JPH06116579A - Lubricating oil for refrigerator - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a lubricating oil suitable for a refrigerator using a hydrogen-containing halogenated hydrocarbon-based alternative CFC refrigerant, particularly a chlorine-free halogenated hydrocarbon refrigerant. [Composition] Lubricating refrigerator containing a fumaric acid alkyl ester polymer or copolymer obtained by polymerizing a linear lower alkyl diester of fumaric acid or maleic acid in a tetrahydrofuran solvent in the presence of a polymerization initiator. oil. [Effect] The temperature range in which the alternative CFC refrigerant R134a is compatible is wide and the viscosity index is high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating machine lubricating oil using a CFC alternative refrigerant, and more particularly to a refrigerating machine lubricating oil using a hydrogen-containing halogenated hydrocarbon refrigerant.

[0002]

2. Description of the Related Art Conventionally, as a refrigerant used in refrigerators such as building air conditioners, refrigerators and air conditioners, R11
Freon-based refrigerants such as ₃ F) and R 12 (CCl ₂ F ₂ ) have been used. However, these fluorocarbons in the form of substituting all of the hydrocarbons with halogens containing chlorine are subject to global regulation because they lead to ozone depletion in the stratosphere. Therefore, for example, R22 (CHClF ₂ ) or R2 is used as an alternative CFC-based refrigerant that does not damage the ozone layer.
123 (CF ₃ CHCl ₂ ) R141b, (CCl ₂ FC
H ₃ ), R134a (CF ₃ CH ₂ F), R152a (CHF ₂
Hydrogen-containing halogenated hydrocarbon refrigerants such as CH ₃ ) have been developed. Among them, non-chlorinated halogenated hydrocarbons,
For example, R134a (CF ₃ CH ₂ F), R152a (CHF ₂ C
H ₃ ) etc. are regarded as influential.

Refrigerant lubricating oils generally have a wide compatibility temperature range with a refrigerant (compatibility), that is, no clouding occurs at high temperatures (the refrigerant has a high solvability with respect to the lubricating oil), and a molecule of the lubricating oil. High polarity, no precipitation of lubricating oil at low temperature (high solubility of lubricating oil in refrigerant, small molecular weight of lubricating base oil) are required, and it is suitable for various refrigerators. Since the kinematic viscosity ranges are different from each other, it is required to have a kinematic viscosity corresponding to each range.

Naphthenic mineral oils, paraffinic mineral oils, alkylbenzenes, polyglycol mineral oils, ester oils and the like have been used as lubricating oils for conventional freon-based refrigerants. It is almost incompatible and cannot be used.

Further, the present inventors have previously found that the fumarate ester copolymer has a wide temperature range in which it is compatibilized with the CFC substitute.
Moreover, since it has a high viscosity index, it was found that it is useful as a component of a lubricating oil for a refrigerator using a CFC substitute refrigerant (Japanese Patent Application No. 3-344484). For radical polymerization of fumaric acid dialkyl esters and radical polymerization after isomerizing maleic acid dialkyl esters,
It is disclosed in Acta Polymerica 39 (1988) No. 1, 5-8.
According to this document, the yields of polymers obtained by these polymerizations are low except in the case of monomers having a special alkyl group, especially linear alkyl groups such as n-propyl group,
When it has an n-butyl group as an ester group, the yield is low (30% or less). Such a polymerization reaction is carried out in a solvent such as tetrahydrofuran in the presence of a polymerization initiator such as 2,2′-azobisisobutyronitrile.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention provides a lubricating oil suitable for a refrigerator using a hydrogen-containing halogenated hydrocarbon-based alternative CFC refrigerant, particularly a non-chlorine halogenated hydrocarbon refrigerant. With the goal.

[0007]

The present invention is directed to a fumaric acid alkyl ester polymer obtained by polymerizing a linear lower alkyl diester of fumaric acid or maleic acid in a tetrahydrofuran solvent in the presence of a polymerization initiator, or Provided is a lubricating oil for a refrigerator, which is characterized by containing a copolymer.

