Dyeing Process

The present invention is directed to a method of dyeing fibres, and more specifically to method wherein a solution is comprised of a dye and an ionic liquid. The present invention is also directed to fibres dyed in accordance with the method disclosed, and fabrics produced from such fibres.

The dyeing of natural cellulosic and protein fibres has been known for centuries. Natural colourings from fruit and plants were initially used. In more recent times, acid dyes, which bond to the hydroxyl or amino groups of the cellulosic or protein fibres, have been found to be particularly useful.

Reactive dyes are a particularly preferred type of dye for such fibres. The dyes contain a reactive functional group - generally a haloheterocycle or an activated double bond - that, when applied to a fibre in an alkaline bath, forms a chemical bond with a hydroxyl group on the fibre.

Reactive dyeing is now one of the most important commercial methods for dyeing cellulosic fibres in industry. Such dyes have also been found to be useful for application with wool and nylon fibres, particularly when applied under weakly acidic conditions.

However, a disadvantage of reactive dyes is that they have low a utilization degree, i.e. are inefficient, compared to other known dyestuffs, as the reactive functional group also reacts with water causing hydrolysis.

An example of a known dyeing process is shown in Scheme 1 below.

Copper

Scheme 1

As noted above, known dyeing processes use water, which is a good solvent for the dye molecules as it dissolves the dye. However, a significant disadvantage is that the reactive group of the dye molecule can undergo reaction with water to inactivate the attaching group. Such a process results in the dye molecule being adsorbed onto the fabric, but not chemically bonding (see Scheme 2 below).

Copper

Scheme 2

The results of water dyeing are shown in Figure 1 , where it can be seen that the dye is not 'colourfast', i.e. is not permanent, and thus the colour of the fabric will fade easily.

Ionic liquids are a novel class of solvents which have been developed over the last few years. The term "ionic liquid" as used herein refers to a liquid that is capable of being produced by melting a solid, and when so produced consists solely of ions. Ionic liquids may be derived from organic salts.

An ionic liquid may be formed from a homogeneous substance comprising one species of cation and one species of anion, or it can be composed of more than one species of cation and/or anion. Thus, an ionic liquid may be composed of more than one species of cation and one species of anion. An ionic liquid may further be composed of one species of cation, and one or more species of anion. Thus, the mixed salts used in the present invention can comprise mixed salts containing anions and cations.

The main advantages of ionic liquids compared to molecular solvents are their non-volatility, low toxicity, low flammability, applicability at wide temperature ranges and the possibility of recycling, which properties make them environmentally friendly. Such solvents are of course greatly desired for industrial processes. In addition, because of their ionic structure, they often change the reactivity of common reagents or the regio- or stereoselectivity of reactions resulting in faster reactions and higher yields.

The term "ionic liquid" includes compounds having both high melting temperature and compounds having low melting points, e.g. at or below room temperature (i.e. 15 to 30 ⁰ C). The latter are often referred to as "room temperature ionic liquids" and often derived from organic salts having pyridinium and imidazolium- based cations. As mentioned above, a feature of ionic liquids is that they have particularly low (essentially zero) vapour pressures. Many organic ionic liquids have low melting points, for example, less than 100 ⁰ C, particularly less than 100 ⁰ C, and around room temperature, e.g. 15 to 30 ⁰ C, and some have melting points well below O ⁰ C. For the purposes of the present invention, it is desirable that the organic ionic liquid has a melting-point of 25O ⁰ C or less, preferably 150 ⁰ C or less, more preferably 100°C and even more preferably 80°C or less, although any compound that meets the criteria of being a salt consisting of an anion and cation, which is liquefied at or near the reaction temperature, or exists in a fluid state during any stage of the reaction can be defined as an organic ionic liquid especially suitable for use in the processes of the present invention.

According to a first aspect of the present invention, there is provided a method of dyeing a fibre comprising the step of bringing the fibre into contact with a dye solution, wherein the solution comprises an ionic liquid.

