JPH07216372A - Working fluid composition for refrigerator - Google Patents

Abstract

PURPOSE:To obtain the subject compsn. excellent in compatibility between its ingredients, lubricity, and hydrolysis resistance. CONSTITUTION:This compsn. comprises a hydrofluorocarbon-contg. refrigerant and a refrigerator oil based on an ester compd. which is obtd. by reacting a hydroxycarboxylic acid polyol ester, an aliph. monocarboxylic acid component comprising 5-80mol% 10-24C aliph. monocarboxylic and 95-20mol% 9C or lower aliph. monocarboxylic acid, and if necessary, the third component comprising an aliph. polycarboxylic acid alone or together with a polyhydric alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a working fluid of a refrigerator, which comprises a refrigerator oil containing an ester compound having excellent hydrolysis resistance and lubricity as a base oil and a refrigerant containing a hydrofluoroalkane. .

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Chlorine-containing CFCs have been widely used as refrigerants in refrigerators, but due to the problem of ozone layer depletion, the use of these CFCs is subject to regulation. As an alternative refrigerant, 1,1,1,2-tetrafluoroethane (HFC1
34a), hydrofluorocarbons containing hydrogen atoms such as difluoromethane (HFC32) are being investigated.
However, because of its chemical structure, hydrofluorocarbon is almost incompatible with conventional refrigerating machine oils such as mineral oils and synthetic oils, so that oil return in the refrigeration system deteriorates and heat transfer performance decreases. It cannot be used due to clogging or poor lubrication.

Various polyol esters have been proposed as lubricating oils having excellent compatibility with hydrofluorocarbons, but these polyol esters are limited in their constituent raw materials, particularly the number of carbon atoms, from the viewpoint of compatibility. (JP-A-5
-263071, JP-A-5-209171). These polyol esters often have negative effects on hydrolysis resistance, lubricity and the like, and lack the long-term reliability essential for refrigerating machine oil.

Further, Japanese Patent Laid-Open No. 5-179267 and Japanese Patent Laid-Open No. 5-19267
The ester described in -179268 may not have sufficient hydrolysis resistance and lubricity depending on the type of refrigerator used.

[0005]

As a result of various studies to solve the above problems, the present inventor has found that hydroxycarboxylic acid polyol ester having a chemical structure excellent in compatibility with hydrofluorocarbons. As a main raw material, by introducing a long-chain carbon chain into the molecule, we found ester compounds excellent in hydrolysis resistance, lubricity as well as compatibility, and refrigerating machine oils and hydrofluorocarbons using them as base oils. The inventors have completed the invention of a refrigerator working fluid composition comprising a refrigerant containing bon.

That is, the present invention is obtained from a hydroxycarboxylic acid polyol ester and an aliphatic monocarboxylic acid, and if necessary, an aliphatic polyvalent carboxylic acid or an aliphatic polyvalent carboxylic acid and an aliphatic polyvalent alcohol. 5 to 80 mol% of the aliphatic monocarboxylic acid in the ester compound
And (a) an aliphatic monocarboxylic acid having 10 to 24 carbon atoms, and 95 to 20 mol% of (b) an aliphatic monocarboxylic acid having 9 or less carbon atoms, a refrigerating machine oil based on the ester compound, and A refrigerating machine working fluid composition comprising a refrigerant containing hydrofluorocarbon.

The hydroxycarboxylic acid polyol ester used in the present invention is produced by a self-condensation reaction of a mono-, di- and polyester compound and a hydroxyalkyl aldehyde produced by an esterification reaction of a hydroxycarboxylic acid and a polyhydric hydroxy compound. There are also monoester compounds and the like, but the manufacturing method thereof is not particularly limited.

As the hydroxycarboxylic acid used for producing the hydroxycarboxylic acid polyol ester, there are glycolic acid, lactic acid, hydroxyisobutyric acid, hydroxypivalic acid, hydroxyoctanoic acid and the like, and as the polyvalent hydroxy compound, neopentyl. Glycol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, trimethylolethane, trimethylolpropane, ditrimethylolpropane, pentaerythrium. Lithol, dipentaerythritol,
Tripentaerythritol, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 2-ethyl-1,3-hexanediol
Le, glycerin, diglycerin, polyglycerin, 1,
2,4-butanol, 1,2,6-hexanetriol, sorbitol, mannitol and the like are exemplified,
As the hydroxyalkyl aldehyde, glyco-
Lualdehyde, hydroxyisobutyraldehyde, 4-
Examples include hydroxy-3-methylbutyraldehyde and hydroxypivalaldehyde. Among hydroxycarboxylic acid polyol esters produced from the above raw materials, those having a structure in which hydrogen at the β-position of the alcohol and the hydrogen at the α-position of the acid are substituted with an alkyl group in terms of hydrolysis resistance and compatibility. Are preferred, and particularly 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropionic acid ester is excellent.

