Shaped abrasive particles with grooves

Background of the invention

Abrasive particles and abrasive products made of abrasive particles are useful in abrasive, finishing or grinding various materials and surfaces during the production of goods. Therefore, there is still a need to improve the cost, performance or life of abrasive particles and / or abrasive products.

United States patents 5,209,916 to Berg, 5,366,523 to Rowenhorst and 5,984,988 to Berg disclose triangular shaped abrasive particles and abrasive products using triangular shaped abrasive particles. In one embodiment, the shape of the abrasive particles included an equilateral triangle. Triangular shaped abrasive particles are useful in the production of abrasive products with increased cutting speeds.

US-A-5,201,916 relates to a method for preparing abrasive particles, the method comprising the following steps: (a) providing a dispersion comprising particles that can be converted into alpha corundum, and preferably alpha corundum monohydrate particles, in a liquid, which liquid includes volatile component; (b) providing a mold having a first generally flat surface and a second surface opposite to said first surface, said first surface having an opening leading to a mold cavity of a certain shape; (c) introducing said dispersion into said mold cavity so that no exposed surface of said dispersion protrudes substantially beyond the plane of said first surface of said mold; (d) removing a sufficient portion of said volatile component of said liquid from said dispersion when said dispersion is in said mold cavity, thereby forming an abrasive particle precursor having a shape roughly corresponding to the shape of said mold cavity; (e) removing said abrasive particle precursor from said mold cavity; (f) calcining said removed abrasive particle precursor; and (g) sintering said calcined precursor to form the desired abrasive particle. Second described embodiment

EP2370232 relates to abrasive particles having shapes that can be described as thin bodies having a triangular, rectangular, including square, round or other geometric shape. The abrasive particles have a front surface and a rear surface, which both surfaces have substantially the same geometric shape.

The surfaces are separated by the thickness of the particle. The ratio of the shortest surface size of the abrasive particle to its thickness is at least 1 to 1.

Summary of the Invention

The shaped abrasive particles can generally have a higher yield than randomly crushed abrasive particles. By controlling the shape of the abrasive particle 10 it is possible to control the resulting efficiency of the abrasive particle. The inventors have found that by making a shaped abrasive particle with multiple grooves on one of the surfaces of the shaped abrasive particle, the shaped parent abrasive particles are released from production equipment with multiple mold cavities used to form the shaped abrasive particles much easier. Surprisingly, despite the increase in the total surface area of ​​the mold cavity due to the plurality of multiple grooves forming, shaped parent abrasive particles with multiple grooves are much easier to remove from the mold cavities.

The inventors have also found that grooves in shaped abrasive particles affect the grinding performance of shaped abrasive particles compared to identical shaped abrasive particles without grooves. In particular, the initial unit loss of material is reduced and the unit loss of material tends to increase over time as the shaped abrasive particles start to wear. The unit loss of abrasive particle material usually tends to decrease over the life of the abrasive particle. A similar result is obtained with shaped abrasive particles that do not contain grooves. In this way, the inventors have found that they can manipulate the unit material loss curve of abrasive products made from shaped abrasive particles by using a mixture of shaped abrasive particles without grooves and with grooves to produce abrasive products with a very uniform unit loss of material throughout the life of the abrasive product.

Therefore, in one embodiment, the invention relates to abrasive particles comprising shaped abrasive particles having a side wall, among which each shaped abrasive particle comprises corundum

EP2370232 alpha and has a first surface and a second surface separated from each other by a side wall as well as the maximum thickness T; the shaped abrasive particles further include a plurality of grooves on the second surface.

In another embodiment, the invention relates to manufacturing tooling for producing shaped abrasive particles that includes a plurality of mold cavities, the plurality of mold cavities comprising a bottom mold surface, a mold side wall, and a height Hc, wherein the mold bottom surface and mold side wall comprise polymeric material and the lower surface covers many protrusions.

io Short description of the figures

One skilled in the art should note that this discussion is only a description of some embodiments and is not intended to limit the broader aspects of the present disclosure, which broader aspects are included in the exemplary construction.

Fig. 1 shows a cross-sectional view of a mold cavity with a plurality of protuberances on the lower surface.

Figures 1A and 1B show cross-sections of various embodiments of the protuberances of Figure 1.

Fig. 2 shows a top view of one embodiment of a shaped abrasive particle with grooves.

Fig. 2A is a side view of the shaped abrasive particle of Fig. 2.

Fig. 3 shows a photomicrograph of a shaped abrasive particle with grooves.

Fig. 4 is a photomicrograph of another embodiment of a shaped abrasive particle with grooves.

Fig. 5 shows another embodiment of a shaped abrasive particle with grooves.

Fig. 6A shows a top view of one embodiment of a shaped abrasive particle.

Fig. 6B is a side view of the shaped abrasive particle of Fig. 6A.

Fig. 6C is a side view of the bulk abrasive manufactured from the shaped abrasive particles of Fig. 6A.

Fig. 7 shows a photomicrograph of shaped abrasive particles.

EP2370232

Fig. 8 is a photomicrograph of the upper surface of the bulk abrasive article made from the shaped abrasive particles of Fig. 7.

Fig. 9A shows a top view of another embodiment of the shaped abrasive particle.

Fig. 9B is a side view of the shaped abrasive particle of Fig. 9A.

Fig. 9C is a side view of the bulk abrasive manufactured from the shaped abrasive particles of Fig. 9A.

Fig. 10A shows a top view of another embodiment of the shaped abrasive particle.

Fig. 10B is a side view of the shaped abrasive particle of Fig. 10A.

Fig. 10C is a side view of the bulk abrasive manufactured from the shaped abrasive particles of Fig. 10A.

Fig. 11 is a graph of unit material loss and total material loss for shaped abrasive particles with and without grooves.

Fig. 12 is a graph of unit material loss versus time for shaped abrasive particles with different convergence angles.

Fig. 13 is a graph of total material loss versus time for shaped abrasive particles with different convergence angles.

Fig. 14 is a photomicrograph of prior art abrasive particles made in accordance with US Patent No. 5,366,523.

Fig. 15 is a cross-sectional photomicrograph of prior art abrasive particles of Fig. 14.

Fig. 16 is a cross-sectional photomicrograph of the prior art abrasive particles of Fig. 14.

Fig. 17 is a cross-sectional photomicrograph of a shaped abrasive particle with an inclined side wall.

The repeated use of reference designations in the description and drawings is intended to show the same or analogous features or elements of the disclosure.

definitions

The expressions "include", "have" and "contain" used herein are legally equivalent and not limiting. Therefore, except for those listed

EP2370232 elements, functions, steps and restrictions may include elements, functions, steps or additional restrictions not listed.

The term "abrasive dispersion" as used herein means an alpha alumina precursor introduced into the mold cavity that can be converted to alpha alumina. The composition refers to an abrasive dispersion until the appropriate volatiles are removed to solidify the abrasive dispersion.

The term "shaped parent abrasive particle" as used herein means a non-sintered abrasive particle formed by removing a sufficient amount of volatile component from an abrasive dispersion disposed in a mold cavity to form a solid solid that can be removed from the mold cavity and can generally retain its formed shape in subsequent processing operations.

The term "shaped abrasive particle" as used herein means a ceramic abrasive particle with at least a portion of the abrasive particle of a predetermined shape that is imparted by the mold cavity used to form the shaped abrasive parent particle. Except for the abrasive pieces, the shaped abrasive particle will generally have a predetermined geometric shape that substantially reflects the mold cavity used to form the shaped abrasive particle.

The shaped abrasive particle used herein does not include abrasive particles obtained by a mechanical crushing operation.

Detailed description of the invention. Shaped abrasive particles

In Figure 1, a portion of the production tool 100 with multiple mold cavities 102 is shown. For clarity, a single mold cavity 102 is shown. The mold cavity 102 includes the side wall of the mold 104 and the bottom surface of the mold 106, in one embodiment, the bottom surface of the mold and the side wall of the mold contained polymeric material. The geometric shape of the side wall of the mold 104 forming the perimeter of the bottom surface of the mold can be different, and in one embodiment as the geometric shape visible from the top of each of the mold cavities in the production tool, an equilateral triangle was selected, so that the mold cavity had three opposite mold side walls . Other geometric shapes may be used for the mold cavity, as described later. Side wall of the mold 104

EP2370232 intersects the bottom surface of the mold (106) at a predetermined angle α. As described later, by selecting an angle α in the range of about 95 degrees to about 130 degrees, the grinding performance of shaped abrasive particles can be improved. However, the predetermined angle α may be 90 degrees or even less than 90 degrees because the shaped abrasive particle formed in the mold cavity 102 may shrink during drying so that it can still be removed from the mold cavity instead of being trapped.

The bottom surface of the mold 106 includes a plurality of protrusions 108 protruding above the bottom surface with a predetermined height Hr.

