other in a direction of use, and a portion of the workpiece is removed.

[0157] Examples of workpiece materials include metals, metal alloys, steel, steel alloys, aluminum exotic metal alloys, ceramics, glass, wood, wood-like materials, composite materials, painted surfaces, plastics, reinforced plastics, stone, and / or combinations thereof. The workpiece can be flat or have an associated shape or contour. Exemplary workpieces include metal parts, plastic parts, particle board, camshafts, crankshafts, furniture, and turbine blades.

[0158] Abrasive articles according to the present invention can be used to abrade a workpiece. Abrasive methods range from rough grinding (i.e., high pressure and high stock removal) to polishing (e.g., polishing a medical implant with an emery belt), the latter typically being made with finer abrasive particles. One such method comprises the steps of frictionally contacting an abrasive article (e.g., a coated abrasive article, a nonwoven abrasive article, or a bonded abrasive article) with a surface of a workpiece and moving at least one of the abrasive article or the workpiece relative to the other to abrade at least a portion of the surface.

[0159] In block 910, an abrasive article is provided. In one embodiment, the abrasive article includes a plurality of abrasive particles designed to have a first orientation of use and a second orientation of use. For example, see Figure 1 , moving the abrasive article in a first use direction refers to moving the abrasive article so that the cutting surface 130 first encounters the workpiece. The second use direction refers to moving the abrasive article in the opposite direction. According to various embodiments, a method of using an abrasive article, such as an abrasive belt or abrasive disk, includes contacting shaped abrasive particles with a workpiece or substrate.

[0160] According to various embodiments, the depth of cut in the substrate or workpiece can be at least 1 μm, about 10 μm, at least about 20 μm, at least about 30 μm, at least about 40 μm, at least about 50 μm, or at least about 60 μm. The depth of cut can depend in part on the size of the abrasive particles. For example, smaller particles can have even smaller depths of cut, such as less than 1 μm, or less than 0.5 μm, or less than 0.1 μm. A portion of the substrate or workpiece is removed by the abrasive article as chips.

[0161] According to various embodiments, the abrasive articles described herein can have several advantages when moved in a preferred direction of use. For example, at the same applied force, cutting speed, or a combination thereof, the amount of material removed from the workpiece, the length of the chip removed from the workpiece, the depth of cut in the workpiece, the surface roughness of the workpiece, or a combination thereof, can be greater in a first direction than in any other second direction.

[0162] For example, at least about 10%, or at least about 15%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 100%, at least about 120%, at least about 130%, at least about 140%, at least about 150% more material is removed from the substrate or workpiece in the first use direction. In some embodiments, about 15% to about 500% more, or about 30% to about 70%, or about 40% to about 60%, or less than, equal to, or greater than about 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 150%, 200%, 250%, 300%, 350%, 400%, 450%, 500%, 550%, 600%, 650%, 700%, 750%, 800%, 850%, 900%, 950%, 1000%, 1500%, 2000%, 2500%, 3000%, 3500%, 4000%, 4500%, 5000%, 5500%, 6000%, 6500%, 7000%, 7500%, 8000%, 8500%, 9000%, 9500%, 10000%, 15000%, 20000%, 25000%, 30000%, 35000 %, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 215%, 220%, 225%, 230%, 235 %, 240%, 245%, 250%, 255%, 260%, 265%, 270%, 275%, 280%, 285%, 290%, 295%, 300%, 305%, 310%, 315%, 320%, 325%, 330%, 335%, 340%, 345%, 350%, 355%, 360%, 365%, 370 %, 375%, 380%, 385%, 390%, 395%, 400%, 405%, 410%, 415%, 420%, 425%, 430%, 435%, 440%, 445%, 450%, 455%, 460%, 465%, 470%, 475%, 480%, 485%, 490%, 495%, or about 500% of the material removed. The amount of material removed can refer to an initial cut (e.g., the first cut of a cutting cycle) or a total cut (e.g., the sum of the amounts of material removed over a set number of cutting cycles).

[0163] As another example, the depth of cut in the substrate or workpiece may be at least about 10%, or at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 100%, at least about 120%, at least about 130%, at least about 140%, or at least about 150% deeper in the first use direction. In some embodiments, the depth in the first direction of use is about 10% to about 500%, or about 30% to about 70%, or about 40% to about 60%, or less than, equal to, or greater than about 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or more. , 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, 180%, 185%, 190%, 195%, 200%, 205%, 210%, 215%, 220%, 225%, 230%, 235 %, 240%, 245%, 250%, 255%, 260%, 265%, 270%, 275%, 280%, 285%, 290%, 295%, 300%, 305%, 310%, 315%, 320%, 325%, 330%, 335%, 340%, 345%, 350%, 355%, 360%, 365%, 37 0%, 375%, 380%, 385%, 390%, 395%, 400%, 405%, 410%, 415%, 420%, 425%, 430%, 435%, 440%, 445%, 450%, 455%, 460%, 465%, 470%, 475%, 480%, 485%, 490%, 495% or about 500%.

