Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Information on Diurea 8

Diurea 8 is a complex polyurea (PU) based grease thickener product. The constituents of Diurea 8 do not exist outside of the grease matrix, but are synthesized during the production of the grease by reacting the starting materials of Diurea 8 within a synthetic or mineral lubricating base oil to form an insoluble fibrous network structure within the grease. Because the Diurea 8 thickener components are created within the grease matrix, their physical-chemical properties and requirements to provide test data on these endpoints should be interpreted with this understanding.

Physico-chemical properties

According to Article 12 of the REACH Regulation, for registration purposes all physicochemical information that is relevant and available to the registrant must be included in the technical dossier, i.e. information such as data on intrinsic properties of the substance (e.g. melting point/freezing point, boiling point, vapour pressure, density, surface tension); data necessary to assess the physical hazards of a substance (e.g. flammability, oxidizing and explosive properties), with the view to determine its classification and labelling according to CLP (and until 1 June 2015, according to DPD, see Article 61 of CLP); and supplementary data for hazard assessment and health and environmental classification (e.g. viscosity, n-octanol/water partition coefficient).

The chemical constituents which make up Diurea 8do not exist outside of the base oil grease matrix in which it is contained. Furthermore, chemical components of Diurea 8 are not expected to leach out or partition from the grease into water due to their poor water solubility and strong physical chemical interactions with the hydrocarbons residing within the grease matrix. On the basis of the information provided, various endpoints are therefore considered irrelevant for the assessment of the hazard of Diurea 8.

Appearance

Diurea 8 is a light brown solid at ambient temperature. The data are taken from substance identification information in a GLP-compliant, guideline study available as an unpublished report (Harlan 2012).

Melting point

Diurea 8 decomposes with softening from approximately 142 °C and as such, no value for melting temperature could be determined. The melting point of Diurea 8 was tested in a differential scanning calorimetry study following guideline OECD 102 (Harlan 2012). As Diurea 8 was heated, a sharp endotherm was observed at approximately 160°C, the first signs of which were taken as the onset temperature, followed by a wide, shallow endotherm, during which Diurea 8 softened to a sticky semi-solid. The test item gradually decomposed, becoming darker in colour, but did not become a fully mobile liquid. Experimental data for melting point suggests that Diurea 8 decomposes at 142°C as opposed to melting. Diurea 8 exists as a solid at ambient temperature and pressure.

The melting point of Diurea 8 has been predicted using EPISuite (MBPBWIN), a well established model programme, validated and mentioned in ECHA's endpoint specific technical guidance documents for the implementation of REACH. The structures of the relevant components of Diurea 8 were converted to SMILES notation using ACD/Labs ChemSketch software package and these were used as the input to the Quantitative Structure Property Relationship (QSPR) model. Based on the MBPBWIN model, the predicted melting points fall within a range of 259-359°C (Dawick 2012). The MBPBWIN model is not capable of predicting the temperature at which a substance decomposes rather than definitively melting, which may explain why there is a large gap between experimental and predicted data.

Boiling point

Diurea 8 decomposes before boiling to give a sticky semi-solid residue. The boiling point test is therefore not technically feasible on Diurea 8.

The boiling point of Diurea 8 has been predicted using EPISuite (MBPBWIN), SPARC and ACD/Labs models. These are well established model programmes, validated and mentioned in ECHA's endpoint specific technical guidance documents for the implementation of REACH. The structures of the relevant components of Diurea 8 were converted to SMILES notation using ACD/Labs ChemSketch software package and these were used as the input to the QSPR models. Based on the model outputs, the predicted boiling points fall within a range of 529 -832°C (Dawick 2012). However, experimental data suggests that Diurea 8 decomposes at 142°C and therefore decomposes before reaching its predicted boiling point temperature.

The predicted boiling point values for the components of Diurea 8, coupled with the fact that it decomposes at 142°C suggests Diurea 8 is not volatile under ambient conditions.

