Pressure restricting means for a liquid outlet of an extruder

In an apparatus, wherein volatile liquid-containing plastic material is mixed and worked and said volatile liquid is separated therefrom, said plastic material being substantially insoluble in said volatile liquid, said apparatus comprising an elongated barrel, feed means including a worm rotatable within said barrel and having flights constructed and arranged for mixing, working, heating and conveying said mixture and separating said liquid therefrom, upstream restrictor means connected to and rotating with said worm means, downstream restrictor means connected to and rotating with said worm means at a location spaced downstream of said upstream restrictor means for providing a high pressure region in the mixture between said upstream restrictor means and said downstream restrictor means, said liquid having the property of volatilizing at the temperature at which said material is treated, but having the property of remaining in the liquid state at said temperature and pressure existing in said high pressure region, means associated with said worm means for forming a feed section spaced upstream from said high pressure region, inlet means for said liquid-containing material in said region of lower pressure upstream of said high pressure region, a high pressure liquid outlet extending from the inside to the outside of said barrel located in said high pressure region for removing from said barrel a significant portion of said liquid separated under said high pressure from said mixture, conveying means associated with said worm means and positioned downstream of said high pressure region for conveying said mixture, and pressure restricting means connected to said liquid outlet for maintaining said separated liquid removed from said high pressure region at a pressure lower than that in said high pressure region but sufficiently high to prevent vaporization of said liquid in said barrel, and for removing said separated liquid from said barrel while in the liquid state.