[0164] As another example, the arithmetic mean roughness value (Sa) of a workpiece or substrate cut by moving the abrasive article in the first use direction 202 or 304 can be higher than that of a corresponding substrate or workpiece cut under the same conditions but in the second movement direction. For example, when the workpiece or substrate is cut in the first direction, the surface roughness can be about 30% higher, or about 40% higher, about 50% higher, about 60% higher, about 70% higher, about 80% higher, about 90% higher, about 100% higher, about 110% higher, about 120% higher, about 130% higher, about 140% higher, about 150% higher, about 160% higher, about 170% higher, about 180% higher, about 190% higher, about 200% higher, about 210% higher, about 220% higher, about 230% higher, about 240% higher, about 250% higher, about 260% higher, about 270% higher, about 280% higher, about 290% higher, about 300% higher, about 310% higher, about 320% higher, about 330% higher, about 340% higher, about 350% higher, about 360% higher, about 370% higher, about 380% higher, about 390% higher, about 400% higher, about 410% higher, about 420% higher, about 430% higher, about 440% higher, about 450% higher, about 460% higher, about 470% higher, about 480% higher, about 490% higher, about 500% higher, about 510% higher, about 520% ​​higher, about 530% higher, about 540% higher, about 550% higher, about 5 0%, about 260% higher, about 270% higher, about 280% higher, about 290% higher, about 300% higher, about 310% higher, about 320% higher, about 330% higher, about 340% higher, about 350% higher, about 360% higher, about 370% higher, about 380% higher, about 390% higher, about 400% higher, about 410% higher, about 420% higher, about 430% higher, about 440% higher, about 450% higher, about 460% higher, about 470% higher, about 480% higher, about 490% higher, or about 500% higher. The arithmetic mean roughness value may be in the range of about 1000 to about 2000, about 1000 to about 1100, or less than, equal to, or greater than about 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, or about 2000.

[0165] Alternatively, the abrasive article may be moved in a second direction different from the first use direction, as shown in block 930. The second direction may be between about 1 degree and 360 degrees, about 160 degrees and about 200 degrees, less than, equal to, or greater than about 1 degree, 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 85 degrees, 90 degrees, 95 degrees, 100 degrees, 105 degrees, 110 degrees, 115 degrees, 120 degrees, 125 degrees, 130 degrees, 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, or a rotation relative to the first use direction. , 160 degrees, 165 degrees, 170 degrees, 175 degrees, 180 degrees, 185 degrees, 190 degrees, 195 degrees, 200 degrees, 205 degrees, 210 degrees, 215 degrees, 220 degrees, 230 degrees, 240 degrees, 250 degrees, 260 degrees, 265 degrees, 270 degrees, 275 degrees, 280 degrees, 285 degrees, 290 degrees, 295 degrees, 300 degrees, 305 degrees, 310 degrees, 315 degrees, 320 degrees, 325 degrees, 330 degrees, 335 degrees, 340 degrees, 350 degrees, 355 degrees or about 360 degrees.

[0166] While it may be desirable to move the abrasive article in a first direction of use, there are some reasons to move the abrasive article in a second direction of movement other than the first direction of use. For example, contacting a substrate or workpiece with the abrasive article and moving the abrasive article in the second direction may be beneficial for polishing the substrate or workpiece. While not intending to be bound by any particular theory, the inventors hypothesize that movement in the second direction may expose the substrate or workpiece to angles other than the rake angle of the abrasive article, which may be more suitable for polishing applications.

[0167] In some embodiments, the shaped abrasive particles described herein can be included in a random orbital sander or a vibrating sander. In these embodiments, it may be desirable to randomly orient the shaped abrasive particles (e.g., with different or random z-direction rotation angles). This is because the orientation of use of such abrasive articles is variable. Therefore, regardless of the specific orientation of use of the random orbital sander or the vibrating sander, randomly orienting the shaped abrasive particles can help expose the cutting surface of the shaped abrasive particles to the workpiece in an appropriate amount.

[0168] Shaped abrasive grains such as those described herein can account for 100 wt % of abrasive grains in any abrasive article.Alternatively, shaped abrasive grains can be a part for the blend of the abrasive grains distributed on the backing.If exist as a part for blend, then shaped abrasive grains can be in the scope of about 5 wt % to about 95 wt %, about 10 wt % to about 80 wt %, about 30 wt % to about 50 wt % of blend, or be less than, equal to or greater than about 5 wt %, 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, 90 wt % or about 95 wt % of blend.In blend, the remainder of abrasive grains can comprise conventional pulverizing abrasive grains.Pulverizing abrasive grains are formed by mechanical pulverization operation and do not have the shape of replication usually. The remainder of the abrasive grains may also comprise other shaped abrasive grains, which may, for example, include equilateral triangle shapes (eg, flat triangular shaped abrasive grains or tetrahedral shaped abrasive grains, wherein each face of the tetrahedron is an equilateral triangle).

[0169] 10A to 10D The embodiment in which the abrasive article is an abrasive belt or abrasive sheet adapted for linear movement is shown. However, in other embodiments, the abrasive article can be an abrasive disc adapted for rotational motion. The tangential direction of rotation for the abrasive disc can be determined by a line tangential to the outer periphery of the abrasive disc.

[0170] Figure 10A An abrasive article 1000 is shown in which a plurality of abrasive particles 1010 are embedded in a make layer 1030 located on a backing 1020. A size layer 1040 and an optional supersize layer 1045 may also be added. In some embodiments, as Figure 10B As shown in the close-up view of FIG, sacrificial portion 1068 may extend beyond coating 1067, which may be comprised of size coat 1040 and / or supersize coat 1045. However, while Figure 10B Sacrificial portions 1068 are shown exposed from the supersize layer 1045 and the size coat 1040. However, it is expressly contemplated that the size coat 1040 and / or supersize coat 1045 may cover the sacrificial portions 1068 of the edges 1066 in some embodiments.

[0171] Figure 10B A close-up view of a single particle 1060 embedded in connection with a backing is shown, wherein a coating 1067 is applied over the primer layer and a sacrificial portion 1068 extends generally above the coating 1067. Figure 10B As shown, the second sacrificial portion 1064 may extend beyond the base edge 1062 embedded within the make coat layer.

[0172] Figure 10C and Figure 10D The abrasive article 1000 is shown after initial contact with a workpiece. Figure 10C As shown, the plurality of particles 1070 remain connected to the backing 1020 via the primer layer 1030. In some embodiments, the second sacrificial portion 1074 remains embedded within the primer layer 1030m.

[0173] like Figure 10D As shown, a sharp edge 1078 is formed by the fracture of the sacrificial portion 1068. The sharp edge 1078 can have a sharp tip with a smaller radius of curvature than can be achieved using conventional molding processes. The fractured particle has a height 1076.

