Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1994-04-29
2001-02-27
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S437000, C106S438000, C106S439000, C106S442000, C106S446000, C106S450000, C106S481000, C106S482000, C106S483000, C241S005000
Reexamination Certificate
active
06193795
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to low structure pyrogenic metal oxide fillers and to a method of producing such low structure pyrogenic metal oxide fillers. In a further aspect, the present invention also relates to products made from and containing the novel low structure pyrogenic metal oxide fillers.
Hydrophilic/hydrophobic pyrogenically produced metallic oxides based on silicon, aluminum, zirconium and titanium are well known in the art. They are produced by various methods known in the art such as described in U.S. Pat. Nos. 3,954,945, 4,067,954, and 4,276,274 assigned to the assignee herein and all relied on and incorporated by reference in their entirety. Also known from the prior art is the fact that such oxides are used as reinforcing fillers in many silicone RTV/HTV/LTV and nonsilicone based polymeric formulations such as rubbery polymers, sealants, caulks and adhesives. A full description of silicone rubber chemistry is found in U.S. Pat. No. 4,307,023 (which is incorporated by reference in its entirety, especially column 1, lines 5-30). The highest loadings possible are desired to obtain maximum reinforcement and improved physical properties including improved tensile strength, higher modulus, improved Shore A hardness and higher extrusion rates. Methods of producing hydrophobic pyrogenically obtained metallic oxide particulates are also well known in the art, as shown in U.S. Pat. Nos. 4,068,024 and 3,948,676 both assigned to the assignee herein.
The current problem when using pyrogenic metallic oxides is their high structure, measured by DBP Absorption, which prevents high filler loadings and causes excessive viscosity build-up and low extrusion rates which makes formulations difficult to handle and process. “Structure” as it relates to fillers is a well recognized and understood term, see Kirk Othmer Encyclopedia of Chemical Technology, volume 4, page 638.
Well known processes have been established to reduce particle/aggregate size and to decrease bulk density. However, simultaneously reducing particle size/aggregate size, increasing bulk density and destructuring of pyrogenically produced metallic oxides is, prior to the present invention, an unknown process.
An object of the present invention is to provide low structure or destructured pyrogenic hydrophilic and hydrophobic metallic oxides which allow for higher loadings in formulations whereby excessive viscosity build-up is drastically reduced, extrusion rates are significantly increased, and mechanical properties are improved. Such low structure or destructured pyrogenic hydrophilic and hydrophobic metallic oxides can also be utilized as fillers and carriers for non-polymer applications such as catalysts, refractories, ceramics, and others. Mechanical destructuring is a irreversible process.
SUMMARY OF THE INVENTION
Disclosed is a method of producing a low structure pyrogenic metal oxide filler; i.e., a pyrogenic metal oxide filler of reduced structure compared with the filler prior to being subjected to the method of the invention. The method involves subjecting pyrogenically produced metal oxide agglomerates and aggregates such as silicon oxide, aluminum oxide, zirconium oxide or titanium oxide to a dry milling process whereby the pyrogenically produced metal oxide is contacted in an agitating zone with an energy specific force created by certain reaction conditions.
The term “dry” as used herein means an extremely low moisture content. This is a condition known in the art as a “non-fluid medium” or a “non-fluid mill base”. Since the pyrogenic methods of preparation of these metallic oxides do not involve an aqueous system, the products obtained are dry, and any moisture picked up would be adsorbed from the environment. In general, as used herein, the term “dry” means silicon dioxide having less than 2.5% moisture; aluminum oxide having less than 3% moisture; zirconium oxide having less than 1% moisture; and titanium oxide having less than 2% moisture.
The dry grinding process of the present invention is an intensive milling process which goes beyond standard particle size reduction to achieve destructuring of pyrogenic metallic oxides.
Agitating media bed used according to the invention are selected from stainless steel, chrome steel, carbon steel, ceramic, aluminum oxide, tungsten carbide, zirconium carbide, zirconium oxide, or zirconium silicate whereby the metallic oxide agglomerates and aggregates are free to move, collide and impinge between the colliding media. The media is kept in constant agitation by a rotating shaft with protruding extensions of a desired length or by a rolling drum. The media diameter is generally one quarter inch to one inch in diameter and being of circular, spherical or cylindrical shape (or equivalents thereof). The shaft speed is between 100 and 1500 rpm or the roller drum speed is between 30 to 120 rpm. It is a feature of the invention that the media fills the volume of the agitating zone to the extent of ¼ to ¾ of the total volume and wherein the dwell time in the zone is controlled by the amount of time the metallic oxide remains in the media bed or by the number of passes through the media bed. The product stream is evaluated to ascertain the structure of the resulting product until a steady state condition is reached. The lowering of the structure of the pyrogenic metallic oxide is a function of the time of compression, the amount of compressive force exerted on the aggregate/agglomerate particles and the conditions of compression.
REFERENCES:
patent: 3126293 (1964-03-01), McSheehy et al.
patent: 3317145 (1967-05-01), Stephanoff
patent: 3622084 (1971-11-01), Ross
patent: 3948676 (1976-04-01), Lauefer
patent: 3954945 (1976-05-01), Lange et al.
patent: 4067954 (1978-01-01), Völling
patent: 4068024 (1978-01-01), Lauefer
patent: 4147760 (1979-04-01), Kratel et al.
patent: 4190632 (1980-02-01), Achenbach
patent: 4208316 (1980-06-01), Nauroth et al.
patent: 4224295 (1980-09-01), Brandt et al.
patent: 4233199 (1980-11-01), Abolins et al.
patent: 4273589 (1981-06-01), Nauroth
patent: 4276274 (1981-06-01), Heckel
patent: 4307023 (1981-12-01), Ettlinger et al.
patent: 4308074 (1981-12-01), Nauroth
patent: 4360388 (1982-11-01), Nauroth et al.
patent: 4427450 (1984-01-01), Kostansek
patent: 4495167 (1985-01-01), Nauroth et al.
patent: 4615741 (1986-10-01), Kobayashi et al.
patent: 4693427 (1987-09-01), Bilimoria et al.
patent: 4770214 (1988-09-01), Ginter et al.
patent: 4857289 (1989-08-01), Nauroth et al.
patent: 4877595 (1989-10-01), Klingle et al.
patent: 5261956 (1993-11-01), Dunaway et al.
Perry's Chemical Engineers' Handbook,6th ed., p. 8-32,33, 1984, TP151.P45.
Herbst, J.A., et al., “Fundamentals of fine and ultrafine grinding in a stirred ball mill”, published in the Proceedings of The Powder and Bulk Solids Handling Conference, Chicago, Illinois, 1978.
Perry's Chemical Engineers' Handbook, 6th ed., McGraw Hill, New York, 1984, p. 8-34. TP151.P45, Dec. 1984.
Allen Sturgis G.
Bush Gary J.
Nargiello Maria R.
Bell Mark L.
Degussa Corporation
DiVerdi Michael J.
Smith , Gambrell & Russell, LLP
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