Section
| HS Code | 630000 |
| Productname | Direct Yellow R |
| Dyeclass | Direct dye |
| Colorindexname | C.I. Direct Yellow 12 |
| Colorindexnumber | 24895 |
| Casnumber | 6486-29-3 |
| Chemicalclass | Stilbene azo direct dye |
| Molecularformula | C30H26N4Na2O8S2 |
| Appearance | Yellow to orange-yellow powder |
| Colorshade | Bright yellow |
| Solubility | Soluble in water |
| Applicationmethod | Exhaust dyeing |
| Substrates | Cotton, viscose, rayon, paper |
| Phrange | Neutral to mildly alkaline |
| Lightfastness | Moderate |
| Washfastness | Moderate to good |
| Storage | Store dry, away from direct sunlight |
As an accredited Direct Yellow R factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Direct Yellow R is packed in 25 kg net multi-wall paper sacks with polyethylene inner liners, securely sealed for transport and storage. |
| Container Loading (20′ FCL) | Direct Yellow R is securely packed and evenly loaded into a 20′ FCL container, with labeled packaging ensuring safe, stable, and compliant transport. |
| Shipping | Direct Yellow R is typically shipped as a non-hazardous industrial dyestuff in sealed, labeled containers. Keep dry and protected from moisture, direct sunlight, and contamination; store in a cool, ventilated area away from strong oxidizers. Follow local transport rules and the SDS. |
| Storage | Store Direct Yellow R in a cool, dry, well-ventilated area, away from direct sunlight, heat, moisture, and strong oxidizers or acids. Keep containers tightly closed, clearly labeled, and upright. Avoid dust generation and contact with incompatible materials. Use secondary containment, keep away from food, drink, and animal feed, and follow local chemical storage regulations. |
| Shelf Life | Direct Yellow R has a shelf life of about 24–36 months when kept cool, dry, and protected from light and moisture. |
In softflow and air-jet dyeing machines operating at liquor ratios between 1:8 and 1:12, Direct Yellow R is introduced to pre-scoured cotton or viscose knit substrates at a starting bath temperature of 40°C. The stock solution is prepared at 5–10 wt% in softened water heated to 60–80°C under low-shear agitation; undissolved aggregate particles larger than the machine circuit filter fineness of 25–50 µm can cause specking on the fabric surface. Sodium chloride or anhydrous sodium sulfate is used as the exhausting agent. For pale shades, salt addition is held at 5–15 g/L, for medium shades 20–40 g/L, and for deep shades 50–80 g/L. The salt is not added in a single charge. The first 25–30% of the total salt dosage is dosed after the dye has circulated for 10 min; the remaining amount is split into two or three portions and added over 20–30 min while the bath is raised to 95–98°C at 1.0–1.5°C/min. The dyeing temperature is held for 30–60 min, depending on the depth, before cooling to 70°C for sampling. The pH of the bath is kept between 7.0 and 8.5; alkaline values above 9.0 are avoided because they can shift the dye toward reduced affinity and increase hydrolysis of the cellulosic substrate. Without cationic aftertreatment, wet fastness of Direct Yellow R under ISO 105-C06 A2S is generally not better than grade 3; application of a cationic dye-fixing compound at 1–3% on weight of goods, at 45–50°C for 20 min at pH 6.0–6.5, can lift washing fastness by 0.5–1.0 grade but may reduce light fastness under ISO 105-B02 by half a grade. The process conflict is primarily levelness: rapid salt dosing or a heating ramp above 1.5°C/min produces agglomerated dye particles and centre-to-selvedge variation in tubular knit. Production-scale air-jet machines with variable-frequency circulation pumps are preferred because the pump curve can be stepped from 40% to 80% of maximum flow during the salt-dosing phase. Evaluation of batch-to-batch reproducibility requires the same residual salt concentration in the final bath; conductometric control at the first rinse is recommended with a conductivity monitor calibrated to ±0.1 mS/cm.
