Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-11-22
2001-10-16
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S155000, C521S170000, C510S177000, C510S273000, C510S408000, C510S412000, C510S415000
Reexamination Certificate
active
06303668
ABSTRACT:
The invention relates to compositions comprising 1,1,1,3,3-pentafluorobutane (also known as HFC-365mfc) and to the use of these compositions, in particular as blowing agents for polymeric cellular foams and more particularly for polyurethane foams.
It is well known that polyurethane foams can be prepared by reacting an isocyanate with an appropriate amount of a polyol or of a mixture of polyols in the presence of a blowing agent consisting of a volatile liquid, which is evaporated by the heat given off by the reaction between the isocyanate and the polyol. Trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and, to a lesser extent, chlorodifluoromethane (HCFC-22), 1,1,2-trichlorotrifluoroethane (CFC-113) and 1,2-dichlorotetrafluoroethane (CFC-114) have been used for a long time as blowing agents. Because of its very low thermal conductivity, CFC-11 makes it possible to obtain particularly insulating rigid polyurethane foams, which are intensively used as thermal insulators, in particular in the fields of construction, refrigeration and transportation.
However, fully halogenated chlorofluorinated hydrocarbons (CFCs) are suspected of causing environmental problems, mainly in the context of the destruction of the stratospheric ozone layer. They are today banned in the majority of their conventional applications.
Chlorine-free hydrofluoroalkanes are completely inert with respect to the stratospheric ozone layer and these compounds are finding increasingly wide use in numerous applications, to the detriment of compounds carrying chlorine atoms. Thus, 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been proposed in various applications. Japanese Patent Applications JP 05/168805 and JP 05/171190 describe solvent compositions comprising 1,1,1,3,3-pentafluorobutane, a cosolvent soluble in 1,1,1,3,3-pentafluorobutane and optionally a surfactant. These compositions can be used in operations for cleaning objects or for the removal of residual water in the electronics industry. The only binary compositions described comprise 4% of n-pentane, 10% of cyclopentane or alternatively 5% of hexane.
Murphy and his coworkers (International CFC and Halon Alternatives Conference, Washington D.C., 1993, pp. 346-355) have described the use of cyclopentane/HFC-365mfc binary mixtures containing at least 54% by weight of cyclopentane as blowing agent for polyurethane foams. However, it has been noticed that there is a risk, in certain cases and under certain circumstances, of HFC-365mfc and the mixtures mentioned above condensing in the cells of the foam, resulting, if the case arises, in a deterioration in its thermal conductivity and optionally in its mechanical properties.
The need thus remains to find blowing agent compositions for polymeric cellular foams which are devoid of harmful effect on the environment, which have a boiling point close to the boiling point of CFC-11 or 1,1-dichloro-1-fluoroethane (HCFC-141b) and which possess the physical properties which make it possible to form polymeric cellular foams of low thermal conductivity in a wide range of temperatures, particularly foams with closed cells of homogeneous size.
One of the objects of the present invention is to provide compositions which perform particularly well when they are used as blowing agents, in particular for the manufacture of polyurethane foams. Another object of the invention is to provide such compositions which are devoid of destructive effect with respect to the ozone layer and which can consequently be used as replacement for compositions based on fully halogenated chlorofluoroalkanes, such as CFC-11, or on partially halogenated hydrocarbons containing chlorine atoms, such as HCFC-141b.
The present invention consequently relates to compositions composed essentially of 1,1,1,3,3-pentafluorobutane and of an alkane possessing 5 or 6 carbon atoms, which are characterized in that they are azeotropic or pseudoazeotropic.
The thermodynamic state of a fluid is fundamentally defined by four interdependent variables: the pressure (P), the temperature (T), the composition of the liquid phase (X) and the composition of the gas phase (Y). A true azeotrope is a specific system containing 2 or more components for which, at a given temperature and at a given pressure, the composition of the liquid phase X is exactly the same as the composition of the gas phase Y. A pseudoazeotrope is a system containing 2 or more components for which, at a given temperature and at a given pressure, X is substantially the same as Y. In practice, this means that the constituents of such azeotropic and pseudoazeotropic systems cannot be easily separated by distillation and, consequently, their composition remains constant in polymeric cellular foam blowing operations.
For the purposes of the present invention, pseudoazeotropic mixture is understood to mean a mixture of two constituents, the boiling of which (at a given pressure) differs from the boiling point of the true azeotrope by at most 0.5° C. Mixtures for which the boiling point differs from the boiling point of the true azeotrope by at most 0.2° C. are preferred. Mixtures for which the boiling point differs from the boiling point of the true azeotrope by at most 0.1° C. are particularly preferred.
The alkanes possessing 5 or 6 carbon atoms which can be used in the compositions according to the invention can be linear, branched or cyclic. Among all the possible isomers of the hydrocarbons possessing 5 or 6 carbon atoms, linear pentane (or n-pentane), isopentane (or 2-methylbutane), cyclopentane and linear hexane (or n-hexane) are preferred. The latter form, with 1,1,1,3,3-pentafluorobutane, azeotropic or pseudoazeotropic compositions with a minimum boiling point.
The azeotropic and pseudoazeotropic binary mixtures formed between 1,1,1,3,3-pentafluorobutane and cyclopentane are particularly preferred.
The relative contents of 1,1,1,3,3-pentafluorobutane and of alkane possessing 5 or 6 carbon atoms in the compositions according to the invention can vary within wide proportions, provided that the compositions thus formed are azeotropic or pseudoazeotropic with a minimum boiling point.
The compositions of the azeotropic mixtures according to the invention were estimated by calculation on the basis of the results of the experimental measurements presented in the examples below.
1,1,1,3,3-Pentafluorobutane and n-pentane form a binary azeotrope or pseudoazeotrope when their mixture contains approximately from 24 to 60% by weight of n-pentane. The binary compositions containing approximately from 30 to 53% by weight of n-pentane are preferred. The binary compositions containing approximately from 32 to 47% by weight are particularly preferred. Under a pressure of 103.5 kPa, the binary composition composed essentially of approximately 66% by weight of 1,1,1,3,3-pentafluorobutane and of approximately 34% by weight of n-pentane constitutes a true azeotrope, the boiling point of which is approximately 27.4° C. This composition is very particularly preferred. 1,1,1,3,3-Pentafluorobutane and cyclopentane form a binary azeotrope or pseudoazeotrope when their mixture contains approximately from 16 to 46% by weight of cyclopentane. The binary compositions containing approximately from 18.5 to 39% by weight of cyclopentane are preferred. The binary compositions containing approximately from 20 to 35% by weight of cyclopentane are particularly preferred.
Under a pressure of 101.4 kPa, the binary composition composed essentially of approximately 78.5% by weight of 1,1,1,3,3-pentafluorobutane and of approximately 21.5% by weight of cyclopentane constitutes a true azeotrope, the boiling point of which is approximately 32.2° C. This composition is very particularly preferred.
1,1,1,3,3-Pentafluorobutane and isopentane form a binary azeotrope or pseudoazeotrope when their mixture contains approximately from 31 to 75% by weight of isopentane. The binary compositions containing approximately from 39 to 70% by weight of isopentane are preferred. The binary compositions containing approximately from 45 to 60% by w
Barthelemy Pierre
Buyle Olivier
Dournel Pierre
Connolly Bove & Lodge & Hutz LLP
Cooney Jr. John M.
Solvay ( Societe Anonyme)
LandOfFree
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