Disperse Violet 28, identified in the Colour Index as C.I. 61102 and chemically as 1,4-diamino-2,3-dichloroanthraquinone with CAS 81-42-5, is a nonionic anthraquinone disperse dye with the molecular formula C14H8Cl2N2O2 and a molecular weight of 307.13 g/mol. The product is manufactured for the coloration of polyester, acetate, and selected polyester-containing blends and is offered in powder, granular 200% strength, presscake, and aqueous liquid dispersion forms. The visible absorption maximum of the neat dye in acetone is typically reported between 550 nm and 570 nm, producing a bluish violet mass tone on polyester. Because the dye has negligible water solubility, all application routes depend on stable aqueous dispersion rather than molecular solution; particle size distribution, dispersant type, and pH control are therefore specification-critical parameters.

What Specification Limits Govern Powder, Presscake, and Liquid Dispersion Grades?

Standard powder grades are standardised with lignosulfonate or naphthalenesulfonate-formaldehyde condensate dispersants and are supplied against an acceptance profile that includes colour strength relative to a master standard, moisture content, sieve residue, and extract pH. The following table summarises the specification band most frequently listed in technical data sheets for textile-grade C.I. 61102.

Liquid dispersion grades replace the dry powder particle-size distribution with a milled aqueous suspension. Laser diffraction data commonly cite a D50 below 0.5 µm and a D90 below 1.5 µm; the dispersed paste is pre-filtered through a 25 µm mesh and checked for storage stability under cyclic temperature exposures between 5°C and 50°C. In production-scale beam dyeing, a D90 greater than 5 µm has been observed to increase filtration differential pressure across package interiors and cause tailing. Equipment operating records from package dyeing machines with pump capacities of 10–15 L/min per kg of material show that pre-dispersion through an external dosing tank, rather than direct powder addition into the main vessel, reduces speck formation and pressure drop during the heating ramp.

High-temperature exhaust is the primary application route for Disperse Violet 28. For polyester/cellulose blends, the dye is applied only to the polyester component, and the cotton is subsequently covered with reactive, vat, or pigment dyeing in a two-bath process. In carrier dyeing at 100°C for acetate or polyester/wool blends, a suitable carrier is used at 3–5 g/L; carrier selection must account for the effect on the absorption spectrum and fibre swelling. Published data for carrier-assisted dyeing of C.I. 61102 on polyester/wool is limited, but production experience shows that low liquor ratios increase aggregation risk if the carrier is added before the dye dispersion is fully stable.

Thermal Migration Thresholds and Reduction Clearing in Package Dyeing

For high-temperature exhaust dyeing of 100% polyester yarn, the starting bath is set at a material-to-liquor ratio of 1:6 to 1:15, adjusted to 4.5–5.5 pH with acetic acid/sodium acetate, and heated at 1–2°C/min to 130°C. Hold time at 130°C is typically 30–60 min for pale-to-medium depths; deep shades above 2.0% owf require extended hold and additional anionic dispersant at 1–2 g/L to suppress aggregation. At 130°C, equilibrium exhaustion from an acidic bath is normally above 95% at 0.5% owf, but drops when the bath contains carrier solvents or excessive levels of levelling agent.

After dyeing, reduction clearing with sodium hydrosulfite at 2–3 g/L and sodium hydroxide at 1–2 g/L is performed at 70–80°C for 20 min because the dye loosely adsorbed on fibre surfaces is removed and wet fastness is typically improved by one full grade under ISO 105-C06:2010 C2S. The same reducing chemistry is not applied during the dyeing step because it destroys the anthraquinone chromophore; accidental addition of hydrosulfite before exhaustion is complete causes rapid shade loss and is a documented batch failure mode. Effluent from this reduction clearing and from rinse baths contains residual anthraquinone degradation products and dispersing agents. Treatment by Fenton oxidation at pH 3–4 or by adsorption on activated carbon is required before discharge; published data for the electrochemical degradation of C.I. 61102 itself is limited, and treatability studies are recommended for each dyehouse waste stream.

The main processing constraint of C.I. 61102 is thermal migration during post-heat-setting or finishing. At dry-heat treatment above 180°C, the dye can migrate to the fibre surface, especially in the presence of residual spinning lubricants or softeners. In thermosol dyeing, padding at 60–80% pick-up, drying at 100–120°C, and fixation at 200–210°C for 60–90 s is used. Fixation above 220°C leads to a dulling of the bluish violet cast and reduces wet rubbing fastness; published production data for this specific configuration is limited to machine-dependent oven residence times and air velocities of 15–20 m/s in forced-convection chambers.

