Section
| HS Code | 452647 |
| Productname | Nigrosine MS Conc |
| Synonym | Nigrosin |
| Dyeclass | Acid phenazine dye |
| Colorindex | CI 50420 |
| Casnumber | 8005-03-6 |
| Appearance | Black to bluish-black |
| Physicalform | Liquid concentrate |
| Solubility | Soluble or dilutable in water |
| Primaryuse | Microbiological negative staining |
| Stainingtype | Negative stain |
| Storageconditions | Store at room temperature and protect from light |
| Concentrationform | Concentrated solution |
As an accredited Nigrosine MS Conc factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Nigrosine MS Conc is packaged in 25 kg net polyethylene-lined fiberboard drums, sealed and labeled according to chemical safety regulations. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL): Nigrosine MS Conc packed in 20′ FCL, palletized, shrink-wrapped, secured, labeled, and documented for ocean transport. |
| Shipping | Nigrosine MS Conc is generally not classified as dangerous goods for transport (DOT/IMDG/IATA/ADR): no UN number, proper shipping name, hazard class, or packing group. Ship in securely closed, labeled containers at ambient temperature, protected from moisture and direct sunlight, and comply with local transport regulations. |
| Storage | Store Nigrosine MS Conc in a cool, dry, well-ventilated area, away from direct sunlight, heat, moisture, and strong oxidizing agents. Keep containers tightly closed, clearly labeled, and upright. Prevent dust generation and contamination, and use secondary containment where appropriate. Store separately from incompatible substances. Maintain good housekeeping and follow local regulations and the supplier’s safety data sheet. |
| Shelf Life | Typically 24 months when stored sealed in a cool, dry, well-ventilated area away from light and moisture. |
Production extrusion of carbon-black-filled polyamide 6 and 66 compounds requires careful selection of soluble dye systems when jet-black surface finish and dimensional stability are specified. Nigrosine MS Conc, a solvent-soluble nigrosine base with high tinting strength, is introduced at 0.1–0.5 wt% relative to polymer matrix when used as a shading component; for full-depth black masterbatch formulations, the addition range extends to 1.0–2.0 wt%. Material handling on twin-screw extrusion lines with L/D 40–48 and vacuum devolatilization at −0.08 MPa gauge pressure is advised because residual moisture above 0.08% in the dye predisposes the melt to hydrolytic chain scission and surface splay. Processing windows observed on production-scale equipment indicate that melt temperatures above 290°C promote thermal degradation of the nigrosine chromophore, shifting shade from neutral black to brown-black and reducing the L* value stability within a lot. Compliance under EU 10/2011 and FDA 21 CFR 178.3297 is typically verified by the compounder through extraction testing using EN 1186-1:2002 migration protocols, with specific migration limits assessed in 3% acetic acid and 95% ethanol simulants. Downstream injection molders processing these compounds report that color dispersion quality correlates with screw back pressure settings between 1.5–3.0 MPa and mold temperatures of 80–95°C for PA6; lower mold temperatures produce visible flow-line accentuation in dark shades. The terminal products include automotive interior clips, cable ties, electrical connector housings, power tool casings, and furniture hardware components where a non-bronzing black is specified.
Finishing of full-grain and corrected-grain leather for automotive interiors and upholstery requires black colorants that resist dry-rub transfer and plasticizer-induced bleeding. Nigrosine MS Conc is incorporated into solvent-borne polyurethane and nitrocellulose base coats at 0.5–2.5% of wet finish formulation weight; above 3.0% of wet formulation, laboratory rub-fastness testing under ISO 11640:2018 shows increased dry crocking values exceeding grey scale rating 4, which falls below automotive OEM specifications for Type I upholstery. In production spray lines, the dye solution is pre-dissolved in a blend of methyl ethyl ketone, ethyl acetate, and isopropanol at 40–50°C under low-shear stirring before addition to the finish base; pigment-black dispersions cannot be fully substituted without raising base-coat viscosity above the 20–25 s Ford Cup No. 4 range required for HVLP atomization. Crosslinking systems based on aromatic isocyanates show no adverse amine-isocyanate competition at dye loadings below 1.5%; above this threshold, the weakly basic nigrosine accelerates pot-life reduction from approximately 6 h to under 90 min at 25°C, requiring split-batch processing on dual-component spray equipment. The finish stack for automotive seating typically comprises two base coats and one matte topcoat, with the nigrosine confined to the base coats to avoid topcoat haze; visual assessment under ISO 105-A02:1993 is used to confirm shade consistency. Compliance requires full disclosure of the dye under REACH Annex XVII entries applicable to restricted aromatic amines; however, nigrosine is not classified as an azo dye and does not release the 24 regulated aromatic amines under EN 14362-1:2012 reductive cleavage conditions. Terminal articles include automotive seat covers, steering wheel leather, furniture upholstery, and leather goods where deep black with low bronzing is required.
