FIBRE COMPRISING COMPOSITE FIBRES OF CELLULOSE AND CELLULOSE ACETATE

The present invention relates to fibres. More specifically, the present invention relates to fibres which can be dyed with a disperse dye.

There are two distinct types of fibres used in the manufacture of textiles, namely natural fibres, for example cellulose fibres, and synthetic fibres, for example polyester, nylon and cellulose acetate fibres.

An important step in the manufacture of fibres, particularly those used in the manufacture of textiles, is the step of dyeing the fibres.

Cellulose fibres are hydrophilic and are therefore commonly dyed using water-soluble dyes such as acid dyes, direct dyes, reactive dyes and sulfur dyes. Alternatively, cellulose fibres are sometimes dyed using vat dyes. Vat dyes are essentially insoluble in water and incapable of dyeing fibres directly. Instead, reduction in alkaline liquor produces a water-soluble alkali metal salt of the dye which has an affinity for the fibre. However, these processes consume large volumes of water and generate significant quantities of coloured aqueous effluent.

Synthetic fibres, such as polyester fibres, nylon fibres and cellulose acetate fibres, tend to be hydrophobic and therefore have poor affinity for the aqueous dyes outlined above. Disperse dyes were developed in the 1920's for dyeing cellulose acetate fibres. Disperse dyes tend to be hydrophobic, non-reactive, traditionally non-ionic, dyes that are used as surfactant-stabilised dispersions in water. Disperse dyes are often selected from substituted monoazo or diazo compounds, anthraquinoid compounds, and nitro or amino ketone compounds.

Disperse dyes have an excellent affinity for synthetic fibres such as polyester, nylon and cellulose acetate. However, conventional processes using disperse dyes are not used to dye cellulose fibres due to the poor affinity of the hydrophobic disperse dyes for the hydrophilic cellulose fibres.

Attempts have been made in the prior art to manipulate cellulose fibres in order to improve their affinity for disperse dyes.

For example, Canadian patent application number 1072260 describes a process for dyeing a cellulose fibre fabric using disperse dyes, which includes reacting a cellulose fibre fabric with an aromatic acylating agent having an acyl group to form a cellulose derivative fabric having a substitution degree between 0.10 and 0.50, and transferring a disperse dye onto the fabric.

United States patent number 5,298,032 describes a process for dyeing cellulosic textile materials with disperse dyes from supercritical CO2 by treating the textile materials with an auxiliary that promotes dye uptake, such as a polyalkylene glycol, an alkanolamine or an aromatic compound with several hydroxyl groups. However, the additional steps required to render the cellulose fibres suitable for dyeing with disperse dyes, significantly increase the cost and complexity of the manufacturing process.

Synthetic fibres offer many advantages over natural fibres, for example synthetic fibres may be strong and light weight, fast drying and/or resistant to wrinkles and creases. However, synthetic fibres may be considered to have an unacceptable feel and/or appearance for certain textile applications. To address this issue, it is known to blend synthetic fibres with other synthetic or natural fibres. Common examples of fibre blends include polyester/cotton blends and polyester/viscose blends.

However, there are drawbacks associated with the use of synthetic/natural fibre blends. In particular, synthetic/natural fibre blends require more complex, multi-stage dyeing processes. For example, a reactive dye may be used to dye the cellulose component e.g. cotton or viscose, and a disperse dye may be used to dye the polyester component. Dyeing times of up to 8 hours for such fibre blends are not uncommon.

Attempts have been made in the prior art to simplify the dyeing process of fibre blends.

For example, United States patent number 3,706,525 describes a process for dyeing water swellable cellulosic materials or mixtures or blends thereof with synthetic materials, which includes contacting the cellulosic material with water in any sequence with water in sufficient amounts to swell the cellulose, a preformed dye of low water solubility, and a dye solvent which is an ethylene glycol or a polyethylene glycol, provided that at some stage during the process the interior of the swollen cellulose is contacted with a solution of the dye in aqueous dye solvent or dye solvent.

