The Preparation Of Silicone Paste With Long-chain Alkyl Silicone Oil And Its Application In Mineral Oil Defoamer

Mineral oil defoaming agent is widely used in water phase systems such as paper making,coating,textile,sewage treatment.It has superior characteristics including excellent dispersibility,low cost and little effect on the performance of orginal products.However,the poor defoaming performance and poor compatibility of the compound components adversely affect its further application.Since the silicon paste is a highly effective defoaming substance in the water phase system,it can be compounded into the mineral oil defoamer to play a synergistic defoaming effect in the water phase system,thereby improving the performances of the mineral oil defoamer.In this paper,long-chain alkyl silicone oil and silicone paste were synthesized.Then,the reaction mechanism of silicone paste was explored.Finally,the silicone paste was compounded into mineral oil defoamer to prepare high performance mineral oil defoamer.The main contents include:?1?The long-chain alkyl silicone oil was successfully prepared through hydrosilylation reaction between hydrogen-containing silicone oil and 1-dodecene under the catalyst of platinum.The process for preparing the long-chain alkyl silicone oil was optimized and analyzed.Under the optimal process conditions,the prepared long-chain alkyl silicone oil had a viscosity of 196 m Pa·s,a surface tension of 22.3 m N·m^-1,and the conversion rate of hydrosilylation reaction was more than 98%.?2?The silicon paste was prepared by stirring long-chain alkyl silicone oil and fumed silica at high temperature.The preparation process of the silicon paste was optimized and the reaction mechanism of the silicon paste was explored.The best preparation process of silicon paste was adding the fumed silica at the begining of stirring,which prepared the long-chain alkyl silicone oil and silicon paste at the same time.The reaction mechanism of silicon paste was a mixture obtained by chemical reaction between unreacted silicon-hydrogen bonds in long-chain alkyl silicone oil and hydroxyl groups on the surface of hydrophobic fumed silica.The particle size of fumed silica was measured by a nanoparticle analyzer.The particle size of the fumed silica increased from 18 nm to 59 nm after the reaction,indicating that the long-chain alkyl silicone oil was grafted on the surface of the fumed silica particles to form a"multi-tail"macromolecular shape.The optimal silicon paste was compounded into mineral oil defoamer.The defoaming time of defoamer was 19s while the foam suppression time was 23.7min.?3?Organic bentonite was used to delay the agglomeration and settling of fumed silicon in the defoamer.The activation process of organic bentonite was optimized as the following:95wt%ethanol solutions was added 30%of the quality of the organic bentonite as the activator,18mm rotor homogenizer was used for high-speed dispersion at 14000rpm for 5min.When the mass fraction of organic bentonite was 1.5%,the storage time of the defoamer achieved up to47 days.At last,the anti-settlement mechanism of organic bentonite was investigated.?4?The high performance mineral oil defoamer was prepared through compound of silicone paste,mineral oil,polyether,compound emulsifier and organic bentonite according to a certain mass ratio,where silicone paste was used as defoaming active substance,mineral oil was used as carrier,polyether was used as defoaming aid and organic bentonite was used as anti settling agent.The single-factor method was carried out to investigate and optimize the preparation process of the defoamer.When the mass fraction of No.26 oil,silicone paste,emulsifier?Span80:Tween80=5:1?,PPG800 and organic bentonite SD 1 were 80%,10%,6%,3%and 1%respectively,the prepared mineral oil defoamer achieved the best performance with a viscosity of 247 m Pa·s,a surface tension of 23.0 m N·m^-1,a storage time of 38 days,a coating shrinkage of grade 5,a defoaming time of 22s,and a foam suppression time of 19.2 min.Compared with the defoamer from Japan,the homemade defoamer had excellent defoaming and dispersing properties,good storage stability,simple preparation process,good economic benefits and application prospects.