JP3387223B2 - Synthetic lubricating oil and refrigerator working fluid composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic lubricating oil, and more particularly to a synthetic lubricating oil used as a refrigerating machine oil for a refrigerator using non-chlorine Freon as a refrigerant. The present invention relates to a refrigerator working fluid composition.

[0002]

2. Description of the Related Art Conventionally, a compression type refrigerator has a CFC-11 (CCl ₃ F, trichlororom) as a refrigerant.
onfluoromethane), CFC-12
(CCl ₂ F ₂ , dichlorodifluorom
Ethane), HCFC-22 (CHClF ₂ , mo
nochlorodifluormethane),
_{CFC-115 (CF 3 -CClF 2} , monochl
CFC refrigerants such as oropentafluoroethane are used. However, chlorofluorocarbons such as CFC-12 are subject to regulation because they lead to the destruction of the ozone layer. Also, HCFC-22 is not subject to regulation at present because of its low ozone depleting ability, but its use is about to be regulated in the medium to long term.

As a substitute for these chlorofluorocarbons, non-chlorine CFCs are about to be used.
HFC with similar thermodynamic properties as an alternative to C-12
_{-134a (CH 2 FCF 3, 1,1,1,2} -tet
rafluoroethane) is likewise HCFC-
HFC-32 (CH ₂ F ₂ , diflu
Proposed is a mixed refrigerant containing oromethane).

Refrigerating machine oil has various required performances, but the compatibility with the refrigerant is extremely important in terms of the lubricating performance of the refrigerating machine and the efficiency of the system. However, HFC-134a
Non-chlorine-based CFC refrigerants such as HFC-32 and HFC-32 are chilled oils such as naphthene-based mineral oils, paraffin-based mineral oils, and alkylbenzenes that have been used as refrigerating machine oils in compression refrigeration systems. It is known that it shows almost no compatibility and causes two-layer separation at low and high temperatures. If two-layer separation occurs, the lubricating oil will accumulate in the condenser and expander, reducing the refrigeration efficiency, and the lubricating oil will not be supplied satisfactorily to the sliding surfaces of the compressor, resulting in poor lubrication. Since it causes inconvenience such as seizure of the compressor, it cannot withstand actual use.

[0005]

Under such circumstances, various lubricating oils which are compatible with a chlorine-free CFC refrigerant have been proposed. For example, US Pat. No. 4,755,316 proposes a polyoxyalkylene glycol-based lubricating oil having a specific molecular weight distribution and having hydroxyl groups at both ends. This is about -40 with HFC-134a.
Shows compatibility in the range of about ℃ to +50 ℃. However, in actual use, compatibility at a higher temperature is required.

On the other hand, HFC-134a is mainly intended for household refrigerators and car air conditioners, and HFC-32 is mainly intended for room air conditioners and industrial refrigerators. In the case of household refrigerators and room air conditioners, the motor that drives the compressor is mostly used in the refrigerant-refrigerating machine oil mixture, and the refrigerating machine oil is required to have excellent electrical insulation. However, the electric insulating property of polyoxyalkylene glycol is remarkably inferior to the conventional naphthene-based mineral oil and paraffin-based mineral oil, and also has high hygroscopicity. Therefore, it is unsuitable as refrigerator oil for household refrigerators and room air conditioners.

In WO90-12849, a polyol ester composed of a monovalent carboxylic acid and a polyvalent alcohol, and a complex ester composed of a monovalent carboxylic acid, a polyvalent carboxylic acid and a polyvalent alcohol are disclosed. It has been proposed as a lubricating oil for chlorine-free CFC refrigerants. The 41st Symposium on Macromolecules (September 1992: Sponsored by Japan Society of Polymer Science: Proceedings Vol. 41, No. 11, pages 4703-4705)
Then, a condensate of a monohydroxycarboxylic acid and a divalent neopentylpolyol and a polyol ester or complex ester derived from a monovalent carboxylic acid or a divalent carboxylic acid is a chlorine-free fluorocarbon refrigerant lubricating oil. Is proposed as.

In the case of these proposed ester compounds, the hygroscopicity is lower than that of polyoxyalkylene glycol, and HFC
-134a is also compatible with polyoxyalkylene glyco-
Better over a wider temperature range than Also, EP40
As described in No. 6,479-A1, the electrical insulating property has a volume resistivity of about 10 ¹³ to 10 ¹⁴ Ωcm at 80 ° C., which is a value that can be sufficiently used as a refrigerator oil such as a refrigerator or a room air conditioner. Have

In addition, refrigerating machine oil is required to have various viscosity grades depending on the type of refrigerating machine and the like.
SO viscosity grades of VG8 to VG320 have been used, but in the case of complex esters, the electrical insulation is good, and it is possible to obtain esters of various viscosity grades.

