WO1999064080A1

WO1999064080A1 - Yarns and wound dressings containing the same

Info

Publication number: WO1999064080A1
Application number: PCT/GB1999/001796
Authority: WO
Inventors: Paul John Ferguson; Stephen John Russell
Original assignee: Akzo Nobel Uk Limited; The University Of Leeds
Priority date: 1998-06-08
Filing date: 1999-06-08
Publication date: 1999-12-16
Also published as: AU4278099A; GB9812329D0

Abstract

A yarn comprises a textile yarn core having gel-forming fibre helically and exteriorly disposed therearound. Such yarns are useful in the manufacture of low-adherent wound dressings.

Description

YARNS AND WOUND DRESSINGS CONTAINING THE SAME

Field of the invention

This invention relates to yarns which comprise gel- forming fibre. It also relates to wound dressings which contain such yarns .

The cleansing and debriding of wounds, and the removal of wound exudate, are known to be important to the healing process. Wound dressings of fibres such as cotton and continuous filament viscose rayon, for example in the form of woven or knitted gauzes, have been known for many years. Such dressings chiefly absorb exudate by capillary action. However, dressings of such textile fibres tend to adhere to the healing wound surface, with consequent trauma on removal. This effect may be particularly severe with staple fibres such as cotton.

Background Art

Gel-forming fibres such as alginate fibres and carboxymethylated cellulose fibres are known, and they have been recommended for use in wound dressings. These fibres swell in contact with wound exudate and suchlike aqueous liquors, and dressings of these fibres are accordingly of low adherency. Residual swollen fibres can be removed from wounds by washing. However, the mechanical properties of these fibres are greatly reduced by swelling, making the dressing difficult to handle and to remove in one piece .

WO-A-93/14724 discloses a wound dressing which comprises a core of gel- forming fibre enclosed within a textile fibre sheath. The sheath may comprise a single yarn looped or wound around the core or several yarns looped, braided, twisted or wrapped around the core.

WO-A-95/19795 discloses a wound dressing which^' comprises in sheet form a blend of textile fibre and gel-forming fibre. Such a dressing is said to be non-adherent to wound tissue while being absorbent and relatively inexpensive, to be retainable upon a wound for longer periods of time than conventional cotton gauze, and to create a moist wound environment which may be beneficial to healing. The dressing may be a nonwoven dressing formed of a blend of textile and gel-forming staple fibres, or it may be a woven or knitted dressing formed of yarn spun from such a blend of fibres . With such dressings, there is a risk that short textile fibres may become detached and be left behind when the dressing is removed from a wound, with the possibility of interference with the healing process and other complications.

Liu et al . , in a paper entitled "Experiments on Making Yarn and Woven Fabrics from Alginate Fibre for

Medical Application" published by The Textile Institute as part of the Proceedings of the Yarn & Fibre Science

Conference held at Manchester on 3-4 December 1996, disclose two kinds of alginate-containing yarns. The first kind is a yarn of 100% alginate fibre spun on the cotton or worsted system. The second kind is a fancy yarn of the type known as a gimp yarn, and consists of an alginate sliver (85-90% by weight of the yarn) between continuous filament polyamide core and binder yarns. This gimp yarn was woven into fabrics, and the water absorbencies of these fabrics were measured.

Disclosure of the invention

According to the invention, there is provided a yarn which comprises a textile yarn core having gel-forming fibre helically and exteriorly disposed therearound.

The yarn may consist solely of the textile yarn and the gel-forming fibre.

The textile yarn which forms the core of the yarn of the invention may be composed of a natural textile fibre, such as cotton, or of a manmade textile fibre such as viscose rayon, lyocell, acetate, polyester, polyamide or polypropylene. The textile yarn may be a spun yarn or, preferably, a continuous filament yarn. When the core is of continuous filament yarn, the risk of textile fibre being left behind upon removal of a dressing containing such yarn from a wound is minimal.

Examples of gel-forming fibre suitable for use in the yarn of the invention include alginate fibres and carboxymethylated cellulose fibres, of known kinds. The fibre disposed helically around the textile yarn core may consist solely of gel-forming fibre or of a blend of textile fibre and gel-forming fibre. The former alternative is preferred, in order to minimise the risk of textile fibre being left behind upon removal of a dressing from a wound.

The textile yarn and/or the gel-forming fibre may, if desired, be medicated. Manmade fibres which incorporate medicaments are known.

The gel-forming fibre may be a carboxymethylcellulose fibre having a degree of substitution of at least 0.1 carboxymethyl group per glucose unit, the fibre being derived from solvent-spun cellulose fibre and having an absorbency of at least 8 grams 0.9% saline solution measured by the free-swell method and having a tenacity of at least 10 cN/tex. Such fibres are disclosed in W093/12275, to which reference may be made for further details .

