Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Partition coefficient

According to Reach-regulation, Annex VII, a value for logKow has to be presented: “…If the test cannot be performed…a calculated value for log P…shall be provided.”

 

1stStep: Experimental Studies

Two experimental studies in accordance with Reach guidance were attempted: A), using the slow stirring method with 14C-MDIPA-Esterquat C16-18 and C18 unsatd. according to guideline OECD 123 and B), the measurements of individual MDIPA-Esterquat C16-18 and C18 unsatd. solubilities in octanol and water.

The results of both studies cannot be used for log Kow derivation. Reasons for the shortcomings of the experimental results are detailed in the “Applicant’s summary” of the corresponding endpoint study records. In summary these studies are valid in view of experimental design and execution of the experiments in the lab, but the usability of the results for logKow derivation is not given due to substance inherent properties. The following observations were made:

- aggregation of individually solubilised MDIPA-Esterquat C16-18 and C18 unsatd. molecules with temperature decrease forming vesicles in water as well as in octanol (forming of precipitates in octanol),

- self solubilisation of vesicles,

- strongly kinetically hindered solution / dissolution equilibrium at room temperature (no steady state in the slow-stir test),

- high adsorbency on surfaces.

As a consequence and conclusion, the direct experimental determination of log Kow, as made for the registration substance, was recognised as not being conclusive and the experimental results of the log Kow tests with MDIPA-Esterquat C16-18 and C18 unsatd. are not considered for the log Kow endpoint.

It is questioned in general whether for substances with properties like MDIPA-Esterquat C16-18 and C18 unsatd., the available guideline studies are appropriate.

 

2ndStep: QSAR

As it turned out that experimental studies cannot be used for the derivation of log Kow, standard increment based QSAR calculations (Epiwin (KOWWIN v1.68), ACD) were considered and evaluated in a second step. These QSAR models have two restrictions: handling of ion pairs and applicability domain. As a consequence, theses QSAR approaches are of limited value for MDIPA-Esterquat C16-18 and C18 unsatd. log Kow derivation.

 

3rdStep: Read-Across

To fill the data gap for this endpoint, a read-across approach to a similar substance was undertaken. Based on OECD QSAR Toolbox Dimethyldioctadecylammonium chloride (DODMAC) was the only substance sufficiently similar to MDIPA-Esterquat C16-18 and C18 unsatd. For this substance the EU RAR (2002) states a log Kow of 3.80 whereas one Reach-registration (CAS: 61789-80-8, DHTDMAC, still containing some oleic acid) states a log Kow of 3.99 (individual solubilities). Another Reach-registration (CAS: 92129-33-4, Quaternary ammonium compounds, di-C16-18-alkyldimethyl, chlorides) with a log Kow of 8.4 (slow-stirring method).

It is questionable to which extent these substances, not having the same composition and containing some different molecular structures can be used as one read-across substance. These substances show inconsistent, strongly diverging log Kow results. The cause for this cannot be judged looking at the present information. It is a strong affirmation for the questioning of experimentally derived log Pow for substances like MDIPA-Esterquat C16-18 and C18 unsatd. as conclusion at “1st Step: Experimental Studies”.

Summarised, all three approaches for an evaluation of a log Kow value for MDIPA-Esterquat C16-18 and C18 unsatd. (experimental, QSAR (increment based), read-across to DODMAC) lead to inconclusive results.

 

4thStep: log Kow – log Koc linear relationship

Finally, instead of the approaches described in the steps 1 to 3, the partitioning coefficient log Kow will be deduced based on other valid, experimentally determined partitioning data for MDIPA-Esterquat C16-18 and C18 unsatd. itself. Instead of the partitioning between water and octanol, the partitioning of MDIPA-Esterquat C16-18 and C18 unsatd. between water and organic carbon (log Koc) is used for log Kow derivation. Reach guidance R7a (2012), detailed in R7a (2008) and EU TGD guidance (2003) report linear correlations between log Kow and log Koc for different classes of substances. These correlations are proposed by the guidances for the deduction of log Koc from log Kow. The registrant however proposes to use this correlation in reverse to deduce log Kow from log Koc.

As the most appropriate correlation, corresponding to the substance class, “pred. hydrophobics” an equation published by Sabljic and Güsten (1995) was recognised. For a detailed rationale for selection of this equation see annex “Rationale for selection of the appropriate log Kow – log Koc linear relationship”.

