reactive-chemistry.pdf

Reactive Chemistry
TECHNICAL INFORMATION
12.11.2015
Murat ŞAHİNLİ

Cellulose… Cellulose structure

Reactive dyes…
has a reactive group which are adsorbed on to the cellulose and than reacted with the
fiber to form covalent bonds.
Chromophore Bridging RG
General structure
Functional groups
Reactive group

Reactive dyes…
has a reactive group which are adsorbed on to the cellulose and than reacted with the
fiber to form covalent bonds.
General structure
Functional groups
Shade
Fastness
Levelness
Substantivity
Solubility
Application temperature
Fastness
Dischargeability
Fixation
Application temperature

Reactive dyes…
When put fabric and dye into the water;
Cell-OH
General reaction
Cell-O¯
HO3S-Dye-X
Cellulose:
Dye:
X-Dye-SO3¯
Electrostatic
repulsion because of
the negative charges
With addition of salt: Cell-O¯ ⁺ Na
X-Dye-SO3¯ ⁺ Na
Reduce the repulsion

Reactive dyes…
After addition alkaline and linking with covalent bond;
General reaction
Na ⁺ ¯O-Cell
X-Dye-SO3¯ ⁺ Na
( Soda ash, caustic …)
+
Na ⁺ ¯O3S – Dye –O-Cell + NaX
Thanks to covalent bond
Linking much more resistant to the
usual conditions of use than the
physicochemical bond between
direct dyes and cellulose.
Bond type App. Relative strength
Covalent 30.0
Ionic 7.0
Hydrogene 3.0
Other
Intermolecular
1.0

Reactive dyes… Description of dyeing mechanism
 Exhaustion of dye in presence of electrolyte by adsorption
 Fixation under the influence of alkali
 Wash off the unfixed dye from material surface
T1: Addition of
alkali and start of
the fixation

Reactive dyes… Exhaustion
 The reactive dyes is adsorbed onto the cellulose surface and than diffuses into the fiber.
 This phase is fully reversible.
 Dye molecules are in equilibrium between fiber and dyebath.
Any change in bath composition
affect the equilibrium
[F] Dyebath [F] Cellulose
So; affect the Substantivity
S=
[F] Cellulose
[F] Dyebath

Reactive dyes… Substantivity: Influencing parameters
Substantivity
Dye
affinity
Dye conc.
Electrolyte
conc.
pH
Temperature
Type of fiber
Liquor
ratio

Standart affinity of dye;
Like substantivity; is a measure for the distribution of a dye between fiber and dyebath.
Unlike substantivity; affinity is constant at dyeing conditions, it is dye-spesific characteristic.
The number of
conjugated double
bonds in chromophore
Substantivity
High affinity for cellulose (Direct dye)
Low affinity for cellulose (Acid dye)

Electrolyte Concentration;
Anion-anion repulsion
Electrolyte conc.
Direct dyes; high affinity, require 5-10 g/lt salt
Reactive dyes; medium to low affinity, require 40-100 g/lt
Substantivity

pH of dyebath;
Cell-O¯
Cell-OH + H2O
OH¯
H⁺
As the pH increases, the cellulose carries more and more negatively charge.
The amount of the OH ion in the dye bath increases.
Without alkaline addition
pH Substantivity
7
8
9
10
11
12
13
RS:
Cell-O¯ (in the fiber)
OH¯ (in the dyebath)

Dye concentration;
Because of the limited adsorption
capacity of fiber surface;
S=
[F] Cellulose
[F] Dyebath
Dye concentration Substantivity
Surface saturation occurs later with high affinity dyes
than low affinity dyes so,
the greater influence on substantivity of low affinity
dyes

Dyeing temperature;
At 80⁰C, speed of diffusion of a dye in cellulose is higher than at 40⁰C.
Dyeing equilibrium is therefore achieved much more rapidly at 80⁰C than 40⁰C.
Temperature Substantivity
Subsantivity seems to be lower at
40⁰C than at 80 ⁰C, but in fact it is
not.

Liquor ratio;
Liquor ratio Substantivity
Don’t forget that the decrease is
also related to :
Dye concentration
Dye own affinity
So;
The Liquor ratio increases, the probability of contact between the dye molecules and the
fiber surface decreases.

