Production of UHMWPE sheet materials
AssigneeQuadrant Epp AG
InventorsJoseph V. Gregg, Wesley Allen Kohler
Life of this patent
Estimating the term…
Abstract
UHMWPE panels of large width may be ram extruded from a slit die in a stable process, by restraining a panel which exits the die below the crystalline melt temperature against movement away from the die by a back pressure device, so as to exert a back pressure between the back pressure device and the die, the back pressure device preferably constructed of a plurality of differentially adjustable elements so as to be able to compensate for changes in processing characteristics over time. Vertically restraining UHMWPE panels as they further cool also greatly improves product characteristics.
Claims12
A process for forming an UHMWPE panel by ram extrusion, said panel having a width equal to or greater than 0.4 m, the process comprising:
- a) ram extruding UHMWPE through a slit die to provide a UHMWPE panel, the temperature of the panel exiting the slit die being below the crystalline melt temperature of the UHMWPE employed;
- b) restraining movement of the UHMWPE panel away from the die to create a back pressure between the die and a back pressure device, said back pressure device comprising a plurality of back pressure generating elements positioned across the width of the panel, the back pressure generated by at least one element being adjustable relative to the back pressure generated by at least one further element such that back pressure exerted on portions of the panel staggered across the width of the panel is differentially adjustable;
- c) establishing a restraining force between each back pressure generating element and the UHMWPE panel to provide stable extrusion conditions.
A process for altering the die shape of a slit die having a width of 0.6 m or greater during ram extrusion of a panel product, comprising altering the back pressure of said panel following its exit from the slit die, thereby increasing or decreasing the internal pressure inside the die, causing an increase or decrease in distortion of the die.
Dependencies are inferred from the claim text.