| Parameter | Pale shade | Medium shade | Deep shade | Test method |
|---|---|---|---|---|
| Liquor ratio | 1:8–1:12 | 1:8–1:12 | 1:8–1:12 | Machine specification |
| Sodium chloride | 5–15 g/L | 20–40 g/L | 50–80 g/L | Conductometric control |
| Peak dyeing temperature | 95–98°C | 95–98°C | 95–98°C | Probe calibration |
| Dwell time | 20–30 min | 40–50 min | 60 min | Shade control |
| Cationic fixative | 1% o.w.g. | 2% o.w.g. | 3% o.w.g. | ISO 105-C06 |
| Final fastness check | Washing, rubbing, light | ISO 105-C06, ISO 105-X12, ISO 105-B02 | ||
When continuous pad-dry or pad-steam sequences are specified for bleached cotton plain-weave shirting, the bath is composed of Direct Yellow R at 10–30 g/L, a low-foam nonionic wetting agent at 1–3 g/L, and an acrylamide or polyacrylate anti-migrant at 2–5 g/L. The padder is set to a liquor expression of 65–80% with a nip pressure of 2–4 bar; roller shore hardness is referenced to 70–85 Shore A because lower hardness increases the contact width and reduces local dye penetration on coarse cotton. Continuous operation produces a tailing effect when the trough volume is small and the dye substantivity is high: the bath concentration rises during the run because water is preferentially taken up by the fabric, while the dye molecule is partially retained in the fibre. The trough is therefore fitted with a level-controlled feed at constant volume and the initial bath concentration is reduced by 10–20% relative to the desired shade standard. After padding, the fabric is dried through a first cylinder section at 100–120°C, then through a hotflue at 130–150°C for 60–120 s. The water extraction should not exceed 30% residual moisture before the hotflue; higher moisture produces migration of Direct Yellow R to the fabric surface, which is visible as edge-darkening on selvedges. The unfixed dye is removed in a counterflow wash range with the first compartment at 60–80°C, the second at 50–60°C, and the final cold rinse. The application is limited to nonperformance woven substrates such as pocketing, lining, and stitched interlining; specifications requiring wet fastness above grade 3 under ISO 105-C06 or perspiration fastness under ISO 105-E04 above grade 3 generally exclude direct dyes without fixation.
In paper and board manufacture, Direct Yellow R is injected after the refining stage into bleached kraft or sulfite stock at consistency 2.5–4.0%, ahead of the machine chest or directly before the fan pump. The dye is anionic and carries little affinity for unmodified fibre without cationic retention; the addition order is therefore pulp → dye → cationic polyamine or polyDADMAC retention aid → alum or PAC. Cationic polyDADMAC is dosed at 0.1–0.5% on dry fibre, and alum is held at 0.5–1.5% on dry fibre at a wet-end pH of 4.5–6.5. If alum is added before the dye, the resulting precipitated aluminium-dye complex can cause coloured spots in the sheet and uneven retention on the wire. In alkaline papermaking with ground or precipitated calcium carbonate, retention of Direct Yellow R is lower; the filler surface competes for cationic retention aid, and the dye may be lost to white water unless the polyDADMAC dosage is raised to 0.3–0.8%. The white water colour should be monitored at 450 nm with a laboratory spectrophotometer; a delta of more than 0.05 absorbance units against the clear filtrate indicates a retention failure. The furnish is formed on a Fourdrinier or gap former at headbox consistency 0.3–0.8%, and the sheet is dried to 4–6% moisture. Finished grades include coloured ledger, folder stock, tissue, and napkin bases. For hygiene or food-contact grades, the final paper must meet the relevant migration limits under 21 CFR 176.170 or BfR Recommendation XXXVI, and the dye supplier’s lot certificate under EN 14362-1 should be reviewed for restricted arylamines. Published data for Direct Yellow R migration in food-contact paper is limited; intended use in food-contact grades therefore requires migration testing on the finished sheet.
