MXPA97002267A - Abrasive article coated, method for preparing it and method for using an abrasive article coated to submit abrasion a working piece d - Google Patents

Abstract

A coated abrasive article having a support and a coated abrasive layer on the first main surface of the support, wherein a cross section of the abrasive layer normal to the thickness and at the center point of the thickness has a total cross-sectional area of agglomerates abrasives which is substantially the same as at a point along the thickness which is 75% of a distance between the center point and the contact side; a coated abrasive article having a joint system with a Knoop hardness number at least 70, a coated abrasive article comprising abrasive agglomerates in the form of truncated truncated or cube pyramids, a method for manufacturing the coated abrasive article and a method for abrading a hard workpiece using an abrasive article coat

Description

ABRASIVE ARTICLE COATED, METHOD FOR PREPARING THE SAME AND METHOD FOR USING AN ABRASIVE ITEM COVERED TO SUBMIT A HARD WORK PIECE TO ABRASION FIELD OF INVEHION This invention pertains to a coated abrasive article having an abrasive layer suitable for abrading very hard workpieces, such as hardened steel, die-cast iron, ceramics and stone workpieces. as well as a method for manufacturing such a coated abrasive article. The invention also pertains to a method for using the abrasive article to abrade hard workpieces.

Abrasive articles made of abrasive particles are used to abrade and / or terminate a wide variety of materials, commonly known as workpieces, in a wide variety of applications. These applications vary from the removal of high pressure and high material by machining of metal forges to polishing of glasses. The abrasive particles, which may include grains and / or agglomerates, have a wide range of REF: 24283 properties which provide their application in the abrasive industry. The selection of a particular type of abrasive particle generally depends on the physical properties of the particles, the workpiece to be abraded, the properties of the surface to be obtained, the operating properties of the abrasive particles and the economy when selecting a particular abrasive particle for a specific application. Aluminum oxide, or alumina, is one of the most popular abrasive particles used in the production of coated abrasives, for example, sandpaper. Alumina is used for a large number of applications, such as sanding paint, grinding or grinding metal and polishing or burnishing plastic. Silicon carbide, also a popular abrasive, generally known as a more rigid mineral than alumina, is mainly used in woodwork, paint and glass grinding applications. Diamond and cubic boron nitride (hereinafter "CBN") commonly referred to as "superabrasives" are especially desirable for abrading very hard workpieces such as hardened steel, ceramics, die-cast iron, and diamond is typically preferred as superabrasive for non-ferrous materials, while CBN is typically preferred as a superabrasive for ferrous materials such as hardened steel. However, superabrasives such as diamond and CBN can cost up to 1000 times more than conventional abrasive particles, ie, aluminum oxide and silicon carbide. Therefore, it is desirable to use superabrasives as much as possible. As indicated above, the abrasive particles may be in the form of single grains or agglomerates. Abrasive agglomerates are particles composed of a plurality of unique abrasive grains that are held together by a binder. During the abrasion process, the agglomerates typically erode or decompose and are expelled using unique abrasive grains to expose new abrasive grains. The agglomerates can be used in abrasive products such as coated abrasives, non-woven abrasives and abrasive wheels and provide a long and useful life and efficient use of the abrasive particles. • U.S. Patent No. 2,001,911 discloses an abrasive article having a flexible support and numerous small portions of bonded abrasive material which are adhered to the support by a layer of flexible and elastic intermediate material. The bonded abrasive material consists of a plurality of abrasive blocks mounted on the support and separated from each other on their sides by narrow fissures. U.S. Patent No. 2,194,472 describes an abrasive article constituted of a support, which can; be flexible, and a coating of abrasive aggregates which are porous, angular and not flattened, and which are constituted by a plurality of unique abrasive grains joined together by a joining system. The preparation of an abrasive article may involve the search for aggregates to provide aggregate particles of a reasonably uniform size. U.S. Patent No. 3,986,847 discloses an abrasive article such as a grinding wheel having an abrasive section constituted of an abrasive phase and a vitreous bond. The abrasive phase comprises both CBN alone or in combination with a second abrasive grain having a coefficient of thermal expansion substantially the same as the thermal expansion coefficient of CBN. The vitreous bond is a glass-type joint that has a thermal expansion coefficient just as the thermal expansion coefficient of CBN. U.S. Patent No. 4,256,467 describes a flexible abrasive article comprising a mesh material that is not electrically conductive, flexible, and a layer of electrodeposited metal, which contains diamond abrasive material embedded therein, and which adheres directly and which it extends through the mesh material so that the mesh material is embedded in the metal layer. U.S. Patent No. 4,393,021 discloses a method for the manufacture of granular screaming particles in which the individual screams are mixed with a binding medium and a filling material to form a doughy mass. The dough can be extruded, heated to harden the dough and then the hardened product can be broken down into granular shred particles, each including several individual shouts. U.S. Patent No. 4,799,939 discloses an abrasive article comprising agglomerates that can be subjected to erosion containing individual abrasive grains placed in an erosive matrix comprising hollow bodies and a binder. Individual abrasive grains may include aluminum oxide, carbides such as silicon carbide, nitrides such as CBN, diamond and flint. Although the binder is preferably a synthetic organic binder, natural organic binders and inorganic binders can also be used. The agglomerates are typically irregular in shape but may be formed into spheres, spheroids, ellipsoids, granaya or granules, rods or other conventional shapes. U.S. Patent No. 4,871,376 discloses a coated abrasive comprising a support substrate, an abrasive material and a bonding system comprising a resinous adhesive, inorganic filler material and a coupling agent. The coupling agent can be selected from the group consisting of silane, titanate and zirconaluminate coupling agents. U.S. Patent No. 5,093,311 discloses an abrasive article comprising an abrasive granule that can be subjected to erosion, comprising a plurality of first abrasive grains that are held together by a first binder to form a base agglomerate that can be subjected to erosion , the base agglomerate is at least partially coated with second abrasive grains bonded to the periphery of the base agglomerate by a second binder. The first and second binders, which may be the same or different, may be organic or inorganic and may contain additives such as fillers, grinding aids, plasticizers, wetting agents and coupling agents. The first and second abrasive grains may be the same or different and may include aluminum oxide, silicon carbide, diamond, flint, CBN, silicon nitride and combinations thereof. The base agglomerate usually has irregular shape but can be formed into spheres, spheroids, ellipsoids, granules, rods or other conventional forms. U.S. Patent No. 5,152,917 discloses a coated abrasive article comprising a backing having at least one main surface and abrasive composite parts on at least one surface: main. The abrasive composite parts comprise a plurality of abrasive grains dispersed in a binder, which can also serve to join the abrasive composite parts to the support, and which has a predetermined shape, eg pyramidal. U.S. Patent No. 5,210,916 describes?An abrasive particle prepared by introducing a boehmite sol into a mold in which the mold cavities are of a specific shape, removing a sufficient portion of the liquid from the sol to form a precursor of the abrasive particle, removing the precursor from the mold , calcining the removed precursor and sintering the calcined precursor to form the abrasive particle. The mold cavity has a specific three-dimensional shape and can be a triangle, circle, rectangle, square or inverse pyramid, truncated pyramid, truncated sphere, truncated spheroid, conical or truncated cone shape.

U.S. Patent No. 5,314,513 discloses an abrasive article having a flexible substrate, at least one layer of abrasive grains bonded to the front side of the substrate by a manufacturing coating and optionally one or more additional coatings, wherein at least one of The coatings comprise a maleimide binder. U.S. Patent No. 5,318,604 discloses an abrasive article comprising abrasive elements dispersed in a binder matrix. The abrasive elements comprise individual particles of abrasive material, substantially all of which are partially embedded in a metal binder. The German patent number OS 2941298-Al, published on April 23, 1981, describes coated abrasive particles constituted of abrasive conglomerates, which have a rough and irregular surface, prepared by intensively mixing abrasive mineral grains with glass fritters and binder; process the mixture, press, dry and sinter the material; and then press the material to form the conglomerate. The American application serial number 08/085, 638 accurately describes shaped particles consisting of an organic-based binder and methods for making such particles. The organic base binder may contain a plurality of abrasive cries dispersed therein. Although abrasive articles are generally selected based on their physical properties and the desire to maximize the abrasion capacity and extend the service life of the abrasive article, particular considerations arise when the industry desires an abrasive article having a long life which can subject abrasive hard materials, such as cam shafts and crankshafts, for example, in a cam shafts stripper as described in U.S. Patent No. 4,833,834, while adapting to design tolerances that include providing a part of precision ground work.

BRBVB DaSGRIPCIQN DB THE IMVBMCIQW This invention, in one embodiment, provides a coated abrasive article constituted of a support having a first major surface; and an abrasive layer coated on the first main surface, the abrasive layer has a contact side adhered to its first main surface, an opposite side and a thickness which extends from the contact side to the opposite side, the abrasive layer comprises a binding system based on organic substances and a plurality of abrasive agglomerates adhered to the bonding system, each of the agglomerates comprises an inorganic binder and a plurality of abrasive grains, and have substantially uniform size and shape, in which a cross section of the abrasive layer normal to the thickness and at the center point of the thickness has a total cross-sectional area of abrasive agglomerates which is substantially the same as that of the point along the thickness which is at 75% of a distance between the central point and the contact side. In another embodiment, this invention provides a coated abrasive article comprising a support having a first major surface; and a layer of abrasive placed as a coating on the first main surface, the abrasive layer comprises a binding system based on organic substances, and a plurality of abrasive agglomerates distributed in the bonding system, each of the agglomerates comprises an inorganic binder and a plurality of abrasive grains and have the shape of a truncated four-sided pyramid. In a further embodiment, the invention provides a coated abrasive article comprising a support having a first major surface, and an abrasive layer applied as a coating on the first major surface, the abrasive layer comprising a union system based on organic substances, the joining system comprises a binder and particles of inorganic filler material and has an average Knoop hardness number of at least 70, and a plurality of abrasive agglomerates distributed in the bonding system, each of the agglomerates comprises an inorganic binder and a plurality of abrasive grains. The invention also provides a method for manufacturing a coated abrasive article comprising (a) providing a support having a first major surface; (b) forming an abrasive layer, the abrasive layer having a contact side adhered to the first main surface of the support, an opposite side and a thickness which extends from the contact side to the opposite side, in which a cross section of the abrasive layer normal to the thickness and at the center point of the thickness, has a total cross-sectional area of abrasive agglomerates which is substantially the same as that at a point along the thickness which is 75% of a distance between the center point and the contact side, comprising (1) applying a manufacturing coating comprising a first binder precursor based on organic substances to the first main surface of the support; (2) providing a plurality of abrasive agglomerates (i) comprising an inorganic binder and a plurality of abrasive grains, and (ii) having a substantially uniform size and shape; (3) distributing the agglomerate in the manufacturing liner; (4) exposing the manufacturing coating to an energy source to at least partially cure the first binder precursor; (5) applying a size coating comprising a second binder precursor based on organic substances on the abrasive agglomerates; and (6) exposing the sizing coating to a second source of energy to cure the second binder precursor and, optionally, completing the curing of the first binder precursor. The invention also relates to a method for abrading a hard workpiece having a Rockwell "C" hardness of at least 25, comprising (1) providing a coated abrasive article which comprises a support and an abrasive layer , the abrasive layer comprises a bonding system and abrasive agglomerates, and the agglomerates comprise (a) an inorganic metal oxide binder substantially free of free metal, and (b) abrasive grains substantially comprising superabrasive grains; (2) contacting the coated abrasive article with the workpiece under sufficient pressure to cause abrasion; and (3) moving the coated abrasive article and the workpiece one relative to the other.

