A Practical Understanding of the Polymer ... - Keller Heckman

More documents

Recommendations

Info

A Practical Understanding of the Polymer Exemption Under TSCA (including residual precursors) that makes the assessment of the water-absorbing status of the polymer, per se, unclear or impractical. The definition that a waterabsorbing polymer is “a polymeric substance that is capable of absorbing its own weight of water” does not provide ample guidance. The capacity of every polymer to absorb water need not always be determined for purposes of establishing compliance with the polymer exemption. In lieu of anything else, the following guidance is offered, although it should be noted that it is unofficial. You might find that the polymer in question is totally soluble in water or in a solvent that consists of water to a significant extent. Alternatively, you might find that, as manufactured, the polymer is dispersed in water or in a solution that contains a significant level of water. The fact that a polymer is formed as a waterborne solution or dispersion does not necessarily mean that the polymer has absorbed its own weight in water. The polymer phase of the emulsion may be hydrophobic with little or no absorbed water — or it may be hydrophilic and pervaded with a great deal of absorbed water. Moreover, the exclusion pertains to the capacity of a polymer to absorb water. Polymers that are manufactured as aqueous solutions or dispersions may escape the water-absorbing exclusion on the basis that they have absorbed as much water as possible and are not capable of absorbing any more. At the other extreme, the polymer might not have sufficient affinity for water to be considered water-absorbing. Clearly, hydrophobic polymers that are not appreciably wet by water do not need to be evaluated for their non-water-absorbing capacity. If a polymer is isolated from its solution or dispersion and cannot be dissolved or dispersed again in water, such a polymer should not be considered water-absorbing. However, if such a polymer will be processed in a manner that creates particles, and those particles are capable of absorbing their own weight of water without dissolving, the polymer should be considered excluded because the risks that the EPA seeks to avoid with this exclusion for high molecular weight polymers might be expected to be realized. In some situations, the water-absorbing capability of a given polymer might need to be evaluated. If a particular polymer might absorb and retain enough water to be considered water-absorbing, the following test is suggested. The test should only be carried out on a properly selected sample. The sample of the polymer should be that version of the polymer that is intended to be commercialized that has the greatest capability for water absorption. The water-absorbing exclusion provided by paragraph (d)(5) applies to all production of the polymer for the exemption’s conditions under paragraph (e)(2) and all versions of polyesters that have a NAMW of 10,000 or greater under paragraph (e)(3). The fact that a particular version of a polymer is not water-absorbing does 9
Polymer Exemption Requirements 10 not qualify any other version of the same polymer if it is water-absorbing. In short, the exclusion must never be violated by any version even if some versions satisfy this limitation. If possible, determine the dry mass of a sample of the polymer in question that is free of precursors and other associated substances. Then contact the sample with a quantity of water equal to twice the polymer’s dry mass. We suggest using normally available, deionized water. Record the pH of the water used to establish that the pH is within the usual bounds of neutrality. Reasonable conditions during the contact would be one hour at room temperature. The nature of the contact should be such that there is a reasonable opportunity for the polymer to absorb the water. Subsequently, physically separate the wet polymer from excess gross water. Determine the mass of the polymer plus whatever mass of water that has been absorbed and retained. If this wet mass is less than double the dry mass or more, the polymer is not sufficiently water-absorbing to be excluded from the exemption by this provision. The EPA has not considered how time, temperature, pH, water purity, apparatus, procedure, nature of the polymer, interpretation of data, kinetics, or other considerations will influence the results. If there is significant water absorption, it might be prudent and appropriate to submit a suitable protocol and data to the EPA for approval before relying on any particular results. 6. Reactive Functional Groups A reactive functional group (RFG) is defined as an atom or associated group of atoms in a chemical substance that is intended or can be reasonably anticipated to undergo further chemical reaction. This provision is expressed in the regulation as a limitation to the (e)(1) condition, not as an exclusion. Although the reactive functional group limitation it is not applicable to the (e)(2) and (e)(3) conditions, it might be better understood as an exclusion, albeit one that only applies to (e)(1). There was an RFG exclusion in the original polymer exemption. In the amended exemption, the RFG exclusion, like the entire exemption itself, is more complex compared to the original version. Nonetheless, it allows more polymers to be exempt. More polymers are potentially exempt due to both the exclusion’s sole applicability to the (e)(1) condition and other complicating refinements. In fact, the refinements can be extremely complicated if one has different kinds of RFGs present in the polymer’s molecules. A “quick and clean” approach is to identify the equivalent weight for all RFGs that will form an ionic or covalent linkage to an amino acid. If that equivalent weight is less than 5000 for all such groups combined, the polymer is probably excluded by this provision, but there is hope that it is not excluded unless the equivalent weight is less than 1000. The (e)(1) limitation only applies when the polymer’s molecular weight is 1000 or more, but less than 10,000 and the oligomer levels are less than 25 and 10
Page 1 and 2: A Practical Understanding of the Po
Page 5 and 6: Introduction determination of eligi
Page 7 and 8: Polymer Exemption Requirements 2. C
Page 9 and 10: Polymer Exemption Requirements Alte
Page 11: Polymer Exemption Requirements 5. (
Page 15 and 16: Polymer Exemption Requirements 7. M
Page 17 and 18: The Two-Percent Rule 14 According t
Page 19 and 20: Reporting and Recordkeeping sustain
Page 23: ® Keller and Heckman LLP Serving B

A Practical Understanding of the Polymer ... - Keller Heckman

Create successful ePaper yourself

Delete template?

Save as template?