JPH0768534B2 - Lubricating oil for compression type refrigerator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel lubricating oil for a compression type refrigerator. More specifically, the present invention is particularly applicable to 1,1,1,2-tetrafluoroethane (hereinafter referred to as fluorocarbon), which can substitute for dichlorodifluoromethane (hereinafter referred to as fluorocarbon 12), which is a refrigerant that is a problem in environmental pollution. (Referred to as 134a)), and to a lubricating oil for a compression type refrigerating machine containing a polyoxyalkylene glycol derivative as a main component, which has a good compatibility with a lubricating oil.

[Conventional technology]

The compression type refrigerator is generally composed of a compressor, a condenser, an expansion valve and an evaporator, and has a structure in which a mixed liquid of a refrigerant and lubricating oil circulates in this closed system. In such a compression type refrigerator, depending on the type of device, in general,
Since the temperature in the compressor is 50 ℃ or higher and the temperature in the cooler is about -40 ℃, the refrigerant and lubricating oil are usually -40 to +50.
It is necessary to circulate within this system without phase separation at temperatures in the range of ° C. If phase separation occurs, it will have a significant adverse effect on the life and efficiency of the device. For example, if phase separation of the refrigerant and lubricating oil occurs in the compressor part, poor lubrication of the moving parts may cause seizure, etc., which significantly shortens the life of the device, while phase separation occurs in the evaporator. However, the presence of high-viscosity lubricating oil causes a decrease in heat exchange efficiency.

In addition, since the lubricating oil for a refrigerator is used for the purpose of lubricating the moving parts of the refrigerator, the lubrication performance is naturally important. Especially, since the temperature inside the compressor becomes high, a viscosity that can retain an oil film necessary for lubrication is required. Required to have. The required viscosity varies depending on the type of compressor used, operating conditions, etc., but the viscosity (kinematic viscosity) of lubricating oil before mixing with a refrigerant is usually in the range of 2 to 50 centistokes at a temperature of 100 ° C. Is preferred. If the viscosity is lower than the above value, the oil film becomes thin and poor lubrication is likely to occur, and if the viscosity is high, the efficiency of heat exchange decreases. In addition, since the lubricating oil for refrigerator is used for lubrication in a wide temperature range from high temperature to low temperature, it is preferable that its viscosity index is high, and usually a viscosity index of 40 or more is required, and as other performance, Low hygroscopicity is required to prevent the expansion valve from blocking due to freezing.

Conventionally, Freon 12 is often used as the refrigerant of a compression refrigerator, and various mineral oils and synthetic oils satisfying the above-mentioned required characteristics have been used as the lubricating oil. However,
Fluorocarbon 12 has recently become stricter in regulations around the world because it may cause environmental pollution such as depletion of the ozone layer.
134a has come to the fore. This Freon 134a
Is a preferable refrigerant for a compression type refrigerator because it has a low risk of destroying the ozone layer and can be replaced with CFC 12 with almost no change in the structure of a conventional refrigerator.

As the refrigerant of the compression type refrigerator, if the Freon 134a is adopted instead of the Freon 12, as the lubricating oil, of course, the compatibility with the Freon 134a is excellent, and the lubricating performance that can satisfy the required performance described above. However, the lubricating oil that has been used with conventional Freon 12 is Freon 134a.
Due to its poor compatibility with, a new lubricating oil suitable for Freon 134a is required. In this case, especially in automobile air conditioners, when substituting CFCs, it is required that the structure of the device is hardly changed.
It is not desirable to make major changes to the structure of existing equipment, and therefore a lubricating oil with very good compatibility with Freon 134a is required.

Examples of the lubricating oil having compatibility with Freon 134a include Ulcon LB-165 and Urcon LB-525 (both manufactured by Union Carbide Co.,
Trade name) is known, and it is reported that these lubricating oils are compatible with Freon 134a in a total composition ratio at a low temperature of at least -50 ° C. ["Research Disclosure" No. 17463 (19
October 1978)].

However, these lubricating oils are polyalkylene glycol derivatives in which one end of polypropylene glycol has a hydroxyl group and the other end has an n-butyl ether bond, and has relatively good compatibility with Freon 134a at low temperatures. However, the compatibility is not sufficient on the high temperature side,
For example, the ulcon LB-525 is a fluorocarbon 1 at room temperature.
It is also known to cause phase separation with 34a (US Pat. No. 4,755,316).

