JPH05179267A - Synthetic lubricating oil - Google Patents

Abstract

PURPOSE:To provide the subject oil composed mainly of a specific esterification reaction product, having excellent lubricating oil characteristics, heat-resistance, weather resistance and hydrolysis resistance, exhibiting compatibility especially with hydrogen-containing fluoroalkane refrigerants over a wide temperature range and, accordingly, useful as a refrigerator oil. CONSTITUTION:The objective synthetic lubricating oil is composed mainly of an esterification reaction product produced from (A) a hydroxycarboxylic acid polyol ester, (B) an aliphatic polybasic carboxylic acid (e.g. oxalic acid and malonic acid), (C) an aliphatic monocarboxylic acid (e.g. acetic acid and propionic acid) and, as necessary, (D) an aliphatic polyhydric alcohol (e.g. neopentyl glycol and trimethylolethane). The component A is e.g. a monoester produced by the esterification reaction of a hydroxycarboxylic acid such as glycolic acid with a polyvalent hydroxy compound such as neopentyl glycol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic ester lubricating oil having a high viscosity index and a low pour point, which is excellent in heat resistance, weather resistance, and hydrolysis resistance, and particularly to a hydrogen-containing fluoroalkane-based refrigerant. The present invention relates to a refrigerator oil having excellent compatibility.

[0002]

2. Description of the Related Art In recent years, with the rapid development of various industries, the operating conditions of lubricating oils have become severer, and it has become necessary to have excellent thermal stability as well as excellent lubricating oil properties such as viscosity index and pour point. However, the performance of conventional mineral oil is not satisfactory. On the other hand, ester synthetic oils have come to be used, but increase in acid value and viscosity change due to oxidation and hydrolysis are likely to occur, and especially as a lubricating oil used at very high temperature such as turbo engine oil. Was not completely satisfied. Refrigerating machine oil must have thermal stability as well as compatibility with the refrigerant, and especially with respect to lubricating oil used in a hydrogen-containing fluoroalkane-based refrigerant atmosphere, conventional lubricating oils can satisfy both compatibility and thermal stability. Not really.

[0003]

In view of the above problems, the present invention has excellent lubricating oil characteristics, heat resistance, and
It is an object of the present invention to provide a refrigerating machine oil that is compatible with a synthetic lubricating oil having excellent weather resistance and hydrolysis resistance, particularly a hydrogen-containing fluoroalkane-based refrigerant in a wide temperature range.

[0004]

As a result of various studies to achieve the above object, the present inventor has found that a specific ester compound can achieve the above object, and completed the present invention. It was That is, the present invention relates to (A) hydroxycarboxylic acid polyol ester, (B) aliphatic polyvalent carboxylic acid, (C) aliphatic monocarboxylic acid and, if necessary, (D) aliphatic polyvalent alcohol. The present invention relates to a synthetic lubricating oil whose main component is an ester reaction product obtained from

The synthetic lubricating oil according to the present invention can be widely used for applications such as automobile engine oils, automobile gear oils, industrial gear oils, rolling lubricating oils, etc., but is particularly wide with hydrogen-containing fluoroalkane-based refrigerants. It can be used as a refrigerating machine oil because it is compatible in the temperature range.

The hydroxycarboxylic acid polyol ester used in the present invention is a monoester, a diester, a polyester or a mixture thereof produced by an esterification reaction of a hydroxycarboxylic acid and a polyhydroxy compound, a self-condensation of a hydroxyalkyl aldehyde. There is a monoester compound or the like produced by the reaction, but the method for producing the product is not particularly limited.

Hydroxycarboxylic acids used for the production of hydroxycarboxylic acid polyol ester include glycolic acid, lactic acid, hydroxyisobutyric acid, hydroxypivalic acid, hydroxyoctanoic acid and the like, and polyvalent hydroxy compounds include 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 can be mentioned.
As the hydroxyalkyl aldehyde, glyco-
Lualdehyde, hydroxyisobutyraldehyde, 4-
Examples thereof include hydroxy-3-methylbutyraldehyde and hydroxypivalaldehyde.

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, etc., and these compounds The lower alkyl esters and acid anhydrides of can be similarly used.

