Grid abrasive and preparation method thereof

Abstract

A method of making a grid abrasive product, the method comprising, in order: 1) providing a production tool having a mold surface defining a plurality of shaped cavities, and filling at least some of the shaped cavities with an abrasive composite precursor slurry, wherein the abrasive composite precursor slurry comprises abrasive particles dispersed in a curable binder precursor; 2) contacting the mold surface with an open grid backing, the open grid backing comprising interlaced wires defining openings and having opposing first and second major sides; 3) ultrasonically vibrating the abrasive composite precursor slurry; 4) curing the curable binder precursor by exposing the curable binder precursor to sufficient actinic electromagnetic radiation to provide isolated shaped abrasive composites contacting and secured to the first major side of the open grid backing; and 5) separating the grid abrasive product from the production tool. An open grid abrasive product that can be made by the method is also disclosed.

Description

Technical Field

[0001] The present disclosure generally relates to methods of making abrasive grids. Background Art

[0002] It is common for dry sanding operations to generate large amounts of airborne dust. To minimize this airborne dust, abrasive disc tools are often used while vacuum is drawn through the abrasive disc from the abrading side through the back of the disc and into a dust collection system. To this end, many abrasives have holes converted into them to facilitate this dust extraction. As an alternative to converting dust extraction holes into the abrasive disc, there are commercial products in which the abrasive is coated onto the fibers of a mesh knit backing in which loops are knitted into the back of the abrasive article. The loops are used as the loop portion of a hook and loop attachment system for attachment to the tool. Mesh products are known to provide excellent dust extraction and / or anti-filling properties when used with substrates that are known to heavily fill with traditional abrasives.

[0003] Structured abrasives have precisely shaped abrasive features on a backing, with the advantage that uniform islands wear at substantially the same rate, so that a uniform wear rate can be maintained to extend service life. They are typically prepared by filling a mold cavity on a mold surface of a production tool with a slurry of abrasive particles in a curable binder precursor, contacting the filled tool with a backing, curing the slurry, and then separating the production tool from the backing and the adhered shaped abrasive composites. Structured abrasive features disposed on a mesh backing are very useful for dust removal sanding applications. However, challenges remain when the slurry is applied to a very open mesh backing, because uncured slurry may migrate to the back of the mesh, contaminating the annular portion of the mesh, rendering the annulus unusable for abrasive attachment or partially sealing an opening in the mesh backing and improving dust removal efficiency. The present invention provides a mesh abrasive product having shaped abrasive composites fixed to a mesh backing, without extending through the mesh backing to its opposite side, or without blocking the openings in the mesh backing between the shaped abrasive composites for dust removal. Summary of the invention

[0004] Advantageously, methods according to the present disclosure can provide a grid abrasive product having shaped abrasive composites secured to a grid backing without clogging the openings in the grid backing between the shaped abrasive composites for dust removal sanding. In addition, methods according to the present disclosure can provide a grid abrasive product having shaped abrasive composites secured to a grid backing with improved adhesion between the grid backing and the shaped abrasive composites.

[0005] Therefore, in one aspect, the present disclosure provides a method for preparing a grid abrasive product, the method comprising, in order:

[0006] providing a production tool having a mold surface defining a plurality of forming cavities;

[0007] filling at least some of the shaped cavities with an abrasive composite precursor slurry, wherein the abrasive composite precursor slurry comprises abrasive particles dispersed in a curable binder precursor;

[0008] contacting the mold surface with an open mesh backing comprising interwoven threads defining openings and having opposing first and second major sides;

[0009] ultrasonically vibrating the abrasive composite precursor slurry;

[0010] curing the curable binder precursor by exposing the curable binder precursor to sufficient actinic electromagnetic radiation to provide isolated shaped abrasive composites contacting and secured to the first major side of the open grid backing; and

[0011] The grid abrasive product is separated from the production tool.

[0012] In another aspect, the present disclosure provides a grid abrasive product, the grid abrasive product comprising:

[0013] an open mesh backing comprising interwoven threads defining openings and having opposing first and second major sides; and

[0014] A plurality of isolated shaped abrasive composites are in contact with and secured to the first major side, wherein the isolated shaped abrasive composites include abrasive particles dispersed in an organic binder, and wherein the isolated shaped abrasive composites are not in contact with each other.

[0015] In a second aspect, the present disclosure provides a method for preparing a grid abrasive product, the method comprising, in order:

[0016] providing a production tool having a mold surface defining a plurality of forming cavities;

[0017] filling at least some of the shaped cavities with an abrasive composite precursor slurry, wherein the abrasive composite precursor slurry comprises abrasive particles dispersed in a curable binder precursor;

[0018] contacting the mold surface with an open mesh backing comprising interwoven threads defining openings and having opposing first and second major sides;

[0019] ultrasonically vibrating the abrasive composite precursor slurry;

[0020] curing the curable binder precursor by exposing the curable binder precursor to sufficient actinic electromagnetic radiation to provide isolated shaped abrasive composites contacting and secured to the first major side of the open grid backing; and

[0021] The grid abrasive product is separated from the production tool.

