JPH1036865A - Lubricant composition used for compressing ammonia refrigerant and method for lubricating compressor for ammonia refrigerant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricant compsn. having a specified viscosity and an excellent compatibility with an ammonia refrigerant by using, as the base oil, a cyclic compd. represented by a specific formula having dioxolane or dioxane rings. SOLUTION: Sorbitol is reacted with a carbonyl compd. (e.g. methyl ethyl ketone) in the presence of an acid catalyst (e.g. p-toluenesulfonic acid) to give a cyclic compd. represented by the formula (wherein R<11> to R<16> are each 1-8C alkyl) having dioxolane or dioxane rings and a hydroxyl value of about 2mgKOH/g or lower. The cyclic compd. as the base oil is compound with about 0.1-1.0wt.% amine antioxidant (e.g. p,p'-dioctyldiphenylamine) to give a lubricant compsn. having a viscosity at 40 deg.C of 8-220mm<2> /s. About 0.1-2wt.% this compsn. is dissolved in an ammonia refrigerant to be used desirably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating oil or a lubricating method used for a refrigerating apparatus, a refrigeration apparatus, an air conditioner, a heat pump apparatus and the like (hereinafter also referred to as a refrigerating apparatus) using an ammonia refrigerant.

[0002]

2. Description of the Related Art Chlorofluorocarbon refrigerants such as dichlorodifluoromethane have been widely used as refrigerants for refrigeration systems. In recent years, the use of chlorofluorocarbon refrigerants has been regulated due to environmental problems such as ozone layer destruction, and hydrofluorocarbon refrigerants that do not destroy the ozone layer have been developed to protect the ozone layer. However, this refrigerant is poorly compatible with conventional refrigerating machine oil using mineral oil base oil, and when used with such a refrigerating machine oil, causes two-layer separation at low temperatures, causing oil to adhere to condensers and evaporators. There is a problem that the heat transfer efficiency is reduced. For this reason, the development of refrigerating machine oils with good compatibility with hydrofluorocarbon refrigerants has been promoted,
Polyether compounds, cyclic ketals or cyclic acetal compounds have been proposed (WO 96/0683).
9). However, fluorinated refrigerants are expensive anyway. Therefore, in recent years, ammonia refrigerants have attracted attention as these alternative refrigerants. Ammonia refrigerant has excellent characteristics as a refrigerant, and does not dissolve in refrigerating machine oil using a mineral oil base oil, so that the refrigerant is stable for a long period of time. However, since the refrigerant and the refrigerating machine oil are not compatible with each other, a configuration different from that of the refrigerating apparatus using fluorocarbon is adopted.

That is, in a refrigerating machine, a refrigerating machine oil is used in a compressor for lubrication, and a part of the refrigerating machine oil is mixed with a refrigerant. Has been introduced. This will be specifically described with reference to the refrigeration system of FIG. The compressor 1 compresses the ammonia refrigerant. At this time, refrigerating machine oil supplied from the oil reservoir 14 is used, and a part thereof is mixed in the ammonia refrigerant. Most of the oil is removed from the refrigerant by the discharge-side oil separator 12. The ammonia refrigerant from which the refrigerating machine oil has been largely removed is cooled and liquefied in the condenser 2. Oil is further removed from the refrigerant liquefied in the receiver 13 in order to remove the remaining oil. Then, the refrigerant from which the oil has been sufficiently removed is guided from the liquid receiver 13 to the evaporator 4. In the evaporator 4, the refrigerant is decompressed and vaporized by the expansion valve 3, and at this time, heat exchange is performed via the evaporator 4. The vaporized refrigerant is circulated to the compressor 1 via the suction-side oil separator 15.

[0004] Therefore, a refrigeration system using an ammonia refrigerant is more complicated than a case using a fluorocarbon. Further, when the refrigerating machine oil is mixed into the evaporator, the refrigerating machine oil adheres to the wall surface of the evaporator, and the cooling efficiency is reduced. For this reason, the application of a refrigeration system using an ammonia refrigerant has been limited.

[0005] In recent years, refrigerating machine oil that dissolves in an ammonia refrigerant has been developed in order to solve such a problem and provide a configuration similar to a refrigerating apparatus using fluorocarbon. As such a refrigerating machine oil, a polyether compound (WO
94/12594) are known.

[0006]

An ammonia refrigerant refrigeration system using a refrigeration oil composed of mineral oil requires a complicated apparatus for sufficiently separating the refrigeration oil, and requires maintenance such as cleaning of the system. It is.

