The present invention concerns the field of fluorinated hydrocarbons, and more particularly relates to novel compositions containing fluorinated hydrocarbons and oxygenated solvents. These novel compositions can be used in particular in all solvent applications of HCFC 141b (hydrochlorofluorocarbon 141b), in particular in various operations for treating solid surfaces, such as the cleaning, degreasing, defluxing or drying of solid surfaces.
1,1-dichloro-1-fluoroethane (known as HCFC 141B) is widely used in industry for the cleaning and degreasing of a very wide variety of solid surfaces (metallic, glass, plastic or composite components) where an absence, or at least the lowest possible residual content, of impurities, in particular of organic nature, is required. Mention may be made of its use for the degreasing of heavy metal components and for the cleaning of high-quality, high-precision mechanical components in the most varied of industries, such as aeronautics, aerospace, electronics, mechanics, the goldsmith trade, the cutlery industry, the manufacture of timepieces, medical prosthesis. Mention may also be made of its use in the field of printed circuit manufacture, for removing residues of the substances used to improve the quality of soldered joints (known as solder flux), this removal operation being referred to as “defluxing”.
Besides its thermal and chemical stability, its non-flammability, its low toxicity and its low boiling point (which preserves thermally fragile components), HCFC 141b is found to be particularly effective in these applications due to its low surface tension (18.4 mN/m) and its relatively high solvent power (Kauri-butanol index KBI=51). These latter two chemical properties allow it to have a good ability to dissolve greasy smears, and most particularly those present on complex components comprising holes, recesses or fluting, as may be found in the fields of precision mechanics, the manufacture of timepieces or the cutlery industry, for example.
However, due to its action on the ozone layer, which is not zero (ozone degradation potential ODP=0.11), HCFC 141b is subject to considerable regulations which are increasingly aimed at eliminating it. Thus, the European regulation regarding substances harmful to the ozone layer (no. 2037/2000) has prohibited the use of HCFCs such as HCFC 141b in solvent applications since 1 Jan. 2002, except for the fields of aeronautics and aerospace, where the ban takes effect from 2008 on European soil.
Substitution solutions aimed at replacing HCFC 141b in the abovementioned applications have been proposed, in particular the use of HFC (hydrofluorocarbons) and/or of HFE (hydrofluoro ethers). HFCs and HFEs have no action on the ozone layer (ODP zero or negligible with respect to the regulations in force).
Among the most well-known and most commonly used HFCs, mention may be made, for example, of 1,1,1,3,3-pentafluorobutane (365 mfc), 1,1,1,2,3,4,4,5,5,5-decafluoropentane (4310 mee), 1,1,1,2-tetrafluoroethane (134 a), pentafluoroethane (125), 1,1,1-trifluoroethane (143 a), difluoromethane (32), 1,1-difluoroethane (152 a), 1-fluoroethane (161), 1,1,1,2,3,3,3-heptafluoropropane (227 ea), 1,1,1,3,3,pentafluoropropane (245 fa), octafluoropropane (218), (perfluorobutyl)ethylene (C4H9CH═CH2), 1,1,2,2,3,4,5-heptafluorocyclopentane (C5H3F7), perfluorohexylethylene (C6F13CHCH2), tridecafluorohexane (C6F13H) and perfluoro(methylmorpholine) (PF 5052) and also their mixtures which may contribute to improving certain properties, such as non-flammability, for example.
Among the most well-known and most commonly used HFEs, mention may be made, for example, of methylheptafluoropropyl ether (C3F7OCH3), methylnonafluorobutyl ether (C4F9OCH3), ethylnonafluorobutyl ether (C4F9OC2H5) and perfluoropyran (C5F10O), and also their mixtures.
HFCs and HFEs exhibit physicochemical properties comparable to those of HCFC 141b: good thermal and chemical stability, low toxicity, low boiling point, low surface tension. However, their solvent power does not reach that of HCFC 141b. The Kauri-butanol indices (KBIs) are respectively 9 and 10 for HFC 4310 mee and HFE C4F9OCH3, compared to 51 for HCFC 141b. As a result of this, the effectiveness of these compounds in applications for treating solid surfaces is clearly less than that of HCFC 141b.