“FOR ADVANCE LEARNERS”
PREVIOUS YEAR UNIVERSITY QUESTION &
ANSWER FOR THE SUBJECT “WET PROCESSING“
PREPARED BY
MRS. D. JEYA PRADHA, B.E., M.B.A
Lecturer in Department of Fashion Technology & Costume Designing.
SHRI MATI INDIRA GANDHI COLLEGE.
Wet Processing
Part – A
Answer the following questions:
1. List out the properties of direct Dyes?
The properties of Direct Dyes are:
Direct dyes are readily soluble in water.
Some of the dyed need a little amount of soda ash (sodium carbonate) to completely
dissolve them in water.
Direct dyes are used for dyeing cotton, viscose rayon, wool and silk fibres.
Direct dyes have poor wash in fastness and poor light fastness.
There fastness properties can be improved by certain after treatments.
2. What are the types of calendaring?
There are seven types of calendaring. They are
a. 7 – Bowl calender
b. Swizzing calender.
c. Chasing calender
d. Transrfer calender
e. Friction calender
f. Schreiner calendar (and)
g. Fett calendar.
3. What is meant by shrinkage?
Shrinkage is the contraction in the dimension of the fabric due to usage. Cotton fabric
suffers from 2 main disadvantages of creasing and shrinkage during subsequent washing.
Creasing is overcome by the Resin finishing where as the shrinkage is prevented by a special
finishing known as sanforising and the machine used for that purpose is known as sanforising
and the machine used for that purpose is known as zero- zero pre shrinkage machine.
4. What is meant by water proofing?
Water proofing:
Water proofing is nothing but preventing the passage of both air and water through a
fabric”.
5.What is meant by continuos Desizing?
Continues Desizing:
Normally when matt extract is used as a desizing agent. It takes about 3-4 hours for
complete desizing. But if use increase the concentration of the malt extract the time will be
reduced to 5 minutes.
6.What is Mercerisation?
Mercerisation:
Mercerisation improves the luster of cotton fibres. It also gives the cotton material a
greater affinity for colouring matters. Tension during mercerization is essential for to
improve the luster. Mercerisation produces a permanent change in the structure of cotton
fibre. Mercerization is a process in which the cotton material is treated with 25% to 30%
(50oC to 65oC Tw) Na OH solution and under tension at room temperature.
7.What is Napping?
Napping:
Napping is chiefly used to obtain a relatively deep hairy surface, but the degree of depth
depends upon the technique used. On the other hand, napping may also serve to cover up a
sleazy construction and weaving imperfections.
8. What are different styles of printing?
Styles of printing:
The different styles of printing are:
direct style
discharge style (and)
resist style
9. What are the Dye molecules?
The Dye molecules:
Dye molecules are organic molecules which can be classified as:
Anionic
Cationic (and)
Disperse
Anionic:
In which the colour is caused by the anionic part of the dye molecule.
Cationic:
In which the colour is caused by the cationic part of the dye molecule.
Disperse:
In which the colour is caused by the whole molecule. The first two dye molecules types
are appliede from an aqueous solution. The hird is applied from an aqueous dispersion.
10. What is finishing?
Finishing is one of the essential processes of a processing mill where all bleached, dyed
and printed material are subjected before they are put on the market. The aim of the tertile
finishing is to render textile goods fit for their and uses.
PART-B
Answer the following questions:
11.a) Write short notes about Scouring ?
Scouring
After desizing and through washing the cloth contains oils, fats,waxes, seed bits , leaf
particals, and natural colouring matter etc.These oils , fats, waxes are hydrophobic or water
hateing characters . so if these compounds present in the cloth., they affect the absorbency of
the cloth. These leads to imoproper dyeing , printing,and printing subsequent
process.scouring is carried out in a boilers called as kier
Two types of kiers are.
Horizontal kier
Vertical kier.
Vertical kiers
Scouring process is carried out commonly in vertical kier boilers usually underhigh
pressure 20 – 30 lbs/sq. inch and temperature 120o-130o with 8 to 24 hrs , depend upon the
type of fabric.
High pressure , high temperature vertical kier:
The vertical kier as shown in the figure . the kiers consists of a cylindrical vessel
made up of a cast iron . The inner portion is coated with a lime wash to prevent the
formation of rust stains on the fabric.
The desized fabric is placed inside the kier uniformly by manually or mechanically . It
is called as packing or pilling Pacing should be done evenly . uneven packing result in
uneven scouring.
The top of the kier is provided with cover known as lid. Usually boiling is carried out
with 3% NAOH.
A requird amount of sodium hydroxide is dissolved in water. This liquor is filled in
liquor is filled in liquor container. From the liquor container. The liquor is pumped with the
help of centrifugal pump.
Them the liquor reach the heater, at that time the solution is heated and the heated
solution is passed through the sprayer.
The sprayer is placed above the fabric. The heated solution is sprayed on the fabric and then
reaches the liquor container with the help of perforated false bottom. This operation is
repeated for 8 hours.
After the time is over the pressure is released. The liquor is taken out through
drainage.
The cloth is washed with hot and cold washes two or three times and then the cloth is
taken out for further process.
