JP2931417B2 - Lubricating oil for refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating oil for a refrigerator using 1.1.1.2-tetrafluoroethane refrigerant, which has excellent compatibility with the refrigerant, low hygroscopicity, thermal stability, and The present invention relates to a lubricating oil for refrigerators having excellent lubricity.

[0002]

2. Description of the Related Art Conventionally, as a refrigerant for a refrigerator, R11 (CCl ₃ F) is mainly used for a cooling machine such as a building, and R12 (CC
l ₂ F ₂ ) is used as a refrigerant for car air conditioners such as electric refrigerators, rotary types and reciprocating types, but stratospheric ozone depletion has recently become a social issue, and the development of alternative CFCs is urgent. .

Recently, as an alternative to R11, R123 (CF ₃ CHC
l ₂ ) has been studied, but it has the problems of high price and no toxicity test. On the other hand, as an alternative to R12, R22 (CHClF ₂ ) has begun to be studied due to its ease of decomposition. However, since the boiling point is low, the operating pressure at room temperature is high, and the hardware is required to have pressure resistance, and packing is required. There is a problem that leakage occurs from the section, the hose section, and the like, and a problem that electrical insulation is poor.

On the other hand, like R22, 1.1.1.2-tetrafluoroethane (R134a) which is known as a substitute for R12
Does not contain chlorine, which in its structure affects ozone depletion,
It has passed acute and subacute toxicity tests, and its use is beginning to attract attention.

[0005]

The lubricating oil for refrigerators generally has a wide range of compatibility temperature with the refrigerant (compatibility), that is, has no fogging at high temperature (the solvability of the refrigerant to the lubricating oil is low). Large), the molecular polarity of the lubricating oil is large, and there is no precipitation of the lubricating oil at low temperatures (the solubility of the lubricating oil in the refrigerant is large, and the molecular weight of the lubricating base oil is small). In addition, various types of refrigerators have different suitable viscosity ranges, and are required to have viscosities and flash points corresponding to the respective ranges.

An object of the present invention is to provide a lubricating oil suitable for a refrigerator using 1.1.1.2-tetrafluoroethane refrigerant.

[0007]

The lubricating oil for a refrigerator according to the present invention is a lubricating oil for a refrigerator using 1.1.1.2-tetrafluoroethane refrigerant. viscosity range of the 2mm ² / s ~30mm ² /
s , the total acid value is 0.05 mg KOH / g or less .

Further, the base oil is an ester of an aliphatic polyhydric alcohol and a fatty acid, or a partial ester of an aliphatic polyhydric alcohol and a fatty acid.

Further, the base oil is a diester of an aliphatic monohydric alcohol and an aliphatic dibasic acid.

[0010] The base oil is a diester of an aliphatic monohydric alcohol and an aromatic dibasic acid.

Further, the lubricating oil for a refrigerator according to the present invention is characterized in that an ester having a viscosity different from that of the base oil is mixed with the base oil,
Alternatively, a polymer selected from polyesters of polyalkyl methacrylate, polyalkylene glycol, neopentyl glycol and fatty acid is added.

Hereinafter, the refrigerating machine oil of the present invention will be described.

First, the organic carboxylic acid ester which is the base oil in the refrigerator oil of the present invention uses the following organic carboxylic acid ester having a high molecular polarity.

(1) First, polyesters of an aliphatic polyhydric alcohol and a linear or branched fatty acid can be used.

The aliphatic polyhydric alcohols forming the polyesters include trimethylolpropane, ditrimethylolpropane, trimethylolethane, ditrimethylolethane, pentaerythritol, dipentaerythritol, and tripentaerythritol. Can use those having 3 to 12 carbon atoms. Preferred fatty acids are propionic acid, butyric acid, valeric acid,
Hexanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, isovaleric acid, neopentanoic acid, 2-methylbutyric acid,
2-ethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2′-dimethyloctanoic acid, 2-butyloctanoic acid and the like.

Further, partial esters of an aliphatic polyhydric alcohol and a linear or branched fatty acid can also be used.

