| HS Code | 966531 |
| Productname | Concentrated Acid Fixative RH-NB-2020 |
| Producttype | Acid dye fixing agent |
| Appearance | Light yellow to yellowish-brown liquid |
| Ionicity | Cationic |
| Phvalue | 3.0-5.0 |
| Solidcontent | 30% ± 2% |
| Solubility | Soluble in water |
| Density | 1.00-1.15 g/cm³ at 20°C |
| Chemicalnature | Cationic polymer compound |
| Application | Fixing agent for acid dyes on nylon and wool |
| Recommendeddosage | 1-3% owf |
| Compatibility | Compatible with nonionic and cationic auxiliaries; avoid anionic agents |
| Storage | Store in a cool, dry, ventilated place |
| Shelflife | 12 months |
| Packaging | 125 kg plastic drum |
As an accredited Concentrated Acid Fixative RH-NB-2020 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Concentrated Acid Fixative RH-NB-2020 is packaged in a 20 kg chemical-resistant polyethylene container with secure closure and hazard labeling. |
| Container Loading (20′ FCL) | Concentrated Acid Fixative RH-NB-2020 is loaded in a 20′ FCL container, securely packaged and labeled for safe transport. |
| Shipping | Concentrated Acid Fixative RH-NB-2020 is shipped as a hazardous corrosive liquid in UN-approved, leakproof containers, labeled with corrosive hazard warnings and the UN number/class specified on its SDS. Keep upright, secure, and segregated from incompatible bases and oxidizers; transport with required documentation and trained personnel. |
| Storage | Store Concentrated Acid Fixative RH-NB-2020 in its original, clearly labeled container in a cool, dry, well-ventilated, locked corrosive-storage cabinet. Keep containers tightly closed and upright with secondary containment. Segregate from bases, oxidizers, metals, and other incompatible materials. Protect from heat, sunlight, and freezing. Keep SDS and spill-control supplies accessible and follow local regulations. |
| Shelf Life | Concentrated Acid Fixative RH-NB-2020 shelf life is typically 12–24 months when kept sealed, cool, dry, and protected from light; confirm with the manufacturer’s label/SDS. |
On overflow softflow dyeing machines processing 40–60 denier nylon 6.6/elastane interlock panels, residual unfixed CI Acid Blue 113 migrates to adjacent white trims during ISO 105-C06:2010 method C2S laundering. The post-dyeing fixation sequence separates the dye bath from the fixation bath by a 10-minute cold rinse and a 5-minute buffer rinse at pH 5.5. RH-NB-2020 is pre-diluted to 10% active liquor and metered into a fresh bath at 2.0–3.0% o.w.f. Acetic acid/sodium acetate buffer holds the bath at pH 4.0–4.2. The machine liquor ratio is kept at 1:8–1:10. The bath is raised at 1.5°C/min to 70–75°C and held for 20 min. The anionic aromatic sulfonate condensate forms low-solubility complexes with unfixed acid dye molecules within the fibre interstices. The same complexes reduce wet-state dye migration through the surface boundary layer. At bath temperatures above 78°C, the complex can redissolve from the fibre surface and produce halo staining on elastane. At pH below 3.8, the condensate may precipitate in the liquor before it diffuses into the fibre. The exhausted bath is then dropped and the fabric is rinsed once at 40°C. Cationic softeners are not applied in the same bath. Cationic softeners form coagulated deposits with residual anionic fixative on pump and heat-exchanger surfaces. After drying at 120–130°C, the panels are tested to ISO 105-E04:2013 acidic and alkaline perspiration. Navy and black shades are accepted at grade 4 or higher on adjacent nylon and grade 3–4 or higher on wool. This is the controlling specification for activewear with white contrast panels.
