Base oil of refrigerating machine oil, preparation method of base oil and mixed composition for refrigerating machine

Abstract

The invention discloses refrigerating machine oil base oil, a preparation method of the refrigerating machine oil base oil and a mixed composition for a refrigerating machine. The refrigerating machine oil base oil is mainly composed of polybasic mixed alcohol ester. In a polybasic mixed alcohol ester molecule, a short-chain fat monobasic acid ester structure and a medium-chain and long-chain fatty acid ester structure exist; in the polybasic mixed alcohol ester, the proportion of the short-chain fat monobasic acid ester structure is 5%-20% by weight. The invention also provides a preparation method of the refrigerating machine oil base oil and a mixed composition for a refrigerating machine containing the refrigerating machine oil base oil. The refrigerant base oil and HFO mixed refrigerant has good intermiscibility, excellent oxidation resistance and chemical stability, and can greatly slow down the decomposition of HFO, thereby reducing the generation of trifluoroacetic acid.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer compound compositions and refrigeration oil products, and relates to a refrigeration oil base oil and a preparation method thereof, and a mixed composition for a refrigerator, and in particular to a refrigeration oil base oil suitable for an HFO mixed refrigerant and a preparation method thereof, and a mixed composition for a refrigerator. Background Art

[0002] On September 15, 2021, the Kigali Amendment to the Montreal Protocol officially came into effect in my country. According to the requirements of the Kigali Amendment to the Montreal Protocol, China needs to freeze the production and use of hydrofluorocarbon refrigerants (HFCs) at the baseline level in 2024, and reduce them by 10%, 30%, 50% and 80% in 2029, 2035, 2040 and 2045 respectively. The hydrofluorocarbon refrigerants listed for reduction include R134a and other high GWP substances. So far, the refrigerant used in China's automotive air conditioners is still mainly R134a.

[0003] HFO refrigerants are expected to replace R134a in the field of automotive air conditioning. However, the refrigeration oil is in a low-temperature, high-pressure working environment in the compressor for a long time. To ensure the long-term reliable operation of the compressor, the oxidation resistance and chemical stability of the refrigeration oil are very important. Therefore, for the new HFO mixed refrigerant, it is necessary to develop a matching refrigeration oil with good compatibility, excellent oxidation resistance and chemical stability.

[0004] The patent application with application number WO2018 / 190354 discloses a refrigeration oil suitable for a mixed refrigerant with an HFO content of ≯40%, which is composed of polyvinyl ethers (PVE) or / and polyol esters (POE). However, HFO refrigerants will decompose to produce trifluoroacetic acid (TFA), resulting in an increase in acid value, thereby increasing the possibility of corrosion of metal parts and accelerating the aging of seals, and also causing the degradation of refrigeration oil (especially POE oil). Existing POE oil (also known as common base oil) is mostly produced by reacting medium-chain fatty acids (such as C8 and C9 acids) with polyols (such as pentaerythritol, dipentaerythritol, etc.), which has the problem of incomplete polyol reaction, and the hydroxyl groups that do not participate in the reaction will accelerate the decomposition of HFO. The patent application with application number WO2022 / 209688 discloses the addition of epoxides to common base oils to suppress the increase in acid value, but the addition of epoxides may lead to a decrease in the oxidative stability and chemical stability of the refrigeration oil. Summary of the invention

[0005] In order to solve the problem that the HFO refrigerant decomposes faster to produce TFA due to the high hydroxyl value of the existing POE oil, the present invention provides a refrigeration oil base oil, which has a significantly reduced hydroxyl value, significantly improved chemical stability, and significantly reduced possibility of reacting with HFO mixed refrigerant. When used in conjunction with HFO mixed refrigerant, the decomposition of HFO can be inhibited, thereby reducing the generation of TFA (trifluoroacetic acid). At the same time, the refrigeration oil base oil of the present invention has excellent compatibility, chemical stability and oxidation resistance when used in HFO mixed refrigerant.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: The invention provides a refrigeration oil base oil, which is particularly suitable for HFO mixed refrigerant. The refrigeration oil base oil is mainly composed of polyhydric mixed alcohol esters; in one polyhydric mixed alcohol ester molecule, there are both short-chain fatty monoacid ester structures and medium-chain fatty acid ester structures; in the polyhydric mixed alcohol esters, the proportion (by weight) of the short-chain fatty monoacid ester structures is 5% to 20%.

[0007] According to an embodiment of the present invention, the one polyvalent mixed alcohol ester molecule further includes a short-chain fatty dibasic acid ester structure.

