Some environments generate a tough combination of dirt, grime, soil, and debris that is very difficult to clean effectively with only one cleaner. One example of such an extreme environment is the vehicle race track, e.g., auto speedway, truck speedway, or the like. In the course of a race, windshields are splattered both with oils (e.g., motor oils and gear oils) and with rubber bits thrown from race tires that erode during racing. Dirty windshields obscure the driver's visibility, impairing the safety of all race participants. Accordingly, it is common practice to try and clean race vehicle windshields during pit stops.
Cleaning a race vehicle windshield at a pit stop is not a simple matter, because this use imposes many stringent demands on a cleaner. In addition to being able to remove oils and rubber and other soil on the windshield, the cleaning agent must act to remove this grime very fast, i.e., within the time constraints of the pit stop. The cleaner also must be easy to remove quickly from the surface. Desirably, therefore, the cleaner must not only act fast, but also evaporate at a quick enough rate so that the time spent wiping the windshield with a clean cloth, squeegee, or the like, will be at a minimum. While quick cleaning action is important, this must also be balanced against residence time. The cleaner components must evaporate at a slow enough rate so that the cleaner has a long enough contact time with the soiled surface to remove the soils. Ideally, the cleaner also should go on and come off without requiring any rinsing with water or any other rinse agent.
Besides being fast and simple to use, the cleaner must be compatible with the race vehicle itself. Importantly, the cleaner must leave no residue behind that might obscure visibility through the windshield. The cleaner also must not damage the LEXAN polycarbonate material that forms the windshield or the silicone sealant around the edge of the windshield. The cleaner must also be compatible with MYLAR polyester, because a clear plastic sheet, often made of MYLAR polyester and called a “tear-away”, often is used to cover the windshield. The “tear-away” is used to dampen impacts from particulate matter during the race and can be removed quickly during a pit stop when the sheet becomes so damaged that it obscures the race vehicle driver's view. Cleaners splashed across a windshield inevitably will contact the race vehicle body, too. Therefore, the cleaner must not damage the race vehicle's body paint. The cleaner also should provide good cleaning performance over a wide temperature range. For example, it would be very desirable to have a cleaner that provides good cleaning performance at temperatures ranging from 25° F. (−4° C.) to 140° F. (60° C.).
Race vehicle bodies and the walls at racetracks need to be cleaned, too. These surfaces also are splattered with the same soils as the windshield, including oils and rubber. Also, race vehicle bodies and/or racetrack walls may be smeared with rubber from the tires of other race vehicles that sideswipe such surfaces during races. For these surfaces, in addition to being able to remove oils and rubber under the stringent conditions described above, the cleaning agent must not unduly damage the inks or the backings of the promotional decals or other graphics that are affixed to the vehicle's body or the racetrack walls.
The racetrack, of course, is just one example of an environment in which oils and rubber collectively challenge a cleaner. There are many others, too. For example, automobiles, trucks, motorcycles, and the like also get splattered with oils, tar, rubber, bugs, and the like during the course of ordinary street driving. Industrial equipment, industrial floors which have been traversed and marked by tires, engines, motors, railways, railway cars, and the like may also suffer from such grime.
With the growth of industry, a significant amount of hazardous waste products and products formerly regarded as useful but now recognized as hazardous have entered the environment. These hazardous materials are frequently present as contaminants on surfaces of equipment, installations of all kinds, civil works, soil, and the like.
For example, a significant amount of radioactive waste, in the form of radionuclides, is present in nuclear power plants, nuclear weapons production plants, mining and milling equipment used for uranium mining, and in apparatus in the medical area where radioactive isotopes are used. The presence of these radionuclides, which contaminate equipment including pumps, pipelines, valves, concrete foundations, and all other equipment and structures with which the radionuclides have come into contact, now pose a serious health problem since their radioactivity is known to be carcinogenic. To qualify as a decontaminated facility, depending upon the type of radioactivity, the NRC requires that the level of radioactivity from radionuclides be reduced to less than 5,000 disintegrations per minute (DPM) in some cases and other lower levels in other cases.
