Stannous Aqueous Solution And Menthol-Loaded Molecular Gels

Stannous aqueous solution and menthol are important ingredients in the toothpaste, which act as tooth decay preventer, perfumery, or bactericide respectively. It is aimed to develop new molecular gels to stabilize them.Sn2+ is easily to be hydrolyzed and oxidized at the state of solution. Two new methods are taken to gelate stannous solution. The first way is to make it micro emulsifycated and then gelated by gelator. The product is called microemulsion-based molecular gel. Pseudo-ternary phase diagram is used to determine the area of micro emulsion for Tween80/1, 2-propylene glycol/IPM/stannous solution system. Span60, glyceryl monostearate, or DBS, et al, is used as gelator. It is hard to meet the content standard of Sn2+ in the toothpaste for Tween 80 system as the mass fraction of stannous solution is too low in the microemulsion area. Span60 system performs better but choice of gelators is restricted by the Cloud Point of OP-10. TGS is too low when span60, glyceryl monostearate, and glyceryl palmitate are chosen as gelators.The second method is to utilize medicinal ethanols with stannous solution as mixed solvents and then add gelators to them. The gelators are called 1,3:2,4-di-O-benzyli dene-D–sorbitol (DBS), 1,3:2,4-di-O-methylbenzylidene-D-sorbitol (MDBS), and 1,3:2,4-di-O-dimethylbenzylidene-D-sorbitol (DMDBS). Research of gel stabilization is carried out through the determination of TGS, high temperature tests, low temperature tests, and frozen & melt tests. Every sample performs well at the low temperature of -20℃. There is little liquid out of the gels when 1,3-butylene glycol (or glycerin) /stannous solution≧ 7:3 in Frozen & Melt Tests. Only one sample meets the requirements of National Standard for high temperature tests which is consisted of as follows: PEG-400: 5%, DBS: 5%, 1,3-butylene glycol/stannous solution = 8:2(w/w). Polyglycol-400(PEG-400) is added to strengthen the molecular gels too, but it works little.The gel carriers for menthol are prepared as follows: medicinal ethanols with water are used as mixed solvents; DBS, MDBS, and DMDBS are used as gelators. Research of gel stabilization is carried out through the determination of TGS and humidity tests. The results showed the absorbent quality of gels is determined by the nature of the solvents, not by gelators. Molecular gels of 1, 2-propylene glycol/water system absorb little water and accord with national standards for humidity tests.