WO2023084362A1 - Nonwoven abrasive articles and methods of making the same - Google Patents

Abstract

A nonwoven abrasive article comprises a lofty open nonwoven fiber web comprising entangled fibers. The fibers have an average diameter, and the fiber web has first and second opposed major surfaces and a porous interior therebetween. An abrasive material is predominantly disposed within the porous interior. The abrasive material comprises abrasive particles at least partially retained in a binder. The abrasive material comprises elongated blobs. Each elongated blob is respectively bonded to at least one of the fibers. The elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees. The abrasive particles are magnetizable, the elongated blobs further comprise magnetizable particles different from the abrasive particles, or both. Methods of making the nonwoven abrasive article are also disclosed.

Description

NONWOVEN ABRASIVE ARTICLES AND METHODS OF MAKING THE SAME

TECHNICAL FIELD

The present disclosure broadly relates to nonwoven abrasive articles and methods of making and using them.

BACKGROUND

Nonwoven abrasive articles commonly have an abrasive material coated on a lofty open fiber web. The abrasive material includes abrasive particles at least partially retained in a binder. Abrasive material is typically distributed throughout the fiber web in a random substantially constant manner.

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 U.S. Patent No. 2,958,593 (Hoover et al.). Exemplary commercial nonwoven abrasive articles include nonwoven abrasive hand pads such as those marketed by 3M Company of Saint Paul, Minnesota under the trade designation SCOTCH-BRITE.

Typically, to make nonwoven abrasive articles, a curable binder precursor can be coated on a lofty open nonwoven fiber web and then the abrasive particles are adhered to the curable binder precursor, or the abrasive particles are mixed with the curable binder precursor and then coated on the fiber web (e.g., as a slurry coat).

SUMMARY

There is a continuing need for nonwoven abrasive articles with improved abrasive properties. Advantageously, nonwoven abrasive articles according to the present disclosure are characterized by unique distribution characteristics of the abrasive material within the porous interior of the fiber web that can improve abrading performance relative to conventional nonwoven abrasive articles.

In a first aspect, the present disclosure provides a nonwoven abrasive article comprising: a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; and an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises abrasive particles at least partially retained in a binder, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees, and further wherein: i) the abrasive particles are magnetizable; or ii) the elongated blobs further comprise magnetizable particles different from the abrasive particles; or iii) both i) and ii).

In another aspect, the present disclosure provides a method of making a nonwoven abrasive article, the method comprising the steps: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing a mixture comprising a curable binder precursor and magnetizable particles predominantly into a portion of the porous interior; c) applying a magnetic field to the mixture; d) disposing abrasive particles onto the mixture; and e) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles and magnetizable at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

In yet another aspect, the present disclosure provides a method of making a nonwoven abrasive article, the method comprising the steps: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor, abrasive particles, and magnetizable particles; c) applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles and the magnetizable particles at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

In yet another aspect, the present disclosure provides a method of making a nonwoven abrasive article, the method comprising: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor and magnetizable abrasive particles; c) applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

As used herein:

The term "abrasive particle" refers to a particle having a Mohs scale hardness of at least 4.

The term "abrasive platelet" refers to an abrasive particle (whether randomly crushed, intentionally shaped and/or molded (e.g., a thin truncated triangular pyramid), or other) resembling a minute flattened body and/or flake that is characterized by a thickness that is substantially less than the width and length. Abrasive platelets generally have two opposed major sides defining the length and width of the abrasive platelet, and with the thickness disposed therebetween, joined along a peripheral edge that includes at least one line and/or at least one surface. For example, the thickness may be less than 1/2, 1/3, 1/4, 1/5, 1/6, 1/7, 1/8, 1/9, or even less than 1/10 of the length and/or width.

The term "blob" refers to mass of material having an irregular shape.

The term "elongated blob" refers to a blob having and elongated shape (e.g., having an aspect ratio length/width of at least 1.5, at least 2, at least 3, at least 4, at least 5, at least 8, or even at least 10).

The term "ferrimagnetic" refers to materials that exhibit ferrimagnetism. Ferrimagnetism is a type of permanent magnetism that occurs in solids in which the magnetic fields associated with individual atoms spontaneously align themselves, some parallel, or in the same direction (as in ferromagnetism), and others generally antiparallel, or paired off in opposite directions (as in antiferromagnetism). The magnetic behavior of single crystals of ferrimagnetic materials can be attributed to the parallel alignment; the diluting effect of those atoms in the antiparallel arrangement keeps the magnetic strength of these materials generally less than that of purely ferromagnetic solids such as metallic iron. Ferrimagnetism occurs chiefly in magnetic oxides known as ferrites. The spontaneous alignment that produces ferrimagnetism is entirely disrupted above a temperature called the Curie point, characteristic of each ferrimagnetic material. When the temperature of the material is brought below the Curie point, ferrimagnetism revives. The term "ferromagnetic" refers to materials that exhibit ferromagnetism. Ferromagnetism is a physical phenomenon in which certain electrically uncharged materials strongly attract others. In contrast to other substances, ferromagnetic materials are magnetized easily, and in strong magnetic fields the magnetization approaches a definite limit called saturation. When a field is applied and then removed, the magnetization does not return to its original value. This phenomenon is referred to as hysteresis. When heated to a certain temperature called the Curie point, which is generally different for each substance, ferromagnetic materials lose their characteristic properties and cease to be magnetic; however, they become ferromagnetic again on cooling.

The term "length" refers to the longest dimension of an object.

The term "longitudinally aligned" in reference to two blobs means aligned with respect to the two blobs' respective longitudinal axes.

The term "magnet" can include a ferromagnetic and/or ferrimagnetic material that responds to a magnetic field and acts as a magnet. A magnet can be any material that exerts a magnetic field in either a permanent, semi-permanent, or temporaiy state. The term "magnet" can be one individual magnet or an assembly of magnets that would act like a single magnet. The term "magnet" can include permanent magnets and electromagnets.

The term "magnetic field" refers to magnetic fields that are intentionally generated and not generated by any astronomical body or bodies (e.g., Earth or the sun) or unintended ambient electromagnetic interference (e.g., due to electrical architectural wiring). In general, magnetic fields used in practice of the present disclosure have a field strength in the region of the magnetizable particles being acted upon of at least about 10 gauss (1 mT), in some cases at least about 100 gauss (10 mT), and in yet other cases at least about 1000 gauss (0.1 T), and in yet other cases at least about 10,000 gauss (1.0 T).

