Chap4- - Disperse dyes are nonionic, have very limited solubility in water at room temperature - They have substantivity for one or more hydrophobic fibers e.g. Polyesters, cellulose acetate and Nylons. - They are usually applied from a fine aqueous dispersion containing some dissolved dye. - In the aqueous solution from which dyeing normally takes place, despite the low water solubility of the dye. Disperse Red 1 Disperse Red 60 81 Disperse dyes O O NH 2 O OH Chap4- Blue 30% Orange 8% Viloet 8% Brown 3% - It reflects the difficulty of synthesizing green and black compounds, which are nonionic and of small enough molecular size to have substantivity for and to be able to diffuse into hydrophobic fibers. 82 Disperse dyes Chap4- Disperse Dyeing Mechanism Dye solid Dye micelles Dye dissolved Dye fiber Dy e Dispersing agent Dispersing agent (0.1mg/L) 83 Disperse dyeing mechanism Chap4- Disperse dyeing recipe - Disperse dye : x(%owf) - pH control agents : pH 4.5-5.5 with acetic acid(0.4g/l) - Dispersing agent : 0.5g/l 30˚C 2 0 C/min 130˚C,60 min 3˚C/min 40˚C Dye, PET, Dispersing agent, pH control agent A general thumb rule has the starting temperature about 70-80C. 70~80˚C 84 → Reduction clearing Disperse dyeing process
Transcript
Chap4-
- Disperse dyes are nonionic, have very limited solubility in water atroom temperature
- They have substantivity for one or more hydrophobic fiberse.g. Polyesters, cellulose acetate and Nylons.
- They are usually applied from a fine aqueous dispersion containingsome dissolved dye.
- In the aqueous solution from which dyeing normally takes place,despite the low water solubility of the dye.
Disperse Red 1 Disperse Red 60
81
Disperse dyes
O
O
NH2
O
OH
Chap4-
Blue30%
Orange8%
Viloet 8%
Brown 3% - It reflects the difficulty of
synthesizing green and black
compounds, which are nonionic
and of small enough molecular
size to have substantivity for
and to be able to diffuse into
hydrophobic fibers.
82
Disperse dyes
Chap4-
Disperse Dyeing Mechanism
Dyesolid
Dyemicelles
Dyedissolved
Dyefiber
Dye
Dispersing agentDispersing agent (0.1mg/L)
83
Disperse dyeing mechanism
Chap4-
Disperse dyeing recipe
- Disperse dye : x(%owf)- pH control agents : pH 4.5-5.5 with acetic acid(0.4g/l)- Dispersing agent : 0.5g/l
30˚C
20 C/min
130˚C,60 min3˚C/min
40˚C
Dye, PET,Dispersing agent, pH control agent
A general thumb rule hasthe starting temperatureabout 70-80C.
cf. Anthraquinone dyes is partially and reversibly reduced to a soluble sodium leuco form which can be washed away
Azo dyes
Solubilized leuco form
Anthraquinone dyes
O
O
R8
R5 R4
R1 O-
O-
R8
R5 R4
R1
Reduction Clearing
Oxidation
Na+
Na+
R2
R3
R2
R3
87
Disperse dyeing process
Chap4-
Phase of exhaust dyeing of polyester
88
Disperse dyeing process
The heating or adsorption phase is the most critical in determining the levelness of the dyed fiber
Molecular diffusion into the fiber, is the rate-determining step
The dyed polyester iscleared of surface-deposited dye by means of treatment with reductive treatments
Chap4-
Round type Tube type
- Batchwise process: . dyeings in small batches
(immersing the goods in one vessel)
- Liquor ratio (liquor-to-goods ratio):. i.e. 50:1 = 50Kg dyebath : 1 Kg textile. higher the liquor ratio, the higher is the
substantivity required to produce a good color yield89
Batch dyeing machines
Chap4-
- Liquor ratio (liquor-to-goods ratio):. i.e. 50:1 = 50Kg dyebath : 1 Kg textile. higher the liquor ratio, the higher is the substantivity required to produce a
good color yield
- Batchwise process: . dyeings in small batches (immersing the goods in one vessel)
90
Reactive dyeing process
Chap4-
Disperse Dyes
Mono Azo DyesAnthraquinoid
DerivativesHeterocyclic Compounds
The largest majority (50%) of disperse dyes are mono azo dyes of relatively low molecular weights. They contain no ionic Solubilizing groups in dye bath conditions. They may be quite strongly polar.
