Sodium Lauroyl Methyl Isethionate CAS 928663-45-0

Introduction to Sodium Lauroyl Methyl Isethionate

Sodium Lauroyl Methyl Isethionate is a white, low-odour acyl isethionate surfactant built on a C12 lauroyl tail esterified to a methyl isethionate sulfonate head. The ester linkage hydrolyses very slowly at skin pH, so the molecule stays intact during cleansing and rinses clean without leaving a soapy residue. Personal care formulators use most global output, dosing 5–25% in sulfate-free facial washes, baby shampoos, and compressed solid cleansing bars.

The main formulation advantage is dense, creamy lather generation at low active concentrations—3% SLMI produces foam volume comparable to 8% SLES in standard foam-height tests. The critical handling risk is moisture uptake. SLMI powder is hygroscopic; an opened drum left above 60% RH will cake within 72 hours. Reseal the PE liner immediately after scooping and store below 30 °C (86 °F).

Key Features of Sodium Lauroyl Methyl Isethionate

• Ultra-low irritation profile. The methyl isethionate head group carries a bulky sulfonate that prevents deep penetration into stratum corneum lipids, keeping transepidermal water loss below 5% in patch tests versus 12–18% for SLS at equivalent concentrations.
• Dense creamy foam in hard water. The sulfonate head resists calcium and magnesium precipitation, so foam height at 250 ppm CaCO3 hardness drops less than 10% compared with soft water—critical for markets with high water hardness.
• Sulfate-free and mild-surfactant compatible. SLMI blends synergistically with cocamidopropyl betaine, decyl glucoside, and amino acid surfactants without viscosity collapse, supporting “no SLS/SLES” marketing claims.
• Biodegradable ester backbone. The ester bond cleaves readily in activated sludge, achieving >60% biodegradation within 28 days per OECD 301B, meeting EU Ecolabel and COSMOS criteria.
• Excellent for solid bar formats. Low water solubility at 25 °C (77 °F) allows direct compression into syndet bars without hot-melt processing, reducing energy cost versus traditional hot-process soap.

Sodium Lauroyl Methyl Isethionate Chemical & Physical Properties

Applications of Sodium Lauroyl Methyl Isethionate

Sulfate-free facial cleansers and gel washes: Dosed at 8–15% active in rinse-off gels, SLMI generates a dense, low-bubble cream that rinses without tight or squeaky feel. The mild head group preserves the skin acid mantle at pH 5.5, supporting “no stripping” positioning. Combine with 2–4% cocamidopropyl betaine for foam boost.

Baby shampoo and head-to-toe wash: At 5–10% active, SLMI meets the no-more-tears threshold (in-vitro HET-CAM score < 1.0 per INVITTOX protocol). The low irritation profile allows preservative reduction in baby formulations. Typical final viscosity 3,000–6,000 mPa·s with NaCl thickening.

Shampoo bars and solid syndet bars: Compressed at 40–60% in solid bar blends with stearic acid, cetearyl alcohol, and SCI (sodium cocoyl isethionate). Low water solubility prevents bar mushiness. Bars maintain structural integrity through 200+ uses without cracking. No hot-melt step required—cold-press at 40–50 °C (104–122 °F).

Shaving cream and foam cleansers: At 3–8% in aerosol or pump foams, SLMI stabilises micro-bubbles and reduces razor drag. The creamy lather provides lubricity without requiring added mineral oil or silicone.

Industrial and institutional mild detergents: In low-irritation hand-wash concentrates for food-processing plants and laboratories, 10–15% SLMI replaces harsher alkyl sulfates while maintaining adequate grease removal on mineral-oil soils.

Storage & Safety Precautions for Sodium Lauroyl Methyl Isethionate

• Storage: Keep sealed in PE-lined drums at 5–30 °C (41–86 °F), relative humidity below 60%. SLMI is hygroscopic; an opened drum exposed to 60% RH will absorb moisture and cake within 72 hours. Store away from strong acids (pH < 3 accelerates ester hydrolysis, releasing lauric acid odour) and strong oxidisers.
• Safety: Not classified as hazardous under GHS. Mild eye irritant (Category 2B); avoid direct contact. Wear safety glasses and standard dust mask when handling powder grades to prevent inhalation of fine particles. Wash skin with water after contact.
• Transport: Sodium Lauroyl Methyl Isethionate is Non-DG under IATA/IMDG/ADR. Not a marine pollutant. Standard 25 kg (55 lb) drums or 500 kg (1,100 lb) jumbo bags ship in dry containers.
• QC note: Verify active matter by two-phase titration (ISO 2271 or equivalent). A fresh lot is white and free-flowing; yellowing or a rancid lauric odour indicates ester hydrolysis from heat or moisture exposure during transit. Reject lots with free fatty acid above 3.0% or active matter below 88%.

Sodium Lauroyl Methyl Isethionate FAQ

Q: Why does my SLMI powder (CAS 928663-45-0) turn into a hard cake inside the drum?

A: Moisture uptake. SLMI is hygroscopic; once the PE liner is breached or left open above 60% RH, powder absorbs water and cements into a block. Chemistry is unchanged—break the cake and dissolve at 70 °C (158 °F). Prevent by resealing immediately and storing below 30 °C (86 °F).

Q: Can I use SLMI as the sole surfactant in a sulfate-free shampoo?

A: Possible but not ideal alone. SLMI at 10–15% gives mild cleansing but limited viscosity. Add 2–3% cocamidopropyl betaine or decyl glucoside for foam volume and salt-thickening response. Final pH 5.0–5.5 keeps ester bond stable.

Q: My SLMI solution smells faintly of lauric acid. Is the lot bad?

A: Slight ester hydrolysis from heat or moisture exposure. Check free fatty acid by titration. If ≤ 2.0%, the lot is usable with minor foam reduction. Above 3.0%, reject. Store below 30 °C (86 °F) and avoid acidic co-ingredients below pH 4.