Sitara Training Report

INTRODUCTION

The SITARA TEXTILE INDUSTRIES LTD is one of the leading textile groups

working in PAKISTAN. They mainly manufacture all type of fabrics required by

the customers. They export their fabrics in all parts of the world. The aim of

SITARA TEXTILE INDUSTRIES LTD is to prepare a fabric of high quality with

good overall fastness properties.

A fabric woven with tender care & dyed in the brilliant shades of nature adds

elegance and magnificence to this world. Sitara Textile is a manufacturer of such

fabulous fabrics; fabrics that speak of unparalleled quality & unmatched comfort.

Sitara Textile specializes in producing high class fabric products made of superior

quality materials & possesses state-of-the-art production facilities in made-ups and

fabrics for various consumer needs. The company makes use of the latest

technology & equipment to make sure that each product is original in style and

shows exquisite craftsmanship. Sitara is a company that believes in originality as

character & quality as foundation. The entrepreneurial spirit of the company

assiduously seeks constant development, steady progress & outstanding

performance.

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This textile mills have following processing departments under one roof such as,

GREIGH DEPARTMENT

PRE-TREATMENTS

FABRIC DYEING

FABRIC PRINTING

FINISHING

PACKING SECTION

TESTING LABORATORY

GREIGH DEPARTMENT2

This Department has mainly two sections.

1) INSPECTION AND MENDING

The section practically approves weaved cloth for further processing.

This department inspects the quality of fabric, count, no. of warp and wefts and

most importantly different defects in cloth.

The cloth is thoroughly inspected in this department. The process is passing the

cloth on the glass plate tables that are illuminated from below by tube lights. The

worker pulls the cloth over the glass plate manually and inspects different defects

in cloth and makes record for quality control purposes.

The greigh cloth faults are being identified and reported and if the cloth is below

the required quality, it is not sent for further process.

Following are the common defects present in the greigh cloth.

Slub

Count variation

Oily stains

Wrong ends

Shuttle cut

Rusting stains

Wrong sizing

Fungus stains

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The quality of cloth is judged by number of warp and weft yarns which is counted

as per square inch by the help of eye piece.

MOSTLY USED QUALITIES

Sr.No Quality Type

1 40x40/140x80 Cotton

2 22x22/60x60 Cotton



5 40x40/100x180 Cotton

6 150x16/84x44 PC

7 30x30/76x68 PC

8 36x36/73x45 PC

9 30x24/96x79 PC

10 40x36/110x74 PC

11 24x16/116x52 PC

12 40x40/133x76 CVC

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2) STITCHING

The second most important operation is to join pieces of fabric into one continuous

sheet of desired length. Good stitching makes the process efficient, reduces

rejection rate and improves process reliability.

Warp of both the pieces being sewn together must be parallel to each other. The

weft is sewn together at parallel and care must be taken to meet both ends properly

tucked-up together to prevent any " Opening" of seam during longitudinal process.

PRETREATMENTS

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This department has following sections

1. SINGEING AND DESIZING

2. SCOURING

3. BLEACHING

4. MERCERIZING

1. SINGEING AND DESIZING

Fabrics made from staple fibers show some protruding fiber ends at the surface of

the cloth, these protruding fibers create hindrance in the process of bleaching and

dyeing so they must have to be removed in order to get even surface.

To improve the surface of cloth, the fiber ends are removed by the help hot plate or

flame and this process is called singeing. Singeing process is done on all types of

cloth i.e. compact and blends but.

The greige cloth is passed through first blower to clean the cloth from fluff and

then the cloth enter into the burner chamber where the protruding fiber ends on

both sides are burnt by hot flame coming at an angle of 90º.

After this the cloth enters into another blow chamber where ash on surface is

removed so that it becomes favorable for desizing.

Singeing of fabric is done in order to achieve the following objectives.

To improve pilling rating of fabric.

To give a uniform luster to the surface.

Removal of protruding fibers.

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PRECAUTIONS DURING SINGEING

Prior to singeing, a heavy brushing treatment should be carried out to raise all fuzz

stuck down under the size coating.

The method of singeing should be appreciable to the type and condition of blended

fabric and 100% cotton.

To make uniform gas flame through out the treatment, the slits of that gas burners,

should be cleaned periodically to avoid dogging.

The process of removing the sized material from surface is called desizing.

There are many types of sizes, which are applied on the fabric during the weaving

process such as:

Water Insoluble size:

These are natural products of starch (Potato/Wheat/Rice etc.)

Modified starch:

In some cases, water-soluble product such as dextrin etc is used for sizing.

Water-soluble size:

These are synthetic products of carboxyl methylcellulose, Polyvinyl alcohol,

polyester resins etc.

The desizing is done after singeing. The fabric is washed in a first tub and then

passed through de-sizing agents. The fabric is desized with desizing agent as well

as wetting agent depending on the temperature/subsequently stored for up to 4-12

hours usually on batching rollers. This process is called “Batching Process”.

The fabric is firstly washed in the first tub, which cleans the fabric after singeing.

