SLES 70% – Низкий уровень диоксана (≤10ppm)

Product designation SLES70-LD10 is supplied as an aqueous sodium lauryl ether sulfate concentrate with a nominal ethoxylation degree of 2 mol EO, an active matter content of 70 ± 1 wt%, and a residual 1,4-dioxane concentration not exceeding 10 mg/kg in the as-received raw material. The material is identified by CAS 68891-38-3 and INCI name Sodium Laureth Sulfate. It appears as a clear to slightly hazy pale liquid at 25°C. The product functions as an anionic surfactant in rinse-off and leave-on cleansing systems, providing detergency, foam generation, and electrolyte-responsive viscosity build. SLES70-LD10 is not a chemically modified surfactant relative to conventional SLES 70%; it is the same lauryl ether sulfate backbone with tighter impurity control on 1,4-dioxane.

Chemically, the product is represented as R(OCH₂CH₂)_nOSO₃Na, where R is predominantly C12–C14 and n averages 2. The hydrophobic chain distribution follows the feedstock alcohol; lauryl alcohol cuts commonly contain 68–75% C12 and 22–28% C14. The anionic sulfate head group provides foaming and emulsification, while the ethoxy spacer improves hard-water tolerance relative to sodium lauryl sulfate. The supplied concentrate contains approximately 28–30 wt% water, with the balance comprising active matter, sodium chloride, sodium sulfate, and minor unsulfated matter.

Release testing for the ≤10 mg/kg dioxane limit uses isotope-dilution headspace GC-MS; the reporting limit should be no higher than 5 mg/kg to support reliable pass/fail decisions. Published standard methods specific to 1,4-dioxane in ethoxylated surfactant matrices are limited; quality control laboratories may adapt US EPA 8260D or equivalent isotope-dilution protocols. Because 1,4-dioxane is volatile, sample handling must minimize evaporative loss before injection. Active matter is determined by anionic titration in a two-phase system under ISO 2271; pH is measured in 5% aqueous solution at 25°C per ISO 4316.

How Does the ≤10 ppm 1,4-Dioxane Limit Affect Surfactant Processing?

1,4-Dioxane is not added to the product. It is formed as a side reaction during ethylene oxide insertion onto the lauryl alcohol backbone, with concentration influenced by catalyst type, ethylene oxide/alcohol molar ratio, reactor temperature, and neutralization pH. Conventional SLES 70% grades may leave the sulfation plant with 1,4-dioxane levels from 20 mg/kg to above 100 mg/kg depending on feedstock and process age. SLES70-LD10 is therefore processed through additional post-neutralization stripping. In production-scale equipment, the neutralized paste is fed to a wiped-film or falling-film stripper operated under vacuum with nitrogen or steam sparging. Typical stripping conditions reported in surfactant process literature include feed temperatures of 80–100°C, absolute pressure below 150 mbar, and controlled residence time to transfer 1,4-dioxane into the vapour phase. Because 1,4-dioxane forms a minimum-boiling azeotrope with water, stripping is often performed before final water adjustment to avoid excessive viscosity and to maintain active matter at 70%.

Removal of 1,4-dioxane from a high-viscosity surfactant paste is mass-transfer limited. The stripper must balance temperature, vacuum, and residence time against colour formation and active-matter preservation. If the paste is held too long at elevated temperature, the sulfate ester can undergo hydrolysis, generating free alcohol and lowering active matter. The stripping operation is therefore typically performed under vacuum 50–150 mbar at the lowest effective temperature, and the product is cooled immediately after discharge. Production plants monitor stripper condensate for 1,4-dioxane to verify removal efficiency rather than relying only on finished product testing. Published equipment-specific removal efficiency data for this exact product matrix is limited; release testing on each batch is required rather than relying solely on fixed process settings.

Batch-to-batch control at the ≤10 mg/kg limit requires upstream ethoxylate dioxane load to be constrained and stripper vacuum stability to be maintained. On continuous sulfation lines, variation arises from upstream ethoxylate quality and from fluctuations in steam sparging rate. In-process verification at the paste stage is used to divert nonconforming material before dilution to final concentration. The product is stored in closed, nitrogen-blanketed vessels to limit atmospheric CO₂ ingress and pH drift. Hydrolysis of the sulfate ester accelerates below pH 5.0 and at temperatures above 50°C. 316L stainless steel or high-density polyethylene are suitable wetted materials; unlined carbon steel is not recommended for prolonged storage.