United States patent number 3,713,767 describes a process for the dyeing of textile materials consisting of mixtures of polyester fibres with cellulose fibres, wherein the textile materials are treated with an alkaline solution which contains a coupling component, a disperse dyestuff and wetting or dispersing agents, dried and subsequently treated with an acid solution which contains, in addition to compounds having an acid reaction, a diazotized aromatic or heterocyclic amine, dried and then subjected to a heat treatment.

United States patent number 5,695,375 describes a textile product comprising regenerated cellulose fibres containing 10 to 40 weight % of polymer fine particles with an average particle size of 0.05 to 5 μιτι, which are dyeable with a disperse dye, and polyester fibre.

However, the prior art processes for dyeing natural/synthetic fibre blends still require complex, multi-stage dyeing processes which result in an increase in manufacturing costs.

There have also been attempts made in the prior art to intimately combine synthetic and natural fibres to impart certain characteristics of one type of fibre to the other.

United States patent number 6,258,304 describes a process for the preparation of lyocell fibre or film by extruding a solution of cellulose in amine oxide through a spinneret or film die at elevated temperature via an air gap into an aqueous precipitation bath, thereby to form said fibre or film.

Our international application number WO201 1/048420 describes a biodegradable fibre comprising composite filaments of cellulose and cellulose acetate, and a process for making such a fibre comprising providing a solution dope comprising a blend of cellulose and cellulose acetate in an ionic liquid or in N-methylmorpholine (NMMO), and spinning the blend into a protic solvent to generate fibres.

The present invention seeks to address the problems associated with the prior art.

In accordance with the present invention there is provided a coloured fibre comprising one or more composite filaments of cellulose and cellulose acetate, wherein the colour is effected by a disperse dye.

Reference herein to composite filaments of cellulose and cellulose acetate shall be understood to mean filaments spun from a dope comprising cellulose and cellulose acetate.

Composite filaments of cellulose and cellulose acetate spun from the dope may comprise: a continuous phase of cellulose containing dispersed phases of cellulose acetate; a continuous phase of cellulose acetate containing dispersed phases of cellulose; and/or a co-continuous phase of cellulose and cellulose acetate, for example. The inventors of the present invention have surprisingly found that fibres comprising one or more composite filaments of cellulose and cellulose acetate have a good affinity for hydrophobic disperse dyes. Such fibres can be manufactured without the need for additional chemical treatments such as the hydrophobisation of the cellulose component through chemical derivatisation as in Canadian patent application number 1072260, or the addition of a coupling component as in Unites States patent number 3,713,767.

Without wishing to be bound by any such theory, the inventors of the present invention believe that the hydrophilic cellulose in the composite filaments swells up when contacted with the aqueous portion of a disperse dye or with the supercritical CO2 used in the disperse dyeing process. It is believed that when the cellulose swells up in this manner, the disperse dye can more easily penetrate the hydrophobic part of the fibre i.e. the cellulose acetate. As a result, the entire fibre can be readily dyed with the disperse dye.

The weight ratio of the cellulose to the cellulose acetate in the composite filaments may be from 99:1 to 1 :99, from 95:5 to 5:95, from 90:10 to 10:90, from 80:20 to 20:80, from 70:30 to 30:70, or from 60:40 to 40:60. The weight ratio of the cellulose to the cellulose acetate in the composite filaments may be from 90:10 to 50:50, from 80:20 to 50:50, from 70:30 to 50:50, or from 60:40 to 50:50.

Advantageously, the affinity of the fibre for the disperse dye can be varied by altering the weight ratio of the cellulose to the cellulose acetate in the composite filaments, thereby making the fibre more or less hydrophilic. This may be useful for varying the colour intensity of the fibre, and means the colour intensity of the fibre can be tailored according to a manufacturer's requirements. In addition, by reducing the hydrophilicity of the fibre i.e. by increasing the cellulose acetate content, the fibre may become less receptive to waterborne stains.

The disperse dye may be any known suitable disperse dye. For example, the disperse dye may be selected from: anthraquinone dyes, for example Colour Index Disperse Red 15, Colour Index Disperse Red 60, Colour Index Disperse Violet 4 and Colour Index Disperse Violet 26; azo dyes, for example Colour Index Disperse Yellow 3, Colour Index Disperse Orange 25, Colour Index Disperse Red 167, Colour Index Disperse Violet 33 and Colour Index Disperse Blue 79; nitroarylamine; coumarin; methine; naphthostyryl; formazan; and benzodifuranone.

