36918570-MERCERIZATION

5/24/2018 36918570-MERCERIZATION

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MERCERIZATION

By

Prof.K.B.Krishna Kumar


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o s a u a

PRESENTATION DETAILS

This presentation has been devided into:

INTRODUCTION

ADVANTAGES OF MERCERIZATION

CLASSIFICATION OF MERCERIZATION

WHAT HAPPENS DURING MERCERIZATION

PARAMETERS OF MERCERIZATION

EFFECT OF CONCENTRATION EFFECT OF DRYING

EFFECT OF TEPARATURE

EFFECT OF TENSION

TEMPARATURE VS SHRINKAGE

SHRINKAGE

EFFECTS ON LUSTRE

EFFECTS ON DYE ABSORPTION EFFECTS ON MOISTURE REGAIN


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PRESENTATION DETAILS contd..

WHAT HAPPENS AFTER MERCERIZATION ?

WHEN MERCERIZATION CAN BE CARRIED OUT ?

CONDITIONS OF MERCERIZATION

CHANGES IN THE PROPERTIES OF CELLULOSE DUE TO

MERCERIZATION

MERCERIZING MACHINES AND PROCESS

HANK MERCERIZATION

CHEESE MERCERIZATION

SINGLE END MERCERIZATION


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PRESENTATION DETAILS contd

TOW MERCERIZATION

WARP MERCERIZATION

CHAINLESS MERCERIZATION

CHAIN MERCERIZATION

BATCH MERCERIZATION ADVANTAGES & DISADVANTAGES OF CHAIN

MERCERIZATION

CHAIN AND CHAINLES MERCERIZINF MACHINES &THEIR COMBINATION

COMPARISION OF CHAIN AND CHAINLESS M/CS

* IMPORTENCE OF WASHING


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PRESENTATION DETAILS contd.

ALTERNATIVE SOURCES TO CAUSTIC SODA

ALTERNATIVE SOURCES TO CAUSTIC- DISADVANTAGES

WHY HOT MERCERIZATION

ADVANTAGES OF HOT MERCERIZATION

DISADVANTAGES OF HOT MERCERIZATION

HOT MERCERIZATION PROCESS

COMPARISION OF HOT AND COLD MERCERIZATION

COMBINED DESIZING, SCOURING, MERCERIZING

LIQUID AMMONIA MERCERIZATION

ADVANTAGES OF LIQUID AMMONIA MERCERIZATION

DISADVANTAGES OF LIQUID AMMONIA MERCERIZATION

MERCERIZATION OF KNIT GOODS

MERCERIZATION OF OPEN WIDTH KNIT FABRICS

CONCLUSIONS


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INTRODUCTION

Alakali treatments of COTTON has been foundto be very advantageous to the processor.

A number of alkali treatments like Desizing,

Scouring, Caustic padding , Causticization,Mercerization etc. are being carried out onCOTTON using NaOH by the processor.

The effectiveness of these treatments depends

on the penetration of the NaOH. However, theviscosity of NaOH poses, the problem ofpenetration to the processor.


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INTRODUCTION cntd

Merecer observed that treatment

OF COTTON with NaOH

increases the Dye Exhaustion andfixation and Horace observed that

treatment with NaOH bypreventing shrinkage the fabric

becomes more lustrous.


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INTRODUCTION contd

Ofall the treatments, treatment with NaOH of a

specific concentration, for a specific period under

control is known as Mercerization

is of considerable importance, wherein the

concentration is 48-52Tw and the time is 30-40 sec.either under control or without control commonly

referred as

Tension Mercerization ( treatment under tension/

Control)

Slack mercerization ( Treatment without tension/

Control)


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Advantages of Mercerization

The mercerization has the following advantages:

Improving luster

Obtaining a silky look

Improving the Tensile strength

Retaining a greater proportion of tensile strength aftereasy care finishing

Obtaining improved Dimensional Stability


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Advantages of Mercerization contd

Improving Elasticity and obtaining stretchproperty

Increasing Uniformity of dyeing

Improving colour yield

Improving % dye exhaustion

improving % dye fixation


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Advantages of Mercerization contd

Improving Moisture absorption

Improving easy care finishing properties

Improvement in CRA

Ability to cover & removal of Immature ( dead)fibres

Improvement in cover factor


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CLASSIFICATION OF MERCERIZATION PROCESS

contd 2. Classification according to the marcerizing conditions

a)Water contentDry mercerizationWet mercerization

b)Tension

Fixed-length mercerizationTension mercerizationTensionless mercerization

c)Alkaline concentrationLow-concentration alkaline mercerization

High-concentration alkaline mercerizationTwo-step mercerization

d)TemperatureAmbient-temperature mercerizationHigh-temperature mercerization

Low-temperature mercerization


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CLASSIFICATION OF MERCERIZATION PROCESS

contd

3. Classification according to timing

a. Gray mercerizationb. Pre-dyeing mercerizationc. Post-dyeing mercerization

4. Classification according to the number of treatments

Single mercerizationDouble mercerization

5. Classification according to the type of alkali useda. Caustic soda mercerization

b. Ammonia mercerization

6. Othera. Alkali pad-dry methodb. Alkali pad-steam method


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WHAT HAPPENS TO COTTON DURING

MERCERIZATION ?

Exothermic reaction and heat is libarated

Swelling of the fibre takes place

Cellulosic chains gets rearranged and become parallel

Convolutions disappear

Horizontal cross sectional view shows that it becomes circular

Shrinkage takes place


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WHAT HAPPENS TO COTTON DURING

MERCERIZATION ? Contd..

Inter chain forces are weakened ( due to the presenceof solvated dipole hydrates )

Change of crystal lattice from Cellulose I to II

Modification of Crystalline net work ( The fibrils do notloose their identity but change in dimension andorientation )

The most important effect of mercerization on thefine structure of cellulose fibre consists of changingthe crystal lattice from cellulose I to II


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WHAT ARE THE PARAMETERS OF

MERCERIZATION ?

Concentration of NaOH

Time of Treatment

Tension applied

Temperature

Impurities of NaOH


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PARAMETERS CONTD

Effect of Concentration

After swelling reaches its greatest point, NaOH

thoroughly penetrates the interior of the micelle, and a

reaction between the alkali and the micelle occurs,

completing the generation of alkali cellulose I.

