JPH09169991A - Composition for working fluid of refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a working fluid of a refrigerator, containing respective specific phosphorus compound, benzotriazole derivative, ester and hydrofluorocarbon, free from ozonosphere destruction problem and having excellent lubricity and abrasion resistance. SOLUTION: This composition contains (A) one or more kinds of phosphorus compounds selected from the formulas I to III (R<1> to R<5> and R<7> to R<9> are each a 6-18C aryl, a 1-18C straight-chain alkyl, etc.; R<6> is H, a 3-18C branched-chain alkyl, etc.), e.g. tricresyl phosphate, (B) a benzotriazole derivative expressed by the formula IV (R<10> is a 0-20C group containing N and/or O; X is H or methyl), (C) an ester for a base oil derived from a 2-10C dihydric to hexahydric saturated aliphatic alcohol and a 2-10C saturated aliphatic monocarboxylic acid (derivative) and (D) a hydrofluorocarbon such as difluoromethane. The amounts of the components A and B are preferably 0.03-5.0pts.wt. and 0.001-5.0 pts.wt. based on 100pts.wt. of the component C, respectively.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for a working fluid of a refrigerator, which contains a phosphorus compound having a specific structure and a benzotriazole derivative and uses a specific ester as a base oil and which is excellent in lubricity and wear resistance. Regarding

[0002]

2. Description of the Related Art Recently, the use of dichlorodifluoromethane (CFC12), which is used in refrigerators and car coolers to protect the ozone layer, has been regulated, and it was decided that it will be prohibited by the end of 1995. In addition, chlorodifluoromethane (HCFC) that is subsequently used in room air conditioners, etc.
The use of 22) is about to be regulated. Therefore, as a substitute for CFC12 and HCFC22, hydrofluorocarbon (HF) that does not destroy the ozone layer is used.
C) type refrigerants such as 1,1,1,2-tetrafluoroethane (HFC134a) and difluoromethane (HFC32)
And pentafluoroethane (HFC125) have been developed.

Since these HFC-based refrigerants have a higher polarity than CFC12 and HCFC22, if naphthene-based mineral oils or poly-α-olefins, alkylbenzenes or other lubricating oils that have been commonly used as refrigerating machine oils are used. However, the compatibility between these lubricating oils and hydrofluorocarbons is poor, and two-layer separation occurs at low temperatures. When two-layer separation occurs, the oil return deteriorates and a thick oil film adheres to the vicinity of the condenser or evaporator as a heat exchanger to prevent heat transfer, and important defects such as poor lubrication and foaming at startup. Cause of. Therefore, the conventional refrigerating machine oil cannot be used as a refrigerating machine oil under these new refrigerant atmospheres.
Therefore, there is a need for a lubricating oil that has good compatibility with hydrofluorocarbons. Further, the refrigerating machine oil used together with hydrofluorocarbon must have good thermal stability in the presence of hydrofluorocarbon.

Therefore, at present, polyalkylene glycol, hindered ester, and carbonate ester which are compatible with the above hydrofluorocarbon are used for refrigerating machine oil.

However, the above-mentioned oxygen-containing compounds such as esters, polyalkylene glycols and carbonic acid esters have a higher polarity than hydrocarbon compounds such as mineral oils and therefore have excellent adsorbability on the metal surface. For this reason, there arises a problem that the adsorption of oiliness improvers, antiwear agents, extreme pressure agents and the like on metal surfaces is hindered, and the effects of these additives are reduced.

Particularly, in a composition for a working fluid of a refrigerator, which comprises HFC containing no chlorine atom and an oxygen-containing compound such as ester, the effect of improving the lubricity by hydrogen chloride generated by the decomposition of CFC containing HC and HCFC. Since it cannot be expected, refrigerating machine oil is required to have even better lubricity, but it does not include triphosphates and triphosphite such as tricresyl phosphate and trioctyl phosphite, which have been generally used for refrigerating machine oil. There is a problem that it is not effective in oxygen compounds.

In order to solve these problems, Japanese Patent Laid-Open No.
No. 28792 and Japanese Patent Application Laid-Open No. 4-100894 disclose acidic phosphoric acid esters and acidic phosphorous acid esters. However, since these phosphorus compounds are acidic, there are problems that they corrode metals and accelerate the hydrolysis of the base oil ester or carbonate. Further, JP-A-6-1008881 discloses a refrigerator oil composition containing a benzotriazole derivative, but it cannot be said that the effect of improving lubricity is sufficient.

On the other hand, it has been proposed to use a reaction product of benzotriazole and phosphoric acid ester as an additive in the field of lubrication. For example, JP-A-55-6
No. 0595 discloses a reaction product of benzotriazole and tricresyl phosphate.
Japanese Patent No. 591 discloses a reaction product of toltriazole, a phosphite and paraformaldehyde.

However, in any case, in order to provide sufficient lubricity, a large amount of additives must be added,
Particularly, in a highly polar lubricating base oil such as ester oil or ether oil, a large amount of additives must be added, and a satisfactory lubricating oil composition has not necessarily been provided.

Further, in JP-A-5-78689 and JP-A-6-293893, a lubricating oil composition obtained by adding triaryl phosphate and / or triaryl phosphite and a benzotriazole derivative to an ester, A refrigerator working fluid composition comprising a fluorocarbon is disclosed. However, the benzotriazole derivative is intended to be added in order to prevent metal corrosion, and there is no mention of a special composition aspect capable of achieving the effect of further improving lubricity and wear resistance.

[0011]

Therefore, an object of the present invention is to provide excellent lubricity and wear resistance even when an ester having a specific structure is used as a base oil having high polarity.
It is an object of the present invention to provide a composition for a refrigerator working fluid that is free from metal corrosion due to an additive.

[0012]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that hydrofluorocarbons have an ester having a specific structure, a phosphorus compound having a specific structure, and a specific structure. It was found that a composition for refrigerating machine working fluid having surprisingly improved lubricity and wear resistance can be obtained by the specific combination of adding a benzotriazole derivative having the structure of, and thus the present invention is completed. Came to.

