JP5519224B2 - Refrigeration circuit - Google Patents

Description

The present invention relates to a refrigeration circuit in which a refrigerant including an unsaturated fluorinated hydrocarbon refrigerant typified by HFO1234yf is used as all or part of the refrigerant.

  Currently, HFC134a, which is a kind of fluorocarbon, is used as a typical refrigerant in a refrigeration circuit used for a vehicle air conditioner and the like, and polyalkylene glycol (PAG) is used as a typical refrigeration oil.

Currently, efforts are being made to prevent global warming on a global scale. In particular, in Freon gas regulation in the EU countries, promoting restrictions on high global warming potential of a typical refrigerant HFC134a for a motor vehicle (GWP1430), the prohibition of the use of the refrigerant to the new models since 2012, also 2017 Later, we decided to ban the use of this refrigerant in all vehicles. In response, similar regulations are spreading throughout the world. In response to this trend, refrigerant manufacturers, refrigeration oil manufacturers, and air conditioning equipment manufacturers are researching and developing new refrigerants and refrigeration oils for new refrigerants with the aim of further reducing and improving the Global Warming Potential (GWP) while being safe. Has been done. As a new refrigerant aiming at such improvement, an unsaturated fluorinated hydrocarbon refrigerant having an evaporating temperature in the range of −50 ° C. to −10 ° C. by introducing an unsaturated bond inside the molecule in search of low GWP is now available. Developed as the next generation refrigerant. In particular, it is probable that unsaturated fluorinated hydrocarbon refrigerants such as HFO1234yf and HFO1234ze will be adopted worldwide. Test research aimed at improving these materials so that they can be applied to refrigeration circuits such as air conditioners for vehicles has become popular.

  However, while unsaturated fluorocarbon refrigerants have a low GWP value, they have an unsaturated bond in the molecule, so they are more reactive than conventional saturated fluorocarbon refrigerants such as HFC134a. High and poor thermal and chemical stability. Therefore, the present inventors conducted an experiment to confirm the thermal and chemical stability when HFO1234yf, which is a representative example of an unsaturated fluorinated hydrocarbon refrigerant, is used in an actual refrigeration circuit. In the experimental refrigeration circuit using a scroll compressor as the compressor, HFO1234yf as the refrigerant, and a typical polyalkylene glycol as the refrigeration oil, a wax-like shape is formed in the compressor particularly under high speed and high load conditions. In contrast, the experimental refrigeration circuit in which the scroll compressor is replaced with a reciprocating compressor in this experimental refrigeration circuit does not produce a waxy solid even under high-speed and high-load conditions. Confirmed the fact. This wax-like solid causes clogging of the refrigeration circuit and deterioration of the refrigeration performance, so that it can be a fatal defect such as a significant performance reduction or failure of the refrigeration circuit. The formation of a wax-like solid is not limited to HFO1234yf, but may be generated in other unsaturated fluorinated hydrocarbon refrigerants having similar unsaturated bonds in the molecule. Therefore, when an unsaturated fluorinated hydrocarbon refrigerant is used in the refrigeration circuit, it is necessary to prevent such wax-like solids from being generated in the compressor or the refrigeration circuit even under high speed and high load conditions.

  Accordingly, the problem to be solved by the present invention is that a scroll compressor is used as a compressor, an unsaturated fluorinated hydrocarbon refrigerant is used as a refrigerant, and an ether-based lubricating oil such as polyalkylene glycol is used as a refrigerator oil. An object of the present invention is to prevent the formation of waxy solids in the refrigeration circuit that cause clogging of the refrigeration circuit and a decrease in refrigeration performance.