[0022] As used in this article:

[0023] The term "grid" means a woven fabric formed by the continuous interweaving of individual curved lines made using one or more threads, which are interwoven and bound by horizontal or vertical crossing;

[0024] The term "open mesh" means a mesh having holes or openings having a size equal to 0.2 and 10 times the wire diameter; and

[0025] The term "thread" includes both threads and yarns.

[0026]

[0026] A further understanding of the features and advantages of the present disclosure will be achieved upon consideration of the detailed description and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A is a schematic top view of an exemplary grid abrasive product according to the present disclosure.

[0028] Figure 1B is a schematic side view of a grid abrasive product 100 according to the present disclosure.

[0029] Figure 1C is a schematic end view of a grid abrasive product 100 according to the present disclosure.

[0030] Figure 2 is a digital micrograph of the grid abrasive product prepared in Comparative Example B.

[0031] Figure 3 is a digital micrograph of the grid abrasive product prepared in Example 1.

[0032] Figure 4A is a digital micrograph of the annular side of the grid abrasive disk prepared in Example 2.

[0033] Figure 4B is a digital micrograph of the grinding side of the grid abrasive disk prepared in Example 2.

[0034] Figure 4C is a higher resolution digital micrograph of the abrasive side of the grid abrasive disc prepared in Example 2.

[0035] Reference symbols used repeatedly in the specification and drawings are intended to represent the same or similar features or elements of the present disclosure. It should be understood that those skilled in the art can design many other modifications and embodiments that fall within the scope and essence of the principles of the present disclosure. The drawings may not be drawn to scale. DETAILED DESCRIPTION

[0036] See now Figures 1A to 1C , the exemplary mesh abrasive product 100 includes an open mesh backing 110 including interwoven wires 112 defining openings 114 and having opposite first and second major sides 116, 118, respectively. A plurality of isolated shaped abrasive composites 120 contact and are secured to the first major side 116. The isolated shaped abrasive composites 120 include abrasive particles (not shown) dispersed in an organic binder (not shown). The isolated shaped abrasive composites 120 do not contact each other. The optional attachment layer 130 includes a loop portion or a hook portion of a two-part hook-and-loop fastening system.

[0037] Any open mesh backing may be used. Examples include open woven, nonwoven or knitted open synthetic and / or natural fiber meshes; open fiberglass meshes; open metal fiber meshes; open molded thermoplastic polymer meshes; open molded thermoset polymer meshes; perforated sheet materials; and combinations thereof.

[0038] In some embodiments, the open mesh backing can be knitted or woven in a network with intermittent openings spaced apart along the surface of the scrim. The scrim need not be woven into a consistent pattern and may also include a nonwoven irregular pattern. Thus, the openings may be spaced apart in a pattern or may be spaced apart irregularly. The openings may be rectangular or have other shapes including: diamond, triangle, hexagon, or a combination of these shapes. However, this is not required.

[0039] The wires may have any diameter. In some preferred embodiments, the average diameter of the wires is from 10 microns to 1500 microns, preferably from 100 microns to 1000 microns, and more preferably from 50 microns to 500 microns.

[0040] Likewise, the openings may have any size and / or shape. For example, the average length and width of the openings may be 0.5 to 10 times the average diameter of the wire.

[0041] The term "shaped abrasive composite" refers to a composite structure comprising abrasive grains retained in a binder, wherein at least a major portion of the side surfaces and the top surface, and optionally the base surface, have a shape that at least substantially corresponds to the mold cavity used to form them. Imperfections that occur during the manufacturing process can be tolerated; for example, due to incomplete filling (resulting in irregular surface features) and / or overfilling of the mold cavity (resulting in flash).

[0042] The shaped abrasive composites can have any shape and / or size. In some preferred embodiments, the average length and / or width of the shaped abrasive composites is 30 microns to 5000 microns, preferably 100 microns to 3000 microns, and more preferably 500 microns to 2500 microns. Exemplary shapes can include at least one of a triangular, square, rectangular, or hexagonal column, pyramid, or truncated pyramid. Combinations of shaped abrasive composites can be used.

[0043] To ensure good adhesion of the shaped abrasive composites to the open grid backing, the shaped abrasive composites may contact at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 12, or even at least 16 wires.

