Refrigerator oil composition, method for producing the same, and use thereof

Abstract

The application discloses a refrigerating machine oil composition, a preparation method and application thereof. The application adopts a combination of polyol ester base oil and polyalkoxy ether base oil, and by changing the ratio of the two base oils, the two-phase separation temperature of the refrigerating machine oil composition and R290 refrigerant can be regulated, so that the application requirement of significantly improving the compatibility with R290 refrigerant can be met, and the composition has good hydrolysis stability.

Description

Technical Field

[0001] This invention belongs to the technical field of refrigeration oil and its base oil, specifically relating to a refrigeration oil composition, its preparation method and application. Background Technology

[0002] In recent years, refrigerants used in refrigeration oils have increasingly favored hydrofluorocarbons (HFCs), which have zero ozone depletion potential (ODP) and a lower global warming potential (GWP). In household air conditioning compressors, R410A and R22 are currently widely used. Although their ODP is zero, their GWP values ​​are relatively high, leading to their gradual restriction and replacement as refrigerants. Lower hydrocarbons with around 2-4 carbon atoms do not deplete the ozone layer and have a very low impact on global warming, thus attracting increasing attention recently. For example, isobutane (R600a) is already used as a refrigerant in refrigerators, and propane (R290), with 3 carbon atoms, has begun to be used in household air conditioning refrigerants.

[0003] Refrigeration oils used with low-carbon refrigerants include cycloalkanes or paraffins, mineral oils, alkylbenzenes, esters, and polyethers that are compatible with the refrigerant.

[0004] First, when using existing mineral oils, alkylbenzenes, and polyol esters as lubricants, since these lubricants are completely compatible with R290 refrigerant, the viscosity of the lubricant will decrease, the lubrication performance of the oil will decline, which will lead to a decrease in the wear resistance and sealing performance of the compressor, ultimately resulting in a significant reduction in the performance and lifespan of the compressor.

[0005] Secondly, although polyether lubricants are widely used in automotive air conditioning compressors that use R134A as the refrigerant, these polyether lubricants are incompatible with R290. Existing public technology CN103089570 mentions this type of polyether; however, if a refrigeration oil incompatible with the refrigerant is used in the refrigeration system, oil and refrigerant stratification can easily occur on the evaporator. The refrigeration oil will not easily return to the compressor, resulting in insufficient lubrication of the compressor's moving parts and affecting its reliability. Simultaneously, the oil remaining in the evaporator will affect the evaporator's heat exchange efficiency, causing a decrease in the efficiency of the refrigeration system.

[0006] Third, refrigeration oil is a special lubricant for refrigeration compressors and a crucial component in the refrigeration system that determines and affects the refrigeration function and effect. High-quality refrigeration oil must possess excellent compatibility and hydrolytic stability when coexisting with the refrigerant. If the refrigeration oil contains synthetic ester components, it is more prone to hydrolysis, producing acidic substances that can cause corrosion of the metal components inside the compressor.

[0007] Therefore, considering the above three aspects, the key to solving the problem lies in selecting a refrigeration oil with suitable solubility for the refrigerant and good hydrolytic stability. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention provides a refrigeration oil composition comprising a polyol ester base oil and a polyalkoxy ether base oil, wherein the polyol ester base oil comprises carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C, and carboxylic acid ester D selected from the structures shown in formula (I) below:

[0009]

[0010] Wherein, R1 is selected from R8-C(O)- or a group represented by the following formula (II):

[0011]

[0012] R2, R3, R4, R5, R6, and R7 may be the same or different, and are independently selected from R8-C(O)-.

[0013] Each R8 may be identical or different, and is independently selected from either straight or branched C. 3-9 alkyl;

[0014] The condition is that, in the carboxylic ester A, at least one R8 is selected from a straight-chain C3 alkyl group:

[0015] In the carboxylic ester B, at least one R8 is selected from linear or branched C atoms. 4-5 One of alkyl and branched C3 alkyl groups:

[0016] In the carboxylic ester C, at least one R8 is selected from straight-chain or branched C. 6-7 alkyl;

[0017] The carboxylic ester D contains at least three distinct R8s, wherein the distinct R8s are independently selected from straight-chain or branched C atoms. 3-7 alkyl;

[0018] The general formula of the polyalkoxy ether base oil is shown in the following formula (III);

[0019]

[0020] In the formula: R9 is selected from the C of straight chains or branches. 1-5 Alkyl groups and hydrogen atoms, m represents the average number of moles added to the alkyl oxide, and m is a number between 15 and 22.

[0021] According to an embodiment of the present invention, the refrigeration oil composition comprises 10-50% polyol ester base oil and 50-90% polyalkoxyether base oil, calculated as 100% by weight percentage of polyol ester base oil and polyalkoxyether base oil.

[0022] For example, the weight percentage of the polyol ester base oil is 10%, 20%, 30%, 40%, or 50%.

[0023] For example, the polyalkoxy ether base oil has a weight percentage of 90%, 80%, 70%, 60%, or 50%.

[0024] According to embodiments of the present invention, for carboxylic ester A, carboxylic ester B, and / or carboxylic ester C, when R1 is selected from R8-C(O)-, R2, R3, and R4 may be the same or different, and are independently selected from R8-C(O)-. For example, 2, 3, or 4 substituents selected from R1, R2, R3, and R4 are the same. As an example, R1, R2, R3, and R4 are the same.

[0025] According to embodiments of the present invention, for carboxylic ester A, carboxylic ester B, and / or carboxylic ester C, when R1 is selected from groups represented by formula (II), R2, R3, R4, R5, R6, and R7 may be the same or different, and are independently selected from R8-C(O)-. For example, 2, 3, 4, 5, or 6 substituents selected from R2, R3, R4, R5, R6, and R7 may be the same. As an example, R2, R3, R4, R5, R6, and R7 may be the same.

