Solvent Yellow 62, assigned CAS registry number 104244-10-2 and Colour Index designation C.I. Solvent Yellow 62, is an anthraquinone-based solvent dye supplied as a yellow powder, low-dust granulate, or pelletized masterbatch. Commercial designations include Macrolex Yellow E2G and Solvaperm Yellow 2G. The dye dissolves molecularly in amorphous thermoplastics at melt temperatures from 240°C to 320°C; unlike particulate pigments, it contributes chromaticity without measurable haze from particle scattering. This character makes it technically relevant for transparent PET preforms, polycarbonate optical components, polystyrene light-diffusion covers, PMMA glazing, and ABS consumer housings.

Representative supplier certificates of analysis define commercial powder lots by high-performance liquid chromatography area percent, typically ≥98.0%, and by moisture content measured by Karl Fischer titration according to DIN EN ISO 15512-1:2020, typically ≤0.3%. Residue after combustion is controlled gravimetrically and commonly specified below 0.2%. Specification bands vary between manufacturers and must be verified against the lot certificate before use. Granulated forms reduce dust formation but do not alter coloristic performance; the chromophore is identical.

What Distinguishes Solvent Yellow 62 from Other Yellow Solvent Dyes in Thermoplastic Processing?

Solvent Yellow 62 is positioned between green-shade Solvent Yellow 93 and red-shade Solvent Yellow 114 in the yellow solvent dye range. In transparent polystyrene transmission spectra, Solvent Yellow 62 exhibits dominant absorption in the violet-blue region near 400–450 nm; this yields a greenish yellow hue under D65 illumination. Solvent Yellow 114 shows stronger absorption at lower wavelengths, producing a warmer yellow hue, while Solvent Yellow 93 is often selected when a brighter yellow-green edge is required. Exact spectral differences depend on host refractive index and UV-stabilizer loading; processors should generate matrix-specific calibration curves rather than rely on solution spectra.

Thermal stability is a critical differentiation point for engineering plastics. Supplier technical literature commonly lists Solvent Yellow 62 as suitable for polycarbonate melt processing up to 300°C with residence times up to 10 min. At 320°C, slow chromophore degradation can increase yellowness index in polycarbonate and shift L*a*b* coordinates, especially in machines with large shot-to-capacity ratios or hot-runner dead spots. By comparison, some pyrazolone and quinophthalone yellows may exhibit faster degradation in polycarbonate at 280–300°C, though published data for specific formulations is limited. The anthraquinone structure contributes to higher thermal endurance but also produces somewhat lower brilliance relative to methine dyes.

Migration behavior is matrix-dependent. In polystyrene and acrylic, plasticization by residual monomer can facilitate dye diffusion; Solvent Yellow 62 demonstrates lower migration than certain lower-molecular-weight yellow solvent dyes, but extraction testing on the finished article remains necessary. Migration to non-polar contact media such as sebum simulants or olive oil simulant may be measurable at high addition levels. Published data for specific migration limits under food-contact conditions for this dye is limited; suppliers typically provide positive-list citations only where a specific regional approval exists.

Compounding of Solvent Yellow 62 is performed on co-rotating twin-screw extruders with length-to-diameter ratios between 40:1 and 48:1. The dye is introduced through a side feeder or with the polymer feed; because the mechanism is dissolution, screw elements with high distributive mixing are preferred over high-intensity dispersive kneading blocks. Dispersive shear is not required and can generate unnecessary melt temperature rise. For single-screw injection molding machines, gravimetric masterbatch dosing at the throat is used; a screw with 20:1 to 24:1 L/D and a mixing tip is generally adequate for melt homogenization. Batch-to-batch color variation is managed by storing masterbatch in sealed aluminum-lined bags and by purging with a 0.1 wt% letdown ratio.

In semi-crystalline PET, the chromophore concentrates in amorphous interlamellar regions; the effective local concentration is therefore higher than the nominal mass fraction. This concentration effect explains why speck defects can appear at nominal loadings below the apparent solubility limit when cooling rates are low or when spherulite growth rejects the dye into the remaining amorphous phase. Processors running cold molds or thick-walled articles may observe dye recrystallization at the gate region. For PET articles with wall thickness above 3 mm, addition levels should be reduced by 10–20% relative to thin-wall preforms. Published data for exact crystalline-phase rejection coefficients is limited, but the phenomenon is well documented for anthraquinone solvent dyes.