[0044] Exemplary organic binder precursors include curable (meth) acrylic compounds, such as monofunctional, difunctional, trifunctional and tetrafunctional polymerizable acrylate monomers, (meth) acrylated polyurethanes, (meth) acrylated epoxy resins, ethylenically unsaturated free radical polymerizable compounds, aminoplast derivatives with α,β-unsaturated carbonyl side groups, isocyanurate derivatives with at least one acrylic side group, and isocyanate derivatives with at least one acrylic side group (vinyl ether), and mixtures and combinations thereof. As used herein, the term "(meth) acryloyl" encompasses acryloyl and / or methacryloyl.

[0045] (Meth)acrylated polyurethanes include di(meth)acrylates of hydroxyl terminated isocyanate extended polyesters or polyethers. Examples of commercially available acrylated polyurethanes include those available as CMD 6600, CMD 8400, and CMD 8805 from Cytec Industries, West Paterson, New Jersey.

[0046] (Meth)acrylated epoxy resins include di(meth)acrylates of epoxy resins, such as diacrylates of bisphenol A epoxy resins. Examples of commercially available acrylated epoxy resins include those available from Cytec Industries as CMD 3500, CMD 3600, and CMD 3700.

[0047] Ethylenically unsaturated free radical polymerizable compounds include monomers and polymer compounds containing carbon atoms, hydrogen atoms and oxygen atoms and optionally nitrogen and halogen. Oxygen atoms or nitrogen atoms or both are usually present in ethers, esters, polyurethanes, amides and urea groups. Ethylenically unsaturated free radical polymerizable compounds usually have a molecular weight lower than about 4,000 grams per mole, and are usually esters made by reacting compounds containing a single aliphatic hydroxyl group or multiple aliphatic hydroxyl groups with unsaturated carboxylic acids (such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid and maleic acid, etc.). Representative examples of ethylenically unsaturated free radical polymerizable compounds include methyl methacrylate, ethyl methacrylate, styrene, divinylbenzene, vinyltoluene, ethylene glycol diacrylate, ethylene glycol methacrylate, hexanediol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol methacrylate and pentaerythritol tetraacrylate. Other ethylenically unsaturated resins include monoallyl, polypropylene and polymethallyl esters and carboxylic acid amides, such as diallyl phthalate, diallyl adipate and N,N-diallyl adipamide, while other nitrogen-containing compounds include tris(2-acryloyloxyethyl)isocyanurate, 1,3,5-tris(2-methacryloyloxyethyl)-s-triazine, acrylamide, n-methacrylamide, N,N-dimethylacrylamide, n-vinylpyrrolidone and n-vinylpiperidone.

[0048] Useful aminoplast resins have at least one α,β-unsaturated carbonyl pendant group per molecule or per oligomer. These unsaturated carbonyl groups can be acrylate, methacrylate or acrylamide type groups. Examples of such materials include N-methylol acrylamide, N,N'-oxydimethylene bisacrylamide, ortho- and para-acrylamidomethylated phenols, acrylamidomethylated novolac resins, and combinations thereof. These materials are further described in U.S. Pat. Nos. 4,903,440 and 5,236,472 (both to Kirk et al.).

[0049] Isocyanurate derivatives having at least one pendant acrylic group and isocyanate derivatives having at least one pendant acrylic group are further described in US Pat. No. 4,652,274 (Boettcher et al.) An example of an isocyanurate material is the triacrylate of tris(hydroxyethyl)isocyanurate.

[0050] Compounds that generate a source of free radicals upon exposure to actinic electromagnetic radiation (eg, ultraviolet or visible electromagnetic radiation) are generally referred to as photoinitiators.

[0051] Examples of photoinitiators include: benzoin and its derivatives such as α-methylbenzoin; α-phenylbenzoin; α-allylbenzoin; α-benzylbenzoin; benzoin ethers such as benzyl dimethyl ketal, benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives such as 2-hydroxy-2-methyl-1-phenyl-1-propanone and 1-hydroxycyclohexyl phenyl ketone; 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone; and 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone. Other useful photoinitiators include, for example, neopentyl ethyl ether, anisole ethyl ether, anthraquinone (e.g., anthraquinone, 2-ethylanthraquinone, 1-chloroanthraquinone, 1,4-dimethylanthraquinone, 1-methoxyanthraquinone or benzanthraquinone), halomethyl triazines, benzophenones and their derivatives, iodonium and sulfonium salts, titanium complexes such as bis(eta..sub.5-2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium; halogenated nitrobenzenes (e.g., 4-bromomethylnitrobenzene), mono- and bis-acylphosphines. Combinations of photoinitiators may be used. One or more spectral sensitizers (e.g., dyes) may be used with the photoinitiator, for example, to increase the sensitivity of the photoinitiator to a particular source of actinic radiation.

[0052] If present, the photoinitiator may be in any amount effective to cure the curable binder precursor. Typical amounts are in the range of 0.1% to 5%, although greater and lesser amounts may be used.

