Section
| HS Code | 179737 |
| Productname | Direct Black VSF |
| Colorindexname | C.I. Direct Black 22 |
| Colorindexnumber | 35435 |
| Casnumber | 6473-13-8 |
| Chemicalclass | Trisazo direct dye |
| Appearance | Black powder |
| Solubility | Soluble in water |
| Ionicity | Anionic |
| Application | Cotton, viscose, paper, leather |
| Dyeingmethod | Direct dyeing with electrolyte |
| Typicaldyeingph | 6-8 |
| Lightfastness | 3-4 |
| Washfastness | 3-4 |
| Rubbingfastness | 3-4 |
| Perspirationfastness | 3-4 |
| Storage | Cool, dry, ventilated area away from moisture and light |
| Packaging | 25 kg bag or drum with inner liner |
As an accredited Direct Black VSF factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Direct Black VSF is packaged in 25 kg net woven bags with inner plastic liners for secure transport and storage. |
| Container Loading (20′ FCL) | Direct Black VSF chemical is securely packed and loaded into a 20-foot FCL container for safe ocean freight transport. |
| Shipping | Direct Black VSF is a direct dye shipped as a dry powder in sealed, moisture-resistant containers. It is generally not regulated as dangerous goods for transport. Handle as a dust irritant, keep dry, avoid contamination, and comply with local labeling, SDS, and carrier requirements. |
| Storage | Store Direct Black VSF in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly closed, clearly labeled, and protected from moisture. Prevent dust generation and avoid contact with strong oxidizers, acids, and alkalis. Do not store near food, feed, or drinking water; use secondary containment and appropriate PPE. |
| Shelf Life | Shelf life is approximately 24 months when stored in a cool, dry, ventilated area away from sunlight and moisture. |
In exhaust dyeing of scoured and bleached 100% cotton twill and viscose staple linings, Direct Black VSF is applied as an anionic direct colorant with a working exhaustion window between 80°C and 98°C, using a declared addition of 1.0% to 4.0% on weight of goods (o.w.f.). The first-fill jigger bath at a liquor ratio of 1:8 to 1:12 contains 5–30 g/L calcined sodium sulphate and 0.5–2.0 g/L sodium carbonate; the dye is pre-dispersed at 60°C before injection to prevent filter-staining tar particles. On a jigger the fabric is passed through 2 to 6 ends at 30–45 m/min; on a winch the rope circulation is held below 100 m/min to avoid rope marks. Scouring and bleaching prior to dyeing must leave no residual hydrogen peroxide, because peroxide residuals above 5 mg/L in the bath can reduce shade depth and produce batch-to-batch red-shift. For skin-contact apparel export lots, compliance is verified against REACH Annex XVII entry 43 for restricted aromatic amines, Oeko-Tex Standard 100 Class II limits, and ZDHC MRSL 3.1 chemical formulation bans. Without aftertreatment, wet rub under ISO 105-X12 on a heavy shade may fall below 2–3 on cotton; a cationic fixing agent at 1–3% o.w.f. applied at 40–50°C for 20 min raises wet fastness but increases handle stiffness and can depress light fastness under ISO 105-B02 by half a grade. The output is used for black viscose linings, cotton pocketing, workwear shell fabric, and trouser drills where mild domestic wash or dry cleaning is specified.
On a continuous pad-dry-steam range processing tight-woven cotton twill, Direct Black VSF is prepared in a pad bath at 10–40 g/L with an anionic/nonionic wetting agent at 1–3 g/L. Pick-up is held at 65–80% on a two-bowl horizontal padder with nip pressure of 2–4 bar. The main process conflict is dyestuff migration during drying: when the cloth enters the infrared predryer at 70–90°C and then a cylinder hotflue at 100–120°C, water evaporating from the surface carries dye to the selvedge and face, producing centre-to-edges variation of more than 0.5 CIELAB ΔE on uncontrolled runs. The standard countermeasure is a staged thermal profile—short-wave infrared predrying to reduce surface wetness before contact drying, and no more than 20–25°C temperature difference between predryer and first cylinders. Fixation occurs in saturated steam at 102–105°C for 45–90 s, followed by countercurrent wash boxes at 60–80°C to remove unfixed dye. Compliance for casual outer shell fabric is assessed under ISO 105-C06 domestic washing, ISO 105-X12 wet and dry rub, and REACH Annex XVII entry 43 for restricted amines in the finished article. Terminal articles produced from this route are black cotton twill, canvas shoe upper fabrics, casual trouser shells, and light-duty apparel where moderate domestic wash is specified.
