Section
| HS Code | 387474 |
| Product Name | Solvent Black 7 |
| Color Index Name | C.I. Solvent Black 7 |
| Color Index Number | 50415 |
| Cas Number | 8005-02-5 |
| Chemical Class | Azine dye |
| Appearance | Black powder or granules |
| Color Shade | Black |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in alcohols, esters, ketones, and aromatic hydrocarbons |
| Density | Approximately 1.2 g/cm³ |
| Light Fastness | Good |
| Heat Stability | Good |
| Moisture Content | Typically ≤1.0% |
| Ash Content | Typically ≤1.0% |
| Primary Uses | Coloring leather, wood, paper, inks, and plastics |
As an accredited Solvent Black 7 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Solvent Black 7 is packaged in a 25 kg fiber drum with a sealed polyethylene inner liner for safe storage and transport. |
| Container Loading (20′ FCL) | Solvent Black 7 is loaded into a 20′ FCL container in sealed drums/pallets, secured, labeled, and documented for transport. |
| Shipping | Solvent Black 7 is typically shipped as a non-hazardous dye in sealed, properly labeled containers. Keep containers closed, dry, and away from oxidizers, strong acids/bases, and ignition sources. Transport at ambient temperature; follow the supplier’s SDS and applicable regulations, and confirm non-DG classification before shipment. |
| Storage | Store Solvent Black 7 in a cool, dry, well-ventilated area away from direct sunlight, heat, sparks, flames, and strong oxidizers. Keep containers tightly closed and clearly labeled, using secondary containment to prevent spills. Avoid dust generation and contact with incompatible materials. Maintain good housekeeping, use appropriate PPE, and follow local regulations and SDS requirements. |
| Shelf Life | Shelf Life: About two years when stored in tightly closed containers, cool, dry, well-ventilated, and away from light. |
Solvent Black 7 is pre-dissolved in a mixture of ethanol, isopropanol, and methyl ethyl ketone before incorporation into the binder phase of nitrocellulose-based wood stains and low-build lacquers. Unlike carbon black dispersions, the azine-class solvent dye enters molecular or near-molecular solution; batch filtration through a 25 µm stainless mesh therefore does not remove colorant, and gloss reduction from pigment particles is avoided. The tinting step is carried out in a closed-top vessel equipped with a low-speed anchor stirrer, typically 20–30 min at 20–25°C, after which the concentrated solution is introduced into the nitrocellulose/cellulose acetate butyrate binder system. Formulators evaluate drawdowns on maple or beech test panels using a wire-wound drawdown bar and compare colorimetric data under ASTM D2244-23 conditions. Because Solvent Black 7 is soluble in the wet film but may migrate into subsequent topcoats if the film is not sealed, compatibility is checked by cross-cut adhesion testing under ISO 2409:2020 after a forced-dry cycle at 50–60°C for 30–45 min. High-humidity application above 70% relative humidity can produce blushing in fast-evaporating solvent blends; the addition rate is therefore reduced or a retarder such as butyl glycol is introduced at 2–4 wt% of the solvent phase. Published data for exterior durability in architectural wood stains is limited; Solvent Black 7 is generally confined to interior or UV-capped topcoat systems where the topcoat carries the weathering load.
In solventborne flexographic and gravure inks based on nitrocellulose/polyurethane or polyamide resin systems, Solvent Black 7 is dissolved in a ketone/ester/alcohol medium before the resin is added. The sequence is critical: resin addition to undissolved dye produces sticky, low-color-development aggregates that require extended bead milling. In a typical pilot-scale batch, the dye is first dissolved at 10–15 wt% in a blend of ethyl acetate and isopropanol at 40–45°C; this concentrate is then let down into the full ink under high-shear mixing using a Cowles dissolver. Viscosity is adjusted to 18–25 s in a DIN 4 mm flow cup according to DIN EN ISO 2431:2020, and viscosity drift is monitored over 72 h at 25°C because residual moisture above 0.2 wt% in the solvent phase can precipitate the dye or reduce gloss on non-absorbent substrates. Solvent retention in the dried print is measured by gas chromatography according to a method aligned with EN 13628-1:2002; if total retained solvent exceeds 10 mg/m², film tack and blocking in roll rewind become visible failures. In polyamide-based inks, the addition of Solvent Black 7 at levels above 5 wt% of dry resin has been observed in production to soften the film; published data for this specific interaction is limited, but redilution checks and 24 h roller stability tests on a table-top multi-roll mill are used to detect incipient resin incompatibility. For lamination inks, the dye must not interfere with the corona-treated polyethylene or polyester film surface energy; offline dyne solutions per ISO 8296:2003 are used to verify that treated film remains at or above 38 mN/m after ink application.