In one embodiment of the invention, the height of the plurality of protrusions Hr is small compared to the total height of the mold cavity Hc. As mentioned above, many protrusions 108 can have the unexpected benefit of making shaped parent abrasive particles easier to remove from mold cavities 102 of production tool 100 after the shaped parent abrasive particles are dried. This result is obtained even despite the increase in the total surface area of ​​the mold cavity due to the presence of many protrusions that could be expected to impede the removal of shaped parent abrasive particles. The ability to easily release shaped abrasive parent particles from mold cavities 102 is an important feature for producing shaped abrasive particles on a continuously operating production line. This advantage is particularly important when increasing the speed on the production line. Trapped shaped mother abrasive particles that clog the production tool not only reduce productivity, but also cause problems when trying to vacuum coat slit production instrumentation with an abrasive dispersion before drying the abrasive dispersion in a continuous furnace.

It is believed that in order to obtain improved release properties, the height of many protrusions Hr should be less than the total height of the mold cavity Hc. As the height Hr approaches the height Hc, the mold cavity 102 is substantially further divided into several smaller mold cavities and the advantage of improved release from the mold cavities may disappear. In various embodiments, the height Hr of the many protrusions 108 may be from 1 micrometer to about 400 micrometers. Moreover, the percentage of the height of the protuberances, Hr / Hc (expressed as a percentage), can be from 0.1% to about 30% or from 0.1% to about 20% or from 0.1% to about 10% or from about 0.5% to about 5%.

EP2370232

In addition, it is believed that the cross-sectional geometry of the plurality of protrusions 108 may be important to improve the release properties of the mold. Referring to Figure 1A, in one embodiment, each protrusion 108 includes a first side 110, a second side 112, and a tip 114. The first side 110 and the other side 112 rise above the bottom surface of the mold 106 at an obtuse angle so that the geometry of the cross-section of the protuberances coincides with the tip 114, forming a truncated triangle. In this respect, the cross-sectional geometry of the protuberance also resembles a gear tooth or wedge.

Referring to Fig. 1B, in another embodiment, each protrusion 108 includes first side 110 and second side 112. First side 110 and second side 112 rise above the bottom surface of the mold 106 at an obtuse angle so that the cross-sectional geometry of the protuberance coincides with vertex forming a triangle. In this respect, the cross-sectional geometry of the protuberance also resembles a gear tooth or wedge. In one embodiment, each protrusion had a height Hr of 0.0127 mm and an angle at the apex, comprised between first side 110 and second side 112, equal to 45 degrees. The mold cavity had a height Hc of 0.7112 mm and a percentage ratio of the protuberance height to the height of the cavity Hr / Hc equal to 1.79%.

It is believed that when the cross-section of the protuberance is in the form of a truncated triangle or triangle, each protuberance acts as a wedge during drying, which leads to a slight elevation of the shaped parent abrasive particle when drying the shaped parent abrasive particle above the bottom surface 106. In some embodiments, it is believed that the shaped parent abrasive particle shrinks during drying, whereby the "wedges" loosen the shaped parent abrasive particle on the bottom surface of the mold, thereby facilitating removal of the shaped parent abrasive particle from the mold cavity. In other embodiments, the cross-sectional geometry of the protuberances may be square, rectangular, hemispherical, concave, parabolic, or may take a different shape.

Since one of the functions of many protrusions 108 is to provide improved release from the mold, the distribution and uniformity of the many protuberances may be important. In particular, the bottom surface of the mold 106 of the mold cavity

EP2370232 should be provided with protuberances in a uniform manner to ensure that the shaped parent abrasive particle does not adhere to the bottom surface. In one embodiment, the plurality of protuberances 108 were continuous lines such that the plurality of protrusions extended completely across the surface of the lower mold 106 from one side wall of the mold to the opposite side wall of the triangular mold cavity. Many of the protrusions had a triangular cross-section as described for Fig. 1B, and included parallel lines spaced approximately every 0.277 mm.

In various embodiments, the percent spacing between protrusions may be from about 1% to about 50%, from 1% to 40%, from 1% to 30%, from 1% to 20%, or from 5% to 20% of the surface size of such like the length of one of the edges of the shaped abrasive particle. In one embodiment, an equilateral triangle with a side length at the bottom surface of the mold 106 of 2.54 millimeters and with 8 protrusions per mold cavity in 277 micron increments had a percentage spacing of 10.9% between the individual protrusions. In other embodiments, the number of protrusions on the surface of the bottom mold may be from 1 to about 100, from about 2 to about 50, or from about 4 to about 25.

Many protrusions can be placed on the surface of the lower mold on arched lines, straight lines, concentric geometric patterns such as nested triangles or intersecting lines at regular or irregular intervals. Many protrusions can run parallel to each other or intersect. Combinations of different patterns can be used.

In other embodiments of the invention, the plurality of protrusions may be in the form of discrete line segments spaced along the bottom surface such that the plurality of protrusions do not run along the opposite side walls of the mold. Alternatively, many subdivided segments can be shortened so that the bottom surface contains a plurality of evenly spaced chamfered pyramids, forming a grid pattern such that the bottom surface resembles a waffle iron. To improve the release properties by providing a surface with a cavity arrangement, protrusions in other discrete geometric shapes may be placed on the bottom surface.

EP2370232

Figs. 2 and 2A show a shaped abrasive particle 20 formed in the mold cavity 102 of Fig. 1 with a plurality of grooves 116. The material from which the shaped abrasive particle 20 is made includes alpha alumina. Alpha corundum particles can be made from an alumina monohydrate dispersion that is gelatinized, shaped, dried to maintain shape, calcined, and then sintered as described later. The shape of the shaped abrasive particle is maintained without the need for a binder to form an agglomerate comprising the abrasive particles in the binder from which the shaped structure is then formed.

Generally shaped abrasive particles 20 with grooves 116 include thin bodies having a first surface 24, a second surface 26 and a thickness T.

The first surface 24 and the second surface 26 are connected to each other by a side wall 22, and the side wall can be angled to form an inclined side wall 22, described later, by using a mold cavity with an angle α between the mold side wall and the surface lower mold greater than 90 degrees. The sidewall can be minimized for shaped abrasive particles with surfaces converging to a thin edge or alternatively a tip or having a thicker sidewall.

In some embodiments, the first surface 24 is substantially flat, the second surface 26 is substantially flat, or both surfaces are substantially flat.

In one embodiment, the first surface 24 and the second surface 26 are substantially parallel to each other. In other embodiments, the first surface 24 and the second surface 26 may not be parallel in such a way that one surface is sloped relative to the surface of the other, and the imaginary tangent lines to each surface intersect at a point. The sidewall 22 of the shaped abrasive particle 20 with grooves 116 can be different and generally forms a perimeter 29 of the first surface 24 and the second surface 26. In one embodiment, the perimeter 29 of the first surface 24 and the second surface 26 is selected to be a geometric shape, and the first surface 24 and the second surface 26 are chosen so that they have the same geometric shape, but still differ in size, with one surface larger than the other

EP2370232 surface. In one embodiment, the perimeter 29 of the first surface 24 and the perimeter 29 of the second surface 26 was illustrated with a triangular shape.

With reference to Fig. 2A, to change the relative dimensions of each surface, the taper angle α between the second surface 26 and the side wall 22 of the shaped abrasive particle 20 can be changed. In various embodiments, the convergence angle α may be 90 degrees or from about 95 degrees to about 130 degrees or from about 95 degrees to about 125 degrees or from about 95 degrees to about 120 degrees or from about 95 degrees to about 115 degrees or from about 95 degrees to about 110 degrees or from about 95 degrees to about 105 degrees or from about 95 degrees to about 100 degrees. As can be seen from the examples, special ranges of the angle of convergence α have been found, allowing for a surprising increase in the grinding efficiency of abrasive coated products manufactured from shaped abrasive particles.

The shaped abrasive particles with grooves can be used to produce the abrasive coated abrasive products described later. If shaped abrasive particles 20 with grooves 116 have a taper angle α greater than 90 degrees (inclined side wall), most shaped abrasive particles 20 with grooves will be inclined to one side in the production of the abrasive article. As described later, this is considered to lead to improved grinding performance.

To further optimize the inclination orientation, shaped abrasive particles with grooves and an inclined side wall can be applied to the ground in the form of an open embankment. Closed embankment is defined as the maximum mass of abrasive particles or a mixture of abrasive particles that can be applied to the backing layer of an abrasive product in a single pass by the manufacturer. An open embankment is the amount of abrasive particles or a mixture of abrasive particles that weigh less than the maximum mass in grams that can be applied to the backing layer of the abrasive product, expressed in grams. With an open embankment, less than 100% of the undercoat will be covered with abrasive particles, leaving open areas and visible resin layers between the particles, which is best seen in Figure 8. In various embodiments, the open area in the abrasive layer may occupy a percentage of from about 10% to about 90% or from about 30% to about 80%.

