PROCESS FOR PRODUCING A THERMOPLASTIC POLYMERIC FOAM

摘要

A process for the preparation of a CFC-free foam from a thermoplastic, a nucleating agent and a blowing agent in an extruder is described, in which a second gaseous nucleating agent and a liquid blowing agent are sprayed into the plasticised plastic through spray orifices arranged downstream one behind the other. A gaseous nitrogen (N2) is sprayed in as a second nucleating agent in an amount of 0.1 to 0.5% by weight, and an alcohol of the group consisting of ethanol (C2H5OH), propan-2-ol (C3H7OH) and 2-methylpropan-2-ol (C4H9OH) or a mixture of these alcohols in liquid form is sprayed in as the blowing agent in an amount of 0.5 to 5% by weight, based on the weight of the plastic and of the first nucleating agent employed. A foam having a low density and a very uniform cell structure was obtained in a surprising and unexpected manner. ……