Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-08-29
2003-11-11
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S403000, C428S404000, C428S407000, C051S307000, C051S309000
Reexamination Certificate
active
06645624
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to composite abrasive particles, also known as agglomerates, and their uses. Specifically, the invention discloses abrasive agglomerates comprising abrasive particles and a crystalline matrix, abrasive articles comprising the agglomerates, methods of manufacturing such abrasive agglomerates and articles, and methods of using such abrasive articles.
BACKGROUND OF THE INVENTION
Abrasive articles comprising abrasive particles are used to abrade and/or modify the surface of a wide variety of materials, commonly referred to as workpieces, in a wide variety of applications. These applications range from high pressure, high stock removal of metal forgings to polishing eyeglasses. 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 (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.
Abrasive particles have a wide range of properties that provide for their application in the abrasives industry. The selection of a particular type of abrasive particle generally depends on the physical properties of the particles, the workpiece to be abraded, the desired resulting surface condition, the performance properties of the abrasive particles, and the economics of selecting a particular abrasive particle for a specific application.
Aluminum oxide, or alumina, is one of the most popular abrasive particles used in the production of coated abrasives, e.g., sandpaper. Alumina is used for many applications, such as paint sanding, metal grinding, and plastic polishing. Silicon carbide, also a popular abrasive, is generally known as a sharper mineral than alumina, and is used mainly in woodworking, paint, and glass grinding applications. Diamond and cubic boron nitride, commonly called “superabrasives,” are used to abrade very hard workpieces such as hardened steel, ceramic, cast iron, silicon wafers and stone. Diamond is typically the used for non-ferrous materials, while cubic boron nitride is typically used for ferrous materials like hardened steel. However, superabrasives such as diamond and cubic boron nitride can cost up to 1000 times more than conventional abrasive particles, i.e., aluminum oxide, and silicon carbide. Therefore, it is desirable to utilize the superabrasives to their full extent.
Agglomerates are composite particles of a plurality of abrasive particles bonded together by a binder matrix. During use, the agglomerates typically erode or break down and expel used single abrasive particles to expose new abrasive particles. Agglomerates can be used in abrasive articles such as coated abrasives, non-woven abrasives, and abrasive wheels and provide a long useful life of the abrasive article and efficient use of the abrasive particles.
Agglomerates have been developed to address inconsistent cut rates with time (see, e.g., U.S. Pat. No. 3,928,949 (Wagner), U.S. Pat. No. 4,132,533 (Lohmer), 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)), which are all herein incorporated in their entirety by reference. In the case of coated abrasives, these agglomerates are bonded to the backing to form an abrasive article.
U.S. Pat. No. 4,311,489 to Kressner, discloses a coated abrasive product having abrasive particles secured to a flexible backing by maker and size coats, each abrasive particle consisting essentially of an agglomerate of fine abrasive grains having an average diameter less than about 200 microns and an inorganic, brittle, matrix.
U.S. Pat. No. 3,916,584 to Howard et al., incorporated herein in its entirety by reference, discloses composite abrasive granules, in which fine, hard abrasive grains are distributed throughout a relatively softer metal oxide matrix.
U.S. Pat. No. 4,918,874 to Tiefenbach, discloses a method of preparing abrasive articles exhibiting improved homogeneity and breakdown properties.
U.S. Pat. No. 5,975,988 to Christianson discloses a coated abrasive having a backing and an abrasive layer coated on the first major surface of the backing, wherein a cross-section of the abrasive layer normal to the thickness and at a center point of the thickness has a total cross-sectional area of abrasive agglomerates which is substantially the same as that at a point along the thickness which is 75% of a distance the same as that at a point and the contact side; a coated abrasive article having a bond system with a Knoop hardness number of at least 70.
What has been desired is an agglomerate and a method of manufacturing the agglomerate which would allow for good grinding performance (e.g., long life, high cut rates, consistent cut rates, consistent surface finish and the like) in all abrasive applications. It has been desired for agglomerates to furnish fresh abrasive particles to the working surface throughout the life of the agglomerate. Additionally, it is desirable to manufacture the agglomerates in such a way to control the porosity of the agglomerate.
SUMMARY OF THE INVENTION
The present application discloses an agglomerate. The agglomerate comprises a crystalline matrix. The agglomerate may additionally comprise abrasive particles. The agglomerate has a normalized bulk density of less than about 0.38.
The present application additionally discloses a method of manufacturing the agglomerate. The agglomerate is manufactured by forming a mixture comprising an abrasive particle with a sol, the sol comprising an oxide and water and introducing the mixture into a spray dryer. The mixture is then dried in the spray dryer. The mixture is then fired, for example in an oven. The resulting agglomerates comprise abrasive particles retained within a crystalline matrix of the oxide.
The present invention additionally discloses methods of using the agglomerates of the resent invention.
In this application:
“Agglomerate” means, without limitation, composite abrasive agglomerates of fired greenware agglomerates. The agglomerates comprise abrasive particles in a matrix as described herein.
“Normalized bulk density” means the bulk density measurement divided by the theoretical density. The theoretical density is calculated by summing the volume fraction of the densities of each component. One skilled in the art of sampling is able to take a sample without affecting the outcome.
Agglomerates according to the present invention may be incorporated into various abrasive articles such as coated abrasives, bonded abrasives (including vitrified and resinoid grinding wheels) and three-dimensional fixed abrasives. The abrasive articles typically comprise agglomerates according to the present invention and binder.
Typically, agglomerates according to the present invention are sufficiently porous to advantageously allow binder to penetrate therein. Porosity also helps swarf removal, wh
Adefris Negus B.
Joseph William D.
Wagle-Peterson Kathleen A.
Blank Colene H.
Kiliman Leszek
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