EP2790878A1

EP2790878A1 - Aqueous resin composition for abrasive articles and resulting articles

Info

Publication number: EP2790878A1
Application number: EP12857822.6A
Authority: EP
Inventors: Clément HOUGA; Boris Jaffrennou; Alix Arnaud
Original assignee: Saint Gobain Abrasifs SA; Saint Gobain Abrasives Inc
Current assignee: Saint Gobain Abrasifs SA; Saint Gobain Abrasives Inc
Priority date: 2011-12-13
Filing date: 2012-12-13
Publication date: 2014-10-22
Also published as: EP2790878A4; FR2983759B1; WO2013090617A1; US20150027064A1; FR2983759A1

Abstract

An aqueous polymer binder composition adapted for the manufacture of abrasive articles, such as coated abrasive articles, comprising at least one saccharide, at least one polycarboxylic organic acid, and at least one crosslinking catalyst. The aqueous composition is formaldehyde-free and can further comprise rheology modifiers, fillers, and hydrophobizing agents.

Description

AQUEOUS RESIN COMPOSITION FOR ABRASIVE ARTICLES AND RESULTING

ARTICLES

FIELD OF THE DISCLOSURE The present invention relates to an aqueous resin binder composition, abrasive articles including the same, and methods of making and using the aqueous resin binder composition and abrasive articles.

BACKGROUND Abrasive articles, such as coated abrasive articles, are used in various industries to abrade work pieces by hand or by machine processes, such as by lapping, grinding, or polishing.

Machining utilizing abrasive articles spans a wide industrial and consumer scope from optics industries, automotive paint repair industries, and metal fabrication industries to construction and carpentry. Machining, such as by hand or with use of commonly available tools such as orbital polishers (both random and fixed axis), and belt and vibratory sanders, is also commonly done by consumers in household applications. In each of these examples, abrasives are used to remove surface material and affect the surface characteristics (e.g., planarity, surface roughness, gloss) of the abraded surface. Additionally, various types of automated processing systems have been developed to abrasively process articles of various compositions and configurations. Surface characteristics include, among others, shine, texture, gloss, surface roughness, and uniformity. In particular, surface characteristics, such as roughness and gloss, are measured to determine quality. Typically, defects in a surface are removed by first sanding with a coarse grain abrasive, followed by subsequently sanding with progressively finer grain abrasives, and even buffing with wool or foam pads until a desired smoothness is achieved. Hence, the properties of the abrasive article used will generally influence the surface quality.

In addition to surface characteristics, users are sensitive to cost related to abrasive operations. Factors influencing operational costs include the speed at which a surface can be prepared and the cost of the materials used to prepare that surface. Typically, a user seeks cost effective materials having high material removal rates. However, abrasives that exhibit high removal rates often exhibit poor performance in achieving desirable surface characteristics. Conversely, abrasives that produce desirable surface characteristics often have low material removal rates. For this reason, preparation of a surface is often a multi-step process using various grades of abrasive. Typically, surface flaws (e.g., scratches) introduced by one step are repaired (e.g., removed) using progressively finer grain abrasives in one or more subsequent steps. Therefore, abrasives that introduce scratches and surface flaws result in increased time, effort, and expenditure of materials in subsequent processing steps and an overall increase in total processing costs.

In an effort to achieve certain abrasive performance characteristics (e.g., cut rate, surface finish, abrasive grain retention, mechanical stress resistance, thermal resistance, and solvent resistance) under demanding conditions (e.g., high-speed abrading and grinding), conventional abrasive articles typically incorporate components, such as polymer binder systems, abrasive grains, and backing materials that contain environmentally harmful chemicals or are themselves environmentally unfriendly due to a lack of biodegradability, recyclability, or re-usability.

For instance, phenol-formaldehyde resins (i.e., novolac and resole resins) and urea- formaldehyde resins are commonly encountered as abrasive binder compositions in conventional abrasive articles. At least one drawback of these phenol-formaldehyde and urea-formaldehyde resins is that they contain formaldehyde, which can be harmful to people and the environment.

Although various efforts have been made to replace various components of abrasive articles, there continues to be a demand for improved, cost effective, abrasive articles, processes, and systems that can promote and achieve efficient abrasion and improved surface

characteristics, but that are at the same time environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.

FIG. 1 is an illustration of a cross-section of a coated abrasive embodiment according to the present invention.

FIG. 2 is an illustration of a cross-section of another coated abrasive embodiment according to the present invention. FIG. 3 is an illustration of a flowchart of a method of making a coated abrasive according to the present invention.

FIG. 4 is an illustration of a flowchart of another method making a coated abrasive according to the present invention. The use of the same reference symbols in different drawings indicates similar or identical items.

DETAILED DESCRIPTION

The present inventors have surprisingly discovered abrasive article embodiments that achieve or exceed the performance characteristics of certain conventional abrasive articles, but that do not rely on phenol-formaldehyde or urea-formaldehyde binder compositions.

