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

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A Practical Understanding of the Polymer Exemption Under TSCA No other atomic elements are permitted such as cerium or lead. Unusual oxidation states of the permitted counterions, and excess combinations of, say, phosphorus and boron also are excluded under this limitation. An important aspect in applying this limitation is that it is not relevant to impurities. Impurities are not considered “an integral part of the polymer’s composition.” 4. (d)(3); Instability Polymers cannot be manufactured under the amended polymer exemption if they substantially degrade, decompose, or depolymerize. Arguably, this exclusion has been modified from the original exclusion for polymer instability. The EPA has now made it explicit that this limitation applies if the polymer substantially degrades, decomposes, or depolymerizes — or is designed (or can be reasonably anticipated) to substantially degrade, decompose, or depolymerize — prior to, during, or after use. Under the original exemption, EPA generally limited its consideration of degradation, decomposition, and depolymerization issues to the use of the polymer and not its eventual disposal. As it now stands, a polymer is not eligible under this exclusion if the polymer substantially degrades, decomposes, or depolymerizes, for example, after disposal in a wastewater treatment plant. EPA maintains that the exclusion in the final rule is substantively the same as in the original rule. The difference in emphasis, however, is potentially significant. On one hand, the exclusion seems to reward the absence of degradation data, assuming susceptibility to degradation is not apparent. On the other hand, alkyd resins and other polymers might be ineligible because they could be “reasonably anticipated to substantially degrade, decompose, or depolymerize … after use, even though they are not actually intended to do so.” Many polymers were judged to be eligible under the original exemption because they were not designed nor reasonably anticipated to substantially degrade, decompose, or depolymerize in use. Now substantial degradation in a wastewater treatment plant might be reasonably anticipated for those same polymers. Further guidance from EPA on the proper application of this exclusion from the 1995 polymer exemption would be very desirable. In the absence of useful guidance, part of the previous exemption scope appears to be lost for polymers that could be substantially degraded during disposal. Rather than filing PMNs, polymer manufacturers and importers could seek pre-exemption determinations from the EPA as to whether degradation will be considered substantial. It may also be useful to note that, although biopolymers are no longer explicitly excluded from the polymer exemption, to be eligible, biopolymers must not substantially degrade, decompose, or depolymerize. Most biopolymers can be reasonably anticipated to substantially degrade, decompose, or depolymerize — prior to, during, or after use. 7
Polymer Exemption Requirements 5. (d)(5); High Molecular Weight, Water-Absorbing Polymers This provision excludes certain water-absorbing polymers from eligibility for the amended polymer exemption. A water-absorbing polymer is defined as one “that is capable of absorbing its own weight of water” and has a number-average molecular weight (NAMW) equal to or greater than 10,000. 8/ In other words, a polymer that has a NAMW of 10,000 or more and that is capable of absorbing a mass of water that is equal to, or more than, the mass of the polymer may not be manufactured or imported under this exemption. As discussed in the preamble of the 1995 polymer exemption rule, 9/ the exclusion for water-absorbing polymers is intended primarily to address concerns for “super absorbent” polymers, which are also known as “super slurpers.” The exclusion responds to information received under section 8(e) of TSCA for a waterabsorbing polyacrylate. In that 8(e) case, the polyacrylate in question had a NAMW of about 1,000,000 and could absorb about 100 times its own mass of water. The EPA believes that it is reasonable to set the exclusion two orders of magnitude below these levels: 10,000 NAMW and water absorption of one times its own mass. The EPA contends that a NAMW of less than 10,000 generally mitigates potential health hazards for polymers because they may be detoxified through different mechanisms in contrast to polymers with higher NAMWs. Perhaps the most useful insight from this information is that “super slurpers” have the capacity to absorb about 100 times their own mass of water, yet not dissolve. The paragraph (d)(5) exclusion for water-absorbing polymers will be problematic mainly for polymers that might be eligible under paragraph (e)(2). While the (d)(5) exclusion applies across the entire exemption, it only applies to polymers with NAMWs of 10,000 or greater. By its own terms, this exclusion does not apply to condition (e)(1). Polyesters manufactured only from reactants that are listed under paragraph (e)(3) and that have molecular weights of 10,000 or more are not likely to meet the definition of water-absorbing. The permissible reactants for (e)(3) polyesters are not conducive to absorbing water after being incorporated into polymers. It sounds obvious to say that the water-absorbing exclusion applies whenever a given polymer is water-absorbing. But it is not as obvious as it sounds. Unlike some other aspects of polymers, the property of water absorption generally does not attach to a polymer’s chemical identity. However, for a particular version of a given polymer, the capability to absorb water can be characterized. Conversely, if some version of a polymer manifests the degree of water absorption that this exclusion prohibits, it does not mean that the polymer is necessarily ineligible for the exemption. Determining whether a given substance is a water-absorbing polymer might not be straightforward. The EPA has not established a test protocol. Moreover, polymers are often manufactured in association with solvents and other substances 8
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A Practical Understanding of the Polymer ... - Keller Heckman

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