That is, the gist of the present invention is [1] (a) General formula (1), (2) or (3)

[0014]

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(In the formula, R ^{1 to} R ⁵ and R ^{7 to} R ⁹ may be the same or different, and are an aryl group having 6 to 18 carbon atoms and a linear alkyl group having 1 to 18 carbon atoms. Represents a branched chain alkyl group having 3 to 18 carbon atoms, a linear alkenyl group having 2 to 18 carbon atoms, or a branched chain alkenyl group having ^{3 to} 18 carbon atoms, provided that at least one of R ^{1 to} R ³ is An aryl group having 6 to 18 carbon atoms, at least one of R ⁴ and R ⁵ is an aryl group having 6 to 18 carbon atoms, and at least one of R ^{7 to} R ⁹ has 6 to 18 carbon atoms;
Is an aryl group. R ⁶ is a hydrogen atom, having 1 to 18 carbon atoms
Linear alkyl group, a branched chain alkyl group having 3 to 18 carbon atoms, a linear alkenyl group having 2 to 18 carbon atoms, or 3 carbon atoms
~ 18 branched alkenyl groups. ) One or more phosphorus compounds selected from the group consisting of compounds represented by
(B) General formula (4)

[0016]

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A benzotriazole derivative represented by the formula (wherein R ¹⁰ represents a group containing a nitrogen atom and / or an oxygen atom and having 0 to 20 carbon atoms, and X represents a hydrogen atom or a methyl group), ( C) As a base oil obtained from a divalent to hexavalent saturated aliphatic polyhydric alcohol having 2 to 10 carbon atoms and a linear or branched saturated aliphatic monocarboxylic acid having 2 to 10 carbon atoms or a derivative thereof. A composition for a working fluid of a refrigerator, which comprises an ester to be used, and (d) a hydrofluorocarbon, [2] In a benzotriazole derivative represented by the general formula (4), R ¹⁰ is a hydroxyl group or an amino group. Or a composition for a working fluid of a refrigerator according to the above [1], which is a group containing a hydroxyl group and / or an amino group, [3] a benzotriazole represented by the general formula (4). In the derivative, R ¹⁰ is

[0018]

[Chemical 6]

A composition for a working fluid of a refrigerator according to the above [1] or [2], wherein [4] the phosphorus compound represented by the general formulas (1) to (3), among R ^{1 to} R ³ At least one, R ⁴ , R
^The composition for a working fluid of a refrigerator according to any one of [1] to [3], wherein at least one of ⁵ and at least one of R ^{7 to} R ⁹ is any one of a phenyl group, a cresyl group and a xylenyl group. [5] The phosphorus compound is one or more compounds selected from the group consisting of tricresyl phosphate, triphenyl phosphate, tricresyl phosphite, and triphenyl phosphite, [1] to
[4] A composition for working fluid of a refrigerator according to any one of [6], wherein the ester is a saturated aliphatic polyhydric alcohol having 2 to 6 carbon atoms and having 5 to 10 carbon atoms, and a straight chain or branched chain having 5 to 9 carbon atoms. A composition for a working fluid of a refrigerator according to any one of [1] to [5] above, which is an ester obtained from a saturated aliphatic monocarboxylic acid having a chain or a derivative thereof.

[7] The mixing ratio of ester, phosphorus compound and benzotriazole derivative and hydrofluorocarbon is hydrofluorocarbon / (ester + phosphorus compound + benzotriazole derivative) = 50/1 to 1
The composition for refrigerator working fluid according to any one of the above [1] to [6], which is / 20 (weight ratio), [8] 0.03 to 5.0 parts by weight of a phosphorus compound with respect to 100 parts by weight of the ester. And a composition for a working fluid of a refrigerator according to any one of [1] to [7], which comprises 0.001 to 5.0 parts by weight of a benzotriazole derivative.

[9] The ratio of the phosphorus compound to the benzotriazole derivative is 0.001 to 2.0 moles of the benzotriazole derivative relative to 1 mole of the phosphorus compound.
[8] A composition for working fluid of a refrigerator according to any one of [1] to [10], wherein the hydrofluorocarbon contains at least difluoromethane (HFC32).
~

[9] A composition for a working fluid of a refrigerator according to any one of the above.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

1. Regarding Phosphorus Compound The phosphorus compound used in the present invention is represented by the general formula (1)
To (3).

[0023]

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(In the formula, R ^{1 to} R ⁵ and R ^{7 to} R ⁹ may be the same or different, and are an aryl group having 6 to 18 carbon atoms and a linear alkyl group having 1 to 18 carbon atoms. Represents a branched chain alkyl group having 3 to 18 carbon atoms, a linear alkenyl group having 2 to 18 carbon atoms, or a branched chain alkenyl group having ^{3 to} 18 carbon atoms, provided that at least one of R ^{1 to} R ³ is An aryl group having 6 to 18 carbon atoms, at least one of R ⁴ and R ⁵ is an aryl group having 6 to 18 carbon atoms, and at least one of R ^{7 to} R ⁹ has 6 to 18 carbon atoms;
Is an aryl group. R ⁶ is a hydrogen atom, having 1 to 18 carbon atoms
Linear alkyl group, a branched chain alkyl group having 3 to 18 carbon atoms, a linear alkenyl group having 2 to 18 carbon atoms, or 3 carbon atoms
~ 18 branched alkenyl groups. )

[0025] (i) the number of carbon atoms of R ¹ to R ⁵ and R ⁷ to R ⁹ for R ¹ to R ⁵ and R ⁷ to R ^9, the polarity is reduced becomes larger, 18 or less from the viewpoint of anti-wear effect is poor Is. It is preferably 12 or less. When this phosphorus compound is used in a composition for a working fluid of a refrigerator, the number of carbon atoms is preferably 18 or less, more preferably 12 or less, and particularly preferably 8 or less from the viewpoint of compatibility with hydrofluorocarbons.

Examples of the aryl group having 6 to 18 carbon atoms are phenyl group, cresyl group, xylenyl group, 4-ethylphenyl group, 4-t-butylphenyl group, naphthyl group and 2-
Methylnaphthyl group, 4-t-octylphenyl group, 2,
4-di-t-butylphenyl group, 2,6-di-t-butyl-4-methylphenyl group, 2,4,6-tri-t-butylphenyl group, 4-nonylphenyl group and the like can be mentioned.

Examples of the linear alkyl group having 1 to 18 carbon atoms include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group and tridecyl group. Group, tetradecyl group, hexadecyl group, octadecyl group and the like.

Examples of the branched chain alkyl group having 3 to 18 carbon atoms include isopropyl group, 1-methylpropyl group, 2-methylpropyl group, t-butyl group, 2-methylbutyl group, 3
-Methylbutyl group, 2,2-dimethylpropyl group, cyclopentyl group, 2-methylpentyl group, 2-ethylbutyl group, 2,3-dimethylbutyl group, cyclohexyl group,
2-methylhexyl group, 3-methylhexyl group, 2-ethylpentyl group, 2-methylheptyl group, 2-ethylhexyl group, 3,5-dimethylhexyl group, 3,5,5-
Trimethylhexyl group, 2,4,6-trimethylheptyl group, 2,4,6,8-tetramethylnonyl group, 2-
(3'-methylbutyl) -7-methyloctyl group, 2-
Examples thereof include a pentylnonyl group, a 2-hexyldecyl group and a 2-heptylundecyl group.

