Method of Dyeing polyester with disperse Dyes
Due to its high degree of orientation, strong cohesive forces, and compact structure, polyester is challenging to colour.
Therefore, it is necessary to choose dyeing conditions that will loosen the fibre structure for the dye to diffuse into the fibre. There are two types of dyeing techniques: exhaust and continuous.
(A) Exhaust Method | (B) Continuous Method |
This technique involves transferring colour from aqueous baths into the fibre. Exhaust dyeing is done at high temperatures with carriers. These techniques are used to colour polyester materials that are woven, knit, and texturized. | The process of mechanically attaching the dye to the fibre and then causing it to diffuse into the fibre is known as "thermosolling." In this process, the dye is mechanically applied to the fibre and then thermofixed at 200–220°C, when the fibre turns thermoplastic and the dye diffuses into the fibre. Prior to the dye being permanently fixed in the fibre during thermal fixation dyeing, the water in the pad liquor is fully eliminated by drying. |
Type : (ii) HTHP | Type : (i) Thermosol |
(B) Continuous Method
(i) Thermosol Dyeing Technique:
Principle - Dry heat is effectively employed in a continual process called the Du Pont thermosol process to colour synthetic fabrics.
It entails drenching a material during a dye dispersion, drying it, and then heating it for roughly a moment at 200°C.
Many disperse dyes are molten at this temperature, and therefore the fibre is plastic with active chain molecule vibrations.
Thus, the "thermosol technique" got its name since the dyeing fundamentally involves a liquid dye dissolving during a fibre that's almost like a "viscous liquid."
In essence, the thermos fixing of the dye uses the identical mechanism to exhaust dyeing.
The dye is dissolved directly within the fibre when exposed to temperatures of the order of 205°C.
Complete penetration is obtained in 60 seconds as seen in the figure below.
Steps:
(i) Padding the fabric with dispersed dye or a mix of dyes used for polyester/cellulosic blends.(ii) Drying the padded fabric.
(iii) Fixation of the dyestuff within the fabric using dry heat at 180-210°C for 90 - 60 seconds (i.e. 90 seconds at 180°C or 60 seconds at 210°C).
(iv) After treatment of the fabric for synthetic fibres and dyeing and development of the opposite component fibre just in case of a blended textile.
Advantages of the Thermosol Process:
(b) Because no carrier is needed, there are no carrier-related issues.
(b) Excellent dye utilisation is attained (75 to 90%).
(d) Because this treatment has an open width, no wrinkles or rope markings are created.
(e) Heat setting and dyeing can be done simultaneously.
The pre-heat setting does not affect the dyeing.
(g) The fabric might have a highly consistent colour throughout.
(h) The cloth has an open-width form of dyeing. By doing this, the risk of abrasion of any cellulosic fibres in a polyester blend is eliminated.
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| Disperse dyed fabric |
Dyeing of Polyester/Cotton Blends
Because the constituent fibres of polyester/cotton blends have different properties, dyeing them requires extra care.
Processes have been developed that colour both components concurrently in one dye bath or separately in two independent dye baths.
Different classes of dyestuff, such as direct, vat, azoic, solubilized vat, sulphur, reactive, etc., are available for colouring the cotton component while the only option for polyester is dispersing colours. T
These mixtures can be dyed to generate a variety of effects, including
(A) Solid Shade Dyeing | (B) Contrast Dyeing |
Both the components of the blend are dyed to the same tone and depth of shade | Two components of the blend are dyed in different shades |
(C) Reserve Dyeing | (D) Two-tone Dyeing |
Only one component of the blend is dyed whereas the second component is let undyed | The same dyeing effect and tone is produced in different depths of shades percentage in the two fibres |
Dyeing
Blends of polyester and cotton may be coloured employing a batch-wise continuous procedure. the kind of cloth, batch size, and specifications for the dyed and finished fabric all play a task in choosing an appropriate dyeing technique.
The following equipment is used for dying using the exhaust method.
(B) Jet dyeing machine
(C) High-temperature winch or jigger.
The thermos technique is crucial for continuous dyeing. Blends of polyester and cotton are often dyed employing a wide range of colours and dyeing techniques. Disperse dyes are always accustomed to colour polyester fibre, but virtually every class of dye which will be accustomed to colour 100% cotton are often wont to colour the cotton component of a mix.
Cross staining is the staining of 1 component of a mix with a dye intended for the opposite component. Polyester is barely stained by reactive dyes, while it's moderately to severely stained by vat, solubilized vat, sulphur, and azoic colours (i.e. staining on the polyester component). Cross staining, however, is eliminated with reduced cleaning.
Questions -
- Explain Thermosol Dyeing Technique for the disperse dyeing process.
- What are the advantages and disadvantages of thermosol dyeing process?
References
Disperse dye additives. (n.d.). Borregaard.com. from https://www.borregaard.com/markets/dyestuffs/applications/disperse-dyes/
Dyeing polyester with disperse dye. (n.d.). Pburch.net. from http://www.pburch.net/dyeing/dispersedye.shtml
Gurr, E. (1971). DISPERSE DYES. In Synthetic Dyes in Biology, Medicine and Chemistry (pp. 691–702). Elsevier.
Holland, A. (n.d.). Disperse Dye for dyeing and printing polyester and sythetic fabrics. Georgeweil.com. from https://www.georgeweil.com/blog/disperse-dyes-for-dyeing-and-printing/
Transfer/disperse dyes - how to. (n.d.). Vycombe-arts.co.uk. from https://www.vycombe-arts.co.uk/transferdyes.html
Wypych, G. (2013). Weathering of compounded products. In Handbook of Material Weathering (pp. 581–717). Elsevier.
(N.d.). Textilelearner.net. from https://textilelearner.net/disperse-dyes-dyeing-and-printing-method/
Continue reading,
Part 2 Method of carrier Dyeing of Disperse dyes
Part 3 Method of HTHP Dyeing of Disperse dyes
Part 4 Other methods for disperse dyeing
