JP2002193882A - Method for producing ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high-quality ester, especially the ester having excellent thermal oxidation stability, and further to provide the ester obtained by the method. SOLUTION: This method for producing the ester comprising reacting an alcohol with a carboxylic acid comprises a step for reacting the alcohol with the carboxylic acid in the presence of 0.00001-0.005 mol Lewis acid catalyst and 0.0003-0.005 mol phosphorus-based reductant based on 1 mol carboxy group of the carboxylic acid, and a step for isolating the obtained ester.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing an ester, which is carried out in the presence of a Lewis acid catalyst and a phosphorus-based reducing agent.
And an ester obtained by this production method. The present invention also relates to an ester-based lubricating base oil comprising the ester for grease, refrigerator oil, and engine oil, and a composition containing the base oil.

[0002]

2. Description of the Related Art Esters are used in a wide range of fields such as cosmetics, pharmaceuticals, foods, electronic equipment, printing and lubrication.
In recent years, along with technological progress in the fields where these esters are used, there is a demand for the quality of the esters adapted to each field. For example, esters used for grease are required to have excellent durability and resistance to evaporation at high temperatures. Esters used in engine oils are required to have a long life and excellent thermal oxidation stability. Esters used for refrigerator oil are:
Demands for functions such as high electrical insulation and heat resistance, low impurities and conductive impurities, low acid value and low hydroxyl value, and excellent hydrolysis stability and heat stability at high temperatures Is required.

[0003] Esters are obtained by reacting a carboxylic acid with an alcohol. Generally, in order to obtain an ester having a low hydroxyl value, the reaction is carried out in a carboxylic acid excess system. In this esterification reaction, generally, sulfuric acid,
Bronsted acids such as hydrochloric acid, paratoluene sulfonic acid, methane sulfonic acid, naphthalene sulfonic acid and the like are used as catalysts. In such an esterification reaction using a Bronsted acid catalyst, a by-product tends to be easily generated. The generated by-products and the remaining catalyst are removed alone or in combination with purification such as deacidification with an alkali, adsorption treatment with an adsorbent, and steaming. However, it is difficult to sufficiently remove by-products and residual catalyst,
Residual by-products and catalysts reduce the thermal oxidative stability of the esters. Thus, an ester satisfying various requirements has not been obtained.

[0004] JP-A-54-91589 and JP-A-54-132502 disclose Bronsted acids,
A method for performing esterification in the presence of an acidic catalyst such as an ion exchange resin and phosphorous acid, hypophosphorous acid or a salt thereof is described. Japanese Patent Publication No. 7-45437 describes a method for producing an ester by performing transesterification in the presence of a monoorganotin compound. Each of these methods has some effect in that an ester with less coloring is obtained, but the long-term thermal oxidation stability is still insufficient.

[0005] In addition to the above, as disclosed in JP-A-7-309937, a low-colored polyester is produced by adding a stabilizer comprising a compound of phosphorus type, phenol type, thioether type or amine type. There are examples. But,
All of these stabilizers are difficult to remove from the reaction product, and the stabilizer remaining in the ester acts as an ester degradation accelerator, generating sludge and discoloration when used at high temperatures for a long period of time. Cause.

In addition, an example of Japanese Patent Publication No. 2000-508691 describes a method using dibutyltin oxide as an esterification catalyst. However, the ester obtained by this method is insufficient in terms of thermal oxidation stability, such as coloring at a high temperature and having a high acid value. Table 1
In the engine oil described in 997-008277, an ester produced without any catalyst is used as a base oil. However, an esterification reaction at a high temperature for a long time at the time of producing the ester is required. Undergoes significant thermal degradation during the reaction. Therefore, the heat resistance of the ester base oil cannot be said to be sufficient, and there is a problem in long-term stability.

As esterification catalysts, basic catalysts are also known, such as N, N'-dicyclohexylcarbodiimide-4- (N, N-dimethylamine) pyridine, triphenylphosphine-2,2'-dipyridyl sulfide and the like. Is used. However, in any case, the reaction product liquid is colored brown, and a high-quality ester cannot be obtained.

As described above, no method for producing an ester satisfying the high quality required in various fields has been found.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for producing a high-quality ester, particularly an ester having excellent thermal oxidation stability, And an ester obtained by the method. Another object of the present invention is to use the ester, especially for a long-life grease, an engine oil, and a refrigerating machine oil, even under severe use conditions such as a recent increase in speed and load of a machine. Base lubricating oil,
And a composition containing these base oils.

[0010]

The process for producing an ester according to the present invention comprises reacting an alcohol with a carboxylic acid.
A step of reacting an alcohol with a carboxylic acid in the presence of 0.000001 to 0.005 mol of a Lewis acid catalyst and 0.0003 to 0.005 mol of a phosphorus-based reducing agent per mol, and separation of the resulting ester The step of performing

[0011] In a preferred embodiment, the Lewis acid catalyst is selected from the group consisting of a titanium Lewis acid catalyst, a tin Lewis acid catalyst, an antimony Lewis acid catalyst, a germanium Lewis acid catalyst, and a zirconium Lewis acid catalyst. At least one selected.

In a preferred embodiment, the alcohol is a di- to hexavalent neopentyl polyol, and the carboxylic acid is a monocarboxylic acid having 5 to 10 carbon atoms.

In a preferred embodiment, the alcohol is a di- or tetravalent neopentyl polyol, and the carboxylic acid is a monocarboxylic acid having 5 to 12 carbon atoms.

The ester of the present invention can be prepared by reacting an alcohol with an alcohol in the presence of 0.000001 to 0.005 mole of a Lewis acid catalyst and 0.0003 to 0.005 mole of a phosphorus-based reducing agent per mole of carboxylic acid carboxyl group. And a step of separating the resulting ester, wherein the acid catalyst and the reducing agent are substantially removed.

The grease ester-based lubricating base oil of the present invention is used in an amount of 0.0 based on 1 mol of carboxylic acid of carboxylic acid.
0001-0.005 mol of Lewis acid catalyst and 0.00
A step of reacting a di- or hexavalent neopentyl polyol with a monocarboxylic acid having 5 to 10 carbon atoms in the presence of 03 to 0.005 mol of a phosphorus-based reducing agent, and a step of separating an obtained ester. And an ester obtained by the method, wherein the acid catalyst and the reducing agent are substantially removed.

The ester-based lubricating base oil for refrigerator oil of the present invention is used in an amount of 0.0 per mol of carboxyl group of carboxylic acid.
0001-0.005 mol of Lewis acid catalyst and 0.00
A step of reacting a di- or hexavalent neopentyl polyol with a monocarboxylic acid having 5 to 10 carbon atoms in the presence of 03 to 0.005 mol of a phosphorus-based reducing agent, and a step of separating an obtained ester. And an ester obtained by the method, wherein the acid catalyst and the reducing agent are substantially removed.