On the other hand, as having good compatibility with Freon 134a,
A polyglycol having at least two hydroxyl groups in one molecule has been proposed (US Pat. No. 4,755,316). However, in this polyglycol,
The compatibility is not always sufficient, and since there are a large number of hydroxyl groups in one molecule, there is a drawback that an increase in hygroscopicity and a decrease in viscosity index cannot be avoided. An increase in hygroscopicity leads to an increase in the amount of dissolved water in the mixture of the refrigerant and the lubricating oil, and as a result, the expansion valve may be clogged with ice, and a decrease in the viscosity index is caused by the low temperature evaporator. However, the viscosity may increase and the heat exchange efficiency may decrease.

In addition, polyglycol, when the mixture with Freon is heated from low temperature to high temperature, the mixture that was generally phase separated,
It is known to show temperature dependence of once compatible and phase separated.

On the other hand, it has been proposed to use Freon 134a and a compound capable of dissolving it in an absorption refrigerator (Japanese Patent Laid-Open No.
-79175), this absorption refrigerator is completely different in mechanism from the compression refrigerator which is the object of the present invention, and since the tetraethylene glycol dimethyl ether described in the examples has a remarkably low viscosity. , Unsuitable as a lubricating oil for compression type refrigerators.

In this way, the compatibility with Freon 134a is sufficiently good, and the lubricating oil for the compression type refrigerator with excellent lubricating performance is not yet found, and its development is strongly desired. It was

[Problems to be Solved by the Invention]

The present invention responds to such a demand, and in particular, a CFC 13 which can be used as a substitute for the CFC 12 refrigerant which is a problem in environmental pollution.
The purpose of the present invention is to provide a lubricating oil for a compression type refrigerator, which has good compatibility with 4a over the entire operating temperature range and has excellent lubricating performance.

[Means for Solving the Problems]

The present inventor has conducted extensive studies to develop a compression type refrigerating machine lubricating oil having both excellent compatibility with Freon 134a and lubrication performance, and as a result, a polyoxyalkylene glycol derivative having a specific structure as a main component. It was found that the above can meet the above-mentioned object, and the present invention has been completed based on this finding.

That is, the present invention is a lubricating oil for a compression type refrigerator using 1,1,2-tetrafluoroethane as a refrigerant, the general formula (In the formula, R ¹ is a methyl group, R ² is an alkylene group having 2 to 4 carbon atoms, R ³ is a methyl group, and m is a number of 6 to 80), and the viscosity at a temperature of 100 ° C. is 5 Provided is a lubricating oil for a compression refrigerator, which comprises a polyoxyalkylene glycol derivative having a content of -50 centistokes as a main component.

Hereinafter, the present invention will be described in detail.

The lubricating oil of the present invention has the general formula The polyoxyalkylene glycol derivative represented by

In the formula, R ¹ represents a methyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, and R ³ represents a methyl group. Furthermore, m is 6-
The number is 80.

R ² in the general formula (I) is an alkylene group having 2 to 4 carbon atoms, and as the oxyalkylene group of the repeating unit,
Examples thereof include oxyethylene group, oxypropylene group, and oxybutylene group. The oxyalkylene groups in one molecule may be the same or two or more kinds of oxyalkylene groups may be contained, but one containing at least an oxypropylene unit in one molecule is preferable, and an oxyalkylene unit is particularly preferable. Those containing 50 mol% or more of oxypropylene units are preferred.

M in the general formula (I) is a number of 6 to 80, and if it deviates from this range, the object of the present invention cannot be sufficiently achieved.

The polyoxyalkylene glycol derivative represented by the general formula (I) used in the lubricating oil of the present invention can be produced by various methods shown below.

Method (A): 2 carbon atoms such as ethylene oxide and propylene oxide
~ 4 alkylene oxide is polymerized with water or an alkali hydroxide as an initiator to give a compound of the general formula (Wherein p is a number from 6 to 80 and R ² has the same meaning as described above), and a polyoxyalkylene glycol having hydroxyl groups at both ends is obtained, and then both of the hydroxyl groups are ether. By conversion to methyl ether (Wherein R ³ and R ⁴ are methyl groups, and R ² and p have the same meanings as described above), a polyoxyalkylene glycol derivative (dimethyl ether of polyoxyalkylene glycol) is obtained.

