# US 2014/0194935 A1 · Antioxidant stabilized crosslinked ultra-high molecular weight polyethylene for medical device applications

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- Number: US 2014/0194935 A1
- Document ID: US20140194935A1
- Status: Published application
- Kind: A1
- Application number: 14/157,708
- Filed: 2014-01-17
- Published: 2014-07-10
- Earliest claimed: 2007-04-10
- Assignees: Zimmer, Inc.
- Applicants: Zimmer, Inc.
- Inventors: Alicia Rufner; John Knight; Toni Rowe; Dirk Pletcher; Ray Gsell; Hallie E. Brinkerhuff; Werner Schneider
- Web page: https://patentgrep.com/patent/US20140194935A1

## CPC

- C08K 5/1545: Six-membered rings
- A61B 17/8085: {with pliable or malleable elements or having a mesh-like structure, e.g. small strips (A61B17/8071, A61B17/8076 take precedence)}
- A61L 27/16: obtained by reactions only involving carbon-to-carbon unsaturated bonds
- A61L 27/505: {Stabilizers}
- A61L 31/048: {obtained by reactions only involving carbon-to-carbon unsaturated bonds (A61L31/041 takes precedence)}
- A61L 31/143: {Stabilizers}
- C08J 3/24: Crosslinking, e.g. vulcanising, of macromolecules (mechanical aspects B29C35/00; crosslinking agents C08K)
- C08J 3/28: Treatment by wave energy or particle radiation
- C08J 2323/26: modified by chemical after-treatment
- C08L 23/06: Polyethylene
- C08L 2312/06: by radiation
- Y10T 428/31: Surface property or characteristic of web, sheet or block
- Y10T 428/315: Surface modified glass [e.g., tempered, strengthened, etc.]
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An antioxidant combined with UHMWPE prior to subjecting the UHMWPE to crosslinking irradiation. In one exemplary embodiment, the antioxidant is tocopherol. After the antioxidant is combined with the UHMWPE, the resulting blend may be formed into slabs, bar stock, and/or incorporated into a substrate, such as a metal, for example. The resulting product may then be subjected to crosslinking irradiation. In one exemplary embodiment, the UHMWPE blend is preheated prior to subjecting the same to crosslinking irradiation. Once irradiated, the UHMWPE blended product may be machined, packaged, and sterilized in accordance with conventional techniques.

## Claims

### Claim 1

(canceled)

### Claim 2

An antioxidant-stabilized crosslinked ultra-high molecular weight polyethylene, comprising:
crosslinked polyethylene comprising tocopherol or a salt or ester thereof that has reacted a free-radical on the polyethylene; and
remaining tocopherol, or a salt or ester thereof.

### Claim 3 (depends on 2)

The antioxidant-stabilized crosslinked ultra-high molecular weight polyethylene of claim 2, wherein the crosslinked polyethylene comprises a repeating unit having Structure A
wherein
A1, A2, and A4 are at each occurrence independently selected from the group consisting of —H, a carbon atom from a repeating unit of a polyethylene, a crosslink to a polyethylene, and -T,
in at least one repeating unit of the polyethylene having Structure A at least one of A1, A3, and A4 is -T, and -T is
wherein R1 and R2 are independently selected from the group consisting of —H and methyl; and
wherein the remaining tocopherol has the structure T-H.

### Claim 4 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the tocopherol ester is tocopherol acetate.

### Claim 5 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the remaining tocopherol ester is tocopherol acetate.

### Claim 6 (depends on 3)

The antioxidant-stabilized crosslinked polyethylene of claim 3, wherein R1 and R2 are methyl.

### Claim 7 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the tocopherol that has reacted with the free radical is d,1-α-tocopherol or an acetate ester thereof.

### Claim 8 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the remaining tocopherol is d,1-α-tocopherol.

### Claim 9 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the remaining tocopherol or salt or ester thereof is contained within the crosslinked polyethylene.

### Claim 10 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the tocopherol or salt or ester thereof that has reacted with the free radical is homogenously distributed within the crosslinked polyethylene.

### Claim 11 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the remaining tocopherol or salt or ester thereof has antioxidant activity.

### Claim 12 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein about 0.011 wt % to about 0.882 wt % of the crosslinked polyethylene is the tocopherol or salt or ester thereof that has reacted with the free radical and the remaining tocopherol or salt or ester thereof.

### Claim 13 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein about 0.016 wt % to about 0.575 wt % of the crosslinked polyethylene is the tocopherol or salt or ester thereof that has reacted with the free radical.

### Claim 14 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein about 0.001 wt % to about 0.592 wt % of the crosslinked polyethylene is the remaining tocopherol or salt or ester thereof.

### Claim 15 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein he crosslinking comprises irradiation.

### Claim 16 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the crosslinking comprises electron beam irradiation or gamma irradiation.

### Claim 17 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the antioxidant-stabilized crosslinked polyethylene has a pin-on-disc wear rate of less than about 2.75 mg/Mc.

### Claim 18 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the antioxidant-stabilized crosslinked polyethylene has a pin-on-disc wear rate of about 0.02 mg/Mc to about 0.58 mg/Mc.

### Claim 19 (depends on 2)

The antioxidant-stabilized crosslinked polyethylene of claim 2, wherein the antioxidant-stabilized crosslinked polyethylene is molded into at least one of a substrate, a polymeric article, and an antioxidant-stabilized polymeric article.

### Claim 20 (depends on 2)

An orthopedic implant comprising the antioxidant-stabilized crosslinked polyethylene of claim 2.

### Claim 21

An antioxidant-stabilized crosslinked ultra-high molecular weight polyethylene, comprising:
polyethylene comprising tocopherol or a salt or ester thereof that has reacted with a free-radical on the polyethylene, wherein the polyethylene comprises a repeating unit having Structure A
wherein
A1, A2, A3, and A4 are independently selected from the group consisting of —H, a carbon atom from a repeating unit of a polyethylene, a crosslink to a polyethylene, and -T,
in at least one repeating unit of the polyethylene having Structure A at least one of A1, A2, A3, and A4 is -T, and -T is
wherein R1 and R2 are independently selected from the group consisting of —H and methyl; and
remaining tocopherol having the structure T-H, or a salt or ester thereof;
wherein the antioxidant-stabilized crosslinked polyethylene has a pin-on-disc wear rate of about 0.02 mg/Mc to about 0.58 mg/Mc.