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Title:
HYDROENTANGLED TUBULAR FABRICS
Document Type and Number:
WIPO Patent Application WO/2009/127816
Kind Code:
A1
Abstract:
There is described a method of manufacturing a tubular nonwoven fabric which comprises forming a nonwoven fabric tube by winding at least one fibre material around a rotatable mandrel and bonding the fibres using hydroentanglement and novel hydroentangled tubular fabrics.

Inventors:
RUSSEL, Stephen, John (41 Hookstone Oval, Harrogate, North Yorkshire HG2 8QE, GB)
TIPPER, Matthew, James (20 Albion Avenue, York, North Yorkshire YO26 8RA, GB)
RATHOD, Manoj, K. (University of Leeds, Leeds LS2 9JT, GB)
Application Number:
GB2009/000958
Publication Date:
October 22, 2009
Filing Date:
April 14, 2009
Export Citation:
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Assignee:
NONWOVENS INNOVATIONS & RESEARCH INSTITUTE LIMITED (Centre for Technical Textile, University of LeedsWoodhouse Lane, Leeds LS2 9JT, GB)
RUSSEL, Stephen, John (41 Hookstone Oval, Harrogate, North Yorkshire HG2 8QE, GB)
TIPPER, Matthew, James (20 Albion Avenue, York, North Yorkshire YO26 8RA, GB)
RATHOD, Manoj, K. (University of Leeds, Leeds LS2 9JT, GB)
International Classes:
D06C29/00; D04H1/4218; D04H1/4234; D04H1/4266; D04H1/4334; D04H1/4342; D04H1/435; D04H1/485; D04H1/492; D04H1/76; D04H3/07; D04H3/11; D04H13/00; D04H18/00
Domestic Patent References:
2001-12-20
2008-03-20
Foreign References:
GB2338494A1999-12-22
US3758926A1973-09-18
US5429847A1995-07-04
USRE38505E2004-04-20
US5290502A1994-03-01
US20040211163A12004-10-28
Attorney, Agent or Firm:
GILHOLM, Stephen, Philip (IPheions Intellectual Property, Buzzard OfficeThe Hawk Creative Business Park,Easingwold, York YO61 3FE, GB)
Download PDF:
Claims:
Claims

1. A continuous method of manufacturing a tubular nonwoven fabric which comprises forming a nonwoven fabric tube by wrapping at least one fibrous material around a rotatable mandrel and simultaneously bonding the fibres using hydroentanglement.

2. A method according to claim 1 in which the bonding of the fibrous material will take place as the material is on the mandrel.

3. A method according to claim 1 in which the bonding is both within and between the regions of the joins in the tube.

4. A method according to claim 1 in which the method comprises the formation of the nonwoven fabric tube and the bonding of the fibres is carried out simultaneously.

5. A method according to claim 1 in which the mandrel is a cylindrical mandrel.

6. A method according to claim 5 in which the mandrel is a solid cylinder.

7. A method according to claim 5 in which the mandrel has a hollow core.

8. A method according to claim 5 in which the mandrel cylinder comprises a solid outer sheath and has a hollow core.

9. A method according to claim 5 in which the mandrel comprises a perforated cylinder.

10. A method according to claim 1 in which the mandrel has a minimum diameter of 1.5 mm.

11. A method according to claim 1 in which the mandrel is mounted across the width of a moving conveyor surface.

12. A method according to claim 1 in which the mandrel is fixed at one end.

13. A method according to claim 7 in which the moving conveyor travels perpendicular to the plane of the mandrel, causing the mandrel to rotate due to frictional contact.

14. A method according to claim 7 in which the moving conveyor is a roller, cylinder or a flat bed conveyor.

15. A method according to claim 1 in which a drive motor is fitted to the mandrel to control the speed of rotation.

16. A method according to claim 1 in which the fibre material is a web or fabric.

17. A method according to claim 16 in which the fibre material is a web selected from one or more of a drylaid web, a wetlaid web or a spunrnelt web.

18. A method according to claim 17 in which the fibre material is a fabric selected from one or more of a pre-formed nonwoven fabric, a pre-bonded fabric or a textile fabric; and combinations thereof.

19. A method according to claim 1 in which the fibre material is a polymer, ceramic or metal material that is capable of being hydroentangled either alone or in a blend.

20. A method according to claim 1 in which the angle of the wrap is from 90 to 165 degrees, relative to the plane of the mandrel.

