SELF-CONTAINED BUFFING ARTICLES
Abrasive articles comprising at least one layer of fibrous nonwoven fabric, woven fabrics and combinations thereof are disclosed. The fabrics or combinations of fabrics may have a hardened adherent coating. The adherent coating may comprise a first coating and a second coating. The second coating may be formed on top of the first coating. The first coating may comprise a crosslinked binder and the second coating may comprise an abrasive particle and a lubricant.
Buffs are most often employed to refine surfaces by a three-body abrasion mechanism. Driven 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. Conversely, polishing, typically a two-body abrasion mechanism, is too aggressive to achieve the refinement necessary to produce a mirror-like finish. Thus, thee-body abrasion mechanisms have been employed to achieve a mirror-like finish.
SUMMARY OF THE INVENTIONThe 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 μ.
Other aspects of the invention relate, in part, to 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 μ.
Other 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 μ, and buffing a surface of the metal for a length of time sufficient to impart a desired luster to the surface of the metal.
Other aspects of the invention relate, in part to, 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 μ.
Other aspects of the invention relate, in part, to, 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.
It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present disclosure, which broader aspects are embodied in the exemplary construction. The Figures are for illustration only and should not be used for scaling the actual size of the nonwoven abrasive web or the resulting nonwoven abrasive articles.
As used herein, “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.
As used herein, “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.
As used herein, forms of the words “comprise”, “have”, and “include” are legally equivalent and open-ended. Therefore, additional non-recited elements, functions, steps or limitations may be present in addition to the recited elements, functions, steps, or limitations.
DETAILED DESCRIPTIONWhile three-body abrasive systems produce mirror finishes, a drawback is that the buffing compound, which must be frequently applied to achieve a consistent finish, can be undesirably transferred onto adjacent surfaces. The resulting residue must then be removed. Attempts to resolve these deficiencies by employing a two-body abrading system, wherein the abrasive composition is hardened to the working surfaces of the buff or pre-impregnated instead of peripherally applied, have been unsuccessful for cut and color buffs. Hence there is a need for cut and/or color buffs having a pre-impregnated abrasive composition for buffing such that the need to apply buffing compound to the buffing wheel is substantially eliminated.
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. In other embodiments, 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. In other embodiments additional coatings may be applied that contribute to the adherent coating of the buffing article.
Nonwoven FabricNonwoven fabrics useful in the practice of this invention may be made by any known web formation system. In some embodiments, the fabric may be spunbonded, hydroentangled, or melt blown. In some embodiments, the nonwoven fabric is a dry laid nonwoven fabric. In some embodiments, the nonwoven fabric is an air-laid nonwoven fabric. In some embodiments, 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. In some embodiments, 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. In some embodiments, natural fibers such as cotton, jute, ramie, and wool are useful alone or in combination. In some embodiments, blends of two, three, or even more fiber constituents may be used.
In some embodiments, fiber denier may be 0.1 denier (0.11 dtex) or greater. In some embodiments, fiber size may be 20 denier (22.5 dtex) or less, 15 denier or less, 6 denier or less, or 3 denier or less. In some embodiments, mixtures of two or more fiber deniers or ranges may be useful. In some embodiments, 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.
In some embodiments, 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/m2 to 500 g/m2, or from 75 g/m2 to 400 g/m2, or from 100 g/m2 to 300 g/m2. 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. In some embodiments, the nonwoven fabric is subsequently needle-tacked. In other embodiments, the nonwoven fabric may be subsequently calendered and/or otherwise thermally-treated (e.g., through-bonding).
Woven FabricSuitable woven fabrics may be selected from those made from synthetic or natural fibers or combinations thereof. Examples of synthetic fibers include polyester, nylon, and rayon. Examples of 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.
In some embodiments 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.
Prebond CoatingThe 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. In some embodiments, the prebond coating can also include abrasive particles, lubricants, and/or optional additives.
Second CoatingThe 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. In some embodiments, 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. In some embodiments, 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. In further embodiments, 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.
Crosslinkable Binder PrecursorsSuitable 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. In some embodiments, the first and second crosslinkable binders are selected to be different chemistries such as a phenolic resin and an acrylic. In other embodiments 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. Typically, 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.