Because Direct Yellow R carries an anionic sulfonic acid group, its compatibility with oxidized starch and cationic starch in a film press depends on the ratio of starch solids to dye and the addition sequence. In surface coloration of sized paper and board, the dye is pre-dissolved and metered into a starch solution at 4–8% dry solids; the addition is made after cooking and cooling to 60°C, immediately before the press supply tank, to limit thermal degradation of the azo chromophore. Dye dosage at the size press ranges from 2 g/L to 10 g/L for pale to medium tinted cover grades. The mixed size is applied with a film press or metering rod at pickup values between 20 g/m² and 60 g/m² wet; the dry pickup of starch is normally 0.5–1.5 g/m². For bleed resistance on tinted board, a cationic fixative solution is dosed separately at 0.5–2.0 g/L into the starch supply line; overdose above 2.0 g/L can flocculate the starch and produce streaks on the sheet. Viscosity is controlled at 15–40 s through a DIN 4 mm flow cup at 60°C; values above 40 s increase the film split and reduce dye transfer uniformity. The final board is evaluated for colour difference under ISO 5631-1 and for water-bleed by a 5 min contact at 23°C with Delta E measured against the dry standard. This surface-dyed route is used for file folders, cover stock, decorative tissue and coloured packaging board. It is not a substitute for wet-end dyeing when high colour penetration is specified.
For package dyeing of cotton sewing thread or weaving yarn in conical carriers, column pressure drop is directly affected by package density and the proportion of direct dye in the bath. The packages are wound on stainless steel cones at a density of 0.35–0.42 g/cm³; values above 0.42 g/cm³ restrict radial flow and produce lighter cores under inside-out pumping. The dyeing machine is configured for bi-directional circulation at 30–40 L/min per kg of yarn, with reversal every 2–4 min for the first 20 min and every 6–8 min once the bath reaches 95–98°C. Direct Yellow R is predissolved at 5–10 wt% and added at 40°C. Sodium chloride is dosed through a side tank in three portions over 30 min; the first portion is 25% of the total, added only after dye circulation is confirmed by a pressure differential across the package column. The heating ramp is not allowed to exceed 1.0°C/min because conical package geometry amplifies temperature lag between the outer and inner package layers. Dwell time at 95–98°C is 45–60 min. After dyeing, the yarn is cooled to 70°C before draining and rinsed in a top-down overflow sequence. The final yarn is assessed for colour difference between inner and outer package zones under ISO 105-J03 and for light fastness under ISO 105-B02. Direct Yellow R is not recommended for yarn used in outdoor furnishings or automotive interiors because light fastness after anionic aftertreatment may remain below grade 4 in pale depths.
Vegetable-tanned split leather and cellulose sponge tinting are peripheral downstream segments for Direct Yellow R, and published data for these specific configurations is limited. For vegetable-tanned crust, the dye is usually screened in a drum at 0.1–0.5% on shaved weight, with wetting agent at 0.2% and at 35–40°C for 20–30 min. The anionic dye has limited penetration into the vegetable-tanned network; crust leather retains colour mainly at the surface, so rub fastness under ISO 11640 should be regarded as the critical gate. For cellulose sponge, the dye is added to the viscose mass before regeneration at 0.05–0.2% on cellulose content. These routes are acceptable only for low-cost nonperformance goods; they are not supported by extended industrial test series for Direct Yellow R, and any scale-up should proceed through laboratory confirmation.
