Methyl Tin Mercaptide

About This Product

Methyl tin mercaptide is a liquid organotin heat stabiliser for rigid PVC. It is a blend of monomethyltin and dimethyltin compounds bonded to sulfur-containing ligands, most commonly esters of thioglycolic acid such as 2-ethylhexyl thioglycolate; in that chemistry the dimethyltin component is CAS 57583-35-4 and the monomethyltin component CAS 57583-34-3. The exact composition differs by grade, so take the identity for any offer from its safety data sheet. Two grades are listed here, DX-181 and DX-980. PVC starts to lose hydrogen chloride at processing temperatures, and each lost molecule leaves a double bond that makes the next loss easier, so colour and properties deteriorate quickly. Tin mercaptides interrupt that chain in two ways: the tin replaces unstable chlorine atoms in the polymer with a stable sulfur-bonded group, and the compound scavenges the hydrogen chloride that is released. Because the stabiliser dissolves in PVC and does not form opaque metal soaps, it gives the best clarity and early colour of any stabiliser family. The monomethyltin component mainly controls early colour, while the dimethyltin component provides long-term stability, so the ratio between them is a key grade parameter. The main applications follow from those properties: clear rigid film and sheet for packaging and thermoforming, clear bottles, rigid pipe and fittings, profiles, and injection-moulded parts that need a long processing window. Pipe formulations typically use a fraction of one part per hundred resin, while clear sheet and film need more. A separate methyltin grade formulated for CPVC is listed for its higher processing temperatures. Buyers usually agree tin content, the mono-to-dialkyl ratio, sulfur content, specific gravity, colour and viscosity, and sometimes volatile matter. Tin content is the best single guide to stabilising power, so compare offers at the same tin level. For food-contact or potable-water articles, ask for a declaration of compliance against the applicable plastics regulations and approvals. Safety data sheets for methyltin mercaptide blends typically carry classifications for skin sensitisation and for organ damage after repeated exposure, often with reproductive toxicity and aquatic hazard classifications depending on composition. Transport classification also depends on the grade, so take it from section 14 of the safety data sheet. Under EU REACH and UK REACH, Annex XVII restricts tri-substituted organotins and certain dibutyltin and dioctyltin compounds in some articles; methyltin compounds are not named in that entry, but an importer should confirm the registration status of each component and ask for impurity data on other organotins. Store drums closed in a cool, dry area away from oxidisers, acids and direct sunlight, because moisture and heat can hydrolyse the ester groups and produce odour. Handle with chemical-resistant gloves, goggles and local exhaust ventilation, and avoid breathing vapour during hot processing. When you enquire, state the process and product (pipe, clear sheet, profile), your current tin level or dosage, the grade you use now, any food-contact requirement, the pack size and your annual volume.