METHOD OF MAKING ABRASIVE BRUSH AND BRUSH MADE THEREBY

Abstract: A process for the manufacture of an abrasive brush of the convolute type, laminate type, flap type or the like is described with an abrasive brush made by such a process. The process comprises the steps of providing a flexible and compressible abrasive substrate, the substrate having first and second major surfaces; coating the substrate on at least the first major surface with a liquid adhesive composition containing a solid epoxy resin, a curing agent and a volatile solvent; drying the coated substrate to volatilize the solvent; cutting the substrate into smaller pieces; assembling a plurality of the pieces to provide an assembly wherein at least a pair of the pieces are oriented with respect to one another so that a first major surface of one of the pieces abuts a second major surface of another of the pieces; heating the assembly at a temperature higher than that of the drying step to cure the solid epoxy resin and thereby bond the pieces to one another within the assembly; and cooling the assembly to provide the brush.

Description: METHODOFMAKINGABRASIVEBRUSH ANDBRUSHMADETHEREBY The present invention relates to an abrasive tool, and more particularly to a process for the manufacture of an abrasive brush and to brushes made by the process ofthe laminate type, the convolute or foil type, the flap type or the like. Background of the Invention Brushes for abrasive applications typically include a shaped abrasive substrate mounted for rotation on a spindle or the like. Brushes ofthe so-called laminate type generally comprise a plurality of compressible abrasive discs laminated to one another in a stack. Each disc includes a central aperture dimensioned to receive a spindle therein and the apertures are aligned with one another within the stack. In assembling such an article, the discs are typically stacked and compressed at the time of their assembly into a brush or sometime prior thereto. Most commonly, the individual discs are stamped or die cut from a compressible and flexible sheet substrate, such as a nonwoven fibrous web which typically includes a plurality of abrasive particles adhered to the fibers ofthe web with a resinous binder. The discs may be maintained in a compressed state within the construction ofthe finished brush in one of several ways. A so called "direct method" maintains the discs in a compressed configuration by exerting continuous compressive force against the ends ofthe stack. Such a method is disclosed, for example, in Japanese Patent application No. 6-161213 where paired end plates and at least one axial spacer are described. The spacer is provided in the form of a pole with means for fixing the relative positions ofthe individual end plates. Preferably, the spacer pole is hollow and is dimensioned so that a spindle may be disposed therein. The end plates are disc shaped and are provided with apertures to receive the pole therein. A stack of nonwoven discs are assembled along the pole and are compressed between the paired end plates and the end plates are locked in place along the pole, thereby retaining the stacked discs in a suitable configuration for use as an abrasive brush. Abrasive brushes assembled in the foregoing manner are relatively inexpensive to manufacture. Moreover, the above described method avoids the use of adhesives in the manufacturing process. One drawback associated with the direct method, however, is the problem of "blooming" illustrated in Figure 1. As shown, the discs 5 form a bulge at the peripheral region ofthe stacked discs beyond the periphery of end plates 3 and 4 in the manner indicated at "F". Bulging or blooming is known to decrease the abrasive effectiveness ofthe brush during an abrasive application. Another approach to the formation of such brushes is shown in Figure 2. A plurality of stacked discs 50 are first retained and compressed between end plates 30 and 40 to provide an assembly 60 which is then dipped in a bath 62 of resinous adhesive to impregnate the stacked discs 50. The assembly 60 is removed from the bath 62 and moved to a heating station such as oven 64 where the adhesive is hardened (e.g., heat cured). The discs 50 are maintained in a compacted configuration by the cured adhesive, and the thus prepared laminate may be further finished to form a useable tool (e.g., a brush) by removing the end plates 30 and 40 and mounting the laminated stack onto a spindle, all in a known manner. The use of adhesives in the formation of a brush avoids the problem of blooming associated with the "direct method" described above. However, the resinous adhesives used in the lamination process may, prior to hardening, drip from the assembly and thereby may present potential environmental or toxicological problems. Moreover, compression ofthe nonwoven discs densifies the web material which can interfere with the effective impregnation ofthe web with adhesive, and the molten adhesive often migrates within the disc assembly under the influence of gravity prior to curing. Following hardening, the impregnated disc assembly may have an adhesive loading distributed in a nonuniform manner throughout the body ofthe assembly. A nonuniform