Ammonia Mercerization Submitted To: - PowerPoint Presentation

Slide1

Ammonia Mercerization

Slide2

Submitted To:

Dr. Ummul Khair Fatema

Presented By :

ID

Name

2011-1-017

Shahanaz

Parvin

2011-1-018

Rifat Jahan

2011-1-098

Nazmun Nahar

2011-1-128

Humayra Akhter Himu

2011-1-208

Nigar Rashida

Slide3

What is

MERCERIZATION?

Mercerization is a pre-treatment or finishing treatment of cellulosic materials with higher concentrated Alkali (NaOH) for short period at lower temperature

. Mercerization gives cotton woven cloth a silky

luster,

and is the foundation

of many

improved and beautiful

finishes.

Mercerization

was discovered by

John Mercer

and

the process

is named

after him

:

M

ercerizing

. Later

Horace

Lowe

found

that the glazing

effect became

even more pronounced when cold caustic soda acted on cotton under

tension. He

discovered the actual mercerizing

process.

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Objectives of mercerization

To improve luster of cotton materials

To increase

ability to absorb

dye and moisture

To improve

reactions with a variety of chemicals

To improve dimensional stability

of

materials

To improve strength/elongation and mechanical properties

To improve

smoothness

To improve

hand

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Effect of mercerization on cotton fiber

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What is AMMONIA MERCRIZATION?

A

mmonia M

ercerization

is a treatment of

cotton

fibre

with Ammonia (NH3) produces effect similar

to that

obtained with

caustic soda.

Among

various amines, the

Liquid Ammonia

appears to be unique in its swelling action on cellulose and its effect on crystal structure

.

Liquid ammonia treatment was first developed by

Coats

in 1960

.

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Why Ammonia mercerization?

Liquid Ammonia treatment is a highly effective and well controlled alternative to caustic soda

mercerization.

Anhydrous

liquid ammonia, being smaller molecule, penetrates cellulose very rapidly and complexes with hydroxyl groups of cellulose after breaking hydrogen bonds in crystalline regions and increases distance between cellulose chain in

crystallites.

Ammonia

treatment results in a more rounded cotton fiber, which scatters light more, in turn resulting in a luster that is less bright

.

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Why Ammonia mercerization

? ( Contd.)

This processing makes the inside of the fiber

swell

equally

.

There

is 

less fiber-swelling

, therefore the fibers are more pliable, which allows them to bend and recover more easily when tension or stress is applied

.

The permanent-press effects are achieved without the use of cross-linking resins

.

The ammonia process was intended as a replacement for conventional mercerizing for both fabrics and in

mercerizing sewing threads

(

Prograde

process).

The

lower pH of ammonia allows safe treatment of more sensitive fibers like

linen (flax) or silk

.

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Application on

types yarns & fabrics

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Sewing Thread

Denim

Corduroy

Chambray

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Pillow Material

Jute

Linen

Cotton PET Blend

Cotton Nylon Blend

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Physical changes

Improvement in strength.

Change in cross section from bean shape to almost circular.

Change in longitudinal view convoluted to cylindrical.

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Cross section of cotton fiber

After Ammonia Mercerization

After

Mercerization

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CHEMICAL CHANGES

Formation of

cellulose-III Improvement

in moisture regain

properties (

more hydroxyl groups

)

Improvement

in dye uptake

Slide15

Absorption of ammonia in cotton fabric

1 Cross section before mercerization

2-5 Swelling process in ammonia

6 Rinsing process after swelling

7 After state

Slide16

Process parameter

Concentration of Ammonia

Time of treatment

Tension applied

Temperature

Surface tension of Ammonia

Impurities of Ammonia

Slide17

Chemicals

Ammonia

Wetting agentTemperature : -33ºc

Absorption period : 0.6 sec

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Schematic Diagram of Ammonia Mercerizing Machine

Two processes known as

PROGRADE

for

yarn

mercerizing and

SANFORSET

for woven

and knitted fabrics are widely used.

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Main Parts Of Ammonia Mercerization Machine

Ammonia Impregnation zone

Ammonia Evaporation ZoneWashing Zone

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Principle Of Ammonia Mercerization Machine

Process consist

of passing the fabric though a bath of liquid ammonia with 100% pickup for approximately 10 seconds.