Wet-end application on a Fourdrinier machine uses Direct Black VSF as a metered anionic dye solution at 0.05–1.5% on oven-dry fibre, added to the machine chest after refining. The stock pH is held at 4.5–6.5 with aluminium sulphate at 0.5–1.5% on dry fibre; a cationic polyacrylamide retention aid is dosed at 0.02–0.2% to retain the dye fines. The stock is diluted to 0.1–0.8% consistency before the headbox and dewatered on the wire. Retention below 70% loads white water with dye and causes shade drift during grade change; a dye shot should therefore be made upstream of the fan pump, not directly in the headbox, to allow at least 15–30 s contact time before dewatering. For food-contact grades, the mill must obtain supplier raw material data sufficient for components under FDA 21 CFR 176.170 and bleed fastness under EN 646; if the board is coated or laminated, EU 10/2011 overall migration rules apply to the finished structure. The application is used for black napkin tissue, wet-strength carrier board, luggage blackboard, and folded carton stock.
| Compliance instrument | Scope | Typical verification point |
|---|---|---|
| FDA 21 CFR 176.170 | Paper and paperboard in contact with aqueous and fatty foods | Component migration limits; dye supplier extractive data |
| EN 646 | Paper and board for food contact—bleed fastness | Visual staining on food simulant or filter paper |
| EU 10/2011 | Food contact plastics and multilayer components | Overall migration limit 10 mg/dm² where applicable |
| REACH Annex XVII entry 43 | Azo colorants releasing restricted aromatic amines | 30 mg/kg per listed amine in dye or finished article |
Where surface colour is required on packaging board without full wet-end changeover, Direct Black VSF is applied in the size press as a top-up stream to an oxidized starch base. The working bath is prepared with oxidized starch at 4–8% solids, dye at 2–15 g/L, and viscosity held between 20–50 cP on a Brookfield LV spindle 1 at 60 rpm and 60°C. Bath temperature is maintained at 55–70°C; wet pick-up on the board is 25–45 g/m², depending on base sheet absorbency. Above 15 g/L dye concentration, bath conductivity may exceed 2,000 µS/cm and destabilize starch viscosity; when this occurs, the dye should be split into two dosing points or the starch solids raised to 8%. For school and office articles that may be handled by children, finished board is checked against EN 71-3 heavy metal migration limits, while dermal contact stationery is assessed for restricted amines under REACH Annex XVII entry 43 and bleed fastness under EN 646. Published data for this specific dye designation in size press operation is limited; mill validation on target board is required. Terminal types are black poster board, file folder stock, tag board, and coated packaging board where surface colour consistency is more important than full bulk penetration.
Package dyeing of viscose sewing thread and cotton knitting yarn with Direct Black VSF becomes process-stable only when package density is controlled to 350–420 g/L and flow reversal is programmed. The dye is added at 0.5–2.5% o.w.f., with calcined sodium sulphate at 10–30 g/L; the machine is ramped at 1–2°C/min to 95°C and held for 30–60 min. Differential pressure across the package is maintained at 0.8–1.5 bar, with inside-to-outside and outside-to-inside reversal every 2–4 min. At package densities above 420 g/L, the high-molecular-weight Direct Black VSF fraction can filter on the package surface and increase package-to-package lightness variation by more than 0.75 CIELAB ΔE. The first 10 min of the dyeing cycle should be salt-free to avoid shock aggregation; dye is pre-dissolved at 60°C and screened through an 80 µm mesh before addition. For finished thread articles, compliance is verified under ISO 105-C06 washing and ISO 105-B02 light, with aromatic amine limits under REACH Annex XVII entry 43. Terminal outputs are black sewing thread, embroidery thread, crochet cotton, and narrow woven webbing yarns.