A significant proportion(20%)of the remainingdisperse dyes areAnthraquinoid derivatives ,but they are beinggradually replaced(except for some brightpinks and blues) becauseof cost and environmentalproblems in manufacture.
Newer disperse dyes are increasingly based on the use of heterocyclic compounds.
91
Chemical structures of disperse dyes
Chap4-
Some of the remaining dyes are unique chemical entities and among the variety of structural type found suitable for disperse dyes are :
Benzodifuranones Coumarins Methines
Naphthalimides Nitrodiphenylamines Quinophthlones
92
Chemical structures of disperse dyes
O
O
O
O
RR
X
X
N
O
O
R1
R2
R3
Chap4-
Diazo Component
Coupling Component
93
N=N
R3
R1 NR7
R2 R4
R5
R6
Monoazo dyes
Chap4-
Dye R1 R2 R3 R4 R5 R6 R7
Yellow H H H H H H H
Orange 3 NO2 H H H H H H
Orange30 NO2 Cl Cl H H C2H4CN C2H4OAc
Red 1 NO2 H H H H C2H5 C2H4OH
Red 13 NO2 Cl H H H C2H5 C2H4OH
Red 195 NO2 SO2CH3 H H CH3 C2H4OAc C2H4OAc
Yellow 3 AcNH H H CH3 OH ---- ------
- It does not extend to bright blues, greens orblacks.
- The brighter and greener shades of yelloware well covered by the heterocyclic azo andother possible chromophores.
- The hydroxy group imparts better light fastness to dyeing on acetate and polyester than corresponding amino group.
- The same hydroxygroup has the reverse effect on nylon dyeings.
94
Monoazo dyes
Chap4-
- The substituent (R) in the secondary amino group can be: -CH3,-C2H4OH, a benzene ring(Ar), or a benzene ring which isitself substituted with a methoxy (-OCH3 ) group or hydroxyethyl group –C2H4OH at the para position.
95
Anthraquinonoid dyes
- The hue is almost totallycontrolled by substituents R1,R4,R5 and R8 and these substituentsare usually hydroxy, amino andsecondary amino groups –NHR.
Chap4-
- While yellow and orange products based on anthraquinone can besynthesized they have not proved to be competitive with yellow andorange disperse dyes based on other chromophores.
- As a result most surviving AQ disperse dyes are bright reds,through violets to blues.
96
- Substituents R2 and R3 positionshave less effect on the hue of theAQ disperse dyes but can haveconsiderable effect on the dyeingand fastness properties of theproduct.
Anthraquinonoid dyes
Chap4-
Dye Name R1 R2 R3 R4 R5 R8
1 Orange OH H H OH H H
2 Red 15 NH2 H H OH H H
3 Red 9 NHCH3 H H H H H
4 Red 60 NH2 OAr H OH H H
5 Violet 1 NH2 H H NH2 H H
6 Blue 1 NH2 H H NH2 NH2 NH2
7 Blue 14 NHCH3 H H NHCH3 H H
O
O
R8
R5 R4
R1
R2
R3
97
Anthraquinonoid dyes
Chap4-
- The aminoazobenzene derivatives do not extend into the area ofgreenish yellows. Although they are often economical and showhigh extinction coefficients, they are not noted for theirbrightness.
- The derivatives of Anthraquinone suitable for bright greenishyellows can be synthesized, but there are other more costeffective alternatives because AQ dyes generally have muchlower extinction coefficients than azo dyes.
Benzodifuranes :- Derivatives of a recently introduced
heterocyclic Chromophore boast abright red disperse dye of very highextinction coefficient.
- Hues range from yellow to blue. Benzodifuranones
Disperse yellow 82. - Some derivatives are used as a fluorescent
brighteners.
Methines:- Although mainly featured in brilliant yellows,
C.I Disperse Yellows 49,82,92 the groupincludes the brightest blue disperse dyecurrently available.
Naphthalimides:- This group includes some brilliant, fluorescent
compounds example C.I Disperse Yellow 11.
Methines
Naphthalimides
99
N
O
O
R1
R2
R3
Other dye chromophores
Chap4-
Nitrodiphenylamines
Quinophthalones
Nitrodiphenylamines:- Chemically simple, economical yellows of
high light fastness on polyester but of lowextinction coefficient.