Leather season systems introduce Solvent Black 7 into the solventborne base coat after plasticizer pre-dispersion and before viscosity adjustment with a toluene/xylene or ethyl acetate diluent. Spray application through a 0.8–1.2 mm nozzle at 0.2–0.3 MPa air pressure produces a transparent jet-black base on corrected grain or split leather when the season is subsequently overcoated with a solventborne acrylic or polyurethane topcoat. The dye must be evaluated for bleed into the adhesive layer at the next processing step; a standard procedure involves pressing a white polyurethane-coated test panel against the finished leather in a heated press at 60–70°C for 24 h and measuring any visual transfer under D65 illumination according to the evaluation principles of ISO 105-A02. Because the dye is soluble in many solvents used for dry cleaning and shoe repair, the base coat is crosslinked or sealed to reduce bleeding; laboratory aging at 50°C and 80% relative humidity for 7 days is used as an accelerated screen before production release. In high-gloss patent leather formulations, Solvent Black 7 can assist in hiding grain imperfections because its low haze in solution does not introduce pigment scattering; however, the final gloss is governed by the topcoat resin rather than by the dye. If the season contains nitrocellulose, the evaporation profile of the mixed solvent must be retarded with diacetone alcohol or butyl glycol to avoid cooling the wet film below the dew point, which causes moisture-induced dye precipitation and dull spots.
Solvent Black 7 is handled in thermoplastics as a pre-blended masterbatch or as a dry-mixed powder additive during compounding on a co-rotating twin-screw extruder with L/D 40:1 and vacuum venting. Dosage is metered by a gravimetric side feeder into the melt zone after the polymer has been partially plasticized, reducing dust exposure and avoiding screw slippage that occurs when powder is added at the main feed throat. In polystyrene and ABS, the dye produces a transparent smoke-black mass tone without the particle specking associated with carbon black dispersion; injection moulding trials typically run at 200–230°C for PS and 220–240°C for ABS with a screw back pressure of 0.6–1.0 MPa. Thermal endurance is the critical process boundary: gas evolution and plate-out on the mould venting surfaces have been observed in production at elevated barrel temperatures, and published mechanistic data for Solvent Black 7 degradation kinetics in polymer melts is limited. Therefore, operators monitor cavity pressure curves and vent block frequency rather than relying on a single thermal decomposition number. For transparent PMMA applications, the dye is pre-dissolved in butyl acetate or propylene carbonate before liquid colour metering; filtration through a 5 µm stainless steel cartridge is required to protect the gear pump. The final moulded article is tested for colour stability under indoor accelerated conditions using ISO 4892-2:2013 method A, with acceptance limits set by the end user. The dye is not used when the polymer enters direct food contact under EU 10/2011 or FDA 21 CFR 176.170 unless specific migration testing demonstrates compliance.
| Regulation | Assessment | Operational condition |
|---|---|---|
| EU 10/2011 | No direct food-contact clearance assumed for Solvent Black 7 | Not recommended without completed specific migration testing |
| FDA 21 CFR 176.170 | Paper and paperboard component use only | Dye not assessed; end-use proof required |
| RoHS 2011/65/EU | No listed heavy metal restriction trigger | Supplier certificate required for Pb, Cd, Hg, Cr(VI) |
| REACH Annex XVII | Azine class, not automatically restricted as azo colourant | Pre-screen for listed aromatic amines if azo-implicated |
Because marker ink reservoirs rely on capillary wicking through polyester fibre, batch filtration at 0.45 µm is implemented before filling the pen body; Solvent Black 7 must remain soluble in the alcohol/ketone ink base after filtration and during prolonged contact with the polyacetal or polyethylene housing. In permanent marker inks, the dye is dissolved in a mixture of ethanol, isopropanol, and methyl ethyl ketone; the ink is then adjusted to a viscosity of 3–8 mPa·s at 25°C using a cone-plate viscometer, because higher viscosity reduces feed through the nib but lower viscosity promotes uncontrolled bleed on paper. Long-term stability is evaluated in sealed glass and in the final marker barrel at 50°C for 14 days, with color strength checked against a retained standard. Solvent evaporation from the nib area causes dye crystals to form if the solvent blend is too fast-evaporating; therefore, a retarder such as propylene glycol monomethyl ether is included at 5–10 wt% of the solvent phase in production batches. The dye is also used in ballpoint ink paste formulations where it is milled into oleic acid and benzyl alcohol vehicles; a three-roll mill with chilled rollers at 20–25°C is used to remove coarse particles, and the grind is checked according to ISO 1524:2020 to a Hegman gauge reading below 15 µm. Because Solvent Black 7 is a soluble dye rather than a pigment, the Hegman reading in paste inks reflects resin aggregates rather than primary dye particles; visual inspection of the drawdown under a stereomicroscope at 20x magnification is therefore required to distinguish dye precipitation from pigment seed formation.
