Presentation on Foam Dyeing

• Presented by:-– Ananna Rahman(18/13)– Naimul Hasan Shuvo(04/13)– Abdullah Al Bitar(09/13)– Khandokar

Hasanuzzaman(20/13)– Md. Anisur Rahman(05/13)– Md. Shariful Huda(35/13)– Sk. Asgar Hossain(08/13)– B.M. Tanimul Islam(06/13)– Md Naim Hasan

Towhid(25/13)

• Presented to:-­ Maitry Bhattacharjee­ Lecturer­ Shayamoli Textile

Engineering College

Foam DyeingWhat is foam? Foam is a dispersion of a gas in a liquid. Here the liquid is generally water and the Gas is generally air but it may also be an inert gas. It’s a colloid system.

Example of foam:

Colloid

• Foam• Smoke• Moist

Dispersion

• Air/Gas• Solid• Water

Medium

• Liquid• Gas• Air/Gas

Structure of foam

Related Definitions Dispersion:A dispersion is a system in which particles are dispersed in a continuousphase of a different composition or state.

Emulsion:An emulsion is the mixture of two or more immiscible liquids which aremixed with the help of an emulsifier.

Related Definitions Emulsifier:An emulsifier is a compound or substance that acts as a stabilizer foremulsion preventing the liquids from separating. Also known as emulsifyingagents.

Solution:A solution is a homogeneous mixture, composed of two or more solutesdissolved in a solvent.

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Difference­between­Foam­and­Emulsion

Foam Emulsion

It’s a dispersion of gas in a liquid. It’s a mixture at two immiscible liquids.

Foam is unstable. Comparatively more stable than foam.

Foaming agent is used Emulsifier is used.

Comparatively complex in formation. Formation is easier.

It contains 2 phases. It contains only 1 phase.

Difference­between­Normal­foam­and­Dyeing­foam

Figure

Stability Less stable More stable

Half life period

4-6 minutes Much longer

Viscosity Less More

Example Foam produced using soap or detergent with water

Foam used in modern textile dyeing

Topic Normal Foam Dyeing Foam

Bubble size Greater Smaller

Foam­DyeingDefinition:The process of dyeing where the main dyeing medium is foam, is called Foam dyeing.

– In foam dyeing a fabric is padded with foam.– Foam is formed from a aqueous solution of a dye stuff, a foaming agent & a

carrier for the dye stuff.– The padded fabric is maintained at elevated temperature to fix the dye.

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Reasons for using foam dyeing:

• To eliminate drying step.• Saving energy.• Reducing environment pollution.• To reduce wet pick up.• To improve product quality.• To reduce investment cost.• To reduce the material : liquor ratio.

Foaming AgentDefinition:A foaming agent is a material that facilitates formation of foam such as a surfactant or blowing agent that helps to maintain it’s integrity bystrengthening individual foam bubbles. Example:- Linear alkaline derivatives such as sodium lauryl sulphate (C12H25OSO3Na)­

The foaming agents can be anionic, cationic, non-ionic or amphoteric.

Requirements of foaming agents:

1. Generate foam readily.2. Offering a good wetting capacity.3. Should perform fast and uniform wetting action.4. Foam generation capacity according to required size & stability.5. It should show little or no effect on color fastness.6. It should not cause yellowing of white materials.7. It should be capable of producing various bubble sizes to meet specific requirements.

Materials used for Foam Dyeing• White fabric – Cotton, rayon, silk or other natural fiber to dye on.• Soda ash fixer.• Synthrapol.• Squeeze bottles to hold the dyes.• Foam shaving cream, preferably containing aloe.• Flat, shallow, plastic or metal pan.• Wire whisk.• Tape.

Types of FoamDepending on the concentration of foaming agent used & method of

foaming properties there are 2 types of foam:- Dry foam:

Density 0.2 gm/l Contain less liquid in bubble. Metastable & more stable. Polyhedral structure which may vary in size.

Wet foam: Density is least 0.35 gm/l Spherical bubble size. Less stable. Not suitable for textile use.

Broadly there are 2 types of foam:-

Dispersion foam: It is produced by the introduction & mixing of gas from an external source into a liquid phase. In textile field dispersion foam is

used.

Condensation foam: It results from the generation of a gas within the liquid either by chemical or by a physical change. This type pf foam is not used in textile field.

StabilizerDefinition:Foam stabilizer slows down the drainage of liquids from the bubbles &

impart workable flow properties.The basic role of a stabilizer in foam is to reinforce the bubble cell wall to acontrollable level or stabilize foam from decay.Example:-

– Hydroxy-ethyl cellulose (HEC)– Methyl cellulose– Ammonium stearate.