Liquor ratio;
Affinity of the dye
Dye concentration (L.R. 10:1=%100)
Dye :C.I. Reactive Red 180
Electrolyte :50 g/lt NaCl
Dyeing temperature :40⁰C
Dye concentration :3%
Electrolyte :50 g/lt NaCl
Dyeing temperature :40⁰C

Fiber type;
Although the fiber structure has some minor effect on substantivity, we will see differences
e.g.; Mercerized cotton dyes to a much deeper shade than non-mercerized
It is merely the result of different optical properties: mercerized cotton has a circular cross
section,which allows better light penetration, less random light reflection.
Therefore, mercerized cotton can be much more easily penetrated by photons, thus a larger
proportion of coming light is selectively adsorbed and this means higher color saturation.
Raw cotton Mercerised and stretched cotton

Reactive dyes… Diffusion rate: Influencing parameters
But fiber type has a significant effect on Diffusion Rate…
 Fiber type
 Dyeing temperature
 Size and shape of dye molecule
 Subsantivity of dye molecule
 Electrolyte concentration in the bath
 Dye concentration

Adsorption equilibrium diffusion
Dye uptake phase consist of successive
states of equilibrium.
Dye repeatedly makes
brief stops on the
crystallite walls
Diffusion rate of a dye , decides its
speed of exhaustion

So, speed of diffusion;
 Speed of exhaustion
 Levelness of dyeing
 Fixation
 Fastness properties

Fiber type;
Cellulose Viscose Modal
Such a large dye molecule can not diffuse into the
highly oriented and tightly packed crystallites.
Dyeing therefore proceeds at the outer walls .
Viscose is still stiff at 40-50⁰C, while at higher
temperatures (60-80⁰C ) the fibres mobility allows
the fibre bundle open.
Crystalline
regions

When cotton is mercerized;
Fiber induces a higher orientation of crystallites, this should reduce the diffusion
rate but;
A large portion of of intermicellar spaces of the cotton is dissolved and extracted
by alkaline.
Large molecules can be penetrated more easily to the empty spaces so;
 Mercerized cotton swells dye more than non-mercerized
 Diffusion speed of a dye is much higher (Despite high orientation)
 Higher speed of exhaustion
 Stronger shade
Mercerized cotton
Raw cotton

Temperature;
Temperature Diffusion rate Temperature has by far the greatest
effect on diffusion
So greatest effect on;
 Migration rate
 Washing-off
 Levelness

Size and shape of dye molecule;
Molecule size Diffusion rate
Larger and bulkier dye molecules have
a much slower rate of diffusion than
smaller ones

Size and shape of dye molecule;
Reactive Blue 15 (Turquoise)
Poor;
 Diffusion
 Levelling
 Washing-off properties
Phthalocyanine
Chromophore tents to
be square and very
bulk in the structure.
Reactive Red 198
MCT/VS
Bifunctional Reactive Dye
>
Diffusion rate:
Reactive Red 198 > Reactive Blue 15

Substantivity;
It promotes adsorption equilibrium but impairs diffusion speed.
High subsantivity dyes while exhausting more completely from the dye bath, diffuse,
migrate and level more slowly.
e.g.; Everzol Yellow LX

Electrolyte concentration;
Diffusion rate
Electrolyte Conc. Subsantivity
There is a small exception to this rule;
At very low electrolytes concentration adding a
trace of electrolytes to the dye bath helps to
improve diffusion.
This exception is rarely encountered in real-life
dyeing operation.

Reactive dyes… Fixation
T1: Addition of
alkali and start of
the fixation

Alkali is necessary for;
 the dyestuff reaction with the fiber (heterocyclic type)
 formulation of reactive site and reaction of dyestuff with the cellulosic
fiber (vinylsulfone type)
Increasing alkali
………………………………
Decreasing reactivity
Soda ash
Soda ash/Caustic soda

Then,
What is the meaning of heterocyclic or vinylsulfone…?
How is the reactive dyes chemical structure…?

Reactive dyes…
Fixation; Dye chemical structure
monofunctional
Chromophore Bridging
Reactive group
Functional groups ;
providing water solubility
RG
Chromophore Bridging RG RG
conjugated
bifunctional
Bridging
RG
isolated
bifunctional

Reactive dyes…
Fixation; Dye chemical structure
Reactive group chemistry;
Cl
•Low reactivity
•Sensitive to acid
•Stable to alkaline
•May generate AOX
N
N
N
rest
Monochlortriazin (MCT)
N
N
N
F
rest
Monofluortriazine (MFT)
N
N
F
F
•High reactivity
•Stable to acid and alkaline
•Splitting with peroxide and light
•AOX free
Cl
N
Cl
•High reactivity
•Not hydrolysable AOX
Dichlorchinoxaline (DCC)
N
Cl
•Medium reactivity
•Stable to acid
•Sensitive to alkaline
•Dischargeable, stripping is possible
•AOX free
Vinyl sulfone (VS)
SO2-CH=CH2
Chromophore
Bridge
Difluorochlorpyrimidine (FCP)
•Medium to high reactivity
•Stable alkali to alkaline
•AOX free
Increasing Reactivity

Hot-dyeing dyes Cold-dyeing dyes
Everzol dyes
Reactivity
Substantivity

Everzol Yellow NPN Everzol Red LX

Dye-fiber reaction:
1. Nucleophilic substitution (MCT, FT, DFCT, DFP, DCQ, DCT)
A mobile halogen atom in the reactive group is substituted by the ionized nucleophilic
group of the cellulose.
Reactive Red 1

Dye-fiber reaction:
2. Nucleophilic addition
Reactive Blue 19
A proton and the ionized group of cellulose are added the active group of dye.
 In this example there is no bridging group
 The dyes react with cellulose by addition to
sulfur oxgen doble bond.

