KR20090102701A - Refrigerating machine oil for refrigerant - Google Patents

Abstract

PURPOSE: Cooling base oil for a refrigerant is provided, which enables to stably operate a refrigerating system for a long term without damage of instrument or the part of the refrigerating system. CONSTITUTION: Cooling base oil for a refrigerant contains a monoester as a main component. The monoester is indicated as the chemical formula. The cooling base oil for a refrigerant has the dynamic viscosity of less than 7mm^2/s at 40 deg.C. In the chemical formula, R1 shows the hydrocarbon radical of the carbon number 5-9, R2 shows the hydrocarbon radical of the carbon number 8-10, and the sum of the carbon number of R1 and R2 are 13-17.

Description

Refrigerating Machine Oil For Refrigerant

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant oil for refrigerants, which can be suitably used in a refrigerant compression refrigeration cycle apparatus using a refrigerant having a low ozone depletion coefficient or a global warming coefficient such as a chlorine-containing hydrogen-containing fluorocarbon refrigerant and a hydrocarbon refrigerant.

In addition, the present invention relates to a refrigerator oil having a low viscosity excellent in energy saving, a working fluid for a refrigerator, and a refrigerator using the same.

Conventionally, refrigerant compression type refrigeration cycle apparatuses used in refrigerators, air conditioners, refrigerators, and the like have a fluorocarbon containing fluorine and chlorine as constituent elements, for example, R-11 (trichloro) which is chlorofluorocarbon (CFC). Lomonofluoromethane), R-12 (dichlorodifluoromethane), and hydrochlorofluorocarbon (HCFC) R-22 (monochlorodifluoromethane), but have been used in connection with recent ozone layer destruction problems. Its production and use are regulated internationally, and hydrogen-containing fluorocarbon refrigerants which currently do not contain chlorine, for example difluoromethane (R-32), tetrafluoroethane (R-134 or R-134a). And hydrocarbon refrigerants that do not contain halogen atoms having a small greenhouse effect, such as ethane, propane, butane, isobutane, and the like.

The present inventors have proposed a refrigerant oil for refrigerants comprising a ester oil using a polyhydric alcohol such as polyol as a refrigerant oil for refrigerants used in these refrigerants (Patent Document 1). Thereby, the effect which prevents generation | occurrence | production of an oligomer (polymeric substance) when the lower hydrocarbon refrigerant etc. were used for a working fluid was obtained. However, in recent years, further energy saving is required for a refrigerator, an air conditioner, a refrigerator, and the like, and an energy saving type refrigeration oil having a low viscosity is also required for the freezer oil.

Patent Document 2 discloses that any kind of fatty acid polyol ester is low in viscosity and excellent in lubricity. However, in order to lower the viscosity with fatty acid polyol esters, the number of fatty acids must be 5 or less, and the hydrolytic stability is significantly reduced.

In addition, Patent Document 3 below proposes a refrigerator oil containing at least one of aliphatic saturated branched carboxylic acid monoalkyl esters as a refrigerator oil having low viscosity and excellent hydrolysis stability, and also a mixture of this ester and a fatty acid polyol ester. Is disclosed. However, the combination of aliphatic saturated branched carboxylic acid monoalkyl ester and fatty acid polyol ester is innumerable, and has low viscosity, excellent lubricity, high flash point, excellent safety, and satisfactory hydrolytic stability. It was very difficult to find.

[Patent Document 1] Japanese Patent Laid-Open No. 2007-254713

[Patent Document 2] Japanese Patent Application Laid-Open No. 2007-248020

[Patent Document 3] Republished Patent Publication WO00 / 68345

As described above, in a refrigerator using a hydrogen-containing fluorocarbon refrigerant that does not contain chlorine or a hydrocarbon refrigerant that does not contain a halogen atom having a low greenhouse effect, a lubricant having a low viscosity may be used to improve energy saving. Although it is effective to use it as refrigeration oil, so-called mineral oil-based refrigeration oil based on paraffinic mineral oil or naphthenic mineral oil has a problem that the flash point is lowered and the risk in handling is increased. On the other hand, when esters using polyhydric alcohols such as polyols are used as base oils, fatty acids having a low carbon number should be used. However, in this structure, the stability is remarkably reduced, and corrosion by fatty acids generated during decomposition is also concerned.

SUMMARY OF THE INVENTION The present invention solves the above problems, and an object of the present invention is to use a low-viscosity, low-viscosity, hydrogen-containing fluorocarbon refrigerant that does not contain chlorine or a hydrocarbon refrigerant that does not contain a halogen atom with a low greenhouse effect. It is to provide a refrigerant oil for refrigerant having excellent safety and stability.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to achieve the said objective, the present inventors found that the refrigeration oil which made the specific monoester as a base oil the main component, or contains the polyol ester further contains the chlorine-containing hydrogen-containing fluorocarbon refrigerant | coolant or hydrocarbon. The present invention has been found to have a low viscosity, good lubricity and energy saving properties, high hydrolysis stability in refrigerants, and excellent lubricating oil for refrigerant compression type refrigeration cycle apparatus, that is, refrigerant oil for refrigerants. .

That is, this invention is the refrigerant oil for refrigerants as follows.

