An in plant training at

Bombay Dyeing and Mfg. Co. ltd.

Presented ByNIKHIL S. SHAIWALE

VJTI (VII L.T.C.)

MATUNGA, MUMBAI 400 019

1) Mercerization (the actual process)2) Conventional Merceriser & Problems faced3) Concept of Hot mercerization & parameters 4) Benefits of hot mercerization5) Benninger Mercerisers6) Padless chain merceriser7) Comparative description of the machines8) Specialties of the design and machine9) Disadvantages and advantages

Mercerization is a treatment of cotton fiber under tension with about 280-290 gpl caustic at low temp (RT instead of low temp) for 45 to 60 seconds.

Gives excellent luster and drape with considerably increased dye uptake.

The machine consists of a trough containing caustic through which cotton fabric is padded.

Machine speed is set according to dwell time required. (dwell time = loop length/speed of machine in mpm)

Problems faced Difficulty in achieving reproducible results. (Due to RT

variation) Poor mercerization at yarn core resulting poorly dyed core of

yarns in fabric. More consumption of utilities. Low production speeds (Due to larger dwell time)

A mercerization process carried out at 60-70˚ C. Affinity of caustic towards cellulose decreases. At this temperature, caustic has low viscosity. Cotton yarns swell more slowly allowing the diffusion of lye upto yarn

core. Core gets mercerized achieving core mercerization.

Hot mercerization – parameters Concentration:- The concentration of the caustic lye should be strictly

controlled between 28 – 30˚ Be as rise or fall in conc. does not achieves the desired result.

Temperature:- The temperature must be controlled in a range of 60 - 70˚ C. Dwell time:- The dwell time required is 25-30 seconds.

We will discuss the merceriser from following point of view. Design Important parts Utility consumption Parameters Variation according to process

The merceriser can process both heavy and light varieties while processing.

The sequence of processing is impregnation -> dwell time ->

stabilization -> washing. This one has better control over shrinkage both weft wise and

warp wise.

Impregnator: For impregnation.

& Timer: For dwell timing Stabilizer: For stabilization and recuperation C.R.P. (caustic recovery plant): For recovery of the caustic

from wash liquor.

IMPREGNATOR Hot 28° Be caustic is sprayed through pipes in the

gap between engraved and hollow rubber roller. This saves the unnecessary amount of caustic and

low amount allows rapid change in concentrations according to the quality.

The overflowed caustic liquor is recirculated with recirculation pumps. And thus this also adds to saving of the caustic lye.

TIMER This compartment is same as the impregnator. But

the caustic is not sprayed on the fabric. This compartment is only used to give a dwell time of 25 to 30 seconds.

RECIRCULATION PUMP

Impregnator concept

Stabilizer In this unit the fabric is stabilized i.e. caustic conc. is lowered

in this zone to 8˚ Be. making the fabric stable . Also in this unit steam is employed to achieve the temperature

of about 85˚ C. This further lowers the affinity of caustic towards fabric to serve easy removal during washing.

CRP In this plant caustic from wash liquor is recovered by means

of evaporation technique to recover about 95% of pure caustic recovery. It delivers the caustic of about 35˚ Be.

These are the important sections of the machine. The parts are mentioned below which are present in these sections.

Engraved roller & Rubber coated rollers (small and big) Baumy sensor Chain Extracta compartments

Engraved roller has a engravings on its surface which ensures firm grip & yarn slippage.

Baumy sensor : it sences the concentration of caustic

Rubber coated hollow roller

The chain is the most important part of this merceriser which enables weft wise control over shrinkage.

Pins & water sprayers

The roller arrangement is unique that is sequence of rollers is engraved steel roller and rubber roller.

The liquor lies between engraved steel roller and hollow rubber roller.

steel steel steelsteel

RCRCRCS.

Caustic lyeRC:- Rubber coated rollerRCS. Small rubber coated roller Steel:- Engraved roller

Reduced power consumption due to Hollow rollers The arrangement of rollers reduces the amount of caustic to

the considerable extend. Better & faster control over concentration (Low amt of

processing caustic). Less labour handling and minimal stoppages. Counter current washing has been provided. Low consumption of lye, water and electricity (up to 30% less

lye consumption). The range is totally automated. Thus once the values are set

rest of the parameters are governed by a computerized system. Increased efficiency due to heat exchangers

The advantages of these hot mercerization ranges are as follows-

1. Uniform core mercerization is achieved.2. Controlled temperature ensures excellent shade

reproducibility.3. Dwelling time is theoretically reduced upto 20-25

seconds giving higher productivity. 4. Upto 30% less consumption of lye, water and electricity.

The disadvantage of this process is that it gives poor luster as compared to cold mercerization.

Difference between the chain & chainless principle.

This process gives core mercerization. Also the dwell time is reduced from 45-60seconds to 25-30

seconds. This increases higher production speeds thus higher

productivity. Also the temperature is strictly maintained at 60˚C thus giving

excellent shade reproducibility. This gives enhanced luster uniformly.

Thank you for your patient co-operation.