Dispersant NNO (sodium naphthalene sulfonate formaldehyde condensate) is an anionic condensation-product dispersant used in selected dye-manufacturing and dyeing processes. Its job is to help prepare and keep a workable dispersion of sparingly soluble dye particles. On its own it does not guarantee shade uniformity, penetration or colour fastness. Those outcomes also depend on the dye, fibre, auxiliaries, water quality and process profile.
For current grades see Dispersant NNO. This guide explains how NNO works, what published research shows, how to read the grade data and how to screen it for dye applications. It does not treat any generic dosage or temperature as a production specification. Pigment formulators should use the separate NNO aqueous pigment dispersion guide.
How NNO stabilizes dye particles
NNO is a polymeric naphthalene sulfonate. Its aromatic segments adsorb onto hydrophobic dye surfaces, and its sulfonate groups face the water. Two effects follow:
- Electrostatic repulsion: the adsorbed layer gives particles a negative surface charge, so they repel one another.
- Steric and hydration barrier: the adsorbed polymer and its bound water physically hinder particles from approaching.
Because the stabilization is largely electrostatic, it is sensitive to electrolytes. Hardness ions (Ca2+, Mg2+) and high salt loads compress the charge layer, and cationic auxiliaries can neutralize it. That is why water quality and the full auxiliary package must be part of any trial. NNO is a dispersant, not a primary wetting agent. Wetting, particle stabilization, levelling and fibre affinity are different functions and may need different auxiliaries.
What published research shows
| Study | System | Reported result | How to read it |
|---|---|---|---|
| Chen, Pei, Shi, Yi & Wang (2023), Polymers 15(4):1046, doi:10.3390/polym15041046 | Polyester dyed with C.I. Disperse Red 177 in a silicone (non-aqueous) dyeing system, comparing dispersant NNO and dispersant MF | With NNO at 1.2%, dye exhaustion rose to 94.18% and K/S to 14.73. MF at 1.2% reduced exhaustion from 90.73% to 82.61%. More NNO lowered the dye’s solubility in silicone, and exhaustion was inversely proportional to that solubility. Uptake was similar to a conventional water bath (93.81%). Wash and rub fastness were grade 4 to 4–5 and light fastness 3–4, unchanged by the dispersant. | The mechanism here is specific to a silicone medium: a more hydrophilic dispersant pushes dye out of the solvent and onto the fibre. The figures apply to that dye, fibre and system only. They are not a dosage for water-based dyeing. |
The study also shows that two closely related naphthalene-sulfonate dispersants (NNO and MF) can move the result in opposite directions in the same system. Grade and chemistry must therefore be qualified in the actual process, not inferred from the product class.
Grade data
Green Agrochem’s current NNO technical data sheets give the following typical values. The TDS values are typical production results; the shipment COA reports batch results.
| Parameter | GAC-NNO-A (Grade A) | GAC-NNO-B (Grade B) | GAC-NNO-C (Grade C) | GAC-NNO-HP (High-Purity) |
|---|---|---|---|---|
| Appearance | Brown powder | Brown powder | Brown powder | Powder |
| Content / solids | Content 95% min | Content 92% min | Content 95% min | Solid content 93% min |
| Dispersing power (vs standard) | 95% min | 90% min | 95% min | Not stated |
| Sodium sulphate | 5% max | 18% max | 22% max | SO4 around 3.0% |
| pH | 7–9 (1% solution) | 7–9 (1% solution) | 7–9 (1% solution) | 7.0–9.0 (2% solution) |
| Calcium & magnesium | 0.4% max | 0.4% max | 0.4% max | Not stated |
| Water-insoluble matter | 0.05% | 0.05% | 0.05% | Not stated |
| Free naphthalene / formaldehyde / quinoline | Not stated | Not stated | Not stated | < 5 ppm / < 50 ppm / < 200 ppm |
For dye work, two parameters matter most. Sodium sulphate (5% max in Grade A, up to 22% max in Grade C) is filler and electrolyte: it lowers active content and adds salt to the bath, which can affect dispersion stability and standardization. Dispersing power is measured against a standard product, so ask for the method before comparing suppliers. The High-Purity TDS gives a 2–5% addition range on total dry solids for pigment and dyestuff dispersion. That is a supplier starting trial range for that grade, not a dye-bath g/L figure.
