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Physical & Chemical properties

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Discussion of physico-chemical properties

The TEA-Esterquats vary only marginally in the fatty acid chain-length distribution and the distribution of mono-, di-, and tri-esters is identical. Therefore their physico-chemical properties are assumed to be within the variation of measured results. Differences are expected according to the amount of C=C double bonds. This is expressed by the fact that fully saturated TEA-Esterquat and partially unsaturated TEA-Esterquat are solids, while the oleic acid-based TEA-Esterquat is a liquid at room temperature.

Partially unsaturated TEA-Esterquat is an organic compound which, at ambient temperature, is a weak yellowish solid and has the character of a waxy, viscous solidified liquid. The test item has no specific melting point. According to the results of a penetrometer-test, the melting point of the test item lies in the range between > 85 and 110 °C.

Therefore, it is assumed that fully saturated TEA-Esterquat and partially unsaturated TEA-Esterquat have a very similar melting range. Oleic acid-based TEA-Esterquat is a liquid at room temperature. Based on the information for partially unsaturated TEA-Esterquat and the UVBC composition of substance of many similar substances, Oleic acid-based TEA-Esterquat is also expected not to have a specific melting point, but rather a solidifying range lower than room temperature (< 20°C). The melting range is reported to be 4 - 10°C.

At atmospheric pressure the boiling point of partially unsaturated TEA-Esterquat cannot be determined as the test item decomposes at temperatures above 260 °C. It is concluded that all TEA-Esterquats should behave in the same way caused by their highly similar structure.

Density and relative density for partially unsaturated TEA-Esterquat were determined to be 1.059 g/cm³ at 20 °C and 1.059 (20/4), respectively. The density and the relative density of TEA-Esterquats are assumed to be very similar for all TEA-Esterquats.

At ambient temperature, partially unsaturated TEA-Esterquat is a weak yellowish solid and has the character of a waxy, viscous solidified liquid. The fully saturated TEA-Esterquatis a weak colourless wax at ambient temperature.Therefore the particle size distribution (granulometry) for partially unsaturatedand fully saturated TEA-Esterquat cannot be determined.The oleic acid-based TEA-Esterquatis a liquid at room temperature. Therefore according to REACH Annex XI, 1. granulometry testing is scientifically not necessary.

Based on experimentally derived results and using the Antoine equation, the vapour pressure at 20 and 25 °C of partially unsaturated TEA-Esterquat was calculated to be 4.4 x 10E-6 hPa/ 4.4 x 10E-4 Pa (at 20 °C) and 6.7 x 10E-6 hPa/6.7 x 10E-4 Pa (at 25 °C). These very low vapour pressures pertain to all three TEA-Esterquats described in this CSR. This is due to practically identical structure. In addition, TEA-Esterquats are salts with ionic structure of one long-chained organic ammonium cation and the anionic counter ion. For these substances, a vapour pressure of almost zero is expected.

The n-octanol/water partition coefficient log Kow of the partially unsaturated TEA-Esterquat was investigated in a study conducted according to OECD Guideline 117 and EU-Method A.8. (HPLC method). The test item was not eluted from the column using methanol/water as the mobile phase. Based on the results with the reference substances (highest log Kow = 6.5 for DDT), the log Kow of the test item was deduced to be >6.5. The results, however, should be treated with care since the guideline itself points to the fact that this guideline is not suitable for surface active substances.

In the frame of this study, the n-octanol/water partition coefficient log Kow of the test substance was estimated via the 'apparent' water solubility. The calculation yielded a log Kow = 1.9 (Kow = 200 g/L/2.5 g/L; 'apparent' water solubility = 2.5 g/L at 20 °C, solubility in n-octanol = 200 g/L at 20 °C). Due to the surface-active properties of the test substance, the 'real' water solubility is overestimated. Therefore, the result should be treated with care.

Moreover, in the frame of this study, the n-octanol/water partition coefficient log Kow of the test substance was estimated via the critical micelle concentration (cmc). The calculation yielded a log Kow = 5.6 (cmc = 0.5 mg/L; solubility in n-octanol = 200 g/L at 20°C). No information, however, is available on how the cmc was determined. Therefore the result should be treated with care. However, it is expected that all TEA-Esterquats would behave in the same way.

Therefore a calculation of the n-Octanol/water-partition coefficient was performed using theSoftware ACD/Labs12 from the companyAdvanced Chemistry Development, incand experimental data of [Me-14C] MDEA Esterquat (NOTOX 489708). This programme is useful to determine log Kow values of ionic substances. For experimental data input to ACD/Labs, adsorption coefficients of [Me-14C] MDEA Esterquat were used for calculation of the logKowaccording to the Lyman-method. Kowvalues for the most lipophilic Mono-, Di- and Triester species (C18chain-length, saturated) were calculated separately. Outputs were then weighted to calculate a mean logKow. The calculated logKowof MDEA Esterquat was 5.38. Mole fractions of Mono-, Di- and Triester used for calculation were 0.37, 0.435 and 0.089, respectively. The middle of the geometric weighted mean of the inverse logarithm of log Kow is 4.725. (Evonik Goldschmidt, 2010a) This value was used as a reasonable worst case for the assessment.

