US20210308834A1 - Self-contained buffing articles - Google Patents

Self-contained buffing articles Download PDF

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Publication number
US20210308834A1
US20210308834A1 US17/250,454 US201917250454A US2021308834A1 US 20210308834 A1 US20210308834 A1 US 20210308834A1 US 201917250454 A US201917250454 A US 201917250454A US 2021308834 A1 US2021308834 A1 US 2021308834A1
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Prior art keywords
coating
abrasive
buffing
canceled
nonwoven fabric
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US17/250,454
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English (en)
Inventor
Robinette S. Alkhas
Ronald D. Apple
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3M Innovative Properties Co
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3M Innovative Properties Co
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Priority to US17/250,454 priority Critical patent/US20210308834A1/en
Assigned to 3M INNOVATIVE PROPERTIES COMPANY reassignment 3M INNOVATIVE PROPERTIES COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ALKHAS, ROBINETTE S., APPLE, Ronald D.
Publication of US20210308834A1 publication Critical patent/US20210308834A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D13/00—Wheels having flexibly-acting working parts, e.g. buffing wheels; Mountings therefor
    • B24D13/14—Wheels having flexibly-acting working parts, e.g. buffing wheels; Mountings therefor acting by the front face
    • B24D13/16—Wheels having flexibly-acting working parts, e.g. buffing wheels; Mountings therefor acting by the front face comprising pleated flaps or strips
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
    • B24D11/001—Manufacture of flexible abrasive materials
    • 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
    • B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
    • B24D18/0027—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for by impregnation
    • 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
    • B24D18/0045—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for by stacking sheets of abrasive material
    • 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
    • B24D18/0072—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using adhesives for bonding abrasive particles or grinding elements to a support, e.g. by gluing
    • 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

Definitions

  • Buffs are most often employed to refine surfaces by a three-body abrasion mechanism.
  • buffs transmit energy to a work piece, but the abrading action is provided by an abrasive composition “buffing compound” that is peripherally applied, but not bound, to the buff's surface.
  • Unbonded buffing compounds situated between the work piece and the buff's surface refines the work piece surface resulting in fewer and smaller scratches being imparted to the work piece surface as the buffing continues.
  • polishing typically a two-body abrasion mechanism, is too aggressive to achieve the refinement necessary to produce a mirror-like finish.
  • thee-body abrasion mechanisms have been employed to achieve a mirror-like finish.
  • the present invention relates, in part, to a unitized abrasive wheel comprising at least one layer of fibrous nonwoven fabric; the nonwoven fabric having a hardened adherent coating comprising a first coating and a second coating, the second coating formed on top of the first coating wherein the first coating comprises a crosslinked binder and wherein the second coating comprises an abrasive particle and a lubricant, wherein the abrasive particle is less than about 15 ⁇ .
  • a method of making a unitized abrasive wheel comprising the steps of providing a nonwoven fabric, coating the nonwoven fabric with a first coating, the first coating comprising a precursor crosslinker, hardening the first coating to form an adherent coated web, compressing the adherent coated web to form a compressed adherent coated web, and coating at least one outside surface of the adherent coated web with a second coating, the second coating comprising a lubricant and an abrasive particle, wherein the abrasive particle is less than about 15 ⁇ .
  • aspects of the invention relate, in part, to a method of imparting a mirror-like finish to metal to comprising the steps of; providing a unitized wheel comprising at least one layer of fibrous nonwoven fabric; the nonwoven fabric having a hardened adherent coating comprising a first coating and a second coating, the second coating formed on top of the first coating, wherein the first coating comprises a crosslinked binder, wherein the second coating comprises an abrasive particle and a lubricant, wherein the abrasive particle is less than about 15 ⁇ , and buffing a surface of the metal for a length of time sufficient to impart a desired luster to the surface of the metal.
  • a self-contained fibrous buffing article comprising, at least one layer of a combination of at least one fibrous nonwoven fabric and at least one woven fabric; the combination having a hardened adherent coating comprising a crosslinked binder, a lubricant, and abrasive particles, wherein the abrasive particles are less than about 15 ⁇ .
  • a method of forming a self-contained unitized buffing wheel comprising the steps of providing a nonwoven fabric, coating the nonwoven fabric with a first coating, the first coating comprising a precursor crosslinker, hardening the nonwoven fabric with the first coating to form an adherent coated web to produce a web, cutting the adherent coated web into a desired shape, coating at least one outside surface of the adherent coated web with a second coating, the second coating comprising a lubricant and an abrasive particle, and compressing the cut adherent coated web to form a self-contained unitized buffing wheel.
  • FIG. 1A illustrates a perspective view of a nonwoven abrasive web.
  • FIG. 1B illustrates an enlarged view of the nonwoven abrasive web of FIG. 1 a.
  • FIG. 2 illustrates a perspective view of an embodiment of a unitized wheel according to the invention.
  • FIG. 3 illustrates a perspective view of an embodiment of a convoluted wheel according to the invention.
  • FIG. 4 illustrates a perspective view of an embodiment of a buffing wheel according to the invention.
  • FIG. 5 illustrates a perspective view an embodiment of a buffing wheel according to the invention.