Examples of the linear alkenyl group having 2 to 18 carbon atoms include a propenyl group, a 2-decenyl group, a 9-decenyl group,
9-undecenyl group, 10-undecenyl group, 2-dodecenyl group, 3-dodecenyl group, 2-tridecenyl group, 4
-Tetradecenyl group, 9-tetradecenyl group, 9-pentadecenyl group, 9-hexadecenyl group, 9-heptadecenyl group, 9-octadecenyl group and the like.

Examples of the branched chain alkenyl group having 3 to 18 carbon atoms include isopropenyl group, 3-methyl-2-nonenyl group, 2,4-dimethyl-2-decenyl group and 2-methyl-
9-heptadecenyl group etc. are mentioned.

The groups represented by R ^{1 to} R ⁵ and R ^{7 to} R ⁹ preferably contain an aromatic ring from the viewpoint of interaction with the benzotriazole derivative, and are preferably aryl groups.
Accordingly, at least one of R ^{1 to} R ³ in the general formula (1), at least one of R ⁴ and R ⁵ in the general formula (2), and among R ^{7 to} R ⁹ in the general formula (3). At least one is preferably an aryl group. More preferably, R ^{1 to} R ⁵ and R ^{7 to} R ⁹ are all aryl groups. Among the aryl groups, a phenyl group, a cresyl group and a xylenyl group are more preferable, and a phenyl group and a cresyl group are particularly preferable.

(Ii) R ⁶ Of the groups represented by R ⁶ , a linear or branched alkyl group,
The carbon number of the straight chain or branched chain alkenyl group is 18 or less from the viewpoint that the polarity becomes smaller as the size becomes larger and the wear preventing effect becomes poor. It is preferably 12 or less. When this phosphorus compound is used in a composition for a working fluid of a refrigerator, the number of carbon atoms is 18 from the viewpoint of compatibility with hydrofluorocarbon.
The following is preferable, and 12 is more preferable. Specific examples of the alkyl group and alkenyl group include R
^The examples shown in ^{1 to} R ⁵ and R ^{7 to} R ⁹ are included.

The method for producing the phosphorus compound used in the present invention is well known, and many phosphorus compounds are commercially available, and these can be used in the present invention.

Therefore, specific examples of the phosphorus compound preferably used in the present invention include triphenyl phosphite, tricresyl phosphite, tris (nonylphenyl) phosphite and tris (2,4-di-t-butyl). Phenyl) phosphite, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, diphenyl hydrogen phosphite, 2-ethylhexyl diphenyl phosphate, 2-ethylhexyl phosphonate diphenyl and the like can be mentioned. Of these, tricresyl phosphite, triphenyl phosphite, tricresyl phosphate and triphenyl phosphate are particularly preferable. In addition, in this invention, the said phosphorus compound may be used individually and may use 2 or more types of phosphorus compounds.

2. Benzotriazole Derivative The benzotriazole derivative used in the present invention is represented by the general formula (4).

[0036]

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(In the formula, R ¹⁰ represents a group containing a nitrogen atom and / or an oxygen atom and having 0 to 20 carbon atoms, and X represents a hydrogen atom or a methyl group.)

The group represented by R ¹⁰ is a group containing a nitrogen atom and / or an oxygen atom from the viewpoint of improving the adsorptive power to the metal surface, and as the carbon number increases, the polarity decreases and the adsorptive power increases. It becomes 20 or less because it becomes weak. It is preferably 18 or less. When this benzotriazole derivative is used in a composition for a working fluid of a refrigerator, it has 20 carbon atoms from the viewpoint of compatibility with hydrofluorocarbon.
The following is preferable, and 18 or less is more preferable. When the carbon number is 0, R ¹⁰ represents a hydroxyl group or an amino group. Further, R ¹⁰ may be a group containing a hydroxyl group and / or an amino group. Specific examples of R ¹⁰ include, for example, the following chemical formulas:

[0039]

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Examples include groups represented by: Since the benzotriazole derivative used in the present invention has more nitrogen atoms and / or oxygen atoms than benzotriazole, it has excellent adsorptivity to a metal surface and is excellent in adsorbing a phosphorus compound on the metal surface. ing. Further, since it has a lower melting point than benzotriazole, it has excellent solubility in base oil.

Therefore, specific examples of the benzotriazole derivative preferably used in the present invention are not particularly limited as long as they satisfy the general formula (4), but 1- [N, N-bis ( 2-ethylhexyl) aminomethyl] benzotriazole, 1- [N, N-bis (2-hydroxyethyl) aminomethyl] benzotriazole, 1- (2 ', 3'-dihydroxypropyl) benzotriazole, 1-hydroxybenzotriazole , 1-hydroxymethylbenzotriazole, 1-
(1 ′, 2′-Dicarboxyethyl) benzotriazole, 1-dioctylaminomethyl-4-methylbenzotriazole, 1-dioctylaminomethyl-5-methylbenzotriazole and the like are mentioned as suitable ones, and particularly preferably, 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole, 1-hydroxybenzotriazole, 1-dioctylaminomethyl-
4-methylbenzotriazole and 1-dioctylaminomethyl-5-methylbenzotriazole. In the present invention, the benzotriazole derivative may be used alone or two or more kinds of benzotriazole derivatives may be used.

The method for producing the benzotriazole derivative used in the present invention is well known, and many benzotriazole derivatives are commercially available, and these can be used in the present invention.

3. Regarding the ester In the present invention, as the ester used as the base oil, a saturated aliphatic polyhydric alcohol having 2 to 6 carbon atoms and having 2 to 6 carbon atoms (component-1) and a straight chain or branched chain having 2 to 10 carbon atoms. Saturated aliphatic monocarboxylic acid or its derivative (component-
2) An ester obtained from and.

Regarding Component-1 The valence of the alcohol of Component-1 is 2 to 6, and preferably 2 to 4. The valence is preferably 2 or more from the viewpoint of having an appropriate viscosity, and is preferably 6 or less from the viewpoint of avoiding unnecessary viscosity and compatibility with the hydrofluorocarbon. The number of carbon atoms is 2 to 10, preferably 5 to 10, and more preferably 5 to 6.
The number of carbon atoms is preferably 2 or more from the viewpoint of having an appropriate viscosity, and is preferably 10 or less from the viewpoint of avoiding unnecessary viscosity and the compatibility with the hydrofluorocarbon. In addition, it is preferable that unsaturated bonds are not included from the viewpoint of heat resistance.

