Refrigerating machine oil and working fluid composition

Abstract

The invention relates to the technical field of refrigerating machine oil products, in particular to refrigerating machine oil and a working fluid composition containing the refrigerating machine oil. The refrigerating machine oil comprises base oil, wherein the base oil comprises first polyol ester and second polyol ester; the first polyol ester is a composite ester synthesized by pentaerythritol and a first carboxylic acid mixture through an esterification reaction, and the first carboxylic acid mixture comprises at least one acid selected from C8-C9 monobasic fatty acids, C5 monobasic fatty acids and C4-C9 binary acids; the second polyol ester is a mixed ester synthesized from dipentaerythritol and a second carboxylic acid mixture through an esterification reaction, and the second carboxylic acid mixture comprises at least one of C8-C9 monobasic fatty acids and C5 monobasic fatty acids. The refrigerating machine oil and an R32 refrigerant can still be completely dissolved in each other at a low temperature, high working viscosity can be maintained after dissolution, the lubricating property and the stability are good, and the refrigerating machine oil can be applied to harsh compressor working conditions or low-temperature refrigerating environments.

Description

Technical Field

[0001] The present application relates to the technical field of refrigeration oil products, and in particular to a refrigeration oil, and also to a working fluid composition containing the refrigeration oil. Background Art

[0002] With the increasing environmental protection requirements, traditional hydrochlorofluorocarbon (HCFCs) refrigerants are being phased out at an accelerated pace, and hydrofluorocarbon (HFCs) refrigerants are about to be frozen to the baseline level. In the domestic market, HFCs are mainly used in household air conditioners, automotive air conditioners, industrial refrigeration and refrigeration maintenance industries. Among them, HFC-R32 refrigerant is becoming more and more mainstream in the refrigeration market due to its environmental protection and high efficiency. However, the refrigeration oil widely used in HFC refrigerants has poor solubility with R32. The poor solubility of refrigeration oil and refrigerant will cause a thicker oil film to form on the inner surface of the heat exchanger, which is likely to cause an increase in thermal resistance and affect the heat exchange effect; at the same time, the oil retained on the pipeline wall is also difficult to return to the compressor, resulting in a lack of oil in the moving friction pair of the compressor, poor lubrication, and reliability problems in the compressor.

[0003] For refrigeration systems, especially large refrigeration systems with long distances between evaporators and condensers, the compatibility of lubricating oil and refrigerant is very important for system oil return. However, existing mineral oils, alkylbenzenes, synthetic POE oils, etc. have poor compatibility with R32 refrigerant. Especially in compressors above 3HP or large refrigeration systems, as well as ultra-low temperature heating and relatively low evaporation temperature conditions, the compatibility of the refrigeration oil used in conjunction with R32 cannot meet the requirements of good mutual solubility. Therefore, the problem of poor compatibility between refrigeration oil and R32 has, to a certain extent, hindered its application in large-capacity refrigeration systems or can only meet some application scenarios. In order to avoid the occurrence of this phenomenon, it is of great significance to develop a refrigeration oil composition with better compatibility with R32 refrigerant.

[0004] On the other hand, in order to ensure that the refrigeration compressor can operate at high speed and reliability for a long time, the lubricity and stability of the refrigeration oil and the refrigerant also need to be improved. Among them, the lubricity of the refrigeration oil composition is also very important for the reliable operation of the compressor, which directly affects the refrigeration effect of the system. While the good mutual solubility of the refrigeration oil and the refrigerant is conducive to the oil return of the system, it will also bring about the problem of excessive dilution of the refrigeration oil by the refrigerant, thereby affecting the working viscosity and lubrication performance of the refrigeration oil. Therefore, the mutual solubility of the refrigeration oil needs to take into account the lubricity and stability of the refrigeration oil in order to better cope with the compatibility and application requirements of the refrigerant R32.

[0005] There are a series of technical solutions for synthetic ester refrigeration oils in the related art, which can solve the problem of poor compatibility with R32 refrigerant to a certain extent. However, there are still some shortcomings in taking into account the lubricity, compatibility and stability of synthetic esters. Summary of the invention

[0006] The technical problem to be solved by the present application is: to provide a refrigeration oil that has good low-temperature compatibility and appropriate solubility with HFCs refrigerants, especially R32 refrigerant, to ensure that the provided refrigeration oil can maintain a thicker oil film and good stability under harsh working conditions.

