lecture - 2&3 - direct dyes

of 40

INDIAN INSTITUTE OF TECHNOLOGYINDIAN INSTITUTE OF TECHNOLOGYContinued M. L. GULRAJANIM. L. GULRAJANI

Direct Dyes

of 40


Direct Dyes

The The "direct dye""direct dye" classification in the Color Index system classification in the Color Index system refers to various planar, highly conjugated molecular refers to various planar, highly conjugated molecular structures that also contain one or more anionic structures that also contain one or more anionic sulphonate group. It is because of these sulphonate sulphonate group. It is because of these sulphonate groups that the molecules are soluble in water. groups that the molecules are soluble in water.

The The "direct dye""direct dye" classification in the Color Index system classification in the Color Index system refers to various planar, highly conjugated molecular refers to various planar, highly conjugated molecular structures that also contain one or more anionic structures that also contain one or more anionic sulphonate group. It is because of these sulphonate sulphonate group. It is because of these sulphonate groups that the molecules are soluble in water. groups that the molecules are soluble in water.

Direct dyesDirect dyes - dyes with a high affinity for cellulose - dyes with a high affinity for cellulose fibresfibres

Substantive dyesSubstantive dyes are dyes used in a process in which are dyes used in a process in which dye molecules are attracted by physical forces at the dye molecules are attracted by physical forces at the molecular level to the textile substrates. The amount of molecular level to the textile substrates. The amount of this attraction is known as this attraction is known as substantivitysubstantivity

Direct dyesDirect dyes - dyes with a high affinity for cellulose - dyes with a high affinity for cellulose fibresfibres

Substantive dyesSubstantive dyes are dyes used in a process in which are dyes used in a process in which dye molecules are attracted by physical forces at the dye molecules are attracted by physical forces at the molecular level to the textile substrates. The amount of molecular level to the textile substrates. The amount of this attraction is known as this attraction is known as substantivitysubstantivity

of 40


Direct Dyes

Congo redCongo red is the sodium salt of benzidinediazo-bis-1- is the sodium salt of benzidinediazo-bis-1-naphthylamine-4-sulfonic acid (formulanaphthylamine-4-sulfonic acid (formula C C3232HH2222NN66NaNa22OO66SS22, , : molecular weight: 696.66 g/mol ): molecular weight: 696.66 g/mol ) brownish-red brownish-red powder, powder,

Congo redCongo red is the sodium salt of benzidinediazo-bis-1- is the sodium salt of benzidinediazo-bis-1-naphthylamine-4-sulfonic acid (formulanaphthylamine-4-sulfonic acid (formula C C3232HH2222NN66NaNa22OO66SS22, , : molecular weight: 696.66 g/mol ): molecular weight: 696.66 g/mol ) brownish-red brownish-red powder, powder,

Congo RedCongo Red (Colour Index(Colour Index, , No. 370), was the first No. 370), was the first member of the direct cotton group of dyes. member of the direct cotton group of dyes.

Patented by Paul Böttiger's (Friedrich Bayer Company in Patented by Paul Böttiger's (Friedrich Bayer Company in Elberfeld, Germany ) B.P. 4,416 of 1884Elberfeld, Germany ) B.P. 4,416 of 1884

Congo RedCongo Red (Colour Index(Colour Index, , No. 370), was the first No. 370), was the first member of the direct cotton group of dyes. member of the direct cotton group of dyes.

Patented by Paul Böttiger's (Friedrich Bayer Company in Patented by Paul Böttiger's (Friedrich Bayer Company in Elberfeld, Germany ) B.P. 4,416 of 1884Elberfeld, Germany ) B.P. 4,416 of 1884x

of 40


Direct Dyes

10.8Å

Cellulose - Cellobiose

Benzedrine

Hydrogen Bonding of Cellulose dyed with Congo Red

of 40


Direct Dyes

Benzopurpurine 4BBenzopurpurine 4B Benzopurpurine 4BBenzopurpurine 4B

Second Second Direct DyeDirect DyeSecond Second Direct DyeDirect Dye

http://upload.wikimedia.org/wikipedia/commons/b/ba/Benzopurpurine_4B.svg

of 40


Direct Dyes

Benzedrine Benzedrine ReplacementReplacementBenzedrine Benzedrine ReplacementReplacement

