WO2019045660A2

WO2019045660A2 - Ecological and sustainable indigo dyeing process with less water

Info

Publication number: WO2019045660A2
Application number: PCT/TR2017/050702
Authority: WO
Inventors: Ali CIFCI; Umit Can KILIC; Fatih CAM
Original assignee: Orta Anadolu Ticaret Ve Sanayi İşletmesi Türk A.Ş.
Priority date: 2017-08-25
Filing date: 2017-12-27
Publication date: 2019-03-07
Also published as: TR201712761A2; WO2019045660A3

Abstract

The invention is an indigo dyeing process; of which harms to environment are reduced and rendered with lower costs in comparison to traditional applications; in order to reduce water consumption and prevent undesired salt formation when dyeing warps, used in denim production; and includes the steps of pre-wetting warp yarns in the form of a rope, prior to indigo dyeing; by making use of solution containing 1-5 cc/L sodium hydroxide (Caustic), 5-8 gr/L wetting agent and 1-5 gr/L ion immobilizer; washing at least 1 time with water at 20-70°C, with the purpose of removal of wetting agent used at pre-wetting step; reduction of indigo coloring agent, resorting to acetol (hydroxyacetone) at the temperature of 27 °C for a period of 10 to 15 minutes, for that water insoluble indigo is made soluble; checking solution's color to check whether the reduction of indigo coloring agent is completed; passing yarns in the form of a rope through vessels, containing dye solution at 27 °C with a pH value of 11 to 13 pH, in which the obtained indigo dye is discharged/put for successive 3 vessels at least, ensuring oxidation of reduced indigo coming out of dye vessel with oxygen in the air, in other words, making it contact with air, with the purpose of stabilizing dye on yarns by rendering it insoluble in water; dipping yarns in the form of a rope, on which oxidized indigo coloring agent there is into solution at 70-75°C with a pH value of 4 to 5, containing 10-20 gr/L polyamine polymer and 5-15 gr/L acetic acid.

Description

ECOLOGICAL AND SUSTAINABLE INDIGO DYEING PROCESS

WITH LESS WATER

Field of the Invention

This invention is an indigo dyeing process, developed and intended for warp dyeing at denim production facilities and is related to the utilization of a stabilizer and chemical substances to reduce water consumption and prevent undesirable salt formation during dyeing.

Description of the Related Art

The permanent coloring of a textile material is called as dyeing, and the coloring agent is denominated as dye. The colorizations, performed using coloring agents, are implemented through various dyeing methods, usually in the form of solution or suspension. One of the oldest coloring agents known to man for dyeing textile materials is the vat coloring agents, generated via chemical reduction treatment, called as "vatting". These have been denominated as vat dyes, due to the fact that they have been fermented inside wooden vats and utilized after bringing into water-soluble state in the past.

Vat dyes are an important coloring agent variety in cotton dyeing treatments, especially regarding merchandise with dyed yarn. This is a water insoluble coloring agent class, generally including keto groups, which is found in leuko form subjected to reduction, brought into keto structure yet again by oxidizing inside the fiber after dyeing. Vat dyes are divided into two chemical groups: anthraquinone and indigo. Indigo (C18H10N2O2), as a vat dye class, is naturally extracted from Indigofera Tinctoria plant. It was synthesized synthetically first by a German chemist, Baeyer; and it is not dissolved in water, alcohol, ether, and aqueous acids as well as alkalis and does not penetrate into fibers. It is the most prevalent organic dye and quite resistant to light, washing, alkalis, and acids. The denim is a fabric, manufactured by cross-weaving weft and warp yarns. Its most important feature is that differing looks and effects through various washing methods and wearing up as used. This feature results from the indigo colorant with which warp yarns are dyed. The indigo colorant is to be activated (into leuco form) in the first place for that the colorant could dye the fiber. A series of chemical reactions is required to convert it into the leuco form. This treatment is called as reduction. The reduction is carried out under appropriate environmental conditions usually with hydrosulfite. An alkali environment is necessary for this treatment. The chemical used to this end is caustic. After dyeing, the dye is fixed onto the fiber by interacting with air. This treatment is called oxidation.

Reduction in indigo dye vessel:

Ci₆Hio0₂N2 + Na₂S0₄ + NaOH => Ci₆Hi₀O₂N₂Na₂ + NaS0₃ + 2H₂0

Indigo Hydro Caustic Indigo Salt

Water

Oxidation through aeration treatment:

C₁₆H₁₀O₂N₂Na₂ + ½ 0₂ + H₂0 => C₁₆H₁₀O₂N₂ + 2 NaOH

Indigo leuco aeration Indigo leuco

The utilization of a stabilizer in textile dyeing and advantages it procures are mentioned in a Chinese patent document, reference number CN105421118, from prior art. The stabilizer is a combination of acrylic acid, ammonium hydrogen sulfite, epoxy chloropropane, benzyl tryethyl ammonium chloride, hydroxy propyl trimethyl ammonium chloride chitosan, polyethylene polyamide, peroxy sulphate, polyethylene glycol ester, metacrylic acid, and distilled water. Moreover, it offers advantages including environmental friendliness and increased color strength. It is related to indigo dyeing treatment of textile substances with cellulose content in a US patent document, reference number WO1994023114A, from prior art. A reducing agent, an hydroxy acetone compound known in the literature, is added for that an alkali environment can be generated during the treatment. The utilization of a stabilizer in textile dyeing and its advantages are mentioned in a Chinese patent document, reference number CN 103469640, from prior art. The stabilizer agent is a composition of the substances A and B, and the compound A contains, by mass, epoxy chloropropane for 60-70%, saturated alcohol- polyoxyethylene ether for 12-15%, and alylmetylamine hydrochloride and the compoound B contains, by mass, multimeric polyamine for 40-48% and dicyandiamide for 52-60%. The resistance of textile dyes is enhanced, when compared to stabilizers from prior art.

The utilization of a reducing agent in textile dyeing and those available for utilization are mentioned in a United Kingdom patent document, reference number GB 1405182 (A), from prior art. It is pointed out that hydroxyacetone, dihydroxyacetone, glycol aldehyde, dihydroxybutanone, 2, 3-di hydroxyacrylaldehyde, ascorbic acid, cyclopentandiolon, ethyl [alpha] -amino- hetobutyrate, cuioid compounds etc. can be used as reducing agents.

The indigo dyeing process is a multi-step process and requires many chemicals. The coloring agent is reduced at first and brought into water soluble state before the treatment. The dye is then oxidized into water-insoluble state to ensure retention after application.. The excessive number of steps results in higher expenses in addition to the cost of the dye. Then, it is environmentally hazardous for excessive chemical utilization and water consumption during dyeing. Furthermore, the hydroxy compound utilized in the technique for indigo dye reduction is also detrimental to the environment and human health.

Brief Summary of the Invention

The aim of the invention is dyeing with lower costs by reducing water and energy consumption during indigo dyeing warp yarns.

The other objective of the invention is to reduce flushing water consumption after dyeing, for approximately 65% by utilizing polyamine polymer as a stabilizer after dyeing aside from the prior art.

The other objective of the invention is to get cleaner waste watersby utilizing acetol (hydroxyacetone) compound during indigo dyeing to prevent salt formation after dyeing.

Detailed Description of the Invention

The invention is an indigo dyeing process, of which harms to the environment are reduced and rendered low cost in comparison to traditional applications, with the purpose of reducing water consumption and preventing undesired salt formation within the course of warp dyeing treatment used in the denim production; including the steps below:

- pre-wetting by implementing a solution of 1-5 cc/L sodium hydroxide (Caustic), 5-8 gr/Lwetting agent, and 1-5 gr/L ion immobilizer onto warp yarns in the form of rope or open width prior to indigo dyeing;

- flushing at least 1 time with water at 20-70°C to remove wetting agent used for pre-wetting;

- reducing indigo coloring agents by utilizing acetol (hydroxyacetone) at 27°C for 10 to 15 minutes, in order to make the water insoluble indigo soluble, - checking the solution's color to check whether the reduction of indigo coloring agent is completed

- alternatively, the reduced liquid indigo can also be utilized in the processes.

- passing yarns in the form of a rope through vessels, into which the obtained indigo dye is discharged/put,containing the dye solution at 27 °C with a pH value of 11 to 13, over 3 vessels at least,

- ensuring oxidation of the reduced indigo, coming out of dye vessels with the oxygen in the air, in other words making it contact air to render the dye insoluble in the water and make it permanent on the yarn,

- dipping yarns in the form of a rope with oxidized indigo coloring agent into the solution at 70-75°C with a pH value of 4 to 5, containing 10- 20 gr/L polyamine polymer and 5-15 gr/L acetic acid.

For the process, subject matter of the invention, the pre-wetting treatment is performed, prior to indigo dyeing treatment, onto the yarns in the form of a rope, which would constitute the denim, resorting to 1-5 cc/L sodium hydroxide (Caustic), 5-8 gr/L wetting agent, and 1-5 gr/L ion immobilizer in order to remove the substances inherent to the cotton's nature, which may spoil dyeing, such as oil and wax, from yarns, increase the hydrophilicity (water absorption) of the yarn, wet the yarn completely, and ensure a better dye penetration.

Washing at 20-70 °C for at least 1 time is intended to remove the chemicals used for pre-wetting from warp yarns.

The reduction of water insoluble indigo (vat) coloring agents and their rendering into water soluble state is called vatting. The reduction of vatting process colorant into leuko (reduced indigo coloring agent) compound, by making use of acetol (hydroxyacetone) is denominated as vatting. A change occurs in the color of the colorant when the vatting treatment is completed. The indigo turned to yellow after reduction dyes the cellulose and this reduction product on the fiber is oxidized to blue colored indigo by ambient oxygen. The temperature, resulting from the reduction is 27°C and the vatting time is approximately 15 minutes. It is required that the solution color is checked to make sure if the reduction of indigo coloring agents is finalized. It is expected that the yellow color turns into green within 12-15 seconds; when a clean glass is dipped into and removed out of the solution. The addition of some acetol is necessary, if it is not clear and yellow or turns into green too fast.

The dyeing is performed by passing the yarns in the form of a rope through vessels at 27 °C with a pH value of 11 to 13, into which indigo coloring agents are discharged/put, for at least successive 3 vessels.

It is required that leuko (reduced indigo) compound, received by warp yarns after the completion of dyeing is transformed into water insoluble vat coloring agent formas a result of oxidation. The reverse vatting is also a form of oxidation.. The ambient oxygen is utilized for oxidation. The dye is stabilized on yarns by rendering the dye insoluble in water via air passage on fabric.

The yarns in the form of a rope or an open width warp having indigo coloring agent oxidized through air passage on them are dipped into a solution at 70-75°C with a pH value of 4 to 5, containing 10-20 gr/L polyamine polymer, and 5- 15 gr/L acetic acid. Thus, the yarns are purged of excessive coloring agent and chemicals, since there is no more need for washing and drying after indigo dyeing, and this allows water savings, nearly for 65%. The salt, which is released due to the reduction reaction of indigo with hydro in classical indigo dyeing process, mixes with washing waters. The waste waters, containing high percentage of salt damage drain pipes. The waste water becomes cleaner as there is no salt formation in the new process. Furthermore, the salt resulting from dyeing takes on the vibrancy of the color and turns it towards a gray hue, compromising the stability of longerdyeing applications.

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Claims

An indigo dyeing process; of which the harms to environment are reduced and rendered with lower costs in comparison to traditional applications in order to reduce water consumption and prevent undesired salt formation when dyeing warp yarns used in denim production dyeing and, including the following steps under its most basic form:

- pre-wetting warp yarns in the form of a rope, prior to indigo dyeing making use of solution, containing 1-5 cc/L sodium hydroxide (Caustic), 5-8 gr/L wetting agent, and 1-5 gr/L ion immobilizer,

- washing at least 1 time with water at 20-70 °C to remove wetting agent used at pre-wetting step

- reduction of indigo coloring agent, resorting to acetol (hydroxyacetone) at 27 °C for 10 to 15 minutes, for that water insoluble indigo is made soluble, or utilization of reduced liquid indigo

- checking solution's color to check whether the reduction of indigo coloring agent is completed,

- passing yarns in the form of a rope and open width through vessels, containing dye solution at 27 °C with a pH value of 11 to 13 pH, in which the obtained indigo dye is discharged/put for successive 3 vessels at least,

- ensuring oxidation of reduced indigo coming out of dye vessel with oxygen in the air, in other words, making it contact with air, in order to stabilize the dye on yarns by rendering it insoluble in water,

- dipping yarns in the form of a rope, on which oxidized indigo coloring agent there is a solution at 70-75°C with a pH value of 4 to 5, containing 10-20 gr/L polyamine polymer, 5-15 gr/L acetic acid and,

- Characterized in that utilization of acetol (hydroxyacetone) for that indigo coloring agents remains in reduced state, - utilization of a solution containing polyamine polymer and acetic acid to remove excessive coloring agent and chemicals from warp yarns after dyeing process.

An indigo dyeing process; as shown in Claim 1, characterized by dipping warp yarns in the form of a rope, on which there is indigo coloring agent oxidized through air passage, into a solution containing 10-20 gr/L polyamine polymer and 5-15 gr/L acetic acid.

An indigo dyeing process, as shown in Claim 1, characterized by passing warp yarns in the form of a rope or open width through dyeing vessels containing indigo coloring agents at 27 °C with a pH value of 11 to 13.

An indigo dyeing process, as shown in Claim 3, characterized by reducing water insoluble indigo (vat) coloring agent with acetol (hydroxy acetone).

An indigo dyeing process; as shown on claim 1, characterized by pre- wetting warp yarns in the form of a rope prior to indigo dyeing with 1- 5 cc/L sodium hydroxide (Caustic), 5-8 gr/L wetting agent, and 1-5 gr/L ion immobilizer.