[0007] In order to achieve the above-mentioned purpose, according to the first aspect of the present technical solution, the present technical solution provides a refrigeration oil.

[0008] According to the refrigeration oil of the embodiment of the present application, the refrigeration oil includes a base oil, characterized in that the base oil includes a first polyol ester and a second polyol ester;

[0009] The first polyol ester is a complex ester synthesized by esterification reaction of pentaerythritol and a first carboxylic acid mixture, wherein the first carboxylic acid mixture includes at least one acid selected from monobasic fatty acids of C8-C9, monobasic fatty acids of C5, and dibasic acids of C4-C9;

[0010] The second polyol ester is a mixed ester synthesized by esterification reaction of dipentaerythritol and a second carboxylic acid mixture, wherein the second carboxylic acid mixture includes at least one acid of a C8-C9 monobasic fatty acid and a C5 monobasic fatty acid.

[0011] Furthermore, the C4-C9 dibasic acid is selected from succinic acid, adipic acid and suberic acid.

[0012] Furthermore, the C5 monobasic fatty acid is selected from n-valeric acid, 2-methylbutyric acid and 3-methylbutyric acid.

[0013] Further, the C8-C9 monobasic fatty acid is selected from octanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, nonanoic acid, 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic acid, 4-ethylheptanoic acid, 2,3,4-trimethylhexanoic acid, 3,4,5-trimethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

[0014] Furthermore, the molar ratio of the pentaerythritol to the dipentaerythritol is (1-9):1.

[0015] Furthermore, the kinematic viscosity of the refrigeration oil at 40°C is 44-200 mm 2 / s, kinematic viscosity at 100℃ is 6.0mm 2 / s or more.

[0016] Furthermore, the refrigeration oil also includes an additive, and the additive includes at least one of an anti-wear agent, an antioxidant, an anti-foaming agent and an acid scavenger.

[0017] Furthermore, the first polyol ester comprises at least one of the structural units represented by formula [I],

[0018]

[0019] Wherein R1-R6 are each independently a C4-C8 hydrocarbon group or 7≥m≥2.

[0020] In order to achieve the above-mentioned purpose, according to the second aspect of the present technical solution, the present technical solution provides a working fluid composition, which includes the refrigeration oil provided by the first aspect of the present technical solution and R32 refrigerant.

[0021] Furthermore, the low-temperature two-phase separation temperature of the refrigeration oil and the R32 refrigerant is not higher than -20°C.

[0022] Furthermore, the dissolution viscosity of the working fluid composition for a refrigerator at 110° C. and 4.2 MPa is not less than 2.0 cp.

[0023] The embodiments of the present application have the following beneficial effects: the refrigeration oil forms a polyol ester refrigeration oil of a specific combination by controlling the raw material ratio of polyols, dibasic acids and fatty acids, and can obtain a refrigeration working extract composition that is still completely miscible with R32 refrigerant at a lower temperature; by controlling the feed ratio of fatty acids and dibasic acids of a specific structure for synthesis, a refrigeration oil that can maintain a higher dissolution viscosity after dissolution can be obtained, thereby ensuring that the working fluid composition has sufficient oil film strength. Compared with existing refrigeration oils, the refrigeration oil of the present invention can still be completely miscible with R32 refrigerant at a lower temperature, and can maintain a higher working viscosity after dissolution, and has good lubricity and stability, so that its product can be used in more demanding compressor conditions or lower temperature refrigeration environments. DETAILED DESCRIPTION

[0024] Hereinafter, preferred embodiments of the present application will be described in detail.

[0025] The refrigeration oil provided by the present application comprises a base oil and a suitable additive, wherein the additive comprises at least one of an anti-wear agent, an antioxidant, an anti-foaming agent and an acid scavenger. Preferably, the main components of the refrigeration oil may include:

[0026]

[0027] There is no specific restriction on the types of additives for the refrigeration oil in the present application. Antioxidants may be selected from hindered phenols, diarylamines, phenothiazines, organic sulfonates, etc.; acid scavengers may be selected from glycidyl ester epoxy compounds, glycidyl ether epoxy compounds and phenyl glycidyl ether, etc.; antiwear agents may be selected from alkyl phosphates and alkyl phosphates, dialkyl dithiophosphates and phosphates, etc.; antifoaming agents may be selected from silicon-containing polydimethylsiloxanes or other non-silicon polyacrylates, etc.

