| abstract |
The invention relates to a new three-part process, which can also be employed on a large industrial scale, for the preparation of polyurea lubricating greases, which is characterised (a) in that polyureas which carry oleophilic groups are prepared by reaction of diisocyanates with amines either in the absence of a solvent on a reaction screw at 80 DEG -120 DEG C., preferably at 85 DEG -95 DEG C., (variant A) or in a toluene medium at 20 DEG -80 DEG C., preferably at 30 DEG -60 DEG C., (variant B), (b) in that, after complete reaction, the polyureas prepared according to (a) are ground in the solid, dry state to give powders (at least 70% by weight of the powder having particle sizes of about 100-400 mu ) and (c) in that the ground crude product, after being made into a "paste" (wetted) at elevated temperature in the base oil employed (10-30 minutes at 140 DEG -180 DEG C.) and cooled again to room temperature, is processed to a grease by complete homogenisation-if appropriate in several passes-in a high-pressure homogeniser under a pressure of 400-1,500 bar (spontaneous heating occurring up to about 100 DEG C.), greases having readily reproducible and essentially the same properties as in the case of the previously customary in situ manufacture being produced. |