Cyclohexanamine, 4,4'-methylenebis[N-(1-methylpropyl)-

Endpoint summary

Additional information

 Clearlink 1000 (4,4-Methylenebis(n-sec-butylcyclohexanamine) is a cyclic secondary diamine which is moderately soluble in water (131 mg/l; OECD 105). In this water solubility study, the pH was not fixed. When amines are added to pure water, the pH becomes more basic.This leads to lower water solubility. Based on the experience with this substance, at alkaline pH’s it has very low water solubility and in neutral or acidic pH's, the material is very water soluble. Also, as Clearlink 1000 has amine functionalities, it will coordinate with metals in solution thereby increasing the solubility.

Based on the aerobic aquatic biodegradation screening test (MITI test; OECD 301C) it is non-biodegradable in water (deg-% 0-2). The results of a supporting biodegradation screening study after 29 days incubation with municipal activated sludge came to the same conclusion (Lange C.C. 2011). In this study, a method for quantitative analysis of Clearlink 1000 was used to directly measure test substance in the test cultures over time. In addition, isomers were qualitatively monitored to determine whether any change in isomer distribution may have occurred due to biodegradation. No degradation products were identified and no change in the isomer pattern was identified after 29 days incubation.

The study by Lange C.C. (2011) also demonstrated that Clearlink 1000 is recalcitrant to normal microbiological degradation processes in municipal WWTP and likely would not biodegrade during those treatment processes. In addition, based on the results of this study, it is unlikely that microbial adaptation toward Clearlink 1000 biodegradation would occur in those processes after prolonged exposures. Low concentrations of Clearlink 1000 did not appear to be detrimental to the microbiological metabolic activity of the activated sludge based on the ability of the microbes to sufficiently biodegrade the positive control substance, sodium dodecyl sulfate (SDS), in the presence of this substance. However, Clearlink 1000 was found to exhibit some toxicity to STP microorganisms (3-hour EC50 160 mg/l) based on the activated sludge respiration study (Desmares-Koopmans M.J.E. 2011).

Based on the preliminary test of OECD 111, the degree of hydrolysis of Clearlink 1000 was <10% after 5 days indicating hydrolytically stable substance with a half-life of over one year. As a conclusion of the biotic (infinite half-life as non-biodegradable) and abiotic degradation half-lives, Clearlink 1000 is considered as very persistent material. The screening of adsorption potential based on the octanol-water partition coefficient (log Kow 1.31; OECD 107) is not indicating Clearlink 1000 to have adsorption potential as the log Kow is less than 3. However, a substance having a low octanol-water partition coefficient does not necessarily always have a low adsorption potential. As Clearlink 1000 is considered to be surface active (surface tension 31.91 mN/m; OECD 115), and exists in ionized form in the pH range of 5.5-7.5 (Perrin calculation method; pKa 11 and 11.6) a measured adsorption coefficient was determined. As the testing of the non-ionized form at pH above 12.6 (> 90% non-ionized) was not environmentally relevant, adsorption coefficient testing was performed only at neutral pH. Based on the adsorption coefficient of 427 000 L/kg (log Koc >5.63; OECD 121), Clearlink 1000 is considered as having a strong potential for adsorption to soil and solid in neutral systems.Therefore, adsorption to suspended matter can be an important physical elimination process of the substance from water in sewage treatment plants (STPs). This in turn may mean that sewage sludge, if spread to land, would a major source of the substance in soil and the agricultural use of sludge need to be avoided (see ES&RC in CSR sections 9 and 10).

Based on the lowest short-term EC50-value of 0.24 mg/l in the algae test (96 h, Pseudokirchnerella subcapitata;OECD 201) and the non-biodegradability Clearlink 1000 is classified as having both acute and chronic hazard class 1. The NOEC-value of 0.0079 mg/l of this key study indicated this substance to be toxic to aquatic environment (NOEC < 0.01 mg/l). Adsorption to suspended matter in receiving waters affects both the concentration in surface water and the concentration in sediment. The adsorption potential of this substance to suspended matter was also proved with the supporting studies on toxicity to algae performed with modification of the standard (EPA 40 CFR 797.1050) by adding humic acid at concentrations of 10 and 20 mg/l into the dilution water. Based on this study, toxicity was determined to be 6-fold lower with humic acid addition compared to the study performed without any humic acid addition (Hoberg J.R. 1995).

