KR20060093116A - Method of making a coated abrasive - Google Patents

Abstract

An abrasive article includes an array of protruding abrasive units (400). Each unit has a base and a distal apex that is off-center from the base when projected on to a plane that is coplanar with the base. The abrasive article includes a backing bonded to an abrasive coating formed to include the aforementioned abrasive units (400). Methods for making the abrasive article include nipping a production tool, an abrasive slurry, and the backing. A binder within the slurry is cured during fabrication. The abrasive article may be used to abrade a workpiece.

Description

METHODS OF MAKING A COATED ABRASIVE

The present invention relates to abrasive arrays, abrasive articles, methods of making such abrasive articles, and methods of using such abrasive articles. The abrasive article includes a back portion having an abrasive coating bonded to at least one surface of the backing. The abrasive coating is shaped to include a protruding unit that exhibits a useful geometry.

Abrasive articles have been used to polish and finish workpiece surfaces for over 100 years. Such applications range from fine removal, fine polishing of ophthalmic lenses to high pressure metal polishing processes. Typically, the abrasive article comprises a plurality of abrasive particles bonded to each other (eg, bonded abrasive or grinding wheels) or coupled to the back (eg, coated abrasive). For coated abrasives, there is typically one or sometimes two layers of abrasive particles. When these abrasive particles wear out, the coated abrasive wears out essentially and is typically discarded.

Structured abrasives are disclosed in US Pat. No. 5,152,917 (Pieper et al.). Importantly, the structured abrasive disclosed by the pipper results in a relatively high cutting rate and a relatively fine surface finish on the workpiece surface. Structured abrasives include non-random, precisely shaped abrasive composites bonded to the back.

Although structured abrasives, such as those disclosed by the pipper, exhibit desirable characteristics such as high cutting rates, structured abrasives still tend to lose their effectiveness over time. Thus, the structured abrasive can yield a specific cutting rate (expressed in grams per cycle, for example) in its initial three or four polishing cycles, but after only five or ten cycles of only a few minutes of its initial value. One-piece cutting rate can be calculated. Such degradation in cutting rate is disadvantageous for the purpose of providing an efficient polishing technique.

As is evident from the above, there is a need for a scheme in which a structured abrasive can be made to extend its service life and minimize its rate of degradation.

The present invention relates to an abrasive array, an abrasive article, a method of making an abrasive article, and a method of using an abrasive article. According to one embodiment of the invention, the polishing array of the plurality of protruding units may have a structure in which each unit has a body in which at least abrasive particles and a binder are mixed. Each body may have a base and a distal end region from the base. The polishing array may comprise a plurality of protruding units distributed in two dimensions. Each protruding unit has a base and a perimeter. For each unit, its respective end region defines an offset vector between the projection of the end region and the center point of the base when projected onto a plane that is coplanar with its respective base. The offset vectors for the plurality of protruding units do not add up to the limit of zero.

According to another embodiment of the invention, the abrasive article comprises a rear portion having a front side and a rear side. The abrasive coating can be bonded to the front face of the rear part. The abrasive coating may comprise a plurality of protruding units distributed in two dimensions. Each protruding unit has a base having a perimeter. For each unit, its respective end region defines an offset vector between the projection of the end region and the center point of the base when projected onto a plane that is coplanar with its respective base. The offset vectors for the plurality of protruding units do not add up to the limit of zero.

1 is an enlarged cross-sectional view illustrating another abrasive article embodiment of the present invention.

FIG. 2 is a schematic diagram of a process for manufacturing the abrasive article of FIG.

3 is a schematic diagram of another process of making the abrasive article of FIG.

4A shows a plan view of a protruding unit according to an embodiment of the invention.

4b shows a plan view of a protruding unit according to an embodiment of the invention.

4C illustrates a top view of an abrasive article in accordance with one embodiment of the present invention.

4D illustrates another top view of an abrasive article in accordance with one embodiment of the present invention.

4E shows another plan view of a protruding unit according to an embodiment of the present invention.

4F shows another plan view of the protruding unit according to an embodiment of the present invention.

4G shows another plan view of the protruding unit according to an embodiment of the present invention.

4H shows another plan view of the protruding unit according to an embodiment of the present invention.

Figure 5 illustrates another abrasive article in accordance with an embodiment of the present invention.

6A shows an array of protruding units in accordance with one embodiment of the present invention.

6B shows another array of protruding units in accordance with one embodiment of the present invention.

The present invention relates to abrasive arrays, abrasive articles, methods of making abrasive articles, and methods of using abrasive articles.

Referring to FIG. 1, the abrasive article 20 includes an abrasive composite 22 separated by an interface 25. The abrasive composite is bonded to the surface of the rear portion 21. The boundary or boundaries associated with the composite shape cause one abrasive composite to be somewhat separated from another adjacent abrasive composite. In order to form the individual abrasive composites, some of the boundaries forming the shape of the abrasive composite must be separated from each other. 2, it should be appreciated that the base or portion of the abrasive composite closest to the rear portion may abut its neighboring abrasive composite. The abrasive composite 22 includes a plurality of abrasive particles 24 and grinding aids 26 dispersed in a binder 23. It is also within the scope of the present invention to have a combination of abrasive composites bonded to the rear portion, with some of the abrasive composites abutting and other abrasive composites having an open space therebetween.

Rear

The back portion of the present invention has a front face and a back face, and may be any conventional polished back portion. Examples of useful backs include polymer films, pretreated polymer films, fabrics, paper, vulcanized fibers, nonwovens, and combinations thereof. Other useful rear portions include reinforcing fiber thermoplastic rear portions as disclosed in US Pat. No. 5,316,812 and infinite seamless rear portions as disclosed in WO93 / 12911. The rear portion may also contain a treatment agent or agents for sealing the rear portion and / or modifying some of the physical properties of the rear portion. Such treatments are well known in the art.

