KR101857425B1 - Lubricant base oil and refrigerator oil - Google Patents

Abstract

[상기 화학식 1에 있어서,
A는 다가 알코올에서 수산기를 제거한 잔기이고,
R은 탄소수 3 내지 7의 알킬기 또는 탄소수 8의 분기 알킬기이고,
n은 2 이상의 정수이다],
에스테르는 동일 분자 중의 R이 탄소수 3 내지 7의 알킬기로 이루어지는 그룹으로부터 선택되는 1종인 제1 에스테르와, 동일 분자 중의 R이 탄소수 8의 분기 알킬기인 제 2 에스테르와, 동일 분자 중의 R이 탄소수 3 내지 7의 알킬기 및 탄소수 8의 분기 알킬기로 이루어지는 그룹으로부터 선택되는 2종 이상인 제3 에스테르를 함유하고, 제1 에스테르와 제2 에스테르와 제3 에스테르의 합계량을 기준으로 하여, 제1 에스테르의 함유량이 0질량% 초과 30질량% 이하이고, 제2 에스테르의 함유량이 0질량% 초과 30질량% 이하이다.The lubricating oil base oil according to the present invention contains an ester represented by the following formula (1)
[Chemical Formula 1]

[In the formula 1,
A is a residue obtained by removing a hydroxyl group from a polyhydric alcohol,
R is an alkyl group having 3 to 7 carbon atoms or a branched alkyl group having 8 carbon atoms,
n is an integer of 2 or more,
Wherein the ester is selected from the group consisting of a first ester in which R in the same molecule is one selected from the group consisting of an alkyl group having 3 to 7 carbon atoms and a second ester in which R in the same molecule is a branched alkyl group having 8 carbon atoms, An alkyl group having 1 to 7 carbon atoms, and a branched alkyl group having 8 carbon atoms, and wherein the content of the first ester is 0% based on the total amount of the first ester, the second ester and the third ester, 30% by mass or more and 30% by mass or less, and the content of the second ester is 0% by mass or more and 30% by mass or less.

Description

LUBRICANT BASE OIL AND REFRIGERATOR OIL}

The present invention relates to a lubricating oil base oil and a freezer oil.

Generally, lubricating oil is used to secure lubricity in mechanical elements such as a sliding part. As a main component for imparting lubricity to the lubricating oil, a lubricating oil base oil such as mineral oil or synthetic oil is used.

In addition, lubricant other than lubricity may be required depending on the application. For example, since lubricating oil for refrigerator is used in the presence of refrigerant, the lubricating oil is required to have compatibility with refrigerant in addition to lubricity in the presence of refrigerant. As a lubricant base oil satisfying such required characteristics, Patent Document 1 discloses a lubricant base oil containing an ester of a carboxylic acid and an alcohol satisfying a predetermined condition.

International Publication No. 00/68345

An object of the present invention is to provide a lubricant base oil which has both sufficient lubricity and can be compatible with a refrigerant in compatibility and lubricity when used as a base oil for a refrigerator. Another object of the present invention is to provide a refrigerator oil containing the above-mentioned lubricating oil base oil.

Esters obtained by using mixed carboxylic acids and polyhydric alcohols are generally ester mixtures containing a plurality of esters differing in structure (that is, types and ratios of carboxylic acids bonded to plural hydroxyl groups of polyhydric alcohols). The inventors of the present invention have conducted studies on such an ester mixture. As a result, the inventors have found that the ratio of the respective esters contained in the ester mixture can be changed depending on the production method or the production conditions even if the kinds and ratios of the mixed carboxylic acids are the same, It was found that the characteristics of the ester mixture as the lubricant base oil could be changed by the difference in the ratios. As a result of further studies based on these findings, the present inventors have found that, in an ester mixture obtained by using a specific mixed carboxylic acid and a polyhydric alcohol, the content ratio of each ester contained in the ester mixture satisfies a predetermined condition It has been found that excellent lubricity can be achieved and compatibility with a refrigerant and lubrication can be compatible when used as a base oil for refrigerator use. The present invention has been accomplished based on these findings.

That is, the present invention provides a process for producing an ester of the formula

[In the formula 1,

A is a residue obtained by removing a hydroxyl group from a polyhydric alcohol,

R is an alkyl group having 3 to 7 carbon atoms or a branched alkyl group having 8 carbon atoms,

n is an integer of 2 or more,

Wherein the ester is selected from the group consisting of a first ester in which R in the same molecule is one selected from the group consisting of an alkyl group having 3 to 7 carbon atoms and a second ester in which R in the same molecule is a branched alkyl group having 8 carbon atoms, A branched alkyl group having 8 carbon atoms and a branched alkyl group having 8 carbon atoms, wherein the content of the first ester is at least one selected from the group consisting of a first ester, a second ester and a third ester, , More than 0 mass% and not more than 30 mass%, and a content of the second ester is not less than 0 mass% and not more than 30 mass%.

