EP3720656A1 - Article abrasif lié et son procédé de réalisation - Google Patents

Article abrasif lié et son procédé de réalisation

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Publication number
EP3720656A1
EP3720656A1 EP18886655.2A EP18886655A EP3720656A1 EP 3720656 A1 EP3720656 A1 EP 3720656A1 EP 18886655 A EP18886655 A EP 18886655A EP 3720656 A1 EP3720656 A1 EP 3720656A1
Authority
EP
European Patent Office
Prior art keywords
bonded abrasive
precursor
abrasive particles
matrix
bonded
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18886655.2A
Other languages
German (de)
English (en)
Inventor
Melissa C. SCHILLO-ARMSTRONG
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Innovative Properties Co
Original Assignee
3M Innovative Properties Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Co filed Critical 3M Innovative Properties Co
Publication of EP3720656A1 publication Critical patent/EP3720656A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
    • B24D5/12—Cut-off wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
    • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
    • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
    • B24D3/28—Resins or natural or synthetic macromolecular compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
    • B24D18/0009—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using moulds or presses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
    • B24D3/001—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as supporting member
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1409—Abrasive particles per se
    • C09K3/1427—Abrasive particles per se obtained by division of a mass agglomerated by melting, at least partially, e.g. with a binder

Definitions

  • the present disclosure broadly relates to bonded abrasive articles and methods of making and using them.
  • Bonded abrasives include abrasive particles retained in a binder.
  • Bonded abrasive types include, for example, grinding wheels, cutoff wheels, hones, whetstones.
  • Two types of binders are commonly used. These include glassy inorganic binders (vitreous bond) and resinous organic binders (resin bond).
  • Many bonded abrasive articles include a phenolic binder that includes the reaction product of one or more curable phenolic resins.
  • Such phenolic bonded abrasive products typically have an unpleasant odor during
  • the odor may be a complex mixture of aromatic components.
  • the interaction between the various smells gives rise to an overall smell, often in a complex manner.
  • a fragrance additives may be included in the phenolic resin- bond formulation that emits a more aesthetically pleasing smell during the wheel use. While many fragrances might be used, the present inventor has serendipitously discovered that ethyl maltol provides an aesthetically pleasing aroma in phenolic resin-bond abrasive wheels, resulting in an aroma similar to that of baking bread during use, that overcomes the problem of unpleasant odor during grinding.
  • the present disclosure provides a bonded abrasive article comprising a bonded abrasive matrix, wherein the bonded abrasive matrix comprises, based on the total weight of the bonded abrasive matrix:
  • the present disclosure provides a method of making a bonded abrasive article, the method comprising:
  • mixing components comprising:
  • curable phenolic binder precursor
  • the curable phenolic binder precursor comprises, based on the total weight of the bonded abrasive matrix, 10 to 30 weight percent of phenolic binder, abrasive particles retained in the phenolic binder, and 0.001 to 9 weight percent of the ethyl maltol.
  • bonded abrasive matrix refers to a unitary mass of abrasive particles, binder resin, and optional additives such as, for example, fillers, pore former, fragrances, reinforcing fibers and scrims, and antiloading compounds. It does not include extraneous components of bonded abrasive articles such as, for example, wheel hubs, shafts, and labels.
  • FIG. 1 is a schematic perspective view of an exemplary bonded abrasive cut-off wheel according to one embodiment of the present disclosure.
  • FIG. 2 is a schematic cross-sectional side view of exemplary bonded abrasive cut-off wheel shown in FIG. 1 taken along line 2-2.
  • Bonded abrasive articles include abrasive particles retained in a bonded abrasive matrix (also known as a binder).
  • the bonded abrasive matrix includes a phenolic binder formed by curing a curable resole phenolic resin, novolac phenolic resin, or preferably a combination of resole phenolic resin and novolac phenolic resin.
  • Novolac phenolic resins are characterized by being acid-catalyzed and having a ratio of formaldehyde to phenol of less than one, typically between 0.5: 1 and 0.8: 1.
  • Resole phenolic resins are characterized by being alkaline-catalyzed and having a ratio of formaldehyde to phenol of greater than or equal to one, typically from 1: 1 to 3: 1.
  • Novolac and resole phenolic resins may be chemically modified (e.g., by reaction with epoxy compounds), or they may be unmodified.
  • Curable phenolic resins are well-known and readily available from commercial sources.
  • novolac resins examples include DUREZ 1364, a two-step, powdered phenolic resin (marketed by Durez Corporation of Addison, Texas, under the trade designation VARCUM (e.g., 29302)), or HEXION AD5534 RESIN (marketed by Hexion Specialty Chemicals, Inc. of Louisville, Kentucky).
  • VARCUM e.g., 29302
  • HEXION AD5534 RESIN marketed by Hexion Specialty Chemicals, Inc. of Louisville, Kentucky
  • resole phenolic resins useful in practice of the present disclosure include those marketed by Durez Corporation under the trade designation VARCUM (e.g., 29217, 29306, 29318, 29338, 29353); those marketed by Ashland Chemical Co.
  • AEROFENE e.g., AEROFENE 295
  • PHENOLITE e.g., PHENOLITE TD-2207
  • Curable phenolic resins may include at least one catalyst to facilitate curing.
  • Exemplary acidic catalysts suitable for curing phenolic resins include sulfuric, hydrochloric, phosphoric, oxalic, and p- toluene sulfonic acids.
  • Alkaline catalysts suitable for curing phenolic resins include sodium hydroxide, barium hydroxide, potassium hydroxide, calcium hydroxide, organic amines, or sodium carbonate.
