Yaa Cationization Of Cotton Wool Past Times Using Chitosan For Reactive Dyeing To Avoid Electrolyte (Part-2)

Cationization of Cotton yesteryear Using Chitosan for Reactive Dyeing to Avoid Electrolyte (Part-2)

Md. Obydullah
Md. Shibli Sadique
Dhaka University of Engineering & Technology,
DUET, Gazipur-1700, People's Republic of Bangladesh

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2.4 Classification of Reactive Dyes:

Reactive dyes may move classified inward diverse ways every bit below:

a) On the solid position down of reactive group:
i) Halogen (commonly chlorine) derivatives of nitrogen containing heterocycle, similar 3 types-

* Triazine group. e.g. Triazine derivatives: procion, cibacron.

* Pyridimine grouping e.g. Pyridimine derivatives: reactone

* Quinoxaline dyes. e.g. Quinoxaline derivatives: levafix E.

ii) Activated vinyl compound:
* Vinyl sulphone e.g. Vinyl sulphone: remazol

Vinyl sulphone dyestuffs possess misfortunate affinity for cellulosic fibers inward absence of common salt together with alkalis. For this reasons, they are suitable for utilization on pad. Their substantivity tin move increased yesteryear add-on of glauber common salt or mutual common salt together with alkali, making the dyestuff suitable on all conventional dyeing machines for unloose material, yarn inward hanks together with packages together with slice goods. The dyeing methods may therefore, move classified nether the padding together with exhaust processes, standing baths are non recommended, every bit inward alkali metal medium inactivation of the dyestuffs yesteryear reaction amongst H2O takes house every bit a side reaction.

These dyes require higher dosage of alkali together with common salt for exhaustion together with fixation. But these dyes cause got on continuous contact amongst the alkali together with H2O medium for longer duration fourth dimension dyeing process, nearly xxx to 40% volition teach hydrolyzed together with move inward active every bit dyestuff. But inward gild to build active together with make on the fiber nosotros quest to laissez passer on higher dose of alkali together with common salt along amongst temperature of upwards to 60°C.

* Vinyl acrylamide e.g. Vinyl acrylamide: primazine

*Vinyl sulphonamide e.g. Vinyl sulphonamide: levafix

b) On the solid position down of reactivity:
i) Lower reactive dye: Medium reactive dye: hither pH is maintained 11-12 yesteryear using Na2CO3 inward dye bath.
ii) Higher reactive dye: hither pH is maintained 10-11 yesteryear using NaHCO3 inward dye bath.

c) On the solid position down of dyeing temperature

i) Cold brand:
These types of dyes comprise reactive grouping of high reactivity. So dyeing tin move done inward lower temperature i.e. 320-600C. e.g. PROCION M, LIVAFIX E.

ii) Medium brand:
This type of dyes contains reactive groups of moderate reactivity. So dyeing is done inward higher temperature than that of mutual coldness build dyes i.e. inward betwixt 600-710C temperatures e.g. Remazol, Livafix are medium build dyes.

iii) Hot brand:
This type of dye contains reactive groups of to the lowest degree reactivity. So high temperature is required for dyeing i.e. 720-930 C temperature is required for dyeing. e.g. PRICION H, CIBACRON are hot build dyes.

d) On the solid position down of functional grouping nowadays

i) Mono functional reactive dyes.
ii) Bi functional reactive dyes.

The dyes were kickoff introduced yesteryear Hoechst, based on ß-sulphato ethyl sulphone every bit a reactive group. The attain made the successful breakthrough due to comprehensive shade range, versatile application, mightiness to move dyed at 60°C together with skilful compatibility amongst other bifunctional dyes. Being a compact structure, it offers stay inward launder off for removal of unfixed dyes at the cease of dyeing during washing. The dye fibre bond offers skilful acid stability. With the limitations to above, at that topographic point may move problems amongst reproducibility associated amongst it, which is non accepted peculiarly for pale shades. There is the possibility of unlevel dyeing amongst a minor variation inward the procedure due to its lower molecular weight. Hetero bifunctional dyes made a teach through inward early on 80's. The dyes were based on a quite uncomplicated but beautiful chemistry. They had filled a large vacuum of diverse hues of brilliant shades, which were non possible amongst vinyl sulphone type. The dyes were conventional dichlorotriazine type, amongst the cease condensation of ß-sulphato ethyl sulphone to cause got dissimilar type of reactive grouping inward a unmarried molecule. Being a dual reactive, the primary trend of fixation is from vinyl sulphone grouping together with the dyeing temperature is same every bit vinyl-sulphone, which enables skilful intercompatibility inward betwixt the 2 classes.

