1. Presentation on: Functions of dyeing auxiliaries
Prepared By:
Tanvir Ahammed Rana
Id. 2012000400038
19th Batch, Textile Department.
SouthEast University.

2. Dyeing auxiliaries
There are different dyeing auxiliaries. They will be
classified according to their functions and various
uses. Dyeing auxiliaries provide high dyeing
quality, process safety and increased reproducibility
on all kinds of substrates and machines, in a variety
of processes and with all classes of dyestuffs.

4. Function of different dyeing auxiliaries are given below:
Sequestrant:
The most undesirable impurities in Fibre, Common salt, Glauber salt, Caustic Soda
and Soda ash are the di- and trivalent cations, e.g., Ca++, Mg ++ Cu ++, Fe+++ etc.
These ions increase hardness of the process bath and generate iron oxides in the bath.
Calcium and Magnesium reacts with alkali and precipitates as a sticky substance on
the textile material, which creates patchy dyeing and discoloration of the fibre. The
ferric oxide with cellulose and creates small pinhole on the fibres also damages the
machinery by scale formation in the nozzles and base.
To overcome these deleterious effects in the scouring and bleaching bath adequate
amount of Sequestrant must be used. Sequestrants prevent di-and tri-valent metal
ions, e.g., Cu++, Fe +++ , Mn ++, Ca++, Mg++ etc. from interfering with the
chemical processing of the textile material. It prevents catalytic damage of cellulosic
fibres in bleaching hath during hydrogen peroxide bleaching.
In Dye-bath Ca++, Mg ++, Fe +++ attack the dye molecules and forms aggregates of
molecules which deposits on the fabric as dye spots and also they prevent the
reaction process. Dye bath sequestrant should be of different strength than that of the
scouring and bleaching baths. Because some dyes have metal compounds and if
powerful chelating agents are used than it will attack the metal compound of dye.

5. Lubricating / Anticreasant:
Wet processing and dye-bath lubricants are used in any operation in
which rope marks, creases, crows feet buffing, abrasion can occur on
textiles. In low liquor ratios, full-loaded winches and jets when heavy
materials re processed, fiber lubricant is essential. The basic
requirement is that is it should from a thin uniform protective coating
around the fiber to lower the surface friction and flexural rigidity, thus
minimizing the formation of durable creases during high temperature
processing. The most suitable lubricant should have the properties so
that it helps to emulsify, it does not undergo phase separation with
extreme changes in pH and temperature, e.g. it is stable in high
temperature and over a wide range of pH; and it should have excellent
compatibility with all the chemicals in treatment bath, Suitable
products are relatively hydrophobic surfactants, many of which also
contain a proportion of solubilized or emulsified oil or wax.

6. Leveling and dispersing agent:
Unleveled dyeing problems can be of two categories: Gross
unlevelness throughout the material or localized unlevelness e.g.
barriness, skitteriness. There are two fundamental mechanisms that
can contribute to a dyeing.
1. Control of the exhaustion dye so that it is taken up evenly.
2. Migration of dye after initially unleveled absorption on the
fibre.
3. Non-ionic agent usually from water soluble complexes with the
dye, some degree of solubilization being involved.
4. Ionic agent are primarily dye-of fibre-substantive ; in the former
case they tend to form complexes with the dye and there is
competition between the leveling agent and the fibre for the dye,
while in the latter case the competition is between the leveling
agent and the dye for the fibre.

7. Sequestering, dispersing and levelling agent for reactive dyeing:
It increases the solubility of dyes and controls the exhaustion of
dyes so that these are taken up evenly on the substrate. It
effectively chelates Ca, Mg ions which otherwise create while spots
on the substrate. It also sequesters other di-and tri-valent metal ions
without impairing the metal complex dyes, and thus yields
uniformly dyed fabric.
Antifoam:
Where the present and persistence of foam is a nuisance,
Defoaming agents or antifoams are used. For maximum efficiency
deform should be added to baths when necessary. There two groups
of defoamers one that is water-soluble surfactants and other is
water insoluble emulsions of silicones of organic-based the most
effective defoamers are where the water-soluble compounds are
used as vehicles for silicones of organic emulsions.