Density

Diurea 8 is not synthesized as a “pure” compound and does not exist except in the presence of a base oil grease matrix. High temperature stability indicates that the structure of Diurea 8 is robust and resistant to diffusion out of the grease matrix. Dissolution of Diurea 8 from the grease into water is very unlikely as the thickener is poorly water soluble and embedded within the hydrophobic grease matrix.

The density of Diurea 8 is 982 kg/m3at 20°C. The density of Diurea 8 was determined in a GLP-compliant, gas comparison pyncometer study following EC method A3 (Harlan 2013).

Vapour pressure

The vapour pressure could not be determined for Diurea 8. The vapour pressure test is not technically feasible for Diurea 8 as the predicted vapour pressure was below the limit of detection of the test methods. Standard test methods, according to OECD guideline 104, are able to measure vapour pressure from 10 E-10 Pa to 10 E+05 Pa. As the predicted vapour pressure for Diurea 8 is below 10 E-10 Pa, the vapour pressure test was not conducted.

The vapour pressure of Diurea 8 has been predicted using EPISuite (MBPBWIN), SPARC and ACD/Labs models, well established model programmes, validated and mentioned in ECHA's endpoint specific technical guidance documents for the implementation of REACH. The structures of the relevant components of Diurea 8 were converted to SMILES notation using ACD/Labs ChemSketch software package and these were used as the input to the QSPR models. Based on the model outputs, the predicted vapour pressures fall within a range of 4.02 E-20 to 2.82 E-11 Pa (Dawick 2012).

Since the vapour pressures of all components of Diurea 8 are predicted to be substantially less than 1 Pa, Diurea 8 is expected to have very little to no tendency to partition to air.

Partition coefficient

Diurea 8 is not synthesized as a “pure” compound and does not exist except in the presence of a base oil grease matrix. High temperature stability indicates that the structure of Diurea 8 is robust and resistant to diffusion out of the grease matrix. Dissolution of Diurea 8from the grease into water is very unlikely as the thickener is poorly water soluble and embedded within the hydrophobic grease matrix.

The octanol-water partition coefficient of Diurea 8 has been predicted using EPISuite (WATERNT), SPARC, VCC Lab and ACD/Labs, well established model programmes, validated and mentioned in ECHA's endpoint specific technical guidance documents for the implementation of REACH. The structures of the relevant components of Diurea 8 were converted to SMILES notation using ACD/Labs ChemSketch software package and these were used as the input to the QSPR models. Based on the results of these models, the predicted log Kows for Diurea 8 fall within a range of 6.6 to 17.2 (Dawick 2012).

Since the predicted log Kow values for Diurea 8 are all greater than 6, Diurea 8 is expected to reside within the grease base oil matrix and is not expected to favourably partition to water. Hence Diurea 8 is expected to have significantly limited bioavailability.

Water solubility

The water solubility of the Diurea 8 has been predicted using EPISuite (WATERNT), SPARC, VCC Lab and ACD/Labs, well established model programmes, validated and mentioned in ECHA's endpoint specific technical guidance documents for the implementation of REACH. The structures of the relevant components of Diurea 8 were converted to SMILES notation using ACD/Labs ChemSketch software package and these were used as the input to the QSPR models. Based on the model outputs, the predicted water solubility values are in the range of 1.83 E-11 to 0.38 mg/L, with a mean average value of 0.0067 mg/L (Dawick 2012). Since the water solubility of Diurea 8 is less than 1 mg/L, Diurea 8 is considered to be poorly water soluble and is not expected to dissolve out of the grease matrix into the water phase.

Diurea 8 is not synthesized as a “pure” compound and does not exist except in the presence of a base oil grease matrix. High temperature stability indicates that the structure of Diurea 8 is robust and resistant to diffusion out of the grease matrix. Dissolution of Diurea 8 from grease into water is very unlikely as the thickener is poorly water soluble and Diurea 8 is embedded in the hydrophobic grease matrix. Since the predicted log Kow values for Diurea 8 are all greater than 6, Diurea 8 is expected to reside within the grease base oil matrix and is not expected to favourably partition to water.

