Direct Extrusion -- A New Challenge for Economical Extrusion Coating, 2003 European PLACE Conference Proceedings

The first processing step in extrusion coating is the melting of the relevant polymers and additives with extruder systems. Single screw extruders have been well established over the last years. However single screw systems are limited in homogenisation capacities and in the ability of adding additives during the melting process or arranging melt degasing tasks.

Precompounded resins including necessary additives have to be used for the achievement of specific product properties . Compounds are produced in a separate process which means extra cost on one hand and on the other hand limiting the flexibility in recipe know how of the manufacturer.

An extrusion cost comparison will prove , that the extrusion of individual components in comparison with the adequate compound will save up to 40% of resin cost. Considering , that resin cost in extrusion share with a 70 to 80% of manufacturing cost , it is obvious , that there is an essential cost saving potential.

The alternative of compound extrusion is laying in the Direct Extrusion of the recipe components as it can be performed with the Reifenhäuser Reitruder system .

This corotating twin screw extruder offers tailored processing steps for the achievement of optimal coating properties. One supposition means microhomogeneity of the extruded melt web coated onto the substrate.This comes true especially for the extrusion of polymer blends which are not compatible and e.g. for highly filled recipes as with calciumcarbonate in a range of up to 70 % or pigments , UV absorbents etc.

The Reitruder fulfills the suppositions for the integration in fully automated coating lines. The design based on modular principle is a further supposition for cotrolling e.g. melt temperature , degree of resin component dispersion and constant melt dosing to the coating die.

Since Direct Extrusion with Reitruder has been proven in the film , sheet and pipe extrusion business a first use in extrusion coating lines was successful. A labline in the Reifenhäuser R&D center has been installed , in order to carry out test runs with customers and to work out processing technics for innovative products. Such service is well accepted especially by those customers who want to produce products for niche markets..