  • Catalysts and/or initiators may be added to the bonded abrasive matrix precursor (i.e., material that after curing forms the bonded abrasive matrix) depending on the desired organic binder material.
  • bonded abrasive matrix precursor i.e., material that after curing forms the bonded abrasive matrix
  • heat is applied to advance curing of the bonded abrasive matrix precursor material; however, other sources of energy (e.g., microwave radiation, ultraviolet light, visible light) may also be used.
  • sources of energy e.g., microwave radiation, ultraviolet light, visible light
  • the bonded abrasive matrix comprises 10 to 30 weight percent, preferably 15 to 25 weight percent, of phenolic binder, based on the total weight of the bonded abrasive matrix.
  • the curable phenolic resin includes a mixture of 4 to 8 parts by weight of resole phenolic resin for every 8 to 16 parts by weight of novolac phenolic resin, preferably 5 to 7 parts by weight of resole phenolic resin for every 9 to 15 parts of by weight novolac phenolic resin, and more preferably 6 parts by weight of resole phenolic resin for about every 10 to 14 parts by weight of novolac phenolic resin.
  • Phenolic resin may be used in both the powder form and liquid state. Although phenolic resins are widely used, it is within the scope of this disclosure to include other organic binder materials including, for example, epoxy resins, urea-formaldehyde resins, aminoplasts, and epoxy-reactive acrylic binders. The organic binder material may also be modified with other binder materials to improve or alter the properties of the binder material.
  • the bonded abrasive articles include from about 10 to about 70 percent by weight of abrasive particles (e.g., shaped and/or crushed abrasive particles), typically 30 to 65 percent by weight, and more typically 45 to 65 percent by weight, based on the total weight of the binder material and abrasive particles.
  • abrasive particles e.g., shaped and/or crushed abrasive particles
  • the bonded abrasive articles may comprise crushed abrasive particles whether by themselves or in combination with shaped abrasive particles. If shaped abrasive particles and crushed abrasive particles are both used, the crushed abrasive particles are typically of a finer size grade or grades (e.g., if a plurality of size grades are used) than the shaped abrasive particles, although this is not a requirement.
  • Useful crushed abrasive particles include, for example, crushed particles of fused aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, ceramic aluminum oxide materials such as those commercially available under the trade designation 3M CERAMIC ABRASIVE GRAIN from 3M Company of St.
  • sol-gel derived abrasive particles can be found in U. S. Patent Nos. 4,314,827 (Leitheiser et al.), 4,623,364 (Cottringer et al.), 4,744,802 (Schwabel), 4,770,671 (Monroe et al.), and 4,881,951 (Monroe et al.). It is also contemplated that the abrasive particles may comprise abrasive agglomerates such, for example, as those described in U. S. Patent Nos. 4,652,275 (Bloecher et al.) or 4,799,939 (Bloecher et al.).
  • Abrasive particles e.g., shaped and/or crushed abrasive particles
  • abrasive particles composed of crystallites of alpha alumina, magnesium alumina spinel, and a rare earth hexagonal aluminate
  • sol-gel precursor alpha alumina particles may be prepared using sol-gel precursor alpha alumina particles according to methods described in, for example, U. S. Patent No. 5,213,591 (Celikkaya et al.) and U. S. Pat. Appln. Publ. Nos. 2009/0165394 Al (Culler et al.) and 2009/0169816 Al (Erickson et al.).
  • alpha alumina based abrasive particles can be made according to a multistep process.
  • the method comprises the steps of making either a seeded or non-seeded sol-gel alpha alumina precursor dispersion that can be converted into alpha alumina; filling one or more mold cavities having the desired outer shape of the shaped abrasive particle with the sol-gel, drying the sol-gel to form precursor abrasive particles; removing the precursor shaped abrasive particles from the mold cavities; calcining the precursor shaped abrasive particles to form calcined, precursor shaped abrasive particles, and then sintering the calcined, precursor shaped abrasive particles to form shaped abrasive particles.
  • the process will now be described in greater detail.
  • the first process step involves providing either a seeded or non-seeded dispersion of an alpha alumina precursor that can be converted into alpha alumina.
  • the alpha alumina precursor dispersion often comprises a liquid that is a volatile component.
  • the volatile component is water.
  • the dispersion should comprise a sufficient amount of liquid for the viscosity of the dispersion to be sufficiently low to enable filling mold cavities and replicating the mold surfaces, but not so much liquid as to cause subsequent removal of the liquid from the mold cavity to be prohibitively expensive.
  • the alpha alumina precursor dispersion comprises from 2 percent to 90 percent by weight of the particles that can be converted into alpha alumina, such as particles of aluminum oxide monohydrate (boehmite), and at least 10 percent by weight, or from 50 percent to 70 percent, or 50 percent to 60 percent, by weight of the volatile component such as water.
  • the alpha alumina precursor dispersion in some embodiments contains from 30 percent to 50 percent, or 40 percent to 50 percent, by weight solids.
  • Boehmite can be prepared by known techniques or can be obtained commercially. Examples of commercially available boehmite include products having the trade designations "DISPERAL”, and “DISPAL”, both available from Sasol North America, Inc. of Houston, Texas, or "HiQ-40” available from BASF Corporation of Florham Park, New Jersey. These aluminum oxide monohydrates are relatively pure; that is, they include relatively little, if any, hydrate phases other than monohydrates, and have a high surface area.
  • the physical properties of the resulting shaped abrasive particles will generally depend upon the type of material used in the alpha alumina precursor dispersion.
  • the alpha alumina precursor dispersion is in a gel state.
