Transparent non-vitreous zirconia microspheres
AssigneeMinnesota Mining and Manufacturing Company
InventorsThomas E. Wood, Roger W. Lange
Life of this patent
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Abstract
Solid, transparent, non-vitreous, zirconia and zirconia-silica ceramic microspheres, useful as lens elements in retroreflective pavement markings. The microspheres are characterized by: (a) containing at least one additive metal oxide selected from alumina, magnesia, yttria and mixtures thereof; (b) an index of refraction greater than 1.6; and (c) being virtually free of cracks. These microspheres are formed by a sol-gel technique of extractive gelation (extracting carboxylic acid away from zirconyl carboxylate) of a sol in liquid medium such as hot peanut oil. The microspheres of this ceramic composition have been made with relatively large diameters, (e.g. 200-1000 micrometers) making them quite useful as lens elements in pavement marking sheet materials.
Claims32
A solid, transparent, non-vitreous, ceramic spheroid substantially free of cracks, having substantially no open porosity detectable by BET nitrogen technique and an index of refraction greater than 1.6 and comprising crystalline zirconia and at least one other metal oxide selected from the group consisting of alumina, magnesia, yttria, and mixtures thereof, and which can in addition contain silica wherein, for those spheroids containing silica, the molar ratio of zirconia to silica is greater than 1.8.
A solid, transparent, non-vitreous, ceramic spheroid substantially free of cracks, having substantially no open porosity detectable by BET nitrogen technique and an index of refraction greater than 1.6 and comprising crystalline zirconia, silica, and at least one other metal oxide selected from the group consisting of alumina, magnesia, yttria, and mixtures thereof, wherein the weight of the other metal oxides combined is greater than 30 percent of the combined weight of zirconia and silica in the spheroid.
A solid, transparent, non-vitreous, ceramic spheroid substantially free of cracks and having an index of refraction greater than 1.6, having a diameter of at least 125 micrometers and comprising crystalline zirconia and at least one other metal oxide selected from the group consisting of alumina, magnesia, yttria and mixtures thereof.
A pavement marking comprising a layer of polymeric binder material in which is embedded a multiplicity of solid, transparent, non-vitreous, ceramic spheroids having substantially no open porosity detectable by BET nitrogen technique and an index of refraction greater than 1.6 and comprising crystalline zirconia and at least one other metal oxide selected from the group consisting of alumina, magnesia, yttria and mixtures thereof.
A pavement marking comprising a layer of polymeric binder material in which is embedded a multiplicity of solid, transparent, non-vitreous, ceramic spheroids having substantially no open porosity detectable by BET nitrogen technique and an index of refraction greater than 1.6 and comprising crystalline zirconia and at least one other metal oxide selected from the group consisting of alumina, magnesia, yttria and mixtures thereof.
A pavement marking comprising a layer of polymeric binder material in which is embedded a multiplicity of solid, transparent, non-vitreous, ceramic spheroids having a diameter of at least 125 micrometers and an index of refraction greater than 1.6 and comprising crystalline zirconia and at least one other metal oxide selected from the group consisting of alumina, magnesia, yttria and mixtures thereof.
A solid, transparent, non-vitreous, ceramic spheroid substantially free of cracks and having an index of refraction greater than 1.6, having a diameter of at least 125 micrometers and comprising crystalline zirconia, alumina, and silica wherein the molar ratio of zirconia to silica is greater than 1.8.
A pavement marking comprising a layer of polymeric binder material in which is embedded a multiplicity of solid, transparent, non-vitreous, ceramic spheroids having substantially no open porosity detectable by BET nitrogen technique and an index of refraction greater than 1.6 and comprising crystalline zirconia, alumina and silica wherein the molar ratio of zirconia to silica is greater than 1.8.
Dependencies are inferred from the claim text.