Black Dye Direct Fast Black VSF600 Direct Black 22.

Solubility: Approximately 45g/L at 90°C (medium to high); soluble in cold water, dissolves faster in hot water

Solvent solubility: Direct Black 22 is slightly soluble in ethanol; insoluble in organic solvents such as acetone and ether

Acid-base reactions:

Concentrated sulfuric acid: Purple-black, turns to black-brown precipitate upon dilution

Concentrated hydrochloric acid: Brown-black precipitate

Concentrated NaOH: Dark blue-red

Metal sensitivity: Direct Fast Black VSF600 shows slight color change in the presence of copper/iron ions (copper shifts towards blue, iron towards dark)

Affinity: Direct Fast Black VSF600 has strong affinity for cellulose (pulp/cotton/viscose) and provides uniform coloration

Color uptake: High absorption in paper dyeing, full blackness, and sufficient blue light

Color fastness (paper, 2% concentration):

Lightfastness: 4–6 grades (high, superior to 19/38)

Water fastness: 2 grades; dry rubbing fastness: 4 grades; wet rubbing fastness: 3 grades

pH range: Neutral to weakly alkaline (pH 6.5–8.5), Direct Black 22 has good resistance to hard water

Dischargeability: Direct Black 22 is dischargeable, suitable for reprocessing of printed paper/colored paper

Form: Powder (mainstream), liquid (for paper mills)

Quality standards:

Moisture: ≤1.0%

Insoluble matter in water: ≤0.15%

Color strength: 100±3%

Fineness (80 mesh): Residue ≤5%

1. Core Advantages and Disadvantages (Compared with 19/38/17)

Advantages

Direct Fast Black VSF600 has high lightfastness: 4–6 grades (19 is 4 grades, 38 is 4–5 grades), outdoor paper is less prone to fading

Direct Black 22 has pure color light: blue-black with sufficient green light, the paper surface is jet black without redness, making it the first choice for high-end paper

Good compatibility: Direct Black 22 can be mixed with Direct Yellow/Red/Blue to create high-end gray/brown/black

Disadvantages

Direct Fast Black VSF600 has average solubility: approximately 45g/L at 90°C (lower than 19's 100g/L), requires heating when preparing the dye solution

Direct Black 22 is relatively expensive: 10%–15% higher than 19, 30%–40% higher than 38

Direct Fast Black VSF600 has average wet fastness: water fastness 2 grades, requires fixation treatment

Direct Black 22 is suitable for the following paper types: high-end packaging paper, food-grade paper, outdoor fruit bag paper, cultural paper, and colored paper

Recommended process:

Temperature: 80–90°C (optimal 85°C)

Time: 30–40 minutes

pH: 7.0–8.0

Dosage: 1%–3% (based on absolute dry pulp)

Compatibility: Direct Black 22 can be mixed with Direct Blue 86 and Direct Yellow 50 to achieve high blackness with blue light.