  The present inventors conducted a chemical analysis of a waxy solid, and confirmed that this solid was a low molecular weight polymerized paraffin having a melting point of about 50 ° C to 72 ° C. Based on this analysis result, the present inventors presume the formation mechanism of a waxy solid as follows. That is, in the scroll compressor, the swirl of the orbiting scroll and the swirl of the fixed scroll slide in a state where they are strongly pressed against each other in order to counteract the action of the high-temperature and high-pressure refrigerant gas. Therefore, the refrigerating machine oil to be used is required to have a high level of lubricating performance. However, the lubricating performance of the ether-based lubricating oil such as polyalkylene glycol with respect to the refrigerant having an unsaturated bond such as HFO1234yf is not always sufficient for the scroll compressor. For this reason, the metal active surface is likely to be locally exposed on the sliding surface of the compression mechanism part with the turning motion of the orbiting scroll under the high temperature and high load condition. On the other hand, unsaturated fluorinated hydrocarbon refrigerants are highly reactive and poor in thermal and chemical stability. As a result, the exposed metal active surface acts as a reaction catalyst, and the polyoxyalkylene structure of the unsaturated fluorinated hydrocarbon refrigerant and the ether-based lubricating oil in the compression mechanism portion of the scroll compressor under a high-temperature and high-pressure refrigerant gas atmosphere. As a result, decomposition of the unsaturated fluorohydrocarbon refrigerant and formation of a polymerizable olefin as a decomposition product occur, and this polymerizable olefin is further applied to the metal active surface under pressure and heat inside the compressor. It is presumed that polymerized paraffin is produced by polymerization under the reaction of polymerization catalyst. Further, it is presumed that hydrogen fluoride produced by the decomposition of the unsaturated fluorinated hydrocarbon refrigerant acts as a catalyst for promoting further decomposition of the unsaturated fluorinated hydrocarbon refrigerant. Therefore, in order to prevent the formation of a wax-like solid, it can be an effective means to supplement the lack of lubricating performance of the ether-based lubricating oil with the combined use of other lubricating oil components having no polyoxyalkylene structure. . It is also effective to use an acid scavenger that captures hydrogen fluoride produced by the decomposition of the unsaturated fluorinated hydrocarbon refrigerant. The present inventors have studied various compounds from this viewpoint, and have found that long-chain aliphatic epoxy alkanes are very effective in preventing the formation of waxy solids. The present invention has been completed based on such technical knowledge and ideas.

That is, the refrigeration circuit of the present invention, by filling a refrigerating machine oil and at least a refrigerant, the refrigeration circuit compressor mechanism as a compressor for compressing the refrigerant comprises aluminum or magnesium or scroll compressor made its alloys, the refrigerant there containing unsaturated fluorinated hydrocarbon refrigerant as part or all of the refrigerating machine oil, the ether-based lubricant having a polyoxyalkylene structure, a long-chain aliphatic epoxy alkane carbon atoms is 8 to 25 It is characterized by containing and. Moreover, it is preferable that the said long-chain epoxy alkane is filled 0.5 to 15 weight% with respect to the filling amount of the said ether type lubricating oil. Furthermore, it is preferable that the long-chain epoxy alkane is filled in an amount of 0.1 to 3% by weight with respect to the amount of the refrigerant. According to the present invention, the epoxy alkane prevents the polymerization of the unsaturated fluorinated hydrocarbon refrigerant caused by the operation of the compressor and the generation of the polymerized paraffin resulting from the polymerization of the polymerizable decomposition product. Functions as an inhibitor.

Especially low molecular terminals thermal and chemical stability in the above structure CH 2 ₌ CH- or CH 2 ₌ if unsaturated fluorinated hydrocarbon refrigerant used with CF- group also effect the production of polymerization paraffin Can be prevented. Moreover, also when typical HFO1234yf and HFO1234ze are used as an unsaturated fluorinated hydrocarbon refrigerant in the above configuration, the formation of polymerized paraffin can be effectively prevented .

The refrigeration circuit of the present invention can be applied to any refrigeration circuit used in home appliances, residential air conditioning, distribution fields, and the like, and is particularly suitable as a refrigeration circuit for a vehicle air conditioner. By applying the present invention to a refrigeration circuit for a vehicle air conditioner, an refrigeration circuit is realized that uses an unsaturated fluorohydrocarbon refrigerant such as HFO1234yf to reduce the environmental load and achieve the same operational stability as before. It becomes possible.

According to the present invention, the compressor mechanism uses a scroll compressor made of aluminum, magnesium, or an alloy thereof as a compressor, is filled with an unsaturated fluorinated hydrocarbon refrigerant as a refrigerant, and has a polyoxyalkylene structure as a refrigerator oil. In a refrigeration circuit filled with ether-based lubricants, the lack of lubrication performance of ether-based lubricants is compensated by the combined use of long-chain epoxy alkanes, and the refrigerant is further decomposed by the decomposition of unsaturated fluorinated hydrocarbon refrigerants. By capturing the promoting hydrogen fluoride with the epoxy group of the long-chain epoxy alkane, the exposure of the metal active surface due to the sliding of the compression mechanism is prevented, so that the high temperature and high pressure refrigerant gas atmosphere is maintained in the compression mechanism. Of metal activity in which unsaturated fluorocarbon refrigerant and polyoxyalkylene structure of ether-based lubricant are exposed Of undergoing catalysis can be prevented from reacting, it is possible to prevent the generation of the result causes a reduction in clogging or freezing performance of the refrigeration circuit polymerization paraffin.

