JPH05132684A - Base oil for lubricating oil and lubricating oil composition for apparatus using refrigerant hfc-134a - Google Patents

Abstract

PURPOSE:To obtain a base oil for a lubricating oil, containing a (di) pentaerythritol ester of caproic acid (containing a branched chain monovalent fatty acid), excellent in lubricity and thermal stability and useful for HFC-134a. CONSTITUTION:The objective for a lubricating oil contains an ester prepared by including (B) <=50wt.% dipentaerythritol ester of a 6C monovalent saturated fatty acid in (A) >=50wt.% pentaerythritol ester of a 6C monovalent fatty acid or without including the component (B). The fatty acid component is composed of (i) only caproic acid or (ii) >=50wt.% caproic acid and <=50wt.% 6C branched fatty acid. The base oil is useful for a small-sized apparatus having a sliding part due to compression and expansion of HFC-134a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fluorocarbons, particularly hydrofluorocarbons (hereinafter abbreviated as HFC) containing no chlorine among fluorocarbons, and particularly HFC-134a.
(1,1,1,2-Tetrafluoroethane) is used as a cold heat medium, and a reciprocating or rotary type of a device (hereinafter, abbreviated as R-134a cold heat machine) having a sliding portion for compression or expansion thereof is used. The present invention relates to a lubricating base oil and a lubricating oil composition suitable for a home-use refrigerator and a small air conditioner other than a car air conditioner (hereinafter, abbreviated as "small R-134a chiller"). ..

[0002]

2. Description of the Related Art Conventionally, in a refrigerator, an air conditioner, a refrigerator, etc., a chlorofluorocarbon (CFC) R-11 (trichloromonofluoromethane), R-12 (fluorocarbon) that contains fluorine and chlorine as a cooling medium is used. Dichlorodifluoromethane), Hydrochlorofluorocarbon (HC
FC) R-22 (monochlorodifluoromethane)
Fluorocarbons such as HFC-134a have been used, but in connection with the recent problem of ozone layer depletion, CFCs containing hydrogen and fluorine have attracted attention as a new type of cooling and heating medium that does not contain chlorine, and HFC-134a is particularly useful. It is in the spotlight as a high-refrigerant refrigerant.

On the other hand, with regard to refrigerating machine lubricating oils, many mineral oil-based and synthetic oil-based lubricating oils are known, but these have poor compatibility with the above-mentioned new HFC-134a.
It turns out that it cannot be used. Therefore, today HFC
Development of a lubricating oil suitable for a device using -134a as a cooling / heating medium has become an important issue.

US Pat. No. 4,755,316 describes H
As a lubricating oil for a refrigerator for FC-134a, polyoxyalkylene glycol (PA having hydroxyl groups at both ends)
Although G) is disclosed, it has a high water absorbing property regardless of the compatibility, and it is difficult to maintain the insulating property and the corrosion resistance of the lubricating oil for a long period of time. In particular, in a cooling / heating machine with a built-in motor in which the motor is in direct contact with the cooling / heating medium and the lubricating oil, where the lubricating oil itself is required to have insulating properties, the deterioration of the electrical system insulation due to the hygroscopicity of the lubricating oil is a fatal defect. Becomes

There is almost no such hygroscopicity, and HFC
Fatty acid esters of polyhydric alcohols are known as a group of compounds having excellent compatibility with -134a.

Japanese Unexamined Patent Publication (Kokai) No. 3-128992 discloses one or more polyhydric alcohols having 16 or less carbon atoms and 3 or more polyhydric alcohols.
A lubricating oil for hydrogen-containing chlorofluorocarbon refrigerant, which is mainly composed of an ester obtained from one or more kinds of linear or branched monovalent fatty acid having 2 to 18 carbon atoms and one or more kinds of polybasic acid having 4 to 14 carbon atoms. It is disclosed.

The composition of the lubricating oil disclosed in this publication is "one or more kinds of linear or branched monovalent fatty acids having 2 to 18 carbon atoms,
Alternatively, the fatty acid and one or more polybasic acids having 4 to 14 carbon atoms "
In addition, since a wide range of acid components for obtaining an ester are included, esters of these fatty acids of trihydric or higher polyhydric alcohols having 16 or less carbon atoms as an alcohol component are compatible with HFC-134a and the like. Not only the small R-134a cooler but also the R-134a cooler does not show an appropriate lubricating oil composition.

[0008] On the other hand, European Patent Publication 040657A1 discloses a straight chain or branched chain saturated fatty acid having ₂ to ₆ carbon atoms in one molecule as a lubricating oil for a refrigerator using a chlorine-free fluorocarbon such as HFC-134a. one or more and one or more of the neopentyl polyol is neopentyl polyol ester obtained by esterifying by conventional esterification conditions indicated, further, the saturated fatty acids in the C _{2 to 6} of Is essential up to 20 mol%, but regarding the remaining fatty acid component,
It is shown that any saturated fatty acid can be selected and used so that the average carbon number of the total fatty acids including _{2 to 6} saturated fatty acids is 6 or less.

However, as the base oil component,
It contains a neopentylpolyol ester of a saturated fatty acid having a C of ₅ or less which has poor lubricity and hydrolyzes to cause a metal corrosive acid component, and it cannot be said that the object of the present invention can be achieved.

[0010]

DISCLOSURE OF THE INVENTION The present invention uses a fluorocarbon-free fluorocarbon, particularly HFC-134a, as a cooling / heating medium and has a sliding portion for compression or expansion (R-134).
a refrigerator / cooler), a reciprocating or rotary type household refrigerator, or a small air conditioner (small R-134a refrigerator / heater) excluding car air conditioners, which is suitable for use as a lubricating base oil and a lubricating oil composition. To do.

