Highly efficient synthesis of polyvinyl butyral (PVB) using a membrane dispersion microreactor system and recycling reaction technology

We herein propose a highly efficient method for the synthesis of polyvinyl butyral (PVB), an important resin material used for laminated glass in vehicles. The condensation reaction between polyvinyl alcohol (PVA) and n-butanal was successfully implemented in a reaction system containing a membrane dispersion microreactor and an aging vessel reactor, allowing the energy costs associated with cooling and mixing of the reactant solutions to be reduced. Upon changing the original reactant from a PVA–butanal emulsion to a PVA–HCl solution, the microreactor system allowed the development of a new recycling technology for the reuse of HCl, water, and excess n-butanal present in the product solution. In addition, with the aid of a two-step n-butanal feeding method, the developed recycling technology resulted in a 98.7% n-butanal utilization ratio, while the consumption of HCl and water during the reaction process was reduced by 85.6%. These results indicate that our novel process represents a more environmentally friendly approach to the PVB synthesis.