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Direct Yellow R is supplied as a water-soluble anionic azo colorant indexed in the Colour Index as C.I. Direct Yellow 11 (CAS 1325-37-7). Commercial presentations include standard-strength powder, dust-reduced granular, and high-concentration preparations; supplier model suffixes vary, but “CONC” or numerical strength designations commonly identify high-strength versions. The colorant is substantive to cellulosic fibres, including cotton, mercerized cotton, viscose, modal, linen, and lyocell, and is exhausted from aqueous baths containing sodium chloride or sodium sulfate. Direct Yellow R does not require oxidative fixation or alkali-catalyzed covalent bonding; the sulfonated chromophore is retained on cellulose by hydrogen bonding and van der Waals forces. This adsorption mechanism permits shade stripping and rework under reducing or alkaline conditions, but it also limits wet fastness unless cationic aftertreatments are applied. Bulk packaging typically comprises 25 kg fibre drums with low-density polyethylene liners, 50 kg paper sacks, or 500 kg flexible intermediate bulk containers. Storage should be maintained below 30 °C and below 60% relative humidity; opened packages must be resealed to prevent hygroscopic caking. The product is intended for aqueous dye bath preparation and should not be blended with cationic agents in the same stock liquor without separate dissolution.
Incoming inspection procedures for Direct Yellow R begin with visual evaluation of a 10 g/L aqueous solution prepared with demineralized water at 60 °C. The solution should be clear after screening through a 100 mesh nylon filter; specks, gelatinous particles, or persistent foam indicate storage moisture ingress or contamination. Colour strength is established spectrophotometrically at the maximum absorbance wavelength, which is typically observed in the 390–410 nm region for this colorant in neutral water. Acceptance of a dye lot is normally based on a strength tolerance of ±3% against a retained reference standard, with high-concentration grades controlled at ±5%. For full technical acceptance, moisture content is commonly limited to 5.0 g/100 g by gravimetric drying, water-insoluble matter to 0.5% by 45 μm filtration, and pH of a 10 g/L solution to 7.0–9.5. Excess moisture accelerates hydrolysis and microbial growth, while insoluble matter causes filter blockage in package dyeing machines.
| Parameter | Typical acceptance window | Test basis |
|---|---|---|
| Appearance | yellow to reddish-yellow powder or granular | visual |
| Colour strength | standard grade 100 ± 3%; CONC grade 200 ± 5% relative to reference | visible spectrophotometry at maximum absorbance |
| Moisture content | ≤ 5.0 g/100 g | gravimetric drying at 105 °C |
| Water-insoluble matter | ≤ 0.5% | aqueous filtration through 45 μm membrane |
| Solution pH | 7.0–9.5 | calibrated electrode in 10 g/L aqueous solution |
| Lead | ≤ 100 mg/kg | ICP-OES after acid digestion; OEKO-TEX Standard 100 Appendix 4 |
| Cadmium | ≤ 20 mg/kg | ICP-OES after acid digestion; OEKO-TEX Standard 100 Appendix 4 |
| Mercury | ≤ 4 mg/kg | ICP-OES after acid digestion; OEKO-TEX Standard 100 Appendix 4 |
Exhaust dyeing of cotton knits with Direct Yellow R is carried out in overflow or soft-flow machines at liquor ratios between 1:8 and 1:12. The dye is first pasted with cold demineralized water, diluted to 60 °C, and screened before addition to the machine. Stirring should be gentle; high-shear mixers above 1500 rpm generate foam because of residual dispersing agents and can alter dye solution clarity without chemical degradation. Sodium sulfate anhydrous is commonly added in divided portions. An initial electrolyte charge of 5 g/L is used before dye injection; after a 10 °C bath temperature rise, an additional 10–20 g/L is dosed over 15–20 min to control strike. The bath is then heated to 95–98 °C at a rate of 1.0–1.5 °C/min and held for 30–45 min. Because Direct Yellow R exhibits strong temperature sensitivity above 80 °C, rapid heating can produce uneven adsorption in hatched portions and seam areas. Anionic or non-ionic leveling agents may be added at 0.5–1.0 g/L for pale shades run at low salt concentrations. After exhaustion, the bath is drained hot at 70–80 °C to prevent redeposition of residual solids. Rinsing is performed with cold water overflow until conductivity falls below 300 μS/cm.
