A fatty acid ester composition for R290 refrigerant refrigerator

Abstract

The invention discloses a fatty acid ester composition for R290 refrigerant refrigerator, wherein the base oil includes pentaerythritol fatty acid ester and benzoate, and the mass ratio of the pentaerythritol fatty acid ester to the benzoate is 70 / 30-90 / 10. The present invention can meet the requirements of a refrigeration system using R290 refrigerant as a working medium, wherein the composition is mainly pentaerythritol fatty acid ester, and part of benzoate is added to ensure that the fatty acid ester composition for refrigerator and R290 refrigerant have a dissolution viscosity of ≥1.7cP at 95°C and 1.680MPa, and a higher dissolution viscosity can be maintained, thereby ensuring the lubrication of the refrigeration compressor and realizing long-term stable operation of the refrigeration system.

Description

Technical Field

[0001] The invention belongs to the technical field of lubricating oils and relates to a fatty acid ester composition for a refrigerator, in particular to a fatty acid ester composition for an R290 refrigerant refrigerator. Background Art

[0002] At present, in the household air-conditioning and refrigerator industries, the refrigerants are mainly hydrofluorocarbons (HFCs), such as R410A and R32. However, hydrofluorocarbons (HFCs) refrigerants have a higher GWP coefficient, while R290 (propane), as a natural public substance, has a GWP of only 3 and an ODP of 0, and its thermal properties are similar to those of R22. Taking household air conditioners as an example, R290 refrigerant is a new type of refrigerant that is very likely to replace hydrofluorocarbons (HFCs) refrigerants.

[0003] However, there is no refrigeration oil on the market that is perfectly suitable for R290 refrigerant refrigerators. The main reason for this is that R290 is an alkane with strong solubility, and has a strong dilution ability for conventional refrigeration oils such as POE and mineral oil, which will greatly reduce the viscosity of the working fluid (solubility viscosity) and reduce the oil film strength, thereby causing wear on the core components of the refrigeration compressor. On the other hand, if an oil with poor compatibility with R290 refrigerant (such as PAG) is selected, due to the small molecular weight and low viscosity of R290, it will cause difficulty in returning oil to the refrigeration system, affecting the heat exchange effect of the system heat exchanger, reducing system performance, and in severe cases, causing blockage of the pipeline. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to propose a fatty acid ester composition, which has good compatibility with R290 and can maintain sufficient oil film and stability to ensure the lubrication of the refrigeration compressor, thereby achieving long-term stable operation of the refrigerator.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A fatty acid ester composition for an R290 refrigerant refrigerator, wherein the base oil comprises pentaerythritol fatty acid ester and benzoic acid ester, wherein the mass ratio of the pentaerythritol fatty acid ester to the benzoic acid ester is 70 / 30-90 / 10.

[0007] Specifically, the pentaerythritol fatty acid ester is prepared by reacting pentaerythritol with two or more normal or isomeric monobasic fatty acids having a carbon number of 4-9. The monobasic fatty acids can be specifically listed as isobutyric acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, isooctanoic acid, n-octanoic acid, and isononanoic acid. Considering the viscosity grade and the oil film strength of the oil, the fatty acid types are preferably isooctanoic acid and isononanoic acid.

[0008] Preferably, the benzoate is prepared by reacting benzoic acid with one or more of diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol.

[0009] The mixed fluid solution viscosity of the fatty acid ester composition of the present invention and R290 refrigerant formed at 95° C. and an absolute pressure of 1.680 MPa is ≥1.7 cP.

[0010] In order to further improve the performance of the fatty acid ester composition, one or more additives may be selectively added, including but not limited to: antioxidants, anti-wear agents, acid scavengers, metal corrosion inhibitors, defoaming agents, etc.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] The fatty acid ester composition for refrigerators of the present invention can maintain a relatively high dissolution viscosity while ensuring sufficient compatibility with the R290 refrigerant, thereby ensuring the lubrication of the refrigeration compressor and realizing long-term stable operation of the refrigeration system. DETAILED DESCRIPTION

[0013] In order to allow those skilled in the art to understand the present invention more clearly and intuitively, the present invention will be further described below.

[0014] The fatty acid ester composition of the present invention contains base oil, wherein the base oil is fatty acid ester, specifically a mixture of pentaerythritol fatty acid ester and benzoic acid ester, wherein the mass ratio of pentaerythritol fatty acid ester to benzoic acid ester is 70 / 30-90 / 10.

[0015] The pentaerythritol fatty acid ester is prepared by reacting pentaerythritol with two or more normal or isomeric monobasic fatty acids having 4 to 9 carbon atoms. Specifically, the fatty acids include isobutyric acid, n-valeric acid, n-hexanoic acid, isooctanoic acid, n-heptanoic acid, n-octanoic acid, and isononanoic acid. Considering the viscosity grade and the film strength of the oil, isooctanoic acid and isononanoic acid are preferred fatty acid types.

[0016] The benzoic acid ester is prepared by reacting benzoic acid with one or more of diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol.

