Refrigeration oil and working fluid composition

Abstract

This application relates to the technical field of refrigeration oil products, specifically to a refrigeration oil and a working fluid composition comprising the refrigeration oil. The refrigeration oil includes a base oil comprising a first polyol ester and a second polyol ester; the first polyol ester is a composite ester synthesized by esterification of a mixture of pentaerythritol and a first carboxylic acid, wherein the first carboxylic acid mixture includes at least one acid selected from C7-C8 monobasic fatty acids, a C5 monobasic fatty acid, and a C4-C9 diabasic acid; the second polyol ester is a composite ester synthesized by esterification of a mixture of pentaerythritol and dipentaerythritol with a second carboxylic acid, wherein the second carboxylic acid mixture includes a C4-C9 diabasic acid and a C5 monobasic fatty acid. The refrigeration oil provided by this invention has low solubility with R290 refrigerant, maintains a high working viscosity after dissolution, exhibits good lubricity and stability, and improves the safety and reliability of R290 refrigeration systems.

Description

Technical Field

[0001] This application relates to the field of refrigeration oil products, and more specifically, to a refrigeration oil, and also to a working fluid composition comprising the refrigeration oil. Background Technology

[0002] With increasingly stringent environmental regulations, traditional hydrochlorofluorocarbon (HCFC) refrigerants are being phased out at an accelerated pace, and HFC refrigerants are about to have their baseline levels frozen. Regulations passed in 2016 added 18 HFC refrigerants to the list of controlled substances and provided a timetable for the gradual reduction of HFCs to address the growing environmental problems. my country will begin reducing the use of HFCs, including R32 and R134a, annually starting in 2029. Based on current refrigerant substitution policies and trends, safe, efficient, green, and environmentally friendly refrigerants, especially natural refrigerants, are likely to become the ultimate choice for replacing refrigerants. Propane (R290), as an environmentally friendly refrigerant, has extremely low global warming potential (GWP=3) and ozone depletion potential (ODP=0). Its critical temperature, boiling point, pressure, and freezing point are similar to those of R22. It also shows significant advantages over R22 in terms of latent heat of vaporization, dynamic viscosity, solubility, heat transfer characteristics, and system energy efficiency. It is a traditional refrigerant alternative with great development potential.

[0003] However, R290 is a gaseous flammable substance at normal temperature and pressure, with a safety class of A3. Its charge quantity is strictly limited when used in residential air conditioning and heat pump products. In refrigeration systems, some refrigerant remains in the pipes and heat exchangers, but a considerable portion dissolves in the refrigeration oil in the oil sump or distributor. Therefore, reducing the miscibility of the refrigerant with the refrigeration oil and thus decreasing its charge quantity can improve the safety of R290 systems.

[0004] On the other hand, while the good miscibility between refrigeration oil and refrigerant is beneficial for system oil return, excessive refrigerant dissolved in refrigeration oil can lead to decreased oil viscosity, high oil discharge, and even problems with the stability of the refrigeration system and the reliability of the compressor. R290 is a short-chain alkane, a weakly polar compound. Traditional mineral oils (MO) and alkylbenzene oils (AB) have similar molecular structures to R290 and high solubility. Direct application of mineral-based refrigeration oil in R290 refrigeration systems may reduce its lubricating performance. Due to its high solubility, the amount of oil carried into the refrigeration system circuit will also increase, affecting the system's heat transfer efficiency and operational stability. Therefore, to improve the safety of R290 refrigerant systems and the reliability of compressors, it is necessary to reduce the solubility of R290 in refrigeration oil.

[0005] Some solutions exist in related technologies to improve the solubility of refrigeration oils with R290, which can solve the problem of miscibility with R290 to a certain extent. However, the base oil components contain more or less unsaturated fatty acids, which still have shortcomings in balancing the lubricity, compatibility, and stability of the refrigeration oil working fluid. Summary of the Invention

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

[0007] To achieve the above objectives, according to the first aspect of this technical solution, this technical solution provides a refrigeration oil.

[0008] The refrigeration oil according to the embodiments of this 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 a mixture of pentaerythritol and a first carboxylic acid. The first carboxylic acid mixture includes at least one acid selected from C7-C8 monobasic fatty acids, a C5 monobasic fatty acid, and a C4-C9 dibasic acid.

