SLES 28% – Personal Care Grade for Shampoo Base

Viscosity Cliff-Edges and Electrolyte Tolerance in Clear Sulfate Shampoo Bases

Clear shampoo manufacturing using SLES 28% – Personal Care Grade for Shampoo Base requires the supplied anionic active to be treated as a salt-responsive wormlike micelle former, not as an inert dilutable detergent. The incoming material is typically a 2 mol ethylene oxide adduct with active content controlled at 27.0–29.0% by mass, sodium chloride below 1.0%, and residual 1,4-dioxane maintained at ≤10 ppm according to the supplier certificate of analysis. Production in a 2,000 L 316L stainless steel jacketed vessel with a bottom-entering propeller and side-sweep anchor begins with demineralized water meeting a conductivity of ≤10 µS/cm at 25°C. Tetrasodium EDTA dihydrate or disodium EDTA is dissolved first at 0.05–0.10 wt% to chelate iron and copper ions that otherwise accelerate oxidative discoloration of the ethoxylated sulfate chain. SLES 28% is added under slow sweep agitation at 20–35 rpm; aeration is minimized because entrained air increases apparent yield and reduces deaeration efficiency during filling. Cocamidopropyl betaine is blended at an active ratio of approximately 3:1 to SLES because the mixed micelles formed at this ratio produce the required rod-like packing geometry for salt-induced viscosity build. After preservative addition, pH is adjusted to 5.0–5.5 with a 50% citric acid solution. Sodium chloride is then added as a 25% predissolved solution at a dosing rate not exceeding 0.05% of batch weight per minute. Viscosity measured on a Brookfield LV-DV2T with spindle 4 at 12 rpm and 25°C in a 9.0% active SLES/CAPB base rises from approximately 1,500 cP at 0.2% added NaCl to 10,000–12,000 cP at 0.8–1.0% added NaCl, then falls below 4,000 cP at 1.8–2.0% added NaCl. This cliff-edge response occurs because charge screening compresses the micellar double layer and forces a transition from wormlike micelles to branched or spherical structures. The final clear shampoo is polished through a 20 µm cartridge filter and packed at 20–25°C; microbiological quality is checked against ISO 21149 and ISO 18415 with limits below 100 CFU/g, and preservation efficacy follows ISO 11930:2019 criteria A for rinse-off products.

Pearlized body wash production lines combine SLES 28% with glycol distearate or ethylene glycol monostearate to create a crystalline platelet network that controls yield stress and bottle flow. The sequence in a 5,000 L jacketed tank with an in-line rotor-stator recirculation loop operated at 1,500–2,000 rpm starts with melting the pearlizing agent at 70–75°C. SLES 28% is added only after the base has cooled below 40°C, because prolonged exposure above 60°C can accelerate sulfate ester hydrolysis and generate free fatty alcohol that dulls the pearlized appearance. Cocamide monoethanolamine at 1.0–2.0 wt% is melted with the pearlizing agent, while cocamidopropyl betaine is blended at 20–30°C. High-shear recirculation is stopped at 45°C during cooling; subsequent agitation is limited to 10–15 rpm to allow growth of glycol distearate lamellar platelets in the 10–50 µm range. Higher shear fragments the platelets and produces a dull or non-pearlescent visual failure. pH is adjusted to 5.5–6.0 with 50% citric acid because below 5.0 CAPB can complex with anionic SLES and cause temporary haze or viscosity loss. Sodium chloride addition for final adjustment is lower than in clear shampoos because the pearlized crystal network contributes yield stress; a target of 2,000–5,000 cP at 25°C on a Brookfield LV-DV2T spindle 4 at 12 rpm is common for flip-top bottle dispensing. Sodium benzoate and potassium sorbate are used at 0.3–0.5% total and require pH below 5.5 for optimal benzoic acid partitioning, which is confirmed by challenge testing per ISO 11930:2019. The finished pearlized body wash is filled through bottom-up nozzles and vacuum deaerated at −0.4 bar to control foam formation on the packaging line.

Why Does SLES 28% Require Counterion and pH Adjustment in Pump Foamers?

