REAXIS® C216 (Dioctyltin Dilaurate), also commonly abbreviated as DOTL, has been one of the most commonly used octyl-based organotins as tin catalysts for polyurethane and silicone condensation reactions. REAXIS® C216 has been the traditional go-to replacement for its butyl analogue, REAXIS® C218 (Dibutyltin Dilaurate). Due to the recent EU regulatory classification of dioctyltin dilaurate as a “Substance of Very High Concern” (SVHC), there has been a demand for alternatives for butyl-based organotins typical either of an octyltin or inorganic tin nature.
Alternative products for DOTL would include other octyl derivatives such as REAXIS® C228 (Dioctyltin Diacetate), REAXIS® C318 (Dioctyltin Dineodecanote) or REAXIS® C314 (Dioctyltin bis-(2-ethylhexyl Maleate). Inorganic tin alternatives would include REAXIS® C125 (Stannous Neodecanoate) and REAXIS® C129 (Stannous Octoate). All the above-mentioned products are neat liquids with varying metal content and ligand make-up.
|Tin Content (%)||15.0 - 16.5|
|Color (Gardner Number)||3 Max|
|Density (g/ml)||1.01 - 1.03|
|Refractive Index (nD @20°C)||1.470 - 1.480|
REAXIS® C216 and its alternatives can be used as a homogeneous catalyst in a wide spectrum of polyurethane and silicone applications including adhesives and sealants, elastomers and plastics, and coatings. Silicone-based applications for DOTL include: acetoxy-, ethoxy- and oxime-based Room Temperature Vulcanizing (RTV) adhesives and sealants, polyethylene crosslinked silanes (PEX), and select silane-modified polymers (SMPs). In regard to polyurethane applications, REAXIS® C216 can be used for most related applications including coatings, adhesives and sealants, elastomers, and foams.
The reactivity and raw material compatibility of REAXIS® C216 should be somewhat similar to its butyl tin analogue, REAXIS® C218. Due to the larger alkyl group and steric effects and lower active tin metal content (16% vs 18%), REAXIS® C216 is expected to be somewhat slower in reactivity compared to REAXIS® C218, although this would be highly formulation specific. This reactivity difference is evidenced both in polyurethane and silicone chemistries in general, across all applications. In regard to silicone reactions, REAXIS® C216, like all tin-based catalysts, will catalyze the silanol/silane condensation reaction thus acting as both a polymerization and crosslinking catalysts. As a polyurethane catalyst, REAXIS® C216, will preferentially catalyze the urethane reaction and to a lesser extent the water reaction, thus acting as a polymerization/gelation catalyst.
REAXIS® C216 should be stored in the original packaging at moderate temperatures and kept from freezing. The container should be closed tightly after each use to maximize shelf life. Characteristic of most Sn(IV) organotins, the primary cause of instability would be hydrolysis. Hydrolysis results in the formation of tin oxide insolubles leading to deactivation of REAXIS® C216.