Presentation Topic:Briefly discussion about Azoic Dye

MD.DIN ISLAM KHAN BTX 130100265NOMAN SIDDIQUE FAYSAL BTX 130100258MD.JULHAS AKTER BTX 130100256MD.MOTIUR RAHMAN TAGAR BTX 130100285

Submitted To:MD.TANJIM HOSSAIN

Azoic Dyes are also called as Azoic or Napthol Dyes. These AZO Dyes consist a group i.e. called AZO group having two nitrogen atoms and this group (covalent bond) connects atomic ring compounds. The two Nitrogen atoms are bonded with each other and form -N=N- as part of their molecular structure. Azoic Dyes are found mainly in three colors and these are red, brown and yellow.

Built in DyeMagic ColorDeveloped Color Ice color Napthol Dye

The coupling component is finally soluble in diazotization reaction. Diazotization is a chemical reaction where the base (Aromatic Amine) is to be converted to a solubilized form by the chemical reaction with NaNO2 at ice temperature (0 – 5˚C).

That’s why this dye is called Ice color.

Two steps are required by dyeing with azoic color. In the first step textile goods are dyed by Napthol color. In the 2nd bath, Base or Salt is used for dyeing. After 2 – 3 minutes dyeing in 2nd bath, the azoic color is seen in the textile goods magically. For this reason this dye is called Magic color

Azoic coupling components are insoluble in water. To make them soluble in water the textile materials are impregnated in a solution of Napthol and NaOH. As the first coupling component is Napthol color.

Azoic dyes contain Azo group and final color is insoluble in water, so it is called Aoic Pigment.

Base + Napthol → Azoic dyes

Soluble Soluble Insoluble

Azo chromophores were first discovered in 1863 when Martius and Lightfoot coupled diazonium ions and amines. Within the year, Peter Greiss prepared Bismarck brown, the first azo dye. By the 1880s numerous other azo dyes, such as para red and primuline red, were developed.

Since that time, most modern dyestuffs have been derived from diazotized aromatic amines, and hence are sometimes known as diazo dyes. The simplest azo dyes are yellow, but changing the number of chromophores or the backbone structure can produce red, violet, blue and even black dyes. Azo dyes are used as textile colorants, and well as in industrial paints, printing inks, varnishes, plastics, crayons and other products.

Naphthols and Bases: Naphthol is also known as azoic coupling

component. These are acylides are of BON (beta-oxy naphthoic acid). Various types of naphthols can be Naphthol AS, Naphthol ASBS, Naphthol ASBR etc.

Base is also known as the Diazotised base. This acts as a coupling reactant along with the naphthol.

These are nomenclatured on the basis of color e.g. Fast Red Base.

The purpose of diazotisation is to improve solubility.

These dyes cannot be applied directly on the fibers as dyes. Actually, these dyes are produced within the fibers itself. For this production, first the fiber is impregnated with one component of these dyes and then the fiber is treated in another component of these dyes. In this way the AZO dyes are formed. This specialty makes these dyes very fast to washing within the fabric market. 

When these dyes are used upon the cellulose fabric then initially this fabric starts to suffer from poor rub fastness. This is due to the deposition of the free pigments on the surface of the fabric. This problem can be rectified by boiling the fabric in soap.

AZO Dyeing Process is such a process in which the insoluble azoic dye is produced on the or within the fiber. By treating a fiber with diazoic and coupling components, this process can be achieved. After adjusting the dye bath conditions appropriately, the two above mentioned components react. From this reaction the required insoluble AZO dye is produced.

First Stage:NaptholationSecond Stage:DiazotationThird Stage:Coupling

When the naptholated cotton is removed from from the naptholated both and squeezed,some solution also accompanies the cotton and when this is entered in to solution of the diazotised base,the napthol taken upby the cotton reacts with the diazotised base and forms the coloured pigment,which is firmly held in the fibre.

Therefore,after dyeing the material is treated with a boiling soap solution when most of the loosely held is pigment is removed from the surface and held in suspension in the soap solution.

The diazotised base solution is not stable.If it is kept even at room temparature for some time it gets decomposed and then it does not react with napthol.Secondly,during diazotization suffocating fumes are liberated.

Diazo components Shadeo-Nitroaniline Orange2-5-Dicholoroanline Scarletp-Nitrianline Red2,5-Methoxy-4-nitroanline Bluish RedDianisidine Reddish Blue

Light fastness: Excellent light fastness which may be very stable electron arrangment in Azoic dyes,light fastness rating is about 6-7.

Wash Fastness:Very good wash fastness to Textile materials fact that Azoic dyes are insoluble.The wash-fastness rating of Azoic dyes is about 4-5.

Bright Colours: Very bright red and orange colors

Rub Fastness: Poor rub fastness,this occurs because of the formation of the insoluble azoic dye on the surface of the fibre which is not removed during the final stage of dyeng\printing.Rinsing stage is referred to as soaping-off.

A. hazardous AZO-dyesB. non-hazardous or safe AZO-dyes

These dyes use AZO-groups as coloring agent,

upon cleavage these chemical groups release amines, which are harmful,

they are used mostly for cotton dyeing, cheapest alternative to “reactive dyes”

( best industrial dye ), good color fastness, dyeing process short

and easy, pollute waste-water with heavy metals, many AZO-dyes are subject to ISO 14000

legislation

Availability:...of product:

1. not easy to purchase2. not widely distributed3. they are sold by weight and price is higher then hazardous azo dyes

...of information:1. information available in English, using international standards

Naphthol, beta naphthol pigment, para red, Lithol red, arylide, diarylide, nickel-azo, disazo pigment, and benzimidazolone.

Advantages of azoic dyes: Available in bright shades mostly deep red,

yellow and orange. Brilliant shape of colour Vary from poor to excellent fastness to to

light. Fastness to washing, perspiration good to

excellent.

Disadvantages of azoic dyes: Heavy shades have poor fastness to crocking. High costly. Limitations of hue selection.

Recipe: NAPTHOLATION: Napthol=3% NaOH=5 g/L Sequestering agent=1 g/L Wetting agent=1 g/L Temp=40 Time=20 minutes pH=10.5-11.5

Diazotization: Base Color=3% NaNO2=2 g/L HCl=2 g/L CH3COOH=2 g/L Sequestering agent=1 g/L Wetting agent=1 g/L Temp.=0-5 degree Time=10 minutes

Printing process:The naphtholated fabric is prepared then it is printed with base printing paste by block and screen printing method.

After treatment :After printing the printed fabric is dried at 100‐105 for 5‐10 minute in a dryer.

If the naphtholation process is not so sufficient. Then the printing becomes uneven.

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