JP2015014395A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner suppressing hydrolysis of refrigeration oil.SOLUTION: An air conditioner includes a compressor, an outdoor heat exchanger, an expansion mechanism, an indoor heat exchanger, R32 refrigerant or mixed refrigerant containing R32 of 50 wt.% or more, and refrigeration oil containing polyol ester oil and acid scavenger. The acid scavenger includes an alkyl glycidyl ester compound and a cyclo glycidyl ether compound. The content rate of the alkyl glycidyl ester compound in the acid scavenger is 10-97%.

Description

  The present invention relates to an air conditioner.

  The refrigerant for room air conditioners has been shifted from R22 to an alternative refrigerant to protect the ozone layer, and currently R410A is mainly used. However, R410A has a high global warming potential (hereinafter referred to as “GWP”) of 2088, and in order to reduce the influence on the global environment, difluoromethane (hereinafter “ R32 ”) is under consideration.

  By the way, the refrigerating machine oil to be compatible varies depending on the type of refrigerant. The refrigeration oil is stored in the compressor, and when the compressor is started, oil is supplied to each sliding portion, and a part is discharged out of the compressor together with the refrigerant. At this time, if the refrigerating machine oil is difficult to dissolve in the refrigerant, the refrigerating machine oil is separated from the refrigerant at a low temperature portion in the refrigerating cycle, the refrigerating machine oil does not return to the compressor, and the amount of the refrigerating machine oil in the compressor decreases.

  In order to avoid such problems, a polyol ester oil (hereinafter referred to as “POE oil”) or a polyvinyl ether oil (hereinafter referred to as “PVE oil”) that is generally compatible with the refrigerant for HFC (Hydro Fluoro Carbons) refrigerants. Is used as refrigeration oil.

  Here, when POE oil is used, if water is mixed in the refrigeration cycle, the POE oil undergoes hydrolysis and deteriorates. Therefore, when using POE oil, in order to suppress hydrolysis of POE oil, an acid scavenger such as an epoxy compound is added.

  In Patent Document 1, at least one selected from glycidyl esters, glycidyl ethers, and α-olefin oxides is used as an acid scavenger for refrigeration oil, and two or more types may be used in combination. Have been described.

JP2008-266423

  Since R32 has a higher specific heat ratio than R410A, when R32 is adopted as a refrigerant, the discharge temperature of the compressor becomes higher than that of R410A. In the case of a high-pressure chamber type compressor, the compressor is filled with a refrigerant that has been compressed to a high temperature.

  Since the hydrolysis of the refrigerating machine oil is promoted at higher temperatures, the acid scavenger described in Patent Document 1 cannot sufficiently suppress the hydrolysis of the refrigerating machine oil.

  Then, an object of this invention is to provide the air conditioner which suppresses hydrolysis of refrigerating machine oil.

  The air conditioner of the present invention includes a compressor, an outdoor heat exchanger, an expansion mechanism, and an indoor heat exchanger, an R32 refrigerant or a mixed refrigerant containing more than 50% by weight of R32, a polyol ester oil, and an acid scavenger. The acid scavenger has an alkyl glycidyl ester compound and a cycloglycidyl ether compound, and the ratio of the alkyl glycidyl ester compound in the acid scavenger is 10 to 97%.

  ADVANTAGE OF THE INVENTION According to this invention, the air conditioner which suppresses hydrolysis of refrigerating machine oil can be provided.

It is the schematic of the air conditioner combined with air conditioning. It is the schematic of a hermetic compressor. It is a figure which shows about the relationship between the mixing ratio of an alkyl glycidyl ester compound and a cycloglycidyl ether compound, the acid scavenger presence rate after a hydrolysis stability test, and an acid value.

  Hereinafter, an air conditioner according to an embodiment of the present invention will be described. FIG. 1 is a schematic view of an air conditioner that is also used for air conditioning. In the air conditioner of the present embodiment, the compressor 1, the outdoor heat exchanger 3, the expansion mechanism 4, and the indoor heat exchanger 5 are connected by piping, and the refrigerant circulates.