  • FIG. 6 illustrates a perspective view of an embodiment of a buffing wheel according to the invention.
  • FIG. 7 illustrates a perspective view of an embodiment of a flap brush according to the invention.
  • FIG. 8 illustrates a perspective view of an embodiment of a flap belt according to the invention.
  • FIG. 9 illustrates a flow diagram of a method according to the invention.
  • self-contained fibrous buffing article means a buffing article containing a pre-applied or pre-impregnated abrasive buffing composition to the fibrous material forming the buffing article.
  • the abrasive buffing composition is suitable for cut or color buffing, and is applied to the buffing article by the manufacturer during the initial manufacturing of the buffing article. As such, the application of a buffing compound to the buffing article by an operator before first using or while using the buffing article to buff a work surface is not required.
  • hardening when used to describe the solidification of a precursor, refers to curing (e.g., polymerization and/or cross-linking, thermally or otherwise), drying (e.g., driving off a volatile solvent) and/or simply by cooling.
  • Certain embodiments of the self-contained fibrous buffing articles are formed into unitized or convoluted wheels and comprise at least one layer of a fibrous nonwoven fabric impregnated with a prebond coating comprising at least a first crosslinkable binder precursor, and at least a second coating comprising abrasive particles, a lubricant, and an optional second crosslinkable binder precursor.
  • the prebond coating and second coating form an adherent coating comprising the pre-impregnated abrasive buffing composition.
  • additional coatings may be applied that contribute to the adherent coating of the buffing article.
  • Certain embodiments of the self-contained fibrous article are formed into a buffing wheel.
  • the buffing wheel comprising a combination of woven and nonwoven fabric.
  • the combination of fabric is impregnated with at least one coating comprising at a least a first crosslinkable binder precursor, an abrasive, and a lubricant.
  • additional coatings may be applied that contribute to the adherent coating of the buffing article.
  • Nonwoven fabrics useful in the practice of this invention may be made by any known web formation system.
  • the fabric may be spunbonded, hydroentangled, or melt blown.
  • the nonwoven fabric is a dry laid nonwoven fabric.
  • the nonwoven fabric is an air-laid nonwoven fabric.
  • the nonwoven fabric is formed by carding and cross-lapping. While web formation methods using staple fibers are typical, continuous filament systems such as spunbond or meltblown may be used. Useful staple fibers lengths include those between 0.05 inch (12.7 mm) and 4 inches (102 mm), inclusive.
  • a prebond coating may be applied to enhance the integrity of the nonwoven fabric.
  • the fiber component of the nonwoven fabric may be synthetic, man-made, or natural in origin.
  • exemplary synthetic fibers are polyester (such as poly(ethylene terephthalate) or poly(butylene terephthalate)), polyamide (such as poly(hexamethylene adipate) or polycaprolactam), polyolefins (such as polyethylene or polypropylene), and melty fibers.
  • Exemplary man-made fibers include cellulose acetate, rayon, and lyocell.
  • natural fibers such as cotton, jute, ramie, and wool are useful alone or in combination.
  • blends of two, three, or even more fiber constituents may be used.
  • fiber denier may be 0.1 denier (0.11 dtex) or greater.
  • fiber size may be 20 denier (22.5 dtex) or less, 15 denier or less, 6 denier or less, or 3 denier or less.
  • mixtures of two or more fiber deniers or ranges may be useful.
  • a majority, 70%, 80%, 90%, or 95% of the fibers forming the nonwoven are selected to have a fiber size from 0.1 denier to 20, 15, 6, or 3 denier.
  • the nonwoven fabric includes cellulose fiber. In some embodiments, the nonwoven fabric is at least 30 wt % cellulose fiber, or at least 50 wt % cellulose fiber, or at least 70 wt %, up to 100% cellulose fiber. Other natural, manmade, or synthetic fibers may be also incorporated, including polyamide (e.g., nylon 6, nylon 6,6), polyester (e.g., polyethylene terephthalate, polybutylene terephthalate), rayon, cellulose acetate, or cotton. In some embodiments, the nonwoven fabric may contain melt-bondable fibers, including melt-bondable fibers that can be crosslinked after melt bonding to render them thermosetting.
  • the nonwoven fabric is prepared to have a basis weight from 50 g/m 2 to 500 g/m 2 , or from 75 g/m 2 to 400 g/m 2 , or from 100 g/m 2 to 300 g/m 2 .
  • the thickness of the nonwoven fabric is typically from 1 mm to 20 mm, or from 1 mm to 15 mm, or from 2 mm to 5 mm.
  • the nonwoven fabric is subsequently needle-tacked.
  • the nonwoven fabric may be subsequently calendered and/or otherwise thermally-treated (e.g., through-bonding).
  • Suitable woven fabrics may be selected from those made from synthetic or natural fibers or combinations thereof.
  • synthetic fibers include polyester, nylon, and rayon.
  • natural fibers include cotton, jute, hemp, bamboo, and silk.
  • Various properties of woven fabrics, such as for example, fiber composition, denier size, and number of weft and warp may be adjusted to provide fabrics of desired characteristics as known by those skill in the art. For example, thread count may be adjusted to produce stiffer or more pliable fabrics as suited for a particular application.
