JPH0381396A - Stabilization of tetrafluoroethane composition for refrigerating machine - Google Patents

Abstract

PURPOSE:To obtain a composition for a refrigerating machine which is compatible at a free ratio, has low moisture absorption properties and is provided with a high stabilizing effect by stabilizing a composition comprising a specific polyether and tetrafluoroethane with a phenolic antioxidant. CONSTITUTION:The title composition is obtained by stabilizing a composition for refrigeration comprising at least one polyether of formula I-III and tetrafluoroethane using a phenolic antioxidant. In the formulae, R<1> is an alkylene group; R<2-4> are each acyl or H provided that 2 or more of R<2-4> are not H atoms at the same time; l, m and n are each a number such that the kinematic viscosity may be 5-300cst (40 deg.C); X<1> is H, acyl or the residue of a hydroxy compound from which the hydroxyl group is removed provided that X<1> and R<2> are not H atoms at the same time: X<2> is the residue of a hydroxy compound from which the hydroxyl groups are removed; and X<3> is the residue of a trihydroxy compound from which the hydroxyl groups are removed.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a refrigerant, tetrafluoroethane, preferably l, 1.1.2-tetrafluoroethane (R-13
For 4a), from a temperature of -20°C or lower,
The present invention relates to a method for stabilizing a composition for a refrigerator consisting of polyether and tetrafluoroethane, which are compatible in any ratio at temperatures of +40° C. or higher and have low hygroscopicity.

[Conventional technology] In the refrigeration cycle of refrigerators and car air conditioners, R
-12 (dichlorodifluoromethane) has been used as a good refrigerant. However, R-12 can destroy the ozone layer in the stratosphere and have a negative impact on biological systems, so alternatives are being considered. R-134a is considered to be the most promising substitute for R-12;
Naphthenic mineral oil and paraffinic mineral oil, which are common refrigeration oils for R-12, are not compatible with R-134a. Therefore, naphthenic mineral oil,
Paraffinic mineral oil cannot be used.

Polyether oils having the structures shown in Table 1 are known as substances that are relatively compatible with R-134a.

Regarding (a), for example, Du Pont's Re5er
chDisclosure(174830ct, 197
g).

Regarding (b), for example, U, S, Pat, 4.7
No. 55.316.

However, polyethers such as those shown in Table 1 contain R-134a
There are problems such as insufficient compatibility with polyether and high hygroscopicity, and the present inventors solved the above problems by esterifying the ends of polyether.

Table 1 Conventional polyether oil, high temperature critical temperature (ne) high temperature critical temperature two oils, and R-134a were mixed at a weight ratio of 15:85 and sealed. As the temperature is increased, the temperature at which turbidity or two-layer separation begins is called the high temperature critical temperature. The better the compatibility, the higher the high-temperature critical temperature.

[Problem to be solved by the invention] However, inside the compressor of a refrigerator, the metal surface is exposed, and refrigerator oil and refrigerant coexist there.
During long-term operation at high temperatures, metals have a catalytic effect, making it easier for the refrigerant oil and refrigerant to react, resulting in an increase in the total acid value, corrosion of metals, and generation of sludge, which can lead to refrigerator malfunctions. .

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and is represented by the following general formula (%) [In the formula, R1 is an alkylene group, R", R", R' is an acyl group or hydrogen, and R'', R'' and R' may be the same or different. (However, two or more selected from Rs, Rs, and R4 cannot become hydrogen at the same time.)
42. m and n are kinematic viscosity of the above compound Φ~■ 5~3
00cst (40°C), and may be the same or different.

xl is hydrogen, an acyl group, or a residue of a monohydroxy compound excluding the hydroxyl group. (However, Xl and R2 do not become hydrogen at the same time.) X2 is the residue of a dihydroxy compound from which the hydroxyl group has been removed.

xs is a residue of a trihydroxy compound excluding the hydroxyl group;] A composition for a tetrafluoroethane refrigerator consisting of at least one polyether selected from the following and tetrafluoroethane is stabilized using a phenolic antioxidant. The present invention relates to a method for stabilizing a tetrafluoroethane-based refrigerator composition.

xl in the general formula (2) is hydrogen, an acyl group, or a residue of a monohydroxy compound from which the hydroxyl group has been removed. If an acyl group is expressed as -C-A, II A is preferably an alkyl group such as a methyl group, ethyl group, propyl group, or butyl group, or an aryl group such as a phenyl group, and is a residue of a monohydroxy compound excluding the hydroxyl group. Examples include methyl group, ethyl group, propyl group, butyl group, 2
- Preferred are alkyl groups such as ethylhexyl and nonyl groups, and aryl groups such as phenyl.

As X2 in the general formula (■), a residue from which the hydroxyl group of a dihydroxy compound such as an ethylene glycol residue or a propylene glycol residue has been removed is preferable, and x in the general formula (■)
3 is preferably a residue from which the hydroxyl group of a trihydroxy compound has been removed, such as a glycerin residue or a trimethylolpropane residue.

R1 in the general formulas ■ to ■ is an alkylene group such as an ethylene group, a propylene group, a butylene group, a tetramethylene group, etc., and these may be used alone or together in a random or block form, and when they exist together, It is preferable that the main component is a propylene group. General formula■～
R1 in (2) may be the same or different.