Caustic Soda boiling is used for Fine counts, super Fine counts varieties and delicate
fabric structured material etc.,
Scouring liqueur is prepared as follows:
NaCh -- 3.0%
Soap -- 0.5%
Wetting agent -- 0.5%
(Turkey Red Oil)
Sodium silicate-- 1.0% (to retain heat stability)
Material to liquor ratic-- 1:4
Temperature -- 120oC to 130oC
Time -- 8 hours
Pressure -- 20 to 30 1bs/sq.inch
Precautions:
1. When the scouring operation is strated , remove the air completely inside the kier ,
changes of formation of oxy cellulose . It will damage the fabric.
2. Packing should be done uniformly . Uneven packing results in uneven scouring.
3. After packing the top portion is converted with heavy stones or thickly variety of
fabric to prevent hot liquor directly falling on the fabric.
4. After scouring is over , washing is also done inside the kier , otherwise oxy
cellulose will degrade the cotton material.
11.b) Explain detail about “J Box Bleaching” ?
Impregnated the material with 5% to 7% NAOH at 70oC
Passed through the pre heater ( 90oc to 100
oC )
Reached „J‟ Box , Time 60 – 90 min . Temperature 90oC- 100
o C
Hot and Cold Wash
Impregnate the scoured material with H2O2 ( 5% -7% )
Passed through the heater ( 90oC – 100
oC)
Reach „J‟ Box (60 -90 min , Temperature 90o -100
oC
( bleaching process)
Cold Wash – Scoured and bleached material.
Ready for further process .
The cloth is now in a perfectly white condition .normal recipe used peroxide
bleaching is as follows .
Hydrogen Peroxide - 5% -7% (Weight of the fabric)
Sodium Silicate - 3% (Weight of the fabric)
NAOH - 0.4 % - 6.0 % (Weight of the fabric)
Soda ash - 0.8% -11.0 % (Weight of the fabric)
PH - 10.3 -10.8
Temperature - 900oC-100
oC
A modern tendency of continuous bleaching process based on the principle of
„J‟Box . both scouring and bleached process is done in a single process .
First the cloth is impregnated with NAOH solution with the help of the guide
roller kept at 71oC and then the cloth is passed through the pre heated chamber . The material
is heated 90oC to 100
oC
The hot material next passes through the „J‟ Box . From „J‟ box to water trough the
time taken is 60 – 90 minutes , at that time scouring process will takes place , this period is
called as dwell period . if „J‟ Box is well insulated to retain heat and it is lined with
stainless steel .
After the scouring is over the material passed through the water trough contains the
hot water to give hot wash and then passed through the another water trough to give cold
wash as shown in the figure . The scoured material is impregnated with Hydrogen Peroxide
(H2O2 ) strength about 3% - 7% and passed through the second heater and the material is
heated .
The hot material is now reaching the „J‟ Box . The time taken is 60 – 90 minutes at
that time bleaching operation is taking place . Finally the material is washed in water trough .
Now we will get scoured and bleached material in single process.
Advantage :
1. It is very fast process than the other process .
2. Production is more
3. Both Scouring and bleaching are done in a single process.
4. It is very economical when longer length of fabric is to be bleached .
12a). Write about the general theory of Dying? And explain the fastness – Properties of
Dyes?
The General theory of Dying:
Dying is the process of colouring textile material by immersing them in an aqueous solution
of dye, called dye, liquor. Normally the dye liquor consists of dye, water and auxiliary.
The general theory of dyeing explains the inter action between dye, water and dye
auxiliary. More specifically, it explains:-
forces of repulsion which are developed between the dye molecules and water and
forces of attraction which are developed between the dye molecules and fitness.
There forces we responsible for the dye molecules leaving the aqueous dye liquor and
entering and attaching themselves to the polymers of the fibres.
FASTNESS – PROPERTIES OF DYES:
COMMON PROPERTIES REQUIRED OF A DYE:
When a dye is present on a fabric, it is expected to have certain properties. When a
dyed (or) printed fabric is exposed to sunlight during its use, the dye should not fade
(or) change in colour. That is it should have high light fastness.
The dye should posses good washing fastness. If the cloth dyed with it is used for
making garment. Otherwise staining of garments with stripped dyestuffs occurs
during the washing of many garments together.
The dye should have good perspiration fastness when people wearing coloured
garments perspire, a part of the dye coming into contact with the perspiration may be
stripped and stain the skin of the water.
Apart from these properties the dyes can be expect to have good fastness to gas fading
incites gases like sulphur, nitrogen – dioxide, may be present in the atmosphere and
the dye may be affected. Dye polyesters and polyamide fabrics are exposed to very
high temperatures during processing -------textile mills. At this temperature some of
the dyes submit off. For this purpose, the dyes used on the fabric should have good
sublimation fastness.
A dye need not have good fastness to all the agencies. A dye intended for dyeing (or)
printing certain cloth need not be fast to perspiration but should have very good light fastness.
Therefore, dyes have to be selected depending on the use of the fabric to which it is put.
12.b).Explain about dying of cotton with sulphur dye ?
The dying is carried out in the following four stages .
1. Dissolving
2. Dyeing
3. Oxidation
4. After treatment.
Dissolving :
In dissolving , the insoluble sulphur dye is converted into soluble leuco dye.
The dye is taken as per shade and pasted with small quantity of Tirkey Red Oil and
cold water .
