JPH0631363B2 - Lubricating oil composition for refrigerator - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a refrigerating machine lubricating oil composition, and in particular, it has excellent viscosity characteristics as a lubricating oil for a refrigerating machine compressor using a halogen-based refrigerant. , There is no separation of the mixture even at low temperature,
The present invention also relates to a lubricating oil composition for a refrigerator, which has excellent heat resistance at high temperatures.

<Background of the Invention> Conventionally, various types of refrigerators have been used.
Among them, in a compression refrigerator, the refrigeration performance is affected by the sealing property between the low-pressure intake gas and the high-pressure discharge gas, so the refrigerating machine oil used in the compressor is required to have the sealing property. . In recent years, as the performance of refrigerating machines has improved, the temperature of discharge gas tends to rise, which is a factor that causes a decrease in viscosity due to a rise in temperature of refrigerating machine oil, and eventually a decrease in hermeticity. Refrigerator compressors are classified into reciprocating type, centrifugal type and rotary type according to their structure.However, since rotary type refrigerators have poor sealability due to their structure, refrigerating machine oil with excellent sealability is especially recommended. is necessary.

Freon 11 (trichloromonofluoromethane), Freon 12 (dichlorodifluoromethane), Freon 22
(Monochlorodifluoromethane) and Freon 113
Halogen-based refrigerants represented by (trichlorotrifluoroethane) and the like are generally known to have high thermal stability alone. For example, the most stable Freon 14 (tetrafluoromethane) does not decompose even when heated at 400 ° C for 500 hours, and even the most unstable Freon 11 does not decompose at less than 200 ° C, and even at 200 ° C, 1
It is said that it decomposes only 2.5% per year. The refrigerating machine oil also has high thermal stability when it is used alone or in an inert atmosphere, and its decomposition temperature is generally 3 although it varies depending on the composition.
The temperature is 00 ° C or higher.

However, when a halogen-based refrigerant and oil coexist, it becomes chemically active, and when it is affected by metal catalytic action and trace contaminants such as air and water, it decomposes and reacts at a lower temperature than when used alone, Metal corrosion and deterioration of lubricating oil,
Furthermore, there is a risk of reducing the compression efficiency due to the generated carbides and sludge and causing a seizure accident. Therefore, refrigerating machine oil is required to have high heat resistance in the presence of a halogen-based refrigerant.

On the other hand, the refrigerating machine oil filled in the crankcase of the compressor for the refrigerating machine is circulated in the refrigeration cycle along with the discharge gas and returns to the crankcase together with the suctioned gas. Therefore, refrigeration oil is the coldest part of the refrigeration cycle,
That is, it is exposed to extremely low temperatures between the expansion valve or the capillary tube and the evaporator. It is not uncommon for temperatures in these parts to reach -20 to -30 ° C, so refrigerating machine oil must not be abnormal at such low temperatures.

The indices showing the low temperature characteristics of refrigerating machine oil include a flock point and a pour point, which play an effective role in preventing troubles caused by deposition of wax in the low temperature part or solidification of oil.

However, when a mixture of two or more kinds of compounds having remarkably different chemical structures is used as a refrigerating machine oil, another problem that cannot be evaluated by the floating point, the pour point, etc.,
That is, when the compatibility of the mixed compounds at low temperature is insufficient, a phenomenon occurs in which the components are separated into individual components at low temperatures. If the refrigerating machine oil that is a mixture separates into each component in the low temperature part of the refrigerator, the solubility of each component in the return refrigerant is different, so the composition of the oil returning from the low temperature part to the compressor and the compressor There is a difference between the composition of the oil discharged with the refrigerant. In other words, this means that the composition of the oil in the compressor crankcase changes economically, and in such a case, it is no longer possible to maintain the smooth lubricity of the compressor for a long period of time. I can't. Therefore, when a mixture of two or more compounds having remarkably different chemical structures is used as a refrigerating machine oil, it is necessary that they are stably and uniformly mixed even at a very low temperature and do not separate at all.

