JP2787083B2 - Tetrafluoroethane refrigerator composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method using a refrigerant, -20 ° C. or less, with respect to tetrafluoroethane, preferably 1,1,1,2-tetrafluoroethane (R-134a). The present invention relates to a refrigerator composition comprising a polyether and tetrafluoroethane which are compatible at a free ratio from a temperature lower than that to + 40 ° C. or higher and have low hygroscopicity.

[Prior art] In refrigeration cycles such as refrigerators and car air conditioners,
R-12 (dichlorodifluoromethane) has been used as a good refrigerant. However, R-12 has the potential to destroy the stratospheric ozone layer and adversely affect biological systems, and alternative materials are being investigated. As a substitute for R-12,
Although R-134a is considered to be the most influential, 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 and paraffinic mineral oil cannot be used as the refrigerating machine oil for R-134a. As a substance relatively compatible with R-134a, a polyether oil having a structure as shown in Table 1 is known.

For (a), for example, Dupont's Research Disclos
ure (17463 Oct. 1978). (A) is described, for example, in US Pat. No. 4,755,316.

[Problems to be Solved by the Invention] However, the polyethers shown in Table 1 have the following problems.

Insufficient compatibility with R-134a-In order to exhibit lubricity, which is the most important role of refrigerating machine oil, it is necessary to be compatible with R-134a and circulate in the system together with R-134a .
The refrigerating machine oils (a) and (b) have a high temperature critical temperature, for example, when the kinematic viscosity at 40 ° C is 100 cst (see the remarks column in Table 1).
Is as shown in Table 1. The compatibility is not sufficient.

-High hygroscopicity-The refrigerating machine oils (a) and (b) have high hygroscopicity and easily absorb moisture. The incorporation of moisture has adverse effects such as a decrease in insulation resistance and an increase in corrosiveness to metals.

[Means for Solving the Problems] In order to solve the above-described problems, the present inventors have presumed that polyether oil has high hygroscopicity due to a terminal hydroxyl group. Therefore, using a polyether having a number of terminal hydroxyl groups in the range of 1 to 3 and using a compound obtained by acylating all or a part of each terminal hydroxyl group, evaluation as a refrigerator oil for R-134a was performed. . As a result, not only improvement in hygroscopicity, but also compatibility with R-134a,
The present inventors have also found that the viscosity index has been improved, and have completed the present invention.

That is, the present invention provides the following general formula [Wherein, R ¹ is an alkylene group, R ² , R ³ , R ⁴ is an acyl group or hydrogen, and R ² , R ³ , R ⁴ may be the same or different (provided that
Two or more selected from R ² , R ³ and R ⁴ are not simultaneously hydrogen, and R ² in the above compound is an acyl group).
l, m, n are compounds having a kinematic viscosity of 10 to 300 cst (40
° C) and may be the same or different.

X ¹ is a residue obtained by removing hydrogen, an acyl group, or a hydroxyl group of a monohydroxy compound.

X ² is a residue obtained by removing a hydroxyl group of a dihydroxy compound.

X ³ is a residue of the trihydroxy compound excluding the hydroxyl group. A tetrafluoroethane-based refrigerator composition comprising at least one polyether selected from the group consisting of:

X ¹ in the general formula is a residue excluding hydrogen, an acyl group or a hydroxyl group of a monohydroxy compound. An acyl group In this case, A is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, or an aryl group such as a phenyl group. Residues except for the hydroxyl group of the monohydroxy compound include a methyl group, an ethyl group, a propyl group,
Alkyl groups such as butyl group, 2-ethylhexyl group and nonyl group and aryl groups such as phenyl group are preferred.

The X ² in the general formula, ethylene glycol residues, residues obtained by removing hydroxyl group of dihydroxy compounds such as propylene glycol residue are preferable, X ³ in the general formula
As such, a residue obtained by removing a hydroxyl group of a trihydroxy compound such as a glycerin residue and a trimethylolpropane residue is preferable.

R ¹ in the general formula ( ¹⁾ is an alkylene group such as an ethylene group, a propylene group, a butylene group, and a tetramethylene group, and one of these may be used alone or two or more of these may be in a random or block form. They may be present together, and when they are present, it is preferable that a propylene group be the main component. R ¹ in formulas ( ¹⁾ to ( ⁵⁾ may be the same or different.