Coated abrasive articles having the characteristics described above and the methods for preparing them result in excellent abrasion quality not previously recognized. In particular, it is surprising that the abrasive articles of this invention are efficient and effective for grinding hard workpieces. Customarily, hard workpieces such as steel are ground with joined wheels to obtain the desired work life, cutting speed and tolerances. Bonded abrasives have two main disadvantages compared to coated abrasives. The bonded abrasives need to be adjusted and checked to prevent the bonded abrasive from nicking and losing its effective cutting rate. Additionally, the bonded abrasives are rigid and are not flexible. This rigidity limits its use in certain abrasion applications. For example, it may be desirable to abrade a slight concavity on the back side of the lobe of a camshaft, which may not be accessible by a bonded abrasive. In contrast, the coated abrasive articles are flexible and can be used in this type of abrasion application. However, previously known coated abrasives are not considered suitable for abrading hard workpieces because they do not provide the proper duration. In contrast, the coated abrasive articles of this invention last a long time, provide good cutting speed and tolerances and are flexible.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an enlarged side view of a cross-sectional segment of a coated abrasive article according to the present invention having abrasive agglomerates in the form of a truncated four-sided pyramid. Figure 2 is an enlarged side view of a cross-sectional segment of another embodiment of the coated abrasive article according to the present invention having agglomerates in the form of cubes and a support of; fiber reinforcement.

DESCRIPTION T My? Ma? Ff TA Tf? VTPtT < ÍH With reference to Figure 1, a coated abrasive article 10 of the invention comprises a support 11 having a fabrication liner 12 present on a first main surface 18 of the support. A plurality of abrasive agglomerates 13 adhere to the manufacturing liner. The manufacturing liner serves to join the abrasive agglomerates to the support. The abrasive agglomerates comprise a plurality of abrasive grains 14 and an inorganic metal oxide binder. In this particular embodiment, the abrasive agglomerates have the shape of a four-sided truncated pyramid. The sizing coating 16 is found on the abrasive agglomerates. One purpose of the sizing review is to strengthen the adhesion of the abrasive agglomerates in the support. The manufacturing coating, the size coating and the abrasive agglomerates in this particular embodiment form an abrasive layer 17. With reference to Figure 2, a coated abrasive article 20 of the invention comprises a support 21 having a manufacturing liner 22 which joins agglomerates 23 in the form of cubes on a first main surface 28 of the support. In this particular embodiment, the support comprises reinforcing fibers 29 and therefore, it is a support of low tension or low stretch capacity. The abrasive agglomerates comprise a plurality of abrasive grains 24 and inorganic metal oxide binder. On the abrasive agglomerates is the sizing coating 26. The manufacturing liner, the sizing coating and the abrasive agglomerates in this particular embodiment form an abrasive layer 27.

Each element of the modalities described above will be described individually below.

Support The support used in an abrasive article of the invention has at least two major surfaces. The surface on which the abrasive layer is coated can be referred to as the first major surface. Examples of typical supports include polymer film, prepared or stabilized polymeric film, raw material, fabric or cloth, paper, vulcanized fiber, non-woven materials and treated versions and / or combinations thereof. The support can additionally be constituted by optional additives, for example fillers, fibers, antistatic agents, lubricants, wetting agents, surfactants, pigments, dyes, coupling agents, plasticizers and agents that improve the suspension. The quantities of these optional materials depend on the desired properties. In general, it is preferred that the support has a strength and that it supports the heat sufficiently to be able to withstand its process conditions and use under abrasive conditions. Additionally, if the abrasive article is considered to be used in a wet or lubrication environment, preferably the support has sufficient resistance to water and / or oil and is obtained by treating the support with a thermosetting resin, such as a phenolic resin, which can optionally be modified with rubber, an epoxy resin, which can optionally be modified with a fluorene compound and / or a bismaleimide resin, so that it does not degrade during abrasion. A preferred support of the invention is a fabric or fabric backing. The genre is usually made up of yarns in the warp direction, that is, the machine direction and the yarns in the loading or filling direction, ie, the transverse direction. The gender support can be a woven fabric support, a knitted support, a fabric support joined by stitching or a weft insertion fabric support. Examples of woven constructions include four satin fabrics on a weave of the warp yarns on the weft yarns (oe weft), three weave weave on a woven fabric or one weave one on one, and a drill or denim fabric, on two fabrics. In a fabric joined by stitching or weft insertion support, the warp and weft or load yarns are not interwoven, but are oriented in two different directions from each other. The warp threads are on top of the load yarns and are fixed together by a sewing thread or by an adhesive. The threads in the gender support can be natural, synthetic or combinations thereof. Examples of natural yarns include cellulosic material such as cotton, hemp, kapok or miraguano, flax, sisal, jute, carbon, manila hemp and combinations thereof. Examples of synthetic yarns include polyester yarns, polypropylene yarns, glass yarns, polyvinyl alcohol yarns, polyaramide yarns, polyimide yarns, aromatic polyamide yarns, rayon yarns, nylon yarns, polyethylene yarns and combinations of the same. Preferred yarns of this invention are polyester yarns, nylon yarns, polyaramide yarns, a mixture of polyester and cotton, rayon yarns and aromatic polyamide yarns. The fabric support can be dyed and stretched, dimensioned or stretched by heat. Additionally, the yarns in the fabric support may contain primer materials, pigments or wetting agents and may also be twisted or textured. Polyester yarns are usually formed from a long chain polymer produced by reacting an ester of dihydric alcohol and terephthalic acid. Preferably, this polymer is linear poly (ethylene terephthalate). There are three main types of polyester yarns: ring spinning, open end and filament yarns. A ring spinning yarn is typically manufactured by continuously removing a polyester yarn, twisting the yarn and winding the yarn in a spool. An open end yarn is usually made directly from a loading belt or a wick, i.e., a series of polyester wicks are opened and then all the wicks are held together in a continuous spinning apparatus to form a continuous thread. A filament yarn is usually a long continuous fiber and has little or no torsion of the polyester fiber. The denier of the fibers of a gender support is usually less than about 2000, preferably ranging from about 100 to 1500. For a coating of coated abrasive fabric, the weight of the raw fabric, ie, the untreated fabric, generally ranges from about 0.15 to 1 kg / m2, preferably from about 0.15. up to 0.75 kg / m2. The support may have an optional saturating coating, pre-sizing coating and / or a support sizing coating to seal the support and / or protect the threads or fibers in the support. The addition of the saturant coating, the pre-sizing coating and / or the support sizing coating can additionally result in a smoother surface on either the front or rear side of the support. The treatment of sizing supports is described further in the North American application serial number 07 / 903,360. These coatings are generally constituted by a resin binder precursor. Examples of such precursors include phenolic resins which include rubber-modified phenolic resins, epoxy resins, which include fluorene-modified epoxy resins, and aminoplast resins having pendant alpha, beta unsaturated carbonyl groups. After coating, these binder precursors are converted into thermoset binders by exposing them to a source of energy, usually heat. An inorganic filler material can also be incorporated into the resin. Examples of such fillers include calcium carbonate, clay, silica and dolomite. If the support is a gender support, preferably at least one of these three coatings is present and preferably the coating comprises a heat resistant organic resin. After either the saturant coating, the support sizing coating or the short coating to the sizing which are applied to the support, the resulting support can be exposed to conditions to at least dry and / or solidify the support treatment, for example through heat. For example, during the heating, which can be dry and / or to carry out the reticu.Late of the binder precursor, the resulting fabric can be placed in a stretcher frame. The stretch frame tends to minimize any shrinkage and keeps the pressed fabric. Additionally, after the support is heated, it can be processed through heating rolls to calender the support. This calendering step can help smooth the surface roughness associated with the backing. The support used in an abrasive article of the invention is preferably a low tension support. A low tension support allows a longer and / or more complete use of the abrasive material. When the coated abrasive article contains superabrasive grains, preferably the support is of low tension so that full utilization of the superabrasive grains can be obtained. If the support is stretched too much, the article may be subjected to traction inappropriately, for example, if the article is an abrasive belt running on drive wheels and / or free, and the full use of superabrasive grains within the agglomerates Can not be obtained.

The term "low tension" refers to the support itself before applying a bonding system and abrasive material. A low tension support results in a coated abrasive strip that can abrade a work piece for a period of time which is usually longer than that observed with conventional supports, without undue stretching in the machine. The concept of "low tension or low stretch capacity" can be defined by a measurement of a tension or stretch test in which the percentage of stretch of the support taken 45 kg / 2.5 cm (100 pounds / inches) (using a bandwidth) is generally less than 10%, usually less than 5%, preferably less than 2% and more preferably less than 1%. More preferably, the percent tension is less than 0.5%. The following procedure indicates the tensile test in which the support is tested before the application of any portion of the bonding system or abrasive material.

Stress Test The support, in the direction of the machine, becomes a strip of 2.5 cm by 17.8 cm. The strip is installed in a voltage tester, for example, a Sintech machine, available from Systems Integration Technology, Inc., Stoughton, Mass., And the samples are pulled in the machine direction. The stretch percent to 45 kg (100 pounds) is measured and calculated by the following equation: sample length taken at 45 ks (100 lbs) - original length of the sample X 100 original length of the sample A more preferred support of the coated abrasive article of this invention includes a laminate of polyester fabric woven with satin, with reinforcing fibers. The polyester fabric can be separated together to form an endless belt. The transferred splice has butt ends in a plane to define a line that is in the form of a sine wave with the line being covered with a reinforced woven polyester tape. The polyester fabric is considered to provide good adhesion to a bonding system based on organic substances and abrasive particles or agglomerates, thereby minimizing peeling or delamination, ie the premature release of abrasive particles or agglomerates. , which is usually undesirable and can shorten the life of the coated abrasive. Generally, the reinforcing fibers are laminated with a strong, heat-resistant, laminating adhesive, and the polyester fabric contains a treatment of saturant material in phenolic-based support size. The reinforced polymeric splice tape comprises polyester or polyaramide reinforcing threads embedded in a polyester film and generally has a thickness of less than about 0.025 cm (0.010 inches). For example, reinforcing fibers or threads can be laminated to the support side of the polyester fabric web, as described in US Pat. No. 03 / 199,835, and can be applied in a continuous manner on the backing side of the web. the genre band. Generally, the purpose of the reinforcement yarns is to increase the tensile strength and minimize the stretch associated with the support. Preferred examples of reinforcement include polyaramide fibers, for example polyaramide fibers having the commercial designation "Kevlar" manufactured by E. I. DuPont, polyester yarns, yarns of / idrio, polyamide yarns and combinations thereof. Preferably, the splices and joints are not associated with the reinforcing threads so that the reinforcement threads serve to provide rigidity to the splice in minimizing the break in the splice.