R'', R'', and R' in general formulas (1) to (2) are the same acyl groups or hydrogen as described above, and these may be the same or different. However, xl and R2 do not become hydrogen at the same time. Moreover, two or more selected from Rz, Rs, and R4 cannot become hydrogen at the same time.

Usually, when synthesizing the compounds represented by the general formulas (1), (2), and (2), the number of active hydrogen groups in the corresponding initiators is 1 and 2.3, respectively.

Using an initiator with the number of active hydrogen groups of 4 or more, the kinematic viscosity is 12c, which is the general kinematic viscosity of refrigeration oil for car air conditioners and refrigerators.
st (40°C) to 200cst (40°C), the numbers of Q, m, and n, i.e.,
The number of moles of alkylene oxide added is undesirable because it becomes too small and the lubricating performance deteriorates.

The compounds represented by the general formulas Φ to ■ have a kinematic viscosity of 5 to 300 cst (40 °C), preferably 12
~200 cst (40°C) is desirable, and the molecular weight or the values of β, m, and n in the general formulas Φ to 2 are preferably selected such that the viscosity falls within this range. The values of A, m, and n are approximately 3 to 60, preferably 6 to 30, and may be the same or different.

The weight ratio of the compound represented by the general formulas Φ to ① and R134a is 1/99 to 99/1, preferably 5/95 to 60.
/40. R134a may contain a small amount of 1,1,2,2-tetrafluoroethane (R134), and the compounds of general formulas Φ to (■) can be used alone or as a mixture thereof.

The composition of the present invention is particularly effective in refrigeration cycle applications for freezing, refrigeration, and air conditioning in the low to high temperature fields, but can also be used in various other heat recovery technologies such as Rankine cycles. be.

Phenolic antioxidants for stabilizing the compositions of the invention include 2,6-di-t-butyl-p-cresol, 2,6-di-t-butylphenol.

2.6-di-tert-butyl-4-5ec-butylphenol.

2.2'-ethylidenebis(4,6-di-t-butylphenol), 4.4'-butylidenebis(3-methyl-6-t-butylphenol), 4.4'-thiobis(3-methyl-6-t) -butylphenol), octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,5-di-t-butyl-4-hydroxypenzylphosphonate diethyl ester, etc. can be mentioned.

In the present invention, the amount of the phenolic antioxidant added to the refrigerating machine oil is 0.01 to 10% by weight, preferably 0.1 to 5% by weight, but if the amount is less than this, the desired effect may not be obtained. Furthermore, even if a large amount is added, the effect will not increase significantly.

In addition, if further improvement in thermal stability is required due to harsh usage conditions, phosphite compounds such as dimethyl phosphite, diisopropyl phosphite, and diphenyl phosphite, and phosphines such as triphenoxyphosphine sulfide and trimethylphosphine sulfide may be used. Add stabilizers such as sulfide compounds and other glycidyl ethers to 0. It is sufficient to add about 1 to 10% by weight of O. In addition, the compounds represented by the general formulas (■) to (■) of the present invention and conventionally used naphthenic mineral oils, paraffinic mineral oils, alkylbenzene-based synthetic oils, poly-α-olefin-based synthetic oils,
It can be used in combination with perfluoropolyether oil, which is a fluorine-based lubricating oil, fluorine-containing silicone oil, or polyether oil other than the polyether oil of the present invention.

Additionally, various additives such as phenol-based or amine-based antioxidants, sulfur- or phosphorus-based extreme pressure additives, silicone-based antifoaming agents, or metal deactivators such as benzotriazole may be added to the composition of the present invention. It may be further added.

[Example] Examples 1-1 to 3, Comparative Examples 1 to 3 The structure of the oil used in Examples 1 to 3 and Comparative Examples 1 to 3, the structure of the kinematic viscosity additive, the acid value before and after the shield tube test [ Table 2 shows the results in mg-KOH/gl.

[Shield Tube Test] In a stainless steel autoclave with a capacity of 300 m1, 70 g of sample oil, 70 g of Freon (R-134a), and copper-iron-aluminum test pieces were placed as metal pieces.
Each sheet was taken out, sealed, and then heated at a temperature of 175° C. for 14 days. After the test was completed, the sample oil was heated under reduced pressure to sufficiently remove the fluorocarbon gas, and then its properties were measured.

[Effects of the Invention] As is clear from the examples, the method for stabilizing a tetrafluoroethane-based refrigerator composition of the present invention provides a high stabilizing effect.

Claims (1)

[Claims] 1. The following general formula (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R^1 is an alkylene group, R^2, R^3, R^
4 is an acyl group or hydrogen, and R^2, R^3, and R^4 may be the same or different. (However, R^2, R^3, R
Two or more selected from ^4 cannot become hydrogen at the same time. ) l, m, and n are positive numbers such that the kinematic viscosity of the compounds (1) to (3) is 5 to 300 cst (40°C), and may be the same or different. X^1 is hydrogen, an acyl group, or a residue of a monohydroxy compound excluding the hydroxyl group. (However, X^1 and R^2 do not become hydrogen at the same time.) X^2 is the residue of a dihydroxy compound from which the hydroxyl group has been removed. X^3 is the residue of the trihydroxy compound from which the hydroxyl group has been removed. ] A tetrafluoroethane-based refrigerator composition comprising at least one polyether selected from the following and tetrafluoroethane, which is stabilized using a phenolic antioxidant. How to stabilize things.