Embodiments described in greater detail below comprise an aqueous resin composition adapted to be used as a binder of abrasive particles and are formaldehyde-free.

Illustrated in FIG. 1 is an embodiment of a coated abrasive article 100, commonly called a "coated abrasive." The coated abrasive 100 includes a backing 101 and an abrasive layer 103 disposed on the backing 101. The abrasive layer 103 comprises a plurality of abrasive particles 105 that are retained by a polymer binder composition 107. The polymer binder composition 107 is commonly called a "make coat" where the abrasive particles 105 are disposed on the surface 109 of the polymer binder composition and are partially embedded in the polymer binder composition. The coated abrasive 100 can also include a size coat 111 overlying the abrasive layer 103. Optionally, a supersize coat (not illustrated) can be overlying the size coat 111.

Further, an adhesion promoting layer (not illustrated) can optionally be located between the backing 101 and the abrasive layer 103.

Illustrated in FIG. 2 is another embodiment of a coated abrasive article 200. The coated abrasive 200 includes a backing 201 and an abrasive layer 203 disposed on the backing 201. The abrasive layer 203 comprises a plurality of abrasive particles 205 dispersed within a polymer binder composition 207. The abrasive layer 203 is commonly called an "abrasive slurry coat" where the abrasive particles 205 are dispersed within the polymer binder composition 207. The coated abrasive 200 can also include a size coat 209 overlying the abrasive layer 203.

Optionally, a supersize coat (not illustrated) can be overlying the size coat 209. Further, an adhesion promoting layer (not illustrated) can optionally be located between the backing 201 and the abrasive layer 203.

Illustrated in FIG. 3 is an embodiment of a process 300 for preparing a coated abrasive article. In step 301, forming a polymer binder composition occurs by mixing together a saccharide, a polycarboxylic organic acid, and a crosslinking catalyst. In step 303, providing a backing occurs. In step 305, forming a make coat occurs by disposing the polymer binder composition overlying the backing. Applying abrasive particles to the make coat occurs in step 307. Curing of the make coat occurs in step 309. The curing in step 309 can be partial curing of the make coat or full curing of the make coat. In an optional step 311, a size coat can be disposed overlying the make coat. Curing of the size coat can occur in step 313. The curing in step 313 can be partial curing of the size coat or full curing of the size coat. In optional step 315, a supersize coat can be disposed overlying the size coat. Curing of the supersize coat can occur in step 317. The curing in step 317 can be partial curing of the supersize coat or full curing of the supersize coat. Illustrated in FIG. 4 is an embodiment of a process 400 for preparing a coated abrasive article. In step 401, mixing together of polymer binder composition of a saccharide, a polycarboxylic organic acid, and a crosslinking catalyst and abrasive particles occurs to form an abrasive slurry composition. In step 403, providing a backing occurs. Applying the abrasive slurry composition to the backing occurs in step 405. Curing of the abrasive slurry composition occurs in step 407. The curing in step 407 can be partial curing of the abrasive slurry

composition or full curing of the abrasive slurry composition. In an optional step 409, a size coat can be disposed overlying the abrasive slurry composition. Curing of the size coat can occur in step 411. The curing in step 411 can be partial curing of the size coat or full curing of the size coat. In optional step 413, a supersize coat can be disposed overlying the size coat. Curing of the supersize coat can occur in step 415. The curing in step 415 can be partial curing of the supersize coat or full curing of the supersize coat.

Abrasive Layer

An abrasive layer can comprise a make coat or an abrasive slurry. The make coat or abrasive slurry can comprise a plurality of abrasive particles, also referred to herein as abrasive grains, retained by a polymer binder composition. The polymer binder composition can be an aqueous composition. The polymer binder composition can be a thermosetting composition. The polymer binder composition can be a thermosetting composition. In an embodiment, the polymer binder composition is an aqueous thermosetting composition comprising comprises at least one saccharide, at least one polycarboxylic organic acid and at least one crosslinking catalyst.

Saccharides

The present embodiments comprise at least one saccharide. The at least one saccharide can include saccharides that are the same or are different. In an embodiment, the at least one saccharide can be a monosaccharide, monosaccharides, an oligosaccharide, oligosaccharides, a polysaccharide, polysaccharides, or combinations thereof.

A monosaccharide can have 3 to 8 carbon atoms. In an embodiment, a monosaccharide can be an aldose having 5 to 7 carbon atoms. In another embodiment, a monosaccharide can be a hexose. In a particular embodiment, a hexose can be glucose, mannose, galactose, or combinations thereof.

