Comparison between Pigment Printing Systems with Acrylate and Butadiene Based Binders
88
formed during some suitable fixing process, which usu-
ally consists of dry heat and change in pH value, bringing
about either self-crosslinking or reaction with other suit-
able crosslinking agents [8]. Elasticity and improved
adhesion of the film to the substrate is achieved by
crosslinking. The crosslinking reaction must produce
covalent bonds, which are insensitive to hydrolyzing
agents (washing liquor, perspiration, industrial atmos-
phere). The reaction should be activated in dry hot air by
curing process [9]. While the prints are being dried, a
film is formed from the dispersed binder. Its formation
takes place in two stages: flocculation (or coagulation)
and coalescence. During the first stage of film formation,
water and surfactants are removed from the binder by
absorption and evaporation. The dispersed solids coagu-
late to form a gel-like layer of very tightly packed ‘balls’,
which have only poor solidity and adhesive properties. If
the mechanically more stable, more redispersible, disper-
sion binders are used, these coagulated particles can be
brought back to th eir original form by rubbing them with
water. During the second phase, the gel particles flow
together to form a continuous film.
The lowest temperature at which a film can be formed
depends upon chemical constitution, but for pigment
printing it is usually around 5˚C. The speed at which the
film is formed depends upon the range of particle size
[10]. The reaction between the binders and the cellulosic
substrate may be represented as follows in equ a tion:
22
Binder-CH-ORHO-CelluloseBinder-CH-O-Cellulose + ROH
where R is CH3 or H.
Cross linking increases the crocking, washing and dry
cleaning fastness properties, but detrimentally affects the
handle of the fabric. When the binder molecule have no
self-crosslinking groups, an additional cross linking agent
such as urea formaldehyde or melamine formaldehyde
condensate, methylolated urethane compounds etc, hav-
ing at least two reactive groups per molecule are added in
the binder system [11].
The present research work demonstrates the comparisons
between pigment printing systems with acrylate and buta-
diene based binders. The influence on the crocking fast-
ness, PVC migration, formaldehyde release and K/S values
of the printed cotton fab ric has also been investigated.
2. Experimental
2.1. Material
An optical brightener free, 100% cotton woven fabric
having construction 25 ends/cm2, 21 picks/cm2 and an
area density of 142 gm/m2 was used for pigment prin ting
purpose. The fabric was desized enzymatically, scoured
and bleached by an exhaust method.
2.2. Chemical & Colorants
Commercial pigment Imparon KB of BASF was used as
a colorant in the printing process. Two different binder,
binder ET (polyacrylate based) and halazarine binder
FRS (butadiene based) of BASF were used. Leutexol HP
was also supplied by BASF and used as a thickener.
Printofix WB liquid (melamine based) used as a fixative.
All other chemicals ammonia, urea, polyvinyl chloride,
TiO2 were purchased from Merck chemicals Pakistan
limited.
2.3. Equipments
Printing was carried out by laboratory hand screen-print-
ing. Samples were cured on curing machine of Rapid.
Crocking fastness evaluated on AATCC Crock meter
(CM-5 SDL Atlas), Fastness rating was evaluated on
color matching cabinet of Verified by comparing with
grey-scale. The viscosity of the thickener paste was de-
termined by Brookfield viscometer (DV-E model) with
spindle number 6.The relative color strength of the prints,
expressed as K/S values L, a, b, c CIE lab of the printed
samples were determined by reflectance measurements
using Data color intern ational spectrophotometer SF600.
2.4. Print Paste Preparation
The print paste was prepared in soft water with heavy
string by adding 15 g/kg acrylate and butadiene based
binder separately, 12 - 14 g/kg thickener, 6 g/kg ammo-
nia to attain a pH 8 - 9 and 0.7% - 0.8% w/w fixative
were also added. Each print paste was prepared with 5%
Imparon KB pigment and 95% stock paste. The viscosity
of the final print paste was 28000 cp s as determined with
Brookfield viscometer.
2.4.1. Prin t Method
The printed fabric dried at 120˚C for 2 min and cured at
155˚C for 5 minutes.
2.4.2. Fastness Testi ng
The fastness properties were determined according to the
international standards of textile testing. The specific
tests used were ISO-105-X10, BS1006:1990 (Assessment
of migration of textile color into polyv inyl chloride coat-
ing), ENISO-14184-1:1998 (Formaldehyde release),
AATCC-08 (color fastness to crocking) [12-14].
3. Results & Discussion
The pigment printing was performed with 5% Imparon
red KB pigment in the laboratory with simple screen
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