Union System The joining system is a joining system based on organic substrates which can be formed, for example, of an abrasive suspension, of at least two adhesive layers, the first of which will be mentioned below as the "coating". of manufacture ", and the second of which will be mentioned as the "sizing coating". The abrasive suspension can be constituted by a strip of abrasive particles and is preferably homogeneous. Typically, fabrication and sizing coatings are formed from binder precursors based on organic substances, for example resins. The precursors used to make the manufacturing coating may be the same as or different from those used to make the sizing coating. By exposing it to appropriate conditions, such as an appropriate energy source, the resin polymerizes to form a cross-linked thermosetting polymer or binder. Examples of typical resinous adhesives include phenolic resins, aminoplast resins having outstanding carbonyl, alpha, beta unsaturated groups, urethane resins, epoxy resins, ethylenically unsaturated resins, acrylated isocyanurate resins, urea-formaldehyde resins, isocyanurate resins, resins acrylated urethane, acrylated epoxy resins, bismaleimide resins, fluorine modified epoxy resins and mixtures thereof. Epoxy resins and phenolic resins are preferred. Phenolic resins are widely used as binder precursors due to their thermal properties, availability, costs and ease of handling. There are types of phenolic resins, phase A and novolac resins. Phenolic resins of the phase A resin type usually have a molar ratio of formaldehyde to phenol of greater than or equal to one to one, usually between 1.5: 1 to 3: 1. Novolac resins typically have a molar ratio of formaldehyde to phenol of less than one to one. Examples of commercially available phenolic resins include those known by the trade names "Durez" and "Varcum" available from Occidental Chemicals Corp.; "Resinox" available from Monsanto; and "Arofene" and "Arotap" available from Ashland Chemical Co. The aminoplast resins typically have at least one alpha, beta unsaturated carbonyl group pendent per molecule or oligomer. Aminoplast resins include those described in U.S. Patent Nos. 4,903,440 and 5,236,472.

The epoxy resins have an oxirane ring and are polymerized by ring opening. Suitable epoxy resins include monomeric epoxy resins and polymeric epoxy resins and may have major structures and substitute groups:? Tes variables. In general, the main structure may be of any type usually associated with epoxy resins, for example bis-phenol A, and the substituent groups may include any free group of an active hydrogen atom that is reactive with the oxirane ring. room temperature. Representative examples of suitable substituent groups include halogens, ester groups, ether groups, sulfonate groups, siloxane groups, nitro groups and phosphate groups. Examples of preferred epoxy resins include 2,2-bis [4- (2,3-epoxypropoxy) -phenyl] propane (a diglycidyl ether of bisphenol) and materials commercially available under the trade designation "Epon 828" "Epon 1004" , and "Epon 1001F" available from Shell Chemical Co., and "DER-331", "DER-332" and "DER-334" available from Dow Chemical Co. Other suitable epoxy resins include glycidyl ethers of phenolformaldehyde novolak, by example, "DEN-431" and "DEN-428" available from Dow Chemical Co. Ethylenically unsaturated resins include both monomeric and polymeric compounds containing carbon, hydrogen and oxygen atoms and, optionally, nitrogen and halogen atoms. The oxygen or nitrogen atoms, or both, are generally present in the ether, ester, urethane, amide and urea groups. Preferably, the ethylenically unsaturated compounds have a molecular weight of less than about 4,000 and preferably are esters made from the reaction of compounds containing aliphatic monohydroxy groups or polyhydroxy aliphatic groups and unsaturated carboxylic acids such as acrylic acid, methacrylic, itaconic acid, crotonic acid, isocrotonic acid and maleic acid. Representative examples of acrylate resins include methyl methacrylate, ethyl methacrylate styrene, divinylbezene, vinyltoluene, ethylene glycol diacrylate, ethylene glycol methacrylate, hexanediol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, methacrylate. of pentaerythritol, pentaerythritol tetraacrylate and pentaerythritol tetraacrylate. - Other ethylenically unsaturated resins include monoalicylic, polyallylic and polymethalilic esters and amides of carboxylic acids such as diallyl phthalate, diallyl adipate and N, N-diallyladolidyl amide. Other suitable nitrogen-containing compounds include tris (2-acryloyloxyethyl) isocyanurate, 1,3,5-tri (2-methyl-acryloxyethyl) -s-triazine, acrylamide, methylacrylamide, N-methylarylamide, N, N-dimethylacrylamide, N- vinylpyrrolidone and N-vinyl;? iperidone. The acrylated urethanes are diacrylate esters of polyesters or polyethers extended in NCO, terminated in hydroxy. Examples of commercially available acrylated urethanes include "Uvithane 782", available from Morton Thiokol Chemical, and "CMD 6600" "CMD 8400" and "CMD 8805" available from Redcure Specialties. The acrylated epoxies are diacrylate esters of epoxy resins, such as bisphenol A epoxy resin diacrylate esters. Examples of commercially available acrylated epoxies include "CDM 3500" "CDM 3600" and "CDM 37 DO" available from Radcure Specialties. The joining system, for example, the manufacturing or sizing coating of this invention, may additionally be constituted by optional additives such as, for example, fillers (including grinding aids), fibers, antistatic agents. , lubricants, wetting agents, surfactants, pigments, dyes, coupling agents, plasticizers and agents that improve the suspension. The amounts of these materials can be selected to provide the desired properties.

Examples of fillers useful for this invention include metal carbonates (such as calcium carbonate (e.g., chalk or chalk, calcite, calcareous clay, travertine, marble and lime), magnesium carbonate and calcium, sodium carbonate and carbonate. of magnesium); silica (such as quartz, glass spheres, glass bubbles and glass fibers); silicates (such as talc, clays (for example montmorillonite), feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate); metal sulfates (such as calcium sulfate, barium sulfate, sodium sulfate, sodium aluminum sulfate, aluminum sulfate); cast; vermiculite; sawdust; aluminum trihydrate; carbon black, metal oxides (such as calcium oxide (lime), aluminum oxide (alumina) and titanium dioxide); and metal sulfites (such as calcium sulfite). The filler material typically has an average particle size ranging from about 0.1 to 100 microns, preferably between 1 and 50 microns, more preferably between 1 and 25 microns. Suitable grinding aids include particulate material, the addition of which has a significant effect on chemical and physical abrasion processes which result in improved performance.

In particular, a grinding assistant must: 1) reduce the friction between the abrasive grains and the work piece that is being subjected to abrasion, 2) prevent the abrasive grain from causing clogging, that is, prevent metal particles from welding to the top of the abrasive grains, 3) decrease the interface temperature between the abrasive grains and the workpiece and / or 4) decrease the grinding forces. In general, the addition of a grinding aid increases the life of the coated abrasive. The grinding aids cover a wide variety of different materials and can be inorganic or organic based. Examples of grinding aids include waxes, organic halide compounds, halide salts and metals, as well as their alloys. The organic halide compounds usually decompose during abrasion and release a halogen acid compound or a gaseous halide. Examples of such materials include chlorinated waxes such as 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. Examples of other grinding aids include sulfur, organic sulfur compounds, graphite and metal sulfides. A combination of different grinding aids may be used, including, for example, a combination of potassium tetrafluoroborate and a halogenated polymer as described in US Application Serial No. 08 / 213,541. The examples mentioned before grinding aids are only a representative sample of grinding aids and does not mean that all grinding aids are covered. Examples of antistatic agents include graphite, carbon egro, vanadium oxide, humectants and the like. These antistatic agents are described in U.S. Patent Nos. 5,061,294; 5,137,542; and 5,203,884. A joining system of this invention, for example, the fabrication coating and the sizing coating, generally have a Knoop hardness number (KHN) of at least 50 KHN (which can also be expressed in units of kgf / mm2). ), typically of at least about 60 KHN, preferably at least about 70 KHN, more preferably at least about 80 KHN, and much more preferably at least about 90 KHN, measured in accordance with ASTM E384-89, in order to be able to withstand the grinding forces without disintegration. Generally speaking, if the joining system comprises fabrication and sizing coatings, at least one of the fabrication and sizing coatings may be constituted with about 5 to 95 parts by weight, preferably 30 to 70 parts by weight of a binder precursor, for example, a thermosetting resin, and between about 5 and 95 parts by weight, preferably 30 to 70 parts by weight of a filler material. If the bonding system comprises an abrasive suspension, the amount of binder precursor can vary from 5 to 95% by weight and the amount of filler material can vary from 5 to 95% by weight, based on the weight of 1. a abrasive suspension. For example, preferred Knoop hardness numbers vary for the bonding system, i.e., preferably at least 70 KHN, more preferably at least 80 KHN, and most preferably at least 90 KHN, which can be obtained by the presence of particles of filler material which are described above. The filler particles will harden the cured thermosetting resin and provide rigidity to the bonding system, for example, the fabrication or sizing coating. The amount of filler particles and the presence of a coupling agent help control the Knoop hardness of the bonding system. In order to achieve the preferred Knoop hardness values, a coupling agent may be present in the filler material and / or in the abrasive particles. The coupling agent provides an association bridge between the joining system and the filler material and / or the abrasive particles. Examples of suitable coupling agents include organosilanes, zircoaluminates and titanates. The coupling agents are usually present in an amount ranging between about 0.1 and 5% by weight, preferably 0.5 and 3.0% based on the total weight of the filler material and the abrasive agglomerates. Preferably, a filler material as described above, can be pretreated with a coupling agent, for example, an organosilane coupling agent. This type of coupling agent is commercially available from Union Carbide under the trade designation "A-1100". More preferably, the particles of calcium metasilicate filler material and alumina filler particles can be pretreated with a silane coupling agent. Alternatively, the coupling agent can be added to a mixture of resin and filler. Although a combination of filler particles can be used, it is preferred to use only calcium metasilicate particles. The treatment with a coupling agent can improve the adhesion between the bonding system and the abrasive particles. Additionally, the presence of the coupling agent tends to improve the rheology of a binder precursor, for example, comprising a phase A resin phenolic resin and particles of calcium metasilicate filler material. In particular, in order to obtain a Knoop hardness of at least 70 KHN, the joining system preferably contains 50 to 90 parts by weight of filler material and from 0.2 to 50 parts by weight of a coupling agent, based on the weight of the union system. For example, it can be made up of 35 parts by weight of a crosslinked phase A resin phenolic resin and 65 parts by weight of calcium metasilicate and particles of alumina filler to make the sizing and / or sizing coating. , which have been pretreated with 0.5 petals by weight of a coupling agent, based on the weight of the manufacturing and / or sizing coating. If a combination of particles is used, for example calcium and alumina metasilicate filler particles, the average particle size can vary from 0.2 to 50, preferably from 1 to 25, and more preferably from 2 to 10 microns.

