JP2009030070A - Refrigerant oil composition and lubrication method using the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide, in a compression refrigerating cycle using a CO<SB>2</SB>-based refrigerant, a refrigerant oil composition having excellent lubricating performance and sealing property and capable of being used stably for a prolonged period; and a lubrication method using the composition. <P>SOLUTION: (1) The refrigerant oil composition comprises a CO<SB>2</SB>-based refrigerant and a lubricant composition. The lubricant composition comprises: a base oil comprising an ester oil as a major component and having a kinematic viscosity at 100°C of 5.5 to 30 mm<SP>2</SP>/s; and a 0.005 to 5% by weight of an extreme pressure agent and/or an acid-trapping agent relative to the base oil. (2) The lubrication method using the composition is used in a compression refrigerating cycle having an oil separator and/or a hot gas line. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a refrigerating machine oil composition, and more particularly, a refrigerating machine oil composition using a refrigerant mainly composed of CO ₂ and a lubrication method using the composition, particularly an oil separator and / or a hot gas line. The present invention relates to a lubrication method in a compression refrigeration cycle.

In general, a compression refrigeration cycle of a refrigerator, for example, a compressor type refrigerator including a compressor, a condenser, an expansion valve, and an evaporator, has a structure in which a mixed liquid of refrigerant and lubricating oil circulates in the sealed system. It has become. In such compression refrigerators, chlorofluorocarbons such as dichlorodifluoromethane (R-12) and chlorodifluoromethane (R-22) are conventionally used as refrigerants, and a number of lubricating oils used in combination therewith. Has been manufactured and used. However, these chlorofluorocarbon compounds, which have been used as refrigerants in the past, may cause environmental pollution such as destruction of the ozone layer existing in the stratosphere when released into the atmosphere. Regulations on its use are becoming stricter. Therefore, hydrogen-containing chlorofluorocarbon compounds such as hydrofluorocarbon and hydrochlorofluorocarbon have attracted attention as new refrigerants. This hydrogen-containing chlorofluorocarbon compound, particularly hydrofluorocarbons represented by 1,1,1,2-tetrafluoroethane (R-134a), has no risk of destroying the ozone layer, but has a long life in the atmosphere. There is concern about the impact on global warming, and in recent years, the use of natural refrigerants without such problems has been considered.

  On the other hand, carbon dioxide gas is harmless to the environment and is excellent in terms of safety to humans. Furthermore, the pressure is close to the optimum level economically, a very small pressure ratio compared to conventional refrigerants, It has advantages such as excellent compatibility with ordinary oils and structural materials of machines, easy availability everywhere, no need for recovery and very low cost. It has been used normally. However, when such a carbon dioxide gas is used as a refrigerant, if it is lubricated with a conventionally used lubricating oil as a lubricating oil for a refrigerator, the lubricity is inferior and the wear resistance becomes insufficient, resulting in a stable It becomes difficult to use for a long time. Further, the system using carbon dioxide gas has a higher discharge pressure than the system using R-134a, resulting in a problem that the viscosity of the lubricating oil is lowered and the sealing performance of the system is deteriorated.

The present invention has been made from the above viewpoint, and in a compression refrigeration cycle using a refrigerant mainly composed of CO ₂ , a refrigerating machine oil composition having good lubrication performance and sealability and capable of long-term stable use, and It is an object of the present invention to provide a lubricating method using the composition.

As a result of extensive research, the present inventor has found that the object of the present invention can be effectively achieved by using a lubricating oil composition comprising a specific lubricating base oil and additives. Is completed. That is, the present invention
(1) A compression refrigeration cycle having an oil separator and / or a hot gas line and a capillary tube, comprising a refrigerant mainly composed of CO ₂ and a lubricating oil composition, wherein the lubricating oil composition contains an ester oil. A base oil having a kinematic viscosity at 100 ° C. of 5.5 to 30 mm ² / s, and 0.005 to 5% by weight of an extreme pressure agent and / or an acid scavenger with respect to the base oil. A lubricating method characterized by using a refrigerating machine oil composition, and (2) an ester oil comprising an ester of dipentaerythritol and a fatty acid having 8 carbon atoms, dipentaerythritol, a mixed fatty acid having 7 and 8 carbon atoms, and The lubricating method according to the above (1), which is at least one selected from the following esters and alicyclic polyvalent carboxylic acid esters:
Is to provide.

