Zirconium octoate 18, stannous octoate T9, potassium octoate 15 in DEG: three labels from three industries, one parent acid. Every commercial metal octoate is a salt of 2-ethylhexanoic acid (2-EHA, CAS 149-57-5) carrying a different metal.
The acid contributes hydrocarbon solubility and liquid handling. The metal decides which reaction the salt drives: cobalt and manganese decompose hydroperoxides to dry alkyd paint, tin and bismuth accelerate urethane gelation, potassium builds the isocyanurate rings in PIR foam.
Selecting one is a two-step exercise. Match the metal to the reaction your formulation needs, then compare grades by delivered metal content and carrier, because the number on every octoate label is metal percent, not purity.
Metal Octoates Are Salts of 2-Ethylhexanoic Acid
Metal octoates are metal salts of 2-ethylhexanoic acid, a branched C8 carboxylic acid. Octoate is the commercial shorthand; chemical databases index the same substances as 2-ethylhexanoates. One acid pairs with cobalt, manganese, zirconium, calcium, zinc, tin, potassium, bismuth, copper, and other metals to give the salts sold as driers, catalysts, and stabilizers.
The branch carries the practical value. A 2-ethyl side chain on the C8 backbone keeps these salts dissolved in white spirit, hydrocarbons, and plasticizers, so the metal ships as a pourable liquid concentrate instead of an insoluble soap.
The parent 2-ethylhexanoic acid is a bulk industrial chemical in its own right, feeding coolant additives and ester plasticizers alongside these salts.
Octoate vs Octanoate
Octoate and octanoate name salts of two different acids. Commercial octoate means 2-ethylhexanoate, from the branched acid; octanoate is, strictly, the salt of linear n-octanoic acid. Both are C8, which is why the labels get swapped, and why stannous octoate still appears mislabeled as tin(II) octanoate in chemical literature.
Copper shows the purchasing consequence. The copper octanoate the EPA registered as a fungicide in 1997 is a linear-acid copper soap, CAS 20543-04-8. Industrial copper octoate is copper 2-ethylhexanoate, CAS 149-11-1, a different substance that shows up in supplier-listed 6% copper grades as a wood-coating fungicide.
Verify by CAS number, not by name, any time an octoate crosses your desk. A name match can deliver the wrong molecule; a CAS match cannot.
How Metal Octoates Are Made From 2-Ethylhexanoic Acid
Two route types cover nearly every commercial metal octoate: direct reaction of the acid with a metal oxide, hydroxide, or carbonate, and double decomposition through the sodium salt and a metal chloride. Both consume industrial-grade 2-ethylhexanoic acid as the only organic feedstock, so salt producers qualify incoming acid on purity and color before anything else.
Direct Reaction
The direct route is a single neutralization: acid plus metal oxide, hydroxide, or carbonate, with water as the by-product. Stannous octoate forms this way from tin(II) oxide and 2-EHA.
The acid itself arrives one step downstream of the oxo process, via its own production route from propylene through n-butyraldehyde.
Double Decomposition
Double decomposition runs in two steps. The acid is first neutralized with sodium hydroxide to give sodium 2-ethylhexanoate; that salt then reacts with a metal chloride in a heated inert solvent, swapping sodium for the target metal.
Stannous chloride is the documented example for tin. Both named examples here are tin chemistry, but the two route types repeat across the family with only the metal source changed.
The Sodium Salt
Sodium 2-ethylhexanoate (CAS 19766-89-3) is the one alkali member that ships as a product, not only a reagent. The double-decomposition step above makes it in bulk, and it then fills two roles the drier and catalyst metals never do.
In pharmaceuticals, it acts as a salt-forming agent in β-lactam antibiotic manufacture, converting free acids to soluble salts such as cefuroxime sodium and sulbactam sodium. In industrial fluids, the sodium and potassium salts inhibit corrosion in organic-acid engine coolants and metalworking fluids.
Sodium and potassium are alkali metals, not driers or catalysts, which is why the salt belongs with the production chemistry rather than the coating or foam sections.
Drier Octoates for Paints and Coatings
Drier octoates split into three working tiers, each tied to a different job inside an oxidatively drying film.
| Drier tier | Metals | Function in the film |
|---|---|---|
| Primary | Co, Mn, Ce | Hydroperoxide decomposition, surface dry |
| Through | Zr, Li | Cross-linking through the film depth |
| Auxiliary | Ca, Zn, Ba | Support primaries, pigment wetting, hardness and gloss |
Cobalt octoate (CAS 136-52-7) is still the benchmark primary. Typical dosing runs 0.05 to 0.4% on vehicle solids, and the same salt has served for decades as the accelerator paired with MEKP peroxide in cold-cure unsaturated polyester systems.
Manganese is the working alternative where cobalt is being formulated out. Hiroaki Nakano of DIC reported in PCI Magazine that its ligand-accelerated manganese drier, DICNATE MV130A, reached hard-dry in 6.3 hours at 0.01% manganese on binder, against 11.3 hours for a conventional cobalt blend.
DICNATE MV130A is a neodecanoate rather than an octoate, which makes it evidence for the cobalt-free and octoate-free trends at once.
Parity is formulation-specific. Trade coverage in Coatings World and PCI around 2016 flagged the catch: simple manganese carboxylates need chelating accelerators to approach cobalt activity, and those complexes can shift color in light tints.
Zirconium earns its through-drier slot on alkyds with high hydroxyl content, where it is most active. Calcium and zinc octoates sit in the auxiliary tier; both also appear as heat-stabilizer chemistry in PVC, a separate acid-scavenging role outside coatings.
Lead octoate survives only as a legacy note. Older systems leaned on it where films had to dry below roughly 10 °C, and lead restrictions have pushed it out of consumer coatings.
