Section
| HS Code | 325204 |
| Product Name | Acid Brilliant Scarlet GR |
| Synonyms | C.I. Acid Red 73; Brilliant Crocein MOO |
| Color Index Name | C.I. Acid Red 73 |
| Color Index Number | 27290 |
| Cas Number | 5413-75-2 |
| Molecular Formula | C22H14N4Na2O7S2 |
| Molecular Weight | 556.48 g/mol |
| Chemical Class | Azo dye |
| Appearance | Red to scarlet powder |
| Solubility | Soluble in water |
| Dyeing Class | Acid dye |
| Primary Application | Dyeing of wool, silk, nylon, and paper |
| Light Fastness | Moderate |
| Washing Fastness | Moderate |
| Ph Application Range | Acidic to neutral |
| Storage Conditions | Cool, dry, well-ventilated place protected from light |
As an accredited Acid Brilliant Scarlet GR factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Acid Brilliant Scarlet GR is packed in 25 kg net polyethylene-lined woven bags, securely sealed for industrial handling and transport. |
| Container Loading (20′ FCL) | Acid Brilliant Scarlet GR is packed in sealed drums and loaded into a 20-foot FCL container, securely stowed for ocean shipment. |
| Shipping | Acid Brilliant Scarlet GR should be shipped in well-sealed, labeled containers in a cool, dry, ventilated area away from oxidizers and moisture. Follow the SDS and local regulations; if classified as non-hazardous, no UN number is required. Include proper documentation, protect from sunlight and physical damage, and prevent spills. |
| Storage | Store Acid Brilliant Scarlet GR in a cool, dry, well-ventilated area, away from direct sunlight, heat, moisture, and ignition sources. Keep containers tightly closed, clearly labeled, and in secondary containment to prevent spills. Separate from strong oxidizers, acids, alkalis, food, feed, and drinking water. Avoid dust generation; use appropriate personal protective equipment when handling. |
| Shelf Life | Typically 24 months when stored cool, dry, well-ventilated, and protected from light, moisture, and contamination. |
Acid Brilliant Scarlet GR is pre-dissolved in softened water at 70–80°C at a stock concentration not exceeding 5% w/v and filtered through a 100-mesh stainless steel screen before dosing into the circulation line of a yarn package dyeing vessel. The machine is loaded with scoured and rinsed wool tops at a package density of 350–380 g/L; the liquor ratio is held at 1:10–1:12. The starting dye bath contains 0.5–3.0% owf Acid Brilliant Scarlet GR, 5–10% owf anhydrous sodium sulphate, and 1–2% owf anionic levelling agent; the pH is adjusted to 4.0 with 60% acetic acid. Circulation is maintained with a differential pressure of 0.5–1.5 bar and flow reversal every 4–6 cycles per minute. The temperature is raised from 40°C to 98°C at 1.5°C/min and held at top temperature for 30 min. Then 85% formic acid, diluted 1:10 with cold water, is metered in two equal portions over 15 min until the bath pH reaches 3.5; dyeing is continued for a further 30–40 min. Below pH 3.3 the dye may aggregate and deposit on the outer package layers as a bronzed surface layer. After exhaustion the bath is cooled to 60°C before overflow rinsing to avoid felting and package deformation. The terminal products are dyed wool tops for woollen and worsted spinning, subsequently converted into woven outerwear, knitwear, and uniform fabrics. Conformity is evaluated according to ISO 105-B02 for light fastness and ISO 105-C06 for domestic wash fastness; pale shades below 0.5% owf may require a UV absorber aftertreatment because light fastness is depth-dependent and may not meet automotive wool specifications requiring a minimum grey scale rating of 6.