[0053] To promote the connection between the above-mentioned binder and the abrasive particles, a silane coupling agent can be included in the slurry of the abrasive particles and the binder precursor; typically, the amount is about 0.01 wt% to 5 wt%, more typically about 0.01 wt% to 3 wt%, more typically about 0.01 wt% to 1 wt%, but other amounts can also be used, for example, depending on the size of the abrasive particles. Suitable silane coupling agents include, for example, methacryloxypropyl silane, vinyl triethoxy silane, vinyl tris (2-methoxyethoxy) silane, 3,4-epoxycyclohexylmethyl trimethoxy silane, γ-glycidoxypropyl trimethoxy silane and γ-mercaptopropyl trimethoxy silane, allyl triethoxy silane, diallyl dichloro silane, divinyl diethoxy silane and m-, p-phenylethyl trimethoxy silane, dimethyl diethoxy silane, dihydroxy diphenyl silane, triethoxy trichlorosilane, pentyltrichlorosilane, phenyltrichlorosilane, phenyltriethoxysilane, methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, dimethyldiethoxysilane and mixtures thereof.

[0054] The organic binder precursor (and therefore also the organic binder) may optionally contain additives such as, for example, colorants, grinding aids, fillers, wetting agents, dispersants, light stabilizers and antioxidants.

[0055] Grinding aids that can be optionally included in the abrasive layer by the binder precursor include a variety of different materials, including both organic compounds and inorganic compounds. Examples of chemical compounds that are effective as grinding aids include waxes, organic halides, halide salts, metals and metal alloys. Specific waxes that are effective as grinding aids specifically include, but are not limited to, halogenated waxes, tetrachloronaphthalene and pentachloronaphthalene. Other effective grinding aids include halogenated thermoplastics, sulfonated thermoplastics, waxes, halogenated waxes, sulfonated waxes and mixtures thereof. Other organic materials that are effective as grinding aids specifically include, but are not limited to, polyvinyl chloride and polyvinylidene chloride. Examples of halide salts that are usually effective as grinding aids include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluoride, potassium chloride and magnesium chloride. Halide salts used as grinding aids usually have an average particle size of less than 100 microns, preferably particles less than 25 microns. Examples of metals that are usually effective as grinding aids include antimony, bismuth, cadmium, cobalt, iron, lead, tin and titanium. Other commonly used grinding aids include sulfur, organic sulfur compounds, graphite and metal sulfides. Combinations of these grinding aids may also be used.

[0056] The abrasive particles should have sufficient hardness and surface roughness to be used as abrasive particles in the grinding process. Preferably, the abrasive particles have a Mohs hardness of at least 4, at least 5, at least 6, at least 7, or even at least 8. Exemplary abrasive particles include crushed abrasive particles, shaped abrasive particles (e.g., shaped ceramic abrasive particles or shaped abrasive composite particles), and combinations thereof.

[0057] Examples of suitable abrasive particles include: fused aluminum oxide; heat-treated aluminum oxide; white fused aluminum oxide; ceramic aluminum oxide materials, such as those commercially available from 3M Company, St. Paul, Minn, under the trade name 3M CERAMIC ABRASIVE GRAIN; brown aluminum oxide; blue aluminum oxide; silicon carbide (including green silicon carbide); titanium diboride; boron carbide; tungsten carbide; garnet; titanium carbide; diamond; cubic boron nitride; garnet; fused alumina-zirconia; iron oxide; chromium oxide; zirconium oxide; titanium dioxide; tin oxide; quartz; feldspar; flint; corundum; abrasive particles prepared by sol-gel method (e.g., including shaped and crushed forms); and combinations thereof. Additional examples include shaped abrasive composites of abrasive particles in a binder matrix, such as those described in U.S. Pat. No. 5,152,917 (Pieper et al.). Many such abrasive particles, agglomerates and composites are known in the art.

[0058] Examples of sol-gel prepared abrasive particles and methods of preparing the same can be found in U.S. Pat. No. 4,314,827 (Leitheiser et al.); U.S. Pat. No. 4,623,364 (Cottringer et al.); U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe et al.); and U.S. Pat. No. 4,881,951 (Monroe et al.). It is also contemplated that the abrasive particles may include grinding agglomerates such as, for example, those described in U.S. Pat. No. 4,652,275 (Bloecher et al.) or U.S. Pat. No. 4,799,939 (Bloecher et al.). In some embodiments, the abrasive particles may be surface treated with a coupling agent (e.g., an organosilane coupling agent) or otherwise physically treated (e.g., iron oxide or titanium oxide) to enhance adhesion of the abrasive particles to the binder. The abrasive particles may be treated before they are combined with the binder, or they may be surface treated in situ by including a coupling agent in the binder.

