ammonia mercerization. submitted to: dr. ummul khair fatema presented by : idname 2011-1-017shahanaz...

AMMONIA MERCERIZATIO

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Submitted To:Dr. Ummul Khair Fatema Presented By :

ID Name2011-1-017 Shahanaz Parvin

2011-1-018 Rifat Jahan

2011-1-098 Nazmun Nahar

2011-1-128 Humayra Akhter Himu

2011-1-208 Nigar Rashida

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 : Mercerizing. 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.

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

EFFECT OF MERCERIZATION ON COTTON FIBER

WHAT IS AMMONIA MERCRIZATION?

Ammonia Mercerization 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.

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.

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.

APPLICATION ON TYPES YARNS & FABRICS

Sewing Thread

Denim Corduroy Chambray

Pillow Material Jute

Linen Cotton PET Blend

Cotton Nylon Blend

PHYSICAL CHANGES

Improvement in strength.

Change in cross section from bean shape to almost circular.

Change in longitudinal view convoluted to cylindrical.

CROSS SECTION OF COTTON FIBER

After Ammonia

Mercerization

After Mercerization

CHEMICAL CHANGES

Formation of cellulose-III

Improvement in moisture regain properties (more hydroxyl groups)

Improvement in dye uptake

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

PROCESS PARAMETER

Concentration of Ammonia

Time of treatment

Tension applied

Temperature

Surface tension of Ammonia

Impurities of Ammonia

CHEMICALS

Ammonia

Wetting agent

Temperature : -33ºc

Absorption period : 0.6 sec

Schematic Diagram of Ammonia Mercerizing Machine

Two processes known as PROGRADE for yarn mercerizing and SANFORSET for woven and knitted fabrics are widely used.

Main Parts Of Ammonia Mercerization Machine

Ammonia Impregnation zoneAmmonia Evaporation ZoneWashing Zone

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 is 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.

Diagram of the “Sanfor-set" process

Ammonia Impregnation zoneThe 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.

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.

Ammonia Evaporation ZoneThe 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.

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.

Property

ConventionalMercerization

HotMercerization

Ammoniamercerization

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

EFFECT OF AMMONIA MERCERIZATION

1. More rounded yarn structure and orientation.

2. Excellent form stability ( having good Wash & Wear properties)

3. Low shrinkage in post washing.

4. Increase in wrinkle resistance.

5. Increase in fiber elasticity.

6. Enhanced tear resistance as well as tensile strength.

7. This process add gentle, elegant luster to the fiber.

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

9. Highly uniform dyeing properties.

10.Dye uptake % increased.

ADVANTAGES OF AMMONIA MERCERISATION

1. Evenness and uniformity of swelling comparatively better.

2. Less pollution.

3. Jute and linen can be mercerized.

4. Safe treatment of more sensitive fibers like flax or silk.

5. Higher productivity.

6. Higher quality fabric.

7. Longer life after long periods of wear and repeated washing.

DISADVANTAGES OF AMMONIA MERCERIZATION

1. Very costly equipments.

2. Non-availability of machine.

3. Lower color yield.

4. Large capital investment for NH3 recovery.

5. NH3 recovery problem.

6. Leakages cause great harm to personnel working.

Thank You