  • a "gel” is a three-dimensional network of solids dispersed in a liquid.
  • the alpha alumina precursor dispersion may contain a modifying additive or precursor of a modifying additive.
  • the modifying additive can function to enhance some desirable property of the abrasive particles or increase the effectiveness of the subsequent sintering step.
  • Modifying additives or precursors of modifying additives can be in the form of soluble salts, typically water-soluble salts.
  • They typically consist of a metal-containing compound and can be a precursor of oxide of magnesium, zinc, iron, silicon, cobalt, nickel, zirconium, hafnium, chromium, yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum, gadolinium, cerium, dysprosium, erbium, titanium, and mixtures thereof.
  • concentrations of these additives that can be present in the alpha alumina precursor dispersion can be varied based on skill in the art.
  • the introduction of a modifying additive or precursor of a modifying additive will cause the alpha alumina precursor dispersion to gel.
  • the alpha alumina precursor dispersion can also be induced to gel by application of heat over a period of time.
  • the alpha alumina precursor dispersion can also contain a nucleating agent (seeding) to enhance the transformation of hydrated or calcined aluminum oxide to alpha alumina.
  • Nucleating agents suitable for this disclosure include fine particles of alpha alumina, alpha ferric oxide or its precursor, titanium oxides and titanates, chrome oxides, or any other material that will nucleate the transformation. The amount of nucleating agent, if used, should be sufficient to effect the transformation of alpha alumina. Nucleating such alpha alumina precursor dispersions is disclosed in U. S. Patent No. 4,744,802 (Schwabel).
  • a peptizing agent can be added to the alpha alumina precursor dispersion to produce a more stable hydrosol or colloidal alpha alumina precursor dispersion.
  • Suitable peptizing agents are monoprotic acids or acid compounds such as acetic acid, hydrochloric acid, formic acid, and nitric acid. Multiprotic acids can also be used but they can rapidly gel the alpha alumina precursor dispersion, making it difficult to handle or to introduce additional components thereto.
  • Some commercial sources of boehmite contain an acid titer (such as absorbed formic or nitric acid) that will assist in forming a stable alpha alumina precursor dispersion.
  • the alpha alumina precursor dispersion can be formed by any suitable means, such as, for example, by simply mixing aluminum oxide monohydrate with water containing a peptizing agent or by forming an aluminum oxide monohydrate slurry to which the peptizing agent is added. Defoamers or other suitable chemicals can be added to reduce the tendency to form bubbles or entrain air while mixing. Additional chemicals such as wetting agents, alcohols, or coupling agents can be added if desired.
  • the alpha alumina abrasive particles may contain silica and iron oxide as disclosed in U. S. Patent No. 5,645,619 (Erickson et al.).
  • the alpha alumina abrasive particles may contain zirconia as disclosed in U. S. Patent No. 5,551,963 (Larmie).
  • the alpha alumina abrasive particles can have a microstructure or additives as disclosed in U. S. Patent No. 6,277,161 (Castro).
  • the second process step involves providing a mold having at least one mold cavity, and preferably a plurality of cavities.
  • the mold can have a generally planar bottom surface and a plurality of mold cavities.
  • the plurality of cavities can be formed in a production tool.
  • the production tool can be a belt, a sheet, a continuous web, a coating roll such as a rotogravure roll, a sleeve mounted on a coating roll, or die.
  • the production tool comprises polymeric material.
  • suitable polymeric materials include thermoplastics such as polyesters, polycarbonates, poly(ether sulfone), poly(methyl methacrylate), polyurethanes, polyvinylchloride, polyolefin, polystyrene, polypropylene, polyethylene or combinations thereof, or thermosetting materials.
  • the entire tooling is made from a polymeric or thermoplastic material.
  • the surfaces of the tooling in contact with the sol-gel while drying, such as the surfaces of the plurality of cavities comprises polymeric or thermoplastic materials and other portions of the tooling can be made from other materials.
  • a suitable polymeric coating may be applied to a metal tooling to change its surface tension properties by way of example.
  • a polymeric or thermoplastic tool can be replicated off a metal master tool.
  • the master tool will have the inverse pattern desired for the production tool.
  • the master tool can be made in the same manner as the production tool.
  • the master tool is made out of metal, e.g., nickel and is diamond turned.
  • the polymeric sheet material can be heated along with the master tool such that the polymeric material is embossed with the master tool pattern by pressing the two together.
  • a polymeric or thermoplastic material can also be extruded or cast onto the master tool and then pressed.
  • the thermoplastic material is cooled to solidify and produce the production tool. If a thermoplastic production tool is utilized, then care should be taken not to generate excessive heat that may distort the thermoplastic production tool limiting its life.
  • Access to cavities can be from an opening in the top surface or bottom surface of the mold.
  • the cavities can extend for the entire thickness of the mold.
  • the cavities can extend only for a portion of the thickness of the mold.
  • the top surface is substantially parallel to bottom surface of the mold with the cavities having a substantially uniform depth.
  • At least one side of the mold, that is, the side in which the cavities are formed, can remain exposed to the surrounding atmosphere during the step in which the volatile component is removed.
  • the cavities have a specified three-dimensional shape to make the shaped abrasive particles.
  • the depth dimension is equal to the perpendicular distance from the top surface to the lowermost point on the bottom surface.
  • the depth of a given cavity can be uniform or can vary along its length and/or width.
  • the cavities of a given mold can be of the same shape or of different shapes.
  • the third process step involves filling the cavities in the mold with the alpha alumina precursor dispersion (e.g., by a conventional technique).
  • a knife roll coater or vacuum slot die coater can be used.