In the aliphatic monocarboxylic acid used in the present invention, 5 to 80 mol% is (a) an aliphatic monocarboxylic acid having 10 to 24 carbon atoms, and 95 to 20 mol% is (b) a carbon number. An aliphatic monocarboxylic acid of 9 or less, preferably 10 to 50 mol% of the component (a), more preferably 10 to 3
It is 0 mol%. When the content of the component (a) is 5% or less, the lubricity is poor, and when it is 80% or more, the compatibility is poor. Also (a)
If the carbon number of the component is larger than 24, the compatibility becomes poor. As the component (b) of the aliphatic monocarboxylic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, 2-methylvaleric acid,
3-methylvaleric acid, 4-methylvaleric acid, 2,2
-Dimethylbutyric acid, 2-ethylbutyric acid, tert-butylbutyric acid, enanthic acid, 2,2-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2-methylhexanoic acid, 4-methylhexanoic acid, 5 -Methylhexanoic acid, caprylic acid, 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 2- Propylpentanoic acid, pelargonic acid,
2,2-Dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, etc. are exemplified, and these lower alkyl esters and acid anhydrides, etc. Can be used as well. As the component (a), capric acid, isodecanoic acid,
Undecanoic acid, methyldecanoic acid, lauric acid, tridecanoic acid, isotridecanoic acid, myristic acid, isomyristic acid, palmitic acid, isopalmitic acid, margaric acid, stearic acid, isostearic acid, aragic acid,
Isoaraginic acid, isohexaconic acid, 2-butyloctanoic acid, 2-butyldecanoic acid, 2-pentylnonanoic acid,
2-hexyl octanoic acid, 2-hexyl decanoic acid, 2-
Octyldecanoic acid, 2-hexylundecanoic acid, 2-hexyldecanoic acid, 2-octyldodecanoic acid, 2-decyltetradecanoic acid, 2-isopentylisononanoic acid, 2
-Isoheptyl isoundecanoic acid, 2,2-dimethylnooctanoic acid, 2-methyl 2-ethylheptanoic acid, 2-methyl 2-propylhexanoic acid, etc. are exemplified, and these lower alkyl esters and acid anhydrides are also the same. Can be used for Further, the component (a) is 5 to 80 mol%, and the component (b) is 9
These may be used alone or as a mixture of two or more kinds, as long as they are in the range of 5 to 20 mol%. From the viewpoints of compatibility with the refrigerant and hydrolysis resistance, branched fatty acids are preferable to linear fatty acids, and branched acids in which the α-position is substituted with an alkyl group are particularly preferable.

As the aliphatic polycarboxylic acid used in the present invention, oxalic acid, malonic acid, methylmalonic acid, succinic acid, ethylmalonic acid, dimethylmalonic acid, methylsuccinic acid, glutaric acid, adipic acid, 2,2 -Dimethylsuccinic acid, 2,2,3-trimethylsuccinic acid, 2-methylglutaric acid, butylmalonic acid, diethylmalonic acid, 2,2-
Dimethyl glutaric acid, 2,4-dimethyl glutaric acid,
Examples of 3,3-dimethylglutaric acid, 2-ethyl-2-methylsuccinic acid, 3-methyladipic acid, pimelic acid, suberic acid, 2,2-dimethyladipic acid, azelaic acid, sebacic acid, and the like compounds The lower alkyl esters and acid anhydrides of can be similarly used.

Examples of the aliphatic polyhydric alcohol used in the present invention include neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1, 3-propanediol, trimethylolethane,
Trimethylol propane, ditrimethylol propane,
Pentaerythritol, dipentaerythritol, tripentaerythritol, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 2-ethyl-1,3-hexanediol, glycerin, diglycerin, polyglycerin, 1,2,4
-Butantholol, 1,2,6-hexanetrio-
And sorbitol and mannitol.

The ester reaction product obtained in the present invention may be produced by a one-step method in which all the constituent raw materials are reacted at the same time, or may be produced by a two-step method in which only the aliphatic monocarboxylic acid is subsequently reacted. The esterification method is carried out by a conventional method while removing reaction byproducts such as water out of the system. For example, the reaction is carried out at a reaction temperature of 100 to 250 ° C. in the presence or absence of a catalyst and, if necessary, in the presence of a solvent such as toluene or xylene. Further, after the reaction, if necessary, post-treatment such as alkali washing, water washing, adsorption and the like can be performed.

