WO2006049504A2

WO2006049504A2 - A method of dyeing a substrate with a reactive dyestuff in supercritical or near supercritical carbon dioxide

Info

Publication number: WO2006049504A2
Application number: PCT/NL2005/050033
Authority: WO
Inventors: Maria Vanesa Fernandez Cid; Jaap Van Spronsen; Wilhelmus Johannes Theodorus Veugelers; Geert Feye Woerlee
Original assignee: Feyecon Development and Implementation BV
Current assignee: Feyecon Development and Implementation BV
Priority date: 2004-11-04
Filing date: 2005-11-04
Publication date: 2006-05-11
Anticipated expiration: 2007-05-04
Also published as: WO2006049504A3

Abstract

The present invention relates to a method of dyeing a substrate selected from the group consisting of cellulose fibres, modified cellulose fibres, protein fibres, synthetic fibres and combinations thereof, wherein the method comprises contacting the substrate with supercritical or near supercritical carbon dioxide containing a reactive dyestuff of the formula (I): wherein Ch represents a chromophoric residue of an aromatic diazo substance or of an anthraquinone substance; Y represents O or NR, in which R represents hydrogen or a C1-C8 alkyl, which is optionally substituted by hydroxy, cyano, chloro, bromo, C1-C5 alkoxy, phenoxy, phenyl or phenoxy C1-C4-alkoxy; X1 represents fluorine; X2 represents fluorine, chlorine, OR1 or N(R2)R3; R1 represents hydrogen, or a C1-C4 alkyl, which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine; R2 and R3 independent ly represent hydrogen, P(O)(OH)R4 or a C1-C3 alkyl which is optionally subst ituted by hydroxy, cyano, fluorine, chlorine or bromine; and R4 represents hydroxy, fluorine, chlorine or bromine.

Description

A METHOD OF DYEING A SUBSTRATE WITH A REACTIVE DYESTUFF IN SUPERCRITICAL OR NEAR SUPERCRITICAL CARBON DIOXIDE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of dyeing a substrate, particularly fibres, with a reactive dyestuff in supercritical or near supercritical carbon dioxide.

BACKGROUND OF THE INVENTION

Dyeing by traditional water-based methods and subsequent washing processes produces large amounts of, usually strongly coloured, waste water. Furthermore, when dyeing, for instance, polyester fibres from an aqueous medium, the dyed fibres need to be subjected to a so called reduction clearing which causes additional effluent problems.

The aforementioned environmental drawbacks of water-based dyeing methods can be overcome by dyeing from supercritical carbon dioxide. Supercritical dyeing additionally offers the advantage that densities and viscosities in supercritical carbon dioxide are lower and diffusion more rapid than in liquids, shortening the process time.

The dyeing of substrate materials in liquid or supercritical carbon dioxide is well-known in the art. It is also known to employ reactive dyeing substances in supercritical dyeing methods that are capable of reacting with the substrate under the formation of a chemical bond. These reactive substances are usually derivatives of

Cθ2-soluble disperse dyestuffs (chromophores) that contain a reactive group that is capable of reacting with specific residues in the substrate.

DE-A 100 64 414 describes a process for dyeing substrates with dyestuffs in densified CO₂, wherein the substrate and/or dyestuffs exhibit OH-, NH₂- or NH- functionalities, said process being characterised in that the substrate is reacted with the dyestuffs using reactive groups that are bound to the substrate and/or dyestuff. The

German application describes dyestuffs that contain a dichlorotriazinyl residue as the reactive group. US-B 5,578,088 describes a process for dyeing fibre materials comprising cellulose fibres or a mixture of cellulose fibres and polyester fibres, which comprises first modifying the fibre material with one or more compounds containing amino groups and then dyeing the modified fibre material with a fibre-reactive disperse dyestuff in supercritical CO₂. In the examples a large number fibre-reactive disperse dyestuffs are listed, including dyestuffs that contain a triazine reactive group that carries a fluorine and an amine substituent.

