Study On Synthesis And Properties Of Fatty Alcohol Polyoxyethylene Ether Silicate

Silicates are important intermediates for the preparation of polysiloxanes in organosilicon compounds,and can be painted on the surface of the substrate to protect material,and used as a special liquid medium with good heat resistance such as refractory materials,adhesives,lubricating oils and insulating oils.Fatty alcohol polyoxyethylene ether silicates were synthesized by ester exchange reaction of ethyl silicate with fatty alcohol polyoxyethylene ether(n=3),fatty alcohol polyoxyethylene ether(n=5),and lauryl alcohol.The preferred conditions for the synthesis of fatty alcohol polyoxyethylene ether silicates were studied.The structures of the products were characterized,and the composition,wettability,defoaming and thermal properties of the products were determined.The preferred processes for the synthesis of fatty alcohol polyoxyethylene ether(n=3)silicates are as follows:The molar ratio of ethyl silicate to fatty alcohol polyoxyethylene ether(n=3)is 3:1.Dimethyl dichlorosilane is used as the catalyst at 0.61%(wt)of fatty alcohol polyoxyethylene ether(n=3).The reaction temperature is about 46?,the reaction time is 5h,and the conversion rate of AEO-3 reaches 88.22%.The preferred processes for the synthesis of fatty alcohol polyoxyethylene ether(n=5)silicates are as follows:The molar ratio of ethyl silicate to fatty alcohol polyoxyethylene ether(n=5)is 4:1.Dimethyl dichlorosilane is used as the catalyst at 0.50%(wt)of the fatty alcohol polyoxyethylene ether(n=5).The reaction temperature is 60?,the reaction time is about 5.5 h,and the conversion rate of AEO-5reaches 80.65%.The preferred processes for synthesis of dodecyl silicates are as follows:The molar ratio of ethyl silicate to lauryl alcohol is 2:1,using dimethyl dichlorosilane as the catalyst at 0.54%(wt)of lauryl alcohol.The reaction temperature is 40?,the reaction time is3.5 h.The conversion rate of lauryl alcohol reaches 94.66%.The wettability of fatty alcohol polyoxyethylene ether silicate is better than that of fatty alcohol polyoxyethylene ether,and the wettability decreases with the number of ethylene oxide increases.By gel chromatography,the yield of the mono-ester products increases,that of the multi-ester products decreases in the products with the increases of n(ethyl silicate)/n(fatty alcohol polyoxyethylene ether).The yield of the transesterification products decreases with the number of ethylene oxide increases at constant molar ratio of ethyl silicate to fatty alcohol polyoxyethylene ether.It was confirmed by the measurement of the foam properties that the fatty alcohol polyoxyethylene ether silicates have good defoaming property and low foaming property.The defoaming rate increases,passes through a maximum,then decreases with the number of ethylene oxide increases.Fatty alcohol polyoxyethylene ether(n=13)silicate poses the best defoaming performance with 92%of foam breaking rate and 1.19 mm·s~-11 of defoaming rate.TGA determination shows that the fatty alcohol polyoxyethylene ether silicates are of good heat resistance.The degradative temperature of multi-ester products is lower than that of mono-ester products.For silicates with the same transesterification number,the degradative temperature of the fatty alcohol polyoxyethylene ether silicate increases with the number of ethylene oxide increases.