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 C7-C8 monobasic fatty acids, C5 monobasic fatty acids and C4-C9 binary acids; the second polyol ester is a composite ester synthesized from dipentaerythritol and a mixture of dipentaerythritol and second carboxylic acid through an esterification reaction, and the second carboxylic acid mixture comprises C4-C9 binary acid and C5 monobasic fatty acid. The refrigerating machine oil provided by the invention has low solubility with an R290 refrigerant, has high working viscosity after being maintained to be dissolved, has good lubricity and stability, and improves the safety and reliability of an R290 refrigerating system.

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 at the baseline level. The relevant regulations passed in 2016 added 18 hydrofluorocarbon (HFC) refrigerants as controlled substances and gave a timetable for the gradual reduction of HFCs to cope with increasingly prominent environmental problems. my country will reduce the use of HFCs, including R32 and R134a, year by year starting from 2029. According to the current refrigerant replacement policies and trends, safe, efficient, green and environmentally friendly refrigerants, especially natural refrigerants, may become the final choice for alternative refrigerants. As an environmentally friendly refrigerant, natural working fluid propane (R290) has extremely low global warming potential (GWP=3) and ozone depletion potential (ODP=0), and its critical temperature, boiling point, pressure and freezing point are close to those of R22. It shows more significant advantages than R22 in terms of latent heat of vaporization, dynamic viscosity, solubility, heat transfer characteristics and system energy efficiency, and is currently a traditional refrigerant substitute with great development potential.

[0003] However, R290 is a gaseous flammable substance at room temperature and pressure, and its safety level is A3. Its charge amount is strictly limited when used in household air conditioners and heat pump products. In the refrigeration system, part of the refrigerant remains in the pipes and heat exchangers, but a considerable part of the refrigerant is dissolved in the refrigeration oil in the oil pool or the liquid distributor. Therefore, by reducing the mutual solubility of the refrigerant in the refrigeration oil and reducing its charge amount, the safety of the R290 system can be improved.

[0004] On the other hand, although the good mutual solubility between refrigeration oil and refrigerant is beneficial to the oil return of the system, too much refrigerant dissolved in refrigeration oil will lead to a decrease in oil dissolution viscosity, high oil discharge, and even cause problems to the stability of the refrigeration system and the reliability of the compressor. R290 is a short-chain alkane and a weakly polar compound. The molecular structure of traditional mineral oil (MO) and alkylbenzene oil (AB) is similar to that of R290 and has a large solubility. The lubrication performance of mineral refrigeration oil may be reduced when it is directly used in the R290 refrigeration system. Due to its good solubility, the amount of oil brought into the refrigeration system circuit will also increase, and the heat transfer efficiency and operating stability of the system will be affected. It can be seen that in order to improve the safety of the R290 refrigerant system and the reliability of the compressor, it is necessary to reduce the solubility of R290 and refrigeration oil.

[0005] There are some solutions in the related art to improve the solubility of refrigeration oil and R290, which can solve the problem of compatibility with R290 to a certain extent. However, its base oil contains more or less unsaturated fatty acids, which is still insufficient in terms of lubricity, compatibility and stability of refrigeration oil working fluid. Summary of the invention

[0006] The technical problem to be solved by the present application is to provide a refrigeration oil that has a low solubility with HFCs refrigerants, especially with R290 refrigerant, and can maintain a thicker oil film under harsh working conditions to improve the safety and stability of the system.

[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] The refrigeration oil according to an embodiment of the present application includes a base oil, wherein 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 C7-C8, monobasic fatty acids of C5, and dibasic acids of C4-C9;

[0010] The second polyol ester is dipentaerythritol and a complex ester synthesized by esterification of dipentaerythritol and a second carboxylic acid mixture, wherein the second carboxylic acid mixture includes a C4-C9 dibasic 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] Furthermore, the C7-C8 monobasic fatty acid is selected from octanoic acid, heptanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 2-methylhexanoic acid, and 3-methylhexanoic acid.