From 18-22B, the range displaying the greatest

degree of swelling, to around 24B, the cotton hair

first contracts momentarily, and then swells again, and

at 24B or above a second swelling peak was

observed. These observations cannot be disregarded

as baseless occurrences.


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PARAMETERS CONTD

The longitudinal changes of a single scoured cotton hair in a single caustic soda

solution (tensile force: 50mg)(Williams, Barratt and Parker)


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PARAMETERS CONTD

Effect of Concentraton on Swelling

According to the behavior observed for woven fabric

and fibers of raw cotton exposed to alkali, woven

fabric only displays around half the degree of swelling

displayed by fibers if both are treated with the sameconcentration of alkaline solution, but no such

difference exists between their respective degrees of

alkali absorption.

The concentration at which yarn showed the

greatest degree of swelling was determined to

be 20% NaOH (26.5B).


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PARAMETERS CONTD

Effect of Concentraton on Swelling contd..

The absorption of alkali solution by fibers & fabrics


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PARAMETERS CONTD

Effect of Concentraton on Swellingcontd..

The amount of NaOH absorbed by raw cotton


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Cotton hair under physical restraint, that is, made into a yarn or a woven fabricthat restrains the hair's freedom due to twisting and to crossing of twisted yarn,

when treated with an alkali, displays different behavior because the shrinking

and swelling displayed originally cannot occur due to the constraining forces.

As an illustration reported by H. Flecken (Textil Praxis, Juni, 365, 1970) shows

that even for the same type of yarn, the behavior of single, double and triple

yarns display differences, as does the shrinkage of woven fabric and hairs.

Cotton hair under physical restraint, when converted into a yarn or a woven

fabric restrains the hair's freedom due to twisting and to crossing of twisted

yarn, when treated with an alkali, displays different behavior because theshrinking and swelling displayed originally cannot occur due to the constraining

forces.

It is reported by H. Flecken that even for the same type of yarn, the behavior

of single, double and triple yarns display differences, as does the shrinkage ofwoven fabric and hairs

PARAMETERS OF MERCERIZATION CONTD.

The concentration of NaOH versus the shrinkage of cotton hairs and cotton fabrics


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The concentration of NaOH versus the shrinkage of cotton hairsand cotton fabrics


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EFFECT OF DRYING- DYE ABSORPTION

Fibers in their wet state at the conclusion ofmercerization have a very high degree of swelling, andhave large internal air gaps. But if the fibers are dried,these gaps will contract as the water evaporates. The

final fixed sizes of the gaps inside the fibers arealtered by different temperature and tension conditionsduring the drying.

in comparison to untreated fiber, absorption of dyestuffis twice as high after mercerization, and 2.4 times as

high after tensionless mercerization. Furthermore, theabsorption of dyestuff is reduced by one third afternatural drying in air, and by nearly one half after dryingat 110C in comparison with non-dried fiber, whichsuggests the contraction of the air gaps inside thefiber.


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a) Alkaline concentration versus the absorption of dyestuff

b)Tension during mercerization versus the absorption of dyestuff


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PARAMETERS OF MERCERIZATION CONTD


Drying conditions after mercerization versus the

absorption of dyestuff


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EFFECT OF DRYING- on CRYSTTALINITY

According to L.E. Hessler (Tex. Res. J., 24,p.822, 1954), the level of crystallization of

cotton before mercerization was 89%, while

after mercerization it was 64%, and that ofviscose rayon was 45%. The results were

particularly severe in cellulose having a low

level of crystallization. Avoid drying on cylinders after mercerization.

Dry at lowest possible temparature.


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EFFECT OF DRYING -contd

It can be concluded that the size of the air gaps

in the cellulose's micelles, that is, the fiber's

internal volumetric capacity, is altered by the

tension and temperature conditions during therinsing and drying at the end of the

mercerization process which, in addition to

altering the hygroscopic characteristics andproducing variations in the absorption and

reactivity of the dye, also significantly influence

the hand of the fabric.


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The heat generated by mercerization

The heat generation due to the reaction between

the cellulose and the alkali, like heat generation inother typical chemical reactions, is not simple, andvaries according to the concentration of the alkaliand other factors.

The results of Neal (J.T.I. 20, 1929, p.373), whichcan be considered to be relatively reliable.

According to these results, from a concentration ofaround 120g/L NaOH, or about 15-16B, the

reaction heat increases sharply, and from around240g/L, or 26B, the reaction heat increases inmore or less constant proportion with increases inconcentration.


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The heat generated by mercerization contd..


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The heat generated by mercerization- contd..

While different researchers recorded differentresults for this heat generation, it is in the range of2.6-4 Cal/g of cotton.

In contrast to this, with an increase in theconcentration of the alkali solution of 1M in therange from 15-16B to 19-20B for which theswelling was greatest, the heat generation was8.93 Cal/g, and from a concentration of around22B, at which the production of alkali cellulose Iwas more or less complete, the rate of increase ofgenerated heat was 3.40 Cal/g cotton/M NaOH.

Above 42B, this became 3.0 Cal/g cotton/M

NaOH.


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The heat generated by mercerization-contd

While the time required for the completion of this heatgeneration for concentrations below about 34-35B wasless than five minutes, above 42B it was ten minutes, andabove 22M NaOH, 100 minutes was required, the reaction

needing a very long period of time to complete.

At concentrations below 22B, significant differences inbehavior with regards to heat generation are displayedbetween fibers that have been mercerized once before and

fibers that have not been mercerized at all. Items that havebeen mercerized once before display the absorption of alkaliand generation of heat even in alkali solutions of lowconcentration.

Th t t d t ti


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The temperature and concentration

for the mercerization of cotton

Sisson analyzed a cotton yarn treated with a

wide range of alkaline concentrations and

processing temperatures with X-ray diffraction,

divided the results into the three divisions ofcomplete mercerization, partial mercerization

and un-mercerized and created a chart showing

the relationship between the alkalineconcentration and the temperature.



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The temperature and concentrationfor the mercerization of cotton

contd..


