JP3145360B2 - Refrigeration oil for non-chlorofluorocarbon refrigerant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating machine oil for a non-chlorinated Freon refrigerant, and more particularly to a refrigerating machine oil for a non-chlorinated Freon refrigerant having pentaerythritol ester having a specific structure as a main component and excellent in various performances. It concerns machine oil.

[0002]

2. Description of the Related Art Conventionally, a refrigeration oil has a kinematic viscosity of 10 to 2 at 40.degree.
Naphthenic mineral oils, paraffinic mineral oils, alkylbenzenes, polyglycol-based oils, ester oils, and mixtures thereof, or mixtures of various base oils with additives are generally used.

On the other hand, CFC-11, CFC-12, CFC-113, HC
FC-22 or the like is used.

[0004] Among these CFC-based refrigerants, CFC-1
CFCs in which all the hydrogens of hydrocarbons such as 1, CFC-12 and CFC-113 are replaced by halogens containing chlorine are subject to regulation because they lead to ozone layer destruction. Accordingly, non-chlorinated chlorofluorocarbons such as HFC-134a and HFC-152a are being used as substitutes for CFCs.
C-134a has similar thermodynamic properties to CFC-12 conventionally used in many refrigerators such as home refrigerators and air conditioners, and is a promising alternative refrigerant.

Although refrigerating machine oils have various required performances, compatibility with refrigerants is extremely important in terms of lubrication and system efficiency of the refrigerating machine. However, refrigeration oils based on naphthenic mineral oils, paraffinic mineral oils, alkylbenzenes, and conventionally known ester oils, etc., are H
Since it has almost no compatibility with non-chlorinated chlorofluorocarbons such as FC-134a, when used in combination with HFC-134a, two-layer separation occurs at normal temperature, and the most important oil return property in the refrigeration system becomes worse The refrigeration efficiency is reduced or the lubricity is poor, causing various practical inconveniences such as seizure of the compressor, which makes it unusable. Polyglycols are also known as refrigerating machine oils having a high viscosity index, and are described, for example, in JP-B-57-42119, JP-B-61-52880, and JP-A-57-51795. However, the polyglycol oils specifically disclosed in these prior arts still have insufficient compatibility with HFC-134a, so that the same problems as described above occur and they cannot be used practically.

US Pat. No. 4,755,316 discloses HFC
A polyglycol-based refrigerating machine oil compatible with -134a is disclosed. In addition, the present inventors have previously developed a polyglycol-based refrigerating machine oil which has significantly better compatibility with HFC-134a than conventionally known refrigerating machine oils, and have already filed an application (Japanese Unexamined Patent Application Publication No. Hei. -256594, 1-271491 and the like). However, it has been found that polyglycol-based oils have problems of high solubility in water and poor electrical insulation.

[0007] On the other hand, refrigerating machine oil used for compressors such as household refrigerators requires high electrical insulation. Among known refrigerating machine oils, those having the highest insulating properties are alkylbenzenes and mineral oils, but as described above, alkylbenzenes and mineral oils have almost no compatibility with non-chlorinated chlorofluorocarbons such as HFC-134a. Therefore, a refrigerating machine oil having both high compatibility with non-chlorinated chlorofluorocarbon such as HFC-134a and high insulating property has not yet appeared.

The inventors of the present invention have conducted studies to develop a refrigerating machine oil which can meet the above-mentioned requirements. As a result, the ester having a specific structure is excellent in compatibility with non-chlorinated chlorofluorocarbons such as HFC-134a and has a high compatibility. The present inventors have found that they have electrical insulation properties and further excellent lubricating properties, and have completed the present invention.

The present invention provides a lubricating oil for a non-chlorinated Freon refrigerant having excellent compatibility with non-chlorinated Freon such as HFC-134a containing an ester having a specific structure as a main component and having high electric insulation. The purpose is to do.

[0010]

That is, the present invention provides pentaerythritol and 2-ethylhexanoic acid and 3,
A refrigeration oil for non-chlorinated chlorofluorocarbon refrigerants, which is mainly composed of an ester consisting of a mixture of 5,5-trimethylhexanoic acid ( provided that phenylglycidyl ether type epoxy
Compound, glycidyl ester type epoxy compound, epoxy
From xylated fatty acid monoesters and epoxidized vegetable oils
At least one epoxy compound selected from the group consisting of
Except when it contains ).