21. A method according to claim 1 in which each successive wrap of the mandrel by the fibre feed material is controlled such that there is an overlap between each layer at their respective edges.

22. A method according to claim 1 in which the process of hydroentanglement is carried out by one or more injectors (or manifolds) optionally mounted around the periphery of the mandrel.

23. A method according to claim 22 in which the one or more injectors comprise water jets.

24. A method according to claim 23 in which the diameter of the nozzle of the water jet is from of 80-150 μm.

25. A method according to claim 1 in which the surface of the mandrel is patterned or embossed.

26. A method according to claim 7 in which the mandrel may be hollow as hereinbefore described or may include a hollow section.

27. A method according to claims 7 or 26 in which the hollow mandrel or hollow section in the mandrel is used to simultaneously introduce a filling material into the fabric.

28. A method according to claim 27 in which the filling material is selected from one or more of filaments, wires, cables, powders, particles, gels, waxes, liquids and gases; and mixtures thereof.

29. A method according to claims 7 or 26 in which a positive air pressure is provided from within the hollow section to aid removal of the tubular fabric from the surface of the mandrel.

30. A method according to claim 29 in which the positive air pressure comprises hot air.

31. A method according to claim 1 in which the fibre material is selected from one or more of natural fibres such as pulp fibres, cotton, bast fibres, wool and hair etc., man-made fibres or filaments e.g. polyesters, polyolefins, regenerated cellulosics and their derivatives, polyamides and the like, aramid fibres e.g. para and meta-aramid fibres such as Kevlar® and Nomex®; inorganic fibres such as glass and metal; and blends of fibres.

32. A method according to claim 1 in which the tubular nonwoven fabric may have incorporated in it one or more of a filament, a pre-formed fabric e.g. nonwoven, woven, knitted, multiaxial, weft insert, circular warp and weft knitted, knitted spacer, braid, knit-braid, monofilament, multifilaments, elastic filaments, spun yarns etc.

33. A method according to claim 1 in which binders or other reinforcing materials e.g. acrylic, vinyl esters, rubber (synthetic and natural), PVA, PVC etc. are included in the tubular nonwoven fabric.

34. Apparatus for the manufacture of a tubular nonwoven fabric, which apparatus comprises a rotatable mandrel about which a fibre feed material may be wound and mounted across a moveable a conveyor surface/hydroentanglement cylinder; and an injector mounted adjacent the periphery of the mandrel.

35. A tubular nonwoven fabric wherein the fabric is a hydroentangled nonwoven fabric.

36. A tubular nonwoven fabric according to claim 35 in which the fabric has an external diameter of as low as 5 mm to a maximum of 500 mm.

37. A tubular nonwoven fabric according to claim 35 in which the fabric has an area density of 15-200 g/m 2 .

38. A tubular nonwoven fabric according to claim 35 in which the fibre material is a web or fabric.

39. A tubular nonwoven fabric according to claim 38 in which the fibre material is a web selected from one or more of a drylaid web, a wetlaid web or a spunmelt web.

40. A tubular nonwoven fabric according to claim 38 in which the fibre material is a fabric selected from one or more of a pre-formed nonwoven fabric, a pre-bonded fabric or a textile fabric; and combinations thereof.

41. A tubular nonwoven fabric according to claim 35 in which the fibre material is a polymer, ceramic or metal material that is capable of being hydroentangled either alone or in a blend.

42. A tubular nonwoven fabric according to claim 35 in which there is an overlap between each layer at their respective edges.

43. A tubular nonwoven fabric according to claim 35 in which the fabric is patterned or embossed.

44. A tubular nonwoven fabric according to claim 35 in which a filling material is introduced into the fabric.

45. A tubular nonwoven fabric according to claim 44 in which the filling material is selected from one or more of filaments, wires, cables, powders, particles, gels, waxes, liquids and gases; and mixtures thereof.

46. A tubular nonwoven fabric according to claim 35 in which the fibre material is selected from one or more of natural fibres such as pulp fibres, cotton, bast fibres, wool and hair etc., man-made fibres or filaments e.g. polyesters, polyolefins, synthetic cellulosics and their derivatives, polyamides and the like, aramid fibres e.g. para and meta-aramid fibres such as Kevlar® and Nomex®; inorganic fibres such as glass and metal; and blends of fibres.