(1) A refrigerant oil for refrigerant containing a monoester represented by the following formula (1) as a main component and having a kinematic viscosity at 40 ° C of less than 7 mm ² / s.

In the formula, R ¹ represents a hydrocarbon group having 5 to 9 carbon atoms, R ² represents a hydrocarbon group having 8 to 10 carbon atoms, R ¹ and R ² may each be branched or straight chain, and R ¹ and R ² The sum is 13 to 17.

(2) The refrigerant oil for refrigerant according to (1), further comprising a polyol ester.

(3) The monoester according to (2) is a monoester of an aliphatic monoalcohol having 8 carbon atoms and a monovalent fatty acid having 8 carbon atoms, and the polyol ester is 2-ethylhexanoic acid and / or 3,5,5-trimethylhexane A refrigerant oil for refrigerants, which is at least one of polyol esters of acids and neopentyl polyols having 5 to 10 carbon atoms.

(4) The refrigerant oil for refrigerant according to (3), which comprises 75 to 95% by mass of the monoester and 5 to 25% by mass of at least one of the polyol esters.

(5) The refrigerator oil according to (4), wherein the kinematic viscosity at 40 ° C is 2 to 4 mm ² / s, the flash point is 130 ° C or more, the acid value is 0.1 mgKOH / g or less, and the volume resistivity at 25 ° C is 10 GΩm or more.

(6) The refrigerant oil for refrigerant according to (3), which contains 25 to 40 mass% of monoester and 60 to 75 mass% of one or more kinds of polyol esters.

(7) The refrigerator oil of (6), wherein the kinematic viscosity at 40 ° C is 4 to 7 mm ² / s, the flash point is 130 ° C or more, the acid value is 0.1 mgKOH / g or less, and the volume resistivity at 25 ° C is 10 GΩm or more.

(8) The refrigerator oil according to any one of (4) to (7), wherein the monoester is an ester of n-octyl alcohol and 2-ethylhexanoic acid.

(9) The refrigerator oil according to any one of (4) to (7), wherein the polyol ester is neopentyl glycol-di-2 ethylhexanoic acid ester or pentaerythritol-tetra-2 ethylhexanoic acid ester.

(10) The refrigerator oil of (8), wherein the polyol ester is neopentylglycol-di-2 ethylhexanoic acid ester or pentaerythritol-tetra-2 ethylhexanoic acid ester.

(11) The refrigerator oil according to (10), wherein 0.01 to 1% by mass of an acid trapping agent containing a compound having an epoxy ring or a carbodiimide compound is added.

(12) The refrigerator oil according to (10), wherein 1 to 100 ppm by mass of a metal deactivator having a benzotriazole structure is added.

(13) The refrigerator oil according to (10), wherein 0.01 to 1% by mass of an oily agent having two or more hydroxyl groups in the molecule is added.

(14) The refrigerator oil according to (10), wherein 1 to 100 ppm by mass of one or more antifoaming agents selected from silicone oil, silicone oil whose terminal is modified with polyalkylene glycol or ester, or fluorinated silicone oil is added.

(15) Operation for refrigerators containing the refrigerator oil according to any one of (4) to (7) and (10) to (14) and at least one hydrocarbon refrigerant selected from ethane, propane, butane, or isobutane. Fluid.

(16) A working fluid for a refrigerator, comprising the refrigerator oil according to (8) and at least one hydrocarbon refrigerant selected from ethane, propane, butane or isobutane.

(17) A working fluid for a refrigerator, comprising the refrigerator oil according to (9) and at least one hydrocarbon refrigerant selected from ethane, propane, butane, or isobutane.

(18) The hermetic compressor comprising a working fluid for a refrigerator according to (15), a hermetic compressor for compressing the fluid, a condenser for condensing the refrigerant, an expansion mechanism for expanding the refrigerant, and an evaporator for evaporating the refrigerant. Is provided with a motor having a rotor and a stator, and the motor is provided with an insulating film of any one of polyethylene terephthalate, polybutylene terephthalate, polyamideimide-coated polyester, polyphenylene sulfide and polyether ether ketone. The stator is provided with a winding coated with an enamel material having a glass transition temperature of 120 ° C. or higher.

(19) a working fluid for a refrigerator according to (16) or (17), a hermetic compressor for compressing the fluid, a condenser for condensing the refrigerant, an expansion mechanism for expanding the refrigerant, and an evaporator for evaporating the refrigerant; The closed compressor includes a motor having a rotor and a stator, and the motor includes any one of polyethylene terephthalate, polybutylene terephthalate, polyamideimide-coated polyester, polyphenylene sulfide, and polyether ether ketone. A refrigerator having an insulation film and having a winding coated on the stator with an enamel material having a glass transition temperature of 120 ° C. or higher.

(20) The refrigerator according to (18), wherein the hermetic compressor is a reciprocating motion.

(21) The refrigerator according to (19), wherein the hermetic compressor is a reciprocating motion.