The lubricating oil of the present invention contains a fumaric acid alkyl ester polymer or copolymer, which is used in a tetrahydrofuran solvent when a diester monomer of fumaric acid or maleic acid is polymerized in the presence of a polymerization initiator. It is manufactured by carrying out in. Here, the fumaric acid alkyl ester polymer or copolymer means the following formula (Formula 1):

[0009]

[Chemical 1] (Here, R represents a linear lower alkyl group), which is a homopolymer or a copolymer having a structural unit.
The copolymer can be any copolymer such as a random copolymer or a block copolymer. Examples of R include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. R may be the same or different.

The above-mentioned fumaric acid alkyl ester polymer or copolymer is obtained by polymerizing the corresponding fumaric acid dialkyl ester monomer in a tetrahydrofuran solvent in the presence of a polymerization initiator. Here, it is known that the polymerization of fumaric acid ester occurs after the isomerization of maleic acid ester (Acta Polymerica 39 (1988) No. 1, 5-
8) Therefore, the corresponding maleic acid alkyl ester can also be used as a raw material. When a maleic acid dialkyl ester is used, a known isomerization catalyst such as morpholine, piperidine, dipropylamine, propylamine and the like are allowed to coexist in the reaction system. The details of the polymerization reaction can follow the method described in the above-mentioned document.

Known polymerization initiators can be used for the polymerization reaction. Azonitrile compounds such as 2,2′-azobisisobutyronitrile, 1-1′-azobiscyclohexanecarbonitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2 '-Azobis (2,4-dimethylvaleronitrile), etc .; Azoamidine compounds such as 2,2'-azobis (2-methyl-N-phenylpropionamidine, 2,2'-azobis (2-methylpropionamidine) dihydrochloric acid Salts, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, etc .; azoamide compounds, such as 2,2'-azobis (isobutyramide) dihydrochloride, 2,2'- Azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide} and the like; alkylazo compounds such as azodi-tert-octane, azodi-tert-butane, dimethyl 2,2 '
-Azobisisobutyrate and the like. Further, organic peroxides are also preferably used, and ketone peroxides,
For example, methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl cyclohexanone peroxide, etc .; peroxyketals such as 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butyl) Peroxy) cyclohexane, 2,2-bis (t-butylperoxy) butane, etc .; hydroperoxides such as t-butyl hydroperoxide, di-isopropylbenzene hydroperoxide, etc .; dialkyl peroxides such as di-t
-Butyl peroxide, di-cumyl peroxide,
t-Butyl cumyl peroxide, etc .; diacyl peroxide, such as acetyl peroxide, isobutyryl peroxide, benzoyl peroxide, etc .; peroxydicarbonate, such as di-isopropyl
Peroxydicarbonate, di-n-propyldicarbonate, di-methoxyisopropyl peroxydicarbonate, etc .; peroxyesters such as t-butylperoxyacetate, t-butylperoxyisobutyrate, cumylperoxyneodecanate , T-butyl peroxybenzoate, t-hexyl peroxy neodecanoate and the like. However, it is not limited to these. Preferred initiators are 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), and di-t-butylperoxide.

The polymerization initiator is at least 1/1 relative to the raw materials.
It is preferably used in a molar ratio of 00. Further, in order to improve the yield, it is preferable to add the initiator to the polymerization reaction system not batchwise but batchwise or continuously.
The polymerization temperature is preferably 60 to 145 ° C., and the reaction time is preferably 24 to 72 hours. If the temperature is too low or the reaction time is too short, the yield will decrease.

Tetrahydrofuran (TH
F) Use solvent. The amount of the solvent used is preferably 1/5 to 8 (volume ratio) with respect to the monomer or the raw material.
If the amount of the solvent is too small, the kinematic viscosity of the polymer becomes too high, so that the compatibility with the refrigerant decreases, and if it is too large, the yield tends to decrease.