The aliphatic monocarboxylic acid used in the present invention includes 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, 4-methylhexanoic acid, 4 -Methylhexanoic acid, 5-methylhexanoic acid, caprylic acid, 2-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 22-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 2-propylpentanoic acid, pelargonic acid, 2 , 2-dimethylheptanoic acid, 3,
3,5-trimethylhexanoic acid, 2-methyloctanoic acid, 2-ethyloctanoic acid, 2-ethylheptanoic acid, 3
-Methyloctanoic acid, capric acid, undecanoic acid, lauric acid and the like are exemplified, and lower alkyl esters and acid anhydrides thereof can be used as well.

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 removing a reaction by-product such as water out of the system by a usual method. 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, a post-treatment such as alkali washing, water washing, adsorption and the like can be carried out if necessary.

The synthetic lubricating 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 the above, and polyester
Synthetic oils such as tellurium, perfluoropolyether, and phosphoric acid ester may be blended. If necessary, a lubricating oil additive such as an antioxidant, an extreme pressure agent, an oiliness improver, an antifoaming agent, a metal deactivator, etc., which is usually used, can be added.

[0013]

The ester synthetic lubricating oil of the present invention is excellent in lubricating oil characteristics such as viscosity index and pour point, and has heat resistance, weather resistance and
It is excellent in hydrolysis resistance and is excellent as a lubricating oil used under severe conditions. Further, it is also excellent in compatibility with a hydrogen-containing fluoroalkane-based refrigerant and is also excellent as a refrigerator oil.

[0014]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples.

[0015]

Example 1 600 g of powdered hydroxypivalaldehyde was charged into a four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer, and a separator equipped with a cooling tube, and dissolved by heating to reach 90 ° C. At that time, 0.03% of tetrakisacetylacetonatozirconium was added as a catalyst to hydroxypivalaldehyde. Stop heating at the same time as catalyst addition. When the temperature reached 148 ° C to 130 ° C, the reaction was stopped by quenching. The product obtained is from 140
Vacuum distillation was performed at 153 ° C./3 to 6 mmHg to obtain 580 g of hydroxypivalic acid neopentyl glycol monoester. Of this, 408 g (2 mol) and adipic acid 14
Charge 6 g (1 mol) and 0.9 g of tetrabutoxytitanium as a catalyst into a four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer, and a separator equipped with a cooling tube.
The mixture was heated to 20 ° C., and the esterification reaction was performed until the theoretical amount of water was produced while removing the produced water outside the system. Then, 260 g (2 mol) of enanthic acid was added, and similarly the esterification reaction was carried out until the theoretical amount of water was produced. After completion of the reaction, the product was washed with a 5% aqueous sodium hydroxide solution and washed with water, dehydrated, and treated with clay to obtain a reaction product A.

[0016]

Example 2 Hydroxypivalic acid neopentyl glycol monoester synthesized in the same manner as in Example 1 in a four-necked flask equipped with a stirrer, a nitrogen blowing tube, a thermometer, and a separator equipped with a cooling tube. 204 g (1 mol), succinic acid 118 g (1 mol), neopentyl glycol 1
04g (1 mol), 144 g (1 mol) of 2-ethylhexanoic acid, 116 g (1 mol) of caproic acid, and 0.9 g of tetrabutoxytitanium as a catalyst are heated to 220 ° C. The esterification reaction was carried out until a quantity of water was produced. After completion of the reaction, the same purification as in Example 1 was carried out to obtain a reaction product B.

[0017]

Example 3 A reactor similar to that of Example 2 was charged with 166.6 g (1.6 mol) of hydroxyisobutyric acid, 104 g (1.6 mol) of neopentyl glycol and 0.2 g of dibutyltin oxide as a catalyst. Heat to ℃,
Esterification reaction was carried out until the theoretical amount of water was produced while removing the produced water out of the system to obtain hydroxyisobutyric acid neopentyl glycol monoester. Adipic acid 14
Charge 6 g (1 mol), 173 g (1.2 mol) of caprylic acid and 0.7 g of dibutyltin oxide, and the maximum temperature is 2.
The mixture was heated to 20 ° C., and the esterification reaction was carried out until the theoretical amount of water was produced while removing the produced water outside the system. After completion of the reaction, the same purification as in Example 1 was carried out to obtain a reaction product C.

