JP5464512B2 - Working fluid for car air conditioner - Google Patents

Description

  The present invention relates to a working fluid for a car air conditioner using tetrafluoropropene as a refrigerant.

  For car air conditioners, a working fluid in which a refrigerant is dissolved in refrigeration oil has been used. Conventionally, considering environmental aspects, it does not contain chlorine like R-134a, etc., and consists of hydrogen, carbon and fluorine. Hydrofluorocarbon (HFC) refrigerants are used, and accordingly, ester-based refrigeration oils such as polyol ester oils compatible with HFC refrigerants and glycol-based refrigeration oils such as PAGs are widely used (for example, patents). Reference 1).

  However, the demand for environmental protection has become more severe. In particular, in car air conditioners for automobiles produced after 2011, tetrafluoropropene (2,3,3,3-tetrafluoro- 1-propene; HFO-1234yf) has been decided to be used (2nd International Workshop on Mobile Air Conditioning and Auxiliary Systems-Trono, Italy Novo 29, 2007, Europ. , 2008).

Japanese Patent No. 2787083

  However, tetrafluoropropene is difficult to dissolve in conventional refrigerating machine oil and has a problem of causing two-layer separation at a relatively low temperature. Tetrafluoropropene has a lower chemical stability than conventional HFC refrigerants, because it decomposes in the atmosphere to suppress reaching the stratosphere. For this reason, there is a high possibility that the piping of the equipment will be blocked by the polymer generated by the decomposition, or the equipment will be corroded by the acidic compound generated by the decomposition. There is also a risk of decline. When the cooling performance decreases due to the two-layer separation and the temperature becomes high, such decomposition of tetrafluoropropene becomes remarkable.

  Therefore, the present invention eliminates problems related to compatibility with tetrafluoropropene and decomposition of tetrafluoropropene in a new automotive air conditioner working fluid that uses tetrafluoropropene as a refrigerant, which will become the mainstream in the future, and provides cooling performance and stability. The purpose is to improve.

In order to achieve the above object, the present invention provides the following working fluid for a car air conditioner.
(1) a tetrafluoropropene refrigerant ;
In average molecular weight of 800 to 1200, polypropylene glycol having an acyl group at both terminals, (A) a phenolic radical reaction inhibitor 0.5-2 wt%, epoxy having no ester group in (B) molecule 0.5 to 4% by mass of a system acid scavenger and (C) (C-1) a phosphorus extreme pressure agent and (C-2) glycerin and a fatty acid having one or two unsaturated bonds in the molecule car air-conditioning working fluid body characterized by containing at least one refrigerating machine oil composition containing 0.5 to 2% by weight of monoester made.

Used in the base oil of the refrigerating machine oil in the present invention, in specific molecular weight, and polypropylene glycol having an acyl group at both ends is excellent in fluidity, also high compatibility with tetrafluoropropene, exploded tetrafluoropropene It also has the effect of making it difficult to do. In addition, the decomposition of tetrafluoropropene is suppressed with a phenol-based radical reaction inhibitor, and even when tetrafluoropropene is decomposed, an acid component is captured with an epoxy-based acid scavenger, and wear and seizure are prevented with a phosphorus-based extreme pressure agent. In combination with these effects, the operation of a car air conditioner using tetrafluoropropene as a refrigerant, which will become the mainstream in the future, can be stably maintained over a long period of time.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the working fluid for a car air conditioner of the present invention, tetrafluoropropene is used as a refrigerant. There are isomers in tetrafluoropropene, including 2,3,3,3-tetrafluoro-1-propene and 1,3,3,3-tetrafluoro-1-propene. Become.

  In order to improve the compatibility with the above tetrafluoropropene, propylene glycol having an acyl group at both ends (hereinafter referred to as “both end acyl group-modified propylene glycol”) is used for the base oil of the refrigerator oil. This two-terminal acyl group-modified propylene glycol increases the two-layer separation temperature, and the refrigerant / refrigerant oil mixture dissolves uniformly and does not become cloudy at normal operating temperatures. Appropriate filling amount can be determined. Even if it is modified with a functional group other than an acyl group, the compatibility with tetrafluoropropene is low and the two-layer separation temperature is also low.

