Indigo - Continuous [Modo de Compatibilidad]

7/27/2019 Indigo - Continuous [Modo de Compatibilidad]

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Asia Pacif ic Cont inuous dyeing of indigo

DyStar

-Continuous Dyeing of Indigo

Page 1June 2003

Regional Business Development Denim


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Content

1. General overview

2. DyStar Product Offer

3. Dyeing machinery and principle

4. Pretreatment5. Dyeing

6. Metering system

7. Guideline recipes

. er rea men

9. Conversion factors for caustic soda

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1. General Overview Indi o

Main application is the continuous dyeing of warp yarn for denim fabric.

The indigo pigment is a water-insoluble vat dye (no affinity to cotton).

Indigo is converted to its water-soluble leuco form by reduction (affinity to

.

With DyStar Indigo Granules the reduction process (vatting) takes place in

the stock vat.

DyStar Indigo Vat 40% Solution and DyStar Indigo Vat 60% Grains have

been reduced by hydrogenation process during their manufacture.

products.

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2. D Star Product Offer

Product Characteristics/main application areays ar n go ranu es ow us ng

z Denim

z No stock vat preparation

z Up to 70 % saving in hydrosulfite

z Contains 9 % NaOH

z Denim

z Contains 15 % NaOH

z Wool, cotta e industr a lications

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3. D ein machiner and rinci le

Rope dyeing:

The yarn is assembled into ropes of about thumb thickness, each containing

round 350 ends; 12 36 ropes (1 3 warps) are run through the dyeing

- - . ,

wound onto section-warp beams.

Slasher dyeing:

The ends (approx. 4000) from several section-warp beams are assembled to, - ,

onto beams for the loom.

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3.1 D ein machiner Ro e D ein

Advantages Disadvantagesg ra e o pro uc on

z No stoppage with lot changes

z No ossibilit of side-to-center shade

e ropes mus e opene a er

dyeing

z Lack of flexibilit owin to the lar e

variations in the finished fabric

z Little yarn wastage, provided that

dyebath volume (up to 40000 l)

zAdditional costs for softener to

leader is used facilitate opening of the ropes

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3.2 D ein machiner Slasher D ein

Advantages Disadvantagesompac range

z Fine yarns (shirting materials) can be

rocessed u to Ne 40/1

oss y o s e- o-cen er s a e

variations in the finished fabric

z Yarn wasta e from lot chan es

z Continuous production from section-

warp beam (undyed) to sized warp

z Short immersion times and/or a small

number of dips which are particularly

beam (dyed)

z Small dyebath volume (1500 8000 l)

likely with older dyeing ranges result

in a lower standard of fastness with

z Produces maximum ring dyeing

changes

z Relatively long stoppages during lot

changes



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3.3 D ein rinci le I

The dyeing process on indigo-dyeing ranges is carried out in a number of

dips, usually from 4 8, i. e. the warp yarn is passed through a dyebath

several times.

The dyebath can consist of one box only or be made up of several boxes.



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3.3 D ein rinci le II

Dipping

immersion time 4 20 s

reduced indigo exhausts onto the cellulosic f ibre

Squeezing

70 80% liquor pick-up

contr ibutes to rapid oxidation

improves the fastness

Air passage

the hydrosulfite and the indigo is oxidized



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3.4 D ein machiner and rinci le



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4. Pretreatment - Surve

Process Process Applicationrewe ng an ar process or s as er ye ng ranges

Boiling off z Standard process for rope dyeing ranges

Causticizingz

Process to obtain extreme ring dyeing and/or specialeffects (e. g. salt and pepper)

Without pretreatment z Only for slasher dyeing ranges

z Higher risk of streakiness

zAddition of wetting agent to the dyebath necessary



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4.1 Prewettin

3 g/L wetting agent e.g. Primasol NF (BASF)

Temperature: room temperature

Immersion t ime: at least 6 s

Replenishment: by level control

Rinse cold



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4.2 Boilin off

10 15 mL/L NaOH 50%

1 - 3 g/L sequesting agent e.g. Kieralon MFB (BASF)

2 - 4 g/L complexing agent e.g. Trilon TA (BASF)

Temperature: 90 C

Immersion time: at least 10 s


2 x rinse hot (approx. 60 C)

Rinse cold



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4.3 Causticizin

NaOH 12 - 22 B

4 g/L wetting agent e.g. Leophen MC (BASF)

2 - 4 g/L complexing agent e.g. Trilon TA (BASF)


Immersion time: 10 15 s


To maintain a NaOH concentration of 20 B in the causticizing box, the liquor

must be replenished with NaOH of 22 B.



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4.3.1 Causticizin with/without neutralization

Causticizing without subsequent neutralization

Causticize

2 3 x rinse hot (approx. 60 C)

Rinse cold several times

Causticizing with subsequent neutralization

Causticize

1 2 x rinse hot (approx. 60 C)

Neutralize/acidify

1 2 x rinse cold



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5. D ein

Irregular dyeing results particularly variations within dyeing lots are a

problem in denim production. As a rule, the finished denim material is classed

into groups according to the dyeing results and the appearance after wash-

down. Maintaining the dyebath parameters constant reduces the number of

these groups and also the proportion of off shades .



