| 摘要 |
PURPOSE:To produce pre-expanded particles which have good moldability and give moldings which suffer less shrinkage and have excellent flexibility, by carrying out pre-expansion while maintaining the temp. of polypropylene resin particles and a dispersion medium within a proper range. CONSTITUTION:0.04-0.20mol of a volatile blowing agent such as propane is incorporated in 100pts.wt. polypropylene resin particles. The mixture is then dispersed in a dispersion medium in a container. While maintaining the temp. T deg.C of said blowing agent-contg. resin particle and said dispersion medium within a temp. range represented by the formula, Tm-20<T<Tm-5 (wherein Tm is the max. temp. of a heat absorption curve obtd. by elevating the temp. of a sample weighing 6-8mg at a rate of 10 deg.C/mm. by DSC method) without elevating the temp. T deg.C to a temp. higher than the temp. Tm deg.C at which the resin particles are completely molten, one end of the container is opened and said resin particles and said dispersion medium are simultaneously discharged into an atmosphere under a pressure lower than that of the container to obtain the desired particles.
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