Initial stage of the chlorination of natural rubber

✍ Scribed by L.B. Krentsel; S.O. Travin; A.D. Litmanovich; K.K. Yutujan

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 290 KB
• Volume: 21
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(85)90199-5

✦ Synopsis

Kinetics of the initial stage of the chlorination of natural rubber(NR), up to chlorine content -<, 1 C1/C5, have been investigated using a stop-flow method in CC14 at room temperature. The chlorination is very fast and is accelerated by the product HC1. The first orders of the reaction rate relative to NR, C12 and HCI were established. A proposed mechanism includes formation of molecular complexes between polymer units, CI 2 and HCI; the corresponding kinetic equation described satisfactorily the experimental data. Kinetic characteristics of the chlorination of the model compound 2-methylpentene-2(MP) are the same as for NR. The noncatalytic and autocatalytic rate constants for MP are close to those for NR. Compositional heterogeneity of chlorinated NR(CNR) containing <1C1/C5 has been studied by cross-fractionation. The sample chlorinated by the routine procedure is markedly heterogeneous whereas the sample prepared in the stop-flow unit (where extremely fast mixing is realized) is quite homogeneous. These results lead to the conclusions: (1) high reaction rate is caused by high reactivity of "kinetically independent" NR units, not by a polymeric effect; (2) great compositional heterogeneity of CN R samples prepared by the routine procedure is caused by macrokinetic factors.