[0010] The second polyol ester is a complex ester synthesized by esterification reaction of pentaerythritol and dipentaerythritol with a second carboxylic acid mixture, wherein the second carboxylic acid mixture includes C4-C9 dicarboxylic acids and C5 monocarboxylic fatty acids.

[0011] Furthermore, the C4-C9 dicarboxylic acids are selected from succinic acid, adipic acid, and octanoic acid.

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

[0013] Furthermore, the C7-C8 monobasic fatty acids are 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 The kinematic viscosity at 100℃ is 5.2 mm / s. 2 / s or more.

[0016] Furthermore, the refrigeration oil also includes additives, which include at least one of anti-wear agents, antioxidants, anti-foaming agents, and acid scavengers.

[0017] Furthermore, the first polyol ester includes at least one of the structural units shown in Formula [I], and the second polyol ester includes at least one of the structural units shown in Formula [II].

[0018]

I

[0019]

II

[0020] Wherein, R1-R6 are independent C4, C6, or C7 hydrocarbon groups or , 7≥m≥2;

[0021] R 1 -R 8 For each independent C4 hydrocarbon group or , 7≥n≥2.

[0022] To achieve the above objectives, according to a second aspect of this technical solution, this technical solution provides a working fluid composition for a refrigeration unit, comprising refrigeration oil and R290 refrigerant provided in the first aspect of this technical solution.

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

[0024] Furthermore, the working fluid composition for the refrigeration machine has a solubility viscosity of not less than 1.826 cp at 110°C and 2.8 MPa.

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

[0026] The following describes in detail the suitable implementation methods of this application.

[0027] The refrigeration oil provided in this application includes a base oil and suitable additives, wherein the additives include at least one selected from anti-wear agents, antioxidants, antifoaming agents, and acid scavengers. Preferably, the main components of the refrigeration oil may include:

[0028] Base oil 90-99.7 parts by weight;

[0029] Antioxidant 0.1-3 parts by weight;

[0030] Acid scavenger 0.1-3 parts by weight;

[0031] Anti-wear agent 0.05-2 parts by weight;

[0032] Antifoaming agent 0.05-2 parts by weight.

[0033] There are no specific restrictions on the types of additives used in the refrigeration oil in this application. Antioxidants may include hindered phenols, diarylamines, phenothiazines, organic sulfonates, etc.; acid scavengers may include glycidyl ester type epoxy compounds, glycidyl ether type epoxy compounds, and phenyl glycidyl ethers, etc.; anti-wear agents may include alkyl phosphates and alkyl phosphates, dialkyl dithiophosphates and phosphates, etc.; and antifoaming agents may include silicone-containing polydimethylsiloxanes or other non-silicone polyacrylates, etc.

[0034] 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 of a mixture of pentaerythritol and a first carboxylic acid, wherein the first carboxylic acid mixture includes at least one acid selected from C7-C8 monobasic fatty acids, a C5 monobasic fatty acid, and a C4-C9 dibasic acid; the second polyol ester is a complex ester synthesized by esterification of a mixture of pentaerythritol and dipentaerythritol with a second carboxylic acid, wherein the second carboxylic acid mixture includes a C4-C9 dibasic acid and a C5 monobasic fatty acid.

[0035] In the raw material of the first polyol ester of the refrigeration oil, the carboxyl group of the diacid accounts for 2 mol% to 20 mol% of the total carboxyl group of the first carboxylic acid mixture raw material, preferably 5 mol% to 15 mol% of the total carboxyl group of the diacid, more preferably 10 mol% to 15 mol% of the total carboxyl group of the diacid; the carboxyl group of the C5 monobasic fatty acid accounts for more than 35 mol% of the total carboxyl group of the first carboxylic acid mixture raw material, preferably 45 mol% to 85 mol% of the total carboxyl group of the first carboxylic acid mixture raw material, more preferably 55 mol% to 75 mol% of the total carboxyl group of the first carboxylic acid mixture raw material.

[0036] In the raw materials for the second polyol ester of the refrigeration oil, the carboxyl groups of the diacid account for 5 mol% to 15 mol% of the total carboxyl groups in the second carboxylic acid mixture raw materials, preferably 10 mol% to 15 mol%; the carboxyl groups of the C5 monobasic fatty acid account for more than 85 mol% of the total carboxyl groups in the second carboxylic acid mixture raw materials, preferably 90 mol% to 95 mol%. In the raw materials for the second polyol ester, dipentaerythritol accounts for 10 mol% to 50 mol% of the total organic alcohols, preferably 10 mol% to 20 mol%.