Conventionally, refrigerating machine oil has a kinematic viscosity of 1 at 40 ° C.
A naphthenic mineral oil of 0 to 200 cSt, a low pour point paraffinic mineral oil, an alkylbenzene, a mixture thereof, or a mixture of these various base oils with an additive is generally used. Regarding these conventional refrigerating machine oils, for example, Japanese Patent Publication No. 40-11940 and Japanese Patent Publication No. 49-4107.
No. 4, Japanese Patent Publication No. 49-13483, Japanese Patent Publication No. 49-1382
No. 9, Japanese Patent Publication No. 49-19084, Japanese Patent Publication No. 51-376
47, Japanese Patent Publication No. 51-45013, Japanese Patent Publication No. 52-39
No. 509, Japanese Patent Publication No. 52-43722, Japanese Patent Publication No. 53-1
7602, JP-A-46-4532, JP-A-48-6
06, JP-A-49-47498, JP-A-51-22
971, JP-A-52-28503, JP-A-52-5.
4707 and JP-A-53-88007. However, these conventional refrigerating machine oils, for example, have a low viscosity index in the case of naphthene-based mineral oil or alkylbenzene and thus have insufficient sealing property at high temperature, and have a relatively high viscosity index in the case of low pour point paraffin-based mineral oil. Since they have poor solubility in a general-purpose refrigerant such as Freon 22 and have a high critical melting temperature, they cannot exhibit excellent performance.

As a refrigerating machine oil having an improved hermeticity, for example, JP-B-57-42119, JP-A-55-58298 and JP-A-57-51795 propose the use of high viscosity index polyglycol oil. However, polyglycol oil has a drawback that it has lower thermal stability in the presence of a halogen-based refrigerant at high temperatures than conventional hydrocarbon-based refrigerating machine oils.

On the other hand, it is generally widely practiced to mix naphthene-based mineral oil or alkylbenzene to enhance the solubility of the low pour point paraffin-based mineral oil in the refrigerant, but in this case, the advantage that the paraffin-based mineral oil has a high viscosity index is advantageous. However, it disappears when naphthenic mineral oil having a low viscosity index or alkylbenzene is added.

As described above, the conventional refrigerating machine oil has various drawbacks. The present inventors have conducted research to develop a refrigerating machine oil having excellent viscosity characteristics, no separation of a mixture even at low temperatures, and excellent heat resistance at high temperatures, and as a result, the present invention Has been completed.

<Purpose of the Invention> The present invention provides: (a) A small change in viscosity with temperature, an appropriate viscosity even at high and low temperatures, and excellent sealability and lubricity of a refrigerator (b) In the presence of a halogen-based refrigerant Even if it is used under the condition of high temperature, deterioration is small, and the above viscosity characteristics are stably maintained. (C) Even though it is a mixture of compounds with significantly different chemical structures, it does not separate at all at low temperature. An object of the present invention is to provide a lubricating oil composition which satisfies all three properties at the same time and is particularly suitable for a refrigerator using a halogen compound as a refrigerant.

<Details of the Invention> The present invention relates to [I] [In the above formula, R ₁ and R ₃ may be the same or different and each represents hydrogen, a hydrocarbon group or an acyl group, R ₂ represents an alkylene group, n is 1 to 6, and m is m × n. Represents a number of 2 or more] and [II] a monocyclic or dicyclic having 1 or 2 straight or branched alkyl group having 12 to 40 carbon atoms as a side chain. A ring alkyl aromatic compound is blended as an essential component, and the ratio of the [I] component is 80% by weight based on the total amount of the [I] component and the [II] component.
The present invention provides a refrigerator lubricating oil composition characterized by the following.

Hereinafter, the content of the present invention will be described in more detail.

The component [I] of the present invention has a viscosity index 1 represented by the following formula (1).
It is a polyglycol oil of 30 or more.

In the formula (1), R ₁ and R ₂ are hydrogen, a hydrocarbon group or an acyl group, and R ₁ and R ₃ may be the same or different.