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for the mercerization of cotton contd

According to these results, regardless of theincrease in the concentration of the alkali,above about 60C, complete mercerization

does not take place. The concentration ofaround 30B in mercerization at roomtemperature, that is, around 20C, is in themiddle of the chart for complete

mercerization, and this, interestingly, is fairlyconsistent with stable conditions determinedby experience in practical mercerization andwith the results of all researchers.


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The shrinkage of yarn in caustic

soda solutions of different temperatures and concentrations

Beltzer in 1902, who investigated the

relationship between shrinkage and theeffects of temperature and alkaline

concentration in the mercerization of

cotton yarn, and the results show that theconcentration of 20B represents a line

beyond which behavior during

mercerization changes.

The shrinkage of yarn in caustic


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g ysoda solutions of different temperatures and

concentrations


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The shrinkage of cotton yarn in

NaOH

Similarly, the results of Birtwell,

Chblenens et al (J.T.I., 21, 1930, p.85)

show that temperature has its greatest

influence on the shrinkage of cotton

yarn at concentrations of 3N NaOH,

(approx. 16B), and above 4N (approx.20B), that influence diminishes.


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The shrinkage of cotton yarn in

NaOH


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Temperature versus shrinkage rate

in the mercerization of cotton yarn contd

H. Flecken (Tex. Praxis., Juni, 365, 1970);

measured the shrinkage of cotton yarn at

concentrations of 30B and 38B for

temperatures from 0C to 40C, and reportedvery small variations for temperatures in the

range of 10-30C at a concentration of 30B,

and this result can also be found in the centerof Sisson's mercerization chart.

T t h i k t


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Temperature versus shrinkage rate

in the mercerization of cotton yarn contd


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The relationship between the degree of stretching of a cotton hair during

mercerization and the resulting luster.



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It is important to bear in mind that tension

plays a key role which brings out not only

luster, but also increases the Tenacity and

Youngs modulus,however the Elongation atbreak decreases.

As the concentration of NaOH increases from150 to 350 gpl similar results as in the case of

tension applied can be seen..


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EFFECT OF TENSION The luster of cotton fibers is decided by the ratio between the long and short

axes of the cross section of the cellulose air, and it improves as the crosssection becomes more circular. (See Fig. 19)

The axial ratio of the cross-section ofsingle cotton fibers and their luster


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EFFECT OF TENSION contd..

While mercerization can greatly improve luster, it

cannot make up for deficiencies in the luster of the

raw cotton itself, and in order to produce products

of superior luster, primary considerations relate tothe choice of raw cotton, the twisting and

manufacture of the cotton yarn and the structure of

the fabric. While changes in the mercerization

process do influence the improvement of luster toa certain extent, any effect that surpasses the

more basic variations cannot be expected.



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Fibre shrinkage in width and lengthdirection is inversely proportional tothe tension applied.

It is important to note that efficiency ofmercerization is not dependent on swellingof cotton in alkali since swelling value ofcotton is the least above 150 gpl conc. OfNaOH.


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WHAT HAPPENS TO COTTON AFTER

MERCERIZATION ?

1. TS increases

2. In case of fabrics reed and pick increases

3. Dye taken up by the fiber increases

4. Luster increases

5. Stiffness increases

6. MR increases

7. Soiling decreases

8. % Exhaustion increases



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At Grey stage ( with the addition of alkali stable,low foaming, efficient Wetting agent)

After Desizing

After Scouring

After Scouring and bleaching

Every stage of mercerizing has its ownadvantages and dis-advantages. It is suggestedto carry out Mercerizing preferably after Scouringto get best of the best of the process.


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CONDITIONS OF MERCERIZATION

Application of NaOH solution around 55-60TW( 31-35% ) at aTemperature of 15 to 18C.

A dwell period of 55 secon an average, to permit diffusion ofalkali into the fibre.

Warp tension during alkali treatment and stretching the weft (

width ) of the fabric during washing to prevent shrinkage.

Finally washing off of the traces of alkali from the treated fibres.

CONDITIONS OF MERCERIZATION td


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CONDITIONS OF MERCERIZATION contd

Investigations reveal that with an impregnationconcentration of 2830Be or 250-300 Gpl of

100% NaOH or 215-240 Gpk (grams of 100%

NaOH per Kg), there is no significant increaseof Iodine absorption or dyestuff uptake.

This means optimum mercerization isaccomplished with a concentration of 220-240

grams of 100% NaOH per Kg of cloth on the

fabric.


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MERCERIZATION

Cellulose undergoes

Chemical

Physico-Chemical

Structural

modifications on treatment with NaOH of

Mercerizing strength


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MERCERIZATION contd.

Chemical reactionslead to the formationof Alkali Cellulose.

Physical reactionslead to a change in

arrangement of units of cellulose. The surface of the of the nearly cylindrical

cotton fibre after mercerizing reflects lightmore evenlyto all sides than the kidneyshaped cotton fibre and the fibre surfacebecomes more lustrous.


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MERCERIZATION contd..

Mercerization reduces the axial ratio and

increase the light scattering within the fibre (

transparency ) and thus increases the luster.

Here it is important to bear in mind that shortfibres on the surface decreases the luster

which can avoided by singeing. It is also

important to note that increase in luster can

be seen from 180 gpl conc. Of NaOH to amaximum of 260-300 gpl NaOH conc. and

then decreases slightly


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MERCERIZATION contd

Swelling and shrinkage are more when

there is no tension in the fibre, but the

alteration in cross sectioncaused by

swelling is more when mercerization iscarried out under tension.

Under optimum conditionseach cotton

fibre may contract nearly 9% in lengthand swell nearly 150%.


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MERCERIZATION contd.

Swellingof the cotton fibre has also has a dis-advantage.

The fibre becomes more compact in its swollencondition.

The compacting further diminishes the furtherpenetration of Caustic.Soda into the fibre .

In other words penetration slows down and the

effect of mercerization in the fibres core islower than on its surface giving rise to non-uniformity of mercerizing.



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MERCERIZATION contd..

Mercerization also affects the size ofcrystallitesand orientation of crystalline

region and the extent of orientation depends on

the tension during mercerization.

