This invention relates to a fibre particularly to a hollow polymeric fibre containing a colour component for use as an artificial hair fibre or as a fabric providing a desired aesthetic effect.

Fibres which provide a functional and/or aesthetic effect such as fibres comprising a colour-change compound, sensor fibres and the like are known. Colour-change fibres typically comprise a colour-change material and undergo colour-change due to changes in the colour of the colour-change material on exposure to an external stimulus such as a change in temperature. Natural pigments and dyes, synthetic dyes, pigments, leuco dyes and liquid crystals have been used to provide colour to a substrate. Leuco dyes and liquid crystals may also provide a colour-change effect dependent on an outside stimulus such as light (photochromic), electrical energy (electrochromic) or heat (thermochromic). The colour-change material is typically applied to the surface of the fibre.

US2008/0279253 describes thermochromic garments which provide an indication of changes of body temperature. Sensor fibres are also known which may be responsive to an external stimulus and providing an indication of the presence of or change in the stimulus, for example thermally responsive wound dressings and temperature monitoring materials used in engineering and construction. Composite sensor fibres are described in US-A-9810587.

Colour products, particularly products which include a colour-change effect, typically have a dye or pigment or a colour-change component applied to the surface of a substrate, for example a fibre. The colour material may be absorbed into the material but in other cases, for example with liquid crystal colour products, the liquid crystal may be bound to the surface of the material or dispersed within an outer layer or coating which may present certain challenges for example cracking, the colour material washing out, undesirable addition of weight or insulation to a fabric and being able to colour a mass of strands in a fabric rather than individual strands or fibres.

We have found that novel a hollow fibre having a colour component contained within the hollow fibre provides an excellent combination of functional and/or aesthetic effects in combination whilst providing desirable physical characteristics including dimensional stability and“feel” for use as an artificial hair product or fabric.

The invention provides in a first aspect a fibre comprising a self-supporting hollow polymeric sheath and, within the hollow sheath, a colour component comprising a liquid crystal providing a desired aesthetic effect wherein the self-supporting sheath imparts dimensional stability to the fibre.

The fibre of the invention may be employed in any suitable applications to provide an aesthetic effect and are especially suitable for use as an artificial hair fibre or for forming a fabric.

The term “self-supporting sheath” as employed herein means the sheath imparting structural form to the fibre and acts to contain the colour component within the cavity of the hollow sheath.

The term“dimensional stability” as employed herein means the material maintains its original properties even when temperature, humidity, pressure or other changes in ambient conditions occur and the fibre retains its flexible characteristics.

The term“feel” as employed herein refers to the sensory perception of the fibre including appearance/visual and tactile characteristics, for example tackiness, weight, width, movement of the fibre and the like in the context of its use. The feel of a fibre employed as artificial hair or artificial fur for example, will be different to the desired feel characteristics of a fibre employed in knitting a fabric.

The hollow sheath retains the liquid crystal in place. The outer polymeric layer is suitably selected such that changes in colour of the liquid crystal provide the desired visual effect to the observer and may be transparent or translucent.

When employed as an artificial hair fibre or fur, the“feel” of the fibre will be gauged against the“feel” characteristics of natural hair or fur, including how the fibre appears, for example the gloss and lustre of the fibre and the degree to which the fibre appears natural, the weight and width of the fibre and sensation to touch and tactility, not forming clumps, movement of the fibre and the like.

When employed in a fabric, the“feel” of the fibre refers to characteristics which are relevant to a fabric and desirably similar to a natural fabric, such as sensation to the touch, especially if worn against the skin, natural flexibility and the like.

Advantageously, the aesthetic effect of the fibre may be tailored according to the desired application by employing a liquid crystal having the desired colour-change, or not changing colour, at temperatures which may be expected in the field of application. Other components may also be included with the liquid crystal to provide a particular aesthetic effect. The user accordingly is afforded a great deal of flexibility in tailoring the product to provide the desired aesthetic effect whilst the liquid crystal is protected by the hollow sheath and considerations of binding the liquid crystal to a substrate or fibre do not arise.

The colour component may provide a colour-change or a fixed colour.

Colour may be imparted to the fibre by the colour component and, optionally as desired, the hollow sheath may comprise a colour component which may be the same or different to the colour component contained within the hollow cavity of the sheath.

The fibre is especially suitable for use as artificial hair, for example a hair extension, a hair sample, wig or the like. Desirably, the colour component within the sheath and, optionally, the sheath itself are coloured so as to mimic a natural hair colour in one state and an artificial colour in a second state once activated, for example under thermal stimulus.

