GUEBITZ GEORG (AT)
KOKOL VANJA (SI)
BOZIC MOJCA (SI)
GUEBITZ GEORG (AT)
KOKOL VANJA (SI)
| JP2006087422A | 2006-04-06 | |||
| DE102005040469A1 | 2007-03-01 |
INVENTION CLAIMS
1. A process for indigo dyeing of cellulose and polyamide-based textile fibre materials comprising a dyeing of textile material with indigo, reduced with reductase enzymes in the presence of redox mediators followed by soaping, washing and indigo oxidation with air or an oxidation agent (e.g. hydrogen peroxide).
2. A method as claimed in claim 1 , wherein the dye bath comprises 0.05 to 0.20 %, preferably 0.05 to 0.10 % indigo dye of the dry weight of the polyamide fabric, 25 to 50 ml/I, preferably 40 ml/I to 50 ml/I enzyme solution (approx. 50 mg/ml of protein content), 1 to 4 mM, preferably 2 to 4 mM final concentration of β-Nicotinamide adenine dinucleotide disodium salt (NADH) and 7.5 to 17.5 μM, preferably 12.5 to 15.5 μM final concentration of 1 ,8-dihydroxy-9,10- anthraquinone.
3. A method as claimed in claim 1 , wherein the dye bath comprises 0.3 to 2.5 %, preferably 0.5 to 2.0 % indigo dye of the dry weight of the cellulose fabric, 25 to 60 ml/l, preferably 40 ml/l to 60 ml/l enzyme solution (approx. 90 mg/ml of protein content), 2 to 4 mM, preferably 3 to 4 mM final concentration of β-
Nicotinamide adenine dinucleotide disodium salt (NADH) and 0.06 to 0.2 mM, preferably 0.1 to 0.15 mM final concentration of 1 ,8-dihydroxy-9,10- anthraquinone.
4. A method as claimed in claim 2 and 3, wherein the dye bath has a pH of 7 to 11.
5. A method as claimed in claims 1 , 2 and 3, wherein the material is treated at a temperature in the range of about 50 0 C to 6O 0 C.
6. A method as claimed in claim 1 , 2 and 3, wherein the reduction system further comprises a chemical mediator which enhances the activity of the one or more enzymes.
7. A method as claimed in claim 6, wherein the chemical mediator is an anthraquinone compound.
8. A method as claimed in claims 1 to 7, wherein the dyed material can be cellulose or polyamide-based fibre, yarn, woven, or knitted material form, or an article of clothing.
9. A method as claimed in claims 1 to 8, wherein the reuse three or more times of enzymatic mediate reduction bath is possible at pH 9 and 11. |
PROCESS OF DYEING CELLULOSE AND POLYAMIDE TEXTILE MATERIALS WITH ENZYME REDUCED INDIGO
Field of the invention
This invention relates to the dyeing process of cellulose and polyamide-based textile materials by indigo dye (C.I. Vat Blue 1) using enzymes for indigo reduction.
Technical problem The technical problem lies in the high cost and negative environmental impact of the current process of dyeing cellulose and polyamide fibers with vat, respectively indigoid dyes.
Conventional indigo dyeing of cellulose fibers is carried out under highly alkaline pH medium in the presence ecologically toxic reducing agent (sodium dithionite). Vat/indigoid dyes in the non-soluble base form do not represent an environmental risk as regards their toxicity and biodegrability, but they still colour the waste water. A big ecological problem of vat dyeing results from the required chemicals. The generation of non-regenerable oxidation products causes various problems in the disposal of the dyeing bath and the washing water, because the sodium dithionite is finally oxidized into compounds as sulphate, sulphite and thiosulphate which upon release affect the environment detrimentally by their toxicity. In addition, the waste water may contain considerable excess of the reducing agent, so an addition of oxidation agent is required for water stabilization. This additionally increases toxicity; effects on the aerobic processes and consequently increase the cost of treatment. Disposal of the dyeing bath also contains excess of alkalies, salts, surfactants and remain dye. Still, the biggest problem in vat dyeing presents reduction agent (sodium dithionite) and their decomposed compounds, so in the last decade many attempts have been made to partly or totally replace this agent. Conventional reduction procedure of indigo in high alkaline medium with sodium dithionite is a technological known process for dyeing cellulose fibers and it is not suitable for dyeing of polyamide fibers. Polyamide is negatively charged in alkaline
medium, which means that both, fiber and the leuko dye form, have the negative charge and no mutual affinity. Consequently, dyeing of polyamide fibers with vat/indigoid dyes by standard procedures is not possible.
A subject of the present invention it is to solve the problem of indigo reduction without the aforementioned disadvantages and in an ecologically advantageous manner. We have found that this goal is achieved by a process for dyeing of cellulose and polyamide-based textile material with indigo which comprises using an aqueous solution of leuco indigo prepared by reductase enzymes and an appropriate redox mediator and, after the leuco indigo has penetrated into the textile material, converting it back into the pigment form with air oxidation. The process also allows reuse of NADH-dependent enzymes from the enzyme reduction bath.