Specific examples of the alcohol as the component-1 include:
Hindered alcohols such as neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane and dipentaerythritol, and ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1 And polyhydric alcohols such as 1,4-butanediol, 1,6-hexanediol, glycerin, diglycerin, triglycerin, sorbitol, and mannitol. Among these, hindered alcohol is particularly excellent from the viewpoint of heat resistance.

Regarding Component-2 The carboxylic acid of Component-2 has 2 to 10 carbon atoms, preferably 5 to 9 carbon atoms. The number of carbon atoms is preferably 2 or more from the viewpoint of suppressing corrosiveness to metals, and is preferably 10 or less from the viewpoint of compatibility with hydrofluorocarbons. From the viewpoint of compatibility with hydrofluorocarbons and hydrolysis resistance, branched saturated fatty acids are more preferable than linear saturated fatty acids. On the other hand, from the viewpoint of lubricity, straight-chain saturated fatty acids are more preferable than branched-chain saturated fatty acids. In the present invention, a suitable material is selected according to the mode of use as the composition for the working fluid of the refrigerator. Also, in terms of heat resistance,
It is more preferable not to include an unsaturated bond.

Specific examples of the carboxylic acid of the component-2 are:
Capric acid, valeric acid, isovaleric acid, 2-methylbutyric acid, caproic acid, enanthic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, 3,5,5- Trimethylhexanoic acid and the like can be mentioned. In addition, specific examples of the carboxylic acid derivative of the component-2 include methyl ester, ethyl ester, and acid anhydride of these carboxylic acids.

Specific examples of such ester include 3,5,5-trimethylhexanoic acid ester of neopentyl glycol, 2-ethylhexanoic acid ester of neopentyl glycol, and 3,5,5-trimethylhexanoic acid of trimethylolpropane. Ester, trimethylolpropane 2-methylhexanoic acid / 2-ethylpentanoic acid / 2-ethylhexanoic acid /
3,5,5-Trimethylhexanoic acid mixed fatty acid ester, trimethylolpropane 2-ethylhexanoic acid ester, trimethylolpropane 2-methylhexanoic acid / 2-ethylpentanoic acid / 2-ethylhexanoic acid mixed fatty acid ester,
Pentaerythritol valeric acid / isovaleric acid /
3,5,5-Trimethylhexanoic acid mixed fatty acid ester, pentaerythritol enanthate / 3,5,5-trimethylhexanoic acid mixed fatty acid ester, pentaerythritol 2-
Ethylhexanoic acid / 3,5,5-trimethylhexanoic acid mixed fatty acid ester, pentaerythritol 2-methylhexanoic acid / 2-ethylpentanoic acid / 2-ethylhexanoic acid mixed fatty acid ester, pentaerythritol caprylic acid / 3,
5,5-Trimethylhexanoic acid mixed fatty acid ester, 2-methylhexanoic acid / 2-ethylpentanoic acid / 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid mixed fatty acid ester of pentaerythritol and the like can be mentioned.

The ester used in the present invention is Component-1.
Can be obtained from one or more of the above alcohols and one or more of the carboxylic acid of Component-2 or one or more of the derivatives thereof by a commonly known esterification reaction or transesterification reaction.

The acid value of the ester obtained as described above, which is used in the present invention, is not particularly limited, but it may cause corrosion of metal materials, deterioration of wear resistance, deterioration of thermal stability, and deterioration of electric insulation. From the viewpoint of suppressing 1 mgKOH / g
The following is preferable, 0.2 mgKOH / g or less is more preferable, 0.1 mgKOH / g or less is further preferable,
0.05 mgKOH / g or less is particularly preferable.

The hydroxyl value of the ester used in the present invention is not particularly limited, but is preferably 0.1 to 50 mgKOH / g, more preferably 0.1 to 30 mgKOH / g,
0.1-20 mg KOH / g is particularly preferred. 0.1 mgKOH / g or more is preferable from the viewpoint of wear resistance, and 50 mgKOH / g or less is preferable from the viewpoint of hygroscopicity.

The iodine value (Img / 100 g) of the ester used in the present invention is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and 3 or less from the viewpoint of thermal oxidation stability of the resulting lubricating oil composition. Is more preferable, and 1 or less is particularly preferable. The temperature of the two-phase separation of the ester used in the present invention from the hydrofluorocarbon at a low temperature is not particularly limited, but is preferably -10 ° C or lower,
30 ° C. or lower is more preferable, and −50 ° C. or lower is further preferable. The kinematic viscosity of the ester used in the present invention at 100 ° C. is not particularly limited, but from the viewpoint of compatibility with hydrofluorocarbon, 100 mm ² / s or less is preferable, usually 15 to 100 mm ² / s is preferable, and 30 to 7
5 mm ² / s is more preferable.

Although various esters are generally known as base oils for refrigerator working fluid compositions, in the present invention, esters having the above-mentioned specific structure are used as base oils. It is presumed that the ester having the structure as in the present invention has an appropriate dissolving power for the phosphorus compound and the benzotriazole derivative, and therefore, the lubricity and the abrasion resistance become remarkable. That is, if the dissolving power is too good, it becomes difficult for the additive to be adsorbed on the metal, and if the dissolving power is bad, a sufficient amount of the additive cannot be added.

4. Hydrofluorocarbon The hydrofluorocarbon used in the present invention is not particularly limited as long as it is usually used for refrigerating machine oil, but preferably difluoromethane (HFC3).
2) 1,1-difluoroethane (HFC152a),
1, 1, 1-trifluoroethane (HFC143a),
1, 1, 1, 2-tetrafluoroethane (HFC134
a) 1,1,1,2,2-tetrafluoroethane (HFC
134), pentafluoroethane (HFC125) and the like, with 1,1,1,2-tetrafluoroethane, difluoromethane, pentafluoroethane, and 1,1,1-trifluoroethane being particularly preferred. These hydrofluorocarbons may be used alone or in combination of two or more kinds. Preferably, at least difluoromethane is contained in the hydrofluorocarbon.

