Binder:
Binders are film forming polymers which play important roles
in achieving optimum properties. Pigments have no affinity towards textile
materials. So actually pigment particles are sticked on the surface of fabric.
Binders are those adhesive type coating forming polymeric materials which
sticks pigment particles on fiber/fabric surface. Binders are white, milk-like
liquid. If forms a very thin invisible film on fabric surface during curing.
Under this film pigment particles are remain sticked. So in pigment dyeing and
printing binder is a very important and essential ingredient.
Binders with a particle size range of 0.05 to 2 microns are
usually available. These contain about 6% by weight of reactive groups for
crosslinking of the binder to textile. The reaction involved is as below:
Binder-CH2-OR + HO-textile = Binder-O-textile +
HOR
[where Ris H or CH3 ]
Crosslinking increases the rubbing washing and drycleaning
fastness properties, but it affects the handle of fabric.
Types of binder:
Binder can be classified according to many aspects, Some are
mentioned below:
1. According
to origin: According to origin there are two types of binder,
I.
Natural binder- glue, gelatin etc.
II.
Synthetic binder- TROL, SLN, IG, Acramin binders
etc.
2. According
to chemical groups: According to chemical group present in binder there are two
types of binder, those are:-
I.
IG Binders: Emulsion copolymer of vinyl acetate
and butyl acrylate with a modified urea formaldehyde.
II.
Ag Binders: They are made by emulsion
copolymerization of olifinic unsaturated monomers in an aqueous medium. These
monomers include:-
a) Acrylic
acid ester(butyl or ethyl acrylate)
b) Styrene
c) Acrylonitrile
d) Vinyl
chloride
e) Asymmetric
dichloroethane
f) Vinyl
acetate
g) Diolifine
such as butadiene
Required properties of a binder:
The binder must have certain qualities. For example:
i.
It should not get coagulated due to shear
forces.
ii.
The binder film must be clear/transparent.
iii.
The binder film must be of even thickness,
smooth, neither too hard nor too soft.
iv.
It should be elastic in nature and should have
good adhesion to the substrate without being tacky.
v.
It should have good resistance to chemical and
mechanical stress.
vi.
It should be easily removable from equipments.