Most people are familiar with tin, the silvery white metal that is found throughout nature. It is a versatile, non-toxic metal, used for everything from food canning, toy soldiers and musical instruments to dental amalgams, electronics, ceramic pigments, soldering and pewter.
When a bond is formed between tin and carbon, a new broad class of compounds called "organotins" is formed. "Organotins" are versatile agents used in a variety of industrial applications, including:
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As heat stabilizers in processing polyvinyl chloride (PVC or vinyl).
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As catalysts in certain polyurethane, polyester and silicone systems to speed up chemical reactions.
They are also used in glass coatings, to add strength and heat reflection.
Heat stabilizers are a necessary ingredient when PVC is processed into products. As part of the manufacturing process, the polymer must be heated to high temperatures and, without stabilizers, these temperatures would cause the polymer to decompose. Tin is only one of several stabilizers that have been used in vinyl products for more than 50 years.
There are three major types of tin stabilizers (organotin stabilizers), distinguished by their respective alkyl groups: octyl, butyl and methyl.
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Octyltin stabilizers are made up of either one octyl group (monooctyl) or two octyl groups (dioctyl) bonded to the tin atom. Some octyltin stabilizer formulations are approved for food contact applications by most regulatory agencies worldwide, including the U.S. Food and Drug Administration (FDA).
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Butyltin stabilizers are made up of one butyl group (monobutyl) or two butyl groups (dibutyl) bonded to the tin atom. Butyltins are used in rigid applications such as siding and window profiles and are approved for use in drinking water pipe in the United States and Canada.
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Methyltin stabilizers are made up of one methyl group (monomethyl) or two methyl groups (dimethyl) bonded to the tin atom. Some octyltin stabilizer formulations are approved for use in water pipe and in food contact applications by most regulatory agencies worldwide, including the U.S. Food and Drug Administration (FDA).
In North America, tin stabilizers are used in a variety of vinyl products, including:
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Building and construction products - vinyl roofing, gutters, window profiles, doors, siding and pipe.
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Packaging - bottles for vegetable oil, fruit juices and wine; bottles for nonfood items such as shampoo and cosmetics; blister packs for pharmaceuticals.
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PVC foams, topcoat layers in flexible vinyl flooring and flexible calendered sheets.
Tin stabilizers are an especially good choice for the packaging market because of their high clarity and transparency. Tin stabilizers also:
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Preserve compound color hold even under the most severe processing conditions, which means whiter products that keep their color.
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Provide excellent weathering characteristics.
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Improve output extrusion rates.
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Provide excellent cost performance and overall value to the customer.
Tin stabilizers have been safely used in vinyl products for more than 50 years. They have been carefully studied and found to be safe when used appropriately. The industry is also in the process of conducting additional studies to update its data so that it is consistent with current standards. TSA member companies have voluntarily committed to providing the information requested under the U.S. Environmental Protection Agency (EPA) program to assess high production volume (HPV) chemicals.
In addition, the use of tin stabilizers has been approved in certain applications by government agencies throughout the world, including the FDA and the National Sanitation Foundation (NSF).
The industry has embraced the principles of Responsible Care®, the chemical industry's commitment to continual improvement in all aspects of health, safety and environmental performance.
October 2001
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