JP2803203B2 - Lubricants for refrigerators - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to tetrafluoroethane, preferably 1,1,1,
The present invention relates to a tetrafluoroethane-based refrigerator composition comprising 2-tetrafluoroethane (R134a) and a specific polyether.

[Prior art] Conventionally, naphthenic mineral oil, paraffin mineral oil, alkylbenzene synthetic oil,
Poly-α-olefin-based synthetic oils are known and used for the purpose of preventing friction, wear, seizure and the like in sliding portions of a compressor.

The characteristics required as lubricating oil for chlorofluorocarbon compressor, unlike general lubricating oil, because it involves contact with chlorofluorocarbon as a refrigerant, good stability to the refrigerant,
It is required to have excellent solubility in a refrigerant and not to dissolve polymer materials such as packings used as a material.

Conventionally, for dichlorodifluoromethane (hereinafter, referred to as R12) used as a refrigerant, conventionally used naphthenic mineral oil, paraffinic mineral oil, alkylbenzene synthetic oil, and poly-α-olefin synthetic oil are used. Despite satisfying the above-mentioned requirements, environmental problems due to the depletion of the ozone layer of completely halogenated chlorofluorocarbons have been pointed out, and there is an urgent need to develop a new refrigerant to replace R12. Although 1,1,1,2-tetrafluoroethane (hereinafter referred to as R134a) is considered to be a promising new refrigerant in place of R12, lubricating oil is indispensable when used as a refrigerant.

[Problems to be Solved by the Invention] As the lubricating oil for R134a compressor, conventionally known naphthenic mineral oil, paraffinic mineral oil, alkylbenzene synthetic oil and poly-α-olefin synthetic oil are required conditions. In terms of solubility of one of the lubricating oils and R134a, it has a disadvantage of not exhibiting solubility.

If the solubility of R134a and the lubricating oil is poor, the lubricating oil taken out from the compressor by entrainment will be separated from the refrigerant in the condenser, evaporator, dryer, piping, etc., resulting in extremely high viscosity. This causes unsatisfactory oil return to the compressor, lowering the amount of oil in the compressor, and further causing problems such as friction and abrasion in the sliding portion and burning of the compressor.

On the other hand, as a lubricating oil having solubility with R134a, polyglycol oil has been proposed (DuPont Research Disc)
losure 17463 Oct. 1978, USP 4,755,316 etc.).

However, since the metal surface is exposed inside the compressor of the refrigerator and the refrigerant oil and the refrigerant coexist there, the metal catalyzes during long-time operation at high temperature, and The refrigerant easily reacts, and the acid value of the refrigerating machine oil increases, deteriorates, etc., causing metal corrosion, abrasion, generation of sludge, and failure of the refrigerating machine.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention has repeatedly studied lubricating oils for R134a compressors. As a result, the present inventors have developed polyglycol oils having a low degree of unsaturation. It has been found that improvement is preferable, and the present invention has been completed. That is, the present invention
As a lubricating oil for R134a, the following general formula R ¹ O (R ² O) _m -R ³ ] _n (I) wherein R ² is an alkylene group, R ¹ and R ³ may be the same or different, and hydrogen , A hydrocarbon group, or an acyl group, n is an integer of 1 to 6, and m is a positive number such that the kinematic viscosity of the compound is 5 to 300 cst (40 ° C). And a tetrafluoroethane-based refrigerator composition comprising a lubricating oil for a refrigerator having a total degree of unsaturation of not more than 0.035 meq / g and tetrafluoroethane.

Since the polyglycol oil used in the present invention has a lower degree of unsaturation than conventional ones, it has excellent thermal stability and lubricating properties, and exhibits an improved effect superior to conventional products.

Such a polyglycol oil is obtained by adding a cyclic ether, particularly propylene oxide or ethylene oxide thereto, to an initiator such as a monohydric alcohol, a polyhydric alcohol, and an organic acid, or modifying a hydroxyl group after the addition.

As an addition reaction catalyst, it is not impossible to produce the catalyst using an alkali metal compound (alkali hydroxide) (in particular, it is considered possible if mild reaction conditions are used).
However, polyglycol oils, preferably produced using other catalysts, are preferred. Examples of the catalyst include metal porphyrin (see JP-A-61-197631), LiPF
₆ (see JP-A-60-197726), a complex metal cyanide complex (see JP-B-59-15336, US Pat. No. 3,929,505), a complex of a metal and a chelating agent having tridentate or higher coordination (See JP-A-60-197726).

The polyglycol oil (I) in the present invention has a kinematic viscosity of 5 to 30 in order to sufficiently achieve functions such as friction, wear, and seizure prevention in the sliding portion of the compressor.
It is necessary to be 0 cst (40 ° C.), and the molecular weight or the values of m and n in the compound (I) are selected to be in such a kinematic viscosity range.

