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Dioctyltin dilaurate (DOTL) is an organotin compound used extensively as a catalyst in polyurethane, silicone, esterification/transesterification and PVC-stabiliser applications.
This review summarizes its synthesis, chemical and physical properties, application chemistry, catalytic mechanisms, dosage and formulations, toxicity and safe handling, environmental behaviour, regulatory issues, supply chain and quality control issues, alternatives and future outlook.
CAS Number: 3648-18-8.
Synonyms:
Dioctyltin dilaurate (DOTL) ,Dioctyl tin dilaurate ,Possibly “dioctyltin(IV) dilaurate” in IUPAC style.
Synthesis and Manufacture
2.1 Raw materials and reaction
Production of dioctyltin dilaurate generally involves the reaction of a dioctyltin precursor with lauric acid (dodecanoic acid) or its ester/derivative under appropriate conditions.
The tin precursor is dioctyltin oxide or dioctyltin dichloride, which reacts with the laurate (C₁₂H₂₃COO⁻) ligand to yield the tin(IV) carboxylate complex.
The stoichiometry: (C₈H₁₇)₂Sn (probably as oxide or hydroxide) + 2 C₁₂H₂₃COOH → (C₈H₁₇)₂Sn(O₂C-C₁₁H₂₃)₂ + H₂O (or HCl if dichloride used) (simplified).
The sum formula C₄₀H₈₀O₄Sn suggests two laurate ligands and two octyl groups bound to tin (i.e., (C₈H₁₇)₂Sn(O₂C-C₁₁H₂₃)₂).
Purification & formulation
The crude product is typically refined (removal of free acid, unreacted tin precursor, catalysts) and then adjusted into the appropriate formulation (liquid grade for TIB KAT 216, or powder grade for analogous product TIB KAT P 216).
Quality control includes tin content, acid value, viscosity, moisture content, and purity (absence of free tin chloride/hydroxide, etc). Shelf-life is commonly given as one year.
Alternative routes
Alternative organotin carboxylates (e.g., dioctyltin diacetate, dioctyltin diketonate) exist; these can serve as analogues when different solubility or reactivity is required.
Manufacturers may vary the alkyl groups or carboxylate ligand to tune activity and toxicity.
Chemical Structure and Properties
Molecular structure
The tin center is in oxidation state +4 (Sn(IV)).
It is bonded to two octyl (C₈H₁₇) groups (organotin alkyl) and two laurate (dodecanoate) ligands via carboxylate. The structural formula may be written as (C₈H₁₇)₂Sn(O₂C-C₁₁H₂₃)₂.
Electronically, the tin has a four‐coordinate geometry (likely tetrahedral or distorted tetrahedral) although in practice organotin carboxylates may dimerize or form bridging structures in solid state or high concentrations.
Physical properties
Sum formula: C₄₀H₈₀O₄Sn.
Appearance: A liquid grade catalyst (TIB KAT 216) – the liquid form suggests it is a low to moderate viscosity oil/solution rather than a crystalline solid.
Density, melting point, boiling point, viscosity and other standard data are not publicly fully disclosed in the open technical datasheets (for example on SpecialChem data is locked).
Solubility: as an organotin carboxylate, likely miscible in many organic solvents (esters, aliphatic hydrocarbons, some silicones) but insoluble or only very low solubility in water.
Reactivity: It is stable under typical storage conditions but can hydrolyse in presence of strong acids, bases or water and may form tin oxides/hydroxides over long term.
Stability and storage
The product shelf‐life is commonly one year when stored under recommended conditions (cool, dry, sealed container).
Storage should avoid moisture ingress, strong acids or bases, and elevated temperatures. Degradation may lead to loss of catalytic activity, formation of tin oxide/hydroxide, or generation of undesirable side products.
Mechanism of Catalysis and Applications
Catalytic mechanism – overview
Organotin carboxylates such as dioctyltin dilaurate act as Lewis acidic catalysts and tin–alkyl/ tin–carboxylate based catalysts.
The tin center is able to coordinate to reactive functional groups (e.g., isocyanates in polyurethane chemistry, silanol groups in silicones, ester/acid groups in esterification/transesterification) and thereby activate them toward nucleophilic attack or rearrangement.
In polyurethane foam or elastomer manufacture, the catalyst accelerates the reaction between the polyol and the isocyanate (urethane formation) and may promote urea/urethane cross‐linking.
In silicone RTVs (room temperature vulcanising silicones), the tin catalyst can activate moisture or silanol condensation.
In esterification/transesterification, the tin carboxylate can coordinate the ester or carboxylic acid, facilitating exchange of alkoxy groups.
Primary applications
According to the manufacturer’s specification for TIB KAT 216:
Catalysis of polyurethane reactions (foams, elastomers, coatings)
Curing of silicone resins and RTV silicones
Transesterification and esterification reactions
Stabiliser for PVC
Dosage and formulation considerations
Typical dosage is between 0.1 – 1 wt% of the formulation.
Formulators must consider: compatibility of the liquid catalyst with the resin system (viscosity, miscibility), pot‐life of the reactive mixture (too high catalyst may lead to very short pot life), and desired curing profile (room temperature vs elevated).
It is important to monitor tin content (for regulatory reasons), to ensure catalyst is dispersed evenly (avoiding hot spots or incomplete cure), and to check that no adverse interactions (colouration, side reactions) occur.
Comparison to alternatives
Compared with the older and more widely used di-butyltin dilaurate (DBTDL) catalysts, dioctyltin dilaurate (DOTL) has been claimed to have a more favourable toxicological profile (i.e., less acute toxicity) while retaining similar catalytic performance in many polyurethane systems.
Its use is often preferred in systems where lower volatility or regulatory pressures on dibutyltin compounds exist.
Specific industrial uses
In polyurethane foam production: improves cure speed, yields higher cross‐link density, allows lower catalyst levels.
In silicone elastomer curing: particularly in acetoxy or oxime cure systems, DOTL can act as a cure promoter for RTV silicones.
In polyester/alkyd resin synthesis and transesterification: tin catalysts like DOTL accelerate ester interchange, polycondensation, and reduce reaction time.
As PVC stabiliser: DOTL acts by replacing harmful lead/organotin stabilisers to provide heat and light stability for PVC processing.
SAFETY INFORMATION ABOUT TIB KAT 216
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