The ester lubricating base oil for an engine oil of the present invention is used in an amount of 0.0 with respect to 1 mol of carboxyl groups of carboxylic acid.
0001-0.005 mol of Lewis acid catalyst and 0.00
A step of reacting a di- or tetravalent neopentyl polyol with a monocarboxylic acid having 5 to 12 carbon atoms in the presence of 03 to 0.005 mol of a phosphorus-based reducing agent, and a step of separating an obtained ester. It is an ester obtained by the method, wherein the acid catalyst and the reducing agent have been substantially removed.

The grease composition of the present invention contains the above-mentioned ester-based lubricating base oil for grease, a thickening agent, and an antioxidant, and contains the ester-based lubricating base oil for grease in a proportion of 10 to 90% by weight. Is done.

The composition for a working fluid of a refrigerator according to the present invention contains the ester lubricant base oil for a refrigerator oil and hydrofluorocarbon in a weight ratio of 10:90 to 90:10.

The engine oil composition of the present invention contains the ester lubricant base oil for engine oil, an antiwear agent, and an antioxidant.
It is contained in a proportion of 95% by weight.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Carboxylic acid] The carboxylic acid used in the present invention includes monocarboxylic acids and polycarboxylic acids. These carboxylic acids may be any of a saturated carboxylic acid and an unsaturated carboxylic acid,
Both linear and branched forms may be used. Preferably, a saturated linear or branched carboxylic acid is used.

The monocarboxylic acids include, for example, the following compounds: valeric acid, isovaleric acid, caproic acid,
2-ethylbutanoic acid, heptanoic acid, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5
-Methylhexanoic acid, 2,2-dimethylpentanoic acid, 2
-Ethylpentanoic acid, 3-ethylpentanoic acid, isoheptanoic acid, caprylic acid, 2-ethylhexanoic acid, nonanoic acid, 3,5,5-trimethylhexanoic acid, neononanoic acid, capric acid, neodecanoic acid, lauric acid, myristic acid , Palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachinic acid, erucic acid, behenic acid, lignoceric acid, serotinic acid, montanic acid, melicic acid and the like.

The polycarboxylic acids include, for example, the following compounds: succinic acid, glutanic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, tridecandioic acid. acid,
Carboxyoctadecanoic acid, carboxymethyloctadecanoic acid, docosandioic acid, dimer acid, phthalic acid, isophthalic acid, fumaric acid, maleic acid, trimellitic acid, pyromellitic acid, and the like.

These carboxylic acids are used alone or in combination.

[Alcohol] Examples of the alcohol used in the present invention include monohydric alcohols, polyhydric alcohols, and ether compounds obtained by adding an alkylene oxide to these alcohols.

The monohydric alcohols include, for example, the following compounds: pentanol, isopentanol,
Hexanol, cyclohexanol, heptanol, octanol, 2-ethylhexanol, nonanol,
3,5,5-trimethylhexanol, isononanol, decanol, isodecanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, eicosanol, docosanol, tetracosanol, hexacosanol, octacosanol,
Nonacosanol, myristyl alcohol, melisyl alcohol, and the like.

The polyhydric alcohols include, for example, the following compounds: ethylene glycol, propylene glycol, polyalkylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1 , 6-hexanediol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, spiro glycol, 1,4-phenylene glycol, 1,2,4-butanetriol, 1,2 , 5-pentanetriol, 1,
2,3,6-hexanetetraol, 2-methyl-1,
2,4-butanetriol, erythritol, arabitol, sorbitol, mannitol, sorbitan, glycerin, 2-methylpropanetriol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2- Ethyl-1,3-propanediol, trimethylolethane, triethylolethane, trimethylolpropane, pentaerythritol,
Dipentaerythritol, tripentaerythritol,
1,3,5-trihydroxymethylbenzene and the like.

The alkylene oxide to be added to these alcohols includes ethylene oxide, propylene oxide, butylene oxide and the like.

These alcohols are used alone or in combination.

[Lewis Acid Catalyst] The Lewis acid catalyst used in the present invention includes a titanium Lewis acid catalyst, a tin Lewis acid catalyst, an antimony Lewis acid catalyst, a zinc Lewis acid catalyst, a germanium Lewis acid catalyst, and a zirconium based catalyst. Lewis acid catalysts, hafnium-based Lewis acids and the like can be mentioned.

Examples of the titanium-based Lewis acid catalyst include tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, tetraoctoxytitanium, titanium ethyl acetoacetate,
Octylene glycol titanate and the like.

Examples of the tin-based Lewis acid catalyst include monoalkyltin esters, dialkyltin esters, monoalkyltin oxides, and dialkyltin oxides. As the alkyl group contained in the compound used as the tin-based catalyst, a linear or branched alkyl having 1 to 12 carbon atoms is preferable. Specific examples of the tin-based catalyst include monobutyltin mono (2-ethylhexanoate), monobutyltin tris (2-ethylhexanoate), and dibutyltin bis (2-ethylhexanoate).
Ethylhexanoate), stannous bis (2-ethylhexanoate), dibutyltin diacetate, monobutyltin oxide, dibutyltin oxide and the like.

Examples of the antimony-based Lewis acid catalyst include triethoxyantimony, tributoxyantimony, and antimony trioxide.

The zinc-based Lewis acid catalyst includes zinc chloride,
Zinc acetate, zinc carbonate, and the like.

Examples of the germanium-based Lewis acid catalyst include germanium selenide, germanium dioxide, germanium tetrachloride, tetra-n-butoxygermanium and the like.

Examples of the zirconium-based Lewis acid catalyst include tetramethoxy zirconium, tetraethoxy zirconium, tetra-n-propoxy zirconium, tetraisopropoxy zirconium, tetra-n-butoxy zirconium, tetra-t-butoxy zirconium, zirconium oxide, and tungstic acid. Zirconium, tetra-2-
Ethyl hectoxy zirconium and the like.

Examples of the hafnium-based Lewis acid catalyst include tetramethoxyhafnium, tetraethoxyhafnium, tetra-t-butoxyhafnium, tetra-2-ethylhexyloxyhafnium, hafnium oxychloride, hafnium tetrachloride and hafnium oxide.

Among these Lewis acid catalysts, titanium catalysts, tin catalysts, zirconium catalysts, antimony catalysts, and germanium catalysts are preferred from the viewpoint of reaction activity. Specifically, the following compounds are suitable: tetraisopropoxytitanium, tetra-n-butoxytitanium,
Monobutyltin mono (2-ethylhexanoate), monobutyltin tris (2-ethylhexanoate), stannous bis (2-ethylhexanoate), tetraethoxyzirconium, tetra-n-propoxyzirconium, tetra- n-butoxyzirconium, triethoxyantimony, tributoxyantimony, tetra-n-butoxygermanium, and germanium tetrachloride.

The Lewis acid catalyst is used in an amount of 0.00000 per mole of the carboxyl group of the carboxylic acid to be subjected to the esterification reaction.
It is used in a ratio of 1 to 0.005 mol. When the amount of the Lewis acid catalyst is less than 0.0001 mol, not only the reaction takes a long time but also the productivity is reduced. When the amount exceeds 0.005 mol, the effect corresponding to the amount used is not improved, and the production cost increases. Further, it becomes difficult to remove the catalyst from the ester, and the thermal oxidation stability of the ester may be deteriorated. When used in the above range,
The residual amount of the metal derived from the Lewis acid catalyst in the formed ester is substantially lower than the measurement limit.

