Patent Description:
Abrasive articles containing from the abrasive particles secured to a backing by a binder are useful for abrading, finishing, or grinding a wide variety of materials and surfaces in the manufacturing of goods. Two common types of abrasive articles are coated abrasive articles and nonwoven abrasive articles.

Coated abrasive articles generally have an abrasive layer typically secured to a relatively dense backing such as, for example, woven or knitted fabric, vulcanized fiber, polymer film, or paper. The abrasive layer comprises abrasive particles and one or more binders that secure the abrasive particles to the backing.

One common type of coated abrasive article has an abrasive layer comprised of a make layer, a size layer, and abrasive particles. In making such a coated abrasive article, a make layer precursor comprising a curable make resin is applied to a major surface of the backing. Abrasive particles are then at least partially embedded into the curable make resin (e.g., via electrostatic coating), and the curable make resin is at least partially cured (that is, crosslinked) to adhere the abrasive particles to the backing. A size layer precursor comprising a curable size resin is then applied over the at least partially cured curable make resin and abrasive particles, followed by curing of the curable size resin precursor, and optionally further curing of the curable make resin.

Some coated abrasive articles additionally have a supersize layer covering the abrasive layer. The supersize layer typically includes grinding aids and/or anti-loading materials.

Some coated abrasive articles have one or more backing treatments such as a backsize layer (i.e., a layer on the major surface of the backing opposite the major surface having the abrasive layer), a presize layer, a tie layer (i.e., a layer between the abrasive layer and the major surface to which the abrasive layer is secured), a saturant, a subsize treatment, or a combination thereof. A subsize is similar to a saturant except that it is applied to a previously treated backing.

Two common forms of coated abrasive articles are discs and belts. During abrading operations using belts, the abrading action of the belt on a workpiece (e.g., wood) increases the load on the drive motor used to drive the belt, and hence an increase in electrical current draw by the motor.

In the case of nonwoven abrasive articles, the binder material precursor is commonly coated on a lofty open nonwoven fiber web, the abrasive particles are secured to the fiber web by a binder material. Typically, to make nonwoven abrasive articles, a curable binder material precursor is coated on a lofty open nonwoven fiber web, the abrasive particles are adhered to the binder material precursor (and/or mixed into the curable binder material precursor, and then the curable binder material precursor is cured sufficiently to form the binder, thereby retaining the abrasive particles during use. Such nonwoven abrasive articles are used extensively in the manufacture of abrasive articles for cleaning, abrading, finishing, and polishing applications on any of a variety of surfaces. Exemplary of such nonwoven abrasive articles are those described in <CIT>). Exemplary commercial nonwoven abrasive articles include nonwoven abrasive hand pads such as those marketed by <NUM> Company of Saint Paul, Minnesota under the trade designation SCOTCH-BRITE.

There continues to be a need for improving the cost, performance, and/or life of abrasive articles such as coated abrasives and nonwoven abrasives.

From <CIT> there is known an abrasive article comprising abrasive particles secured to a substrate by at least one binder material.

In one aspect, the present disclosure provides an abrasive article comprising abrasive particles secured to a substrate by at least one binder material, wherein the at least one binder material comprises a cured reaction product of components comprising:.

wherein, based on the total solids weight of components a) and b), the components comprise <NUM> to <NUM> percent by weight of component a) and <NUM> to <NUM> percent by weight of component b).

In a second aspect, the present disclosure provides a method of abrading a workpiece, the method comprising frictionally contacting an abrasive article according to the present disclosure with a surface of the workpiece and moving at least one of the abrasive article or the workpiece to abrade the surface of the workpiece.

In a third aspect, the present disclosure provides a method of making an abrasive article, the method comprising:.

Advantageously, phenolic/polyurethane binder materials according to the present disclosure may impart desirable toughness and brittleness/stiffness properties to abrasive articles in which they are incorporated.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure.

Abrasive articles according to the present disclosure comprise abrasive particles secured to a substrate (e.g., a coated abrasive backing or a lofty open nonwoven fiber web) by at least one binder material.

Referring to <FIG>, an exemplary coated abrasive article <NUM> has backing <NUM> and abrasive layer <NUM> according to the present disclosure. Abrasive layer <NUM>, in turn, includes abrasive particles <NUM> secured to major surface <NUM> of backing <NUM> by make layer <NUM> and size layer <NUM>.

Suitable materials for the substrate include polymeric films, metal foils, woven fabrics, knitted fabrics, paper, vulcanized fiber, nonwovens, foams, screens, laminates, combinations thereof, and treated versions thereof. The backing may also be a laminate of two materials (e.g., paper/film, cloth/paper, or film/cloth). The backing may also be a fibrous reinforced thermoplastic such as described, for example, as described, for example, in <CIT>), or an endless spliceless belt, as described, for example, in <CIT>). The backing may be a polymeric substrate having hooking stems projecting therefrom such as that described, for example, in <CIT>), or the backing may be a loop fabric such as that described, for example, in <CIT>). For applications where stiffness of the backing is desired, a flexible backing may also be used by affixing it to a rigid backup pad mounted to the grinding tool.

The choice of backing material may depend on the intended application of the coated abrasive article. The thickness and smoothness of the backing should also be suitable to provide the desired thickness and smoothness of the coated abrasive article, wherein such characteristics of the coated abrasive article may vary depending, for example, on the intended application or use of the coated abrasive article. For disc grinding applications where stiffness and cost are concerns, vulcanized fiber backings are typically preferred.

Optionally, an antistatic material may be applied to the backing. The addition of an antistatic material can reduce the tendency of the coated abrasive article to accumulate static electricity when sanding wood or wood-like materials. Additional details regarding antistatic backings and backing treatments can be found in, for example, <CIT>); <CIT>); <CIT>); and <CIT>).