[0014] Furthermore, the molar ratio of pentaerythritol in the raw material of the first polyol ester to the total amount of pentaerythritol and dipentaerythritol in the raw material of the second polyol ester is (1-9):1.

[0015] Furthermore, the kinematic viscosity of the refrigeration oil at 40°C is 33-120 mm 2 / s, kinematic viscosity at 100℃ is 5.2mm 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 includes at least one of the structural units represented by formula [I], and the second polyol ester includes at least one of the structural units represented by formula [II],

[0018]

[0019]

[0020] Among them, R 1 -R 6 are each independently a C4-C7 hydrocarbon group or 7≥m≥2;

[0021] R 1 -R 8 are each independently a C4 hydrocarbon group or 7≥n≥2.

[0022] 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 for a refrigerator, which includes the refrigerator oil provided by the first aspect of the present technical solution and R290 refrigerant.

[0023] Furthermore, the solubility of the R290 refrigerant in the refrigeration oil is less than 15% under the conditions of 50° C. and 2.2 MPa.

[0024] Furthermore, the dissolution viscosity of the working fluid composition for a refrigerator at 110° C. and 2.8 MPa is not less than 1.826 cp.

[0025] The embodiments of the present application have the following beneficial effects: by controlling the raw material ratio of polyols, polyacids and fatty acids to form a composite ester refrigeration oil of a specific combination, a refrigeration oil composition with low mutual solubility with R290 refrigerant can be obtained, which can effectively reduce the R290 refrigerant charge of the refrigeration system; by controlling the feed ratio of fatty acids and diacids of specific structures for synthesis, a composite ester refrigeration oil that can maintain a high dissolution viscosity after dissolution can be obtained, thereby ensuring that the refrigeration oil composition has sufficient oil film strength. Compared with the existing mineral type and PAG type refrigeration oils for R290, the refrigeration oil provided by the present invention has a lower solubility with R290 refrigerant, maintains a higher working viscosity after dissolution, has good lubricity and stability, and improves the safety and reliability of the R290 refrigeration system. DETAILED DESCRIPTION

[0026] Hereinafter, preferred embodiments of the present application will be described in detail.

[0027] 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:

[0028]

[0029] 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.

[0030] 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 an esterification reaction between pentaerythritol and a first carboxylic acid mixture, and the first carboxylic acid mixture includes at least one acid selected from monobasic fatty acids of C7-C8, a monobasic fatty acid of C5, and a dibasic acid of C4-C9; the second polyol ester is a complex ester synthesized by an esterification reaction between dipentaerythritol and a second carboxylic acid mixture, and the second carboxylic acid mixture includes a dibasic acid of C4-C9 and a monobasic fatty acid of C5.

[0031] In the raw material of the first polyol ester of refrigeration oil, the carboxyl groups of the dibasic acid account for 2 mol% to 20 mol% of the total carboxyl groups of the first carboxylic acid mixture raw material, preferably the carboxyl groups of the dibasic acid account for 5 mol% to 15 mol% of the total carboxyl groups of the first carboxylic acid mixture raw material, and more preferably the carboxyl groups of the dibasic acid account for 10 mol% to 15 mol% of the total carboxyl groups of the first carboxylic acid mixture raw material; the carboxyl groups of the C5 monobasic fatty acid account for more than 35 mol% of the total carboxyl groups of the first carboxylic acid mixture raw material, preferably the carboxyl groups of the C5 monobasic fatty acid account for 45 mol% to 85 mol% of the total carboxyl groups of the first carboxylic acid mixture raw material, and more preferably the carboxyl groups of the C5 monobasic fatty acid account for 55 mol% to 75 mol% of the total carboxyl groups of the first carboxylic acid mixture raw material.