The hydrocarbon group referred to herein is (i) saturated or unsaturated, straight-chain or branched C _1-
C ₂₀ chain hydrocarbon group, preferably a C ₁ -C ₁₅ alkyl C ₁ -C ₁₅ derived from aliphatic monohydric alcohol, particularly preferably a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group A hexyl group, an octyl group, a decyl group and a pentadecyl group, (ii) a hydrocarbon residue derived from a dihydric to hexahydric alcohol, preferably glycol, glycerin, trimethylolpropane, pentaerythritol and sorbitol, and (iii) carbon A substituted or unsubstituted aromatic hydrocarbon group having 6 to 26 carbon atoms, preferably a phenyl group and 1 to 16 carbon atoms
An alkylphenyl group having an alkyl group, specifically, for example, a tolyl group, an ethylphenyl group, a propylphenyl group, a butylphenyl group, a pentylphenyl group, a hexylphenyl group, a heptylphenyl group, an octylphenyl group, a nonylphenyl group, a decylphenyl group. , Dodecylphenyl group, pentadecylphenyl group, hexadecylphenyl group, and the like.

Further, the acyl group referred to herein is preferably one derived from a carboxylic acid, particularly a saturated monocarboxylic acid having 2 to 20 carbon atoms or an unsaturated monocarboxylic acid, and specific examples of the carboxylic acid include acetic acid and propione. Acid, butyric acid, lauric acid, stearic acid, oleic acid and the like can be mentioned.

Further, in the formula (1), R ₂ is an alkylene group, and the alkylene group preferably has 2 to 8 carbon atoms, and alkylene groups having different carbon numbers may be present in one molecule.
Particularly preferred alkylene groups are ethylene groups and propylene groups, and preferred polyoxyalkylene groups include polyoxyethylene groups, polyoxypropylene groups and polyoxyethylene-polyoxypropylene groups.

Further, in the formula (1), n represents a number of 1 to 6, preferably 1 to 3, and m represents a number of m × n of 2 or more, preferably 5 or more.

The viscosity index of the polyglycol oil as the component [I] of the present invention is 130 or more, preferably 150 or more. When a polyglycol oil having a viscosity index of less than 130 is used, the viscosity index of the mixture obtained by blending the alkyl aromatic compound is not high enough to maintain the hermeticity of the refrigerator compressor, which is preferable. Absent.

As the polyglycol oil satisfying the above properties, one having an average molecular weight of 250 or more, more preferably 300 to 6000 is preferably used. These are commercially available under the trade names of, for example, Newpole LB series and Newpole HB series manufactured by Sanyo Kasei Co., Ltd., or Unilube series and Unisafe series manufactured by NOF Corporation. It is also possible to mix various polyglycol oils in such a range that the viscosity index when mixed is 130 or more.

On the other hand, the component [II] of the present invention is a monocyclic or bicyclic alkyl aromatic compound having 1 to 2 linear or branched alkyl groups having 12 to 40 carbon atoms as side chains.

The alkylaromatic compounds referred to in the present invention are generally produced synthetically. Benzene as the aromatic ring, carbon number 1-2
Of alkylbenzene, naphthalene, alkylnaphthalene having 1-3 alkyl groups having 1 to 2 carbon atoms, and a lower monoolefin such as ethylene, propylene or butylene as an alkylating agent. A straight-chain or branched olefin having 12 to 40 carbon atoms, wax, heavy oil, petroleum fraction, polyethylene, polypropylene, etc., obtained by thermal cracking or direct cracking having 12 to 40 carbon atoms A chain or branched olefin, and a linear olefin having 12 to 40 carbon atoms obtained by separating n-paraffin from a petroleum fraction such as kerosene or light oil and olefin-catalyzing this olefin can be used.

As the alkylation catalyst, a Friedel-Crafts type catalyst such as aluminum chloride, zinc chloride or hydrofluoric acid, or a known catalyst such as sulfuric acid, phosphoric acid, silicotungstic acid or activated clay is used.

