General Type Chelating Disperse Agent RH-NB-2306

General Type Chelating Disperse Agent RH-NB-2306 is an aqueous anionic/nonionic polymeric preparation formulated for simultaneous hardness-ion chelation and colloidal dispersion in textile wet processing. The model designation RH-NB-2306 identifies a production concentration range, not a single diluted batch: active polymer content is specified as 25–30 wt% by ISO 2271 two-phase titration, and the delivered pH is 7.0–9.0 in 1% aqueous solution by ISO 4316. The preparation is miscible in deionized water at 20–60 °C and exhibits a low-foam profile that permits dosing in closed high-turbulence circulation systems such as package dyeing machines and jet dyeing machines. Its functional difference from conventional single-purpose chemicals is the combination of a carboxylate-sulfonate polymeric dispersant with a chelating segment that retains surface activity after metal saturation; separate EDTA or sodium polyacrylate additions do not provide this coupled behavior without compatibility testing.

Why Is the Chelation–Dispersion Combination Critical in Hard-Water Disperse Dyeing?

Calcium and magnesium cations introduced by hard water reduce the repulsive barrier between disperse dye particles. In a package dyeing machine with liquor flow rates of 30–40 L/kg/min, the shear forces generated by the main pump can produce localized particle collisions. If hardness cations exceed 150 mg/L as CaCO₃, dye aggregates may form and deposit on yarn layers. RH-NB-2306 is charged into the bath before dye addition and alkali adjustment; its calcium binding capacity is normally 80–120 mg CaCO₃/g when titrated against 0.1 mol/L calcium chloride at pH 10 using Eriochrome Black T. The residual polymeric dispersion function remains measurable after the chelating sites are saturated, which is not observed with monomeric aminopolycarboxylate chelators such as EDTA-4Na. Iron and copper ions are also sequestered; Fe³⁺ at 2–5 mg/L in caustic scouring baths can catalytically decompose peroxide and produce fabric pin-holes, so sufficient product must be present before alkali addition. The product maintains Fe³⁺ solubility at pH 10–11 under typical continuous bleaching conditions.

Production batches are released against the following physical specification; the methods are the same as those referenced on batch certificates of analysis and are suitable for incoming inspection at a dyehouse laboratory.

When Calcium Carbonate Precipitation Potential Exceeds 300 mg/L in Continuous Pad Baths

High-hardness water supplies containing calcium and magnesium chlorides can produce calcium carbonate precipitation potential above 300 mg/L when alkalinity is introduced into a continuous pad bath. In a pad trough of 50 L working volume running fabric at 40 m/min, evaporation and alkali carryover gradually concentrate inorganic ions. The product is metered into the saturator before sodium hydroxide and hydrogen peroxide addition at 0.5–1.5 g/L. If the product is added after alkali, localized precipitates of calcium carbonate and magnesium hydroxide can form within seconds and deposit on pad rolls, causing fabric creasing and uneven wet pick-up. The chelating function acts rapidly enough to hold hardness ions in soluble form during the transition from neutral to alkaline pH; the dispersing function then prevents insoluble reaction products from agglomerating if local hardness exceeds the chelation stoichiometric limit. At pH 10.5 and 60 °C, the product remains clear and does not form the calcium chelate sludges sometimes seen with lower-solubility phosphonate-only agents.

In package dyeing of polyester yarn on random-wound packages with density 0.35–0.42 g/cm³, liquor flow is routinely reversed at 2–3 min intervals to reduce channeling. The main circulation pump may generate pressure differentials of 0.5–1.2 bar across the column. Under these conditions, dye bath additives that foam or produce insoluble flocs cause differential pressure rise and non-uniform dye penetration. RH-NB-2306 at 0.5–1.0 g/L is added before the dispersed dye; after 10 min circulation at 80 °C, alkali is dosed. In a 100 kg yarn carrier with 1,500 L total liquor, the product addition is 0.75–1.50 kg per batch, with pre-dilution in 50 L water. The low-foam characteristic is critical because air entrainment in the pump can reduce flow rate below the 30 L/kg/min threshold and cause shade variation between inner and outer package layers.

Chelation Capacity, Salt Tolerance, and Comparative Behavior Against Aminopolycarboxylates

Compared with EDTA-4Na, RH-NB-2306 shows lower stoichiometric calcium-binding per gram of active solids in standard complexometric titration, because the product contains a polymeric dispersant fraction as well as chelating sites. EDTA-4Na may bind 150–200 mg CaCO₃/g as pure tetrasodium salt, but it does not contribute residual dispersancy after saturation. Sodium polyacrylate dispersants used in boilers and water treatment provide dispersion but negligible chelation of soluble hardness cations at textile processing concentrations. Naphthalene sulfonate condensates reduce dye particle aggregation but are more foam-prone and can increase liquor turbidity when hard water cations exceed 200 mg/L. RH-NB-2306 is formulated to remain clear in electrolyte solutions containing 40 g/L sodium sulfate and 10 g/L sodium carbonate at 25 °C; conventional polycarboxylate thickeners or dispersants may salt out under these conditions. The product’s foam height by ISO 696 at 50 °C is ≤10 mm after 5 min, whereas many anionic surfactants produce 50–150 mm under the same test, making RH-NB-2306 suitable for closed jet machines and high-shear pumps where foam causes pump cavitation and fabric rope flotation.

Published data for this specific product in full-scale production dyehouses is limited; the comparative values are class-typical laboratory evaluations under controlled dye bath conditions, not batch certification results. In high-temperature disperse dyeing, the operational difference is most evident when hardness ions and disperse dye oligomers are present simultaneously. EDTA controls hardness but leaves oligomer agglomerates unmodified. Naphthalene sulfonate condensates disperse oligomers but do not prevent calcium bridging on dye particle surfaces. RH-NB-2306 addresses both mechanisms, but its dosage must be raised above the stoichiometric hardness demand before additional dispersing action becomes detectable by filtration tests.

Operational limitations are defined by ion compatibility and storage. The product should not be mixed directly with concentrated mineral acids because the resulting pH shock can protonate carboxylate groups and reduce chelation performance. Avoid combination with benzalkonium chloride-based cationic antistats or strong cationic dye-fixing agents in the same bath; coacervation may occur at pH 7–9. Do not use with oxidizing agents before dilution: concentrated hydrogen peroxide in contact with the undiluted product can generate localized heat. Pre-dilution is required whenever the storage temperature falls below 5 °C because viscosity increases and metering accuracy declines. For long-term storage above 40 °C, polymer hydrolysis may reduce active content to below 25 wt% within 6 months; storage below 30 °C in closed HDPE or stainless steel vessels is recommended. The product is not recommended for continuous dyeing of polyamide with acid dyes where strong anionic auxiliary may alter strike rates; compatibility tests with a 10 g/L stock solution and the target dye mixture are required before scale-up.