Preferably, the dyes used in the methods of the present invention comprise one or more reactive dyes. The dyes may be monofunctional, bifunctional and/or trifunctional, and more preferably, comprise at least one reactive functional group selected from haloquinoxaline, halotriazine, vinyl sulfone, vinyl amide and/or halopyrimidine.

Still more preferably, the at least one reactive functional group may be selected

from monochlorotriazine, monofluoro-chlorotriazine, dichlorotriazine, difluorochloropyrimidine, dichloroquinoxaline, trichloropyrimidine, vinyl sulfone, vinyl monofluorotriazine amide, bis(aminochlorotriazine), bis(amino- nicotinotriazine), aminochlorotriazine-sulfatoethylsulfone and/or aminofluorotriazine-sulfatoethylsulfone.

Suitable reactive dyes for use in the methods of the present invention include those available commercially under the tradenames Basilen, Cibacron, Drimarene, Intracron, Levafix, Procion, Remazol and Sumafix.

The methods of the present invention are suitable for dyeing cellulose, silk, wool and/or polyester fibres. Preferably, the fibres are cellulose, silk and/or polyester, and most preferably cellulose. By fibre, it will be understood that it is not preferably intended to include hair on a human or animal body.

Examples of cellulose fibres include cotton, rayon, linen, hemp, jute, pulp fluff and lyocell.

The methods of the present invention may be operated at temperatures in the range of 20 to 150 ⁰ C, preferably 30 to 100 ⁰ C. The temperature required may depend on the dye being used, and the rate at which dyeing is to occur. For example, a list of preferred temperature ranges for the dyes is:

- monochlorotriazine: 75 - 85°C, preferably 80 ⁰ C

- dichlorotriazine: 25 - 35°C, preferably 30 ⁰ C

- monofluorotriazine: 45 - 55 ⁰ C, preferably 50 ⁰ C

- monofluorochlorotriazine: 35 - 45°C, preferably 4O ⁰ C

- difluorochlorotriazine: 35 - 45°C, preferably 40°C°

- dichloroquinoxaline: 35 - 55°C, preferably 40 - 50 ⁰ C

- trichloropyrimidine: 80 - 98°C, preferably 95°C

- vinyl sulfone: 35 - 65°C, preferably 40 - 60 ⁰ C

- vinyl amide: 35 - 65°C, preferably 40 - 60 ⁰ C

The methods of the present invention may be operated at a pH of from 5 to 11. It will be appreciated that it is well within the knowledge of the person skilled in the

art to select and maintain a pH level according to the dye being used, and the fibre type to be dyed. For example, where the pH is alkaline, certain alkaline materials or combinations of an alkaline material and a mild acid, may be used to obtain the necessary pH. Suitable compounds may include caustic soda, potash, sodium silicate, trisodium phosphate (TSP), soda ash, tetrasodium pyrophosphate (TSPP), sodium tripolyphosphate, borax, disodium phosphate, sodium bicarbonate and sodium hexametaphosphate. Where the pH is acidic, suitable compounds may include monosodium phosphate, monopotassium phosphate, and monosodium sulphate and/or monopotassium sulphate.

More preferably the pH level may be adjusted by the use of a dye solution which comprises a basic ionic liquid, an acidic ionic liquid, or a mixture of basic and acidic ionic liquids.

The term "basic" refers to Brόnsted bases having the ability to react with (neutralise) acids to form salts. Bases have a pH greater than 7.0 when dissolved in water.

The term "acidic" refers to Brδnsted acids having the ability to react with (neutralise) bases to form salts. Acids have a pH less than 7.0 when dissolved in water.

In accordance with the present invention, the ionic liquid may have the formula:

[Cat ⁺ ][X ]

wherein: Cat ⁺ is a catonic species; and X ^" is an anion species.

Preferably, [Cat ⁺ ] is a catonic species selected from imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiazolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrrolium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, /so-oxazolium, /so-triazolium, tetrazolium, benzofuranium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium,

morpholinium, pyranium, annulenium, phthalazinium, quinazolinium, quinoxalinium, quinolinium, isoquinolinium, thiazinium, azaannulenium, ammonium, pyrrolidinium, diazabicycloundecenium, diazabicyclononenium, diazabicyclodecenium, phosphonium or triazadecenium.

