JPH03217495A - Polycarbonate-based synthetic lubricating oil - Google Patents

Abstract

PURPOSE:To obtain the title synthetic lubricating oil consisting essentially of a specific polycarbonate derivative, having good compatibility with a hydrogen- containing fluorocarbon compound and excellent lubricating performance and especially suitable for compression type refrigerating machine. CONSTITUTION:The aimed synthetic lubricating oil containing a polycarbonate derivative having an unit expressed by the formula [R<1> to R<4> are H, 1-6C alkyl, 6-10C aryl, 7-10C arylalkyl or 2-6C alkoxyalkyl (except when all of R<1> to R<4> are H); n is integer of 2-10 (preferably 2-4)] and having 300-3000 (preferably 400-1500) molecular weight as a main component.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to polycarbonate-based synthetic lubricating oils, and more specifically, as an alternative to fluorocarbon compounds such as frozen dichlorofluoromethane (Freon-12), which has become an environmental pollution problem. Mainly uses aliphatic polycarbonate derivatives that have good compatibility with hydrogen-containing fluorocarbon compounds such as l,1,1,2-tetrafluoroethane (hereinafter referred to as Freon 134a) and have excellent lubrication performance. This invention relates to synthetic lubricating oils, particularly lubricating oils for compression type refrigerators.

[Prior art and problems to be solved by the invention] In general, a compression type refrigerator is composed of a compressor, a condenser, an expansion valve, and an evaporator, and a liquid mixture of refrigerant and lubricating oil flows through this closed system. It has a circular structure. In such compression refrigerators, although it depends on the type of equipment, the temperature inside the compressor is generally 50°C or higher, while the temperature inside the cooler is -
Since the temperature is approximately 40°C, it is necessary for the refrigerant and lubricating oil to circulate within this system without phase separation within the temperature range of 40°C to +50°C.

If phase separation occurs during operation of the refrigerator, it will have a significant negative impact on the lifespan and efficiency of the equipment. For example, if phase separation occurs between the refrigerant and lubricating oil in the compressor, the moving parts will suffer from poor lubrication, causing seizures and other problems that will significantly shorten the life of the equipment.On the other hand, if phase separation occurs in the evaporator, , the presence of highly viscous lubricating oil reduces the efficiency of heat exchange.

Furthermore, since lubricating oil for refrigerators is used for the purpose of lubricating the moving parts of refrigerators, lubrication performance is naturally important. In particular, since the temperature inside the compressor is high, it is important to have a viscosity that can maintain the oil film necessary for lubrication. The required viscosity varies depending on the type of compressor used and operating conditions, but usually
The viscosity of the lubricating oil before mixing with the refrigerant is 5-1 at 40°C.
000 cSt is preferred. If the viscosity is lower than this, the oil film will be thinner and lubrication failure will easily occur, and if it is higher than this, the efficiency of heat exchange will decrease.

Conventionally, Freon 12 has been widely used as a refrigerant in compression type refrigerators, and various mineral oils and synthetic oils that meet the above-mentioned required characteristics have been used as lubricating oils. However, since Freon-12 has the potential to cause environmental pollution such as depleting the ozone layer, its regulations have recently become stricter worldwide. Therefore, hydrogen-containing fluorocarbon compounds typified by fluorocarbon 134a have been attracting attention as new refrigerants. This hydrogen-containing fluorocarbon compound,
In particular, Freon 134a is preferable as a refrigerant for compression type refrigerators because it has little risk of destroying the ozone layer and can be substituted for Freon 12 without changing the structure of conventional refrigerators. .

When a hydrogen-containing fluorocarbon compound such as Freon 134a is used instead of Freon 12 as a refrigerant for a compression type refrigerator, it naturally has excellent compatibility with the hydrogen-containing fluorocarbon compound such as Freon 134a as a lubricating oil. A material with excellent lubrication performance that can satisfy the above-mentioned performance requirements is required.

However, the lubricating oil that has been used with conventional Freon 12 does not have good compatibility with hydrogen-containing fluorocarbon compounds such as Freon 134a, so a new lubricating oil suitable for these compounds is required. In this case, especially in automotive air conditioners, it is desired to make almost no changes to the structure of the device when replacing Freon 12, and it is not desirable to make major changes to the structure of the current device for lubricating oil. do not have. Therefore, a lubricating oil is required that has extremely good compatibility with hydrogen-containing fluorocarbon compounds such as fluorocarbon 134a.

As a lubricating oil that is compatible with Freon 134a, for example, Urukon LB-1 made of polyalkylene glycol type
65 and Urukon LB-5 25 (both manufactured by Union Carbide, trade names) are known, and these lubricating oils are compatible with Freon 134a in all composition ratios at low temperatures of at least 50°C. It has been reported that
“Research Disclosure”
Disclosure) J No. 17463 (197
(October 2008)]. Furthermore, a high viscosity refrigerating machine oil composition using polyoxypropylene glycol monobutyl ether as a base oil is also known (Japanese Patent Publication No. 57-42119).

However, these lubricating oils are polypropylene glycol derivatives having a hydroxyl group at one end and an n-butyl ether bond at the other end, and have relatively good compatibility with Freon 134a at low temperatures. However, the compatibility is not sufficient at high temperatures; for example, it is known that Urukon LB-52 5 undergoes phase separation from Freon 134a at room temperature (U.S. Pat. No. 4,755,316). ).

On the other hand, polyoxyalkylene glycol having at least two hydroxyl groups in one molecule has been proposed as having good compatibility with Freon 134a (US Pat. No. 4,755,316).

However, the compatibility of this polyoxyalkylene glycol is not necessarily sufficient.

It is known that polyoxyalkylene glycol exhibits temperature dependence in that when a mixture with a fluorocarbon compound is heated from a low temperature to a high temperature, the mixture, which would normally phase separate, becomes compatible and then phase separates. There is. Furthermore,
It is also known that as the molecular weight of polyoxyalkylene glycol increases, its compatibility decreases.

As described above, a lubricating oil for compressor-type refrigerators that has sufficiently good compatibility with Freon 134a and has excellent lubrication performance has not yet been found, and its development is highly desired. It was rare.

In response to such demands, the present invention has developed a system that is compatible with hydrogen-containing fluorocarbon compounds such as fluorocarbon 134a, which can be used as a substitute for fluorocarbon 12, which is a refrigerant that has become a problem due to environmental pollution, or other fluorocarbon compounds that are difficult to decompose. , a lubricating oil that is good over the entire operating temperature range and has excellent lubrication performance.
In particular, this invention was developed for the purpose of providing a lubricating oil for compression type refrigerators.

[Means to solve the problem]

The inventors of the present invention have conducted intensive research based on the above objective, and have discovered that a polycarbonate-based synthetic oil having a specific structural unit has desired properties.

The present invention was completed based on this knowledge.

That is, the present invention relates to the general formula [wherein R1 to R4 are each hydrogen, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and 7 to 1 carbon atoms]
0 arylalkyl group or an alkoxyalkyl group having 2 to 6 carbon atoms. However, the case where all of R1 to R4 are hydrogen is excluded. n represents an integer from 2 to IO. ] and has a molecular weight of 300 to 3
000 polycarbonate derivative as a main component.

The polycarbonate derivative in the present invention has a structural unit represented by the general formula (1) as described above. In the formula, R
I, R 4 are each hydrogen or an alkyl group having 1 to 6 carbon atoms (e.g., methyl group, ethyl l, n-propyl group, isopropyl group, various butyl groups, various bentyl groups,
various hexyl groups), aryl groups with 6 to 10 carbon atoms (phenyl group, tolyl group, xylyl group, ethylphenyl group, cumenyl group, naphthyl group, etc.), arylalkyl groups with 7 to 10 carbon atoms (benzyl group, α-phenyl group), Ethyl group, β-
phenylethyl group, etc.) or an alkoxyalkyl group having 2 to 6 carbon atoms (methoxymethyl group, methoxyethyl group, ethoxymethyl group, etc.). Among them, especially R
Preferably, one of I and R 4 is an alkyl group such as a methyl group or an ethyl group, and the remainder is hydrogen.

