Cleaning and liquid contact with solids – Processes – Gas or vapor condensation or absorption on work
Patent
1997-11-10
1999-08-17
El-Arini, Zeinab
Cleaning and liquid contact with solids
Processes
Gas or vapor condensation or absorption on work
134 11, 134 12, 134 19, 134 30, 134 38, 134 40, 510412, 510255, 510256, 510264, 510273, 510365, 510461, 510175, 510266, 252364, C11D 730, C11D 724, C11D 726, B08B 308
Patent
active
059388595
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates generally to molecular level cleaning of parts by vapor degreasing. More particularly, the invention relates to a solvent mixture comprising n-propyl bromide, a mixture of low boiling solvents and, preferably, a defluxing and/or ionics removing agent and/or at least one saturated terpene, as well as to a method of cleaning an article in a vapor degreaser using the solvent mixture. The solvent mixture of the invention is non-flammable, non-corrosive, non-hazardous, and has a low ozone depletion potential.
BACKGROUND OF THE INVENTION
Molecular level cleaning by vapor degreasing has found wide acceptance in industry. In fact, molecular level cleaning by vapor degreasing is a preferred method of cleaning precision parts, such as electronics, machined metallic parts, etc., since vapor cleaning leaves virtually no residue on the parts. Generally, vapor degreasing involves the heating of a solvent to its boiling point to generate a vapor layer into which the object to be cleaned is placed. The vapor condenses on the object and subjects the surface to a solvent-flushing action as it flows downward. The solvent-flushing action dissolves the hydrocarbon contaminants and removes them from the object, thereby cleaning it. The liquid drops are then collected in a reservoir and are revaporized, typically through the use of steam-heating coils. Thus, the surface of the object is continually rinsed with fresh solvent.
There are four general types of vapor phase degreasers. The simplest form of a vapor phase degreaser is the straight vapor cycle degreaser which utilizes only the vapor for cleaning. As the parts are lowered into the hot vapor, the vapor condenses on the cold parts and dissolves the surface oils and greases. The oily condensate drops back into the liquid solvent at the base of the tank. The solvent is evaporated continuously to form a vapor blanket. Since the oils are not vaporized, they remain in the bottom of the tank in the form of a sludge. The scrubbing action of the condensing vapor continues until the temperature of the part reaches the temperature of the vapor whereupon condensation ceases, the part appears dry, and it is removed from the degreaser. The time required to reach this point depends on the particular solvent employed, the temperature of the vapor, the weight of the part, its specific heat and the type of contamination material to be removed. This particular vapor phase degreaser does an excellent job of drying parts after aqueous cleaning and before plating and, thus, it is frequently used for this purpose in the jewelry industry. Unfortunately, however, it is not as effective on small, light weight parts because such parts frequently reach the temperature of the vapor before the condensing action has fully cleaned the parts.
A second type of vapor phase degreaser, i.e., the vapor-spray cycle degreaser, is frequently used to solve the problems associated with the straight vapor cycle degreaser. In this vapor-spray cycle degreaser, the part to be cleansed is first placed in the vapor zone as is done in the straight vapor cycle degreaser. A portion of the vapor is condensed by cooling coils and fills a liquid solvent reservoir. This warm liquid solvent is pumped to a spray nozzle that can be used to direct the solvent on the part, washing off surface oils and cooling the part, thereby cleaning by vapor condensation.
The third type of vapor phase degreaser is a liquid-vapor cycle degreaser which has one compartment with warm solvent and another compartment with a vapor zone. This degreaser is particularly useful for heavily soiled parts or for cleaning a basket of small parts that nest together. The fourth type of vapor phase degreaser is the ultrasonic degreaser. Such degreasers are useful for cleaning critical parts. An ultrasonic degreaser has a transducer mounted at the base of the tank which operates in the range of 20 kHz to 40 kHz. The transducer alternately compresses and expands the solvent forming small bubbles which, in turn, cavita
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Clark Lawrence A.
Priest James L.
El-Arini Zeinab
Lawrence Industries, Inc.
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