# Patent

## Title
Shaped abrasive particles and methods of forming same

## Abstract

A method of forming a shaped abrasive particle includes applying a mixture into a shaping assembly within an application zone and directing an ejection material at the mixture in the shaping assembly under a predetermined force, removing the mixture from the shaping assembly and forming a precursor shaped abrasive particle.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. patent application Ser. No. 14/925,191, entitled “SHAPED ABRASIVE PARTICLES AND METHODS OF FORMING SAME,” by Bauer et al., filed Oct. 28, 2015, which is a continuation of U.S. patent application Ser. No. 13/901,362, entitled “SHAPED ABRASIVE PARTICLES AND METHODS OF FORMING SAME,” by Bauer et al., filed May 23, 2013, which claims priority under 35 U.S.C. §119(e) to U.S. Patent Application No. 61/650,673 entitled “SHAPED ABRASIVE PARTICLES AND METHODS OF FORMING SAME,” by Bauer et al., filed May 23, 2012, which are assigned to the current assignee hereof and incorporated herein by reference in their entireties.


BACKGROUND
Field of the Disclosure
The following is directed to shaped abrasive particles, and more particularly, to a process of forming shaped abrasive particles and the resulting particles.
Description of the Related Art
Abrasive articles incorporating abrasive particles are useful for various material removal operations including grinding, finishing, polishing, and the like. Depending upon the type of abrasive material, such abrasive particles can be useful in shaping or grinding various materials in the manufacturing of goods. Certain types of abrasive particles have been formulated to date that have particular geometries, such as triangular shaped abrasive particles and abrasive articles incorporating such objects. See, for example, U.S. Pat. Nos. 5,201,916; 5,366,523; and 5,984,988.
Previously, three basic technologies that have been employed to produce abrasive particles having a specified shape, which are fusion, sintering, and chemical ceramic. In the fusion process, abrasive particles can be shaped by a chill roll, the face of which may or may not be engraved, a mold into which molten material is poured, or a heat sink material immersed in an aluminum oxide melt. See, for example, U.S. Pat. No. 3,377,660. In sintering processes, abrasive particles can be formed from refractory powders having a particle size of up to 10 micrometers in diameter. Binders can be added to the powders along with a lubricant and a suitable solvent to form a mixture that can be shaped into platelets or rods of various lengths and diameters. See, for example, U.S. Pat. No. 3,079,242. Chemical ceramic technology involves converting a colloidal dispersion or hydrosol (sometimes called a sol) to a gel or any other physical state that restrains the mobility of the components, drying, and firing to obtain a ceramic material. See, for example, U.S. Pat. Nos. 4,744,802 and 4,848,041.
Rudimentary molding processes have been disclosed as potentially useful in forming limited shaped abrasive particles, such as those disclosed in U.S. Pat. Nos. 5,201,916, 5,366,523, 5,584,896, and U.S. Pat. Publs. 2010/0151195, 2010/0151195. Other processes of forming shaped abrasive particles have been disclosed, see for example, U.S. Pat. Nos. 6,054,093, 6,228,134, 5,009,676, 5,090,968, and 5,409,645.
The industry continues to demand improved abrasive materials and abrasive articles.
SUMMARY
According to one aspect, a method includes applying a mixture into a shaping assembly within an application zone, and directing an ejection material at the mixture in the shaping assembly under a predetermined force, removing the mixture from the shaping assembly and forming a precursor shaped abrasive particle.
According to a second aspect, a method includes forming a precursor shaped abrasive particle in less than about 18 minutes, wherein forming includes applying a mixture into a shaping assembly within an application zone and removing the mixture from the shaping assembly to form a precursor shaped abrasive particle.
In yet another aspect, a method includes extruding a mixture having a viscosity of at least about 4×103 Pa s into an opening in a shaping assembly within an application zone and removing the mixture from the opening by applying an external force to the mixture to form a precursor shaped abrasive particle.
For another aspect, a system for forming shaped abrasive particles includes an application zone comprising a shaping assembly, a first portion having an opening and configured to be filled with a mixture, a second portion abutting the first portion, and an ejection zone comprising an ejection assembly configured to direct an ejection material toward the opening in the first portion of the shaping assembly.
According to another aspect, a system for forming precursor shaped abrasive particles can have a batch productivity of at least about 0.1 kg/min/m2 shaping surface.
In another aspect, a batch of shaped abrasive particles can include a first portion comprising a shaped abrasive particle having tortuous contour.
For another aspect, a shaped abrasive particle includes a body having a tortuous contour.
Still, in another aspect, a shaped abrasive particle has a body including an arrowhead shape.



BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.
FIG. 1 includes a schematic of a system for forming a shaped abrasive particle in accordance with an embodiment.
FIG. 2 includes an illustration of a portion of the system of FIG. 1 in accordance with an embodiment.
FIGS. 3A-3C include perspective view illustrations of shaped abrasive particles in accordance with an embodiment.
FIG. 4 includes a coated abrasive including shaped abrasive particles according to an embodiment.
FIG. 5 includes a bonded abrasive including shaped abrasive particles according to an embodiment.
FIG. 6 includes a side view image of a shaped abrasive particle according to an embodiment.
FIG. 7 includes a side view image of a shaped abrasive particle according to an embodiment.
FIG. 8 includes an illustration of a side view of a shaped abrasive particle having flashing in accordance with an embodiment.
FIG. 9 includes a perspective view image of a shaped abrasive particle according to an embodiment.
FIG. 10 includes a top view image of a shaped abrasive particle according to an embodiment.
FIG. 11A includes side view images of shaped abrasive particles formed according to an embodiment.
FIG. 11B includes a top view image of a plurality of shaped abrasive particles formed according to an embodiment.
FIG. 12 includes a plot of specific grinding energy versus cumulative material removed for a conventional sample and a sample representative of an embodiment.
FIG. 13 includes a top view image of a plurality of shaped abrasive particles formed according to an embodiment.



