A3.4 Solvents and Cleaning Agents
Less than 3% of projected demand for CFCs solvents has been replaced by HFCs
and PFCs (McFarland, 1999).The high cost of fluorocarbons, regulatory prohibitions
on HFC and hydrofluoroethers and hydrofluoroesters (HFE) solvents, and investment
in emission reduction measures are expected to maintain carbon equivalent use
and emissions in 2010 to current baseline levels. Annual PFC solvent emissions
are estimated at 3,0004,000 tonnes (UNEP, 1999b; Harnisch et al., 1999)
and HFC emissions are estimated to be 1,0002,000 tonnes (UNEP, 1999b).
These values convert to less than 7.5MtCeq for PFCs and less than
1 MtCeq for HFCs.
Perfluorocarbons (PFCs such as C5F12, C6F14,
C7F16, and C8F18) were introduced
in the early 1990s as substitutes for ozone-depleting CFC-113 solvents and are
also used in some applications where ODS solvents were never used. HFC-43-10mee
and its azeotropic blends with alcohol, hydrochlorocarbons, and hydrocarbons
were introduced in the mid-1990s to replace CFC-113 and PFCs. HFE solvents became
commercially available in the late 1990s to replace PFCs, CFCs, HCFCs, and HFCs.
HFCs and HFEs are used in specialized cleaning of delicate materials, oxygen
systems, and precision parts; as a flush fluid for particulate removal in precision
cleaning; as a rinsing agent in a co-solvent process for cleaning printed circuit
boards and mechanical components; and to dry electronics and precision parts
after aqueous or semi-aqueous processing. In some circumstances, HFC drying
may have a lower LCCP than thermal drying. HFCs and HFEs are also replacing
PFCs and CFC-113 as carrier fluids for specialized fluorocarbon lubricants,
as dielectric and heat transfer fluids, in developing latent fingerprints off
porous surfaces, in rain repellent sprays for aircraft windshields, and in other
applications demanding unique solvency properties (UNEP, 1998e, 1999b).
The four emission reduction options are: (1) changing production processes
and product designs to avoid the need for fluorocarbon solvents (e.g., no-clean
soldering and aqueous cleaning); (2) switching to lower GWP fluorocarbon or
non-fluorocarbon solvents; (3) reducing emissions through process improvements
(UNEP, 1999b); and (4) utilizing solvent recovery and recycling where possible.
Progress is being made in each of these options.
One source estimates that process improvements could reduce fluorocarbon solvent
emissions in the European Union by 20% by 2010 at a cost effectiveness of about
US$160/tCeq and that an 80% reduction could be achieved at about
US$330/tCeq (March, 1998).