[0174] Figure 11 FIG. 1 shows a fractured abrasive particle according to an embodiment of the present invention. The particle 1100 is shown as having a generally triangular shape 1110, however, it should be understood that the concept extends to other suitable shapes. The generally triangular shape 1110 is imparted to the particle 1100 by a molding process, as described below with respect to FIG. Figure 13 Descriptive.

[0175] The particle 1100 has one or more fractured portions 1120 that break away from the particle 1100 during an initial drying step in the mold or during firing or sintering due to increased stress on the particle 1100. As described herein, the particle 1100 can be formed from a sol-gel, a slurry, or another suitable process. Abrasive particles are made by a variety of methods that require at least an initial drying step before removal from the mold. During the drying step, a certain degree of shrinkage occurs. The particle 1100 is formed so that at one or more fracture points 1130, the strain from the shrinkage caused during drying causes fracture at the fracture point, resulting in the fractured portion 1120. As Figure 11 As shown, the fractured portion 1120 represents a small volume of the triangular shape 1110 of the particle 1100. For example, in one embodiment, less than about 15%, or less than about 10%, or less than about 5% of the hypothetical polygonal shape is lost due to fracture.

[0176] Figure 12A and Figure 12BA mold for fracturing abrasive particles according to an embodiment of the present invention is shown. Mold 1200 shows a plurality of cavities after an initial drying process in which particles 1210 have been fractured along fracture points, thereby breaking fracture portions 1220. As shown in FIG. 12 , mold 1200 includes a cavity shape 1202 having a generally triangular shape 1204 and one or more fracture cavity portions 1206. During drying, the abrasive particle material shrinks and breaks away from the sides of the cavity. The fracture cavity portions 1206 are designed so that the fractured portions of the particles cannot retreat inwardly with the shape portions 1204, thereby causing fracture at fracture points 1230. As shown in FIG. Figure 12A and Figure 12B As shown, by angling the rupture portion away from the particle-shaped portion, a rupture point 1230 can be formed within the mold cavity 1202. The angle must be large enough to hinder shrinkage and, in turn, cause fracture. An acute angle 1208 relative to the particle-shaped portion 1204 is sufficient, however, a right angle or an obtuse angle may also be sufficient, depending on the drying conditions, solution composition and concentration, and the shaped portion 1204. Alternatively, the rupture portion 1230 may be curved, such as Figure 7E shown, for example, or simply wedge-shaped, as Figure 7C shown.

[0177] The fractured portion 1206 is shown as a rod-like shape extending from the corner of the shaped portion 1204. However, other shapes and other locations may also be suitable. However, in the context of a triangular abrasive particle, the presence of a fracture at each of the three vertices ensures that a sharp edge is available on the abrasive article, wherein the opposing edge can still be used to form a stable base for embedding within the make layer of the abrasive article.

[0178] Figure 13 Components of fractured shaped abrasive particles according to embodiments of the present invention are shown. Mold 1300 includes a plurality of cavities 1310. Each cavity 1310 includes a depth 1320 that can be constant or variable. For example, fractured portion 1314 can be deeper or shallower to promote fracture during drying. Cavity 1310 can also include a textured surface along the side or along the bottom to impart a textured surface to the abrasive particles.

[0179] Each of cavities 1310 may also include a shape 1330 imparted to the produced abrasive grain. Shape 1330 includes a grain portion 1312, which may have a polygonal or other intentionally selected shape, and one or more fracture portions 1314 designed to break away from grain portion 1312 at or near stress points 1316 during drying, firing, or sintering.

[0180] Figure 14A method for preparing fractured abrasive particles according to an embodiment of the present invention is shown. Method 1400 can be used in conjunction with, for example, FIG. Figure 13 The molds of those or any other suitable molding process are used together.

[0181] In frame 1410, a mold is provided. The mold includes at least one cavity having a shape 1412. The shape 1412 can be designed to produce any suitable shaped abrasive particles. For example, the suitable shape can include any polygonal shape (including regular polygons, irregular polygons), a shape with curved edges (such as a convex portion or a concave portion), or can have a straight shape. The shape 1412 can also have one or more fractured portions designed to fracture during manufacture. The fractured portion can be located at the vertex of the suitable shape or along the edge of the suitable shape. The cavity can also have a depth 1414, which can be constant or variable within the region of the cavity. For example, the cavity can have a first depth of a suitable shape portion and a second depth of a fractured portion.

[0182] In block 1420, a release agent is applied to the mold. The release agent can be applied to the entire inner surface of each cavity. The release agent can promote shrinkage during the drying period and remove the resulting abrasive grains from the cavity. For aqueous solutions of abrasive grain precursors, the release agent can include oil.

[0183] In block 1430, the mold cavity is filled with abrasive particle precursors. The cavity may be overfilled 1432, underfilled 1434, or uniformly filled 1436.

[0184] In block 1440, the particles are dried during an initial drying step while the particle precursor is still in the mold cavity. Although further processing may be required to complete the abrasive particles, the initial drying step can occur in the mold. Drying in the mold may cause cracking 1442 of the cracked portions. Drying may also cause shrinkage 1444 of the abrasive particle shape. Drying may also have other effects, such as settling or separation of layers, or solidification of the abrasive particle mixture.

[0185] 15A to 15D Shown are other shapes of abrasive particles according to embodiments herein. Most of the description herein relates to exemplary embodiments in which the resulting abrasive particles have a triangular or substantially triangular shape. However, other shapes are clearly contemplated. FIG. 15A to FIG. 15B Some example shapes are shown.

[0186] Figure 15A and Figure 15B The shapes of the individual fractured or sacrificial parts may not be formed during the fracture step. Instead, the fracture releases each abrasive particle. For example, Figure 15AA particle 1500 is shown having a first portion 1502 and a second portion 1504 that can be broken into two separate abrasive particles during a fracturing step that occurs during a drying step, each of which can become part of a final abrasive article.