R ² , R ³ , and R ⁴ in Formulas (1) to ( ⁴⁾ are the same acyl groups or hydrogen as described above, and may be the same or different. Here, R ^{2 in the above} is an acyl group. Also, R ² , R ³ ,
Two or more selected from R ⁴ are not simultaneously hydrogen.

Usually, when synthesizing the compound represented by the general formula, And the number of active hydrogen groups is 1, 2, and 3, respectively.
12cst which is the general kinematic viscosity of refrigerating machine oil for car air conditioners and refrigerators using an initiator with 4 or more active hydrogen groups
When trying to obtain a compound in the range of (40 ° C.) to 200 cst (40 ° C.), the number of l, m, and n, that is, the number of moles of alkylene oxide added becomes too small, and the lubricating performance decreases. Absent.

As the compound represented by the general formula (1), a kinematic viscosity of 10 to 300 cst (40 ° C.) is used as a refrigerating machine oil in order to sufficiently achieve functions such as friction, wear and seizure prevention in sliding parts of a compressor or the like. , Preferably 12-200 cst
(40 ° C.), and the molecular weight or the values of l, m, and n in the general formulas (1) to (4) are preferably selected so as to fall within the above viscosity range. The values of l, 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 formula (1) to 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). Compounds of the general formulas
Alternatively, they can be used as a mixture thereof.

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, an osphin sulfide compound such as triphenyl phosphine sulfide or trimethyl phosphine sulfide, or a stabilizer such as glycidyl ether may be added.
Further, a compound represented by the general formula (1) of the present invention and a conventionally used naphthenic mineral oil, paraffinic mineral oil,
Alkylbenzene synthetic oil, poly-α-olefin synthetic oil, perfluoropolyether oil which is a fluorine-based lubricating oil, fluorinated silicone oil or polyether oil other than the polyether oil of the present invention can be mixed and used. It is.

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

[Operation] In the present invention, it is considered that by acylating a terminal hydroxyl group, hydrophilicity is reduced and hygroscopicity is reduced. Further, although the mechanism of compatibilization between the oil of the present invention and tetrafluoroethane as a refrigerant is not always clear, it involves a certain interaction between the carbonyl group of the ester bond and tetrafluoroethane. it is conceivable that.

[Examples] Examples 1 to 9, Comparative Examples 1 to 5 Structures of oils used in Examples 1 to 9 and Comparative Examples 1 to 5, R
Tables 2 and 3 show the results of compatibility with -134a, hygroscopicity and kinematic viscosity at 40 ° C.

・ Hygroscopicity test method Into a 150 mm diameter petri dish, add 15 g of oil confirmed to have a water content of 0.03% or less. With the petri dish open,
Leave in a constant temperature room with a room temperature of 20 ° C and a humidity of 50%. Assuming that the weight of the oil after 30 hours is Yg, the rate of weight increase is determined by the following equation.

[Effect of the Invention] The composition of the present invention has a high compatibility between tetrafluoroethane and polyether oil, and can sufficiently exhibit functions such as friction, abrasion, and seizure prevention in sliding parts such as a compressor. . Further, since the moisture absorption is low, the incorporation of moisture is reduced, so that a decrease in insulation resistance can be prevented, and the progress of metal corrosion of a copper pipe or the like due to moisture can be prevented.

Claims (1)

(57) [Claims] 1. The following general formula [Wherein, R ¹ is an alkylene group, R ² , R ³ , R ⁴ is an acyl group or hydrogen, and R ² , R ³ , R ⁴ may be the same or different (provided that
Two or more selected from R ² , R ³ and R ⁴ are not simultaneously hydrogen, and R ² in the above compound is an acyl group). l, m, n are compounds having a kinematic viscosity of 10 to 300 cst (40
° C) and may be the same or different. X ¹ is hydrogen, an acyl group, or a residue excluding a hydroxyl group of a monohydroxy compound). X ² is a residue obtained by removing a hydroxyl group of a dihydroxy compound. X ³ is a residue of the trihydroxy compound excluding the hydroxyl group. ] A tetrafluoroethane-based refrigerator composition comprising at least one polyether selected from the group consisting of: and tetrafluoroethane.