Hair fibres typically have a diameter of 15 to 150 microns, more usually 40 to 120 microns. The invention also provides artificial hair comprising fibres according to the invention wherein the fibres have a diameter of 15 to 150 microns, preferably 40 to 120 microns.

The colour component may provide a fixed colour or a change in colour due to an external stimulus, for example a change in temperature, pressure or tension and electrical energy.

An encapsulated liquid crystal or an unencapsulated liquid crystal may be employed but an unencapsulated liquid crystal is preferred. The liquid crystal may be reversible such that it may pass from one state to another and return to the original state or irreversible in which case, it remains in the changed state and is not able to revert to its original state.

Liquid crystals comprise optically active organic chemicals which may be sealed or encapsulated, for example by microencapsulation, or unsealed for example in a poly- disperse form, as an oil.

Liquid crystals may be encapsulated through a variety of means and materials and suitably comprises a known encapsulation material which is compatible with the liquid crystal such as a gelatin and gum arabic mixture, for example gum arabic and/or a gluteraldehyde cross-linked gelatin. Other encapsulate materials which are known or subsequently devised may be employed. Examples of other types of capsules include siloxane based capsules, thermoplastic polymer based capsules and thermoset polymer based capsules. .

Suitable liquid crystals include cholesteric liquid crystals which are typically based on or comprise cholesterol or other sterol derived compounds including cholesteryl carbonate esters. Other suitable liquid crystals include non-sterol based compounds including chiral nematic liquid crystals, for example phenyl benzoate esters. Preferably, the liquid crystal consists of a chiral nematic liquid crystal, for example a phenyl benzoate ester or a combination of a chiral nematic liquid crystal as a major component and a cholesteric liquid crystal as a minor component.

Suitable liquid crystals are available from a range of sources including LCR Hallcrest. Non-cholesterol based liquid crystals such as phenyl benzoate esters provide bright, strong colour effects with high reflectance, suitable for premium products. Cholesteric- type liquid crystals typically provide colour effects which are less intense than non cholesteric liquid crystals but are of lower cost and may be suited to larger volume markets. A mixture of non-cholesteric and cholesteric liquid crystals may be employed to optimise product performance and cost. In a preferred embodiment, the liquid crystal suitably comprises only non-cholesteric liquid crystals.

Liquid crystals show colour by selectively reflecting incident white light. Liquid crystals may reflect particular wavelengths of light according to an increase or decrease in the temperature from colourless to red through the other colours of the visible spectrum (red, orange, yellow, green, blue) in sequence and then colourless again at a higher temperature, known as the“clearing point”. The duration of each colour appearance can be tuned by altering the bandwidth to enable a specific colour to be observed for a prolonged period, also meaning that certain colours can be“deselected” in favour of others, for example red to blue, discounting green, creating a two-tone effect, or red, orange, yellow creating a tri-tone effect. When the liquid crystal is in its colourless state, the underlying colour of the core or other components in the fibre may be visible. Such colour changes are reversible such that on cooling the colour change occurs in reverse. The temperature at which commencement of colour change, referred to as the “starting point” or clearing point occurs and the temperature spread over which colour change occurs, referred to as the“bandwidth” may be tuned according to the composition of the liquid crystal.

The colour component comprising the liquid crystal may also comprise a dye and/or a pigment which is a fixed colour. The dye may be any colour, for example black, red or blue. In a preferred embodiment, the colour component comprises an oil soluble dye, carbon black, iron oxide, mica, graphite synthetic melanin and polydopamine pigment. Examples of suitable black dye or pigments include products available under the trade name Ml NISO. A dye and/or pigment may accordingly be selected according to the intended desired effect. A pigment may provide a more singular colour change.

In an especially preferred embodiment, the colour component further comprises a black component, for example an oil soluble black dye, carbon black and carbon nanotubes, available for example as VANTA BLACK.

In some embodiments, a“static” colour may be required. The term“static” as employed herein refers to a colour-change material which does not present a change in colour within the range of normal usage for the particular application. Thus while the colour component is capable of colour, it does not typically exhibit colour change under the conditions of use and shows a fixed colour. The colour component may comprise any material which presents a single colour in the conditions in which the composition is to be is used. A single colour may be provided by a colourant which does not change colour, for example a dye and/or a pigment or by a liquid colourant which is capable of colour change for example a liquid crystal or leuco colourant, but which colour change does not occur under the conditions of normal usage of the composition.