[0059] Preferably, the abrasive particles comprise ceramic abrasive particles, such as, for example, polycrystalline alpha alumina particles prepared by a sol-gel process. The abrasive particles may be crushed abrasive particles or shaped abrasive particles or a combination thereof.

[0060] Shaped ceramic abrasive particles composed of crystallites of alpha alumina, magnesia aluminate spinel, and rare earth hexaaluminate can be prepared using a sol-gel alpha alumina particle precursor according to the methods described in, for example, U.S. Pat. No. 5,213,591 (Celikkaya et al.) and U.S. Published Patent Application Nos. 2009 / 0165394 A1 (Culler et al.) and 2009 / 0169816 A1 (Erickson et al.).

[0061] Shaped ceramic abrasive particles based on alpha-alumina can be prepared according to a well-known multi-step process. Briefly, the method includes the steps of preparing a sol-gel alpha alumina precursor dispersion that can be converted to alpha alumina, either with or without seeds; filling one or more mold cavities having shaped abrasive particles of the desired shape with the sol-gel, drying the sol-gel to form shaped ceramic abrasive particle precursors; removing the shaped ceramic abrasive particle precursors from the mold cavities; calcining the shaped ceramic abrasive particle precursors to form calcined shaped ceramic abrasive particle precursors, and then sintering the calcined shaped ceramic abrasive particle precursors to form shaped ceramic abrasive particles.

[0062] More details on methods of making sol-gel prepared abrasive particles can be found, for example, in U.S. Pat. No. 4,314,827 (Leitheiser); U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,435,816 (Spurgeon et al.); U.S. Pat. No. 5,672,097 (Hoopman et al.); U.S. Pat. No. 5,946,991 (Hoopman et al.); U.S. Pat. No. 5,975,987 (Hoopman et al.); and U.S. Published Patent Application No. 2009 / 0165394 Al (Culler et al.).

[0063] Although there is no particular limitation on the shape of the shaped ceramic abrasive particles, the abrasive particles are preferably formed into a predetermined shape, for example, by forming precursor particles containing a ceramic precursor material (e.g., boehmite sol-gel) using a mold and then sintering. The shaped ceramic abrasive particles can be shaped into, for example, prisms, pyramids, truncated pyramids (e.g., truncated triangular pyramids) and / or some other regular or irregular polygons. The abrasive particles can include a single abrasive particle or an abrasive aggregate formed by an abrasive mixture of two or more abrasives or two or more abrasives. In some embodiments, the shaped ceramic abrasive particles are precisely shaped, and a single shaped ceramic abrasive particle will have a shape that is substantially the shape of a portion of a cavity of a mold or production tool in which the particle precursor is dried before optional calcination and sintering.

[0064] The shaped ceramic abrasive particles used in the present disclosure can generally be prepared using a tool (i.e., a mold) and cut using precision machining, thereby providing a higher definition of features than other fabrication alternatives (such as, for example, stamping or punching). Typically, the cavities in the tool surface have planar faces that meet along sharp edges and form the sides and tops of truncated pyramids. The resulting shaped ceramic abrasive particles have a corresponding nominal average shape corresponding to the shape of the cavities in the tool surface (e.g., truncated pyramids); however, variations (e.g., random variations) from the nominal average shape can occur during fabrication, and shaped ceramic abrasive particles that exhibit such variations are included within the definition of shaped ceramic abrasive particles as used herein.

[0065] In some embodiments, the base and top of the shaped ceramic abrasive particles are substantially parallel, resulting in a prism or truncated pyramid shape, but this is not required. In some embodiments, the sides of the truncated pyramid have equal dimensions and form a dihedral angle of about 82 degrees with the base. However, it should be understood that other dihedral angles (including 90 degrees) can also be used. For example, the dihedral angle between the base and each of the sides can independently be in the range of 45 to 90 degrees, typically 70 to 90 degrees, and more typically 75 to 85 degrees.

[0066] As used herein, when referring to shaped ceramic abrasive particles, the term "length" refers to the largest dimension of the shaped abrasive particle. "Width" refers to the largest dimension of the shaped abrasive particle perpendicular to the length. The terms "thickness" or "height" refer to the dimension of the shaped abrasive particle perpendicular to the length and width.