When Disperse Violet 28 Replaces Disperse Violet 33 in Continuous Thermosol Ranges

Substitution of C.I. Disperse Violet 33 with C.I. 61102 is not a direct charge-for-charge exchange because the two products belong to different chromophore classes. Disperse Violet 33 is generally supplied as a monoazo formulation with lower molecular weight and different tinctorial build-up, whereas Disperse Violet 28 is a chlorinated anthraquinone. A visual shade match at equal depth therefore requires reformulation of the tristimulus recipe and, in many cases, a higher absolute loading of the anthraquinone component. The thermosol fixation window should be checked on the production range with pads prepared at 60–80% pick-up, dried at 100–120°C, and fixed at 200–210°C for 60–90 s. Width-direction temperature variation greater than ±5°C in the stenter can produce visible side-centre shade drift; such variation is more critical with C.I. 61102 than with some high-molecular-weight azo violets because the anthraquinone chromophore has a narrower fixation plateau under dry-heat conditions.

At fixation temperatures above 220°C, thermal migration of the dye to the fibre surface is accelerated; wet rubbing fastness measured under ISO 105-X12:2016 is typically lowered by 0.5–1.0 grade compared with a 200°C fixation. Published data for the specific combination of C.I. 61102 with aminoplast resin finishing is limited; however, production trials on pad-thermosol lines have demonstrated that cationic softeners and aminoplast precondensates can extract surface dye during curing and should be screened with a crock transfer test before bulk scale-up.

Relative to unsubstituted 1,4-diaminoanthraquinone C.I. Disperse Violet 1, the 2,3-dichloro substituent in Disperse Violet 28 shifts the absorption maximum bathochromically and modifies the electron density of the anthraquinone nucleus. This structural modification produces a bluer violet and changes resistance to photofading; however, it also raises the melting point above 300°C, which limits melt-phase plastic coloration to high-temperature engineering resins. Compared with azo violet disperse dyes of similar visual hue, C.I. 61102 has a narrower absorption band and better reproducibility in trichromatic formulations, but lower saturation and a greater risk of thermal migration at dry-heat fixation above 180°C.

Fastness Data and Operational Boundaries for Light, Washing, and Dry Heat

Published supplier fastness data for Disperse Violet 28 on polyester at 1/1 standard depth are summarised below. These values are laboratory data from finished fabric after reduction clearing; they are not universal guarantees.

On blended substrates, wet fastness may drop by 0.5–1.0 grade when the cellulosic or wool component is not scoured free of residual size. For automotive polyester specifications requiring light fastness above 7, C.I. 61102 is generally not used as the sole violet chromophore; it is blended with high-molecular-weight anthraquinone or benzodifuranone dyes to improve end-use performance. The operational boundary for this product is therefore standard apparel and home textile polyester up to light fastness ratings of 5–6; applications demanding 7 or above require reformulation, often at a loss of shade brightness.

Why Are Reduction Clearing and Effluent Oxidation Treated as Non-Optional Steps?

Reduction clearing after dyeing with sodium hydrosulfite at 2–3 g/L and sodium hydroxide at 1–2 g/L is performed at 70–80°C for 20 min because the dye loosely adsorbed on fibre surfaces is removed and wet fastness is typically improved by one full grade under ISO 105-C06:2010 C2S. The same reducing chemistry is not applied during the dyeing step because it destroys the anthraquinone chromophore; accidental addition of hydrosulfite before exhaustion is complete causes rapid shade loss and is a documented batch failure mode. Effluent from this reduction clearing and from rinse baths contains residual anthraquinone degradation products and dispersing agents. Treatment by Fenton oxidation at pH 3–4 or by adsorption on activated carbon is required before discharge; published data for the electrochemical degradation of C.I. 61102 itself is limited, and treatability studies are recommended for each dyehouse waste stream.

In transfer printing, Disperse Violet 28 is dispersed in an aqueous or solvent-based ink and printed onto release paper. The paper is then pressed against polyester fabric at 200–210°C for 30–45 s. Transfer efficiency depends on the sublimation pressure of the dye; anthraquinone C.I. 61102 transfers at a slower rate than many low-molecular-weight azo dyes, requiring sufficient contact time and pressure. Production printers monitor residual dye on the paper by reflectance densitometry; a residual colour difference ΔE CMC(2:1) below 1.0 is considered acceptable for repeat shade control.

Disperse Violet 28 can be used in mass coloration of polyesters and selected engineering thermoplastics, but processing temperatures above 300°C require high thermal stability. The dye’s melting point above 300°C permits compounding in PET at 280–290°C; however, residence times longer than 5 min can shift the shade and volatilise low-molecular-weight fractions. Published data for this specific configuration is limited.

Compliance assessment of Disperse Violet 28 under REACH Annex XVII and Oeko-Tex Standard 100 must treat the technical formulation rather than the neat dye molecule alone. As an anthraquinone chromophore, it does not undergo reductive cleavage to the regulated aromatic amines listed in REACH Annex XVII entry 43 under the conditions of ISO 17234-1:2010; for this reason, it is not classified as an azo dye that releases restricted arylamines. However, dispersing agents, residual solvents, and synthesis intermediates must be monitored in the final formulation. The neat compound is considered nonionic and sparingly soluble in water, so effluent treatment by adsorption or Fenton oxidation is necessary before discharge from finishing plants; published data for the electrochemical destruction of this specific dye in spent dyebaths is limited.