4,4’ - diaminobenzanilide4,4’ - diaminobenzanilide4,4’ - diaminobenzanilide4,4’ - diaminobenzanilide

C.I. Direct Black 166C.I. Direct Black 166

of 40


Direct Dyes

2,2'-dimethyl-5,5'- dipropoxybenzidine 2,2'-dimethyl-5,5'- dipropoxybenzidine is non-mutagenicis non-mutagenic

2,2'-dimethyl-5,5'- dipropoxybenzidine 2,2'-dimethyl-5,5'- dipropoxybenzidine is non-mutagenicis non-mutagenic

Synthesis and Evaluation of Non-genotoxic Direct Synthesis and Evaluation of Non-genotoxic Direct Dyes, Jin-Seok Bae* and Harold S. Freeman, Dyes, Jin-Seok Bae* and Harold S. Freeman, fibres fibres and Polymers and Polymers 2002, Vol.3, No.4, 140-1462002, Vol.3, No.4, 140-146

of 40


Direct Dyes

C.I. Direct C.I. Direct Yellow 59Yellow 59C.I. Direct C.I. Direct Yellow 59Yellow 59

Phenyalbenzothiazole GroupPhenyalbenzothiazole GroupPhenyalbenzothiazole GroupPhenyalbenzothiazole Group

Yellow substantive dyesYellow substantive dyes

of 40


Direct Dyes

C.I. Direct C.I. Direct Green 28Green 28C.I. Direct C.I. Direct Green 28Green 28

Blue Yellow

Non-substantive anthrquinone based blue dye is Non-substantive anthrquinone based blue dye is attached to substantive monoazo yellow dye via triazine attached to substantive monoazo yellow dye via triazine molecule to get green dyemolecule to get green dye

Non-substantive anthrquinone based blue dye is Non-substantive anthrquinone based blue dye is attached to substantive monoazo yellow dye via triazine attached to substantive monoazo yellow dye via triazine molecule to get green dyemolecule to get green dye

of 40


Direct Dyes

C.I. Direct C.I. Direct Yellow 12Yellow 12

Chrysophenine GChrysophenine GChrysophenine GChrysophenine G

Stilbene and azo chromophore: Stilbene and azo chromophore: Dyeable on cotton, wool and silkDyeable on cotton, wool and silk

of 40


Direct Dyes

PhthalocyaninePhthalocyanine

Direct DyesDirect Dyes

PhthalocyaninePhthalocyanine

Direct DyesDirect Dyes

Water soluble Water soluble

sodium salts of sodium salts of

sulphonated sulphonated

copper copper

phthalocyaninephthalocyanine

Water soluble Water soluble

sodium salts of sodium salts of

sulphonated sulphonated

copper copper

phthalocyaninephthalocyanine

Turquoise Blue shadesTurquoise Blue shadesTurquoise Blue shadesTurquoise Blue shades

of 40


Direct Dyes

Chemical Chemical ClassClass YELYEL ORGORG REDRED VIOVIO BLUBLU GREGRE BRBR BLBL %%

MonoazoMonoazo 44 77 1414 44 -- 88 33 55

DisazoDisazo 5858 5353 7171 8383 5252 2121 2222 2323 4949

PolyazoPolyazo 88 1616 1010 33 3131 6464 6767 6868 3333

Cu-Cu-ComplexComplex -- -- 33 99 1212 44 11 88 55

StilbeneStilbene 1717 2323 22 -- -- -- -- -- 55

ThiazoleThiazole 1313 11 -- -- -- -- -- -- 11

DioxazineDioxazine -- -- -- 11 33 -- -- -- 11

Phthalo-Phthalo-

cyaninecyanine-- -- -- -- 22 22 -- -- 11

of 40


Direct Dyes

Reactant Fixable Reactant Fixable DyesDyesReactant Fixable Reactant Fixable DyesDyes

