COATED ABRASIVE ARTICLE INCLUDING BIODEGRADABLE THERMOSET RESIN AND METHOD OF MAKING AND USING THE SAME

TECHNICAL FIELD

The present disclosure broadly relates to coated abrasive articles and methods of making and using the same.

BACKGROUND

Abrasive articles generally comprise abrasive particles (also known as "grains") retained in an abrasive layer secured to a backing.

One type of coated abrasive article includes make and size layers. To make such coated abrasive articles, a make layer precursor (or make coat) containing a first binder material precursor is applied to a backing (e.g., paper, woven/knit fabric, vulcanized fiber, or plastic film), and then the abrasive particles are partially embedded into the make layer precursor. Frequently, the abrasive particles are embedded in the make layer precursor with a degree of orientation; e.g., by electrostatic coating or by a mechanical placement technique. The make layer precursor is then at least partially cured in order to retain the abrasive particles when a size layer precursor (or size coat) containing a second binder material precursor is overlaid on the at least partially cured make layer precursor and abrasive particles. Next, the size layer precursor, and the make layer precursor if not sufficiently cured, are cured to form the coated abrasive article. In some instances, a supersize layer (e.g., containing grinding aid and/or antiloading additive), which may be formed from a corresponding supersize layer precursor, the size layer.

Another type of coated abrasive article has a slurry -coated abrasive layer, wherein abrasive particles are dispersed throughout a binder layer that is secured to the backing. In some cases, the slurry layer is molded to have a desired surface topography prior to curing. Such coated abrasives are commonly known by the term "structured abrasives".

Most binders used in coated abrasive manufacture are thermoset synthetic materials that are neither easily recycled nor biodegradable. As such, today most coated abrasive products are regarded as disposable items that are either incinerated or committed to landfill at the end of their useful working life.

SUMMARY

The present disclosure advantageously provides coated abrasive articles that include a biodegradable, non-toxic polyester binder that is water-soluble, even after cross-linking, and can be practically recycled or disposed of with reduced environmental impact.

In one aspect, the present disclosure provides a coated abrasive article comprising: a backing having first and second opposed major surfaces; and an abrasive layer disposed on and secured to at least a portion of the first major surface of the backing, wherein the abrasive layer comprises a first binder material at least partially retaining abrasive particles and comprising a first water-soluble crosslinked polyester. In some embodiments, the abrasive layer comprises: a make layer comprising the first binder material secured to the backing, wherein the abrasive particles are partially embedded in the make layer; and a size layer comprising a second binder material overlaying and secured to the make layer and the abrasive particles.

Coated abrasive articles according to the present disclosure are useful, for example, for abrading a workpiece. Accordingly, in another aspect the present disclosure provides a method of using a coated abrasive product, the method comprising; frictionally contacting the abrasive layer of a coated abrasive article according to the present disclosure with a workpiece; and moving the coated abrasive article relative to the workpiece, thereby abrading the workpiece.

In yet another aspect, the present disclosure provides a method of making a coated abrasive article, the method comprising: a) providing a backing having first and second opposed major surfaces b) disposing a curable precursor make layer on the first major surface of the backing, wherein the curable precursor make layer comprises a first curable water-soluble polyester; c) embedding abrasive particles in the curable precursor make layer; and d) at least partially curing the curable precursor make layer to provide an at least partially cured make layer.

In some embodiments, the method further comprises: e) disposing a curable precursor size layer onto the at least partially cured make layer and the abrasive particles; and f) at least partially curing the curable precursor size layer.

In another aspect, the present disclosure provides a method comprising: a) providing a backing having first and second opposed major surfaces; b) disposing a layer of curable precursor slurry on the first major surface of the backing, wherein the curable precursor slurry layer comprises abrasive particles and a first curable water-soluble polyester; and c) at least partially curing the curable precursor slurry.

In some embodiments, disposing the layer of curable precursor slurry on the first major surface of the backing comprises: disposing the curable precursor slurry into mold cavities of a production tool; contacting the production tool and curable precursor slurry with the backing; curing the curable precursor slurry to provide a slurry layer adhered to the backing; and separating from the production tool from the backing.

As used herein, the term "water-soluble" means that a material dissolves in water at 25 °C and one atmosphere of pressure at a level of at least 20 grams per liter of the resulting solution. 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 cross-sectional view of an exemplary coated abrasive article 100;

FIG. 2 is a cross-sectional view of another exemplary coated abrasive article 200.

FIG. 3 is a cross-sectional view of another exemplary coated abrasive article 300.

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

Coated abrasive articles according to the present disclosure comprise a backing and an abrasive layer disposed on and secured to the backing. The abrasive layer comprises a binder material at least partially retaining abrasive particles. Advantageously, the binder, which comprises a water-soluble crosslinked polyester, can be recycled by dissolution in hot water and/or biodegradation.