In phenolic and urea-formaldehyde moulding compounds, Solvent Black 7 is added at the dry blending stage before the compound is processed on a two-roll mill or in an internal mixer. The dye dissolves partially in the resin system and contributes a transparent black undertone that avoids the grey haze of dispersed carbon black at low loadings. Typical compression moulding of phenolic compounds occurs at 150–170°C and 20–40 MPa for 3–6 min; under these conditions, the dye is exposed to both heat and hexamethylenetetramine decomposition products. Batch-to-batch variation in compound flow must be checked with a disc cure test or a screw-type plastometer before release, because the dye may influence the cure exotherm or the viscosity profile in ways not fully documented in the literature. In urea-formaldehyde compounds, free formaldehyde and acidic cure catalysts can react with the azine structure of Solvent Black 7, leading to a loss of color intensity if the dye is added before the catalyst; therefore, the catalyst and dye are preferably added at separate stages of the mixing cycle. Electrical properties of the final moulded part, particularly surface resistivity, can be affected if the dye contains ionic residuals; procurement specifications therefore include a conductivity screening of a 10% extract in deionized water, with acceptance limits set by the moulder’s internal laboratory. The coloured compound is not used in applications where contact with food or drinking water is regulated unless specific migration or extraction testing under the relevant national standards demonstrates compliance.
Solvent-based shoe polish and automotive wax formulations receive Solvent Black 7 as a pre-dissolved solution in white spirit or in a paraffin/microcrystalline wax melt at 80–90°C before the solvent dilution step. The dye must be free of undissolved crystalline agglomerates to prevent streaking on leather or painted surfaces; therefore, the melt is filtered through a 20 µm stainless steel mesh directly after dissolution and before filling. Addition levels are kept low, often in the range 0.05–0.5 wt% of the final polish, because the dye has strong color strength and may stain adjacent carpet or clothing if free dye is present on the wax surface. Hardness and buffability of the finished wax are dominated by the paraffin and ester wax ratio rather than by the dye; however, a change in the cooling curve can occur if the dye is introduced as a concentrated solution with an improper solvent. Batch stability is checked by cycling the final product between 5°C and 40°C for five cycles and examining the surface for dye bloom. The product is not intended for food-contact packaging or toys where migration into skin contact surfaces must meet the restrictions of Directive 2009/48/EC; if toy applications are contemplated, migration testing under EN 71-3 is used to evaluate trace elements, but Solvent Black 7 itself is an organic dye and the standard does not provide a specific limit without additional toxicological review.
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Solvent Black 7, indexed as C.I. 50420 and assigned CAS 8005-02-5, is a nigrosine-type solvent dye produced through controlled acid-catalyzed condensation of aniline, nitrobenzene, and iron chloride. Industrial grades are supplied as free-base powder, low-dusting granules, and predispersed masterbatch granules. A high-purity grade intended for gravure and flexographic inks typically carries a dye assay of 85–100 %, moisture below 1.0 wt% by ISO 787-2, ash below 1.0 wt% by ISO 787-4, and a pH of 6.0–9.0 in a 5 % aqueous extract by ISO 787-9. The chromophore is essentially insoluble in neutral water, but dissolves in ethanol, methyl ethyl ketone, ethyl acetate, and aromatic hydrocarbon blends; exact saturation values are grade-dependent and vary with the Hansen solubility parameter distance of the carrier. Because the dye is a soluble organic chromophore rather than a dispersed particle, it transmits color without adding the haze or visible-particle defects associated with carbon black. However, this same feature limits UV opacity: outdoor weatherability in alkyd coatings at 1/3 standard depth under ISO 105-B02 is generally reported as blue-wool rating 2–3, and full-shade ratings are frequently 3–4. This is lower than selected modified Solvent Black 27/29 types used in UV-cured packaging inks.
