HFCs are used as solvents due to their specific properties that are: non- flammability, thermal and chemical stability, excellent dielectric properties, high material compatibility, low surface tension and viscosity, high liquid density, and low toxicity. HFCs are only used where other solvents cannot provide the required technical performance, and a range of other organic solvents and cleaning processes replaced ozone depleting substances during their phase-out.
Member States that report HFC solvent use all report HFC-43-10mee is used and some include small amounts of HFC-134a. HFC-365mfc is also reported as being used as a solvent.
HFCs are used where high performance is required. HFCs are mainly used for degreasing of metal prior to precision coating and in the optics and electronics sector. The properties of HFC-43-10mee, enable it to be used for micro-particulate removal and its solvency can be modified by other solvents which form azeotropes with HFC-43-10mee.
Solvent cleaning equipment can have charges of 50 to 1,200 litres. Modern equipment design and improved low temperature condensing minimises solvent loss. Used solvent is heated to remove impurities (distillation) and the recovered solvent is reused. The residue is sent for incineration. Normally it consists of 75% oil/impurities and 25% of solvent [see Preparatory study for a review of Regulation (EC) No 842/2006 on certain fluorinated greenhouse gases Final Report September 2011]. In addition, HFC 134a has suitable technical and safety properties for the specialist extraction of natural active pharmaceuticals, nutraceuticals, flavours and fragrances. The use of HFC134a compliments other methods of extraction, being both highly selective and allowing extraction to high quality and high yield.
Recently HFOs, such as HFO-1336mzz(Z), are being developed and implemented for solvent applications due to their similar technical properties to HFCs and their extremely low GWPs and may be suitable as lower GWP alternatives to HFCs and some hydrofluoroethers. HFOs also have suitable properties for the extraction of natural substances including for example artemisinin used in the treatment of malaria. In addition, the specific solvency properties due to the presence of chlorine in HCFOs (hydrochlorofluoroolefins), may provide particular benefits for some solvent applications. HCFO-1233zd(E) (CF3-CH=CH-Cl, trans isomer) has boiling point 19°C and useful solvency property. [TEAP Chemicals Technical Options Committee (CTOC) 2014 Assessment Report]