- They have poor light fastness on nylon.
Quinophthalones:- The unsubstituted parent compound C.I
Disperse Yellow 54 is a low energy dyesuitable for many general applications alongwith C.I Disperse Red 60 and C.I disperseBlue 56.
- C.I Disperse Yellow 64 and 67 have higherenergy and have better resistance tosublimation.
100
Other dye chromophores
Chap4-
The heterocyclic diazo components and coupling components which have been used to improve the brightness and color range of mono azo disperse dyes.
Azothiophenes
Azobenzothiazoles
Azothiophenes : - These range from C.I. Disperse Blue 284
to the only available Disperse Green, C.I Disperse green 9.
Azobenzohiazoles :- Noteworthy for scarlets through bordeaux
reds - C.I Disperse Reds 153,177,263.
Azopyridones: - Often used for bright yellows- C.I. Disperse Yellow 119 Azopyridones
101
Other dye chromophores
S
NN=N N
R3
R4
R1
R2
Chap4-
Azo Disperse Dyes
Diazo Component Coupling Component
- The coupling component conventionally drawn at the right hand side, contains groups which tend to donate electrons such as the substituted amino groups,-N(R6 )R7.
102
Other dye chromophores
N=N
R3
R1 NR7
R5
R4R2R6
- The Diazo component side of the molecule normally contains the groups tending to attract electrons R1 –R3 .
Chap4-
Substitution Effects
E2
E E1
Excited State
Ground State
E1 > E2 ,↓
1 < 2
Excited State
NXN N
R1
R2
+
Ground State
NXN N
..R1
R2
E = hc/
Bathochromic shift : → to longer wavelength
103
Color and constitution in dyes
Chap4-
Azo Disperse Dyes
Yellow
Orange
Red
Violet
Blue
Green
Bathochromic Shift(Increase in the wavelength of maximum absorption by the dye, Red shift)
The greater the tendency of groups at the left sideof the azo group to accept electrons and thegroups at the right hand side to donate electronsthe further move the molecule is calledBathochromic shift. (cf. Hypsochromic shift)
104
Color and constitution in dyes
Chap4-
Azo Disperse Dyes
Dye Name R1 R2 R3 R4 R5 R6 R7
1 Yellow H H H H H H H2 Orange 3 NO2 H H H H H H3 Orange30 NO2 Cl Cl H H C2 H4 CN C2 H4 OAc
4 Red 1 NO2 H H H H C2 H5 C2 H4 OH5 Red 13 NO2 Cl H H H C2 H5 C2 H4 OH6 Red 195 NO2 SO2CH3 H H CH3 C2 H4 OAc C2 H4 OAc
- Tertiary amines do not lead to satisfactory dye structures for they arebulky and eliminate the possibility of hydrogen bonding betweenadjacent amino and carbonyl groups( > N-H∙ ∙ ∙ ∙ O=C<).
NHAr> -NHAlk> -NH2.> -OH
- The interaction between the electronaccepting groups of the chromophore itself,the two anthraquinone carbonylgroups >C=O and electron donatingsubstituent groups in the (R1 ,R4 ,R5 ,R8).
- Electron Donating Groups :
106
Color and constitution in dyes
Chap4-
Anthraquinone Disperse Dyes
- The appropriate substituents at the R2 and R3 positions can be used toaugment desired properties of the dye molecule e.g. light fastness.
- Progressive substitutions of the R1 ,R4 ,R5 ,R8 positions with –OH and –NH2 groups carry the color from the orange intermediate (Quinizarin)dye=1 to the blue dye=7 with four donor groups.
- The more powerful the effect of the electrondonor substituents, the more marked is thebathochromic shift (in the direction yellow toblack)
- Substitution in both the benzoid rings ofanthraquinone R1 ,R4 ,R5 ,R8 is more effectivethan substitution in only one.
107
Color and constitution in dyes
Chap4-
Dye Name R1 R2 R3 R4 R5 R8
1 Orange OH H H OH H H
2 Red 15 NH2 H H OH H H
3 Red 9 NHCH3 H H H H H
4 Red 60 NH2 OAr H OH H H
5 Violet 1 NH2 H H NH2 H H
6 Blue 1 NH2 H H NH2 NH2 NH2
7 Blue 14 NHCH3 H H NHCH3 H H
108
Color and constitution in dyes
Chap4-
- The chemical group frequently found in disperse dyes is anester group, often an acetyl group, -O-CO-CH3 and like theacetyl groups in cellulose acetate it is susceptible tohydrolysis in neutral and alkaline conditions:
- The products are acetic acid and a different azo disperse dye whose color may be quite different from that of the parent dye.