  • the woven fabric is selected such that it imparts durability without marring or scratching the surface that it is polishing. In some embodiments the woven comprises a greige good. In one embodiment, the woven fabric comprises a cotton woven, such a J-Cloth such as that available from Indecraft Textile Mills, India.
  • the prebond coating comprises a first crosslinkable binder precursor. Suitable first crosslinkable binders are discussed later, but preferred cross linkable binders are polyurethanes.
  • Useful prebond coatings are formulated to maximize the desired web properties (tear, tensile, flexibility) and provide the desired final product performance (e.g., cut, wear, finish) during use.
  • Useful compositions of the prebond coating comprise 3-85 wt. %, 30-85 wt. %, 51-85 wt. %, and 70-85 wt. % binder precursor.
  • the coating may be applied by any conventional means such as, for example, roll coating, spray coating, or saturation coating.
  • the prebond coating can also include abrasive particles, lubricants, and/or optional additives.
  • the second coating comprises a dispersion of abrasive particles, a lubricant, and an optional second crosslinkable binder precursor.
  • Useful second coatings are formulated to maximize the desired abrasive effects (cut or color buffing), maximize the buff's flexibility, and minimize both smearing (unwanted transfer of buffing components onto the work piece) and dusting during use.
  • Useful compositions of the second coating are 0-50 wt. % binder precursor, 5-99 wt % lubricant, and 0-80 wt % mineral.
  • the nonwoven fabric is coated with the second coating and other optional additives in one or more coating steps.
  • the coatings may be applied by any conventional means such as, for example, roll coating, spray coating, or saturation coating.
  • three coatings are applied: a lubricant coating followed by a hardening step; a phenolic resin coating followed by a hardening step; and a lubricant coating followed by a hardening step.
  • the coatings are applied in at least two separate steps with the binder precursor and mineral applied and then hardened followed by the lubricant coating and hardening.
  • two lubricant coatings are applied and hardened.
  • Single Coating Single coatings comprise a dispersion of a crosslinkable binder precursor, abrasive particles, and a lubricant.
  • Singles coatings may optionally contain a second binder precursor and/or other additional other additives.
  • Single coatings are formulated to produce abrasive articles bypassing the prebonding coating process.
  • Useful single coatings are formulated to maximize the desired abrasive effects (cut or color buffing), maximize the buff's flexibility, and minimize both smearing (unwanted transfer of buffing components onto the work piece) and dusting during use.
  • Useful compositions of the single coating are 0-50 wt. % binder precursor, 5-80 wt % lubricant, and 0-70 wt % mineral.
  • the nonwoven fabric may be coated with additional coating layers and/or other optional additives in one or more coating steps.
  • the coatings may be applied by any conventional means such as, for example, roll coating, spray coating, or saturation coating.
  • Suitable binder precursors for the first and second crosslinkable binders include urethane resins such as polyurethane polymers or prepolymers, epoxy resins, phenolic resins, acrylic resins, urea-formaldehyde resins, melamine-formaldehyde resins, styrene-acrylics, styrene-butadienes, and combinations thereof.
  • the first and second crosslinkable binders are selected to be different chemistries such as a phenolic resin and an acrylic.
  • the first and second crosslinkable binders are the same chemistry, but may be applied at the same or different coating weights.
  • Examples of useful urethane prepolymers include polyisocyanates and blocked versions thereof.
  • blocked polyisocyanates are substantially unreactive to isocyanate reactive compounds (e.g., amines, alcohols, thiols, etc.) under ambient conditions (e.g., temperatures in a range of from about 20 degrees C. to about 25 degrees C.), but upon application of sufficient thermal energy the blocking agent is released, thereby generating isocyanate functionality that reacts with the amine curative to form a covalent bond.
  • Useful polyisocyanates include, for example, aliphatic polyisocyanates (e.g., hexamethylene diisocyanate or trimethylhexamethylene diisocyanate); alicyclic polyisocyanates (e.g., hydrogenated xylylene diisocyanate or isophorone diisocyanate); aromatic polyisocyanates (e.g., tolylene diisocyanate or 4,4′-diphenylmethane diisocyanate); adducts of any of the foregoing polyisocyanates with a polyhydric alcohol (e.g., a diol, low molecular weight hydroxyl group-containing polyester resin, water, etc.); adducts of the foregoing polyisocyanates (e.g., isocyanurates, biurets); and mixtures thereof.
  • aliphatic polyisocyanates e.g., hexamethylene diisocyanate or trimethylhexamethylene diis
  • polyisocyanates include, for example, those available under the trade designation “ADIPRENE” from Chemtura Corporation, Middlebury, Conn. (e.g., “ADIPRENE L 0311”, “ADIPRENE L 100”, “ADIPRENE L 167”, “ADIPRENE L 213”, “ADIPRENE L 315”, “ADIPRENE L 680”, “ADIPRENE LF 1800A”, “ADIPRENE LF 600D”, “ADIPRENE LFP 1950A”, “ADIPRENE LFP 2950A”, “ADIPRENE LFP 590D”, “ADIPRENE LW 520”, and “ADIPRENE PP 1095”); polyisocyanates available under the trade designation “MONDUR” from Bayer Corporation, Pittsburgh, Pa.