In some instances, it may be desirable to incorporate a pressure-sensitive adhesive onto the backside of the coated abrasive article such that the resulting coated abrasive article can be secured to a backup pad. Exemplary pressure-sensitive adhesives include latex crepe, rosin, acrylic polymers, and copolymers including polyacrylate esters (e.g., poly(butyl acrylate)), vinyl ethers (e.g., poly(vinyl n-butyl ether)), alkyd adhesives, rubber adhesives (e.g., natural rubber, synthetic rubber, chlorinated rubber), and mixtures thereof.

Abrasive disc backings are generally circular and preferably rotationally symmetric around their center. Preferably, they have a circular perimeter, but may have additional features along the perimeter such as, for example, in the case of a scalloped perimeter.

Abrasive belt backings are generally flexible and durable. They may be spliced or spliceless.

To promote adhesion of binder resins to the backing, one or more surfaces of the backing may be modified by known methods including corona discharge, ultraviolet light exposure, electron beam exposure, flame discharge, and/or scuffing.

Likewise, the backing may include one or more treatments selected from a backsize layer, a presize layer, a tie layer, a saturant, a subsize treatment, or a combination thereof.

Details concerning coated abrasive articles comprising abrasive particles and make, size, and optional supersize layers are well known and are described, for example, in <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); and <CIT>).

The abrasive layer may comprise a single binder layer having abrasive particles retained therein, or more typically, a multilayer construction having make and size layers. Coated abrasives according to the present disclosure may optionally include additional layers such as, for example, a supersize layer that is superimposed on the abrasive layer, or a backing antistatic treatment layer may also be included, if desired.

Exemplary suitable binders can be prepared from thermally curable resins, radiation-curable resins, and combinations thereof.

According to the present disclosure, at least one binder material (e.g., the make layer or a slurry layer - including a structure abrasive layer)) secures the abrasive particles to the backing and comprises a cured reaction product of components comprising:.

Suitable phenolic resins are generally formed by condensation of phenol or an alkylated phenol (e.g., cresol) and formaldehyde, and are usually categorized as resole or novolac phenolic resins. Novolac phenolic resins are acid-catalyzed and have a molar ratio of formaldehyde to phenol of less than <NUM>:<NUM>. Resole (also resol) phenolic resins can be catalyzed by alkaline catalysts, and the molar ratio of formaldehyde to phenol is greater than or equal to one, typically between <NUM> and <NUM>, thus presenting pendant methylol groups. Alkaline catalysts suitable for catalyzing the reaction between aldehyde and phenolic components of resole phenolic resins include sodium hydroxide, barium hydroxide, potassium hydroxide, calcium hydroxide, organic amines, and sodium carbonate, all as solutions of the catalyst dissolved in water.

Resole phenolic resins are typically coated as a solution with water and/or organic solvent (e.g., alcohol). Typically, the solution includes about <NUM> percent to about <NUM> percent solids by weight, although other concentrations may be used. If the solids content is very low, then more energy is required to remove the water and/or solvent. If the solids content is very high, then the viscosity of the resulting phenolic resin is too high which typically leads to processing problems.

Phenolic resins are well-known and readily available from commercial sources. Examples of commercially available resole phenolic resins useful in practice of the present disclosure include those marketed by Durez Corporation under the trade designation VARCUM (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>); those marketed by Ashland Chemical Co. of Bartow, Florida under the trade designation AEROFENE (e.g., AEROFENE <NUM>); and those marketed by Kangnam Chemical Company Ltd. of Seoul, South Korea under the trade designation PHENOLITE (e.g., PHENOLITE TD-<NUM>).

Typically, it is preferred that the phenolic resin comprise a resole resin; however, this is not a requirement.

Suitable polyurethane dispersions may include aliphatic and/or aromatic polyurethane dispersions. More specifically, the polyurethane may comprise a polycarbonate polyurethane, a polyester polyurethane, or polyether polyurethane. The polyurethane may comprise a homopolymer or a copolymer.

Examples of commercially available polyurethane dispersions include aqueous aliphatic polyurethane emulsions available as NEOREZ R-<NUM>, NEOREZ R-<NUM>, NEOREZ R-<NUM>, NEOREZ R-<NUM>, and NEOREZ R-<NUM> from DSM Neo Resins, Inc. , Wilmington, Massachusetts; aqueous anionic polyurethane dispersions available as ESSENTIAL CC4520, ESSENTIAL CC4560, ESSENTIAL R4100, and ESSENTIAL R4188 from Essential Industries, Inc. , Merton, Wisconsin; polyester polyurethane dispersions available as SANCURE <NUM>, SANCURE <NUM>, and SANCURE <NUM> from Lubrizol, Inc. of Cleveland, Ohio; an aqueous aliphatic self-crosslinking polyurethane dispersion available as TURBOSET <NUM> from Lubrizol, Inc. ; and an aqueous anionic, co-solvent free, aliphatic self-crosslinking polyurethane dispersion, available as BAYHYDROL PR240 from Bayer Material Science, LLC of Pittsburgh, Pennsylvania.

Additional suitable commercially available aqueous polyurethane dispersions include:.

Optional additives including rheological modifiers, anti-foaming agents, water-based latexes and crosslinkers may be added to the aqueous polyurethane dispersion. Suitable crosslinkers include, for example, polyfunctional aziridine, methoxymethylolated melamine, urea resin, carbodiimide, polyisocyanate and blocked isocyanate. Additional water may also be added to dilute the formulation of the aqueous polyurethane dispersion, the phenolic resin, or combination thereof.

It will be understood that the first binder may be formed using, for example, an aqueous polyurethane dispersion and a water-based latex.