Further, n in the above general formula (I) is 2 to 10, preferably 2 to 4. If n is less than 2, it is not suitable as a lubricating oil due to its low boiling point. Conversely, if it exceeds 10, the solubility of Freon 134a will be insufficient.

Furthermore, the polycarbonate derivative having the structural unit of general formula (1) has a molecular weight (weight average molecular weight) of 300.
~3000, preferably 400~1500. If the molecular weight is less than 300, the kinematic viscosity is too low and it is unsuitable for use as a lubricating oil, whereas if it exceeds 3,000, it becomes waxy and difficult to use as a lubricating oil.

The polycarbonate derivative of the present invention can be produced by various methods, but is usually produced using a carbonate diester or a carbonate-forming derivative such as phosgene and an aliphatic dihydric alcohol as raw materials. Preferred examples of carbonic diesters include dimethyl carbonate and diethyl carbonate. Examples include dipropyl carbonate, dibutyl carbonate, diisobutyl carbonate, etc.

In addition, as aliphatic dihydric alcohols, general formulas (Ninaka,
R'-R' and n are the same as above. ), specifically dipropylene glycol, tripropylene glycol. Propylene glycol condensates such as tetrapropylene glycol, 1,2-butanediol dimer, 1,2-butanediol trikeite, 1,2-
Examples include butanediol tetramer, 2,3-butanediol dimer, 23-butanediol trimer, 2,3-butanediol tetramer, and the like. Among these, condensates of propylene glycol are particularly inexpensive and have high performance. It is obtained as a by-product when propylene glycol is produced by hydrolyzing propylene oxide. It can also be obtained by condensing propylene glycol in the presence of a basic catalyst such as NaOH or ZnO. Furthermore,■
, 2-butanediol dimers, trikeids, and the like can be produced by condensing the corresponding glycols in the presence of the above-mentioned basic isocatalyst.

In order to produce the polycarbonate derivatives used in the present invention using these, the usual polycarbonate production method may be followed, and generally (1) the transesterification method or (2) the phosgene method may be used.

First, according to (1) the transesterification method, an aliphatic dihydric alcohol and a carbonic acid diester are condensed in the presence of a catalyst or in the absence of a catalyst. Catalysts that can be used here include single alkali metals or alkaline earth metals, oxides,
Hydroxide, amidide, alcoholate, phenolate or ZnOP b O , S b 20 :l
Basic metal oxides such as organic titanium compounds, soluble manganese compounds, Ca+ Mg+ Zn, Pb, Sn
, Mn, Cd, Co acetate and antimony compound mixture, hydrosulfite and 2,6-ditertiarybutyl-p-cresol mixture, basic catalyst and phosphoric acid diaryl ester or its salt mixture, quaternary ammonium , quaternary phosphonium or quaternary arsonium salt,
In particular, common basic compounds such as boronate silane compounds are known. Acidic catalysts such as boric acid, P-toluenesulfonic acid, and zinc chloride are generally not effective in transesterification reactions, but they have an apparent pK value of 2 to 10 in a water-methanol solution (1:1). Organic acidic catalysts such as

This transesterification reaction is theoretically an equimolar reaction between an aliphatic monohydric alcohol and a carbonic acid diester. The ratio of both can be varied depending on the desired molecular weight and terminal group of the polycarbonate. For example, by using an excess amount of aliphatic dihydric alcohol, it is possible to obtain a polycarbonate whose terminal groups are hydroxyl groups. Furthermore, a polycarbonate having a high molecular weight can be obtained by using carbonic acid diester in an equimolar amount or in a slightly excessive amount with respect to the aliphatic dihydric alcohol. Usually, from the viewpoint of stability, using an excess of carbonic acid diester leads to good results. Therefore, the ratio of the two used is aliphatic dihydric alcohol/carbonic diester=0.3 to 3.0, preferably 0.9 to 1.2. In addition, the reaction temperature can be appropriately selected depending on the case of no catalyst or the catalyst used, but it is usually 50 to 400"C, preferably 100 to 300"C.
It is done in C. If the reaction temperature is too low, the reaction will not occur, and if it is too high, the raw materials may come out of the system or the molecular weight may increase too much, which is not preferable.