[0037] In refrigeration 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.

[0038] Optionally, from the perspective of obtaining structural stability of the first and second polyol esters, the C4-C9 dicarboxylic acids are selected from succinic acid, adipic acid, and octanoic acid, and more preferably adipic acid.

[0039] Optionally, the monobasic fatty acid C5 is selected from valeric acid, 2-methylbutyric acid, and 3-methylbutyric acid. Considering compatibility, the monobasic fatty acid C5 in the first polyol ester raw material is preferably 2-methylbutyric acid or 3-methylbutyric acid, which can form a complex ester with relatively high molecular polarity. Since R290 refrigerant has a weakly polar structure, when the formed complex ester has relatively high polarity, the solubility of R290 can be reduced. The monobasic fatty acid C5 in the first polyol ester raw material is preferably valeric acid, which can yield a complex ester with superior viscosity-temperature characteristics and low-temperature flowability.

[0040] Optionally, the C7-C8 monobasic fatty acids are 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.

[0041] Optionally, the kinematic viscosity of the refrigeration oil at 40°C is 33-120 mm. 2 The kinematic viscosity at 100℃ is 5.2 mm / s. 2 / s or more.

[0042] In some embodiments, the first polyol ester includes at least one of the structural units shown in Formula [I], and the second polyol ester includes at least one of the structural units shown in Formula [II].

[0043]

I

[0044]

II

[0045] Wherein, R1-R6 are independent C4, C6, or C7 hydrocarbon groups or , 7≥m≥2;

[0046] R 1 -R 8 For each independent C4 hydrocarbon group or , 7≥n≥2.

[0047] It should be noted that the second polyol ester may also contain other structural units besides the structure shown in formula [II]. For example, the second polyol ester may also contain the structural unit shown in formula [I], where the carbonyl groups on both sides of the diacid structure are connected to a pentaerythritol ester structure, where R1-R6 are independent C4 hydrocarbon groups; another example is that the carbonyl groups on both sides of the diacid structure in the second polyol ester are connected to a bispentaerythritol ester structure.

[0048] The refrigeration oil provided in this application embodiment can be mixed with R290 refrigerant to form a working fluid composition for refrigeration machines. The solubility of R290 refrigerant and the refrigeration oil is less than 15% at 50°C and 2.2 MPa. The working fluid composition for refrigeration machines has a solubility viscosity of not less than 1.826 cp at 110°C and 2.8 MPa.

[0049] By controlling the raw material ratio of polyols, polyacids, and fatty acids to form a specific combination of composite ester refrigeration oils, a refrigeration oil composition with low miscibility with R290 refrigerant can be obtained, effectively reducing the R290 refrigerant charge in the refrigeration system. By controlling the feeding ratio of fatty acids and diacids with specific structures during synthesis, a composite ester refrigeration oil that maintains a high dissolution viscosity after dissolution can be obtained, thus ensuring sufficient oil film strength in the refrigeration oil composition. Compared with existing mineral-based and PAG-type refrigeration oils for R290, the refrigeration oil provided by this invention has lower solubility with R290 refrigerant, maintains a high working viscosity after dissolution, and exhibits good lubricity and stability, improving the safety and reliability of the R290 refrigeration system.

[0050] The present application will now be described in more detail through preferred embodiments and comparative examples, but the present application is not limited to any of the embodiments described below.

[0051] In each embodiment and comparative example, under necessary catalytic conditions, an esterification reaction was carried out with a raw material ratio of 1:1.1 for hydroxyl and carboxyl groups to obtain the corresponding components, thereby achieving a complete esterification reaction. (A-1)-(A-18) are the first polyol esters, and (B-1)-(B-6) are the second polyol esters.

[0052] [First Polyol Ester]

[0053] (A-1) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-ethylhexanoic acid in a carboxyl molar ratio of 2:45:53 (viscosity at 40°C is 40.72 mm). 2 / s, kinematic viscosity at 100℃: 5.974 mm³ / s 2 ( / s, viscosity index 86).