The degree of polymerization of the above fumaric acid alkyl ester polymer or copolymer is adjusted so as to have an appropriate kinematic viscosity as a lubricating oil for a refrigerator, which will be described later, and a molecular weight as a lubricating oil for a refrigerator. Is preferably 400 to 20
00, more preferably 400 to 1600. Also,
The kinematic viscosity is preferably in the range of 2 to 100 cst (100 ° C). When the molecular weight is large, the viscosity index is improved, but it tends to be solid at room temperature and the compatibility with the refrigerant tends to be lowered.

In the lubricating oil of the present invention, one type of fumaric acid alkyl ester polymer or copolymer may be used, or two or more types of copolymers having different structures, molecular weights and the like may be used. it can. For example, if the fumaric acid alkyl ester polymer or copolymer having the above-mentioned molecular weight range is mainly used and a small amount of the fumaric acid alkyl ester polymer or copolymer having a molecular weight of 3,000 to 10,000 is added, the kinematic viscosity and the viscosity index Is improved, which is preferable.

The refrigerating machine lubricating oil of the present invention is added to the above-mentioned fumaric acid alkyl ester polymer or copolymer for the purpose of adjusting its kinematic viscosity and viscosity index for various refrigerating machines. Further, for example, a conventionally used lubricating oil component for a refrigerator such as an organic carboxylic acid ester, polyalkylene glycol, alkylbenzene, and mineral oil can be mixed and used at a desired ratio. Preferred as the refrigerator lubricating oil of the present invention is, in addition to the above-mentioned fumaric acid alkyl ester polymer or copolymer, further an organic carboxylic acid ester having a kinematic viscosity range at 100 ° C. of 2 to 30 cst and / or Alternatively, it contains a polyalkylene glycol. The organic carboxylic acid ester and / or polyalkylene glycol is preferably an alkyl fumarate ester polymer or copolymer 1
It is mixed in a ratio of 1 part by weight or less based on parts by weight. If the amount of the organic carboxylic acid ester or the polyalkylene glycol is too large, the compatibility on the high temperature side tends to deteriorate and the viscosity tends to decrease.

Examples of such organic carboxylic acid esters include those having high molecular polarity. (1) First, polyesters of an aliphatic polyhydric alcohol and a linear or branched fatty acid can be used.

As the aliphatic polyhydric alcohol forming such polyesters, trimethylolpropane,
Examples thereof include ditrimethylolpropane, trimethylolethane, ditrimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol and the like. The fatty acid preferably has 3 to 12 carbon atoms, and preferable examples thereof include propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, Isovaleric acid, neopentanoic acid, 2-methylbutyric acid, 2-ethylbutyric acid,
Examples thereof include 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2′-dimethyloctanoic acid, 2-butyloctanoic acid and the like.

The preferred polyesters of the above-mentioned aliphatic polyhydric alcohols and fatty acids include pentaerythritol, dipentaerythritol, tripentaerythritol and the like, or a mixture thereof, with 5 to 12 carbon atoms, more preferably 5 to 7 carbon atoms. Fatty acids such as valeric acid, hexanoic acid, heptanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,2'-dimethyloctanoic acid, 2-butyloctanoic acid, etc. or Ester oils with these mixtures, which can improve the compatibility with the refrigerant, especially at low temperatures.

Further, partial esters of an aliphatic polyhydric alcohol and a linear or branched fatty acid can also be used. At this time, the above-mentioned polyhydric alcohol can be used as the polyhydric alcohol. The fatty acid preferably has 3 to 9 carbon atoms, and preferable examples thereof include propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, 2-methylhexanoic acid and 2-ethylhexanoic acid. , Isooctanoic acid, isononanoic acid and the like. These partial esters can be obtained by appropriately controlling the number of moles of the reaction between the aliphatic polyhydric alcohol and the fatty acid and causing the reaction. (2) Neopentyl glycol is used as the aliphatic polyhydric alcohol, and a linear or branched fatty acid having 6 to 9 carbon atoms such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, 2-ethylbutyric acid , 2-methylhexanoic acid, 2-
It is also possible to use diesters with ethylhexanoic acid, isooctanoic acid, isononanoic acid and the like. (3) Partial esters of an aliphatic polyhydric alcohol and a linear or branched fatty acid having 3 to 12 carbon atoms, and a linear or branched aliphatic dibasic acid and / or aromatic polybasic acid It is also possible to use complex esters with basic acids.