Referring to Fig. 1, exemplary coated abrasive article 100 according to the present disclosure comprises abrasive layer 130 disposed on and secured to major surface 115 of backing 110. Abrasive layer 130, includes make layer 140, abrasive particles 160 partially embedded in make layer 140, and size layer 150 which is disposed over make layer 140 and abrasive particles 160. In this embodiment, the make layer and/or the size layer comprises a water-soluble crosslinked polyester.

The water-soluble crosslinked polyester can be any water-soluble crosslinked polyester. As used herein, the term "polyester" refers to a polymer having monomer units joined through divalent ester linkages (i.e., carbonyloxy and/or oxycarbonyl groups).

The water-soluble crosslinked polyester may comprise a reaction product obtainable by condensation of a water-soluble polyol having at least two hydroxyl groups and a water-soluble polycarboxylic acid having at least two carboxyl groups. Often, the water-soluble crosslinked polyester is aliphatic. Generally, it is desirable that at least one of the polyol and the polycarboxylic acid has at least three hydroxyl or carboxyl groups. In some preferred embodiments, both of the polyol and the polycarboxylic acid have at least three hydroxyl or carboxyl groups. In many embodiments, the water- soluble crosslinked polyester consists of carbon, hydrogen and oxygen atoms.

Exemplary water-soluble polyols include ethylene glycol, 1,2-propylene glycol, 1,3- dihydroxypropane, diethylene glycol, erythritol, xylitol, lactitol, sorbitol, galactose, glucose, sorbitol, maltitol, isomalt, mannitol, raffinose, cyclodextrin, dextran, inulin, lactose, leucrose, maltose, trehalose, 1,2,3,4-butaneterol, glycerol, a-D-gluco-pyranosyl-l-6-mannitol, a-D-gluco-pyranosyl-l-6-sorbitol, and combinations thereof. Synthetically produced polyols include, for example, ethylene glycol, 1,2- propylene glycol, 1,3-dihydroxypropane, and diethylene glycol. Naturally occurring polyols include, for example, erythritol, xylitol, lactitol, sorbitol, galactose, glucose, sorbitol, maltitol, isomalt, mannitol, raffinose, cyclodextrin, dextran, inulin, lactose, leucrose, maltose, trehalose, 1,2,3,4-butaneterol, glycerol, a-D-gluco-pyranosyl-l-6-mannitol, a-D-gluco-pyranosyl-l-6-sorbitol. Of these, glycerol is especially useful.

Exemplary water-soluble polycarboxylic acids include citric acid, tartaric acid, glutaric acid, adipic acid, succinic acid, oxalic acid, fumaric acid, citric acid, maleic acid, malonic acid, and combinations thereof. Of these, citric acid is often preferred. Synthetically produced water-soluble polycarboxylic acids include, for example, fumaric acid and maleic acid. Naturally occurring water- soluble polycarboxylic acids include citric acid, tartaric acid, glutaric acid, adipic acid, succinic acid, oxalic acid, citric acid, and malonic acid.

In addition, to carboxyl group functionality, carboxylic acid equivalent functionality may also be used. Examples include acid halides, anhydrides, and simple esters (e.g., methyl esters and ethyl esters, and combinations thereof). However, the acid forms are generally preferred due to their good solubility in water.

To facilitate condensation a strong acid may be added to the water-soluble polycarboxylic acids and water-soluble polyols. Exemplary strong acids include mineral acids such as hydrochloric acid and sulfuric acid and organic acids such as methanesulfonic acid. Generally, strong acids, if present, are included in a low catalytically effective amount (e.g., up to about 3 percent by weight).

Generally, condensation of the polycarboxylic acid and polyol can be accomplished by heating; for example, in an oven. The relative stoichiometry of the polycarboxylic acid and polyol may be have any value capable of resulting in crosslinking. In some embodiments, the relative stoichiometry is from about 1.2:1 to 1:1.2 (equivalents of polycarboxylic acid or chemical equivalent thereof: equivalents of polyol).

In many preferred embodiments, the water-soluble crosslinked polyester comprises a condensation polymer of components comprising a naturally occurring polyol and a naturally occurring polycarboxylic acid. In many preferred embodiments, the water-soluble crosslinked polyester comprises a condensation polymer of components comprising a naturally occurring polyol and a naturally occurring polycarboxylic acid. In many preferred embodiments, the water-soluble crosslinked polyester comprises a condensation polymer of components comprising a biodegradable polyol and a biodegradable polycarboxylic acid. Typically, the water-soluble crosslinked polyester can be synthesized by heating to condense the polyol and polyacids together. Polyol and/or polycarboxylic acid crosslinkers, as well as hydrolytically reversibly bound ions may also facilitate crosslinking of the water-soluble crosslinked polyester. Example may include alkaline earth ions (e.g., Mg^ , Ca ), zinc (2+) ions, and boron (3+) ions. Useful backings typically have first and second opposed major surfaces, although only one major surface is need ed to practice the present disclosure. Suitable backings include those known in the art for making coated abrasive articles. The thickness of the backing generally ranges from 0.02 to 5 millimeters, desirably from 0.05 to 2.5 millimeters, and more desirably from 0.1 to 0.4 millimeter, although thicknesses outside of these ranges may also be useful.