The colour component may comprise a static liquid crystal, and optionally a dye and/or a pigment which is a fixed colour. The dye may be black or blue, for example carbon black. In a preferred embodiment, the colourant comprises carbon black, iron oxide, mica, graphite synthetic melanin and polydopamine pigment. Examples of suitable black dye or pigments include products available under the trade name MINISO. A dye and/or pigment may accordingly be selected according to the intended desired effect. A pigment may provide a more singular colour change.

The term “singular” refers to a“two-tone” colour system, either a static colour or a marked colour change from colourless to coloured, or coloured to colourless, or from a first colour to a second colour, or a fluctuating colour between two colours as opposed to the traditional spectrum of colours, red, green and blue and transition between them typically observed with liquid crystal. For example a singular liquid crystal system may fluctuate between two colours such as green and blue without showing red. The term “singular” also refers to a single colour being observed above or below a certain pre determined or tailored temperature.

In one embodiment, the colour change properties may be enhanced by combining different systems of liquid crystal within the same fibre, by mixing different liquid crystals, for example, combining a liquid crystal mixture that activates between 20 to 25 °C with a mixture that activates between 30 to 35 °C. Advantageously, a fibre with multiple liquid crystals with different activation ranges allows multiple colour changes to occur within the same fibre, at different temperatures, providing a dynamic effect across a broader temperature range. In addition, multiple fibres containing different temperature responsive liquid crystals may be combined within the same fabric and interweaved so that they may be activated at different times.

The self-supporting hollow polymeric sheath defines a cavity which the colour component is disposed and retains the flowable colour component. In addition to the colour component in the cavity, a further colour component may be present within the sheath, for example as a dispersed phase within the polymer wall. Such a further colour component may comprise an unencapsulated liquid crystal, encapsulated liquid crystal, dye, pigment, or other materials which contribute to the appearance of the fibre

The polymeric sheath layer suitably comprises a polymer which is suitably melt-flowable and exhibits good flexibility, particularly in an undrawn state. The material suitably also is clear and desirably translucent or transparent to facilitate observance of the desired effect, and the colour component in the cavity. The polymeric sheath is also suitably resistant to physical wear and abrasion especially where the fibre is employed in making a fabric, to provide resilience in a typical knitting process to preserve the appearance of the fibres and to protect the internal components of the fibre from physical damage or the hollow sheath from rupture and leakage. Desirably, the polymer is also resistant to stress-whitening in the knitting process. Suitably, the polymer is selected to obtain a non- tacky finish to allow for it to be used in standard knitting processes without sticking to itself or production apparatus.

Suitably, the outer polymeric sheath comprises a polymer which is immiscible or at most partially miscible with the liquid crystal and may be selected from a wide range of polymers including poly olefins, polyethylene terephthalate, nylon, modacrylic, that is any thermoplastic polymer modified with from about 35 to 85% of acrylonitrile units, thermoplastic polyurethanes for example the ELASTOLLAN range from BASF, thermoplastic elastomers, for example the AFFINITY range from Dow, thermoplastic olefins, for example EPDM, polyesters, polyethylene, polypropylene, thermoplastic vulcanizate, for example SANTOPRENE from Exxon.

In a preferred embodiment, the polymer is selected from a polyurethane, nylon and modacrylic. Suitable polyurethanes include ether based polyurethanes and, preferably ester based polyurethanes, for example ELASTOLLAN 1180 Other polymers may be employed but are less preferred. Examples of suitable polymers include polyurethane available under the trade name ELASTOLLAN B85A 1000 from BASF and NYLON 6 NATURAL BS10 available from Schulman.

In a preferred embodiment, the polymer sheath comprises a polyolefin, more preferably, polyethylene, polybutylene and polypropylene. The polymer sheath may comprise a copolymer, preferably a thermoplastic elastomer suitable for polymer modification, more preferably a copolymer of 2 or more alkenes, especially a copolymer of a 1 to 4 carbon alkene and a 6 to 10 carbon alkene, for example ethylene-1 -octene , available under the trade name LUCENE from LG Chem, for example LUCENE LC670 and isotactic polypropylene, for example VISTAMAXX 6202 available from ExxonMobil. In a preferred embodiment, the polymer sheath consists of solely polypropylene or comprises from 50 to 99%, 60 to 90% and especially 70 to 85% polypropylene and from 1 to 50%, 10 to 40% and especially 15 to 30% of a thermoplastic elastomer, preferably a copolymer of two olefins, especially ethylene-1 -octene. The fibre may comprise one or more additional components in the colour component within the cavity of the sheath and/or within the polymeric sheath. In one embodiment, additional components include one or more further colour components. If used within the cavity, the further colour component preferably comprises a dye which may be oil-based or a powder pigment, especially a dark colour component, for example carbon black, carbon nano tubes, such as VANTA BLACK. For inclusion within the polymeric sheath, the additional colour component may be a powder pigment or dispersion of a pigment, for example an inorganic powder pigment but is preferably an oil soluble dye, for example a red dye and a black dye. Examples of suitable dyes include SUDAN Black B and SUDAN III. Suitably the further colour component is employed at a level of 0.1 to 3 %, and especially from 0.2 to 0.6%.