Peripheral Coating Layer The joining system can be constituted by a peripheral coating layer. For example, if the joining system comprises a fabrication coating and a sizing coating, the peripheral coating layer, also known as a supersize coating, can be coated on the sizing coating of the peripheral coating layer which may be coated on an abrasive suspension. The peripheral coating layer can be formed of a binder precursor based on an organic substance, for example, resins, as described for the manufacturing and sizing coatings, and can be constituted by a grinding aid. Suitable grinding aids include those described above for the joining system. "For example, a peripheral coating layer can comprise particles of potassium tetrafluoroborate distributed through a cross-linked epoxy resin.The peripheral coating layer is usually applied as roller or spray coating on the cured sizing coating or the suspension is separately cured from the sizing / abrasive coating suspension.

Abrasive Particles The abrasive particles used in the coated abrasive articles of this invention include agglomerates comprising a plurality of abrasive grains bonded by an inorganic binder to form a defined mass. The abrasive agglomerates, as opposed to the individual abrasive grains in an abrasive article, provide the advantage of a longer duration, since the abrasive agglomerate is made up of a multitude of aoreive grains. During use, worn and used abrasive grains are expelled from the abrasive agglomerate, whereby new fresh abrasive grains are exposed. Useful abrasive agglomerates generally have an average particle size ranging from about 20 to about 3000 microns, preferably between 50 to 2000 microns and more preferably between 200 to 1500 microns. Each of the abrasive agglomerates comprises an inorganic binder and a plurality of abrasive grains. Examples of suitable abrasive grains include those made of fused aluminum oxide, aluminum ceramic oxide, aluminum oxide heat treated, silicon carbide zirconia alumina, ceria, garnet, boron carbonitride, boron oxides in the form of Bs0. and B10O, diamond, CBN and combinations thereof. Examples of ceramic aluminum oxide are described in the following U.S. Patent Nos. 4,314,827; 4,770,671, 4,744,802; 4,881,951; 5,011,508; 5,139,978; 5,164,348; 5,201,916; and 5,213,591. Preferably, the abrasive grains are "superabrasive" grains or consist substantially of "superabrasive grains". "Superabrasive" grains typically have a hardness of at least about 35 GPa, preferably, at least about 40 GPa, for example diamond, CBN, or combinations thereof. Preferably, the abrasive grains are CBN. The term "substantially comprised" used to describe the superabrasive grains means that at least 30%, preferably 50%, more preferably 75% and up to 100% of the abrasive grains are superabrasive grains. The superabrasive grains are especially effective in abrading very hard workpieces such as hardened steel, ceramic materials, die-cast iron and stone. Super-abrasive grains, both diamond and CBN, are usually available from many commercial sources such as, for example, General Electric, American Boarts Company, and DeBeers. In particular, diamond grains can be manufactured naturally or synthetically. CBN is manufactured synthetically and is available from General Electric Corp., under the commercial designation "Borazon". There are several types of diamond and CBN available, each with different qualities. Hardness, stiffness, mono or multicrystalline condition, natural or synthetic condition and grain or particle shape may vary. The abrasive grains typically have a particle size ranging from about 0.1 to 1500 microns, preferably between about 1 and 1300 microns. The particle size of the abrasive grains is generally determined by the desired rate of cuts and the surface finish to be produced by the coated abrasive. Since the agglomerates comprise the abrasive grits, the particle size of the abrasive grains in a given agglomerate is substantially smaller than the particle size of the agglomerate so that the agglomerates can comprise a plurality of abrasive grains. The abrasive grains of this invention may also contain a surface coating. Surface coatings are known to improve the adhesion between the abrasive grain and the binder in the agglomerate and between the agglomerate and the bonding system and, therefore, improve the abrasion characteristics of the abrasive / agglomerated grains. Suitable surface coatings include those described in U.S. Patent Nos. 1,910,444, 3,041,156; 5,009,675; 4,997,461, 5,011,508; 5,213,591; and 5, 042, 991. For example, the diamond and / or CBN may contain a surface treatment, for example, a metal or metal oxide to improve adhesion to the inorganic binder in the agglomerate. In addition, a coating, such as a thin nickel layer, may be present on the abrasive grain. Examples of the inorganic binder include inorganic metal oxides such as vitreous binders, vitrea ceramic binders and ceramic binders. Preferably, the inorganic metal oxide binder is substantially free of free metals. The term "free metal" means elemental metal, and the term "substantially free" typically means that it no more gives about 1%, preferably 0.5%, more preferably 0.25%, and less than, and even 0% of the free metal, by weight, based on the total weight of the inorganic metal oxide binder, is present in the inorganic metal oxide binder.

Examples of inorganic metal oxides include silica or silicon oxide, silicates, alumina or aluminum oxide, sodium or sodium oxide, calcium or calcium oxide, potassium or potassium oxide, titania or titanium oxide, iron oxide, oxide of zinc, lithium oxide, magnesia or magnesium oxide, boria or borium oxide, lithium aluminum silicate, borosilicate glass and combinations thereof. Preferably, the inorganic metal oxides are lithium aluminum silicate and borosilicate glass. Inorganic binders can be prepared by melting a milled mixture of metal oxides and then cooling the melt to form a solid glass; the glass is then milled to form a fine powder. Preferably, the coefficient of thermal expansion of the inorganic binder is the same or substantially the same as that of the abrasive grains. When the coefficient of thermal expansion of the inorganic binder is the same or substantially the same as that of the abrasive grains, there is a more uniform shrinkage of both the individual abrasive grains and the inorganic binder during the manufacture of the abrasive agglomerate (eg, during the process of vitrification), which results in less internal stresses at the inorganic binder / abrasive grain interface, which in turn minimizes any premature breakage of the agglomerates. The term "substantially" refers to the coefficient of thermal expansion and typically means that there is a difference of less than about 80 percent, preferably a difference of less than about 50 percent, and more preferably a difference of less than about 30 percent. percent in the coefficient of thermal expansion of the binder and the coefficient of thermal expansion of the abrasive grains. This embodiment is additionally preferred when the inorganic binder is a vitrified binder. For example, CBN has a thermal expansion of approximately 3.5 x 10 ~ 6 / ° C. A suitable vitreous binder can have a thermal expansion which differs from the thermal expansion of CBN by less than about 80%, that is, from about 2.8 x 10"6 / ° C to 4.4 x 10-" 7 ° C. Vitrified agglomerate comprising abrasive grains and a vitreous binder, the binder, before being subjected to vitrification, is preferably milled so that the resulting powder is passed through a 325 mesh screen. For example, a glassy binder preferred comprises, by weight, 51.5% silica, 27.0% boria, 8.7% alumina, 7.5% magnesia, 2.0% zinc oxide, 1.1% calcium, 1.0% sodium oxide, 1.0% oxide, potassium and 0.5% lithium oxide. The addition of Boria can improve the adhesion of the CBN abrasive grains. In general, each abrasive agglomerate will be constituted, by weight, between about 10 to 80%, preferably between about 20 to 60% of inorganic agglutinate and between about 20 to 90%, preferably between about 40 to 80% of abrasive grains, based on the weight of the agglomerate. The abrasive agglomerates may additionally contain other additives such as fillers, grinding aids, pigments, adhesion promoters and other processing materials. Examples of fillers include small glass bubbles, solid glass spheres, alumina, zirconia, titania and metal oxide fillers, which can improve the erosion capacity of the agglomerates. Examples of grinding aids include those described above. Examples of pigments include iron oxide, titanium dioxide and carbon black. Examples of processing materials, i.e. processing aids, include temporary organic binder and liquids. The liquids can be water, an organic solvent or combinations thereof. Examples of organic solvents include alkanes, alcohols such as isopropanol, ketones such as methyl ethyl ketone, esters and ethers. Examples of temporary organic precursors, which can be used to make a homogeneous flowable mixture that can be processed easily include thermoplastic and thermosetting binders such as waxes, polyamide resins, polyester resins, phenolic resins, acrylate resins, epoxy resins, urethane resins and urea / formaldehyde resins. Based on the chemistry of the selected inorganic binder, a curing agent or crosslinking agent may also be present together with the temporary organic binder precursor. The temporary organic binder aids in the shaping process of the abrasive agglomerate. During the vitrification process, the temporary organic binder decomposes, leaving gaps or voids in the abrasive agglomerates. The abrasive agglomerates preferably contain a coating of inorganic particles. The coating results in an increased surface area, whereby the adhesion between the bonding system and the abrasive agglomerates is improved. Examples of inorganic particles for coating agglomerates include fillers and abrasive grains, for example, metal carbonates, silica, silicates, metal sulfates, metal carbides, metal nitrides, metal borides, gypsum, metal oxides, graphite and metal sulfites. . Preferably, the inorganic particles are abrasive grains, more preferably the same abrasive grains as in the abrasive agglomerate. The abrasive grains for the coating can also be selected from those described above in the discussion of the abrasive grains. The inorganic particles may have the same: particle size as the abrasive grains in the abrasive agglomerate, or they may be larger or smaller than the abrasive grains. Preferably, the inorganic particles have a size ranging from about 10 to 500, more preferably from 25 to 250 microns. The abrasive agglomerate may also be encapsulated with an organic or inorganic coating. Therefore, the joining system, for example the manufacturing and / or sizing coatings, only penetrate a minimum portion into the encapsulated abrasive agglomerate. In one embodiment, each of the agglomerates comprises an inorganic binder and a plurality of abrasive grains, and has a substantially uniform size and shape. When referring to the size and shape of the agglomerate, the phrase "substantially uniform" means that the size and shape of the agglomerates do not vary by more than 50%, preferably 40%, more preferably 30%, and much more preferable 20% with respect to the size and average shape of the agglomerates. Preferably, each of the agglomerates comprises an inorganic binder and a plurality of abrasive grains, and is in the form of a truncated four-sided pyramid or cube.

Abrasive Coat The abrasive layer as described above comprises a bonding system based on organic substances and a plurality of abrasive agglomerates. The abrasive layer which is coated on the first main surface of the support therefore has a side which adheres to the first main surface (a "contact" side) and an opposite side. The thickness of the abrasive layer extends from the contact side to the opposite side and is an imaginary line defining the shortest distance between the contact side and the opposite side. In one embodiment, a cross section of the abrasive layer normal to the thickness and at the center point of the thickness having a total cross-sectional area of abrasive agglomerates which is substantially the same as at the point along the thickness which is 75% of a distance between the center point and the contact side. ("75% of a distance between the center point and the contact side" is calculated from the center point to the contact side). The phrase "cross-sectional area of abrasive agglomerates" refers to the amount of abrasive agglomerates available to contact a workpiece within a cross-section of the abrasive layer. When reference is made to the total cross-sectional area of agglomerates, the term "substantially" means that the total cross-sectional area of the abrasive agglomerates at the center point of the thickness will not vary more than 40%, preferably not more than 30. %, more preferably no more than 20% and much more preferably no more than 10% from the point which is 75% of the distance between the center point and the contact side of the abrasive layer.

