Water-Repellent Fibre

This application is a continuation of U.S. patent application Ser. No. 18/562,619, filed 20 Nov. 2023, which claims benefit to International Patent Application No. PCT/GB2022/051277 filed 20 May 2022, which claims benefit of Great Britain Patent Application No. 2107272.3, filed on 20 May 2021. The disclosures of which are incorporated hereby by reference in their entirety.

The present invention relates to a water-repellent fibre, a yarn, plied yarn or garment comprising a water-repellent fibre and a method of manufacturing a water-repellent fibre.

Yarns used in making clothing fabrics such as sportswear fabric often require a number of properties including being water repellent and oil repellent, being anti-stain or stain resistant, being lightweight and being abrasion resistant.

Typically, water repellency, oil repellency and anti-stain properties are provided by using a repellent surface coating such as a durable water repellent (DWR) coating applied to a fabric surface, in line with industry standards. DWR surface coatings are often made from perfluorinated compounds (PFCs) such as perfluorinated sulfonic acids (PFOS) and perfluorinated carboxylic acids (PFOA), or a silicone-based material.

However, PFCs are toxic and therefore PFC-based DWR coatings based on PFCs are harmful to the environment. In addition, DWR coatings wear away due to abrasion during use, resulting in a decrease in water repellency, oil repellency and anti-stain properties over time.

The present invention has been devised with the foregoing in mind.

According to a first aspect, there is provided a water-repellent fibre for a yarn and/or a fabric or textile. The fibre may comprise a hydrophobic material. The fibre may have or comprise a shape or configuration comprising one or more micro and/or nano-sized structures.

One or more micro and/or nano-sized structures may enhance or amplify the inherent characteristics (e.g., physical and/or chemical properties) of a material. In the case of a hydrophobic material (which is due to a low surface energy of the material), the chemical property of hydrophobicity of the material may be enhanced by one or more micro and/or nano-sized structures. The one or more micro and/or nano-sized structures of the fibre may therefore enhance the inherent properties of the hydrophobic material of the fibre. In addition to hydrophobicity, other chemical properties that are commonly exhibited by materials with a low surface energy, such as oleophobicity, anti-stain properties and anti-fouling properties, may similarly be enhanced by one or more micro and/or nano-sized structures. That may result in a fibre having enhanced water repellent, oil repellent, anti-fouling and anti-stain properties without requiring a separate coating on a surface of the fibre. In addition, because the enhanced hydrophobic properties (and other enhanced properties such as oleophobicity, anti-stain and anti-fouling properties) of the fibre are not reliant on a surface coating which can be worn away due to abrasion, the enhanced hydrophobic properties of the fibre may be retained for an increased length of time. The fibre may be used to form fabrics and/or textiles and/or garments having enhanced hydrophobic performance without requiring a separate coating on the surface of the fabric and/or textile and/or garment. It will be appreciated that when referring to enhanced hydrophobic properties in this disclosure, reference is also made to other enhanced properties such as oleophobicity, anti-stain and anti-fouling properties.

The one or more micro and/or nano-sized structures may have or comprise a size of between substantially 10 nm and substantially 100 μm, or between substantially 50 nm and substantially 10 μm, or between substantially 100 nm and substantially 1 μm. In principle, the smaller the structure(s), the greater the enhancement of the hydrophobic properties. However, the above size ranges may be an optimal size range providing an optimal balance between enhancement of hydrophobic properties and manufacturability.

The one or more micro and/or nano-sized structures may form at least a part of, or be located on, an outer surface of the fibre. The structures forming part of or being located on an outer surface of the fibre may ensure the structures are easily able to provide the enhanced hydrophobic properties when the fibres are brought into contact with a liquid.

The fibre may have or comprise a cross-sectional shape or configuration that forms or provides the one or more micro and/or nano-sized structures. The cross-sectional shape or configuration may be substantially uniform along at least a part of a length of the fibre or substantially a full length of the fibre. The one or more micro and/or nano-sized structures may each extend partially or substantially fully along a length of the fibre.