The rear portion may also have attachment means on its rear surface to enable securing the resulting coated abrasive to a support pad or backup pad. Such attachment means may be pressure sensitive adhesive, one surface of a hook and loop attachment system, or a threaded protrusion as disclosed in the aforementioned US Pat. No. 5,316,812. Alternatively, there may be an interlocking attachment system as described in the assignee's US Pat. No. 5,201,101, which is hereby incorporated by reference in its entirety.

The back side of the abrasive article may also contain a slip resistant or frictional coating. Examples of such coatings include inorganic particles (eg calcium carbonate or quartz) sprayed into the abrasive.

Abrasive coating

Abrasive particles

The abrasive particles typically have a particle size in the range of about 0.1-1500 μm, usually about 0.1-400 μm, preferably 0.1-100 μm, most preferably 0.1-50 μm. It is preferred that the abrasive particles have a shear hardness of at least about 8, more preferably greater than 9. Examples of such abrasive particles are molten aluminum oxide (including brown aluminum oxide, heat treated aluminum oxide, and white aluminum oxide), ceramic aluminum oxide, green silicon carbide, silicon carbide, chromia, alumina zirconia, diamond, iron oxide, Ceria, cube boron nitride, boron carbide, garnets, and combinations thereof.

The term “abrasive particles” also includes the single abrasive particles being combined with each other to form abrasive masses. Abrasive masses are described in detail in US Pat. Nos. 4,311,489, 4,652,275, and 4,799,939, which are incorporated herein by reference in their entirety.

It is also within the scope of the present invention to have a surface coating on the abrasive particles. Surface coatings can have different functions. In some cases, the surface coating increases the adhesion of the abrasive particles to the binder and alters the abrasive characteristics of the abrasive particles. Examples of surface coatings include coupling agents, halogen salts, metal oxides including silica, refractory metal nitrides, refractory metal carbides, and the like.

In the abrasive composites, there may also be dilute particles. The particle size of such dilute particles may be about the same size as the abrasive particles. Examples of such dilution particles include gypsum, marble, limestone, flint, silica, glass bubbles, glass beads, aluminum silicate and the like.

Binder

The abrasive particles are dispersed in the organic binder to form an abrasive composite. The binder is derived from a binder precursor comprising an organic polymerizable resin. During manufacture of the abrasive pools of the present invention, the binder precursor is exposed to an energy source that aids in initiation of the polymerization or curing process. Examples of energy sources include thermal energy and radiation energy, the latter including electron beams, ultraviolet light, and visible light. During this polymerization process, the resin is polymerized and the binder precursor is converted into a solidified binder. Upon solidification of the binder precursor, an abrasive coating is formed. The binder in the abrasive coating is also usually responsible for attaching the abrasive coating to the back.

Two classes of resins suitable for use in the present invention are condensation curable and addition polymerizable resins. Preferred binder precursors include additive polymerizable resins because such resins are easily cured by exposure to radiation energy. The addition polymerizable resin can be polymerized via a cationic mechanism or a free radical mechanism. Depending on the energy source and binder precursor chemistry used, the curing agent, initiator, or catalyst is sometimes good at helping to initiate polymerization.

Examples of typical and preferred organic resins are phenolic resins, urea-formaldehyde resins, melamine formaldehyde resins, acrylic urethanes, acrylic epoxys, ethylenically unsaturated compounds, aminoplast derivatives with branched unsaturated carbonyl groups, at least one Isocyanurate derivatives having branched acrylate groups, isocyanate derivatives having at least one branched acrylate group, vinyl ethers, epoxy resins, and mixtures and combinations thereof. The term "acrylate" includes acrylates and methacrylates.

Phenolic resins are widely used in abrasive article binders because of their thermal properties, availability, and cost. There are two types of phenolic resins, resols and novolacs. Resol phenolic resins have a molar ratio of formaldehyde to phenol of at least one to one, typically 1.5: 1.0 to 3.0: 1.0. Novolak resins have a molar ratio of formaldehyde to phenol of less than one to one. Examples of commercially available phenolic resins include "Durez" and "Varcum" from Occidental Chemicals Corp. and "Resinox" from Monsanto. ), And "Aerofene" by Ashland Chemical Co. and those known by the trade names of "Aerotap" by Ashland Chemicals Co.

Acrylate urethanes are diacrylate esters of hydroxy terminated, isocyanate NCO extended polyesters or polyethers. Examples of commercially available acrylic urethanes include "UVITHANE 782", available from Morton Thiokol Chemical, "CMD 6600", "CMD 8400", available from Radcure Specialties, and Includes those known under the trade name "CMD 8805".

Acrylate epoxy is a diacrylate ester of an epoxy resin, such as a diacrylate ester of a bisphenol A epoxy resin. Examples of commercially available acrylic epoxies include those known under the trade names "CMD 3500", "CMD 3600" and "CMD 3700" available from Radcure Specialties.

Ethylenically unsaturated resins include monomers and polymeric compounds containing atoms of carbon, hydrogen, and oxygen, and optionally nitrogen and halogens. Oxygen or nitrogen atoms or both are usually present in ether, ester, urethane, amide, and urea groups.

