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reactive dyes in dyeing

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classification of reactive dyes

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reactive dyes in dyeing

  1. 1. Dyeing Dyeing operation is performed by the reaction between fiber and dyes. Some dyes are water solubleand some are water insoluble. Some fiber has affinity to dye somehave no affinity to dyes. So dyeing depends on both fiber and dyes chemical properties. Reactive dyes are the most common and huge uses dyes all over the world. Most of the dyeing operation of naturalfiber is done by reactive dyes. Reactive Dye In a reactive dye a chromophorecontains a substituentthat reacts with the substrate. Reactive dyes have good fastness properties owing to the bonding that occurs during dyeing. Reactive dyes are mostcommonly used in dyeing of cellulose like cotton or flax, but also wool is dyeable with reactive dyes. Reactive dyeing is the most importantmethod for the coloration of cellulosic fibres. Reactive dyes can also be applied on wool and nylon in the latter case they are applied under weakly acidic conditions. Reactive dyes have a low utilization degree compared to other types of dyestuff, sincethe functional group also bonds to water, creating hydrolysis.
  2. 2. Reactive dye is only class of dyes which makes covalent bond with the fiber and becomes a part of it. This can be described as: Reactive dyes +Fiber = Reactive dye-Fiber If the general structureof a reactive dye is “R-B-X” then, R-B-X + Fiber = R-B-X-Fiber (Dyed fiber) where, R = ChromophoreGroup (Azo, Anthaquinone, Phthalocyanine, Metal complex group) B = Bridging Group ( Imino, Ethyl & Methyl, Oxide, Sulphide group) X = Reactive Group (-Cl, -Br, -SH, -OCH, etc) Chemical structure of reactive dyes Characteristics of reactive dyes
  3. 3. Belowstructures are the examples of reactive dyes ß-Sulphato ethyl Sulphone Type Dye-SO2 –CH2-CH2-OSO3H The electron attracting sulphonegroup causes electron deficiency on the terminal carbon atom enabling nucleophilic attack to take place. . (Addition reaction) Dye-SO2-CH=CH2 +O-R1  H (+) Dye-SO2-CH2- CH2-OR1 Where [O-R1]- is [Cellulose O -] or [OH -] of water, etc. Remazols are reactive dyes based on Vinyl Sulphonesystem
  4. 4. Classification of Reactive Dyes: 1) By depending on chemical constitution reactive dyes can be classified as:  ChlorotriazineDyes (MCT)  Vinyl SulphoneDyes (VS)  Heterocyclic Helogen Containing Dyes (HHC)  Mixed Dyes (MCT-VS) 2) By depending on application methods of temperature, reactive dyes can be classified as: I.Cold brand reactive dyes: This type of reactive dyes is applied in very low temperature. Temperature lies between 25 -50 degree Celsius. They are highly reactive with fiber on this temperature. II.Mediumbrand reactive dyes: This type of dyes is applied in a medium temperature rangeis 40 – 60 degree Celsius. Their reactivity is medium with fiber. III.Low brand reactive dyes: This type of dyes has very low reactivity properties with fiber with comparison with medium and high brand reactive dyes. Dyeing is carried out on 60 -90 degree Celsius. React ivedyeisonlyclassof dyeswhichmakesco- val entbondwi tht hef iber andbecomesapar tof it.Thiscanbedescribedas: React ivedyes+Fiber=Reactivedye-Fiber (Co-valent bonding) I f t hegeneral structureofar eactivedyeis“R-B-X”then,
  5. 5. R- B- X+Fiber=R-B-X- Fiber(Dyedfiber) Her e, R = Chromophor eGroup(Azo, Ant haquinone, Pht halocyanine,Metal compl exgroup) B = BridgingGroup(Imino,Ethyl&Methyl,Oxide,Sulphidegroup) X = ReactiveGroup(-Cl ,-Br,-SH, -OCH, etc) Exam plesof reactivedyes:

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