[0032] In the raw material of the second polyol ester of the refrigeration oil, the carboxyl group of the dibasic acid accounts for 5mol% to 15mol% of the total carboxyl group of the second carboxylic acid mixture raw material, preferably 10mol% to 15mol% of the total carboxyl group of the dibasic acid; the carboxyl group of the C5 monobasic fatty acid accounts for more than 85mol% of the total carboxyl group of the second carboxylic acid mixture raw material, preferably 90mol% to 95mol% of the total carboxyl group of the C5 monobasic fatty acid. In the raw material of the second polyol ester, dipentaerythritol accounts for 10mol% to 50mol% of the total amount of organic alcohols, preferably 10mol% to 20mol% of the total amount of organic alcohols.

[0033] In the refrigerating machine oil, the molar ratio of pentaerythritol in the raw material of the first polyol ester to the total amount of pentaerythritol and dipentaerythritol in the raw material of the second polyol ester is (1-9):1.

[0034] Optionally, in view of obtaining the structural stability of the first polyol ester and the second polyol ester, the C4-C9 dibasic acid is selected from succinic acid, adipic acid and suberic acid, more preferably adipic acid.

[0035] Optionally, the monobasic fatty acid of C5 is selected from n-pentanoic acid, 2-methylbutanoic acid and 3-methylbutanoic acid. From the perspective of compatibility, the monobasic fatty acid of C5 in the first polyol ester raw material is preferably 2-methylbutanoic acid or 3-methylbutanoic acid that can form a complex ester with a larger molecular polarity. R290 refrigerant is a weakly polar structure. When the polarity of the formed complex ester is larger, the solubility of R290 can be reduced. The monobasic fatty acid of C5 in the first polyol ester raw material is preferably n-pentanoic acid that can obtain a complex ester with better viscosity-temperature characteristics and low-temperature fluidity.

[0036] Optionally, the C7-C8 monobasic fatty acid is selected from octanoic acid, heptanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 2-methylhexanoic acid, and 3-methylhexanoic acid.

[0037] Optionally, the kinematic viscosity of the refrigeration oil at 40°C is 33-120 mm 2 / s, kinematic viscosity at 100℃ is 5.2mm 2 / s or more.

[0038] In some embodiments, the first polyol ester includes at least one of the structural units represented by formula [I], and the second polyol ester includes at least one of the structural units represented by formula [II],

[0039]

[0040] Among them, R 1 -R 6are each independently a C4-C7 hydrocarbon group or 7≥m≥2;

[0041] R 1 -R 8 are each independently a C4 hydrocarbon group or 7≥n≥2.

[0042] It should be noted that the second polyol ester may also contain other structural units in addition to the structure shown in formula [II]. For example, the second polyol ester may also contain the structural unit shown in formula [I], where both carbonyl groups on both sides of the dibasic acid structure are connected to the pentaerythritol ester structure, wherein R 1 -R 6 They are independent C4 hydrocarbon groups; for example, the carbonyl groups on both sides of the dibasic acid structure in the second polyol ester are connected to the dipentaerythritol ester structure.

[0043] The refrigeration oil provided in the embodiment of the present application can be mixed with R290 refrigerant to form a working fluid composition for a refrigerator. The solubility of R290 refrigerant and the refrigeration oil under the conditions of 50°C and 2.2Mpa is less than 15%. The dissolution viscosity of the working fluid composition for a refrigerator at 110°C and 2.8MPa is not less than 1.826cp.

[0044] By controlling the raw material ratio of polyols, polyacids and fatty acids to form a composite ester refrigeration oil of a specific combination, a refrigeration oil composition with low mutual solubility with R290 refrigerant can be obtained, which can effectively reduce the R290 refrigerant charge of the refrigeration system; by controlling the feed ratio of fatty acids and diacids of specific structures for synthesis, a composite ester refrigeration oil that can maintain a high dissolution viscosity after dissolution can be obtained, thereby ensuring that the refrigeration oil composition has sufficient oil film strength. Compared with the existing mineral type and PAG type refrigeration oils for R290, the refrigeration oil provided by the present invention has a lower solubility with R290 refrigerant, maintains a higher working viscosity after dissolution, has good lubricity and stability, and improves the safety and reliability of the R290 refrigeration system.