The ethylenically unsaturated compound preferably has a molecular weight of less than about 4,000, preferably a compound containing an aliphatic monohydroxy group or an aliphatic polyhydroxy group and acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, male Esters made from the reaction of unsaturated carboxylic acids such as acids. Representative examples of acrylate resins are methyl methacrylate, ethyl methacrylate styrene, divinylbenzene, vinyl toluene, ethylene glycol diacrylate, ethylene glycol methacrylate, hexanediol diacrylate, triethylene glycol diacrylate , Trimethylolpropane triacrylate, glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol methacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetraacrylate. Other ethylenically unsaturated resins include monoallyl, polyallyl, and polymethallyl esters, and amides of carboxylic acids such as diallyl phthalate, diallyl adipate, and N, N-diallyl adipamide. Another nitrogen-containing compound is tris (2-acryloyloxyethyl) isocyanurate, 1,3,5-tri (2-methacryloxyethyl) -triazine, acrylamide, methylacrylamide, N-methyl Acrylamide, N, N-dimethylacrylamide, N-vinylpyrrolidone, and N-vinylpiperidone.

Aminoplast resins have at least one branched α, β unsaturated carbonyl group per molecule or oligomer. Such unsaturated carbonyl groups can be groups of the acrylate, methacrylate, or acrylamide type. Examples of such materials are N- (hydroxymethyl) acrylamide, N, N'-oxydimethylenebisacrylamide, o- and p- acrylamidomethylated phenols, acrylamidomethylated phenolic novolacs , And combinations thereof. Such materials are described in detail in US Pat. Nos. 4,903,440 and 5,236,472, which are incorporated herein by reference in their entirety.

Isocyanurate derivatives having at least one branched acrylate group and isocyanate derivatives having at least one branched acrylate group are described in detail in US Pat. No. 4,652,274, which is incorporated herein by reference in its entirety. Preferred isocyanurate materials are triacrylates of tris (hydroxyethyl) isocyanurate.

The epoxy resin has an oxirane and is polymerized by ring opening. Such epoxide resins include monomeric epoxy resins and oligomer epoxy resins. Examples of some preferred epoxy resins are 2,2-bis [4- (2,3-epoxypropoxy) -phenyl propane] (daglycidyl ether of bisphenol) and from Shell Chemical Co. Commercially available "Epon 828", "Epon 1004" and "Epon 1001F" and Dow Chemical Co. "DER-331", "DER-332" and "DER-334" Contains commercially available materials under trade names. Other suitable epoxy resins include glycidyl ethers of phenol formaldehyde novolacs (eg, "DEN-431" and "DEN-428" available from Dow Chemical Co.).

The epoxy resins of the present invention can be polymerized via a cationic mechanism by the addition of a suitable cationic curing agent. Cationic curing agents generate an acid source to initiate the polymerization of the epoxy resin. Such cationic curing agents may include salts with onium cations and halogens containing complex ions of metals or metalloids. Other cationic curing agents are complexes of metals or metalloids with salts having organometallic cations described in detail in US Pat. No. 4,751,138 (columns 6 to 65, line 9 to column 45), which is hereby incorporated by reference in its entirety. Halogens containing anions. Other examples are organometallic salts and onium salts, which are U.S. Patent Nos. 4,985,340 (4th column 65 to 14th column 50) and European Patent Applications 306,161 and 306,162, published March 8, 1989. Which are hereby incorporated by reference in their entirety. Another cationic curing agent is an ionic salt of an organometallic complex selected from elements of Groups IVB, VB, VIIB, and VIIIB described in European Patent Application No. 109,581, published November 21, 1983, to which metals are incorporated by reference in their entirety. Include.

Regarding the free radical curable resin, in some cases, it is preferred that the polishing slurry further comprises a free radical curing agent. However, in the case of electron beam energy sources, hardeners are not always required because the electron beam itself generates free radicals.

Examples of free radical thermal initiators include peroxides such as benzoyl peroxide, azo compounds, benzophenones, and quinones. For ultraviolet or visible energy sources, these curing agents are sometimes called photoinitiators. Examples of initiators that generate free radical sources when exposed to ultraviolet light include organic peroxides, azo compounds, quinones, benzophenones, nitrozo compounds, acryl halides, hydrozones, mercapto compounds, pyryllium compounds, triacrylimidazoles , Bisimidazole, chloroalkytriazine, benzoin ether, benzyl ketal, chioxanthone, and acetophenone derivatives, and mixtures thereof. Examples of initiators that generate free radical sources when exposed to visible light can be found in US Pat. No. 4,735,632, which is a coated abrasive binder, including the three-way photoinitiator system, of the invention, which is incorporated herein by reference in its entirety. A preferred initiator for use with visible light is "Irgacure 369", commercially available from Ciba Geigy Corporation.

Grinding aid

Grinding aids are materials, preferably granular materials, whose addition to the abrasive article has a significant impact on the chemical and physical processes of polishing to improve performance. Typically and preferably, the grinding aid is added to the slurry as particles, but may be added to the slurry as a liquid. The presence of the grinding aid will increase the grinding efficiency or cutting rate of the corresponding abrasive article (defined as the weight of the workpiece removed per weight of abrasive article loss) relative to the abrasive article that does not contain the grinding aid. In particular, the grinding aid can either 1) increase the friction between the abrasive particles and the workpiece being polished, or 2) prevent the abrasive particles from "capping", i.e. metal particles (in the case of metal workpieces) on top of the abrasive particles. It is believed in the art to prevent welding, 3) to reduce the interface temperature between abrasive particles and the workpiece, 4) to reduce the grinding force required, or 5) to prevent oxidation of the metal workpiece. Typically, the addition of grinding aids increases the service life of the abrasive article.