The experimental Koc used for log Kow calculation is measured for 14C-MDIPA-Esterquat C16-18 and C18 unsatd. in a GLP batch equilibrium study according to OECD guideline 106. For two sludges (high organic carbon content, mean 34%) and three soils (low organic carbon content, mean 1.4%) the partitioning constant is measured and the geometric mean calculated to be log Koc = 3.69.

With the “predominantly hydrophobic” log Koc – log Kow relationship the log Kow is calculated as 4.43.

 

Surface Tension

The OECD harmonized ring method was applied for the determination of the surface tension of MDIPA-Esterquat C16-18 and C18 unsatd. The surface tension of a test solution at a concentration of 0.9 mg/L at 20°C was in the same order as water. Based on the results of this OECD harmonized ring method, the test substance would not be considered as being surface active. However, this result is not in line with the expected surface tension behaviour of the test substance. Cationic surfactants carrying two C16/C18 alkyl chains, such MDIPA-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 (crystallisation) of this double-chain cationic amphiphiles 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. This can be seen i.e. at the test on hydrolysis with low correlation rates for pseudo-first order curve determination for 20°C but high correlation rates at 50 and 60°C.

 

Auto flammability

For this endpoint a read-across approach was made to the closely related substance MDIPA Esterquat C18 unsatd. The read-across substance contains mainly unsaturated fatty acids and therefore is expected to have a lower auto-ignition temperature compared to the target substance MDIPA-Esterquat C16-18 and C18 unsatd. This read-across approach represents a worst-case with respect to classification.

The auto-ignition temperature of the source substance MDIPA Esterquat C18 unsatd. was determined according to EU Method A.15 (30 May 2008) and DIN 51794 (2003). The auto-ignition temperature was determined to be 340°C at 1012 hPa.

 

Flammability

For this endpoint a read-across approach was made to the closely related substance MDEA-Esterquat C16-18 and C18 unsatd. The fatty acid composition, as well as all functional groups of the read-across substance are identical (see below). An additional methyl-group in the amine backbone of the registration substance and chloride instead of methosulfate is expected to have no significant impact on flammability.

In a preliminary screening test according to EC no. 440/2008, A.10., the flammability of the source substance MDEA-Esterquat C16 -18 and C18 unsatd. was investigated. After removal of the ignition source, no propagation of combustion of the test substance was observed. With this result the outcome of the screening test is negative and according to CLP (2012) classification criteria the substance is not classified.

 

JUSTIFICATION FOR READ-ACROSS 

Substance identities

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

The source 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 MDIPA Esterquat C18 unsatd. is a UVCB substance composed of diesters of unsaturated C18 fatty acids with MDIPA (Methyldiisopropanolamine) as amine backbone.

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

 

 Source substances

 

 

 Target substance

 

MDEA-Esterquat C16-18 and C18 unsatd.

MDIPA-Esterquat C18 unsatd.

 

DODMAC

MDIPA-Esterquat C16-18 and C18 unsatd.

CAS number

1079184-43-2

95009-13-5

 61789-80-8

NA

EC number

620-174-7

305-741-6

 263-090-2

 941-174-6

Fatty Acid

C16-18, C18‘

C18‘, C18‘‘, C18‘‘‘

 C16-18, C18‘

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%

<C16 -

C16 </=7%

C18 </= 4%

C18‘ 55-65%

C18‘‘ 18-25%

C18‘‘‘ 6-12%

>C18 </= 5%

C12: </=2 %

C14: 1 - 5 %

 C16: 25 - 35 %

 C18: ca. 65 %

 C 20: </=2 %

< C16: <= 6%

C16 - < C18: 20-65%

C18: 4-60%

C18 unsatd.: 10-43%

> C18: <= 5%

Amine

MDEA

MDIPA

 ---

MDIPA

Anion

Chloride

Methyl sulphate

 Chloride

Methyl sulphate

Structural similarity

The target substance, MDIPA-Esterquat C16-18 and C18 unsatd., consists of an amine backbone (MDIPA = Methyldiisopropanolamine) esterified with long chain fatty acids C16, C18 and C18 unsaturated. 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 Methosulfate.

 

The first source 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. 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 second source substance, MDIPA-Esterquat C18 unsatd., consists of an amine backbone (MDIPA = Methyldiisopropanolamine) esterified with long chain fatty acids C18 unsaturated. 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 Methosulfate.

 

The source and the target substances share structural similarities with common functional groups (quaternary amines), esters, and fatty acid chains with comparable length and degree of saturation. The amine backbones based on MDEA and MDIPA, respectively, differ only by one methyl group in each chain, all functional groups are identical.

 

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.