[Phosphorus Reducing Agent] Examples of the phosphorus reducing agent used in the present invention include phosphorous acid, hypophosphorous acid, and salts thereof. Of these, phosphite and hypophosphite are preferably used. As the salts of phosphorous acid and hypophosphorous acid,
Salts of sodium, potassium, calcium, zinc, magnesium, barium, ammonium and the like can be mentioned, and a sodium salt is preferably used.

The phosphorus-based reducing agent is used in an amount of 0.0003 per mole of the carboxyl group of the carboxylic acid to be subjected to the esterification reaction.
It is used in a proportion of ~ 0.005 mol. 0.001-0.00.
003 mol is preferred. If the amount is less than 0.0003 mol, the effect of improving the thermal oxidation stability of the ester becomes insufficient.
Even if the amount exceeds 0.005 mol, the effect corresponding to the amount used is not improved, the removal becomes difficult, and the thermal oxidation stability of the ester may be deteriorated. When used in the above range, the residual amount of phosphorus in the produced ester is substantially lower than the measurement limit.

[Method for Producing Ester] Next, the method for producing the ester of the present invention will be described. In the esterification reaction, the carboxylic acid and the alcohol are usually adjusted such that the carboxyl group of the carboxylic acid is 1.0 to 1.5 equivalents to 1 equivalent of the hydroxyl group of the alcohol. In order to obtain an ester having a low hydroxyl value, it is necessary to carry out an esterification reaction in excess of carboxylic acid. The equivalent ratio is 1.0
It is more than equivalent. If the amount exceeds 1.5 equivalents, the excess carboxylic acid must be removed after the completion of the reaction, resulting in low productivity.

In the method of the present invention, the carboxylic acid and alcohol adjusted to the above-mentioned appropriate ratios are subjected to an esterification reaction in the presence of an appropriate amount of a Lewis acid catalyst and a phosphorus-based reducing agent. The reaction is usually performed at 120 to 260 ° C. for 3 hours.
15 hours. After completion of the reaction, the ester of the present invention is obtained by performing a purification method usually used by those skilled in the art, for example, purification such as deacidification with an alkali, adsorption treatment with an adsorbent, steaming, and distillation, alone or in combination.
Among these, a method of performing a combination of deacidification with an alkali and adsorption treatment with an adsorbent is preferable as a purification method from the viewpoint of thermal oxidation stability of the ester.

Examples of the alkali used for deacidification include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal salts such as sodium carbonate, potassium carbonate and sodium hydrogen carbonate; and ammonium salts such as ammonium carbonate. Can be Of these, sodium hydroxide and potassium hydroxide are preferred. The amount of the alkali used is 1-2 times equivalent to the acid value of the ester, and deacidification is carried out as an aqueous alkaline solution having a concentration of 5 to 20% by weight.

Examples of the adsorbent include activated clay, acid clay, activated carbon, zeolite, activated alumina, diatomaceous earth, silicon dioxide, aluminum oxide, magnesium oxide, and silica-alumina synthetic adsorbent. Activated clay and silica-alumina synthetic adsorbents are preferred. The amount of the adsorbent used is based on 1 part by weight of the obtained ester.
It is preferably 0.1 to 5.0 parts by weight.

In a conventional ester produced using a Bronsted acid or the like as a catalyst, by-products and the catalyst are not completely removed. On the other hand, the Lewis acid catalyst and the phosphorus-based reducing agent used in the present invention may be used at a low concentration, and an ester from which by-products, the catalyst, and the reducing agent are almost completely removed is produced. . The concentration of the metal and phosphorus derived from the Lewis acid catalyst in the resulting ester is below the detection limit, and is substantially not contained in the ester. Esters having such properties exhibit excellent effects of excellent thermal oxidation stability and no coloration for a long period of time, as shown in Examples below.

The ester obtained by the method of the present invention is
It is used as a base oil for various applications, for example, ester lubricating oil for grease, ester lubricating oil for refrigerator oil, or ester lubricating oil for engine oil.

[Ester Lubricating Base Oil for Grease and Grease Composition] The ester used as the ester lubricating base oil for grease is an ester composed of di- or hexavalent neopentyl polyol and monocarboxylic acid having 5 to 10 carbon atoms. It is formed in the presence of 0.000001 to 0.005 mol of a Lewis acid catalyst and 0.0003 to 0.005 mol of a phosphorus-based reducing agent per 1 mol of carboxyl groups of the carboxylic acid. These catalysts and reducing agents are removed below the measurement limit in the purification step and are not substantially contained in the ester. The ester obtained in this way has excellent hue, excellent thermal oxidation stability, low volatility even after long-term use (low weight loss rate), and An excellent effect of no coloring (excellent hue) and little generation of sludge can be obtained.

The divalent to hexavalent neopentyl polyol is preferably used because the resulting ester is excellent in heat resistance. As the divalent to hexavalent neopentyl polyol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and the like are preferable. Trimethylolpropane, pentaerythritol and dipentaerythritol are more preferred from the viewpoint of the resistance of the resulting ester to evaporation at high temperatures.
From the viewpoint of extending the life of grease, pentaerythritol and dipentaerythritol having high heat resistance are particularly preferable.

The monocarboxylic acids include those having 5 to 10 carbon atoms.
Are preferred. From the viewpoint that the obtained ester is excellent in low-temperature fluidity, it is preferred that the monocarboxylic acid contains a branched monocarboxylic acid. The branched monocarboxylic acid is preferably contained in an amount of 25% by weight or more of the entire monocarboxylic acid. On the other hand, if the proportion of the branched monocarboxylic acid is too large, the resistance to evaporation at high temperatures is reduced. Therefore, in the monocarboxylic acid, the branched monocarboxylic acid is 25 to 7
Preferably, it is contained in a proportion of 5% by weight. As the branched monocarboxylic acid having 5 to 10 carbon atoms, a branched monocarboxylic acid having 7 or more carbon atoms is preferable from the viewpoint of evaporation resistance, and a branched monocarboxylic acid having 9 or less carbon atoms is preferable from the viewpoint of low-temperature fluidity. Is preferred. The branched carboxylic acid is preferably an α- or β-branched carboxylic acid, and more preferably an α-branched carboxylic acid, from the viewpoint of heat resistance and hydrolysis stability. Specific examples include the following compounds: 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid,
2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, neononanoic acid and the like.

From the viewpoint of heat resistance and hydrolysis stability, the acid value of the ester is preferably 0.1 mgKOH / g or less, more preferably 0.05 mgKOH / g or less. From the viewpoints of high-temperature evaporation resistance and low-temperature fluidity, the hydroxyl value of the ester is preferably 10 mgKOH / g or less. When the hydroxyl value exceeds 10 mgKOH / g, thermal oxidation stability at high temperatures is poor, and when sealing is performed using grease containing the ester, the sealing material expands.