5. Refrigerator Working Fluid Composition The refrigerator working fluid composition of the present invention comprises the above-mentioned phosphorus compound, benzotriazole derivative, ester as a lubricating base oil, and hydrofluorocarbon. . The refrigerator working fluid composition of the present invention,
It has excellent lubricity and wear resistance, and is suitable for lubricating rotary compressors and scroll compressors.
In terms of applications, it is suitable for use as a compressor for room air conditioners and package air conditioners.

The mixing ratio of the hydrofluorocarbon, the ester, the phosphorus compound and the benzotriazole derivative in the composition for a working fluid for a refrigerator of the present invention is not particularly limited, but the hydrofluorocarbon / (ester + phosphorus compound). + Benzotriazole derivative) = 50 /
1 to 1/20 (weight ratio) is preferable, and more preferably 1
It is 0/1 to 1/5 (weight ratio). From the viewpoint of obtaining a sufficient refrigerating capacity, it is preferable that the mixing ratio is higher than 1/20 in the ratio of hydrofulcarbon, and from the viewpoint of optimizing the viscosity of the working fluid composition for a refrigerator, ester + phosphorus is higher than 50/1. A high ratio of compound + benzotriazole derivative is preferred.

In the composition for refrigerator working fluid of the present invention, the quantitative relationship between the ester, the phosphorus compound and the benzotriazole derivative is such that at least the composition for refrigerator working fluid of the present invention is in contact with the metal surface. Is not particularly limited as long as it is an amount sufficient to suppress wear,
Preferably, the phosphorus compound is 0.03 to 5.0 parts by weight and the benzotriazole derivative is 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the ester. The phosphorus compound content is more preferably 0.05 to 3.0 parts by weight, particularly preferably 0.1 to 2.0 parts by weight, and further preferably 0.3 to 1.0 parts by weight. From the viewpoint of obtaining the desired effect of suppressing wear, the content is preferably 0.03 parts by weight or more, and from the viewpoint of the thermal stability of the ester, 5.0 parts by weight or less is preferable. Further, even if the amount exceeds 5.0 parts by weight, the effect of suppressing wear wears off, which is economically disadvantageous.

The blending amount of the benzotriazole derivative is more preferably 0.003 to 1.5 parts by weight, particularly preferably 0.005 to 0.5 part by weight, and further preferably 0.005 to 0. 05 parts by weight. From the viewpoint of obtaining the desired effect of suppressing wear, the amount is preferably 0.001 part by weight or more, and from the viewpoint of thermal stability of the ester, 5.
It is preferably 0 parts by weight or less.

The mixing ratio of the phosphorus compound and the benzotriazole derivative is not particularly limited, but 0.001 to 2.
0 mol. The compounding ratio of the phosphorus compound and the benzotriazole derivative is more preferably 0.005 to 1.0 mol, particularly preferably 0.01 to 0.5 mol, of the benzotriazole derivative relative to 1 mol of the phosphorus compound. It is preferably 0.01 to 0.2 mol. From the viewpoint of exerting the lubricity improving effect by the synergistic effect, the ratio of the phosphorus compound and the benzotriazole derivative is preferably 0.001 or more, and from the viewpoint of suppressing the deterioration of the lubricity due to the higher ratio of the benzotriazole derivative, 2. It is preferably 0 or less.

Particularly preferred examples of the composition for a working fluid of a refrigerator include pentaerythritol 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid mixed fatty acid ester and pentaerythritol 2-ethylpentanoic acid / 2-. Methylhexanoic acid / 2-ethylhexanoic acid /
To 100 parts by weight of one ester selected from the group consisting of 3,5,5-trimethylhexanoic acid mixed fatty acid ester and 3,5,5-trimethylhexanoic acid ester of trimethylolpropane, tricresyl phosphate is added. 0.5 to 1.0 parts by weight of triphenyl phosphate or triphenyl phosphite, 1- [N,
N-bis (2-ethylhexyl) aminomethyl] benzotriazole in an amount of 0.005 to 0.01 parts by weight, and R407C (HFC32 / HFC125 / HFC
134a = 23/25/52 (wt%)), R410A
(HFC32 / HFC125 = 50/50 (wt%))
Or R410B (HFC32 / HFC125 = 45/5
5 (wt%)).

In 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid mixed fatty acid ester of pentaerythritol, 2-ethylhexanoic acid and 3,5,5-
The mixing ratio of trimethylhexanoic acid is 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid = 8 from the viewpoint of compatibility with hydrofluorocarbon, melting point, and viscosity.
0 to 35 mol% / 20 to 65 mol% is preferable, and 76 to 48 mol% / 24 to 52 mol% is more preferable.

2-ethylpentanoic acid / 2-methylhexanoic acid / 2-ethylhexanoic acid / of pentaerythritol
In 3,5,5-trimethylhexanoic acid mixed fatty acid ester, the mixing ratio of 2-ethylpentanoic acid / 2-methylhexanoic acid / 2-ethylhexanoic acid / 3,5,5-trimethylhexanoic acid is the same as that of hydrofluorocarbon. From the viewpoint of compatibility, melting point and viscosity, 3 to 10/17 to 39 /
5 to 13/45 to 72 (molar ratio) is preferable, and more preferably 3 to 9/17 to 35/5 to 11/50 to 67.
(Molar ratio).

The following additives may be appropriately added to the composition for refrigerator working fluid of the present invention. (I) An additive for removing water may be added to the composition for refrigerator working fluid of the present invention. When water coexists, the ester which is the base oil is hydrolyzed, carboxylic acid may be generated to clog the capillary tube and the like, and non-condensable CO ₂ may be generated to reduce the refrigerating capacity. .
In addition, the PET film, which is an insulating material, is hydrolyzed and PE
This is because T oligomer may be generated and the capillary tube or the like may be clogged. Examples of the additive for removing water include compounds having an epoxy group, and additives such as orthoester, acetal (ketal), and carbodiimide.

As the compound having an epoxy group,
It has 4 to 60 carbon atoms, preferably 5 to 25 carbon atoms. Specifically, glycidyl ethers such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, neopentyl glycol diglycidyl ether, glycidyl esters such as glycidyl adipate and glycidyl 2-ethylhexanoate, and epoxidized stearic acid Epoxidized fatty acid monoesters such as methyl, epoxidized vegetable oils such as epoxidized soybean oil,
Alicyclic epoxy compounds such as 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, bis (3,4-epoxycyclohexylmethyl) adipate, and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate Is mentioned.

In the present invention, these epoxy group-containing compounds may be used alone or in combination of two or more kinds. The amount added is usually 0.0 with respect to 100 parts by weight of the ester.
5 to 2.0 parts by weight, preferably 0.1 to 1.5 parts by weight,
More preferably, it is 0.1 to 1.0 part by weight.

