Presented by : GOVIND CHINTARAMBISSOONAUTH RISHTA
To analyse the effect of reactive dyes on Wool To observe the dye left in the bath at the end of dyeing. To observe the amount of dye coming out during after treatment
Wool can be dyed with non mets dyes , mordantdyes, pre met dyes, acid dyes and reactive dyes,our practical has been based on the reactive dyes. wool is positively charge while the dye are negatively charge and dye absorption takes place in in the positive sites of the fiber. wool dyeing is done under an acidic condition.
Reaction to alkalis: Wool is quickly damaged by strong alkalis. Reaction to acids: 1. Wool is damaged by hot sulphuric acid. 2. The fibre is not affected by other acids. Affinity for dyes: Wool fibre has high affinity for certain types of dyes, i.e. Acid, reactive dyes, Basic dye
Reactive Dyes„ Form a covalent bond between the dye and fiber „ Simplify dyeing procedure ‰No oxidation is used „ Introduced to the market by ICI in 1956 „ Show improved fastness properties ‰Great improvement for cellulosic fibers
Dyeing occurs in two stages: Exhaustion and Fixationexhaustion occurs by normal physical forces of attraction between dye and fibre.Fixing involves the formation of the covalent bond between the dye and the fibre. The dye is covalently bound to the fibre High Fixation;fibre tippiness -All anionic dyes on wool exhibit uneven strike which can result in tippiness With reactive dyes, if covalent attachment at tips occurs before boiling.
A sample of wool fiber was used Wool was scoured Mass of sample : 3g Reactive dye : Lanasol 2% O.M.F Glauber Salt: 0.5% Acetic Acid: 2.0% Ammonium Sulphate
Liquor Ratio = 50:1Vol of dye = 2 *3 = 6 ml Vol of Ammonium Sulphate = 6ml Vol of Glauber salt =3ml Acetic Acid = 6 ml Vol of Bath = 50 *3 = 150 ml Water = 150 – 6- 6- 3 – 6 = 129 ml
Continue dyeing for 60mins Drop the bath 60’ 100oC A: 20’ 1. Ammonium sulphate, 10’ 2. Acetic acid, 3. Glauber’s Salt, 4. Under pH 4.5-5.0.A B B: Dye After Treatment Washing off: 1. Hot rinse 70-80 oC for 5-10 mins 2. Treat with Ammonia Solution(pH 9-10) at 80oC for 20mins 3. Hot Rinse at 70oC for 5mins 4. Rinse under tap.
An alkaline treatment is important in achieving excellent wet fastness properties with reactive dyes on wool.Wool was treated with Ammonia Solution( pH 9 – 10) at 80oC for 20 minutesThen hot rinse was done at 70 oC for 5 minutes. To be effective the after treatment has to remove most of the dye that is not covalently bonded to the substrate.
The amount of dye left in the bath at the end of the dyeing: It was observed with naked eyes that comparing to the initial concentrated solution before dyeing , the amount to dye left in the beaker after dyeing is very m few. We can derived approximately that 4% of dyes has been left in the solution and 96% has been exhausted by the fiber. Solution before dyeing Dye left after dyeing
As wool is positively charged and reactive dyes are anionic, so there is a strong linkage which occur between the positive fiber and negative dye and the substantively is very high which facilities the exhaustion of the bath. The molecule of the fiber is covalently bond to that of the dye, and this bond cannot be break down, so once the dyes is migrated into the fiber under acidic conditions, the maximum dyes is being taken up by the fiber retains inside and the hydrolysed dyes remains into the bath itself, which are the 4% estimated remaining dyes in the bath. While dyeing, the pH is kept under acidic conditions which is (pH 4.5-5) and the dyes reacts more with the fiber and More dyes go into the fiber.
The amount of dye coming out during washing off: It was observed that during the after treatment, a little dye was coming out from the wool fiber, approximately 1% when observed with naked eyes. This proves that the dyeing was done properly as a good wash fastness was observed. Also , it can be noted that the tip of the fibers have been uniformly dyed. This means that the problem of tippiness has not taken place.
The dye left in the beaker during after treatment are the few hydrolised dyes which has more affinity for the solution rather than the fiber. As ammonium sulphate is used, it is a swelling agent,so it swells the fiber and all dead dyes get out which are the remaining dyes in the beaker after treatment.