Study On Preparation And Surface Characteristics Of Polyether Modified Polysiloxane, And Its Defoaming Formula

Polyether modified polysiloxane, which combined the good properties of polyether and polysiloxane, was a particular surfactants used in many areas.Chloroplatinic acid/isopropanol catalyst, whose catalytic activity was weak and shelf life determination was short, were used in preparation of polyether modified polysiloxane. In this paper, the method of preparing Karstedt's catalyst was improved based on following two differences:Divinyl tetramethyl siloxane was 31 times the mole of chloroplatinic acid and sodium carbonate was 24 times the mole of chloroplatinic acid. Reaction temperatrue was 70℃. Reaction condition was at 30 minutes, which was also placed more than 10 hours, then filtered and diluted.The innovative method of preparation of polyether modified polysiloxane without solvent was based on the traditional processes with improved Karstedt's catalyst, polyhydrosiloxanes and allyl alcohol polyoxyethylene polyoxypropylene ether. The mixture of Karstedt's catalyst and polyether were heated to 50-60℃, then polyhydrosiloxanes was added. Reaction temperatrue was kept around 65～70℃for about 2.5-2.5 hours to get the polyether modified polysiloxane. The color of the product was light yellow. The amount of catalyst was decreasing sharply for about 60 percent. An average conversion of Si-H bond was increased from 87% to 91.4%, the former is the average conversion of original Speier's method.The relationship between surface properties such as surface tension and cloud point in water solution of polyether modified polysiloxane with the structure of polyether was useful to prepare polyether modified polysiloxane, which was applied for defoamer or other products.Studying on the properties of defoamer by mixed polyether modified polysiloxane with silicon ointment, emulsifier, and thickener, a good formula had been obtained,and followed as(wt%):2～3% silicon ointment,7～8% polyether modified polysiloxane, 2.4-2.6% methyl glucose sesquistearate(SS)/PEG-20 methyl glucose sesquistearate (SSE-20),0.4～0.5% hydroxyethyl cellulose (HEC) and 87～90% water, which had a better defoaming ability by comparing with different kinds of merchant defoamers under hard conditions of 90℃, strong acidicity and alkalinity.The mathematical method of stability test for emulsion had also been set up. The period of storage of polyether modified polysiloxane defoamer could be estimated by this method.