Then fabric is desized. The fabric is padded at low pressure to keep the required

moisture level. The purpose of rolling is to penetrate the solution in the cloth

equally. The de-sizing solution when reacts with sizing solution, it makes bacteria

after few hours which helps to maximum de-size the fabric.

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Properties of good de-sizing agent:

High wetting power

Compatibility whitest enzymes

High emulsifying dispersing power

Low foam formation

MACHINE SPECIFICATIONS

Name SITARA SINGEING & DESIZING MACHINE (PAKISTAN)

Speed 10-----150 m/min

Flame distance 10 cm

Burner position 90º

Fabric temperature 100---140 ºc

If Fabric Temperature Exceeds 150ºC the Machine Stops.

RECIPE FOR DESIZING

Desizer ( ALKALASE) 6g/l

Sandozen NI soap 2g/l

Acetic acid 1g/l

Salt 3g/l

Temperature of fabric 60----70ºC

PH of Fabric 5.5—6.5

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2. SCOURING

In continuous process, preference is given to the scouring. The treatment of

the fabric is done with soda solution and heating up with steam combine at the

same time with the dwell period in a steamer at temperature of around 100-102°C.

Treatment with hot caustic soda causes cotton to swell the fabric impurities being

solubilized and partially removed, the few cellulose as well as the proteins which

are mainly located in the primary wall are degraded until soluble in water,

impurities and dispersed.

AIMS OF SCOURING

To permit the subsequent dyeing.

To permit an optimum increase in the degree of whiteness during subsequent

bleaching.

Solubilized the seed coats to extent where they can be removed during bleaching.

Removal of hardness of heavy metal ions by addition of suitable sequestering

agent.

GOLLER’S SCOURING MACHINE

The speed of running machine is as follow:

BOX SPEED 95m/min.

LINE SPEED 70m/min.

RECIPE FOR SCOURING

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NaOH 30ml/kg

SOAP (Sandopan DTC) 1ml/kg

Reaction Time 15min.

Speed 50-70m/min.

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3. BLEACHING

Natural fibres, i.e. cotton, wool, linen etc. are off-white in colour due to colour

bodies present in the fibre. The degree of off-whiteness varies from batch-to-batch.

Bleaching therefore can be defined as the destruction of these colour bodies. White

is also an important market colour so the whitest white has commercial value.

Yellow is a component of derived shades. For example, when yellow is mixed with

blue, the shade turns green. A consistent white base fabric has real value when

dyeing light to medium shades because it is much easier to reproduce shade

matches on a consistent white background than on one that varies in amount of

yellow.

Bleaching may be the only preparatory process or it may be used in conjunction

with other treatments, e.g. desizing, scouring and mercerizing. The combination of

such treatments for an individual situation will depend on the rigorousness of the

preparation standard and economic factors within the various options. Other

chemicals will be used in addition to the bleaching agent. These serve various

functions such as to activate the bleaching system, to stabilize or control the rate of

activation, to give wetting and detergent action, or to sequester metallic impurities.

This section gives consideration to the selection of bleaching agents and to the role

of the various chemicals used in conjunction.

The purpose of bleaching is to remove coloured impurities from the fibre and

increase the whiteness level of fabric.

The aim of bleaching can be described as following:

Removal of coloured impurities.

Removal of the seed coats.

Minimum tendering of fibre.

Technically reliable & simple mode of operation.

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Low chemical & energy consumption.

Increasing the degree of whiteness.

MAJOR BLEACHING AGENTS

SODIUM HYPOCHLORITE (NaOCl)

HYDROGEN PEROXIDE (H2O2)

SODIUM CHLORITE (NaClO2)

GOLLER BLEACHING MACHINE (GERMANY).

NO OF TANKS 8

BOX SPEED 90m/min

LINE SPEED 70m/min

RECIPE FOR BLEACHING

NaOH 17ml/kg

SOAP (DTC) 2ml/kg

STABILIZER 5ml/kg

H2O2 30ml/kg

Reaction Time 25min.

Speed 50-70m/min.

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4. MERCERIZING

Both Mercerizing and causticizing require cotton to be treated with concentrated

solutions of sodium hydroxide (caustic soda). Mercerization requires higher

concentrations of caustic soda (19 to 26 % solutions) whereas causticizing is done

with concentrations ranging between 10 to 16 %. Both procedures are effective in

completing the removal of motes that may have escaped the scouring and

bleaching steps. One major difference between the two is that causticizing

improves the dyeing uniformity and dye affinity of cotton without improving

lustre. Caustic soda solution swells cotton fibres breaking hydrogen bonds and

weak Vander-Wall forces between cellulose chains. The expanded, freed chains

rearrange and re-orient and when the caustic soda is removed, the chains form new

bonds in the reorganized state. When done tensionless, the cotton fibre swells, the

cross section becomes thicker and the length is shortened. Because of fibre

thickening, the fabric becomes denser, stronger and more elastic. Held under

tension, the coiled shape of the fibre is straightened and the characteristic lumen

almost disappears. The fibres become permanently round and rod like in cross

section and the fibre surface is smoother. Decrease in surface area reduces light

scattering, adding to fibre lustre. Tension increases alignment of cellulose chains

which results in more uniform reflection of light. The strength of the fibre is

increased about 35 %. The fibre also becomes more absorbent. The cellulose

crystal unit cell changes from cellulose I to cellulose II and the amorphous area

become more open, therefore more accessible to water, dyes and chemicals.

