ABSORPTIVE FABRIC

Abstract: A composite fabric comprising a combination of a gel-forming yarn and a reinforcing yarn. A method of making a reinforced absorptive fabric comprising the steps of weaving, knitting or braiding together gel-forming yarn with reinforcing yarn, such that the network of reinforcing yarn provides structural integrity to the fabric independent of the gel-forming yarn. A composite fabric or structure may also comprise a composite yarn in which is incorporated both gel-forming fibre and reinforcing fibre. Gel-forming fabrics or structure may be made by first forming fabrics or structures of gel-forming fibre precursor and then converting the precursor to its gel-forming state.

Description: ABSORPTIVE FABRIC FIELD OF INVENTION The present invention pertains to fabrics that are capable of absorbing a relatively large quantity of a fluid. Certain embodiments of such fabrics are particularly useful for the control of bleeding. BACKGROUND OF INVENTION It is known to use, for various medical and other purposes, fibrous materials, including yarns, which gel when wet and which absorb body fluids. Such materials are used as swabs during surgery, as hemostatic agents and wound dressings. The problem with such materials is that they tend to become weak when wet. Structures formed from these materials tend to break or lose integrity upon absorption of blood or body fluids. Among the materials used for this purpose are collagen, oxidized cellulose, calcium alginate and hemostatic gelatin. Such materials will be referred to generically herein as gel-forming materials and yarns made therefrom as gel-forming yarns. One particular material of this kind is sodium carboxymethylcellulose (CMC), staple fibre forms of which are used in non- woven fabrics that are commonly used in post-trauma and post-surgical situations as wound dressings. CMC gels upon contact with water, blood or body fluids, and swells to absorb such materials. CMC also facilitates blood clotting while absorbing any exude and is, therefore, hemostatic. In addition, it is well known that CMC is hydroscopic so it does not readily dry into clotted blood, and therefore can be removed easily without causing re-bleeding. If it does dry, it can be easily re-gelled by wetting with water or saline solution. A composite structure, incorporating gel-forming fibres and conventional textile fibres, is disclosed in international patent application, WO 98/46818. The materials described in WO 98/46818 as gel-forming fibres are essentially the same as those which are useful, in yarn form, in the present invention. In the structure disclosed in WO 98/46818, the gel-forming fibres are said to be "laid-in" to a knitted fabric. Applicant believes, however, that a knitted structure as disclosed there would, to a significant degree, lose its physical integrity upon gelling of the gel-forming fibres and would not be suitable in an application in which the fabric is stretched when the gel forming fibres are gelled. SUMMARY OF INVENTION The present invention provides a composite knit, woven or braided fabric comprised of a combination of gel-forming yarn and reinforcing yarn, wherein the reinforcing yarn is knit, woven or braided such that the fabric is capable of retaining its structural integrity independent of the gel-forming yarn. In one embodiment of the present invention, the gel-forming yarn is composed of a hemostatic material such as sodium carboxymethylcellulose (CMC). Typically the reinforcing yarn is a thin strong synthetic material, such as nylon. In the knit, woven or braided fabric of this invention, the gel- forming yarn may follow the same yarn path as some or all of the reinforcing yarn courses. The gel-forming yarn may also follow a different path by which it is laid in or interwoven with the reinforcing yarn. In one form of the present invention, the fabric may be made by weaving, knitting or braiding a composite fabric comprised of reinforcing yarn and a gel-forming yam such as oxidized cellulose or CMC. Alternatively, such a fabric may be made by weaving, knitting or braiding, with a reinforcing yarn, a cellulosic yarn, the woven, knit or braided structure being such that the structural integrity of the fabric is dependent on the reinforcing yam only, and then converting the cellulosic yarn therein to oxidized cellulose or sodium carboxymethylcellulose. This conversion process is