adhesive distribution can adversely affect the abrasive effectiveness ofthe resulting brush. For the foregoing reasons, the use of adhesives can be time consuming, result in significant unrecoverable waste and can provide a finished article with a nonuniform density and unsatisfactory abrasive performance. In light ofthe foregoing problems associated with known methods for the manufacture of abrasive brushes, it would be desirable to provide an improved brush having a compact body that has been impregnated with adhesive and cured in a manner to provide a substantially uniform density throughout the body ofthe brush. It would also be desirable to provide an improved process for making the foregoing brush using a minimal amount of adhesive in a manner that allows easy handling ofthe adhesive impregnated material and the resulting intermediate and final products. Summary of the Invention The present invention provides a process for the manufacture of an abrasive brush ofthe convolute type, laminate type, flap type or the like for use in any of a variety of abrasive applications. The invention also provides an abrasive brush made by the foregoing process. In one aspect, the invention provides a process for producing an abrasive brush, comprising the steps of: providing a flexible and compressible abrasive substrate, the substrate having first and second major surfaces; coating the substrate on at least the first major surface with a liquid adhesive composition containing a solid epoxy resin, a curing agent and a volatile solvent; drying the coated substrate to volatilize the solvent; cutting the substrate into smaller pieces; assembling a plurality ofthe pieces to provide an assembly wherein at least a pair ofthe pieces are oriented with respect to one another so that a first major surface of one ofthe pieces abuts a second major surface of another ofthe pieces; heating the assembly at a temperature higher than that ofthe drying step to cure the solid epoxy resin and thereby bond the pieces to one another within the assembly; and cooling the assembly to provide the brush. . In the foregoing process, the cutting step may be performed prior to coating the substrate with a liquid adhesive composition, or the coating step may be performed after the cutting step. The substrate is preferably a material selected from nonwoven webs, woven materials and foamed polymeric materials. Preferably, the substrate is a nonwoven web of fibers bonded to one another at their mutual contact points and having abrasive particles adhered to the fibers ofthe web. The process may further comprise forming a lofty nonwoven web of fibers bonded to one another at their mutual contact points; and bonding a plurality of abrasive particles to the fibers ofthe nonwoven web. In another aspect ofthe invention, an abrasive brush made according to the foregoing process is provided. Those skilled in the art will further appreciate the features and advantages of the invention upon further consideration ofthe remainder ofthe disclosure, including the detailed description ofthe preferred embodiment as well as the appended claims. Brief Description of the Drawings In describing the various features ofthe prefened embodiments ofthe invention, reference is made to the various figures wherein: Figure 1 is an elevational view, in cross-section, of a conventional abrasive brush produced without adhesive; Figure 2 is a schematic illustration of a conventional process for producing an abrasive brush using adhesives; Figure 3 is a schematic illustration of a portion of a process for producing an abrasive brush according to the present invention; Figure 4 is a schematic illustration of a portion of a process for producing an abrasive brush according to the present invention and specifically illustrating the steps subsequent to those illustrated in Figure 3; and Figures 5a to 5c are perspective views of various types of abrasive brushes according to the present invention. Detailed Description ofthe Preferred Embodiment The preferred embodiment ofthe invention is now described in detail. In discussing certain features ofthe described embodiment, reference is made to the various Figures wherein structural features ofthe described embodiment are designated with reference numerals and wherein like reference numerals indicate like structures. The articles ofthe invention may be described by reference to the process for their manufacture. Figures 3 and 4 show a process of producing an abrading brush ofthe laminate type (e.g., shown in Figure 5) according to the present invention. Referring to Figure 3, a material roll 100 of substrate 10 is provided in the form of a continuous strip having upper and lower major surfaces. Roll 100 is unwound, typically by an unwinder (not shown). The roll 100 is wound on a rotatable shaft to allow the substrate 10 to run or travel continuously along an operational path (indicated by the arrow of Figure 3). The roll 100 is subjected to treatment along the operational path to transform the substrate 10 into a strip of abrasive material 20. Material 20 may be wound, such as by another winder (not shown), around a horizontal shaft to form abrasive roll 200. The abrasive