Minnesota Mining and Manufacturing Company

3m Innovative Properties Company

James A Laird

Robert A Haenggi

James L Gibb

Kenji Matsumoto

Kenton D Budd

Chikafumi Yokoyama

Stephen L Lieder

Hirohiko Ono

Toshinori Naruse

Chi F Tung

Warren R Beck

William C Whitcomb

George W Lee

Leslie G Berntson

Gerald M Benson

Joseph Graham

Timothy J Gennrich

Benjamin T Fellows

Transparent solid, fused microspheres are provided. In one embodiment, the microspheres contain alumina, zirconia, and silica in a total content of at least about 70% by weight, based on the total weight of the solid, fused microspheres, wherein the total content of alumina and zirconia is greater than the content of silica, and further wherein the microspheres have an index of refraction of at least about 1.6 and are useful as lens elements.

Transparent beads and their production method

Retroreflective cube-corner articles having randomly oriented cube-corner elements exhibiting rotational symmetry and entrance angularity like microsphere-based sheeting but having increased retroreflective efficiency from cube-corners. The inventive sheeting may contain cube-corner elements typically of different cube-corner geometries, different cube-corner dimensions, and different central axis heights. The cube-corner elements are positioned randomly and are typically not adjacent to one another. Also, methods of making such articles are provided.

Method of making randomly oriented cube-corner articles

A skid-resistant, surface marking material is disclosed. The skid-resistant, surface marking material comprises a polymer matrix phase and a plurality of opaque ceramic spheroids partially embedded in and protruding from the top surface of the matrix layer. The ceramic spheroids have rounded surfaces and no substantial points.

Skid-resistant surface marking material

A skid-resistant pavement marking sheet including a top surface and a plurality of skid-resistant ceramic spheroids embedded in and protruding from the surface. The ceramic spheroids are fired from a raw material mixture including 10-97 wt. % mineral particulates, 3-90 wt. % alumina, and at least 1 wt. % binder, at a temperature of about 1300.degree. C., have an outer surface rich in alumina concentration relative to the center of the spheroid, and are resistant to crushing and fracturing.

Skid-resistant pavement markings

Process for making particulate ceramics having an alumina rich region near their surface, comprising the following steps:

Particulate ceramic useful as a proppant

Ceramic particulates useful as a proppant in hydraulic fracturing and in gravel packing operations is provided which comprises a ceramic (sometimes vitreous) core surrounded by an epoxy resin coating. Novolac epoxy resin compounds without any substantial acid soluble filler are used to coat ceramic particulates similar to those discloses in U.S. Pat. Nos. 4,680,230 and 4,632,876. The result is a product which combines the excellent solvent resistance of the ceramics with the acid resistance of the resin. The resin coating gives the added benefits of lower specific gravity and improved crush resistance.

Novolac coated ceramic particulate

Ceramic particulate useful as a proppant in hydraulic fracturing and in gravel packing operations is provided which comprises a ceramic (sometimes vitreous) core surrounded by an epoxy resin coating. Novolac epoxy resin compounds without any substantial acid soluble filler are used to coat ceramic particulates similar to those disclosed in U.S. Pat. Nos. 4,680,230 and 4,632,876. The result is a product which combines the excellent solvent resistance of the ceramics with the acid resistance of the resin. The resin coating gives the added benefits of lower specific gravity and improved crush resistance.

Epoxy novolac coated ceramic particulate

A process for making ceramic spheriods by mixing and converting spheroids, with the aid of water, raw materials of 50-99.8 parts by weight mineral particulate (e.g. blend of orthoclase, nepheline, hornblende and diopside) which particulate includes at least one mineral having chemically bound water or sulphur in a form which is not substantially water soluble and in amounts sufficient to yield 0.5 to 5 weight percent water or 0.04 to 2 weight percent sulphur in the total mass; 0.1 to 50 parts by weight silicon carbide; and 0.1 to 15 parts binder. The wet spheroids are dried and the dry spheroids are fired in contact with a parting agent (e.g. aluminum oxide) for a sufficiently long time to form a shell containing parting agent on the ceramic mineral having a fired density of less than about 2.9 grams per cubic centimeter when fired above 1,100.degree. C. The binder is typically bentonite clay.

Process for making ceramic spheroids

A two-phase ceramic particulate useful as a proppant in hydraulic fracturing operations is provided which comprises a vitreous matrix phase containing a crystalline alumina phase. The new ceramic particles are characterized by:

Ceramic spheroids having low density and high crush resistance

A fire retardant, intumescent composition is provided which comprises a mixture of alkali metal silicate, represented by the formula M.sub.2 O:xSiO.sub.2 in which M is the alkali metal; an oxy boron compound selected from boric acid or salts of Group I and II elements; and water; in which the weight ratio x ranges from about 1.5 to about 4, the molar ratio of boron to M is between 0.2 and 0.9, and the water comprises about 5 to 15 weight percent of the total composition. These compositions are made by mixing an alkali metal silicate sol with a borate (e.g., boric acid) to form a gel which is dried in an oven. The resulting residue is crumbled to granules. A fire retardant which is relatively insoluble and has improved stability to long term exposure to water and humidity is formed. Various parameters (e.g., the weight ratio x, the amount of water present, and the ratio of boron to sodium) can be adjusted to control the amount of intumescence retained after exposure to water and also to control the temperature of intumescence. Granules made of these compositions have many applications, including incorporation into asphalt roofing materials.

Growing community of inventors

St. Joseph, WI, United States of America

James A Laird