Mercerization, both slack and with tension,

increases the strength uniformity along the fibrelength. The increase in TS is due to the

elimination of weakest points in the fibre.


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MERCERIZATION contd

Mercerized fibre with tension shows greatergain in strength than that of without tension.Mercerization increases the cohesion betweenindividual cotton hairs and this closerembedding of the hairs in the yarn not onlyincreases the strength but makes it moreuniform in strength and less in diameter.

In practice, the improvements in strength arenoticed mostly on mercerized yarn only, withfabric the major effect is only on the surface,along with dye fixation.


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INFLUENCE OF ALKALI CONCENTRATION ON CRYSTALLINE

STRUCTURE

The properties of cellulose can be manipulatedwith the selection of

Proper Concentration of Alkali,

Time,

Tension and

Temperature during Mercerization.

Washing conditions

Formation of different celluloses on


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structural modification

1. At 12-19% ( by wt) NaOH conc. SodaCellulose I formed

2. At 20-45% ( by wt ) NaOH conc. Soda Cellulose IIformed

3. By drying Soda Cellulose I Soda Cellulose IIIformed

4. At 20-25% (by wt) NaOH conc.And above 30C Soda Cellulose II and III formed

5.At 40-45% conc. Of NaOh

Between -10 and 20C Soda Cellulose V formed

Formation of different celluloses on


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structural modification

Cellulose I content and total crystallinityindex decreases as the temperature of

mercerization increases.

Cellulose II follows an opposite course due

to the better penetration of NaOH hydrates.

Cellulose III , IV and X can also be obtained

on treatment of cotton with Ammonia at -

35C , hot Glycerene and Phosphoric acid.

M i i M hi


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Mercerizing Machines.

Genarally a mercerizing machine consists of four sections which willhave different tasks according to the process technique.

Mercerizing Section : Impregnation with Caustic

Intermediate sqeezing aggregate : Dividing of mercerizing sectionagainst stabilizing section.

Here itself the required time factor is taken care to allow the Caustic topenetrate and mercerizing to take place.

Stabilising Section : water treatment and thinning down concentration

of the lye. At this zone structural modifications will take place.

Intermediate sqeezing aggregate : Dividing of stabilising sectionagainst washing section

Washing section : Washing off the alkali and nuetralisation


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Hank Mercerizing

Yarn mercerizing generally entails rolling a 54-inch

long (the length of one loop) hank weighing about500g a number of times between two adjustablerollers. The yarn is moved by the turning of therollers, with penetration of the alkali, application oftension and rinsing occurring automatically.

In this, one cycle takes about three to five minutes,and four to eight kilograms can be treated at onetime. In the latest machines, all operations are

automated, including control of the alkaline solution'sconcentration and temperature and the addition andrecovery of the alkali, along with application oftension on the yarn and rinsing.

Hank Mercerizing contd


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Hank Mercerizing contd.

An advantage of hank mercerization is that during

the yarn's absorption of the alkali, treatment can becarried out without tension, and so the alkali solution

is able to penetrate the inside of the yarn sufficiently,

and after the fibers have swelled sufficiently, any

level of tension can be applied and the yarn rinsed

for removal of the alkali. This allows the production

of goods with satisfactory mercerization effects.

Uneven mercerizing due to uneven tension is an

unavoidable problem in current methods of

mercerization.

H k M i i td


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Hank Mercerizing contd..

yarn that has been hank mercerized and then dyed forfinishing into solid-color fabrics can result in a barreeffect.

Hank mercerized pre-dyed yarn is mainly used forproducts with narrow stripes or a checkered designwhen barre is not noticeable.

Another problem in hank mercerization is thatconventional rinsing after mercerization is insufficient,and without neutralization through separate rinsingwith hot water, the remaining alkali can cause

problems.



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Carrying out mercerization, scouring, bleaching, and, in somecases, dyeing, along with oiling or sizing, with the yarn incheese form results in a major rationalization, which can raiseproductivity and reduce costs.

However, mercerization in cheese form can only be expected

to achieve half-mercerization, and not the same degree ofevenness as hank mercerization or other types ofmercerization.

One problem is how to limit the difference in shrinkagebetween the inside and the outside of the cheese. Important

factors in this are the adjustment of the twisting and thedensity of the winding of the yarn, the size of the take-up tube,the thickness of the layers during the winding, and the alkaliconcentration and temperature during the treatment.

SINGLE END MERCERIZATION


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SINGLE END- MERCERIZATION

This method, also called, cone-to-cone, or cheese-to-cheese, involves taking up yarn into a cheese or

cone shape, and, with one machine per cone,

conducting alkali penetration, rinsing (with hot and

cold water), neutralization, rinsing again, and dryingin consecutive order with the correct scheduling, and

then taking up into a cheese or cone form.

The yarn speed in this being approximately

450m/min, the productivity per machine is low, and

the equipment costs are high, but because the

sequence is automated, it only requires a very small

number of staff.

SINGLE END MERCERIZATION td


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SINGLE END- MERCERIZATION contd..

The mechanism for conducting mercerization with these machines involves three

revolving rollers: two squeezing rollers which are pressed tightly together and a thirdroller placed, at a certain distance, more or less parallel to these two. Yarn is lined upin parallel from one end to the other of the third roller, which is removed from the nipspace of the two squeezing rollers, and moved in a spiral perpendicular to the roller,during which time the alkali penetrates, tension is applied and rinsing (both with hotand cold water) and neutralization occur.

A problem in this form of mercerization is the relative difficulty of controlling thetension on the yarn as it is introduced, and differences in the level of tension betweenmachines and between cheeses or cones can occur easily and lead to patchydyeing.

Other problems relate to yarn breakage, yarn overlap, and yarn skewing.

In general, this method of treatment requires two-fold yarn with a yarn count lessthan 60, and it is unsuitable for the treatment of yarn with fine yarn counts higherthan this. In general, this method of treatment requires two-fold yarn with a yarncount less than 60, and it is unsuitable for the treatment of yarn with fine yarn countshigher than this.

TOW MERCERIZATION


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TOW MERCERIZATION Normally, 400 or so yarns are wrapped around a beam or a ball with a warper and 8

to 10 of these beams or balls are set in a stand. Yarn is unreeled from the balls orthe beams at the same time and lined up in ropes made with light twisting, which aremercerized continuously in a manner similar to that of roller mercerization of fabric.