Bifunctional reactive dyes: CI Reactive Black five - (3) Remazol Black B, Dystar.

(4) MCT-VS type. (5) Sumifix Supra dyes (Sumito)

iii) Poly functional or multifunctional reactive dyes.

2.5 Reactive Dyes for Cellulosic Fibers:
Cellulosic fibers are significantly dominated yesteryear cotton. Other cellulose based fibers include viscose rayon, linen, cupraammonium rayon, jute together with lyocell, together with these tin move dyed amongst dyes used on cotton. The construction of cellulosic fibers is characterized yesteryear the poly-(1, 4)-β-D-glucopyranose molecule (fig 3.2), together with consequently may move considered every bit a polyhydric alcohol. Each glucopyranose band on the cellulose chain contains 3 hydroxyl groups, a primary hydroxyl grouping inward the six seat together with secondary hydroxyl groups inward the 2 together with 3 positions.

Figure: 2.2 Poly-(1, 4)-β-D-glucopyranose Molecule

A polyhydric alcohol such every bit cellulose is to a greater extent than acidic than a uncomplicated alcohol and, inward fact is comparable amongst H2O every bit shown yesteryear the dissociation constants (K) listed below.

Water K= 2.09x10-14
Methanol K= 8.1x10-15
Manitol K= 7.5x10-14
Cellulose K= 1.84x10-14

The dissociation constant for cellulose refers to the ionization of the hydroxyl grouping inward the six seat of the glucopyranose ring. The hydroxyl groups inward positions 2 together with 3 of the band are less acidic. Therefore, cellulose is ionized nether alkali metal atmospheric condition together with tin deport every bit a nucleophile towards compounds containing electron-deficient carbon atoms (e.g. reactive dyes).

A diversity of attempts cause got been made to select nearly the formation of a covalent bond betwixt a dye together with a fiber. In this respect, at that topographic point are 2 full general approaches: producing a dye inside the fiber, together with producing a dye that is reactive towards the fiber. H5N1 covalent dye cellulose combination was achieved inward 1895 yesteryear Cross together with Bevan. These workers showed that cellulose (Cell-OH) treated amongst potent alkali was changed into “soda cellulose” which could move treated amongst benzoyl chloride to cast benzoyl cellulose. The resultant benzoyl cellulose was nitrated, the nitro grouping was reduced, together with the amino grouping was diazotized. The diazo grouping was coupled amongst N, N-dimethylaniline to laissez passer on “dyed” fibers.

Figure: 2.3 Preparation of Red Cellulose

The kickoff commercial reactive dyes for cellulose were developed yesteryear Rattee together with Stephen together with marketed yesteryear ICI inward 1956 nether the merchandise cite Procion M. These dyes were introduced for the production of fast brilliant shades on cellulosic fibers using continuous dyeing methods. Procion Brilliant Red M-2B inward (Fig. 3.4) is ane of the early on members of this family. Procion one thousand dyes contained the highly reactive dichlorotriazine group, together with reacted amongst cellulose nether alkali metal atmospheric condition at room temperature.

Figure: 2.4 Procion Brilliant Red M-2B

The major element contributing to the long delay inward producing the kickoff reactive dye for cellulose was the belief that cellulose was a relatively inert substrate together with that atmospheric condition required to number a chemic reaction would movement serious fiber degradation. Therefore, inward early on studies dyestuff chemists were led astray inward thinking that they needed to convert cellulose to the to a greater extent than reactive soda cellulose to build fiber reactivity possible. No ane expected that whatever reactive grouping would prefer to react amongst a hydroxyl grouping of cellulose when cotton fiber was placed inward an aqueous dyebath containing numerous competitive hydroxyl groups from water. However, a large number of reactive dyes amongst varieties of reactive groups cause got been developed.

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