[0028] The base oil of the refrigeration oil includes a first polyol ester and a second polyol ester. The first polyol ester is a complex ester synthesized by esterification reaction of pentaerythritol and a first carboxylic acid mixture, the first carboxylic acid mixture includes at least one acid selected from monobasic fatty acids of C8-C9, monobasic fatty acids of C5, and dibasic acids of C4-C9; the second polyol ester is a mixed ester synthesized by esterification reaction of dipentaerythritol and a second carboxylic acid mixture, the second carboxylic acid mixture includes at least one acid of monobasic fatty acids of C8-C9 and monobasic fatty acids of C5.

[0029] In refrigeration oil, the dibasic acid of C4-C9 accounts for 2 mol%-20 mol% of the total amount of the first carboxylic acid mixture, preferably the dibasic acid of C4-C9 accounts for 3 mol%-15 mol% of the total amount of the first carboxylic acid mixture, and more preferably the dibasic acid of C4-C9 accounts for 5 mol%-10 mol% of the first carboxylic acid mixture.

[0030] The C5 monobasic fatty acid in the second carboxylic acid mixture is preferably n-valeric acid, which accounts for more than 25 mol% of the total amount of the second carboxylic acid mixture, and more preferably, n-valeric acid accounts for 75 mol%-95 mol% of the total amount of the second carboxylic acid mixture.

[0031] In the base oil raw material of refrigeration oil, dipentaerythritol accounts for 10mol%-50mol% of the total amount of organic alcohol raw material, preferably 15mol%-45mol% of the total amount of organic alcohol raw material, and more preferably 20mol%-40mol% of the total amount of organic alcohol raw material.

[0032] Optionally, in view of obtaining the structural stability of the first polyol ester, the C4-C9 dibasic acid is selected from succinic acid, adipic acid and suberic acid, more preferably adipic acid.

[0033] Optionally, the C5 monobasic fatty acid is selected from n-valeric acid, 2-methylbutyric acid and 3-methylbutyric acid. In terms of compatibility, the C5 monobasic fatty acid is preferably 2-methylbutyric acid or 3-methylbutyric acid, which have better performance.

[0034] Optionally, the C8-C9 monobasic fatty acid is selected from octanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 2-ethylhexanoic acid, nonanoic acid, 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic acid, 4-ethylheptanoic acid, 2,3,4-trimethylhexanoic acid, 3,4,5-trimethylhexanoic acid, 3,5,5-trimethylhexanoic acid. 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid, which have better stability, are preferred.

[0035] Optionally, the molar ratio of the pentaerythritol to the dipentaerythritol is (1-9):1.

[0036] Optionally, the kinematic viscosity of the refrigeration oil at 40°C is 44-200 mm 2 / s, kinematic viscosity at 100℃ is 6.0mm 2 / s or more.

[0037] In some embodiments, the first polyol ester comprises at least one of the structural units represented by formula [I],

[0038]

[0039] Wherein R1-R6 are each independently a C4-C8 hydrocarbon group or 7≥m≥2.

[0040] The refrigeration oil provided in the embodiment of the present application can be mixed with R32 refrigerant to form a working fluid composition for a refrigerator. The low-temperature two-phase separation temperature of the refrigeration oil and the R32 refrigerant is not higher than -20°C. At the same time, the dissolution viscosity of the working fluid composition for a refrigerator at 110°C and 4.2MPa is not less than 2.0cp.

[0041] The refrigeration oil provided by the embodiment of the present invention forms a composite ester refrigeration oil of a specific combination by controlling the raw material ratio of polyols, dibasic acids and fatty acids, and can obtain a refrigeration working extract composition that is still completely miscible with R32 refrigerant at a lower temperature; by controlling the feed ratio of fatty acids and dibasic acids of a specific structure for synthesis, a refrigeration oil that can maintain a higher dissolution viscosity after dissolution can be obtained, thereby ensuring that the working fluid composition has sufficient oil film strength. Compared with existing refrigeration oils, the refrigeration oil of the present invention can still be completely miscible with R32 refrigerant at a lower temperature, and can maintain a higher working viscosity after dissolution, and has good lubricity and stability, so that its product can be used in more demanding compressor working conditions or lower temperature refrigeration environments.

[0042] Hereinafter, the present application will be described in more detail through preferred embodiments and comparative examples, but the present application is not limited to the following embodiments.