Indosol SF dyes of Clariant have been one of the Indosol SF dyes of Clariant have been one of the major developmentmajor development

Original range had 12 copper complex dyes: C.I. Original range had 12 copper complex dyes: C.I. Direct Violet 66Direct Violet 66

Indosol CR is the special dye fixing agent: N-Indosol CR is the special dye fixing agent: N-methylol dicyandiamide methylol dicyandiamide

Indosol SF dyes of Clariant have been one of the Indosol SF dyes of Clariant have been one of the major developmentmajor development

Original range had 12 copper complex dyes: C.I. Original range had 12 copper complex dyes: C.I. Direct Violet 66Direct Violet 66

Indosol CR is the special dye fixing agent: N-Indosol CR is the special dye fixing agent: N-methylol dicyandiamide methylol dicyandiamide

C.I. Direct Violet 66

of 40


Direct Dyes

Dyeing Cycle of a Direct DyeDyeing Cycle of a Direct Dye

SorptionStage

Diffusion and

MigrationStage

CoolingStage

of 40


Direct Dyes

Classification of Direct Classification of Direct DyesDyes

Classification of Direct Classification of Direct DyesDyes

Class AClass A - dyes that can be dyed with out salt and - dyes that can be dyed with out salt and have good migration and levelling propertieshave good migration and levelling propertiesClass AClass A - dyes that can be dyed with out salt and - dyes that can be dyed with out salt and have good migration and levelling propertieshave good migration and levelling properties

Class B Class B – dyes have a low rate of exhaustion and – dyes have a low rate of exhaustion and the rate of exhaustion may be adequately the rate of exhaustion may be adequately controlled by carefully regulated addition of controlled by carefully regulated addition of common salt.common salt.

Class B Class B – dyes have a low rate of exhaustion and – dyes have a low rate of exhaustion and the rate of exhaustion may be adequately the rate of exhaustion may be adequately controlled by carefully regulated addition of controlled by carefully regulated addition of common salt.common salt.

Class C Class C – dyes that are highly sensitive to salt, and – dyes that are highly sensitive to salt, and temperature. These are temperature – controlable temperature. These are temperature – controlable dyesdyes

Class C Class C – dyes that are highly sensitive to salt, and – dyes that are highly sensitive to salt, and temperature. These are temperature – controlable temperature. These are temperature – controlable dyesdyes

500C500C

Slide 16 of 40


Direct Dyes

Log (Time of Dyeing) Sec

Dye-b

ath

exhaust

ion %

500C500C

900C

900C

Time, min Effect of Effect of TemperatureTemperature

Temperature Temperature increasesincreasesthe rate of the rate of diffusion of diffusion of dyes in the dyes in the fibrefibre

Temperature Temperature increasesincreasesthe rate of the rate of diffusion of diffusion of dyes in the dyes in the fibrefibre

Temperature Temperature lowerslowersthe the equilibrium equilibrium dye uptake of dye uptake of the fibrethe fibre

Temperature Temperature lowerslowersthe the equilibrium equilibrium dye uptake of dye uptake of the fibrethe fibre

Dye - X

Dye - Y

of 40


Direct DyesD

ye-b

ath

exhaust

ion %

Time, min

3%3%

1%

0%

Gla

uber’

s Salt

Effect of Effect of SaltSaltEffect of Effect of SaltSalt

Salt Sensitive dye Salt Sensitive dye

Durazol Fast Blue Durazol Fast Blue 4GS4GS

Salt Sensitive dye Salt Sensitive dye

Durazol Fast Blue Durazol Fast Blue 4GS4GS

of 40


Direct Dyes

-

-

-

-

-

-

-

-

100Å

- +++++++++++

4Å

Dye Dye ionsions

AffinityAffinity

Electrostatic Electrostatic RepulsionRepulsion

Effect of Effect of SaltSaltEffect of Effect of SaltSalt

Sodium Sodium IonsIons

DyebathDyebathDyebathDyebath

FabricFabric

of 40


Direct Dyes

Adsorption of direct dyes on cellulosic Adsorption of direct dyes on cellulosic

fibres is influenced by the nature of the fibres is influenced by the nature of the