It is a schematic block diagram which shows the example of fundamental apparatus arrangement | positioning of the refrigerating circuit which this invention makes object.

FIG. 1 shows a basic configuration of a refrigeration circuit used in a vehicle air conditioner or the like. In FIG. 1, a refrigeration circuit 1 includes a compressor 2 that compresses refrigerant, a condenser 3 that condenses the compressed refrigerant, an expansion valve 4 that depressurizes and expands the condensed refrigerant, And an evaporator 5 for evaporating the expanded refrigerant . The refrigeration circuit 1 is filled with a refrigerant and a predetermined mixture, and the refrigerant circulates in the refrigeration circuit 1 while changing its state.

  There is no restriction | limiting in particular in the scroll compressor used by this invention. In addition to iron-based materials, light metal materials such as aluminum, magnesium, or alloys thereof can be used as the constituent material of the compressor. In order to reduce the inertial force, a light metal material such as aluminum, magnesium, or an alloy thereof having a smaller specific gravity than the iron material is often used for the scroll on the movable side in the compression mechanism. Although these iron-based materials and light metal-based materials are both highly reactive in the state of pure metal materials, their surfaces are usually covered with an oxide film and the activity of the metal materials is suppressed. . However, when the lubricating performance of the refrigerating machine oil is insufficient, the oxide film is lost due to friction accompanying the orbiting motion of the orbiting scroll and the metal active surface is exposed. When the metal active surface is exposed, the metal active surface exhibits a very high catalytic action due to the high reactivity of the metal material. Therefore, when an ether type lubricating oil and an unsaturated fluorinated hydrocarbon refrigerant come into contact with the metal active surface in a high-temperature and high-pressure refrigerant atmosphere, the metal active surface is catalyzed and the polyoxyalkylene of the ether type lubricating oil. The structure reacts with the unsaturated fluorinated hydrocarbon refrigerant. This reaction causes the decomposition of the unsaturated fluorinated hydrocarbon refrigerant and the production of a polymerizable olefin as a decomposition product, and this polymerizable olefin undergoes polymerization catalysis on the metal active surface and polymerizes in a high-temperature and high-pressure refrigerant gas atmosphere. As a result, polymerized paraffin is produced. However, according to the present invention, the ether-based lubricating oil contains a long-chain epoxy alkane, and this long-chain epoxy alkane does not react with the unsaturated fluorinated hydrocarbon refrigerant even in a high-temperature and high-pressure refrigerant gas atmosphere. This compensates for the lack of lubrication performance of ether-based lubricants and prevents exposure of the active metal surface, while reacting with hydrogen fluoride, which is generated by the decomposition of unsaturated fluorinated hydrocarbon refrigerant and promotes further decomposition of the refrigerant. As a result, the decomposition of the unsaturated fluorinated hydrocarbon refrigerant and the production of the polymerizable olefin as a decomposition product are prevented, and the production of polymerized paraffin due to the polymerization of the polymerizable olefin is prevented.

