Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2001-10-05
2004-09-14
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S526000, C451S533000, C451S534000, C451S540000, C051S295000, C051S296000, C051S307000, C051S308000, C051S309000
Reexamination Certificate
active
06790126
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to agglomerate abrasive grain comprising a plurality of abrasive particles bonded together via a sintered, alumina-based bonding material, and a method of making the agglomerate abrasive grain. The agglomerate abrasive grain can be incorporated into a variety of abrasive articles, including bonded abrasives, coated abrasives, nonwoven abrasives, and abrasive brushes.
BACKGROUND OF THE INVENTION
There are a variety of abrasive particles (e.g., diamond particles, cubic boron nitride particles, fused abrasive particles (including fused alumina, heat treated fused alumina, fused alumina zirconia, and the like), and sintered, ceramic abrasive particles (including sol-gel-derived abrasive particles) known in the art. In some abrading applications, the abrasive particles are used in loose form or a slurry, while in others the particles are incorporated into abrasive products (including: bonded abrasives, coated abrasives and nonwoven abrasives).
Bonded abrasives typically comprise a plurality of abrasive particles bonded together to form a shaped mass. Coated abrasives typically comprise a plurality of abrasive particles bonded to a backing. Nonwoven abrasives typically comprise a plurality of abrasive particles bonded onto and into a lofty, porous, nonwoven substrate. Typical bonding materials for bonded abrasives are organic binders, vitreous binders, and metallic binders, while for coated and nonwoven abrasives they are typically organic binders. Criteria used in selecting abrasive particles used for a particular abrading application typically include: abrading life, rate of cut, substrate surface finish, grinding efficiency, and product cost.
The abrasive industry and their customers are continually looking for ways to improve one or more of these abrading criteria. For the past one hundred years or so, fused alumina abrasive particles have been widely utilized. Fused alumina abrasive particles are typically made by charging a furnace with an alumina source (such as aluminum ore or bauxite), as well as other desired additives, heating the material above its melting point, cooling the melt to provide a solidified mass, crushing the solidified mass into particles, and then screening and grading the particles to provide the desired abrasive particle size distribution. Over the past thirty years or so, there have been numerous inventions and developments concerning abrasive particles. One of these inventions was the development of co-fused alumina-zirconia abrasive particles. Additional information on alumina-zirconia abrasive particles can be found, for example, in U.S. Pat. No. 3,891,408 (Rowse et al.), U.S. Pat. No. 3,781,172 (Pett et al.), U.S. Pat. No. 3,893,826 (Quinan et al.), U.S. Pat. No. 4,126,429 (Watson), U.S. Pat. No. 4,457,767 (Poon et al.), and U.S. Pat. No. 5,143,522 (Gibson et al.).
Although fused alpha alumina abrasive particles and fused alumina-zirconia abrasive particles are still widely used in abrading applications (including those utilizing coated and bonded abrasive products), the premier abrasive particles for many abrading applications since about the mid-1980's are sol-gel-derived alpha alumina particles (also referred to as sintered, ceramic alpha alumina particles). The sol-gel-derived alpha alumina abrasive particles may have a microstructure made up of very fine alpha alumina crystallites, with or without the presence of secondary phases added (see, e.g., U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat. No. 4,518,397 (Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer et al.), U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe et al.), U.S. Pat. No. 4,881,951 (Wood et al.), U.S. Pat. No. 4,960,441 (Pellow et al.), (Pellow), U.S. Pat. No. 5,139,978 (Wood), U.S. Pat. No. 5,201,916 (Berg et al.), U.S. Pat. No. 5,366,523 (Rowenhorst et al.), U.S. Pat. No. 5,429,647 (Larmie), U.S. Pat. No. 5,547,479 (Conwell et al.), U.S. Pat. No. 5,498,269 (Larmie), U.S. Pat. No. 5,551,963 (Larmie), and U.S. Pat. No. 5,725,162 (Garg et al.)).