Japanese patent application 2002-201575 describes a method for dyeing a cellulosic fibre containing material, said method comprising pre-treatment with a polar solvent capable of swelling the fibre, such as an ethylene glycol derivative, and an alkali agent, and dying with a reactive disperse dye in a mixed fluid of supercritical carbon dioxide and a polar solvent such as ethanol, acetone, etc. The reactive dyestuffs employed in accordance with the present invention are not disclosed in the Japanese patent application. Japanese patent application 2004- 107804 describes a method of dyeing a cellulosic fibre structure with a reactive disperse dye using a supercritical or high- pressure carbon dioxide medium containing a sold alkaline agent. The reactive dyestuffs employed in the present method are not disclosed in the Japanese patent application. The supercritical dyeing methods described in the prior art suffer from the drawback that despite the use of reactive dyestuffs colour yields as well as wash- fastening properties are often disappointing and/or the dyeing methods employing these reactive dyestuffs are laborious and/or make use of aggressive agents (e.g. alkaline agents) that may cause damage to the substrate.

SUMMARY OF THE INVENTION

The inventors have unexpectedly found that the drawbacks of the supercritical dyeing methods from the prior art can be reduced significantly by employing a reactive dyestuff of the formula:

wherein

Ch represents a chromophoric residue of an aromatic diazo substance or of an anthraquinone substance;

Y represents O or NR, in which R represents hydrogen or a C₁-C₈ alkyl, which is optionally substituted by hydroxy, cyano, chloro, bromo, C₁-C₅ alkoxy, phenoxy, phenyl or phenoxy Ci-C₄-alkoxy; X₁ represents fluorine;

X₂ represents fluorine, chlorine, OR₁ Or N(R₂)R₃;

R₁ represents hydrogen, or a C₁-C₄ alkyl, which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine;

R₂ and R₃ independently represent hydrogen, P(O)(OH)R₄ or a C₁-C₃ alkyl which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine; and R₄ represents hydroxy, fluorine, chlorine or bromine.

The present method is particularly suited for dyeing substrates selected from the group consisting of cellulose fibres; modified cellulose fibres; protein fibres; synthetic fibres containing a plurality of reactive groups selected from the group consisting of hydroxyl, thiol, primary amine and secondary amine; and combinations of these fibres.

The present method provides excellent fixation of the dyestuff in combination with exceptionally high reaction rates without the need of using e.g. alkaline agents. Furthermore, the present method enables the production of dyed substrates that exhibit outstanding washfastness and fastness to rubbing. An important advantage of the present method is that very good dyeing results can be obtained without prior chemical modification of the substrate. Although the inventors do not wish to be bound by theory, it is believed that the benefits of the present method are largely due to the exceptionally high reactivity of the reactive dyestuff under supercritical dyeing conditions. This unusually high reactivity appears to be linked to the presence of a fluor substituted triazine radical in the reactive dyestuff. DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the present invention concerns a method of dyeing a substrate with a reactive dyestuff in supercritical or near supercritical carbon dioxide, said substrate being selected from the group consisting of cellulose fibres; modified cellulose fibres; protein fibres; synthetic fibres containing a plurality of reactive groups selected from the group consisting of hydroxyl, thiol, primary amine and secondary amine; and combinations of these fibres, wherein the method comprises contacting the substrate with supercritical or near supercritical carbon dioxide containing a reactive dyestuff of the formula (I):

wherein

Ch represents a chromophoric residue of an aromatic diazo substance or of an anthraquinone substance; Y represents O or NR, in which R represents hydrogen or a C₁-C₈ alkyl, which is optionally substituted by hydroxy, cyano, chloro, bromo, C₁-C₅ alkoxy, phenoxy, phenyl or phenoxy Ci-C₄-alkoxy; X₁ represents fluorine;

X₂ represents fluorine, chlorine, OR₁ Or N(R₂)R₃; R₁ represents hydrogen, or a C₁-C₄ alkyl, which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine;

R₂ and R₃ independently represent hydrogen, P(O)(OH)R₄ or a C₁-C₃ alkyl which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine; and R₄ represents hydroxy, fluorine, chlorine or bromine. The fibre substrate in the present method can suitably take the shape of yarn or fabric. The present method is particularly suitable for dyeing fabrics, e.g. woven or knitted fabrics.

The term "reactive dyestuff as used in here refers to dyestuffs, which are capable of reacting and forming a covalent bond with reactive groups in the substrate under the conditions employed in the present method. Examples of reactive groups include hydroxyl groups (cellulose based materials such as cotton), amino and thiol groups (wool, silk, polyamides).