[0011]

The inventors of the present invention have found that the HFC-
In view of the present situation where 134a is in the spotlight as a cooling / heating medium for various cooling / heating equipment, in order to develop an optimum lubricating base oil for a device using HFC-134a as the cooling / heating medium and a lubricating oil composition containing the base oil. I have accumulated a lot of research.

The required characteristics of the lubricating oil of the equipment using HFC-134a as the cooling / heating medium differ depending on the characteristics of each equipment. Also, regarding various required characteristics for one application field, it is necessary to find an optimum composition that simultaneously satisfies all of them. On the other hand, when considering the characteristics of the lubricating oil, it is of course necessary for the lubricating oil that is the final composition to satisfy the conditions, but the lubricating oil additive that is added to the lubricating base oil adjusts the initial characteristics. However, it is possible to reinforce, but it is not possible to change the characteristics of the base oil itself, so the exhaustion of the additive causes the effect of the addition to disappear, and then it cannot recover to the most important part of the equipment that comes into contact with the lubricating oil. In order to prevent damage to the product and cause a serious accident, it is desirable that the base oil of the lubricating oil itself satisfies all of the essential characteristics required for the lubricating oil. This is the condition for obtaining oil.

The lubricating base oil or the lubricating oil used in the cold heat machine includes a cold heat medium to be used, a kind and characteristics of the cold heat machine to be used,
Although the lubricating oil base oil and the lubricating oil composition for the "small R-134a refrigerator / cooler" which are the objects of the present invention have different required characteristics depending on the operating conditions and the like, they simultaneously have the following characteristics. Satisfaction is required.

1) HF a lubricating base oil or lubricating oil composition
A mixture obtained by adding 10 to 15% by weight to C-134a maintains a compatible state in a temperature range of at least -30 ° C to + 80 ° C.

2) The lubricating base oil or the lubricating oil composition has a kinematic viscosity at 40 ° C. of 12 to 43 cSt and a kinematic viscosity at 100 ° C. of 3 to 7 cSt. 3) The Falex seizure load according to the method of ASTM D-3233 is 1000 pounds or more.

4) Lubricating base oil is stable in continuous operation for a long period of time, and even if water or moisture is absorbed and hydrolyzed by an accident, its hydrolysis product is
Do not show strong corrosiveness to metal materials that come into contact with the cooling machine lubricating oil.

However, a small-sized R-134a lubricating base oil for a refrigerator / cooler and a lubricating oil composition which simultaneously satisfy these characteristics have not yet been known.

The present inventors, in the process of pursuing a lubricating base oil and a lubricating oil composition that simultaneously satisfy the above-mentioned required characteristics: a linear and / or branched monovalent saturated fatty acid having 6 carbon atoms. Pentaerythritol ester (1) alone, or a dipentaerythritol ester (2) of a linear and / or branched monovalent fatty acid having 6 carbon atoms and a weight equal to or less than that of the ester (1) and the ester. In the mixture with (1), the caproic acid alone or the ester or mixed ester containing 50% by weight or more of caproic acid in which the fatty acid component of the total ester is a C ₆ linear fatty acid is always the above-mentioned in any composition range. The present invention has been completed by finding the fact that all of the above four conditions are satisfied.

The lubricating base oil of the present invention contains, as an essential component, 50% by weight or more of pentaerythritol ester (1) of a linear and / or branched monovalent saturated fatty acid having 6 carbon atoms, and mixed. An ester component containing dipentaerythritol ester (2) of a linear and / or branched monovalent saturated fatty acid having 6 carbon atoms as an ester component in an amount of 50 wt% or less or not containing only caproic acid HFC-13, which is composed of 50% by weight or more of caproic acid and 50% by weight or less of a branched monovalent saturated fatty acid having 6 carbon atoms.
4a is a lubricant base oil for a small device having a sliding portion related to compression or expansion of 4a.

The lubricating oil composition of the present invention comprises the above lubricating base oil and one or more additives selected from the group consisting of at least an antioxidant, a deoxidizer and an extreme pressure agent. Is a lubricating oil composition for small equipment having a sliding portion related to compression or expansion of HFC-134a, wherein the antioxidant further contains a hindered phenol in the molecule. And the deoxidizing agent is a compound having an epoxy group, and the extreme pressure agent is a phosphoric acid ester of a linear monovalent saturated aliphatic alcohol or a phosphoric acid ester of a phenol optionally substituted with a lower alkyl group. A lubricating oil composition for a small device having a sliding portion relating to compression or expansion of the characteristic HFC-134a.

In the present invention, the C ₆ straight chain monovalent saturated fatty acid is caproic acid, and the C ₆ branched chain monovalent saturated fatty acid includes methylvaleric acid, ethylbutyric acid, neohexanoic acid and the like and mixtures thereof. included.

The fatty acid component in the present invention is mainly a C ₆ straight-chain monovalent saturated fatty acid, and a C ₆ branched chain fatty acid is in a position to supplement this. Therefore, the blending ratio of these fatty acid components is at least 50:50, preferably 65:35 or more, in terms of straight-chain to branched-chain (weight ratio). In addition, pentaerythritol is mainly used as the polyhydric alcohol component in the present invention, and dipentaerythritol is used in an appropriate amount for the purpose of compensating for it, that is, for adjusting the kinematic viscosity to be high. In the present invention, the range of small equipment (small R-134a chiller) having a sliding portion related to the compression or expansion of HFC-134a is 1/2 horsepower or less as the output of the power source motor, and usually 1 / Often 4 horsepower or less. In addition, the rotation speed of sliding parts such as car air conditioner is 500r. p. m to thousands of r. p. Large-sized ones that are used while fluctuating by m or more are not included in the object of using the lubricating base oil or the lubricating oil composition of the present invention. The lubricating base oil of the present invention is usually an ester mixture or a mixed ester of a mixed polyhydric alcohol and a mixed fatty acid, but as a special case, a pure pentaerythritol caproic acid ester is contained, and this ester is Inventive Lubricating oil has various characteristics required for base oil.