Because foamer pump meshes are highly sensitive to liquid viscosity and microfoam, SLES 28% must be diluted to a final active range of 8.0–12.0% before use in facial cleansing formats. The supplied material is diluted 1:2 to 1:3 with demineralized water before secondary surfactants such as sodium lauroyl sarcosinate or disodium cocoamphodiacetate are introduced. Process water is softened to total hardness below 10 ppm CaCO3 because calcium above 50 ppm can precipitate calcium lauryl sulfate and clog the foamer mesh. The product pH is adjusted to 5.0–5.5 with 50% lactic acid; lactic acid contributes less chelating capacity than citric acid and has a narrower impact on the salt response. Finished foamer base viscosity must remain below 500 cP at 25°C measured with a Brookfield LV spindle 1 at 60 rpm; above this level, the pump mechanism loses priming and delivers less than 0.75 mL per stroke, causing foam density failure at the packaging line. Sodium chloride is omitted or limited to ≤0.1% because SLES in this low-active system can still form wormlike micelles in the presence of alkanolamides and amphoterics. Phenoxyethanol at 0.5–0.8% combined with ethylhexylglycerin at 0.1% is used for preservation, and efficacy is verified by ISO 11930:2019 challenge testing. The production vessel is a 1,000 L stainless steel tank with a low-shear axial flow impeller at 30 rpm; entrained air must be limited to ≤2% by volume because microfoam causes incorrect fill volumes and poor pump priming. The final facial cleanser is packed into airless pump foamers and subjected to 24-hour leak testing at 40°C; documentation follows ISO 22716 and finished product compliance with EC 1223/2009 Annex IV preservative restrictions.

Liquid hand cleanser manufacturing in shared personal care facilities uses SLES 28% as the primary anionic load at 15–25% as supplied, with cocamidopropyl betaine at 5–10% and alkyl polyglucoside at 1–3% to reduce the defatting effect of the sulfate head group. The mixing vessel is a 2,000 L 316L stainless steel tank with a variable-speed disperser operated at 300–500 rpm during water and surfactant addition and reduced to 50 rpm after thickening. Glycerin at 1–2% and sorbitol at 1–3% are used as humectants; their presence lowers the cloud point of the surfactant mixture and shifts the salt curve, requiring lower NaCl addition than in standard shampoo bases. The pH is adjusted to 5.5–6.5 using 50% citric acid or 10% sodium hydroxide; cationic polymers are added only where the amphoteric content is sufficient to prevent anionic-cationic precipitation. The viscosity target for pump bottles is 1,500–3,000 cP at 25°C on a Brookfield LV-DV2T spindle 4 at 12 rpm; for refill pouches, viscosity is reduced to 800–1,200 cP to allow complete evacuation. Preservative systems containing phenoxyethanol at 0.4–0.6% and ethylhexylglycerin at 0.05–0.1% are verified by ISO 21149 plate counts below 100 CFU/g and absence of Candida albicans per ISO 18415. Filled product is stored at 20–25°C for 48 hours before release because immediate filling after thickening can result in a 20–30% viscosity increase in the package as the wormlike micelle network equilibrates. The final hand cleanser meets the EU Ecolabel criteria for rinse-off cosmetic products under Commission Decision (EU) 2017/1218, including ready biodegradability assessed by OECD 301B with >60% degradation in 28 days for the sum of organic ingredients.

When SLES 28% Replaces Alpha-Olefin Sulfonate in High-Foam Bath Products

Substitution of alpha-olefin sulfonate with SLES 28% in bubble bath formulations changes foam morphology from a fast-draining, brittle lather to a denser, slower-draining foam, but only when electrolyte and pH are controlled within a narrow operational window. In a typical bubble bath base with 8.0–12.0% active SLES and 2.0–4.0% active CAPB, pH is set to 6.0–6.5 with 50% citric acid. Foam volume under agitated dilution at 1:100 in water at 25°C with 150 ppm CaCO3 hardness is evaluated by the Ross-Miles pour test method DIN 53902 or ISO 696; published data for this specific configuration is limited, so batch-specific foam screening is required. The product contains 0.1–0.3% sodium chloride contributed by the SLES 28% raw material and may require an additional 0.5–1.5% NaCl to reach 2,000–4,000 cP at 25°C. If the replacement is made without reformulating the preservative, the cloud point can fall below 40°C when polymeric thickeners are present; sodium xylene sulfonate at 1–2% is added to maintain clarity and prevent phase separation during storage at 5°C. Manufacturing in a 5,000 L jacketed vessel with a counter-rotating side-scraping agitator at 20 rpm avoids high-shear dispersion because foam generation in the vessel is the primary failure mode. Vacuum deaeration at −0.4 to −0.5 bar is applied for 30 minutes after blending. The bubble bath is filled into PET bottles with submerged nozzles; if foam persists, simethicone emulsion at 0.1–0.2% may be added, but this can reduce in-use foam volume and must be balanced against packaging throughput. Preservation efficacy follows ISO 11930:2019 criteria B for high-dilution bath products; undiluted product must maintain a bacterial count below 100 CFU/g. Eye irritation is assessed against OECD 404 or the BCOP assay; formulations with total active surfactant below 15% and pH above 5.5 typically require finished product testing because fragrance and preservative components can dominate the irritation profile.

