Enzymes used in textile and their effects

 Amylase:  Amylase enzyme is used in desizing that hydrolyzes and reduces the molecular weight of amylose and amylopectin molecules in starch, rendering it water-soluble enough to be washed off the fabric.

Cellulase: Cellulase enzymes are used in cotton bio-polishing which selectively acts on the loose fibres protruding from the fabric or yarn surface. This enzyme can also be used in bio-stoning of jeans.

Pectinase: Pectinase enzyme is used in bio-scouring of cotton to remove hydrophobic (oils, fats) and other non-cellulosic components (dust, dirt).

Catalse: After bleaching with hydrogen peroxide (H2O2), Catalase enzyme is used in the subsequent process which functions to catalyze the decomposition of hydrogen peroxide to water and oxygen.

Protease: Protease enzyme is used in the scouring of animal fibres, degumming of silk and modification of wool fibre properties.

Chemistry involved in dyeing of Polyester with solvents

 Natural fibres cannot be dyed with solvents. Man made fibres especially polyester is now-a-days dyed with solvents. In case of polyester dyeing, it is seen that water is not attracted to both dye molecules and fibre polymer. Because they are hydrophobic, so in polyester dyeing solvent can be conventionally used as dyeing media. The dye is attracted to fibre surface and forms a layer on it. When at high temperature the gap between polymeric chains in polyester fibre is increased the dye molecules enter inside the fibre polymer system. It occurs at about 1300C temperature in case of high temperature dyeing. We can reduce the temperature by using carriers. But, carriers are phenolic compounds which may dissolve the polyester fibre. So, carrier is not used.

Solvent recovery

 The solvent is somehow expensive than water. So, it should be recoverable easily. Therefore, it
should be stable to several distillations. There are 3 main methods of solvent recovery namely- 

1)Air drying
2) Heated cylinder drying and 
3) Steaming.

1) Air drying: Hot air is circulated in closed chambers in where the temperature of air exceeds the
evaporating temperature of solvents. Vaporized solvent is condensed and hence recovered.

2) Heated cylinder drying: A number of heated cylinders are used through which the materials are
passed. The temperature of cylinders exceeds the evaporating temperature of solvents.

3) Steaming: As steam and solvent do not mix with each other steam can be used to evaporate and
carry the solvent out.

In an efficient solvent recovery system up to 95% solvent can be recycled.

Advantages and disadvantages of solvent dyeing

 

Advantages of solvent dyeing:
1) Effluent control & treatment problems have been eliminated.
2) Rapid dyeing is possible with minimum energy consumption.
3) Better levelness and dye yield coupled with better fabric aesthetics.
4) Solvent can be recycled and reused.
5) Solvents require lower temperature lesser time for some shades that compares to water.

Disadvantages of solvent dyeing:
1) Higher cost of solvents. Again, 100% solvent recovery is not possible.
2) Problems in equipment availability.
3) Existing dyestuffs cannot be reused in full range.
4) All fibres are not suitable for solvent dyeing. Only man made hydrophobic fibres can be dyed

Process flow chart of Garments Merchandising

 

Introduction: Merchandising means to promote and sell a product to the potential customer/buyer. The person, who do this job is called merchandiser. Since the sales process often starts with the eyes, merchandising typically involves presenting products in a visually favorable light, to try and encourage purchases.

But in textile sector merchandising is a process which starts from buyer developing to price submitting, order confirming and then execute the order to ship goods in time with quality is called garments/apparel merchandising. It is the garments whole selling business with foreign buyer or countries.

Job responsibilities of a merchandiser: A merchandiser do some specific work. These are;

1.  Fabric requirements calculations: Merchandisers calculated total fabric consumption for a garment.
2.  Accessories requirements calculations: They calculated how many types of accessories and quantity required for a garment.
3.  Sourcing of fabric: They collected buyer required fabric from different countries and fabric manufacturer.
4. Sourcing of accessories: They collected buyer required accessories from recommended company.
5. Costing and pricing: The most important work of a merchandiser is costing and pricing. Here merchandiser negotiate a reasonable price with buyer including all types of cost to produce this garments and profit.
6. Communication to buyers: A merchandiser need to communicate with buyer from confirming the order to final shipment.

Skilled required for a successful merchandiser: Merchandising is the most valuable and attractive job in recent times for a textile engineer. There are so many foreign and local buying house who offers this type of jobs. Some industries also offer merchandising jobs. But there need some skilled for become a successful merchandiser;

Ø  Good command in English.

Ø  Good knowledge in fiber, yarn, fabrics, dying, printing, colorfastness etc.

Ø  Clear knowledge about quality and quantity production of garments.