Soda ash (Na2Co3-1/2 the quantity of dye ) and sodium sulphide (Na2S -1.5 times of
dye ) are added one by one and stirred. Boiling water is poured in and stirred . The
solution is boiled for 5-10 minutes if necessary . Sodium sulphide reduces the dye into its
leuco form . Soda ash neutralizes the acidity of the dye . The insoluble sulphur dye is
converted into soluble sodium salt ( Leuco Form ). Original colour of the solution is
changes into reduced colour .
Dyeing :
Fabric is loaded in the machine. The dye bath is set up as Per M:L ratio.Bath
temperature is raised to 50oc. Circulation of liquor or material is started . The dye bath
should have sufficient quality of sodium sulphide and soda ash . PH of the bath is10 -11.
5 min
The pre dissolved dye solution is added. Bath temperature is raised to 90oC - 100oC.
The fabric should not expose in the atmosphere as the oxygen in the air may oxidize the
dye and causes „ Patches „.
5 min
10 – 20 20 gpl Glabour salt or comman salt is added in two instalments with a time of
interval of 15 minutes . The dyeing is continued is continued for further process
45 min – 60 min . Dye penetrates well into the fibre molecule .
The material is squeezed ( It should not be washed )
Oxidation :
The leuco dye inside the fibre molecule is oxidized into its original insoluble form.
The dye molecule is mechanically trapped inside the fibre molecule and hence it can not
come out in subsequent washing . There are two types of oxidation namely
I) Air oxidation
II) Chemical oxidation
In air oxidation , the material is exposed to atmospheric air for 15 min
In chemical oxidation , the material is treated with 1-3 gpl sodium perborate or
2 gpl H2O2 with 1 gpl acedic acid .
After Treatment:
The fastness to light and washing of sulphur dyes is improved by after treatment with
the following solution . It should never be done for sulphur black .
1.25% Potassium dichromate ( K2Cr2O7 – To improve wash fastness)
1.25% Acedic acid (60%)
1.25% copper sulphate ( CUSO4 – To improve the light fastness )
at 60oC for 30 min
Hot Soaping – 5gpl soap and ash at 80oC for 15 min
Cold wash for 15 min
Bronziness :
Bronzing of shade is nothing but an unwasnted glittering patches on surface of fabric , most
commonly occurring fault with sulphur blacks and blues which is caused by
1. Excessive delay in washing off the material after it is taken out from the dye bath .
2. Excess of dyestuff on the material or too much salt in the bath .
3. Insufficient sodium sulphide in the dye bath and due to it incomplete solution of
the dye stuff which results in surface dyeing of the material where it is quickly
oxidized by contact with the atmosphere
Bronziness can be removed by treating the dyed material in boiling soap or sodium
sulphide solution.
Sulphur Black Tendering :
Sulphur black tenders and dyed material . It has been attributed to the presence of
free sulphur , which gets converted in to sulphuric acid on storage that degrade cotton by
hydrolysis of cellulose . The sulphur black dted material should not be treated with copper
sulphate as it is tendered more rapidly . the danger of tendering on storage can bre reduced by
treating with potassium dichromate followed by washing with 8 gpl soda ash .
13a) Brief on Block Printing ?
Block printing is the oldest and the simplest method of printing . Because of its
artistic and decorative value and the purity and richness of colour produced by it the method
it still used in many countires of the world .
The blocks used in this method are made of several layers of comman timber which
are comented together and the portions to be printed are carved or raised in relief on a thick
block of wood . Metalic blocks such as „T „ japs are used for special work as in Batik Printing
In block printing 10 – 40 needles is used in this instrument . Colour in the form of a
thickened paste is applied to the raised parts of the block and the impression of the design is
obtained by stamping the block by hand with a wooden mallet and the cloth should be
printed .
Each shade of a colour requires a separate block and in very large3 patterns , each
individual colour may require more than one block . Thus in a design called “ Dutch Boquet “
Which has 23 colours in it , 126 Blocks are used for printing the designs .
Procedure :
The colour paste is spread on the woollen cloth of the sleve „a‟ . the block is carefully
placed on this sieve and pressed twice (or more ) so that it picks up auniform layer of paste ,
it is picks up auniform nlayer of paste , it is then stamped on to the cloth on the table by
giving belows or striking it with a small but heavy mallet ( or hammer ) to ensure a clear
impression . A separate sieve „a‟ is required for each colour but the same swimming tup can
be used over and over again . By repeate stamping of the colour paste , the pattern is built up
and process is repeated until all the colours are seperatly applied and the whole piece of cloth
is printed . It is then removed , dried and given appropriate after treatment .
Advantage :
a. The method is simple to operate and does not reouire elobrate and expensive
equipment .
b. Designs in any number of colours and on any scale can be reproduced with ease
and certainly by this method .
c. First – rate block prints possess richnss , fullness and purity of colours
Disadvantage :
a. The method is slow and therefore , has a low output and its cost is high .
b. For printing block designs or designs with very long or wide repeats , it is not
possible to use a large – sized block of great weight because the printer will not be
able to manipulate properly such a block .
c. The method involves manual work , it is therefore ,quite laborious .
13. b ) Write notes on Duplex Printing and Warp printing ?
