| 摘要 |
A process is proposed for producing polyethylene terephthalate (PET) pellets, in which a PET melt is mixed and extruded with a blowing agent or blowing agent mixture and optionally additives. The process is characterized in that the mixture is supplied via the extruder to an underwater pelletizer comprising a water bath and pelletized, the operating parameters being selected such that the PET after the pelletization is amorphous and has foamed only slightly, if at all. As a result, foamable pellets are obtained, which consist of amorphous unfoamed or barely foamed PET pellets permeated with a blowing agent or a blowing agent mixture. The unfoamed or barely foamed PET pellets are advantageous for further processing. For instance, it is possible to use them to produce mouldings with high isotropy in relation to density and structure, more particularly with avoidance of interstitial spaces. In the case of spatial separation of pellet production and further processing, the low volume of the pellets in particular is advantageous for transport and storage. |