The fibre may have or comprise a diameter of between substantially 100 nm and substantially 500 μm. In this disclosure, the term diameter also encompasses a width and/or thickness of substantially non-circular fibres. The small radius of curvature of the outer surface of a fibre having a size in that range may enable the outer surface of the fibre to act as or provide a micro and/or nano-sized structure. That may provide the fibre with enhanced hydrophobic properties.

The one or more micro and/or nano-sized structures may be or comprise one or more projections from and/or recesses in an outer surface of the fibre. The fibre may have or comprise a cross-sectional shape or configuration that forms or provides the one or more projections and/or recesses. A height and/or depth of the one or more projections and/or recesses may be between substantially 100 nm and substantially 10 μm. A height and/or depth of the one or more projections and/or recesses may be up to substantially 10% of a diameter or thickness of the fibre. A greater height and/or depth of the one or more projections and/or recesses may provide greater enhancement of the hydrophobic properties of the fibre. A fibre comprising an outer surface having a high radius of curvature in addition to one or more projections and/or recesses in the outer surface of the fibre may have a hierarchical surface structure that further enhances the hydrophobic properties of the fibre. The hierarchical surface structure may create one or more air pockets that prevent or inhibit water (or other liquids) from contacting the surface of the fibre.

The one or more micro and/or nano-sized structures may comprise a plurality of micro and/or nano-sized structures. The fibre may have or comprise a cross-sectional shape or configuration that forms or provides the plurality of structures. The fibre may have or comprise a multi-lobal cross-section (e.g., trilobal, quadlobal, pentalobal, hexalobal and so on). The fibre may have a star-shaped (e.g., a n-pointed star, where n is greater than or equal to 3) cross-section, a cross-shaped cross-section, a v-shaped cross-section, or a substantially flat or planar cross-section, although any suitable cross-sectional shape or configuration may be used. The cross-sectional shape or configuration (e.g., lobes, star points, cross arms, v arms) may at least partially form or define the micro and/or nano-sized structures, such as projections from and/or recesses in an outer surface of the fibre. The fibre may have between substantially 3 and substantially 50 micro and/or nano-sized structures, although any suitable number of structures may be used. In principle, the higher the number or density of micro and/or nano-sized structures, the greater the enhancement of the hydrophobic properties. However, that number of micro and/or nano-sized structures may provide an optimal balance between enhancement of hydrophobic properties and manufacturability.

A spacing between adjacent micro and/or nano-sized structures may be between substantially 100 nm and substantially 10 μm, or between substantially 100 nm and substantially 1 μm. A smaller spacing between adjacent structures may provide greater enhancement of the hydrophobic properties of the fibre. A cross-section of the fibre may have a substantially regular shape. The structures may be distributed around a cross-section of the fibre substantially uniformly or homogeneously. For example, a substantially uniform or similar spacing may be provided between adjacent structures. Alternatively, a cross-section of the fibre may have a substantially irregular shape. The structures may be concentrated at one or more locations around a cross-section of the fibre. A spacing between the structures may be variable or non-uniform.

The hydrophobic material may be or comprise an oleophobic material. Oleophobic materials are inherently hydrophobic, due to oleophobicity requiring a lower surface energy than hydrophobicity.

The hydrophobic material may be or comprise a hydrophobic or oleophobic polymeric material. A polymeric material may be simple to manufacture into a fibre having or comprising one or more micro and/or nano-sized structures.

The fibre may be or comprise a mixture of the hydrophobic polymeric material and one or more other polymeric materials. The one or more other polymeric materials may not be or comprise hydrophobic polymeric materials, or may be or comprise one or more polymeric materials that are less hydrophobic than the hydrophobic polymeric material. The one or more other polymeric materials may be included to improve one or more other properties of the fibre, for example one or more mechanical properties such as tensile strength, elongation at break, stiffness or flexibility, temperature resistance, and/or one or more aesthetic properties such as colour etc.

