A highly compatible refrigeration oil

Abstract

The present invention provides a highly compatible refrigeration oil, and the main component of the base oil is a composite ester. The highly compatible refrigeration oil of the present invention meets the requirements for use in refrigerators with difluoromethane (R32 refrigerant) as the working medium under various operating conditions (refrigeration condition / heat pump condition), and can also be compatible with refrigerators using other HFCs refrigerants. This refrigeration oil uses a composite ester as the main base oil and a composite additive formulation, so as to be used together with the R32 refrigerant in the refrigerator system. The refrigeration oil of the present invention can have good low-temperature compatibility with the R32 refrigerant, and at the same time, the mixed fluid formed with the refrigerant can have good dissolution viscosity, good stability, and can protect the normal operation of the refrigerator for a long time.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration oils, and particularly to a highly compatible refrigeration oil. The refrigerators preferred by the present invention more refer to large systems such as scroll compressors and large-capacity rotary compressors. Background Art

[0002] Currently, the use of R32 refrigerant in the refrigerator market is mainly concentrated in scroll compressors and rotary compressors. Due to its environmental friendliness and high efficiency, R32 refrigerant is increasingly becoming the mainstream in the market. Its application scenarios have also changed from simple refrigeration to both cooling and heating, and then to heat pump systems.

[0003] Although R32 has many advantages as a working fluid, due to its strong polarity and high gas pressure, there are still certain defects in the current refrigeration oils in the market, or they can only be applied to small-capacity compressors, or they can only meet some application scenarios.

[0004] For larger refrigeration systems and operating conditions with relatively low evaporation temperatures, the poor compatibility between the current refrigeration oil and R32 often affects the system. The problem of oil return not only fails to ensure the lubrication of the compressor, but also often triggers high-temperature and high-pressure alarms. Therefore, a refrigeration oil with good low-temperature compatibility is needed.

[0005] When using refrigerants with relatively high pressures such as R32, the exhaust temperature of the compressor is also higher than that of other refrigerants. At this time, the viscosity of the mixed fluid composed of the refrigeration oil and the refrigerant will become smaller, the oil film will become thinner, and the lubrication conditions will be more severe. Therefore, higher requirements are imposed on the oil film strength and lubricity of the refrigeration oil. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a highly compatible refrigeration oil for R32 refrigerant, which has good dissolution viscosity, can maintain a relatively thick oil film, has excellent wear resistance, and at the same time has excellent compatibility with the refrigerant, can meet different usage scenarios of refrigerators, especially the emerging heat pump application scenarios, so as to protect the long-term and reliable operation of the refrigerator, especially the refrigeration compressors of large systems.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions to achieve:

[0008] A highly compatible refrigeration oil for R32 refrigerant mainly consists of a composite ester, which is synthesized from neopentyl glycol, adipic acid, and a monocarboxylic acid with 4-9 carbon atoms. This composite ester serves as the main base oil of the refrigeration oil.

[0009] The low-temperature two-phase separation temperature of the refrigeration oil composed of the composite ester and R32 is less than -20°C, and the viscosity of the working fluid composition for the refrigerator formed with the refrigerant is not less than 2.0 cP and not higher than 3.0 cP at 100°C and an absolute pressure of 4.35 MPa.

[0010] The monobasic fatty acid constituting the composite ester can only be one or two; when there is only one monobasic fatty acid constituting the composite ester base oil, the carbon number of the monobasic fatty acid is 4 or 5; when there are two monobasic fatty acids constituting the composite ester base oil, the carbon number of one monobasic fatty acid is 4 or 5, and the carbon number of the other monobasic fatty acid is 6-9.

[0011] In order to further improve the comprehensive performance of the refrigeration oil composition, one or more of various lubricating oil additives can be selectively added, including antioxidants, acid scavengers, anti-wear agents, rust inhibitors, metal deactivators, defoamers, etc.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] For the refrigeration oil of the present invention, it can be completely miscible with the R32 refrigerant at a relatively low temperature. At the same time, the viscosity of the refrigeration oil can be maintained after dissolution, improving the lubricity of the refrigeration oil and having good stability, protecting the normal operation of the refrigerator under various operating conditions in the long term. Detailed Embodiments

[0014] To enable those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below.

