Method for making ultra high molecular weight polyethylene
AssigneeBiomet Manufacturing, LLC
InventorsJordan H. Freedman, David W. Schroeder
Life of this patent
Estimating the term…
Abstract
Heat treating UHMWPE by applying pressure with radial constraint at suitable times during a heating protocol reduces or eliminates cavitation, which is otherwise observed to occur when the UHMWPE is heated to a temperature above 300° C. Heat treated UHMWPE can undergo subsequent processing involving crosslinking, deformation, doping with antioxidant, and homogenizing or annealing. Heating during these steps can be carried out even above the onset melt temperature of the UHMWPE without loss of physical properties.
Claims28
A method comprising:
- inserting a consolidated UHMWPE, in the form of a cylindrical bar of diameter from 2 inches to 4 inches, into a rigid sleeve, wherein the sleeve has a diameter greater than that of the UHMWPE bar, and wherein upon insertion, an inner wall of the sleeve contacts some but not all of the UHMWPE bar,
- heating the UHMWPE in the sleeve to a temperature of 330° C. or higher, wherein the sleeve is dimensioned so that the heated UHMWPE thermally expands and contacts the entire inner wall of the sleeve during the heating so that the sleeve provides radial pressure to the heated UHMWPE and simultaneously leaves a longitudinal direction of the heated UHMWPE unconstrained,
- cooling the heated UHMWPE, to provide a UHMWPE product, wherein during the cooling, the temperature of the UHMWPE is lowered to such an extent that the UHMWPE shrinks and loses contact with the inner wall of the sleeve, so that it can be removed from the sleeve, and
- removing the UHMWPE from the sleeve,
- wherein the UHMWPE product has less cavitation than a UHMWPE product made by a corresponding method free of the radial pressure.
A process for reducing or eliminating cavitation in a heat-treated UHMWPE product, the method comprising:
- heating a consolidated UHMWPE at a temperature of 330° C. or higher while applying transverse pressure on the UHMWPE and simultaneously leaving an axial direction of the UHMWPE unconstrained, to provide the heat-treated UHMWPE product;
- wherein the heat-treated UHMWPE product has less cavitation than a heat-treated UHMWPE product made by a corresponding method free of the transverse pressure.
A method of producing wear resistant UHMWPE for use in bearing components of medical implants, comprising:
- heat treating a consolidated UHMWPE by heating to 330° C. or higher while applying radial pressure and simultaneously leaving a longitudinal direction of the consolidated UHMWPE unconstrained, to form a UHMWPE product, wherein the UHMWPE product has less cavitation than a UHMWPE product made by a corresponding heat treatment free of the radial pressure;
- crosslinking the UHMWPE product;
- and
- subjecting the crosslinked UHMWPE to heating below its melting temperature or above its melting temperature, to provide the wear resistant UHMWPE.
A method of making an oxidation resistant UHMWPE for use in making a bearing component for a medical implant, the method comprising:
- heat treating a consolidated UHMWPE by heating to 330° C. or higher while applying radial pressure and simultaneously leaving a longitudinal direction of the consolidated UHMWPE unconstrained, to form a UHMWPE product, wherein the UHMWPE product has less cavitation than a UHMWPE product made by a corresponding heat treatment free of the radial pressure;
- doping the UHMWPE product with an antioxidant;
- and
- homogenizing the doped UHMWPE by heating above room temperature, to provide the oxidation resistant UHMWPE.
A method of processing UHMWPE for subsequent use in an artificial joint bearing component, comprising:
- heat treating a consolidated UHMWPE by heating to 330° C. or higher while applying radial pressure and simultaneously leaving a longitudinal direction of the consolidated UHMWPE unconstrained, to form a UHMWPE product, wherein the UHMWPE product has less cavitation than a UHMWPE product made by a corresponding heat treatment free of the radial pressure;
- crosslinking the UHMWPE product;
- and
- mechanically deforming the crosslinked UHMWPE to reduce the concentration of free radicals resulting from the crosslinking, to provide the UHMWPE for subsequent use in the artificial joint bearing component.
Dependencies are inferred from the claim text.