[0008] According to an embodiment of the present invention, the polyhydric mixed alcohol ester is a complex ester in which a short-chain fatty monoacid and a medium-chain fatty acid, as well as an optionally added short-chain fatty diacid, react simultaneously with an alcohol reactant, so that in one polyhydric mixed alcohol ester molecule, there are both a short-chain fatty monoacid ester structure and a medium-chain fatty acid ester structure.

[0009] The basis for judging the proportion of short-chain fatty monoester structures and medium-chain fatty acid ester structures (and optionally short-chain fatty diester structures) in the present invention is to calculate the weight ratio of short-chain fatty acids and medium-chain fatty acids to the total fatty acids after hydrolyzing the complex ester.

[0010] According to an embodiment of the present invention, the refrigeration oil base oil is composed of the polyhydric mixed alcohol ester.

[0011] According to an embodiment of the present invention, in the polyhydric mixed alcohol ester, the proportion (by weight) of short-chain fatty monoester structures is 7% to 15%, preferably 9% to 12%, and exemplified by 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 18% or 20%, and the rest are medium- and long-chain fatty acid ester structures.

[0012] According to an embodiment of the present invention, the alcohol reactant is, for example, a polyol. Specifically, the carbon number of the polyol is 3 to 12, more preferably 4 to 10, and most preferably 5 to 6. For example, the polyol includes, but is not limited to, at least one of pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylolpropane, polymethylolethane, and glycerol.

[0013] According to an embodiment of the present invention, the short-chain fatty monoacid, the medium-chain fatty acid and the short-chain fatty diacid which is optionally added or not added can be either normal or isomeric.

[0014] In one embodiment of the present invention, the carbon number of the short-chain fatty monoacid is 2 to 6, preferably 3 to 5, and more preferably 4 to 5; for example, the short-chain fatty monoacid includes but is not limited to at least one of propionic acid, isopropionic acid, butyric acid, valeric acid, hexanoic acid, isobutyric acid, isovaleric acid, pivalic acid, and isomers of hexanoic acid.

[0015] In one embodiment of the present invention, the carbon number of the medium-long chain fatty acid is 7 to 18, preferably 7 to 12, and more preferably 8 to 10. Among them, the proportion of long-chain fatty acids with a carbon number of not less than 10 (by weight) does not exceed 40% of the total fatty acids (short-chain fatty acids and medium-long chain fatty acids). For example, the medium-long chain fatty acids include, but are not limited to, at least one of caprylic acid, nonanoic acid, capric acid, lauric acid, palmitic acid, stearic acid, arachidic acid, isodecanoic acid, isolauric acid, isopalmitic acid, isostearic acid, isooctanoic acid, isononanoic acid, azelaic acid, linoleic acid, linolenic acid, dodecanedioic acid, neodecanoic acid, 2-ethylheptanoic acid and isononanoic acid. Preferably, it is a mixture of the above two acids, such as a mixture of isononanoic acid and isooctanoic acid, the ratio of the two is (50 to 80): (40 to 10) (a total of 90 parts by mass), for example, 83:12, or 55:35.

[0016] In one embodiment of the present invention, the short-chain fatty dibasic acid includes but is not limited to at least one of succinic acid (i.e., butanedioic acid), glutaric acid, adipic acid, methylsuccinic acid, 2-methylglutaric acid, neopentanoic acid, and the like.

[0017] According to an embodiment of the present invention, the kinematic viscosity of the refrigeration oil base oil at 40°C is 20 to 200 mm 2 / s, preferably 30~150 mm 2 / s, 50~110 mm is the most preferred 2 / s.

[0018] According to an embodiment of the present invention, the hydroxyl value of the refrigerator oil base oil is not greater than 5 mg KOH / g, preferably not greater than 2 mg KOH / g, and more preferably not greater than 1 mg KOH / g.

[0019] According to an embodiment of the present invention, the flash point (opening point) of the refrigerator oil base oil is not lower than 210°C, preferably not lower than 230°C.

[0020] According to an embodiment of the present invention, the pour point of the refrigerator oil base oil is not higher than -30°C, preferably not higher than -35°C.

[0021] According to an embodiment of the present invention, the two-phase separation temperature of the refrigeration oil base oil and the HFO mixed refrigerant in the low temperature section between the weight ratio of 5% and 60% is not higher than -50°C, and the two-phase separation temperature in the high temperature section is not lower than 40°C, that is, the two-phase separation phenomenon will not occur within -50°C to 40°C.

