Patent ID: 8795112

Claim:
An oil-free chain constructed by alternately connecting a pair of outer link plates connected by two pins and a pair of inner link plates connected by two oil-impregnated bushings into which the adjacent pins of said outer link plates adjacent to said inner link plates are fitted, wherein said oil-impregnated bushings are impregnated with a lubricant comprising a base oil selected from the group consisting of mineral oil, synthetic oil, animal oil, and plant oil, having a kinematic viscosity measured by an ISO viscosity grade number in the range of VG 140 to 460, a weight % of an elution ingredient of the base oil having the highest content among elution ingredients obtained is less than 95 wt %, and a number average molecular weight in a range from about 800 to 2300, when the base oil is subjected to GPC (gel permeation chromatography) measurement conditions, wherein the GPC measurement conditions include: a GPC system as a measuring instrument; a column that is about 300 mm in length and 8 mm in inside diameter in three pieces; a guard column that is about 10 mm in length and 4.6 mm in inside diameter; a column temperature of about 40° C.; a mobile phase including a GC grade tetrahydrofuran; a flow rate of about 0.7 ml/min; a pressure of about 2.9×10-2 Pa; a detector including a differential refractive index detector; and a standard reference material including standard polystyrene, and a ratio of the weight average molecular weight obtained under the GPC measurement conditions to said number average molecular weight is in a range from about 1.0 to 2.0.