| 摘要 |
<p>A process for producing pre-expanded particles of a thermoplastic resin, wherein said particles are of a polyolefin obtained by polymerizing an olefin in the presence of a Ziegler-Natta catalyst, and contain not more than 1% by weight of particles of diameter up to 105 mu m and having a particle size distribution represented by: R(Dp) = 100exp[-(Dp/De)<n>] where Dp is300 or more and represents a particle diameter ( mu m); R(Dp) represents a cumulative weight percentage; De represents an absolute size constant that is a particle diameter ( mu m) corresponding to R(Dp) 36.8% by weight; and n is 25 or more and is a distribution constant. The process can be carried out by dispersing the particles in a liquid medium (e.g. water) containing a blowing agent (e.g. an aliphatic hydrocarbon) and a phenolic antioxidant, heating to above the softening point of the polymer, and releasing the dispersion into a zone of lower pressure. Pre-expanded polyolefin particles free from scatters of cell diameter or particle diameter and having a high expansion ratio are obtained, which can be put into a mold for expansion molding to easily provide a uniformly expanded article.</p> |