DETAILED DESCRIPTION
The systems and methods herein may be utilized in forming shaped abrasive particles. The shaped abrasive particles may be utilized in various applications, including for example coated abrasives, bonded abrasives, free abrasives, and a combination thereof. Various other uses may be derived for the shaped abrasive particles.
FIG. 1 includes an illustration of a system for forming a shaped abrasive particle in accordance with an embodiment. As illustrated, the system 100 can further include a die 103 configured to facilitate delivery of a mixture 101 contained within a reservoir 102 of the die 103 to a shaping assembly 151. The process of forming a shaped abrasive particle can be initiated by forming a mixture 101 including a ceramic material and a liquid. In particular, the mixture 101 can be a gel formed of a ceramic powder material and a liquid, wherein the gel can be characterized as a shape-stable material having the ability to hold a given shape even in the green state (i.e., unfired or undried gel). In accordance with an embodiment, the gel can be formed of the ceramic powder material as an integrated network of discrete particles.
The mixture 101 can be formed to have a particular content of solid material, such as the ceramic powder material. For example, in one embodiment, the mixture 101 can have a high solids content, including for example, a solids content of at least about 25 wt %, such as at least about 35 wt %, at least about 42 wt %, at least about 44 wt %, at least about 46 wt %, at least about 48 wt %, at least about 50 wt %, or even at least about 51 wt % for the total weight of the mixture 101. Still, in at least one non-limiting embodiment, the solid content of the mixture 101 can be not greater than about 80 wt %, not greater than about 75 wt %, such as not greater than about 70 wt %, not greater than about 65 wt %, not greater than about 60 wt %, not greater than about 58 wt %, not greater than about 56 wt %, or even not greater than about 54 wt %. It will be appreciated that the content of the solids materials in the mixture 101 can be within a range between any of the minimum and maximum percentages noted above.
According to one embodiment, the ceramic powder material can include an oxide, a nitride, a carbide, a boride, an oxycarbide, an oxynitride, and a combination thereof. It will be appreciated, that in certain alternative embodiments, in place of a ceramic powder material, one may choose to use a precursor of a ceramic powder material. A precursor can be a material, which may or may not be in a powder form that is configured to change at least a portion of its composition or physical properties during processing to form a ceramic material. In particular instances, the ceramic material can include alumina. More specifically, the ceramic material may include a boehmite material, which may be a precursor of alpha alumina. The term “boehmite” is generally used to denote alumina hydrates including mineral boehmite, typically being Al2O3.H2O and having a water content on the order of 15%, as well as pseudoboehmite, having a water content higher than 15%, such as 20-38% by weight. It is noted that boehmite (including pseudoboehmite) has a particular and identifiable crystal structure, and accordingly unique X-ray diffraction pattern, and as such, is distinguished from other aluminous materials including other hydrated aluminas such as ATH (aluminum trihydroxide) a common precursor material used herein for the fabrication of boehmite particulate materials.
Furthermore, the mixture 101 can be formed to have a particular content of liquid material. Some suitable liquids may include inorganic materials, such as water or various organic media such as alcohols and the like. In accordance with one embodiment, the mixture 101 can be formed to have a liquid content less than the solids content of the mixture 101. In more particular instances, the mixture 101 can have a liquid content of at least about 20 wt %, such as at least about 25 wt % for the total weight of the mixture 101. In other instances, the amount of liquid within the mixture 101 can be greater, such as at least about 35 wt %, at least about 40 wt %, at least about 42 wt %, or even at least about 44 wt %. Still, in at least one non-limiting embodiment, the liquid content of the mixture can be not greater than about 80 wt %, such as not greater than about 65 wt %, not greater than about 60 wt %, not greater than about 55 wt %, not greater than about 52 wt %, not greater than about 49 wt %. It will be appreciated that the content of the liquid in the mixture 101 can be within a range between any of the minimum and maximum percentages noted above.
Furthermore, to facilitate processing and forming shaped abrasive particles according to embodiments herein, the mixture 101 can have a particular storage modulus. For example, the mixture 101 can have a storage modulus of at least about 1×104 Pa, such as at least about 4×104 Pa, such as at least about 4.4×104 Pa, at least about 5×104 Pa, at least about 6×104 Pa, at least about 8×104 Pa, at least about 10×104 Pa, at least about 15×104 Pa, at least about 20×104 Pa, at least about 30×104 Pa, or even at least about 40×104 Pa. In at least one non-limiting embodiment, the mixture 101 may have a storage modulus of not greater than about 80×104 Pa, not greater than about 70×104 Pa, not greater than about 65×104 Pa, or even not greater than about 60×104 Pa. It will be appreciated that the storage modulus of the mixture 101 can be within a range between any of the minimum and maximum values noted above. The storage modulus can be measured via a parallel plate system using ARES or AR-G2 rotational rheometers, with Peltier plate temperature control systems. For testing, the mixture 101 can be extruded within a gap between two plates that are set to be approximately 8 mm apart from each other. After extruding the gel into the gap, the distance between the two plates defining the gap is reduced to 2 mm until the mixture 101 completely fills the gap between the plates. After wiping away excess mixture, the gap is decreased by 0.1 mm and the test is initiated. The test is an oscillation strain sweep test conducted with instrument settings of a strain range between 0.01% to 100%, at 6.28 rad/s (1 Hz), using 25-mm parallel plate and recording 10 points per decade. Within 1 hour after the test completes, lower the gap again by 0.1 mm and repeat the test. The test can be repeated at least 6 times. The first test may differ from the second and third tests. Only the results from the second and third tests for each specimen should be reported.
Furthermore, to facilitate processing and forming shaped abrasive particles according to embodiments herein, the mixture 101 can have a particular viscosity. For example, the mixture 101 can have a viscosity of at least about 4×103 Pa s, at least about 5×103 Pa s, at least about 6×103 Pa s, at least about 8×103 Pa s, at least about 10×103 Pa s, at least about 20×103 Pa s, at least about 30×103 Pa s, at least about 40×103 Pa s, at least about 50×103 Pa s, at least about 60×103 Pa s, at least about 65×103 Pa s. In at least one non-limiting embodiment, the mixture 101 may have a viscosity of not greater than about 100×103 Pa s, not greater than about 95×103 Pa s, not greater than about 90×103 Pa s, or even not greater than about 85×103 Pa s. It will be appreciated that the viscosity of the mixture 101 can be within a range between any of the minimum and maximum values noted above. The viscosity can be measured in the same manner as the storage modulus as described above.
In at least one embodiment, to facilitate processing and forming shaped abrasive particles according to embodiments herein, the mixture 101 can have a particular yield stress. For example, the mixture 101 can have a yield stress of at least about 1.5×103 Pa, at least about 4×103 Pa at least about 5×103 Pa, at least about 6×103 Pa, at least about 8×103 Pa, at least about 10×103 Pa, at least about 12×103 Pa s, at least about 20×103 Pa s, at least about 30×103 Pa, at least about 40×103 Pa, or even at least about 65×103 Pa. In at least one non-limiting embodiment, the mixture 101 may have a yield stress of not greater than about 100×103 Pa, not greater than about 80×103 Pa, not greater than about 60×103 Pa, or even not greater than about 50×103 Pa. It will be appreciated that the yield stress of the mixture 101 can be within a range between any of the minimum and maximum values noted above. The yield stress can be measured in the same manner as the storage modulus as described above.
The rheological characteristics of the mixture 101 can be distinct from conventional mixtures and gels, such as those described in certain references. Moreover, the mixture 101 can be formed to have a particular relationship between one or more rheological characteristics (e.g., viscosity, yield stress, storage modulus, etc.) to facilitate forming. Notably, the gel may be significantly more “stiff”, having a shear thinning characteristic, which may be entirely distinct from mixtures used in other forming methods.
Moreover, the mixture 101 can be formed to have a particular content of organic materials, including for example, organic additives that can be distinct from the liquid, to facilitate processing and formation of shaped abrasive particles according to the embodiments herein. Some suitable organic additives can include stabilizers, binders, such as fructose, sucrose, lactose, glucose, UV curable resins, and the like. It will be appreciated that the total content of all materials in the mixture (e.g., ceramic powder material, water, additives, etc.) add up to and do not exceed 100%.
Notably, the embodiments herein may utilize a mixture 101 that can be distinct from certain types of slurries. For example, the content of organic materials within the mixture 101, particularly, any of the organic additives noted above may be a minor amount as compared to other components within the mixture 101. In at least one embodiment, the mixture 101 can be formed to have not greater than about 30 wt % organic material for the total weight of the mixture 101. In other instances, the amount of organic materials may be less, such as not greater than about 15 wt %, not greater than about 10 wt %, or even not greater than about 5 wt %. Still, in at least one non-limiting embodiment, the amount of organic materials within the mixture 101 can be at least about 0.5 wt % for the total weight of the mixture 101. It will be appreciated that the amount of organic materials in the mixture 101 can be within a range between any of the minimum and maximum values noted above. In at least one alternative aspect, the mixture 101 may be essentially free of organic material.
Moreover, the mixture 101 can be formed to have a particular content of acid or base distinct from the liquid, to facilitate processing and formation of shaped abrasive particles according to the embodiments herein. Some suitable acids or bases can include nitric acid, sulfuric acid, citric acid, hydrochloric acid, tartaric acid, phosphoric acid, ammonium nitrate, and/or ammonium citrate. According to one particular embodiment, the mixture 101 can have a pH of less than about 5, and more particularly, within a range between at least about 2 and not greater than about 4, using a nitric acid additive. Alternatively, the rheology of the acidic gel can be further modified by converting the acidic gel to a basic gel through the use of bases such as ammonium hydroxide, sodium hydroxide, organics amines such as hexamehylenetetramine and the like
Referencing FIG. 1, the mixture 101 can be provided within the interior of the die 103 and configured to be extruded through a die opening 105 positioned at one end of the die 103. As further illustrated, extruding can include applying a force 180 (or a pressure) on the mixture 101 to facilitate extruding the mixture 101 through the die opening 105. In accordance with an embodiment, a particular pressure may be utilized during extrusion. For example, the pressure can be at least about 10 kPa, such as at least about 500 kPa, at least about 1,000 kPa, at least about 2,000 kPa, or even at least about 3,000 kPa. Still, in at least one non-limiting embodiment, the pressure utilized during extrusion can be not greater than about 10,000 kPa, such as not greater than about 8,000 kPa, or even not greater than about 6,000 kPa. It will be appreciated that the pressure used to extrude the mixture 101 can be within a range between any of the minimum and maximum values noted above. Moreover, in certain instances, the die opening can have an area of approximately 3000 to 4000 square millimeters.
In accordance with one embodiment, the mixture 101 can have a coil value of at least about 1800 N. The coil value can be measured on an instrument called a Shimpo compression tester manufactured by Shimpo Instruments, Itasca Ill., using a sample of mixture ranging from 30-60 grams in mass, which is manually pressed into a plastic/stainless steel cylinder of 2′′ in diameter. At the extrusion end of the cylinder, a plastic insert with a cylindrical hole establishes the compressed extrudate size of generally 2 mm in diameter. A plunger slides into the cylinder and when the test is started, the plunger will extrude the gel once the threshold coil force is reached. When the cylinder assembly is in position, the Shimpo compression tester moves a force probe down towards the plunger at a constant rate of 95-97 mm/min. When the threshold coil force is reached, the gel is extruded out of the insert hole and an output meter generates a peak force, which is the coli value. In another embodiment, the coil value can be at least about 1900 N, such as at least about 2000 N, at least about 2100 N, at least about 2200 N, or even at least about 2300 N. In one non-limiting embodiment, the coil value can be not greater than about 8000 N, such as not greater than about 6000 N, or even not greater than about 5000 N. Typically, coil values utilized for mixtures and gels used in conventional screen printing and molding processes, such as the processes described in U.S. Pat. Nos. 5,201,916 and 6,054,093 are less than about 1700 N, and more typically around 1000 N. Thus, certain mixtures according to the embodiments herein can be significantly more flow resistant compared to conventional mixtures.
As further illustrated in FIG. 1, the system 100 can include a shaping assembly 151. The shaping assembly can include a first portion 152 and a second portion 153. Notably, within the applications zone 183, the first portion 152 can be adjacent to the second portion 153. In more particular instances, within the application zone 183, the first portion 152 can be abutting a surface 157 of the second portion 153. The system 100 can be designed such that a portion of the shaping assembly 151, such as the first portion 152, may be translated between rollers. The first portion 152 may be operated in a loop such that the forming process can be conducted continuously.
As illustrated, the system 100 can include an application zone 183, including the die opening 105 of the die 103. The process can further include applying the mixture 101 into at least a portion of the shaping assembly 151. In particular instances, the process of applying the mixture 101 can include depositing the mixture 101 via a process, such as, extrusion, molding, casting, printing, spraying, and a combination thereof. In particular instances, such as that illustrated in FIG. 1, the mixture 101 may be extruded in a direction 188 through the die opening 105 and into at least a portion of the shaping assembly 151. Notably, a least a portion of the shaping assembly 151 can include at least one opening 154. In particular instances, such as that illustrated in FIG. 1, the shaping assembly 151 can include a first portion 152 having an opening 154 configured to receive the mixture 101 from the die 103.
In accordance with an embodiment, the shaping assembly 151 can include at least one opening 154 that can be defined by a surface or multiple surfaces, including for example, at least three surfaces. In particular instances, the opening 154 can extend through an entire thickness of the first portion 152 of the shaping assembly 151. Alternatively, the opening 154 can extend through an entire thickness of the shaping assembly 151. Still, in other alternative embodiments, the opening 154 can extend through a portion of the entire thickness of the shaping assembly 151.