47. A tubular nonwoven fabric according to claim 35 in which the tubular nonwoven fabric may have incorporated in it one or more of a filament, a pre-formed fabric e.g. nonwoven, woven, knitted, multiaxial, weft insert, circular warp and weft knitted, knitted spacer, braid, knit-braid, monofilament, multifilaments, elastic filaments, spun yarns etc.

48. A tubular nonwoven fabric according to claim 35 in which binders or other reinforcing materials e.g. acrylic, vinyl esters, rubber (synthetic and natural), PVA, PVC etc. are included in the tubular nonwoven fabric.

49. A tubular nonwoven fabric wherein the fabric is coated or infused with one or more of a thermoplastic resin or a thermosetting resins e.g. PP, PET, PVC, to create a tubular composite structure.

50. An article comprising a tubular nonwoven fabric as hereinbefore described.

51. A method, apparatus or tubular nonwoven fabric substantially as hereinbefore described with reference to the accompanying examples.

Description:

Hydroentangled Tubular Fabrics

Field of the invention

The present invention relates to a novel method of manufacturing tubular nonwoven fabrics, to apparatus for use in such methods and to the fabrics which are novel per se.

Background of the invention

Nonwoven fabrics are conventionally produced as flat, sheet-like products that are wound in to rolls prior to being converted into different two and three-dimensional forms depending on the needs of the final product .

Tubular nonwoven fabrics generally comprise a hollow centre and have applications in, for example, filtration (e.g. bag filtration), pipe linings, composite reinforcement, medical dressings and the formation of medical devices, such as synthetic blood vessels and tissue engineering scaffolds. Conventionally, the formation of a tubular structure from a nonwoven fabric involves first manufacturing the fabric in sheet form and then forming it into the shape of a tube in a secondary step. To produce a self- supporting tubular structure a means of joining edges together is required, such as sewing, stitching or bonding overlapped edges using chemical, thermal or ultrasonic bonding. One disadvantage of the existing joining methods is that they produce a seam running the length of the tubular nonwoven fabric which introduces an area of weakness in the fabric and a region that is structurally dissimilar to the rest of the fabric

Attempts have been made to simplify the production of tubular nonwoven fabrics using continuous methods.

Thus, for example, UK Patent application No. GB 1324661 describes the assembly of individual filaments to form a nonwoven tube.

International Patent application No. WO 94/23915 describes a method in which segmented tubular products are produced for filters.

Also in the field of filter manufacture, International Patent application No. WO 95/09942 describes an apparatus and method for producing a melt blown continuous and seamless nonwoven tube, which comprises a melt blowing die for extruding two groups of polymer thermoplastic filaments onto a rotating mandrel to form a multilayer layer tube thereon.

Similarly, US Patent application No. US2003/034296 describes the formation of tubular nonwoven filter products using a rotating mandrel.

Japanese Patent application No. JP2005/238517 describes the production of tubular nonwoven laminates for composite reinforcement.

US Patent No. 6,679,966 describes laminated tubular pipe lining fabrics which may be produced by a method comprising shaping a resin impregnated fibre band into a tubular body; winding a fleece layer/plastic film laminate onto the tubular body and subjecting the tubular body to a curing process.

Also, methods of producing tubular nonwoven fabrics for medical uses such as artificial blood vessels with sufficient strength for suturing have been described in JP2006291397 and JP2004188037.

Furthermore, it is taught in the prior art that a tubular nonwoven fabric with a hollow core can be formed by needlepunching. The resulting tubes can be made with varying diameters. A principal method of forming such structures is described in UK Patent application No. GBl 189736 which discloses a nonwoven fabric produced by winding overlapping helices of fibrous assembly onto a drum containing spaces for the penetration of reciprocating needles, the layers being secured together by forcing fibres through between the overlapping layers by means of barbed needles. However, such a process is disadvantageous in that, inter alia, it produces a non-uniformly bonded fabric and the fabric is unsuitable for simultaneous introduction and containment of other materials, such as powders with a very small particle size or liquids and gels, which is especially undesirable if producing, for example, medical dressings. Furthermore, due to the mode of operation and penetration of needles into the drum it is not possible to (i) produce tubular fabrics of less than 0.5 mm wall thickness by such a process (ii) produce tubular fabrics of less than 4 mm tube diameter; (iii) continuously produce high density, light-weight tubular fabrics from unbonded webs or lightly pre-consolidated webs; (v) produce tubular fabrics free of needle holes or marks; (vi) continuously produce tubular fabrics from delicate electrospun webs containing microfibres and/or nanofibres; (vii) continuously produce tubular fabrics from weak wet-laid or air-laid webs comprised of fibres less than 5 mm mean fibre length; (viii) prevent filling materials from coming in to contact

with the reciprocating needles or being lost through the openings that are provided to allow penetration of the needles.