| Downstream Sector | Primary Standard Reference | Specific Clause or Test Method | Compliance Parameter Monitored |
|---|---|---|---|
| Polymer extrusion | FDA 21 CFR 178.3297 | Colorants for polymers, extraction testing per EN 1186-1:2002 | Specific migration in food simulants |
| Polymer extrusion | EU 10/2011 | Annex I and Annex II, overall migration limit 10 mg/dm² | Total migration from finished article |
| Leather finishing | REACH Annex XVII | Entry 43, azocolourants restrictions | Absence of regulated aromatic amines |
| Leather finishing | ISO 11640:2018 | Method B, dry and wet rubbing | Rub fastness grey scale rating |
| Offset inks | EuPIA Exclusion Policy | Raw material exclusion lists, heavy metals limit 100 ppm | Total heavy metal content |
| Offset inks | ISO 2846-1:2017 | Colorimetric specification, CIELAB ΔE ≤ 1.5 | Shade reproducibility between batches |
| Wood coatings | EN 71-3:2019 | Migration of certain elements, Category III scraping materials | Element migration limits |
| Gravure inks | CONEG Model Legislation | Sum of four heavy metals ≤ 100 ppm | Packaging heavy metal compliance |
Offset sheet-fed and cold-set web ink formulations employ Nigrosine MS Conc as a shading agent to move carbon black dispersions toward a blue-black undertone without the rheological compromises associated with high pigment loading. The dye is added to the let-down stage at 2–6% of finished ink weight, typically as a pre-dissolved 20% solution in a high-boiling mineral oil or fatty acid ester vehicle. Addition directly as dry powder to the ink base is avoided on production three-roll mills because undissolved dye particles act as nuclei for ink fountain sedimentation and plate blinding on press units. Viscosity of the finished news ink shifts from approximately 8–12 Pa·s at 25°C and 2.5 s⁻¹ shear rate to 12–16 Pa·s with nigrosine addition above 4%; pressroom fountain solution emulsification behavior is characterized by ISO 12634:2017 for emulsification rate. In cold-set web offset printing on uncoated mechanical papers, the dye migrates into the paper sizing layer under heat-set dryer conditions only if dryer web temperatures exceed 110°C for more than 2 s; below this threshold, the nigrosine remains within the ink film and contributes to rub-off resistance as defined by ISO 2834-1:2019. Heavy metal content of the dye batch is controlled to ≤ 100 ppm total for lead, cadmium, mercury, and chromium VI to satisfy EuPIA exclusion policy and the US CONEG model legislation for printed matter. Terminal printed matter includes newspapers, telephone directories, mass-market paperback books, and direct mail advertising where neutral black print density above 1.8 is required on uncoated stock.
