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Tin stabilisers


17 December 2014

DOTE Classification and SVHC/Candidate List

DOTE Regulatory Update


By far the largest use for tin compounds is in the stabilisation of PVC. Contrary to North America, where tin systems are used for almost all-rigid PVC applications, the main usage in Europe is for rigid, transparent applications where rigorous processing conditions require an outstanding stabilisation.

In addition to maintaining high transparency, tin stabilisers also provide a very good early colour (no yellowing) and very good colour retention (delay of yellowing). Due to their fast and complete mechanism of stabilisation, tin stabilisers are also suitable for use in opaque applications and particularly where light colours are required, or when process requirements are demanding (thick plate extrusion, furniture films). Additionally, tin stabilisers provide a very good processability with high through put and no plate out.

Moreover tin stabilisers are approved for use in food contact applications, potable water applications and some tin stabilisers are approved for use in rigid medical applications.

Examples of applications where tin stabilisers are widely used are: calendered films for pharmaceutical or food packaging, foils such as credit cards, sheets and sidings, extruded pipes and profiles, extruded blown films, injection moulding fittings and other technical articles.

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 is 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 food contact, for the production of PVC blown films, like candy wrapping.

The second group is often described as Tin mercaptides. These stabilisers are highly efficient and allow the production of rigid PVC articles even under high-demanding processing conditions (calendering, extrusion and injection moulding). Tin mercaptides have a typical characteristic strong odour, detectable during processing and in many cases on PVC finished articles. 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 suitable stabilisers with best performance, mainly dependent upon process technologies and PVC end-use application. The alkyl groups are Octyls, Methyls and Butyls.

Health and environmental concerns and restrictions on specific organotins used in anti-fouling paints (TBT) generated some questions about the future of organotin compounds. Risk assessments on various organotin compounds including stabilisers have been conducted between 2002 and 2007. The final decisions resulting from these risk assessments led to some restrictions on specific applications, and clarified that there is still a future for organotin stabilisers. Most organotin stabilisers have already been successfully REACH registered.


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