JPS6333520B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lubricating oil for refrigerators, and more particularly to a refrigerator oil composition of high viscosity polyether-based synthetic oil that exhibits excellent stability when coexisting with fluorocarbons in a refrigerator. Conventionally, highly refined naphthenic or paraffinic mineral oils have been used in refrigerators such as household refrigerators, air conditioners, and small commercial refrigerators. However, in recent years, there has been a strong demand for miniaturization and improved cooling efficiency for refrigerators, and the conditions for using refrigerator oils have become stricter, and conventional mineral oils have become increasingly unsatisfactory in terms of performance. In other words, refrigerator compressors need to be airtight against the refrigerant fluorocarbons, but if high viscosity mineral oil is used to improve airtightness, wax will precipitate and the compatibility with fluorocarbons will decrease. , the lubricating properties deteriorate significantly and various troubles occur. In order to improve these points, high viscosity polyether-based synthetic oils with good compatibility with fluorocarbons have been developed, but even this polyether-based synthetic oil can be used under harsh operating conditions such as refrigeration oil. A stand-alone product without any additives is insufficient in terms of performance. In other words, inside the compressor of a refrigerating machine, the metal surface is exposed, and refrigerating machine oil and fluorocarbons coexist there. Therefore, during long-term operation at high temperatures, the metal can catalyze and cause a chemical reaction. oxidation, generation of hydrochloric acid, corrosion of metals, and generation of sludge, which can cause refrigerator failure. The inventors of the present invention have conducted intensive studies on this polyether-based synthetic oil in order to solve the above-mentioned problems as a refrigerating machine oil, and as a result, they have found that a compound having an epoxycycloalkyl group is blended into the polyether-based synthetic oil. They discovered that this product has excellent chemical stability, and completed the present invention. In the present invention, 0.1 to 4% by weight of a compound having an epoxycycloalkyl group is added to polyether synthetic oil.
and, if necessary, a refrigerating machine oil composition containing 0.1 to 4% by weight of an aromatic antioxidant having 1 to 2 nitrogen atoms or 1 nitrogen atom and 1 sulfur atom in the molecule. It is. In the present invention, the polyether-based synthetic oil that serves as the base oil for the refrigeration oil is a compound obtained by adding a predetermined amount of alkylene oxide to a mono- to hexavalent alcohol, or a compound in which the terminal group of the above adduct is substituted, and the kinematic viscosity is 10~200cst (100℃) can be used. Examples of the above-mentioned polyether-based synthetic oils include polyoxypropylene glycol, polyoxyethylene glycol, polyoxy-1,2-butylene glycol, polyoxy-2,3-butylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene poly Oxytetramethylene glycol; and monomethyl ether, monoethyl ether, monobutyl ether, monooctyl ether, mono-2-ethylhexyl ether, monododecyl ether, monotetradecyl ether, monooctadecyl ether, monoallyl ether of the above polyoxyalkylene glycol, Monobenzyl ether, methylene glycol diether, 1,4-butanediol diether, glycerin triether, trimethylolpropane triether, pentaerythritol tetraether, sorbitan hexaether,
Ethers such as monobutyl monobenzyl ether, monobutyl monoallyl ether, diallyl ether, bisphenol-A-diether, di-2-ethylhexyl ether; monobutyl ether monocaprylic acid ester of the above polyoxyalkylene glycol, monobutyl ether monolauric acid Examples include ether esters such as esters. Examples of compounds having an epoxycycloalkyl group include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, vinylcyclohexene dioxide, 2
-(3,4-epoxycyclohexyl-5,5-
Spiro-3,4-epoxy)cyclohexane-meta-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, cyclohexene oxide, cyclooctene oxide, cyclopentadiene monooxide, 4-vinylcyclohexene-1,2-oxide, bis (methylcyclohexenyl) dioxide, dicyclopentadiene diepoxide, bis(2,3-epoxycyclopentyl)ether, bis(3,4 oxalate)
-epoxycyclohexylmethyl) ester,
4,10-dioxatetracyclo[5,4,O,
Examples include O ^3,5 , O ^9,11 ] undecane. Examples of aromatic antioxidants having 1 to 2 nitrogen atoms in the molecule include phenyl-α-naphthylamine, N-nitrosodiphenylamine, and 4-nitrosodiphenylamine.
aminodiphenylamine, N-isopropyl-
N'-phenyl-p-phenylenediamine, N,
N'-diphenyl-p-phenylenediamine, N,
N'-di-sec-butyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine, diphenylamine, dioctylphenylamine, etc., and nitrogen atoms and Examples of aromatic antioxidants each containing one sulfur atom include phenothiazine. Among these, aromatic amines having 1 to 2 nitrogen atoms in the molecule are preferred, and among these, phenyl-α-naphthylamine provides particularly good effects. The amounts of the two types of additives added to the polyether synthetic oil are 0.1 to 4% by weight of the compound having an epoxycycloalkyl group and 0.1 to 4% by weight of the aromatic antioxidant if necessary. If the amount is less than these, the desired effect cannot be obtained, and even if a large amount is blended, the effect will not increase significantly. Adding aromatic antioxidants will color the refrigerating machine oil composition, so it is not always necessary to use them.
When used in combination, metal corrosivity (especially copper) can be significantly improved. The refrigerating machine oil composition of the present invention has excellent chemical stability, does not cause a chemical reaction even when in contact with fluorocarbons and metals at high temperatures for a long time, and maintains excellent lubricating oil properties. The refrigerating machine oil composition of the present invention exhibits excellent effects when used in rotary refrigerators, more specifically screw type, rotary blade type, or rotary piston type refrigerators. The effectiveness of the composition of the present invention will be explained below using Examples and Comparative Examples. Example 1 A refrigerating machine oil composition (sample oil) prepared by blending additives with the base oil shown in Table 1 was subjected to a sealed tube test to evaluate its chemical stability at high temperatures. The base oil, additives, metal pieces, Freon (refrigerant), test container, and test method used here are as follows. Base oil (polyether-based synthetic oil) Synthetic oil polyoxypropylene (53) Monobutyl ether [The number in parentheses is the number of moles added] Kinematic viscosity 94.9cst (100℃) Synthetic oil polyoxyethylene (20) Polyoxy Tetramethylene (12) glycol Kinematic viscosity 68.4cst (100℃) Synthetic oil Polyoxypropylene (61) glycerol ether Kinematic viscosity 42.6cst (100℃) Additives Vinyl cyclohexene dioxide (A-), a compound with an epoxycycloalkyl group 1),
3,4-epoxycyclohexylmethyl-3,
4-epoxycyclohexanecarboxylate (A-2), bis(3,4-epoxycyclohexylmethyl)adipate (A-3), aromatic antioxidant phenyl-α-naphthylamine (B-1), N
- Nitrosodiphenylamine (B-2) Metal piece Material: steel, copper and aluminum Shape: 80 x 13 x 0.8 mm rectangular plate test piece. Freon (refrigerant) Freon R-12 (chemical formula CCl ₂ F ₂ ) Test container SUS-316 stainless steel autoclave (content 100ml) Test method (shielded tube test) Sample oil 25.0% in stainless steel autoclave
g, 25.0 g of fluorocarbons, and metal pieces such as steel, copper,
Take a total of three aluminum test pieces, seal them, and store them at a temperature of 175°C for 14 days (336°C).
time) heating was performed. 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. Further, the test pieces were washed with a solvent (toluene and ethanol), and then the weight change and appearance were observed. Test Results The test results are shown in Table 1. Refrigerating machine oil compositions 1 to 8 of the present invention all have a viscosity change rate of -15 to +
Within the range of 10%, no sludge was observed after the test, and no rust, copper plating, pitting, corrosion, etc. were observed on any of the test pieces.
It can be seen that chemical stability is excellent when CFCs coexist. Furthermore, in Compositions 7 and 8, in which aromatic antioxidants were used in combination, the weight change of metals (especially copper) was extremely small. Comparative Example For comparison, a shield tube test was conducted in the same manner as in Example 1 for the compositions (sample oils) shown in Table 2. The display symbols for the base oil and additives are the same as in Example 1. The test results are shown in Table 2. As shown by the results of Composition Ratio-1 and Ratio-2, both polyether-based synthetic oils without additives caused gelation after the test and were extremely corrosive to metal test pieces. Not suitable for use as refrigeration oil. In addition, when only aromatic antioxidants were blended with polyether synthetic oil, as shown by the results for composition ratios -3 to -4, improvements were observed compared to cases without additives, but still after the test. Stability is insufficient due to significant changes in sample oil viscosity, changes in appearance, and corrosion of metal test pieces.

