High Temperature Leveling Agent for Polyester RH-NB-2117

High-temperature leveling agent RH-NB-2117 is applied in polyester dyeing processes where disperse dye migration, package or beam filtration, and thermal protection of elastane components are process-limited. Dosages are expressed as mass per volume of total dyeing liquor and require adjustment when hard water, alkaline carryover, or high-shear circulation alters dispersion stability. The application tracks below cover separate downstream manufacturing sectors and are not interchangeable without laboratory verification.

Package dyeing of polyester sewing thread and technical yarn

On vertical cone package machines processing continuous-filament polyester sewing thread in package densities of 0.35 g/cm³ to 0.42 g/cm³, RH-NB-2117 is dosed into the prepared bath at 0.8 g/L to 1.5 g/L before disperse dye predispersion is introduced. The bath is buffered to pH 4.5–5.0 with acetic acid/sodium acetate; pH values below 4.3 increase disperse dye aggregation on package end faces, while pH values above 5.5 slow final exhaustion. Predispersion of powder dyes at 35°C–40°C with 0.3 g/L–0.5 g/L dispersing agent prevents coarse particles from being retained in the package matrix. The heating ramp is divided into two zones: from 70°C to 110°C the temperature increase is limited to 1.0°C/min; from 110°C to 130°C the ramp is reduced to 0.5°C/min. Holding time at 130°C is 30 min–45 min depending on shade depth, with flow reversal inside-out to outside-in every 3 min–5 min. In production-scale machines, differential pressure across the package carrier often rises from approximately 0.8 bar to 1.4 bar during the heating phase; if differential pressure exceeds 1.5 bar, package winding density or predispersion stability should be adjusted rather than increasing leveling agent dose. After dyeing, reduction clearing with sodium hydrosulfite and caustic soda at 80°C removes unfixed surface disperse dye; RH-NB-2117 does not replace reduction clearing. Shade consistency across package layers is evaluated by unwinding dyed cones and measuring reflectance per ISO 105-J01, with tolerance ΔECMC(2:1) ≤ 0.5. Wash fastness is assessed per ISO 105-C06:2010, method C2S. Hard water above 150 mg/L CaCO₃ reduces dispersion stability; a sequestrant may be required, but heavy-metal-containing sequestrants should be excluded where final thread is used for infant or skin-contact articles.

On single-rope and multi-rope soft-flow jet dyeing machines processing circular-knit polyester/elastane jersey, RH-NB-2117 is added at 1.0 g/L to 2.0 g/L after pre-scouring and before disperse dye dispersion. The liquor ratio is maintained at 1:8 to 1:12, with fabric speed controlled between 200 m/min and 350 m/min and nozzle pressure not exceeding 1.2 bar. High shear during rope circulation can strip loosely associated dye from the fibre surface and redeposit it on adjacent ends; the leveling agent reduces this risk by maintaining a fine and stable disperse dye dispersion under pump shear. The heating profile for elastane-containing goods is limited to a hold temperature of 120°C–125°C; above 125°C, elastane tenacity loss accelerates, and recovery after repeated home laundering may drop below acceptable limits. From 85°C to 115°C, ramp rate is held at 1.0°C/min or less, and the final hold at 120°C is 20 min–30 min for medium-depth shades. Post-dyeing reduction clearing is run at 70°C–80°C to avoid elastane embrittlement. Finished fabric is tested for colour fastness to washing per ISO 105-C06:2010, method C2S, and for crocking per ISO 105-X12:2016. Shade variation from selvedge to centre is measured against the cut-off standard using CIELAB coordinates from ISO 105-J01; ΔE values above 0.8 indicate uneven dye migration, usually caused by inconsistent rope speed rather than insufficient auxiliary concentration. Hard water, excessive anionic surfactant residues, or carrying over alkaline pre-scour liquors can reduce dispersion stability; pre-scour rinse conductivity should be below 200 µS/cm before dye bath preparation.

What limits leveling performance on microfilament polyester suede?

Microfilament polyester suede with single-filament linear density below 0.5 dtex presents a larger specific surface area than conventional polyester; disperse dye strike between 95°C and 115°C is often rapid and can produce superficial coloration before dye migration into the fibre core. RH-NB-2117 is used at 1.5 g/L to 2.5 g/L in airflow dyeing machines or soft-flow jet machines at liquor ratios of 1:4–1:8. The leveling agent forms a transient association with disperse dye particles during the critical migration window, retarding surface strike without permanently blocking dye uptake. Pre-dyeing alkali weight reduction of 4%–8% produces a low-density fibre surface that accelerates dye diffusion; residual alkali must be neutralised to pH 6.0–6.5 before the dye bath is set, because residual pH above 7.0 can destabilise disperse dye dispersion and reduce the effect of the leveling agent. Heating ramp from 70°C to 110°C is controlled at 0.7°C/min–1.0°C/min; above 115°C, ramp is lowered to 0.5°C/min and the batch is held at 130°C for 25 min–40 min. Overdosing above 3.0 g/L may reduce final colour yield and leave unexhausted dye in the bath; published exhaustion data for this specific configuration are limited, and laboratory verification on the actual airflow machine is required before bulk production. Rubbing fastness of the dyed suede is assessed per ISO 105-X12:2016; wash fastness per ISO 105-C06:2010, method C2S. Because microfilament suede is often finished with polyurethane or acrylic coatings, residual leveling agent on the fabric surface after reduction clearing should be checked by measuring wetting time or surface tension of the final rinse bath; incomplete clearing can reduce coating adhesion in subsequent lamination.

Beam dyeing of warp-dense polyester filament wovens places the leveling agent under filtration stress because the liquor must pass through a wound fabric roll under differential pressure. In a typical high-temperature beam machine, the fabric roll is wound to a density of 0.30 g/cm³–0.38 g/cm³ and the bath is circulated at an initial pressure differential of 0.4 bar–0.6 bar. RH-NB-2117 is added at 0.5 g/L to 1.0 g/L; the lower dose compared with jet dyeing is used because excessive auxiliary can create foam and raise circulation resistance inside the beam. The disperse dye dispersion is prepared separately and filtered through a 100 µm screen before addition to the machine. Heating is carried out at not more than 1.0°C/min from 80°C to 110°C and then at 0.5°C/min to 130°C. Flow direction is reversed every 2 min–4 min to minimise side-to-centre shade variation. If the pressure differential across the beam rises above 1.2 bar before reaching 110°C, the ramp is stopped and the bath is cooled to 80°C to release trapped air; continued heating under high differential pressure causes channeling and unlevel dyeing. RH-NB-2117 can disperse partially agglomerated dye particles under hydraulic shear, but it does not dissolve polyester oligomer deposits that accumulate on beam ends and shells; a separate oligomer dispersant is added during cooling or in the reduction clearing bath. End-use woven constructions include downproof and outerwear fabrics where seam slip and water repellency are coated after dyeing. Fabric is tested for wash fastness per ISO 105-C06:2010, method C2S, and for colour difference across the roll width per ISO 105-J01; end-to-end ΔE beyond 0.7 generally correlates with uneven beam winding density or insufficient flow reversal rather than insufficient leveling agent concentration.

When polyester/elastane warp-knitted structures enter high-temperature jet dyeing

Warp-knitted polyester/elastane constructions used in performance sports textiles and technical underwear require leveling control under conditions that differ from circular knits because the fabric's load-bearing yarn path is more sensitive to rope marking and stretch recovery loss. RH-NB-2117 is charged at 1.0 g/L to 1.5 g/L into a soft-flow jet with a liquor ratio of 1:10–1:14 and fabric reel speed below 250 m/min. The lower mechanical intensity reduces deformation of the warp-knit pillars; nozzle pressure is set between 0.4 bar and 0.8 bar. Dyeing is limited to 115°C–120°C for elastane-containing articles; the ramp from 70°C to 105°C is held at 0.8°C/min–1.0°C/min, followed by a hold at 120°C for 20 min–30 min. Since warp-knit fabric surfaces are more open than woven or circular-knit structures, dye migration can be affected by local liquor exchange rates. RH-NB-2117 reduces dye aggregation in low-flow zones near the fabric selvedge; however, if the machine has poor flow distribution, no leveling agent concentration within the safe use range can compensate for mechanical flow imbalance. Post-dyeing reduction clearing is run at 70°C–80°C, and the fabric is checked for stretch recovery and growth after the standard shaping cycle; polyester/elastane warp knits with excessive growth after 60 min relaxation generally indicate thermal damage from overheating rather than a leveling problem. Colour fastness to washing is tested per ISO 105-C06:2010, method C2S, and staining on multifibre DW is assessed under the same method; no separate harsher cleaning test is routinely required for these articles unless the end use specifies medical or cleanroom washing protocols.

Polyester automotive upholstery fabrics woven from air-textured filament yarns are dyed in high-temperature beam or jet machines with RH-NB-2117 at 0.5 g/L to 1.0 g/L. Automotive specifications often require light fastness results per ISO 105-B02:2014 of at least grade 6 after 400 h, and fogging behaviour per DIN 75201-A is checked on the finished laminate. The leveling agent is used only in the dyeing stage; it is not introduced into later coating or foam lamination baths. Because residual surface auxiliaries can migrate into the fogging condensate, reduction clearing and hot rinsing after dyeing are run until rinse-bath conductivity falls below 50 µS/cm. The dyeing temperature is held at 130°C for 30 min–45 min; for air-textured automotive grades with low filament cohesion, the ramp between 90°C and 115°C is limited to 0.7°C/min to prevent differential dye strike on filament loops and straight segments. This substrate is sensitive to high-shear circulation damage; jet nozzle pressure is kept below 0.9 bar, and reel speed is reduced compared with standard PES wovens. The dose is not increased beyond 1.0 g/L because excess nonionic character can reduce lightfastness by altering disperse dye distribution in the fibre surface. Fastness to rubbing after finishing is tested per ISO 105-X12:2016, wash fastness per ISO 105-C06:2010, method C2S. In production, shade mismatch between autoclave lots is traced more often to variation in pre-drying temperature and air-texturing tension than to leveling agent concentration.