Referring briefly to FIG. 2, a segment of a first portion 152 is illustrated. As shown, the first portion 152 can include an opening 154, and more particularly, a plurality of openings 154. The openings 154 can extend into the volume of the first portion 152, and more particularly, extend through the entire thickness of the first portion 152 as perforations. As further illustrated, the first portion 152 of the shaping assembly 151 can include a plurality of openings 154 displaced from each other along a length of the first portion 152. In particular instances, the first portion 152 may be translated in a direction 186 through the application zone 183 at a particular angle relative to the direction of extrusion 188. In accordance with an embodiment, the angle between the directions of translation 186 of the first portion 152 and the direction of extrusion 188 can be substantially orthogonal (i.e., substantially 90°. However, in other embodiments, the angle may be different, such as acute, or alternatively, obtuse.
In particular instances, the shaping assembly 151 can include a first portion 152 that may be in the form of a screen, which may be in the form of a perforated sheet. Notably, the screen configuration of the first portion 152 may be defined by a length of material having a plurality of openings 154 extending along its length and configured to accept the mixture 101 as it is deposited from the die 103. The first portion can be in the form of a continuous belt that is moved over rollers for continuous processing. In certain instances, the belt can be formed to have a length suitable for continuous processing, including for example, at length of at least about 0.1 m, such as at least about 0.5 m. Still, in another embodiment, the length of the belt may not need to be particularly long to facilitate efficient and productive processing. For example, in one non-limiting embodiment, the belt may be less than about 10 m, not greater than about 8 m, not greater than about 5 m, not greater than about 3 m, not greater than about 2 m, or even not greater than about 1 m.
In a particular instance, the openings 154 can have a two-dimensional shape as viewed in a plane defined by the length (l) and width (w) of the screen. While the openings 154 are illustrated as having a triangular two-dimensional shape, other shapes are contemplated. For example, the openings 154 can have a two-dimensional shape such as polygons, ellipsoids, numerals, Greek alphabet letters, Latin alphabet letters, Russian alphabet characters, Arabic alphabet characters (or alphabet letters of any language), complex shapes including a combination of polygonal shapes, and a combination thereof. In particular instances, the openings 154 may have two-dimensional polygonal shapes such as, a triangle, a rectangle, a quadrilateral, a pentagon, a hexagon, a heptagon, an octagon, a nonagon, a decagon, and a combination thereof. Moreover, a first portion 152 can be formed to include a combination of openings 154 having a plurality of different two-dimensional shapes. It will be appreciated that the first portion 152 may be formed to have a plurality of openings 154 that may have different two-dimensional shapes as compared to each other.
In other embodiments, the shaping assembly 151 may be in the form of a mold. In particular, the shaping assembly 151 can be in the shape of a mold having openings 154 defining side surfaces and a bottom surface configured to accept the mixture 101 from the die 103. Notably, a mold configuration may be distinct from a screen configuration such that the mold has openings that do not extend through the entire thickness of the shaping assembly 151.
In one design, the shaping assembly 151 can include a second portion 153 configured to be adjacent to the first portion 152 within the application zone 183. In particular instances, the mixture 101 can be applied into the opening 154 of the first portion 152 and configured to abut a surface 157 of the second portion 153 within the application zone 183. For one particular design, the second portion 153 can be configured as a stop surface allowing the mixture 101 to fill the opening 154 within the first portion 152.
According to one embodiment, the surface 154 of the second portion 153 can be configured to contact the mixture 101 while it is contained within the opening 154 of the first portion 152. The surface 157 may have a particular coating to facilitate processing. For example, the surface 157 may include a coating including an inorganic material, an organic material, and a combination thereof. Some suitable inorganic materials can include a ceramic, a glass, a metal, a metal alloy, and a combination thereof. Certain suitable examples of an inorganic material can include a polymer, including for example, a fluoropolymer, such as polytetrafluoroethylene (PTFE).
Alternatively, the surface 157 may include features, including for example protrusions and grooves such that during processing the mixture 101 contained within the opening 154 of the first portion 152 may replicate features contained on the surface 157 of the second portion 153.
In an alternative embodiment, the second portion 153, and more particularly the surface 157 of the second portion 153 may include a specific composition that may be imparted to the mixture 101 contained in the opening 154 of the first portion 152. For example, the surface 157 may be coated with an additive. The additive may be an inorganic material, organic material, and a combination thereof. In certain instances, the additive may be a dopant. In such embodiments, the surface of the mixture 101 in contact with the surface 157 of the second portion 153 may be doped while it is contained in the shaping assembly 151, and more particularly, within the opening 154 of the first portion 152.
As described herein, in particular instances, the first portion 152 may be translated in a direction 186. As such, within the application on 183, the mixture 101 contained in the openings 154 of the first portion 152 may be translated over the surface 157 of the second portion 153. In accordance with an embodiment, the first portion 152 may be translated in a direction 186 at a particular rate to facilitate suitable processing. For example, the first portion 152 may be translated through the application zone 183 at a rate of at least about 0.5 mm/s. In other embodiments, the rate of translation of the first portion 152 may be greater, such as at least about 1 cm/s, at least about 3 cm/s, at least about 4 cm/s, at least about 6 cm/s, at least about 8 cm/s, or even at least about 10 cm/s. Still, in at least one non-limiting embodiment, the first portion 152 may be translated in a direction 186 at a rate of not greater than about 5 m/s, such as not greater than about 1 m/s, or even not greater than about 0.5 m/s. It will be appreciated that the first portion 152 may be translated at a rate within a range between any of the minimum and maximum values noted above.
After applying the mixture 101 in the openings 154 of the first portion 152 of the shaping assembly 151, the first portion 152 may be translated to an ejection zone 185. Translation may be facilitated by a translator configured to translate at least a portion of the shaping assembly from the application zone 183 to the ejection zone 185. Some suitable examples of a translator may include a series of rollers, about which the first portion 152 may be looped and rotated around.
The ejection zone may include at least one ejection assembly 187 that can be configured to direct an ejection material 189 at the mixture 101 contained within the openings 154 of the first portion 152. In a particular embodiment, during the translation of the first portion 152 from the application zone 183 to the ejection zone 185, only a portion of the shaping assembly 151 may be moved. For example, the first portion 152 of the shaping assembly 151 may be translated in a direction 186, while at least the second portion 153 of the shaping assembly 151 may be stationary relative to the first portion 152. That is, in particular instances the second portion 153 may be contained entirely within the application zone 183 and may be removed from contact with the first portion 152 within the ejection zone 185. In particular instances, the second portion 153, which in certain embodiments may be alternatively referred to as the backing plate, terminates prior to the ejection zone 185.
The first portion 152 can be translated from the application zone 183 into the ejection zone 185, wherein opposing major surfaces of the mixture 101 contained within the openings 154 of the first portion 152 may be exposed. In certain instances, exposure of both major surfaces of the mixture 101 in the openings 154 can facilitate further processing, including for example, ejection of the mixture 101 from the openings 154.
As further illustrated in the assembly 100, in particular embodiments, the first portion 152 of the shaping assembly 151 can be in direct contact with the second portion 153 of the shaping assembly 151 within the application zone 183. Moreover, prior to translating the first portion 152 from the application zone 183 to the ejection zone 185, the first portion 152 can be separated from the second portion 153. As such, the mixture 101 contained within the openings 154 can be removed from at least one surface of a portion of the shaping assembly 151, and more particularly, the surface 157 of the second portion 153 of the shaping assembly 151. Notably, the mixture 101 contained within the opening 154 can be removed from the surface 157 of the second portion 153 prior to ejection of the mixture 101 from the openings 154 in the ejection zone 185. The process of removing the mixture 101 from the first portion 152 of the shaping assembly 151 can be conducted after removing the second portion 153 from contact with the first portion 152.
In one embodiment, the ejection material 189 can be directed at the first portion 152 of the shaping assembly 151 to facilitate contact with the mixture 101 in the openings 154 of the first portion 152. In particular instances, the ejection material 189 can directly contact an exposed major surface of the mixture 101 and an opening 154 of the first portion 152 of the shaping assembly 151. As will be appreciated, at least a portion of the ejection material 189 may also contact a major surface of the second portion 152 as it is translated by the ejection assembly 187.
In accordance with an embodiment, the ejection material 189 can be a fluidized material. Suitable examples of fluidized materials can include a liquid, a gas, and a combination thereof. In one embodiment, the fluidized material of the ejection material 189 can include an inert material. Alternatively, the fluidized material can be a reducing material. Still, in another particular embodiment, the fluidized material may be an oxidizing material. According to one particular embodiment, the fluidized material can include air.
In an alternative embodiment, the ejection material 189 may include an aerosol comprising a gas phase component, a liquid phase component, a solid phase component, and a combination thereof. In yet another embodiment, the ejection material 189 can include an additive. Some suitable examples of additives can include materials such as an organic material, an inorganic material, a gas phase component, a liquid phase component, a solid phase component, and a combination thereof. In one particular instance, the additive can be a dopant material configured to dope the material of the mixture 101. In accordance with another embodiment, the dopant can be a liquid phase component, a gas phase component, a solid phase component, or a combination thereof that can be contained within the ejection material. Still, in one particular instance, the dopant can be present as a fine powder suspended in the ejection material.
Directing the ejection material at the mixture 101 in the opening 154 of the first portion 152 of the shaping assembly 151 can be conducted at a predetermined force. The predetermined force may be suitable to eject the mixture from the opening 154 to form a precursor shaped abrasive particle, and may be a function of the rheological parameters of the mixture 101, the geometry of the cavity, the materials of construction of shaping assembly, surface tension forces between the mixture 101 and the materials of the shaping assembly 151, and a combination thereof. In one embodiment, the predetermined force can be at least about 0.1 N, such as at least about 1 N, at least about 10 N, at least about 12 N, at least about 14 N, at least about 16 N, at least about 50 N, or even at least about 80 N. Still, in one non-limiting embodiment, the predetermined force may be not greater than about 500 N, such as not greater than about 200 N, not greater than about 100 N, or even not greater than about 50 N. The predetermined force may be within a range between any of the minimum and maximum values noted above.
Notably, the use of the ejection material 189 may be essentially responsible for the removal of the mixture 101 from the opening 154. More generally, the process of removing the mixture 101 from an opening 154 can be conducted by applying an external force to the mixture 101. Notably, the process of applying external force includes limited strain of the shaping assembly and an application of an outside force to eject the mixture 101 from the opening 154. The process of ejection causes removal of the mixture 101 from the opening 154 and may be conducted with relatively little or essentially no shearing of the first portion 152 relative to another component (e.g., the second portion 153). Moreover, ejection of the mixture may be accomplished with essentially no drying of the mixture 101 within the opening 154. As will be appreciated, the precursor shaped abrasive particle 191 may be ejected from the opening 154 and collected. Some suitable methods of collecting can include a bin underlying the first portion 152 of the shaping assembly 151. Alternatively, the mixture 101 can be ejected from the opening 154 in such a manner that the precursor shaped abrasive particle 191 falls back onto the first portion 152 after ejection. The precursor shaped abrasive particle 191 can be translated out of the ejection zone on the first portion 152 to other zones for further processing.
In accordance with an embodiment, the mixture 101 can experience a change in weight of less than about 5% for the total weight of the mixture 101 for the duration the mixture 101 is in the opening of the first portion 152 of the shaping assembly 151. In other embodiments, the weight loss of the mixture 101 while it is contained within the shaping assembly 151 can be less, such as less than about 4%, less than about 3%, less than about 2%, less than about 1%, or even less than about 0.5%. Still, in one particular embodiment, the mixture 101 may have essentially no change in weight for the duration the mixture 101 is in the opening 154 of the shaping assembly 151.
Furthermore, during processing, the mixture 101 may experience a limited change in volume (e.g., shrinkage) for the duration the mixture 101 is in an opening 154 of the shaping assembly 151. For example, the change of volume of the mixture 101 can be less than about 5% for the total volume of the mixture 101 for the duration between applying the mixture 101 in the opening and ejection of the mixture from the opening 154. In other embodiments, the total change in volume may be less, such as less than about 4%, less than about 3%, less than about 2%, less than about 1%, or even less than about 0.5%. In one particular embodiment, the mixture may experience essentially no change in volume for the entire duration the mixture 101 is in an opening 154 of the shaping assembly 151.
In accordance with an embodiment, the mixture 101 may undergo a controlled heating process, while the mixture is contained within the shaping assembly 151. For example, the heating process may include heating the mixture at a temperature greater than room temperature for a limited time. The temperature may be at least about 30° C., such as at least about 35° C., at least about 40° C., such as at least about 50° C., at least about 60° C., or even at least about 100° C. Still, the temperature may be not greater than about 300° C., such as not greater than about 200° C., or even not greater than about at least about 150° C., or even not greater than about 100° C. The duration of heating can be particularly short, such as not greater than about 10 minutes, not greater than about 5 minutes, not greater than about 3 minutes, not greater than about 2 minutes, or even not greater than about 1 minute.
The heating process may utilize a radiant heat source, such as infrared lamps to facilitate controlled heating of the mixture 101. Moreover, the heating process may be adapted to control the characteristics of the mixture and facilitate particular aspects of the shaped abrasive particles according to embodiments herein.
