| Tin
stabilisers can be divided into two main groups, the first
containing stabilisers with tin-oxygen bonds and the second
stabilisers with tin-sulphur bonds.
The first group are Tin
carboxylates, which provide an excellent light- and
weathering stability to PVC products and find rising use
particularly in outdoor applications. Some examples are
transparent panels and translucent double-wall panels for
greenhouses. Specific stabilisers within this group –
Octyltinmaleates – are approved for the production
of blow moulding films, like candy wrapping.
The second group is often described
as Tin mercaptides. These stabilisers are highly
efficient and allow the production of crystal clear, rigid
vinyl articles even under high-demanding processing conditions.
Tin mercaptides have a typical characteristic odour, which
might be nuisance during processing. They show moderate
light-stability. The most powerful compounds within the
mercaptide class are the mercapto-acetate (thioglycolate)
ester derivates and these are the most common tin compounds
applied today. The Tin mercaptides are usually mixtures
of di-alkyl –and mono-alkyl tin-compounds, of which
the ratio can be varied to create stabilisers with best
performance, mainly dependent upon the used PVC-Type and
the end-use application.
The alkyl groups are Methyl,
Butyl, Octyl or Lauryl.
Methyl-, Octyl- and Lauryltins
are approved by health authorities of various countries
for the stabilisation of rigid PVC for packaging in contact
with food.
Butyltins are used in technical
applications.
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