pretreatment of textile

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singeing, desizing, bleaching & other textile processes

Transcript of pretreatment of textile

TYPES OF SINGEING

PLAT SINGEING MACHINEPlat singeing machine consist of one or two copper plate in form of curve.Heater of plat using charcoal or mixture between air and gas. Fabric overcome by friction at hot damper smolder with speed 125 250 metre/minute so that fur will burning. Description of figure: 1. Guide rollers 2. Singeing plat 3. Fabric

Figure of plat singeing machine

CYLINDER CIRCULAR OF SINGEING MACHINECylinder singeing machine is development of plate singeing machine,its made cylinder of copper, hot from within using gas fuel, charcoal, oil, electrics. Fabrics overcome at circular cylinder of giration by two surface,

like at burner of plate fur, burner of cylinder fur also yield lustrous fabric.Both types of this machine very good to heavy cotton fabric type.

Description of figure : 1.Guide rollers 2. Fabric 3. cylinder

DISADVANTAGES

GAS SINGEING

UNWINDING

PRE-BRUSHING

SINGEING

POST-BRUSHING

IMPREGNATION

BIG-BATCH

GAS SINGEING

SINGEING

BEFORE SINGEING

AFTER SINGEING

SINGEING

This is fabric going through a singeing machine

DESIZINGOnto de-sizing

SINGEING

DE-SIZING

SCOURING

BLEACHING

MERCERIZING

PRE-TREATMENT

DESIZINGThe reason for de-sizing because during the spinning and weaving process, the fabric goes through sizing.

SIZING is when SIZE is applied to the fabric to protect it from the abrasive action of the loom.

DESIZINGWHAT IS SIZE?

Natural sizing agents are mostly based on starch and starchderivatives. There are also synthetic sizing agents such as modified polyesters

DESIZINGDe-sizing is the removal of sizing agents from the fabric using enzymes, acid, oxidative agents, etc. Enzymatic de-sizing is the most common.

STARCH (AMYLOSE)

TYPE OF DESIZINGROT STEEPING

ACID STEEPING

ENZYME DESIZING

dextrins Attack randomly FAST REACTION and produceSTARCH Attack at particular places and produce SLOW REACTION

maltose

ENZYME DESIZINGAmylase Optimum PH Optimum Temp(C) Effect of NaCl Effect of CaCl2

PancreasMalt Malt Bacterial

6.8-7.04.6-5.2 4.6-6.2 5.0-7.0

40-5555-65 40-50 60-70

+ O

++ __ +

DESIZINGIrrespective of what kind of de-sizing, the process includes: Impregnation of fabric with de-sizing agent Allowing the de-sizing agent to solubilize or degrade the size Washing out the degradation products

Process route

DESIZING

OXIDATIVE DESIZING

(1) Sodium Hypochlorite (2) Hydrogen Peroxide Sodium Hydroxide pH Steamed for Temperature Pad cold and store overnight

2 g/l at room temperature 1 to 2 volume 7 to 15 g/l 10.0 2 to 3 minutes 30 to 40 C

The residual starch content on the weight of the fabric after desizing should be less than 1.0%

DESIZING EFFECIENCYCONVENTIONAL METHOD

TEGEWA RATING

CONVENTIONAL METHODWEIGHING

W1

DESIZING TREATMENT WITH HCl

W2W3 .

W1 W3 W2 W3

TEGEWA METHODPREPARTION OF TEGEWA SOLUTION METHOD & ASSESSMENT

Potassium iodide (10 gm. Of KI (100%) in 100 ml waterAdd 0.6358 gm of iodine (100%) stir and shake Fill up to 800 ml with water then complete to 1000 ml with ethanol

Spot drop wise Tegewa solution onto fabric Rub in gently and Assess change of colour

Shelf life approx 6 months only

Grey fabric: No change of colour = no starch size present. Desized fabric: Pale blue to bluish violet = refer to violet scale TEGEWA This indicates residual Starch contentViolet =of starch size with synthetic size

FABRIC IN OPEN WIDTH

CONTINUOUS DESIZING IN j- BOX

CONTINUOUS PROCESS FABRIC FORM

SCOURINGLets talk about scouring.

SINGEING

DE-SIZING

SCOURING

BLEACHING

MERCERIZING

PRE-TREATMENT

SCOURING

FATTY ACIDS FATTY ALCOHOLS OLEIC ACIDS INSOLUBLE IN WATER

PECTIC ACID COOH GROUP PRESENT INSOLUBLE IN WATER

FAT & WAXES

PECTINS

IMPURTIES

PROTEINS NITROGENOUS COMPOUNDS COLOURING MATERIALS PRESENT IN PRIMARY WALL AND LUMEN

MINERALS POTASSIUM CHLORIDE POTASSIUM CARBONATES CALCIUM SULPHATES

SCOURINGSCOURING can be carried out as a separate step of the process OR in combination with other treatments (usually bleaching or desizing) on all kind of substrates (fiber, woven fibers, knitted fibers).

Cotton chemical structure

SCOURING

TYPE OF SCOURINGSOLVENT SCOURING

AQUEOUS SCOURING

SOLVENT SCOURING

SOLVENT SCOURING

DRY CLEANING

SOLVENT SCOURING

ADVANTAGESdissolvelow liquid surface tensions penetrate

evaporate

DISADVANTAGESflammable explosion hazards carcinogens atmospheric ozone depletion phosgene and hydrochloric acids corrosive to met

damage cellulosic fibersexpensive recovered

removal of motes, metal ions, starch and other solvent

SOLVENT SCOURINGCOMMON SOLVENTS

PROPERTIES OF SOLVENTS

Boiling Point

Specific Heat:

Latent Heat of Evaporation:

AQUEOUS SCOURING1. WATER 2. CAUSTIC 3. SEQUESTERING AGENT 4. WETTING AGENT OR SURFACTANT

SEQUESTERING AGENT

CHEMICAL REACTIONSREACTION WITH CAUSTIC SODA

FAT & OILS

SOAP soap of sodium dissolve easy in water

REACTION WITH SODA ASH(SODIUM CARBONATE)

FAT & OILS

SOAP

RECIPE SCOURING PROCESS

scouring process of cotton with Na2CO3 and NaOH used exhaustion method

PROCEDUREWeigh Materials and chemical agents as according to calculation of recipe Water and chemical agent prepared as according to liquor ratio at recipe Fabric done at solution process with temperature 95oC,then stir to flatten during 60 minute

Afterwards cloth cleaned by hot water ,then cleaned to be chill water Materials dried is later,then weigh and perceived, do test of fabric absorpsion