The term "magnetizable" means that the item being referred to is magnetic, or can be made magnetic, using an applied magnetic field and has a magnetic moment of at least 0.001 electromagnetic units (emu), in some cases at least 0.005 emu, and yet other cases 0.01 emu, or even at least 0.1 emu, although this is not a requirement.

The term "Mohs hardness" refers to hardness judged according to the Mohs scale of mineral hardness.

The term "non-magnetizable" means not magnetizable at 20°C.

The term "nonwoven" means made of entangled and/or bonded fibers that are not the result of a conventional weaving process.

The term "precisely-shaped abrasive particle" refers to an abrasive particle with at least at portion of the abrasive particle having a predetermined shape that is replicated from a mold cavity used to form the shaped precursor abrasive particle. A precisely-shaped abrasive particle may have a predetermined geometric shape having planar surfaces and sharp edges and vertices, for example. The term "shaped abrasive particle" refers to an abrasive particle that has a non-random shape imparted by the method (e.g., a molding, screen printing, or 3D fabrication process) used to make it, and expressly excludes mechanically crushed and/or milled particles.

The term "thickness" refers to the remaining dimension that is perpendicular to the length and the width.

The term "width" refers to the longest dimension of an object that is perpendicular to the length.

The terms "magnetic" and "magnetized" mean being ferromagnetic or ferrimagnetic at 20°C, unless otherwise specified.

Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view digital photograph of nonwoven abrasive article 100 prepared in Example 1.

FIG. 2 is a side view digital photograph of nonwoven abrasive article 100 prepared in Example 1. FIG. 3 is a top view digital photograph of nonwoven abrasive article 300 prepared in Example 2. FIG. 4 is a side view digital photograph of nonwoven abrasive article 300 prepared in Example 2. FIG. 5 is a top view digital photograph of nonwoven abrasive article 500 prepared in Example 3. FIG. 6 is a side view digital photograph of nonwoven abrasive article 500 prepared in Example 3. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

Exemplary nonwoven abrasive articles according to the present disclosure are shown in FIGS. 1-6 which correspond to Examples 1 to 3 described hereinbelow.

Referring now to FIGS. 1 and 2, nonwoven abrasive article 100 comprises a lofty open nonwoven fiber web 110 comprising entangled fibers 120. Lofty open nonwoven fiber web 110 has first and second opposed major surfaces (112, 114 shown in FIG. 2) and a porous interior 116 (also shown in FIG. 2) disposed therebetween. Abrasive material 130 comprises abrasive particles at least partially retained in binder (not shown). Abrasive material 130 is predominantly disposed within porous interior 116 and comprises elongated blobs 140 that are bonded to at least one fiber 120. The elongated blobs have a minimum width of at least two times the average diameter of the fibers. A majority of the elongated blobs are longitudinally aligned within 40 degrees (i.e., of each other).

In FIGS. 1 and 2 the abrasive particles are partially retained in the binder at its surface (visible in FIG. 1, which further comprises magnetizable particles different than the abrasive particles.

In one alternative, shown in FIGS. 3 and 4 (corresponding to Example 2) nonwoven abrasive 300 includes magnetizable abrasive particles distributed throughout the abrasive material (not shown). In another alternative, shown in FIGS. 5 and 6 (corresponding to Example 3) nonwoven abrasive 500 includes magnetizable particles and abrasive particles distributed throughout the abrasive material (not shown).

Lofty open nonwoven fiber webs suitable for use are known in the abrasives art. Such nonwoven fiber webs comprise an entangled web of fibers. The lofty open nonwoven fiber web has a porous interior generally comprising a network of interconnected voids.

The fibers may comprise continuous fiber, staple fiber, or a combination thereof. For example, the fibers 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, i.e., grams/10000 meters), 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 lofty open nonwoven 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 from Rando Machine Company of Macedon, New York.

Nonwoven fiber webs are typically selected to be compatible with adhering binders and abrasive particles while also being compatible 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 binder precursor. 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), nylon (e.g., hexamethylene adipamide, poly caprolactam), polypropylene, acrylonitrile (i.e., acrylic), rayon, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymers, and vinyl chlorideacrylonitrile copolymers. Examples of suitable natural fibers include cotton, wool, jute, and hemp. The fiber 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 but may also be continuous filaments such as those formed by an extmsion process. Combinations of fibers may also be used.

Prior to coating with the abrasive material precursor, the nonwoven fiber web often has a weight per unit area (i.e., basis weight) of at least about 50 grams per square meter (gsm), at least about 100 gsm, or at least about 150 gsm; and/or less than about 600 gsm, less than about 500 gsm, or less than about 400 gsm, as measured prior to any coating (e.g., with the curable binder precursor or optional pre-bond resin), although greater and lesser basis weights may also be used. In addition, prior to coating with the curable binder precursor, the fiber web typically has a thickness of at least about 3 mm, at least about 6 mm, or at least about 10 mm; and/or less than about 100 mm, less than about 50 mm, or less than about 25 mm, although greater and lesser thicknesses may also be useful.

Frequently, as known in the abrasives art, it can be useful to apply a prebond resin to the nonwoven fiber web prior to coating with the abrasive material precursor. The prebond 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 prebond 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 toward the minimum amount consistent with bonding 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 abrasive material is generally provided by at least partially curing (typically at least substantially curing) an abrasive material precursor. In some embodiments, the abrasive material precursor comprises magnetizable abrasive particles dispersed in a curable binder precursor. In some embodiments, the abrasive material precursor comprises magnetizable particles and abrasive particles other than the magnetizable particles, which may or may not be magnetizable, dispersed in a curable binder precursor.

In some embodiments, the abrasive material is formed by disposing abrasive particles on a curable binder precursor containing dispersed magnetizable particles and then at least partially curing the curable binder precursor.

Regardless of how formed, the abrasive material predominantly is disposed within the porous interior. In some embodiments it is entirely disposed within the porous interior. In other embodiments, a minor portion of the abrasive material extends partially beyond one or both surface(s) of the lofty open nonwoven fiber web. The abrasive material may be disposed randomly, pseudo-randomly, or at predetermined locations within the porous interior, for example.