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5.1 Process Parameters I

Parameter Nature of the change Effecte uce n go se n concen ra on

Fall in concentration

ncrease n ep o s a e

z Decrease in depth of shade

content

z Less contrast in wash-down

Immersion time Extending z Greater dye penetration

z Increase in depth of shade

Shortening z More pronounced ring dyeing

z Decrease in depth of shade



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5.2 Process Parameters II

Parameter Nature of the change Effectaus c

concentration

a s ng a ses e p

z Greater dye penetration

z Shade becomes redder clearer

Lowering z Lowers the pH

z More pronounced ring dyeing

z Shade becomes greener, duller

z Risk of formation of the vat acid at

pH


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5.2 Process Parameters III

Parameter Nature of the change Effecty rosu e

concentration

a s n g

z Shade becomes greener, clearer

z Lowers the pH

Loweringz

More pronounced ring dyeingz Promotes oxidation of the indigo in

the air assa e

z Risk of increased formation of indigo

pigment in the dyebath

z Shade becomes redder, duller

z Raises the pH



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5.3 Exam les of H variation de ree of rin d ein

pH 13.2 pH 11.5

Cross-section of a yarn bundle with approx. 200 threads (magnification 7 : 1)

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5.4 Exam les of H variation chan e in shade

pH 13.2 pH 11.5

Surface view of a yarn bundle

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5.4 Exam les of h drosulfite variation chan e in shade

0.5 g/L excess 2.0 g/L excess

hydrosulfite hydrosulfite

Surface view of a yarn bundle

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6.1 Stock vat without chemical re lenishin additions

Little flexibility when there is

NaOHHydrosulfite

Auxilliaries

a change in the style to be

dyed

Little flexibility when it is

necessary to change the

processing parameters

instable because of

ecompos on o y rosu e

not recommended

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6.2 Stock vat with se arate chemical re lenishin additions

Most frequently used methodMore flexible than the stock vat

method without chemical

replenishmentsNaOH

NaOHHydrosulfite

Auxilliaries

Does not allow automatic pH

controllimited stability of dissolved

y rosu e

y rosu e

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6.3 Stock vat with se arate chemical additions and meterin

of the caustic soda

Particularly flexibleProcessing parameters can be

readily changed by altering the

setting of the metering pumpsNaOH

NaOHHydrosulfite

Auxilliaries

Allows automatic pH control

Allows several dyeing ranges tobe supplied from one mixing

y rosu e

s a on

The recipes for the stock vat

and chemical replenishment

limited stability of dissolved

hydrosulfite

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6.4 D Star Indi o Vat 40% Solution with se arate chemical

replenishment additions

No stock vat preparationDye metered direct from the

storage tank

Particularly flexibleNaOH

DyStar Indigo Vat40 % Solution

Storage tank

Allows automatic pH controlHydrosulfite

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6.5 D Star Indi o Vat 40% Solution with se arate chemical

additions and metering of the caustic soda

No stock vat preparationDye metered direct from the

storage tank

Does not allows automatic pHNaOH

DyStar Indigo Vat40 % Solution

Storage tank

controlHydrosulfite

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7.1 Stock Vat Pre aration I

80 g/L DyStar Indigo Granules

1 g/L wetting agent e.g. Primasol NF (BASF)

4 8 g/L complexing agent e.g. Trilon TA (BASF)

1 g/L dispersing agent e.g. Setamol WS (BASF)70 mL/L NaOH 50%

65 g/L hydrosulfi te

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7.1 Stock Vat Pre aration II

Fill cold water into the mixing vessel to approx. 75% of the final volume

Add auxiliaries

Strew in and disperse indigo.

Add caustic soda Slowly strew in hydrosulfite. Stirring for 3 5 min dissolves the hydrosulfite.

Fill up with water to the final volume. The mix is f inally stirred again for

3060 s.

Depending on the temperature, vatting of the indigo is completed in 2 3

hours

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7.2 Chemical re lenishment

135 g/L hydrosulfite

70 mL/L NaOH 50%


Chemical liquors should be stored under cool conditions and protected from

exposure o a r. e amoun s prepare s ou e suc a ey are

consumed within 60 90 min .

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7.3 D ebath re aration

40 g/L salt (common salt or Glauber salt)

2 mL/L NaOH 50%

1.5 g/L hydrosulfite

5 mL/L stock vat (cf. 7.1) = 2.0 g/L DyStar Indigo Granules

The dyebath is set cold with salt, caustic soda and hydrosulfite, followed by

addit ion of the stock vat.

12.5 mL/L of the stock vats described in 7.1 corresponds to 1 g/L DyStar

Indigo Granules.

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7.4 Exam le calculation I

7 Ne yarn

4000 number of ends

25 m/min running speed

7.4 kg/min yarn throughput1.8 % indigo concentration based on weight of yarn

0.5 g/L hydrosulfite concentration

11.7 pH

6 dips

75 % liquor pick-up

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7.4 Exam le calculation II

130 g/min replenishment of DyStar Indigo Granules250 g/min replenishment of hydrosulf ite

190 mL/min replenishment of NaOH 50%

oc va : . m n rep en s men

80 g/L Dystar Indigo Granule

70 mL/L NaOH 50%

Chemical liquor : 0.7 L/min replenishment135 g/L hydrosulfite

70 mL/L NaOH 50%

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8. Aftertreatment

2 3 x rinse hot (up to 50 C)

The dyed warp yarns are rinsed at least twice with cold or, better, warm

water of u to 50 C to wash out an unfixed d e and chemicals.

With rope-dyeing ranges, a softener should be used. The last rinsing bath to

.

Warp yarns dyed on slasher machines are given an intermediate drying to

a residual moisture content of approx. 30% and are then sized.

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9. Conversion factors Caustic soda I

1 L NaOH 50% = 1.74 L NaOH 38 B1 L NaOH 50% = 1.09 L NaOH 48 B

1 L NaOH 50% = 766 g NaOH 100%

1 L NaOH 50% = 1525

1 L NaOH 38 B = 0.57 L NaOH 50%

a = . a

1 L NaOH 38 B = 441 g NaOH 100%

1 L NaOH 38B = 1358 g

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Indigo - Continuous [Modo de Compatibilidad]

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