Commercial differentiation between Solvent Black 7 and Solvent Black 5 requires attention to solvent polarity and heat history. Solvent Black 5, indexed as C.I. 50415, is typically more readily soluble in ethanol-rich flexographic blends and mineral-spirit-based offset inks. Solvent Black 7, by contrast, is selected when the formulation contains a higher proportion of aromatic or oxygenated solvents and when the printed film or injection-molded part must survive thermal excursion above 240 °C. Supplier certificate-of-analysis data and extraction tests through a 10 µm PTFE membrane in toluene show that Solvent Black 7 grades can exhibit lower filtration residue than Solvent Black 5 at equivalent 15 % dye loading. The hue of Solvent Black 7 in alkyd varnish also trends toward a more neutral to red-shifted black undertone, while Solvent Black 5 often appears bluer in thin films. For rotogravure inks printed on high-speed presses above 80 m/min, the lower plate-out tendency of Solvent Black 7 during cylinder doctoring is the primary selection criterion, although published comparative wear data for this specific configuration is limited.
In rotogravure ink manufacture, viscosity stability after 24 h of circulation through a closed-head horizontal bead mill with 1.2–1.6 mm zirconia beads is governed by the dye's solubility in the letdown solvent. Solvent Black 7 premixes are typically prepared at 20–30 wt% in a high-shear dissolver equipped with a cowles blade tip speed of 15–20 m/s; batch temperature is held at 40–50 °C to prevent solvent loss. If the premix is cooled too rapidly, nigrosine crystals can precipitate as needle agglomerates. Therefore, letdown is performed under controlled agitation and filtered through a 25 µm absolute cartridge before printing. In nitrocellulose-based flexographic inks, Solvent Black 7 provides optical density comparable to an equivalent carbon black dispersion at lower viscosity—typically 25–40 % lower high-shear viscosity at 2500 s⁻¹ in a cone-and-plate rheometer—but with lower opacity and lower rub resistance unless a wax overprint is applied.
A recurring production constraint in LLDPE masterbatch dilution on co-rotating twin-screw extruders with L/D 40 and screw diameter 27 mm is screen-pack pressure increase caused by nigrosine agglomeration. Melt-temperature set points are commonly maintained at 180–220 °C across zones from feed to die, with the dye fed downstream after the polymer melt seal to limit residence time. Under these conditions, a 30 % Solvent Black 7 masterbatch diluted to 2 wt% in LLDPE with a 150 µm screen pack typically shows pressure rise below 0.8 bar/h. When barrel set points exceed 230 °C or when residence time exceeds 45 s due to high screw fill, non-linear pressure increases above 2.5 bar/h are observed, consistent with partial charring of nigrosine at the barrel wall. The processing window is therefore narrow: polymer melt temperature should be held within ±5 °C of the validated set point, and screw speed should remain within ±10 % to avoid shear-induced temperature excursions. Predrying in a desiccant dryer at 60–70 °C for 4 h is required when ambient RH exceeds 60 %, because hygroscopic powder grades can introduce splay defects and hydrolytic degradation of the carrier resin. Compatibility in polyolefins is generally strong, but amine-containing UV stabilizers should be screened under accelerated storage at 40 °C for 14 days to detect potential hue shift. In injection molding, melt pressure during filling of a plaque mold with 2 mm wall thickness is typically 800–1200 bar; the soluble dye does not alter mold pressure compared with natural resin at equivalent viscosity, but it can reduce the transmittance of laser welds due to near-infrared absorption.
Because nigrosine chromophores are soluble rather than particulate, Solvent Black 7 does not generate the low-angle light scattering associated with carbon black at loadings below 1 wt%. In clear coatings and transparent PET, PC, or PMMA substrates, the dye is used when a neutral black appearance is required without haze values exceeding 5 % under ASTM D1003. Spectrophotometric transmission curves measured with a dual-beam UV-Vis spectrophotometer typically show broad absorption from 400 nm to 700 nm, with a slight transmission maximum near 550–580 nm that creates the characteristic warm black undertone. In acrylic lacquers, dosage levels of 0.05–0.2 % based on vehicle solids are sufficient for smoked-glass effects; in cellulose acetate eyeglass frames, loadings of 0.5–1.0 wt% in plasticized compound yield optical density above 2.0 at 1 mm thickness. No grinding step is required, but predissolution in hot plasticizer under high-shear agitation reduces undissolved residue and prevents visible specking.