  • a mold release can be used to aid in removing the particles from the mold if desired.
  • Typical mold release agents include oils such as peanut oil or mineral oil, fish oil, silicones, polytetrafluoroethylene, zinc stearate, and graphite.
  • mold release agent such as peanut oil, in a liquid, such as water or alcohol, is applied to the surfaces of the production tooling in contact with the sol-
  • the top surface of the mold is coated with the alpha alumina precursor dispersion.
  • the alpha alumina precursor dispersion can be pumped onto the top surface.
  • a scraper or leveler bar can be used to force the alpha alumina precursor dispersion fully into the cavity of the mold.
  • the remaining portion of the alpha alumina precursor dispersion that does not enter cavity can be removed from top surface of the mold and recycled.
  • a small portion of the alpha alumina precursor dispersion can remain on the top surface and in other embodiments the top surface is substantially free of the dispersion.
  • the pressure applied by the scraper or leveler bar is typically less than 100 psi (0.7 MPa), less than 50 psi (0.3 MPa), or even less than 10 psi (69 kPa).
  • no exposed surface of the alpha alumina precursor dispersion extends substantially beyond the top surface to ensure uniformity in thickness of the resulting shaped abrasive particles.
  • the fourth process step involves removing the volatile component to dry the dispersion.
  • the volatile component is removed by fast evaporation rates.
  • removal of the volatile component by evaporation occurs at temperatures above the boiling point of the volatile component.
  • An upper limit to the drying temperature often depends on the material the mold is made from.
  • the temperature should be less than the melting point of the plastic.
  • the drying temperatures can be between about 90 °C to about 165 °C, or between about 105 °C to about 150 °C, or between about 105 °C to about 120 °C. Higher temperatures can lead to improved production speeds but can also lead to degradation of the polypropylene tooling limiting its useful life as a mold.
  • the fifth process step involves removing resultant precursor shaped abrasive particles with from the mold cavities.
  • the precursor shaped abrasive particles can be removed from the cavities by using the following processes alone or in combination on the mold: gravity, vibration, ultrasonic vibration, vacuum, or pressurized air to remove the particles from the mold cavities.
  • the precursor abrasive particles can be further dried outside of the mold. If the alpha alumina precursor dispersion is dried to the desired level in the mold, this additional drying step is not necessary. However, in some instances it may be economical to employ this additional drying step to minimize the time that the alpha alumina precursor dispersion resides in the mold.
  • the precursor shaped abrasive particles will be dried from 10 to 480 minutes, or from 120 to 400 minutes, at a temperature from 50 °C to 160 °C, or at 120 °C to 150 °C.
  • the sixth process step involves calcining the precursor shaped abrasive particles.
  • calcining essentially all the volatile material is removed, and the various components that were present in the alpha alumina precursor dispersion are transformed into metal oxides.
  • the precursor shaped abrasive particles are generally heated to a temperature from 400 °C to 800 °C, and maintained within this temperature range until the free water and over 90 percent by weight of any bound volatile material are removed.
  • a water-soluble salt can be introduced by impregnation into the pores of the calcined, precursor shaped abrasive particles. Then the precursor shaped abrasive particles are pre-fired again. This option is further described in U. S. Patent No. 5,164,348 (Wood).
  • the seventh process step involves sintering the calcined, precursor shaped abrasive particles to form alpha alumina particles.
  • the calcined, precursor shaped abrasive particles Prior to sintering, the calcined, precursor shaped abrasive particles are not completely densified and thus lack the desired hardness to be used as shaped abrasive particles.
  • Sintering takes place by heating the calcined, precursor shaped abrasive particles to a temperature of from l000°C to l650°C and maintaining them within this temperature range until substantially all of the alpha alumina monohydrate (or equivalent) is converted to alpha alumina and the porosity is reduced to less than 15 percent by volume.
  • the length of time to which the calcined, precursor shaped abrasive particles must be exposed to the sintering temperature to achieve this level of conversion depends upon various factors but usually from five seconds to 48 hours is typical.
  • the duration for the sintering step ranges from one minute to 90 minutes.
  • the shaped abrasive particles can have a Vickers hardness of 10 GPa, 16 GPa, 18 GPa, 20 GPa, or greater.
  • Shaped abrasive particles are preferably made using tools (i.e., molds) cut using diamond tooling, which provides higher feature definition than other fabrication alternatives such as, for example, stamping or punching.
  • the cavities in the tool surface have planar faces that meet along sharp edges, and form the sides and top of a truncated pyramid.
  • the resultant shaped abrasive particles have a respective nominal average shape that corresponds to the shape of cavities (e.g., truncated pyramid) in the tool surface; however, variations (e.g., random variations) from the nominal average shape may occur during manufacture, and shaped abrasive particles exhibiting such variations are included within the definition of shaped abrasive particles as used herein.
  • the base and the top of the shaped abrasive particles are substantially parallel, resulting in prismatic or truncated pyramidal shapes, and the dihedral angle between the base and each of the sides may independently range from 45 to 90 degrees, typically 70 to 90 degrees, more typically 75 to 85 degrees, although these are not requirements.
  • the term "length” refers to the maximum dimension of a shaped abrasive particle.
  • Width refers to the maximum dimension of the shaped abrasive particle that is perpendicular to the length.
  • Thinness or “height” refer to the dimension of the shaped abrasive particle that is perpendicular to the length and width.
  • the shaped abrasive particles are typically selected to have a length in a range of from 0.001 mm to 26 mm, more typically 0.1 mm to 10 mm, and more typically 0.5 mm to 5 mm, although other lengths may also be used.