material 20 of roll 200 may be used in the formation ofthe articles ofthe invention. Substrate 10 preferably is a material comprised of a compressible and flexible structure that is relatively thin in comparison with its axial width. Preferred materials for use as the substrate 10 include nonwoven webs, woven fibrous materials or sponge-like materials such as foamed polymers and the like. Where substrate 10 is a nonwoven web, the web suitable may be made of an air-laid, carded, stitch-bonded, spunbonded, wet laid, or melt blown construction. A preferred nonwoven web is the open, lofty, three-dimensional air-laid nonwoven substrate described by Hoover et al. in U.S. Patent No. 2,958,593, incorporated herein by reference. The nonwoven web preferably comprises a first major web surface, a second major web surface, and a middle web portion extending between the first and second major web surfaces. The web is made of a suitable synthetic fiber capable of withstanding the temperatures at which impregnating resins and adhesive binders are cured without deterioration. Fibers suitable for use in the articles ofthe invention include natural and synthetic fibers, and mixtures thereof. Synthetic fibers are preferred including those made of polyester (e.g., polyethylene terephthalate), nylon (e.g., hexamethylene adipamide, polycaprolactum), polypropylene, acrylic (formed from a polymer of acrylonitrile), rayon, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymers, vinyl chloride- acrylonitrile copolymers, and so forth. Suitable natural fibers include those of cotton, wool, jute, and hemp. The fiber used may be virgin fibers or waste fibers reclaimed from garment cuttings, carpet manufacturing, fiber manufacturing, or textile processing, for example. The fiber material can be a homogenous fiber or a composite fiber, such as bicomponent fiber (e.g., a co-spun sheath-core fiber). It is also within the scope ofthe invention to provide an article comprising different fibers in different portions ofthe web (e.g., the first web portion, the second web portion and the middle web portion). Preferably, the web comprises polyester or polyamide fibers having a linear density ranging from about 1.5 to about 500 denier and preferably between 10 and 30 denier per filament. Fiber thickness preferably range between 10 and 50 mm per filament with lengths between 100 and 1000 mm. Those skilled in the art will understand that the invention is not limited by the nature ofthe fibers employed or by their respective lengths, linear densities and the like. The aforementioned nonwoven web is readily formed on a "Rando Webber" machine (commercially available from Rando Machine Company, New York) or may be formed by other conventional processes. Useful nonwoven webs preferably have a weight per unit area at least about 50 g/m 2 , preferably between 50 and 200 g/m 2 , more preferably between 75 and 150 g/m 2 . Lesser amounts of fiber within the nonwoven web will provide articles which may be suitable in some applications, but articles with lower fiber weights may have somewhat shorter commercial work lives. The foregoing fiber weights typically will provide a web, before needling or impregnation, having a thickness from about 5 to about 200 millimeters, typically between 6 to 75 millimeters, and preferably between 10 and 30 millimeters. The nonwoven web may optionally be reinforced and consolidated by needle tacking, a treatment which mechanically strengthens the nonwoven web by passing barbed needles therethrough. During this treatment, the needles pull the fibers of the web with them while they pass through the nonwoven web so that, after the needle has retracted, individual collections of fibers ofthe web are oriented in the thickness direction ofthe nonwoven fabric. The amount or degree of needle tacking may include the use of about 8 to about 20 needle penetrations per square centimeter of web surface when 15 x 18 x 25 x 3.5 RB, F20 6-32-5.5B/3B/2E/L90 needles (commercially available from Foster Needle Company, Manitowoc, Wisconsin) are used. Needle tacking is readily accomplished by use of a conventional needle loom which is commercially available from, for example, Dilo, Inc. of Charlotte, North Carolina. A prebond resin, is typically used to bond fibers in the web to one another at their mutual contact points. The prebond resin preferably comprises a coatable resin such as a thermosetting water based phenolic resin. The prebond is applied to the web in a relatively light coating, typically providing a dry add-on weight within the broad range from about 50 to 200 g/m 2 for phenolic prebond resins applied to a nonwoven web having a fiber weight within the above ranges. Polyurethane resins may also be employed as well as other resins, and those skilled in the art will appreciate that the selection and amount of resin actually applied can depend on any of a variety of factors including, for example, the fiber weight in the nonwoven web, the fiber density, the fiber type as well as the contemplated end use for the finished article. Of course, the present invention is not to be construed as being limited to nonwoven webs comprising any particular prebond resin. Moreover, the fibers