Drying and gas or vapor contact with solids – Process – Congealing or thickening
Patent
1998-01-16
2000-07-25
Gravini, Stephen
Drying and gas or vapor contact with solids
Process
Congealing or thickening
34329, 502402, 502418, F26B 506
Patent
active
060923024
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND FIELD OF THE INVENTION
The present invention relates to the field of fibrous granules or agglomerates used as absorbents.
Small particulate-like or agglomerate absorbents have long been used for absorbing liquids particularly water and/or oils. However, the nature of the specific absorbents designed and used for particular end uses has changed significantly over time. Depending on the particular end use requirements and available materials, absorbents in use today are quite different in regard to their composition, physical properties and/or chemistry. Typical large volume end uses for particulate-like absorbents include animal bedding, cat liter, oil absorbents, water absorbents or absorbents used to remove oil from water surfaces. For example, with animal bedding absorbents it has been described as important that the absorbent material be non-toxic, have antibacterial properties and have high absorption capacity for urine and the like. With cat liter, some of the same considerations are present as with animal bedding, however, there is also a need for more rapid absorption and the ability of the material to clump or hold together when wetted becomes important. With oil absorbent materials generally the absolute oil absorbing capacity has been considered important in the prior art, as well as the density and integrity of the material. For absorbing oil from a (e.g., factory) floor generally a more dense, coherent material is required so as to avoid airborne dust, which causes difficulties with people and machinery, ease of removal and safety concerns. For absorbing oil from the surface of water, it is generally considered necessary that the absorbents be both coherent when wet and less dense than water, both before and after the material absorbs oil and/or water.
For example, U.S. Pat. No. 2,649,759 describes that for animal bedding typical common absorbents used are organic-type materials such as straw, peat moss, wood shavings as well as diatomaceous earth. This patent proposed use of a specific clay which is alleged as superior in view of its high absorbency, anti-bacterial properties, non-dusting properties and the fact that it is non-toxic.
U.S. Pat. No. 3,617,564 proposes an absorbent of low density corn cob granules which are formed of the cob with the center core removed. These granules are stated as having suitable properties, without any further treatment, for removing oil from fresh or salt water. Hydrophilic organic fibers have also been described as acceptable oil and/or water absorbents without a resin treatment. U.S. Pat. Nos. 4,829,045 and 4,409,925 propose adding calcium sulfate and Plaster of Paris, respectively to augment the properties of organic hydrophilic fibers. In U.S. Pat. No. 4,829,045 the natural fibers are peat fibers, which are pelletized. Calcium sulfate is added to act as a binding agent and a fire retardant. In U.S. Pat. No. 4,409,925 ground waste paper is dry mixed with Plaster of Paris and then agglomerated by the addition of water droplets. The size and density of the particles formed depend on the size of the water droplets. The resulting material is described as an oil and water absorbent and as performing superior to a clay product. The Plaster of Paris, although described as used in the prior art as an oil absorbent by itself, is used in this patent primarily for sanitizing purposes and is reported as actually reducing the oil and water absorption properties of the fibrous agglomerate material.
Resins are often used to modify the surface properties of organic fibers or particles to allegedly make the fibers or particulates better oil absorbents. For example, U.S. Pat. No. 2,692,861 describes an oil absorbent material for use as a floor sweeping composition. It describes conventional materials as sawdust, clays and sand. In order to improve the properties of these conventional materials the patent proposes coating the materials with resins which are "substantially free of paraffinic hydrocarbons". U.S. Pat. No. 5,308,497 proposes using a phenolic resi
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3M Innovative Properties Company
Bond William J.
Gravini Stephen
Griswold Gary L.
Sprague Robert W.
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