New technique using light for fixing solubilized vat dyes

Abstract: In this study the researcher tries to work out a new technique using light for fixing solubilized vat dyes, Innovations that have increased recently for creating smart textiles, That interact with surrounding environmental conditions like photochromism , Thermochromism and Chemochromism, However the dyes that are affected by these environmental conditions here are called Anthrasol Blue IBC solubilized vat dyes .


Introduction
Vat dyes are important dyes for dyeing and printing on cotton and cellulosic fibers .They have excellent all round fastness, which includes perspiration and rubbing fastness [4]. The soluble vat dye applied in practical procedure of dyeing on cotton fabric but it difference between insoluble vat dyes and soluble vat dyes that instead of oxygen free bath, it developed by sunlight [13.] Photochromism When discussing the term photochromic, one should first clear out the term "chromic ". chromism is a process that induces changes on the molecular level like cleavage of the chemical bonds or changes on the level of molecular conformations [6]. In most of the cases chromism is based on changes occurring inside of the molecule, among electrons. this especially implies ,, Pi " and ,, d" electron positions so that the phenomenon is induced by various outside stimulus bearing the ability of altering electronic density of the compound or a substance [3] . chromism refers to the phenomenon in which color is the result of abroad spectral interactions among incident light and material [9].These interactions may be categorized into following five groups : o Reversible change in color.
o Absorption and reflection of light.
o Absorption of energy followed by the emission of light .
o Absorption of light and energy transfer or transformation of energy.
o Use manipulation of light [1].

These chromic effects are caused by :
o Per cyclic reactions.
o Intermolecular group transfers.
o Intermolecular hydrogen transfers.
o Dissociation (cleavage of the bonds).
Phenomenon including a change in color of a chemical compound is named according to external stimulus causing the reaction, either physically or chemically. Many but not all of these reactions are reversible [10].

Soluble vat dyes
It's inconvenient to have to reduce your vat dyes in order to dissolve them. However, it is impractical to sell the reduced form of the dye, because it will oxidize in the air, back to the insoluble form [5] .The solution to this problem nowadays is for the manufacturer to convert the soluble leuco acid form of the dye to the leuco ester, such as by reacting the leuco acid with sulfuric acid. The leuco form of this solubilized dye can be regenerated by removing the ester group chemically [13]. On exposure to air this soluble leuco form of the dye gets converted to colored insoluble form of the dye [1]. Unlike the past dyes when the dye was done in the original form and convert the color in the dye bath to its original color with oxidation process, However, The powder form of the solubilized vat dyes are stable to storage, if properly stored away from sunlight and air (moisture, oxygen and carbon dioxide).Their solutions are also stable if properly stored if they come in contact with acidic fumes or oxygen a part of the dye is wasted [7].
In such work, the researcher would get back to using vat dyes before reduction. This piece of work focus on regenerating such process for coloring different cellulosic materials including cotton fabrics. The aim is to provide individual designs facilitates everyday consumer needs.

MATERIALS:
Fabric: the fabric used for the work was finer counts of 100% bleached, mercerized cotton fabric. The fabric structure of used cotton is plain weave. It produced from GIZA Company [8].

Dyeing process
Immerse the cotton fabric (2gm weight of the sample) in the dye bath containing (100 ml water, 5gm sodium carbonate, 5gm soluble vat dye and 5gm nitrite sodium) raise the temperature to 60 -70 •c for 45 min, extract the sample from the dye then immerse it in Azo and P.V.A liquor ratio (1:10) solution to make the dye developed by sunlight and get dark shades, let it in presence of direct sunlight for 20 min. Washing off: Dyed samples were rinsed with zinc formaldehyde sulfoxalate (5g/L) then immerse in sulfuric acid (10%) for 1 min to get dark shades , soaped with a solution containing 5g/l nonionic detergent for 1 Fig (3) shows the color strength (K\S), results which revealed that the higher K\S values for the sample dyed with 5gm salt, was better than higher concentrations of salt . When the concentration of sodium carbonate was 30gm and 50gm the samples failed because after immersed in Azo:P.V.A solution it made like a plastic film coating the fiber.
It is obvious that increasing the salt affects the results which could be due to the alkaline medium of the dye bath, it should not be so high and also it reacts with the polyvinyl alcohol turns into plastic film. Results obtained and shown in Fig (4), shows that samples dyed for 15 and 30 min shows similar results ,but the best results was at 45 min. Best results were obtained while increasing the time, probably such results could be due to the reaction was sufficient with the fiber in 45 min. Accordingly 45 min would be an optimum time for dyeing .  Fig (5) shows the color strength (K\S), the results revealed that were a higher K\S values for the sample dyed with 5gm of nitrite sodium was the best . Increasing the amount of sodium nitrite could affect the process badly this may be due to making the dye molecules less attached with the fiber. Best results were obtained at 5gm dye due to this amount was sufficient to 2gm of the fabric and 100 ml water, for 7gm the dye will be redundant for the liquor ratio for the fabric.    2) the results show such a good performance, the laundering fastness were as good as grade 4 in color change .also the staining on the multi-fiber was between 3.5 and 5 and the self-staining 4.5 . The acidic perspiration shows an excellent performance to staining between 4.5 and 5 with respect to color change that shows a grade 4.5. Also the fastness to water and sea water shows a great performance in color change and staining according to Table (1) grades between 4.5 and 5. According to Table (2) the color change in fastness to light gave a very good grade 4, and for the crocking the dry sample shows a 4.5 grade and the wet sample grade 4 and this such an excellent result due to the vat dyes. The pH value of the solution was extracted from the sample 6.75 and this a convenient result for using the dye in any field.

Conclusion
The performance of Anthrasol Blue IBC (solubilized vat dyes) was successfully achieved , the dye was fixed by sunlight ,on industrial purpose the dyed samples have a very good impact on fastness properties ( laundering ,water ,seawater ,perspiration ,crocking , light and pH value ) and have an artistic view to get light and dark shades , From these results it was clearly that solubilized vat dyes has a good impact on the functional properties of the fabric. Extra work is needed in the same direction to improve vat dyes in order to make them more competitive in such work, we used Anthrasol Blue IBC dye it is important for such dye to back to life, since we used other different dyes for such work and did not success .and manufactures no longer use this dye in its original form, they modified it to suit their production. But we proved that the original form we use in this study has various uses artistic or industrial.