Method for producing microcellular foamed plastic material with smooth integral skin

摘要

The present invention is directed to the continuous production of microcellular plastic web material having integral unmodified laminar skin. In accordance with the invention a web of plastic material impregnated with an inert gas is delivered continuously to a degassing device in which the degree to which gas diffuses out of the surfaces of the web can be selectively and continuously controlled, whereupon the web enters a foaming station where it is reheated to induce foaming. The temperature of the reheated web and the duration of the foaming process prior to quenching are also selectively controllable to produce the desired web characteristics. The gas-impregnated plastic web can be produced initially by any of several novel means including a continuous device for impregnating a previously formed web and several versions of die devices which operate either by rapidly quenching the extruded gas- impregnated plastic material before any significant foaming has occurred or by maintaining the material above its foaming pressure within the die until the material has cooled to below the temperature at which foaming occurs.