Mercerized cotton will absorb more dye than unmercerized cotton and in addition,

yields an increase in colour value a given quantity of dye. The amount of fibre

shrinkage is a measure of the effectiveness of caustic soda's ability to swell cotton.

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RECIPE FOR MERCERIZING

Tank volume 3000 litres

NAOH 335g/L

Speed 50-60m/min.

Pick up ratio 2.5ml/m

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FABRIC DYEING

When the greigh fabric from weaving, comes to processing, it is desized (process

of removing starch from fabric), scoured (process of removing natural and added

impurities from fabric) and bleached (process of making fabric uniformly white).

Then it is treated with caustic soda in a process called mercerization, to increase

fabric’s lustre and dye ability. Just after mercerization, the fabric comes for dyeing

process.

The white fabric is coloured in dyeing. Dyeing is of three types:

1. Exhaust method

2. Semi-continuous method

3. Continuous method

Continuous method, being the most productive, is being used at Sitara textiles.

TYPES OF MACHINES

Two types of machines are used for continuous dyeing method:

1. Pad-Thermosol (dyeing and then washing on pad steam)

2. Pad-Steam

Pad steam and thermosol are used here in SITARA TEXTILE INDUSTRIES

LIMITED for quality dyeing of fabric with maximum production. These are

modern and popular dyeing machines. These machines are used for dyeing 100%

cotton and P/C blends.

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The deep shades are dyed at high temperature and light shades are dyed low

temperature. The squeezing pressure is adjusted according to the shade

requirement. Any shade variation is adjusted by making appropriate adjustments.

Pure dark cotton shades on heavy weight fabric can also be dyed on pad batch

giving very good result saving the cost of curing or steaming. While planning the

production schedule, dyeing, bleaching and finishing department’s co-ordinate

with each other in order to make the production process consistent. The

process/route of the dyeing should be decided in time and changes must be

reported with considerable time margin to avoid the wastage of time.

Let’s describe the main parts of both one by one.

PAD-THERMOSOL

Company “Môn forts” makes this machine. This machine is mainly used to apply

colour to fabric and transfer the dye molecules to the surface of fabric. The main

parts are as under:

PADDER

Two big rollers are called padders. The company “Kusters” makes them. The

padders of Kusters are very much popular in continuous dye houses due to the

versatility that it can control pressure from three places, i.e. left, centre and right,

between two padders.

There is a trough for liquor (water + dyes), whose capacity is about 44 litres, along

with padders. There are eight small nip rollers in the trough to help liquor to

penetrate into the fabric. There are two feed tanks, available separately, to give

continuous supply to trough. The pressure is usually adjusted at 2 bars. After

padding, a few second dwell times is given to fabric on VTG rollers.

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VTG ROLLERS

Vertical tensioning guide rollers are just above the padders. They allow fabric to

contact with air in a spread form with air before the fabric is exposed to IR heaters.

IR HEATERS

Infra red heaters are very important part of the machine. Two sets of heaters are

there. One along with other and their temperature can be individually controlled in

terms of efficiency. The main function of these heaters is to avoid uneven dye.

They ensure uniform dyeing same shade throughout the whole width of the fabric.

The actual phenomenon is that when a fabric is padded, there is always some free

water on the surface of the fabric which try to migrate on some slightly dry part of

the fabric and unevenness in shade occurs.

A slight prevention to that is anti migrating agents, which are added in dye liquors,

to bind the movements of free water. But theses agents will not be too efficient in

dyeing chambers (after IR). So, one logical solution of it is to dry the fabric at high

temperature, like above 1200C, so that free water goes into air, rapidly, without

having chances of free water migration to other parts of the fabric. So, IRs is for

this purpose and they remove about 30-40% moisture form fabric. IR heaters are

also called pre-dryers.

DRYING

There are three drying chambers after IRs. They contain hot air from top and

bottom to make fabric dry. Steam is used to heat the air and hot air dries the fabric.

CURING

There are two curing chambers to give fabric high temperature for fixation of dyes.

Hot air is again used to give temperature to fabric but instead of steam, oil is used

to heat air since high temperature of air is required.

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MACHINE SPECIFICATIONS

Speed 40-60 m/min

Drying Temperature 100-130C

Curing Temperature 200-230C

PAD STEAM MACHINE

This is relatively a simple machine as compared to pad thermo sol. The company

“GOLLER” manufactures this. Machine consists of the following parts

PADDERS

These are of the same shape as of pad thermo sol. Trough size is smaller and there

are no nip or VTG rollers. Pressure is also controlled from left and right instead of

left, centre and right.

STEAMER

After padding for one minute or so, depending upon the speed of machine, fabric is

treated with steam in a steamer.

WASHERS

There are fourteen washers to wash the fabric. Each contain water and temperature

of water for each washer is individually controlled. Usually first 3-4 washers,

temperature is kept at 40 0C. Then gradually raised to 95 0C form washers 5-12.