Hereinafter, the contents of the present invention will be described in more detail. The pentaerythritol ester used in the present invention is an ester of pentaerythritol and a monocarboxylic acid, and usually reacts pentaerythritol with a mixture of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid. It can be obtained by: The obtained product may be purified to remove by-products and unreacted substances,
A small amount of by-products and unreacted products may be present even if present, as long as they do not adversely affect the excellent performance of the refrigerating machine oil of the present invention.

The pentaerythritol ester comprising a mixture of pentaerythritol and 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid used in the present invention has a kinematic viscosity of 2 to 150 cSt at 100 ° C., preferably 5 to 150 cSt. Preferably, it is 100 cSt.

In the refrigerating machine oil of the present invention, the above-mentioned pentaerythritol ester may be used alone, but if necessary, another refrigerating machine oil base oil may be mixed and used. Preferred examples of the base oil include the following. General formula

[0014]

Embedded image[Wherein, R₅And R₆Is hydrogen or C1-18
Represents an alkyl group; ₇Is an alkylene group having 2 to 4 carbon atoms
And a represents an integer of 5 to 70].
Xyalkylene glycol or its ether. General formula

[0015]

Embedded image[Wherein, R₈~ R₁₀Is hydrogen or an atom having 1 to 18 carbon atoms.
A alkyl group;_{1 1}~ R₁₃Is an alkyl having 2 to 4 carbon atoms
And a b-d represents an integer of 5 to 7].
Polyoxyalkylene glycol glycerol A
Tell. General formula

[0016]

Embedded imageAnd R₁₄And R₂₀Is an alk having 1 to 8 carbon atoms
Len group, R_FifteenAnd R ₁₇Is an alkyl having 2 to 16 carbon atoms
Kylene group, R₁₆And R₂₁Is an alkyl having 1 to 15 carbon atoms
Kill group, R₁₈And R₁₉Is alk having 1 to 14 carbon atoms
And e and f each represent 0 or 1
And g represents an integer of 0 to 30].
ester. General formula

[0017]

Embedded image [Wherein, R _{22 to} R ₂₇ represent an alkyl group having 3 to 15 carbon atoms, and R ₂₈ represents a divalent hydrocarbon group having 1 to 8 carbon atoms.
H represents an integer of from 1 to 5]; pentaerythritol dicarboxylate;

These oils may be used alone or in combination of several kinds. Oils such as paraffinic and naphthenic mineral oils, poly-α-olefins, and alkylbenzenes may be mixed, but in this case, the compatibility with the non-chlorinated fluorocarbon solvent is reduced.

The blending amount of these other refrigerating machine oil base oils is not particularly limited as long as the excellent performance of the refrigerating machine oil of the present invention is not impaired, but pentaerythritol, 2-ethylhexanoic acid and 3 The proportion of the ester consisting of a mixture of 5,5,5-trimethylhexanoic acid is usually more than 50% by weight, preferably 70% by weight, based on the total amount of the refrigerator oil.
It is blended so that it becomes above.

In order to further improve the stability of the refrigerating machine oil of the present invention, it is selected from the group consisting of phenylglycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, epoxidized fatty acid monoesters and epoxidized vegetable oils. At least one epoxy compound can be blended. Examples of the phenylglycidyl ether type epoxy compound referred to here include phenylglycidyl ether and alkylphenylglycidyl ether. The alkylphenyl glycidyl ether referred to herein is one having 1 to 3 alkyl groups having 1 to 13 carbon atoms, among which 4 to 10 carbon atoms.
Those having one alkyl group such as butylphenylglycidyl ether, benzylphenylglycidylether, hexylphenylglycidylether, heptylphenylglycidylether, octylphenylglycidylether, nonylphenylglycidylether and decylphenylglycidylether are preferred. Examples of the glycidyl ester type epoxy compound include phenyl glycidyl ester, alkyl glycidyl ester, and alkenyl glycidyl ester, and preferable examples include glycidyl benzoate, glycidyl acrylate, and glycidyl methacrylate.

