UDC 628.31:678.7

L. P. Boltromeyuk

Stability of ED-5 Epoxy Resin in Water

Institute of Biophysics, Ministry of Health of the USSR, Moscow

During a sanitary and hygienic survey of wastewater from facilities using ED-5 epoxy resin, a condensation product of epichlorohydrin (ECH) and diphenylolpropane (DPP), we found the resin as a viscous mass in the bottom deposits of collectors. Examination of the production process showed that the principal operations potentially responsible for the entry of resin into wastewater were the washing of equipment and containers.

Table 1

Effect of temperature on the release of ECH, DPP, and T from resin into water (initial resin concentration: 5 g/L)

Because epoxy resin itself and its monomers are highly toxic compounds (the maximum permissible concentrations of ECH and DPP in water bodies are 0.01 mg/L), the stability of the resin in water, its possible degradation, and the release of monomers under the action of water were of hygienic interest in assessing the extent to which wastewater might be contaminated by the starting monomers ECH and DPP.

The extraction by water of the starting monomers, as well as of toluene, which is used in resin synthesis, from uncured resin has not been addressed at all in the literature.

To assess the possible entry of resin degradation products into water, we determined the oxidizability of aqueous extracts. The dichromate oxidizability of the aqueous extracts increased with increasing resin sample mass, indicating that organic substances entered the water. The aqueous extracts were analyzed for ECH, DPP, and toluene (T), confirming that all these substances passed into the water at appreciable concentrations that depended on the amount of resin in the water.

We then studied the effects of temperature, solution pH, and resin contact time on the release of monomers and T. The temperature range was selected with possible fluctuations in mind—

…temperature of wastewater and water in bodies of water at different times of the year. The results are presented in Table 1.

As the temperature decreased, the concentrations of ECH, DPP, and T in the water decreased, but even at 6° they remained very high compared with the maximum permissible concentrations for water in bodies of water. Thus, the concentration of ECH was 1,800 times, and that of DPP 750 times, the maximum permissible concentration.

The concentration of ECH in the aqueous extract did not depend on the pH of the medium over the range investigated, pH 2–12. The observations also showed that the concentrations of monomers in the water increased over the 30-day observation period.

Table 2

Dependence of ECH and DPP concentrations in the aqueous layer on the duration of contact between the resin and water (initial resin concentration: 10 g/L)

Immediately after the addition of water, the concentration of ECH in the water was 9.2 mg/L and that of DPP was 2.4 mg/L; after 30 days, the concentration of ECH had increased more than 50-fold and that of DPP 20-fold (Table 2). Thus, the resin acts as a virtually continuous source of the original monomers over a prolonged period.

Conclusions

1. When ED-5 epoxy resin enters wastewater, it may contaminate the water with the highly toxic monomers ECH and DPP, as well as toluene.
2. The concentrations of monomers in the aqueous extract of the resin are considerably higher than the maximum permissible concentrations of these substances in bodies of water and depend on the water temperature and the duration of contact between the resin and water.
3. ED-5 epoxy resin is a highly stable compound when introduced into water. The original resin monomers ECH and DPP, as well as toluene, also proved highly stable in water.

Received May 3, 1973.