JPH0598275A - Lubricating oil for compression refrigerating machine - Google Patents

Abstract

PURPOSE:To obtain the title oil excellent in lubricating properties and compatibility with a hydrochlorofluorocarbon consisting mainly of a specified polyoxyalkylene glycol derivative and having a kinematic viscosity in a specified range. CONSTITUTION:When a lubricating oil for a compression refrigerating machine consisting mainly of a polyoxyalkylene glycol derivative of the formula (wherein R<1> to R<6> are each H or 1-6C alkyl; A<1> to A<6> are each a polyoxyalkylene group having a main chain comprising repeating oxyethylene groups; and the content of R<1> to R<6> which are hydrogen atoms is 70% or below) (e.g. D-sorbitol-initiated ethylene oxide/propylene oxide copolymer), optionally containing various additives and having a kinematic viscosity of 2-50cSt at 100 deg.C, is used in a compression refrigerating machine containing a hydro-chlorofluorocarbon (e.g. 1,1,1,2-tetrafluoromethane, Flon 134a) as a refrigerant, it exhibits good compatibility with the refrigerant and excellent lubricating properties and stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lubricating oil for a compression type refrigerator. More specifically, 1,1,1,2-tetrafluoroethane (hereinafter, Freon 134a, which can be a substitute for a Freon compound such as dichlorodifluoromethane (hereinafter, Freon 12), which is a problem in environmental pollution, is used. (Hereinafter referred to as)) and the like, and a lubricating oil for a compression refrigerating machine containing a polyoxyalkylene glycol derivative as a main component, which has good compatibility with a hydrogen-containing CFC compound and has excellent lubricating performance and stability.

[0002]

2. Description of the Related Art In general, a compression type refrigerator comprises a compressor, a condenser, an expansion valve and an evaporator, and a mixed liquid of a refrigerant and a lubricating oil flows in this closed system. It has a circulating structure. In such a compression type refrigerator, the temperature is generally 50 ° C. or higher in the compressor, while it depends on the type of the device, while it is − in the cooler.
Since the temperature is about 40 ° C., it is usually necessary that the refrigerant and the lubricating oil circulate in the system without phase separation in the temperature range of −40 ° C. to + 50 ° C. If phase separation occurs during operation of the refrigerator, it will have a significant adverse effect on the life and efficiency of the device. For example, if phase separation occurs between the refrigerant and the lubricating oil in the compressor section, the moving parts will be poorly lubricated,
It will cause seizure, etc., and shorten the life of the device significantly,
On the other hand, when the phase separation occurs in the evaporator, the efficiency of heat exchange is lowered because the lubricating oil having high viscosity exists.

Lubricating oil for refrigerating machines is also used for the purpose of lubricating the moving parts of the refrigerating machine, so that the lubricating performance is naturally important. In particular, since the temperature inside the compressor is high, the viscosity that can hold the oil film necessary for lubrication is important. The required viscosity depends on the type of compressor used and the operating conditions, but the viscosity of the lubricating oil before mixing with the refrigerant is usually 10
2-50 cSt at 0 ° C is preferred. If the viscosity is lower than this, the oil film becomes thin, and poor lubrication is likely to occur. If the viscosity is higher, the heat exchange efficiency decreases. Furthermore, since the lubricating oil for refrigerators is circulated and used in a wide temperature range from high temperature to low temperature, it is desirable that its viscosity index is high.

Conventionally, Freon 12 is often used as a refrigerant for a compression type refrigerator, and various mineral oils and synthetic oils satisfying the above-mentioned required characteristics have been used as a lubricating oil.
However, since the CFC 12 may cause environmental pollution such as depletion of the ozone layer, its regulation is becoming stricter worldwide recently. Therefore, a hydrogen-containing CFC compound represented by CFC134a has attracted attention as a new refrigerant. This hydrogen-containing Freon compound, especially Freon 134a, is less likely to destroy the ozone layer, and can be replaced with Freon 12 with almost no change in the structure of the conventional refrigerator. It is preferable as a refrigerant.