[0054] (A-2) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-ethylhexanoic acid in a carboxyl molar ratio of 2:65:33 (viscosity at 40°C is 36.13 mm). 2 / s, kinematic viscosity at 100℃: 5.537 mm³ / s 2 (s, viscosity index 85).

[0055] (A-3) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-ethylhexanoic acid in a carboxyl molar ratio of 2:75:13 (viscosity at 40°C is 31.05 mm). 2 / s, kinematic viscosity at 100℃: 4.962 mm³ / s 2 (s, viscosity index 74).

[0056] (A-4) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 5:45:50 (viscosity at 40°C is 54.37 mm). 2 / s, kinematic viscosity at 100℃: 7.451 mm³ / s 2 (s, viscosity index 97).

[0057] (A-5) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 5:65:30 (viscosity at 40°C is 42.29 mm). 2 / s, kinematic viscosity at 100℃: 6.252 mm³ / s 2 ( / s, viscosity index 92).

[0058] (A-6) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 10:75:15 (viscosity at 40°C is 52.67 mm). 2 / s, kinematic viscosity at 100℃: 7.429 mm³ / s 2 (s, viscosity index 102).

[0059] (A-7) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 10:65:25 (viscosity at 40°C is 65.86 mm). 2 / s, kinematic viscosity at 100℃: 8.271 mm³ / s 2 (s, viscosity index 93).

[0060] (A-8) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 10:45:45 (viscosity at 40°C is 74.84 mm). 2 / s, kinematic viscosity at 100℃: 9.037 mm³ / s 2 ( / s, viscosity index 94).

[0061] (A-9) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 10:35:55 ​​(viscosity at 40°C is 79.69 mm). 2 / s, kinematic viscosity at 100℃: 9.522 mm³ / s 2 (s, viscosity index 96).

[0062] (A-10) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and heptanoic acid in a carboxyl molar ratio of 10:45:45 (viscosity at 40°C is 68.81 mm). 2 / s, kinematic viscosity at 100℃: 9.105 mm³ / s 2 (viscosity index 107).

[0063] (A-11) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and heptanoic acid in a carboxyl molar ratio of 15:45:40 (viscosity at 40°C is 80.42 mm). 2 / s, kinematic viscosity at 100℃: 11.02 mm³ / s 2 (s, viscosity index 125).

[0064] (A-12) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-ethylhexanoic acid in a carboxyl molar ratio of 15:45:40 (viscosity at 40°C is 93.69 mm). 2 / s, kinematic viscosity at 100℃: 10.83 mm² 2 / s, viscosity index 99).

[0065] (A-13) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-ethylhexanoic acid in a carboxyl molar ratio of 15:55:30 (viscosity at 40°C is 87.94 mm). 2 / s, kinematic viscosity at 100℃: 10.28 mm³ / s 2 (s, viscosity index 98).

[0066] (A-14) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 15:65:20 (viscosity at 40°C is 85.32 mm). 2 / s, kinematic viscosity at 100℃: 9.993 mm² / s 2 (s, viscosity index 96).

[0067] (A-15) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 2:35:63 (viscosity at 40°C is 40.19 mm). 2 / s, kinematic viscosity at 100℃: 5.788 mm³ / s 2 (s, viscosity index 78).

[0068] (A-16) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 2:85:13 (viscosity at 40°C is 37.64 mm). 2 / s, kinematic viscosity at 100℃: 5.361 mm³ / s 2 / s, viscosity index 61).

[0069] (A-17) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 20:75:5 (viscosity at 40°C is 108.28 mm). 2 / s, kinematic viscosity at 100℃: 11.82 mm³ / s 2 (s, viscosity index 97).

[0070] (A-18) An ester obtained by esterification of pentaerythritol with a mixture of adipic acid, 2-methylbutyric acid, and 2-methylhexanoic acid in a carboxyl molar ratio of 20:45:35 (viscosity at 40°C is 129.16 mm). 2 / s, kinematic viscosity at 100℃: 14.02 mm³ / s 2 (viscosity index 106).

[0071] [Second Polyol Ester]

[0072] (B-1) An ester obtained by esterification of a mixture of pentaerythritol and dipentaerythritol in a molar ratio of 90:10 and adipic acid and valerate in a carboxyl group molar ratio of 5:95 (viscosity at 40°C: 30.06 mm). 2 / s, kinematic viscosity at 100℃: 5.508 mm³ / s 2 / s, viscosity index 121).