The grease composition of the present invention comprises a base oil comprising the above-mentioned ester, a thickener, an antioxidant, and, if necessary, a commonly used extreme pressure agent, rust inhibitor, defoamer, demulsifier and the like. Contains additives.

Examples of the above thickener include complex soaps such as lithium complex soap, calcium complex soap, aluminum complex soap and calcium complex soap; calcium soap,
Alkali metal soaps such as sodium soap and lithium soap; urea, terephthalic acid amide and the like. From the viewpoint of heat resistance, lithium complex soap, lithium soap and urea are preferred.

The above antioxidants include the following compounds: 2,6-di-tert-butyl-4-methylphenol, 4,4'-methylbis (2,6-di-tert-butyl-4) -Methylphenol); phenolic antioxidants such as p, p'-dioctylphenylamine, monooctyldiphenylamine, phenothiazine, 3,7-dioctylphenothiazine, phenyl-1-naphthylamine;
Phenyl-2-naphthylamine, alkylphenyl-1
Amine antioxidants such as naphthylamine and alkylphenyl-2-naphthylamine; zinc dialkyldithiophosphate, zinc diallyldithiophosphate and the like. These antioxidants can be used alone or in combination of two or more.

[Ester lubricating base oil for refrigerating machine oil and composition for working fluid of refrigerating machine] The ester used as the ester lubricating base oil for refrigerating machine oil is the same as the ester used for the ester lubricating base oil for grease described above. An ester of a di- or hexavalent neopentyl polyol and a monocarboxylic acid having 5 to 10 carbon atoms, wherein 0.0001 to 0.005 mol of a Lewis acid catalyst is used per 1 mol of a carboxyl group of the carboxylic acid; It is formed in the presence of 0.0003 to 0.005 mol of a phosphorus-based reducing agent. These catalysts and reducing agents are removed below the measurement limit in the purification step and are not substantially contained in the ester. The ester thus obtained is superior in hue and thermal oxidative stability as compared with the conventional ester, the acid value in the shield tube test does not substantially change, and there is no coloring for a long time ( (Excellent hue).

The divalent to hexavalent neopentyl polyol is preferably used because the resulting ester has excellent heat resistance. As the divalent to hexavalent neopentyl polyol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and the like are preferable.

The monocarboxylic acids include those having 5 to 10 carbon atoms.
Is preferable, and a monocarboxylic acid having 5 to 9 carbon atoms is more preferable. Since the resulting ester has excellent low-temperature fluidity and CFC compatibility, it has 5 carbon atoms.
It is preferable that the branched monocarboxylic acid is contained in the monocarboxylic acids of Nos. 9 to 9. The branched monocarboxylic acid is preferably contained in an amount of 50% by weight or more of the whole monocarboxylic acid.
More preferably 0% by weight or more, 70% by weight
It is more preferable that the above is included. The branched carboxylic acid is preferably an α- or β-branched carboxylic acid from the viewpoint of heat resistance and hydrolysis stability of the obtained ester,
Branched carboxylic acids are more preferred.

The acid value of the ester used as the ester-based lubricating base oil for refrigerator oil is preferably 0.05 mg KOH / g or less, and is 0.0 from the viewpoint of heat resistance and hydrolysis stability.
1 mgKOH / g or less is more preferable. Further, the hydroxyl value is preferably 5 mgKOH / g or less, and 3 mgKOH / g in view of compatibility with a sealing material, heat resistance and hydrolysis stability.
g or less is more preferable. When the ester of the present invention is used as a base oil for refrigerator oil, an increase in the acid value and an increase in the hue after the shield tube test are suppressed low (see Examples described later).

The composition for a working fluid of a refrigerator according to the present invention comprises a base oil comprising the above ester, a hydrofluorocarbon, and, if necessary, additives commonly used by those skilled in the art.
It contains antioxidants, extreme pressure agents, metal deactivators, foaming agents and the like.

In the above composition, if the content of the hydrofluorocarbon is too high, the viscosity of the composition for the working fluid of the refrigerator may decrease, and lubrication failure may occur. for that reason,
The content of the hydrofluorocarbon is preferably 90% by weight or less, more preferably 80% by weight or less. On the other hand, if the content of the hydrofluorocarbon is too low, the refrigeration efficiency may decrease, and the content is preferably 10% by weight or more. Therefore, in consideration of lubricity and refrigeration efficiency, the content ratio of ester lubricant base oil (ester) for refrigerator oil to hydrofluorocarbon is 10:90 to 90:10.
(Weight ratio) is preferred. More preferably, 20: 80-
90:10 (weight ratio).

As the hydrofluorocarbon, 1,
1,1,2-tetrafluoroethane (HFC134
a), pentafluoroethane (HFC125), difluoromethane (HFC32) and the like are suitable, and these can be used alone or in combination.

[Ester Lubricating Base Oil for Engine Oil and Engine Oil Composition] The ester used as the ester lubricating base oil for engine oil is a di- or tetravalent neopentyl polyol and a monocarboxylic acid having 5 to 12 carbon atoms. Which is formed in the presence of 0.000001 to 0.005 mol of a Lewis acid catalyst and 0.0003 to 0.005 mol of a phosphorus-based reducing agent per 1 mol of carboxyl groups of a carboxylic acid. . These catalysts and reducing agents are removed below the measurement limit in the purification step and are not substantially contained in the ester. The ester thus obtained does not substantially contain a catalyst and a reducing agent, is excellent in hue, is excellent in thermal oxidation stability, and has a stability of 10% or more in a rotating cylinder type thermal oxidation stability test (described later). , Preferably 20% or more, more preferably 30% or more.

Examples of the divalent to tetravalent neopentyl polyol include neopentyl glycol, trimethylolpropane, pentaerythritol and the like.

The monocarboxylic acid having 5 to 12 carbon atoms is
The resulting ester is preferably used because it has excellent lubricity and heat resistance. It is preferable that a linear carboxylic acid is contained in the monocarboxylic acid from the viewpoint of the temperature viscosity characteristics and lubricity of the obtained ester. This linear carboxylic acid is preferably contained in an amount of at least 40% by weight, more preferably at least 50% by weight, even more preferably at least 60% by weight of the entire monocarboxylic acid. When a branched carboxylic acid is used, an α- or β-branched carboxylic acid is preferable, and an α-branched carboxylic acid is more preferable, from the viewpoints of heat resistance and hydrolysis stability of the obtained ester.

The kinematic viscosity at 40 ° C. of an ester used as an ester lubricating base oil for an engine oil is 8 to 50.
It is preferably mm ² / s, 10~40mm ² /
More preferably, s. When the kinematic viscosity is less than 8 mm ² / s, there is a disadvantage that the evaporation loss at a high temperature is large and the lubricity is reduced. When the kinematic viscosity is more than 50 mm ² / s, power loss due to viscosity resistance is too large, which is not preferable. The hydroxyl value of the ester is preferably 5 mgKOH / g or less, more preferably 3 mgKOH / g or less. If it exceeds 5 mgKOH / g, the oxidation stability of the ester at high temperatures is poor, and the detergency is insufficient.

