| 摘要 |
PURPOSE:To provide the titled pre-expanded particle having excellent foamability, giving a foamed article having improved heat-resistance without lowering the flexibility and cushioning property and usable at a high expansion ratio, by using a specific resin obtained by the vapor-phase polymerization of ethylene and 1-butene as a base. CONSTITUTION:The objective pre-expanded particle contains, as a base, a resin having a melt index of 0.3-3.0g/10min, a density of 0.915-0.935g/cm<3>, a melting point of 110-130 deg.C, the ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw/Mn) of 3-7, and Mw of 5X10<4>-20X10<4> and produced by the vapor-phase polymerization of ethylene and 1-butene. The polyethylene particles containing said resin as a base and a volatile foaming agent are dispersed in water in the presence of a dispersant, and the dispersion is heated at a temperature higher than the melting point of the particle by -25-+10 deg.C to effect the impregnation of the foaming agent to the particle. The temperature and pressure in the vessel are maintained at definite levels above the vapor pressure of the foaming agent, and the mixture of the particles and water is released to an atmosphere having lower pressure than the pressure in the vessel.
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