As the aliphatic polyhydric alcohol, trimethylolpropane, ditrimethylolpropane, trimethylolethane, ditrimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol and the like can be used. Fatty acids have 3 to 9 carbon atoms, such as propionic acid, butyric acid, valeric acid,
Hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, 2-
Examples include methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2′-dimethyloctanoic acid, and 2-butyloctanoic acid.

As esters of these aliphatic polyhydric alcohols and linear or branched fatty acids, particularly, pentaerythritol, dipentaerythritol, and tripentaerythritol have 5 to 12 carbon atoms, more preferably 5 to 12 carbon atoms. 7 fatty acids such as valeric acid, hexanoic acid, heptanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2 ′
The ester oils formed by -dimethyloctanoic acid, 2-butyloctanoic acid or mixtures thereof can improve the compatibility with refrigerants, especially at low temperatures.

These partial esters can be obtained by appropriately adjusting the number of moles of the aliphatic polyhydric alcohol and the fatty acid to be reacted.

(2) Neopentyl glycol as an aliphatic polyhydric alcohol and a linear or branched fatty acid having 6 to 9 carbon atoms, for example, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, 2-ethylbutyric acid, Diesters with 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid and the like can also be used.

(3) Aliphatic polyhydric alcohol and C3-C3
9 partial esters with a linear or branched fatty acid;
Complex esters with linear or branched aliphatic dibasic acids or aromatic dibasic acids can also be used.

Examples of such aliphatic polyhydric alcohols include trimethylolpropane, trimethylolethane,
Pentaerythritol, dipentaerythritol and the like can be used.

The fatty acids having 3 to 12 carbon atoms include propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid,
2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2'-dimethyloctanoic acid, 2-butyloctanoic acid, and the like can be used.

In this complex ester, it is preferable to use a fatty acid having 5 to 7 carbon atoms, more preferably 5 to 6 carbon atoms. Can improve the compatibility.

As such a fatty acid, valeric acid, hexanoic acid, isovaleric acid, 2-methylbutyric acid, 2-ethylbutyric acid or a mixture thereof is used.
Fatty acids obtained by mixing the above components at a weight ratio of 10:90 to 90:10 can be suitably used.

The aliphatic dibasic acids used for esterification with polyhydric alcohols together with this fatty acid include succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid and dodecane acid. Diacid,
It is preferable to use tridecandioic acid, carboxyoctadecanoic acid, carboxymethyloctadecanoic acid, docosanedioic acid, etc. Also, as the aromatic dibasic acid, phthalic acid, isophthalic acid, and as the aromatic tribasic acid, trimellitic acid, aromatic Examples of the tetrabasic acid include pyromellitic acid.

The ratio of the fatty acid to the aliphatic dibasic acid or aromatic dibasic acid, aromatic tribasic acid or aromatic tetrabasic acid is preferably 6: 1 (molar ratio). In this case, the ratio of the total amount of the fatty acid and the aliphatic dibasic acid or the aromatic dibasic acid to the amount of the aliphatic polyhydric alcohol to be used is preferably 7: 1 (molar ratio).

In the esterification reaction, first, a polyhydric alcohol and an aliphatic dibasic acid or an aromatic dibasic acid are reacted at a predetermined ratio to partially esterify, and then the partially esterified product is reacted with a fatty acid. The lubricating oil for refrigerators of the present invention may be prepared, the reaction order of the acids may be reversed, or the acids may be mixed and subjected to esterification.

(4) A linear or branched dialkyl ester of an aliphatic dibasic acid (having 16 to 22 carbon atoms) may be used.

Examples of the aliphatic dibasic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, tridecandioic acid, carboxyoctadecanoic acid and carboxymethyloctadecane. Acids, docosandioic acids and those having properties equivalent to these are exemplified. Preferred aliphatic dibasic acids are succinic acid, adipic acid, sebacic acid, undecandioic acid, dodecandioic acid, carboxyoctadecanoic acid, carboxymethyloctadecanoic acid and the like.