In some embodiments, the aqueous polyurethane dispersion contains less than about <NUM>%, <NUM>%, <NUM>% or <NUM>% organic solvent. In a specific embodiment, the aqueous polyurethane dispersion is substantially free of organic solvent. In some embodiments, it has been found that the aqueous polyurethane dispersion comprises at least about <NUM>%, <NUM>%, or <NUM>% solids, and no greater than about <NUM>% or <NUM>% solids. The aqueous polyurethane dispersion may comprise no greater than about <NUM>%, <NUM>% ,or <NUM>% water. In some embodiments, it has been found that the aqueous polyurethane dispersion forms a film having a Koenig hardness of at least about <NUM> and no greater than about <NUM> seconds when measured according to ASTM <NUM>-<NUM>. Further, in some embodiments, it has been found that the aqueous polyurethane dispersion may have a surface tension that is at least about <NUM>% of the surface tension of water and no greater than about <NUM>% of the surface tension of water. And in some embodiments, the aqueous polyurethane dispersion may have a viscosity of at least about <NUM> mPa s to no greater than about <NUM> mPa s, or at least about <NUM>%, <NUM>% or <NUM>% of the viscosity of water and no greater than about <NUM>%, <NUM>% or <NUM>% of the viscosity of water.

In addition, in some embodiments, the aqueous polyurethane dispersion may comprise at least about <NUM>, <NUM>, or even at least about <NUM> parts per million (ppm) of dimethylolpropionic acid. Optional additives including rheological modifiers, anti-foaming agents, and crosslinkers may be added to the aqueous polyurethane dispersion, for example. Suitable crosslinkers include, for example, polyfunctional aziridine, methoxymethylolated melamine, urea resin, carbodiimide, polyisocyanate and blocked isocyanate. Additional water may be added to reduce viscosity of the aqueous polyurethane dispersion. Likewise, addition of up to <NUM> percent by weight of organic solvent (e.g., propyl methyl ether or isopropanol) to the aqueous polyurethane dispersion may be used to reduce viscosity and/or improve the miscibility of ingredients.

Preferably, the dispersed polyurethane includes at least one polycarbonate segment, although this is not a requirement.

The phenolic resin and aqueous polyurethane dispersion components are mixed in a solids weight ratio of <NUM> to <NUM> percent by weight phenolic resin to <NUM> to <NUM> percent by weight of polyurethane. In some embodiments, the phenolic resin and aqueous polyurethane dispersion components are mixed in a solids weight ratio of <NUM> to <NUM> percent by weight phenolic resin to <NUM> to <NUM> percent by weight of polyurethane. In some embodiments, the phenolic resin and aqueous polyurethane dispersion components are mixed in a solids weight ratio of <NUM> to <NUM> percent by weight phenolic resin to <NUM> to <NUM> percent by weight of polyurethane. In some embodiments, the phenolic resin and aqueous polyurethane dispersion components are mixed in a solids weight ratio of <NUM> to <NUM> percent by weight phenolic resin to <NUM> to <NUM> percent by weight of polyurethane. In some embodiments, the phenolic resin and aqueous polyurethane dispersion components are mixed in a solids weight ratio of <NUM> to <NUM> percent by weight phenolic resin to <NUM> to <NUM> percent by weight of polyurethane. In some embodiments, the phenolic resin and aqueous polyurethane dispersion components are mixed in a solids weight ratio of <NUM> to <NUM> percent by weight phenolic resin to <NUM> to <NUM> percent by weight of polyurethane.

The make layer precursor may be applied by any known coating method for applying a make layer to a backing such as, for example, including roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, and spray coating.

The basis weight of the make layer utilized may depend, for example, on the intended use(s), type(s) of abrasive particles, and nature of the coated abrasive disc being prepared, but typically will be in the range of from <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> grams per square meter (gsm) to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM> gsm. The make layer may be applied by any known coating method for applying a make layer (also referred to in the art as a make coat) to a backing, including, for example, roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, and spray coating.

Once the make layer precursor is coated on the backing, the abrasive particles are applied to and embedded in the make layer precursor.

Crushed abrasive or non-abrasive particles may be included in the abrasive layer between the abrasive elements and/or abrasive platelets, preferably in sufficient quantity to form a closed coat (i.e., substantially the maximum possible number of particles of nominal specified grade(s) that can be retained in the abrasive layer).

Examples of suitable abrasive particles include: fused aluminum oxide; heat-treated aluminum oxide; white fused aluminum oxide; ceramic aluminum oxide materials such as those commercially available under the trade designation <NUM> CERAMIC ABRASIVE GRAIN from <NUM> Company, St. Paul, MN; brown aluminum oxide; blue aluminum oxide; silicon carbide (including green silicon carbide); titanium diboride; boron carbide; tungsten carbide; garnet; titanium carbide; diamond; cubic boron nitride; garnet; fused alumina zirconia; iron oxide; chromia; zirconia; titania; tin oxide; quartz; feldspar; flint; emery; sol-gel-derived abrasive particles; and combinations thereof. Of these, molded sol-gel derived alpha alumina triangular abrasive platelets are preferred in many embodiments. Abrasive material that cannot be processed by a sol-gel route may be molded with a temporary or permanent binder to form shaped precursor particles which are then sintered to form triangular abrasive platelets, for example, as described in <CIT>.

Examples of sol-gel-derived abrasive particles and methods for their preparation can be found in <CIT>); <CIT>); <CIT>), <CIT>); and <CIT>). It is also contemplated that the abrasive particles could comprise abrasive agglomerates such, for example, as those described in <CIT>) or <CIT>). In some embodiments, the triangular abrasive platelets may be surface-treated with a coupling agent (e.g., an organosilane coupling agent) or other physical treatment (e.g., iron oxide or titanium oxide) to enhance adhesion of the abrasive particles to the binder (e.g., make and/or size layer). The abrasive particles may be treated before combining them with the corresponding binder precursor, or they may be surface treated in situ by including a coupling agent to the binder.