The additive for obtaining the lubricating oil composition of the present invention by adding it to the lubricating base oil of the present invention is intended to make up for the drawbacks of the lubricating base oil of the present invention or contribute to the maintenance of its performance. Such additives include, as typical examples, antioxidants, deoxidizers and extreme pressure agents.

The antioxidant prevents deterioration due to the oxidation of alcoholic hydroxyl groups, fatty chains, etc., the deoxidizer reacts with the free fatty acid to remove it, and the extreme pressure agent starts the use of rotating equipment. It is intended to prevent the sliding part from deteriorating at a certain time, and each has a compound having a hindered phenol group in the molecule, a compound having an epoxy group, and a phosphoric acid ester and / or a lower alkyl of a monovalent saturated aliphatic alcohol. Phosphoric acid esters of phenol optionally substituted with groups are used.

The preferred examples of these are as follows.

Antioxidant: 2,6-di-t-butyl-4
-Methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-hydroxyphenol, 2,2'-methylenebis (4-methyl-6-t-butylphenol) ), 2,2′-methylenebis (4-ethyl-6-t-butylphenol), 2,
2'-butylidene bis (4-methyl-6-t-butylphenol), 4,4'-butylidene-bis (3-methyl-6-t-butylphenol), 1,1,3-tris (2-methyl-4-) Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene and the like. Deoxidizing agent: phenyl glycidyl ether, butyl glycidyl ether, bisphenol A epichlorohydrin condensate, vinylcyclohexene dioxide, 2- (3,4
-Epoxycyclohexyl-5,5-spiro-3,4-
Epoxycyclohexane) -meta-dioxane, 3,4
-Epoxy cyclohexylmethyl-3,4-epoxy-
Cyclohexane carboxylate, polypropylene glycol diglycidyl ether, resorcin diglycidyl ether, polyethylene glycol diglycidyl ether, etc.

Extreme pressure agents: tricresyl phosphate, trisnonylphenyl phosphite, distearyl phosphate, tributyl phosphate, trilauryl phosphate, trilauryl phosphite, mono-di mixed lauryl phosphate, mono-di mixed Tridecyl phosphate, 2-ethylhexyl phosphate mono-2-ethylhexyl, di-2-ethylhexyl phosphate and the like.

[0028]

According to the research results of the present inventors, polyhydric alcohols include glycols such as ethylene glycol and propylene glycol, and trihydric alcohols such as glycerin, all of which have carbon atoms having a hydroxyl group. Β of
The ester is not stable to heat due to the presence of a hydrogen atom at the carbon atom at position. However, the polyhydric alcohol used in the present invention is pentaerythritol and dipentaerythril, both β-position of the carbon atom having a hydroxyl group is the central carbon atom of neopentyl skeleton,
Since all of the four bonds are carbon-carbon bonds and there are no hydrogen atoms that are easily moved in response to polarization or electron transfer, the ester is extremely stable for any of these polyhydric alcohols. In terms of long-term operation stability, which is the most important condition as a lubricant, it has the highest properties among ester compounds.

Regarding the fatty acid which is another component of the ester, unsaturated fatty acid is sensitive to oxidation, cleavage, polymerization and the like, and such ester cannot withstand stable operation for a long period of time. In the present invention, saturated fatty acids are used.

The ester of a straight chain saturated fatty acid is more compatible with HFC-134a as a short chain saturated fatty acid ester, but is inferior in lubricity. Further, the short-chain saturated fatty acid is C ₂ : acetic acid, C ₃ : propionic acid, C ₄ : butyric acid, C ₅ : valeric acid, and the acidity at the time of liberation, contact with a metal, particularly a lubricating oil such as copper or iron. Since there is a possibility that an adverse effect may occur due to reactivity with a metal material inside the small-sized R-134a cooler or corrosiveness to the metal material, in the present invention, a straight chain saturated fatty acid having C ₅ or less is used as an ester. Not used as an acidic component in.

The long-chain linear saturated fatty acid ester is HF
Since the compatibility with C-134a is poor, it is necessary to limit the chain length to 6 in order to obtain the excellent lubricating base oil of the invention. That is, although there is a desire to increase lubricity by extending the chain length more than C6, the compatibility with HFC-134a is remarkably decreased, so that a long-chain linear saturated fatty acid of C7 or more is used as the acid component of the ester. There is almost no merit to introduce as.

The same applies to the straight-chain saturated fatty acid ester as in the case of the straight-chain ester. That is, the short-chain saturated fatty acid is excellent in compatibility with HFC-134a, but is inferior in lubricity and avoids adverse effects due to metal corrosiveness when liberated. Branched saturated fatty acids of ₅ or less are not used.
Further, the ester of a long-chain branched saturated fatty acid is HFC-
The compatibility with 134a is slightly better than that of the straight chain, but the lubricity is conversely worse than that of the straight chain. Therefore, the advantage of introducing a C ₇ or more branched chain fatty acid as an acid component of the ester, for which the effect of chain length extension cannot be sufficiently expected in terms of lubricity, is hardly considered. In the present invention, such branched fatty acid is used. Is not used.

