Lubricants containing multifunctional additives based on secondary plant substances

Each year in Germany about 1 million tonnes of lubricants are used (hydraulic fluids, transmission oils, engine oils, and metal-working fluids). Crude oil based lubricants dominate the market. Over recent years there has been a trend towards biobased and biodegradable lubricants, although their current market share is only about 3.5%.

Development work in this area has hitherto only focused on biobased base fluids (e.g. plant oils, biopolymers). Various additives also have to be added to achieve the necessary lubricating properties (e.g. to provide protection against oxidation, corrosion, and abrasion) and up until now these have continued to be based on fossil raw materials. For wholly biobased lubricants there is a need therefore to manufacture biobased additives.

Secondary plant substances as biobased additives

The Fraunhofer IVV possesses many years of experience and knowledge in the recovery of proteins, dietary fiber, and secondary plant substances from a variety of raw materials. Several previous R&D projects have developed extraction methods on both a laboratory and technical scale for the manufacture of polyphenol-rich extracts using different solvents. In addition to the development of innovative and efficient extraction processes, the focus of Fraunhofer IVV projects is on the application of secondary plant metabolites (in particular antioxidants) in product formulations (e.g. cosmetics and lubricants). The Fraunhofer IVV possesses all the required equipment to recover secondary plant substances. This includes equipment for the pretreatment of the raw materials (e.g. mills, sieves) and batch extraction units up to a volume of 2 m³ for organic solvents and aqueous systems. We also have the necessary analytical facilities for characterizing the extracts and functionalities of secondary plant metabolites.

Development of multifunctional plant-based lubricant additives

The overall goal of the MAPLub project is to develop new multifunctional lubricant additives based on plant raw materials. To achieve this, secondary plant substances (SPSs) having high functionality are being recovered from waste materials. To increase their functionality these substances are being modified using chemical-enzymatic methods. This enables biobased multifunctional additives (with antioxidative, anticorrosive, and anti-abrasion properties) to be manufactured.

The first step is to manufacture SPS-rich functional extracts. These are then converted into multifunctional additives by chemical-enzymatic synthesis. As lubricants are generally non-polar, the synthesized SPSs are made lipophilic in a subsequent step. This guarantees they are soluble in hydrophobic media.

One of the scientific challenges of the project is the combined chemo-enzymatic process and the utilization of the individual SPS functionalities. The economic challenge is to manufacture multifunctional biobased additives for the first time. This enables a completely new generation of lubricants to be commercialized whose base medium and additives are wholly made from renewable raw materials.

Secondary plant substances from waste materials from the food industry and agricultural sector

The task of the Fraunhofer IVV is the extractive recovery and purification of secondary plant substances (SPSs) from waste materials from the food and agricultural sectors. Although different raw and waste materials are being used as the starting materials for the extraction of secondary plant substances, there are often similarities between the classes of molecules (e.g. polyphenols). This project is therefore developing efficient extraction methods involving organic solvents to recover valuable molecules from different raw materials in a single extraction step.

In order to identify suitable extract compositions for the subsequent synthesis step it is important to separate any contaminants. That is why effective purification methods are being evaluated, tailored to the subsequent synthesis and application in lubricants. In parallel, suitable strategies for separating the extraction solvents are being developed.

Thereafter, the formulation and stabilization of the new SPS additives in different non-polar base fluids will be investigated. Amongst other aspects this will look at possible interactions between the new additives and other lubricant components in order to identify viable additive systems.