Examples of the unsaturated fluorinated hydrocarbon refrigerant used in the present invention include 1,2,3,3-tetrafluoro-1-propene ( HFO 1234ye); 1,3,3,3-tetrafluoro-1-propene. ( HFO 1234ze); 2,3,3,3-tetrafluoro-1-propene ( HFO 1234yf); 1,1,2,3-tetrafluoro-1-propene ( HFO 1234yc); 1,1,3,3 -Tetrafluoro-1-propene ( HFO 1234zc); 2,3,3-trifluoro-1-propene ( HFO 1243yf); 3,3,3-trifluoro-1-propene ( HFO 1243zf); 1,1, 2-trifluoro-1-propene (HFO 1243yc); 1,1,3- trifluoro-1-propene (HFO 1243zc); 1,2, - trifluoro-1-propene (HFO 1243ye); 1,3,3- trifluoro-1-propene (HFO 1243ze); 3,3,3- trifluoropropene (HFO 1243zf) hydrofluoropropenes such: 2, 3,3,4,4,4-hexafluoro-1-butene (CF ₃ CF ₂ CF═CH ₂ ); 3,3,3-trifluoro-2- (trifluoromethyl) -1-propene (CH ₂ ) = C (CF ₃ ) ₂ ); 1,1,1,3,4-pentafluoro-2-butene (CF ₃ CH═CFCH ₂ F); 3,3,4,4,4-pentafluoro-1- butene _{(CF 3 CF 2 CH = CH} 2); 2,3,3,4,4- pentafluoro-1-butene _{(CH 2 = CFCF 2 CHF 2} ); 3,3,4,4- tetrafluoro -1 -Bu Emissions _{(CH 2 = CHCF 2 CHF 2} ); 3,3- difluoro-2- (difluoromethyl) -1-propene _{(CH 2 = C (CHF 2} ) 2); 3,3,4,4,4- penta fluoro-2- (trifluoromethyl) -1-butene _{(CH 2 = C (CF 3} ) CF 2 CF 3); 3,4,4,4- tetrafluoro-3- (trifluoromethyl) -1-butene ((CF ₃ ) ₂ CFCH═CH ₂ ); 2,4,4,4-tetrafluoro-3- (trifluoromethyl) -1-butene (CH ₂ ═CFCH (CF ₃ ) ₂ ); Hydrofluorobutenes such as 4-trifluoro-3- (trifluoromethyl) -1-butene (CH ₂ ═C (CF ₃ ) CH ₂ CF ₃ ): 3,3,4,4,5,5,5- heptafluoro-1-pentene (CF _{3 F 2 CF 2 CH = CH 2} ); 2,3,3,4,4,5,5- heptafluoro-1-pentene _{(CH 2 = CFCF 2 CF 2} CHF 2); 3,3,4,5, 5,5-hexafluoro-1-pentene (CH ₂ ═CHCF ₂ CHFCF ₃ ); 4,5,5,5-tetrafluoro-4- (trifluoromethyl) -1-pentene (CH ₂ ═CHCH ₂ CF ( CF _{3) 2)} hydrofluoroether pentene like: 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene _{(CF 3 CF 2 CF 2 CF} 2 CH = CH 2); 4 , 4, 5, 5, 6, 6, 6-heptafluoro-1-hexene (CH ₂ ═CHCH ₂ CF ₂ CF ₂ CF ₃ ) and the like. Particularly the molecular terminal among unsaturated fluorinated hydrocarbon refrigerant CH 2 ₌ CH- or CH 2 ₌ CF- those having groups react with ether lubricating oil and a scroll compressor having a polyoxyalkylene structure polymerisation paraffin Is more prominent than those not having these groups at the molecular ends. Therefore, the application of the present invention is particularly effective for a refrigeration circuit using an unsaturated fluorinated hydrocarbon refrigerant having these groups.

The said compound is used individually or in mixture of 2 or more types. In addition, a saturated halogenated hydrocarbon refrigerant or a hydrocarbon refrigerant can be used in combination with the above compound. Typical saturated fluorinated hydrocarbon refrigerants and hydrocarbon refrigerants include, for example, 1,1,1,2-tetrafluoroethane ( HFC 134a), 1,1-difluoroethane ( HFC 152a), difluoromethane ( HFC 32). , Pentafluoroethane ( HFC 125), 1,1,1-trifluoroethane ( HFC 143a), 1,1,1,2,3,3,3-heptafluoropropane ( HFC 227ea), 1,1,1 , 3,3-pentafluorobutane ( HFC 365mfc), 2,2, -dichloro-1,1,1-trifluoroethane ( HFC 123), 1,1,1,3,3-pentafluoropropane ( HFC 245fa) ), 1,2-dichloro-1,1,2,2-tetrafluoroethane (HFC 124), 1,1,1,3,3,3- Hexa fluoro propane (HFC 236fa) and the like. Typical hydrocarbon refrigerants include, for example, propane, propylene, cyclopropane, n-butane, isobutane, n-pentane, 2-methylbutane (isopentane), cyclobutane, cyclopentane, 2,2-dimethylpropane, 2,2- Dimethylbutane, 2,3-dimethylbutane, 2,3-dimethylpentane, 2-methylhexane, 3-methylhexane, 2-methylpentane, 3-ethylpentane, 3-methylpentane, cyclohexane, n-heptane, methylcyclo Examples include pentane and n-hexane.

