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MDEA-Esterquat C16-18 and C18 unsatd. is an organic substance which is characterized as white waxy substance at 20°C and 1013 hPa.

The melting point was determined to be 54°C at atmospheric pressure (OECD Guideline 102 and EU Method A.1).

The boiling point of MDEA-Esterquat C16-18 and C18 unsatd. could not be determined up to a temperature of 250°C at 1013 hPa (OECD Guideline 103 and EU Method A.2).

The density and relative density (D20/4) of MDEA-Esterquat C16-18 and C18 unsatd. were determined to be 1.04 g/cm³ and 1.04 (at 20°C each), respectively (OECD Guideline 109 and and EU Method A.3).

According to REACH regulation (Annex VII, 7.14, column II), testing for particle size analysis is not required for those substances which are marketed or used in a non solid or non granular form.

According to REACH regulation (Annex XI, 2.), the vapour pressure does not need to be determined if the measurement is technically not feasible due to the substance properties. MDEA-Esterquat C16-18 and C18 unsatd. represents a ionic solid at standard conditions (20°C, 1013 hPa), therefore a very low vapour pressure is to be expected. According to OECD guideline 104 vapour pressures lower than 10E-5 Pa cannot be determined.

According to REACH regulation (Annex XI, 2.), a study does not need to be done if it is technically not feasible: The determination of the n-octanol/water partition coefficient log Kow is technically not feasible due to the surface-active properties of the test substance. In the EU RAR 'DODMAC' (CAS 107 -64 -2), a chemical structurally similar to MDEA-Esterquat C16-18 and C18 unsatd., a measured log Kow=3.8 is reported. A justification for read across is given below.

The water solubility of MDEA-Esterquat C16-18 and C18 unsatd. was estimated to be 17.6 mg/L at 19.7°C based on the results of turbidity measurements (Method 2 of ASTM International E 1148 – 02); according to the classification scheme, the test substance can be regarded as slightly soluble in water.

The surface tension of MDEA-Esterquat C16-18 and C18 unsatd. was investigated in a study conducted according to OECD Guideline 115 and EU Method A.5. A mean surface tension (5 -9 measurements) of 68.3 mN/m at 20°C was determined. The result in this test is not in line with the expected surface tension behaviour of the test substance. Cationic surfactants carrying two C18 alkyl chains, such as MDEA-Esterquat C16-18 and C18 unsatd., are designed to possess surface active properties and typically exhibit surface tension values as low as 27 mN/m (depending on the area per molecule) when studied on a Langmuir film balance. Therefore due to the intrinsic properties (crystallization) of this double-chain cationic amphiphile at temperatures below the melting point no reliable results were obtained using the ring method. At temperatures of 20°C, the inner-molecular mobility of the fatty acid C-chains is hindered. Corresponding to this hinderance, on the one hand, the time to reach solubilisation equilibrium is long and on the other hand, there is a tendency to form vesicles.

According to REACH regulation (Annex XI, 1.), a test for determination of the flash point is scientifically not necessary, because the flash point refers to liquids (Reach R7.1.9). The test item is a solid at ambient temperature. Therefore determination of the flash point is not required.

MDEA-Esterquat C16-18 and C18 unsatd. proved to be not self-ignitable between 20°C and the melting temperature (54°C; EU Method A.16). The test substance MDEA-Esterquat C16-18 and C18 unsatd. is not highly flammable.

According to the REACH regulation (Annex VII, 7.11, column II), the study on explosiveness does not need to be conducted, if the substance does not contain chemical groups indicating explosive properties.

According to REACH regulation (Annex VII, 7.13, column II), testing of MDEA-Esterquat C16-18 and C18 unsatd. for oxidising properties does not need to be conducted, as the substance does not contain any structural groups known to be correlated with a tendency to react exothermically with combustible material.

According to REACH regulation (Annex XI,1.), the study on stability in organic solvent has to be conducted only if the stability in organic solvent is considered to be critical.

According to REACH regulation (Annex XI, 1.), the study on dissociation does not need to be conducted if the available data are sufficient for assessment. MDEA-Esterquat C16-18 and C18 unsatd. represents a salt which will dissociate completely in aqueous solution.

According to REACH regulation (Annex XI, 2.), viscosity is relevant only to liquids, therefore this determination is not required.  

 

 

JUSTIFICATION FOR READ-ACROSS 

Substance identities

The target substance MDEA-Esterquat C16-18 and C18 unsatd. is a UVCB substance composed of diesters of mainly saturated C16 and C18 fatty acids with MDEA (Methyldiethanolamine) as amine backbone.

The source substance DODMAC (Dimethyldioctadecylammonium chloride) exhibits large structural similarities with the target substance. Details are described below.

 

 

Target substance

Source substance

 

MDEA-Esterquat C16-18 and C18 unsatd.

DODMAC

CAS number

1079184-43-2

 61789-80-8

EC number

620-174-7

 263-090-2

Fatty Acid

C16-18, C18‘
(IV = 20)

 C16-18, C18‘

Chain length distribution

<C16 <7%

C16, 16‘, 17 26-35%

C18 42-52%

C18‘ 15-20%

C18‘‘, 18‘‘‘ </= 1.5%

>C18 </= 2%

C12: </=2 %

C14: 1 - 5 %

 C16: 25 - 35 %

 C18: ca. 65 %

 C 20: </=2 %

Amine

MDEA

 ---

Anion

Chloride

 Chloride

 

Structural similarity

The target substance, MDEA-Esterquat C16-18 and C18 unsatd., consists of an amine backbone (MDEA = Methyldiethanolamine) esterified with long chain fatty acids C16, C18 and C18 unsaturated (IV = 20). The main reaction product is the dialkylester compound, next to that small amounts of the monoalkylester may be formed. The amine function is quaternised with two methyl groups. The counter ion is Chloride.