conventional and requires only that the reinforcing yam be resistant to chemical attack in the conversion process. The cellulosic yam thus converted is in fact gel-forming, highly absorptive and may be hemostatic. In knit form, the resultant fluid absorbing fabric is stretchable, to the degree the reinforcing yarn and/or the structure of the fabric is stretchable. Such a fabric retains its structural integrity even when stretched and when the gel-forming yarn has absorbed water or blood or body fluid and formed a gel therewith. This conversion process may be useful also with unreinforced knitted, woven or braided cellulosic fabric, that is cellulosic fabrics without reinforcing yam, and to non-woven structures comprised of precursors of gel- forming fibres or yarns. Still another form of reinforced gel-forming absorbent fabric, within the scope of this invention, may be made by forming the fabric or other structure with a composite yarn, the yarn itself comprising a composite or combination of gel-forming fibre (or a precursor thereof, convertible as described above) with a reinforcing fibre. Such a composite yarn may comprise a yarn spun from a combination of such fibres or a core spun yarn, wherein the core fibre is a continuous strand of a reinforcing filament, or filaments, made of a material such as nylon. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a diagrammatic view of one knitted embodiment of the present invention. Figure 2 is a diagrammatic view of another knitted embodiment of the present invention. DETAILED DESCRIPTION OF INVENTION The present invention, in one embodiment, comprises a composite fabric, which retains its structural integrity while absorbing a large quantity of fluid, and particularly to such a fabric useful for the control of bleeding. One application for such a fabric is in an expandable hemostatic device for the control of bleeding in body cavities, as disclosed and claimed in a separate patent application of partial common inventorship herewith, U.S. Application Serial No. 09/406/166, filed September 27, 1999. As used herein, the term "hemostatic" refers to a material that retards or prevents bleeding. Some gel-forming materials, such as CMC, are hemostatic. The term "reinforcing" yarn refers to a yarn that has greater tensile strength in a wet phase than a gel-forming yam with which it is combined. The word "yam," as used herein, refers to an indefinite length of material suitable for weaving, knitting or braiding, typically comprised of one or more continuous strands of material or a multiplicity of relatively short length fibres spun into a fibre bundle of indefinite length, or some combination of continuous strands and spun fibres. Gel-forming materials or yarns, of the type generally referred to herein, typically soften to form a gel or partially dissolve when brought into contact with a suitable liquid such as blood. Such a material absorbs liquid and will absorb many times its own weight. Certain gel-forming materials are referred to as hemostatic because they tend to cause blood to clot while absorbing any exudate. Hemostatic, gel-forming materials, such as CMC, are particularly useful for medical purposes wherein the absorption of body fluids is important. Such materials are also used during surgery, or other medical procedures, as hemostatic agents and wound dressings. The composite fabric of the present invention comprises a reinforcing yarn woven, knitted or braided with a gel-forming yarn. Typically, the reinforcing yarn is a relatively strong synthetic material, with which the gel- forming yarn is placed side by side during the weaving, knitting or braiding of the gel-forming and reinforcing yams into a woven, knitted or braided fabric. Alternatively, all or less than all of the yam courses of the reinforcing yarn may be accompanied by gel-forming yarn. Alternatively also, still other yarn courses or picks of the woven or knitted fabric may comprise gel-forming yarn only, so long as the network of woven or knitted reinforcing yarn retains its structural integrity independent of the gel-forming yarn. In general, it is preferred for present purposes to maximize the proportion of gel-forming yarn in the fabric and incorporate as little as possible of the reinforcing yarn, while still ensuring adequate strength in the fabric after the gel-forming yarns have gelled. As a practical matter, at least 5% (by