Duplex Printing :
Duplex printing stimulates a woven pattern by printing the fabric on both sides . The
fabric may be passed through the roller printing machine in two separate operations or
through a duplex printing machine in a single operation or through a duplex printing
machine in a single operation . Duplex printing produces an equally clear outline on both
sides of the fabric . The designs is applied so skillfully by careful registration of the printing
cylinders that the result may be mistaken for a woven designs . The difference can be
detected by raveling a yarn .
Warp Printing:
Warp printing is roller printing applied to warp yarns before they are woven into
fabric . fine white or neutral – colored filling yarns are generally used for weaving so that the
designs on the warp will not be obscured . This methods produces designs with soft ,
nebulous , but striking effects . Great care must be taken to keep the warp yarns in their
proper position so the outline of the designs will be preserved , warp printing is used for
expensive cretonnes are upholstery fabrics .
A variation of warp printing is vigoreux printing of mélange . Utilizing a variation of
roller printing , horizontal or cross – striped designs are printed on the ropelike woll tops or
slubbings . Subsequently when the tops are spun in to yarn , the stripes are attenuated and
pulled apart so that they appear scattered flecks of color in the woven cloth.
14 . a) Write Short Note on Friction Calender ?
Calendering :
Object:
To upgrade the fabric handle and to impart a smooth silky touch to the fabrics.
To compress the fabric and reduce its thickness
To improve the opacity of the fabric
To reduce the air permeability of the fabric by changing its porosity
To impart different degree of Lustre to the fabric.
To reduce the Yarn Slippage.
Friction Calender :
For producing this effect , the top four bowls of a 7 bowl calendar can be lifted up ,
disconnecting the contact between the third and the fourth bowls so as to use only three
bowls.
The above diagram is a friction calendar with a 7 bowl calendar after disconnecting the
top four bowls .
The three bowl calendar , one of which is cotton and the other two or of chilled iron .
Friction calendering gives a higher Gloss and greater closing of the yarns , it is produced
by bringing the cloth in contact with a heated polished chilled iron bowl is rotated at double
the speed of the fabric and of the lower two bowls .
As the variation , the top bowl may be run at 11/2 times the speed of the lowest bowl , with
the middle bowl running at an inter mediate speed .
The top bowl with its higher surface speed produces the friction effect by polishing the
cloth .
This finish is generally imparted to loose construction cloth such as binding cloth , low
quality printed cloth etc., .
It is generally run at a speed of 32 mts/min .
The speed of the calendar when used in friction calendaring is determined by the amount
of finish desired on the fabric and by the number of bowls used.
14.b) write notes on Flame Retardan Finish for cotton ?
Theories and mechanism of flame Retardency :
1. Coating theory:
Flame retardance is due to formation of alayer of a fusible substances which
melt s and forms a coating thus excluding the air necessary for the propogation
of flame . carbonates and ammonium salts liberates gases like CO2, NH3 and
exclude air .
2. Gas theory :
The flame retardant decomposes at burning temperature and develops non
combustible gases which obstruct and dilute the combustible gases . Eg .
Mixtures of titanium and antimony oxides .
3. Thermal theory :
Heat supplied from the source is conducted from the fibres very rapidly that
the fabric never reaches the temperature of the combustion .
4. Chemical theory :
The flame retardants react with cellulose on burning and forms chemicals
such as phosphoric and sulphuric acid which are dehydrating agents , these
brings about catalytic dehydration of cellulose , which on combustion
produces mainly carbon water .
Flame retardant finish for cotton:
First method:
By depositing insoluble metallic compounds , the effect of fire proofing
obtained is permanent as it does not wash out .
Out of all Antimony Oxychloride is the best .
It is precipitated on the fibre by the double decomposition of tartaremetic and
stannic Oxychloride and then washed in running water .
In the same manner . Metallic Salts such as Magnesium Borate , Ammonium Sulphate and
Magnesium Silicate also produce fire proofing
Second Method :
Soluble Compounds such as Borax . Sodium Phosphate are used . A mixture
as given below is found to be effective for this finish .
Borax - 50 Parts
Boric Acid - 35 Parts
Sodium Phosphate - 15 Parts
Only 5% Solution of the mixture is used .
Most of the fire proofing agents can be fixed by synthetic resins .
Most of the fire proofing agents can be fixed by synthetic resins.
Tetrakis Hydroxy Methyl Phosphonium Chloride (THPC) . when used with Urea and
Methylol . Melamine produce good wet fastness flame proofing properties .
The fabric is padded through the solutiojn containing .
THPC - 15.8 %
Methylol melamine - 9.5%
Tri ethanol amine - 3%
Urea - 9.9%
Dried and cured at 140oC for 5 mins and washed . This process is known as „proban „
finishing .
Process Sequence :
Pad – Dry – Cure
15 a). Classification of finishes? Explain types of finishing?
Finishing:
Finishing is one of the essential processes of a processing mill where all bleached,
dyed and printed material are subjected before they are put on the market. The aim of the
textile finishing is to render textile goods fit for their and uses
Classification of Finishes
Textile finishing
Chemical mechanical
Reactive type of finish Deposition Temporary Permanent
Eg:- parchmentising (stiff and Eg . Calendering Eg.Raising
Transparent chlorination of wool Sanforising
(anti shrink) mercersing velan
PF (Flame retardant) Ethylene Temporary Permanent
Oxide-Formaldehtyde (soil release) Eg:- starch china clay Eg:- synthetic
phosphorus and Nitrogen waxes (soft) optical Brightening.
compounds (stiff) oils fats and Brightening. china clay (stiff)
Flame retardant) rubber, coating
All ARE PERMANENT. (water proof)
cellulose acetate,
cellulose
Types of finish:
Finishing mainly falls into three groups:
Temporary finish.