Adjustment and Rectification The abrasive article is preferably ground and adjusted before abrading and can be adjusted and grinded at intervals during the abrasion process. The adjustment is a process which eliminates the bonding of the abrasive particles and provides empty spaces for abrasion. Rectification is a process which levels or equalizes the abrasion surface resulting in a more strict tolerance during abrasion. The rectification and adjustment of the coated abrasives of this invention can be carried out, for example, as described in WO 93/02837. For example, a means of knitting. which has a width at least substantially equal to the width of the supports of the coated abrasive articles to be adjusted and which has a cutting surface constructed of a harder material than the abrasive grains can be used to cut lifts the abrasive particles to form generally coplanar surfaces, generally parallel to the support surface. The cutting means may have surfaces constructed of diamonds, boron nitride or any other suitable cutting material in the medical field in which the material is harder than the abrasive grains. A multi-point cutting means can be used to substantially reduce the time required to adjust a coated abrasive when compared to the time required to adjust a coated abrasive with a single-point cutting tool. The cutting surfaces of the cutting machine can be separated from the same separation, whatever it may be, on a work piece, if this is appropriate.

Method for Making an Abrasive Agglomerate A method for manufacturing an abrasive agglomerate useful in the present invention comprises, for example, mixing starting materials comprising an inorganic binder precursor, abrasive grains and a temporary organic binder precursor. The temporary organic binder precursor allows the mixture to adapt more easily and retain its shape during further processing. Optionally, other additives and processing aids can be used, as described in the above, for example inorganic fillers, grinding materials and / or a liquid medium. These initial materials can be mixed together by any conventional technique which results in uniform mixing. Preferably, the abrasive grains are carefully mixed with a temporary organic binder precursor in a mechanical mixing device such as a planetary mixer. The inorganic binder precursor is then added to the resulting mixture and stirred until a homogenous mixture is obtained, usually 10 to 30 minutes. The mixture is then shaped and processed to form agglomerated precursors. The mixture can be formed, for example, by molding, extrusion or troqu cut 1. Usually there will be some shrinkage associated with the loss of the temporary organic binder precursor and the inorganic binder precursor, and this shrinkage should be considered when determining the shape and size initials. The conformation process can be carried out in a batch process or in a continuous manner. A preferred technique for forming the abrasive agglomerate is to place the initial materials, which have been combined and formed into a homogeneous mixture, in a flexible mold. For example, if abrasive agglomerates are formed in the form of a truncated pyramid, the mold will be printed * on this form. The flexible mold can be any mold which allows an easy release of the particles, for example, a silicone mold. Additionally, the mold can contain a release agent to aid in detachment. The mold, which contains the mixture is then placed in an oven and heated to remove at least partially any liquid. The temperature depends on the temporary organic binder precursor, and is typically between 35 and 200 ° C, preferably between 70 and 150 ° C. The mixture dries at least partially after it is removed from the mold. It is also possible to completely destroy, i.e., remove by chelating the mold completely in order to release the agglomerates. As described above, the abrasive agglomerates preferably contain a coating of inorganic particles which increases the surface area and also minimizes aggregation of abrasive agglomerates among themselves during their manufacture. One method for obtaining the coating is to mix the agglomerate precursors after they have been formed, for example, when they are removed from the mold, with the inorganic particles in order to apply the inorganic particles, for example abrasive particles, to the agglomerated precursor. A small amount of water and / or solvent, or a temporary organic binder precursor may also be added, for example, in an amount ranging from 5 to 15% by weight, preferably from 6 to 12% by weight, based on to the agglomerated precursor, in order to secure the inorganic particles to the surface of the abrasive agglomerate precursor. The agglomerate precursors are then heated to heat-remove the organic materials used to prepare the agglomerated precursors, for example, the temporary organic binder, and to melt or vitrify the inorganic binder, which can be carried out separately or as a step. continuous, adapting the necessary temperature changes. The temperature for burning off the organic materials is selected to avoid an excess of bubbles which can result in undesirable pores in the abrasive agglomerate and generally depends on the chemistry of the optional ingredients that include the temporary organic binder precursor. Typically, the temperature for burning off organic materials ranges from about 50 to 600 ° C, preferably from 75 to 500 ° C, although higher temperatures can be used. The temperature to melt or vitrify the inorganic binder usually varies between 650 and 1150 ° C, preferably between 650 and 950 ° C. The resulting agglomerates can then be thermally processed to optimize the binding properties. The thermal processing comprises heating to a temperature ranging between 300 and 900 ° C, preferably between 350 and 800 ° C, and more preferably between 400 and 700 ° C.

Method for Making a Coated Abrasive Article The following description is a preferred, although not exclusive, method for making a coated abrasive. This preferred method is described with reference to a joining system comprising a fabrication coating and sizing coating, and a support comprising a first major surface. However, the method may also include applying an abrasive suspension to the first major surface of a support, wherein the abrasive suspension comprises a plurality of abrasive agglomerates of a binder precursor, each as described above, and exposing the suspension at conditions which cause the binder precursor to solidify so that an abrasive layer is formed. For example, the conditions may include heating, as described below, to cure the fabrication and sizing coatings. If a support of low tension or low stretch capacity is to be used, it can be prepared as described in US Patent Serial No. 08 / 199,835 or WO 93/12911. For example, a type of reinforced support can be prepared by winding a netting material, for example a mesh material, a conventional cotton or polyester backing, or a non-woven fabric on a support structure (for example a drum) to provide a base layer. This base layer may include several layers of rolled material, or may be a single layer, which may optionally be spliced with a conventional smoothing or splicing system. On this basis a liquid organic polymeric binder is applied, on which the fibrous reinforcement material is wound. The fibrous reinforcement material can be in the form of individual fibrous strands, a fibrous plush structure or a combination thereof. The resulting characteristics of the final web support will depend on the selection of the type of fibrous reinforcement material, for example, glass fiber filaments, polyester yarn or aramid fibers. The material of r6fii &Y2 fibrous di? Preferably, it is embedded in the organic polymeric binder material. The abrasive coating is then applied as a coating on the support without splices and without seams by any known method. Otherwise, a conventional coated abrasive support can be used. A manufacturing coating which compresses a first binder precursor based on organic substances can be applied to the first main surface of the support by any suitable technique such as spray coating, roll coating, die coating, powder coating, coating by Hot melt or coating by blades. The abrasive agglomerates, which can be prepared as described above, can be projected onto, and adhered to, the manufacturing cladding precursor, i.e., distributed in the manufacturing cladding precursor. Typically, the abrasive agglomerates are coated upon dropping them, preferably to obtain a monolayer. The coating should not be of a thickness which can braid or adhere a layer of abrasive particles and join a second layer. In addition, the agglomerates are preferably evenly distributed. In order to obtain an abrasive layer having a cross-section normal to the thickness at the center point of the thickness which has a total cross-sectional area of abrasive agglomerates which is substantially the same as that of the point along the thickness which is 75% of a distance between the center point and the contact side, for example, the abrasive particles having a substantially uniform size and shape are randomly supplied to the manufacturing lining so as to eliminate the slight averaged variations . The resulting construction is then exposed to a first source of energy, for example heat, ultraviolet light or electron beam, to at least partially cure the first binder precursor to form a manufacturing coating that does not flow. For example, the resulting construction can be exposed to heat at a temperature between 50 and 130 ° C, preferably 80 and 110 ° C, for a period ranging from 30 minutes to 3 hours. After this, a size coating consisting of a second binder precursor based on organic substances in which it can be the same or different than the first binder precursor based on organic substances, on the abrasive agglomerates is applied by any conventional technique, for example by spray coating, roller coating and curtain type coating. Finally, the resultant abrasive construction is exposed to a second energy source eg, an ultraviolet source or an electron beam, which may be the same or different as the first source of energy to fully cure or polymerize the manufacturing coating. , and the second binder precursor, in thermosetting polymers. In particular, a coated abrasive article having a bonding system with a Knoop hardness of at least 70 KHN can be prepared as described above, except that the filler particles used in the first and second binders are combined calcium metasilicate with a silane coupling agent.

Method of Using the Coated Abrasive Article The abrasive article can be used to abrade a work piece. The workpiece can be any type of material such as metal, metal alloys, exotic metal alloys, ceramics, glass, wood, wood-like materials, composite materials, painted surfaces, plastics, reinforced plastics, stones and combinations thereof. The work piece may be flat or may have a shape or contour associated therewith. Examples of workpieces include eyeglass lenses, plastic lenses, plastic lenses, glass television screens, metal automotive components, plastic components, particle boards, camshafts, crankshafts, furniture, turbine blades, automotive components painted and magnetic media. During abrasion, the abrasive article moves relative to the workpiece or vice versa, so that the abrasive article abrades the workpiece. Based on the application, the strength of the abrasion interface can vary from approximately 0.1 kg to more than 1000 kg. Typically, this range is between 1 kg and 500 kg of force at the abrasion interface. In addition, abrasion may occur under wet conditions. Wet conditions may include water and / or a liquid organic compound. Liquid organic compounds include lubricants, oils, emulsified organic compounds, cutting fluids and soaps. These liquids may also contain other additives such as defoamers, degreasers and corrosion inhibitors. The abrasive article may oscillate at the abrasion interface during use, which may result in a thinner surface on the workpiece that is being abraded. The abrasive article of the invention can be used by hand or can be used in combination with a machine, for example a belt grinder. The abrasive article can be converted into, for example, a band, tape rollers, disc or sheet. For belt applications, the two free ends of the abrasive belt are joined and spliced, so that an endless belt is formed. A band without splices, as described in WO 93/12911, can also be used. Generally, an endless abrasive belt can pass over at least one free roller and a flattener or contact wheel. The hardness of the flattener or contact wheel is adjusted to obtain the desired cutting rate and the finish of the work piece's surface. The speed of the abrasive belt depends on the desired cutting speed and surface finish, and generally varies anywhere from about 20 to 100 meters of surface per second, usually between 30 to 70 meters of surface area per second. The dimensions of the band may vary from about 0.5 cm to 100 cm wide, preferably from 1.0 to 30 cm, and from about 5 cm to 1,000 cm long, preferably from 50 to 500 cm.