The term "supercritical carbon dioxide" as used in here refers to carbon dioxide that exhibits a pressure and temperature equal to or above its critical pressure and critical temperature (73.8 bar; 31.1 ⁰C). The dyeing method according to the present invention can also employ carbon dioxide under near supercritical conditions, i.e. at a pressure of at least 50 bar and a temperature of at least 15 ⁰C.

The term "chromophoric residue" as used in here refers to the part of the reactive dyestuff molecule that is primarily responsible for its colouring imparting properties.

According to a particularly preferred embodiment of the invention the chromophoric residue in the reactive dyestuff is a residue of an aromatic diazo substance. Even more preferably, the residue Ch represents an arylazoarylamino residue wherein each of the aryl groups can carry 1-5 substituents.

Substrates that may be dyed by the method of the present invention include, but are not limited to fibres formed from cotton, wool, silk, polyester, nylon, rayon, acrylic fibres, acetate (particularly cellulose acetate), including blends thereof such as cotton/polyester blends, as well as leather. Preferably, the substrate is a fibre formed from cotton, wool, silk, polyester, nylon, rayon or any combination thereof. Even more preferably, the substrate is a fibre formed from cotton, wool, silk or polyester. Best results are obtained when the present method is employed in the dyeing of cotton.

In particular, textile substrates are advantageously dyed by the present method and encompass a larger number of materials. Examples of such substrates include, for example, cloth, garments, upholstery, carpets, tents, canvas, leather, footwear, silks and other water sensitive fabrics.

In a preferred embodiment, the substrate is contacted with the supercritical or the near supercritical carbon dioxide containing the reactive dyestuff at a temperature in the range of 80-300 °C, preferably in the range of 90- 180 °C, and a pressure in the range of 60-500 bar, preferably in the range of 73-400 bar.

Typically, in the present method the substrate is dyed employing a ratio substrate to carbon dioxide of less than 2:1, preferably of less than 1:1 and even more preferably of less than 1:2. The aforementioned ratio usually exceeds 1:100. More preferably, the ratio exceeds 1 :20.

In the aforementioned formula (I) X₂ preferably represents fluorine, (NH)R₂ or OR₁. Most preferably, X₂ represents fluorine, OCH₃, OCH₂CH₃, NH₂ or NHCH₃. In another preferred embodiment of the invention R₁ represents a C₁-C₃ alkyl, which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine. Even more preferably, R₁ represents a C₁-C₃ alkyl, which is optionally substituted by hydroxy, fluorine or chlorine. Most preferably, R₁ represents methyl or ethyl.

In formula (I) Y preferably represents NR. The residue R in NR preferably represents hydrogen or a C₁-C₅ alkyl, which is optionally substituted by hydroxy, cyano, chloro, bromo or C₁-C₃ alkoxy. Even more preferably, R represents hydrogen, methyl or ethyl. Most preferably, R represents hydrogen.

As explained herein before, the method of the present invention offers the important advantage that it produces excellent results without the need to chemically modify the substrate prior to the dyeing. Thus, in a preferred embodiment, the present method does not employ pre-treatment of the substrate with one or more compounds containing amino groups as described in US 5,578,088. In an even more preferred embodiment, the present method does not employ any chemical modification of the substrate prior to the dyeing. Here the term "chemical modification" refers to the alteration of the chemical nature of the substrate by allowing reactive groups in the substrate to react with a modifying agent.

Pre-treatment in the form of chemical modification is not to be confused with pre-treatment with inert materials, e.g. organic liquids. Indeed, in a particularly preferred embodiment of the present method, the substrate is pre-treated with a fluid medium containing at least 10 wt.%, preferably at least 20 wt.% and more preferably at least 40 wt.% of one or more organic hydrogen bond acceptor compounds with 1-10 carbon atoms, said hydrogen bond acceptor compounds containing organic one or more functionalities selected from hydroxyl, ester, ketone, sulfoxide, sulfone, ether, amine oxide, tertiary amide, phosphate, carbonate, carbamate, urea, phosphine oxide and nitrile, prior to contacting the substrate with supercritical or near supercritical carbon dioxide containing the reactive dyestuff. Here the term "fluid medium" encompasses liquid as well as supercritical media. Pre-treatment with a fluid medium containing the aforementioned hydrogen bond acceptor compounds was found to substantially improve fastening of the dyestuff to the substrate. Although the inventors do not wish to be bound by theory, it is believed that such pre-treatment makes the reactive sites in the substrate more accessible to the reactive dyestuff. Furthermore, the pre-treatment appears to have a favourable effect on the reaction rate.