cation in dyebaths containing the alkali cation in dyebaths containing the alkali

chlorides in equimolar concentrations, the chlorides in equimolar concentrations, the

extent of dye adsorption increasing extent of dye adsorption increasing

markedly in the order Li' < Na' < K' < Rb' markedly in the order Li' < Na' < K' < Rb'

< Cs'.< Cs'.

Adsorption of direct dyes on cellulosic Adsorption of direct dyes on cellulosic

fibres is influenced by the nature of the fibres is influenced by the nature of the

cation in dyebaths containing the alkali cation in dyebaths containing the alkali

chlorides in equimolar concentrations, the chlorides in equimolar concentrations, the

extent of dye adsorption increasing extent of dye adsorption increasing

markedly in the order Li' < Na' < K' < Rb' markedly in the order Li' < Na' < K' < Rb'

< Cs'.< Cs'.

Effect of Effect of ElectrolytesElectrolytesEffect of Effect of ElectrolytesElectrolytes

Sivaraja lyer, Srinivasan and Baddi, Text. Research J., 38 (1968) 693Sivaraja lyer, Srinivasan and Baddi, Text. Research J., 38 (1968) 693

of 40


Direct Dyes

Bio-salt trisodium citrate in the Bio-salt trisodium citrate in the dyeing of cottondyeing of cotton


Direct Dye Direct Dye dyed with dyed with sod. chloridesod. chloride

Direct Dye Direct Dye dyed with dyed with trisodium trisodium citratecitrate

of 40


Direct Dyes



Sodium ChlorideSodium Chloride Trisodium citrateTrisodium citrate

DyeDye TDSTDS Dye Dye uptakeuptake TDSTDS Dye Dye

uptakeuptake

ReactiveReactive 3480034800 66.766.7 1230012300 89.189.1

DirectDirect 38003800 58.258.2 20002000 76.876.8

S. VatS. Vat 69006900 62.762.7 40004000 83.883.8

of 40


Direct Dyes

PretreatmentPretreatmentNo salt DyeingNo salt Dyeing

Treatment of cotton Treatment of cotton with cationic agents with cationic agents introduces positively introduces positively charged group. These charged group. These cationic groups form cationic groups form electrovalent bonds electrovalent bonds with the anionic dyes with the anionic dyes such as Direct and such as Direct and Reactive Dyes.Reactive Dyes. There There by eliminate the need by eliminate the need of salt during dyeingof salt during dyeing

Treatment of cotton Treatment of cotton with cationic agents with cationic agents introduces positively introduces positively charged group. These charged group. These cationic groups form cationic groups form electrovalent bonds electrovalent bonds with the anionic dyes with the anionic dyes such as Direct and such as Direct and Reactive Dyes.Reactive Dyes. There There by eliminate the need by eliminate the need of salt during dyeingof salt during dyeing

Polyepichlorohydrin dimethyl Polyepichlorohydrin dimethyl amine (PECH-amine) is prepared amine (PECH-amine) is prepared bu initial polymerization of of bu initial polymerization of of epichlorohydrin, followed by epichlorohydrin, followed by amination with diamineamination with diamine

Polyepichlorohydrin dimethyl Polyepichlorohydrin dimethyl amine (PECH-amine) is prepared amine (PECH-amine) is prepared bu initial polymerization of of bu initial polymerization of of epichlorohydrin, followed by epichlorohydrin, followed by amination with diamineamination with diamine

