The newest and most technologically advanced soap grease chemistry — calcium sulfonate complex (CaSX) uses overbased calcium sulfonate concentrate as the structuring agent, converted in situ from amorphous calcite to crystalline vaterite morphology to form the grease gel. The chemistry delivers inherent extreme pressure performance, outstanding rust protection, water washout below 1%, and no true drop point — all in a single thickener without external EP additives. This guide covers the gel-conversion SOP, raw-material specifications, NLGI grade range, ASTM performance targets, and the reactor capability for premium-tier production.
CaSX grease is fundamentally different from soap-thickened greases. Where lithium and calcium soap greases rely on long fibres of saponified fatty acid to trap base oil, CaSX uses crystalline calcium carbonate as the structuring agent — specifically, calcium carbonate in the vaterite crystal morphology, dispersed inside calcium sulfonate micelles.
The starting raw material is overbased calcium sulfonate concentrate (typically TBN 350–400 mg KOH/g, ~40% active material in mineral oil) — the same overbased detergent used in engine oils. Inside this concentrate, surplus calcium beyond the stoichiometric sulfonate is held as amorphous calcium carbonate (calcite) inside surfactant micelles. In CaSX manufacturing, a conversion process — involving a facial acid (12-HSA or stearic), a promoter alcohol (n-hexanol or isopropanol), water, and a calcium hydroxide top-up — transforms this amorphous calcite into the crystalline vaterite polymorph of CaCO₃. The vaterite particles, supported by the surrounding sulfonate surfactant, inter-lock to form a three-dimensional gel structure that thickens the oil.
The performance consequences are striking. Because the structuring agent is calcium carbonate, which does not melt but decomposes only above 800°C, the grease has no true drop point — in ASTM D2265 testing, the result is typically "no drop observed at 300°C". Because the sulfonate surfactant component is itself an EP additive (the same chemistry used in industrial gear oil EP packages), the grease has inherent four-ball weld points of 315–500 kgf without any added EP. Because calcium carbonate is hydrophobic and the sulfonate is highly oleophilic, water washout per D1264 is typically 1–3% — the best of any soap-thickened chemistry. The trade-off is cost: the raw material is expensive, 25–35 wt% sulfonate loading is required, and the conversion process is sensitive to control.
| Component | Grade / Specification | Treat Rate (NLGI 2) | Function & Sourcing |
|---|---|---|---|
| Overbased Ca sulfonate | TBN 350–400 mg KOH/g, ~40% active, in mineral oil | 25–35% | The structuring raw material. From Chevron Oronite (OLOA 219), Lubrizol, Infineum or domestic producers. The single largest cost item in CaSX. |
| Base oil — primary | Group II SN500, KV40 95–105 cSt | 45–55% | Main carrier fluid. Group II preferred for oxidation life. Brightstock blend possible for very heavy-duty industrial CaSX. |
| Base oil — secondary | Group II SN150, KV40 28–32 cSt | 5–10% | Diluent for additive dispersion and viscosity control. |
| Facial acid | 12-HSA or stearic acid, AV 175–205 | 1.5–3.0% | Promotes the calcite-to-vaterite conversion. 12-HSA preferred; small dose only. |
| Promoter alcohol | n-Hexanol or isopropanol (IPA), tech grade | 0.5–2.0% | Critical for the conversion — provides the polar environment for vaterite crystallisation. Evaporated during dehydration step. |
| Water | Demineralised | 0.5–1.5% | Conversion catalyst. Evaporated during dehydration. |
| Calcium hydroxide / oxide | Ca(OH)₂ or CaO, fine powder, tech grade | 0.5–1.5% | Top-up calcium to ensure adequate calcium carbonate formation. Some recipes use lime, some quicklime. |
| EP / AW top-up | Sulfurised olefin (optional) | 0–2% | Optional — only for the most demanding specs requiring >500 kgf weld. Base chemistry is already EP-capable. |
| Antioxidant | Aryl-amine + hindered phenol | 0.5–1.0% | Standard antioxidant package — CaSX needs less than LiX because thermal exposure during manufacturing is lower. |
| Rust inhibitor | Amine carboxylate (top-up only) | 0–0.3% | Often skipped — the overbased sulfonate itself provides rust protection. Top-up only for extreme salt-spray specs. |
CaSX manufacturing is not a saponification — it is a controlled phase-conversion of an amorphous solid to a crystalline polymorph inside a colloidal carrier. The chemistry is sensitive and the conversion exotherm requires careful temperature control. The following SOP is for a typical 200–500 kg batch in a stainless-steel jacketed reactor. Total cycle time is approximately 8–10 hours.
