Effects of carboxylic additives on the polymerization characteristics of nylon-6 reactors with diffusional water removal

The effects of carboxylic acid on the polymerization characteristics of nyl on-6 were investigated in reactor models that consist of a continuous-flow stirred tank reactor (CSTR) and a tubular reactor with a diffusional water- removal system, which are connected in series. Mathematical models for the CSTR and the tubular reactor were established and solved by numerical metho ds. In the CSTR, with an increase of the feed acetic acid content, the mono mer conversion, and the molecular weights are increased. In the tubular rea ctor, the acid behaves like a catalyst and a modifier at the same time in t he polymerization of nylon 6. The effects of the feed acetic acid content a nd the diffusional water removal on the zeroth, first, and second moments a nd the polydispersity index of the polymer were investigated. The polydispe rsity index is greatly affected by the feed content of carboxylic acid in t he CSTR, but it finally approaches to values of similar to 2 in the tubular reactor. The diffusional water removal is found to have little effect on t he polydispersity index of the polymer. (C) 2001 John Wiley & Sons, Inc.