Polyepichlorohydrin dimethyl Polyepichlorohydrin dimethyl amine (PECH-amine)amine (PECH-amine)

of 40


Direct Dyes


Chitosan Chitosan derivative having derivative having a fibre-reactive a fibre-reactive group, namely group, namely OO--crylamidomethyl-crylamidomethyl-NN-[(2-hydroxy-3--[(2-hydroxy-3-trimethyl trimethyl ammonium)ammonium)propyl] chitosan propyl] chitosan chloride (NMA-chloride (NMA-HTCCHTCC

This compound This compound when applied to when applied to cotton under cotton under alkalinealkalineconditions and is conditions and is able to form a able to form a covalent bond covalent bond with thewith thefibre giving it fibre giving it good durability good durability as anas anantimicrobial antimicrobial textile finishtextile finish

of 40


Direct Dyes

Fixation of Fixation of Direct DyesDirect Dyes

Mostly cation-active compounds are used as Mostly cation-active compounds are used as the fixation the fixation chemicals. These compounds form a complex of high chemicals. These compounds form a complex of high molecular weight and low aqueous solubility with the dye molecular weight and low aqueous solubility with the dye resulting in high wet fastness of dyed fabricsresulting in high wet fastness of dyed fabrics

CC+ + + D+ D- - = CD= CDAmines, quaternary ammonium, phosphonium and tertiary Amines, quaternary ammonium, phosphonium and tertiary sulphonium compounds can be used as dye fixing agents. sulphonium compounds can be used as dye fixing agents. By far the most important type of cationic fixing agents By far the most important type of cationic fixing agents used in textile processing is quaternary ammonium saltused in textile processing is quaternary ammonium salt

Mostly cation-active compounds are used as Mostly cation-active compounds are used as the fixation the fixation chemicals. These compounds form a complex of high chemicals. These compounds form a complex of high molecular weight and low aqueous solubility with the dye molecular weight and low aqueous solubility with the dye resulting in high wet fastness of dyed fabricsresulting in high wet fastness of dyed fabrics

CC+ + + D+ D- - = CD= CDAmines, quaternary ammonium, phosphonium and tertiary Amines, quaternary ammonium, phosphonium and tertiary sulphonium compounds can be used as dye fixing agents. sulphonium compounds can be used as dye fixing agents. By far the most important type of cationic fixing agents By far the most important type of cationic fixing agents used in textile processing is quaternary ammonium saltused in textile processing is quaternary ammonium salt

of 40


Direct Dyes

Fixation of Fixation of Direct DyesDirect Dyes

CyanamideCyanamide

Fibrofix – Fibrofix – Cyanamide Cyanamide condensation condensation productproduct

Formaldehyde Formaldehyde condensation condensation product of product of dicyandiamidedicyandiamide

Formaldehyde Formaldehyde condensation condensation product of product of dicyandiamidedicyandiamide

of 40


Direct Dyes


Azetidinium chlorideAzetidinium chloride

1,1-diethyl-3-hydroxy 1,1-diethyl-3-hydroxy azetidinium chlorideazetidinium chloride

Sandene 8425Sandene 8425 (Clariant) (Clariant)

of 40


Direct Dyes


Phenyl MonochlorotriazinePhenyl Monochlorotriazine Based compoundBased compound

of 40


Direct Dyes

All dyes have a tendency to associate in aqueous solution. All dyes have a tendency to associate in aqueous solution.

An understanding of the association of dyes in water is of An understanding of the association of dyes in water is of

importance in both thermodynamic and kinetic studies of importance in both thermodynamic and kinetic studies of

dyeing systems since almost all textile dyes are applied dyeing systems since almost all textile dyes are applied

from aqueous systemsfrom aqueous systems.

All dyes have a tendency to associate in aqueous solution. All dyes have a tendency to associate in aqueous solution.

An understanding of the association of dyes in water is of An understanding of the association of dyes in water is of

importance in both thermodynamic and kinetic studies of importance in both thermodynamic and kinetic studies of

dyeing systems since almost all textile dyes are applied dyeing systems since almost all textile dyes are applied

from aqueous systemsfrom aqueous systems.