  • AIRTHANE and “VERSATHANE” from Air Products and Chemicals, Allentown, Pa.
  • AIRTHANE APC-504 e.g., “AIRTHANE PST-95A”, “AIRTHANE PST-85A”, “AIRTHANE PET-91A”, “AIRTHANE PET-75D”, “VERSATHANE STE-95A”, “VERSATHANE STE-P95”, “VERSATHANE STS-55”, “VERSATHANE SME-90A”, and “VERSATHANE MS-90A”).
  • polyisocyanates such as, for example, those mentioned above may be blocked with a blocking agent according to various techniques known in the art.
  • blocking agents include ketoximes (e.g., 2-butanone oxime); lactams (e.g., epsilon-caprolactam); malonic esters (e.g., dimethyl malonate and diethyl malonate); pyrazoles (e.g., 3,5-dimethylpyrazole); alcohols including tertiary alcohols (e.g., t-butanol or 2,2-dimethylpentanol), phenols (e.g., alkylated phenols), and mixtures of alcohols as described.
  • ketoximes e.g., 2-butanone oxime
  • lactams e.g., epsilon-caprolactam
  • malonic esters e.g., dimethyl malonate and diethyl malonate
  • pyrazoles
  • Exemplary useful commercially available blocked polyisocyanates include those marketed by Chemtura Corporation under the trade designations “ADIPRENE BL 11”, “ADIPRENE BL 16”, “ADIPRENE BL 31”, and blocked polyisocyanates marketed by Baxenden Chemicals, Ltd., Accrington, England under the trade designation “TRIXENE” (e.g., “TRIXENE BL 7641”, “TRIXENE BL 7642”, “TRIXENE BL 7772”, and “TRIXENE BL 7774”).
  • TRIXENE e.g., “TRIXENE BL 7641”, “TRIXENE BL 7642”, “TRIXENE BL 7772”, and “TRIXENE BL 7774”.
  • Suitable amine curatives include aromatic, alkyl-aromatic, or alkyl polyfunctional amines, preferably primary amines.
  • useful amine curatives include 4,4′-methylenedianiline; polymeric methylene dianilines having a functionality of 2.1 to 4.0 which include those known under the trade designations “CURITHANE 103”, commercially available from the Dow Chemical Company, and “MDA-85” from Bayer Corporation, Pittsburgh, Pa.; 1,5-diamine-2-methylpentane; tris(2-aminoethyl) amine; 3-aminomethyl-3,5,5-trimethylcyclohexylamine (i.e., isophoronediamine), trimethylene glycol di-p-aminobenzoate, bis(o-aminophenylthio)ethane, 4,4′-methylenebis(dimethyl anthranilate), bis(4-amino-3-ethylphenyl)methane (e.g., as marketed under the
  • the amine curative should be present in an amount effective (i.e., an effective amount) to cure the blocked polyisocyanate to the degree required by the intended application; for example, the amine curative may be present in a stoichiometric ratio of a range from 0.8 to 1.05 or in a range from 0.85 to 1.0.
  • Phenolic materials are useful binder precursors because of their thermal properties, availability, cost, and ease of handling.
  • Resole phenolics have a molar ratio of formaldehyde to phenol of greater than or equal to one, typically from 1.5:1.0 to 3.0:1.0.
  • Novolac phenolics have a molar ratio of formaldehyde to phenol of less than 1.0:1.0.
  • Examples of commercially available phenolics include those known by the trade names DUREZ and VARCUM from Occidental Chemicals Corp., RESINOX from Monsanto, AROFENE from Ashland Chemical Co., and AROTAP from Ashland Chemical Co.
  • the amount of phenolic binder precursor present in the phenolic binder coating is in an amount from 2 to 50 percent by weight, or in an amount from 5 to 40 percent by weight, or even in an amount from 5 to 35 percent by weight based on the total weight of the coating composition, although amounts outside of these ranges may also be used.
  • Emulsions of crosslinked acrylic resin particles may also find utility in the present invention.
  • Some binder precursors include a phenolic mixed with a latex.
  • latexes include materials containing acrylonitrile butadiene, acrylics, butadiene, butadiene-styrene, and combinations thereof.
  • These latexes are commercially available from a variety of different sources and include those available under the trade designations RHOPLEX and ACRYLSOL commercially available from Rohm and Haas Company, FLEXCRYL and VALTAC commercially available from Ashland Inc., SYNTHEMUL, TYCRYL, and TYLAC commercially available from Mallard Creek Polymers Inc., HYCAR commercially available from The Lubrizol Corporation, GOODRITE commercially available from B. F. Goodrich, CHEMIGUM commercially available from Goodyear Tire and Rubber Co., NEOCRYL commercially available from ICI, BUTAFON commercially available from BASF, and UCAR commercially available from Union Carbide.