According to the present invention, in a compression refrigeration cycle using a refrigerant mainly composed of CO ₂ , a refrigerating machine oil composition having good lubrication performance and sealability and capable of long-term stable use and the composition are used. A lubrication method can be provided.

The present invention is described in detail below.
The refrigerating machine oil composition of the present invention comprises a refrigerant mainly composed of CO ₂ and a lubricating oil composition. The lubricating oil composition has an ester oil as a main component and a kinematic viscosity at 100 ° C. of 5.5 to 5.5. It contains a base oil of 30 mm ² / s and 0.005 to 5% by weight of an extreme pressure agent and / or an acid scavenger with respect to the base oil. As a refrigerant mainly composed of CO ₂ used in the present invention, in addition to the case of using CO ₂ as it is, it is used as a hydrocarbon, a fluorinated hydrocarbon such as R-134a (or chlorofluorinated hydrocarbon), an ether. What mixed with refrigerant | coolants, such as these, can be used.

As the viscosity of the base oil of the lubricating oil composition constituting the present invention, one having a kinematic viscosity at 100 ° C. of 5.5 to 30 mm ² / s is used. A kinematic viscosity at 100 ° C. of 5.5 to 30 mm ² / s, particularly 7.5 to 20.5 mm ² / s is preferable from the viewpoint of compressor efficiency and lubricity. Examples of ester oils that are the main components of the base oil include polyhydric alcohol esters, aliphatic or aromatic polycarboxylic esters, alicyclic polycarboxylic esters, other organic carboxylic esters, carbonates, and fumaric acids. Mention may be made of ester oils of ester oligomers, hydroxypivalate esters and combinations thereof. These will be described in order.

(1) Polyhydric alcohol ester Examples of the polyhydric alcohol ester include esters of an aliphatic polyhydric alcohol and a linear or branched fatty acid. The aliphatic polyhydric alcohols that form the esters include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, trimethylol ethane, ditrimethylol ethane, trimethylol propane, ditrimethylol propane, glycerin, pentaerythritol, dipentaerythritol. , Tripentaerythritol, sorbitol and the like.

  As the fatty acid, those having 3 to 12 carbon atoms can be used, and preferable fatty acids include propionic acid, butyric acid, pivalic acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, Isovaleric acid, neopentanoic acid, 2-methylbutyric acid, 2-ethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2-dimethyloctanoic acid, 2-butyloctane Mention may be made of acid and 3,5,5-trimethylhexanoic acid. A partial ester of an aliphatic polyhydric alcohol and a linear or branched fatty acid can also be used.

  As esters of these aliphatic polyhydric alcohols and linear or branched fatty acids, particularly preferred are pentaerythritol, dipentaerythritol, tripentaerythritol and 5 to 12 carbon atoms, more preferably 5 to 9 carbon atoms. Fatty acids such as valeric acid, hexanoic acid, heptanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2-dimethyloctanoic acid, 2-butyloctanoic acid, 3, Mention may be made of esters with 5,5-trimethylhexanoic acid and the like.

  It is also possible to use a complex ester of a partial ester of an aliphatic polyhydric alcohol and a linear or branched fatty acid having 3 to 9 carbon atoms and an aliphatic dibasic acid or an aromatic dibasic acid. it can. In this complex ester, it is preferable to use a fatty acid having 5 to 7 carbon atoms, more preferably 5 or 6 carbon atoms. As such a fatty acid, valeric acid, hexanoic acid, isovaleric acid, 2-methylbutyric acid, 2-ethylbutyric acid or a mixture thereof is used, and those having 5 carbon atoms and 6 carbon atoms in a weight ratio of 10: The fatty acid mixed in the ratio of 90-90: 10 can be used conveniently. The aliphatic dibasic acids used for esterification with polyhydric alcohols together with this fatty acid include succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanediic acid Examples include acid and docosanna diacid, and examples of aromatic dibasic acid include phthalic acid and isophthalic acid. The esterification reaction for preparing the complex ester may be carried out by first reacting a polyhydric alcohol and a dibasic acid at a predetermined ratio to form a partial ester, and then reacting the partial ester with a fatty acid. The reaction order of the basic acid and the fatty acid may be reversed, or the dibasic acid and the fatty acid may be mixed and used for esterification. Furthermore, the following general formula (I)

(Wherein R ^{1 to} R ³ are alkyl groups having 1 to 13 carbon atoms, those having 4 or more carbon atoms all have one or more branches, and the total carbon number of R ^{1 to} R ³ is ^{3 to} 23 A polyhydric alcohol ester obtained by reacting an acid fluoride with a polyhydric alcohol can also be suitably used because of its low saturated moisture absorption (JP-A-9-157219).

