Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
  • B24D11/001—Manufacture of flexible abrasive materials

Definitions

• the present disclosure broadly relates to abrasive articles and methods of using them.
• Coated abrasive articles containing from the abrasive particles secured to a backing by a binder are useful for abrading, finishing, or grinding a wide variety of materials and surfaces in the
• coated abrasive articles have an abrasive layer secured to a backing.
• the abrasive layer comprises abrasive particles and a binder that secures the abrasive particles to the backing.
• coated abrasive article has an abrasive layer comprised of a make layer, a size layer, and abrasive particles.
• a make layer precursor comprising a curable make resin is applied to a major surface of the backing. Abrasive particles are then at least partially embedded into the curable make resin (for example, via electrostatic coating), and the curable make resin is at least partially cured (that is, crosslinked) to adhere the abrasive particles to the backing.
• a size layer precursor comprising a curable size resin is then applied over the at least partially cured curable make resin and abrasive particles, followed by curing of the curable size resin precursor, and optionally further curing of the curable make resin.
• Some coated abrasive articles additionally have a supersize layer covering the abrasive layer.
• the supersize layer typically includes grinding aids and/or anti-loading materials.
• Some coated abrasive articles have one or more backing treatments such as a backsize layer (that is, a coating on the major surface of the backing opposite the major surface having the abrasive layer), a presize layer, a tie layer (that is, a coating between the abrasive layer and the major surface to which the abrasive layer is secured), a saturant, a subsize treatment, or a combination thereof.
• a subsize is similar to a saturant except that it is applied to a previously treated backing.
• Two common forms of coated abrasive articles are discs and belts.
• the abrading action of the belt on a workpiece e.g., wood
• increases the load on the drive motor used to drive the belt and hence an increase in electrical current draw by the motor.
• the present disclosure provides a coated abrasive belt comprising:
• an endless backing comprising:
• a fabric backing having first and second opposed major surfaces and a basis weight in range of from 200 to 500 grams per square meter;
• the polymeric presize layer has a basis weight in range of from 190 to 230 grams per square meter;
• At least one polymeric backsize layer on the second major surface wherein the at least one backsize layer has a combined basis weight in range of from 200 to 500 grams per square meter;
• a make layer comprising a first polymeric binder
• abrasive particles affixed to the make layer in an amount of from 300 to 800 grams per square meter, wherein the abrasive particles comprise from 40 to 60 percent by weight of shaped alpha alumina abrasive particles having particle sizes of from 0.5 millimeter to 2 millimeters, and from 60 to 40 percent by weight of crushed alpha alumina particles having a particle size of 2000 microns or less; and
• a size layer comprising a second polymeric binder disposed on the make layer and abrasive particles.
• coated abrasive belts according to the present disclosure are suitable for rapid wood stock removal while drawing a low current load that makes them suitable for use in shops having older and/or low power belt sanders.
• abrasive dispersion means an alpha alumina precursor that can be converted into alpha alumina that is introduced into a mold cavity.
• the composition is referred to as an abrasive dispersion until sufficient volatile components are removed to bring solidification of the abrasive dispersion.
• the term "precursor shaped abrasive particle” means the unsintered particle produced by removing a sufficient amount of the volatile component from the abrasive dispersion, when it is in the mold cavity, to form a solidified body that can be removed from the mold cavity and substantially retain its molded shape in subsequent processing operations.
• shaped abrasive particle means a ceramic abrasive particle with at least a portion of the abrasive particle having a predetermined shape that is replicated from a mold cavity used to form the precursor shaped abrasive particle. Except in the case of abrasive shards (e.g. as described in U.S. Patent Appl. Publ. 2009/0165394 Al (Culler et al.)), the shaped abrasive particle will generally have a predetermined geometric shape that substantially replicates the mold cavity that was used to form the shaped abrasive particle. Shaped abrasive particle as used herein excludes abrasive particles obtained by a mechanical crushing operation.
• Exemplary shaped abrasive particles are disclosed in U.S. Patent Nos. 5,201,916 (Berg et al.); 5,366,523 (Rowenhorst et al.) (Re 35,570); 5,984,988 (Berg et al.); 8, 142,531 B2 (Adefris et al.); 8,142,891 (Culler et al.); 8,142,532 B2 (Erickson et al.); and in U.S. Patent Appl. Publ. No. 2010/146867 Al (Boden et al.).