In one embodiment, Cat ⁺ is selected from:-

and

wherein: R ^a , R ^b , R ^c , R ^d , R ^e , R ^f , R ⁹ and R ^h can be the same or different, and are each independently selected from hydrogen, a Ci to C ₄₀ , straight chain or branched alkyl group, a C ₃ to C ₈ cycloalkyl group, or a Cβ to Ci ₀ aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C ₁ to C ₆ alkoxy, C ₆ to C ₁₀ aryl, CN, OH, NO ₂ , C ₇ to C ₃₀ aralkyl and C ₇ to C ₃₀ alkaryl, or any two of R ^b , R ^c , R ^d , R ^e and R ^f attached to adjacent carbon atoms form a methylene chain -(CH ₂ J _q - wherein q is from 8 to 20.

More preferably, Cat ⁺ is selected from:-

wherein: R ^a , R ^b , R ^c , R ^d , and R ⁹ are as defined above.

Still more preferably, R ^b , R ^c and R ^d may each be hydrogen; and R ^a and R ⁹ may be selected from Ci to C ₂ o, linear or branched, alkyl, and one of R ^a and R ⁹ may be hydrogen. Even more preferably, one of R ^a and R ⁹ may be hydrogen or methyl; and the other is selected from C ₁ to C ₂ o linear or branched alkyl. Most preferably, one of R ^a and R ⁹ may be hydrogen or methyl, and the other is selected from Ci to Ci ₈ linear or branched alkyl.

Further examples include wherein one of R ^a and R ⁹ is hydrogen or methyl, and the other is selected from methyl, ethyl, butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl.

In accordance with the methods of the present invention, Cat ⁺ may be selected from: methylimidazolium, 1 ,3-dimethylimidazolium, 1-ethyl-3- dimethylimidazolium, 1-butyl-3-dimethylimidazolium, 1-hexyl-3- methylimidazolium, 1-octyl-3-methylimidazolium, 1-decyl-3-methylimidazolium, 1- dodecyl-3-methylimidazolium, 1 -methyl-3-tetradecylimidazolium, 1 -hexadecyl-3- methylimidazolium and i-methyl-3-octadecylimidazolium.

In another embodiment of the present invention, Cat ⁺ may be selected from:

[N(R ^a )(R ^b )(R ^c )(R ^d )] ⁺ and [P(R ^a )(R ^b )(R ^c )(R ^d )] ⁺

wherein: R ^a , R ^b , R ^c , and R ^d can be the same or different, and are each independently selected from, C ₁ to C ₄₀ , straight chain or branched alkyl group, a C ₃ to C ₈ cycloalkyl group, or a C ₆ to C _1O aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C ₁ to C ₆ alkoxy, C ₁ to C ₆ alkoxy, C ₆ to C ₁₀ aryl, CN, OH, NO ₂ , C ₇ to C ₃₀ aralkyl and C ₇ to C ₃₀ alkaryl.

Preferably, R ^a , R ^b , R ^c , and R ^d can be the same or different, and are each independently selected from, Ci to C ₂₀ , straight chain or branched alkyl group, a C ₃ to C ₆ cycloalkyl group, or a C ₆ to Ce aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C ₁ to C ₆ alkoxy, Ci to C ₆ alkoxy, C ₆ to C ₁₀ aryl, CN, OH, NO ₂ , C ₇ to C ₃₀ aralkyl and C ₇ to C ₃₀ alkaryl.

More preferably, Cat ⁺ may be selected from tetrasubstituted ammonium, tetramethyl ammonium, tetraethyl ammonium, tetrapropyl ammonium, tetrabutyl ammonium, tetrapentyl ammonium, tetrahexyl ammonium, 2-hydroxyethyl- trimethyl ammonium and ethers thereof, tetrasubstituted phosphonium, tetraethyl phosphonium, tetrapropyl phosphonium, tetrabutyl phosphonium, tetrapentyl phosphonium, tetrahexyl phosphonium, and trihexytetradecyl phosphinium.