According to the present invention, there is provided a refrigerant oil for refrigerant having low viscosity and excellent stability, which is used for a hydrogen-containing fluorocarbon refrigerant containing no chlorine or a hydrocarbon refrigerant containing no halogen atom having a low greenhouse effect. Made it possible. Therefore, the effect on the environment such as global warming is small, low viscosity, excellent energy saving property, excellent lubricity, high flash point, high safety, and also satisfies hydrolysis stability and oxidation stability. It can be effective. In addition, the working fluid for a refrigerator of the present invention using such a refrigerator oil exhibits the effect of stably operating the refrigeration system for a long time without damaging each device or component of the refrigeration system. In addition, the freezer using the freezer oil has an effect that can be operated stably for a long time while saving energy.

The present invention will be described in detail.

The present invention is a refrigerant oil for a refrigerant containing a monoester represented by the following formula (1) as a main component, the kinematic viscosity at 40 ℃ less than 7 mm ² / s.

<Formula 1>

In formula (1), R ¹ represents a hydrocarbon group of 5 to 9 carbon atoms, R ² represents a hydrocarbon group of 8 to 10 carbon atoms, R ¹ and R ² may be branched or straight chain, respectively, and R ¹ and R ² The total number of carbon atoms is 13 to 17.

The refrigerant oil for the refrigerant of the present invention can be preferably used together with a refrigerant not containing chlorine and furthermore a refrigerant not containing halogen. That is, the refrigerant oil for the refrigerant of the present invention does not contain chlorine and has a hydrogen-containing fluorocarbon refrigerant having a low ozone depletion coefficient, for example, difluoromethane (R-32), tetrafluoroethane (R-134 or R). -134a) or a hydrocarbon refrigerant containing no halogen and having a low ozone depletion coefficient and a global warming coefficient, for example, ethane (R170), propane (R290), butane (R600), isobutane (R600a), and the like. It can use suitably as a refrigerator used for the.

In the present invention, the monoester used as the main component of the refrigerant oil for refrigerant is represented by the following formula (1).

<Formula 1>

In the formula, R ¹ represents a hydrocarbon group having 5 to 9 carbon atoms. The hydrocarbon group may have an unsaturated bond, but is preferably a saturated hydrocarbon group from the viewpoint of chemical stability. In addition, although R ¹ may be a hydrocarbon group in which an alkyl group and an aromatic ring or a naphthenic ring are combined, a linear or branched alkyl group is particularly preferable. R ² represents a hydrocarbon group having 8 to 10 carbon atoms. R ² , like R ¹ , may have an unsaturated bond, and may also be a hydrocarbon group in which an alkyl group, an aromatic ring or a naphthenic ring are combined, and a linear or branched alkyl group is particularly preferable. When the carbon number of R ² is less than 8, the ester viscosity of the obtained product is too low to cause poor lubricity, the flash point is lowered, and the risk of handling increases, and when it exceeds 10, the energy saving effect Will not be obtained.

Moreover, when the sum total of carbon number of R <^1> and R <^2> is 13-17, and if the sum total of carbon number is less than 13, there exists a problem that a viscosity falls too much and it lacks lubricity, and also flash point falls and handling risk increases. It is not preferable because it occurs. Moreover, when the sum total of carbon number exceeds 17, a viscosity will become high and the problem that the energy saving effect in a compressor will run short will arise. In addition, when the number of carbon atoms of R ¹ is less than 5, monovalent fatty acids (carboxylic acids) having stronger acid strength are generated as the number of carbon atoms becomes smaller when hydrolysis is used, which is harmful since it may damage the surrounding equipment materials. Not.

Such monoesters used in the present invention can be synthesized by esterifying monohydric fatty acids (carboxylic acids) having 6 to 10 carbon atoms and monohydric alcohols having 8 to 10 carbon atoms, as can be seen from the general formula (1). In this invention, it does not limit the manufacturing method of a monoester, It can also synthesize | combine using the chloride, carboxylic anhydride, etc. of monovalent fatty acid as a compound corresponded to monovalent fatty acid, and also the alkoxyl group and acyl of a monoester. The group can be synthesized using a transesterification reaction in which the group is exchanged with another alkoxyl group or acyl group.

In the present invention, monovalent fatty acids which can be preferably used for the synthesis of the monoester of the formula (1) include hexanoic acid, heptanoic acid, n-octanoic acid, isooctanoic acid, 2-ethylhexanoic acid, 1-methylheptanoic acid, 2 -Methylheptanoic acid, 2-propylpentanoic acid, dimethylcyclohexanoic acid, nonanoic acid, 3,5,5-trimethylhexanoic acid, decanoic acid, and among these, octanoic acid or 2-ethylhexanoic acid having 8 carbon atoms desirable.

In the present invention, monohydric alcohols which can be preferably used for the synthesis of the monoester of the formula (1) include n-octyl alcohol, isooctyl alcohol, 1-methylheptanol, 2-methylheptanol, 2-propylpentanol, Dimethyl cyclohexanol, 2-ethylhexanol, and decanol are mentioned, Among these, a C8 octanol or 2-ethylhexanol is preferable.

In addition, the monoester obtained from a monovalent fatty acid having 8 carbon atoms and a monohydric alcohol having 8 carbon atoms can achieve low viscosity, increase the flash point, and is particularly excellent in hydrolysis stability.

