US20040098923A1

US20040098923A1 - Nonwoven abrasive articles and methods for making and using the same

Info

Publication number: US20040098923A1
Application number: US10/304,041
Authority: US
Inventors: Sherri Hood; Loc Van
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2002-11-25
Filing date: 2002-11-25
Publication date: 2004-05-27
Also published as: WO2004048042A1; AU2003302424A1

Abstract

Nonwoven abrasive articles comprise a porous reinforcing material, a fiber web affixed to the porous reinforcing material, abrasive particles, and a non-elastomeric binder. Methods of making and using nonwoven abrasive articles are also disclosed.

Description

TECHNICAL FIELD

The present invention relates to nonwoven abrasive articles.

BACKGROUND

Nonwoven abrasive articles typically comprise an open porous fiber web having abrasive particles bonded thereto by a binder. For applications requiring added dimensional stability and/or high strength, a reinforcing scrim or fabric is typically affixed to the fiber web. Such reinforced articles are known, for example, in forms such as discs and belts.

The reinforcing scrim or fabric is typically affixed to the fiber web by an adhesive resin and/or by mechanical means such as needletacking. To aid in maintaining the integrity and/or structure of the reinforced fiber web during the nonwoven abrasive manufacturing process, an elastomeric binder precursor (i.e., prebond precursor) is commonly applied to the fiber web, and cured to form a prebonded reinforced fiber web.

Conventional abrasive nonwoven discs and belts are typically made from prebonded reinforced fiber web by one of two methods. In one method, prebonded reinforced fiber web is typically coated with a slurry of abrasive particles in a curable binder precursor (i.e., slurry coat precursor), and then the binder precursor is cured to form a slurry coat on the reinforced non-woven web. In a second method, a curable binder precursor (i.e., make coat precursor) is typically coated onto prebonded reinforced fiber web, abrasive particles are applied to the make coat precursor, and then the make coat precursor is at least partially cured to form a make coat. Another curable binder precursor (i.e., size coat precursor) is then typically applied onto the make coat, and then cured to form an abrasive composition (i.e., the make coat, abrasive particles, and size coat taken collectively) on the reinforced non-woven web.

While abrading a workpiece with nonwoven abrasive articles, portions of the abrasive article may detach in phenomena commonly referred to as “shelling” (i.e., loss of abrasive particles) or “chunking” (i.e., loss of chunks of binder, fiber web, and abrasive particles). Chunking may be especially troublesome in the case of nonwoven abrasive endless belts. Shelling and chunking are typically undesirable, as they generally degrade the performance of the nonwoven abrasive article. There is a continuing need for nonwoven abrasive articles that have an acceptable level of chunking and/or shelling during use.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a nonwoven abrasive article comprising:

a porous reinforcing material having first and second opposed major surfaces;

a fiber web, wherein the fiber web is affixed to the first major surface of the porous reinforcing material; and

an abrasive composition comprising abrasive particles and a non-elastomeric binder, wherein the abrasive composition contacts at least a portion of the fiber web and the first major surface of the porous reinforcing material, wherein the abrasive composition extends through at least a portion of the porous reinforcing material and contacts at least a portion of the second major surface of the porous reinforcing material, and wherein, on a weight basis, there is a first average ratio of abrasive particles to the non-elastomeric binder at the first major surface, and a second average ratio of abrasive particles to the non-elastomeric binder at the second major surface, and wherein the first average ratio is greater than the second average ratio.

In another aspect, the present invention provides a method for making a nonwoven abrasive article comprising:

providing a fiber web;

providing a porous reinforcing material having first and second opposed major surfaces;

affixing the fiber web to the first major surface of the reinforcing material;

applying a first binder precursor and abrasive particles onto the fiber web, wherein at least a portion of the first binder precursor penetrates through the porous reinforcing material and contacts at least a portion of the first and second major surfaces; and

at least partially curing the first binder precursor to form a non-elastomeric first binder, wherein on a weight basis, there is a first average ratio of abrasive particles to the non-elastomeric binder at the first major surface, and a second average ratio of abrasive particles to the non-elastomeric binder at the second major surface, and wherein the first average ratio is greater than the second average ratio.

In another aspect, the present invention provides a method of abrading a surface, the method comprising:

providing a nonwoven abrasive article according to the present invention;

contacting at least one of the abrasive particles of the abrasive article with the surface of the workpiece; and

moving at least one of the abrasive particles or the contacted surface relative to the other to abrade at least a portion of the contacted surface.

Nonwoven abrasive articles, according to the present invention, typically have an acceptable level of shelling and/or chunking during use, for example, if used as an endless belt mounted onto equipment (e.g., belt sander) having small diameter pulleys and/or rollers.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of an exemplary nonwoven abrasive article according to the present invention; [0021]
FIG. 2 is a cross-sectional view of another exemplary nonwoven abrasive article according to the present invention; [0022]
FIG. 3 is a perspective view of an exemplary nonwoven abrasive disc according to one embodiment of the present invention; and [0023]
FIG. 4 is a perspective view of an exemplary endless nonwoven abrasive belt according to one embodiment of the present invention. [0024]