[0045] 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.

[0046] 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-6) is the second polyol ester.

[0047]

First polyol ester

[0048] (A-1) 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 2:45:53 (viscosity at 40° C.: 40.72 mm 2 / s, kinematic viscosity at 100°C 5.974mm 2 / s, viscosity index 86).

[0049] (A-2) 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 2:65:33 (viscosity at 40° C.: 36.13 mm 2 / s, kinematic viscosity at 100°C 5.537mm 2 / s, viscosity index 85).

[0050] (A-3) 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 2:75:13 (viscosity at 40° C.: 31.05 mm 2 / s, kinematic viscosity at 100°C 4.962mm 2 / s, viscosity index 74).

[0051] (A-4) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 5:45:50 (viscosity at 40° C.: 54.37 mm 2 / s, kinematic viscosity at 100°C 7.451mm 2 / s, viscosity index 97).

[0052] (A-5) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 5:65:30 (viscosity at 40° C.: 42.29 mm 2 / s, kinematic viscosity at 100°C 6.252mm 2 / s, viscosity index 92).

[0053] (A-6) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 10:75:15 (viscosity at 40° C.: 52.67 mm 2 / s, kinematic viscosity at 100°C 7.429mm 2 / s, viscosity index 102).

[0054] (A-7) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 10:65:25 (viscosity at 40° C.: 65.86 mm 2 / s, kinematic viscosity at 100°C 8.271 mm 2 / s, viscosity index 93).

[0055] (A-8) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 10:45:45 (viscosity at 40° C.: 74.84 mm 2 / s, kinematic viscosity at 100°C 9.037mm 2 / s, viscosity index 94).

[0056] (A-9) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 10:35:55 ​​(viscosity at 40° C.: 79.69 mm 2 / s, kinematic viscosity at 100°C 9.522mm 2 / s, viscosity index 96).

[0057] (A-10) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and heptanoic acid in a carboxyl molar ratio of 10:45:45 (viscosity at 40° C.: 68.81 mm 2 / s, kinematic viscosity at 100°C 9.105mm 2 / s, viscosity index 107).

[0058] (A-11) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and heptanoic acid in a carboxyl molar ratio of 15:45:40 (viscosity at 40° C.: 80.42 mm 2 / s, kinematic viscosity at 100°C 11.02mm 2 / s, viscosity index 125).

[0059] (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 15:45:40 (viscosity at 40° C.: 93.69 mm 2 / s, kinematic viscosity at 100°C 10.83 mm 2 / s, viscosity index 99).

[0060] (A-13) 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 15:55:30 (viscosity at 40° C.: 87.94 mm 2 / s, kinematic viscosity at 100°C 10.28 mm 2 / s, viscosity index 98).

[0061] (A-14) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 15:65:20 (viscosity at 40° C.: 85.32 mm 2 / s, kinematic viscosity at 100°C 9.993mm 2 / s, viscosity index 96).

[0062] (A-15) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 2:35:63 (viscosity at 40°C: 40.19 mm 2 / s, kinematic viscosity at 100°C 5.788mm 2 / s, viscosity index 78).

[0063] (A-16) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 2:85:13 (viscosity at 40° C.: 37.64 mm 2 / s, kinematic viscosity at 100°C 5.361mm 2 / s, viscosity index 61).

[0064] (A-17) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 20:75:5 (viscosity at 40° C.: 108.28 mm 2 / s, kinematic viscosity at 100°C 11.82mm 2 / s, viscosity index 97).

[0065] (A-18) An ester obtained by esterification of pentaerythritol with a mixed acid of adipic acid, 2-methylbutyric acid and 2-methylhexanoic acid in a carboxyl molar ratio of 20:45:35 (viscosity at 40° C.: 129.16 mm 2 / s, kinematic viscosity at 100°C 14.02mm 2 / s, viscosity index 106).

