1. Study of Microencapsulation in
Dyeing
Presented By
Arka Das
Entry No- 2012TTF2404

2. Introduction
Micro-encapsulation is a process in which tiny particles
or droplets are surrounded by a coating to give small
capsules many useful properties. In a relatively simplistic
form, a microcapsule is a small sphere with a uniform wall
around it. The material inside the microcapsule is referred to
as the core, internal phase, or fill, whereas the wall is
sometimes called a shell, coating, or membrane.
The potential size range of the microcapsules produced is
enormous, with typical diameters being between 2 and 2000
µm.
Capsule walls are typically 0.5-150 µm thick, although
walls measuring less than 0.5 µm can be achieved.

3. Cont…………..
The proportion of core material in the capsule is usually
between 20 and 95% by mass.
There are over 50 different known wall materials; both
natural and synthetic polymers can be used to form the
microcapsules. These include the natural polymers
gelatin, gum arabic, carrageenan and alginate, and synthetic
polymers such as ethylcellulose.
In recent years microencapsulation techniques have been
used in the pharmaceutical, agricultural, bulk chemical, food
processing, and cosmetic and toiletry industries.
The textile industry, although initially slow to exploit the
technology, is now generating innovative ideas and inventions
within the field.

4. Shapes of Microencapsulation

5. Microencapsulation Process
(a) Spray coating methods, e.g Wurster air suspension
Coating
(b) Wall deposition from solution, e.g. coacervation or
phase separation
(c) Interfacial reaction
(d) Physical processes, e.g. annular jet encapsulation
(e) Matrix solidification, e.g. spray drying or chilling
(f)Naturally occuring microcapsules

6. Spray Coating methods
This spray technique coats finer
particle while they are suspended in an
upwards moving air steam. The process
simultaneously applies and hardens
the wall materials onto the particles.
Heated air flows into the chamber
through small holes in the base plate
and the particle rise within the
chamber.
Small amounts of coating solution
from a spray nozzle at the centre of the
chamber are deposited on the particles.

7. Wall deposition from solution
Microcapsules produced can range in size between 2 and
50 µm.
Coacervation can be divided into two distinct
categories, simple and complex, the former involving only
with a single colloidal solute and the latter more than one
colloid.

8. Interfacial reaction
This process is based on interfacial polycondensation
polymerisation.
The capsule shell will be formed at the surface of the
droplet or particle by polymerization of the reactive
monomers.
The substances used are multifunctional monomers.
Generally used shell forming material include diamines
and diacid chlorides.
it will be dispersed in aqueous phase containing dispersing
agent.

9. Physical Processes
A dual fluid stream of liquid core and shell
materials is pumped through concentric tubes
and forms droplets under the influence of
vibration.
A membrane of wall material is formed across a
circular orifice at the end of the nozzle and the
core material flows into the membrane, causing
the extrusion of a rod of material.
Droplets break away from the rod and The shell
is then hardened by chemical cross
linking, cooling, or solvent evaporation.
Solid capsules are removed by filtration or other
mechanical means and the immiscible carrier
fluid, after passing through the filter, is reheated
and recycled.
This process is capable of producing capsules
ranging from 400- 2000µm in diameter.

10. Matrix Solidification
Microencapsulation is achieved using
spray drying or chilling techniques by
atomising a combined solution of core and
wall material.
The process of spray drying consists of four
stages.
The first of these involves atomisation of
the core/wall material solution, which
governs the size of the capsules (generally
10-200 µm)
The solution may be heated to keep the
ingredients in solution and to ensure that
premature hardening or drying does not
take place.
The small droplets formed on atomisation
quickly assume their equilibrium spherical
shape and, on contact with the air
stream, drying of the product begins.

11. Naturally ocurring microcapsules
Filamentous fungi,
protozoa and yeast have
been mentioned as a
possible sources of capsules;
however, most of the
examples given and claims
presented have involved
yeast.
These micro-organisms
appear to lend themselves to
the microencapsulation
process and therefore
further work has
concentrated on utilising
waste yeast (Saccharomyces
cerevisiae) from the brewing
and baking industries.

12. Textile Applications of Microencapsulation
Microencapsulation of Disperse dye
Microencapsulation of Acid dyes
These will be discussed briefly.

13. Dyeing of polyester using microencapsulated
disperse dyes in the absence of auxiliaries
Dyeing of polyester requires water and certain chemical
auxiliaries such as dispersing agents, penetrating agents
and levelling agents, in the dyebath. Unfortunately, residual
auxiliaries and dyestuff may be present in the effluent and
may cause pollution.
Polyester fabric was dyed with microencapsulated CI
Disperse Blue 56 using a high temperature dyeing process
without dispersing agents, penetrating agents, levelling
agents or other auxiliaries. The quality of the polyester
fabric dyed in this manner without reduction clearing was
at least as good as that dyed traditionally after washing and
reduction clearing. After separating off the polyurea
microcapsules, the dyebath was virtually colourless and
was shown to be suitable for reuse.