The coloured fibre may be used as a bleach activator.

In this context, the term 'bleach activator' is used to describe a material that is capable of reacting with a peroxide and/or a peroxide precursor, to form peracetic acid.

Also provided in accordance with the present invention is a fibre blend comprising fibres comprising one or more composite filaments of cellulose and cellulose acetate; and synthetic fibres, wherein the fibre blend is dyeable with a disperse dye.

Also provided in accordance with the present invention is a coloured fibre blend comprising fibres comprising one or more composite filaments of cellulose and cellulose acetate; and synthetic fibres, wherein the colour is effected by a disperse dye.

Advantageously, the fibre blend of the present invention is capable of being dyed using a disperse dye in a single-stage process. Thus, the cost and complexity of the dyeing process are significantly reduced compared to prior art dyeing processes for fibre blends. As previously outlined, the prior art processes for dyeing natural/synthetic fibre blends require complex, multi-stage processes which result in an increase in manufacturing costs.

The synthetic fibres may be any known suitable synthetic fibres, for example polyester fibres, nylon fibres, acrylic fibres, elastane fibres, cellulose acetate fibres, cellulose triacetate fibres, polylactic acid fibres, polypropylene fibres, or polyphenylene sulfide fibres.

The fibre blend may be used as a bleach activator.

Also provided in accordance with the present invention is a textile manufactured from the coloured fibres comprising one or more composite filaments of cellulose and cellulose acetate as hereinbefore described.

Also provided in accordance with the present invention is a textile manufactured from the fibre blend as hereinbefore described. Also provided in accordance with the present invention is a textile manufactured from the coloured fibre blend as hereinbefore described.

Also provided in accordance with the present invention is a textile manufactured from fibres comprising composite filaments of cellulose and cellulose acetate, and synthetic and/or natural fibres, wherein the fibres comprising composite filaments and the synthetic and/or natural fibres are provided in separate yarn or thread.

Advantageously, the textile is capable of being dyed using disperse dyes in a single- stage process. Thus, the cost and complexity of the dyeing process are significantly reduced compared to prior art dyeing processes for textiles having both natural and synthetic fibres. The prior art processes for dyeing textiles having both natural and synthetic fibres require complex, multi-stage processes which result in an increase in manufacturing costs.

The textile provided in accordance with the present invention will have a unique combination of physical, aesthetic and tactile properties. These properties can be adjusted through the optimisation of the weight ratio of the cellulose to the cellulose acetate in the composite filaments and/or by altering the fibre morphology, for example the denier, cross-sectional shape and degree of elongation during the spinning of the fibres.

The denier per filament may be from about 0.1 to about 100 g/9000m. Preferably, the denier per filament is from about 0.3 to about 50 g/9000m or from about 0.5 to about 25 g/9000m. The cross-sectional shape may be selected from flat, circular, elliptical, triangular, hexagonal, rounded triangular, trilobal, lobular, mushroom-shaped, dog-bone-shaped, ribbon-shaped, star-shaped, hollow/tubular and collapsed tube.

The degree of elongation may be from about 0% to about 100%, from about 0% to about 75% or from about 0% to 50%.

The textiles as hereinbefore described may be used as a bleach activator.

Also provided in accordance with the present invention is a garment or soft furnishing made at least partly from the textile as hereinbefore described.

Also provided in accordance with the present invention is a process for manufacturing the coloured fibre as hereinbefore described, comprising: providing a solution dope comprising a blend of cellulose and cellulose acetate in an ionic liquid or in N- methylmorpholine-N-oxide; spinning the solution dope into a coagulant to generate fibres; and dyeing the fibres with a disperse dye.