Examples of suitable curable binder precursors include phenolic resins (e.g., resole phenolic resins and novolac phenolic resins); epoxy resins; polymerizable acrylic monomers, oligomers, and polymers; alkyd resins; cyanate resins; aminoplast resins; urea-formaldehyde resins; urethane resins (one- part and two-part); and combinations thereof. Depending on the curable binder precursor selected, an appropriate curative (e.g., a crosslinker, catalyst, or free radical initiator (thermal or photo-)) may also be present. Selection and amounts of suitable such curatives are well known in the abrasives art. Curable binder compositions may contain various additives. For example, conventional resin filler(s) (e.g., calcium carbonate or fine fibers), lubricant(s) (e.g., alkali metal salts of stearic acid and light petroleum oils), grinding aid(s) (e.g., potassium fluoroborate), wetting agent(s) or surfactant(s) (e.g., sodium lauryl sulfate), defoamer(s), pigment(s), dye(s), biocide(s), coupling agent(s) (e.g., organosilanes), plasticizer(s) (e.g., polyalkylene polyols or phthalate esters), thickeners, and combinations thereof. The curable binder precursor may include at least one solvent (e.g., isopropyl alcohol, methyl ethyl ketone, water) to facilitate coating of the curable binder precursor on the nonwoven fiber web, although this is not a requirement.

In some embodiments, the curable binder precursor can be a urethane prepolymer. Examples of useful urethane prepolymers include polyisocyanates and blocked versions thereof. Typically, blocked polyisocyanates are substantially unreactive to isocyanate reactive compounds (e.g., amines, alcohols, thiols) under ambient conditions (e.g., temperatures in a range of from about 20 °C to about 25 °C), but upon application of sufficient thermal energy the blocking agent is released, thereby generating isocyanate functionality that reacts with the amine curative to form a covalent bond.

Useful polyisocyanates include, for example, aliphatic polyisocyanates (e.g., hexamethylene diisocyanate or trimethylhexamethylene diisocyanate); alicyclic polyisocyanates (e.g., hydrogenated xylylene diisocyanate or isophorone diisocyanate); aromatic polyisocyanates (e.g., tolylene diisocyanate or 4,4'-diphenylmethane diisocyanate); adducts of any of the foregoing polyisocyanates with a polyhydric alcohol (e.g., a diol, low molecular weight hydroxyl group-containing polyester resin, and/or water); adducts of the foregoing polyisocyanates (e.g., isocyanurates, biurets); and mixtures thereof.

Useful commercially available polyisocyanates include, for example, those available under the trade designation ADIPRENE from Chemtura Corporation, Middlebury, Connecticut (e.g., ADIPRENE L 0311, ADIPRENE L 100, ADIPRENE L 167, ADIPRENE L 213, ADIPRENE L 315, ADIPRENE L 680, ADIPRENE LF 1800 A, ADIPRENE LF 600D, ADIPRENE LFP 1950 A, ADIPRENE LFP 2950 A, ADIPRENE LFP 590D, ADIPRENE LW 520, and ADIPRENE PP 1095); polyisocyanates available under the trade designation MONDUR from Bayer Corporation, Pittsburgh, Pennsylvania (e.g., MONDUR 1437, MONDUR MP-095, or MONDUR 448); and polyisocyanates available under the trade designations AIRTHANE and VERSATHANE from Air Products and Chemicals, Allentown, Pennsylvania (e.g., AIRTHANE APC-504, AIRTHANE PST-95A, AIRTHANE PST-85A, AIRTHANE PET-91 A, AIRTHANE PET-75D, VERSATHANE STE-95A, VERSATHANE STE-P95, VERSATHANE STS-55, VERSATHANE SME-90 A, and VERSATHANE MS-90A).

To lengthen pot-life, polyisocyanates such as, for example, those mentioned above may be blocked with a blocking agent according to various techniques known in the art. Exemplary blocking agents include ketoximes (e.g., 2-butanone oxime); lactams (e.g., epsilon-caprolactam); malonic esters (e.g., dimethyl malonate and diethyl malonate); pyrazoles (e.g., 3,5-dimethylpyrazole); alcohols including tertiary alcohols (e.g., t-butanol or 2,2-dimethylpentanol), phenols (e.g., alkylated phenols), and mixtures of alcohols as described. Exemplary useful commercially available blocked polyisocyanates include those marketed by Chemtura Corporation under the trade designations ADIPRENE BL 11, ADIPRENE BL 16, ADIPRENE BL 31, ADIPRENE BL 46, and ADIPRENE BL 500; and blocked polyisocyanates marketed by Baxenden Chemicals, Ltd., Accrington, England under the trade designation TRIXENE (e.g., TRIXENE BL 7641, TRIXENE BL 7642, TRIXENE BL 7772, and TRIXENE BL 7774).

Typically, the amount of any urethane prepolymer present in the curable binder precursor is in an amount of from 10 to 40 percent by weight, more typically in an amount of from 15 to 30 percent by weight, and even more typically in an amount of from 20 to 25 percent by weight based on the total weight of the curable binder precursor, although amounts outside of these ranges may also be used.

Exemplary curatives for urethane prepolymers include aromatic, alkyl-aromatic, or alkyl polyfunctional amines, preferably primary amines. Examples of useful amine curatives include 4,4'- methylenedianiline; polymeric methylene dianilines having a functionality of 2.1 to 4.0 which include those known as CURITHANE 103, commercially available from the Dow Chemical Company, and MDA-85 from Bayer Corporation, Pittsburgh, Pennsylvania; l,5-diamine-2 -methylpentane; tris(2- aminoethyl) amine; 3-aminomethyl-3,5,5-trimethylcyclohexylamine (i.e., isophoronediamine), trimethylene glycol di-p-aminobenzoate, bis(o-aminophenylthio)ethane, 4,4'-methylenebis(dimethyl anthranilate), bis(4-amino-3-ethylphenyl)methane (e.g., marketed as KAYAHARD AA by Nippon Kayaku Company, Ltd., Tokyo, Japan), andbis(4-amino-3,5-diethylphenyl)methane (e.g., marketed as LONZACURE M-DEA by Lonza, Ltd., Basel, Switzerland), and mixtures thereof. If desired, polyol(s) may be added to the curable binder precursor, for example, to modify (e.g., to retard) cure rates as required by the intended use. The amine curative should be present in an amount effective (i.e., an effective amount) to cure the blocked polyisocyanate to the degree required by the intended application; for example, the amine curative may be present in a stoichiometric ratio of curative to isocyanate (or blocked isocyanate) in a range of from 0.8 to 1.35; for example, in a range of from 0.85 to 1.20, or in a range of from 0.90 to 0.95, although stoichiometric ratios outside these ranges may also be used.

