Compositions – Water-softening or purifying or scale-inhibiting agents – Plant or organic material containing
Reexamination Certificate
2001-07-26
2004-01-06
Lovering, Richard D. (Department: 1712)
Compositions
Water-softening or purifying or scale-inhibiting agents
Plant or organic material containing
C210S730000, C210S930000, C427S421100
Reexamination Certificate
active
06673263
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions useful in paint overspray removal processes. More particularly, the present invention relates to compositions for detackifying and flocculating paint, which compositions are useful in water-based and solvent-based paint denaturant systems.
BACKGROUND OF THE INVENTION
Automatic spraying techniques have long been employed for painting large articles such as cars, trucks, refrigerators, etc. The items being sprayed are generally advanced along a conveyor line which passes through a water wash paint spray booth where a fine spray of paint is directed at the articles being painted from spray guns which are located at the sides of the conveyor. Overspray paint, that is, paint which does not contact the article being painted, forms a fine mist of paint in the air space surrounding the painted article. This paint mist must be removed from the air. To accomplish this, the contaminated air is pulled through the paint spray booth by air exhaust fans. A curtain of circulating water is maintained across the path of the air in a manner such that the air must pass through the water curtain to reach the exhaust fans. As the air passes through the water curtain, the paint mist is “scrubbed” from the air and carried to a sump basin usually located below the paint spray booth. In this area, the paint particles are separated from the water so that the water may be recycled and the paint particles disposed of.
The term “paint” as used herein is intended to encompass a mixture of resin, pigment, and a suitable liquid vehicle that is reasonably fluid and provides a thin and adherent coating when applied to a substrate. As such, the term “paint” is intended to encompass paints, lacquers, varnishes, base coats, clear coats, primers and the like.
Paint is a tacky material and it tends to coagulate and adhere to the spray booth surfaces, particularly in the sump and drain areas, and must constantly be removed from the sump to prevent clogging of the sump drain and recirculating system. In order assist in the removal of the oversprayed paint from the air and to provide efficient operation of paint spray booths, detackifying agents are commonly employed in the water used in such systems, and are typically incorporated into the water wash recirculated in the paint spray system. Detackifying the paint eliminates or minimizes the adhesive properties, or tackiness, of the paint, thereby preventing the oversprayed paint from adhering to the walls of the spray booth.
One of the difficulties with recovering paint overspray in a water wash spray booth as described above is the limited amount of paint which can be incorporated into the water. As such, detackifying agents should have a high load capacity, such that the water wash recirculated through the spray booth can detackify, coagulate and flocculate a high volume of oversprayed paint before exhaustion.
Moreover, in recent years, the need to reduce solvent emission has resulted in the reduction of solvent-based or solventborne paints, and an increase in the use of water-based or waterborne paints. The organic content in solvent-based paints, however, requires the use of different detackifying processes in paint spray booths.
For example, U.S. Pat. No. 5,259,976 discloses the use of cationic polymers such as acrylamide polymers for detackifying paint and improving paint spray booth efficiency, and using sodium aluminate to adjust the pH of the system. U.S. Pat. No. 5,019,138 discloses the use of an organic solvent, i.e., N-methyl pyrrolidone, to scrub the paint overspray from the surrounding air. However, the use of high quantities of organic solvent needed for this process is expensive and a potential health and environmental hazard. In addition, such detackifying agents are not effective for detackifying both water-based and solvent-based paints.
U.S. Pat. No. 5,223,141 discloses a method for removing and recovering solvent-based paint overspray through contact with an agitated dispersion of an organic solvent in water, and then allowing the dispersion to phase separate, for separation of the organic phase from the aqueous phase. Such dispersion, however, is often difficult to separate for removal of the paint from the water.
U.S. Pat. No. 4,888,386 discloses a composition for use in detackifying both waterborne and solvent enamels, which includes a melamine-formaldehyde polymer, a polyvinyl alcohol and a styrene acrylate copolymer. Such materials, however, are not readily biodegradable, and therefore pose environmental concerns for disposal.
Accordingly, a need exists for a composition which is useful for detackifying both water-based and solvent-based paints, which is capable of effectively decreasing emulsion formation in solvent-based paint denaturant systems, and which is biodegradable.
SUMMARY OF THE INVENTION
The present invention includes a composition for treating oversprayed paints. The composition includes: (a) an aqueous solution of a compound having the following structure:
such as an aqueous solution of chitosan; (b) a complex metal salt, such as aluminum chlorohydrate, which is capable of flocculating the oversprayed paint; and (c) water. The aqueous solution of chitosan preferably includes a mixture of water, chitosan, and an acid, such as acetic acid, capable of rendering the chitosan soluble in water. The composition is particularly useful as a liquid concentrate, which can be added to circulating water systems in paint spray booths, for use with both water-based and solvent-based paints. Bentonite clay may optionally be included in the composition, particularly when the composition is used in connection with solvent-based paints.
In a further embodiment, the present invention involves a method of treating oversprayed paint particles in a paint spray booth including a circulating water system. In such a method, oversprayed paint is contacted with a water system including a composition comprising a) an aqueous solution of a compound having the following structure:
(b) a complex metal salt capable of flocculating the oversprayed paint; and (c) water. The aqueous solution of the compound is preferably an aqueous solution of chitosan in water. The composition detackifies and flocculates the oversprayed paint particles. Such a method may further include a step of separating the flocculated oversprayed paint particles from the water system.
In yet a further embodiment, the present invention includes a method of treating oversprayed paint in a paint spray booth including a solvent-based paint denaturant system. Such a method includes contacting the oversprayed paint with a dispersion of an organic solvent component in water, which dispersion further includes an aqueous solution of a compound as set forth above and a complex metal salt. Such contacting collects the oversprayed paint in the dispersion. The dispersion is then phase separated into an organic phase containing paint overspray, and an aqueous phase, which phases are then separated. The inclusion of the aqueous solution of chitosan and the complex metal salt within the dispersion decreases the time for phase separation of the organic phase and the aqueous phase. This causes the waterborne paint solids to migrate into the organic phase.
DETAILED DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by app
Albu Michael L.
Beauchamp Phillip J.
Lovering Richard D.
PPG Industries Ohio Inc.
Uhl William J.
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