Alkylbenzene semi-synthetic refrigerating machine oil composition for R290 refrigerant and preparation method of alkylbenzene semi-synthetic refrigerating machine oil composition

Abstract

The invention relates to the technical field of preparation of refrigerating machine oil compositions, in particular to an alkylbenzene semi-synthetic refrigerating machine oil composition for R290 refrigerants and a preparation method of the alkylbenzene semi-synthetic refrigerating machine oil composition, the alkylbenzene semi-synthetic refrigerating machine oil composition comprises base oil and additives, and the base oil is composed of mineral type lubricating oil fractions and alkylbenzene. The alkylbenzene semi-synthetic refrigerator oil composition for the R290 refrigerant is moderate in viscosity, relatively good in low-temperature performance, relatively low in two-phase separation temperature with the R290 refrigerant, and excellent in anti-oxidation stability and lubricity. The alkylbenzene semi-synthetic refrigerator oil composition for the R290 refrigerant has the kinematic viscosity of 20.8 mm < 2 > / s to 24.4 mm < 2 > / s at 40 DEG C, the pour point of-50 DEG C or below, the open flash point of 185 DEG C or above and the two-phase separation temperature of-50 DEG C or below, and is particularly suitable for a compressor with R290 as the refrigerant.

Description

Technical Field

[0001] This invention relates to the field of refrigeration oil composition preparation technology, and specifically to an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant and its preparation method. Background Technology

[0002] With the increasing demand in the light-duty commercial refrigeration sector, primarily encompassing commercial refrigerators, freezers, display cases, showcases, and vehicle-mounted refrigerators, there is a growing trend towards using environmentally friendly R290 refrigerant. Light-duty commercial refrigeration compressors have significant cooling capacity and require rapid cooling, typically demanding the lowest possible low-temperature performance (low pour point) and highest possible flash point for their compatible refrigeration oils. Simultaneously, to ensure lubrication, the refrigeration oil needs to have a suitable viscosity to guarantee sufficient oil film thickness and lubrication. Currently, most refrigeration oils used are ester-based synthetic refrigeration oils. However, ester-based synthetic refrigeration oils are highly hygroscopic and hydrolyzable, and are expensive. For compressor manufacturers, low-cost oils with good refrigerant compatibility and reliability are the preferred choice.

[0003] Hydrocarbon oils exhibit good miscibility with R290 refrigerant. Hydrocarbon oils include naphthenic mineral oils, paraffinic mineral oils, alkylbenzenes, polyethers, and esters. Among these, synthetic refrigeration oils such as polyethers and esters are expensive; paraffinic mineral oils have poor low-temperature fluidity, high wax content, and are prone to clogging capillary tubes and other parts, causing a decrease in system cooling; naphthenic mineral oils have excellent low-temperature performance and are inexpensive, but their viscosity index and flash point are relatively low; alkylbenzenes, especially linear alkylbenzenes, have excellent low-temperature performance and a high flash point.

[0004] Chinese patent document CN113388429A discloses a synthetic refrigeration oil and its preparation method. The refrigeration oil composition synthesized by this method has a kinematic viscosity of 5 to 6 mm at 40°C. 2 / s, pour point not greater than -50℃. This refrigeration oil composition does not specify the applicable refrigerant. If this refrigeration oil composition is used in an R290 refrigeration system, because the refrigeration oil composition and R290 refrigerant are highly compatible, the viscosity of the refrigeration oil will decrease, which will affect the effective circulation of the refrigeration oil in the compressor and affect its lubrication. Summary of the Invention

[0005] This invention provides an alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant and its preparation method, overcoming the shortcomings of the prior art. It can effectively solve the problems of low viscosity and poor lubricity after mixing existing refrigeration oil compositions with R290 refrigerant.

[0006] One of the technical solutions of the present invention is achieved by the following measures: an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant, the raw materials including base oil and additives in a weight ratio of 100:1.8 to 3.0, wherein the base oil is composed of mineral lubricating oil fraction and alkylbenzene.

[0007] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The additives mentioned above include anti-wear agents, which are added at an amount of 1.2% to 2.0% of the base oil weight.

[0008] The aforementioned anti-wear agent is one of the following: tricresyl phosphate, a mixture of tricresyl phosphate and triphenyl thiophosphate, and a mixture of tricresyl phosphate and dialkyl dithiophosphate.

[0009] The additives mentioned above also include antioxidants, which are added at a rate of 0.4% to 0.8% of the base oil weight.

