Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
1998-09-25
2001-06-05
Gupta, Yogendra (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C510S408000, C510S412000, C252S067000
Reexamination Certificate
active
06242410
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an azeotropic composition (or an azeotropic mixture) of hexafluoropropylene dimer and acetonitrile and a separation processes by distillation utilizing the azeotropic composition. For example, the hexafluoropropylene dimer can be used as a heating medium for a high temperature, or a solvent, and also as a starting material for producing, for example various industrial surfactants such as a water/oil-repellent.
2. Description of the Related Art
A production process of the hexafluoropropylene dimer has been known.
The processes for selectively obtaining hexafluoropropylene dimer are disclosed in Japanese Patent Kokai Publication Nos. 49-134614 (A) and 51-125307 (A), in which, there is provided, as an example, a reaction process for the selective production of hexafluoropropylene dimer in which acetonitrile is used as a medium (or solvent). Mutual solubility of the hexafluoropropylene dimer and acetonitrile is limited, and thus, in the reaction wherein acetonitrile is used as the medium, liquid-liquid separation (namely phase separation into two liquid phases) occurs: one liquid phase is an acetonitrile phase containing a small amount of hexafluoropropylene dimer; and the other liquid phase is a hexafluoropropylene dimer phase containing a small amount of acetonitrile. There is an advantage of such a reaction in that the formed hexafluoropropylene dimer is not converted to a hexafluoropropylene trimer because a large amount of the formed hexafluoropropylene dimer is separated from the acetonitrile phase, i.e. transferred outside of the reaction system.
It is noted that in the reaction, two kinds of the following hexafluoropropylene dimers are synthesized:
(1) (CF
3
)
2
CFCF═CFCF
3
(of which normal boiling point is 48° C.); and
(2) (CF
3
)
2
C═CFCF
2
CF
3
(of which normal boiling point is 51° C.).
Hereinafter, the compound of formula (1) is also referred as “hexafluoropropylene dimer (1)” or simply “dimer (1)”, and the compound of formula (2) is also referred as “hexafluoropropylene dimer (2)” or simply “dimer (2).” Further, hereinafter the above two compounds are also generically referred as “hexafluoropropylene dimer” or simply “dimer.”
The hexafluoropropylene dimer phase obtained by the liquid-liquid separation in the above reaction does not provide the dimer of which purity is high because it contains a small amount of acetonitrile. Japanese Patent Kokai Publication No. 49-134614 (A) discloses a process for production of the dimer, comprising the step of adding water to a reaction mixture containing the dimer and acetonitrile as main components, which is followed by the liquid-liquid separation and distillation. However, the process is disadvantageous to the industrial process since acetonitrile as the solvent contains water which must be removed for reuse thereof.
SUMMARY OF THE INVENTION
The inventors have conducted studies on a separation process of acetonitrile from a hexafluoropropylene dimer phase containing acetonitrile, and found that a hexafluoropropylene dimer and acetonitrile form a minimum boiling point azeotropic composition. Further, the inventors have found a separation process in which acetonitrile or hexafluoropropylene dimer is effectively separated from a mixture comprising acetonitrile and the hexafluoropropylene dimer by utilizing the azeotropic composition with a minimum amount of loss, and thus the inventions have been completed.
In the first aspect, the present invention provides an azeotropic composition (or a mixture) which consists essentially of a hexafluoropropylene dimer and acetonitrile. Namely, the present invention provides two kinds of the azeotropic compositions: one is composed of hexafluoropropylene dimer (1) and acetonitrile; and the other is composed of hexafluoropropylene dimer (2) and acetonitrile. The azeotropic composition is useful as a reflux when a distillation is performed in order to separate one of the hexafluoropropylene dimer and acetonitrile from a mixture comprising, or preferably consisting substantially of them (e.g. a reaction product containing the synthesized hexafluoropropylene dimer).
In the second aspect, the present invention provides a process of separating acetonitrile or a hexafluoropropylene dimer from a mixture comprising the dimer and acetonitrile by subjecting the mixture to a distillation operation and distilling off an azeotropic composition which consists substantially of the dimer and acetonitrile. According to the process, acetonitrile which does not substantially contain the dimer, or the hexafluoropropylene dimer which does not substantially contain acetonitrile is available as a bottom product. For example, a concentration of the dimer or acetonitrile as an impurity of the bottom product is less than 0.1 mol %, and preferably less than 0.001 mol %.
The hexafluoropropylene dimer separated in this process may be hexafluoropropylene dimer (1) or hexafluoropropylene dimer (2) or a mixture of dimer (1) and dimer (2).
In the above separation process, substantially all of one component of the mixture is removed as the azeotropic composition by subjecting the mixture to the distillation operation, and thus, the bottom product is obtained which consists substantially of the other component. The component which is obtained as the bottom product is determined by comparing an amount of acetonitrile with an amount of the dimer in the mixture to be subjected to the distillation operation.
When the amount of acetonitrile in the mixture is larger than an amount of acetonitrile which forms, under conditions of the distillation operation, especially an operation pressure and temperature, the azeotropic composition with all the dimer in the mixture, acetonitrile can be obtained as the bottom product while the dimer is distilled off as the azeotropic composition. In other words, in case in which a ratio of acetonitrile to the dimer in the mixture is larger than a ratio of acetonitrile to the dimer in the azeotropic composition, acetonitrile which does not substantially contain the dimer can be effectively obtained as the bottom product.
To the contrary, when the ratio of acetonitrile to the dimer of the mixture is smaller than the ratio of acetonitrile to the dimer of the azeotropic composition under the conditions of the distillation operation, acetonitrile is distilled off as the azeotropic composition, while the dimer which does not substantially contain acetonitrile can be obtained as the bottom product.
When both dimers (1) and (2) are contained in the mixture, it is considered that the mixture is consisted of a mixture of dimer (1) and acetonitrile and a mixture of dimer (2) and acetonitrile. The obtainable component as the bottom product is determined by comparing the amount of acetonitrile actually contained in the mixture with a sum of the amounts of acetonitrile required to form the azeotropic compositions with all dimers (1) and (2) in the mixture under the given operation condition (especially an operation temperature and pressure).
That is, when the amount of acetonitrile in the mixture is smaller than the above sum, a mixture of dimers (1) and (2) is obtained as the bottom product. In other words, the component of which the amount is larger than the amount required to form the azeotropic compositions, is obtainable as the bottom product.
REFERENCES:
patent: 4042638 (1977-08-01), Ozawa et al.
patent: 5387728 (1995-02-01), Gisser et al.
patent: 5395540 (1995-03-01), Gisser et al.
patent: 1511083 (1978-05-01), None
patent: 49-134614 (1974-12-01), None
patent: 51-125307 (1976-11-01), None
Aoyama Hirokazu
Tabuchi Akikazu
Birch & Stewart Kolasch & Birch, LLP
Daikin Industries Ltd.
Gupta Yogendra
Mruk Brian P.
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