  In the case of the cooling operation, the high-temperature and high-pressure gas refrigerant compressed by the compressor 1 flows to the outdoor heat exchanger 3 via the four-way valve 2. The high-temperature and high-pressure gas refrigerant is cooled by the outdoor heat exchanger 3 functioning as a condenser, and becomes a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is expanded by the expansion mechanism 4 and becomes a low-temperature and low-pressure liquid refrigerant containing a slight amount of gas and flows to the indoor heat exchanger 6. The low-temperature and low-pressure liquid refrigerant is heated by the indoor heat exchanger 6 functioning as an evaporator, becomes a low-temperature gas refrigerant, and returns to the compressor 1 through the four-way valve 2 again. In the heating operation, the refrigerant flow is changed by the four-way valve 2, and the refrigerant flows in the opposite direction to the cooling operation.

  In addition, you may comprise so that it may have only the function of either cooling or heating, without using the four-way valve 2. As the expansion mechanism 4, an electronic expansion valve, a capillary tube, a temperature type expansion mechanism, or the like can be used.

  FIG. 2 is a schematic view of the compressor. The compressor 1 engages a fixed scroll member 6 having an end plate 7 and a spiral wrap 8 and a orbiting scroll member 9 having a wrap 10 with the wrap 8 and the wrap 10 facing each other to engage the compression mechanism portion. Then, the orbiting scroll member 9 is orbited by the crankshaft 11. Of the compression chambers 12 (12a, 12b...) Formed by the fixed scroll member 6 and the orbiting scroll member 9, the outermost compression chamber is gradually reduced in volume with the orbiting motion. The fixed scroll member 6 and the orbiting scroll member 9 move toward the center. When the compression chamber 12 reaches the vicinity of the center of the fixed scroll member 6 and the orbiting scroll member 9, the compression chamber 12 communicates with the discharge port 13, and the gas refrigerant compressed in the compression chamber 12 passes through the discharge pipe 16. It is discharged outside.

  The compressor 1 has a built-in electric motor 17 in the pressure vessel 15, and the compressor 1 performs a compression operation by rotating the crankshaft 11 at a constant speed or at a rotational speed corresponding to a voltage controlled by an inverter (not shown). Do. The electric motor 17 operates in an atmosphere of refrigerant and refrigeration oil. An insulating film is arranged between the phases of coils (not shown) of the motor 17 and between the laminated steel plates in order to maintain the insulation. However, an inexpensive film such as polyethylene terephthalate or polyethylene naphthalate is used as the insulating film.

  Further, an oil sump is provided at the lower part of the electric motor 17, and the refrigerating machine oil accumulated in the oil sump passes through the oil hole 19 provided in the crankshaft 11 due to a pressure difference, and the orbiting scroll member 9 and the crank. It is used for lubrication of the sliding portion with the shaft 11, the sliding bearing 18, and the like.

  In this example, R32 is used as the refrigerant, and POE oil that is compatible with R32 and has excellent lubricity is used as the refrigerating machine oil.

  POE oil is excellent in lubrication performance, but has the property of decomposing with moisture to produce fatty acids. When the fatty acid is produced, the metal surface is corroded, and the deterioration of the refrigerating machine oil may proceed using the produced fatty acid as a catalyst.

  Furthermore, since R32 has a high polarity, when R32 is used as a refrigerant, the amount of moisture brought in is larger than that of R410A. Moreover, since R32 has a higher specific heat ratio than R410A compared to R410A that has been used as a refrigerant, the discharge temperature of the compressor 1 is likely to rise, and the discharge temperature of the compressor 1 may exceed 100 ° C. . In the case of a high-pressure chamber type compressor, the compressor is filled with a refrigerant that has been compressed to a high temperature. That is, when R32 is used as the refrigerant, the amount of moisture brought in increases, and the hydrolysis of the refrigerating machine oil is promoted by the high temperature of the compressor, so that the refrigerating machine oil is more likely to deteriorate than when R410A is used.

  Examples of the acid scavenger include an epoxy compound and carbodiimide. In this embodiment, an epoxy compound is used. Epoxy compounds have the property of trapping moisture and acid and turning them into stable materials. Moreover, since the epoxy compound has an effect of capturing moisture present in the refrigeration cycle in addition to the acid generated by the deterioration of the refrigerating machine oil, it also has an effect of protecting the insulating film used for the motor.