US Patents Nos. US3,758,926 and US3,530,557 each describe continuous fabric tubing prepared by helically winding nonwoven webs onto a rotating drum in a partly overlapping relationship and stitching the partly superimposed turns to each other by needling then axially pulling the tubing so formed away from the drum.

Summary of the Invention In order to overcome the limitations of the prior art a continuous method of producing hollow nonwoven fabric tubes is required that enables fabrics to be formed that are more intensively and uniformly bonded than can be achieved by needlepunchmg during tube formation. In particular, a method is required of producing, thin tubular nonwoven fabrics, for example, with wall thicknesses as low as 0.1 mm and external diameters of as low as 2 mm to a maximum of 500 mm; light-weight tubular nonwoven fabrics, e.g. produced from webs or fabrics with an area density of 8-200 g/m 2 ; and/or using a method that is capable of being retrofitted to conventional, existing production machinery to facilitate a cost-effective process and industrial production rates.

We have now surprisingly found a novel method of meeting these requirements by forming nonwoven fabric tubes with a hollow core using one or more continuous, high velocity, fluid jets (hydroentanglement, water/steam jet entanglement)) in place of needle punching and optionally adopting the use of a perforated or non-perforated tubular mandrel in place of the normal conveyor or drum system.

Alternatively, the mandrel may be a solid cylinder with no perforations and no hollow section in the core. In general terms hydroentanglement is a process for mechanically bonding and consolidating a web of loose fibres by intertwining, displacing and rotating fibres around their neighbours to produce a tightly bonded fibrous assembly. The process comprises exposing the fibres to a non-uniform spatial pressure field created by rows of closely-spaced, continuous high-velocity water jets. The person skilled in the art will understand that the process of hydroentanglement is different to that of needle punching and which is sometimes referred to as "needling".

Thus, according to a first aspect of the invention we provide a continuous method of manufacturing a tubular nonwoven fabric which comprises forming a nonwoven fabric tube by wrapping at least one fibrous material around a rotatable mandrel and simultaneously bonding the fibres using hydroentanglement

In the method of the invention the bonding of the fibrous material will take place as the material is on the mandrel. Furthermore, the bonding is advantageously both within and between the regions of the joins in the tube.

In a preferred aspect of the present invention the method comprises the formation of the nonwoven fabric tube and the bonding of the fibres is carried out simultaneously.

The mandrel is preferentially a cylindrical mandrel and as hereinbefore described, may have a solid surface and a hollow core. Although the diameter of the mandrel may vary, preferably the mandrel will have a minimum diameter of 1.5mm mm which is mounted across the width of a moving conveyor surface. The mandrel may be a solid cylinder, a tubular cylinder or a microperforated tubular cylinder. In a further

preferred embodiment the mandrel comprises a solid tubular cylinder. Alternatively, the mandrel cylinder may comprise a solid outer sheath having a hollow core. Alternatively, the hollow core may comprise of two hollow cores in annular cross- sectional arrangement.

In use the mandrel may be fixed at one end, e.g. by a bearing system, that enables the mandrel to rotate whilst maintaining its geometric position relative to the moving conveyor. The mandrel is interchangeable and the length and diameter are varied depending on the dimensions of the tube that is to be produced. Pressure is exerted between the mandrel and the moving conveyor and one or both of the mandrel and the conveyor may be adjustable so that the pressure may be varied. Preferentially, the moving conveyor may travel perpendicular to the longitudinal axis of the mandrel, thus causing the mandrel to rotate due to frictional contact. The driving conveyor surface may be either a roller or cylinder or a flat bed conveyor as is usually encountered in conventional hydroentanglement processes. Alternatively, additional drive rollers may be introduced. The surface of at least one drive roller may have an elastomeric or rubberised surface. It will be understood by the person skilled in the art that multiple driving conveyors may be employed. Optionally, a separate drive motor may also be fitted to the mandrel to control the speed of rotation.