Reactive dyes… Fixation; influencing parameters
 Chromophore
 Reactivity of reactive groups
The more unstable the leaving group, the more reactive dye
 pH of the dyebath
With every increase bye one unit of the pH, the concentration of ionized nucleophilic
groups on cellulose increase, so the speed of reaction increase
 Temperature of the dyebath
 Substantivity of the dye
The reaction speed increasing as temperature rises and substantivity

Dye-fiber reaction:
Competitive reaction results; Inactivation of the reactive groups
OH¯
N
N
N
Cl
Cl
N
N
N
OH
OH
+
Dye-SO2- CH=CH3 + OH¯ Dye-SO2- CH=CH2CH2OH

Bireactivity and its consequences;
When considering:
A is a mono reactive dye with fixation of about 60%
B is a bireactive dye which have two reactive groups, each capable of achieving a
fixation of 60%
For B; fixed 84%
hydrolyzed 16%
For A: fixed 60%
hydrolysed 40%
Residue dyestuff (unfixed) in the dyebath
R-R can be either the same (homo-bireactive)
or different (hetero-bireactive)

Bireactivity and its consequences;
Skillful combination of two different reactive groups can ensure elimination of each
group’s spesific fastness weakness.
MCT; stable to alkali
VS; stable to acid By comparison to
monofunctional dyes;
 more stable dye/fiber
bond to acid and alkali
 a longer shelf life
 much better chemical
stability

Reactive dyes… Washing
T1: Addition of
alkali and start of
the fixation

Easy Wash-Off
Less Effluent
Value-Adding
Fixed dye molecules
Unfixed dye molecules
Chemicals
Washing
Dyed
fiber

As a general rule of thumb;
The best results are obtained if washing off is carried out;
Substantivity of the dye is as low as possible and diffusion rate as high as possible.
-at high temperatures
-with lowest possible electrolytes conc.
-at higher liquor ratio
to reduce the affinity/substantivity
of dye molecules to fiber

Dye with low affinity and good diffusion;
Most of dye extracted cold, which shows that it was only adhering to the fibre surface.
An insignificant amount of unfixed dye remains inside the fiber matrix.
30⁰C 60 ⁰C 98 ⁰C 80 ⁰C 60 ⁰C 30 ⁰C

Reactive dyes… Fastness of reactive dyes
-N=N-
Reactive
anchor Fiber
water & light
perspiration & light
Light Fastness
Bleaching Fastness
Chromophore
Chlorine
Peroxide
Wash Fastness
Detergent, heat, water
Heat
Acid
Alkali

Reactive
anchor
Fiber
Wash Fastness
Problems may result from;
1. uncomplate washed off hydrolyzed dyestuff
2. washing conditions which destroy the Chromophore e.g. washing
detergents with bleaching agents
3. conditions which split the dyestuff-fibre bond
Chromophore
Light Fastness
Highly dependent on chromophore

Reactive
anchor
Fiber
Bleaching Fastness
1. Strong dependent on chromophor
2. Chromophore class is important with pattern on substituent adjacent to the azo
group
3. Even similar elements in the chemical structure big differences in chlorinated and
bleaching fastness
Chromophore
Oxidation agent

Rubbing Fastness
 Material
 Construction of material (knitted, textured..)
 Dye (molecule size, chemistry…)
 Dyeing method
 Washing
 Finishing
 Wet/dry rubbing

Cotton;
Raw material
Cotton;
Dyeing reactive dyes, than wet rubbing

Viscose;
Raw material
Viscose;
Dyeing reactive dyes, than wet rubbing

Reactive dyes… Hints
The molecules of most colored organic compounds
contain two parts:
i) An aromatic ring such as benzene, naphthalene or
anthrhracene
ii) Conjuge double bond system containing unsaturated
groups
The intensity of color can be increased in a dye molecule
by addition of substituents;

For Printers…
Pint-paste is should be stable several days without any noticeable inactivation (hydrolysis)
of the reactive dye. MCT reactive groups are suitable with;
 Hydrolyze slowly at room temperature
 Fix rapidly under the usual steaming conditions.
For Viscose…
MCT is a good choice when dyeing viscose by the exhaust method at 80°C .
The higher temperature reduces the risk of poor levelness because:
 The swollen viscose is more accessible to the dyebath than at lower temperatures
and the dye more evenly distributed in the material.
 The levelling effect of dye diffusion is more effective at high temperatures.

For Cold Pad-Batch dyers…
Prefer dyes that are;
 completely fixed at room temperature at (pH: 11.5-12.5)
 To be resistant to hydrolyze
these conditions are met for example by VS, MFT, DFP or DFCP bireactive dyes
which combining two reactive groups of similar, medium reactivity.

Reactive dyes… Exhaust dyeing method

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