Grinding aids useful in the present invention include a wide variety of different materials and may be inorganic or organic based. Examples of the chemical group of grinding aids include waxes, organic halogen compounds, halogen salts, and metals and alloys thereof. Organic halogen compounds typically decompose during polishing to release halogen acids or halogen compounds in the gas phase. Examples of such materials include chlorine-based waxes such as tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride. Examples of halogen salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluoride, potassium chloride, magnesium chloride. Examples of metals include tin, lead, bismuth, cobalt, antimony, cadmium, iron, titanium, and other incidental grinding aids include sulfur, organic sulfur compounds, graphite, and metallic sulfides. It is also within the scope of the present invention to use a combination of different grinding aids, which in some cases can produce a synergistic effect.

The foregoing examples of grinding aids are merely representative. Preferred grinding aids for use in the present invention are cryolites and most preferred is potassium tetrafluoroborate (KBF.sub.4).

Grinding aids are considered non-abrasive, ie the molar hardness of the grinding aid is less than 8. Grinding aids may also contain impurities, which should not significantly affect the performance of the abrasive article.

The grinding aid particle size is preferably in the range of about 0.1 to 100 μm, more preferably 10 to 70 μm. Usually, the particle size of the grinding aid is preferably equal to or less than the size of the abrasive particles.

The abrasive coating is generally at least about 1% by weight, typically at least about 2.5% by weight, preferably at least about 5% by weight, more preferably at least about 10% by weight of the grinding aid and most preferably at least about 20% by weight. Grinding aids. Grinding aids of greater than about 50% by weight can be disadvantageous because of the theory that grinding performance is reduced (because there are less abrasive particles present). Surprisingly, as the amount of grinding aid increased, the relative grinding performance measured by the cutting rate also increased. This was unexpected because the relative amount of abrasive particles decreases as the amount of grinding aid in the abrasive coating increases. Abrasive particles, not grinding aids, are responsible for cutting the workpiece surface. Typically, the abrasive coating is 5 to 90% by weight, preferably 20 to 80% by weight abrasive particles, 5 to 80% by weight, preferably 5 to 40% by weight binder, 5 to 60% by weight, preferably Comprises from 10 to 40% by weight of a grinding aid.

Optional additives

Slurries useful in the present invention may further comprise optional additives such as, for example, fillers, fibers, lubricants, wetting agents, thixotropic materials, surfactants, dyes, pigments, antistatic agents, coupling agents, caustic agents, and suspending agents. Can be. The amount of these materials is chosen to provide the desired properties. Their use can affect the erosion of abrasive composites. In some cases, additives are intentionally added to make the abrasive composites more erosive, thereby releasing dull abrasive particles and exposing new abrasive particles.

Examples of antistatic agents useful in the present invention include graphite, carbon black, vanadium oxide, humectants and the like. Such antistatic agents are disclosed in US Pat. Nos. 5,601,294, 5,137,542, and 5,203,884, which are hereby incorporated by reference in their entirety.

The coupling agent can provide a connecting bridge between the binder precursor and the filler particles or abrasive particles. Examples of useful coupling agents include silanes, titanates, and zircoaluminates. Useful slurries preferably contain about 0.01 to 3 weight percent coupling agent.

Examples of suspending agents useful in the present invention are amorphous silica particles having a surface area of less than 150 m ² / g commercially available under the trade name "OX-50" from DeGussa Corp.

Abrasive Coatings Including Abrasive Composites

In one preferred aspect of the present invention, the abrasive coating is in the form of a plurality of abrasive composites bonded to the back. It is generally good for each abrasive composite to have a precise shape. The precise shape of each composite is determined by clear and distinguishable boundaries. These clear and distinguishable boundaries are easily visible and clear when the cross section of the abrasive particles is examined under a microscope such as a scanning electron microscope. In comparison, in abrasive coatings comprising composites that do not have precise shapes, the boundaries are not clear and can be difficult to read. These clear and distinguishable boundaries form a precise shape or contour. This boundary separates the abrasive composites to some extent and also distinguishes the abrasive composites.

Referring to FIG. 1, the abrasive article 10 includes abrasive composites 22 separated by a boundary 25. The boundary or boundaries associated with the composite shape cause one abrasive composite to be somewhat separated from another adjacent abrasive composite. In order to form the individual abrasive composites, some of the boundaries forming the abrasive composites must be separated from each other. In Fig. 1, it should be appreciated that the base or portion of the abrasive composite closest to the rear portion may abut its neighboring abrasive composite. The abrasive composite 22 includes a plurality of abrasive particles 24 dispersed in the binder 23 and a grinding aid 26. It is also within the scope of the present invention to have a combination of abrasive composites bonded to the rear, where some of the abrasive composites abut and other abrasive composites have an open space therebetween.

In some cases, the boundaries forming the shape are flat. For shapes with planes, there are at least three planes. The number of planes for a given shape can vary depending on the desired geometry, for example the number of planes can range from 3 to 20 or more. Usually there are 3 to 10 planes, preferably 3 to 6 planes. These planes intersect to form the desired shape, and the angle at which these planes intersect will determine the shape dimension.

In another aspect of the invention, some of the abrasive composites have neighboring abrasive composites of different dimensions. In this aspect of the invention, at least 10%, preferably at least 30%, more preferably at least 50%, and most preferably at least 60% of the abrasive composites have adjacent abrasive composites with different dimensions. These different dimensions may relate to the abrasive composite shape, the angle between the flat boundaries, or the dimensions of the abrasive composite. The result of these different dimensions for neighboring abrasive composites results in an abrasive article that produces a relatively finer surface finish on the workpiece being polished or refined. This aspect of the invention is described in detail in US patent application Ser. No. 08 / 120,300, filed September 13, 1993, co-pending with the assignee.