The abrasive material and it precursors include magnetizable particles dispersed in the binder and/or precursor.

Exemplary magnetizable materials that can be suitable for use as magnetizable particles can include: iron; cobalt; nickel; various alloys of nickel and iron marketed as Permalloy in various grades; various alloys of iron, nickel and cobalt marketed as Fernico, Kovar, FerNiCo I, or FerNiCo II; various alloys of iron, aluminum, nickel, cobalt, and sometimes also copper and/or titanium marketed as Alnico in various grades; alloys of iron, silicon, and aluminum (typically about 85:9:6 by weight) marketed as Sendust alloy; Heusler alloys (e.g., Ch^MnSn); manganese bismuthide (also known as Bismanol); rare earth magnetizable materials such as gadolinium, dysprosium, holmium, europium oxide, alloys of neodymium, iron and boron (e.g., Nd2Fe 4B), and alloys of samarium and cobalt (e.g., SmCo^): MnSb; MnOFc2CL: Y^Fe^O | ⁽- ^r(^2- MnAs; and ferrites such as magnetite; zinc ferrite; nickel ferrite; cobalt ferrite, magnesium ferrite, manganese zinc ferrite, barium ferrite, and strontium ferrite; yttrium iron garnet; and combinations of the foregoing such as nickel zinc ferrite, cobalt nickel zinc ferrite, and magnesium manganese zinc ferrite. In some embodiments, the magnetizable material includes at least one metal selected from iron, nickel, and cobalt, an alloy of two or more such metals, or an alloy of at one such metal with at least one element selected from phosphorus and manganese. In some embodiments, the magnetizable material is an alloy (e.g., Alnico alloy) containing 8 to 12 weight percent (wt. %) aluminum, 15 to 26 wt. % nickel, 5 to 24 wt. % cobalt, up to 6 wt. % copper, up to 1 wt. % titanium, where the balance of material to add up to 100 wt. % is iron. In some embodiments, the magnetizable particles are carbonyl iron particles. Carbonyl iron can be prepared by the chemical decomposition of purified iron pentacarbonyl. In some embodiments, the magnetizable particles include iron. In some embodiments, the magnetizable particles include carbon and iron. In some embodiments, the magnetizable particles include nickel.

The magnetizable particles can have a major dimension of any size relative to a thickness of the layer they are a part of but can be much smaller than the thickness of the layer in some instances. For example, they can be 1 to 2000 times smaller in some embodiments, in yet other embodiments 100 to 2000 times smaller, and in yet other embodiments 500 to 2000 times smaller, although other sizes can also be used.

Suitable magnetizable particles include particles formed from any of the magnetizable materials described elsewhere, optionally coated with another material, and particles formed from a non- magnetizable material and coated with a magnetizable material. For example, suitable magnetizable particles include nickel-coated graphite flakes, nickel-coated glass spheres, and nickel-coated plastic particles (e.g., nickel coated polymethyl methacrylate (PMMA) particles).

In some embodiments, the magnetizable particles may also be abrasive particles (i.e., provided that they have a Mohs hardness of at least 4). Examples may include stainless steel particles, many synthetic diamonds, abrasive agglomerates containing magnetizable particles and abrasive particles, and otherwise non-magnetizable abrasive particles (grains) that have various magnetizable coatings thereon, for example, as described in U.S. Pat. Appl. Publ. Nos. 2019/0249052 Al (Eckel et al.), 2019/0264081 Al (Anderson et al.), 2019/0270183 Al (Eckel et al.), 2019/0270922 Al (Eckel et al.), 2019/0329380 Al (Eckel et al.), 2019/0344403 Al (Eckel et al.), and 2020/0071584 Al (Anderson et al.).

In some embodiments, the magnetizable particles may have a Mohs hardness of less than.

Exemplary abrasive particles, which may be magnetizable or non-magnetizable, include abrasive particles having the shape of rods, shaped (e.g., precisely -shaped) platelets, or crushed abrasive particles conforming to an abrasives industry specified nominal grade, and wherein each one of the ridges is irregularly shaped and is oriented along at least a portion of its length substantially parallel to adjacent ridges.

Useful abrasive particles may be the result of a crushing operation (e.g., crushed abrasive particles that have been sorted for shape and size) or the result of a shaping operation (i.e., shaped abrasive particles) in which an abrasive precursor material is shaped (e.g., molded), dried, and converted to ceramic material. Combinations of abrasive particles resulting from crushing with abrasive particles resulting from a shaping operation may also be used. The abrasive particles may be in the form of, for example, individual particles, agglomerates, composite particles, and mixtures thereof.

The abrasive particles should have sufficient hardness and surface roughness to function as crushed abrasive particles in abrading processes. In many embodiments, the abrasive particles have a Mohs hardness of at least 5, at least 6, at least 7, or even at least 8.

Suitable abrasive particles include, for example, crushed abrasive particles comprising fused aluminum oxide, heat-treated aluminum oxide, white fused aluminum oxide, ceramic aluminum oxide materials such as those commercially available as 3M CERAMIC ABRASIVE GRAIN from 3M Company, St. Paul, Minnesota, 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 ceramic (e.g., alpha alumina), and combinations thereof. Examples of sol-gel-derived abrasive particles from which the abrasive particles can be isolated, and methods for their preparation can be found, in U.S. Pat. Nos. 4,314,827 (Leitheiser et al.); 4,623,364 (Cottringer et al.); 4,744,802 (Schwabel), 4,770,671 (Monroe et al.); and 4,881,951 (Monroe et al.). It is also contemplated that the abrasive particles could comprise abrasive agglomerates such, for example, as those described in U.S. Pat. Nos. 4,652,275 (Bloecher et al.) or 4,799,939 (Bloecher et al.). In some embodiments, the abrasive particles 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 crushed abrasive particles to the binder. The abrasive particles may be treated before combining them with the binder, or they may be surface treated in situ by including a coupling agent to the binder.