The backing may be flexible or rigid, and may be made of any number of various materials including those conventionally used as backings in the manufacture of coated abrasives. Examples include paper, fabric, film, polymeric foam, vulcanized fiber, woven and nonwoven materials, combinations of two or more of these materials. The backing may also be a laminate of two materials (for example, paper/film, cloth/paper, film/cloth).

Exemplary flexible backings include polymeric film (including primed films) such as polyolefin film (for example, polypropylene including biaxially oriented polypropylene, polyester film, polyamide film, cellulose ester film), metal foil, mesh, scrim, foam (for example, natural sponge material or polyurethane foam), fabric, paper, vulcanized paper, nonwoven materials, and combinations thereof.

Cloth backings may be woven or stitch bonded.

Fabric backings can be made from any known fibers, whether natural, synthetic or a blend of natural and synthetic fibers. Examples of useful fiber materials include fibers or yams comprising polyester (e.g., polyethylene terephthalate), polyamide (e.g., hexamethylene adipamide, polycaprolactam), polypropylene, acrylic, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymers, vinyl chloride-acrylonitrile copolymers, graphite, polyimide, silk, cotton, linen, jute, hemp, or rayon. Useful fibers may be of virgin materials or of recycled or waste materials reclaimed from garment cuttings, carpet manufacturing, fiber manufacturing, or textile processing, for example. Useful fibers may be homogenous or a composite such as a bicomponent fiber (for example, 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.

The backing may be a fibrous reinforced thermoplastic such as described, for example, as described, for example, in U. S. Pat. No. 5,417,726 (Stout et al.), or an endless spliceless belt, for example, as described, for example, in U. S. Pat. No. 5,573,619 (Benedict et ah). Likewise, the backing may be a polymeric substrate having hooking stems projecting therefrom such as that described, for example, in U. S. Pat. No. 5,505,747 (Chesley et ah). Similarly, the backing may be a loop fabric such as that described, for example, in U. S. Pat. No. 5,565,011 (Follett et ah).

Exemplary rigid backings include vulcanized fiber discs, metal plates, and ceramic plates.

Another example of a suitable rigid backing is described, for example, in U. S. Pat. No. 5,417,726 (Stout et ah).

The backing may have any suitable basis weight; typically, in a range of from 100 to 1250 grams per square meter (gsm), more typically 450 to 600 gsm, and even more typically 450 to 575 gsm. In many embodiments (e.g., abrasive belts and sheets), the backing typically has good flexibility; however, this is not a requirement (e.g., vulcanized fiber discs). To promote adhesion of binder resins to the backing, one or more surfaces of the backing may be modified by known methods including corona discharge, ultraviolet light exposure, electron beam exposure, flame discharge, and/or scuffing.

Optionally, backings used in coated abrasive articles may further include one or more applied backing treatments. Examples of typical backing treatments are a backsize layer (that is, a coating on the major surface of the backing opposite the abrasive layer), a presize layer or a tie layer (that is, a coating on the backing disposed between the abrasive layer and the backing), and/or a saturant that saturates the backing. A subsize is similar to a saturant, except that it is applied to a previously treated backing. Additional details regarding backing treatments can be found in, for example, U. S. Pat. Nos. 5,108,463 (Buchanan et ak); 5,137,542 (Buchanan et al.); 5,328,716 (Buchanan); and 5,560,753 (Buchanan et ak).

The make layer, size layer, and optional supersize layer are formed by at least partially curing corresponding precursors (i.e., a make layer precursor, a size layer precursor, a supersize layer precursor).

Typically, the make layer is prepared by coating at least a portion of the backing (treated or untreated) with a make layer precursor. Abrasive particles are then at least partially embedded (for example, by electrostatic coating) in the make layer precursor which is then at least partially cured.

Often, the make layer precursor is partially cured prior to coating with abrasive particles and further cured at a later point in the manufacturing process.

Next, the size layer is prepared by coating at least a portion of the at least partially cured make layer precursor and abrasive particles with a size layer precursor (which may be the same as, or different from, the first binder precursor), and at least partially curing the size layer precursor.

The make and size layers may comprise any binder resin that is suitable for use in abrading applications as long as at least one, and preferably both, comprise a water-soluble crosslinked polyester. Suitable make and/or size layer precursor resins, other than water-soluble crosslinkable polyesters, are well known in the abrasive art and include, for example, free-radically polymerizable monomers and/or oligomers, epoxy resins, phenolic resins, melamine-formaldehyde resins, aminoplast resins, cyanate resins, or combinations thereof.

The make layer precursor and/or size layer precursor may be modified by various additives (e.g., fibers, lubricants, wetting agents, surfactants, pigments, dyes, antistatic agents (e.g., carbon black, vanadium oxide, and/or graphite.), coupling agents (e.g., silanes, titanates, zircoaluminates, etc.), plasticizers, suspending agents).