Since the monoester used in the present invention constitutes the main component of the refrigerant oil for refrigerant, it is preferable that the kinematic viscosity at 40 ° C is less than 7 mm ² / s as in the refrigerant oil for refrigerant. More preferably, it is less than 6 mm <^2> / s, More preferably, it is 2-5 mm <^2> / s. If it exceeds 7 mm ² / s, the energy saving effect is not obtained. The kinematic viscosity and the flash point are not necessarily proportional, but when the kinematic viscosity is low, the flash point is usually low. Although refrigeration oil is often used in a closed system, the flash point is rarely a problem. However, in order to ensure safety during handling before being filled in the freezer, the flash point is preferably 120 ° C or higher. More preferably, it is 130 degreeC or more, Especially preferably, it is 140 degreeC or more.

In another embodiment of the present invention, a polyol ester of 2-ethylhexanoic acid and / or 3,5,5-trimethylhexanoic acid and neopentylpolyol having 5 to 10 carbon atoms is used. By mix | blending predetermined amount of this polyol ester with the predetermined amount of the said monoester, it can be matched with desired kinematic viscosity, and hydrolysis stability can be improved.

A neopentyl polyol is a divalent or more alcohol which has a structure of neopentane, and uses a C5-C10 thing in this invention. If the carbon number exceeds 10, it is difficult to adjust the kinematic viscosity, and the compatibility with the refrigerant deteriorates. Neopentyl glycol, trimethylol propane, pentaerythritol and dipentaerythritol can be used as this neopentyl polyol, but it is preferable to use neopentyl glycol and pentaerythritol especially.

The ester used in the present invention is used for the esterification reaction by dehydration of the specific alcohol or polyol with a specific fatty acid, or for the general esterification reaction or the transesterification reaction of each derivative via an acid anhydride, an acid chloride or the like of a fatty acid derivative. Can be obtained by

In addition, in the production of the refrigeration oil containing the monoester and the polyol ester of the present invention, first, after the synthesis of the monoester and the polyol ester separately by the above means, both may be mixed in a predetermined ratio, first, monoalcohol, Monovalent fatty acids, 2-ethylhexanoic acid and / or 3,5,5-trimethylhexanoic acid, and neopentylpolyol, or derivatives thereof may be mixed in necessary amounts and synthesized by the above means. In this case, the polyol ester may be one kind or a mixture of two or more kinds.

The ester obtained by the above method does not particularly limit the acid and the alcohol remaining unreacted, but it is preferable that the carboxyl group is not as long as possible. If the residual amount of carboxyl groups is large, undesirable phenomena such as the formation of metal soap and the like by precipitation with the metal used in the refrigerator also occur, and the acid value of the refrigerator oil of the present invention is 0.1 mgKOH / g or less. desirable. This acid value is based on the method prescribed | regulated to JISK2501 "petroleum product and lubricating oil-neutralization test method, indicator titration method."

It is preferable that the kinematic viscosity in 40 degreeC is less than 10 mm <^2> / s so that the base material for mixing of a monoester and a polyol ester may not become too high when it mixes. More preferably, it is less than 8 mm ² / s.

As a preferable compounding ratio of a monoester and a polyol ester, the thing which contained 75 to 95 mass% of said monoester and 5 to 25 mass% of polyol ester is mentioned. By setting it as this mixing ratio, it can be set as the refrigeration oil of the low viscosity, ie, the VG3 grade viscosity, and it is excellent in lubricity, high flash point and volume resistivity, and can be excellent in safety, hydrolysis stability, and compatibility.

In addition, in order to obtain a refrigeration oil having a viscosity of VG3 grade, the kinematic viscosity at 40 ° C is preferably 2 to 4 mm ² / s.

As another preferable compounding ratio, what contains 25-40 mass% of said monoesters and 60-75 mass% of polyol esters is mentioned. By setting it as this mixing ratio, it can be set as the refrigeration oil of low viscosity, ie, the VG5 grade viscosity, excellent lubricity, high flash point and volume resistivity, and excellent safety, hydrolysis stability, and compatibility.

In addition, in order to use a refrigeration oil having a viscosity of VG5 grade, the kinematic viscosity at 40 ° C is preferably 4 to 7 mm ² / s.

In order to ensure the safety in handling, the refrigeration oil of the present invention preferably has a volume resistivity of 25 ° C. of 10 GΩm or more from a safety point of 130 ° C. or higher and electric shock prevention.

Kinematic viscosity at 40 ° C is measured by the method specified in JIS K 2283 "Crude oil and petroleum products-Kinematic viscosity test method and viscosity index calculation method", and flash point is JIS K 2265-4 "How to obtain flash point-Part 4: Cleveland development The volume resistivity at 25 ° C is measured at a sample temperature of 25 ° C in accordance with the method specified in JIS C 2101 "Electric insulating oil test method, 24. Volume resistivity test".

The monoester is preferable because the viscosity of VG3 grade or VG5 grade can be easily adjusted by using n-octyl alcohol and 2-ethylhexanoic acid ester, that is, 2-ethylhexanoic acid-n-octyl.

