Dyes

DYES Compile By

Dr. Amish B. Patel Asst. Prof. Prof. in Ch emistry Faculty of Engineering Technology And Research.

Introduction A dye dye   or a dyestu   is usually a coloured organic compound or miture   that may !e used for miture imparting colour to a su!strate  su!strate   such as cloth" paper" plastic or leather. A Pigment   particles Pigment remain clustered together in suspension. Pigment molecules carry their o#n color

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Diference between Pigments and Dyes Pigment

Dye

color theory complex phenomenon that combines the physics of light chemistry of colored objects biology of the eye behavioral sciences—social & cultural meaning of color • •

• •

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Colour And Constitution Colour &   The psychological sensation  #hich is produced #hen the light of certain #a'elength reaches the eye  is (no#n as the colour.   The colour is dependent on and 'aries #ith the nature of the light illuminating the coloured su!stance. )hen #hite light is incident on a su!stance" If #hite light is re*ected  completely" the su!stance #ill appear light. If #hite light is a!sor!ed  completely" the su!stance #ill appear !lac(. +

)hen a !eam of 'isi!le light stri(es a coloured su!stance" certain #a'elengths are a!sor!ed and others are re*ected. Those re*ected compose the colour of the su!stance.  The su!stance a!sor!s #a'elength in the !lue-green region of the spectrum" it appears red. ,

/ight is made up of !ands of 'arying #a'elengths

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Re*ection •

•

)hite can only !e !ro(en up !y prisms or !y colorants such as pigments and dyes  This surface has no colorant so the light is re*ected

0

It can !e fully a!sor!ed !y the surface

1

4r a transparent surface may let all of the light pass through or a colored surface may a!sor! part of the spectrum

23

Relationship of colour a!sor!ed and complementary colour o!ser'ed

Wavelength Absorbed (nm)

Colour absorbed

Comlementar y colour

%33-%5+

6iolet

7ello#-green

%5+-%03

Blue

7ello#

%03-%13

Blue-green

orange

%13-+33

8reen-!lue

Red

+33-+,3

8reen

Purple

+,3-+03

7ello#-green

6iolet

+03-+1+

7ello#

Blue

+1+-,3+

orange

8reen- Blue

,3+-+3

red

Blue-8reen

22

Colour And Constitution  The colour of a compound is related to its chemical constitution. According to 4tto )itt9s theory :20,;" a dye is made up of t#o parts" Chromophores and Auochromes.

2$

Chromohores !  The colour of organic compounds is due to the presence of certain multiple !onded groups called chromophores. The compound containing a chromophoric group #ere called as chromogens. : 8ree( Chroma < colour and phorein < to !ear; Au"ochromes ! Certain groups" #hile not producing colour themsel'es" #hen present along #ith chromophores in an organic su!satance" intensify the colour" such colour assisting groups are called Auochromes. : 8ree( Auanein < to increase and Chroma < colour; 25

 The auochromes ser'e t#o functions" 

 They increase the intensity of the colour" e.g. :i; Ben=ene : >o Chromophores ; is colourless. :ii; >itro!en=ene : ->4$ as a Chromophores ; is pale 7ello# colour. :iii; p->itroaniline :->4$ as a Chromophores and ->? $ as a Auochrome ; is dar( 7ello#.

  They

ma(e the chromogen a dye !y @ing it to the fa!ric  or the material to !e dye either !y association or !y salt formation.  The @ing of the dye to the @!er is due to the formation of chemical !ond !et#een the @!er and auochrome. 2%

ome Typical Chromophores

2+

ome Typical Auochromes

2,

>omenclature of Dyes #$ Commercial %aming o& Dyes!  The trademar( name of the class comes @rst and is follo#ed !y #ords" letters or num!ers. These descri!e the shade and other characteristics" strength" physical form etc. e.g. 7 or 8 < 7ello# : 8erman #ord gel! < yello#; R < Red :8erman #ord rot < red; B < Blue 4 < 4range e.g. 6at Pin( R" R9 indicates the red tone of the pin(. 2

ometimes the letters are used to represent the class of dye. e.g. Ali=arin Blue D" the letter D9 indicates that dye is a direct cotton colour.

