Ultrahigh molecular weight linear polyethylene processes of manufacture
AssigneeE. I. Du Pont de Nemours and Company
InventorsEdward George Howard, Jr., Allan R. Champion
Life of this patent
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Abstract
Novel ultrahigh molecular weight linear polyethylene (UHMWLPE) in the form of a shaped article, exhibiting a unique combination of properties making the material useful as a bearing surface, in general, but particularly useful as a prosthetic hip joint cup and as other prosthetic shapes for replacement of other joints of the human body. A novel process for preparing this article is also disclosed.
Claims19
A process for preparing an ultrahigh molecular weight linear polyethylene having a molecular weight of at least 800,000, and being substantially free of internal stresses consisting essentially of the following steps:
- (a) forming an article from ultrahigh molecular weight linear polyethylene having a molecular weight of at least 800,000;
- (b) heating the article in a liquid that is inert to the polymer under process conditions to a temperature of 190.degree.-300.degree. C., until the article is molten, then raising the pressure to at least 280 MPa;
- (c) cooling to about 160.degree.-170.degree. C. or lower while maintaining a pressure of at least 280 MPa, the rate of cooling being such that temperature gradients in the article are substantially avoided;
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- (d) cooling to a temperature below about 130.degree. C. and reducing the pressure to about 100 kPa in a manner such that remelting of the article is prevented.
A process for preparing an ultrahigh molecular weight linear polyethylene having a molecular weight of at least 800,000, and being substantially free of internal stresses consisting essentially of the following steps:
- (a) forming an article from ultrahigh molecular weight linear polyethylene having a molecular weight of at least 4,000,000;
- (b) heating the article in a liquid that is inert to the polymer under process conditions to a temperature of 190.degree.-300.degree. C., until the article is molten, then raising the pressure to between 230 MPa and less than 280 MPa;
- (c) cooling to about 160.degree.-170.degree. C. or lower while maintaining a pressure of between 230 MPa and less than 280 MPa, the rate of cooling being such that temperature gradients in the article are substantially avoided;
- and
- (d) cooling to a temperature below about 130.degree. C. and reducing the pressure to about 100 kPa in a manner such that remelting of the article is prevented.
Dependencies are inferred from the claim text.