Reactive Chemistry
TECHNICAL INFORMATION
Murat ŞAHİNLİ 12.11.2015 Cellulose… Cellulose structure Reactive dyes… General structure has a reactive group which are adsorbed on to the cellulose and than reacted with the fiber to form covalent bonds.
Chromophore Bridging RG
Reactive group
Functional groups Reactive dyes… General structure
has a reactive group which are adsorbed on to the cellulose and than reacted with the fiber to form covalent bonds.
Chromophore Bridging RG
Functional groups
Shade Fastness Fastness Dischargeability Levelness Fixation Substantivity Application temperature Solubility Application temperature Reactive dyes… General reaction
When put fabric and dye into the water;
Cellulose: Cell-OH Cell-O¯ Electrostatic repulsion because of Dye: the negative charges HO3S-Dye-X X-Dye-SO3¯
With addition of salt: Cell-O¯ ⁺ Na Reduce the repulsion X-Dye-SO3¯ ⁺ Na Reactive dyes… General reaction
After addition alkaline and linking with covalent bond;
Thanks to covalent bond X-Dye-SO3¯ ⁺ Na + Na ⁺ ¯O-Cell Linking much more resistant to the usual conditions of use than the ( Soda ash, caustic …) physicochemical bond between direct dyes and cellulose.
Na ⁺ ¯O3S – Dye –O-Cell + NaX Bond type App. Relative strength
Covalent 30.0
Ionic 7.0
Hydrogene 3.0 Other 1.0 Intermolecular 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 [F] Cellulose S= [F] Dyebath Reactive dyes… Substantivity: Influencing parameters
pH Electrolyte Temperature conc.
Dye conc. Type of fiber
Dye Liquor Substantivity affinity ratio Reactive dyes… Substantivity: Influencing parameters
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 Substantivity bonds in chromophore High affinity for cellulose (Direct dye)
Low affinity for cellulose (Acid dye) Reactive dyes… Substantivity: Influencing parameters
Electrolyte Concentration;
Electrolyte conc. Anion-anion repulsion Substantivity
Direct dyes; high affinity, require 5-10 g/lt salt Reactive dyes; medium to low affinity, require 40-100 g/lt Reactive dyes… Substantivity: Influencing parameters pH of dyebath;
OH¯ Cell-OH Cell-O¯ + H2O H⁺
As the pH increases, the cellulose carries more and more negatively charge. The amount of the OH ion in the dye bath increases.
pH Substantivity 7 8 9 Cell-O¯ (in the fiber) 10 RS: 11 OH¯ (in the dyebath) 12 13
Without alkaline addition Reactive dyes… Substantivity: Influencing parameters
Dye concentration;
Because of the limited adsorption capacity of fiber surface;
[F] Cellulose S= [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 Reactive dyes… Substantivity: Influencing parameters
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. Reactive dyes… Substantivity: Influencing parameters
Liquor ratio;
The Liquor ratio increases, the probability of contact between the dye molecules and the fiber surface decreases.
Liquor ratio Substantivity
Don’t forget that the decrease is also related to :
Dye concentration Dye own affinity So; Reactive dyes… Substantivity: Influencing parameters
Liquor ratio;
Dye concentration (L.R. 10:1=%100) Affinity of the dye
Dye :C.I. Reactive Red 180 Dye concentration :3% Electrolyte :50 g/lt NaCl Electrolyte :50 g/lt NaCl Dyeing temperature :40⁰C Dyeing temperature :40⁰C Reactive dyes… Substantivity: Influencing parameters
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 Reactive dyes… Diffusion rate: Influencing parameters
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 Reactive dyes… Diffusion rate: Influencing parameters
So, speed of diffusion;
. Speed of exhaustion . Levelness of dyeing . Fixation . Fastness properties Reactive dyes… Diffusion rate: Influencing parameters
Fiber type; Cellulose Viscose Modal
Crystalline regions
Such a large dye molecule can not diffuse into the Viscose is still stiff at 40-50⁰C, while at higher highly oriented and tightly packed crystallites. temperatures (60-80⁰C ) the fibres mobility allows Dyeing therefore proceeds at the outer walls . the fibre bundle open. Reactive dyes… Diffusion rate: Influencing parameters 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
Raw cotton Mercerized cotton Reactive dyes… Diffusion rate: Influencing parameters
Temperature;
Temperature Diffusion rate Temperature has by far the greatest effect on diffusion