Examples of the orthoester used in the present invention include compounds described in JP-A-6-17073, column 10, lines 27 to 41.
The addition amount of orthoester is usually 0.01 to 100 parts by weight, preferably 0.0 to 100 parts by weight of ester.
5 to 30 parts by weight.

Examples of acetals or ketals used in the present invention include JP-A-6-17073, column 11,
Compounds such as those described in line 21 are mentioned.
The amount of acetal or ketal added is usually 0.01 to 100 parts by weight, preferably 0.05 to 30 parts by weight, based on 100 parts by weight of the ester.

Examples of the carbodiimide used in the present invention include those represented by the following general formula (20). ^{R 26 -N = C = N-} R 27 (20) ( wherein, R ²⁶ and R ²⁷ .R ²⁶ and R ²⁷ represents a hydrocarbon group having 1 to 18 carbon atoms may be the same or different. The carbon number of R ²⁶ and R ²⁷ is more preferably 1-12. Specific examples of R ²⁶ and R ²⁷ include alkyl groups and aryl groups having up to 15 carbon atoms among those listed in R ^{1 to} R ⁵ and R ^{7 to} R ⁹ , and aralkyl groups such as benzyl. Group, 4-methylbenzyl group, phenethyl group, 4-butylbenzyl group, naphthylmethyl group and the like.

Specific examples of the carbodiimide include 1,3-diisopropylcarbodiimide and 1,3-diisopropylcarbodiimide.
Di-t-butyl-carbodiimide, 1,3-dicyclohexylcarbodiimide, 1,3-di-p-tolylcarbodiimide, 1,3-bis- (2,6-diisopropylphenyl) carbodiimide and the like. The addition amount of carbodiimide is usually 0.01 to 100 parts by weight of ester.
10 parts by weight, preferably 0.05 to 5 parts by weight.

(Ii) Further, to the composition for a working fluid for a refrigerator of the present invention, a phenolic compound having a radical trapping ability for improving thermal stability and a metal deactivator having a chelating ability are added. May be.

As the phenolic compound having a radical trapping ability used in the present invention, there is disclosed Japanese Patent Laid-Open No. 6-170.
73, columns 12, 32 to columns 13, 18 include compounds. Although not particularly limited, preferably 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4,4'-methylenebis (2,6-di- t-butylphenol), 4,4′-isopropylidene bisphenol, 2,6-di-t-butyl-4-ethylphenol and the like. The amount of the phenolic compound added is usually 0.05 to 2.0 parts by weight, preferably 0.05 to 0.5 parts by weight, based on 100 parts by weight of the ester.

The metal deactivator used in the present invention preferably has a chelating ability and is disclosed in JP-A-5-20917.
Compounds such as those described from column 1, lines 13 and 38 to columns 14 and 8 are mentioned. Although not particularly limited, preferably N, N'-disalicylidene-
1,2-diaminoethane, N, N'-disalicylidene-1,2-
Examples include diaminopropane, acetylacetone, acetoacetate, alizarin, quinizarin and the like. The amount of the metal deactivator used in the present invention is 10
The amount is usually 0.001 to 2.0 parts by weight, preferably 0.003 to 0.5 parts by weight, based on 0 parts by weight.

The refrigerating machine working fluid composition of the present invention in which a phosphorus compound and a benzotriazole derivative are combined with a specific ester as a base oil has high lubricity and wear resistance. The reason is presumed as follows. Phosphorus compounds are added to base oils to impart lubricity and wear resistance. When the base oil is a mineral oil, the effect of the addition is sufficiently shown, but when it is polar like an ester, it is difficult to adsorb on the metal surface and the effect is not sufficiently exhibited. The factors involved in the adsorption on the metal surface are considered to be the polarity of the adsorbed molecule and the solubility in the base oil. That is, it is considered that the higher the polarity of the molecule to be adsorbed, the easier it is to adsorb, and the higher the solubility in the base oil, the more stable it exists in the base oil and the harder it is to adsorb on the metal surface. The benzotriazole derivative used in the present invention has a stronger adsorptive power to a metal surface than benzotriazole by introducing a group containing a nitrogen atom or an oxygen atom into the benzotriazole skeleton.
Further, the ester having a specific structure used in the present invention has a good dissolving power for phosphorus compounds and benzotriazole derivatives.

On the other hand, in the interaction between the phosphorus compound and the benzotriazole derivative, it is considered that the molecules of the phosphorus compound and the benzotriazole derivative approach each other through the aryl group of the phosphorus compound and the aromatic ring of the benzotriazole derivative. In the composition for refrigerator working fluid of the present invention, the group containing a nitrogen atom or an oxygen atom of the benzotriazole derivative has high polarity and is adsorbed on the metal surface. It is considered that the phosphorus compound can approach the metal surface by the interaction with the benzotriazole derivative, and thus has high lubricity and wear resistance.

[0075]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The phosphorus compounds, benzotriazole derivatives, and base oils used in Examples and the like are shown below. Phosphorus Compound i: Tricresyl Phosphate Phosphorus Compound ii: Triphenyl Phosphate Phosphorus Compound iii: Tricresyl Phosphite Phosphorus Compound iv: Triphenyl Phosphite Phosphorus Compound v: Cresyl Diphenyl Phosphate Phosphorus Compound vi: Diphenyl Hydrogen Phosphite phosphorus compound vii: 2-Ethylhexyl diphenyl phosphate Phosphate phosphorus compound viii: 2-Ethylhexyl diphenyl phosphonate

Benzotriazole derivative a: 1- [N,
N-bis (2-ethylhexyl) aminomethyl] benzotriazole benzotriazole derivative b: 1- [N, N-bis (2
-Hydroxyethyl) aminomethyl] benzotriazole benzotriazole derivative c: 1- (2 ', 3'-dihydroxypropyl) benzotriazole benzotriazole derivative d: 1-hydroxybenzotriazole benzotriazole derivative e: 1-dioctylaminomethyl-4 -Methylbenzotriazole and 1-dioctylaminomethyl-5-methylbenzotriazole in equal (v / v) mixture

Base oil A: pentaerythritol (1.0 mol) and 2-ethylhexanoic acid (1.93 mol) and 3,
Ester of 5,5-trimethylhexanoic acid (2.07 mol) Viscosity at 40 ° C. (hereinafter abbreviated as Vis 40) 70.2
mm ² / s Viscosity at 100 ° C (hereinafter abbreviated as Vis 100) 8.
63mm ² / s Acid value 0.01mgKOH / g Hydroxyl value 2.4mgKOH / g