In PMMA optical moldings, the choice of Solvent Black 7 is constrained by metal-content specifications and lens haze requirements. A high-purity grade filtered through a 5 µm absolute filter exhibits undissolved particulate counts below 100 particles/g when tested by gravimetric extraction in butyl acetate through a 5 µm PTFE membrane. Haze in a 3 mm molded plaque at 0.05 wt% dye loading is typically below 3 % under ISO 14782; at 0.2 wt%, haze rises above 8 % if the dye is not fully dissolved, indicating that stock solution filtration and metering are critical. Heavy-metal limits for toy and packaging applications are commonly verified by ICP-OES after microwave digestion to EN 71-3; typical high-purity grades report lead below 5 mg/kg, cadmium below 1 mg/kg, mercury below 1 mg/kg, and arsenic below 3 mg/kg. For food-contact packaging, no blanket approval exists for nigrosine dyes under EU 10/2011 or FDA 21 CFR; each food-contact structure must be tested for specific migration of nigrosine components into food simulants. Solvent Black 7 should not be assumed to be water-white-extraction neutral; HPLC-DAD analysis of 3 % acetic acid and 10 % ethanol simulants after 10 days at 40 °C may show quantifiable peaks, and positive-list verification is required before production.
| Parameter | Test method | High-purity grade | Technical grade |
|---|---|---|---|
| Colour Index Generic Name | — | Solvent Black 7 | |
| C.I. Constitution Number | — | 50420 | |
| CAS number | — | 8005-02-5 | |
| Dye assay | UV-Vis spectrophotometry after Soxhlet extraction | 90–100 % | 85–95 % |
| Moisture | ISO 787-2 | ≤0.5 % | ≤1.0 % |
| Ash | ISO 787-4 | ≤0.5 % | ≤1.5 % |
| pH of 5 % aqueous extract | ISO 787-9 | 6.5–8.0 | 6.0–9.0 |
| Bulk density | ISO 60 | 0.35–0.55 g/cm³ | 0.40–0.65 g/cm³ |
| Lead | ICP-OES after EN 71-3 digestion | ≤5 mg/kg | ≤10 mg/kg |
Leather-finish formulations using medium-boiling glycol ethers or methyl ethyl ketone typically require predissolution of Solvent Black 7 in a separate high-shear vessel at 30–40 % solids before addition to polyurethane or nitrocellulose lacquer emulsions. The dye's uniform solvent penetration reduces the streak defects observed with carbon black pigments in curtain-coating lines. For wood stains, a 1–3 wt% solution in isopropanol or ethyl acetate yields a walnut to black tone without grain hiding, provided the solution is filtered through a 10 µm bag filter. Industrial lubricants and greases use Solvent Black 7 at 0.01–0.05 wt% in bright stock to impart color for brand identification; solubility in mineral oil is limited compared with aromatic carrier oils, so predispersion in a co-solvent such as heavy aromatic naphtha is common. In polyurethane shoe soles, Solvent Black 7 at 0.1–0.5 phr in the polyol side avoids the viscosity increase and metering-pump wear caused by carbon black.
| Property | Solvent Black 7 | Solvent Black 5 | Solvent Black 27/29 types |
|---|---|---|---|
| C.I. constitution | 50420 | 50415 | varies by type |
| Solubility in ethanol | moderate | high | low to moderate |
| Heat resistance in polyolefin | 220–240 °C short-time | 180–200 °C short-time | 250–300 °C for selected types |
| Undertone in alkyd paint | neutral to red-black | blue-black | neutral to yellow-black depending on chemistry |
| Lightfastness full shade ISO 105-B02 | 3–4 | 2–3 | 5–7 for modified anthraquinone types |
In white PVC extrudates for profile coextrusion, Solvent Black 7 is metered into the capstock layer at 0.02–0.08 phr to suppress yellowing without producing visible haze or black speck contamination. Capstock extrusion on a single-screw extruder with L/D 25 and a barrier screw is typically operated at 170–190 °C; higher melt temperatures can shift the nigrosine hue toward brown. The predispersed grade is preferred over powder to reduce electrostatic dust accumulation around the feed throat and to maintain gravimetric dosing accuracy within ±0.5 %. Unlike cosmetic carbon black grades, Solvent Black 7 does not raise the viscosity of plasticized PVC at this dosage, but it requires an organotin or calcium-zinc stabilizer package that is free of strongly basic amine co-stabilizers to avoid prolonged heat-history chromatic drift.