Abrasive tapes are continuous lengths of an abrasive article and may vary in width from about 1 mm to 1,000 mm, preferably between 5 mm and 250 mm. The abrasive tapes are usually not rolled, they are traversed on a support pad which urges the tape against the work piece and then re-rolls up. The abrasive belts can be supplied continuously through the abrasion interface and can be disconnected. The abrasive discs, which may also include those which are in the form known in the abrasive technique as "margarita" may vary from about 50 mm to 1,000 mm in diameter, preferably from 50 to 100 mm. Typically, the abrasive discs are fixed to a support pad by a joining means and can rotate between 100 to 20,000 revolutions per minute, usually between 1,000 to 15,000 revolutions per minute. A coated abrasive article of this invention is particularly abrasive to abra hard workpiece having a Rockwell "C" hardness of at least about 25 Rockwell "C" typically of at least about 35 Rockwell "C" so preferable at least about 45 Rockwell "C", and most preferably at least about 50 Rockwell "C". Such workpieces include steel and die-cast iron. In particular, a coated abrasive article of this invention is particularly effective in precision abrasion of hard workpieces in which the coated abrasive article is ground, as described above, prior to its contact of the abrasive article with the workpiece. . During the duration of the article, the article can be rectified when it is not within the desired specifications, for example, when the surface finish and / or the precision of grinding are not obtained. Hardness measurements can be maccording to ASTM, standard number A370-90. Examples of hardened steel or die-cast iron workpieces include camshafts, crankshafts, engine components, bearing surfaces and, generally, any machine component that is to be subjected to aggressive resistance or moderate wear conditions for a period of time. of extended time. The abrasion method comprises providing a coated abrasive article of this invention, contacting the coated abrasive article with a hard workpiece, and moving the coated abrasive article and the workpiece relative to one another. Workpieces can be subjected to abrasion under a jet of water or in the presence of a lubricant. In a preferred embodiment, the coated abrasive article comprises a support and an abrasive layer, wherein the abrasive layer comprises a bonding system and abrasive agglomerates, the agglomerates comprise a vitrified binder and superabrasive grains. A preferred aspect of this invention is the grinding of camshafts as described in U.S. Patent No. 4,833,834 which uses an abrasive article of this invention.

The following non-limiting examples illustrate the invention in a conventional manner. All parts, percentages, proportions, etc., in the examples are by weight, unless indicated otherwise. The weights indicated for the fabrication, sizing coating and the vitrified agglomerate suspension formulations are wet weights. During all of the following the following abbreviations are used.

SIW • EP1 epoxy resin deionized water, commercially available from Shell Chemical Company (Hoston, TX), under the trade designation "Epon 828", EPH1 epoxy hardener, commercially available from Henkel Corporation (Minneapolis, MN) under the trade designation "Versamid 125"; EP2 epoxy resin, commercially available from Shell Chemical Co. (Houston, TX) under the trade designation "Epon 871"; EPH2 epoxy hardener, commercially available from Henkel Polymers Division (LaGrande, IL) under the trade designation "Genamid 747"; PR resin phenolic resin phase A, which contains between 0.75 and 1.4% free formaldehyde and 6 to 8% free phenol, the percent solids is about 78%, and the rest is water, pH about 8.5 and viscosity between approximately 2400 and 2800 centipoise; SCA silane coupling agent, commercially available from Union Carbide under the trade designation "A-1100"; PH2 2-benzyl-2-N, N-dimethylamino-1- (4-morpholinophenyl) -, 1-butanone, commercially available from Ciba Geigy Corp. (Hawthorne, NY) under the trade designation "Irgacure 369"; SWA1 humidifying agent, commercially available from Akzo Chemie America (Chicago, IL) under the trade designation "Interwet 33"; SWA2 humidifying agent, commercially available from Union Carbide Corp. (Danbury, CT) under the trade designation "Silwet L-7604"; SAG1 cubic boron nitride, which has a 60% nickel coating, commercially available from General Electric Co. (Worthington, OH) under the trade designation "CBN II"; SAG2 cubic boron nitride, commercially available from General Electric Co. (Worthington, OH) under the trade designation "CBN I"; AO abrasive grain of aluminum oxide; MDA methylene dianaline, commercially available from BASF Corporation (Parsippany, NJ); MAA methacrylic acid, commercially available from Rhom and Haas (Philadelphia, PA); PMA polypropylene glycol methyl ether acetate; UPR urethane polymer, commercially available from Uniroyal Chemical Company, Inc. (Middlebury, CT) under the trade designation "Adiprene BL-16"; PEG4D polyethylene glycol 400 diacrylate, commercially available from Sartomer Company, Inc. (Exton, PA); UAO urethane acrylate, commercially available from Morton International (Chicago, IL) under the trade designation "Uvithane 893"; AC amine curative, commercially available from Albemarle Corporation (Baton Rouge, LA), under the trade designation "Ethacure 100"; EGME ethylene glycol monobutyl ether, also known as polysolve, commercially available from 01in Company (Stamford, CT); PS100 hydrocarbon solvent, commercially available from Exxon Chemical Co. (Houston, TX) under the trade designations "WC-100" and "Aromatic 100"; CMST calcium metasilicate, commercially available from NYCO (Willsboro, NY) under the trade designation "325 Wollastonite"; CMSK calcium metasilicate, commercially available from NYCO (Willsboro, NY) under the trade designation "400 Wollastokup"; ASF2 > silica filler material, commercially available from DeGussa GmbH (Germany) under the trade designation "Aerosil R-972"; ASC acrilla, commercially available from Engelhard Corporation (Edison, NJ), under the trade designation "ASP 600".

Coated abrasive strips are prepared as Comparative Examples A and B and Examples 1 to 6 as follows: E? Fnpl rvmmrfttivp A The support used for Comparative Example A is a polyester support (360 g / m2) which is pre-prepared with 60 parts of EP1 / 40 parts of EPH1 and re-sized with 50 parts of EP1 / 50 parts of EPH1 of filled resin with CaCo3 and bronze powder. An abrasive suspension formulation is applied as a coating as indicated below in Table 1, on this support by blade coating, and the resulting construction is cured at room temperature for 10 minutes, then at 90 ° for 90 minutes, and subsequently at 113 ° C for 14 hours. A conventional polishing splice is used to provide endless bands, 335.3 cm (132 inches) long. The bronze filler support sizing is scraped off during splicing so as not to provide gauge variation in the splice area. Bands are cut in widths of 2.38 cm (15/16 inches).

Table 1 - Abrasive Suspension Comparative example A is tested on a single-belt camshaft grinder, commercially available from Litton Landis Industries as a "3L CNC" model. The machine has a 50 cm diameter coranada rubber drive wheel, a three segment polycrystalline diamond support shoe, and free wheels located above and below the shoe, with ridges to guide the belts. Bands are placed on the machine at a belt tension of 14-17.6 N / mm (80-100 pounds / inch) of bandwidth and run at a speed of 35 meters / seconds (7000 surface feet per minute). The frosted work pieces are automotive cam shafts that have hardened steel lobes with hardness of 58-60 Rockwell "C". The shafts are rotated at 20 rpm during grinding. However, before the grinding, the bands are adjusted and rectified so that the resulting ground workpieces can be adapted to the tolerances of manufacturers A of 10.2 cm (4 inches) in diameter of the adjustment bar, electrodeposited with diamonds, which is rotated at 5,000 rpm and placed in contact with the surface of the driving belt. The coolant used during the adjustment and also during the grinding is a synthetic oil, Masterchemical Trim VHO E200, at 6% in water. To obtain an acceptable surface finish and a taper of the cam lobes that are being ground, the bands are required to be adjusted and rotated with a diamond adjusting wheel. The adjustment process removes protruding parts and provides a surface finish of the workpiece surface down from 1.6 micrometers (62 microns) to 0.4-0.8 micrometers (16-30 microns).

Kj implo ffin > nr * friyp B The support used for comparative example B is a splice-free construction prepared according to the description of Benedict et al., WO 93/12911. The epoxy / urethane material mixture shown below in Table 2 is coated with a knife over a thin non-woven polyester fleece. 12 strands per centimeter (thirty strands per inch), each alternating with 200 denier fiberglass and polyester filaments, are wound helically into the resin. The process is performed on a 335.2 cm (132 in) wheel circumference.

Table 2 - Fiber Bonding Resin The support is applied as a spray coating with a manufacturing resin having the formulation described in Table 3. It is applied as a drip coating SAG1 (average particle size of 125 microns) on the manufacturing coating at a density of 0.0088 g / cm2 (0.057 grams / square inch) (or 0.022 g / cm2, 0.143 g / square inch if the nickel coating is included). After pre-curing for one hour at 82 ° C, the size resin shown in Table 4 is applied as a spray coating on the abrasive grains. The bands are cured for 1 hour at 82 ° C, for 14 hours at 103 ° C and then cured for an additional 3 hours at 143 ° C. The bands are cut to a width of 22.2 mm (7/8 inch).

Table 3 - Manufacturing Coating Formulation Table 4 - Formulation of Sizing Coating The grinding conditions were the same as for the comparative example A. The adjustment and rectification of the bands decreases the surface finish from 2. 6 micrometers (105 microinches) up to 0.4 to 1 micrometer (16-40 micropulgadas), and the irregular surface is eliminated. After a successful fit, 120 lobes of cam shaft are ground before the flat part through the lobe is left to specification. The wear of the band is measured and r, e calculates the proportion G, which is equal to the volume of metal removed from the cam lobes, divided by the volume of band lost during the grinding. The G ratio can be calculated as follows: (ircun erencia of the lobe of cam) (width of the lobe) (depth of raw material removed) Proportion G. ______ ^ __ (band length) (band width) (loss of band thickness) The comparative example B has a G-ratio of approximately 140. The observed maximum stretch or tension is 0.6%.

The support used for Example 1 is a polyester satin fabric (285 g / m2) saturated with a mixture of phenolic / latex material 90/10 to obtain a weight of 360 g / m2. An epoxy support sizing coating is added and the weight is increased to 420 g / m2, and an epoxy pre-prepared coating is added and the weight is increased to 450 g / m2, and an epoxy pre-charged coating is added and the weight at 450 g / m2. The support is cut in 30.5 cm (12 inch) widths. A length of 335.5 cm [132.1 inches] is cut and spliced in a conventional manner using a sine wave die at an angle of approximately 67 ° and spliced using a 3/4 inch (1.9 cm) jointing means. width. The spliced band then slides over a 335.3 cm (132 inch) circumference of a 38 cm aluminum cube (15 inches) wide. A resin of the formulation in the Table 5 is applied as a knife coating on the support to a thickness of approximately 102 to 152 micrometers (4 to 6 thousandths of an inch) and a weight of 0.036 g / cm2. After coating, the drum is rotated to 3 rpm and the acrylate portion of the resin is cured using a Fusion Systems "D" lamp 157. 5 watt / cm (600 watt / inch) for 40 seconds.

Table 5 - Resin, Fiber Union A second layer of the same resin is applied to a thickness of 406 to 508 micrometers (16 to 20 mils). Alternating polyester fibers of 400 are rolled (under the trade designation "Kevlar 49" available from EI DuPont Corp.) and denier polyester fibers 440 in the stock, at 9.5 threads per centimeter (24 threads per inch) in width band. The resin is smoothed and cured for 40 seconds with the same Fusion Systems lamp. The coated band is then exposed to two infrared curing lamps for about 30 minutes while the drum is rotated to cure the resin.