weight) of reinforcing yarn is required but a larger proportion of reinforcing yarn may be used to yield a fabric of greater strength. CMC, a prefeπed gel-forming material in the present invention, may be made by the chemical conversion of a variety of cellulosic materials, such as viscose rayon, cotton, etc. One cellulosic yarn suitable for the present invention is a Lyocell yarn. It is available from Spinneroff Streif AG, Zurichstrasse 170, Uathal, Switzerland. Lyocell is a solvent spun cellulose, produced from the natural cellulose in wood pulp by dissolution of the pulp in a solvent and then extruding the solution through a multiple-hole die, called a spinneret, to form a yam comprised of a plurality of continuous strands. The solvent is vaporized in the process, leaving a continuous multi-filament yarn composed of pure cellulose. The filaments in such a yarn may be chopped into staple form and spun into a yarn in a way similar to that used in processing cotton fibre. In accordance with one aspect of the present invention, such an unconverted cellulose yam is readily woven, knit or braided into a precursor fabric, from which the fabric of the present invention is made by conversion of the cellulose to sodium carboxymethylceUulose or to oxidized cellulose, in accordance with well-known techniques. In the conversion of cellulose to sodium carboxymethylceUulose, less than aU of the ceUulose buUding blocks may be converted to the sodium carboxymethylceUulose form and the degree of this conversion wiU dictate the degree to which a resultant CMC yarn wiU absorb water and form a gel therewith. This proportion is sometimes refeπed to as the conversion factor. W Ue the present invention is not limited to sodium carboxymethylceUulose of any particular conversion factor, such materials with a conversion factor of 50 to 70% are preferred in the fabric of the present invention. Oxidized ceUulose, which is conventionaUy used in knitted form as a hemostatic agent during surgery, may also be used in the reinforced fabric of the present invention and may also be converted (oxidized) after cellulosic yarn is first woven, knit or braided into a precursor fabric. Yet another hemostatic material, useful in the present invention, is calcium alginate, which is a material derived from seaweed, and, in matted fibre form, is also used as a wound dressing. Other fibrous polysaccharides, with simUar chemistry and properties to CMC, may also be used. Combinations of different gel-forming agents may be used within the scope of the present invention. Such combinations may be made by forming a yarn from different gel-forming or hemostatic fibres and/or by weaving, knitting or braiding combinations of different gel-forming yarns. In the case where a precursor fabric is first formed with ceUulose yarn, and the knitted j woven or braided ceUulose yarn is then converted to gel- forming oxidized ceUulose or sodium carboxymethylceUulose, the reinforcing yarn must be non-reactive with the reactants and the products of the process of converting the ceUulosic material into the gel-forming, chemicaUy modified form thereof. Referring to Figure 1, the step of weaving, knitting or braiding involves conventional methods, which are known. In accordance with the present invention, each of the multiple yarn end feeds to a weaving loom, knitting machine or braiding machine may comprise, in effect, two yam ends, fed in paraUel, one the gel-forming yarn (or a precursor yarn suitable for subsequent conversion to a gel-forming yarn), and one the reinforcing yarn. With a weft knit fabric constructed in this way as an example, the knit fabric product would include, as shown in Figure 1 , a thin reinforcing yarn 2, combined in aU yarn courses with a thicker (but weaker) yarn 1 , which is either a gel-forming fibre or is convertible to a gel-forming yarn (i.e. a gel-forming yarn precursor). In such a structure, at least some of the gel-forming yarn courses may be omitted, depending on the relative degree of strength and absorptive capacity desired. Shown in Figure 2 is another knit fabric of the present invention. Reinforcing yarns 3 are knit so as to provide structural integrity to the fabric, whUe gel-forming (or precursor to gel-forming) yarns 4 are inlaid therewith. The inlaying of gel-forming yarns 4 is such that even if the gel- forming yarns 4 are fuUy dissolved, the network of reinforcing yarns