[0043] In each embodiment and comparative example, under necessary catalyst conditions, the esterification reaction was carried out according to the raw material ratio of hydroxycarboxyl substances being 1:1.1 to obtain the corresponding components, so as to achieve sufficient esterification reaction. Wherein (A-1)-(A-18) is the first polyol ester, and (B-1)-(B-8) is the second polyol ester.

[0044]

First polyol ester

[0045] (A-1) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 3:80:17.

[0046] The viscosity at 40°C is 61.25 mm 2 / s, kinematic viscosity at 100°C 7.964mm 2 / s, viscosity index 95.

[0047] (A-2) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 3-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 3:85:12.

[0048] The viscosity at 40°C is 58.78 mm 2 / s, kinematic viscosity at 100°C 7.709mm 2 / s, viscosity index 93.

[0049] (A-3) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 5:45:50.

[0050] The viscosity at 40°C is 69.91 mm 2 / s, kinematic viscosity at 100°C 8.672mm 2 / s, viscosity index 95.

[0051] (A-4) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 5:50:45.

[0052] The viscosity at 40°C is 45.86 mm 2 / s, kinematic viscosity at 100°C 6.625mm 2 / s, viscosity index 94).

[0053] (A-5) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 5:65:30.

[0054] The viscosity at 40°C is 42.29 mm 2 / s, kinematic viscosity at 100°C 42.29mm 2 / s, viscosity index 92.

[0055] (A-6) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 5:75:20.

[0056] The viscosity at 40°C is 49.79 mm 2 / s, kinematic viscosity at 100°C 6.869mm 2 / s, viscosity index 91.

[0057] (A-7) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 5:75:20.

[0058] The viscosity at 40°C is 41.68 mm 2 / s, kinematic viscosity at 100°C 6.133 mm 2 / s, viscosity index 90.

[0059] (A-8) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 5:85:10.

[0060] The viscosity at 40°C is 43.16 mm 2 / s, kinematic viscosity at 100°C 43.16 mm 2 / s, viscosity index 98.

[0061] (A-9) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 10:70:20.

[0062] The viscosity at 40°C is 61.72 mm 2 / s, kinematic viscosity at 100°C 8.237mm 2 / s, viscosity index 103.

[0063] (A-10) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 10:75:15.

[0064] The viscosity at 40°C is 52.67 mm 2 / s, kinematic viscosity at 100°C 7.426mm 2 / s, viscosity index 102.

[0065] (A-11) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 12:65:23.

[0066] The viscosity at 40°C is 75.84 mm 2 / s, kinematic viscosity at 100°C 9.568mm 2 / s, viscosity index 104.

[0067] (A-12) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 12:70:18.

[0068] The viscosity at 40°C is 73.47 mm 2 / s, kinematic viscosity at 100°C 9.279mm 2 / s, viscosity index 102.

[0069] (A-13) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 15:80:5.

[0070] The viscosity at 40°C is 77.16 mm 2 / s, kinematic viscosity at 100°C 9.737mm 2 / s, viscosity index 105.

[0071] (A-14) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 15:80:5.

[0072] The viscosity at 40°C is 64.80 mm 2 / s, kinematic viscosity at 100°C 8.601mm 2 / s, viscosity index 104.

[0073] (A-15) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 2:50:48.

[0074] The viscosity at 40°C is 64.71 mm 2 / s, kinematic viscosity at 100°C 7.973mm 2 / s, viscosity index 86.

[0075] (A-16) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 20:75:5.

[0076] The viscosity at 40°C is 108.28 mm 2 / s, kinematic viscosity at 100°C 12.79mm 2 / s, viscosity index 112.

[0077] (A-17) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 15:40:45.

[0078] The viscosity at 40°C is 95.94 mm 2 / s, kinematic viscosity at 100°C 11.58mm 2 / s, viscosity index 109.

[0079] (A-18) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 2:88:10.

[0080] The viscosity at 40°C is 31.07 mm 2 / s, kinematic viscosity at 100°C 5.077mm 2 / s, viscosity index 85.

[0081]

Second polyol ester

[0082] (B-1) An ester obtained by esterification of dipentaerythritol with a mixed acid of n-pentanoic acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 75:25.

[0083] The viscosity at 40°C is 78.58 mm 2 / s, kinematic viscosity at 100°C 10.78 mm 2 / s, viscosity index 124.

