Abstract:
The invention relates to a composition including a polyol ester (POE) or PVE lubricant and a refrigerant F including 3,3,3-trifluoropropene. The invention also relates to the use of said composition for refrigeration, air-conditioning, and for heat pump.

Description:
This application claims priority to and is the national phase under 35 USC §371 of prior PCT International Application Number PCT/FR2011/051870 filed Aug. 4, 2011 which designated the United States of America and claimed priority to French Patent Application serial number 1057484 Filed Sep. 20, 2010. 
     FIELD OF THE INVENTION 
     The present invention relates to a composition containing 3,3,3-trifluoropropene and at least one lubricant, which can be used in refrigeration, air conditioning and heat pumps. 
     BACKGROUND OF THE INVENTION 
     The problems posed by substances which deplete the atmospheric ozone layer were addressed in Montreal, where the protocol imposing a reduction in the production and use of chlorofluorocarbons (CFCs) was signed. This protocol has been the subject of amendments which have required the abandoning of CFCs and have extended regulation to other products, including hydrochlorofluorocarbons (HCFCs). 
     The refrigeration and air conditioning industries have invested a great deal in the replacement of these refrigerants and it is because of this that hydrofluorocarbons (HFCs) have been marketed. 
     In the motor vehicle industry, the air conditioning systems of vehicles sold in many countries have been changed from a refrigerant comprising chlorofluorocarbon (CFC-12) to that of hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a), which is less harmful to the ozone layer. However, from the viewpoint of the objectives set by the Kyoto protocol, HFC-134a (GWP=1430) is regarded as having a high heating power. The contribution to the greenhouse effect of a refrigerant is quantified by a criterion, the GWP (Global Warming Potential), which summarizes the heating power by taking a reference value of 1 for carbon dioxide. 
     Hydrofluoroolefins (HFOs) have a low heating power and therefore meet the objectives set by the Kyoto protocol. Document JP 4-110388 discloses hydrofluoropropenes as heat transfer agents. 
     In the industrial sector, the refrigerating machines most commonly used are based on cooling by evaporation of a liquid refrigerant. After vaporization, the refrigerant is compressed and then cooled in order to return to the liquid state and thus continue the cycle. 
     The refrigerant compressors used are of reciprocating, centrifugal, scroll or screw type. In general, internal lubrication of compressors is essential in order to reduce wear and heating of the moving parts, to render them completely leak-tight and to protect them from corrosion. 
     In addition to having good properties as a heat transfer agent, in order for a refrigerant to be accepted commercially, it must in particular be thermally stable and be compatible with lubricants. This is because it is highly desirable for the refrigerant to be compatible with the lubricant used in the compressor, present in the majority of refrigeration systems. This refrigerant and lubricant combination is important for the use and the effectiveness of the refrigeration system; in particular, the lubricant must be sufficiently soluble or miscible in the refrigerant throughout the operating temperature range. 
     Thus, polyalkylene glycols (PAGs) have been developed as lubricants of HFC-134a in motor vehicle air conditioning. 
     Tests for compatibility of 1,1,3,3,3-pentafluoropropene, of 1,3,3,3-tetrafluoropropene and of 3,3,3-trifluoropropene with PAGs have been described in example 3 of document WO 2004/037913. This document is content with giving only the visual appearance of the samples after the tests. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The applicant has now developed a refrigerant and lubricant pairing which can be used in refrigeration, air conditioning and heat pumps. This pairing has the advantage of being particularly stable for the lubricant and/or the refrigerant. 
     A subject of the present application is therefore a composition comprising at least one lubricant based on polyol esters (POEs) or on polyvinyl ether (PVE) and a refrigerant F comprising 3,3,3-trifluoropropene (HFO-1243zf). 
     According to the present invention, the refrigerant F can comprise, in addition to the HFO-1243zf, other hydrofluoropropenes, for instance 2,3,3,3-tetrafluoropropene (HFO-1234yf) and trans-1,3,3,3-tetrafluoropropene. 
     The refrigerant F can also comprise hydrofluorocarbons such as 1,1,1,2-tetrafluoroethane, 1,1-difluoromethane and pentafluoroethane. 
     Compared with the other hydrofluoropropenes, 3,3,3-trifluoropropene has the advantage of already being a commercial product. 
     Polyol esters are obtained by reaction of a polyol (an alcohol containing at least 2 hydroxyl groups —OH) with a monofunctional or plurifunctional carboxylic acid or with a mixture of monofunctional carboxylic acids. The water formed during this reaction is eliminated in order to prevent the reverse reaction (i.e. hydrolysis). 
     According to the present invention, the preferred polyols are those which have a neopentyl backbone, such as neopentyl glycol, trimethylol propane, pentaerythritol and dipentaerythritol; pentaerythritol is the preferred polyol. 
     The carboxylic acids may comprise from 2 to 15 carbon atoms, it being possible for the carbon backbone to be linear or branched. Mention may particularly be made of n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, 2-ethylhexanoic acid, 2,2-dimethylpentanoic acid, 3,5,5-trimethylhexanoic acid, adipic acid and succinic acid, and mixtures thereof. 
     Some alcohol functions are not esterified, but their proportion remains low. Thus, the POEs can comprise between 0 and 5 relative mol % of CH 2 —OH units relative to the —CH 2 —O—(C═O)-units. 
     The preferred POE lubricants are those which have a viscosity of from 1 to 1000 centiStokes (cSt) at 40° C., preferably from 10 to 200 cSt, and advantageously from 30 to 80 cSt. 
     The polyvinyl ether (PVE) oils are preferably copolymers of the following 2 units: 
     