The present invention also provides a refrigerator oil containing the above-mentioned lubricating oil base oil.

The present invention also provides a refrigerator oil and a refrigerant-containing working fluid composition for a refrigerator.

According to the present invention, there is provided a lubricating base oil capable of satisfying both compatibility and lubricity with respect to a refrigerant when used as a base oil for refrigerating machine oil, and refrigerator oil containing the lubricating base oil.

The lubricating base oil according to the present embodiment contains an ester represented by the following formula (1).

[Chemical Formula 1]

In Formula 1,

A is a residue obtained by removing a hydroxyl group from a polyhydric alcohol,

R is an alkyl group having 3 to 7 carbon atoms or a branched alkyl group having 8 carbon atoms,

n is an integer of 2 or more.

The ester is a mixture of a first ester in which R in the same molecule is one selected from the group consisting of an alkyl group having 3 to 7 carbon atoms and a second ester in which R in the same molecule is a branched alkyl group having 8 carbon atoms, A tertiary ester having at least two kinds selected from the group consisting of an alkyl group having 3 to 7 carbon atoms and a branched alkyl group having 8 carbon atoms. The content of the first ester is more than 0 mass% and not more than 30 mass%, and the content of the second ester is more than 0 mass% and 30 mass% or less based on the total amount of the first ester, the second ester and the third ester.

The first ester has a chemical structure in which R in the same molecule of the ester represented by the formula (1) is one kind selected from the group consisting of an alkyl group having 3 to 7 carbon atoms. In other words, the first ester is one kind of complete ester selected from the group consisting of a polyhydric alcohol and a monovalent fatty acid having 4 to 8 carbon atoms.

The second ester has a chemical structure in which R in the same molecule of the ester represented by the formula (1) is a branched alkyl group having 8 carbon atoms. In other words, the second ester is a complete ester of a polyhydric alcohol and a branched monovalent fatty acid having 9 carbon atoms.

The third ester has a chemical structure in which R in the same molecule of the ester represented by the formula (1) is at least two selected from the group consisting of an alkyl group having 3 to 7 carbon atoms and a branched alkyl group having 8 carbon atoms. In other words, the third ester is a complete ester composed of a polyhydric alcohol and a fatty acid, wherein the fatty acid is at least two kinds of mixed fatty acids selected from the group consisting of a monovalent fatty acid having 4 to 8 carbon atoms and a branched monovalent fatty acid having 9 carbon atoms It is completely ester.

The third ester is preferably selected from the group consisting of at least one selected from the group consisting of alkyl groups having 3 to 7 carbon atoms and branched alkyl groups having 8 carbon atoms in the same molecule in view of improvement in lubricity and improvement in compatibility with refrigerant It has a chemical structure containing at least one species. In other words, the mixed fatty acid constituting the third ester is preferably at least one selected from monovalent fatty acids having 4 to 8 carbon atoms and at least one mixed fatty acid selected from branched monovalent fatty acids having 9 carbon atoms.

As the polyhydric alcohol, for example, a polyhydric alcohol having 2 to 6 hydroxyl groups can be used. In this case, n in the general formula (1) can take an integer of 2 to 6 according to the number of hydroxyl groups of the polyhydric alcohol.

Examples of dihydric alcohols (diols) include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, , Neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, etc. .

Examples of the trivalent or higher alcohol include trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), pentaerythritol, dipentaerythritol, tri- (pentaerythritol) Polyhydric alcohols such as polyglycerin (trimer of glycerin), 1,3,5-pentanetriol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol and mannitol, , Arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose and cellobiose, and partial etherified products thereof.

Among them, hindered alcohols such as neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), pentaerythritol, dipentaerythritol, Is used.

Examples of monohydric aliphatic acids having 4 to 8 carbon atoms include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid and octanoic acid. These fatty acids may be linear or branched. Examples of the branched fatty acids include 2-methylpropanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic acid, 3- Butanedioic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 3-methylhexanoic acid, 2-methylbutanoic acid, , 2,2-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4- Ethylpentanoic acid, 1,1,2-trimethylbutanoic acid, 1,2,2-trimethylbutanoic acid, 1-ethyl-1-methylbutanoic acid, 1-ethyl- , 2-ethylhexanoic acid, 3-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 4,5- Hexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanosane, 6-methylheptanoic acid and 2-propylpentanoic acid are preferably used.

Examples of branched monovalent fatty acids having 9 carbon atoms include 2,2-dimethylheptanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, 3,5,5-trimethylhexanoic acid, 2 -Ethyl-2,3,3-trimethylbutanoic acid, 2,2,4,4-tetramethylpentanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylphene Carbonic acid, and 2,2-diisopropylpropanoic acid.