• the term "diluent particles” means either: (1) a plurality of individual abrasive particles bonded together by an adhesive to form an agglomerate, (2) a plurality of individual non- abrasive particles bonded together by an adhesive to form an agglomerate, (3) a plurality of individual abrasive particles and a plurality of individual non-abrasive particles bonded together by an adhesive to form an agglomerate, (4) individual non-abrasive particles; (5) individual abrasive particles, or (6) combinations of the foregoing.
• abrasive particles have a Mohs hardness greater than or equal to 7 and "non- abrasive particles” have a Mohs hardness less than 7.
• Exemplary abrasive particles can include without limitation: fused aluminum oxide, silicon carbide, garnet, fused alumina zirconia, cubic boron nitride, and diamond.
• Exemplary non-abrasive particles can include without limitation: solid particles or hollow bubbles of glass, mullite, gypsum, marble, cryolite, and resin or plastic materials.
• FIG. 1 is a schematic side view of an exemplary coated abrasive belt according to the present disclosure.
• FIG. 1A is an enlarged view of region 1A in FIG. 1.
• coated abrasive belt 100 comprises backing 1 10 and abrasive layer 120 secured to backing 1 10.
• backing 1 10 comprises a fabric backing 130 having first and second opposed major surfaces (132, 134).
• First polymeric presize layer 140 is disposed on first major surface 132.
• Optional second polymeric presize layer 142 is disposed on first polymeric presize layer 140.
• First polymeric backsize layer 150 is disposed on second major surface 134.
• Optional second polymeric backsize layer 152 is disposed on first polymeric backsize layer 150.
• Abrasive layer 120 contacts optional second polymeric presize layer 142 (or first polymeric presize layer 140 if it is not present).
• Abrasive layer 120 comprises make layer 160 comprising a first polymeric binder; shaped alpha alumina abrasive particles 170 and crushed alpha alumina abrasive particles 172 affixed to make layer 160; and size layer 180 comprising a second polymeric binder disposed on make layer 160, shaped alpha alumina abrasive particles 170, and crushed alpha alumina abrasive particles 172.
• Suitable fabric backings include, for example, those known in the art for making flexible coated abrasive articles such as belts. Selection of materials for the fabric backing and treatments typically involves balancing flexibility, strength, and durability, e.g., for use as a sanding belt,
• Exemplary suitable fabric backings include nonwoven fabrics (for example, including needletacked, meltspun, spunbonded, hydroentangled, or meltblown nonwoven fabrics), knitted, stitchbonded, and woven fabrics; scrim; combinations of two or more of these materials; and treated versions thereof.
• the fabric backing can be made from any known fibers, whether natural, synthetic or a blend of natural and synthetic fibers.
• useful fiber materials include fibers or yarns comprising polyester (for example, polyethylene terephthalate), polyamides (for example, hexamethylene adipamide, polycaprolactam), polypropylene, acrylics and modified acrylics, cellulose acetate, polyvinylidene chloride, vinyl chloride copolymers, vinyl chloride-acrylonitrile copolymers, graphite, polyimide, silk, cotton, linen, jute, hemp, or regenerated cellulose.
• Useful fibers may be of virgin materials or of recycled or waste materials reclaimed from garment cuttings, carpet manufacturing, fiber manufacturing, or textile processing, for example.
• Useful fibers may be homogenous or a composite such as a bicomponent fiber (for example, a co-spun sheath-core fiber).
• the fibers may be tensilized and crimped, but may also be continuous filaments such as those formed by an extrusion process.
• the thickness of the fabric backing generally ranges from about 0.02 to about 5 millimeters, desirably from about 0.05 to about 2.5 millimeters, and more desirably from about 0.1 to about 2 millimeter, although thicknesses outside of these ranges may also be useful, for example, depending on the intended use.
• the strength of the backing should be sufficient to resist tearing or other damage during abrading processes.
• the thickness and smoothness of the backing should also be suitable to provide the desired thickness and smoothness of the coated abrasive article; for example, depending on the intended application or use of the coated abrasive article.
