Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
1999-08-16
2001-07-03
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C510S175000, C510S177000, C510S408000, C510S412000, C510S415000, C134S002000
Reexamination Certificate
active
06255273
ABSTRACT:
The present invention relates to azeotropic or near azeotropic compositions based on hydrofluoropolyethers (HFPE) to be used as substitutes of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC 113) as a solvent.
More specifically the present invention relates to azeotropic or near azeotropic mixtures characterized by ODP (ozone Depletion Potential) values equal to zero or lower than 0.02, by low GWP (Global Warming Potential) and VOC (Volatile Organic Compounds) values to be used as detergents, i.e. as solvent for cleaning and drying agents in substitution of CFC 113.
As it is known, CFC 113 has been widely used as solvent and/or drying agent for industrial applications requiring the removal of organic substances (greases, waxes, oils, resins) and/or water from solid surfaces of various nature (metal, glass, plastics or composites surfaces).
For example, CFC 113 has been commonly used for the degreasing and removal of abrasives from metal surfaces of mechanical parts having complex shapes, for the cleaning of high quality and high precision metallic components for which an accurate surface cleaning is required and for the removal of water traces from valuable articles and from high quality components previously subjected to washing with aqueous mediums.
Specifically in the electronic field CFC 113 has been used for the removal of organic products and moisture traces present on the surface of molded circuits characterized by an high density of hardly washable components and for which an high reliability is required.
Contaminant removal processes from solid surfaces (metals, plastic materials, glass) are carried out by methods implying the solvent action in liquid phase (cold or hot) and/or by vapour action; in the latter case the article is exposed to the fluid vapours at its boiling temperatures. Vapours, by condensing on the article cold surface perform the solvent and cleaning action.
In these applications CFC 113 has often been used also in combination with organic solvents, in particular as azeotropic or near azeotropic mixtures in order to substantially have the same composition in the vapour and in the liquid phase and to avoid fractionations during the application phases in industrial cleaning processes, during the handling, distillation and recovery steps of the exhausted solvent.
CFC 113 is characterized by particular chemical-physical properties such as to be advantageously used in the previously described field and allows, furthermore, a simple, cheap and safe use since it is stable, non flammable and non toxic.
CFCs and specifically CFC 113 have, however, the drawback to involve an high destroying power on the stratospheric ozone layer, wherefore, the production and commercialization have been subjected to regulations and then banned since Jan. 1, 1995.
The need was felt to identify substitutes able to replace CFC 113 in the mentioned use fields while respecting and protecting the environment.
To this purpose, in the solvency field, the use of alternative systems based on aqueous solutions, of non halogenated organic solvents and of hydrohalogenated solvents of HCFC type has been proposed.
The alternatives using the aqueous system imply however various inconveniences.
In particular it happens that articles with microhollow, capillary holes and surface irregularities, are insufficiently washed due to the relatively high water surface pressure, also in the presence of surfactants.
The water removal rate is very low and if this is not completely removed, it can be the cause of corrosion phenomena of the metal articles previously subjected to washing. Therefore such surfaces must be suitably dried after they have been cleansed.
Hydrocarbons, alcohols or other non halogenated organic solvents, due to their high flammability, have not a generalized use and require in any case great investments in order to avoid fire and explosion risks in the plants using them.
Furthermore, these solvents represent an atmospheric pollution source, since, if exposed to the sun light in the presence of nitrogen oxides, undergo oxidative degradation phenomena, with the formation of the so called ozone-rich oxidizing smog. For this negative characteristic these products are classified as VOC (Volatile Organic Compound) compounds.
The hydrohalogenated solvents represent a class of products more similar to CFC 113, they give lower use complications and allow more generalized applications in comparison with the above mentioned alternative systems.
HCFC 141b, which is one of the most valid substitutes for these applications, has however the disadvantage to be moderately flammable and especially to be characterized by an ODP value equal to 0.11 (CFC 11 has ODP=l) and therefore it has been subjected to limitations.
