| 摘要 |
Ethyl acrylate is polymerized in aqueous suspension with benzoyl peroxide catalyst and in the presence of a -alumina particles and the polymeric suspension is treated with an aqueous mixture of FeSO4 and Na4P2O7 to form polyacrylate granules having alumina particles embedded therein.ALSO:A polishing agent suitable for use in a dentifrice comprises carrier particles of a material having a Moh's hardness less than 6 and an average size in the range 1 to 50 microns, the said carrier particles having embedded therein abrasive particles of a material having a Moh's hardness greater than that of the material of the carrier particles and an average size of less than 1 micron. Suitable carrier materials are plastics materials, e.g. natural and synthetic rubbers, polyolefines, poyvinyl chloride and co-polymers of vinyl chloride and other unsaturated monomers such as vinyl acetate or vinylidene chloride, nylons, polyacrylates and polymethacrylates. The abrasive materials may be aluminas, natural or synthetic silicas, calcium phosphates such as b -tricalcium or thophosphate, and thermosetting resins such as urea-formaldehyde or melamine-formaldehyde resins. Optional ingredients in the dentifrice may be soap or synthetic detergents, flavouring materials, buffers, sweeteners, colouring materials and therapentic materials, e.g. sodium fluoride, stannous fluoride and sodium monofluorophosphate. The dentifrice may contain conventional carriers and abrasives, as well as particles of a plastics material not impregnated with abrasive particles.
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