Similarly, neopentylglycol-di-2-ethylhexanoic acid ester which is an ester of 2-ethylhexanoic acid and neopentyl glycol as a polyol ester, or pentaerythritol-tetra-2- which is an ester of 2-ethylhexanoic acid and pentaerythritol Preference is given to using ethylhexanoic acid esters.

The refrigerant oil for refrigerant of the present invention can be blended with various additives used in the refrigerator oil in order to further enhance the performance as the refrigerator oil. For example, in order to improve hydrolysis stability, it is preferable to add acid scavengers, such as a compound which has an epoxy ring, and a carbodiimide compound, to what contains the said ester. Examples of the compound having an epoxy ring include glycidyl ether group-containing compounds, glycidyl ester group-containing compounds, epoxidized fatty acid monoesters, epoxidized fats and oils, and epoxycycloalkyl group-containing compounds. Among them, glycidyl ether group-containing compounds, glycidyl ester group-containing compounds, epoxidized fatty acid monoesters, epoxidized fats and oils, and epoxycycloalkyl group-containing compounds are more preferable.

The amount of the acid trapping agent added is preferably 0.01 to 1 mass%, more preferably 0.2 to 0.7 mass%, based on the entire refrigerator oil.

As extreme pressure additive containing phosphorus, the phosphoric acid ester in which one or more hydroxyl groups of phosphoric acid were esterified is mentioned. Phosphoric acid esters may be triesters, diesters, or monoesters, but triesters are most preferred. Specifically, triphenyl phosphate, tricresyl phosphate, triethyl phenyl phosphate, tripropyl phenyl phosphate, tributyl phenyl phosphate, cresyl diphenyl phosphate, ethyl phenyl diphenyl phosphate, propyl phenyl diphenyl phosphate, butyl phenyl diphenyl phosphate And triaryl phosphates such as dicresyl phenyl phosphate, diethyl phenyl phenyl phosphate, dipropyl phenyl phenyl phosphate and dibutyl phenyl phenyl phosphate. Among these, tricresyl phosphate (TCP) is particularly preferable. 0.1-2.0 mass% is preferable, and, as for a compounding quantity, 0.2-1.5 mass% is more preferable.

In addition, in order to improve the hydrolysis stability, it is also preferable to add a compound having a benzotriazole structure which is a metal deactivator. The compound having a benzotriazole structure is a compound represented by the following formula (1), preferably added in an amount of 1 to 100 ppm by mass, and more preferably 10 to 80 ppm by mass, based on the entire refrigerator oil.

In the formula, R ¹ represents a hydrogen atom or a methyl group, and R ² represents a group having 0 to 20 carbon atoms containing a hydrogen atom or a nitrogen atom and / or an oxygen atom.

In addition, in order to improve lubricity, it is preferable to add an oily agent having two or more hydroxyl groups in the molecule. Examples of the oily agent having two or more hydroxyl groups in the molecule include glycerin monooleate, glycerin monooleyl ether, glycerin monolauryl ether, and the like, and glycerin monooleate or glycerin monooleyl ether is particularly preferable. 0.01-1 mass% is preferable with respect to the whole refrigeration oil, and 0.1-0.5 mass% is more preferable.

In addition, in order to prevent the refrigeration oil from foaming in the refrigeration system, it is preferable to add at least one antifoaming agent selected from silicone oil, silicone oil modified at the end of polyalkylene glycol or ester, or fluorinated silicone oil. Do. As addition amount, 1-100 ppm is preferable based on the whole refrigerator oil, and 10-80 ppm is especially preferable.

In the refrigerator oil of this invention, the additive of that excepting the above can be mix | blended suitably as needed. As such an additive, for example, 2,6-di-tert-butylbutylphenol, 2,6-di-tert-butylbutyl-p-cresol, 4,4-methylene-bis- (2,6-di-tert-butyl phenolic or amine antioxidants such as -p-cresol), p, p'-di-octyl-di-phenylamine, other well-known clean dispersants, viscosity index improvers, rust inhibitors, corrosion inhibitors, pour point depressants, and the like. An additive can also be mix | blended suitably as needed. These additives are usually added so as to contain about 1% by mass to 2% by mass in the refrigerator oil of the present invention. In particular, by adding about 0.01-0.5 mass% antioxidant of a phenol type or an amine system, stability and durability of a lubrication agent can be improved significantly.

The refrigerator oil of the present invention can be preferably used together with a refrigerant not containing chlorine and furthermore a refrigerant not containing halogen. That is, the refrigeration oil of the present invention does not contain chlorine and has a hydrogen-containing fluorocarbon refrigerant having a low ozone depletion coefficient, for example, difluoromethane (R-32), tetrafluoroethane (R-134 or R-134a). Or a hydrocarbon refrigerant having no ozone layer destruction coefficient and global warming coefficient, for example, ethane (R170), propane (R290), butane (R600), isobutane (R600a), or two of them. It is preferably used for a refrigerator using the above mixed refrigerant and the like.

The refrigeration oil of the present invention becomes a working fluid by mixing with these refrigerants to be responsible for lubrication of the refrigerating device. It is possible to use the working fluid by mixing the refrigerator oil and the refrigerant of the present invention in a ratio of 5:95 to 80:20. If there is little oil out of this range, there is a risk of poor lubrication, and if too much oil is not preferable because the efficiency is lowered.