The pre-treatment according to the present invention may suitably be carried out by rinsing or soaking the substrate in the fluid medium. The subsequent step of contacting the substrate with supercritical or near supercritical carbon dioxide containing the reactive dyestuff may be effected by simply adding the supercritical or near supercritical carbon dioxide or by separating the substrate from the fluid medium and subsequently adding the carbon dioxide. It is preferred to first separate the substrate from the fluid medium before the dyeing step. Following removal of the substrate from the fluid medium some of the fluid medium clinging to the substrate may be removed by e.g. wiping, wringing or evaporation. However, it is strongly preferred that a significant amount of the fluid medium remains attached to the substrate when it is contacted with the carbon dioxide containing the reactive dyestuff. Typically, when contacted with the reactive dyestuff, the substrate contains at least 25 %, preferably at least 50% of fluid medium by weight of the substrate (including said fluid medium).

According to a preferred embodiment, the hydrogen bond acceptor compounds employed in the pre-treatment are selected from the group consisting OfC₁-C₆ alkanols, dimethyl sulfoxide, dimethylformamide, acetone, butan-2-one, dimethyl ether, methyl acetate and ethyl acetate. More preferably, the hydrogen bond acceptor compounds are selected from the group OfC₁-C₅ alkanols, particularly C₁-C₅ alkanols comprising not more than 2 hydroxyl groups, even more particularly C₁-C₅ alkanols comprising one hydroxyl group. Especially suited hydrogen bond acceptor compounds are primary alcohols, secondary alcohols and combinations thereof.

Examples of alcohols that may advantageously be employed in the pre-treatment of the substrate include methanol, ethanol, propanol, iso-propanol, n-butanol and 2- butanol.

The one or more hydrogen bond acceptors are advantageously employed in the pre-treatment in an amount of at least 30%, preferably at least 50% by weight of the substrate. In one particular embodiment of the invention, the present pre-treatment is carried out with a fluid medium essentially consisting of one or more organic hydrogen bond acceptor compounds. In another embodiment, the fluid medium employed in the pre-treatment may suitably contain other fluid components beside the hydrogen bond acceptor compounds. Examples of fluid components that may be included additionally are densified carbon dioxide, water, C₁-C₈ alkanes, acetone and acetonitrile. Preferably, the fluid medium employed in the treatment essentially consists of a blend of the hydrogen bond acceptor compounds and a fluid component selected from the group consisting of densified carbon dioxide, water, C₁-C₈, alkanes, acetonitrile and combinations thereof. Even more preferably, the latter fluid component is selected from the group consisting of densified carbon dioxide, acetonitrile and combinations thereof. Most preferably, the fluid component is densified carbon dioxide, especially supercritical or near supercritical carbon dioxide. The use of a mixture of the hydrogen bond acceptor compounds and supercritical or near supercritical carbon dioxide offers the advantage that pre-treatment and dyeing may be carried out in the same equipment.

The pre-treatment step is suitably carried out at a temperature of 5-160 °C and a pressure of 0.5-300 bar. In case the fluid medium does not contain densified carbon dioxide, pre-treatment is preferably carried out at a temperature of 5-50 °C and a pressure of 0.5-2 bar.

During pre-treatment the substrate is preferably contacted with the fluid medium for at least 5 minutes, more preferably for at least 10 minutes and most preferably for at least 15 minutes. Furthermore, the substrate is advantageously pre- treated employing a substrate to medium ratio (w/w) of 1 : 1 to 1 : 100, more preferably of l:l to l:10.