In this example, an alkyl glycidyl ester compound and a cycloglycidyl ether compound are used as the acid scavenger. The alkyl glycidyl ester compound has a structure represented by chemical formula (1) (wherein R ¹ is an alkyl group having 4 to 9 carbon atoms), and the cycloglycidyl ether compound of this example has the chemical formula (2) The structure shown in FIG.

  The alkyl glycidyl ester compound is highly reactive with moisture and reacts at a low temperature. Therefore, the alkyl glycidyl ester compound reacts quickly with moisture in the refrigeration cycle and can suppress hydrolysis of the refrigerating machine oil. That is, it is fast-acting and can reduce the initial moisture in the refrigeration cycle. However, since alkyl glycidyl ester compounds are fast-acting, the remaining amount decreases rapidly, and the refrigeration oil may deteriorate after long-term operation.

  On the other hand, the cycloglycidyl ether compound reacts at a relatively high temperature, has higher heat resistance than the alkyl glycidyl ester compound, and is slow-acting while the alkyl glycidyl ester compound is fast-acting. However, the cycloglycidyl ether compound is less reactive with moisture than the alkyl glycidyl ester compound, and the cycloglycidyl ether compound alone cannot sufficiently capture moisture and the refrigerating machine oil cannot prevent hydrolysis. Will rise.

  Therefore, in this example, an alkyl glycidyl ester compound and a cycloglycidyl ether compound are mixed and used, and moisture in the refrigeration cycle is captured by the alkyl glycidyl ester compound at the initial stage of operation, and the inside of the compressor becomes hot during operation. Thus, when the refrigerating machine oil deteriorates to generate an acid, it is captured by a cycloglycidyl ether compound.

In this embodiment, as described above, POE oil that is compatible with R32 and has excellent lubricity is used as the refrigerating machine oil. Here, the compatibility is a characteristic that the refrigerant and the refrigerating machine oil dissolve without being separated. If the compatibility is poor, the refrigeration oil discharged into the refrigeration cycle together with the refrigerant from the compressor may be separated at the low temperature portion of the refrigeration cycle, and may not return to the compressor, resulting in insufficient oil supply. Here, the low temperature side critical dissolution temperature is used as a compatibility index. It can be said that the higher the low-temperature critical solution temperature, the worse the compatibility, and the lower, the better the compatibility. for that reason. The low temperature side critical dissolution temperature with R32 is desirably 10 ° C. or lower. As the lubricity, kinematic viscosity is desirably used POE oil in the range of 40mm ² / s~100mm ² / s.

  In order to produce a refrigerating machine oil that satisfies such conditions, examples of polyhydric alcohols include neopentyl glycol, trimethylolpropane, pentaerythritol, and dipentaerythritol. Examples of monovalent fatty acids include fatty acids having 4 to 5 carbon atoms such as butanoic acid, pentanoic acid, 2-methylpropanoic acid, and 2-methylbutanoic acid, and a relatively small number of carbon atoms. In order to prevent the above, relatively carbon having 8 to 12 carbon atoms such as octanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, 3,5,5-trimethylhexanoic acid, etc. A large number of fatty acids are used alone or in combination.

In particular, considering the stagnation at low temperatures in an actual room air-conditioner cycle, the low-temperature critical solution temperature of the refrigerating machine oil and R32 used is preferably 0 ° C. or lower. The POE oil having a low temperature side critical dissolution temperature with R32 of 0 ° C. or lower is preferably one having a structure represented by the following chemical formulas (3) to (6) alone or in combination of two or more (wherein R ² is (Represents an alkyl group having 4 to 9 carbon atoms), and in order to maintain high viscosity and improve lubricity, any of formula (5) and formula (6) or a mixture thereof is preferred.