[0026] According to an embodiment of the present invention, when present, 1, 2, 3, 4, 5 or 6 R8s in the carboxylic acid ester A are selected from straight-chain C3 alkyl groups, i.e., n-propyl groups.

[0027] According to an embodiment of the invention, when present, 1, 2, 3, 4, 5, or 6 R8 atoms in the carboxylic ester B are selected from branched C3 alkyl or C4 alkyl groups. 4-5 Alkyl groups, preferably n-pentyl, 2-methylpropyl, isopropyl, 1-methylbutyl, n-butyl, and more preferably straight-chain C4 alkyl groups, i.e., n-butyl.

[0028] According to an embodiment of the present invention, when present, the 1, 2, 3, 4, 5, or 6 R8s in the carboxylic acid ester C are selected from C6 alkyl or C7 alkyl groups, preferably n-heptyl, n-hexyl, 1-ethylpentyl, 1-methylpentyl, or 1-methylhexyl, more preferably branched C groups. 6-7 Alkyl groups, such as 1-methylpentyl, 1-methylhexyl, and 1-ethylpentyl.

[0029] According to an embodiment of the invention, for the carboxylic ester D, there are at least three distinct R8s, for example, three, four, five, or six distinct R8s. The distinct R8s are independently selected from linear or branched C-chains. 3-7 Alkyl groups, and the other groups R8 in the carboxylic ester D may be the same or different, and are independently selected from R8-C(O)-.

[0030] Alternatively, for the carboxylic ester D, when R1 is selected from R8-C(O)-, the groups R8 in R1, R2, R3 and R4 may all be different from each other; or, when there are 3 different R8s among R1, R2, R3 and R4, the other R8 may be the same as any one of the 3 different R8s.

[0031] Alternatively, for the carboxylic ester D, when R1 is selected from the group shown in formula (II), there may be 3, 4, 5, or 6 different R8s. For example, R2, R3, R4, R5, R6, and R7 may all be different; or, when there are 3, 4, or 5 different R8s among R2, R3, R4, R5, R6, and R7, the remaining R8s may be the same as any one of the different R8s.

[0032] According to an embodiment of the present invention, the carboxylic ester D contains at least three distinct R8s, wherein the distinct R8s are independently selected from each other as straight-chain or branched C3 alkyl groups, straight-chain or branched C4 alkyl groups, or C5 alkyl groups. 4-5 Alkyl groups and straight-chain or branched C 6-7 Alkyl group. Preferably, in the carboxylic ester D, at least one R8 is selected from a straight-chain C3 alkyl group (n-propyl group), and at least one R8 is selected from a branched straight-chain or branched C3 alkyl group. 4-5 Alkyl groups (such as n-butyl, 2-methylpropyl, n-pentyl, 1-methylbutyl) and branched C3 alkyl groups (isopropyl), and at least one R8 selected from straight-chain or branched C3 alkyl groups. 6-7 Alkyl groups (such as 1-methylpentyl, 1-methylhexyl, 1-ethylpentyl).

[0033] According to embodiments of the present invention, carboxylic ester A, carboxylic ester B, carboxylic ester C, and carboxylic ester D may be independently selected from compounds of formula (I) with R1 selected from R8-C(O)-, compounds of formula (I) with R1 selected from the group shown in formula (II), or mixtures thereof. The mixture includes, but is not limited to: a mixture of two or more compounds of formula (I) with R1 selected from R8-C(O)-, a mixture of two or more compounds of formula (I) with R1 selected from the group shown in formula (II), or a mixture of at least one compound of formula (I) with R1 selected from R8-C(O)- and at least one compound of formula (I) with R1 selected from the group shown in formula (II).

[0034] When carboxylic ester A, carboxylic ester B, carboxylic ester C, and carboxylic ester D are selected from the mixtures described above, there is no particular limitation on the ratio between the components in the mixture. For example, when the mixture contains two components, the mixing ratio between them can be 1:100 to 100:1, such as 50:1 to 1:50. Examples of such ratios can be selected from the following mixing ratios: 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15. 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, 1:41, 1:41 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, or 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21, 22:1 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1, 40:1, 41, 41, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, 50:1.

[0035] According to an embodiment of the present invention, based on the total mass of the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D, the content of carboxylic acid ester A can be greater than 0% by mass and less than 15% by mass, preferably greater than 0% by mass and less than 10% by mass, more preferably greater than 0% by mass and less than 5% by mass, and even more preferably greater than 0.1% by mass and less than 5% by mass.

[0036] According to an embodiment of the present invention, based on the total mass of the carboxylic ester A, carboxylic ester B, carboxylic ester C and carboxylic ester D, the content of carboxylic ester B can be greater than 0% by mass and less than 15% by mass, preferably greater than 0% by mass and less than 10% by mass, more preferably greater than 0% by mass and less than 5% by mass, and even more preferably greater than 0.1% by mass and less than 5% by mass.

[0037] According to an embodiment of the present invention, based on the total mass of the carboxylic ester A, carboxylic ester B, carboxylic ester C and carboxylic ester D, the content of carboxylic ester C can be greater than 0% by mass and less than 15% by mass, preferably greater than 0% by mass and less than 10% by mass, more preferably greater than 0% by mass and less than 5% by mass, and even more preferably greater than 0.1% by mass and less than 5% by mass.

[0038] According to embodiments of the present invention, when the content of any of the above-mentioned carboxylic esters is described as greater than 0% by mass and less than 15% by mass, it should be understood that the content of the carboxylic ester can be selected from the following mass percentage contents: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%. %, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.0%, or mass percentages between the above values.

[0039] According to an embodiment of the present invention, the content of carboxylic acid ester D can be 55% by mass or more, based on the total mass of carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D.

[0040] According to embodiments of the present invention, the content of the carboxylic ester D may be selected from the following mass percentage contents: 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.9%, or mass percentages between the above values.