Viscosity Build and Electrolyte Response in Clear Cleansing Formulations

In rinse-off personal-care formulations, SLES70-LD10 is typically used at 5–20 wt% as supplied, corresponding to 3.5–14 wt% active surfactant. The product does not produce significant viscosity in water alone; final viscosity is developed by electrolyte addition. Sodium chloride at 0.5–2.5 wt% is the most common modifier, and the response curve passes through a maximum. In a representative shampoo base containing 10 wt% SLES70-LD10, 3 wt% cocamidopropyl betaine, and 1 wt% cocamide DEA, viscosity after sodium chloride addition can be tuned from approximately 2,000 mPa·s to 12,000 mPa·s at 25°C depending on salt concentration. Overdosing beyond the peak causes viscosity collapse due to micelle structural changes and eventual phase separation in the presence of co-surfactants. The exact peak depends on the co-surfactant ratio, pH, and temperature. Rotational viscosity is measured by Brookfield RV at 20°C and 20 rpm, with method alignment to ASTM D2196-20.

Production-scale mixing of SLES70-LD10 requires slow agitation or low-shear blending during dilution to avoid air entrainment. High-shear dispersion is not necessary for complete hydration and may generate stable foam that requires vacuum deaeration. The product should be added to water at 30–40°C to reduce viscosity and improve pump transfer. After combining with co-surfactants, pH is adjusted to 5.0–7.0 with citric acid or sodium hydroxide. Preservative is added below 40°C where the preservative is temperature-sensitive. SLES70-LD10 is compatible with amphoteric surfactants such as cocamidopropyl betaine, nonionic alkyl polyglucosides, and alkanolamides in clear shampoo and body wash systems. Cationic conditioning polymers may be included at low charge density; strong complexation with high-charge cationic polymers can reduce foam and form precipitates. Preservative selection should follow challenge testing under ISO 11930; the unpreserved surfactant feed must not be assumed to protect finished formulations.

When the Low-Dioxane Grade Replaces Conventional SLES in Leave-On Applications

Replacement of a conventional SLES 70% with SLES70-LD10 is primarily a risk-control measure rather than a change in surfactant activity. For a formulation containing 10 wt% of a conventional 70% grade with 50 mg/kg 1,4-dioxane, the contributed residual is 5 mg/kg in the finished product. The same formulation using SLES70-LD10 at ≤10 mg/kg contributes ≤1 mg/kg. This difference is relevant in leave-on cleansers, baby care, facial wipes, and other products where dermal exposure time is longer and where retailers or regulators request trace CMR control. The grade does not remove 1,4-dioxane from other ethoxylated raw materials; formulators must sum contributions from all ethoxylates. Under California Proposition 65, 1,4-dioxane is listed as a carcinogen, and the no significant risk level for oral exposure is 30 µg/day. Low-dioxane SLES reduces the surfactant contribution but does not by itself confer compliance.

Under EU CLP, 1,4-dioxane is classified as Carcinogenicity Category 1B; under IARC it is Group 2B. EU Cosmetic Regulation 1223/2009 does not establish a numerical limit for 1,4-dioxane as an impurity in finished cosmetics, but control in practice occurs through raw material quality and trace CMR management. The low-dioxane grade is therefore used when the surfactant contribution must be minimized before final product testing or exposure assessment is performed.

The principal operational difference is analytical and process-related rather than a shift in foaming or detergency. Because the low-dioxane grade receives additional stripping, the odour profile may be slightly lower in volatile ethoxylate residuals, but the active surfactant functionality is not altered. In manufacturing trials, no reformulation is required when substituting at equal active matter; however, the viscosity response curve should be revalidated because trace electrolyte and unsulfated matter differences between suppliers can shift the salt peak by 0.2–0.5 wt% sodium chloride.

In high-foaming manual dishwash concentrates, SLES70-LD10 is commonly combined with linear alkylbenzene sulfonic acid neutralized with sodium hydroxide or triethanolamine. The final pH is adjusted to 7.0–8.5, and hydrotropes such as sodium xylene sulfonate are used to maintain clarity. The low-dioxane grade does not alter enzyme stability or builder compatibility; however, the contribution of alcohol ethoxylates and other ethoxylated nonionics to the total 1,4-dioxane burden must still be evaluated. Published data for finished detergent matrices is limited; final product testing is required when a downstream specification is imposed.

Bulk storage of SLES70-LD10 should avoid freezing and temperatures above 40°C. If separation or viscosity stratification occurs after long static storage, gentle recirculation or low-shear mixing should be used to homogenize the batch before sampling. The product is not intended for use under strongly acidic conditions below pH 4.0, because acid-catalyzed hydrolysis of the sulfate ester will reduce active matter and generate free fatty alcohol. Strong oxidizing agents and high concentrations of cationic surfactants should also be avoided in concentrated systems because of incompatibility and potential precipitation.