Synthesis of Polyvinyl Butyral via Soap-free Precipitation Method

A novel soap-free precipitation method was adopted to prepare polyvinyl butyral(PVB).Nano-silica was selected as a dispersant in place of the surfactant.Butyraldehyde was dispersed into the aqueous solution of polyvinyl alcohol(PVA)by high pressure homogenization.The resulted PVB powder was aggregates of primary particle which was less than 10microns,indicating that the reaction was carried out within a small volume.Nano-silica adhered to the surface of the particle,and effectively inhibited the agglomeration of PVB via the physical isolation.The acetal group content of the PVB was above 75%and the viscosity of its ethanol solution was similar to that of the commercial resins.The soap-free precipitation method evidently reduced the consumption of washing water and improved the quality of the resin.The optimized reaction conditions were:mass ratio of PVA to butyraldehyde 1∶(0.6~0.65),starting temperature 20℃,gradient heating rate 5℃/30min,pH value 1.3,dosage of nano-silica 0.07% of the total system.