The water solubility of partially unsaturatedTEA-Esterquatwas determined to be 2171 (pH 3.73, 10°C), 2244 (pH 3.86, 20°C), and 2359 mg/L (pH 3.83, 30°C; solubility in water without pH adjustment; distilled water being in equilibrium with atmospheric carbon dioxide) and 5.30 (pH 4.05), 3.39 (pH 7.08), and 19.4 mg/L (pH 9.11; solubility in buffered water at pH 4-9 and 20°C). Based on the results in buffered systems it can be assumed that the water solubility is dependent on pH. However, due to the bipolarity of the molecules, it is noted that the counter ions phosphate, citrate and borate, respectively obviously have a more distinct influence on solubility than pH, since the solubility is almost three orders of magnitude below that in pure water. Finally, at higher pH values, a change in composition due to hydrolysis may have a greater influence on the absolute solubility of the test item.
Water solubility of all TEA-Esterquats is assumed to be the same due to practically identical molecular structure. This is supported by a second result from a study on surface activity for the
partially unsaturated TEA-Esterquat, showing a water solubility of < 4852 mg/L.

The mean surface tension of an aqueous solution of 1 g/L of the partially unsaturated TEA-Esterquat was determined to be 41.8 mN/m at 20 °C and can therefore be considered as a surface active substance.
In a second study the surface tension of the
partially unsaturated TEA-Esterquat was investigated in a study conducted according to OECD Guideline 115 (Surface Tension of Aqueous Solutions) and ISO 304. According to ISO 304 the advised concentration should be at approx. 90 % of the saturated solution. In any case maximum advised concentration should be 1 g/L and the minimum one 1 ppm. It was found that at a concentration of 1 g/L the test substance was not soluble and not well dispersed. Therefore, the solution was diluted till a concentration was reached where the test substance seemed to be well dispersed. In the concentration range tested (0.4852 -1.0044 g/L), the surface tension seems to be more or less independent from the test substance concentration (surface tension: 36.46 -39.4 mN/m at 24.7 °C). Based on the results, the test substance possesses surface-active properties.
Therefore, it is assumed that the surface tensions of the saturated TEA-Esterquat and the oleic acid-based TEA-Esterquat are in the same range of 36.46 – 41.8 mN/m at 20 – 24.7 °C.

At ambient temperature, the fully saturated TEA-Esterquat and the partially unsaturated TEA-Esterquat are solids and therefore the determination of the flash point is not required. No self-ignition temperature was observed for partially unsaturated TEA-Esterquat until the maximum temperature of 402 °C. Because of practically identical molecular structure, TEA-Esterquats are considered not to be susceptible to self ignition. The fully saturated TEA-Esterquat  and the partially unsaturated TEA-Esterquat are not highly flammable solids.

However the oleic acid-based TEA-Esterquat is a liquid at room temperature. The flash-point is 149°C at 1013 hPa.

As indicated by structural aspects and underlined by estimated thermodynamic properties for partially unsaturated TEA-Esterquat, TEA-Esterquats must not be considered to have explosive and oxidising properties. Based on the results obtained with the capillary method, the decomposition of TEA-Esterquats starts at 260 °C at atmospheric pressure.

The pH of the partially unsaturated TEA-Esterquat was determined to be 3.86 at a test substance concentration of 2244 mg/L (saturated aqueous solution) at 20 °C. Based on their structure, TEA-Esterquats are surface active, zwitterionic substances which dissociate in water to quaternary ammonium ions and sulphate counter ions and have no acid-base properties at environmental relevant pH. Since no analytical method, which is sensitive enough, is available for the determination of the undissociated test items, the performance of further experimental verification was not considered to be technically or scientifically feasible.

The dissociation constants of the ions were obtained by QSAR-calculations using SPARC On-line Calculator v3.1. The pKa value of methylsulfuric acid was calculated to be 1.14. Therefore, the salt can be regarded as completely dissociated over almost the entire pH-range. Based on the QSAR-calculations, it is to be expected that the mono- and diester of TEA-Esterquats have high pKa values (monoester: 12.42 (pKa2) and 13.68 (pKa3); diester: 12.52 (pKa2)) and therefore will not dissociate under environmental conditions. As the QSAR calculations were performed with structurally well defined molecules that are components of  the fully saturated, partially unsaturated and oleic acid-based TEA-Esterquat as well, these calculations are also true without restriction.

Fully saturated TEA-Esterquat and partially unsaturated Esterquat are solids, Oleic acid-based TEA-Esterquat is a highly viscous liquid. Therefore the kinematic viscosity at 40°C was determined for Oleic acid-based TEA-Esterquat according to DIN 53015 (rolling ball viscosimeter by Höppler). Since test item is a highly viscous liquid with air bubbles enclosed, the kinematic viscosity was estimated after homogenization of the sample using a rolling ball viscosimeter by Höppler. The kinematic viscosity of the consumer item is therefore > 2500 mm²/s. There is no concern for aspiration toxicity hazard, since the viscosity is well above the kinematic viscosity of 20.5mm²/s, measured at 40°C.