Also provided in accordance with the present invention is a process for manufacturing the coloured fibre as hereinbefore described, comprising: providing a solution dope comprising a blend of cellulose and cellulose acetate in an ionic liquid or in N- methylmorpholine-N-oxide; adding a disperse dye to the solution dope; and spinning the solution dope with the disperse dye into a coagulant to generate coloured fibres. This process does not require a separate dyeing step after the fibres have been generated. Rather, by adding the disperse dye to the solution dope i.e. by 'in-dope' dyeing, coloured fibres are directly generated from the spinning step. This is advantageous as it simplifies the manufacturing process and may reduce manufacturing costs.

In addition, the 'in-dope' dyeing process may reduce chemical waste by eliminating the use of dye baths. This may reduce both the manufacturing costs and the environmental impact of the process.

Further advantageously, the ability to dose the disperse dye into the solution dope enables excess dye uptake by the fibres to be avoided, which eliminates the presence of fugitive dye. The resulting coloured fibres may, therefore, exhibit enhanced colourfastness to light, washing, crocking (rubbing), perspiration, and bleach.

The following description applies to both manufacturing processes outlined above.

The use of ionic liquids and N-methylmorpholine-N-oxide (NMMO) for dissolving cellulose and other polymers is known in the art. A wide range of ionic liquids are suitable for dissolving cellulose and cellulose acetate to form a solution dope and for spinning fibres therefrom. Suitable ionic liquids include those based on imidazole, pyrrole, thiazole, or pyrazole cations in combination with halogen, phosphite, carboxylate or metal chloride anions. Particularly preferred ionic liquids of this type include 1 -butyl-3-methylimidazolium chloride (BMIM-CI), 1 -butyl-3-methylimidazolium acetate (BMIM-Ac) and 1 -ethyl-3-methylimidazolium acetate (EMIM-Ac). Suitable ionic liquids also include those comprising a conjugate acid formed from a strong organic base, for example a substituted amidine or guanidine, in combination with a weaker Bronsted acid, for example a carboxylic acid. Particularly preferred ionic liquids of this type include 1 ,1 ',3,3'-tetramethylguanidinine carboxylates, 1 ,8- diazabicyclo[5.4.0]undec-7-ene carboxylates and 1 ,5-diazabicyclo[4.3.0]non-5-ene carboxylates.

The solution dope may also comprise a suitable co-solvent, for example an aprotic solvent. Examples of suitable co-solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), tetrahydrofuran (THF), and dioxane. The co-solvent may aid dissolution of the cellulose and cellulose acetate. A particularly preferred co- solvent is DMSO.

Where a co-solvent is used, the ratio of the ionic liquid or NMMO to the co-solvent may be selected to ensure dissolution of both the cellulose and cellulose acetate, whilst providing a solution suitable for spinning into fibres.

The weight ratio of the cellulose to the cellulose acetate in the solution dope may be from 99:1 to 1 :99, from 95:5 to 5:95, from 90:10 to 10:90, from 80:20 to 20:80, from 70:30 to 30:70, or from 60:40 to 40:60. The weight ratio of the cellulose to the cellulose acetate in the solution dope may be from 90:10 to 50:50, from 80:20 to 50:50, from 70:30 to 50:50, or from 60:40 to 50:50.

Typically, the solution dope comprises a solids content of up to about 50% by weight, up to about 45% by weight, up to about 40% by weight, up to about 35% by weight, up to about 30% by weight, up to about 25% by weight, or up to about 20% by weight. Preferably the solution dope comprises a solids content of from about 5% by weight to about 25% by weight, or from about 10% by weight to about 20% by weight.

The solution dope is preferably spun using a spinneret.

The coagulant may be any suitable non-solvent. Preferably, the coagulant comprises water, methanol and/or ethanol. Water is a particularly preferred coagulant.

The disperse dye may be any known suitable disperse dye. For example, the disperse dye may be selected from those previously outlined.

The process may further include the application of a spin finish, for example an emulsifier, lubricant and/or antistatic spin finish. Preferably, an emulsifier, lubricant and antistatic spin finish are applied.

