| 摘要 |
Water-impervious, cross-linked, thermosetting, highly polymerized resins are prepared by the acid setting and/or heating of commercially available melamine-formaldehyde, phenolformaldehyde, urea-formaldehyde, alkyd and epoxy resins. In general the heating may be at temperatures in the range 100 DEG to 180 DEG C. for up to 16 hours. Preliminary acid setting, e.g. with HNO3, is stated to be especially useful in the case of melamine-formaldehyde, ureaformaldehyde and melamine-urea-formaldehyde resins. Specific examples are given of the treatment of known resins of each of the abovementioned types. The resultant highly rigid and brittle resins may be used in particle form as cleaning agents in dentifrice compositions comprising at least 25 p.p.m. by weight of fluoride ions and, optionally, stannous ions which are supplied by suitable innocuous water-soluble compounds, e.g. sodium, potassium, ammonium, indium, palladium, ferrous and lithium fluorides, organic fluorides, e.g. ethanolamine hydrofluorides, complex fluorides, e.g. fluorosilicates, fluorotitanates, fluorostannites, fluorozirconates and fluoroborates, stannous fluoride and mixed stannous halides, e.g. SnClF and Sn2ClF3. The dentifrices may additionally comprise conventional humectants, sudsers, binders, sweeteners and flavours, e.g. glycerine, hydroxyethyl cellulose, sodium coconut sulphate, sodium coconut monoglyceryl sulphonate, sucrose monomyristate, saccharin, sorbitol and colouring. Specifications 746,550, 804,486 and 810,345 are referred to.ALSO:Dentifrices e.g. powders and pastes comprise at least 25 p.p.m by weight of fluoride ions as a water-soluble, fluoride ion supplying substance and, as cleaning agent, at least 20% and up to 95% by weight of a substantially water-impervious, cross-linked, thermosetting, highly polymerized synthetic resin in the form of particles all of which desirably have a diameter of less than 50m (5-20m preferred), not more than 10% of the particles having a diameter of less than 10m . In addition to conventional humectants, sudsers, binders, sweeteners and flavourings there is preferably also present a source of stannous ions, these and the fluoride ions being supplied by innocuous water-soluble compounds, e.g. sodium, potassium, ammonium, indium, palladium, ferrous and lithium fluorides, organic fluorides, e.g. ethanolamine hydrofluorides, complex fluorides, e.g. fluorosilicates, fluorotitanates, fluorozirconates, fluorostannites and fluoroborates, stannous fluoride and mixed fluorine containing stannous halides e.g. SnClF and Sn2ClF3. Suitable resins are commercially available melamine-formaldehyde (preferred), phenol-formaldehyde, urea-formaldehyde, polyester (alkyd) and epoxy resins which have been further polymerized by treatment with acids and/or heating (see Group IV (a)). Specifications 746,550, 804,486 and 810,345 are referred to. |
