REFRIGERATOR OIL AND REFRIGERATOR WORKING FLUID COMPOSITION

Abstract

One aspect of the present invention is a refrigerating machine oil comprising a base oil, a dithiophosphoric acid ester, and an amine salt of an acidic phosphoric acid ester.

Claims

1. A refrigerating machine oil comprising: a base oil; a dithiophosphoric acid ester; and an amine salt of acidic phosphoric acid ester.

2. The refrigerating machine oil according to claim 1, wherein the dithiophosphoric acid ester is a compound represented by the following formula (A-1): ##STR00019## wherein R.sup.1 and R.sup.2 each independently represent hydrogen atom or a monovalent hydrocarbon group, R.sup.3 represents a monovalent organic group, and at least one of R.sup.1 and R.sup.2 represents a monovalent hydrocarbon group.

3. The refrigerating machine oil according to claim 1, wherein a mass ratio of the content of the dithiophosphoric acid ester to the total content of the dithiophosphoric acid ester and the amine salt of acidic phosphoric acid ester is 0.1 or more and 0.9 or less.

4. The refrigerating machine oil according to claim 1, wherein the refrigerating machine oil has a sulfur content of 0.2% by mass or less.

5. The refrigerating machine oil according to claim 1, wherein the refrigerating machine oil is used with a refrigerant comprising a hydrofluorocarbon refrigerant.

6. A working fluid composition for a refrigerating machine, comprising: the refrigerating machine oil according to claim 1; and a refrigerant.

7. The working fluid composition for a refrigerating machine according to claim 6, wherein the refrigerant comprises a hydrofluorocarbon refrigerant.

Description

EXAMPLES

[0131] The present invention will be described in more detail with reference to Examples below, but the present invention shall not be limited to these Examples.

Example 1

[0132] A refrigerating machine oil was prepared by mixing a base oil, a dithiophosphoric acid ester, and an amine salt of acidic phosphoric acid ester shown below with 1.7% by mass of other additives (including triphenyl phosphorothionate (thiophosphoric acid triester), an acid scavenger, and an antioxidant). The types and contents of the dithiophosphoric acid esters and the amine salts of acidic phosphoric acid ester are as shown in Table 1, and the content of the base oil is the remainder obtained by subtracting the total content of components (additives) other than the base oil from the total amount of the refrigerating machine oil. The content of each component is based on the total amount of the refrigerating machine oil (% by mass). Table I shows the mass ratio (A/(A+B)) of the content of the dithiophosphoric acid ester (A) to the total content of the dithiophosphoric acid ester and the amine salt of acidic phosphoric acid ester (A+B), and the sulfur content (% by mass) in the refrigerating machine oil.

[0133] Base oil: mixture of the following base oil 1 (70% by mass) and base oil 2 (30% by mass)

[0134] Base oil 1: polyol ester of pentaerythritol and mixed fatty acid of 2-methylpropanoic acid/3,5,5-tritnethylhexanoic acid (mixture ratio (mass ratio): 60/40) (40° C. kinematic viscosity: 46 mm.sup.2/s, 100° C. kinematic viscosity: 6.3 mrn.sup.2/s)

[0135] Base oil 2: complex ester obtained by reacting neopentyl glycol (1 mol) and 1,4-butanediol (0.2 mol) with adipic acid (1.5 mol) to obtain an ester intermediate, then further reacting the ester intermediate with 3,5,5-trimethylhexanol (1.1 mol) and removing the remaining unreacted substance by distillation (40° C. kinematic viscosity: 146 mm.sup.2/s, viscosity index: 140)

[0136] Dithiophosphoric acid ester A1: compound represented by the following formula (A1):

##STR00017##

[0137] Dithiophosphoric acid ester A2: compound represented by the following formula (A2):