  Next, the result of having evaluated the hydrolysis resistance of the refrigerating machine oil by the shield tube test about a present Example is demonstrated. The hydrolysis resistance test method is as follows. A glass ampoule tube having an outer diameter of 13 mm and an inner diameter of 10 mm was filled with 0.5 g of refrigerant and 5 g of refrigerating machine oil. Examples 1 to 3 and Comparative Examples 1 to 7 use a base oil mixed with the structure shown in chemical formulas (3) and (4) excellent in compatibility with R32 as a refrigerant and R32 as a refrigerating machine oil. 1-2 used the base oil of the structure shown to Chemical formula (3) excellent in compatibility with R410A as a refrigerant | coolant, and R410A as refrigerating machine oil.

  In Examples 1 to 3, Comparative Examples 1 to 7, and Conventional Examples 1 to 2, the alkyl glycidyl ester compound represented by the chemical formula (1) and the cycloglycidyl ether compound represented by the chemical formula (2) are used as refrigerating machine oils as the acid scavenger. Added. Table 1 shows the addition ratio of the alkyl glycidyl ester compound and the cycloglycidyl ether compound to the refrigerating machine oil.

  The acid scavenging ability per unit of the alkyl glycidyl ester compound and the cycloglycidyl ether compound is different. Then, the ratio of the alkyl glycidyl ester compound and the cycloglycidyl ether compound was changed and added so that the acid scavenging ability would be equivalent to that of the conventional acid scavengers of R410A refrigerant oil for conventional R1-2A. The acid scavenging ability of the acid scavengers of Examples 1 to 3, Comparative Examples 1 to 2 and 7 and Conventional Examples 1 to 2 are equivalent.

  In addition, when the theoretical value of the acid scavenger of the acid scavenger is represented by the same unit (mgKOH / g) as the acid value, it is represented by the formula (7). The molecular weight of the alkyl glycidyl ester compound is 158 to 228, and the molecular weight of the cycloglycidyl ether compound is 252.

  Adjusting the water content of the refrigerating machine oil to 1,000 ppm and coexisting iron, copper, and aluminum (each φ1.6 mm, length 50 mm), which are frequently used as catalysts in the refrigeration cycle, at 175 ° C. for 14 days The heating of the refrigerating machine oil after heating was observed, and the acid value and additive residual ratio were measured. As for the foaming, the state of bubbles generated when the glass ampule tube was opened and the refrigerant was degassed was observed, and the bubbles that did not disappear and overflowed from the glass ampule tube were determined as NG. The acid value was in accordance with JIS K2501 “Petroleum and lubricating oil—neutralization number test method”. The additive residual ratio was measured with a gas chromatograph.

  Table 2 shows the results of a hydrolysis resistance test in which the acid scavenger shown in Table 1 was measured under the conditions described above.

  First, the results of Conventional Example 1 and Conventional Example 2 showed no increase in acid value. In particular, in Conventional Example 2, the acid scavenger remaining rate is also 50% or more, and the acid scavenger remains sufficiently. The life of a room air conditioner is normally assumed to be 10 years. However, when analyzing the refrigerator oil after 10 years of operation of the room air conditioner using R410A as the refrigerant and Conventional Example 2 as the refrigerator oil, the acid value is 0.01 mgKOH / g Hereinafter, the residual rate of the acid scavenger was about 50%, and the amount of metal in oil was 0.1 ppm or less for each of the three elements of aluminum (Al), copper (Cu), and iron (Fe). That is, it can be said that the test of continuing heating at 175 ° C. for 14 days reproduces the state in which the room air conditioner has been operated for 10 years.

  Therefore, the acid scavenger in this example was also subjected to a test that continued heating at 175 ° C. for 14 days, and if a result equivalent to that of the acid scavenger of Conventional Example 2 was obtained, a reliable acid scavenger was used. I decided that there was.

  Comparative Example 1 is obtained by adding the acid scavenger of Conventional Example 1 to R32 refrigerating machine oil. As shown in Table 2, the acid scavenger remaining rate of the acid scavenger of Comparative Example 1 was 0, which resulted in an increase in the acid value of the refrigerating machine oil. Therefore, it was found that the acid scavenger of Comparative Example 1 cannot prevent hydrolysis of R32 refrigerating machine oil.