A post-dyeing fixation bath is prepared on a beam dyeing machine at a liquor ratio of 1:10 for flat warp-knitted nylon 6 seat upholstery. The substrate has an amino end group content below 40 meq/kg. This low AEG reduces the number of protonated sites available for acid dye attachment and increases the pool of unfixed dye that can migrate under load. The fixation bath is set at pH 4.0 with acetic acid and a non-volatile acid donor. RH-NB-2020 is dosed at 3.0–4.0% o.w.f. for medium-depth shades dyed with 1:2 metal-complex acid dyes. The bath is heated from 40°C to 72°C at 1.0°C/min and held for 20–25 min. The low heating rate prevents unlevel fixation on tightly wound beams. Differential pressure across the beam is maintained at 0.5–0.8 bar during the fixation step. Dyehouse trials show that below 3.0% o.w.f. the adjacent nylon staining grade in ISO 105-C06:2010 method C2S drops below 4 for deep grey shades. At above 4.5% o.w.f. the same metal-complex dyeings lose 0.5 grade in ISO 105-B02:2014 method 2 light fastness. The fixation bath must not fall below pH 3.6. At lower pH, nylon 6 can retain acid and exhibit tensile strength loss after heat ageing. After fixation, the beam is rinsed at 50°C for 10 min. No alkaline after-scour is used. Alkaline conditions reverse the fixative–dye complex and increase cross-staining.
Package dyeing of 2/28 Nm wool/nylon blend yarn with CI Acid Black 172 leaves a surface-active dye fraction that reads as low wet fastness on AATCC TM61-2013 test 2A. After the dye bath is dropped, the packages are rinsed until the conductivity of the outflow is below 200 µS/cm. The fixation bath is prepared with 2.5% o.w.f. RH-NB-2020 and adjusted to pH 4.0–4.5 with acetic acid/sodium acetate. The package dyeing machine is run with inside-out flow during the first 5 min and outside-in flow for the remaining 15 min. Differential pressure is set at 0.4–0.7 bar. The bath temperature is raised to 75°C and held for 20 min. Fixation on wool at temperatures above 80°C increases the risk of yellowing on pastel shades and is not used. At pH above 5.0, fixation efficiency falls because the anionic condensate remains too water-soluble to deposit inside the fibre. At pH below 4.0, wool packages can show uneven acid adsorption. After fixation, the yarn is rinsed once at 40°C and then hydro-extracted. A final acid-donor softener may be applied only if it is non-cationic. The target for heavy black and navy hosiery yarn is grade 4 on adjacent wool and nylon in ISO 105-C06:2010 C2S. The fixation time is controlled to avoid exceeding 25 min to limit visible shade dulling on CI Acid Black 172.
On a continuous nylon 6.6 carpet line equipped with a Kuster fluid applicator and a horizontal steamer, the fixative is applied after the wash boxes rather than in the dye pad. Pre-dyed carpet enters the finishing section with a moisture content of 35–45%. RH-NB-2020 is metered into an applicator trough at 1.5–2.5 g/L of bath. The pH is adjusted to 4.2–4.5 with a non-foaming acid donor. Wet pickup is controlled at 60–70% by applicator pressure. The carpet then passes through a steam chamber at 98–102°C for 8–12 min. Saturated steam provides the heat for complex formation without disturbing pile definition. The finish bath must not exceed 2.5 g/L for cut-pile constructions. Higher concentrations produce a gummy deposit on the suction slot after the steamer and increase soiling tendency. The pH must not fall below 4.0. At lower pH, residual dye in the wet carpet can redeposit as a stain on the backing. The process is validated against ISO 105-E01:2013 water fastness and ISO 105-X12:2016 wet crocking. Target grades for medium-depth acid dyeings are 4 for water fastness colour change and 3–4 for wet crocking. Drying is then carried out at 135–145°C in a three-zone stenter. Published data for this exact configuration is limited. Plant trials are required to define lot-specific pH buffering and antifoam addition.