Background of invention Indigo (C.I. Vat Blue 1 ) is one of the oldest dyes, which is used for dyeing cellulose textiles, especially for dyeing cotton (popularity of jeans). Indigo is a vat dye which is insoluble in water. However, when the vat dye is vatted to the leuco form by addition reducing agent, it is dissolved into a reduced form, which, having penetrated into the material to be dyed, is oxidized back to the insoluble pigment. In the customary dyeing processes, indigo is vatted in an alkali medium in a vessel upstream of the dyebath using inorganic reducing agents such as sodium dithionite and thiourea dioxide or organic reducing agents such as hydroxyacetone. In addition, machine-dependent portions of reducing agent are consumed during the dyeing process, since part of the leuco indigo is oxidized by air contact when air passages at the dyebath surface and is re-vatted, which is why the dyebath has reducing agent added to it (up to 70% of the total required). The disadvantage of vatting indigo with the reducing agents mentioned is in high concentration of sulfate (from about 3500 to 5000 mg/l) and sulphur content which result from the release of sulphide (S 2" ) ions of the indigo wastewater in the case of using sodium dithionite, or high concentration of oxygen-consuming substances (COD values about 8000 mg/l) in the case of hydroxyacetone usage. In addition, a high level of ecological unfriendly alkali is required.
In the last decade, many attempts have been made to replace the environmentally unfriendly reduction agents by ecologically more attractive alternatives using
ecological advanced chemical, electrochemical reduction, electro catalytic hydrogenation and bacterium reducing methods.
According to the paper by U. Baumgarte, published in the Rev. Prog. Coloration, 17, 1987, reducing systems, based on sulphur containing substances, have been recommended (i.e. hydroxyalkyl sulphinate, thiourea, etc). The relatively low sulphur content and lower equivalent mass than that of sodium dithionite lead to lower amounts of sodium sulphates and toxic sulphide in the effluent. U.S. Pat. No. 4,950,306 describes a process of dyeing and printing of cellulosic fibre materials using mono- or di-hydroxyacetone as reducing agent. In the thesis 'Investigation using examples of α-hydroxyketones systems and the electrochemical oregonator' by R. W. Bolinger, Zurich, 2000, a research was focused on replacement of sulphide containing reducing agent with α- hydroxyketones. Replacement of sodium dithionite in the vat dyeing process by α- hydroxyketones seems to meet the requirements in terms of reductive efficiency and biodegradability. However, work on the reduction of vat dyes, in particular indigo, with enediols gave unsatisfactory results, since the reduction process was incomplete and the dyeings obtained were unable to meet the high requirements, for example in respect of constancy of shade and levelness. Beside, some substances are expensive and the use of some α-hydroxyketones is restricted to closed systems because they form strong-smelling condensation products in alkaline solution.
Glucose and other reducing sugars have been suggested as possible "green" reducing agents: U.S. Pat. No. 6,093,221 describes process for reduction of sulphur and vat dyes using isomaltulose or a mixture containing isomaltulose as reducing agent.
An article by A. Vuorema, P. John, M. Keskitalo, M. A. Kulandainathan and F. Marken, published in the Dyes and Pigments, 2006, describes reduction of indigo with D-(+)-glucose. Although glucose has high ecological advantage, it turns out to be disadvantage in respect that the equilibrium of the redox potential is reached comparatively slowly and unsatisfactory for complete reduction.
Catalytic hydrogenation of indigo is also possible and well known process; however, it is impossible to use this technique directly in the dye house due to the high explosion and fire risk. U.S. Pat. No. 1 ,247,927 and U.S. Pat. No. 5,586,992 describes dyeing with hydrogenated indigo.
An article by N. Comisso and G. Mengoli, published in the Environ. Chem. Lett., 1 , 2004, report that vat and sulphur dyes can be reduced in alkaline media by H 2 using an appropriate catalytic system involving the production of environmentally safe water. According to the article of A. Roessler, O. Dossenbach, W. Marte and P. Rys, published in the Dyes and Pigments, 54, 2002, electrocatalytic hydrogenation involves the electrochemical reduction of water to produce adsorbed hydrogen that chemically reacts with an organic substrate on electrically conductive metal powder catalyst surface. The catalytic material serves both as an electrode (to generate the hydrogen) and as a catalyst for the hydrogenation. There are severe drawbacks in this technique, such as the big pressure drop built up, the persistent danger of blocking the reactor and low performance.
Different electrochemical reduction techniques, especially for indigo dyeing, have been investigated as an alternative route for ecological and economic reasons. Electrochemical reduction can be achieved by direct and indirect electrochemical reduction.
According to the article by A. Roessler, D. Crettenand, O. Dossenbach, W. Marte and P. Rys, published in Electrochimica Acta, 47, 2002, and article A. Roessler, D. Crettenand, O. Dossenbach, W. Marte and P. Rys, published in Journal of Applied Electrochemistry, 32, 2002, the direct reduction process is based on a reaction mechanism in which an indigo anion radical is formed by a disproportionation reaction between the dye and the leuco dye form, followed by the electrochemical reduction of this radical. The leuco dye is acting as an electron-shuttle between the electrode and the surface of the dye pigment. Anyhow, the electrochemical reaction rate is limited by the diffusion transport of the intermediate radical anion and at potentials more negative than -1100 mV the current density increases due to the cathodic liberation of hydrogen.
Article by A. Roessler and D. Crettenand published in Dyes and Pigments, 63, 2004, describes direct electrochemical reduction of vat dyes in fixed bed of graphite granules, where leuco dye is produced (in contrast to the process based on the electrochemical reduction of the dye anion radical) directly from the dye suspension, thus direct electron transfer between the dye and the graphite is obtained. Although this technique is ideal, the stability of reduced dye species formed is poor and thereby affecting on the colour yield of the dyed material.