EP2370232

It is believed that when too many shaped abrasive particles with grooves and an inclined sidewall are placed on the substrate, there will be insufficient spacing between the particles to allow the particles to lean before curing the primer and flooding layer. In various embodiments of the invention, more than 50, 60, 70, 80, or 90 percent of shaped abrasive particles are inclined in an open abrasive bulk product.

Fig. 3 is a photomicrograph of shaped abrasive particles 20 with grooves 116 and an inclined side wall. In Fig. 3, the convergence angle α is about 98 degrees, and the shaped abrasive particles included an equilateral triangle. The sides of each triangle are approximately 1.6 mm in circumference of the larger first surface 24. Disc-shaped abrasive particles had a concave first surface 24, which can be seen by the varying thickness of the sidewall and the fact that the shaped abrasive particles rest mainly on the vertices or corners of the triangles.

Fig. 4 is a photomicrograph of shaped abrasive particles 20 with grooves 116. In Fig. 4, the convergence angle α of the mold was 98 degrees, and the shaped abrasive particles included an equilateral triangle. The sides of each triangle are approximately 1.6 mm in circumference of the larger first surface

24. Disc-shaped abrasive particles had a concave first surface 24 and a convex second surface 26 (initially formed on the surface of the lower mold). More information about disc shaped abrasive particles with concave surface is disclosed in the above-mentioned Ombudsman Register No. 64716US002.

The grooves 116 on the second surface 26 are formed by a plurality of protrusions 108 on the bottom surface of the mold. Thus, the pattern of grooves on the second surface 26 will be a representation of any of the patterns described above for protuberances. In one embodiment, the plurality of grooves comprise parallel lines extending completely across the other surface and intersecting along the periphery at a 90 degree angle. The cross-sectional geometry of the grooves was a triangle or may be other geometries discussed above.

In various embodiments, the depth D of the multiple protuberances 116 may be from about 1 to 400 microns. What's more, attitude

EP2370232 the percentage of the groove depth D to the maximum depth of the shaped abrasive particle T (D / T expressed as a percentage) can be from 0.1% to about 30% or from 0.1% to about 20% or from 0.1% to about 10 % or from about 0.5% to about 5%.

After placing multiple grooves on the shaped abrasive particle, to improve the release capacity from the production tooling, it was surprisingly found that this affects the grinding performance of the resulting shaped abrasive particles with grooves. This result is obtained even despite the small depth of the D groove compared to the maximum thickness

T shaped abrasive particle. It is not known if this is the result of greater cracking of the shaped abrasive particles during use along the grooves, which can create new sharp edges, or that the grooves themselves, without cracking the shaped abrasive particle, provide fresh sharp edges and a slightly smaller wear plane, because the shaped the abrasive particle with grooves is consumed by the exposure of the given groove. Due to the fact that there are many grooves in each abrasive particle, there are many chances for self-sharpening the shaped abrasive particle with grooves.

As discussed in more detail on the basis of examples, many grooves in one embodiment tend to reduce the initial unit loss of material of the shaped abrasive particle, which unit loss of material then increases as the abrasive product is used. Similarly shaped shaped abrasive particles with a tendency tended to have a greater initial unit loss of material, which unit loss of material then decreases during use of the abrasive product. By mixing shaped abrasive particles with grooves with shaped abrasive particles without grooves, you can achieve a unit loss of material removed by a more uniform abrasive product at the beginning of use and later on. The constant unit loss of material is often important for consumers of abrasive products to avoid having to re-adjust the production equipment associated with abrasive wear in the production of standardized parts. In various embodiments, at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 can be mixed with shaped abrasive particles without grooves. , or 95 weight percent of shaped abrasive particles with grooves. In one of

EP2370232 embodiments have found that a very uniform unit loss of material over time is provided by a blend of 50% -50% equilateral triangle-shaped abrasive particles with multiple grooves and equilateral triangle abrasive particles without multiple grooves. In various embodiments, the blend of shaped abrasive particles may comprise from about 40% to about 60% of shaped abrasive particles with multiple grooves and from about 40% to about 60% of shaped abrasive particles without multiple grooves.

Figure 5 illustrates another embodiment of the plurality of grooves on the second surface 26. Many of the grooves included an arrangement of intersecting parallel lines extending over the entire second surface 26.

The first set of 17 parallel lines, at intervals equal to 6.25% of the edge length of the triangle, crossed at one angle by 90 degrees one of the perimeter edges, and the second set of 17 parallel lines, at intervals equal to 6.25% of the length of the edge of the triangle, crossed at an angle 90 degrees the other edge of the perimeter, thus forming on the other surface a system of intersecting lines at an angle and forming many raised rhombuses. In various embodiments, intersecting parallel lines may have parallel or non-parallel lines, different line spacing, intersecting arc lines, or different groove cross-sectional geometries.

Shaped abrasive particle with inclined side wall

Figures 6A, 6B and 6C illustrate an exemplary shaped abrasive particle 20 with an inclined side wall 22. Hereinafter, any embodiments of shaped abrasive particles with an inclined side wall (convergence angle α greater than 90 degrees) can be combined with any of the embodiments of the abovementioned shaped abrasive particles with grooves 116. The material from which the shaped abrasive particle 20 is made with the inclined side wall 22 includes alpha corundum. Alpha corundum particles can be made from an alumina monohydrate dispersion that is gelatinized, shaped, dried to maintain shape, calcined, and then sintered as described later.

Generally shaped abrasive particles 20 with an inclined sidewall include thin bodies having a first surface 24, a second surface 26 and a thickness T. The first surface 24 and the second surface 26 are connected to each other by at least one inclined side wall 22. In some

In embodiments, there may be more than one inclined sidewall 22, and the slope or angle of each inclined sidewall 22 may be the same as shown in Fig. 6A or different than that shown in Fig. 9A.

In some embodiments, the first surface 24 is substantially flat, the second surface 26 is substantially flat, or both surfaces are substantially flat.

In one embodiment, the first surface 24 and the second surface 26 are substantially parallel to each other. In other embodiments, the first surface 24 and the second surface 26 may not be parallel in such a way that one surface is sloped relative to the surface of the other, and the imaginary tangent lines to each surface intersect at a point. The inclined side wall 22 of the shaped abrasive particle 20 with the inclined side wall 22 may be different and generally forms a perimeter 29 of the first surface 24 and the second surface 26. In one embodiment, the perimeter 29 of the first surface 24 and the second surface 26 is selected to be a geometric shape, and the first surface 24 and the second surface 26 are selected to have the same geometric shape, but still differ in size, with one surface larger than the other surface. In one embodiment, the perimeter 29 of the first surface

24 and the perimeter 29 of the second surface 26 was illustrated with a triangular shape.

With reference to Figs. 6B and 6C, to change the relative dimensions of each surface, the taper angle α between the second surface 26 and the inclined sidewall 22 of the shaped abrasive particle 20 may be changed. In various embodiments, the taper angle α may range from about

95 degrees to about 130 degrees or from about 95 degrees to about 125 degrees or from about 95 degrees to about 120 degrees or from about 95 degrees to about 115 degrees or from about 95 degrees to about 110 degrees or from about 95 degrees to about 105 degrees or from about 95 degrees to about 100 degrees. As can be seen from the examples, special ranges of angle of convergence α have been found to achieve a surprising increase in the grinding efficiency of abrasive coated articles made of shaped abrasive particles with an inclined side wall.

In Fig. 6C, an abrasive dump 40 is shown having a first major surface 41 of a substrate 42 coated with an abrasive layer. Layer

EP2370232 abrasive includes a backing layer 44 and a plurality of shaped abrasive particles 20 with an inclined side wall 22 attached to the substrate 42 by means of the backing layer 44. To further attach or adhere the shaped abrasive particles 20 with the inclined side wall 22 to the substrate 42, a pouring layer 46 is applied .

As can be seen, most shaped abrasive particles 20 with an inclined side wall 22 are inclined to one side. As a result, most shaped abrasive particles 20 with an inclined side wall 22 have an orientation angle β relative to the first major surface 41 of the substrate 42 less than 90 degrees. This result is unexpected because the electrostatic coating method with which shaped abrasive particles with an inclined sidewall are applied tends to initially orient the particles at the first application to the substrate with an β orientation of 90 degrees. The electrostatic field, which is above shaped abrasive particles with an inclined side wall, tends to position the particles vertically when applied to the primer. What's more, the electrostatic field tends to accelerate and propel the particles towards the backing layer at an orientation angle of 90 degrees. At a certain point after the network has been rotated, before or after the application of the flooding layer 46, due to gravity or the surface tension of the primer and / or flooding layer, the particles tend to tilt and rest on the inclined side wall 22. It is believed that the time sufficient in the process of producing the abrasive bulk product to tilt and attach shaped abrasive particles via the inclined side wall 22 to the backing layer is that before solidification and hardening of the backing layer to prevent further rotation. As can be seen in the figure, after the shaped abrasive particles have been applied and allowed to tilt, the tops of the shaped abrasive particles 48 are generally at the same height h.