| Parameter | Test method | Reporting limit |
|---|---|---|
| Free formaldehyde | ISO 14184-1:2011 | < 16 mg/kg |
| APEO | ISO 18254-1:2016 | < 100 mg/kg |
| Chlorophenols | EN 17137:2018 | < 0.5 mg/kg |
| AOX in process effluent | ISO 9562:2004 | < 5 mg/L |
Rotary drum garment dyeing of silk habotai at a liquor ratio of 1:20 requires a lower fixation temperature than wool or nylon. After the acid dye bath is drained, the garments are rinsed at 25°C until the rinse water is visually clear. The fixation bath is set at pH 4.0–4.2 with acetic acid. RH-NB-2020 is added at 2.0% o.w.f. The bath is heated to 60–65°C and held for 15 min. The drum speed is kept at 12–15 rpm to avoid rope marks. At 65°C, silk fibroin is not hydrolysed, and the fixative–dye complex forms with minimal loss of lustre. The process is used for acid-dyed silk scarves and garment pieces that must pass ISO 105-E04:2013 perspiration testing with grade 4 colour change and grade 3–4 staining. Fixation dosage above 3.0% o.w.f. produces a detectable stiffening of the hand. Cationic softeners are not used after fixation. A non-ionic or amphoteric softener is used only at 0.5–1.0% o.w.f. if the garment requires additional surface slip. After fixation, the garments are cold-rinsed and tumble-dried at 50°C. The fixation step does not remove the need for a wet-fastness-improving afterwash for certain poorly fixed CI Acid Red 249 shades. In those cases, a second exhausted fixation at 55°C for 10 min is preferred over a higher initial dose.
For woven polyamide webbing used in industrial harness and load-securing applications, the fixation step is transferred from an exhaust bath to a pad–dry sequence. The dyed webbing is padded with a bath containing 20–30 g/L RH-NB-2020 and 0.5–1.0 g/L wetting agent. The bath pH is maintained at 4.0–4.5. Wet pickup is controlled at 40–60% with a vertical padder. Pickup below 40% produces uneven edge-to-centre fixation and fail results in ISO 105-X12:2016 wet crocking. Pickup above 60% causes surface film formation on the webbing edges. The padded webbing is dried in a hot-air stenter at 110–120°C for 2–3 min. The short dwell time at this temperature fixes the complex without excessive migration. Published data for high-tenacity nylon 66 webbing under this exact product code is limited. A plant trial is required to set pad pressure and trough concentration for each webbing weight. The target after drying is grade 4 or higher dry crocking and grade 3–4 wet crocking. The fixation bath should not be reused for more than 4 h because acrylic padder troughs accumulate precipitates from residual anionic auxiliaries.
Printed polyamide swimwear panels carry residual print thickener and unreacted dye after steaming and washing. The exhaust fixation step with RH-NB-2020 is run at 2.0% o.w.f. in a winch or softflow drum. The bath is set at pH 4.0–4.2 and preheated to 50°C before loading. The panels are moved for 10 min to allow the fixative to penetrate residual print paste interfaces. The bath is then raised to 68°C at 1.0°C/min and held for 15 min. The lower maximum temperature is selected because printed polyamide fabrics can contain localized dye concentrations that become surface-staining under high-humidity storage. The fixation bath reduces vapour-phase migration of unreacted acid dye from print areas to unprinted ground fabric. Panel samples are tested to ISO 105-E01:2013 water fastness and ISO 105-C06:2010 C2S. Grade 4 colour change and grade 3–4 staining are the minimum acceptance for multi-colour swimwear panels. Over-dosing above 3.0% o.w.f. alters the hand of lycra-containing panels and increases the risk of print area stiffness. The fixation bath is dropped immediately at the end of the hold. A cold rinse at 20°C follows. Warm rinsing above 40°C is avoided because it can reopen the heat-set polyamide structure and release bound dye.
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Concentrated Acid Fixative RH-NB-2020 is supplied as a concentrated aqueous liquid. The model designation RH-NB-2020 identifies a specific acid-donor preparation for exhaust and continuous dyeing of polyamide, wool, and polyamide/elastane blends with acid dyes, metal-complex dyes, and selected reactive dyes. Specification categories to be confirmed from the batch certificate include appearance, ionic character, density at 20 °C, pH of a 10 g/L dilution, dilution stability in soft water at 50 °C, and low-shear viscosity. Published numerical limits for this specific configuration are limited and are not reproduced here. The product releases acid progressively as the dyeing temperature increases, shifting the initial bath pH from a weakly neutral start range of pH 6.5–7.0 toward a fixation plateau of pH 4.0–4.5. This controlled pH shift distinguishes it from direct additions of acetic or formic acid, which can overshoot the target pH in high-temperature jet machines. In contrast to cationic aftertreatment fixing agents, RH-NB-2020 is applied during the dyeing phase as a pH-control and exhaustion aid rather than as a post-dyeing surface treatment.
In acid dyeing, the fibre develops protonated amino groups at low pH, and dye anions are attracted to these sites. The acid donor does not directly bond dye to fibre; it supplies protons required to generate dye-fibre ionic interaction and to convert some acid dyes to their exhaustible state. The advantage of a buffered donor over a strong acid is the reduction in acid shock at the fibre surface. Published data for this specific formulation is limited, but the pH trajectory is the main process variable controlling final exhaustion and fixation ratio.
Incoming quality control for this product class commonly includes pH measurement on a 10 g/L aqueous dilution according to ISO 4316:1977 and density at 20 °C according to ISO 758:1976. Because numerical specification limits for RH-NB-2020 are not publicly available, acceptance criteria should be fixed from the supplier certificate of analysis and validated against plant compatibility trials. The product is intended for use in soft water with total hardness below 150 mg/L as CaCO₃; hard-water cations can reduce clarity and buffer capacity. It should not be premixed with concentrated anionic levelling agents or cationic softeners in the same dosing line, because localised ionic incompatibility can cause coagulation in the dosing manifold. Storage should follow the current Safety Data Sheet and REACH Regulation (EC) No 1907/2006 Article 31 provisions.
Dosage determination for RH-NB-2020 is not a fixed weight-per-litre parameter; it is driven by initial water alkalinity, fibre amine end-group content, and depth of shade. For textile-grade nylon 6.6, amine end-group content typically lies between 30 and 45 meq/kg, and the dyebath pH response is therefore affected by fibre buffering. Published data for this specific configuration is limited. A pH-return titration on a blank dyebath at 98 °C is used to establish the required acid donor volume before production dyeings.
Production-scale overflow jet equipment operating at liquor ratios from 1:8 to 1:15 has been used to evaluate acid-donor behaviour in nylon 6.6 exhaust dyeing. Bath samples are typically taken at 10 °C intervals during a ramp from 40 °C to 98 °C. A slow ramp of 1 °C/min permits gradual acid release, while ramp rates above 2 °C/min can compress acid generation into the upper hold stage and produce a pH undershoot below pH 3.5. Under those conditions, nylon 6.6 may exhibit increased dye strike at the liquor inlet, causing axial shading on jet machines operating with high circulation pressure. The final hold at 98 °C for 30–45 min is the usual fixation window for high-wet-fastness nylon automotive and sportswear textiles; pH should be verified with a calibrated electrode system according to ISO 4316:1977 before unloading.
Acid release kinetics in ester-based acid donors are temperature-dependent; a 10 °C rise can double the hydrolysis rate. This explains why ramp rates above 2 °C/min are risk factors for pH undershoot. Heat-up and cool-down profiles should be recorded with the machine PLC to ensure that the rate of pH change does not exceed the fibre’s dye uptake rate at the critical migration zone between 70 °C and 85 °C. That zone is where acid dyes redistribute from water to the fibre surface; rapid pH drop in this window can produce permanent skittery dyeing on taffeta and warp knits.
Dosing RH-NB-2020 after full wetting and dye migration is critical. When the acid donor is charged too early, batch-to-batch pH drift of ±0.2 units has been observed across multiple jet loads, causing tailing in pale tertiary shades. The product should be pre-diluted with soft water before addition to the circulation side; direct injection into the dyestuff dosing leg can produce transient low-pH zones and package filtration marks. Published data for this specific configuration is limited, so the dosing point and ramp profile should be confirmed in a side-by-side trial against the incumbent acid donor.
Depending on the donor chemistry, hydrolysis may release low-molecular-weight organic acids or alcohols into the dyebath. These by-products can influence dye solubility, foaming, and effluent chemical oxygen demand. Published data for RH-NB-2020 is limited; therefore, the Safety Data Sheet and wastewater permit limits must be checked before changeover. The product is not intended for use in closed-loop dyebath reuse systems without verification of accumulating by-products.
On continuous pad-steam lines processing wool/polyamide flat goods, RH-NB-2020 is metered into the pad trough at a pick-up of 60–80%. Accurate flow control is required to avoid concentration drift during selvedge-to-centre dye migration. Plant comparisons against acetic acid at equal final bath pH use reflectance spectrophotometer readings at the same wavelength of maximum absorption to quantify shade depth and side-to-centre variability. Published data for this specific configuration is limited; the acid donor is therefore evaluated for pad-bath stability and tailing rather than by absolute specification values. A single mixing constraint applies: dilute with soft water before injection into the pad trough.
Metering systems for RH-NB-2020 should use positive-displacement pumps with stroke frequency controlled by line speed. A feed accuracy of ±2% of set point is a reasonable acceptance criterion for pad trough pH stability; this is based on general chemical dosing practice rather than on product-specific data. The pH of the pad trough is measured with an in-line electrode calibrated against ISO 4316:1977 and maintained within ±0.1 units of the target final pH. Failure to maintain this band can cause selvedge-to-centre colour variation on wide goods above 1800 mm working width.
For pad-bath stability, the acid donor is tested by measuring pH and dye absorbance immediately after mixing and after 2 h at 25 °C. A stable pad bath should show no visible precipitation and no significant change in absorbance at the dye’s λmax. Published data for this specific formulation is limited, so plant compatibility trials are required with the full pad-bath recipe, including anti-migrant and wetting agents.
| Parameter | Standard method |
|---|---|
| Colour fastness to domestic and commercial laundering | ISO 105-C06:2010 |
| Colour fastness to water | ISO 105-E01:2013 |
| Colour fastness to rubbing | ISO 105-X12:2016 |
| Aqueous extract pH | ISO 3071:2005 |
| pH of aqueous dilution | ISO 4316:1977 |
| Density at 20 °C | ISO 758:1976 |
Incompatibility boundaries for RH-NB-2020 are derived from process observation rather than from published formulation data. The product should be kept separate from strong alkalis, concentrated anionic levelling agents, and cationic polymer aftertreatments unless separated by a full drain and rinse. Avoid combination with amine-based additives because alkaline pH can consume the acid donor and reduce fixation efficiency. When changing from a conventional acetic acid donor, a pre-production trial is necessary because the buffering components in RH-NB-2020 may alter the shape of the exhaustion curve and the final dyebath pH.
Evaluation of acid-donor performance in dyehouses is based on multi-fibre adjacent staining and shade change rather than on absolute product specifications. Test panels are exposed to a liquid detergent solution under steel-ball action according to ISO 105-C06:2010 condition A1S, which uses 40 °C wash temperature, 150 mL wash liquor, 10 steel balls, and 30 min mechanical action. Staining on multi-fibre adjacent fabric conforming to ISO 105-F10:1989 is rated against the grey scale in ISO 105-A05:1996, and shade change is reported with AATCC Evaluation Procedure 1. Published data for RH-NB-2020 in this specific configuration is limited, so comparisons against a formic acid control at equal final pH are used. In such controlled comparisons, the acid donor is expected to produce a measurable reduction in staining of polyamide and wool adjacent fibres only when the reference acid addition causes pH undershoot and non-bound dye surface deposition.
Specimens are conditioned at 21 °C and 65% relative humidity for at least 4 h according to ASTM D1776-20 before testing. Water fastness is performed at 37 °C for 4 h under a load of 12.5 kPa according to ISO 105-E01:2013, and adjacent fibre staining is rated against ISO 105-A03:2019. Rubbing fastness under ISO 105-X12:2016 applies a 9 N vertical force on a cotton rubbing cloth over 10 cycles. Colour data are collected with a reflectance spectrophotometer using D65 illuminant and 10° observer geometry; the CIELAB colour difference is computed to reduce visual grading variability.
Unlike cationic fixing agents, RH-NB-2020 does not form a polymeric surface barrier on the dyed fibre. Its contribution to wet fastness arises from improved dye exhaustion and fixation during the dyeing stage. This can be checked by residual dyebath absorbance measurements and by subsequent water fastness testing under ISO 105-E01:2013. In high-liquor package dyeing with cross-wound packages, residual acid donor in the package centre can shift wash-off pH; a post-fixation rinse at 60 °C for 10 min is commonly used to restore neutral extraction conditions before subsequent finishing.
In package dyeing machines with cross-wound packages, differential pressure across the package column is a process parameter that can be disturbed by localised pH gradients. The acid donor is therefore introduced through the flow-reversal side after full yarn wet-out. A pH drop over at least 20 min is recommended to reduce radial shade variation. Batch records show that package filtration marks are more likely when the donor is injected directly into the main circulation pump suction without pre-dilution.
In continuous space dyeing of polyamide carpet yarn, steam hoods and dye applicators can contain volatile acid vapours when acetic or formic acid is used. RH-NB-2020 is positioned as a concentrated acid donor with lower vapour pressure than acetic acid, although quantitative vapour pressure data for this specific product is limited. Plant audits record odour exposure and steam hood corrosion against baseline acetic acid operation. The donor is metered with a piston pump into the dye solution; the dosing rate is established by pH measurement and is not reproduced here because the required concentration varies with dye depth, water alkalinity, and line speed.
In high-speed space dyeing, line speed can exceed 400 m/min, and residence time in the steam chamber may be less than 120 s. Under these short dwell conditions, acid release must occur rapidly enough to achieve fixation before the yarn enters the wash box. A buffered acid donor that releases too slowly may leave unfixed dye at the first rinse. Published data for RH-NB-2020 under these conditions is limited; a laboratory steamer trial with a residence-time gradient is required to verify fixation efficiency.
Operational boundaries include storage above 5 °C and below 40 °C unless otherwise specified by the current Safety Data Sheet. The product should not be diluted in hard water exceeding 150 mg/L total hardness as CaCO₃. In changing from ammonium sulfate, effluent sulfate load may be reduced, but the buffering salts in RH-NB-2020 can influence the ion-exchange profile of the dyed substrate; a plant-scale trial under ISO 3071:2005 aqueous extract pH measurement is required before bulk replacement.
For textile mills bound by ZDHC or bluesign chemical input management, the supplier’s certification status for RH-NB-2020 must be verified before process registration. The absence of published formulation data does not imply the presence or absence of restricted substances; a current ZDHC MRSL Level 1 certificate is the appropriate documentary control. Verification is performed against the latest ZDHC Manufacturing Restricted Substances List, not against legacy test reports.
Compared with ammonium sulfate, RH-NB-2020 is a liquid acid donor that allows direct volumetric dosing. Compared with acetic acid, it is less volatile in steamers and reduces pH overshoot. Compared with cationic fixing agents, it does not alter fabric handle or affect light fastness through surface deposition. These distinctions are process-relevant, but published data for this specific formulation is limited; bench-scale comparisons to the incumbent auxiliary are required before bulk replacement.
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