[0041] As an example, based on the total mass of the carboxylic acid esters A, B, C, and D, the content of carboxylic acid ester D is preferably 55-99.7% by mass, for example 60-99% by mass, 70-98% by mass, 70-97% by mass, 75-97% by mass, or 80-97% by mass.

[0042] In the context of this application, the sum of the contents of the carboxylic acid esters A, B, C, and D is 100% based on the total mass of the carboxylic acid esters A, B, C, and D.

[0043] According to embodiments of the present invention, the carboxylic acid esters A, B, C and D in the polyol ester base oil have the selection and content shown in Table 2 and Table 2 (continued).

[0044] According to an embodiment of the present invention, the refrigeration oil composition has a polyol ester base oil and a polyalkoxy ether base oil composition as shown in Table 4.

[0045] According to an embodiment of the present invention, the method for preparing the polyol ester base oil includes mixing the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D.

[0046] Preferably, the method involves reacting a polyol selected from pentaerythritol, dipentaerythritol, or a mixture thereof with an aliphatic carboxylic acid R8-COOH or a mixture of two or more aliphatic carboxylic acids R8-COOH to obtain the polyol ester base oil, wherein R8 has the definition described above.

[0047] According to an embodiment of the present invention, the carboxylic ester A, carboxylic ester B, carboxylic ester C or carboxylic ester D is prepared by a method comprising reacting a polyol selected from pentaerythritol, dipentaerythritol or a mixture thereof with an aliphatic carboxylic acid R8-COOH or a mixture of two or more aliphatic carboxylic acids R8-COOH to obtain the carboxylic ester composition, wherein R8 has the definition described above;

[0048] According to an embodiment of the present invention, the reaction is an esterification reaction;

[0049] According to an embodiment of the present invention, the reaction is a heating reaction; for example, the temperature of the reaction can be above 40°C, such as above 60°C, such as above 80°C, above 100°C, above 120°C, above 140°C, preferably 160-250°C;

[0050] According to an embodiment of the present invention, the method for preparing the carboxylic ester D comprises: reacting a polyol selected from pentaerythritol, dipentaerythritol, or mixtures thereof with three or more aliphatic carboxylic acids R8-COOH simultaneously or sequentially to obtain carboxylic ester D, wherein among the three or more aliphatic carboxylic acids, R8 is independently selected from different straight-chain or branched C-chains. 4-8 alkyl;

[0051] According to the method for preparing carboxylic ester D of the present invention, in the three or more aliphatic carboxylic acids, R8 is not the same and is independently selected from straight-chain or branched C3 alkyl groups, straight-chain or branched C4 alkyl groups, and C5 alkyl groups.4-5 Alkyl groups and straight-chain or branched C 6-7 Alkyl group; preferably, among the three or more aliphatic carboxylic acids, at least one R8 is selected from a straight-chain C3 alkyl (n-propyl) aliphatic carboxylic acid, and at least one R8 is selected from a branched straight-chain or branched C3 alkyl group. 4-5 Aliphatic carboxylic acids of alkyl groups (such as n-butyl, 2-methylpropyl, n-pentyl, 1-methylbutyl) and branched C3 alkyl groups (isopropyl), and at least one R8 selected from straight-chain or branched C3 groups. 6-7 Alkyl groups (such as 1-methylpentyl, 1-methylhexyl, 1-ethylpentyl) aliphatic carboxylic acids;

[0052] According to an exemplary embodiment of the method for preparing carboxylic ester D of the present invention, the method for preparing carboxylic ester D may include reacting a polyol selected from pentaerythritol, dipentaerythritol, or mixtures thereof sequentially with three or more aliphatic carboxylic acids R8-COOH, for example:

[0053] (1) The polyol is reacted with the first aliphatic carboxylic acid among the three or more aliphatic carboxylic acids to prepare a first metaester;

[0054] (2) The first ester is reacted with the second aliphatic carboxylic acid among the three or more aliphatic carboxylic acids to prepare the second ester;

[0055] (3) The second ester is reacted with a third aliphatic carboxylic acid among the three or more aliphatic carboxylic acids to prepare the carboxylic acid ester D;

[0056] Alternatively, a polyol selected from pentaerythritol, dipentaerythritol, or mixtures thereof may be reacted simultaneously with three or more aliphatic carboxylic acids R8-COOH to prepare the carboxylic acid ester D.

[0057] According to an embodiment of the present invention, when the polyol is reacted sequentially with the three or more aliphatic carboxylic acids R8-COOH, the acid value of the reaction solution after each reaction can be less than 5 mg KOH / g, for example less than 3 mg KOH / g, such as less than 2 mg KOH / g; for example, it can be carried out under reduced pressure.

[0058] According to an embodiment of the present invention, the preparation method further includes a post-treatment step after the reaction is completed, such as vacuum distillation, pH adjustment, water washing, or other treatment methods known to those skilled in the art.

[0059] According to an embodiment of the present invention, the pH adjustment can be achieved by adding an alkali, such as sodium hydroxide.

[0060] According to an embodiment of the present invention, m is 15, 15.5, 16, 16.5, 17, 17.1, 18, 19, 19.5, 20, 21, 21.8, 22 or any number between any two pairs of values.

[0061] According to an embodiment of the present invention, the polyalkoxy ether base oil is prepared by a method comprising polymerizing propylene oxide in the presence of an initiator and a catalyst.

[0062] According to an embodiment of the invention, the polymerization reaction is carried out in an inert atmosphere, such as a nitrogen atmosphere;

[0063] According to an embodiment of the present invention, the polymerization reaction is carried out at a temperature of 80°C or higher, for example, 100-150°C, such as 110-120°C;

[0064] According to an embodiment of the present invention, the initiator may be selected from at least one of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, n-butanol, etc.; as an example, the initiator may be selected from at least one of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol;

[0065] According to an embodiment of the present invention, the catalyst may be selected from at least one of alkali metal hydroxides or compounds in which the hydrogen of the hydroxyl group of an alcohol is replaced by an alkali metal, such as at least one of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide.

