Although the market trend for the production of embossed back sheet for disposable nappies (diapers) favours the cast process based on single, three or five-layer coex technology, a certain amount of film is still produced by bubble coex lines up to three layers for particular purposes. Dolci Extrusion has recently supplied both cast and bubble coex lines to two destinations.
The cast installation is producing three layer embossed films using three extruders in widths ranging from 1,600-2,100mm. The most common thickness patterns are 30 – 40 – 30 per cent, 20 – 50 – 20 per cent or 30 – 30 – 30 per cent.
The automatic die, supplied by EDI, includes an internal deckling device to modify the web width and a three-layer feed block adjustable by restriction bars for equalizing the speed of each polymer flowing into the die.
The design of the extrusion screws provides for better melt uniformity by improving the melting and mixing efficiency of different polymers. The chilling station is composed of a sequence of three refrigerated rolls. The rubber lined lay-on roll is also cooled by direct water immersion. The embossing surface of the first chill roll is achieved by laser etching according to a particular sinusoidal pattern. This increases the silk-like appearance of the web. A fully automatic and reversible contact winder can wind the embossed side of the web inside or outside the roll. Tension control is achieved by loadcells and can be adjusted for constant or taper tension, and up to seven blades can be applied on top of a slitting bar to produce up to eight rolls. The powerful supervising computer can memorize all the production parameters for repeat production.
In the blown, three-layer, coex line each extrusion feeding system is suitable for mixtures of up to eight different polymers, says Dolci. The haul-off station has large diameter rolls that can laminate the lay-flat tube as a single sheet.
The design includes only one embossing station, with two heating systems – heated rolls and infra red radiation. Line speed can be up to 100m/min, claims the company, and the single station contact winder offers a multiple slit reel system, reel change without adhesive tape and robotized automatic reel unloading and shaft loading.
Tel: +39 02 2529621
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