Paper Dye Direct Fast Black G Direct Black 19.
Product Characteristics
Direct Black 19 is a multi-azo direct dye, suitable for paper, cotton, and viscose. It has high solubility, a greenish black color, medium lightfastness, and a high cost-performance ratio.
Physical and Chemical Properties
Solubility: Approximately 100g/L at 80°C (extremely high); easily soluble in cold water, Direct Black 19 is suitable for high-speed dyeing.
Solvent Solubility: Direct Black 19 is slightly soluble in ethanol/acetone; insoluble in other organic solvents.
Acid-Base Reaction:
Concentrated sulfuric acid: Greenish black, turns to reddish black precipitate upon dilution
10% sulfuric acid: Microscopic red
Concentrated NaOH: Greenish blue
Metal Sensitivity: Direct Fast Black G shows a slightly greenish color when exposed to copper ions and darkens slightly when exposed to iron ions.
Paper Dyeing Performance
Affinity: Direct Black 19 has strong affinity for cellulose fibers (pulp/cotton/viscose), and colors quickly.
Coloring Rate: High uptake and low loss in paper dyeing, with full blackness.
Color Fastness (Paper):
Lightfastness: 4 (medium, better than Direct Black 38)
Waterfastness: 3-4; Rubfastness: 3
pH Range: Neutral to weakly alkaline (pH 6.5-8.5), good resistance to hard water (better than Direct Black 38)
Dischargeability: Direct Fast Black G is dischargeable, suitable for reprocessing of printed paper and colored paper.
Form and Quality Indicators (Industrial Grade)
Form: Powder (mainstream), liquid (rare)
Quality Standards:
Moisture: ≤1.0%
Insoluble in water: ≤0.5%
Color Strength: 100±3%
Fineness (80 mesh): Residue ≤5%
Core Advantages and Disadvantages (Compared with Direct Black 38/17)
Advantages
Direct Fast Black G has extremely high solubility: 100g/L at 80°C, fast dyeing, no dust, suitable for high-speed paper machines.
Direct Black 19 has better lightfastness than 38: 4 (Direct Black 38 is 4-5 at the lower limit), less prone to fading.
Direct Black 19 has pure blackness: greenish black with sufficient blue tone, the paper surface is dark black without reddish tint.
Disadvantages
Direct Fast Black G has lower lightfastness than 17: 4 (Direct Black 17 is 7-8), not suitable for long-term outdoor paper.
Wet fastness is average: waterfastness/rubfastness 3-4, Direct Black 19 requires fixation treatment.
- Paper Application Scenarios and Processes
Direct Black 19 is suitable for the following paper types: packaging paper, boxboard, cultural paper, newsprint, fruit bag paper, and colored paper.
Recommended Process:
Temperature: 75-85°C (optimal 80°C)
Time: 30-40 minutes
pH: 7.0-8.0
Dosage: 1%-3% (based on absolute dry pulp)
Compatibility: Direct Black 19 can be mixed with Direct Yellow/Red/Blue for color matching, creating gray/brown/black; suitable for high blackness and high solubility requirements.