[0015] The refrigeration oil of the present invention contains a base oil and an additive, and the base oil is a composite ester mixture.

[0016] The composite ester is synthesized from neopentyl glycol, adipic acid, and a monobasic fatty acid with a carbon number of 4-9. The synthesized product has a low-temperature two-phase separation temperature with R32 refrigerant lower than -20°C, and the dissolved viscosity of the working fluid composition after dissolution is 2.0 cP or more and not higher than 3.0 cP at a temperature of 100°C and an absolute pressure of 4.35 MPa.

[0017] Compared with the existing refrigeration oil, the above composite ester has the following characteristics: it can still be completely miscible with R32 at a relatively low temperature, thus ensuring good circulation of the refrigeration oil in the system. In addition, even if it is well dissolved with the refrigerant, a relatively thick oil film can be maintained, thereby improving the wear resistance of the working fluid.

[0018] The composite ester of the present invention is synthesized by the following method: adjust the molar ratio of neopentyl glycol to adipic acid (alcohol in excess of acid), synthesize an intermediate with hydroxyl groups of polyol remaining in the first stage, raise the temperature to 180 °C in this stage, and keep the reaction at a constant temperature for 3 hours; in the second stage, esterify the excess hydroxyl groups with a monobasic fatty acid to form the final product. After adding the monobasic fatty acid, gradually raise the temperature from 180 °C to 245 °C and keep it at a constant temperature for 5 hours to obtain the target product.

[0019] For the polyol and polybasic acid that constitute the composite ester of the present invention, in order to facilitate viscosity adjustment and have better low-temperature characteristics, neopentyl glycol and adipic acid are selected to possess the key characteristics of the above invention. No other polyol and polybasic acid have been found to meet the requirements.

[0020] In addition, on the basis of selecting neopentyl glycol as the polyol, for the consideration of improving lubricity, other diols with 2-10 carbon atoms can be selectively introduced. Such diols can include ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, etc. From the aspect of characteristic balance, butylene glycol is preferred. Butylene glycol includes 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 2,3-butylene glycol, etc., and 1,4-butylene glycol is preferred. The molar proportion of this diol relative to neopentyl glycol is preferably 40% or less, and more preferably 20% or less.

[0021] As described above, the diol and dibasic acid react to form a composite ester intermediate with hydroxyl groups remaining, and then it is esterified by a monobasic fatty acid with 4-9 carbon atoms.

[0022] For the consideration of characteristics, one or two monobasic fatty acids are selected. When one is selected, the carbon number is 4-5, and straight-chain or branched butyric acid and straight-chain or branched valeric acid can be cited; when two are selected, one monobasic fatty acid has a carbon number of 4-5, and the other has a carbon number of 6-9. Straight-chain or branched hexanoic acid, straight-chain or branched heptanoic acid, straight-chain or branched octanoic acid, and straight-chain or branched nonanoic acid can be listed. The carbon numbers of 7 and 9 are preferred, and the molar number of the monobasic fatty acid with 4-5 carbon atoms constituting the composite ester should account for a larger proportion. The ratio of the molar number of the monobasic fatty acid with 4-5 carbon atoms to the molar number of the monobasic fatty acid with 6-9 carbon atoms is preferably 1:0.25-0.66.

[0023] The kinematic viscosity of the refrigeration oil in this embodiment at 40 °C is preferably 32-200 mm 2 / s, more preferably 46-150 mm 2 / s, and further preferably 60-100 mm 2 / s. In addition, the viscosity index of the refrigeration oil is preferably 100 or more, and more preferably 120 or more.

[0024] The pour point of the refrigeration oil in this embodiment is preferably -10 °C or lower, and more preferably -20 °C or lower.

[0025] In order to prevent the deterioration of the refrigeration oil itself during use and the corrosion of the refrigeration system, the acid value of the refined oil product is preferably 0.1 mgKOH / g or less, more preferably set to 0.05 mgKOH / g or less, and even more preferably 0.02 mgKOH / g or less.

[0026] In addition, the flash point of the refrigeration oil in this embodiment is preferably 200 °C or higher, more preferably 225 °C or higher; for a closed refrigeration system, a low water content contributes to the stability of the oil product and electrical insulation. Therefore, the water content of the refrigeration oil in this embodiment is preferably 100 ppm or less, and most preferably 50 ppm or less.