Base oil B: pentaerythritol (1.0 mol) and 2-methylhexanoic acid (0.90 mol), 2-ethylpentanoic acid (0.21 mol), 2-ethylhexanoic acid (0.25 mol) ), And an ester of 3,5,5-trimethylhexanoic acid (2.64 mol) Vis 40: 68.0 mm ² / s Vis 100: 8.58 mm ² / s Acid value 0.01 mgKOH / g Hydroxyl value 1.3 mgKOH / g

Base oil C: trimethylolpropane (1.0
Ester of 3,5,5-trimethylhexanoic acid (3.0 mol) with Vis 40: 51.9 mm ² / s Vis 100: 7.13 mm ² / s Acid value 0.01 mgKOH / g Hydroxyl value 0.9 mgKOH / g

Base oil D: pentaerythritol (1.0 mol) and 2-ethylhexanoic acid (1.88 mol), 2-ethylpentanoic acid (0.46 mol), and 2-ethylhexanoic acid (1.66 mol). ester ^{mole) Vis 40: 30.9mm 2 / s} Vis 100: 5.21mm 2 / s acid value 0.01 mg / g hydroxyl value 1.1mgKOH / g

Base oil E: neopentyl glycol (1.0
Ester of 2-ethylhexanoic acid (0.68 mol) and glutaric acid (0.68 mol) Vis 40: 87.2 mm ² / s Vis 100: 11.7 mm ² / s Acid value 0.01 mg KOH / g Hydroxyl value 13.40mgKOH / g

Base oil F: neopentyl glycol (1.0
Ester) with adipic acid (1.67 mol) and 2-ethylhexanol (1.40 mol) Vis 40: 51.2 mm ² / s Vis 100: 8.43 mm ² / s Acid value 0.01 mg KOH / g hydroxyl group Value 7.1mgKOH / g

Base oil G: Naphthenic mineral oil (manufactured by Nippon San Oil Co., Ltd .: SUNISO 4GS) Vis 40: 54.1 mm ² / s Vis 100: 6.05 mm ² / s The viscosity of the above base oil is JIS. It was measured based on K-2283. The acid value and the hydroxyl value are JIS K-2.
501.

Example 1 In order to evaluate the lubricity and wear resistance of the product of the present invention, a high-pressure wear tester (manufactured by Shinko Machinery Co., Ltd.) was used to measure the friction coefficient and wear resistance as indexes of lubricity. The amount of wear, which is an index of, was measured. Lubricating oil composition (480 g) and 1,1,1,2-tetrafluoroethane (240 g) were placed in a test container at 100 ° C.
Was kept warm. The test piece uses a vane and a disc.
A load of kg was applied and the test was performed at 500 rpm for 6 hours. The friction coefficient was calculated from the friction torque during the test. The amount of wear was calculated from the weight of the vane and the disk before the test and the weight after the test. The results are shown in Tables 1 and 2.

Comparative Example 1 In the same manner as in Example 1, the friction coefficient and wear amount of the lubricating oil composition were measured. Table 3 shows the results.

[0086]

[Table 1]

[0087]

[Table 2]

[0088]

[Table 3]

From the results of Example 1 and Comparative Example 1, the following was found. From the results of Nos. 1 to 3 in Comparative Example 1, it was found that adding the phosphorus compound and the benzotriazole derivative in the present invention was very effective in improving the lubricity and the wear resistance. Further, even if only the phosphorus compound as the antiwear agent was added, the effect was insufficient as can be seen from Nos. 4 and 6 of Comparative Example 1. On the other hand, even if only the benzotriazole derivative was added, as can be seen from the result of No. 5 of Comparative Example 1, there was no effect. Further, when benzotriazole was used instead of the benzotriazole derivative and was used in combination with the phosphorus compound, the numbers 7 to 1 of Comparative Example 1 were used.
As can be seen from the result of 0, the effect on lubricity and wear resistance as shown in Example 1 was not obtained. Further, as can be seen by comparing the numbers 4 and 7 and 8 in Comparative Example 1,
There is no difference between the phosphorus compound alone and the combined use of the phosphorus compound and benzotriazole, and the combined effect of the phosphorus compound and benzotriazole is not recognized. On the other hand, it was found that the combination of the phosphorus compound and the benzotriazole derivative according to the present invention exhibits a surprising synergistic effect.

As can be seen from the results of Nos. 11 and 12 of Comparative Example 1, the difference in the effect depending on the type of ester as the base oil was also remarkable. That is, Nos. 11 and 12 of Comparative Example 1 use an ester of the type generally called a complex ester as a base oil, and Example 1 is an ester of the type generally called a hindered ester. Therefore, it can be seen that the lubricity and wear resistance are dramatically improved when the hindered ester is used as the base oil. In addition, the wear amount of the disk and vane in Nos. 1 to 20 of Example 1 which is the product of the present invention has a value of about 1.0, which is the same as that of the conventional composition using CFC12 as a CFC (Comparative Example 1 No. 13) of No. 13). From the above, it was found that the refrigerating machine working fluid of the present invention in which the phosphorus compound and the benzotriazole derivative were used in combination exhibited a surprising effect on lubricity and wear resistance.

Example 2 In order to examine the compatibility of the lubricating oil composition with the hydrofluorocarbon in the composition for refrigerator working fluid of the present invention, the lubricating oil composition shown in Table 4 and R-407C were mixed on 10/9.
Weight ratio of 0-50 / 50 (lubricating oil composition / R-407
Mix in C) and measure the two phase separation temperature at low temperature. Table 4 shows the results.

Comparative Example 2 In the same manner as in Example 2, the lubricating oil composition shown in Table 4 and R-
The two phase separation temperature at the low temperature of 407C was measured. Table 4 shows the results.

[0093]

[Table 4]

As can be seen from Example 2 and Comparative Example 2 in Table 4, the compatibility between the lubricating oil composition and the hydrofluorocarbon, which constitutes the composition for refrigerator working fluid of the present invention, was excellent. In addition, the effect of adding the phosphorus compound or the benzotriazole derivative was hardly seen.

Example 3 In order to examine the thermal stability of the product of the present invention, a shield tube test was conducted under the following conditions. That is, 10 g of the lubricating oil composition shown in Table 5 and Table 6 in which the water concentration was adjusted to 10 ppm or less in advance and 5 g of HFC134a were placed in a glass tube,
Iron, copper and aluminum were added as a catalyst and the tube was sealed. 1
After maintaining at 75 ° C. for 14 days, the appearance of the mixture of HFC134a and the lubricating oil composition and the presence or absence of deposits were examined. The appearance was evaluated by comparing the hue before the test with the hue after the test and dividing the color degree into four ranks of "none, a little, there is and dark". The results are shown in Tables 5 and 6.