The equipment used in this method looks like a row of soapers, and each treatmentbath is driven separately, tension on the yarn is controlled, and the shrinkage due toswelling during absorption of the alkali and the level of strain after this can be

adjusted freely.

This type of equipment can produce a large amount of yarn of consistent quality andso this method is suitable for the production of mercerized yarn for use in knits, andthe treatment of fine yarn that is two-fold yarn with a yarn count of around 100-110 isalso possible.

One problem concerning the type of equipment used is the separation of the yarns inthe rope after it is dried at the conclusion of the mercerization process, and the wayin which the yarns are unwound is very important for ensuring the smoothness of theoperation.

WARP MERCERIZATION


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WARP MERCERIZATION

While tow mercerization involves the treatment of alot of yarn lined up in rope-form, in warpmercerization yarn is wound onto a beam and fedinto a machine with the same system as in a slasher-sizing machine. Mercerization takes place with

sheets of separate threads, and the machinery usedcan be exactly the same as that in tow mercerization.

Thus, in the warp-beam method and the tow method,only the handling is different.

problem, however, is that during treatment thebreakage of a single thread can lead to majordifficulties, and so if the yarn is not of very good evenquality, industrial implementation of this method isdifficult.

Chainless Mercerizing Machine


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Chainless Mercerizing Machine

This method of mercerization involves running fabric through a

number of rollers without the use of a clip stenter is also calledroller mercerization.

The machine used has a number of stainless rollers, orstainless and rubber rollers, of a relatively-large diameter tieredzigzag in close contact to each other inside a long trough, withthe lower tier designed to submerge in alkaline solution formercerization.

The absorption of alkaline solution and fabric swelling takeplace as fabric sequentially glides through the surface of these

rollers, and, although this movement from roller to roller in closecontact with them reduces the widthwise contraction to aminimum, the resulting fabric expansion remains within alimited range, thus displaying the mechanism of mercerizationat fixed length.

Chainless Mercerizing Machine contd


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Chainless Mercerizing Machine contd.

A similar device is used for the removal of most alkalifollowing this initial stage of alkali penetration and

fabric swelling, and an open-width soaping machine

for further removal and neutralization.

Therefore, the machinery required is extremely

concise and the cost is low, in comparison with the

chain mercerization. However, this method is subject

to a considerable number of constraints due toinflexible widthwise control over fabric depending on

the kind and use.

Chainless Mercerizing Machine contd


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Chainless Mercerizing Machine contd..

Mercerizing of Pet and cotton blends poses a littleproblem to the processor with respect toDimensional stability.

This problem looks larger when the PET content is

much low since the dimensional stability to thefabrics of higher PET content can be aceived byHeat setting which is not the case with lowerpolyester

Roller mercerization is not at all suitable, particularlyfor these sheer plain weaves. This type of machine iswidely in use in India, Europe, in contrast to itsscarce usage in Japan.

Chain Mercerizing Machine


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Chain Mercerizing Machine

In order to make up for the shortcomings of the roller

mercerizing machine, a clip stenter is used for post-mercerization treatment, in which a widthwise tension isapplied.

The critical alkali content is showered off ( removed) from the

fabric during the passage of the fabric through the stenter,followed by thorough alkali removal and neutralization using anopen-width washing machine.

In practice a heavy padding mangle is used for the applicationof alkaline solutionusing a 2 dip, 2 nip mangle, while allowing

the fabric to have sufficient time for penetration and swelling ofthe cellulose in a timing cylinder, instead of undergoing anoperation using so many rollers and so much solution as inroller/chainless mercerization, to ensure reduced use of thealkali.

Chain Mercerizing Machine contd


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Chain Mercerizing Machine contd. Since the chain mercerizing machine operates at an

extremely high speed of 120-200m/min, a clip stenteris commonly used after two consecutive treatments ofalkali application/penetration.

It is a device of considerable size, capable of holding,while maintaining a widthwise tension, 70-90m fabricat a speed of 120m/min., or 117-150m at 200/m, sothat sufficient time is allowed, approximately 35seconds for polyester/cotton blends, and 45 secondsfor 100% cotton, between the initial application of

alkali solution and the subsequent start of showeringthe alkali of the fabric.

Furthermore, thorough removal of the alkali is ensuredin this stenter stage, through repeated showering oflow concentrated alkali and vacuum treatment.



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Chain Mercerizing Machine contd.. The efficiency of the vacuum treatment will be most

influential in the removal of alkali, especially in casesof using heavy cotton weaves, deficiencies in alkaliremoval makes the showering, even in an increasedamount, an ineffective flow over the fabric surface andallows the fabric to be released from the stenter while

still immature, resulting not only in incomplete settingof the widthwise dimension but also in fluctuations inthe dyeing stages that follow.

Moreover, in the case of sheer cotton weaves,

sufficient application of alkali solution will be important,since the relationship between controls over tensilestrength for the obviation of crease production duringthe timing cylinder stage, controls over the fabric widthon the stenter and the amount of alkaline solution

required is extremely delicate.



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Considering the points mentioned above, the

performance of chain mercerizing machinesdeveloped to date seems hardly satisfactory.

The removal of the remaining alkali after thestenter stage barely comes into question in

terms of the resulting mercerization effect,

however, a crucial watershed will be whetherthe remaining alkali can be reduced to less than

3B before the fabric leaves the stenter.

BATCH MERCERIZATION


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In this method, an alkaline solution is padded onto fabric whichis then rolled up, and when padding is completed the alkali is

removed through continuous cold rinsing. Although the use of the method is not common in Japan, a

certain degree of application, including in knits, can be found inin India & Western Europe.

Despite costs for facilities being remarkably low, it is not aninteresting method except for some special cases, as qualitymanagement and productivity remain problematic.

Still, for the growing cases of carrying out alkali reduction for

the polyester side of cotton/polyester blends to achieve both themercerization of cotton and the alkali reduction of polyester in asingle treatment, the application of this cold batch method isparticularly interesting as a device that can combine the twoseparate stages which would otherwise raise facility problems.

