Prevention of crystal formation in toothpaste
View Patent ↗In dentifrices containing sodium bicarbonate and anionic species which can react with sodium and water to precipitate hydrated crystals, the ratio of water to humectants, abrasives, and/or thickeners is adjusted so that the dentifrice has a water activity of no greater than 0.60 so as to greatly reduce the salting out of the anionic species.
1. A dentifrice or dentifrice phase comprising sodium bicarbonate, an anionic component reactive with sodium and water to form hydrated crystals, said anionic component being selected from the group consisting of orthophosphates, pyrophosphates, polyphosphates, metaphosphates, borates, thiosulfates, and glycerolphosphates, a water content of at least 5 wt. % based on the weight of the dentifrice or dentifrice phase, a humectant in an amount of at least 10 weight % relative to the weight of the dentifrice or dentifrice phase, and optionally at least one of a thickener, or abrasive, said dentifrice or dentifrice phase having a water activity of less than about 0.60.
2. The dentifrice or dentifrice phase of claim 1 wherein said water content is at least 7 wt. % based on the weight of the dentifrice or dentifrice phase.
3. The dentifrice or dentifrice phase of claim 1 wherein said anionic component is a pyrophosphate or polyphosphate anti-tartar agent.
4. The dentifrice or dentifrice phase of claim 1 wherein said anionic component is an orthophosphate, and wherein said dentifrice or dentifrice phase further includes a water-soluble or partially water-soluble calcium salt kept separate from said orthophosphate.
5. The dentifrice or dentifrice phase of claim 1 wherein said sodium bicarbonate is present in amounts of from about 7 to 65% by weight of the dentifrice or dentifrice phase.
6. The dentifrice or dentifrice phase of claim 1 further including a thickener in amounts of from about 0.1 to 10 weight %, based on the weight of the dentifrice or dentifrice phase.
7. The dentifrice or dentifrice phase of claim 1 further including a fluoride salt.
8. The dentifrice or dentifrice phase of claim 6 comprising at least 7 weight % of water.
9. The dentifrice or dentifrice phase of claim 8 further including a fluoride salt.
10. The dentifrice or dentifrice phase of claim 1 further including a surfactant.
11. The dentifrice or dentifrice phase of claim 1 in the form of a toothpaste.
12. The dentifrice or dentifrice phase of claim 1 in the form of a dental cream or gel.
13. The dentifrice or dentifrice phase of claim 3 wherein said pyrophosphate is a mono, di, tri, or tetra-alkali metal pyrophosphate.
14. The dentifrice or dentifrice phase of claim 4 wherein said orthophosphate is selected from alkali metal and ammonium salts of orthophosphoric acid.
15. The dentifrice or dentifrice phase of claim 3 wherein said pyrophosphate is present in amounts of from about 1.5 to 15% by weight of the dentifrice or dentifrice phase.
16. The dentifrice or dentifrice phase of claim 3 wherein said sodium bicarbonate is present in amounts of from about 7 to 65% by weight of the dentifrice or dentifrice phase.
17. The dentifrice or dentifrice phase of claim 4 wherein said sodium bicarbonate is present in amounts of from about 7 to 65% by weight of the dentifrice or dentifrice phase.
18. A dentifrice or dentifrice phase comprising about 7 to 65% by weight sodium bicarbonate, dentifrice or dentifrice phase an anionic component reactive with sodium and water to form hydrated crystals, said anionic component being selected from the group consisting of orthophosphates, pyrophosphates, polyphosphates, metaphosphates, borates, thiosulfates, and glycerolphosphates, a water content of at least 5 wt. % based on the weight of the dentifrice or dentifrice phase, and at least one of a humectant, thickener or abrasive, said dentifrice or dentifrice phase having a water activity of less than about 0.60.
19. The dentifrice or dentifrice phase of claim 18 further including a fluoride salt.
20. The dentifrice or dentifrice phase of claim 18 wherein said anionic component is a pyrophosphate or polyphosphate anti-tartar agent.
21. The dentifrice or dentifrice phase of claim 18 wherein said anionic component is an orthophosphate, and wherein said dentifrice or dentifrice phase further includes a water-soluble or partially water-soluble calcium salt kept separate from said orthophosphate.
22. The dentifrice or dentifrice phase of claim 18 further including a surfactant.