To further optimize the inclination orientation, shaped abrasive particles with an inclined side wall are applied to the ground in the form of an open embankment. Closed embankment is defined as the maximum mass of abrasive particles or a mixture of abrasive particles that can be applied to the backing layer of an abrasive product in a single pass by the manufacturer. earthwork

EP2370232 is open with an amount of abrasive particles or a mixture of abrasive particles that weigh less than the maximum usable mass in grams that can be applied to the backing layer of the abrasive article. With an open embankment, less than 100% of the undercoat will be covered with abrasive particles, leaving open areas and visible resin layers between the particles, which is best seen in Figure 8. In various embodiments, the open area in the abrasive layer may occupy a percentage of from about 10% to about 90% or from about 30% to about 80%.

It is believed that if too many shaped abrasive particles with an inclined side wall are placed on the substrate, there will be insufficient spacing between the particles to allow them to lean before curing the primer and flooding layer. In various embodiments of the invention, more than 50, 60, 70, 80, or 90 percent of shaped abrasive particles with an β orientation angle of less than 90 degrees are inclined in an open abrasive bulk product.

Without wishing to be bound by theory, it is believed that an orientation angle β of less than 90 degrees leads to increased cutting performance of shaped abrasive particles with an inclined side wall. Surprisingly, this result is generally obtained regardless of the rotational orientation of the shaped abrasive particles about the Z axis in the bulk abrasive. While fig. 6C was idealized to show that all particles are in the same direction, the actual sanding disc would have the particles arranged and rotated more randomly, which is best seen in Fig. 8. Because the abrasive wheel rotates and the shaped abrasive particles are randomly distributed, some shaped abrasive particles will be directed to the workpiece at an β orientation angle less than 90 degrees, with the workpiece initially striking the second surface 26, while the adjacent shaped abrasive particle may be rotated exactly 180 degrees, with the working element hitting the rear surface of the shaped abrasive particle and the first surface 24. With the random distribution of particles and the rotation of the disc, the working element will initially hit the second surface 26 instead of the first surface 24 for less than half of the shaped abrasive particles. Nevertheless, for abrasive belts with a defined direction of rotation and a defined point of contact with the working element, it is possible to set

EP2370232 shaped abrasive particles with an inclined sidewall on the belt so as to ensure that each shaped abrasive particle is directed at an β orientation angle of less than 90 degrees and the workpiece is first directed to the second surface 26 as idealized in Fig. 6C. In various embodiments of the invention, the orientation angle β for at least most shaped abrasive particles with an inclined side wall in the abrasive layer of the bulk abrasive article may be from about 50 degrees to about 85 degrees or from about 55 degrees to about 85 degrees or from about 60 degrees to about 85 degrees or from about 65 degrees to about 85 degrees or from about 70 degrees to about 85 degrees or from about

75 degrees to about 85 degrees or from about 80 degrees to about 85 degrees.

Figures 7 and 8 show photomicrographs of shaped abrasive particles 20 with an inclined side wall 22. In Figure 7, the convergence angle α is approximately 120 degrees, and the shaped abrasive particles included an equilateral triangle. The sides of each triangle are approximately 1.6 mm in circumference over the larger first surface 24. The shaped abrasive particles have a thickness of about 0.38 mm. The surface of the resulting sanding disc made from the shaped abrasive particles of Fig. 7 is shown in Fig. 8. As can be seen in the figure, most of the shaped abrasive particles rest in the backing layer on one of the inclined side walls. The angle of orientation β for most shaped abrasive particles with an inclined sidewall in the abrasive layer of the bulk abrasive product in Fig. 3 is about 60 degrees.

Figures 9A-C show a second embodiment of a shaped abrasive particle 20 with an inclined side wall 22. The material from which the shaped abrasive particle 20 with an inclined side wall 22 is made includes alpha corundum. Alpha corundum particles can be made from an alumina monohydrate dispersion that is gelatinized, shaped, dried to maintain shape, calcined, and then sintered as described later.

The shaped abrasive particles 20 with the inclined side wall 22 generally include thin bodies having a first surface 24 and a second surface 26 and having a thickness T. The first surface 24 and the second surface 26 are connected to each other by at least a first inclined side wall 50 having a first convergence angle 52 and a second inclined side wall 54 having a second convergence angle 56, the value of which is selected to be different from the first convergence angle. In the embodiment shown, the first surface

EP2370232 and the second are also connected by a third inclined side wall 58 having a third convergence angle 60, which has a value different from the other two convergence angles.

In the illustrated embodiment, the first, second and third convergence angles have values ​​different from each other. For example, the first convergence angle

52 it can be 120 degrees, the second convergence angle 56 can be 110 degrees, and the third convergence angle 60 can be 100 degrees. The resulting loose abrasive 40 shown in Fig. 4C made from shaped abrasive particles with three different convergence angles will tend to have an even distribution of shaped abrasive particles based on each of three different inclined side walls. In this way, the bulk abrasive will tend to have the tops of 48 shaped abrasive particles at three different heights relative to the substrate. The first sloping side wall 50 with the largest angle of convergence in contact with the base layer will have the smallest vertex height h1, the second sloping side wall

54 the intermediate angle of convergence will have an intermediate vertex height h2, and the third inclined side wall 58 with the smallest convergence angle will have the largest vertex height h3. As a result, the abrasive dump will have shaped abrasive particles having three different orientation angles β relative to the substrate and three different tip heights. It is believed that such an abrasive bulk product will have a more uniform cutting performance, since the abrasive product is worn in such a way that the unused shorter tops of the shaped abrasive particles begin to contact the workpiece when the higher tops of the shaped abrasive particles wear and dull.

In some embodiments, the first surface 24 is substantially flat, the second surface 26 is substantially flat, or both surfaces are substantially flat.

In one embodiment, the first surface 24 and the second surface 26 are substantially parallel to each other. In other embodiments, the first surface 24 and the second surface 26 may not be parallel in such a way that one surface is sloped relative to the surface of the other, and the imaginary tangent lines to each surface intersect at a point. The first, second and third inclined sidewall of the shaped abrasive particle 20 with the inclined sidewall 22 may be different and generally form a perimeter 29 of the first surface 24 and the second surface 26.

EP2370232

In one embodiment, the perimeter 29 of the first surface 24 and the second surface 26 is selected to be a geometric shape, and the first surface 24 and the second surface 26 are selected to have the same geometric shape, but still differ in size, with one surface larger than the other surface. In one embodiment, the perimeter 29 of the first surface 24 and the perimeter 29 of the second surface 26 was illustrated with a triangular shape.

Referring to Figs. 9B and 9C, the first, second and third convergence angles between the second surface 26 and the corresponding inclined side wall of the shaped abrasive particle 20 may be different, with at least two values ​​of the convergence angle being different, and it is desirable to differ all three values. In various embodiments, the first convergence angle, second convergence angle, and third convergence angle may range from about 95 degrees to about 130 degrees or from about 95 degrees to about 125 degrees or from about 95 degrees to about 120 degrees or from about 95 degrees to about 115 degrees or from about 95 degrees to about 110 degrees or from about 95 degrees to about 105 degrees or from about 95 degrees to about 100 degrees.

In Fig. 9C, a loose abrasive 40 is shown having a first major surface 41 of a substrate 42 coated with an abrasive layer. The abrasive layer includes a backing layer 44 and a plurality of shaped abrasive particles 20 with a first, second or third inclined wall attached to the substrate 42 by means of the backing layer 44. To further attach or adhere the shaped abrasive particles 20 with the inclined side wall 22 to the substrate 42, is applied floodplain 46.

As can be seen, most shaped abrasive particles 20 with an inclined side wall 22 are inclined to one side. As discussed earlier for the first embodiment, as a result, most shaped abrasive particles 20 with an inclined side wall 22 have an orientation angle β relative to the first major surface 41 of the substrate 42 of less than 90 degrees.

To further optimize the inclination orientation, shaped abrasive particles with an inclined side wall are applied to the ground in the form of an open embankment. In the case of an abrasive layer with an open coating, less than 100% of the backing layer will be covered with abrasive particles, leaving open areas and visible resin layers between the abrasive particles, which is best seen in Figure 8. In various examples

In an embodiment of the invention, the open area in the abrasive layer may occupy a percentage of from about 10% to about 90% or from about 30% to about 80%.

It is believed that if too many shaped abrasive particles with an inclined side wall are placed on the substrate, there will be insufficient spacing between the shaped abrasive particles to allow them to lean before curing the primer and potting layer. In various embodiments of the invention, more than 50, 60, 70, 80, or 90 percent of shaped abrasive particles with an β orientation angle of less than 90 degrees are inclined in an open abrasive bulk product.

Without wishing to be bound by theory, it is believed that an orientation angle β of less than 90 degrees leads to increased cutting performance of shaped abrasive particles with an inclined side wall, which has already been discussed. In various embodiments of the invention, the orientation angle β for at least most shaped abrasive particles with an inclined side wall in the abrasive layer of the bulk abrasive article may be from about 50 degrees to about 85 degrees or from about 55 degrees to about 85 degrees or from about 60 degrees to about 85 degrees or from about 65 degrees to about 85 degrees or from about 70 degrees to about 85 degrees or from about 75 degrees to about 85 degrees or from about 80 degrees to about 85 degrees.