A polysaccharide has a number- average molecular weight of less than 5000. In an embodiment, a polysaccharide can have a polydispersity index (IP), defined as the ratio of the weight- average molecular weight of the polysaccharide to the number- average molecular weight of the polysaccharide that is less than or equal to 12. In an embodiment, a polysaccharide comprises at least two saccharide units. The at least two saccharide units can be the same or different. In an embodiment the at least two saccharide units can be aldoses. In a specific embodiment the at least two saccharide units are glucose. In a particular embodiment, a polysaccharide is predominantly (more than 50% by weight) glucose units.

In another embodiment, the at least one saccharide can be a mixture of monosaccharides, oligosaccharides, polysaccharides, or combinations thereof that are obtained from plants. In a particular embodiment, the at least one saccharide is corn syrup. Corn syrup is a liquid mixture of partially hydrolyzed starch comprised of oligosaccharides, maltose, and dextrose.

In another embodiment, the at least one saccharide is a dextrin or combination of dextrins. Dextrins are compounds corresponding to the general formula (C6H10O5)n, usually obtained by partial hydrolysis of starch. In a particular embodiment, the dextrin is a solid low molecular weight crystalline polysaccharide. Polycarboxylic Organic Acids

The polymer binder composition can also in include one or more polycarboxylic organic acids. The expression "polycarboxylic organic acid" as used herein is meant to encompass an organic acid comprising at least two carboxylic functions and at most 1000 carboxylic functions. In a specific embodiment, a polycarboxylic organic acid can have two to 500 carboxylic functions. Polycarboxylic organic acids are capable of reacting with hydroxyl groups of the saccharide under the effect of heat to form ester bonds that result in a polymer network being obtained in the final binder. Said polymer network makes it possible to establish bonds at the points of contact with the abrasive particles. Polycarboxylic organic acids can be the same or different. The polycarboxylic organic acid can be a monomeric or polymeric polycarboxylic organic acid.

In an embodiment, the polycarboxylic organic acid can be a monomeric polycarboxylic organic acid or a dicarboxylic acid. Dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, malic acid, tartaric acid, tartronic acid, aspartic acid, glutamic acid, fumaric acid, itaconic acid, maleic acid, traumatic acid, camphoric acid, phthalic acid and its derivatives, especially containing at least one boron or chlorine atom, tetrahydrophthalic acid and its derivatives, especially containing at least one chlorine atom such as chlorendic acid, isophthalic acid, terephthalic acid, mesaconic acid, citraconic acid and 2,5-furanedicarboxylic acid; tricarboxylic acids, such as citric acid, tricarballylic acid, 1,2,4-butanetricarboxylic acid, aconitic acid, hemimellitic acid, trimellitic acid and trimesic acid; tetracarboxylic acids, such as 1,2,3,4- butanetetracarboxylic acid and pyromellitic acid, and mixtures of these acids. In a specific embodiment, the polycarboxylic organic acid is citric acid.

Polymeric polycarboxylic organic acids also includes homopolymers of an unsaturated carboxylic organic acid such as (meth)acrylic acid, crotonic acid, isocrotonic acid, maleic acid, cinnamic acid, 2-methylmaleic acid, fumaric acid, itaconic acid, 2-methylitaconic acid, α,β- methyleneglutaric acid and unsaturated dicarboxylic acid monoesters, such as CI -CIO alkyl maleates and fumarates, and copolymers of at least one aforementioned unsaturated carboxylic acid and of at least one vinyl monomer, such as styrene, which may or may not be substituted by alkyl, hydroxyl or sulphonyl groups, or may be substituted by a halogen atom,

(meth)acrylonitrile, (meth)acrylamide, or may not be substituted by C1-C10 alkyl groups, alkyl (meth)acrylates, especially methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate and isobutyl (meth)acrylate, glycidyl (meth)acrylate, butadiene and a vinyl ester, especially vinyl acetate.

In an embodiment, the polymer binder composition contains at least one polymeric polycarboxylic organic acid. In another embodiment, the polymer binder composition contains at least one polymer or one copolymer of (meth)acrylic acid. In a specific embodiment, the at least one polymer or one copolymer of (meth)acrylic acid is in a mixture with citric acid.

Cross-Linking Catalyst

The polymer binder composition comprises at least at least one crosslinking catalyst. The crosslinking catalyst functions to adjust the crosslinking start temperature of the saccharide with the polycarboxylic organic acid.

The crosslinking catalyst is chosen from compounds that contain phosphorus, such as an alkali metal hypophosphite salt, an alkali metal phosphite, an alkali metal polyphosphate, an alkali metal hydrogenphosphate, a phosphoric acid or an alkylphosphonic acid. Preferably, the alkali metal is sodium or potassium.

The crosslinking catalyst may also be chosen from Lewis acids and bases, such as clays, colloidal or non-colloidal silica, organic amines, quaternary amines, metal oxides, metal sulphates, metal chlorides, urea sulphates, urea chlorides and silicate-based catalysts.