The vapour pressure of the substance is low (0.00113 Pa at 25 °C; OECD 104) and indicates low evaporation rate (0.001 vol-% at ambient temperature) of Clearlink 1000 in the atmosphere. In addition, the Henry’s law constant of 0.00278 Pa m³/mol calculated from molecular weight, vapour pressure and water solubility indicates low volatility of the substance from water compartment.

The MacKay fugacity III level calculations using LEV3EPI model in EPISUITE™ (USEPA 2011) also indicated that, if simultaneously released to soil, water and air, this substance mainly distributes to soil and sediment compartment (60 % and 28 %), and when released to water the percentage of theoretical distribution is 70 % to sediments. If released to soil, the substance will adsorb into soil (100 %) and evaporation to air or mobility to water is negligible.

However, based on the BCF conducted on fish (Cyprinus carpio; OECD 305) Clearlink 1000 is not bioaccumulative as the BCF is between 6.1 and 11 L/kg at test concentrations of 0.1 and 0.01 mg/l.

In general, degradation rates in sediment and soil are assumed to be reduced by default if a substance is highly sorptive. Strong binding behavior to soil particles (log Koc > 4) might also justify long-term soil organism toxicity testing if particular sensitivity and/or persistence is anticipated. As Clearlink 1000 is not rapidly biodegradable and has strong adsorption potential to solid particles, the need of soil/sediment simulation testing and terrestrial toxicity testing was taken into account in the chemical safety assessment based on the following exposure considerations.

Part of a two part system, Clearlink 1000 is used as the activator for cross-linking in the production of polyurea coatings. A polyurea linkage is formed from the reaction of an amine and isocyanate component.The reaction in this system, does not need a heat source or catalyst to initiate the reaction. The mixing of the amine and the isocyanate components initiates an exothermic reaction that continues to drive the reaction to completion. This is a very rapid reaction that occurs, gel time is 1 minute and set time is 10 minutes.The processes in this formulation are enclosed processes where process losses are reduced to the absolute minimum and there are no discharges to waste waters or to soil. Activities related to formulation and storage and waste handling as well as prevention of air emission are controlled by valid LAPPC permit (The Pollution Prevention and Control Act 1999; the Environmental Permitting Regulations 2007).

In polymerized form, the polyurea coating is used for in-situ pipe rehabilitation coatings to repair/or extend the life of buried drinking water supply pipes which have corroded and diminished structural integrity.The coating is intentionally designed to have a ~30% overcharge of the reactive isocyanate component, so by design there is a minimal chance for any uncured amine to be present. This is validated by the migration reports from various drinking water approval agencies that show low levels of total organic content from the cured coating. Products that are designed to be in contact with potable water must receive third party approval before the products can be applied in those applications. The requirements of these approvals vary by country, but typically there is a review of a product's formulation to perform some risk assessment on the raw materials. Then, migration testing looking for specific compounds, or other test requirements like total organic content, microbiology testing, and taste and odor testing are completed. There are several migration study results available for this polyurea coating product from different countries. These results are discussed in the ES&RC of this CSR (see sections 9.2 and 10.2).

During this coating application small amount of Clearlink 1000 is overspread on soil in polymerized form as compared to the use in this application (ca. losses 11 kg/a in polymerized form; 0.01 % of total use of the substance). This release is considered very low as it represents ca. 0.01 % release when compared to the amount of annual tonnage (99 t/a). In addition, the risks are considered controlled since the over sprayed material will react in few seconds to form a cured polymer product. No emissions of Clearlink 1000 are expected from the reacted material as has been concluded by the migration studies. This coating product has received third party approval from different countries to be applied in drinking water applications (section 9.2 and 10.2 of the CSR).

As a conclusion on the exposure based considerations of both use applications, the chemical safety assessment of this substance does not indicate the need for further testing of degradation in soils and sediments or toxicity testing on soil organisms.