Permanent finish (and)Semi – Permanent finish
Temporary finish:
A finish which is not stable and goes off after the first wash is known as
“TEMPORARY FINISH‟
If the finishing effect in the fabric disappears during subsequent washing and usage
then it is called “TEMPORARY FINISH”
For example : Mechanical : Calendering, Embossing etc.,
Chemical : starching, softening (Except Reactive softness)
Permanent finish:
If the finishing effect in the fabric does not disappear and remains unaffected through
all the conditions of wear and washing treatments, then the finish is said to be a
“PERMANENT FINISH”.
For Example:
Mechanical : sanforising, mechanical mills of wool, etc.,
Chemical : Resin finishing, water proof, flame proof finish, etc.,
Semi – permanent finish:
A finishing on the fabric is said to be “ SEMI PERMANENT FINSH” if it is stable to
more than 5 to 10 wases and not agterwards.
For Example: Mechnical : schreiner Calendering
Chemical : Buckram finish
5.b) What is Decatising ? Explain with Diagram?
Decatising:
This is also a finish similar to felt calendaring mostly meant for woolenfabrics. But
today all suitings are decatisod.
Both batch and continuous methods are available:
Essentially, this is a stress – Relaxation process.
The function of setting is to relax the various
Stresses built up in the material during spinning and weaving to stabilize the fibres in the new
and desired construction.
Wool fibre contains small quantity of Thiol groups (-SH). It can be converted into
Disulphide bond (-S-S) by reaction of wool with a reducing agent or by the action of hot
water, steam or alkalies.
This interchange reaction and hydrogen bond rearrangement are important in wool
setting.
Mechanism:
The fabric is compresse between two layers of woolen felt and steam is blown
simulttareously. The fabric acquires body, suppleness with ironing effect on both the faces.
These are due to the swelling of the fibre by steam.
Parameters:
The effectiveness of decatusubg depends on
1. Type of fibre.
2. Time of contact
3. Amount of contact
4. Tension
5. Type of finish desired
DECATISING MACHINE
1. Steam Heated Cylinder
2. Exgayst
3. Steam kube
4. woolen felt.
5. Table
6. Finished Material
process:
Without the fabric felt is run forward and backward for 15-30 minutes. The fabric is
fed along with the woolen felt. The amount of fabric to be fed depends on the length of the
woolen blanket.
Normally one piece is fed. The piece is cut at the joint. The chamber door is shut and
the steam is opened and maintained at a pressure of 10- 15 PSI. the felt is run forward and
backward with the help of reversible motor for 5 minutes.
After the treatment time, (Normally 7 minutes) steam is shut off and the fabric is
collected and laid on the table.
Chemical Decatising:
It will give a full soft feel.
Normally sodium Bisulphide is used at a concentration of 10-20 gpl.
Pad – Dry – Steam
Padding is done at an expression of 50% on a padding mangle.
Steaming is done by winding the material on a perforated beam of a decatising
machine and steamed for 3-5 minutes followed by the application of vacuum till the fabric
cools.
10 Marks
16. Write about the process sequence for cotton? Explain?
Cotton:
Process sequence for cotton:
Row Meteraial (cotton Grey fabric)
Singeing
Desizing
Scouring
Souring
Bleaching
Mercerizing Dyeing printing
After treatment (Both chemical
Mechanical process)
Singing :
Removal of loose hairy fibres protruding (or) projecting from the surface of fabric by
burning is called “singeing”
Object of singeing:
Singeing is the process of removing the loose hairy fibres protruding from the surface
of the fabric by burning. These are done to give a smooth, even and clean looking face to the
fabric.
Desizing
Desiing is the process of removal of siaing material deposited on the fabric during the
sizing operations.
Object of Desizing :
The object of desizing up of the pores of the fibres. This makes the fabric soft & more
absorbent.
Recipe:
Hydrochloric acid = 0.5-1%
Sodium chloride = 0.5-1%
Condition :
Time =1-2hrs
Temperature = room temperature(R.T)
Ph = 4-4.5
Material to liquor ratio = 1:20
Scouring:
After desizing and through washing the cloth contains oils, fats, waxes, seed bits, leaf
particles and nature clouring matters, etc., these oils, fats, waxes are hydropholic or water
hating characters. So if these compounds present in the cloth, they affect the absorbency of
cloth. This leads to improper dyeing, printing and finishing in subsequent process.
Recipe:
Sodium hydroxide = 3%
Soda ash = 2%
Wetting = 1%
Condition:
Material to liquor ratio = 1:30
Temperature = boiling temp
Duration = 2-3 hours.
Souring
This process is done to neutralize the fabric. This process is done mostly after every
process.