Such aliphatic polyhydric alcohols include trimethylolpropane, trimethylolethane,
Pentaerythritol and dipentaerythritols can be used.

Examples of the linear or branched fatty acid having 3 to 12 carbon atoms include propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid and decanoic acid. , Dodecanoic acid, 2-methylbutyric acid,
2-ethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, isodecanoic acid, 2,
2'-Dimethyloctanoic acid, 2-butyloctanoic acid, etc. can be used.

The complex esters preferably have 5 to 7 carbon atoms, more preferably 5 to 6 carbon atoms.
With the use of fatty acids of, the resulting ester oil may have improved compatibility with the refrigerant, especially at low temperatures. As such a fatty acid, isovaleric acid, valeric acid, hexanoic acid, 2-methylbutyric acid, 2-ethylbutyric acid or a mixture thereof is used, and those having 5 carbon atoms and 6 carbon atoms are contained in a weight ratio of 10 : 90-9
Fatty acids mixed in a ratio of 0:10 can be preferably used.

As the aliphatic dibasic acid which can be used for esterification with polyhydric alcohol together with this fatty acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and undecanedioic acid are used. , Dodecanedioic acid, tridecanedioic acid, carboxyoctadecanoic acid, carboxymethyloctadecanoic acid, docosanedioic acid and the like. Further, examples of the aromatic dibasic acid include phthalic acid and isophthalic acid, examples of the aromatic tribasic acid include trimellitic acid, and examples of the aromatic tetrabasic acid include pyromellitic acid. To be

The fatty acid and the aliphatic dibasic acid and / or aromatic polybasic acid may be used in a ratio of 6: 1 (molar ratio). In the esterification reaction, these acids (fatty acid, aliphatic or The ratio of the total amount of the aromatic polybasic acid) and the amount of the polyhydric alcohol used may be 7: 1.

In the esterification reaction, first, a polyhydric alcohol is reacted with an aliphatic dibasic acid and / or an aromatic polybasic acid at a predetermined ratio to partially esterify, and then the partially esterified product is reacted with a fatty acid. Alternatively, the reaction order of the acids may be reversed, or the acids may be mixed and subjected to esterification. (4) Linear or branched dialkyl esters of aliphatic dibasic acids (having 16 to 22 carbon atoms) may be used.

As the aliphatic dibasic acid, the aliphatic dibasic acid shown in (3) above can be used. Preferred aliphatic dibasic acids are succinic acid, adipic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, carboxyoctadecanoic acid, carboxymethyloctadecanoic acid and the like.
As the alkyl alcohol component, an alcohol having 5 to 8 carbon atoms can be used, and examples thereof include amyl alcohol, hexyl alcohol, heptyl alcohol and octyl alcohol, and isomers thereof, preferably isoamyl alcohol, isohexyl alcohol and octyl alcohol. Is. Specific examples include dioctyl adipate, diisoheptyl adipate, dihexyl sebacate, and diheptyl succinate. (5) Dialkyl esters of aromatic dibasic acids (having 18 to 26 carbon atoms) can also be used.

Examples of the aromatic dibasic acid include phthalic acid, isophthalic acid and their derivatives. Also,
As the alkyl alcohol component, the alcohol having 5 to 8 carbon atoms shown in (4) above can be used. Preferred alcohols are isoamyl alcohol, isoheptyl alcohol and octyl alcohol. Such diesters include dioctyl phthalate, diisoheptyl phthalate, diisoamyl phthalate and the like. (6) In addition, methanol as an alcohol component,
Monohydric alcohols selected from ethanol, propanol, butanol, etc. and their isomers, polyhydric alcohols such as glycerin, trimethylolpropane, etc. and, for example, selected from ethylene oxide, propylene oxide, butylene oxide, amylene oxide, etc. and their isomers. 1 to 10 mol, preferably 1 of alkylene oxide
It is also possible to use organic carboxylic acid esters using ~ 6 mol adducts.