Examples of the epoxidized fatty acid monoester include esters of an epoxidized fatty acid having 12 to 20 carbon atoms and an alcohol or phenol or alkylphenol having 1 to 8 carbon atoms. Particularly, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butylphenyl esters of epoxystearic acid are preferably used. Examples of the epoxidized vegetable oil include epoxy compounds of vegetable oils such as soybean oil, linseed oil, and cottonseed oil.

In the refrigerating machine oil composition of the present invention, in order to further improve its wear resistance and load resistance, phosphate ester, acidic phosphate ester, amine salt of acidic phosphate ester, chlorinated phosphate ester and At least one phosphorus compound selected from the group consisting of phosphites can be blended. These phosphorus compounds are esters of phosphoric acid or phosphorous acid with alkanols or polyether alcohols or derivatives thereof. Specifically, examples of the phosphoric ester include tributyl phosphate, triphenyl phosphate, tricresyl phosphate, and the like. Examples of the acidic phosphate include ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, and dioctadecyl acid phosphate. Examples of the acidic phosphate ester amine salt include the acidic phosphate esters methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, and the like. Dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine,
Salts with amines such as tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine and the like can be mentioned. Examples of the chlorinated phosphate include tris-dichloropropyl phosphate, tris-chloroethyl phosphate, polyoxyalkylene bis [di (chloroalkyl)] phosphate, and tris-chlorophenyl phosphate. Examples of the phosphite include dibutyl phosphite, tributyl phosphite, dipentyl phosphite, tripentyl phosphite, dihexyl phosphite, trihexyl phosphite, diheptyl phosphite, triheptyl phosphite, dioctyl phosphite, and trioctyl phosphite. Phyt, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, triundecyl phosphite, didodecyl phosphite, tridodecyl phosphite, diphenyl phosphite, triphenyl phosphite, dicresyl phosphite, tris Chloroethyl phosphate, polyoxyalkylene bis [di (chloroalkyl)] phosphate, tris-chlorophenyl phosphate and the like can be mentioned. Examples of the phosphite include dibutyl phosphite, tributyl phosphite, dipentyl phosphite, tripentyl phosphite, dihexyl phosphite, trihexyl phosphite, diheptyl phosphite, triheptyl phosphite, dioctyl phosphite, and trioctyl phosphite. Phyto, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, triundecyl phosphite, didodecyl phosphite, tridodecyl phosphite, diphenyl phosphite, triphenyl phosphite, dicresyl phosphite, tricresyl Phosphite and the like. Also, a mixture of these can be used. When these phosphorus compounds are blended, it is desirable that they be contained in a proportion of 0.1 to 5.0% by weight, preferably 0.2 to 2.0% by weight, based on the total amount of the refrigerating machine oil.

Preferred among these epoxy compounds are phenylglycidyl ether type epoxy compounds and epoxidized fatty acid monoesters. Above all, a phenylglycidyl ether type epoxy compound is more preferable, and phenylglycidyl ether, butylphenylglycidyl ether and a mixture thereof are particularly preferable. When these epoxy compounds are blended, 0.1 to 5.0% by weight, preferably 0.2 to 5.0% by weight based on the total amount of the refrigerator oil.
Desirably, the content is 2.0% by weight. Also, the epoxy compound and the phosphorus compound may be used in combination.

Further, with respect to the refrigerating machine oil of the present invention,
In order to further improve its performance, conventionally known refrigerator oil additives such as phenols such as di-tert-butyl-p-cresol and bisphenol A, phenyl-α-naphthylamine, N, N- Di (2-
Amine antioxidants such as naphthyl) -p-phenylenediamine; antiwear agents such as zinc dithiophosphate; extreme pressure agents such as chlorinated paraffins and sulfur compounds; oily agents such as fatty acids;
Additives such as silicone-based antifoaming agents and metal deactivators such as benzotriazole may be used alone or in combination of several kinds. The total amount of these additives is usually 10% by weight or less based on the total amount of the refrigerating machine oil,
It is preferably at most 5% by weight.