BATCH MERCERIZATION MACHINE


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BATCH MERCERIZATION MACHINE

MERCERIZATION UNDER TENSION


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MERCERIZATION UNDER TENSION


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DISADVANTAGES OF CHAIN MERCERIZING

The inherent disadvantage of chainmercerizing is; as the force for

keeping the material under tensionacts mainly on the outer edges andthe line of force diminishes

towards the middle, a greaterelongation takes place at the edgesthan at the middle of the fabric.

DISADVANTAGES OF CHAIN MERCERIZINGcontd


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contd..

The warp density, threads per cm areuniform before stentering and afterstentering it is less at the edges than at themiddle of the fabric.

It is also note worthy to remember that thecontrol over shrinkage in warp way is

better when compared with weft way.

In other words weft tension control isstandard and not satisfactory.

Ch i & Ch i l d bi ti hi


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Chain & Chainless and combination machines

BENNIGERS CHAIN & CHAINLESS COMBINATION


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BENNIGER S CHAIN & CHAINLESS COMBINATION

MACHINERY

COMPARISION OF CHAIN CHAINLESS MACHINES


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COMPARISION OF CHAIN, CHAINLESS MACHINES

IMPORTENCE OF WASHING


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IMPORTENCE OF WASHING

Many of the processors do not attach muchimportence to washing after mercerization.

In fact it is very important and as important asmercerizing itself.

The reorientation of the fibre takes place only at this

stage.

Effective and efficient washing only results in thestrength gains, increased colour yield etc.

Washing


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Washing

WASHING


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WASHING


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ALTERNATIVE SOURCES TO CAUSTIC


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Among the kinds of alkali with which the same kind ofeffect as mercerization is observed through bonding

itself with cellulose fiber and making it swell, apart

from caustic soda, lithium hydroxide and caustic

potash are known.

What is notable is that, with lithium hydroxide, an

extremely high level of swelling can be observed at a

concentration one half that of caustic soda and, as forcaustic potash, that the effect of mercerization can be

attained without causing damage in rayon fiber, its

action being more moderate than caustic soda.



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contd..

Other than inorganic alkalis, there are also organic amines,quaternary ammonium bases and ammonia referred to asammonia mercerization.

Although no effect of mercerization is observed when ammoniais used in a solution or in its gas state, when it is allowed to act

on cellulosic fiber while in a liquid form the swelling can becompleted within an extremely short time span. Mercerizationeffects will result through applying tension to the swollen fiberand removing alkali from it.

Because the surface tension of liquid ammonia at the ambient

temperature is 25.95dyn cm-1, which is smaller than one thirdof around 90dyn cm-1 in caustic soda mercerization, its wettingand penetrating properties are so extremely good that completepenetration is possible with a half to two thirds of a second ofsoaking, and the swelling of the cellulose within a few to 15seconds.



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-disadvantages

As far as the use of Lithium hydroxide and caustic potash areconcerned, with the cost of both chemicals being particularlyhigh compared to caustic soda, cases of their application arescarce in contrast to the almost exclusive use of caustic soda.

Moreover, this tendency is expected to remain unchanged fora long time to come.

When ammonia-mercerized products are compared to theiralkali-mercerized counterparts, the former is said to be

considerably inferior to the latter in the degree of improvementin dyestuff absorption and insufficient in luster, but superior inthe degree of improvement in strength and the durability ofdimension stability, as well as in maintaining cottons softhand.

WHY HOT MERCERIZATION ?


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Due to rapid and extensive swelling of cotton during

their impregnation with cold NaOH, the structure iscompacted at the surface of the mercerized goods.

This makes further penetration of NaOH difficult andalmost impossible.

The result is lack of uniformity.

Mercerization at elevated temperatures to avoid

lower swelling offer some advantages, which is

known as HOT MERCERISATION.


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HOT MERCERIZATION


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HOT MERCERIZATION

ADVANTAGES OF HOT MERCERISATION


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Higher Degree of penetration

Uniformity

Higher productivity

Desired effect is achieved rapidly

Contact time between fabric and NaOH is reduced by 50%

When the fabric is impregnated in hot NaOH the fabricbecomes highly plastic and less elastic and can bestretched to greater extent.

ADVANTAGES OF HOT MERCERISATION contd


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ADVANTAGES OF HOT MERCERISATION contd..

Higher Tensile strength can be anticipated. ( if

stretching takes place while cooling )

Higher degree of Luster can be anticipated ( if

streaching takes place while cooling )

Improved dye exhaustion

Improved Colour Yield / dye-uptake

Improvement in Easy-care finishing property.


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DIS- ADVANTAGES OF HOT MERCERISATION


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1. Lower swelling

2. Conversion of Crystalline structure from CelluloseI to II is retarded

3. Cross sectional view reveals a skin-coreappearance

4. Higher energy consumption

5. Costlier

THEN


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HOW TO DO HOT MERCERIZATION?

A reasonable approach is to usehot caustic for better penetration

and allow the impregnatedmaterial to cool to an adequate

temperature in order to have good

swelling Known as TWO STEP

PROCEES


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TWO STEP PROCEES

STEP 1 : Saturation of the cotton material withNaOH, preferably under relaxed conditions, at a

temperature between 50oC and boiling temperature

of NaOH. The immersion time ranges from 4-60 sec.

STEP 2: Controlled hot stretching following thesaturation and cooling of the stretched material to

less than 25oC.

Tension controlled washing to a NaOH concentration

of 60 gpl ( Stabilization), followed by final washing

under normal conditions.

ANOTHER METHOD


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In another possible method of hotmercerizationconsists of wet-on-wet

impregnation of the fabric immediately after

washing at 95oC and a subsequent hotsqueezing with high speed steam injection.

The heated fabric is impregnated with NaOH

solution at 30o

C in the first step and at 20o

Cin the second step.

Thereafter the stabilization sequence is

normally carried out.

HOW IS IT POSSIBLE ?


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HOW IS IT POSSIBLE ?

The above best

results are due to;

Impregnation with hot

alkali of 250-300 gpl

concentration leads tothe formation of only

Soda cellulose I.

The transformation of

soda cellulose I to Vtakes place only

during cooling step.