 

Differences

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

Comparison of physicochemical properties

 

 Source substances

 

 

 Target substance

Endpoints

MDEA-Esterquat C16-18 and C18 unsatd.

 

MDIPA Esterquat C18 unsatd.

DODMAC

MDIPA-Esterquat C16-18 and C18 unsatd.

 

Molecular weight

697 g/mol

ca. 796 g/mol

586.52 g/mol

ca. 761 g/mol

Physical state at 20°C / 1013 hPa

solid (waxy)

liquid

Solid

solid (waxy)

Melting point

OECD Guideline 102; RL1; GLP

 

54°C

OECD Guideline 102; RL1; GLP

 

Amorphous solidification between -55 and -10°C

72-122 °C

OECD Guideline 102; RL1; GLP

 

36°C

 

Boiling point

OECD Guideline 103; RL1; GLP

 

No boiling point up to 250°C

OECD Guideline 103; RL1; GLP

 

Decomposition at ca. 200°C

decomposition at 135°C

OECD Guideline 103; RL1; GLP

 

Decomposition at > 250°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

OECD Guideline 115; RL1, GLP

 

37.5 mN/m at 20°C

 

 

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

OECD Guideline 115; RL2, GLP

 

73.9 mN/m at 20°C - not in line with the expected surface active behaviour of the substance

Water solubility

ASTM International E 1148 – 02, RL1, GLP

 

 

17.6 mg/L at 19.7°C

ASTM International E 1148 – 02; RL1, GLP

 

 

1.22 mg/L at 20°C

2.7 mg/L

ASTM International E 1148 – 02; RL1, GLP

 

1.01 mg/L at 20°C

ASTM International E 1148 – 02, RL1; ISO17025

 

7.4 mg/L at 20±0.3°C

ASTM International E 1148 – 02, RL1; ISO17025

 

1.9 mg/L at 20±0.3°C

Log Kow

Determination technically not feasible due to the surface-active properties; read-across from DODMAC

 

Determination technically not feasible due to the surface-active properties; read-across from DODMAC

 

3.8

Determination technically not feasible due to the surface-active properties; calculationbased on Koc

 

4.43

Vapour pressure

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

 

7.33E-18 Pa at 25°C

OECD TG 104, RL1, GLP

 

 

 

 

5E-08 Pa at 20°C

negligible because of the salt character

OECD Guideline 104, RL1, GLP

 

 

 

< 8.4E-07 Pa at 20°C

Auto flammability

---

EU Method A.15/DIN 51794; RL 1, GLP

 

340°C at 1012 hPa

 No data

No data; read-across

Flammability

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

 

not highly flammable

---

 No data

No data; read-across

The molecular weights of the target and source substances are in a comparable range. Experimental data on log Kow are not available for the source substances MDEA-Esterquat C16-18 and C18 unsatd. and MDIPA-Esterquat C18 unsatd. A read-across approach from the structurally similar substance DODMAC was applied, resulting in a log Kow of 3.8. For the target substance MDIPA-Esterquat C16-18 and C18 unsatd. the log Kow of 4.43 was calculated based on the available Koc (organic carbon normalised adsorption coefficient).

All four substances have a very low vapour pressure. The differences in order of magnitude most probably result from the differences of the applied methods (measurement vs. estimation by calculation).

There are, however, differences in physical state, melting point, surface tension and water solubility. The differences in melting point and physical state result from the higher degree of unsaturation of the source substance MDIPA Esterquat C18 unsatd.

The results from the studies on surface tension with the source substance MDEA-Esterquat C16-18 and C18 unsatd. as well as the target substance MDIPA-Esterquat C16-18 and C18 unsatd. were 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. or MDIPA-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. This can be seen i.e. at the test on hydrolysis with low correlation rates for pseudo-first order curve determination for 20°C but high correlation rates at 50 and 60°C.The result obtained with the source substance MDIPA Esterquat C18 unsatd. of 37.5 mN/m at 20°C was in the expected range for substances with this structure.

Water solubility 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.

Due to differences in the methodological approach the results for the water solubility measurement are not directly comparable between MDEA- and MDIPA-Esterquats. For the source substance MDEA-Esterquat C16-18 and C18 unsatd. the solubility of the test substance in water was considered equal to the intercept with the x-axis. Whereas for the target substance MDIPA-Esterquat C16-18 and C18 unsatd. as well as for the source substance MDIPA-Esterquat C18 unsatd. a baseline turbidity was calculated, and the intercept with this baseline was considered to represent the water solubility. This may lead to the differences in water solubility values.