Refrigerator oil and working fluid compositions

Abstract

The application relates to the technical field of refrigeration oil products, in particular to a refrigeration oil and a working fluid composition containing the refrigeration oil. The refrigeration oil comprises a base oil, and the base oil comprises a complex ester formed by esterification of an organic alcohol and an organic carboxylic acid, wherein the organic alcohol comprises a polyhydric alcohol and an isomeric alcohol, and the organic carboxylic acid comprises a dibasic acid and a C4-C5 aliphatic acid. The refrigeration oil with a polyhydric alcohol complex ester as the base oil is composed of the polyhydric alcohol complex ester base oil and necessary additives, the refrigeration oil composition has suitable phase solubility with HFCs (R32), HFOs (R1234yf) or HCs (R290) refrigerants, and can also maintain a relatively thick oil film and good viscosity-temperature performance under relatively harsh working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigeration oil products, in particular to a refrigeration oil, and to a working fluid composition comprising the refrigeration oil. BACKGROUND

[0002] With the intensification of global climate change, environmental problems have become the focus of global attention. In this context, international organizations and governments have introduced a series of laws and regulations to limit and reduce greenhouse gas emissions to address the challenges of global climate change. Among them, the refrigeration industry, as an important energy consumption field, has also been subject to increasingly stringent environmental protection requirements. In order to meet these requirements, the refrigeration industry needs to find new environmentally friendly alternatives to reduce the impact on the environment. The initial ozone layer protection program internationally is to replace R22 with R410A, and it has been well applied in the industry. However, R410A has a high global warming potential (GWP), and in order to meet the agreed emission reduction standards, R410A has been listed as a limited substance by the European Union and Japan, and R32, as a transitional refrigerant, also faces the problem of being phased out in the future. Internationally, the main approach to replacing new low-GWP refrigerants is to replace single refrigerants and refrigerant compositions, mainly new HFCs, HFOs, and HCs natural refrigerants, in order to find suitable compositions to meet the requirements of air conditioning systems for refrigerants. Among them, R290, as an environmentally friendly HC refrigerant, has a low GWP value and high refrigeration performance, and its environmental protection performance has been widely recognized. However, it has not been widely used due to problems such as flammability and cost.

[0003] On the other hand, in order to ensure that the refrigeration compressor can operate reliably and at high speed for a long time, the miscibility, stability, and lubricity of the refrigeration oil and the refrigerant also need to be improved. The miscibility of the refrigerant and the refrigeration oil is very important for the refrigeration system, and directly affects the performance of the system. In small air conditioning systems without an oil separator, it is desirable to have good miscibility of the refrigerant and the refrigeration oil to facilitate oil return and to avoid the formation of an oil film on the surface of the heat exchanger, thereby improving the heat exchange effect. Therefore, the development of special refrigeration oil has always been a necessary condition for the practical application of new refrigerants and energy-saving and emission-reducing compressors. However, existing refrigeration oil compositions have the disadvantages of high GWP of the compatible refrigerant and poor refrigerant universality. Therefore, it is necessary to develop refrigeration oil compositions with better lubricity, better compatibility with existing environmentally friendly refrigerants, and better safety and stability to address the problems caused by the replacement of refrigerants and meet environmental protection requirements. SUMMARY

[0004] The technical problem to be solved by the present application is to develop a refrigeration oil with better lubricating performance, better compatibility with existing environmentally friendly refrigerants, and better safety and stability, so as to solve the problems caused by the replacement of refrigerants and meet the environmental protection requirements.

[0005] In order to achieve the above-mentioned purpose, according to a first aspect of the technical solution, the technical solution provides a refrigeration oil.

[0006] The refrigeration oil according to the embodiments of the present application comprises a base oil, characterized in that the base oil comprises a complex ester formed by esterification of an organic alcohol and an organic carboxylic acid, wherein the organic alcohol comprises a polyhydric alcohol and an isomeric alcohol, and the organic carboxylic acid comprises a dibasic acid and a C4-C5 fatty acid.