DETAILED DESCRIPTION

Referring now to FIG. 1, exemplary nonwoven abrasive article according to the [0025] present invention 100 comprises fiber web 110 affixed to porous reinforcing material 120 of thickness 185 and having first and second opposed major surfaces 122 and 124, respectively. Slurry coat 130, comprising abrasive particles 135 and non-elastomeric binder 138, contacts at least a portion of fiber web 110 and first major surface 122 of porous reinforcing material 120. Optional size coat 170 contacts slurry coat 130, porous reinforcing material 120, fiber web 110, and fibers 192. Non-elastomeric binder 138 extends through at least a portion of porous reinforcing material 120, and contacts at least portion of second major surface 124 of porous reinforcing material 120. The average ratio on a weight basis of abrasive particles 135 to non-elastomeric binder 138 is higher at first major surface 122 than at second major surface 124.
For purposes of determining the average ratio on a weight basis of [0026] abrasive particles 135 to non-elastomeric binder 138 at a surface of the backing, the phrase “at the first surface” is to be construed as referring to zone 180 a, which is the combination of zones 187 a and 189 a. Zone 187 a is the outer 20 percent of thickness 185 that contacts first major surface 122. Zone 189 a, which has the same thickness as zone 187 a, contacts zone 187 a, and extends beyond first major surface 122. Similarly, the phrase “at the second surface” is to be construed as referring to zone 180 b, which is the combination of zones 187 b and 189 b. Zone 187 a is the outer 20 percent of thickness 185 that contacts first major surface 124. Zone 189 b, which has the same thickness as zone 187 b, contacts zone 187 b, and extends beyond first major surface 124.
Optionally (e.g., as in the case wherein [0027] fiber web 110 is needletacked to the porous reinforcing material 120), a portion of fibers comprising fiber web 110 may extend outwardly from second major surface 124 as exposed fibers 192. In some embodiments, exposed fibers 192 remain substantially free of non-elastomeric binder 138 and abrasive particles 135, as the presence of such materials may tend to hinder proper functioning of the nonwoven abrasive in some embodiments (e.g., endless belts).
In another exemplary embodiment of the present invention, shown in FIG. 2, nonwoven [0028] abrasive article 200 comprises fiber web 110 affixed to porous reinforcing material 120 of thickness 185 and having first and second opposed major surfaces 122 and 124, respectively. Make coat 230, comprising non-elastomeric binder 138, has abrasive particles 135 bonded thereto, and contacts at least a portion of fiber web 110 and first major surface 122 of porous reinforcing material 120. Optional size coat 170 contacts make coat 230, abrasive particles 135, porous reinforcing material 120, fiber web 110, and fibers 192. Non-elastomeric binder 138 extends through a portion of porous reinforcing material 120 and contacts a portion of second major surface 124 of porous reinforcing material 120. The average ratio on a weight basis of abrasive particles 135 to non-elastomeric binder 138 is higher at first major surface 122 than at second major surface 124.
Typically, the fiber web comprises an entangled web of fibers (i.e., a fibrous nonwoven). Many suitable fiber webs are known and used in the arts of nonwovens and abrasives. The fiber web 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 under the trade designation “RANDO WEBBER” commercially available from Rando Machine Company of Macedon, N.Y. Prior to affixing the fiber web to the porous reinforcing material, the fiber web is typically open (e.g., lofty and open). After affixing the fiber web to the porous reinforcing material, depending on the method used (e.g., needletacking), the fiber web may be denser and thinner. [0029]
The fiber web is selected to be suitably compatible with adhering binders and abrasive particles while also being processable in combination with other components of the article (e.g., binder precursors, hardened binders, abrasive materials), and typically can withstand temperatures at which such binder precursors and other materials are applied and processed. In addition, the fiber may be chosen to affect properties of the abrasive article such as 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 of polyester (e.g., polyethylene terephthalate), nylon (e.g., hexamethylene adipamide, polycaprolactam), polypropylene, acrylic (formed from a polymer of acrylonitrile), rayon, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymers, vinyl chloride-acrylonitrile copolymers, and so forth. Suitable natural fibers include cotton, wool, jute, and hemp. The fiber may be of virgin materials or of recycled or waste materials reclaimed from garment cuttings, carpet manufacturing, fiber manufacturing, or textile processing, for example. The fiber 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, but may also be continuous filaments such as those formed by an extrusion process. It is also within the scope of the invention to provide an article comprising different fibers in different portions of the nonwoven (e.g., at a first major surface, a second major surface, and within the middle portion therebetween). [0030]
The fiber web may comprise staple fibers having a length of at least about 20 millimeters (mm), at least about 30 mm, or at least about 40 mm, and less than about 110 mm, less than about 85 mm, or less than about 65 mm, 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 1.7 decitex (dtex), at least about 6 dtex, or at least about 17 dtex, and less than about 560 dtex, less than about 280 dtex, or less than about 120 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 an abrasive article that upon use will result in a specifically preferred surface finish. If a spunbond nonwoven is used, the filaments may be of substantially larger diameter, for example, up to 2 mm or more in diameter. The fiber web may optionally be reinforced and/or consolidated by any of various methods known and understood in the art of nonwoven materials, including thermal or chemical bonding, hydroentanglement, and the like. [0031]
The fiber web typically has a weight per unit area (i.e., basis weight) of at least about 50 grams per square meter (g/m[0032] ²), at least about 100 g/m², or at least about 200 g/m²; and/or less than about 400 g/m², less than about 350 g/m², or less than about 300 g/m², as measured prior to any coating (e.g., prior to application of any binder precursors), although greater and lesser basis weights may also be used. In addition, the fiber web (prior to any optional reinforcement and/or consolidation as discussed below) typically has a thickness of at least about 5 mm, at least about 6 mm, or at least about 10 mm; and/or less than about 200 mm, less than about 75 mm, or less than about 30 mm, although greater and lesser thicknesses may also be useful.
Further details concerning suitable fiber webs and methods for their manufacture may be found, for example, in U.S. Pat. No. 6,207,246 (Moren et al.); No. 5,591,239 (Larson et al.); No. 4,227,350 (Fitzer); and No. 2,958,593 (Hoover et al.), the disclosures of which are incorporated herein by reference. [0033]
The reinforcing material may be affixed to the nonwoven by methods that are useful or known in the art of nonwoven materials, using conventional materials such as adhesives and needletacking techniques. For example, in some embodiments of the invention, (e.g., where the web is to be incorporated into a machine driven abrasive article such as a belt or abrasive disc), a porous reinforcing material may be contacted with a surface of the nonwoven material before needletacking. In such embodiments, the nonwoven is typically needletacked while contacting the porous reinforcing material, such that fibers of the nonwoven are pushed or pulled from the first major surface of the porous reinforcing material, through the porous reinforcing material, and extend outwardly out from the second major surface. Although other methods for affixing the fiber web to the porous reinforcing material may be used (e.g., adhesive bonding), needletacking is generally preferred. Needletacking processes are well known in the art of nonwoven materials, and are readily accomplished by use of conventional needle loom equipment commercially available, for example, from Dilo, Charlotte, N.C. or DOA, Linz, Austria. [0034]