[0017] In the present invention, the above-mentioned benzoic acid ester provides the following characteristics in the refrigeration oil: it has suitable compatibility with the R290 refrigerant, and will not cause viscosity reduction due to excessive solubility, nor will it cause oil return difficulties or even blockage of pipelines due to excessive solubility. This characteristic is mainly determined by the special structure of the benzoic acid ester: it has a highly polar ether bond, which can reduce its solubility in the non-polar R290 refrigerant, reduce the significant decrease in viscosity caused by excessive solubility, reduce the strength of the oil film, and reduce the lubricity; at the same time, the benzene ring structure in the benzoic acid ester can ensure a certain compatibility with R290.

[0018] Pentaerythritol fatty acid ester has a kinematic viscosity of 22-100 mm at 40°C 2 / s, and the more preferred kinematic viscosity at 40°C is 40-90 mm 2 / s, particularly preferably 40 ° C kinematic viscosity 63-85mm 2 / s.

[0019] The kinematic viscosity of benzoic acid esters at 40°C is 10-60 mm 2 / s, and the more preferred kinematic viscosity at 40°C is 15-40 mm 2 / s, particularly preferably 40 ° C kinematic viscosity 20-35mm 2 / s.

[0020] After pentaerythritol fatty acid ester and benzoic acid ester are blended into a base oil composition according to the required mass ratio of pentaerythritol fatty acid ester to benzoic acid ester of 70 / 30-90 / 10, the overall kinematic viscosity at 40°C is 46-100mm 2 / s, preferably 46-68mm 2 / s.

[0021] The dissolving viscosity of the mixed fluid formed by the fatty acid ester composition and the R290 refrigerant at 95° C. and an absolute pressure of 1.680 MPa is ≥1.70 cP.

[0022] In order to further improve the performance of the refrigeration oil composition, one or more additives may be selectively added, including but not limited to: antioxidants, anti-wear agents, acid scavengers, metal corrosion inhibitors, defoaming agents, etc.

[0023] In order to improve the antioxidant capacity of the oil, an antioxidant should be added to the composition; suitable antioxidants include hindered phenols such as di-tert-butyl-p-cresol, and amine compounds such as alkyl diphenylamine; among them, hindered phenol compounds are preferred; the amount of antioxidant added is 0.01-2.00%, preferably 0.01-1.00%, based on the total mass of the composition.

[0024] In order to improve the stability of the oil and reduce the corrosion of the acid generated by ester hydrolysis to the refrigeration system, an acid scavenger should be added to the composition. The acid scavenger is selected from one or more of neodecanoic acid glycidyl ester, octyl glycidyl ether, glycidyl benzoate, and glycidyl acrylate; wherein the amount of the acid scavenger added is 0.1-3.0%, preferably 0.1-1.5%, based on the total mass of the composition.

[0025] In order to further improve the lubrication performance of the composition, an anti-wear agent should be added to the composition. The anti-wear agent is selected from one or more of triphenyl phosphate, tricresyl phosphate, and triphenyl thiophosphate. Considering the lubricity and stability of the composition, the added amount is 0.1-2.0% based on the total mass of the composition, preferably 0.1-1.5%.

[0026] In order to reduce corrosion to the refrigeration system and prevent oil degradation, the acid value of the composition should be controlled at ≤0.1 mgKOH / g, preferably ≤0.05 mgKOH / g, and particularly preferably ≤0.02 mgKOH / g.

[0027] Examples and Comparative Examples

[0028] The present invention is better illustrated by the following examples and comparative examples.

[0029] The following base oils were used in the Examples and Comparative Examples.

[0030] A: Pentaerythritol fatty acid ester

[0031] A-1 Ester (kinematic viscosity at 40°C: 80 mm) prepared by acidification of a mixture of pentaerythritol, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in a molar ratio of 30:70 2 / s);

[0032] A-2 Pentaerythritol and 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in a molar ratio of 45:55 were acidified to form an ester (40°C kinematic viscosity 66 mm 2 / s);

[0033] A-3 Pentaerythritol and 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in a molar ratio of 80:20 acid ester (40 ° C kinematic viscosity 50mm 2 / s);

[0034] B: Parabens

[0035] B-1 ester made by esterification of benzoic acid and diethylene glycol in a molar ratio of 1:2 (kinematic viscosity at 40°C is 26 mm 2 / s);

[0036] B-2 ester made by esterification of benzoic acid and propylene glycol in a molar ratio of 1:2 (kinematic viscosity at 40°C is 25 mm 2 / s);

[0037] B-3 ester made by esterification of benzoic acid and dipropylene glycol in a molar ratio of 1:2 (kinematic viscosity at 40°C is 34 mm 2 / s);

[0038] The base oils in Examples 1-7 and Comparative Examples 1-6 were blended into test samples according to Table 1 and Table 2, and relevant tests were performed.