【table】

【table】

[Table] Example 2 Using composition 1 shown in Table 1 of Example 1,
A 1000-hour actual test run was conducted using a small rotary refrigerator. Similar tests were also conducted on synthetic oil without additives as a comparative product. The results are shown in Table 3.

[Table] Composition 1 was able to maintain high airtightness until the end of the actual machine test run, and the sample oil viscosity did not show any significant change after the test. On the other hand, the comparative product showed good airtightness initially, but the airtightness deteriorated as the operating time progressed, and the viscosity of the sample oil after the test also decreased significantly.

Claims (1)

[Claims] 1. 0.1 to 4% by weight of a compound having an epoxycycloalkyl group in the molecule in polyether synthetic oil
and, if necessary, 0.1 to 4% by weight of an aromatic antioxidant having 1 to 2 nitrogen atoms or 1 nitrogen atom and 1 sulfur atom in the molecule. 2. Refrigerating machine oil composition according to claim 1, wherein the compound having an epoxycycloalkyl group is a compound having an epoxycyclohexyl group, and the aromatic antioxidant is an aromatic amine having 1 to 2 nitrogen atoms. thing. 3 A compound having an epoxycycloalkyl group is 3,4-epoxycyclohexylmethyl-3,4
-Epoxycyclohexane carboxylate, vinylcyclohexene dioxide, bis(3,4
-epoxycyclohexylmethyl)adipate,
or 2-(3,4-epoxycyclohexyl-
5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, and the aromatic antioxidant is phenyl-α-naphthylamine or N-
The refrigerating machine oil composition according to claim 1 or 2, which is nitrosodiphenylamine.