[0010] The antioxidants mentioned above are phenol-shielded antioxidants, specifically 2,6-di-tert-butyl-p-cresol or 2,6-di-tert-butylphenol.

[0011] The additives mentioned above also include metal deactivators, which are added at a rate of 0% to 0.01% of the base oil weight.

[0012] The aforementioned metal deactivator is one of 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole and N,N-dialkylaminomethylenetriazole.

[0013] The additives mentioned above also include antifoaming agents, which are added at a rate of 0.0008% to 0.001% of the base oil weight.

[0014] The aforementioned antifoaming agent is a silicone-based antifoaming agent, which is one or more of polydimethylsiloxane and polyether silicone.

[0015] The above is obtained by the following method: at a temperature of 60°C to 80°C, the required amount of mineral-type lubricating oil fraction and alkylbenzene are mixed to obtain a base oil. The required amounts of anti-wear agent, antioxidant, metal deactivator and antifoaming agent are added to the base oil in sequence and mixed evenly to obtain an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0016] The second technical solution of the present invention is achieved through the following measures: A method for preparing an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant: The method is as follows: at a temperature of 60°C to 80°C, a required amount of mineral lubricating oil fraction and alkylbenzene are mixed to obtain a base oil. A required amount of anti-wear agent, antioxidant, metal deactivator and antifoaming agent are added to the base oil in sequence and mixed evenly to obtain an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0017] The alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant of this invention has moderate viscosity, good low-temperature performance, and a low phase separation temperature with R290 refrigerant. It also exhibits excellent oxidation stability and lubricity. The kinematic viscosity of the alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant of this invention is 20.8 mmHg at 40°C. 2 / s to 24.4mm 2 / s, pour point below -50℃, open flash point above 185℃, two-phase separation temperature below -50℃, especially suitable for compressors using R290 as refrigerant. Detailed Implementation

[0018] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0019] The present invention will be further described below with reference to embodiments: Example 1: The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant includes base oil and additives in a weight ratio of 100:1.8 to 3.0. The base oil is composed of mineral lubricating oil fraction and alkylbenzene.

[0020] In this invention, the mineral-based lubricating oil fraction is produced and supplied by the high-pressure hydrogenation unit of PetroChina Karamay Petrochemical Co., Ltd.

[0021] Example 2: As an optimization of the above example, the additive includes an anti-wear agent, and the amount of anti-wear agent added is 1.2% to 2.0% of the weight of the base oil.

[0022] Example 3: As an optimization of the above examples, the anti-wear agent is one of tricresyl phosphate, a mixture of tricresyl phosphate and triphenyl thiophosphate, and a mixture of tricresyl phosphate and dialkyl dithiophosphate.

[0023] Example 4: As an optimization of the above examples, the additive also includes an antioxidant, and the amount of antioxidant added is 0.4% to 0.8% of the weight of the base oil.

[0024] Example 5: As an optimization of the above example, the antioxidant is a shielded phenolic antioxidant, which is 2,6-di-tert-butyl-p-cresol or 2,6-di-tert-butylphenol.

[0025] Example 6: As an optimization of the above examples, the additive also includes a metal deactivator, the amount of which is 0% to 0.01% of the weight of the base oil.

[0026] Example 7: As an optimization of the above examples, the metal deactivator is one of 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole and N,N-dialkylaminomethylenetriazole.

[0027] Example 8: As an optimization of the above examples, the additive also includes an antifoaming agent, the amount of which is 0.0008% to 0.001% of the weight of the base oil.

[0028] Example 9: As an optimization of the above example, the antifoaming agent is a silicone-type antifoaming agent, which is one or more of polydimethylsiloxane and polyether silicone.

[0029] Example 10: As an optimization of the above example, the following method was used to obtain a base oil by mixing a required amount of mineral-based lubricating oil fraction and alkylbenzene at a temperature of 60°C to 80°C. The required amounts of anti-wear agent, antioxidant, metal deactivator and antifoaming agent were added to the base oil in sequence and mixed well to obtain an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: The alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant of this invention consists of a base oil and additives. The base oil is composed of a mineral-based lubricating oil fraction produced by high-pressure hydrogenation and alkylbenzenes. The kinematic viscosity (40°C) of the mineral-based lubricating oil fraction is 15 mm. 2 / s to 55mm 2 / s, pour point not greater than -20℃, open flash point not less than 200℃, kinematic viscosity of alkylbenzene (40℃) is 17mm. 2 / s to 30mm 2 / s, pour point not greater than -60℃, open flash point not less than 190℃, base oil is obtained by blending mineral-based lubricating oil fraction and alkylbenzene components, and then additives are added to the base oil for compounding. This results in an alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant, which, at low temperatures (pour point not greater than -50℃), increases the kinematic viscosity by 40℃ (the kinematic viscosity at 40℃ is 20.8 mm). 2 / s to 24.4mm 2 / s), effectively solving the problem of low viscosity and poor lubricity after existing refrigeration oil compositions are mixed with R290 refrigerant.