(2) Aliphatic or aromatic polyvalent carboxylic acid ester Examples of dicarboxylic acid esters include dialkyl esters of aliphatic or aromatic dicarboxylic acids (having 16 to 22 carbon atoms). Examples of aliphatic dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, docosanedioic acid, and aromatic Examples of the dicarboxylic acid include phthalic acid and isophthalic acid. On the other hand, the alcohol component is an alcohol having 5 to 8 carbon atoms, and examples thereof include amyl alcohol, hexyl alcohol, heptyl alcohol, and octyl alcohol. Preferred esters include dioctyl adipate, diisoheptyl adipate, dihexyl sebacate, diheptyl succinate, dioctyl phthalate, diisoheptyl phthalate, and diisoamyl phthalate.

As polyvalent carboxylic acid constituting trivalent or higher polyvalent carboxylic acid ester, aliphatic polyvalent carboxylic acid such as 1,2,3,4-butanetetracarboxylic acid, aromatic such as trimellitic acid and pyromellitic acid Mention may be made of polyvalent carboxylic acids. A monohydric alcohol having a linear or branched alkyl group having 3 to 12 carbon atoms as an alcohol, or H- (AO) _n -R
(In the formula, A is an alkylene group having 2 to 8 carbon atoms, R is an alkyl group having 1 to 10 carbon atoms, and n is an integer of 1 to 10)
The monoalcohol body of the polyalkylene glycol represented by these can be mention | raise | lifted.
Obtained by esterifying the polyhydric carboxylic acid ester obtained by esterifying the polyhydric carboxylic acid and alcohol, or adding polyhydric alcohol such as ethylene glycol and propylene glycol to the polyhydric carboxylic acid and alcohol. Can be used.

(3) Alicyclic polyvalent carboxylic acid ester As alicyclic polyvalent carboxylic acid ester, the following general formula (II)

(In the formula, A represents a cyclohexane ring or a cyclohexene ring. R ⁴ represents a hydrogen atom or a methyl group. X represents a hydrogen atom or COOR ^7. Y represents a hydrogen atom or COOR ^8. R ^{5 to} R ^8. Each represents an alkyl group having 3 to 18 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms, which may be the same as or different from each other. This ester is prepared by esterifying a predetermined acid component and alcohol component according to a conventional method, preferably in an inert gas atmosphere such as nitrogen, in the presence or absence of an esterification catalyst and with stirring. .

  Examples of the acid component include cycloalkane polycarboxylic acid or cycloalkene polycarboxylic acid and acid anhydrides thereof, and one or two or more kinds of compounds can be mixed and used. Specifically, 1,2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 1-cyclohexene-1,2-dicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 3-methyl-4-cyclohexene-1,2-dicarboxylic acid, 4-methyl-4-cyclohexene-1, Examples include 2-dicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid and acid anhydrides thereof. 2-cyclohexanedicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl 1,2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-methyl-4-cyclohexene-1,2-dicarboxylic acid, 4-methyl-4-cyclohexene-1,2-dicarboxylic acid And their anhydrides are preferred.

  As said alcohol component, C3-C18 linear or branched aliphatic alcohol or C3-C10 alicyclic alcohol can be mentioned. Specific linear aliphatic alcohols include n-propyl alcohol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, Examples thereof include n-dodecanol, n-tetradecanol, n-hexadecanol, and n-octadecanol.

  Specific branched aliphatic alcohols include isopropanol, isobutanol, sec-butanol, isopentanol, isohexanol, 2-methylhexanol, 2-methylheptanol, isoheptanol, 2-ethylhexanol, 2-octanol, isooctanol, 3,5,5-trimethylhexanol, isodecanol, isoundecanol, isotridecanol, isotetradecanol, isohexadecanol, isooctadecanol, 2,6-dimethyl-4 -A heptanol etc. can be illustrated.