• the fabric backing has a basis weight in the range of from 200 to 500 grams per square meter (gsm), preferably from 250 to 500 grams per square meter, and more preferably from 300 to 400 grams per square meter.
• the fabric backing should have sufficient flexibility to function as a mechanically driven abrasive belt.
• one or more surfaces of the backing may be modified by known methods including corona discharge, ultraviolet light exposure, electron beam exposure, flame discharge, and/or scuffing.
• the fabric backing has at least one presize layer on its outer surface facing the abrasive layer to seal the backing, protect yarn or fibers in the backing, and/or promote adhesion of the make layer to the fabric backing.
• at least one of these backing treatments is used, although this is not a requirement.
• the inclusion of a presize layer or backsize layer may additionally result in a "smoother" surface on either the front and/or the backside of the fabric backing.
• the polymeric presize layer(s) and backsize layer(s) independently comprise polymeric materials that result from at least partial curing of a curable binder precursor.
• suitable curable binder precursors include epoxy resins, phenolic resins (e.g., novolac resins), free-radically polymerizable acrylic resins, melamine- formaldehyde resins, aminoplast resins, cyanate resins, and combinations thereof.
• suitable curable binder precursors comprise, based on the total weight of components a) to g): a) from 1 to 12 percent of at least one polyepoxide preparable by reaction of epichlorohydrin with at least one of bisphenol A or bisphenol F; b) from 70 to 90 percent of at least one polyfunctional urethane (meth)acrylate, wherein homopolymerization of the polyfunctional urethane (meth)acrylate results in a polymer having a glass transition temperature of less than 50 °C; c) from 1 to 10 percent of at least one non-urethane polyfunctional (meth)acrylate; d) from 1 to 10 percent of at least one acidic free-radically polymerizable monomer; e) dicyandiamide; f) photoinitiator; and g) optional epoxy cure catalyst. Further details concerning such binder precursors can be found in U.S. Pat. No. 7,344,574 (Thurber et al.).
• the polymeric presize layer has a basis weight (or a total combined basis weight if two or more stacked presize layers are present) of from 190 to 230 grams per square meter, preferably from 195 to 225 grams per square meters, and more preferably from 200 to 225 grams per square meter.
• the backsize layer(s) has a basis weight (or a total combined basis weight if two or more stacked backsize layers are present) of from 200 to 500 grams per square meter, preferably from 200 to 300 grams per square meters, and more preferably from 200 to 270 grams per square meter.
• Additional materials useful as backing treatments include, for example, one or more fillers, thickeners, tougheners, pigments, fibers, tackifiers, lubricants, wetting agents, surfactants, antifoaming agents, dyes, coupling agents, plasticizers, antistatic agents, suspending agents, or a combination thereof.
• Useful antistatic agents include, e.g., carbon black particles and/or vanadium pentoxide particles.
• the backsize layer(s) contains carbon black particles in sufficient amount to mitigate static buildup during use.
• an antistatic agent may reduce the tendency of the coated abrasive article to accumulate static electricity when sanding wood.
• the make layer is disposed on the presize layer by applying a curable make layer precursor, optionally followed by partial curing).
• suitable make layer precursors include epoxy resins, phenolic resins (e.g., novolac resins), free-radically polymerizable acrylic resins, melamine-formaldehyde resins, aminoplast resins, cyanate resins, and combinations thereof.
• the curable make layer precursor will one or more catalysts, curative, hardeners, thermal initiators, and/or photoinitiators in at least an amount effective to cure the curable make layer precursor.
• additives e.g., fillers, grinding aids, plasticizers, wetting agents, surfactants, pigments, coupling agents, fibers, lubricants, thixotropic materials, antistatic agents, suspending agents, and/or dyes.
• Suitable curing methods include, for example, application of heat, light, electron beam radiation, and combinations thereof.
• the make layer precursor may be applied by any known coating method for applying a make layer precursor to a backing including, e.g., roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, and spray coating.
• the basis weight of the make layer in the coated abrasive belt is typically in the range of from 50 to 500 grams per square meter, although other basis weight may also be used.
• the basis weight of the make layer is in the range of from 70 to 400 grams per square meter and more preferably from 100 to 300 grams per square meter.
• abrasive particles are deposited onto the make layer precursor.
• abrasive particles Two types are used: shaped abrasive particles, and crushed abrasive particles, both comprising alpha alumina.