'$Colour nde" %aming o& Dyes!  The !est method for the nomenclature of dyes is Colour Inde" a pu!lication sponsored !y the" society of Dyers  colourists :England; and American Association of Tetile Chemists  colourists. In this" each dye is gi'en t#o reference 20 num!ers" one relating to its class #ith

Basic Tetile De@nitions Fi!ers < A smallest unit of tetile materials. sually classi@ed !y *ei!ility" @neness" and a ratio !et#een length and diameter :/D ratio; >atural Fi!ers  < Fi!ers that come from animals :#ool" sil( etc.;" plants :cotton" ute etc.; or mineral material :as!estos;. ynthetic Fi!ers  < Gan-made @!ers or arti@cial @!ers #hich is usually comes from chemical agents. 21

 7arns <  7arn is a long continuous length of interloc(ed @!ers. The com!inations of @!ers using some t#isting :H and  t#ists; in order to ma(e strong and sta!le yarns. Fa!rics < The products of #ea'ing" (nitting or non-#o'en processes. >ormally" fa!rics ha'e a certain thic(ness and can #ithstand tear and tensile forces.

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tructure of Cotton : Bioglucose unit in cotton;

 The side groups of these units are primary and secondary alcoholic hydroy groups #hich ma(e the @!re hydrophilic. This property of cotton @!re is responsi!le for its dyeing. $2

tructure of )ool

)ool

is the natural animal @!re. It is composed of protein su!stance. It is dyed #ith either acidic or !asic dyes through the formation of salt lin(age #ith amino or car!oylic acid end groupings. It may also !e dyed #ith reacti'e dyes  that form co'alent !onds #ith a'aila!le amino groups. $$

tructure of il(

il(

is also the natural animal @!re and also a protein @!re. It is linearly arranged polypeptide structures called @!roin. )hensil( hydrolysed" the main aminoacids isolated are glycine" alanine" serine and tyrosine. $5

Classi@cation of Dyes Dyes are classi@ed in 'arious #ays according to" : 2 ;  The method of application to the @!er" : $ ;  Their chemical constitution" : 5 ; The types of material to !e dyed" and : % ; The intermediates from #hich they are   prepared.

%$ Dyestus can !e classi@ed !y many methods as follo#s& 2. !y their ionic :e.g. cationic" anionic and non-ionic; $. !y their @!er dyea!ilities  :e.g. on cellulosic" protein" polyester" polyamide etc.; 5. !y their names :e.g. acid" direct" disperse" reacti'e" !asic etc.; %. !y their chemical structures  :e.g. a=o" anthrauinone" stil!ene etc.; +. !y their origins :e.g. natural" synthetic;

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Classi@cation of dyes according to applications.

#$ Acid dyes ! .  These

dyes are usually the sodium salts of the colour acids" #hich may contain sulphonic acid or phenolic group. . )hich are used to dye @!ers ha'ing !asic groups" such as #ool" sil( and polyamides. . Application is generally made under acidic condition" #hich cause protonation of the !asic groups. Dye- J ?J J Fi!er → Dye- ?J - Fi!er .  This is a re'ersi!le process and it can !e remo'ed !y #ashing. . Eamples& Picric acid" 4range II" >aphthol 7ello#.

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tructure of 4range II

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'$ asic dyes !      

)hich ha'e a !asic amino group. )hich is protonated under the acidic conditions of the @!ers. It gi'es intense and !rilliant shades.  They are used for dyeing sil( and #ool directly. For dyeing cotton it needs a mordant li(e tannic acid. Eamples& Crystal 'iolet" Gethylene Blue.

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tructure of Crystal 6iolet

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*$ Direct dyes !   







 These are a class of dyes that !ecome strongly adsor!ed on cellulose. Direct dyes are large" *at and linear molecules. A direct dye contains acidic or !asic auochrome #ith the opposite polar group present in the chemical structure of the @!er. it is used for dyeing #ool" sil( and cotton. Fi!er->?$ J ?4-D7E → Fi!re->?5J - 4- - D7E 8enerally common salt is used to promote dyeing !ecause i.p.o. salt it fa'ors esta!lishment of euili!rium  #ith a minimum of dye remaining in the dye !ath. Eamples& Congo Red. 53

tructure of Congo Red

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+$ ,at dyes !  

 

 

6at dyes are insolu!le !ut their reduced forms are solu!le. Reduced forms of 'at dye are o!tained !y treating the dye compound #ith some reducing agent such as al(aline sodium hyposulphite.  The cloth to !e dyed is immersed in the 'at. After the reduced dye has !een adsor!ed on the @!er" the original insolu!le dye is reformed !y oidation #ith air or chemicals. 6at dyes are uite epensi'e and used on cotton fa!rics. Eamples& Indigo" Anthrauinone 5$

tructure of Indigo

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-$ Diserse dyes !    

Disperse dye molecules are small  and ha'e some hydroyl or amino groups. Disperse dyes are insolu!le in #ater !ut can !e dispersed in a colloidal form in #ater.  The @ne dye particles are a!sor!ed into the crystal structure9 of the fa!ric. It is used for dyeing of cellulose acetate" nylon" polyester and polyacrylonitrile @!ers.