As the acid for the alkylene oxide adduct of monohydric alcohol, the aliphatic dibasic acids and aromatic polybasic acids shown in (3) above can be used. Further, as the acid for the alkylene oxide adduct of polyhydric alcohol,
The linear or branched fatty acid having 3 to 12 carbon atoms shown in (1) above can be used.

As the fatty acid constituting the above-mentioned organic carboxylic acid ester, a linear or branched fatty acid can be used, but when a branched fatty acid is used, it is more excellent in hydrolysis stability, Further, compatibility with a hermetic coil or the like can be achieved.

These organic carboxylic acid esters can be obtained by esterifying alcohols and fatty acids in the presence of an acid catalyst such as phosphoric acid. Normal,
Total acid value 0.1-0.5 mgKOH / g, peroxide value 0.
1-5 meq / kg, aldehyde value 0.1-5 mg KOH /
g, bromine number index 1-100 mg / 100g, ash content 5-50 ppm,
A water content of 300 to 1000 ppm is obtained.

However, if the total acid value of the refrigerating machine lubricating oil is high, a problem such as corrosion of the metal part occurs, and the refrigerating machine lubricating oil itself is hydrolyzed to function as a refrigerating machine lubricating oil. In general, in refrigerators and the like, the motor part is arranged in the lubricating oil, so that high insulation is required, so that the lubricating oil for refrigerators has a total acid value of 0. It is preferably not more than 05 mgKOH / g.

Further, the peroxide value, the aldehyde value, and the bromine number index are kept low in order to further improve the refrigerant stability, and the ash content is restrained in order to suppress sludge and the like. Therefore, it is preferable to suppress the water content. Therefore, by refining the above-mentioned esters obtained by a normal esterification reaction and adjusting the indexes showing the above-mentioned properties of the ester oil to a range suitable as a refrigerating machine oil, a more excellent refrigerating machine oil can be obtained. .

The organic carboxylic acid ester may be purified by contacting it with silica gel, activated alumina, activated carbon, zeolite or the like. The contact conditions at this time may be appropriately determined according to various situations, but the temperature is preferably 100 ° C. or lower.

Examples of the polyalkylene glycol that can be used in the present invention include homopolymers of alkylene glycols such as polyethylene glycol and polypropylene glycol, and copolymers of alkylene oxides such as ethylene oxide and propylene oxide. The terminal group may be substituted with a methyl group, an ethyl group, a propyl group, a butyl group or the like. Average molecular weight is usually 500-18
00, preferably 800 to 1600, and when it is less than 500, the compatibility with the refrigerant at high temperature is high, but the kinematic viscosity is low and the thermal stability tends to be low. If it exceeds 1800, the kinematic viscosity is high, but the compatibility with the refrigerant tends to decrease.

A viscosity index improver may be added to the lubricating oil for refrigerator of the present invention for the purpose of obtaining desired kinematic viscosity and viscosity index required for various refrigerators. As such a viscosity index improver, a conventional one can be used, and examples thereof include polyolefin (for example, polybutene, poly α-olefin, ethylene / α-olefin copolymer and the like, including hydrogenated products), polymethacrylate (for example, methacrylate, Acrylic homopolymers and copolymers containing acrylic acid and methacrylic acid as components), polyisobutylene, polyalkylstyrene, ethylene-propylene copolymer, styrene-diene copolymer, styrene-maleic anhydride copolymer Examples include coalescence. The content of these viscosity index improvers is usually 0.1 to 20% by weight, preferably 1 to 10% by weight, based on the base oil.