Examples of the long-chain epoxy alkane used in the present invention include 1,2-epoxynonane, 1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytetradecane, Epoxyalkanes having 8 to 25 carbon atoms such as 1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,2-epoxyoctadecane and 1,2-epoxynonadecane are preferred. The addition amount of the long-chain epoxy alkane with respect to the ether lubricant is preferably 0.5 to 15 % by weight, and the addition amount with respect to the amount of the enclosed refrigerant is preferably 0.1 to 3% by weight.

The effect of preventing formation of polymerized paraffin according to the present invention can be confirmed by the following examples and comparative examples. In the examples and comparative examples, the refrigeration circuit shown in FIG. 1 is used. The scroll compressor of the refrigeration circuit includes a fixed scroll made of aluminum alloy and a turning scroll made of aluminum alloy and anodized. A predetermined amount of HFO1234yf refrigerant is filled in the refrigeration circuit, and a predetermined amount of the mixture of the formulations shown in Table 1 is filled in the scroll compressor. To the ether-based lubricating oils of Examples and Comparative Examples, tricresyl phosphate as an extreme pressure agent is added to 1.0% of the lubricating oil. The rotation speed of the scroll compressor is set to 6000 rpm, and the refrigeration circuit is continuously operated at this rotation speed for 400 hours. After completion of the operation, the inside of the compressor and the piping of the refrigeration circuit are inspected to confirm whether waxy solids (polymerized paraffin) are generated. The results shown in Table 1 are obtained by this confirmation experiment. The judgment criteria in the column of effect in Table 1 are as follows.
○: There is no solid matter that can be visually confirmed.
X: A solid substance that can be visually confirmed exists.

上表において、ＰＰＧはポリプロピレングリコールを主構造として分子末端をエーテル変性処理したポリアルキレングリコールを表し、％は封入冷媒量に対する重量％を表す。

In the above table, PPG represents polyalkylene glycol in which polypropylene glycol is the main structure and the molecular ends are ether-modified, and% represents weight% with respect to the amount of encapsulated refrigerant.

As shown in Table 1, when adding a long-chain epoxy alkane as a polymerized paraffin inhibitor to an ether-based lubricating oil (PPG) as in Examples 1 and 2 , the rotation speed was 6000 rpm and the continuous operation time was 400 hours. Polymerized paraffin is not generated even under high load conditions, whereas polymerized paraffin is generated under the same conditions when no long-chain epoxy alkane is added as in the comparative example.

  The present invention can be applied to any refrigeration circuit used in home appliances, residential air conditioning, distribution fields, etc., and particularly in a refrigeration circuit for a vehicle air conditioner, using an unsaturated fluorinated hydrocarbon refrigerant such as HFO1234yf to reduce environmental impact. It is possible to realize a refrigeration circuit that reduces and achieves the same operational stability as conventional ones.

DESCRIPTION OF SYMBOLS 1 Refrigeration circuit 2 Compressor 3 Condenser 4 Expansion valve as decompression / expansion means 5 Evaporator

Claims (5)

In a refrigeration circuit that is filled with at least a refrigerant and refrigeration oil, and the compression mechanism includes a scroll compressor made of aluminum, magnesium, or an alloy thereof as a compressor that compresses the refrigerant.
The coolant, containing the unsaturated fluorinated hydrocarbon refrigerant as part or the whole,
Refrigeration circuit to which the refrigerating machine oil, to the ether-based lubricant having a polyoxyalkylene structure, characterized in that the number of carbon atoms contains a long-chain epoxy alkanes is 8-25. 2. The refrigeration circuit according to claim 1, wherein the long-chain epoxy alkane is filled in an amount of 0.5 wt% to 15 wt% with respect to a filling amount of the ether-based lubricant. 3. The refrigeration circuit according to claim 1, wherein the long-chain epoxy alkane is filled in an amount of 0.1 wt% to 3 wt% with respect to a filling amount of the refrigerant. 4. The unsaturated fluorinated hydrocarbon refrigerant according to claim 1, wherein the unsaturated fluorinated hydrocarbon refrigerant is an unsaturated fluorinated hydrocarbon refrigerant having a CH ₂ ═CH— or CH ₂ ═CF— group at a molecular end. Refrigeration circuit. The unsaturated fluorinated hydrocarbon refrigerant, a refrigeration circuit according to any one of claims 1 to 3 is at least one HFO1234yf and HFO1234ze.

Images