Method and device for producing at least partially open-celled foam films from styrene polymers
AssigneeReifenhauser GmbH & Co. Maschinenfabrik
InventorsUlrich Berghaus, Stephan Homer, Hubert Jansen
Life of this patent
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Abstract
A method for producing an at least partially open-celled foam foil on a basis of styrene polymers, nucleating agents, surfactants, physical foaming agents and, if required, further additives, such as foreign polymers and auxiliary materials, comprising a twin-screw extruder with identical parallel screws rotating in the same direction, wherein the twin-screw extruder has a length of at least 25 D (D=screw diameter), in particular 30 to 42 D, with a draw-in and plastification zone of a length of 10 to 15 D, and a mixing zone of a length of 3 to 6 D, and a following cooling zone.
Claims25
A method for producing an at least partially open- celled foam foil from styrene polymers, characterized in that a mixture containing
- 0.5 to 3 parts by weight of at least one nucleating agent,
- 0.5 to 3.5 parts per weight of at least one surfactant, and
- 1 to 3 parts per weight of a foreign polymer, which cannot be mixed with polystyrene,
- per 100 parts per weight of styrene polymer, is melted in a twin-screw extruder with screws rotating in the same direction at a temperature of up to 270° C. and
- 2 to 6 wt.-% of at least one physical foaming agent in relation to the amount of styrene polymer employed is injected into the polymer melt at an injection pressure, which lies above the cylinder pressure of the twin-screw extruder at the injection point and is higher than that for dissolving the foaming agent in the polymer, or sufficiently high for making possible a homogeneously distributed, two-phase system of melt/foaming agent, preferably at a pressure between 30 and 160 bar, and the polymer melt is brought to a material temperature between 160 and 180° C. while being homogeneously mixed and prior to moving out of the twin-screw extruder into the nozzle tool with an annular nozzle, and is extruded under a pressure of up to 55 bar out of the nozzle into the atmosphere in the form of a tube, the tube is cooled on the inside and the outside while expanding and is pulled over a cooling and calibration mandrel, and is cut open after it has solidified and is laid flat as the foamed foil.
A device for device for producing an at least partially open-celled foam foil on the basis of styrene polymers, nucleating agents, surfactants, physical foaming agents and, if required, further additives, such as foreign polymers and auxiliary materials, comprising a twin-screw extruder with a draw- in and plastification zone, mixing zone and cooling zone, wherein the styrene polymers with the nucleating agent, surfactant, additives are conducted, if required at least partially as a pre- mix, to the twin-screw extruder and are melted to form a polymer melt, and the physical foaming agent is injected under increased pressure into the polymer melt, the polymer melt already injected with gas is cooled to a temperature suitable for foaming and lying below the melt temperature of the styrene polymer, and thereafter exits into the atmosphere from the nozzle of the twin-screw extruder in the form of a tube while expanding, the tube is cooled and cut open in the longitudinal direction and laid flat as the foamed foil, characterized in that as the extruder for melting the polymer, mixing the polymer melt with the physical foaming agent and cooling the expandable polymer melt obtained in this manner, a twin-screw extruder of a length of at least 25 D, in particular 30 to 42 D and having identical parallel screws rotating in the same direction is provided, and the physical foaming agent can be introduced into the melted polymer by the conveying device at a sufficient pressure at the end of the draw-in and plastification zone of an approximate length of 10 to 15 D of the twin-screw extruder and can be mixed with the molten polymer in the mixing zone of a length corresponding to 3 to 6 D of the twin-screw extruder adjoining the draw-in and plastification zone to form an expandable polymer melt.
Dependencies are inferred from the claim text.