During alkylation of the aromatic ring, not only one but two alkyl groups may be bonded to one molecule of aromatic hydrocarbon, but the dialkyl aromatic compound thus obtained is also [II] of the present invention. It can be effectively used as an ingredient.

In the present invention, the mixing ratio of the [I] component is 80% by weight or less based on the total amount of the [I] component and the [II] component, and in order to keep the viscosity index of the mixture high, [I] /
Both are preferably blended in a ratio such that [II] = 80/20 to 20/80 (weight ratio). Also, the viscosity of the mixture containing both is usually 15 to 500 cSt at 40 ° C.
Is.

With respect to the refrigerating machine lubricating oil composition of the present invention, if necessary, a conventionally known additive for refrigerating machine oil, for example, phenol-based, amine-based antioxidant, sulfur-based, phosphorus-based oiliness improver, It is also possible to add a silicone-based defoaming agent, a metal deactivator such as benzotriazole, an epoxy-based or a phosphite-based inexpensive hydrogen scavenger, and the like.

The lubricating oil composition for a refrigerator of the present invention can be used in various refrigerators, but is particularly effectively used in a reciprocating or rotary compression refrigerator. Further, the lubricating oil composition for a refrigerator according to the present invention is particularly effective for a refrigerator using a halogen-based refrigerant. The halogen-based refrigerant here is a nonflammable compound in which hydrogen in a hydrocarbon is replaced with hydrochloric acid or fluorine,
Typically, there is CFC commercially available under the trade name of Freon from Du Pont, USA. For this CFC, CFC 1
1, 12, 13, 22, 113, 114, 500 and 502 can be exemplified, and among these, the composition of the present invention is more effective for a refrigerator using Freon 12 or 22 as a refrigerant.

<Examples of the Invention> Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples. The base oils used are as follows.

Polyglycol oil ([I] component) A; Polyoxypropylene glycol monoether Nippon Oil & Fat Co., Ltd. Nitsusan Unilube MB-11 Kinematic viscosity 56.1 cSt (@ 40 ° C), Viscosity index 187 B; Polyoxypropylene glycol monoether Ether Nippon Oil & Fat Co., Ltd. Nitsusan Unilube MB-38 kinematic viscosity 227cSt (@ 40 ° C), viscosity index 212 C; polyoxypropylene glycol monoether Sansei Kasei Co., Ltd. Newpol LB-1300 kinematic viscosity 289cSt (@ 40 ° C), viscosity index 226 D; polyoxypropylene glycol monoether Nippon Oil & Fats Co., Ltd. Nissan Unilube MB-700 kinematic viscosity 616cSt (@ 40 ° C), viscosity index 250 E; polyoxypropylene glycol diether Nippon Oil & Fats Unisafe AJ-8, kinematic viscosity 40.8 cSt (@ 40 ° C), viscosity index 158 F; polyoxypropylene glycol monoether (5)
0% by weight) + polyoxypropylene glycol diether (50% by weight) manufactured by NOF CORPORATION Unisafe DEF-40 Kinematic viscosity 249 cSt (@ 40 ° C), viscosity index 225 Alkyl aromatic compound ([II] component) A; A branched long-chain alkylbenzene obtained by alkylating a propylene polymer into benzene using hydrofluoric acid as a catalyst was collected by distillation and had 12 to 39 carbon atoms.
A branched alkylbenzene mixture having 1 to 2 branched alkyl groups of kinematic viscosity 29.4 cSt (@ 40 ° C.), viscosity index of 0 or less B; n-paraffin extracted from kerosene was converted to terminal olephine by a platinum catalyst, and fluorinated. A straight-chain long-chain alkylbenzene obtained by alkylating this terminal olefin to benzene using hydrogen acid as a catalyst is collected by distillation, and is a straight-chain alkylbenzene having 1-2 straight-chain alkyl groups having 12 to 35 carbon atoms. Mixture Kinematic viscosity 25.7cSt (@ 40 ℃), Viscosity index 45 Mineral oil A; Middle east crude oil is distilled, and the obtained lubricating oil fraction is subjected to furfural treatment, hydrogen purification, deep-dewaxing treatment, and then clay treatment. The resulting refined paraffinic mineral oil has a kinematic viscosity of 31.5 cSt (@ 40 ° C) and a viscosity index of 98 B; the Gulf Coast crude oil in the United States is distilled, and the resulting lubricating oil fraction is subjected to hydrogen purification and white clay treatment. The refined naphthene-based mineral oil obtained by the treatment has a kinematic viscosity of 29.8 cSt (@ 40 ° C.) and a viscosity index of 0 or less. Examples 1 to 12 and Comparative Examples 1 to 19 [I] component and [ The component [II] was heated to uniformly dissolve and mix the ingredients to produce a lubricating oil composition for refrigerator according to the present invention (Examples 1 to 12). The performance of this composition was evaluated by the test methods shown below, and the results are also shown in Table 1.