##STR00018##

[0138] Amine Salt of Acidic Phosphoric Acid Ester B1

[0139] C11-14 branched alkyl amine salt of mono-/di-hexyl phosphoric acid ester (salts of acidic phosphoric acid esters (mixture) in which R.sup.11 is linear alkyl group having 6 carbon atoms (hexyl group) and n is 1 or 2 in the above formula (B-1) and amines (mixture) in which two of R.sup.12, R.sup.13 and R.sup.14 are any of C11-14 branched alkyl groups and the other one is hydrogen atom in the above formula (B-2))

[0140] Amine Salt of Acidic Phosphoric Acid Ester B2

[0141] 2-ethylhexyl amine salt of mono-ldi- oleyl phosphoric acid ester (salts of acidic phosphoric acid esters (mixture) in which R.sup.11 is unsaturated alkyl group having 18 carbon atoms (oleyl group) and n is 1 or 2 in the above formula (B-1) and amine in which one of R.sup.12, R.sup.13 and R.sup.14 is 2-ethylhexyl group and the other two is hydrogen atom in the above formula

Examples 2 to 5 and Comparative Examples 1 and 2

[0142] Refrigerating machine oils were prepared in the same manner as in Example 1, except that the types and contents of the dithiophosphoric acid esters and the amine salts of acidic phosphoric acid ester were changed as shown in Table 1.

[0143] [Evaluation of Antiwear Property]

[0144] The antiwear property was evaluated by the following procedure. First, a friction testing apparatus using a vane (SKH-51) as an upper test piece and a disk (SNCM220 HRC50) as a lower test piece was mounted inside a sealed container. 600 g of each refrigerating machine oil was introduced to the friction test site, and inside of the system was degassed under vacuum. Then, 100 g of a refrigerant (difluoromethane (R32)) was introduced into the system, and the system was heated. After the temperature in the sealed container was set to 110° C., a wear test was performed under the conditions of a load of 1000 N and a rotation speed of 750 rpm, and the wear amounts of the vane and the disk were measured after the test for 60 minutes. Smaller value of the wear amount means better antiwear property. The results are shown in Table 1.

[0145] Evaluation of Stability

[0146] The stability was evaluated in accordance with ES K2211-09 (autoclave test). Specifically, 30 g of the refrigerating machine oil having a moisture content adjusted to 1000 ppm was weighed in an autoclave, catalysts (iron, copper or aluminum wire, each having an outer diameter of 1.6 mm and a length of 50 mm) and 30 g of refrigerant (difluoromethane (R32)) were sealed in the autoclave, the autoclave was heated to 175° C., and the acid value (JIS 02101) of the refrigerating machine oil after 168 hours was measured. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Example Comparative Comparative Example Example Example Example 1 Example 1 Example 2 2 3 4 5 Content Dithiophosphoric A1 0.03 0.03 — 0.03 0.05 — 0.03 (% by mass) acid ester A2 — — — — — 0.3 — Amine salt of B1 0.06 — 0.06 0.03 0.03 0.06 — acidic phosphoric B2 — — — — — — 0.06 acid ester A/(A + B) 0.33 1 0 0.5 0.625 0.83 0.33 Sulfur content (% by mass) 0.05 0.05 0.05 0.05 0.06 0.07 0.05 Antiwear Wear amount of vane (μm) 0.8 3.0 1.9 1.1 1.3 1.5 0.85 property Wear amount of disk (μm) 0.07 0.37 1.1 0.10 0.33 0.31 0.07 Stability Acid value (mgOH/g) 0.41 0.53 0.54 0.41 0.26 0.38 0.43

[0147] As can be seen from Table 1, Examples 1 to 5 in which the dithiophosphoric acid ester and the amine salt of acidic phosphoric acid ester were used in combination as a phosphorus-based antiwear agents were superior in antiwear property and stability to Comparative Examples 1 and 2 in which only one of them was used. It is a particularly surprising effect that the stability is improved by the combined use of the dithiophosphoric acid ester and the amine salt of acidic phosphoric acid ester, which are known as phosphorus-based antiwear agents.