Compositions of hydraulic fluids based on rapeseed oil and its derivatives.

The awareness on the harmful impact of lubricants and industrial fluids entering the environment due to leakage or spillage has increased considerably during the last years. Hydraulic fluids can be classified as “high risk loss” lubricants they are used in large volumes in equipment that is susceptible to spills. Hydraulic fluids currently used in Latvia in wood harvesting and other environmentally sensitive areas still are mainly based on mineral oils which are not biodegradable and are dangerous to the environment. Completely different is the situation in other EU countries, e.g., in Sweden, where the Swedish standard SS 155434 is a legal requirement: lubricants not fulfilling these criteria for biodegradable hydraulic fluids are not permitted on the Swedish market. There is an obvious need for elaboration of compositions of hydraulic fluids based on renewable natural resources in order to initiate and to promote production of such products in Latvia. Vegetable oil-based lubricants have excellent lubricity and biodegradability, but two major problems exist with vegetable oils as functional fluids: low resistance to thermal oxidation and poor performance at low temperatures. We developed compositions of hydraulic fluids using as base stocks rapeseed oil and esters of its fatty acids with polyols neopentyl glycol (NPG), trimethylolpropane (TMP) and pentaerythritol (PE) – as well as 2-ethylhexyl esters of estolides of rapeseed oil. Besides that mixture of rapeseed oil with pentaerythritol esters of fatty acids (7:3) also was made. We used tert-butylhydroquinone (TBHQ) as oxidation inhibitor, Lubrizol 7671A as pour point depressant and polymethylsiloxane as antifoam agent in our formulations. The following technical parameters of our compositions were tested: kinematic viscosity at 40 C and 100 C, viscosity index, oxidative stability, coldflow properties, acid value, foaming, air release, flash point. The elaborated formulations corresponded to the main requirements set for biodegradable hydraulic fluids.