Direct Black EX/Direct Black 38 Powder - China Suppliers and Factory for Quality Dye Solutions
Product Features
Direct Black 38 is a commonly used black dye for paper, cotton, linen, and viscose. It has a greenish black color, fast coloration, and low price.
Basic Physical and Chemical Properties
| Property Type | Specifications & Reactions |
|---|---|
| Appearance | Uniform brownish black powder |
| Color | Standard greenish black (in water) |
| Solubility (water) | Approximately 40g/L at 85℃; soluble in cold water and more soluble in hot water |
| Solvent solubility | Direct Black EX is slightly soluble in ethanol (greenish blue black) and soluble in cellulose; insoluble in other organic solvents |
| Acid-base reaction |
|
Dyeing Performance (Paper / Fiber)
Direct Black 38 has good absorption to cellulose (cotton / linen / viscose / paper), with the highest affinity at 80℃; coloration is slightly lower at low temperatures.
High color yield and low loss in paper dyeing; Direct Black 38 is suitable for cultural paper / packaging paper / boxboard paper.
- Lightfastness: 4–5 grades (medium, lower than Direct Black 17's 7–8 grades)
- Water fastness: 3–4 grades
- Rub fastness: 3 grades
- Dischargeability: Dischargeable; Direct Black EX is suitable for reprocessing of printed paper / colored paper
- pH range: Neutral to weakly alkaline (pH 6.5–8.5), moderate resistance to hard water
Form and Quality Indicators (Industrial Grade)
Form: Powder (mainstream), liquid (less common)
- Moisture: ≤1.0%
- Insoluble matter in water: ≤0.5%
- Color strength: 100±3%
- Fineness (80 mesh): Residue ≤5%
Core Advantages and Disadvantages
- Low price: Direct Black 38 is 30%–40% cheaper than Direct Black 17, offering high cost performance
- Fast coloration: Dyeing completed in 30–40 minutes at 80℃, suitable for high-speed paper machines
- Pure color: Greenish black with no red / brown impurities, uniform paper surface color
- Wide application: Direct Black EX can be used in paper, cotton, linen, viscose, leather, wood, and ink
- Moderate lightfastness of Direct Black EX: 4–5 grades, not suitable for long-term outdoor / high lightfastness requirements
- Poor resistance to hard water of Direct Black 38: Easy to precipitate in high-hardness water, requires soft water / chelating agents
Key Points for Paper Dyeing Application
Applicable paper types for Direct Black EX: Cultural paper, packaging paper, boxboard paper, tissue paper, colored paper.
Dosage: 1%–3% (based on absolute dry pulp)
Compatibility: Direct Black 38 can be mixed with Direct Yellow / Red / Blue for color matching, to achieve gray / brown / black tones.
Frequently Asked Questions
What are the main applications of Direct Black 38?
Direct Black 38 is widely used to color paper (such as cultural paper, packaging paper, boxboard paper, and tissue paper), cotton, linen, viscose, leather, wood, and ink.
What is the solubility of Direct Black 38 in water?
Direct Black 38 has a solubility of approximately 40g/L in water at 85℃. It is soluble in cold water and becomes highly soluble in hot water.
How does Direct Black EX react to acid and base solutions?
When mixed with concentrated sulfuric acid, it turns deep reddish blue and yields a reddish black precipitate upon dilution. With concentrated hydrochloric acid, it turns dark reddish black and precipitates purple-brown. In concentrated NaOH, it yields a blue-gray precipitate.
What is the lightfastness grade of Direct Black EX?
Direct Black EX has a moderate lightfastness rating of 4–5 grades, which is lower than the 7–8 grades offered by Direct Black 17.
What precautions should be taken regarding water hardness?
Direct Black 38 has poor resistance to hard water and is prone to precipitation. It is recommended to use soft water or add chelating agents during the dyeing process.
Can Direct Black 38 be mixed with other dyes?
Yes, Direct Black 38 is highly compatible and can be mixed with Direct Yellow, Direct Red, and Direct Blue for color matching to achieve gray, brown, and black tones.