When a hydrogen-containing freon compound such as freon 134a is used as the refrigerant of the compression type refrigerator instead of freon 12, naturally, the freon 1 is used as the lubricating oil.
It is required to have excellent compatibility with a hydrogen-containing CFC compound such as 34a and excellent lubricating performance capable of satisfying the above required performance. However, since the lubricating oil used together with the conventional Freon 12 does not have good compatibility with the hydrogen-containing Freon compounds such as Freon 134a, new lubricating oils suitable for these compounds are required. In this case, especially in an air conditioner for automobiles, it is desired that the structure of the device is hardly changed when substituting the Freon 12, and it is not desirable to greatly change the structure of the existing device due to the lubricating oil. Absent. Therefore, a lubricating oil having extremely good compatibility with the hydrogen-containing CFC compound such as CFC134a is required. In particular, a refrigerator having a rotary compression mechanism used in an automobile needs a lubricating oil having a high viscosity of 15 cSt or more at 100 ° C.

As a lubricating oil compatible with Freon 134a, a polyalkylene glycol type is known. For example, "Research Disclosure (Resear
ch Disclosure), No. 17463 (10th 1978)
U.S. Pat. No. 4,755,316, JP-A-1-
No. 256594, 1-259093 to 25909.
No. 4, JP-A 1-27491, and JP-A 2-43290.
Publication No. 2-84491 Publication No. 2-132176.
No. 13179, No. 2-173195, No. 2
-180986 to 180987 gazettes and 2-1827.
No. 80-182781, No. 2-242888, No. 2-258895, No. 2-269195, No. 2-272097, No. 2-305893.
No. 3, 282896, No. 3-33193, No. 3-103496-103497, No. 3
-50297, 3-52995, 3-
70794 to 70795, 3 to 79696, 3 to 106992, 3 to 109492, and 3 to 121195. Among these, there are compounds having a low viscosity and a relatively good compatibility with CFCs 134a, but the polyalkylene glycol-based compounds generally decrease in compatibility with CFCs 134a as the viscosity increases. For this reason, an example having a viscosity of 15 cSt or more, especially 20 cSt or more at 100 ° C. and sufficiently satisfying the compatibility has not been shown yet.

In addition to polyalkylene glycol-based compounds, compounds having compatibility with Freon 134a include
British Patent Publication No. 221654 as an ester compound
No. 1, International Publication No. 6979/1990, Japanese Unexamined Patent Publication No. 2-276894, No. 3-128992,
No. 3-88892, No. 3-179091, etc. are known. However, it is hard to say that it is desirable because the inside of the compressor is easily corroded by the generation of acid by hydrolysis. Also, as a carbonate-based compound,
JP-A-3-149295, European Patent Publication No. 421
No. 298, etc., but their stability against hydrolysis cannot be said to be sufficient. In addition, sulfone-based compounds and sulfoxide-based compounds
/ 1990) and amide compounds (US Pat. No. 50211)
79 specification) and the like, but the compatibility of the high-viscosity compound with Freon 134a is unknown. A mixture containing one or more of the above compounds is also known, but it does not necessarily have satisfactory performance.

As described above, the lubricating oil for the compressor type refrigerator, which has a sufficiently good compatibility with the Freon 134a and is excellent in the lubricating performance, has not yet been found. It was strongly desired. The present invention responds to such a demand, and is particularly compatible with hydrogen-containing CFC compounds such as CFC12, which is a refrigerant which is a problem in environmental pollution, or CFC134a which can substitute for other CFC compounds which are difficult to decompose. The object of the present invention is to provide a lubricating oil for a compression type refrigerator, which is good over the entire operating temperature range and has excellent lubricating performance.