- Usually the wavelength of maximum light absorption is shifted to a longer wavelength (Bathochromic shift)
- The pH has no fundamental role in the dyeing mechanism as such and some disperse dyes without ester groups do not need a weakly acidic dye bath.
109
Hydrolysis of dye ester
Chap4-
- These compounds often benzotriazoles work much likesunscreen, screening out and dissipating UV radiationto prevent sunburn.
110
Fastness properties on polyester
- Wet fastness tests are frequently conducted after the goods have beenreduction cleared and heatset at 180c for 30 seconds.
- They are assessed in terms of the staining on multifiber or adjacent nylonpiece goods. Rating of 4+ out of 5 are readily achieved on regular denierfibers.
- Fastness to crocking or rubbing as well as dry cleaning suffers if dyemigrates to the fiber surface or surface layer.
- If extremely high light fastness is needed (automotive fabrics) a nonionicUV inhibitor may be added to the dye bath and applied to the fiber alongwith the dye.
Chap4-
Drawing :
→ Increase in orientation and crystallinity
→ close packing→ dyeability ↓
111
Physical factors of polyester fiber
Chap4-
Drawing : refractive index vs dye adsorption
Refractive index Refractive index
15m
in d
ye a
dsor
ptio
n
equi
libriu
m d
ye a
dsor
ptio
n
112
Physical factors of polyester fiber
Chap4-
Drawing vs diffusion coefficient
Draw ratio
Diff
usio
n co
effic
ient
113
Physical factors of polyester fiber
Chap4-
- Fabric set at 120oC showed 53% exhaustion- fell to minimum values of about 34% exhaustion at heat setting
temperatures between 150-190oC- rising rapidly to 75% at 230oC.
Heat setting
114
Physical factors of polyester fiber
Chap4-
- The temperature at which the moveable segments of thepolymer chains become quite suddenly susceptible todeformation and displacement
- The polymer properties change from glassy to rubbery and inthe increasing thermal agitation of the polymer segments.
- Polyester fibers are intrinsically slow dyeing at the boil. Below70-80˚C they are for all practical purposes undyeable.
- The temperature 70-80˚C which polyester dyeing begins tooccur more rapidly has been called the dyeing transitiontemperatures.
115
Glass transition temperature, Tg
Chap4-
The inclusion of alternative co-monomers into regular polyester as like as follows:
5-sulphoisopthalic acid 1,4 butane diol
- The possibility of making the fiber dyeable with cationic dyes, hasthe effect of lowering both the melting point of the fiber and also itsglass transition temperature.
- The effect can be attributed to the new monomer disrupting themolecular orderliness of the structure making it easier to leave theglassy state.
- A useful preliminary relationship between the percentages of dye on weight of goods (C) needed to achieve a particular depth of shade on polyester fibers of two different fineness (D, denier) is given below:
- The microfiber will dye approximately three times as first which could lead to the need for procedural changes in dyeing to counter possible unevenness due to inadequate circulation.
- If the same apparent depth is dyed on both fibers the wet fastness after heat setting of the shade on the microfiber will be significantly reduced. This is because of both the increased surface area and the greater percentage dye on the fiber.
CC
DD
2
1
1
2
118
Fiber finess
Chap4-
Disperse Dyes
Powders Grains Pastes
Solid formsconstitute two thirdsof the total dye solid.
Dusting can be controlled by incorporation of small amounts of oil.
Grains are free from dust
Pouring characteristics are very easy.
One third of disperse dye sold on paste form.
With stored pastes it is important to prevent sedimentation.
119
Commercial products
Chap4-
Reactive Dyes and Their Application
120
Chap4-121
Viscose rayonViscose rayon (DP=200~280)High Tenacity Viscose rayon : Fortisan, Cordura,
It is Convenient to write as a simple representation of cellulose: Cell-OH. In the presence of even dilute alkalis, cellulose behaves a very weak acid and will ionize according to the normal basic dissociation equation:
Cell-OH + OH- Cell-O- + H2O
KB = Cell-OH X OH- f / Cell-O-
-------------(a)
-------------(b)
KB known as the basic dissociation constant of cellulose. where, [Cell-O- ] : the conc. Of cellulosate anion
[OH-]f : hydroxide ion within cellulosic fibers
122
Reactive groups in cellulose
Chap4-
In 1956 ICI introduced the first dyes for cellulosic's which would actually reactwith the fiber molecules, to form covalent dye-fiber bonds.