Based on the above experimental results, the alcohol component and the acid component of the ester suitable for the lubricating base oil of the present invention were screened. Surprisingly, pentaerythritol was selected as the essential alcohol component of the ester. Further, dipentaerythritol may be selected as an alcohol component to be added or mixed and used, and caproic acid, which is a C ₆ linear monovalent saturated fatty acid, may be added or mixed and used as an essential fatty acid component of an ester. select branched chain monovalent fatty acid C ₆ as the fatty acid component, the weight ratio of pentaerythritol and dipentaerythritol, the amount always such that the weight of the ester of pentaerythritol is or greater than equal to the weight of the ester of dipentaerythritol and the ratio, also the weight of the branched-chain monovalent saturated fatty acids caproic acid and C ₆ If always when caproic acid is adjusted to be above or equal to the weight of the branched-chain monovalent saturated fatty acid C ₆ are mixed by combining the pre ester or,
Or, regardless of whether the desired ester mixture is obtained by mixing the alcohol component and the fatty acid component in an appropriate amount so as to obtain the desired ester mixture, the esterification reaction is not impaired, regardless of whether the desired ester mixture is obtained. All of the above four conditions were satisfied. In other words, in the composition range of the present invention that satisfies the performance as a lubricating base oil for a small-sized R-134a in principle, when the sliding speed is high or the pressure on the sliding surface is high (for example, vanes). In order to increase the kinematic viscosity, the amount of polyhydric alcohol having a large number of hydroxyl groups, that is, the ester of dipentaerythritol, contained in one molecule is included in a rotary type having a roller and a roller or a refrigerator having a large refrigerating capacity or a high refrigerating efficiency. If the sliding speed is slow or the pressure on the sliding surface is low, the kinematic viscosity is decreased and the number of hydroxyl groups contained in one molecule is small in order to increase the energy efficiency of the refrigerator / cooler. It is possible to increase the amount of polyhydric alcohol, ie the ester of pentaerythritol, to meet these requirements. The ratio selection of fatty acid components is required for compatibility (corresponding to operating temperature range), kinematic viscosity (corresponding to rotational speed).
Further, it can be appropriately changed between 50 to 100% by weight of caproic acid and 50 to 0% by weight of C ₆ branched monovalent saturated fatty acid according to the requirement of lubricity (corresponding to the number of rotations, load, etc.).

The esterification rate of the ester used in the present invention is preferably 100%, but even if the reaction is carried out stoichiometrically with an excess of fatty acid, the reaction mixture is reacted so as to completely eliminate alcohol residues. Requires a long time to complete the reaction, and from an industrial point of view, a state in which 1 to 2 equivalent% of unreacted alcohol residue remains, that is, an esterification rate of 98 equivalent%
Since the above esters have substantially no adverse effect, there is no problem in accepting them as the ester of the present invention.

When the esterification rate decreases, HFC-134
Although the compatibility with a decreases, this tendency changes sharply with the esterification rate of 90 equivalent% as the boundary line, and deviates from the required characteristics of the lubricating base oil of the invention. The lower limit of the esterification rate is 90 equivalent%, and those having an average esterification rate of 90 equivalent% or less are not included in the present invention.

The blending of the ester in the present invention is HFC.
-134a is intended to enhance the lubrication performance and adjust the kinematic viscosity within the range where the compatibility with -134a is allowed. Therefore, it is recommended to use a linear fatty acid ester having a good lubrication performance in a large amount as much as possible. It The branched chain fatty acid ester should be used in a small amount within a range that does not impair other properties such as lubricating performance when it is necessary to enhance the compatibility with HFC-134a. When it is necessary to increase the kinematic viscosity, it can be efficiently adjusted by adding a linear fatty acid ester of dipentaerythritol. Therefore, the kinematic viscosity is increased by adding a C ₆ branched chain fatty acid ester of pentaerythritol. Things like that shouldn't be done on a large scale.

In the present invention, different kinds of esters are mixed,
Alternatively, the use of a mixed fatty acid ester of a polyhydric alcohol as a lubricating base oil effectively acts to prevent the crystallization, separation, etc. of the component ester when it is contained in the ester. Is preferable.

[0038]

EXAMPLES Next, synthetic examples of the lubricating oil base oil ester of the present invention, addition ester and lubricating oil base oil of the present invention, and formulation examples of the lubricating oil of the present invention are shown together with comparative synthesis examples and comparative formulation examples.

(Synthesis Example 1) Pentaerythritol cap
Lonic acid ester (esterification rate 99.1%; lubricating base oil)
Synthesis of ester A1) 108.9 g (0.8 mol) of pentaerythritol and 557.8 g (4,8 mol) of caproic acid were placed in a 2 liter round bottom flask and mixed, and 3 drops of sulfuric acid and activated carbon (Katayama) were used as a catalyst. Chemical, granular) 1 g was added to this. The reaction was carried out by heating to 180 ° C. and refluxing under a nitrogen stream. The water produced by the esterification reaction is a moisture quantitative receiver (Dean
Separation and removal with Stark column), theoretical amount (57.7m
The reaction was stopped by using l) water production as a guide for completion of the reaction.
The required reaction time was about 3 hours. The crude ester obtained by filtering off activated carbon from the viscous liquid remaining in the flask was purified by passing through a column packed with alumina (Katayama Chemical Co., for chromatograph) to obtain a purified ester 381 having a total acid value of 0.01 mgKOH / g or less. 0.99g was obtained. The esterification rate of this purified ester was 99.1% as calculated from the OH group value obtained by the method of JIS K0070. Yield of purified ester (yield to pentaerythritol in consideration of esterification rate) 90.9%.

