Since entering force in 2007, REACH has become one of the world’s most influential chemical management frameworks, driving innovation, substitution of hazardous substances and stricter compliance standards worldwide. It reshaped the global chemicals industry by placing responsibility for safety squarely on manufacturers and importers.
Nearly 20 years after its introduction, many in industry expected REACH would be “finished,” yet work continues, albeit often in a more focused way than the initial rush to meet the registration deadlines.
For the grease industry, it was decided at the start that the individual components of grease would be registered separately, with base oils typically handled by Concawe, additives by the Additive Technical Committee, and thickeners by the European REACH Grease Thickeners Consortium. This allows companies to alter their grease formulations — concentrations of components within a mixture — without needing to re-register the mixture.
Although most thickeners are produced in situ in base oil during grease formulation, the separate registration of individual components of grease necessitates that thickeners are registered in isolated form, that is outside of base oil. This also means that registrations cover any thickeners produced in water and sold as a powder rather than in situ in base oil.
The ERGTC was initiated under the European Lubricating Grease Institute (ELGI) then separately established as a non-profit in 2008 to assist companies with their REACH obligations. Although initially focused on EU REACH, the consortium has expanded its scope to assist with REACH-like registrations around the world, including the United Kingdom, South Korea and Turkey.
The consortium enables companies to pool knowledge and resources to encourage a consistent approach in the registration of thickeners. It consists of around 40 companies, with sub-groups focusing on specific groups of substances. The scope of the sub-groups, along with a summary of the approach used for their registration, is outlined in Table 1.
Table1.
ERGTC Task Force | Number of substances | Highest Annex | Classification | Status |
Lithium salts of long-chain (C14-C22) carboxylic acids | 8 | 9 | Some substances: Eye irritation (H319) | Dossiers updated with additional hazard testing to support category read across approach; Waiting response on testing proposals submitted to ECHA |
Lithium isooctadecanoate | 1 | 7 | Eye irritation (H319) | |
Lithium salts of medium-chain (C6-C10) dicarboxylic acids | 3 | 9 | Acute oral category 4 (H302); testing ongoing to confirm genetic toxicity classification | |
Calcium salts of long-chain (C14-C22) carboxylic acids | 6 | 9 | Some substances: Eye irritation (H319) | |
Polyureas (sub-groups for different types of isocyanates) | 13 | 8 | Some substances: Chronic aquatic toxicity (H413) and/or flammability (H228) | Testing following ECHA decisions letters |
Lithium salts of boric acid | 4 | 8 | Eye corrosion (H318); reprotoxic category 2 (H361) | No updates planned |
Lithium and zinc salts of naphthenic acids | 2 | 8 | Lithium: Skin and eye corrosion (H314, H318)Zinc: Eye irritation (H319), skin sensitization (H317), aquatic chronic category 2 (H411) | |
Aluminum benzoate fatty acids complexes | 2 | 9 | Not classified | |
Sodium terephthalamates | 1 | 7 | Not classified |
Carboxylates
The carboxylate salt thickeners are divided into sub-groups:
A. Lithium salts of carboxylic acids with C14-C22 carbon chain lengths, with or without unsaturated double bonds and/or hydroxyl group
B. Lithium isooctadecanoate — Lithium salts of saturated C18 carboxylic acids with simple branching
C. Dilithium salts of dicarboxylic acids C6-C10, saturated, straight chain
D. Calcium salts of carboxylic acids with C14-C22 carbon chain lengths, with or without unsaturated double bonds and/or hydroxyl group
The carboxylate salt thickeners have generally been registered using category read across approaches, whereby the data for one or more substance is used to predict the properties of another substance. For each category, physico-chemical and in vitro testing was undertaken on each substance with testing of key structures for other endpoints, covering the carbon chain length range and functional groups across the category.
