Influence Of Initiator System On Polymerization In Butyl Rubber Production

Butyl rubber features good air tightness, oxygen aging resistance, chemical resistance, wet resistance, and very good shock absorption function. 30,000t/a butyl rubber unit of BYPC is traditional slurry type production process, using H₂O-AlCl₃ as initiator, methane chloride as diluent. Polymerization proceeds in low temperature of -88～-98℃. Butyl rubber polymerization is typical positive ion reaction. In polymerization, initiator AlCl₃ and H₂O form ion complex, contribute H+ to isobutylene molecule, form a positive carbon ion, subsequently initiate polymerization and form polymer chain. From polymerization principle we know that water has very important influence on positive ion reaction. It can impact size, distribution and conversion of molecular weight. When adding trace water to initiator AlCl₃ solution, initiator efficiency(rubber output(kg/h)/initiator amount(kg/h))will be improved, hereinto the proportion of main initiator to co-initiator([AlCl₃]/[ H₂O] mol ratio)is very important. We know from several years production experience that controlling [AlCl₃]/[ H₂O] mol ratio in 8-12 can get high conversion. In polymerization system, polymerization speed will quicken with AlCl₃ dosage increase, this attributes to amount of initiating activity center increasing with AlCl₃ dosage increase, namely (WAl³⁺)/(W monomer)increase, and reaction speed quickens and conversion increases. Combining actual situation of configuration and reaction adjustment, 0.10%⁰.15% concentration is suitable. In addition, in configuration of initiator solution, purity of refining methane chloride is also very important. Water, DME, isobutylene content in methane chloride must be strictly controlled to guarantee stability of initiator system.