of the web may be bonded to one another at their mutual contact points by use of melt bondable fibers within the substrate or by a combination of melt bondable fibers and a prebond resin, all as known to those skilled in the art. Equipment is provided along the operational path, including an abrasive composition impregnating equipment 110, a heating oven 112, a spray coater 114 for the application of an adhesive and a drying oven 116. The abrasive composition impregnating equipment is provided to impregnate the sheet substrate strip 10 with an abrasive slurry while the strip is unwound from the starting roll 100. The abrasive slurry is preferably comprised of abrasive particles in a binder such as an epoxy resin or a phenolic resin and a solvent such as xylene or carbitol, for example. As needed, a curing agent may be added to the composition. The substrate 10 runs continuously into and passes through heating oven 112 where the abrasive slurry is cured by volatilizing the solvent and heating the binder to adhere the abrasive particles to the substrate 10. The heating oven 112 is preferably maintained at a temperature sufficient to cure the binder and thereby adhere abrasive particles to the substrate 10. Oven 112 may be of a hot air blowing type, but must be controllable so as to keep a temperature ofthe oven at a desired temperature between about 100 and 300°C, preferably with a variation of ±10°C. Suitable abrasive particles for inclusion in the abrasive slurry can be selected from inorganic abrasive particles and organic based particles. The inorganic abrasives particles can be divided into hard inorganic abrasive particles (i.e., they have a Moh hardness greater than 8) and soft inorganic abrasive particles (i.e., they have a Moh hardness less than 8). Examples of conventional hard abrasive particles include fused aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, tungsten carbide, titanium carbide, diamond, cubic boron nitride, garnet, fused alumina zirconia, sol gel abrasive particles and the like. Examples of sol gel abrasive particles can be found in U.S. Patent Nos. 4,314,827, 4,623,364; 4,744,802, 4,770,671; 4,881,951, all incoφorated herein after by reference. Examples of conventional softer inorganic abrasive particles include silica, iron oxide, chromia, ceria, zirconia, titania, silicates and tin oxide. Still other examples of soft abrasive particles include: metal carbonates (such as calcium carbonate (chalk, calcite, marl, travertine, marble and limestone), calcium magnesium carbonate, sodium carbonate, magnesium carbonate), silica (such as quartz, glass beads, glass bubbles and glass fibers) silicates (such as talc, clays, (montmorillonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate) metal sulfates (such as calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate), gypsum, aluminum trihydrate, graphite, metal oxides (such as calcium oxide (lime), aluminum oxide, titanium dioxide) and metal suifites (such as calcium sulfite), metal particles (tin, lead, copper and the like) and the like. Plastic abrasive particles can be formed from a thermoplastic material such as polycarbonate, polyetherimide, polyester, polyethylene, polysulfone, polystyrene, acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetal polymers, polyvinyl chloride, polyurethanes, nylon and combinations thereof. In general, preferred thermoplastic polymers are those having a high melting temperature or good heat resistance properties. Plastic abrasive particles can be formed from a crosslinked polymer such as from phenolic resins, aminoplast resins, urethane resins, epoxy resins, melamine-formaldehyde, acrylate resins, acrylated isocyanurate resins, urea-formaldehyde resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy resins and mixtures thereof. These crosslinked polymers can be made, crushed and screened to the appropriate particle size and particle size distribution. The abrasive article may also contain a mixture of two or more different abrasive particles. This mixture may comprise a mixture of hard inorganic abrasive particles and soft inorganic abrasive particles or a mixture of two soft abrasive particles. In the mixture of two or more different abrasive particles, the individual abrasive particles may have the same average particle size, or alternatively the individual abrasive particles may have a different average particle size. In yet another aspect, there may be a mixture of inorganic abrasive particles and organic abrasive particles. The abrasive particle can be treated to provide a surface coating thereon. Surface coatings are known to improve the adhesion between the abrasive particle and the binder in the abrasive article. Additionally, the surface coating may also improve the dispersibility ofthe abrasive particles in the binder precursor. Alternatively, surface coatings can alter and improve the cutting characteristics of the resulting abrasive particle. Most preferably, the abrasive particles are selected from ceramic materials such as aluminum oxide (Al 2 O3), chromium oxide (Cr 2 O 5 ) or the like having a size within the range from about 0.1 to 100 μm. The abrasive coated substrate passes under a spray coater 114 which