Understanding vinyl acetate polymerization accidents

Vinyl acetate is processed to produce polymers and copolymers used in water based paints, adhesives, paper coatings or non-woven binders and various applications at moderate temperatures. The polymerization processes used include solution, suspension and emulsion processes. Many incidents involving the runaway polymerization of vinyl acetate monomers (VAM) are known.

In processes where the polymerization initiator was dissolved in the monomer, the initiator premix polymerized violently in the premix vessel.

In polymerization processes where vinyl acetate monomer conversion ratio was not 100%, storages of recycled monomers containing no polymerization inhibitor and possibly some traces of polymerization initiator exploded due to VAM violent bulk polymerization.

Incidents happened either in batch or semi-batch polymerization processes in connection with wrong initiator introduction.

In this paper, a review of polymerization incidents is given. Radical chain polymerization kinetics are used to explain some accident features such as polymerization isothermal induction periods. Experimental results on bulk VAM polymerization are given.