Unless otherwise specified, the reagents used in this synthesis example and the following synthesis examples are special grade or first grade reagents manufactured by Katayama Chemical Co., Ltd.

(Synthesis Examples 2 and 3 and Comparative Synthesis Example 1) Penta
Erythritol caproic acid ester (esterification rate 9
8.4%, 94.6% and 87.5%; Lubricating base oil S
Tellur A2, A3 and comparative lubricant base oil ester E1)
136.2 g (1.0 mol) of formed pentaerythritol and A2: 488.0 g (4.2 mol), A3: 464.8 g (4.0 mol) and E1: 4 of caproic acid, respectively.
29.9 g (3.7 mol) were mixed, and 3 drops of sulfuric acid as a catalyst and 1 g of activated carbon were further added.
The synthetic reaction of the seed was performed. The theoretical amount of water produced corresponding to caproic acid added in each batch was 72.1
ml, 72.1 ml, and 66.7 ml, and the reaction was stopped based on the production of the theoretical amount of water for each batch.
The required reaction times were each about 3 hours.

The same purification as in Synthesis Example 1 was carried out, the esterification rate was measured, and the yield was obtained. The results are shown in Table 1.

[0043]

[Table 1]

(Note) As mentioned above, the lubricant base oil ester A of the present invention
All of 1, A2 and A3 are pentaerythritol caproic acid esters, which are collectively referred to as lubricating oil base oil esters because they serve as a base for blending a lubricating base oil. These can be used as the lubricating base oil of the present invention by themselves, and when used as the lubricating base oil, they are referred to as the lubricating base oil A1, the lubricating base oil A2, ...

Further, the ester shown in the B series in Synthesis Example 5 and below is an ester added for blending the lubricating base oil of the present invention, and is hereinafter referred to as "additional ester". However, in the present specification, when it is used as a comparative lubricating base oil, it is referred to as “comparative lubricating base oil B1 ...”. E1 having an esterification rate of less than 90% is HFC-134.
It cannot be used as the lubricating base oil or base oil ester of the present invention because of its drawbacks such as a marked decrease in compatibility with a. As the A series, there are A4, A5, etc., which will be described later, but these are the same as A1, A2, A3 and can be the lubricating base oil of the present invention alone, and A4 is
It is a lubricating base oil ester which is a base for blending with a B series additive ester.

(Synthesis Example 4) Pentaerythritol cap
2-Methyl valeric acid mixed with rhonate (weight ratio 1: 1)
Synthesis of (lubricating oil base oil ester A4) 136.2 g (1.0 mol) of pentaerythritol were added with caproic acid and 2-methylvaleric acid, respectively.
The mixture was placed in a 2 l round bottom flask for 8.6 g (3.0 mol) and the esterification reaction was carried out in the same manner as in Synthesis Example 1. The reaction was stopped using the theoretical amount of water produced (72.1 ml) as a guide for completion of the reaction. The required reaction time was about 3 hours. Ester 47 having an esterification rate of 98.1% was purified by the same purification method as in Synthesis Example 1.
0.2 g was obtained. The yield was 90.0%.

(Synthesis Example 5) Dipentaerythritol
2-Methylvaleric acid pronate mixed (weight ratio 1: 1)
Synthesis of ester (additional ester B1) to 127.2 g (0.5 mol) of dipentaerythritol, caproic acid and 2-methylvaleric acid were each added to 26 parts.
Esterification reaction was carried out in the same manner as in Synthesis Example 1 by placing in a 2 l round bottom flask for 1.5 g (2.25 mol). The reaction was stopped using the theoretical amount of water produced (54.1 ml) as a guide for completion of the reaction. The required reaction time was about 6 hours. Ester 3 with an esterification rate of 92.0% was obtained by the same purification as in Synthesis Example 1.
37.3 g was obtained. The yield was 84.7%.

(Synthesis Example 6) Pentaerythritol di
Pentaerythritol 2-caproic acid 2-methyl valeric acid mixture
(Weight ratio 1: 1) Ester (Lubricant base oil ester A5)
231.2g of synthetic pentaerythritol 50 g (0.37 mol) and caproic acid with respect dipentaerythritol 50 g (0.20 mol) and 2-methyl valeric acid, respectively
(1.99 mol) was added to a 2 liter round bottom flask and Synthesis Example 1
The esterification reaction was carried out in the same manner as in. Theoretical water production (4
The reaction was stopped using 9.8 ml) as a guide for completion of the reaction.
The required reaction time was about 5 hours. The same purification as in Synthesis Example 1 was carried out to obtain ester 298. with an esterification rate of 97.5%.
6 g was obtained. The yield was 84.4%. As a result of analysis by liquid chromatography, the blending ratio (weight ratio) of pentaerythritol ester and dipentaerythritol ester was 54:46. The ratio of caproic acid in the acid component in the total ester was 54.8% by weight.

(Comparative Synthesis Examples 2 to 9) Comparative lubricating base oil d
Stells (E2-E9) and comparative addition ester (E1
3) Synthesis According to Synthesis Example 1, an excess amount of fatty acid was reacted with a polyhydric alcohol, the reaction was terminated with the theoretical amount of water generation as a guide, and comparative base oil esters E2 to E9 were obtained after alumina purification. .. Table 2 shows the types of polyhydric alcohols, the types of monohydric fatty acids, and the mixing ratios (weight ratio).