       
                 
         
             
             
         
      
     
     The properties of the oil (viscosity, solubility of the refrigerant and miscibility with the refrigerant in particular) can be adjusted by varying the m/n ratio and the sum m+n. The preferred PVE oils are those having 50% to 95% by weight of unit 1. 
     According to one preferred embodiment of the invention, the lubricant(s) represent(s) between 10% and 50%, inclusive, by weight of the composition. POE is particularly preferred. 
     The refrigerant F can also comprise additives such as odorous compounds. 
     A subject of the present invention is also the use of the abovementioned composition in refrigeration, in particular domestic refrigeration, commercial refrigeration, cold rooms, the food industry, the processing industry, refrigerated transport (trucks, ships); air conditioning, in particular domestic, commercial or industrial air conditioning, where the equipment used is either chillers or direct expansion equipment; and heat pumps, in particular medium-temperature and high-temperature heat pumps. 
     EXPERIMENTAL SECTION 
     The thermal stability tests are carried out according to standard ASHRAE 97-2007: “sealed glass tube method to test the chemical stability of materials for use within refrigerant systems”. 
     The test conditions are the following: 
     weight of refrigerant F: 22 g 
     weight of lubricant: 5 g 
     temperature: 200° C. 
     duration: 14 days 
     The lubricant is introduced into a 42.2 ml glass tube. A vacuum is subsequently pulled in the tube and then the refrigerant F is added thereto. The tube is then welded shut and placed in an oven at 200° C. for 14 days. 
     At the end of the test, various analyses are carried out:
         the gas phase is recovered in order to be analyzed by gas chromatography: the main impurities are identified by GC/MS (coupled gas chromatography/mass spectrometry). The impurities coming from the refrigerant F and those coming from the lubricant can thus be grouped together;   the lubricant is analyzed: color (by spectrocolorimetry, Labomat DR Lange LICO220 model MLG131), water content (by Karl Fischer coulometry, Mettler DL37) and acid number (by quantitative determination with 0.01N methanolic potassium hydroxide).       

     3 commercial lubricants were tested: the oil PAG ND8, the oil POE Ze-GLES RB68 and PVE FVC 68D. 
     The refrigerant F essentially contains HFO-1243zf. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 PAG ND8 
                 POE Ze-GLES B68 
                 PVE FVC 68D 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 gerant 
                 HFO-1243zf 
                 HFO-1243zf 
                 HFO-1243zf 
               
               
                 By-products in 
               
               
                 the gas phase: 
               
               
                 from the 
                 1300 ppm 
                 500 ppm 
                 0.7% 
               
               
                 refrigerant 
               
               
                 from the 
                 2% 
                 1100 ppm 
                 5% 
               
               
                 lubricant 
               
               
                 Analysis of the 
               
               
                 lubricant: 
               
               
                 color 
                 6.5 Gardner 
                 100 Hazen 
                 6.2 Gardner 
               
               
                 water 
                 1000 ppm 
                 400 ppm 
                 350 ppm 
               
               
                 content 
               
               
                 acid number 
                 3.7 mg KOH/g 
                 0.3 mg KOH/g 
                 0.5 mg KOH/g 
               
               
                   
               
             
          
         
       
     
     It is noted that the acid number is lower in the presence of the POE or PVE. In addition, in the presence of the POE, the stability of the refrigerant is also improved.