theory of reactive dyeing

Theory of reactive ydyeing

Structure of reactive dyesThe four characteristics feature of a typical reactive dyes are:

The chromophoric grouping, contributing the color and much of the substantivity for cellulose;The reactive system, enabling the dye to react with the hydroxy group with water and cellulose;A bridge group that links the reactive system to theA bridge group that links the reactive system to the chromophore;One or more solubilizing groups, usually sulphonic acid g g p , y psubstituents attached to the chromophoric grouping.

Structure of Reactive Blue 4

Structure of Reactive Black 5

Reactive systemReactive system

Mono-functional Bi-functional Poly-functional

Homo HetroTriazine Pyrimidine Quinoxaline VS

Chloro Trichloro Triazine VS-Cl

Fluro Chlorodifluro VS VS-F

Reaction for triazine type reactive system

C-OH + D-CLC-OH + D-CL

Alkaline pH

C-CL + HCL

Reaction for VS type reactive system

D-SO2-CH2CH2OSO3Na

NaOH

D-SO2-CH=CH2 + Na2SO4

Cell-OH

D-SO2-CH2CH2-O-Cell + OH-

Mono functional VS Bi-functional

Bi-Functional

Fixed 60% Unfixed 40%

Fixed 24% Unfixed 16%

Controllable dyeing variablesExhaustion phase

Rate of exhaustionSubstantivitySubstantivityMigrationDiffusionLevel factor in exhaustion

Fixation PhaseReactivityReactivityT50

Secondary exhaustionLevel factor in fixationFinal fixationWash offWash off

Exhaustion phaseRate of exhaustion

At the rate dye adsorb to the fiber. Initially this rate remain very high but it reduces uponthis rate remain very high but it reduces upon time. So primary control is very important.We can measure it in two wayWe can measure it in two way

Transfer rate per minuteMeasuring the angle of dyes transfer.

Exhaustion phaseRate of exhaustion

Suppose in 1st 5 minutes 40% dyes has

Exhaustion curve

transferred so dyeing rate is 8%.

Θ

Exhaustion phaseExhaustion phaseSubstantivity or primary exhaustion (PE)

The total amount of dyes transfer in

Exhaustion curve

exhaustion phase.

Exhaustion phaseExhaustion phaseSubstantivity or primary exhaustion (PE)

Substantivity determinatorAffinityAffinityLiquor ratioTemperatureTemperatureEletrolytes concentration.pHFiber situation.

Exhaustion phaseMigration

It is accumulated effect of Adsorption and desorption.Higher Migration is always ensure more possibility of level A B

dyeing.B

Migration = ---------x 100 A

gA

Exhaustion phaseDiffusion

It is really difficult for us to measure diffusion rate with our present equipment.We shall have to give sufficient time to achieveWe shall have to give sufficient time to achieve proper diffusion since there is a huge possibility of having false equilibrium.Some of the factors effect diffusion, such as:

pH of the bath.S bstanti itSubstantivityDyes aggregation.Pretreatment of the fabric.Etc.

Exhaustion phaseLevel dyeing factor (LDF)

It determines possibility of dyes level out in MI

LDF (E ) X 100exhaustion phase.Higher indicate better

LDF (Ex) = ---- X 100PE

levelling.

Fixation phaseReactivity

It determines reaction rate of the dyes.Reactivity determines amount of alkaliReactivity determines amount of alkali, temperature and dyeing time.Al d i t f lk liAlso dosing system of alkali.Control of this factor is very important for y puniform dyeing.Most of the quazi problem (running shade) isMost of the quazi problem (running shade) is happening for this factor.

Fixation phase or Half Dyeing Timep y gT50

Time for fixing of 50% of total dyestuff.

Exhaustion & fixation curve.

Generally, people think that this factor is consider as a reactivityconsider as a reactivity of dyestuff.It is a very importantIt is a very important factor for other dyes but not that important for reactive dyes.

Fixation phaseSecondary exhaustion

E h ti & fi tiFinally total amount of dyes transfer from bath

Exhaustion & fixation curve.

to fiber.It is the total effect of exhaustion and fixation.

Fixation phaseLevel Dyeing Factor for fixation

It has been claimed that it is the determining factor for ultimate dyeing.

PE X MILDF (Fix) = ------------

SEIt also ensure reproducibility of dyes.

SE

Fixation phaseWash off (W)

The amount of unfixed dyestuff to be removed from the fabric.removed from the fabric.The more wash off, more difficult to control the shade i e show less reproducibilitythe shade i,e show less reproducibility.More wash off roughly shows amount of hydrolysis of dyestuff.

Fixation phaseFinal fixation

Exhaustion & fixation curveGenerally higher functional group

Exhaustion & fixation curve.

ensures higher fixation of dyestuff.Now it is important on the effluent treatment FF = SE - W

point of view.