Tetravalent tin(IV) bis-acetate; clear yellow liquid; MW 351.0; lower steric bulk than DBTDL with acetate byproduct.

DOTL — dibutyltin diacetate, CAS 1067-33-0 — is a tetravalent organotin compound with two n-butyl groups and two acetate (CH₃COO⁻) ligands on the tin centre. Molecular formula C₁₂H₂₄O₄Sn, molecular weight 351.0 g/mol, density 1.31 g/cm³ at 20°C. SEMITECH supplies DOTL as a clear pale-yellow to amber liquid at ≥98% active content, with tin assay 33.0–34.0% by ICP-OES (substantially higher than DBTDL’s 18% because acetate is far lighter than laurate), water content ≤0.1% by Karl Fischer, and APHA colour ≤150. The acetate ligand is volatile and odorous when the compound is heated above 80°C — handling at room temperature presents no air-quality issue.

The acetate ligand structure is what differentiates DOTL from DBTDL operationally. Acetate is a smaller, more electron-donating carboxylate than laurate, which paradoxically reduces the Lewis acidity of the tin centre — DOTL is approximately 30–50% slower than DBTDL at equivalent molar loading despite higher tin content per gram. The benefit is process latitude: formulators get a longer pot-life and tack-free window without dropping the tin content low enough to risk under-cure in deep sections. The drawback is acetate byproduct release on cure (mild vinegar odour, possible copper/marble staining if applied to those substrates).

Same fundamental chemistry as DBTDL — silanol activation and alkoxide condensation — at 30–50% lower rate.

DOTL operates by the same Lewis-acid catalysis mechanism as DBTDL: it coordinates to the silanol oxygen of α,ω-dihydroxy-PDMS, activates it for nucleophilic attack by alkoxysilane crosslinker, and accelerates release of the alcohol byproduct. The rate constant is approximately 0.5–0.7× that of DBTDL at equivalent molar concentration, giving tack-free times of 60–120 minutes at 23°C and 50% RH at 0.20% loading in alkoxy-cure RTV-1 (vs 30–60 minutes for DBTDL at the same loading).

• Loading 0.10–0.20% — long-pot-life RTV-1 sealants, vertical-bond overhead applications
• Loading 0.20–0.40% — standard cast-in-place RTV-2 mould rubber for prototype tooling, candle moulds
• Loading 0.40–0.80% — fast-cure DOTL formulations approaching DBTDL kinetics; rare in practice

DOTL is the catalyst of choice when the formulation requires extended hand-tooling time — large bead architectural sealants, decorative cast-in-place mould rubber where the moulder needs 30+ minutes of open time to register the master, or production lines where a slow tack-free is acceptable but skin-over within the catalyst-to-skin window must be predictable. Like DBTDL, DOTL poisons platinum addition-cure systems at ppm levels — segregate handling and metering.

Cast-in-place RTV moulds, hand-tooled architectural sealants, slow-cure RTV-2, alkyd transesterification.

RTV-2 condensation cast moulds are the largest single application — prototype tooling, decorative resin casting moulds, candle moulds, and food-contact silicone moulds. DOTL at 0.20–0.40% paired with TEOS or ethyl-silicate-40 gives a 45–90 minute pot-life and 24-hour cure, allowing the moulder to mix, degas, pour, and register the master without rushing. Hand-tooled architectural sealants (large building joints, expansion seal cast in place) use DOTL at 0.10–0.20% paired with methyltrimethoxysilane crosslinker to deliver a 60–90 minute working time before skin formation begins.

Alkyd resin transesterification at 200–230°C uses DOTL at 0.05–0.15% on resin solids — the higher reaction temperature compensates for the lower intrinsic catalyst activity, giving an acceptable rate while reducing residual catalyst activity in the finished resin. Polyurethane-modified alkyds use DOTL at 0.02–0.08% for the urethane formation step before alkyd transesterification, leveraging its lower activity to suppress side reactions. Avoid DOTL for sealants on copper, brass, marble, or carbonate stone — the acetate byproduct will stain or corrode these substrates; specify TBT or TET titanate dealcoholisation cure for those applications.

CoA on every shipment, 25 kg HDPE under nitrogen blanket, 12-month shelf life sealed, 2–4 week ex-China.

SEMITECH issues a Certificate of Analysis on every batch with: tin assay (ICP-OES, target 33.0–34.0%), active content (titration vs. potassium iodate, target ≥98%), water content (Karl Fischer, target ≤0.1%), APHA colour (target ≤150), and density. Standard packing is 25 kg HDPE jerrycans under nitrogen blanket; 200 kg lined steel drums for bulk. MOQ 25 kg. Lead time ex-Zhejiang: 1–2 weeks to Asia ports, 4–6 weeks to Europe and North America after sea freight.

DOTL hydrolyses on prolonged moisture exposure — the acetate ligand cleaves more easily than laurate, so DOTL has a slightly faster degradation profile than DBTDL once the seal is broken. Recommended: re-blanket with dry nitrogen after each draw and consume opened drums within 45 days for consistent activity. Store sealed below 25°C, away from oxidisers and strong bases. REACH and regulatory note: DOTL (CAS 1067-33-0) is REACH-registered for industrial catalyst use; the 2010 Annex XVII restrictions on organotins target skin-contact and food-contact articles, not industrial silicone catalysts. SEMITECH issues REACH compliance and SDS in EU/GHS format on every shipment.

DOTL is the long-pot-life tin catalyst — 30–50% slower than DBTDL at equivalent loading, delivering 60–120 minute tack-free times and 45–90 minute hand-tooling windows in RTV-1 sealants and RTV-2 cast moulds. Specify when working time matters more than peak cure speed. Avoid on copper, brass, and carbonate stone substrates.

SEMITECH stocked grade; CoA per batch.