Provided is a lubricating oil composition containing a base oil (A) and a viscosity index improver (B) and satisfying the following requirements (I) and (II): Requirement (I): a kinematic viscosity at 80° C., V.sub.80 of the lubricating oil composition is 11.5 mm.sup.2/s or less; Requirement (II): a ratio [V.sub.80/T.sub.80] of a kinematic viscosity at 80° C., V.sub.80 (m.sup.2/s) to an oil film thickness measured at a sliding speed of 2.0 m/s, a maximum Hertz pressure of 0.8 GPa, and an oil temperature of 80° C., T.sub.80 (nm) of the lubricating oil composition is less than 0.105 ((m.sup.2/s)/nm). The lubricating oil composition is excellent in fuel saving properties and anti-wear properties even when it is used in a temperature environment of around 80° C. which is assumed to fall within a range where an engine is practically used.

An object of the present invention is to provide a solid lubricant supplied to a surface of an image carrier of an electrophotographic image forming apparatus, wherein the solid lubricant comprises a fatty acid metal salt and polypropylene, and the polypropylene has an acid value of 1 mg KOH/g or more.

A lubricant composition of an oil of lubricating viscosity; an esterified copolymer with a backbone comprising units derived from (i) an α-olefin monomer of at least about 6 carbon atoms and (ii) an ethylenically unsaturated carboxylic acid in a mole ratio of 1:3 to 3:1; and a polymer comprising olefin monomer units of 3 to 5 carbon atoms, wherein at least 50 percent by weight of such units contain fewer than 6 carbon atoms and wherein less than 5 percent by weight of such units are ethylene monomer units; exhibits good power transfer efficiency and elastohydrodynamic film thickness.

[Problem]

From the points of view of improving the fuel efficiency of automobiles and industrial machines and saving energies thereof, the present invention provides lubricants having outstanding shear stability and low-temperature viscosity characteristics.

[Solution]

A lubricant composition includes a lubricant base oil (A) having a kinematic viscosity at 100° C. of 1 to 10 mm.sup.2/s, and an ethylene/α-olefin copolymer (B) in which (B1) the peak top molecular weight is 3,000 to 10,000, (B2) the copolymer shows no melting peak, (B3) the value B is not less than 1.1 and (B4) the kinematic viscosity at 100° C. is 140 to 500 mm.sup.2/s. The lubricant composition has a kinematic viscosity at 100° C. of not more than 20 mm.sup.2/s, a peak top of molecular weight in the range of 3,000 to 10,000, and a weight fraction of components having a molecular weight not less than 20,000 of 1 to 10% relative to all components having a molecular weight not less than the molecular weight that gives the peak top.

The present disclosure provides for a lubricant formulation and a method of forming the lubricant formulation for use in an internal combustion engine. The lubricant formulation includes a base oil and an esterified oil-soluble polyalkylene glycol (E-OSP) of Formula (I): R.sup.1 [O(R.sup.2O).sub.n(R.sup.3O).sub.m(C═O)R.sup.4].sub.p wherein R.sup.1 is a linear alkyl having 1 to 18 carbon atoms, a branched alkyl having 4 to 18 carbon atoms or an aryl with 6 to 30 carbon atoms; R.sup.2O is an oxypropylene moiety derived from 1, 2-propylene oxide; R.sup.3O is an oxybutylene moiety derived from butylene oxide, wherein R.sup.2O and R.sup.3O are in a block or a random distribution; R.sup.4 is a linear alkyl with 1 to 18 carbon atoms, a branched alkyl with 4 to 18 carbon atoms or an aryl with 6 to 18 carbon atoms; n and m are each independently integers ranging from 0 to 20 wherein n+m is greater than 0, and p is an integer from 1 to 4.

A high-molecular-weight compound having a plurality of polymer chains linked through a divalent or higher-valent linking group, in which the divalent or higher-valent linking group has a thiol group and at least one of a thioether structure and a thiourethane structure, and a ratio of an absolute weight-average molecular weight to a relative weight-average molecular weight (absolute Mw/relative Mw) of the high-molecular-weight compound is 1.25 or more; and a method for producing the same are provided.

A lubricating oil composition comprising at least 50 percent by mass, based on the mass of the composition of an oil of lubricating viscosity and 0.01 to 25 percent by mass, based on the mass of the composition of a polymer comprising units (a) and one or both units (b) and (c):
—N(COR.sup.1)(CH.sub.2).sub.x—  (a)
—NH(CH.sub.2).sub.y—  (b)
—N(CH.sub.2CH.sub.2-k(CH.sub.3).sub.kCOOR.sup.2)(CH.sub.2).sub.z   (c) where the total number (n) of units (a), (b) and (c) is an integer between 4 and 500; wherein x, y and z are independently 2 or 3; wherein k is zero or 1. The polymer shows good solubility in the lubricating oil and provides friction modification. A method of synthesising a polymer is also disclosed.

A lubricating oil composition may include a base oil (A), an olefin copolymer (B), and a poly(alkyl(meth)acrylate) (C), in which a weight average molecular weight of the olefin copolymer (B) is 10,000 to 80,000, a content of the olefin copolymer (B) is 0.01% to 0.23% by mass based on the total amount of the lubricating oil composition, and a content of the poly(alkyl(meth)acrylate) (C) is 0.02% to 0.40% by mass based on the total amount of the lubricating oil composition.

An oil composition comprises at least 50 percent by mass, based on the mass of the composition, of an oil and 0.01 to 25 percent by mass, based on the mass of the composition, of a polymer comprising at least one poly(lactone) segment. The at least one poly(lactone) segment is derived from a lactone substituted by one or two hydrocarbyl groups, or substituted hydrocarbyl groups, at least one such group having at least 4 carbon atoms. The oil compositions are suitable for use in the lubrication of the crankcase of internal combustion engines.

An industrial base oil formulation comprising a base oil, preferably a hydrocarbon base oil, having a kinematic viscosity of more than 100 centiStokes, preferably 150 centiStokes or more, at 40 degrees Celsius and an AC-OSP where the AC-OSP has the structure of Formula I: R.sup.1[O(R.sup.2O).sub.n(R.sup.3O).sub.mR.sup.4].sub.p (I) where R.sup.1 is an alkyl having from one to thirty carbons, R.sup.2 and R.sup.3 are independently selected from alkyl groups having three or four carbons and can be in block form or randomly combined, R.sup.4 is an alkyl having from one to 18 carbon atoms, n and m are independently numbers ranging from zero to 20 provided that n+m is greater than zero and p is a number within a range of one to three; wherein the industrial base oil formulation has a kinematic viscosity of greater than 100 centiStokes, preferably 150 centiStokes or more, at 40 degrees Celsius is useful in a lubricant for mechanical devices.