The refrigerator lubricating oil of the present invention is usually (100
A kinematic viscosity range (at ° C.) Of 2 to 100 cst, preferably 2 to 80 cst, is used. When it is less than 2 cst, the compatibility with the refrigerant at high temperature is high, but the kinematic viscosity is low, the lubricity and sealing properties are deteriorated, and the thermal stability tends to be low. If it exceeds 100 cst, the compatibility with the refrigerant tends to decrease. However, even within this range, the range of kinematic viscosity used differs depending on the model used. For refrigerators, for example, it is 2 to 9 cst, preferably 3 to 7 cst. 7 to 4 for car air conditioners
It is 0 cst. Among car air conditioners, the reciprocating type compressor has 7 to 15 cst, preferably 8 to 11 cst, and the rotary type compressor has 15 to 40 cst, preferably 20 to 20 cst.
35 cst. In the refrigerator, if it exceeds 9 cst, there is a problem that the friction loss in the sliding portion becomes large. Further, in the reciprocating type car air conditioner, there is a problem that lubricity is deteriorated when it is less than 7 cst, and there is a problem that the friction loss in the sliding portion becomes large when it exceeds 15 cst. If it is less than cst, there is a problem that the sealing property is deteriorated.

Various additives usually used can be used in the lubricating oil for refrigerator of the present invention. As the antiwear agent, for example, a general formula (RO) ₃ P = S (wherein R is an alkyl group,
A compound represented by an allyl group or a phenyl group, which may be the same or different, for example, a sulfur-based antiwear agent such as trialkylphosphorothionate, triphenylphosphorothionate, and alkyldiallylphosphorothionate , Diphenyl sulfide, diphenyl disulfide, di n-butyl sulfide, di-n-butyl disulfide, di-tert-dodecyl disulfide, di-tert-
Sulfides such as dodecyl trisulfide, sulfurized spalm oil, sulfurized oils and fats such as sulfurized dipentene, thiocarbonates such as xanthic disulfide, zinc primary alkylthiophosphate, zinc secondary alkylthiophosphate, alkyl Examples include zinc thiophosphate antiwear agents and phosphorus antiwear agents such as zinc allylthiophosphate and zinc allylthiophosphate. Examples of phosphorus antiwear agents include benzyl diphenyl phosphate, allyl diphenyl phosphate, triphenyl phosphate, tricresyl phosphate, ethyl diphenyl phosphate, tributyl phosphate, dibutyl phosphate, cresyl diphenyl phosphate, dicresyl Phenyl phosphate, ethyl phenyl diphenyl phosphate, diethyl phenyl phenyl phosphate, propyl phenyl diphenyl phosphate, dipropyl phenyl phenyl phosphate, triethyl phenyl phosphate, tripropyl phenyl phosphate, butyl phenyl diphenyl phosphate, dibutyl phenyl phenyl phosphate Phosphates such as phosphates and tributylphenyl phosphate, tris Sodium phosphite ester, phosphite ester such as diisopropyl phosphite ester, hexamethylphosphoric triamide, n-butyl-n-dioctylphosphinate, di-n-butylhexylphosphonate, amine dibutylphosphonate, dibutylphosphonate Other phosphorus compounds such as roamidate can be used.

These antiwear agents may be used alone or in combination of two or more. The proportion of the antiwear agent used is usually 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the base oil.

It is also possible to use antioxidants, for example dioctyldiphenylamine, phenyl-α-naphthylamine, alkyldiphenylamine, amine antioxidants such as N-nitrosodiphenylamine, 2,6-di-t-butylparacresol, 4,4'-Methylenebis (2,6-di-t-butylphenol), 2,6-di-t-butyl-α-dimethylamine para-cresol, 2,6-di-t-butylphenol and other phenolic antioxidants Examples thereof include phosphorus antioxidants such as agents, tris (2,4-di-t-butylphenyl) phosphite, trisnonylphenylphosphite, and triphenylphosphite. These may be used alone, but 2
It is also possible to use a combination of two or more species. The proportion of the antioxidant used is usually 0.01 to 10% by weight, preferably 0.01 to 1.0% by weight, based on the base oil.