Coated abrasives tend to be “more flexible” than bonded abrasives; thus coated abrasives are widely utilized where the abrasive article needs to conform to the workpiece surface. Coated abrasives tend to have one or several layers of abrasive particles. It is generally preferred to orient these abrasive particles to enhance their cutting ability. However in some instances during the initial abrading, coated abrasives provide relatively very high cut rates. With time, the cut rate diminishes until the coated abrasive no longer provides acceptable cut rates.
To address the inconsistent cut rates with time, agglomerate abrasive grains have been developed (see, e.g., U.S. Pat. No. 3,928,949 (Wagner), U.S. Pat. No. 4,132,533 (Lohrner), U.S. Pat. No. 4,311,489 (Kressner), U.S. Pat. No. 4,393,021 (Eisenberg), U.S. Pat. No. 4,562,275 (Bloecher et al.), U.S. Pat. No. 4,799,939 (Bloecher et al.), U.S. Pat. No. 5,318,604 (Gorsuch), U.S. Pat. No. 5,550,723 (Holmes et al.), and U.S. Pat. No. 5,975,988 (Christiansen)). In the case of coated abrasives, these agglomerate abrasive grains are bonded to the backing to form an abrasive article. The agglomerate abrasive grains typically comprises a plurality of abrasive particles bonded together with a binder; usually an organic binder or inorganic binder.
One disadvantage with these abrasive agglomerate particles is that they are composite particles (i.e., abrasive particles and binder). The binder may adversely influence the abrading characteristics of the agglomerate grain. What is desired in the industry is a coated abrasive that provides a relatively long life and a cut rate that is relatively consistent over time.
Bonded abrasives are three dimensional in structure. Ideal bonded abrasive abrade the workpiece and when the abrasive particles are worn and dulled, these abrasive particles are expelled from the bonded abrasive to expose new, fresh cutting abrasive particles. In adequate adhesion between the abrasive particles and the bond material, can lead to premature release of the abrasive particles from the abrasive article. If the abrasive particles are prematurely released, the resulting bonded abrasive life is typically less than desired. What is desired in the industry is a bonded abrasive that exhibits good adhesion between the abrasive particles and the bond material.
In another aspect, to minimize inventory, and other associated manufacturing associated costs, it is typically preferred to make an abrasive grain that provides good grinding performance (e.g., long life, high cut rates, consistent cut rates, consistent surface finish and the like) in both coated abrasive and bonded abrasive applications. What is desired often in a coated abrasive is an abrasive grain that exhibits long life. What is desired often in a bonded abrasive is long life associated with good adhesion between the abrasive particles and the bonded abrasive binder.
SUMMARY OF THE INVENTION
The present invention provides agglomerate abrasive grain comprising a plurality of abrasive particles bonded together via sintered bonding material. The abrasive particles may comprise one or more abrasive particles including, but not limited to, fused aluminum oxide (including white fused alumina, heat-treated aluminum oxide, and brown aluminum oxide), silicon carbide, boron carbide, titanium carbide, diamond, cubic boron nitride, garnet, fused alumina-zirconia, sintered alpha alumina-based abrasive particles, and the like. Preferably, the bonding material comprises, on a theoretical oxide basis, at least 50 percent by weight Al
2
O
3
, based on the total metal oxide content of the bonding material. The bonding material may comprise, on a theoretical oxide basis, at least 60, 65, 70, 75, 80, 85, 90, 95, 97, 98, 99, 99.5, or even 100 (i.e., consists essentially of) percent by weight Al
2
O
3
, based on the total metal oxide content of the bonding material. In another aspect, the bonding material typically is at least 70, 75, 80 85, 90, 95, 97, 98, 99, 100 pe
McArdle James L.
Wood William P.
3M Innovative Properties Company
Allen Gregory D.
Hail III Joseph J.
McDonald Shantese
Wright Bradford B.
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