[0018]

Example 4 354 g (3 mol) of hydroxypivalic acid, 208 g (2 mol) of neopentyl glycol and 0.3 g of dibutyltin oxide as a catalyst were charged in the same reactor as in Example 2 and heated to 220 ° C. The esterification reaction was carried out until the theoretical amount of water was generated while removing the generated water out of the system to obtain hydroxypivalic acid neopentyl glycol ester. Adipic acid 146 g (1 mol), acetic acid 60.5 g (1 mol), caprylic acid 144 g
(1 mol) and 0.7 g of dibutyltin oxide were charged and heated to 220 ° C., and the esterification reaction was carried out until the theoretical amount of water was produced while removing the produced water out of the system. After completion of the reaction, the same purification as in Example 1 was carried out to obtain a reaction product D.

[0019]

Example 5 118 g (1 mol) of hydroxypivalic acid, 134 g (1 mol) of trimethylolpropane and 0.2 g of dibutyltin oxide as a catalyst were charged in the same reactor as in Example 2 and heated to 220 ° C. to produce The esterification reaction was carried out while removing water out of the system until a theoretical amount of water was produced to obtain hydroxypivalic acid trimethylolpropane monoester. Adipic acid 146g (1
Mol), neopentyl glycol 104 g (1 mol),
432.6 g (3 mol) of caprylic acid and 0.7 g of dibutyltin oxide were charged and heated to 220 ° C., and the esterification reaction was carried out until the theoretical amount of water was produced while removing the produced water out of the system. After completion of the reaction, the same purification as in Example 1 was carried out to obtain a reaction product E.

[0020]

Comparative Example 1 A reactor similar to that of Example 2 was charged with 152 g (2 mol) of propylene glycol and 146 g (1 mol) of adipic acid.
Mol) and lauric acid 400 g (2 mol) were charged and reacted in the same manner as in Example 2 to obtain an ester reaction product F.

[0021]

Comparative Example 2 Comparative Example 1 using 136 g (1 mol) of pentaerythritol and 520 g (4 mol) of enanthate.
Was reacted in the same manner as in to obtain pentaerythritol tetraenanthate (G).

[0022]

Comparative Example 3 Adipic acid dioctyl ester (H) was obtained by the same reaction as in Comparative Example 1 using 146 g (1 mol) of adipic acid and 260 g (2 mol) of 2-ethylhexanol.

The physical properties of the compounds of the above Examples and Comparative Examples are shown in Table 1, and the evaluation results of thermal stability, hydrolyzability and compatibility are shown in Table 2. The evaluation methods were as follows.

Thermal stability: 60 g of sample oil was placed in a 100 ml sample bottle, and the increase in acid value and kinematic viscosity ratio (40 ° C.) after heating at 140 ° C. for 168 hours were measured.

Hydrolysis resistance: In a 250 ml sample bottle, 60 g of sample oil, 10,000 ppm of water, copper, iron and aluminum having a diameter of 3 mm and a length of 27 mm as a catalyst were put and sealed, and the acid value after heating at 140 ° C. for 168 hours. The increase amount and the kinematic viscosity ratio (40 ° C.) were measured.

Compatibility with CFCs: inner diameter 7 mm, length 24
Freon HFC134a and sample oil were sampled and sealed in a 0 mm Pyrex glass tube so that the oil ratio was 10%.
The two-phase separation temperature at 70 ° C to 80 ° C was measured.

[0027]

[Table 1]

[0028]

[Table 2]

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Claims (4)

[Claims] 1. From (A) hydroxycarboxylic acid polyol ester, (B) aliphatic polyvalent carboxylic acid, (C) aliphatic monocarboxylic acid and, if necessary, (D) aliphatic polyvalent alcohol. A synthetic lubricating oil containing the obtained ester reaction product as a main component. 2. The synthetic lubricating oil according to claim 1, wherein the hydroxycarboxylic acid polyol ester is a hydroxycarboxylic acid alkylene glycol ester. 3. The hydroxycarboxylic acid alkylene glycol ester is represented by the general formula 1 The synthetic lubricating oil according to claim 2, wherein 4. The synthetic lubricating oil according to claim 1, wherein the lubricating oil is a refrigerating machine oil used in a hydrogen-containing fluoroalkane-based refrigerant atmosphere.