Yet, in another aspect, the mixture 101 may undergo a limited change in temperature within the shaping assembly 151, and particularly, the system may utilize a limited temperature differential between the application zone 183 and the ejection zone 185. For example, the mixture 101 can experience a change in temperature of not greater than about 10° C. in a duration between applying the mixture 101 into the shaping assembly 151 and removing the mixture 101 from the shaping assembly 151. In other embodiments, the difference can be less, such as not greater than about 8° C., not greater than about 6° C., not greater than about 4° C., or even essentially no change in temperature in the duration the mixture 101 is contained within the shaping assembly 151.
In certain instances, the method may utilize a particular distance between the application zone 183 and the ejection zone 185, and more particularly, between the point of filling the shaping assembly 151 with the mixture 101 and the ejection assembly 187, including for example, at least about 0.2 m. Still, in other designs, the distance between the application zone 183 and ejection zone 185 may be not greater than about 10 m, such as not greater than about 1 m. This may facilitate a smaller footprint of the system and improved productivity.
The method of forming a precursor shaped abrasive particle may be conducted in a rapid fashion facilitating efficient processing. For example, the mixture may have an average residence time in an opening 154 of the shaping assembly 151 that is less than about 18 minutes. In other embodiments, the average residence time can be less than about 14 minutes, less than about 12 minutes, less than about 10 minutes, less than about 8 minutes, less than about 7 minutes, less than about 6 minutes, less than about 5 minutes, less than about 2 minutes, less than about 1 minute, less than about 50 seconds, less than about 40 seconds, less than about 30 seconds, less than about 20 seconds, or even less than about 15 seconds. Still, in at least one non-limiting embodiment, the average residence time can be at least about 1 second. It will be appreciated that the average residence time can be within a range between any of the minimum and maximum times noted above.
In accordance with an embodiment, the process of ejecting the mixture 101 from an opening 154 of the shaping assembly 151 can be conducted at a particular temperature. For example, the process of ejection can be conducted at a temperature of not greater than about 300° C. In other embodiments, the temperature during ejection can be not greater than about 250° C., not greater than about 200° C., not greater than about 180° C., not greater than about 160° C., not greater than about 140° C., not greater than about 120° C., not greater than about 100° C., not greater than about 90° C., not greater than about 60° C., or even not greater than about 30° C. Alternatively, in a non-limiting embodiment, the process of directing an ejection material at the mixture and ejecting the mixture 101 from an opening 151 may be conducted at certain temperatures, including those temperatures that may be above room temperature. Some suitable temperatures for conducting the ejection process can be at least about −80° C., such as at least about −50° C., at least about −25° C., at least about 0° C., at least about 5° C., at least about 10° C., or even at least about 15° C. It will be appreciated that in certain non-limiting embodiments, the process of ejecting the mixture 101 from an opening 154 may be conducted at a temperature within a range between any of the temperatures noted above.
Furthermore, it will be appreciated that the ejection material 189 may be prepared and ejected from the ejection assembly 187 at a predetermined temperature. For example, the ejection material 189 may be at a temperature significantly less than the surrounding environment, such that upon contact with the mixture 101 within the opening 154, the mixture is configured to be reduced in temperature. During the ejection process, the mixture 101 may be contacted by the ejection material 187 that can be cooler in temperature than the temperature of the mixture 101 causing contraction of the material of the mixture 101 and ejection from the opening 154.
In accordance with an embodiment, the ejection assembly 187 can have a particular relationship with respect to the openings 154 of the shaping assembly 151 to facilitate suitable formation of precursor shaped abrasive particles according to an embodiment. For example, in certain instances, the ejection assembly 187 can have an ejection material opening 176 from which the ejection material 189 exits the ejection assembly 187. The ejection material opening 176 can define an ejection material opening width 177. Furthermore, the openings 154 of the first portion 152 can have a shaping assembly opening width 178 as illustrated in FIG. 1, which may define a largest dimension of the opening in the same direction as the ejection material opening width 177. In particular instances, the ejection material opening width 177 can be substantially the same as the shaping assembly opening width 178. In still another embodiment, the ejection material opening width 177 can be different than the shaping assembly opening width 178, such as for example, the ejection material opening width 177 can be significantly less than the shaping assembly opening width 178. According to one particular embodiment, the ejection material opening width 177 can be not greater than about 50% of the shaping opening width 178. In yet another embodiment, the ejection material opening width 177 can be not greater than about 40%, such as not greater than about 30%, not greater than about 20%, not greater than about 10%, not greater than about 8%, not greater than about 6%, not greater than about 5%, not greater than about 4%, not greater than about 3%, or even not greater than about 2% of the shaping opening width 178. Still, in at least one non-limiting embodiment, the ejection material opening width 177 can be at least about 0.01%, such as at least about 178.
Moreover, the gap distance 173 between the surface of the ejection assembly 187 and the first portion 152 of the shaping assembly can be controlled to facilitate formation of shaped abrasive particles according to an embodiment. The gap distance 173 may be modified to facilitate forming shaped abrasive particles with certain features or limiting the formation of certain features.
It will further be appreciated that a pressure differential may be created on opposite sides of the first portion 152 of the shaping assembly 151 within the ejection zone 185. In particular, in addition to use of the ejection assembly 187, the system 100 may utilize an optional system 179 (e.g., a reduced pressure system) configured to reduce the pressure on the opposite side of the first portion 152 from the ejection assembly 187 to facilitate pulling the precursor shaped abrasive particle 191 from the opening 154. The process may include providing a negative pressure difference on the side of the shaping assembly opposite the ejection assembly 187. It will be appreciated that balancing the predetermined force of the ejection material and the negative pressure applied to the back side 172 of the first portion 152 of the shaping assembly within the ejection zone 185 can facilitate formation of different shape features in the precursor shaped abrasive particles 191 and the final-formed shaped abrasive particles.
After ejecting the mixture 101 from the opening 154 of the first portion 152, a precursor shaped abrasive particle is formed. According to a particular embodiment, the precursor shaped abrasive particle can have a shape substantially replicating the shape of the openings 154.
The system and methods of the embodiments herein may have a particular efficiency and productivity associated with forming precursor shaped abrasive particles. In one particular instance, the method can include forming a batch of precursor shaped abrasive particles having a weight of not less than about 1 kg in not greater than about 30 minutes. In yet another embodiment, the system and the method of forming can be configured to have a batch efficiency of at least about 0.05 kg/min, such as at least about 0.07 kg/min, at least about 0.08 kg/min, at least about 0.09 kg/min, at least about 0.1 kg/min, at least about 0.13 kg/min, at least about 0.15 kg/min, such as at least about 0.17 kg/min, at least about 0.2 kg/min, at least about 0.3 kg/min, at least about 0.4 kg/min, at least about 0.5 kg/min, at least about 0.6 kg/min, or even at least about 0.8 kg/min.
The system and method of the embodiments herein may have a particular productivity associated with forming precursor shaped abrasive particles. In one particular instance, the system can be configured to have a batch productivity of at least about 0.1 kg/min/m2 of shaping surface, wherein the area of the shaping surface is the total surface area of a single side of the first portion (including openings), which may be in the form of a belt. In another embodiment, the system can have a batch productivity of at least about 0.15 kg/min/m2, at least about 0.2 kg/min/m2, at least about 0.25 kg/min/m2, at least about 0.3 kg/min/m2, at least about 0.35 kg/min/m2, at least about 0.4 kg/min/m2, such as at least about 0.45 kg/min/m2, at least about 0.5 kg/min/m2, at least about 0.55 kg/min/m2, at least about 0.6 kg/min/m2, at least about 0.7 kg/min/m2, at least about 0.8 kg/min/m2, or even at least about 1 kg/min/m2.
In certain instances, the precursor shaped abrasive particle can be gathered and undergo further processing. For example, further processing can include shaping, applying a dopant material, drying, sintering, and the like. In fact, the precursor shaped abrasive particle may be translated through a shaping zone, wherein at least one exterior surface of the particles may be shaped. Shaping can include altering a contour of the precursor shaped abrasive particle through one or more processes, such as, embossing, rolling, cutting, engraving, patterning, stretching, twisting, and a combination thereof. In one particular embodiment, the process of shaping can include contacting a shaping structure, having a particular texture to an exterior surface of the precursor shaped abrasive particle to impart the texture to the exterior surface of the particle. It will be appreciated that the shaping structure can take various forms, including for example, a roller having various features on its surface.
In certain other instances, after ejection, the precursor shaped abrasive particle may have a dopant material applied to at least one exterior surface of the precursor particle. A dopant material may be applied utilizing various methods including for example, spraying, dipping, depositing, impregnating, transferring, punching, cutting, pressing, crushing, and any combination thereof. In particular instances, the application zone may utilize a spray nozzle, or a combination of spray nozzles to spray dopant material onto the precursor shaped abrasive particle. It will be appreciated that the process of applying a dopant material during further processing can be performed at various processing stages, including for example, before drying or after drying, or before calcining or after calcining, before sintering or after sintering.
In accordance with an embodiment, applying a dopant material can include the application of a particular material, such as a salt, which can be a precursor salt material that includes a dopant material to be incorporated into the finally-formed shaped abrasive particles. For example, a metal salt can include an element or compound that is the dopant material. It will be appreciated that the salt material may be in liquid form, such as in a dispersion comprising the salt and liquid carrier. The salt may include nitrogen, and more particularly, can include a nitrate. In one embodiment, the salt can include a metal nitrate, and more particularly, consist essentially of a metal nitrate.
In one embodiment, the dopant material can include an element or compound such as an alkali element, alkaline earth element, rare earth element, hafnium, zirconium, niobium, tantalum, molybdenum, vanadium, or a combination thereof. In one particular embodiment, the dopant material includes an element or compound including an element such as lithium, sodium, potassium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cesium, praseodymium, niobium, hafnium, zirconium, tantalum, molybdenum, vanadium, chromium, cobalt, iron, germanium, manganese, nickel, titanium, zinc, silicon, boron, carbon and a combination thereof.
And further, the precursor shaped abrasive particle may undergo further processing, including for example, heating, curing, vibration, impregnation, and a combination thereof. In one embodiment, the precursor shaped abrasive particle may be dried. Drying may include removal of a particular content of material, including volatiles, such as water. In accordance with an embodiment, the drying process can be conducted at a drying temperature of not greater than about 300° C., such as not greater than about 280° C., or even not greater than about 250° C. Still, in one non-limiting embodiment, the drying process may be conducted at a drying temperature of at least about 10° C. It will be appreciated that the drying temperature may be within a range between any of the minimum and maximum temperatures noted above.
In accordance with an embodiment, the process of forming the shaped abrasive particle may include additional processes, including calcination, impregnation, sintering and a combination thereof. Calcination may occur to remove volatiles and cause a phase change in the material, including for example, a high-temperature phase material (e.g., alpha alumina). In one instance, a shaped abrasive particle can comprise at least about 80 wt % alpha alumina for the total weight of the particle. In other instances, the content of alpha alumina may be greater, such that the shaped abrasive particle may consist essentially of alpha alumina. Impregnation may occur to incorporate other materials into the material of the mixture 101, including for example, a dopant. Sintering of the precursor shaped abrasive particle may be utilized to densify the particle. In a particular instance, the sintering process can facilitate the formation of a high-temperature phase ceramic material. For example, in one embodiment, the precursor shaped abrasive particle may be sintered such that a high-temperature phase of alumina, such as alpha alumina is formed.
Additional processes, such as cleaning, may be completed on any portions of the shaping assembly 151, to facilitate regular and repetitive processing. For example, cleaning may be conducted on the first portion 152 after ejecting the mixture, and more particularly cleaning the openings 154 of the first portion 152 after translating the first portion 152 through the ejection zone 185. Additionally, the portions of the shaping assembly 151, may undergo a drying process.
After the precursor shaped abrasive particle is sintered, a finally-formed shaped abrasive particle results, which may be incorporated into an abrasive tool, including for example, a coated abrasive, a bonded abrasive, and the like. According to one embodiment, the shaped abrasive particle can have a particular size, as measured by the length of the body. For example, the shaped abrasive particle may have a median particle size of not greater than about 5 mm. Alternatively, the median particle may be less, such as not greater than about 4 mm, not greater than about 3 mm, not greater than about 2 mm, or even not greater than about 1.5 mm. In still another aspect, the median particle size of the shaped abrasive particle can be at least about 10 microns, at least about 100 microns, at least about 200 microns, at least about 400 microns, at least about 600 microns, or even at least about 800 microns. It will be appreciated that the median particle size of the shaped abrasive particle can be within a range between any of the above minimum and maximum values.
The shaped abrasive particle of one embodiment can have a particular grain size, particularly for grains of alpha alumina. For example, the shaped abrasive particle may have an average grain size of not greater than about 500 microns, such as not greater than about 250 microns, or even not greater than about 100 microns, not greater than about 50 microns, not greater than about 20 microns, or even not greater than about 1 micron. In another aspect, the average grain size can be at least about 0.01 microns, such as at least about 0.05 microns, at least about 0.08 microns, or even at least about 0.1 microns. It will be appreciated that the average grain size of the shaped abrasive particle can be within a range between any of the above minimum and maximum values.