The properties of the reinforcing material may also influence physical properties of an abrasive article prepared therefrom, including stiffness, flexibility, durability, etc. The porous reinforcing material may comprise a porous dimensionally stable, woven, fibrous material (e.g., scrim). The porous reinforcing material should typically be capable of withstanding processing into an abrasive article as described herein, and is preferably stable at temperatures at which binder precursors are applied and/or processed. [0035]
The term “porous” as applied herein to the reinforcing material means that the reinforcing material is sufficiently porous that a binder precursor (e.g., slurry coat precursor, make coat precursor) may penetrate through the thickness of the reinforcing material. The reinforcing material may be a woven stretch-resistant fabric, and may have tensile strain in at least one direction of less than about 5 percent stretch or less than about 2.5 percent stretch, at tensile loads up to 100 pounds/inch (174 N/cm). Suitable reinforcing materials include, for example, thermo-bonded fabrics, knitted fabrics, stitch-bonded fabrics. The reinforcing material may include fibers of nylon and/or polyester. [0036]
Optionally, the second major surface of the porous reinforcing material may be coated with a thermoplastic polymer or thermosetting resin to encapsulate outwardly extending fibers and provide a smooth surface as described, for example, in U.S. Pat. No. 5,482,756 (Berger et al.), the disclosure of which is incorporated herein by reference. If used, such thermoplastic polymer or thermosetting resin is typically applied after any coatings (e.g., make, size, slurry, and/or supersize) have been applied, in order that the backing is at least partially permeable to such coatings. [0037]
Any binder precursor used in preparation of the abrasive composition (e.g., slurry coat precursor, make coat precursor) is typically applied to the fiber web after it is affixed to the porous reinforcing material. The binder 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 and porous reinforcing material. [0038]
In a first exemplary method, a slurry coat precursor comprising abrasive particles and a first binder precursor is applied to the fiber web and the first major surface of the porous reinforcing material, and then at least partially cured. Typically, prior to curing, the first binder precursor component diffuses through at least a portion of the porous reinforcing material (i.e., from the first major surface of porous reinforcing material to at least a portion of the second major surface of the reinforcing material). Optionally, a second binder precursor (i.e., a size coat precursor), which may be the same as or different from the slurry coat precursor may be applied to the slurry coat, typically after at least partially curing the slurry coat precursor. [0039]
In a second exemplary method, a make coat precursor comprising a first binder precursor is typically applied to the fiber web, abrasive particles are deposited on the make coat, and then the make coat precursor is hardened (e.g., by evaporation, cooling, and/or at least partially curing). Typically, prior to curing, the make coat precursor diffuses through at least a portion of the porous reinforcing material (i.e., from the first major surface of porous reinforcing material to at least a portion of the second major surface of the reinforcing material). Subsequently, a second binder precursor (i.e., a size coat precursor), which may be the same as or different from the make coat precursor, is typically applied over the make coat and abrasive particles, and then at least partially cured. [0040]
Typically, binder precursors employed in slurry coat precursors, or at least one of make coat precursors and/or size coat precursors (e.g., as described above), comprise a monomeric or polymeric material that may be at least partially cured (i.e., polymerized and/or crosslinked). Typically, upon at least partial curing, such binder precursors form a non-elastomeric binder (e.g., a hard brittle binder) that may have a Knoop hardness number (KHN, expressed in kgf/mm[0041] ²) of, for example, at least about 20, at least about 40, at least about 60, or at least about 80 as measured in accordance with ASTM Test Method D1474-98(2002) “Standard Test Methods for Indentation Hardness of Organic Coatings”) that bonds abrasive particles to the fiber web.
Examples of binder precursors that may be at least partially cured to form a non-elastomeric binder material include condensation curable materials and/or addition polymerizable materials. Such binder precursors may be solvent based, water based, or 100 percent solids. Exemplary binder precursors include phenolic resins, bismaleimides, vinyl ethers, aminoplasts, urethanes, epoxy resins, acrylates, acrylated isocyanurates, urea-formaldehyde resins, isocyanurates, acrylated urethanes, acrylated epoxies, or mixtures of any of the foregoing. Phenolic resins and epoxy resins, and combinations thereof, are among preferred binder precursors due to their high performance, wide availability, and low cost. [0042]
Exemplary phenolic resins suitable for use in binder precursors include resole phenolic resins and novolac phenolic resins. Exemplary commercially available phenolic materials include those having the trade designations “DUREZ” or “VARCUM” (available from Occidental Chemical Corporation, Dallas, Tex.); “RESINOX” (available from Monsanto Company, St. Louis, Mo.); “AROFENE” or “AROTAP” (available from Ashland Chemical Company, Columbus, Ohio); and “BAKELITE” from Dow Chemical Company, Midland, Mich. Further details concerning suitable phenolic resins may be found, for example, in U.S. Pat. No. 5,591,239 (Larson et al.) and No. 5,178,646 (Barber, Jr. et al.), the disclosures of which are incorporated herein by reference. [0043]
Exemplary epoxy resins include the diglycidyl ether of bisphenol A, as well as materials that are commercially available under the trade designations “EPON” (e.g., “EPON 828”, “EPON 1004”, and “EPON 1001F”) from Shell Chemical Co., Houston, Tex.; and under the trade designations “DER” (e.g., “DER-331”, “DER-332”, and “DER-334”) or “DEN” (e.g., “DEN-431” and “DEN-428”) from Dow Chemical Company, Midland, Mich. [0044]
Exemplary urea-formaldehyde resins and melamine-formaldehyde resins include those commercially available under the trade designation “UFORMITE” (e.g., from Reichhold Chemical, Durham, N.C.); “DURITE” (from Borden Chemical Company, Columbus, Ohio); and “RESIMENE” (e.g., from Monsanto, St. Louis, Mo.). [0045]
Suitable methods for applying slurry coat precursors, make coat precursors, size coat 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 coat and make coat precursors. Exemplary slurry coating techniques are described, for example, in U.S. Pat. No. 5,378,251 (Culler et al.) and No. 5,942,015 (Culler et al.), the disclosures of which are incorporated herein by reference. [0046]
A slurry coat precursor or make coat precursor, depending on the specific embodiment of the present invention, is applied to the fiber web and porous reinforcing material. The slurry coat precursor or make coat precursor typically penetrates into pores of a first major surface of the porous reinforcing material, and extends through at least a portion of the porous reinforcing material (as opposed to mere edge contact), emerging at the second major surface of the porous reinforcing material. During penetration, abrasive particles that are present in the slurry coat precursor, are typically at least partially filtered out such that the average ratio of abrasive particles to binder precursor is substantially higher at the first major surface of the porous reinforcing material than at the second major surface. For example, the average ratio of abrasive particles to binder precursor at the first major surface may be at least 2, at least 10, at least 50, or a least 100 times the average ratio of abrasive particles to binder precursor at the second major surface. [0047]
The optional size coat 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 coat may comprise an elastomer (e.g., a polyurethane elastomer). Exemplary useful elastomers include those known for use as a size coat 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, Conn.; and “MONDUR” or “DESMODUR” from Bayer Corporation, Pittsburgh, Pa. [0048]