Method (B): Using a monohydric alcohol (methanol) having 1 carbon atom or an alkali metal salt thereof as an initiator, an alkylene oxide having 2 to 4 carbon atoms is polymerized to obtain a compound represented by the general formula: (Wherein R ⁵ is a methyl group, R ² and p have the same meanings as described above), and has an ether bond (methyl ether bond) at one end and a hydroxyl group at the other end. After obtaining a certain polyoxyalkylene glycol monomethyl ether,
By etherifying the hydroxyl group of this product (methyl etherification), the general formula (Wherein R ² , R ³ , R ⁵ and P have the same meanings as described above), a polyoxyalkylene glycol derivative (dimethyl ether of polyoxyalkylene glycol) is obtained.

In these production methods, in order to etherify (methyl etherify) the hydroxyl group of the polyoxyalkylene glycol or its derivative having a hydroxyl group at the terminal, it is usually necessary to add an alkali metal such as sodium metal or sodium methoxide A method of reacting an alkali metal salt to obtain an alkali metal salt of the polyoxyalkylene glycol or its derivative, and then reacting it with an alkyl halide having 1 carbon atom, a sulfuric acid ester or a sulfonic acid ester, or A method of converting the hydroxyl group of polyoxyalkylene glycol or a derivative thereof into a sulfonate or a halide and then reacting this with an aliphatic alcohol (methanol) having 1 carbon atom or an alkali metal salt thereof is usually used.

In the polyoxyalkylene glycol derivative of the present invention thus obtained, the bonding mode of oxyalkylene units is usually head-to-tail in the case of oxypropylene units and oxybutylene units, but head-to-head and tail-to-tail. There may be a small amount of the binding mode of. The lubricating oil of the present invention is a polyoxyalkylene glycol derivative represented by the general formula (I) thus obtained (provided that the average molecular weight is 700
However, the polyoxyalkylene glycol derivative may be used alone or in combination of two or more kinds. In addition to the polyoxyalkylene glycol derivative represented by the general formula (I), the lubricating oil is a polyoxyalkylene glycol derivative having a hydroxyl group at the terminal, and the content of the hydroxyl group is based on all terminals, If the ratio is 30 mol% or less, it can be suitably used even if it is contained. If the content of the hydroxyl group exceeds 30 mol%, the hygroscopicity increases and the viscosity index decreases, which is not preferable.

When neither R ¹ nor R ³ in the general formula (I) is a methyl group, the compatibility becomes insufficient.

Further, the lubricating oil of the present invention has a viscosity (kinematic viscosity) at a temperature of 100 ° C. of 5 to 50 centistokes, preferably 5 to 30 centistokes in order to maintain an oil film thickness necessary for lubrication. is necessary. The lubricating oil of the present invention includes various additives conventionally used in conventional lubricating oils, such as load bearing additives, chlorine scavengers, antioxidants, metal deactivators, defoamers, detergent dispersants, and viscosity agents. Index improvers, oiliness agents, antiwear agents, extreme pressure agents, rust inhibitors, corrosion inhibitors, pour point depressants, etc. can be added as desired.

Examples of the load-bearing additives include organic sulfur compounds such as monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes, thiazoles, and methanesulfonic acid esters. Phosphoric acid ester-based compounds such as phosphoric acid monoesters, phosphoric acid diesters, phosphoric acid triesters (tricresyl phosphate), phosphorous acid monoesters, phosphorous acid diesters, phosphorus Phosphite-based compounds such as acid triesters, thiophosphoric acid-based compounds such as thiophosphoric acid triesters, higher fatty acids, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters, fatty acids such as metal soaps Type, polyhydric alcohol esters, acrylic acid esters, etc. Fatty acid ester type, chlorinated hydrocarbons, chlorinated carboxylic acid derivatives and other organic chlorine type, fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkyl polysiloxanes, fluorinated black smoke, etc. Organic fluorine compounds, alcohol compounds such as higher alcohols, naphthenates (lead naphthenate),
Fatty acid salts (lead fatty acid), thiophosphates (zinc dialkyldithiophosphates), thiocarbamates, organomolybdenum compounds, organotin compounds, organogermanium compounds, metal compounds such as borate esters, chlorine scavengers Are glycidyl ether group-containing compounds, epoxidized fatty acid monoesters, epoxidized oils and fats, epoxycycloalkyl group-containing compounds, and as antioxidants, phenols (2,6-ditertiarybutyl-p-cresol), aromatic compounds Amines (α-naphthylamine),
As the metal deactivator, a benzotriazole derivative,
Defoaming agents include silicone oil (dimethylpolysiloxane) and polymethacrylates, detergent and dispersants such as sulfonates, phenates and succinimides, and viscosity index improvers such as polymethacrylate, polyisobutylene and ethylene- Examples thereof include a propylene copolymer and a styrene-diene hydrogenated copolymer.