The engine oil composition of the present invention comprises a base oil comprising the above ester, an antioxidant, and, if necessary, other synthetic lubricating oils and mineral oils, commonly used detergent / dispersants, viscosity index improvers, Contains additives such as antiwear agents, extreme pressure agents, oiliness agents, rust inhibitors, and defoamers. Examples of the synthetic lubricating oil and mineral oil include polyalphaolefin, high viscosity index semi-synthetic oil, polyalkylene glycol, alkylbenzene, naphthenic mineral oil, paraffinic mineral oil, aromatic mineral oil, polybutene, and the like. Among these, polyalphaolefin and high viscosity index semi-synthetic oil are preferable from the viewpoint of compatibility with the sealing material and high temperature viscosity characteristics. Examples of the above antiwear agent include zinc dithiophosphate, zinc dithiocarbamate, dialkyl polysulfide, triallyl phosphate, and trialkyl phosphate. These antiwear agents can be used alone or in combination of two or more.

The antioxidants include 2,6-di-t
-Butyl-4-methylphenol, 4,4'-methylbis (2,6-di-t-butyl-4-methylphenol)
Phenolic antioxidants such as p, p'-dioctylphenylamine, monooctyldiphenylamine, phenothiazine, 3,7-dioctylphenothiazine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, alkylphenyl-1-naphthylamine, alkyl Amine antioxidants such as phenyl-2-naphthylamine; zinc dialkyldithiophosphate, zinc diallyldithiophosphate, and the like; These antioxidants can be used alone or in combination of two or more.

In the present specification, the characteristics according to each application are described, but the ester used in each application may be common. In that case, it goes without saying that the respective applications may have the same characteristics as those used for other applications.

[0069]

EXAMPLES The present invention will be specifically described below with reference to production examples of esters.

The methods for evaluating the esters prepared in Examples and Comparative Examples are described below.

(I) Kinematic viscosity of ester (40 ° C.), pour point, acid value, hydroxyl value and hue (APHA) (1) Kinematic viscosity (40 ° C.): Measured according to JIS K2283. (2) Pour point: Measured according to JIS K 2269. (3) Acid value: Measured according to JIS C 2101. (4) Hydroxyl group: Measured according to JIS K0070. (5) Hue (APHA): JOCS 2.2.1.4-1
Measured according to 996. (6) Residual concentration of catalyst and reducing agent components in ester (6.1) Residual concentration of tin (ppb): JIS K012
It is measured under the following conditions by an atomic absorption spectrophotometry according to 1. Background correction method: deflection Zeeman method Atomization method: graphite furnace Wavelength (nm): 224.6 Slit (nm): 1.3 (6.2) Residual concentration of titanium (ppb): JIS K 0
It was measured by the atomic absorption spectrophotometry based on the following conditions under the following conditions. Background correction method: Deflected Zeeman method Atomization method: Graphite furnace Wavelength (nm): 364.3 Slit (nm): 0.4 (6.3) Residual concentration of antimony (ppm): JIS K
It is measured under the following conditions by an atomic absorption spectrophotometry based on 0121. Background correction method: deflection Zeeman method Atomization method: graphite furnace Wavelength (nm): 217.6 Slit (nm): 0.4 (6.4) Residual concentration of germanium (ppm): JIS
It is measured under the following conditions by an atomic absorption spectrophotometry based on K0121. Background correction method: deflection Zeeman method Atomization method: graphite furnace Wavelength (nm): 265.2 Slit (nm): 0.4 (6.5) Residual concentration of zirconium and phosphorus (ppm):
After performing pre-processing according to JIS K 0102,
The measurement is performed using an emission spectrometer (manufactured by JASCO Corporation) using inductively coupled high frequency plasma (ICP) as a light source. (6.6) Residual sulfur concentration (ppm): JIS K2
541. (6.7) Nitrogen residual concentration (ppm): Mitsubishi Kasei Corporation
It is measured by a double tube type vaporization combustion method using a “trace nitrogen analyzer TN-05” manufactured by Toshiba Corporation. (6.8) Aromatic compound (ppm): JIS K 0
Measured according to No. 115.

(II) Heating Test This test is performed to examine the thermal oxidation stability of the obtained ester as an ester-based lubricating base oil for grease. The ester was heated in a high-temperature bath at 180 ° C. for 500 hours in an air atmosphere, and the weight loss (%) of the ester after the heating was measured, and the hue (Gardner, JOCS 2.2.1.3.
1996) and the presence or absence of sludge. Regarding the weight loss rate (%), when each of the weight loss rates (%) in each example is set to “100”, the weight reduction rate in the corresponding comparative example is calculated as a relative value.

(III) Rotating Bomb Type Thermal Oxidation Stability Test (RBOT) This test is performed to examine the thermal oxidation stability of the obtained ester as an ester-based lubricating base oil for engine oil. 50 g of the ester, 5 g of water and 3 m of the copper catalyst coil are put in a container, and oxygen is press-fitted to 620 KPa and sealed.
This is put in a thermostat at 150 ° C., the container is rotated at 100 rpm at an angle of 30 °, and the time (minute) (RBOT life value) until the pressure is reduced to 172 KPa is measured.

(IV) Shield tube test This test is performed to examine the thermal oxidation stability of the obtained ester as an ester-based lubricating base oil for refrigerator oil. In a glass tube, 10 g of the ester whose water concentration was previously adjusted to 2,000 ppm, Freon R-407C (weight ratio of 1,1,1,2-tetrafluoroethane (HFC134
a): pentafluoroethane (HFC125): difluoromethane (HFC32) = 52: 25: 23) 5g,
Then, each piece of iron, copper, and aluminum having a length of 10 mm is sealed and sealed. After heating at 175 ° C. for 14 days, the acid value rise and hue (APH
A) Examine the rise. Separately, the above CFC R-4
The same test is performed by changing 07C to difluoromethane (HFC32) alone.

Example 1 1200.0 g (8.81 m) of pentaerythritol was placed in a 5-liter four-necked flask equipped with a thermometer, a nitrogen inlet tube, a stirrer and a condenser tube.
ol); 884.6 g (7.63 mol) of caproic acid;
1767.4 g (11.26 mol) of n-nonanoic acid,
2736.6 g of 3,5,5-trimethylhexanoic acid (1
7.43 mol), tetraisopropoxy titanium.
6 g (0.07 mol; carboxyl group 1 of carboxylic acid)
0.002 mol) and 3.9 g of sodium hypophosphite (0.04 mol; 0.001 mol relative to 1 mol of carboxylic acid carboxyl group) were added thereto while distilling off water produced at 240 ° C. under a nitrogen stream. The reaction was carried out at normal pressure, and the reaction was terminated when the hydroxyl value of the product became 3 mgKOH / g or less.