Optionally , a supersize layer precursor may be applied onto at least a portion of the abrasive layer. Upon drying and/or curing a supersize layer is formed. Additional details concerning size layer precursors may be found in U.S. Pat. No. 4,588,419 (Caul et al.), U.S. Pat. No. 4,751,138 (Tumey et ak), and U.S. Pat. No. 5,436,063 (Follett et al.). The size layer precursor may also be modified by various additives such as, for example, fibers, lubricants, wetting agents, surfactants, pigments, dyes, antistatic agents (e.g., carbon black, vanadium oxide, and/or graphite), coupling agents (e.g., silanes, titanates, zircoaluminates, etc.), plasticizers, and/or suspending agents. Examples of useful supersize layer precursor compositions include those comprising at least one of a metal salt of a fatty acid, urea-formaldehyde resin, novolac phenolic resin, epoxy resin, wax, mineral oil, and combinations thereof. If present, a supersize layer typically has a basis weight of 5 to 1100 grams per square meter (gsm), preferably 50 to 700 gsm, and more preferably 250 to 600 gsm, although this is not a requirement.

The basis weight of the make layer, size layer, and optional supersize layer typically depend at least in part on the abrasive particle size grade and the particular type of abrasive article.

The make layer, size layer, and optional supersize layer and their precursors may also contain additives such as fibers, lubricants, wetting agents, surfactants, pigments, dyes, antistatic agents (e.g., carbon black, vanadium oxide, and/or graphite), coupling agents (e.g., silanes, titanates, and/or zircoaluminates), plasticizers, suspending agents, and the like. The amounts of these optional additives are selected to provide the preferred properties. The coupling agents can improve adhesion to the abrasive particles and/or filler. The curable composition may be thermally -cured, radiation-cured, or a combination thereof.

The make layer, size layer, and optional supersize layer and their precursors may also contain filler materials, diluent abrasive particles (e.g., as described hereinbelow), or grinding aids, typically in the form of a particulate material. Typically, the particulate materials are inorganic materials. Examples of useful fillers for this disclosure include: metal carbonates (e.g., calcium carbonate (e.g., chalk, calcite, marl, travertine, marble and limestone), calcium magnesium carbonate, sodium carbonate, magnesium carbonate), silica (e.g., quartz, glass beads, glass bubbles and glass fibers) silicates (e.g., talc, clays, (montmorillonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate) metal sulfates (e.g., calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate), gypsum, vermiculite, wood flour, aluminum trihydrate, carbon black, metal oxides (e.g., calcium oxide (lime), aluminum oxide, titanium dioxide), and metal sulfites (e.g., calcium sulfite).

Heat energy is commonly applied to advance curing of the thermosetting/curable resins used in the make layer precursor/size layer precursors and optional supersize layer precursor; however, other sources of energy (e.g., microwave radiation, infrared light, ultraviolet light, visible light, may also be used). The selection will generally be dictated by the particular resin system selected.

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. Preferably, the abrasive particles have a Mohs hardness of at least 4, 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, inU.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 inU.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. An exemplary such precisely-shaped abrasive particle 200 is shown in FIG. 2.

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 ak); 5,011,508 (Wald et ak); 1,910,444 (Nicholson); 3,041,156 (Rowse et ak); 5,009,675 (Kunz et ak); 5,085,671 (Martin et ak); 4,997,461 (Markhoff- Matheny et ak); and 5,042,991 (Kunz et ak). 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 could be used such as -90+100.

A grinding aid is a material that has a significant effect on the chemical and physical processes of abrading, which results in improved performance. Grinding aids encompass a wide variety of different materials and can be inorganic or organic based. Examples of chemical groups of grinding aids include waxes, organic halide compounds, halide salts and metals and their alloys. The organic halide compounds will typically break down during abrading and release a halogen acid or a gaseous halide compound. Examples of such materials include chlorinated waxes like tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride. Examples of halide salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluorides, potassium chloride, and magnesium chloride. Examples of metals include, tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium.

Other miscellaneous grinding aids include sulfur, organic sulfur compounds, graphite, and metallic sulfides. A combination of different grinding aids may be used, and in some instances, this may produce a synergistic effect.

Grinding aids can be particularly useful in coated abrasives. In coated abrasive articles, grinding aid is typically used in a supersize layer, which is applied over the surface of the size layer. Sometimes, however, the grinding aid is added to the size layer. Typically, the amount of grinding aid incorporated into coated abrasive articles are about 50-800 grams per square meter (g/m¾ preferably about 80-475 g/m^, however, this is not a requirement.

Fig. 2 shows another embodiment of a coated abrasive article in which the abrasive layer comprises a slurry layer instead of make and size layers. Referring now to Fig. 2, exemplary coated abrasive article 200 has backing 210 and abrasive layer 230 secured to backing 210. Abrasive layer 230 includes abrasive particles 260 dispersed in binder 240.