Dichlorotriazine dyes
123
Reactive dyes
Chap4-
Physical sorption : This relies on the same forces which attracted the dyes to thefiber initially being strong enough to hold onto the dyes through subsequent wettreatments example with direct dyeings on cellulosic fibers.
Mechanical retention : This relies on the formation of insoluble pigmentarymaterials out of the soluble chemicals which first diffused into the fibers with vat andsulfur dyeings, those of azoic combinations, and also dyeings for mordant andingrain dyes.
Fiber Reaction: The dye molecules or ions do not lose all their Solubilizing groupsafter diffusion into the fibers but in the correct conditions they react and attachthemselves by covalent chemical bonds to form new colored derivatives of the fibers.The small number of dye Solubilizing group is totally inadequate to cause the largenew dye fiber molecules dissolve in water.
Three ways in which dyes can be retained by fibers
124
General nature of reactive dyes
Chap4-
For the chemist the different types of bonds involved in dyeing processes-
Covalent Bonds:
- The carbon hydrogen bonds of most organic chemicals (C-H).
- Both atoms donate an electron to the bond and the resulting pair of electrons is shared between them. Bonds between reactive dyes and cellulose are of this type.
125
OOH
OH
HOHO
OS
OO
Dye
General nature of reactive dyes
Chap4-
- This tendency does not normally lead to ion formation. It is called Polarization.
- Carbon atoms adjacent to nitrogen in the aromatic heterocyclic rings which make up many reactive groups. Such negatively charged species are called nucleophile.
- Hydroxide and cellulosate ions are nucleophilic reagents.
δ+
δ-
Polarization and reactivity :
- Some of atoms share of the available electrons
- e.g.Nitrogen,oxygen,fluorine,chlorine and sulfur whereby they themselves tend to electronegative character and their carbon neighbors an electropositive character.
126
Nucleophile and nucleophilic agents
Chap4-
- Cellulosic fibers contain considerable numbers of hydroxyl groups (OH)- Reactive dyes are those whose ions or molecules contain groups which
are reactive with other groups present in fibers to form covalent dye-fiber bonds.
127
Dye-fiber reaction
Chap4-
- Wool contains thiols, amino and hydroxy groups –SH, -NH2 , and –OH respectively, listed in decreasing order of reactivity
- Reactive dyes has a full range of bright shades across the spectrum.
- It shows excellent wet fastness with minimal color loss and excellent ratings for the staining of adjacent white goods, with moderate to good light fastness.
- They have moderate tending to poor fastness to chlorine.
- Dyes and chemical costs are comparatively cheap.
- The utilization of color used to be relatively poor and the waste color going to drain can be easily 30 to 40% but this deficiency is undergoing serious recent improvements to perhaps 10%.
- The salt content of the effluent has also been very high but is rapidly falling with the use of low liquor ratios in dyeing.
129
Properties of reactive dyes
Chap4-
- The end of 1961, BASF,Bayer, Ciba and Giegy,Hoechst, Sandoz andSumitmo had joined ICIin the market place withno less than 12different ranges ofreactive dyes betweenthem.
10%
- In 1988 the AATCC Buyers Guide lists almost 200 different reactivedyes by color index name, representing more than 400 differentcommercial products.
130
Importance of reactive dyes
Chap4-
NN
CuO O
OHH
O3SNa HNSO3Na N
NN
Cl
Cl
NaO3S
Solubilizing agentChromophore
BridgeReactive group
Leaving group
- The differences in reactivity results for the most part from theincorporation of chemically different reactive groups in the dye molecules.
131
Reactive dye sub-groups
Chap4-
ChromophoreBridgeReactive groupLeaving group
High reactive groups required lowtemperature and less amount ofsalt and alkali.
Chromophore
Reactive group
132
Reactive dye sub-groups
Chap4-
The features of Reactive dyes are-
S C B R-X
S= Solubilizing groupsC= chromogenB= Bridging groupsR= Reactive groupsX= leaving groups