  • the length may be expressed as a fraction of the thickness of the bonded abrasive article (e.g., wheel) in which it is contained.
  • the shaped abrasive particle may have a length greater than half the thickness of the bonded abrasive wheel.
  • the length of the shaped abrasive particles may be greater than the thickness of the bonded abrasive wheel.
  • the shaped abrasive particles are typically selected to have a width in a range of from 0.001 mm to 26 mm, more typically 0.1 mm to 10 mm, and more typically 0.5 mm to 5 mm, although other lengths may also be used.
  • the shaped abrasive particles are typically selected to have a thickness in a range of from 0.005 mm to 1.6 mm, more typically, from 0.2 to 1.2 mm.
  • the shaped abrasive particles may have an aspect ratio (length to thickness) of at least 2, 3, 4, 5, 6, or more.
  • Surface coatings on the shaped abrasive particles may be used to improve the adhesion between the shaped abrasive particles and a binder material in abrasive articles, or can be used to aid in electrostatic deposition of the shaped abrasive particles.
  • surface coatings as described in U. S. Patent No. 5,352,254 (Celikkaya) in an amount of 0.1 to 2 percent surface coating to shaped abrasive particle weight may be used. Such surface coatings are described in U. S. Patent Nos.
  • the surface coating may prevent the shaped abrasive particle from capping.
  • Capping is the term to describe the phenomenon where metal particles from the workpiece being abraded become welded to the tops of the shaped abrasive particles. Surface coatings to perform the above functions are known to those of skill in the art.
  • crushed abrasive particles are independently sized according to an abrasives industry recognized specified nominal grade.
  • Exemplary abrasive industry recognized grading standards include those promulgated by ANSI (American National Standards Institute), FEPA (Federation of European Producers of Abrasives), and JIS (Japanese Industrial Standard).
  • Such industry accepted grading standards include, for example: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 30, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600; FEPA P8, FEPA P12, FEPA P16, FEPA P24, FEPA P30, FEPA P36, FEPA P40, FEPA P50, FEPA P60, FEPA P80, FEPA P100, FEPA P120, FEPA P150, FEPA P180, FEPA P220, FEPA P320, FEPA P400, FEPA P500, FEPA P600, FEPA P800, FEPA P1000, FEPA P1200; FEPA F8, FEPA F12, FEPA F16, and FEPA F24;.and
  • the crushed aluminum oxide particles and the non-seeded sol-gel derived alumina-based abrasive particles are independently sized to ANSI 60 and 80, or FEPA F36, F46, F54 and F60 or FEPA P60 and P80 grading standards.
  • the abrasive particles can be graded to a nominal screened grade using U. S.A. Standard Test Sieves conforming to ASTM E-l 1 "Standard Specification for Wire Cloth and Sieves for Testing Purposes".
  • ASTM E-l l prescribes the requirements for the design and construction of testing sieves using a medium of woven wire cloth mounted in a frame for the classification of materials according to a designated particle size.
  • a typical designation may be represented as -18+20 meaning that the shaped abrasive particles pass through a test sieve meeting ASTM E-l l specifications for the number 18 sieve and are retained on a test sieve meeting ASTM E-l l specifications for the number 20 sieve.
  • the shaped abrasive particles have a particle size such that most of the particles pass through an 18 mesh test sieve and can be retained on a 20, 25, 30, 35, 40, 45, or 50 mesh test sieve.
  • the shaped abrasive particles can have a nominal screened grade
  • a custom mesh size could be used such as -90+100.
  • the abrasive particles may, for example, be uniformly or non-uniformly distributed throughout the bonded abrasive article.
  • the abrasive particles may be concentrated toward the middle (e.g., located away from the outer faces of a grinding or cut-off wheel), or only in the outer edge, i.e., the periphery, of a grinding or cut-off wheel.
  • the center portion may contain a lesser amount of abrasive particles.
  • first abrasive particles may be in one side of the wheel with different abrasive particles on the opposite side. However, typically all the abrasive particles are homogenously distributed among each other, because the manufacture of the wheels is easier.
  • Bonded abrasive articles according to the present disclosure may comprise additional abrasive particles beyond those mentioned above, subject to weight range requirements of the other constituents being met.
  • Examples include fused aluminum oxide (including fused alumina-zirconia), brown aluminum oxide, blue aluminum oxide, silicon carbide (including green silicon carbide), garnet, diamond, cubic boron nitride, boron carbide, chromia, ceria, and combinations thereof.
  • Ethyl maltol (i.e., 2-ethyl -3 -hydroxy-4//-py ran -4-one: CAS No. 4940-11-8) is available from many sources of fragrances and fine chemicals (e.g., Sigma-Aldrich Chemical Co., St. Louis, Missouri). Ethyl maltol is present in an amount of 0.001 to 9 weight percent, preferably 0.001 to 5 weight percent, and preferably 0.01 to 2 weight percent, based on the total weight of the bonded abrasive matrix (i.e., the cured matrix). Ethyl maltol may be included as a solid or as a dispersion or solution in a solvent, for example. If included as a solid, it is preferably ground to a small size such as, for example, 1 micron to 3 mm, preferably 0.1 micron to 1 mm, or 0.5 mm to 1 mm, although this is not requirement.
  • ethyl maltol While the solubility of ethyl maltol in water is limited (1-2 grams/liter at room temperature), it is higher in hot water and alkaline aqueous solutions. Accordingly, depending on conditions, the ethyl maltol will typically be partially or completely dissolved in the bonded abrasive matrix precursor prior to curing. Without wishing to be bound by theory, the present inventor believes that upon curing at least a portion of the ethyl maltol is dissolved throughout the bonded abrasive matrix. This would potentially reduce porosity and may lead to improved abrading properties in some instances.