Solvent-based gravure printing of polypropylene and polyester films for confectionery and snack food packaging requires black inks that do not transfer odor or color to the sealed food contact surface. Nigrosine MS Conc is dissolved at 3–8% of ink weight in a toluene/isopropanol/ethyl acetate solvent blend with a polyurethane-polyvinyl chloride copolymer binder. The dye solution is compounded under high-shear dispersion in a closed dissolver at 20–25 m/s tip speed for 30–45 min, after which filtration through 10 µm absolute filter cartridges removes undissolved nigrosine agglomerates before the ink enters the gravure press sump. Print viscosity is maintained at 18–22 s efflux time on a DIN 4 mm cup at 25°C via automatic solvent addition; nigrosine addition above 8% raises the ink viscosity beyond the range controllable by the automatic viscometer and increases cylinder wipe marks on the printed film. Lamination bond strength of the printed film to aluminum foil or polyethylene sealant webs is measured at 2.0–4.0 N/15 mm according to ASTM F904; nigrosine at loadings below 5% shows no detectable effect on adhesive cure, while higher loadings retard polyurethane adhesive crosslinking because the weakly basic dye competes for isocyanate groups in the laminating adhesive. Odor and taint transfer are assessed by EN 1230-1:2009 sensory evaluation of the printed film against a food simulant; production lots with nigrosine purity below 98% show elevated trimethylamine and pyridine odor thresholds. The terminal packaging types are printed polypropylene wrappers for biscuits, polyester pouches for dry snacks, and laminated film structures for frozen food overwrap.
Solvent-borne nitrocellulose wood lacquers and pre-stain conditioners use Nigrosine MS Conc to achieve transparent black and dark walnut tones on oak, ash, and rubberwood substrates. The dye is incorporated at 0.5–1.5% of total lacquer solids, pre-dissolved in methanol or acetone at 10% concentration, then added to the nitrocellulose base under paddle stirring at 500–800 rpm. Application on production spray machines with air-assisted airless guns at 0.15–0.25 MPa fluid pressure and 0.10–0.18 MPa atomization air pressure yields a wet film thickness of 120–180 µm, which after solvent release produces a dry film of 30–45 µm. Penetration into open-pored wood varies with substrate moisture content; at wood moisture above 12%, the dye migrates into earlywood tracheids unevenly, producing blotchy inter-grain contrast that requires re-sanding and a second spray pass. Lightfastness of nigrosine in nitrocellulose lacquer is inferior to carbon black; accelerated weathering under ISO 4892-3:2016 Cycle 1 for 100 h shows a ΔE shift of 3–5 CIELAB units toward red-brown, limiting the formulation to interior furniture, picture frames, and interior millwork not exposed to direct sunlight. Compatibility with acid-catalyzed urea-formaldehyde lacquers is prohibited; the amine groups of nigrosine neutralize the para-toluenesulfonic acid catalyst, slowing cure and leaving a tacky surface. Toy safety compliance under EN 71-3:2019 requires testing of the dried film for migration of barium, cadmium, chromium, lead, mercury, and selenium; nigrosine batches must be specified with heavy metal content below 10 ppm for each regulated element when toy applications are commercialized. Terminal articles include wooden furniture, musical instrument bodies, interior door panels, decorative moldings, and wooden stationery items.
| Formulation Parameter | PA6 Compound | PA66 Compound | Sheet-fed Offset Ink | Toluene Gravure Ink |
|---|---|---|---|---|
| Nigrosine loading, wt% | 0.3 | 0.5 | 4.0 | 6.0 |
| Processing temperature window, °C | 240–270 | 270–290 | 25–40 | 25–35 |
| Viscosity at processing condition | 1200 Pa·s @ 100 s⁻¹ | 850 Pa·s @ 100 s⁻¹ | 10 Pa·s @ 2.5 s⁻¹ | 18 s DIN 4 cup |
| Critical threshold beyond which defect appears | 0.8 wt% plate-out on die lips | 1.0 wt% brown shift | 6.0 wt% plate blinding | 8.0 wt% lamination bond drop |
| Test standard for critical property | ISO 1133-1:2022 | ISO 1133-1:2022 | ISO 12634:2017 | ASTM F904 |
Nitrile rubber and styrene-butadiene rubber compounds for industrial gaskets, conveyor belts, and vibration damping pads require black colorants that survive sulfur cure cycles without generating bloom. Nigrosine MS Conc is added on open two-roll mills at 0.3–1.0 phr along with zinc oxide and stearic acid; addition is performed as a pre-dispersed paste in dioctyl phthalate at 33% dye content to prevent dusting and uneven color streaks. Mill roll temperatures are held at 50–65°C during incorporation, and the nip gap is maintained at 5–8 mm for the first pass; production batches exceeding 1.0 phr show visible dye agglomerates that survive subsequent Banbury mixing at 77 rpm rotor speed. The dye does not participate in accelerated sulfur vulcanization as an amine accelerator at levels below 0.5 phr; above this, cure rheometer testing under ISO 6502:2016 shows a reduction in scorch time from 4.2 min to 2.8 min at 160°C, necessitating reformulation with a prevulcanization inhibitor. Migration of the dye from cured rubber into adjacent white or light-colored polymer surfaces is tested by ISO 3865:2005 contact and penetration methods; nigrosine shows slight contact staining on plasticized PVC at 70°C for 24 h, rated as grey scale 4. The terminal rubber articles are black industrial hoses, oil-resistant gaskets, anti-vibration pads for machinery, and conveyor belt covers where a non-blooming black surface is specified. Published data for nigrosine-specific migration kinetics in filled nitrile rubber compounds are limited; compounders are advised to run production-scale contact-staining trials with the actual white or light-colored mating surface before releasing multi-material assemblies.