If an encapsulated liquid crystal is present in the cavity or the outer sheath, any additional colour component will be water-based to avoid compromising the encapsulation of the liquid crystal. Where an unencapsulated liquid crystal is employed, the dye is suitably comprises an oil soluble dye, preferably a black oil soluble dye or a red oil soluble dye. Where an encapsulated liquid crystal is employed, an oil soluble dye may be employed within the encapsulate, intimately mixed with the encapsulated liquid crystal. If a soluble dye is employed outside of the encapsulate, such a dye should be water soluble so as to reduce the risk of adverse interaction with the encapsulating material

Further optional components that may be included within the cavity of the sheath and/or in the polymeric sheath alone or in combination itself include a component which undergoes a solid liquid phase change at a temperature under 50°C, to provide a change in rigidity between being flexible when warm and solid when cool, for example gallium, wax to provide opacity and structural change due to a change in temperature, typically being translucent and flexible when warm and opaque and hard when cold The fibre may further comprise a further colour component in the outer sheath. The colourant is suitably a fixed colour which enables or enhances visual appearance or enhancement of the properties of the liquid crystal. The colourant may be any colour for example red, orange, yellow, green, blue, indigo, violet, brown and black. Lighter colours may offer a pearlescent or opalescent effect. The colourant may be incorporated into the polymer sheath as a powder at any desired level. Examples of suitable colourants include the Sicopal®, Magnapearl® DF Series, Eupolen®, Micranyl®, Microlen® ranges available from BASF. The outer sheath may comprise a leuco dye, which may be reversible or irreversible as regards colour -change.

The fibre composition may further comprise a UV stabiliser. Liquid crystals may be prone to degradation due to the impact of UV radiation. Any known approved UV stabilisers that are compatible with the system may be employed. Preferred UV stabilisers include UVA stabilisers such as Tinuvin® from BASF, Benzophenone-4, Avobenzone, Homosalate, Octocrylene, Benzophenone-5, Ethylhexyl Dimethyl PABA, Titanium oxide, Zinc oxide, Phenylbenzimidazole sulfonic acid, PEG-25 PABA, disodium phenyl dibenzimidazole tetrasulfonate.

The polymer sheath may contain other additives. Examples of suitable additives include additives to provide biodegradability and antibacterial characteristics, for example silver, suitably as nanoparticles. Suitably UV stabilisers and other additives are employed in conventional amounts, typically from 0.1 to 5% by weight of the polymer sheath..

The fibre suitably provides a yarn which may be used as a single yarn as a hair extension or other hair product or to provide an artificial fur or a fabric, for example a knitted fabric. Fibres or fabric according to the invention may be in the form of a knitted fabric, woven tassle, embroidered, crochet, a wig-extensions, hair extension, artificial fur, toys, dolls, brushes and colour boards where samples of artificial hair may be displayed to illustrate effects.

The invention provides in a further aspect, a fabric comprising a multitude of fibres according to the invention interlinked, for example by weaving or knitting. The yarn monofilament may also be used in bulk to create a multifilament yarn, by entwining several monofilaments together. The fibre or yarn may also be used as a mono or multi filament for fine detail embroidery of patterns or designs onto existing clothing or fabric by hand or by machinery.

The thickness of the fibre or yarn, traditionally referred to as the yarn weight, can be tuned for specific applications by modifying the drawing process during extrusion of the fibre or yarn whereby increasing the draw reduces the thickness of the fibre or yarn. The fibre or yarn weight can range from 0.1 ply to 16 ply therefore enabling a variety of fabric applications ranging from embroidery to chunky knit. Some example yarn weights (ply) and knit application are given in Table 1. Table 1

The fibre is suitably adapted to provide an effect as required by the user, for example transparent to opaque, matt to shiny, reversible colour-change and irreversible colour- change.