[0031] Example 11: This R290 refrigerant uses an alkylbenzene-based semi-synthetic refrigeration oil composition. The raw materials include base oil and additives. The base oil consists of mineral-based lubricating oil fraction and alkylbenzene in a mass ratio of 10:90. The additives include anti-wear agents, antioxidants, and anti-foaming agents. The anti-wear agents are tricresyl phosphate and triphenyl thiophosphate, added at 1.6% of the base oil weight (the amounts of tricresyl phosphate and triphenyl thiophosphate are each 0.8% of the base oil weight). The antioxidant is 2,6-di-tert-butylphenol, added at a certain amount based on the base oil weight. 0.4% of the base oil; the antifoaming agent is polydimethylsiloxane and polyether silicone oil, and the amount of antifoaming agent added is 0.0008% of the weight of the base oil (the amounts of polydimethylsiloxane and polyether silicone oil added are 0.0006% and 0.0002% of the base oil, respectively); it is obtained by the following method: at a temperature of 70°C, the required amount of mineral lubricating oil fraction and alkylbenzene are mixed to obtain the base oil, and the required amounts of antiwear agent, antioxidant and antifoaming agent are added to the base oil in sequence and mixed evenly to obtain the alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0032] Example 12: This R290 refrigerant uses an alkylbenzene-based semi-synthetic refrigeration oil composition. The raw materials include base oil and additives. The base oil consists of mineral-based lubricating oil fraction and alkylbenzene in a mass ratio of 25:75. The additives include anti-wear agents, antioxidants, metal deactivators, and antifoaming agents. The anti-wear agents are tricresyl phosphate and triphenyl thiophosphate, added at 1.4% of the base oil weight (tricresyl phosphate and triphenyl thiophosphate are added at 1.2% and 0.2% of the base oil weight, respectively). The antioxidant is 2,6-di-tert-butyl-p-cresol, added at 0.8% of the base oil weight. The metal deactivator is 2,5-bis(tert-nonyldisulfide). The composition consists of 1,3,4-thiadiazole (a type of alkylbenzene), with the metal deactivator added at 0.01% of the base oil weight; the antifoaming agents are polydimethylsiloxane and polyether silicone oil, with the antifoaming agent added at 0.001% of the base oil weight (the amounts of polydimethylsiloxane and polyether silicone oil added are 0.0006% and 0.0004% of the base oil weight, respectively); and is obtained by mixing the required amount of mineral-based lubricating oil fraction and alkylbenzene at a temperature of 70°C to obtain the base oil. The required amounts of antiwear agent, antioxidant, metal deactivator, and antifoaming agent are then added to the base oil in sequence and mixed thoroughly to obtain an alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant.