There are numerous publications about indirect electrochemical reduction; e.g. by T. Bechtold, E. Burtscher, D. Gmeiner and O Bobleter published in Melliand Textilberichte, 72, 1991 , describing indirect electrochemical reduction of vat dyes through different reversible redox mediators systems. According to article by T. Bechtold, E. Burtscher and A. Turcanu published in Journal of Electroanalytical Chemistry, 465, 1999, anthraquinones could be used as mediators for indirect cathodic reduction. Articles by T. Bechtold, E. Burtscher, D. Gmeiner and O. Bobleter published in J. Electroanal. Chem., 306, 1991 ; T. Bechtold, E. Burtscher, A. Turcanu and O. Bobleter published in Journal of Applied Electrochemistry, 27, 1997, T. Bechtold, E. Burtscher, A. Turcanu and O. Bobleter published in Textile Research Journal, 67, 1997, W. Blatt, L. Schneider published in Melliand International, 3, 1999 and M.A. Kulandainathan, A. Muthukumaran, K. Patil and R.B. Chavan published in Dyes and Pigments, 73, 2007, suggested iron- triehanolamine complex (iron-TEA) as a mediator system. In article by T. Bechtold and A. Turcanu, published in Journal of Electroanalytical Chemistry, 591 , 2006, iron-complexes of bis(2-hydroxyethyl)-amino-compounds as mediators for indirect reduction of dispersed vat dyes are used. According to the article by T. Bechtold, E. Burtscher, O. Bobleter, W. Blatt and L. Schneider published in Chem. Eng. Technol., 21 , 1998 and article by W. Blatt and L. Schneider published in Melliand Textilberichte, 80, 1999, the optimization of multi-cathode membrane electrolysers for the indirect electrochemical reduction of vat/indigo dyes has been suggested in order to meet all requirements in an economical way.
U.S. Pat. No. 6,767,448 B1 describes method for producing aqueous alkaline solutions of reduced indigoid dyes, using mediator system obtain by mixing one or more salts.
U.S. Pat. No. 0088926 A1 describes a mediator systems based on mixed metal complexes, used for reducing dyes. Finally, WO 90/15182 discloses a dyeing process wherein indigo is added to the dyebath using mediators. However, reduction to the total amount of indigo necessary for dyeing requires enormous amounts of charge and large electrode surfaces. In addition, conducting salt has to be added to the dying solution in major quantities (about 1.5 g/l of NaOH, 30 g/l Na 2 SO 4 ) to ensure adequate electrical conductivity and hence to minimize the resistance losses and also electrode surface area. This in turn leads to undesirably high levels of sulfate in the dyehouse waste water.
Both electrochemical reduction techniques are described by A. Roessler and X. Jin in review article published in Dyes and Pigments, 59, 2003 and thesis "New electrochemical methods for reduction of vat dyes" by A. Roessler from Swiss Federal Institute of Technology (ETH), Zurich, 2003; and are not yet industrially commercialized.
An article by A.N. Padden, P. John, M. D. Collins, R. Hutson and A.R. Hall published in Journal of Archaeological Science, 27, 2000, describes Clostridium isatidis, unique indigo-reducing bacterium isolated from a woad dye vat that could be employed in a biotechnological indigo-reduction process. The mechanism of bacterial indigo reduction remains unknown, but the unique features of the indigo- reducing C. isatidis indicate possible mechanisms for biotechnological indigo- reduction process.
There are no publications about enzymatic-reducing dyeing vat process yet, but enzymatic re-oxidation is patented with U.S. Pat. No. 6129769.
Most dyeing application using vat and indigoid dyes is confined to the cellulose fibres, and only little attention has been paid to the application of vat/indigoid dyes on other natural (wool, silk, etc.) and especially synthetic fibres.
There are two patents U.S. Pat. No. 2007/0107144 A1 and WO 2007/000775 A2 about indigo dyeing of wool, silk and their blends, where reducing agent employed is sodium dithionite.
Article by Y.A. Son, J. P. Hong and T.K. Kim published in Dyes and Pigments, 61 , 2004 and article by Y.A. Son, HT. Lim, J. P. Hong and T.K. Kim published in Dyes and Pigments, 65, 2005, describes approach of polyester fiber dying with indigo using thiourea dioxide as reducing agent.
It is known that polyamide PA (PA6 [-HN-(CH 2 ) 5 -CO-] n and PA6.6 [-HN-(CH 2 ) 6 - NHCO-(CH 2 ) 4 -CO-]n) exhibits free amino (NH 2 -PA-COOH) and imino (=NH) groups on the side-chains thus in an acid solution, PA is positively charged through absorption of hydrogen ions (NH 2 -PA-COO " * ^ HOOC-PA-
NH 2* ^ HOOC-PA-NH 3 + or =NH ^^=NH 2 + ). The resulting electric charge can be counter balanced with negatively charged anions of the dye, whilst dyeing with anionic dyes such as acid, metal complex, direct and reactive dyes.
Conventional indigo dyeing is carried out under highly alkaline pH values and the leuco indigo produced has an anionic charge. However, PA has a tendency to lose its cationic properties in the presence of alkali. Both, the fibre and the dye, being anionic under alkaline conditions, the net result is loss of dye-fibre affinity. Thus, it would be apparent that normal known steps of PA dyeing can not be employed for dyeing of PA by vat/indigoid dyes in general. An appropriate ecological batch process for the indigo dyeing of PA fibres has not been described in any literature yet.
