Polyether Modified Siloxane Surfactant Synthesis And Performance

Organic silicone surfactants have excellent wettability and permeability, can greatly promote liquids expanding, make the solution enter into the plant tissue through the stomata. For this reason, the organic silicone surfactants play an important role in reducing pesticide residues lingering on crops, reducing pesticide quantity losing in soil and groundwater, then it can reduce the pollution of pesticide to soil and water and other natural resources, and ease the increasingly tensions of water resources in China. The research of organic silicone surfactants has been started relatively late, the kind of products is single, and a large production scale has not been formed, the most of products are imported. It will decrease the imports of similar products, reduce the dependence of domestic enterprises to foreign enterprise on technology, and improve competitiveness if the organic silicon additive is developed successfully, which will be beneficial to wide application of organic silicone surfactant. So there is a practical significance in designing and synthesizing polyether modified siloxane surfactant.The high purity 1,1,1,3,5,5,5-Heptamethyltrisiloxane(MDHM) has been prepared with hexamethydisiloxane and full-hydrogen silicone oil in this paper, by acid catalyzed equilibrium reaction and distillation purification techniques. By gas chromatography internal standard method, the best conditions for synthesis were determined as follows: the reaction molar ratio of m (MM): m (DH) = 13:1, the reaction time is 7h, the reaction temperature is 30℃, and the amount of catalyst is 5%.The 1,1,1,3,5,5,5-heptamethyltrisiloxane has been modified by methoxy-terminated polyether polyols. The trisiloxane surfactant has been prepared with efficient Pt catalyst, under no solvent condition and the protection of nitrogen. The conversion of MDHM in reaction was determined with hydrogen content determination method, orthogonal experiment was used to establish the optimum technological parameters. The optimum technical parameters were as follows: n(AEM):n(MDHM)=0.9:1,temperature and time can be identified as 100℃and 9h, catalyst dosage (in terms of Pt) is 12×10-4%. The conversion rate reached 86.7% under the optimum conditions.According to the corresponding national standard methods, the surface tension, CMC value, HLB value and emulsification performance were determined. The hydrolytic stability of product was compared to other three kinds of organic silicon surfactants, the result shows that the hydrolytic stability of product is better than the similar products. The key to reduce the hydrolysis rate of polyether modified polysiloxane surfactants is to reduce the contact of polysiloxane chain in surfactant molecules and water solution. For methoxy-terminated polyether modified polysiloxane, the methyl ether open as the umbrella, which can reduce the contact of polysiloxane chain in surfactant molecules and water solution to a certain extent, so the hydrolysis stability of product raise.