In making such a coated abrasive article (a slurry coated abrasive article), a slurry comprising a binder precursor and abrasive particles is typically applied to a major surface of the backing, and the binder precursor is then at least partially cured (e.g., using heat and/or electromagnetic radiation). The binder precursor comprises a water-soluble crosslinked polyester as described hereinabove. Useful backings particles include those described hereinabove. Useful abrasive particles include those described hereinabove, often in fine grades.

In yet another exemplary embodiment, a coated abrasive article according to the present invention may comprise a structured abrasive article. Referring now to Fig. 3, exemplary structured abrasive article 300 has backing 310 and abrasive layer secured to major surface 315 of backing 310. Abrasive layer 330 includes a plurality of shaped abrasive composites 355. The abrasive composites comprise abrasive particles 360 dispersed in binder 350. Useful binders and abrasive particles include those mentioned hereinabove. Structured abrasive articles are made similarly to slurry coated abrasive articles, except that the slurry is coated onto a releasable production tool, contacted with the backing, at least partially cured, and removed from the production tool. The production tool is often a belt or web having a structured surface of shaped features (e.g., an array of pyramidal cavities) that are the inverse shaped of the shaped abrasive composites. The shaped abrasive composites may have a variety of shapes including, for example, those shapes selected from the group consisting of cubic, block-like, cylindrical, prismatic, pyramidal, truncated pyramidal, conical, truncated conical, cross-shaped, and hemispherical.

Further details regarding coated abrasive articles of the types described hereinabove and methods of their manufacture can be found, for example, in U.S. Pat. Nos. 4,734,104 (Broberg); 4,737,163 (Larkey); 5,014,468 (Ravipati et al.); 5,152,917 (Pieper et al); 5,203,884 (Buchanan et al); 5,304,223 (Pieper et ak); 5,378,251 (Culler et al.); 5,436,063 (Follett et al.); 5,496,386 (Broberg et al.); 5,609,706 (Benedict et ak); 5,681,217 (Hoopman et al.); 5,520,711 (Helmin); 5,855,632 (Stoetzel et ak); 5,961,674 (Gagliardi et ak); 5,975,988 (Christianson); 8,142,531 (Adefris et ah); 8,142,891 (Culler et ah); 8,142,532 (Erickson et al.); and 9,771,504 (Adefris).

Coated abrasive articles according to the present invention may be converted, for example, into belts, rolls, discs (including perforated discs), and/or sheets. For belt applications, two free ends of the abrasive sheet may be joined together using known methods to form a spliced belt.

Coated abrasive articles according to the present disclosure are useful, for example, for abrading a workpiece. Such a method may comprise frictionally contacting an abrasive article according to the present disclosure with a surface of the workpiece, and moving at least one of the coated abrasive article and the surface of the workpiece relative to the other to abrade at least a portion of the surface of the workpiece. Methods for abrading with coated abrasive articles according to the present disclosure include, for example, snagging (i.e., high-pressure high stock removal) to polishing (e.g., polishing medical implants with coated abrasive belts), wherein the latter is typically done with finer grades (e.g., ANSI 220 and finer) of abrasive particles. The size of the abrasive particles used for a particular abrading application will be apparent to those skilled in the art.

Abrading may be carried out dry or wet. For wet abrading, the liquid may be introduced supplied in the form of a light mist to complete flood. Examples of commonly used liquids include water, water- soluble oil, organic lubricant, and emulsions. The liquid may serve to reduce the heat associated with abrading and/or act as a lubricant. The liquid may contain minor amounts of additives such as bactericide, antifoaming agents, and the like.

Examples of workpieces include aluminum metal, carbon steels, mild steels (e.g., 1018 mild steel and 1045 mild steel), tool steels, stainless steel, hardened steel, titanium, glass, ceramics, wood, wood- like materials (e.g., plywood and particle board), paint, painted surfaces, and organic coated surfaces.

The applied force during abrading typically ranges from about 1 to about 100 kilograms (kg), although other pressures can also be used.

SELECT EMBODIMENTS OF THE PRESENT DISCLOSURE

In a first embodiment, the present disclosure provides a coated abrasive article comprising: a backing having first and second opposed major surfaces; and an abrasive layer disposed on and secured to at least a portion of the first major surface of the backing, wherein the abrasive layer comprises a first binder material at least partially retaining abrasive particles and comprising a first water-soluble crosslinked polyester.

In a second embodiment, the present disclosure provides a coated abrasive article according to the first embodiment, wherein the abrasive layer comprises: a make layer comprising the first binder material secured to the backing, wherein the abrasive particles are partially embedded in the make layer; and a size layer comprising a second binder material overlaying and secured to the make layer and the abrasive particles.

In a third embodiment, the present disclosure provides a coated abrasive article according to the first embodiment, wherein the abrasive layer wherein the abrasive particles are dispersed throughout the first binder material.

In a fourth embodiment, the present disclosure provides a coated abrasive article according to any of the first to third embodiments, wherein the second binder material comprises a second water-soluble crosslinked polyester.