  Comparative Example 2 is obtained by adding the acid scavenger of Conventional Example 2 to R32 refrigerating machine oil. As shown in Table 2, the acid scavenger of Comparative Example 2 is different from the acid scavenger of Comparative Example 1 in that an acid scavenger residual ratio of 50% or more can be secured, but the acid value of the refrigerating machine oil increases. It became. That is, it was found that the acid scavenger of Comparative Example 2 could not suppress hydrolysis of the refrigerating machine oil. This is presumably because the cycloglycidyl ether compound has low reactivity with moisture and cannot capture moisture sufficiently.

  From the above results, it was found that the additive added to the R410A refrigerating machine oil cannot suppress hydrolysis of the R32 refrigerating machine oil.

  Next, a description will be given of the results of tests conducted using the additive added to the R410A refrigerating machine oil with the addition amount increased. In Comparative Example 3, the addition amount of the alkyl glycidyl ester compound is increased with respect to Comparative Example 1, and the ratio of the alkyl glycidyl ester compound in the total weight of the refrigerating machine oil is 2 wt%. The acid scavenger remaining in Comparative Example 3 has an acid scavenger remaining rate of less than 50%, but unlike Comparative Example 1, an increase in acid value can be suppressed. However, as shown in Table 2, the detection of copper ions was recognized in the metal in oil, and it is assumed that the copper catalyst was affected. This is because if the alkyl glycidyl ester compound is added in excess, it affects the compressor and the metal material in the refrigeration cycle, and in particular, components such as copper ions are easily dissolved in the oil.

  In Comparative Example 4, the addition amount of the alkyl glycidyl ester compound is further increased with respect to Comparative Example 3, and the ratio of the alkyl glycidyl ester compound in the total weight of the refrigerating machine oil is 5 wt%. Although the acid scavenging residual rate of the acid scavenger of Comparative Example 4 is larger than that of Comparative Example 3, it is 50% or less, and the detected amount of copper ions is increased in the metal in oil.

  In Comparative Example 5, the addition amount of the cycloglycidyl ether compound is increased with respect to Comparative Example 2, and the ratio of the cycloglycidyl ether compound in the total weight of the refrigerating machine oil is 2 wt%. The residual rate of the acid scavenger was 100% and did not decrease at all, but the acid value increased. That is, the acid scavenger cannot suppress the hydrolysis of the refrigerating machine oil.

  In Comparative Example 6, the addition amount of the cycloglycidyl ether compound is further increased with respect to Comparative Example 5 so that the ratio of the cycloglycidyl ether compound in the total weight of the refrigerating machine oil is 5 wt%. The acid scavenger remaining rate is 96.9%, and the acid scavenger remains sufficiently, and the increase in acid value can be suppressed. However, when the addition amount of the cycloglycidyl ether compound is 5 wt% or more, the turbidity of the refrigerating machine oil is high, and the amount of oil supplied to the sliding portion is reduced, which may cause poor lubrication due to insufficient oil supply during use. .

  From the above results, it was found that there was no effect even when the amount of the alkyl glycidyl ester compound or cycloglycidyl ether compound was increased, and that excessive addition had an effect on other performances of the metal member and the refrigerating machine oil. It was also found that at least the addition amount of the alkyl glycidyl ester compound needs to be less than 2 wt% with respect to the total weight of the refrigerating machine oil. Furthermore, since the viscosity of the additive itself is low, the viscosity of the refrigerating machine oil is lowered and the sealing property is lowered. Therefore, it is desirable that the addition amount of the acid scavenger is not increased as much as possible.

  Next, a case where an acid scavenger is constituted by mixing an alkyl glycidyl ester compound and a cycloglycidyl ether compound as the acid scavenger for R32 refrigerant will be described. In Examples 1 to 3 and Comparative Example 7, an alkyl glycidyl ester compound and a cycloglycidyl ether compound are mixed and added. The amount of addition was adjusted according to the acid scavenging ability of the acid scavengers of Conventional Example 1 and Conventional Example 2, and the ratio of the alkyl glycidyl ester compound and the cycloglycidyl ether compound was changed to perform the test.