In the methods of the present invention, X ^" may be selected from: F ^" , Cl ^" , Br ^" or I ^" , HSO ₄ ^" , H ₂ PO ₄ ^" , HPO ₄ ^2" , OMs ^" (CH ₃ SO ₃ ^" ), CH ₃ (C ₆ H ₄ )SO ₃ ^" , CH ₃ OSO ₃ ^" , C ₂ H ₅ OSO ₃ ^" . SO ₄ ^2" , BF ₄ ^" , PF ₆ ^" , OTf (CF ₃ SO ₃ ^" ), CF ₃ COO ^" , SbF ₆ ^" , CuCI ₂ ^" , A ₅ F ₆ ^" , SO ₄ ^" , CF ₃ CH ₂ CH ₂ COO ^" , (CF ₃ SOz) ₃ C ^" , CF ₃ (CF ₂ ) ₃ SO ₃ \ NTf ₂ ^" ([CF ₃ SOz] ₂ N ^" ) and an inorganic metal anion.

Preferably, X ^" is selected from Cl ^" , EtSO ₄ ^" , OMs ^" , NTf ₂ ^" and OTf.

In a further embodiment of the present invention, the ionic liquid may be, or comprise, a basic ionic liquid. A basic ionic liquid may comprise a basic cation, or a basic anion, or both a basic cation and a basic anion.

Suitable basic cations for use in the present invention include those represented by the formula:

[Cat ⁺ -Z-Bas]

wherein: Cat ⁺ is a cationic species; Bas is a basic moiety; and

Z is a covalent bond joining Cat ^* and Bas, or 1 , 2 or 3 aliphatic divalent linking groups each containing 1 to 10 carbon atoms and each optionally containing one, two or three oxygen atoms.

Preferably, Bas comprises at least one nitrogen, phosphorus, sulphur, oxygen or boron atom. For example, Bas may comprise at least one primary, secondary or tertiary amino group.

Preferably, Bas is selected from -N(R ₁ )(R ₂ ), and -P(Ri)(R ₂ ); and wherein R ₁ and R ₂ can be the same or different and are each independently selected from hydrogen, linear or branched alkyl, cycloalkyl, aryl and substituted aryl.

Preferably, R ₁ , R ₂ and R ₃ are each selected from hydrogen, methyl, ethyl, isopropyl, propyl, butyl, sec-butyl, isobutyl, pentyl, hexyl, cyclohexyl, benzyl and phenyl.

Still more preferably, Bas is a hindered basic moiety.

The term "hindered basic moiety" refers to a functional group that acts as a base, but because of steric hinderance, does not chemically bond to the reagents or products.

For hindered basic ionic liquids the group R should have low nucleophilicity such as that described for Hunig's base (bis-(diisopropyl)ethylamine) (see Tetrahedron Letters 1981 , 31 , 1483). Also in this respect, reference is made to paper, "Hindered non-nuclepohilic base with high protein affinity", Chem. Ber. 1958, 91 , p380 ad Chem. Ber., 1993, 29, p1042. This means that the basic group R is capable of forming a chemical bond with free hydrogen ions, but does not form chemical bonds with the reagents or products in a chemical process.

Suitable hindered basic moieties include -N(CH ₃ ) ₂ or -N(CH(CH ₃ ) ₂ ) ₂ .

In accordance with the present invention Z may be selected from linear or branched C ₁ to C _1S alkanediyl, substituted alkanediyl, dialkanylether or dialkanylketone, preferably C ₁ to C ₈ and more preferably C ₂ to C ₆ .

Preferably, Z is selected from -(CH ₂ -CH ₂ )-, -(CH ₂ -CH ₂ -CH ₂ )-, -(CH ₂ -CH ₂ -CH ₂ - CH ₂ )-, -(CH ₂ -CH ₂ -CH ₂ -CH ₂ -CH ₂ )-, -(CH ₂ -CH ₂ -CH ₂ -CH ₂ -CH ₂ -CH ₂ )-,

-(CH ₂ -CH ₂ -O-CH ₂ -CH ₂ )- and -(CH ₂ -CH ₂ -O-CH ₂ -CH ₂ -CH ₂ )-.