For package dyeing of cotton yarn, the same temperature curve is used, but circulation reversal is mandatory. Typical package density is 300–340 g/L, and pump flow is maintained at 30–40 L/kg/min. Pressure differential across the package column should remain below 1.5 bar; higher values indicate clogging by yarn finish, insoluble dye, or cellulose fines. Batch-to-batch shade variation in package dyeing has been observed when greige yarn extractable wax content exceeds 0.8%. The cause is uneven wet-out and locally retarded dye adsorption. A pre-wetting stage at 80 °C with 1.0 g/L alkaline detergent for 20 min improves reproducibility.
In laboratory dyeing trials, direct dyes are often screened using an infrared-heated polyglycol bath with sealed stainless steel pots. The liquor ratio is fixed at 1:10, and the temperature programmer is set to match the bulk machine ramp. In these systems, Direct Yellow R shows sensitivity to bath ratio: increasing the liquor ratio from 1:5 to 1:20 at constant salt and dye concentration can reduce final depth by 20–30%, consistent with direct dye equilibrium behavior. Published data for this specific dye configuration is limited; bulk recipes are therefore usually verified by a scale-up factor of 1.0–1.1 from laboratory to production rather than by direct transfer.
Substitution of Direct Yellow R for C.I. Direct Yellow 12 on a pad-steam range is not a simple recipe change. Direct Yellow R produces a redder yellow shade on cotton; the hue difference must be confirmed by reflectance spectrophotometry using D65 illuminant and 10° observer geometry. The continuous pad liquor is prepared at 20–80 g/L dye depending on depth, with 5–10 g/L urea to maintain pad-bath solubility and 2–5 g/L non-ionic wetting agent. Padder pickup is maintained at 70–80% for woven cotton; lower pickup produces tailing because the pad bath concentration increases as dye is removed preferentially. The padded fabric is dried in infrared units followed by hot air at 110–120 °C. Migration during intermediate drying is a critical failure mode: rapid surface evaporation draws dye to the fabric face, producing a darker face and lighter back. Control is achieved by reducing the first hot-air zone to 110 °C and by maintaining fabric speed below 40 m/min for lightweight cotton weighing 120–160 g/m². After drying, steaming at 100–102 °C for 30–60 s completes exhaustion. Because no covalent bond forms with cellulose, wet fastness after steaming remains below that of reactive dyes. Cationic aftertreatment with a quaternary ammonium fixing agent at 2–4 g/L is common for apparel requirements; the wet fastness limit is then often measured as 2–3 grey scale grades on ISO 105-C06:2010 without aftertreatment and 3–4 after aftertreatment, while light fastness under ISO 105-B02:2014 remains controlled by the chromophore.
| Parameter | Direct Yellow R (C.I. Direct Yellow 11) | C.I. Direct Yellow 12 |
|---|---|---|
| Shade direction on cotton | redder yellow | greener yellow |
| Fixation mechanism | non-covalent direct dye adsorption | non-covalent direct dye adsorption |
| Typical exhaust dyeing temperature | 95–98 °C | 90–95 °C |
| Sodium sulfate addition range | 15–25 g/L total | 10–20 g/L total |
| Wet fastness after cationic aftertreatment | typically 3–4 grey scale grades by ISO 105-C06:2010 | typically 3–4 grey scale grades by ISO 105-C06:2010 |
| Light fastness on cotton | mid-range blue wool scale rating; exact grade depends on depth | mid-range blue wool scale rating; exact grade depends on depth |
| Common application area | cotton and viscose apparel, lining, paper | cellulosic textiles, paper, wood stain |
Direct Yellow R is also used in wet-end paper coloration, where its anionic character requires adjustment of fibre charge. In bleached kraft furnish containing cationic starch or alum, direct dyes are fixed by electrostatic retention. The stock solution is prepared at 10–20 g/L and added after refining; the addition point should be located away from concentrated alum streams because aluminium ions produce insoluble lakes. Retention aid dosage based on cationic polyacrylamide at 0.5–1.0 kg/t dry fibre is typical, but mill-specific conditions require a drainage and retention pilot. Hydraulic shear in stock chests above 1500 rpm can cause foaming; a silicone-free defoamer may be added at 0.1–0.3 g/L. The resulting dyed paper shows limited bleed resistance when wet; direct dyes are therefore generally selected for grades that do not require high wet fastness, such as tissues, packaging board, and colored testliner. Published data for Direct Yellow R on specific head-box retention systems is limited, so dye demand is established by a laboratory handsheet trial using the target furnish and retention program.