8. pH control and buffer system:
Many disperse dyes required controlled 4.5-5 and
practically all disperse dyes give good results in this pH
range and are much more sensitive to minor changes in pH.
Thus there is greater awareness of the actors that not only
determine pH but also helps to stabilize it against
interferences, in particular, from any acids or alkalis carries
over from previous process. A buffered system is necessary
for precise control of pH. By the use of that tends to resist
changes arising from contaminations entering y way of the
substrate of the water supply.

9. Desizing agent:
Desizing is essentially a part of the scouring process, and
rapid removal of size is very important in the present trend
towards continuous preparation processes. Starch-based
products and especially solubilized starches are still the
sizes, most commonly used on cellulosic goods. The are
most frequently removed y enzymes treatment, which since
effect it affects only the starch product ensure that the
cellulosic fibre is undamaged; bacterial amkulase id
increasingly replacing malt and pancreatic enzymes. The
efficiency of desizing is often taken for granted, whereas
incomplete of uneven size removal is just likely to be the
cause of uneven dyeing or printing as inadequate scouring

10. Yarn Lubricant:
In the textile industry, a smooth production process is essential for
perfect results and smooth production needs yarn and sewing thread
lubricants. Yarn lubricant are essential for dyed yarn used in modern
knitting machine. They significantly improve the slip properties of
yarn and sewing thread, increased heat resistance, better sewability,
reduced thread breakage and increase the lustre.
Mercerizing Agent:
The objective of mercerizing is to oil the cotton fibre, increase its
lustre strength and dyeability. Traditionally a cold solution of 25-26%
by mass of sodium hydroxide is used, although better penetration and
more even treatment is obtained with the more recent hot mercerizing
technique. The addition of a wetting agent to the mercerizing liquor
give better penetration and more even treatment, the main
requirements being for a combination of stability and powerful wetting
action.

11. Dye Fixing Agent:
Properties of a good fixing agent includes good capability with cross
linking agents without promoting yellowing effect; good leveling and
migration properties, does not affect the shade, has good affinity for
the fiber, stable to steaming and dry heat, and improved all round
fastness properties of the fabric or yarn. Fixative is generally used
after completing the dyeing or in printing paste.
Optical Brightener:
An Optical Brightening Agent (OBA), also called Fluorescent
Brightening Agent (FBA) or Fluorescent whiteners (FW), are strongly
fluorescent substance that emits light in the blue-violet region of the
visible spectrum. In the Color Index, OBA or FBA’s are classified and
are given C.I. number, i.e. they are treated as dyes. When present on a
substrate, OBA increase the apparent reflectance of the substrate and
makes it appear “whiter than white”. To evaluate an OBA it is
necessary to apply the product and measure the whiteness, preferably
with a spectrophotometer.

12. Soaping agent / washing off agent:
The important of proper washing after dyeing is painfully known
to all dyers, particularly the difficulty in washing off the unfixed
dye in order to meet the required fastness standard. The main
functions of soaping agent are to:
1. Disperse the unfixed substanted hydrolyzed dyes, and
solubilize and emulsify these into the aqueous medium and
keep these substances in suspension.
2. Prevent redeposition of hydrolyzed dyes and other particles
of colloidal substance into the textile material.
3. Removes the alkaline earth metal ions which have already
deposited on the dyed material.
4. Prevent the precipitation of insoluble calcium or magnesium
salt.

13. Finishing chemicals:
The Quality of softness is very difficult to define, although it is
often confused with only lubricity. Softness is more than
lubricity, but these other attributes are difficult to define
scientifically. The various products used soften are divided into
silicone, anionic, non-ionic, amphoteric and reactive types, all of
which falls under two basic chemical classes:
1. Fatty acid derivatives and
2. Silicon derivatives, by far the most important softness
today are the silicon derivatives and fatty acid cationic types;
however non-ionic softeners is used for textile materials
because of its non-yellow effect and compatibility with OBA.
Relevant properties of softeners include aqueous solubility,
exhaustion, durability to washing, and compatibility with
other additives to the textile materials.