The research group of the present inventors has already found a polyalkylene glycol derivative having good compatibility with Freon 134a, as shown in JP-A-3-14894, and in European Patent Publication No. 401969. The compatibility was improved. Furthermore, as a result of intensive research to develop a lubricating oil for a compression type refrigerator, which has excellent compatibility with a hydrogen-containing CFC compound such as CFC134a, stability, and lubrication performance, as a result of repeated research, It was found that the compatibility of oxyalkylene glycol is specifically high. The present invention has completed the present invention based on this finding.
That is, the present invention has the general formula

[0010]

[Chemical 2]

(In the formula, R ^{1 to} R ⁶ each represent hydrogen or an alkyl group having 1 to 6 carbon atoms, and A ^{1 to} A ⁶ each represent a polyoxyalkylene group having a repeating main chain of an oxyethylene group. The present invention provides a lubricating oil for a compression refrigerator, which has a polyoxyalkylene glycol derivative represented by the formula (4) as a main component and has a kinematic viscosity at 100 ° C. of 2 to 50 cSt.

R ^{1 to} R ⁶ in the above general formula (I) each represent hydrogen or an alkyl group having 1 to 6 carbon atoms.
This alkyl group is specifically a methyl group, an ethyl group, an n group
-Propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, various pentyl groups, and various hexyl groups are shown. As the carbon number of the alkyl group increases, the compatibility with Freon 134a decreases, so hydrogen or an alkyl group having 3 or less carbon atoms is desirable. R
^{1 to} R ⁶ may be the same or different from each other. When the proportion of hydrogen in R ^{1 to} R ⁶ is high, not only the viscosity index becomes low, but also the compatibility is lowered, so 70% or less, especially 50% of the whole R ^{1 to} R ⁶ is caused.
The following is desirable. Further, A ^{1 to} A ⁶ are polyoxyalkylene groups having a repeating main chain of oxyethylene groups, which is, for example, a polymer of propylene oxide of the formula (II)

[0013]

[Chemical 3]

(Wherein n represents an integer of 1 to 80) is a polyoxypropylene group. Further examples of these A ^{1 to} A ⁶ include ethylene oxide; propylene oxide; 1,2-butylene oxide;
Butylene oxide; isobutylene oxide; glycidyl methyl ether; ethyl glycidyl ether; propyl glycidyl ether; butyl glycidyl ether; 2-
Ethylhexyl glycidyl ether; 2-Methyloctyl glycidyl ether; Vinyl glycidyl ether; Allyl glycidyl ether; Phenyl glycidyl ether; sec-Butyl phenyl glycidyl ether;
7-Dioxa-1,2-epoxyoctane; 1,2-epoxy-4,7,10-trioxaundecane; 1,2
-Epoxy-4,7,10,13-tetraoxatetradecane; 4,7-Dioxa-1,2-epoxy-5-methyloctane; 4,7-Dioxa-1,2-epoxy-
6-methyloctane; 1,2-epoxy-4,7,1
0,13-tetraoxa-6,9,12-trimethyltetradecane; 1,2-epoxy-5-methyl-4,7,
10-trioxaundecane; 1,2-epoxy-8-
Methyl-4,7,10-trioxaundecane; 2,7
-Dioxa-4,5-epoxyoctane; 4,5-epoxy-9-methyl-2,7,10-trioxaundecane; 4,5-epoxy-2,7,10,13-tetraoxatetradecane; 8-epoxy-2,5,10,
13-tetraoxatetradecane; 1,2-epoxy-
3-methoxy-5-oxahexane; 4,8-dioxa-1,2-epoxy-6-methoxynonane; 4,7-dioxane-1,2-epoxy-5- (2-oxapropyl) -octane; 3 , 5-bis (2-oxapropyl)
-4,7-Dioxa-1,2-epoxyoctane; 3,
6-bis (2-oxapropyl) -4,7-dioxa-
1,2-epoxyoctane; homopolymers or plural copolymers of epoxy compounds such as 6,9-bis (2-oxapropyl) -1,2-epoxy-4,7,10-oxaundecane (provided that These are divalent groups) and the like. The A ^{1 to} A ⁶ may be the same or different from each other.

When the viscosity of the lubricating oil of the present invention is too low, the oil film thickness required for lubrication cannot be maintained, and when the viscosity is too high, the compatibility becomes insufficient, so that the kinematic viscosity at 100 ° C. It is preferably 2 to 50 cSt, particularly 5 to 40 cSt.