wiU maintain the structural integrity of the fabric. Knit forms of the composite fabric of this invention have some inherent stretchabiHty. In certain embodiments of the fabrics, such as those shown in Figures 1 and 2, still more stretchabiHty may be provided. More specificaUy, the reinforcing yarn itself may be stretchable so that the fabric itself is more stretchable. This is particularly useful when the fabric is intended for disposition around a baUoon-expanding device, as described in the above- referenced co-pending U.S. patent appUcation. For that purpose, a tubular fabric is preferred. In fact, one particularly effective use for the fabric of the present invention is as a hemostatic shroud covering an expansible device, adapted for disposition in a body cavity or passageway, such as a nasal passageway, to control bleeding therein, as disclosed in the above-referenced U.S. Patent AppUcation Serial No. 09/406,166, filed September 27, 1999. While the range of fabrics required for different applications is very wide, an exemplary fabric, made for use in a nasal hemostatic device, comprises a knit construction, as iUustrated in Figure 1, knitted into a tubular form in accordance with weU-known methods. In this exemplary fabric, a gel forming precursor yam (12 tex lyoceU spun yam is knit together with a reinforcing yarn comprised of 17 decitex 3 filament nylon. The fabric stmcture is a plain weft, knitted in circular form with 36 needles. The loop length is 5 mm and the weight of the finished fabric is 1.6 grams per metre (wet relaxed and dried to normal moisture regain). The reinforcing yam comprises about 12%, by weight, of this fabric before conversion of the LyoceU to CMC and about 11 % after that conversion. The conversion of the LyoceU in this exemplary fabric is accompnshed by methods weU known in the art. WhUe the nylon reinforcing yarn used in this embodiment would not be considered stretchable, the fabric stmcture itself is stretchable and deformable, that is it wiU expand in diameter at the expense of its length. Apart from the composite fabric as described above, the present invention also includes the process of making a gel-forming or hemostatic stmcture, including a matted fibre or laid-in knit stmcture, as disclosed in the above-referenced WO 98/46818, by first forming the stmcture with gel-forming fibre precursors, such as ceUulose fibre or yarn, and then converting the structure to the gel-forming state thereof, namely oxidized ceUulose or CMC. StiU other composites and fabrics within the scope of this invention comprise a composite yarn, the stmcture of which includes both reinforcing fibres, such as nylon, and gel-forming fibres (or precursors thereof). The most elementary method of combining two different fibres within one yarn is to simply spin the yarn from a mixture of the two fibres in staple form. However, this may lead to an overly weakened yarn once the geUing has taken place. A preferred example of such a composite yarn is a core spun yarn, that is a yam wherein staple fibres are spun around a preformed yarn. This preformed yam may be another spun yarn, or, more commonly, a continuous filament yam. This preformed yarn may comprise a reinforcing material, such as nylon. Gel-forming, or precursors of gel-forming, fibres comprise a second component of the final yarn product. The gel-forming fibres therein (converted from precursor materials either prior to or after spinning) provide absorptive and hemostatic capacity to the yarn and the reinforcing fibres or central filament of the preformed yarn provide strength. Such a yarn may be woven, knit or otherwise incorporated into a fabric or other stmcture, wherein fluid or blood absorption are important. W le the product and method of making the product of this invention have been described in connection with several specific embodiments, it should be understood that numerous modifications could be made by persons of skiU in this art without departing from the true spirit and scope of the invention. Accordingly, the above description is intended to be merely iUustrative and not Umiting. The scope of the invention claimed should be understood as including aU those alternatives and modifications which may be devised by one skiUed in the art from the above description whUe nevertheless embodying the true spirit and scope thereof, and aU equivalents or obvious variants thereof.