is set to apply a second adhesive composition on the upper major surface ofthe substrate 10. The spray coating equipment 114 comprises a container for an adhesive composition, an air compressor, and jet nozzle. A venturi is provided to admix a compressed air feed with the adhesive composition added through the venturi from the container. The resulting aerated composition is sprayed through the jet nozzle toward the upper major surface ofthe substrate 10. The adhesive composition preferably comprises a solid epoxy resin having a softening point of not less than 60°C, a curing agent and a volatile solvent. The composition may have a viscosity within the range of 1 to 100 cps. More preferably, the adhesive composition comprises a curable solid resin selected from any of a variety of resins such as, for example, a solid epoxy resin, solid urea resin, solid urethane resin, solid phenol resin or the like. Preferably, the resin is a solid epoxy resin, most preferably the solid epoxy is that disclosed in Japanese Patent application No. 7-20813. As used herein, "solid epoxy resin" refers to an epoxy resin soluble in a volatile solvent and kept solid at temperatures of around 25° C without being cured so long as it is not dissolved in the solvent. In other words, the adhesive component forms a solid phase ofthe resin with curing agent dispersed therein so that the solid phase is neither tacky nor flowable. Further, while the resin remains solid, it does not deteriorate the compressibility or flexibility ofthe substrate sheet strip. Additionally, the above mentioned binder for the abrasive particles applied to the substrate 10 at station 1 10 (Figure 3) preferably is an epoxy resin, and it may be the same solid epoxy resin or a different epoxy resin. The solid epoxy resin may be selected from the group consisting of a cresol novolak type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a phenol novolak type epoxy resin, a trishydroxyphenylmethane type epoxy resin, a naphthalene epoxy resin, a fluorene epoxy resin and a glycidylamine compound. The curing agent can be selected from any of a variety of known agents, and preferably is selected from the group comprising or consisting of dicyandiamide, acid gydrazide, boron trifluoride complex, imidazol compound, amine*imide and zinc salt. A particularly preferred curing agent is dicyandiamide ("DICY"). Most preferred is a composition comprising 100 parts of bisphenol A type epoxy resin, 4 parts of dicyandiamide and the balance of propyleneglycol monomethylether, wherein the viscosity at room temperature is about 50 cps. The adhesive composition is sprayed onto the upper surface ofthe substrate 10 so that its solid content of about 3 g/m 2 is coated on the upper surface ofthe substrate while the sheet strip travels at a speed of 10 to 100 m/rnin. The spray equipment 1 14 may be operated at a jet pressure within the range of 0.5 to 5 kg/cm 3 , and a jet rate of 100 to 1000 g/min. In coating the substrate 10 with the adhesive composition, the composition is typically applied to only one ofthe major surfaces ofthe substrate 10. During the aforementioned spraying step, the adhesive readily enters the interior ofthe uncompressed substrate 10 under the force of gravity and due to the fluidity ofthe adhesive composition, resulting in a substrate that is impregnated with the adhesive. Under the above pressures and due to the open structure ofthe preferred substrate, the adhesive impregnating step typically does not require a substantial amount of time as compared with conventional dip coating, for example. A drying oven 116 is provided to dry the adhesive coated substrate 10 and may be of a hot air blowing type or an EREMA heater type, but must be controlled so as to keep a temperature ofthe oven at a desired level of 50 to 150°C with a variation of ±10°C. Substrate 10 travels into and pass through oven 116 where the solvent in the adhesive composition applied by the coater 1 14 is volatilised. The dwell time for the substrate 10 in oven 116 and the drying temperature are set to dry the composition without curing the adhesive. When the above mentioned preferred adhesive containing a bisphenol A type epoxy resin, dicyandiamine and propyleneglycol monomethylether, drying may be carried out at 100°C with a dwell time within oven 1 16 of about 5 minutes. As the adhesive treated substrate 20 exits oven 116, the solid epoxy resin is in an uncured non-tacky solid phase. The epoxy treated abrasive substrate 20 can be further processed immediately or, as shown, it may be rolled into intermediate roll 200 for subsequent use. Roll 200 can be stored at the ordinary temperature (e.g., room temperature) and can readily be transported to any location where the roll 200 can be unwound for subsequent processing, as described below. In an important aspect ofthe present invention, the preferred adhesive applied to the substrate is in an uncured state on roll 200. In contrast, epoxy resins known in the art belonging to the so called "curable non-solid resin" type, the binder component ofthe above mentioned abrasive composition would become cured due to the heating step used to volatilize solvent from liquid adhesive composition. The