SLES 50% Industrial Grade

CAS 9004-82-4, designated SLES-50-IND in the manufacturer’s industrial surfactant range, is a 50% aqueous sodium laureth sulfate with a nominal ethoxylation degree of 2.0. The product is neutralized with sodium hydroxide and appears as a clear to slightly hazy, pale-yellow liquid at 25°C. Its anionic active matter, determined by two-phase titration in accordance with ISO 2271, is controlled within 48.0–52.0 wt%. The residual unsulfated alcohol content is maintained below 1.2 wt%, sodium sulfate below 1.0 wt%, and sodium chloride below 0.3 wt% to limit viscosity drift in downstream formulations. The product is intended for industrial detergents, emulsifier packages, fire-fighting foam intermediates, textile wetting baths, and hard-surface cleaning compounds where a pumpable anionic feed with intermediate water content is required. Because the material is an ethoxylated alcohol sulfate rather than a simple alkyl sulfate, it carries 2.0 mol of ethylene oxide per mole of fatty alcohol on average; this structural feature lowers the Krafft point below 0°C and reduces precipitation in hard water relative to sodium lauryl sulfate. The as-supplied pH at 10% aqueous dilution is controlled between 6.8 and 8.8 according to ISO 4316, and the color is held at or below 30 Hazen units by ISO 6271 to avoid tinting in light-colored formulations. This industrial grade is not a personal-care-grade material. The residual 1,4-dioxane ceiling is set at 30 mg/kg by purge-and-trap GC-MS using EPA 8260D. That control limit is suitable for industrial detergent compounding but is not automatically compatible with the tighter cosmetic-grade impurity limits commonly required in the European Union under Regulation (EC) No 1223/2009. Formulators transferring the product into consumer rinse-off goods must perform additional purification or confirm that the final diluted product meets relevant cosmetic impurities limits.

Specification Window and Analytical Control Points

Batch release limits are set to keep the product usable across a wide range of industrial dosing systems. The active matter window is deliberately wider than the ±1% often seen in cosmetic grades because industrial detergent plants typically trim final viscosity with salt or polymeric rheology modifiers.

Sodium chloride is controlled below 0.3 wt% by potentiometric titration, but is not always listed as a separate release parameter. The sulfate and chloride ceilings are more relevant than active matter alone; sulfate at 1.0 wt% can compete for water of hydration and shift the salt curve peak by several hundred millipascal-seconds.

Batch-to-batch variation in the 50% feed is most visible in the salt-thickening response of finished detergent systems, not in the as-supplied viscosity alone. When the concentrate is diluted to 10–15% active and thickened with sodium chloride, the viscosity maximum for SLES with 2.0 mol EO is typically observed between 0.8 wt% and 1.5 wt% added NaCl. The peak is sharp; a salt addition error of ±0.2 wt% can shift a 12% active system from 4,000 mPa·s to 8,000 mPa·s or drop it below 2,000 mPa·s. On a production line using a 3,000 L jacketed vessel and a top-entering propeller at 45 rpm, dry salt is best added as a 25% brine through a ring sparger located below the liquid surface to avoid localized over-thickening. Aeration from high-shear dispersers is a common failure mode; if an in-line rotor-stator mixer is used, tip speeds above 15 m/s should be paired with vacuum deaeration at -0.8 bar to prevent foam entrainment. Plants that fix a single salt dosage without in-line viscometry often see finished batch viscosity drift of ±15% when the SLES active matter moves from 48% to 52%. Published formulation data for exact peak shift in the presence of cocamidopropyl betaine or lauramine oxide is limited; the practical operating range is therefore confirmed by benchtop salt curves on each new lot.

How Does SLES 50% Industrial Grade Differ from SLS, 70% Paste, and 28% Liquid?

The presence of the polyoxyethylene chain distinguishes SLES from sodium lauryl sulfate and alters precipitation behavior in hard water. In formulations at 300 mg/kg CaCO₃ hardness, SLS can precipitate as calcium dodecyl sulfate, whereas SLES 2EO remains clear at typical laundry wash temperatures above 10°C. The Krafft point of SLES 2EO is below 0°C, allowing cold-water dilution; the exact value depends on alkyl chain distribution and residual unsulfated alcohol. Foam volume measured by ISO 696 is generally lower for SLES 2EO than for SLS under identical anionic active, but the foam is more tolerant to sebum and hardness. The table below summarizes typical handling differences among liquid grades.

The comparative figures are typical industrial release data, not guaranteed values for any single producer. The 50% product is selected when ambient pumpability and intermediate active content reduce freight and storage volume relative to 28% liquid, while avoiding the heated transfer infrastructure required for 70% paste. For formulators switching from SLS powder or needles, the 50% liquid eliminates dust and pre-dissolution time. SLS powder with 92–95% active must be dispersed in cold water before heating, and dust can cause operator exposure; SLES 50% can be metered directly into a closed line. The trade-off is that the sulfate ester linkage in SLES is susceptible to acid-catalyzed hydrolysis, so the product should not be held at pH below 2.0 for prolonged periods. SLS is more hydrolytically robust at low pH but less tolerant to hard water.

