Chemical Formula of Common Chemicals used in Textile Dyeing
After the washing and bleaching processes the next stage is dyeing in the textile industry .in this process the fabric is so cleaned that no contamination or other chemical content remain attach with fabrics as it is so important otherwise the dyeing process will be damaged .In the white cloths hydrogen per oxide or sodium hypo -chlorate use for this purpose to bring the whiteness in the fabrics.
How to prepare the dyeing solution?
For dying the fabrics color and sodium sulfide mix together in the hot water for a short period of time after that lowering the temperature and allow to mixture cool. In the end of this process soda ash and color dye mix in water to make color paste then treated it sodium sulfide solution until it become a clear solution which is used in the dyeing of the cotton fabrics.
Hundreds of chemicals used in the textile dying bleaching and finishing process according to their function and properties .turkey red oil, alum ,soda ash and tannin mordant widely use in the dying process whereas the dyeing in textile based on these agents like
Leveling agents, retarding agents, dispersing agents, carriers ,after treating agents, dye fixing agents, stripping agents, rubbing fasteners improves, detergents, sequestering agents etc
There are surfactants added to the dye bath to ensure penetration of dye liquor into the yarns and fabrics. Sulphated fatty alcohol, sulphated oil and anionic surfactants like sulphonic acidsare used
Dispersing agents are also surfactants used for uniform dye dispersion. These are particularly used in disperse and vat dyes.Sulphated fatty alcohol, alkyl aryl sulphonates, sulphated fatty acid and amide are used.
Sequestering agents are chemicals which complexes heavymetal and do not allow these heavy metal to react with fibre or dyes. EDTA, NTA are common sequestering agents.
Antifoaming agents are used in dye bath to prevent foaming of the bath which affects dyeing adversely. The best antifoaming agentsare silicone polymers such as dimethyl polysiloxane with a viscosityof 100-500 centiposie at 25ºC. Polyamino alkyl substitutedhydrocarbons are based organo poly siloxanes are also used aseffective agents.
Carriers are used in dyeing of synthetics particularly polyesters with disperse dyes. It imbibes deep shades on the polyester and blended fabrics. O phenyl phenol, monochloro o phenyl phenol, p phenyl phenol, diphenyl, mono methyl naphthalene, trichloro benzene, dimethyl pterephthalate, methyl salicylate etc.
Levelling agents are added in dye bath to uniformly due theyarns or fabrics. An ionic surfactants like alkyl aryl sulphonates ,fatty alcohol sulphates fatty amide sulphonates are used. Nonionic surfactants are used for direct dyes, cationic surfactants andnon ionic surfactants are used in vat dyeing process.
Antifoaming agents are the same used for dye bath. They areusually siloxanes. Hygroscopic agents used are glycerine,diethylene glycol etc.
Oxidising and reducing agents
Oxidising and reducing agents are sodium chlorate, chromate,dichromate, nitrate, ferrocyanide hydrosulphite, bisulphite, glucoseand stannous and ferrous salts.
Optical whiteners are classified primarily into two large groups, direct whiteners and disperse whiteners. Direct optical whiteners are water soluble substances used mainly for the whitening of natural fibers, whereas disperse optical whiteners are water insoluble. As with disperse dyes, they are applied either to the coloured material from an aqueous dispersion or they can be used for mass coloration. They are mainly used for synthetic materials such as polyamide, polyester, poly-acrylonitrile, acetate silk and polyvinyl chloride.
Printing is a process to decorate textile fabrics with colors a n d c o l o r m o t if. Tex t I l e printing may b e c o n s i d e r e d a s a s p e c I a l i zed d y e i n g p r o c e s s. It is a controlled application of dyes and pigments to exactly defined locations on the fabric leaving rest of the fabric essentially unaffected. There are three major methods of printing viz. direct printing, resist printing and discharge printing. In the direct printing method a paste of dyes and auxiliary chemicals are directly fixed on the fabric by a pattern block or silk screen. In discharge printing a reducing agent is used to destroy the oxidizing agent at the printed area needed to develop a particular dye (vatdye) or an acid is used to destroy the alkali needed for development and fixing of a dye. In discharge printing stable reducing agents are used to discharge the dye on the fabric. Vat dyes, pigments, basic dyes, are used for discharge printing
There are four main types of animal fats-edible tallow, inedible
tallow, lard and inedible grease. Typically, tallow is the fat of cattle,
and lad and grease are the fats of hogs. These are the primary
sources of stearic and oleic acids.Coconut oil is an important raw material for fatty acid and fatty
ester production, because of its high C8, C10 and C12 fatty acid content\
This is the most common naturally occurring fatty acid, and is
obtained from animal and vegetable oils and fats. Commercial stearic
acid contains about 50% stearic acid, 45% palmitic acid and 5%
This is a mono unsaturated, straight chain C18 fatty acid
(double bond in between C9 and C10). It occurs in almost all natural
fats. Most oleic acid is obtained from animal tallow or vegetable oils.
Of the various octyl alcohols (straight chain and branched chain), 2-ethyl hexanol is the most important raw material for the
manufacture of textile auxiliaries. This is a colourless liquid, miscible
with most organic solvents, but immiscible with water. it boils at
183ºC and has a specific gravity of 0.83. it is combustible and has
low toxicity. Its oral LD50 value in rats in 12.46 ml/kg. It is used in
the manufacture of dioctyl sulphosuccinate, which is the rapid
wetting agents; for producing non-cresylic wetting agent in
mercerising liquors, after sulphation and neutralisation. Octyl alcohol
is also a defoaming agent
This is a straight chain aliphatic alcohol, also called dodecyl
alcohol. This is a colourless solid, with a melting point of 24ºC and
a boiling point of 259ºC. It is immiscible with water. It has low
toxicity. It is made by the reduction of coconut oil fatty acids (which
contain about 47% lauric acid). After sulphation and neutralisation,
it produces sodium lauryl sulphate (SLS), which is a detergent, as
well as a levelling agent in dyeing acid dyes on nylon. Lauryl alcohol
can be used as a defoaming agent.
This is the straight chain C16 aliphatic (saturated) alcohol;
also called palmityl alcohol. It is combustible and is non-toxic. It is
a white waxy solid with a faint odour and melts at 49.3ºC and boils
at 344ºC. Cetyl alcohol is partly miscible with ethyl alcohol and
ether but is immiscible with water. It is made by saponifying
spermaceti with caustic soda or by reducing palmitic acid.