Ø  Should be hard worker.

Ø  Should be responsible for this job.

Ø  Must have knowledge in computer literacy, specially in E-mail, Microsoft Office etc.

Ø  Should have ability to improve public relation.

Ø  Should have well behaved personality.

Ø  Should have well knowledge on calculation.

Flow chart or Sequence of merchandising:

Receive order from Buyer

(Sketch or picture, measurement chart, material details)

↓

Consumption

↓

Costing

↓

Negotiation with Buyer

↓

Order receiving

↓

L/C receiving

↓

Back to back L/C opening

↓

Sample developing and Approving

↓

Approval for bulk production

↓

Related work to production planning

↓

Start bulk production

↓

Line inspection

↓

Final inspection by Buyer

↓

Shipment to Buyer

Direct Dye

 

Direct Dye:

Direct Dye is a class of dyestuffs that are applied directly to the substrate in a neutral or alkaline bath. They produce full shades on cotton and linen without mordanting and can also be applied to rayon, silk, and wool. Direct dyes give bright shades but exhibit poor wash fastness. Various after treatments are used to improve the wash fastness of direct dyes, and such dyes are referred to as “after treated direct colors.”Direct Dyes are molecules that adhere to the fabric molecules without help from other chemicals. Direct dyes are defined as anionic dyes with substantively for cellulosic fibres, normally applied from an aqueous dye bath containing an electrolyte, either sodium chloride (NaCl) or sodium sulphate (Na2SO4).

Direct Dyes

The dyeing process with direct dyes is very simple, Direct dyeing is normally carried out in a neutral or slight alkaline dye bath, at or near boiling point , but a separate after treatment such as cationic dye fixing , to enhance wet fastness has been necessary for most direct dyeing .

Direct dyes are used on cotton, paper, leather, wool, silk and nylon.

·         Chemicals Nature of Direct Dyes:  Chemically they are salts of complex sulfonic acids.

·         Structure : More than 75% of all direct dyes are un-metallised azo structures, great majority of them are disazo or polyazo types.

·         Ionic Nature:  Anionic.

·         Solubility : Soluble in water .

Affinity:-They have an affinity for a wide variety of fibers such as cotton ,viscose, silk jute ,linen etc.. They do not make any permanent chemical bond with the cellulosic fibers but are attached to it via very week hydrogen bonding as well as vander waals forces. Their flat shape and their length enable them to lie along-side cellulose fibers and maximize the Van-der-Waals, dipole and hydrogen bonds.

Types of Direct Dyes:

The SDC classification of direct dyes is follows

(1) Class A – dyes that are self-levelling, i.e. dyes of good migration or leveling properties.

(2) Class B – dyes that are not self-levelling, but which can be controlled by addition of salt to give level results; they are described as salt-controllable.

(3) Class C – dyes that are not self-levelling and which are highly sensitive to salt, the exhaustion of these dyes cannot adequately be controlled by addition of salt alone and they require additional control by temperature; they are described as temperature-controllable.

Application of Direct Dyes

Direct dyes are usually applied with the addition of electrolyte at or near the boil in the machines capable of running at atmospheric pressure .But in HTHP dyeing machines it is carried out at temperatures above the boil in case of pure as well as blended yarns.

An addition of alkali, usually sodium carbonate, may be made with acid-sensitive direct dyes and with hard water as well as to enhance the dye solubilisation. When cellulose is immersed in a solution of a direct dye it absorbs dye from the solution until equilibrium is attained, and at this stage most of the dye is taken up by the fibre. The rate of absorption and equilibrium exhaustion vary from dye to dye. The substantivity of the dye for cellulose is the proportion of the dye absorbed by the fibre compared with that remaining in the dye bath.

Dye bath variables which must be considered for level dyeing,

Ø  Temperature of Dyeing and rate of heating

Ø  Electrolyte concentration and addition

Ø  Time

Ø  Dye solubility

Ø  Use of leveling agent

After Treatment of Direct Dyed Material

The wet fastness properties (particularly washing, water and perspiration) of virtually all dyeing of direct dyes are inadequate for many end uses but notable improvements can be brought about by after treatments.

Ø  Diazotisation and development

Ø  Metal salt treatments

Ø  Cationic fixing agents

Ø  Formaldehyde treatment

Ø  Cross linking agents and resin treatments

Stripping:- Most direct dyes can be stripped of the use of stripping salts (Sodium Hydrosulphite) and/or by using a chlorine bleaching agent such as sodium hypochlorite, without harmful effects on the fibres.

Ø  Color fastness properties of Direct Dyed material: Generally these dyes are used where high wash fastness is not required.