Preferably, sol-gel-derived abrasive particles comprise shaped (e.g., triangular) abrasive platelets. Triangular abrasive platelets composed of crystallites of alpha alumina, magnesium alumina spinel, and a rare earth hexagonal aluminate may be prepared using sol-gel precursor alpha alumina particles according to methods described in, for example, <CIT>) and <CIT>) and<CIT>).

Alpha-alumina-based triangular abrasive platelets can be made according to well-known multistep processes. Briefly, the method comprises the steps of making either a seeded or non-seeded sol-gel alpha alumina precursor dispersion that can be converted into alpha alumina; filling one or more mold cavities having the desired outer shape of the triangular abrasive platelet with the sol-gel, drying the sol-gel to form precursor triangular abrasive platelets; removing the precursor triangular abrasive platelets from the mold cavities; calcining the precursor triangular abrasive platelets to form calcined, precursor triangular abrasive platelets, and then sintering the calcined, precursor triangular abrasive platelets to form triangular abrasive platelets. The process will now be described in greater detail.

Further details concerning methods of making sol-gel-derived abrasive particles can be found in, for example, <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); and <CIT>); and in <CIT>).

The abrasive particles may include a single kind of triangular abrasive particles or a blend of two or more sizes, shapes, and/or compositions of abrasive particles. In some preferred embodiments, triangular abrasive platelets are precisely-shaped in that individual triangular abrasive platelets will have a shape that is essentially the shape of the portion of the cavity of a mold or production tool in which the particle precursor was dried, prior to optional calcining and sintering.

Triangular abrasive platelets used in the present disclosure can typically be made using tools (i.e., molds) cut using precision machining, which provides higher feature definition than other fabrication alternatives such as, for example, stamping or punching. Typically, the cavities in the tool surface have planar faces that meet along sharp edges, and form the sides and top of a truncated pyramid. The resultant triangular abrasive platelets have a respective nominal average shape that corresponds to the shape of cavities (e.g., truncated pyramid) in the tool surface; however, variations (e.g., random variations) from the nominal average shape may occur during manufacture, and triangular abrasive platelets exhibiting such variations are included within the definition of triangular abrasive platelets as used herein.

In some embodiments, the base and the top of the triangular abrasive platelets are substantially parallel, resulting in prismatic or truncated pyramidal shapes, although this is not a requirement. In some embodiments, the sides of a truncated trigonal pyramid have equal dimensions and form dihedral angles with the base of about <NUM> degrees. However, it will be recognized that other dihedral angles (including <NUM> degrees) may also be used. For example, the dihedral angle between the base and each of the sides may independently range from <NUM> to <NUM> degrees, typically <NUM> to <NUM> degrees, more typically <NUM> to <NUM> degrees.

As used herein in referring to triangular abrasive platelets, the term "length" refers to the maximum dimension of a triangular abrasive platelet. "Width" refers to the maximum dimension of the triangular abrasive platelet that is perpendicular to the length. The terms "thickness" or "height" refer to the dimension of the triangular abrasive platelet that is perpendicular to the length and width.

Examples of sol-gel-derived triangular alpha alumina (i.e., ceramic) abrasive platelets can be found in <CIT>); <CIT>(<CIT>)); and <CIT>). Details concerning such abrasive particles and methods for their preparation can be found, for example, in <CIT>); <CIT>); and <CIT>); and in <CIT>); <CIT>. ); and <CIT>).

The triangular abrasive platelets are typically selected to have a length in a range of from <NUM> micron to <NUM> microns, more typically <NUM> microns to about <NUM> microns, and still more typically from <NUM> to <NUM> microns, although other lengths may also be used.

Triangular abrasive platelets are typically selected to have a width in a range of from <NUM> micron to <NUM> microns, more typically <NUM> microns to <NUM> microns, and more typically <NUM> microns to <NUM> microns, although other lengths may also be used.

Triangular abrasive platelets are typically selected to have a thickness in a range of from <NUM> micron to <NUM> microns, more typically from <NUM> micron to <NUM> microns, although other thicknesses may be used.

In some embodiments, triangular abrasive platelets may have an aspect ratio (length to thickness) of at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more.

Surface coatings on the triangular abrasive platelets may be used to improve the adhesion between the triangular abrasive platelets and a binder in coated abrasive discs, or can be used to aid in electrostatic deposition of the triangular abrasive platelets. In one embodiment, surface coatings as described in <CIT>) in an amount of <NUM> to <NUM> percent surface coating to triangular abrasive platelet weight may be used. Such surface coatings are described in <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); and <CIT>). Additionally, the surface coating may prevent the triangular abrasive platelet from capping. Capping is the term to describe the phenomenon where metal particles from the workpiece being abraded become welded to the tops of the triangular abrasive platelets. Surface coatings to perform the above functions are known to those of skill in the art.

The abrasive particles may be independently sized according to an abrasives industry recognized specified nominal grade. Exemplary abrasive industry recognized grading standards include those promulgated by ANSI (American National Standards Institute), FEPA (Federation of European Producers of Abrasives), and JIS (Japanese Industrial Standard). ANSI grade designations (i.e., specified nominal grades) include, for example: ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, ANSI <NUM>, and ANSI <NUM>. FEPA grade designations include F4, F5, F6, F7, F8, F10, F12, F14, F16, F16, F20, F22, F24, F30, F36, F40, F46, F54, F60, F70, F80, F90, F100, F120, F150, F180, F220, F230, F240, F280, F320, F360, F400, F500, F600, F800, F1000, F1200, F1500, and F2000. JIS grade designations include JIS8, JIS12, JIS16, JIS24, JIS36, JIS46, JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS600, JIS800, JIS1000, JIS1500, JIS2500, JIS4000, JIS6000, JIS8000, and JIS10000. According to one embodiment of the present disclosure, the average diameter of the abrasive particles may be within a range of from <NUM> to <NUM> microns in accordance with FEPA grades F60 to F24.