On the other hand, in order to simplify the apparatus, a polyether compound compatible with the ammonia refrigerant as described above can be used as the refrigerating machine oil. However, such a polyether compound has high water absorption and low electrical insulation.

An object of the present invention is a method of lubricating a compressor for a refrigeration system using an ammonia refrigerant, which simplifies the configuration of the refrigeration system, is easy to maintain, and can be used for a long time. Another object of the present invention is to provide a method of lubricating a compressor which does not cause problems such as corrosion, and a lubricating oil used for the method.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a lubricating oil composition using a cyclic compound having a plurality of dioxolane rings or dioxane rings as a base oil has been developed. , Compatible with ammonia refrigerant,
In addition, it was found that the reactivity with the ammonia refrigerant was low.

That is, the lubricating oil composition used for compressing the ammonia refrigerant according to the present invention contains a cyclic compound having a plurality of dioxolane rings or dioxane rings as a base oil and has a viscosity at 40 ° C. of 8 to 220 mm ² / s. It is. It is particularly preferable that the cyclic compound contains a compound represented by the following general formula (1) as a main component, and it is particularly preferable that these lubricating oil compositions contain an amine antioxidant. Here, the compound represented by the following general formula (1) includes its stereoisomer.

[0011]

Embedded image

(Where R ¹¹ , R ¹² , R ¹³ , R ¹⁴ ,
R ¹⁵ and R ¹⁶ are the same or different hydrogen atoms or alkyl groups having 1 to 8 carbon atoms. Where R ¹¹ and R ¹² , R
¹³ and R ¹⁴ , and R ¹⁵ and R ¹⁶ are not simultaneously hydrogen atoms. The lubricating method for an ammonia refrigerant compressor using the lubricating oil composition is as follows: after compressing and coagulating the ammonia refrigerant, introducing the ammonia refrigerant in which the lubricating oil composition is dissolved into an evaporator;
It circulates. Since the lubricating oil composition is dissolved in the ammonia refrigerant, even if the lubricating oil composition is circulated in a dissolved state, the lubricating oil composition does not remain in the refrigeration system, and there is no need to clean the system. A refrigeration apparatus that is simple and easy to operate can be configured.

The viscosity of the lubricating oil of the present invention containing a cyclic compound having a plurality of dioxolane rings or dioxane rings as a base oil at 40 ° C. may be 15 to 150 mm ² / s, particularly 32 to 100 mm ² / s. It is preferable from the viewpoint of efficiency and lubricity of the compressor. In order to obtain a predetermined viscosity, the lubricating oil composition of the present invention usually has a two or three ring structure. A carbon atom in a ring structure is directly bonded to a carbon atom in another ring structure. Is preferred because they are chemically stable and have high electric insulation. In particular, a structure having only a 1,3 dioxolane ring is preferable because of low reactivity with ammonia.

The hydroxyl value is 10 mgKOH / g or less, particularly 5 mgKOH / g or less, and more preferably 2 mgKOH / g.
The following is low reactivity with the ammonia refrigerant,
It is preferable because the system is hardly corroded.

When the compressor includes a motor or the like that requires electrical insulation, the volume resistivity of the lubricating oil composition is 10 ¹¹ Ω.
Cm or more, preferably 10 ¹² Ω · cm or more.

As the cyclic compound constituting the lubricating oil composition of the present invention, a cyclic compound having a plurality of dioxolane rings or dioxane rings is used, and the following examples can be given.

[0017]

Embedded image

(Where R ¹¹ , R ¹² , R ¹³ , R ¹⁴ ,
R ¹⁵ and R ¹⁶ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Where R ¹¹ and R ¹² ,
R ¹³ and R ^14, R ¹⁵ and R ¹⁶ are not simultaneously hydrogen atoms. )

[0019]

Embedded image

(Where R ²¹ , R ²² , R ²³ , R ²⁴ ,
R ²⁵ and R ²⁶ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Where R ²¹ and R ²² ,
R ²³ and R ^24, R ²⁵ and R ²⁶ are not simultaneously hydrogen atoms. )

[0021]

Embedded image

(Where R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, provided that R ¹¹ , R ¹² , R ¹³ and R ¹⁴ is not simultaneously a hydrogen atom.)

[0023]

Embedded image

(Wherein R ²¹ , R ²² , R ²³ , and R ²⁴ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, provided that R ²¹ , R ²² , R ²³ and R ²⁴ is not simultaneously a hydrogen atom.)

[0025]

Embedded image

(Wherein R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, provided that R ¹¹ , R ¹² , R ¹³ and R ¹⁴ is not simultaneously a hydrogen atom.)

