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Chemical Engineering

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Safer, more sustainable control of runaway polymerization

| By Mary Page Bailey

Runaway polymerizations of acrylic monomers can lead to catastrophic fires and explosions in production plants and storage terminals, as well as during transportation. Special chemical products called shortstop inhibitors are used to minimize the likelihood of runaway polymerization reactions. A new shortstop inhibitor technology developed by Solvay S.A. (Brussels, Belgium;, Phenothiazine (PTZ) LVT 2330, claims to bring several unique environmental, health and safety benefits to the market.

The product is based on a non-toxic, non-volatile and biodegradable solvent, which reduces worker exposure to harmful solvents, and was developed as an alternative to N-methyl-2-pyrrolidone (NMP). Also, while other shortstop inhibitors on the market incorporate “green” solvents, these products contain only about half the active-ingredient concentration compared to Solvay’s formulation (30% active solids PTZ), which means that more of the shortstopping agent can immediately enter the acrylic monomer solution. Lower-concentration formulations not only exhibit slower shortstopping rates due to lower dosage rates, but they also require larger volumes, and therefore bigger storage requirements, to achieve the same performance. Storage considerations are key for such products, since users will only need them in emergency circumstances.

It is also worth noting that Phenothiazine LVT 2330 can be stored at temperatures as low as –50°C, which is a major benefit for acrylics storage and transport in cold climates. “The PTZ active ingredient in Phenothiazine LVT terminates the uncontrolled, free-radical polymerization of the acrylic monomers, and it is noted that the product does not require the presence of oxygen to be effective. Other inhibitors require oxygen to function, which can further increase the likelihood of catastrophic events,” explains David Vanzin, technical service development manager for Solvay’s Aroma Performance business unit. Furthermore, “Shortstopping solutions are like fire extinguishers and insurance policies, something that you purchase and hope you never have to use,” adds Vanzin.