After cooling to room temperature, the support is removed from the bucket and cut into widths of 12.7 centimeters (5 inches) for coating. The abrasive agglomerates are formed by mixing the formulation shown in Table 8 and coating it with an orifice silicone mold having a square top portion of approximately 1270 microns in length (0.050 inches) and a width and a square base of approximately 635 micrometers (0.025 inches) in length and width; the depth of the hole is 890 micrometers (0.035 inches). The glass powder listed in Table 8 for each of Examples 1 to 4 is described in Table 11. The suspension is dried and cured in the mold at 90 ° C for 30 minutes. The resulting cubes were removed from the mold. To prevent the agglomerates from sticking during the burning process, 100 grams of AO grade 220 (average particle size of 74 microns) and 10.0 grams of DIW are mixed with 200 grams of agglomerated cubes previously burned. The bottom of an alumina carburizing box is covered with 75 grams of AO grade 220 and the mixed material is placed on top. The cement box is placed in a small oven that is open to the air. The temperature of the oven increases from 25 ° C to 900 ° C for a period of four hours, after which they are kept at 900 ° C for 3 hours, and then turned off and allowed to cool to room temperature overnight . The incinerated, vitrified agglomerates are passed through a 16 mesh screen to separate them from one another and also to remove any fine AO. The manufacturing resin of the formulation shown in Table 9 is applied as a knife coating on the polyester cloth side of the backing to a wet weight of 0.034 g / cm2 (0.22 grams per square inch). The agglomerates made above are drip-coated onto the manufacturing resin to a weight of 0.053 g / cm2 (0.34 grams per square inch). The bands are placed in an oven at 90 ° C for 90 minutes to precure the coating for manufacturing and fixing the agglomerates to the support. The sizing resin shown in TabLa 10 is coated on the web using a soft rubber roller (Shore A = 30). The weight of the sizing resin is 0.064 g / cm2 (0.41 grams per square inch). The bands are then precured in the oven for 16 hours at 90 ° C and subjected to final curing for 3 hours at 130 ° C. The band is flexed after completing curing and cut into 2.54 cm (1.0 inch) widths for testing. The bands are tested to determine their frosted operation as follows. The grinding used is the same as that described in comparative example A. The ground workpieces are automotive cam shafts having hardened lobes with a width of approximately 1.15 cm (0.453 inches) with a hardness of 58-64 Rockwell "C " Before grinding, the bands are adjusted and rectified under the same conditions. However, the concentration of the oil in the water for cooling is 5.75%. . The band is ground and adjusted by grinding the band in contact with a diamond adjustment wheel and is traversed by a narrow diamond slightly back and forth, across the width of the band. When the belt thickness reaches 0.176 cm (0.0692 inches), the belt has been adjusted enough to allow successful grinding of the camshafts. The first lobe is ground at a feed rate of 25 micrometers (0.001 inches) per revolution, and the lobe has a variation from peak to total valley, with respect to the flat part of 1.5 micrometers (0.000060 inches), and a finish of surface of 0.5 micrometers (20 micropulgadas). After grinding the 48 lobes the surface finish is 0.7 micrometers (28 microinches) and the variation of the flat part is 3.3 micrometers (0.000130 inches). Band wear is measured at 0.114 micrometers (0.0000045 inches) per ground lobe. It is estimated that the G ratio is 96. The band is adjusted and verified again. The thickness of the band decreases to 0.172 cm (0.0677 inches). The first lobe is ground at a feed rate of 25.4 micrometers (0.001 inches) per revolution of the camshaft. The surface finish is 0.55 micrometers (21 microinches) in the first lobe, and the variation from peak to total valley with "respect to the flat part is 2.03 micrometers. (0.000080 inches). After grinding 48 lobes, the surface finish is 0.7 micrometers (28 microinches), and the total variation with respect to the plaaa part is 2.54 micrometers (0.000100 inches). The wear of the band is measured and is 0.078 micrometers (0.0000031 inches) per ground lobe. The G ratio is calculated to be 139. The band is adjusted and ground to a band thickness of 1.78 mm (0.0669 inches). The feed rate increases to 0.381 mm (0.0015 inches) per revolution. The surface finish is 6 micrometers (24 microinches) in the first lobe and the variation from peak to total valley with respect to the flat part is 2.54 micrometers (0.000100 inches). After grinding 48 lobes, the surface finish is 8.9 micrometers (35 micropulgadas) and the total variation with respect to the flat part is 5.3 micrometers (0.000210 inches). The wear of the band is measured and is 1.9 micrometers (0.0000075 inches) per ground lobe. It is estimated that the G ratio is 58. The band is adjusted and rectified to a band thickness of 1.67 mm (0.0659 inches). The feed rate is decreased to 1.7 micrometers (0.00067 inches) per revolution. The surface finish is 5.3 micrometers (21 microinches) in the first lobe and the variation from peak to total valley with respect to the flat part is 2.2 micrometers (0.000085 inches). After grinding 48 lobes, the surface finish is 5.8 micrometers (23 microinches) and the total variation with respect to the flat part is 3 micrometers (0.00012C inches). After grinding 118 lobes, the surface finish is 6.1 microns (24 microinches) and the total variation with respect to the flat part is 4.3 micrometers (0.000170 inches). The strip wear is measured, which is 0.05 micrometers (0.0000021 inches) per ground lobe. It is calculated that the G ratio is 206. The flat part of the lobe is never reached in the comparative examples in the same equipment and under the same conditions using abrasive belts prepared with individual abrasive grain (not agglomerated). The band construction described above, adjusted and rectified to an acceptable flat part each time. By consistently obtaining a flat part of the ground cam lobes is critical to the success and utility of an abrasive belt for the grinding of cam shafts, Bjtimólo, 2 The support used for Example 2 is prepared in a manner similar to that of Example 1, except that the formulation for adhering the fibers is as shown in Table 6, and other variations of Example 1 are described below.

Table 6 - Fiber Bonding Resin After coating the resin on the fibers, the drum is rotated at 3 rpm and the resin is cured using a Fusion Systems "V" lamp of 157.5 watt / cm (400 watt / inch) for 60 seconds. A second layer of the same resin is applied at a thickness of 406 to 105 micrometers (16 to 20 mils). Denier 800 fibers having the commercial designation "Kevlar 69" are available from E. I.

DuPont Corp., on support at 16.5 threads per centimeter (42 threads per inch) bandwidth. The resin becomes smooth and is cured for 60 seconds with the same Fusion Systems lamp. The coated band is then exposed to two infrared curing lamps for approximately 120 minutes, while the drum is rotated to cure the resins. After cooling to room temperature, the support is removed from the hub and cut to 5 inches (12.7 cm) in width for coating. Vitrified agglomerates are formed by mixing a suspension as shown in Table 8 in the same manner as in Example 1. The suspension is dried and cured in the mold at 0 ° C for 30 minutes and then the cubes are removed from the mold. mold using an ultrasonic oven. To prevent the pre-incinerated agglomerates from sticking together during the incineration process, AO grade 150 (average particle size of approximately 105 microns) is mixed with the agglomerates. The bottom of an alumina carburizing box is coated with AO grade 150 and the mixed material is placed on top. The cement box is placed in a small oven that opens to the outside. The agglomerates are incinerated at 900 ° C. The vitrified and incinerated agglomerates are then passed through a sieve through a 16 ANSI screen to separate them from each other. They are also separated by sieved fine AO. The processing of the resin as shown in Table 9 is coated with a knife on the support up to a weight of 0.033 g / cm2 (0.21 grams per square inch). The agglomerates from the top are drip coated to make a resin to a weight of 0.088 g / cm2 (0.57 grams per square inch). The strips are placed in an oven at 90 ° C for 90 minutes to pre-cure the manufacturing lining and to fix the agglomerates to the support. The sizing resin, as shown in the Table is coated as a coating on the bands using a soft rubber roller (Shore A = 30). The weight of the sizing resin is 0.0775 g / cm2 (0.50 grams per square inch). The bands are then sealed in the oven for 90 minutes at 90 ° C, and finally cured during hours at 105 ° C and 3 hours at 130 ° C. Bands are then flexed after completing curing and cut into widths of 1.9 to 2.5 cm (0.75 to 1.0 inches) for testing. The bands are tested for grinding operation on hardened steel cam lobes. The grinding used is a prototype band grinder of J.D. Phillips Corp. (Alpena, MI) but basically it is similar to the Litton Landis grinder. The support shoe is a polycrystalline diamond shoe and the free wheels are located above and below the shoe, with , flanges on each side of the shoe to guide the band. The bands are run at a tension of 8.8-12.8 N / mm (50-73 pounds / inch) and are driven at a speed of 39. 3 m / s (7740 feet of surface per minute), by a rubberized drive wheel of 30.5 cm diameter (12 inches). The bands are then adjusted and ground with a diamond wheel of 7.6 cm (3 inches) in diameter that rotates at 10 rpm (counter-rotation, against the direction of the bands). The contact width of the diamond wheel on the bands is approximately 1.27 cm (1/2 inch). The rotating diamond wheel is indexed on the left side of the band and traverses the band from the left to the right. The ground work pieces are automotive cam shafts for a V-8 engine, each lobe is approximately 1.14 cm (0.45 inches) with a hardness 60-62 Rockwell "C". The cooler used is synthetic oil, Cimperial 1010, in water at a concentration of approximately 5%. The thickness of the abrasive belt after adjusting, grinding and grinding is approximately 0.25 cm (0.100 inches). The abrasive belt is ground and adjusted by placing the belt in contact with the diamond adjustment wheel and by traversing the diamond wheel slowly across the width of the belt. When the thickness of the strip reaches 2.2 mm (0.085 inches) the band has been adjusted enough to allow successful grinding of cam lobes. Each of the eight test grinding heads can be ground with two lobes on the cam shaft. The first two lobes on each axis are frosted, and the band then moves to the second head to grind the third and fourth lobes. The largest number of lobes that can be ground without moving the band is 94. It grinds 428 lobes with a single band. The bands have been used only slightly at this point.

Therefore, it is not possible to successfully measure the wear of this banding and, therefore, calculate a proportion of G. The surface finish in the base circle of the lobes initially is approximately 0.325 micrometers (13 micropulgadas) immediately after adjustment. The surface finish in the circle of the base after grinding 180 lobes is still less than 0.5 micrometers (20 micropulgadas). The final band tension is less than about 1.8%.

E?? Mplo__3_ The support for Example 3 is prepared in the same way as that of the Axis, mplo 2, except that the fiber-binding resin is used as shown in Table 7.