[0066]

Second polyol ester

[0067] (B-1) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 90:10 and adipic acid and n-valeric acid in a carboxyl molar ratio of 5:95 (viscosity at 40° C.: 30.06 mm 2 / s, kinematic viscosity at 100°C 5.508mm 2 / s, viscosity index 121).

[0068] (B-2) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 90:10 and adipic acid and n-valeric acid in a carboxyl molar ratio of 15:85 (viscosity at 40° C.: 65.29 mm 2 / s, kinematic viscosity at 100°C 9.918mm 2 / s, viscosity index 137).

[0069] (B-3) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and n-valeric acid in a carboxyl molar ratio of 5:95 (viscosity at 40° C.: 39.77 mm 2 / s, kinematic viscosity at 100°C 6.735mm 2 / s, viscosity index 126).

[0070] (B-4) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and n-valeric acid in a carboxyl molar ratio of 10:90 (viscosity at 40° C.: 63.57 mm 2 / s, kinematic viscosity at 100°C 9.816mm 2 / s, viscosity index 132).

[0071] (B-5) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and n-valeric acid in a carboxyl molar ratio of 15:85 (viscosity at 40° C.: 96.29 mm 2 / s, kinematic viscosity at 100°C 13.52mm 2 / s, viscosity index 141).

[0072] (B-6) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 50:50 and adipic acid and n-valeric acid in a carboxyl molar ratio of 5:95 (viscosity at 40° C.: 63.47 mm 2 / s, kinematic viscosity at 100°C 9.417mm 2 / s, viscosity index 128).

[0073] (B-7) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 90:10 and adipic acid and 2-methylbutyric acid in a carboxyl molar ratio of 5:95 (viscosity at 40° C.: 49.17 mm 2 / s, kinematic viscosity at 100°C 6.369mm 2 / s, viscosity index 68).

[0074] (B-8) An ester obtained by esterification of a mixed acid of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and 3-methylbutyric acid in a carboxyl molar ratio of 15:85 (viscosity at 40° C.: 188.06 mm 2 / s, kinematic viscosity at 100°C 17.790mm 2 / s, viscosity index 103).

[0075] The first polyol ester and the second polyol ester were mixed at a ratio of 9:1 of the amount of polyol in each raw material to obtain Examples 1-8 and Comparative Examples 1-8; the first polyol ester and the second polyol ester were mixed at a ratio of 1:1 of the amount of polyol in each raw material to obtain Examples 9-16 and Comparative Examples 9-24. 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.

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080] Table 3

[0081]

[0082] Table 4

[0083]

[0084] Table 5

[0085]

[0086] Refer to "GB / T265-1988 Determination of kinematic viscosity of petroleum products and calculation method of dynamic viscosity": a certain mass of experimental oil and refrigerant are filled into an explosion-proof pressure-resistant autoclave (with a glass sight glass), and the liquid level of the solution in the autoclave can be accurately measured through the glass sight glass and the scale. Connect the online pressure sensor, temperature sensor and related accessories and ensure the sealing, place the pressure autoclave in a water bath thermostatic bath for heating and turn on the magnetic stirring at the same time, and monitor the temperature and pressure in real time. Observe the pressure in the pressure autoclave, and then release some of the excess refrigerant after it stabilizes. Finally, the mass and solubility of the refrigerant can be obtained by weighing and calculating. Refrigerant solubility ω = (mass of refrigerant - density of gaseous refrigerant * volume of gaseous refrigerant) / (mass of oil + mass of refrigerant - density of gaseous refrigerant * volume of gaseous refrigerant) × 100%, where the volume of gaseous refrigerant can be converted by liquid level, and its density can be obtained by looking up the table. The refrigerant is R290.

[0087] 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 R290.

