Extrusion International 4-2024

29 Extrusion International 4/2024 ber of polymer channels depends on pipe layer struc - ture and can reach up to 5 layers in one single head. The structure is: basic pipe / barrier structure / outer protection layer. Option 2 : standard pipe production + multilayer coat - ing technology The PE basic pipe is produced on a new or existing monolayer pipe extrusion line. The barrier layer is ap- plied via a multilayer cross head located in front of the last spray tank. Option 3 : standard pipe production + aluminium foil coating technology which can be made via wrapping or covering. The PE basic pipe is produced on a new or ex- isting monolayer pipe extrusion line. The Aluminium foil is applied having glue coating on both sides or single side. The glue layer has to be activated by heat up to 180 °C by infrared or high frequency heaters, to get best adhesion to the basic pipe. Finally a cross head has to make the protection layer with PE or PP on top. Due to some major disadvantages of option 1 the pre- ferred system is to work with cross heads for option 2 and 3. Cross head Technology CONEXTRU has a concept of cross heads to cover pro- cess option 2 and 3 within a range from 32 up to 630 mm with different sizes of heads. The concept is based on a 4 layer cross head. For all layers the proven helical spiral melt distribution system is used. For low viscosity materials like EVOH, glue, or PA and low throuput is a special very tiny and small ge- ometry available. For the outer protection layer a con- ventional spiral geometry for high throuput, also used in standard heads, suitable for PP and PE is installed. In case of using a polymer as barrier material the cross head version with 4 distributors is used. In case of using aluminium foil the number of layers are depending on the type of Aluminium foil. For Aluminium foils with double side coated glue lay- er, only the outer distributor needed. I this case 3 spiral distributor blocks are replaced against one block with- out melt distributor – just a simple blind block. In case the Aluminium foil has a single side coating with glue – than the block without distributors is re- placed by another block having one melt distributor for the glue. Than the cross head is in a 2 layer version. In this version the Aluminium foil has the glue coating on a side to generate bonding to the basic PE pipe. The adhesive layer for bonding the aluminium to the outer layer is generated in the head. The change from 1 layer to 2 layer or 4 layer can be done easy without dismantling the whole head. The ex- change of blind block or block with distributors is done from backside of the head. Due to this special engineer- ing design the cross head is flexible and can be used as cross head for barrier pipes with polymers as well as with aluminium or even as a simple one layer cross head for applying a PP protection layer. A side channel compressor is foreseen to generate the vacuum. The vacuum is PLC controlled by the speed of the motor of the small compressor. The die and mandrel change can be done from front side which make work easy in handling in case of dimen- sion change. A special tool is part of delivery to make the horizontal mandrel change easy and simple. CONEXTRU GmbH Klosterstr. 19, 3011 Irenental, Austria Josef Dobrowsky, Dobrowsky.j@conextru.eu www.conextru.eu Backside of the cross head with temperature resistant sealing for vacuum Side view of : PO 4 400 CR with control box to operate motorised turning as well PLC control via FC and motor speed of the blower. Melt inlet main layer outside and the melt inlet of other 3 layers at 0 / 45 degree and 90 degree from top