The textile jigger
carries out wet chemical processes such as dyeing and bleaching,
most typically on synthetic polymer fabrics. Jiggers work by unrolling
a length of fabric through a heated impregnation liquid made up
of reactive dyes or bleach in accordance with set formulae.
The industrial jigger has benefited from a number of improvements
in recent years, including increased programming and automation
and the improved control of dyebath composition. Nevertheless, the
basic principles of jigger operation have not changed and the procedure
remains lengthy and often poorly regulated. The treated fabric spends
relatively little time in contact with the hot liquid before moving
on to an uptake roller where temperature is not controlled. The
inevitable cooling which occurs reduces the effectiveness of the
Breaking with tradition
This project, launched in September1994, proposed
the introduction of microwave irradiation, which was complementary
to traditional heating techniques, to maintain optimum temperatures
throughout jigger operations. The project followed upon an Electricité
De France (EDF)-supported study which demonstrated that such a system
was not only capable of cutting treatment time, but also of improving
dye yields irrespective of the type of material treated. The principle
of using electromagnetic waves in a textile jigger was subsequently
patented by EDF and the Institut Textile de France (ITF).
The specific aim of this project was the production of an industrial-scale
system for textile preparation and dyeing using microwave assistance.
This pilot system was to be fitted with control instrumentation
to allow for the accurate measurement of energy consumed and the
evaluation of ecological performance. Comparisons were made with
traditional methods using the same machine, with particular attention
being paid to final product quality.
A prototype machine was created based on a LAJTOS
industrial jigger. Machine operation was managed by an automated
system, allowing predetermined injection of dyes and auxiliaries,
fabric unwinding, and management of microwave power and safety systems.
A heating coil immersed in the liquid served as the main source
of heat. Additional heating was provided by microwave generators
located on top of the machine and operating at up to 30 kW of power.
Microwave radiation was distributed over the length of the fabric
The most significant results were obtained in the treatment of cotton,
where improvements were observed on all of the major efficiency
measures. Dyeing efficiency was increased by 10%, chemical pollution
was reduced by 5%, salt consumption went down by 25% and finishing
time was reduced by about 7%.
Material benefits for cotton
Project partners emphasise that while the results
for cotton treatment were highly significant and clearly demonstrated
the economic viability of the new system, the improvements achieved
in the treatment of synthetic polymers, already a more efficient
process than for cotton, probably do not in themselves justify its
installation - the cost of the equipment is simply too high when
compared with the benefits obtained. If, on the other hand, cotton
is being treated, then the system offers clear economic benefits.
The use of heat-generating microwaves is a radical development in
terms of the mechanism of reactive dye transfer. Partners say the
new process will mean enormous cost savings and increased productivity
for European textile producers, many of which are SMEs. Furthermore,
the system is extremely environmentally friendly and represents
a real improvement in terms of working conditions. Environmental
benefits include energy savings, a reduction of the quantity of
chemicals used, and reduced water and salt consumption.
Increasing demands for faster delivery
of smaller lots and a larger diversity of products have had profound
effects on the textile-finishing sector, making the use of automated
processes such as jigging even more attractive and, indeed, necessary.
The use of microwave technology to maintain optimum temperature
conditions represents an important advance for European textile
finishers at a time when textile manufacturing is moving away from
Europe towards countries with lower labour costs. Market research
has identified at least 150 jiggers in Europe which could benefit
substantially by using the new system in the treatment of cotton.