JPH02173195A - Lubricating oil for fluorocarbon compressor - Google Patents

Abstract

PURPOSE:To obtain the subject lubricating oil capable of sustaining sufficient compatibility with a fluorocarbon 1,1,1,2-tetrafluoroethane (R-134a) as a refrigerant within a wide temperature range by using a cyanoethylated polyoxyalkylene glycol compound as a base oil. CONSTITUTION:The objective lubricating oil obtained by using a cyanoethylated polyoxyalkylene glycol compound expressed by formula I [R is 1-12C hydrocarbon, cyanoethyl or H (preferably H); AO is 2-18C oxyalkylene (preferably a copolymer of oxypropylene and <=75% oxyethylene)] as a base oil. Furthermore, the above-mentioned compound is synthesized by a method for reacting a compound expressed by formula II with a required amount of acrylonitrile in the presence of sodium hydroxide, potassium hydroxide, etc., as a catalyst.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a lubricating oil for a compressor that uses fluorocarbons as a refrigerant, and in particular, fluorocarbons R134a (1,1 The present invention relates to a lubricating oil suitable for use in compressing 1,2-tetrafluoroethane).

(Prior Art) Conventionally, refrigerators, air conditioners, refrigerators, etc. have used CFCs containing fluorine and chlorine as refrigerants, such as R11 (dichloromonofluoromethane), R12 (dichlorodifluoromethane), and R22 (monochloromethane). However, due to the recent issue of ozone layer depletion, R134a fluorocarbons have begun to appear as a new type of refrigerant that does not have any impact on the ozone layer depletion problem.

On the other hand, many mineral oil-based and synthetic oil-based lubricants have been known for CFC compressor lubricants, but these cannot be used because they are completely incompatible with the new CFC R134a at low temperatures. I understand. Therefore, this countermeasure has become an important issue today. In addition, other performances required of the refrigerating machine oil include lubricity, energy saving properties, wear resistance, sealing properties, heat resistance, and sludge precipitation prevention properties, and these points also need to be taken into consideration.

Incidentally, polyether-based synthetic lubricating oil is an example of conventionally known synthetic oil, and this is described in Oil Chemistry Journal, Vol. 2.
9, No. 9, pp. 336-343 (1980) and Belotchik, Vol. 8, No. 6, pp. 562-566 (1985). Also, JP-A-61-281
No. 199 has the following formula: R,+0-(R,0)-R3).

JP-A No. 57-63395 discloses a mixture of polyglycol and alkylbenzene represented by the above formula, and an oil obtained by mixing an epoxycycloalkyl compound with a polyether, such as polyoxypropylene monobutyl ether having a high molecular weight of 53 moles. , also JP-A-59-11759
Publication No. 0 introduces high viscosity mixed oils of polyether compounds and paraffinic or naphthenic mineral oils.

(Problems to be Solved by the Invention) However, none of the above-mentioned known synthetic oil-based lubricating oils could be used as a lubricating oil for R-134a Freon compressors due to problems such as compatibility.

Under such circumstances, U.S. Patent No. 4,755,316 describes a refrigerating machine oil for Freon R134a that has hydroxyl groups at both ends (
-OH) polyoxyalkylene glycol (hereinafter abbreviated as PAG) has been introduced, and this PAG has a wider temperature range in terms of compatibility with Freon R134a compared to general PAG whose terminals have a hydroxyl group and an alkyl group. This improves oil return to the compressor in refrigeration systems and prevents seizure when the compressor is started at high temperatures. The compatible temperature range with Freon R134a is introduced as -40°C to +50°C.

On the other hand, Freon R134a is a candidate refrigerant alternative to Freon R12, and is mainly used in car air conditioners and refrigerators. In particular, in the case of a car air conditioner, the temperature can far exceed +50°C when the compressor starts up in the summer. In this case, with the refrigerating machine oil described in U.S. Pat. No. 4,755,316, the oil and refrigerant undergo two-phase separation in the compressor at startup, and the refrigerant with a higher specific gravity becomes the lower layer, resulting in startup without lubricating oil. The compressor may seize up. In other words, it can be said that a two-layer separation temperature of +50°C is insufficient.

Therefore, the object of the present invention is to use a new refrigerant, Freon R.
The object of the present invention is to provide a lubricating oil for a Freon compressor that has extremely good compatibility with No. 134a over a wide temperature range.

(Means for Solving the Problems) The present inventor conducted intensive research on various synthetic oils to solve the above problems, and found that a specific cyanoethylated polyoxyalkylene glycol was effective in achieving the object of the present invention. This discovery led to the completion of the present invention.

That is, the present invention is based on the following general formula (1) % formula % (1) (R in the formula is a hydrocarbon group having 1 to 12 carbon atoms, a cyanoethyl group, or a hydrogen atom, and AO is a hydrogen atom having 2 to 18 carbon atoms. The present invention relates to a lubricating oil for a Freon compressor, characterized in that the base oil is a compound represented by the following oxyalkylene group, n = 1 to 50.

The oxyalkylene group represented by AO in the above general formula (1) includes oxyethylene, oxypropylene, oxybutylene, oxyhexylene, oxystyrene, oxyoctene, oxidodecene, oxytetradecene, oxyhexadecene, and oxyoctadecene. etc. Among them, oxyethylene and oxypropylene have a broader temperature range of compatibility with Freon R134a, and copolymers of both are also preferred, and copolymers with an oxyethylene ratio of 75% or less are particularly preferred.

