MOQ | 100 KGS |
Port | AS PER DISCUSSION |
Packaging | 25KG / CUSTOM |
Lead Time | AS PER DISCUSSION |
ACID DYES
Acid dyes
are highly water soluble, and have better light fastness than
basic dyes. The textile acid dyes are effective for protein
fibers such as silk, wool, nylon and modified acrylics. They
contain sulphonic acid groups, which are usually present as
sodium sulphonate salts. These increase solubility in water, and
give the dye molecules a negative charge. In an acidic solution,
the -NH2 functionalities of the fibres are protonated to give a
positive charge: -NH3+. This charge interacts with the negative
dye charge, allowing the formation of ionic interactions. As well
as this, Van-der-Waals bonds, dipolar bonds and hydrogen bonds
are formed between dye and fibre. As a group, acid dyes can be
divided into two sub-groups: acid-leveling or
acid-milling.
Chemical structure of acid dyes
These dyes are normally very complex in structure but have large
aromatic molecules, having a sulphonyl or amino group which makes
them soluble in water. Most of the acid dyes belongs to following
three main structural molecules,
1. Anthraquinon type
2. Azo dye type
3. Triphenylmethane type.
Different types of acid dyes
The
basic dyes are classified into several groups , based on the
leveling properties, economy of the dyeing and fastness
properties, however generally these are classified into these
three classes,
1. Neutral acid dyes :-
These are supra milling or fast acid dyes, having medium to good
wet fastness properties , some of the dyes have poor light
fastness in pale shades . many of the dyes are used as self
shades only. These are applied to the fiber in a weakly acid or
neutral pH.
2. Weak acid dyes
These dyes belongs to the milling class of dyes. These dyes have
good fastness properties but light fastness is moderate to
poor.
3. Strong acid dyes
These dyes are applied in a strongly acidic medium and also
called leveling dyes, however there wet fastness properties is a
limitation. These dyes are very good to produce the combination
shades.
Classification according to dyeing
characteristics
Acid
dyes are commonly classified according to their dyeing behaviour,
especially in relation to the dyeing pH, their migration ability
during dyeing and their washing fastness. The molecular weight
and the degree of sulphonation of the dye molecule determine
these dyeing characteristics. The original classification of this
type, based on their behaviour in wool dyeing, is as
follows:
1. Level dyeing or equalising acid dyes;
2. Fast acid dyes;
3. Milling acid dyes;
4. Super-milling acid dyes.
Milling is the process in which a woollen material is treated, in
weakly alkaline solution, with considerable mechanical action to
promote felting. Dyes of good fastness to milling are essential
to avoid colour bleeding during the process.
Properties of acid dyes
Since these are sold as a sodium salt, therefore these form a
large anion in the aqueous medium.
1. These dyes are anionic in nature.
2. These dyes are suitable for wool, silk, polyamide and modified acrylics.
3. These are applied from a strongly acidic to neutral pH bath.
4. These dyes have no affinity for cotton cellulose’s , hence not suitable for cellulosics.
5. These dyes combine with the fiber by hydrogen bonds , vander waals forces or through ionic linkages.
Shades - ALL COLOURS available.