After completion of the reaction, unreacted fatty acids were distilled off under reduced pressure of 1 kPa. At this time, the obtained crude esterified product was 3150.4 g, and the acid value was 3.1 mg KO.
H / g. The acid value of the esterified crude product is 1.
A 10% aqueous potassium hydroxide solution corresponding to 5 equivalents was added, and the mixture was stirred at 90 ° C. for 30 minutes. The mixture was allowed to stand for 30 minutes to remove the aqueous layer, and the deoxidizing step was completed. 20 parts by weight of ion-exchanged water was added to 100 parts by weight of the crude esterified product, and the mixture was stirred at 90 ° C. for 30 minutes, and then allowed to stand for 30 minutes to discharge the aqueous layer. This washing step was repeated three times. Subsequently, dehydration was performed by performing a reduced pressure operation at 100 ° C. and 1 kPa, and 32.0 g of Kyoward 500SH (manufactured by Kyowa Chemical Industry Co., Ltd.) was added to carry out adsorption treatment. The adsorption temperature, pressure and time are each 100
° C, 1 kPa, and 3 hours. After filtration, a kinematic viscosity (40 ° C.) of 52.79 mm ² / s, a pour point of −50 ° C. or less, an acid value of 0.01 mg KOH / g or less, and a hydroxyl value of 1.5
2835.4 g of the final target ester having a mgKOH / g and a hue (APHA) of 20 was obtained. The ester yield was 89.6% of theory.

Example 2 1300.0 g (9.55 m) of pentaerythritol was placed in a 5-liter four-necked flask equipped with a thermometer, a nitrogen inlet tube, a stirrer and a condenser tube.
ol), 1369.0 g of n-heptanoic acid (11.80 m
ol), 1246.2 g of caprylic acid (8.65 mo)
l), 2719.1 g of 2-ethylhexanoic acid (18.8)
8 mol), 13.4 g of tetra-n-butoxytitanium
(0.04 mol; 1 mo of carboxyl group of carboxylic acid)
0.001 mol per 1) and 4.2 g (0.04 mol, 0.001 mol per 1 mol of carboxyl group of carboxylic acid) of sodium hypophosphite, and water generated at 240 ° C. is distilled off under a nitrogen stream. The reaction was continued at normal pressure while the reaction was terminated when the hydroxyl value of the product became 3 mgKOH / g or less.

After completion of the reaction, unreacted fatty acids were distilled off under reduced pressure of 1 kPa. The obtained esterified crude product was 314.1 g, and the acid value was 2.1 mgKOH / g. A 10% aqueous potassium hydroxide solution corresponding to 1.5 equivalents of the acid value of the crude esterification product was added, and 90 ° C.
For 30 minutes. After leaving still for 30 minutes, the aqueous layer was removed to complete the deoxidizing step. 20 parts by weight of ion-exchanged water was added to 100 parts by weight of the crude esterified product, and the mixture was stirred at 90 ° C. for 30 minutes, and then allowed to stand for 30 minutes to discharge the aqueous layer. This washing step was repeated three times. Then
A decompression operation was performed at 100 ° C. under a pressure of 1 kPa for dehydration. Then, 0 g was added and the adsorption treatment was performed. The adsorption treatment temperature, pressure and time were 100 ° C., 1 kPa and 3 hours, respectively. After filtration, kinematic viscosity (40 ° C) 30.34m
m ² / s, pour point −50 ° C. or less, acid value 0.01 mg KO
H / g or less, hydroxyl value 1.7 mgKOH / g, hue (A
2811.7 g of the final product ester of PHA) 15 was obtained. The ester yield was 89.3% of theory.

Example 3 800.0 g (5.96 m) of trimethylolpropane was placed in a 5-liter four-necked flask equipped with a thermometer, a nitrogen inlet tube, a stirrer and a condenser.
ol), 391.3 g (2.28 mol) of capric acid,
2636.3 g of 3,5,5-trimethylhexanoic acid (1
6.69 mol), 19.1 g of monobutyltin mono (2-ethylhexanoate) (0.06 mol; 0.003 mol per mol of carboxyl group of carboxylic acid) and 5.4 g of sodium phosphite (0.03 mol, carboxylic acid) 0.001mo per 1mol of carboxyl group
l) was added thereto and reacted at normal pressure while distilling off water generated at 240 ° C. under a nitrogen stream, and the product had a hydroxyl value of 3 mg KOH.
/ G or less when the reaction was completed.

After completion of the reaction, unreacted
The fatty acids were distilled off. The esterification crude obtained at this time
The product weighs 3483.5 g and has an acid value of 4.1 mg KO.
H / g. The acid value of the esterified crude product is 1.
Add 10% aqueous potassium hydroxide solution equivalent to 5 equivalents.
And stirred at 90 ° C. for 30 minutes. Water layer for 30 minutes
The part was removed to complete the deoxidation step. Esterified crude product
Add 20 parts by weight of ion-exchanged water to 100 parts by weight.
After stirring for 30 minutes at 90 ° C.
The layer was drained. Repeat this washing step three times
Was. Then, the pressure was reduced at 100 ° C. and 1 kPa.
Go to dehydrate, and use Tomita AD300P (Tomita Pharmaceutical Co.
Manufactured) and Galleon Earth V2 (Mizusawa Chemical Industry Co., Ltd.)
(15.0 g each) was subjected to an adsorption treatment. Adsorption treatment temperature
The degree, pressure and time were respectively 100 ° C., 1 kPa,
And 3 hours. After filtration, kinematic viscosity (40 ° C) 6
9.29mm ²/ S, pour point -50 ° C or less, acid value 0.0
1 mgKOH / g or less, hydroxyl value 1.0 mgKOH / g
g, ester 31 of final product of hue (APHA) 15
55.1 g were obtained. The ester yield was 90.6 of theory.
%Met.

Example 4 100 mL of trimethylolpropane (7.4 g) was placed in a 5-liter four-necked flask equipped with a thermometer, a nitrogen inlet tube, a stirrer, and a cooling tube.
5 mol), 1426.8 g of capric acid (8.30 mo)
l), 1016.8 g of 2-methylhexanoic acid (7.82)
mol), 1092.2 g of 2-ethylhexanoic acid (7.
58 mol), tetra-n-butoxyzirconium 2
3.3 g (0.07 mol; 0.003 mol per mol of carboxylic acid carboxyl group) and 1.6 g of hypophosphorous acid (0.02 mol, 0.001 mol per mol of carboxyl group of carboxylic acid) were added, and a nitrogen gas flow was applied. At 240 ° C, the reaction was carried out at normal pressure while distilling off the generated water,
The reaction was terminated when the hydroxyl value became 3 mgKOH / g or less.

After completion of the reaction, unreacted fatty acids were distilled off under reduced pressure of 1 kPa. The crude esterified product obtained at this time was 3005.8 g, and the acid value was 8.1 mg KO.
H / g. The acid value of the esterified crude product is 1.
A 10% aqueous potassium hydroxide solution corresponding to 5 equivalents was added, and the mixture was stirred at 90 ° C. for 30 minutes. After standing for 30 minutes, the aqueous layer was removed to complete the deoxidizing step. 20 parts by weight of ion-exchanged water was added to 100 parts by weight of the crude esterified product, and the mixture was stirred at 90 ° C. for 30 minutes, and then allowed to stand for 30 minutes to discharge the aqueous layer. This washing step was repeated three times. Next, dehydration was performed by performing a reduced pressure operation at 100 ° C. and 1 kPa.