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Then again 40 0C washing is left to washers. For some processes, acid is used in

left washers to adjust pH of fabric, for subsequent finishing process.

DRYING

There are four rows of drying cylinders, each containing 12 cylinders after washers

to dry the fabric. Speed of machine is adjusted from 90-120 meters/minute.

DYEING PROCESSES

The dyeing processes are divided into the followings:

1. The padding process applying dyes and chemicals on the fabric

2. The drying process after padding

3. The fixation process to fix dyes on the fabric

4. The washing process to remove unfixed dyes.

PADDING PROCESS

In this process, the fabric to be dyed passes through a padding bath containing dyes

and chemicals, where the material should be penetrated with padding solution and

evenly squeeze.

DRYING PROCESS

The padded fabric should be immediately applied “drying” to satisfy the next

fixation treatment for the padded fabric. Since dyestuffs have not yet fixed firmly

with fibres in this process, the migration phenomenon is occurred whereby dyes

tend to move alongside moisture evaporating during drying not only from the

inside of fabric to the surface but also from centre to both edges. Even if dyestuffs

have been applied uniformly on fabric in padding process, migration during drying

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process is liable to create such problems as unlevelness and poor appearance. It is

therefore necessary to formulate padding recipes and drying conditions that will

minimize migration as much as possible.

FIXATION PROCESS

This process is applied for fixing disperse dyes on polyester fibres and reactive/vat

dyes on cotton fibres. For this purpose higher temperature and steam are used.

WASHING PROCESS

During this cross dyeing process, treatments of washing, neutralization, and

oxidation of fabric are carried out at many places. If the washing treatment is not

done properly then insufficient soaping and rinsing eventually cause serious

problems in fastness of the dyeing.

DYEING METHODS

Usually cotton, polyester and polyester-cotton blends are dyed at Sitara Textile

Industries Ltd. Two types of methods can be used, depending upon the machine

availability and customers requirements of fabric fastness property.

1st METHOD

The flow diagram of this method is:

Pad Dry Chemical Pad Steam Wash Dry

2nd METHOD

The flow diagram of this method is:

Pad dry cure washing drying

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COTTON DYEING

It can be dyed by three different types of dyes:

1. Reactive

2. Vat

3. Sulphur

Sulphur dyes are not commonly used.

REACTIVE DYES

Reactive dyes are available in a wide variety of dyes for dyeing all types of

shades from brilliant to black. Due to their superiority over vat dyestuffs in cost

performance, alongside relatively excellent fastness properties, these reactive dyes

are recommended for medium to heavy shades. As many kinds of dyeing methods

applicable for reactive dyes, they have advantage in dyeing facilities and

equipments. There are three types of reactive dyes i.e., Remazol, Cibacrone,

Drimarine.

REMAZOL DYES

These dyes are used from medium to dark shades and their fastness properties are

very good. The flow diagram for these dyes is:

Pad Dry Cure Cold Wash Hot Wash Ironing

The drying temperature should be 100C and the curing should be done at

150C/min.

Recipe for the Remazol dyes is as:

Dyes 10 g/l

Urea 100 g/l

Soda Ash 20 g/l

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Migration Inhibitor 0.4-1 g/l

Penetrating Agent 1-3 g/l

Urea is a wetting agent that is used to keep the fabric moist while the colour is

setting. Soda ash (sodium carbonate) is used to raise the acidity of the dye bath and

"lock" the dye onto the fibre. Soda ash is also caustic; while plant-based fibres can

take the harshness, it can make protein-based fibres harsh and brittle.

CIBACRONE DYES

These dyes are also used from medium to dark shades and like the Remazol dyes,

their fastness properties are also very good. The flow diagram for these dyes is:


The drying temperature is 100C but the curing temperature is 160C/1½ min.

Recipe for Cibacrone dyes is:

Dyes 10 g/l

Urea 100 g/l

Soda Ash 20 g/l



DRIMARINE DYES

These dyes are used from light to medium shades and fastness properties are

not so good. The flow diagram for these dyes is:


The drying temperature is 100C but the curing temperature is 180C/1min.

Recipe for Drimarine dyes is:

Dyes 10 g/l

Urea 100 g/l

Sodium Bicarbonate 20 g/l

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VAT DYES

Vat dyes provide the best fastness properties on cellulose fibres, thus making

these dyes ideal for dyeing required high fastness. Due to comparatively higher

costs, however, these vat dyes are generally applied in pale to medium shades

dyeing. These dyes are less used as compared to reactive dyes because of less

shade. So, the use of vat dyes is specific for certain colours.

The flow diagram of these dyes is as:

Pad Dry Chemical Pad Steam Washing Ironing

For chemical padding first of all developing of dyes is done. For the developing

30-120 g/l caustic and 38-130 g/l sodium hydrosulphite is used at 102C for 1½

min. on pad-steam. After this the oxidation is done to remove the effects of caustic,

which is applied during the developing process. For the oxidation 2-5 ml/L water

and 3-5 ml/L acetic acid is used at 50-60C for 2 min and then finally washing and

ironing is done.

Recipe for vat dyes is:

Dyes 10 g/l

Dispersing Agent 3-5 g/l


POLYESTER DYEING

Polyester fabrics are dyed with disperse dyes.