Description of the invention
Dyeing of cellulose and polyamide-based textile materials is carried out with leuko indigo obtained by enzymatic reduction of indigo in the presence of a redox mediator followed by penetration into the textile material and converting it back into the pigment form with air oxidation.
In accordance with the present invention, a dyebath for dyeing of cellulose and polyamide materials is prepared with indigo pigments being mixed reductase (e.g. NADH-dependent from Bacillus subtilis enzymes in presence of NADH) and a mediator (e.g. 1 ,8-dihydroxy-9,10-anthraquinone) causing the indigo particles to become negatively charged. As the particles become charged in this way, they also become rapidly and evenly dispersed within the bath, apparently due to the fact that these similarly charged particles repel one another.
The dye liquor, which comprises the polyamide material, used in the method of the present invention may have a material - liquor ratio in the range from about 1 :5 to about 1 :120, preferably from about 1 :50 to about 1 :80. In accordance with this invention, the dye bath comprises:
- 0.05% to 0.20%, preferably 0.05% to 0.10% indigo dye on the dry weight of the polyamide fabric; 0.3% to 2.5%, preferably 0.5% to 2.0% indigo dye on the dry weight of the cellulose fabric; - 25 to 50 ml/l, preferably 40 to 50 ml/I enzyme solution (approx. 50 mg/ml of protein content) for the polyamide fabric; 25 to 60 ml/l, preferably 40 to 60 ml/l enzyme solution (approx. 90 mg/ml of protein content) for the cellulose fabric;
- 1 to 4 mM, preferably 2 to 4 mM final concentration of β-Nicotinamide adenine dinucleotide disodium salt (NADH) for the polyamide fabric; 2 to 4 mM, preferably 3 to 4 mM final concentration of β-Nicotinamide adenine dinucleotide disodium salt (NADH) for the cellulose fabric;
- and 7.5 μM to 17.5 μM, preferably 12.5 μM to 15.5 μM final concentration of 1 ,8-dihydroxy-9,10-anthraquinone for the polyamide fabric; 0.06 mM to 0.2 mM, preferably 0.1 mM to 0.15 mM final concentration of 1 ,8-dihydroxy-
9,10-anthraquinone for the cellulose fabric.
Used reductase enzymes are active at pH in the range from about 7.0 to about 12.0, preferably from 8.0 to about 10.0. Enzymes exhibit good thermostability as well as good stability towards commonly used dyeing additives such as non-ionic, cationic, or anionic surfactants, salts, polymers, etc. Enzymes with reductase activity are wide-spread in nature and maybe from bacteria such as Bacillus sp. or Escherichia coli or eukaryotic organisms.
In a preferred embodiment, the enzymatic reduction system comprises one or more chemical mediator agents which enhance the activity of the enzyme exhibiting reductases activity. The term "chemical mediator" is defined herein as a chemical compound which acts as a redox mediator to effectively shuttle electrons between the enzyme exhibiting reductases activity and the dye. The chemical mediator may be anthraquinone compound, for example, 1 ,8- dihydroxy-9,10-anthraquinone. The chemical mediator may also be 9,10- anthraquinone-2,6-disulfonic acid disodium salt or 9,10-anthraquinone-2-sulfonic acid sodium salt.
The cellulose and polyamide materials to be dyed may be in the form of fibres, yarn, woven or knitted cloth, or finished articles of clothing. In accordance to the present invention, this material is prepared by wetting treatment in distillated water for 30 to 60 minutes, preferably from about 30 to about 40 minutes at room temperature, preferably at about 30 0 C to about 50 0 C.
In the prepared reduction bath, under the nitrogen atmosphere, the indigo pigment is reduced to its soluble leuco form (reduction of the keto =0 groups to -0 " ), which is attracted to and hold in place on the cellulose or polyamide substrate to enter the fibres.
The leuco dye adsorption and diffusion step in a dyeing process can be performed at a temperature in the range from about 40 0 C to about 65°C, preferably from about 5O 0 C to about 60 0 C, and at pH in the range of about 7 to about 11 , preferably from about 8 to about 10 for a period of about 60 minutes to about 120 minutes, preferably from about 80 minutes to about 100 minutes.
Afterwards, an oxidation process is applied to return the indigo dye in its leuco state to its blue pigment form. Oxidation may be accomplished in several ways. For example, dyed textile material can be passed through air and oxidized with oxygen or oxidizing agent such as hydrogen peroxide can be added in the dyeing bath or in separate oxidizing bath.
After the rinsing, dyed textile material is dipped into the bath with soaping agent. Soaping is performed at boiling temperature 15 minutes for cellulose fabric and 30 minutes for polyamide fabric to improve the colour fastness and to remove precipitated dye and mediator. Then, the material is rinsed with plain water at 25°C, before being dried on the air.
EXAMPLE 1
Enzymatic indigo dyeing of PA6 and PA6,6 material at pH 7
Knitted PA6.6 and woven PA6 (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperture. During its application to the textile material, the dyestuff was reduced to the water- soluble form by means of a NADH-dependent from Bacillus subtilis enzymes in presence of NADH. Process was carried out in TRIS/HCI buffer system, pH 7, at 60 0 C (starting from about 25°C) for at least one hour. The material - liquor ratio was 1 :80.