[0067] Preferably, the ceramic abrasive particles include shaped ceramic abrasive particles. Examples of shaped α-alumina (i.e., ceramic) abrasive particles produced by a sol-gel process can be found in U.S. Pat. No. 5,201,916 (Berg), U.S. Pat. No. 5,366,523 (Rowenhorst (Re 35,570)); and U.S. Pat. No. 5,984,988 (Berg). U.S. Pat. No. 8,034,137 (Erickson et al.) describes alumina abrasive particles that have been formed into a specific shape and then crushed to form fragments that retain a portion of their original shape features. In some embodiments, the shaped α-alumina particles produced by a sol-gel process are precisely shaped (i.e., the particles have a shape that is at least partially determined by the shape of the cavity in the production tool used to produce them). Details regarding such abrasive grains and methods for making them can be found, for example, in U.S. Pat. No. 8,142,531 (Adefris et al.), U.S. Pat. No. 8,142,891 (Culler et al.), and U.S. Pat. No. 8,142,532 (Erickson et al.); and U.S. Patent Application Publication Nos. 2012 / 0227333 (Adefris et al.); 2013 / 0040537 (Schwabel et al.) and 2013 / 0125477 (Adefris).

[0068] In some preferred embodiments, the abrasive particles include shaped ceramic abrasive particles (eg, shaped sol-gel derived polycrystalline alpha-alumina particles) that are generally triangular in shape (eg, triangular prisms or truncated three-sided pyramids).

[0069] The length of the shaped ceramic abrasive particles is typically selected to be in the range of 1 micron to 15,000 microns, more typically 10 microns to about 10,000 microns, and still more typically 150 microns to 2,600 microns, although other lengths may be used. In some embodiments, the length may be expressed as a fraction of the thickness of the bonded abrasive wheel in which it is contained. For example, the shaped abrasive particles may have a length greater than half the thickness of the bonded abrasive wheel. In some embodiments, the length may be greater than the thickness of the bonded abrasive cut-off wheel.

[0070] The width of the shaped ceramic abrasive particles is typically selected to be in the range of 0.1 micrometers to 3500 micrometers, more typically 100 micrometers to 3000 micrometers, and more typically 100 micrometers to 2600 micrometers, although other lengths can be used.

[0071] The thickness of the shaped ceramic abrasive particles is typically selected to be in the range of 0.1 micrometers to 1600 micrometers, more typically 1 micrometer to 1200 micrometers, although other thicknesses can be used.

[0072] In some embodiments, the shaped ceramic abrasive particles can have an aspect ratio (ratio of length to thickness) of at least 2, 3, 4, 5, 6, or more.

[0073] The grid abrasive product according to the present disclosure can be prepared, for example, by a method comprising the following sequential and optionally consecutive steps.

[0074] First, a production tool having a mold surface defining a plurality of shaped cavities is coated with an abrasive composite precursor slurry to fill the shaped cavities. The abrasive composite precursor slurry includes abrasive particles dispersed in a curable binder precursor.

[0075] Next, the mold surface is contacted with an open grid backing comprising interwoven wires defining openings and having opposing first and second major sides.

[0076] Once in contact, the composite assembly is ultrasonically vibrated to ensure good coating of the wire by the abrasive composite precursor slurry.

[0077] Suitable ultrasonic devices are well known in the art and may include, for example, commercially available ultrasonic processing generators equipped with a horn, a cutter, a blade, or a plate. As used herein, the term "ultrasonic" refers to a vibration frequency greater than about 20,000 Hz. Examples of commercially available suitable ultrasonic devices include those available from Branson Ultrasonics, Danbury, Connecticut, USA.

[0078] Next, the curable binder precursor is exposed to enough actinic electromagnetic radiation to cause curing. Suitable actinic (e.g., ultraviolet and / or visible light) electromagnetic radiation sources are well known in the art, and include, for example, low, medium and / or high pressure mercury lamps, lasers, microwave driven lamps and xenon flash lamps. Exposure conditions generally depend on lamp type, intensity and exposure duration, and are within the capabilities of those skilled in the art.

[0079] Once cured, the production tool is removed, leaving behind an open-grid abrasive product including isolated shaped abrasive composites contacting and secured to the first major side.

[0080] Selected Embodiments of the Disclosure

[0081] In a first embodiment, the present disclosure provides a method for preparing a grid abrasive product, the method comprising, in order:

[0082] providing a production tool having a mold surface defining a plurality of forming cavities;

[0083] filling at least some of the shaped cavities with an abrasive composite precursor slurry, wherein the abrasive composite precursor slurry comprises abrasive particles dispersed in a curable binder precursor;

[0084] contacting the mold surface with an open mesh backing comprising interwoven threads defining openings and having opposing first and second major sides;

[0085] ultrasonically vibrating the abrasive composite precursor slurry;

[0086] curing the curable binder precursor by exposing the curable binder precursor to sufficient actinic electromagnetic radiation to provide isolated shaped abrasive composites contacting and secured to the first major side of the open grid backing; and

[0087] The grid abrasive product is separated from the production tool.

[0088] In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the wire has an average diameter, and wherein the average length and width of the openings are 0.5 to 10 times the average diameter of the wire.