[0027] In the refrigeration system, the refrigeration oil acts after being mixed with the refrigerant to form a mixed fluid, so the dissolved viscosity of this mixed working fluid composition is crucial. In this embodiment, the working fluid composition formed by the refrigeration oil and the R32 refrigerant has a dissolved viscosity of not less than 2.0 cp and not higher than 3.0 CP at a temperature of 100 °C and an absolute pressure of 4.35 MPa.

[0028] In order to further improve the comprehensive performance of this refrigeration oil composition, it is necessary to add one or more of various lubricating oil additives, including antioxidants, acid scavengers, anti-wear agents, rust inhibitors, metal deactivators, defoamers, etc.

[0029] As an acid scavenger, it can absorb free acidic substances during the use of the refrigeration oil, thereby further ensuring the stability of the synthetic ester refrigeration oil. Epoxy compounds are often selected, such as glycidyl ester type epoxy compounds and glycidyl ether type epoxy compounds. Examples of glycidyl ester type epoxy compounds include glycidyl benzoate, glycidyl acrylate, glycidyl neodecanoate, glycidyl tert-butylbenzoate, etc.; examples of glycidyl ether type epoxy compounds include neopentyl glycol diglycidyl ether, phenyl glycidyl ether, octyl glycidyl ether, 1,6-hexanediol diglycidyl ether, etc. The epoxy compound is preferably a glycidyl ester type epoxy compound. The addition amount is preferably 0.1%-5% of the mass of the base oil, more preferably 0.5%-2% of the mass of the base oil, which can more effectively improve the stability of the refrigeration oil.

[0030] As antioxidants, commonly selected are phenolic compounds and amine compounds. Phenolic compounds such as 2,6-di-tert-butyl-p-cresol, and amine compounds such as alkyl diphenylamine. The most preferred are phenolic compounds, and the addition amount is most preferably 0.1%-0.5% of the mass of the base oil.

[0031] In addition, according to the different performance requirements of the refrigeration oil, among the different additives added, as metal deactivators, benzotriazole and benzotriazole derivatives can be listed, and the addition amount is preferably 0.001%-0.01% of the mass of the base oil; as rust inhibitors, succinate esters etc. can be listed, and the addition amount is preferably 0.001%-0.05% of the mass of the base oil; as defoamers, polyester compounds, silicone compounds etc. can be listed, and the addition amount is preferably 0.001%-0.1% of the mass of the base oil.

[0032] Finally, in order to further improve the lubricity of the lubricating oil composition for refrigerators in this embodiment, an anti-wear agent is added thereto. There are phosphate esters, preferably phenyl phosphate (TPP), tricresyl phosphate (TCP); phosphorus-sulfur based additives can also be selected, preferably triphenyl thiophosphate (TPPT). Considering the lubricity and stability of the refrigeration oil composition, the addition amount of the above anti-wear agent is preferably 0.01%-5% of the mass of the base oil, and most preferably 0.1%-1% of the mass of the base oil.

[0033] Examples

[0034] The present invention is better illustrated by the following examples and comparative examples.

[0035] The set examples and comparative examples must illustrate the importance of some features.

[0036] Example 1:

[0037] An ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-butyric acid, and removing the residual acid by distillation;

[0038] Comparative Example 1:

[0039] An ester obtained by reacting trimethylolpropane (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-butyric acid, and removing the residual acid by distillation;

[0040] Comparative Example 2:

[0041] An ester obtained by reacting neopentyl glycol (2.4 mol) with succinic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-butyric acid, and removing the residual acid by distillation;

[0042] Example 2:

[0043] An ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0044] Comparative Example 3:

[0045] The ester obtained by reacting trimethylolpropane (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0046] Comparative Example 4:

[0047] The ester obtained by reacting neopentyl glycol (2.4 mol) with succinic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0048] Comparative Example 5:

[0049] The ester obtained by reacting trimethylolpropane (2.4 mol) with succinic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0050] Example 3:

[0051] The ester obtained by reacting neopentyl glycol (2.04 mol), 1,4-butanediol (0.36 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0052] Example 4:

[0053] The ester obtained by reacting neopentyl glycol (2.04 mol), ethylene glycol (0.36 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0054] Comparative Example 6:

[0055] The ester obtained by reacting neopentyl glycol (2.04 mol), pentaerythritol (0.36 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0056] Comparative Example 7:

[0057] The ester obtained by reacting neopentyl glycol (2.04 mol), isononanol (0.36 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.6 mol of n-valeric acid, and removing the residual acid by distillation;

[0058] Example 5

[0059] The ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1 mol of n-valeric acid and 0.6 mol of isononanoic acid, and removing the residual acid by distillation;

[0060] Example 6

[0061] The ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.28 mol of n-valeric acid and 0.32 mol of isononanoic acid, and removing the residual acid by distillation;

[0062] Example 7

[0063] The ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 0.96 mol of n-valeric acid and 0.64 mol of isononanoic acid, and removing the residual acid by distillation;

[0064] Example 8

[0065] The ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1 mol of isobutyric acid and 0.6 mol of isooctanoic acid, and removing the residual acid by distillation;

[0066] Comparative Example 8

[0067] The ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 1.33 mol of n-valeric acid and 0.27 mol of isononanoic acid, and removing the residual acid by distillation;

[0068] Comparative Example 9

[0069] The ester obtained by reacting neopentyl glycol (2.4 mol) with adipic acid (1 mol) to obtain an ester intermediate, and then reacting with 0.94 mol of n-valeric acid and 0.66 mol of isononanoic acid, and removing the residual acid by distillation;

[0070] Example 9

[0071] The ester obtained by reacting neopentyl glycol (2.04 mol) and 1,4-butanediol (0.36 mol) to obtain an ester intermediate, and then reacting with 1 mol of n-valeric acid and 0.6 mol of isononanoic acid, and removing the residual acid by distillation;

[0072] Then, 0.1% of antioxidant - 2,6-di-tert-butyl-p-cresol based on the mass of the base oil and 1% of acid scavenger - glycidyl benzoate based on the mass of the base oil were added to the base oils of Examples 1 - 9 and Comparative Examples 1 - 9 in all cases to prepare refrigeration oils.

[0073] For the refrigeration oils of the examples and comparative examples, the following tests were carried out: the dissolved viscosity test of the mixed fluid formed with R32, the low-temperature two-phase separation temperature test, and the lubricity test to evaluate the anti-wear property of the refrigeration oil.

[0074] Measurement of the Dissolution Viscosity of the Mixed Fluid with R32 Refrigerant

[0075] Add 100 g of refrigeration oil to a 250 ml autoclave equipped with an on-line viscometer. First, evacuate the entire container, and then inject enough refrigerant at a low temperature to form a fluid mixture. Then measure the dissolution viscosity at 100 °C and 4.35 MPa.

[0076] Measurement of the Low-temperature Two-phase Separation Temperature with R32 Refrigerant

[0077] Inject 7 g of the oil sample to be tested into a pressure-resistant test tube, and then inject 28 g of a quantitative R32 refrigerant to make the oil content in the pressure-resistant test tube 20%; place the pressure-resistant test tube in a low-temperature bath, slowly heat it up from a lower temperature, observe and record the temperature point at which the liquid in the test tube becomes clear, which is the low-temperature two-phase separation temperature.

[0078] Bench Accelerated Life Test

[0079] Conduct an accelerated life durability test on the refrigeration oil sample on a durability life test bench composed of a rotary compressor model QXFS-H446sN330 (manufactured by Geli Lingda, 5P model with R32 refrigerant). The test duration is 1000 h. After the test, conduct a comparative analysis of the oil before and after the bench test. In addition, dissect the compressor after the test, observe and evaluate the wear degree of the core component piston, and measure it with roughness.

[0080] The test results are shown in Table 1 and Table 2 below.

[0081] Table 1: Test Results of Examples 1-9

[0082]

[0083] Table 2: Test Results of Comparative Examples 1-9

[0084]

[0085] From the above experimental data, it can be seen that Examples 1-9 have good low-temperature compatibility with R32 refrigerant, and at the same time have a relatively high dissolution viscosity, within the preferred viscosity range of 2.0-3.0 cP, and have good lubrication and anti-wear performance.

[0086] The lubrication and anti-wear performance of the comparative examples all decreased to varying degrees.

[0087] For the refrigeration oil of the present invention, it can still be well dissolved with R32 at low temperatures, and can have a relatively high dissolution viscosity, and also has excellent lubrication and wear resistance performance. It is applicable to the use of large-capacity compressors and various operating conditions. The present invention demonstrates that the characteristics of the product synthesized from neopentyl glycol, adipic acid and monobasic fatty acids with 4-9 carbon atoms cannot be achieved by other raw materials.

[0088] The above description of the embodiments is to enable those of ordinary skill in the art to understand and apply the present invention. Obviously, those who are familiar with the technology in this field can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the embodiments herein, and the improvements and modifications made by those skilled in the art to the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A highly compatible refrigeration oil, whose base oil is a composite ester mixture; the composite ester mixture is obtained by esterifying partial hydroxyl groups of a dibasic acid and a diol, and then further esterifying the remaining hydroxyl groups of the diol with a monobasic fatty acid having 4 to 9 carbon atoms; The diol is neopentyl glycol and a diol having 2 to 10 carbon atoms, and the dibasic acid is adipic acid; the diol having 2 to 10 carbon atoms is selected from at least one of ethylene glycol and 1,4-butanediol, and the molar proportion of the diol having 2 to 10 carbon atoms relative to neopentyl glycol is less than 20%; There are two kinds of monobasic fatty acids for synthesizing the composite ester mixture; among the two kinds of monobasic fatty acids, one monobasic fatty acid has 4 to 5 carbon atoms, and the other monobasic fatty acid has 6 to 9 carbon atoms, and the ratio of the molar number of the monobasic fatty acid having 4 to 5 carbon atoms to the molar number of the monobasic fatty acid having 6 to 9 carbon atoms is 1:0.25 - 0.

66.

2. The highly compatible refrigeration oil according to claim 1, characterized in that It also includes one or more of antioxidants, acid scavengers, antiwear agents, rust inhibitors, metal deactivators, and defoamers.

3. The highly compatible refrigeration oil according to claim 2, characterized in that The acid scavenger is selected from glycidyl ester type epoxy compounds and / or glycidyl ether type epoxy compounds in epoxy type compounds; among them, the glycidyl ester type epoxy compound is selected from glycidyl benzoate, glycidyl acrylate, glycidyl neodecanoate, glycidyl tert-butylbenzoate; the glycidyl ether type epoxy compound is selected from neopentyl glycol diglycidyl ether, phenyl glycidyl ether, octyl glycidyl ether, 1,6-hexanediol diglycidyl ether; the addition amount of the acid scavenger is 0.1%-5% of the mass of the base oil.

4. The highly compatible refrigeration oil according to claim 2, characterized in that The antioxidant is selected from phenolic compounds and / or amine compounds; among them, the phenolic compound is selected from 2,6-di-tert-butyl-p-cresol; the amine compound is selected from alkyl diphenylamine; the addition amount of the antioxidant is 0.1%-0.5% of the mass of the base oil.

5. The highly compatible refrigeration oil according to claim 2, characterized in that The metal deactivator is selected from benzotriazole and its derivatives, and the addition amount is 0.001%-0.01% of the mass of the base oil.

6. The highly compatible refrigeration oil according to claim 2, characterized in that The rust inhibitor is selected from succinate esters, and the addition amount is 0.001%-0.05% of the mass of the base oil.

7. The highly compatible refrigeration oil according to claim 2, characterized in that The defoamer is selected from polyester compounds and silicone compounds, and the addition amount is 0.001%-0.1% of the mass of the base oil.

8. The highly compatible refrigeration oil according to claim 2, characterized in that The antiwear agent is selected from phosphate esters or phosphorus-sulfur based additives; among them, the phosphate ester is selected from phenyl triphosphate, tricresyl phosphate; the phosphorus-sulfur based additive is selected from triphenyl thionophosphate; the addition amount of the antiwear agent is 0.01%-5% of the mass of the base oil.

9. The synthesis method of the highly compatible refrigeration oil according to claim 1, characterized in that It includes a preparation method of the base oil, and the preparation method of the base oil includes the following steps: Add a diol and a dicarboxylic acid for the first-stage esterification, and there is a hydroxyl group-containing intermediate of the diol remaining after the first-stage esterification; Add a monocarboxylic acid with 4-9 carbon atoms for the second-stage esterification to form the final product.

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