Fatty acids, montan-wax, lithium salts

Endpoint summary

Additional information

Appearance/physical state/colour Lithium salts of fatty acids predominantly C24 – C28 (saturated) is a beige solid at room temperature. The data are taken from substance identification information in a GLP-compliant, guideline study available as an unpublished report (Envigo 2017).

 

Melting point/freezing point

Lithium salts of fatty acids predominantly C24 – C28 (saturated) decomposes at approximately 180°C. The melting point of lithium salts of fatty acids predominantly C24 – C28 (saturated) was determined in a GLP-compliant thermal analysis test, following OECD guideline 102 (Envigo 2017) This result falls within the range of melting points for the substances in the lithium salts of monocarboxylic acids C14-C22 category, 166 to 231°C with all category members slowly decomposing after melting.

 

Boiling point

Lithium salts of fatty acids predominantly C24 – C28 (saturated) decomposes and the boiling point test is therefore not technically feasible on this substance. This is the same as for the substances in the lithium salts of monocarboxylic acids C14-C22 category.

 

Density

All of the substances in the lithium salts of monocarboxylic acids C14-C22 category have relative densities just greater than 1 at 20°C, with a range from 1.025 to 1.07. The data were taken from GLP-compliant pycnometer tests following OECD guideline 109 (Harlan 2012, 2013) or published peer-reviewed papers (CIR 1982). The relative densities of lithium myristate, lithium stearate, lithium 12-hydroxystearate and lithium behenate are all very similar, being just greater than 1.

 

As all of these substances show similar densities, it can be justifiably expected that the density of lithium salts of fatty acids predominantly C24 – C28 (saturated) would be similar as well. As the relative density varies only by 0.045 over the 8 carbon chain length range in the category (C14 – C22), it is not expected that it would vary significantly if extended to a 14 carbon chain range, from C14 to C28, for the lithium salts of fatty acids predominantly C24 – C28 (saturated). Therefore, read across of the relative density from lithium salts of monocarboxylic acids C14 – C22 of 1.025 to 1.07, and particularly the relative density of lithium behenate of 1.04, to lithium salts of fatty acids predominantly C24 – C28 (saturated) is considered to be robust.

 

Furthermore, lithium salts of fatty acids predominantly C24 – C28 (saturated) is not synthesised as a ‘pure’ compound and does not exist except in the presence of a base oil grease matrix. High temperature stability indicates that the structures of the substance are robust and resistant to diffusion out of the grease matrix. Therefore, the relative density of lithium salts of fatty acids predominantly C24 – C28 (saturated) is not relevant under the conditions in which it is manufactured and used.

 

Granulometry

As the substance is manufactured and used in situ in base oil and is not marketed or used in isolated solid or granular forms, the particle size distribution test has been waived.

 

Vapour pressure

The vapour pressure of lithium salts of fatty acids predominantly C24 – C28 (saturated) was determined to be 3.9 x 10(-8) Pa at 25°C. The vapour pressure of lithium salts of fatty acids predominantly C24 – C28 (saturated) was determined in a GLP-compliant test, using a vapour pressure balance, following OECD guideline 104 (Envigo 2017).

This result cannot be compared to the vapour pressure for lithium salts of monocarboxylic acids C14-C22. The vapour pressures of lithium salts of monocarboxylic acids C14-C22 category were not determined as they were predicted to be less than 10 x 10(-10) Pa and therefore the studies would not be technically feasible for these substances as the vapour pressures would be below the limit of detection. However, this result for lithium salts of fatty acids predominantly C24 – C28 (saturated) is in line with the results for other salts of montan wax. The ‘Reaction mass of Fatty acids montan wax and Fatty acids montan wax calcium salts and Montan wax’ has a vapour pressure result of 0.00000067 Pa and the ‘Reaction mass of Fatty acids, montan-wax and Fatty acids, montan-wax, sodium salts and Montan wax’ has a vapour pressure of 0.00025 Pa.

 

Water solubility

The water solubility of lithium salts of fatty acids predominantly C24 – C28 (saturated) is 5.0 x 10(-5) g/L. The water solubility of lithium salts of fatty acids predominantly C24 – C28 (saturated) was determined in a GLP-compliant test, following OECD guideline 105 (Envigo 2017).

The water solubilities of the lithium salts of monocarboxylic acids C14-C22 category could not be determined. The water solubility for lithium behenate (C22) was determined to be ≤0.000046 g/L. The remaining substances in the category, those with a carbon chain length of less than C22, have surface active properties. As the substances formed stable dispersions in water rather than being truly soluble, the water solubility could not be determined.