[0187] Figure 15B A plurality of abrasive grains 1512 that may be made from a single mold having shape 1510 are shown connected at fracture points 1514. Mold-like 1510 may cause the grains 1512 to fracture from one another during drying or during a removal step due to weak connections between the grains at stress points 1514.

[0188] Figure 15C A mold 1520 is shown that can be used to prepare particles 1512. Figure 15D A 3D representation of particles 512 is shown in . According to various embodiments, the abrasive article can have a cutting speed of at least about 100 m / min, at least about 110 m / min, at least about 120 m / min, at least about 130 m / min, at least about 140 m / min, at least about 150 m / min, at least about 160 m / min, at least about 170 m / min, at least about 180 m / min, at least about 190 m / min, at least about 200 m / min, at least about 300 m / min, at least about 400 m / min, at least about 500 m / min, at least about 1000 m / min, at least about 1500 m / min, at least about 2000 m / min, at least about 2500 m / min, at least about 3000 m / min, or at least about 4000 m / min.

[0189] Abrasive articles according to the present invention can be used manually and / or in conjunction with a machine. During grinding, at least one of the abrasive article and the workpiece is moved relative to the other. Grinding can be performed under wet or dry conditions. Exemplary liquids for wet grinding include water, water containing conventional rust-inhibiting compounds, lubricants, oils, soaps, and cutting fluids. The liquid may also contain, for example, a defoaming agent or a degreasing agent.

[0190] While many of the embodiments discussed herein have been discussed, fractured portions generated during manufacturing can also be used in abrasive products. The fractured portions can provide some of the same benefits of shaped abrasive particles in a smaller size.

[0191] A mold for producing abrasive grains includes a surface and a plurality of cavities extending downwardly from the surface. Each cavity includes a particle-shaped portion having a polygonal shape and a fracture portion connected to the particle-shaped portion. The fracture portion is configured to break from the particle-shaped portion during a stress event, thereby producing a fractured-shaped abrasive grain.

[0192] The mold may be implemented so that the rupture portion has a rupture shape.

[0193] The mold may be implemented so that the fracture shapes extend from the sides of the polygonal shape.

[0194] The mold may be implemented so that the fracture shapes extend from the corners of the polygonal shape.

[0195] The mould may be implemented such that the fractured shapes extend further into the surface than the particle shaped parts.

[0196] The die may be implemented so that the fracture shape is angled relative to the sides of the polygonal shape.

[0197] The mold may be implemented so that the angle is acute.

[0198] The mold may be implemented so that the angle is a right angle.

[0199] The mold may be implemented so that the angle is obtuse.

[0200] The mold may be implemented so that the fractured portion is the second particle shape portion.

[0201] The mold can be implemented such that the fracture shape is at least about 90% similar to the polygonal shape.

[0202] The mold can be implemented so that the stress event is a drying phase that occurs while the abrasive particle precursors are in the mold.

[0203] The mold may be implemented so that the stress event is the first grinding operation.

[0204] The mold may be implemented such that the stress event is a firing event.

[0205] The mold may be implemented such that the stress event is the sintering step.

[0206] The mold may be implemented so that the stress event is a cooling step.

[0207] A shaped abrasive particle is provided, comprising a first face and a second face. The first face is substantially parallel to the second face, and the first face and the second face are separated by a thickness of the shaped abrasive particle. The first face comprises a first molded edge and a second molded edge, and a fracture vertex located at the intersection of the first molded edge and the second molded edge. The fracture vertex has a first radius of curvature that is smaller than a second radius of curvature associated with the first edge.

[0208] The shaped abrasive particles can be implemented such that the first face and the second face are generally triangular in shape, with the fracture apex being located at a first corner of the generally triangular shape.

[0209] The shaped abrasive particles can be embodied such that the generally triangular shape includes a second fracture apex located at a second corner.

[0210] The shaped abrasive particles can be embodied such that the generally triangular shape includes a third fracture apex located at a third corner.

[0211] The shaped abrasive particles can be embodied so that a fracture apex is formed at a fracture point of the shaped abrasive particle precursor. Fracture occurs at the fracture point during a stress event. The stress event is selected from the group consisting of drying, cooling, firing, sintering, abrasive article manufacturing, and initial contact with a workpiece.

[0212] The shaped abrasive particles can be embodied such that the fracture apex has a smaller radius of curvature than the pre-fracture apex of the shaped abrasive particle precursor.

[0213] A method for manufacturing abrasive grains is provided. The method includes filling a mold cavity with an abrasive grain precursor mixture. The mold cavity includes a particle-shaped portion and a fractured portion extending from the particle-shaped portion. The particle-shaped portion and the fractured portion are connected together at a stress point. The method also includes drying the abrasive grain precursor mixture in the mold cavity to form abrasive grain precursors. Drying causes the fractured portion to break from the particle-shaped portion near the stress point.

[0214] The method may be implemented so that the particle shape portion has a regular polygonal shape.

[0215] The method may be implemented so that the particle shape portion has an irregular polygonal shape.

[0216] The method may be implemented such that the fractured portion extends from the particle-shaped portion along an edge of the particle-shaped portion.

[0217] The method may be performed such that the fractured portion comprises the second particle shape.

[0218] The method may be implemented such that the fractured portion extends from the particle-shaped portion at a corner of the particle-shaped portion.

[0219] The method may be implemented such that the fractured portion extends from a face of the particle-shaped portion.

[0220] The method may be implemented such that the particle-shaped portion comprises a first face and a second face. The first face is parallel to the second face.

[0221] The method may be implemented such that the mold cavity has a depth.

[0222] The method may be implemented such that the depth is a variable depth.

[0223] The method may be implemented such that the rupture portion is a first rupture portion extending from a first point of the particle-shaped portion, and further includes a second rupture portion extending from the particle-shaped portion at a second point of the particle-shaped portion.

[0224] The method can be performed such that after drying, the particle shape of the abrasive particle precursors is approximately 90% similar to the particle shape portion of the mold cavity.

