Direct Red 28

Direct Red 28 (Direct red 4B) alias direct red, direct red 4BE, direct red, Congo red. Appearance is generally brown powder. Dissolved in water is yellow red, sensitive to hard water. Dissolved in alcohol is orange, very slightly soluble in acetone. It is blue in sulfuric acid, turns blue light after dilution, has a blue precipitate; it is olive brown to blue-grey precipitate in concentrated nitric acid. The aqueous solution is concentrated with red hydrochloric acid and has a red-blue precipitate. Yellow light, yellowish red in concentrated ammonia water. When the copper ion color is yellow and dark, the iron ion color is slightly yellow.

TRADE NAME:Congo Red,Direct red 4B,Direct Scarlet 4B,Direct Scarlet 4BE

Technical Specifications

• ‍CAS NO: 573-58-0
• CI.NO: 22120
• Molecular Formula: C32H22N6Na2O6S2
• Molecular Weight: 696.67
• Shade:yellow light red powder, tan powder.‍

Colour Fastness Test

Application:

Direct Red 28 has been widely used in the dyeing of cotton and viscose fiber.

Use condition:

• ‍1. Direct Red 28 (Direct red 4B) has been used to dye cotton or viscose fiber to get bright yellow red, good dyeing rate, poor transferability, slow temperature rise during dyeing and salt addition to control dyeing, can get uniform color. After dyeing The stage dyeing solution should be naturally cooled to 80 ° C, which is beneficial to the dye exhaustion. The dye bath should be slightly alkaline to maintain a bright color.
• 2. It has also been used for dyeing silk and wool, and should be dyed with neutral bath. When cotton, viscose fiber and other fibers are dyed in the same bath, silk and wool are lighter than cotton or viscose fiber yellow, and nylon is heavily stained. Color, the second vinegar fiber is slightly stained, polyester, acrylic fiber does not stain.
• 3. It is not used for direct printing on cotton or viscose fabrics.
• 4.It is very sensitive to acid, dyed fabrics are exposed to the air for a long time or stored for a long time, and can also absorb carbon dioxide from the air to change the color. It is blue-dark and can be treated with a dilute soda solution to restore its original color.‍

Precautions

Direct Red 28 can be used to decompose benzidine, which is a banned dye. The alternative dyes are C.I.Direct Red 81 and C.I.Direct Red 89.

FAQ

What are the basic dyeing conditions?

Typical exhaustion dyeing uses warm water and salt/saline assist; follow supplier guidance and run lab trials to optimize temperature and liquor ratio.

How can I improve wash and light fastness?

Use after-treatments such as cationic fixing agents, optical brightener-compatible processes, or crosslinking aids; testing is essential for target fastness levels.

Is Direct Red 28 suitable for inks or coatings?

It can be used in water-based inks and coatings, but check solubility, migration and binder compatibility before scale-up.

How should it be handled and stored?

Store sealed in a cool, dry place. Use standard PPE (gloves, goggles, dust control) and follow local safety/data sheet recommendations.