In jet dyeing of polyamide 6 and polyamide 66 woven and warp-knitted constructions, high strike rates with Acid Brilliant Scarlet GR make levelling sensitive to fibre thermal history and fabric sett; PA 6 should be scoured at 60°C with 0.5 g/L nonionic surfactant and 1 g/L sodium carbonate to remove oligomers before dyeing. In jet or beam equipment, the liquor ratio is set at 1:10–1:15, the nozzle pressure at 1.5–2.5 bar, and fabric speed at 300–500 m/min. The bath is prepared with 0.3–2.0% owf dyestuff, 2–3 g/L ammonium sulphate, and 1–2 g/L anionic blocking/levelling agent; the pH is buffered to 5.0–5.5. The temperature is raised from 40°C to 98°C at 1–1.5°C/min, and the machine is run at top temperature for 30–45 min. A pH excursion below 4.5 accelerates strike and produces barrel-type unlevelness on PA 66 barriers; above 6.0 exhaustion falls below acceptable limits. After dyeing, the fabric is rinsed cold and may be aftertreated with a formaldehyde-free syntan at 2–4% owf and 70°C for 20 min at pH 4.0–4.5 to improve wet fastness. Because Acid Brilliant Scarlet GR is a non-metallised anionic azo dyestuff, the resulting shades are bright but wet fastness on nylon is moderate without aftertreatment; chlorine resistance is not claimed for swimwear unless a chlorine-resist agent is applied. Terminal uses include lingerie, non-chlorine activewear, lining fabrics, and sheer hosiery. Compliance testing should include ISO 105-C06 wash fastness, ISO 105-E04 perspiration fastness, and OEKO-TEX Standard 100 criteria; REACH Annex XVII azo limits apply to reductive cleavage products from the dyestuff.
| Substrate | Dye dosage | pH | Temperature/time | Key auxiliaries | Equipment |
|---|---|---|---|---|---|
| Scoured wool tops | 0.5–3.0% owf | 3.5–4.0 | 98°C / 45–60 min | Sodium sulphate 5–10% owf, acetic/formic acid | Package dyeing vessel |
| Polyamide 6/66 woven or knit | 0.3–2.0% owf | 5.0–5.5 | 98°C / 30–45 min | Ammonium sulphate 2–3 g/L, anionic levelling agent | Jet or beam dyeing machine |
| Degummed silk yarn or fabric | 0.5–2.0% owf | 4.2–5.5 | 85–90°C / 45–60 min | Glauber’s salt 10–15% owf, acetic acid | Hank or overflow dyeing machine |
| Chrome-tanned crust leather | 0.8–2.5% of shaved weight | 3.8–4.0 final | 50–60°C / 60–70 min | Formic acid, anionic penetrator | Tannery drum |
| Sulphuric acid anodised aluminium | 1–5 g/L | 5.0–5.5 | 55–65°C / 5–15 min | Acetate buffer, deionised water | Agitated dye tank with filtration |
| Wool-polyamide carpet yarn | 0.5–2.5% owf | 4.0–5.5 | 98°C / 45–60 min | Ammonium sulphate, sodium sulphate, blocking agent | High-flow package machine |
Degummed silk fibre loses surface lustre and fibrillar integrity when processed above 90°C; the two-stage acid dosing profile is therefore used to control strike while keeping the wet-processing temperature low. At pH values above 5.5, silk fibroin carries a weak negative charge and the anionic dyestuff adsorbs slowly through ion exchange and hydrogen bonding; if pH is dropped below 4.0 too early, the dyestuff strike becomes excessively rapid and produces unlevel hank shading. The yarn or fabric is wetted in demineralised water for at least 12 h and loaded into a star-frame hank dyeing machine at a liquor ratio of 1:20. The bath is set at 40°C with 0.5–2.0% owf Acid Brilliant Scarlet GR, 10–15% owf Glauber’s salt anhydrous, and pH adjusted to 5.5 with 10% acetic acid. The temperature is raised to 85–90°C at 1°C/min. After 20 min at top temperature, a 1:10 dilution of 30% acetic acid is metered over 15 min to lower the pH to 4.2–4.5; dyeing continues for 30–40 min. The goods are rinsed and acid-soured with 0.3–0.5 g/L citric acid. Terminal products include silk scarves, neckties, saree borders, and embroidery threads. Because wet fastness on silk is limited, deep shades may require dry cleaning rather than domestic laundering; testing is performed according to ISO 105-C06 hand wash and ISO 105-B02 light fastness.