  • lubricants for use in the self-contained fibrous buffing article include fatty acids (e.g., stearic acid, lauric acid, palmitic acid, myristic acid, oleic acid, palmitoleic acid, linoleic acid, and linolenic acid), metallic salts of fatty acids (e.g., lithium stearate, zinc stearate), solid lubricants (e.g., poly(tetrafluoroethylene) (PTFE), graphite, and molybdenum disulfide), mineral oils and waxes (including micronized waxes), carboxylic acid esters (e.g., butyl stearate), poly(dimethylsiloxane) fluids, poly(dimethylsiloxane) gums, and simple polyol compounds such as glycerin, and combinations thereof.
  • fatty acids e.g., stearic acid, lauric acid, palmitic acid, myristic
  • Useful lubricants include, for example, Stearic Acid (from Acme Hardesty Oleochemicals, Blue Bell, Pa.), “INDUSTRENE 4516” (from PCM Biogenics, Memphis, Tenn.), Lithium Stearate (from Ashland, Inc., Covington, Ky.), Zinc Stearate “ZINCUM SW”, “ZINCUM AV”, Calcium Stearate “CEASIT SW” and “CEASIT AV” (from Baerlocher Do Brasil S.A, Americana, SP, Brazil), “COMAX A”, “COMAX T”, “QUIMIPEL COAT 9327” and “QUIMIPEL COAT 9330” (from Quimipel Industria Quimica LTDA, Piracaia, SP, Brazil), “Natural Graphite” (from Nacional de Grafite LTDA, Itapecerica, MG, Brazil), “MP-22 Wax” (from Microw Powders, Inc., Tarrytown N.Y.), “Drak
  • Suitable abrasive particles are those useful in buffing operations.
  • the abrasive particles may be of any suitable composition, but those comprising chromium oxide, titanium oxide, aluminum oxide, calcined micronized aluminum oxide, iron oxide or silicon carbide are typical.
  • Appropriate abrasive particle size distributions include those with median particle diameters of less than 15 micrometers or less than 10 micrometers.
  • abrasive particles examples include “E2616 GREEN” (from Akrochem Corporation, Akron, Ohio), “KRONOS 2310” (from Kronos Inc., Houston, Tex.), Iron Oxide “BK-5099” I (from Elementis Pigments Inc., Fairview Heights, Ill.), “MICROGRIT WCA” or MICROGRIT PXA, or Microclear DD, (from Micro Abrasives Corporation, Westfield, Mass.), Precipitated Silicas (from Evonik Industries, Parsippany, N.J.), Hydrotalcite DHT (from Kisuma Chemicals, Veendam, Netherlands), Alumina Trihydrate (from Huber, Edison, N.J.) and combinations thereof.
  • E2616 GREEN from Akrochem Corporation, Akron, Ohio
  • KRONOS 2310 from Kronos Inc., Houston, Tex.
  • Iron Oxide “BK-5099” I from Elementis Pigments Inc., Fairview Heights, Ill.
  • MICROGRIT PXA
  • the abrasive particles may be larger, depending on the needs of the application.
  • the present invention contemplates the use of any suitable abrasive.
  • Abrasives can be selected by various factors as known to those of the skill in the art.
  • additives that may be beneficial in the second or other coatings that form the adherent coating include surfactants, wetting agents, antifoaming agents, colorants, coating modifiers, and coupling agents.
  • An anionic surfactant is beneficial to incorporate the lubricant into the second coating.
  • An example of an effective anionic surfactant is sodium dioctyl sulfosuccinate, available as “Aerosol OT-75” (from Cytec Do Brasil Ltda., Sao Paulo, SP, Brazil).
  • Another useful emulsifier is triethanolamine, such as that available as “Triethanolamine 99% TECH” (from Ashland Chemical Company, Columbus, Ohio).
  • a wetting agent is useful to promote impregnation of the fibrous buffing material with the coatings.
  • Useful wetting agents include surfactants that are at least partially non-ionic, such as “NopcoWet BR” (from Gap Quimica Ltda., Guarulhos, SP, Brazil).
  • Other useful nonionic surfactants include “TERGITOL 15-S-40” and “TERGITOL XJ”, (both from Dow Chemical, Midland, Mich.), and “PEG DS6000” (from BASF, Florham Park, N.J.).
  • Coating modifiers and VOC reducers such as hydroxyethyl ethylene urea are useful to promote film formation.
  • Useful coating modifiers include “SR-511” (from Sartomer Company, Exton, Pa.).
  • Other coating modifiers and pH adjusters such as citric acid are useful to control coating viscosity.
  • a coupling agent is useful to improve adhesion between the nonwoven buffing material, the binder, and the abrasive mineral.
  • Useful coupling agents include “Z-6020 Silane” and “Z-6040 Silane”, both available from Dow Corning, Midland, Mich.
  • Colorants or pigments such as iron oxide, titanium oxide, or carbon black may be added to visually identify different buffing articles and/or type of buffing article.
  • pigments such as chromium oxide may also serve as an abrasive particle.
  • Suitable colorants pigments include “KRONOS 2310” (Kronos Inc., Houston, Tex.), “E2616 GREEN” (Akrochem Corporation, Akron, Ohio), “BK-5099 PIGMENT” (Elementis Pigments Inc., Fairview heights, Ill.), and “Copperas Red Iron Oxide R5098D” (Elementis Pigments Inc., Fairview heights, Ill.).