The emulsifier may be selected from one or more of: alkali surfactants; amine surfactants; glycerol mono-di-fatty acid esters; sorbitan esters; polyoxyethylene sorbitan esters; polyglycerol esters, polyoxyethylene esters; polyoxyethylene ethers; polyoxyethylene polyol ether esters; polyoxyethylene amines; polyoxyethylene amides; partial polyol ester ethoxylates; sulfated vegetable oils; and sulfonated aromatic petroleum. The lubricant may be selected from one or more of: mineral oils; alkyl esters; glycerides; silicone oils; waxes, for example paraffinic wax, naphthenic wax or polyolefinic wax; polyalkene glycols; polyoxalkylene glycols; and glycol esters.

The antistatic agent may be selected from one or more of: cationic species, including quaternary ammonium, pyridinium, imidazolium, or quinolinium species; phosphate alcohols; phosphate ethoxylates of fatty acids and fatty alcohols; amines; amides; organic sulfates; and organic sulfonates.

The process may further include drying of the fibres, preferably at raised temperatures, for example between 50°C and 150°C.

Also provided in accordance with the present invention is a process for dyeing fibres comprising one or more composite filaments of cellulose and cellulose acetate, comprising: contacting the fibres with a disperse dye; and washing the dyed fibres with water.

Also provided in accordance with the present invention is a process for dyeing the fibre blend as hereinbefore described, comprising: contacting the fibre blend with a disperse dye; and washing the dyed fibre blend with water.

The disperse dye may be applied from an aqueous dispersion or using supercritical CO2, for example. Applying the disperse dye using supercritical CO2 may have the advantages of reducing the amount of dye-containing effluent, increasing the rate of dye uptake and enabling the recycling of dyes and solvents. Advantageously, the fibre blend of the present invention can be dyed using disperse dyes in a single-stage process. The dyeing time for the fibre blend of the present invention may be significantly reduced compared to prior art dyeing processes.

The invention will now be more particularly described with reference to the following non-limiting figures and examples.

Figure 1 undyed fibres comprising composite filaments of cellulose and cellulose acetate

Figure 2: a scanning electron microscopy image of an undyed fibre comprising composite filaments of cellulose and cellulose acetate

Figure 3a a cotton fabric sample dyed with Colour Index Disperse Violet 1

Figure 3b a sample of the coloured fibres in accordance with the present invention dyed with Colour Index Disperse Violet 1

Figure 4a a cotton fabric sample dyed with Colour Index Disperse Red 279

Figure 4b a sample of the coloured fibres in accordance with the present invention dyed with Colour Index Disperse Red 279 Figures 5a to 5g: samples of fibres with varying cellulose to cellulose acetate ratios in the composite filaments dyed with Colour Index Disperse Violet 1

Figure 6: a graphical representation of the CIE L ^* a ^* b ^* colour space data for the fibre samples of Figures 5a to 5g

Figures 7a to 7g: samples of fibres with varying cellulose to cellulose acetate ratios in the composite filaments dyed with Colour Index Disperse Red 1

Figure 8: a graphical representation of the CIE L ^* a ^* b ^* colour space data for the fibre samples of Figures 7a to 7g

Figure 9: a photograph showing the difference in colour intensity of in-dope dyed fibres according to the present invention compared to in- dope dyed cellulose-only fibres

Examples

Example 1 - Preparation of Fibres

Using standard wet-spinning equipment, fibres were spun from a solution of 8 wt. % cellulose (DP ~ 450) and 8 wt. % cellulose acetate (Eastman, CA-398-30), at 16% solids in EMIM-Ac:DMSO (26:74). A cluster head containing 7 x 560-orifice spinnerets with an orifice diameter of 40 μιτι was used. The spinnerets were submerged in a water coagulation bath heated to a temperature of 80°C. The fibres were washed extensively with water, dried at 120°C and reeled up.

Figure 1 is a photograph of the resulting fibres once reeled up.

Figure 2 is a scanning electron microscopy (SEM) image of a resulting fibre.

Example 2 - Dyeing of Fibres

Violet

2 wt. % of Colour Index Disperse Violet 1 (1 ,4-Diaminoanthraquinone, Aldrich) in water was used as the disperse dye liquor. A sample of fibres prepared according to Example 1 was dyed using a disperse dye liquor to fibre ratio of 10:1 (wt./wt.), with a liquor of pH 5. The temperature of the disperse dye liquor was raised to 98°C for 45 minutes. The sample was washed thoroughly with water until the washings were colourless.