The refrigerating machine oil of the present invention mainly comprising an ester composed of a mixture of pentaerythritol and 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid,
Usually, it is only necessary to have a kinematic viscosity and a pour point of a degree used as a refrigerating machine oil, but in order to prevent solidification of the refrigerating machine oil at a low temperature, the pour point is −10 ° C. or less, preferably −20 ° C.
C. to -80.degree. C. is desirable. Further, in order to maintain the hermeticity with the compressor, the kinematic viscosity at 100 ° C is preferably 2 cSt or more, preferably 3 cSt or more.In consideration of fluidity at low temperature and efficiency of heat exchange in the vaporizer, the kinematic viscosity at 100 ° C The kinematic viscosity is desirably 150 cSt or less, preferably 100 cSt or less.

The refrigerating machine oil of the present invention has significantly better compatibility with non-chlorinated fluorocarbons than conventionally known refrigerating machine oils. Specific examples of the non-chlorinated chlorofluorocarbon include 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1-difluoroethane. (HFC-152a), trifluoromethane (HFC
-23) and the like, but preferred is HFC-134a
It is. Further, the refrigerating machine oil of the present invention is an excellent refrigerating machine oil having not only high compatibility with non-chlorinated chlorofluorocarbons and high electric insulation but also high lubricity and low hygroscopicity.

[0027] The refrigerating machine oil of the present invention is particularly useful for air conditioners having reciprocating or rotary compressors, dehumidifiers, refrigerators, freezers, freezing and refrigerated warehouses, vending machines, showcases, and cooling devices for chemical plants and the like. Although it can be used preferably, it can also be used preferably with a centrifugal compressor.

[0028]

The present invention will now be described by way of examples and comparative examples.
Will be described more specifically. Examples, Reference Examples 1 to 6 and Comparative Examples 1 to 6 The refrigerating machine oil used in the present example, reference example and comparative example is as follows.
Shown in Example: with pentaerythritol (1 mol)
2-ethylhexanoic acid (2 mol) and 3,5,5-
Tetraester of trimethylhexanoic acid (2 mol).

Reference Example 1: Pentaerythritol (1 mol)
And 2-ethylhexanoic acid (4 mol) tetraester.

[0030]

Embedded image

Reference Example 2: Pentaerythritol (1 mol
) And a tetraester of 3,5,5-trimethylhexanoic acid (4 mol).

[0032]

Embedded image

Reference Example 3 Dipentaerythritol (1mo
l) and hexaesters of n-hexanoic acid (3 mol) and 2,4-dimethylpentanoic acid (3 mol).

[0034]

Embedded image

Reference Example 4 Dipentaerythritol (1mo
l) Hexaester of 3,5,5-trimethylhexanoic acid (6 mol).

[0036]

Embedded image

Reference Example 5: A mixture obtained by mixing 50 parts by weight of the ester of Example 1 and 50 parts by weight of the ester of Example 5. Reference Example 6: 30 parts by weight of the ester of Example 2, 40 parts by weight of the ester of Example 5, and the following tripentaerythritol (1 mol), 3-methylbutanoic acid (4 mol) and 3-
A mixture of 30 parts by weight of octaester of methylpentanoic acid (4 mol).

[0038]

Embedded image

Comparative Example 1: Naphthenic mineral oil (kinematic viscosity at 100 ° C .; 5.2 cSt). Comparative Example 2: Branched alkylbenzene (kinematic viscosity at 100 ° C; 5.0 cSt). Comparative Example 3: Polyoxypropylene glycol monobutyl ether (kinematic viscosity at 100 ° C; 5.4 cSt). Comparative Example 4: Polyoxypropylene glycol dimethyl ether (kinematic viscosity at 100 ° C; 9.5 cSt). Comparative Example 5: Tetraester of pentaerythritol (1 mol) and n-nonanoic acid (4 mol). Comparative Example 6: Tetraester of pentaerythritol (1 mol) and coconut oil.

Examples Related to the Invention and Reference Examples 1 to 6
The solubility of HFC-134a with HFC-134a, insulation properties, and a Falex wear test were evaluated for the performance evaluation of the base oil of the refrigerating machine oil. For comparison, Table 1 also shows the test results of mineral oil, alkylbenzene, polypropylene glycol monoalkyl ether and polypropylene glycol dialkyl ether conventionally used in refrigerator oil.