The catalyst may also be a compound that contains fluorine and boron, for example tetrafluoroboric acid or a salt of this acid, especially a tetrafluoroborate of an alkali metal, such as sodium or potassium, a tetrafluoroborate of an alkaline-earth metal, such as calcium or magnesium, a zinc tetrafluoroborate and an ammonium tetrafluoroborate.

In an embodiment, the crosslinking catalyst is sodium hypophosphite, sodium phosphite, and mixtures of these compounds.

Rheology Modifiers

The polymer binder composition can include one or more rheology modifiers. A rheology modifier can be used to influence the viscosity of the polymer binder composition and thus influence the orientation of abrasive particles applied to a make coat. In an embodiment, a rheology modifier can be a single type of rheology modifier or a mixture of rheology modifiers. In an embodiment, a rheology modifier can be derived from environmentally sustainable materials. In a specific embodiment, a rheology modifier can be starch, Bentonite clay, ethyl cellulose, methyl cellulose, fumed silica, a polysaccharide based gum, or combinations thereof. In a specific embodiment, a rheology modifier can be pectin, xanthan gum, gum Arabic, or combinations thereof. In a particular embodiment, a rheology modifier is Xanthan gum. A rheology modifier can be activated by exposure to heat prior to use.

Fillers

The polymer binder composition can include one or more fillers. The filler can be a single type of filler or a mixture of fillers. The filler can serve to increase the Young's modulus of the polymer binder composition. The filler can serve to modify the pH of the polymer binder composition. Suitable fillers can be synthetic materials or naturally occurring materials. A filler can be an inorganic or organic material. In an embodiment, the filler is derived from an environmentally sustainable material. Suitable inorganic fillers can include calcium sulfate (gypsum). Suitable organic fillers can include hard materials that are biodegradable. In an embodiment, an organic filler can include ground nut shells.

Hydrophobic Additives/Hydrophobizing Agents

The polymer binder composition can include one or more hydrophobic additives, also called hydrophobizing agents herein they impart improved water resistance. The hydrophobic additives can be a single type of hydrophobic additive or a mixture of hydrophobic additives. The hydrophobic additives can serve to reduce water absorption and preserve mechanical strength. Further, hydrophobic additives can reduce surface tackiness, thus avoiding blocking problems during production of rolled coated abrasive product, as well as avoiding excessive swarf pick up during sanding operations. Moreover, because steam is commonly used during the production of coated abrasives to mitigate edge curl, degradation of a coated abrasive's size coat and/or make coat can be avoided by the inclusion of hydrophobic additives. Suitable

hydrophobic additives can be synthetic materials or naturally occurring materials. A

hydrophobic additive can be an inorganic or organic material. In an embodiment, the hydrophobic additive is derived from an environmentally sustainable material. Suitable organic hydrophobic additives can include materials that are biodegradable. In an embodiment, an organic hydrophobic additive can be tall oil fatty acid dimer emulsions, abietic acid salts, tree rosin soaps, vegetable based waxes, levulinic acid, and combinations thereof. In a specific embodiment, a hydrophobic additive is a vegetable based wax, such as a sunflower wax, rice bran wax, or combinations thereof.

Other Additives

The aqueous resin composition may also comprise other additives that aid the

manufacture of an abrasive article. Other additives can include clays; such as kaolin; salts, pH modifiers, adhesion promoters, thickeners, plasticizers, lubricants, bactericides, fungicides, wetting agents, antistatic agents, pigments, dyes, coupling agents; such as alkoxysilanes; flame retardants, degassing agents, anti-dusting agents, thixotropic agents, dual function materials, initiators, surfactants, chain transfer agents, stabilizers, dispersants, reaction mediators, pigments, dyes, colorants, and defoamers.

Abrasive Particles

A plurality of abrasive particles can be applied to the polymer binder composition. The term abrasive particles, as used herein also encompasses abrasive grains, abrasive agglomerates, abrasive aggregates, green-unfired abrasive aggregates, shaped abrasive particles, and combinations thereof. As described previously, the plurality of abrasive particles can be applied to a make coat of the polymer binder composition, or be dispersed in a slurry coat of the polymer binder composition. Thus, the abrasive particles can be disposed on the polymer binder composition, be at least partially embedded in the polymer binder composition, or a combination thereof. The abrasive particles can generally have a Mohs hardness of greater than about 3, and preferably in a range from about 3 to about 10. For particular applications, the abrasive particles can have a Mohs hardness of at least 5, 6, 7, 8, or 9. In an embodiment, the abrasive particles have a Mohs hardness of 9. Suitable abrasive particles include non-metallic, inorganic solids such as carbides, oxides, nitrides and certain carbonaceous materials. Oxides can include silicon oxide (such as quartz, cristobalite and glassy forms), cerium oxide, zirconium oxide, and various forms of aluminum oxide (including fused aluminas, sintered aluminas, seeded and non- seeded sol-gel aluminas). Carbides and nitrides can include silicon carbide, aluminum carbide, aluminum nitride, aluminum oxynitride, boron nitride (including cubic boron nitride), titanium carbide, titanium nitride, and silicon nitride. Carbonaceous materials can include diamond, which broadly includes synthetic diamond, diamond-like carbon, and related carbonaceous materials such as fullerite and aggregate diamond nanorods. Suitable abrasive particles can also include a wide range of naturally occurring mined minerals, such as garnet, cristobalite, quartz, corundum, and feldspar. In particular embodiments, the abrasive particles can be diamond, silicon carbide, aluminum oxide, cerium oxide, or combinations thereof. Abrasive particles can be mixtures of two or more different abrasive particles or can be a single type of abrasive particle. In a particular embodiment, the abrasive particles are derived from an environmentally sustainable material, a recyclable material, or a reusable material. In an embodiment, the abrasive particles are recycled abrasive particles. In a specific embodiment, the abrasive particles are recycled aluminum oxide particles.

