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ReactiveReactiveDyesDyes

Dr Kelvin N TapleyDepartment of Colour ChemistryUniversity of Leeds, Leeds, UK

September 2003

Kaliakor Dye Managers Workshop

Outline• History• General Features• Advantages & Disadvantages• Factors influencing performance• Common Types of Reactive Dyes• Reactions of Reactive Dyes• Application Methods• Summary

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History• Cyanuric chloride reaction with cotton and then amines• Remazol (vinyl sulphone) chemistry intorduced• 1956 Rattee + Stephen (ICI) “first” reactive dyes

– chlorotriazines• Various developments – including new chemical types• 1980’s Mixed bifunctional dyes (esp. Sumitomo – Sumifix Supra

dyes)

General Features of a Reactive Dye Molecule

W = water solubilising groupD = chromophoreB = bridging groupRG = reactive groupX = leaving group

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Advantages?• Full Colour Gamut• Brilliant, bright colours• Colvalent fixation high WashFastness (WF)• Varying reactivities

– Various temperaturesincluding low energy (cold dyeing)

• Various methods of application• Inexpensive to apply (but dyes expensive)

Disadvantages?

• Incomplete fixation (problem with hydrolysis)• Need for wash-off (for high WF)• Need for high concentrations of salt

– Affect natural balance of watercourses• High pH• Some dyes are “AOX” – potentially harmful to

the environment

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• Loss of colour fading problems

• Transfer of colorants to “adjacent” fabrics leads to staining problems

• NB some of the WF tests have got tougher!

The major issuesThe major issues

Importance of Washing Fastness (WF) Importance of Washing Fastness (WF)

Poor wash fastness

Laundry washing

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During the laundry process the fabric is subjected to some severe conditions and very often dye is “beaten” from the

fabric.

This results in dye entering the washing liquors.

Once in the washing liquors 3 things can happen to the dye...

1. Re-adsorb onto original fibre

2. Adsorb to a different substrate

3. Remain in the wash liquor

affinity of dye for original fibre

Degree of stainingDegree of staining

=

+affinity of dye for adjacent fibre

affinity for water

(staying in solution)

+

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Factors that affect the dyeing of cotton with reactive dyes

Dyebath (liquor ratio/flow)

Pre-treatmentCotton

Method:eg.Temperature and duration

of dyeing

Reactive dye

Auxiliaries

Factors Influencing the Performance of Reactive Dyes

• Molecular structure of Dye– Number of reactive groups– Chemical nature of reactive groups– Molecular mass (size)– Number of sulphonic acid groups– Ratio of sulphonic acid groups to aromatic carbons

• hydrophobic – hydrophilic balance– Linear / planar structure (shape)– Other functional groups present– Realtive positions of functional groups (incl. reactive groups)

Plus characteristics and quantity of impurities / additives

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Factors Influencing the Performance of Reactive Dyes

• Material being dyed– Chemical type (assume cellulosic)– (Macro) physical structure (yarn, fabric, garment)– (Micro) physical structure (crystallinity vs

amorphous)– Material preparation or damage prior to coloration

• Exposure to physical, chemical and biological agents

PrePre--treatmenttreatment

PrePre--treatment is crucial to a dyer if he wants to achieve righttreatment is crucial to a dyer if he wants to achieve right--firstfirst--time dyeings. After pretime dyeings. After pre--treatment he can trust his fabrictreatment he can trust his fabric..

It is easy to appreciate that what happens to the fabric before It is easy to appreciate that what happens to the fabric before dyeing will affect dyeing itself !dyeing will affect dyeing itself !

PrePre--treatment for cotton treatment for cotton principally involves: principally involves:

Scouring and bleachingScouring and bleaching

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Exha

usti o

nEx

haus

ti on

TimeTime

Scoured Scoured

UnscouredUnscoured

ScouringScouringEssentially cleaning!Essentially cleaning!

removal of waxes, fatty acids etc. removal of waxes, fatty acids etc.

Definition of scour: To remove natural impurities, dirt or grease from (cloth or fibers) by means of a detergent.

Factors Influencing the Performance of Reactive Dyes

• Application conditions– Quality of the water employed– Temperature programme employed– pH programme employed (incl type + conc of alkali)– Electrolyte programme employed– Any other additives/chemicals present (eg. Auxiliaries)– Liquor to materials ratio (LR)– Chemical (incl Dye) addition programme employed– Agitation / liquor circulation method– Time – at each stage

[Rinse/Wash/After treatment conditions are also important]

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Factors Influencing the Performance of Reactive Dyes

• Application conditions – the “Human Factor”– You may not be using an optimum method– Do you / your operatives actually do what you say you do?