The alcohol component is an alcohol having 5 to 8 carbon atoms, specifically, amyl alcohol, hexyl alcohol, heptyl alcohol and octyl alcohol, and isomers thereof, preferably isoamyl alcohol, isohexyl alcohol. And octyl alcohol.

Specifically, dioctyl adipate, di-
Isoheptyl adipate, dihexyl sebacate, diheptyl succinate and the like.

(5) Dialkyl esters of aromatic dibasic acids (having 18 to 26 carbon atoms) can also be used.

The aromatic dibasic acid includes phthalic acid, isophthalic acid and the like, and the alcohol component in the dialkyl ester has 5 carbon atoms.
-8 alcohols, such as amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, and isomers thereof. Preferred alcohols include isoamyl alcohol, isoheptyl alcohol, and octyl alcohol. The aromatic diester includes dioctyl phthalate, diisoheptyl phthalate, diisoamyl phthalate and the like.

(6) As alcohol components, trihydric alcohols such as monohydric alcohol, glycerin, and trimethylolpropane selected from methanol, ethanol, propanol, butanol and the isomers thereof, and ethylene oxide, propylene oxide, 1 mol to 1 mol of alkylene oxide selected from butylene oxide, amylene oxide and the like, and isomers thereof
0 mol, preferably 1 to 6 mol of adduct is used.

As the organic carboxylic acid ester, an alkylene oxide adduct of a monohydric alcohol is prepared by adding adipic acid,
Pimelic acid, suberic acid, azelaic acid, sebacic acid,
There are diesters obtained by esterification with an aliphatic dibasic acid such as undecandioic acid, dodecandioic acid, carboxyoctadecanoic acid, carboxymethyloctadecanoic acid, docosantioic acid, or an aromatic dibasic acid such as phthalic acid.

Further, alkylene oxides of polyhydric alcohols such as glycerin and trimethylolpropane are 1 to 10
The molar adduct is converted to a linear or branched fatty acid having 3 to 12 carbon atoms such as propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, 2-methyl acid Hexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid,
Esters obtained by esterification with 2,2'-dimethyloctanoic acid, 2-butyloctanoic acid or the like can be used.

As the fatty acid constituting the above-mentioned organic carboxylic acid ester, a linear or branched fatty acid can be used. When a branched fatty acid is used, the hydrolysis stability is improved and the hermetic coil is used. And so on.

Next, a method for purifying an organic carboxylic acid ester will be described.

The organic carboxylic acid esters can be obtained by a conventional esterification reaction in which an alcohol and a fatty acid are esterified in the presence of an acid catalyst, for example, phosphoric acid. The ester has a total acid value of 0.1 to 0.5 mg KOH / g, a peroxide value of 0.1 to 5 meq./Kg, and an aldehyde value of 0.1 to 5 mg KOH / g.
g, bromine number index 1-100mg / 100g, ash content 5-50pp
m and a water content of 300 to 1000 ppm are obtained.

However, if the total acid value of the lubricating oil for refrigerators is high, problems such as corrosion of metal parts occur, and the lubricating oil for refrigerators themselves is hydrolyzed, thereby functioning as lubricating oil for refrigerators. In addition, since a refrigerator or the like generally has a motor portion disposed in a lubricating oil and thus requires a high insulating property, the lubricating oil for refrigerators has a total acid value of 0.1. It should be less than 05mg KOH / g.

Further, the peroxide value, the aldehyde value and the bromine value index are kept low to further enhance the stability of the refrigerant, and the ash content is suppressed to suppress sludge and the like. In addition, it is necessary to suppress the water content for insulation.

Therefore, the above-mentioned esters obtained by a usual esterification reaction are purified, and the index indicating the above-mentioned properties of the ester oil is adjusted to a range suitable for the refrigerating machine oil, thereby obtaining a more excellent refrigerating machine oil. be able to.

The purification of the organic carboxylic acid ester may be carried out by contact treatment with silica gel, activated alumina, activated carbon, zeolite or the like. The contact conditions at this time may be appropriately determined according to various situations, but it is preferable that the temperature be 100 ° C. or less.

