Basic polymer doctrine

Very small amounts (low ppm) of alkali, alkaline earth metal salts or quaternary ammonium compounds are added to the reactors to control the amounts of DEG that are generated in the polymerisation reaction. The use of these materials in the manufacture of polymers for food contact packaging is covered under the basic polymer doctrine for use in the US, by EU legislation and legislation in some member states. 

Melt stabilisers such as phosphoric acid and its salts and esters are added to the polymerisation process to reduce thermal degradation and colour formation (yellow). They also have the added effect of stabilising the polymer when it is being later processed into food packaging. Many of the phosphorus based stabilisers are listed in 2002/72/EC for use in food contact applications and are covered by the basic polymer doctrine of the US EDA. 

Basic Polymer Doctrine Substances such as catalysts, chain regulators, chain transfer agents and other material used at low levels (generally used at 1% or below) and which are required to produce the resin are considered part of the basic resin and are not subject to independent regulatory consideration. Therefore, a clearance which applies to a basic resin extends to the substances that are necessarily used during the polymerisation stage to produce it. 

---