GB1144089A - An extrusion adaptor - Google Patents

Abstract

1,144,089. Extrusion adapters; extruding multilayer sheets. DOW CHEMICAL CO. 9 June, 1967, No. 26787/67. Headings B5A and B5B. In an extrusion adapter 10, used in the production of multi-layer films or sheets, a housing 11 defines a central passageway 13 having an inlet end 15 communicating with a polymer source, and an outlet 14 connected to a sheeting die (not shown). The housing also defines at least one annular plenum 57, the plenum being supplied with a second polymer through passageway 59, and being connected to the central passage by annular passageway 58; at least one bushing 61 disposed within the central passageway and having an orifice 66 of elongate cross-sectional configuration in a plane normal to the axis of the central passage, the elongate end being disposed between the annular passageway and the discharge end of the central passage and the bushing defining a bushing passageway through the said central passage; a restriction means, which may comprise a sleeve 33 of cylindrical configuration adjustably mounted adjacent to the elongate orifice of the bushing, and an adjustment means, which may comprise an annular collar 35 having camming surfaces 36 and 37 which co-operate with screws 22 and 23, to selectively restrict a space 44 between the bushing and the inner wall of the central passage. In operation a polymer is introduced into the central passage and attains an elongate configuration at the orifice 66 of bushing 61, where it is encapsulated by a second polymer introduced from plenum 57 through annular passageway 58, the restricting means selectively restricting the flow of the material forming the outer layer at the location where the two layers are combined and so varying the thickness of the said outer layer, the composite stream then being extruded from the sheeting die. Other restricting and adjusting means mentioned include adjustable pins movably positioned adjacent to the discharge end of the bushing, or the position of the bushing may be altered relative to a conical wall of the central passage. The number of layers in the resultant composite film may be increased by using more than one annular plenum, each plenum being connected to a different polymer source. The housing may comprise a plurality of portions held together in sealing relationship, the annular plenums being defined by means of adjacent body portions.