Free Radical Polymerization of Acrylic Acid at High Monomer Concentration in a Continuous Flow Reactor

Most of the world's polyacrylic acid (PAA) is produced by batch or semi-batch processes. In the case of free-radical polymerization (FRP), continuous processes may offer advantages concerning safety, productivity, product quality, and cost. Designing a continuous process for a polymer with a high total polymer concentration imposes challenges like its likelihood of polymer deposition on the walls of the reactor, and runaway reactions, which were addressed in this work. In addition, a continuous lab-scale process using a tubular reactor was evaluated for the polymerization of acrylic acid in an aqueous solution to transition from the batch to continuous flow production of high monomer content or total solid (TS) polyacrylic acid with the aim of meeting product specifications 300,000 g/mol molecular weight, a polydispersity of 10 or below, and PAA concentration of 25% with ≥99% conversion. The feasibility of producing waterborne polyacrylic acid with ammonium persulfate via a lab-scale continuous-flow tubular reactor was investigated experimentally. Initially, the FlowSyn microreactor (Uniqsis Ltd., United Kingdom) was used for experimentation but was replaced by a two-monomer feed tubular configuration. These lab-scale data provided experimental and theoretical bases for process scale-up to the pilot-scale plant. The thesis also includes a literature review discussing various approaches to establish a way to safely switch from the discontinuous to the continuous flow process for the production of polyacrylic acid