Dyeing/reduction bath was as follows:
- 0.05% indigo on the dry weight of the fabric
- 50 ml/l enzyme solution from Bacillus subtilis (approx. 50 mg/ml of protein content)
- 2 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH) - and 12.5 μM mediator 1 ,8-dihydroxy-9,10-anthraquinone
Buffer (TRIS/HCI, pH 7) Na 2 S 2 O 4 solution (1g/L Na 2 S 2 O 4 ) was used as the reducing agent in a comparative test.
After the dyeing, 30% of H 2 O 2 (1 :100 diluted) as oxidizing agent was added in the same bath for 5 minutes, and then rinse with the distillated water.
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were soaped with 2 g/l Cotoblanc at boiling point for 30 minutes and rinse with plain water for 15 minutes. During soaping the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 6O 0 C) and cold rinse (1 minute at 20 0 C). All dyed fabrics were air dried overnight before measuring colour values, wash fastness, alkaline and acid perspiration fastness and light fastness.
Evaluation of the colour
Upon the dyeing, the colour and the colour fastness properties of the dyed fabrics were evaluated. The CIEL*a*b* colour values were used to quantify the colour. Colour evaluation of the dyed samples was carried out using a Data Color SF 600 Plus spectrophotometer under illuminate D 65 using a 10° standard observer.
Wash fastness properties evaluation
The ISO 105-C04 (Part C04) Standard Wash Fastness to Laundering Test method
4 (95°C, 30 min) was followed. Dyed specimens (4 cm x 10 cm) were placed between two adjacent fabrics and sew along to form a composite specimen. The composites were treated in 5 g of standard prepared soap and 5 g of anhydrous sodium carbonate per litre of distilled water with ten non-corrodible (stainless) steel balls for 30 minutes at 95 0 C with 50:1 liquor ratio. Removed composite specimens were rinsed with water and dried at air. Colour changes in the specimens and the adjacent fabric were assessed using the Gray Scale method.
Alkaline and acid perspiration fastness properties evaluation
The ISO 105-E04 (Part E04) Standard Perspiration fastness was followed. Dyed specimens (4 cm x 10 cm) were placed between two adjacent fabrics and sew
along to form a composite specimen. The composites were treated in a standard prepared alkaline and acid solution for 30 minutes at room temperature with 50:1 liquor ratio. After drained, the composites were placed between two plates under a specified pressure in a testing device for 4 hour at 37°C. Removed composite specimens were rinsed with water and dried at air. Colour changes in the specimens and the adjacent fabric were assessed using the Gray Scale method.
Light fastness properties evaluation
Light fastness was measured following the ISO 150 B04 standard. Dyed specimens (4 cm * 10 cm) were stapled to the black side of test mask. The mask was placed in a XENOTEST 150S (No. 55007101 , Heraeus) and exposed to a Xenon light source at an irradiance of 1154 W/m 2 for 15 hours. Colour changes in the specimens were assessed using the Blue Scale method.
Fastness testing attests to the resistance of a dyed material against influences during textile production (production usability) and during the use of the textile (wear usability). Fastness to washing, perspiration, as well as light fastness, of the reducing agents used in accordance with the invention must be graded "good" and considered to be comparable to those obtained with the classical chemical (i.e. sodium dithionite) procedure.
Results:
Table 1 displays the CIEL * a * b* colour values of both, Na2S 2 θ 4 and enzyme (at pH 7) indigo dyed polyamide materials before and after soaping. It is evident that when compared CIEL*a*b* data of both dyeing procedures before and after soaping, the value L * increases after soaping, which indicate on the removal of remaining leuco dyes and surface adsorbed dyes, and consecutive results to brighter colour. With the soaping also decreases the values a* and b*, which indicates on decreasing of the green and blue colour portion.
Final CIEL*a*b * data of chemically and enzymatically indigo reduced and dyed samples are comparable. Table 1 shows CIEL*a * b * colour values of differently indigo dyed PA6 in PA6,6 samples at pH 7.
Table 2 shows wash, perspiration and light fastness of both, chemically and enzymatically, indigo dyed PA6 and PA6.6 materials at pH 7 after soaping
Table 2 displays the wash, perspiration and light fastness of both, chemically (with Na 2 S 2 O 4 ) and enzymatically (at pH 7), indigo reduced and dyed polyamide materials after soaping and rinsing. Wash fastnesses of chemically dyed polyamide materials are slightly better compared with the enzymatically dyed polyamide. There are also differences between PA6 and PA6.6: PA6 possess better wash fastness both chemically and enzymatically dyed compared with PA6,6 material. Perspiration fastnesses of all dyed polyamide materials are excellent for both, alkaline and acid perspiration. Light fastnesses of chemical and enzymatic dyeings are comparable.
EXAMPLE 2
Enzymatic indigo dyeing of PA6 and PA6,6 material at pH 10
Knitted PA6.6 and woven PA6 (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperatus. During its application to the textile material, the dyestuff was reduced to the water- soluble form by means of a NADH-dependent enzyme / mediator reducing system. The process was carried out in TRIS/NaOH buffer system, pH 10, at 60 0 C (starting from about 25°C) for at least one hour. The material - liquor ratio was 1 :80.
Dyeing/reduction bath was as follows:
- 0.05% indigo on the dry weight of the fabric
- 50 ml/I enzyme solution from Bacillus subtilis (approx. 50 mg/ml of protein content) - 2 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH)
- and 12.5 μM mediator 1 ,8-dihydroxy-9,10-anthraquinone
Buffer (TRIS/NaOH, pH 10) Na 2 S 2 O 4 solution (1g/L Na 2 S 2 O 4 ) was used as the reducing agent in a comparative test.
