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AssigneeW. R. Grace & Co.-Conn.
InventorsMichael Bruce Thomas, Michael Vance Ernest, Sandra Joan Kempske
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Silica compositions for abrasive systems in dentifrice formulations are disclosed. The silica abrasive system comprises (a) silica gels having a median particle size below 7 microns, a pH of from about 6 to about 11 and powder RDA's of from 100 to about 200 and (b) silica gels or precipitates having a median particle size of 7 microns or greater and powder RDA's of from 50 to about 180. Silica (a) is preferably prepared by contacting a hydrous silica gel with an alkaline medium. Dentifrice compositions comprising the abrasive system has an RDA of 150 or less and PCR's of at least 80 and up to about 150, and an REA of less than about 30 (as measured on the IU scale).
A method of preparing a dentifrice composition comprising adding a silica gel additive (a):
Dependencies are inferred from the claim text.
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Containing inorganic ingredients: silicon; Compounds thereof
Preparations for care of the teeth, of the oral cavity or of
Particular ingredients further characterized by their size: microsized, i.e. having sizes between 0.1 and 100 microns
Medicines and medical preparations
Term ended 8 Apr 2018 (estimated)
1. Field of the Invention
This invention relates to silica compositions useful as an abrasive system in a dentifrice. The invention also relates to dentifrices, preferably toothpastes, which effectively clean teeth without a high degree of dentin and/or enamel abrasion.
2. Relevant Art
A hard, small silica component of the invention is prepared using methods disclosed in U.S. Pat. No. 4,303,641. In particular, a conventional acid set hydrogel is washed, dried and coarsely ground before being milled and dried under standard conditions. The moisture content of the silica feed material entering the mill is about 70% by weight.
Sodium carbonate powder is metered into the mill's inlet stream along with the hard small component precursor feed so that as it enters the mill, a constant concentration of alkalinity is maintained in the product.
The resulting milled product is characterized with a median particle size of 2-3 microns and a total volatiles, e.g., moisture, content of about 20% by weight. The small hard silica component has a pH of 8.5 as measured in a 5% by weight aqueous slurry. Powder RDA values measured on a number of batches range from 121 to 139. The particle size distributions for five of the batches of the small hard silica component are provided in Table I. Particle size distributions were measured using a Horiba LA900 laser diffraction analyzer.