Synthesis Of A Self-emulsification Defoaming Agent-siloxane-oxyalkylene Copolymers

In the past several years, siloxane-oxyalkylene copolymers are much researched. By graft reaction, hydrophilic polyoxyalkylene make the copolymer soluble, and hydrophobic polysiloxane make the copolymer low surface tension. So, the defoaming agent made by the copolymers can be self-emulsified in the water and is stable. It has a better defoaming ability than the silicon defoaming agent and the polyoxyalkylene defoaming agent.In this thesis, polyhydrosiloxanes is synthesized with octamethylcyclotetra-siloxane(D4) and high hydrogen-containing polyhydrosiloxanes as materials. In the presence of allyl alcohol as initiator and sodium hydroxide as catalyst, the polyoxyalkylene is synthesized. Then the graft reaction is made., the catalyst concentration and the temperature were examined. The effecting factors such as the catalyst,the time, the temperature and the mol ratio of reactants on the graft reaction was studied, and gained a reasonable experimental condition.In this thesis, we also discussed the polyoxyalkylene's structure (the mol ratio of EO/PO,the molecular weight and the blocking agent)and the polysiloxane's structure(the hydrogen content and the molecular weight )on the graft reaction, and their relationship with the the graft reaction conversion of polyoxyalkylene and the properties of the products self-emulsification defoaming agent. The defoaming agent which need not add any additive is stable, and the defoaming effect is excellent. It can quickly dissolve in the water, and can be used not only solely but also together with other emulsifiers and additive. When it is used, the emulsion breaking and the "oil-floating" will not happen, and no deposit appears. Besides, it is also effective to nonaqueous system. It has low surface tension, can quickly defoam, and the dosage is little. So the foreground of this defoamer's application is bright.