[0027]

Embedded image

(Where R ²¹ , R ²² , R ²³ , and R ²⁴ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, provided that R ²¹ , R ²² , R ²³ and R ²⁴ is not a hydrogen atom at the same time.) The sum of the carbon numbers of the two alkyl groups bonded to the same carbon element of R ^{11 to} R ²⁶ in the above formula is 2 to 5, especially 3 to 4
Is preferable from the viewpoint of solubility in an ammonia refrigerant. Further, the alkyl group may be linear or branched.

Particularly preferred as the lubricating oil composition of the present invention is a cyclic compound represented by the above general formula (1). Further, the lubricating oil composition of the present invention may be composed of a single cyclic compound, or may be composed of a mixture of cyclic compounds. Further, other lubricating oil compositions may be mixed and used within the scope of the present invention. Compatible with ammonia refrigerant at room temperature (20 ° C) or less,
Mixing other lubricating base oils within a range where the volume resistivity is high (for example, 10 ¹³ Ω · cm or more), and using the cyclic compound represented by the general formula (1) as a main component. Is preferred.

The cyclic compound constituting the lubricating oil composition of the present invention is known per se. The production method is also disclosed, for example, in the above-mentioned WO 96/06839.

For example, the general formulas (1) and (2)
Can be obtained by reacting sorbitol with a carbonyl compound or a reactive derivative thereof in the presence of an acid catalyst such as paratoluenesulfonic acid.

The compounds represented by the general formulas (3) and (4) are obtained by reacting erythritol with a carbonyl compound or a reactive derivative thereof in the presence of an acid catalyst such as paratoluenesulfonic acid. be able to.

With respect to the compounds represented by the general formulas (5) and (6), diglycerin or ditrimethylolpropane is reacted with a carbonyl compound or a reactive derivative thereof in the presence of an acid catalyst such as paratoluenesulfonic acid. Can be obtained by:

In the lubricating oil composition of the present invention, additives such as an antioxidant, an antiwear agent, a metal deactivator and an antifoaming agent can be used, if necessary. As the antioxidant, an amine-based antioxidant is preferable, and an aromatic amine compound containing no oxygen atom is particularly preferably used because of its low reactivity with ammonia. Specifically, alkylated diphenylamines such as p, p′-dioctyldiphenylamine and 3,3′-dioctyldiphenylamine are particularly preferably used, and phenyl-1-naphthylamine, phenyl-2-naphthylamine, phenothiazine, 3,7-dioctyl Phenothiazine, alkylphenyl-1-naphthylamine, alkylphenyl-2-naphthylamine are also used. The amount of addition is usually 0.05 to 2.0% by weight based on the lubricating oil composition.
1-1.0% by weight is preferred.

Since the lubricating oil composition of the present invention dissolves in the ammonia refrigerant, the lubricating oil composition does not accumulate in the evaporator, and there is no possibility that the heat transfer efficiency is reduced. Further, separation of the refrigerant and the lubricating oil composition is also easy.

The amount of the ammonia refrigerant dissolved in the lubricating oil composition may be 5% by weight or less of the ammonia refrigerant, and may be used by dissolving 0.1 to 2% by weight. preferable.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 Structure and production method of compound of base oil: having a structure represented by the above general formula (1), wherein R ¹¹ , R ¹³ and R ¹⁵ are ethyl groups,
^12, R ¹⁴ and R ¹⁶ with a compound is a methyl group.

In the presence of an acid catalyst (p-toluenesulfonic acid), D-sorbitol was reacted with methyl ethyl ketone, purified by distillation, and then purified by column chromatography. The hydroxyl value of the obtained compound was 1 mg KO
H / g.

Formulation of refrigerating machine oil: 1.
0% by weight of p, p'-dioctyldiphenylamine was blended to obtain a refrigerator oil. The properties are shown below.

Viscosity: 4.45 mm ² / s at 100 ° C., 4
64.4 mm ² / s at 0 ° C. Total acid value: 0.01 mg KOH / g Saturated water absorption: 0.26% (temperature 25 ° C., humidity 80%) Electrical insulation: 6 × 10 ¹³ Ω · cm ammonia at 25 ° C. Compatibility with: Figure 2, Refrigeration oil: ammonia =
1: 9 (volume ratio) compatible at -2 ° C Stability (shield tube test): 7 ml of ammonia
And 3 ml of refrigerant oil together with an iron wire as a catalyst were sealed in a glass tube and left at 150 ° C. for 14 days. As a result, there was no change in the appearance of the refrigerant oil, and no sludge was generated.