  • the self-contained fibrous buffing articles are made by impregnating a length of suitable fibrous nonwoven fabric with a prebond coating followed by thermal lamination and/or hardening.
  • Prebond coatings may be applied by conventional application means, such as roll coating, curtain coating, die coating, or spraying.
  • a second coating comprising abrasive particles, a lubricant, and optionally a second crosslinkable binder precursor and wetting agent and/or a surfactant may be applied over the prebond coating and subsequently hardened to form a hardened second coating on the fibers and surfaces of the nonwoven fabric.
  • the adherent coating may be incorporated into the fibrous material in one or more steps with either one or more hardening steps as previously discussed.
  • a second coating is incorporated and hardened, followed by a subsequent coating comprising additional lubricant, followed by an additional hardening step.
  • Adherent coatings may be applied by conventional application means, such as roll coating, curtain coating, die coating, or spraying.
  • both the prebond coating and the second coating comprise abrasive particles.
  • the particles in the prebond coating may be of the same or different composition, size, and quantity (absolute or weight % of total weight of coating composition).
  • the prebond coating and second coating are combined, this is referenced as a “single coating”.
  • the single coating may comprise one or more crosslinked precursor(s), one or more abrasive(s), and lubricant.
  • the total dry add-on weight of the coating(s) is from 50 g/m 2 to 2000 g/m 2 , or from 200 g/m 2 to 1500 g/m 2 , or from 200 g/m 2 to 1100 g/m 2 . In some embodiments, the total weight of the final coated buffing fabric is from 200 g/m 2 to 1500 g/m 2 .
  • the self-contained fibrous articles formed in accordance with the invention must not only be capable of withstanding the strenuous use conditions typically encountered in buffing operations, but it must also be capable of holding the adherent buffing composition on the buffing surface.
  • Self-contained fibrous buffing articles may be any design or style presently known or contemplated in the future.
  • Non-limiting examples of fibrous buffing articles include buffing wheels, unitized wheels, surface conditioning, flap brush and convolute wheels.
  • One method of making nonwoven abrasive webs according to the present invention includes the steps in the following order: applying a prebond coating to the nonwoven fiber web (e.g., by roll-coating or spray coating), curing the prebond coating, impregnating the nonwoven fiber web with the second coating composition (e.g., by roll-coating or spray coating), and curing the curable composition.
  • a prebond coating e.g., by roll-coating or spray coating
  • the second coating composition e.g., by roll-coating or spray coating
  • curing the curable composition e.g., by roll-coating or spray coating
  • a single coating can be applied (e.g., by roll-coating or spray coating) and curing the single coating advantageously bypassing the need for multiple coating and curing steps.
  • a lamination step in place of curing
  • other processes such as molding, cutting, or others occurring prior to the application of the second coating.
  • curing takes place after the article has been formed as in the case of unitized and convoluted wheels, for example.
  • the cutting and molding processes may occur subsequent to the curing of the second coating.
  • the curable composition is coated onto the nonwoven fiber web in an amount of from 50 to 1500 gsm, more typically 75-800 gsm, and even more typically 100-500 gsm, although values outside these ranges may also be used.
  • FIGS. 1 a and 1 b An exemplary embodiment of a nonwoven abrasive article is shown in FIGS. 1 a and 1 b, wherein lofty open low-density fibrous web 100 is formed of entangled filaments 110 held together by polyurethane binder 120 .
  • Abrasive particles 140 are dispersed throughout fibrous web 100 on exposed surfaces of filaments 110 .
  • Polyurethane binder 120 coats portions of filaments 110 and forms globules 150 which may encircle individual filaments or bundles of filaments, adhere to the surface of the filament and/or collect at the intersection of contacting filaments, providing abrasive sites throughout the nonwoven abrasive article.
  • Webs of the types described may be formed into variety of abrasive articles.
  • Such buffing articles may be any design or style presently known or contemplated in the future.
  • Non-limiting examples include; convolute wheels, unitized wheels, buffing wheels, and flap brushes or belts.
  • Convolute abrasive wheels may be provided, for example, by winding the nonwoven fiber web that has been impregnated with the curable composition under tension around a core member (e.g., a tubular or rod-shaped core member) such that the impregnated nonwoven fiber layers become compressed, and then curing the curable composition to provide a polyurethane binder binding the abrasive particles to the layered nonwoven fiber web and binding layers of the layered nonwoven fiber web to each other.
  • a convolute abrasive wheel 200 is shown in FIG.
  • layered nonwoven fiber web 210 coated with polyurethane binder binding the abrasive particles to the layered nonwoven fiber web and binding layers of the layered nonwoven fiber web to each other is spirally disposed around and affixed to core member 230 .
  • convolute abrasive wheels may be dressed prior to use to remove surface irregularities, for example, using methods known in the abrasive arts.
  • Unitized abrasive wheels can be provided, for example, by layering the impregnated nonwoven fiber web (e.g., as a layered continuous web or as a stack of sheets) compressing the nonwoven fiber layers, curing the curable composition (e.g., using heat), and die cutting the resultant abrasive article to provide a unitized abrasive wheel having a central hole.