  Furthermore, examples of the alicyclic alcohol include cyclohexanol, methylcyclohexanol, and dimethylcyclohexanol. Among the alicyclic polycarboxylic esters obtained from the above polycarboxylic acids and alcohols, in particular, diisobutyl 1,2-cyclohexanedicarboxylate, dicyclohexyl 1,2-cyclohexanedicarboxylate, diisoheptyl 1,2-cyclohexanedicarboxylate 1,2-cyclohexanedicarboxylic acid (2-ethylhexyl), 1,2-cyclohexanedicarboxylic acid di (3,5,5-trimethylhexyl), 1,2-cyclohexanedicarboxylic acid di (2,6-dimethyl-4-l) Heptyl), 1,2-cyclohexanedicarboxylate diisodecyl, 1,2-cyclohexanedicarboxylate diisoundecyl, 4-cyclohexene-1,2-dicarboxylate dicyclohexyl, 4-cyclohexene-1,2-dicarboxylate diisoheptyl, 4-cyclohex Sen-1,2-dicarboxylic acid di (2-ethylhexyl), 4-cyclohexene-1,2-dicarboxylic acid di (3,5,5-trimethylhexyl), 3-methyl-1,2-cyclohexanedicarboxylic acid di ( 3,5,5-trimethylhexyl), 4-methyl-1,2-cyclohexanedicarboxylic acid di (3,5,5-trimethylhexyl), 3-methyl-4-cyclohexene-1,2-dicarboxylic acid di (3 , 5,5-trimethylhexyl), 4-methyl-4-cyclohexene-1,2-dicarboxylic acid di (3,5,5-trimethylhexyl), 1,2,4,5-cyclohexanetetracarboxylic acid tetra (3 , 5,5-trimethylhexyl).

  In order to improve physical property balance, such as volume resistivity and a viscosity, other ester (henceforth a combined use ester) can be mixed with said alicyclic polyhydric carboxylic acid ester. Examples of the combined ester include adipic acid ester, azelain ester, sebacic acid ester, phthalic acid ester, trimellitic acid ester, and polyhydric alcohol ester. Examples of the polyhydric alcohol component of the polyhydric alcohol ester include neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like, and examples of the acid component include isobutyric acid, 2-ethylbutyric acid, isovaleric acid, and pivalic acid. , Cyclohexanecarboxylic acid, 2-methylpentanoic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid and the like. The content of the combined ester in the lubricating oil is 10 to 90% by weight.

(4) Other organic carboxylic acid esters As other organic carboxylic acid esters other than the above (1) to (3), an alkylene oxide adduct of a monohydric alcohol is selected from adipic acid, pimelic acid, suberic acid, azelaic acid, Examples thereof include diesters obtained by esterification with aliphatic dicarboxylic acids such as sebacic acid, undecanedioic acid, dodecanedioic acid, and docosanedioic acid, or aromatic dicarboxylic acids such as phthalic acid. Moreover, 1-10 mol addition products of alkylene oxides of polyhydric alcohols such as glycerin and trimethylolpropane are converted to fatty acids having 3 to 12 carbon atoms such as propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonane. Esters obtained by esterification with acid, decanoic acid, dodecanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2-dimethyloctanoic acid, 2-butyloctanoic acid, etc. Can be mentioned.

(5) Carbonate ester As carbonate ester, the following general formula (III)

(In the formula, R ⁹ represents an alkyl group having 2 to 10 carbon atoms, R ¹⁰ represents an alkylene group or cycloalkylene group having 2 to 10 carbon atoms, and a represents an integer of 1 to 4).
Or a compound represented by the following general formula (IV)

(Wherein R ¹¹ is a polyhydric alcohol residue having a hydroxyl group having 2 to 6 carbon atoms, R ¹² is an alkyl group having 2 to 10 carbon atoms, and b is an integer of 2 to 6). Can be mentioned. The carbonate ester is prepared by transesterification of dimethyl carbonate and alcohol in the presence of a basic catalyst. In addition, the following general formula (V)

(In the formula, R ¹³ represents an alkyl group having 1 to 10 carbon atoms, R ¹⁴ represents an alkyl group having 2 to 10 carbon atoms, c represents an integer of 2 to 10, d represents an integer of 2 to 100, and —BO - is _{-CH 2 -CH (CH 3) -O-} , or -CH ₂ shows a -CH ₂ -O-).
The compound represented by these can also be used. The carbonate ester is obtained, for example, by reacting carbonic acid with alkylene oxide. The addition form of the alkylene oxide may be ethylene oxide alone, propylene oxide alone, or a mixture.

(6) Fumarate ester oligomer A fumarate ester oligomer is a homopolymer of a fumarate ester or a copolymer of a fumarate ester and an unsaturated aliphatic hydrocarbon.