Backing In accordance with an embodiment, the backing can be an organic material, inorganic material, natural material, synthetic material, or combinations thereof. The backing can be flexible or rigid and can be made of a single material or combination of various materials. A particular flexible backing includes a polymeric film (for example, a primed film), such as polyolefin film (e.g., polypropylene including biaxially oriented polypropylene), polyester film (e.g., polyethylene terephthalate), polyamide film, or cellulose ester film; metal foil; mesh; foam (e.g., natural sponge material or polyurethane foam); cloth (e.g., cloth made from fibers or yarns comprising polyester, nylon, silk, cotton, poly-cotton, or rayon); paper; vulcanized paper;

vulcanized rubber; vulcanized fiber; nonwoven materials; any combination thereof; or any treated version thereof. Cloth backings can be woven or stitch bonded. In a particular embodiment, the backing includes a thermoplastic film, such as a polyethylene terephthalate

(PET) film. In particular, the backing can be a single layer polymer film, such as a single layer PET film. In particular embodiment, the backing is a flexible support material, sheet of paper, a film or a network of fibers, for example a mat, a felt, a fabric or a knit of natural or synthetic fibers, including mineral fibers, glass fibers, polymer fibers, plant fibers, or combinations thereof.

In a particular embodiment, the backing material is derived from an environmentally sustainable material, a recyclable material, or a reusable material. In a particular embodiment, the backing material is a recycled paper backing. In another particular embodiment, the backing material is a paper backing derived from plant material that originates from a well-managed forest, such as a Forest Stewardship Council managed forest, a controlled source of natural and recycled wood, natural and recycled plant fibers, and combinations thereof. Size Coat

The coated abrasive article can comprise a size coat overlying the abrasive layer. The size coat can be the same as or different from the polymer binder composition used to form the abrasive layer. The size coat can comprise any conventional compositions known in the art that can be used as a size coat. In an embodiment, the size coat comprises a conventionally known composition overlying the polymer binder composition of the abrasive layer. In another embodiment, the size coat comprises the same ingredients as the polymer binder composition of the abrasive layer. In a specific embodiment, the size coat comprises the same ingredients as the polymer binder composition of the abrasive layer and one or more hydrophobic additives. In a specific embodiment, the hydrophobic additive can be a wax, a halogenated organic compound, a halogen salt, a metal, or a metal alloy.

Supersize Coat

The coated abrasive article can comprise a supersize coat overlying the size coat. The supersize coat can be the same as or different from the polymer binder composition or the size coat composition. The supersize coat can comprise any conventional compositions known in the art that can be used as a supersize coat. In an embodiment, the supersize coat comprises a conventionally known composition overlying the size coat composition. In another embodiment, the supersize coat comprises the same ingredients as at least one of the size coat composition or the polymer binder composition of the abrasive layer. In a specific embodiment, the supersize coat comprises the same composition as the polymer binder composition of the abrasive layer or the composition of the size coat plus one or more grinding aids.

Suitable grinding aids can be inorganic based; such as halide salts, for example sodium cryolite, and potassium tetrafluoroborate; or organic based, such as sodium lauryl sulphate, or chlorinated waxes, such as polyvinyl chloride. In an embodiment, the grinding aid can be an environmentally sustainable material.

Coated Abrasive Article Preparation

Polymer Binder Preparation

As shown in FIG. 3 an embodiment of a process 300 for preparing a coated abrasive article is given. At step 301, forming a polymer binder composition can be accomplished by mixing together a saccharide, a polycarboxylic organic acid, and a crosslinking catalyst in the presence of water. The saccharide, a polycarboxylic organic acid, crosslinking catalyst, and water are combined together until thoroughly mixed. The polymer binder composition can additionally comprise other ingredients, such as rheology modifiers, fillers, hydrophobic additives, and other additives.

