ACRYLATED OLIGOMER/THERMOPLASTIC POLYAMIDE PRESIZE COATINGS FOR ABRASIVE ARTICLE BACKINGS

Abstract: The present invention provides a composition for use in coated abrasives. The curable composition comprises a mixture of: i) from about 25 to about 75 weight percent of acrylated oligomer; ii) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer, the weight percents being based on the total resin content; and iii) a sufficient amount of a catalyst for the curable acrylated oligomer, said catalyst being stable at a temperature of mixing of the components. The present invention also provides single and multilayered treated backing substrates for use in coated abrasives.

Description: ACRYLATED OLIGOMER/THERMOPLASTIC POLYAMIDE PRESIZE COATINGS FOR ABRASIVE ARTICLE BACKINGS This invention relates to coating compositions for abrasive backings containing an acrylated oligomer resin and a thermoplastic polyamide resin. Coated abrasives generally comprise a flexible backing upon which a binder holds and supports a coating of abrasive grains. The backing can be selected from paper, cloth, film, vulcanized rubber, etc., or a combination of one or more of these materials. The abrasive grains can be formed of flint, garnet, aluminum oxide, alumina-zirconia, ceramic aluminum oxide, diamond, silicon carbide, and the like. Binders are commonly selected from phenolic resins, hide glue, urea-formaldehyde resins, urethane resins, epoxy resins, and varnish. Phenolic resins include those of the phenol-aldehyde type. Coated abrasives may employ a make coat of resinous binder material in order to secure the abrasive grains to the backing, and a size coat of resinous binder material can be applied over the make coat and abrasive grains in order to more firmly bond the abrasive grains to the backing. The resinous material of the make and size coats may be the same material or may be different materials. A common resinous material used for both make and size coatings is generically referred to as phenolic resin. Phenolic resins are a class of materials made from the reaction of phenol with various aldehydes. Phenolic resins are commonly used in binders for coated abrasive articles because of their high adhesive strength to abrasive particles, durability, and high thermal stability. However, phenolic resins do not adhere well to some types of backing materials. Poor adhesion may cause the phenolic binder to peel away or "shell off' prematurely as the abrasive article is subjected to normal use. This lack of adhesion limits the types of backings that can be used in coated abrasive articles that use phenolic resin binders. In one embodiment, the invention is a substrate for an abrasive article comprising: a) a backing; and b) a crosslinked treatment coat on the backing, said treatment coat is formed from a curable precursor composition comprising a mixture of: i) from about 25 to about 75 weight percent of an acrylated oligomer; ii) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer; and iii) a sufficient amount of a catalyst for the curable acrylated oligomer resin, said catalyst being stable at temperature of mixing of the components. In another embodiment, the treatment coat is made from a binder precursor which comprises a difunctional acrylated epoxy oligomer, a thermoplastic polyamide, and a catalyst for crosslinking or curing the difunctional acrylated oligomer. In another embodiment, the invention provides a composition useful for treating backing substrates for abrasive articles, the composition comprising a mixture of: a) from about 25 to about 75 weight percent of an acrylated oligomer; b) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer; and c) a sufficient amount of a catalyst for the curable acrylated oligomer resin, said catalyst being stable at temperature of mixing of the components. The cured composition of the invention is useful as a presize coat, a backsize coat, a make coat, and a size coat for coated abrasive articles; and is useful as an adhesive for making multi-layer laminated backings. As used herein, "acrylated oligomer" means a polymer molecule having a molecular weight of from about 300 to about 5,000 and having at least one acrylate or methacrylate functional group per each oligomeric unit. As used herein, "difunctional" and "trifunctional" means two and three acrylate and/or methacrylate functional groups per each oligomeric unit. As used herein, "epoxy resin" means a thermosetting resin containing reactive epoxide groups. The term "precursor" means the binder is uncured and not crosslinked. The term "crosslinked" means a material having polymeric sections that are interconnected through chemical bonds (that is, interchain links) to form a three-dimensional molecular network. Thus, the binder precursor is in an uncured state when applied to the backing. In general, the treatment coat comprises a semi-interpenetrating polymer network of a cured or crosslinked thermosetting polymer and a thermoplastic polymer. As used herein, a "semi-interpenetrating polymer network (semi-IPN)" is