Grease composition, pivot assembly bearing, and bearing apparatus including the bearing

A grease composition for a pivot assembly bearing, comprising an aromatic ester-based base oil and a thickener,

• the aromatic ester-based base oil comprises an aromatic ester compound having an ester group *—C(═O)O— as a substituent on an aromatic ring, where * is a bonding site to the aromatic ring, and having an alkyl group with a total of 8 or more carbon atoms bonded to an oxygen atom of the ester group, and
• the alkyl group is selected from the group consisting of:
• a branched alkyl group formed with a branched chain bonded to a linear alkyl group with 8 or more and 11 or less carbon atoms, and
• a branched alkyl group formed with two or more branched chains bonded to a linear alkyl group with 6 or more and 11 or less carbon atoms,
• wherein
• the grease composition for a pivot assembly bearing comprises a urea-based thickener as a thickener,
• the urea-based thickener comprising a diurea compound represented by Formula (1):
• R1—NHCONH—R2—HNOCHN—R3 Formula (1)
• where in Formula (1), R1 and R3 are monovalent alicyclic hydrocarbon groups or monovalent aliphatic hydrocarbon groups, and a molar ratio of the alicyclic hydrocarbon group to the aliphatic hydrocarbon group is from 6:4 to 8:2, and R2 represents a divalent aromatic hydrocarbon group,
• wherein the grease composition has:
• a storage elastic modulus at 25° C. of from 1200 to 3000 Pa as measured under conditions of a film thickness of 1 mm and a shear strain of 1%, and
• an oil separation amount at 80° of from 200 to 270 mm2/mg.