Patent GB-1284478-A (GB)
Title: An extrusion head for the manufacture of multi-layered blown films from thermoplastic materials
Inventor: SCHIPPERS HEINZ
IPC: B29C48/335
Filed: 1970-06-08
Abstract: 1284478 Extruding multilayer tubular films BARMAG BARMER MASCHINENFABRIK AG 8 June 1970 [19 June 1969] 27599/70 Heading B5A An extrusion head for the manufacture of multi-layered blown films of thermoplastic materials comprises a plurality of concentric annular orifices with first conduits leading to the orifices, wherein an additional ring or annular gap conduit which is designed to be supplied from outside the head is provided for applying a liquid or molten adhesifying intermediate layer to at least one of the tubular films, the ring or annular gap conduit being connected inside the head, in a region where the melt pressure has not yet fallen, to at least one of the first conduits leading to the annular orifices, this connection to at least one of the first conduits being effected over the entire circumference of said conduits. In one embodiment, Fig. 2, thermoplastic melts are supplied to the dies 3 and 4 from pipes 5 and 6 by way of branching points 9 and 10 situated behind one another in an axial direction exactly in the middle of the extrusion head 1, connecting conduits 11, 11<SP>1</SP>, and 12, 12<SP>1</SP>, ring conduits 13 and 14 and annular gap conduits 15 and 16. The ring conduits 13 and 14 help to homogenize the materials and portions of increased internal width 17 and 18 in the conduits 15 and 16 serve to reduce the velocity of flow of the melts to the dies. An additional ring conduit 19, which is supplied with an adhesifying agent from outside the body of the extrusion head through radial duct 22, ring conduit 20 and connecting channels 21, connects with annular conduits 15 via restriction 24 and a zone of increased cross-section 25 which forms a reservoir for the molten or liquid adhesifying agent. The additional ring conduit 19 is partially embedded in a replaceable annular element 26 which may, if desired, be replaced with an element with no ring conduit worked into it to enable multi-layered films without intermediate zones also to be extruded using the same extrusion head. The extrusion head may be heated via sleeves 30 and the dimensions of the zone 33 in the head where the extruded films coalesce may be adjusted by adjusting the size of the gaps 37 and 32 by shifting the parts 35 and 36 of the calibrating device 34 in relation to each other with the aid of, for example, a feeler gauge and tightening screws 43 and 44. The temperature of the calibrating device 34 may be regulated by means of heating or cooling sleeve 42, when used as a cooling sleeve it enables extruded tubular films 31 and 32 to be cooled quite rapidly prior to being blown by gas supplied through conduit 41. Fig. 1 (not shown) shows another embodiment of the invention in which the ring conduit 19 used for supplying adhesifying agents to one surface of the film forming materials is connected by way of an annular gap conduit 23 which opens at an acute angle of about 30 degrees, into the conduit 15 which supplies the die 3 with molten material, this arrangement serving the same purpose as the restriction 24 of Fig. 2.