In the method of the invention a continuous fibre material, e.g. a web or fabric, is fed in open width to the nip point, i.e. between the mandrel and the conveyor surface, at one side of the machine. Preferentially, the fibre material is in the form of a thin and narrow strip or tape. When the fibre feed material is an unbonded web it may be one or more of a drylaid, wetlaid, electrospun or spunmelt web, introduced alone or in

various combinations. When the fibre feed material is a fabric it may be a pre-bonded nonwoven fabric, a textile fabric e.g. a knitted or woven fabric, introduced alone or in various combinations. In addition, combinations of fabrics and webs may also be introduced provided that fibre segments can be effectively migrated and intertwined by the action of water jets. The fibre composition may be any polymer, ceramic or metal material that is capable of being hydroentangled either alone or in blends. The correct positioning of the feed material can be assisted by the use of appropriate rotating guides, such as rollers or nipped apron conveyors between which the material is sandwiched immediately prior to being introduced to the mandrel, taking care not to damage the potentially tenuous structure. Positive let-off and delivery of the feed material assists in controlling the tension as the feed material enters the mandrel nip point.

In the method of the invention the fibre feed material is wrapped around the mandrel due to the mandrel's rotation. The wrapping angle may vary depending upon the angle of feed to the mandrel. The angle is adjustable depending upon the required tubular nonwoven fabric. Thus, the wrap angle may be from 90 degrees (feed material enters the mandrel nip point perpendicular to the longitudinal axis of the mandrel) to 165 degrees, relative to the plane of the mandrel. Each successive wrap of the mandrel by the fibre feed material, i.e. each layer of the tubular nonwoven fabric may be controlled such that there is an overlap between each layer at their respective edges.

The degree of overlap may be controlled by, inter alia, the input and output speeds of the fibre feed material wrapped onto the mandrel and the angle the material is fed to the mandrel. It will be understood that the mandrel is interchangeable depending on the diameter of the nonwoven fabric tube that is required to be produced.

Alternatively, in the formation of the tubular fabric, the fibre feed material may be wrapped around the mandrel in such a manner that the projecting fibrous edges of successive wraps are abutted rather than overlapped to minimise the thickness and structural heterogeneity of the resulting hydroentangled join.

In the method of the invention the process of hydroentanglement may be carried out by one or more injectors (or manifolds) optionally mounted around the periphery of the mandrel and extending along the longitudinal axis of the mandrel. The one or more injectors are adapted to direct multiple high velocity jets of water or steam at the fibres/fabric in the feed material wrapped around the mandrel. Preferably the formation of the nonwoven fabric tube and the hydroentanglement is carried out simultaneously. Preferentially, the one or more injectors comprise high velocity water jets.

The impinging water jets are issued substantially perpendicular to the longitudinal axis of the mandrel. However, it will be understood by the person skilled in the art that one or more water jets may be oriented at different positions if required.

Furthermore, the size of the water jets may vary. Thus, for example the diameter of the nozzle of the water jets may be from of 80-150 μm. The diameters of the nozzles of each of the water jets may be the same or different. Preferentially, the nozzle spacing may be from 10 - 30 jets/cm in single or twin rows.

The action of the incident water jets and vorticity inside the feed material during hydroentanglement introduces intensive mechanical fibre entanglement of the fibres

on the surface of the mandrel, which serves to interconnect the fibres in the overlapped or abutted areas of the feed material and increases the level of bonding in the other regions of the feed material. In this fashion, a continuous and uniformly bonded fabric is formed that is free from needling marks or holes. If two or more feed materials are simultaneously introduced, simultaneously lamination of the layers is effected as well as joining in the overlap or abutted areas. Thus, the bonding/entanglement may be substantially uniform throughout the whole of the overlapped/abutted region. For example, the bonding/entanglement may be substantially the complete depth (i.e. the thickness of the fabric around the mandrel) of the fabric and/or the overlapped/abutted areas. Alternatively, the jets may be set so that the bonding/entanglement is slightly less than the complete thickness of the fabric, e.g. up to about 95% of the thickness, or up to about 90% of the thickness, or up to about 80% of the thickness, or up to about 70% of the thickness.

A further advantage of the entanglement method of the present invention is that when the entanglement is throughout the thickness of the fabric, the resulting tubular fabric will have an external surface which is substantially the same or similar to the internal surface. This contrasts with tubular fabrics produced by conventional needle punching methods. Thus, the surface of the hydroentanglement fabric according to the invention may be denser than conventionally produced fabrics and free from needle marks.