[0045] are those generally as a refrigeration lubricant in a refrigerator viscosity at 100 ° C. of ^{2mm 2 / s ~9mm 2 / s} , preferably ^{3mm 2 / s ~7mm 2 / s} , also in a car air conditioner the refrigeration lubricant 7mm ² / s ~30mm
^It is good to use ² / s. For car air conditioners, 7mm ² / s ~ for reciprocating compressors
15 mm ² / s, preferably ^{8mm 2 / s ~11mm 2 / s} , 15mm 2 / s ~3 in rotary type compressors
0 mm ² / s, preferably an ester oil having a viscosity range of 20mm ² / s ~27mm ² / s is preferably used.

The lubricating oil for refrigerators of the present invention has a viscosity range of 2
but is of ^{mm 2 / s ~30mm 2 / s} , only even low viscosity in the high compatibility with the refrigerant at a high temperature is less than 2 mm ² / s, lubricity, sealing properties can be used poor In addition, heat stability is also low, so that it is not preferable. If it exceeds 30 mm ² / s, compatibility with the refrigerant decreases, which is not preferable.

Further, even within this range, the viscosity range of use differs depending on the model used as described above. For refrigerators, if the viscosity exceeds 9 mm ² / s, the friction loss in the sliding portion becomes large. There's a problem.

Further, in a car air conditioner of a reciprocating type, if it is less than 7 mm ² / s, there is a problem of lubricity, and
^If it exceeds ² / s, there is a problem that the friction loss in the sliding portion is large, and in the case of a rotary type air conditioner, if it is less than 15 mm ² / s, there is a problem of sealing properties,
If it exceeds 0 mm ² / s, there is a problem of compatibility with the refrigerant.

Therefore, the organic carboxylic acid ester may be used alone, but in order to adjust the viscosity range according to the above-mentioned various uses, it is preferable to use the organic carboxylic acid ester in combination as appropriate.

For example, when the complex type organic carboxylic acid ester of the above (3) has a high viscosity, it is necessary to maintain the compatibility with the refrigerant and adjust the viscosity to the required viscosity as a refrigerating machine oil. An ester oil of an aliphatic polyhydric alcohol and a fatty acid having 3 to 9 carbon atoms having a viscosity at 100 ° C. of 6 mm ² / s or less can be added to adjust the viscosity range according to the application.

As another method for obtaining a viscosity suitable for lubricating oil for refrigerators, a polymer capable of maintaining compatibility with a refrigerant may be added to an organic carboxylic acid ester oil to adjust the viscosity. . The polymer has a viscosity at 100 ° C of 10 mm ² /
s or more are preferred.

Examples of such a polymer include polyalkyl methacrylates (for example, when the alkyl group has 4 to 8 carbon atoms).
), Polyalkylene glycol (for example, polypropylene glycol, or a copolymer composed of a polyethylene glycol component and a polypropylene glycol component, a copolymer composed of a polypropylene glycol component and a polytetramethylene glycol component), neopentyl glycol and a fat Polyester with aromatic dibasic acid, represented by the following formula

[0053]

Embedded image

And the like.

The amount of the polymer to be added is not particularly limited as long as an ester oil having a desired viscosity can be obtained.
Usually, it can be in the range of 1% by weight to 99% by weight.

The refrigerating machine oil of the present invention may contain a sulfur-based antiwear agent.

As such an antiwear agent, a compound represented by the general formula (RO) ₃ P = S (where R is an alkyl group, an allyl group, or a phenyl group;
They may be the same or different. ), And specifically, a sulfur-based antiwear agent such as trialkyl phosphorothionate, triphenyl phosphorothionate, or alkyl diallyl phosphorothionate may be used.