In tannery drum processing, Acid Brilliant Scarlet GR is charged after neutralisation and washing of chrome-tanned crust leather; the stock should be shaved to 1.2–1.6 mm and the float pH adjusted to 4.5–5.0 before dye addition. The stainless steel drum is run at 6–10 rpm with a float volume of 150–200% based on wet blue weight and a liquor temperature of 50–60°C. The dyestuff is pre-dissolved at 1:10 in hot water at 70°C and fed through the hollow axle in three equal portions over 20 min. The dosage ranges from 0.8–2.5% of shaved weight for medium to deep red leather. After 30–40 min penetration, 85% formic acid diluted 1:10 is added in two equal feeds over 20 min until the float pH reaches 3.8–4.0, and drumming continues for another 30 min to exhaust. If penetration is incomplete, 0.5–1.0% anionic penetrator may be added before the dye; cationic fatliquors and cationic retain agents must not be used in the same bath because precipitation with the sulphonated dye occurs immediately. After dyeing, the float is drained and fatliquoring is performed with anionic or nonionic fatliquors; the final shade should be checked after fatliquoring because emulsion components can shift the red hue by 5–10% visual strength. The terminal products are full-grain shoe upper leather, handbag leather, belt leather, and garment leather. Compliance is assessed with ISO 11640 for colour fastness to rubbing, ISO 11641 for perspiration, and REACH Annex XVII for restricted aromatic amines; dyed leather intended for European consumer goods should fall below the 30 mg/kg limit for each restricted amine.
Sulphuric acid anodised aluminium develops a porous oxide layer with pore diameters of 10–30 nm when processed to ISO 7599 Type II; the profile is rinsed free of electrolyte and transferred wet to the colour bath. Acid Brilliant Scarlet GR is dissolved in deionised water at 1–5 g/L, and the pH is adjusted to 5.0–5.5 with an acetic acid/sodium acetate buffer. The bath is maintained at 55–65°C with continuous agitation and filtration through 1–5 µm cartridge filters; immersion time is 5–15 min depending on oxide thickness 10–25 µm and target red depth. Higher dye concentrations above 5 g/L can produce surface precipitation on the oxide film and should be avoided unless the bath is tested for clouding. After colouring, the rack is rinsed in clean deionised water and sealed in hot deionised water at 96–98°C for 30 min; nickel acetate sealing at 90–95°C gives slightly different hue and is used where additional corrosion resistance is required. Cold sealing processes may shift the shade and require re-qualification of colour matching under ASTM D2244. Terminal components include indoor architectural trims, appliance fascias, nameplates, and consumer electronics housings. Published comparative data for this specific colorant on anodised aluminium under ISO 2135 is limited; job-shop qualification panels are therefore recommended before bulk architectural runs. Outdoor use is an operational boundary: UV exposure may fade the dye unless a UV-stable seal or organic topcoat is specified.
Wool-nylon blended carpet yarns are dyed in package machines equipped with high-flow pumps and flow reversal at 4–6 cycles/min because the two fibre types show different strike rates and swelling behaviour. Acid Brilliant Scarlet GR is applied at 0.5–2.5% owf of fibre weight, together with 5–10% owf anhydrous sodium sulphate and 1–3% owf anionic blocking/levelling agent. The bath is buffered with 2–3 g/L ammonium sulphate to pH 5.0–5.5, and the temperature is raised from 40°C to 98°C at 1°C/min. After 30 min at 98°C, diluted acetic acid may be added to reduce the pH to 4.0–4.5 and force additional exhaustion. The wool/nylon partition of the dye depends on pH: below pH 4.5 more dye transfers to nylon, causing barrel effects in blended skeins; above pH 5.5 the wool component takes a deeper share. Holding time at top temperature is 45–60 min, after which the bath is cooled to 60°C before rinsing. The dyed stock is then dried at 70–80°C in a radio-frequency dryer to avoid fibre yellowing. Terminal products are residential cut-pile carpets, area rugs, and decorative wool-nylon floorcoverings. Fastness is checked according to ISO 105-B02 for light and ISO 105-C06 for wet washing; because light fastness is limited in pale depths, the dye is not recommended for high-UV automotive carpet applications unless a light-stable top treatment is added.
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Acid Brilliant Scarlet GR is the commercial designation most commonly associated with C.I. Acid Red 73, a disazo anionic dyestuff identified by C.I. 27290 and CAS 5413-75-2. The product is supplied as a red-to-scarlet powder or granular preparation with tinctorial strength normalized against a supplier reference. Its molecular formula is C22H14N4Na2O7S2 and its molar mass is 556.48 g/mol. Sulphonate groups ionize in water and give an anionic character that governs exhaust dyeing on wool, silk, nylon, and leather. The principal visible absorbance maximum in aqueous solution lies in the 505–515 nm region; the exact λmax shifts with pH and solvent composition. Commercial strengths are commonly standardized at 100% or 150% relative to the supplier standard, and the product is normally sold on a dry-weight dye content basis. Dyehouses calibrate dispensing systems against the supplier certificate because batch-to-batch drift in dye strength and moisture can alter shade reproducibility on production machines. Published data for specific application configurations is limited; incoming inspection and dyehouse-specific calibration are therefore used rather than generic strength figures.
