Abstract: A kind of modified silicone oil (PMS) was synthesized by hydrosilylation with allyl alcohol polyethoxy polypropoxy ether (FB),lauryl methacrylate (LMA) and hydrosilicone oil (PHMS) as starting materials,as well as chloroplatinic acid as catalyst.Optimum reaction conditions were investigated via orthogonal designed experiments as:molar ratio,n(Si-H)∶n(C=C)=1∶1.20;dosage of catalyst,30 μg·g^-1;reaction temperature,90 ℃ for 6 h.Under these conditions,the conversion achieves 93.45%.The polysiloxane defoamer was prepared by emulsifying of aqueous phase into the oil phase,which was composed of silicone oil paste,blended emulsifying agent and the prepared PMS in a high speed shearing emulsification mixer.The optimized formulation was obtained via application tests as:mass fraction of silicone oil paste,10%;mass fraction of PMS,6%;and mass fraction of blended emulsifying agent (composed of Span 60,Tween 60 and OP-10 with mass ratio of 3∶2∶1), 4%.The polysiloxane defoamer product shows good stability and its defoaming property and foam inhibition property is superior to other similar products.

Key words: defoamer, polyether modified silicone oil, hydrosilylation, polysiloxane, application