[0066] According to an embodiment of the present invention, the method further includes purifying the crude product obtained from the polymerization reaction; preferably, the purification includes adding water, phosphoric acid and magnesium silicate polyether refining agent, as well as dehydration and filtration steps;

[0067] As an example, 1–5 wt% of deionized water, 0.15–0.45 wt% of phosphoric acid, and 0.03–0.1 wt% of magnesium silicate polyether refining agent were added to the crude product.

[0068] According to an embodiment of the present invention, after adding water, phosphoric acid and magnesium silicate polyether refining agent, the resulting mixture is stirred at 75-95°C for 1-2 hours, then vacuum dehydrated until the water content reaches below 0.01%, and then subjected to circulating filtration to finally obtain polyalkoxy ether base oil.

[0069] According to an embodiment of the present invention, the refrigeration oil composition further comprises an acid scavenger, which includes, but is not limited to, carbodiimide compounds, such as at least one selected from the following: dialkylcarbodiimide, diphenylcarbodiimide, bis(alkylphenyl)carbodiimide, diisopropylcarbodiimide, dicyclohexylcarbodiimide, xylylcarbodiimide, bis(isopropylphenyl)carbodiimide, bis(diisopropylphenyl)carbodiimide, bis(triisopropylphenyl)carbodiimide, bis(butylphenyl)carbodiimide, bis(dibutylphenyl)carbodiimide, or bis(nonylphenyl)carbodiimide, etc.

[0070] According to an embodiment of the present invention, the refrigeration oil composition further contains an anti-wear agent. For example, the anti-wear agent includes, but is not limited to, at least one selected from the following: phosphate esters, thiophosphate esters, zinc dialkyl dithiophosphate, triphenyl phosphate (TPP), tricresyl phosphate (TCP), or triphenyl thiophosphate (TPPT).

[0071] According to an embodiment of the present invention, the refrigeration oil composition further contains antioxidants, including but not limited to di-tert-butyl-p-cresol and / or alkyl diphenylamine.

[0072] The present invention also provides a method for preparing the above-described refrigeration oil composition:

[0073] The above-mentioned polyol ester base oil and polyalkoxy ether base oil are mixed to obtain the refrigeration oil composition.

[0074] According to an embodiment of the present invention, the polyol ester base oil and the polyalkoxy ether base oil are mixed in a certain weight percentage, such as 10:90, 20:80, 30:70, 40:60, or 50:50, and stirred evenly to obtain a refrigeration oil composition.

[0075] The present invention also provides a fluid composition comprising the refrigeration oil composition described above and a refrigerant.

[0076] According to an embodiment of the present invention, the refrigerant is selected from alkane refrigerants, such as R290 refrigerant (propane refrigerant).

[0077] According to an embodiment of the present invention, when the content of the refrigeration oil composition in the fluid composition is 20 wt%, the two-phase separation temperature of the refrigeration oil composition and R290 refrigerant is -25°C to 20°C.

[0078] According to an embodiment of the present invention, the total acidity (TAN) of the refrigeration oil composition is less than 0.1 mg KOH / g, preferably less than 0.01 mg KOH / g.

[0079] The present invention also provides the application of the refrigeration oil composition or fluid composition in compression refrigeration, air conditioning or heat pump systems.

[0080] Terminology Definitions and Explanations

[0081] Unless otherwise defined, all technical terms in this document have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent applications, and publications cited in this document are incorporated herein by reference in their entirety.

[0082] It should be understood that the above summary and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of this application. In this application, unless otherwise specifically stated, the singular is used to include the plural. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “containing” are not for limiting purposes.

[0083] The numerical ranges described in this application specification and claims, when defined as "integers," should be understood to include the two endpoints of the range and every integer within that range. For example, "integers from 0 to 10" should be understood to include every integer of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. When the numerical range is not defined as "integers" or is defined as "numbers," it should be understood to include the two endpoints of the range, every integer within that range, and every decimal within that range. For example, "greater than 0 and less than 15" should be understood to include not only every integer greater than 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15, but also at least the sum of 0 or any other integer with 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9.

[0084] The terms “optional / arbitrary” or “optionally / arbitrarily” mean that the event or situation described below may or may not occur, including both the occurrence and non-occurrence of the event or situation.

[0085] The term "alkyl" should be understood to preferably refer to a straight-chain or branched saturated monovalent hydrocarbon group. For example, the term "straight-chain or branched C64" is used to refer to a saturated monovalent hydrocarbon group. 3-9"alkyl" should be understood to preferably represent a straight-chain or branched saturated monovalent hydrocarbon group having 1, 2, 3, 4, 5, 6, 7, 8, or 9 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl (2-methylpropyl), sec-butyl (1-methylpropyl), tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, 1,2-dimethylbutyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, etc., or their isomers.

[0086] It should be understood that, unless otherwise defined, when the prefix "n" is omitted in the description, alkyl such as propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl should be understood as n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and n-nonyl.

[0087] The term "partial ester" refers to the product formed by the esterification of some of the hydroxyl groups of an alcohol with multiple hydroxyl groups.

[0088] The term "total ester" refers to the product formed by the esterification of all the hydroxyl groups of an alcohol with multiple hydroxyl groups.