Alternatively, the abrasive particles can be graded to a nominal screened grade using U. Standard Test Sieves conforming to ASTM E-<NUM> "Standard Specification for Wire Cloth and Sieves for Testing Purposes". ASTM E-<NUM> prescribes the requirements for the design and construction of testing sieves using a medium of woven wire cloth mounted in a frame for the classification of materials according to a designated particle size. A typical designation may be represented as -<NUM>+<NUM> meaning that the abrasive particles pass through a test sieve meeting ASTM E-<NUM> specifications for the number <NUM> sieve and are retained on a test sieve meeting ASTM E-<NUM> specifications for the number <NUM> sieve. In one embodiment, the abrasive particles have a particle size such that most of the particles pass through an <NUM> mesh test sieve and can be retained on a <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> mesh test sieve. In various embodiments, the abrasive particles can have a nominal screened grade of: -<NUM>+<NUM>, -<NUM>/+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>/+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, -<NUM>+<NUM>, or -<NUM>+<NUM>. Alternatively, a custom mesh size can be used such as -<NUM>+<NUM>.

After deposition of the abrasive particles, the make layer precursor is at least partially cured; for example, using heat and/or electromagnetic radiation.

A size layer precursor is the disposed over at least a portion of the at least partially cured make layer and abrasive particles and at least partially cured to further secure the abrasive particles to the backing. The size layer precursor may comprise, for example, glue, phenolic resin, aminoplast resin, urea-formaldehyde resin, melamine-formaldehyde resin, urethane resin, free-radically polymerizable polyfunctional (meth)acrylate (e.g., aminoplast resin having pendant α,β-unsaturated groups, acrylated urethane, acrylated epoxy, acrylated isocyanurate), epoxy resin (including bis-maleimide and fluorene-modified epoxy resins), isocyanurate resin, and mixtures thereof. If phenolic resin is used to form the make layer, it is likewise preferably used to form the size layer. The size layer precursor may be applied by any known coating method for applying a size layer to a backing, including roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, spray coating, and the like. If desired, a presize layer precursor or make layer precursor according to the present disclosure may be also used as the size layer precursor.

The basis weight of the size layer will also necessarily vary depending on the intended use(s), type(s) of abrasive particles, and nature of the coated abrasive disc being prepared, but generally will be in the range of from <NUM> or <NUM> grams per square meter (gsm) to <NUM> gsm, <NUM> gsm, or even <NUM> gsm, or more. The size layer precursor may be applied by any known coating method for applying a size layer precursor (also referred to in the art as a size coat) to a backing including, for example, roll coating, extrusion die coating, curtain coating, and spray coating.

In some embodiments, the size layer comprises components a) and b) of the first binder precursor, although different ratios of the components may be used. In some embodiments, the make layer and the size layer are the same.

In another exemplary embodiment of a coated abrasive article according to the present disclosure, the abrasive layer may comprise a cured slurry of a binder precursor and abrasive particles. Referring to <FIG>, exemplary coated abrasive article <NUM> has backing <NUM> and abrasive layer <NUM>. Abrasive layer <NUM>, in turn, includes abrasive particles <NUM> and binder <NUM> according to the present disclosure.

In this embodiment, the abrasive particles are dispersed throughout a binder precursor which may be any composition described as for the make layer precursor above and coated on the backing. Likewise, the abrasive particles may be as described hereinbefore. In preferred embodiments, such coated abrasive articles may have a desired topography imparted to the abrasive surface. For example, the abrasive layer may comprise shaped abrasive composites, which in some embodiments are precisely-shaped, secured to the backing. Structured abrasive articles fall in this category.

Further details concerning structured coated abrasive articles may be found, for example, in <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); and <CIT>).

Once applied, the size layer precursor, and typically the partially cured make layer precursor, are sufficiently cured to provide a usable coated abrasive disc. In general, this curing step involves thermal energy, although other forms of energy such as, for example, radiation curing may also be used. Useful forms of thermal energy include, for example, heat and infrared radiation. Exemplary sources of thermal energy include ovens (e.g., festoon ovens), heated rolls, hot air blowers, infrared lamps, and combinations thereof.

In addition to other components, binder precursors, if present, in the make layer precursor and/or presize layer precursor of coated abrasive discs according to the present disclosure may optionally contain catalysts (e.g., thermally activated catalysts or photocatalysts), free-radical initiators (e.g., thermal initiators or photoinitiators), curing agents to facilitate cure. Such catalysts (e.g., thermally activated catalysts or photocatalysts), free-radical initiators (e.g., thermal initiators or photoinitiators), and/or curing agents may be of any type known for use in coated abrasive discs including, for example, those described herein.

In addition to other components, the make and size layer precursors may further contain optional additives, for example, to modify performance and/or appearance. Exemplary additives include grinding aids, fillers, plasticizers, wetting agents, surfactants, pigments, coupling agents, fibers, lubricants, thixotropic materials, antistatic agents, suspending agents, and/or dyes.

Exemplary grinding aids, which may be organic or inorganic, include waxes, halogenated organic compounds such as chlorinated waxes like tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride; halide salts such as sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride; and metals and their alloys such as tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium. Examples of other grinding aids include sulfur, organic sulfur compounds, graphite, and metallic sulfides. A combination of different grinding aids can be used.

Exemplary antistatic agents include electrically conductive material such as vanadium pentoxide (e.g., dispersed in a sulfonated polyester), humectants, carbon black and/or graphite in a binder.

Examples of useful fillers for this disclosure include silica such as quartz, glass beads, glass bubbles and glass fibers; silicates such as talc, clays, (montmorillonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate; metal sulfates such as calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate; gypsum; vermiculite; wood flour; aluminum trihydrate; carbon black; aluminum oxide; titanium dioxide; cryolite; chiolite; and metal sulfites such as calcium sulfite.