As a comparative example, a sample of cotton fabric was dyed using a disperse dye liquor to fibre ratio of 10:1 (wt./wt.), with a liquor of pH 5. The temperature of the disperse dye liquor was raised to 98°C for 45 minutes. The sample was washed thoroughly with water until the washings were colourless. Figure 3a shows the sample of cotton fabric dyed with Colour Index Disperse Violet 1 (comparative).

Figure 3b shows a sample of the fibres in accordance with the present invention dyed with Colour Index Disperse Violet 1 .

From these figures it can be seen that the sample of fibres in accordance with the present invention exhibits a much deeper, more intense violet colour and the dye is more evenly dispersed through the sample, compared to the pure cotton fabric sample.

Red

2 wt.% of Colour Index Disperse Red 279 (Terasil Red GS LA supplied by Ciba) in water was used as the disperse dye liquor. A sample of fibres prepared according to Example 1 was dyed using a disperse dye liquor to fibre ratio of 10:1 (wt./wt.), with a liquor of pH 5. The temperature of the disperse dye liquor was raised to 98°C for 45 minutes. The sample was washed thoroughly with water until the washings were colourless.

As a comparative example, a sample of cotton fabric was dyed using a disperse dye liquor to fibre ratio of 10:1 (wt./wt.), with a liquor of pH 5. The temperature of the disperse dye liquor was raised to 98°C for 45 minutes. The sample was washed thoroughly with water until the washings were colourless. Figure 4a shows the sample of cotton fabric dyed with Colour Index Disperse Red 279 (comparative).

Figure 4b shows a sample of the fibres in accordance with the present invention dyed with Colour Index Disperse Red 279.

From these figures it can be seen that the sample of fibres in accordance with the present invention exhibits a much deeper, more intense red colour and the dye is more evenly dispersed through the sample, compared to the pure cotton sample.

Example 3 - Preparation of Fibres

Using standard wet-spinning equipment, fibres were spun from solutions of cellulose (DP ~ 450) and cellulose acetate (Eastman, CA-398-30), at ratios of 100:0 (comparative), 0:100 (comparative), 90:10, 80:20, 70:30, 60:40 and 50:50, at 16% solids in EMIM-Ac:DMSO (50:50). A cluster head containing 7 x 560-orifice spinnerets with an orifice diameter of 40 μιτι was used. The spinnerets were submerged in a water coagulation bath heated to a temperature of 80°C. The fibres were washed extensively with water, dried at 120°C and reeled up.

Example 4 - Dyeing of Fibres

Violet 2 wt. % of Colour Index Disperse Violet 1 (1 ,4-Diaminoanthraquinone, Aldrich) in water was used as the disperse dye liquor. Fibre samples prepared according to Example 3 were dyed using a disperse dye liquor to fibre ratio of 10:1 (wt./wt.), with a liquor of pH 5. The temperature of the disperse dye liquor was raised to 98°C for 45 minutes. The samples were washed thoroughly with water until the washings were colourless. The samples were dried at 50°C overnight.

Figures 5a to 5g show the samples dyed with Colour Index Disperse Violet 1 , as follows:

The CIE L ^* a ^* b ^* colour space data for each of the dyed samples was determined using a Gretag Macbeth Colour-Eye 7000A Spectrophotometer in reflectance mode with D65 illumination. The CIE L ^* a ^* b ^* colour space data for the dyed samples is shown in Table 1 , where:

L ^* represents Lightness, where 0 is absolute black and 100 is absolute white a ^* represents the green to red axis, where -128 is green and +128 is red b ^* represents the blue to yellow axis, wherein -128 is blue and +128 is yellow

Table 1

Figure 6 is a graphical representation of the CIE L ^* a ^* b ^* colour space data.

From the data and figures it can be seen that the samples of fibres in accordance with the present invention exhibit good violet colouring following dyeing with the disperse dye, particularly when compared to the 100% cellulose sample.