40 ° C. of the ester reaction product obtained by the present invention
The kinematic viscosity at 2 is usually 2 cSt or more and 1000 cSt or less, preferably 8 cSt or more and 460 cSt or less, and more preferably 10 cSt or more and 100 cSt or less. 40
If the kinematic viscosity at 1000C is larger than 1000 cSt, the compatibility with hydrofluorocarbon becomes poor and the load on the refrigerator becomes large.

The acid value of these ester compounds is usually 0.
1 mgKOH / g or less, preferably 0.05 mgKOH
/ G or less, more preferably 0.01 mgKOH / g or less, and if the acid value is greater than 0.1 mgKOH / g, corrosiveness to metals may increase.

The refrigerating machine oil of the present invention contains the above ester as a main component, but depending on the purpose of use, mineral oil, poly α-olefin, alkylbenzene, esters other than those mentioned above, and polyether
Synthetic oils such as tellurium, perfluoropolyether, and phosphoric acid ester may be blended. If necessary, an antioxidant,
A lubricating oil additive such as an extreme pressure agent, an oiliness improver, an antifoaming agent, a metal deactivator and a hydrolyzable inhibitor such as an epoxy compound may be added.

Hydrofluorocarbon used in the present invention
As the bon, 1,1,1,2-tetrafluoroethane (HFC134a), 1,1,2,2-tetrafluoroethane (HFC134), pentafluoroethane (HF)
C125), 1,1,2-trifluoroethane (HFC
143), 1,1,1-trifluoroethane (HFC1
43a), trifluoromethane (HFC23), 1,1
-Difluoroethane (HFC152a), difluoromethane (HFC32), fluoromethane and mixtures thereof. Further, these may include hydrocarbon such as propane and butane, and other substances having a function as a refrigerant.

[0017]

EFFECT OF THE INVENTION A composition comprising a refrigerating machine oil containing the ester compound of the present invention as a base oil and a refrigerant containing hydrofluorocarbon is compatible with the composition, stability, as well as lubricity, It also has excellent hydrolysis resistance.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The ester compound evaluated in the present invention was prepared by a conventional esterification method. Properties of various ester compounds are shown in Table 1, compatibility evaluation results are shown in Table 2, and hydrolysis resistance and lubricity evaluation results are shown in Table 3. Each evaluation was performed by the method shown below.

[Hydrolysis resistance] Sample oil 15 was added to a glass tube.
g, 1,000 ppm of water, and HCF by adding copper, iron and aluminum with a diameter of 3 mm and a length of 27 mm as a catalyst
It was replaced with 134a, sealed, and sealed, and the acid value, color tone change and catalyst change of the test oil after 14 days of test at 175 ° C. were examined.

[Compatibility] A HFC134a refrigerant and a test oil were added to a glass tube so that the oil ratio was 10%, the tube was sealed, and the two-phase separation temperature at -60 ° C to 100 ° C was examined.

[Lubricity] 8 using a Falex tester
HFC at 0 ° C, load 300 lbs, rotation speed 200 rpm
The test was carried out for 1 hour while blowing the 134a refrigerant at 10 l / hr to examine the amount of pin wear and the change in color tone of the test oil after the test.

[Table 1]

[Table 2]

[Table 3]

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Claims (5)

[Claims] 1. An ester compound obtained from a hydroxycarboxylic acid polyol ester and an aliphatic monocarboxylic acid, and if necessary, an aliphatic polyvalent carboxylic acid or an aliphatic polyvalent carboxylic acid and an aliphatic polyvalent alcohol. In 5 to 80 mol% of the aliphatic monocarboxylic acid is (a) carbon number 1
Refrigerating machine oil and hydrofluorocarbon based on the ester compound having 0 to 24 aliphatic monocarboxylic acids and 95 to 20 mol% (b) aliphatic monocarboxylic acids having 9 or less carbon atoms. A refrigerating machine working fluid composition comprising a refrigerant contained therein. 2. The composition for a working fluid of a refrigerator according to claim 1, wherein the aliphatic monocarboxylic acid having 10 to 24 carbon atoms is a branched acid. 3. The refrigerator working fluid composition according to claim 2, wherein the branched acid is an acid substituted with an alkyl group at the α-position. 4. The composition for refrigerator working fluid according to claim 1, wherein the hydroxycarboxylic acid polyol ester is a hydroxycarboxylic acid alkylene glycol ester. 5. The frozen product according to claim 4, wherein the hydroxycarboxylic acid alkylene glycol ester is 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropionic acid ester. Composition for machine working fluid.