Furthermore, in this transesterification reaction, in order to obtain the target product in high yield, the alcohol produced by transesterification should be completely removed from the reaction mixture. Therefore, it is preferable to stir during the reaction process, and it is also preferable to proceed with the reaction in a vacuum system (under reduced pressure). In addition, it is also possible to perform a two-stage reaction to obtain a half ester having a desired molecular weight by synthesizing the half ester at normal pressure and then reducing the pressure.

The reaction time for the transesterification reaction is usually 1 minute to 8 hours, preferably 30 minutes to 3 hours, and a continuous process can also be used.

In the transesterification reaction, making it easier to distill off the produced alcohol will improve the yield, so it is also effective to use inert gas purge, dry steam purge, thin film evaporator, etc.

Note that after the reaction, the catalyst can be removed by water washing or ion exchange to purify the product, if necessary.

Next, according to the (2) phosgene method, an aliphatic dihydric alcohol and phosgene are reacted using pyridine in a solvent or in the absence of a solvent. Note that this pyridine forms an adduct with phosgene, and this adduct is more reactive with aliphatic dihydric alcohol than with phosgene itself.

Here, the solvent is preferably an organic solvent that is soluble in the polymer and inert to the reaction. Although a large amount of pyridine can be used, it is expensive, so methylene chloride is used. Carbon tetrachloride, chloroform, 1,1,2-trichloroethane, etc. can be suitably used, and methylene chloride is most suitable.

In addition, during the reaction, the charging ratio of aliphatic dihydric alcohol, phosgene, and pyridine should theoretically be selected based on the stoichiometric amounts of the compounds necessary to obtain polycarbonate with the desired degree of polymerization; It is most preferable to use phosgene in a slightly larger amount than the theoretical amount and to use pyridine in a slightly larger amount than the theoretical ratio to the phosgene because this results in a high yield. That is, the ratio of aliphatic dihydric alcohol and phosgene used is such that the aliphatic dihydric alcohol/phosgene (molar ratio) is 0.3 to 10. 0, preferably 0.9~
1.5, and the ratio of pyridine and phosgene used is pyridine/phosgene (molar ratio) of 1.0 to 20. O, preferably 1.1 to 10.0.

Furthermore, the reaction temperature is usually 0 to 200°C, preferably 10
The temperature is set to 100°C to 100°C, more preferably 15 to 60°C. The reaction pressure may normally be normal pressure, but may also be increased or reduced pressure. The reaction time is usually 1 minute to 8 hours, preferably 30 minutes to 3 hours, and a continuous process is also possible.

After the reaction, purification is performed by washing with water or the like, if necessary.

The polycarbonate derivative used in the present invention can be produced by the method described above, but by deriving all or part of the terminal hydroxyl groups into esters or esters, solubility can be improved and hygroscopicity can be reduced. Improved viscosity index,
It is possible to improve lubricity. Note that the hydrocarbon group in the ester and ether residues preferably has 1 to 10 carbon atoms.

In order to esterify the hydroxyl group of the above-mentioned polycarbonate derivative, usually an aliphatic carboxylic acid having 1 to 10 carbon atoms, an acid anhydride thereof, or an aliphatic carboxylic acid having 1 to 10 carbon atoms is added to the hydroxyl group. Reactive agents such as acid halides and esters! or a method in which the hydroxyl group of the polycarbonate derivative is converted into a sulfonic acid ester or halide and then reacted with a carboxylic acid or a salt thereof.

Specific examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid. Examples include valeric acid, caproic acid, cabrylic acid, cabric acid, and cyclohexanecarboxylic acid.