  • the bonded abrasive matrix is free of vitreous binder.
  • vitreous binder By this is meant that there is, at most, insufficient vitreous binder to retain the abrasive particles, and/or the vitreous binder is not uniformly enough distributed to retain the abrasive particles. Most preferably, there is no vitreous binder present at all.
  • Exemplary vitreous binders include silicaceous glasses.
  • the bonded abrasive matrix precursor may be free of silicaceous glasses.
  • FIG. 1 shows an exemplary bonded abrasive article.
  • bonded abrasive cut-off wheel 100 bonded abrasive cut-off wheel 100.
  • Bonded abrasive matrix 110 forms an annulus around central hole 112 used for attaching cut-off wheel 100 to, for example, a power-driven tool (not shown).
  • cut-off wheel 100 includes shaped abrasive particles 20 and optional conventionally-crushed abrasive particles 30, and phenolic binder 25. Cut-off wheel 100 has optional first scrim 115 and optional second scrim 116, which are disposed on opposed major surfaces 132, 134 of cut-off wheel 100.
  • bonded abrasive articles according to the present disclosure contain additional grinding aid(s) such as, for example, polytetrafluoroethylene particles, cryolite, sodium chloride, FeS 2 (iron disulfide), potassium aluminum fluoride, or KBF 4 ; typically, in amounts of from 1 to
  • Grinding aids are added to improve the cutting characteristics of the cut-off wheel, generally by reducing the temperature of the cutting interface.
  • the grinding aid may be in the form of single particles or an agglomerate of grinding aid particles. Examples of precisely shaped grinding aid particles are taught in U. S. Patent Publ. No. 2002/0026752 Al (Culler et al.).
  • the bonded abrasive matrix contains plasticizer such as, for example, that available as SANTICIZER 154 PLASTICIZER from UNIVAR USA, Inc. of Chicago, Illinois.
  • Bonded abrasive articles according to the present disclosure may contain additional components such as, for example, filler particles, subject to weight range requirements of the other constituents being met. Filler particles may be added to occupy space and/or provide porosity. Porosity enables the bonded abrasive article to shed used or worn abrasive particles to expose new or fresh abrasive particles. Bonded abrasive articles (e.g., wheels) according to the present disclosure have any range of porosity; for example, from about 1 percent to 50 percent, typically 1 percent to 40 percent by volume.
  • fillers include bubbles and beads (e.g., glass, ceramic (alumina), clay, polymeric, metal), cork, gypsum, marble, limestone, flint, silica, aluminum silicate, and combinations thereof.
  • At least some of the abrasive particles may be surface-treated with a coupling agent to enhance adhesion of the abrasive particles to the phenolic binder.
  • the abrasive particles may be treated before combining them with the curable phenolic resin(s), or they may be surface-modified in situ by including the coupling agent in the bonded abrasive matrix precursor.
  • the abrasive particles are coated with a coupling agent (e.g., an epoxy-functional silane coupling agent) prior to mixing with the curable phenolic resins(s).
  • the amount of coupling agent is generally selected to be in an effective amount.
  • the epoxy-functional silane the such that it is present in an amount of 0.01 to 3 parts, preferably 0.1 to 0.3, for every 100 parts of abrasive particles, although amounts outside this range may also be used.
  • Useful epoxy-functional silane coupling agents are disclosed in PCT Appln. Publ. No. WO 2017/062482 (Schillo-Armstrong et al.).
  • Bonded abrasive wheels according to the present disclosure are useful, for example, as cut-off wheels and abrasives industry Type 27 (e.g., as in American National Standards Institute standard ANSI B7.1-2000 (2000) in section 1.4.14) depressed-center grinding wheels.
  • Cut-off wheels are typically 0.80 millimeter (mm) to 16 mm in thickness, more typically 1 mm to 8 mm, and typically have a diameter between 2.5 cm and 100 cm, more typically between about 7 cm and 13 cm, although other dimensions may also be used (e.g., wheels as large as 100 cm in diameter are known).
  • An optional center hole may be used to attaching the cut-off wheel to a power-driven tool. If present, the center hole is typically 0.5 cm to 2.5 cm in diameter, although other sizes may be used.
  • the optional center hole may be reinforced; for example, by a metal flange.
  • a mechanical fastener may be axially secured to one surface of the cut-off wheel. Examples include threaded posts, threaded nuts, Tinnerman nuts, and bayonet mount posts.
  • bonded abrasive wheels may further comprise a scrim and/or backing that reinforces the bonded abrasive wheel; for example, disposed on one or two major surfaces of the bonded abrasive wheel, or disposed within the bonded abrasive wheel.
  • a scrim and/or backing that reinforces the bonded abrasive wheel; for example, disposed on one or two major surfaces of the bonded abrasive wheel, or disposed within the bonded abrasive wheel.
  • Examples include paper, polymeric film, metal foil, vulcanized fiber, synthetic fiber and/or natural fiber nonwovens (e.g., lofty open nonwoven synthetic fiber webs and meltspun scrims), synthetic and/or natural fiber knits, synthetic fiber and/or natural fiber wovens (e.g., woven glass fabrics/scrims, woven polyester fabrics, treated versions thereof, and combinations thereof).
  • porous reinforcing scrims examples include porous fiberglass scrims and porous polymeric scrims (e.g., comprising polyolefin, polyamide, polyester, cellulose acetate, polyimide, and/or polyurethane) which may be melt-spun, melt-blown, wet-laid, or air-laid, for example.