Ø  Wash Fastness: Poor unless treated with suitable dye fixing agent and/or fastness improving finishing agent.

Ø  Light Fastness:-Good

Ø  Rubbing Fastness: Moderate to Good

Ø  Chemical Wash Fastness:- Poor

Enzyme Washing process (Drak shade)

 

Introduction: Enzyme is a substance produced by a living organism which acts as a catalyst to bring about a specific biochemical reaction. The enzymes under a chemical point of view is their high specificity or in other words, their ability to attack selectively a given substrate.

The action of enzyme during enzyme wash is to hydrolyze the cellulose, at first it attacks the having projecting fiber and hydrolyzed them. Then it attacks the yarn portion inside fabric and partly hydrolyzed the yarn portion and faded effect is produced.

Textile Enzymes called "Aurum". Enzymes (Greek for "in the cell" formerly also called ferments) are biologically the most important group of proteins. Aurum PC enzyme is used in washing technology.

Some features of Enzyme:

Enzyme wash is done on the garments made from heavy fabrics like jeans and denims.

• Enzyme Create bright to low effect:

1. Bright effect 
2.  Medium effect3
3. Light effect

•  Enzyme attacks as chemically not mechanically for this reason low damage/wastage then stone wash.
• Especially develop the "Bio-Polishing" effect of cotton/denim.
•  Enzyme improves the anti-pilling properties of garments.
•  Enzyme attacks more on the surface of the fabrics and gives a very smooth surface.

Process flow chart of Enzyme wash (Dark shade):

Batching

↓

Loading

↓

De-sizing

↓

Bio-abrasion

↓

Softening

↓

Hydro extraction

↓

Drying

↓

Delivery

Procedure of Enzyme wash (Dark Shade):

The enzyme washing process of a batch size 60 kgs denim men's long pants (Trouser) is described below:

1.   De-sizing:

•  Lot weight (80 pcs) - 60 kg denim long pant.
•   Add water @ L : R = 1 : 9 - 540 Litre
• Machine Running.
• Temperature - 60°c.
• Add Desizing agent @ 0.6 gm / litre - 324 gm. 
• Add Detergent @ 0.8 gm / litre - 432 gm.
• Time - 10-20 mts.
•  Drop the liquor.
• Wash 1 time by cold water.

2.   Bio-Abrasion (mechanical and chemical action):

• Add water L : R = 1 : 8 - 450 Litre
• Temperature - 45°c.
• Add Acetic Acid - 0.6 gm / litre - 270 gm.
• Add Anti back staining - 0.6 gm / litre - 270 gm.
• Add Acid Enzyme - 2.00 gm / litre - 900 gm.
• Pumic stone - 20 to 100 %.
• Time (Depend upon the shade ) - 40-60 min.
• Increase temperature to 90°c and run 1 minute (enzyme killing).
• Drain the bath.
• Rinse Twice, each 3 minutes.

3.   Softening: 

•  Add water L : R = 1 : 8 - 450 Litre.
• Add Acetic Acid - 0.6 gm / litre - 270 gm. 
• Cat ionic Softener - 1 gm / litre - 450 gm.
• Temperature - Cold.
• Time - 15 to 20 mts.
• Drain the bath.
• Then unload the garments on trolley.

4.   Hydro extraction:

Hydro-extractor is used to remove excess water from the Garments.

5.   Drying:

• Load 60 kg garments to gas dryer.
• Temperature set - 75°c to 85°c.
• Run about 40 mts.
• After then run 10 mts in cold dryer.

6.   Delivery:

After drying, garment goes to quality section for quality checking and good one is delivered.

Super White washing process

 

Introduction: Super white washing is a washing process which is carried out in mainly for increasing the whiteness effects of a white fabric. Super white wash is done specially on the garments made from cotton grey fabric. The garments after washing look extremely white. In this washing mainly used chemical is optical brightening or whitening agent.

Fig: Super White washed pant.

Process flow chart of Super white garments washing –

Batching

↓

Loading

↓

De-sizing

↓

Bleaching

↓

Hot Wash

↓

Neutralization

↓ 

Brightening

↓ 

Softening/finishing

↓

Hydro extraction

↓

Drying

↓

Delivery

 

 

Working procedure of super white washing process: 

Super white washing process for 100 kg garments-

 1. De-sizing: 

• Batch size: 100 kg cotton grey fabrics.
• Water and Liquor -  L:R: 1:8
• Machine running
• Temperature up to 90°C
• Add detergent - 2%(OWF)
• Cold caustic soda - 8% (OWF)
• Add Soda ash - 5% (OWF)
• Hydrogen per oxide - 12% (OWF)
• Stabilizer - 5% (OWF)
• Time: 70 minutes
• Drop the liquor

