Sulphur dyes are a class of Dyes and Pigments Company in India used for coloring textiles made from natural and synthetic cellulosic fibers, such as cotton and rayon. They are water-insoluble and require a reducing agent, such as sodium hydrosulphite or sodium supplied, and caustic soda to make them soluble and reactive with the fibers. Sulphur dyes are primarily used for dark shades, such as browns, blacks, and navy blues, but newer versions are also available in bright color's. They are widely used for dyeing heavy woven and knitted cotton fabrics, as well as linen and jute. The relatively low cost of Sulphur dyes has made them a popular choice for producing dark colors in the textile industry.

Characteristics:

● Sulphur dyes are named after the presence of sulphur atoms in their molecules, and were first produced in 1879.

● They have excellent colour fastness properties for washing, light and perspiration.

● Excessive use of chlorine bleach can cause the colour to fade.

● Sulphur dyes are not soluble in water.

● They produce dull colours like navy blue, brown and black, and are most commonly used for black dyeing.

● Over time, textiles dyed with sulphur dyes may become fragile.

● Sulphur dyes are relatively inexpensive, and perform well when used correctly.

● Textiles dyed with sulphur dyes have good resistance to washing but may be affected by chlorine bleaches.

Suitability to Textiles:

Sulphur dyes are highly suitable for colouring natural and man-made cellulosic fibres, including cotton and rayon. They are particularly well-suited for achieving deep shades such as browns, blacks, and navy blues, although newer varieties are now available in bright colours as well.

These dyes can be applied to textiles at various stages of production, including stock, yarn, and piece goods. They are commonly used in heavy woven and knitted cotton fabrics, as well as linen and jute.

One of the notable applications of sulphur dyes is in the production of khaki and other heavy work clothes. Their effectiveness in colouring these types of fabrics has made them a popular choice in this industry.

Sulphur Black

Application Process:

The application of sulphur dyes to textiles involves a multi-step process. Initially, the dye must be made soluble by adding caustic soda and sodium sulphide to the dye bath. This converts the dye into a water-soluble form, which is substantive to cellulosic fibres.

To achieve adequate penetration and a satisfactory rate of dyeing, the dye bath must be heated to a high temperature and a large quantity of salt can be added. An electrolyte, such as Nacl, may also be added to the dye liquor to promote the exhaustion of the dye.

Once the dye has penetrated the fibre polymer system, it is converted back to its insoluble form by oxidation. This process is carefully controlled to prevent premature oxidation, which can retard the penetration of the dye.

After dyeing, excess chemicals and dye are removed through a thorough washing. The fabric is then oxidised to achieve the desired shade, either by exposure to air or by using chemicals such as acetic acid or sodium perborate.

Sulphur dyes are known for their excellent penetration, which is achieved due to the high temperature and alkaline conditions of the dye bath.

Fastness Characteristics:

Sulphur dyes exhibit fair light fastness, with a rating of about 4. However, an after-treatment with Meta salts can improve the light fastness to a rating of approximately 5. The wash fastness rating of sulphur-dyed textiles is also fair, with a rating of about 3–4.

The colour range of sulphur dyes is somewhat limited, mainly encompassing black, brown, blue, and olive shades. Additionally, these dyes may produce an undesirable metallic or bronze sheen known as bronzing, which can compromise the aesthetic appeal of the dyed textile material and result in poor rub-fastness.

Despite these limitations, sulphur dyes continue to be popular due to their relatively low cost and effectiveness in producing dark colours, such as navy and black.

Sulphur dyes have continued to be used because of their inexpensive cost, especially for dark colours like navy and black.

Conclusion

Veeraco Colourants Private Limited is one of the most well-known dye manufacturers in India, providing high-quality dyes for a wide range of industries. The company has grown to become one of the top manufacturers of dyes and pigments in India, serving a wide range of industries such as textiles, paper, and plastics.

Their product portfolio includes acid dyes, reactive dyes, direct dyes, and pigment dispersions, which are known for their excellent color strength and high purity. The company is committed to quality and sustainability, using state-of-the-art technology and eco-friendly manufacturing processes.