Provided is a lubricating oil composition to be used in an internal combustion engine having a sliding mechanism including a piston ring and a liner, the lubricating oil composition including: a base oil; (A) a poly(meth)acrylate; and (B) an organic molybdenum compound, in which: (A) the poly(meth)acrylate contains a polymer (A1) including a repeating unit derived from a (meth)acrylate represented by the following formula (1) and having a mass-average molecular weight of from 1,000 to 500,000; and a content of (B) the organic molybdenum compound in a total amount of the composition is from 0.01 mass % to 0.2 mass % in terms of a molybdenum atom: wherein R.sup.1 represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a hydrocarbon group having 1 to 60 carbon atoms, or a functional group-containing hydrocarbon group having 1 to 60 carbon atoms.

A lubricating oil composition for an internal combustion engine including: (A) a lubricant base oil having a kinematic viscosity at 100° C. of 2 to 5 mm.sup.2/s; (B) a metallic detergent in an amount of 500 to 2500 mass ppm in terms of Ca and 100 to 1000 mass ppm in terms of Mg, on the basis of the total mass of the composition, the metallic detergent including both (B1) a Ca-containing metallic detergent and (B2) a Mg-containing metallic detergent; (C) a boron-containing additive in an amount of 50 to 1000 mass ppm in terms of boron on the basis of the total mass of the composition, wherein the boron-containing additive is oil-soluble or oil-dispersible and is stable in oil, and wherein the boron-containing additive may compose at least a part of the component (B); and (D) an oil-soluble organic Mo compound in an amount of 100 to 2000 mass ppm in terms of Mo on the basis of the total mass of the composition, wherein a mass ratio (MB/Mg) of boron content of the composition (MB) to Mg content of the composition (Mg) is 0.5 to 10.

Provided are lubricant compositions comprising a base oil, a polyoxypropylene polymer, and a butyleneoxy based polyoxyalkylene polymer. The base oil, polyoxypropylene polymer and polyoxyalkylene polymer are soluble with one another.

A water-soluble working fluid of the invention is used for cutting a brittle material using a wire saw. The water-soluble working fluid is provided by blending water, alkylene oxide adduct of acethylene glycol, and glycols. The water-soluble working fluid of the invention is capable of providing favorable cutting accuracy when the brittle material is cut using a wire, and thus is suitable for cutting out a large-diameter wafer. The water-soluble working fluid of the invention is especially suitably applicable to an abrasive-grain-fixed wire saw.

A method of reducing the incidence of deposits on the pistons of a 4-stroke marine diesel engine during operation of the engine when it is fuelled with a marine residual fuel meeting the ISO 8217 2017 fuel standard for marine residual fuels and having a sulphur content of more than 0.1% and less than 0.5% by mass. The method includes the step of lubricating the engine using a lubricating oil composition comprising: a) at least 50% by mass, based on the mass of the composition, of an oil of lubricating viscosity; (b) 5 to 25% by mass, based on the mass of the composition, of an oil-soluble or oil-dispersible alkali metal or alkaline earth metal salicylate detergent, or a mixture of two or more oil-soluble or oil-dispersible alkali metal or alkaline earth metal salicylate detergents; (c) 0.1 to 10% by mass, based on the mass of the composition of one or more oil-soluble or oil-dispersible ashless dispersants; and optionally, (d) 0.1 to 10% by mass, based on the mass of the composition of a polyalkylene-substituted succinic anhydride.

A method of reducing the incidence of deposits on the pistons of a 4-stroke marine diesel engine during operation of the engine when it is fuelled with a marine residual fuel meeting the ISO 8217 2017 fuel standard for marine residual fuels and having a sulphur content of more than 0.1% and less than 0.5% by mass. The method includes the step of lubricating the engine using a lubricating oil composition comprising: a) at least 50% by mass, based on the mass of the composition, of an oil of lubricating viscosity; (b) 5 to 25% by mass, based on the mass of the composition, of an oil-soluble or oil-dispersible alkali metal or alkaline earth metal salicylate detergent, or a mixture of two or more oil-soluble or oil-dispersible alkali metal or alkaline earth metal salicylate detergents; (c) 0.1 to 10% by mass, based on the mass of the composition of one or more oil-soluble or oil-dispersible ashless dispersants; and optionally, (d) 0.1 to 10% by mass, based on the mass of the composition of a polyalkylene-substituted succinic anhydride.

A method for the preparation of a copolymer containing at least one alkyl methacrylate and maleic anhydride having a number average molecular weight of 4000 to 18000 g/mol proceeds by solution polymerization in the presence of a radical initiator.

A comb copolymer viscosity modifier may be made by polymerization comprising at least, or consisting essentially of, the following monomers: (a) (optionally from 7.0 wt % to 18 wt %, by repeat units, of) a hydrogenated polybutadiene-based (alk)acrylate ester macromonomer; (b) (optionally from 33 wt % to 64 wt %, by repeat units, of) a C.sub.3-C.sub.8alkyl (alk)acrylate ester monomer; (c) a C.sub.12-C.sub.24 alkyl (alk)acrylate ester monomer; and (d) (optionally from 3.0 wt % to 25 wt %, by repeat units, of) H-endcapped, C.sub.1-C.sub.18 alkyl-endcapped, or C.sub.6-C.sub.20 aryl-, aralkyl-, or alkaryl-endcapped C.sub.2-C.sub.6 oxyalkyl or C.sub.2-C.sub.6 oligo(alkylene glycol)-based (alk)acrylate ester monomer, wherein repeat units based on monomer (c) and/or monomer (d) comprise at least 21.0 wt % (and optionally up to 35.0 wt %) of repeat units of the comb copolymer viscosity modifier. Lubricant compositions comprising the comb copolymer viscosity modifier, as well as uses thereof and methods for modifying viscosity and dispersancy, are also contemplated.

The invention provides a grease composition for lubricating resins which contains a base oil, a diurea compound represented by formula (I) as a thickener: R.sup.1—NHCONH —R.sup.2—NHCONH—R.sup.3 (I) (wherein R.sup.2 represents a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sup.1 and R.sup.3 each independently represent a straight-chain or branched alkyl group having 8 to 22 carbon atoms), and a chained hydrocarbon polymer having a weight-average molecular weight of 20,000 to 300,000.

The method for producing a polyalkylene glycol of the present invention is a method for producing a polyalkylene glycol, including performing a polymerization reaction of an alkylene oxide with a composite metal catalyst, the polymerization reaction being performed in the presence of an organic solvent in an amount of 10 to 90 mass % based on the polyalkylene glycol to be produced.