When Transparent PET Preforms Demand Low-Haze Yellow Coloration

Solvent Yellow 62 is introduced into PET preform molding primarily through a liquid colorant or pelletized masterbatch. PET resin must be dried to below 50 ppm moisture before processing; typical dryers operate at 160°C with a dew point of −40°C or lower for 4–6 h. Melt temperatures are held between 270°C and 300°C, mold temperatures between 8°C and 15°C, and injection pressures are established to fill 48-cavity or 96-cavity preform tools without exceeding shear-induced acetaldehyde. Under these conditions, molecularly dissolved Solvent Yellow 62 does not create particulate haze; the measured transmission loss comes only from absorption. Processors should monitor preform haze by ASTM D1003 and yellowness index by ASTM E313. If haze exceeds 2%, the cause is usually moisture, crystallization, or mold fouling rather than dye particulate.

Addition levels above 0.1 wt% can approach the solubility limit of the dye in PET at 280°C; beyond this limit, recrystallization upon cooling can appear as surface speck defects or increased haze. Because published data for the exact solubility limit in PET at processing temperature is limited, pre-production trials should use a gradient from 0.005 wt% to 0.08 wt% with transmission spectrophotometry at 10 nm intervals. A suitable method is a double-monochromator instrument with 0/0 geometry or an integrating sphere for total transmittance. The relationship between absorbance and concentration follows the Beer-Lambert law only in the absence of crystallization; strained amorphous regions may produce polarization-dependent color in polarizers.

In polycarbonate, Solvent Yellow 62 competes technically with Solvent Yellow 93 and Solvent Yellow 163. PC melt processing at 280–310°C requires pre-drying to 0.02% moisture or below; otherwise, hydrolytic chain scission causes a drop in molecular weight and a simultaneous increase in yellowness index. The dye is metered at 0.01–0.20 wt%. Because polycarbonate contains bisphenol A residues and develops oxidative species at high temperatures, regular purge cycles are necessary; deposits on hot-runner gates can cause black specks and gate blush. Solvent Yellow 62 tends to leave less mold plate-out than some quinophthalone yellows, but published quantitative comparisons are limited. Optical applications such as colored lenses or light pipes require absorbance stability after 1,000 h of xenon arc exposure per ISO 4892-2; the resulting color shift is a function of the polycarbonate stabilizer package rather than the dye alone.

Regulatory and Migration Boundaries in Food-Contact and Medical Packaging

Food-contact use of Solvent Yellow 62 is not automatically authorized; approval must be confirmed against the positive list of the target regulatory domain. Under the European Union, migration from finished plastic articles is assessed under Regulation (EU) 10/2011 with food simulants assigned in Annex III; extraction conditions are selected from Annex V according to the worst foreseeable contact time and temperature. Under U.S. FDA jurisdiction, a colorant may be covered by a food-contact notification, a threshold of regulation exemption, or a specific regulation in 21 CFR; supplier letters should be requested with the exact use temperature, food type, and polymer matrix stated. If a supplier asserts compliance for medical applications, guidance under ISO 10993-1:2018 and ISO 10993-17:2023 is applied for leachables and toxicological risk assessment.

Electrical and electronic equipment applications require verification of heavy metal content against Directive 2011/65/EU Annex II. The accepted analytical framework is the IEC 62321 series; for plastic colorants, screening by X-ray fluorescence followed by confirmatory acid digestion and ICP-OES or ICP-MS is typical. Toy applications must satisfy element migration limits in EN 71-3:2019+A1:2021 on the finished article rather than on the raw dye. Because solvent dyes are intended to dissolve in the polymer, extraction results are heavily influenced by article thickness, crystallinity, and surface-to-volume ratio; published data for Solvent Yellow 62 in thin-walled food packaging is limited and cannot substitute for finished-article testing.

Solvent Yellow 62 in acrylic and polystyrene extrusion is metered by masterbatch into single-screw extruders with barrier screws. In polystyrene light-diffusion covers, the dye is combined with light-scattering additives such as bead-type diffusers; the yellow absorbance corrects the blue-shift of LED spectra. At addition levels below 0.05 wt%, the color shift in PMMA after 1,500 h of xenon arc exposure per ISO 4892-2 is typically small, but UV absorber selection dominates. No further post-treatment is required if extrusion melt temperature is kept below 260°C and residence time remains under 5 min.