[0084] (B-2) An ester obtained by esterification of dipentaerythritol with a mixed acid of n-pentanoic acid and 3,5,5-trimethylhexanoic acid having a carboxyl molar ratio of 85:15.

[0085] The viscosity at 40°C is 82.99 mm 2 / s, kinematic viscosity at 100°C 11.28mm 2 / s, viscosity index 125.

[0086] (B-3) An ester obtained by esterification of dipentaerythritol with a mixed acid of n-pentanoic acid and 2-ethylhexanoic acid having a carboxyl molar ratio of 95:5.

[0087] The viscosity at 40°C is 64.17 mm 2 / s, kinematic viscosity at 100°C 9.594mm 2 / s, viscosity index 131.

[0088] (B-4) An ester obtained by esterification of dipentaerythritol with a mixed acid of n-pentanoic acid and 3,5,5-trimethylhexanoic acid having a carboxyl molar ratio of 95:5.

[0089] The viscosity at 40°C is 63.59 mm 2 / s, kinematic viscosity at 100°C 9.475mm 2 / s, viscosity index 129.

[0090] (B-5) An ester obtained by esterification of dipentaerythritol with a mixed acid of n-pentanoic acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 35:65.

[0091] The viscosity at 40°C is 117.85 mm 2 / s, kinematic viscosity at 100°C 13.09mm 2 / s, viscosity index 105.

[0092] (B-6) An ester obtained by esterification of dipentaerythritol with a mixed acid of n-pentanoic acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 25:75.

[0093] The viscosity at 40°C is 284.35 mm 2 / s, kinematic viscosity at 100°C 20.17 mm 2 / s, viscosity index 81.

[0094] (B-7) An ester obtained by esterification of dipentaerythritol with a mixed acid of 2-methylbutyric acid and 3,5,5-trimethylhexanoic acid in a carboxyl molar ratio of 45:55.

[0095] The viscosity at 40°C is 172.57 mm 2 / s, kinematic viscosity at 100°C 15.73mm 2 / s, viscosity index 93.

[0096] (B-8) An ester obtained by esterification of dipentaerythritol with a mixed acid of 3-methylbutyric acid and 2-ethylhexanoic acid in a carboxyl molar ratio of 55:45.

[0097] The viscosity at 40°C is 123.64 mm2 / s, kinematic viscosity at 100°C 13.09mm 2 / s, viscosity index 99.

[0098] The first polyol ester and the second polyol ester were mixed at a molar ratio of 9:1 to obtain Examples 1-8 and Comparative Examples 9-24, i.e., the molar ratio of pentaerythritol to dipentaerythritol was 9:1; the first polyol ester and the second polyol ester were mixed at a molar ratio of 1:1 to obtain Examples 9-16 and Comparative Examples 1-8, i.e., the molar ratio of pentaerythritol to dipentaerythritol was 1:1. The types and specific compositions of the first polyol ester and the second polyol ester selected in each Example and Comparative Example are shown in Tables 1 to 5.

[0099] Table 1

[0100]

[0101] Table 2

[0102]

[0103] Table 3

[0104]

[0105] Table 4

[0106]

[0107] Table 5

[0108]

[0109] Refer to "SH / T 0699-2000 Refrigeration Oil and Refrigerant Compatibility Test Method": a certain mass of test oil and refrigerant are filled into a test tube, heated at room temperature or in a water bath to make the test oil and refrigerant a uniform, transparent solution, then cool the test tube in a cold bath, test the refrigeration oil and refrigerant mixture with an oil content of 5%-50% and slowly cool from 45°C to -40°C, and take the temperature at which the mixture produces phase separation or white turbidity as the two-phase separation temperature under the oil content; draw a two-phase separation curve with the two-phase separation temperature data of different oil contents, and the highest measured temperature on the curve is the two-phase separation temperature of the test oil and refrigerant. The lower the two-phase separation temperature, the better the compatibility of the refrigeration oil and refrigerant. It should be noted that "immiscible" means that no two-phase separation is observed in the test temperature range of this test and the turbidity is always present, that is, two-phase separation or turbidity occurs when the refrigeration oil is at room temperature 25°C. The refrigerant used in the test is R32.