Mechanism of DyeingMechanism of DyeingAggregationAggregation

One can study the aggregation behaviour of dyes in One can study the aggregation behaviour of dyes in

solution by spectrophotometric analysis since dye solution by spectrophotometric analysis since dye

aggregates normally have a lower extinction coefficient aggregates normally have a lower extinction coefficient

and their maximum absorbance is at shorter wavelengths and their maximum absorbance is at shorter wavelengths

compared to the monomolecular species with some compared to the monomolecular species with some

exceptionsexceptions

One can study the aggregation behaviour of dyes in One can study the aggregation behaviour of dyes in

solution by spectrophotometric analysis since dye solution by spectrophotometric analysis since dye

aggregates normally have a lower extinction coefficient aggregates normally have a lower extinction coefficient

and their maximum absorbance is at shorter wavelengths and their maximum absorbance is at shorter wavelengths

compared to the monomolecular species with some compared to the monomolecular species with some

exceptionsexceptions

of 40


Direct Dyes


Dye*

Dye + Surfactant

Dye + Salt

Wavelength, nm

Abso

rbance

Promotes Promotes AggregationAggregationPromotes Promotes AggregationAggregation

Promotes Promotes AggregationAggregationPromotes Promotes AggregationAggregation

*CI Direct Yellow 162

of 40


Direct Dyes

Initially it was suggested that hydrogen bonds are Initially it was suggested that hydrogen bonds are

responsible for the association of direct dyes. However responsible for the association of direct dyes. However

layer studies suggest that the the aggregating forces are layer studies suggest that the the aggregating forces are

of the van der Waals’ type of the van der Waals’ type , , including dipole-dipole (and including dipole-dipole (and

induced dipole) forces and particularly dispersion forces, induced dipole) forces and particularly dispersion forces,

which are active over large numbers of planar-stacked which are active over large numbers of planar-stacked

molecules.molecules.

Initially it was suggested that hydrogen bonds are Initially it was suggested that hydrogen bonds are

responsible for the association of direct dyes. However responsible for the association of direct dyes. However

layer studies suggest that the the aggregating forces are layer studies suggest that the the aggregating forces are

of the van der Waals’ type of the van der Waals’ type , , including dipole-dipole (and including dipole-dipole (and

induced dipole) forces and particularly dispersion forces, induced dipole) forces and particularly dispersion forces,

which are active over large numbers of planar-stacked which are active over large numbers of planar-stacked

molecules.molecules.




of 40


Direct Dyes

Mechanism of Mechanism of DyeingDyeing

AggregationAggregation

Aggregated direct Aggregated direct dye with ionized salt dye with ionized salt is aqueous solutionis aqueous solution

Aggregated direct Aggregated direct dye with ionized salt dye with ionized salt is aqueous solutionis aqueous solution

of 40


Direct Dyes

Cotton is a hydrophilic natural cellulose fibre whose porous Cotton is a hydrophilic natural cellulose fibre whose porous

structure facilitates the penetration of various solutes, structure facilitates the penetration of various solutes,

including organic dyes. As a cellulose-based polymer, it including organic dyes. As a cellulose-based polymer, it

consists of D-glucose units joined by b-1,4-glycosidic consists of D-glucose units joined by b-1,4-glycosidic

linkages, and it is well known that the cellulose chains linkages, and it is well known that the cellulose chains

associate with one another via intermolecular hydrogen associate with one another via intermolecular hydrogen

bonds. The resultant system of polymer chains coalesces to bonds. The resultant system of polymer chains coalesces to

form microfibrils that are organized into macrofibrils and form microfibrils that are organized into macrofibrils and

subsequently into fibres.subsequently into fibres.

Cotton is a hydrophilic natural cellulose fibre whose porous Cotton is a hydrophilic natural cellulose fibre whose porous

structure facilitates the penetration of various solutes, structure facilitates the penetration of various solutes,

including organic dyes. As a cellulose-based polymer, it including organic dyes. As a cellulose-based polymer, it

consists of D-glucose units joined by b-1,4-glycosidic consists of D-glucose units joined by b-1,4-glycosidic

linkages, and it is well known that the cellulose chains linkages, and it is well known that the cellulose chains

associate with one another via intermolecular hydrogen associate with one another via intermolecular hydrogen

bonds. The resultant system of polymer chains coalesces to bonds. The resultant system of polymer chains coalesces to

form microfibrils that are organized into macrofibrils and form microfibrils that are organized into macrofibrils and

subsequently into fibres.subsequently into fibres.

Mechanism of DyeingMechanism of DyeingStructure of CottonStructure of Cotton

of 40


Direct Dyes

Lumen

Reversal

S3

S2

20-30

S1

20-35

Primary Wall

Cuticle

Pectin

Wax

Fats

Crystalline fibrils

Macro Structure Macro Structure of Cottonof Cotton

of 40


Direct Dyes

Micro Structure Micro Structure of Cottonof Cotton

FibrilFibril

FibrilFibril

FibrilFibril

FibrilFibril

PorePore

PorePore

PorePore

PorePore

of 40


Direct Dyes

MechanismMechanismof Dyeingof Dyeing

Diffusion Diffusion of Dyesof Dyes

Static PoreStatic Pore

Model of Dye Model of Dye DiffusionDiffusion

Static PoreStatic Pore

Model of Dye Model of Dye DiffusionDiffusion

of 40


Direct Dyes

Direct dyes are absorbed on the internal surface of Direct dyes are absorbed on the internal surface of

cellulosic substrates, the amount of surface cellulosic substrates, the amount of surface

accessible to a dye anion depending on the form accessible to a dye anion depending on the form

and size of the anion. The internal surface of the and size of the anion. The internal surface of the

fibre also possesses an electric charge. The extent fibre also possesses an electric charge. The extent

to which this initial charge is reinforced depends on to which this initial charge is reinforced depends on

the different absorption of the dye anions by the different absorption of the dye anions by

different surfaces. Besides competition for dye different surfaces. Besides competition for dye

sites, a mutual electrostatic repulsion occurs.sites, a mutual electrostatic repulsion occurs.

Direct dyes are absorbed on the internal surface of Direct dyes are absorbed on the internal surface of

cellulosic substrates, the amount of surface cellulosic substrates, the amount of surface

accessible to a dye anion depending on the form accessible to a dye anion depending on the form

and size of the anion. The internal surface of the and size of the anion. The internal surface of the

fibre also possesses an electric charge. The extent fibre also possesses an electric charge. The extent

to which this initial charge is reinforced depends on to which this initial charge is reinforced depends on

the different absorption of the dye anions by the different absorption of the dye anions by

different surfaces. Besides competition for dye different surfaces. Besides competition for dye

sites, a mutual electrostatic repulsion occurs.sites, a mutual electrostatic repulsion occurs.

Mechanism of DyeingMechanism of DyeingSorption on Internal SurfaceSorption on Internal Surface

of 40


Direct Dyes

It is known that the accessible area on cellulosic It is known that the accessible area on cellulosic

substrates is a function of the molecule size. substrates is a function of the molecule size.

Recent research has shown that the accessible Recent research has shown that the accessible

volume of a cellulosic fibre for a molecule with volume of a cellulosic fibre for a molecule with

an effective diameter of 2.5 nm was about four an effective diameter of 2.5 nm was about four

times higher than that for a molecule with an times higher than that for a molecule with an

effective diameter of 5 nmeffective diameter of 5 nm

It is known that the accessible area on cellulosic It is known that the accessible area on cellulosic

substrates is a function of the molecule size. substrates is a function of the molecule size.