 

The source substance DODMAC (Dimethyldioctadecylammonium chloride) is one of the active components of the technical product DHTDMAC (dihydrogenated tallow alkyl dimethyl ammonium chloride). DHTDMAC is produced of tallow fatty acid via the nitrile to result in the amine, which is then methylated twice to the quaternised amine. The counter ion is Chloride. DODMAC has a similar chain length distribution as the target substance and contains a quaternised and dimethylated amine function.

Fig. 1 Structures of MDEA-Esterquat C16-18 and C18 unsatd. ans DODMAC (see attached image file)

 

Differences

The chemical structure of the target substance of MDEA-Esterquat C16-18 and C18 unsatd.  contains, in contrast to the source substance DODMAC, two polar ester moieties which are susceptible to hydrolysis and /or degradation.

 

Comparison of physicochemical properties

 

Target substance

Source substance

Endpoints

MDEA-Esterquat C16-18 and C18 unsatd.

 

DODMAC

Molecular weight

697 g/mol

586.52 g/mol

Physical state at 20°C / 1013 hPa

solid (waxy)

Solid

Melting point

OECD Guideline 102; RL1; GLP

 

54°C

72-122 °C

Boiling point

OECD Guideline 103; RL1; GLP

 

No boiling point up to 250°C

decomposition at 135°C

Surface tension

OECD Guideline 115; RL2, GLP

 

68.3 mN/m at 20°C - not in line with the expected surface active behaviour of the substance (see discussion below table)

11 mN/m at 20 °C (saturated solution; method: film balance)

Water solubility

ASTM International E 1148 – 02, RL1, GLP

 

 

17.6 mg/L at 19.7°C

2.7 mg/L

Log Kow

read-across from DODMAC

 

3.8

Vapour pressure

Measurement is technically not feasible due to the substance properties; estimation

 

7.33E-18 Pa at 25°C

negligible because of the salt character

Auto flammability

---

 No data

Flammability

EU Method A.10 (Flammability (Solids)); RL 1, GLP

 

not highly flammable

 No data

 

The molecular weights of the target and source substances are in a comparable range. Experimental data on log Kow are not available for the target substance MDEA-Esterquat C16-18 and C18 unsatd. A read-across approach from the structurally similar substance DODMAC was applied, resulting in a log Kow of 3.8

Both substances have a very low vapour pressure.

There are, however, differences in melting point, surface tension and water solubility. The differences in melting point result from the higher degree of unsaturation of the target substance MDEA-Esterquat C16-18 and C18 unsatd. in comparison to the source substance DODMAC.

The result from the study on surface tension with MDEA-Esterquat C16-18 and C18 unsatd. was not in line with the expected surface tension behaviour of the test substances. Cationic surfactants carrying two C16/C18 alkyl chains, such as MDEA-Esterquat C16-18 and C18 unsatd.  are designed to possess surface active properties and typically exhibit surface tension values as low as 27 mN/m. However, at temperatures of 20 °C, the inner-molecular mobility of the fatty acid C-chains is hindered. Corresponding to this hinderance, on the one hand, the time to reach solubilisation equilibrium is long and on the other hand, there is a tendency to form vesicles.

Water solubility of MDEA-Esterquat C16-18 and C18 unsatd. was determined by measurement of turbidity instead of analytical determination of concentration, since no suitable method was available to remove undissolved test substance. The standard tests for this endpoint are intended for single substances and are not appropriate for these complex substances. It is stated in the OECD guideline 105 (1995) that:“The water solubility of a substance can be considerably affected by the presence of impurities. This guideline addresses the determination of the solubility in water of essentially pure substances […]”. Although impurities are per definition not present in UVCB substances, the complex and variable composition of the target and source substances may nevertheless influence the outcome in a similar manner.

No details on the method used to determine the water solubility of the source substance DODMAC were available. Thus, due to possible methodological differences, the results from these measurements are not directly comparable.

Conclusion

The structural similarities between the source and the target substance support the read-across hypothesis. Therefore, it can be concluded that the log Kow of the target substance MDEA-Esterquat C16-18 and C18 unsatd. will be in a comparable range as the log Kow of the source substance DODMAC. However, the log Kow is not an appropriate hydrophobicity parameter for reliably predicting environmental behavior of surfactants because cationic substances in the environment instantaneously form complexes with naturally occurring negatively charged constituents in sewage, soils, sediments and with dissolved humic substances in surface waters.The predictive power of the log Kow for the partitioning to soil, sediment and sludge or its bioaccumulation potential is considered to be limited, because the common Koc derivations are not valid for surface active substances like MDEA-Esterquat C16-18 and C18 unsatd. Therefore the log Kow values cannot be used to derive the environmental distribution constants. Instead as a more reliable basis, the data on sorption and bioaccumulation will be used.

 

References

EU, 2009: European Union Summary Risk Assessment Report - dimethyldioctadecylammonium chloride (DODMAC) - with addendum, available online: http: //publications. jrc. ec. europa. eu/repository/handle/111111111/5276

 

HERA, 2008: Esterquats Environmental Risk Assessment Report, available online: http: //www. heraproject. com/files/17-E-01-03-2008%20%20HERA%20EQ%20Environment%20Final%20Draft. pdf