Further, when esterification is carried out using the carboxylic acid or its acid anhydride, or when esterification is carried out by transesterification using the ester of the carboxylic acid, the condensation is carried out without a catalyst or in the presence of a catalyst. When using a catalyst, an acid catalyst such as sulfuric acid or P-1-luenesulfonic acid is usually used. On the other hand, when carrying out esterification using an acid halide, amines are usually used as the dehydrohalogenating agent.

In order to etherify the hydroxyl group, usually a dialkyl sulfate having 1 to 10 carbon atoms is added to the polycarbonate derivative. A method of reacting an alkyl halide or sulfonic acid ester having 1 to 10 carbon atoms, or after converting the hydroxyl group of a polycarbonate derivative to a sulfonic ester or halide, an aliphatic alcohol having 1 to 10 carbon atoms or an alkali metal salt thereof A method of reacting is usually used.

Note that the kinematic viscosity of lubricating oil before mixing with normal refrigerant is 40
Since 5 to 1000 cst at °C is preferable, the raw materials,
Preferably, the reaction conditions are selected. The polycarbonate derivative obtained in this way may be used alone,
Also, two or more types may be combined. Further, even if the kinematic viscosity is outside the above range, the kinematic viscosity can be adjusted to a preferable range by mixing several kinds of kinematic viscosity.

The lubricating oil of the present invention has the above-mentioned polycarbonate derivative as its main component, but it can also be used in combination with other lubricating oils. Furthermore, various additives used in conventional lubricating oils, such as load-bearing additives, chlorine scavengers, antioxidants, metal deactivators, antifoaming agents, detergent dispersants, viscosity index improvers, oiliness agents, Anti-wear additive. Extreme pressure agents, rust preventives, corrosion inhibitors, pour point depressants, etc. can be added as desired.

Examples of the load-bearing additives include monosulfides, polysulfides, sulfoxides, and sulfones. Thiosulfinates. Sulfurized oils and fats, thiocarbonates. Thiophenes, thiazoles. Organic sulfur compounds such as methanesulfonic acid esters, phosphoric acid monoesters. Phosphate esters such as phosphoric acid diesters and phosphoric triesters (tricresyl phosphate), phosphorous acid monoesters, and phosphorous acid diesters. Phosphite esters such as phosphite triesters, thiophosphoric acid esters such as thiophosphoric triesters, higher fatty acids, hydroxyaryl fatty acids, carboxylic acid-containing polyhydric alcohol esters. Fatty acid-based products such as metal soaps, polyhydric alcohol esters. Fatty acid esters such as acrylic esters, chlorinated hydrocarbons, organochlorine such as chlorinated carboxylic acid derivatives, fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkyl polysiloxanes Organic fluorine-based products such as fluorinated graphite, alcohol-based products such as higher alcohols, naphthenates (lead naphthenate),
There are metal compound types such as fatty acid salts (fatty acid lead), thiophosphates (zinc dialkyldithiophosphate), thiocarhamates, organic molybdenum compounds, organic tin compounds, organic germanium compounds, and borate esters.

Examples of chlorine scavengers include glycidyl ether group-containing compounds and eboxidized fatty acid monoesters. eboxidized fat,
Examples include epoxycycloalkyl group-containing compounds. Examples of antioxidants include phenol i (2,6-ditertiarybutyl-p-cresol) and aromatic amines (α-naphthylamine). As a metal deactivator,
Examples include henzotriazole derivatives. Examples of antifoaming agents include dilicon oil (dimethylpolysiloxane) 3 and polymethacrylates. As a detergent and dispersant,
Sulfonates, phenates. These include succinimides. As the viscosity index improver, polymethacrylate, polyisobutylene, ethylene-propylene copolymer,
Examples include styrene-diene hydrogenated copolymers.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples in any way.