[0089] Beneficial effects

[0090] The composition of the present invention, consisting of a polyol ester base oil and a polyalkoxy ether base oil, can be used to control the two-phase separation temperature between the refrigeration oil composition and R290 refrigerant by changing the ratio of the two base oils. This significantly improves the compatibility with R290 refrigerant and meets the application requirements. At the same time, the composition has good hydrolytic stability. Detailed Implementation

[0091] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0092] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0093] To ensure that the refrigeration oil composition has good viscosity-temperature properties and thermal stability, when selecting polyol ester base oil and polyalkoxy ether base oil for blending, it is necessary to first test the kinematic viscosity of each component at 40°C. Preferably, the kinematic viscosity of components A and B at 40°C differs by less than ±20%, more preferably by less than ±10%, and even more preferably by less than ±5%.

[0094] The ratio of the difference in kinematic viscosity between compound A and compound B is calculated using equation (1):

[0095] The difference ratio = (kinematic viscosity of compound A - kinematic viscosity of compound B) / kinematic viscosity of compound B × 100%.

[0096] Preparation of carboxylic ester A

[0097] The following carboxylic acid ester A samples 1a-1d were synthesized according to methods known in the art:

[0098] 1a: A tetraester synthesized from pentaerythritol and n-butyric acid;

[0099] 1b: A hexaester synthesized from dipentaerythritol and n-butyric acid;

[0100] 1c: A mixture of tetraesters and hexaesters synthesized from pentaerythritol (50% by mass) and dipentaerythritol (50% by mass) with butyric acid, respectively;

[0101] 1d: A mixture of tetraesters and hexaesters synthesized from pentaerythritol (50% by mass) and dipentaerythritol (50% by mass) with 3,5,5-trimethylhexanoic acid.

[0102] Preparation of carboxylic acid ester B

[0103] The following carboxylic acid esters B samples 2a to 2f were synthesized according to methods known in the art:

[0104] 2a: A mixture of tetraesters and hexaesters synthesized from pentaerythritol (90% by mass) and dipentaerythritol (10% by mass) with 2-methylpropionic acid, respectively;

[0105] 2b: A hexaester synthesized from dipentaerythritol and n-valeric acid;

[0106] 2c: A mixture of tetraesters and hexaesters synthesized from pentaerythritol (10% by mass) and dipentaerythritol (90% by mass) with n-valeric acid, respectively;

[0107] 2d: A tetraester synthesized from pentaerythritol and 3-methylbutyric acid;

[0108] 2e: A mixture of tetraesters and hexaesters synthesized from pentaerythritol (50% by mass) and dipentaerythritol (50% by mass) with hexanoic acid, respectively;

[0109] 2f: A hexaester synthesized from dipentaerythritol and 2-methylvaleric acid.

[0110] Preparation of carboxylic acid ester C

[0111] The following carboxylic acid esters C samples 3a to 3c were synthesized according to methods known in the art:

[0112] 3a: A hexaester synthesized from dipentaerythritol and 2-methylhexanoic acid;

[0113] 3b: A tetraester synthesized from pentaerythritol and 2-methylheptanoic acid;

[0114] 3c: A mixture of tetraesters and hexaesters synthesized from pentaerythritol (50% by mass) and dipentaerythritol (50% by mass) with 2-ethylhexanoic acid.

[0115] Preparation of carboxylic acid ester D

[0116] Prepare samples 4a to 4g of carboxylic acid ester D according to the raw materials and molar ratios listed in Table 1 below:

[0117] Table 1. Molar ratio of fatty acids and polyols for each sample of carboxylic acid ester D.

[0118]

[0119]

[0120] Note: "-" indicates that it is not used.

[0121] The synthesis steps for samples 4a to 4g are as follows:

[0122] (1) Polyol and fatty acid 2 were added to a four-necked flask equipped with a thermometer, a nitrogen bubbling tube, a stirrer, and an oil-water separator, in the amounts shown in Table 1. Under nitrogen bubbling, the temperature was gradually increased to 180°C, allowing the polyol and fatty acid 2 to react until the acid value of the reaction solution became below 10 mg KOH / g. Subsequently, the reaction was subjected to vacuum distillation until the acid value of the reaction solution became below 2 mg KOH / g. After cooling the reaction to 70°C, 0.5% by mass of a sodium hydroxide aqueous solution (30% by mass) relative to the total amount of the reaction solution was added. The mixture was stirred at 70°C for 15 minutes, allowed to stand for 60 minutes, and then the water layer separated from the bottom of the mixture was removed. Then, 5% by mass of water relative to the total amount of the reaction solution was added, the mixture was stirred at 70°C for 15 minutes, allowed to stand for 60 minutes, and then the water layer separated from the bottom of the mixture was removed. This operation was repeated twice. Thus, the first metaester formed by the reaction of polyol and fatty acid 2 was obtained.

[0123] (2) The first metaester was added to the amounts of fatty acid 3 shown in Table 1. Under nitrogen bubbling, the temperature was gradually increased to 215°C, allowing the first metaester and fatty acid 3 to react until the acid value of the reaction solution became below 10 mg KOH / g. Subsequently, the reaction was subjected to vacuum distillation until the acid value of the reaction solution became below 3 mg KOH / g. After cooling the reaction to 70°C, 0.7% by mass of a sodium hydroxide aqueous solution (30% by mass) relative to the total amount of the reaction solution was added. The mixture was stirred at 70°C for 15 minutes, allowed to stand for 60 minutes, and then the water layer separated from the bottom of the mixture was removed. Then, 5% by mass of water relative to the total amount of the reaction solution was added, the mixture was stirred at 70°C for 15 minutes, allowed to stand for 60 minutes, and then the water layer separated from the bottom of the mixture was removed. This operation was repeated twice. Thus, the second metaester formed by the reaction of the first metaester and fatty acid 3 was obtained.