[0088] In terms of the solubility viscosity of the refrigeration oil, by comparing the embodiments and comparative examples in Tables 1-4, it is found that the presence of dipentaerythritol complex ester can increase the solubility viscosity of the complex ester composition, such as Example 1 and Comparative Example 1, and the test results of Comparative Examples 11-13 in Reference Table 4 show that the increase in the proportion of dipentaerythritol raw materials can increase the solubility viscosity of the refrigeration oil; further analysis shows that the introduction of adipic acid can also increase the solubility viscosity of the complex ester composition. For example, it can be seen from Examples 4, 6 and Comparative Example 3 that the second polyol ester used is B-5, and as the proportion of dibasic acid in the first polyol ester gradually increases, the solubility viscosity of the refrigeration oil shows a trend of gradually increasing.

[0089] With regard to the solubility of refrigerant R290 in refrigeration oil, further analysis and comparison of the embodiments and comparative examples in Tables 1-5 revealed that the solubility of refrigerant R290 in refrigeration oil is affected by both the amount of short-chain C5 monobasic fatty acid and the amount of adipic acid used; as the proportion of C5 monobasic fatty acid in the total organic acid in the base oil raw material increases, the solubility of refrigerant R290 in refrigeration oil gradually decreases, as shown in Examples 1-3 and 12-14; as the proportion of adipic acid in the base oil raw material increases, the solubility of refrigerant R290 in refrigeration oil gradually increases, as shown in Examples 14-16. In Examples 14-16, the adipic acid content in the first polyol ester and the second polyol ester raw materials both show a downward trend, and their corresponding solubilities also show a downward trend.

[0090] In order to control the compatibility between the base oil and the refrigerant, it is necessary to control the amount of adipic acid and C5 fatty acid. The amount of C5 fatty acid needs to be increased and the amount of adipic acid needs to be reduced to minimize the solubility of refrigerant R290 in refrigeration oil. On the other hand, in order to obtain a better dissolution viscosity, the amount of adipic acid needs to be increased. Therefore, in order to obtain a product with suitable solubility and dissolution viscosity, it is necessary to reasonably optimize the dosage ratio of adipic acid, C5 fatty acid and dipentaerythroid.

[0091] 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 measured, and the anti-wear performance was evaluated by comparing the size of the average wear spot diameter. As shown in Table 1, the solubility of the R290 refrigerant in Examples 6-8 is below 12%, and is at a level of poor miscibility. There is no obvious difference in the miscibility between the oil product and the R290 refrigerant, and it appears that as the amount of C5 monobasic fatty acid in the base oil raw material component decreases, the average wear spot diameter of the oil product also decreases accordingly. In addition, when R290 refrigerant is well compatible with oil products, as shown in the test results of Comparative Examples 2-5 in Table 3, as the proportion of adipic acid raw materials in the base oil raw material components increases, the average wear spot diameter decreases with the increase of its dosage; when R290 refrigerant is less compatible with oil products, as shown in the test results of Comparative Examples 11-13 in Table 4, as the proportion of dipentaerythritol raw materials in the base oil raw materials increases, the average wear spot diameter decreases with the increase of its dosage. Of course, in order to obtain better anti-wear and lubrication effects, necessary anti-wear additives can also be added to the composite ester refrigeration oil.

[0092] It can be seen that under the goal of the present invention to pursue a lower miscibility between R290 refrigerant and oil products to improve its safety, an increase in the proportion of dipentaerythritol raw materials will reduce its anti-wear performance. Based on the conclusion of the previous article, an increase in the proportion of dipentaerythritol complex ester can increase the solubility viscosity of the refrigeration oil. Therefore, it is necessary to reasonably optimize the dosage ratio of dipentaerythritol to balance the anti-wear performance and solubility viscosity of the refrigeration oil.