Then, using a Smith-type distillation apparatus, the amount of flowing oil was 4 mL at 180 ° C. and 0.1 to 3 torr.
/ Min. Thereby, the kinematic viscosity (40
℃) 23.19mm ² / s, pour point -37.5 ° C., an acid value 0.01mgKO Date / g or less, a hydroxyl value 0.5mgKO
H / g and 2804.9 g of the final target ester of hue (APHA) 20 were obtained. The yield of the ester was 92.4% of theory.

The alcohols, carboxylic acids, catalysts and reducing agents used in the production of the esters in Examples 1 to 4 are shown in Table 1 below. Table 4 summarizes the above physical properties of the obtained ester. Table 4 also shows the residual concentrations of the catalyst and the reducing agent component in the ester and the results of the heating test. Examples 5 to 20 and Comparative Examples 1 to be described later.
Table 20 is also shown in Tables 1-3 and 4-5.

Examples 1 to 4 and Example 5 to be described later
The ester prepared in No. 20 to No. 20 is used for various applications, and is particularly suitable as an ester-based lubricating base oil for grease.

(Comparative Examples 1 to 4) Using the materials shown in Table 1, the same operations as in Examples 1 to 4 were performed to produce esters.

(Examples 5 to 20) Using the materials shown in Tables 1 to 3, Examples 5 to 8 are Example 1, Examples 9 to 12 are Example 2, and Examples 13 to 16 are Example 3. And Example 1
For 7 to 20, the same operation as in Example 4 was performed to produce an ester.

(Comparative Examples 5 to 20) Using the materials shown in Tables 1 to 3, Comparative Examples 5 to 8 were Example 1, Comparative Examples 9 to 12 were Example 2, and Comparative Examples 13 to 16 were Example 3. Comparative Examples 17 to 2
0 performed the same operation as in Example 4 to produce an ester.

[0089]

[Table 1]

[0090]

[Table 2]

[0091]

[Table 3]

[0092]

[Table 4]

[0093]

[Table 5]

As is clear from the above results, Example 1
The esters prepared at ２０20 have a low weight loss rate in the heating test, a small degree of deterioration of the hue (Gardner), and do not generate sludge. On the other hand, Comparative Examples 1, 7, 1
In Nos. 1, 15, and 19, a large amount of sulfur remained in the produced ester because para-toluenesulfonic acid or sulfuric acid was used as the Bronsted acid catalyst. Although it is unknown whether this effect is present or not, sludge was generated or the hue was deteriorated in the heating test. Comparative Examples 2, 8, 12,
In the cases of 16 and 20, since the amount of the reducing agent is excessive,
When a heating test was performed on the obtained ester, sludge was generated or the hue was deteriorated. Comparative Examples 3, 5,
In Nos. 9, 13 and 17, the amount of the reducing agent was too small to fall within the range of the present invention. Therefore, when the obtained ester was subjected to a heating test, sludge was generated or the hue was deteriorated. In Comparative Examples 4, 6, 10, 14, and 18, since the sulfuric acid-based reducing agent was used instead of the phosphorus-based reducing agent, the color of the produced ester was poor, and sludge was generated in the heating test. However, deterioration of hue was inevitable.
As described above, all of the esters obtained in Comparative Examples 1 to 20 showed a large weight loss in the heating test, and showed a hue (Gard
ner) worsened and sludge was generated.

(Examples 21 to 40) The materials shown in Tables 6 to 8 were used, and Examples 21 to 25 were Examples 1 and 26 to 3.
0 was the same as in Example 2, Examples 31 to 35 were Example 3, and Examples 36 to 40 were the same as in Example 4, to produce an ester. Tables 9 to 10 summarize the physical properties of the obtained esters. Further, Tables 9 to 10 also show the residual concentrations of the catalyst and the reducing agent component in the ester and the results of the oxidation stability test (RBOT) of a rotating cylinder type. Similarly, Tables 9 to 1 also apply to Comparative Examples 21 to 40 described below.
0 is shown.

The esters prepared in these examples are:
Although used for various applications, it is particularly suitable as an ester-based lubricating base oil for engine oils.

(Comparative Examples 21 to 40) The materials shown in Tables 6 to 8 were used, and Comparative Examples 21 to 25 were Examples 1 and Comparative Examples 26 to 3.
0 was the same as that of Example 2, Comparative Examples 31 to 35 was Example 3, and Comparative Examples 36 to 40 were the same as Example 4, respectively, to produce an ester.

[0098]

[Table 6]

[0099]

[Table 7]

[0100]

[Table 8]

[0101]

[Table 9]

[0102]

[Table 10]

As is clear from the above results, Example 2
Each of the esters prepared in 1 to 40 has a larger RBOT lifetime value in the rotary cylinder type thermal oxidation stability test than the corresponding value in the comparative example. That is, it is shown that the thermal oxidation stability is excellent. In Comparative Examples 21, 25, 33, and 37, since the sulfuric acid-based reducing agent was used instead of the phosphorus-based reducing agent, the color of the produced ester itself was poor. Comparative Examples 22, 26, 29, 30,
In Nos. 34 and 38, since a phenol-based reducing agent is used instead of the phosphorus-based reducing agent, a phenol compound (aromatic compound) remains in the produced ester, and the color of the ester itself is poor. Poor thermal oxidation stability. In Comparative Examples 23, 27, 31, 35, and 39, the Brönsted acid catalyst was used instead of the Lewis acid catalyst, and the hue of the ester was probably because a large amount of sulfur remained in the produced ester. bad. Poor thermal oxidation stability. Comparative Example 2
In each of 4, 28, 32, 36, and 40, methanesulfonic acid is used as the Brönsted acid catalyst instead of the Lewis acid catalyst, so that the formed ester has poor color and poor oxidation stability. Thus, Comparative Example 21
Ester Nos. 40 to 40 all have poor hue, and the results of the rotary cylinder type thermal stability test are inferior to those of the present invention.

(Examples 41 to 60) Using the materials shown in Tables 11 to 13, Examples 41 to 46 and 48 to 50 performed the same operations as Example 1, and Examples 51 to 60 performed the same operations as Example 2. Performed to produce the ester. For Example 47,
The same reaction procedure as in Example 1 was performed to obtain a crude esterified product, and then 10 parts by weight of toluene was added to 100 parts by weight of the crude esterified product to perform a deoxidizing step.
The water washing step was performed three times in the same manner, dehydration and removal of toluene were performed at 150 ° C. and 1 kPa, and the same adsorption treatment was performed to obtain an ester.

Table 14 summarizes the physical properties of the obtained esters.
~ 15. Tables 14 and 15 also show the residual concentrations of the catalyst and the reducing agent component in the ester and the results of the shield tube test. Comparative Examples 41 to 6 to be described later
0 is similarly shown in Tables 11 to 13 and 14 to 15.