Aqueous flexographic and gravure printing inks for uncoated paper use Direct Black VSF as a dissolved dye colorant at 1–5% by weight of finished ink, introduced from a predissolved dyestuff solution rather than as dry powder. The let-down vehicle contains 20–40% styrene-acrylic or acrylic emulsion solids and a coalescing glycol in the range 2–6%; final viscosity is adjusted to 20–50 s on a DIN 4 cup at 25°C. The production process uses a high-speed disperser with tip speed of 15–25 m/s for resin dispersion, followed by dye solution addition under low shear to avoid foaming, and filtration through a 10 µm bag. In a flexo deck, the ink is run at 2–4 g/m² dry film weight on newsprint or kraft; pH is held at 8.0–9.5 with ammonia or organic amine to maintain solubility and prevent precipitation. Compliance for printed paper articles is verified under REACH Annex XVII entry 43 for restricted amines and, where printed paper enters toys, under EN 71-3 migration limits. Undissolved aggregates above 10 µm produce plate plugging and print mottle; dye solution addition under low shear is therefore used instead of dry powder addition. Published data for this dye designation in flexo ink is limited to supplier solubility certificates, so drawdown validation on the target paper substrate is required. Terminal outputs are pre-printed paper bags, corrugated liner, paper labels, and gift wrap printed on water-based flexo or gravure units.
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Direct Black VSF is manufactured as a high-strength direct dye supplied against C.I. Direct Black 22. The standardised powder grade carries a declared nominal strength of 600% relative to the unstandardised colorant, with the final lot adjusted using sodium sulfate or dextrin to maintain reproducible colour strength under the supplier’s spectrophotometric comparison method. A representative certificate of analysis for the powder form lists moisture content at ≤ 5.0%, water-insoluble matter at ≤ 0.5%, pH of a 1% aqueous solution at 25 °C between 8.0 and 10.0, and solubility in demineralised water at 80 °C not less than 60 g/L. Liquid grades standardised at 300% are also available for automated dosing systems, with the same Colour Index designation and reduced dusting potential. The dye is a sulfonated polyazo sodium salt that fixes to cellulosic substrates through hydrogen bonding, van der Waals aggregation, and fibre internal surface area rather than through covalent bond formation. Exhaustion is therefore salt-dependent and partially reversible at elevated temperature. This product is not intended for food-contact packaging applications unless separate regulatory clearance under FDA 21 CFR 178.3297 has been obtained for the specific final article.
Direct Black VSF is supplied as a non-benzidine replacement for C.I. Direct Black 38 in markets where EU Directive 2002/61/EC and REACH Annex XVII entry 43 prohibit the placement of azo colorants that can release restricted aromatic amines above 30 mg/kg. C.I. Direct Black 22 is not manufactured from benzidine or benzidine-derived precursors; however, synthesis impurities in any polyazo dye require batch-level confirmation because trace amine formation is process-dependent. The applicable analytical method is EN 14362-1:2012. The shade of Direct Black VSF is a neutral black with a redder under-tone than sulphur black and a greener under-tone than many oxide blacks when assessed under D65 illuminant and 10° observer using a spectrophotometer configured to ISO 105-J01:2009. Colour difference decisions should be based on ISO 105-A02 grey-scale assessment and ISO 105-A03 staining assessment rather than visual inspection alone.