Preferably, the abrasive particles (and especially the abrasive particles) comprise ceramic abrasive particles such as, for example, sol-gel-derived polycrystalline alpha alumina particles. Ceramic abrasive particles 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, U.S. Pat. No. 5,213,591 (Celikkaya et al.) and U.S. Publ. Pat. Appln. Nos. 2009/0165394 Al (Culler et al.) and 2009/0169816 Al (Erickson et al.). Further details concerning methods of making sol-gel-derived abrasive particles can be found in, for example, U.S. Pat. Nos. 4,314,827 (Leitheiser); 5,152,917 (Pieper et al.); 5,435,816 (Spurgeon et al.); 5,672,097 (Hoopman et al.); 5,946,991 (Hoopman et al.); 5,975,987 (Hoopman et al.); and 6,129,540 (Hoopman et al.); and in U.S. Publ. Pat. Appln. No. 2009/0165394 Al (Culler et al.).

In some preferred embodiments, useful abrasive particles (especially in the case of the abrasive particles) may be shaped abrasive particles can be found in U.S. Pat. Nos. 5,201,916 (Berg); 5,366,523 (Rowenhorst (Re 35,570)); and 5,984,988 (Berg). U.S. Pat. No. 8,034,137 (Erickson et al.) describes alumina abrasive particles that have been formed in a specific shape, then crushed to form shards that retain a portion of their original shape features. In some embodiments, the abrasive particles are precisely-shaped (i.e., the particles have shapes that are at least partially determined by the shapes of cavities in a production tool used to make them. Details concerning such abrasive particles and methods for their preparation can be found, for example, in U.S. Pat. Nos. 8,142,531 (Adefris et al.); 8,142,891 (Culler et al.); 8,142,532 (Erickson et al.); 9,771,504 (Adefris); and in U.S. Pat. Appl. Publ. Nos. 2012/0227333 (Adefris et al.); 2013/0040537 (Schwabel et al.); and 2013/0125477 (Adefris). One particularly useful precisely-shaped abrasive particle shape is that of a platelet having three-sidewalls, any of which may be straight or concave, and which may be vertical or sloping with respect to the platelet base; for example, as set forth in the above cited references.

Surface coatings on the abrasive particles may be used to improve the adhesion between the abrasive particles and a binder material, or to aid in electrostatic deposition of the abrasive particles. In one embodiment, surface coatings as described in U.S. Pat. No. 5,352,254 (Celikkaya) in an amount of 0.1 to 2 percent surface coating to abrasive particle weight may be used. Such surface coatings are described in U.S. Pat. Nos. 5,213,591 (Celikkaya et al.); 5,011,508 (Wald et al.); 1,910,444 (Nicholson); 3,041,156 (Rowse et al.); 5,009,675 (Kunz et al.); 5,085,671 (Martin et al.); 4,997,461 (Markhoff- Matheny et al.); and 5,042,991 (Kunz et al.). Additionally, the surface coating may prevent shaped abrasive particles 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 abrasive particles. Surface coatings to perform the above functions are known to those of skill in the art.

In some embodiments, the abrasive particles may be selected to have a length and/or width in a range of from 0.1 micrometers to 3.5 millimeters (mm), more typically 0.05 mm to 3.0 mm, and more typically 0.1 mm to 2.6 mm, although other lengths and widths may also be used.

The abrasive particles may be selected to have a thickness in a range of from 0.1 micrometer to 1.6 mm, more typically from 1 micrometer to 1.2 mm, although other thicknesses may be used. In some embodiments, abrasive particles may have an aspect ratio (length to thickness) of at least 2, 3, 4, 5, 6, or more.

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). Such industry accepted grading standards include, for example: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 30, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600; FEPA P8, FEPA P12, FEPA P16, FEPA P24, FEPA P30, FEPA P36, FEPA P40, FEPA P50, FEPA P60, FEPA P80, FEPA P100, FEPA P120, FEPA P150, FEPA P180, FEPA P220, FEPA P320, FEPA P400, FEPA P500, FEPA P600, FEPA P800, FEPA P1000, FEPA P1200; FEPA F8, FEPA F12, FEPA F16, and FEPA F24; and JIS 8, JIS 12, JIS 16, JIS 24, JIS 36, JIS 46, JIS 54, JIS 60, JIS 80, JIS 100, JIS 150, JIS 180, JIS 220, JIS 240, JIS 280, JIS 320, JIS 360, JIS 400, JIS 600, JIS 800, JIS 1000, JIS 1500, JIS 2500, JIS 4000, JIS 6000, JIS 8000, and JIS 10,000. More typically, the crushed aluminum oxide particles and the non-seeded sol-gel derived alumina-based abrasive particles are independently sized to ANSI 60 and 80, or FEPA F36, F46, F54 and F60 or FEPA P60 and P80 grading standards.

Alternatively, the abrasive particles can be graded to a nominal screened grade using U.S.A. Standard Test Sieves conforming to ASTM E-l 1 "Standard Specification for Wire Cloth and Sieves for Testing Purposes". ASTM E-l 1 prescribes the requirements for the design and construction of testing sieves using a medium of woven wire cloth mounted in a frame for the classification of materials according to a designated particle size. A typical designation may be represented as -18+20 meaning that the shaped abrasive particles pass through a test sieve meeting ASTM E-l 1 specification for the number 18 sieve and are retained on a test sieve meeting ASTM E-l 1 specification for the number 20 sieve. In one embodiment, the shaped abrasive particles have a particle size such that most of the particles pass through an 18 mesh test sieve and can be retained on a 20, 25, 30, 35, 40, 45, or 50 mesh test sieve. In various embodiments, the shaped abrasive particles can have a nominal screened grade comprising: -18+20, -20+25, -25+30, -30+35, -35+40, -40+45, -45+50, -50+60, -60+70, -70+80, -80+100, -100+120, -120+140, -140+170, -170+200, -200+230, -230+270, -270+325, -325+400, -400+450, -450+500, or -500+635. Alternatively, a custom mesh size can be used such as -90+100.