[0050]

[Table 2]

(Formulation Example 1) Pentaerythritol cap
Lonic acid ester (lubricating oil base oil ester A1) and dipenta
Erythritol caproic acid 2-methyl valeric acid mixed (added
50/50 (weight ratio) with the ester B1) (lubricant base)
The blended lubricating base oil ester A1 of the oil C1) and the addition ester B1 were precisely weighed in a 100 ml beaker for 25.0 g and stirred for 30 minutes with a magnetic stirrer. The compounded oil (C3) thus obtained was measured by using an Ubbelohde viscometer to obtain J
It was used for measuring the kinematic viscosity at 40 ° C. and 100 ° C. by the method of ISK2283.

(Formulation Examples 2 and 3 and Comparative Formulation Examples E10 and 11) Lubricating Base Oil Ester A1 and (Additional Ester B1)
Various formulations (C2, C3, E10 and E11) of lubricating oil base oil ester A1 and addition ester B1 were weighed in predetermined amounts in a 1 liter round bottom flask equipped with a stirrer and kept at about 60 ° C. for 30 minutes. 500 with heating and stirring
g of compounded lubricating base oils C2 and C3 and comparative compounded lubricating base oils E10 and E11 were obtained.

These formulations are shown in Table 3 together with the formulation example 1.

[0054]

[Table 3]

[0055] (Formulation Examples 4 and 5 and Comparative Formulation Example E12) Jun
Each of lubricating oil base oil ester A4 and (additional ester B1)
Seed formulation (C4, C5, E12) Lubricating base oil ester A4 and addition ester B1 were weighed in predetermined amounts in a 1 liter round bottom flask equipped with a stirrer, and heated and stirred as in Formulation Example 2. As a result, a blended lubricating oil base oil C4 and C5 and a comparative blended lubricating oil E12 were obtained.
These formulations are shown in Table 4.

[0056]

[Table 4]

(Compounding Examples 6 to 17) Lubricating Oil Base Oil Ester A
Composition of 1 and various additives (D1 to D12) Blending Table 5 shows blending examples of the lubricating oil composition of the present invention.

[0058]

[Table 5]

(Note) The above values are the weight (g) of each additive added to the lubricating base oil ester A1 (100 g).
Represents. The additives are the compounds shown below.

Antioxidant 1 1,1,3-Tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (Topanol CA manufactured by ICI, UK) Antioxidant 2 2,6-di-t -Butyl-4-methylphenol Deoxidizer 1 Polypropylene glycol diglycidyl ether (DER736, a product of Dow Chemical Company, USA) Deoxidizer 2 3,4-epoxycyclohexylmethyl-
3,4-Epoxy-cyclohexane carboxylate (ERL-4221 manufactured by Union Carbide Co., USA) Extreme pressure agent 1 Mono / di mixed lauryl phosphate (Sakai Chemical Industry product Phorex A12) Extreme pressure agent 2 Trilauryl phosphate (Dahachi) Chemical Industry Products) Extreme Pressure Agent 3 Tricresyl Phosphate (Product of Akzo Japan) (Test Example 1) Pentaerythritol ester of caproic acid (A1), valeric acid having 5 carbon atoms and valeric acid having 5 carbon atoms An accelerated test was conducted on the pentaerythritol ester of mixed fatty acid (E3) and the ester of dipentaerythritol of mixed fatty acid (E4) with 2-methylbutyric acid, which is a branched chain fatty acid, on hydrolysis stability and iron solubility of hydrolyzed oil. Carried out.

The test oil had a total acid value of 0.01 mg KO beforehand.
The water content was adjusted to 2000 ppm or less at H / g or less.
600 g of this test oil was enclosed together with 80 g of HFC-134a in an iron autoclave having a capacity of 1 liter, and the mixture was heated to 175 ° C. for 3 hours.
I kept it for 0 days. After cooling to room temperature, take out all the oil,
The total acid value of each sample oil was measured, and the concentration of iron dissolved in the oil was quantified by fluorescent X-ray spectroscopy. The results are shown in Table 6.

[0062]

[Table 6]

From the above results, it was found that E3 and E4 C5 fatty acid esters are easily hydrolyzed and a large amount of iron is eluted by the acceleration test.

(Test Example 2) In the examples, the lubricating base oils (A and C) and the lubricating oil composition (D) of the present invention shown in each synthesis example and formulation example of the present invention shown as a comparative example are shown. The kinematic viscosity at 40 ° C and 100 ° C, the compatibility with HFC-134a, the thermal stability and the lubricity were tested in comparison with the comparative lubricating base oil (E) and the additive ester (B) out of the range. , Each test result was obtained. The test method is as shown below.

Kinematic Viscosity Measurement Test Using an Ubbelohde viscometer, the kinematic viscosity at 40 ° C. and 100 ° C. of each sample oil is measured by the method of JISK2283.

Compatibility test Taking 0.9 g of the test oil, refrigerant HFC-134a 5.1 g
A glass autoclave was charged together with it, thoroughly mixed with a shaker, cooled in a freezer, and observed in a range of up to -50 ° C to determine the temperature at which cloudiness occurs. On the high temperature side, the temperature is elevated to 80 ° C., the same observation is performed, and the temperature for phase separation is determined.

Thermal stability test 50 g of the test oil and 25 g of the refrigerant HFC-134a were enclosed in a stainless steel autoclave together with 3.7 g of metal pieces (copper, iron and aluminum) as a catalyst, and after heating at 175 ° C. for 14 days, After cooling, the sample oil is taken out from the autoclave. For the lubricating base oil, the hue according to JISK2580, and for the lubricating oil composition, JISK2580.
Total acid number is measured according to 2501.

Falex seizure load test Using a Falex tester, the seizure load (lbs) of the sample oil is determined by the method of ASTM D-3233.