Optionally, the slurry coat, make coat, and/or size coat 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, photoinitiator) as well as in addition, or alternatively, other known additives such as fillers, thickeners, tougheners, grinding aids, pigments, fibers, tackifiers, lubricants, wetting agents, surfactants, antifoaming agents, dyes, coupling agents, plasticizers, suspending agents, and the like. [0049]
Exemplary lubricants include metal stearate salts such as lithium stearate and zinc stearate, or materials such as molybdenum disulfide, and mixtures thereof. [0050]
As used herein, the term “grinding aid” refers to a non-abrasive (e.g., having a Mohs hardness of less than 7) 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. [0051]
Binder precursors utilized in practice according to the present invention 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 infrared lamps. [0052]
Abrasive particles suitable for use in abrasive compositions utilized in practice according to the present invention include any abrasive particles known in the abrasive art. Exemplary useful abrasive particles include fused aluminum oxide based materials such as aluminum oxide, ceramic aluminum oxide (which may include one or more metal oxide modifiers and/or seeding or nucleating agents), and heat-treated aluminum oxide, silicon carbide, co-fused alumina-zirconia, diamond, ceria, titanium diboride, cubic boron nitride, boron carbide, garnet, flint, emery, sol-gel derived abrasive particles, and mixtures thereof. Desirably, the abrasive particles comprise fused aluminum oxide, heat-treated aluminum oxide, ceramic aluminum oxide, silicon carbide, alumina zirconia, garnet, diamond, cubic boron nitride, sol-gel derived abrasive particles, or mixtures thereof. Examples of sol-gel abrasive particles include those described U.S. Pat. No. 4,314,827 (Leitheiser et al.); No. 4,518,397 (Leitheiser et al.); No. 4,623,364 (Cottringer et al.); No. 4,744,802 (Schwabel); No. 4,770,671 (Monroe et al.); No. 4,881,951 (Wood et al.); No. 5,011,508 (Wald et al.); No. 5,090,968 (Pellow); No. 5,139,978 (Wood); No. 5,201,916 (Berg et al.); No. 5,227,104 (Bauer); No. 5,366,523 (Rowenhorst et al.); No. 5,429,647 (Larmie); No. 5,498,269 (Larmie); and No. 5,551,963 (Larmie), the disclosures of which are incorporated herein by reference. The abrasive particles may be in the form of, for example, individual particles, agglomerates, composite particles, and mixtures thereof. Exemplary agglomerates and composite particles are described, for example, in U.S. Pat. No. 4,652,275 (Bloecher et al.); No. 4,799,939 (Bloecher et al.); No. 5,549,962 (Holmes et al.), the disclosures of each of which is incorporated herein by reference. [0053]
The abrasive particles may, for example, have an average diameter of at least about 0.1 micrometer, at least about 1 micrometer, or at least about 10 micrometers, and less than about 2000, less than about 1300 micrometers, or less than about 1000 micrometers, although larger and smaller abrasive particles may also be used. Coating weights for the abrasive particles may depend, for example, on the binder precursor used, the process for applying the abrasive particles, and the size of the abrasive particles. For example, the coating weight of the abrasive particles may be at least 200 grams per square meter (g/m[0054] ²), at least 600 g/m², or at least 800 g/m²; and/or less than 2000 g/m², less than about 1600 g/m², or less than about 1200 g/m², although greater or lesser coating weights may be also be used.
Abrasive particles may be applied to a fiber web having a make coat thereon by methods known in the abrasive art for application of such particles. For example, the abrasive particles may be applied to the make coat by blowing, dropping, electrostatically coating the particles onto uncured binder precursor, or by a combination thereof. [0055]
Various optional conventional treatments and additives may be used in conjunction with the fiber web and/or reinforcing material such as, for example, a prebond coating (i.e., a material applied to the fiber web and hardened or thermoset to provide chemical bonding between fibers of the fiber web), antistatic agents, lubricants, or corona treatment. However, if used, such treatments should typically not prevent penetration of diffusion of the binder precursor of the abrasive composition precursor through the porous reinforced backing. If the fiber web is affixed to the porous reinforcing material by needletacking, the optional prebond may be applied, for example, after the needletacking step. [0056]
It is also within the scope according to the present invention to have additional coatings (e.g., a supersize), which for example, may be present as a continuous or discontinuous layer in contact with at least a portion of the abrasive composition. For example, it may be desirable to include a supersize to provide, for example, a grinding aid, and/or as an anti-loading coating. The supersize is typically derived from a curable binder precursor. Optional supersize may be applied by methods well known in the abrasive arts, for example, by spraying or metered roll coating. Further details concerning supersizes may be found, for example, in U.S. Pat. No. 3,256,076 (Duwell et al.); No. 5,520,711 (Helmin); No. 5,213,589 (Ronning et al.); No. 5,306,319 (Krishnan); No. 5,556,437 (Lee et al.); and No. 6,039,775 (Ho et al.), the disclosures of which are incorporated herein by reference. [0057]
Nonwoven abrasive articles according to the present invention (e.g., nonwoven [0058] abrasive articles 100 or 200, as shown in FIG. 1 or FIG. 2, respectively) may be used in sheet form, stacked together with or without additional adhesive or binder to form a wheel or brush product, or may be further processed to provide finished articles (e.g., hand pads, discs, endless belts) suitable for use in surface finishing applications.
For example, in one embodiment according to the present invention (shown in FIG. 3), nonwoven [0059] abrasive disc 300 having optional center arbor hole 310 therein, is formed from nonwoven abrasive article 100. Nonwoven abrasive discs having a diameter in a range of from about 2 centimeters (cm) to about 20 cm may typically be used with a right-angle power tool having a suitable attachment means (e.g., via a center arbor hole, pressure-sensitive adhesive, “hook-and-loop” or another type of mechanical fastener).
In another exemplary embodiment according to the present invention (shown in FIG. 4), nonwoven abrasive [0060] endless belt 400 comprises a strip of nonwoven abrasive material 100 joined at both ends by splice 410, such that fiber web 110 is outwardly disposed.
In the formation of endless belts, strips are typically cut having a length and a width suitable for the formation of endless belts that will fit, for example, on an abrasive belt sander. Conventional splicing techniques may be used to form the finished belt. One such technique, known as a butt splice, generally requires that the ends of the composite strips be angled in a mating configuration, and the ends may then be spliced using a conventional urethane splicing adhesive and a heated belt splicing technique. Of course, other belt forming materials and techniques may be used such as conventional nonwoven abrasive belt manufacturing techniques and adhesives. [0061]
In use, endless belts according to the present invention may be mounted on a conventional belt sander. As used with conventional belt sanders, endless belts typically travel around wheels that may be small in diameter, which in turn may cause the belt to chunk. Nonwoven abrasive articles according to the present invention typically have acceptable levels of chunking and are well suited for use as endless belts. [0062]
Nonwoven abrasive articles according to the present invention are typically useful for abrading a workpiece. One such method includes frictionally contacting a nonwoven abrasive article with a surface of the workpiece, and moving at least one of the nonwoven 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. [0063]
Nonwoven abrasive articles according to the present invention, may be used by hand and/or used in combination with a machine. 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. [0064]
The present invention will be more fully understood with reference to the following non-limiting examples in which all parts, percentages, ratios, and so forth, are by weight unless otherwise indicated. [0065]