The nature of and weight of the nonwoven fabrics produced in accordance with the invention will vary widely depending upon the intended use of the tubular fabric. Thus, for example, very light-weight fabrics in the range of from 40 g/m 2 to 80 g/m 2 .

Alternatively, heavier weight fabrics, in the range of from 50-100 g/m 2 may be used. Furthermore, still heavier fabrics in the range of from 100-300 g/m 2 may be used.

As is known in the art of hydroentanglement, the physical and mechanical properties of the fabric are modified to suit requirements by adjustment of, inter alia, the water pressure, specific energy, the flow rate, the nozzle diameter, the surface speed of the feed material relative to the jets, the jet frequency, etc.

Furthermore, as hereinbefore described the mandrel preferably comprises a tubular cylinder with no perforations or spaces. If the surface of the mandrel is patterned or embossed, patterns or apertures may be simultaneously introduced in to the continuous fabric that is formed on the mandrel.

In the method of the invention water may be removed from the system by drainage around the mandrel and/or suction below the mandrel applied under the feed conveyor. Alternatively, if the mandrel is hollow and/or perforated as hereinbefore described, suction can be applied directly within the mandrel, enabling water to be drawn from the surface and removed from the process.

As hereinbefore described the injectors may comprise water jets or steam jets. It will be understood by the person skilled in the art that high velocity, columnar water jets are preferred but that combinations of water and steam jets may be used. Furthermore, if one or more thermoplastic fibres are present then thermal bonding in addition to hydroentanglement can be introduced after the tubular fabric is formed to increase its dimensional stability. In a further aspect of the invention the

hydroentanglement and optional thermal bonding may also be combined with mechanical entanglement of fibres.

Thus, prior art methods are not suitable for producing thin-walled bonded tubular fabrics, because the reciprocating needles used in the process must repeatedly penetrate a sufficient thickness of material to enable the collection of multiple fibre segments on the needle barbs and re-orient them in to the transverse direction. This can lead to needle marks on the fabric surface due to the needle penetration. Furthermore, the number of needles that can be introduced per unit area to the fibre material to introduce bonding using one needling machine is limited by the fineness of the needles, how closely they can be packed together, their reciprocating speed (which is mechanically limited) and the processing speed, which affects the punches per cm 2 . Consequently, the degree and uniformity of bonding of the fabric that can be achieved during manufacture of the tubular fabric is limited using one needling machine. Furthermore, as occurs in high density needling, it can be disadvantageous to transversely migrate a large proportion of fibres in the fabric since fibre orientation directly influences tensile properties, permeability, wicking, gas flow resistance and anisotropy in fabric properties.

The current method of hydroentanglement hereinbefore described is advantageous in that, inter alia, the water jets treat a much large larger surface area of the fibre material and may penetrate the whole of the fabric and may produce a substantially uniformly bonded , i.e. entangled or hydroentangled, fabric.

In a preferred aspect of the invention the mandrel may be hollow as hereinbefore described or may include a hollow section. The use of such a hollow mandrel or hollow section is advantageous in that, inter alia, filling materials may be simultaneously introduced in to the fabric. Such filling materials may include but shall not be limited to filaments, wires, cables, powders, particles, gels, waxes, liquids and gases; and mixtures thereof. If the mandrel sheath is solid, these materials are protected from direct contact with the incident water jets. The filling materials are then trapped within the core of the tube once formed; this provides a convenient means of functionalising the tube and avoids the need for a secondary operation.

The unfilled or filled hydroentangled nonwoven fabric tube may be removed from the mandrel at one end by applying tension to the structure in plane with the longitudinal axis of the mandrel. In the simplest embodiment, the tube may be slid off the mandrel for collection. The collected tube may be wound or otherwise collected depending on the production process in which it forms a part. Removal from the mandrel can be assisted by using a twin-part mandrel in which a discrete second section of the mandrel is provided. The second section of the mandrel may comprise a hollow section and may extend beyond the last water jet. In such a case positive air pressure may be provided from within this section to aid removal of the tubular fabric from the surface of the mandrel. The air may at a high or low temperature or may be at ambient temperature. The use of hot air is advantageous in that simultaneous drying of the fabric may be achieved. Alternatively, hot air may be introduced to achieve curing or heat setting of materials in the tubular fabric as it is delivered.