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Disperse dyes are insoluble in water; however, they are soluble to some extent in

hot water and solubility increases with temperature and by the addition of

dispersing agents. A good disperse dye should have good light fastness, washing

fastness and perspiration fastness. For the polyester dyeing, disperse dyes are used.

The flow diagram of the disperse dyes is:

Pad Dry Cure skeletoning Neutralization washing drying

In making the skeleton, 70% sulphuric acid is used for 7-10 min at 40C. After this,

the neutralization is done. For this 2-5 g/l soda ash is used at normal temperature.

These both processes are done to develop the dyes on the fabric. At the end

washing and drying is done. Recipe for the disperse dyes is as:

Dyes 10 g/l

Dispersing Agent 4-5 g/l



The drying temperature is 100C and the curing temperature is 180-200C/1min.

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POLYESTER/COTTON DYEING

For polyester disperse dyes are used and for cotton reactive dyes are used.

DISPERSE/REACTIVE DYEING

This method is used to dye the light shades because of lower fastness properties.

Dyeing Conditions

1. Composition Of Padding Solution:

Disperse dyes 10 g/l

Reactive dyes 10 g/l

Dispersing agent 2-5 g/l (dispergator BL)

Migration inhibitor 0.4-1.0 g/l (sodium alginate)

Penetrating agent 1-3 ml

Sequestering agent 0.5-1.0 g/l

2. Padding:

20-25C, pick up 50-70%

3. Drying:

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110-130C

4. Thermosoling:

190-220C, 60-120 seconds

5. Chemical Padding: (developing on Pad Steam)

Caustic soda 38-50 g/l

Hydrosulphite 30-38 g/l

15-25C, pick up 70-90%

6. Steaming:

100-130C, 30-40 seconds

7. Oxidizing:

Hydrogen per oxide 2-5 ml/l

Acetic acid 3-5 ml/l

At 60C for 2-3 minutes

8. Washing.

Temperature 45C

Conditions for Method

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In general particle size of disperse dyes is relatively larger than that of reactive

dyes. When both of dyes are mixed and padded together, this variation of particle

size often leads to different degrees of tailing, listing and migration.

In order to prevent such troubles, especially since particles dyes varies from

manufacturers to manufacturers, it is recommendable to select both disperse dyes

and reactive dyes as much as possible from same manufacturer.

It is important to carry out a thorough washing process in order to remove all

decomposed disperse dyes during steaming.

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FABRIC PRINTING Textile printing is the most versatile and important of the methods used for

introducing colour and design to textile fabrics.

“Printing is a localized dyeing in which dye is transferred onto the fabric with the

help of a vehicle & fixed by some fixation process.”

However, instead of colouring the whole substrate (cloth, carpet or yarn) as in

dyeing, print colour is applied only to defined areas to obtain the desired pattern.

This involves different techniques and different machinery with respect to dyeing,

but the physical and chemical processes that take place between the dye and the

fibre are analogous to dyeing.

A typical printing process involves the following steps:

1) Colour Paste Preparation

When printing textiles, the dye or pigment is not in aqueous liquor, it is usually

finely dispersed in a printing paste, in high concentration.

All the necessary ingredients are mixed together in colour kitchen.

Paste For Pigment Printing

Thickener 1.85%

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Binder 5%

Liq. Ammonia 1.5%

Water 93%

Paste For Reactive Printing

Thickener 2.5%

Reserves salts(luddi Cole) 1.25%

Sodium bicarbonate 5%

Urea 15%

Water 76%

Recipe For Black Colour

Dark Shade

Paste 75%

Water 19%

Dye 6%

Light Shade

Paste 75%

Water 24.4%

Dye 0.6%

Recipe For Other Colours

Dark Shade

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Paste 75%

Water 22%

Dye 3%

Light Shade

Paste 75%

Water 24.7%

Dye 0.3%

2) Printing

The dye or pigment paste is applied to the substrate using different techniques.

3) Fixation

After printing, the fabric is dried. Water evaporation leads to an increase in dye

concentration and at the same time prevents the colours from smearing when the

fabric is transported over the guide rollers. At this stage the dye is not yet fixed.

The aim of the subsequent fixation step is to transport as much as possible of the

dye, which is retained by the thickener, into the fibres.

Fixation is usually carried out with steam. Water vapour condenses on the printed

material, swells up the thickener, heats the print and provides the necessary

transport medium for the diffusion of the dye. The distribution of the dye between

fibre and thickener is an important factor in determining the fixation degree of the

dye, which is called the "retaining power" of the thickener. The thickener, in fact,

is often composed of polysaccharides and therefore competes with cellulose in

retaining the dye. This is the main reason why the fixation rate of a given dye is 10

% lower in printing than in dyeing.30

4) After-Treatment This final operation consists in washing and drying the fabric (it is not

necessary when printing with pigments ).

Auxiliary Operations

At the end of each batch and at each colour change various cleaning operations are

carried out:

The rubber belt, to which the fabric is glued during printing is cleaned in

continuous mode with water to remove excess adhesive and printing paste.