[0124] (3) The obtained second ester was added with the amount of fatty acid 1 shown in Table 1. Under nitrogen bubbling, the temperature was gradually increased to 160°C to allow the second ester and fatty acid 1 to react until the hydroxyl value of the reaction solution became below 5 mg KOH / g. Subsequently, the reaction was subjected to vacuum distillation until the acid value of the reaction solution became below 2 mg KOH / g. After cooling the reaction to 70°C, 0.5% by mass of sodium hydroxide aqueous solution (30% by mass) relative to the total amount of the reaction solution was added, and the mixture was stirred at 70°C for 15 minutes. After standing for 60 minutes, the water layer separated from the bottom of the mixture was removed. Then, 5% by mass of water relative to the total amount of the reaction solution was added, and the mixture was stirred at 70°C for 15 minutes. After standing for 60 minutes, the water layer separated from the bottom of the mixture was removed, and this operation was repeated twice. Next, 3% by mass of activated clay and 3% by mass of activated carbon relative to the total amount of the reaction solution were added, and the mixture was stirred at 100°C to dehydrate. Finally, the adsorbent was removed by filtration to obtain the full ester, which is the sample of carboxylic acid ester D.

[0125] Preparation of polyol ester base oils

[0126] Using the samples of carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C, and carboxylic acid ester D mentioned above, and mixing them according to the mass percentages in Table 2 below, polyol ester base oil 1-13 was prepared.

[0127] Table 2. Content of various carboxylic acid esters in polyol ester base oils

[0128]

[0129] Note: "-" indicates that it is not used.

[0130] Table 2 (continued) Content of various carboxylic acid esters in polyol ester base oils

[0131]

[0132] Note: "-" indicates that it is not used.

[0133] Preparation of polyalkoxy ether base oils

[0134] Preparation Example 14

[0135] First, 9 wt% propylene glycol and 0.02 wt% potassium hydroxide catalyst were added sequentially to the reactor. Nitrogen was used to purge the reactor three times, and the pressure was evacuated to 0.06 MPa. The temperature was raised to 110°C, and 92 wt% propylene oxide was continuously introduced while controlling the reaction temperature to not exceed 120°C. After the feed was completed, the reactor was aged and absorbed for 0.5 h, evacuated for 10 min, cooled, and discharged to obtain crude ether. Then, 0.1 wt% deionized water, 0.03 wt% phosphoric acid, and 0.03 wt% magnesium silicate polyether refining agent were added to the crude ether. The mixture was stirred at 90°C for 1 h, and then vacuum dehydrated until the water content reached below 0.01%. After circulating filtration, polyalkoxy ether base oil B was finally obtained.

[0136] The average molar addition number m of propylene oxide in the prepared polyalkoxy ether base oil B is 15.5.

[0137] Preparation Example 15

[0138] First, 8 wt% propylene glycol and 0.02 wt% potassium hydroxide catalyst were added sequentially to the reactor. Nitrogen was used to purge the reactor three times, and the pressure was evacuated to 0.06 MPa. The temperature was raised to 110°C, and 92 wt% propylene oxide was continuously introduced while controlling the reaction temperature to not exceed 120°C. After the feeding was completed, the reactor was aged and absorbed for 0.5 h, evacuated for 10 min, cooled, and discharged to obtain crude ether. Then, 0.1 wt% deionized water, 0.03 wt% phosphoric acid, and 0.03 wt% magnesium silicate polyether refining agent were added to the crude ether. The mixture was stirred at 90°C for 1 h, and then vacuum dehydrated until the water content reached below 0.01%. After circulating filtration, polyalkoxy ether base oil B was finally obtained.

[0139] The average molar addition number m of propylene oxide in the prepared polyalkoxy ether base oil B is 16.5.

[0140] Preparation Example 16

[0141] First, 7.5 wt% propylene glycol and 0.02 wt% potassium hydroxide catalyst were added sequentially to the reactor. The reactor was purged with nitrogen three times, evacuated to 0.06 MPa, and heated to 110°C. 92.5 wt% propylene oxide was continuously introduced, and the reaction temperature was controlled not to exceed 120°C. After feeding, the reactor was aged and absorbed for 0.5 h, evacuated for 10 min, cooled, and discharged to obtain crude ether. Then, 0.1 wt% deionized water, 0.03 wt% phosphoric acid, and 0.03 wt% magnesium silicate polyether refining agent were added to the crude ether. The mixture was stirred at 90°C for 1 h, and then vacuum dehydrated until the water content reached below 0.01%. After circulating filtration, polyalkoxy ether base oil B was finally obtained.

[0142] The average molar addition number m of propylene oxide in the prepared polyalkoxy ether base oil B is 17.1.

[0143] Preparation Example 17

[0144] First, 7 wt% propylene glycol and 0.02 wt% potassium hydroxide catalyst were added sequentially to the reactor. Nitrogen was used to purge the mixture three times, and the pressure was evacuated to 0.06 MPa. The temperature was raised to 110°C, and 93 wt% propylene oxide was continuously introduced. The reaction temperature was controlled to not exceed 120°C. After the feeding was completed, the mixture was aged and absorbed for 0.5 h, evacuated for 10 min, cooled, and discharged to obtain crude ether. Then, 0.1 wt% deionized water, 0.03 wt% phosphoric acid, and 0.03 wt% magnesium silicate polyether refining agent were added to the crude ether. The mixture was stirred at 90°C for 1 h, and then vacuum dehydrated until the water content reached below 0.01%. After circulating filtration, polyalkoxy ether base oil B was finally obtained.

[0145] The average molar addition number m of propylene oxide in the prepared polyalkoxy ether base oil B is 19.5.

[0146] Preparation Example 18

[0147] First, 6 wt% propylene glycol and 0.2 wt% potassium hydroxide catalyst were added sequentially to the reactor. The reactor was purged with nitrogen three times, evacuated to 0.06 MPa, and heated to 110°C. 94 wt% propylene oxide was continuously introduced, and the reaction temperature was controlled not to exceed 120°C. After feeding, the reactor was aged and absorbed for 0.5 h, evacuated for 10 min, cooled, and discharged to obtain crude ether. Then, 0.1 wt% deionized water, 0.03 wt% phosphoric acid, and 0.03 wt% magnesium silicate polyether refining agent were added to the crude ether. The mixture was stirred at 90°C for 1 h, and then vacuum dehydrated until the water content reached below 0.01%. After circulating filtration, polyalkoxy ether base oil B was finally obtained.