The fabric suitably complies with any applicable regulations or industry standards in the field in which the fabric or fibre is being employed, for example weight requirements for performance fabrics, wash-fastness, rub-fastness, UV-fastness and regulations in the automotive, airline and other industries where fibres and fabrics of the present invention may be employed.

Suitably, the fibre has a light fastness which meets the criteria set out in ISO 105- B02:2014. As desired, the fibre may comprise a known UV absorber, preferably within the outer polymeric layer.

The fibre or a fabric produced from the fibre is suitably resistant to abrasion and meets the criteria set out in ISO 12947-2:2016.

Where the fibre is knitted or woven into a fabric, the yarn preferably provides suitable twist and recovery when tension is released to determine if it is suitable for knitting. The fibre may be incorporated in an article or a fabric as a component part of the whole or as a“patch” as a discrete area of the fabric, for example a knitted yarn or article. The invention further comprises an article, for example an item of apparel, clothing, footwear or the like, comprising a surface patch comprising a colour change fibre or fabric according to the invention.

In a further aspect, the invention provides a process for the production of a fibre according to the invention which comprises feeding a polymer melt into an extrusion channel so as to produce an extruded hollow polymeric tube, feeding a flowable colour component comprising a liquid crystal into a zone within the hollow tube so as to fill the polymeric hollow tube whereby the polymer is extruded to form a sheath around the liquid crystal component thereby to form a fibre according to the invention.

Preferably, the polymer melt is extruded through a“spider” die which facilitates a more even flow of the melt and provides a more stable fibre.

Suitably, a fibre of the invention is produced by employing an extruder preferably a “spider” die, as illustrated in Figure 1. A polymer melt for forming the outer polymeric sheath is passed though outer channel 1 (Feed B) to form a hollow sheath. Liquid crystal and optionally other components are mixed together and tailored according to the desired colour effect to provide a colour component. The colour component is passed through channel 2 (Feed A) and out of the die nozzle 3 with the nozzle 3 being position such that the polymer forms a sheath around the colour component. The channel 2 is equal to or suitably extends beyond the exit of nozzle 3 such that the liquid crystal may flow into the cavity within the formed outer sheath. Suitably, the formed fibre is carefully withdrawn by attachment to a winder at a controlled speed. By varying the speed of the winder, the thickness of the outer sheath may be adjusted to the desired thickness.

Figures 2a to 2f show photographs of fibres according to the invention with the fibres in Figures 2a, 2c, 2e being in the unactivated or“natural” state and the same fibres being shown in Figures 2b, 2d and 2f respectively in their activated or“coloured” state.

Figure 3 shows a schematic perspective view and cross-sectional view of a fibre according to the invention.

The invention is illustrated by the following non-limiting examples. All percentages and parts are parts by weight and all measurements made are at 25° C, unless otherwise stated. Examples

Fibres according to the invention were prepared by passing a colour component through a dye with an outer coaxial zone for passage of the outer polymeric sheath. The outer polymeric sheath enclosed the colour component to produce a fibre according to the invention.

Fibres having the components listed in Table 2 were prepared and the colour component is referred to as the“core”. Where the colour component or outer layer comprised additional components to the liquid crystal or polymer respectively, the respective components were pre-mixed with the main component before extrusion. The polymer sheath was extruded at a draw speed of between 30 and 60 rpm and with an inlet/middle/outlet barrel temperature of 240-320/240-260/250-260. The colour component was introduce manually.

Table 2

The fibres were produced by extruding the polymer and the core component. All fibres were adequately formed and flexible and were suitable for processing into a yarn and weaving into a fabric.

On application of heat, the liquid crystal to change colour. Those examples containing solely nematic liquid crystal provided the greater vibrancy and intensity of colour change.

Examples 5 and 6 included an oil soluble dye in the liquid crystal which provided enhanced brightness of colour

Example 7

An artificial hair product comprising fibres produced in Example 2 was prepared, the fibres having a diameter of 40 to 120 microns. After production of the fibre, the fibre was dyed using a sublimation dye bath for 30 minutes, heated to a temperature of 80 °C. The sublimation dye bath can be tuned to obtain any natural hair colour in the fibre, using different dilutions of black or brown dye. The artificial hair product in its initial state was a natural hair colour. On application of heat to provide a temperature change of less than 5°C, the colour component changed colour as a result of the liquid crystal changing state to provide a desirable aesthetic effect.