Production of Denim Fabric By The Use Of Slasher Dyeing

Traditionally, denim was dyed with various shades of indigo, yarn-dyed, different costs, and over-dyed with various types finishes at fabric as well as garments state.. To make a denim

“PRODUCTION OF DENIM FABRIC BY THE USE OF

SLASHER DYEING”

DEPARTMENT OF TEXTILE ENGINEERING

Project Report On

“PRODUCTION OF DENIM FABRIC BY THE USE OF SLASHER DYEING”

Introduction

Denim is the oldest, most widely used, most fashionable and most

versatile fabric of the world At present denim is mainly used for producing garments particularly trousers for the young people The gross production

of denim fabric is approximately 3,000 million metres per year

Denims are produced from 4 oz to 16 oz./ sq yds in weight

Technically Denim is defined as a 3/1 warp faced twill but also produced from weaves like: Left hand twill, right hand twill, broken twill, cross

hatches, cords, dobby's, structures, etc

Denims are made from yarn dyed warp and undyed weft

Traditionally, denim was dyed with various shades of indigo, yarn-dyed, different costs, and over-dyed with various types finishes at fabric as well

as garments state Denims are manufactured different types of after

treatments or washes like stone wash, bleach wash, hand wash, acid wash, over dyed, printed denims and even embossed.

Denim fabrics are used as jeans trousers both for men and ladies

It is extensively used in the world as casual garments, Shirts, jackets,

children wears are also made of denim fabrics Its versatility, finds

applications in furniture upholstery, bed covers, curtains, etc Denim

now-a-days is a very demandable product To make a denim fabric the

required yarn for the definite construction should be dyed then make a

weavers beam to go to weaving to make fabric

TYPE OF FABRIC :

Normal Fabric

Ring Fabric

Half Cross Fabric

Cross Latch Fabric

FABRIC IDENTIFICATION :

Normal Fabric = 6 OE * 6 OE / 66 * 35

Ring Fabric = 6, 9, 12 * 7 OE / 66 * 35

Half Cross Fabric = 6 slub * 7 OE / 66 * 35

Cross Latch Fabric = 10 slub * 10 slub / 66 * 35

TYPE:

'Some typical denim fabric

100%Cotton light Indigo Slub

98.5%cotton 1 5%lycra park

indigo stretch slub 11.50 65X46/7.5RsX8+70D 3/1 RHT 100% Cotton indigo normal 12 10 OE+10 OE*12

Most of the denims are produced with 100% cotton and cotton-based blends with Lycra®, Polyester, Tencel®, Bamboo, Jute, Nylon, and Linen etc An ideal cotton mix for denim should have the following quality parameters.

In Bangladeshi mills, in most cases substantial quantity of waste yarns are used This is

mainly done to reduce the cost of production A well established mix for denim yarns are as follows;

i 80% waste, which consists of

(i) Dropping-1,

(ii) Dropping-2,

(iii) Flat strip,

(iv) Comber noil.

ii 20% Fresh Cotton

FIBRE

YARN

(i) Rotor yams are the best and most widely used yarns in Denim production Because of their very high speed rotor yams are much cheaper than ring spun yams Off course rotor can only produce yarns of up to 30Ne Though cheap

rotor yarns are associated with greater imperfections than corresponding ring yarns therefore knit goods are produced from ring yarns.

(ii) Count range from 6 to 16 Ne but most widely used range is 7 to 12 Ne For slub yarn the range is 9 to 20 Ne.

(iii) Quality- Counf CV-<1.2, Single yarn strength> 12.8 gm/tex, Elongation> 6.0,U% <9.5.

(iv)As huge amount of slub yarns are used today the idea of too much strict U% is not considered.

The diameter of slub varies froml.SD to 2.2D (Where D is the normal dia of yarn) The periodicity of slub also varies widely Test results show mat the distances between two adjacent slubs varies within certain range Some of the usual range distances between two adjacent slubs are from 6cm to 10cm, 7 cm to 20 cm, 30cm to 60cm.

Some more information on yarns are given in weaving section later

Fig: Creel stand with creel

Fig: Unwinding of creel

Fig: Warpers beam

The thread from the packages in the creel is wound on to a beam to make warp beam.

PARTICULARS OF A DIRECT WARPING MACHINE

Setup parameter

>• *

Range Set value

-99,999m Based on quantity yarn count, warping beam, capacity

Cone/Cheese no in the creel !

min 650 m/min; Based on yarn count and qualityLength correction % 1 156%

Stop motion I

Carrier Pressure 1-160 50/55 psi

Normally the process of dyeing dictates the technology of denim manufacturing

The following twoDyeing methods are most popular processes for manufacture of

denim

SLASHER DYEING:

Slasher dyeing dyes the yarns in the warp beam form It is a continuous process which combines dyeing & sizing in a single operation Dyeing is done by

continuously passing warp yarns through several (at least 5) troughs of indigo dye

liquor The dyed yarns are then sized & wound onto a warp beam to be ready for use in the weaving process Slasher dyeing is usually of inferior quality as compared to rope dyeing shade evenness or side-to-side shade variations With the slasher dyeing, the penetration of dyestuff is poorer, and it is easily reveals an uneven pick-up along its width with the distortion of the pad-roll.