In yet another embodiment, the shaped abrasive particle can include a dopant material, which can include an element or compound such as an alkali element, alkaline earth element, rare earth element, hafnium, zirconium, niobium, tantalum, molybdenum, vanadium, or a combination thereof. In one particular embodiment, the dopant material includes an element or compound including an element such as lithium, sodium, potassium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cesium, praseodymium, niobium, hafnium, zirconium, tantalum, molybdenum, vanadium, silicon, boron, carbon or a combination thereof.
In certain instances, the shaped abrasive particle can be formed to have a specific content of dopant material. For example, the body of a shaped abrasive particle may include not greater than about 20 wt % dopant material for the total weight of the body. In other instances, the amount of dopant material can be less, such as not greater than about 16 wt %, not greater than about 14 wt %, not greater than about 12 wt %, not greater than about 11 wt %, not greater than about 10 wt %, not greater than about 9 wt %, not greater than about 8 wt %, not greater than about 7 wt %, not greater than about 6 wt %, or even not greater than about 5 wt % for the total weight of the body. In at least one non-limiting embodiment, the amount of dopant material can be at least about 0.5 wt %, such at least about 1 wt %, at least about 1.3 wt %, at least about 1.8 wt %, at least about 2 wt %, at least about 2.3 wt %, at least about 2.8 wt %, or even at least about 3 wt % for the total weight of the body. It will be appreciated that the amount of dopant material within the body of the shaped abrasive particle can be within a range between any of the minimum or maximum percentages noted above.
A shaped abrasive particle according to one embodiment can have a body defined by a length (l), which can be the longest dimension of any side of the shaped abrasive particle, a width (w) defined as a longest dimension of the shaped abrasive particle through a midpoint of the shaped abrasive particle, and a thickness (t) defined as the shortest dimension of the shaped abrasive particle extending in a direction perpendicular to the length and width. In specific instances, the length can be greater than or equal to the width. Moreover, the width can be greater than or equal to the thickness.
Additionally, the body of the shaped abrasive particle can have particular two-dimensional shapes. For example, the body can have a two-dimensional shape as viewed in a plane define by the length and width having a polygonal shape, ellipsoidal shape, a numeral, a Greek alphabet character, Latin alphabet character, Russian alphabet character, or any alphabet character, complex shapes utilizing a combination of polygonal shapes and a combination thereof. Particular polygonal shapes include triangular, rectangular, quadrilateral, pentagon, hexagon, heptagon, octagon, nonagon, decagon, any combination thereof.
FIGS. 3A-3C include perspective view illustrations of shaped abrasive particles that can be formed through the processes of the embodiments herein. FIG. 3A includes a perspective view illustration of a shaped abrasive particle in accordance with an embodiment. In particular, the body 301 of the shaped abrasive particle can have a length (l), a width (w) extending through a midpoint 302 of the body 301, and a thickness (t). In accordance with an embodiment, the body 301 can have a primary aspect ratio defined as a ratio of length:width. In certain instances, the primary aspect ratio of the body 301 can be at least about 1.2:1, such as at least about 1.5:1, at least about 2:1, at least about 3:1, or even at least about 4:1. Still, the primary aspect ratio may be not greater than about 100:1. It will be appreciated that the primary aspect ratio of the body 301 may be within a range between any of the minimum and maximum ratios noted above.
Furthermore, the body 301 can have a secondary aspect ratio defined by a ratio of length:thickness. In certain instances, the secondary aspect ratio of the body 301 may be at least about 1.2:1, such as at least about 1.5:1, at least about 2:1, at least about 3:1, at least about 4:1, at least about 5:1, or even at least about 10:1. Still, in at least one non-limiting embodiment, the body 301 can have a secondary aspect ratio that is not greater than about 100:1. It will be appreciated that the secondary aspect ratio may be within a range between any of the minimum and maximum ratios provided above.
Furthermore, the shaped abrasive particle of an embodiment can have a tertiary aspect ratio defined by a ratio of the width:thickness. In certain instances, the tertiary aspect ratio of the body 301 may be at least about 1.2:1, such as at least about 1.5:1, at least about 2:1, at least about 3:1, at least about 4:1, at least about 5:1, or even at least about 10:1. Still, in at least one non-limiting embodiment, the body 301 can have a tertiary aspect ratio that is not greater than about 100:1. It will be appreciated that the tertiary aspect ratio may be within a range between any of the minimum and maximum ratios provided above.
FIG. 3B includes a perspective view illustration of a shaped abrasive particle in accordance with an embodiment. As illustrated, the shaped abrasive particle can have a corner-truncated triangular shape, wherein two edges and a side surface extending between the edges replace a position that would normally be occupied by a single corner in a typical triangular-shaped body. In particular, the body 301 of the shaped abrasive particle can have a length (l), a width (w) extending through a midpoint 302 of the body 301, and a thickness (t).
FIG. 3C includes a perspective view illustration of a shaped abrasive particle formed in accordance with an embodiment. Notably, the body 301 can have a generally quadrilateral shape. However, in one particular embodiment, the body 301 may be a corner truncated quadrilateral, and more particularly a corner truncated parallelagram or trapazoidal shape, wherein two edges and a side surface extending between the edges replace a position that would normally be occupied by a single corner in a typical quadrilateral-shaped body. In particular, the body 301 of the shaped abrasive particle can have a length (l), a width (w) extending through a midpoint 302 of the body 301, and a thickness (t). The body 301 can have the any of the features of any shaped abrasive particle described in the embodiments herein.
FIG. 4 includes a cross-sectional illustration of a coated abrasive article incorporating the abrasive particulate material in accordance with an embodiment. As illustrated, the coated abrasive 400 can include a substrate 401 and a make coat 403 overlying a surface of the substrate 401. The coated abrasive 400 can further include abrasive particulate material 406. The abrasive particulate material 406 can include a first type of particles including shaped abrasive particles 405 and a second type of abrasive particulate material 407 in the form of diluent abrasive particles. The diluent abrasive particles can have a random shape, and may not necessarily be shaped abrasive particles. The coated abrasive 400 may further include size coat 404 overlying and bonded to the abrasive particulate material 406 and the make coat 404.
According to one embodiment, the substrate 401 can include an organic material, inorganic material, and a combination thereof. In certain instances, the substrate 401 can include a woven material. However, the substrate 401 may be made of a non-woven material. Particularly suitable substrate materials can include organic materials, including polymers, and particularly, polyester, polyurethane, polypropylene, polyimides such as KAPTON from DuPont, or paper. Some suitable inorganic materials can include metals, metal alloys, and particularly, foils of copper, aluminum, steel, and a combination thereof.
The make coat 403 can be applied to the surface of the substrate 401 in a single process, or alternatively, the abrasive particulate material 406 can be combined with a make coat 403 material and applied as a mixture to the surface of the substrate 401. Suitable materials of the make coat 403 can include organic materials, particularly polymeric materials, including for example, polyesters, epoxy resins, polyurethanes, polyamides, polyacrylates, polymethacrylates, poly vinyl chlorides, polyethylene, polysiloxane, silicones, cellulose acetates, nitrocellulose, natural rubber, starch, shellac, and mixtures thereof. In one embodiment, the make coat 403 can include a polyester resin. The coated substrate can then be heated in order to cure the resin and the abrasive particulate material to the substrate. In general, the coated substrate 401 can be heated to a temperature of between about 100° C. to less than about 250° C. during this curing process.
The abrasive particulate material 406 can include shaped abrasive particles according to embodiments herein. In particular instances, the abrasive particulate material 406 may include different types of shaped abrasive particles. The different types of shaped abrasive particles can differ from each other in composition, two-dimensional shape, three-dimensional shape, size, and a combination thereof as described in the embodiments herein. As illustrated, the coated abrasive 400 can include a shaped abrasive particle 405 having a generally triangular two-dimensional shape.
The other type of abrasive particles 407 can be diluent particles different than the shaped abrasive particles 405. For example, the diluent particles can differ from the shaped abrasive particles 405 in composition, two-dimensional shape, three-dimensional shape, size, and a combination thereof. For example, the abrasive particles 407 can represent conventional, crushed abrasive grit having random shapes. The abrasive particles 407 may have a median particle size less than the median particle size of the shaped abrasive particles 405.
After sufficiently forming the make coat 403 and the abrasive particulate material 406, the size coat 404 can be formed to overlie and bond the abrasive particulate material 406 in place. The size coat 404 can include an organic material, may be made essentially of a polymeric material, and notably, can use polyesters, epoxy resins, polyurethanes, polyamides, polyacrylates, polymethacrylates, poly vinyl chlorides, polyethylene, polysiloxane, silicones, cellulose acetates, nitrocellulose, natural rubber, starch, shellac, and mixtures thereof.
FIG. 5 includes an illustration of a bonded abrasive article incorporating the abrasive particulate material in accordance with an embodiment. As illustrated, the bonded abrasive 500 can include a bond material 501, abrasive particulate material 502 contained in the bond material, and porosity 508 within the bond material 501. In particular instances, the bond material 501 can include an organic material, inorganic material, and a combination thereof. Suitable organic materials can include polymers, such as epoxies, resins, thermosets, thermoplastics, polyimides, polyamides, and a combination thereof. Certain suitable inorganic materials can include metals, metal alloys, vitreous phase materials, crystalline phase materials, ceramics, and a combination thereof.
In some instances, the abrasive particulate material 502 of the bonded abrasive 500 can include shaped abrasive particles 503, 504, 505, and 506. In particular instances, the shaped abrasive particles 503, 504, 505, and 506 can be different types of particles, which can differ from each other in composition, two-dimensional shape, three-dimensional shape, size, and a combination thereof as described in the embodiments herein. Alternatively, the bonded abrasive article can include a single type of shaped abrasive particle.
The bonded abrasive 500 can include a type of abrasive particulate material 507 representing diluent abrasive particles, which can differ from the shaped abrasive particles 503, 504, 505, and 506 in composition, two-dimensional shape, three-dimensional shape, size, and a combination thereof.
The porosity 508 of the bonded abrasive 500 can be open porosity, closed porosity, and a combination thereof. The porosity 508 may be present in a majority amount (vol %) based on the total volume of the body of the bonded abrasive 500. Alternatively, the porosity 508 can be present in a minor amount (vol %) based on the total volume of the body of the bonded abrasive 500. The bond material 501 may be present in a majority amount (vol %) based on the total volume of the body of the bonded abrasive 500. Alternatively, the bond material 501 can be present in a minor amount (vol %) based on the total volume of the body of the bonded abrasive 500. Additionally, abrasive particulate material 502 can be present in a majority amount (vol %) based on the total volume of the body of the bonded abrasive 500. Alternatively, the abrasive particulate material 502 can be present in a minor amount (vol %) based on the total volume of the body of the bonded abrasive 500.
According to one aspect, the system and method herein may facilitate the formation of shaped abrasive particles having certain features. For example, in one embodiment, a shaped abrasive particle can include a body having a tortuous contour, which may be facilitated by particular aspects of the forming process. In particular instances, the tortuous contour can include a first curved portion, a second curved portion, and a planar portion joining the first curved portion and the second curved portion. FIG. 6 includes a side view (inverted color) image of a shaped abrasive particle made according to an embodiment herein. The shaped abrasive particle 600 can include a body 601 having a first major surface 603, a second major surface 604, and a side surface 605 extending between and separating the first major surface 603 and the second major surface 604. In particular, and in accordance with an embodiment, the first major surface 603 can have a tortuous contour, which may include a first curved portion 606, a second curved portion 608, and a substantially planar or linear region 607 connecting and extending between the first curved portion 606 and the second curved portion 608. In one particular embodiment, the first curved portion 606 may define a substantially arcuate curvature, which may include a substantially convex curvature. The second curved portion 608 can be spaced apart from the first curved portion 606 and define a substantially arcuate curvature, and particularly, a substantially concave portion.
In certain embodiments, such as illustrated in FIG. 6 the first curved portion 606 can define a first radius of curvature and the second curved portion 608 can define a second radius of curvature according to a portion of the curve best fit to a circle. Such analysis may be completed using imaging software, such as ImageJ. In one embodiment, the first curved portion 606 and the second curved portion 608 can have different radiuses of curvatures compared to each other. In still another embodiment, the radius of curvatures associated with the first curved portion 606 and second curved portion 608 may be substantially similar. Moreover, in another particular embodiment, it has been observed that the tortuous contour of the first major surface 603 can include a first curved portion 606 having a radius of curvature that is greater than an average height of the body 601, wherein the height can be measured as the average distance between the first major surface 603 and second major surface 604. Additionally, in another embodiment, it has been observed that the tortuous contour of the first major surface 604 can include a second curved portion 608 having a radius of curvature that is greater than the average height of the body 601.
In accordance with one particular embodiment, the tortuous contour can include a particular waviness. The waviness can be defined as a portion of any surface having the tortuous contour including a first curved portion extending above a line and further comprising a second curved portion extending below the line. Referring again to FIG. 6, a line 610 is drawn between the corners of the first major surface 603 and the side surface 605 of the body 601. In some instances, the line 610 may be parallel to the opposing major surface if the opposite major surface defines a substantially planar surface, such as the second major surface 604 of the body 601 shown in FIG. 6. As illustrated, the first major surface can have a tortuous contour including a waviness, wherein the first curved portion 606 includes a region of the first major surface 603 that extends on one side (i.e., below in the orientation illustrated) and the second curved portion 608 includes a region of the first major surface 603 that extends on the opposite side (i.e., above in the orientation illustrated) of the line 610 relative to the region of the first major portion 606.