In another preferred embodiment of the present method, the supercritical or near supercritical carbon dioxide contains between 1 and 35 % by weight of carbon dioxide of a co-solvent selected from the group consisting of one or more organic hydrogen bond acceptor compounds with 1-10 carbon atoms, said hydrogen bond acceptor compounds containing organic one or more functionalities selected from hydroxyl, ester, ketone, sulfoxide, sulfone, ether, amine oxide, tertiary amide, phosphate, carbonate, carbamate, urea, phosphine oxide and nitrile. The use of a co- solvent offers the advantage that it accelerates transfer of the reactive dye to the substrate and improves the reaction of the dyestuff with the substrate.

According to preferred embodiments of the invention the co-solvent is selected from the same group of hydrogen bond acceptor compounds as defined above in relation to the embodiment using a pre-treatment step. In case the present method employs such a pre-treatment step, the co-solvent is preferably identical to the hydrogen bond acceptor compound that was used in the pre-treatment.

According to yet another preferred embodiment of the present dyeing method the supercritical or near supercritical carbon dioxide contains at least 0.05 mol.%, more preferably at least 0.2 mol.% and most preferably at least 1 mol.% acids calculated on the molar amount of reactive dyestuff that is used in the dyeing process. It was unexpectedly found that the addition of acids to the supercritical or near supercritical carbon dioxide substantially increases the reaction rate of the dyestuff with the substrate. The acidification of the carbon dioxide is believed to result in the protonation of the triazinyl ring. As a result the carbon atom in the triazinyl ring attached to a leaving group (e.g. fluorine) is positively activated. The activated reactive dyestuff will react rapidly with the reactive groups in the substrate.

The one or more acids employed in accordance with this embodiment of the invention preferably exhibit an acid dissociation constant K at 25 ⁰C within the range of 4xlO^"7 to IxIO⁷, more preferably within the range of 7.2x10^ to όxlO^"1. In case the present method employs a strong acid, a relatively low acid concentration may be employed whereas much higher concentrations of a weak acid may be required to achieve the same effect. Thus, in a preferred embodiment, the one ore more acids employed in the method meet the following requirement: K x C > 0.03; wherein K represents the acid dissociation constant at 25 ⁰C and C represents the molar concentration of dissolved acids in the carbon dioxide. In case the carbon dioxide contains more than one acid, the above equation is applied to each acid and the results are added up to produce the final number.

The one or more acids are advantageously selected from the group consisting of HCl, C₆H₅SO₃, HNO₃, CF₃COOH, H₃PO₃, HClO₂, H₃PO₄, CH₂ClCOOH, HF, HNO₂, HCOOH, C₆H₅COOH, CH₃COOH and H₂CO₃.

The invention is further illustrated by means of the following examples.

EXAMPLES

Example 1

A piece of 0.25 g of mercerized cotton was pre-treated in a fluid medium consisting of 20 g methanol as hydrogen bond acceptor. The pre-treatment was carried out at 40 °C and 1 bar by immersing the cotton in the methanol and gently shaking for 12 h. The pre-treated cotton was removed from the fluid medium and transferred as such for dyeing treatment. The remaining methanol in the cotton after the pre- treatment was about 60% by weight of the cotton substrate. The dyeing test was carried out in a high-pressure batch reactor designed to carry out experiments under supercritical conditions. The reactor consisted of a 150 mL pressure vessel provided with a pressure manometer and a needle valve.

The piece of pre-treated cotton was placed into the batch reactor together with the reactive disperse dye (4,6-difluoro-N-[4-(phenyldiazinyl)phenyl]-l,3,5-trazin-2- amine) and a co-solvent. The amount of dye used was 10% by weight of the fibre (owf). The applied co-solvent was methanol at a concentration of 2% by weight of carbon dioxide. The reactor was sealed and afterwards, 9Og of liquid carbon dioxide were introduced into the reactor via the needle valve. The reactor was subsequently placed in a thermostatic bath at 120 °C. The initial pressure in the reactor was 60 bar and after a period of approximately 10 min the pressure was 300 bar. The cotton was dyed for 4 hours at 120 °C and 300 bar. Subsequently, the reactor was removed from the thermostatic bath and cooled down till the pressure was 60 bar. At this pressure the reactor was depressurized by opening the needle valve.

The piece of cotton was removed from the reactor and was found to display an evenly distributed yellow colour. No traces of the pre-treatment fluid media or co- solvent were found in the piece of cotton, i.e. the cotton was completely dry after the dyeing process.

