This invention provides a composition comprising a refrigerant, the composition being non-flammable like R404A (R125/R134a/R143a=44/4/52 wt %), and having a refrigerating capacity that can replace that of R404A, a COP that is equal or superior to that of R404A, and a GWP of 1500 or less. Specifically, the invention provides a composition comprising a refrigerant, the refrigerant comprising a mixture of fluorinated hydrocarbons, the mixture comprising difluoromethane (R32), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) at specific concentrations, the fluorinated hydrocarbons contained in the mixture having a specific composition ratio. This composition is for use as an alternative refrigerant for R22 or an alternative refrigerant for R404A.

A lubricating oil composition excellent in the wear resistance and a refrigerator oil composition excellent in the oxidation stability using the lubricating oil composition are provided by a lubricating oil composition containing a base oil (A) and a phosphine derivative (B) having one or more oxygen atom in a molecule.

A lubricating oil composition excellent in the wear resistance and a refrigerator oil composition excellent in the oxidation stability using the lubricating oil composition are provided by a lubricating oil composition containing a base oil (A) and a phosphine derivative (B) having one or more oxygen atom in a molecule.

The present invention provides a refrigerating machine oil comprising: a lubricating base oil; and 40 mass % or less of a polymer, based on a total amount of the refrigerating machine oil, the polymer having a structural unit represented by the following formula (I) and a weight average molecular weight of from 500 to 100000. ##STR00001## [In formula (I), R.sup.a, R.sup.b and R.sup.c each independently represents a hydrogen atom or a hydrocarbon group, and R.sup.d represents an oxygen-containing organic group or a C.sub.1-18 hydrocarbon group.]

The present invention provides a refrigerating machine oil comprising: a lubricating base oil; and 40 mass % or less of a polymer, based on a total amount of the refrigerating machine oil, the polymer having a structural unit represented by the following formula (I) and a weight average molecular weight of from 500 to 100000. ##STR00001## [In formula (I), R.sup.a, R.sup.b and R.sup.c each independently represents a hydrogen atom or a hydrocarbon group, and R.sup.d represents an oxygen-containing organic group or a C.sub.1-18 hydrocarbon group.]

An object of the present invention is to provide a grease composition which has little influence on the environment and has good rust prevention and water resistance against salt water such as sea water. The grease composition comprises a biodegradable base oil and a rust-preventive agent comprising a calcium sulfonate complex and a sorbitan fatty acid ester, wherein a total content of biodegradable organic substances in the grease composition is 75% by mass or more, and wherein a content of the rust-preventive agent is 2.5 to 30% by mass.

An object of the present invention is to provide a grease composition which has little influence on the environment and has good rust prevention and water resistance against salt water such as sea water. The grease composition comprises a biodegradable base oil and a rust-preventive agent comprising a calcium sulfonate complex and a sorbitan fatty acid ester, wherein a total content of biodegradable organic substances in the grease composition is 75% by mass or more, and wherein a content of the rust-preventive agent is 2.5 to 30% by mass.

A refrigeration oil composition includes: a mixture of a naphthenic mineral oil and at least one of a polyol ester oil and a polyvinyl ether oil; and at least one of a sorbitan compound and a glycerin fatty acid ester and a working fluid for a refrigeration system includes: the refrigeration oil composition; and one or more refrigerants selected from a hydrofluorocarbon refrigerant, a hydrofluoroolefin refrigerant and a carbon dioxide refrigerant.

A refrigeration oil composition includes: a mixture of a naphthenic mineral oil and at least one of a polyol ester oil and a polyvinyl ether oil; and at least one of a sorbitan compound and a glycerin fatty acid ester and a working fluid for a refrigeration system includes: the refrigeration oil composition; and one or more refrigerants selected from a hydrofluorocarbon refrigerant, a hydrofluoroolefin refrigerant and a carbon dioxide refrigerant.

A refrigerant compressor comprises an electric component; and a compression component which is driven by the electric component and compresses a refrigerant. At least one of slide members included in the compression component is made of an iron-based material. An oxide coating film (150) is provided on a slide surface of the iron-based material, the oxide coating film including a first portion (151), a second portion (152), and/or a third portion (153). The first portion (151) contains at least fine crystals (155). The second portion (152) contains columnar grains (156). The third portion (153) contains layered grains (157).