In addition, the working fluid for a refrigerator of the present invention is used as a working fluid such as a refrigerant compression type refrigeration apparatus having at least a compressor, a condenser, an expansion mechanism, and an evaporator, for example, a refrigerator, an air conditioner, a refrigerator, etc. It is preferable to use for the refrigerator used.

In the refrigerator in which the working fluid of the present invention is used, a hermetic rotary or reciprocating compressor is generally used. As an insulating film which is an electrical insulation system material of the motor part of these refrigerant compressors, a crystal having a glass transition temperature of 50 ° C. or higher is used. A resin layer having a high glass transition temperature on a plastic film such as polyethylene terephthalate, polybutylene terephthalate, polyamideimide coated polyester, polyphenylene sulfide, polyether ether ketone, or a film having a low glass transition temperature The composite film which coat | covers the cover is used.

Similarly, the magnet wire used for the motor part also has an enamel coating of glass transition temperature of 120 ° C. or higher, for example, a single layer such as polyesterimide, polyamide, polyamideimide or the like, or a lower glass transition temperature. Enamel coating etc. which composited in the upper layer with a high thing are used.

Moreover, since the working fluid for refrigerators of this invention is low viscosity, it is used suitably for the hermetic compressor of high reciprocation type sealing property.

Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to an Example.

In order to evaluate the present invention, refrigeration oils for the refrigerants of the Examples and Comparative Examples were prepared.

The base oil and additives used for the test oil are as follows.

Equipment oil

Monoester 1 to 8: Monoester shown in Table 1

Polyol ester 1 (PE-1): pentanic acid ester of neopentyl glycol (NPG)

Polyol ester 2 (PE-2): hexanoic acid ester of NPG

Polyol ester 3 (PE-3): 2-ethylhexanoic acid ester of NPG

Mineral oil 1 (MO-1): paraffinic lubricant base oil (40 ℃ kinematic viscosity: 7.8 mm ² / s)

Mineral oil 2 (MO-2): paraffinic lubricant base oil (40 ℃ kinematic viscosity: 5.2 mm ² / s)

Mineral oil 3 (MO-3): Naphthenic lubricant base oil (40 degreeC kinematic viscosity: 5.0 mm ² / s)

additive:

Acid scavenger: 2-ethylhexyl glycidyl ether

Extreme pressure agent: tricresyl phosphate

Oily Agent: Glycerin Monooleate

The refrigerator oil of the Example and the comparative example was obtained by combining in the ratio (mass%) shown in the upper part of Table 2, Table 3, and Table 4 using the said base oil and the additive. Table 2 shows the refrigerator oil of Examples 1 to 8, Table 3 shows the refrigerator oil of Examples 9 to 13, and Table 4 shows the refrigerator oil of Comparative Examples 1 to 9.

The refrigeration oils of these Examples and Comparative Examples were measured and evaluated for their properties such as physical properties, compatibility and stability. The results are shown in the lower part of Table 2 and Table 3.

In addition, the physical property measurement and the performance evaluation test were performed as follows.

Kinematic Viscosity (40 ° C):

In accordance with JIS K 2283, it measured using the improved type of an Atlantic viscometer.

flash point:

It measured by the test method of the cleblend open type | mold (COC) based on JISK2265.

Acid value:

The total acid value was measured by indicator titration method in accordance with JIS K 2501.

Compatibility:

Two-layer separation temperature was measured in accordance with annex 3 of JIS K 2211. In addition, isobutane (R600a), propane (R290), and 1,1,1,2-tetrafluoroethane (R-134a) are used as the refrigerant, and the fuel oil / refrigerant ratio (weight) is 2/8. It measured on condition.

stability:

A so-called autoclave test was conducted to test the color and acid value of the refrigeration oil after deterioration. That is, 30 g of the test oil, 10 g of refrigerant, and wires of Fe, Cu, and Al as a catalyst were put in a 100 ml stainless steel pressure vessel (autoclave) of inner volume and sealed, and left for 14 days in a thermostatic bath at 175 ° C. The sample after deterioration was taken out and the color and acid value were confirmed. The refrigerants were evaluated for each using R600a and R-134a. In addition, the acid value was measured by the same method as the above.

Lubricity:

The Falex test (290 rpm, room temperature) based on ASTMD 3233 was done, and the load at the time of the baking of the test piece was measured.

Example 1-8 and ME-4 which used ME-2-6 whose sum total of R <^1> and R <^2> of monoester were 13-17 as base oil are made into one of base oils, and PE-3 is another base oil. Examples 9 to 13 have low viscosity, high flash point, and excellent compatibility and stability with refrigerant. Lubricity is also good.

In Comparative Example 1 using ME-1 as the base oil, since the total of R ¹ and R ² is 11, the viscosity and flash point are too low to be practically used. The stability with the refrigerant was also poor, and the acid value after the test was increased.

Since Comparative Examples 2 and 3 using ME-7 and ME-8 as base oils have poor compatibility, in particular, compatibility with refrigerants, it is difficult to use them practically.

Comparative Examples 4 and 5 based on PE-1 and PE-2 were inferior in stability. Moreover, in the comparative example 6 which made PE-3 the base oil, it is difficult to make dynamic viscosity into the target range.