The polyhydric alcohols used in the first ester, the second ester and the third ester may be the same or different. In other words, A in formula (1) may be the same or different in the first ester, the second ester and the third ester.

The monovalent fatty acids having 4 to 8 carbon atoms used in the first ester and the third ester may be the same or different from each other and branched monovalent fatty acids having 9 carbon atoms and used in the second and third esters , They may be the same or different. In other words, the alkyl group having 3 to 7 carbon atoms represented by R in formula (1) may be the same or different from each other in the first ester and the third ester, and the branched alkyl group having 8 carbon atoms represented by R in formula (1) The second ester and the third ester may be the same or different.

The content of the first ester is preferably more than 0% by mass, more preferably not less than 0.1% by mass, based on the total amount of the first ester, the second ester and the third ester from the viewpoint of compatibility with the refrigerant , More preferably 0.2 mass% or more, and particularly preferably 0.3 mass% or more. The content of the first ester is preferably 30% by mass or less, more preferably 29% by mass or less, and still more preferably 30% by mass or less, based on the total amount of the first ester, the second ester and the third ester, Is not more than 28% by mass, particularly preferably not more than 27% by mass.

The content of the first ester is preferably from 0% by mass to 30% by mass or less, more preferably from 0% by mass or more to 30% by mass or less based on the total amount of the first ester, the second ester and the third ester, , More than 0 mass% and not more than 29 mass%, more than 0 mass% and not more than 28 mass%, more than 0 mass% and not more than 27 mass%, 0.1 to 30 mass%, 0.1 to 29 mass%, 0.1 to 28 mass% 0.2 to 30 mass%, 0.2 to 30 mass%, 0.2 to 29 mass%, 0.2 to 28 mass%, 0.2 to 27 mass%, 0.3 to 30 mass%, 0.3 to 29 mass%, 0.3 to 28 mass% 27% by mass.

The content of the second ester is preferably not less than 0% by mass, more preferably not less than 0.1% by mass, more preferably not less than 0.1% by mass, more preferably not less than 0.1% by mass, more preferably not less than 5% by mass based on the total amount of the first ester, Is not less than 0.2% by mass, particularly preferably not less than 0.3% by mass. The content of the second ester is preferably not more than 30% by mass, more preferably not more than 29% by mass, more preferably not more than 30% by mass, and more preferably not more than 30% by mass, based on the total amount of the first ester, the second ester and the third ester, More preferably 28% by mass or less, and particularly preferably 27% by mass or less.

The content of the second ester is preferably from 0% by mass to 30% by mass or less, more preferably from 0% by mass or less to 30% by mass or less based on the total amount of the first ester, the second ester and the third ester from the viewpoint of compatibility between lubricity and compatibility with the refrigerant, More than 0 mass% and not more than 29 mass%, more than 0 mass% and not more than 28 mass%, more than 0 mass% and not more than 27 mass%, 0.1 to 30 mass%, 0.1 to 29 mass%, 0.1 to 28 mass% 0.2 to 30 mass%, 0.2 to 30 mass%, 0.2 to 29 mass%, 0.2 to 28 mass%, 0.2 to 27 mass%, 0.3 to 30 mass%, 0.3 to 29 mass%, 0.3 to 28 mass%, or 0.3 to 27 mass% Mass%.

The content of the third ester is suitably adjusted so that the content of the first ester and the second ester is in a predetermined condition. The content of the third ester may be, for example, less than 40 mass% and less than 100 mass% based on the total amount of the first ester, the second ester and the third ester, but from the viewpoint of precipitation at low temperatures, More preferably not less than 60 mass%, more preferably not less than 70 mass%, further preferably not less than 80 mass%, and most preferably not less than 85 mass%. In view of abrasion resistance, the content is preferably not more than 97 mass% Is 95 mass% or less, and more preferably 93 mass% or less.

The content of the third ester is preferably 60 to 97% by mass, 60 to 95% by mass based on the total amount of the first ester, the second ester and the third ester from the viewpoint of compatibility between precipitation and abrasion resistance at low temperatures, 70 to 93 mass%, 80 to 97 mass%, 80 to 95 mass%, 80 to 93 mass%, 85 to 97 mass%, 70 to 95 mass%, 70 to 95 mass%, 70 to 93 mass% , 85 to 95 mass%, or 85 to 93 mass%.

The ester represented by the general formula (1) may contain at least one of the first ester, the second ester and the third ester, and two or more kinds of the first ester, the second ester and the third ester May be contained. When the ester represented by the general formula (1) contains two or more kinds in any one or all of the first ester, the second ester and the third ester, the content of the first ester, the second ester and the third ester , And the total amount of two or more esters in each ester.