The lubricating base oils (A1 to A5) of the present invention and the compounded base oil lubricants (C1 to C5) of the present invention are compared for comparison. The addition ester (B1) of the present invention and the comparative lubricant base oil (E1) Table 7 shows the measured values of kinematic viscosity compatibility, thermal stability, and Falex seizure load, in contrast to E13) to E13).

[0070]

[Table 7]

As a result of the kinematic viscosity measurement, all the base oils of the present invention were in the range of the required kinematic viscosity of the present invention (kinematic viscosity at 40 ° C .: 12 to 43 cSt, kinematic viscosity at 100 ° C .: 3 to.
7 cSt), and it was confirmed that this condition was satisfied.

Regarding the compatibility with HFC-134a, pentaerythritol ester (E6) of enanthic acid, which is a linear monovalent saturated fatty acid having 7 carbon atoms, requires a low temperature two-layer separation temperature of 5 ° C. It was confirmed that the temperature did not reach far below -30 ° C. On the other hand, in the case of a pentaerythritol ester of a branched chain monovalent fatty acid, in the case of a mixed fatty acid ester (E8) having 7 and 8 carbon atoms, the two-layer separation temperature on the low temperature side is similarly insufficient at −26 ° C. It was confirmed that the pentaerythritol ester of a branched chain fatty acid having 9 carbon atoms (E9) had a remarkably high separation temperature of + 25 ° C. or higher and could not be used. Similarly, the dipentaerythritol ester of enanthate (E13), which is a linear fatty acid having 7 carbon atoms, also has a low-temperature two-layer separation temperature of +2.
It cannot be used because it causes layer separation at room temperature above 5 ° C.

Regarding the Falex baking load, the C6 straight-chain pentaerythritol ester (A1) was 1200
While it shows a high value of lb, it has an increased proportion of branched chain fatty acids, such as pentaerythritol ester (for example, C
No. 4, C5), the lubricity was found to be reduced, but it was confirmed that the lubricating base oil of the present invention always had a seizure load of 1000 lb or more. Also, an ester of 100% branched chain fatty acid (C8, C7 + 8, C9: E7,
It was found that E8 and E9) cannot be used due to a significant decrease in lubricity. The thermal stability test results confirmed that all the esters had an ASTM color within L0.5, and that the fatty acid ester of a polyhydric alcohol having a neopentyl skeleton was stable to heat.

Next, the total acid value measured in the thermal stability test of the lubricating oil compositions D1 to D7 of the present invention are shown in Table 8 in comparison with the lubricating base oil A1 of the present invention, and the lubricating oils of the present invention were also used. The measured values of the seizure load of the oil compositions D8 to D12 are shown in Table 9 in comparison with the base oil A1.

[0075]

[Table 8]

[0076]

[Table 9]

In the lubricating oil composition of the present invention, a deoxidizer,
Alternatively, it was found that the total acid number in the thermal stability test of D2, D3, D5 and D7 added with the deoxidizer and the antioxidant was significantly improved.

Further, an extreme pressure agent, particularly D9 containing the extreme pressure agent 1 was added.
The improvement of D11 with the addition of extreme pressure agent 2 was remarkable.

(Test Example 3) In order to obtain a lubricating base oil having a desired kinematic viscosity, the mixing ratio of A1 and B1 was appropriately mixed with the lubricating base oil ester A1 of the present invention and the additive ester B1. The relationship between (wt% of A1) and the kinematic viscosity (cSt) at 40 ° C and 100 ° C was determined. The results are as shown in Table 10, and the curves obtained by plotting these are as shown in FIGS. 1 and 2. According to these curves, the lubricating base oil of the present invention having a desired kinematic viscosity (50% by weight or more of A1)
Can be obtained.

[0080]

[Table 10]

(Test Example 4) Compressor actual machine test Using a domestically produced HFC-134a compliant closed reciprocating compressor (130 W), sample oils (A1, C2, E2) containing no extreme pressure additive were added to 250 ml of HF.
With C-134a, the discharge pressure was set to 25 kg / cm ² (gauge pressure) and the suction pressure was set to 1 kg / cm ² (gauge pressure), and continuous operation was performed in a room controlled at 30 ° C. for 1000 hours.

After the operation was completed, the compressor was disassembled and the piston tip was roundness meter (Tokyo Seimitsu Roncom 3A type).
The roundness was measured by the method of JIS B0621 using, and the states of wear were compared. The results are shown in Table 11.

[0083]

[Table 11]

In the tests using the lubricating base oils A1 and C2 of the present invention, the lubricity was excellent and good roundness was maintained even after long-term operation. On the other hand, the lubricating base oil E7, which is out of the range of the present invention, was inferior in lubricity and showed a large slippage on the piston head after the operation test.

[0085]

The lubricating base oil of the present invention is HFC-134.
Excellent compatibility with a, satisfying the viscosity range required for small equipment with sliding parts related to compression or expansion of HFC-134a, having sufficient lubrication performance, and operating for a long time even if water is mixed. Hydrolysis and acid formation hardly occur therein, and even if hydrolysis occurs, it shows almost no corrosiveness to the metal material inside the device. In addition, the lubricating oil composition of the present invention has remarkably improved lubricity at the start of operation and, depending on the composition, can significantly suppress an increase in total acid value during operation.

[Brief description of drawings]

FIG. 1 Lubricating base oil ester A1 and additive ester B1
It is a graph which shows the relationship between the compounding ratio of and and the kinematic viscosity at 40 degreeC.

FIG. 2 Lubricant base oil ester A1 and additive ester B1
It is a graph which shows the relationship between the compounding ratio of and and the kinematic viscosity at 100 degreeC.