In addition, the viscosity necessary for practical use as a base oil is 9 mm ² / s or more in terms of kinematic viscosity at 100 ° C. In order to satisfy such viscosity, the molecular weight of both end acyl group-modified propylene glycol is converted to polystyrene. The GPC measurement is 800 to 1200, preferably 950 to 1100.

The above base oil, may be added various additives, you added phenolic radical reaction inhibitor to inhibit the decomposition of tetrafluoropropene. The phenol-based radical reaction inhibitor can effectively suppress decomposition / deterioration due to the unsaturated bond of tetrafluoropropene. As a radical reaction inhibitor, thiophosphoric acid-based inhibitors are widely used in addition to phenol-based compounds. However, sulfur compounds are not preferable because they are precipitated. Examples of the phenol-based radical reaction inhibitor, but may in a known, 2,6 - ditertiary butyl - 4 - methylphenol, 4,4'-bis (2,6 - such as ditertiary butylphenol is preferred.

Moreover, by adding an epoxy-based acid scavenger, when tetrafluoropropene is decomposed, the generated acid component can be captured and corrosion in the refrigeration system can be suppressed. Since the acid scavenging effect is high, both ends of polypropylene glycol from affinity epoxy acid scavenger having no ester group in the molecule such as glycidyl Jill ethers are preferred, especially tetrafluoroethylene pro pen and base oils It is preferable to use an epoxy-based acid scavenger obtained by glycidylation. In addition, an epoxy acid scavenger obtained by glycidylating an alcohol having 10 or less carbon atoms is preferable because of its high dispersibility in tetrafluoropropene, thereby improving the acid scavenging ability.

  In addition, by adding a phosphoric acid extreme pressure agent, the extreme pressure agent acts on the metal surface of the sliding portion to prevent wear and seizure, and further, lubricity increases and frictional heat decreases. Therefore, decomposition of tetrafluoropropene can also be suppressed. In addition, since the phosphoric acid extreme pressure agent hardly causes metal corrosion, it has an effect of suppressing corrosion in the refrigeration system. As extreme pressure agents, those other than phosphoric acid are widely used. However, sulfur compounds are not preferable because they are precipitated. The phosphoric acid extreme pressure agent may be a known one, but tricresyl phosphate, trioctyl phosphate, and the like are suitable.

The above-mentioned phenol-based radical reaction inhibitor, epoxy-based acid scavenger and phosphoric acid-based extreme pressure agent are more effective when used in combination with the three than when used alone. Moreover, each addition amount is 0.5-2 mass% for a phenol radical reaction inhibitor with respect to the base oil, 0.5-4 mass% for an epoxy acid scavenger, and 0 for a phosphoric acid extreme pressure agent. 0.5 to 2% by mass. If the addition amount is less than this, the respective effects cannot be sufficiently exhibited, and if the addition amount is more than this, not only the effect is saturated, but also the base oil amount is relatively reduced and the lubricity becomes inferior.

  In addition, since a phosphoric acid extreme pressure agent generates an acid when it is decomposed, a part or all of it is a monoester composed of glycerin and a fatty acid having one or two unsaturated bonds in the molecule. It is preferable that the content of the phosphoric acid extreme pressure agent be 0.5% by mass or less. This monoester functions as an oiliness improver and suppresses the generation of frictional heat and suppresses thermal decomposition of tetrafluoropropene. Moreover, since it is hard to generate | occur | produce an acid, decomposition | disassembly of tetrafluoropropene by an acid can also be suppressed.

  In addition, additives that are usually used for the purpose of improving the performance other than the above may be added.

  Hereinafter, the present invention will be further described with reference to test examples, but the present invention is not limited thereto. In addition, Test Examples 3 and 4 confirm the effect of the additive, and all are examples.

(Test Example 1: High-temperature refrigerant solubility)
2,3,3,3-tetrafluoro-1-propene was used as a refrigerant, sealed in a specified glass tube together with the base oil shown in Table 1, and slowly heated in a hot water bath. The temperature at which the oil layer and the refrigerant layer were separated from the uniform layer was measured. The base oil amount was 5% by mass or 15% by mass. The results are also shown in Table 1.