Figures 10A-B show a third embodiment of the invention.

In this embodiment, the inclined side wall 22 is defined by the radius R, instead of the angle of convergence α as for the embodiments of Figs. 6A-6C. It has been found that the sloping sidewall 22 defined by the radius R also leads to the tilting of the shaped abrasive particles 20 when forming the bulk abrasive product shown in Fig. 10C. Grinding tests have shown that shaped abrasive particles including an equilateral triangle in which the sides of each triangle have a dimension of about 1.6 mm on the circumference of the larger first surface 24 and which have a thickness of about 0.38 mm have the same cutting performance at a taper angle of 120 degrees or radius R equal to 0.51 mm. In various embodiments, the radius R may be from about 0.5 to about 2 the thickness T of the shaped abrasive particle.

EP2370232

As in the second embodiment, the radius R may be different for each of the side walls to lead to the shaped abrasive particles in the abrasive article being inclined at different angles.

It is believed that if too many shaped abrasive particles with an inclined side wall are placed on the substrate, there will be insufficient gaps between the shaped abrasive particles to allow them to lean before curing the primer and potting layer. In various embodiments of the invention, more than 50, 60, 70, 80, or 90 percent of shaped abrasive particles with an β orientation angle of less than 90 degrees are inclined in an open abrasive bulk product.

In the case of the first embodiment, the second embodiment or the third embodiment, the shaped abrasive particles 20 with the inclined side wall 22 may have different three-dimensional shapes. The geometric shape of the perimeter 29 may be a triangular, rectangular, round, elliptical, star-shaped or other of regular or irregular polygons. In one embodiment, an equilateral triangle was used, and in another embodiment an isosceles triangle was used. For the purposes of this disclosure, the substantially triangular shape also includes triangular polygons in which one or more sides may be the arcuate side and / or the vertices of the triangle may be arcuate.

Furthermore, different inclined side walls of the shaped abrasive particles may have the same angle of convergence or different angles of convergence. In addition, as long as one of the side walls is an inclined side wall with a convergence angle of about 95 degrees or greater, a convergence angle of 90 degrees may be used for one or more side walls.

The shaped abrasive particles 20 with an inclined side wall can have different volumetric shape factors. The volumetric aspect ratio is defined as the ratio of the maximum cross-sectional area passing through the center of gravity of the volume to the minimum cross-sectional area passing through the center of gravity. For some shapes, the maximum or minimum cross-sectional area may be a skewed plane, angled, or inclined to the geometry

EP2370232 outer shape. For example, a sphere would have a volumetric aspect ratio of 1,000, and a cube would have a volumetric aspect ratio of 1,414. A shaped abrasive particle in the form of an equilateral triangle having each side of length A and equal thickness A will have a volumetric aspect ratio of 1.54, and if the thickness is reduced to 0.25A, the volumetric aspect ratio will increase to 2.64. It is believed that shaped abrasive particles with a larger volumetric shape factor have increased cutting efficiency. In various embodiments, the volumetric aspect ratio of shaped abrasive particles with an inclined sidewall may be greater than about 1.15 or greater than about 1.50 or greater than about 2.0, or may be from about 1.15 to 10.0 or from about 1.20 to about 5.0 or from about 1.30 to about 3.0.

Shaped abrasive particles with an inclined side wall can have a much smaller radius of curvature at the tops or corners of the shaped abrasive particles. Shaped equilateral triangle abrasive particles disclosed in US Patent No. 5,366,523 to Rowenhorst et al. 14, had a radius of curvature at the vertices of the triangle (measured from one side around the top to the next side) of 103.6 microns for the average radius of curvature. The radius of curvature can be measured on the polished cross-section of the first or second surface by image analysis, such as with a Clemex Image Analysis program coupled with an inverse light microscope or other suitable image analysis software. The radius of curvature of each of the vertices of the triangle can be estimated by definition at each vertex of three points, looking at the cross-section at 100x magnification. The point is placed at the beginning of the vertex curve, where the straight edge passes to the beginning of the curve, at the highest point of the vertex and at the point of re-transition from the curved vertex to the straight edge. The image analysis software then draws an arc defined by three points (start, middle and end) and calculates the radius of curvature. The radius of curvature is measured for at least 30 vertices and is averaged to determine the mean radius of curvature. The shaped abrasive particles produced by the current method are produced much more precisely, which is best seen by comparing figures 7 to 14. In this way, the average radius

EP2370232 the tip of shaped abrasive particles is much smaller. The average radius of curvature of the shaped abrasive particles produced according to the present disclosure was measured to be less than 19.2 microns. In various embodiments, the average apex radius may be less than 75 microns or less than 50 microns, or less than 25 microns. It is believed that the sharper tip promotes more aggressive machining and better cracking of shaped abrasive particles during use.

In addition to the sharper tip, shaped abrasive particles can have a much more precisely defined side wall. Figs. 15 and 16 are photomicrographs of polished cross-sections lying perpendicular to the surface of the shaped abrasive particles known in the prior art of Fig. 14. It can be seen that the sidewall (upper surface) tends to be concave or convex and not constantly flat. Depending on the position of the cross-section, the same cross-wall can go from one shape to another. With reference to Fig. 16, the side wall is convex in the foreground, while in the background it is concave.

Fig. 17 shows a polished cross-section perpendicular to the surface of the shaped abrasive particle with an inclined side wall with a taper angle of 98 degrees. The first surface 24 (right vertical surface) is concave. It is believed that the concave surface increases the grinding efficiency, removing more material during use, similar to a bucket, spoon or blade of a concave ground chisel. The second surface 26 is substantially flat (left vertical surface). And finally, the side wall (upper surface) is constantly flat. A permanently flat sidewall means one that does not have from one surface to another surface of convex areas or from one surface to another surface of concave areas and at least 50% or at least 75% or at least 85% or more of the side wall surface is flat. As can be seen in the cross-section, when the sidewall is cut at 90 degrees and polished, a substantially linear edge appears (where the upper surface of the sidewall meets the front surface of the intersection). A permanently flat side wall would normally have this substantially linear edge in substantially all cross-sectional planes along the length of the side wall. The permanently flat side wall provides better defined (sharper) edges

EP2370232 at the intersection of the sidewall with the first surface and the second surface, which is also considered to increase grinding efficiency.

Shaped abrasive particles 20 with an inclined sidewall 22 and / or grooves 116 produced in accordance with the present disclosure may be incorporated into the abrasive product or used in a loose form. Prior to use, abrasive particles are generally classified according to the given distribution of particle sizes . Such distributions usually include particles ranging from coarse particles to fine particles. In the field of abrasives, this range is sometimes called "coarse", "medium" and "fine". Abrasive particles classified in accordance with the classification standards adopted in the abrasive industry determine the particle size distribution for each nominal class in the range of numerical values. Such industry-accepted classification standards (i.e., nominal classes defined in the abrasive industry) include standards known as American standards

National Institute of Standardization (ANSI), standards of the Federation of European Abrasives Manufacturers (FEPA) and Japanese Industrial Standards (JIS).

ANSI class designations (i.e. specific nominal classes) include: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 40, ANSI 50, ANSI 60,

ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400 and ANSI 600. FEPA class designations include: P8, P12, Pl6, P24, P36 , P40, P50, P60, P80, P100, P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000 and P1200. JIS class designations include: JIS8, JIS12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80, JIS100,

JIS150, JIS180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS600, JIS800, JIS1000, JIS1500, JIS2500, JIS4000, JIS6000, JIS8000 and JIS10000.

Alternatively, shaped abrasive particles 20 with inclined sidewall 22 and / or grooves 116 can be classified according to sieve classification based on US standard test sieves in accordance with ASTM E-11 "Standard

Specification for Wire Cloth and Sieves for Testing Purposes ("Standard specification of wire mesh and sieves for test purposes"). ASTM E-11 contains requirements for the design and construction of test screens for the classification of materials based on the indicated particle size, using as a medium woven wire mesh mounted in the frame. A typical designation may be in the form 25

EP2370232

18 + 20, which means that the shaped abrasive particles 20 pass through the test sieve in accordance with ASTM E-11 specifications for the No. 18 sieve and are retained on the test sieve in accordance with ASTM E-11 specifications for the No. 20 sieve. In one embodiment, the shaped abrasive particles 20 with the inclined side wall 22 have a particle size such that most particles pass through the 18 mesh test screen and can be retained on the 20, 25, 30, 35, 40, 45 or 50 mesh test screen. In various embodiments of the invention, shaped abrasive particles 20 with an inclined side wall 22 may have a nominal grain class including: -18 + 20, -20 + 25, -25 + 30, -30 + 35, -35 + 40, 10 40 + 45 , -45 + 50, - 50 + 60, -60 + 70, -70 + 80, -80 + 100, -100 + 120, -120 + 140, -140 + 170, 170 + 200, -200 + 230, - 230 + 270, -270 + 325, -325 + 400, -400 + 450, -450 + 500 or 500 + 635.