The abrasive composite shape can be any shape, but it is preferably a geometric shape such as square, cone, semicircle, circle, triangle, square, hexagon, pyramid, octagon, and the like. Embodiments of the preferred shape are presented in the section entitled "Geometric Features" below. Individual abrasive composite shapes may be referred to herein as “protrusion units”. The preferred shape is a pyramid, and the base of this pyramid may be three or four sides. It is also preferred that the abrasive composite cross section surface area decreases away from the back or decreases along its height. This variable surface area results in uneven pressure as the abrasive composites wear out in use. Additionally, during the manufacture of the abrasive article, this variable surface area releases the abrasive composites more easily from the fabrication tool. Typically, there are at least five separate abrasive composites per square cm. In some cases, there may be at least 500 abrasive composites per square cm.

How to Make an Abrasive Article

An essential step for making one of the abrasive articles of the present invention is to prepare a slurry. The slurry is prepared by combining the binder precursor, grinding aid, abrasive particles, and optional additives with each other by any suitable mixing technique. Examples of mixing techniques include low shear and high shear mixing, with high shear mixing being good. Ultrasonic energy can also be used in combination with the mixing step to lower the polishing slurry viscosity. Typically, abrasive particles and grinding aids are added gradually into the binder precursor. The amount of air bubbles in the slurry can be minimized by drawing in vacuum during the mixing step. In some cases, it is preferable to heat the slurry generally in the range from 30 ° C. to 70 ° C. in order to lower the viscosity. It has the theoretical property of allowing the slurry to be well coated, and it is important that the abrasive particles and grinding aids do not settle out of the slurry.

Energy source

After the slurry is coated onto the backside by transfer from a fabrication tool (described below), the slurry can be exposed to an energy source to initiate polymerization of the resin in the binder precursor. Examples of energy sources include thermal energy or radiation energy. The amount of energy depends on several factors such as binder precursor chemistry, dimensions of the polishing slurry, amount and type of abrasive particles, and amount and type of optional additives. For thermal energy, the temperature may range from about 30 ° C. to 150 ° C., generally 40 ° C. to 120 ° C. The exposure time may range from about 5 minutes to 24 hours or more.

Suitable radiation energy sources include electron beams, ultraviolet light, or visible light. Electron beam radiation, also known as ionizing radiation, can be used at energy levels of about 0.1 to about 10 Mrad, preferably at about 1 to about 10 Mrad. Ultraviolet radiation refers to non-granular radiation having a wavelength in the range of about 200 to about 400 nm, preferably in the range of about 250 to 400 nm. Visible light radiation refers to non-granular radiation having a wavelength in the range of about 400 to about 800 nm, preferably in the range of about 400 to about 550 nm. Preferably, visible light of 300 to 600 Watt / inch is used.

After this polymerization process is complete, the binder precursor is converted to a binder and the slurry is converted to an abrasive coating. The resulting abrasive article is usually ready for use. However, in some cases, other processes may be needed, such as humidification or flexibilization. The abrasive article can be converted into any desired form, such as cones, endless belts, sheets, disks, etc., before the abrasive article is used.

Fabrication tools

With respect to the third and fourth aspects of the present invention, in some cases, it is preferred that the abrasive coating be present as a precisely shaped abrasive composite. In order to produce this type of abrasive article, a fabrication tool is generally required.

The fabrication tool includes a plurality of cavities. These cavities are essentially the inverse of the abrasive composite and are responsible for generating the shape of the abrasive composite. The dimensions of the cavity are selected to provide the desired shape and dimensions of the abrasive composites. If the shape or dimensions of the cavity are not properly produced, the resulting fabrication tool will not provide the desired dimensions of the abrasive composites.

The cavities can be in a dot pattern with spaces between adjacent cavities, or the cavities can abut against each other. It is preferred that the cavities abut against each other. In addition, the shape of the cavity is selected such that the cross-sectional area of the abrasive composites decreases away from the rear.

The fabrication tool may be a belt, sheet, continuous sheet or web, a coating roll such as a gravure roll, a sleeve mounted on the coating roll, or a die. The fabrication tool may be composed of metal (eg nickel), metal alloys, or plastics. Metal fabrication tools can be manufactured by any conventional technique such as engraving, boring, electroforming, diamond turning, and the like. One good technique for metal fabrication tools is diamond turning.

The thermoplastic tool can be replicated in the metal master tool. The master tool has the necessary reverse pattern for the production tool. The master tool can be manufactured in the same manner as the production tool. The master tool is preferably made from metal, for example nickel, and diamond turned. The thermoplastic sheet material may optionally be heated with the master tool such that the thermoplastic material is embossed into the master tool pattern by pressing it and the master tool. The thermoplastic material may also be extruded or cast onto the master tool and then pressed. The thermoplastic material is cooled to solidify and produce a fabrication tool. Examples of preferred thermoplastic fabrication tool materials include polyester, polycarbonate, polyvinyl chloride, polypropylene, polyethylene, and combinations thereof. If a thermoplastic fabrication tool is used, care must be taken not to generate excessive heat that can deform the thermoplastic fabrication tool.

The fabrication tool may also include a release coating to allow easier release of the abrasive article from the fabrication tool. Examples of such release coatings for metals include hard carbide, nitride or boride coatings. Examples of release coatings for thermoplastic materials include silicon and fluorine compounds.

