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US 5,964,937 AGranted
Amorphous silicas
AssigneeCrosfield Limited
InventorPeter William Stanier
Life of this patent
Estimating the term…
Abstract
An amorphous silica having an RDA value of between 30 and 70, an oil absorption capacity of between 100 and 155 cc/100 g and a moisture loss of less than 7% w/w, can be incorporated at a 10% to 25% loading into a transparent toothpaste having a refractive index of above 1.445, this toothpaste having an RDA value of between 30 and 60.
Claims19
Amorphous silica which comprises:
- an RDA value of between 30 and 70;
- an oil absorption capacity of between 100 and 155 cm.sup.3 /100 g;
- and
- a BET surface area of up to 200 m.sup.2 /g.
1 more element
Process for the production of amorphous silicas having an RDA value of between 30 and 70;
- an oil absorption capacity of between 100 and 155 cm.sup.3 /100 g;
- and a BET surface area of up to 200 m.sup.2 /g, said process comprising:
- a) adding a 17.0 to 21.5% solution of 2.1 to 2.5 Molar Ratio silicate solution to water,
- b) then further adding a 17.0 to 21.5% solution of 2.1 to 2.5 Molar Ratio silicate solution together with a 15 to 20% sulfuric acid solution, over period of over 40 minutes at such flow rates that the pH is maintained in the range from 8.0 to 9.0,
- c) then aging the resultant slurry for a perod of 0 to 30 minutes at a temperature of 90 to 100.degree. C.,
- d) doing a second addition to a 15 to 20% sulfuric acid solution to bring the pH down to pH 3 to 5,
- e) aging the resulting slurry for a period of 0 to 20 minutes at pH 5 at a temperature of between 90 and 100.degree. C.,
- f) adjusting the pH to pH 3.5 to 5, and
- g) eventually filtering, washing and drying the final slurry.
6 more elements
Dependencies are inferred from the claim text.