One of the objects of the present disclosure is a plurality of shaped abrasive grains having a nominal class specified in the abrasive industry or a nominal grain class, among which at least some of the many abrasive particles are shaped abrasive particles 20 with an inclined wall 22 and / or grooves 116. Another subject of the present disclosure is a method that includes the classification of shaped abrasive particles manufactured in accordance with the present disclosure to provide a plurality of shaped abrasive particles 20 having a nominal class defined in the abrasive industry or a nominal grain class.

If desired, shaped abrasive particles having a nominal class specified in the abrasive industry or a nominal grain class can be mixed with other known abrasive or non-abrasive particles. In some embodiments, at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or even 100 weight percent of many particles abrasives having a nominal class specified in the abrasive industry or a nominal grain class are shaped abrasive particles made according to the present disclosure, based on the total mass of many abrasive particles.

Particles suitable for mixing with shaped abrasive particles 20 with inclined sidewall 22 and / or grooves 116 include conventional abrasive grains, dilution grains or erodible agglomerates such as those described in US Patent Nos. 4,799,939

EP2370232 and 5 078 753. Representative examples of traditional abrasive grains include alumina, silicon carbide, garnet, zirconium alumina, regular boron nitride, diamond, etc. Representative examples of dilution grains include marble, gypsum and glass. Mixtures of differently shaped abrasive particles 20 with an inclined side wall 22 (e.g. triangles or squares) or mixtures of shaped abrasive particles 20 with different angles of convergence (e.g. particles with a convergence angle of 98 degrees mixed with particles having convergence angle of 120 degrees).

The shaped abrasive particles 20 may also have a surface coating. Surface coatings are known to improve the adhesion between abrasive grains and the binder in abrasive products, or they can be used to assist in electrostatic application of shaped abrasive particles 20. Such surface coatings are described in US Patent Nos. 5,213,591; 5,011,508; 1 910 444; 3 041 156; 5,009 675; 5,085 671; 4 997 461 and 5 042 991. Furthermore, the surface coating can protect the shaped abrasive particle from sizing. Sizing is a term describing the phenomenon in which metal particles from a ground workpiece are ground to the tops of shaped abrasive particles. Surface coatings fulfilling the above functions are known to those skilled in the art.

Abrasive product with shaped abrasive particles with an inclined side wall

Referring to Figures 1C, 4C and 5C, the abrasive coated product 40 includes a backing 42 with a first binder layer, herein referred to as a backing layer 44, which is applied to the first main surface 41 of the backing 42. In the backing layer 44, fixed or partially embedded a plurality of shaped abrasive particles 20 with an inclined wall 22 and / or grooves 116 forming an abrasive layer. Above the shaped abrasive particles 20 with the inclined side wall 22 is a second adhesive layer, here referred to as the flooding layer 46. The purpose of the backing layer 44 is to attach the shaped abrasive particles 20 with the inclined side wall 22 to the substrate 42, and the purpose of the flooding layer 46 is to reinforce the shaped abrasive particles 20 with an inclined side wall 22. Most shaped particles

EP2370232 abrasive 20 with an inclined side wall 22 is oriented such that the tip 48 is away from the substrate 42 and the shaped abrasive particles rest on the inclined side wall 22 and are inclined or skewed as shown.

The backing layer 44 and the potting layer 46 comprise a resin binder. The resin binder of the backing layer 44 may be the same or different from that in the flooding layer 46. Examples of resin binders suitable for said layers include phenol resins, epoxy resins, urea formaldehyde resins, acrylic resins, aminoplast resins, melamine resins, acrylic epoxy resins , urea resins and combinations thereof.

In addition to the resin binder, the primer layer 44 or flooding layer 46 or both layers may also contain additives known in the art such as, for example, fillers, grinding aids, moisturizing agents, surfactants, dyes, pigments, coupling agents, adhesion promoters and their combinations. Examples of fillers include calcium carbonate, silica, talc, clay, calcium metasilicate, dolomite, aluminum sulfate and combinations thereof.

A grinding aid can be added to the abrasive coated product. The grinding aid is defined as a particulate material, the addition of which significantly affects the chemical and physical processes of material abrasion, ensuring improved performance. Grinding aids include a wide range of different materials and can be inorganic or organic. Examples of chemical groups of grinding auxiliaries include waxes, organic halide compounds, halide and metal salts and their alloys. Organic halide compounds typically break down during abrasion and release halogen acid or gaseous halide compound. Examples of such materials include chlorinated waxes such as tetrachloronaphthalene, pentachloronaphthalene and polyvinyl chloride. Examples of halide salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride. Examples of metals include tin, lead, bismuth, cobalt, antimony, cadmium, iron and titanium. Other grinding auxiliaries include sulfur, organic sulfur compounds, graphite and metal sulfides. The scope of the present invention also includes the use of a combination of various grinding auxiliaries, which in some cases may give rise to a synergistic effect. In one embodiment, the agent

EP2370232 grinding aid was cryolite or potassium tetrafluoroborate. The amount of such additives can be adjusted to give the desired properties. The use of a top coat is also included within the scope of the present invention. The top coat usually contains a binder and a grinding aid. The binders can be formed from materials such as phenol resins, acrylic resins, epoxy resins, phenol resins, urea formaldehyde resins, melamine resins, urea resins and combinations thereof.

Also included within the scope of the present invention is that shaped abrasive particles 20 with an inclined side wall 22 and / or grooves

116 can be used in bonded abrasive, non-woven abrasive or abrasive brushes. The bonded abrasive may include a plurality of shaped abrasive particles bonded together by means of an adhesive to form a shaped mass. The bonded bonded abrasive binder may be a metallic, organic or glassy binder. The nonwoven abrasive material includes a plurality of shaped abrasive particles bonded by means of an organic nonwoven binder.

A method for producing shaped abrasive particles with an inclined side wall

The first step of the method is to provide an nucleated ("seeded") or non-nucleated ("un-seeded") abrasive dispersion that can be converted to alpha alumina. The alpha alumina precursor composition often includes a liquid that is a volatile component. In one embodiment, the volatile component is water. The abrasive dispersion should contain an amount of liquid that is sufficient to ensure that the abrasive dispersion has a low enough viscosity to allow the mold cavities to be filled and the mold surface to be restored, but not too high, as this can make the subsequent removal of liquid from the mold cavity too expensive. In one embodiment, the abrasive dispersion comprises from 2% to 90% by weight of the particles that can be converted to alpha corundum, such as alumina (boehmite) monohydrate particles, and at least 10% by weight or from 50% to 70% or from 50% to 60% by weight of a volatile component such as water. Conversely, the abrasive dispersion in some embodiments contains from 30% to 50% or from 40% to 50% by weight solids.

EP2370232

Alumina hydroxides other than boehmit can also be used.

Boehmit can be prepared using known techniques or obtained commercially. Examples of commercially available boehmite include products under the trade names "DISPERAL" and "DISPAL", which Sasol North America, Inc. offers or "HiQ5 40" available from BASF Corporation. These alumina monohydrates are relatively pure, i.e. they contain less (if any) hydride phases than other monohydrates and have a large surface area. The physical properties of the resulting shaped abrasive particles 20 with an inclined side wall 22 will generally depend on the type of material used in the abrasive dispersion.

In one embodiment, the abrasive dispersion is in the form of a gel. The term "gel" as used herein corresponds to the three-dimensional network of solid particles dispersed in a liquid. The abrasive dispersion may contain a modifying additive or a modifying additive precursor. The modifying additive may have the task of improving some desired property of the abrasive particles or increasing the efficiency of the next sintering step. Modifying additives or precursors of modifying additives may be in the form of soluble salts, usually water-soluble salts. They consist mainly of a metal-containing compound and can be a precursor of magnesium oxide, zinc, iron, silicon, cobalt, nickel, zirconium, hafnium, chromium, yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium, cerium, dysprosium, erbium , titanium and mixtures thereof. The specific concentrations of said additives that may be present in the abrasive dispersion may be different, based on the skill in the art. The introduction of a modifying additive or modifier precursor will usually result in the transformation of the abrasive dispersion into a gel. The abrasive dispersion can be turned into a gel by applying heat for a certain period of time.

To enhance the conversion of hydrated or calcined alumina to alpha alumina, the abrasive dispersion may also contain a nucleating agent. Nucleating agents suitable for the present disclosure include alpha alumina particles, alpha iron oxide or precursor thereof, titanium oxides and titanates, chromium oxides or any other materials that will nucleate transformation. The amount of nucleating agent, if used, should be adequate to affect alpha corundum transformation. The nucleation of such abrasive suspensions has been disclosed in US Patent No. 4,744,802 to Schwabel.