resulting substrate 20 would become rigid, and its compressibility and flexibility would be reduced. Consequently, the substrate 20 would find no utility in the manufacture of abrasive brushes, as are described herein. Referring to Figure 4, the intermediate roll 200 may be transported, if necessary, and mounted to another unwinder (not shown). In any event, roll 200 is unwound and the substrate 20 is directed along another operational path. A conventional stamping machine (not shown) is preferably used to cut disc sheets 25 from the strip 20. The sheets 25 are of a disc form having a central hole 26 with keyways extending therethrough and adapted to fit with counterpart keys on a rotation spindle. For commercial applications, the disc sheets 25 preferably have an outer diameter of 300 to 500 mm, but may be prepared with other diameters, as needed. The disc sheets 25 may be stored for a desired period of time and/or transported to a workshop where a sixth step of assembling the disc sheets with provisional tools is carried out. The provisional tools correspond to those used in the conventional dipping method as mentioned above and include a base end plate 6, a push plate 7 having a central hole extending therethrough, a dummy shaft 8 for alignment releasably fixed to the base plate 7 and extending upwards at a center thereof and means for releasably retaining the push plate 7 relative to the base plate 6 (not shown). The dummy shaft 8 has a cross-sectional configuration corresponding to the configuration ofthe rotation spindle, and is allowed to extend through the central holes ofthe stamped disc sheets 25 and push plate 7. In assembling the brushes ofthe invention a given number ofthe disc sheets 25 are slipped onto the dummy shaft 8 and stacked on the base plate 6 while the dummy shaft 8 extends through the central holes ofthe stacked disc sheets 25. In this case, each disc sheet 25 is slipped onto the dummy shaft 8 with its major surface opposite to the dried and uncured adhesive coated major surface facing toward the base plate 6, except for the last or uppermost disc sheet. The last disc sheet is stacked on the neighboring lower disc sheet so as to have its coated side surface in contact with the coated side surface ofthe disc sheet beneath it. In this arrangement, the base plate 6 and push plate 7 are prevented from contacting the coated side surfaces of adjacent disc sheets. Alternatively, one or more disc sheets belonging to a lower group are stacked so as to have the coated side surface positioned as an upper surface facing away from the base plate 6, and a plurality of the disc plates belonging to an upper group are stacked on the lower group so as to have the coated side surfaces positioned as lower surfaces facing toward the base plate 6, whereby the lowermost disc sheet in the upper group and the uppermost disc sheet in the lower group are brought in contact with each other at their coated side surfaces. It will be appreciated, however, that the invention is not limited to any particular arrangement for the disc sheets 25. The stacked disc sheets are compressed against the base plate 6 by pushing the push plate 7 downwards. The base plate 6, the push plate 7, the dummy shaft 8 and the compressed disc sheets are retained as a unit by suitable retaining means to form an assembly. Suitable retaining means may comprise nuts and a plurality of threaded rods equi-spaced circumferentially and extending upwards from the base plate 6 at a peripheral region thereof outside ofthe laminate. Each rod having a threaded upper portion to be engaged with the nut. Holes may be provided in the push plate 7 to allow the rods to extend therethrough. When the laminate is compressed downwards by the push plate 7, the nuts may be engaged with the threaded portions ofthe rods to thereby maintain the stacked discs 25 laminate in their compressed configuration. As the result, the laminate is kept compressed to have a desired thickness corresponding to 1/3 to 1/5 ofthe original thickness (e.g., prior to compression). Dummy shaft 8 may then be removed from the assembly. One or more assemblies may be transported to a heating oven 27 similar to that for curing the abrasive composition. Oven 27 is maintained at a temperature sufficient to cure the dried adhesive within the laminate. In this manner, the solid epoxy resin is cured , typically with the aid ofthe curing agent. For the above mentioned preferred epoxy resin, curing may be carried out by heating at 160°C for about 2 hours. Thereafter, the assembly is removed from oven 27 and allowed to cool. Base plate 6 and end plate 7 may then be removed from the stacked to provide a finished abrasive brush of laminated abrasive discs. In the manufacture of other brush configurations such as the convolute type and the flap type shown in Figures 5 c and 5 b, respectively, the aforementioned steps prior to stacking and compressing are applicable, as known by those skilled in the art. Moreover, the roll 100 of substrate 10 may be effectively used to produce brushes ofthe flap type as well as the convolute type. In the formation ofthe foregoing laminate brush structure, the substrate is relatively thin in comparison with its