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Economy and Ecology in Continuous Dyeing of Cotton Fabrics Using

Reactive Dyes

The textile finishing industry is faced with more or less the same problems world-wide.

Environmental protection regulations (waste water and exhaust air) energy consumption,

personel problems, and cheap imports are just a few of the diffuculties to be overcome. Only

through close co-operation between the textile finisher, machine maker and chemicals

industries, can these problems be addressed. This article details a success in the field of

continuous dyeing of cellulose fibres using reactive dyestuffs achieved as a result of this type

of co-operation.

Processes There are presently three main processes in use world wide for continuous dyeing of woven

cellulosic fabrics, eg. 100% cotton, using reactive dyestuffs

1- Pad batch or CPB process.

2- Pad-dry thermofixing process

3- E-control process.

The first of these requires the smallest machine range, whilst the other three demand more or

less complex ranges.

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Cold pad-batch dyeing is a more enviromentally sound and higher quality dyeing

method for woven and knitted cotton/viscose fibers. The process removes salt from the

effluent, reduces the use of water, energy, reduces the volume of effluent and occupiess less

space on the production floar.

Benefits of CPB dyeing can be summented as follows;

-Relatively low cost of equipment

-Less surface area

-Low amount of effluent. Less water consumption

-No salt residue in effluent water

-Conventional exhaust dyeing system emits up to 1,0 kg salt per kg of fabric

-Low steam consumption, 50 percent less

-Low electricty requirement, 30-40% less

-Improved fabric quality

-Reduced labor cost

POINTS TO BE CONSIDERED

1)Machinery and production Area, Laboratory

-Padding cylinders should be horizontally mounted.

-Padding trough should have small volume of 15-25 liter

-For the coolingfront and back side of entering fabric, two water cooled cylinder should be

available.

-Padding trough should be clad in a cooling jacket to maintain a constant liquor temp. Ideal

temperature is around 22-230C

-Lab. padder should be also horizondal and liquor should be placed between the nips of

cylinders.

-Dyed lab. samples should be kept at the same temp. of production dwelling area-best in

dwelling salon

-Dwelling area should be air conditioned and kept 3-50C above padder temperature

-Lab, padder and batching area should be away from sun shine, air current, chemical fumes.

-Dye/alkali supplying pump should run always at 4/1 ratio and be checked regularly.

-Batch rotation should be around 5-10 rpm.

2) FABRIC

-Fabrics should be uniformly bleached, and if possible mercerized.

-Absorbancy should be high and be same along width of fabric

-Fabric should be uniformly dried and cooled down prior to padding

-Fabric stitching should not be overlapped

3) DYE

-Dyes should have high solubility at room temp. water

-Dyes should have similar substantivity in order to prevent tailing

-Dyes should have similar reactivity to obtain excellent reproducibility

-Dyes should have higher alkali stability to prevent hydrolyzation

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4) CHEMICALS

Urea: As an excellent hydrofobic chemical, urea is preferred to disolve the reactive dyes.

Consumption amount is 50-100 g/lt. Half of the amount is supplied into dye dissolving tank

prior tos sprinkling. Rest is supplied into stock dye solution to cool down the temp, due to its

endothermic nature.

Ewet CNT New: For uniform absorbtion of dye along with fabric, Ewet CNT is a power full,

foamless, alkali resistant penetratior. Usage amount is 1-3 ml/lt. It is silicon antifoam free.

Exoline PAD: This chemical increases the pick-up the fabric resulting uniform and tailing

free dyeing. Exoline PAD is particularly advised for light, narrow and tighter woven fabric.

Usage amount is 3-5 ml/lt

Antisil ACC or ECO: In order to diminish calcium and silicate deposition on the fabric and

cylinders, Antisil ACC/ECO is a strong sequestering and dispersing chemical. Application

amount is 1-3 ml/lt

Silicate: Silicate is used as hydroltic stabilizer of dyes in alkaline medium with NaOH.

Normally 50 ml or 95 ml used but in tropical conditions 110 ml is preferred. Silicate gravity is

38-40 Be’. By increasing dosage amount, stability is promoted but fabric hardness and silicate

sedimentation on cylinders is inevitable.

Recipe

NaOH --

A Silicate --

Ewet CNT New 1-3

Antisil ACC/ECO 1-3

B Exoline PAD 2-3 (ıf necessery)

Urea 50-100

Dye --

B/A proportion is 4/1 and regulated by dosage pump

-NaOH / Silicate amount

Dye g/lt

Silicate Baume Silicate

ml/lt <20 30 40 50 60 >60

NaOH

38-40 Be’ 50 10 14 14 14 17 20

38-40 Be’ 95 14 17 17 20 20 22

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DWELLING TIME

Batching area should be conditioned kept at 3-5

0C above the padder temperature. Dwelling

time varies according to the chemical reaction group of dye.

Dye group Batching time, hrs

Vinyl sulfon 4-6

Bifunctional 8-12

Phthalocyanın, Turquoise 20-24

Extension of dwelling time has no effect on the tone or yield of Kimsolıne dyes.

WASHING

For effecient washing of CPB dyed fabrics, 7-8 chamber washing tank is sufficient. In the first

2-3 tank, excess amount water is used, to remove Silicate and to drop the pH 8-8,5.

Temperature in these tanks should not be above, 500C. If pH does not drop or washing

machine is short, it is wiser to wash rest of the chambers at 500C and in the second pass at

boiling temp.

1. Chamber 500C

2. Chamber 500C

3. Chamber 500C pH 8,0 – 8,5

4. Chamber 980C Exoline 3025 2ml/lt

5. Chamber 980C

6. Chamber 980C

7. Chamber 700C

8. Chamber 400C

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Kimsolıne Dyes for CPB System

Since alkaline stability of vinyl sulfon dyes is rather low, we prefer Kimsoline bifunctional

reactive dyes for CPB dyeing Reproducibility ratio is much higher and washing off property

is superior. We recommend the following Kimsoline range for CPB dyeing

Light Shades

Kimsoline Yellow K-LL

Kimsoline Red K-LL

Kimsoline Blue BRF

Kimsoline Grey K-LL

Medium- Dark Shades

Kimsoline K-EM Range

Kimsoline K-ED Range

Additionally

Kimsoline Turquoise HFG

Kimsoline Brill. Blue Rsp

Kimsoline Liquid Black Dyes.

Solubility of Blue Rsp and Turquoise HF-G is superior in presence of alkali.