Production Example 1 In a 1L three-neck glass flask equipped with a stirrer, a thermometer, and a distillation head for concentrating the distillate, 1 liter of diethyl carbonate was added.
22g (1.03mol), dipropylene glycol 1
34 g (1.00 mol), 0.34 g (1.00 mol) of metallic sodium as a catalyst. 0.5 g was added and heated in an oil bath at 130°C for 3 hours.

When no more ethanol was distilled out, the heating was stopped and the solution was passed through a column of cation exchange resin 2001, and then passed through a column of anion exchange resin 200 to remove sodium.

Next, under reduced pressure with a vacuum pump (0.4 torr), 1
The mixture was heated at 50°C for 30 minutes to obtain 150 g of the target polycarbonate of dipropylene glycol.

Production Example 2 In Production Example 1, under reduced pressure (0.4 torr),
The same operation as in Production Example 1 was performed except that heating was performed at 160°C for 40 minutes, and 147 g of dipropylene glycol polycarbonate was obtained.

Production Example 3 In Production Example 1, under reduced pressure (0.4 torr),
The same operation as in Production Example 1 was performed except that heating was performed at 170°C for 30 minutes, and 145 g of dibrobylene glycol polycarbonate was obtained.

Production Example 4 In Production Example 1, under reduced pressure (0.4 torr),
The same operation as in Production Example 1 was performed except that heating was performed at 180°C for 60 minutes, and 140 g of polycarbonate of dipropylene glycol was obtained.

Production Example 5 The same operation as in Production Example 1 was performed, except that 6 g (1.00 mol) of diethylene glycol LO was used instead of 134 g (1.00 mol) of dipropylene glycol as the raw material. 125 g of polycarbonate of diethylene glycol was obtained.

Examples 1-4. Comparative Examples 1 and 2 Using the polycarbonates obtained in Production Examples 1 to 5 or commercially available polyoxypropylene glycol mono-n-butyl ether as samples, their compatibility was measured according to the following procedure.

Add a predetermined amount of sample to a pressure-resistant glass ampoule so that the concentration is 10% by weight based on Freon 134a (1,1,1,2-tetrafluoroethane), and add this to the vacuum piping and Freon 134a (1,1,1,2-tetrafluoroethane).
Connected to 34a gas pipe.

The ampoule was vacuum degassed at room temperature, then cooled with liquid nitrogen, and a predetermined amount of Freon 134a was collected.

Next, the ampoule was sealed, and the temperature was raised from -40'C in a constant temperature bath, and the temperature at which phase separation started was measured.

The higher the phase separation temperature is, the more preferable it is.

The results are shown in Table 1. show.

(Left below) [Effects of the Invention] The lubricating oil of the present invention can be used for various purposes, but because it has excellent compatibility with refrigerants and lubrication performance, it is suitable for use in refrigerators, especially compression type refrigerators. It is suitable as a lubricating oil. In particular, unlike conventional lubricating oils, the lubricating oil of the present invention does not contain hydrogen-containing fluorocarbon compounds such as Freon 134a (specifically,
Including the above Freon 134a, 1,1-dichloride 2,22-trifluoroethane (Freon-123);
1chloro-1,1-difluoroethane (Freon-142
b); 1,1-difluoroethane (Freon 152a);
It has good compatibility with chlorodifluoromethane (Freon-22) or trifluoromethane (Freon-23).

Therefore, the lubricating oil of the present invention is suitable for use in compression type refrigerators that use these hydrogen-containing fluorocarbon compounds, particularly fluorocarbon 134a as a refrigerant.

Claims (2)

[Claims] (1) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R^1 to R^4 are hydrogen, and carbon numbers 1 to 6
Alkyl group with 6 to 10 carbon atoms, aryl group with 7 carbon atoms
-10 arylalkyl group or C2-6 alkoxyalkyl group. However, this excludes the case where all of R^1 to R^4 are hydrogen. n represents an integer of 2 to 10. ] and has a molecular weight of 300 to 3
A polycarbonate-based synthetic lubricating oil whose main component is a polycarbonate derivative known as 000. (2) A synthetic lubricating oil for compression type refrigerators, the main component of which is the polycarbonate derivative according to claim 1.