[0096]

[Table 5]

[0097]

[Table 6]

Comparative Example 3 In the same manner as in Example 3, the thermal stability of the lubricating oil composition was examined. Table 7 shows the results.

[0099]

[Table 7]

In Nos. 7 and 13 of Example 3, in which the addition amount of the benzotriazole derivative was increased, although the coloring was slightly, there was no precipitate and there was no problem. In all of the other Examples 3, the appearance was good, and there was no precipitate and the heat stability was good. On the other hand, as shown in Nos. 7 to 10 of Comparative Example 3, the composition of the phosphorus compound and benzotriazole was strongly colored, and a deposit was also confirmed. It is considered that this is because benzotriazole has acidic hydrogen in the molecule, so that the interaction with the metal is too strong, which causes generation of precipitates and coloring. Further, from the results of Nos. 3, 11 and 12 of Comparative Example 3 in which the complex ester was used as the base oil, it was found that the hindered ester was superior to the complex ester in thermal stability. From the above, it was found that the refrigerator working fluid of the present invention in which the phosphorus compound and the benzotriazole derivative were used in combination was also excellent in the thermal stability test.

[0101]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a composition for a working fluid of a refrigerator, which is excellent in lubricity and wear resistance even when an ester having a specific structure with high polarity is used as a base oil. became.

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[Procedure amendment]

[Submission date] April 22, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0052

[Correction method] Change

[Correction contents]

The iodine value (Img / 100 g) of the ester used in the present invention is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and 3 or less from the viewpoint of thermal oxidation stability of the resulting lubricating oil composition. Is more preferable, and 1 or less is particularly preferable. The temperature of the two-phase separation of the ester used in the present invention from the hydrofluorocarbon at a low temperature is not particularly limited, but is preferably -10 ° C or lower,
The temperature is preferably 30 ° C or lower, more preferably -50 ° C or lower. The kinematic viscosity at 40 ° C. of the ester used in the present invention is not particularly limited, but from the viewpoint of compatibility with hydrofluorocarbons, 100 mm ² / s or less is preferable, usually 15 to 100 mm ² / s is preferable, and 30 to 7 are preferable.
5 mm ² / s is more preferable.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display section C10M 137: 02 137: 04 137: 12 133: 44 105: 38) C10N 30:06 30:08 40:30 ( 72) Inventor Toshiya Hagiwara 1334 Minato Minato, Wakayama City Kao Corporation Research Laboratory

Claims (10)

[Claims] 1. (a) General formula (1), (2) or (3): (In the formula, R ^{1 to} R ⁵ and R ^{7 to} R ⁹ may be the same or different, and are an aryl group having 6 to 18 carbon atoms,
A straight chain alkyl group having 1 to 18 carbon atoms, a branched chain alkyl group having 3 to 18 carbon atoms, a straight chain alkenyl group having 2 to 18 carbon atoms,
Alternatively, it represents a branched chain alkenyl group having 3 to 18 carbon atoms. However, at least one of R ^{1 to} R ³ has 6 to 18 carbon atoms.
At least one of R ⁴ and R ⁵ is an aryl group having 6 to 18 carbon atoms, and R ^{7 to} R 5
^At least one of ⁹ is an aryl group having 6 to 18 carbon atoms. R ⁶ is a hydrogen atom, a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group having 3 to 18 carbon atoms, or 2 to
It represents a linear alkenyl group having 18 carbon atoms or a branched alkenyl group having 3 to 18 carbon atoms. ) One or more phosphorus compounds selected from the group consisting of compounds represented by the following formulas: (b) General formula (4) (In the formula, R ¹⁰ represents a group having 0 to 20 carbon atoms containing a nitrogen atom and / or an oxygen atom, and X represents a hydrogen atom or a methyl group.),
(C) A base oil obtained from a C2-C10 divalent to hexavalent saturated aliphatic polyhydric alcohol and a C2-C10 linear or branched saturated aliphatic monocarboxylic acid or a derivative thereof. A composition for a working fluid of a refrigerator, which comprises an ester used as above, and (d) hydrofluorocarbon. 2. The benzotriazole derivative represented by the general formula (4), wherein R ¹⁰ represents a hydroxyl group or an amino group, or a group containing a hydroxyl group and / or an amino group. Composition for refrigerator working fluid. 3. A benzotriazole derivative represented by the general formula (4), wherein R ¹⁰ is The composition for a working fluid of a refrigerator according to claim 1 or 2, which is 4. The phosphorus compound represented by any one of formulas (1) to (3), wherein at least one of R ^{1 to} R ³ is
The composition for a working fluid of a refrigerator according to claim 1, wherein at least one of R ⁴ and R ⁵ and at least one of R ^{7 to} R ⁹ is any one of a phenyl group, a cresyl group and a xylenyl group. Stuff. 5. The phosphorus compound is one or more compounds selected from the group consisting of tricresyl phosphate, triphenyl phosphate, tricresyl phosphite, and triphenyl phosphite. A composition for a refrigerator working fluid as described above. 6. The ester comprises a divalent to hexavalent saturated aliphatic polyhydric alcohol having 5 to 10 carbon atoms and a linear or branched saturated aliphatic monocarboxylic acid having 5 to 9 carbon atoms or a derivative thereof. The composition for a refrigerator working fluid according to claim 1, which is an ester obtained. 7. The mixing ratio of ester, phosphorus compound and benzotriazole derivative and hydrofluorocarbon is hydrofluorocarbon / (ester + phosphorus compound + benzotriazole derivative) = 50/1 to 1/20.
It is (weight ratio), The composition for refrigerator working fluids in any one of Claims 1-6. 8. A phosphorous compound in an amount of 0.03 to 5.0 parts by weight and a benzotriazole derivative in an amount of 0.001 to 5.0 parts by weight with respect to 100 parts by weight of an ester. A composition for a working fluid of a refrigerator as described above. 9. The ratio of the phosphorus compound to the benzotriazole derivative is 0.001 to 2.0 mol of the benzotriazole derivative with respect to 1 mol of the phosphorus compound.
8. The composition for a working fluid of a refrigerator according to any one of 8 above. 10. The composition for refrigerator working fluid according to claim 1, wherein the hydrofluorocarbon contains at least difluoromethane (HFC32).