EXAMPLES

Unless otherwise noted, all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Aldrich Chemical Company, Milwaukee, Wis., or may be synthesized by known methods. [0066]

The following abbreviations are used throughout the examples that follow:



AO60	ANSI Grade 60 brown aluminum oxide abrasive particles obtained
	under the trade designation “DURALUM G52” from Washington
	Mills Electro Minerals Company, Niagara Falls, New York
AO80	ANSI Grade 80 brown aluminum oxide abrasive particles obtained
	under the trade designation “DURALUM G52” from Washington
	Mills Electro Minerals Company
AO100-150	Brown aluminum oxide abrasive particles having the trade
	designation “DURALUM G52” (ANSI grade 100-150, 2 percent
	100 grit particles, 41 percent 120 grit particles, 26 percent 140 grit
	particles, 17 percent 170 grit particles, and 14 percent particles finer than 170 grit)
	obtained from Washington Mills Electro Minerals Company
HTAO60	P60 grit heat-treated aluminum oxide particles obtained under the
	trade designation “ALODUR BFRPL” from Treibacher
	Schleifmittel AG, Villach, Austria
HTAO80	P80 grit heat-treated aluminum oxide particles obtained under the
	trade designation “ALODUR BFRPL” from Treibacher
	Schleifmittel AG
BC	Bentonite clay obtained under the trade name “VOLCAY 325” from
	American Colloid Company, Arlington Heights, Illinois
BR2	A reaction product of one equivalent of poly(tetramethylene glycol)
	polymer with two equivalents of toluene diisocyanate to produce a
	difunctional isocyanate prepolymer that was subsequently blocked
	with methyl ethyl ketoxime (equivalent weight of the blocked
	adduct was 757) obtained under the trade designation “ADIPRENE
	BL-16” from Crompton & Knowles Corporation, Stamford,
	Connecticut
BR4	A reaction product of one equivalent of poly(tetramethylene glycol)
	polymer with two equivalents of toluene diisocyanate to produce a
	difunctional isocyanate prepolymer that was subsequently blocked
	with methyl ethyl ketoxime (equivalent weight of the blocked
	adduct was 1000) obtained under the trade designation
	“ADIPRENE BL-11” from Crompton & Knowles Corporation
BR5	A 49.5-52.5 percent solids acrylic copolymer latex obtained under
	the trade designation “TYCRYL BS 2100” from Dow Reichhold
	Specialty Latex, Research Triangle Park, North Carolina
BR6	A resole phenolic resin obtained under the trade designation
	“BB077” from Neste Resins Canada, Mississauga, Ontario, Canada
CaCO₃	Calcium carbonate obtained under the trade designation
	“HUBERCARB Q325” from Huber Engineered Materials, Atlanta,
	Georgia
CR1	A high molecular weight, crosslinked copolymer of acrylic acid and
	a hydrophobic co-monomer obtained under the trade designation
	“PEMULEN 1621” from Noveon, Cleveland, Ohio
CR2	A high molecular weight, crosslinked copolymer of acrylic acid and
	a hydrophobic comonomer obtained under the trade designation
	“PEMULEN 1622” from Noveon
CUR1	4,4′-methylene-bis-(2,6-diethyl)aniline obtained under the trade
	designation “LONZACURE M-DEA” from Lonza AG, Switzerland
CUR2	An amidoamine curing agent obtained under the trade designation
	“EPI-CURE 3015 CURING AGENT” from Resolution
	Performance Products, Houston, Texas
CUR3	A mixture of 31.7 parts of the diglycidyl ether of bisphenol A
	obtained under the trade designation “EPON RESIN 828” from
	Shell Chemical Company, Houston, Texas; 28.3 parts isophorone
	diamine obtained from Degussa Corporation, Calvert City,
	Kentucky; and 40 parts PMA
FS	Fumed silica obtained under the trade designation “CAB-O-SIL
	UNTREATED FUMED SILICA M5” from Cabot Corporation of
	Boston, Massachusetts
HEU	Hydroxyethyl ethylene urea obtained under the trade designation
	“SR511” from Sartomer Company, Exton, Pennsylvania
LIST	A 44.1 percent by weight solution of lithium stearate in PMA
LUB	Hydrocarbon distillate obtained under the trade designation
	“ACELUBE 23N” from Gopher Oil Company, Minneapolis,
	Minnesota
MDA	A 35 percent by weight solution of 4,4′-methylenedianiline in PMA
NH₄OH	Aqueous ammonium hydroxide (26° Baume) obtained from
	LaRoche Industries, Atlanta, Georgia
PMA	Propylene glycol monomethyl ether acetate obtained from Lyondell
	Chemical Company, Houston Texas
PME	Propylene glycol monomethyl ether obtained under the trade
	designation “POLYSOLV MPM” from Arch Chemicals,
	Brandenburg, Kentucky
SURF	Polyethylene glycol sorbitan monooleate (i.e., polysorbate 80)
	obtained under the trade designation “TWEEN 80” from Uniqema,
	New Castle, Delaware