Examples of fibres which may be used in the nonwoven fabrics of the invention include, but are not limited to, natural fibres such as pulp fibres, cotton, bast fibres, wool and hair etc., man-made fibres or filaments e.g. polyesters, polyolefins, acrylics, PVC, regenerated cellulosics and their derivatives, polyamides and the like, aramid fibres e.g. para and meta-aramid fibres such as Kevlar® and Nomex®. Inorganic fibres such as glass and metal may also be used. Blends of any of the above fibres may also be used and laminated fabrics may be produced by introducing multiple feeds of one of more fibre types to the mandrel.

The process can be used to incorporate filaments and pre-formed fabrics e.g. nonwoven, woven, knitted, multiaxial, weft insert, circular warp and weft knitted, knitted spacer, braid, knit-braid, monofilament, multifilaments, elastic filaments, spun yarns etc

The technology may also be combined with the addition of binders or other reinforcing materials e.g. acrylic, vinyl esters, rubber (synthetic and natural), PVA, PVC etc

The tubes are suitable for coating and infusion of thermoplastic and thermosetting resins e.g. PP, PET, PVC, PUR to create a tubular composite structure.

The apparatus used in the method of the invention is novel per se. Therefore, according to a further aspect of the invention we provide apparatus for the manufacture of a tubular nonwoven fabric as hereinbefore described, which apparatus comprises a rotatable mandrel about which a fibre feed material may be wound and

mounted across a moveable a conveyor surface/hydroentanglement cylinder; and an injector mounted adjacent the periphery of the mandrel.

Hydroentangled tubular nonwoven fabrics are novel per se. Therefore, according to a further aspect of the invention we provide a tubular nonwoven fabric wherein the fabric is a hydroentangled nonwoven fabric as hereinbefore described.

Thermal bonding of nonwoven generally, for example, in the case of blended cellulosic materials, masks the soft feel of the fibres. Hydroentanglement avoids the dilution of fibre effects which accompany other bonding systems. It is particularly suited for the manufacture of durable materials, thus, tubular nonwoven fabrics may be manufactured which look and feel like woven or knitted textiles. The hydroentangled tubular nonwoven fabrics according to this aspect of the invention possess the properties and/or advantages as hereinbefore described in the method of the invention.

Thus, the tubular nonwoven fabrics produced according to the invention may have a thickness of from 2 mm to 500 mm, or from 10 mm to 250 mm, or from 25 mm to 125 mm, or from 50 mm to 100 mm.

As hereinbefore described tubular nonwoven fabrics have applications in articles such as, filters, e.g. filtration bags, pipe linings, composite reinforcement, medical dressings and the formation of medical devices, such as synthetic blood vessels and tissue engineering scaffolds.

Thus, according to a yet further aspect of the invention we provide an article comprising a tubular nonwoven fabric as hereinbefore described.

Detailed Description of the Invention The invention will now be described solely by way of example and with reference to the accompanying drawings in which:

Figure 1 is an illustration of the method and apparatus of the invention for manufacturing an unfilled tubular nonwoven fabric material; and

Figure 2 is an illustration of the method and apparatus of the invention for manufacturing a filled tubular nonwoven fabric material.

Referring to Figure 1, apparatus 1 for the manufacture of a tubular nonwoven fabric, comprises a rotatable mandrel 2 about which a fibre feed material 3 is wound. The mandrel 2 is mounted across a rotatable hydroentanglement cylinder 4. In this example, the rotation of the hydroentanglement cylinder 4 drives the rotation of the mandrel 2. A high pressure injector 5 which continuously delivers a curtain of high velocity water jets is mounted adjacent to the periphery of the mandrel 2.

Referring to Figure 2, apparatus 6 for the manufacture of a tubular nonwoven fabric, comprises a tubular rotatable mandrel 7 with no perforations or holes about which a fibre feed material 8 is wound. The tubular mandrel 7 is mounted across a rotatable hydroentanglement cylinder 9. In this example, the rotation of the hydroentanglement cylinder 9 drives the rotation of the mandrel 7. A high pressure injector 10 is

mounted adjacent to the periphery of the mandrel 7. A separate pumping system or feed unit introduces a filler material 11 directly in to the hollow part of the tubular mandrel 7. The filler material 11 is protected from the water jets within the tubular mandrel 7 as the tubular fabric is being formed.

0081P.WO.Speo(3)