The method for producing the ester represented by the general formula (1) is not particularly limited and a known production method may be used. The ester represented by the general formula (1) is obtained, for example, by separately synthesizing the first ester, the second ester and the third ester, and then mixing these esters.

The third ester is synthesized, for example, by the following synthesis procedure. First, partial esters of a polyhydric alcohol and one kind (hereinafter referred to as "fatty acid A") selected from the group consisting of a monovalent fatty acid having 4 to 8 carbon atoms and a monovalent fatty acid having 9 carbon atoms are synthesized. Specifically, for example, by reacting an excessive amount of a polyhydric alcohol with the fatty acid A, a partial ester of the polyhydric alcohol and the fatty acid A is obtained. Subsequently, by reacting the above partial ester with one kind (hereinafter referred to as "fatty acid B") selected from the group consisting of a monovalent fatty acid having a carbon number of 4 to 8 and a monovalent fatty acid having a carbon number of 9, Ester is obtained. However, fatty acid A and fatty acid B are different fatty acids.

The lubricant base oil according to the present embodiment may contain other base oils in addition to the ester represented by the general formula (1). Examples of other base oils include hydrocarbon oils such as mineral oils, olefin polymers, naphthalene compounds and alkylbenzenes, esters other than esters represented by the formula (1), polyglycols, polyvinyl ethers, ketones, polyphenyl ethers, silicones, polysiloxanes, perfluoroethers And the like.

The content of the ester represented by the general formula (1) may be, for example, 10% by mass or more, 50% by mass or more, or 80% by mass or more based on the total amount of the lubricant base oil.

Examples of applications of the lubricating base oil according to the present embodiment include engine oils such as gasoline engine oil and diesel engine oil; Gear oils such as automotive gear oils (automatic transmission, manual transmission, differential gear) and industrial gear oils; Refrigerator oil; Turbine oil; Hydraulic oil; Air compressor oil; Cutting oil; Grinding oil; Metal working oils such as baking oil (rolling oil, press oil, forging oil, drawing oil, drawn oil, blanking oil and the like), heat treatment oil and discharge oil; Machine tool oil; Sliding guide surface oil; Bearing oil; Rust prevention oil; Thermal oil; Electric insulating oil; And grease base oils. The lubricating base oil according to the present embodiment is particularly suitably used as a base oil of a refrigerator.

The refrigerator oil according to the present embodiment contains the lubricating base oil according to the present embodiment. The content of the lubricating base oil may be, for example, 50% by mass or more, 70% by mass or more, or 90% by mass or more, based on the flow rate of the freezer.

The refrigerator oil may further contain an additive in addition to the lubricating oil base oil. Examples of the additive include an acid capturing agent, an antioxidant, an extreme pressure agent, an oil agent, a defoaming agent, a metal deactivator, a wear inhibitor, a viscosity index improver, a pour point depressant, a clean dispersant, a friction modifier and an antirust agent. The content of the additive is preferably 5% by mass or less, more preferably 2% by mass or less, based on the refrigerating machine flow rate.

Among the above additives, the refrigerator oil preferably further contains an acid capturing agent from the viewpoint of further improving thermal and chemical stability. As the acid trapping agent, an epoxy compound and a carbodiimide compound are exemplified.

Examples of the epoxy compound include a glycidyl ether type epoxy compound, a glycidyl ester type epoxy compound, an oxirane compound, an alkyloxysilane compound, an alicyclic epoxy compound, an epoxidized fatty acid monoester, and an epoxidized vegetable oil. These epoxy compounds may be used singly or in combination of two or more.

As the glycidyl ether type epoxy compound, for example, an aryl glycidyl ether type epoxy compound or an alkyl glycidyl ether type epoxy compound represented by the following formula (2) can be used.

In Formula 2,

R ¹ is an aryl group or an alkyl group having 5 to 18 carbon atoms.

Examples of the glycidyl ether type epoxy compound represented by the formula (2) include n-butylphenyl glycidyl ether, i-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, Pentylphenyl glycidyl ether, hexylphenyl glycidyl ether, heptylphenyl glycidyl ether, octylphenyl glycidyl ether, nonylphenyl glycidyl ether, decylphenyl glycidyl ether, decyl glycidyl ether, undecyl Glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether and 2-ethylhexyl glycidyl ether are preferable.

As the glycidyl ether type epoxy compound, besides the epoxy compound represented by the formula (2), neopentyl glycol diglycidyl ether, trimethylol propane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol di Glycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, polyalkylene glycol diglycidyl ether, and the like.

As the glycidyl ester type epoxy compound, for example, those represented by the following formula (3) can be used.

In Formula 3,

R ² is an aryl group, an alkyl group having 5 to 18 carbon atoms, or an alkenyl group.

