High Quality Direct Blue 71 Suppliers - China Factory Direct Fast Blue B2RL - C.I. No. 71, CAS 4399-55-7
Product Characteristics
Direct Blue 71 is a triazene-based direct sun-resistant dye.
Physical and Chemical Properties
Direct Blue 71 has moderate water solubility. The aqueous solution appears as a bright blue color; it is slightly soluble in cellulose and extremely slightly soluble in ethanol. It does not dissolve in other organic solvents.
Solubility: 60°C ≈ 10 g/L | 97°C ≈ 20 g/L
Alkali resistance stability: Stable at pH 7–10; highly alkaline (pH > 11) causes precipitation easily — car wash solution should control pH ≤ 10.
Aqueous solution + concentrated hydrochloric acid: blue precipitate
Aqueous solution + concentrated alkali: red-purple precipitate
Concentrated sulfuric acid: blue to gray-black, diluted to red-purple precipitate
Color: Deep red blue, rich and stable
Affinity: Direct Fast Blue B2RL has good affinity for cellulose fibers such as cotton, viscose, and linen
Dyeing rate: Medium to high; uniformity and removability are average
Color Fastness Indicators (Reference)
Core Advantages & Limitations
- Unique deep blue-red color tone — more intense than ordinary direct blue, ideal for dark coloring.
- Better sun resistance: 5–6 exposure grades, does not fade easily when used outdoors.
- High cost-effectiveness: moderate price, widely applicable across industries.
- Alkali resistance is limited: pH > 11 causes precipitation. Not suitable for strong alkaline car washing solutions (pH 11–12).
- Sensitive to iron ions: color becomes darker when encountering iron ions during dyeing. Dissolve in soft water is recommended.
Application Scope
Neutral / weakly alkaline car wash solution and glass water: suitable for deep blue coloring. Caution should be exercised with strong alkaline systems.
Direct Blue 71 can also be used in water-based cleaners, laundry detergents, paper, leather, soap, bamboo and wood fiber coloring.
Direct Fast Blue B2RL delivers rich red-light deep blue in cotton, viscose, hemp, non-woven fabric, home textiles, and knitted products.
Silk, nylon, and blended fabrics of viscose/nylon are also suitable for dyeing.
Usage Process of Direct Blue 71
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1
Mixing Solution: Stir and dissolve in 50–60°C warm water. Avoid lumps and do not use strong alkaline water.
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2
Dosage: 0.2–0.5 g/kg (0.002–0.005% by weight); 3% by weight is sufficient for deep blue color.
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3
pH Control: Strictly control pH 8–10. Beyond this range, precipitation tends to occur.
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4
Compatibility: Direct Fast Blue B2RL has good compatibility with non-ionic / anionic surfactants and does not affect foaming performance.
Frequently Asked Questions
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Q What is Direct Blue 71 and what type of dye is it?Direct Blue 71 (also known as Direct Fast Blue B2RL) is a triazene-based direct dye with excellent sun resistance. It belongs to the azo dye family and is primarily used for dyeing cellulose fibers such as cotton, viscose, and linen, as well as for industrial coloring in car wash solutions, water-based cleaners, and paper.
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Q What is the recommended pH range when using Direct Blue 71?The optimal pH range for Direct Blue 71 is 8–10. The dye remains stable at pH 7–10. When the pH exceeds 11 (highly alkaline conditions), precipitation is likely to occur. Therefore, strong alkaline systems such as car washing solutions at pH 11–12 are not recommended.
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Q How do you dissolve Direct Blue 71 correctly?Dissolve Direct Blue 71 in warm water at 50–60°C while stirring continuously to prevent clumping. Always use soft water, as iron ions present in hard water can cause the color to darken and affect the final result. Avoid using strongly alkaline water during the mixing stage.
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Q What fabrics and materials is Direct Blue 71 suitable for?Direct Blue 71 is well-suited for cellulose-based fibers including cotton, viscose, linen, and hemp. It is also applicable to silk, nylon, viscose/nylon blended fabrics, non-woven fabrics, home textiles, and knitted products. For industrial use, it works in paper, leather, soap, laundry detergents, and water-based cleaners.
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Q What are the sunlight fastness and washing fastness ratings of Direct Blue 71?Direct Blue 71 offers sunlight fastness of 5–6 grades, which is superior to many other direct blue dyes and makes it suitable for outdoor applications. Washing fastness is 3–4 grades, dry rubbing fastness is 4 grades, and wet rubbing fastness is 2–3 grades.
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Q Is Direct Blue 71 compatible with surfactants used in cleaning products?Yes. Direct Blue 71 (Direct Fast Blue B2RL) has good compatibility with non-ionic and anionic surfactants commonly found in cleaning and detergent formulations. It does not negatively affect foaming performance, making it a practical choice for coloring liquid detergents, car wash solutions, and similar products within the recommended pH range.