Hydrogenated Castor Oil (HCO): Chemistry, Grades and Application Examples
Hydrogenated castor oil — also known as castor wax when fully saturated — is the catalytically hydrogenated derivative of natural castor oil, in which the ricinoleic acid double bonds are reduced to give predominantly 12-hydroxystearic acid triglycerides. The result is a hard, waxy solid with higher melting point, superior oxidative stability, and a cleaner odour profile compared to unhydrogenated castor oil. When ethoxylated, hydrogenated castor oil yields surfactants (HCO ethoxylates, often designated HCO-25, HCO-40, or by INCI as PEG-40 hydrogenated castor oil) that combine the solubilizing and emulsifying power of castor chemistry with the shelf-life advantages of saturated chains. Unethoxylated HCO itself serves as a structurant, opacifier, and matrix former in cosmetic sticks, pharmaceutical ointments, and industrial greases. Venus Ethoxyethers manufactures hydrogenated castor oil ethoxylates and supplies HCO-based formulation inputs from ethoxylation facilities in Goa, India — leveraging India's position as the world's largest castor seed producer.
What is hydrogenated castor oil?
Castor oil is a triglyceride derived from Ricinus communis seeds, composed predominantly (~90%) of ricinoleic acid — a C18 fatty acid with a hydroxyl group at the 12-position and a cis-9 double bond. Hydrogenation saturates the double bond, converting ricinoleic acid to 12-hydroxystearic acid. The hydroxyl group remains intact, preserving the unique hydrogen-bonding and lubricating properties that distinguish castor derivatives from conventional fatty alcohol surfactants.
Fully hydrogenated castor oil (HCO) is a hard, brittle wax with melting point 86–88°C, acid value <5, and saponification value ~175–185. Partially hydrogenated grades retain some unsaturation for specific rheology requirements. HCO is insoluble in water but soluble in hot polar solvents and mineral oil; it disperses in aqueous systems when ethoxylated or when emulsified with appropriate surfactants.
India produces approximately 75% of the world's castor seed, with Gujarat as the primary growing region. Venus Ethoxyethers, headquartered in Goa, India, is positioned within this supply chain for castor oil derivatives and their ethoxylated products. See the hydrogenated castor oil product page and castor oil ethoxylates range.
HCO chemistry: hydrogenation and ethoxylation
Step 1 — Hydrogenation: Refined castor oil is reacted with hydrogen gas at elevated temperature and pressure in the presence of a nickel or palladium catalyst. Each ricinoleic acyl chain is converted from C18:1 (one double bond) to C18:0 (saturated). The product is bleached, deodorized, and filtered to yield pharmaceutical or cosmetic grade HCO.
Step 2 — Ethoxylation (optional): HCO is reacted with ethylene oxide under base catalysis. EO adds to the hydroxyl groups on the hydroxystearic chains and the glycerol backbone, producing a complex mixture of ethoxylated triglycerides, diesters, and monoesters. Common commercial grades are defined by total EO moles per mole of oil: HCO-25 (25 EO), HCO-30, HCO-40 (40 EO).
The saturated C18 chains of HCO ethoxylates offer improved oxidative stability versus standard castor oil ethoxylates (COE) from unhydrogenated oil — important in cosmetic products containing fragrance, unsaturated botanical oils, or long shelf-life requirements.
HCO ethoxylates versus castor oil ethoxylates (COE)
| Property | HCO ethoxylate (HCOE) | Castor oil ethoxylate (COE) |
|---|---|---|
| Feedstock | Hydrogenated castor oil (saturated) | Natural castor oil (unsaturated) |
| Oxidative stability | Superior — no double bonds | Moderate — ricinoleic unsaturation present |
| Odour | Lower, cleaner | Characteristic castor note |
| Melting point (high-EO grades) | Higher — saturated chains pack tighter | Lower |
| HLB range (commercial grades) | Similar at equal EO: HCO-40 ≈ HLB 16–17 | COE-40 ≈ HLB 16–17 |
| Solubilization power | Excellent for fragrances, vitamin oils | Excellent — nearly equivalent at same EO |
| Primary advantage | Shelf life, oxidative stability, regulatory preference | Lower cost, slightly better lubricity |
| INCI (40 EO grade) | PEG-40 hydrogenated castor oil | PEG-40 castor oil |
For most cosmetic solubilization and O/W emulsification applications, HCO-40 and COE-40 are functionally interchangeable — the choice depends on oxidative stability requirements, odour sensitivity, cost, and customer INCI preferences. Full COE background is in our castor oil ethoxylates guide.
HCO ethoxylate grades and HLB
| Grade | EO moles | Form at 25°C | HLB (approx.) | Primary function |
|---|---|---|---|---|
| HCO-5 | 5 | Soft paste | ~6 | W/O co-emulsifier |
| HCO-15 | 15 | Soft solid | ~10 | Wetting, dispersing |
| HCO-25 | 25 | Paste | ~13 | O/W emulsifier |
| HCO-30 | 30 | Soft solid | ~14–15 | Emulsifier, detergent |
| HCO-40 | 40 | Hard wax / flake | ~16–17 | Solubilizer for fragrances and oils |
High-EO HCO grades (30, 40) require heating to 50–60°C before incorporation into formulations. Pre-melt and add to oil phase or pre-mix with fragrance before water dilution for solubilization applications.
Cosmetic stick formulations
Unethoxylated HCO is a cornerstone structurant in cosmetic sticks — deodorant sticks, lip balms, sunscreen sticks, and pharmaceutical suppositories — where it provides rigidity, pay-off, and thermal stability without the rancidity risk of unsaturated waxes.