| Parameter | Direct Black VSF C.I. Direct Black 22 | Direct Black 38 C.I. 30235 | Sulphur Black 1 C.I. 53185 | Reactive Black 5 C.I. 20505 |
|---|---|---|---|---|
| Fixation mechanism | Substantive; hydrogen bonding and dye aggregation | Substantive; hydrogen bonding | Leuco form oxidised to insoluble dye within the fibre | Covalent vinyl sulfone linkage to cellulose |
| Regulatory status | Benzidine-free; batch verification required under EN 14362-1:2012 | Restricted carcinogen; benzidine release | Sulfide process; no azo amine issue | No azo amine issue |
| Application temperature | 95–100 °C | 95–100 °C | 85–95 °C | 60–80 °C |
| Salt or chemical demand | 10–30 g/L anhydrous sodium sulfate | 10–30 g/L anhydrous sodium sulfate | 5–15 g/L sodium sulfide plus 5–10 g/L soda ash | 40–80 g/L sodium sulfate plus 10–20 g/L sodium carbonate |
| Wet fastness after fixation | Moderate; improves with cationic fixative to ISO 105-C06 rating 3–4 | Moderate; not used in contemporary production | High without aftertreatment | High |
| Operational hazard | Low; no reducing agent required | Carcinogen handling prohibited | Hydrogen sulfide gas if acidified | Alkali and electrolyte handling required |
The process bands shown are representative laboratory values at a liquor ratio of 1:10. Production jiggers, package dyeing machines, and continuous dyeing ranges require machine-specific profiling because circulation rate, fabric contact time, and temperature distribution alter the effective exhaustion curve.
For woven and knitted cotton, Direct Black VSF is dissolved in demineralised water at 80–90 °C at a dyebath ratio of 1:10–1:20. The dyebath is set at 40 °C with 0.5–1.0 g/L wetting agent and sufficient acetic acid or soda ash to maintain pH 7.0–8.5. Dye addition is followed by a linear temperature ramp of 1.0–1.5 °C/min to 95–100 °C, with a hold time of 45–60 min. Anhydrous sodium sulfate is added in three equal portions at 80 °C, 90 °C, and 95 °C to a total of 10–30 g/L, depending on shade depth. Salt dosing rate is the dominant source of batch-to-batch unlevelness on package-dyeing machines; dosing pumps set to 10–20% of the final salt solution per minute are used to prevent rapid exhaustion at the package surface. Hard water above 150 mg/L CaCO3 reduces dye solubility and requires a polyacrylate or EDTA-based sequestering agent at 1–2 g/L. Viscose is started at 60 °C because of higher fibre swelling; the final hold is shortened to 30–40 min to avoid excessive loss of tensile strength in wet processing. After rinsing, the dyeing is evaluated against ISO 105-A02 for change in colour and ISO 105-A03 for staining, with formal colour difference measured under D65 illuminant and 10° observer using a spectrophotometer configured to ISO 105-J01:2009.
In wet-blue chrome-tanned leather, Direct Black VSF is applied at 1.5–4.0% on shaved weight after neutralization with sodium formate and sodium bicarbonate to pH 5.5–6.5. The drum float is 80–120% at 60 °C; penetration is checked on a full-thickness cross-section every 15 min. Because the dye is anionic, it competes with anionic fatliquors and retanning syntans for cationic sites on chrome leather. Direct Black VSF is therefore added before acidic fixation to pH 3.8–4.2 with dilute formic acid. The degree of fibre penetration on a laboratory tanning drum of 0.8 m diameter and 12 rpm rotation is strongly influenced by float temperature; below 55 °C dye uptake can be unacceptably slow, while above 65 °C grain roughening may occur. Published data for this specific drum configuration is limited; production trials are required before standardisation.
Selection of Direct Black VSF instead of C.I. Sulphur Black 1 is determined by process chemistry rather than by colour strength. Sulphur black requires reduction with sodium sulfide to a water-soluble leuco form and subsequent oxidation, which can generate hydrogen sulfide when spent baths are acidified. Direct Black VSF avoids sodium sulfide entirely because the dye is already water-soluble. This substitution is preferred when waste-water sulfide discharge limits are below 2 mg/L and when the process cannot guarantee separate alkaline discharge. The trade-off is wet fastness: Sulphur Black 1 has higher washing fastness without cationic aftertreatment, whereas Direct Black VSF requires aftertreatment to meet ISO 105-C06 rating 3–4 on cotton at 4% o.w.f. Direct Black VSF also does not produce the bronze-prone surface deposits observed with heavy sulphur black oxidation. Crocking values under ISO 105-X12 are more stable when the dry crock rating is 4 and wet crock rating is 2–3 after fixation. Colour matching between the two dye classes is not direct because the sulphur black exhaustion curve is slower at 70–85 °C; a minimum of three laboratory dyeings under the production liquor ratio should be generated before plant-scale substitution.
