Berstorff supplies butyl extruder to Carlisle Hardcast

Weesp, Netherlands - Carlisle Hardcast Europe BV located in the Dutch city of Weesp is the only company in Europe to apply a continuous process on a co-rotating twin-screw extruder for the production of hot melt adhesives used for high-quality sealing tapes. The company needs to apply butyl rubber to the tape, but dislikes the batch-wise mixing process.

"The time involved is a major disadvantage of batch processes" explains Theo Steenvoorden, managing director of Carlisle and gives an example: "While the batchwise production of 1000 kg of butyl rubber takes between six and eight hours, the same quantity can be produced on our new Berstorff extrusion line in only one hour."

Carlisle's product range comprises single-sided and double-sided sealing tapes with different supporting materials ranging from aluminium, paper, nonwoven up to polyester and EPDM. "Thanks to our wide variety of products and our in- house conversion division, we are in a position to satisfy almost all customer requirements. As a matter of course, we also sell semi-finished products that can be further processed by our customers", explains Steenvoorden. "As compared to bitumen, butyl rubber presents the advantage of being free from solvents and thus offers lower environmental impact combined with outstanding durability."

The butyl rubber bale is first led on a conveyor belt into a granulator where it is cut into a sort of granules and before it is covered with a release agent in a mixer. After this first preparatory step, the butyl rubber is conveyed together with various additional formulation components by a pneumatic conveying system and a gravimetric metering unit into the ZE 90 UTX twin-screw extruder

The "sticky melt" is applied on the laminate to be coated by the wide slot die after having passed the gear pump and the screen changer. The semi-finished product is produced on the subsequently arranged coating line, composed of let-off station, laminating unit, cooling section and winder, and processed to the desired final product by means of slitters and appropriate conversion equipment.