The use of non toxic solvents having a low environmental impact, constituted by hydrofluoropolyethers and compositions thereof having limited concentrations of polar substances selected from alcohols, ketones and ethers as described in the European patent application EP 805,199 is known in the field of oil, grease, wax etc., removal from surfaces.
In said application no reference is made to mixtures having azeotropic or near azeotropic behaviour to be used in the industrial solvency field.
In connection with what described in the prior art the need was felt to have available substitutes to CFC 113.
It was indeed necessary to have available products able to remove oily substances similarly to CFC 113, i.e. by partial or total solubilization of the substances to be removed, therefore differently from pure or additivated hydrofluoropolyethers, in order to guarantee a more accurate and quicker cleaning of articles having complex shapes and microhollows, with remarkable advantages in efficiency and economic saving terms of the same cleaning operation.
Preferably the substitutes of CFC 113 should be drop-in, i.e. the substitutes should be used in the existing plants without involving substantial modifications and allow to maintain practically unchanged the various operating steps of the article cleaning process.
Finally, the need was evident to limit or eliminate the environmental and safety problems typical of the conventional solvents (hydrocarbons, HCFC), and to reduce the cleaning operation costs deriving from the pure or only addivitated HFPE use, since, as known, these products are obtained by complex and expensive processes.
The Applicant has surprisingly and unexpectedly found that as substitutes of CFC 113 hydrofluoropolyether-based (HFPE) mixtures, object of the present invention, have azeotropic or near azeotropic behaviour, they are drop-in of CFC 113, have an environmental impact expressed in ODP terms equal to zero or <0.02 and low GWP and VOC values.
It is therefore an object of the present invention azeotropic or near azeotropic compositions, based on difluoromethoxy-bis(difluoromethyl ether) (HFPE1) and on 1-difluoromethoxy-1,1,2,2-tetrafluoroethyl (AF 9925/031.EST) difluoromethyl ether (HFPE2), to be used as substitutes of CFC 113, consisting essentially of:
composition
% by weight
general
preferred
I)
difluoromethoxy
2-60
2-54
bis(difluoromethyl ether)
(HCF
2
OCF
2
OCF
2
H);
1,1-dichloro-2,2,2-trifluoroethane
98-40
98-46
(CHCl
2
CF
3
, HCFC 123)
II)
difluoromethoxy
1-95
25-95
bis(difluoromethyl ether)
(HCF
2
OCF
2
OCF
2
H);
n-pentane
99-5
75-5
III)
difluoromethoxy
1-99
25-98
bis(difluoromethyl ether)
(HFC
2
OCF
2
OCF
2
H);
iso-pentane
99-1
75-2
IV)
difluoromethoxy
1-60
20-60
bis(difluoromethyl ether)
(HCF
2
OCF
2
OCF
2
H);
dimethyl ketone (acetone)
99-40
80-40
V)
difluoromethoxy
1-99
10-98
bis(difluoromethyl ether)
(HCF
2
OCF
2
OCF
2
H);
1,1,1,3,3-pentafluorobutane
99-1
90-2
(CF
3
CH
2
CF
2
CH
3
, HFC 365 mfc)
VI)
difluoromethoxy
1-40
10-40
bis(difluoromethyl ether)
(HCF
2
OCF
2
OCF
2
H);
1,1,1,4,4,4-hexafluorobutane
99-60
90-60
(CF
3
CH
2
CH
2
CF
3
, HFC 356 ffa)
VII)
difluorometoxy
1-96
25-96
bis(difluoromethyl ether)
(HCF
2
OCF
2
OCF
2
H);
methoxymethyl methylether
99-14
75-14
VIII)
d
Basile Giampiero
Girolomoni Sauro
Musso Ezio
Arent Fox Kintner & Plotkin & Kahn, PLLC
Ausimont S.p.A.
Gupta Yogendra N.
Webb Gregory E.
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