One method for making the abrasive article of the present invention shown in FIG. 2 is shown in FIG. The rear portion 41 leaves the unwinding station 42, and at the same time the production tool 46 leaves the unwinding station 45. Fabrication tool 46 is coated with the slurry by coating station 44. It is possible to heat the slurry prior to coating and / or to ultrasonically apply the slurry to lower the viscosity. The coating station can be any conventional coating means such as a drop die coater, knife coater, curtain coater, vacuum die coater, or die coater. During coating, the formation of air bubbles should be minimized. Preferred coating techniques are vacuum fluid bearing dies such as those disclosed in US Pat. Nos. 3,594,865, 4,959,265, and 5,077,870, which are incorporated herein by reference in their entirety. After the fabrication tool is coated, the rear portion and slurry are contacted by any means such that the slurry wets the front face of the rear portion. In Fig. 2, the slurry is brought into contact with the rear part by the contact nip roll 47. Next, the contact nip roller 47 also presses the resulting construction against the support drum 43. An energy source 48 (preferably a source of visible light) delivers an amount of energy into the slurry sufficient to at least partially cure the binder precursor. The term partial curing means that the binder precursor polymerizes without the slurry flowing from the inverted test tube. The binder precursor can be fully cured by any energy source once it is removed from the manufacturing tool. Subsequently, the fabrication tool is rewound onto the mandrel 49 so that the fabrication tool can be reused again. Optionally, the fabrication tool can be removed from the binder precursor prior to any curing of the precursor. After removal, the precursor can be cured and the fabrication tool can be rewound on the mandrel 49 for reuse. In addition, the abrasive article 120 is wound on the mandrel 121. If the binder precursor is not fully cured, the binder precursor may be fully cured by exposure to time and / or energy sources. Additional steps for making an abrasive article according to this first method are described in detail in US Pat. No. 5,152,917 and US Patent Application No. 08 / 004,929, filed Jan. 14, 1993, which are incorporated herein by reference in their entirety. have. Randomly shaped abrasive composites can be prepared by the tools and procedures described in co-pending US patent application Ser. No. 08 / 120,300, filed Sep. 13, 1993, which is incorporated herein by reference in its entirety.

It is preferred that the binder precursor is cured by radiation energy. Radiation energy can be delivered through the fabrication tool as long as the fabrication tool does not absorb radiation energy significantly. In addition, the radiation energy source should not significantly degrade the fabrication tool. Preference is given to using thermoplastic fabrication tools and ultraviolet or visible light.

The slurry can be coated onto the back, not into the cavity of the build tool. The slurry coated back portion then contacts the fabrication tool so that the slurry flows into the cavity of the fabrication tool. The remaining steps for producing the abrasive article are the same as described above.

Another method is shown in FIG. The rear portion 51 leaves the unwinding station 52, and the slurry 54 is coated by the coating station 53 into the cavity of the manufacturing tool 55. The slurry may be coated onto the tool by one of many techniques, such as drop die coating, roll coating, knife coating, curtain coating, vacuum die coating, or die coating. Again, it is possible to heat the slurry and / or apply ultrasonication to the slurry prior to coating to lower the viscosity. During coating, the formation of air bubbles should be minimized. Next, the fabrication tool containing the rear portion and the polishing slurry is brought into contact by the nip roll 56 so that the slurry wets the front face of the rear portion. Next, the binder precursor in the slurry is at least partially cured by exposure to the energy source 57. After this at least partial curing, the slurry is converted to an abrasive composite 59 bonded or attached to the rear portion. The resulting abrasive article is removed from the fabrication tool by the nip roll 58 and wound onto the rewind station 60. Optionally, the fabrication tool can be removed from the binder precursor prior to any curing of the precursor. After removal of the fabrication tool, the precursor can be cured. In each case, the energy source can be thermal energy or radiation energy. If the energy source is ultraviolet light or visible light, it is preferable that the rear portion is transparent to ultraviolet light or visible light. An example of such a back part is a polyester back part.

The slurry can be coated directly onto the front side of the rear part. The slurry coated back portion then comes into contact with the fabrication tool such that the slurry wets the cavity of the fabrication tool. The remaining steps for producing the abrasive article are the same as described above.

How to Clean Workpiece Surface

Another aspect of the invention is directed to a method of polishing a metal surface. Such a method includes frictionally contacting an abrasive article of the present invention with a workpiece having a metal surface. The term "polishing" means that a portion of the metal workpiece is cut or removed by the abrasive article. In addition, the surface finish associated with the workpiece surface is typically reduced after this purification process. One typical surface finish measurement is Ra, where Ra is an algebraic surface finish, typically measured in microinches or micrometers. Surface finish can be measured by a profilometer, such as a Perthometer or Surtonic.

Work piece

The metal workpiece may be any type of metal, such as mild steel, stainless steel, titanium, metal alloys, special metal alloys, and the like. The workpiece may be flat or may have a shape or a contour associated with it.

Depending on the application, the force at the polishing interface may range from about 0.1 kg to 1000 kg or more. Typically, this range is from 1 kg to 500 kg of force at the polishing interface. In addition, depending on the application, there may be a liquid present during polishing. Such liquids may be water and / or organic compounds. Examples of typical organic compounds include lubricants, oils, emulsified organic compounds, cutting fluids, soaps, and the like. Such liquids may also contain other additives such as defoamers, grease removers, corrosion inhibitors, and the like. The abrasive article may vibrate at the abrasive interface during use. In some cases, this vibration can result in finer surfaces on the workpiece being polished.

