Continuous Emulsion Polymerization of Styrene and Butadiene. Reduction of Off-Spec Product between Steady-States

VEGA, J. R.; GUGLIOTTA, L. M.; MEIRA, G. R.

LATIN AMERICAN APPLIED RESEARCH

Año: 1995 vol. 25 p. 77 - 82

0327-0793

A copolymerization of styrene and butadiene carried out in a train of continuous stirred-tank reactors is investigated, with the aim of reducing the off-spec product generated during transients between steady states (SS's). The following changes between SS's are investigated : 1) in the production level, for approximately the same polymer quality; and 2) in the polymer grade, for the same total feed rate. Changes in production level are optimized by manipulating the total feed into the first reactor; in this case being possible to completely eliminarte the oscillations in the final solid contents. For changes in the grade, the recipe into the first reactor is instantaneously adjusted at time zero, while an independent modifier feed into the last reactor is manipulated during the transient. This procedure allows to maintain the number-average molecular weight in the last reactor in the lowest of the two desired SS values during most of the transient period. The required feed profiles were calculated by application of a "virtual" P+1 controller, and in the case of changes in grade, an inversion of the mathematical model was also possible. The P+1 controller approach is potentially applicable in a real closed-loop situation, with the advantage of not necessitating an exact plant model description. The resulting policies are superior to the "bang-bang" operations that are normally implementad in industry.