[0089] In a third embodiment, the present disclosure provides a method according to the first or second embodiment, wherein the curable binder precursor comprises a curable acrylic binder precursor.

[0090] In a fourth embodiment, the present disclosure provides a method according to any one of the first to third embodiments, wherein the isolated shaped abrasive composites comprise at least one of triangular, square, rectangular, or hexagonal columns.

[0091] In a fifth embodiment, the present disclosure provides a method according to any one of the first to fourth embodiments, wherein at least some of the isolated shaped abrasive composites contact at least six wires, preferably at least nine wires.

[0092] In a sixth embodiment, the present disclosure provides a method according to any one of the first to fifth embodiments, wherein the open mesh backing further includes an attachment layer secured to the second major side of the open mesh backing, wherein the attachment layer includes a loop portion or a hook portion of a two-part hook-and-loop fastening system.

[0093] In a seventh embodiment, the present disclosure provides a method according to any one of the first to sixth embodiments, wherein the isolated shaped abrasive composites do not contact the second major side.

[0094] In an eighth embodiment, the present disclosure provides a grid abrasive product comprising:

[0095] an open mesh backing comprising interwoven threads defining openings and having opposing first and second major sides; and

[0096] A plurality of isolated shaped abrasive composites are in contact with and secured to the first major side, wherein the isolated shaped abrasive composites include abrasive particles dispersed in an organic binder, and wherein the isolated shaped abrasive composites are not in contact with each other.

[0097] In a ninth embodiment, the present disclosure provides a grid abrasive product according to the eighth embodiment, wherein the wire has an average diameter, and wherein the average length and width of the openings are 0.5 to 10 times the average diameter of the wire.

[0098] In a tenth embodiment, the present disclosure provides a web abrasive product according to the eighth or ninth embodiment, wherein at least a portion of each isolated abrasive composite comprises a shaped abrasive composite.

[0099] In an eleventh embodiment, the present disclosure provides a grid abrasive product according to any one of the eighth to tenth embodiments, wherein the organic binder comprises an acrylic binder.

[0100] In a twelfth embodiment, the present disclosure provides a grid abrasive product according to any one of the eighth to eleventh embodiments, wherein the isolated shaped abrasive composites include at least one of triangular, square, rectangular, or hexagonal columns.

[0101] In a thirteenth embodiment, the present disclosure provides a grid abrasive product according to any one of the eighth to twelfth embodiments, wherein at least some of the shaped abrasive composites contact at least six wires.

[0102] In a fourteenth embodiment, the present disclosure provides a grid abrasive product according to any one of the eighth to thirteenth embodiments, wherein at least some of the shaped abrasive composites contact at least nine wires.

[0103] In a fifteenth embodiment, the present disclosure provides a web abrasive product according to any one of the eighth to fourteenth embodiments, wherein the isolated shaped abrasive composites do not contact the second major side.

[0104] In a sixteenth embodiment, the present disclosure provides a grid abrasive product according to any one of the eighth to fifteenth embodiments, further comprising an attachment layer secured to the second major side of the open grid backing, wherein the attachment layer comprises a loop portion or a hook portion of a two-part hook-and-loop fastening system.

[0105] Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

[0106] Example

[0107] Unless otherwise indicated, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight.

[0108] The digital micrographs of the examples were obtained using a KEYENCE optical microscope, Model VK-5000, available from Keyence Corp., Osaka, Japan.

[0109] Table 1 below reports the materials used in the examples.

[0110] Table 1

[0111]

[0112]

[0113] General Procedure for Preparing Structured Grid Abrasive Products :

[0114] The production tool is used to prepare a structured abrasive having a precise shape and distribution on a grid backing. The production tool having a plurality of precisely shaped recesses is coated with an abrasive slurry so as to fill the precisely shaped recesses. The front surface of the backing is then contacted with the abrasive slurry. To promote contact between the slurry and the grid backing, the production tool or the grid backing is ultrasonically treated for 5 to 20 seconds. With the aid of ultrasonic vibrations, the yarns of the grid backing absorb the wet slurry in the cavity to form contact between the slurry and the yarns. Upon contact, the abrasive slurry is exposed to actinic radiation for 5 to 20 seconds, which is sufficient to at least partially cure or harden the binder precursor of the abrasive slurry. Optionally, additional curing may be applied to fix the contact between the slurry and the yarns of the grid backing. For example, by facing the grid backing toward the source of actinic radiation, the sample is further cured by actinic radiation. Finally, the backing with the abrasive coating bonded thereon is removed from the mold surface of the production tool to produce a grid abrasive product.

[0115] Comparative Example A

[0116] A production tool with closely packed hexagonal cavities was used to prepare Comparative Example A. The hexagonal cavities were evenly distributed into the mold cavities on the mold surface of the production tool and had a side length of 3500 microns, a depth of 450 microns, and a wall thickness of 2000 microns between cavities.