[0093] In order to fully reduce the compatibility between R290 refrigerant and refrigeration oil, the C5 monobasic fatty acid is preferably a branched C5 fatty acid that can form a complex ester with a large molecular polarity, such as 2-methylbutyric acid or 3-methylbutyric acid, which can greatly reduce the solubility of the R290 refrigerant with a weak polar structure. However, it is found from the data in Tables 1 to 5 that the structural form of the C5 monobasic fatty acid in the second polyol ester has a direct impact on the low-temperature fluidity of the refrigeration oil. When the selected second polyol ester contains a branched C5 monobasic fatty acid, for example, in Comparative Examples 17-24, referring to the pour point index of the refrigeration oil in Table 5, except for Comparative Example 21 which is -29°C, the C5 monobasic fatty acid in the second polyol ester has a direct impact on the low-temperature fluidity of the refrigeration oil. Except for the above, the others are in the higher range of -16°C to -2°C, and the low-temperature fluidity of the refrigeration oil is poor. When n-pentanoic acid is used instead of the branched C5 fatty acid in the selected second polyol ester, for example, Examples 1-16, the pour point indicators of the refrigeration oil in Reference Table 1-2 are all in a lower range that is significantly lower than those in Comparative Examples 17-24, and the low-temperature fluidity of the refrigeration oil is good. Therefore, in order to balance the compatibility and low-temperature fluidity, the C5 fatty acid in the first carboxylic acid mixture of the raw material of the first polyol ester is preferably a branched structure, and the C5 fatty acid in the second carboxylic acid mixture of the raw material of the second polyol ester is preferably n-pentanoic acid instead of a branched C5 fatty acid.

[0094] It can be seen from the test data in Table 1-2 that the solubility of R290 refrigerant in refrigeration oil at 50°C and 2.2MPa is less than 15%, which greatly improves the safety of R290 refrigerant during use; the solubility viscosity of refrigeration oil is above 1.826cp when the compressor is in working condition of 110°C and 2.8MPa, which can ensure that there is a sufficiently thick oil film between the friction pairs of the compressor pump body parts, thereby improving the lubrication performance of the working fluid composition and meeting the reliability of compressor operation. For the refrigeration oil of the present invention, having a lower solubility with R290 refrigerant can reduce the charge amount of the refrigerant, and the lubricity is good.

[0095] It should be noted that the above description is only a preferred embodiment of the present invention, and for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which should also be considered within the scope of protection of the invention. Some embodiments in this specification are described in a progressive or parallel manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0096] 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 C7-C8, monobasic fatty acids of C5, and dibasic acids of C4-C9; The second polyol ester is dipentaerythritol and a complex ester synthesized by esterification of dipentaerythritol and a second carboxylic acid mixture, wherein the second carboxylic acid mixture includes a C4-C9 dibasic 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 C7-C8 monobasic fatty acid is selected from octanoic acid, heptanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 2-methylhexanoic acid, and 3-methylhexanoic acid.

5. The refrigerating machine oil according to claim 1, characterized in that The molar ratio of pentaerythritol in the raw material of the first polyol ester to the total amount of pentaerythritol and dipentaerythritol in the raw material of the second polyol ester 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 33-120 mm 2 / s, kinematic viscosity at 100℃ is 5.2mm 2 / s or more.

7. The refrigerating machine oil according to claim 1, characterized in that The invention also includes 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 includes at least one of the structural units represented by formula [I], and the second polyol ester includes at least one of the structural units represented by formula [II], Wherein R1-R6 are each independently a C4-C7 hydrocarbon group or 7≥m≥2; R 1 -R 8 are each independently a C4 hydrocarbon group or 7≥n≥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 R290 refrigerant.

10. The working fluid composition for refrigerator according to claim 9, characterized in that: The solubility of R290 refrigerant in the refrigeration oil is less than 15% under the conditions of 50° C. and 2.2 MPa.

11. The working fluid composition for refrigerator according to claim 9, characterized in that: The working fluid composition for a refrigerator has a dissolving viscosity of not less than 1.826 cp at 110° C. and 2.8 MPa.

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