Process for removing residual spin solvent from a gel spun filament, the filament, multi-filament yarn and products comprising the filament

Abstract

Processes for removing residual spin solvent from a gel spun, UHMwPE filament having an effective diameter of above 16 μm, comprise the steps of removing residual spin solvent from the filament to a level of below 100 ppm at elevated temperature, while keeping the filament taut. Gel spun UHMwPE filaments having an effective diameter of above 16 μm and a residual spin solvent residue of less than 100 ppm are also provided. Preferably the filament has a creep rate, measured at 50° C., under a load, so that the initial stress is 600 MPa, of less than 5·10−6 sec−1.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of commonly owned U.S. Ser. No. 12 / 593,469, filed Dec. 7, 2009, (now U.S. Pat. No. 9,260,801), which is the national phase application under 35 USC §371 of PCT / EP2008 / 002298, filed Mar. 21, 2008, which designated the U.S. and claims priority to European Application No. 07006238.5, filed Mar. 27, 2007, the entire contents of each of which are hereby incorporated by reference.FIELD[0002]The invention relates to a process for removing residual spin solvent from a gel spun, ultra high molecular weight UHMwPE (UHMwPE) filament, the filament as well as a multi-filament yarn and products for medical applications containing the filament.BACKGROUND AND SUMMARY[0003]A process for producing gel spun, UHMwPE filaments is for example disclosed in PCT / NL2003 / 000872.[0004]It is also known to use gel spun, UHMwPE multi-filament yarn in products for medical applications. Examples of such products are sutures and cables. ...

AI Technical Summary

Benefits of technology

The filaments used in the patent have residual spin solvent, which can affect their properties. To remove the solvent, the filaments can be heated or exposed to extended extraction, but this can negatively affect their strength, smoothness, and resistance to clumping and creeping. This negativity is especially true when using filaments with a high diameter. However, using larger filaments may be advantageous because they are easier to produce and have greater strength and durability.

Problems solved by technology

A gel spun filament however has the draw back that without special treatment it contains residual spin solvent.

Although the level of residual spin solvent normally is very low, it is still high enough to make the filament less suitable for use in medical applications like sutures and cables, since the residual spin solvent may cause unwanted reactions of the human or animal body, like for instance inflammations.

Problems that occur because of such treatments are that filament properties are adversely affected, if a residual spin solvent level of at most 100 ppm is obtained, but even more if very low levels of residual spin solvent are obtained, below 80 ppm or even further down.

This is especially true if filaments with a high diameter are used, since removal of solvents by extraction or evaporation becomes increasingly difficult with increasing diameter.

One of the properties that is adversely affected is the tensile strength of the yarn.

Furthermore the smoothness of the surface of the filament may be adversely affected, so that the coefficient of friction of the filament increases.

This makes it for example more difficult to stitch a wound with a suture comprising the filament.

Also the creep rate of the filament increases.

However the filament has a very low diameter of below 8 μm and no special process step for removing residual spin solvent is disclosed.

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