The substances were initially registered by the 2013 or 2018 registration deadline, depending on their tonnage, and the dossiers have subsequently been updated. The lithium, lithium isooctadecanoate and dicarboxylate substances were included in a voluntary dossier improvement program with the European Chemicals Agency, initiated in 2021. Further studies were conducted to support the category read across approach, and updated dossiers were submitted in 2024 including testing proposals for Annex IX studies, which require approval from ECHA before being conducted. The ERGTC is currently waiting for approval from ECHA, but preliminary method development has started due to foreseen challenges with analysis and media preparation being expected to cause delays. Calcium salts were not included in the voluntary program, but these dossiers have been updated too, following a similar approach as applied to the lithium salts but without in vivo mammalian toxicity testing.
Borates
The borate salt thickeners have been grouped based on their starting materials and manufacturing method. The substances are produced by reaction of boric acid and lithium hydroxide and for one substance also calcium dihydroxide. Data have been read across between category members, with additional one-to-one read across for the substance containing calcium salts.
It can be difficult to extract the borate salt thickeners from the base oil in which they are usually produced, so most of the category data have been generated on the one category substance which is routinely produced in water as well as base oil, so that an isolated form could be used for testing.
No further work on this category is currently planned, beyond that required to maintain a robust registration dossier — in case of, for example, changes to guidance.
Polyureas
Polyureas are formed by a reaction of isocyanate and amines. There are three sub-groups within the ERGTC, depending on the isocyanate structure: toluene diisocyanate, methylenediphenyl diisocyanate and naphthylene diisocyanate. Within those sub-groups, substances vary by the amine component (C8 to C18 chain lengths, cyclic and aromatic structures) and their overall structure (potential for oligomers).
Read across within the sub-categories follows a similar approach to other ERGTC categories, with physico-chemical and in vitro data generated for each substance and testing of key structures across the category for other endpoints. Testing proposals for long-term aquatic toxicity have been submitted due to the poor solubility of the substances, and some studies have been completed or are ongoing while others are awaiting approval from ECHA.
Naphthenate Salts
The naphthenate thickeners are complex substances of unknown or variable composition, complex reaction products or biological materials, with hundreds of constituents consisting of both metal salts and unreacted organic constituents. The compositions are not clearly identified as the substances are difficult to analyze.
Although these thickeners are grouped based on raw materials (naphthenic acids and zinc or lithium hydroxide), category read across is not applied and dossiers have been completed using a combination of testing on each substance, modelling and one-to-one read across from raw materials (naphthenic acids, metals) and structural analogues (other naphthenate salts, individual constituents within naphthenic acids, individual metal salt constituents).
Other Thickeners Handled by the ERGTC
Other thickeners handled by the ERGTC include aluminum salts of benzoic acid and fatty acid, where testing was conducted on one substance and read across to the only other substance in the group based on the substances having very similar, clearly defined compositions; and sodium terephthalamate, which consists of only a single substance on which testing was conducted, supported by one-to-one read across from the raw materials.
Lithium Hydroxide Classification
The ERGTC is working with Metals Europe and the International Lithium Association on responding to the harmonized classification for lithium hydroxide of reproductive toxicity category 1A – Fertility and Development and effects on or via lactation (H360FD, H362). The European authorities are currently also reviewing further actions on this substance, including Occupational Exposure Limits, Environmental Quality Standards and classification for endocrine disruption.
Lithium hydroxide is a raw material for lithium-based thickeners, and the lithium hydroxide concentration in thickeners and formulated greases will impact their classification. Currently, there are no analytical methods to determine lithium hydroxide content, so this is calculated by comparing measured and theoretical lithium, though titrimetric determination methods are being developed by an industry group.
The threshold for reproductive toxicity Category 1 is 0.3%, therefore if a thickener contains ≥0.3% lithium hydroxide it would meet the criteria for classification. However, classification is determined separately for thickeners (substances) and greases (mixtures). Therefore, even if a grease contains a thickener that is classified based on its lithium hydroxide content, classification of the grease is based on the lithium hydroxide content in the whole grease mixture. For example, if a grease contains 15% thickener and the thickener contains 1% lithium hydroxide, the grease contains 0.15% lithium hydroxide, or less than 0.3%.
Potential Future Work
Currently, the ERGTC is waiting for ECHA’s response to submitted testing proposals before conducting additional studies and updating the dossiers.
We will continue to monitor any changes in the obligations or expectations for registrants under EU REACH and work with companies to ensure that suitable registrations for grease thickeners are in place.