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Classi@cation of dyes according to their Chemical Constitution %o $

Class

Subcl ass

2

>itro

---

E"amles

Picric acid  7ello#  $

>itroso

>aphthol

---

Fast 8reen 4 5+

%o $

Class

Subcl ass

5

A=o

Gonoa=o

E"amles

Gethyl 4range Bisa=o

Congo Red  Trisa=o

Direct Blac( E) Polya=o

----

5,

%o $

Class

Subcl ass

5

A=o

Gordant a=o

E"amles

Eriochrome Blac( T til!ene a=o

Chrysophenine 4 Pyra=olo ne a=o

 Tartra=ine

5

%o $

Class

Subcl ass

%

Diphenyl Gethane

----

E"amles

Auramine 4 +

Triphenyl Gethane

----

Galachite 8reen ,

Kanthene

----

Fluorescein

50

%o $

Class

Subcl ass



Indigoid

----

E"amles

Indigo 0

Thia=ole

----

Basic 7ello# T 1

Thia=ine

----

Gethylene Blue

51

%o $

Class

Subcl ass

23

Cyanine

Gethine

E"amles

Astra*oine FF 22

Anthrauinono id

----

Perion Fast 8reen BR 2$

?ydroy Letone

----

Ali=arin Dar( 8reen )

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A=o Dyes If one a=o group → Gonoa=o dyes t#o a=o group → Dia=o dyes  Three a=o group → Trisa=o dyes Four a=o group → Tetro(isa=o dyes Fi'e a=o group → Polya=o dyes  The dia=otisation process #as disco'ered !y Petter 8reess in 20,$" according to him" A=o dyes are prepared !y t#o process& 2; Dia=otising primary aromatic amine !y treatment of >itrous acid :?>4 $; in aueous medium at 3+°C to form dia=onium salts. $; Coupling the a!o'e dia=onium salt #ith phenols  aromatic amines etc. to gi'e a a=o compound. %2

Application of A=o Dyes they are applica!le to"  All the natural  synthetic @!er  Paper" leather" ru!!er and other material   Pure form of certain dye are used for colouring foodstu.   sed as Indicator" drugs" stain in !acteriological analysis.  Com!ination of a=odyes  metallic salt are 'alua!le in the paints" 'arnishes" lacuers and allied industries. %$

Acid Dyes sed mainly on #ool" sil(" and nylon  They ha'e acid chemical groups in their dye molecules Reaction in'ol'es acid" salt" heat" agitation and time Amount of acid and rate at #hich it is added aects the rate at #hich the dye !onds alt slo#s the !onding process" helping the dye color the @!er e'enly. It attaches to the dye @rst. ?eat aects the le'eling of the dye !ath !y speeding up the chemical reaction 8enerally the dye !onds slo#ly until 2,3M F Agitation helps (eep !oth chemicals and heat e'enly distri!uted •

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•

 –

 –

•

•

•

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,A. DYES •

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%D/0" pro!a!ly the oldest dye (no#n to man" is one of the most important mem!ers of this group. >atural indigo etracted from the plant NIndigofera tinctorieN #as used !y the Egyptians in $33 BC.  The @rst synthetic indigo #as introduced to the tetile trade in 201  had the eect of completely replacing the natural product. %%

ynthesis of Gethyl 4range

: 2 ; Dia=onium salt of sulphanilic acid :It$ is ; >">-Dimethyl Aniline for acid-!ase titrations a 'alua!le indicator !ecause it gi'es yello# colour in !asic solution and red color in acid solution. The change in colour is due to the change in the structure of the ion. %+

ynthesis of Congo Red

: 2 ; Tetra=otised !en=idine direct dye andacid used for dyeing cotton. Also used : It$ is; >aphthionic as indicator" !eing red in al(ali and !lue in acid solution. %,

ynthesis of Bismar( Bro#n

: 2 ; Tetra=otised mdiamino!en=ene :It $is; used m-diamino!en=ene in !oot polishes and for dyeing #ool and cotton. %

ynthesis of Galachite 8reen

8ree( #orld /euco < Colourless It has a deep green !lue colour. It is used as a direct dye for #ool and sil(. %0

ynthesis of Ali=arin

It forms ru!y red crystals #hich dissol'e in al(ali to gi'e purple solutions. It used to dye #ool and cotton. %1

ynthesis of Indigo Dyes

It contain car!onyl chromophore. It is a dar(-!lue crystalline compound" insolu!le in #ater. It is used for dyeing cotton. +3

ynthesis of Eriochrome Blac(-T

It is used as an indicator in EDTA +2

ynthesis of Fluorescein

It is red po#der and it is insolu!le in ? $ 4. )hen it is dissol'ed in al(alies" it gi'es a reddish!ro#n solution #hich on dilution gi'es a strong yello#ish-green *uorescence. It9s sodium salt is (no#n as ranine and used to dye #ool  sil(. +$

ynthesis of >aphthol  7ello#-

It is used as the sodium or potassium salt. It is cheap dye for #ool and sil( in an acid !ath" gi'ing pure yello# shade. It is non poisonous  is used as food colour. +5