[0073] (B-2) An ester obtained by esterification of a mixture of pentaerythritol and dipentaerythritol in a molar ratio of 90:10 and adipic acid and valerate in a carboxyl group molar ratio of 15:85 (viscosity at 40°C is 65.29 mm). 2 / s, kinematic viscosity at 100℃: 9.918 mm³ / s 2 (viscosity index 137).

[0074] (B-3) An ester obtained by esterification of a mixture of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and valerate in a carboxyl group molar ratio of 5:95 (viscosity at 40°C: 39.77 mm). 2 / s, kinematic viscosity at 100℃: 6.735 mm³ / s 2 (s, viscosity index 126).

[0075] (B-4) An ester obtained by esterification of a mixture of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and valerate in a carboxyl group molar ratio of 10:90 (viscosity at 40°C is 63.57 mm). 2 / s, kinematic viscosity at 100℃: 9.816 mm³ / s 2 (viscosity index 132).

[0076] (B-5) An ester obtained by esterification of a mixture of pentaerythritol and dipentaerythritol in a molar ratio of 80:20 and adipic acid and valerate in a carboxyl group molar ratio of 15:85 (viscosity at 40°C: 96.29 mm). 2 / s, kinematic viscosity at 100℃: 13.52 mm³ / s 2 / s, viscosity index 141).

[0077] (B-6) An ester obtained by esterification of a mixture of pentaerythritol and dipentaerythritol in a molar ratio of 50:50 and adipic acid and valerate in a carboxyl group molar ratio of 5:95 (viscosity at 40°C is 63.47 mm). 2 / s, kinematic viscosity at 100℃: 9.417 mm² / s 2 (viscosity index 128).

[0078] (B-7) An ester obtained by esterification of a mixture 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℃: 6.369 mm² / s 2 (s, viscosity index 68).

[0079] (B-8) An ester obtained by esterification of a mixture 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℃: 17.790 mm³ / s 2 (s, viscosity index 103).

[0080] The first polyol ester and the second polyol ester were mixed at a molar ratio of 9:1 for the polyols in their respective raw materials to obtain Examples 1-8 and Comparative Examples 1-8; the first polyol ester and the second polyol ester were mixed at a molar ratio of 1:1 for the polyols in their respective raw materials to obtain Examples 9-16 and Comparative Examples 9-24. The types and specific compositions of the first and second polyol esters used in each example and comparative example are shown in Tables 1-5.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085] Table 3

[0086]

[0087] Table 4

[0088]

[0089] Table 5

[0090]

[0091] Referring to GB / T265-1988, "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products": A certain mass of test oil and refrigerant is filled into an explosion-proof pressure vessel (equipped with a glass sight glass). The liquid level in the vessel can be accurately measured using the sight glass and a ruler. Connect the online pressure sensor, temperature sensor, and related accessories, ensuring sealing. Place the pressure vessel in a water bath for heating while simultaneously activating magnetic stirring, monitoring the temperature and pressure in real time. Observe the pressure in the pressure vessel; after it stabilizes, release some of the excess refrigerant. Finally, the mass and solubility of the refrigerant can be obtained through weighing and calculation. 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 calculated from the liquid level, and its density can be obtained from a table. The refrigerant used is R290.

[0092] Referring to SH / T 0699-2000 "Test Method for Compatibility of Refrigeration Oil and Refrigerant": A certain mass of test oil and refrigerant were filled into an explosion-proof autoclave. An online viscometer and related accessories were connected and sealed. A vacuum pump was used to evacuate the autoclave. The initial temperature of the heater was set to 30℃. The viscosity of the mixture under certain temperature and pressure conditions was measured, with a temperature gradient interval of 10℃. The pressure inside the autoclave was controlled by switching valves to control the refrigerant content. A platinum resistance pressure sensor and a temperature sensor and related accessories were connected, and the temperature and pressure were monitored in real time. After the temperature inside the autoclave stabilized, the pressure inside the autoclave was observed and recorded approximately every 10 minutes. The online viscometer could directly read the viscosity of the mixed solution, which is the solubility viscosity (dynamic viscosity) under specific conditions. The lower the solubility viscosity, the lower the lubricating film strength and the poorer the anti-wear lubrication performance of the combination of refrigeration oil and refrigerant; the higher the solubility viscosity, the higher the lubricating film strength and the better the anti-wear lubrication performance of the combination of refrigeration oil and refrigerant. The refrigerant used in the test was R290.