Examples of the glycidyl ester type epoxy compound represented by the formula (3) include glycidyl benzoate, glycidyl neodecanoate, glycidyl-2,2-dimethyl octanoate, glycidyl acrylate, glycidyl Methacrylate is preferred.

The alicyclic epoxy compound is a compound represented by the following general formula (4) having a partial structure in which the carbon atom constituting the epoxy group constitutes a straight chain alicyclic ring.

Examples of the alicyclic epoxy compound include 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3 ', 4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis (3,4- Epoxy cyclohexylmethyl) adipate, exo-2,3-epoxy norbornane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 2- (7-oxabicyclo [4.1.0] 3-yl) -spiro (1,3-dioxane-5,3'- [7] oxabicyclo [4.1.0] heptane, 4- (1'-methyl epoxyethyl) 2-methylcyclohexane, and 4-epoxyethyl-1,2-epoxycyclohexane.

Examples of the allyloxysilane compound include 1,2-epoxystyrene and alkyl-1,2-epoxystyrene.

Examples of the alkyloxysilane compound include 1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, - epoxy decane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, Decane, 1,2-epoxyheptadecane, 1,2-epoxyoctadecane, 1,2-epoxynonadecane, and 1,2-epoxycyclohexane.

Examples of the epoxidized fatty acid monoesters include esters of epoxidized fatty acids having 12 to 20 carbon atoms and alcohols having 1 to 8 carbon atoms or phenols or alkyl phenols. As the epoxidized fatty acid monoester, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of epoxystearic acid are preferably used.

Epoxidized vegetable oils include epoxy compounds of vegetable oils such as soybean oil, linseed oil and cottonseed oil.

The carbodiimide compound is not particularly limited, and for example, dialkylcarbodiimide, diphenylcarbodiimide and bis (alkylphenyl) carbodiimide can be used. Examples of dialkylcarbodiimides include diisopropylcarbodiimide and dicyclohexylcarbodiimide. Examples of the bis (alkylphenyl) carbodiimide include ditolylcarbodiimide, bis (isopropylphenyl) carbodiimide, bis (diisopropylphenyl) carbodiimide, bis (triisopropylphenyl) carbodiimide, bis (Butylphenyl) carbodiimide, bis (dibutylphenyl) carbodiimide and bis (nonylphenyl) carbodiimide.

Further, among the above additives, the refrigerator oil preferably further contains an abrasion preventing agent. Suitable antiwear agents include, for example, phosphoric acid esters, thiophosphoric acid esters, sulfide compounds and zinc dialkyldithiophosphates. Of the phosphoric esters, triphenyl phosphate (TPP) and tricresyl phosphate (TCP) are preferred. Of the thiophosphoric acid esters, triphenylphosphorothionate (TPPT) is preferred. As the sulfide compound, a monosulfide compound is preferable in that stability of refrigerator oil is ensured and deterioration of copper, which is frequently used in refrigeration equipment, can be suppressed.

Further, among the above-mentioned additives, the refrigerator oil preferably further contains an antioxidant. Examples of the antioxidant include di-tert. Butyl-p-cresol and the like, and amine compounds such as alkyl diphenylamine. The refrigerator oil may contain a phenolic compound as an antioxidant in an amount of 0.02 to 0.5 mass% based on the flow rate of the refrigerating machine.

It is also preferable that the refrigerator oil further contains a friction modifier, an extreme pressure agent, a rust inhibitor, a metal deactivator, and a defoaming agent among the above additives. Examples of the friction modifier include aliphatic amines, aliphatic amides, aliphatic imides, alcohols, esters, phosphoric acid ester amine salts and phosphorous acid ester amine salts. Examples of the extreme pressure agent include olefin sulfide and sulfurized oil. Examples of the rust inhibitor include esters or partial esters of alkenylsuccinic acids. Examples of the metal deactivator include benzotriazole and benzotriazole derivatives. Examples of the antifoaming agent include a silicone compound and a polyester compound.

The kinematic viscosity at 40 캜 of refrigerator oil is preferably 3 mm 2 / s or more, more preferably 4 mm 2 / s or more, and still more preferably 5 mm 2 / s or more, from the viewpoint of improvement in lubricity. The kinematic viscosity at 40 캜 of refrigerator oil is preferably 1000 mm 2 / s or less, more preferably 500 mm 2 / s or less, further preferably 400 mm 2 / s or less, from the viewpoint of improvement in oil returnability. The kinematic viscosity at 100 캜 of the refrigerator oil is preferably 1 mm 2 / s or more, and more preferably 2 mm 2 / s or more from the viewpoint of improvement in lubricity. The kinematic viscosity at 100 캜 of the refrigerator oil is preferably 100 mm 2 / s or less, more preferably 50 mm 2 / s or less, from the viewpoint of improvement in oil returnability. The kinematic viscosity in the present invention means the kinematic viscosity measured in accordance with JIS K2283: 2000.

