DYEING PROCESS OF COTTON FABRIC WITH REACTIVE DYES

Dyeing process is the process of giving of colour at textile material equally ( uniformly ).

Cloth result which is desired after process of dyeing was :

1. On Colour horizon

Non happening ” defect ” dyeing like :

-       piebald of fold ( crease-mark / rope mark )

-       piebald of friction ( abrasion mark )

-       white stripe ( chalk mark )

2. Not happened deviation of colour.

3. Fade-proof colour

Following steps are required to Textile material which is required to be dyed to determine quality of dyestuff type and auxilliaries .

In principle mechanism of dyeing process consists of 3 step :

1. Migration dyestuff towards fibre

2. Adsorption molecule dyestuff at surface of fibre

3. Diffusion dyestuff from surface of fibre to fibre interior

To get good dyeing result hence there are 6 important thing which must be taken care of :

1. Hardness of water

2. Chemicals balance ( dyes , auxilliaries , salt , alkali )

3. Liquor Ratio ( comparison of  water with fabric weight )

4. pH dye solution ( beginning of process and phase process of fixation )

5. Dyeing temperature

6. Dyeing time

100% cotton knitted fabric can be dyed / are coloured with following types of dyes , :

-       Reactive  Dyes

-       Direct  Dyes

-       Sulphuric Dyes

-       Vat  Dyes

-       Pigment Dyes

Among some of the above dyes , reactive dye is most applied at 100% cotton fabric good in the form of knitted fabric or woven fabric .

Reactive dye are applied for following reasons :

1. Simple dyeing process.

2. Choice of more colours available

3. Good colour resilience

Based on its reactivity , reactive dye are divided into 2 types, that is :

1. Hot reactive dyes
Reactive dyes which  have low reactivity

2. Cool reactive dyes
Reactive dyes which  have high reactivity

Reactive Dyes are applied to for following reasons :

-  Good dye condensation
-  Good colour resilience
-  Dyeing at hot temperature so that penetrating of dye into fibre is better
-  Have good levelness of dyeing result
-  Have choice of complete colour
-  Easier process control
-  Very suited for mercerized cotton cloth
-  Generally resistant to process “  post  bleach ”

In principle process of dyeing 100% cotton knitted fabric with reactive dye is with circulation  material textile with dye solution and some auxiliaries, with certain concentration , certain time and certain temperature applies of dyeing machine.

PROCESS OF DYEING WITH HE TYPE REACTIVE DYES WITH EXHAUST DYEING SYSTEM

1.  METHOD SALT ADDITION STEP BY STEP

This method is suited for all dyeing colours and for machine in which dyeing solution do not have circulation , for example Winch machine .

2. METHOD ADDITION SALT IN THE BEGINNING OF PROCESS ( SALT-AT-START )

This method is more compatibly applied for dyeing colour from medium to depth colour and for machine with dyeing solution circulation and its the textile material , the example jet dyeing machine , jet flow machine.

Example of dyeing  recipe for red colour :

R/

-  Reactive Orange HER       2.0 %
-  Reactive Red HE-7B         1.5 %
-  Glauber  salt                      70 g/l
-  Soda Ash                           20 g/l
-  Dispersing-sequestering  agent   1 – 2 g/l
-  Anti crease mark agent     1 – 2 g/l
-  Anti foam agent                 1  g/l

Liquor Ratio /  vlot  1 : 10
Temperature 80 ⁰C
The time 60 minute
Jet dyeing machine

Auxilliaries and its function

1. SALT (  GLAUBER  SALT / SULPHATE SODIUM / Na2SO4 )
function to increase absorbtion of reactive dye into fibre

2. ASH SODA ( CARBONATE SODIUM / Na2CO3 )
function to react dye with fibre ( fixation )

3. DISPERSING-SEQUESTERING
functions to tie metal ion ( iron, calcium, copper, magnesium and other ) which is in the dyeing solution be so that got by colour better dyeing result. Besides functioning to increase reactive dye solution in high rate electrolyte.

4. ANTI CREASE MARK AGENT
functions to prevent incidence of crease-mark / rope mark ( piebald of fold ) during process of dyeing takes running.

5. ANTIFOAM  AGENT
functions to eliminate foam arising during dyeing process because it can cause piebald dyeing colour and colour scraggly. Foam  arises from water circulation and material which quickly by, also from auxilliaries which can generate foam. Too much foam can result in machine stucks.

Reactive dyeing process of HE  type  done by at temperature

80 C while for vinilsulfon type is done by at temperature 60 C.

NB :
Liquor Ratio ( LR ) or  Vlot  1 : 10 the meaning is amount of comparison of textile material which will be died with amount of water required, that is its example cloth counted 1 kg requires 10 water litre to process .

For example to dye cotton knitted fabric  200 kg in one jet dyeing machine requires water for dyeing solution 2000 litre.

Clauses requirement of salt and alkali with depth of colour

Dyes ( % )                      glauber  salt ( g/l )            soda ash ( g/l )

-       up  to 0.5                              30                                   10

-       0.51 – 1.0                              45                                   15

-       1.01 – 2.0                              60                                   15

-       2.01 – 4.0                              70                                    20

-       > 4.0                                     90                                    20

Illustrating reaction which happened by at dyeing process between reactive dye with cellulose fibre

Reactive dye which has been dissolved with water is enterred into machine dyes containing cotton fabric which is under water , so that absorption of dye is done into fibre. Absorption of dye into fibre is an exothermic process and balanced reaction. Some auxiliiaries , like salt , soda ash / alkali, dispersing  sequestering  agent, anti crease agent mark , antifoam  agent is enterred by into dyeing solution and dyeing process is continued with temperature and when certain colour, which is desired, is climbed.

WASHING PROCESS

There are 4 phase process of wash which is done after dyeing process :

1. Hot rinsing before soaping process
-   Eliminate or drop concentration of salt and alkali as many as possible
-   Avoid from the happening of precipitation of reactive dye
-   Eliminate the happening of wrinkling line at fabric as result of degradation
of dyeing temperature solution which would thrown ( “  rapid  cooling “)

2. Soaping
-   Eliminate reactive dye pickings which is hydrolysis by nit and is not
fixation / reacts with fibre
-   Increase power reactive dye diffusion to exit from surface of fibre

3. Hot rinsing after soaping.
-      Help to prevents reactive dye pickings to return to surface of fabric (  back  staining )

Phase of washing process for light colour fabric , medium colour and deep of colour

A. LIGHT COLOUR ( dyes < 1% , concentration of salt < 30 g/l )
- Hot rinsing ( 70 ⁰C , 10 minutes )
-  Soaping ( 95 ⁰C, 10 minutes )
-  Hot rinsing ( 70 ⁰C , 10 minutes
-  Cold rinsing ( 30 ⁰C , 10 minutes ) , overflow

B. MEDIUM COLOUR ( dyes  1  -  4  % , concentration of salt  30 – 60 g/l  )

-  Hot rinsing ( 70 ⁰C , 10 minutes )
-  Hot rinsing ( 70 ⁰C , 10 minutes )
-  Soaping  ( 95 ⁰C , 10 minutes )
-  Hot rinsing  ( 70 ⁰C , 10 minutes )
-  Hot rinsing  ( 70 ⁰C , 10 minutes
-  Cold rinsing  ( 30 ⁰C , 10 minutes ) , overflow

C. DEEP OF COLOUR ( dyes  > 4% , concentration of salt  > 70 g/l  )

-   Hot rinsing ( 70 ⁰C , 10 minutes )
-   Hot rinsing ( 70 ⁰C , 10 minutes )
-   Soaping ( 95 ⁰C , 10 minutes )
-   Soaping ( 95 ⁰C , 10 minutes )
-   Hot rinsing ( 70 ⁰C , 10 minutes )
-   Cold rinsing ( 30 ⁰C , 10 minutes ) , overflow
-   Fixing process

Note :
For old colour (  deep  colour ) as does navy colour , marron ( red of liver ) , turquise , washing of temperature after process of soaping was done twice

FIXING PROCESS

For medium colour and deep colour the process fixing by using of fixing  agent.  Fixing  agent functions for :

1. Strengthen strong tying dye with fabric fibre.
2. Increase resilience cleans fabric.

Simple mode of process of fixing is to enlarge reactive dye molecule in fibre so that dye will be more difficult having migration compatible exits fibre.

fixing agent-e

Process of workmanship with  fixing  agent :

R/
-       Fixing  agent  1 -  2  % ( medium colour ) or 2 -  3  % ( deep colour )
-       pH  5
-       temperature 50 – 60 ⁰C
-       time  20 minutes
after completing in cold rinsing then dried.

DYEING PROBLEM WITH HE TYPE REACTIVE DYES  AND ITS PREVENTION

1. Result of piebald dyeing

Preventive :

-  Dye selection truly and precisely
-  Apply of dyeing standard suggested
-  Apply of auxiliaries suggested

2. Repetition colour,  unequal dyeing results

Preventive

-  Dye selection truly and precisely.

-  Correct liquor ratio

-  Control temperature and time process

3. Result of young or older dyeing from laboratory standard

Preventive :
-   Liquor ratio between laboratory and production must equal
-  Apply of auxiliaries which is used in production at laboratory recipe
-  Dyeing recipe in laboratory must equal with production

4. Problem of crease-mark

-  Apply anti-crease agent mark

-  Heavy cloth which is dyed accommodate  with machine capacities suggested