Azeotrope-like compositions and their use

Details Azeotrope-like compositions and their use Azeotrope-like compositions and their use

2001-02-14

2001-08-21

Gupta, Yogendra N. (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

Liquid composition

C510S410000, C252S364000, C106S311000, C134S042000

Reexamination Certificate

active

06277807

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to azeotropes and methods of using azeotropes to clean substrates, deposit coatings and transfer thermal energy.
BACKGROUND
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) have been used in a wide variety of solvent applications such as drying, cleaning (e.g., the removal of flux residues from printed circuit boards), and vapor degreasing. Such materials have also been used in refrigeration and heat transfer processes. While these materials were initially believed to be environmentally-benign, they have now been linked to ozone depletion. According to the Montreal Protocol and its attendant amendments, production and use of CFCs must be discontinued (see, e.g., P. S. Zurer, “Looming Ban on Production of CFCs, Halons Spurs Switch to Substitutes,”
Chemical
&
Engineering News,
page 12, Nov. 15, 1993). The characteristics sought in replacements, in addition to low ozone depletion potential, typically have included boiling point ranges suitable for a variety of solvent cleaning applications, low flammability, and low toxicity. Solvent replacements also should have the ability to dissolve both hydrocarbon-based and fluorocarbon-based soils. Preferably, substitutes will also be low in toxicity, have no flash points (as measured by ASTM D3278-89), have acceptable stability for use in cleaning applications, and have short atmospheric lifetimes and low global warming potentials.
Certain perfluorinated (PFCs) and highly fluorinated hydrofluorocarbon (HFCs) materials have also been evaluated as CFC and HCFC replacements in solvent applications. While these compounds are generally sufficiently chemically stable, nontoxic and nonflammable to be used in solvent applications, PFCs tend to persist in the atmosphere, and PFCs and HFCs are generally less effective than CFCs and HCFCs for dissolving or dispersing hydrocarbon materials. Also, mixtures of PFCs or HFCs with hydrocarbons tend to be better solvents and dispersants for hydrocarbons than PFCs or HFCs alone.
Many azeotropes possess properties that make them useful solvents. For example, azeotropes have a constant boiling point, which avoids boiling temperature drift during processing and use. In addition, when a volume of an azeotrope is used as a solvent, the properties of the solvent remain constant because the composition of the solvent does not change. Azeotropes that are used as solvents also can be recovered conveniently by distillation.
There currently is a need for azeotrope or azeotrope-like compositions that can replace CFC- and HCFC-containing solvents. Preferably these compositions would be non-flammable, have good solvent power, cause no damage to the ozone layer and have a relatively short atmospheric lifetime so that they do not significantly contribute to global warming.
SUMMARY OF THE INVENTION
In one aspect, the invention provides azeotrope-like compositions consisting essentially of hydrofluorocarbon ether and one or more organic solvents. The hydrofluorocarbon ether is represented by the general formula R
f
OCH
3
, where R
f
is a branched or straight chain perfluoroalkyl group having 4 carbon atoms, and the ether may be a single compound or a mixture of the branched and straight chain ether compounds. The organic solvents are selected from the group consisting of: straight chain, branched chain and cyclic alkanes containing 6 to 8 carbon atoms; cyclic and acyclic ethers containing 4 to 6 carbon atoms; ketones having 3 carbon atoms; chlorinated alkanes containing 1, 3 or 4 carbon atoms; chlorinated alkenes containing 2 to 3 carbon atoms, alcohols containing 1 to 4 carbon atoms, partially fluorinated alcohols containing 2 to 3 carbon atoms, 1-bromopropane, acetonitrile, HCFC-225ca (1,1,-dichloro-2,2,3,3,3 pentafluoropropane) and HCFC-225cb (1,3-dichloro-1,1,2,2,3-pentafluoropropane). While the concentrations of the hydrofluorocarbon ether and organic solvent included in an azeotrope-like composition may vary somewhat from the concentrations found in the azeotrope formed between them and remain a composition within the scope of this invention, the boiling points of the azeotrope-like compositions will be substantially the same as those of their corresponding azeotropes. Preferably, the azeotrope-like compositions boil, at ambient pressure, at temperatures that are within about 1° C. of the temperatures at which their corresponding azeotropes boil at the same pressure.
In another aspect, the invention provides a method of cleaning objects by contacting the object to be cleaned with one or more of the azeotrope-like compositions of this invention or the vapor of such compositions until undesirable contaminants or soils on the object are dissolved, dispersed or displaced and rinsed away.
In yet another aspect, the invention also provides a method of coating substrates using the azeotrope-like compositions as solvents or carriers for the coating material. The process comprises the step of applying to at least a portion of at least one surface of a substrate a liquid coating composition comprising: (a) an azeotrope-like composition, and (b) at least one coating material which is soluble or dispersible in the azeotrope-like composition. Preferably, the process further comprises the step of removing the azeotrope-like composition from the liquid coating composition, for example, by evaporation.
The invention also provides coating compositions consisting essentially of an azeotrope-like composition and a coating material which are useful in the aforementioned coating process.
In yet another aspect, the invention provides a method of transferring thermal energy using the azeotrope-like compositions of this invention as heat transfer fluids (e.g. primary or secondary heat transfer media).


REFERENCES:
patent: 5756002 (1998-05-01), Chen et al.
patent: 450855 (1991-10-01), None

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