  As shown in Table 1, the base oils of Examples 1 and 2 are both terminal acyl group-modified propylene glycol having a molecular weight in the range of 800 to 1200, but 2,3,3,3-tetrafluoro-1-propene. And the two-layer separation temperature is also high. On the other hand, propylene glycol modified with other than acyl groups has low compatibility with 2,3,3,3-tetrafluoro-1-propene, and the two-layer separation temperature is also low. Moreover, although the base oil of the comparative example 11 is a both-ends acyl group modification | denaturation propylene glycol, molecular weight exceeds 1200, two-layer separation temperature is low, and it is not practical as an object for car air conditioners.

(Test Example 2: Kinematic viscosity)
The kinematic viscosity and viscosity index of each base oil of Examples 1 and 2 and Comparative Examples 1, 3, 9, 11, and 12 used in Test Example 1 were measured. The results are shown in Table 2, and the base oils of Examples 1 and 2 are practical in both kinematic viscosity and viscosity index. On the other hand, the base oil of Comparative Example 12 is a propylene glycol modified with acyl groups at both ends, but has a molecular weight of less than 800 and is not practical because of poor fluidity.

(Test Example 3: Chemical stability)
An additive was added to the base oil of Example 1 as shown in Table 3 and mixed with 2,3,3,3-tetrafluoro-1-propene to prepare a sample. In addition, the addition amount is a ratio with respect to the base oil. And the discoloration of a sample, the total acid value, and the presence or absence of the deposit were evaluated by the shield tube test (JISK2211 conformity). The test conditions are as follows, and the results are shown in Table 3.
・ Oil / refrigerant: 2mL / 2mL
Test temperature: 175 ° C
・ Test period: 14 days ・ Water content in oil: 2000 ppm
・ Pipe air volume: Partial pressure 0.1mmHg or less ・ Catalyst: Iron wire, copper wire, aluminum wire 3cm each

Phenolic radical reaction inhibitor: Dialkylmethylphenol thiophosphate radical reaction inhibitor: Zinc dialkyldithiophosphate zinc glycidyl ether acid scavenger: Alkyl glycidyl ether imide acid scavenger: Bis (dialkylphenyl) carbodiimide phosphate extreme pressure agent : Triaryl phosphate thiophosphate extreme pressure agent: Trialkylphenyl thiophosphate glyceride oil improver: Glycerin monoester sulfurized oil: Sulfur rapeseed oil

As shown in Trial Examples 1 to 9 in Table 3, phenol radical reaction inhibitors, glycidyl ether acid scavengers, phosphoric acid extreme pressure agents, or glycerides instead of part or all of phosphoric acid extreme pressure agents By adding a system oiliness improver, the stability of both terminal acyl group-modified polypropylene glycols can be greatly improved. Moreover, as shown in Trial Examples 11 to 20, if any of these additives is not included, the stability improvement effect is reduced.

(Test Example 4: Lubricity)
1% by mass of the phenol-based radical reaction inhibitor used in Test Example 3 and 1% by mass of the glycidyl ether-based acid scavenger were added to the base oil of Example 1, and further used in Test Example 3 as shown in Table 4. A phosphoric acid extreme pressure and a glyceride oiliness improver were added and mixed with 2,3,3,3-tetrafluoro-1-propene to prepare a sample. In addition, the addition amount is a ratio with respect to the base oil. Then, seizure resistance and wear resistance were evaluated by a FALEX test (Pin-Vee Block). The test conditions are as follows, and the results are shown in Table 4.
Seizure resistance: 50 ° C., break-in 250 lbs × 5 minutes, rotation speed 290 rpm
Abrasion resistance: 50 ° C., 300 lbs × 2 hours, rotation speed 290 rpm

  As shown in Trial Examples 21 to 24 in Table 4, by adding an appropriate amount of at least one of a phosphoric acid extreme pressure agent and a glyceride oiliness improver, Trial Example 25 not added at all or Trial Example 26 added excessively. , 27 can improve seizure resistance and wear resistance while improving chemical stability and refrigerant solubility.

Claims (1)

A tetrafluoropropene refrigerant ;
In average molecular weight of 800 to 1200, polypropylene glycol having an acyl group at both terminals, (A) a phenolic radical reaction inhibitor 0.5-2 wt%, epoxy having no ester group in (B) molecule 0.5 to 4% by mass of a system acid scavenger and (C) (C-1) a phosphorus extreme pressure agent and (C-2) glycerin and a fatty acid having one or two unsaturated bonds in the molecule And a refrigerating machine oil composition containing 0.5 to 2% by mass of at least one of the resulting monoesters .