Belt Chunking Test [0068]
An endless ½ inch×24 inch (1.2 cm×61 cm) belt was mounted and maintained in tension via an air cylinder under 20 psi (140 kPa) pressure between a 2.5 inch (6.4 cm) diameter driving wheel and a {fraction (7/16)} inch (1.1 cm) steel contact wheel. The driving wheel was driven by a motor having the trade designation “GOLDLINE BRUSHLESS P. M. SERVOMOTOR” obtained from Kollmorgen Corporation, Waltham, Mass., and operating at 7500 rpm. The belt was weighed before each test, again after 1 minute, and again either after 3 minutes or at the end of belt life as determined by excessive belt stretch, whichever occurred first. [0069]
Disc Wear Test [0070]
A carbon steel bar 4 inches×18 inches×½ inch (10.2 cm×46.0 cm×1.3 cm) was mounted on a bench with one 18 inch×½ inch (46.0 cm×1.3 cm) face in full contact with the bench. A nonwoven abrasive disc to be tested was mounted on a 7-inch (18 cm) diameter back-up pad obtained from 3M Company (Saint Paul, Minn.) under the trade designation “3M DISC PAD HOLDER [0071] 917”. The resultant disc/back-up pad assembly was then mounted on an air driven right angle grinder capable of rotating the disc at 6000 rpm (under zero load). Power was supplied to the grinder and the disc/backup pad assembly was moved in a reciprocating motion along the length of the workpiece at a rate of 32-36 cycles per minute, with the abrasive surface of the disc maintained at an angle of 7° to the steel bar against the distal surface of the bar. The grinder assembly and the bar were urged together under the weight of the grinder assembly, which was 7 pounds (3.2 kg). The above test procedure was conducted for one minute (i.e., one test cycle). The bar was weighed to measure the cut (i.e., weight loss). The test cycle was repeated until a portion of the outer ½ inch of disc diameter of the working face of the disc was worn down to the scrim.

Comparative Example 1

A 24-inch×½-inch (61 cm×1.2 cm) nonwoven abrasive belt obtained under the trade designation “BRITERITE RAPID CUT BELT (COARSE GRADE)” from Standard Abrasives, Simi Valley, Calif. [0072]

Comparative Example 2

A 24-inch×½-inch (61 cm×1.2 cm) nonwoven abrasive belt obtained under the trade designation “BRITERITE RAPID CUT BELT (MEDIUM GRADE)” from Standard Abrasives. [0073]

Comparative Example 3

A 7-inch (18 cm) diameter nonwoven abrasive disc obtained under the trade designation “BRITERITE RAPID CUT DISC (COARSE GRADE)” from Standard Abrasives. [0074]

Comparative Example 4

A 7-inch (18 cm) diameter nonwoven abrasive disc obtained under the trade designation BRITERITE RAPID CUT DISC (MEDIUM GRADE) from Standard Abrasives. [0075]

Comparative Example 5

A surface conditioning VELCRO disc (178 mm), medium grit (grit [0076] 100-120) aluminum oxide commercially available from Bibielle, Margarita, Italy.

Example 1

An air-laid fiber web having a thickness of ¾ inch (1.8 cm), a basis weight of 293 g/m[0077] ², and consisting of a 75/25 blend of 70 and 58 denier (74 and 68 dtex) nylon staple fibers, respectively, was laid onto the surface of a low-stretch polyester sateen reinforcing fabric (thread count per inch: warp=11, fill=43; basis weight=303 g/m²at 55 percent relative humidity obtained from Milliken & Company, Spartanburg, S.C.), and then passed through a needletacking machine (obtained under the trade designation “FIBERLOCKER” from James Hunter Machine Company, North Adams, Mass.) fitted with a needle board with 23 rows of 15×18×25×3.5 RB needles (Foster Needle Company, Manitowoc, Wis.) spaced 1.1 cm apart with adjacent needles within each row spaced 1.3 cm apart. The needletacking machine was operated at 560 punches per minute, a penetration depth of 2.2 cm, and at a fiber web rate of 3.1 m/minute. Needletacking affixed the fiber web to the reinforcing fabric. The resultant reinforced fiber web, with a total thickness of ¼ inch (0.6 cm), had approximately 60 percent of its thickness above the center plane of the polyester reinforcing fabric and approximately 40 percent of its thickness below the center plane. The composite web was then brought into contact with a roll heated at 177° C. A slurry coat precursor consisting of the ingredients in Table 1 (below) was sprayed onto the composite web at a target dry add-on weight of 1340 g/m², and then heated for 10 minutes at 150° C.