  • porous fiberglass scrims and porous polymeric scrims (e.g., comprising polyolefin, polyamide, polyester, cellulose acetate, polyimide, and/or polyurethane) which may be melt-spun, melt-blown, wet-laid, or air-laid, for example.
  • porous polymeric scrims e.g., comprising polyolefin, polyamide, polyester, cellulose acetate, polyimide, and/or polyurethane
  • Bonded abrasive articles are generally made by a molding process.
  • a precursor binder material either liquid organic, powdered inorganic, powdered organic, or a combination of thereof, is mixed with the abrasive particles.
  • a liquid medium either resin or a solvent
  • Bonded abrasive articles e.g., bonded abrasive wheels
  • the molding can be done either by hot or cold pressing or any suitable manner known to those skilled in the art.
  • Curing temperatures of organic binder precursor materials will vary with the material chosen and bonded abrasive article type and design (e.g., wheel design). Selection of suitable conditions is within the capability of one of ordinary skill in the art. Exemplary conditions for a phenolic binder may include an
  • Bonded abrasive wheels according to the present disclosure are useful, for example, for abrading a workpiece.
  • they may be formed into grinding or cut-off wheels that exhibit good grinding characteristics while maintaining a relatively low operating temperature that may avoid thermal damage to the workpiece.
  • Cut-off wheels can be used on any right angle grinding tool such as, for example, those available from Ingersoll-Rand, Sioux, Milwaukee, and Apex Brands, Apex, North Carolina.
  • the tool can be electrically or pneumatically driven, generally at speeds from about 1000 to 50000 RPM.
  • the bonded abrasive wheel can be used dry or wet. During wet grinding, the wheel is used in conjunction with water, oil-based lubricants, or water-based lubricants. Bonded abrasive wheels according to the present disclosure may be particularly useful on various workpiece materials such as, for example, carbon steel sheet or bar stock and more exotic metals (e.g., stainless steel or titanium), or on softer more ferrous metals (e.g., mild steel, low alloy steels, or cast irons).
  • workpiece materials such as, for example, carbon steel sheet or bar stock and more exotic metals (e.g., stainless steel or titanium), or on softer more ferrous metals (e.g., mild steel, low alloy steels, or cast irons).
  • the present disclosure provides a bonded abrasive article comprising a bonded abrasive matrix, wherein the bonded abrasive matrix comprises, based on the total weight of the bonded abrasive matrix:
  • the present disclosure provides a bonded abrasive article according to the first embodiment, wherein the bonded abrasive matrix is free of vitreous bond precursor.
  • the present disclosure provides a bonded abrasive article according to the second embodiment, wherein the vitreous bond precursor comprises a silicaceous glass or a precursor thereof.
  • the present disclosure provides a bonded abrasive article according to any one of the first to third embodiments, wherein the phenolic binder comprises resole and novolac phenolic components.
  • the present disclosure provides a bonded abrasive article according to any one of the first to fourth embodiments, wherein the ethyl maltol is at least partially dissolved in the phenolic binder.
  • the present disclosure provides a bonded abrasive article according to any one of the first to fifth embodiments, wherein the ethyl maltol is present in an amount of from 0.1 to 2 weight percent based on the total weight of the bonded abrasive matrix.
  • the present disclosure provides a bonded abrasive article according to any one of the first to sixth embodiments, wherein the bonded abrasive matrix comprises an annulus disposed around a central hole.
  • the present disclosure provides a method of making a bonded abrasive article, the method comprising:
  • mixing components comprising:
  • curable phenolic binder precursor
  • the bonded abrasive matrix comprises, based on the total weight of the bonded abrasive matrix, 10 to 30 weight percent of phenolic binder, abrasive particles retained in the phenolic binder, and 0.001 to 9 weight percent of the ethyl maltol.
  • the present disclosure provides a method of making a bonded abrasive article according to the eighth embodiment, wherein the bonded abrasive matrix is free of vitreous bond precursor.
  • the present disclosure provides a method of making a bonded abrasive article according to the ninth embodiment, wherein the vitreous bond precursor comprises a silicaceous glass or a precursor thereof.
  • the present disclosure provides a method of making a bonded abrasive article according to any one of the eighth to tenth embodiments, wherein the phenolic binder comprises a resole phenolic binder.
  • the present disclosure provides a method of making a bonded abrasive article according to any one of the eighth to eleventh embodiments, wherein the ethyl maltol is at least partially dissolved in the curable phenolic binder precursor.
  • the present disclosure provides a method of making a bonded abrasive article according to any one of the eighth to twelfth embodiments, wherein the ethyl maltol is present in an amount of from 0.1 to 2 weight percent based on the total weight of the bonded abrasive matrix.
  • the present disclosure provides a method of making a bonded abrasive article according to any one of the eighth to thirteenth embodiments, wherein the bonded abrasive matrix comprises an annulus disposed around a central hole.
  • Precisely-shaped alpha alumina abrasive particles SAP1 & SAP2 in the examples were prepared according to the disclosure of Example 1 of U. S. Pat. No. 8,142,531 (Adefris et al.) by molding alumina sol-gel in equilateral triangular polypropylene mold cavities. Further, SAP1 and SAP2 had a coating of fine (about 0.5 micron) particles of alumina (HYDRAL COAT 5, obtained from Almatis, Pittsburgh, Pennsylvania), this particle coating was applied according to the method of U. S. Pat. No. 5,213,591 (Celikkaya, et al.).
