| Dibutyltin and monobutyltin compounds are used as
esterification catalysts for the manufacture of organic esters and/or
polyesters. Examples of simple organic esters include plasticizers,
lubricants, and heat-transfer fluids.
Polyesters produced by the use of organotin compounds
are used as binders for formulating coatings for industrial use, or
when modified with fatty acids they are used as binders for air drying
coatings for decorative and protective applications. Dibutyltin
compounds are also used as catalysts for transesterification and
polycondensation of dimethyl terephthalate into polyethylene
terephthalate or manufacturing of high molecular weight copolyester
elastomers. The use of these materials is either in packaging
applications or engineering plastics.
The esterification reactions catalyzed by organotin
compounds require temperatures above 200°C, which is much
higher than those involving strong acid catalysts, such as
p-toluenesulfonic acid. Though, number of advantages justifies the use
of organotin catalysts. The side reactions are minimized so the end
products have better color and odor properties because fewer
by-products are formed, there is no need for refining to remove the
catalyst residues and the equipment corrosion is eliminated. Usual
levels of tin catalysts are 0.05–0.3 wt % based on the total
reactants charged. |
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