Further, the lubricating oil of the present invention includes various additives used in conventional lubricating oils, such as load-bearing additives, chlorine scavengers, antioxidants, metal deactivators, defoamers, If desired, a detergent dispersant, a viscosity index improver, an oiliness agent, an antiwear additive, an extreme pressure agent, a rust inhibitor, a corrosion inhibitor, a pour point depressant, etc. can be added. Examples of the load-bearing additive include monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils,
Organic sulfur compounds such as thiocarbonates, thiophenes, thiazoles, methanesulfonic acid esters, phosphoric acid such as phosphoric acid monoesters, phosphoric acid diesters, phosphoric acid triesters (tricresyl phosphate) Ester type, phosphite monoesters, phosphite diesters, phosphite triesters and other phosphite types, thiophosphate triesters and other thiophosphate type higher fatty acids , Hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters, fatty acid-based compounds such as metal soaps, polyhydric alcohol esters, acrylate-based fatty acid ester-based compounds, chlorinated hydrocarbons, chlorination Organic chlorinated compounds such as carboxylic acid derivatives, fluorinated aliphatic carboxylic acids, fluorine Ethylene resins, fluorinated alkyl polysiloxanes, those organic fluorine-based, such as fluorinated graphite, those of alcohol, such as higher alcohol, naphthenic acid salts (lead naphthenate), fatty acid salts (fatty acid lead),
There are metal compounds such as thiophosphates (zinc dialkyldithiophosphate), thiocarbamates, organic molybdenum compounds, organic tin compounds, organic germanium compounds, and boric acid esters. Examples of chlorine scavengers include glycidyl ether group-containing compounds, epoxidized fatty acid monoesters, epoxidized oils and fats, and epoxycycloalkyl group-containing compounds. Examples of antioxidants include phenols (2,6-ditertiarybutyl-p-cresol) and aromatic amines (α-naphthylamine). Examples of the metal deactivator include a benzotriazole derivative. Examples of the defoaming agent include silicone oil (dimethyl polysiloxane) and polymethacrylates. Examples of the detergent dispersant include sulfonates, phenates, and succinimides. Examples of the viscosity index improver include polymethacrylate, polyisobutylene, ethylene-propylene copolymer, and styrene-diene hydrogenated copolymer.

[0017]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Production Example 1 In a 300 ml eggplant-shaped flask, 100 g of a propylene oxide ring-opening polymer (hydroxyl value 400) using D-sorbit as an initiator and 5.9 g of potassium methoxide (0.
(084 mol) was added, and methanol was removed under reduced pressure (1.0 mmHg) at 90 ° C. for 2 hours. This compound 44.5
g was added to a 300 ml stainless steel autoclave equipped with a stirrer and a liquid introduction tube, the atmosphere was replaced with nitrogen, the vessel was sealed and heated to 110 ° C., and a mixture of ethylene oxide and propylene oxide (molar ratio 1: 1) was added with stirring.
00 g was pressed into the autoclave through the liquid introduction tube over 10 hours and stirred for 4 hours. After cooling, 120 ml of water, 240 ml of methanol and 100 g of ion exchange resin DIAION SMNI (manufactured by Mitsubishi Kasei Co., Ltd.) were added to the reaction mixture, and the mixture was stirred for 30 minutes and then filtered. After distilling off the solution methanol and water,
It was dried at 100 ° C. for 1 hour under reduced pressure of a vacuum pump (0.4 mmHg) to obtain 135 g of an ethylene oxide-propylene oxide copolymer. To 50 g of the product was added 30 g (0.16 mol) of a 28 wt% sodium methoxide methanol solution, and the methanol was removed under reduced pressure (1.0 mmHg) at 120 ° C. for 3 hours. Stir the reaction product 3
The mixture was transferred to a 00 ml stainless steel autoclave, 30 g (0.21 mol) of methyl iodide was added thereto, the atmosphere was replaced with nitrogen, the vessel was sealed, the temperature was gradually raised to 90 ° C. with stirring, and the mixture was further stirred for 4 hours. After cooling, the methyl iodide was distilled off, then 120 ml of water and 240 ml of methanol were added.
200 ml of milliliter and DIASION SMNI were added, and the mixture was stirred for 30 minutes and then filtered. After distilling off the methanol and water of the solution, the vacuum pump was depressurized (0.4 mmH
g) After drying at 100 ° C. for 1 hour, 38 g of the target polyoxyalkylene glycol was obtained.