The abrasive article of the present invention can be used by hand or in combination with a machine. At least one or both of the abrasive article and the workpiece are moved relative to each other during grinding. The abrasive article can be converted into a belt, tape roll, disc, sheet, and the like. For belt applications, the two free ends of the polishing sheet are joined to each other to form a splice. It is also within the scope of the present invention to use a muspless belt as described in US Patent Application No. 07 / 919,541, filed July 24, 1992, filed on July 24, 1992, herein incorporated by reference herein in its entirety. Typically, the endless abrasive belt pivots on at least one idler roll and platen or contact wheel. The hardness of the platen or contact wheel is adjusted to achieve the desired cutting rate and workpiece surface finish. The polishing belt speed depends on the desired cutting rate and surface finish. Belt dimensions can range from about 5 mm to 1,000 mm wide and from about 5 mm to 10,000 mm long. The abrasive tape is the continuous length of the abrasive article. It may range from about 1 mm to 1,000 mm in width, generally 5 mm to 250 mm. The abrasive tape is usually loosened, pivoted on a support pad that presses the tape against the workpiece, and then rewound. The abrasive tape can be fed continuously and indexed through the abrasive interface. The abrasive disc may range in diameter from about 50 mm to 1,000 mm. Typically, the abrasive disc is fixed to the backup pad by the attachment means. Such abrasive disks can be rotated at 100 to 20,000 revolutions per minute, typically at 1,000 to 15,000 revolutions per minute.

Geometric features

As mentioned in the section of this specification entitled "Abrasive Coatings Including Abrasive Composites," the abrasive composites may be molded into units that protrude from the back portion to which they are bonded. Individually shaped composite abrasives are referred to herein as "protrusion units". Certain geometrical features selected for the protruding unit can affect the performance of the structured abrasive article in which it is located. The geometric feature schemes presented below are chosen to provide elevated initial cutting rates (measured in mass per cycle) and to exhibit minimal degradation of the cutting rates in each successive polishing cycle.

The protruding units shown in Figs. 4A-4H, 5, 6A and 6B, and other protruding units referred to herein, can be structured from the aforementioned materials, using the manufacturing method described above. Although FIGS. 4A-4H, 5, 6A, and 6B do not show abrasive particles and binders in the protruding unit, since the protruding units have abrasive particles and binders as constituent materials, it is understood that such particles and binders are present. I understand.

4A shows a top view of the protruding unit 400. The protruding unit has a base 401 that is square in shape. In addition to the base 401, the protruding unit 400 has four sides extending from each of the various sides of the base 401 to the linear vertex 406. Due to the perspective of FIG. 4A, only the sides 403 and 406 are visible.

As can be seen from FIG. 4A, the linear vertex 406 extends between opposingly disposed sides of the base 401 when projected onto a plane that is coplanar with the base 401. When referring to the projection of a vertex such as vertex 406 onto a plane that is coplanar with the base of the protruding unit, the term "projection of vertex" or "projection of linear vertex" may be used herein. The center points of the opposingly disposed sides on which the projection of the linear vertex 406 extends between are identified by small hashing. The projection of the linear vertex 406 does not extend between the center points of the oppositely disposed sides.

The protruding units of FIG. 4A may be arranged in a two dimensional array as shown in FIG. 4B. 4B shows an array of generally identical protrusion units 400 disposed such that the base of each protrusion unit 400 abuts the base of an adjacent protrusion unit 400. The protruding units 400 are shown to be coupled to the rear portion 408 to produce an abrasive article. Although the array shown in FIG. 4B is shown as 2 × 2, the array can in principle be of any size. Also, as shown in FIG. 4C, the array may be configured such that the bases of adjacent protruding units 400 do not abut one another.

4d shows the protruding unit 410. As can be seen, the protruding unit has a linear vertex 412 having an insufficient length so that its projection extends from one side of the base 414 to the other side. Thus, each of the sides tapers inward from the base 414 to the distal linear vertex. In particular, if the projection of linear vertex 412 is extrapolated, its extrapolation does not meet the center points of each opposing disposed side of base 414. In this manner, it can be said that the projection of the linear vertex 412 does not extend between "centers" of the center points of oppositely disposed sides of the base 414.

4E shows another protruding unit 416. The protruding units shown in FIGS. 4A, 4B, 4C, and 4D are linear vertices whose linear vertices 412 do not extend between the center points of oppositely disposed sides of their respective base by employing a similar scheme. Are oblique features for all aspects of their respective base. As shown in FIG. 4E, the projection of the linear vertex 418 may be parallel to some of the sides of the base 420, but does not extend between the center points of the oppositely disposed sides of the base 420.

4F shows another protruding unit 422. 4F shows that the vertices of the protruding unit can be linear, but need not be straight. The protruding unit 422 has vertices 424 that are curved (as opposed to straight lines). The projection of the curve vertex 424 does not extend between the center points of the oppositely disposed sides of the base 426.

The bases shown in Figs. 4A, 4B, 4C, 4D, 4E, and 4F were all square in shape. Such a restriction is not essential. In principle, the base can be of any closed shape. For example, the base can be any regular or irregular polygon, or can be parallelogram, square, or any quadrilateral. Base may be round or oval. The sides of the base can be straight or curved. For example, the protruding unit 428 shown in FIG. 4G has four sides, two of which are curves 430 and 432. The center point of the oppositely disposed curved sides of the base can be found by dividing the curved side into two segments, the length of the first segment being equal to the length of the second segment. For example, side 430 has been divided into two segments, segments AB and BC. Point B, the center point, is positioned so that the length of segment AB is equal to the length of segment BC. Those skilled in the art will appreciate that other measures of centrality can be used to identify the center point of a line rather than a straight line. Again, the projection of linear vertices 434 extends between opposingly disposed sides 430 and 432 but not at their respective center points.