All the mixture ingredients are thoroughly mixed together using, for example, a high shear mixer. Mixing can be conducted using high shear conditions, medium shear conditions, or low shear conditions, as desired. Typically, mixing occurs until the ingredients are thoroughly mixed. During mixing of the ingredients, the ingredients may be added to the mixture one by one, in batches, or all at once.

The viscosity of the polymer binder mixture can be monitored as it is being prepared. In an embodiment, the viscosity of the polymer binder mixture can be kept in a particular range by the addition of rheology modifiers, thickeners, plasticizers, diluents, thixotropic agents, or combinations thereof. In the event of the addition of any solid components, such as abrasive particles during abrasive slurry preparation, the mixture can have a viscosity adjusted in a particular range.

The pH of the aqueous polymer binder composition is generally acidic. In an

embodiment, the pH is in a range from 1 to 5. In a specific embodiment, the pH is greater than or equal to 1.5. The pH can vary depending on the nature of the polycarboxylic organic acid used. In an embodiment the pH is maintained at a value at least equal to 2. A pH of at least equal to 2 can limit instability problems of the aqueous resin composition. The pH can be adjusted by the addition of an acid or other pH modifier.

The viscosity of the aqueous polymer binder composition can vary depending on the desired application conditions but will generally remain less than or equal to 15,000 mPa.s, preferably less than or equal to 10,000 mPa.s, measured at 25°C using a Brookfield machine fitted with an LV1 spindle operating at a speed of 60 rpm.

In an embodiment, the polycarboxylic organic acid comprises a mixture of monomeric polycarboxylic organic acid and polycarboxylic acid. In another embodiment, the amount by weight of monomeric polycarboxylic organic acid ranges from 5 to 50%, such as from 15 to 40%, of the total weight of monomeric polycarboxylic organic acid and polymeric polycarboxylic organic acid.

In the aqueous resin composition, the amount, by weight, of saccharide represents 10% to 90%, such as 40% to 70%, of the total weight of the saccharide and polycarboxylic organic acid. The amount of catalyst introduced into the aqueous resin composition represents 1% to

15%, such as 3% to 10%, of the total weight of the saccharide and polycarboxylic organic acid.

The solids content of the aqueous polymer binder composition can be calculated. In an embodiment, the solids content can be calculated on the basis of all the organic constituents. In a specific embodiment, the solids content can be in a range from 30% to 75%, preferably from 45% to 70%.

In step 305, a make coat can be formed by disposing the polymer binder composition onto a backing. The polymer binder composition can be coated onto the backing using a blade spreader to form a make coat. Alternatively, the polymer binder composition can be applied using slot die, smooth rolling, gravure, or reverse gravure coating methods. Abrasive particles can be applied to the make coat in step 307 through electrostatic attraction (sometimes called "upcoating") or simply down through gravity (e.g., sprinkled onto the backing). Both approaches are well understood in the art, generally first depositing a 'make coat' on the backing, followed by abrasive aggregate application onto the make coat, and subsequent deposition of a 'size coat' in step 311. Optionally, a supersize coat may be deposited over the size coat as in step 313.

Deposition of the supersize coat can be accomplished by the same methods as for the make coat and size coat.

In sum, the aqueous polymer binder composition can be used to form the make coat, the size coat or the supersize coat. Preferably, the aqueous composition is used to form the size coat, and where appropriate the make coat.

Applying an Abrasive Slurry to a Backing

As shown in FIG. 4, in an alternative method 400, an abrasive slurry containing the polymer binder composition and abrasive particles is mixed together. The aqueous polymer binder composition can be mixed as described above with the addition that a desired amount of abrasive particles are added in during the mixing process to form an abrasive slurry. The abrasive slurry is preferably applied to the backing using a blade spreader. Alternatively, the slurry coating can be applied using slot die, smooth rolling, gravure, or reverse gravure coating methods.

Curing the Make Coat, Abrasive Slurry, Size Coat, and Supersize Coat

The coated backing is then heated in order to cure the polymer binder composition and bond the abrasive particles (aggregates, grains, or combination thereof) to the backing. The polymer binder composition; whether in the form of a make coat, abrasive slurry, size coat, or supersize coat; can be at least partially cured or fully cured. Additional molding or shaping of a partially cured coating can be performed prior to full curing, if desired. Said molding and shaping can be performed on an abrasive slurry so that an engineered abrasive article, also called a structured abrasive article, is formed. Full curing completes crosslinking of the constituents contained in a coat. In general, the coated backing is heated to a temperature in a range of about 100 oC to less than about 250 oC during the curing process. In certain embodiments the curing step can be carried out at a temperature of less than about 200 oC. In an embodiment, the application of each make coat or supersize coat is followed by a heat treatment at a temperature of less than or equal to 150°C, preferably less than or equal to 120°C, and advantageously between 50°C and 100°C. The heat treatment can last from 1 to 120 minutes, preferably 1 to 90 minutes.

Once the resin is fully cured, the abrasive aggregates are bonded to the backing and the coated backing may be used for a variety of stock removal, finishing, and polishing applications.