defined as a polymer network of two or more polymers wherein at least one polymer is crosslinked and at least one is uncrosslinked. For purposes of this application, "cured," "crosslinked," and "polymerized" can be used interchangeably. For purposes of this invention, the binder precursor is "energy- curable" in the sense that it can crosslink (that is, cures) upon exposure to radiation, for example, actinic radiation, electron beam radiation, and/or thermal radiation. The binder precursor may be in the form of a molten mixture or may be a solid at room temperature. For instance, the binder precursor may be a solid film that is transfer coated to the backing. Upon heating to elevated temperatures, this binder precursor is capable of flowing, increasing the tack of the hot melt adhesive, allowing the hot melt adhesive to penetrate and/or bond intimately with the backing substrate. Alternatively, for instance, if the resin is solvent-borne (aqueous or organic), or blended with low molecular weight reactive diluents, the binder precursor may be liquid at room temperature. As used herein, a "hot melt" refers to a composition that is a solid at room temperature (about 20 to 22 °C) but which, upon heating, melts to a viscous liquid that can be readily applied to a backing for a coated abrasive article. A "melt processable" composition refers to a composition that can transform; for example, by heat and/or pressure, from a solid to a viscous liquid by melting, at which point it can be readily applied to a backing. Desirably, the binder precursors of the invention can be formulated as solvent free systems (that is, they have less than 1 percent solvent in the solid state). However, if so desired, it may be feasible to incorporate solvent or other volatiles into the binder precursor. A "cloth" is a generic term which includes all textile fabrics or felts. A "cloth" as used herein, may contain any of the commonly known textile fibers, natural or manmade, or a combination thereof, and which are formed by weaving, knitting, felting, needling, or other processes known in the textile industry. A "continuous filament yarn" is a yarn comprising indefinitely long fibers such as those found in silk, or those manufactured fibers which are extruded into filaments and then assembled into a yarn with or without a twist. The compositions of the invention combine the toughness, the improved adhesion to other phenolics, and the meit-processibilty of thermoplastic polyamides with the rapid curing, high temperature stability, and phenolic resin compatibility of the functionalized oligomeric material. The resulting solventless compositions are processed at moderate temperatures (200-280 °F (83-138 °C)) as compared with typical thermoplastic materials processed in excess of 204 °C, and thus allow the use of temperature sensitive backing materials in coated abrasives. The compositions of the invention may also be used as laminating or transfer coating adhesives in composite backings that provide strength and durability similar to that of cloth at less cost. A preferred binder precursor of the invention contains from about 30 to about 70 weight percent of an acrylated oligomer and from about 70 to about 30 weight percent of thermoplastic polyamide, the weight percent being based on the total resin content of the composition. A more preferred binder precursor of the invention contains from about 30 to about 50 weight percent of an acrylated oligomer and from about 70 to about 50 weight percent of thermoplastic polyamide, the weight percent being based on the total resin content of the composition. A preferred acrylated oligomer is an acrylated epoxide. A preferred catalyst for the acrylated oligomer containing material is a free radical producing photoinitiator. The compositions of the invention contain one or more acrylated oligomers. Useful acrylated oligomers are radiation curable and include acrylated epoxy resins and acrylated urethane resins. As used herein, the term acrylate includes both acrylates and methacrylates. Acrylated epoxies are multifunctional acrylate esters of epoxy resins, such as the acrylated esters of bisphenol A epoxy resin. Examples of commercially available acrylated epoxies include those known by the trade designations EBECRYL 600 (bisphenol A epoxy diacrylate of 525 molecular weight), EBECRYL 629 (epoxy novolak acrylate of 550 molecular weight), EBECRYL 860 (epoxidized soya oil acrylate of 1200 molecular weight), EBECRYL 3700 (bispenol A diacrylate of 524 molecular weight) and EBECRYL 3720 (bisphenol A diacrylate of 524 molecular weight) available from UCB Chemical, Smyrna, GA; and PHOTOMER 3016 (bisphenol A epoxy acrylate), PHOTOMER 3038 (epoxy acrylate tripropylene glycol diacrylate blend), and PHOTOMER 3071 (modified bisphenol A acrylate, etc.) available from Henkel Corp., Hoboken, NJ. Acrylated urethanes are multifunctional acrylate esters of hydroxyterminated isocyanate extended polyesters or polyethers. Examples of commercially available acrylated urethanes include those known by the trade