Spherical silica for tubule occlusion
A technology of silica and precipitated silica, applied in the direction of silica, silicon oxide, silicon compounds, etc., can solve the problems of not being able to provide cleaning effect, low brightness level, etc.
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Embodiment 1A
[0075] Irregular silica particles
[0076] Table I summarizes certain characteristics of Comparative Silica Material 1A, which has irregular and non-spherical particle morphology. Example 1A is a conventional silica material commercially available from Huber Engineered Materials.
Embodiment 2A
[0078] Spherical silica particles
[0079] A continuous loop reactor process (see, e.g., U.S. Patent Nos. 8,945,517 and 8,609,068) was used to produce the silica particles of Example 2A, which had a spherical morphology and a tighter particle size distribution (e.g., Less 325 mesh residue in the final silica product). No milling step was used.
[0080] For Example 2A, 1.5 kg of precipitated silica, 1.34 kg of sodium sulfate, 11.1 L of sodium silicate (3.32MR, 13.3%) and 20 L of water were added to the recirculation loop followed by heating to 83 °C, Recirculating at 80L / min, the Silverson runs at 60Hz (3485RPM). Sodium silicate (3.32MR, 13.3%) and sulfuric acid (11.4%) were added to the loop simultaneously at a silicate rate of 2.1 L / min and at an acid rate sufficient to maintain a pH of 7.5. The acid rate was adjusted accordingly to maintain the pH, if necessary. Acid and silicate were added under these conditions for 40 minutes to purge unwanted silica from the system be...
Embodiment 1B-2B
[0083] Toothpaste formulation and vial closure test
[0084] As summarized in Table II, samples of silica 1A-2A were used in toothpaste formulations 1B-2B. Since the pour density of the 3.1 μm spherical silica of Example 2A is about 6 times that of Example 1A, additional spherical silica was added to Formulation 2B to make approximately the same number of silica particles in the formulation (5% by weight of 3.1 μm spherical silica in Example 2B versus 0.8% by weight of Example 1A silica in Example 1B).
[0085] For the vial closure test, bovine incisors were obtained from a local slaughterhouse. Teeth were rinsed in water and sterilized in an autoclave, then rinsed in water to remove any residual tissue, and stored in isopropanol.
[0086] Figure 2A Bovine incisor teeth before sectioning are shown. The facets of the teeth were removed with a diamond cutting wheel on a Dremel tool ( Figure 2B ). Slicing is performed by first resecting the proximal surface ( Figure 2C ...
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