  • a unitized abrasive wheel 300 is shown in FIG. 3 having a plurality of nonwoven abrasive layers 310 , which have been compressed and cured. After curing the abrasive layers, the resulting slab can be die cut to form the abrasive wheel having a central hole 320 .
  • the one or more layers When compressing the layers of impregnated nonwoven fiber web in making an abrasive wheel, the one or more layers are typically compressed to form a slab having a density that is from 1 to 10 times that of the density of the layers in their non-compressed state.
  • the slab is then typically subjected to heat molding (e.g., for from 1 to 60 minutes) at elevated temperature (e.g., at 135° C.), typically depending on the urethane prepolymer and dimension of the unitized slab.
  • Buffing wheels can be formed, for example, from layers of a fibrous material which are stacked or fastened together.
  • Fastening methods include, for example, compression, sewing, stapling, adhesive bonding, plastic or metal clinch rings, and combinations thereof.
  • the buffing wheel is typically attached to a shaft and supported for rotation.
  • Buffs have long been used to finish items such as machined parts, stamped parts, and cast articles which often have surfaces which must be modified, generally for aesthetic purposes.
  • Buffing is a finishing process which is typically accomplished after more rigorous stock removal treatment of the surface. Buffs are typically rotated to obtain working surface speeds of from 1000 m/min to 3500 m/min.
  • FIG. 4 shows a buff 400 composed of layers 410 of fibrous buffing material, optionally sewn with one or more circles of stitching 420 with suitable thread which is known for this purpose between the outer edge 430 and central opening 440 for attachment to a rotating spindle or mandrel.
  • Layers of fibrous buffing material have a generally circular shape and they are stacked (or the entire assembly is cut) so that the edges of each of the layers define a cylindrical surface which is the peripheral edge of the buff.
  • FIG. 5 shows a buff 500 composed of layers 50 of fibrous buffing material sewn together with several circular patterns 520 of stitching with suitable thread.
  • the sewing pattern may be concentric, spiral, square, radial, radial arc, or combinations thereof.
  • Buff 500 has a central opening 540 for attachment to a rotating spindle or mandrel.
  • FIG. 6 depicts what is known as a “puckered” buff 600 which is produced by cutting a continuous strip of fibrous buffing material and convolutely wrapping this strip around the separated ends of axially aligned cylindrical mandrels, radially constricting the wrapped strip at its middle to form a flattened “puckered” annulus, and installing a rigid clinch ring 620 of either plastic or metal within the opening of the annulus.
  • a “puckered” fibrous buffing material annulus may also be fastened by stapling, sewing or adhesive bonding to a suitable rigid annulus such as an annulus formed of cardboard.
  • a sewn buff The particular construction of a sewn buff will depend upon its ultimate use. Buffs formed of layers of fabric, which are sewn together, as shown in FIG. 5 are typically used for cut buffing. Very close rows of stitching increase the stiffness of the sewn buff to increase cut.
  • the sewing patterns for such buffs may vary, depending upon the needs of the user, from concentric sewn, radial sewn, square sewn, spiral sewn, to radial arc sewn and radial arc with spiral center. Concentric sewing results in non-uniform density when the buff wears as it is used. As the buff wears closer to the stitches, the buff will become harder and just past a row of stitches it becomes softer. Spiral sewing results in a more uniform density, although the buff surface will still have a density variation. Square and non-concentric sewing patterns produce pockets that may aid in the buffing process.
  • the puckered or pleated buff is popular for its cool running capability, provided by pleats or puckers in its fabric.
  • the type of the construction of a puckered buff depends upon its ultimate use also.
  • a Different hardness may be required for various cutting and/or color buffing applications. Hardness may be controlled somewhat by the spacing of buffs on the mandrel, but more commonly is regulated by the degree of puckering, the diameter of the buff relative to the clinch ring diameter, or the stiffness of the buff fabric.
  • fibrous buffing articles may also find utility, including “flap brush” constructions 700 as illustrated in FIG. 7 having individual buffing flaps 710 , or “flap belt” constructions 800 as illustrated in FIG. 8 having individual buffing flaps 810 .
  • Buffing articles such as needletacked belts or discs may also find utility.
  • FIG. 9 illustrates a method 900 for producing a web that can be formed into a self-contained buffing article.
  • the operations of method 900 presented below are intended to be illustrative. In some embodiments, method 900 may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of method 900 are illustrated in FIG. 9 and described below is not intended to be limiting.
  • a woven fabric is incorporated into a fibrous nonwoven fabric, such as those described previously is provided 910, 920.
  • the combination web is then coated with a dispersion comprising at least one crosslinked binder, lubricant, and abrasive particle 90 .
  • Such coatings are described above under the subheading “Single Coating”.
  • the coating may be applied by any conventional means such as, for example, roll coating, spray coating, or saturation coating or other suitable techniques. Webs thus coated can be cured 940 to produce an adherent web, which in turn can be processed accordingly to produce self-contained buffing wheels 950 .
  • a nonwoven web was formed on an air laid fiber web forming machine, available under the trade designation “RANDO-WEBBER” from the Rando Machine Corporation of Ard, N.Y.
  • the fiber web was formed from a 50% blend of FIB1 and FIB2 and weighed about 84 gsm.