The printing gears (all systems responsible for feeding and applying the paste to

the substrate) are cleaned by first removing as much as possible of the paste

residues and then rinsing with water.

The remaining paste in the containers, in which the paste is prepared (paste vats)

are in general previously cleaned up by means of sucking systems before being

washed out with water. The residual printing paste collected in this manner is then

disposed of.

A variety of different machines can be used for printing fabrics.

Machines used in STIL are

1. Flat Bed printing machine (Rejhani)

2. Rotary printing machine (Zimmer)

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Flat-Screen Printing

The fabric is first glued to a moving endless belt. A number of stationary

screens (from 8 to 12, but some machines are equipped with up to 14

different screens) are placed along the printing machine. The screens are

simultaneously lifted, while the textile, which is glued to a moving

endless rubber belt, is advanced to the pattern-repeat point.

Then the screens are lowered again and the paste is squeezed through the

screens onto the fabric. The printed material moves forward one frame at

each application and as it leaves the last frame it is finally dried and it is

ready for fixation.

The rubber belt, after pulling away the fabric, is moved downward in

continuous mode over a guide roller and washed with water and rotating

brushes to remove the printing paste residues and the glue, if necessary.

After this, the belt is sent back to the gluing device.

Rotary-Screen Printing

Rotary-screen printing machines use the same principle as flat bed

machine, but instead of flat screens, the colour is transferred to the fabric

through lightweight metal foil screens, which are made in the form of

cylinder rollers. The fabric moves along in continuous mode under a set

of cylinder screens while at each position the print paste is automatically

fed to the inside of the screen from a tank and is then pressed through

onto the fabric. A separate cylinder roller is required for each colour in

the design.

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A suction pipe leads from the paste vat to a pump, from where a printing

hose leads to the squeegee (dye pipe with squeegee). From here the paste

is directed inside the cylinder screen. The fill volume of this so-called

printing paste input system is quite high and as a consequence the

amount of paste residue that has to be removed at each colour change is

also fairly significant.

Rotary-screen printing machines are equipped with both gluing and

washing devices as flat-screen printing. The belt is washed in order to

remove the residues of paste and adhesive. Not only the belt, but also the

screens and the paste input systems (hoses, pipes, pumps, squeegees,

etc.) have to be cleaned up at each colour change.

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FABRIC FINISHINGTextile finishing is a term that is commonly applied to different processes that the

textile materials undergo after bleaching, dyeing or printing for final

embellishment to enhance their effectiveness and sale appeal. The finishing

treatments are basically meant to give the textile material certain desirable

properties like lustre, drape, softness, dimensional stability, crease recovery, anti-

static, soil-release etc. However these also include finishes that meet certain

specific end uses such as water repellency, flame retardancy, mildew proofing etc

are certain specific ones.

Function Of The Finishing Processes

The main function of applying various finishes may be as:

1. High Sales Appeal. To impart properties of attractive appearance and good drape.

2. High wear quality. This refers to adequate tensile and abrasion strengths,

dimensional stability, crease recovery and freedom from pilling.

3. Body protections and comfort. This relates to proper heat insulation, moisture

absorption and air permeability.

4. Special effects. These include water repellency, flame retardancy, mildew and

moth proofing, anti-static behaviour and soil release.

STENTER

This is the most effective machine in the finishing unit. This machine performs

many functions such as;

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1. Maintain the edges length.

2. Apply finishes by batching process.

3. Thermal fixation of the applied finish.

In STIL stenter method is used. There are six stenters in STIL.1. Monfort 1 2. Monfort 23. Monfort 34. Monfort 45. MW-2000(Marshal & William)6. Babcock

Features of Stenters

a) MONFORT 1

5 chambers Having EVAC arrangement Bow & skew arrangement Double purpose use (finishing and dying) 110” working width with width adjustment arrangement temp range 180-200Cb) MONFORT 2 & 4 7 chambers used for narrow width fabric working width is 78 inches remaining features are samec) MONFORT 3 Also have 7 chambers Working width is 102 inches Remaining features are same

d) BABCOCK 5 chambers Runs on furnace oil Working width is 102 inches

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Bowing arrangemente) MW-2000 stenter

Working width is 132 inches 8 chambers

Recipe For Finishing

FOR COTTON

Starch 50kg

Ceranine HCS 10kg

Polysoft L 25kg

Belfasin Si 10kg

For Polyester/Cotton Blend

Starch 50kg

Unisoft CT 40kg

Polysoft L 35kg

Unisoft CS 10kg

Belfasin Si 10kg

CALENDERING

Calendaring is a high speed ironing process that primarily imparts lustre and is

usually the final treatment for the fabrics in the finishing sequence. The basic

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principle of calendaring is to expose the cloth to the combined effect of moisture,

heat and pressure until the fabric acquires a very smooth and light reflecting

surface and gets a good lustre. The calendaring effect on the fabric is usually

temporary and disappears after first washing. Semi permanent lustre is sometimes

achieved by padding fabric in a sparingly soluble polyvinyl acetate emulsion

before calendaring, where the solution acts as a binding agent. More permanent

finish can be obtained by treating fabric with a solution of crease recovery reagent,

followed by drying, calendaring and curing the fabric at about 150 ºC. The

calendars are basically an assembly of heavy rolls, alternatively of iron and paper

or cotton that are normally mounted in vertical frames. The rolls are bearing one on

the other under a high pressure that is applied by compound levers or hydraulic or

pneumatic equipment.