 

The water solubility of lithium myristate and lithium 12-hydroxystearate could not be analytically determined because, after static equilibration, centrifugation and filtration, excess undissolved test item remained in the dispersion. The water solubility studies on lithium myristate and lithium 12-hydroxystearate were tested in GLP-compliant preliminary studies (Harlan 2012). The tests demonstrated that lithium myristate and lithium 12-hydroxystearate have surface active properties. The water solubility of lithium behenate is ≤0.000046 g/L at 20°C. The water solubility of lithium behenate was determined in a GLP-compliant test following EU method A6 (Harlan 2013).

 

Partition Coefficient

Based on the similarity in structures and properties between the lithium salts of fatty acids predominantly C24 – C28 (saturated) and substances in the lithium salts of monocarboxylic acids C14 – C22 category, it is expected that the partition coefficient tests would not technically be feasible for lithium salts of fatty acids predominantly C24 – C28 (saturated).

 

The partition coefficient could not be determined for any of the substances in the lithium salts of monocarboxylic acids C14-C22 category as the partition coefficient tests are not technically feasible on these substances. No determination was carried out using the shake-flask method or HPLC estimation method as lithium myristate and lithium 12-hydroxystearate had demonstrated significant surface active properties and the procedures are not suitable for surface active substances. No determination was carried out using the shake-flask method or HPLC estimation method as lithium behenate was insufficiently soluble in n-octanol and water which prevented the use of the shake-flask method and the HPLC method is not suitable for salts of organic acids.

 

Although lithium salts of fatty acids predominantly C24 – C28 (saturated) is not expected to be surface active, the results of the water solubility test indicate that it would not be sufficiently soluble to determine the partition coefficient by the shake flask method. The results from the QSAR model KOWWIN (KOWWIN v1.67 in EPISuite v4.11, US EPA 2009b) for the main constituents of lithium salts of fatty acids predominantly C24 – C28 (saturated) give an estimated log Kow value for lithium tetracosanoate of 7.6445, for lithium hexacosanoate of 8.63 and for lithium octacosanoate of 9.61.

 

The lithium salts of fatty acids predominantly C24 – C28 (saturated) is typically not synthesized as the “pure” compound and seldom exists except in the presence of the oil matrix. High temperature stability indicates that the grease thickener structure is robust and resistant to diffusion out of the oil. Dissolution of grease thickener from grease into water is very unlikely as the thickener is poorly water soluble and the thickener is embedded in the hydrophobic grease matrix and thus less likely to leach out. Thus, the partition coefficient of the substance is not expected to be relevant. Since the predicted log Kow values for the substance is greater than 6, the thickener is expected to reside within the grease base oil matrix and is not expected to favourably partition to water. Hence the substance is expected to have significantly limited bioavailability.

 

Surface tension

It is considered to be robust to read across data on surface tension from lithium behenate to lithium salts of fatty acids predominantly C24 – C28 (saturated) as the surface tension of the substances in the lithium salts of monocarboxylic acids C14 – C22 category increases with increasing carbon chain length. Lithium behenate slightly exceeds the cut-off of 60 mN/m for being considered surface active, it is expected that lithium salts of fatty acids predominantly C24 – C28 (saturated) would not be surface active.

 

Substances in the lithium salts of monocarboxylic acids C14-C22 category have increasing surface tension with increasing carbon number. The surface tension of a saturated solution of 1.02 to 1.03 g/L lithium myristate (C14) is 34.0 mN/m at 21.5°C. The surface tension of a saturated solution of 1.00 to 1.01 g/L lithium 12-hydroxystearate (C18) is 51.9 to 52.0 mN/m at 21.5°C. The surface tension of a saturated solution of 1.00 to 1.07 g/L lithium behenate (C22) is 61.8 to 65.9 mN/m at 21.0°C. The surface tensions of substances in the lithium salts of monocarboxylic acids C14-C22 category were determined in GLP-compliant ring balance tests following OECD guideline 115 (Harlan 2012, 2013).

 

All of the substances in the category have a structure which is representative of the "soap" surfactant class (the lithium ion being the hydrophilic head and the fatty acid being the hydrophobic tail). However, the surface tension of the substances increases with increasing carbon chain length and lithium behenate slightly exceeds the cut-off of 60 mN/m for being considered surface active. Therefore, only category members with carbon chain lengths of less than 22 are considered to have surface active properties, which is consistent with the observed characteristics of substances in the lithium salts of monocarboxylic acids C14-C22 category in water. As lithium salts of fatty acids predominantly C24 – C28 (saturated) has a carbon chain length of predominantly longer than C22, it is not expected to meet the criteria for surface activity.

 

Furthermore, the inclusion of read across data from lithium behenate is only considered to be additional weight of evidence for this endpoint. On the basis of the data read across from lithium behenate and the results of the water solubility study, there is sufficient justification for waiving the surface tension endpoint. In accordance with column 2 of REACH Annex VII, the surface tension study does not need to be conducted as this substance has a water solubility below 1 mg/L at 20°C.