After the dyeing, 30% of HbO 2 (1 :100 diluted) as oxidizing agent was added in the same bath for 5 minutes, and then rinse with the distillated water.
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were washed with 2 g/l Cotoblanc at boiling point for 30 minutes and rinse with plain water for 15 minutes. During soaping the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 60 0 C) and cold rinse (1 minute at 20 0 C). All dyed fabrics were air dried overnight before measuring colour values, colour depth, wash fastness, alkaline and acid perspiration fastness and light fastness.
Results:
Table 3 displays the CIEL * a * b* data of both chemically (Na 2 S 2 O 4 ) and enzymatic (at pH 10) indigo dyed polyamide materials before and after the soaping. CIEL * a * b* data changes are similar to those obtained at pH 7. Enzymatic dyeing at pH 10 is better in the case of PA6 material used and worse in the case of PA6.6 material comparable to sodium dithionite dyed materials, although the enzymatic dyeing at pH 10 of both materials are more effective than those at pH 7. There are small difference in dyeing efficiency between PA6 and PA6.6 materials: in the case of PA6.6 material the effect of enzymatic reduction on the dyeing, i.e. the coloration, is less effective comparable to PA6 at both pH. Table 3 shows CIEL * a*b* colour values of differently indigo dyed PA6 in PA6,6 samples at pH 10.
Table 4 shows wash, perspiration and light fastness of both, chemically and enzymatically, indigo dyed PA6 and PA6.6 materials at pH 10 after soaping.
Wash fastnesses of chemically dyed PA6 materials are similar with enzymatically dyed PA6, meanwhile chemically dyed PA6.6 has better wash fastnesses as
enzymatically dyed PA6.6. Perspiration fastnesses for both, alkaline and acid perspiration, of chemically and enzymatic dyed polyamide materials are excellent. Light fastnesses of chemically dyed materials are better as enzymatic dyed, but still comparable.
EXAMPLE 3
Enzymatic indigo dyeing of cotton material at pH 7
Woven cotton (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperture. During its application to the textile material, the dyestuff was reduced to the water-soluble form by means of a NADH-dependent enzyme / mediator reducing system. Process was carried out in TRIS/HCI buffer system, pH 7, at 60 0 C (starting from about 25°C) for 90 min. The material - liquor ratio was 1 :80.
Dyeing/reduction bath was as follows:
- 0.3% indigo on the dry weight of the fabric
- 25 ml/1 enzyme solution from Bacillus subtilis (approx. 90 mg/ml of protein content) - 1.8 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH)
- and 0.06 mM mediator 1 ,8-dihydroxy-9,10-anthraquinone.
3g/l Na 2 S 2 O 4 solution in alkaline medium (5 ml/I 32% NaOH) for reduction of 0.3% indigo on the dry weight of the fabric was used as the reducing agent in a comparative test. Dyeing was carried out after the same procedure as with enzymatic dyeing.
After the dyeing, samples were removed from the dye bath, rinsed with the distillated water, and air oxidized (more then 12 hours).
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were washed with 2 g/l Cotoblanc at boiling point for 15 minutes and rinse with plain water for 15 minutes. During soaping, the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often
producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 60°C) and cold rinse (1 minute at 20 0 C). For the air dried samples colour values, wash fastness, alkaline and acid perspiration fastness and light fastness were determined.
Evaluation of the colour
Upon the dyeing, the colour and the colour fastness properties of the dyed fabrics were evaluated. The CIEL * a*b* colour values were used to quantify the colour. Colour evaluation of the dyed samples was carried out using a Data Color SF 600 Plus spectrophotometer under illuminate D 65 using a 10° standard observer.
Wash fastness properties evaluation The ISO 105-C01 Standard Wash Fastness to Laundering Test method 1 (40 0 C, 30 min) was followed. Dyed specimens (4 cm * 10 cm) were placed between two adjacent fabrics and sew along to form a composite specimen. The composites were treated in 5 g of standard prepared soap and 5 g of anhydrous sodium carbonate per litre of distilled water with ten non-corrodible (stainless) steel balls for 30 minutes at 95°C with 50:1 liquor ratio. Removed composite specimens were rinsed with water and dried at air. Colour changes in the specimens and the adjacent fabric were assessed using the Gray Scale method.
Alkaline and acid perspiration fastness properties evaluation The ISO 105-E04 (Part E04) Standard Perspiration fastness was followed. Dyed specimens (4 cm x 10 cm) were placed between two adjacent fabrics and sew along to form a composite specimen. The composites were treated in a standard prepared alkaline and acid solution for 30 minutes at room temperature with 50:1 liquor ratio. After draining, the composites were placed between two plates under a specified pressure in a testing device for 4 hour at 37°C. Removed composite specimens were rinsed with water and dried at air. Colour changes in the specimens and the adjacent fabric were assessed using the Gray Scale method.
Light fastness properties evaluation
Light fastness was measured following the ISO 150 B04 standard. Dyed specimens (4 cm * 10 cm) were stapled to the black side of test mask. The mask was placed in a XENOTEST 150S (No. 55007101 , Heraeus) and exposed to a Xenon light source at an irradiance of 1154 W/m 2 for 15 hours. Colour changes in the specimens were assessed using the Blue Scale method.