– Try to identify real / potential problem areas, for example:• Volume of water used (LR). Why?

• Housekeeping• Use of Chemicals (dyes, electrolyte, alkali, auxiliaries)

• Temperature (including storing/dissolving dyes)

• Time

Types of Reactive Dyes

[Some examples!]

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O

O

NH2

SO3Na

NH

SO2CH2CH2OSO3Na

Vinyl sulphone dye (Remazol Brilliant Blue R, C.I. Reactive Blue 19)

Sulphatoethyl sulphone dyes

SO3Na

NH N

NN

Cl

NH

SO3NaNaSO3

OHN

N

Monochloro-s-triazine dye (Procion Red H-3B, C.I. Reactive Red 3)

Monochloro-s-triazine dyes

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NaSO3SO3Na N

N

N

NH N

NN

Cl

NH

SO3NaNaSO3

OH NH NH

Cl

NaSO3 SO3Na

OHN

NN

N

Bis(monochloro-s-triazine) dye (Procion Red HE-3B, C.I. Reactive Red 120)

Bis (monochloro-s-triazine) dyes

N

NN

F

FCl

SO3Na

N N

NaSO3

OH NH

O

H

SO3Na

SO3Na

2,4-difluoro-5-chloro-pyrimidine dye (Levafix Brilliant Red E 3BA, C.I. Reactive Red 147)

2,4-difluoro-5-chloro-pyrimidine dyes

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NN

SO3Na

OHNH

NaSO3

SO3Na

N

N

Cl

Cl

Cl

Trichloro pyrimidine dye (Drimarene Red Z 2B, C.I. Reactive Red 17)

2,4,5-trichloro-pyrimidine dyes

N

NN

NH

SO2CH2CH2OSO3Na

NH

Cl

Dye

General structure of Sumifix Supra dyesMCT-SES or MCT-VS[Reactron Supra F dyes are similar]

Mixed Bifunctional reactive dyes

eg.

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Reactions of Reactive Dyes

[Some examples!]

Nucleophilic addition

Reactive group

The reactive group is usually the vinylsulphone group

SO2 - CH = CH2

Sulphone (SO2) Vinyl (CH = CH2)

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DYE SO

ODYE S

O

O

DYE SO

O

NaHSO4

DYE SO

O

CH2

+Cellulose O-

CelluloseSO

O

DYE-

Cellulose

+

C C CH

C

C C

OSO3Na

H H

H H

CHCH

H

H

O

H2O

+ OH-O

H H

HH

CH2

-

ß-elimination of ß-sulphatoethylsulphone to vinyl sulphone and reaction with cellulose.

Nucleophilic addition

Nucleophilic substitution

Reactive group

The reactive groups is usually a halogenated heterocyclic group

e.g.

a dichloro-s-triazine reactive group

N

N

N

ClCl

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N

NN

Cl

Cl

NH

DyeN

NN

Cl

NH

Dye

ClX

N

NN

OH

Cl

NH

Dye

N

NN

O

Cl

NH

Dye

Cellulose

OR+ X-

..- Cl-

Competing nucleophilic substitution reactions of s-triazine dyes

Nucleophilic substitution

0.03

0.13

0.23

0.33

0.43

6 10 14 18 22

Time / minutes

Separation of bis-Monochlorotriazinyl ReactiveDyes and Hydrolysates in Dyehouse Effluent by

Capillary Zone Electrophoresis

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Application Methods

• Continuous– eg. Pad - Thermofix

• Semi-Continuous– eg. Pad - Batch

• Batchwise Exhaustion *– eg. Winch, Jet, Package and Beam Dyeing

• Printing– eg. Print - Thermofix

Typical dyeing conditions for a bifunctionalmonochlorotriazine dye

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Typical dyeing conditions for a bifunctional dichlorotriazine dye

Typical dyeing conditions for a bifunctional sulphatoethyl sulphone dye

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Summary

• Dominant dye class for cotton• Importance of nature and number of reactive

groups ( covalent fixation)• Different types/chemistries

many different application methods• Problem of dye hydrolysis• Potential impact on environment

AcknowledgementsDepartment of

Colour Chemistry,University of Leeds

DFID

K.Tapley@leeds.ac.ukK.Tapley@leeds.ac.ukDepartment of Colour Chemistry, University of Leeds, Leeds, LS2 9JTwww.leeds.ac.uk/ccd

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Questions ?Questions ?