Fig: Diagram of Slasher Dyeing

FLOWCHART OF DYEING & SIZING:

Warper’s Beam

 Pretreatment (Scouring) bath

 Dryer- wash bath (1, 2, 3)

 Color box - 1

 Dryer - 1

 Color box- 2

 Dryer - 2 (Air oxidation is done here)

 Color box - 3

 Steam box

 Color box - 4

 Yarn pass between a set of guide roller for oxidation

 Color box - 5

 Oxidation

 Color box - 6

 Guide Roller

 Color box - 7

 Oxidation

 Color box - 8

 Oxidation

 Wash box (1, 2, 3)

 Dryer

 Sizing box

 Dryer

 Accumulator

 Leasing

 Winding

 Weaver’s beam

•Type- Sliding creel

•Arrangement- Two creels are placed parallel to each others.

•Creel capacity-16 warp beams can be placed in each creel

•Electronic motor is available to slide the creel as well as mount the beams.

Beam creel section:

Fig: Beam creel

Capacity of cooking tank: 1000

Fig: Sizing Tank

1 01 To remove natural & added impurities like oil, wax, gum, fatty material as completely as possible.

2 02 To get a clean & even fabric surface for the next process.

3 03 To increase the absorbency of the fabric, i.e to make the fabric hydrophilic, so that it can absorb dye molecule, water & other processing easily.

FUNCTION OF THE CHEMICALS USED IN SCOURING:

1 Alkali: It converts the oil into water soluble fatty acid & soap.

02 Wetting agent: A soluble or dispersible material that reduces the surface tension between the material & liquid Detergency effect helps to clean the material.

03 Sequestering agent: It reacts with metallic ions & thus makes the metallic compounds to become a part of complex anion.

For black preparation the following ratio is followed:

Dyeing process that is maintained as follows:

Pure Indigo- Continuous Indigo Dyeing

Bottoming- Sulphur(Bottom) & Indigo(Topping)

Topping- Indigo(Bottoming) & Sulphur (Topping)

Black Denim-Continuous Sulphur Black Dyeing

Color Denim

LIST OF SOME CHEMICALS ARE USED & AND THEIR FUNCTION:

Pimazol ws:

Use as pre-wetting agent to reduce the surface tension of the liquor and allow to penetrated in to the fibers.

Sodium Hydrosulphite / Hydrose:

It is a reducing agent It converts the insoluble vat dye to soluble leuco form & also to remove dissolved oxygen

Ladiquest: It is a sequestering agent and use to remove the hardness of water.

It is used to protect oxidation of dye molecule in dye bath It is used as reducing agent while Sulphur black is

used It is also known as monohydrate glucose

SIZING

Sizing Mills coat yarn with polyvinyl alcohol and starch for strength, and paraffin to make it easier to weave into cloth and handle in sewing It is a film- forming polymeric materials, which is applied to a warp sheet for the purpose of protecting it during the weaving process.

Objects:-

• To increase the strength of yarn Up to 20% after the size application.

• To improve the hairiness, thick and thin places, Neps knots in the warp yarn.

• To protect the warp yarn from breakage during weaving process Which is subjected to abrasion width varies loom parts such as reed heald shaft Shuttle, Splitting rod

Sizing composition depends on the following factors:

• Types of fibers

•Types of yarn

• Yarn quality

• Quality particulars of fabric to be woven

• M/c condition & ambient condition of the loom shade

• Cost of various ingredients

The Starch & Softener are used in the sizing bath are given below:

Starch: Trefin Wax

These are products from grains & tubers These are mixture of carbohydrate, oil, nitrogenous substances & mineral matter Carbohydrate is a polymer consisting of 25% amylase and 75% amylopectin

Structurally it is a highly branched glucose polymer Starches are cheap & easily available & have proved to valuable adhesives over a many years especially for cellulosic yarns This is manufactured mainly from maize, wheat, rice etc When starch is boiled with water, the starch granules swell & break up forming a smooth & homogenous gelatinous mass.

Kind of product: Potato starch derivatives

Appearance: Off white powder

Moisture content: < 20%

pH value (5% conc): 6-8

Viscosity:

Preparation of the solution:

The required quantity of product is added to cold water Under stirring the slurry should be heated up till 95ºc and kept for at least 10 minutes at this temperature Preparation in an autoclave has to be heated up to 110ºc and kept for at least 10 mins at this temperature.