To determine the fixation of the dye in the piece of cotton, a Soxhlet extraction was carried out. A half piece of the dyed cotton was extracted for 1 hour in a 15:35 (v/v) mixture of water and acetone at 85 °C. The colour intensity, in terms of the K/S, was determined in the dyed and the extracted piece of cotton. The Kubelka-Munk equation, K/S = (1-R)²/2R, is used to determine the colour intensity in the dyed and the extracted piece of cotton. In this equation R is the minimum value of the reflectance curve, which is measured between 350 and 750 nm with a spectrophotometer.

The results showed a K/S value of the dyed cotton of 19.6 and a K/S value of the extracted cotton of 15.8. These results show that the dyeing process produced a good colour yield as well as excellent fixation of the colour to the cotton. Example 2

The experimental procedure described in example 1 was applied to 0.25 g of mercerized cotton. In this experiment instead of methanol as co-solvent, ethanol was used, also in a concentration of 2% by weight of carbon dioxide. The result after 4 hours dyeing at 140 °C and 300 bar was a yellow piece of cotton that was evenly dyed. The K/S value after dyeing was 25.3 and K/S after extraction was 19.7

Example 3 Example 1 was repeated using a different reactive disperse dye: i.e. 6-fluoro-

N-[4-(phenyldiazinyl)phenyl]-l,3,5-trazin-2,4-diamine.

The piece of dyed cotton so obtained was found to be evenly dyed. The K/S values observed for the aminomonofluorotriazinyl dye were 15.5 after dyeing and

12.3 after extraction.

Example 4

The experimental procedure described in example 3 was repeated except that the piece of pre-treated cotton was placed into the batch reactor together with the reactive disperse dye, the co-solvent and an acid (CH₃COOH). The concentration of CH₃COOH was 4545 mol% calculated on the molar amount of reactive dye substance. The result after 4 h dyeing was a yellow piece of cotton that was evenly dyed.

The K/S value after dyeing was 17.5 and K/S after extraction was 17.3, corresponding to an excellent fixation of 98%.

Example 5

Example 1 was repeated using 4-fluoro-6-methoxy-N-[4-

(phenyldiazenyl)phenyl]-l,3,5-triazin-2-amine as the reactive dyestuff and employing a dyeing time of 7 hours.

The dyed cotton piece so obtained was found to be evenly dyed. The K/S values observed were 15.6 after dyeing and 10.1 after extraction.

Example 6

The experimental procedure described in example 5 was repeated except that the piece of pre-treated cotton was placed into the batch reactor together with the reactive disperse dye, the co-solvent and an acid (H₃PO₄). The concentration OfH₃PO₄ was 4 mol.% calculated on the molar amount of reactive dye substance.

The result after 4 h dyeing was a yellow piece of cotton that was evenly dyed.

The K/S value after dyeing was 26.5 and K/S after extraction was 20.4.

Comparative Example A

A piece of 0.25 g of mercerized cotton was dyed following the procedure described in example 1, except that this time the reactive disperse dye employed was

4,6-dichloro-N-[4-(phenyldiazinyl)phenyl]-l,3,5-trazin-2-amine. The dichlorotriazinyl derivative was applied at an owf of 5% as an owf of 10% was found to cause damage to the cotton as a result of the production of significant quantities of hydrochloric acid.

The dyeing process with the dichlorotriazinyl derivatised dyestuff was carried out for

7 h.

The result of this experiment was a yellow piece of cotton that was evenly dyed. The K/S values after dyeing and extraction were 9.0 and 7.7 respectively. Thus, it can be concluded that the piece of cotton dyed with the difluorotriazinyl derivatised dye shows a stronger colouration than the cotton dyed with the dichlorotriazinyl derivatised dye, even when the dyeing time employed for the latter dye was 3 hours longer than for the difluorotriazinyl derivatised dye.