The pour point of the refrigerator oil is preferably -10 ° C or lower, more preferably -20 ° C or lower. The pour point in the present invention means the pour point measured in accordance with JIS K2269-1987.

The volume resistivity of the refrigeration oil is preferably 1.0 x 10 ⁹ Ω · m or more, more preferably 1.0 × 10 ¹⁰ Ω · m or more, and still more preferably 1.0 × 10 ¹¹ Ω · m or more. Particularly, when it is used in a refrigerating machine oil of a closed type, it is preferable that the electric insulation is high. The volume resistivity in the present invention means the volume resistivity at 25 占 폚 measured in accordance with JIS C2101: 1999.

The moisture content of the refrigerator oil may be preferably 200 ppm or less, more preferably 100 ppm or less, and further preferably 50 ppm or less, based on the refrigerating machine flow rate. Particularly, in the case of using in a refrigerating machine oil of a closed type, it is preferable that the moisture content is small in view of heat and chemical stability of the refrigerator oil and the effect on electrical insulation.

From the viewpoint of preventing the corrosion of the metal used in the refrigerator or the piping and the prevention of the decomposition of the ester contained in the refrigerating machine oil, the acid value of the refrigerator oil is preferably 10.0 mgKOH / g or less, more preferably 1.0 mgKOH / / g or less, and more preferably 0.1 mgKOH / g or less. From the same viewpoint, the hydroxyl value of the refrigerator oil is preferably 50.0 mgKOH / g or less, more preferably 30.0 mgKOH / g or less, and still more preferably 10.0 mgKOH / g or less. The acid value in the present invention means the acid value measured in accordance with JIS K2501: 2003. The hydroxyl value in the present invention means the hydroxyl value measured in accordance with JIS K0070: 1992.

The refrigerator oil content can be preferably 100 ppm or less, more preferably 50 ppm or less, from the viewpoint of increasing the heat and chemical stability of the refrigerator oil and suppressing the occurrence of sludge and the like. The ash in the present invention means the ash measured in accordance with JIS K2272: 1998.

The refrigerator oil according to the present embodiment is used together with the refrigerant. The working fluid composition for a refrigerator according to the present embodiment contains a refrigerator oil according to the present embodiment and a refrigerant. Examples of the refrigerant include a fluorinated ether refrigerant such as a saturated fluorohydrocarbon refrigerant, an unsaturated fluorohydrocarbon refrigerant, a hydrocarbon refrigerant and a perfluoroether, a bis (trifluoromethyl) sulfide refrigerant, a trifluoromethyl iodide methane refrigerant, and ammonia (R717) And carbon dioxide (R744). Examples of the refrigerant include a saturated fluorohydrocarbon refrigerant, an unsaturated fluorohydrocarbon refrigerant, a hydrocarbon refrigerant, and a natural refrigerant such as ammonia (R717) and carbon dioxide (R744) Is suitable.

Saturated fluorohydrocarbon refrigerants are preferably saturated fluorinated hydrocarbons having 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms. Specifically, it is preferable to use at least one of difluoromethane (R32), trifluoromethane (R23), pentafluoroethane (R125), 1,1,2,2-tetrafluoroethane (R134) 2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), fluoroethane (R161), 1,1,1,2 , 3,3,3-heptafluoropropane (R227ea), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoro Propane (R236fa), 1,1,1,3,3-pentafluoropropane (R245fa), and 1,1,1,3,3-pentafluorobutane (R365mfc), or a mixture of two or more thereof It is suitably used.

The saturated fluorohydrocarbon refrigerant is appropriately selected from among the above in accordance with the purpose of use and the required performance, for example, R32 alone; R23 alone; R134a alone; R125 alone; A mixture of R134a / R32 = 60 to 80 mass% / 40 to 20 mass%; A mixture of R32 / R125 = 40 to 70 mass% / 60 to 30 mass%; A mixture of R125 / R143a = 40 to 60 mass% / 60 to 40 mass%; A mixture of R134a / R32 / R125 = 60 mass% / 30 mass% / 10 mass%; A mixture of R134a / R32 / R125 = 40 to 70 mass% / 15 to 35 mass% / 5 to 40 mass%; A mixture of R125 / R134a / R143a = 35 to 55 mass% / 1 to 15 mass% / 40 to 60 mass% may, for example, be mentioned as a particularly preferable example. More specifically, a mixture of R134a / R32 = 70/30 mass%; A mixture of R32 / R125 = 60/40 mass%; A mixture of R32 / R125 = 50/50 mass% (R410A); A mixture of R32 / R125 = 45/55 mass% (R410B); A mixture of R125 / R143a = 50/50% by mass (R507C); A mixture of R32 / R125 / R134a = 30/10/60 mass%; A mixture of R32 / R125 / R134a = 23/25/52 mass% (R407C); A mixture (R407E) of R32 / R125 / R134a = 25/15/60 mass%; A mixture (R404A) of R125 / R134a / R143a = 44/4/52 mass% may be used.