(Solubility with HFC-134a) Inner diameter 6 mm length
In a 220 mm glass tube, 0.2 g of the sample oil of the example, the reference example, and the comparative example was collected, and the refrigerant (HFC-134a) 1.8 g
Collect g and seal the glass tube. The glass tube is placed in a low-temperature bath or a high-temperature bath at a predetermined temperature, and it is observed whether the refrigerant and the sample oil are mutually dissolved, separated or clouded. (Insulation Characteristics) The volume resistivity of the sample oil at 25 ° C. was measured in accordance with JIS C 2101. (FALEX abrasion test) In accordance with ASTM D 2670, run-in operation at sample oil temperature of 100 ° C and 150 lb load
After 1 minute, run for 2 hours under a 250lb load,
The wear amount of the test journal was measured. (Hygroscopicity) Take 30g of sample oil in a 300ml beaker,
After allowing to stand in a thermo-hygrostat maintained at 30% humidity for 7 days, the water content was measured by the Karl Fischer method.

[0042]

[Table 1] As shown in the example of Table 1, the refrigerating machine oil according to the present invention is:
Compared with Comparative Examples 1-2 and 5-6, the refrigerant solubility in HFC-134a is very excellent.

When all the alkyl groups on the acid side are linear as in Comparative Example 5, the solubility is poor. Further, tetraesters of pentaerythritol and natural fats and oils conventionally used in lubricating oils, refrigerator oils and the like as in Comparative Example 6 also have poor refrigerant solubility.

As shown in Comparative Examples 3 and 4, polyalkylene glycol is excellent in refrigerant solubility, but has poor insulating properties and cannot be used in a closed type compressor. Also,
The alkylene glycols shown in Comparative Examples 3 and 4 have a moisture absorption of 5 to 10 times that of the examples, and are inferior to the examples in terms of electrical insulation, ice chalk, abrasion resistance, stability and the like.

Also, in the wear test by Falex, it can be seen that the examples are equal to or more than the comparative examples 3 and 4.

[0046]

As is apparent from the above description and the examples, the refrigerating machine oil of the present invention is suitable for use in a refrigerating machine for chlorofluorocarbon and has excellent electrical insulation essential for a hermetic compressor. It is a refrigerating machine oil that has excellent wear resistance and non-hygroscopicity.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tatsuyuki Ishikawa No. 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Prefecture, Japan Central Oil Research Institute Co., Ltd. (56) References JP-A-3-200895 (JP, A) JP-A-11-315293 (JP, A) JP-A-3-227397 (JP, A) JP-A-3-88892 (JP, A) JP-A-3-128992 (JP, A) JP-A-54-64264 (JP, A) JP-A-56-131548 (JP, A) JP-A-3-505602 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C10M 105/32 C10N 40: 30 CA (STN) REGISTRY (STN)

Claims (5)

(57) [Claims] 1. A refrigerating machine oil for non-chlorinated chlorofluorocarbon refrigerants , wherein phenyl erythritol and an ester composed of a mixture of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid are used as a main component. Glycidile
-Tel type epoxy compound, glycidyl ester type epoxy
Compound, epoxidized fatty acid monoester and epoxy
At least one type selected from the group consisting of
Excluding the case containing a oxy compound ). 2. The refrigerating machine oil for chlorine-free Freon refrigerant according to claim 1, wherein an ester comprising a mixture of the pentaerythritol and 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid is used as a base oil. 3. A phosphoric acid ester, based on the total amount of the refrigerating machine oil,
Acid phosphate, amine salt of acid phosphate,
At least one phosphorus compound selected from the group consisting of chlorinated phosphates and phosphites 0.1 to 5.0
The refrigerating machine oil for non-chlorine-based fluorocarbon refrigerants according to claim 1 or 2, which contains, by weight, as an essential component. 4. The kinematic viscosity of the ester at 100 ° C.
4. The method according to claim 1, wherein the pressure is 2 to 150 cSt.
The refrigerating machine oil for a non-chlorinated chlorofluorocarbon refrigerant according to any one of the preceding claims . 5. The volume resistance of the ester at 25 ° C.
The rate is 4 × 10 ¹⁴ Ωcm or more.
The non-chlorinated chlorofluorocarbon refrigerant refrigerant according to any one of 1 to 4,
Freezing machine oil .