axial width formed by the disc sheets, and the disc sheets are stacked, compressed and then subjected to the curing treatment to form a disc brush. These process features cause the density ofthe cured adhesive within the brush to be distributed uniformly throughout the substrate. Additionally, the substrate 20 carrying the dried adhesive is easy to handle and can readily be for stamped into disc sheets. The disc sheets can be easily stacked in forming a brush according to the invention without possible environmental and toxicological concerns. With respect to the above described preferred solid epoxy resin, the softening point ofthe resin is preferably not less than 60°C to ensure that the adhesive remains uniformly distributed while it is being cured. If the softening point ofthe solid epoxy resin is less than 60°C, the resin may excessively soften at the curing step to such an extent that it will flow within the stacked and compressed disc sheets and become redistributed in the stacked disc sheets in a nonuniform manner. More preferably, the softening point is in the range from 60°C to 300°C and most preferably from 60°C to 160°C. Those skilled in the art will also appreciate that the invention is not limited to the foregoing process or to articles wherein the substrate 10 is coated along only one of its major surfaces with adhesive. Articles and process involving a substrate coated with adhesive along both of its major surfaces may be alternatively employed according to the present invention. However, the above described embodiment wherein only one ofthe major surfaces ofthe substrate 10 is coated with adhesive is generally preferred in order to minimize the amount of adhesive required in the manufacture ofthe finished brush and to provide a surface on the disc sheets that are free of the uncured adhesive for use as the end pieces in the compressed stack of disc sheets. Disc sheets with both major surfaces coated with resin can adhere to the base and end plates (members 6 and 7, Figure 4) during curing ofthe adhesive. In this latter case, removal ofthe base plate and the end plate may damage the abrasive brush. The above mentioned compression ofthe stacked disc sheets brings the two major surfaces of each disc sheet into close proximity so that the thickness and the volume ofthe disc sheets are considerably reduced. As a result, the density ofthe dried adhesive in each disc sheet is significantly increased, even though the amount ofthe dried adhesive is not changed between the non-compressed state and the compressed state. The increased density ofthe adhesive ensures that the laminate is compacted in such a manner that neighboring compressed disc sheets are bound to each other and that each compressed disc sheet is fixed in thickness when the adhesive is cured. The increase in adhesive density caused by compression ofthe stacked disc sheets also lessens the total amount of adhesive needed to manufacture an acceptable abrasive brush, especially when compared the use of a dipping method for the application of adhesive, for example. Variations to the described process are also contemplated within the scope ofthe invention. For example, cutting ofthe substrate material (e.g., into discs 25) can be performed prior to coating the substrate either with the abrasive slurry at station 110 (Figure 3) or before application ofthe second adhesive composition applied at spray coater 1 14, for example. The cut discs can then be treated with abrasive slurry, cured and treated with the second adhesive composition, as described above. Any process for the manufacture of an abrasive article wherein the substrate material is laminated to form a compressed substrate assembly, in the above described manner, is considered within the scope ofthe present invention. In the comparison of an abrasive brush made according to the present invnetion with those prepared by the so called "direct method" and "dipping method, Table 1 sets forth the expected properties ofthe brushes. "Production Time" indicates the amount of time required to assemble each ofthe brushes, and the time requires for production ofthe inventive brush is represented by "1 " as a reference value. The production times for the Comparative Examples are relative to that required for the inventive article. Table 1 2. available under the trade designat on CP-L Brush", commercially available from Sumitomo 3M Ltd. of Japan As indicated in the data, the inventive brush provides a uniform density distribution and no blooming while both ofthe comparative examples exhibit at one of these undesired properties. Although the method for the manufacture ofthe inventive brush is more lengthy than that for a brush mad according to the direct method, the finished brush is superior in its construction. Moreover, the time required and the amount of adhesive needed for the manufacture ofthe inventive brush are substantially less than that required for the brush made by the dipping method. While the invention has been described in terms of its preferred embodiment, those skilled in the art will appreciate that changes or modification to the described embodiment may be possible without departing from the spirit ofthe invention.