Function and Requirements Function:-• Slow down drainage.• Reinforce bubble cell-wall.• Controls life time of foam.

Requirements of stabilizer:-­ Easy solubility.­ Compatible with a foam finishing system.­ Effective at low concentration.­ It should be easily soluble.­ It should be least affected by fabric handle.­ Resistance of bacterial attack.

Factors considered for foam dyeing and finishing

• Dilution factor:- Related to fabric cover factor. If cover factor is higher (dense or coarse fabric in general) lamella size should be higher. i.e. – large cover factor, more dilution. Less cover factor, less dilution.

• Foam stability:- If bubble size is higher foam will be less stable.• Foam decay half-life:- time required to drain out half of the foam.• Foam decay:- Self drainage of a foamed liquid.• Foam density:- The foam must have uniform density.

𝛿 = volume of solution consumed / volume of foam.• Blow ratio:- It expresses the volumetric ratio of liquid to foam. It’s a

measure of dilution of foam. Blow ratio =

Factors considered for foam dyeing and finishing

• Drop escape time:- The time taken to drain out the first drop of liquid from the foam is called drop escape time. The drop escape time normally ranges from 45s-90s.

• Viscosity:- If blow ratio increases, viscosity of foam decreases. If viscosity increases foam stability decreases.

• Homogeneity:- For uniform application homogeneous bubbles of smaller size are essential. They should be made of constant size as nearly as possible.

• Bubble size:- The size of the bubbles and it’s rate of changes determines foam penetration into the textiles. Foam of smaller bubble size is generally more stable than that of larger one.

Methods of Foam DyeingThere are 6 methods currently available for foam dyeing. They are:- 1. Foam application on a horizontal padding mangle.2. Foam application with a coating blade.3. Foam application by pressure nozzle.4. Foam application with a rotary printing screen and slit doctor.5. Two sided foam application with transfer rollers and dosage shoots.6. Foam application by indirect doctor blade dosage foam collapse by

vacuum cylinder suction.

Foam application on a horizontal padding mangle.

• Contains 2 horizontal padding bowls side by side.• The foam is applied to the both side of fabric at the nip of the bowl.• Suitable for woven fabric.

Foam application with a coating blade

• Uniform and consistent foam is generated and afix amount of foam is deposited on the fabric.

• The rate of dosing is controlled by setting of blade.• The foam is deposited by laying it on the fabric.• The fabric then goes through the nip of two rollers to completely

collapse the foam.• A double coating knife coater is useful in this method.

Foam application by pressure nozzle

• Specified amount of active chemical is delivered to a mixing head and then to a fabric.

• The foam is applied to a pressurized zone .• The pressure is slightly above the atmospheric pressure.• The pick up of foam system depends on whether light or dense foam is

applied.• The foam is driven upwards through the slot nozzle.• The foam causes rapid collapse as soon as it touches the fabric.

Foam application with a rotary printing screen and slit doctor

• Brand name: RSF FOAM APPLICATION• Foam is pressed through the triangular screen by a specially designed slit

doctor.• For both side application a dual application is available.

Two sided foam application with transfer rollers and dosage shoots

• Foam shoots by inclined plates situated at the base.• Foam is trapped between the fabric and roller.• As fabric is pressing against the roller and passing, the foam collapse.• The uniformity of foam application depends on fabrics moisture content,

roller pressure etc.

Foam application by indirect doctor blade dosage foam collapse by vacuum cylinder suction.­­

• Doctor blade doses the foam onto and endless rubber belt which come in contact with the fabric.

• The rubber belt seals the vacuum cylinder creating high vacuum which draws the foam forcibly into the fabric.

• There the bubble expand and break and the foam collapse. The dosage rate is controlled by the slit setting of doctor blade.

Advantages of Foam Dyeing Save water. Save chemicals(0-20% minimum) Reduce water pollution. Save cost. Faster production . Less heat generation., Save energy. Reduction of shrinkage in width because of low liquor application Printing do not need thickener. Greater productivity which is around 25-50% more than conventional

ones. Low liquor ratio . Lower dyes migration. Scope for the development of novel fabrics.

Disadvantages of Foam Dyeing

Limited application, only for cotton and polyester products. i.e. carpets , carpet backing coating etc are popular.

Investment cost is more ( for equipment ) Skilled man power is required. In some cases problem arises in penetration of levelness. More attention required. New machine required.