Study On Highly Reactive Polyisobutylene Initiated By Boron

High Reactive Polyisobutylene (HRPIB) were selectively synthesized by the cationic polymerization of isobutylene (IB) directly from C4fraction with BF3/MBO, BF3/MEKO or TiCl4/ED initiating systems. The effects of BF3initiating system, dosage of catalyst, polymerization temperature and time on the IB conversion, number-average molecular weight (Mn) and molecular weight distribution (MWD, Mw/Mn) and microstructure of the PIB products were studied in detail in this paper. Mn and MWD were characterized by GPC method. And The microstructure of HRPIB was characterized by1H-NMR and13C-NMR. Perceiving these results, the following conclusions can be drawn.1. The said BF3initiating system possessed high reactivity and high selectivity. It can be directly used in C4fraction which even contains some impurities, such as butadiene and allylene. And the outcome products commonly have Mn of600～3000, MWD of less than2.5, a%of more than80%. While being respectively compared with BASF HRPIB products which are produced from pure IB/nHex system in the same Mn catalog, the identical results showed that, the said BF3initiating system has excellent selectivity to IB polymerization in different C4fractions.2. For BF3initiating system, the typical reaction conditions are as follows:BF3/IB=3×10-3～5×10-3, polymerization temperature=-35～-20℃polymerization time=5～15minutes.3. The BF3initiating system showed great reserve stability under the atmosphere of pure N2. After being sealed under-10℃for10days, the said initiating system could still yield products. The typical HRPIB has Mn of1000, MWD of1.3and a%of89.5%.Furthermore, the cationic polymerization of IB coinitiated by TiCl4in nHex/CH2Cl2mixed solvent or in C4fractions was also investigated. The following results can be given:4. It is revealed for the first time that ED/TiCl4initiating system can be used in the preparation of HRPIB. Polyisobutylene with Mn of6100, MWD of2.5and a%of72.6%was produced by ETE/TiCl4initiating system in50/50CH2Cl2/nHex; The content of a-structures could reach84.9%by using IPO/TiCl4initiating system.5. More significantly, HRPIBs with Mn of around8600, a%of ranging from70%-76%could be obtained by MEO/TiCl4initiating system directly from C4fraction.