SLES 28% – класс личного ухода для шампуневой базы

SLES 28% – Personal Care Grade for Shampoo Base is the aqueous delivery form of the sodium salt of a sulfated ethoxylated lauryl alcohol with a nominal average of 2 moles of ethylene oxide per mole of fatty alcohol. The INCI designation is Sodium Laureth Sulfate, and the substance is commonly listed under CAS 68891-38-3 in safety data sheets. The grade designation 28% refers to nominal active matter, not to a model number; release specifications typically control the active concentration between 27.0 wt% and 28.5 wt%, with the balance predominantly water and controlled electrolyte residuals. In rinse-off shampoo bases, the substance functions as the primary anionic surfactant and is selected for its pumpable viscosity at 20–40 °C, suitability for ambient-temperature compounding, and lower dilution-gel risk compared with high-active concentrates.

Why Does the 28% Aqueous Delivery Form Reduce Ambient-Temperature Compounding Risk?

On production lines using side-entry agitators and positive-displacement lobe or diaphragm pumps, SLES 28% can be metered directly from HDPE IBCs without heated storage. By contrast, SLES 70% concentrate passes through a high-viscosity gel zone when diluted through roughly 40–60% active matter; unless the plant uses controlled in-line dilution with static mixers, local water addition can create clear gel lumps that are slow to disperse. The 28% version avoids this because the active-matter concentration is already below the critical gel phase. The principal trade-off is volumetric efficiency: preparing 100 kg of a final shampoo base at 10% active SLES requires approximately 36 kg of SLES 28%, whereas the same formula can be built from approximately 14 kg of SLES 70% plus dilution water. The additional water introduced by the 28% raw material must be included in preservation calculations and in the total batch water balance.

Typical release and quality parameters for the personal care grade are compiled in Table 1. The values are representative of supplier technical data sheets and are not a substitute for a lot-level certificate of analysis.

From a formulation-control perspective, the unsulfated matter and electrolyte residuals are not inert. A lot at the upper chloride limit of 0.5 wt% may require 0.2–0.3% less added sodium chloride in the finished shampoo than a lot at the lower chloride limit. Elevated sodium sulfate narrows the salt-thickening window because sulfate competes for water of hydration and can shift the micellar transition. Personal care grade SLES 28% is therefore not interchangeable with industrial detergent grades that may carry higher sulfate, higher free oil, and higher color without immediate loss of foam but with measurable shifts in clarity and viscosity robustness.

Counterion sodium, average ethoxylation, and the electrolyte envelope

SLES 28% differs from sodium lauryl sulfate principally by the presence of a polyoxyethylene spacer between the C12/C14 hydrophobic chain and the sulfate head group. This spacer lowers the Krafft point to below 0 °C in most commercial lots, allowing the surfactant to remain water-soluble in cold hard water, whereas SLS may form calcium lauryl sulfate precipitate at 200–300 mg/L CaCO₃. The ethoxylation also shifts the surfactant toward a lower critical micelle concentration relative to SLS, although published values vary with electrolyte background. The 2-EO average is a compromise within the SLES series: SLES-1 has a lower molecular weight and higher anionic charge density, while SLES-3 is more hydrophilic and may be milder but builds salt viscosity less efficiently in CAPB-containing formulas. Ammonium laureth sulfate shares similar ethoxylation chemistry but has an ammonium counterion; it can release ammonia at high pH and gives a lower-density final liquid, whereas the sodium counterion is preferred when a clear shampoo base above pH 6.0 must remain odor-stable.

If the Shampoo Base Is Preserved with Sodium Benzoate and Potassium Sorbate at pH Below 5.5

Because SLES 28% contributes approximately 70 wt% water to the batch, the raw-material water must be treated as a microbial input. Sodium benzoate relies on the undissociated benzoic acid fraction; at pH 5.5 this fraction is sufficient for preservation in many rinse-off formulas, but at pH 6.5 the activity falls rapidly. Citric acid is added after surfactant dissolution to bring the final shampoo base to pH 5.0–5.5. Within this window, the sulfate ester of SLES 28% remains chemically stable; sustained processing below pH 4.0 is not recommended because acid-catalyzed hydrolysis can liberate fatty alcohol and reduce active anionic titre. Preservation efficacy should be confirmed by ISO 11930 challenge testing, and bulk-water microbial acceptance should follow ISO 17516 limits. The product itself is not a preservative and does not replace Annex V biocides under EC 1223/2009.

Cold compounding with SLES 28% is normally performed by charging the water phase at 20–35 °C, adding the anionic under low agitation, and then adding CAPB. The pH is adjusted after surfactant mixing; adding acid before the anionic is fully hydrated can create localized low-pH zones that increase hydrolysis risk. Once the preservative is dissolved, the batch is thickened with sodium chloride. Mixing for 30–60 min after the final addition is required for micellar equilibrium; viscosity measured immediately after salt addition often drifts upward for several hours. In pearlescent shampoo bases, ethylene glycol distearate is dispersed at 65–70 °C before cooling; the 28% liquid can tolerate this short thermal excursion, but holding above 80 °C for extended periods is not recommended.

In bulk storage, SLES 28% is preferably held at 20–30 °C in HDPE or 316L stainless steel under ISO 22716 hygiene controls. At temperatures below 5 °C, the material may become temporarily opaque or layered; it should be recirculated gently and allowed to reach 20–25 °C before use. Storage above 40 °C for extended periods can accelerate oxidative color development, especially in the presence of iron from carbon steel piping. Air-entrained transfer with centrifugal pumps is a common production problem: entrained air increases apparent volume, slows viscosity equilibration, and can produce foam that interferes with level sensors. Diaphragm pumps, oval-gear meters, or Coriolis mass flow meters are preferred because they avoid excessive shear and air incorporation.

Sodium Chloride Addition Does Not Behave as a Linear Thickener

In a clear shampoo base containing 10 wt% active SLES and 2.5–3.0 wt% active CAPB, the salt curve typically rises from 0.5% to approximately 1.5–2.0% added NaCl and then declines if more salt is added. The exact peak depends on total active concentration, the SLES/CAPB ratio, pH, residual sulfate, and the presence of nonionic or cationic conditioning polymers. This is a micellar transition phenomenon, not a simple electrolyte thickening effect. On a production scale, NaCl is added as a 20% aqueous solution under slow mixing to avoid local over-salting and gel-pocket formation. Viscosity is measured after complete hydration at 25 °C using a Brookfield viscometer at fixed spindle and speed; shear-thinning makes single-point readings valid only for comparison under identical conditions.

SLES 28% can be combined with CAPB at an active-weight ratio of approximately 3:1 to 4:1. CAPB is not a drop-in replacement for the anionic ester sulfate; it has a different charge profile and does not provide the same primary detergency. In hard water, CAPB supports foam quality and can reduce the total anionic required, but the shampoo base still relies on SLES 28% for sebum emulsification and viscosity build. The product can also be blended with nonionic alkoxylates or amine oxides, but severe viscosity loss or clarity instability can occur at high nonionic levels due to mixed-micelle packing changes. Table 2 compares the product with common alternative surfactant raw materials.

SLES 28% is not appropriate for sulfate-free claims because the molecule bears a sulfate ester head group. Sulfate-free platforms based on alkyl polyglucosides, amino acid surfactants, or methyl cocoyl taurates require different pH buffering, preservative partitioning, and viscosity-building strategies; direct substitution without reformulation is not technically valid. The product is also not intended to replace amphoteric or nonionic co-surfactants; it remains the anionic backbone of the shampoo base.

SLES 28% should not be combined with highly charged cationic polymers in concentrated form. In diluted and pH-adjusted shampoo bases, cationic guar or polyquaternium-10 can be incorporated for deposition, but pre-mixing the concentrated anionic with cationic polymer can produce insoluble coacervates. Tanks sanitized with hypochlorite should be rinsed thoroughly before charging SLES 28%, because low-pH hypochlorite residues can oxidize the ether sulfate and generate off-spec color.