(In the formula, R ¹⁵ represents an alkylene group, a substituted alkylene group or an alkylene oxide group, R ¹⁶ and R ¹⁷ represent an alkyl group having 1 to 9 carbon atoms, an allyl group, or a terminal substituted or unsubstituted polyalkylene oxide group. May be the same or different, e is 0 or more, f is an integer of 1 or more, and R ¹⁵ is 50 mol% or less of the whole). Specific examples include diethyl fumarate ester oligomers and dibutyl fumarate ester oligomers. In addition, both ends in the above formula (VI) are polymerization initiation residues used in the polymerization reaction, and the description is omitted. In addition, the following structural formula (VII)

1 to 50 mol% of the structural unit represented by the following general formula (VIII)

(In the formula, R ¹⁸ and R ¹⁹ each represent an alkyl group having 3 to 8 carbon atoms, and they may be the same or different.)
And a fumaric acid alkyl ester copolymer containing 50 to 99 mol% of a structural unit represented by the formula:

(7) Hydroxypivalic acid ester As hydroxypivalic acid ester, general formula (IX)

(In the formula, R ²⁰ and R ²¹ are alkyl groups having 2 to 10 carbon atoms, and g is an integer of 1 to 5)
Can be mentioned.
The ester oils described in (1) to (7) may be used singly or in combination of two or more of the same type of ester oil, or may be used by mixing different types of ester oil. In addition, it is necessary to adjust the kinematic viscosity in 100 degreeC about the viscosity of a base oil to 5.5-30 mm < ² > / s as mentioned above. When the above ester oil is used as a base oil, if the viscosity is not within the range, it may be added and adjusted with other components. When the viscosity is high, for example, an ester oil of an aliphatic polyhydric alcohol and a fatty acid having 3 to 9 carbon atoms and a kinematic viscosity at 100 ° C. of 6 mm ² / s or less is appropriately added to adjust to an appropriate range. be able to. When the viscosity is low, the viscosity may be adjusted by adding polymers. The polymer preferably has a kinematic viscosity at 100 ° C. of 10 mm ² / s or more.

  Examples of such polymers include polyalkyl methacrylates (for example, those having an alkyl group of 1 to 8), polyalkylene glycols (for example, polypropylene glycol, a copolymer comprising a polypropylene glycol component and a polyethylene glycol component, polypropylene glycol component and poly A copolymer of a butylene glycol component), a polyester of neopentyl glycol and an aliphatic dicarboxylic acid, represented by the following formula (X)

(H shows the integer of 1-20, i shows the integer of 1-10) etc. can be mentioned. The lubricating oil composition constituting the present invention is prepared by blending 0.005 to 5% by weight of an extreme pressure agent and / or an acid scavenger with the above base oil. Examples of the extreme pressure agent include sulfur-based extreme pressure agents such as sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiocarbamates, thioterpenes, and dialkylthiodipropionates. Here, sulfurized fats and oils are obtained by reacting sulfur and sulfur-containing compounds with fats and oils (lard oil, whale oil, vegetable oil, fish oil, etc.), and the sulfur content is not particularly limited, but generally 5 to 30 weights. % Is preferred. Specific examples include sulfurized lard, sulfurized rapeseed oil, sulfurized castor oil, sulfurized soybean oil, and sulfurized rice bran oil. Examples of the sulfurized fatty acid include sulfurized oleic acid, and examples of the sulfurized ester include sulfurized methyl oleate and sulfurized rice bran fatty acid octyl.

As the sulfurized olefin, for example, the following general formula (XI)
R ²² -S _j -R ²³ (XI)
(In the formula, R ²² represents an alkenyl group having 2 to 15 carbon atoms, R ²³ represents an alkyl group or alkenyl group having 2 to 15 carbon atoms, and j represents an integer of 1 to 8)
The compound etc. which are represented by these can be mentioned. This compound is obtained by reacting an olefin having 2 to 15 carbon atoms or a dimer to tetramer thereof with a sulfurizing agent such as sulfur and sulfur chloride, and propylene, isobutene, diisobutene and the like are preferable.

Dihydrocarbyl polysulfide is represented by the following general formula (XII):
R ²⁴ -S _k -R ²⁵ (XII)
(In the formula, R ²⁴ and R ²⁵ are each an alkyl group having 1 to 20 carbon atoms or a cyclic alkyl group, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, or 7 to 20 carbon atoms. An arylalkyl group, which may be the same or different from each other, and k represents an integer of 2 to 8)
It is a compound represented by these. Here, when R ²⁴ and R ²⁵ are alkyl groups, they are called alkyl sulfides.