Claims: What is claimed is: 1. A composite knitted, woven or braided fabric comprising a combination of: yarn which is either gel-forming or is a precursor yarn, capable of being converted to a gel-forming yam; said gel-forming yam or gel-forming yam precursor being woven, knitted or braided with a reinforcing yam, the knitting, weaving or braiding of such reinforcing yarn comprising a network capable of providing physical integrity to said fabric independent of said gel-forming yarn or gel-forming yarn precursor. 2. The fabric of claim 1 wherein said gel-forming yarn precursor is a ceUulosic yam. 3. The fabric of claim 1 wherein said gel-forming yarn is comprised of sodium carboxymethylceUulose. 4. The fabric of claim 1 wherein said gel-forming yarn is selected from the group consisting of sodium carboxymethylceUulose, oxidized ceUulose, and calcium alginate. 5. The fabric of claim 1 wherein said reinforcing filament is a nylon continuous mono or multifilament yarn. 6. A composite fabric comprising a woven, knit or braided combination of: one or more yarns capable of geUing upon contact with Uquid, and one or more reinforcing yarns, wherein said reinforcing yarn has greater tensUe strength than said geUing yam in a wet phase, and wherein said fabric is highly absorbent to blood and body fluids and wherein the woven, knit or braided network of said reinforcing yarn is capable of providing stmctural integrity to said fabric independent of said yarn capable of geUing upon contact with Uquid. 7. A method of making a composite fabric comprised of a combination of gel-forming yarn and reinforcing yarn, said method comprising the steps of: weaving, knitting or braiding together a pluraUty of courses of said gel- forming and said reinforcing yarns, said pluraUty of yarns including at least one said yarn having hemostatic properties and at least one said yarn having a tensile strength greater than the tensUe strength of said hemostatic yarn in a wet phase, said higher strength yam being woven, knit or braided so as to provide structural integrity to said fabric independent of said hemostatic yarn. 8. The method of claim 7 wherein said yam having hemostatic properties is converted ceUulose yarn. 9. The method of claim 8 wherein said converted ceUulose yarn is sodium carboxymethylceUulose, converted after the knitting, weaving or braiding of a ceUulose precursor yarn. 10. The method of claim 8 wherein said ceUulose yarn is oxidized to produce oxidized ceUulose fibre. 11. The method of claim 10 wherein said ceUulose yarn is oxidized after the step of said weaving, knitting or braiding. 12. The method of claim 7 wherein said yam having hemostatic properties is calcium alginate. 13. A precursor fabric capable of being converted into a composite woven, knitted or braided fabric having a capacity for absorbing a quantity of a selected fluid without losing its stmctural integrity, said precursor fabric comprising a network of woven, knitted or braided yarns capable of retaining the stmctural integrity thereof in the presence of said selected fluid and, combined therewith, precursor yarn capable of being converted to gel- forming yarn, which gel-forming yarn has a capacity to absorb said preselected fluid by forming a gel therewith. 14. A self-reinforcing composite yarn comprising (a) reinforcing fibres or filament, and (b) gel-forming fibres, or gel-forming fibre precursors, wherein (b) is combined with (a) to form a continuous yarn. 15. A yam, as in claim 14, wherein said yarn is a core-spun yam. 16. A reinforced, gel-forming, fluid-absorbing stmcture comprised of a yarn, as recited in claim 14. 17. A method of making a gel-forming stmcture by first making a structure of a material including fibrous material which is chemicaUy convertible to a gel-forming absorptive material, and then chemicaUy converting said material to its gel-forming, absorptive form. 18. A method, as recited in claim 17, wherein said precursor material is a ceUulosic yam. 19. A method, as recited in claim 18, wherein said converted material is CMC. 20. A method, as recited in claim 17, wherein the finished stmcture is a knitted fabric 21. A method, as recited in claim 17, wherein the finished stmcture is a woven fabric. 22. A method, as recited in claim 17, wherein the finished stmcture is a braided fabric. 23. A stmcture, as recited in claims 20, 21 or 22, wherein the fabric is in tubular form.

Inventors: HUDSON JOHN OVERTON, HUDSON, JOHN, OVERTON
Applicants: HUDSON JOHN OVERTON, HUDSON, JOHN, OVERTON
Application year: 2000
Main classification: D04B1
IPC codes: A61F13, D03D1, D03D15, D04B1, D04B21, D04C1