Corrosion inhibitors can also be used, for example isostearates, n-octadecyl ammonium stearate, duomine T.diolate, lead naphthenate, sorbitan oleate, pentaerythritol oleate, oleylsarcosine, alkylsuccinates. Examples thereof include acids, alkenylsuccinic acids, and derivatives thereof. These may be used alone or in combination of two or more. The proportion of the corrosion inhibitor used is usually 0.001 to 1.0% by weight, preferably 0.0 to 1.0% by weight, based on the base oil.
It is 1 to 0.5% by weight.

It is also possible to use an antifoaming agent such as silicone. The use ratio is usually 0.0001 to 0.003% by weight, preferably 0.00
It is from 01 to 0.001% by weight.

Further, a metal deactivator can be used, and examples thereof include benzotriazole, benzotriazole derivatives, thiadiazole, thiadiazole derivatives, triazole, triazole derivatives and dithiocarbamates. These may be used alone or in combination of two or more. The proportion of the metal deactivator used is usually 0.01 to 10% by weight, preferably 0.01 to 1.0% by weight, based on the base oil.

Further, a rust preventive may be used, and examples thereof include succinic acid, succinic acid ester, oleic acid tallow amide, barium sulfonate, calcium sulfonate and the like. These may be used alone or in combination of two or more. The proportion of the rust preventive used is usually 0.01 to 10% by weight, preferably 0.01 to 1.0% by weight, based on the base oil.

The lubricating oil for refrigerator according to the present invention can be used as a lubricating oil in refrigerators used in refrigeration systems in a wide range of fields such as building and home air conditioners, refrigerators, freezers, car air conditioners and the like.

Further, the lubricating oil of the present invention can be added as an additive to a lubricating oil for refrigerating machines containing other substances such as organic carboxylic acid ester, polyalkylene glycol, alkylbenzene, mineral oil and the like as a base oil. .

[0047]

When a diester of fumaric acid or maleic acid having a linear lower alkyl group as an ester group is reacted in a tetrahydrofuran solvent in the presence of a polymerization initiator, a polymer can be obtained in high yield. In addition, since this polymer has a wide temperature range in which it is compatible with the CFC-based alternative refrigerant and has a high viscosity index, when it is used as a lubricating oil for refrigerators using the CFC-based alternative refrigerant, excellent lubricating oil can be obtained. To be

The present invention will be described in more detail by the following examples.

[0049]

EXAMPLES Example 1 In a 200 ml single neck flask, di-n-butyl fumarate 21 was added.
After adding 7 mmol (49.5 g, 50 ml) and attaching a cooling tube, this was set in an oil bath. While stirring with a magnetic stirrer, the temperature was kept at 60 ° C and 2,2'-azobisisobutyronitrile (AIBN) 1
0 mmol (1.6 g) and tetrahydrofuran 10
0 ml was added and heating and stirring was continued at this temperature for 72 hours.
Then, the light fraction was distilled off under reduced pressure to obtain 49.6 g of a polymer. Yield 100%.

The kinematic viscosity of the obtained polymer was measured to determine the viscosity index. A compatibility test was also conducted.
The results are shown in Table 1.

