Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
2000-05-01
2002-04-02
Boyer, Charles (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C510S273000, C134S040000, C134S042000, C252S364000
Reexamination Certificate
active
06365565
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions of 1-bromopropane and at least one organic solvent selected from the group consisting of methanol, ethanol, 1 -propanol, 2-propanol, 2-methyl-2-propanol, 2,2,2-trifluoroethanol, tetrahydrofuran, nitromethane, ethyl acetate, acetonitrile, hexane, 1,3-dioxolane, 1-chloro-2-methylpropane, 1,1,1,2,3,4,4,5,5,5-decafluoropentane (HFC-4310), methyl ethyl ketone and cyclohexane and more particularly to azeotrope-like compositions based on these compounds. These mixtures are useful as solvents for use in refrigeration flushing, oxygen system cleaning, and vapor degreasing applications including electronics cleaning.
BACKGROUND OF THE INVENTION
1-Bromopropane based fluids have found widespread use in industry for solvent cleaning, i.e. vapor degreasing, cold cleaning and ultrasonic cleaning of complex metal parts, circuit boards, electronic components, implantable prosthetic devices, optical equipment and others.
In its simplest form, vapor degreasing or solvent cleaning consists of exposing a room temperature object to be cleaned to the vapors of a boiling solvent. Vapors condensing on the object provide clean distilled solvent to wash away grease or other contamination. Final evaporation of solvent from the object leaves no residue on the object.
For difficult to remove soils where elevated temperature is necessary to improve the cleaning action of the solvent, or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently, a vapor degreaser is employed. The conventional operation of a vapor degreaser consists of immersing the part to be cleaned in a sump of boiling solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room temperature, and finally exposing the part to solvent vapors over the boiling sump which condense on the cleaned part. The part can also be sprayed with distilled solvent before final rinsing.
Azeotropic or azeotrope-like compositions are particularly desired because they do not fractionate upon boiling. This behavior is desirable because in the previously described vapor degreasing equipment in which these solvents are employed, redistilled material is generated for final rinse-cleaning. Thus, the vapor degreasing system acts as a still. Unless the solvent composition exhibits a constant boiling point, i.e., is azeotrope-like, fractionation will occur and undesirable solvent distribution may act to upset the cleaning and safety of processing.
The art is continually seeking new solvent mixtures which offer alternatives for the above-described applications. Currently, environmentally acceptable materials are of particular interest because the traditionally used fully halogenated chlorocarbons and chlorofluorocarbons have been implicated in causing environmental problems associated with the depletion of the earth's protective ozone layer. Mathematical models have substantiated that 1-bromopropane will not adversely affect atmospheric chemistry because its contribution to stratospheric ozone depletion and global warming in comparison to the fullly halogenated chlorocarbons and chlorofluorocarbons species is negligible. The ozone depletion potential of 1-bromopropane is 0.002-0.03 which is significantly lower than the ozone depletion potential of 1,1,2-trichloro-1,2,2-trifluoroethane, CFC-113 (0.8) and 1,1-dichloro-1-fluoroethane, HCFC-141b (0.11). The global warming potential of 1-bromopropane (0.31) is also significantly lower than CFC-113 (5000) and HCFC-141b (630).
The art has also looked to compositions which include components which contribute additionally desired characteristics, such as polar functionality, increased solvency power, and stabilizers while retaining those properties exhibited by the prior art chlorofluorocarbons including chemical stability, low toxicity, and non-flammability.
It is accordingly an object of this invention to provide novel compositions based on 1-bromopropane, and preferably azeotrope-like compositions, which are useful in solvent and other applications and which meet the above criteria.
The present compositions are advantageous for the following reasons. The 1-bromopropane component has an ozone depletion potential of 0.002-0.03 and has reasonable solvency characteristics. The organic solvent component has good solvent properties to enable the cleaning and dissolution of flux resin and oils. Thus, when these components are combined in effective amounts, an efficient, environmentally acceptable solvent composition results.
DESCRIPTION OF THE INVENTION
The invention relates to novel compositions comprising effective amounts of 1-bromopropane and at least one organic solvent selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 2,2,2-trifluoroethanol, tetrahydrofuran, nitromethane, ethyl acetate, acetonitrile, hexane, 1,3-dioxolane, 1-chloro-2-methylpropane, 1,1,1,2,3,4,4,5,5,5-decafluoropentane, methyl ethyl ketone and cyclohexane. The invention further relates to azeotrope-like compositions comprising from about 27 to about 99.9 weight percent 1-bromopropane and from about 0.1 to about 73 weight percent of at least one organic solvent selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 2,2,2-trifluoroethanol, tetrahydrofuran, nitromethane, ethyl acetate, acetonitrile, hexane, 1,3-dioxolane, 1-chloro-2-methylpropane, 1,1,1,2,3,4,4,5,5,5-decafluoropentane, methyl ethyl ketone and cyclohexane, which compositions boil at from about 50.4° C. to about 69.8° C.± about 2.0° C. at 760 mmHg.
The 1-bromopropane and organic solvent components of the invention are commercially available and may be obtained readily in pure form.
The term “azeotrope-like” is used herein for the preferred mixtures of the invention because in the claimed proportions, the compositions of 1-bromopropane and organic solvent are constant boiling or essentially constant boiling. All compositions within the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like, as defined more particularly below.
From fundamental principles, the thermodynamic state of a fluid is defined by four variables: pressure, temperature, liquid composition, and vapor composition, or P-T-X-Y, respectively. An azeotrope is a unique characteristic of a system of two or more components where X and Y are equal at a stated P and T. In practice, this means that the components cannot be separated during a phase change, and therefore are useful in solvent and aerosol solvent applications.
For the purposes of this discussion, by azeotrope-like composition is intended to mean that the composition behaves like a true azeotrope in terms of its constant boiling characteristics or tendency not to fractionate upon boiling or evaporation. Thus, in such systems, the composition of the vapor formed during evaporation is identical or substantially identical to the original liquid composition. Hence, during boiling or evaporation, the liquid composition, if it changes at all, changes only slightly. This is contrasted with non-azeotrope-like compositions in which the liquid and vapor compositions change substantially during evaporation or condensation.
One way to determine whether a candidate mixture is azeotrope-like within the meaning of this invention, is to distill a sample thereof under conditions (i.e., resolution—number of plates) which would be expected to separate the mixture into its separate components. If the mixture is not an azeotrope or azeotrope-like, the mixture will fractionate, i.e., separate into its various components with the lowest boiling component distilling off first, and so on. If the mixture is azeotrope-like, some finite amount of the first distillation cut will be obtained which contains all of the mixture components and which is constant boiling or behaves as a single substance. This phenomenon cannot occur if the mixture is not azeotrope-like, i.e
Cook Kane David
Paonessa Martin Richard
Stachura Leonard Michael
Thenappan Alagappan
Boyer Charles
Honeywell International , Inc.
Synnestvedt & Lechner LLP
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