designations PHOTOMER (for example, PHOTOMER 6010) available from Henkel Corp.; EBECRYL 220 (hexafunctional aromatic urethane acrylate of 1000 molecular weight), EBECRYL 284 (aliphatic urethane diacrylate of 1200 molecular weight diluted with 1 ,6-hexanediol diacrylate), EBECRYL 4827 (aromatic urethane diacrylate of 1600 molecular weight), EBECRYL 4830 (aliphatic urethane diacrylate of 1200 molecular weight diluted with tetra ethylene glycol diacrylate), EBECRYL 6602 (trifunctional aromatic urethane acrylate of 1300 molecular weight diluted with trimethylolpropane ethoxy triacrylate), and EBECRYL 8402 (aliphatic urethane diacrylate of 1000 molecular weight) available from UCB Chemical; SARTOMER (for example, SARTOMER 9635, 9645, 9655, 963-B80, 966-A80, etc.) available from Sartomer Co., West Chester, PA; and UVITHANE (for example, UVITHANE 782) available from Morton International, Chicago, IL. Preferred acrylated oligomers are di-and tri-functional acrylated oligomers. More preferred acrylated oligomers include Bisphenol A based di-functional acrylated epoxy resins. Preferred commercially available di-functional acrylated Bisphenol A based epoxy resins are EBECRYL 3700and 3720, available from UCB Chemicals. Compositions of the invention also contain at least one thermoplastic polyamide. The thermoplastic polyamides of the invention are compatible with the acrylated oligomers in the melt phase. "Compatible" means that the acrylated oligomer and the thermoplastic polyamide are sufficiently miscible and the melt viscosities of the thermoplastic polyamide and of the acrylated oligomer are sufficiently similar such that a uniform mixture can be obtained with conventional extrusion compounding equipment. Useful thermoplastic polyamides of the invention have a melting point temperature in the range of about 95 to about 150 °C as measured by differential scanning calorimetry (DSC). Preferred thermoplastic polyamides of the invention have a DSC melting point of about 95 to about 110 °C, and a more preferred thermoplastic polyamide has a melting point of about 103 °C. The viscosities of the polyamides of the invention are similar to those of the acrylated oligomers of the invention at the processing temperature of the mixture. Useful thermoplastic polyamides of the invention have a melt flow rate of from about 10 to 90 g/10 min, preferably from about 15-90 g/10 min, more preferably from about 50 - 90 g/10 min, and even more preferably about 90 g/10 min, at a temperature of 160 °C. Preferred thermoplastic polyamides are terpolymers produced from lactams and diamines. Preferred polyamides contain lauryl lactam as one of the monomers. Preferred commercially available thermoplastic polyamides are terpolymers produced from lactams and diamines. The preferred commercially available thermoplastic polyamides have the trade designations VESTAMELT 732, VESTAMELT 730, VESTAMELT 742, VESTAMELT 750/751, VESTAMELT 755, and VESTAMELT 760, and are available from Creanova, Somerset, NJ. The compositions of the invention contain at least one catalyst for curing the acrylated oligomer. The acrylated oligomer can be cured by radiation energy. Since the acrylated oligomer is cured by radiation, the amount of radiation depends upon the degree of cure desired of the crosslinkable components. Examples of radiation energy sources include ionizing radiation, ultraviolet radiation, and visible light radiation. Ionizing radiation preferably has an energy level of 0.1 to 10 megarad, more preferably 1 to 10 megarad. Ultraviolet radiation is non-particulate radiation having a wavelength of from about 200 to 700 nanometers, more preferably from 250 to 400 nanometers. Visible light radiation is non-particulate radiation having a wavelength of from about 400 to 760 nanometers. The rate of curing of the binder composition depends upon the thickness as well as the optical density and nature of the composition. Useful radiation source intensities range from about 300 to about 600 Watts/in (118 to 236 Watts/cm). If the binder precursor composition is to be cured by ultraviolet radiation, a photoiniator is required to initiate free radical formation. Examples of such photoinitiators include organic peroxides, azo compounds, quinones, benzophenones, nitro compounds, acyl halides, hydrazones, mercapto compounds, pyrylium compounds, triacrylimidizoles, bisimidizoles, chloroalkyltriazines, benzoin ethers, benzil ketals, thioxanthones, and acetophenone derivatives. If the binder precursor composition is to be cured by visible light radiation, a photoinitiator is required to initiate free radical polymerization. Examples of useful visible light photoinitiators can be found in U.S. Patent No. 4,735,632. Preferably, the catalysts are activated photochemically. Useful commercially available photocatalysts or photoinitiators include those under the trade designation IRGACURE and have product numbers 369, 651, and 961, all available from Ciba Geigy Chemicals, Hawthorne, NY. Any known and compatible additive useful in coatings used in the abrasives art may be