Paper or cotton rolls are made by compressing sheets of paper and cotton under

heavy pressure of hundreds of tons and then finely turned to produce a smooth

surface. The iron rolls are also called chilled rolls because these are hardened by

sudden chilling of the red-hot rolls. These are hollow so as to allow passage of

steam or sometimes gas-fire to heat these to different temperatures.

NIPCO-FLEX CALENDER

The pressure application concept of this calender is different from the

conventional calendering system. The pressing roller consists of a rotating shell

that is covered with a highly elastic plastic material named as RACOLAN. The

roller has fixed axels on which hydrostatic support elements are mounted that press

the racolan shell against either steel or a cotton/paper roller. The hydrostatic

pressure is applied with oil and is adjustable according to width of the cloth. The

NIPCO roller can be arranged in vertical position or in L shape with a hot steel

roller at top and a cotton bowl in front of it.

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The main advantages of NIPCO calender over a conventional calender are;

1. Attainment of very high pressure.

2. Adjustment of pressure line according to width of cloth.

3. No over load at the fabric selvedge.

4. Easy installation and removal of the rollers.

FELT CALENDER

Felt calenders are mainly used for imparting lustre and smoothness to silk, rayon

and cotton knitwear materials. These work at low pressure and temperature than

used for cotton. The cloth is pressed between an endless felt blanket and a hot steel

cylinder at a speed of 20 to 40 meters/minutes. By adjusting speeds of the feed and

take up rollers the tubular knitwear can be compacted to some extent on this

calender.

SANFORIZING

This process involves feeding the fabric b/w a stretched blanket and a highly

polished and heated metal shoe. The fabric is fed on the drying cylinder and when

the blanket retracts to the concave section of the cylinder. The cloth is physically

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forced to comply with the curvature and shrinks according to the thickness of the

blanket. The shoe serves to hold the fabric on to the blanket and does not let it slip

back. The fabric is treated with liquid ammonia at a low temperature prior to pre-

shrinkage treatment. This process confers more permanent pre-shrinkage and

garments made from such a fabric don’t shrink at all on laundering but it is

expensive to apply.

TESTING LABORATORYSitara Textile is powered by the determination of setting the highest standards in

quality. It has the technology of transforming the dreams of true quality into reality.

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Its quality management makes sure that all weaved grey fabrics is subjected to a 100%

inspection in accordance with our in house established Lab quality inspection

standards; a part of Quality Management System (ISO 9001). Thorough quality

checks are conducted at every phase of production in order to meet the increasing

demands of high standard materials by national and international consumers.

Quality Policy

“No Compromise on Quality” It is our aim to produce quality fabric according to

the requirements of our customers under continually improved organized quality

management system”

Greigh cloth quality, Piling resistance, Abrasion, Colour fastness, washing fastness

and light fastness are a few of the carefully monitored checks conducted at Sitara to

fully insure the highest quality standards

QUALITY CHECKING OF GREIGH CLOTH

Cut the sample with GSM cutter.

Pick Glass Method.

Place fabric sample on light table.

Place pick glass on sample.

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Count the number of yarns along warp and weft side with the help of needle.

COUNT CHECKING OF GREIGH CLOTH

Pull of the yarn along weft side and warp side respectively.

Cut off six inches length.

Place the sample at right side of McMorran balance.

Balance the lever.

Count the number of yarns.

Calculate the count with the formula.

Count = No of yarns ×6 4.2

BLEND RATIO

Cut the circular sample of greigh cloth with GSM cutter.

Weigh it in grams on electronic balance.

Then desize the sample.

Dip the sample in 70% H2SO4 for 30 minutes.

Wash in cold water.

Dry in oven at 110 Co.

Weigh again.

Calculate the percentage of polyester by subtracting weights.

TEGWA TEST

This test is used for testing the size remaining on the fabric

Prepare the tegwa solution according to recipe.

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KI 10 g

I2 0.635 g

Ethanol 200ml

Water 800ml

Take sample of the fabric.

With the help of stirrer drop off tegwa solution on fabric sample.

Dip the sample in water.

Compare the spot on the fabric with tegwa scale.

Standard

4-5

ABSORBANCY TEST

Cut the sample of 2×10 cm

Dip the lower end of sample in turquoise blue solution tray for 5 minutes.

Note the distance covered by the dye on the sample.

Standard

3 cm for reactive

1 cm for pigment

COLOUR FASTNESS TO RUBBING

PURPOSE AND SCOPE

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This method is used for determination of resistance of the colour of textiles to

rubbing off and staining other materials. Two tests are made one with dry rubbing

and other with the wet rubbing.

RUBBING TESTER Crock meter

APPARATUS AND REAGENT

Crock meter

White bleached cotton lawn or similar cloth free from starch or other finishes cut

into 5-cm squares.