TABLE 1

COMPONENT PARTS

BR6 25.8

PME 21.8

LUB 3.5

BC 0.9

CUR2 5.9

AO80 92.9
The heated composite web was then saturated with the size coat precursor composition shown in Table 2 (below). The size coat precursor saturated web was compressed between a pair of rubber rolls to remove excess size coating precursor. The size composition was coated at a dry add-on weight of 627 g/m[0078] ², and the size-coated web was then cured for 20 minutes at 135° C. resulting in a nonwoven abrasive article.

TABLE 2

COMPONENT PARTS

BR6 25.4

Water 9.8

BR5 146.6

CaCO₃ 15.8

Example 2

A nonwoven abrasive article was prepared as in Example 1, except that the size coat precursor of TABLE 2 was replaced by the size coat precursor composition of Table 3 (below), which was applied to heated composite web at a dry add-on of 481 g/m[0079] ².

TABLE 3

COMPONENT PARTS

BR2 25.3

Water 42.0

CUR1 4.8

CR1 3.0

SURF 0.6

NH₄OH 0.0257

Example 3

A nonwoven abrasive article was prepared as in Example 1, except that HTAO80 was substituted for AO80, and the size coat precursor of Table 2 was replaced with a size coat precursor having the composition given in Table 4 (below), which was applied to heated composite web at a dry add-on of 481 μm[0080] ².

TABLE 4

COMPONENT PARTS

BR4 77.0

CUR3 39.0

LIST 9.5

PME 33.9

Example 4

A nonwoven abrasive article was prepared as in Example 3, except that the size coat precursor having the composition given in Table 4 was replaced by a size coat precursor having the composition given in Table 3. [0081]

Example 5

A nonwoven abrasive article was prepared as in Example 4, except that AO100-150 was substituted for HTAO80 in the slurry coat precursor, the slurry coat dry add-on weight was 1190 g/m[0082] ², and the air-laid web consisted solely of 58 den (64 dtex) fibers.

Example 6

A nonwoven abrasive article was prepared as in Example 1, except that the slurry coat precursor of Table 1 was replaced by a slurry coat precursor consisting of the components listed in Table 5 (below) and sprayed at a dry add-on of 1338 g/m[0083] ², and that the size coat precursor having the composition given in Table 2 was replaced by a size coat precursor having the composition given in Table 4, which was applied to the heated web to achieve a dry add-on weight of 481 g/m²and then heated for 10 minutes at 135° C.

TABLE 5

COMPONENT PARTS

BR6 58.5

PME 6.2

HEU 7.8

Water 24.7

HTAO60 201.3

FS 1.5
The nonwoven abrasive articles of Examples 1-6 were converted into endless belts (0.5 inch (1.3 cm)×24 inches (61 cm)) endless belts as follows: [0084]

The nonwoven abrasive was cut into a ½ inch (1.3 cm)×24 inches (61 cm), 45 parallelogram-shaped strip. Two-part urethane adhesive was mixed and applied onto the same side of each end of the strip. The ends were abutted and attached together by a 1 inch (2.5 cm) splice tape. Pressure (40-60 psi (0.3-0.4 MPa)) was applied until the adhesive cured. These belts and the belts of Comparative Examples 1 and 2 were then evaluated using the Belt Chunking Test. Each belt exhibited chunking under conditions of the test. Results are presented in Table 6 (below).

TABLE 6


			WEIGHT	WEIGHT	WEIGHT
		WEIGHT	LOSS	AFTER 3	LOSS
	INITIAL	AFTER 1	AFTER 1	MIN-	AFTER 3
	WEIGHT,	MINUTE,	MINUTE,	UTES,	MINUTES,
BELT	g	g	percent	g	percent

Example 1	15.73	15.32	2.6	15.04	4.4
Example 2	16.21	15.94	1.7	15.93	1.7
Example 3	17.54	17.15	2.2	16.75	4.5
Example 4	19.58	19.32	1.3	19.1	2.5
Example 5	18.02	17.82	1.1	17.73	1.6
Example 6	18.58	18.18	2.2	18.06	2.8
Com-	17.09	12.2	18.6	9.8	42.7
parative
Example 1
Com-	18.02	14.41	13.0	6.3	62.0
parative
Example 2

Example 7

Mixture 7D was prepared as follows: [0086]
BR2 (39.62 parts, at 43° C.) was stirred at sufficient speed that a vortex formed. CUR1 (7.52 parts, at 107° C.) was added into the vortex, and then SURF (0.47 parts, at 21° C.) was added into the vortex. The mixture was stirred until it appeared homogenous (Mixture 7A). [0087]
Water (3.40 parts, at 21° C.) was stirred at sufficient speed that a vortex formed. CR2 (0.14 parts, at 21° C.) was added into the vortex, and the mixture (Mixture 7B) was stirred until it appeared homogenous. [0088]
Water (43.96 parts, at 49° C.) was stirred at sufficient speed that a vortex formed. Mixture 7B (3.54 parts, at 21° C.) was added into the vortex. The mixture was stirred until it appeared homogenous, and then NH[0089] ₄OH (0.11 parts, at 21° C.) was added into the vortex with continued mixing until homogenous (Mixture 7C).
Mixture 7C (47.62 parts, at 60° C.) was stirred at sufficient speed that a vortex formed. Mixture 7A (47.62 parts, at 21° C.) was added into the vortex, and the mixture was stirred until it appeared homogenous. Water (4.76 parts, at 49° C.) was added into the vortex, and the mixture was stirred until it appeared homogenous (Mixture 7D). [0090]
A nonwoven abrasive article was prepared as in Example 1, except that the fabric was a plain weave nylon scrim (16×16 nylon scrim; Type 6,6; Style [0091] 6703832 obtained from Highland Industries, Greensboro, N.C.), the slurry coat precursor of Table 1 was replaced by a slurry coat precursor consisting of the components listed in Table 7 (below) and sprayed at a dry add-on of 1338 g/m², and the size coat precursor having the composition listed in Table 2 was replaced by Mixture 7D applied at a dry add-on weight of 481 g/m².