The reason why R and n (degree of polymerization) in general formula (1) 2 are limited as described above is to keep the compatible temperature range above a certain level, and other characteristics as lubricating oil for fluorocarbon compressors. Regarding lubrication performance and thermal stability performance, there is no problem even if it is outside the limited range. Note that as n increases (that is, as the molecular weight increases), the compatibility temperature range tends to become narrower.

The cyanoethylated polyoxyalkylene glycol compound represented by the above general formula (1)2 is not available commercially, but was discovered as a result of trial production and study. Such a compound has the following general formula (2), R-0-→AO mother H(2) (R, AO and n in the formula are the same as those of the compound of the above general formula (1)). It can be obtained by reacting the represented compound with a required amount of acrylonitrile using sodium hydroxide, potassium hydroxide, etc. as a catalyst.

The compound of the above general formula (2) is an alcohol having a hydrocarbon group represented by R, or a glycol which can be regarded as a reaction product of oxyalkylene represented by AO and water, in which oxyalkylene is added in the presence of a catalyst. It can be obtained by letting The alcohols or glycols mentioned here include methanol, ethanol, propatool, butanol, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol,
These include octenediol, dodecenediol, tetradecenediol, hexadecenediol, octadecenediol, and the like.

As mentioned above, R134a fluorocarbons behave differently from conventional refrigerants and have the problem of two-phase separation not only at low temperatures but also at high temperatures. In either case, the compatibility is excellent, and the lubrication performance and thermal stability performance in the fluorocarbon atmosphere are also good.

It goes without saying that the fluorocarbon compressor lubricating oil of the present invention may contain appropriate antioxidants, hydrochloric acid scavengers, and anti-wear agents that have been conventionally used in refrigeration oils.
In addition, for viscosity adjustment, etc., a boat fishing PAG can be mixed and used.

(Examples) The present invention will be explained in more detail below using Examples and Comparative Examples.

-11 to 8 6 1 to 5 cyanethylated polyoxyalkylene glycol as the following first
The test oils A1 to 8 shown in the table were used as comparative examples, and the common PAGs B1 to B5 (commercial product Nippon Oil Co., Ltd.) shown in Table 2 were used as comparative examples.
The performance of Freon R134a as a lubricating oil for compressors was evaluated. Regarding A1-8,
Both are prototypes.

” Limb-Jishi-1 = ? , D R1+ R2+ AO,n is the following general formula (3)
, corresponds to that in the compound represented by RO-f-AO R2 (3).

The performance of the test oils shown in Tables 1 and 2 as lubricating oils for compressors was evaluated under the conditions shown below in terms of lubricity, compatibility, and thermal stability.

The Falex seizure load was measured in accordance with ASTM D-3233-73 under a controlled atmosphere of R134a Freon blowing (70 mffi/m1n).

'AMJ± 0.6 g of sample oil and 2.4 g of refrigerant (Freon R134a)
was sealed in a glass tube, and then cooled and heated at a rate of 1°C per minute, and the temperature at which two-phase separation occurs, that is, the two-phase separation temperature, was measured.

After sealing 1 g of rough skin test oil, 1 g of refrigerant (Freon RI34a), and catalyst (iron, copper, and aluminum wires) in a glass tube, it was heated to 175°C, and after 10 days, the hue of the test oil was determined. Judgment was made using ASTM display.

The above evaluation results are shown in Table 3 below.

"Δ-" L-1- From the evaluation results shown in Table 3, the following was confirmed.

Regarding the test oils, the seizure load and thermal stability are all problematic (the key point is the two-layer separation temperature.The low-temperature two-layer separation temperature is 83. It can be seen that the temperatures in all Examples are 60°C or higher, which is sufficiently higher than Comparative Example 1, which corresponds to the range disclosed in U.S. Pat. No. 4,755,316.Among them, Examples 1, 2.4 is particularly high, Freon R134,
It can be said that the temperature range of compatibility with a is wide.

(Effects of the Invention) As explained above, the fluorocarbon compressor lubricating oil of the present invention maintains sufficient compatibility with fluorocarbon R134a as a refrigerant and has excellent overall performance. Even if R134a Freon is used in place of R12 or R22 Freon, the effect is that the conventional system can be used as is.

Claims (1)

[Claims] 1. The following general formula (1) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (1) (R in the formula is a hydrocarbon group having 1 to 12 carbon atoms, a cyanoethyl group, or hydrogen lubricating oil 2 for fluorocarbon compressors, characterized in that the base oil is a compound represented by atom, AO is an oxyalkylene group having 2 to 18 carbon atoms, n = 1 to 50, the above formula (1) The lubricating oil for a fluorocarbon compressor according to claim 1, wherein AO is oxypropylene and R is a hydrogen atom. 3. The lubricating oil for fluorocarbon compressors according to claim 1, wherein in the above formula (1), AO is composed of a copolymer of oxypropylene and oxyethylene, the ratio of oxyethylene is 75% or less, and R is a hydrogen atom. . 4. Claim 1 for use in compressing R134a Freon
The lubricating oil for a Freon compressor according to any one of 3 to 3.