The esters prepared in these examples are:
Although it can be used for various applications, it is particularly suitable as an ester-based lubricating base oil for refrigerator oil.

(Comparative Examples 41 to 60) By using the materials shown in Tables 11 to 13, Comparative Examples 41 to 50 were operated in the same manner as in Example 1, and Comparative Examples 51 to 60 were manufactured in the same manner as in Example 2 to produce esters. .

[0108]

[Table 11]

[0109]

[Table 12]

[0110]

[Table 13]

[0111]

[Table 14]

[0112]

[Table 15]

As is clear from the above results, Example 4
Esters prepared from 1 to 60 are CFC R-407C
(Weight ratio is 1,1,1,2-tetrafluoroethane (H
FC134a): pentafluoroethane (HFC12
5): Difluoromethane (HFC32) = 52: 25:
23) In both fluorocarbons of difluoromethane (HFC32), an increase in the acid value and an increase in the hue in the shield tube test are suppressed to a low level.

In Comparative Examples 41, 42, 48, 51, 56, and 59, a sulfuric acid-based or nitric acid-based reducing agent was used in place of the phosphorus-based reducing agent, and a large amount of the component was contained in the produced ester. It remains. As a result, the color of the formed ester is poor, the acid value after the test is extremely high, and the thermal oxidation stability is lacking. In Comparative Examples 43, 50, and 52, since a large amount of the phosphorus-based reducing agent was used, a large amount of the phosphorus-based reducing agent remained in the produced ester. Therefore, the hue of the ester at the time of preparation is the same as that of the corresponding example, but the hue deteriorates in the shield tube test,
The acid value also increases and lacks thermo-oxidative stability. Comparative Examples 44 and 4
In 5, 53, 57, 58, and 60, since a reducing agent (aromatic-based reducing agent) other than the phosphorus-based reducing agent is used, an aromatic compound remains in the produced ester. Therefore, the hue of the ester deteriorates in the shield tube test, the acid value increases, and the thermal oxidation stability becomes extremely poor. In Comparative Examples 46, 47, 54, and 55, p-toluenesulfonic acid or methanesulfonic acid was used as the Bronsted acid catalyst instead of the Lewis acid catalyst, so that a large amount of sulfur remained in the produced ester, The hue of the ester deteriorates. Further, in the shield tube test, the hue deteriorates and the acid value also increases, so that the thermal oxidation stability is poor.

[0115]

According to the present invention, there is provided a method for producing a high-quality ester, particularly an ester having excellent thermal oxidation stability, and an ester obtained by the method. This ester is useful as an ester-based lubricating base oil for greases, engine oils, and refrigeration oils, and has a long life even under severe operating conditions such as high speed and high load of machines.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C07C 69/587 C07C 69/587 C10M 105/38 C10M 105/38 // C07B 61/00 300 C07B 61/00 300 C10N 30:06 C10N 30:06 30:08 30:08 30:10 30:10 40:25 40:25 40:30 40:30 50:10 50:10 F term (reference) 4H006 AA02 AA03 AB60 AC48 AD10 BA10 BA11 BA13 BA35 BA67 BC34 4H039 CA66 CD10 CD30 4H104 BB34A EB06 EB08 EB09 LA03 LA04 LA05 PA20 PA41 QA18

Claims (11)

[Claims] 1. A method for producing an ester, comprising reacting an alcohol with a carboxylic acid, wherein the ester is 0.000 to 1 mol of carboxyl groups of the carboxylic acid.
0.01-0.005 mole of Lewis acid catalyst and 0.0003
Reacting an alcohol with a carboxylic acid in the presence of ~ 0.005 mol of a phosphorus reducing agent; and separating the resulting ester. 2. The Lewis acid catalyst includes a titanium-based Lewis acid catalyst, a tin-based Lewis acid catalyst, an antimony-based Lewis acid catalyst,
The method according to claim 1, wherein the method is at least one selected from the group consisting of a germanium Lewis acid catalyst and a zirconium Lewis acid catalyst. 3. The method according to claim 1, wherein the alcohol is neopentyl polyol having 2 to 6 valences, and the carboxylic acid has 5 to 10 carbon atoms.
The method according to claim 1, wherein the compound is a monocarboxylic acid. 4. The method according to claim 1, wherein the alcohol is a di- to tetravalent neopentyl polyol, and the carboxylic acid has 5 to 12 carbon atoms.
The method according to claim 1, wherein the compound is a monocarboxylic acid. 5. In the presence of 0.000001 to 0.005 mol of a Lewis acid catalyst and 0.0003 to 0.005 mol of a phosphorus-based reducing agent per 1 mol of carboxyl groups of a carboxylic acid.
An ester obtained by a method comprising a step of reacting an alcohol with a carboxylic acid; and a step of separating the obtained ester, wherein the acid catalyst and the reducing agent are substantially removed. 6. In the presence of 0.000001 to 0.005 mole of a Lewis acid catalyst and 0.0003 to 0.005 mole of a phosphorus-based reducing agent per mole of carboxyl group of a carboxylic acid.
A method comprising a step of reacting a di- to hexavalent neopentyl polyol with a monocarboxylic acid having 5 to 10 carbon atoms, and a step of separating an obtained ester, wherein the acid catalyst and the reducing agent are substantially An ester-based lubricating base oil for grease, consisting of an ester that has been removed. 7. In the presence of 0.000001 to 0.005 mol of a Lewis acid catalyst and 0.0003 to 0.005 mol of a phosphorus-based reducing agent per 1 mol of a carboxyl group of a carboxylic acid,
A method comprising a step of reacting a di- to hexavalent neopentyl polyol with a monocarboxylic acid having 5 to 10 carbon atoms, and a step of separating an obtained ester, wherein the acid catalyst and the reducing agent are substantially Ester-based lubricating base oil for refrigerating machine oil, which is composed of an ester removed in water. 8. In the presence of 0.000001 to 0.005 mol of a Lewis acid catalyst and 0.0003 to 0.005 mol of a phosphorus-based reducing agent per 1 mol of carboxyl groups of a carboxylic acid,
It is obtained by a method including a step of reacting a di- or tetravalent neopentyl polyol with a monocarboxylic acid having 5 to 12 carbon atoms, and a step of separating an obtained ester, wherein the acid catalyst and the reducing agent are substantially An ester-based lubricating base oil for engine oil consisting of the removed ester. 9. A grease composition containing the grease ester-based lubricating base oil according to claim 6, a thickener, and an antioxidant, wherein the grease ester-based lubricating base oil comprises 10 to 10.
A grease composition contained in a proportion of 90% by weight. 10. The ester-based lubricating base oil for refrigerating machine oil of claim 7 and hydrofluorocarbon in a weight ratio of 10:
A composition for a working fluid of a refrigerator, containing the composition in a ratio of 90 to 90:10. 11. An engine oil composition comprising the ester lubricating base oil for engine oil according to claim 8, an antiwear agent, and an antioxidant, wherein the ester lubricating base oil for engine oil is 5-95. An engine oil composition, which is contained in a proportion by weight.