Monomers - the basic building blocks

Terephthalic acid (TA) (diacid) is now the major monomer used in the production of PET. It is produced on a world-wide scale and is available in a number of purities. These can be generally referred to as PTA (pure TA), MTA (medium purity TA) or CTA (cmde TA). These descriptions are subjective and used in different ways by manufacturers. The purity of TA is the self-limiting process in PET manufacture. The major impurity in any TA grade is 4-carboxybenzaldehyde and it is a chain growth inhibitor. As the level of impurity increases less reaction can take place. From a food contact point of view the purity or impurities in the TA is important. Both US and EU law state that monomers should be of good technical quality but do not define what that technical quality should be. If no other information is available the 

Most petitions require a dossier of information on the substance and details of how to prepare these dossiers are given in ref. 5 for submission to the US authorities and in ref. 6 for Europe. One issue for both European and US authorities to consider is that although they require similar information to be submitted to the authorities, the information requirement is not the same and this can result in extra and unnecessary costs for the petitioner. 

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Vinyl chloride monomer, the basic building block of polyvinylchloride (PVC), is commercially manufactured by dehydrochlorination of 1,2-dichloroethane. The modern process for producing 1,2-dichloroethane involves oxychlorination of ethylene in a fluidized bed catalytic reactor ... 

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