Optionally a supersize layer may be applied to at least a portion of the size layer. If present, the supersize typically includes grinding aids and/or anti-loading materials. The optional supersize layer may serve to prevent or reduce the accumulation of swarf (the material abraded from a workpiece) between abrasive particles, which can dramatically reduce the cutting ability of the coated abrasive disc. Useful supersize layers typically include a grinding aid (e.g., potassium tetrafluoroborate), metal salts of fatty acids (e.g., zinc stearate or calcium stearate), salts of phosphate esters (e.g., potassium behenyl phosphate), phosphate esters, urea-formaldehyde resins, mineral oils, crosslinked silanes, crosslinked silicones, and/or fluorochemicals. Useful supersize materials are further described, for example, in <CIT>). Typically, the amount of grinding aid incorporated into coated abrasive articles is about <NUM> to about <NUM> gsm, more typically about <NUM> to about <NUM> gsm. The supersize may contain a binder such as for example, those used to prepare the size or make layer, but it need not have any binder.

Further details concerning coated abrasives comprising an abrasive layer secured to a backing, wherein the abrasive layer comprises abrasive particles and make, size, and optional supersize layers are well known, and may be found, for example, in <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); <CIT>); and No. <CIT>).

Nonwoven abrasive articles typically include a porous (e.g., a lofty open porous) polymer filament structure having abrasive particles bonded thereto by a binder. An exemplary embodiment of a nonwoven abrasive article according to the present disclosure is shown in <FIG>, wherein lofty open nonwoven web <NUM> is formed of entangled fibers <NUM> and is impregnated with binder <NUM> according to the present disclosure. Abrasive particles <NUM> are dispersed throughout fibrous web <NUM> on exposed surfaces of fibers <NUM>. Binder resin <NUM> uniformly coats portions of fibers <NUM> and forms globules <NUM> which may encircle individual fibers or bundles of fibers, adhere to the surface of the fibers and/or collect at the intersection of contacting fibers, providing abrasive sites throughout the nonwoven abrasive article.

The lofty open fiber web is a lofty nonwoven fibrous material having a substantially continuous network of voids extending therethrough. By use of the term "lofty open fiber web", what is intended is a layer of nonwoven web material composed of a plurality of randomly oriented fibers, typically entangled, having a substantially continuous network of interconnecting voids extending therethrough.

Nonwoven fiber webs are typically selected to be suitably compatible with adhering binders and abrasive particles while also being processable in combination with other components of the article, and typically can withstand processing conditions (e.g., temperatures) such as those employed during application and curing of the curable composition. The fibers may be chosen to affect properties of the abrasive article such as, for example, flexibility, elasticity, durability or longevity, abrasiveness, and finishing properties. Examples of fibers that may be suitable include natural fibers, synthetic fibers, and mixtures of natural and/or synthetic fibers. Examples of synthetic fibers include those made from polyester (e.g., polyethylene terephthalate), polyamides (e.g., nylon <NUM>, nylon <NUM>/<NUM>, and nylon <NUM>), polyolefins (e.g., polyethylene, polypropylene, and polybutylene), acrylic polymers (e.g., polyacrylonitrile and copolymers containing acrylic monomers), rayon, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymers, and vinyl chloride-acrylonitrile copolymers. Examples of suitable natural fibers include cotton, wool, jute, and hemp. The fibers may be of virgin material or of recycled or waste material, for example, reclaimed from garment cuttings, carpet manufacturing, fiber manufacturing, or textile processing. The fibers may be homogenous or a composite such as a bicomponent fiber (e.g., a co-spun sheath-core fiber). The fibers may be tensilized and crimped. They may be chopped fibers (i.e., staple fibers) or continuous filaments such as those formed by an extrusion process. Combinations of fibers may also be used.

The fibers may comprise continuous fiber, staple fiber, or a combination thereof. For example, the fiber web may comprise staple fibers having a length of at least about <NUM> millimeters (mm), at least about <NUM>, or at least about <NUM>, and less than about <NUM>, less than about <NUM>, or less than about <NUM>, although shorter and longer fibers (e.g., continuous filaments) may also be useful. The fibers may have a fineness or linear density of at least about <NUM> decitex (<NUM> dtex, <NUM> grams/<NUM> meters), at least about <NUM> dtex, or at least about <NUM> dtex, and less than about <NUM> dtex, less than about <NUM> dtex, or less than about <NUM> dtex, although fibers having lesser and/or greater linear densities may also be useful. Mixtures of fibers with differing linear densities may be useful, for example, to provide a nonwoven abrasive article that upon use will result in a specifically preferred surface finish.

Nonwoven fiber webs may be made, for example, by conventional air laid, carded, stitch bonded, spun bonded, wet laid, and/or melt blown procedures. Air laid fiber webs may be prepared using equipment such as, for example, that available as a RANDO WEBBER from Rando Machine Company of Macedon, New York.

Frequently, as known in the abrasive art, it is useful to apply a pre-bond resin to the nonwoven fiber web prior to coating with the curable composition. The pre-bond resin serves, for example, to help maintain the nonwoven fiber web integrity during handling, and may also facilitate bonding of the urethane binder to the nonwoven fiber web. Examples of pre-bond resins include phenolic resins, urethane resins, hide glue, acrylic resins, urea-formaldehyde resins, melamine-formaldehyde resins, epoxy resins, and combinations thereof. The amount of pre-bond resin used in this manner is typically adjusted to bond the fibers together at their points of crossing contact. In those cases, wherein the nonwoven fiber web includes thermally bondable fibers, thermal bonding of the nonwoven fiber web may also be helpful to maintain web integrity during processing.

The lofty open fiber web typically has a thickness of at least <NUM>, more typically at least <NUM> millimeters, and more typically at least <NUM> millimeters, although other thicknesses may also be used. Common thicknesses for the lofty open fiber web are, for example, <NUM> (<NUM>/<NUM> inch) and <NUM> (<NUM>/<NUM> inch). Addition of a pre-bond binder onto the fibrous mat does not significantly alter the thickness of the lofty open fiber web.

