Process for the preparation of polyurea-thickened lignin derivative-based lubricating greases, such lubricant greases and use thereof

A method for preparing a lignin derivative-containing lubricating grease comprising the following steps:

• bringing together an amine component having reactive amine groups including optional reactive —OH groups with an isocyanate component in a base oil and reacting the same to become a polyurea thickener;
• heating at least the polyurea thickener above 120° C. to produce a base grease comprising at least the polyurea thickener and the base oil;
• and
• cooling the base grease;
• wherein the method comprises subjecting a lignin derivative to an elevated temperature greater than 110° C. in base oil to obtain a heated lignin derivative and wherein the heated lignin derivative and the polyurea thickener and/or the amine component and the isocyanate component are brought in contact with each other and are subjected to a temperature greater than 120° C. in the base oil, for at least 30 minutes, and
• wherein the isocyanate component is used with a stoichiometric excess of isocyanate groups with respect to the reactive amine groups and the optional reactive —OH groups of the amine component so that a portion of the isocyanate groups of the isocyanate component reacts with the lignin derivative,
• wherein the lignin derivative is a lignosulfonate or a kraft lignin or an organosolv lignin or their mixtures;
• and the lignin derivative-containing lubricating grease comprises:
• 55 to 92 weight percent base oil;
• 5 to 20 weight percent polyurea thickener;
• and
• 0.5 to 15 weight percent lignin derivative,
• and optionally:
• 0 to 40 weight percent additives;
• 0 to 20 weight percent soap thickener or complex soap thickener based on calcium, lithium or aluminum salts;
• 0 to 20 weight percent inorganic thickener;
• 0 to 10 weight percent solid lubricant.