Refrigeration oil, POE, HFO refrigerant, Low GWP, Lubrication
HFC (Hydrofluorocarbon) refrigerants, whose ODP (Ozone Depletion Potential) is 0, are used in refrigeration and air conditioning equipments recently. It is known that HFCs are high GWP (Global Warming Potential) refrigerants. In October 2016, Kigali Amendment to the Montreal Protocol was stated to achieve the phase-down of HFC refrigerants to prevent global warming. Transition of current HFCs to low GWP refrigerants would be accelerated around the world. HFO (Hydrofluoroolefin) refrigerants such as R1234yf, R1234ze etc. are low GWP refrigerants. Refrigerant manufacturers are introducing not only HFO itself, but also mixture of HFC and HFO. HFO is known to be less chemically stable compared to HFC since there is double bond in its molecular structure. Also, HFOs tend to dissolve well with refrigeration oil compared to HFCs. As a result, amount of refrigerant dissolving in the oil increase and the kinematic viscosity of the oil decrease. We investigated ways to solve problems which may occur by using HFOs. In particular, it is important to maintain the stability and lubricity of oil. To improve stability, we optimized the amount of the stabilizer. To improve lubricity, since the kinematic viscosity of the oil decrease because the refrigerant dissolve in the oil more than necessary, we applied original base oil formulation to prevent the refrigerant from dissolving too much to the oil. In the presentation, properties of POE refrigeration oils which solve problems of low GWP refrigerants by investigating appropriate base oil and additive formulation are introduced.