The coated abrasive obtained may be cut to the desired size, for example to produce sheets, or collected in the form of a winding. The winding may undergo an additional heat treatment with a view to completing the crosslinking of the aqueous composition forming the size coat or the supersize coat. This heat treatment may be carried out at a temperature less than or equal to 150°C, preferably less than or equal to 120°C, for at most 36 hours, preferably at most 20 hours.

Coated abrasive articles incorporating the aqueous polymer binder composition according to the embodiments can be, in particular, in the form of abrasive papers and abrasive fabrics. The examples given below make it possible to illustrate the invention without however limiting it.

In the examples, the viscosity (in mPa.s) is measured at 25°C using a Brookfield machine equipped with an LV1 spindle rotating at a speed of 60 rpm. The viscosity is measured immediately after the manufacture of the aqueous resin composition and after storing for one day at 25°C.

In the examples, the Young's modulus is measured by the nanoindentation technique which makes it possible to evaluate the mechanical properties of a thin film deposited on a substrate, without these properties being influenced by the substrate. The Young's modulus is measured under the following conditions: a layer of aqueous resin composition (thickness: 150 μιη) is deposited on a square glass plate having 1 cm sides, and the assembly is heated at 60°C for 60 minutes, then at 120°C for 120 minutes. The glass plate is placed in a nanoindenter (XP sold by MTS Systems Corp.) equipped with a diamond Berkovich tip of triangular-based pyramid shape, and the curve of the load as a function of the displacement is established. The Young's modulus, in GPa, is determined from this curve. The value of the Young's modulus is an average of 10 measurement points.

In the examples, the loss of mass is determined by thermogravimetric analysis (TGA). The aqueous resin composition is deposited in an aluminium pan and heated at 60°C for 60 minutes, then at 120°C for 120 minutes. 10 to 20 mg of the residue obtained (binder) are placed in an alumina crucible which is put into a machine that continuously measures the loss of mass during a temperature cycle ranging from 25°C to 700°C at a rate of 10°C/minute. The loss of mass at 300°C, 400°C and 500°C is determined from the recorded curve.

EXAMPLES 1 TO 8

Aqueous resin compositions are manufactured by mixing in a container, with stirring, the compounds that appear in Table 1, the amounts being expressed in parts by weight. The solids content of these compositions is between 50% and 60% and their viscosity appears in Table 1.

The loss of mass (see Table 1) is measured in parallel on a portion of the resin compositions. Each of the aqueous resin compositions obtained and also a conventional composition based on a urea-formaldehyde resin, denoted by Reference (sold under the reference R2130 by the company Schenectady International, Inc.) are applied in the form of a film (thickness 150 μιη) to a glass plate. The glass plate is introduced into an oven and brought to a temperature of 60°C for 60 minutes, then 120°C for 120 minutes. The properties indicated in Table 1 are measured on the cooled plate.

The viscosity of the resin compositions of Examples 1 to 8 is compatible with a use to produce coated abrasive articles. The Young's modulus of the examples according to the invention is higher than that of the Reference.

The loss of mass of Examples 1 to 8 remains lower than that of the Reference, irrespective of the measurement temperature. Examples 1 to 5, which contain a polymeric polycarboxylic organic acid, have the lowest loss of mass. EXAMPLES 9 AND 10

These examples illustrate the preparation of a coated abrasive article on a pilot line.

From a reel, a sheet of paper (ARJOREG-185-MS-WHITE sold by ARJO WIGGINS; width: 30 cm; basis weight: 185 g/m²; thickness 0.21 mm) is unwound and a make coat is deposited, continuously, using a transfer roll, then abrasive particles are deposited using an electrostatic coating device. The coated sheet is collected in the form of festoons on a suitable device which is then introduced into an oven at 85°C for 20 minutes.

After cooling, the sheet is again wound in the form of a reel which is placed in the preceding unit in order to deposit the size coat on the face bearing the abrasive particles. The sheet is collected and treated under the following temperature conditions: 85°C for 50 minutes (Example 9) and 50°C for 50 minutes (Example 10).

The sheet of Example 9 is again wound in the form of a reel and introduced into an oven at 115°C for 120 minutes. The make coat is constituted of the urea-formaldehyde (Reference) resin described in Examples 1 to 8, to which 10 parts by weight of kaolin have been added. The make coat is deposited in a proportion of 52 g/m² (dry weight).

The abrasive particles are constituted of alumina (sold under the reference

"Electrocorundum EKP, P80 grit" by the company Kuhmichel Abrasiv GmbH) and are deposited in a proportion of 165 g/m².

The size coat is constituted of the aqueous resin composition of Example 5 (Example 9) or of the aforementioned Reference resin (comparative Example 10). The size coat is deposited in a proportion of 120 g/m² (dry weight).