The mixture may comprise or be arranged in a core-sheath structure, an island-in-sea structure or a random blend structure. In a core-sheath structure, the hydrophobic polymeric material may be or comprise or form the sheath and substantially surround the non-hydrophobic or less hydrophobic polymeric material(s) to form an outer surface of the fibre. Similarly, in an island-in-sea structure, the hydrophobic polymeric material may be or comprise or form the sea and substantially surround the non-hydrophobic or less hydrophobic polymeric material(s) to form an outer surface of the fibre. In a random blend, the hydrophobic polymeric material may form a greater proportion of an outer surface of the fibre than the non-hydrophobic or less hydrophobic polymeric material(s). That arrangement may occur naturally during formation of the fibre, or during post-formation annealing of the fibre. In either case. the lower-surface energy of the hydrophobic polymeric material may cause the hydrophobic polymeric material in the random blend to diffuse towards an outer surface of the fibre. A random blend may comprise a higher proportion (e.g., by volume) of the hydrophobic polymeric material than the non-hydrophobic or less hydrophobic materials. Additionally or alternatively, the hydrophobic polymeric material and the one or more other polymeric materials in a random blend may have a similar melting point, or the hydrophobic polymeric material may have a lower melting point than the one or more other polymeric materials. One or more of those features may enable the lower surface energy hydrophobic polymeric material to more easily diffuse towards an outer surface of the fibre.

The mixture may comprise substantially 5% or more by volume of the hydrophobic polymeric material, or between substantially 60% and substantially 80% by volume of the hydrophobic polymeric material. The mixture may comprise up to substantially 95% by volume of the one or more other polymeric materials, or between substantially 20% and substantially 40% by volume of the one or more other polymeric materials.

The hydrophobic polymeric material may be or comprise a polymethylpentene polymer or polymethylpentene based material. Polymethylpentene inherently has a low surface energy, meaning that polymethylpentene is strongly hydrophobic and oleophobic. Polymethylpentene is also a thermoplastic polymer, which may enable easy processing of the material to form a fibre. Polymethylpentene also has a low density, which may result in a lightweight water-repellent fibre. Polymethylpentene also has a high melting point and good chemical resistance, making it suitable for use in a wide variety of applications.

The polymethylpentene polymer may be or comprise a 4-methyl-1-pentene polymer. The polymethylpentene polymer may be or comprise a copolymer of 4-methyl-1-pentene with one or more α-olefins. The one or more α-olefins may each have or comprise between 2 and 20 carbon atoms.

Additionally or alternatively, the hydrophobic polymeric material may be or comprise one or more of an α-polyolefin (such as polypropylene, polyethylene, polybutylene, polybutene etc.), a polyester, a nylon, a thermoplastic polymer, a polysaccharide (such as cellulosic polymers, chitosan etc.) or a protein-based material.

According to a second aspect, there is provided a water-repellent yarn for a fabric or textile comprising at least one water-repellent fibre according to the first aspect. The yarn may be or comprise a plurality of fibres twisted together, wherein at least one of the fibres is a water-repellent fibre according to the first aspect.

The yarn may have or comprise a diameter of between substantially 200 nm and substantially 1000 μm. The yarn may have or comprise between substantially 15 twists/m and substantially 2000 twists/m.

According to a third aspect, there is provided a water-repellent plied yarn for a fabric or textile comprising at least one water-repellent yarn according to the second aspect. The plied yarn may be or comprise a plurality of yarns twisted together, wherein at least one of the yarns is a water-repellent yarn according to the second aspect.

The plied yarn may have or comprise a diameter of between substantially 400 nm and substantially 5000 μm. The plied yarn may have or comprise between substantially 15 twists/m and substantially 2000 twists/m.

According to a fourth aspect, there is provided a fabric or textile comprising at least one water-repellent fibre according to the first aspect, and/or at least one water-repellent yarn according to the second aspect and/or at least one waterproof plied yarn according to the third aspect.