Comparative Example 7 using MO-1 as the base oil also has the same kinematic viscosity as the Comparative Example 6. In Comparative Example 9 using MO-2 and 3 as the base oil, the flash point was low, resulting in poor safety.

In order to evaluate the refrigerator oil of this invention containing a monoester and a polyol ester, the refrigerant oil for a refrigerant | coolant (a disclosure oil) of the Example and the comparative example was prepared.

The base oil and additives used for the test oil are as follows.

(Material existence)

ME-9: n-hexanoic acid-n-hexyl

ME-10: 2-ethylhexanoic acid-n-octyl

ME-11: n-decanoic acid-n-decyl

PE-4: neopentylglycol-di-n-hexanoic acid ester

PE-5: neopentylglycol-di-2-ethylhexanoic acid ester

PE-6: pentaerythritol-tetra-2-ethylhexanoic acid ester

PE-7: ester of a mixed acid of 2-ethylhexanoic acid (50% by mass) and 3,5,5-trimethylhexanoic acid (50% by mass) with pentaerythritol

(additive)

Acid scavenger: 2-ethylhexyl glycidyl ether [EPO]

           Dialkylphenylcarbodiimide [CDI]

Oily agent: glycerin monooleate [GMO]

Metal scavenger: Benzotriazole [BTA]

Antifoam: Dimethylsiloxane (1000 mPa.s@25°C) [silicone oil]

Using the said base oil and an additive, it combined with the ratio (mass%) shown to the upper part of Table 5, and obtained the test oil (refrigerated base oil) of an Example and a comparative example.

The refrigeration oils of these examples and comparative examples were measured and evaluated for their physical properties, compatibility, and performance. The results are shown in Table 6.

In addition, the physical property measurement and performance evaluation test other than the measuring method mentioned above were performed as follows.

Produce bubble:

Foam formation and foam stability at 24 ° C. were measured by the method specified in JIS K 2518 “Petroleum Product-Lubricant Foam Formation Test Method”.

Two layer separation temperature:

The two-layer separation temperature was measured by the method specified in annex 3 "Compatibility Testing Method with Refrigerants" of JIS K 2211. In addition, isobutane (R600a) was used as a refrigerant | coolant, and the test oil / refrigerant ratio (weight) was measured on condition of 2/8.

Hydrolysis Stability:

A mixture of 7 ml of the test oil and 3 ml of isobutane refrigerant (R600a) was prepared by the method specified in Annex 2 "Test method for chemical stability with refrigerant (shielded tube test) of JIS K 2211, water content in water 500 ppm, temperature 175 degreeC. Under 14 days, the total acid value was measured.

Lubricity (Palex Sobu):

The Falex test (290 rpm, room temperature) based on ASTMD 3233 was done, and the load at the time of a dent at the test piece was measured.

Lubricity ( SRV Wear scar ):

By using the SRV friction tester of the ball (manufactured by SUJ-2) / disc (manufactured by SUJ-2), wear marks after 25 minutes of test time under conditions of 100 N load, 50 Hz amplitude, 1 mm amplitude, and 60 ° C temperature Measured.

Compressor testing:

220 ml of test oil was put into the compressor for refrigerators, and the durability test was done on the following conditions using 30 g of isobutanes as a refrigerant.

<Condition> Discharge pressure: 10 kg / cm ² G, Suction pressure: 0 kg / cm ² G, Compressor surface temperature (normal): 100 ° C, Operating time: 1000 hours

After the endurance test, the compressor was disassembled and the contamination of the discharge valve and the wear of the sliding part were evaluated.

ME-10 which is an ester of n-octanol which is a C8 aliphatic monoalcohol, and 2-ethylhexanoic acid which is a monovalent fatty acid of C8: 2-ethylhexanoic acid (n-octyl), 2-ethylhexanoic acid, or 3 Examples 14 to 27 using a mixture of 5,5-trimethylhexanoic acid and neopentylglycol having 5 to 10 carbon atoms or PE-4 to PE-7 which are esters of pentaerythritol as base oils are low viscosity oils. It has a high flash point, excellent compatibility with the refrigerant, hydrolysis stability, volume resistivity, and good lubricity.

On the other hand, Comparative Examples 10 to 12 using monoesters ME-9 to ME-11 and ester PE-4 of neopentylpolyol alone as base oils had poor hydrolysis stability, and in Comparative Examples 10 to 12, lubricity of SRV wear was observed. It is also bad. In particular, Comparative Example 10 is also poor in flash point, volume resistivity, and lubricity of Palex. Moreover, the comparative example 13 which used PE-5 alone is high in viscosity, and energy saving cannot be fully achieved. Moreover, even if it uses the ester of a C6 or C10 alcohol or an acid, even if it mixes with the ester of neopentyl polyol (Comparative Examples 14-16), hydrolysis stability is bad, and Comparative Examples 14-15 have low volume resistivity. The use of these base oils could not be improved even if an additive was added (Comparative Examples 17 to 19).

