DENIM WASHING PROCESS

DENIM WASHING PROCESS

ABSTRACT

As denim is one of the tradition item and the denim washing have very stable performance. However, there are some of the comments that when the fabric has longer washing time, use of the chemical on the washing procedure will affect the physical performance such as the tensile strength will decrease. In order to achieve an optimum the effect of washing process on the denim woven fabric in different washing time, Enzyme Wash, Enzyme wash with bleach, Enzyme wash with stone and Enzyme wash with stone and bleach were carried out for cotton and cotton - spandex denim fabric. The effect of the washing parameters, such as the temperature, time and pH on the result of the cotton and cotton spandex denim after treatment were studied by assessment of the tensile physical properties and elongation to break

KEYWORDS: Enzyme, stone, pH, elongation to break

Origin

The word 'denim' comes from the name of a sturdy fabric called serge, originally made in Nimes, France, by the André family. Originally called Serge de Nimes, the name was soon shortened to denim. Denim has been used in America since the late 18th century. Denim was traditionally colored blue with indigo dye to make blue "jeans", though "jean" then denoted a different, lighter cotton textile; the contemporary use of jean comes from the French word for Genoa, Italy , where the first denim trousers were made

 

The history of denim

A popular conception of the entomology of the denim is that it is a contraction or derivative of the french term SERGE DE NIMES. Denim was traditionally colored blue with indigo dye to make blue “Jeans“Though “Jean“ then denoted a different , lighter cotton textile ; the contemporary use of jean comes from the French word for Genoa ,Italy,(Genes ) , from which the first denim trousers were made .Similarly woven traditional American cotton textile is the diagonal warp-striped hickory cloth that was once associated with railroad men’s overalls, in which blue or black contrasting with undyed white threads from the woven pattern . Records of a group of New Yorkers headed for the California gold fields in 1849 show that they took along four “hickory shirts “ apiece. Hickory cloth would later furnish the material for some “fatigue” pantaloons and shirts in the American civil war.

 

Objects of garments washing:

1.    To develop softness in garments: Size materials applied during manufacturing present in the fabric are removed which enhances soft hand feel . Additional softness may be attained by using softener.

2.     To introduce fading effect: Dyes or pigments are present in the fabric , used during coloration, are washed out locally or partially which result fading or worn out effects in the garments.

3.     To create new fashion: Washing Process of garments bring different outlook ( faded, color tinted etc ) thus creating new fashion for the new generation especially for teenagers.

4.    To satisfy the consumer: As the contraction or extraction (shrinkage ) occur due to washing , the wearer can use the garments after purchase satisfactory

Advantages of garments washing:

The following advantages are obtained could be gained from the garments washing—

1. Removal of starch or size materials makes the fabric soft hand feels.
2. Softness could be increased by the addition of softener just at the last stage of washing.
3. Dirt, spots, impurities, gum etc, if accumulated in the garments during manufacturing could be removed.
4. During washing shrinkage may takes place, therefore after washing there is no possibility to create such problem.
5. Washed garments could be worn directly after purchase.
6. Faded or worn out effect could introduced to the garments which creates new fashion
7. Similar outlook can be obtained by different washing techniques.
8. Comparatively lower capital is required to set up a washing plant.
9. Lower land space and least manpower cost are required to run a washing plant.

Unavoidable changes / limitations of garments washing

Like other processes the garments washing is also not without some limitations. They included as below-

1. Garments size change: Size change takes place due to shrinkage properties of fabric. The amount of shrinkage properties of fabric determines the size change of the garments.
2. Size material is partly removed: Unfixed dyes may remain on the surface of the garments and it is necessary to remove completely after washing.

TYPES OF DENIM WASH:

1. Denim washes are of following two type :–

1.               Chemical washes

2. Denim bleaching
3. Enzyme wash
4. Acid wash

2.                 Mechanical washes

5. Stone wash
6. Microsanding

v Chemical washes

1.   DENIM BLEACHING:

In the process a strong oxidative bleaching agent like sodium hypochlorite or KMnO4 is added during the washing with or without stone addition. Discoloration produced is usually more apparent depending on strength on the bleach liquor quality, temperature and treatment time. It is preferable to have strong bleach with short treatment time. Care should be taken for the bleached goods so that they should be adequately antichlor or after washed with peroxide to minimize yellowing. Materials should be carefully stored before processing for color uniformity,

 Process cycle:

Desizing

Ø  Load the garments into the washing machine (100 kg) ;

Ø  Add water (liquor ratio 1:5) and start the machine running(12-15 rpm) ;

Ø  Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;

Ø  Add detergent (1% i.e. 1kg) ;

Ø  Supply steam to raise temp.(60°C) ;

Ø  Continue the process for 20 min and then drain the liquor ;

Ø  Hot wash (at temp. of 40°C to 50°C for 5 minutes).

Bleaching

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Start m/c running ( 12 to 15 rpm ) and add soda ash (Na2CO3) to liquor (2% i.e. 2kg)

Ø  Add costic soda (NaOH) to liquor (2% i.e. 2kg) ;

Ø  Add bleaching chemical (H2O2) to liquor (5ml per liter, i.e. 2.5 liters) ;

Ø  Add stabilizer to liquor (2ml per liter, i.e. 1 liter) ;

Ø  Supply steam to raise temp.(70°-800C) ;

Ø  Continue the process for 60 to 70 min. and drain the liquor ;

Ø  Hot wash (at 60°C for 5 minutes).