The fabric or textile may be woven. The at least one water-repellent fibre, at least one water-repellent yarn and/or at least one water-repellent plied yarn may form or provide one or more warp threads and/or one or more weft threads of the fabric or textile. Alternatively, the fabric or textile may be knitted, or may be non-woven.

According to a fifth aspect, there is provided a garment comprising the fabric or textile of the fourth aspect. The garment may be or comprise a top such as a t-shirt, a vest, a shirt, a jumper, a sweatshirt, a hoodie or a coat. Alternatively or additionally, the garment may be or comprise a pair of shorts, a pair of trousers, a pair of tights, a pair of leggings, a sock or a shoe. The garment may be or comprise an item of personal protective equipment (PPE), for example an item of PPE for healthcare such as a mask.

According to a sixth aspect, there is provided an apparatus comprising the fabric or textile of the fourth aspect. The apparatus may be or comprise an item of outdoor equipment, for example camping equipment such as a tent, sleeping bag, or a geotextile. Alternatively, the apparatus may be an upholstered item, for example an item of furniture such as a chair or sofa, or a vehicle seat etc. The apparatus may be an interior textile product for a building (for example a house) such as a carpet, curtains etc., or for a vehicle (for example a car, train, aeroplane etc.) such as a vehicle floor, vehicle seat etc.

According to a seventh aspect, there is provided a method of manufacturing a fibre for a yarn and/or a fabric or textile. The method may comprise forming a fibre comprising a hydrophobic material. The method may comprise providing the fibre with a shape or configuration comprising one or more micro and/or nano-sized structures.

The method may comprise extruding a material comprising a hydrophobic material to form a fibre. Providing the fibre with a shape or configuration comprising one or more micro and/or nano-sized structures may comprise extruding the material through a nozzle. The nozzle may have or comprise a structure configured to impart one or more micro and/or nano-sized structures on an outer surface of the fibre (for example, during extrusion of the fibre).

The material may comprise a mixture of a hydrophobic material and a filler material. Providing the fibre with a shape or configuration comprising one or more micro and/or nano-sized structures may comprise removing the filler material after formation of the fibre. Removing the filler material may comprise dissolving the filler material.

Removing the filler may provide the fibre with one or more recesses and/or projections in an outer surface of the fibre.

The method of the seventh aspect may be used to produce a fibre according to the first aspect. The method of the sixth aspect may be particularly suitable for producing a fibre according to the first aspect comprising a hydrophobic polymeric material.

Features which are described in the context of separate aspects and embodiments of the invention may be used together and/or be interchangeable wherever possible. Similarly, where features are described in the context of a single embodiment for brevity, those features may also be provided separately or in any suitable sub-combination. Features described in connection with the fibre of the first aspect may have corresponding features definable with respect to one or more of the yarns of the second and third aspects, the fabric or textile of the fourth aspect, the garment of the fifth aspect, the apparatus of the sixth aspect or the method of the seventh aspect, and vice versa, and these embodiments are specifically envisaged.

Like reference numerals in different Figures may represent like elements.

show a conventional durable water repellent (DWR) coatingdisposed on or applied to a fabric or textile substrate. The coatingis a separate and distinct layer from the substrate. DWR coatings are typically made from perfluorinated compounds (PFCs) or silicone-based materials. The molecular structure of the coatingis shown schematically in.

shows the coatingon or shortly after initial application onto the substrate. On or shortly after initial application, the coatingis substantially intact and provides a substantially continuous water repellent (and typically oil repellent and anti-stain) layer across the substratethat protects the fabric from moisture.

shows the coatingafter a period of use. After a period of use, the coatingis no longer intact or continuous across the substrate. Rather, due to abrasion and/or contamination of the coating during use, areas of the coatingbecome ineffective or are removed from the substrate entirely. That means that the coatingno longer provides a water repellent layer across the substrate. Where the underlying substrateis exposed or no longer protected due to abrasion and/or contamination of the coating, moisture can easily reach the substrateas shown. The water repellent properties of the coatingare therefore significantly compromised. In addition, the water repellent performance of the coatingcontinues to decrease as the coatingis further abraded and/or contaminated during further use.