-Low temperature separability test The composition was allowed to stand in a thermostat with variable temperature, the appearance was observed while the atmospheric temperature was lowered, and the temperature at which the separation of the components occurred was taken as the separation temperature.

-Kinematic viscosity Measured based on JIS K2283.

-Viscosity index Measured based on JIS K2284.

-Shield tube test An equal volume mixture of the composition and the refrigerant (Freon 12) was sealed in a glass tube together with copper and an iron catalyst, and after heating at 150 ° C for 240 hours, the degree of discoloration and precipitation of the composition were observed. The degree of color change is 0 for colorless and 8 for dark brown, and the smaller the numerical value of the degree of color change, the more preferable.

For comparison, as shown in Table 2, the composition of
When mineral oil was used instead of the [II] component (Comparative Examples 1 to 1)
2), when the component [II] is not used (Comparative Examples 13 to 18)
And a large proportion of [I] component (Comparative Example 19)
The same performance evaluation was performed for the above, and the results are also shown in Table 2.

Examples 1-12 are compositions according to the invention. As is clear from the results of the performance evaluation shown in Table 1, no separation of both components was observed even at extremely low temperatures in any of the compositions, and the viscosity index was the same as that of the compounded [II] component. It is significantly higher than the viscosity index of certain alkylaromatic compounds, and it is thought that this shows extremely excellent hermeticity when used in a refrigerator compressor. In addition, the results of the shield tube test are very good in that all compositions have a low degree of discoloration and no precipitate is formed, and it can be seen that they have remarkably good heat resistance in the presence of a halogen-based refrigerant.

On the other hand, Comparative Examples 1 to 12 are compositions using low pour point paraffinic mineral oil or naphthenic mineral oil, which is usually used as a refrigerating machine oil, as the blending material for the polyglycol oil, instead of the alkyl aromatic compound. As can be seen from the results of the performance evaluation in Table 2, most of the components separate at a high temperature of 0 ° C. or higher except for a few exceptional combinations, and it is clear that they cannot be practically used as refrigerating machine oil. In addition, even in an exceptionally low combination temperature, the results of the shield tube test are significantly inferior to those of the compositions of the examples of the present invention, and it can be seen that the composition has insufficient performance as a refrigerating machine oil. .

Further, Comparative Examples 13 to 18 use the polyglycol oil which is the component [I] of the present invention alone, and Comparative Example 19 uses the components [I] and [II] in combination, but the component [I] is used. However, the results of the shield tube test are extremely poor, and are significantly inferior to the compositions of the examples of the present invention.

Example 13 and Comparative Example 20 According to the composition shown in Table 3, a lubricating oil composition for a refrigerator according to the present invention (Example 13) and a composition using a naphthenic mineral oil in place of the [II] component for comparison ( Comparative example 20) was produced.

