Vinyl sulphone dyes or Remazol dyes are good quality Reactive dyes

Vinyl sulphone dye:
The vinyl sulphone group has played an important part in the field of reactive dyes. In1944 Farbwerke Hoech AG prepared reactive dyes with the name of Remazol Which have the formulae

  D-SO₂ –CH₂  -CH₂ –OSO₃H    and    D- SO₂- CH₂ –CH₂Cl

These substance are precursor from which, in the presence of mild alkali, sulphone derivatives are formed in the dyebath.
Other precursor are:
Thio sulphato ethyl sulphone
Dialkayl aminoethyl sulphone
Phosphato ethyl sulphone

In case of both P^H  and temp promote the liberation of the vinyl sulphone group which confers reactivity with cellulosic and protein fibers.

D-SO₂- CH=CH₂  + HO-Cell   =   D-SO₂-CH₂-CH₂-O-Cell

D-SO₂-CH=CH₂  + H₂HR       =     D-SO₂-CH₂-CH₂-HNR  

The dyes according to their type, can be applied at ambient temperature 40⁰C and 60⁰C, the total time required for absorption and fixation being 2 hours, 1.5 hours and 1 hours respectively. 

Application of Remazol dye:

    The application in winch dyeing with Remazol dyes is very easy process. The dyebath is raised between 20⁰ C and  30⁰C and polyphosphate(e.g Calgon), the dissolved dye, electrolyte and appropriate quantity alkali are added. The temperature and the corresponding times of dyeing are as following:

20-30⁰C         Dye for 2 hours

40⁰C               Raise to 40⁰C in 10 minutes and continue to run for 90 minutes in 1.5 hours

60⁰C               Raise to 60⁰C in 20-30 minutes and continue to run for 60 minutes

Dyeing instruction regarding quantities of phosphate, electrolyte and alkali are tabulated below:

Liquor ratio is 1:15 to 1: 30

Dyeing temp                              60⁰C                  40⁰C                  20-30⁰C

Phosphate (g/l)                            1                           1                        1

NaCl (g/l)                                   50                         50                       50

Tri sodium phosphate (g/l)          5-10                    10-15                      -

Or Na₂CO₃(g/l)                          20                          -                          -

NaOH 32.5% ml/l                       1                          1-2                      2-4  

The main feature of vinyl sulphone dyes are:

           • Possess excellent brightness and good wet fastness.

           • The dyes are dischargeable.

           • The dyes are suitable for exhaust and different paddyeing methods and discharge printing.

           • Ease of washing off unfixed dyestuffs i.e.minimum staining of the white ground in printing.

           • They are applicable at 40°C and 60°C.

  

Precaution for dyeing with vinyl sulphone dves:

 For dyeing with vinyl sulphone dyes, it is advisable to ensure that the residual alkali has been removed from the fibre surface or neutralized prior to soaping since hydroxide ion can catalyse hydrolysis of the ether type dye-fibre bond and result in additional colour bleeding from the dye-fibre bond stability at around PH 4-5, whereas the corresponding value for dyes based on halogenated nitrogen heterocles is 6-7. the later type have dye-fibre bonds that are more sensitive to acid-catalysed hydrolysis.

Dye – O – Cell + H2 0 = Dye – OH + Cell – OH

The dyeing temperature and the nature and concentration of the alkali required are determined by the reactivity of the dye. Its degree of sulphonation and its substantivity.

Bi-functional reactive dyes:

The most obvious deficiency of reactive dyes lies in the fact that their dyeing efficiency is significantly less than 100% and may be nearer 70%. More recently, improvements have been made by introducing more than one reactive group into the reactive dye molecule so that even though one group may hydrolyse, there is another left for reaction with cellulose. Dyes with suitable diffsubstantivity properties, but carrying two reactive groups, have been carefully selected.

Bi - functional reactive dyes with two reactive groups of different reactivity towards the cotton, which have different optimal fixation conditions, sjive a more uniform decree of fixation over a wide range of dyeing temperature and fixation PH than dyes containing two identical groups.

Therefore, process control does not need to be so stringent. These types of reactive dyes give quite high fixation yields and thus less colour in the dye house effluent. Other important types of bi-functional reactive dyes include the MFT-VS type (Cibacron C, Ciba) and the MCT-Vs type used in the Sumifix Supra dyes (Sumito). The Kayacelon react range of dyes (Nippon Kayaku) are also bi-functional reactive dyes, having two NT reactive groups in each dye molecule.

There are two types of bi-functional reactive dyes, where one type is homo-functional which have two reactive groups are similar type in nature and another is haterofunctional which have two reactive groups are dissimilar type in nature reactive dyes.      

A major advantage of MCT/VS, dyes over the dyes containing either MCT or VS reactive group is the higher degree of fixation of the former and is 1.3 to 2.3 times  more than the latter. It can easily be assessed that dyeswith two identical reactive groups and dyes with two different reactive group exhibit a higher fixation yield than dyes with one group.

Studies have demonstrated that their excellent solubility, higher degree of fixation, good leveling and good –to-excellent fastness properties etc.

Dyeing method of bi-functional reactive dyes

Exhaust dyeing method:

Bi-functional reactive dyes are applicable by exhaust dyeing method in following different ways.

              1.Increase temperature method

              2.Constant temperature method

              3.All-in method 

Increase temperature method of bi-functional Reactive dye:
Procedure:

 Set the dye bath at 25⁰ C with dye solution and carry out dyeing for 10 minutes. Then add half amount of salt and continue dyeing by raising temperature to 45°C in 10 minutes. Add remaining half the amount of salt at 45°C and. Raise the temperature to 60°C in 10 minutes with continued dyeing. Continue dyeing at 60°C for further 5 minutes and then add half amount of soda ash and continue dyeing for 10 minutes. Add the remaining half amount of soda ash and dyeing is continued for further 50minutes at 60°C. The goods are then washed off. 

Constant temperature method of bi-functional Reactive dye:
Procedure:

Set theusion anSet the dye bath at 60°C with dye solution and carry out dyeing at 60°C for 10 minutes. Then add salt at 60°C and continue dyeing 25 minutes. Add half amount of soda ash

and continue dyeing for 10 minutes. Then add the remaining half amount of soda ash and dye ing is continued for further 50 minutes at 60°C. The goods are

then washed off.

All-in method

This method is particularly suitable for unmercerised cotton to produce deep shades. Moreover this method is applicable to vinylsulphone dyes and hence combination of vinylsulphone dyes is possible.

Procedure

Set the dye bath at 20-30°C. Add salt and continue dyeing for 5-10 minutes. Then add dye solution and continue for 15-20 minutes. Now add half amount of alkali and dye for 5-10 minutes. Add remaining half the amount of alkali and dye for further 5-10 minutes. Then raise the temperature to 60 C in 20 minutes (1-5⁰ C rise/minutes) and continue dyeing at 60°C for 45-60 minutes.

Salt and alkali requirements:

% shade	Glaubers salt (g/l)	Soda ash (g/l)
1.0 to 2.0	35-50	15
2.0 to above	50	15-20

For light shades of less than 1%, quantity of Glauber’s salt and soda ash to be reduced appropriately.

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