[Procedure amendment]

[Submission date] October 9, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

However, as the base oil component,
And contains lubricity to poor and neopentyl polyol ester of C ₅ or less saturated fatty acids <br/> Yu away the metal corrosiveness of the acid component by hydrolysis, as capable of achieving the object of the present invention I can not say.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

(Synthesis Example 4) Pentaerythritol cap
2-Ethyl butyric acid mixed acid (weight ratio 1 : 1) ester
(Lubricant base oil ester A4) 136.2 g (1.0 mol) of pentaerythritol were mixed with 348. of caproic acid and 2-ethylbutyric acid , respectively.
The mixture was placed in a round-bottomed flask containing 6 g (3.0 mol) of 21 and subjected to the esterification reaction in the same manner as in Synthesis Example 1. Theoretical water production (7
The reaction was stopped using 2.1 ml) as a guide for completion of the reaction.
The required reaction time was about 3 hours. The same purification as in Synthesis Example 1 was carried out to prepare ester 470.
2 g was obtained. The yield was 90.0%.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

(Synthesis Example 5) Dipentaerythritol
Ester of 2-ethylbutyric acid mixed with protic acid (weight ratio 1: 1)
Synthesis of (Ester for Addition B1) 127.2 g (0.5 mol) of dipentaerythritol were added to caproic acid and 2-ethylbutyric acid , respectively.
The mixture was placed in a round bottom flask with 1.5 g (2.25 mol) of 21 and the esterification reaction was carried out in the same manner as in Synthesis Example 1. The reaction was stopped using the theoretical amount of water produced (54.1 ml) as a guide for completion of the reaction. The required reaction time was about 6 hours. Ester 3 with an esterification rate of 92.0% was obtained by the same purification as in Synthesis Example 1.
37.3 g was obtained. The yield was 84.7%.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

(Synthesis Example 6) Pentaerythritol di
Pentaerythritol caproic acid 2-ethylbutyric acid mixture
(Weight ratio 1: 1) Ester (Lubricant base oil ester A5)
Of 50 g (0.37 mol) of pentaerythritol and 50 g (0.20 mol) of dipentaerythritol, 231.2 g of caproic acid and 2-ethylbutyric acid , respectively.
(1.99 mol) was added to a round-bottomed flask with a diameter of 21 to prepare Synthesis Example 1.
The esterification reaction was carried out in the same manner as in. Theoretical water production (4
The reaction was stopped using 9.8 ml) as a guide for completion of the reaction.
The required reaction time was about 5 hours. The same purification as in Synthesis Example 1 was carried out to obtain ester 298. with an esterification rate of 97.5%.
6 g was obtained. The yield was 84.4%. As a result of analysis by liquid chromatography, the blending ratio (weight ratio) of the ester of pentaerythritol and dipentaerythritol ester was 54:46. The ratio of caproic acid in the acid component in the total ester was 54.8% by weight.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction content]

(Formulation Example 1) Pentaerythritol cap
Lonic acid ester (lubricating oil base oil ester A1) and dipenta
Erythritol caproic acid 2-ethylbutyric acid mixed ester
50/50 (weight ratio) with (additional ester B1)
Lubricating base oil C1) blended lubricating base oil ester A1 and addition ester B1 were precisely weighed and collected in a 100 ml beaker for 25.0 g each, and stirred with a magnetic stirrer for 30 minutes. The compounded oil (C3) thus obtained was measured by using an Ubbelohde viscometer to obtain J
It was used for measuring the kinematic viscosity at 40 ° C. and 100 ° C. by the method of ISK2283.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0066

[Correction method] Change

[Correction content]

Compatibility test Taking 0.9 g of the test oil, refrigerant HFC-134a 5.1 g
Together sealed in a glass autoclave, after combined sufficiently vibration 盪 mixed <br/>, cooled in a freezer, was observed in the range up to -50 ° C., determine the temperature resulting a cloudy. On the high temperature side, the temperature is elevated to 80 ° C., the same observation is performed, and the temperature for phase separation is determined.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction content]

The lubricating base oils (A1 to A5) of the present invention and the compounded base oil lubricants (C1 to C5) of the present invention are compared for comparison. The addition ester (B1) of the present invention and the comparative lubricant base oil (E1) ～E13) compared to the kinematic viscosity of compatibility, a measure of thermal stability and Falex seizure load are shown in Table 7.

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Claims (3)

[Claims] 1. A straight chain having 6 carbon atoms and / or an essential component
Or dipentaerythritol ester of a straight chain and / or branched chain monovalent saturated fatty acid having 6 carbon atoms as an ester component which may contain 50% by weight or more of pentaerythritol ester (1) of branched chain monovalent saturated fatty acid and may be mixed. An ester containing (2) 50% by weight or less or not containing the fatty acid component only of caproic acid, or 50% by weight or more of caproic acid and 50% by weight of a branched monovalent saturated fatty acid having 6 carbon atoms. A lubricating base oil for a small device having a sliding portion related to compression or expansion of HFC-134a, characterized by comprising: 2. The lubricating base oil according to the above paragraph, wherein at least one additive selected from the group consisting of antioxidants, deoxidizers and extreme pressure agents is added. A lubricating oil composition for a small device having a sliding portion related to compression or expansion of HFC-134a. 3. The lubricating oil composition according to claim 1, wherein the antioxidant has a compound having a hindered phenol in the molecule,
Compression of HFC-134a, wherein the deoxidizing agent is a compound having an epoxy group, and the extreme pressure agent is a phosphoric acid ester of a monovalent saturated aliphatic alcohol or a phosphoric acid ester of phenol optionally substituted with a lower alkyl group. Alternatively, a lubricating oil composition for a small device having a sliding portion related to expansion.