FOAMED POLYPROPYLENE

摘要

A process for the branching and foaming of a polypropylene resin, being performed continuously in an extruder, comprising: (i) mixing the polypropylene resin with a peroxide selected from the group comprising the structures represented by: R>1<-O-O-C(O)-C=C-C(O)-O-O-R>2<, R>3<-R>5<-O-C(O)-O-O-C(O)-O-R>6<-R>4<, wherein each R>1< and R>2< represents linear or branched alkyl groups having 1-15 carbon atoms, each R>3< and R>4< represents linear or branched alkyl groups having 4-30 carbon atoms, and each R>5< and R>6< represents cyclic or linear aliphatic groups having 6 carbon atoms, (ii) heating the constituents to a temperature higher than the melting temperature of the polypropylene resin and the decomposition temperature of the peroxide while being mixed and conveyed forward, (iii) keeping the polymer melt at said temperature for a period of 3 to 100 times the half-life of the peroxide at said temperature, (iv) introducing a foaming agent, optionally also a bubble initiator, into the polymer melt inside the extruder at a position where the branching is substantially complete, (v) extruding the processed polymer melt through an extrusion die into ambient atmosphere, whereupon the polymer composition expands. The obtained polymer resins may be used in manufacturing articles by pipe extrusion, thermoforming and blow molding. Branched polypropylene resins not being subjected to foaming may be used as such in manufacturing articles by injection molding, extrusion, thermoforming, blow molding, calandering and fibre spinning.