METHOD OF PREPARING THICKENING ADDITIVES Russian patent published in 2001 - IPC

FIELD: lubricants. SUBSTANCE: invention relates to preparing thickening additives used in production of various-type motor and transmission oils, hydraulic fluids, etc. Process is accomplished in two apparatuses. One of them is loaded with polyisobutylene with molecular weight 4000 to 30000 in amounts 20 to 50 wt %, whereas industrial oil is fed portionwise at constant stirring and temperature 20 to 150 C, each portion constituting 5-10% of the weight of oil fed into apparatus and time interval between two feedings being at least 2 h. Second apparatus is loaded with polyisobutylene with molecular weight 40000 to 250000 in amounts 10 to 50 wt %, whereas industrial oil is fed portionwise at constant stirring and temperature 90 to 150 C, each portion constituting 2-5% of the weight of oil fed into apparatus and time interval between two feedings being at least 3 h. Solutions obtained in the two apparatuses are then combined at weight ratio of first- to second-apparatus solution between 5:1 and 10:1. Oil can also contain modifying additive selected from group including agidol-1 and/or agidol-2, or dilauryl dipropionate in quantities from 0.005 to 0.1 wt %. EFFECT: increased depolymerization stability and improved thickening ability and viscosity stability index combined with long-time preservation of solution homogeneity. 2 cl, 1 tbl, 6 ex