Surface tension

According to the adaptation possibilities according to column 2 of Annex VII to REACH, the specific rules for adaptation of the standard information requirement for surface tension state that the study need only be conducted if based on structure, surface activity is expected or can be predicted; or surface activity is a desired property of the material. If the water solubility is below 1mg/L at 20 °C the test does not need to be conducted.

Experimental surface tension determination of Diurea 8 has therefore been waived on the basis that the surface activity is not expected as Diurea 8 does not contain a combination of the necessary functional groups required to impart surface active properties in water. Also, as Diurea 8 is made in-situ within lubricating base oils to physically interact with and thicken the oil into grease, Diurea 8 is not a surfactant and surface activity is not a desired property of the material.

The water solubility of Diurea 8 is predicted to be in the range 1.83 E-11 - 0.38 mg/L using Quantitative Structure Property Relationship (QSPR) models (Dawick 2012). The water solubility varies depending on the carbon chain length and type of the alkyl moiety of the diurea functional group. Overall, the water solubility of Diurea 8 is expected to be below 1 mg/L.

In summary, the limited solubility and physical interaction of the chemical constituents comprising Diurea 8 components with hydrocarbons contained within the base grease indicates that Diurea 8 is unlikely to dissolve out of the grease matrix into the water phase and cause surface active impacts on the properties of aqueous solutions.

Self-ignition temperature

According to the adaptation possibilities according to column 2 of Annex VII to REACH, the specific rules for adaptation of the standard information requirement for self-ignition properties testing states that the study does not need to be conducted if Diurea 8 is explosive or ignites spontaneously with air at room temperature or for solids, if Diurea 8 has a melting point ≤ 160°C or preliminary results exclude self-heating of Diurea 8 up to 400°C.

Isolated Diurea 8 thickener exists as a light brown solid at ambient temperature and pressure. Diurea 8 was found to decompose at approximately 142°C during an experimental melting point determination study (Harlan 2012). As Diurea 8 decomposes rather than undergoes true melting, a definitive melting point could not be determined. However, since Diurea 8 decomposes at temperatures <160°C it can also be expected that a phase change from solid to liquid also occurs at <160°C.

Furthermore, Diurea 8 thickener is synthesised, and always expected to reside within a base oil grease matrix. The flash point and self-ignition temperature of typical grease product formulations containing concentration of approximately 5-25% Diurea 8 thickener are >150°C and >320°C, respectively.

Flammability

According to the adaptation possibilities according to column 2 of Annex VII to REACH, the specific rules for adaptation of the standard information requirement for flammability testing state that the study does not need to be conducted if the substance is a solid which possesses explosive or pyrophoric properties or the substance spontaneously ignite when in contact with air.

Although none of the standard waiving possibilities apply to Diurea 8, it is unique in that it is synthesised and only ever expected to reside within a base oil grease matrix. Diurea 8 thickener isolated from base grease exists as a light brown solid at ambient temperature and pressure which decomposes at 142°C (Harlan 2012). The flash point and self-ignition temperature of typical grease product formulations containing Diurea 8 thickener are >150°C and >320°C respectively, which indicates these materials are not flammable. Further, the vapour pressure of the chemical constituents of Diurea 8 are predicted to be extremely low (i.e. <<1 Pa at 25°C) using Quantitative Structure Property Relationship (QSPR) models (Dawick 2012). These compounds are therefore not expected to partition from the grease into air and are not expected to be flammable except at very high temperatures.

On the basis of the above arguments, coupled with the fact that Diurea 8 is only present inside a grease matrix (which implies that this endpoint is considered irrelevant for the assessment of the potential hazard of Diurea 8), the requirement to undertake an experimental determination of flammability is waived.