Fastness testing attests to the resistance of a dyed material against influences during textile production (production usability) and during the use of the textile (wear usability). Fastness to washing, perspiration, as well as light fastness, of the reducing agents used in accordance with the invention must be graded "good" and considered to be comparable to those obtained with the classical chemical (i.e. sodium dithionite) procedure.
Results:
Table 5 displays the CIEL * a * b* data of both chemically (Na 2 SaO 4 ) and enzymatic (at pH 7) indigo dyed cotton materials before and after the soaping. It is evident that when compared CIEL*a*b* data of both dyeing procedures before and after soaping, the value L* increases after soaping, which indicates the removal of remaining leuco dyes and surface adsorbed dyes, and consecutive results to brighter colour. With soaping, the values a* and b* decreases, which indicates on decreasing of the green and blue colour portion, except in the case of enzymatic dyeing, where value b * increase; blue colour portion is increase. In the case of enzymatic dyeing also increase chrome (C*) and hue (h) from 239.4 to 252.68 (shifting to blue).
Final CIEL * a * b* data of samples dyed with chemically and enzymatically indigo reduced are comparable, respectively better in the case of enzymatic dyeing at pH 7.
Table 6 shows wash, perspiration and light fastness of both, chemically and enzymatically, indigo dyed cotton materials at pH 7 after soaping
Table 6 displays the wash, perspiration and light fastness of cotton samples dyed with either, chemically (with Na 2 S 2 O 4 ) and enzymatically (at pH 7) reduced indigo and after soaping and rinsing. Wash fastness of chemical dyed cotton samples are a bit better comparison with enzymatic dyed one. Perspiration fastnesses of all dyed cotton samples are excellent for both, alkaline and acid perspiration. Light fastnesses of chemical and enzymatic dyeings are comparable.
EXAMPLE 4
Enzymatic indigo dyeing of cotton material at pH 9
Woven cotton (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperture. During its application to the textile material, the dyestuff was reduced to the water-soluble form by means of a NADH-dependent enzyme / mediator reducing system. The process was carried out in TRIS/HCI buffer system, pH 9, at 60 0 C (starting from about 25°C) for 90 min. The material - liquor ratio was 1 :80.
Dyeing/reduction bath was as follows:
- 0.3% indigo on the dry weight of the fabric - 25 ml/l enzyme solution from Bacillus subtilis (approx. 90 mg/ml of protein content)
- 1.8 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH)
- and 0.06 mM mediator 1 ,8-dihydroxy-9,10-anthraquinone.
3g/l Na 2 S 2 O 4 solution in alkaline medium (5 ml/l 32% NaOH) for reduction of 0.3% indigo on the dry weight of the fabric was used as the reducing agent in a comparative test. Dyeing was carried out after the same procedure as with enzymatic dyeing.
After the dyeing, samples were removed from the dye bath, rinsed with the distillated water, and air oxidized (more then 12 hours).
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were washed with 2 g/l Cotoblanc at boiling point for 15 minutes and
rinse with plain water for 15 minutes. During soaping the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 60 0 C) and cold rinse (1 minute at 20 0 C). For air dried samples colour values, wash fastness, alkaline and acid perspiration fastness and light fastness were determined.
Results:
Table 7 displays the CIEL * a*b* data of cotton materials dyed with either chemically (Na 2 S 2 O 4 ) and enzymatically (at pH 9) reduced indigo before and after the soaping. CIEL * a * b * changes are similar to those obtained at pH 7. L* values are a bit smaller than those at pH 7 for enzymatic dyeing, but still comparable to chemical dyeing. Also value a* is decreased, but still higher comparable to chemical dyeing. Hue (h) is increased from 235.33 to 254.46, indicates shifting to blue axle.
Table 8 shows wash, perspiration and light fastness of both, chemically (Na 2 S 2 O 4 ) and enzymatically, indigo dyed cotton materials at pH 9 after soaping and rinsing.
Wash fastness properties of chemical dyed cotton material are similar to enzymatic dyed samples. Perspiration fastnesses (alkaline and acid) of all dyed cotton samples are excellent. Wash fastness properties of enzymatic dyeing at pH 9 are improved with comparison at pH 7.
EXAMPLE 5
Enzymatic indigo dyeing of cotton material at pH 11
Woven cotton (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperatus. During its application to the textile material, the dyestuff was reduced to the water-soluble form by means of a NADH-dependent enzyme / mediator reducing system. The
process was carried out in TRIS/NaOH buffer system, pH 11 , at 60 0 C (starting from about 25°C) for 90 min. The material - liquor ratio was 1 :80.
Dyeing/reduction bath was as follows: - 0.3% indigo on the dry weight of the fabric
- 25 ml/I enzyme solution from Bacillus subtilis (approx. 90 mg/ml of protein content)
- 1.8 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH)
- and 0.06 mM mediator 1 ,8-dihydroxy-9,10-anthraquinone.
3g/l Na 2 S 2 O 4 solution in alkaline medium (5 ml/I 32% NaOH) for reduction of 0.3% indigo on the dry weight of the fabric was used as the reducing agent in a comparative test. Dyeing was carried out after the same procedure as with enzymatic dyeing.
After the dyeing, samples were removed from the dye bath, rinsed with the distillated water, and air oxidized (more then 12 hours).
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were washed with 2 g/l Cotoblanc at boiling point for 15 minutes and rinse with plain water for 15 minutes. During soaping the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 60 0 C) and cold rinse (1 minute at 20 0 C). Air dried samples were determinate colour values, wash fastness, alkaline and acid perspiration fastness and light fastness.