Direct Yellow R solutions are sensitive to polyvalent metal ions. Hard water containing more than 150 mg/L calcium carbonate equivalent can produce a faint bronze scum or precipitate; the effect increases when the dyebath is heated above 90 °C. Calcium and magnesium form sparingly soluble salts with sulfonated direct dyes. The precipitate deposits on package mandrels, jigger rolls, and fabric edges, and is difficult to remove without alkaline reduction. Softened water or condensate should be used for stock dissolution. If only hard water is available, a chelating agent such as EDTA or sodium polyphosphate is added at 1–2 g/L after the dye is fully dissolved; adding the chelating agent before dissolution can reduce dye solubility by complexing with residual metal ions in the powder. The dye bath pH is controlled between 7.0 and 9.0. Below pH 6.0, weak acid may shift shade and accelerate strike, producing uneven results on circulating machines. Above pH 10.0, cellulose acquires greater negative surface charge and exhaustion falls; salt may be increased, but total dissolved solids limits in discharge permits must be considered. In routine production, a pH of 7.5 ± 0.5 is commonly specified for repeatable shade. Buffered systems containing phosphate above 3 g/L should be avoided because phosphate films can develop on stainless steel surfaces over time.
After dyeing, the non-covalent bond between Direct Yellow R and cellulose is susceptible to hydrolysis and desorption in hot alkaline washing. Washing tests under ISO 105-C06:2010 use detergent bases that can extract loosely bound dye; the resulting staining on multifibre is evaluated against grey scale. The fastness of Direct Yellow R is depth-dependent: pale shades show lower wet fastness because less dye is present and the relative desorption is more visible. Cationic fixing agents based on dicyandiamide or quaternary ammonium polymers are applied at 2–4 g/L at 40–50 °C for 15–20 min. Overdosage above 5 g/L can cause handle stiffening and loss of light fastness. After fixing, the dyed fabric is rinsed and dried below 120 °C to avoid thermal yellowing of the cationic polymer. Light fastness is assessed by ISO 105-B02:2014; direct dyes generally occupy the middle range of the blue wool scale, and Direct Yellow R should not be selected for automotive or outdoor textiles unless the specification requires only low light exposure. Perspiration fastness under ISO 105-E04:2013 is controlled by acid and alkaline perspirometer tests; alkaline perspiration often gives more staining with direct azo colorants. Dry cleaning fastness is usually acceptable, but chlorinated water exposure can cause fading.
Direct Yellow R differs from acid dyes and reactive dyes in application chemistry. Acid dyes require acidic pH and are substantive to polyamide and protein fibres; Direct Yellow R is formulated for cellulosic substrates and is normally exhausted at neutral pH. Reactive dyes form covalent ether linkages with cellulose in the presence of alkali and exhibit high washing fastness; Direct Yellow R remains in the fibre by adsorption and therefore wet fastness is lower. Unlike vat dyes, no reduction-oxidation step is needed. This distinction matters in shade matching: a colorant with the same visual hue but different fixation class cannot be substituted without changing fastness and process parameters.
Material handling is based on dust generation and alkalinity. The powder should be handled with local exhaust ventilation and a dust mask meeting national workplace exposure limits for organic dust. Direct Yellow R may contain residual sodium chloride or sodium sulfate from processing; total electrolyte content can be determined by conductivity of a 10 g/L solution. Transport classification is generally non-hazardous, but suppliers should provide a safety data sheet under REACH. For textile articles, the dye lot should be screened against OEKO-TEX Standard 100 limits for aromatic amines from azo reduction; supplier certification is required and should be verified against the lot-specific certificate of analysis.