Bleaching:
Bleaching is the process of removal of natural coluoring matter (yellouwish grey
colour) persent in the textile material by using NaOcL, CaOcl, H2 –O2, SO2, etc.,
Recipe:
M2 O2 = 4
Sodium silicate = 4.8 gms / lit
Sodium Carbonate = 0.5-1 gms/lit
Condition:
Ph = 10.5 -10.8
Temperature = 1 to 2 hrs
Time = 1 to 2 hrs
Material to liquor ratio= 1:50
Mercerizing:
Mercerisation improves the luster of cotton fibres also gives the cotton material a
greater affinity for colouring matters. Mercersing consists of impregnating the cotton material
with cold 25% to 27% caustic soda.
Object
To improve luster of the fabric
To increase the strength of material.
To give good dye absorbing capacity to cotton
To remove crease from fabric
To increase hydroscopicity property
Dyeing:
Dyeing is the process of colouring textile materials by immersing them in an aqueous
solution of dye, called dye liquor. Normally the dye liquor consists of dye, water and
auxiliary.
A dye stuff is a substance which is capable of colouring a textile materials in such a
manner that it associates closely with the fibres.
There are 2 types of colouring matters. They are Dyes & pigments. Dyes also is
divided into 2, they are insoluble dyes.
For Example:
Vat, sulpher, etc, are insoluble dyes. Reactive dyes are soluble dyes and are widely
used for dyeing cotton products because of their wide range of shades availability. Excellent
fastness property moderate dyeing rate (or) cost of dye/kg.
Printing :
It is a process of producing attractive designs on textile fabrics using one (or) more
dye stuffs. Printing is localized dyeing. Printing is nothing bur applying colors with in
boundaries of the designs.
Styles of printing:
Direct style
Discharge style
Resist style
The different styles can be done by using different printing methods like block, screen
flat bed screen, rotary screen, transfer printing, etc.,
After treatment:
After dyeing (or) printing, fabric is taken to after treatment by means of washing and
soaping treatment.
Objective:
To remove the unfixed dye stuff and chemicals from the fabric.
To avoid the bleeding of colours during subsequent washing.
Finieshing:
Finishing is one of the essential process of a processing mill. The aim of textile finishing is
render textile goods fit for their end uses.
Objects:
improved appearance – luster, whiteness, etc.,
improved feel which depends on the handle of the fabric and its softness, suppleness,
fullness, etc.,
it improves the wearing qualities – Non soiling
it increase the weight of the fabric
it increases the sale value of the material
it improves the serviceability of the fabric
Hence, finishing is essential for a textile good before they are put on the market. There are
different types of finish but are applied on the fabric according to its end uses.
17. What is singeing? Explain it briefly?
Singeing is the process of removing the loose hairy fibres projecting from the surface
of the fabric by burning. There are done to give a smooth, even and clean looking face to the
fabric.
IMPORTANCE OF SINGEING:
The fabric should be singed because:
1. The fabric should be mercerized must be singed to develop maximum luster in the
fabric.
2. The fabric to be printed must be singed to import clearly defined and sharp
designs on the cloth.
So, the singeing is considered as important and essential process before mercerishing and
printing.
The main types of singing are,
hot plate singeing
roller singeing
gas singeing
Hot plate singeing:
It is the process of burning away the protruding or projection fibres, by passing the
fabric in full width form over the surface of the heated copper plates.
Roller singing:
Instead of using heated plates heated revolving rollers or hollow cylinders are used to
burn the protruding or projecting fibres.
Gas singeing:
It is the process of burning of protruding fibres by passing the fabric in between
flames of a gas burner. It is more economical, more conuenient and more efficient singeing.
Types of yarns to be singed:
Combed cotton yarns.
Sewing threads
High twisted voile threads
Polyester cotton blended yarns
Mosiery yarns meant for knitting
Types of fabrics should be singed:
Shirting, suiting, sarees, dress materials, voile cloths, poplins, polyester, cotton
blended fabric etc.,
WORKING OF GAS SINGEING MACHINE
GAS SINGEING MACHINE:
Gas singeing is more economical, more convenient and more efficient singeing. It is
mostly used in all processing mills in India. The machine of the following parts.
Guide Rollers
Drying cylinder
Brush roller
Burners
Water trough
Drag roller
Squeeze roller (and)
Steam chamber
Guide rollers:
The main function of guide rollers is to guide the fabric and also to give tension to the
fabric. The guide rollers after the burness are to extinguish any fire sparks present in the
fabric.
Dyeing Cylinder:
The main function of drying cylinder is to evaporate the moisture present in the
fabric. Sometimes more than one cylinder is used in this machine.
Brush Roller:
The main function of the brush roller is to raise the projecting fibres present in the
fabric.
Gas Burner’s:
The number of burners in a singeing unit may vary from 4 to 6. this burners are
arranged in both sides of the fabric which singed at a single passage. The flame is obtained by
burning a mixture of air and cool gas or air and petroleum. The intensity of the flame and its
distance from the fabric can be adjusted.
Water trough:
The object of the water through is to extinguish any fire spark present in the fabric.
Drag Roller:
The function of drag roller is to maintain the speed of the fabric.
Squeeze roller:
The function of the squeeze roller is to squeeze excess amount of water present in the
fabric.
Steam chamber (or) Quench box:
This chamber is filled with wet steam under low pressure. The water tap is sometimes
replaced by steam chamber. The function is to extinguish any fire span present in fabric.