In a particular embodiment, the curved portions can define a peak height or valley height depending on the relationship of the curved portions 606 and 608 relative to the line 610. The peak height can be the greatest distance between a point within the curved portion and the line 610. For example, the second curved portion 608 can have a peak height 620 as the greatest distance between a point on the first major surface 602 within the second curved portion 608 and the line 610, in a direction perpendicular to the line and generally extending in the direction of the height of the particle as viewed from the side. According to one embodiment, the peak height 620 can be at least about 5% of an average height of the body 601. In other instances, it can be greater, such as at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, or even at least about 50%. In still another non-limiting embodiment, the peak height 620 can be less than about 150%, such as less than about 90% of the average height of the particle. It will be appreciated that the peak height can be within a range between any of the above minimum and maximum percentages.
Moreover, while not illustrated, the first curved portion 606 can define a valley height, as the maximum distance between the line 610 and a portion of the first major surface 603 within the first curved portion 606. The valley height can have the same features as the peak height 620 associated with the second curved portion 608.
In another embodiment, the tortuous contour can be defined by a portion of the body wherein a slope of a trace line extending along the tortuous contour changes slope from a region defining a positive slope of the trace line, to a slope of zero, to a negative slope. For example, referring to FIG. 6, a trace line 612 can be formed along the tortuous surface and define a first region 613 having a positive slope, a region 614 including a slope of zero, and a region wherein the slope of the trace line 612 changes to a negative value. It will be appreciated that a tortuous surface can include additional changes in slope, including for example, an additional transition to a region having a slope of zero, and a transition to a region having a positive or negative slope. Such characteristics may be defined generally as a sinusoidal-like curve, which is not to be interpreted as requiring the trace line 612 to comply with the exact mathematical formula of a sine wave function, but rather as a description of the approximate change in curvature of the trace line 612.
Notably, as illustrated in the embodiment of FIG. 6, the tortuous contour can extend along a first major surface 603 of the body 601. However, it will be appreciated that in other embodiments, the tortuous contour may extend along other surfaces of the body 601, including, but not limited to, the second major surface 604 and the side surface 605. Moreover, it will be appreciated that more than one surface of the body 601 of a shaped abrasive particle according to embodiments herein can exhibit a tortuous contour.
The tortuous contour can extend along at least a portion of any surface of the body 601. In particular instances, the tortuous contour can extend along a majority of at least one surface (e.g., the first major surface 603, second major surface 604, or side surface 605) of the body 601. In more particular instances, the tortuous contour can define at least about 60%, such as at least about 70%, at least about 80%, at least about 90%, or even essentially all of at least one surface of the body 601.
Moreover, other surfaces not exhibiting a tortuous surface may have other features, including other features of the embodiments herein (e.g., a fractured surface, an arrowhead shape, etc.) or even a substantially planar contour. For example, any one of the surfaces of the body 601 including but not limited to, the first major surface 603, second major surface 604, and side surface 605, not having a tortuous surface, may exhibit a substantially planar surface. Still, it will be appreciated that surfaces exhibiting a tortuous surface may have additional features, including other features of the embodiments herein, including for example, a fractured surface, an arrowhead shape, and the like.
In accordance with another aspect, the body 601 can have a first corner 631 comprising a first height, measured as the distance between the first major surface 603 and the second major surface 604 along the side surface 605, and more particularly, the distance between the corner 631 and the corner 631 in a direction of the height perpendicular to the line 610. The body 601 can have a second height at the second corner 635, measured as the distance between the first major surface 603 and the second major surface 604 along the side surface 605, and more particularly, the distance between the corner 635 and the corner 634 in a direction of the height perpendicular to the line 610. In particular, the first height can be significantly different than the second height. In certain embodiments, the first height can be significantly less than the second height.
In accordance with an embodiment, the body 601 of the shaped abrasive particle 600 can include a first upper angle 641 between the first major surface 603 and the side surface 605 as viewed from the side as illustrated in FIG. 7. The first upper angle 641 can be at least about 80 degrees, such as at least about 85 degrees. In other embodiments, the first upper angle can be not greater than about 110 degrees. In at least one embodiment, the side surface 605 can extend at a generally orthogonal angle relative to at least one of the first major surface 603 and the second major surface 604. More particularly, the side surface 605 can extend at a generally orthogonal angle relative to the first major surface 603 and the second major surface 604.
The body 601 of the shaped abrasive particle 600 can include a second lower angle 642 between the second major surface 603 and the side surface 605 as viewed from the side as illustrated in FIG. 7. The second lower angle 642 can be at least about 80 degrees, such as at least about 85 degrees. In other embodiments, the second lower angle 642 can be not greater than about 110 degrees.
The shaped abrasive particles of the embodiments herein can have a percent flashing that may facilitate improved performance. Notably, the flashing can define an area of the particle as viewed along one side, such as illustrated in FIG. 8, wherein the flashing extends from a side surface of the body 801 within the boxes 802 and 803. The flashing can represent tapered regions proximate to the upper surface and bottom surface of the body 801. The flashing can be measured as the percentage of area of the body 801 along the side surface contained within a box extending between an innermost point of the side surface (e.g., 821) and an outermost point (e.g., 822) on the side surface of the body to define the box 803. The flashing within the box 802 can be measured as the percentage of area of the body along the side surface contained within a box extending between an innermost point of the side surface 824 and an outermost point at 823 on the side surface of the body 801. In one particular instance, the body 801 can have a particular content of flashing, which can be the percentage of area of the body contained within the boxes 802 and 803 compared to the total area of the body contained within boxes 802, 803, and 804. According to one embodiment, the percent flashing (f) of the body can be at not greater about 10%. In another embodiment, the percent flashing can be less, such as at not greater than about 9%, not greater than about 8%, not greater than about 7%, not greater than about 6%, not greater than about 5%, or even not greater than about 4%. Still, in one non-limiting embodiment, the percent flashing can be at least about 0.1%, at least about 0.5%, at least about 1%, or even at least about 2%. It will be appreciated that the percent flashing of the body 801 can be within a range between any of the above minimum and maximum percentages. Moreover, it will be appreciated that the above flashing percentages can be representative of an average flashing percentage or a median flashing percentage for a batch of shaped abrasive particles.
The percent flashing can be measured by mounting the shaped abrasive particle on its side and viewing the body 801 at the side to generate a black and white image, such as the orientations illustrate in FIGS. 6 and 7. A suitable program for such includes ImageJ software. The percentage flashing can be calculated by determining the area of the body 801 in the boxes 802 and 803 compared to the total area of the body as viewed at the side (total shaded area), including the area in the center 804 and within the boxes. Such a procedure can be completed for a suitable sampling of particles to generate average, median, and/or and standard deviation values.
FIG. 9 includes a perspective view illustration of an abrasive particle in accordance with an embodiment. The body 901 includes an upper surface 903 a bottom major surface 904 opposite the upper surface 903. The upper surface 903 and the bottom surface 904 can be separated from each other by side surfaces 905, 906, and 907. As illustrated, the body 901 of the shaped abrasive particle 900 can have a generally triangular shape as viewed in a plane of the upper surface 903. In particular, the body 901 can have a length (Lmiddle), which may be measured at the bottom surface 904 of the body 901 and extending from a corner 913 through a midpoint 981 of the body 901 to a midpoint at the opposite edge 914 of the body. Alternatively, the body can be defined by a second length or profile length (Lp), which can be the measure of the dimension of the body from a side view at the upper surface 903 from a first corner 913 to an adjacent corner 912. Notably, the dimension of Lmiddle can be a length defining a distance between a height at a corner (hc) and a height at a midpoint edge (hm) opposite the corner. The dimension Lp can be a profile length along a side of the particle.
The body 901 can further include a width (w) that is the longest dimension of the body and extending along a side. The shaped abrasive particle can further include a height (h), which may be a dimension of the shaped abrasive particle extending in a direction perpendicular to the length and width in a direction defined by a side surface of the body 901. Notably, body 901 can be defined by various heights depending upon the location on the body where the height is measured, such as at the corners versus the interior of the body 901. According to at least the embodiment of FIG. 9, the width can be greater than or equal to the length, the length can be greater than or equal to the height, and the width can be greater than or equal to the height.
Moreover, reference herein to any dimensional characteristic (e.g., height, length, width, etc.) can be reference to a dimension of a single particle of a batch, a median value, or an average value derived from analysis of a suitable sampling of particles from a batch. Unless stated explicitly, reference herein to a dimensional characteristic can be considered reference to a median value that is a based on a statistically significant value derived from a sample size of suitable number of particles of a batch of particles. For certain embodiments herein, the sample size can include at least 15 randomly selected particles from a batch of particles.
In accordance with an embodiment, the body 901 of the shaped abrasive particle can have a first corner height (hc) at a first region of the body defined by a corner 913. Notably, the corner 913 may represent the point of greatest height on the body 901. However, the height at the corner 913 does not necessarily represent the point of greatest height on the body 901. The corner 913 can be defined as a point or region on the body 901 defined by the joining of the upper surface 903, and two side surfaces 905 and 907. The body 901 may further include other corners, spaced apart from each other, including for example, corner 911 and corner 912. As further illustrated, the body 301 can include edges 914, 915, and 916 that can separated from each other by the corners 911, 912, and 913. The edge 914 can be defined by an intersection of the upper surface 303 with the side surface 906. The edge 915 can be defined by an intersection of the upper surface 903 and side surface 905 between corners 911 and 913. The edge 916 can be defined by an intersection of the upper surface 903 and side surface 907 between corners 912 and 913.
The shaped abrasive particle can have a body having a particular amount of dishing, wherein the dishing value (d) can be defined as a ratio between an average height of the body at the corners (Ahc) as compared to smallest dimension of height of the body at the interior (hi), which may be a position spaced away from the corners 911, 912, and 913 and within the interior of the body 901, such as proximate to the midpoint 981 within region 919. The average height of the body at the corners (Ahc) can be calculated by measuring the height of the body at all corners 911, 912, and 913 and averaging the values, and may be distinct from a single value of height at one corner (hc). For example, in the case of a shaped abrasive particle having a triangular shape, three height values can be taken at the three corners of the triangular shape. The average height of the body at the corners or at the interior can be measured using a STIL (Sciences et Techniques Industrielles de la Lumiere—France) Micro Measure 3D Surface Profilometer (white light (LED) chromatic aberration technique). Alternatively, the dishing may be based upon a median height of the particles at the corner (Mhc) calculated from a suitable sampling of particles from a batch. Likewise, the interior height (hi) can be a median interior height (Mhi) derived from a suitable sampling of shaped abrasive particles from a batch. According to one embodiment, the dishing value (d) can be not greater than about 2, such as not greater than about 1.9, not greater than about 1.8, not greater than about 1.7, not greater than about 1.6, or even not greater than about 1.5, not greater than about 1.3, or even not greater than about 1.2. Still, in at least one non-limiting embodiment, the dishing value (d) can be at least about 0.9, such as at least about 1.0. It will be appreciated that the dishing ratio can be within a range between any of the minimum and maximum values noted above. Moreover, it will be appreciated that the above dishing values can be representative of a median dishing value (Md) for a batch of shaped abrasive particles.
In another embodiment, the shaped abrasive particle can include a body comprising an arrowhead shape. FIG. 10 includes an image of a shaped abrasive particle having an arrowhead shape according to an embodiment. As illustrated, the shaped abrasive particle 1000 can include a body 1001 including a first major surface 1003, a second major surface opposite the second major surface, and a first side surface 1005, a second side surface 1006, and a third side surface 1007. The body 1001 can have any of the other features of shaped abrasive particles described herein, and in particular, can utilize one or more substantially planar contours and/or tortuous contour surfaces.
In accordance with a particular embodiment, first side surface 1005 can extend into a volume of the body 1001, and the second side surface 1006 and the third side surface 1008 can be substantially planar. In particular instances, such as illustrated in FIG. 10, at least a portion of the first side surface 1005 can define an arcuate portion, and in particular may define a substantially concave portion. Accordingly, the angle between the second side surface 1006 and the third side surface 1007, as viewed top-down as shown in FIG. 10, can be different than the angle of the corner between the first side surface 1005 and the second side surface 1006. Additionally, or alternatively, the angle between the second side surface 1006 and the third side surface 1007, as viewed top-down as shown in FIG. 10, can be different than the angle of the corner between the first side surface 1005 and the third side surface 1007. More particularly, the angle between the first side surface 1005 and the second side surface 1006 can be less than the angle between the second side surface 1006 and the third side surface 1007. Likewise, in certain instances, the angle between the first side surface 1005 and the third side surface 1007 can be less than the angle between the second side surface 1006 and the third side surface 1007.