Results:
Table 9 displays the CIEL*a*b * data of both chemically (Na 2 S 2 O 4 ) and enzymatic (at pH 11 ) indigo dyed cotton materials before and after the soaping. CIEL*a*b*
values of chemical and enzymatic dyeings are comparable. The levelness of the colour shade at pH 11 is better with comparison at pH 7 and 9.
Table 10 shows wash, perspiration and light fastness of both, chemically (Na 2 S 2 O 4 ) and enzymatically, indigo dyed cotton materials at pH 11 after soaping and rinsing.
Fastness properties of chemical dyed cotton material are comparable to enzymatic dyed samples.
EXAMPLE 6
Indigo dyeing of cotton material with repeated reused enzymatic reduction bath at pH 7,9 and 11 Woven cotton (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperture. During its application to the textile material, the dyestuff was reduced to the water-soluble form by means of a NADH-dependent enzyme / mediator reducing system. The process was carried out in TRIS/HCI (pH 7 and 9) and TRIS/NaOH (pH 11 ) buffers system, at 60 0 C (starting from about 25°C) for 90 min. The material - liquor ratio was 1 :80. After removal the sample from dye bath, new fabric sample was placed in the remained enzymatic-bath with the addition starting concentration of indigo and dyed 90 min at 60 0 C. Procedure was repeated five times using one enzymatic reduction bath.
Dyeing/reduction bath was as follows:
- 0.3% indigo on the dry weight of the fabric
- 25 ml/l enzyme solution from Bacillus subtilis (approx. 90 mg/ml of protein content) - 1.8 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH)
- and 0.06 mM mediator 1 ,8-dihydroxy-9,10-anthraquinone.
After the dyeing, samples were removed from the dye bath, rinsed with the distillated water, and air oxidized (more then 12 hours).
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were washed with 2 g/l Cotoblanc at boiling point for 15 minutes and rinse with plain water for 15 minutes. During soaping the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 60 0 C) and cold rinse (1 minute at 2O 0 C). Air dried samples were determinate colour values and colour depth (K/S) using the Kubelka-Munk equation.
(I- R) 2
KIS = -
2R
where R is the reflectance of the fibre at the wavelength of maximum absorption (650 nm).
Results:
Picture 1 shows K/S values indigo dyed cotton samples with repeated reused enzymatic reduction bath at pH 7, 9 and 11. Reusing of enzymatic reduction bath is possible for five and more repetitions at pH 11 , three repetitions at pH 9 and two repetitions at pH 7. Decreased colour depth at pH 7 can be associated with decreased enzymes activity at acid-neutral pH. At pH 9 and 11 colour depth is increased with every repetition, which is result of addition of new concentration of indigo in dye bath with residue unexhausted dye. The enzyme based reduction bath is capable repeatedly reduce new indigo concentration at pH 9 and 11.
EXAMPLE 7
Indigo dyeing of polyamide material with repeated reused enzymatic reduction bath at pH 7,9 and 11
Knitted PA6.6 and woven PA6 (pre-wetted for 30 minutes in distillated water at room temperature) was dyed in indigo solution in the laboratory dyeing aperture. During its application to the textile material, the dyestuff was reduced to the water- soluble form by means of a NADH-dependent enzyme / mediator reducing system. Process was carried out in TRIS/HCI (pH 7 and 9) and TRIS/NaOH (pH 11 ) buffers system, at 60 0 C (starting from about 25°C) for 90 min. The material - liquor ratio was 1 :80. After removal the sample from dye bath, new fabric sample was placed in the remained enzymatic-bath with the addition starting concentration of indigo and dyed 90 min at 60 0 C. Procedure was repeated five times using one enzymatic reduction bath.
Dyeing/reduction bath was as follows:
- 0.05% indigo on the dry weight of the fabric
- 50 ml/1 enzyme solution from Bacillus subtilis (approx. 50 mg/ml of protein content)
- 2 mM cofactor β-Nicotinamide adenine dinucleotide disodium salt (NADH)
- and 12.5 μM mediator 1 ,8-dihydroxy-9,10-anthraquinone
After the dyeing, samples were removed from the dye bath, rinsed with the distillated water, and air oxidized (more then 12 hours).
Sodium metasilicate-5-hydrate (Cotoblanc) was used for the soaping step. Samples were washed with 2 g/l Cotoblanc at boiling point for 15 minutes and rinse with plain water for 15 minutes. During soaping the isolated molecules of indigo pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The samples were finally passed through a hot rinse (1 minute at 60 0 C) and cold rinse (1 minute at 20 0 C). Air dried samples were determinate colour values and colour depth (KJS) using the Kubelka-Munk equation.
KIS =
2R
where R is the reflectance of the fibre at the wavelength of maximum absorption (650 nm).
Results:
Picture 2 shows K/S values indigo dyed PA6.6 samples with repeated reused enzymatic reduction bath at pH 7, 9 and 11. Reusing of enzymatic reduction bath is possible for five and more repetitions at pH 9 and 11. Decreased colour depth at pH 7 can be associated with decreased enzymes activity at acid-neutral pH. At pH 9 and 11 colour depth is increased with every repetition, which is result of addition of new concentration of indigo in dye bath with residue unexhausted dye. Enzymatic reduction bath is capable repeatedly reduce new indigo concentration at pH 9 and 11.
Picture 3 shows K/S values indigo dyed PA6 samples with repeated reused enzymatic reduction bath at pH 7, 9 and 11.