Back to results
US 2021/0061666 A1Published application
Ultra-white silica-based filler
AssigneeCovia Holdings Corporation
InventorsGregory Kenneth Bedford, Claud Eric Westbrook, III
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeCovia Holdings Corporation
InventorsGregory Kenneth Bedford, Claud Eric Westbrook, III
Estimating the term…
An ultra-white granular silica-based filler comprises at least 99.5 wt. % silica, wherein the crystal structure of the silica is such that the silica-based filler comprises 40 to 80 wt. % cristobalite, 1 to 25 wt. % tridymite, 2-60 wt. % quartz and <5 wt. % amorphous silica, wherein the temperature of the ultra-white granular silica-based filler is no higher than 50° C. and further wherein the ultra-white granular silica-based filler exhibits an L* value in the CIELAB color space of 95-98. In addition, an ultra-white powder filler is obtained by milling, grinding or comminuting the ultra-white granular silica-based filler. The ultra-white powder filler exhibits an L* value in the CIELAB color space of 95-98.5.
An ultra-white granular silica-based filler comprising at least 99.5 wt. % silica, wherein the crystal structure of the silica is such that the ultra-white granular silica-based filler comprises 40 to 80 wt. % cristobalite, 1 to 25 wt. % tridymite, 2-60 wt. % quartz and ≤2 wt. % amorphous silica, wherein the temperature of the ultra-white granular silica-based filler is 50° C. or less and further wherein the ultra-white granular silica-based filler exhibits an L* value in the CIELAB color space of 95-98.
A process for producing an ultra-white granular silica-based filler comprising heating a silica starting material comprising at least 95% quartz silica for a time and at a temperature sufficient so that at least some of the silica in the silica starting material is converted from a quartz crystal structure to a cristobalite crystal structure and thereafter cooling the heated product so made to 50° C. or less, wherein the silica starting material is heated sufficiently so that ≥2 to 60 wt. % of the silica in the ultra-white granular silica-based filler ultimately obtained has a quartz crystal structure and further so that the ultra-white granular silica-based filler contains ≤2 wt. % amorphous silica and exhibits an L* value in the CIELAB color space of 95-98.
Dependencies are inferred from the claim text.