Commercial batch-release criteria for Acid Brilliant Scarlet GR generally include dye strength, shade difference in CIELAB units, moisture and volatile matter, water-insoluble matter, and pH of a 1% aqueous extract. The product is a sodium salt; aqueous extracts tend to be neutral to mildly alkaline, and the dyebath must be buffered independently with acetic acid, formic acid, or ammonium sulphate rather than depending on the dye preparation to lower pH. Colorimetric evaluation is carried out after conditioning under 20 ± 2 °C and 65 ± 4% relative humidity. A spectrophotometer with d/8 geometry and specular component excluded is used; the measurement standard is ISO 11664-4. Batch-to-batch shade difference against the internal reference is generally controlled within 0.8–1.0 CIELAB ΔE*ab; tighter limits require automated sorting and may not be feasible for all substrate types. Incoming inspection in dyehouses commonly uses the method references in Table 1 as a quality matrix; actual limits are set by the manufacturer and may vary with trade strength and physical form.
| Test parameter | Method reference | Scope |
|---|---|---|
| Moisture and volatile matter | ISO 787-2 | Mass loss at 105 °C |
| pH of 1% aqueous extract | ISO 787-9 | Aqueous extract acidity or alkalinity |
| Color fastness to light | ISO 105-B02 | Xenon-arc exposure of dyed substrate |
| Color fastness to washing | ISO 105-C10 | Domestic washing of dyed textile |
| Color fastness to water | ISO 105-E01 | Water immersion bleed |
| Color fastness to perspiration | ISO 105-E04 | Acid and alkaline perspiration bleed |
Acid Brilliant Scarlet GR occupies an intermediate position among red acid dyes. It is not a metal-complex dye, nor is it a fluorescent xanthene colorant. Its disazo structure yields a yellow-red scarlet that dyes wool and nylon with moderate migration during the exhaustion phase. The GR suffix is a legacy shade and product designation used by dye manufacturers; it does not identify a single chemical entity, so buyers should verify C.I. Acid Red 73 and CAS 5413-75-2 on the safety data sheet. Different manufacturers may supply the same C.I. generic name with different salt content, grinding, and dust-control treatments, which influences handle and stock-solution filtration. In comparison with C.I. Acid Red 18, a monoazo bluish red, Acid Brilliant Scarlet GR is yellower and may require more careful pH control to avoid unlevel strike on nylon 6. In comparison with C.I. Acid Red 87, a halogenated xanthene dye with pronounced fluorescence, Acid Brilliant Scarlet GR has better light fastness but lacks the fluorescence used in microscopy and selected specialty inks. Table 2 summarizes the main application differences.
| Property | C.I. Acid Red 73 / Acid Brilliant Scarlet GR | C.I. Acid Red 18 | C.I. Acid Red 87 |
|---|---|---|---|
| Chromophore class | Disazo | Monoazo | Xanthene |
| Shade on wool | Bright scarlet with yellow-red cast | Bluish red | Pink-red with fluorescence |
| Leveling on nylon 6 in exhaust dyeing | Moderate; benefits from anionic levelling agent | Good | Moderate |
| Light fastness on wool per ISO 105-B02 | Moderate; lower than many milling reds but higher than C.I. Acid Red 87 | Moderate to good | Low |
| Wet fastness after fixation | Moderate; aftertreatment recommended for dark shades | Moderate | Low to moderate |
| Primary application scope | Wool, silk, nylon, leather, paper, inks | Wool, silk, nylon, selected certified grades | Microscopy, inks, specialty colorants |
Before addition, the dye is dissolved to avoid specks and filter blockages. A paste is made with cold water and then diluted with hot water at 75–85 °C. For package dyeing, a 1:10 to 1:20 stock solution is typically used and passed through a 10–20 µm screen before entering the machine. Water hardness above 150 mg/L CaCO3 should be sequestered with a chelating agent at 0.5–1.0 g/L to prevent calcium or magnesium salts of the sulphonated dye from reducing solubility.