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Nigrosine MS Conc is a solvent-soluble azine dye classified under C.I. Solvent Black 7, constitution number 50415. Commercial technical data sheets identify the product as a concentrated medium-shade grade supplied as a black free-flowing powder or compacted granular solid. The product is used for the high-strength tinting of solvent-borne wood stains, publication gravure and flexographic inks, nitrocellulose leather finishes, and non-aqueous polymer masterbatches. The designation “MS Conc” distinguishes the grade from oil-soluble nigrosine base and water-soluble acid nigrosine by its optimised dissolution in aliphatic alcohols, ketones, esters, and aromatic hydrocarbons. Water is not a compatible carrier; neutral aqueous dispersions remain sedimented and impractical for colour development.
Physical specification data for Nigrosine MS Conc typically include colour strength of 100 ± 3% relative to a manufacturer reference, moisture content not exceeding 0.5 wt% by Karl Fischer titration, and residue on ignition not exceeding 1.0 wt% measured according to ISO 787-4. Melting behaviour is often reported as a broad endotherm between 270°C and 280°C; above this range thermal decomposition dominates. Specific gravity measured under ISO 2811-1 falls between 1.35 g/cm³ and 1.45 g/cm³, with the spread reflecting powder packing rather than molecular mass changes. The product is insoluble in water at pH 5 to 7, and a 10 wt% distilled-water dispersion cannot be standardised for pH because phase separation occurs without wetting agent.
| Property | Value or range | Test method or condition |
|---|---|---|
| Colour Index designation | C.I. Solvent Black 7 / 50415 | Colour Index International |
| Appearance | Black free-flowing powder | Visual inspection |
| Moisture content | ≤ 0.5 wt% | Karl Fischer titration |
| Residue on ignition | ≤ 1.0 wt% | ISO 787-4 |
| Colour strength | 100 ± 3% | Spectrophotometric comparison to reference |
| Specific gravity | 1.35–1.45 g/cm³ | ISO 2811-1 |
| Melting range | 270–280°C | Differential scanning calorimetry, 10 K/min |
Incoming material storage should prevent humid-air contact when handling bulk sacks in tropical production facilities. Exposure at relative humidity above 60% for periods longer than 4 h increases moisture pickup and can reduce feed consistency on loss-in-weight gravimetric dosing units. Silos and holding bins should be blanketed with dry air at a dew point below −20°C. Dust collection equipment on bag dump stations should be explosion-rated because nigrosine dye powders can form combustible dust clouds; published minimum ignition energy data for this specific configuration is limited.