The Cat ⁺ moiety in [Caf-Z-Bas] may comprise or consist of a heterocyclic ring structure selected from imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiozolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, benzotriazolium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholenium, pyranium, annolinium, phthalazinium, quinazolinium, quinoxalinium, quinolinium, isoquinolinium, thazinium, azaannulenium, pyrrolidinium, diazabicycloundecenium, diazabicyclononenium, diazabicyclodecenium or triazadecenium.

Preferred [Cat ⁺ -Z-Bas] in accordance with the present invention may be selected from:

and

wherein: Bas and Z are as defined above; and

R ^b , R ^c , R ^d , R ^e , R ^f , R ⁹ and R ^h can be the same or different, and are each independently selected from hydrogen, a C ₁ to C ₄₀ , straight chain or branched alkyl group, a C ₃ to C ₈ cycloalkyl group, or a C ₆ to C ₁₀ aryl group, wherein said

alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C ₁ to C ₆ alkoxy, C ₆ to Ci ₀ aryl, CN, OH, NO ₂ , C ₇ to C ₃₀ aralkyl and C ₇ to C ₃₀ alkaryl, or any two of R ^b , R ^c , R ^d , R ^e and R ^f attached to adjacent carbon atoms form a methylene chain -(CH ₂ ) _q - wherein q is from 8 to 20.

More preferably [Cat ⁺ -Z-Bas] is selected from:-

wherein: Bas, Z and R ^b are as defined above.

Still more preferably, [Cat ⁺ -Z-Bas] may be selected from the group consisting of:-

(all of the above compounds being considered "hindered")

The Cat ⁺ moiety in [Cat ⁺ -Z-Bas] may also comprise or consist of an acyclic organic cation.

When the Cat ⁺ moiety in [Cat ⁺ -Z-Bas] is acyclic, it preferably comprises or consists of a group selected from amino amidino, imino, guanidino, phosphino, arsino, stibino, alkoxyalkyl, alkylthio, alkylseleno and phosphinimino.

When the Cat ⁺ moiety in [Cat ⁺ -Z-Bas] is acyclic, [Cat ⁺ -Z-Bas] is preferably selected from:

+ +

N(Z-Bas)(R ^b )(R ^c )(R ^d )| and P(Z-Bas)(R ^b )(R ^c )(R ^d )l

wherein: Bas, Z, R , R ^c , and R are as defined above.

Suitable basic anions for use in the present invention include [F] ^" , [OH] ^" , [OR] ^" , [RCO ₂ ] ^" , [PO ₄ ] ^3" and [SO ₄ ] ^2" , wherein R is C ₁ to C ₆ alkyl.

As noted above, in an embodiment of the present invention, an acidic ionic liquid may be used. The present invention, acidic ionic liquid may comprise an acidic cation or an acidic anion, or both an acidic cation and an acidic anion.

Suitable acidic cations for use in the present invention include those represented by the formula:

[Cat ⁺ -Z-Acid]

wherein: Cat ⁺ is a cationic species;

Acid is an acidic moiety; and Z is as defined above.

Acid is preferably selected from -SO ₃ H, -CO ₂ H, -SO ₃ -Ph-R, -SO ₃ R, RPO(OH) ₂ and R ₂ PO(OH); wherein R is, for example, C ₁ to C ₆ alkyl.

The Cat ⁺ moiety in [Cat ⁺ -Z-Acid] may comprise or consist of a heterocyclic ring structure selected from imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiozolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium,

isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, benzotriazolium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholenium, pyranium, annolinium, phthalazinium, quinazolinium, quinoxalinium, quinolinium, isoquinolinium, thazinium, azaannulenium, pyrrolidinium, diazabicycloundecenium, diazabicyclononenium, diazabicyclodecenium or triazadecenium.