Examples of the unsaturated fluorohydrocarbon (HFO) refrigerant include fluoroethylene having 3 fluorine atoms and fluoropropene having 3 to 5 fluorine atoms. Specific examples thereof include 1,1,2-trifluoroethylene (HFO-1123), 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 1,3,3,3- Tetrafluoropropene (HFO-1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3-tetrafluoropropene (HFO-1234ye) , And 3,3,3-trifluoropropene (HFO-1243zf) are preferably used. From the viewpoint of refrigerant properties, one or more selected from HFO-1123, HFO-1225ye, HFO-1234ze and HFO-1234yf are particularly preferably used.

Examples of the hydrocarbon refrigerant include hydrocarbons having 1 to 5 carbon atoms. Specific examples thereof include at least one of methane, ethylene, ethane, propylene, propane (R290), cyclopropane, n-butane, isobutane, cyclobutane, methylcyclopropane, Mixture is used. Of these, hydrocarbon refrigerants which are gaseous at 25 ° C and 1 atmosphere, such as propane, normal butane, isobutane, 2-methylbutane or mixtures thereof, are preferably used.

The lubricant base oil and the refrigerator oil according to the present embodiment are suitably used together with a refrigerant commonly used under the conditions of an oil / refrigerant ratio (mass ratio) of 3/2 and 0 ° C and a mixed refrigerant containing the refrigerant. Whether the oil and the refrigerant are compatible or not is judged on the basis of the test in accordance with JIS K2211: 2009 " Refrigerant compatibility test with refrigerant ". The lubricating oil base oil and the freezer oil are useful in that they can be widely applied if they are the refrigerants commonly used under the above conditions. As the refrigerant used in the above-mentioned conditions, it is preferable to use one or more refrigerants selected from R134a, R410A, R32, R1234yf, R1234ze, R1123, R290, R600a and R744, Mixed refrigerants are preferred.

The mixing ratio of the refrigerator oil and the refrigerant in the refrigerating machine working fluid composition may be, for example, 1 to 500 parts by mass, or 2 to 400 parts by mass relative to 100 parts by mass of the refrigerant.

Example

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the examples.

As the first ester and the second ester, the following esters were used respectively.

(First ester)

1a: tetraester of pentaerythritol and 2-methylpropanoic acid

1b: hexaester of dipentaerythritol and 2-methylbutanoic acid

1c: tetraester of pentaerythritol and n-pentanoic acid

1d: tetraester of pentaerythritol and n-heptanoic acid

1e: tetraester of pentaerythritol and 2-ethylhexanoic acid

1f: hexaester of dipentaerythritol and 2-ethylhexanoic acid

(Second ester)

2a: tetraester of pentaerythritol and 3,5,5-trimethylhexanoic acid

2b: hexaester of dipentaerythritol and 3,5,5-trimethylhexanoic acid

As the third ester, esters 3a to 3g were synthesized using fatty acid A, fatty acid B and polyhydric alcohol shown in Tables 1 and 2 below. The abbreviations in Table 1 and Table 2 represent the following compounds, respectively.

iC4: 2-Methylpropanoic acid

iC5: 2-methylbutanoic acid,

nC5: n-pentanoic acid,

nC7: n-heptanoic acid,

iC8: 2-Ethylhexanoic acid

iC9: 3,5,5-trimethylhexanoic acid

PET: pentaerythritol

DiPET: dipentaerythritol

The synthetic procedures of the esters 3a to 3g are as follows.

(Synthesis procedure of the third ester)

A 2-liter four-necked flask (reactor) equipped with a thermometer, a nitrogen inlet tube, a stirrer, and a Dimroth condenser tube and a water separating tube having a capacity of 30 mL was charged with the alcohol and fatty acid A in the amounts shown in Tables 1 and 2. The reactor was heated with a mantle heater under a nitrogen stream, and after the reactor reached 190 ° C, the alcohol and fatty acid A were reacted until the acid value of the reaction solution became 5 mgKOH / g or less. Thereafter, the reactor was cooled to 85 캜, 20% by mass of ion-exchanged water was added to the total amount of the reaction solution, and the mixture was stirred at 85 캜 for 10 minutes to obtain a mixture of the reaction solution and water. Subsequently, the mixture was allowed to stand for 15 minutes, and then the organic layer separated in the mixture was removed to obtain an aqueous layer. Thereafter, the reactor was cooled to 50 캜, 20% by mass of hexane was added to the entire aqueous layer, and the mixture was stirred at 50 캜 for 10 minutes. After standing for 15 minutes, the separated organic layer was removed twice. Thus, an aqueous layer containing a partial ester of alcohol and fatty acid A was obtained.

