Patent ID: 8501671

Claim:
A process for producing a grease composition, characterized by homogeneously treating a mixture of a non-fluorine-based base oil blended with a first thickening agent and a fluorine-based base oil, blended with a second thickening agent which are not mutually compatible at a shear rate of 150 s −1 or higher to form a sea-island structure, in which one of the non-fluorine-based base oil and fluorine-based base oil is homogeneously dispersed in a particulate form having a mean particle diameter of not more than 25 μm in the other base oil, a mixture composed of a non-fluorine-based base oil blended with a first thickening agent making up 5% to 95% by volume of the composition and a fluorine-based base oil blended with a second thickening agent making up 95 to 5% volume of the composition, the total amount of the first and second thickening agents accounting for 10 to 50% by volume of the composition, being submitted to said homogeneous treatment, wherein the non-fluorine-based base oil is an ester-based synthetic oil; wherein the first thickening agent is an urea-based compound; wherein the fluorine-based base oil is selected from the group consisting of RfO[(CF(CF 3 )CF 2 O)] p (CF 2 CF 2 O) q (CF 2 O) r Rf, wherein p+q+r =3 to 200, including a case wherein q and/or r is 0, and CF(CF 3 )CF 2 O CF 2 CF 2 O and CF 2 O groups are bound randomly in the main chain; RfO[(CF(CF 3 )CF 2 O)] s (CF 2 CF 2 O) t Rf, wherein s+t =2 to 200, including a case where t is 0; t/s=0 to 2, and CF(CF 3 )CF 2 O and CF 2 O groups are bound randomly in the main chain; and wherein the second thickening agent is a fluorine resin.