[0110] Refer to "SH / T 0699-2000 Refrigeration Oil and Refrigerant Compatibility Test Method": Fill a certain mass of test oil and refrigerant into an explosion-proof autoclave, connect the online viscometer and related accessories and ensure sealing, and use a vacuum pump to evacuate the autoclave. The initial temperature of the heater is set to 30°C, and the mixed viscosity under certain temperature and pressure conditions is measured, with a temperature gradient interval of 10°C. The pressure in the autoclave controls the refrigerant content by switching the valve, and the platinum resistance pressure sensor and temperature sensor and accessories are connected at the same time, and the temperature and pressure are monitored in real time. After the temperature in the autoclave is constant, observe and record the pressure in the autoclave every 10 minutes. The online viscometer can directly read the viscosity of the mixed solution, which is the dissolution viscosity (dynamic viscosity) under specific conditions. The smaller the dissolution viscosity, the lower the lubricating oil film strength of the composition composed of the refrigeration oil and the refrigerant, and the poorer the anti-wear lubrication performance; the larger the dissolution viscosity, the higher the lubricating oil film strength of the composition composed of the refrigeration oil and the refrigerant, and the better the anti-wear lubrication performance. The refrigerant used in the test is R32.

[0111] A primary purpose of the refrigerator oil implemented by the present invention is to be applicable to low temperature or extremely low temperature working conditions, so the low temperature fluidity of the refrigerator oil needs to be considered. It is found from Tables 1 to 5 that the structural form of the monobasic fatty acid of C5 in the second polyol ester has a direct impact on the low temperature fluidity of the refrigerator oil. When the selected second polyol ester contains a monobasic fatty acid of C5 with a branch, such as Comparative Examples 17-24, the pour point index of the refrigerator oil in Table 5 is in a higher range of -32°C to -1°C, and the low temperature fluidity of the refrigerator oil is poor. When n-pentanoic acid is selected to replace the branched C5 fatty acid in the selected second polyol ester, such as Examples 1-16 and Comparative Examples 1-16, the pour point index of the refrigerator oil in Table 1-4 is in a lower range than Comparative Examples 17-24, and the low temperature fluidity of the refrigerator oil is good. Therefore, n-pentanoic acid is preferably used in the second carboxylic acid mixture of the raw material of the second polyol ester, rather than the branched C5 fatty acid.

[0112] By comparing the examples and comparative examples in Tables 1-4, it is found that the compatibility of refrigeration oil with refrigerant is affected by the amount of dibasic acid in the first carboxylic acid mixture and the double influence of n-pentanoic acid in the second carboxylic acid mixture. When the proportion of adipic acid in the total amount of the first carboxylic acid ring mixture reaches or exceeds 15 mol%, it is easy to make the refrigeration oil and R32 refrigerant incompatible or poorly miscible, such as Comparative Examples 4-7 and Comparative Examples 15-16; especially when the proportion of adipic acid in the total amount of the first carboxylic acid ring mixture reaches or exceeds 20 mol%, the compatibility of the synthesized refrigeration oil with R32 refrigerant is worse. It can also be found through experimental data that the greater the proportion of n-pentanoic acid in the total amount of the second carboxylic acid ring mixture, the more favorable the compatibility of refrigeration oil with R32 refrigerant. When the proportion of n-pentanoic acid in the total amount of the second carboxylic acid ring mixture is less than or equal to 35 mol%, the compatibility of refrigeration oil with R32 refrigerant is poor, such as Comparative Examples 2, Comparative Example 3, Comparative Example 5, Comparative Example 7, Comparative Examples 13-16. And by increasing the proportion of n-pentanoic acid in the total amount of the second carboxylic acid ring mixture, the problem of poor compatibility between the refrigeration oil and the R32 refrigerant caused by the excessive proportion of adipic acid in the total amount of the first carboxylic acid ring mixture can be compensated. Specifically, reference can be made to Example 13 and Example 14. Although the proportion of adipic acid in the total amount of the first carboxylic acid ring mixture reached 15 mol%, the proportion of n-pentanoic acid in the total amount of the second carboxylic acid ring mixture reached 95 mol% and 85 mol%, respectively, and the proportion of the second polyol ester reached 50 mol% of the total amount of the first polyol ester and the second polyol ester. The overall proportion of n-pentanoic acid will be relatively high, so that the compatibility of the obtained refrigeration oil with the R32 refrigerant is still maintained at a good level. Therefore, in order to improve the index of the working fluid composed of the base oil and the refrigerant, the amount of adipic acid and n-pentanoic acid should be limited here to balance their dissolution viscosity and compatibility.