Polychlorinated biphenyls (PCBs) were once widely used industrial chemicals, especially as insulating or hydraulic fluids in electrical capacitors, transformers, vacuum pumps, gas-transmission turbines, machinery, and various other devices and products. Their chemical stability and non-flammability contributed to their commercial usefulness. However, it has since been found that PCBs are carcinogens and the United States Environmental Protection Agency (EPA) currently lists PCBs and any surfaces or equipment containing PCBs as hazardous. Consequently, these chemicals are no longer recommended or used in new applications. However, a large amount of existing capital equipment, installed before the listing of PCBs as hazardous, contains PCBs. These installations pose a hazard whenever a spillage of PCBs occurs thereby contaminating the surrounding area or whenever routine repairs expose workers or the environment to PCBs.
While it is desirable to remove PCBs and dispose of these in a suitable hazardous waste facility, PCBs are not easily removed from apparatus or spilled areas because of their capability to enter into the tiniest of pores and microscopic voids and spaces in surfaces with which they come into contact. For example, in transformers which frequently contain wood, paper, metal joints, and electrical components with minute crevices, the PCBs soak into pores and microscopic voids in the steel and concrete and fill the tiniest of microscopic spaces such as pores and microscopic voids, and the like, in metals. When PCBs have spilled onto a surface, such as a concrete surface, the PCBs over time will soak into pores and microscopic voids in the concrete and contaminate the concrete to well below the exposed surface and into the underlying substrate. Current techniques that merely clean the surface of concrete that has been exposed to the PCBs for a long period of time are not able to adequately clean the surface and do not reach PCBs held in the substrate below the surface in the pores and microscopic voids. Moreover, once surface cleaning has been completed, PCBs leach from the pores and microscopic voids to the surface over time due to the effect of a concentration gradient. Thus, the surface becomes recontaminated and further cleaning is necessitated. Likewise, while the bulk of the PCBs can be readily drained from some PCB-containing equipment, the residual PCB contaminant in pores, microscopic voids, crevices, and joints is not easily removed. It is found that upon refilling the drained apparatus with a replacement fluid for PCBs, PCBs will continue to leach from surfaces of the apparatus into the replacement fluid thereby contaminating it and rendering it hazardous.
Likewise, heavy metals have been identified as hazardous to human health and the EPA requires their removal from environments where they pose a health hazard. Like PCBs and radionuclides, heavy metals have the capability to migrate into pores, joints, crevices, and microscopic voids in interior and exterior surfaces and thereby cause contamination in the substrate to well below the apparent surface of any apparatus, device, or ground surface with which they come into contact. Mere surface cleaning is therefore ineffective to remove heavy metals contamination from substrates.
Certain pesticides and herbicides are also now known to be hazardous to human health. These compositions contaminate surfaces and substrates, such as concrete, but more especially particulate surfaces, such as soil, clay, gravel, and the like.
There is a need for methods and cleaning compositions for the removal of contaminants including radionuclides, PCBs, herbicides, pesticides, and heavy metals from porous and non-porous interior and exterior surfaces, particulate surfaces, and surfaces having minute spaces, crevices, pores, or microscopic voids into which these contaminants migrate and from which they are not readily extractable. Further, the method and cleaning compositions should desirably not only extract these contaminants from well below the surface to be cleaned, but should extract these to such a level that any remaining contaminants do not pose a hazard, i.e., a surface and its underlying substrate cleaned of PCBs would meet EPA regulations for reclassification from a hazardous to a non-hazardous material; a surface and its substrate cleaned of heavy metals, herbicides, or pesticides, would meet the EPA's TCLP standard setting the upper limit for their concentration; and a surface and its substrate cleaned of radionuclides would test at less than 5,000 DPM. The method and cleaning compositions should also desirably extract these contaminants without significant surface damage or scarring. Further, the method and cleaning compositions should desirably extract these contaminants with a minimum amount of hazardous waste byproduct which must be disposed of and, in the case of radionuclides, the byproduct waste should preferably be water soluble to assist in ease of disposal. Finally, cleaning compositions should desirably not be flammable.
What is needed is a cleaner that has the power to clean oil, tar, rubber, bug residue, and other soils over a wide temperature range, yet will not damage metal, many paints, many inks, ceramic, wood, concrete, many plastics and/or the like.