[0033] Example 13: This R290 refrigerant uses an alkylbenzene-based semi-synthetic refrigeration oil composition. The raw materials include base oil and additives. The base oil consists of mineral-based lubricating oil fraction and alkylbenzene in a mass ratio of 40:60. The additives include anti-wear agents, antioxidants, and anti-foaming agents. The anti-wear agent is tricresyl phosphate, added at 1.2% of the base oil weight; the antioxidant is 2,6-di-tert-butyl-p-cresol, added at 0.6% of the base oil weight; and the metal deactivator is N,N-dialkylaminomethylenetriazole, added at a specific amount... The base oil is 0.01% by weight; the antifoaming agent is polydimethylsiloxane and polyether silicone oil, and the amount of antifoaming agent added is 0.0008% by weight of the base oil (the amounts of polydimethylsiloxane and polyether silicone oil added are 0.0006% and 0.0002% of the base oil, respectively); it is obtained by the following method: at a temperature of 70°C, the required amount of mineral lubricating oil fraction and alkylbenzene are mixed to obtain the base oil, and the required amounts of antiwear agent, antioxidant and antifoaming agent are added to the base oil in sequence and mixed well to obtain the alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0034] Example 14: This R290 refrigerant uses an alkylbenzene-based semi-synthetic refrigeration oil composition. The raw materials include base oil and additives. The base oil consists of mineral-based lubricating oil fraction and alkylbenzene in a mass ratio of 48:52. The additives include anti-wear agents, antioxidants, metal deactivators, and antifoaming agents. The anti-wear agents are tricresyl phosphate and dialkyl dithiophosphate, added at 1.61% of the base oil weight (tricresyl phosphate and dialkyl dithiophosphate are added at 1.6% and 0.01% of the base oil weight, respectively). The antioxidant is 2,6-di-tert-butyl-p-cresol, added at 0.8% of the base oil weight. The metal deactivator is N,N- Dialkylaminomethylenetriazole, the amount of metal deactivator added is 0.01% of the base oil weight; the antifoaming agent is polydimethylsiloxane and polyether silicone oil, the amount of antifoaming agent added is 0.001% of the base oil weight (the amounts of polydimethylsiloxane and polyether silicone oil added are 0.0006% and 0.0004% of the base oil weight, respectively); it is obtained by the following method: at a temperature of 70°C, the required amount of mineral lubricating oil fraction and alkylbenzene are mixed to obtain the base oil, and the required amounts of antiwear agent, antioxidant, metal deactivator and antifoaming agent are added to the base oil in sequence and mixed well to obtain the alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0035] Example 15: This R290 refrigerant uses an alkylbenzene-based semi-synthetic refrigeration oil composition. The raw materials include base oil and additives. The base oil consists of mineral-based lubricating oil fraction and alkylbenzene in a mass ratio of 26:74. The additives include anti-wear agents, antioxidants, metal deactivators, and antifoaming agents. The anti-wear agents are tricresyl phosphate and dialkyl dithiophosphate, added at 1.605% of the base oil weight (tricresyl phosphate and dialkyl dithiophosphate are added at 1.6% and 0.005% of the base oil weight, respectively). The antioxidant is 2,6-di-tert-butyl-p-cresol, added at 0.8% of the base oil weight. The metal deactivator is 2,5-bis(tert-butyl-p-cresol). The base oil is composed of nonyldithio-1,3,4-thiadiazole, with the metal deactivator added at 0.01% of the base oil weight; the antifoaming agent is polydimethylsiloxane and polyether silicone oil, with the antifoaming agent added at 0.001% of the base oil weight (the amounts of polydimethylsiloxane and polyether silicone oil added are 0.0006% and 0.0004% of the base oil weight, respectively); it is obtained by the following method: at a temperature of 70°C, the required amount of mineral-based lubricating oil fraction and alkylbenzene are mixed to obtain the base oil, and the required amounts of antiwear agent, antioxidant, metal deactivator and antifoaming agent are added to the base oil in sequence and mixed well to obtain the alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

[0036] Example 16: This R290 refrigerant uses an alkylbenzene-based semi-synthetic refrigeration oil composition. The raw materials include base oil and additives. The base oil consists of mineral-based lubricating oil fraction and alkylbenzene in a mass ratio of 90:10. The additives include anti-wear agents, antioxidants, metal deactivators, and antifoaming agents. The anti-wear agents are tricresyl phosphate and triphenyl thiophosphate, added at 2.0% of the base oil weight (tricresyl phosphate and triphenyl thiophosphate are added at 1.6% and 0.4% of the base oil weight, respectively). The antioxidant is 2,6-di-tert-butyl-p-cresol, added at 0.8% of the base oil weight. The metal deactivator is 2,5-bis(tert-nonyldisulfide). The composition consists of 1,3,4-thiadiazole (a type of alkylbenzene), with the metal deactivator added at 0.01% of the base oil weight; the antifoaming agents are polydimethylsiloxane and polyether silicone oil, with the antifoaming agent added at 0.001% of the base oil weight (the amounts of polydimethylsiloxane and polyether silicone oil added are 0.0006% and 0.0004% of the base oil weight, respectively); and is obtained by mixing the required amount of mineral-based lubricating oil fraction and alkylbenzene at a temperature of 70°C to obtain the base oil. The required amounts of antiwear agent, antioxidant, metal deactivator, and antifoaming agent are then added to the base oil in sequence and mixed thoroughly to obtain an alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant.

[0037] Comparative Example 1: The existing refrigeration oil composition is No. 22 POE oil.

[0038] Experimental Example 1: To investigate the performance of the alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant of the present invention.