[0148] The average molar addition number m of propylene oxide in the prepared polyalkoxy ether base oil B is 21.8.

[0149] The average molar addition number of propylene oxide to the polyalkoxy ether base oils of the preparation examples 14-18 above is shown in Table 3 below.

[0150] Table 3. Average molar addition of propylene oxide to polyalkoxy ether base oils.

[0151]

[0152] Preparation of Refrigeration Oil Composition

[0153] Preparation of Examples 1-22: The polyol ester base oil and polyalkoxy ether base oil prepared above were mixed according to the mass percentages in Table 4 below. After mixing, the mixture was stirred evenly to prepare refrigeration oil compositions 1-22.

[0154] Table 4. Content of polyol ester base oil and polyalkoxy ether base oil in Examples 1-22

[0155]

[0156]

[0157] Preparation of Comparative Examples 1-7

[0158] The above-mentioned polyol ester base oil and polyalkoxy ether base oil are mixed according to the mass percentages in Table 5 below, and stirred evenly to prepare refrigeration oil compositions 1-7.

[0159] Table 5. Content of polyol ester base oil and polyalkoxy ether base oil in Comparative Examples 1-7

[0160]

[0161] Note: "-" indicates that it is not used.

[0162] Test Example 1

[0163] Test method:

[0164] Compatibility: The test shall be conducted in accordance with the test method described in SH / T 0699-2000 "Test Method for Compatibility of Refrigeration Oil and Refrigerant". The two-phase separation temperature when the content of the refrigeration oil composition sample is 20% by mass shall be used to characterize the compatibility (miscibility).

[0165] Chemical stability: The chemical stability of refrigeration oil compositions in refrigeration systems was tested using the method specified in SH / T 0698-2000.

[0166] Hydrolytic stability: Referring to SH / T 0698-2000, steel, copper, and aluminum metal test rods as catalysts and 2000 ppm water were added to a beaker containing a sample of the refrigeration oil composition. The beaker was then placed in a pressure-resistant stainless steel reactor, and a certain amount of R32 refrigerant was injected before sealing the reactor. The sealed reactor was then heated at 150℃ for 14 days. The hydrolytic stability of the refrigeration oil and refrigerant was evaluated based on the appearance and color of the metal test rods and the acid value of the refrigeration oil composition after the test. Acceptance standard: The acid value of the oil sample after the hydrolytic stability test should not exceed 0.05 mg KOH / g.

[0167] Test results:

[0168] The refrigeration oil compositions of Examples 1-22 and Comparative Examples 1-7 were subjected to compatibility, chemical stability and hydrolytic stability tests. The test results are shown in Tables 6 and 7 below.

[0169] Table 6 Test results of Examples 1-22

[0170]

[0171] Table 7 Test results of Comparative Examples 1-7

[0172]

[0173]

[0174] Note: "-" indicates that this performance was not tested.

[0175] The test results in Table 6 above show that the refrigeration oil compositions in Examples 1-22 of this application all have good compatibility and hydrolytic stability with R290 refrigerant.

[0176] Comparative Examples 1 and 2 used polyol ester base oils without adding polyalkoxy ether base oils. Although they both have good compatibility with R290, their two-phase separation temperatures are both below -50℃. When they are combined with refrigerant, the refrigerant will dilute the viscosity of the refrigeration oil significantly, resulting in a large decrease in viscosity. The decrease in viscosity will reduce lubricity and cause wear on sliding parts. Therefore, it is meaningless to continue with other test items.

[0177] Comparative Examples 3 and 4 used polyalkoxy ether base oils without adding polyol ester base oils, which are incompatible with R290 refrigerant; therefore, further testing was meaningless. Comparative Example 5 prepared a mixed ester (carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C, and carboxylic acid ester D) by reacting a polyol with n-butyric acid, 3-methylbutyric acid, and 2-methylheptanoic acid. The content of carboxylic acid esters A, B, and C in the mixed ester was greater than 15%. The test results showed that the mixed carboxylic acid ester had a low two-phase separation temperature. Furthermore, after hydrolysis stability testing, the acid value of the above oil sample reached 0.3 mg KOH / g, which did not meet the requirements of the compressor OEM manufacturer.

[0178] Comparative Example 6 used a polyol and a full ester of 3,5,5-trimethylhexanoic acid to replace carboxylic acid ester A. However, the ratio of the two components did not meet the requirements. The test results showed that the base oil had poor compatibility with R290 and was not suitable for heat pump and low-temperature applications. Therefore, it was meaningless to continue with other test items.

[0179] Comparative Example 7 uses polyol ester base oil and polyalkoxy ether base oil that meet the requirements. However, the ratio of the two components does not meet the requirements, resulting in the two-phase separation temperature of the components and R290 refrigerant being close to -45°C. This will cause the lubrication performance to fail to meet the application requirements.

[0180] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A refrigeration oil composition, characterized in that, The composition comprises polyol ester base oil and polyalkoxy ether base oil, calculated as 100% by weight of the total weight percentage of polyol ester base oil and polyalkoxy ether base oil, and the refrigeration oil composition contains 10-50% polyol ester base oil and 50-90% polyalkoxy ether base oil. The polyol ester base oil comprises carboxylic acid esters A, B, C, and D selected from the structures shown in formula (I) below: （I） Wherein, R1 is selected from R8-C(O)- or a group represented by the following formula (II): (II) R2, R3, R4, R5, R6, and R7 may be the same or different, and are independently selected from R8-C(O)-. Each R8 may be identical or different, and is independently selected from either straight or branched C. 3-9 alkyl; The condition is that, in the carboxylic acid ester A, R8 is selected from a straight-chain C3 alkyl group: In the carboxylic acid ester B, R8 is selected from straight-chain or branched C. 4-5 One of alkyl and branched C3 alkyl groups: In the carboxylic ester C, R8 is selected from straight-chain or branched C. 6-7 alkyl; In the carboxylic ester D, at least one R8 is selected from a straight-chain C3 alkyl group, and at least one R8 is selected from a straight-chain or branched C3 alkyl group. 4-5 Alkyl groups and branched C3 alkyl groups, and at least one R8 selected from straight-chain or branched C3 alkyl groups. 6-7 alkyl; Based on the total mass of the carboxylic acid esters A, B, C, and D, the content of carboxylic acid ester A is greater than 0% by mass and less than 15% by mass, the content of carboxylic acid ester B is greater than 0% by mass and less than 15% by mass, the content of carboxylic acid ester C is greater than 0% by mass and less than 15% by mass, and the content of carboxylic acid ester D is greater than 55% by mass. The general formula of the polyalkoxy ether base oil is shown in the following formula (III); (III) In the formula: R9 is selected from the C of straight chains or branches. 1-5 Alkyl groups and hydrogen atoms, m represents the average number of moles added to the epoxide, and m is a number between 15 and 22.

2. The composition according to claim 1, characterized in that, The weight percentage of the polyol ester base oil is 10%, 20%, 30%, 40% or 50%, and the weight percentage of the polyalkoxy ether base oil is 90%, 80%, 70%, 60% or 50%.

3. The composition according to claim 1, characterized in that, For the carboxylic ester A, the carboxylic ester B and / or the carboxylic ester C, when R1 is selected from R8-C(O)-, R2, R3, and R4 are the same or different and are independently selected from R8-C(O)-. For the carboxylic ester A, the carboxylic ester B and / or the carboxylic ester C, when R1 is selected from the group shown in formula (II), R2, R3, R4, R5, R6 and R7 are the same or different, and are independently selected from R8-C(O)-. And / or, for the carboxylic ester D, there are at least three distinct R8s, wherein the distinct R8s are independently selected from linear or branched C-chains. 3-7 Alkyl groups, and the other groups R8 in the carboxylic ester D are the same or different, and are independently selected from R8-C(O)-.

4. The composition according to claim 1, characterized in that, For the carboxylic ester D, when R1 is selected from R8-C(O)-, the groups R8 in R1, R2, R3 and R4 are all different from each other; or, when there are 3 different R8s in R1, R2, R3 and R4, the other R8 is the same as any of the 3 different R8s; when R1 is selected from the group shown in formula (II), there are 3, 4, 5 or 6 different R8s.

5. The composition according to claim 1, characterized in that, The carboxylic acid esters A, B, C, and D are independently selected from compounds of formula (I) when R1 is selected from R8-C(O)-, compounds of formula (I) when R1 is selected from the group shown in formula (II), or mixtures thereof; The mixture includes: a mixture of two or more compounds of formula (I) with R1 selected from R8-C(O)-, a mixture of two or more compounds of formula (I) with R1 selected from the group shown in formula (II), or a mixture of at least one compound of formula (I) with R1 selected from R8-C(O)- and at least one compound of formula (I) with R1 selected from the group shown in formula (II).

6. The composition according to claim 1, characterized in that, Based on the total mass of the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D, the content of carboxylic acid ester A is greater than 0% by mass and less than 10% by mass; And / or, based on the total mass of the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D, the content of carboxylic acid ester B is greater than 0% by mass and less than 10% by mass; And / or, based on the total mass of the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D, the content of carboxylic acid ester C is greater than 0% by mass and less than 10% by mass; And / or, based on the total mass of the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D, the content of carboxylic acid ester D is 55 to 99.7% by mass.

7. The composition according to any one of claims 1-6, characterized in that, The refrigeration oil composition also contains an acid scavenger, which includes a carbodiimide compound; And / or, the refrigeration oil composition further contains an anti-wear agent; And / or, the refrigeration oil composition also contains antioxidants.

8. A method for preparing the refrigeration oil composition according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: mixing polyol ester base oil and polyalkoxy ether base oil to obtain the refrigeration oil composition.

9. The preparation method according to claim 8, characterized in that, The method for preparing the polyol ester base oil includes mixing the carboxylic acid ester A, carboxylic acid ester B, carboxylic acid ester C and carboxylic acid ester D; And / or, the polyalkoxy ether base oil is prepared by a method comprising polymerizing propylene oxide in the presence of an initiator and a catalyst.

10. The preparation method according to claim 8, characterized in that, The method for preparing the polyol ester base oil includes reacting a polyol selected from pentaerythritol, dipentaerythritol, or a mixture thereof with an aliphatic carboxylic acid R8-COOH or a mixture of two or more aliphatic carboxylic acids R8-COOH to obtain the polyol ester base oil.

11. A fluid composition, characterized in that, The composition comprises the refrigeration oil composition according to any one of claims 1-7 and the refrigerant.

12. The fluid composition according to claim 11, characterized in that, The refrigerant is selected from alkane refrigerants.

13. The fluid composition according to claim 11, characterized in that, The refrigerant is R290 refrigerant.

14. The fluid composition according to claim 13, characterized in that, When the content of the refrigeration oil composition in the fluid composition is 20 wt%, the two-phase separation temperature of the refrigeration oil composition and R290 refrigerant is -25°C to 20°C. The total acidity (TAN) of the refrigeration oil composition is less than 0.1 mg KOH / g.

15. The use of the refrigeration oil composition of any one of claims 1-7 or the fluid composition of any one of claims 11-14 in a compression refrigeration, air conditioning or heat pump system.

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