Useful commercially available 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. (e.g., “MONDUR 1437”, “MONDUR MP-095”, or “MONDUR 448”); and polyisocyanates available under the trade designations “AIRTHANE” and “VERSATHANE” from Air Products and Chemicals, Allentown, Pa. (e.g., “AIRTHANE APC-504”, “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”).
To lengthen pot-life, polyisocyanates such as, for example, those mentioned above may be blocked with a blocking agent according to various techniques known in the art. Exemplary 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.
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”).
Suitable amine curatives include aromatic, alkyl-aromatic, or alkyl polyfunctional amines, preferably primary amines. Examples of 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 trade designation “KAYAHARD AA” by Nippon Kayaku Company, Ltd., Tokyo, Japan); an unmodified aromatic amine curative believed to comprise 3,3′ diethyl 4,4′ diaminodiphenyl methane, marketed under the trade designation “LAPOX K-450” by Royce International, East Rutherford, New Jersey; and bis(4-amino-3,5-diethylphenyl)methane (e.g., as marketed under the trade designation “LONZACURE M-DEA” by Lonza, Ltd., Basel, Switzerland), and mixtures thereof. If desired, polyol(s) may be added to the hardenable composition, for example, to modify (e.g., to retard) cure rates as required by the intended use.
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.
In some embodiments, 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. Examples of such 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.
LubricantExamples of 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. Such lubricants and commercial sources are known in the art. Other suitable lubricants may be apparent to those skilled in the art after reviewing the present disclosure.
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.), “Drakeol Mineral Oil—USP Grades ” (from Penreco, Karns City, Pa.), KAYDOL White Mineral Oil (from Sonneborn, Mahwah, N.J.), mineral oil (from Univar USA, Redmond, Wash.) and glycerin (from Acme Hardesty Oleochemicals, Blue Bell, Pa.).
Abrasive ParticlesSuitable 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.
Examples of useful abrasive particles 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.
In some embodiments 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.
Other Optional AdditivesOther optional 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. In some embodiments, 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.).
Coating Impregnation ProcessThe 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. In some embodiments, 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.
In some embodiments 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). In other embodiments 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.
In some embodiments, the total dry add-on weight of the coating(s) is from 50 g/m2 to 2000 g/m2, or from 200 g/m2to 1500 g/m2, or from 200 g/m2to 1100 g/m2. In some embodiments, the total weight of the final coated buffing fabric is from 200 g/m2 to 1500 g/m2.
Self-Contained Fibrous ArticlesThe 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. Alternately, 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.
The aforementioned steps may be performed in different order. For example, according to some embodiments, application of the prebond coating may be followed by a lamination step (in place of curing) and other processes such as molding, cutting, or others occurring prior to the application of the second coating. In these embodiments, curing takes place after the article has been formed as in the case of unitized and convoluted wheels, for example. In other embodiments the cutting and molding processes may occur subsequent to the curing of the second coating.
Typically, 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.
An exemplary embodiment of a nonwoven abrasive article is shown in
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
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
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.
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
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.
Other self-contained fibrous buffing articles may also find utility, including “flap brush” constructions 700 as illustrated in
The inventors have surprisingly discovered that incorporating a combination of woven and nonwoven fabrics in buffing wheels not only increases the durability of the wheel, but also advantageously allows the prebond coating step to be bypassed thereby significantly simplifying the manufacturing process. Thus, self-contained buffing wheels made in accordance with embodiments of the invention can be made by a simple one pass process, wherein the crosslinking agent, abrasive, and lubricant can be coated onto the fabric simultaneously to produce durable buffing wheels.
Heretofore, self-contained buffing wheels have been produced by methods involving multiple coating and/or curing steps. An example of a multi-step process is described in U.S. Pat. No. 9,08,299, the entire contents of which are hereby incorporated by reference. Multiple steps can undesirably increase production time and cost. Applicants have developed a method whereby the coating of the web can be accomplished in a one pass coating process thereby significantly reducing production time and costs.
In accordance with embodiments of the invention, 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.
Examples of suitable of woven and nonwoven fabrics are provided above. However, it will be appreciated that the description of such fabrics is exemplary and the invention encompasses any suitable woven and nonwoven fabric and combinations thereof.
EXAMPLESVarious embodiments of the present invention can be better understood by reference to the following Examples which are offered by way of illustration. The present invention is not limited to the Examples given herein.