However, the above proposed ester compound is liable to hydrolyze in the presence of water, which may cause corrosion of the refrigeration system. In the case of a polyol ester, it is possible to suppress hydrolysis to the extent that there is no practical problem by using a branched fatty acid as the starting monovalent carboxylic acid. However, in the case of complex ester, lubricity and HFC are higher than those of polyol ester.
Good compatibility with -134a, but poor hydrolysis resistance. It is considered that this is because most of the polyvalent carboxylic acids that are industrially available are linear, and the site where the linear polyvalent carboxylic acid is bonded is easily hydrolyzed.

In addition, in the polyol ester and complex ester which have been proposed so far, HFC-134 is used.
Although the compatibility with “a” is satisfied to some extent, it cannot be said that the compatibility with the mixed refrigerant containing HFC-32 is sufficiently obtained.

Furthermore, the ester proposed at the 41st Symposium on Polymers uses a hydroxycarboxylic acid as one of the raw material components, and its molecular structure is an ester of divalent alcohol and monohydroxycarboxylic acid. In order to obtain a highly viscous ester, this unit is crosslinked with a divalent carboxylic acid to form a complex ester. Therefore, a high-viscosity ester is inferior in hydrolysis resistance like other complex esters. Further, when there is no cross-linking with a divalent carboxylic acid, it is difficult to obtain a high-viscosity ester having good compatibility with a non-chlorine CFC refrigerant.

From the above, the present invention provides HFC-13.
4A and HFC-32 and other non-chlorine CFC refrigerants have excellent compatibility in a wide temperature range, excellent electrical insulation and hydrolysis resistance, and can be used in a wide range of viscosity grades. It is an object of the present invention to provide a synthetic lubricating oil, and a refrigerating machine working fluid composition comprising the synthetic lubricating oil and the non-chlorine CFC refrigerant.

[0014]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, by using an ester synthesized from a specific raw material component as a lubricating base oil, chlorine-free The present invention has been completed, knowing that the above-mentioned various performances desired as a refrigerating machine oil for fluorocarbon refrigerants can be satisfied.

That is, the first aspect of the present invention is: a) a monovalent alcohol having 4 to 18 carbon atoms in which branched alcohol accounts for 50 mol% or more, or neopentylpolyol having 30 or less carbon atoms, b) Formula (1) (R ¹ and R ² are a hydrogen atom, a hydroxyl group, or a —CH ₂ OH group.
Is an alkyl group, and R ¹ and R ² are both hydrogen atoms.
Hydroxycarboxylic acid represented by Nalco not a), or
Or equation (2) (R ³ and R ⁴ are a hydrogen atom, a hydroxyl group or an alkyl group.
Yes, R ³ and R ⁴ are not both hydrogen atoms)
Any of 2-hydroxycarboxylic acid represented by
Derived from one or both condensates of a hydroxycarboxylic acid having an average degree of polymerization of 1.2 or more and c) a monovalent carboxylic acid having 4 to 18 carbon atoms in which a branched carboxylic acid accounts for 50 mol% or more. The present invention relates to a synthetic lubricating oil composed of ester.

The second aspect of the present invention is that a) a branched alcohol
Mono-alcohol having 4 to 18 carbon atoms or occupying 50 mol% or more, or neopentylpolyol having 30 or less carbon atoms
And b) formula (1) (R ¹ and R ² are a hydrogen atom, a hydroxyl group, or a —CH ₂ OH group.
Is an alkyl group, and R ¹ and R ² are both hydrogen atoms.
Hydroxycarboxylic acid represented by Nalco not a), or
Or equation (2) (R ³ and R ⁴ are a hydrogen atom, a hydroxyl group or an alkyl group.
Yes, R ³ and R ⁴ are not both hydrogen atoms)
Any of 2-hydroxycarboxylic acid represented by
Derived from one or both condensates of a hydroxycarboxylic acid having an average degree of polymerization of 1.2 or more and c) a monovalent carboxylic acid having 4 to 18 carbon atoms in which a branched carboxylic acid accounts for 50 mol% or more. It is composed of synthetic lubricating oil consisting of ester and non-chlorine Freon, and its weight ratio is 1: 99-9.
It relates to a refrigerator working fluid composition which is 9: 1.

In the present invention, either the monovalent alcohol or the neopentylpolyol as the component a may be used alone, or both may be used at the same time. When used at the same time, the ratio of the two can be arbitrarily selected.

The monovalent alcohol as the component a used in the present invention is required to have 4 to 18 carbon atoms, preferably 4 to 13 and more preferably 4 to 10. A monovalent alcohol having 3 or less carbon atoms adversely affects the hydrolysis resistance, and a monovalent alcohol having 19 or more carbon atoms reduces the compatibility with a chlorine-free CFC refrigerant.

The monovalent alcohol includes straight-chain monovalent alcohol and branched monovalent alcohol, of which the branched monovalent alcohol accounts for 50 mol% or more of the whole. Is necessary, preferably 70 mol% or more, more preferably 80 mol% or more, and further preferably 90 mol% or more. If the branched monovalent alcohol is less than 50 mol%, favorable results cannot be obtained in terms of hydrolysis resistance and compatibility with a chlorine-free fluorocarbon refrigerant.

As the straight-chain monovalent alcohol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1 -Decanol, 1-dodecanol, 1-tridecanol, 1
-Tetradecanol, 1-hexadecanol, 1-octadecanol and the like.

As the branched monovalent alcohol, 2-methyl-1-propanol, 2-methyl-2-propanol,
2-methyl-1-butanol, 2-ethyl-1-propanol, 2-methyl-1-pentanol, 2,2-dimethyl-1-butanol, 2-methyl-2-ethyl- 1-
Propanol, 2-methyl-1-hexanol, 2,2
-Dimethyl-1-pentanol, 2-methyl-2-ethyl-1-butanol, 1-isoheptanol, 2-ethyl-1-hexanol, 2,2-dimethyl-1-hexanol , 2-methyl-2-ethyl-1-pentanol,
1-isooctanol, 3,5,5-trimethyl-1-
Hexanol, 1-isononanol, 1-isodecanol
And isododecanol, isotridecanol, isotetradecanol, isohexadecanol and isooctadecanol.

From the viewpoint of heat resistance and oxidation stability, the hydroxyl group of the monovalent alcohol is preferably a primary hydroxyl group, and more preferably when the hydrogen atom is not bonded to the carbon atom at the 2nd position from the hydroxyl group. Is. In addition, the presence of a branch at the carbon atom at the 2-position with respect to the hydroxyl group is preferable from the viewpoint of obtaining good hydrolysis resistance. Further, from the viewpoint of compatibility with a chlorine-free CFC refrigerant, the alkyl group of the alcohol preferably has a methyl group or an ethyl group as a branched chain. From these facts, among the monovalent alcohols, the branched alcohol having two methyl groups or ethyl groups at the carbon atom at the 2-position counting from the hydroxyl group shows heat resistance, oxidation stability, hydrolysis resistance, It is especially excellent in terms of compatibility with chlorine-based CFC refrigerants.

Examples of the a-component neopentylpolyol used in the present invention include neopentyl glycol, 2,2-diethyl-1,3-propanediol, and 2-butyl-2-.
In addition to ethyl-1,3-propanediol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, etc., ditrimethylol-
Examples thereof include dehydrated condensates of neopentylpolyol represented by propane, tritrimethylolpropane, dipentaerythritol and tripentaerythritol. Regarding the dehydration condensate, the degree of condensation can be determined according to the viscosity required of the ester after synthesis.

This neopentylpolyol is required to have 30 or less carbon atoms, preferably 5 to
24, more preferably 5-18. When the number of carbon atoms is larger than 30, the compatibility with the chlorine-free fluorocarbon refrigerant decreases. Also, this neopentylpolyol has 2
Although those having a valence of 3 or more can be used, those having a valence of 3 or more are more preferable in terms of lubricity.

The hydroxycarboxylic acid condensate of component b used in the present invention is required to have an average degree of polymerization of 1.2 or more, preferably 1.5 to 20, more preferably 2.0.
~ 15. If the average degree of polymerization is less than 1.2, the lubricity is insufficient. The hydroxycarboxylic acid that constitutes this condensate includes 4-hydroxybutanoic acid, 4-hydroxy-2-methylbutanoic acid, 5-hydroxypentanoic acid,
3-hydroxy-2,2-dimethylpropanoic acid, 2,2
It is also possible to use dimethylolpropanoic acid, 2-hydroxyisobutanoic acid, and lactones and lactides which are dehydration condensation products thereof.

From the viewpoint of heat resistance and oxidative stability, the hydroxyl group of hydroxycarboxylic acid is preferably a primary hydroxyl group, and more preferably a hydrogen atom is not bonded to the carbon atom at the 2-position as viewed from the hydroxyl group. Also, from the viewpoint of hydrolysis resistance,
The hydroxycarboxylic acid preferably has an alkyl group, more preferably 2 adjacent to the carboxyl group carbon.
In this case, the carbon atom at the position has one or more alkyl groups. From the viewpoint of compatibility with a chlorine-free fluorocarbon refrigerant, the alkyl group of hydroxycarboxylic acid is particularly preferably a methyl group or an ethyl group.

Such a hydroxycarboxylic acid is represented by the formula (1) (R ¹ and R ² are a hydrogen atom, a hydroxyl group, a —CH ₂ OH group or an alkyl group, and neither R ¹ nor R ² is a hydrogen atom).
¹ , R ² is a methyl group, an ethyl group, a hydroxyl group, —CH ₂ OH
Those such as groups are preferred. In particular, a hydroxycarboxylic acid having a neopentyl skeleton is the most optimal, and good results are obtained in terms of heat resistance, oxidation stability, hydrolysis resistance, and compatibility with a chlorine-free CFC refrigerant. In addition, from the viewpoint of lubricity and low temperature fluidity, dihydroxycarboxylic acid is 10
It is desirable that the composition is such that the content is at least mol%, especially at least 20 mol%. As the dihydroxycarboxylic acid, 2,2-dimethylolpropanoic acid is particularly preferably used.

From the viewpoint of hydrolysis resistance, those having one or more branches at the carbon atom at the 2-position adjacent to the hydroxyl group of hydroxycarboxylic acid are preferable. Such a hydroxycarboxylic acid has the formula (2) (R ^3, R ⁴ is a hydrogen atom, a hydroxyl group or an alkyl group, R ³ and R ⁴ are not both be a hydrogen atom)
Among them, those in which R ³ and R ⁴ are a methyl group, an ethyl group, a hydroxyl group and the like are most preferable, and favorable results can be obtained in terms of hydrolysis resistance. For example, 2-hydroxybutanoic acid, 2-hydroxyisobutanoic acid, 2-
Examples thereof include hydroxypentanoic acid.

As described above, the hydroxycarboxylic acid condensate of the component b in the present invention is preferably a condensate of hydroxycarboxylic acid represented by the formula (1) and 2-hydroxy represented by the formula (2). Condensate of kilbonic acid,
Alternatively, a condensate of the hydroxycarboxylic acid represented by the formula (1) and the 2-hydroxykilbonic acid represented by the formula (2) can be used.

In the present invention, the proportion of the hydroxycarboxylic acid condensate used as the component b can be arbitrarily selected within a range that does not impair the various properties of the produced ester. It is preferable to use about 0.2 to 20 mol per 1 mol of the monovalent alcohol or neopentylpolyol.

The monovalent carboxylic acid as the component c used in the present invention is required to have 4 to 18 carbon atoms, preferably 4 to 13 and more preferably 4 to 10. When a monovalent carboxylic acid having 3 or less carbon atoms is used, hydrolysis resistance is adversely affected and corrosion resistance is enhanced, and when a monovalent carboxylic acid having 19 or more carbon atoms is used,
Compatibility with non-chlorine CFC refrigerant decreases.

The monovalent carboxylic acid of the component c includes straight chain 1
Carboxylic acids and branched monovalent carboxylic acids are included,
Of these, it is necessary that the branched monovalent carboxylic acid accounts for 50 mol% or more of the whole, preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more. When the content of the branched monovalent carboxylic acid is less than 50 mol%, preferable results cannot be obtained in terms of hydrolysis resistance and compatibility with a chlorine-free fluorocarbon refrigerant.

Examples of the linear monovalent carboxylic acid include, for example,
Examples thereof include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myriphosphoric acid, palmitic acid, stearic acid, and acid anhydrides thereof.

Examples of the branched monovalent carboxylic acid include 2-methylpropanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropanoic acid, 2-methylpentanoic acid, 3-methylpentanoic acid and 4-methyl. Pentanoic acid,
2,2-dimethylbutanoic acid, 2-ethylbutanoic acid, 3,
3-dimethylbutanoic acid, 2,2-dimethylpentanoic acid,
2-methyl-2-ethylbutanoic acid, 2,2,3-trimethylbutanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5 -Methylhexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 2- Propylpentanoic acid, isooctanoic acid,
2,2-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, isononanoic acid, neononanoic acid, 2,2-dimethyloctanoic acid, 2-methyl-2-
Ethylheptanoic acid, 2-methyl-2-propylhexanoic acid, isodecanoic acid, neodecanoic acid, isotridecanoic acid,
Examples thereof include isomyristic acid, isopalmitic acid, isostearic acid, and acid anhydrides thereof.

Among such branched monovalent carboxylic acids,
Those having a branched alkyl group at the carbon atom at the 2-position adjacent to the carboxyl group are preferred. From the viewpoint of compatibility with a chlorine-free CFC refrigerant, the branched alkyl group of the carboxylic acid is preferably a methyl group or an ethyl group.

In the present invention, the amount of the monovalent carboxylic acid as the component c used is within a range not hindering the various performances of the produced ester, and the monovalent alcohol or neopentylpolyol as the component a, and It can be appropriately determined according to the kind of the hydroxycarboxylic acid condensate of the component b.

The ester used in the present invention is the above ac.
It is obtained by reacting the components by a conventional method, which is used alone or as a naphthene-based mineral oil, paraffin-based mineral oil, poly α-olefin, alkylbenzene, ester other than the ester used in the present invention, and polyoxyalkylene glycol. It can be used as a lubricating oil for a chlorine-free fluorocarbon refrigerant by mixing with another lubricating oil such as a fluorinated oil typified by fluorine-containing polyether.

When the ester used in the present invention is mixed with these other lubricating oils, the proportion of the ester used in the present invention in the mixture is such as hydrolysis resistance and compatibility with a non-chlorine Freon refrigerant. It can be arbitrarily selected within a range not hindering the performance, but generally 10% by weight or more,
Preferably 30% by weight or more, more preferably 50% by weight
The above is preferable.

The synthetic lubricating oil of the present invention has a kinematic viscosity at 100 ° C. of 1 to 150 cSt (10 ^-6 m ² / s), preferably 1.5 to 100 cSt, more preferably 2 to 50 cSt.
It is St. If the kinematic viscosity is lower than 1 cSt, the lubrication performance is insufficient, and if the kinematic viscosity is higher than 150 cSt, the compatibility with the non-chlorine CFC refrigerant is decreased, which is not preferable.

The refrigerating machine working fluid composition of the present invention comprises a synthetic lubricating oil comprising an ester used in the present invention and a chlorine-free CFC as a refrigerant. Oil: Non-chlorine CFCs are generally
1:99 to 99: 1, preferably 5:95 to 70:30
It should be

Examples of the non-chlorine flon used in the refrigerator working fluid composition of the present invention include HFC-134a and HFC-3.
2, HFC-125 (1, 1, 1, 2, 2-pe
ntafluoroethane) or the like can be used. Any one of these or a mixture thereof can be appropriately selected depending on the application, cooling temperature, shape of the cooling device, and the like.

In order to further improve the performance of the synthetic lubricating oil and refrigerator working fluid composition of the present invention, conventionally known additives for refrigerator oils such as antioxidants, extreme pressure agents, and The metal deactivator and the like can be added alone or in combination of several kinds. The amount of these additives added is usually 10% by weight or less, preferably 5% by weight or less, based on the total amount of the refrigerating machine oil.

[0043]

INDUSTRIAL APPLICABILITY The synthetic lubricating oil of the present invention is excellent in electrical insulation and hydrolysis resistance, and there are lubricating oils having various viscosities in a wide range. Further, the synthetic lubricating oil of the present invention and HFC-1
The refrigerating machine working fluid composition of the present invention comprising non-chlorine-based CFCs represented by 34a, HFC-32, and HFC-125 exhibits good compatibility in a wide temperature range.

[0044]

EXAMPLES Next, the present invention will be specifically described with reference to Examples.

Example A-1 Preparation of Hydroxycarboxylic Acid Condensate In a 1-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser, 3-hydroxy-2,2 was added. -Dimethylpropanoic acid 236.3 g
(2 mol), 2,2-dimethylolpropanoic acid 536.
6 g (4 mol) and 3.4 g (0.018 mol) of p-toluenesulfonic acid monohydrate as an esterification catalyst were charged, and nitrogen was blown at a flow rate of 300 cm ³ / min to appropriately measure the acid value. The reaction was carried out at 120 to 150 ° C. When the acid value of the reaction product reached 305 mgKOH / g, the flask was cooled and the reaction was completed. At this time, the produced water collected in the water separator was 36 ml, and the average degree of polymerization of the hydroxycarboxylic acid condensate obtained from the acid value was 1.5.

Production of ester In a 2-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser, 52.9 g (0.6 g) of 2-methyl-1-butanol was added. Mol) and 280.8 g (2.4 mol) of isoheptanol, and a hydroxycarboxylic acid condensate 5 having an average degree of polymerization of 1.5
51.9 g (3 mol), 2-methylbutanoic acid 245 g
(2.4 mol), 468.7 g of isoheptanoic acid (3.6
Mol) and 6.02 g (0.032 mol) of p-toluenesulfonic acid monohydrate as an esterification catalyst,
200 ° C while blowing nitrogen at a flow rate of 300 cm ³ / min
The reaction was allowed to proceed for 22 hours while removing the distilled water.

In the above esterification reaction, a
Component (monovalent alcohol consisting of 2-methyl-1-butanol and isoheptanol): Component b (hydroxycarboxylic acid condensate): Component c (monovalent consisting of 2-methylbutanoic acid and isoheptanoic acid) The carboxylic acid) molar ratio is 1:
It was 1: 2. The composition ratio of 2-methyl-1-butanol and isoheptanol in the component a was 20:80.
(Equivalent%), the composition ratio of 2-methylbutanoic acid and isoheptanoic acid in the c component was 40:60 (equivalent%).

After the reaction, in order to remove unreacted acid and low-boiling substances, distillation was performed under reduced pressure (10 mmHg) at 200 ° C. for 8 hours. The product, which is the residue of distillation, was neutralized with a 10% by weight aqueous solution of potassium hydroxide, washed with water, and then under reduced pressure (1
It was dehydrated at 90 ° C for 1 hour. In addition, activated clay 2
After adding 0 g and stirring at 70 degreeC for 1 hour, it filtered and obtained the ester of acid value 0.04 mgKOH / g. Table 1 shows the contents of each component, the ratio of components a / b / c, and the acid value of the obtained ester.

Examples A-2 to A-38 3-hydroxy-2,2-dimethylpropanoic acid, 2,2
In the same manner as in Example A-1, the molar ratio of dimethylolpropanoic acid and 2-hydroxyisobutanoic acid was changed as shown in Tables 1 to 5 to give a hydroxycarboxylic acid condensate having the average degree of polymerization shown in the same table. Obtained. The component b consisting of this condensate, the component a consisting of monovalent alcohol or neopentyl alcohol shown in the same table, and the component c consisting of the monovalent carboxylic acid shown in the same table are shown in the same table. The esters shown in Tables 1 to 5 were obtained in the same manner as in Example A-1 using the same molar ratio.

Comparative Examples B-1 to B-3 3-hydroxy-2,2-dimethylpropanoic acid and 2,2
The molar ratio with dimethylolpropanoic acid was changed as shown in Table 6, and a hydroxycarboxylic acid condensate having the average degree of polymerization shown in the same table was obtained in the same manner as in Example A-1. The component b consisting of this condensate, the component a consisting of the monovalent alcohol shown in the same table, and the component c consisting of the monovalent carboxylic acid shown in the same table were used in the molar ratios shown in the table. Esters shown in Table 6 were obtained in the same manner as in A-1. Comparative Example B-
The esters obtained in 1 and B-3 are examples in which the carbon number of the monovalent alcohol of the component a and the carbon number of the monovalent carboxylic acid of the component c are outside the scope of the present invention, and Comparative Example B The ester obtained in -2 is an example in which the proportion of the branched alcohol used in the monovalent alcohol as the component a and the proportion of the branched carboxylic acid used in the monovalent carboxylic acid as the component c are outside the scope of the present invention. .

Comparative Example B-4 2-ethyl-1-hexanol (512.8 g, 4) was placed in a 2-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser. Mol), 3-
Hydroxy-2,2-dimethylpropanoic acid 472.5 g
(4 mol), 520.8 g (4 mol) of isoheptanoic acid and 4.56 g (0.024 mol) of p-toluenesulfonic acid monohydrate as an esterification catalyst were added, and nitrogen was added to 3
The reaction was carried out for 22 hours at 200 ° C. while removing the distilled water while blowing at a flow rate of 00 cm ³ / min. In this esterification reaction, 2-ethyl-1-hexanol (1
The molar ratio of (valent alcohol): 3-hydroxy-2,2-dimethylpropanoic acid (hydroxycarboxylic acid): isoheptanoic acid (monovalent carboxylic acid) was 1: 1: 1.
Thereafter, the same treatments as in Example A-1 were carried out to obtain the esters shown in Table 6.

Comparative Example B-5 Into a 2-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser, neopentyl glycol 416.6 g (4 mol), 2 -576.8 g (4 mol) of ethylhexanoic acid, 631.2 g (4 mol) of 3,5,5-trimethylhexanoic acid and p-toluenesulfonic acid monohydrate 4.5 as an esterification catalyst.
Add 6 g (0.024 mol) and add nitrogen to 300 cm ³ /
The reaction was carried out at 200 ° C. for 15 hours while removing the distilled water while blowing at a flow rate of minutes. In this esterification reaction, the molar ratio of neopentyl glycol: (monovalent carboxylic acid of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid) was 1: 2. The composition ratio of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid was 50:50 (equivalent%). Thereafter, the same treatments as in Example A-1 were carried out to obtain the esters shown in Table 6.

Comparative Examples B-6 to B-9 The types and compositions of neopentylpolyol and monovalent carboxylic acid were changed as shown in Table 6, and the same ester as obtained in Comparative Example B-5 was used. Shown in the table.

Comparative Example B-10 In a 2-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser, 429.4 g (3.2 mol) of trimethylolpropane was added. -Ethylhexanoic acid 415.4 g (2.88 mol), 3,
45,5 g of 5,5-trimethylhexanoic acid (2.88)
Mol), adipic acid 280.6 g (1.92 mol), and p-toluenesulfonic acid monohydrate 5.7 g (0.030 mol) as an esterification catalyst were added, and nitrogen was added to 300
The reaction was carried out at 200 ° C. for 15 hours while removing the distilled water while blowing at a flow rate of cm ³ / min. In this esterification reaction, trimethylolpropane: (1-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid
The molar ratio of (carboxylic acid): adipic acid was 5: 9: 3. The composition ratio of 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid and adipic acid is 30: 3.
It was 0:40 (equivalent%). Then, the same treatment as in Example A-1 was performed to obtain complex esters shown in Table 7. In the same table, polyvalent carboxylic acid was used as the d component.

Comparative Examples B-11 and B-12 The types and compositions of neopentylpolyol, monovalent carboxylic acid and polyvalent carboxylic acid were changed as shown in Table 7 in the same manner as Comparative Example B-10. The obtained complex ester is shown in the same table.

Comparative Examples B-13 to B-15 3-hydroxy-2,2-dimethylpropanoic acid and 2,2
In the same manner as in Example A-1, the molar ratio with dimethylolpropanoic acid was changed to obtain a hydroxycarboxylic acid condensate having the average degree of polymerization shown in the same table. Component b consisting of this condensate and neopentylpolyol shown in the table.
Example A-1 using the component a consisting of
The ester shown in Table 7 was obtained in the same manner as in. The esters obtained in Comparative Examples B-13 and B-14 are examples in which the carbon number of the monovalent carboxylic acid as the component c is outside the range of the present invention.
The ester obtained in Comparative Example B-15 is an example in which the proportion of the branched carboxylic acid used in the monovalent carboxylic acid as the component c is outside the range of the present invention.

Comparative Example B-16 A 2-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser was charged with 312.5 g (3 mol) of neopentyl glycol and 3 mol. -Hydroxy-2,2-dimethylpropanoic acid 354.4 g (3 mol), isoheptanoic acid 390.6 g (3 mol), 2-ethylhexanoic acid 432.6 g (3 mol) and p-toluenesulfonic acid as an esterification catalyst. Monohydrate 5.16
g (0.027 mol) was added and the reaction was carried out for 22 hours at 200 ° C. while distilling water was removed while blowing nitrogen at a flow rate of 300 cm ³ / min. In this esterification reaction, neopentyl glycol: 3-hydroxy-2,
The molar ratio of 2-dimethylpropanoic acid: (monovalent carboxylic acid of isoheptanoic acid and 2-ethylhexanoic acid) is 1:
It was 1: 2. The composition ratio of isoheptanoic acid and 2-ethylhexanoic acid was 50:50 (equivalent%). Then, the same treatment as in Example A-1 was carried out to obtain the esters shown in Table 7.

Comparative Example B-17 In a two-liter four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer and a water separator equipped with a condenser, neopentyl glycol 384.6 g (3.8 mol) was added. , 2, 2
-Dimethylolpropanoic acid 509.7 g (3.8 mol), isoheptanoic acid 296.4 g (2.3 mol),
26,8 g of 3,5,5-trimethylhexanoic acid (1.
7 mol), 124.9 g (0.86 mol) of adipic acid and 5.42 g (0.028 mol) of p-toluenesulfonic acid monohydrate as an esterification catalyst were added, and nitrogen was added to 3 mol.
The reaction was carried out for 22 hours at 200 ° C. while removing the distilled water while blowing at a flow rate of 00 cm ³ / min. In this esterification reaction, neopentyl glycol: 2,2-
Dimethyl propanoic acid: (isoheptanoic acid and 3,5,5)
The molar ratio of 5-trimethylhexanoic acid to monocarboxylic acid): adipic acid was 10: 10: 14: 3.
The composition ratio of isoheptanoic acid, 3,5,5-trimethylhexanoic acid and adipic acid was 40:30:30 (equivalent%). Then, the same treatment as in Example A-1 was performed to obtain complex esters shown in Table 7.

In Tables 1 to 7, the abbreviations of the components used in Examples and Comparative Examples are as follows.

<Monovalent alcohol of component a> bC4: 2-methyl-1-propanol bC5: 2-methyl-1-butanol bC6: 2-ethyl-1-butanol bC7: Isoheptanol bC8: 2-ethyl-1-hexanol bC9: 3,5,5-trimethyl-1-hexanol bC10: 1-isodecanol bC13: 1-isotridecanol bC14: Isotetradecanol bC18: Isooctadecanol bC20: isoeicosanol nC3: 1-Propanol nC4: 1-butanol nC7: 1-heptanol nC8: 1-octanol

<A-component neopentylpolyol> NPG: Neopentyl glycol TMP: trimethylolpropane PE: Pentaerythritol DTMP: Ditrimethylol propane DPE: Dipentaerythritol TPE: Tripentaerythritol

<Raw material of hydroxycarboxylic acid condensate of component b> HC5: 3-hydroxy-2,2-dimethylpropanoic acid DHC5: 2,2-dimethylolpropanoic acid 2HC4: 2-hydroxyisobutanoic acid

<Monovalent carboxylic acid of component c> bC4: 2-methylpropanoic acid bC5: 2-methylbutanoic acid bC6: 2-ethylbutanoic acid bC7: Isoheptanoic acid bC8: 2-ethylhexanoic acid bC9: 3,5,5-trimethylhexanoic acid bC10: Isodecanoic acid bC13: Isotridecanoic acid bC14: isomyristic acid bC18: isostearic acid bC20: isoarachidic acid nC3: propanoic acid nC4: butanoic acid nC6: Hexanoic acid nC8: octanoic acid

<Polyvalent carboxylic acid> 2C4: succinic acid 2C6: adipic acid 2C10: sebacic acid

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[0068]

[Table 4]

[0069]

[Table 5]

[0070]

[Table 6]

[0071]

[Table 7]

The performance of the esters obtained in Examples A-1 to A-38 and Comparative Examples B-1 to B-17 as a refrigerator lubricating oil was measured in the following manner. The results are shown in Tables 8-11.

<Kinematic viscosity> The kinematic viscosity is 40 ° C. and 100 ° C.
It was measured at. (JIS K 2283)

<Pour Point> The pour point was measured. (JIS
K 2269)

<Electrical Insulation> The volume resistivity was measured at 80 ° C. (JIS C 2101)

<Compatibility> 20 parts by weight of sample (0.6 g)
And a chlorine-free fluorocarbon refrigerant [HFC-134a and mixed refrigerant (HFC-32: HFC-125: HFC-134
a = 23: 25: 52)] 80 parts by weight (2.4 g) are enclosed in a thick-walled pyrex tube (total length 300 mm, outer diameter 10 mm, inner diameter 6 mm) cooled in an ethanol bath containing dry ice. Then, the temperature was raised and cooled at a rate of 1 ° C./min, and the two-layer separation temperature at high temperature and low temperature was visually measured in the range of −70 ° C. to + 80 ° C.

