Shortstop with Improved Popcorn Inhibition for SBR/NBR Emulsion Polymerization

Free radical emulsion polymerization reactions are used for production of Styrene/Butadiene rubber (SBR) and Acrylonitrile/Butadiene rubber (NBR). These reactions are stopped short of complete conversion of monomers to polymer to produce elastomers having the optimum physical properties for end use application; mostly in automotive tires. The unreacted monomers are separated from the latex and recycled back into the polymerization. Highly crosslinked material, known as popcorn polymer, can form in the monomer recovery areas of the copolymerization plants and also in storage facilities for diene monomers such as butadiene. The unwanted popcorn polymerization not only causes loss of valuable raw material but also, by clogging the pipelines, condensers, storage tanks, etc., greatly increases the difficulty and expense of maintaining continuous operation plants. ANGUS Chemical Company is developing a new shortstop product for industrial polymerization. It effectively shortstops the free radical emulsion polymerization while offering improved popcorn inhibition, thus allowing for longer run-times for production plants compared to the current offerings in the market. Another important advantage of the new shortstop system is that it allows for the production of rubber in ccompliance with German regulation TRGS 552 (N-Nitrosamines). This paper discusses the key performance benefits of the developmental shortstop/popcorn inhibitor and presents enhanced performance data compared to

current shortstop systems in use.