The performances of the abrasive sheet are evaluated under the conditions of the following abrasion test: discs with a diameter of 125 mm bearing 8 holes of 8 mm are cut from the abrasive sheet and one disc is placed on an electric sander (Bosch PEX 220A). The sander is used by an operator to manually sand a sheet of wood made of pine (length: 80 cm; width: 20 cm; thickness: 1.5 cm) with a linear movement in the length direction.

The loss of mass of the sheet of wood as a function of the sanding time is measured. The results are given in Table 2, expressed as cumulative loss of mass.

Example 9 has abrasive properties equivalent to those of comparative Example 10.

Table 1

n.d. : not determined

⁽¹⁾ acrylic acid homopolymer ; sold by Dow Chemicals

⁽²⁾ maltodextrin ; number-average molecular weight : 1725 g/mol ; polydispersity index (IP) : 10.6 ; sold by Roquette

⁽³⁾ dextrin ; number-average molecular weight : 1165 g/mol ; polydispersity index (IP) : 8.6 ; sold by Roquette

⁽⁴⁾ maltodextrin ; number-average molecular weight : 2490 g/mol ; polydispersity index (IP) : 5.2 ; sold by Roquette

⁽⁵⁾ glucose syrup ; number-average molecular weight : 675 g/mol ; polydispersity index (IP) : 5.4 ; sold by Roquette

Table 2

Claims

1. A coated abrasive article comprising:

a backing; and

an abrasive layer overlying the backing;

wherein the abrasive layer comprises

abrasive particles and

a polymer binder composition including

at least one saccharide,

at least one polycarboxylic organic acid, and

at least one crosslinking catalyst.

2. A coated abrasive article comprising:

a backing; and

an abrasive layer overlying the backing; and

a size coat comprising

a polymer binder composition including

at least one saccharide,

at least one polycarboxylic organic acid, and

at least one crosslinking catalyst.

3. A coated abrasive article according to claim 1 or 2 wherein the saccharide is corn syrup, dextrin, or a combination thereof.

4. A coated abrasive article according to claim 1 or 2 wherein the polymer binder further comprises at least one member selected from the group consisting of rheology modifiers and hydrophobic additives.

5. A polymer binder composition adapted to bind abrasive particles, wherein it comprises at least one saccharide, at least one polymeric polycarboxylic organic acid, and at least one crosslinking catalyst.

6. A composition according to claim 5, wherein the saccharide is a monosaccharide, a polysaccharide, or a combination thereof.

7. A composition according to Claim 6, wherein the monosaccharide contains 3 to 8 carbon atoms, and is preferably an aldose containing 5 to 7 carbon atoms.

8. A composition according to Claim 7, wherein the aldose is glucose, mannose or galactose.

9. A composition according to Claim 7, wherein the polysaccharide has a number- average molecular weight of less than 5000.

10. A composition according to Claim 7 or 9, wherein the polysaccharide has a polydispersity index (IP), defined by the ratio of the weight- average molecular weight to the number- average molecular weight, which is less than or equal to 12.

11. A composition according to one of Claims 7, 9 or 10, wherein the polysaccharide consists predominantly (contains more than 50% by weight) of glucose units.

12. A composition according to one of Claims 7 to 11, wherein the polycarboxylic organic acid comprises at most 1000 carboxylic functions.

13. A composition according to one of Claims 6 to 12, further comprising a monomeric polycarboxylic organic acid.

14. A composition according to Claim 13, wherein it is citric acid.

15. A composition according to one of Claims 6 to 14, wherein the polymeric polycarboxylic organic acid is chosen from homopolymers of an unsaturated carboxylic organic acid and unsaturated dicarboxylic acid monoesters, and copolymers of at least one aforementioned unsaturated carboxylic acid and of at least one vinyl monomer.

16. A composition according to one of claims 6 to 15, wherein it contains at least one polymer or one copolymer of (meth)acrylic acid, said polymer or copolymer preferably being in a mixture with citric acid.

17. A composition according to one of Claims 6 to 16, wherein the amount, by weight, of saccharide represents 10% to 90% of the total weight of the saccharide and polycarboxylic organic acid.

18. A composition according to one of Claims 6 to 17, wherein the crosslinking catalyst is chosen from compound salts that contain phosphorus, Lewis acids and bases, organic amines, metal oxides, metal sulphates, metal chlorides, urea sulphates, urea chlorides and silicate-based catalysts and compounds that contain fluorine and boron.

19. A composition according to Claim 18, wherein the crosslinking catalyst is sodium hypophosphite, sodium phosphite, or a combination thereof.

20. A composition according to one of Claims 6 to 19, wherein the amount of crosslinking catalyst represents 1% to 15% of the total weight of the saccharide and polycarboxylic organic acid.

21. A composition according to one of Claims 6 to 20, wherein the solids content, calculated on the basis of all of the organic constituents, varies from 30% to 75%.