used as long as the amount of the additive used does not adversely affect the performance characteristics of the end-use product or article. Common additives include optically transparent fillers such as feldspar and silica, and materials useful for dissipating static charges such as carbon black and graphite. Useful backings of the invention may be comprised of cloth, vulcanized fiber, paper, nonwoven materials, fibrous reinforced thermoplastic backing, polymeric films, substrates containing hooked stems, looped fabrics, metal foils, mesh, foam backings, and transfer coated multilayer combinations thereof and are of the appropriate weight for the end use application. The raw backings can be provided as woven fabrics using yarns composed of natural or synthetic fibers, as polymeric films, or as laminates of different types of polymeric materials, or as laminates of polymeric materials with a non-polymeric materials. The woven polymeric fabrics may have different yarns in the warp and weft directions. Examples of useful commercially available cloth backing materials include polyester backings woven with either spun yarns or continuous filament yarns, available from Milliken, Spartansburg, SC. Cloth backings can be porous or sealed and they may be woven or stitch bonded. The cloth backings can be provided as laminates with different backing materials described herein. Paper backings can also be barrier coated, backsized, untreated, or fiber-reinforced. The paper backings also can be provided as laminates with a different type of backing material. Nonwoven backings include spunbonded webs and laminates to different backing materials mentioned herein. Laminates may include those constructions having a network of filaments adhesively bonded or melt bonded to a nonwoven web. The nonwovens may be formed of cellulosic fibers, synthetic fibers, or blends thereof. Examples of commercially available nonwoven backing materials include TYPAR spunbonded polypropylene and REEMAY spunbonded polyester, available from Typar/Reemay, Old Hickory, TN; and STABILON scrims, available from Milliken. A "scrim" is defined as a fabric with an open construction used as a base fabric in the production of coated or laminated substrates. The foam backing may be a natural sponge material or polyurethane foam and the like. The foam backing also can be laminated to a different type of backing material. The mesh backings can be made of polymeric or metal open- weave scrims. Additionally, the backing may be a spliceless belt such as that disclosed in U.S. Patent 5,609,706, or a reinforced thermoplastic backing that is disclosed in U.S. Patent No. 5,417,726. Preferred backing materials for use in the coated backings of the invention include cloth backings such as that woven from polyester, cotton, polyester/cotton, rayon, or lyocell yarns. The binder precursor may be prepared by mixing the various ingredients in a suitable vessel at an elevated temperature sufficient to liquefy the materials so that they may be efficiently mixed with stirring but without thermally degrading them until the components are thoroughly melt blended. This temperature depends in part upon the particular chemistry. For example, this temperature may range from about 30 to 150 °C, typically 50 to 140 °C, and preferably ranges from 60 to 125 °C. The components may be added simultaneously or sequentially, although it is preferred to first blend the acrylated oligomer resin and the thermoplastic polyamide component. Then the catalysts are added, followed by any optional additives including fillers or grinding aids (for peripheral coating use). The binder precursor should be compatible in the uncured, melt phase. That is, there should preferably be no visible gross phase separation among the components before curing is initiated. Preferably, the viscosity ratio of the acrylated oligomer and the thermoplastic polyamide is approximately 0.1 at the processing temperature. The binder precursor may be immediately coated after melt blending or may be packaged in pails, drums, or other suitable containers, as a solid or a powder, preferably in the absence of light, until ready for use. The binder precursors so packaged may be delivered to a hot-melt applicator system with the use of pail unloaders, block melters equipped with rotating screws, and the like. Alternatively, the hot melt binder precursors of the invention may be delivered to conventional bulk hot melt applicator and dispenser systems in the form of sticks, pellets, slugs, blocks, pillows, or billets. It is also feasible to incorporate organic solvent into the binder precursor; although this may not always be preferred. It is also possible to provide the hot melt binder precursors of the invention as uncured, unsupported rolls of adhesive film. In this instance, the binder precursor is extruded, cast, or coated to form the film. Such films are useful in transfer coating the binder precursor to an abrasive article backing. It is desirable to roll up the film with a release liner (for example, silicone-coated