Gray scale for assessing staining .(ISO grey scale)

Two pieces of the specimen are required, not less than 22×5 cm for dry rubbing

and wet rubbing.

Distilled water

PROCEDURE

Dry Rubbing

Place the white dry cloth over the end of the finger of the testing device; rub it in to

and fro in a straight line along a track 10 cm long on the dry specimen, 10 times in

10 second, with a 900gm. Test warp and weft directions separately.

Wet Rubbing

Repeat the test with a fresh dry specimen and white cloth which has been wetted

with water and squeezed. Dry the cloth at room temperature. Assess the staining of

the cloth with greigh scale.

Standard

Dry Rubbing 3-4

Wet Rubbing 3-4

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COLOUR FASTNESS TO PRESSING

PURPOSE AND SCOPE

This method is used for determining the resistance of the colour of textile of all

kinds and in all forms to ironing and processing on hot cylinders. Tests are given

for hot pressing when the textiles are wet, when it is damp, and when it is dry.

Apparatus and Reagent

Hand iron of proper weight to give a pressure of approximately 30g/sq.cm at the

temperature indicated in the following ;

Cotton & Linen 190-200C˚

Wool, Silk & Viscose 140-160C˚

Cellulose acetate & Polyamide 115-120C˚

White bleached cotton cloth weighting approximately 125g/sq.meter. Five pieces

not less than 14×4 cm are required.

Gray scale by assessing change in colour and staining.(ISO scale)

The size of the specimen is 10×4cm

Procedure

Specimen preparation

Specimen of materials, which has been subjected to any heat or drying treatment,

must be allowed to condition at 65% RH, Temp. 20±2C˚, before they tested.

Dry Pressing

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Place the specimen on the piece of dry cotton cloth on a smooth horizontal surface.

Place the iron on the specimen and leave it for 15 Sec.

Wet pressing

Soak the specimen and cotton cloth in distilled water and squeeze or extract them

to contain their own weight of water. Place the wet specimen on a piece of the dry

cotton cloth and place the wet cotton cloth on the specimen, press by moving the

iron to and fro over the wet cloth (without additional pressure) for 15 sec.

Assessment

Assess the change in colour of the specimen with appropriate grey scale.

Standard

Dry Pressing 4

Wet Pressing 3-4

COLOUR FASTNESS TO PERSPIRATION

Tester Perspirometer

PURPOSE AND SCOPE

This method is used to determine the resistance of the colour of textile of all kinds

and in all forms to perspiration.

APPARATUS AND REAGENT

Perspirometer

Oven maintained at 37±2C˚

Solution freshly prepared, containing 0.5g 1-histidine mono-hydrochloride mono-

hydrate, 5g sodium chloride, and 2.5g disodium hydrogen ortho phosphate per litre

brought to PH 8.0 with 0.1N sodium hydroxide.

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Solution freshly prepared, containing 0.5g 1-histidine mono-hydrochloride mono-

hydrate, 5g sodium chloride, and 2.2g sodium dihydrogen ortho phosphate per litre

brought to PH 5.5 with 0.1N sodium hydroxide.

Two undyed cloths for each specimen each 6×6cm of the same kind of fibre as the

sample. Place the specimen between the two pieces of white cloth and sew along

one side to form a composite sample.

Procedure

Thoroughly wet one composite sample in a solution of PH8.0 at the liquor ratio of

20:1 and allow it to remain in this solution at room temperature for 30min. pour off

the solution and place the composite sample between two glasses plates measuring

about 7.5×6.5cm under a force of about 4.5kg.

Treat the other sample in the same way but with the solution at PH 5.5.

Place the apparatus containing the samples in the oven for 4 hour at 37±2C˚

Separate the sample from the white cloth and dry them apart in air at the

temperature not exceeding 60C˚

Assess the change in colour of the specimen and the staining of the white cloth

with the greigh scale.

COLOUR FASTNESS TO WASHING

ISO 1989 CO3 STANDARD WASHING TEST

Place the composite sample in the solution containing 5gm neutral soap 2gm Soda

Ash heated to 60c for 30 min. Rinse the composite specimen twice in cold

distilled water and then in cold running water ,and squeeze it. Assess the change in

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colour of the uncovered portion of the sample and the staining of the white cloth

with the gray scale.

Neutral soap 5g/l

Soda ash 2g/l

Specimen size 4×10cm

Time 30 min

Temperature 60˚C

Liquor ratio 1:50

PILLING RESISTANCE TEST

ABRASION AND PILLING TESTER JAMES H HEAL

PURPOSE AND SCOPE

This method is intended for the determination of the resistance of textiles of all

kinds in all forms to the action of an applied resistive force. This causes pilling in

the tested fabrics

APPARATUS

Pilling tester

Metal plates 4 inch diameter and 1 inch thick

Standard for assessing the pilling grade

PROCEDURE

A piece of fabric measuring 10×10 inch is sewn to a firm fit when placed round a

rubber tube. The out end of the fabrics is covered by cellophane tape and metal

plates are placed on the tester .Run the tester for 300 cycles. Remove the sample

and compare the sample with standard scale.

Standard

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PILLING STANDARD 3-4 gray scale matching

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Sitara Training Report

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