Materials used in the Examples are described in Table 1. Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.
Preparation of unitized prebonds. 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 Macedon, 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. (105° C.) for 2 minutes, yielding a prebonded, nonwoven web of having a basis weight of 190 gsm. 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. After 10 minutes, the two sections of web had fused together into a single, unitized slab. This slab was placed in a forced air oven set at 275° F. (135° C.) for 180 minutes. After removal from the oven, the slab was cooled to room temperature, and an 8.0inch (20.32-centimeter) diameter 0.5-inch (1.27-centimeter) thick unitized abrasive wheel with a 1.25-inch (3.175-centimeter) center hole was die cut from it using a SAMCO SB-25 swing beam press manufactured by Deutsche Vereinigte Schuhmaschinen GmbH & Co., Frankfurt, Germany. The unitized wheels were impregnated with an abrasive slurry having the formula described in Table 2. The slurry was prepared in batches with a weight of about 3 Kg using a high-shear mixer with the speed adjusted to generate a strong vortex in the slurry while mixing.
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.
Example 2 Testing of Unitized WheelsThe 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
Each example was compared to a conventional sewn cotton buff and green compound and ranked as follows:
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 Macedon, 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. In the examples using a woven cotton cloth, a needle tacking method was used to mechanically place the fibers within the woven cloth. For examples using a thermoset prebond resin, 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 9-10Examples 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 11-12Examples 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.
After removal from the oven, the abrasive slurry coated webs were cooled to room temperature, and six 4-inch (10.16-centimeter) diameter abrasive discs with a 0.5-inch (1.27-centimeter) center hole were die cut using a SAMCO SB-25 swing beam press manufactured by Deutsche Vereinigte Schuhmaschinen GmbH & Co., Frankfurt, Germany.
Six-four-inch (10.16 cm) diameter discs were mounted on a rotary tool that was disposed over an X-Y table having a secured pre-conditioned 304 stainless-steel plate measuring 10 inches (25.4 centimeter) long by 6 inches (15.24 centimeter) wide by 0.028 inches (0.071 centimeter) thick. 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). This sequence was repeated for a total of 1.20 passes in the V direction. 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.
Other modifications and variations to the present disclosure may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present disclosure, which is set forth in the claims. It is understood that various embodiments may be interchanged in whole or part or combined with other aspects of the various embodiments. The preceding description, given to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure.
Claims
1. 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 μ.
2. (canceled)
3. The unitized abrasive wheel of claim 1, wherein the nonwoven fabric comprises a combination of a synthetic fiber and a natural fiber.
4. The unitized wheel of claim 3, where in the synthetic fiber comprises nylon and the natural fiber comprises cellulose.
5-7. (canceled)
8. The unitized wheel of claim 10, wherein the crosslinked binder comprises a polyurethane and an amine.
12. (canceled)
9. The unitized wheel of claim 1, wherein less than all of the abrasive particles are fixed to the nonwoven web.
10. The unitized wheel of claim 1, wherein substantially all of the abrasive particles are fixed to the nonwoven web.
15-18. (canceled)
11. 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 μ.
12. (canceled)
13. (canceled)
14. The method of claim 19, wherein the nonwoven fabric comprises a combination of a synthetic fiber and a natural fiber.
15. (canceled)
16. (canceled)
26-28. (canceled)
19. The method of claim 19, wherein substantially all of the abrasive particles are fixed to the nonwoven web.
20. The method of claim 19, wherein the first coating comprises abrasive particles.
32-44. (canceled)
21. 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 μu.
46-48. (canceled)
22. The self-contained buffing article of claim 45 wherein the ratio of non-woven to the woven is about 1.5.
23. The self-contained buffing article of claim 45, wherein the woven fabric comprises cellulose.
24. The self-contained buffing article of claim 45, wherein the lubricant comprises at least a fatty acid, mineral oil, and glycerin.
25. The self-contained buffing article of claim 45, wherein the woven and nonwoven fabrics are mechanically entangled.
53-61. (canceled)
Type: Application
Filed: Jul 18, 2019
Publication Date: Oct 7, 2021
Inventors: Robinette S. Alkhas (St. Paul, MN), Ronald D. Apple (Apple Valley, CA)
Application Number: 17/250,454
