Acid Light Yellow G, indexed as C.I. Acid Yellow 11, is supplied as an anionic sulfonated monoazo sodium salt. The technical data below cover industrial application segments in which the dye is used as a soluble colorant for protein fiber, polyamide, paper stock, chrome-tanned leather, aqueous flexographic ink, and anodized aluminum substrates. All processing windows are to be confirmed against the supplier certificate of analysis and the current regulatory text applicable to the destination market.

In wool sliver and wool/polyamide blended yarn exhaust dyeing, Acid Light Yellow G is applied at 0.2–2.0% on weight of fiber for pale-to-medium yellow shades. Deep shades sometimes require up to 4.0% owf, but above this loading wet fastness decreases unless a cationic aftertreatment is used after rinsing. The dye bath is set with acetic acid/sodium acetate buffer at pH 4.5–5.5, liquor ratio 10:1–20:1, and 5–10 g/L anhydrous sodium sulfate for controlled exhaustion in package dyeing machines, top dyeing kettles, or overflow dyeing equipment. The liquor is raised to 95–98 °C at 1–2 °C/min, held for 30–60 min, then cooled to 80 °C before formic acid addition drives final exhaustion to at least 95%. The wet-fastness limitation of this sulfonated monoazo dye on wool is addressed by rinsing and, for dark shades, by aftertreatment with a quaternary ammonium fixing agent.

For textile articles sold into the EU, converters must verify that the sulfonated monoazo colorant does not cleave under EN 14362-1 reductive conditions into any aromatic amine listed in REACH Annex XVII entry 43 above 30 mg/kg. Finished fabric is tested against ISO 105-B02 for light fastness, ISO 105-C06 A1S for washing fastness, ISO 105-E04 for perspiration fastness, and, where pale shades are packed in polyethylene, ISO 105-X18 for phenolic yellowing. Compliance with Oeko-Tex Standard 100 and ZDHC MRSL v3.1 requires additional laboratory screening for extractable heavy metals and restricted solvent residues. Terminal outputs include wool suit serge, wool/PA blended carpet yarn, woven upholstery, and pressed felt components. The dye’s moderate light fastness on wool restricts selection in automotive or outdoor furniture programs unless UV absorbers are applied in finishing.

What Restricts Levelness on Nylon 6.6 Warp Knits?

The high strike rate of C.I. Acid Yellow 11 on polyamide substrates is the primary process variable in warp-knit dyeing. When the bath is acidified directly to pH 4.0, the dye can exhaust more than 60% within the first 15 min on nylon 6.6, producing barre from chemical and physical filament variation. Production-scale overflow jet machines and beam dyeing frames therefore use a two-phase pH control strategy: the initial bath is buffered to pH 5.0–5.5 with sodium acetate and acetic acid, and 0.2–1.0 g/L of an ethoxylated alkylamine leveling agent is dosed before dye addition. Acid Light Yellow G is pre-dissolved at 60 °C at a 1:10 dye-to-water ratio and screened through a 100 µm in-line filter before metering into the machine over 30–45 min. The substrate is raised to 98 °C at 1 °C/min, held for 30–45 min, then acidified to pH 4.0–4.5 with dilute formic acid to approach final exhaustion above 95%.

Addition ratio ranges from 0.1–2.5% owf depending on target shade; concentrations above 2.5% owf generally require a fixing agent for wet fastness. Compliance requires ISO 105-C06 A1S washing fastness, ISO 105-E04 perspiration fastness, and ISO 105-B02 light fastness on finished articles. European REACH Annex XVII entry 43 documentation and ZDHC MRSL v3.1 conformance are part of the technical dossier for dyed polyamide goods. Terminal products include nylon 6.6 warp-knit sportswear linings, swimwear fabric, automotive seat belt webbing where UV exposure is limited, and military webbing. The main operational boundary is the dye’s sensitivity to yarn physical variation: textured nylon with high crystalline variability will show skittery dyeing unless the leveling agent and pH ramp are adjusted to the specific yarn lot.

When Acid Light Yellow G Replaces Pigment Dispersions in Paper Stock

In fine paper and packaging board stock coloring, the adoption of Acid Light Yellow G as a soluble anionic dye occurs where processors require a low-retention yellow with cleaner broke handling and reduced abrasion compared with pigment dispersions. The dye is added at 0.01–0.50% on dry fiber mass in the machine chest after refining, where the stock temperature is held between 40–60 °C and the pH is adjusted to 4.5–5.5 with aluminum sulfate at 1.0–2.0% on pulp. A cationic polyacrylamide retention aid at 0.02–0.05% on dry fiber is fed separately to the thin stock line after the screen to bind the sulfonated dye to fines and fiber surfaces, reducing two-sided coloration and white-water load. Dye fixation is further developed during the drying section at cylinder surface temperatures of 90–120 °C.