Comparative Example B

Example 1 was repeated using a different reactive disperse dye, i.e. 6-chloro-

N-[4-(phenyldiazinyl)phenyl]-l,3,5-trazin-2,4-diamine This time the dyeing time employed was 7 hours. The dyed piece of cotton was found to be evenly dyed. The K/S values of aminomonochlorotriazinyl dye were 11.1 after dyeing and 5.2 after extraction. The comparison of the results obtained in this experiment with those described in example

3 demonstrates that not only the colour yield obtained with the aminomonofluorotriazinyl dye, but also the fixation, are superior to that of the aminomonochlorotriazinyl dye.

Claims

1. A method of dyeing a substrate with a reactive dyestuff in supercritical or near supercritical carbon dioxide, said substrate being selected from the group consisting of cellulose fibres; modified cellulose fibres; protein fibres; synthetic fibres containing a plurality of reactive groups selected from the group consisting of hydroxyl, thiol, primary amine and secondary amine; and combinations of these fibres, wherein the method comprises contacting the substrate with supercritical or near supercritical carbon dioxide containing a reactive dyestuff of the formula:

wherein

Y represents O or NR, in which R represents hydrogen or a C₁-C₈ alkyl, which is optionally substituted by hydroxy, cyano, chloro, bromo, C₁-C₅ alkoxy, phenoxy, phenyl or phenoxy Ci-C₄-alkoxy;

X₁ represents fluorine;

X₂ represents fluorine, chlorine, OR₁ or N(R₂)R₃;

R₁ represents hydrogen, or a C₁-C₄ alkyl, which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine; R₂ and R₃ independently represent hydrogen, P(O)(OH)R₄ or a C₁-C₃ alkyl which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine; and

R₄ represents hydroxy, fluorine, chlorine or bromine.

2. Method according to claim 1, wherein the chromophoric residue is a residue of an aromatic diazo substance.

3. Method according to claim 2, wherein the chromophoric residue is an arylazoarylamino residue wherein each of the aryl groups can carry 1-5 substituents.

4. Method according to any one of the preceding claims, wherein X₂ represents fluorine, (NH)R₂ or OR₁.

5. Method according to claim 4, wherein X₂ represents fluorine, OCH₃, OCH₂CH₃, NH₂Or NHCH₃.

6. Method according to any one of the preceding claims, wherein R₁ represents a C₁- C₃ alkyl which is optionally substituted by hydroxy, cyano, fluorine, chlorine or bromine.

7. Method according to any one of the preceding claims, wherein Y represents NR.

8. Method according to any one of the preceding claims, wherein the substrate is pre- treated with a fluid medium containing at least 10 wt.%, preferably at least 40 wt.% of one or more organic hydrogen bond acceptor compounds with 1-10 carbon atoms, said hydrogen bond acceptor compounds containing organic one or more functionalities selected from hydroxyl, ester, ketone, sulfoxide, sulfone, ether, amine oxide, tertiary amide, phosphate, carbonate, carbamate, urea, phosphine oxide and nitrile, prior to contacting the substrate with supercritical or near supercritical carbon dioxide containing the reactive dyestuff.

9. Method according to claim 8, wherein the hydrogen bond acceptor compounds are selected from the group consisting OfC₁-C₆ alkanols, dimethyl sulfoxide, dimethylformamide, acetone, butan-2-one, dimethyl ether, methyl acetate and ethyl acetate.

10. Method according to claim 9, wherein the hydrogen bond acceptor compounds are selected from the group consisting of methanol, ethanol, propanol, iso-propanol, n- butanol and 2-butanol.

11. Method according to any one of claims 8-10, wherein the one or more hydrogen bond acceptors are employed in an amount of at least 30%, preferably at least 50% by weight of the substrate.

12. Method according to any one of the preceding claims, wherein the supercritical or near supercritical carbon dioxide contains at least 0.05 mol.%, preferably at least 1 mol.% acids calculated on molar amount of reactive dyestuff that is used in the dyeing process.

13. Method according to claim 12, wherein the one or more acids are selected from the group consisting of HCl, C₆H₅SO₃, HNO₃, CF₃COOH, H₃PO₃, HClO₂, H₃PO₄, CH₂ClCOOH, HF, HNO₂, HCOOH, C₆H₅COOH, CH₃COOH and H₂CO₃.

14. Method according to any one of the preceding claims, wherein the substrate is a fibre material selected from the group consisting of cotton, wool, silk, polyester, nylon, rayon and combinations thereof.