4H shows a protruding unit 436 having a base 438 that is pentagonal in shape. The center point of the side AB is identified by a small hash mark. In particular, the protruding unit 436 does not appear to have a side that is disposed opposite the side AB. In order to orient the linear vertex 440 to extend between the non-center points on oppositely disposed sides of the base, the side AB may be considered opposite to the composite segment ACDEB. The center point of the side surface ACDEB is the point D, since the length of the segment ACD is equal to the length of the segment DEB. Thus, it is apparent that the linear vertex 440 does not extend between the center points of the oppositely disposed sides of the base 438.

The general principle extracted from the discussion with respect to FIG. 4H is that a particular plan can be used to find the side that is placed against a given side of the base. Briefly, a set of sides facing a given side of the base may be considered collectively as a single side disposed opposite the given side (eg, side ACDEB faces side AB, May be considered arranged opposite to (AB)).

FIG. 5 shows a perspective view of an abrasive article 500 that includes a two-dimensional array of protruding units, some of which are identified with reference 502. Each protruding unit 502 has a base that is rectangular. According to one embodiment of the invention, the length and width of the base may be between 25.4 and 3,810 μm (1 to 150 mil). Each base has a linear vertex 504. According to one embodiment of the invention, the linear vertices may be oriented up to 1524 microns (mil) above the base. Although each of the bases of FIG. 5 is shown to have the same size and geometrical features, this condition is not essential. Bases can be of various sizes and / or geometrical features. Also, although each of the linear vertices 504 is shown parallel to one another, this condition is not essential. The linear vertices 504 may not be parallel to each other. Finally, although each of the linear vertices is shown at a certain distance from their respective base, this condition is also not essential. The distance between the base and its respective linear vertex 504 may vary from protrusion unit 502.

6A shows an array of protruding units 600-606. Each of the protruding units 600-606 has vertices 608-614 that are generally pointed. Any linear vertex in any of the above examples may be implemented as a point, as opposed to being implemented as a linear segment. Referring back to FIG. 6A, in each of the protruding units 600-606, the vertices 608-614 are positioned away from the center. The projection of each vertex 608-614 defines an offset vector v ₁ , v ₂ , v ₃ , v ₄ extending from the center and / or center of mass of each base to the projection of vertices 608-614. do. In particular, the sum of the offset vectors v ₁ , v ₂ , v ₃ , v ₄ is not zero. For example, if each of the offset vectors v ₁ , v ₂ , v ₃ , v ₄ is a unit vector, the sum of the vectors is 2y. For a large array of protruding units, the sum of the offset vectors should not approach the limit of zero as the number of summed vectors approaches infinity.

lim _{n → ∞} (∑v _n ) ≠ 0

In other words, when viewed as a whole, the array should exhibit a forward direction relative to the location of the vertices 608-614.

6B shows the concept of net proportions when applied to a protruding unit having linear vertices 616-622. As can be seen in FIG. 6B, the projection of linear vertices 616-622 is offset vector v ₁ , v ₂ extending from the center and / or center of mass of each base to the projection center of vertices 616-622. , v ₃ , v ₄ ). Once again, for a large array of protruding units, the sum of the offset vectors should not approach the limit of zero as the number of summed vectors approaches infinity.

lim _{n → ∞} (∑v _n ) ≠ 0

In other words, when viewed as a whole, the array should exhibit a forward direction relative to the location of the vertices 608-614.

Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments described herein.

Claims (16)

Each unit has a body with at least a mixture of abrasive particles and binder, each body being a polishing array of a plurality of protruding units having a base and a distal end region from the base, It includes a plurality of protrusion units distributed in two dimensions, Each protruding unit has a base and a periphery, For each unit, when its respective distal region is projected onto a plane that is coplanar with its respective base, it is projected inside the perimeter of the base and defines an offset vector between the projection of the distal region and the center point of the base. and, And said offset vector for the plurality of protruding units does not add up to an limit of zero. The polishing array of claim 1, wherein each end region is linear. The polishing array of claim 2, wherein each end region is straight. 3. The polishing array of claim 2 wherein each end region is curved. The polishing array of claim 1, wherein each base is parallelogram. 6. The polishing array of claim 5 wherein none of the sides of the parallelogram are parallel to the edge of the article on which the polishing array is disposed. The polishing array of claim 1, wherein for each unit its respective distal region is projected inside the perimeter of the base when projected onto a plane that is coplanar with its respective base. The polishing array of claim 1 wherein the successive bases do not contact. A rear part having a front face and a rear face, An abrasive coating bonded to the front face of the rear portion, The abrasive coating comprises a plurality of protruding units distributed in two dimensions, Each protruding unit has a base having a perimeter, For each unit, when its respective distal region is projected onto a plane that is coplanar with its respective base, it is projected inside the perimeter of the base and defines an offset vector between the projection of the distal region and the center point of the base. and, Wherein said offset vector for a plurality of protruding units does not add up to an limit of zero. 10. The abrasive article of claim 9, wherein each end region is linear. The abrasive article of claim 10, wherein each distal region is straight. The abrasive article of claim 10, wherein each distal region is curved. 10. The abrasive article of claim 9, wherein each base is parallelogram. The abrasive article of claim 13, wherein none of the sides of the parallelogram is parallel to the edge of the article on which the abrasive array is disposed. 10. The abrasive article of claim 9, wherein for each unit its respective distal region is projected inside the perimeter of the base when projected onto a plane that is coplanar with its respective base. 10. The abrasive article of claim 9, wherein the continuous base is not in contact.

Images