Working :
The fabric from the guide roller is passed under the drying cylinder . It is to evaporate
the moister in the fabric with a help of guide roller , the fabric is comeing under the brush
roller, the fabric . It is to raise the projecting fibres from the surface of the fabric and passes
over and under the guide roller . During that stage over and under the guide roller . During
that stage , the fabric is passed in between their burners.
The burners are present as shown in the figure . the function of burners are present is
to burn the projecting fibres and their immediately the cloth is comeing to the water trough .
this is to extinguish any fire spark present in the fabric and then the fabric is passed in
between drag and squeeze roller and reaches the steam chamber . The
Purpose of steam chamber is to extinguish any fire mark without wetting the fabric. Finally,
we will get signed fabric. The speed of the cloth vary from 180 to 250yards % minutes.
Advantages of Gas singeing;
Both sides of a fabric can be singed at a single passage.
Their production is more because of high speed.
There is a possibility to maintain the temperature evenly throughout the fabric.
Fibers in the interstices are brunt
Different varieties of cloth can be singed.
Disadvantage Of Gas Singeing
When the flame is not controlled there is a chance of fire on the cloth.
Precaution in Gas singeing Machine:
The singeing machine must be kept separately from other machines.
The before singeing, the cloth should be died well.
Correct amount of heat should be given to the cloth. Otherwise, the cloth may be
tendered.
The speed of the cloth should be controlled properly
When stopping the machine, the flames are first extinguished and then the machine
will be stopped.
After singeing the cloth must be passed through water trough
The machine is enclosed with cover and exhaust fan otherwise the dust affecting the
eyes.
For observing, Glass, windows to be fitted on the nood.
18. What is shrinkage? Explain it briefly?
Shrinkage:
Shrinkage is the contraction in the dimension of the fabric due to usage. Cotton fabric
suffers from 2 main disadvantages of creasing and shrinkage during subsequent washing.
Creasing is overcome by the Resin finishing where as the shrinkage is prevented by a
special finishing known as sanforizing and the machine used for that purpose is known as
zero – zero pre shrinking machine.
How Cotton Shrinks:
Cotton has the property of swelling in water and this effects shrinking.
Also the weaving stress, strain and tension during spinning and weaving etc., when released
causes the fabric to shrink.
The cotton fabric when put in water swelling takes place and rearrangement of
internal forces takes place. The fibres will become free from tension and it comes to the
original tensionless state.
There are reasons the warp yarns are under much strain due to interlacement than the
weft yarns. Hence, when a fabric is allowed to shrink the warp your shrinkage will be more
than weft yarn.
To overcome this the fabric is extended in width wise to some extent in the stenter
machine during finishing process. Then it is subjected to the pure shrink process.
Mechanism:
The mechanism (or0 principle adopted to produce shrinkage is “to place the fabric on
the fabric on the extended surface of a rubber blanket represented by the concave surface.
When the tension is releared on the blanket, it shrinks, the fabric which is in close contact
with the rubber blanket at the concave surface has no way other than shrinking along with the
blanket”.
This principle is used to produce pre shrinking finish with the help of a sanforising
(or)Zero – Zero machine.
The amount or % of shrinkage depends on:
1. The tension / stretch on the rubber blanket
2. Thickness of the rubber blanket
3. Diameter of the roller
Generally three sizes are available:
Thickness of Blanket to be used If shrinkage of fabric before sanforising
is
0.275”
0.4”
0.45”
6-8 cm / m
8-11 cm / m
11-15 cm /m
The optimum moisture content of cotton and viscose fabric priors to compressive shrinkage
treatment in the machine must be 20-25% At lower moisture content different deformation of
the fabric may result. The deformation of the rubber blanket is 6-22% and the fabric
shrinkage is 3-4%. If the pressure exerted by the metal atm. Pressure, the rubber blanket is
deformed to 15% while the fabric shrinks
Machine Description:
This is a mechanical method of shrinkage control. The cloth is fed into the machine
through the feed rollers of a mangle. It is used to hold back the cloth and only allow the felt
blanket to contract to the required amount. Otherwise Over shrinking of the cloth occurs.
From the feed rollers the cloth passes between sprayers to moisten the cloth there by
making the yarn soft and plastic so that it can be easily compressed by the blanket.
The moistening is assisted by a steaming unit called skier. Then the cloth passed through a
short clip stender to control the width of the cloth.
The cloth is passed to the blanket over the feed roller and is placed in firm contact with the
stretched surface of the blanket by electrically heated shoes.
If main cylinder of the machine may be either 60” (or0 84” in diameter to the material for
which it is interned.
After passing a round of the drum of the palmer machine, the finished material may
be passed on to a auxiliary finisher.
It has an additional palmer unit.
It can be used
1. when both sides of the material are to be finished a like (or)
2. when additional shrinkage is required
if the additional palmer unit is used, the range is called as Duplex otherwise is called as
“Simplex”.
There is a blanket centering device to keep the blanket in a straight path on the
cylinder and also and indicator for giving the tension on the blanket.
The electrically heated shoes are lifted from the blanket automatically when the
machine is stopped to eliminate scorching. Before leaving the sanforiser, the fabric should be
thoroughly dried otherwise it will elongate.
Proper use of the sanforiser enables shrinkage on laundering. (Residual Shrinkage) to
be reduced to 0.75% or less.
