Design of Emulsion Polymerization Reactors for Monomer-Transport Limited Emulsion Polymerization

Abstract

Damkohler Number (Da) analysis can identify monomers and emulsion polymerization operating regimes where the polymerization may be monomer-transport, rather than reaction-limited. In these cases, the expected monomer concentration in the growing polymer particles will be reduced due to the transport limitation. This will reduce the expected rate of polymerization, and require the design of a larger polymerization reactor for a given production rate. In heterogenous catalysis, an effectiveness factor is used to quantify the reduction in reaction rate and necessarily increase reactor size to compensate. This paper will show that it is possible to use Da (functionally equivalent to the Thiele Modulus in heterogeneous catalysis) to estimate an effectiveness factor for emulsion polymerization. Also shown is a procedure for calculating the monomer feed ratio during binary copolymerization when one must not only take into account the reactivity ratios but also the possibility that one of the monomers is monomer-transport limited. The method provides the monomer feed ratio during the semibatch phase of a binary copolymerization. This alternative to starved-feed polymerization shall result in much faster polymerization and higher polymerization kettle utility.