Claims: What is claimed is: 1. A process for producing an abrasive brush, comprising the steps of: providing a flexible and compressible abrasive substrate, the substrate having first and second major surfaces; coating the substrate on at least the first major surface with a liquid adhesive composition containing a solid epoxy resin, a curing agent and a volatile solvent; drying the coated substrate to volatilize the solvent; cutting the substrate into smaller pieces; assembling a plurality ofthe pieces to provide an assembly wherein at least a pair ofthe pieces are oriented with respect to one another so that a first major surface of one ofthe pieces abuts a second major surface of another ofthe pieces; heating the assembly at a temperature higher than that ofthe drying step to cure the solid epoxy resin and thereby bond the pieces to one another within the assembly; and cooling the assembly to provide the brush. 2. The process of claim 1 wherein cutting is performed prior to coating. 3. The process of claim 1 wherein coating is performed prior to cutting. 4. The process of claim 1 wherein the substrate is a material selected from the group consisting of nonwoven webs, woven materials and foamed polymeric materials. 5. The process of claim 1 wherein providing a flexible and compressible abrasive substrate comprises: forming a lofty nonwoven web of fibers bonded to one another at their mutual contact points; and bonding a plurality of abrasive particles to the fibers ofthe nonwoven web. 6. The process of claim 5 wherein the abrasive particles are selected form the group consisting of inorganic abrasive particles and organic based particles. 7. The process of claim 6 wherein the inorganic abrasive particles are selected from the group consisting of aluminum oxide, silicon carbide, titanium diboride, boron carbide, tungsten carbide, titanium carbide, diamond, cubic boron nitride, garnet, fused alumina zirconia, sol gel abrasive particles, silica, iron oxide, chromia, ceria, zirconia, titania, silicates, tin oxide, metal carbonates, silicon oxides, silicates, metal sulfates, gypsum, aluminum trihydrate, graphite, metal oxides, metal sulfites, metal particles and mixtures ofthe foregoing materials. 8. The process of claim 6 wherein the inorganic abrasive particles are selected from the group consisting of polycarbonate, polyetherimide, polyester, polyethylene, polysulfone, polystyrene, acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetal polymers, polyvinyl chloride, polyurethanes, nylon, phenolic resins, aminoplast resins, urethane resins, epoxy resins, melamine- formaldehyde, acrylate resins, acrylated isocyanurate resins, urea-formaldehyde resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy resins and mixtures ofthe foregoing materials. 9. The process as defined in claim 5 wherein bonding a plurality of abrasive particles to the fibers ofthe nonwoven web comprises impregnating the web with a slurry comprised of abrasive particles dispersed within a curable binder; and heating the substrate to cure the curable binder and bond the abrasive particles to the fibers ofthe nonwoven web. 10. The process as defined in claim 1 wherein coating is performed by spraying the liquid adhesive onto the first major surface ofthe substrate. 11. The process as defined in claim 1 wherein the solid epoxy resin has a softening point of 60° C and is selected from the group consisting of cresol novolak epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolak epoxy resin, trishydroxyphenylmethane epoxy resin, naphthalene epoxy resin, fluorene epoxy resin and a glycidylamine compound. 12. The process as defined in claim 1 wherein the curing agent is selected from the group consisting of dicyandiamide, acid hydrazide, boron trifluoride complex, imidazol compound, amine«imide compound and zinc salt. 13. The process as defined in claim 1 wherein the solid epoxy resin comprises 100 parts by weight bisphenol A epoxy resin, 4 parts by weight dicyandiamide and the balance propyleneglycol monomethylether. 14. The process as defined in claim 1 wherein the smaller pieces are disc shaped; and assembling comprises stacking a plurality ofthe pieces and compacting the plurality of pieces prior to heating, the pieces arranged in the assembly in a manner to ensure bonding to one another during heating. 15. An abrasive brush formed by the process of claim 1.

Inventors: OHTSUBO MASAO, OHTSUBO, MASAO
Applicants: MINNESOTA MINING & MFG, OHTSUBO MASAO, MINNESOTA MINING AND MANUFACTURING COMPANY, OHTSUBO, MASAO
Application year: 1997
Main classification: B24D18
IPC codes: A46B7, A46B13, A46D1, B24D13, B24D18