The lubricating oil of the present invention has excellent compatibility with a refrigerant and lubrication performance and is used for a compression type refrigerator, but unlike conventional lubricating oils, it has good compatibility with Freon 134a, so that Freon 134a is particularly used as a refrigerant. Is suitable for a compression type refrigerator using. Further, for the purpose of improving the compatibility with the refrigerant, it can be used by being mixed with many lubricating oils for a compression type refrigerator.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

Reference Production Example 1 A glass 300 ml three-necked flask equipped with a stirrer and a distillation head was charged with polyoxypropylene glycol mono n-.
65 g of butyl ether (average molecular weight 1120) and 70 ml of toluene were added, and about 20 ml of toluene was distilled off under heating and stirring to remove water. After cooling, 25 g (0.13 mol) of a 28 wt% sodium methoxide methanol solution was added, and the mixture was heated to distill off methanol and about 20 ml of toluene. Then, after cooling, the distillation head was removed, a condenser and a dropping funnel were attached, and the mixture was heated to 50 ° C. and stirred with 30 g of ethyl iodide (0.1 g
(9 mol) was added from a dropping funnel over 30 minutes. 1 at 50 ° C
The mixture was heated at 70 ° C. for 3 hours and at 105 ° C. for 1.5 hours, stirred, and then cooled to room temperature. Then, the reaction mixture was transferred to a separating funnel and washed 5 times with 50 ml of saturated saline each. After distilling off the toluene, depressurize with a vacuum pump at 100 ° C for 1 hour.
After drying for an hour, the target ethyl ether derivative of polyoxypropylene glycol mono-n-butyl ether (polyoxypropylene glycol monoethyl-mono-n-
Butyl ether) 58 g was obtained.

Reference Production Example 2 To a glass 300 ml three-necked flask equipped with a stirrer and a distillation head, 60 g of Unilube MB-11 (polyoxypropylene glycol mono-n-butyl ether (average molecular weight 1000)) made by NOF CORPORATION and 80 ml of toluene were added. About 20 ml of toluene was distilled off under heating and stirring to remove water.

After cooling, 14 g (0.073 mol) of a 28 wt% sodium methoxide methanol solution was added and heated to distill off methanol and about 20 ml of toluene.

After cooling, the contents were transferred to a stainless steel 300 ml autoclave equipped with a stirrer, 12 g (0.085 mol) of methyl iodide was added, and after sealing, the temperature was raised from 50 ° C to 70 ° C over 4.5 hours with stirring, and 85 The reaction was carried out at ℃ for 4 hours. After cooling to room temperature,
The reaction mixture was dissolved in a mixture of 100 ml of water and 200 ml of methanol, 200 ml of cation exchange resin, then 20 ml of anion exchange resin.
Pass through a 0 ml column.

After distilling off the solvent, vacuum pump under reduced pressure (0.4mmHg), 100 ℃, 1
After drying for an hour, 55 g of the target methyl ether derivative of Unilube MB-11 (monomethyl mono n-butyl ether of polyoxypropylene glycol) was obtained. This derivative has an infrared absorption spectrum (3450c
m ^-1 ) had disappeared.

Production Example 1 Sanyo Kasei Kogyo Co., Ltd. Sannix PP-in a glass 300ml three-necked flask equipped with a stirrer and a distillation head.
50 g of 1000 (polyoxypropylene glycol having hydroxyl groups at both ends, average molecular weight 1000) and 80 ml of toluene were added, and about 20 ml of toluene was distilled off while heating and stirring to remove water.

After cooling, 25 g (0.13 mol) of a 28 wt% sodium methoxide methanol solution was added, and the mixture was heated to distill off methanol and about 20 ml of toluene.