Pet Grooming Shampoo with Reduced Salt and Mild Surfactant Partitioning

Pet grooming shampoo production selects SLES 28% for its high foam profile but typically uses the material at 20–35% as supplied in a dilution-ready product mixed 1:10 with water at the grooming table. The formulation pH is adjusted to 6.5–7.5, closer to canine skin pH than human skin pH; sodium lactate or lactic acid is used as a buffer, and final alkalinity is controlled by titration against 0.1 N hydrochloric acid to a phenolphthalein endpoint. Sodium chloride is kept below the human shampoo salt curve because the higher dilution factor requires lower packaged viscosity; a target of 1,500–2,500 cP at 25°C on a Brookfield LV-DV2T spindle 4 at 12 rpm prevents difficulty in bottle squeezing during washing. Cocamidopropyl betaine is added at 10–15% active to reduce the irritancy of the sulfate head group and to build viscosity without additional electrolyte. Hydrolyzed oat protein at 0.5–1.0 wt% may be included for conditioning, but it can reduce foam and requires broad-spectrum preservation. Phenoxyethanol at 0.6–0.8% and ethylhexylglycerin at 0.1% is preferred over sodium benzoate in this protein-containing matrix, and a challenge test per ISO 11930:2019 is performed on the finished formulation. The mixing equipment is a 1,000 L stainless steel tank with a slow-speed paddle impeller at 25 rpm because the protein and cationic conditioners can be denatured by high-shear dispersion. Filling into HDPE bottles with graduated dilution caps is performed at room temperature; hot filling above 35°C is avoided because rapid cooling can cause cloud-point hazing. The final product is not regulated by EC 1223/2009 if it is explicitly marketed for animals; regional animal health or veterinary medicine regulations apply, and the label must avoid human cosmetic claims. Because no harmonized global standard exists for pet shampoo preservation, contract manufacturers often apply ISO 22716 as a GMP reference and use OECD 301B ready biodegradability data to support environmental claims.

Brushless shave cream and aerosol shave gel lines employ SLES 28% as a secondary foaming agent in a soap-based stearate system, not as the primary structurant. The base is prepared by melting triple-pressed stearic acid at 8.0–10.0 wt% and palmitic acid at 3.0–5.0 wt% in a jacketed 2,000 L 316L stainless steel tank at 70–75°C; triethanolamine or potassium hydroxide is then added in an amount equivalent to 80–90% neutralization of the acid value, producing a lamellar soap gel with a pH of 8.5–9.5. Adding SLES 28% directly to this hot soap phase at 75°C can lead to localized hydrolysis of the sulfate ester and the formation of free fatty alcohol, which reduces foam stability and changes product odor. Therefore, the SLES 28% is diluted with a portion of the formula water and added below 45°C after the soap phase has cooled. The final active surfactant level from SLES is 2.0–4.0%, while CAPB or cocamidopropyl hydroxysultaine is included at 1.0–2.0% active to improve flash foam and reduce stearate soap film after shaving. Glycerin at 5.0–10.0% is used as a humectant and viscosity modifier; propylene glycol at 1.0–2.0% may be included for aerosol valve compatibility. Bulk viscosity for brushless cream is 50,000–80,000 cP at 25°C on a Brookfield helipath stand with a T-bar spindle at 5 rpm, whereas aerosol shave gel bases are thixotropic and are evaluated by yield stress rather than single-point viscosity. Aerosol filling uses an isobutane/propane blend at 4–6% by weight; can internal pressure at 25°C is 3.0–4.0 bar, and hot-water leak testing at 55°C is conducted per batch. Microbiological preservation in high-pH soap systems is less demanding because pH above 9.0 limits most bacterial growth, but phenoxyethanol at 0.4–0.6% is used to control yeast and mold at the air-product interface and is verified by ISO 11930:2019. The finished shave cream is packed into aluminum barrier tubes or laminated tubes, while the aerosol gel is packed into aluminum monobloc cans with internal epoxy-phenolic lacquer to prevent corrosion at the high-pH stearate soap interface.