Hydrophilic Liquid Soft Flake RHQ

Hydrophilic Liquid Soft Flake RHQ is supplied as an off-white to pale-yellow flake with a fully quaternized fatty acid amidoamine backbone and hydroxyethyl substituents. The product is not a ready-to-use liquid at ambient temperature; the liquid designation refers to the molten state obtained at 55–65 °C, at which point viscosity drops to 80–150 mPa·s at 60 °C as measured with a Brookfield LV spindle 2 at 60 rpm. The certificate of analysis identifies model RHQ with an active content not less than 98.0%, moisture not more than 1.5%, and pH 4.5–6.0 in a 5% aqueous dispersion at 25 °C according to ISO 4316:1977. The product is classified as weak cationic; its solubility in cold water is limited, and stock dispersions are normally prepared at 55–65 °C under low-shear agitation. Published independent data for this specific configuration are limited, and the values cited here reflect the supplier’s technical dossier and should be verified against the lot certificate before production use.

The supplier reports a hydrophilic-lipophilic balance of 13.5–14.5 calculated from the hydrophilic moiety molecular weight. The long-chain content is predominantly C16–C18 saturated, with unsaturation below 2.0% iodine value to limit oxidative yellowing. Differential scanning calorimetry at 10 K/min gives a melting range of 48–58 °C and a melt enthalpy of 120–140 J/g. The molten product exhibits near-Newtonian behaviour between 10 s^-1 and 100 s^-1; dynamic viscosity is 250–350 mPa·s at 55 °C, 80–150 mPa·s at 60 °C, and 60–90 mPa·s at 65 °C. These rheological values are useful for specifying heated transfer lines and gear pumps in bulk handling, but they do not describe the aqueous dispersion viscosity.

What limits dispersion stability below liquor ratio 1:5?

In high-shear jet dyeing and low-liquor-ratio exhaust equipment, dispersion stability of RHQ is controlled by temperature, pH, and electrolyte load. Laboratory dispersion tests using an overhead stirrer at 400 rpm show that a 10% stock dispersion prepared at 60 °C remains single-phase for 24 h at 25 °C when pH is adjusted to 5.5 with acetic acid. At pH above 7.5, ester cleavage accelerates; titratable active content by two-phase titration according to ISO 2871:2017 decreases by 12–18% after 60 min at 60 °C. Hydrolysis follows pseudo-first-order behaviour in the pH range 7.0–8.5; the observed rate constant at 60 °C is approximately 0.002–0.004 min^-1 at pH 7.5 and 0.010–0.015 min^-1 at pH 8.5. A 60 min residence at pH 8.5 can therefore reduce titratable active content by 45–60%. Below liquor ratio 1:5, sodium sulfate concentrations above 2.0 g/L compress the electrical double layer and cause visible agglomeration. Published production data for this specific configuration are limited; pilot-scale trials in a soft-flow machine with 1:4 liquor ratio are therefore required before bulk adoption.

Pre-drying of the flake is necessary when warehouse relative humidity exceeds 60%. In an unheated bulk warehouse at 28 °C and 75% relative humidity, moisture uptake of 1.2% was observed within 6 h in opened bags, leading to bridging in loss-in-weight screw feeders and inconsistent gravimetric dosing. A desiccant dehumidifier maintaining 25–30% relative humidity at the feed hopper is recommended. The product should be stored in sealed 25 kg polyethylene-lined paper bags or 500 kg FIBCs at 5–35 °C; storage below 5 °C does not damage the chemistry but increases flake fracture and dust formation during conveying. Bulk silos should be stainless steel 316L or coated mild steel; contact with copper alloys should be avoided because trace copper accelerates oxidative yellowing during subsequent heat setting.

Specification boundaries for RHQ and the supplier’s certificate of analysis

Table 1 lists the production control parameters used for lot release. The values are nominal and must not be interpreted as guarantees for every batch without reviewing the lot-specific certificate. Moisture content is measured by Karl Fischer titration because the flake is not fully soluble in cold methanol; the method follows ISO 760:1978. Apparent bulk density is reported using a 100 mL cylinder method aligned with the supplier’s internal procedure SM-104, as no single ISO method is fully representative of flake geometry.

For textile applications, a stock solution is prepared by adding molten or flake RHQ to water at 60 °C under agitation; direct addition of cold flakes into a bath below 40 °C produces gels that are difficult to disperse. In pad applications on cotton knit fabric, typical working concentrations are 10–30 g/L with 0.5–1.0 g/L acetic acid to maintain bath pH at 5.0–5.8. Exhaust application on cotton or polyester-cotton uses 2.0–6.0% on weight of fabric at 40–50 °C for 20 min; lower temperatures reduce exhaustion, while higher temperatures can increase softness but may also increase yellowing on white goods after drying at 150–170 °C. Exhaustion kinetics in a laboratory Ahiba IR dyeing machine at 40 °C show 85–90% substantivity onto bleached cotton knit within 10 min at a 1:10 liquor ratio. When electrolyte concentration exceeds 2.0 g/L sodium sulfate, exhaustion falls to 70–75% due to charge screening, and the bath should be set with softened water or a nonionic dispersing agent. On polyester, the product exhausts less completely; published data for this specific configuration are limited, and a separate wetting agent is normally required to obtain an even film.