The fatty acid B in the amounts shown in Tables 1 and 2 was added to the obtained aqueous layer. The partial ester was reacted with the fatty acid B until the reactor had reached a temperature of 210 占 폚 and the hydroxyl value of the obtained ester became 3 mgKOH / g or less by heating the reactor with a mantle heater under a nitrogen gas stream. Thereafter, the pressure in the reactor was reduced to 50 Torr, and excess fatty acid was distilled off until the acid value of the reaction solution became 5 mgKOH / g or less. After the reactor was cooled to 85 deg. C, 1.5 equivalents of the amount of potassium hydroxide calculated from the above acid value was diluted with ion-exchanged water to prepare an aqueous solution of 10%, which was added to the reaction solution and stirred for 1 hour. After the stirring was stopped, the mixture was allowed to stand for 30 minutes to remove the water layer separated into the lower layer to obtain an organic layer. Next, 20% by mass of ion-exchanged water was added to the entire organic layer, stirred at 85 캜 for 10 minutes, allowed to stand for 15 minutes, and then the separated aqueous layer was removed five times. Thereafter, the mixture was dehydrated by stirring at 100 ° C and 30 Torr for 1 hour. Finally, 2 mass% of active white clay was added to the organic layer, and the mixture was stirred at 80 DEG C and 30 Torr for 1 hour and filtered to remove the adsorbent, thereby obtaining a complete ester as a third ester.

Using the above-mentioned first ester, second ester and third ester, a base oil having the composition shown in Tables 3 to 5 was prepared.

A refrigerator oil containing each of the base oils of each of the examples and comparative examples was used for the compatibility test and the abrasion resistance test described below. The results are shown in Tables 6 to 8.

(Refrigerant compatibility test)

In accordance with JIS K2211: 2009 "Method for testing compatibility with refrigerant" of "Refrigeration oil", 12 g of refrigerator oil was blended with 8 g of evaluation refrigerant, and it was observed whether refrigerant and refrigerator oil were mutually dissolved at 0 ° C.

(Abrasion resistance test)

A refrigerant pressure fluctuation abrasion resistance test was performed using a high-pressure atmosphere tribo-tester (rotary perturbation method of a rotating vane material and a fixed disk material) manufactured by Shinko Industries Co., Ltd., in which a coolant atmosphere similar to that of an actual compressor can be obtained. The test conditions were as follows: a flow rate of 600 ml; a test temperature of 110 캜; a rotational frequency of 630 rpm; a load load of 90 kgf; and a test time of 1.2 hours (these conditions were common to all evaluated refrigerants).

R134a: 1.6 MPa

R410A: 1.6 MPa

R32: 1.6 MPa

HFO-1234yf: 1.6 MPa

n-hexane (hydrocarbon refrigerant such as R290 is used as an alternative because of safety concerns): pressure slightly higher than normal pressure

CO ₂ : 1.6 MPa

SKH-51 was used as a bain material, and FC250 was used as a disc material. The evaluation of abrasion resistance was performed by the wear depth (占 퐉) of the veneer because the abrasion amount of the disc material was very small.

Claims (3)

1. A composition comprising an ester represented by the following formula (1)
[Chemical Formula 1]

[In the formula 1,
A is a residue obtained by removing a hydroxyl group from a polyhydric alcohol,
R is an alkyl group having 3 to 7 carbon atoms or a branched alkyl group having 8 carbon atoms,
n is an integer of 2 or more,
The polyhydric alcohol is at least one selected from the group consisting of neopentyl glycol, trimethylol ethane, trimethylol propane, trimethylol butane, di- (trimethylol propane), tri- (trimethylol propane), pentaerythritol, and dipentaerythritol One paper,
The ester may be,
A first ester in which one of R 1 to R 3 in the same molecule is selected from the group consisting of an alkyl group having 3 to 7 carbon atoms,
A second ester in which R in the same molecule is a branched alkyl group having 8 carbon atoms,
Wherein the R in the same molecule is at least two selected from the group consisting of an alkyl group having 3 to 7 carbon atoms and a branched alkyl group having 8 carbon atoms
≪ / RTI >
Wherein the content of the first ester is more than 0 mass% and 30 mass% or less based on the total amount of the first ester, the second ester and the third ester, and the content of the second ester is more than 0 mass% % Or less by mass of lubricating oil base oil. A refrigerator oil containing the lubricating base oil according to claim 1. A refrigerator operating fluid composition comprising the refrigerator oil according to claim 2 and a refrigerant.