Specific examples of R ²⁴ and R ²⁵ in the general formula (XII) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, Various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, cyclohexyl groups, cyclooctyl groups, phenyl groups, naphthyl groups, tolyl groups, xylyl groups, benzyl groups, Examples thereof include a phenethyl group.

Preferred examples of the dihydrocarbyl polysulfide include dibenzyl polysulfide, di-tert-nonyl polysulfide, didodecyl polysulfide, di-tert-butyl polysulfide, dioctyl polysulfide, diphenyl polysulfide, and dicyclohexyl polysulfide.

  Further, as thiocarbamates, for example, zinc dithiocarbamate, etc., as thioterpenes, for example, a reaction product of phosphorus pentasulfide and pinene, and as dialkylthiodipropionates, for example, dilauryl thiodipropionate. , Distearyl thiodipropionate and the like.

  Examples of the extreme pressure agent include phosphate ester, acidic phosphate ester, phosphite ester, acidic phosphite ester, thiophosphate ester, thioacid phosphate ester, and amine salts thereof, Phosphorus extreme pressure agents such as phosphorous terpenes such as a reaction product of phosphorus sulfide and pinene can be mentioned. Here, the phosphoric acid ester, the acidic phosphoric acid ester, the phosphorous acid ester, and the acidic phosphorous acid ester include those represented by the following general formulas (XIII) to (XVII).

In the general formulas (XIII) to (XVII), R ^{26 to} R ²⁸ represent an alkyl group, alkenyl group, alkylaryl group, and arylalkyl group having 4 to 30 carbon atoms, and R ^{26 to} R ²⁸ are the same or different. May be. Examples of the phosphate ester include triaryl phosphate, trialkyl phosphate, trialkylaryl phosphate, triarylalkyl phosphate, and trialkenyl phosphate. Specifically, for example, triphenyl phosphate, tricresyl phosphate, benzyldiphenyl phosphate, Ethyl diphenyl phosphate, tributyl phosphate, ethyl dibutyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, ethyl phenyl diphenyl phosphate, diethyl phenyl phenyl phosphate, propyl phenyl diphenyl phosphate, dipropyl phenyl phenyl phosphate, triethyl phenyl phosphate, tripropyl phenyl phosphate , Butylphenyl Phenyl phosphate, dibutylphenyl phenyl phosphate, tributylphenyl phosphate, trihexyl phosphate, tri (2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, trioleyl phosphate, etc. Can be mentioned.

  Specific examples of the acidic phosphate ester include 2-ethylhexyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate. , Stearyl acid phosphate, isostearyl acid phosphate, and the like.

  Specific examples of the phosphite ester include triethyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphite, tri (nonylphenyl) phosphite, tri (2-ethylhexyl) phosphite, tri Examples thereof include decyl phosphite, trilauryl phosphite, triisooctyl phosphite, diphenylisodecyl phosphite, tristearyl phosphite, trioleyl phosphite, and 2-ethylhexyl diphenyl phosphite.

  Specific examples of the acidic phosphite include dibutyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, distearyl hydrogen phosphite, diphenyl hydrogen phosphite and the like. In addition, examples of the thiophosphate ester and the thioacid phosphate ester include those corresponding to the phosphate ester and the acid phosphate ester exemplified above, respectively.

Furthermore, as amines that form amine salts with these, for example, the general formula (XVIII),
R _m NH _3-m (XVIII)
(In the formula, R represents an alkyl group or alkenyl group having 3 to 30 carbon atoms, an aryl group or aralkyl group having 6 to 30 carbon atoms, or a hydroxyalkyl group having 2 to 30 carbon atoms, and m represents 1, 2 or 3) In addition, when there are a plurality of R, the plurality of Rs may be the same or different.) And mono-substituted amines, di-substituted amines, or tri-substituted amines. The alkyl group or alkenyl group having 3 to 30 carbon atoms in R in the general formula (XVIII) may be linear, branched or cyclic.