show schematically how surface roughness can alter, for example enhance or amplify, the inherent physical and/or chemical properties of a material or surface. In particular,show how surface roughness can alter the hydrophobic or hydrophilic nature of a material or surface. For an inherently hydrophobic material, the contact angle of a liquid dropleton a surface is significantly higher for a rough surfacethan for a smooth surfaceas shown in. Similarly, for an inherently hydrophilic surface, the contact angle of a liquid dropleton the surface is significantly lower for a rough surfacethan for a smooth surfaceAlthough surface roughness is depicted schematically by a plurality of substantially rectangular projections in, it will be appreciated that the same principle of altering the inherent physical and/or chemical properties of a material or surface may be applied using any suitable structure to provide surface roughness.

shows a water-repellent fibrein accordance with an embodiment of the invention. The fibreis formed from or comprises a hydrophobic material, and comprises one or more micro and/or nano-sized structures. In the embodiment shown, the fibreis formed from a polymethylpentene polymer and comprises a star-shaped cross-section. The star-shaped cross-section has six micro and/or nano-sized structures, each structureforming a point or arm of the star, but that is not essential. The fibrehas a diameter of approximately 1 μm (e.g., from an outer point of one structureto an outer point of another structurepositioned directly opposite), but that is not essential. Each structurehas a height or depth of approximately 100 nm (e.g., from a base of the structurewhere it joins a central part of the fibreto an outer point of the structure), but that is not essential. The structureshave a substantially uniform height and are distributed around the cross-section of the fibresubstantially uniformly (e.g., the fibrehas a substantially regular cross-sectional shape), but that is not essential.

By combining a hydrophobic material with one or more micro and/or nano-sized structures, the fibrehas enhanced hydrophobic performance relative to the inherent hydrophobic properties of the hydrophobic material. Incorporating the fibreinto a yarn for a fabric or textile, or directly into a fabric or textile, may provide a yarn, fabric or textile having enhanced water repellent, oil repellent, anti-fouling and anti-stain properties without requiring a separate coating. The improved properties of the yarn, fabric or textile may be more durable and longer lasting than those provided by a separate coating. A separate coating is susceptible to contamination and abrasion during use of the yarn, fabric or textile, leading to reduced hydrophobic performance over time. In contrast, because the hydrophobic properties of the fibreare integral to the fibreitself, the hydrophobic performance of the yarn, fabric or textile is also integral to the yarn, fabric or textile and is not dependent upon a coating that can be removed from the yarn, fabric or textile.

The star-shaped cross-section may alternatively have any suitable number of micro and/or nano-sized structuresthat each form a point or arm of the star, for example three or more structures. The fibremay alternatively have any suitable diameter, for example between substantially 100 nm and substantially 500 μm. Each structuremay alternatively have any suitable height or depth, for example between substantially 10 nm and substantially 100 μm, or up to substantially 10% of the diameter or thickness of the fibre. Adjacent structuresmay be spaced any suitable distance apart, for example between substantially 10 nm and substantially 100 μm apart.shows an example of how the diameter D, structure height I and structure spacing L may be determined or measured for a fibre such as the fibre.

show other possible cross-sectional shapes or configurations for a water-repellent fibrein accordance with embodiments of the invention.

shows a fibrehaving a cross-shaped cross-section. Each arm of the cross forms or provides a micro and/or nano-sized structure.

shows a fibrehaving a v-shaped cross-section. Each arm of the v-shape forms or provides a micro and/or nano-sized structure.

shows a fibrehaving a substantially flat or planar cross-section (e.g., the fibrehas a tape-like configuration) comprising serrations or undulating ridges in an outer surface. The tape-like configuration of the fibremay have a slight curve to form an overall C-shape or lima bean shape.

shows a fibrehaving an annular cross-section comprising a bore through a length of the fibre. In that embodiment, the internal bore forms or provides a micro and/or nano-sized structure. The internal bore may enable the fibreto be lightweight as well as having enhanced hydrophobic properties.