2. Bleaching:

•   Add detergent - 1% (OWF)
•  Add Caustic soda - 3-4% (OWF)
•  Hydrogen per oxide - 6-8% (OWF)
•  Stabilizer - 2% (OWF)
•  Time: 45-60 minutes
•  Temperature: 90°C

3. Hot Wash:

• Temperature: 50°C-80°C
• Time: 5-10 minutes
•  Drop the liquor

4. Neutralization:

• Add Acetic acid - 1%
• Time: 5-10 minutes
• Cold wash

5. Brightening:

• Add optical brightener agent - 0.5-0.6%
• Time: 5-10 minutes

6. Softening/finishing:

• Add softener - 0.5-1%
• Time: 5-10 minutes

7. Hydro extraction:

Extracted extra water (up to 70%) from the garments.

8. Drying:

• Load 60kg garments to gas dryer
• Machine running
• Temperature: 75°C-85°C
• Time: 40 minutes in hot dryer
• After then run 10 minutes in cold dryer.

9. Delivery:

After final inspection of quality control department garments are ready for delivering.

Soap in Textile Wet processingSoap in Textile Wet processing

 

Soaps:  

•            Soaps are sodium or potassium salts of higher fatty acids (are organic acids that have carbon atoms within 9-17 in their molecules) like stearic, palmitic and oleic acids.  
•       Soap is a metallic salt of saturated (CnH2n+1COOH) or unsaturated (CnH2n-1COOH) higher fatty acid.
•      There may be Pb, Mg, Ca or other metallic salts.  
•      The sodium soaps are called hard soaps and The potassium soaps are known as soft soaps.
•      Soaps are obtained from oils and fats.
•       For example, tri-stearin is got from beef and mutton tallow, tri-palmitin from palm oil and tri-olein from lard (pig fat), olive oil and cotton seed oil.

Properties of soaps:

1. Soap dissolves very slowly in cold water but rapidly in hot water.

2. Soap dissolves in hot alcohol but is only carefully soluble in other organic solvents such as acetone, ether or petroleum.

3. Sometimes there are free fatty acid molecules in soap to form what is known as acid soaps.

4. Soap reacts with hard water to form insoluble soap.

5.  The number of carbon atoms in the aliphatic chain of soap is very important.

  

  The number of carbon atoms (C) < 9 : No detergency power  

  The number of carbon atoms within (C) 9-17 : Extremely good detergent

  The number of carbon atoms (C) 17 : Poor solubility

Cleansing action of soap:

Soap has two dissimilar ends. At one end it has the hydrocarbon chain that is non-polar and hydrophobic (soluble in oil/dirt). At the other end there is the carboxylate ion that is polar and hydrophilic (water soluble). When soap is added to water, its molecules make a unimolecular film on the surface of water with their carboxyl groups dissolved in water and the hydrocarbon chains standing on end to form a hydrocarbon layer. When a dirty cloth is soaked into a soap solution, soap dissolves fat or oil with dust by micelle formation. 

The fat or oil with dust is dissolved in water by hydrophobic hydrocarbon chains of soap. The water soluble carboxylate ions make a hydrophilic surface in water and render the micelles of oil or fat from the cloth to the water. Thus, the micelle is dissolved in water and is washed away. Soap tends to concentrate on the solution surface and therefore lowers its surface tension, causing foaming. This helps it to penetrate the fabric. It emulsifies fat and dirt to form micelles and make all the micelles water-soluble. Thus, the water washes the dirt away.

The structure of a micelle

The hydrophobic tails ‘burrow’ into the droplet of oil or grease. The hydrophilic heads are left to face the surrounding water. This results in the formation of a ball-like structure (a micelle).

Saponification:

 In simple terms, saponification is the name for a chemical reaction between an acid and a base to form a salt.

The vegetable oil is a glyceride of fatty acid (Oleic, stearic, palmitic acid), which is immiscible with water.  

When such oil is heated with a solution of sodium hydroxide in water, the oil is split into fatty acid and glycerine.  

This fatty acid reacts with sodium hydroxide solution and form sodium salt like soap which is soluble in water.  

This reaction is called saponification. As a result of saponification, the insoluble and water immiscible oil is converted to water soluble products.

SOAP  

  Soaps are sodium or potassium salts of long chain fatty acids.

  When triglycerides in fat/oil react with aqueous NaOH or KOH, they are converted into soap and glycerol.  

  This is called alkaline hydrolysis of esters. Since this reaction leads to the formation of soap, it is called the Saponification process.