The body 1001 can further include a fractured region 1009 on at least a portion of the first side surface 1005. For example, the body 1001 can have a fractured region 1009 intersecting at least a portion of an edge defining the first major surface 1003 or second major surface. The fractured region 1009 can be characterized by having a surface roughness greater than a surface roughness of at least the first major surface 1003 or the second major surface of the body 1001. The fractured region 1009 can be characterized by irregularly shaped protrusions and grooves extending from the first side surface 1005. In certain instances, the fractured region 1009 can appear as and define a serrated edge. In certain instances, the fracture region 1009 may be preferentially located at or near the corners of the arms of the body. In still other instances, it has been noted that a fractured region 1009 may be formed at a center of the first side surface 1005 defining an arcuate surface giving the body 1001 an arrowhead shape. The fractured region 1009 can extend from the second major surface and extend vertically for a fraction of the entire height of the first side surface 1005 or even for the entire height of the first side surface 1005.
It will be appreciated that any of the characteristics of the embodiments herein can be attributed to a batch of shaped abrasive particles. A batch of shaped abrasive particles can include, but need not necessarily include, a group of shaped abrasive particles made through the same forming process. In yet another instance, a batch of shaped abrasive particles can be a group of shaped abrasive particles of an abrasive article, such as a fixed abrasive article, and more particularly, a coated abrasive article, which may be independent of a particular forming method, but having one or more defining features present in a particular population of the particles. For example, a batch of particles may include an amount of shaped abrasive particles suitable for forming a commercial grade abrasive product, such as at least about 20 lbs. of particles.
Moreover, any of the features of the embodiments herein (e.g., aspect ratio, planar portions, tortuous contour, arrowhead shape, fractured region, two-dimensional shape, etc.) can be a characteristic of a single particle, a median value from a sampling of particles of a batch, or an average value derived from analysis of a sampling of particles from a batch. Unless stated explicitly, reference herein to the characteristics can be considered reference to a median value that is a based on a statistically significant value derived from a random sampling of suitable number of particles of a batch. Notably, for certain embodiments herein, the sample size can include at least 10, such as at least about 15, and more typically, at least 40 randomly selected particles from a batch of particles.
Any of the features described in the embodiments herein can represent features that are present in at least a first portion of a batch of shaped abrasive particles. Moreover, according to an embodiment, that control of one or more process parameters can control the prevalence of one or more features of the shaped abrasive particles of the embodiments herein. Some exemplary process parameters include, but is not limited to, the characteristics of the mixture (e.g., viscosity, storage modulus, coil value), the rate of translation, the rate of extrusion, the batch efficiency, the batch productivity, the composition of the ejection material, the predetermined force, the ejection material opening width relative to the shaping assembly opening width, the gap distance, and a combination thereof.
The first portion may be a minority portion (e.g., less than 50% and any whole number integer between 1% and 49%) of the total number of particles in a batch, a majority portion (e.g., 50% or greater and any whole number integer between 50% and 99%) of the total number of particles of the batch, or even essentially all of the particles of a batch (e.g., between 99% and 100%). The provision of one or more features of any shaped abrasive particle of a batch may facilitate alternative or improved deployment of the particles in an abrasive article and may further facilitate improved performance or use of the abrasive article.
A batch of particulate material can include a first portion including a first type of shaped abrasive particle and a second portion including a second type of shaped abrasive particle. The content of the first portion and second portion within the batch may be controlled at least in part based upon certain processing parameters. Provision of a batch having a first portion and a second portion may facilitate alternative or improved deployment of the particles in an abrasive article and may further facilitate improved performance or use of the abrasive article.
The first portion may include a plurality of shaped abrasive particles, wherein each of the particles of the first portion can have substantially the same features, including for example, but not limited to, the same two-dimensional shape of a major surface. Other features include any of the features of the embodiments herein. The batch may include various contents of the first portion. For example, the first portion may be present in a minority amount or majority amount. In particular instances, the first portion may be present in an amount of at least about 1%, such as at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, or even at least about 70% for the total content of portions within the batch. Still, in another embodiment, the batch may include not greater than about 99%, such as not greater than about 90%, not greater than about 80%, not greater than about 70%, not greater than about 60%, not greater than about 50%, not greater than about 40%, not greater than about 30%, not greater than about 20%, not greater than about 10%, not greater than about 8%, not greater than about 6%, or even not greater than about 4% of the total portions within the batch. The batch can include a content of the first portion within a range between any of the minimum and maximum percentages noted above.
The second portion of the batch can include a plurality of shaped abrasive particles, wherein each of the shaped abrasive particles of the second portion can have substantially the same feature, including for example, but not limited to, the same two-dimensional shape of a major surface. The second portion can have one or more features of the embodiments herein, which can be distinct compared to the plurality of shaped abrasive particles of the first portion. In certain instances, the batch may include a lesser content of the second portion relative to the first portion, and more particularly, may include a minority content of the second portion relative to the total content of particles in the batch. For example, the batch may contain a particular content of the second portion, including for example, not greater than about 40%, such as not greater than about 30%, not greater than about 20%, not greater than about 10%, not greater than about 8%, not greater than about 6%, or even not greater than about 4%. Still, in at least on non-limiting embodiment, the batch may contain at least about 0.5%, such as at least about 1%, at least about 2%, at least about 3%, at least about 4%, at least about 10%, at least about 15%, or even at least about 20% of the second portion for the total content of portions within the batch. It will be appreciated that the batch can contain a content of the second portion within a range between any of the minimum and maximum percentages noted above.
Still, in an alternative embodiment, the batch may include a greater content of the second portion relative to the first portion, and more particularly, can include a majority content of the second portion for the total content of particles in the batch. For example, in at least one embodiment, the batch may contain at least about 55%, such as at least about 60% of the second portion for the total portions of the batch.
It will be appreciated that the batch can include additional portions, including for example a third portion, comprising a plurality of shaped abrasive particles having a third feature that can be distinct from the features of the particles of the first and second portions. The batch may include various contents of the third portion relative to the second portion and first portion. The third portion may be present in a minority amount or majority amount. In particular instances, the third portion may be present in an amount of not greater than about 40%, such as not greater than about 30%, not greater than about 20%, not greater than about 10%, not greater than about 8%, not greater than about 6%, or even not greater than about 4% of the total portions within the batch. Still, in other embodiments the batch may include a minimum content of the third portion, such as at least about 1%, such as at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or even at least about 50%. The batch can include a content of the third portion within a range between any of the minimum and maximum percentages noted above. Moreover, the batch may include a content of diluent, randomly shaped abrasive particles, which may be present in an amount the same as any of the portions of the embodiments herein.
For example, in accordance with one particular aspect, a batch of shaped abrasive particles can include a first portion, which can include a shaped abrasive particle having a tortuous contour. The first portion can include any one or combination of features described in accordance with shaped abrasive particles having a tortuous contour. The first portion can be a majority of a total number of shaped abrasive particles of the batch. Alternatively, the first portion can be a minority of a total number of shaped abrasive particles of the batch. In yet one particular aspect, as noted herein, the first portion can be at least 1% of a total number of shaped abrasive particles of the batch. In yet another particular embodiment, as noted herein, the first portion can be not greater than about 99% of a total number of shaped abrasive particles of the batch.
Furthermore, in one particular aspect, the batch can also include a second portion of shaped abrasive particles, wherein the second portion of shaped abrasive particles have a discrete shape feature different than the tortuous contour of the shaped abrasive particles of the first portion. More particularly, exemplary discrete shape features can include, but are not limited to, dish-shaped particles, substantially planar particles, concavo-convex particles, shaped abrasive shards, molded shaped abrasive particles, screen-printed shaped abrasive particles, cast-and-cut shaped abrasive particles, multilayered abrasive particles, arrowhead-shaped particles, shaped abrasive particles having a complex shape, diluent abrasive particles, and a combination thereof.
It will be appreciated that the batch of shaped abrasive particles are part of a fixed abrasive article, which can include, but is not limited to, bonded abrasive articles (see, for example, FIG. 5), coated abrasive articles (see, for example FIG. 4), and a combination thereof. In one particular embodiment, the fixed abrasive article can include a coated abrasive article, wherein the first portion of the batch includes a plurality of shaped abrasive particles, and each of the shaped abrasive particles of the plurality of shaped abrasive particles are arranged in a controlled orientation relative to a backing. Some exemplary types of controlled orientation can include at least one of a predetermined rotational orientation, a predetermined lateral orientation, and a predetermined longitudinal orientation. In such instances, the shaped abrasive particles may be oriented with respect to each other or with respect to a particular predetermined abrasive direction (i.e., direction for conducting material removal relative to a workpiece). Moreover, in certain instances, the shaped abrasive particle can be coupled to the backing in a side orientation relative to the backing, such that a side surface is closest to the surface of the backing. In an alternative embodiment, at least a significant portion of the shaped abrasive particles of the first portion can be coupled to the backing in a flat orientation relative to the backing, such that a major surface of the body is closest to the surface of the backing.
According to another aspect, the first portion of the batch can have a predetermined classification characteristic selected from the group consisting of average particle shape, average particle size, particle color, hardness, friability, toughness, density, specific surface area, and a combination thereof. Likewise, any of the other portions of the batch may be classified according to the above noted classification characteristics.
Example 1
A mixture in the form of a gel is obtained having approximately 52 wt % solids loading of boehmite commercially available as Catapal B from Sasol Corp. combined with 48 wt % water containing a minority content of nitric acid and organic additives. The gel has a viscosity of approximately 70,000 Pa·s and a storage modulus of approximately 450,000 Pa, and a coil value of approximately 3000 N.
The gel is extruded from a die using a pressure of approximately 90 psi (552 kPa) into a screen comprising a metal material and having openings are in the shape of an equilateral triangle, and wherein the sides of the triangle have a length of approximately 3.4 mm and the openings have a depth of approximately 0.6 mm. During extrusion in the application zone, the screen is abutting a backing plate.
The gel is extruded into the openings and the screen with the gel in the openings is translated to an ejection zone at a rate of 1 m/min. Prior to entering the ejection zone, the gel passes through a heating zone including infrared lamps and having an average temperature of between approximately 50-90° C. The gel and the shaping assembly pass through the heating zone in approximately 30 seconds and essentially no volatiles are removed from the gel. Note that the heating zone is optional and may not be utilized in all instances.
The ejection zone includes an air knife, operated at a pressure of 90 psi and exerting approximately 20 N of force and a resulting pressure of approximately 0.3 N/mm2 on the gel in the mold. The ejection material is air. The air knife has an ejection material opening that is approximately 2% of the shaping assembly opening width. As the gel contained within the openings of the screen passes the air knife, the gel is ejected and precursor shaped abrasive particles are formed.
The precursor shaped abrasive particles are then dried for approximately 20 hours in air at approximately 95° C. under standard atmospheric conditions of pressure and composition. The precursor shaped abrasive particles were calcined in a box furnace at approximately 600° C. for an 1 hour, and thereafter, the precursors shaped abrasive particles were sintered in a tube furnace up to 1320° C. for 3 to 20 minutes.
FIG. 11A includes images (inverted color) of 15 particles, each viewed from the side. The images were taken with a light microscope. The 15 particles were taken from a sample of the batch made according to Example 1. As illustrated, at least a portion of the batch of shaped abrasive particle, and more particularly, 8 discrete shaped abrasive particles 1101, 1102, 1103, 1104, 1105, 1106, 1107, and 1108 of the 15 sampled particles, demonstrated a tortuous contour of at least one surface (e.g., the first major surface or second major surface).
FIG. 11B includes a top view image of a sample of grains from the batch of Example 1. Notably, a portion of the shaped abrasive particles of the batch have an arrowhead shape, including for example, the shaped abrasive particles 1121, 1122, 1123, and 1124.
The batch of shaped abrasive particles were then incorporated into a coated abrasive article as Sample 1 and tested according to the conditions provided below in Table 1. Notably, 2 sample coated abrasives were tested in each case to derive the results. Sample 1 represents a coated abrasive including the shaped abrasive particles of Example 1, and having a median width of approximately 1.5 mm, a median height of approximately 300 microns, a median flashing percentage of less than 10%, a dishing value of approximately 1.2, wherein approximately 80% of the abrasive particles were positioned in a predetermined, side orientation on the backing such that the side surface was in contact with the backing. Sample 1 had a normalized weight of shaped abrasive particles of 40 lbs/ream.
A second sample, (CS1) is a Cubitron II belt commercially available from 3M as 3M984F. Approximately 70% of the shaped abrasive particles, which have a generally planar shape, were positioned in a predetermined side orientation on the backing. The shaped abrasive particles appear to be molded particles, such as those disclosed in U.S. Pat. No. 5,366,523 to Rowenhorst.