In production dye kitchens, Nigrosine MS Conc is dissolved in stainless steel tanks with turbine agitation at 500–800 rpm and no high-shear rotor-stator work. A solvent sequence based on initial wetting with ethanol, followed by methyl ethyl ketone addition and final dilution with butyl acetate avoids lump formation. Published values for clear solution concentration in ethanol at 25°C are commonly 30–50 g/L; however, published data for this specific configuration is limited where low-water-content blends are involved because hygroscopic ketones shift the precipitation boundary. In methanol-acetone blends, solutions remain transparent above 20°C but become hazy if water content exceeds 5–8 vol%. Filtration through 10 µm polypropylene bag filters is specified before gravure ink loading to remove undissolved resin and dye aggregates. Differential pressure across the filter housing should not exceed 0.05 MPa at the start of a batch; higher pressure indicates premature dye precipitation or gross contamination.
Dissolution rate is temperature-dependent. With rising solvent temperature from 20°C to 40°C, the time to visual clarity in ethanol/methyl ethyl ketone 50:50 v/v typically decreases from 45 min to 20 min under low-shear stirring. Cooling below 10°C can cause precipitation in high-toluene gravure diluents, especially when aromatic hydrocarbon content exceeds 70 vol%. Plant trials with recirculation through in-line 25 µm cartridge filters show stability over 8 h shifts provided solvent loss by evaporation is replenished with anhydrous butyl acetate.
Substitution of carbon black with Nigrosine MS Conc in solvent-based gravure inks is evaluated primarily where gloss retention and filtration pressure are critical. In a typical publication gravure formulation with nitrocellulose/polyurethane binder, 5–8 wt% dye on liquid ink produces optical density comparable to 0.8–1.2 depending on cell depth and substrate; however, published data for this specific configuration is limited. Viscosity of the final ink is adjusted to 20–24 s through a DIN 53211 flow cup at 25°C. Unlike carbon black, the soluble dye does not require bead milling; this reduces energy input and avoids abrasive wear on ceramic gravure cylinders. However, the dye contributes less hiding power at equal film weight, and opacity must be corrected with opaque titanium dioxide where full coverage is specified.
Doctor blade polishing and cylinder scoring are reduced when the formulation is free of dispersed particles above 5 µm. A production-scale ink plant with a 200 kg batch size can reduce cycle time by eliminating the bead-milling pass; blending time in a stationary dissolver at 1,200 rpm is typically 30 min before filtration. Lightfastness of nigrosine-tinted gravure inks is lower than carbon black under ISO 105-B02 exposures; the dye is therefore confined to packaging and publication printing where long-term archival lightfastness is not specified. Resistance to rub-off measured by ASTM D5264-98 for printed film should be validated for each binder system because nigrosine can plasticise certain nitrocellulose grades when present above 8 wt%.
Thermoplastic masterbatch production with Nigrosine MS Conc is confined to polymers processed below 230°C. Compounding on a co-rotating twin-screw extruder with L/D ratio 32:1 to 44:1 and screw diameter 25–40 mm achieves acceptable dispersion at dye loadings of 0.1–0.5 wt% in rigid PVC and polystyrene. Melt temperatures above 240°C are associated with strength loss and generation of decomposition residue; published degradation data for this specific configuration is limited because residence time distribution varies with screw profile, polymer viscosity, and throughput. The product should not be processed in polyamide or polycarbonate above 260°C, where abrupt chromophore decomposition can produce gas defects in extrudates.
The dye is not considered a suitable replacement for carbon black in polyolefins requiring UV weathering stability tested under ISO 4892-2 because lightfastness values fall below the thresholds needed for exterior automotive or building profiles. Pre-drying for 2 h at 60°C is required in plants where silo storage relative humidity exceeds 60% to prevent feeding unevenness and steam hydrolysis. Feed-throat temperature should remain below 60°C in twin-screw extruders to prevent premature sintering of the dye powder.
Leather finishing lines using solvent-borne nitrocellulose lacquers incorporate Nigrosine MS Conc at 1–4 wt% of the basecoat. The dye is dissolved in butyl acetate/ethanol mixtures before addition to the lacquer; spray viscosity is maintained at 18–22 s through a Zahn cup 2. Precipitation occurs when water is introduced above 15–20 vol% in acetone-rich diluents, so aqueous topcoats must not be layered directly onto wet nigrosine-containing basecoats without an intermediate seal coat. Air-assisted spray nozzles with tip diameters of 0.8–1.2 mm require final filtration at 25 µm to reduce nozzle blockage.
