PRE-EXPANDED BEAD OF UNCROSSLINKED LINEAR-CHAIN LOW-DENSITY POLYETHYLENE RESIN AND ITS PRODUCTION

摘要

PURPOSE: To produce a pre-expanded bead having excellent fusion-formability in the mold and giving an expansion molded article having excellent specific compression strength, repeated compression set and shearing impact resistance by a specific method using a specific uncrosslinked linear-chain low-density polyethylene resin particle as a raw material. ;CONSTITUTION: This pre-expanded particle having an expansion ratio of 8-60-cm³/g and a closed cell ratio of ≥90% is produced by preparing an uncrosslinked linear-chain low-density polyethylene resin particle having a Cw/Cn ratio of 1.1-2.5 (Cw and Cn are weight average distribution and number-average distribution of the polymer component fractionated by increasing temperature dissolution process using 13C-NMR), contacting the polyethylene resin particle with a foaming agent (preferably CO₂) in a closed vessel, heating and expanding the obtained expandable resin particle at a temperature higher than the softening temperature of the particle by 5-15°C and cooling below the softening temperature within 15sec by blowing a refrigerant to the particle. The low-density polyethylene resin is preferably synthesized by using a metallocene catalyst.;COPYRIGHT: (C)1995,JPO