Neutralization

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 liters );

Ø  Start m/c running ( 12 to 15 rpm );

Ø  Add acetic acid ( CH3COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);

Ø  Continue the process for 10-15 min and then drain the liquor.

Brightening treatment

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Add Fluorescent Whitening agent/Fluorescent Brightening agent to liquor (% as required );

Ø  Supply steam to raise temperature (800C);

Ø  Continue the process for 10 min and then drain the liquor.

Softening

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Start m/c running ( 12 to 15 rpm );

Ø  Add softener to the liquor (0.1 to 0.5%, i.e. 100g to 500g);

Ø  Supply steam to raise the temperature (as required 400 to 600C );

Ø  Continue the process for 5 minutes and then drain the liquor and unload the garments.

Limitations of denim bleaching:

Ø  Process is difficult to control i.e. difficult to reach the same level of bleaching in repeated runs.

Ø  When desired level bleaching reached the time span available to stop the bleaching is very narrow. Due to harshness of chemical, it may cause damage to cellulose resulting in severe strength losses and or breaks or pinholes at the seam, pocket, etc.

Ø  Harmful to human health and causes corrosion to stainless steal.

Ø  Required antichlor treatment.

Ø  Problem of yellowing is very frequent due to residual chlorine.

Ø  Chlorinated organic substances occur as abundant products in bleaching and pass into the effluent where they cause severe environmental pollution.

 

2.   ENZYME WASH

It is environmentally friendly wash. It involves the application of organic enzymes that eat away at the fabric, i.e. the cellulose. When the desired color is achieved, the enzyme can be stopped by changing the alkalinity of the bath or its temperature. Post treatment includes final ringing and softening cycle.

 The effects produced by cellulose enzyme are :—-

Ø  Use of cellulose making the seams, hems, and pockets more noticeable;

Ø  Salt paper effect is color contrast effect.

Ø  Faded garment washed with acid cellulose enzyme provides less color contrast in proportion to garment washed neutral cellulose enzymes.

Ø  Garment load size of the m/c is 35-40 jeans per m/c and it cannot be overloaded.

3.   ACID WASH

It is done by tumbling the garments with pumice stones presoaked in a solution of sodium hypochlorite or potassium permanganate for localized bleaching resulting in a non uniform sharp blue/white contrast. In this wash the color contrast of the denim fabric can be enhanced by optical brightening. The advantage of this process is that it saves water as addition of water is not required.It consists of soaking pumice stones with chlorine and using their abrasive power to bleach jeans into sharp contrasts. Also known as moon, fog, marble, ice and frosted.

  

Process cycle :

Desizing

Ø  Load the garments into the washing machine (100 kg) ;

Ø  Add water into the machine(1:5 liquor ratio i;e. 500 liters) ;

Ø  Start machine running (12 to 15 rpm) ;

Ø  Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;

Ø  Add detergent (1% i.e. 1kg) ;

Ø  Supply steam to raise temp.(60°C) ;

Ø  Continue the process for 20 min and then drain the liquor ;

Ø  Hot wash at temp. of 40°C to 50°C for 5 minutes.

 Bleaching

To carry out the Bleaching process, the following two steps are to be passed over :

Step  1.

Ø  Take stone of some volume of the volume of garments ;

Ø  Soak the sfone with the following chemical solution for 2 to 3 minutes ;

Ø  Water 100 litres

Ø  Potassium permanganate 1 kg

Ø  Phosphoric acid 300 ml (3ml per litres)

Ø  Here the porous of stones are dried in the open air for 60 to 90 min.

Step  2.

Ø  Load the garments treated in step # 1 and step # 2 in a dry m/c. Lot size should be 20 to 30kg.

Ø  Run the m/c for 5 to 7 minutes. Due to the rotation of m/c the socked stones will hit the garments surfaces and the chemicals in the stone will destroy color of the fabric. Multilayer fabric areas like collar, cuff, pocket, pocket side seam etc. area will be brushed more than the single layer areas, therefore more fading effect will be produced in those areas resulting new color effect in the garments.

Ø  Unload the garments and separate the stones from the batch.

Ø  In this stage KMnO4 and H3PO4 reacts with each other and gives Oxygen which oxidize the color. Here a byproduct MnO2 is produced which should be neutralized.

Ø  6KMnO4 + 4H3PO4 = 2K3PO4 + Mn3(PO4)2 + 6H2O + 3MnO2 + 2O2

Ø  This MnO2 is solubilized by Sodium Metabisulfite (Na2S2O5).

Ø  Na2S2O5 + H2O = 2NaHSO3

Ø  NaHSO3 + MnO2 = MnSO4 + NaOH

Ø  Load the garments to the m/c ;

Ø  Add water into the m/c (1:5 liquor ratio, i.e. 500 litres) ;

Ø  Continue the process (12 to 15 rpm) ;

Ø  Add sodium metabisulfite (1 to 2 gpl, i.e. 500 g to 1kg) ;

Ø  Continue the process for 5 to 10 min and then drain the liquor ;

Ø  Hot wash (at 40o to 50o C for 5 minutes).

Nutralization

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Start m/c running ( 12 to 15 rpm );

Ø  Add acetic acid ( CH3COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);

Ø  Continue the process for 10-12 min and then drain the liquor.

(To be Continued in November 2013 issue)

Magazine Article :DYE CHEM PHARMA (October  2013)