[0022] The present invention also provides a method for preparing the above-mentioned refrigeration oil base oil, the method comprising: reacting an alcohol reactant with a fatty acid to obtain the refrigeration oil base oil; wherein the fatty acid comprises a short-chain fatty monoacid and a medium-chain fatty acid, and the content (by weight) of the short-chain fatty monoacid in the fatty acid is 5% to 20%.

[0023] According to an embodiment of the present invention, the alcohol reactant has the above definition.

[0024] According to an embodiment of the present invention, the reaction molar ratio of the alcohol reactant to the fatty acid is calculated based on the molar ratio of the alcohol hydroxyl group to the fatty acid carboxyl group, and the molar ratio of the alcohol hydroxyl group to the fatty acid carboxyl group is 1:1.1~1:1.2. Exemplarily, the molar ratio of the alcohol hydroxyl group to the fatty acid carboxyl group is 1:1.1, 1:1.12, 1:1.14, 1:1.16, 1:1.18 or 1:1.2.

[0025] According to an embodiment of the present invention, the fatty acid is a mixture of short-chain fatty monoacids and medium-chain fatty acids. Preferably, the content (by weight) of short-chain fatty monoacids in the fatty acid is 7% to 15%, preferably 9% to 12%.

[0026] According to an embodiment of the present invention, the short-chain fatty monoacid has the definition as above.

[0027] According to an embodiment of the present invention, the medium-chain fatty acid has the definition as above.

[0028] According to an embodiment of the present invention, the short-chain fatty dibasic acid has the above definition.

[0029] According to an embodiment of the present invention, the reaction temperature is 180°C to 260°C. Specifically, if the reaction is carried out in the presence of a catalyst, the reaction temperature may be 180°C to 260°C; if no catalyst is added during the reaction, the reaction temperature is 230°C to 260°C; exemplary temperatures are 180°C, 200°C, 230°C, 240°C, 250°C, and 260°C.

[0030] According to an embodiment of the present invention, the reaction time is 6h~24h, preferably 6h~12h, and exemplified by 6h, 8h, 10h, 12h, 15h, 20h, and 24h.

[0031] According to an embodiment of the present invention, the reaction can be carried out in the presence of a catalyst. Preferably, the catalyst can be at least one of an inorganic acid, an organic acid, a solid acid, a metal and a metal compound. For example, the catalyst is selected from at least one of p-toluenesulfonic acid, tributyl phosphate, sodium bisulfate, phosphotungstic acid and silicon-supported phosphotungstic acid. The addition of a catalyst can reduce the temperature of the reaction of the polyol and the fatty acid and shorten the reaction time.

[0032] According to an embodiment of the present invention, the preparation method of the refrigeration oil base oil comprises: in the presence of a catalyst, reacting an alcohol reactant with a fatty acid at 180° C. to 260° C. for 6 h to 12 h to obtain the refrigeration oil base oil; wherein the fatty acid is a mixture of short-chain fatty monoacids and medium-chain fatty acids, and the content (by weight) of short-chain fatty monoacids in the fatty acid is 5% to 20%.

[0033] The present invention also provides use of the above refrigerator oil base oil in an air conditioner including an HFO mixed refrigerant.

[0034] According to an embodiment of the present invention, the HFO mixed refrigerant consists of two parts: component (a) and component (b), wherein: component (a) is selected from at least one of R1132a, R1132 (E), R1123, R1234yf, and R1216; component (b) is selected from at least one of R32, R744, R290, R1311, R1141, R1114, R161, RE143a, and R152a.

[0035] According to an embodiment of the present invention, in the mixture of HFO mixed refrigerant and the above-mentioned refrigeration oil base oil, the content (by weight) of the refrigeration oil base oil can be 1% to 99%, for example, 10% to 90%, and for example, 5% to 60%.

[0036] The present invention also provides a mixed composition for a refrigerator, comprising the refrigerator oil base oil.

[0037] According to an embodiment of the present invention, the mixed composition for a refrigerator further includes an HFO mixed refrigerant.

[0038] According to an embodiment of the present invention, the HFO mixed refrigerant has the above definition.

[0039] According to an embodiment of the present invention, in the mixed composition for refrigerator, the content of the refrigerator oil base oil can be added arbitrarily as needed. For example, the content (by weight) of the refrigerator oil base oil can be 1% to 99%, for example, 10% to 90%, and for example, 5% to 60%.

[0040] According to an embodiment of the present invention, the mixed composition for refrigerators may further include functional additives. Specifically, various functional additives may be selectively added to improve the antioxidant property and chemical stability of the mixed composition for refrigerators.

[0041] According to an embodiment of the present invention, the functional additive includes one or more of an antioxidant, an acid scavenger, and a metal passivator.

[0042] Beneficial effects of the present invention: The present invention provides a refrigeration oil base oil. The base oil has a significantly reduced hydroxyl value, significantly improved chemical stability, and significantly reduced possibility of reacting with an HFO mixed refrigerant. When used in combination with an HFO mixed refrigerant, the base oil can inhibit the decomposition of HFO and thereby reduce the generation of TFA (trifluoroacetic acid).

[0043] Meanwhile, the base oil of the present invention has excellent compatibility with the HFO mixed refrigerant, and the two have excellent chemical stability and oxidation resistance when mixed and used.

[0044] The present invention adds a short-chain fatty monoacid to the existing POE oil, and the short-chain fatty monoacid reacts completely with the hydroxyl groups of the remaining unreacted polyols (such as pentaerythritol, dipentaerythritol, etc.) to generate a short-chain fatty monoacid ester structure, thereby significantly reducing the hydroxyl value of the existing POE oil, improving its chemical stability, reducing the possibility of reaction with HFO refrigerant, thereby inhibiting the decomposition of HFO, and further reducing the generation of TFA (trifluoroacetic acid). DETAILED DESCRIPTION

[0045] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations 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 included in the scope that the present invention is intended to protect.

[0046] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0047] The test methods involved in the following embodiments and comparative examples of the present invention are as follows: Density at 25℃, viscosity at 40℃: GB / T 29617-2013; Flash point (open): GB / T 267-1988; Pour point: GB / T 3535-2006; Hydroxyl value: GB / T 7383-2020; Compatibility with refrigerants: NB / SH / T 0699-2023; Chemical stability: SH / T 0698-2000; Chroma: SH / T 0168-1992; Fluorine content: GB / T 40111-2021; Acid value: GB / T 7304-2014.

[0048] Pentaerythritol (purchased from Anhui Jinhe Industrial Co., Ltd.); isononanoic acid (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.); 2-ethylhexanoic acid (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.); n-valeric acid (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.); oleic acid (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.); KunLun D6603 refrigeration oil compound (purchased from Lubricant Branch of PetroChina Co., Ltd.).

[0049] Example 1 The refrigeration oil base oil is composed of the following components in percentage by weight: 83% of isononanoate structure, 12% of isooctanoate structure, and 5% of n-valerate structure.

[0050] The preparation method of the refrigeration oil base oil is as follows: 100 g of pentaerythritol, 443.75 g of isononanoic acid, 58.47 g of isooctanoic acid and 17.25 g of n-pentanoic acid are weighed and poured into a reactor, and then 6.19 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 min, and then heated to 200°C and reacted for 8 h. After the reaction is completed, the reaction is cooled to room temperature, and the refrigeration oil base oil is obtained through post-treatment processes such as alkali washing and water washing.

[0051] Example 2 The refrigeration oil base oil is composed of the following components in percentage by weight: 55% of isononanoate structure, 35% of isooctanoate structure, and 10% of n-valerate structure.

[0052] The preparation method of the refrigeration oil base oil is as follows: 100 g of pentaerythritol, 294.05 g of isononanoic acid, 170.53 g of isooctanoic acid and 34.51 g of n-pentanoic acid are weighed and poured into a reactor, and then 5.99 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 min, and then heated to 200°C and reacted for 8 h. After the reaction is completed, the reaction is cooled to room temperature, and the refrigeration oil base oil is obtained through post-treatment processes such as alkali washing and water washing.

[0053] The refrigeration oil is prepared by mixing the refrigeration oil base oil of this embodiment and the KunLun D6603 refrigeration oil compound at a weight ratio of 98.5:1.5.

[0054] Example 3 The refrigeration oil base oil is composed of the following components in weight percentage: 80% of isooctanoic acid ester structure and 20% of normal valeric acid ester structure.

[0055] The preparation method of the refrigeration oil base oil is as follows: 100 g of dipentaerythritol, 299.45 g of isooctanoic acid and 53.02 g of n-pentaerythritol are weighed and poured into a reaction kettle, and then 4.52 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 minutes and then heated to 200°C and reacted for 8 hours. After the reaction is completed, the refrigeration oil base oil is obtained by post-treatment processes such as alkali washing and water washing.

[0056] Comparative Example 1 The POE base oil without short-chain fatty acid esters is composed of the following components in weight percentage: 80% isononanoate structure and 20% isooctanoate structure.

[0057] The preparation method of POE base oil without short-chain fatty acid esters is as follows: 100 g of pentaerythritol, 427.71 g of isononanoic acid and 97.45 g of isooctanoic acid are weighed and poured into a reactor, and then 6.25 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 min and then heated to 200°C and reacted for 8 h. After the reaction is completed, the reaction is cooled to room temperature, and the POE base oil without short-chain fatty acid esters is obtained through post-treatment processes such as alkali washing and water washing.

[0058] Comparative Example 2 The POE base oil containing 50% short-chain fatty acid esters is composed of the following components in weight percentage: 50% isononanoate structure and 50% normal valerate structure.

[0059] The preparation method of POE base oil containing 50% short-chain fatty acid esters is as follows: 100 g of pentaerythritol, 255.70 g of isononanoic acid and 165.04 g of n-pentanoic acid are weighed and poured into a reactor, and then 5.21 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 min and then heated to 200°C and reacted for 8 h. After the reaction is completed, the mixture is cooled to room temperature, and a POE base oil containing 50% short-chain fatty acid esters is obtained through post-treatment processes such as alkali washing and water washing.

[0060] Comparative Example 3 The unreacted short-chain fatty acid ester POE base oil is composed of the following components in weight percentage: 55% of isononanoate structure, 35% of isooctanoate structure, and 10% of n-valerate structure.

[0061] The preparation method of the unreacted short-chain fatty acid ester POE base oil is as follows: 100 g of pentaerythritol, 294.05 g of isononanoic acid, 170.53 g of isooctanoic acid and 34.51 g of n-pentanoic acid are weighed and poured into a reactor, and then 5.99 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 min and then heated to 200°C and reacted for 4 h. After the reaction is completed, the mixture is cooled to room temperature and subjected to post-treatment processes such as alkali washing and water washing to obtain a refrigeration oil base oil.

[0062] Comparative Example 4 The POE base oil with excess long-chain fatty acid esters is composed of the following components in weight percentage: 50% oleate structure and 50% n-valerate structure.

[0063] The preparation method of POE base oil with excess long-chain fatty acid esters is as follows: 100 g of dipentaerythritol, 366.57 g of oleic acid and 132.54 g of n-pentaerythritol are weighed and poured into a reactor, and then 5.99 g of p-toluenesulfonic acid is added, and nitrogen is introduced for 5 min and then heated to 200°C and reacted for 8 h. After the reaction is completed, the reaction is cooled to room temperature, and the POE base oil with excess long-chain fatty acid esters is obtained through post-treatment processes such as alkali washing and water washing.

[0064] 1. Physical and chemical properties analysis The chromaticity, density at 25° C., viscosity at 40° C., flash point, pour point, and hydroxyl value of the POE base oils obtained in Examples 1-3 and Comparative Examples 1-4 were measured, and the results are shown in Table 1 below.

[0065] Table 1 Physical and chemical properties

[0066] As can be seen from Table 1, the hydroxyl value of the refrigeration oil base oil obtained in Example 1 is significantly lower than that in Comparative Example 1, which shows that the present invention can significantly reduce the hydroxyl value of the POE base oil by adding short-chain fatty acids to the POE oil to react with the remaining unreacted polyols without affecting other important physical and chemical properties.

[0067] In Comparative Example 3, due to the presence of incompletely esterified pentaerythritol, the POE base oil obtained has a higher hydroxyl value, resulting in poor chemical stability in the refrigerant, and the possibility of reacting with the HFO refrigerant, accelerating the decomposition of HFO, and further promoting the formation of TFA (trifluoroacetic acid).

[0068] In Comparative Example 4, by adding short-chain fatty monobasic acids with a total fatty acid content of 50% to long-chain fatty acids, the POE base oil obtained has a lower flash point and a pour point higher than -30°C, resulting in its chemical stability in the refrigerant being worse than that in the embodiment; and the acid value and fluorine content of the POE base oil are higher than those in the embodiment of the present invention, so it is corrosive to metals; and the two-phase separation temperature of the POE base oil and the refrigerant is about 10°C lower than that in the embodiment.

[0069] 2. Compatibility test of mixed refrigerants with HFO at different oil contents The POE base oil obtained in the above examples and comparative examples was mixed with an HFO mixed refrigerant, and the compatibility of the POE base oil and the HFO mixed refrigerant at different oil contents was measured. The results are shown in Tables 2 and 3 below.

[0070] In this embodiment, the HFO mixed refrigerant is composed of the following components in weight percentage: R1132 (E) 28%, R1234yf 50.5% and R32 21.5%.

[0071] It can be seen from Tables 2 and 3 that the refrigerator oil base oil of the embodiments with different contents are miscible with the HFO mixed refrigerant at -50°C to 40°C, indicating that the present invention is fully compatible with the HFO mixed refrigerant in terms of performance and can meet various usage scenarios of this type of refrigerant.

[0072] Table 2 Low temperature (-70℃~20℃) compatibility test results (℃)

[0073] Table 3 High temperature (20℃~60℃) compatibility test results (℃)

[0074] 3. Chemical stability test The refrigeration oil base oils of Examples 1-3 and Comparative Examples 1-4 and HFO mixed refrigerants were heated at 175° C. for 14 days to conduct a chemical stability test. The results are shown in Table 4.

[0075] In this embodiment, the HFO mixed refrigerant is composed of the following components in weight percentage: R1132 (E) 28%, R1234yf 50.5% and R32 21.5%.

[0076] Table 4 Chemical stability test

[0077] As shown in Table 4, after 14 days of chemical stability test, the chromaticity of the refrigeration oil base oil of Examples 1 and 2 did not change, and the acid value and fluorine content were lower than those of Comparative Examples 1 and 2. This shows that the present invention can effectively slow down the decomposition of HFO to produce fluorine-containing acidic substances such as TFA and slow down metal corrosion by adding short-chain fatty monoesters to the refrigeration oil base oil.

[0078] In summary, the present invention can slow down the decomposition of HFO components in HFO mixed refrigerants to produce TFA by adding short-chain fatty monoesters to the refrigeration oil base oil. The physical and chemical properties of the POE base oil added with short-chain fatty monoesters still meet the relevant national standards, and the low-temperature and high-temperature compatibility with the HFO mixed refrigerant are excellent, and can be miscible with the HFO mixed refrigerant at a ratio of 5% to 60% oil content between -50°C and 40°C.

[0079] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A refrigeration oil base oil, characterized in that: It is mainly composed of polyhydric mixed alcohol esters; in one polyhydric mixed alcohol ester molecule, there are both short-chain fatty monoacid ester structures and medium-chain fatty acid ester structures; in the polyhydric mixed alcohol ester, the proportion of the short-chain fatty monoacid ester structure is 5% to 20% by weight.

2. The refrigerator oil base oil according to claim 1, characterized in that In the polyvalent mixed alcohol ester, the short-chain fatty monoacid ester structure accounts for 7% to 15%, and the rest are medium- and long-chain fatty acid ester structures.

3. The refrigerator oil base oil according to claim 1, characterized in that The carbon number of the short-chain fatty monoacid is 2 to 6; And / or, the carbon number of the medium-chain fatty acid is 8 to 10.

4. The refrigerator oil base oil according to claim 1, characterized in that The polyvalent mixed alcohol ester is a complex ester obtained by reacting short-chain fatty monoacids, medium-chain fatty acids, and optionally added or unadded short-chain fatty diacids with alcohol reactants at the same time; the alcohol reactant is a polyol, and the polyol is selected from at least one of pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylolpropane, polymethylolethane and glycerol.

5. The refrigerator oil base oil according to any one of claims 1 to 4, characterized in that The hydroxyl value of the refrigeration oil base oil is not greater than 5 mg KOH / g; and / or, the flash point of the refrigeration oil base oil is not less than 210°C; And / or, the pour point of the refrigeration oil base oil is not higher than -30°C.

6. The method for preparing a refrigerator oil base oil according to any one of claims 1 to 5, characterized in that: The preparation method comprises: in the presence of a catalyst, reacting an alcohol reactant with a fatty acid at 180° C. to 260° C. for 6 h to 12 h to obtain the refrigeration oil base oil; wherein the fatty acid comprises a short-chain fatty monoacid and a medium-chain fatty acid, and the content of the short-chain fatty monoacid in the fatty acid is 5% to 20% by weight.

7. The preparation method according to claim 6, characterized in that: The molar ratio of the hydroxyl group of the alcohol reactant to the carboxyl group of the fatty acid is 1:1.1 to 1:1.

2.

8. A mixed composition for a refrigerator, comprising the refrigerator oil base oil according to any one of claims 1 to 5.

9. The mixed composition for refrigerator according to claim 8, characterized in that: The mixed composition for refrigerators further includes an HFO mixed refrigerant.

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