[0007] Further, the isomeric alcohol accounts for 5mol% to 60mol% of the total amount of the organic alcohol; the dibasic acid accounts for 5mol% to 35mol% of the total amount of the raw material of the organic carboxylic acid, and the balance is a C4-C5 linear or branched fatty acid.

[0008] Further, the 40℃ kinematic viscosity of the refrigeration oil is 16-300mm 2 / s.

[0009] Further, the polyhydric alcohol comprises at least one of pentaerythritol, neopentyl glycol, trimethylol ethane, trimethylol propane and dipentaerythritol.

[0010] Further, the dibasic acid is a C4-C12 dibasic acid; and the isomeric alcohol is a C6-C12 monohydric alcohol.

[0011] Further, the isomeric alcohol comprises isooctanol and / or isononyl alcohol.

[0012] Further, at 80℃ and 3.4Mpa, the solubility of the refrigeration oil in the refrigerant is in the range of 10-20%.

[0013] Further, the complex ester comprises at least one of a compound shown in formula

I

II

[0014]

[0015] In formula

I

II

[0016] Further, the refrigeration oil further comprises an additive, and the additive comprises at least one of an anti-wear agent, an antioxidant, an anti-foaming agent and an acid capture agent.

[0017] In order to achieve the above object, according to a second aspect of the present technical solution, the present technical solution provides a working fluid composition comprising the refrigeration oil provided by the first aspect of the present technical solution and a refrigerant.

[0018] The present application has the following beneficial effects: a refrigeration oil with a polyhydric alcohol complex ester as a base oil is provided, the refrigeration oil is composed of a polyhydric alcohol complex ester base oil and necessary additives, the refrigeration oil composition has suitable phase solubility with HFCs (R32), HFOs (R1234yf) or HCs (R290) refrigerants, and can also maintain a thick oil film and good viscosity-temperature performance under harsh working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A gas chromatogram of an intermediate product in a preparation process of the refrigeration oil base oil provided by the present application after GC-MS testing is provided;

[0020] Figure 2 A mass spectrum of pentaerythritol tetraisovalerate obtained after GC-MS testing of an intermediate product in a preparation process of the refrigeration oil base oil provided by the present application. DETAILED DESCRIPTION

[0021] Hereinafter, a suitable embodiment of the present application is described in detail.

[0022] The refrigeration oil provided by the present application comprises a base oil and suitable additives, wherein the additives comprise at least one of an anti-wear agent, an antioxidant, an anti-foaming agent and an acid capture agent. Preferably, the main components of the refrigeration oil can comprise:

[0023]

[0024]

[0025] The types of the additives of the refrigeration oil in the present application are not specifically limited, the antioxidant can be selected from hindered phenol, diarylamine, phenothiazine, organic sulfonate and the like; the acid capture agent can be selected from glycidyl ester type epoxy compound, glycidyl ether type epoxy compound and phenyl glycidyl ether and the like; the anti-wear agent can be selected from alkyl phosphate ester and alkyl phosphate, dialkyldithiophosphate and phosphate ester and the like; the anti-foaming agent can be selected from polydimethylsiloxane containing silicon or other non-silicon polyacrylate and the like.

[0026] The base oil of the refrigeration oil comprises a complex ester formed by esterification of an organic alcohol and an organic carboxylic acid, wherein the organic alcohol comprises a polyhydric alcohol and an isomeric alcohol, and the organic carboxylic acid comprises a dibasic acid and a C4-C5 fatty acid. The base oil of the refrigeration oil in the present embodiment is a complex ester, which is an esterification product composed of a polyhydric alcohol, an isomeric alcohol, a dibasic acid and a C4-C5 fatty acid.