Also, diphenyl sulfide, diphenyl disulfide, di-n-butyl sulfide, di-n-butyl disulfide, di-tert-dodecyl disulfide, di-ter
Sulfides such as t-dodecyl trisulfide, sulfurized fats such as sulfurized palm oil and sulfurized dipentene, thiocarbonates such as xanthic disulfide, primary alkyl zinc thiophosphate, secondary alkyl zinc thiophosphate, alkyl -Zinc thiophosphate-based wear inhibitors such as zinc allyl thiophosphate and zinc allyl thiophosphate can be used.

The wear inhibitor is used in an amount of 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the ester oil.

The above-mentioned abrasion inhibitors may be used alone or in combination of two or more.

Examples of the antioxidant include amine antioxidants such as dioctyldiphenylamine, phenyl-α-naphthylamine, alkyldiphenylamine and N-nitrosodiphenylamine, 2.6-di-t-butylparacresol, 4.4′-. A phenolic antioxidant such as methylenebis (2.6-di-t-butylphenol), 2.6-di-t-butyl-α-dimethylamine paracresol, 2.6-di-t-butylphenol, tris (2 .4-
It is preferable to use a phosphorus-based antioxidant such as di-t-butylphenyl) phosphite, trisnonylphenylphosphite, triphenylphosphite, and the like, and its use ratio is preferably 0.01 to 10% by weight based on the base oil. Is preferably used in an amount of 0.01 to 1.0% by weight.

Examples of the corrosion inhibitor include isostearate, n-octadecyl ammonium stearate, duomine T-diolate, lead naphthenate, sorbitan oleate, pentaerythritol oleate, oleyl sarcosine, alkyl succinic acid, alkenyl succinic acid , And derivatives thereof, and the like, in an amount of 0.001 to 1.0% by weight, preferably 0.01 to 0.
It is better to use 5% by weight.

As an antifoaming agent, silicone is preferably used, and its use ratio is from 0.0001 to 0.1 with respect to the base oil.
003% by weight, preferably 0.0001 to 0.001% by weight.

As the metal deactivator, for example, benzotriazole, benzotriazole derivative, thiadiazole, thiadiazole derivative, triazole, triazole derivative, dithiocarbamate and the like may be used. 0.01% by weight to 1%
0% by weight, preferably 0.01% to 1.0% by weight may be used.

Further, as a rust preventive, for example, succinic acid, succinic acid ester, oleic acid tallow amide, barium sulfonate, calcium sulfonate and the like are preferably used.
The use ratio is preferably 0.01% by weight to 10% by weight, and more preferably 0.01% by weight to 1.0% by weight.

[0066]

At present, a high viscosity polyether synthetic oil has been developed as a lubricating oil for a refrigerator, but the operating temperature of the refrigerator oil is usually -30 to 100 ° C. -When mixed with a tetrafluoroethane refrigerant, the reason is not clear, but there are problems such as phase separation at high temperature, hygroscopicity and lubricity.

It is important that the refrigerating machine oil has good compatibility with the refrigerant, and it is required that the oil does not separate from the refrigerant at high or low temperature and does not react. Poor compatibility with the refrigerant causes problems such as burning of hardware in a high-temperature portion of the refrigerator.

The present inventors have found that organic carboxylic acid esters and
It has been found that it has good compatibility with 1.1.1.2-tetrafluoroethane, is thermally and chemically stable, and has excellent lubricity. Moreover, refrigerating machine oil car air, are used in a refrigerator or the like, as a refrigeration lubricant viscosity at 100 ° C. as the refrigeration lubricant is ^{2mm 2 / s ~9mm 2 / s} , in the car air conditioner in the refrigerator 7mm ² / s ~
30 mm ² / s of can be used esters of viscosity, in 7mm ² / s ~15mm ² / s rotary-type compressor also in reciprocating type compressor in a car air conditioner of 15mm ² / s ~30mm ² / s Ester oils in the viscosity range are preferably used.

Accordingly, the lubricating oil for refrigerators of the present invention can be prepared by selecting an ester having a suitable viscosity range, mixing an ester having a different viscosity range with the base oil while maintaining compatibility with the refrigerant, or mixing the polymer with the base oil. It has been found that a lubricating oil suitable for various refrigerators can be obtained by adding it.