After cooling, the contents were transferred to a stainless steel 300 ml autoclave equipped with a stirrer, 36.8 g (0.26 mol) of methyl iodide was added, and after sealing, the temperature was raised from 50 ° C to 70 ° C over 4.5 hours with stirring, The reaction was carried out at 85 ° C for 4 hours. After cooling to room temperature, the reaction mixture was dissolved in a mixture of 100 ml of water and 200 ml of methanol and passed through a column of 200 ml of cation exchange resin and then 200 ml of anion exchange resin.

After distilling off the solvent, vacuum pump vacuum (0.1mmHg), 100 ℃, 1
After drying for an hour, 42.5 g of the desired dimethyl ether derivative of Sannix PP-1000 (dimethyl ether of polyoxypropylene glycol) was obtained. In this derivative, the infrared absorption spectrum (3450 cm ⁻¹ ) based on the hydroxyl group disappeared.

Production Example 2 60g, Nissan Uniol D-1200 (polyoxypropylene glycol having hydroxyl groups at both ends, average molecular weight 1200) manufactured by NOF CORPORATION instead of Sannix PP-1000
Using exactly the same procedure as in Production Example 1 except for using, the dimethyl ether derivative of Nissan Uniol D-1200 (dimethyl ether of polyoxypropylene glycol) 49
got g. In this derivative, the infrared absorption spectrum (3450 cm ⁻¹ ) based on the hydroxyl group disappeared.

Production Example 3 Powdered sodium methoxide (3.0 g) was added to a 200 ml stainless steel autoclave equipped with a stirrer and a liquid introduction tube.
(056 mol) was added and the mixture was sealed, heated to 105 ° C., and 100 g of propyne oxide was pressure-inserted into the autoclave through the liquid introduction tube for 10 hours while stirring. After cooling the autoclave to room temperature, add 19 g of methyl iodide while cooling in ice water.
(0.13 mol) was added. 90 ° C in an autoclave with stirring
After gradually heating to 90 ° C., the mixture was reacted at 90 ° C. for 4 hours. The reaction mixture was transferred to a glass 300 ml flask, heated under reduced pressure to distill off toluene, and then sodium iodide deposited by centrifugation was removed. Water 100 ml, methanol 20
After dissolving by adding 0 ml, the solution is 200 m of cation exchange resin.
l, then passed through a column of 200 ml of anion exchange resin.

After distilling off the solvent, vacuum pump vacuum (0.1mmHg), 100 ℃, 1
After heating for an hour, 93 g of the target polyoxypropylene glycol dimethyl ether (average molecular weight 1247) was obtained.

Examples 1 to 4, Reference Examples 1 to 4 The compatibility of the compounds obtained in Production Examples 1 to 3 and Reference Production Examples 1 and 2 and the predetermined samples shown in Table 1 was measured.

1 for chlorofluorocarbon 134a (1,1,1,2-tetrafluoroethane)
A predetermined amount of sample was added to the pressure resistant glass ampoule so that it would be 0% by weight and 20% by weight.
Connected to gas line 134a. 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.

[Effects of the Invention] The compression type refrigerator melt lubricating oil of the present invention has polyoxyalkylene glycol with both ends of methyl ether (methoxy group).
Fluorocarbons that are mainly composed of polyoxyalkylene glycol derivatives with the structure
The compatibility with 4a is good over the entire operating temperature range, and the lubricating performance is excellent.
It is extremely suitable as a lubricating oil for a compression type refrigerator using 134a.

Further, the polyoxyalkylene glycol derivative is
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 (2)

[Claims] 1. A lubricating oil for a compression type refrigerator using 1,1,1,2-tetrafluoroethane as a refrigerant, which has a general formula: (In the formula, R ¹ is a methyl group, R ² is an alkylene group having 2 to 4 carbon atoms, R ³ is a methyl group, and m is a number of 6 to 80), and the viscosity at a temperature of 100 ° C. is 5 Lubricating oil for compression type refrigerating machine containing polyoxyalkylene glycol derivative (excluding those having an average molecular weight of 700 or less) that is up to 50 centistokes as the main component. 2. The lubricating oil according to claim 1, wherein the viscosity of the polyoxyalkylene glycol derivative at a temperature of 100 ° C. is 5 to 30 centistokes.