EMSIZE E-14:

Application: Emsize is a starch sizing agent for spun

yarns

Characteristics:

Kind of product: High modified polymer

Appearance: Off white granules

Moisture content: 9-14%

pH value (5% conc): 9.5-11.5

Viscosity:

Preparation of the solution:

The required quantity of product is added to cold water Under stirring the slurry should be heated

up till 95ºc and kept for at least 20 minutes at this temperature Preparation in an autoclave has to be heated up to 110ºc and kept for at least 10 mins at this temperature.

Both the starch has the following common properties:

excellent sizing effect

transparent flexible film

high adhesion power

compatible with other sizing agents

washed out quickly without enzymes

good biological degradability

Modified starch:

It is manufactured from natural starches mainly maize.

Advantage:

They are water soluble.

Can gelatinize easily & quickly

They penetrate well into the yarn because of their small particle Size, & pick up

percentage increases for this reason

Mutton tallow:

It is prepared from the sheep & is chemically composed of the glycerides of stearic, oleic & palmitic acids.

After warping, dyeing and sizing a weaver's beam is produced The

weaver's beam, after drawing and denting is then mounted in the loom to produce the fabric Weaving of denim fabric is not much different from weaving all other fabric except the idea about the warp and weft way shrinkage percent It is well known that fabric shrinks after relaxation and also after any wet process treatment

In order to accommodate the aspect of both way shrinkages it is

necessary to use a very decisive EPI and PPI in the loom state so

that after relaxation and wet treatments the fabric will conform to

the customers supplied fabric details It was found that in general

that the fabric shrinkage percent in the length direction varies

from I2%-15% while in the width direction the shrinkage percent

lies around 4.5% to 5.5 % The higher shrinkage in the warp direction

is mainly due to greater warp tension during weaving and also due to

the coarser weft yams than that of the warp yarns In order to comply

with the customer's requirements it will be necessary to choose both

EPI and PPI very precisely so that the final EPI and PPI of the ultimate fabric conform to the buyer's requirement

The typical reed and picks of some commonly produced fabric is given below;

EPI Loom StateEPI Finish PPI Loom State

PPI

Finished Cover Factor warp Cover

factor

Weft Cover factor

And weft Cover factor, K2 = PPI/√ count

Denim fabrics are highly sensitive to the fault incidence

Warping Ring

yarn Rotor yarn Dyeing Ring yam Rotoryarn

End break per

million metres l<08 <0.5 End break per million

metres

Loss of extension <0.5% <0.4% Loss of extension <1.3 <1.3

Imperfection also plays an important role in the production of a fault

free denim fabric The norms for some of the important indicator of

yarn quality for denim are given below.

^ Parameter Norms for Rotor

Imperfection < 10 (at 280%) <35'9(At200%)

N:B: The CV% can not be applicable to the slub yarns.

GSM Calculation

Yarn count = Length (cm) X 0.0059

Wt(gm)Yarn weight =

Sample weight X 100X100 / Sample Length X SampleWidthX 33.9063

=11.83 oz / yd2

Crimp % :

Warp Length – Actual Warp Length Production / Warp Length * 100

Shrinkage % : Actual Production – Finishing Production / Actual Production * 100

Fig: Front view of a weaving m\c

Fig: weaving m\c (Picanol omni plus 800)

Fig: J Box of a finishing m\c

Fig: Brushing unit of a finishing m\c

Fig: Singing unit of a finishing m\c

Fig: Scew roller of a finishing m\c

Fig: Drying cylinder of a finishing m\c

Fig: Calendering unit of a finishing m\c

Fig: Spreading unit of a finishing m\c

After weaving, the woven denim fabrics undergo for various finishing processes depending on the end uses This is because denim fabric

produced in a loom is somewhat dirty and very stiff and difficult to make

garment from them Apart from this, the technical specification like width

and threads per inch cannot always be achieved straightway from the loom Therefore some physical and chemical treatments are carried out before

delivering the fabric to the customer/garment factory These processes

are discussed under finishing section Finishing of denim is carried out in

both fabrics as well as garment state The fabric finishing is carried out in

the weaving factory where the fabric is produced but the garment state

finishing is carried out in the garments washing plant

Finishing section placed along a line:

Finishing Line Fabric Finishing

The typical flowchart of the denim fabric finishing is as below

Loom state fabric

↓ Brushing

↓ Singeing

↓ Brushing

↓ Softening ↓ Correction of skewing

↓ Compressive shrinkage

↓ Palmer (Calendaring cum drying)

↓ Inspection ↓ folding

Description of the processes:

Brushing:

The purpose of this process is to remove the lint, fluffs and loose impurities This is achieved by subjecting the fabric to kind

of roller beating action Singeing:

The objective of this process is to burn out the protruding

pair of squeeze rollers and the correction roller is either pushed up

or down In the later case two sets of rollers are set at the two extreme ends, the rollers are capable of pulling fabric at differentspeeds What ever is the method of correcting the skew ness, in all

cases attempt is made to compact the fabric sufficiently so that the

tendency of skewing is eliminated