[0093] Regarding the solubility viscosity of refrigeration oil, a comparison of the examples and comparative examples in Tables 1-4 reveals that the presence of dipentaerythritol complex esters can increase the solubility viscosity of the complex ester composition, as seen in Example 1 and Comparative Example 1. Furthermore, referring to the test results of Comparative Examples 11-13 in Table 4, it is shown that increasing the proportion of dipentaerythritol raw materials can improve the solubility viscosity of refrigeration oil. Further analysis reveals that the introduction of adipic acid can also increase the solubility viscosity of the complex ester composition. For example, as can be seen from Examples 4, 6, and Comparative Example 3, the second polyol ester used is B-5. As the proportion of dicarboxylic acid in the first polyol ester gradually increases, the solubility viscosity of the refrigeration oil shows a gradual increasing trend.

[0094] Further analysis of the solubility of refrigerant R290 in refrigeration oil, comparing the examples and comparative examples in Tables 1-5, reveals that the solubility of refrigerant R290 in refrigeration oil is affected by both the amount of short-chain C5 monobasic fatty acids and adipic acid. As the proportion of C5 monobasic fatty acids in the total organic acids in the base oil feedstock increases, the solubility of refrigerant R290 in refrigeration oil gradually decreases, as seen in Examples 1-3 and 12-14. Conversely, as the proportion of adipic acid in the base oil feedstock increases, the solubility of refrigerant R290 in refrigeration oil gradually increases, as seen in Examples 14-16. In Examples 14-16, the adipic acid content in both the first and second polyol ester feedstocks shows a decreasing trend, and their corresponding solubility also shows a decreasing trend.

[0095] To control the compatibility between the base oil and the refrigerant, it is necessary to control the amounts of adipic acid and C5 fatty acids. This requires increasing the amount of C5 fatty acids and decreasing the amount of adipic acid to minimize the solubility of refrigerant R290 in the refrigeration oil. Conversely, to obtain a better solubility viscosity, the amount of adipic acid needs to be increased. Therefore, to obtain a product with suitable solubility and viscosity, the ratio of adipic acid, C5 fatty acids, and dipentaerythritol needs to be rationally optimized.

[0096] According to the petrochemical industry standard SH / T 0189-92 "Test Method for Anti-wear Performance of Lubricating Oil", the anti-wear performance of the oil was determined, and its quality was evaluated by comparing the average wear scar diameter. Table 1 shows that the solubility of R290 refrigerant in Examples 6-8 was all below 12%, indicating poor miscibility. There was no significant difference in miscibility between the oil and R290 refrigerant. Furthermore, as the amount of C5 monobasic fatty acid in the base oil feedstock decreased, the average wear scar diameter of the oil also decreased accordingly. Furthermore, when R290 refrigerant has good compatibility with the oil, as shown in the test results of Comparative Examples 2-5 in Table 3, the average wear scar diameter decreases with increasing adipic acid content in the base oil feedstock. Conversely, when R290 refrigerant has low compatibility with the oil, as shown in the test results of Comparative Examples 11-13 in Table 4, the average wear scar diameter decreases with increasing dipentaerythritol content in the base oil feedstock. Of course, to obtain better anti-wear and lubrication effects, necessary anti-wear additives can also be added to the composite ester refrigeration oil.

[0097] It can be seen that, in order to improve the safety of R290 refrigerant and oil by pursuing low compatibility, the increase of the proportion of dipentaerythritol raw material will reduce its anti-wear performance. However, based on the conclusion above, the increase of the proportion of dipentaerythritol complex ester can increase the solubility viscosity of refrigeration oil. Therefore, it is necessary to reasonably optimize the dosage ratio of dipentaerythritol in order to balance the anti-wear performance and solubility viscosity of refrigeration oil.