When 50% Industrial Grade Replaces 70% Paste in Continuous Detergent Compounding

In continuous compounding lines where 70% SLES paste is replaced with the 50% grade, the primary operating change is the removal of hot-room storage and heat tracing. A 70% SLES 2EO paste typically requires storage at 35–40°C and transfer piping maintained at 30–35°C; viscosity can exceed 20,000 mPa·s at 25°C. The 50% industrial grade at 25°C usually falls between 600 and 1,800 mPa·s, allowing unheated transfer in climate-controlled plants. This reduces energy load but increases water introduction; a formulation with 11.0 kg of 70% paste per 100 kg batch is replaced by 15.4 kg of 50% product to deliver equivalent active matter, adding roughly 4.4 kg of water. If the final product has a water content specification, the added water must be subtracted from process water or accounted for in the preservative system. In high-active laundry gels, this water load may push the formulation outside the desired water activity (aw) window; used without adjustment, the final viscosity can fall below target and require a higher salt dosage.

Process control in continuous lines should include a Coriolis mass flow meter on the SLES feed line. Because density at 20°C is 1.07–1.09 g/cm³ by ISO 2811-3, volumetric displacement pumps can overfeed by 0.5–1.0% if product temperature varies between 20°C and 35°C. The SLES feed should be interlocked with the water flow to avoid high-local anionic concentration, which can produce gel specks when surfactants contact alkaline builders. Static mixers with 6–8 elements are sufficient for low-shear inline dilution.

Textile, Leather, and Fire-Fighting Foam Intermediates

Textile pretreatment lines use the product as a wetting agent in desizing and scouring baths at 0.2–1.0 g/L active matter. In pad-batch operations, the low gel tendency at ambient temperature allows direct injection into troughs without pre-dilution vessels. Leather soaking and degreasing formulations use SLES 2EO at 0.5–2.0% by wet weight to emulsify natural fats; the ethoxylated structure improves electrolyte tolerance when sodium carbonate or sodium formate is present. For fire-fighting foam intermediates, the product is blended with hydrocarbon or fluorinated surfactants and solvent packages; the 50% concentration gives sufficient active matter for 3% proportioning systems while avoiding the viscosity peak that can block eductor pickups. Published data for specific foam expansion ratios with this exact industrial grade is limited, but the material is used under raw-surfactant qualification protocols in several foam concentrate production lines.

For bulk storage, sealed, top-discharge tanks made of 316L stainless steel or high-density polyethylene are used. Carbon steel is incompatible because sulfate and chloride residuals can initiate pitting corrosion. The product remains pumpable at 15–35°C; below 10°C viscosity increases and the liquid may become hazy or gel-like. If cold storage has occurred, the concentrate should be reheated to 25°C with low-shear circulation before transfer. Positive-displacement pumps with EPDM or Neoprene stators are used for volumetric dosing; centrifugal pumps can be used for transfer at temperatures above 20°C but may aerate the product if suction piping is undersized. Diaphragm pumps with PTFE wetted parts have been used on textile preparation lines to deliver shot doses from 0.5 kg to 5.0 kg per batch. Slip-stream sampling should avoid dead legs longer than 1.5 m; stagnant product can stratify and produce higher local viscosity. Agitation in storage tanks should be intermittent rather than continuous; continuous high-shear mixing can increase foam and entrained air, which later destabilizes density-based dosing.

In agrochemical suspension concentrates, SLES 50% functions as a co-surfactant with calcium dodecylbenzene sulfonate or nonionic block copolymers. The sodium sulfate residual in the 50% grade is relevant because divalent salts can compress the electrical double layer and reduce suspension stability; the ≤1.0 wt% sulfate limit is tight enough for most suspension concentrate systems but should be checked against the final electrolyte tolerance. Emulsion tests are typically run by CIPAC MT36 or equivalent; the product passes initial emulsification when used at 2–5 wt% of the total formulation, but published data for this specific industrial grade in all solvent systems is limited.

Under REACH Regulation (EC) No 1907/2006, the substance is registered for industrial detergent and cleaning product manufacture; downstream users must review the extended safety data sheet exposure scenarios for process workers. The 50% industrial grade should not be used in leave-on cosmetics or food-contact cleaners unless further purification and compliance testing are performed, because the 1,4-dioxane ceiling and microbial limits are broader than personal-care equivalents. In formulations with cationic polymers or quaternary ammonium actives, incompatibility should be confirmed by turbidity measurement at the intended use pH; insoluble complexes can form at anionic:cationic molar ratios near unity. For oxidizer-containing systems, compatibility with sodium hypochlorite is limited because the ethoxylate chain can undergo oxidative degradation at available chlorine levels above 2,000 mg/L. Alkaline formulations above pH 11 should be evaluated for hydrolytic stability of the sulfate ester linkage over shelf life.