A variety of constructions is envisaged for the yarn of the invention. In general, these constructions fall within the field of fancy yarns, of known type as regards yarns consisting solely of textile fibre. In one embodiment of the invention, the yarn is a spiral yarn made by doubling (folding) the textile yarn and a yarn which comprises the gel-forming fibre, the former being fed to the doubling head at slower speed than the latter. The yarn which comprises the gel-forming fibre may be a continuous filament yarn or a spun yarn. In another embodiment, the speed difference of the two yarns fed to the doubling head is greater, thereby forming a gimp yarn. In a further embodiment, the yarn of the invention may be a friction-spun yarn made using the method and apparatus described below under the heading "Friction Spinning Method and Apparatus", wherein a filament or spun yarn of textile fibres is introduced between deposition rollers together with gel-forming staple fibres to yield a yarn having a textile fibre core helically overwrapped with gel-forming fibre.

The yarn construction of the invention, in which the gel-forming fibre is exposed at the outside of the yarn, has the advantage that the possibility of contact between the textile fibre and a wound, with the accompanying risk of adherence, is minimised. Furthermore, gel-forming fibres are relatively expensive in comparison with textile fibres, and they are used most efficiently when exposed at the yarn and dressing surface.

The textile yarn core confers mechanical integrity on the yarn of the invention even after exposure to liquors such as wound exudate .

The invention further provides a wound dressing which contains or consists of yarn of the invention. Such a dressing may take the form of a fabric, of woven or knitted construction. It may consist solely of the yarn of the invention, or it may contain for example a proportion of continuous filament viscose rayon yarn. Such a fabric may be used alone (as a single or multiple ply) , or as a wound contact layer in a composite dressing. The wound dressings of the invention exhibit low adherent properties .

Friction Spinning Method and Apparatus Friction-spun yarns may be made by the friction spinning method and apparatus described in unpublished British Patent Application 9806622.8 entitled "Friction Spinning Machine" filed on 30th March 1998 in the name of The University of Leeds. No claim is made herein to any method or apparatus as described below or as illustrated in Figure 1 (a) or (b) of the accompanying drawing, which description and illustration are derived from British Patent Application 9806622.8 by permission of The University of Leeds.

The invention of GB 9806622.8 concerns a novel friction spinning machine suited to the production of single component and bi-component yarn structures from all fibre types, including technical fibres in particular, alginate and other superabsorbent fibres designed for application in medical woven and knitted wound dressing structures . The novel feature of the spinning approach concerns the manner in which fibres are deposited from an air-stream and assembled into the form of a yarn.

In the new machine, the fibre deposition or landing is carried out as a discrete operation and takes place separately to yarn twisting (whereas in conventional friction spinning the two operations take place simultaneously) . Operation of the new friction spinning concept is illustrated in Figure 1 (b) of the accompanying drawing as compared to the previously known concept which is illustrated in Figure 1 (a) of the accompanying drawing. Referring to the drawing, fibres 10 separated by a pinned or toothed roller 11 are transported to the surface of a perforated deposition roller 12 through an air-flow duct 13. In contrast to conventional friction spinning systems (current art - Figure 1 (a) ) , the fibre landing zone in Fig 1 (b) is located behind the central axis of the deposition rollers and in front of the roller nip between the perforated roller 12 and a non-perforated roller 14, whose position is shown by dotted lines - offset in Fig 1 (b) as shown in the drawing. A ribbon of fibres 15 is formed behind the nip in Fig 1 (b) and held on the surface of the perforated deposition roller 12 by means of suction. Rotation of the deposition rollers 12, 14 of Fig 1 (b) causes the continuously forming ribbon 15 to pass between the nip of the two deposition rollers 12, 14. A pair of twisting rollers 17 is mounted perpendicular to the roller nip, and a yarn is formed as the twist runs up into the roller nip to roll the emerging fibre ribbon 15 into a yarn 16. Means (not shown) are also provided to allow the introduction of one or more filament or pre-formed yarns to allow the production of bi-component structures .

Claims

1. A yarn which comprises a textile yarn core having gel-forming fibre helically and exteriorly disposed therearound.

2. A yarn according to claim 1, characterised in that the textile yarn core is a continuous filament yarn.

3. A yarn according to either claim 1 or claim 2 , characterised in that the gel-forming fibre is an alginate fibre .

4. A yarn according to either claim 1 or claim 2, characterised in that the gel-forming fibre is a carbcxymethylated cellulose fibre.

5. A yarn according to claim 4, characterised in that the gel-forming fibre is carboxymethylcellulose fibre having a degree of substitution of at least 0.1 carboxymethyl group per glucose unit, the fibre being derived from solvent-spun cellulose fibre and having an absorbency of at least 8 grams 0.9% (by weight) saline solution measured by the free-swell method and having a tenacity of at least 10 cN/tex.

6. A yarn according to any one of the preceding claims, characterised in that it is a spiral yarn.

7. A yarn according to any one of claims 1 to 5, characterised in that it is a gimp yarn.

8. A yarn according to any of claims 1 to 5, characterised in that it is a friction-spun yarn.

9. A wound dressing, characterised in that it contains or consists of a yarn according to any one of the preceding claims .

10. A wound dressing according to claim 9, characterised in that it is in the form of a woven or knitted fabric.