  Here, examples of the mono-substituted amine include butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, laurylamine, stearylamine, oleylamine, and benzylamine. Examples of the disubstituted amine include Dibutylamine, dipentylamine, dihexylamine, dicyclohexylamine, dioctylamine, dilaurylamine, distearylamine, dioleylamine, dibenzylamine, stearyl monoethanolamine, decyl monoethanolamine, hexyl monopropanolamine, benzyl Examples include monoethanolamine, phenyl monoethanolamine, tolyl monopropanol, and the like. Examples of tri-substituted amines are tributylamine, tripentylamine, trihexylamine, tricyclohexylamine, trioctylamine, trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl monoethanolamine, dilauryl.・ Monopropanolamine, dioctyl monoethanolamine, dihexyl monopropanolamine, dibutyl monopropanolamine, oleyl diethanolamine, stearyl dipropanolamine, lauryl diethanolamine, octyl dipropanolamine, butyl diethanolamine, benzyl diethanolamine , Phenyl diethanolamine, tolyl dipropanolamine, xylyl diethanolamine It may be mentioned triethanolamine, tripropanolamine and the like.

  Among these phosphorus-based extreme pressure agents, tricresyl phosphate, tri (nonylphenyl) phosphite, dioleyl hydrogen phosphite, 2-ethylhexyl diphenyl phosphite and the like are preferable from the viewpoint of extreme pressure properties and friction characteristics. In the present invention, the extreme pressure agent may be used singly or in combination of two or more. Moreover, the compounding quantity has the preferable range of 0.005 to 5 weight% with respect to base oil. If this amount is less than 0.005% by weight, extreme pressure properties and frictional characteristics may be insufficient, and if it exceeds 5% by weight, sludge generation may be promoted.

  Next, the acid scavenger is blended for the purpose of hydrolytic stability in the refrigerator oil composition. For example, phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxide, Mention may be made of epoxy compounds such as epoxidized soybean oil. Of these, phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, and α-olefin oxide are preferable in terms of compatibility.

  In the present invention, the acid scavenger may be used singly or in combination of two or more. Moreover, the compounding quantity has the preferable range of 0.005 to 5 weight% with respect to base oil. If this amount is less than 0.005% by weight, the acid scavenging ability may not be exhibited. If it exceeds 5% by weight, sludge generation may occur. In addition, when using both said extreme pressure agent and an acid scavenger, the total amount is the range of 0.005 to 5 weight% with respect to base oil.

  In the lubricating oil composition constituting the refrigerating machine oil composition of the present invention, various known additives such as phenol-based and amine-based antioxidants are added as necessary, as long as the object of the present invention is not impaired. In addition, copper deactivators such as benzotriazole and its derivatives, antifoaming agents such as silicone oil and fluorinated silicone oil, and the like can be appropriately blended. These additives are contained in the lubricating oil composition in an amount of 0.5 to 10% by weight.

In the present invention, the use amount of the CO ₂ refrigerant and the lubricating oil composition is preferably in the range of 99/1 to 10/90 by weight ratio of the refrigerant / lubricating oil composition. When the amount of the refrigerant is less than the above range, the refrigerating capacity is lowered, and when it is more than the above range, the lubricating performance is lowered, which is not preferable. From such a viewpoint, the weight ratio of the refrigerant / lubricating oil composition is more preferably in the range of 95/5 to 30/70.

The refrigerating machine oil composition of the present invention can be used in various refrigerating machines, but can be preferably applied particularly to a compression refrigeration cycle of a compression refrigerating machine. In particular, the refrigerating machine oil composition of the present invention effectively exhibits its effect when applied to, for example, a compression refrigeration cycle having an oil separator and / or a hot gas line as shown in each of FIGS. . Usually, the compression refrigeration cycle consists of a compressor-condenser-expansion valve-evaporator. In addition, as the lubricating oil for the refrigerator, one having good compatibility with the refrigerant used in the refrigerator is generally used. However, when a refrigerant mainly composed of carbon dioxide gas is used in the above refrigeration cycle, if the refrigerator is lubricated with commonly used lubricating oil, the wear resistance is insufficient or the stability is insufficient. Long-term stable use. In particular, this tendency is remarkable when a capillary tube is used as an expansion valve as in a refrigeration cycle such as an electric refrigerator or a small air conditioner. Therefore, the lubrication method of the present invention provides a lubricating oil composition having a temperature of 100 ° C. when a compression refrigeration cycle having an oil separator and / or a hot gas line is operated using a refrigerant mainly composed of carbon dioxide. A base oil having a kinematic viscosity of 5.5 to 30 mm ² / s and a composition containing 0.005 to 5% by weight of an extreme pressure agent and / or an acid scavenger with respect to the base oil. It is what.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these examples. Examples 1 to 4 and Comparative Examples 1 and 2 To the base oils having the properties shown in Table 1, 1% by weight of tricresyl phosphate (TCP) and 1.5% by weight of α-olefin oxide (based on the base oil) Examples 1 and 2) and lubricating oil compositions to which 1.5% by weight of phenylglycidyl ether (Examples 3 and 4 and Comparative Examples 1 and 2) were added were evaluated by performing each test by the above-described method. The results are shown in Table 2.