 

Self-ignition temperature

 

There is no trigger to indicate that lithium salts of fatty acids predominantly C24 – C28 (saturated) would have different properties to lithium salts of monocarboxylic acids C14 – C22 and therefore it is not expected that lithium salts of fatty acids predominantly C24 – C28 (saturated) would be a self-heating substance.

 

All of the substances in the lithium salts of monocarboxylic acids C14-C22 category have self-ignition temperatures above their melting points and therefore none of the substances in the category meet the criteria for classification as a self-heating substance. Lithium myristate was determined not to have a relative self-ignition temperature below its melting point (i.e. >231°C). Lithium 12 -hydroxystearate was determined not to have a relative self-ignition temperature below its melting point (i.e. >216°C). Lithium behenate was determined not to have a relative self-ignition temperature below its melting point (i.e. >167°C). The relative self-ignition temperatures were tested in GLP-compliant studies following EC 440/2008 A16 method (Harlan 2013).

 

As all of these substances show the same result, it can be justifiably expected that the self-ignition temperature of lithium salts of fatty acids predominantly C24 – C28 (saturated) would be similar. The same result is returned for substances over the 8 carbon chain length range in the category (C14 – C22) and it is not expected that the result would vary if this was increased to a 14 carbon chain range, from C14 to C28, for the lithium salts of fatty acids predominantly C24 – C28 (saturated). Therefore, read across of the self-ignition temperature from lithium salts of monocarboxylic acids C14 – C22, and particularly the flammability record for lithium behenate, to lithium salts of fatty acids predominantly C24 – C28 (saturated) is considered to be robust.

 

Furthermore, the lithium salts of fatty acids predominantly C24 – C28 (saturated) is typically not synthesized as the “pure” compound and seldom exists except in the presence of the oil matrix. High temperature stability indicates that the grease thickener structure is robust and resistant to diffusion out of the oil. Dissolution of grease thickener from grease into water is very unlikely as the thickener is poorly water soluble and the thickener is embedded in the hydrophobic grease matrix and thus less likely to leach out.

 

Flammability

 

There is no trigger to indicate that lithium salts of fatty acids predominantly C24 – C28 (saturated) would have different properties to lithium salts of monocarboxylic acids C14 – C22 and therefore it is not expected that lithium salts of fatty acids predominantly C24 – C28 (saturated) would be flammable.

 

None of the substances in the lithium salts of monocarboxylic acids C14-C22 category are considered to be highly flammable and therefore none of the substances meet the criteria for classification as flammable solids. Lithium myristate, lithium 12 -hydroxystearate and lithium behenate have been determined to be not highly flammable as they failed to ignite in the preliminary screening tests. The flammability of the substances was tested in GLP-compliant tests following the method EC440/2008 A10 (Harlan 2013).

 

As all of these substances show the same result, it can be justifiably expected that the flammability of lithium salts of fatty acids predominantly C24 – C28 (saturated) would be similar. The same result is returned for substances over the 8 carbon chain length range in the category (C14 – C22) and it is not expected that the result would vary if this was increased to a 14 carbon chain range, from C14 to C28, for the lithium salts of fatty acids predominantly C24 – C28 (saturated). Therefore, read across of the flammability from lithium salts of monocarboxylic acids C14 – C22, and particularly the flammability record for lithium behenate, to lithium salts of fatty acids predominantly C24 – C28 (saturated) is considered to be robust.

 

Experience in manufacture and handling shows that the lithium salts of fatty acids predominantly C24 – C28 (saturated) does not ignite spontaneously on coming into contact with air at normal temperatures and is stable at room temperature for prolonged periods of time (days). Experience has also shown that the substance does not react with water and therefore does not meet the criteria for classification as a pyrophoric substance or a substance which in contact with water emit flammable gases.

 

Furthermore, the lithium salts of fatty acids predominantly C24 – C28 (saturated) is typically not synthesized as the “pure” compound and seldom exists except in the presence of the oil matrix. High temperature stability indicates that the grease thickener structure is robust and resistant to diffusion out of the oil. Dissolution of grease thickener from grease into water is very unlikely as the thickener is poorly water soluble and the thickener is embedded in the hydrophobic grease matrix and thus less likely to leach out.

 

Other physico-chemical endpoints

As the lithium salts of fatty acids predominantly C24 – C28 (saturated) is a solid, the viscosity and flash point endpoints are not required. Based on the structure of the substance, the explosiveness and oxidising properties studies have not been conducted as there are no structural alerts that would indicate explosive or oxidising properties. As the substance is manufactured and used in situ in a base oil, the substance is not marketed or used in solid or granular forms and so the particle size distribution test has been waived.

 

Classification and labelling

The lithium salts of fatty acids predominantly C24 – C28 (saturated) is not classified for physico-chemical hazards under the CLP or the DSD. Based on the structure of the substance, it does not meet the criteria for oxidising or explosive properties and, based on read across data, the substance would not meet the criteria for flammable solid or self-heating substance.