In a fifth embodiment, the present disclosure provides a coated abrasive article according to any of the first to fourth embodiments, wherein the first water-soluble crosslinked polyester comprises a first condensation polymer of components comprising a naturally occurring polyol and a naturally occurring polycarboxylic acid.

In a sixth embodiment, the present disclosure provides a coated abrasive article according to any of the first to fifth embodiments, wherein the first water-soluble crosslinked polyester comprises a condensation polymer of components comprising a biodegradable polyol and a biodegradable polycarboxylic acid.

In a seventh embodiment, the present disclosure provides a coated abrasive article according to the seventh embodiment, wherein the biodegradable polyol comprises at least three hydroxyl groups. In an eighth embodiment, the present disclosure provides a coated abrasive article according to the six or seventh embodiment, wherein the biodegradable poly carboxylic acid comprises at least three carboxyl groups.

In a ninth embodiment, the present disclosure provides a coated abrasive article according to any of the sixth to eighth embodiments, wherein the biodegradable polyol comprises glycerol and the biodegradable poly carboxylic acid comprises citric acid.

In a tenth embodiment, the present disclosure provides a coated abrasive article according to any of the first to ninth embodiments, wherein the backing comprises at least one of paper or a polymer film.

In an eleventh embodiment, the present disclosure provides a coated abrasive article according to any of the first to tenth embodiments, wherein the coated abrasive article comprises a coated abrasive disc or a coated abrasive endless belt.

In a twelfth embodiment, the present disclosure provides a method of using a coated abrasive product, the method comprising; frictionally contacting the abrasive layer of the coated abrasive article of any of the first to twelfth embodiments with a workpiece; and moving the coated abrasive article relative to the workpiece, thereby abrading the workpiece.

In a thirteenth embodiment, the present disclosure provides a method of making a coated abrasive article, the method comprising: a) providing a backing having first and second opposed major surfaces b) disposing a curable precursor make layer on the first major surface of the backing, wherein the curable precursor make layer comprises a first curable water-soluble polyester; c) embedding abrasive particles in the curable precursor make layer; and d) at least partially curing the curable precursor make layer to provide an at least partially cured make layer.

In a fourteenth embodiment, the present disclosure provides a method according to the thirteenth embodiment, further comprising e) disposing a curable precursor size layer onto the at least partially cured make layer and the abrasive particles; and f) at least partially curing the curable precursor size layer.

In a fifteenth embodiment, the present disclosure provides a method according to the fourteenth embodiment, wherein the curable precursor size layer comprises a second binder material comprising a second curable water-soluble polyester.

In a sixteenth embodiment, the present disclosure provides a method of making a coated abrasive article, the method comprising: a) providing a backing having first and second opposed major surfaces b) disposing a layer of curable precursor slurry on the first major surface of the backing, wherein the curable precursor slurry layer comprises abrasive particles and a first curable water-soluble polyester; and c) at least partially curing the curable precursor slurry.

In a seventeenth embodiment, the present disclosure provides a method according to the sixteenth embodiment, wherein the first curable water-soluble polyester comprises a condensation polymer of components comprising a naturally occurring polyol and a naturally occurring polycarboxylic acid.

In an eighteenth embodiment, the present disclosure provides a method according to any of the thirteenth to sixteenth embodiments, wherein the first curable water-soluble polyester comprises a condensation polymer of components comprising a biodegradable polyol and a biodegradable polycarboxylic acid.

In a nineteenth embodiment, the present disclosure provides a method according to the eighteenth embodiment, wherein the biodegradable polyol comprises at least three hydroxyl groups.

In a twentieth embodiment, the present disclosure provides a method according to the eighteenth or nineteenth embodiment, wherein the biodegradable polycarboxylic acid comprises at least three carboxyl groups.

In a twenty -first embodiment, the present disclosure provides a method according to any of the nineteenth to twentieth embodiments, wherein the biodegradable polyol comprises glycerol and the biodegradable polycarboxylic acid comprises citric acid.

In a twenty-second embodiment, the present disclosure provides a method according to any of the eighteenth to twenty -first embodiments, wherein the backing comprises at least one of paper or polymer film

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. Chemicals used in the examples below were obtained from, or are available from general chemical suppliers, such as, for example, Sigma-Aldrich, Saint Louis, Missouri unless otherwise specified.

GLYCA PREPARATION

A cross-linkable water-soluble biodegradable polyester resin (GLYCA) was prepared as follows. Citric acid monohydrate, 56.33 parts, of citric acid monohydrate was added to 42.55 parts of glycerol in a flask on a hot plate and the mixture was heated to 100°C whilst gently and continuously stirring with a magnetic stirrer. This created a pale, straw-colored viscous liquid. Hydrochloric acid (1.12 parts of 35% concentrated HC1) was added with stirring at 100°C for a further 10 minutes. Some small bubbles emerged upon acid addition which soon disappeared during stirring. The liquid was allowed to cool to room temperature for subsequent use in preparing coated abrasives.

COMPARATIVE EXAMPLE A

3M WetorDry sandpaper, 180 grit alumina, phenolic binder, phenolic size coat, C-weight backing from 3M Company, Maplewood, Minnesota.