Kraft paper), with subsequent packaging in a bag or other container that is not transparent to actinic radiation. The hot melt binder precursors of the invention may be applied to the abrasive article backing by extrusion, gravure printing, coating, (for example, by using a coating die, a heated knife blade coater, a roll coater, a curtain coater, or a reverse roll coater), or transfer coating. When applying by any of these methods, it is preferred that the binder precursor be applied at a temperature of about 50 to 140 °C, more preferably from about 80 to 125 °C. The hot melt binder precursors can be supplied as free standing, unsupported films that can be transfer coated to the backing and, if necessary, die cut to a predefined shape before transfer coating. Transfer coating temperatures and pressures are selected so as to minimize both degradation of the backing and bleed through of the binder precursor and may range from room temperature to about 120 °C and about 30 to 1000 psi (0.03 to 1 kPa). A typical profile is to transfer coat at room temperature and about 400 - 500 psi (0.4 to 0.5 kPa). Transfer coating is a particularly preferred application method for use with highly porous backings. It is also within the scope of this invention to coat the binder precursor as a 100 percent solids liquid, or from a solvent, although the solvent dilution method is not always preferred. A liquid binder precursor can be applied to the backing by any conventional technique such as roll coating, spray coating, die coating, knife coating, and the like. After coating the resulting binder precursor, it may be exposed to an energy source to activate the catalyst before the abrasive grains are embedded into the binder precursor. Alternatively, the abrasive grains may be coated immediately after the binder precursor is coated before partial cure is effected. The coating weight of the hot melt binder precursor of the invention to a backing can vary depending on the grade of the abrasive particles to be used. In general, the application rate of the binder precursor composition of this invention (on a solvent free basis) is between about 4 to 500 g/m^, preferably between about 20 to about 300 g/m^. Preferably, the hot melt binder precursor is applied to the abrasive article backing by any of the methods described above, and once so applied is exposed to an actinic, preferably UV, energy source to initiate at least partial cure of the photosensitive materials. The partial curing facilitates further processing, web handling, and prevents the coated side of the backing from sticking to the backside of the backing when the coated backing is in the form of a roll. Final cure may be completed at any later date using an energy source, typically thermal energy. Curing of the hot melt binder precursor begins upon exposure of the binder precursor to an appropriate energy source and continues for a period of time thereafter. The energy source is selected for the desired processing conditions and to appropriately activate the chosen photoactive catalyst system. The energy may be actinic (for example, radiation having a wavelength in the ultraviolet or visible region of the spectrum), accelerated particles (for example, electron beam radiation), or thermal (for example, heat or infrared radiation). Preferably, the energy is actinic radiation (that is, radiation having a wavelength in the ultraviolet or visible spectral regions). Suitable sources of actinic radiation include mercury, xenon, carbon arc, tungsten filament lamps, sunlight, and so forth. Ultraviolet radiation, especially from a medium pressure mercury arc lamp, is most preferred. Exposure times may be from less than about 1 second to 10 minutes or more (to preferably provide a total energy exposure from about 0.1 to about 10 Joule/square centimeter (J/cm^)) depending upon both the amount and the type of reactants involved, the energy source, web speed, the distance from the energy source, and the thickness of the binder precursor to be cured. The binder precursors may also be cured by exposure to electron beam radiation. The dosage necessary is generally from less than 1 megarad to 100 megarads or more. The rate of curing may tend to increase with increasing amounts of photocatalyst and/or photoinitiator at a given energy exposure. Curing of the mixture can also be effected by use of electron beam energy with no photoinitiator. The rate of curing also tends to increase with increased energy intensity. Objects and advantages of this invention are further illustrated by the following 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 invention. EXAMPLES Glossary ABCN 1,1 -azo bis( cyclohexanecarbonitrile), available from Wako Chemicals USA Inc., Richmond, VA., under the trade designation VAZO 88 AF7 an antifoam, available from The Dow Chemical Co., Midland, MI, under the trade designation DOW 7 API Grade P220 green silicon carbide abrasive particles, having a median particle size of about 89 micrometers, available from Exolon-ESK Company, Tonawanda. NY, under the