Production Example 2 In a 300 ml eggplant type flask, 100 g of a propylene oxide ring-opening polymer (hydroxyl value 400) using D-sorbit as an initiator and 5.9 g of potassium methoxide (0.
(084 mol) was added, and methanol was removed under reduced pressure (1.0 mmHg) at 90 ° C. for 2 hours. This compound 20.0
g to a 300 ml four-necked flask equipped with a stirrer and a dropping funnel, heated to 110 ° C.,
50 g of dioxa-1,2-epoxy-5-methyloctane (obtained by distillation after reacting epichlorohydrin, 1-methoxy-2-propanol and sodium hydroxide at 40 ° C.) was added dropwise and stirred for 14 hours. did. After cooling, 30 g (0.16 mol) of a 28 wt% sodium methoxide methanol solution was added to the product, and the product was added under reduced pressure (1.0 m
mHg) The methanol was removed at 90 ° C. for 3 hours. The reaction product was transferred to a 300 ml stainless steel autoclave equipped with a stirrer, and 30 g of methyl iodide (0.2
(1 mol) was added, the atmosphere was replaced with nitrogen, the vessel was sealed, the temperature was gradually raised to 90 ° C. with stirring, and the mixture was further stirred for 4 hours. After cooling, the methyl iodide was distilled off, then 120 ml of water, 240 ml of methanol and DIAION
200 g of SMNI was added, and the mixture was stirred for 30 minutes and then filtered. After distilling off the methanol and water of the solution, it was dried at 100 ° C. for 1 hour under reduced pressure of a vacuum pump (0.4 mmHg),
Target 4,7-dioxa-1,2-epoxy-5-
45 g of polyoxyalkylene glycol, which is a polymer of methyloctane, was obtained.

Production Example 3 In a 300 ml eggplant-shaped flask, 100 g of a propylene oxide ring-opening polymer (hydroxyl value 400) using D-sorbit as an initiator and 5.9 g of potassium methoxide (0.
(084 mol) was added, and methanol was removed under reduced pressure (1.0 mmHg) at 90 ° C. for 2 hours. This compound 46.8
g was added to a 300 ml stainless steel autoclave equipped with a stirrer and a liquid introduction tube, the atmosphere was replaced with nitrogen, then sealed, and heated to 110 ° C, and 100 g of propylene oxide was stirred in the autoclave for 10 hours through the liquid introduction tube. It was pressed in and stirred for another 4 hours. After cooling, 40 g (0.21 mol) of a 28 wt% sodium methoxide methanol solution was added to 50 g of this product, and the mixture was added under reduced pressure (1.0
(mmHg) Methanol was removed at 120 ° C. for 3 hours. The reaction product was transferred to a 300 ml stainless steel autoclave equipped with a stirrer, and 40 g of methyl iodide (0.
(28 mol) was added, the atmosphere was replaced with nitrogen, the vessel was sealed, the temperature was gradually raised to 90 ° C. with stirring, and the mixture was further stirred for 4 hours.
After cooling, the methyl iodide was distilled off, then 120 ml of water, 240 ml of methanol and DIAIO
After adding 200 g of NSMNI and stirring for 30 minutes,
Filtered. After distilling off the methanol and water of the solution, it was dried at 100 ° C. for 1 hour under reduced pressure of a vacuum pump (0.4 mmHg) to obtain 43 g of polyoxyalkylene glycol which was a target polymer of propylene glycol.