[0225] The method may be practiced such that the force required to rupture the fractured portion from the particle-shaped portion is less than 50% of the force required to rupture the particle portion to half the height of the particle portion.

[0226] A method for preparing an abrasive article is proposed, the method comprising providing a plurality of abrasive grains. The plurality of abrasive grains are formed by filling a plurality of mold cavities with an abrasive grain precursor mixture. Each of the plurality of mold cavities comprises a grain portion and a fractured portion. Forming the abrasive grains further comprises: drying the abrasive grain precursor mixture to form an abrasive grain precursor; removing the plurality of abrasive grain precursors from the mold; and firing the plurality of abrasive grain precursors to form shaped abrasive grains. The method further comprises: embedding the fired plurality of shaped abrasive grains into a make coat located on a backing of the abrasive article. The method further comprises: fracture the plurality of shaped abrasive grains so that the fractured portions provide substantially no abrasive effect during the life of the abrasive article.

[0227] The method can be performed such that the particle portion has a polygonal shape. After the sacrificial portion is broken open, 75% of the abrasive particles have at least about 90% similarity to the polygonal shape.

[0228] The method can be implemented so that it further comprises: coating the abrasive grains with a magnetically responsive material; and orienting the abrasive grains on the backing by providing a magnetic field so that a majority of the abrasive grains are individually oriented so that the cutting faces face in the same direction.

[0229] The method can be practiced such that the fractured portion remains intact during the orienting step.Fracturing the plurality of abrasive grains occurs during a first use of the abrasive article.

[0230] The method can be practiced such that the plurality of abrasive grains are fractured during the drying step.

[0231] The method may be implemented such that the fractured portions extend from the particle portion at corners of the polygonal shape of the particle portion.

[0232] The method may be carried out such that the rupture portion extends from the perimeter of the polygonal shape of the article portion.

[0233] The method may be practiced such that the fractured portion extends further into the mold than the particle portion.

[0234] The method may be implemented such that each mold cavity in the plurality of mold cavities has a depth.

[0235] The method may be implemented such that the depth is variable.

[0236] A shaped abrasive particle precursor is provided, comprising a first portion including a first surface and a second surface. The first surface and the second surface are substantially parallel to each other and separated by a thickness. The shaped abrasive particle precursor further comprises: a second portion extending from the first portion; and a rupture point located between the first portion and the second portion. The second portion is configured to break away from the first portion at the rupture point in response to a stress event. The rupture point becomes a cutting point for the shaped abrasive particle.

[0237] The shaped abrasive particle precursors can be implemented so that the stress event is a drying step.

[0238] The shaped abrasive particle precursors can be implemented such that the stress event is a cooling step.

[0239] The shaped abrasive particle precursors can be implemented such that the stress event is the firing step.

[0240] The shaped abrasive particle precursors can be implemented such that the stress event is a sintering step.

[0241] The shaped abrasive particle precursors can be implemented so that the stress event is initial contact with the working surface.

[0242] The shaped abrasive particle precursors can be embodied such that the force required to fracture the second portion is less than 50% of the force required to fracture the first portion to half its height.

[0243] The shaped abrasive particle precursor can be implemented so that it also includes a magnetically responsive coating. The magnetically responsive coating causes the shaped abrasive particle to respond to a magnetic field. When exposed to the magnetic field, the shaped abrasive particle experiences a net torque greater than the torque of the regular portion alone, which orients the shaped abrasive particle relative to the magnetic field so that each of the first surface and the second surface is approximately perpendicular to the backing.

[0244] The shaped abrasive particles can be implemented such that the second portion extends from the first surface.

[0245] The shaped abrasive particle precursor can be implemented such that the second portion extends from the thickness.

[0246] The shaped abrasive particle precursor can be implemented such that the first surface and the second surface each include a surface profile. The surface profile has edges and corners.

[0247] The shaped abrasive particle precursor can be implemented such that the second portion extends from the edge.

[0248] The shaped abrasive particle precursor can be embodied such that the second portion is collinear with the edge.

[0249] The shaped abrasive particle precursor can be implemented such that the second portion is angled relative to the edge.

[0250] The shaped abrasive particle precursor can be implemented such that the second portion extends from the corner.

[0251] The shaped abrasive particle precursor can be implemented such that the second portion has a surface that is coplanar with the first surface.

[0252] The shaped abrasive particle precursor can be implemented such that the second portion has a surface that is angled relative to the first surface.

[0253] The shaped abrasive particle precursor can be embodied such that the first portion is generally triangular in shape.The second portion extends from a side of the triangle that is not the hypotenuse.

[0254] The shaped abrasive particle precursor can be embodied such that the second portion has a length that is at least 10% of the hypotenuse of the triangle.

[0255] The shaped abrasive particle precursor can be embodied such that the second portion length is at least 20% of the bevel edge.

[0256] The shaped abrasive particle precursor can be implemented such that the first portion is in the shape of a rod, and the sacrificial portion extends from the end of the rod.

[0257] The shaped abrasive particle precursor can be implemented such that the second portion extends from the end of the rod at an angle.

[0258] The shaped abrasive particle precursor can be implemented such that the second portion extends from the first surface of the first portion.

[0259] The shaped abrasive particle precursor can be implemented such that the second portion and the first portion are formed from a continuous material.

[0260] The shaped abrasive particle precursor can be shaped such that the abrasive particle has a cutting face having a side length and a thickness, wherein an aspect ratio of the side length to the thickness is at least 2.

[0261] The shaped abrasive particle precursors can be implemented such that the aspect ratio of height to thickness is less than 10.

[0262] The shaped abrasive particle precursors can be embodied such that the magnetic field is at least 100 Gauss.

[0263] The shaped abrasive particle precursors can be embodied such that the magnetic field is at least 1000 Gauss.