[0117] Abrasive slurry is applied to the tool using a tongue depressor to fill the opening in the production tool. Abrasive slurry (110.3 grams) is applied to a 9 inch x 11 inch (23 cm x 28 cm) surface area on the production tool to fill all cavities. With a 2 inch (5.1 cm) wide masking tape, the grid backing is affixed to the tool surface of the coating, wherein the ringless side faces the tool surface. The grid backing is clamped with a friction roller so that the grid backing is laminated to the slurry on the production tool surface. The grid is cured together with the tool by passing through a curing chamber (Fusion UV Systems, Gaithersburg, Maryland) of DRE 410Q UV, which is equipped with two 600 watt "D-type" Fusion lamps set at high power. The production tool is then separated from the grid backing, so that the shaped abrasive composite cured is retained in the production tool cavity and will not adhere to the grid backing.

[0118] Comparative Example B

[0119] The procedure of Comparative Example A was repeated, except that 160.8 g of slurry was applied to a 9 inch x 11 inch (23 cm x 28 cm) surface area on the production tool to fill all cavities. Excess slurry was applied to the tool to provide a slight excess landing area to facilitate abrasive coating transfer. After UV curing, the production tool was separated from the grid backing to obtain a cured structured abrasive composite fixed to the grid backing; however, the cured abrasive composite covered all openings of the grid backing between the shaped abrasive composites. Figure 2 A digital micrograph of the grinding side of the structured grid abrasive prepared in Comparative Example B is shown in FIG.

[0120] Example 1

[0121] The procedure of Comparative Example A was repeated, except that after the grid backing was attached to the production tool, the combined assembly was clamped with an ultrasonic horn. The horn was vibrated at a frequency of 19100 Hz with an amplitude of about 130 microns. The horn was made of 6-4 titanium and driven by a 900 watt 184V Branson power supply coupled with a 2:1 Booster 802 piezoelectric converter. After passing through the ultrasonic horn, the grid backing was cured in a UV curing chamber together with the tool. After UV curing, the production tool was separated from the grid backing to obtain a grid abrasive product having a shaped abrasive composite adhered to the isolation of the grid backing. All cured abrasive slurries were successfully transferred to the grid backing, and all openings on the grid backing between the hexagons remained substantially open. Figure 3 A digital micrograph of the grinding side of the structured grid abrasive prepared in Example 1 is shown in FIG.

[0122] Example 2

[0123] The procedure of Example 1 was repeated except that: (1) a production tool having closely packed square mold cavities (3600 microns in side length, 500 microns in depth, and 2500 microns in wall thickness between cavities) was used; and (2) a blend ore of 10 parts P220 grade SAP and 90 parts P220 grade AO was used. Figure 4A and Figure 4B Images of the annular side and the abrasive side, respectively, of a 3.5 inch (8.9 cm) grid abrasive disk prepared according to Example 2 are shown. Figure 4C Shows Figure 4B A magnified view of .

[0124] All references, patents, and patent applications cited in this application are incorporated by reference in a consistent manner. In the event of inconsistencies or conflicts between the incorporated references and this application, the information in this application shall prevail. The foregoing description given to enable one of ordinary skill in the art to practice the disclosure protected by the claims should not be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereof.

Claims

1. A method for preparing a grid abrasive product, the method comprising in order: providing a production tool having a mold surface defining a plurality of forming cavities; filling at least some of the shaped cavities with an abrasive composite precursor slurry, wherein the abrasive composite precursor slurry comprises abrasive particles dispersed in a curable binder precursor; contacting the mold surface with an open mesh backing comprising interwoven threads defining openings and having opposing first and second major sides; ultrasonically vibrating the abrasive composite precursor slurry; curing the curable binder precursor by exposing the curable binder precursor to sufficient actinic electromagnetic radiation to provide isolated shaped abrasive composites contacting and secured to the first major side of the open grid backing; and The grid abrasive product is separated from the production tool. 2 . The method of claim 1 , wherein the wire has an average diameter, and wherein the average length and width of the openings are 0.5 to 10 times the average diameter of the wire.

3. The method of claim 1, wherein the curable binder precursor comprises a curable acrylic binder precursor.

4. The method of claim 1, wherein the isolated shaped abrasive composites comprise at least one of triangular, square, rectangular, or hexagonal columns.

5. The method of claim 1, wherein at least some of the isolated shaped abrasive composites contact at least six wires.

6. The method of claim 1 wherein the open mesh backing further comprises an attachment layer secured to the second major side of the open mesh backing, wherein the attachment layer comprises a loop portion or a hook portion of a two-part hook and loop fastening system.

7. The method of claim 1, wherein the isolated shaped abrasive composites do not contact the second major side.

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