Preferably, [Cat ⁺ -Z-Acid] is selected from:

and

wherein: Acid and Z are as defined above; and

R ^b , R ^c , R ^d , R ^θ , R ^f , R ⁹ and R ^h can be the same or different, and are each independently selected from hydrogen, a C ₁ to C ₄₀ , straight chain or branched alkyl group, a C ₃ to C ₈ cycloalkyl group, or a Ce to C ₁₀ aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to Ce alkoxy, C ₆ to Ci ₀ aryl, CN, OH, NO ₂ , C ₇ to C ₃₀ aralkyl and C ₇ to C ₃₀ alkaryl, or any two of R ^b , R ^c , R ^d , R ^e and R ^f attached to adjacent carbon atoms form a methylene chain -(CH2) _q - wherein q is from 8 to 20.

Most preferably, Cat ⁺ -Z-Acid is:

The Cat ⁺ moiety in [Cat ⁺ -Z-Acid] may also comprise or consist of an acyclic organic cation.

When the Cat ⁺ in [Cat ⁺ -Z-Acid] moiety is acyclic, it preferably comprises or consists of a group selected from amino amidino, imino, guanidino, phosphino, arsino, stibino, alkoxyalkyl, alkylthio, alkylseleno and phosphinimino.

Where the Cat ⁺ moiety in [Cat ⁺ -Z-Acid] is acyclic, [Cat ⁺ -Z-Acid] is preferably selected from:

+ N(Z-Acid)(R ^b )(R ^c )(R ^d )| and f N(Z-Acid)(R ^b )(R ^c )(R ^d j

wherein: Acid, Z, R , R ^c , and R are as defined above.

Suitable acidic anions for use in the present invention include [HSO ₄ ] ^" , [H ₂ PO ₄ ] ^" , [HPO ₄ ] ^2" , [HCI ₂ ] ^" and [HX ₂ ] ^" ; wherein X = F, Cl, Br or I.

The dye solution used in the methods of the present invention preferably comprises between 0.1 and 10Og, more preferably between 0.5 and 5Og, and most preferably between 1.0 and 3Og of reactive dye per litre of dye solution. The exact concentration used depends on a number of parameters such as the type of dye, the type of fibre to be dyed and the depth of colour that is required.

The dye solution used in the methods of the present invention may also comprise dispersing agents, cosolvents, emulsifiers, surfactants, minor amounts of salts, pH buffers and/or other auxiliaries, for example, dye assists.

Examples of suitable cosolvents include water, alcohols (such as methanol and ethanol), ethers, esters (such as ethyl acetate), ketones (such as acetone) and other organic solvents, for example, acetonitrile and nitromethane. Where the dye is a reactive dye, preferred cosolvents are those which are not able to inactivate the reactive functional group of the dye. When cosolvents are used, the dye composition preferably comprises from 0.01 to 90 volume percent, more preferably 0.1 to 50 volume percent, still more preferably 0.5 to 20 volume percent, and most preferably 1.0 to 10 volume percent of the cosolvent based on the total volume of ionic liquid and cosolvent.

Examples of suitable emulsifiers include ethylene oxide nonylphenols, ethylene oxide condensates, polyethylene glycols, amine condensates, alkyl and glycol esters, glycerol esters, alkanolamides, glycols, such as hexylene glycol, ethylene glycol, propylene glycol, diethylene glycol and the like, soaps formed by the reaction of a strong alkali with a mixture of a fat and an acid, sulfonated castor oils, sulfonated red oil, sorbitan fatty acid esters, ethoxylated sorbitan esters, ethoxylated fatty acids, ethoxylated alcohols, ethoxylated triglycerides, ethoxylated fatty amines, dodecyl benzene sulfonic acid and modified forms of same, sodium di-2-ethylhexyl sulfosuccinate, alkyl aryl sulfonates, alkoxylated aromatics, polyoxypropylene/polyoxyethylene condensates, and synthetic alcohol alkoxylates. When the dye composition comprises emulsifiers, the emulsifiers are preferably present in the dye composition in a range of from 0.1 to 2.0 percent by weight, more preferably from 0.5 to 1.5 percent by weight.

