Contamination of soil and water by lubricants is caused by loss lubrication, leakage, inefficient operating conditions and accidents. A compiete and fast lubricant biodegradation is therefore, among other requirements, a major demand especially in environmentally sensitive areas. Low mobility of the lubricant in soil also favours rapid degradation. These requirements can be met only by vegetable or animal oils and selected organic esters.
In western Europe rape seed oil raffinates are used for base oils. In the beginning it was enthusiastically considered that all industrial lubricants could be formulated by the use of vegetable oils. But more severe operating conditions e.g. increased temperatures or the influence of emulsified water caused serious problems by the formation of deposits, corrosion, filter plugging and others. The first application of vegetable oil based lubricants therefore should be assessed by careful oil analysis and machine service.
For these severe conditions the use of synthetic organic esters e.g. dicarboxylic acid esters or polyolesters is essential. But not ali of these base oils demonstrate satisfactory biodegradability. Seal compatibility and high prices too play an important role.
But there are not only ecological advantages in the application of vegetable oils and synthetic esters, because existing recycling processes are negatively affected by the presence of esters.
Biodegradable lubricants have obtained a fixed place in the lubricant market today. But it should be decided carefully from case to case whether the application of biodegradable lubricants is reasonable in terms of ecological and economical demands.
the other hand oil quantities remain constant. More In Western European countries the slogan ‘biodegradable lubricants’ summarises both, lubricants and their various properties, that minimise environmental impact (Table I). Regarding the various applications for lubricants we can estimate that most of the desired performance properties are met by fatty oils. But lubricants increasingly have to meet severe and also steadily increasing performance criteria of engine and machine manufacturers too.
The specific thermal and oxidative stress on lubricants is increasing permanently due to higher temperature levels and increased oil drain intervals. On TABLE I Environmental compatibility of lubricants J renewable resources J environmentally unobjectionable process J J ecological compatible J readily biodegradable after use J no disposal and recycling problems (low energy demand, waste and emissions) non toxic (fresh and used oil) and more we become aware that increased performance requirements can be met only by synthetic fo