Dyeing Process Dyeing Processes can !e applied in many stages such as 2.Gass-coloration of the molten @!ers $.Fi!er Dyeing 5.7arn Dyeing %.Fa!ric Dyeing +.8arment Dyeing +%

2. Gass-coloration of the molten @!ers  This method is for dyeing the molten @!ers or plastic chips or tetile polymers #ith pigment dyes. After that" the molten polymers #ill etrude from a spinneret to form @!ers. Disad'antage& 'ery diOcult to clean. $. Fi!er Dyeing is the method of dyeing @!ers !efore !lending  #ith other colors to gi'e fancy yarns or fa!rics. >ote& This is used for special purposes only. 5. 7arn Dyeing is the method of dyeing yarns in forms of pac(ages dyeing. ++

%. Fa!ric Dyeing is the method after #ea'ing" (nitting" or non-#o'en to ma(e fa!rics. This is 'ery popular method of dyeing as the dyed fa!rics #ill !e processed further to garment industries 'ery easily.

Dyeing &orms  of the fa!ric dyeing can !e used in $ #ays& 2. 4pen #idth form using the fa!rics to spread #ithout any creases and dye them. $. Rope form using the fa!rics #ith the form li(e a rope :many creases and loo( li(e a ropeQ; +,

It is a (no#n fact that the main material for fa!ric construction  is yarn. Lnitting is the second most freuently used method" after #ea'ing" that turns yarns or threads into fa!rics. )ea'ing  is the most !asic process in #hich t#o dierent sets of yarns or threads are interlaced #ith each other to form a fa!ric or cloth. 4ne of these sets is called #arp #hich is the length#ise yarn running from the !ac( to the front of the loom. The other set of cross#ise yarns are the @lling #hich are called the #eft or the #oof. A (nitted fa!ric may !e made #ith a single yarn #hich is formed into interloc(ing loops #ith the help of hoo(ed needles. +

ome people classify into& 2. Ehaustion Process  This method is using lot of #ater as sho#n in /iuor Ratio :ratio !et#een #ater and goods;Q This should immerge the goods into dye solution for a long time in order to let the dye penetrate into the goods. This #ill lead to produce more #aste #ater than the continuous process. Ad'antage&  inepensi'e" no need to train the #or(er to loo( after and run them properly. Disad'antage&  lots of #ater needed" 'ery slo# process :,3-2$3 min!atch.; +0

$. Continuous Process  This method is designed !y putting dierent machinery into a seuence so that it can produce the dyed fa!ric in one pass. Ad'antage&  'ery fast process :23-233 mmin;" small amount of #ater in the process. Disad'antage&  'ery epensi'e" need to train the #or(er to loo( after and run +1

+. 8arment Dyeing  This method is the last process of the dyeing of goods. ?o#e'er" the penetration of the dye solution may not !e completely passed to the @!ers such as !et#een the !uttons" =ippers  etc. >ormally" it is used for soc(s  s#eater dyeing etc.

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>ame of Dyestus

Fi!ers that can !e

dyed Acid

il(" #ool" polyamide" leather

Basic

Acrylic

Direct

Cellulosic" 'iscose

Disperse

Acetate" triacetate"

polyamide" Reacti'e 6at ulphur

polyester" acrylic Cellulosic" 'iscose" protein

Cellulosic Cellulosic

,2

Dyeing method Direct Dyeing )hen a dye is applied directly to the fa!ric #ithout the aid of an aOing agent" it is called direct dyeing. In this method the dyestu is either fermented :for natural dye; or chemically reduced : for synthetic 'at and sulfur dyes; !efore !eing applied. The direct dyes" #hich are largely used for dyeing cotton" are #ater solu!le and can !e applied directly to the @!er from an aueous solution. Gost other classes of synthetic ,$ dye" other than 'at and sulfur dyes" are also

 Yarn Dyeing )hen dyeing is done after the @!er has !een spun into yarn" it is called 7arn dyeing.  There are many forms of yarn dyeingPac(age Dyeing" pace Dyeing.

Pac1age ,5

Fastness Properties .hese are the roerties o& the dye which indicate the tolerance o& the dyes on the 2bers  towards the action o& various

&oreign

agencies

li1e3

light3

washing3 heat (sublimation)3 rubbing3 ersiration3 milling (rotating in wash wheel)$ ,%