On a production padder running at 25 m/min with a 70% wet pickup, a 20 g/L RHQ finish produced no visible roll build-up over an 8 h shift when bath pH was held at 5.5. At pH 6.5, deposit accumulation on the nip rollers increased and required a water cleanup stop at approximately 6 h. Foam generation in the trough was controlled below 50 mL in a 500 mL graduated cylinder by adding 0.01 g/L of a silicone-free defoamer; excessive defoamer reduced fabric rewetting. These observations are from a standard two-roll vertical padder with 5 mm rubber hardness 70 Shore A and are reproducible, but they are not a substitute for site-specific process validation.

When RHQ replaces amino-functional silicone microemulsion in cotton-polyester finishing

The primary difference between RHQ and amino-functional silicone microemulsions is the balance between hydrophilicity and surface smoothness. Silicone microemulsions deposit a highly flexible siloxane film that reduces fibre-fibre friction and produces a slick, elastic handle; RHQ instead adsorbs via electrostatic interaction with negatively charged cotton and hydrophobic interaction with polyester, leaving a thinner, less occlusive layer. The resulting fabric retains higher moisture transit. In a comparative trial on 65/35 polyester/cotton poplin, fabric finished with 20 g/L RHQ and dried at 150 °C for 3 min showed a drop absorbency below 5 s after one wash under AATCC 79, compared with 30–60 s for a conventional ditallow dimethyl ammonium chloride softener at equal active solids. The silicone microemulsion produced the lowest friction coefficient but reduced vertical wicking height by approximately 40% relative to the RHQ-treated fabric after 5 min in distilled water. Table 2 summarizes these directional performance differences.

The data in Table 2 are representative values from a single supplier trial using equal active solids at 20 g/L; they are not normalized for differences in molecular weight or film thickness. Independent published data for this specific configuration are limited, and therefore the values should be used for screening rather than final specification setting. In blends with high polyester content, the differences in moisture regain are smaller because the substrate itself is hydrophobic; in 100% cotton, the advantage of RHQ over conventional quaternary ammonium softeners is more pronounced. After five home laundering cycles according to AATCC 135, drop absorbency remained below 8 s for RHQ-treated cotton interlock, while the ditallow quaternary ammonium control exceeded 30 s.

Do not store above 30°C or combine with anionic fixatives

The product’s operational boundaries are defined by thermal stability and charge incompatibility. Prolonged storage above 30 °C can soften the flakes and promote inter-particle adhesion, causing clumping in the bag and non-uniform feed from auger metering systems. Short-term exposure up to 40 °C for 24 h does not immediately reduce active content, but caking increases. At temperatures above 70 °C, molten RHQ undergoes progressive hydrolysis of ester groups; after 4 h at 80 °C, the aqueous dispersion pH falls by 0.4–0.8 units, indicating acid release, and the product’s rewetting performance deteriorates. Anionic additives, such as naphthalene sulfonate dye-fixing agents, anionic wetting agents, or sulfonated fluorescent whitening agents, must not be added directly to the same bath without a nonionic colloid stabilizer. Complex coacervation occurs at charge ratios below approximately 0.85, visible as a greasy precipitate that deposits on fabric edges and dryer cylinders. If an anionic agent is unavoidable, a pre-mixed nonionic emulsifier at 1–2 g/L can temporarily reduce precipitation, but robust compatibility tests under actual bath conditions are required before production use.

On continuous ranges with closed-loop water recycling, residual anionic dyes and electrolytes concentrate in the process water. The product shows acceptable dispersion stability in water hardness up to 200 ppm CaCO₃ according to DIN 38409-6. Above 250 ppm CaCO₃, turbidity increases and the dispersion may form a ring at the liquid surface after standing for 30 min. Chelating agents such as sodium tripolyphosphate at 0.5–1.0 g/L mitigate hard-water effects but may alter the ionic balance and should be evaluated for exhaustion yield. On optically brightened cotton poplin, thermal yellowing after 150 °C/30 min is generally lower than ditallow quaternary ammonium controls because RHQ contains fewer amine or amide chromophores. Lightfastness ratings under ISO 105-B02:2014 are typically unchanged when RHQ is applied at 20 g/L; discoloration arises mainly from residual metal catalysts or from interaction with phenolic antioxidants in polyester, not from the softener itself. For critical white goods, a plant trial with the exact fluorescent whitening agent and resin finish is necessary.