TABLE 7

COMPONENT PARTS

BR6 20.0

Water 8.4

HEU 2.7

FS 0.2

AO80 68.7
The resultant nonwoven abrasive article was die cut into a 7-inch diameter disc. [0092]

Example 8

A nonwoven abrasive article was prepared as in Example 7, except that AO100-150 was substituted for AO80 in the slurry coat precursor. [0093]

Example 9

A nonwoven abrasive article was prepared as in Example 7, except that size coat precursor having the composition of Mixture 7D was replaced by a size coat precursor having the composition listed in Table 8 (below), which was coated and the resultant coated article was then heated at 110° C. for 30 minutes. [0094]

TABLE 8

COMPONENT PARTS

BR5 63.3

BR6 11.8

water 24.9

Example 10

A nonwoven abrasive article was prepared as in Example 9, except that AO100-150 was substituted for AO80 in the slurry coat precursor. [0095]

Example 11

A nonwoven abrasive article was prepared as in Example 9, except that the size coat precursor having the composition listed in Table 8 was replaced by a size coat precursor having the composition listed in Table 4. [0096]

Results of the Disc Wear Test are listed in Table 9 (below).

TABLE 9


NO. OF 1-	CUT, g

MINUTE	EXAMPLE	EXAMPLE	EXAMPLE	EXAMPLE	EXAMPLE	COMPARATIVE	COMPARATIVE	COMPARATIVE
CYCLES	7	8	9	10	11	EXAMPLE 3	EXAMPLE 4	EXAMPLE 5

1	11.4	8.1	11.8	8.2	15	12.2	4.1	8.6
2	11.8	7.5	11.3	8.0	14.7	10.2	4.1	7.0
3	12	7.9	12.2	7.0	14.7	—	5.3	6.2
4	10.4	7.7	10.6	8.0	12.1	—	—	6.8
5	11.2	8.4	10.9	8.6	14.5	—	—	4.8
6	11.3	8.2	11.2	7.4	12.5	—	—	—
7	13.5	7.5	8.4	7.1	11.5	—	—	—
8	10.6	7.5	10.5	7.0	10.0	—	—	—
9	11.3	9.2	8.3	5.6	9.2	—	—	—
10	11.7	7.7	8.5	5.4	9.8	—	—	—
11	—	—	8.7	6.2	10.0	—	—	—
12	—	—	5.8	7.6	7.8	—	—	—
13	—	—	—	7.1	—	—	—	—
14	—	—	—	6.4	—	—	—	—

Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrated embodiments set forth herein. [0098]

Claims

What is claimed is:

1. A nonwoven abrasive article comprising:

a porous reinforcing material having first and second opposed major surfaces;

2. A nonwoven abrasive article according to claim 1, wherein the fiber web is needletacked to the first major surface of the porous reinforcing material.

3. A nonwoven abrasive article according to claim 1, wherein the article is a disc.

4. A nonwoven abrasive article according to claim 1, wherein the article is an endless belt.

5. A nonwoven abrasive article according to claim 1, wherein the binder comprises at least partially cured phenolic resin.

6. A nonwoven abrasive article according to claim 1, wherein the abrasive composition comprises a slurry coat.

7. A nonwoven abrasive article according to claim 6, further comprising a size coat contacting at least a portion of the abrasive composition.

8. A nonwoven abrasive article according to claim 6, wherein the size coat comprises an elastomer.

9. A nonwoven abrasive article according to claim 6, wherein the size coat comprises at least one of a lubricant or a grinding aid.

10. A nonwoven abrasive article according to claim 7, wherein the article comprises a disc or an endless belt.

11. A nonwoven abrasive article according to claim 1, wherein the abrasive composition comprises a make coat and a size coat.

12. A nonwoven abrasive article according to claim 11, wherein the size coat comprises an elastomer.

13. A nonwoven abrasive article according to claim 11, wherein the size coat comprises at least one of a lubricant or a grinding aid.

14. A nonwoven abrasive article according to claim 11, wherein the article is a disc or an endless belt.

15. A nonwoven abrasive article according to claim 11, wherein the first binder comprises at least partially cured phenolic resin.

16. A method for making a nonwoven abrasive article comprising:

providing a fiber web;

affixing the fiber web to the first major surface of the reinforcing material;

17. A method according to claim 16, wherein affixing comprises needletacking.

18. A method according to claim 16, wherein applying comprises spraying.

19. A method according to claim 16, further comprising forming the nonwoven abrasive article into at least one of a disc or an endless belt.

20. A method according to claim 16, wherein the first binder precursor comprises phenolic resin.

21. A method according to claim 16, wherein the first binder precursor and abrasive particles comprise a slurry coat precursor.

22. A method according to claim 16, wherein the first binder precursor comprises a make coat precursor.

23. A method according to claim 16, further comprising:

applying a second binder precursor to at least a portion of the non-elastomeric first binder, wherein the second binder precursor; and

at least partially curing the second binder precursor.

24. A method according to claim 23, further comprising forming the nonwoven abrasive article into at least one of a disc or an endless belt.

25. A method according to claim 23, wherein the second binder precursor is at least partially curable to form an elastomer.

26. A method of abrading a surface, the method comprising:

providing a nonwoven abrasive article, wherein the nonwoven abrasive article comprises:

a porous reinforcing material having first and second opposed major surfaces;

a fiber web affixed to the first major surface of the porous reinforcing material;

an abrasive composition comprising abrasive particles and binder, wherein the abrasive composition contacts at least a portion of the fiber web and the first major surface of the reinforcing material, wherein the abrasive composition extends through at least a portion of the reinforcing material and contacts at least a portion of the second major surface of the reinforcing material, wherein on a weight basis, there is a first average ratio of abrasive particles to the non-elastomeric binder at the first major surface, and a second average ratio of abrasive particles to the non-elastomeric binder at the second major surface, and wherein the first average ratio is greater than the second average ratio;

contacting at least one of the abrasive particles with the surface of the workpiece; and

27. A method of abrading a workpiece according to claim 26, wherein the nonwoven abrasive article further comprises a size coat contacting at least a portion of the slurry coat.

28. A method of abrading a workpiece according to claim 26, wherein the first binder comprises at least partially cured phenolic resin.