trade designation CGW-3 Asi amorphous silica, available from Degussa Inc., New York, NY, under the trade designation R-972 DS1227 a high molecular weight polyester, available from Creanova Inc., under the trade designation DYNAPOL SI 227 EB 3720 a diacrylate of a bispenol A epoxy resin having a molecular weight of about 524, available from UCB Chemical, under the trade designation of EBECRYL 3720 EP1 a bisphenol A epoxy resin, available from Shell Chemical, Houston TX, under the trade designation EPON 828 and having an epoxy equivalent weight of 185-192 g/eq EP2 a bisphenol A epoxy resin, available from Shell Chemical, under the trade designation of EPON 100 IF and having an epoxy equivalent weight of 525-550 g/eq ETMPTA ethoxylated trimethylolpropane triacrylate, available from Sartomer, under the trade designation SR351 HDDA hexanediol diacrylate, available from Sartomer, under the trade designation SR 238 1-369 2-benzyl-2-N,N-dimethylamino- 1 -(morpholinophenyl)-butan- 1 -one, photoinitiator, available from Ciba Geigy Corp., under the trade designation IRGACURE 369 1-651 free radical photoinitiator, available from Ciba Geigy, under the trade designation IRGACURE 651 RP1 a resole phenolic having 75 percent solids (non-volatiles) TPGDA tripropylene glycol diacrylate, available from Sartomer, under the trade designation SR 306 UV-893 acrylated urethane oligomer, available from Morton, under the trade designation UVITHANE 893 V-732 polyamide thermoplastic pellet, having a melting point of 105 °C by differential scanning calorimetry (DSC), available from Creanova, Inc., under the trade designation VESTAMELT 732 Cloth PCF filament polyester fill yarns and ring-spun polyester warp yarns (10.0 oz/sq yd (339g/m.2), sateen), available from Milliken PE polyester drills cloth (240 g/n -), available from Johnston Industries, Akron, OH PF polyester cloth woven with ring-spun yarns (8.43 oz/sq yd (286g/m2), sateen), available from Milliken Tencel jeans cloth (158 g/m^), dyed and stretched, available from Milliken Benchtop Procedure for Making Presized Backings Seventy grams of thermoplastic polyamide and 30 grams of acrylated oligomer were weighed into a glass container. The mixture was heated at 140 °C for about one hour, with occasional mixing by hand with a tongue depressor. After one hour the blend was easily mixed to form a viscous, homogeneous solution. One gram of photoinitiator was dissolved into the hot solution, and the material was immediately knife coated directly onto a backing; the knife and bed were both previously heated to 138 °C, and the knife gap was set at approximately 75 micrometers. After the coating had cooled to room temperature and solidified, the acrylated oligomer was crosslinked by exposure to ultraviolet light (2 passes under a 236 W/cm Fusion Systems "D" bulb at 14 m min). General Procedure 1 For Making Coated Abrasive Articles A presized backing was prepared using the above method. The abrasive slurry compositions used are described below in Table 2. A production tool was made by casting polypropylene material on a metal master tool having a casting surface comprised of a collection of adjacent truncated pyramids. The production tool contained cavities that were in the shape of truncated pyramids. The pyramidal pattern was such that their adjacent bases were spaced apart from one another no more than about 510 micrometers. The height of each truncated pyramid was about 80 micrometers, the base was about 178 micrometers per side and the top was about 51 micrometers per side. There were about 50 lines per centimeter delineating the array of composites. The backing associated with the presize coating was secured to a metal carrier plate using a masking type pressure sensitive adhesive tape. With the production tool secured to a flat surface, the abrasive slurry was coated into the cavities of the tool using a rubber squeegee such that the abrasive slurry completely filled the cavities. Next, the abrasive slurry contained in the cavities of the production tool was brought into contact with the backing that had previously been secured to the metal carrier plate. The production tool and backing were passed through rubber squeeze rolls to ensure that the abrasive slurry wetted the surface of the presize coating on the backing and to remove any undesired air bubbles. The article was cured by passing the tool together with the backing and binder precursor, at a speed of about 20 feet per minute (6.1 m/min), under two ultraviolet light medium pressure mercury bulbs, available from American Ultraviolet Company, Murray Hill, NJ. Each bulb operated at 400 watts/inch (158 watts/cm) and the radiation passed through the production tool. Upon exposure to the ultraviolet light, the curable abrasive composite layer was essentially converted into a cured abrasive composite layer. The abrasive composite layer, now adhered to the presized backing, was then removed from the cavities of the production tool. General Procedure 2 for Making Coated Abrasive Articles Coated abrasive articles were also