In addition, the dye may further comprise a dye assist which aids in penetration of the cellulosic fiber, reduces the amount of fiber reactive color build up on the surface of the fiber, aids in minimizing crack marks, chafe marks and the like, assists in leveling of the dispersed dyestuffs, and due to excellent dispersing characteristics, aids in preventing agglomeration of the disperse dyes. Known dye assists include without limitation by sulfonated castor oil, sulfonated sperm oil, soaps, phosphated nonyl phenols, amine condensates, reacted forms of polyethylene glycols, and various blends of same. It is preferred to use a blend of ingredients such as a blend of low foaming, anionic surface active agents of sulfonated oils; triethanolamine; soaps, such as those prepared from a fat of a distilled coconut oil, oleic acid and potassium hydroxide; isopropyl alcohol; amine-coconut oil condensates, and a neutralized, free acid form of a phosphated 9-mole ethylene oxide nonylphenol. When the dye composition contains dye assist, the dye assist is preferably present in a range of from 0.5 to 3.0 percent by weight, more preferably 1.0 to 2.0 percent by weight.

It will be appreciated that the parameters of dye concentration in the solution, amounts of auxiliaries and cosolvents, temperature, the type of fibre, pre- treatment of the fibre, and/or immersion time period of the fibre in the solution will all in their own right affect the amount and rate of dyeing. The person skilled in

the art will select the parameters as necessary according to his requirements, and taking into account factors such as the type of dye used, thickness of the fibre, and the type of fibre. The selection of such parameters is well within the ability of the person skilled in the art, and can be made without any undue burden. Any preferred ranges for such parameters given above are not intended to be limiting.

The fibre to be dyed in accordance with the present invention may be scoured prior to dyeing in order to remove any oils, grease, starches, waxes, dirt or sizing from the fibre which might resist fixation of the dyestuff, thereby affecting the level and uniformity of dyeing, or which might interfere with the dyestuff itself. Typically scouring involves treating the fibre with an alkali, such as soda ash or caustic soda, together with various detergents, solvents and the like. The choice of scouring parameters will depend on the type of fibre, the type of dye to be used and the type of contaminants to be removed. Suitable methods of scouring are well known in the art.

The fibre to be dyed in accordance with the present invention may also be bleached prior to dyeing so that the fibre is whitened sufficiently that the desired shade may be obtained, particularly when dyeing bright or pastel shades. Bleaching may be combined with the scouring of the fabric, or may be conducted separately. Suitable methods of bleaching are well known in the art.

The fibre dyed in accordance with the present invention may be subject to an after-scour treatment to remove residual dye which is not covalently fixed to the fibre. Suitable after-scour agents are known in the art, and include triethanolamines, soaps, amine condensates, nonyl phenols and dodecylbenzenesulfonic acid compounds, or a mixture thereof.

The methods of dyeing in accordance with the present invention may be incorporated into known dyeing processes, for example, conventional bath procedures, reverse bath procedures and one-bath multi-step procedures. The methods of the present invention may also be used together with other known dyeing methods, especially where there are one or more different types of fibre being dyed, for example, cellulose and polyester.

According to a second aspect of the present invention, there is provided a dyed fibre produced in accordance with the methods of the first aspect of the present invention.

According to a third aspect of the present invention there is provided a fabric material comprising dyed fibres produced in accordance with the present invention.

According to a fourth aspect of the present invention, there is provided a dye composition for use in a method according to the first aspect of the present invention comprising an ionic liquid and a reactive dye.

The dye composition may be as described above with respect to the methods of the present invention. The compositions may also consist essentially of an ionic liquid and a dye, preferably a reactive dye, and optionally one or more of a cosolvent, dispersing agent, emulsifier, surfactant, minor amounts of salts, pH buffers and/or auxiliaries, for example, dye assists.

According to a fifth aspect of the present invention there is provided a kit of parts for use in dyeing fibres comprising an ionic liquid and a reactive dye for combining with the ionic liquid.

