Process for extruding polymer shapes with smooth, unbroken surface
AssigneeSymplastics Limited
InventorsGregory J. Courval, Dermot R. M. Thomas, Steven G. Allen
Life of this patent
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Abstract
A solid state extrusion process extrudes a semi-crystalling polymer billet through a die at the end of a pressure chamber. The temperature of the die is controlled so that a thin surface layer of the polymer profile being extruded is melted to form a thin, smooth surface layer on the profile of reduced orientation and increased toughness and which is substantially free of surface imperfections.
Claims15
A solid state extrusion process in which a semi-crystalline polymer billet in a pressure chamber is forced through a die to form an oriented polymer profile, comprising the steps of:
- preheating the pressure chamber to a temperature below the melting point of the polymer billet;
- preheating the die to a temperature at least as high as the temperature of the pressure chamber;
- extruding the polymer billet through the pressure chamber and die to form an oriented polymer profile oriented in the longitudinal direction;
- and
- controlling the temperature of the die so that a thin surface layer of the oriented polymer profile being extruded is melted to form a thin, smooth surface layer on the oriented polymer profile of reduced orientation in the longitudinal direction and increase toughness.
A solid state extrusion process in which a semi-crystalline polymer billet in a pressure chamber is forced through a die to form an oriented polymer profile, comprising the steps of:
- providing a deforming area in the die for producing an oriented polymer profile with a cross-sectional area greater than 0.5 cm.sup.2 ;
- preheating the pressure chamber to a temperature below the melting point of the polymer billet;
- preheating the die to a temperature at least as high as the temperature of the pressure chamber;
- extruding the polymer billet through the pressure chamber and die at a rate greater than 50 cm/min to form an oriented polymer profile oriented in the longitudinal direction;
- and
- controlling the temperature of the die so that a thin surface layer of the oriented polymer profile being extruded is melted to form a thin, smooth surface layer on the oriented polymer profile of reduced orientation in the longitudinal direction and increase toughness.
Dependencies are inferred from the claim text.