[0039] Table 1

[0040]

[0041] Table 2

[0042]

[0043]

[0044] From the above data, it can be seen that while ensuring sufficient compatibility of R290, Examples 1-7 significantly increase the oil solution viscosity and improve the lubrication performance to a certain extent;

[0045] It can be seen from Comparative Example 4 that when the addition amount of component B is less than 5%, the dissolution viscosity and lubricity of the oil can be slightly improved, but the improvement is not obvious and cannot reach the expected level;

[0046] It can be seen from Comparative Examples 5 and 6 that when the addition amount of component B is >30%, although the dissolution viscosity will increase, the compatibility with the refrigerant R290 will deteriorate, and the two-phase separation temperature will be >15°C. Application in the refrigeration system may cause oil return difficulties, so it is not a feasible solution.

[0047] Test method description:

[0048] (1) Determination of refrigerant solution viscosity

[0049] 70 g of refrigeration oil was added to a 250 mL pressure-resistant container equipped with an online viscometer. After the container was evacuated, a certain amount of refrigerant was charged, and the temperature and pressure were adjusted to the specified values ​​to measure the viscosity. The measurement conditions of the above-provided dissolution viscosity data were 95°C and an absolute pressure of 1.680 MPa.

[0050] (2) Determination of two-phase separation temperature

[0051] The test method complies with SH / T 0699. Please refer to this standard for specific operations.

[0052] (3) Four-ball tester wear resistance and friction characteristics evaluation test

[0053] The refrigeration oil is subjected to a wear test on a four-ball tester (SH / T0189-92) according to the following method.

[0054] Test material: steel ball

[0055] Experimental temperature: 80℃

[0056] Test time: 30min

[0057] Speed: 1200r / min

[0058] Load: 100N

[0059] In the above experiment, the wear resistance of the refrigeration oil was evaluated by observing the diameter of the wear spot on the surface of the worn part after the steel ball four-ball test.

[0060] (4) High temperature stability test

[0061] Place an appropriate amount of oil and catalyst (Cu, Fe, Al) in a stainless steel pressure-resistant reactor, fill it with R290 refrigerant, and keep it at 175°C and 0.5MPa for 14 days. Then measure the acid value, low-temperature precipitation property, etc. of the refrigeration oil.

[0062] (5) Accelerated life of the test bench

[0063] On the R290 explosion-proof durability test bench composed of household air-conditioning compressor model DSF340V1UFT (manufactured by GM, R290 refrigerant 2P model), the refrigeration oil samples were subjected to accelerated life durability test, and the test duration was 1000 hours. After the experiment, the oil products behind the bench were analyzed, and the test compressor was disassembled to comprehensively observe and evaluate the wear of the core component piston, and the lubrication performance of the oil products was measured by the piston roughness.

[0064] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims

1. A fatty acid ester composition for R290 refrigerant refrigerator, characterized in that: The base oil comprises pentaerythritol fatty acid ester and benzoic acid ester, wherein the mass ratio of pentaerythritol fatty acid ester to benzoic acid ester is 70 / 30-90 / 10; The pentaerythritol fatty acid ester is prepared by reacting pentaerythritol with two or more normal or isomeric monobasic fatty acids having 4 to 9 carbon atoms; the monobasic fatty acids are isooctanoic acid and isononanoic acid; The benzoate is prepared by reacting benzoic acid with one or more of diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol; The overall 40°C kinematic viscosity of the fatty acid ester composition for R290 refrigerant refrigerator is 46-68 mm 2 / s.

2. The fatty acid ester composition according to claim 1, wherein It also includes one or more of antioxidants, anti-wear agents, acid scavengers, metal corrosion inhibitors, and defoaming agents.

3. The fatty acid ester composition according to claim 2, wherein The antioxidant is selected from hindered phenols and amine compounds; the added amount of the antioxidant is 0.01-2.00% based on the total mass of the composition.

4. The fatty acid ester composition according to claim 3, wherein The amount of the antioxidant added is 0.01-1.00% based on the total weight of the composition.

5. The fatty acid ester composition according to claim 3, wherein The acid scavenger is selected from one or more of neodecanoic acid glycidyl ester, octyl glycidyl ether, glycidyl benzoate, and glycidyl acrylate; the amount of the acid scavenger added is 0.1-3.0% based on the total mass of the composition.

6. The fatty acid ester composition according to claim 4, wherein The amount of the acid scavenger added is 0.1-1.5% based on the total mass of the composition.

7. The fatty acid ester composition according to claim 5, wherein The anti-wear agent is selected from one or more of triphenyl phosphate, tricresyl phosphate, and triphenyl thiophosphate; the amount of the anti-wear agent added is 0.1-2.0% based on the total mass of the composition.

8. The fatty acid ester composition according to claim 7, wherein The amount of the anti-wear agent added is 0.1-1.5% based on the total weight of the composition.

9. The fatty acid ester composition according to claim 1, wherein The acid value of the fatty acid ester composition is ≤0.1 mgKOH / g.

10. The fatty acid ester composition according to claim 8, wherein The acid value of the fatty acid ester composition is ≤0.05 mgKOH / g.

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