Synergistic effects on blending multiple additives in UHMWPE

Patent metadata

Field	Value
Publication number	US-9971267-B2
Application number	US-201715420716-A
Country	US
Kind code	B2
Filing date	Jan 31, 2017
Priority date	May 4, 2009
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

Oxidation resistant crosslinked ultrahigh molecular weight polyethylene (UHMWPE) is described, wherein at least two different additives in the manufacture synergistically increase the oxidation resistance of crosslinked UHMWPE. This allows the manufacture of oxidation resistant crosslinked UHMWPE using lower levels of additives and/or lower levels of crosslinking irradiation or chemicals. The lower levels of additives and/or crosslinking produce crosslinked UHMWPE having desired physical properties not possible without the synergistic interaction of the additives. This crosslinked UHMWPE may be used in medical prostheses such as in bearing components having desired physical properties such as wear resistance and oxidation resistance not possible without the synergistic interaction of the additives.

First claim

What is claimed is:

1. A process for preparing crosslinked oxidation resistant UHMWPE for use in medical prostheses comprising the steps of: (i) combining a UHMWPE resin with a first amount of a first additive; (ii) consolidating the UHMWPE that has been combined with the first additive; (iii) crosslinking the consolidated UHMWPE to create combined, consolidated, crosslinked UHMWPE, and (iv) adding a second amount of a second additive to the combined, consolidated, crosslinked UHMWPE to create oxidation resistant UHMWPE, wherein the first and the second additives are different additives, wherein the first and second additives synergistically increase the oxidation resistance of the crosslinked UHMWPE, wherein the amount of the first additive that is combined with the UHMWPE resin in step (i) is about 50 ppm to about 5,000 ppm, and wherein the amount of the second additive that is combined with the combined, consolidated, crosslinked UHMWPE in step (iv) is about 50 ppm to about 5,000 ppm.

2. The process of claim 1 , further comprising the step of machining the oxidation resistant UHMWPE into a bearing component for a medical prosthesis.

3. The process of claim 2 , wherein the crosslink densities of the oxidation resistant and machined UHMWPE bearing component are about 0.03 mol/dm 3 to about 0.50 mol/dm 3 .

4. The process of claim 1 , wherein the first additive is selected from the group consisting of phenolic antioxidants and hindered amines, and wherein the second additive is selected from the group consisting of phosphorous additives, polyhydric alcohols, phenolic antioxidants, hindered amines, carotenoids, amino-acid-based additives, thiosynergists, and acid antioxidants.

5. The process of claim 1 , wherein the crosslinking is selected from the group consisting of irradiation crosslinking and chemical crosslinking.

6. The process of claim 1 , wherein the crosslinking is irradiation crosslinking.

7. The process of claim 6 , wherein the dose of the crosslinking is about 1.5 MRad to about 30 MRad.

8. The process of claim 1 , wherein the first additive is dl-alpha-tocopherol and the second additive is curcumin.

9. A process for preparing crosslinked oxidation resistant UHMWPE for use in medical prostheses comprising the steps of: (i) combining a UHMWPE resin with a first amount of a first additive; (ii) consolidating the UHMWPE that has been combined with the first additive; (iii) crosslinking the consolidated UHMWPE to create combined, consolidated, crosslinked UHMWPE, and (iv) adding a second amount of a second additive to the combined, consolidated, crosslinked UHMWPE to create oxidation resistant UHMWPE, wherein the first additive is dl-alpha-tocopherol and the second additive is curcumin, wherein the first and second additives synergistically increase the oxidation resistance of the crosslinked UHMWPE, wherein the first additive dl-alpha-tocopherol is combined with the UHMWPE resin in step (i) at about 500 ppm, wherein the second additive curcumin is added to the combined, consolidated, crosslinked UHMWPE in step (iv) at about 500 ppm, and wherein the crosslinking in step (iii) is by irradiation at a dose of about 10 MRad.

10. A process for preparing crosslinked oxidation resistant UHMWPE for use in medical prostheses comprising the steps of: (i) combining a UHMWPE resin with a first amount of a first additive; (ii) consolidating the UHMWPE that has been combined with the first additive; (iii) crosslinking the consolidated UHMWPE to create combined, consolidated, crosslinked UHMWPE, and (iv) adding a second amount of a second additive to the combined, consolidated, crosslinked UHMWPE to create oxidation resistant UHMWPE, wherein the first and the second additives are different additives, wherein the first and second additives synergistically increase the oxidation resistance of the crosslinked UHMWPE, and wherein the first additive is dl-alpha-tocopherol and the second additive is dipentaerythritol.

11. The process of claim 10 , wherein the first additive dl-alpha-tocopherol is combined with the UHMWPE resin in step (i) at about 300 ppm, wherein the second additive dipentaerythritol is added to the combined, consolidated, crosslinked UHMWPE in step (iv) at about 300 ppm, and wherein the crosslinking in step (iii) is by irradiation at a dose of about 10 MRad.

12. A process for preparing crosslinked oxidation resistant UHMWPE for use in medical prostheses comprising the steps of: (i) combining a UHMWPE resin with a first amount of a first additive; (ii) consolidating the UHMWPE that has been combined with the first additive; (iii) crosslinking the consolidated UHMWPE to create combined, consolidated, crosslinked UHMWPE, and (iv) adding a second amount of a second additive to the combined, consolidated, crosslinked UHMWPE to create oxidation resistant UHMWPE, wherein the first and the second additives are different additives, wherein the first and second additives synergistically increase the oxidation resistance of the crosslinked UHMWPE, and wherein the first additive is curcumin and the second additive is dipentaerythritol.

13. The process of claim 12 , wherein the first additive curcumin is combined with the UHMWPE resin in step (i) at about 300 ppm, wherein the second additive dipentaerythritol is added to the combined, consolidated, crosslinked UHMWPE in step (iv) at about 300 ppm, and wherein the crosslinking in step (iii) is by irradiation at a dose of about 10 MRad.

14. The process of claim 1 , wherein the crosslinking is chemical crosslinking.

15. The process of claim 1 , further comprising the step of heat treating the consolidated UHMWPE prior to the crosslinking.

Assignees

• Smith & Nephew Inc

Inventors

• Morrison Mark L
• Pawar Vivek D
• Brunner Lorenz
• Jani Shilesh C

Classifications

• A61F2/38

  for elbows or knees · CPC title

• C08K5/053

  Polyhydroxylic alcohols · CPC title

• G03G9/097 Primary

  Plasticisers; Charge controlling agents · CPC title

• A61L27/16 Primary

  obtained by reactions only involving carbon-to-carbon unsaturated bonds · CPC title

• C08F110/02

  Ethene · CPC title