Abstract: An annular co-extrusion die for extruding multi-layer tubular plastic film has inner die members stacked one upon another and having radially outwardly extending surfaces forming radially outwardly extending helical passages between respective pairs of inner die members. An annular outer die member surrounds the stacked inner die members and forms a longitudinally extending annular passage therebetween for conveying plastic material from the radially outwardly extending helical passages to an annular extrusion orifice. A lower inner die member has a first feed passage extending from a lower surface thereof to a substantially horizontal upper surface thereof at a position spaced from a central longitudinal axis of the longitudinally extending annular passage, the substantially horizontal upper surface having a first groove extending from the upper end of the first feed passage to the longitudinal axis.

Abstract: An extrusion die for extruding plastic material as a tubular film has mututally engaging first and second body members which form an annular extrusion orifice therebetween. One of the body members has main feed grooves in a surface thereof adjacent the other body member and extending in a spiral manner relative to the annular extrusion orifice, and one of the body members has supply grooves in a surface thereof adjacent the other body member for receiving plastic material from one or more extruders. Each supply groove has an end portion adjacent but spaced from an initial portion of a main feed groove, whereby plastic material from the extruder or extruders is received by the supply grooves and forced from the end portions thereof along a passage between the body members and into the initial portions of the spiral feed grooves.

Abstract: An extrusion die for extruding plastic material as a tubular film has mututally engaging first and second body members which form an annular extrusion orifice therebetween. One of the body members has main feed grooves in a surface thereof adjacent the other body member and extending in a spiral manner relative to the annular extrusion orifice, and one of the body members has supply grooves in a surface thereof adjacent the other body member for receiving plastic material from one or more extruders. Each supply groove has an end portion adjacent but spaced from an initial portion of a main feed groove, whereby plastic material from the extruder or extruders is received by the supply grooves and forced from the end portions thereof along a passage between the body members and into the initial portions of the spiral feed grooves.

Abstract: A method of extruding plastic material in multi-layer form includes: providing an extrusion die having a first body member and a second body member surrounding the first body member and forming an annular passage therebetween which communicates with an annular extrusion orifice, the body members having a series of helical grooves extending around the die and each commencing at a separate location, the separate locations being spaced around a lower portion of the first body member. A single encapsulating unit provides a flow of encapsulated plastic material comprising a first plastic material surrounded by a second plastic material at an outlet thereof. The first body member having a series of cross-holes extending from the encapsulating unit output and each communicating with a respective separate location.

Abstract: An apparatus for extruding plastic materials in multilayer tubular form includes an annular extrusion die having an annular extrusion orifice and annular passage for conveying plastic material to the extrusion orifice, the die also having at least one arcuate passage extending at least partly around the annular passage such that the arcuate passage completely surrounds, or where there is more than one arcuate passage in combination completely surround, the annular passage inwardly or outwardly thereof and is or are in communication therewith. A melt stream of plastic material is encapsulated with a different plastic material in a circumferentially continuous manner to produce an encapsulated melt stream, and at least a portion of the encapsulated melt stream is fed to an arcuate passage to cause at least partially encapsulated plastic material to pass into the annular passage with subsequent extrusion in multilayer tubular form from the annular die orifice.

Abstract: An annular co-extrusion die for extruding multi-layer tubular plastic film has a lower part and an upper part. The lower part has concentric radially spaced lower die members of different diameters forming at least two lower concentric radially spaced annular passages communicating with a common annular passage for separately feeding different plastic materials along the lower annular passages to the common annular passage for extrusion therefrom. The upper part has upper annular die members located above the lower die members and stacked one upon another. The upper annular die members forms at least one upper annular passage for separately feeding different plastic materials along each upper annular passage to the common annular passage for extrusion therefrom with the plastic materials from the lower annular passages as a multi-layer tubular plastic film.

Abstract: An annular co-extrusion die for extruding multi-layer tubular plastic film has inner die members stacked one upon another. The inner die members have radially outwardly extending surfaces forming radially outwardly extending helical passages between respective pairs of die members. An annular outer die member surrounds the stacked inner die members and forms a longitudinally extending annular passage therebetween for conveying plastic material from the radially outwardly extending helical passages to an annular extrusion orifice. Each inner die member forms with an adjacent die member a first feed passage extending at least partly around the inner die member radially inwardly of the helical passages, the inner die member and the adjacent die member having a circumferentially extending clearance therebetween to enable plastic material fed into the first feed passage to pass through the clearance into the helical passages.