Deodorant stick (W/O anhydrous matrix):
- 25% HCO (castor wax) — primary structurant, MP ~86°C
- 20% cyclomethicone + 15% isopropyl myristate — emollient carrier
- 20% stearyl alcohol — secondary structurant and slip agent
- 5% active (aluminum chlorohydrate or alternative)
- 5% fragrance + 5% talc + preservative, antioxidant
HCO forms a rigid crystalline network that melts on skin contact (pay-off) and re-solidifies. The saturated structure resists oxidation over 24–36 month shelf life in stick format. Stearyl alcohol modulates hardness — increase for firmer stick in tropical climates; decrease for smoother application in cold markets.
Lip balm stick:
- 30% HCO + 25% beeswax + 20% castor oil (natural, for gloss) + 15% shea butter + 5% vitamin E + 5% flavour oil
- HCO provides hardness; beeswax adds gloss and film; natural castor oil adds shine without compromising oxidative stability at low concentration
Venus HCO is available for stick compounders through the personal care and co-surfactants and emulsifiers product lines.
Pharmaceutical and cosmetic ointments
HCO and HCO ethoxylates appear in pharmaceutical ointment bases where emulsification, solubilization of actives, and compatibility with skin are required.
Hydrophilic ointment (O/W, USP-style):
- 25% white petrolatum + 25% stearyl alcohol + 12% HCO-25 (emulsifier) + 37% purified water + 1% methylparaben
- HCO-25 emulsifies the petrolatum/staryl alcohol oil phase into the aqueous continuous phase
- Heat oil phase to 70°C, add water phase at 70°C with stirring, cool to form stable O/W ointment
Fragrance-free moisturizing ointment:
- 10% mineral oil + 5% lanolin + 3% HCO-40 (solubilizer for lanolin components) + 2% cetyl alcohol + 80% water
- HCO-40 solubilizes lanolin alcohols and provides O/W emulsification with minimal irritation profile
For HLB matching in ointment emulsification, see our HLB scale guide and cosmetic emulsifiers guide.
Industrial applications of HCO and HCO ethoxylates
Metal working and lubricants: HCO provides boundary lubrication in greases and drawing compounds. Ethoxylated grades (HCO-5 to HCO-15) emulsify mineral oil lubricants into stable O/W emulsions for coolant recirculation systems. The 12-hydroxystearic hydroxyl group adsorbs on metal surfaces, reducing friction and tool wear.
Textile auxiliaries: Low-EO HCO ethoxylates serve as fiber lubricants in spinning and knitting, similar to COE but with better thermal stability during heat setting. Higher-EO grades assist dye bath leveling.
Leather processing: HCO-25 emulsifies fatliquoring oils into leather fibers. Saturated chain stability resists rancidity in stored fatliquor concentrates. See leather applications.
Agrochemical emulsions: HCO-36 and HCO-40 disperse pesticide actives in EC and suspoemulsion formulations. Oxidative stability is an advantage in concentrates stored for extended periods in tropical warehouses. Pair with calcium dodecylbenzene sulfonate for hard-water dilution stability per EC formulation guide.
Paint and coatings: HCO ethoxylates disperse pigments and emulsify latex binders in waterborne coatings. See paint and coating applications.
Concrete and construction: HCO acts as a release agent and curing compound additive in formed concrete applications.
Formulation and handling notes
HCO-40 and HCO-30 are waxy solids at ambient temperature. Store above 40°C or flake before use. Pre-melt at 55–60°C and add to the oil phase or pre-combine with fragrance/actives before aqueous dilution.
HCO ethoxylates are generally compatible with anionic, cationic, and amphoteric co-surfactants at typical use levels. Electrolyte tolerance is moderate — high salt may salting-out high-EO grades. Test clarity across 5°C to 40°C temperature cycling for cosmetic products.
Compared to glycerol esters (GMS, GMO) used as W/O emulsifiers, HCO ethoxylates offer higher HLB and solubilization capacity. GMS/GMO remain preferred for low-HLB W/O systems where unethoxylated lipophilic emulsifiers are required.
Regulatory and sustainability profile
HCO is derived from renewable castor seed — a non-food crop that grows on marginal land with low irrigation requirements compared to palm or soybean. Castor cultivation supports rural economies in Gujarat, Andhra Pradesh, and Karnataka. HCO ethoxylates carry INCI names recognized in EU, US, ASEAN, and Indian cosmetic regulations (PEG-X hydrogenated castor oil).
Residual ethylene oxide and 1,4-dioxane are monitored on every Venus COA to customer specification limits. Pharmaceutical and cosmetic customers should confirm compliance with relevant pharmacopoeia and cosmetic directive limits.
Manufacturing and quality at Venus Ethoxyethers
Venus ethoxylates hydrogenated castor oil in dedicated pressurized reactors in Goa, India. Quality parameters include saponification value, hydroxyl value, cloud point, pH, colour Gardner, EO mole ratio, and residual ethylene oxide. With 90,000 MT group manufacturing capacity, 24/7 R&D, and toll ethoxylation services, Venus supplies HCO ethoxylates from 5 to 40+ EO moles for cosmetic, pharmaceutical, textile, leather, and industrial markets.
Related products: castor oil ethoxylates guide, polysorbates, emulsifiers range, ethoxylated alcohols. Application pages: personal care, textile chemicals, agrochemicals. Request samples and TDS via contact Venus Ethoxyethers.