Abstract: In the production of foamed plastic articles using a screw extruder, it is known to introduce a gaseous foaming agent into the plastic while the latter is passing through the extruder. It has been found that a foamed thermoplastic with pores or cells of uniform size and distribution can be produced by passing a gaseous foaming agent, e.g. nitrogen gas through a central passage extending substantially the entire length of the extruder screw, discharging the agent into the thermoplastic proximate the discharge end of the extruder, and mixing the foaming agent with the plastic immediately prior to discharge of the mixture into a mold.

Abstract: In general, used thermoplastic liquid containers such as oil and solvent bottles are discarded. When recycling oil bottles, the usual practice is to wash the bottles with a solvent to remove oil therefrom. Washing of the bottles results in large quantities of used, oil-containing solvent, which present a disposal problem. A simple solution to the problem of recycling liquid containers with no preliminary washing or cleaning operation includes the steps of tumbling the bottles to promote liquid separation, shredding the bottles into small pieces and draining the liquid therefrom, grinding the pieces of plastic to yield a particulate thermoplastic, and mixing the particulate thermoplastic and any liquid remaining therein with an additive, e.g. an oil absorbent and a filler such as calcium carbonate, glass, mica or talc, and when the liquid is an oil, an absorbent to produce an extrudable mixture which can be used to form new containers.

Abstract: When blow molding elongated serpentine tubes or similar articles, loading of the mold cavity with the parison can present a problem. The parison can stick against the wall of the mold cavity. Moreover, a large diameter parison must be used, i.e. the parison must have a diameter equal to the total width dimension of the article, and consequently a large volume of flash is produced. The flash must be trimmed and recycled. In order to avoid these problems, inserts are placed in the mold to define portions of the mold cavity, particulary at corners. Air under pressure is fed into passages in the outer surfaces of the inserts and discharged through small orifices in such inserts against the parison to guide and drive the latter fully into the mold cavity. A vacuum can also be applied to the end of the cavity remote from the parison entry point for drawing the parison into the mold.