A home 2-door refrigerator with an effective internal volume of about 200 was placed in a temperature-controlled room maintained at an ambient temperature of 30 ° C. and a humidity of 75%, and Example 1 was used.
Using the compositions of 3 and Comparative Example 20, the freezer was -18
A continuous operation test was carried out for 500 hours under conditions that the temperature of the refrigerator was 3 ° C., and the operability of the refrigerator was evaluated and the power consumption was measured. In addition, a sampling valve for collecting return oil was attached between the evaporator and the compressor of the refrigerator, and the state of return oil during operation was evaluated. The results are also shown in Table 3.

As is clear from the results in Table 3, the composition of Example 13 according to the present invention showed no change in viscosity before and after the test, and the operating state was good throughout the entire operating period. Further, the return oil that was entrained in the suction refrigerant and returned to the compressor was uniformly transparent, no separation of components occurred in the low temperature part of the refrigeration cycle, and its composition was exactly the same as the initial filling oil. Further, it was found that the power consumption was lower than that of Comparative Example 20, and an energy saving effect can be expected.

On the other hand, in the composition of Comparative Example 20, the viscosity of fresh oil was almost the same as that of Example 13, but a remarkable decrease in viscosity was observed after 500 hours of operation. In addition, although the initial operating conditions were good, it gradually became unsuccessful, and it became clear that the appearance of the returned oil was cloudy and separation of components occurred in the low temperature part. Furthermore, looking at the composition of the return oil, the proportion of naphthenic mineral oil increased compared to the initial filling oil.This is because the composition separated into high viscosity polyglycol oil and low viscosity naphthenic mineral oil in the low temperature part. Since only the naphthenic mineral oil has a low viscosity, it is easily entrained in the suction refrigerant and returned to the crankcase. For this reason, it is considered that the viscosity of the crankcase oil decreases and the operating condition gradually deteriorates.

Examples 14 and 15 and Comparative Example 21 With the composition shown in Table 4, a lubricating oil composition for refrigerator according to the present invention (Examples 14 and 15) and a naphthenic mineral oil alone (Comparative Example 21) for comparison were used. The vane rotary refrigerant compressor was operated for 1000 hours, and the operability was evaluated and the refrigerating capacity and the coefficient of performance were measured. In addition, the state of return oil from the evaporator was also evaluated. The results are shown in Table 4. Freon 12 was used as the refrigerant, and the operating conditions of the refrigerant compressor were a high pressure of 15 kg / cm ² G, a low pressure of 2 kg / cm ² G, and a rotation speed of 1800 rpm.

As is clear from the results of Table 4, in the case of the compositions of Examples 14 and 15 according to the present invention, the refrigerating capacity and the coefficient of performance were high, no deterioration in the performance of the refrigerant compressor was observed before and after the test, and the composition was used. The returned oil from the evaporator was uniform and transparent without any decrease in the viscosity of the oil. Furthermore, when the refrigerant compressor was disassembled after the test, no abnormal flaws or wear was observed on the vane, cylinder, or rotor.

On the other hand, in the case of Comparative Example 21, the initial refrigerating capacity and the coefficient of performance were low, and these were further lowered after 1000 hours of operation, and the viscosity of the oil after use was also lowered. When the refrigerant compressor was disassembled after the test, the vanes and cylinders were greatly worn and the rotor was found to be flawed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location C10N 40:30 (56) Reference JP-A-60-88094 (JP, A) JP-A-59- 113095 (JP, A) Japanese Patent Sho 53-17602 (JP, B1) Japanese Patent 57-42119 (JP, B2)

Claims (1)

[Claims] 1. [I] The following equation [In the above formula, R ₁ and R ₃ may be the same or different and each represents hydrogen, a hydrocarbon group or an acyl group, R ₂ represents an alkylene group, n is 1 to 6, and m is m × n. Represents a number of 2 or more], and [II] a monocyclic ring having 1 or 2 straight or branched alkyl groups having 12 to 40 carbon atoms as a side chain, or A bicyclic alkyl aromatic compound is blended as an essential component, and the ratio of the [I] component is 80% by weight based on the total amount of the [I] component and the [II] component.
A lubricating oil composition for a refrigerator, characterized in that: