Process for preparing a complex calcium sulphonate grease

A process for the preparation of a calcium sulphonate complex grease comprising at least the following steps:

• a) preparing, in a reactor, a calcium sulphonate complex soap comprising calcium carbonate, the calcium carbonate being presented in the form of calcite, said preparing comprising the steps of:
• a.i) mixing, in the reactor, at least one base oil and at least one overbased calcium sulphonate,
• a.ii) adding at least one carboxylic acid comprising at least 12 carbon atoms, and optionally at least one OH group, at a temperature of at least 20° C.,
• a.iii) adding at least one sulphonic acid comprising at least 12 carbon atoms at a temperature of at least 50° C.,
• a.iv) adding water at a temperature of at least 50° C.,
• a.v) adding at least one carboxylic acid comprising at least 2 carbon atoms at a temperature of at least 50° C.,
• a.vi) closing the reactor,
• a.vii) raising the temperature to a temperature of at least 80° C.,
• a.viii) opening the reactor, and
• a.ix) adding lime at a temperature ranging from 90° C. to 95° C.,
• wherein the at least one base oil, the at least one overbased calcium sulphonate, the at least one carboxylic acid comprising at least 12 carbon atoms and optionally at least one OH group, the at least one sulphonic acid, the water, the least one carboxylic acid comprising at least 2 carbon atoms, and the lime are starting reagents,
• b) closing the reactor,
• c) raising the temperature in the reactor from the temperature ranging from 90° C. to 95° C. to a temperature ranging from 130° C. to 160° C. under a pressure ranging from 400 kPa to 700 kPa, said temperature and pressure being maintained for a duration of at least 60 min,
• d) depressurizing and removing the water contained in the reactor, and
• e) cooling the reactor to lower the temperature to a temperature of less than or equal to 90° C.,
• the process not comprising the addition of boric acid or a derivative of boric acid.