• the total weight of abrasive particles is in the range of from 300 to 800 grams per square meter, preferably 350-700 grams per square meter, and more preferably 375- 650 grams per square meter.
• the shaped abrasive particles comprise from 40 to 60 percent by weight of the abrasive particles based on the total weight of the abrasive particles.
• the shaped abrasive particles have a particle size of from 0.1 millimeter to 2 millimeters, preferably 0.5 to 1.5 mm, and more preferably from 0.7 to 1.5 mm.
• abrasive particle size is determined based on the ability of the abrasive particles to pass through U.S. Standard Testing Sieves (ASTM-E- 1 1, e.g., as available from The Murdock Co., Mundelein, Illinois) having openings corresponding to the specified size of the abrasive particle.
• shaped abrasive particles having a size between 0.5 millimeter and 1.4 millimeters will pass through a No. 14 testing sieve (1.40 mm openings), but be retained on a No. 35 testing sieve (500 micron openings).
• Suitable shaped alpha alumina abrasive particles, prepared by a sol-gel molding process are known in the art; see, for example, U.S. Patent Nos. 5,201,916 (Berg et al.); 5,366,523 (Rowenhorst et al.) (Re 35,570); 5,984,988 (Berg et al.); 8, 142,531 B2 (Adefris et al.); 8,142,891 (Culler et al.);
• the shaped abrasive particles comprise truncated triangular prisms with sloping sidewalls, and optionally parallel grooves in the base, e.g., as described in U.S. Patent No. 8,142,531 B2 (Adefris et al.).
• the crushed abrasive particles comprise from 40 to 60 percent by weight based on the total weight of the abrasive particles.
• Exemplary useful crushed alpha alumina abrasive particles include crushed particles of fused aluminum oxide based materials such as aluminum oxide, ceramic aluminum oxide (which may include one or more metal oxide modifiers and/or seeding or nucleating agents), and heat-treated aluminum oxide, sol-gel derived alumina abrasive particles, and blends thereof. Examples of sol-gel abrasive particles include those described in U.S. Pat. Nos.
• the crushed abrasive particles have a particle size of less than or equal to from 2000 microns
• the crushed abrasive particles have a particle size between 50 and 1500 microns, preferably between 75 to 1300 microns.
• the abrasive particles are preferably deposited on the make layer precursor according to the two step procedure described in U.S. Publ. Pat. Appl. No. 201 1/0289854 Al (Moren et al.). In that procedure, a first layer of particles (e.g., crushed alpha alumina particles) is created over a second layer of particles (shaped abrasive particles) on a support surface and the first layer of particles is different in at least one property from the second layer of particles.
• the make layer precursor-coated backing is positioned above the first and second layer of particles. An electrostatic field is applied simultaneously to the first and second layer of particles such that the first layer of particles closer to the coated backing are preferentially attracted to the coated backing first before the second layer of particles.
• the abrasive particles Once the abrasive particles have been embedded in the make layer precursor, it is at least partially cured in order to preserve orientation of the mineral during application of the size layer precursor.
• the size layer precursor is applied over the at least partially cured make layer precursor and abrasive particles.
• the size layer precursor may be applied by any known coating method for applying a size layer precursor including, e.g., roll coating, extrusion die coating, curtain coating, knife coating, gravure coating, and spray coating.
• the basis weight of the size layer in the coated abrasive belt is typically in the range of from 100 to 600 grams per square meter, although other basis weight may also be used.
• the basis weight of the size layer is in the range of from 100 to 500 grams per square meter, more preferably from 100 to 400 grams per square meter.
• the size layer may be applied by any known coating method for applying a size layer to a backing including, for example, roll coating, extrusion die coating, curtain coating, and spray coating.
• a supersize layer may be applied to at least a portion of the size layer.
• the supersize typically includes grinding aids and/or anti-loading materials.
• the optional supersize layer may serve to prevent or reduce the accumulation of swarf (the material abraded from a workpiece, e.g., wood particles) between abrasive particles, which can dramatically reduce the cutting ability of the coated abrasive article.