Example 2 Structure and production method of compound of base oil: R ¹¹ , R ¹³ , R ¹⁵ , R ¹⁵ having the structure represented by the above general formulas (1) and (2)
²¹ , R ²³ and R ²⁵ are hydrogen atoms, R ¹² , R ¹⁴ , R ¹⁶ and R
²² , R ²⁴ and R ²⁶ are propyl groups, and are represented by the general formula (1)
35% by weight of the compound of the formula, 65% by weight of the compound of the general formula (2)
Were used in a mixture of the following ratios.

In the presence of an acid catalyst (p-toluenesulfonic acid), D-sorbitol and butyraldehyde were reacted and purified by distillation. The resulting mixed compound has a hydroxyl value of 1 mgKOH / g.

Mixing of refrigeration oil: 1.0% by weight of p, p'-dioctyldiphenylamine was added to the above compound to obtain a refrigeration oil. The properties are shown below.

Viscosity: 5.5 mm ² / s at 100 ° C., 40
68.2 mm ² / s at 25 ° C. Saturated water absorption: 0.25% (temperature 25 ° C., humidity 80%) Electrical insulation: 2 × 10 ¹³ Ω · cm at 25 ° C. Compatibility with ammonia: Refrigeration oil: ammonia = 1: 9
Compatibility at + 10 ° C. (volume ratio) Stability (shield tube test): As a result of evaluation in the same manner as in Example 1, there was no change in the appearance of the refrigerant oil and no sludge was generated.

The structure and operation of the refrigerator to be used will be described with reference to the refrigeration system shown in FIG. The ammonia refrigerant is compressed by the compressor 1 which is lubricated using the refrigerating machine oil of the present embodiment. The compressed ammonia refrigerant contains a small amount of refrigerating machine oil, but is cooled and liquefied in the condenser 2 as it is.
The liquefied refrigerant is guided to the evaporator 4 via the expansion valve 3 and is vaporized under reduced pressure, and heat exchange is performed via the evaporator 4. The vaporized refrigerant is circulated to the compressor 1 as it is.

Although a small amount of refrigerating machine oil is mixed with the refrigerant in the compressor 1, the refrigerating machine oil of this embodiment dissolves in the ammonia refrigerant. Therefore, the heat transfer coefficient does not deteriorate. Therefore, since it is not necessary to strictly separate the refrigerant and the lubricating oil, the apparatus is simplified and the refrigerant used is small. Further, there is no need to wash the inside of the system.

Table 1 shows a comparison with other refrigerating machine oils.

[0048]

[Table 1]

[0049]

As described above, the lubricating oil composition of the present invention is compatible with an ammonia refrigerant and is stable against active ammonia. This refrigerant system is used in place of a conventional Freon refrigerant. This contributes to the preservation of the ozone layer and makes it possible to simplify the refrigeration system itself using the ammonia refrigerant, so that the apparatus can be simplified, downsized, and reduced in cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a refrigeration system using an ammonia refrigerant using a lubricating oil composition of the present invention.

FIG. 2 shows a lubricating oil composition of the present invention (wherein R ¹¹ , R ¹³ and R ¹⁵ in the general formula (1) are ethyl groups, R ¹² , R ¹⁴ and R
FIG. ¹⁶ is an explanatory diagram showing the compatibility between ammonia and ¹⁶ ).

FIG. 3 is an explanatory diagram showing a conventional refrigeration system using an ammonia refrigerant.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Toshiya Hagiwara 1334 Minato, Wakayama City, Kao Corporation Research Institute (72) Inventor Yuichiro Kobayashi 1334 Minato, Wakayama City, Kao Corporation Research Center

Claims (4)

[Claims] 1. A lubricating oil composition for compressing an ammonia refrigerant having a viscosity of 8 to 220 mm ² / s at 40 ° C., comprising a cyclic compound having a plurality of dioxolane rings or dioxane rings as a base oil. 2. The cyclic compound represented by the following general formula (1)
The lubricating oil composition used for compressing an ammonia refrigerant according to claim 1, comprising a compound represented by the following formula: Embedded image (Here, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and R ¹⁶ are the same or different and are a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, provided that R ¹¹ , R ¹² , R ¹³ and R ^14, R ¹⁵
And R ¹⁶ are not simultaneously hydrogen atoms. ) 3. The composition according to claim 1, further comprising an amine antioxidant.
3. A lubricating oil composition for use in compressing an ammonia refrigerant according to any one of claims 1 to 2. 4. After compressing and coagulating the ammonia refrigerant using the lubricating oil composition according to claim 1 to compress the ammonia refrigerant, introducing the ammonia refrigerant in which the lubricating oil composition is dissolved into an evaporator, A method for lubricating the compressor of the circulating ammonia refrigerant.