[0098] To significantly reduce the miscibility between R290 refrigerant and refrigeration oil, the C5 monobasic fatty acid should ideally be a branched-chain C5 fatty acid capable of forming highly polar complex esters, such as 2-methylbutyric acid or 3-methylbutyric acid. This can greatly reduce the solubility of the weakly polar R290 refrigerant. However, data from Tables 1-5 show that the structural form of the C5 monobasic fatty acid in the second polyol ester directly affects the low-temperature fluidity of the refrigeration oil. When the selected second polyol ester contains a branched C5 monobasic fatty acid, such as Comparative Examples 17-24, referring to the pour point indices of the refrigeration oils in Table 5, except for Comparative Example 21 which is -29°C... Apart from the others, all others are in the higher range of -16℃ to -2℃, resulting in poor low-temperature fluidity of the refrigeration oil. However, when valeric acid is used instead of branched C5 fatty acids in the second polyol ester, for example, in Examples 1-16, referring to the pour point index of the refrigeration oil in Table 1-2, they are all in the lower range significantly lower than those in Comparative Examples 17-24, resulting in better low-temperature fluidity of the refrigeration oil. Therefore, in order to balance compatibility and low-temperature fluidity, the C5 fatty acid in the first carboxylic acid mixture of the raw material for the first polyol ester is preferably branched, and the C5 fatty acid in the second carboxylic acid mixture of the raw material for the second polyol ester is preferably valeric acid, rather than branched C5 fatty acids.

[0099] As can be seen from the test data in Table 1-2, the solubility of R290 refrigerant in the refrigeration oil is less than 15% under conditions of 50℃ and 2.2MPa, which greatly improves the safety of R290 refrigerant during use. Under compressor operating conditions of 110℃ and 2.8MPa, the viscosity of the refrigeration oil is above 1.826cp, ensuring 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 requirements of compressor operation. For the refrigeration oil of this invention, the low solubility with R290 refrigerant reduces the refrigerant charge and provides excellent lubrication.

[0100] It should be noted that the above description is only a preferred embodiment of the present invention, and those skilled in the art can make various modifications and improvements 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, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to mutually.

[0101] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed 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 composite ester synthesized by esterification reaction of pentaerythritol and a mixture of the first carboxylic acid. The first carboxylic acid mixture includes at least one acid selected from C7-C8 monobasic fatty acids, C5 monobasic fatty acids and C4-C9 dibasic acids. The carboxyl group of the dibasic acid accounts for 2 mol% to 20 mol% of the total carboxyl group of the raw material of the first carboxylic acid mixture, and the carboxyl group of the C5 monobasic fatty acid accounts for more than 35 mol% of the total carboxyl group of the raw material of the first carboxylic acid mixture. The second polyol ester is a complex ester synthesized by esterification reaction of pentaerythritol and dipentaerythritol with a second carboxylic acid. The second carboxylic acid mixture includes C4-C9 diacids and C5 monocarboxylic acids. The carboxyl groups of the diacids account for 5 mol% to 15 mol% of the total carboxyl groups in the second carboxylic acid mixture raw materials, the carboxyl groups of the C5 monocarboxylic acids account for more than 85 mol% of the total carboxyl groups in the second carboxylic acid mixture raw materials, and dipentaerythritol accounts for 10 mol% to 50 mol% of the total organic alcohols.

2. The refrigeration oil according to claim 1, characterized in that, The C4-C9 dicarboxylic acids are selected from succinic acid, adipic acid, and octanoic acid.

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

4. The refrigeration oil according to claim 1, characterized in that, The C7-C8 monobasic fatty acids are 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 refrigeration 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 refrigeration oil according to claim 1, characterized in that, The kinematic viscosity of the refrigeration oil at 40°C is 33-120 mm. 2 The kinematic viscosity at 100℃ is 5.2 mm / s. 2 / s or more.

7. The refrigeration oil according to claim 1, characterized in that, It also includes additives, which include at least one of anti-wear agents, antioxidants, anti-foaming agents and acid scavengers.

8. The refrigeration oil according to claim 1, characterized in that, The first polyol ester includes at least one of the structural units shown in Formula [I], and the second polyol ester includes at least one of the structural units shown in Formula [II]. 【I】 【II】 Wherein, R1-R6 are independent C4, C6, or C7 hydrocarbon groups or , 7≥m≥2; R 1 -R 8 For each independent C4 hydrocarbon group or , 7≥n≥2.

9. A working fluid composition for a refrigeration unit, characterized in that, Includes the refrigeration oil and R290 refrigerant as described in any one of claims 1-8.

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

11. The working fluid composition for a refrigeration unit according to claim 9, characterized in that, The working fluid composition for the refrigeration machine has a solubility viscosity of not less than 1.826 cp at 110°C and 2.8 MPa.

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