Abstract: This invention relates to a method and apparatus for sweeping dust and debris from the needles of a wand which is for applying an electrostatic charge to a plexifilamentary film-fibril web. The needles of the wand tend to acquire dust and debris from the polymer and by the present invention the dust and debris are efficiently swept away by a gaseous fluid flow over the needles preferably so that the fluid passes circumferentially over the needles through an annular passage.

Abstract: A method of improving solvent vapor containment in a process for extruding a solvent-polymer mixture into a process vessel operated substantially at atmospheric pressure while continuously removing solvent vapor and polymer product from said process vessel is disclosed. The improvement involves connecting, by means of a passage, the process vessel with a containment tank, which containment tank is provided at the bottom thereof with means for solvent vapor removal and recovery. The top of the containment tank is provided with an atmospheric vent to ensure that the solvent vapor in the containment tank is at atmospheric pressure. The passage is further provided with a vapor siphon breaker to prevent siphoning of the solvent vapor from the containment tank back into the process vessel.