While hot mercerizationappears to be

advantages, it is

important to remember

that cotton fibers

impregnated with Conc.

Alkali solution are

subject to AKKALI

DEGRADATION ANDTHIS WILL BE HIGHER

IN PRESENCE OF AIR

AND TEMPARATURE.

HOT MERCERIZING MACHINE


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HOT MERCERIZING - FEED SIDE VIEW


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Comparison of Hot and Cold Mercerization


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processes

COMBINED SCOURING AND MERCERISATION ?


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Yes, it is possible. Hot mercerization can permit an elimination of scouring or

rather simplification or in other words combined process ofscouring and mercerization, which can be carried out underthe following conditions;

Hot saturation stage with concentrated alkali.

Steaming process immediately after saturation, the materialbeing relaxed or stretched.

The time of steaming may be of the order of 10 min atatmospheric pressure or even can be reduced to 5 sec underpressure which is often called flash scour step in pressurechamber at 130oC - 140oC .

COMBINED DESIZING , SCOURING AND MERCERIZATION

contd..


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contd..

Cooling step and mercerization ( Chain or

Chainless stabilization )

Furthermore the desizing step can be

eliminated, since desizing will take placeduring this combined process.

However the danger of alkalidegradation chances increases whichshould be borne in mind while adoptingthis process.

LIQUID AMMONIA MERCERIZATION


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Treatment of cotton fibre with liquidAmmonia produces similar effect that of

Mercerization developed by Coats in 1960.

The liquid ammonia treatment is widely

accepted for yarns used in sewing

threads, and special fabrics like Denims,

Corduroys, chmbays, Pillow material,

linen, Jute and blends of cellulose with

PET and/ or Nylon.

LIQUID AMMONIA MERCERIZATION contd..


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QU O C O

Among various amines, the liquid ammoniaappears to be unique in its swelling actionon cellulose and its effect on crystalstructure.

Anhydrous liquid Ammonia being smallermolecule, penetrates cellulose rapidly andcomplexes with hydroxyl groups of

cellulose after breaking hydrogen bonds incrystalline regions and increases thedistance between cellulose chain incrystallites.

PROGRAE- SANFORSET PROCESSES


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Two processes known as PROGRAE for Yarnmercerizing and SANFORSET for Woven and Knittedfabrics are widely used.

Prograde Process

in this process the yarn is treated with liquid ammonia atits boiling point of -33oC for less than a second, followedby immersion of yarn under tension in hot water for about 0.1second to produce a 40% increase in tensile strength,improved luster etc.

The yarn after ammonia treatment is streached andammonia is removed by hot water washing.

Sanforset Process


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This process represents acombination of exclusive liquidammonia processing and controlled

compressive shrinkage to provideWash & wear characteristics with outstrength loss on cotton denims alongwith an unusual soft and supple

handle. Monforts, Germany hassuccessfully developed Sanforsettreatment range.

Sanforset Process


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After entering process The material passes over 5 pre drying cylinders

Then through a cooling station

The drying cylinders reduce the moisture content of the material below the humidity,while the cooling station takes care of the cooling of the material.

Then the material pases into actual treatment chamber whre it is impregnated with liquidammonia in a trough.

The treatment chamber is kept under slight vacuum to prevent ammonia from escaping.

Finally it is squeezed off in a padder and the ammonia is driven off in two felt calanders.

In this heat treatment 90-95% of ammonia is recovered. The rest which is chemicallybound to the cellulose is removed in a steaming compartment consisting of a pre-dwelling zone and a steaming zone. The entering and take off compartments are sealedby locks.

Sanforset Process


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An after dwelling zone and take off zone complete the process.

In this heat treatment 90-95% of ammonia is recovered. The restwhich is chemically bound to the cellulose is removed in asteaming compartment consisting of a pre-dwelling zone and asteaming zone. The entering and take off compartments are sealed

by locks.

The evoparated ammonia is led to a recovery uni where it iscompressed, cooled and liquefied to be led to a storage tank.

The chemically bound ammonia is removed from the material

separately, by dissolving in water and reusing it as chemical ormanure.

It can also be heated until it escapes and is oxidized.

However, care must be taken to see that no pollution occurs.

ADVANTAGES OF AMMONIA MERCERIZATION


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1. Less pollution

2. Higher productivity

3. Blends can be mercerized

4. Jute and linen can be mercerized

5. Even ness and uniformity of swelling is

comparatively better

ADVANTAGES OF AMMONIA MERCERIZATION contd..


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6. Comparatively softer feel.

7. Very suitable for heavy weight fabrics like denims.

8. Moisture regain is comparatively better

9. Absorbency is comparatively better.

10. Fabrics will not shrink during domestic laundering.

11. Wash & wear properties improved.

12. better CRAs if finished with resins.

DIS ADVANTAGES OF AMMONIA MERCERIZATION


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Degree of swelling is less

Higher shrinkage

Lower luster

Lower Colour yield

Very costly

Ammonia recovery even though not a problemwith the machinery developed, leakages will dogreat harm to the personnel working.

MERCERIZING OF KNITTED GOODS


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The world-wide demand for knit goods is growing. Knittedfabrics are increasingly being used for outer and underwearand are also enjoying greater acceptance amongst variousconsumers.

The very fact that knitted fabrics are being used for outerwear

explains the higher demands placed on the quality as well asthe appearance of the fabrics in order to meet the ever-changing fashion trends.

Although most processing of knitted fabrics today is carried

out in tubular form, the need to process in the open width formis becoming increasingly necessary in order to satisfy thequality requirements.

This PRESENTATION deals with the various machineconcepts being offered by Benninger for the open width

processing of knitted fabrics.

MERCERIZING OF OPEN WIDTH KNITTED GOODS CONTD..


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Knitted fabrics are extremely sensitive to tension and therefore requirecareful handling during processing.

This means that tensions exerted by the machinery on the fabric must bekept to a minimum.

This is the reason for the special design of the entry to the range whichconsists of a centre driven unwinding arrangement.

Due to its versatile design, the Benniger mercerizing machine BEN-DIMENSA masters the special structure, load and tension instability ofknitted fabrics brilliantly, so much so that even single jersey fabrics can be

run on the BEN-DIMENSA without any problems.

