| 摘要 |
<p>In a process for preparing pre-expanded particles of a polyolefin resin which comprises dispersing polyolefin resin particles in water in a pressure vessel, impregnating the particles with a volatile blowing agent, elevating the temperature of the mixture of the particles and water to a temperature close to the melting point of the resin particles under a pressure equal to or higher than a vapor pressure of the blowing agent and releasing the mixture into a low pressure zone, the improvement which comprises using a butane containing not less than 70 % by weight of isobutane. According to the present invention, the obtained pre-expanded particles are not fused together or adhered to each other, and are not shrinked. Also, since fluoro chloro carbon is not used as the blowing agent, environmental pollutions such that the ozon layer encompassing the earth is destroied by fluoro chloro carbon are not caused at all.</p> |