Ammonia is

removed with dry heat applied by passing over blanketed, steam heated dry cans which

removes

about 90% of the ammonia which i

s recovered

by a recovery

plant

and made available for

recycling.

The

rest of the ammonia, which chemically bonded to the cellulose, was removed by light

steaming.

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Diagram

of the “Sanfor-set"

process

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Ammonia Impregnation

zone

The untreated fabric in dry condition, is passed over smoothing rolls and then around some heated dry cans. The dry cans assure an adequate level of dryness(water content less than 10%) in the fabric.

Then the fabric

is cooled by a

fan before entering

through a gas lock

to the processing

chamber

.

In the

treatment chamber, the

fabric

passes over a guide

roller

and is directed downward and around an immersion roll

disposed

in the lower portion of a liquid

pan, which

retains

liquid

ammonia

.

The liquid ammonia bath

is

at a temperature of -

33°

C.

After passing the liquid ammonia bath, fabric is directed upward to a guide roller. The fabric web advances at a rate such that its immersion in the liquid ammonia bath may be for only a fraction of a second.

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Ammonia

Impregnation

zone (Contd.)

The atmosphere within the chamber is saturated with ammonia vapor, such that the liquid ammonia does not evaporate from the impregnated fabric emerging from the bath.

The guide roll serves to smooth and apply a slight widthwise tension to the fabric before it enters the pad rollers.

After

having passed through the pad rollers , the fabric passes over a tension control roller ,to impart a desired amount of

warpwise

tension.

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Ammonia Evaporation

Zone

The

fabric passes around some guide rollers and is brought

into a

pressure contact with the surface of a heated dryer drum.

The

dryer includes a blanket which serves to both press the fabric tightly against the surface of the heated drum and to geometrically confine the fabric by frictional forces.

The

dryer drum typically may be heated by high temperature steam.

Thus

, when the fabric, saturated with liquid ammonia at -33° C, comes into contact with the heated drum surface, the ammonia is almost instantly washed off, to a level at which no further substantial reaction occurs.

Thus

, the reaction period is effectively terminated almost instantly upon contact of the fabric with the heated drum

.

In this heat treatment

some

90-95% of the ammonia is removed.

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Recovery of

ammonia

Recovery of ammonia occurs by the reaction between ammonia water and gas that is discharged. Ammonia water is to mix with air, it goes outside and is then separated through the distillation column. Ammonia is distilled then send to the storage unit finally.

In the recovery device of ammonia, there are gas vents to wash the top of the tower, to control the ammonia content, and to lower than the amount for environment protection.

Slide26

Property

Conventional

Mercerization

Hot

Mercerization

Ammonia

mercerization

Swelling

speed

Low

Fast

Very fast

Evenness

Uneven

Good

Good

Luster

Good

Good

Very good

Dye up take

Good

Not quite good

Good

Dimensional stability

Good

Good

Good

Alkaline chemical

Sodium

hydroxide

Sodium

hydroxide

Ammonia

Comparison among different mercerization process

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EFFECT OF AMMONIA MERCERIZATION

More rounded yarn structure and orientation.

Excellent form stability ( having good

Wash

&

Wear

properties)

Low shrinkage in post washing.

Increase in wrinkle resistance.

Increase in fiber elasticity.

Enhanced tear resistance as well as tensile strength.

This process add gentle, elegant luster to the fiber

.

F

ibers

keep their soft feel as no damage is done by this processing.

Highly uniform dyeing properties.

Dye uptake %

increased.

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ADVANTAGES OF AMMONIA MERCERISATION

Evenness and uniformity of swelling comparatively better.

Less pollution.

Jute and linen can be mercerized.

Safe treatment of more sensitive fibers like flax or silk.

Higher productivity.

Higher quality fabric.

Longer life after long periods of wear and repeated washing.

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DISADVANTAGES OF AMMONIA MERCERIZATION

Very costly equipments.

Non-availability of machine.

Lower color yield.

Large capital investment for NH3 recovery.

NH3 recovery problem.

Leakages cause great harm to personnel working.

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Thank You