Hereinafter, the present invention will be described with reference to Examples.
First, a method for evaluating the refrigerating machine oil employed in the examples will be described.

(Compatibility test method) A sample oil and a refrigerant (1.1.1.2-tetrafluoroethane) were collected in a glass tube so that the sample oil / refrigerant was 3% by weight and 10% by weight to a total of 2 ml. Mix. A glass tube is placed in a thermostat having a heating device and a cooling device, and the separation temperature of the sample oil and the refrigerant is measured.

(Test Method for Hygroscopicity) A sample oil was placed in a desiccator containing water, and the hygroscopicity with time at room temperature and 95% humidity was measured.

[0073]

EXAMPLE 1 Sample Oil 1, dioctyl adipate oil sample 2 is an ester of pentaerythritol and C ₅ -C ₉ fatty acids, C ₅ components 30% by weight of C ₅ -C ₉ fatty acids, C ₇ component 40 wt%, which consist of C ₉ component 30 wt%, pentaerythritol and C ₅ ~
1 and C ₉ fatty acid in a molar ratio: which is reacted at a ratio of 4, the sample oil 3 is a ester of dipentaerythritol and C ₅ -C ₇ fatty acid, C ₅ components in the C ₅ -C ₇ fatty acid 30 wt%, C ₆ component 60 wt%, which consist of C ₇ component 10 wt%, 1 and dipentaerythritol and C ₅ -C ₇ fatty acid in a molar ratio: 6 ratio of those reacted, sample Oil 4 is dihexyl succinate, sample oil 5
Has a molar ratio of dipentaerythritol to oleic acid of 1:
It is an ester obtained by reacting in step 6.

Table 1 shows the performance evaluation results as a refrigerating machine oil when various ester oils were added to 1.1.1.2-tetrafluoroethane.

[0075]

[Table 1]

[0076] As can be seen from Table 1, sample oil 1-3 good compatibility with the refrigerant, and hygroscopicity is low, it can be seen that that can be used as the base oil in the refrigeration lubricant, viscosity of 2 mm ² / It can be seen that sample oil 4 less than s has low thermal stability, and sample oil 5 has high thermal stability but low compatibility.

[0077]

Example 2 Sample oil 6 was composed of dipentaerythritol and C
₅ -C ₆ esters of fatty acids, C ₅ components 30% by weight of C ₅ -C ₆ fatty acids, which consist of C ₆ components 70 wt%, dipentaerythritol and C ₅ -C
₆ fatty acids reacted at a molar ratio of 1: 6,
Sample oil 7, an ester of pentaerythritol and C ₅ -C ₆ fatty acids, C ₅ in C ₅ -C ₆ fatty acid
Component 50% by weight, which consists of C ₆ components 50 wt%, and pentaerythritol and C ₅ -C ₆ fatty acids in a molar ratio of 1: obtained by reacting at a ratio of 4, the sample oil 8, and pentaerythritol an ester of C ₅ -C ₇ fatty acid, C ₅ components 30% by weight of C ₅ -C ₇ fatty acid,
C ₆ component 40 wt%, which consist of C ₇ component 30 wt%, 1 to pentaerythritol and C ₅ -C ₇ fatty acid in a molar ratio: which is reacted at a ratio of 4, the sample oil 9,
An ester of tripentaerythritol and C ₅ -C ₆ fatty acids, C ₅ component 40 in C ₅ -C ₆ fatty acid
Wt%, which consist of C ₆ components 60 wt%, a molar ratio of 1 and tripentaerythritol and C ₅ -C ₆ fatty acids: those reacted in 8 ratio of the sample oil 10, pentaerythritol and C ₇ an ester of -C ₉ fatty acids, C ₇ component 50 wt% in the C ₇ -C ₉ fatty acids, C
₉ is made of a component 50 wt%, 1 to pentaerythritol and C ₇ -C ₉ fatty acids in a molar ratio: which is reacted at a ratio of 4, the sample oil 11 mixed alcohols of trimethylol propane and pentaerythritol and an ester of a C ₅ fatty acid, those mixing ratio of trimethylolpropane and pentaerythritol are 50:50 (weight ratio), the sample oil 12, pentaerythritol and C ₅
An ester of -C ₆ fatty acids, C ₅ components 40% by weight of C ₅ -C ₆ fatty acids, which consist of C ₆ components 60 wt%, a molar ratio of pentaerythritol and C ₅ -C ₆ fatty acid in 1: obtained by reacting at a ratio of 4, the sample oil 13 is an ester of trimethylolpropane and C ₈ -C ₁₂ fatty acid, trimethylolpropane and C ₈ ~
1 and C ₁₂ fatty acids in a molar ratio: which is reacted at a ratio of 3, sample oil 14 is an ester of a fatty acid having a carbon number of trimethylolpropane and C ₈ or higher, trimethylolpropane and C ₈ or higher Reacted with a fatty acid having a carbon number of 1: 3 in a molar ratio of 1: 3, sample oil 15
It is a trimethylolpropane (C ₈ ~C ₁₂₎ fatty acid +
Complex ester with adipic acid, sample oil 16
, The ester component and the sample oil 15 is the same, is obtained by different mixing ratio of the C ₈ -C ₁₂ fatty acids and adipic acid.