Table 7 - Fiber Bonding Resin Abrasive agglomerates are manufactured in the same manner as in Example 2, using the suspension formulation as shown in Table 8. To prevent the pre-incinerated agglomerates from sticking together during the incineration process, SAG 2 grade 200/230 is mixed. (average particle size, 74 micrometers) with the agglomerates. The lower part of an alumina cementation box is covered with SAG2 grade 200/230 and the mixed material is placed on top. The cement box is placed in a small oven that opens to the air. The agglomerates are incinerated at 900 ° C. The incrusted vitrified agglomerates are then passed through a sieve through a 16 ANSI sieve to separate them from each other. They are also separated by fine sieving SAG2.The manufacturing resin as shown in Table 9 is applied as a knife coating on the side of polyester fabric in the support at a weight of approximately 0.0388 g / cm2 (0.25 grams per square inch). The incinerated agglomerates are applied by dripping onto the manufacturing resin at a weight of 0.11 g / cm2 (0.73 grams per square inch). The bands are placed in an oven at 90 ° C for 90 minutes to pre-fabricate or fix the agglomerates to the support. The sizing resin as shown in Table 10 is applied as a coating on the web using a soft rubber roller (Shore A = 30). The weight of the sizing resin is 0.06 g / cm2 (0.43 grams per square inch). The bands are then precured in the oven for 90 minutes at 90 ° C, and finally cured for 10 hours at 105 ° C and for 3 hours at 130 ° C. The bands are flexed after completing curing and cut in widths of 1.9 to 2.5 cm (0.75 to 1.0 inches) for testing. The bands are tested for performance in the grinding of hardened steel and hardened cast iron lobes. The grinding conditions are as follows. The grinder used is the same Litton Léindis grinder used in the previous examples. Belt tension is 14-17.6 N / mm (80-100 1 / inch), and is driven at 30.5 to 55.9 m / s (6000 to 11,000 surface feet per minute) by a rubber wheel crowned in diameter 50.8 cm (20 inches) that has been corrugated with a strong abrasive to minimize the slippage of the bands on the drive wheel. The bands are adjusted and rectified in the same way as in the previous. The contact width of the diamond adjustment wheel on the surface of the band is approximately 0.32 cm (1/8 inch) and the rotating wheel is indexed on the left side of the band and traverses through the band to the right side, after which it is indexed again and crosses to the left. Frosted workpieces are hardened steel automotive cam shafts, Rockwell "C" 58-64 hardness, and die-cast iron cam shafts, with 48/50 Rockwell "C" hardness. During grinding, the cam is rotated at 20 rpm, and also oscillated at 0.3 cm (0.120 inches) at 1.4 Hz. The cooler used is Masterchemical Trip VHP E200, at a concentration between 3 and 6%. The thickness of the band before adjustment, grinding and grinding is approximately 0.33 cm (0.130 inches). The thickness of the support is 0.127 cm (0.050 inches). The band is coated with a single layer of agglomerates with a diameter of approximately 0.102 cm (0.040 inches). Several agglomerates are applied as a coating unintentionally as a second layer. However, these foreign agglomerates are eliminated by striking the band during the initial adjustment / rectification sequence. The abrasive belt is ground and adjusted by placing the belt in contact with a diamond adjusting wheel and traversing the narrow diamond slowly back and forth across the width of the belt.

When the thickness of the belt reaches 0.226 cm (0.089 inches), the belt has been adjusted and rectified enough to allow the successful grinding of cam lobes. In the hardened steel cam shaft lobes, under a variety of grinding conditions, the G-ratio range is from 60 to 110. In hardened die-cast iron lobes, under a variety of grinding conditions, the interval of proportion G is from 98 to 427. The tension of the band is less than 1.0% during the test. These bands returned to a smaller amount of 0. 5% of its original length when the tension is suppressed during the night.

Example 4 is prepared by the same method as Example 3. The support and the abrasive agglomerates are manufactured in the same manner as in the support of Example 3, except that the resultant abrasive strips have a length of 400 cm (158). inches) and a width of 2.54 cm (1.0 inch). The manufacturing resin, as shown in Table 9, is applied as a knife coating on the polyester cloth side of the backing to a weight of approximately 0.033 g / cm2 (0.21 grams per cured inch). The agglomerates of the above are applied as a drip coating on the sizing resin to a weight of 0.105 g / cm2 (0.68 grams per square inch). The bands are placed in an oven at 90 ° C for 90 minutes to pre-cure the manufacturing and fixing of the agglomerates to the support. The sizing resin, as shown in Table 10, is applied as a coating on the web using a soft rubber roller (Shore A = 30). The weight of the sizing resin is 0.042 g / cm2 (0.27 grams per square inch). The bands are then precured in the oven for 90 minutes at 90 ° C and subjected to final curing for 10 hours at 105 ° C and for 3 hours at 130 ° C. Bands are flexed after curing is completed and cut into 2.54 cm (1.0 inch) widths for testing. The bands are tested as follows. The grinder used is a Schaudt single-belt cam shaft grinder from Germany, model CBS1. The support shoe has a width of 2.73 cm (1.07 inches) and crowned freewheels are located above and below the shoe. The belt tension is 8.8 N / mm (50 pounds per inch), and the belts are driven at 45 m / s (9000 surface feet per minute) by a 38 cm rubber wheel (15 inches) in diameter and 7.5 cm (3 inches) in width which has become rough with a strong abrasive to minimize the sliding of the belt on the drive wheel. The ground work pieces are hardened die-cast iron self-driving cam shafts (the Rockwell hardness "C" is 54 on the ramp and nose, and 42 on the base) and approximately 13 mm (0.005 inches) wide. The coolant used during grinding is Oemeta Frigimet MA 174-N, 2.5% in water. The abrasive belts are adjusted and ground using a 15 cm (5.9 inch) diameter, 0.3 mm (0.012 inch) diameter diamond wheel that rotates in the opposite direction to 15 m / s (3000 ft / min). The rotating diamond wheel is indexed on the right side of the band and citraviesa through the band from the right to the left, and then indexed and again crosswise from the right to the left. One hundred and ninety cam shafts, or 1520 cam lobes, are ground using a grinding cycle that requires 34 seconds per lobe. The band is adjusted and rectified, every five cam axes (40 lobes) at the beginning of the test. The number of ground axes between adjustments and rectifications is gradually increased to 36 (288 lobes) and it is confirmed that the parts still remain within specification. The total G ratio calculated to grind the 1520 lobes is 300, which is low, however, because the bands were adjusted and rectified too frequently at the beginning of the tests. The G ratio calculated for the last 560 ground lobes with this time cycle is 1000. The web tension is less than 0.7% during the tests. Table 8 shows the formulations used for the preparation of the abrasive agglomerate suspensions of the abrasive agglomerates of Examples 1 to 4.

Table 8 - Suspension of Vitrified Agglomerate Tables 9 and 10 describe the formulations of the manufacturing coating and the size coating, respectively, for Examples 1 to 4.

Table 9 - Manufacturing Coating Formulations Table 10 - Sizing Coating Formulations The glass powder shown in Table 11 is used in the suspensions according to Table 8. The glass powder is milled to be finer than a 325 mesh. The glass is formulated so that its coefficient of thermal expansion is approximately the same as the coefficient of thermal expansion of the superabrasive grains used in the Examples (3.5 x 10"6 / ° C) The epoxy resin acts as a temporary binder for the agglomerates Boron oxide is added to the formulation for Improve adhesion between glass and abrasive grains. labia 11 - Glass Dust Formulation It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

REIVINDIC CrEQamS

1. A coated abrasive article, characterized in that it comprises: (a) a support of low tension or low stretch capacity having a first main surface; and (b) an abrasive layer applied as a coating on the first main surface, the abrasive layer has a contact side adhered to the first main surface, an opposite side and a thickness which extends from the contact side to the opposite side , the abrasive layer comprises (i) a binding system based on organic substances, and (ii) a plurality of abrasive agglomerates adhered to the bonding system, each of the agglomerates (1) comprises an inorganic binder and a plurality of grains. abrasives, and (2) has a substantially uniform size and shape, in which a cross section of the adhesive layer normal to the thickness and at the center point of the thickness has a total cross-sectional area of abrasive agglomerates which are substantially the same that the point along the thickness which is 75% of a distance between the center point and the contact side.

2. The coated abrasive article according to claim 1, characterized in that the low tension support has a tension or percent stretch of less than about 2%.

3. The coated abrasive article according to claim 1, characterized in that the bonding system based on organic substances comprises a manufacturing coat and a size coat, and at least one of the manufacturing coat and the size coat has a hardness Knoop average of at least 70 KHN.

4. The coated abrasive article according to claim 1, characterized in that the plurality of abrasive grains are superabrasive grains of the group consisting of diamond, cubic boron nitride and combinations thereof.

5. The coated abrasive article according to claim 1, characterized in that each of the agglomerates is in the form of a four-sided truncated pyramid.

6. The coated abrasive article according to claim 1, characterized in that each of the agglomerates is in the form of a cube.

7. A coated abrasive article, characterized in that it comprises: (1) a low tension or low stretch support having a first major surface; and (2) a layer of abrasive applied as a coating on the first main surface, the abrasive layer comprises: (a) a bonding system based on organic substances, and (b) a plurality of abrasive agglomerates distributed in the bonding system , each of the agglomerates comprises an inorganic binder and a plurality of abrasive grains is in the form of a truncated four-sided pyramid or cube.

8. A method for making a coated abrasive article, characterized in that it comprises: (a) providing a low tension or low stretch support having a first major surface; (b) forming an abrasive layer, the abrasive layer has a contact side adhered to the first main surface of the support, an opposite side and a thickness which extends from the contact side to the opposite side, in which a cross section of the abrasive layer normal to the thickness and at the center point of the thickness has a total cross-sectional area of abrasive agglomerates which is substantially the same as at a point along the thickness which is at 75% of a distance between the center point and contact side, comprising: (1) applying a manufacturing coating comprising a first binder precursor based on organic substances to the first main surface of the support; (2) providing a plurality of abrasive agglomerates 5 (i) comprising an inorganic binder and a plurality of abrasive grains, and (ii) having a substantially uniform size and shape; 10 (3) distribute the agglomerates in the manufacturing liner; (4) exposing the manufacturing liner to a power source to at least partially cure the first 15 binder precursor: (5) apply the sizing coating comprising a second binder precursor based on organic substances on the agglomerates 20 abrasives; and (6) exposing the sizing coating to a second energy source to cure the second binder precursor and, optionally, completing the curing of the first binder precursor.

9. A method for abrading a hard workpiece having a Rockwell "C" hardness of at least 25, the method is characterized in that it comprises (1) providing a coated article which comprises a low tension or low stretch support and an abrasive layer, the abrasive layer comprises a bonding system and abrasive agglomerates, and the agglomerates comprise (a) an inorganic metal oxide binder substantially free of free metal, and (b) abrasive grains substantially comprising superabrasive grains; (2) contacting the coated abrasive article with the workpiece; and (3) moving the coated abrasive article and the workpiece one relative to the other.

10. The method according to claim 9, characterized in that the hard workpiece is subjected to abrasion with precision when grinding the coated abrasive article before contacting the abrasive article with the workpiece. A coated abrasive article having a backing and a coated abrasive layer on the first main surface of the backing, wherein a cross section of the abrasive layer normal to the thickness and at the center point of the thickness has a total cross-sectional area of abrasive agglomerates which is substantially the same as at a point along the thickness which is 75% of a distance between the center point and the contact side; a coated abrasive article having a bonding system with a Knoop hardness number of at least 70; a coated abrasive article comprising abrasive agglomerates in the form of pyramids of four truncated or cube sides; a method for manufacturing the coated abrasive article and a method for abrading a hard workpiece using a coated abrasive article.