| Property | ASTM Test Method | Typical Value | Premium Industrial Spec |
|---|---|---|---|
| Worked penetration, 60 strokes | ASTM D217 | 265–295 (0.1 mm) | 265–295 |
| Penetration change, 100,000 strokes | ASTM D217 | +5 to +15 dmm | +30 max |
| Dropping point | ASTM D2265 | >300°C (no drop observed) | 260°C min |
| Water washout @ 79°C | ASTM D1264 | 1–3% | 5% max |
| Four-ball wear scar | ASTM D4172, 40 kg, 75°C, 1h | 0.35–0.45 mm | 0.50 max |
| Four-ball EP weld point | ASTM D2783 | 400–500 kgf (no EP additive) | 315 kgf min |
| Four-ball Load Wear Index | ASTM D2783 | 65–80 kgf | 50 kgf min |
| Rust protection (Emcor) | ASTM D6138 / IP 220 | 0/0 pass | 0/1 max |
| Copper corrosion, 24h @ 100°C | ASTM D4048 | 1a | 1b max |
| Salt spray, 500h | ASTM B117 | No rust pass | Pass |
| Oxidation stability, 100h @ 99°C | ASTM D942 | 2–5 psi pressure drop | 10 psi max |
| Failure Mode | Root Cause | Diagnostic Test | Fix |
|---|---|---|---|
| Conversion does not initiate; mass stays liquid | Promoter package incomplete; water content too low; sulfonate concentrate TBN too low | Bulk viscosity; sulfonate TBN; water content | Verify promoter alcohol 1–2%, water 0.5–1.5%, facial acid 1.5–3%; verify TBN 350+ on incoming sulfonate; warm reactor to 100°C and add more promoter |
| Runaway exotherm; bulk overshoots 130°C | Heat-up rate too fast; cooling not on standby; agitation inadequate to dissipate heat | Reactor temperature log | Slow ramp rate into conversion zone; have cooling jacket water on standby below 95°C; verify stirrer baffle design |
| Grease soft / no gel structure | Conversion incomplete (held at too low temperature); or facial acid dose too low | D217 penetration; conversion temperature log | Re-process: raise temperature to 105–110°C and hold 30 min; verify facial acid 1.5–3% of total batch |
| Grease grainy / gritty texture | Inhomogeneous conversion — local hot spots converted before bulk; agitation poor | Microscope; sensory check | Improve stirrer design (anchor + frame); slower temperature ramp; ensure pre-mixing before conversion temperature |
| Water washout above 5% | Promoter water/alcohol not fully driven off; or sulfonate-to-base-oil ratio too low | D1264; water content; FTIR | Extend dehydration hold to 60 min at 180°C; verify sulfonate loading 25%+ of total batch |
| Drop point reported <300°C | Test artefact — oil bleed at high temperature, not gel collapse; or sulfonate loading too low | D2265 retest; verify oil separation | Increase sulfonate loading; reduce free oil content; CaSX typically reports as 'no drop observed at 300°C' |
| Stirrer drive trips during conversion | Viscosity rise during conversion exceeds drive capacity | Stirrer torque log | Specify variable-frequency drive sized for 3× the base oil viscosity load; reduce stirrer speed during conversion peak |
A CaSX plant requires more specific reactor capability than a lithium plant: 304 or 316 stainless steel construction (preferred over mild steel due to potential mild corrosion from overbased sulfonate and conversion intermediates), oversized stirrer drive to handle the viscosity rise during conversion, and rapid cooling capacity for exotherm management. See our Plant Setup service for complete specification, layout and commissioning.
Overbased calcium sulfonate concentrate contains amorphous calcium carbonate (calcite) particles dispersed inside calcium sulfonate micelles. CaSX manufacturing converts these particles from amorphous calcite to crystalline vaterite morphology — a polymorph of CaCO₃ with a different crystal habit.
The vaterite particles inter-lock to form the grease gel structure. Without this conversion, the overbased sulfonate is just a liquid additive (the same chemistry sold for engine-oil EP packages). The conversion uses a facial acid + promoter alcohol + water + calcium hydroxide system at controlled temperature.
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