  As shown in Table 2, since Examples 1 to 3 and Comparative Example 7 do not show an increase in acid value, the deterioration of the refrigerating machine oil can be suppressed by mixing and adding two types of acid scavengers. You can see that However, although the acid scavenger residual rate of 50% or more was secured for Examples 1 to 3, the acid scavenger residual rate was less than 50% of the previous history for Comparative Example 7.

  FIG. 3 is a diagram showing the relationship between the mixing ratio of the alkyl glycidyl ester compound and the cycloglycidyl ether compound, the acid scavenger existing rate after the hydrolysis stability test, and the acid value. FIG. 3 is a table summarizing the acid value and acid scavenger remaining rate after hydrolysis stability tests for Examples 1 to 3 and Comparative Examples 1 to 2 and 7.

  In order to prevent the acid value, it is necessary to configure the acid scavenger by mixing an alkyl glycidyl ester compound and a cycloglycidyl ether compound. However, even if an alkyl glycidyl ester compound and a cycloglycidyl ether compound are mixed to form an acid scavenger, if the ratio of the alkyl glycidyl ester compound in the acid scavenger is too small, moisture in the refrigerating machine oil is captured at the initial stage. Can not. As shown in FIG. 3, when the ratio of the alkyl glycidyl ester compound is less than 10%, hydrolysis of the POE oil cannot be suppressed, and the acid value of the refrigerating machine oil increases.

  Moreover, when there are too many ratios of the alkylglycidyl ester compound in an acid scavenger, consumption will increase from a heat resistant problem. As shown in FIG. 3, when the ratio of the alkyl glycidyl ester compound exceeds 97%, hydrolysis of the POE oil cannot be suppressed, and the acid value of the refrigerating machine oil increases.

  Therefore, in order to prevent the acid value of the refrigerating machine oil, in addition to constituting an acid scavenger by mixing an alkyl glycidyl ester compound and a cycloglycidyl ether compound, the ratio of the alkyl glycidyl ester compound in the acid scavenger is 10 to 97%. It is necessary to.

  In addition, the ratio of the alkyl glycidyl ester compound in an acid scavenger was calculated using Formula (8).

  Furthermore, in order to maintain the acid scavenger remaining rate of 50% or more, the ratio of the alkyl glycidyl ester compound in the acid scavenger needs to be 10 to 70%. By maintaining the acid scavenger remaining rate of 50% or more, stability can be maintained over a long period of time without affecting the metal member in the refrigeration cycle.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  The refrigerant of this embodiment may be composed of a mixed refrigerant containing more than 50% by weight of R32. For example, a refrigerant composed of R32 and R125, a refrigerant composed of R32 and R1234yf, or a refrigerant composed of R32, R1234yf and R1234ze can be used. It can also be used for other refrigerants that are difficult to prevent the hydrolysis of refrigeration oil.

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Expansion means, 5 ... Indoor heat exchanger

Claims (5)

A compressor, an outdoor heat exchanger, an expansion mechanism, and an indoor heat exchanger;
R32 refrigerant or a mixed refrigerant containing more than 50% by weight of R32;
A refrigerating machine oil having a polyol ester oil and an acid scavenger,
The acid scavenger has an alkyl glycidyl ester compound and a cycloglycidyl ether compound,
The air conditioner in which the ratio of the alkyl glycidyl ester compound in the acid scavenger is 10 to 97%.   The air conditioner according to claim 1, wherein a ratio of the alkyl glycidyl ester compound in the acid scavenger is 10 to 70%.   The air conditioner according to claim 1 or 2, wherein a ratio of the alkyl glycidyl ester compound in the total weight of the refrigerating machine oil is less than 2 wt%. The alkyl glycidyl ester compound is of the formula (1) (wherein R ¹ is an alkyl group having 4 to 9 carbon atoms),
The air conditioner according to any one of claims 1 to 3, wherein the cycloglycidyl ether compound is represented by formula (2).
The polyol ester oil is a single or mixed of the formula (3), (4), (5), or (6) (wherein R ¹ is an alkyl group having 4 to 5 carbon atoms or an alkyl group having 8 to 12 carbon atoms. 5. The air conditioner according to claim 1, wherein the air conditioner is an alkyl group, and at least one of R ^{1 in} the formula is an alkyl group having 4 to 5 carbon atoms.