Background of the Invention The present invention is drawn to an improved formulation for polypropylene. This improved formulation is useful in the production of surgical sutures and the like. Until now, surgical sutures made of polypropylene have suffered from the drawbacks of: (1) lacking suppleness and softness; (2) being prone to fraying when a surgical knot is slid down the suture; and (3) not maintaining skin slipperiness.

Menezes et al., in U.S. Patent Nos. 4,520,822 and 4,620,542 disclose surgical monofilament sutures. The sutures are said to possess improved compliance, compared with polypropylene homopolymer sutures. However, these sutures suffer from the above drawbacks. The sutures of the present invention possess superior suppleness, softness, fray resistance, knot retention and skin slipperiness.

Hinsch, in U.S. Patent No. 4,577,264 discloses surgical filaments such as sutures and ligatures made of a blend of polypropylene and linear low density polyethylene. These sutures are not subject to the above drawbacks. However, the present invention overcomes the same drawbacks without the need for a low density polyethylene additive. The present invention attains these superior properties by incorporating a branched chain polyolefin wax, such as a polyethylene wax, into the blend. Additionally, the present invention attains these superior properties with lower concentrations of additive than is taught by the Hinch reference.

Object of the Invention The object of present invention is to provide an improved formulation for polypropylene useful in the production of surgical sutures and the like. It is a further objective of the present invention to provide for a surgical suture material having improved suppleness, softness, fray resistance, knot retention and having improved skin slipperiness.

A further object of the present invention is to provide for an improved additive package to be used in combination with typical extrusion grade polypropylene formulations.

Another object of the invention is to provide for a suture material suitable for use within the human body. As is required in the art, the improved suture material must be suitable for use in surgical material. That is, the material must be approved by the relevant governmental agency(s) regulating materials suitable for use in medical application.

The present invention provides for a polypropylene surgical material comprising extrusion grade polypropylene. The polypropylene is made as is common in the art. For example, as disclosed in the '264 reference. The improvement comprises the addition of a branched chain polyolefin wax, to a typical additive package for polypropylene blend suture material. Typical polypropylene suture material composition additive packages are well known in the art. For example, additive packages as disclosed in any of the cited references.

Detailed Description of the Invention The present invention is an improved material suitable for use as a surgical suture material. The material comprises extrusion grade polypropylene suitable for use as a surgical suture material and the like. These materials are well known in the art. Preferably, the material comprises a polypropylene homopolymer. For example, F-040-A suture grade polypropylene material manufactured by Aristech Chemical Corporation.

The improvement of the present invention comprises the addition of a branched chain polyolefin wax to the polypropylene blend formulation.

Preferably, the olefin wax is a branched chain low molecular weight polyolefin wax such as a branched chain low molecular weight polyethylene wax. For example, AC-617, manufactured by Allied Signal. The was is added in an amount of about 0.1 to 2.0 wt%. Preferably, 0.5 to 0.95 wt%.

The invention is illustrated by the following Example: Example 1 To a set quantity of a 2 melt flow homopolymer reactor powder is blended in: 0.2 wt% of a lubricant such as calcium stearate; 0.2 wt% anti-static agent, 0.4 wt% of a thermal stabilizer, 0.2 wt% of a primary anti-oxidant, and 0.75 wt% AC-617 branched chain low molecular weight polyethylene wax.

Wherein all additive quantities measured +/- 20%. The above composition is extruded into pellet form. The pellets are later extruded into suture filaments.