supercritical co2

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Supercritical Carbon Dioxide (CO2)-The Dyeing Technique Of Future



To demonstrate and quantify dye-fiber

covalent bond formation between selected

dyes and nylon, wool and cotton fibers in

a supercritical carbon dioxide medium

To optimize reaction conditions

(temperature, pressure and time)

OBJECTIVES:OBJECTIVES:



BACKGROUND:BACKGROUND:

Conventional dye-fiber reactions use water as a transport medium, and

result in:

1. Low reaction efficiency due to the competing hydrolysis reaction with

hydroxyl ions in water (hydrolyzed dye cannot react w/fiber)

2. Environmental problems due to residual, unreacted/hydrolyzed dye

present in effluent

Replacing water with supercritical fluids (SCF) as a transport medium can

result in:

1. Eliminating toxic waste (no hydrolyzed by-product)

2. Lower costs for the entire dyeing process



SUPERCRITICALSUPERCRITICAL COCO22::

ProminentProminent substancessubstances exhibitingexhibiting super super criticalcritical phases phases

areare COCO22,, HH22OO andand Propane,Propane, of of whichwhich COCO22 isis thethe secondsecond

mostmost abundantabundant andand secondsecond leastleast costlycostly solventsolvent..

LowLow temperaturetemperature andand pressure pressure areare neededneeded toto convertconvert

carboncarbon dioxidedioxide gasgas intointo super super criticalcritical fluidfluid..



WHYWHYONLYONLYCOCO22::

1. Abundantly available

2. Recovery and reuse is easier

3. Easily Handel able and environment friendly

4. Non toxic, non hazardous and low cost.

5. No waste generation

6. Chemically inert.



DYEING PROCESS:DYEING PROCESS:

The dyeing takes place in following steps:The dyeing takes place in following steps:

A. Dissolution of dye in CO2

B. Transport to the fibers

C. Adsorption of dye on fiber surface and finally

D. Diffusion of dye into the fiber takes place



DYEING PROCEDURE:DYEING PROCEDURE:

Add fiber and dye to vessel

Pressurize system (with CO2) up to 800 psi

and stir at approximately 850 rpm

Heat to required temperature (100 -180 ºC)

Pressurize to 3500 psi; hold for 2 hours

Release pressure, remove fabric



(1) Gas cylinder of CO(1) Gas cylinder of CO22,,

(2) High pressure pump,(2) High pressure pump,

(3) Autoclave reactor vessel with stirrer, V = 1000 ml,(3) Autoclave reactor vessel with stirrer, V = 1000 ml,

(4) Circulation pump(4) Circulation pump-- acquisition in futureacquisition in future

(5) Electrical heating jacket(5) Electrical heating jacket

1

2

3

4

5

CO2 DYEING SYSTEM:



SUPERCRITICAL CO2 DYEING

MACHINE:



COMPARISONCOMPARISON WITHWITH CONVENTIONALCONVENTIONAL

DY

EINGDY

EING PROCESSPROCESS:: In conventional method of dyeing, water, dyes, and other auxiliaries

are used to enhance the efficiency of dyeing process.

Compared to this, use of supercritical CO2 completely avoids the use

of water and other auxiliaries, thus creating no effluent.

Drying is also not required as CO2 is released in gaseous state.

CO2 can also be recycled upto 90% and energy required is about 80%

less compared to conventional dyeing.

Dyeing is only carried on for 2 hrs compared to 3 or 4 hrs of

conventional dyeing.



ADVANTAGESADVANTAGES::

Elimination of water treatment and water pollution No need of drying textiles

Gives good rubbing fastness

Dyeing occurs with high degree of levelness

CO2 is non toxic obtained from natural resources and can be

easily recycled in dyeing process

Dyeing houses may be started on sites where there is water

scarcity

supercritical co2

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