As the proportion of cellulose acetate was increased in the fibre samples the lightness of the samples was reduced i.e. the intensity of the violet colour increased. An intense violet colour which was a close colour match to the 100% cellulose acetate sample was exhibited by the fibre sample with a cellulose to cellulose acetate ratio of 50:50. As the proportion of cellulose acetate was increased in the fibre samples both the red and the blue components increased, approaching those of the 100% cellulose acetate sample at around 50% cellulose acetate content.

Red

2 wt.% of Colour Index Disperse Red 1 (N-Ethyl-N-(2-hydroxyethyl)-4-(4- nitrophenylazo) aniline, Aldrich) in water was used as the disperse dye liquor. Fibre samples prepared according to Example 3 were dyed using a disperse dye liquor to fibre ratio of 10:1 (wt./wt.), with a liquor of pH 5. The temperature of the disperse dye liquor was raised to 98°C for 45 minutes. The samples were washed thoroughly with water until the washings were colourless. The samples were dried at 50°C overnight.

Figures 7a to 7g show the samples dyed with Colour Index Disperse Red 1 , as follows:

The CIE L ^* a ^* b ^* colour space data for each of the dyed samples was determined using a Gretag Macbeth Colour-Eye 7000A Spectrophotometer in reflectance mode with D65 illumination. The CIE L ^* a ^* b ^* colour space data for the dyed samples is shown in Table 2, where:

L ^* represents Lightness, where 0 is absolute black and 100 is absolute white a ^* represents the green to red axis, where -128 is green and +128 is red

b ^* represents the blue to yellow axis, wherein -128 is blue and +128 is yellow

Table 2

Figure 8 is a graphical representation of the CIE L ^* a ^* b ^* colour space data.

From the data and figures it can be seen that the samples of fibres in accordance with the present invention exhibit good red colouring following dyeing with the disperse dye, particularly when compared to the 100% cellulose sample. As the proportion of cellulose acetate was increased in the fibre samples the lightness of the samples was reduced i.e. the intensity of the red colour increased. An intense red colour which was a close colour match to the 100% cellulose acetate sample was exhibited by the fibre samples with a cellulose to cellulose acetate ratio of 70:30, 60:40 and 50:50.

As the proportion of cellulose acetate was increased in the fibre samples both the red and yellow components increased, approaching those of the 100% cellulose acetate sample at around 50% cellulose acetate content.

Example 5 - In-Dope Dyeing of Fibres

A solution dope according to the invention was prepared by combining 8 wt. % cellulose (DP ~ 450) and 8 wt. % cellulose acetate (Eastman, CA-398-30), at 16% solids in EMIM-Ac:DMSO (26:74).

0.25 wt. % (by weight of cellulose/cellulose acetate) of Colour Index Disperse Red 1 (N-Ethyl-N-(2-hydroxyethyl)-4-(4-nitrophenylazo) aniline, Aldrich) was added to the solution dope and stirred for 1 minute to ensure even distribution of the disperse dye.

The solution dope (including the disperse dye) was injected into a water bath using a syringe submerged into a coagulation bath, whereby the coagulant was water with a temperature of 18°C. Upon coagulation, the solution dope formed coloured fibres. The coloured fibres were washed thoroughly with clean water, and then air dried at ambient temperature. As a comparative example, a solution dope was prepared with 8 wt. % cellulose (DP ~ 450) in EMIM-Ac:DMSO (26:74). The remaining process steps were carried out as above.

It was observed that for the in-dope dyed fibres according to the present invention, there was no bleeding of the disperse dye from the fibres into the coagulation bath or during subsequent washings.

In contrast, for the in-dope dyed fibres of the comparative example (cellulose-only fibres), extensive bleeding of the disperse dye from the fibres into the coagulation bath and during subsequent washings, was observed.

As a result, the colour intensity of the fibres according to the present invention was significantly better than the colour intensity of the cellulose-only fibres.

Figure 9 shows the difference in colour intensity of the in-dope dyed fibres according to the present invention (right-hand side) compared to the in-dope dyed cellulose-only fibres (left-hand side).