With respect to these sample oils, the viscosity (mm ² / s) at 100 ° C. and the refrigerant compatibility at high and low temperatures (oil separation temperature) at an oil content of 10% were measured. It is shown in the table.

[0079]

[Table 2]

As can be seen from the above table, the sample oils 6 to 12 have excellent compatibility with the refrigerant at both high and low temperatures and can be used as a base oil in lubricating oil for refrigerators. It can be seen that oil 13 to sample oil 16 have poor compatibility with the refrigerant.

[0081]

Embodiment 3 The following table shows an example in which the sample oils of Embodiments 1 and 2 are used in combination.

[0082]

[Table 3]

As described above, although the sample oil 10 and the sample oil 2 themselves have poor low-temperature compatibility with the refrigerant, the sample oils 6 and
It can be seen that when the sample oil 12 is used as a base oil and mixed and used, it becomes compatible with the refrigerant and the viscosity can be adjusted.

[0084]

Example 4 Sample oils 17, 18, and 19 were prepared by adding viscosity 1 to sample oil 2.
A 3.0 mm ² / s (100 ° C.) polyalkylene glycol was added in varying amounts and lubricating oils for refrigerators were prepared and tested for compatibility with refrigerants and hygroscopicity.

The results are shown in the table below.

[0086]

[Table 4]

As can be seen from the table, sample oils 17-19
Shows good compatibility with the refrigerant and low hygroscopicity.

[0088]

Embodiment 5 Next, a case where a branched carboxylic acid is used as an organic carboxylic acid ester in a refrigerator lubricating oil will be described.

Sample oil 20 obtained by reacting pentaerythritol and 2-ethylbutyric acid at a ratio of 1: 4 (molar ratio) Sample oil 21 was prepared by mixing pentaerythritol and 2-ethylhexanoic acid at a ratio of 1: 4 (molar ratio). The sample oil 22 was prepared by reacting pentaerythritol and isononanoic acid at a molar ratio of 1: 4. Table 5 shows that 1.1.1.2-tetrafluoroethane was added to each of these organic carboxylic acids. The performance evaluation result as a refrigerating machine oil when ester and sample oil 2 are added is shown.

[0090]

[Table 5]

As can be seen from the table, the sample oils 20 to 22 have good compatibility with the refrigerant, low hygroscopicity, and excellent hydrolysis stability.

The hydrolysis stability was as follows: 250 ml of oil, aluminum and copper wires (inner diameter 8 mm, length 30 mm) as catalysts, and water 10 ml in an iron container having an inner volume of 350 ml.
After adding 40 ppm of Freon 134a as a refrigerant and heating at 175 ° C. for 20 days, the oil was taken out.
The total acid value was measured by the JIS K 2501 neutralization value test method.