The properties and performance of the lubricating oil composition were determined according to the following method.
(1) Carbon dioxide gas was blown into 100 g of soluble oil under a pressure of 50 kg / cm ² , and the amount (% by weight) of carbon dioxide dissolved in the oil was measured.
(2) Shield tube test The catalyst Fe / Cu / Al was put into a glass tube, and the sample was filled at a ratio of carbon dioxide gas / oil / water = 0.5 g / 4 g / 0.02 g and sealed. After holding at 175 ° C. for 10 days, the oil appearance, the catalyst appearance, the total acid value, and the presence or absence of sludge were evaluated.

(3) Hygroscopicity test 10 g of oil is 85% humidity. H. The amount of moisture absorption (% by weight) after standing at (30 ° C.) for 120 hours was determined.
(4) Falex stoving test Using a Falex tester, the pin / block material was AISI 1137 / SAE3135. A pin / block was set, 200 g of sample oil was put into a test container, and carbon dioxide gas was blown at 5 liter / h, and then the baking load was measured at a rotation speed of 290 rpm and an oil temperature of 50 ° C.

Examples 5-8 and Comparative Examples 3-5
1% by weight of tricresyl phosphate (TCP) and 1.5% by weight of α-olefin oxide (Examples 5 and 6), 1.5% by weight of the base oil shown in Table 1 The lubricating oil compositions to which the phenyl glycidyl ether (Examples 7 and 8 and Comparative Examples 3 and 4) were added were subjected to an actual machine test and evaluated by the following method. The results are shown in Table 3.

In addition, the actual machine test about a lubricating oil composition was done using the compression-type refrigeration cycle shown below.
Compressive refrigeration cycle system A: "Compressor-condenser-expansion valve-evaporator" compression refrigeration cycle with oil separator (see Fig. 2) The expansion valve used was a capillary tube type.

In the actual machine test, a refrigeration test was conducted for a refrigerator with an output of 100 W using carbon dioxide as a refrigerant at a ratio of 70% by weight of carbon dioxide and 30% by weight of a lubricating oil composition for one year under the following conditions.
Operating status inhalation temperature: 0 ° C
Discharge temperature: 100 ° C
Condenser outlet temperature: 10 ° C
The evaluation method was stopped when an abnormality occurred in the operating state, and each part was observed to investigate the cause.

According to the present invention, in a compression refrigeration cycle using a refrigerant mainly composed of CO ₂ , a refrigerating machine oil composition having good lubrication performance and sealability and capable of long-term stable use and the composition are used. A lubrication method can be provided.

It is a flowchart which shows an example of the compression-type refrigeration cycle of the "compressor-condenser-expansion valve-evaporator" which has an oil separator and a hot gas line. It is a flowchart which shows an example of the compression-type refrigeration cycle of "compressor-condenser-expansion valve-evaporator" which has an oil separator. It is a flowchart which shows an example of the compression-type refrigerating cycle of "compressor-condenser-expansion valve-evaporator" which has a hot gas line. It is a flowchart which shows an example of the compression-type refrigeration cycle of "compressor-condenser-expansion valve-evaporator".

Explanation of symbols

1: Compressor 2: Condenser 3: Expansion valve 4: Evaporator 5: Oil separator 6: Hot gas line 7: Hot gas line valve

Claims (2)

A compression refrigeration cycle having an oil separator and / or a hot gas line and a capillary tube, comprising a refrigerant mainly composed of CO ₂ and a lubricating oil composition, wherein the lubricating oil composition is mainly composed of ester oil. A refrigerating machine oil composition comprising a base oil having a kinematic viscosity at 100 ° C. of 5.5 to 30 mm ² / s and 0.005 to 5% by weight of an extreme pressure agent and / or an acid scavenger with respect to the base oil. Lubrication method characterized by using an object.   The ester oil is at least selected from an ester of dipentaerythritol and a fatty acid having 8 carbon atoms, an ester of dipentaerythritol and a mixed fatty acid having 7 and 8 carbon atoms, and an alicyclic polyvalent carboxylic acid ester. The lubricating method according to claim 1, which is a kind.

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