Synthesis And Performances Of Trisiloxane Surfactant

Trisiloxane surfactant is a kind of organosilicone surfactants with a trisiloxane hydrophibic group and a polyether hydrophilic group. Compared with other kinds of surfactant, it can promote solutions wetting and expanding quickly at low-energy surfaces, such as PE film, leaves, and has the ability of superspreading. It can be used as wetting agent, foam stabilizer, lubricant and emulsifier in the industry of coating, pesticides and cosmetic. Si-C type of trisiloxane surfactant is the main research direction because of its hydrolytic stability.1,1,1,3,5,5,5-Heptamethyltrisiloxane (MD^HM) was synthesized through hydrolytic condensation reaction of trimethylchlorosilane (Me₃SiCl) and methyldichlorosilane (MeSiHCl₂), then nonionic trisiloxane surfactants was prepared through hydrosilylation of MD^HM and allyl-ending polyether.This thesis studied three different kinds of hydrolytic condensation methods of Me₃SiCl and MeSiHCl₂: co-hydrolytic condensation reaction, step-by-step hydrolytic condensation reaction and reversive hydrolytic condensation reaction, and analysized the hydrolytic condensation mechanism of chlorosilane. It was conclued that step-by-step hydrolytic condensation method colud be more convenient for reaction selectivity. Then the influencing factors of step-by-step hydrolytic condensation reaction were systematically discussed, such as the selectivity of hydrolysis solution, the amount of hydrolysis solution, the molar ratio of Me₃SiCl and MeSiHCl₂, the dropping speed of MeSiHCl₂, temperature. And in the optimum condition, the selectivity of MeSiHCl₂ could reach 32.40%.Three kind of trisiloxane surfactants (TSS) were syntheized through hydrosilylation of MD^HM and allyl-ending polyether, first activating Si-H by Speier catalyst, then dropping ally-ending polyether continually, hexamethyldisiloxane(MM) produced by hydrolytic condensation reaction was used as solvent, the molar ratio of C=C and Si-H was about 1.2:1. The optimal reaction temperature was 80-100℃, the reaction was stopped until no Si-H peakwas evident by FTIR. Trisiloxane and tetrasiloxane mixed surfactants (TTS) was also prepared through hydrosilylation of hydrogen-containing intermediate 2 and allyl-ending polyether with the same method.The surface performance of synthesized TSS and TTS was studied, it was shown that TSS and TTS could both reduce the surface tension of water down to the low value of about 20 mN/m. TSS-450, TTS-450 could show excellent superspreading behavior on glass and PE film surfaces, and the spreading capability of TTS-450 was better than that of TSS-450.