For wool exhaust dyeing, the dyebath is set at 30–40 °C with 1.0–3.0% owf Acid Brilliant Scarlet GR, 5–10% owf Glauber’s salt, and acetic acid to maintain pH 4.5–5.5. The bath is heated at 1.0–2.0 °C/min to 95–98 °C and held for 45–60 min. In package dyeing machines with bidirectional flow and circulation rates of 30–40 L/kg/min, medium-depth shades usually level without additional auxiliaries, provided that air is vented before the temperature exceeds 80 °C. In hank and beam machines, low-flow zones may retain dye-rich liquor and produce streakiness unless flow reversals are frequent and the liquor ratio is maintained above 1:15 for heavy wool yarns. For dark shades, an anionic levelling agent is added at 1–2% owf and the pH is kept near 5.0–5.5 to suppress the initial strike. When dyeing nylon 6, the bath is started at 40 °C and the temperature is raised to 95–98 °C over 30–45 min; ammonium sulphate at 1–2 g/L releases acid gradually, or acetic acid is added to achieve pH 4.0–5.0. Nylon 6,6 is processed at 98–100 °C for 30–50 min. Silk is dyed at 85–90 °C to limit lustre loss; electrolyte use is reduced because excessive Glauber's salt can stiffen the fibre. The exhausted bath is cooled to 60–70 °C before rinsing to avoid thermal shock.
The process window for this dye is bounded at low and high pH extremes. Below pH 3.5 the strike rate is too high on nylon and can produce skittery dyeings; above pH 6.0 exhaustion falls below economically acceptable depth. Temperature control is similarly narrow for wool: below 90 °C exhaustion is incomplete, while prolonged exposure above 100 °C requires pressurized equipment and may damage protein fibre.
Because Acid Brilliant Scarlet GR is a levelling-type acid dye, unfixed dye on wool and nylon presents moderate wet fastness. End uses requiring ISO 105-C10 or ISO 105-E01 ratings above 4 typically require a cationic fixing agent after exhaustion. The dyebath is drained, the substrate is rinsed, and the fixative is applied at 50–60 °C and pH 4.5–5.5 for 20–30 min. Residual anionic levelling agents must be removed before fixation to prevent precipitation with the cationic fixative. Overdosing the fixative stiffens the hand and can reduce light fastness by promoting dye aggregation at the fibre surface. For nylon automotive or upholstery applications, treatment with a synthetic mordant or tannic acid improves water and perspiration fastness but produces a duller, yellower shade; redyeing after such treatment is difficult because cationic sites are blocked. At 4.0% owf dark shades, unfixed dye can stain nylon adjacent fabric in ISO 105-C10 testing at a rating of 2–3; after fixation, ratings may increase by 1–1.5 units, but published data for this specific product configuration is limited, and production trials on the target substrate are required.
Strong reducing agents should be avoided in hot dyebaths because they can cleave the azo groups and destroy the chromophore. The product is not intended for food-contact packaging unless a specific grade is cleared under the relevant national legislation. REACH registration dossiers for C.I. Acid Red 73 should be consulted for risk-management measures before use in articles marketed in the EU.
In leather drum dyeing, Acid Brilliant Scarlet GR is applied in the retanning or dyeing float at 0.5–2.0% of shaved weight, with a float ratio of 200–300% and pH adjusted to 4.0–5.5 using formic or acetic acid. The drum is run at 30–45 °C for 30–60 min, followed by fatliquoring and acid fixation. On chrome-tanned leather, the anionic dye binds to cationic chrome sites; penetration slows in stock with a tight grain or high basification, in which case a penetrating auxiliary may be required. In paper mass coloration, the dye is added as a 1–5% aqueous solution to the pulp slurry before web formation. Retention is influenced by alum dosage and furnish; overdosing alum can shift the shade toward a yellower red. For water-based ink and surface coating formulations, the dye is dissolved at 5–10% in hot water and filtered through a 10–20 µm mesh. Acid Brilliant Scarlet GR is not recommended for solvent-based ink systems because the sulphonated molecule has limited solubility in nonpolar solvents.
Dust and caking are the main physical failure modes for powder batches. The product should be stored in closed containers below 30 °C and away from strong acids, strong bases, and reducing agents. At relative humidity above 60% the powder may absorb moisture and become difficult to dispense; localized heating should be avoided because it can alter dye strength. Inventory should follow first-in-first-out rotation because strength can drift after 24 months in unlined kraft bags. Local exhaust ventilation and dust masks are used when handling bulk powder to limit inhalation exposure. Effluent containing Acid Brilliant Scarlet GR should not be discharged untreated. The disazo structure is not readily biodegradable under aerobic activated-sludge conditions; adsorption onto activated carbon or advanced oxidation may be required for color removal. Exact removal efficiencies should be confirmed with site-specific pilot tests.