EXAMPLE 1

A make layer precursor composition was prepared by combining 82.17 parts of GLYCA, 0.36 parts of BYK-348 silicone surfactant wetting agent (BYK-Chemie GmbH, Wesel, Germany), and 17.47 parts of water.

A size layer precursor composition was prepared by combining 87.23 parts of GLYCA, 0.91 parts of BYK-348 silicone surfactant wetting agent, and 11.86 parts of water.

The make layer precursor composition was coated onto C-weight waterproof paper backing at a nominal wet thickness of 40 microns using a wire-wound rod. Abrasive mineral (Treibacher ALODUR BFRPL fused alumina, P180 grit size, Treibacher Chemische Werke AG, Villach, Austria), was electrostatically coated onto the wet make layer precursor-coated backing at a nominal wet coat weight of 65 grams per square meter. The resultant mineral-coated backing was heated at 120 °C for 50 minutes to crosslink the make layer precursor.

The size layer precursor was coated over the crosslinked make layer precursor and abrasive particles using a hand-held rubber roller while applying pressure. The wet coat weight was about 60 grams per square meter. The size layer precursor-coated abrasive article was given a final cure at 120 °C for 50 minutes.

Rocking Drum Testing

Coated abrasive articles were converted into 10 inch by 2.5 inch (25. 4 cm by 6. 4 cm) sheets. These samples were installed on a cylindrical steel dram of a testing machine, which oscillated (rocked), back and forth in a small arc. A 1018 carbon steel workpiece, 10 mm x 10 mm abraded face, was fixed in a lever arm arrangement above the abrasive sample, and total load of 2 lb ( 6 kg) was applied to the workpiece. As the abrasive article rocked back and forth, the workpiece was abraded, and a 3/16 inch by 5.5 inch (1cm by 14 cm) wear path was created on the abrasive article. There were approximately 60 strokes per minute on this wear path. A compressed air stream (20 psi) was directed onto the sample to clear grinding swarf and debris from the wear path. The amount of steel removed after 50 cycles (one cycle being one back-and-forth motion) was recorded as the interval cut, and the total cut was the cumulative amount of steel removed at the endpoint of the test. In wet test mode, 5 drops of water were applied to the workpiece by pipette where abraded. TABLE 1

COMPARATIVE EXAMPLE B

A Trizact 3M 443 SA 3000 foam abrasive disc containing green SiC, mineral size JIS 2500, from 3M Company, Maplewood, Minnesota.

EXAMPLE 2

An abrasive slurry composition was prepared by combining 24.01 parts GLYCA, 0.23 parts of BYK-348 silicone surfactant wetting agent (BYK-Chemie GmbH, Wesel, Germany), 57.58 parts of abrasive mineral (GC 2500 SiC, JIS 2500 grade, Fujimi Incorporated, Aichi, Japan) and 18.18 parts of water.

A draw down slurry coating was produced using a wire-wound rod to give a nominal wet coating thickness of 60 microns equating approximately to the total dry coating thickness of 3M 443 SA 3000. The slurry was coated onto the same foam backing material as in Comparative Example B and the coated backing was subjected to a cure regimen of 120 °C for 120 minutes so as to crosslink the adhesive and leave a dry, non-tacky surface to the coating. Once at room temperature discs of 150mm diameter were cut from the coated foam material.

COMPARATIVE EXAMPLE C

A 3M Trizact 443 S A foam backed abrasive disc, green SiC mineral, size JIS 6000, from 3M Company.

EXAMPLE 3

An abrasive slurry composition was prepared by combining 31.97 parts GLYCA, 0.32 parts of BYK-348 silicone surfactant wetting agent (BYK-Chemie GmbH, Wesel, Germany), 0.51 parts of Cabosil (Cabot Corporation, Illinois, USA), 52.31 parts of abrasive mineral (GC 6000 SiC, green silicon carbide, grade JIS 6000, Fujimi Incorporated, Aichi, Japan) and 14.89 parts of water.

A draw down slurry coating was produced with a wire-wound rod to give a nominal wet coating thickness of 60 microns equating approximately to the total dry coating thickness of Comparative Example C. The slurry was coated onto the same foam backing material as in Comparative Example C, and the coated backing was subjected to a cure regimen of 120 °C for 120 minutes so as to crosslink the adhesive and leave a dry, non-tacky surface to the coating. Once at room temperature discs of 150 mm diameter were cut from the coated foam material.

Clear Coat Abrading Test

The performance of coated abrasive articles prepared in Example 2 was measured by wet dual action (DA) disc sanding as is normal practice in refining the surface finish during automotive paint defect repair after the previous step of defect removal and prior to final polishing.

This test was undertaken using flat steel panels of dimensions 50 cm x 50 cm. Each panel was over-sprayed using black color and NEXA AUTOCOLOR 6690 CLEAR COAT (Nexa Autocolor, PPG, Pittsburgh, Ohio). Before testing was performed the clear coat was aged at least 2 weeks since application.