So greatest effect on;
. Migration rate . Washing-off . Levelness Reactive dyes… Diffusion rate: Influencing parameters
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 Reactive dyes… Diffusion rate: Influencing parameters Size and shape of dye molecule; Reactive Blue 15 (Turquoise)
Reactive Red 198
>
MCT/VS Bifunctional Reactive Dye Phthalocyanine Poor; Chromophore tents to . Diffusion Diffusion rate: be square and very . Levelling Reactive Red 198 > Reactive Blue 15 bulk in the structure. . Washing-off properties Reactive dyes… Diffusion rate: Influencing parameters
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 Reactive dyes… Diffusion rate: Influencing parameters
Electrolyte concentration;
Electrolyte Conc. Subsantivity Diffusion rate
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 Reactive dyes… 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 Reactive dyes… Fixation
Then, What is the meaning of heterocyclic or vinylsulfone…? How is the reactive dyes chemical structure…? Reactive dyes… Fixation; Dye chemical structure
Chromophore Bridging RG monofunctional
Reactive group
Functional groups ; providing water solubility
conjugated Chromophore Bridging RG RG bifunctional
isolated RG Bridging Chromophore Bridging RG bifunctional Reactive dyes… Reactive group chemistry; Fixation; Dye chemical structure
Monochlortriazin (MCT) Monofluortriazine (MFT) Difluorochlorpyrimidine (FCP) Cl N rest N rest F N N N N N N Cl F F •Low reactivity •Medium to high reactivity •High reactivity •Sensitive to acid •Sensitive to acid •Stable to acid and alkaline •Stable to alkaline •Stable alkali to alkaline •Splitting with peroxide and light •May generate AOX •AOX free •AOX free
Vinyl sulfone (VS) Dichlorchinoxaline (DCC) Chromophore N Cl SO2-CH=CH2 Bridge •Medium reactivity Cl N •Stable to acid •High reactivity •Sensitive to alkaline •Sensitive to acid •Dischargeable, stripping is possible •Not hydrolysable AOX •AOX free Increasing Reactivity Reactive dyes… Fixation
Hot-dyeing dyes Cold-dyeing dyes Substantivity
Everzol dyes
Reactivity Reactive dyes… Fixation Reactive dyes… Fixation
Everzol Yellow NPN Everzol Red LX Reactive dyes… Fixation
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 Reactive dyes… Fixation
Dye-fiber reaction:
2. Nucleophilic addition
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 Blue 19 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 Reactive dyes… Fixation Dye-fiber reaction:
Competitive reaction results; Inactivation of the reactive groups
N Cl + OH¯ N OH
N N N N Cl OH
Dye-SO2- CH=CH3 + OH¯ Dye-SO2- CH=CH2CH2OH Reactive dyes… Fixation 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) Reactive dyes… Fixation 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 Reactive dyes… Washing Dyed fiber
Washing
Value-Adding
Less Effluent Fixed dye molecules Unfixed dye molecules Easy Wash-Off Chemicals Reactive dyes… Washing
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 Reactive dyes… Washing
30⁰C 60 ⁰C 98 ⁰C 80 ⁰C 60 ⁰C 30 ⁰C
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. Reactive dyes… Fastness of reactive dyes
Wash Fastness Light Fastness Detergent, heat, water water & light perspiration & light
Reactive Chromophore -N=N- anchor Fiber
Heat Bleaching Fastness Acid Chlorine Alkali Peroxide Reactive dyes… Fastness of reactive dyes
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
Light Fastness
Highly dependent on chromophore Reactive Fiber Chromophore anchor Reactive dyes… Fastness of reactive dyes
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
Oxidation agent
Reactive Fiber Chromophore anchor Reactive dyes… Fastness of reactive dyes
Rubbing Fastness
Material Construction of material (knitted, textured..) Dye (molecule size, chemistry…) Dyeing method Washing Finishing Wet/dry rubbing Reactive dyes… Fastness of reactive dyes
Cotton; Cotton; Raw material Dyeing reactive dyes, than wet rubbing Reactive dyes… Fastness of reactive dyes
Viscose; Viscose; Raw material 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; Reactive dyes… Hints
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. Reactive dyes… Hints
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