  • the web was conveyed to a two-roll coater, where a prebond resin was applied.
  • the prebond resin had the following composition (all percentages relative to component weight): 33.8% PMA, 1.0% LiSt, 52.7% BL16, 2.1% SD, 1.9% EB, and 8.5% AA.
  • the prebond resin was cured to a tacky condition by passing the coated web through a convection oven at 221° F.
  • a single, unitized slab of nonwoven, abrasive material was formed by stacking pre-bonded nonwoven webs one on top of the other and placed in a hydraulic, heated platen press set at 320° F. (160° C.). A release liner was placed on both sides of the stack prior to placing it in the oven. Consistent thickness of the unitized slab was maintained by placing 0.5 inch (1.27 centimeters) thick metal spacers in each corner of the platen. Pressure (15,000 psi, 103.4 megapascal), was applied to the platens.
  • the coated unitized wheels were placed in a forced air oven set at 300° F. (149° C.) for 8 minutes to remove the solvent. After removal from the oven, the wheels were cooled to room temperature.
  • the unitized wheels were tested to measure the polishing performance of the sample wheels compared to a conventional spirally sewn cotton buff (Osborne, Hamilton, Ohio), and a green solid polishing compound (Osborne, Green C-3). Testing was conducted using polishing equipment manufactured by Hammond, Kalamazoo, Mich. The unitized wheel was rotated at 2100 revolutions per minute. An orthopedic knee implant device (cobalt chrome) was preconditioned using a 3M Company Trizact abrasive belt 307EA Grade A16. The orthopedic knee implant device was urged to the face of the rotating wheel and polished to remove the scratch marks left by the abrasive belt. Visual observations were made regarding the reflection or mirror like finish left on the part, the part cleanliness, work area cleanliness, and the wear of the buffing article.
  • Finish quality was accessed by visual inspection for presence of scratches and level of reflectivity exhibited the surface.
  • Durability was accessed by visual inspection to determine level of wear of abrasive.
  • Part cleanliness was accessed by visual inspection to determine amount of buffing compound residue remaining on surface after polishing operation.
  • Work area cleanliness was accessed by visual inspection to determine amount of debris
  • a nonwoven web was formed on an air laid fiber web forming machine, available under the trade designation “RANDO-WEBBER” from the Rando Machine Corporation of Ard, N.Y.
  • the fiber web was formed from cellulosic fibers or a blend of cellulosic fibers and synthetic fibers and incorporated into a woven cotton cloth as shown in Table 4.
  • a needle tacking method was used to mechanically place the fibers within the woven cloth.
  • the coated web was passed through a convection oven at 300° F. (149° C.) for 8 minutes, yielding a cured prebond.
  • the lubricant and slurry coating was applied on top of the cured prebond.
  • the lubricant and slurry coating was cured as follows:
  • Examples 4-8 webs were formed from a blend of FIB1 and FIB2, and impregnated with a thermoset prebond resin, followed by a subsequent coating comprising the lubricant and abrasive slurry.
  • Examples 9-10 were formed from a blend of FIB1 and FIB2 and incorporated into a woven cotton cloth that was subsequently impregnated with a thermoset prebond resin, followed by a subsequent coating comprising the lubricant and abrasive slurry, and a thermoset resin in-situ.
  • Examples 11-12 were formed from FIB1 and incorporated into a woven cotton cloth. It is notable that example 11 did not use a thermoset prebond resin and was followed by a subsequent coating comprising the lubricant and abrasive slurry, with a thermoset resin in-situ.
  • the stainless-steel plate was preconditioned before the performance test with a random orbital sander obtained from 3M Company rated at 12,000 RPM, with a one minute run time on the plate using 5 inch diameter discs (12.7 cm) of P800 and P1200 (260 L obtained from 3M Company).
  • the tool was then set to traverse a 8-inch (20.32 cm) path at a rate of 4.00 inches/second (10 1 cm/see) in the +Y direction; followed by a 0.0375-inch (0.095 cm) path in the +X direction at a rate of 4.00 inches/second (10.16 cm/sec); followed by a 8-inch (20.32 cm) path in the +Y direction at a rate of 4.00 inches/second (10.16 cm/see).
  • the rotary tool was then activated to rotate at 2750 rpm under no load.
  • the abrasive article was then urged radially against the stainless-steel at a load of 3.5 lbs. (1.59 kg' with its axis of rotation parallel to the direction.
  • the tool was then activated to move through the prescribed path.
  • the mass of the discs was measured before and after each test to determine the total percent mass loss.
  • the stainless-steel plate's surface gloss was measured in gloss units at a 20° angle using a “micro-TRI-gloss” obtained from BYK-Gardner GmbH, and the surface roughness was measured using a “Pocket Surf PS1” obtained from Mahr GmbH.
  • the “Pocket Surf PS1” traversing length was set to 5.6 mm, the length cut off was set to 0.8 mm, and the sampling number was set to 5.
  • the data generated from the performance is provided in Table 5.

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US11292102B2 (en) 2017-12-29 2022-04-05 Saint-Gobain Abrasives, Inc. Abrasive buffing articles
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