Don’t substitute one metal octoate for another without re-qualifying the mechanism it’s actually driving. A zirconium bump will not rescue a film that lost its surface-dry catalyst.
Catalyst Octoates for Polyurethane, PIR, and Polyester Systems
Catalyst octoates accelerate addition and ring-forming reactions instead of oxidation. Tin drives urethane gelation, potassium drives isocyanurate trimerization, and bismuth covers the tin-free urethane role.
Stannous Octoate (T9)
Stannous octoate, tin(II) 2-ethylhexanoate (CAS 301-10-0), is the gelation catalyst behind flexible polyether slabstock foam, and the commercial grade carries roughly 28% tin. The same salt initiates ring-opening polymerization of lactide for polylactic acid and cures room-temperature-vulcanizing silicone rubber.
T9 is also the family’s most fragile member. The salt hydrolyzes on water contact and oxidizes from Sn(II) toward Sn(IV), so it cannot sit in water-containing polyol premixes, and aged material often runs yellow. When a foam line gels slow, I check T9 dosing and T9 condition first.
Potassium Octoate
Potassium octoate drives the trimerization that builds isocyanurate rings in PIR board stock and rigid spray foam. The potassium ion stabilizes the trimerization transition state and lowers the activation energy for ring formation, which is what buys PIR its thermal stability.
Grades ship as solutions: Milliken’s Hex-Cem line runs 15% potassium, and Umicore lists VALIREX K 15 in diethylene glycol. The same listing adds a second role, co-accelerating cobalt in unsaturated polyester gelcoats to cut cobalt dosage and color.
Bismuth Octoate
Bismuth 2-ethylhexanoate (CAS 67874-71-9) is the lead candidate wherever tin has to leave a polyurethane formulation. Shepherd positions its BiCAT catalysts against tin, lead, and mercury chemistry in 1K and 2K systems and has placed them in HFO-blown spray foam, with reaction rate scaling in proportion to bismuth concentration.
Read the acid as well as the metal here. BiCAT 8106 itself is a 20% bismuth C10 carboxylate, not an octoate, and the no-side-reaction claims are producer positioning: bismuth still needs qualification in your own water-blown system.
How to Read an Octoate Grade Label
An octoate label encodes three things: the metal, the delivered metal content as a weight percent, and the carrier. Cobalt 10 D60 is 10% cobalt metal in dearomatized hydrocarbon; zirconium 18 is 18% zirconium in mineral spirits; potassium 15 DEG is 15% potassium in diethylene glycol.
| Grade example | Delivered metal | Carrier | Producer |
|---|---|---|---|
| VALIREX Co 10 D60 | 10% Co | Dearomatized hydrocarbon | Umicore |
| Accelerator COB 6 | 6% Co | Solvent solution | United Initiators |
| MORDRY Zirconium 18 | ~18% Zr | Mineral spirits | Delta |
| VALIREX K 15 DEG | 15% K | Diethylene glycol | Umicore |
The percentage is metal, not salt content and not purity. Two drums at equal net weight can carry very different active metal, so quote comparisons belong on cost per kilogram of delivered metal.
Carrier compatibility is the second read. Diethylene glycol suits PIR polyol blends, mineral spirits suit solventborne alkyds, and plasticizer carriers belong only in systems that tolerate them; the right metal in the wrong carrier still fails the batch.
The metal-content percentage on the label is the real spec. Everything else on an octoate COA is downstream of that number.
Cobalt-Free, Tin-Free, and Octoate-Free Substitution
Cobalt-free, tin-free, and octoate-free product lines all trace to one regulatory driver: the EU classification of 2-ethylhexanoic acid and its salts as Reproductive Toxicant Category 1B (H360D) under CLP ATP 18.
The classification has been in force since 3 May 2022, became legally binding on 1 December 2023, and replaced the 4.5% specific concentration limit with the generic 0.3% threshold for Repr. 1B mixtures.
The 0.3% figure is where formulated products feel it. FUCHS notified coolant customers that any product carrying 0.3% or more 2-EHA or its salts needed reclassification from that date. The same arithmetic applies to a paint or foam system dosed with an octoate drier or catalyst.
The classification bans nothing. What it changes is the labeling cost of keeping an octoate in a consumer-facing product, and that economics drives three parallel substitution tracks:
- Cobalt-free driers: manganese and iron systems, often ligand-accelerated, chasing cobalt’s surface-dry performance.
- Tin-free catalysts: bismuth carboxylates taking over T9’s slots in polyurethane systems.
- Octoate-free carboxylates: whole product lines rebuilt on neodecanoic, isononanoic, or ricinoleic acid. Umicore has run this track since California’s Proposition 65 listing of 2-EHA drew attention in 2013.
The pressure lands unevenly. Umicore points the restrictions at decorative paints and bedding and furniture foam; industrial coatings and closed B2B channels are moving slower. Octoates remain the cost-effective default where the finished product stays below the 0.3% threshold.
What Most Buyers Get Wrong
The recurring mistake is buying octoates by name and by drum price. A name match can cross the octoate-octanoate line without anyone noticing, and a drum-price comparison hides that the label percent is delivered metal. The checks that protect a purchase are the CAS number and the cost per kilogram of metal, in a carrier your system accepts.
The deeper habit is mechanism-first selection. A cobalt drier, a tin gelation catalyst, and a potassium trimerization catalyst are not variations on one product; they are three different reactions wearing the same acid. The COA gives you four numbers; the spec sheet gives you the window; the application tells you which corner of the window you actually need.
The regulatory side matters commercially for the same reason: a 0.3% labeling threshold on the shared acid touches every branch of the family at once. A substitution plan is worth writing across your whole octoate list, not one product at a time.