According to a sixth aspect of the present invention, there is provided use of a dye composition in accordance with the above disclosure in a method for dyeing fibres as described above.

A dyeing method in accordance with the present invention will now be described by way of example and with reference to Figures 1 and 2 in which:

Figure 1 is a photograph of fabric samples dyed using water as a solvent; and

Figure 2 is a photograph of fabric sample dyed using an ionic liquid/dye solution.

Examples

In order to demonstrate the present invention, linen (a cellulose type material) samples were used.

A. Comparative Aqueous System

Three linen samples were placed in an aqueous solution of Reactive Blue 116 under the following conditions:

(1) 1 minute at 25 ⁰ C;

(2) 1 minute at 8O ⁰ C; and

(3) 150 minutes at 8O ⁰ C.

The results are shown in Figure 1 , and it can be seen that it took 150 minutes for the sample to become 'fully' dyed. In addition, it was noted that none of the sample was colourfast, and thus significant dye leaching occurred when placed in hot water.

B. Comparative Classic Salt System

Three linen samples were placed in a 10% NaCI solution and Reactive Blue 116 under the following conditions:

(4) 1 minute at 25 ⁰ C;

(5) 1 minute at 8O ⁰ C; and

(6) 150 minutes at 80 ⁰ C.

The results are shown in Figure 1 , and it can be seen that it again took 150 minutes for the sample to become close to 'fully' dyed (In general the samples were not dyed as efficiently as the aqueous solution). In addition, it was noted that none of the samples was colourfast, and thus significant dye leaching occurred when placed in hot water.

C. Ionic Liquids

Three ionic liquids were chosen:

(1) [C ₄ mim]CI;

(2) [C ₈ mim]CI;

(3) [C ₆ ,6,6,i4P]CI; and

(4) [Choline][OMs]

Experimental Procedure

(1) For [C ₄ mim]CI, 4 linen samples were prepared and dyed for 5 to 60 seconds at 80-110 ⁰ C.

The resulting samples, as shown in Figure 2, all produced a medium blue colour, and all samples were considerably more colourfast than those prepared using the aqueous system.

Full dyeing was obtained within 10 minutes, considerably faster than the 150 minutes for the non-ionic liquid solutions.

(2) For [C ₈ mim]CI, it was noted that the degree of dyeing was for the most part independent of temperature and time - see results in Figure 2.

(3) Similar to [C ₈ mim]CI, [C ₆ , ₆ , ₆ ,i ₄ P]CI produced amounts of dyeing which for the most part seemed independent of temperature and time - see results in Figure 2.

(4) [Choline][OMs] (results not shown) produced very poor dyeing results. However, such an outcome was not unexpected due to the presence of a reactive -OH group.

D. Other Ionic Liquids

[C ₂ mim][NTf ₂ ] and [C ₂ mim][OTf] were also tested but were found to have low solubility for the Reactive Blue 116 dye. Accordingly, in their pure form they are not suitable for this dye. However, the addition of a minor amount of a co-solvent would increase the dye solubility, and the co-solvent could then be removed by evaporation.

[C ₂ mim][EtSO ₄ ] gave similar results to [C ₈ mim]CI. Again, the solubility of the dye in this ionic liquid could be improved by using a co-solvent to get the dye into solution, followed by evaporation of the co-solvent.

Conclusions

Ionic liquids provide a viable alternative to known dyeing solutions, especially those that are aqueous based.

It has been demonstrated that the use of ionic liquids in the dyeing of fibres can significantly increase the rate of dyeing, especially for reactive dyes.

It has also been demonstrated that the fibres produced, when an ionic liquid is used in the dyeing process, are more colourfast than those produced using known salt-solutions, and are therefore less likely to fade over time. This is especially true when used with reactive dyes.

It will also be appreciated that careful selection of the ionic liquids used allows for control over the degree of dyeing of the fibre, and thus the resulting colour of the fibre, especially when the ionic liquid is used in combination with a reactive dye.