The machine has a specialized entry system.

The low tension and gentle treatment is also ensured by the ratio meteredAC drive. Each drive position can be adjusted up or down by 20%.

MERCERIZING OF OPEN WIDTH KNITTED GOODS CONTD


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The fabrics are impregnated in a short impregnating zone followed by dwelling in thechainless section of the machine.

A minimum tension is exerted on the fabric during transportation in the chainlessdwelling zone. The tension is controlled by the ratio metered AC drives located at thefabric transportation drums.

The dwelling zone is followed by a vertical return pin chain / stenter section, where

the fabric is uniformly stretched during the gradual removal of the caustic content.

This means an initial stabilization of the fabric already begins in the chain zonefollowed by further stabilization in the chainless section of the machine.

Fabrics stabilized in this manner are subsequently washed and neutralised in

Trikoflex washing compartment.

The combination of the chain and chainless principles ensure the dimensionalstability of the knitted fabric. The dimensions set during the processing are fixed andmemorised permanently.

The results after mercerising on the BEN -DIMENSA are representative of the finalproduct and any deviation can be corrected immediately in the stenter frame.

MERCERIZING OF OPEN WIDTH KNITTED GOODS CONTD.


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The advantages of open width mercerising of knitted fabrics

using the Ben-Dimensa are :

--Constant stitch counts

--No differences in the number of wales over width

--Controllable lengthening up to +15% and shrinkage up to -10%

Further, stitch thickening in the selvedge zones, which cause

dark selvedges leading to quality loss and even rejects, areovercome in the BEN-DIMENSA as

--the lye in the selvedge is methodically extracted

--the fabric is positively guided throughout the stabilizing zone

OPEN KNIT FABRIC


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OPEN KNIT FABRIC

MERCERIZING MACHINE

OPEN KNIT FABRIC MERCERIZING MACHINE


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Benninger has successfully been using a ratiodrive in mercerizing machines for processingknitted fabrics since 1977. This technique wasfirst realised for woven fabrics on the BEN -

DIMENSA in 1987. Since then there are more than 150

successfully operating installations. Based onthese experiences, low tension washing of

knitted fabrics posed a new challenge. Thisknowledge has been integrated intoBenningers concept for knitted goods

MERCERIZATION OFOPEN WIDTH KNITGOODS


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TUBE KNIT MERCERIZING MACHINE


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TUBE KNIT MERCERIZING MACHINE


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CONCLUSIONS


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Thanking you


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Thanking you

OPEN WIDTH KNIT FABRIC PRETREATMENT RANGE


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Although most processing of knitted fabrics today is carried out

in tubular form, the need to process in the open width form isbecoming increasingly necessary in order to satisfy the qualityrequirements. This article deals with the various machineconcepts being offered by Benninger for the open widthprocessing of knitted fabrics.

Pre-treatment of cotton and blends. In order to achieve a high quality fabric, a thorough preparation

to improve its absorbency as well as whiteness is in most casesimperative. In view of this, the pre-treatment assumes great

importance and is the primary step. A typical machine layout forpre-treatment of 100%cotton, as well as cotton and elastaneblends, is shown in picture



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Generally a range is comprised of a suitable entry

followed by a pre-washing zone. Here, spinning oils as

well as the other impurities present in the grey knitted

fabric are thoroughly washed out and removed.

Subsequent to the pre-washing zone, impregnation ofthe fabric with scouring and bleaching chemicals takes

place. Thereafter steaming occurs in a steamer

specially executed for knitted fabrics which is followed

by series of washers. Then finally neutralization andrinsing takes place before the fabric reaches the

outlet.



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Knitted fabrics are extremely sensitive to tension

and therefore require careful handling duringprocessing.

This means that tensions exerted by the machineryon the fabric must be kept to a minimum.

This is the reason for the special design of the entryto the range which consists of a centre drivenunwinding arrangement.

The unwinding tension on the fabric is independent

to the size of the batch. The fabric enters the pre-washing zone with a

constant low tension which is maintained throughoutthe process.



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The pre-washing zone includes one or more Trikoflex

washers depending on the production and speed ofthe machine. Demineralization chemicals can be

introduced in the pre-washing zone to remove loose

metals and residual iron left over from the knitting

process. There are two methods of demineralization.

--Demineralization in the Trikoflex washing

compartment at 60C to 80C for approx. 30 to 60

sec. --Impregnation with demineralization chemicals

followed by a small reaction chamber at room

temperature for 5 min



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The impregnation with scouring and bleaching

chemicals is carried out in a small Trikoflex LT-S impregnation chamber followed by steamingin a specially designed steamer containing a

roller bed dwelling zone. The fabric is passed,in a so-called free run, through a steam lockinto the steamer and is immediately brought upto the reaction temperature. A folding

mechanism plaits the fabric onto the roller bed.Depositing and draw off during the entireprocess occurs under stable pre-definedconditions.



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Each chemical has a station consisting of a

feed pump, inductive flow meter and controlvalve. This ensures the reproducibility of

chemical quantities.

The concentrated chemicals are fed into thecirculation pipe of the Trikoflex LT-S, where by

thorough mixing is effected. The set point is

calculated according to the recipe entered (mlchemicals / kg fabric) and depends on the

fabric flow (running meter weight x speed).

WASHING RANGE FOR REACTIVE DYED FABRICS


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The range generally comprises of a suitable entry (as alreadydescribed) followed by one or two Trikoflex washers for theinitial rinsing and thorough removal of unfixed / hydrolyseddyestuff.

At the heart of the Trikoflex washing system is a grooved drum.The drum surface has a grooved profile with a mesh covering.

As the fabric passes through the spray section, it is supportedby the drum surface and is thus unable to avoid thehydrodynamic water pressure. The penetrating washing liquorresults in a liquor film on both sides of the fabric. This facilitatesthe quick removal of impurities.

Simultaneously, a cleaning effect is created within the mesh.

The washing effect is increased considerably compared to thestandard mesh and screen drum systems [2].



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A dwell unit for soaping and other processes

follows the initial washing compartments.

Final rinsing and neutralisation are repeated in

the subsequent Trikoflex washing

compartments.

This machine can be successfully utilised for

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