[0264] A method of using an abrasive article includes contacting the abrasive article with a workpiece. The abrasive article includes a backing and a plurality of magnetically responsive particles secured to the backing. Each of the plurality of magnetically responsive particles is secured to the backing along a base edge such that the base edges of the plurality of particles are substantially parallel to one another and such that cutting faces of some of the plurality of magnetic particles are parallel to one another. Each of the particles includes a sacrificial portion. The method further includes moving the abrasive article relative to the workpiece to abrade the surface of the workpiece. Moving the abrasive article causes the sacrificial portion to fracture under a load lower than the abrading load.

[0265] The method may be implemented such that the load is less than 50% of the force that would cause one of the magnetically responsive particles to break to half the particle height.The particle height is the height of the particle measured from the backing.

[0266] The method can be implemented such that fracturing includes breaking a sacrificial portion of each of the plurality of particles.

[0267] The method can be implemented such that the abrasive article has a coating. The sacrificial portion extends at least partially over the coating.

[0268] The method may be implemented such that the cutting face of each of the plurality of magnetic particles has a cutting edge that contacts the workpiece during grinding.

[0269] The method can be implemented such that the plurality of magnetically responsive particles have a rake angle between -29° and 90°.

[0270] The method can be implemented such that each of the plurality of magnetically responsive particles has a cutting portion and a base portion. The cutting portion has an aspect ratio between 2 and 10. The base portion has an aspect ratio between 1.5 and 10.

[0271] The method may be implemented such that the base edges of a portion of the plurality of particles are substantially parallel to each other so that the cut faces of a portion of the plurality of magnetic particles are parallel to each other. The portion is a percentage greater than a percentage that would occur randomly.

[0272] The method may be implemented such that the base edges of a majority of the plurality of particles are substantially parallel to one another so that the cut faces of a majority of the plurality of magnetic particles are parallel to one another.

[0273] Example

[0274] Various embodiments of the present disclosure may be better understood by reference to the following examples which are provided by way of illustration.The present disclosure is not limited to the examples given herein.

[0275] Preparation of boehmite sol-gel

[0276] A boehmite sol-gel sample was prepared using the following recipe: Alumina monohydrate powder (1600 parts) sold under the trademark "DISPERAL" was dispersed by high shear mixing a solution containing water (2400 parts) and 70% aqueous nitric acid (72 parts) for 11 minutes. The resulting sol-gel was aged for 3 hours before coating.

[0277] Preparation of molds (tools)

[0278] Will contain 16A to 16C A print file of an embossing plate (EP1) with equally spaced protrusions of the shown geometry was loaded into a stereolithography 3D printer (ProJet 7000HD, 3D Systems, Littleton, CO). The machine printed EP1 using Accura 25 resin (3D Systems, Littleton, CO). EP1 was pressed into a sheet of polypropylene film that was heated to 400*F to form cavities in the film, forming TOOL1. TOOL1 was allowed to cool at room temperature for 60 minutes. The mold was coated with a release agent, a 1% solution of peanut oil in methanol, with approximately 0.5 mg / sqin of peanut oil applied to TOOL1. Excess methanol was removed by placing the mold sheet in an air convection oven at 45°C for 5 minutes.

[0279] Will contain 17A to 17C The print file of the embossing plate (EP2) with equally spaced protrusions of the shown geometry was loaded into a stereolithography 3D printer (ProJet 7000HD, 3D Systems, Littleton, CO). The machine printed EP2 using Accura 25 resin (3D Systems, Littleton, CO). EP2 was pressed into a sheet of polypropylene film that was heated to 400*F to form cavities in the film, forming TOOL2. TOOL2 was allowed to cool at room temperature for 60 minutes. The mold was coated with a release agent, a 1% solution of peanut oil in methanol, with approximately 0.5 mg / sqin of peanut oil applied to TOOL2. Excess methanol was removed by placing the sheet of mold in an air convection oven at 45°C for 5 minutes.

[0280] Comparative Example A

[0281] The sol-gel of TOOL1 is used for the preparation of the particle size distribution of the present invention.Then, the particle size distribution of the particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.The particle size distribution of the present invention is quantified.

[0282] Example 1

[0283] Use a putty knife to force excess boehmite sol-gel into the cavity of TOOL2 so that the cavity is completely filled. Allow the filled mold to dry at 70F for 24 hours. Photographic results are available at Figure 12A and Figure 12B The particles were then removed from the mold and fired in a box furnace at 650°C for 30 minutes, followed by another box furnace at 1400°C for 30 minutes. The resulting fracture tip particle samples were analyzed using a scanning electron microscope (JSM-7600F from Jeol USA, Peabody, MA). The radius of curvature (ROC) value of the sharpest point of each tip was determined by fitting a circle with the curvature of the peak. The fitted circle radius measurements are reported in Table 1.

[0284] ROC value measured in micrometers

[0285]

[0286]

[0287] Table 1

Claims

1. A mold for preparing abrasive particles, the mold comprising: surface; a plurality of cavities extending downwardly from the surface, each cavity comprising: a particle-shaped portion having a polygonal shape and configured to define a non-sacrificial portion of a shaped abrasive particle precursor; and a ruptured portion connected to the particle-shaped portion at a rupture point; and wherein the fractured portion is configured to define a sacrificial portion of the shaped abrasive particle precursor, and the fractured portion is bent from the fracture point relative to the sides of the polygonal shape of the particle shape portion, so that the sacrificial portion cannot shrink within the cavity together with the non-sacrificial portion during a stress event but can at least partially break from the non-sacrificial portion, thereby obtaining a fractured-shaped abrasive particle. The mold according to claim 1 , wherein the rupture portion has a rupture shape.

3. The mold of claim 2, wherein the fracture shape extends from a side of the polygonal shape. The mold of claim 2 , wherein the fracture shapes extend from corners of the polygonal shape.

5. The mold of claim 2, wherein the fractured shape extends further into the surface than the particle-shaped portion.

6. The mold of claim 2, wherein the fracture shape is angled relative to the sides of the polygonal shape. The mold according to claim 6 , wherein the angle is an acute angle.