The basis weight of the lofty open fiber web (fibers only, with no pre-bond binder layer) is typically from about <NUM> grams per square meter to about <NUM> kilogram per square meter, and more typically from about <NUM> to about <NUM> grams per square meter, although other basis weights may also be used. Typically, a pre-bond binder is applied to the lofty open fiber web to lock the fibers. The basis weight of the lofty open fiber web, with pre-bond binder, is typically from about <NUM> grams per square meter to about <NUM> kilograms per square meter, and more typically from about <NUM> grams to about <NUM> kilogram per square meter, although this is not a requirement.

The lofty open fiber web can be prepared by any suitable web forming operation. For example the lofty open fiber web may be carded, spunbonded, spunlaced, melt blown, air laid, or made by other processes as are known in the art. For example, the lofty open fiber web may be cross-lapped, stitchbonded, and/or needletacked.

In this embodiment, the abrasive particles are dispersed throughout a binder precursor which may be any composition described as for the make layer precursor above and coated on the backing. Likewise, the abrasive particles may be as described hereinbefore.

The nonwoven abrasive member may be manufactured through well-known conventional processes that include steps such as, for example, applying a curable binder precursor material (hereinafter referred to as "binder precursor") and abrasive particles to a lofty open nonwoven fiber web followed by curing the binder precursor. The abrasive particles may be applied in combination with the binder precursor as a slurry, or more desirably the abrasive particles may be applied (e.g., by dropping, blowing, or spraying) to the binder precursor after it is coated onto the lofty open nonwoven fiber web. The binder precursor typically comprises a thermosetting resin and an effective amount of a curative for the thermosetting resin. The binder precursor may also include various other additives such as, for example, fillers, plasticizers, surfactants, lubricants, colorants (e.g., pigments), bactericides, fungicides, grinding aids, and antistatic agents.

One exemplary method of making nonwoven abrasive members suitable for use in practice of the present disclosure includes sequentially: applying a pre-bond coating to a nonwoven fiber web (e.g., by roll-coating or spray coating), curing the pre-bond coating, impregnating the pre-bonded nonwoven fiber web with a binder precursor (e.g., by roll-coating or spray coating), and curing the curable composition.

Typically, the binder precursor (including any solvent and abrasive particles that may be present) is coated onto the nonwoven fiber web in an amount of from <NUM> grams per square meter (gsm) to <NUM> gsm , more typically <NUM>-<NUM> gsm, and even more typically <NUM>-<NUM> gsm, although values outside these ranges may also be used.

The slurry layer precursor is typically applied to the fiber web in liquid form (e.g., by conventional methods), and subsequently hardened (e.g., at least partially cured) to form a layer coated on at least a portion of the fiber web. Slurry layer precursors utilized in practice according to the present disclosure may typically be cured by exposure to, for example, thermal energy (e.g., by direct heating, induction heating, and/or by exposure to microwave and/or infrared electromagnetic radiation) and/or actinic radiation (e.g., ultraviolet light, visible light, particulate radiation). Exemplary sources of thermal energy include ovens, heated rolls, and/or infrared lamps.

In one exemplary method, a slurry layer precursor comprising abrasive particles and a slurry layer precursor material is applied to the fiber web and then at least partially cured. Optionally, a second binder precursor material (i.e., a size layer precursor), which may be the same as or different from the slurry layer precursor may be applied to the slurry layer, typically after at least partially curing the slurry layer precursor.

In another exemplary method, a make layer precursor (e.g., as described hereinabove) is applied to the lofty open nonwoven fiber web, abrasive particles are deposited on the make layer, and then the make layer precursor is hardened (e.g., by evaporation, cooling, and/or at least partially curing). Subsequently, a size layer precursor (as described hereinabove), which may be the same as or different from the make layer precursor, is typically, but optionally, applied over the make layer and abrasive particles, and then at least partially cured.

Suitable methods for applying slurry layer precursors, make layer precursors, size layer precursors, etc. are well known in the art of nonwoven abrasive articles, and include coating methods such as curtain coating, roll coating, spray coating, and the like. Typically, spray coating is an effective and economical method for applying slurry layer and make layer precursors. The optional size layer may be elastomeric or non-elastomeric and may contain various additives such as, for example, one or more of a lubricant and/or a grinding aid. The optional size layer may comprise an elastomer (e.g., a polyurethane elastomer). Exemplary useful elastomers include those known for use as a size layer for nonwoven abrasive articles. For example, elastomers may be derived from isocyanate-terminated urethane prepolymers such as, for example, those commercially available under the trade designations VIBRATHANE or ADIPRENE from Crompton & Knowles Corporation, Middlebury, Connecticut; and MONDUR or DESMODUR from Bayer Corporation, Pittsburgh, Pennsylvania.

Optionally, a slurry layer, make layer, and/or size layer may further include one or more catalysts and/or curing agents to initiate and/or accelerate the curing process (e.g., thermal catalyst, hardener, crosslinker, photocatalyst, thermal initiator, and/or photoinitiator) as well as in addition, or alternatively, other known additives such as, for example, fillers, thickeners, tougheners, grinding aids, pigments, fibers, tackifiers, lubricants, wetting agents, surfactants, antifoaming agents, dyes, coupling agents, plasticizers, and/or suspending agents. Exemplary lubricants include metal stearate salts such as lithium stearate and zinc stearate, or materials such as molybdenum disulfide, and mixtures thereof.