[0027] The solubility of the refrigeration oil with refrigerant is in the range of 10-20% at 80℃ and 3.4MPa, the further solubility can be controlled in the range of 10-15%, and the refrigeration oil has higher viscosity index, lower pour point and excellent anti-wear performance. The refrigeration oil can be used together with HCs hydrocarbon refrigerant R290, HFCs hydrofluorocarbon refrigerant R32 or HFO hydrofluoroolefin refrigerant R1234yf, has suitable phase solubility, and can maintain thick oil film and good viscosity-temperature performance under the condition of lower kinematic viscosity.

[0028] The isomeric alcohol accounts for 5-60 mol%, preferably 15-55 mol%, and more preferably 30-50 mol% of the total amount of the organic alcohol; the dibasic acid accounts for 5-35 mol% of the total amount of the organic carboxylic acid raw material, and the balance is C4-C5 linear or branched fatty acid. The kinematic viscosity of the refrigeration oil at 40℃ is 16-300mm 2 / s, preferably 40-130mm 2 / s, more preferably 60-110mm 2 / s.

[0029] Optionally, the polyhydric alcohol includes at least one of pentaerythritol, neopentyl glycol, trimethylol ethane, trimethylol propane and dipentaerythritol. From the stability of the formed ester structure, the better steric alcohol such as pentaerythritol, trimethylol ethane, trimethylol propane or dipentaerythritol is preferred; trimethylol propane and pentaerythritol are more preferred; from the thermal stability and oxidation stability of the formed ester, pentaerythritol is further preferred.

[0030] Optionally, the dibasic acid is selected from one or more of C4-C12 dibasic acids, including but not limited to succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc.; the isomeric alcohol is one or more of C6-C12 monohydric alcohols, including but not limited to isooctanol and isononyl alcohol.

[0031] In some embodiments, the complex ester includes at least one of the compounds shown in formula

I

II

[0032]

[0033] In formula

I

II

[0034] It should be noted that the polyol and dibasic acid esterification polyester component in the complex ester can have a molecular weight range of 400-10000 g / mol. The base oil in the refrigerant oil provided in the application has a relatively high molecular weight due to its special structure of isomer complex ester, which makes it have strong molecular polarity, good stability and lubricity, and can be used as a working fluid component in R290, R32 or R1234yf refrigeration compressor system.

[0035] In order to obtain the refrigerant oil base oil with the required components, the application also provides a preparation method of the refrigerant oil base oil. As an example, the raw material components of the complex ester of the refrigerant oil base oil are selected as pentaerythritol, isooctanol, adipic acid, and C4-C5 fatty acids such as isobutyric acid and isovaleric acid. The base oil adopts a step-by-step synthesis strategy, i.e., first, an excess of pentaerythritol is reacted with isobutyric acid and isovaleric acid to obtain an incompletely esterified pentaerythritol ester intermediate, then adipic acid is added to synthesize an adipic acid derivative, and finally isooctanol is added to continue esterification with the adipic acid derivative to obtain the target product. The total raw material ratio is 1:1 according to the hydroxyl-carboxyl molar ratio.

[0036] Specifically, in the step-by-step synthesis process of the refrigerant oil base, further control is carried out by the following method.

[0037] First, an excess of pentaerythritol is reacted with fatty acids, wherein the material feeding ratio is controlled to be pentaerythritol:fatty acid≥1:3, and the fatty acids are a mixture of isobutyric acid and isovaleric acid. The above ratio is the molar ratio of the substances. After the reaction, an incompletely esterified pentaerythritol triester intermediate is mainly obtained. The composition and distribution of the intermediate are monitored by sampling using a gas chromatograph-mass spectrometer (GC-MS) instrument. The obtained GC spectrum is shown in Figure 1 The MS spectrum is shown in Figure 2 The mass spectrum is only exemplarily shown by taking pentaerythritol tetraisovalerate in the intermediate product as an example. Through spectrum analysis, it is found that in the target intermediate product, the proportion of pentaerythritol tetraester is about 41%, the proportion of pentaerythritol triester is about 56%, the proportion of pentaerythritol diester is about 3%, and the content of pentaerythritol monoester is less than 1%.

[0038] Then, adipic acid is added to the intermediate product of the previous step, and the appropriate amount of adipic acid is further esterified with the incompletely esterified pentaerythritol ester intermediate. The reaction process is controlled by programmed temperature, and the pentaerythritol adipic acid derivative is obtained. In this step, by controlling the amount of reactants and the reaction process by programmed temperature control, the pentaerythritol adipic acid derivative can have adipic acid mono-pentaerythritol ester as the dominant intermediate product, so that these dominant amounts of adipic acid derivatives still retain a carboxyl group for reaction.

[0039] Finally, isooctanol was added into the above intermediate product by dropwise feeding, and the esterification with adipic acid derivative was continued until complete reaction. The product was detected by GC-MS instrument. By analyzing the GC-MS spectrum, the content of pentaerythritol tetraester in the final product composition was less than 25%, and the content of pentaerythritol complex ester represented by formula (II) was more than 30%, which was the most dominant product.

[0040] The application will be described in more detail by preferred examples and comparative examples below, but the application is not limited by the examples below.

[0041] In each of the examples and comparative examples, the raw material components of the complex ester as the refrigeration oil base oil were selected as pentaerythritol, isooctanol, adipic acid, isobutyric acid and isovaleric acid. The refrigeration oil base oil was prepared by using the step-by-step synthesis strategy provided in the examples of the application, i.e. first, using excess pentaerythritol to react with isobutyric acid and isovaleric acid to obtain an intermediate product of pentaerythritol ester which was not completely esterified, then adding adipic acid to synthesize adipic acid derivatives, and finally adding isooctanol to continue the esterification with the adipic acid derivatives to obtain the target product. The raw materials were prepared according to the molar ratio of hydroxyl group to carboxyl group of 1:1, and the specific preparation control process can be referred to the previous examples. Examples 1-9 were obtained. For comparative examples 1-9, the raw materials in Table 2 were prepared according to the molar ratio of hydroxyl group to carboxyl group of 1:1, first, pentaerythritol was added to react with isobutyric acid and isovaleric acid, then adipic acid was added (if any), and finally isooctanol was added (if any) to continue the reaction to obtain the target product.

[0042] The specific composition of each example and comparative example is shown in Table 1 and Table 2, and the viscosity parameters, acid value, pour point and flash point of the obtained oil product were measured and recorded in Table 1 and Table 2.

[0043] Table 1

[0044]

[0045] Table 2

[0046]

[0047] Note: * Because the synthesized product is a viscous solid at room temperature, no test was performed.

[0048] Referring to SH / T 0699-2000 "Refrigerator oil and refrigerant solubility test method": a certain mass of test oil and refrigerant of each example and comparative example is filled into a test tube, and the test oil and refrigerant are warmed in a room temperature or water bath to make the test oil and refrigerant into a homogeneous and transparent solution; then the test tube is cooled in a cold bath, and the temperature at which the solution separates into two phases or the whole solution is emulsified is measured, which is taken as the two-phase separation temperature at the oil content. By measuring the two-layer separation temperature at different mixed oil contents, a two-layer separation temperature curve can be obtained, and the highest separation temperature point on the curve is taken as the two-layer separation temperature of the refrigerator oil and the refrigerant, so as to evaluate the phase solubility of the refrigerator oil and the refrigerant. The experimental results are recorded in Table 1-2. It should be noted that the separation of the oil and the refrigerant indicates that the base oil and the refrigerant are not compatible at a specific oil content of 10% to 40% under the condition that the base oil and the refrigerant are not compatible at room temperature or when warmed.

[0049] It can be seen from the comparative examples and the comparative examples that the viscosity of the polyol complex ester formed by isooctanol and pentaerythritol is obviously affected by the addition amount of adipic acid; when the adipic acid accounts for more than 40 mol%, the base oil directly becomes viscous or solid after synthesis; it is further found that when the adipic acid accounts for less than 5 mol% or the isooctanol accounts for more than 70%, the viscosity of the oil product will be obviously reduced. Therefore, in order to control the phase solubility of the base oil and the refrigerant, it is necessary to control the amount of adipic acid and isooctanol here to adjust the balance between the viscosity and the phase solubility.

[0050] According to the petroleum and chemical industry standard SH / T 0189-92 "Lubricating oil anti-wear performance test method", the anti-wear performance of the oil products of each example and comparative example is determined, and the average wear scar diameter and the friction coefficient are obtained to evaluate the advantages and disadvantages of the anti-wear performance. The test is carried out on a MMW-1 vertical universal friction tester under the test conditions of load 392N, temperature 75℃ and rotation speed 1200r / min, and the results are shown in Table 3.

[0051] Table 3 Four-ball friction test results

[0052]

[0053]

[0054] As can be seen from Table 3, the anti-wear effects of the base oils of Examples 1-5 are obviously different, and the phenomenon of the decrease of the wear scar diameter and the wear scar coefficient with the increase of the adipic acid component appears; at the same time, the analysis of the test results of base oils 1 and 2, base oils 3 and 4, and base oils 8 and 9 shows that the wear scar diameter and the friction coefficient of the polyol complex ester oil synthesized by adding the isooctanol raw material component are obviously related to the addition amount of isooctanol, and the phenomenon of the decrease of the wear scar diameter and the wear scar coefficient with the increase of the isooctanol component in a certain range appears. The experimental results show that the introduction of the adipic acid and isooctanol components has a positive effect on the improvement of the anti-wear and friction reduction performance, and embodies the synergistic effect. Of course, in order to obtain high-quality anti-wear lubrication effect, other necessary anti-wear additives can also be added to the refrigerator oil.

[0055] In addition, as can be seen from the test data in Tables 1-2, the application can be used as a refrigerator oil working fluid composition in an HFC hydrocarbon and HFO unsaturated olefin refrigeration system; at the same time, the base oil and the composition provided by the examples of the application have low phase solubility with the hydrofluorocarbon R290 refrigerant, which is beneficial to reducing the charge amount of the refrigerant and improving the safety of the system; under the actual operating conditions of the compressor 110℃, 4.2MPa, the solubility viscosity is 2.1mm 2 / s or more, which can ensure that the compressor pump body parts have a thick enough oil film between the friction pairs, thereby improving the wear resistance of the working fluid composition and improving the reliability of the compressor operation. Therefore, the refrigerator oil takes into account the low-temperature fluidity, lubricity, and good compatibility with specific refrigerants.

[0056] In the description, some embodiments are described in a progressive or parallel manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0057] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications of these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A refrigeration oil, comprising a base oil, characterized in that, The base oil comprises a complex ester formed by esterification of organic alcohols and organic carboxylic acids, wherein: the organic alcohols include polyols and isooctanol, the organic carboxylic acids include adipic acid and C4-C5 fatty acids, the isooctanol accounts for 5 mol% to 60 mol% of the total organic alcohols; the adipic acid accounts for 5 mol% to 35 mol% of the total organic carboxylic acid raw materials, and the balance is C4-C5 straight-chain or branched fatty acids.

2. The refrigeration oil according to claim 1, characterized in that, The kinematic viscosity of the refrigeration oil at 40°C is 16–300 mm. 2 / s.

3. The refrigeration oil according to claim 1, characterized in that, The polyols include at least one of pentaerythritol, neopentyl glycol, trimethylolethane, trimethylolpropane, and dipentaerythritol.

4. The refrigeration oil according to claim 1, characterized in that, At 80°C and 3.4 MPa, the solubility of the refrigeration oil and refrigerant is in the range of 10-20%.

5. The refrigeration oil according to claim 1, characterized in that, The complex ester includes at least one of the compounds represented by formula [I] or formula [II]. 【I】 【II】 In formulas [I] and [II], R1, R2, R3, R4, R5, and R6 are each independently methyl or ethyl.

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

7. A working fluid composition for a refrigeration unit, characterized in that, Includes the refrigeration oil and refrigerant as described in any one of claims 1-6.

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