8. The mold according to claim 6, wherein the angle is a right angle.

9. The mold according to claim 6, wherein the angle is an obtuse angle.

10. The mold according to claim 2, wherein the ruptured portion is a second particle shape portion.

11. The mold according to any one of claims 1 to 10, wherein the fracture shape is at least 90% similar to the polygonal shape.

12. The mold of any one of claims 1 to 10, wherein the stress event is a drying phase that occurs while abrasive particle precursors are in the mold.

13. The mold according to any one of claims 1 to 10, wherein during the first grinding operation, the sacrificial portion is further fractured or completely broken away from the non-sacrificial portion.

14. The mold according to any one of claims 1 to 10, wherein the stress event is a firing event.

15. The mold according to any one of claims 1 to 10, wherein the stress event is a sintering step.

16. The mold according to any one of claims 1 to 10, wherein the stress event is a cooling step.

17. A method of making an abrasive article, the method comprising: Filling a plurality of mold cavities with an abrasive grain precursor mixture, wherein each of the mold cavities comprises: a particle-shaped portion configured to define a non-sacrificial portion of a shaped abrasive particle precursor; a fractured portion extending from the particle shape portion and configured to define a sacrificial portion of the shaped abrasive particle precursor; and wherein the particle-shaped portion and the fractured portion are connected together at a stress point; and The abrasive particle precursor mixture in the mold cavity is dried to form the shaped abrasive particle precursor, wherein the fractured portion is bent from the stress point relative to the edge of the particle shape portion so that the sacrificial portion cannot shrink with the non-sacrificial portion in the mold cavity and the drying causes the sacrificial portion to at least partially break from the non-sacrificial portion near the stress point. The method according to claim 17 , wherein the particle-shaped portion has a regular polygonal shape. The method according to claim 17 , wherein the particle-shaped portion has an irregular polygonal shape.

20. The method of claim 19, wherein the fractured portion extends from the particle-shaped portion along an edge of the particle-shaped portion.

21. The method of claim 19, wherein the fractured portion has a second particle shape.

22. The method of claim 19, wherein the fractured portion extends from the particle-shaped portion at a corner of the particle-shaped portion.

23. The method of claim 19, wherein the fractured portion extends from a face of the particle-shaped portion.

24. The method of any one of claims 17 to 23, wherein the particle-shaped portion comprises a first face and a second face, and wherein the first face is parallel to the second face.

25. The method of any one of claims 17 to 23, wherein each of the mold cavities has a depth.

26. The method of claim 25, wherein the depth is a variable depth.

27. The method according to any one of claims 17 to 23, wherein the breaking portion comprises a first breaking portion extending from a first point of the particle-shaped portion and a second breaking portion extending from the particle-shaped portion at a second point of the particle-shaped portion.

28. The method of any one of claims 17 to 23, wherein after drying, the particle shape of the shaped abrasive particle precursors is 90% similar to the particle shape portion of each mold cavity.

29. The method of claim 28, wherein the force required to rupture the sacrificial portion from the non-sacrificial portion is less than 50% of the force required to rupture the non-sacrificial portion to half the height of the non-sacrificial portion.

30. A method of preparing an abrasive article, the method comprising: Providing a plurality of abrasive grains, the plurality of abrasive grains being formed by: filling a plurality of mold cavities with an abrasive grain precursor mixture, wherein each of the plurality of mold cavities comprises a grain portion and a fracture portion; drying the abrasive grain precursor mixture to form a plurality of abrasive grain precursors, the grain portion being configured to define a non-sacrificial portion of the abrasive grain precursors, the fractured portion being configured to define a sacrificial portion of the abrasive grain precursors, wherein the grain portion and the fractured portion are connected to each other at a fracture point, and the fractured portion is bent from the fracture point relative to an edge of the grain portion; as well as removing the plurality of abrasive particle precursors from the mold cavity; firing the plurality of abrasive grain precursors to form a plurality of shaped abrasive grains; embedding the fired plurality of shaped abrasive particles into a make coat layer on a backing of the abrasive article; as well as The plurality of precursor abrasive particles is fractured by preventing the sacrificial portion from shrinking within the mold cavity along with the non-sacrificial portion so that the sacrificial portion can at least partially break away from the non-sacrificial portion during a stress event.

31. The method of claim 30, wherein the particle portion has a polygonal shape, and wherein after the sacrificial portion is fractured, 75% of the abrasive particles have at least 90% similarity to the polygonal shape.

32. The method of claim 30, further comprising: coating the abrasive particles with a magnetically responsive material; as well as The abrasive grains are oriented on the backing by providing a magnetic field so that a majority of the abrasive grains are individually oriented with cutting faces facing in the same direction.

33. The method of claim 32, wherein the sacrificial portion remains partially intact during the orienting step, and wherein fracturing the plurality of abrasive grains occurs during a first use of the abrasive article.

34. The method of any one of claims 30 to 33, wherein the plurality of abrasive grains are fractured during the drying step.

35. The method of claim 34, wherein the fractured portions extend from the particle portion at corners of the polygonal shape of the particle portion.

36. The method of claim 34, wherein the fractured portion extends from a perimeter of a polygonal shape of the particle portion.

37. The method of claim 34, wherein the fractured portion extends further into the mold than the particle portion.

38. The method of any one of claims 30 to 33, wherein each of the plurality of mold cavities has a depth.

39. The method of claim 38, wherein the depth is variable.

40. A shaped abrasive particle precursor comprising: a first portion, the first portion comprising a first surface and a second surface, wherein the first surface and the second surface are parallel to each other and separated by a thickness; a second portion extending from the first portion; as well as a rupture point between the first portion and the second portion, wherein the second portion bends from the rupture point relative to an edge of the first portion such that the second portion cannot contract with the first portion within a plurality of cavities of a mold, wherein the second portion is configured to at least partially break away from the first portion at the rupture point in response to a stress event, and wherein the rupture point becomes a cutting point for the abrasive particles.

