Cleaning and liquid contact with solids – Processes – Using solid work treating agents
Reexamination Certificate
2001-10-19
2004-05-18
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Using solid work treating agents
C134S022120, C051S295000, C051S298000, C451S040000
Reexamination Certificate
active
06736905
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to methods for removing adherent materials, for example, undesirable residues, precipitates, scale and other materials from internal surfaces such as pipes and tanks, especially internal surfaces used to transport or deliver liquids in closed systems. In particular, the method employs an improved cleaning media comprising core/shell particles.
BACKGROUND OF THE INVENTION
For various types of structures, it is often desirable to remove a coating that has been formed on an interior surface area. Numerous techniques exist for removing paint, rust, scale, biogrowth and other adherent materials from virtually any type of surface. Surface cleaning or stripping methods range from mechanical abrasion to the use of strong chemicals and involve varying degrees of time, effort and expense. This invention relates to compositions and methods for removing unwanted deposits or build-up on surfaces of internal surfaces in fluid delivery/transport systems (referred to herein as “fluid transport systems”) or parts thereof, including conduits, tanks, and related equipment, for example, the throughput parts of pumps. The invention is particularly useful for cleaning substantially closed systems. Large quantities of fluids with suspended, dispersed or dissolved materials (hereinafter referred to as “carried materials”) are often circulated through fluid transport systems and over time the material may deposit or settle on various interior surfaces of the fluid transport system. For example, paints, inks, or components thereof are circulated or re-circulated in piping of delivery systems in industrial manufacturing plants. During the course of normal operation, the carried materials in a fluid may build up or deposit on the inside of fluid delivery systems, especially in areas of reduced flow such as in filters, tees, elbows and valves. As a consequence fluid delivery systems are cleaned on a periodic basis to remove the unwanted carried materials adhering to the insides of pipes, tubing, filters and/or valves. Since these systems are enclosed, at least to a substantial extent, removal of unwanted material adhering to the insides of tubes, pipes and other conduits is difficult to achieve because access is difficult, and, in fact, frequently it is difficult even to determine the extent of cleaning.
Industrial applications where internal surfaces need to be cleaned include, for example, food (e.g. dairy and beverages), pharmaceuticals, inks and pigments, paints, oil pipelines, oil refinery lines, power plants, marine lines in ships, and polymer and chemical manufacturing pipelines in general.
For example, coating or paint delivery systems are utilized for the finishing of a wide variety of manufactured items such as motor vehicles, household appliances and the like. A typical industrial paint delivery system may comprise a central paint supply having a number of painting stations communicating therewith. Such paint delivery systems can selectably deliver a variety of different paints to a given painting station and include complex fluid pathways involving various tanks, pumps and conduits. These paint delivery systems tend to become clogged with encrustations in the course of their use and such deposits can decrease and even block the flow of paint there through. Such clogging is occasioned by deposits of pigment, resins or other components of the paint within the tanks and lines of the system. In addition to causing clogging, such deposits can also contaminate the paint color, and can cause surface defects in the finished, painted product. Cleaning the paint delivery system reduces the amount of surface repairs to paint finishes. The build-up of residues necessitates periodic cleaning of paint delivery systems and because of the complexity of the systems and the necessity of avoiding expensive downtime, it is generally preferable that such systems be cleaned without or with minimum disassembly. The prior art approach to cleaning involves passing a variety of solvents, detergents or other cleaners through the system, and tends to involve numerous steps and multiple compositions. It should be noted that these processes often do not provide full removal of deposits, particularly pigment residues.
A typical prior art process can involve flushing five or more different cleaning compounds of varying polarity through the paint system and can include 30 separate operational steps. The numerous cleaning compounds are needed in order to fully remove the residues in the system and to ensure compatibility of any cleaner residue remaining in the system with subsequently introduced paint. As a result, the system must be sequentially rinsed with various materials in a predetermined order such that the final rinse is with a paint-compatible thinner. Clearly, it would be most advantageous to reduce the number of steps by utilizing a cleaning composition which is fully paint-compatible, and to improve the efficiency of the process by utilizing a composition capable of removing all residues. In addition to toxicity and waste disposal problems, another of the shortcomings of prior-art paint system cleaning, especially ones requiring organic solvents, is that they do not provide sufficient cleaning action, particularly with regard to encrusted pigment deposits and, as a consequence, long flush times and/or repeated cleaning cycles have been generally required.
It has been known to utilize abrasive materials to clean closed lines and one such process is disclosed in U.S. Pat. No. 4,572,744 which describes the use of sand or similar material entrained in a flow of air to clean the interior of boiler tubes. Also mentioned in the '744 patent is the similar use of liquid based abrasive slurries to clean pipes. Various attempts have been made to utilize abrasive based materials for cleaning paint lines and it is known to employ mica, or sand particles in conjunction with a flush liquid to scour the interior of paint lines. Problems have arisen with the use of such inorganic abrasives insofar as they can be relatively hard and tend to damage or clog pumps and passageways through which they flow. Additionally, such inorganic abrasive materials are also relatively dense and tend to settle out of a cleaning fluid unless vigorous agitation is maintained or thickeners are added to increase the solution viscosity.
For example, it is known to utilize a specific paint system cleaning composition comprised of sand or mica suspended in a solution of xylene and methyl isobutyl ketone thickened with a resinous material. Compositions of this type present problems insofar as the resin and abrasive are difficult to rinse from the system thereby presenting problems of contamination, particularly when the resin is not compatible with subsequently employed paint compositions. Additionally, the viscous composition presents problems of waste disposal insofar as the resin is difficult to incinerate and inhibits the ready evaporation and recovery of the xylene and ketone. Obviously, the inorganic abrasive residue presents significant waste disposal problems insofar as it cannot be readily incinerated.
U.S. Pat. No. 4,968,447, to Dixon and Maxwell, proposes the use of polymeric particulates made of polypropylene, polyethylene, polyvinylchloride, polytetrafluoroethylene, and various other hydrophobic organic polymers and copolymers.
Organic, polymeric materials are not generally thought of as being abrasive; however the present invention relies in part upon the counter intuitive finding that organic materials can function very well to facilitate the cleaning of encrustations from paint delivery systems. Dixon et al. utilize polymeric particles of relatively low density that can be maintained in suspension without resort to thickeners or vigorous agitation. Dixon et al. state that, although these organic materials perform an excellent job of cleaning residues from paint lines, they are not sufficiently abrasive to damage pumps, valves and the like.
The rheological additive “Viscotrol”, avai
Gruszczynski David W.
Puccini Christopher J.
Smith Dennis E.
Chaudhry Saeed
Eastman Kodak Company
Gulakowski Randy
Konkol Chris P.
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