MULTIPLE RESPONSE OPTIMIZATION OF THE CTA ADDITION IN SBR RUBBER PRODUCTION

GERARDO MARTINEZ DELFA; CARLOS EUGENIO BOSCHETTI

Los Cocos

Conferencia; V Argentine-Chilean Polymer Symposium; 2009

Archipol

Styrene–butadiene rubber (SBR) is one of the most important synthetic polymers. It accounts for about 40% of the total synthetic elastomer production, its major consumption being in tyres and tyre products. SBR can be obtained by styrene and butadiene emulsion copolymerization. The molecular weight distribution in SBR emulsion polymerization is controlled by means of a chain transfer agent (CTA), usually a mercaptan like dodecyl mercaptan. The lack of this CTA will cause a decrease in the rubber processability, due to the high molecular weight obtained. Incremental addition of CTA is proposed in several works as an effective strategy for molecular weight control (Booth et al.,1961; Uraneck and Burleigh, 1965). The resulting delay in the formation of branches and cross-link points, makes this technique to be a suitable option for increasing the reaction conversion maintaining the quality properties (Uraneck, 1976).  However, due to the complex behaviour of some rubber characteristics such as Mooney viscosity, the optimization of several properties is difficult to achieve. In a previous work (Martinez Delfa et al.,2009), the combined use of artificial neural networks (ANNs) and desirability function D(x) was successfully employed for the modeling of SBR properties followed by a multiresponse optimization of polymerization reagents at laboratory scale. With this basis, we proposed to broaden the optimization of the emulsion polymerization in order to obtain an enhanced polymer production of SBR 1712-grade by a CTA incremental addition strategy. Mooney viscosity (MV) and number- and weight-average molecular weights were kept in specification whereas the conversion (x) was maximized.