Minnesota Mining and Manufacturing Company

David K Douden

Thomas J Scanlan

Hydrated sodium silicate particles can be expanded by heat to form thin-walled bubbles that can be broken, neutralized, washed and dried to provide hydrated silica flakes. These flakes can be mixed with non-swelling sorptive particles such as TLC grade silica and used to make chromatographic articles. One such article is a composite of a poly(tetrafluoroethylene) fibril matrix in which those particles and hydrated or fired silica flakes are enmeshed. The hydrated silica flakes can be fired to a refractory state and then incorporated into protective coatings to enhance their resistance to abrasion while also better protecting the coated substrates from corrosion.

Method of making thin silica flakes

Thin flakes can be made from a sol of metal oxides by a method analogous to blowing soap bubbles, preferably by directing a laminar flow of air through a narrow, annular orifice. The bubbles can be dried and broken into fragments which are fired to produce refractory flakes that can be incorporated into protective coatings. The resulting coatings can be pearlescent while also affording good resistance to abrasion and to corrosive materials.

Method of making thin refractory flakes

Thin silica flakes and method of making

Process for making hollow, ceramic macrospheres by making a paste of a continuous phase material (e.g., sodium silicate or potassium silicate) and an insolubilizing agent (e.g., kaolin clay). Pellets are formed from the paste and expanded by subjection to heat to form hollow spheroids. The spheroids are fired at a temperature (typically 600.degree.-1000.degree. C.) and for a time sufficient to insolubilize the continuous phase material. The process may further include coating the fired spheroids with an epoxy resin (to reduce porosity) and/or bonding a plurality of the fired spheroids together to form a rigid mass of bonded spheroids.

Process for making hollow, ceramic spheroids

A hollow, ceramic macrosphere or spheroid comprising a relatively smooth outer skin and cellular shell is produced in the 2-20 mm diameter range with specific gravities in the 0.2-1.2 range. The spheroids can be rendered inert to water and are stable at temperatures of 800.degree. to 1000.degree. C., depending on their composition. The porosity of the shell can be controlled through various additives and/or epoxy resin coating. The spheroids may be made from common clay and sodium silicate.

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Richfield, MN, United States of America

David K Douden