41. The shaped abrasive particle precursor of claim 40, wherein the stress event is a drying step.

42. The shaped abrasive particle precursor of claim 40, wherein the stress event is a cooling step.

43. The shaped abrasive particle precursor of claim 40, wherein the stress event is a firing step.

44. The shaped abrasive particle precursor of claim 40, wherein the stress event is a sintering step.

45. The shaped abrasive particle precursor of claim 40, wherein the stress event is initial contact with a working surface.

46. ​​The shaped abrasive particle precursor of any one of claims 40 to 44, wherein the force required to rupture the second portion is less than 50% of the force required to rupture the first portion to half height.

47. A shaped abrasive particle precursor according to any one of claims 40 to 44, further comprising a magnetically responsive coating, wherein the magnetically responsive coating causes the shaped abrasive particle precursor to respond to a magnetic field, and wherein the shaped abrasive particle precursor, when exposed to the magnetic field, experiences a net torque greater than the torque of the first portion alone, the net torque orienting the shaped abrasive particle precursor relative to the magnetic field so that each of the first surface and the second surface is perpendicular to a backing.

48. The shaped abrasive particle precursor of any one of claims 40 to 44, wherein the second portion extends from the first surface.

49. The shaped abrasive particle precursor of any one of claims 40 to 44, wherein the second portion extends from the thickness.

50. The shaped abrasive particle precursor of any one of claims 40 to 44, wherein the first surface and the second surface each comprise a surface profile, and wherein the surface profile has edges and corners.

51. The shaped abrasive particle precursor of claim 50, wherein the second portion extends from the edge.

52. A shaped abrasive particle precursor according to claim 51, wherein the second portion is colinear with the edge.

53. A shaped abrasive particle precursor according to claim 51, wherein the second portion is angled relative to the edge.

54. The shaped abrasive particle precursor of claim 50, wherein the second portion extends from the corner.

55. A shaped abrasive particle precursor according to claim 54, wherein the second portion has a surface coplanar with the first surface.

56. A shaped abrasive particle precursor according to claim 54, wherein the second portion has a surface that is angled with the first surface.

57. A shaped abrasive particle precursor according to any one of claims 40 to 44, wherein the first portion is triangular in shape, and wherein the second portion extends from a side of the triangle that is not the hypotenuse.

58. A shaped abrasive particle precursor according to claim 57, wherein the second portion has a length that is at least 10% of the hypotenuse of the triangle.

59. A shaped abrasive particle precursor according to claim 58, wherein the second portion length is at least 20% of the bevel edge.

60. The shaped abrasive particle precursor of any one of claims 40 to 44, wherein the first portion is in the shape of a rod, and wherein the second portion extends from an end of the rod.

61. A shaped abrasive particle precursor according to claim 60, wherein the second portion extends from the end of the rod at a certain angle.

62. The shaped abrasive particle precursor of any one of claims 40 to 44, wherein the second portion extends from the first surface of the first portion.

63. A shaped abrasive particle precursor according to any one of claims 40 to 44, wherein the second portion and the first portion are formed of a continuous material.

64. A shaped abrasive particle precursor according to any one of claims 40 to 44, wherein the abrasive particle has a cutting face, the cutting face having an edge length and a thickness, and wherein the aspect ratio of the edge length to the thickness is at least 2.

65. A shaped abrasive particle precursor according to claim 64, wherein the aspect ratio of height to thickness is less than 10.

66. The shaped abrasive particle precursor of claim 47, wherein the magnetic field is at least 100 Gauss.

67. The shaped abrasive particle precursor of claim 47, wherein the magnetic field is at least 1000 Gauss.

68. A method of using an abrasive article, the method comprising: contacting the abrasive article with a workpiece, wherein the abrasive article comprises: Backing; a plurality of magnetically responsive particles secured to the backing, wherein each of the plurality of magnetically responsive particles is secured to the backing along a base edge such that the base edges of the plurality of magnetically responsive particles are parallel to each other, and such that cut faces of some of the plurality of magnetically responsive particles are parallel to each other, and wherein each of the plurality of magnetically responsive particles comprises a sacrificial portion according to any one of claims 1, 17, and 30; and The abrasive article is moved relative to the workpiece such that a surface of the workpiece is abraded, and wherein the abrasive article is moved such that the sacrificial portion fractures at a load lower than the abrading load.

69. The method of claim 68, wherein the load is less than 50% of the force that would cause one of the plurality of magnetically responsive particles to break to half the particle height, wherein the particle height is the height of the particle measured from the backing.

70. The method of claim 68, wherein the rupturing comprises breaking the sacrificial portion of each of the plurality of magnetically responsive particles.

71. A method according to any one of claims 68 to 70, wherein the abrasive article has a coating, and wherein the sacrificial portion extends at least partially over the coating.

72. The method of any one of claims 68 to 70, wherein the cutting face of each of the plurality of magnetically responsive particles has a cutting edge that contacts the workpiece during grinding.

73. The method of any one of claims 68 to 70, wherein the plurality of magnetically responsive particles have a rake angle, and wherein the rake angle is between -29° and 90°.

74. A method according to any one of claims 68 to 70, wherein each of the plurality of magnetically responsive particles has a cutting portion and a base portion, wherein the cutting portion has an aspect ratio between 2 and 10, and wherein the base portion has an aspect ratio between 1.5 and 10.

75. A method according to any one of claims 68 to 70, wherein the base edges of a portion of the plurality of magnetically responsive particles are parallel to each other so that the cut surfaces of a portion of the plurality of magnetically responsive particles are parallel to each other, and wherein the portion is a percentage greater than the percentage that would occur randomly.

76. The method of any one of claims 68 to 70, wherein the base edges of a majority of the plurality of magnetically responsive particles are parallel to each other so that the cut faces of a majority of the plurality of magnetically responsive particles are parallel to each other.

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