After exhaustion dyeing, wet fastness is upgraded with a polyamine or dicyandiamide-formaldehyde cationic fixative. The bath is set at 40–50 °C and pH 5.5–6.5; fixative dosage is 2–4% o.w.f. for medium-depth blacks. At dosages above 4% o.w.f., the fixative may form large dye-fixative aggregates that scatter light and reduce light fastness by 0.5–1.0 blue wool scale points. The treated fabric is rinsed at 25–30 °C to avoid desorption of the fixative-dye complex. Wet fastness is checked to ISO 105-C06:2010, light fastness to ISO 105-B02:2014, and rubbing to ISO 105-X12:2016. Incompatibility is observed with anionic optical brighteners in the same bath; quaternary ammonium groups of the fixative precipitate the anionic brightener and produce uneven fluorescence. Formaldehyde-free fixatives are required for Oeko-Tex Standard 100, product class I.
In paper beater dyeing, Direct Black VSF is added to refined pulp at 0.5–2.0% on dry fibre after alum addition has been completed. Because the dye is anionic, cationic retention aids such as high-charge-density polyacrylamide can precipitate the dye before it penetrates the fibre wall; retention aid addition should be staged or the dye added earlier in the beating cycle. The resulting black paper is checked by ISO 2470 for brightness and ISO 5631 for colour measurement. For water-based ink applications, the high electrolyte content of standardised powder may alter ink conductivity; a low-salt granular grade or liquid grade is specified when conductivity of the finished ink must remain below 1 mS/cm. Direct Black VSF is not solvent-soluble and is not suitable for solventborne ink or nitrocellulose lacquer systems unless compatibility is demonstrated through phase separation testing.
Direct Black VSF is classified as a textile dyestuff, not as a food-contact colorant. No claim should be made for FDA 21 CFR 178.3297 compliance for food-contact polymers unless a separate regulatory opinion has been issued for the specific final article. The dye is subject to EN 14362-1:2012 for azo amine release. Heavy metal content should be reported in the certificate of analysis and assessed against Oeko-Tex Standard 100 or ZDHC MRSL limits where applicable. Batch-level verification is required because dye synthesis impurities and standardising diluents can differ by manufacturing site.
| Standard or test designation | Property measured | Typical acceptance boundary | Direct Black VSF batch control |
|---|---|---|---|
| EN 14362-1:2012 | Restricted aromatic amines from azo colourants | 30 mg/kg | Not detected in supplier declaration; independent batch test required |
| ISO 105-B02:2014 | Colour fastness to light | 3–4 at 4% o.w.f. on cotton | Lot-to-lot variation within ±0.5 blue wool scale |
| ISO 105-C06:2010 | Colour fastness to washing | 3–4 after cationic fixation | Reported on certificate of analysis |
| ISO 105-X12:2016 | Colour fastness to rubbing | Dry 4, wet 2–3 after fixation | Reported per lot |
| ISO 105-E01:2013 | Colour fastness to water | 3–4 after fixation | Reported per lot |
| Oeko-Tex Standard 100, class I–IV | Heavy metals, restricted amines, formaldehyde | Annex 4 limits by product class | Supplier declaration required |
Operational boundary: pre-dissolve Direct Black VSF in 80–90 °C demineralised water and avoid storing concentrated dye solution below 10 °C because dye aggregation can produce filter plugging in package or beam dyeing machines. Do not mix the anionic dye with cationic fixatives in the same pre-tank before transfer to the dyebath; precipitation occurs at pH below 5.0.