As Diurea 8 only occurs contained in a grease matrix designed to minimise leaching or partitioning to water, Diurea 8 is considered not to occur in its isolated form. Experience in manufacture and handling shows that the Diurea 8 in grease base 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 Diurea 8 does not react with water and therefore it does not meet the criteria for classification as pyrophoric substance or substance which in contact with water emit flammable gases.

Stability in organic solvents

The stability in organic solvents has not been conducted as the stability of Diurea 8 is not considered to be critical. As Diurea 8 only occurs contained in a grease matrix designed to minimise leaching or partitioning to water, Diurea 8 is considered not to occur in its isolated form.

Diurea 8 is only manufactured and used in a grease matrix and therefore the stability in organic solvents other than the grease base is considered to be irrelevant. Experience in manufacture, handling and technical performance shows that Diurea 8 is stable in the base grease.

Dissociation constants

The dissociation constant study has not been conducted as it is not scientifically possible to perform the test because the test item is insufficiently soluble in water.

OECD guideline 112 lists three potential methods for determining dissociation constant: titration, spectrophotometric and conductometric procedures. For the titration method and the conductometric method, the chemical substance should be dissolved in distilled water. For the spectrophotometric and other methods buffer solutions are used. If the substance is only sparingly soluble it may be dissolved in a small amount of a water miscible solvent prior to adding. Solutions should be checked for the presence of emulsions using a Tyndall beam.

As Diurea 8 is insoluble in water, with an estimated solubility of significantly less than 1 mg/L (Dawick 2012), testing of the dissociation constant by the three potential methods listed in OECD guideline 112 is not technically feasible.

As Diurea 8 only occurs contained in a grease matrix designed to minimise leaching or partitioning to water, Diurea 8 is considered not to occur in its isolated form. On the basis of both the isolated properties and the form in which it is manufactured and used, Diurea 8 is expected not to be available in the aqueous environment and therefore the dissociation constant is considered to be not scientifically relevant.

Other physico-chemical endpoints

The granulometry and viscosity endpoints have been waived using standard column 2 adaptations.

Based on the chemical structure of Diurea 8, the results for explosive and oxidising properties are predicted to be negative. On this basis, coupled with the fact that Diurea 8 is only present inside a grease matrix (which implies that these endpoints are considered irrelevant for the assessment of the potential hazard of Diurea 8), the requirement to undertake experimental determinations of explosive and oxidising properties is waived.

Conclusion

Physical-chemical properties for chemical constituents of Diurea 8 have been measured or predicted as if they existed outside the grease matrix. However, as Diurea 8 is created within the base oil grease matrix, the physical-chemical properties should be interpreted with this understanding.

Isolated Diurea 8 is a solid with QSPR predicted negligible water solubility and very low vapour pressure. However, as mentioned above, Diurea 8 only ever occurs in a base oil grease matrix designed to minimise leaching or partitioning to water. Furthermore, the predicted log octanol-water partition coefficient (log Kow) values for constituents of Diurea 8 are all greater than 6 and therefore Diurea 8 is expected to preferentially reside within the base oil grease matrix if exposed to water. The predicted physical-chemical properties (water solubility, vapour pressure and partition coefficient), coupled with the fact that Diurea 8 is only ever manufactured within a base oil grease indicate that environmental exposures of Diurea 8 to air, soil and water compartments will be severely limited.

On the basis of the chemical structure and experience in handling Diurea 8 in the grease form in which it is manufactured and used, Diurea 8 is considered not to be flammable, self-heating, oxidising or explosive. Based on information available on the properties of Diurea 8, experimental data are not presented for the following endpoints: boiling point, granulometry, vapour pressure, water solubility, surface tension, flash point, self-ignition temperature, flammability, oxidising properties, explosiveness, stability in organic solvents, dissociation constant and viscosity. Appropriate waiving statements are provided to indicate why these REACH endpoints are not applicable.