According to the present invention, there is provided a refrigerant oil for refrigerant having low viscosity and excellent stability, which is used for a hydrogen-containing fluorocarbon refrigerant containing no chlorine or a hydrocarbon refrigerant containing no halogen atom having a low greenhouse effect. Made it possible. Therefore, since the influence on the environment, such as global warming, is small, and also low viscosity and energy saving are expected, it can be effectively used for the refrigerator, air cleaner, refrigerator, etc. which use a refrigerant | coolant compression type refrigeration cycle.

Claims (21)

The refrigerant oil for refrigerant containing a monoester represented by the following formula (1) as a main component, the kinematic viscosity at 40 ℃ less than 7 mm ² / s. <Formula 1> Wherein, R ¹ represents a hydrocarbon group of a carbon number of 5 to 9, R ² represents a hydrocarbon group having 8 to 10, R ¹ and R ² may be each branched or straight chain, and the carbon number of R ¹ and R ² The sum is 13 to 17. The refrigerant oil for refrigerant according to claim 1, further comprising a polyol ester. The monoester according to claim 2, wherein the monoester is a monoester of an aliphatic monoalcohol having 8 carbon atoms and a monovalent fatty acid having 8 carbon atoms, and the polyol ester is 2-ethylhexanoic acid and / or 3,5,5-trimethylhexanoic acid having 5 carbon atoms. Refrigerator oil for refrigerant | coolants which is 1 or more types of polyol ester with the neopentyl polyol of 10-10. The refrigerant oil for refrigerant according to claim 3, comprising 75 to 95% by mass of monoester and 5 to 25% by mass of at least one of polyol esters. The refrigerator oil according to claim 4, wherein the kinematic viscosity at 40 ° C is 2 to 4 mm ² / s, the flash point is 130 ° C or more, the acid value is 0.1 mgKOH / g or less, and the volume resistivity at 25 ° C is 10 GΩm or more. The refrigerant oil for refrigerant according to claim 3, comprising 25 to 40 mass% of monoester and 60 to 75 mass% of one or more kinds of polyol esters. The refrigerator oil according to claim 6, wherein the kinematic viscosity at 40 ° C is 4 to 7 mm ² / s, the flash point is 130 ° C or more, the acid value is 0.1 mgKOH / g or less, and the volume resistivity at 25 ° C is 10 GΩm or more. The refrigerator oil according to any one of claims 4 to 7, wherein the monoester is an ester of n-octyl alcohol and 2-ethylhexanoic acid. The refrigerator oil according to any one of claims 4 to 7, wherein the polyol ester is neopentyl glycol-di-2 ethylhexanoic acid ester or pentaerythritol-tetra-2 ethylhexanoic acid ester. The refrigerator oil according to claim 8, wherein the polyol ester is neopentyl glycol-di-2 ethylhexanoic acid ester or pentaerythritol-tetra-2 ethylhexanoic acid ester. The refrigerator oil of Claim 10 which added 0.01-1 mass% of acid trapping agents containing the compound or carbodiimide compound which have an epoxy ring. The refrigeration oil of Claim 10 which added 1-100 mass ppm of metal deactivators which have a benzotriazole structure. The refrigeration oil of Claim 10 which added 0.01-1 mass% of oil-based agents which have 2 or more hydroxyl groups in a molecule | numerator. The refrigeration oil of Claim 10 which added 1-100 mass ppm of antifoamers chosen from silicone oil, the silicone oil in which the terminal was modified by polyalkylene glycol or ester, or the fluorinated silicone oil. A working fluid for a refrigerator comprising the refrigerator oil according to any one of claims 4 to 7 and 10 to 14 and at least one hydrocarbon refrigerant selected from ethane, propane, butane or isobutane. A working fluid for a refrigerator comprising the refrigerator oil according to claim 8 and at least one hydrocarbon refrigerant selected from ethane, propane, butane or isobutane. A working fluid for a refrigerator comprising the refrigerator oil according to claim 9 and at least one hydrocarbon refrigerant selected from ethane, propane, butane or isobutane. The working fluid for a refrigerator of Claim 15, the hermetic compressor which compresses this fluid, the condenser which condenses a refrigerant, the expansion mechanism which expands a refrigerant, and the evaporator which evaporates a refrigerant, The said hermetic compressor is a rotor. And a motor having a stator, wherein the motor is provided with an insulating film of any one of polyethylene terephthalate, polybutylene terephthalate, polyamideimide coated polyester, polyphenylene sulfide, and polyether ether ketone. A stator comprising a winding coated with an enamel material having a glass transition temperature of 120 ° C. or higher. The closed type working fluid for a refrigerator according to claim 16 or 17, a hermetic compressor for compressing the fluid, a condenser for condensing the refrigerant, an expansion mechanism for expanding the refrigerant, and an evaporator for evaporating the refrigerant; The compressor includes a motor having a rotor and a stator, and the motor includes an insulating film of any one of polyethylene terephthalate, polybutylene terephthalate, polyamideimide-coated polyester, polyphenylene sulfide and polyether ether ketone. And a stator having a winding coated with an enamel material having a glass transition temperature of 120 ° C. or higher. 19. The refrigerator of claim 18, wherein the hermetic compressor is reciprocating. 20. The refrigerator of claim 19, wherein the hermetic compressor is reciprocating.