[0039] Experimental Methods: The performance of the alkylbenzene semi-synthetic refrigeration oil compositions for R290 refrigerant prepared in Examples 11 to 16 of this invention was tested. The composition of the alkylbenzene semi-synthetic refrigeration oil compositions for R290 refrigerant prepared in Examples 11 to 16 of this invention is shown in Table 1. The performance test indicators included kinematic viscosity (40°C), pour point, flash point (open cup), two-phase separation temperature (this invention: R290 refrigerant = 20:80), and maximum non-seizure load P. B Meanwhile, Comparative Example 1 will be used as a comparison.

[0040] Experimental Results: The properties of the alkylbenzene semi-synthetic refrigeration oil compositions for R290 refrigerant prepared in Examples 11 to 16 of this invention are shown in Table 2. As can be seen from Table 2, the refrigeration oil compositions prepared in this invention do not exhibit excessive miscibility with R290 refrigerant, and their kinematic viscosity at 40°C is 20.8 mm. 2 / s~24.4mm 2 / s, pour point below -50℃, open flash point above 185℃, two-phase separation temperature below -50℃, maximum non-seize load P BGreater than 47 kg. The additives include anti-wear agents, antioxidants, metal deactivators, and anti-foaming agents. The combination of different types of additives significantly improves the lubricity, anti-wear properties, and oxidation stability of the refrigeration oil. Compared to Comparative Example 1 (No. 22 POE oil), the alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant of this invention has a higher open-cup flash point and better high-temperature resistance, meeting the requirements of light commercial refrigeration compressors.

[0041] In summary, the alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant of this invention has moderate viscosity, good low-temperature performance, and a low phase separation temperature with R290 refrigerant. It also exhibits excellent oxidation stability and lubricity. The kinematic viscosity of the alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant of this invention is 20.8 mmHg at 40°C. 2 / s to 24.4mm 2 / s, pour point below -50℃, open flash point above 185℃, two-phase separation temperature below -50℃, especially suitable for compressors using R290 as refrigerant.

[0042] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. An alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant, characterized in that... The raw materials include base oil and additives in a weight ratio of 100:1.8 to 3.0, with the base oil consisting of mineral lubricating oil fractions and alkylbenzenes.

2. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to claim 1, characterized in that... Additives include anti-wear agents, which are added at a rate of 1.2% to 2.0% of the base oil weight.

3. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to claim 2, characterized in that... The anti-wear agent is one of the following: tricresyl phosphate, a mixture of tricresyl phosphate and triphenyl thiophosphate, and a mixture of tricresyl phosphate and dialkyl dithiophosphate.

4. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to claim 1, 2, or 3, characterized in that... The additives also include antioxidants, which are added at a rate of 0.4% to 0.8% of the base oil weight.

5. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to claim 4, characterized in that... The antioxidant is a shielded phenolic antioxidant, specifically 2,6-di-tert-butyl-p-cresol or 2,6-di-tert-butylphenol.

6. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to any one of claims 1 to 5, characterized in that... The additives also include metal deactivators, which are added at a rate of 0% to 0.01% of the base oil weight.

7. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to claim 6, characterized in that... The metal deactivator is one of 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole and N,N-dialkylaminomethylenetriazole.

8. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to any one of claims 1 to 7, characterized in that... The additives also include an antifoaming agent, which is added at an amount of 0.0008% to 0.001% of the base oil weight; and / or the antifoaming agent is a silicone-based antifoaming agent, which is one or more of polydimethylsiloxane and polyether silicone.

9. The alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant according to any one of claims 2 to 8, characterized in that... The following method is used to obtain a base oil by mixing a required amount of mineral-based lubricating oil fraction and alkylbenzene at a temperature of 60°C to 80°C. The required amounts of anti-wear agent, antioxidant, metal deactivator and antifoaming agent are added to the base oil in sequence and mixed well to obtain an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

10. An alkylbenzene-based semi-synthetic refrigeration oil composition for R290 refrigerant according to any one of claims 2 to 8, characterized in that... The following method is used: at a temperature of 60°C to 80°C, the required amount of mineral-based lubricating oil fraction and alkylbenzene are mixed to obtain a base oil. The required amounts of anti-wear agent, antioxidant, metal deactivator and antifoaming agent are added to the base oil in sequence and mixed well to obtain an alkylbenzene semi-synthetic refrigeration oil composition for R290 refrigerant.

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