The process of refining defects in the clear coat surface, also known as lacquer, entailed:

1. Removal of dust nibs and other post-spray defects using a coated abrasive disc of sufficient abrading capability so as to completely remove defects. This is commonly referred to as ‘denibbing’ and can be achieved by dry sanding an area much larger than the defective area so as to permit subsequent finish blending with the surrounding panels.

2. Scratch refinement is necessary since the surface finish after defect removal is visibly dull and markedly different from the unblemished surrounding panels of the vehicle. Surface finish refinement can be achieved using wet dual action sanding with, for example a 3M 443 SA 3000 disc up to such point that the surface is ready for polishing.

3. Optionally, further scratch refinement can be performed by wet sanding to further refine the surface finish of the clear coat to result in a shorter time required for the final polishing step.

4. Performed via rotary motion rather than DA motion, polishing entails the use of progressively finer grit polishing liquid and foam pad combinations such that the surface finish from preceding steps is refined to the extent that it matches the appearance of the surrounding unblemished panels to complete the repair.

Step 1: A 150 mm-diameter Trizact 3M 260L finishing film abrasive disc containing alpha aluminum oxide, mineral size P1500, was used to sand the 50 cm x 50 cm panel area using a dual action, random orbital (rotary and vibratory) sander using a 5 mm orbit. The sander was of type 28508 from 3M Company. The disc was first attached to a 10 mm thickness foam interface pad prior to attaching the interface pad to the sander. The 50 cm x 50 cm area panel was sanded in a dry sanding mode for a total of 60 seconds using a vacuum extraction method to extract dust from the sanded area during the sanding process. Overlapping sanding lanes were used to ensure that the whole of the panel was sanded and no defects remained. Once completed, any remnant dust was removed using a microfiber cloth prior to commencing Step 2.

Step 2: Scratch refinement was performed using a 150 mm diameter disc attached to a 5 mm thickness interface pad on a dual action random orbital sander. This test was performed on separate panels each using Comparative Example 2 or a disc from Example 2 to enable performance comparison. Each 50 cm x 50 cm panel was sanded in a wet sanding mode for 60 seconds by applying 3 squirts of water to the panel and 2 squirts of water to the disc, prior to sanding. Overlapping sanding lanes were used in a direction orthogonal to those used in Step 1 to ensure that the whole of each panel was sanded and the scratches from the previous step refined using the scratch refinement sanding disc.

Almost immediately upon contact with water the abrasive coating of the Example 2 disc started to dissolve leaving a greenish slurry on the painted panel. When sanding, the greenish slurry traced a path following the sander as is often seen when using a liquid polishing compound.

Testing results are reported in Table 2, below.

TABLE 2

Step 3: Further scratch refinement was performed using a 150 mm-diameter disc attached to a 5mm thickness interface pad on a dual action random orbital sander. This test was performed on the same panel using half of the panel for each sanding disc tested such that one half of the panel was sanded using a 3M TRIZACT 443 S A JIS 8000 grade disc and the other half of the panel was sanded using the disc from Example 3 to enable finish performance comparison. Prior to testing the panel had undergone Steps 1 and 2, above. Each half of the 50 cm x 50 cm panel was sanded in a wet sanding mode for 60 seconds by applying 3 squirts of water to the panel and 2 squirts of water to the disc, prior to sanding. Overlapping sanding lanes were used in a direction orthogonal to those used in Step 2 to ensure that the whole of the panel was sanded using the scratch refinement sanding disc.

Further scratch refinement sanding observations: As was also observed for Example 2, the sanding swarf from Example 3 using GC6000 SiC abrasive had a green hue indicating the coating on the disc was dissolving and the green colored GC6000 SiC mineral was dropping out and forming a liquid paste like substance.

Test results are reported in Table 3, below.

TABLE 3 EXAMPLE 4

An abrasive slurry composition was prepared by combining 26.46 parts GLYCA, 0.26 parts of BYK-348 silicone surfactant wetting agent (BYK-Chemie GmbH, Wesel, Germany), 64.50 parts of abrasive mineral (WA 2500 AI2O3, Fujimi Incorporated, Aichi, Japan) and 8.78 parts of water.

A draw down slurry coating was produced with a wire-wound rod to give a nominal wet coating thickness of 60 microns equating approximately to the total dry coating thickness of Comparative Example D. The slurry was coated onto the same foam backing material as in Comparative Example B and the coated backing was subjected to a cure regimen of 120 °C for 120 minutes so as to crosslink the adhesive and leave a dry, non-tacky surface to the coating. Once at room temperature discs of 150mm diameter were cut from the coated foam material.

Unlike Example 2 where almost immediately upon contact with water the abrasive coating started to dissolve leaving a greenish slurry on the painted panel, it was found that the abrasive disc of Example 4 did not dissolve but instead the coating was observed to swell and wrinkle. When sanding, there was no greenish slurry.

Test results are reported in Table 4, below.

TABLE 4

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.