EP2370232

To produce a more stable hydrosol or colloidal abrasive dispersion, a peptizing agent may be added to the abrasive dispersion. Suitable peptizing agents are monobasic acids or acidic compounds such as acetic acid, hydrochloric acid, formic acid or nitric acid.

Polybasic acids can also be used, but they can quickly gel the abrasive dispersion, making it difficult to perform operations on it, or to add additional ingredients to it. Some commercial sources of boehmite contain titers of acid (such as absorbed formic or nitric acid) that will assist in the formation of a stable abrasive dispersion.

The abrasive dispersion may be formed by any suitable methods such as simply mixing the alumina monohydrate with water containing the peptizing agent or by forming an alumina monohydrate suspension to which the peptizing agent is added. To reduce the tendency to form bubbles or air bubbles while mixing, anti-foaming agents or other suitable chemicals may be added. Additional chemicals such as wetting agents, alcohols or coupling agents can be added as needed. As disclosed in US Patent No. 5,645,619 of July 8, 1997 to Erickson et al., Abrasive alpha alumina grain may contain silicon or iron oxide. As disclosed in US Patent

No. 5 551 963 of September 3, 1996 to Larmie, abrasive alpha alumina grain may contain zirconium. Alternatively, as disclosed in US Patent No. 6,277 161 of August 21, 2001 to Castro, abrasive alpha corundum grain may have a microstructure or additives.

The second step of the method is to provide a mold having at least one cavity, and preferably a plurality of mold cavities. The mold may generally have a flat bottom surface and multiple mold cavities. Multiple sockets can be created in the production tool. The production tool can be a tape, sheet, continuous web, coating roller such as a rotogravure roller, sleeve mounted on a coating roller, or die. The production tool includes polymer material. Examples of suitable polymeric materials include thermoplastics such as polyesters, polycarbonates, poly (ether sulfone), poly (methyl methacrylate), polyurethanes, polyvinyl chloride, polyolefins, polystyrene, polypropylene, polyethylene or combinations thereof, as well as materials

EP2370232 thermosetting. In one embodiment, all instrumentation is made of a polymer or thermoplastic material. In another embodiment, polymeric or thermoplastic materials are embraced by instrumentation surfaces that contact the sol-gel during drying, such as multiple cavity surfaces (bottom mold surface and mold side wall), and other instrumentation parts can be made of other materials. A suitable polymer coating can, for example, be applied to metal tooling to change the surface tension properties.

A polymer or thermoplastic tool can be restored based on a metal reference tool. The reference tool will be the reverse of the one desired for the production tool. The reference tool can be created in the same way as the production tool. In one embodiment, the reference tool is made of metal, e.g., nickel, by diamond cutting. The polymer or thermoplastic material in the form of a sheet can be heated together with the master tool so that after compressing these two elements, the master tool pattern is embossed. The polymer or thermoplastic material can also be squeezed or poured onto a master tool and only then pressed. The thermoplastic material is cooled to solidify and produce a production tool. If a thermoplastic production tool is used, care must be taken not to generate too much heat that could distort the thermoplastic production tool limiting its service life. More information on the design and manufacture of production instrumentation or reference tools can be found in US patents

United States Nos. 5 152 917 (Pieper et al.), 5 435 816 (Spurgeon et al.), 5 672 097 (Hoopman et al.), 5,946,091 (Hoopman et al.), 5,975,987 (Hoopman et al.) And 6,129 540 (Hoopman et al.).

Access to the sockets may be possible through a hole in the upper surface or the bottom surface of the mold. In some cases, the cavity may run through the entire thickness of the mold. Alternatively, the seat may extend only through part of the thickness of the mold. In one embodiment, the top surface is substantially parallel to the bottom surface of the mold, whose seats have a substantially constant depth. At least one side of the mold

EP2370232, i.e. the side in which the seat is formed, can remain open to the atmosphere at the stage where the volatile component is removed.

The nest has a certain three-dimensional shape. In one embodiment, the shape of the socket may be described as being a triangle, viewed from above, having an inclined side wall such that the lower surface of the mold is slightly smaller than the hole in the upper surface. The inclined sidewall is believed to improve grinding performance and facilitate removal of parent abrasive particles from the mold. In another embodiment, the mold contained a plurality of triangular sockets. Each of these many triangular nests includes an equilateral triangle.

Alternatively, other socket shapes such as circles, rectangles, squares, hexagons, stars, or combinations thereof may all be used, all of which have a substantially constant depth dimension. The depth dimension is equal to the perpendicular distance from the top surface to the lowest point of the bottom surface. The depth of a given nest may be constant or may vary in length and / or width. The sockets of a given mold can have the same shape or have different shapes.

The third step of the method is to fill the sockets in the form with an abrasive dispersion using any traditional technique. In some embodiments, a knife roller coater or a slotted vacuum coater may be used. If desired, removal of particles from the mold can be assisted by the use of a release agent. Typical release agents include oils such as peanut oil or mineral oil, fish oil, silicones, polytetrafluoroethylene, zinc stearate and graphite. When a release aid is desired, from about 0.1% to about 5% by weight of the release agent from the mold, such as peanut oil, is applied to the surfaces of the sol-gel contacting equipment in a liquid such as water or alcohol, so that there is from 0.02 mg / cm per unit of mold surface² up to about 0.47 mg / cm² (from about 0.1 mg / inch² up to about 3.0 mg / inch²) or from about 0.02 mg / cm² up to about 0.78 mg / cm² (from about 0.1 mg / inch² to about 5.0 mg / inch²) a release agent. In one embodiment, the upper surface of the mold is covered with an abrasive dispersion. Abrasive dispersion can be pumped to the upper surface. Then, to push the abrasive dispersion completely into the mold cavities, you can use a scraper or leveling bar.

EP2370232

The remaining part of the abrasive dispersion that is not in the socket can be removed from the upper side of the mold and recycled. In some embodiments, a small portion of the abrasive dispersion may remain on the upper surface, and in other embodiments, there is essentially no dispersion on the upper surface. The pressure exerted by the scraper or leveling bar is usually less than 690 kPa (100 psi) or less than 345 kPa (50 psi) or less than 69 kPa (10 psi). In some embodiments, to ensure a constant thickness of the resulting shaped abrasive particles 20, no exposed abrasive dispersion surface projects substantially beyond the top surface.

The fourth step of the method is to remove the volatile component to dry the dispersion. It is desirable that the volatile component is removed by rapid evaporation. In some embodiments, removal of the volatile component by evaporation occurs at temperatures above the boiling point of the volatile component. The upper limit of drying temperature often depends on the material from which the mold is made. For polypropylene instrumentation, the temperature should be less than the melting point of the plastic.

In one embodiment, with an aqueous dispersion containing from about 40 to 50 percent solids and a polypropylene form, the drying temperatures 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. The use of higher temperatures can lead to the creation of larger holes, but can also lead to degradation of polypropylene, limiting its service life in the form.

In one embodiment, a sample of boehmit gel sol was prepared based on the following recipe: alumina monohydrate powder (1600 parts) with the trade name "DISPERAL" was dispersed by high shear mixing of a solution containing water (2400 parts) and 70% aqueous for 11 minutes nitric acid (72 parts). The resulting sol-gel was aged before coating for at least 1 hour.

The sol-gel has been pushed into the production tooling with triangular shaped mold cavities having a depth of 0.71 mm (28 miles), individual sides 2.8 mm (110 miles) long and a predetermined angle of convergence α between the side wall of the mold and the bottom surface of the mold equal to 98 degrees. During the production tooling, 50% of the mold cavities contained

EP2370232 on the lower surface of the protuberances, thus forming the shaped abrasive particles of Figures 3 and 4, and the remaining 50% of the mold cavities had a smooth bottom surface.

The sol-gel was pressed into the nests using a spatula so that the holes of the production tooling were completely filled. As a release agent from the mold, 1% peanut oil in methanol was used, which was used to cover the production instrumentation so that about 0.08 mg / cm was applied to the mold surfaces.² (0.5 mg / inch²) peanut oil. Excess methanol was removed by placing production instrumentation sheets for 5 minutes at 45 ° C in a convection oven. The production equipment coated with sol-gel was placed in an oven in a convection oven at 45 ° C for at least 45 minutes to dry. The shaped parent abrasive particles were removed from the production tooling by passing it over the sonotrode. The shaped abrasive mother particles can be burned to produce shaped abrasive particles 20 with an inclined wall 22 and / or grooves 116.

The fifth step of the method is to remove shaped parent abrasive particles with an inclined side wall from the mold cavities. Shaped mother abrasive particles with an inclined side wall can be removed from the mold cavities using the following methods, individually or combined:

by gravity, with the use of vibrations, with the use of ultrasonic vibrations, by vacuum or with compressed air to remove particles from the mold cavities.