TABLE 1









Test platform:
Okuma Screening Test



Test conditions:
Dry, Rise and Fall




Constant MRR′ = 4 inch3/min inch




Belt speed = Vs = 7500 sfpm (38 m/s)




Work material: 304 ss,




Hardness: 104 HRB




Size: 0.5′′ × 0.5′′ × 6 inches




Contact width = 0.5′′ inch



Measurements:
Power, Grinding Forces, MRR′ and SGE










FIG. 12 includes a plot of specific grinding energy versus cumulative material removed (at a material removal rate of 4.0 inch3/min/inch) for Sample 1 and Sample CS1. As shown, while Sample 1 had a slightly higher specific grinding energy relative to Sample CS1, the specific grinding energy was relatively steady through 75% of the life of the belt. By contrast, Sample CS1 demonstrates a steadily rising specific grinding energy throughout the majority of the life the abrasive article. Moreover, and also remarkable, Sample 1 has essentially the same life (i.e., Cum MR) as compared to Sample CS1.
FIG. 13 includes an image of a sample of shaped abrasive particles formed according to Example 1. Notably, at least a portion of the shaped abrasive particles of Sample 1 demonstrate a tortuous contour, including for example, shaped abrasive particles 1301, 1302, and 1303.
Moreover, as further illustrated in FIG. 13, a portion of the shaped abrasive particles of Sample 2 have an arrowhead shape, including for example, the shaped abrasive particles 1311, 1312, 1313, 1314, 1315, and 1316. Additionally, as illustrated in FIG. 13, a portion of the shaped abrasive particles of Sample 2 have side surfaces having a fractured region, including for example, the shaped abrasive particles 1303, 1314, 1316, 1321, 1322, 1323, and 1324.
The present application represents a departure from the state of the art. While the industry has recognized that shaped abrasive particles may be formed through processes such as molding and screen printing, the processes of the embodiments herein are distinct from such processes. Notably, the embodiments herein utilize particular systems and methods, having a combination of features, including but not limited to the type and rheological characteristics of the mixture, aspects of the application zone, length of the belt, relative size of openings in the ejection assembly and the openings in the first portion of the shaping assembly, predetermined force of ejection material, batch efficiency, batch productivity, and the like. Moreover, the resulting precursor shaped abrasive particles and sintered shaped abrasive particles have features unique to the forming process, including for example, tortuous contours, fractured regions, arrowhead shapes, dishing, flashing percentage, and others described herein. Notably, it is remarkable and unexpected that shaped abrasive particles can be formed with such precision and speed, which results in little to no change in the quality of an abrasive product incorporating the mass-produced particles as compared to other conventional abrasive products incorporating molded shaped abrasive particles. Furthermore, it has been discovered that in addition to the production capabilities of the new process, the system and process may be controlled in a manner to allow for control of certain features of shaped abrasive particles and formation of batches of shaped abrasive particles having certain features or combinations of features.
The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.
The Abstract of the Disclosure is provided to comply with Patent Law and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description of the Drawings, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description of the Drawings, with each claim standing on its own as defining separately claimed subject matter.

## Claims

1. A shaped abrasive particle having a body comprising an arrowhead shape, wherein the body comprises a tortuous contour.

2. The shaped abrasive particle of claim 1, wherein the body comprises a first major surface, a second major surface, and a first surface joining the first major surface and second major surface, wherein at least a portion of the side surface comprises a concave curvature.

3. The shaped abrasive particle of claim 2, wherein the body comprises a length, a width, and a height, wherein the length is a longest dimension of any side of the shaped abrasive particle, wherein the width is a longest dimension of the shaped abrasive particle through a midpoint of the shaped abrasive particle, wherein the thickness is the shortest dimension of the shaped abrasive particle extending in a direction perpendicular to the length and width, wherein the body comprises a primary aspect ratio of at least 1.2:1, wherein the primary aspect ratio is a ratio of length:width, wherein the body comprises a secondary aspect ratio of at least 3:1, wherein the secondary aspect ratio is a ratio of length:height.

4. The shaped abrasive particle of claim 1, wherein the body comprises a percent flashing of not greater than about 10%.

5. The shaped abrasive particle of claim 4, wherein a side surface of the body comprises a fractured region.

6. A method comprising:
forming a precursor shaped abrasive particle in less than about 18 minutes, wherein forming comprises:
applying a mixture into a shaping assembly within an application zone; and
removing the mixture from the shaping assembly to form a precursor shaped abrasive particle.

7. The method of claim 6, wherein the mixture comprises a gel comprising a ceramic powder material as an integrated network of discrete particles.

8. The method of claim 6, wherein the mixture comprises at least 0.5 wt % and not greater than about 30 wt % organic materials for the total weight of the mixture.

9. The method of claim 6, wherein the mixture comprises a storage modulus of at least about 20×104 Pa and not greater than 80×104 Pa.

10. The method of claim 6, wherein the mixture comprises a viscosity of at least about 30×103 Pa s and not greater than 100×103 Pa s.

11. The method of claim 6, wherein applying comprises extruding the mixture through a die opening and into the shaping assembly, and wherein extruding is conducted at a pressure of at least 500 kPa and not greater than 10,000 kPa.

12. The method of claim 6, wherein the shaping assembly comprises an opening configured to receive the mixture and defined by at least three surfaces.

13. The method of claim 6, wherein the shaping assembly comprises a first portion comprising a screen and a second portion comprising a backing plate, wherein the first portion and the second portion are adjacent to each other in the application zone.

14. The method of claim 6, wherein the mixture has an average residence time in the shaping assembly of at least 1 second and not greater than 10 minutes.

15. The method of claim 6, wherein the mixture comprises a change in weight of less than about 5% for a total weight of the mixture for a duration the mixture is in an opening of the shaping assembly.

16. The method of claim 6, wherein applying the mixture comprises extruding the mixture through a die opening and into an opening in the shaping assembly, wherein during extrusion into the opening, the mixture flows into a first portion of the shaping assembly and abuts a surface of a second portion of the shaping assembly.

17. The method of claim 6, further comprising translating at least a portion of the shaping assembly from the application zone to an ejection zone.

18. The method of claim 6, further comprising removing the mixture from at least one surface of a portion of the shaping assembly prior to removing the mixture from the shaping assembly.

19. The method of claim 6, wherein removing the mixture comprises directing an ejection material at the mixture in the shaping assembly under a predetermined force of at least 12 N and not greater than 20 N, removing the mixture from the shaping assembly and forming a precursor shaped abrasive particle.

20. The method of claim 19, wherein the ejection material directly contacts an exposed major surface of the mixture in an opening of the shaping assembly.

21. The shaped abrasive particle of claim 1, wherein the tortuous contour extends along at least a portion of a first major surface, wherein the tortuous contour comprises a first curved portion, a second curved portion, and a planar portion joining the first curved portion and the second curved portion.

22. The method of claim 6, wherein during applying the mixture has a solids content of at least 42 wt % and not greater than 65 wt %.

23. The method of claim 6, further comprising a batch productivity of at least 0.2 kg/min/m2 of shaping surface.

24. The method of claim 13, wherein the backing plate of the second portion is coated with a fluoropolymer.

25. The method of claim 13, further comprising forming a batch of precursor shaped abrasive particles having a weight of at least 1 kg in not greater than 30 minutes.

26. The method of claim 16, wherein the second portion is stationary relative to the first portion, and wherein the second portion terminates prior to removing the mixture.

27. The method of claim 20, wherein the method further comprises drying, wherein drying is conducted at a temperature of at least 10° C. and not greater than 300° C., and wherein drying comprises removing a portion of the water content of the mixture.

28. The method of claim 6, wherein the mixture comprises a coil value of at least 2000 N and not greater than 6000 N.