[0093]

Example 6 A shield tube test at a high temperature was performed on a compatible material obtained by mixing 1.1.1.2-tetrafluoroethane refrigerant with the sample oil 2 of Example 1.

The test method (shield tube test) is as follows.
First, 1 g of sample oil 2 and 1 g of 1.1.1.2-tetrafluoroethane were sealed in a glass tube, and test pieces (shape: diameter 1.7 mm, length 40 mm) of iron, copper, and aluminum as metal pieces were each sealed. Then, at a temperature of 175 ° C, 14
Heated for days (336 hours). After the test, the degree of discoloration of the sample oil was measured and the state of the metal piece was observed.

Further, the following additives were blended with the above sample oil 2,
Further, a similar test was conducted on a mixed solution mixed with 1.1.1.2-tetrafluoroethane refrigerant, and as an evaluation of lubricity, SR
The V vibration friction wear test was performed under the following conditions.

As additives, a metal deactivator benzotriazole (BTA) 0.1% by weight, an antioxidant 2.6-
0.5% by weight of di-t-butylparacresol (DBPC) or tricresyl phosphate (TC)
P) was added at 0.5% by weight.

Test conditions for SRV vibration friction wear test Specimen: 10 mmφ steel ball (SUJ2) / aluminum plate (A390) Oil temperature: 140 ° C. Stroke: 1.25 mm Load: 50 N Frequency: 15 Hz Time: 30 minutes The results are shown in Tables 6 and 7.

[0098]

[Table 6]

[0099]

[Table 7]

The compatible solution of the refrigerator lubricating oil and the 1.1.1.2-tetrafluoroethane refrigerant according to the present invention has little hue deterioration after the test, little generation of the sludge after the test, and the test piece of the test piece after the test. It can be seen that the appearance is good, the chemical and thermal stability is excellent, and the lubricity is also excellent.

[0101]

The lubricating oil for refrigerators of the present invention has excellent compatibility with refrigerants, low moisture absorption, and heat resistance as lubricating oils for refrigerators using 1.1.1.2-tetrafluoroethane refrigerant as an alternative Freon. Lubricating oil with excellent properties and lubricity.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 20:02 30:00 30:08 40:30 (72) Inventor Hideki Kosaka 1-3-3 Nishitsurugaoka, Oimachi, Iruma-gun, Saitama No. 1 Tonen Co., Ltd. (72) Inventor Kenji Ashibe 1-3-1, Nishitsurugaoka, Oi-machi, Iruma-gun, Saitama 1st Tonen Co., Ltd. (56) References JP 555-155093 ) "ASHHRE Winter Meeting in January 1989" Abstracts, p. 211-216 (58) Field surveyed (Int. Cl. ⁶ , DB name) C10M 105/32 C10M 169/04 C10M 129/68 C10N 40:30 CA (STN) WPI / L (QUESTEL)

Claims (5)

(57) [Claims] 1. A lubricating oil for a refrigerator using 1.1.1.2-tetrafluoroethane refrigerant, comprising an organic carboxylic acid ester as a base oil and a viscosity range at 100 ° C. of 2 mm ² / s.
~30mm ² / s, the refrigeration lubricant, wherein the total acid number is less than 0.05 mg KOH / g. 2. The lubricating oil for a refrigerator according to claim 1, wherein the base oil is an ester of an aliphatic polyhydric alcohol and a fatty acid or a partial ester of an aliphatic polyhydric alcohol and a fatty acid. 3. The lubricating oil for a refrigerator according to claim 1, wherein the base oil is a diester of an aliphatic monohydric alcohol and an aliphatic dibasic acid. 4. The lubricating oil for a refrigerator according to claim 1, wherein the base oil is a diester of an aliphatic monohydric alcohol and an aromatic dibasic acid. 5. The method according to claim 1, wherein the base oil is mixed with an ester having a viscosity different from that of the base oil, or a polymer selected from polyesters of polyalkyl methacrylate, polyalkylene glycol, neopentyl glycol and fatty acid is added. The lubricating oil for a refrigerator according to claim 1, wherein: