indigo dyeing

5/20/2018 Indigo Dyeing

1/20

INDIGO DYEING

PREPARED BY-

RAJDEEP SINGH

B-Tech 4

th

Sem.


2/20

CONTENTS

Introduction To Indigo Dye

Chemical Property And Synthesis Of Indigo

Why Indigo ?

Indigo Dyeing Briefing

Indigo Dyeing Methods

Recent Developments In Indigo Dyeing

References


3/20

Indigo dye is an organic compound with adistinctive blue colour. Historically, indigo

was a natural dye extracted from plants, and

this process was important economically

because blue dyes were once rare. Nearly all

indigo dye produced today several thousand

tons each year is synthetic. It is the blueof blue jeans. The primary use for indigo is

as a dye for cotton yarn, which is mainly for

the production of denim cloth for blue jeans.

On average, a pair of blue jean trousers

requires 3 12 g of indigo.

INTRODUCTION


4/20

CHEMICAL PROPERTIES INDIGO DYE

Indigo is a dark blue crystalline powder that sublimes at 390392 C.

It is insoluble in water, alcohol or ether but soluble in DMSO, chloroform,

nitrobenzene, and concentrated sulfuric acid.

The chemical formula of indigo is C16H10N2O2.

The molecule absorbs light in the orange part of the spectrum (max= 613 nm).

HEUMANN'S SYNTHESIS OF INDIGO

It involves heating N-(2-carboxyphenyl)glycine to 200 C in an inert atmosphere with

sodium hydroxide. Indoxyl-2-carboxylic acid is generated.This material readily

decarboxylates to give indoxyl, which oxidizes in air to form indigo.


5/20

WHY INDIGO ?It supplies favoured shades from black to navy to sky blue.

Pleasant colour shade.

Possibility to dye cotton in cold dye bath.

Competitive in price.

Gives acceptable colour fastness and the exceptional advantage by

repeated washing of fading colour, to keep the colour shade that always a

clear, pleasant blue shade result.

Its soluble form is not sensitive to water hardness and this allows thedyeing of greige or minimum pretreated cotton.


6/20

The warp yarn in denim jeans is traditionally dyed with INDIGO,

whereas the weft yarn is white.

In indigo dyeing there is symbolic built-up of dye stuff on the yarn

according to the multi-deep process. Indigo sticks to the surface of the

cotton yarn, resulting in a blue surface, while the interior of the yarn

will remains white.

INDIGO DYEING


7/20

DIFFERENT INDIGO DYEING METHODS

Indigo rope dyeing process

Indigo-Slasher-or Sheet-dyeing

Loop dye 1 for 6 (continuous dye slashing)

Loop dye 1 for 6 with dyemer (continuous

mercerization dyeing and sizing).


8/20

INDIGO ROPE DYEING WITH SUBSEQUENT SIZING PROCESS

Step 1: Ball Warper

Step 2: Rope Dyeing

Step 3: Long Chain Beamer

Step 4: Sizing


9/20

Yarn from the ring spinning machine is wound into suitable package,assembled into a

rope and wound into a ball.

Usually 18 24 ropes are simultaneously processed.

Prior to dyeing, the ropes are boiled out and treated with caustic-soda and wetting agent.

The ropes are immersed into the dye-bath.

Immersion time 30 60 seconds .

Oxidation time 60 180 seconds for uniform dyeing.

For deep shade 5 6 times the ropes are immersed in a sequence of dye boxes.

After dyeing and oxidation range the ropes are guided through 2 or 3 washing boxes to

wash off excessive dye.

They are dried in a series of cans and deposited into large coilers.

After this rebeaming and opening of the ropes takes place for sizing operation.

Processing -An overview


10/20

INDIGO-SLASHER-OR SHEET-DYEING


11/20

Processing of single sheet slasher dyeing..

In continuous slasher dyeing and sizing back beams are used.

Here the total number of ends required for a weavers beam are dyed, dried, sized

and dried simultaneously.

Number of ends are pretreated (washed),dyed in 4 dye boxes and oxidized, no

softener are used in the last wash box.

The squeezing effect here is lower and therefore the danger of streakiness and

shade variation from centre to out side is also higher.

The immersion time in the dye boxes is approx. 10 15 seconds

Time for oxidation 30 60 second.

This system allows the installation of less expensive dye range and less additional

preparatory machinery.


12/20

In this system dyeing, sizing is done in 2 operations.

The main reason for dyeing of 2 sheet simultaneously is that it gives more even

dyed sheet .

These beams are dyed, oxidized and dried.

These beams are transported to the sizing machine and the yarn sheet sized in

double size boxes.

Immersion time and oxidation time is the same as with continuous slasher

dyeing.

With double sheet dyeing the linear warp thread density is doubled which have

following additions:

Squeezing effect is increased.

An even squeezing over the whole width is achieved.

There is no colour strips formation, streakiness or shading in the finished fabric.

The production out put of the dyeing is increased by 75%.

Processing of double sheet dyeing.


13/20

COMPARISION ON SLASHER DYEING ROPE DYEING

Required Space

Less

More

Mercerizing Easy Difficult

Manpower Less More

Dye bath

Less capacity

More

Yarn Can use Ne 1-30 without major

change

Can use Ne 1-16 without

major change

Flexibility

Flexibility to produce denim in

different colors and small

quantities

Less flexible. Difficult to

change colours.

Cost

Cost of production is lesser

compared to Rope Dyeing

Cost of production is more

compared to Sheet Dyeing

SLASHER DYEING VS ROPE DYEING- A COMPARISON


14/20

LOOP DYE 1 FOR 6 (CONTINUOUS DYE SLASHING)

In this system 10 16 warper beams with the total number of ends required for the

weaver beams are used.

The warper beams are placed in a moveable warp creel of which one can be loadedwhile other one set is in rotation.

The yarn sheet is guided to the soaking bath through a feed-in system

The soaking bath has the task to prepare the yarn for the following dyeing operation.


15/20

There is only a single Indigo dye box through which the yarn passes 4-5 times.

The yarn sheet after having been immersed into a single indigo dye instead of

moving forward runs into a long loop where oxidation takes place.

One of the advantages is ideal, utilization of hydrosulphite through squeezing 4 6

layers simultaneously and oxidation of yarn in a comparatively long oxidation loop.

After the oxidation the yarn sheet is guided through 2 washing boxes ,finally on to a

series of drying cans.

After that yarn is immersed into size boxes, dried and wound onto a weavers beam.

Continued


16/20

There is growing demand for dark shades specially dark marine blue for super

blue denims.

For this new indigo dyeing ranges which have increased the number of dye boxesbetween 8-15 with corresponding oxidation ranges.

In some cases hydroxyaceton is used which gives a darker shade with the desire

greenish touch .

In order to achieve ring dyeing, mercerized yarn has also been used. Mercerizing

gives an optical blue effect and superior colour fastness and behaviour in washing.

Mercerizing is very costly, therefore new ways in continuous mercerizing and indigodyeing was found.And so dyemer was introduced.

DYEMER

The dyemer range is integrated. For impregnation;padder for hot caustic solution is

placed after the heating system . The yarn is guided over cold cylinders and with anadjustable roller the tension of the yarn sheet can be adjusted according to the

required tension prior to the scouring in 2 more boxes.

After having passed this, the yarn sheet is immersed into the dye box and the same

process as with the loop dye method is repeated.

LOOP DYE 1 FOR 6 COMBINED WITH DYEMER


17/20

PARAMETER EFFECT IN CASE THE REFERRING PARAMETER IS

INCREASED,SUPPOSED ALL THE OTHERS ARE KEPT THE

SAME

1. Indigo concentration -deeper shade

-higher degree of penetration

-in extreme cases: inferior fastness level

2. pH

(alkali concentration)


-clearer, more reddish shade-increased indigo concentration due to inferior affinity

3. Hydrosulphite

concentration


-clearer, more bluish shade

--bronzing shade in absence of hydrosulphite and high indigo

concentration

4. Temperature -higher degree of penetration

-higher indigo concentration due to inferior affinity

-higher demand for hydrosulphite

-higher demand for caustic soda

IMPORTANT INDIGO DYEING PARAMETERS


18/20

RECENT DEVELOPMENTS IN INDIGO DYEING

Latest loop dye machines are equipped with nitrogen units which use

nitrogen gas as protective blanket over the surface of the Indigo dye. Thenitrogen gas prevents oxygen in the air from attacking sodium hydrosulphite

resulting in more consistent dyeing and reducing consumption of

hydrosulphite,which lowers the costs and pollution. There are other claimed

advantages such as higher speeds and darker Indigo colour.

DyStar and RedElec in regard of global awareness of environmental issueshave decided to use join forces to develop electrochemical dyeing of Indigo, a

sustainable solution that will eliminate harmful substances in dyeing and waste

water. The team will use its patented products, DyStar Indigo Vat 40%

Solution and RedElec's electrochemical technologies, throughout the

development process.


19/20

REFERENCES

Indigo-eBook-by-Bluconnection-May-2011

http://en.wikipedia.org/wiki/Indigo_dye

http://www.denimsandjeans.com/denim/manufacturing-process/indigo-

dyeing-%E2%80%93-various-methods-explained-and-compared/

http://www.expresstextile.com/20030904/dyeschemicals01.shtml

http://www.denimsandjeans.com/denim/manufacturing-process/indigo-

dyeing-with-loop-dyeing-machinery/

http://www.textileworld.com/Articles/2012/March/DyStar_And_RedElec

_Start_Sustainable_Indigo_Dyeing.html


20/20

indigo dyeing

Documents