Compliance for packaging and graphical paper grades requires conformance with REACH restrictions, EU Packaging and Packaging Waste Directive 94/62/EC heavy metal limits, and supplier documentation that the dye does not contain restricted substances under ZDHC MRSL. For food-contact board, the mill must conduct migration testing under EU 1935/2004/EC or 21 CFR 176.170 component requirements because many industrial Acid Light Yellow G lots are not supplied with food-contact clearance. Terminal products include tinted writing paper, cover stock, colored tissue, packaging board, and decorative paper where the pale yellow shade is maintained at low intensity. The operational limitation is light fastness: prolonged retail display under fluorescent or indirect daylight can shift the shade, so archival or long-life graphical papers may require a light-stable pigment alternative.

Leather Drum Dyeing Penetration and Fixation in Chrome-Tanned Wet-Blue

Chrome-tanned wet-blue leather is dyed in drum processing after neutralization and retanning. Acid Light Yellow G is charged at 0.5–4.0% based on shaved wet-blue mass. The dye is added as a 1:10 dilution with water at 60 °C after the neutralization float has been drained and a fresh float of 100–200% at 60 °C is established. If the dye is introduced before neutralization or while the float pH remains below 5.0, the sulfonate groups exhaust rapidly on the grain surface and produce bronzing; therefore the neutralization stage uses sodium formate and sodium bicarbonate to reach a cross-section pH of 5.0–5.5. The drum runs 30–45 min to allow penetration, then formic acid is split into two additions over 20 min to lower the float to pH 3.8–4.2 for fixation. After dyeing, the leather is rinsed, acidified, and transferred to fatliquoring.

Compliance for leather requires ISO 11640 rub fastness testing under wet and dry conditions, ISO 105-B02 light fastness, and conformance with REACH Annex XVII and ZDHC MRSL v3.1 substance restrictions. The anionic dye competes with anionic retanning polymers; when a full retanning is performed before dyeing, the penetration depth improves but surface intensity decreases. Terminal products include garment leather, shoe upper leather, leather lining, and upholstery leather for interior furniture. Heat yellowing under prolonged storage in alkaline wrapping should be evaluated because the yellow chromophore can shift on chrome-tanned substrate if residual alkalinity exceeds pH 4.5.

Controlling Viscosity Stability in Water-Based Flexographic Ink Concentrates

Water-based flexographic ink formulations are prepared as a dispersion of acrylic resin, co-solvent, neutralizing amine, and soluble colorant. Acid Light Yellow G is introduced as a 10–20% aqueous concentrate into the final ink at 5–15% of total formula mass. The concentrate is prepared with deionized water and 10–20% propylene glycol or dipropylene glycol monomethyl ether, adjusted to pH 8.0–9.5 with ammonia or 2-amino-2-methyl-1-propanol, and filtered through a 1–5 µm absolute bag filter before letdown. The dye’s sulfonate groups provide solubility and reduce the need for pigment dispersion shear, but the dye can contribute to viscosity drift if the neutralizer is allowed to evaporate during open press operation; therefore press-side pH is monitored and adjusted with dilute ammonia to hold pH 8.5–9.5.

Compliance for printed paper and board under EU 94/62/EC requires the sum of lead, cadmium, mercury, and chromium VI not to exceed 100 mg/kg. REACH SVHC screening and Swiss Ordinance SR 817.023.21 conformity are included in technical documents for packaging inks. Terminal products include flexographic prints on corrugated board, paper bags, gift wrap, and coated folding cartons. The operational boundary is light fastness: prints exposed to retail display lighting for more than 12 months may require a light-stable pigment alternative or UV overprint varnish.

Sulfuric-acid-anodized aluminum components are colored in a post-anodizing immersion bath containing 0.5–5.0 g/L Acid Light Yellow G. The anodizing process that precedes dyeing uses 150–200 g/L sulfuric acid at 18–22 °C, direct current density 1.0–1.5 A/dm², and anodizing time of 30–60 min to produce an oxide layer of 10–20 µm. The rinsed and still-porous anodic film is immersed in the dye bath at 60–70 °C and pH 5.5–6.5, adjusted with acetic acid and sodium acetate, for 10–30 min. Deeper yellow shades use higher dye concentration and longer immersion, but overlong immersion above 40 min can cause dye aggregation in the pore mouths and reduce seal quality.

The dyed parts are sealed in nickel acetate at 95–100 °C for 15–30 min to close the anodic pores and immobilize the dye. Compliance with ISO 7599 and Qualanod specifications requires seal quality testing by ISO 3210 or ASTM B680 acid dissolution test, and the dye system must meet REACH restrictions and customer-specific ionic impurity limits in the rinsing water. Terminal products include interior architectural aluminum profiles, consumer electronics housings, nameplates, lamp reflectors, and optical component housings. Acid Light Yellow G is not recommended for exterior architectural anodizing without a UV-resistant topcoat because the yellow chromophore can fade after 12–24 months of direct outdoor exposure.