Recent research has shown that the accessible Recent research has shown that the accessible

volume of a cellulosic fibre for a molecule with volume of a cellulosic fibre for a molecule with

an effective diameter of 2.5 nm was about four an effective diameter of 2.5 nm was about four

times higher than that for a molecule with an times higher than that for a molecule with an

effective diameter of 5 nmeffective diameter of 5 nm

Mechanism of DyeingMechanism of DyeingSorption on Internal SurfaceSorption on Internal Surface

of 40


Direct Dyes

Mechanism of DyeingMechanism of DyeingVoid Size and AreaVoid Size and Area

Viscose RayonViscose RayonViscose RayonViscose Rayon Modal FibresModal FibresModal FibresModal Fibres Lyocell FibresLyocell FibresLyocell FibresLyocell Fibres

Lyocell fibres consist of longer molecules, they have a Lyocell fibres consist of longer molecules, they have a greater degree of crystallinity, its crystallites are oriented in greater degree of crystallinity, its crystallites are oriented in the fibre axis direction, and its void structure is similar to that the fibre axis direction, and its void structure is similar to that of viscose fibres. Differences in the molecular and fine of viscose fibres. Differences in the molecular and fine structure of these fibres cause different sorption properties.structure of these fibres cause different sorption properties.

Lyocell fibres consist of longer molecules, they have a Lyocell fibres consist of longer molecules, they have a greater degree of crystallinity, its crystallites are oriented in greater degree of crystallinity, its crystallites are oriented in the fibre axis direction, and its void structure is similar to that the fibre axis direction, and its void structure is similar to that of viscose fibres. Differences in the molecular and fine of viscose fibres. Differences in the molecular and fine structure of these fibres cause different sorption properties.structure of these fibres cause different sorption properties.

of 40


Direct Dyes

2.2 2.4 2.6 2.8 3.0 3.2 3.4

0.75

0.70

0.65

0.60

0.55

0.50

0.45

0.40

500

475450

425

400

375350

325

300275

250

Internal Surface of VoidsVoid volume

Void Diameter, nm

Void

Volu

me V

p, cm

/g

Speci

fic

Iner

Surf

ace

, Sp [

m2/g

MOD

LYO

VIS

Void Void DiameterDiameter

Void Void DiameterDiameter

Viscose:3.1Viscose:3.1

Lyocell: 3.0Lyocell: 3.0

Modal : 2.4Modal : 2.4




Void Void VolumeVolume

Void Void VolumeVolume







of 40


Direct Dyes

References• The Diamond Jubilee of the Discovery of Direct Cotton Dyes, 1884 – 1944. By C.

M. WHITTAKER, JSDC, 1945, 201.• Direct Cotton Dyes, Common Salt, and Commonsense, By C. M. WHITTAKER, JSDC,

1942, 253. • Effect of the bio-salt trisodium citrate in the dyeing of cotton, H Gurumallesh Prabu

and M Sundrarajan, Color. Technol., 118 (2002) 131• Synthesis and Evaluation of Non-genotoxic Direct Dyes, Jin-Seok Bae* and Harold S.

Freeman, fibres and Polymers 2002, Vol.3, No.4, 140-146. • An investigation into direct dye aggregation, Martin Ferus-Comelo* and Andrew J

Greaves, Color. Technol., 118 (2002) 15. • Description of dyeing equilibria in the application of direct dyes, H Gerber, JSDC

VOLUME11 2 MAY/JUNE 1996 153. • The Application of Direct Dyes to Viscose Rayon Yarn and Staple, J. BOULTON,

J.S.D.C. 67 (1951) 522. • Structural Characteristics of New and Conventional Regenerated Cellulosic Fibers,Tatjana

Kreze and Sonja Malej, Textile Research Journal 2003; 73; 675. • Role of quaternary ammonium salts in improving the fastness properties of anionic dyes on

cellulose fibres Saima Sharif,a,b Saeed Ahmadb,* and Mian Muhammad Izhar-ul-Haqa, Color. Technol., 123, 8–17

INDIAN INSTITUTE OF TECHNOLOGYINDIAN INSTITUTE OF TECHNOLOGYM. L. GULRAJANIM. L. GULRAJANI

Direct Dyes

End End

of of

Lecture – 2 & 3Lecture – 2 & 3

End End

of of

Lecture – 2 & 3Lecture – 2 & 3

lecture - 2&3 - direct dyes

Documents