The yield was determined as the ratio of the weight of the residue to the total weight of the starting ester monomers after removing the light components from the polymerization reaction system by distillation under reduced pressure. The kinematic viscosity was measured according to JIS K 2283. Further, the compatibility test was conducted as follows. That is, sample oil and refrigerant (1,1,1,2-tetrafluoroethane, R13
4a) is a total of 2 at a ratio of 15% by volume of the sample oil.
The glass tube was sampled and mixed so that the glass tube was placed in a constant temperature bath having a cooling device, and the separation temperature of the sample oil and the refrigerant at low temperature was measured. Next, the sample oil and the refrigerant are put into another glass tube, and the total amount of the sample oil is 10% by volume of 2 ml in total.
The glass tube was sampled and mixed so that the glass tube was placed in a constant temperature bath having a heating device, and the separation temperature of the sample oil and the refrigerant at high temperature was measured. Example 2 A polymerization reaction was performed in the same manner as in Example except that the amount of tetrahydrofuran was changed to 10 ml using a 100 ml one-necked flask. Thus, 45.1 g of a polymer was obtained. Yield 9
1%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Example 3 Di-n-butyl maleate 2 in place of di-n-butyl fumarate
A polymerization reaction was carried out in the same manner as in Example 1 except that 19 mmol (50 g, 50 ml) was used and 1.14 mmol (0.1 ml) of morpholine was further added to the reaction system. Thus, 49.2 g of a polymer was obtained. Yield 98
%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 1 A polymerization reaction was carried out in the same manner as in Example 2 except that 10 ml of tetrahydrofuran was not added. Thus, 10.9 g of a polymer was obtained. Yield 22%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 2 A polymerization reaction was performed in the same manner as in Example 1 except that 100 ml of isopropyl alcohol was used as the solvent instead of tetrahydrofuran. Thus, 33.2 g of a polymer was obtained. Yield 67%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 3 Heptane 10 was used instead of tetrahydrofuran as the solvent.
The polymerization reaction was performed in the same manner as in Example 1 except that 0 ml was used. Thus, 33.2 g of a polymer was obtained. Yield 67
%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 4 A polymerization reaction was performed in the same manner as in Example 1 except that 100 ml of p-xylene was used instead of tetrahydrofuran as the solvent. Thus, 33.7 g of a polymer was obtained. Yield 6
8%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 5 A polymerization reaction was performed in the same manner as in Example 1 except that 100 ml of γ-butyrolactone was used instead of tetrahydrofuran as the solvent. Thus, 28.7 g of a polymer was obtained.
Yield 57%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 6 Toluene 10 was used instead of tetrahydrofuran as the solvent.
The polymerization reaction was performed in the same manner as in Example 1 except that 0 ml was used. Thus, 26.7 g of a polymer was obtained. Yield 54
%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 7 A polymerization reaction was performed in the same manner as in Example 1 except that 100 ml of o-xylene was used instead of tetrahydrofuran as the solvent. Thus, 26.2 g of a polymer was obtained. Yield 5
3%.

With respect to the obtained polymer, the kinematic viscosity was measured in the same manner as in Example 1 to obtain the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 8 The polymerization reaction was performed in the same manner as in Example 1 except that 100 ml of methyl ethyl ketone was used as the solvent instead of tetrahydrofuran. Thus, 31.2 g of a polymer was obtained.
Yield 63%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 9 Ethanol 1 instead of tetrahydrofuran as the solvent
Polymerization was carried out in the same manner as in Example 1 except that 00 ml was used. Thus, 34.2 g of a polymer was obtained. Yield 69
%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 10 A polymerization reaction was performed in the same manner as in Example 1 except that 100 ml of n-butanol was used instead of tetrahydrofuran as the solvent. Thus, 23.8 g of a polymer was obtained. Yield 48%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1. Comparative Example 11 Benzene 10 was used as a solvent instead of tetrahydrofuran.
The polymerization reaction was performed in the same manner as in Example 1 except that 0 ml was used. Thus, 31.7 g of a polymer was obtained. Yield 64
%.

The kinematic viscosity of the obtained polymer was measured in the same manner as in Example 1 to determine the viscosity index. Also,
Compatibility tests were also conducted. The results are shown in Table 1.

[0065]

[Table 1] (Note) THF = tetrahydrofuran, i-PA = isopropyl alcohol, p-XY = p-xylene, GBL = γ-butyrolactone, o-XY = o-xylene, MEK = methyl ethyl ketone, EtOH = ethanol, BuOH = n-butanol

[0066]

The refrigerating machine lubricating oil of the present invention is an alternative fluorocarbon refrigerant such as a hydrogen-containing halogenated hydrocarbon, especially R13.
Wide temperature range compatible with 4a and high viscosity index. Therefore, it is very useful industrially.

Front page continued (72) Inventor Hiro Ueno 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture Tonen Corporation Research Institute

Claims (1)

[Claims] 1. A fumaric acid alkyl ester polymer or copolymer obtained by polymerizing a linear lower alkyl diester of fumaric acid or maleic acid in a tetrahydrofuran solvent in the presence of a polymerization initiator. Lubricating oil for refrigerators.