14. Dye Used
CI Disperse Blue 56 (1) and CI Disperse Red 60 (2)

15. Preparation of microcapsules
Polyurea microcapsules (PMs) were prepared using
an interfacial polymerisation reaction in emulsion form
as described earlier.
PMs contained Diphenylmethane-
4,4′diisocyanate(MDI)(wall material) and disperse dye
(core material) and were prepared at an adequate ratio
with GPE2040 (2% w/w) as the emulsifier and PVA (1%
w/w) as the stabiliser.
The reaction being carried out at 50 C for 180 min.
After reaching room temperature microcapsules were
seperated by decantation.
After washing with 10% w/w ethanol to remove
unreacted isocyanate, the microencapsulated material
was dried in a vacuum oven at 25 °C for 24 h.

16. Results and Discussion
Thermal properties of the PMs
In the DSC analysis, thermal change
was not apparent below 280 °C, with
an absorption peak around that
temperature (Figure a). Between 160
and 230 °C the curve was more
uniform, and endothermic transition
of the dyes was not detected.
TG showed that the microcapsule
weight decreased with increasing
temperature by as much as 40%
(Figure b). A small initial weight loss
occurred between 160 and 230 °C due
to progressive release of core material
from the microcapsule.

17. Particle Size and distribution
The mean size of all the resulting particles after
emulsification stirring at 10 000 rpm was about 23
μm, and the size distribution was narrow (ca. 6–60 μm).

18. Morphological structure of
microcapsules

19. Dyeing behavior
The dyeing behavior of the dyes in PM form was compared with
fabric dyed traditionally.
The results show that the levelness and fastness to soaping and
rubbing of PET samples dyed with 1 in PM form, without
auxiliaries or reduction clearing, were at least as good as those
obtained by traditional disperse dyeing after washing and
reduction clearing.
The excellent wash-off properties of the PET fabric dyed with
the PM disperse dyes may be attributed to reduced staining of the
surface of the fibre, making the need for washing much less
important.

20. Dyebath wastewater

21. Reuse of recovered wastewater
PET fabric samples were dyed
under similar conditions using
dyes 1 and 2 in PM form in
filtered wastewater.
The dyeing rate curves are
shown in Figure 3. In each case
the dyeing rate curves are
similar, which means that
residual dye 1 remaining in the
wastewater had little influence on
the dyeing behaviour of this dye
in PM form.

22. Reuse of recovered wastewater

23. Reuse of recovered wastewater

24. Effect of Microencapsulation on Dyeing Behaviors of
Disperse Dyes Without Auxiliary Solubilization
Microencapsulated disperse dye can be used to dye
hydrophobic fabric in the absence of auxiliaries and without
reduction clearing. However, little available information for
dyeing practice is provided with respect to the effect of
microencapsulation on the dyeing behaviors of disperse dyes.
In this research, disperse dyes were microencapsulated under
different conditions. The dyeing behaviors and dyeing kinetic
parameters of microencapsulated disperse dye on PET fiber,
e.g. dyeing curves, build up properties, equilibrium
adsorption capacity C1, dyeing rate constant K, half dyeing
time t1/2, and diffusion coefficient D were investigated
without auxiliary solubilization and compared with those of
commercial disperse dyes with auxiliary solubilization. The
results show that the dyeing behaviors of disperse dye are
influenced greatly by microencapsulation.

25. Dyes Used

26. Preparation of microencapsulated disperse dyes
with different shell materials and mass ratios
of core to shell
Disperse dye microcapsules were prepared by in situ
polymerization.
Disperse dyes (C.I. disperse red 73 or C.I. disperse blue 56, no
any additives, 1 g) and MS aqueous solution (1% w/w, 100 mL)
were mixed by high-speed emulsifier (10,000 rpm) for 5 min.
The pH of the mixture was adjusted to 4–5
The mixture was then put immediately into a flask with stirring.
Designated amount of shell material (1 g, 2 g, 3 g, 4
g, trimethylolmelamine or hexamethylolmelamine) was added at
ambient temperature.
After being stirred uniformly, the reaction system was heated to
65C (heating rate 1C/min) and maintained for 120 min to form
microencapsulated disperse dyes with different mass ratios of
core to shell (1 : 1, 1 : 2, 1 : 3, 1 : 4 w/w).
Reaction system was cooled down and its ph was adjusted to 7–
8 using ammonia.

27. RESULTS AND DISCUSSION
Characterization of microencapsulated disperse dyes
The microcapsules shown
in Figure 4 are nearly
spheric with rough surface
and irregular pores on the
surface.
The surface of
microcapsules prepared by
hexamethylolmelamine is
much looser than the
surface of microcapsules
produced by
trimethylolmelamine.
The more looser
microcapsule shell is, the
faster dye release rate it will
be.