After coming out of the felt calendaring unit the fabric is guided to the plater which
plaits the fabric in to trolley.
19.what is Reactive Dye? Explain Dyeing of cotton with Reactive cold brand Dyes?
Reactive Dyes:
The reactive dye originally reacts and form covalent bond with the fibre and hence
they are called as “Reactive Dyes”. Because of the strong covalent bond with the fibre, it has
good fastness properties.
Classification of Reactive Dyes:
Classification of reactive dyes :
1. Hot brand dyes – mono chloro tri azine dyes . These dyes have only one cl- group as
the reactive group which needs higher temperature to be available for reaction with
fibre . Hence they are called as HOT brand dyes .
2. Cold brand dyes – Di chloro Tri azine dyes . These dyes have two CL – groups and
hence they react with fiber even at room temperature . so they are called as cold brand
reactive dyes.
3. Vinyl sulphone dyes – Ramzol dyes.
4. Drimarine dyes – Ex….Levafix dyes
5. High Exhaustion dyes – HE dyes
6. Bi-functional dyes – ME dyes., FN dyes etc.,
Dyeing of cotton with reactive cold brand dyes
Dissolving the dyestuff
The dye is taken as per the shade% and pasted with a little quantity of wetting agent.
Then warm water is added and stirred.
Dyeing (Exhaust Method)
The dyeing procedure in winch dyeing machine is explained below. The fabric is loaded in
the cachine. The water is filled as per M:L ratio (1:20). The circulation of material is started.
5 min
Dye solution is added
5 min
½ of 30-50 gpl Sodium Chloride (Common salt) or 20-30 gpl Sodium Sulphate (Glabour salt)
is added as Exhausting agent It exhausts the dissolved dye from the solution and transfers the
same to the same to the substrate. (Refer mechanism of dyeing)
15 min
Remaining salt is added and the dyeing is continued.
45 min
10-20 gpl Sodium carbonate is added as fixing agent. This alkali enables the dye to form
covalent bond with the fibre.
30min – 60 min depending on shade
Hot wash at 50oC for 15 min
Cold washing 1% Acetic acid for 15 min
Hot soaping in 5 gpl soap and 1 gpl soda ash at 50oC for 15 min
Cold – washing for 15 min
20. Explain the mechanism of textiles finishes like glazing ,cireing andGigging on
fabrics?
FINISHING
Finishing is one of the essential processes of a processing mill where all bleached,
dyed and printed material are subjected before they are put on the market.
The aim of the textile finishing is to render textile goods fit for their end uses.
Finishing gives the following advantages:
1. Improved appearance – Lustre, Whiteness etc.,
2. Improved Feel which depends on the handle of the fabric and its Softness,
Suppleness, Fullness etc.,
3. It improves the wearing qualities – Non soiling, Anticrease.
4. It gives special properties required for particular uses – Water proofing , Flame
proofing etc.,
5. It covers the faults of the original cloth.
6. It increases the weight of the fabric.
7. It improves the sale value of the material.
8. It improves the natural attractiveness of the fabric.
9. It improves the serviceability of the fabric.
Hence, Finishing is essential for a textile good before they are put on the market.
TYPES OF FINISH
Finishing mainly falls into three groups;
1. Temporary Finish
2. Permanent Finish
3. Semi – Permanent Finish.
TEMPORARY FINISH
A finish which is not stable and goes off after the first wash is known as
TEMPORARY FINISH.
If the finishing effect in the fabric disappears during subsequent washing and usage
then it is called TEMPORARY FINISH.
Eg. Mechanical : Calendaring, Embossing etc.,
Chemical : Starching, Softening (Except Reactive softeners)
PERMANENT FINISH
If the finishing effect in the fabric does not appear and remains unaffected through all
the conditions of wear and washing treatments, then the finish is said to be a permanent
finish.
Eg., Mechanical : Sanforising, Mechanical milling of Wool etc.,
Chemical : Resin Finishing, Water proof, Flame proof finish etc.
Glazing
A stiff polished or glazed surface can be obtained by the application of starch, glue,
mucilage, or shellac followed by friction calendaring. The process makes a fabric resistant to
dust and spots and minimizes shrinkage. This finish is found principally on chintz. Vita-
Glaze is a typical trademark.
Cireing :
The cier process may be applied to silk , rayon , or nylon woven fabric usually satins
and taffetas – but may be also be used on knitted goods. Wax are another appropriate
compound is applied to the fabric, followed by hot calendaring. The result is a super gloss
almost metallic in appearance . ( A shiny surface given by a hot calendaring alone to a fabric
of a thermoplastic fiber is also called cire.
Gigging :
Wool fabrics may be napped ,or they may be subjected to a raising process called
gigging . when the fibers is first saturated with water . when the fibres of a rated with .when
the fibres of a moist wool fabric are raised, thay tend to curl and shrink . when brushed in one
direction a smooth and lustrus appreance result.
Tigering :
Fabric having a high ile or nap may be given a tingering finish to lift and comb the
nap so as to improve or modify , its height and remove loose fibres. The tiger roll has long
fine wires then penetrate to the ground of the fabric to lift up the fibres not raised by the
napper rolls. The effectiveness is dependent upon the wires , their nature of their hooks.
Tigering may be done to such be done such fabrics as velour ,limitations and imitations fiber