In the production of high impact polypropylene (hiPP) by in-reactor processes

the ethylene content of hiPP was limited at a low level for the lack of a suitable antisticking method and that by now a deficient antisticking method with low purity nitrogen (LPN) was commonly adopted. A new antisticking method by in-situ adding tiny (<0.1%) superfines was adopted in Hypol process to produce hiPP with high ethylene content (>20%) and good flowability

showing the possibility to take the place of LPN method. Moreover

the comparison of the product with hiPP prepared by LPN method showed that the anti-impact performance rose from 36.44 kJ·m-2 to 60.56 kJ·m-2 at 23℃ and from 14.78 kJ·m-2 to 35.12 kJ·m-2 at -20℃

respectively. It was found that hiPP with high ethylene content presented excellent anti-impact performance at both 23℃ and -20℃.