28. Thermogravimetric analysis
results of microcapsule shells
prepared with different materials
are given in Figure.
Melamine resin as a
thermosetting polymer exhibits
good thermal stability below
250˚C.
Due to possessing more
hydroxyl
groups, hexamethylolmelamine
shows more severe weight loss
TGA curves of microcapsule shells
than trimethylolmelamine above
prepared with different materials (a)
250C. trimethylolmelamine; (b)
hexamethylolmelamine.

29. The particle size distribution of
microencapsulated disperse dyes
are shown in figure.
The mean size of C.I. disperse
red 73 microcapsules prepared by
trimethylolmelamine is 8.9 μm.
While the mean size of C.I.
disperse blue 56 microcapsules
prepared by
hexamethylolmelamine is 11.5
μm.
Two microcapsule samples
Size distribution curves of
reveal relatively concentrated microencapsulated disperse dyes: (a)
particle size distribution. core material, C.I. disperse red 73;
shell material, trimethylolmelamine;
mass ratio of core to shell, 1 : 2; (b)
core material, C.I. disperse blue 56;
Shell
material, hexamethylolmelamine;
mass ratio of core to shell, 1 : 2.

30. Effect of microencapsulation conditions
on diffusibility

31. Effect of microencapsulation conditions
on diffusibility
Dyeing curves of commercial and microencapsulated disperse dyes: (a) Commercial disperse dyes; (b) microencapsulated
disperse dyes (microencapsulated C.I. disperse red 73: trimethylolmelamine as shell material, mass ratio of core to shell 1 : 2;
microencapsulated C.I. disperse blue 56: hexamethylolmelamine as shell material,
mass ratio of core to shell 1 : 2).

32. Effect of microencapsulation on
build-up properties

33. Microencapsulation of Disperse Dye Particles with Nano Film
Coating Through Layer by Layer Technique
In this study, weak polycation poly(allylamine hydrochloride)
and strong polyanion poly(sodium styrene sulfonate) were used
for fabrication of nano film through layer by layer technique on
the surface of disperse dye particles. Then micron-sized
particles were surrounded by poly(urea formaldehyde) using in-
situ polymerization. Chemical structure, surface
morphology, and size distribution of these novel microcapsules
were characterized by Fourier transform infrared
spectrometry, differential scanning calorimetry, optical
microscopy, and scanning electronic microscopy.

34. Chemical structure of microcapsules containing disperse dye:
Doublet bands at 3445 and 3355 cm-1 are presented by the FTIR spectrum of
urea.
As it can be seen, polycondensation reaction between urea and formaldehyde were
proved by the absence of absorption band owing to urea at 2806 and 2640 cm -1
and manifestation of absorption peak of poly(urea formaldehyde), which is
assigned at 3707–3050 (NH and OH), 1649 ( ), 1544 ( ) and 1027 ( ) cm -1. On the
other hand, the absorption peaks of 1556, 1035, and 630 cm -1 are appeared in
both microcapsules and dyes spectra.

35. Microencapsulation of Acid Dyes in Mixed
Lecithin/Surfactant Liposomic Structures
Non-uniformity occurring in polyamide dyeing, caused by the
rapid uptake of dye by the fibers, can be reduced by retarding
and leveling agents.
Liposomes release the microencapsulated dye slowly,
promoting a retarding effect, comparable with the one
obtained with retarding agents, making them a good alternative
to commercial levelling products.
The objective of this work is to study microencapsulation of
the dye in liposomes with lecithin from soy, as an alternative to
retarding and leveling agents.
The effect on the dyeing rate of the microencapsulated dyes is
compared with that from common retarding and leveling
agents.
The influence of surfactants on the stability of the liposomes
and hence on the exhaustion curves of the dyeing is evaluated

36. Results and Discussion
Dyeing with lecithin liposomes
The best lecithin
concentration to obtain a
dyeing rate close to that
with the commercial
retarding and leveling
agents was l g/L
Figure. Exhaustion curves of microencapsulated
c.I. Acid blue
113 using different lecithin concentrations

37. Influence of surfactants in the liposolles

38. Influence of surfactants in the liposolles

39. Conclusion
Microencapsulation of disperse dyes provides the
opportunity to carry out dyeing in absence of auxiliaries
and without dyeing without affecting other properties.
Thus this techniques results in reduced BOD and COD of
dye baths from dyeing.
Different disperse dyes having different dyeing behavior
can be make to behave similarly by microencapsulation.
So this technique is a very useful tool in compound shade
dyeing.
Microencapsulation of acid dyes can be used for
improving leveling. This can also be used improve barre
dyeing. As this technique retard the rate of dyeing it can
be used successfully.

40. Thank You