• Useful supersize layers typically include a grinding aid (for example, potassium tetrafluoroborate), metal salts of fatty acids (for example, zinc stearate or calcium stearate), salts of phosphate esters (for example, potassium behenyl phosphate), phosphate esters, urea-formaldehyde resins, mineral oils, crosslmked silanes, crosslmked silicones, and/or fluorochemicals.
• Useful supersize materials are further described, for example, in U.S. Pat. No. 5,556,437 (Lee et al.).
• the abrasive article may be converted into a coated abrasive belt; for example, by trimming and splicing the abrasive article according to conventional methods. Suitable methods are described in, for example, U.S. Pat. Nos. 2,391,731 (Miller et al.); 2,309,305 (Dahlstrom et al.);
• Coated abrasive belts according to the present disclosure are particularly useful for abrading wood, and especially for wood stock removal. Without wishing to be bound by theory, it is believed that coated abrasive belts according to the present disclosure function at least in part by skiving the wood, resulting in high rates of removal with relatively low electrical current draw by the sanding apparatus.
• titanium dioxide filler obtained from Kemira Pigments, Inc.
• fumed silica obtained as '"Cab-O-Sil" from Cabot Corporation, Cab-
• a 3 in. (7.6 cm) wide endless coated abrasive belt to be tested was mounted on a belt sander fitted with an 8 in. (20.6 cm) steel contact wheel.
• a 16 in. (40.6 cm) long x 5/8 in. (1.6 cm) thick particle board workpiece was secured to a test fixture in a position to be abraded on its edge by the endless coated abrasive belt.
• the test fixture was adjusted to provide a 10 mm interference between the proximal surface of the edge of the workpiece and the surface of the coated abrasive belt.
• the belt sander was activated to a surface speed of 5750 ft/min (1753 m/min) and the workpiece traversed along the 16 in.
• a woven polyester sateen greige backing cloth (366.2 g/m 2 , 32 mils (0.8 mm) thick) obtained from Milliken and Company, Spartanburg, South Carolina) was coated on the "coat" side with the Presize composition shown in Table 2 to provide a presized backing weighing 1 160 cg/200 cm (580 g/m 2 ).
• the presized backing was heated to 140 °C for 3 minutes.
• a first backsize coating of the Backsize 1 composition shown in Table 2 was then applied to the opposite (back) side of the presized backing to achieve a total weight of 1536 cg/200 cm 2 (768 g/m 2 ) and heated to 100/120/135 °C for 1 minute at each temperature.
• a second backsize coating of the Backsize 2 composition shown in Table 2 was then applied over the first backsize coating to achieve a total weight of 1700 cg/200 cm 2 (850 g/m 2 ) and heated in an oven set at 100/120/135 °C for 1 minute at each temperature.
• a make composition 55 grains/24 in 2 (183 g/m 2 ) shown in Table 2) was then applied to the coat side of the presized and backsized backing.
• 165 grains/24 in 2 (550 g/m 2 ) of abrasive particles of the mineral composition shown in Table 2 was then applied via the electrostatic coating process described in U.S. Publ. Pat. Appln. No. 201 1/0289854 Al (Moren et al.), whereby a layer of API was applied over a layer of AP2 on the conveyor belt.
• the particle-coated composition was then heated to 93 °C for 85 minutes.
• a size composition (80 grains/24 in 2 (267 g/m 2 ) of the size composition shown in Table 2) was then applied over the particle coating and heated to 89 °C for 85 minutes.
• This abrasive composite was then cured at 100 °C for 12 hours. The cured composite was then flexed over a 1 inch (2.5 cm) diameter bar and converted in to an endless belt.
• Comparative Example A was a commercially-available endless coated abrasive belt containing only crushed abrasive particles, obtained as "SG R963 grade 36" from Saint-Gobain Abrasives, Inc., Worcester, Massachusetts.
• Comparative Example B was a commercially-available endless coated abrasive belt containing only crushed abrasive particles, obtained as "970DZ grade 36" from 3M, Saint Paul, Minnesota.

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• 2014
  • 2014-04-17 WO PCT/US2014/034484 patent/WO2014176108A1/en active Application Filing
  • 2014-04-17 DE DE212014000110.2U patent/DE212014000110U1/de not_active Expired - Lifetime
  • 2014-04-17 CN CN201490000602.0U patent/CN205497246U/zh not_active Expired - Lifetime
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