[0113] According to the petrochemical industry standard SH / T 0189-92 "Determination of anti-wear performance of lubricating oil", the anti-wear performance of the oil product was determined, and the anti-wear performance was evaluated by comparing the size of the average wear spot diameter. As shown in Table 1, there is no obvious difference in the compatibility between the oil products of Examples 1-5 and R32 refrigerant, and as the amount of C5 monobasic fatty acid in the base oil component decreases, the average wear spot diameter of the oil product also decreases accordingly. In addition, when the oil product is well compatible with the R32 refrigerant, as shown in the results of the comparative examples 9-12 in Table 4, as the proportion of the raw acid of n-pentanoic acid in the base oil increases, its compatibility is also "improved", but the solubility viscosity of the base oil and R32 refrigerant is adversely affected under the conditions of 110°C and 4.2MPa, and its anti-wear lubrication effect is significantly deteriorated. The experimental results of Example 9 and Comparative Example 1 also show that the addition of dipentaerythritol mixed ester plays a key role in the balance between the lubrication effect and compatibility of the oil product. Of course, in order to obtain better anti-wear and lubrication effects, necessary anti-wear additives may also be added to the refrigeration oil.

[0114] It can be seen from the test data in Table 1-2 that under the actual operating conditions of the compressor at 110°C and 4.2MPa, the dissolving viscosity is above 2.0cp, which can ensure that there is a sufficiently thick oil film between the friction pairs of the compressor pump body parts, thereby improving the wear resistance of the working fluid composition and improving the operating reliability of the compressor. Therefore, the refrigeration oil takes into account low-temperature compatibility, lubricity and high-temperature stability.

[0115] Some embodiments in this specification are described in a progressive or parallel manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other.

[0116] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A refrigeration oil, comprising a base oil, characterized in that: The base oil includes a first polyol ester and a second polyol ester; The first polyol ester is a complex ester synthesized by esterification reaction of pentaerythritol and a first carboxylic acid mixture, wherein the first carboxylic acid mixture includes at least one acid selected from monobasic fatty acids of C8-C9, monobasic fatty acids of C5, and dibasic acids of C4-C9; The second polyol ester is a mixed ester synthesized by esterification reaction of dipentaerythritol and a second carboxylic acid mixture, wherein the second carboxylic acid mixture includes at least one acid of a C8-C9 monobasic fatty acid and a C5 monobasic fatty acid.

2. The refrigerating machine oil according to claim 1, characterized in that The C4-C9 dibasic acid is selected from succinic acid, adipic acid and suberic acid.

3. The refrigerating machine oil according to claim 1, characterized in that The C5 monobasic fatty acid is selected from n-valeric acid, 2-methylbutyric acid and 3-methylbutyric acid.

4. The refrigerating machine oil according to claim 1, characterized in that The C8-C9 monobasic fatty acid is selected from octanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, nonanoic acid, 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic acid, 4-ethylheptanoic acid, 2,3,4-trimethylhexanoic acid, 3,4,5-trimethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

5. The refrigerating machine oil according to claim 1, characterized in that The molar ratio of the pentaerythritol to the dipentaerythritol is (1-9):

1.

6. The refrigerating machine oil according to claim 1, characterized in that The kinematic viscosity of the refrigeration oil at 40°C is 44-200 mm 2 / s, kinematic viscosity at 100℃ is 6.0mm 2 / s or more.

7. The refrigerating machine oil according to claim 1, characterized in that The invention also comprises additives, wherein the additives include at least one of an anti-wear agent, an antioxidant, an anti-foaming agent and an acid scavenger.

8. The refrigerating machine oil according to claim 1, characterized in that The first polyol ester comprises at least one of the structural units represented by formula [I], Wherein R1-R6 are each independently a C4-C8 hydrocarbon group or 7≥m≥2.

9. A working fluid composition for a refrigerator, characterized in that: The method comprises the refrigeration oil as described in any one of claims 1 to 8 and R32 refrigerant.

10. The working fluid composition for refrigerator according to claim 9, characterized in that: The low-temperature two-phase separation temperature of the refrigeration oil and the R32 refrigerant is not higher than -20°C.

11. The working fluid composition for refrigerator according to claim 9, characterized in that: The working fluid composition for a refrigerator has a dissolution viscosity of not less than 2.0 cp at 110° C. and 4.2 MPa.

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