The abrasive material comprises elongated blobs (i.e., elongated blobs of the abrasive material) that are bonded to at least one fiber. Not all of the abrasive material need be in elongated blobs. For example, the abrasive material may be present in spherical/spheroidal blobs or it may be present as a sheath of substantially uniform thickness on one or more of the fibers. The elongated blobs can each be characterized by a respective length (i.e., longitudinal dimension), width, and thickness.

The elongated blobs often collectively occupy at least 5, at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, or even at least 80 volume percent of the porous interior, but not a requirement.

The elongated blobs have a minimum width of at least two 2 times, at least 3 times, at least 4 times, at least 5 times, at least 6 times, at least 8 times, at least 10 times, or even at least 15 times the average diameter of the fibers. In many embodiments, the elongated blobs have a minimum width of at least 3 times, at least 6 times, at least 8 times, at least 10 times, or even at least 15 times the average diameter of the thickest fibers.

Due to the application of the magnetic field during manufacture a majority (e.g., at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, or even at least 90 percent) of the elongated blobs are longitudinally aligned within 40 degrees, 30 degrees, or even within 20 degrees of each other. The direction of the longitudinal alignment is determined by the orientation characteristics of the applied magnetic field during manufacture.

In some embodiments, a majority (e.g., at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, or even at least 90 percent) of the elongated blobs have longitudinally oriented sides that are aligned within 20 degrees of being parallel to a thickness dimension of the lofty open fiber web. In some embodiments, at least some (often a majority) of the elongated blobs extend beyond at least one of the first or second major surfaces of the lofty open nonwoven fiber web.

Nonwoven abrasive articles according to the present disclosure can be made by various methods, generally depending on the specific embodiment of the nonwoven abrasive article desired.

In one method, a mixture of curable binder precursor and magnetizable particles is disposed at least predominantly (also including completely) into the porous interior of the lofty open nonwoven fiber. The mixture comprises a curable binder precursor and magnetizable particles as described hereinbefore. The magnetizable particles are typically dispersed throughout the abrasive material precursor, however this is not a requirement. The curable binder precursor and magnetizable particles can be mixed by any suitable mixing technique. Selection of the particular mixing technique is within the capabilities of those having ordinary skill in the art. Likewise, any suitable technique for dispensing the mixture can be used, one useful method is by using a hollow needle extrusion die.

Once the mixture is dispensed, a magnetic field is applied to the mixture which forms the blob structure. In general, the strength of the magnetic field and whether it is constant or variable will affect the length of time that the magnetic field must be applied to create the blob structure. Likewise, the viscosity of the mixture will also be a factor. Thicker mixtures may require stronger a magnetic field and/or longer dwell times to form the blob structure but may be able to substantially retain their structure for a period of time after the magnetic field is removed and during which subsequent operations such as dispensing abrasive particles and curing can take place. On the other hand, mixtures that are very low viscosity may be difficult to work with even in the presence of a magnetic field due to shape instability. In some instances, the dispensing of the abrasive particles (and optionally also curing of the curable binder precursor) is carried out while the magnetic field is still being applied, while in other embodiments dispensing of the abrasive particles and/or curing of the curable binder precursor occurs after the magnetic field is no longer being applied.

The applied magnetic field can be supplied by any external magnet. Examples include permanent magnets and electromagnets. The magnet(s) and correspondingly its/their magnetic field may be fixed or movable (e.g., rotating or oscillating).

Preferably, the magnetic field is substantially uniform on the scale of individual blobs of the abrasive material. The magnetic field may be substantially uniform or it may be uneven or even effectively separated into discrete sections.

Examples of magnetic field configurations and apparatuses for generating them are described in U.S. Pat. Appln. Publ. No. 2008/0289262 Al (Gao) and U.S. Pat. Nos. 2,370,636 (Carlton), 2,857,879 (Johnson), 3,625,666 (James), 4,008,055 (Phaal), 5,181,939 (Neff), and British Pat. No. GB 1 477 767 (Edenville Engineering Works Limited). The selection of magnets and suitable configurations is within the capabilities of those skilled in the art. In order to achieve adequate formation of the blobs prior to curing the strength (i.e., magnetic flux density) of the applied magnetic field is preferably at least 0.05 tesla, more preferably at least 0.2 tesla in the vicinity of the porous lofty open nonwoven fiber web during the blob forming step.

Curing of the curable binder precursor may be accomplished by any suitable means, typically depending on the nature of the curable binder precursor itself and is within the capabilities of those having ordinary skill in the art. Examples include application of heat, ultraviolet light, visible light, gamma radiation, e-beam radiation, or a combination thereof.

In another method, an abrasive material precursor is disposed at least predominantly (also including completely) into the porous interior of the lofty open nonwoven fiber. The abrasive material precursor comprises a curable binder precursor, abrasive particles, and magnetizable particles as described hereinbefore. The magnetizable particles and abrasive particles (which are different than the abrasive particles) are typically dispersed throughout the abrasive material precursor, however this is not a requirement. Mixing and dispensing techniques as previously described can be used in this embodiment. Once the mixture is dispensed, a magnetic field is applied to the mixture which forms the blob structure. Again, the strength of the magnetic field and whether it is constant or variable will affect the length of time that the magnetic field must be applied to create the blob structure. Likewise, the viscosity of the mixture will also be a factor. Thicker mixtures may require stronger a magnetic field and/or longer dwell times to form the blob structure but may be able to substantially retain their structure for a period of time after the magnetic field is removed and during which curing can take place. Once the blob structure has been created by the magnetic field the abrasive material precursor is at least partially cured (e.g., as described above) to provide the abrasive material.

In another method, an abrasive material precursor comprising the curable binder precursor and magnetizable abrasive particles is disposed at least predominantly (also including completely) into the porous interior of the lofty open nonwoven fiber. The magnetizable abrasive particles are typically dispersed throughout the abrasive material precursor, however this is not a requirement. Mixing and dispensing techniques as previously described can be used in this embodiment. Once the mixture is dispensed, a magnetic field is applied to the abrasive material precursor which forms the blob structure. Once the blob structure has been created by the magnetic field the abrasive material precursor is at least partially cured (e.g., as described above) to provide the abrasive material and hence also the nonwoven abrasive article.

Nonwoven abrasive articles prepared as described above may be converted into specific articles such as, for example, discs, hand pads, unitized wheels that are useful for abrading a workpiece. SELECT EMBODIMENTS OF THE PRESENT DISCLOSURE

In a first embodiment, the present disclosure provides a nonwoven abrasive article comprising: a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; and an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises abrasive particles at least partially retained in a binder, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees, and further wherein: i) the abrasive particles are magnetizable; or ii) the elongated blobs further comprise magnetizable particles different from the abrasive particles; or iii) both i) and ii).

In a second embodiment, the present disclosure provides a nonwoven abrasive article according to the first embodiment, wherein the elongated blobs collectively occupy at least 20 volume percent of the porous interior.

In a third embodiment, the present disclosure provides a nonwoven abrasive article according to the first or second embodiment, wherein the elongated blobs collectively occupy at least 40 volume percent of the porous interior.

In a fourth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to third embodiments, wherein the abrasive particles comprise at least one of abrasive rods, shaped abrasive platelets, or crushed abrasive particles conforming to an abrasives industry specified nominal grade.

In a fifth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to third embodiments, wherein the abrasive particles comprise shaped abrasive platelets.

In a sixth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to fifth embodiments, wherein the abrasive particles comprise a material having a Mohs scale hardness of at least 8.

In a seventh embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to sixth embodiments, wherein the abrasive particles are magnetizable.

In an eighth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to sixth embodiments, wherein the elongated blobs comprise the magnetizable particles different from the abrasive particles. In a ninth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to seventh embodiments, wherein a majority of the elongated blobs extend at least between the first and second opposed major surfaces.

In a tenth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to ninth embodiments, wherein the elongated blobs have longitudinally oriented sides that are aligned within 20 degrees of being parallel to a thickness dimension of the lofty open fiber web.

In an eleventh embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to tenth embodiments, wherein a majority of the elongated blobs have an aspect ratio of at least 5:1.

In a twelfth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to eleventh embodiments, wherein the magnetizable particles comprise ferromagnetic material.

In a thirteenth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to twelfth embodiments, wherein the abrasive particles comprise alpha alumina, zirconia, silicon carbide, or a combination thereof.

In a fourteenth embodiment, the present disclosure provides a nonwoven abrasive article according to any of the first to thirteenth embodiments, wherein at least some of the elongated blobs extend beyond at least one of the first or second major surfaces.

In a fifteenth embodiment, the present disclosure provides a method of making a nonwoven abrasive article, the method comprising the steps: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor and magnetizable particles; c) disposing abrasive particles onto the abrasive material precursor while applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles and magnetizable at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

In a sixteenth embodiment, the present disclosure provides a method according to the fifteenth embodiment, wherein the magnetic field is an oscillating magnetic field. In a seventeenth embodiment, the present disclosure provides a method of making a nonwoven abrasive article, the method comprising the steps: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor, abrasive particles, and magnetizable particles; c) applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles and the magnetizable particles at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

In an eighteenth embodiment, the present disclosure provides a method according to the seventeenth embodiment, wherein the magnetic field is an oscillating magnetic field.

In a nineteenth embodiment, the present disclosure provides a method according to the seventeenth or eighteenth embodiment, wherein steps b) and c) are sequential.

In a twentieth embodiment, the present disclosure provides a method of making a nonwoven abrasive article, the method comprising: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor and magnetizable abrasive particles; c) applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees. In a twenty -first embodiment, the present disclosure provides a method according to the twentieth embodiment, wherein the magnetic field is an oscillating magnetic field.

In a twenty-second embodiment, the present disclosure provides a method according to the twentieth or twenty first embodiment, wherein steps b) and c) are sequential. Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

EXAMPLES Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. Table 1 (below) reports materials used in the Examples.

TABLE 1

EXAMPLE 1

A resin mix was created by combining 50 grams of EPX1 with 50 grams of FLK1. The resin mix was stirred by hand in a plastic container until evenly mixed. NWN 1 was threaded through a notch bar coater. The resin mix (20 grams) was poured into the notch bar coater with a gap set at 0.0 inches with respect to the top of NWN 1 being in slight contact with the notch bar. NWN 1 was passed through the notch bar coater and moved downweb at a rate of 10 feet per minute (3.0 m/min).

The resin-coated NWN 1 was then passed over the top of MAGI with a gap maintained of 0.25 inches. MAGI was rotated at 2000 RPM about its axis by a DC electric motor with a 1/4-inch (0.64 cm) diameter shaft mounted through the center of MAGI. MAGI was mounted on its side with its N-S axis underneath and oriented cross-web to resin-coated NWN1.

Upon passing over MAGI, the resin mix formed into periodic blob structures within the porous interior of NWN1, MINI was drop coated onto the top of the periodic structures at an approximate weight of 170 grains per 24 square inches (155 cm -). As the resultant material continued downweb, the periodic structures maintained the majority of their shape. The resultant article was placed into an oven and heated at 65.6 °C for 15 minutes followed by 90 minutes at 98.9 °C.

The resultant nonwoven abrasive article is shown in FIGS. 1 and 2.

EXAMPLE 2

Example 2 was created with identical steps as Example 1, except that MINI was not applied to the article.

The resultant nonwoven abrasive article is shown in FIGS. 3 and 4.

EXAMPLE 3

Sample was created identical to Example 2, except that the resin mix was created by combining 40 grams of EPX1, 40 grams of FLK, and 10 grams of MINI.

The resultant nonwoven abrasive article is shown in FIGS. 5 and 6.

EXAMPLE 4

BACK1 was coated with MAKE1 by a roll-coater to achieve an evenly distributed coat weight of approximately 375 grains per 4-inch (10.2-cm) by 6-inch area (15.2 cm). Resin-coated BACK1 was passed over the top of MAGI with a gap maintained of 0.25 inch (6.4 mm) at a web speed of 10 feet per minute. MAGI was rotated at 2000 revolutions per minute (RPM) about its axis using a direct current (DC) electric motor with a 0.25 inch (6.4 mm) diameter shaft mounted through the center of MAGI. MAGI was mounted on its side with its axis underneath and cross-web to BACK1.

Upon passing over MAGI, MAKE1 formed into regions of periodic structures within the lofty structure of BACK1.

MIN2 was drop coated onto the top of BACK1 to adhere to the regions of periodic structures at an approximate weight of 230 grains per 4-inch (10.2-cm) by 6-inch area (15.2 cm) while still in the presence of the magnetic field.

Samples (4-inch (10.2-cm) by 6-inch (15.2-cm)) of the resulting construction were cut out and placed into an oven. Oven was heated at 240 °F (116 °C) for 240 minutes. These samples were size coated with SIZE1 by passing through a roll coater to achieve a dry coat weight of approximately 10 grains per 4-inch (10.2-cm) by 6-inch area (15.2-cm). The samples were returned to the oven at 160°C for approximately 4.5 minutes.

EXAMPLE 5

An abrasive article was created using identical process and material weights as described in Example 4, except that MIN2 had been pre-coated with a magnetic responding coating of 304 stainless steel by a vapor deposition process at an estimated thickness of 0.002 mm around the entire outer surface of the particles. This enabled the abrasive mineral to become responsive to the magnetic field. This sample had the same formation of regions of periodic structures form as described in Example 4. When the abrasive mineral was adhered to the resin coated surfaces, the particles maintained a z-dimensional orientation (i.e., parallel to the thickness dimension of the fiber web).

COMPARATIVE EXAMPLE A

An abrasive article was created as described in Example 4, except that the sample did not pass over MAGI at any time. This sample did not have the formation of regions of periodic structures within the nonwoven structure.

OFF HAND ABRADING TEST

Abrasive discs (2 -inch (5.1 -cm) diameter) were converted out of the cured samples. A mechanical fastener button (3M Roloc, 3M Company) was thermally secured onto the back side of the backing for mounting on a 3M pneumatic right-angle grinder (Model 20231, 20000 rpm) with a hard 2- inch Roloc backup pad from 3M Company. The abrasive discs were tested off hand on 1018 carbon steel panel measuring 6 in * 14 in x'A in (150 mm x 360 mm x 13 mm) by attempting to remove a scratch introduced from a coated abrasive fiber disc (982C 80+ from 3M Company).

The abrasive article was introduced at an angle of approximately 5 degrees against the panel at a load of approximately 3 lbs (1.4 kg) working in a back and forth motion. The mass of the panel was measured before and after each cycle and the mass difference was calculated as cumulative mass loss (cut) at the end of 2 minutes of use. Results are reported in Table 2, below.

TABLE 2

All cited references, patents, and patent applications in this application are incorporated by reference in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in this application shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

What is claimed is:

1. A nonwoven abrasive article comprising: a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; and an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises abrasive particles at least partially retained in a binder, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees, and further wherein: i) the abrasive particles are magnetizable; or ii) the elongated blobs further comprise magnetizable particles different from the abrasive particles; or iii) both i) and ii).

2. The nonwoven abrasive article of claim 1, wherein the elongated blobs collectively occupy at least 20 volume percent of the porous interior.

3. The nonwoven abrasive article of claim 1, wherein the elongated blobs collectively occupy at least 40 volume percent of the porous interior.

4. The nonwoven abrasive article of any of claims 1 to 3, wherein the abrasive particles comprise at least one of abrasive rods, shaped abrasive platelets, or crushed abrasive particles conforming to an abrasives industry specified nominal grade.

5. The nonwoven abrasive article of any of claims 1 to 3, wherein the abrasive particles comprise shaped abrasive platelets.

6. The nonwoven abrasive article of any of claims 1 to 5, wherein the abrasive particles comprise a material having a Mohs scale hardness of at least 8.

7. The nonwoven abrasive article of any of claims 1 to 6, wherein the abrasive particles are magnetizable.

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8. The nonwoven abrasive article of any of claims 1 to 6, wherein the elongated blobs comprise the magnetizable particles different from the abrasive particles.

9. The nonwoven abrasive article of any of claims 1 to 7, wherein a majority of the elongated blobs extend at least between the first and second opposed major surfaces.

10. The nonwoven abrasive article of any of claims 1 to 9, wherein the elongated blobs have longitudinally oriented sides that are aligned within 20 degrees of being parallel to a thickness dimension of the lofty open fiber web.

11. The nonwoven abrasive article of any of claims 1 to 10, wherein a majority of the elongated blobs have an aspect ratio of at least 5:1.

12. The nonwoven abrasive article of any of claims 1 to 11, wherein the magnetizable particles comprise ferromagnetic material.

13. The nonwoven abrasive article of any of claims 1 to 12, wherein the abrasive particles comprise alpha alumina, zirconia, silicon carbide, or a combination thereof.

14. The nonwoven abrasive article of any of claims 1 to 13, wherein at least some of the elongated blobs extend beyond at least one of the first or second major surfaces.

15. A method of making a nonwoven abrasive article, the method comprising the steps: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing a mixture comprising a curable binder precursor and magnetizable particles predominantly into a portion of the porous interior; c) applying a magnetic field to the mixture; d) disposing abrasive particles onto the mixture; and e) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles and magnetizable at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

16. The method of claim 15, wherein the magnetic field is an oscillating magnetic field.

17. A method of making a nonwoven abrasive article, the method comprising the steps: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor, abrasive particles, and magnetizable particles; c) applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles and the magnetizable particles at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

18. The method of claim 17, wherein the magnetic field is an oscillating magnetic field.

19. The method of claim 17 or 18, wherein steps b) and c) are sequential.

20. A method of making a nonwoven abrasive article, the method comprising: a) providing a lofty open nonwoven fiber web comprising entangled fibers, wherein the fibers have an average diameter, and wherein the lofty open nonwoven fiber web has first and second opposed major surfaces and a porous interior therebetween; b) disposing an abrasive material precursor predominantly into a portion of the porous interior, and wherein the abrasive material precursor comprises a curable binder precursor and magnetizable abrasive particles; c) applying a magnetic field to the abrasive material precursor; and d) at least partially curing the curable binder precursor to form an abrasive material predominantly disposed within the porous interior of the lofty open fiber web, wherein the abrasive material comprises the abrasive particles at least partially retained in a binder material, wherein the abrasive material comprises elongated blobs, wherein each one of the elongated blobs is respectively bonded to at least one of the fibers, wherein the elongated blobs have a minimum width of at least two times the average diameter of the fibers, wherein a majority of the elongated blobs are longitudinally aligned within 40 degrees.

21. The method of claim 20, wherein the magnetic field is an oscillating magnetic field.

22. The method of claim 20 or 21, wherein steps b) and c) are sequential.