In the compound of the present invention, the hydrocarbon group is defined as (1) a saturated linear or branched C _{1 to} C ₂₀ chain hydrocarbon group, preferably a C _{1 to} C ₇ aliphatic monohydric alcohol. A C ₁ -C ₇ alkyl group, particularly preferably a methyl group, an ethyl group, a butyl group, a hexyl group, a benzyl group, and (2) a saturated linear or branched C ₁ -C ₂₀ chain carbon atom containing a halogen atom. A hydrogen group, preferably an alkyl group derived from a C ₁ -C ₆ halogen atom-substituted monohydric alcohol, preferably a trifluoroethyl group, a hexafluoroisopropyl group, a trifluoroethyl group; Is a hydrocarbon residue derived from propylene glycol, glycerin, trimethylolpropane, pentaerythritol and sorbitol; (4) C6-C26 substitution or Is an unsubstituted aromatic hydrocarbon group, preferably a phenyl group, and an alkylphenyl group having an alkyl group having 1 to 16 carbon atoms, specifically, a tolyl group, an isopropylphenyl group, a nonylphenyl group, or the like. Group.

The acyl group referred to herein is preferably a carboxylic acid, particularly one derived from a saturated monocarboxylic acid having 2 to 20 carbon atoms. Specific examples of the carboxylic acid include acetic acid,
Examples include propionic acid, butyric acid, stearic acid, trifluoroacetic acid, and trichloroacetic acid.

R ¹ is an n-valent group and R ³ is a monovalent group. Further, in the formula (I), 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 include an ethylene group, a propylene group, a butylene group and a tetramethylene group. A case where an ethylene group and a propylene group are present, that is, a case where (R ² O) is a polyoxyethylene-polyoxypropylene group is also included.

In the formula (I), n is 1 to 6, preferably 1 to 3.
Indicates an integer.

The weight ratio of the compound (I) to R134a is 1/99 to 99/1, preferably 5/95 to 60/40. The composition of the present invention is particularly effective in the application of a refrigeration cycle for low-temperature to high-temperature refrigeration, refrigeration and air conditioning, but can also be used for various other heat recovery technologies such as a Rankine cycle. is there.

The composition of the present invention is excellent in thermal stability and does not require a stabilizer under normal use conditions, but when the heat stability needs to be improved due to severe use conditions, dimethyl phosphite is used. A small amount of a phosphite compound such as diisopropyl phosphite or diphenyl phosphite, a phosphine sulfide compound such as triphenyl phosphine sulfide or trimethyl phosphine sulfide or a stabilizer such as glycidyl ether may be added.
The compound (I) of the present invention and conventionally used naphthenic mineral oils, paraffinic mineral oils, alkylbenzene synthetic oils, poly-α-olefin synthetic oils, and fluorinated polyether oils which are fluorine lubricating oils And a fluorine-containing silicone oil or the like, or a polyalkylene glycol oil having a hydroxyl group.

Also, various additives such as a phenolic or amine-based antioxidant, a sulfur or phosphorus-based extreme pressure additive, a silicone-based defoamer, or a metal deactivator such as benzotriazole may be used in the composition of the present invention. May be further added.

[Examples] Examples 1-4, Comparative Examples 1-4 The structures, kinematic viscosities, total unsaturations, and acid values before and after the shield tube test of the oil used in Examples 1-4 and Comparative Examples 1-4 [mg] -KOH / g] and physical properties of color are shown in Table 1.

[Shield tube test] In a 300 ml stainless steel autoclave, take 70 g of sample oil, 70 g of chlorofluorocarbon (R134a), and one piece of copper-iron-aluminum test piece as a metal piece, seal, and seal at 175 ° C. For 14 days. After the test was completed, the sample oil was heated under reduced pressure to sufficiently remove the chlorofluorocarbon gas, and then the properties were measured.

[Effect of the Invention] The lubricating oil for a tetrafluoroethane-based refrigerator of the present invention comprises:
It has excellent stability at high temperatures and can sufficiently exhibit functions such as friction, wear, and seizure prevention in sliding parts such as a compressor.

Continued on the front page (58) Fields investigated (Int.Cl. ⁶ , DB name) C10M 107/34 C10M 105/18 C10M 105/54 C10M 105/34 C10M 107/38 C10M 129/18 C10M 129/70 C10M 129 / 95 C10M 131/10 C10M 131/12 C10M 145/26 C10N 40:30 C10N 20:00

Claims (1)

(57) [Claims] 1. A compound represented by the following general formula (I): R ¹ O (R ² O) _m -R ³ ] _n (I) wherein R ² is an alkylene group, and R ¹ and R ³ may be the same or different. , Hydrogen, a hydrocarbon group, or an acyl group, n is an integer of 1 to 6, and m is a positive number such that the kinematic viscosity of the compound is 5 to 300 cst (40 ° C). A polyglycol oil represented by the formula
A tetrafluoroethane-based refrigerator composition comprising a lubricating oil for a refrigerator at 0.030 meq / g or less and tetrafluoroethane.