Where NNO can be evaluated
NNO may be screened during dye grinding, standardization or dye-bath preparation where particle dispersion is a defined requirement. The trial must name the dye class and process. A result with one disperse dye, vat dye or pigment preparation does not transfer automatically to another colour index, fibre or machine.
- Grinding: milling time, particle-size distribution, filtration residue, viscosity, colour strength and storage stability.
- Dye bath: dispersion stability through the temperature cycle, filtration, deposits, specking, shade reproducibility and compatibility with the full auxiliary package.
Process variables that influence performance
- Dye surface and particle size: adsorption and workable addition level change with surface area and surface treatment.
- Water quality: record hardness and electrolytes rather than assuming universal hard-water tolerance.
- pH and temperature: test the real profile, including heating, holding and cooling.
- Solids loading and shear: laboratory and production equipment give different dispersion histories.
- Addition sequence: pre-dissolution, point of addition and mixing time can change the result.
- Other auxiliaries: wetting agents, levelling agents, carriers, salts, defoamers and cationic components need compatibility testing.
Screening procedure
- Confirm product identity, batch, TDS/SDS revision and a representative COA.
- Run the currently approved dispersant as a control under identical conditions.
- Bracket the supplier’s recommended trial range around the control; do not adopt a universal online dosage.
- Record dye, fibre, liquor ratio, pH, water hardness, temperature curve, shear and addition sequence.
- Evaluate the agreed dispersion and shade endpoints, including filtration or deposit tests used by the plant.
- Confirm the result in a controlled pilot before changing the production recipe.
Silk and silk/wool systems
Silk is a protein fibre. The NNO TDS notes an affinity for protein and polyamide fibres, which makes silk and wool behaviour a specific point to test rather than assume. A dispersant qualified for polyester cannot be moved directly into a silk process. Identify the silk construction, any wool or synthetic component, the dye class, target shade, bath pH and temperature profile, and treat NNO as a particle-dispersion aid only. It should not be assumed to give levelling, fibre protection or selective dye blocking.
For blends, check each fibre separately as well as the finished fabric: bath clarity and filtration residue, deposits or specks, shade on each fibre, tone change, levelness, handle and the required fastness tests. Where selective coloration is intended, confirm that the complete dye and auxiliary package produces the differential uptake.
High-temperature processing
A single temperature number is not evidence of process stability. Qualification should define the dye, concentration, pH, time at temperature, heating rate and evaluation method. Ask whether a quoted thermal-stability rating is a chemical assay, a dispersion grade or an application-specific result.
Figures in older content and their status
| Figure | Status |
|---|---|
| 0.5–1.5 g/L (disperse/polyester), 1–3 g/L (vat/acid), 2–5 g/L (naphthol), 0.5–5 g/L (general), 15–20 g/L (reducing bath), “0.5–2% of dye-bath weight” | No exact grade, basis, liquor ratio or process was identified. Not current recommendations. |
| Stable above 130 °C | A process example without dye, time, pH or method; not evidence of stability. |
| 94% exhaustion at about 1.2% NNO | Verified, but only for Disperse Red 177 on polyester in a silicone waterless system (Chen et al., 2023). Not a water-bath result. |
| Fixed molecular formula for the commercial condensate | A condensation polymer is not defined by one catalogue formula; use the supplier’s SDS identity. |
| Universally stable to acid, alkali, salts and hard water; non-foaming; non-toxic | Unsupported as universal statements; test the actual system and use the current SDS. |
Incoming quality, safety and wastewater
Once a grade is approved, set incoming limits that can be measured consistently, such as appearance, solids or content basis, pH, sodium sulphate and water-insoluble matter, with methods. Keep retained samples and ask for notification of material or process changes. Follow the current SDS and site hygiene controls. Dye-house wastewater management depends on the whole chemical load and local discharge rules, not on the dispersant alone. Where residual monomers matter, the High-Purity grade specifies free naphthalene, free formaldehyde and quinoline limits.
Request a sample
Send the dye class, process, current benchmark, test method, estimated quantity, packaging and destination to info@greenagrochem.com. Related reading: NNO in aqueous pigment dispersions, dispersant MF in textile auxiliaries.