  • Precisely-shaped alpha alumina abrasive particles SAP3 in the examples were prepared according to the disclosure of Example 1 of U. S. Pat. Appln. Publ. No. 2015/0267097 (Rosenflanz et al.) by molding a slurry of non-colloidal solid alumina particles dispersion in equilateral triangular
  • Abrasive grains of 100 g of SAP1, 50 g of SAP2 and 450 g of AM1 were combined and mixed by hand.
  • RP 60 g was added to the combined grain and the combination was mixed in a KitchenAid Commercial mixer (Model KSM C50S) for 7 minutes at speed 1.
  • PP 340 g
  • 6 g of EM was combined with 6 g of EM and mixed by hand.
  • the grain mixture was then combined with 340 g of the combined PP-EM mixture and mixed for an additional 7 minutes.
  • 5 mL PO was added to the mixture.
  • Example 1 was repeated, except the PP-EM mixture was made by combining 340 g PP and 12 g EM. The grain mixture was still combined with a total of 340 g of the combined PP-EM mixture.
  • Example 1 was repeated, except the PP-EM mixture was made by combining 340 g PP and 30 g EM. The grain mixture was still combined with a total of 340 g of the combined PP-EM mixture.
  • Example 1 was repeated, except the PP-EM mixture was made by combining 340 g PP and 60 g EM. The grain mixture was still combined with a total of 340 g of the combined PP-EM mixture.
  • Example 1 was repeated, except no EM was utilized so the grain mixture was combined with 340 g PP.
  • Abrasive grains of 185.5 g of SAP3, 87 g of AM2 and 346 g AM3 were combined and mixed by hand.
  • EM (3 g) was added to 60 g RP and heated to 50 °C to solubilize the EM into the RP.
  • the RP was then cooled to 20 °C.
  • the EM and RP mixture was added to the combined grain and the combination was mixed in a KitchenAid Commercial mixer (Model KSM C50S) for 7 minutes at speed 1.
  • the grain mixture was then combined with 320 g of PP and mixed for an additional 7 minutes. In the middle of the second mixing step, 6 mL PO was added to the mixture.
  • Example 6 was repeated, except that 6 g EM was combined with 60 g RP.
  • Example 6 was repeated, except that 12 g EM was combined with 60 g RP.
  • Example 6 was repeated, except that 18 g EM was combined with 60 g RP.
  • Example 6 was repeated, except that 6 g EM was combined with 60 g RP.
  • Example 6 was repeated, except that 12 g EM was added to 320 g PP. The combined 332 g was mixed with the grain and RP mixture for 7 minutes. In the middle of the second mixing step, 6 mL PO was added to the mixture.
  • a metal flange 28 mm x 22.45 mm x 1.2 mm from Lumet PPUH in Jaslo, Poland was placed on top of each label. The mold was closed and the scrim-fill-scrim sandwich was pressed at a load of pressed 30 tons (244.5 kg/cm 2 ) at room
  • the wheels were cured in a stack with a 30 hr cure cycle: 2 hr to 75 °C, 2 hr to 90 °C, 5 hr to 110 °C, 3 hr to 135 °C, 3 hr to 188 °C, 13 hr at 188 °C, and a then 2 hr cool-down to 60 °C.
  • the final thickness of the wheel was approximately 0.053 inch (1.35 mm).
  • a 40-inch (l0l.6-cm) long sheet of 1/8 inch (3.2 mm) thick stainless steel was secured with its major surface inclined at a 35 -degree angle relative to horizontal.
  • a guide rail was secured along the downward-sloping top surface of the inclined sheet.
  • a DeWalt Model D28114 4.5-inch (1 l.4-cm)/5-inch (l2.7-cm) cut-off wheel angle grinder was secured to the guide rail such that the tool was guided in a downward path under the force of gravity.
  • a cut-off wheel for evaluation was mounted on the tool such that the cut-off wheel encountered the full thickness of the stainless steel sheet when the cut-off wheel tool was released to traverse downward, along the rail under gravitational force.
  • the cut-off wheel tool was activated to rotate the cut off wheel at 10000 rpm, the tool was released to begin its descent, and the length of the resulting cut in the stainless steel sheet was measured after 60 seconds (One Minute Cut). Dimensions of the cut-off wheel were measured before and after the cutting test to determine wear. Three cut-off wheels from Examples 1-9 and Comparative Examples A and B were tested.
  • One minute cut was measured as the distance that the cutting wheel abraded through the stainless steel sheet in one minute.
  • the wear rate is the loss of wheel volume as a function of the time the wheel cut.
  • the engineering performance is the length of the cut multiplied by the wheel thickness and then divided by the change in mass of the wheel.
  • Table 3 shows the performance results. Examples 1-4 and Comparative Example A show that performance of thin cut-off wheels drops off as the ethyl maltol amount is increased from 1% to 5.15% and the novolac dropped from 13.42% to 11.52%. Examples 5-9 and Comparative Example B show that performance of thin cut-off wheels drops off as the ethyl maltol amount is increased from 1% to 2%, but that it is better to add the EM to the PP than to RP or to avoid heating of the RP. Wheels made from Examples 1-9 emitted an aesthetically pleasing smell during the cutting test.

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  • Mechanical Engineering (AREA)
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  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Polishing Bodies And Polishing Tools (AREA)

Abstract

L'invention concerne un article abrasif lié comprenant une matrice abrasive liée. La matrice abrasive liée comprend, sur la base du poids total de la matrice abrasive liée : de 10 à 30 pour cent en poids d'un liant phénolique ; des particules abrasives retenues dans le liant phénolique ; et de 0,001 à 9 pour cent en poids de maltol d'éthyle. L'invention concerne également des procédés de fabrication et d'utilisation.
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