Reference Example 1 1.24 g (0.018 mol) of powdered sodium methoxide was added to a 200 ml stainless steel autoclave equipped with a stirrer and a liquid introduction tube, and the mixture was sealed.
The mixture was heated to 0 ° C. and, under stirring, 50 g of 4,7-dioxa-1,2-epoxy-5-methyloctane was injected under pressure into the autoclave through the liquid introduction tube for 20 hours. Water for reaction mixture 12
After 0 ml and 240 ml of methanol were added and dissolved, the solution was passed through a column of 200 ml of cation exchange resin and then 200 ml of anion exchange resin.
Sodium ions were removed by passing through a milliliter column. After distilling off methanol and water, the product was dried under reduced pressure in a vacuum pump (0.4 mmHg) at 100 ° C. for 1 hour to obtain the desired polymer of 4,7-dioxa-1,2-epoxy-5-methyloctane. 45 g of a certain polyoxyalkylene glycol (methyl ether at one end and hydroxyl group at the other end) was obtained.

Reference Example 2 To a 200 ml stainless steel autoclave equipped with a stirrer and a liquid introduction tube, 1.6 g of methanol and 0.2 g of sodium hydroxide were added, and the mixture was sealed and heated to 110 ° C. and propylene oxide was stirred. 130 g of the liquid was introduced into the autoclave through the liquid introducing tube for 10 hours, and then 20 more
Stir for hours. After cooling, 120 ml of water and 240 ml of methanol were added to the reaction mixture to dissolve it, and then the solution was passed through a column of 200 ml of a cation exchange resin and then a column of 200 ml of an anion exchange resin to remove sodium ions. .. After distilling off methanol and water, the vacuum pump was depressurized (0.4 m
mHg) It was dried at 100 ° C. for 1 hour to obtain 115 g of the target polyoxyalkylene glycol monomethyl ether.

Examples 1 to 3 and Comparative Examples 1 to 2 The compatibility of the compounds obtained in Production Examples 1 to 3 and Reference Examples 1 to 2 was measured by the following method. That is, a predetermined amount of sample was added to a pressure-resistant glass ampoule so that the amount was 5 and 10% by weight with respect to Freon 134a (1,1,1,2-tetrafluoroethane), and this was applied to a vacuum pipe and Freon 134a gas pipe. Connected The ampoule was vacuum degassed at room temperature and then cooled with liquid nitrogen to collect a predetermined amount of Freon 134a. Then, the ampoule was sealed, and the temperature was raised from -40 ° C in a thermostat to measure the temperature at which phase separation started. The higher the phase separation temperature, the better. The results are shown in Table 1.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

EFFECT OF THE INVENTION The lubricating oil of the present invention has excellent compatibility with a refrigerant and lubricating performance and is used for a compression type refrigerator, but unlike conventional lubricating oils, a hydrogen-containing flon compound such as Freon 134a (specifically, Specifically, in addition to the Freon 134a,
1,1-Dichloro-2,2,2-trifluoroethane (CFC 123); 1-chloro-1,1-difluoroethane (CFC 142b); 1,1-difluoroethane (CFC 152a); chlorodifluoromethane (CFC 22) ) Or trifluoromethane (Freon 23) and the like). Therefore, the lubricating oil of the present invention is suitable for a compression type refrigerator that uses these hydrogen-containing CFC compounds, especially CFC 134a as a refrigerant. Further, for the purpose of improving the compatibility with the refrigerant, it can be used by mixing with other lubricating oil for a compression type refrigerator.

Claims (3)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R ^{1 to} R ⁶ each represent hydrogen or an alkyl group having 1 to 6 carbon atoms, and A ^{1 to} A ⁶ each represent a polyoxyalkylene group having a repeating main chain of an oxyethylene group). It has a polyoxyalkylene glycol derivative as a main component and has a kinematic viscosity of 2 at 100 ° C.
Lubricating oil for compression type refrigerators of up to 50 cSt. 2. The lubricating oil for a compression refrigerator according to claim 1, wherein the proportion of R ^{1 to} R ⁶ in the general formula (I) is hydrogen is 70% or less. 3. A compression type refrigerator uses 1,1, as a refrigerant.
The lubricating oil for a compression type refrigerator according to claim 1, wherein 1,2-tetrafluoroethane is used.