What Dibutyltin Dilaurate Is
Dibutyltin dilaurate, usually abbreviated DBTDL or DBTL, is a diorganotin compound in which a central tin atom carries two n-butyl groups and two laurate (dodecanoate) ester groups. It is one of the most widely used organotin catalysts in the polymer industry because it combines strong Lewis acid activity with good solubility in the resins and solvents that polyurethane, silicone and ester systems actually use. Unlike tin-free alternatives, it remains active at very low addition rates, which keeps formulation costs and side reactions low.
| Parameter | Value |
|---|---|
| Common name | Dibutyltin dilaurate (DBTDL) |
| CAS number | 77-58-7 |
| Molecular formula | C32H64O4Sn |
| Molecular weight | 631.6 g/mol |
| Theoretical tin content | 18.8 % |
| Appearance | Pale yellow to yellow clear liquid with a mild fatty odour |
| Density | Approximately 1.05 g/cm³ at 25 °C |
| Solubility | Miscible with esters, ketones, alcohols and aromatic or aliphatic hydrocarbons; negligible solubility in water |
| Stability | Slowly hydrolyses in the presence of moisture; keep containers closed |
| Catalyst type | Lewis acid organotin catalyst |
Catalytic Mechanism and Why Low Loadings Are Used
DBTDL accelerates reactions in which a nucleophile attacks an electrophilic carbon centre. In polyurethane chemistry it promotes the reaction between isocyanate groups and hydroxyl groups to form urethane linkages, and it also favours the isocyanate–water reaction that generates carbon dioxide in flexible foams. In silicone chemistry it catalyses the condensation of silanol groups, which is the basis of room-temperature-vulcanising sealants and coatings.
Because the catalyst is not consumed in the reaction, typical addition rates are low, generally in the range of a few hundred parts per million up to about 0.5 % based on resin solids. Overdosing speeds curing but shortens pot life and can cause premature gelation, discolouration or loss of elongation in the finished polymer, so the dosage should always be established through a pot-life and cure-profile trial rather than by rule of thumb.
Main Industrial Applications
Polyurethane systems: flexible and rigid foams, adhesives, coatings, sealants and cast elastomers, where it balances gel and blowing reactions.
Silicone sealants and RTV rubber: silanol condensation catalyst for moisture-curing sealants, mould-making rubbers and release coatings.
Esterification and transesterification: catalyst for producing plasticisers, polyesters and specialty esters, including alkyd and unsaturated polyester resins.
Adhesives, caulks and mastics: accelerates cure in moisture-curing and two-component formulations while improving adhesion and filler loading.
Coatings and inks: promotes crosslinking, which raises hardness, chemical resistance and gloss retention of the cured film.
PVC processing: used in some formulations as a lubricating organotin stabiliser component alongside the main heat stabiliser.
Dibutyltin Dilaurate and Dibutyltin Diacetate Are Not the Same Product
The two organotin catalysts are frequently confused in online descriptions because both are dibutyltin diesters, but they are distinct substances: dibutyltin dilaurate has CAS 77-58-7 and is based on lauric acid, while dibutyltin diacetate has CAS 1067-33-0 and is based on acetic acid. The acetate releases acetic acid and is more hydrolytically sensitive, giving faster cure in some systems; the laurate is more hydrophobic, has a longer open time and is the standard choice where hydrolytic stability and low odour matter. Buyers should specify the intended CAS number rather than the generic term organotin catalyst, otherwise an unsuitable grade may be supplied.
Regulatory Status, Handling and Storage
Dibutyltin compounds are classified for reproductive toxicity and are covered by restrictions on organotin compounds in several jurisdictions, including REACH Annex XVII in the European Union. Industrial users should therefore work from the supplier's SDS, apply the specified exposure controls and avoid any use in applications where consumer contact is foreseeable unless the specific legal conditions are met.
Use local exhaust ventilation and impervious gloves, goggles and protective clothing when handling the concentrate.
Avoid contact with skin and eyes, and never allow the material to enter drains or water courses; organotin compounds are toxic to aquatic life.
Store in tightly closed original containers in a dry, cool, ventilated place away from oxidisers, acids, food and feed.
Protect from moisture, which hydrolyses the ester groups and produces turbidity and reduced catalytic activity.
Typical shelf life is 12 to 24 months in unopened drums; rotate stock and re-test turbid or aged lots before use.
Frequently Asked Questions
Q: What is dibutyltin dilaurate used for?
It is used as a catalyst for polyurethane foams, coatings, adhesives and elastomers, for silanol condensation in silicone sealants, and for esterification and transesterification reactions.
Q: What is the CAS number of dibutyltin dilaurate?
The CAS number is 77-58-7; the molecular formula is C32H64O4Sn and the molecular weight is 631.6 g/mol.
Q: Is dibutyltin dilaurate the same as dibutyltin diacetate?
No. Dibutyltin diacetate is a different substance with CAS 1067-33-0 and different cure behaviour; the two must not be used interchangeably without reformulation testing.
Q: How much catalyst should be added?
Additions typically run from a few hundred parts per million to about 0.5 % on resin solids; the working level should be fixed by a pot-life and cure-profile trial for each formulation.
Q: Is dibutyltin dilaurate hazardous?
Yes. Dibutyltin compounds carry a reproductive toxicity classification, so the concentrate must be handled with the exposure controls specified in the safety data sheet.
Q: How should dibutyltin dilaurate be stored?
Keep it in closed original containers in a dry, ventilated area away from oxidisers and acids, protected from moisture, and re-test aged or turbid material before use.