prepared according to the following procedure: A presized backing was prepared as described above. A coatable mixture for producing a make coating for the backing was prepared by mixing 64 parts of 75 percent solids phenolic resin (RP1) (48 parts phenolic resin), 52 parts non-agglomerated calcium carbonate filler (dry weight basis), and 4.5 parts water to form a make coating which was 2 83 percent solids, with a wet coating weight of 239 g/m . The make coating was applied in each case via knife coating. Next, graded ceramic aluminum oxide particles were electrostatically coated onto the uncured make coating. Then, the resulting constructions received a precure of 20 minutes at 85 °C, followed by 70 minutes at 93 °C. A size coating comprising a conventional resole phenolic resin, a filler, and water was applied over the abrasive particles and the make coated via a two roll coater. The resulting product was cured at a temperature of 79 °C for 30 minutes, 88 °C for 75 minutes, and then at 100 °C for 10 hours. The resulting coated abrasive articles were single flexed, that is, passed over a one inch diameter (2.54 centimeters) roller at an angle of 90 ° to allow a controlled cracking of the make and size coatings. The coated abrasive articles were then converted into coated abrasive belts using commonly known methods. Test Methods: 90 Peel Test The coated abrasive sheet to be tested was converted into a sample about 8 centimeters wide by 25 centimeters long. One-half the length of a wooden board (17.78 centimeters by 7.62 centimeters by 0.64 centimeters thick) was coated with an adhesive. The entire width of, but only the first 15 centimeters of the length of, the coated abrasive sample was coated with an adhesive on the side bearing the abrasive material. The adhesive was 3M JET MELT Adhesive #3779 applied with a POLYGUN™ II glue applicator, both available from Minnesota Mining and Manufacturing Co, St. Paul, MN. Then, the side of the sample bearing the abrasive material was attached to the side of the board containing the adhesive coating in such a manner that the 10 centimeters of the coated abrasive sample not bearing the adhesive overhung from the board. Pressure was applied such that the board and the sample were intimately bonded and sufficient time was allowed for the adhesive to cure. For samples to be tested at 250 °F (121 °C), a filled phenolic adhesive such as that described in "General Procedure 2 for Making Coated Abrasive Articles" was utilized and cured for 6 hours at 100 °C. Next, the sample to be tested was scored along a straight line such that the width of the coated abrasive test specimen was reduced to 5.1 centimeters. The resulting coated abrasive sample/board composite was mounted horizontally in the lower jaw of a tensile testing machine having the trade designation SINTECH, and approximately 1 centimeter of the overhanging portion of the coated abrasive sample was mounted into the upper jaw of the machine such that the distance between jaws was 12.7 centimeters. The machine separated the jaws at a rate of 0.5 cm/sec, with the coated abrasive sample being pulled at an angle of 90 ° away from the wooden board so that a portion of the sample separated from the board. Preferably, separation occurs between the cloth treatments and the cloth. The machine charted the force per centimeter of specimen width required to separate the cloth from the treatment coating. The higher the required force, the better adhesion of the treatment coating to the cloth backing. The force required to separate the treatment was expressed in lbF/in-width. It is preferred that the force value be at least 10.2 lbF/in (17.8 N/cm), more preferably at least 11.2 lbF/in (19.6 N/cm), and even more preferably at least 16.8 lbF/in (29.4 N/cm), because inadequate adhesion and weakness at the make coat-backing interface will result in inferior performance particularly under use conditions. TABLE 1 shows the formulations of the presize compositions used in making the tested articles. TABLE 2 shows the formulations of the abrasive-binder slurries used to make the tested articles. TABLE 3 shows the presize formulation, slurry formulations, and cloth type used to make the tested articles. TABLE 4 shows the results of the stripback adhesion test performed on the articles described in TABLE 3. All of the backing materials were presized using the benchtop procedure above. Examples 1 - 4 and the comparative examples were prepared according to General procedure 1 and Examples 5 - 8 were prepared according to General Procedure 2. TABLE 1 Presize Compositions (Parts by Weight) 1 I TABLE 2 Slurry Compositions (Parts by Weight) TABLE 3 Coated Abrasive and Presized Backing Samples TABLE 4 Stripback Adhesion * Adhesion failure between the abrasive slurry coat and the presize coat. Examples 1 - 3 and 5 - 8 showed adhesion failure between the presize and the cloth backing material, which is preferred. All of the above examples of the invention provided good adhesion between the presize coating and the backing at room temperature.