<Hydrolysis resistance> Into a hard glass ampoule having a capacity of 6 ml, 5 ml of a sample having a water content adjusted to 1,500 ± 300 ppm was injected. Headspace inside ampoule
After replacing the nitrogen gas in the sputum site and sealing the tube, 300 at 150 ° C
Heated for hours. After the test was completed, the package was opened and the acid value of the sample was measured.

<Abrasion resistance (lubricity)> ASTM D-2
According to 670, 150 HFC-134a in the sample
The Falex abrasion test was performed while blowing at a rate of ml / min. The sample temperature was set to 100 ° C., a running operation was carried out for 1 minute under a load of 150 pounds, and then an operation under a load of 250 pounds was carried out for 2 hours, and the wear amount of the pin after the operation was measured.

Tables 9 and 11 also show the results of measurement of the lubricating oils of the following samples C-1 to C-3 as commercially available refrigerating machine oils as reference examples. C-1: Polyoxyalkylene glycol (ISO viscosity grade: VG56) C-2: Mineral oil type refrigeration oil (ISO viscosity grade: VG56)
32) C-3: Alkylbenzene refrigerating machine oil (ISO viscosity grade: VG46)

[0080]

[Table 8]

[0081]

[Table 9]

[0082]

[Table 10]

[0083]

[Table 11]

From the results shown in Tables 8 to 11, the ester used in the synthetic lubricating oil of the present invention has a wide viscosity range, a pour point of -25 ° C or lower, and a compatibility range of HFC-.
134a is -30 ℃ or less on the low temperature side, + 80 ℃ on the high temperature side.
As described above, the mixed refrigerant containing HFC-32 is -20 on the low temperature side.
Over a wide temperature range of not higher than + 80 ° C on the high temperature side and + 80 ° C on the high temperature side, the volume resistivity is as large as 10 ¹³ to 10 ¹⁴ Ωcm, and the acid value increase of the sample after the hydrolysis resistance test is small.

As described above, the synthetic lubricating oil of the present invention is excellent in electric insulation and hydrolysis resistance, and further, the working fluid composition of the refrigerator of the present invention comprising the synthetic lubricating oil of the present invention and a non-chlorine Freon. The product exhibits very good compatibility in a wide temperature range and a wide viscosity range of the synthetic lubricating oil of the present invention, and has extremely excellent properties.

Continuation of front page (56) Reference JP-A-55-123695 (JP, A) JP-A-55-145638 (JP, A) JP-A-48-43003 (JP, A) JP-A-55-58297 (JP , A) JP 5-1291 (JP, A) JP 5-5098 (JP, A) JP 5-179267 (JP, A) JP 5-179268 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C10M 105/32-105/46 C10N 40:30 C09K 5/04

Claims (3)

(57) [Claims] 1. A) monovalent alcohol having 4 to 18 carbon atoms, or neopentylpolyol having 30 or less carbon atoms, wherein the branched alcohol accounts for 50 mol% or more, and b) the formula (1). (R ¹ and R ² are a hydrogen atom, a hydroxyl group, or a —CH ₂ OH group.
Is an alkyl group, and R ¹ and R ² are both hydrogen atoms.
Hydroxycarboxylic acid represented by Nalco not a), or
Or equation (2) (R ³ and R ⁴ are a hydrogen atom, a hydroxyl group or an alkyl group.
And R ³ and R ⁴ are not both hydrogen atoms)
Either one of the 2-hydroxycarboxylic acid
Or a condensate of both, which is a hydroxycarboxylic acid condensate having an average degree of polymerization of 1.2 or more, and c) a monovalent carboxylic acid having 4 to 18 carbon atoms in which the branched carboxylic acid accounts for 50 mol% or more. Synthetic lubricating oil consisting of ester. 2. A) monovalent alcohol having 4 to 18 carbon atoms, or neopentylpolyol having 30 or less carbon atoms, wherein the branched alcohol accounts for 50 mol% or more, and b) the formula (1). (R ¹ and R ² are a hydrogen atom, a hydroxyl group, or a —CH ₂ OH group.
Is an alkyl group, and R ¹ and R ² are both hydrogen atoms.
Hydroxycarboxylic acid represented by Nalco not a), or
Or equation (2) (R ³ and R ⁴ are a hydrogen atom, a hydroxyl group or an alkyl group.
And R ³ and R ⁴ are not both hydrogen atoms)
Either one of the 2-hydroxycarboxylic acid
Or a condensate of both, which is a hydroxycarboxylic acid condensate having an average degree of polymerization of 1.2 or more, and c) a monovalent carboxylic acid having 4 to 18 carbon atoms in which the branched carboxylic acid accounts for 50 mol% or more. A refrigerating machine working fluid composition comprising a synthetic lubricating oil composed of an ester and a non-chlorine CFC and having a weight ratio of 1:99 to 99: 1. 3. A non-chlorine flon is HFC-134a.
(1,1,1,2-tetrafluoroethane
e), HFC-32 (difluoromethan)
e) or HFC-125 (1,1,1,2,2-pe
The refrigerator working fluid composition according to claim 2 , wherein the refrigerator working fluid composition is a ntafluoroethane).