Inclined abrasive parent particles can be dried further out of the mold. If the abrasive dispersion is dried to the desired level in the mold, this additional drying step is not necessary. However, in some cases, it may be economical to use this additional drying step to minimize the time the abrasive dispersion remains in the mold. The shaped abrasive mother particles will be dried for typically 10 to 480 minutes or 120 to 400 minutes at a temperature of 50 ° C to 160 ° C or 120 ° C to 150 ° C.

The sixth step of the method consists in calcining shaped abrasive parent particles with an inclined side wall 22. During calcining, substantially all volatile material is removed and the various components present in the abrasive dispersion are converted to metal oxides. Shaped particles

EP2370232 abrasive stocks are generally heated to a temperature of 400 ° C to 800 ° C and maintained in this temperature range until free water is removed or more than 90 weight percent of any bound volatile material. In an optional step, it may be desirable to introduce a modifying additive through the impregnation process. By impregnation into the pores of the calcined shaped parent abrasive particles, water-soluble salt may be introduced. The shaped mother abrasive particles are then fired again. This option is described further in European Patent Application No. 293 163.

The seventh step of the method is sintering the calcined shaped parent abrasive particles to form alpha corundum particles. Before sintering, the calcined shaped parent abrasive particles are not completely compacted and thus do not have the desired hardness for use as shaped abrasive particles. Sintering is carried out by heating calcined shaped parent abrasive particles to a temperature of 1000 ° C to 1650 ° C and keeping them in this temperature range until essentially all of the algae monohydrate (or equivalent) is converted to alpha alumina and the porosity drops below 15 % volume. The time for which calcined shaped parent abrasive particles must be subjected to the sintering temperature to achieve this level of conversion depends on various factors, but is usually from five seconds to 48 hours. In another embodiment, the duration of the sintering step is from one minute to 90 minutes. After sintering, shaped abrasive particles with an inclined side wall may have a hardness of 10 GPa, 16 GPa, 18 GPa, 20 GPa or more on the Vickers scale.

To modify the method described, other steps may be used such as rapid heating of the material from the calcining temperature to the sintering temperature, centrifugation of the abrasive dispersion to remove deposits, waste, etc. In addition, if desired, the method can be modified by combining two or more method steps. Conventional method steps that can be used to modify the method of the present disclosure are described in more detail in US Patent No. 4,314,827 to Leitheiser.

EP2370232

Examples

The objects and advantages of the present disclosure are further illustrated by the following non-limiting examples. You should not interpret certain materials and the quantities declared in these examples, as well as other conditions and particulars, as excessively limiting this disclosure. Unless otherwise specified, all parts, percentages, ratios, etc. in the examples and the rest of the specification are given by weight.

Preparation of shaped abrasive particles of rare earth oxides (REO)

A boehmite sol-gel sample was prepared based on the following recipe: alumina monohydrate powder (1600 parts) with the trade name "DISPERAL" was dispersed by high shear mixing of a solution containing water (2400 parts) and 70% aqueous nitric acid (72 parts) by 11 minutes. The resulting sol-gel was aged before coating for at least 1 hour. The sol-gel was pushed into the production tooling with triangular shaped mold cavities 0.71 mm (28 miles) deep and 2.8 mm (110 miles) long sides. The angle of convergence α between the side wall of the mold and the bottom surface of the mold was different for each production tooling. The convergence angle α was

90 degrees for first instrumentation, 98 degrees for second instrumentation, 120 degrees for third instrumentation and 135 degrees for last instrumentation. Production equipment with a 98 degree convergence was made so as to have 50% of the mold cavities with 8 parallel protuberances rising above the bottom surfaces of the cavities that intersect with one of the sides of the triangle at an angle of 90 degrees and the other cavities with a smooth bottom surface of the mold. The parallel protuberances were spaced every 0.277 mm, and the cross-sectional protuberances were triangular in shape 0.0127 mm high and had an angle between the sides of each protuberance at the apex, as described above. The sol-gel was pressed into the nests using a spatula so that the holes of the production tooling were completely filled. As a release agent from the mold, 1% peanut oil in methanol was used, which was used to cover the production instrumentation so that about 0.08 mg / cm was applied to the production instrumentation.² (0.5 mg / inch²) peanut oil. Excess methanol has been removed

EP2370232 by placing production instrumentation sheets for 5 minutes at 45 ° C in a convection oven. The production equipment coated with sol-gel was placed in an oven in a convection oven at 45 ° C for at least 45 minutes to dry. The shaped parent abrasive particles were removed from the production tooling by passing it over the sonotrode. The shaped abrasive mother particles were calcined at about 650 ° C, and then saturated with mixed nitrate solution with the following concentration (given for oxides): 1.8% of each of the following: MgO, Y2O3, Nd2O3 and La2O3. Excess nitrate solution was removed and saturated shaped abrasive mother particles with holes were allowed to dry, after which the particles were again calcined at 650 ° C and sintered at about 1400 ° C. Both calcining and sintering were carried out using rotary kilns.

After producing four different angles of convergence of shaped abrasive particles with inclined walls, abrasive abrasive discs were produced. Shaped abrasive particles with sloping walls and / or grooves 116 were electrostatically deposited onto a 17.8 cm (7 inch) diameter fibrous disc with a central hole of 2 and 1/5 cm (7/8 inch) using phenolic resins of the backing layer and layer floodplain according to table 1. Phenolic resin can be made from phenol formaldehyde resole resin, and condensate from 1.5: 1 to 2.1: 1 (phenol: formaldehyde) can be catalyzed by potassium hydroxide in an amount of 1% to 5%.

Table 1: Composition of the undercoat and flooding layer

<td>Ingredient</td><td>Undercoat layer</td><td>Flood layer</td>

<td>Phenolic resin</td><td> 49,15%</td><td> 29,42%</td>

<td>Water</td><td> 10,19%</td><td> 18,12%</td>

<td>Calcium carbonate</td><td> 40,56%</td><td> 0,0%</td>

<td>Cryolite</td><td> 0,0%</td><td> 50,65%</td>

<td>Emulon A (BASF)</td><td> 0,10%</td><td> 1,81%</td>

<td></td><td> 100,0%</td><td> 100,0%</td>

EP2370232

The grinding performance of shaped abrasive particles with an inclined sidewall and / or grooves 116 was evaluated by grinding medium carbon steel 1045 using the following procedure. The 17.8 cm (7 inch) diameter grinding wheels to be evaluated were attached to a rotary grinder with a 17.8 cm (7 inch) finned backing disc ("80514 Extra Hard Red" from 3M Company, St. Paul, Minnesota) . The grinder was then switched on and pressed under a load of 54 N (12 lb) to the face of a previously weighed 1045 steel 1.9 x 1.9 cm (0.75 x 0.75 inch) bar. The resulting rotational speed of the grinder at this load and at this workpiece was 5000 rpm. The workpiece was ground in these conditions in fifty (50) 10 second periods (passes). After each 10-second period, the workpiece was allowed to cool to room temperature and weighed to determine the amount of material removed during the grinding operation. The test results were given as the incremental loss of material for each period of time and the total loss of removed material. If necessary, tests can be automated using appropriate equipment.

Fig. 11 is a graph of unit material loss versus time and total material loss for shaped abrasive particles having a 98 degree convergence with and without grooves. As can be seen from the graph, the initial unit material loss for shaped abrasive particles without grooves is greater than for shaped abrasive particles of the same size with grooves. The unit loss of material of shaped abrasive particles without grooves tends to decrease over time of the test, while the unit loss of material of shaped abrasive particles with grooves tends to increase over time of the test.

Figures 12 and 13 are graphs of unit material loss versus time and total material loss versus time. As can be seen in the graph, shaped abrasive particles having an inclined side wall and a convergence angle greater than 90 degrees outperformed shaped abrasive particles having a 90 degree convergence angle. As the angle of convergence approaches 135 degrees, the performance of shaped abrasive particles with an inclined side wall begins to decrease rapidly. When comparing particles having a convergence angle of 135 degrees with particles having a convergence angle of 98 degrees, the initial unit

EP2370232 material loss was more or less the same, but the total material loss was much smaller. Particles having a 120 degree convergence showed an approx. 20% improvement in the initial unit material loss, and the total material loss was about the same as for particles with a 98 degree convergence, which was unexpected. Even more surprising was that a large performance jump occurred for particles for which the convergence angle changed only by 8 degrees, from 90 degrees to 98 degrees. When the abrasive product was a mixture of 50% shaped abrasive particles with grooves and 50% shaped abrasive particles without grooves, the unit loss of material was approximately doubled and the unit loss of material remained relatively constant throughout the test.

Within the scope of this disclosure, those skilled in the art may use in practice other modifications and variations of this disclosure, as set forth in detail in the appended claims. It should be noted that aspects of the various embodiments may be replaced in whole or in part, or combined with other aspects of the various embodiments. The above description, which was given to enable those skilled in the art to put the claimed disclosure into practice, should not be construed as limiting the scope of the disclosure that is defined by the claims.

Reference designations used in the claims should not be considered as limiting the scope of the subject protected by the claims. Their sole function is to facilitate the understanding of the reservations.

EP2370232