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Direct Blue 2B — Product Overview
Direct Blue 2B (C.I. Direct Blue 6, CAS No. 2602-46-2) is a classic di-azo direct dye. It appears as a dark blue powder and has excellent water solubility and dyeing properties.
CAS No. 2602-46-2
C.I. Direct Blue 6
Di-Azo Direct Dye
Dark Blue Powder
Solubility
Dissolves in water to form a blue to navy blue solution. Slightly soluble in ethanol; insoluble in other organic solvents.
Acid-Base Reaction
Turns bright blue in concentrated sulfuric acid; after dilution, turns purple to reddish-blue. Forms a navy blue precipitate with concentrated hydrochloric acid; forms a deep purple precipitate with sodium hydroxide solution.
Dyeing Properties
Good dye uptake performance for cellulose fibers. Maximum affinity at 60–80 ℃ with good fading resistance.
Appearance
Dark blue powder. Industrial product specifications are typically 100% and 200% strength.
Application Scope
Textile Printing & Dyeing
Silk Dyeing
Paper Dyeing
Biological Dyeing
Textile Printing and Dyeing (Core Application)
This is the main application field of Direct Blue 2B.
- Applicable Fibers: Cotton, viscose, linen and other cellulose fibers
- Good Dye Absorption: High dye uptake rate for reliable, consistent results
- Optimal Dyeing Temperature: Maximum affinity at 60–80 ℃
- Good Bleaching Property: Facilitates correction of dyeing defects
- Silk Dyeing: Direct Blue 6 can be used for dyeing natural silk fabrics to obtain a blue tone
- Blending Application: Can be used as a blue component mixed with other direct dyes for obtaining different color lights
Paper Dyeing
Direct Blue 2B is clearly applicable for paper coloring:
- Applicable Paper: Cultural paper, packaging paper, etc.
- Usage Method: Pulp dyeing or surface sizing dyeing
- Advantages: Good water solubility, uniform dyeing, strong affinity with paper pulp fibers
Biological Dyeing
Direct Blue 2B has specific applications in laboratory and biological research fields:
- Biological Sample Dyeing: Used to reveal cell and tissue structures under a microscope
- Biological Molecule Detection: Specifically binds to proteins and nucleic acids, facilitating observation
- Biochemical Research: Used for the purification and separation of biological macromolecules
The biological application is limited to scientific research experiments and cannot be used for clinical diagnosis or treatment of humans or animals.
Other Application Fields
- Leather Dyeing: Direct Blue 6 is used for coloring leather products
- Wood Dyeing: Direct Blue 6 can be used for surface dyeing of wood
- Fertilizer / Seeds Dyeing: Used as a marking dye
- Laboratory Reagents: Analytical standards used for dye detection and quality control
Key Points of the Direct Blue 2B Dyeing Process
1
Dissolution
Dissolve thoroughly in 80–90 ℃ hot water before use
2
Dyeing Temperature
60–80 ℃ for maximum affinity and best uptake
3
Boosting Agent
Use salt or monocalcium phosphate; add in several portions
4
Fixation
Use fixation agent Y to enhance wash fastness
Usage Restrictions & Safety Requirements
- Direct Blue 6 is not recommended for textiles that come into direct contact with the skin.
- For export products, check whether such dyes are prohibited in the target country.
- For industrial applications, compliance with local environmental protection regulations is required.
- Safety: When handling Direct Blue 2B, wear protective equipment to avoid inhaling dust.
Frequently Asked Questions (FAQ)
Q
What is Direct Blue 2B and what is its CAS number?
Direct Blue 2B, also known as C.I. Direct Blue 6, is a classic di-azo direct dye with CAS No. 2602-46-2. It appears as a dark blue powder with excellent water solubility and is widely used in textile, paper, and biological dyeing applications.
Q
What fibers can be dyed with Direct Blue 2B?
Direct Blue 2B is primarily used to dye cellulose fibers such as cotton, viscose, and linen. It is also suitable for dyeing natural silk fabrics and can be blended with other direct dyes to achieve different color tones.
Q
What is the recommended dyeing temperature for Direct Blue 2B?
The optimal dyeing temperature for Direct Blue 2B is 60–80 ℃, at which point it achieves maximum affinity with cellulose fibers. For dissolution, the dye should first be thoroughly dissolved in hot water at 80–90 ℃ before use.
Q
Can Direct Blue 2B be used for paper and biological applications?
Yes. For paper dyeing, Direct Blue 2B can be applied via pulp dyeing or surface sizing dyeing for cultural and packaging paper. In biological research, it is used for staining biological samples, detecting biological molecules such as proteins and nucleic acids, and for the purification of biological macromolecules. Note that biological use is strictly limited to scientific research and not for clinical purposes.
Q
How can wash fastness be improved when using Direct Blue 2B?
To enhance wash fastness, it is recommended to apply fixation agent Y after the dyeing process. Additionally, using salt or monocalcium phosphate as a boosting agent (added in several portions during dyeing) helps improve dye uptake and overall color fastness performance.
Q
Are there any restrictions or safety precautions for using Direct Blue 2B?
Direct Blue 6 is not recommended for textiles that come into direct contact with the skin. For export products, users must verify whether this dye is restricted or prohibited in the destination country. All industrial applications must comply with local environmental protection regulations. When handling Direct Blue 2B, always wear appropriate protective equipment to avoid inhaling dust or powder.