Filter loading tests are performed at constant flow through 47 mm disc filters with 10 µm rated porosity. A rise in differential pressure above 0.03 MPa within 30 min indicates incomplete dissolution or water contamination in the solvent blend. Batch adjusters in leather finishing plants use triacetyl citrate or diethylene glycol monoethyl ether at 1–2 wt% to slow solvent loss and reduce dye migration into seal coats; solvent ratios must be revalidated after each adjustment using a gloss meter calibrated to ISO 2813.
Nigrosine MS Conc differs from adjacent grades in solvent selectivity and application fit. Nigrosine Base is an oil-soluble C.I. Solvent Black 7 grade supplied as a hard resinous solid or coarse powder; dissolution in ethanol is slower, whereas mineral oil and aromatic hydrocarbon compatibility is better. Spirit-soluble nigrosine, often classified as C.I. Solvent Black 5, dissolves rapidly in ethanol and methyl ethyl ketone but exhibits lower heat resistance in hot-melt and thermoplastic systems. Acid nigrosine, C.I. Acid Black 2, constitution number 50420, is water-soluble and is used for leather dyeing and aqueous ink jet formulations; it cannot be substituted directly into solvent-borne wood stains or gravure inks without phase separation. The “Conc” designation indicates tinting strength approximately twice that of regular nigrosine powder on an equal-weight basis; however, comparative strength must be verified by spectrophotometric absorbance at 590 ± 2 nm in the same solvent matrix.
| Grade | C.I. Designation | Solubility Character | Typical Application | Key Operational Difference |
|---|---|---|---|---|
| Nigrosine MS Conc | C.I. Solvent Black 7 / 50415 | Ethanol, methyl ethyl ketone, ethyl acetate, toluene | Solvent wood stains, gravure inks, leather finishes | Water-insoluble; concentrated tinting strength |
| Nigrosine Base | C.I. Solvent Black 7 / 50415 | Aromatic hydrocarbons, mineral oil; slower in ethanol | Alkyd paints, oleoresinous inks | Lower alcohol solvency |
| Spirit-Soluble Nigrosine | C.I. Solvent Black 5 / 50405 | Ethanol, methyl ethyl ketone | Ballpoint pen inks, spirit inks | More rapid alcohol dissolution; lower heat tolerance |
| Acid Nigrosine | C.I. Acid Black 2 / 50420 | Water | Aqueous inks, leather dyeing | Not compatible with solvent-borne systems |
Batch release testing in production environments typically uses a validated spectrophotometric method. A stock solution is prepared at 0.10 wt% in ethanol/methyl ethyl ketone 50:50 v/v, filtered through 0.45 µm PTFE, and measured in a 1 cm quartz cell over 400–700 nm. Absorbance at the long-wavelength maximum is compared against the reference; colour strength lower than 97% triggers batch rejection for high-speed gravure applications. Viscosity of the final ink or lacquer is checked after 24 h because undissolved dye can generate delayed filter loading in printing presses. CIELAB colour difference measured according to ASTM D2244 between consecutive batches should not exceed ΔE*ab 1.0 for wood coatings where end panels are assembled side by side.
Regulatory compliance for Nigrosine MS Conc is lot-specific. RoHS screening under IEC 62321-3-1 is commonly performed for cadmium, lead, mercury, and hexavalent chromium; values below 100 mg/kg are typical for products sold into electrical and electronic applications, but certificates of analysis must be reviewed because impurity profiles differ between manufacturers. REACH registration applies when importing into the European Economic Area at volumes above 1 tonne per annum; the dye is not listed as a Substance of Very High Concern. It is not cleared for direct food-contact applications under FDA 21 CFR 175.300 unless a specific supplier submission demonstrates migration below the applicable limits. Strong oxidising agents and concentrated mineral acids should be avoided because the azine chromophore may degrade exothermically. Combustible dust precautions apply in bulk handling operations; published minimum ignition energy data for this specific configuration is limited.