Claims: What is claimed is: 1. A substrate for an abrasive article comprising: a) a backing; and b) a crosslinked treatment coat on the backing, said treatment coat is formed from a curable precursor composition comprising a mixture of: i) from about 25 to about 75 weight percent of an acrylated oligomer, ii) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer; wherein the sum of i) and ii) is 100 percent, and iii) a sufficient amount of a catalyst for the curable acrylated oligomer resin, said catalyst being stable at a temperature of mixing the components. 2. A curable precursor composition comprising a mixture of: a) from about 25 to about 75 weight percent of an acrylated oligomer; b) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer; wherein the sum of a) and b) is 100 percent; and c) a sufficient amount of a catalyst for the curable acrylated oligomer resin, said catalyst being stable at a temperature of mixing the components. 3. The substrate of claim 1 or the composition of claim 2, wherein the acrylated oligomer is difunctional or trifunctional. 4. The substrate or the composition of claim 3, wherein the acrylated oligomer is an acrylated epoxide, acrylated urethane, or a mixture thereof. 5. The substrate or the composition of claim 4, wherein the acrylated epoxide is an acrylate of bisphenol A, an acrylate of a novolak, an acrylate of epoxidized soya oil, or combinations thereof. 6. The substrate or the composition of claim 4, wherein the acrylated urethane is an hexafunctional acrylate of an aromatic urethane, a trifunctional acrylate of an aromatic urethane, an acrylate of an aliphatic urethane, or combinations thereof. 7. The substrate or the composition of claim 6, wherein the melting point of the thermoplastic polyamide ranges from about 95 to 150 °C as measured by DSC. 8. The substrate of claim 1 , wherein the backing is constructed from materials comprising vulcanized fiber, paper, nonwoven materials, woven materials, fibrous reinforced thermoplastic materials, polymeric films, metal foils, foams, or transfer coated multilayer constructions thereof. 9. The substrate of claim 1 or the composition of claim 2, wherein the thermoplastic polyamide is present in the binder precursor or the composition at a level of from about 30 to about 70 weight percent. 10. The substrate of claim 1 or the composition of claim 2, wherein the acrylated oligomer is present in the binder precursor or the composition at a level of from about 70 to about 30 weight percent. 11. The substrate of claim 1 or the composition of claim 2, wherein the catalyst is activated by ionizing radiation, ultraviolet radiation, or visible light radiation. 12. The substrate or the composition of claim 7, wherein the thermoplastic polyamide has a melt flow rate of from 10 to 90 g/10 min at 160 °C. 13. A composite backing comprising: a) a first backing layer; b) a second backing layer; and c) a cured composition bonding said first and second substrates together to form a composite backing, the cured composition comprising the reaction product of a mixture of: i) from about 25 to about 75 weight percent of an acrylated oligomer; ii) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer; wherein the sum of i) and ii) is 100 percent, and iii) a sufficient amount of a catalyst for the curable acrylated oligomer resin, said catalyst being stable at a temperature of mixing the components. 14. The composite backing of claim 13, wherein the acrylated oligomer is difunctional or trifunctional. 15. The composite backing of claim 13, wherein the acrylated oligomer is an acrylated epoxide, an acrylated urethane, or a combination thereof. 16. A method of making a coated or treated backing for an abrasive article comprising the steps of: a) coating a backing with a precursor composition comprising a mixture of: i) from about 25 to about 75 weight percent of an acrylated oligomer, ii) from about 75 to about 25 weight percent of a thermoplastic polyamide miscible in said acrylated oligomer; wherein the sum of i) and ii) is 100 percent, and iii) a sufficient amount of a catalyst for the curable acrylated oligomer resin, said catalyst being stable at a temperature of mixing the components; and b) curing said coating by exposing said coating to a source of radiation energy.

Inventors: DAHLKE GREGG D, FOLLENSBEE ROBERT A, PETERSON SCOTT W, DAHLKE, GREGG, D., FOLLENSBEE, ROBERT, A., PETERSON, SCOTT, W.
Applicants: 3M INNOVATIVE PROPERTIES CO, 3M INNOVATIVE PROPERTIES COMPANY
Application year: 1999
Main classification: C09D4
IPC codes: B24D3, B32B27, C08F299, C08J7, C08L77, C09D4, C09D133, C09D151, C09D155, C09D163, C09D175, C09D177