As used herein, the term "grinding aid" refers to a non-abrasive (e.g., having a Mohs hardness of less than <NUM>) particulate material that has a significant effect on the chemical and physical processes of abrading. In general, the addition of a grinding aid increases the useful life of a nonwoven abrasive. Exemplary grinding aids include inorganic and organic materials, include waxes, organic halides (e.g., chlorinated waxes, polyvinyl chloride), halide salts (e.g., sodium chloride, potassium cryolite, cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, magnesium chloride), metals (e.g., tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium and their alloys), sulfur, organic sulfur compounds, metallic sulfides, graphite, and mixtures thereof.

Coated abrasive articles according to the present invention are useful for abrading a workpiece. One such method includes frictionally contacting at least a portion of the abrasive layer of a coated abrasive article with at least a portion of a surface of the workpiece, and moving at least one of the coated abrasive article or the workpiece relative to the other to abrade at least a portion of the surface.

Examples of workpiece materials include metal, metal alloys, exotic metal alloys, ceramics, glass, wood, wood-like materials, composites, painted surfaces, plastics, reinforced plastics, stone, and/or combinations thereof. The workpiece may be flat or have a shape or contour associated with it. Exemplary workpieces include metal components, plastic components, particleboard, camshafts, crankshafts, furniture, and turbine blades.

Coated abrasive articles according to the present invention may be used by hand and/or used in combination with a machine. At least one or both of the coated abrasive article and the workpiece is generally moved relative to the other when abrading.

Abrading may be conducted under wet or dry conditions. Exemplary liquids for wet abrading include water, water containing conventional rust inhibiting compounds, lubricant, oil, soap, and cutting fluid. The liquid may also contain defoamers, degreasers, and/or the like.

Materials used in the Examples are listed in Table <NUM>, below.

Two nonwoven abrasive article test specimens were prepared as <NUM>-cm diameter discs that are stacked and then secured to a foam back-up pad by means of a hook-and-loop fastener. The back-up pad/fastener assembly had a Shore Durometer OO hardness of <NUM>. The abrasive disc and back-up pad assembly was installed on a Schiefer Uniform Abrasion Tester (available from Frazier Precision Instrument Company, Inc. Hagerstown, Maryland), and the abrasive disc was used to abrade an annular ring (<NUM> outside diameter (OD) x <NUM> inside diameter (ID)) of cellulose acetate butyrate polymer from Seelye-Eiler Plastics Inc. , Bloomington, Minnesota. The load was <NUM> lb (<NUM>). The test duration was <NUM> cycles. The amount of cellulose acetate butyrate polymer removed (cumulative cut) was measured at the end of the test period. Wear, measured as percent weight loss of the working nonwoven abrasive article test specimen, was also recorded.

A lightweight, open, low-density air-laid nonwoven web was prepared from Fiber Fb1 or Fb2 using a RANDO-WEBBER machine, commercially available from the Rando Machine Corporation of Macedon, New York. The resulting lofty open fiber web had a nominal basis weight of <NUM> grains per <NUM> square inches (<NUM> gsm), and the thickness was <NUM> inches (<NUM>). The web was conveyed to a horizontal two-roll coater, where a pre-bond resin consisting of <NUM> wt. % of PMA, <NUM> wt. % of K450, <NUM> wt. % of BL16, <NUM> wt. % of GEO, and <NUM> wt. % of P4 was applied to the fiber web at a wet add-on weight of <NUM> grains/<NUM> square inches (<NUM> gsm).

The coated web was conveyed through an oven maintained at <NUM>-<NUM> with a residence time of <NUM> minutes. The resulting pre-bonded fiber web was conveyed to a spray booth where a resin/abrasive slurry consisting of <NUM>. % of L1, <NUM> wt. % of SR, <NUM> wt. % of D1, a pre-blend of <NUM> wt. % of B7 and <NUM> wt. % of U0, <NUM> wt. % of S2, <NUM> wt. % of Wa, and <NUM> wt. % of Alox <NUM> was sprayed on the top surface of the web. Within the booth, spray nozzles (which are mounted to reciprocate perpendicularly to the direction of web movement) apply the slurry at a wet weight of about <NUM> grains/<NUM> square inch (<NUM> gsm).

The slurry-coated web was then heated in an oven maintained at <NUM> for <NUM> minutes. The web was then inverted and the slurry spray coating was applied to the opposite side of the web. The coated web was finally heated in an oven maintained at <NUM> for <NUM> minutes, to yield a nonwoven abrasive article, which was tested according to the Schiefer Test, Test results are reported in Table <NUM>.

COMPARATIVE EXAMPLE B was made as COMPARATIVE EXAMPLE A, except using the following raw materials weight percentages: <NUM> wt. % of L1, <NUM> wt. % of U0, <NUM> wt. % of SR, <NUM> wt. % of D1, <NUM> wt. % of B7, <NUM> wt. % of S2, <NUM> wt. % of Alox <NUM>, <NUM> wt. % of 14EQ <NUM>, <NUM> wt.

Examples <NUM> - <NUM> were made exactly the same as COMPARATIVE EXAMPLE A, except using the raw materials weight percentages shown in TABLE <NUM> (below).

Table <NUM>, below, reports results from the Schiefer Test hereinabove. None of Examples <NUM>-<NUM> contained a blend of B7 with U0. Wear percentages were higher while Cumulative Cut results were about the same.

A curable composition was prepared, under high speed dispersion, using a high shear blade between <NUM> rpm to <NUM> rpm, until a homogeneous mix is obtained, by blending B7 with U0, then under shear adding D1, GEO, Coll, Sic, Fil1, Ant and slowly adding Fil2. The proportions of each component are given in Table <NUM>.

Claim 1:
An abrasive article (<NUM>) comprising abrasive particles (<NUM>) secured to a substrate by at least one binder material, wherein the at least one binder material comprises a cured reaction product of components comprising:
a) at least one phenolic resin; and
b) an aqueous dispersion of at least one polyurethane,
wherein, based on the total solids weight of components a) and b), the components comprise <NUM> to <NUM> percent by weight of component a) and <NUM> to <NUM> percent by weight of component b).