Compositions: coating or plastic – Materials or ingredients – Vehicles or solvents
Reexamination Certificate
1999-04-07
2001-08-28
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Vehicles or solvents
C106S236000, C106S237000, C106S238000, C106S239000, C252S364000, C244S232000
Reexamination Certificate
active
06280519
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the selection and use of environmentally preferred fluids and fluid blends which exhibit low or reduced reactivity with respect t o ozone formation. These environmentally preferred fluids and fluid blends are useful in a number of applications, particularly as industrial solvents, and allow formulators an effective means to improve the environmental preference of their formulations or products.
BACKGROUND OF THE INVENTION
Fluid applications are broad, varied, and complex, and each application has its own set of characteristics and requirements. Proper fluid selection and fluid blend development have a large impact on the success of the operation in which the fluid is used. For instance, in a typical industrial coatings operation, a blend of several fluids is used in order to get an appropriate evaporation profile. Such a blend must also provide the appropriate solvency properties, including formulation stability, viscosity, flow/leveling, and the like. The fluid blend choice also affects the properties of the dry film, such as gloss, adhesion, and the like. Moreover, these and other properties may further vary according to the application method (e.g., spray-on), whether the substrate is original equipment (OEM), refinished, etc., and the nature of the substrate coated.
Other operations involving the use of fluids and fluid blends include cleaning, printing, delivery of agricultural insecticides and pesticides, extraction processes, use in adhesives, sealants, cosmetics, and drilling muds, and countless others. The term “fluid” encompasses the traditional notion of a solvent, but the latter term no longer adequately describes the possible function of a fluid or blend in the countless possible operations. As used herein the term “fluid” includes material that may function as one or more of a carrier, a diluent, a surface tension modifier, dispersant, and the like, as well as a material functioning as a solvent, in the traditional sense of a liquid which solvates a substance (e.g., a solute).
The term “industrial solvent” applies to a class of liquid organic compounds used on a large scale to perform one or more of the numerous functions of a fluid in a variety of industries. Relatively few of the large number of known organic compounds that could be used as fluids find use as industrial solvents. Fluids that are used in large quantities have heretofore been selected because they can be produced economically and have attractive safety and use characteristics in manufacturing, consumer and commercial environments. Examples of important industrial solvents are toluene, the xylenes, and mineral spirits, n-butyl acetate, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIK), and butanol.
In addition to the problems with fluid and fluid blend selection mentioned at the outset, there is also the problem that, in most applications, at least some of the fluid evaporates and can escape into the environment. In some applications, such as in certain coating operations, it is intended that the fluid evaporate. This evaporative property causes environmental problems. Although many industrial coating operations, such as in original equipment manufacturing (OEM) and auto refinishing, utilize control equipment to capture >95% solvent emissions, nevertheless at least some inevitably enters the atmosphere.
The United States Environmental Protection Agency (EPA) has developed National Ambient Air Quality Standards (NAAQS) for six pollutants: ozone, nitrogen oxides (NO
x
), lead, carbon monoxide, sulfur dioxide and particulates. Of all the NAAQS standards, ozone non-attainment has the greatest impact on solvent operations.
Solvents typically are volatile organic compounds (VOC), which are involved in complex photochemical atmospheric reactions, along with oxygen and nitrogen oxides (NO
x
) in the atmosphere under the influence of sunlight, to produce ozone. Ozone formation is a problem in the troposphere (low atmospheric or “ground-based”), particularly in an urban environment, since it leads to the phenomenon of smog. Since VOC emissions are a source of ozone formation, industrial operations and plants using solvents are heavily regulated to attain ozone compliance. As different regulations have been adopted, the various approaches to controlling pollution have evolved. Certain early regulations controlled solvent composition, while later regulations primarily concerned overall VOC reduction. A more recent regulation has combined VOC reduction with composition constraints. While the traditional source of emission reduction is large stationary industrial facilities, the EPA and other governmental entities have turned increasingly to consumer and commercial products for reduction in their solvent usage as an additional means to lower VOC emission and therefore ozone formation.
The EPA has developed a list of compounds with negligible photochemical reactivity, such as methane, ethane, acetone, and various halogenated compounds. The agency has determined that these compounds do not contribute appreciably to ozone formation, and granted them VOC exempt status. Numerous government and trade publications discuss VOC's, and information is readily available on the internet. See, for instance, http://www.paintcoatings.netVOCW97.html.
Various measurements of reactivity with respect to ozone formation are known. For instance, reactivity can be measured in environmental smog chambers, or they may be calculated using computer airshed models. See, for instance, Dr. William P. L. Carter, “Uncertainties and Research Needs in Quantifying VOC Reactivity for Stationary Source Emission Controls”, presented at the California Air Resources Board (CARB) Consumer Products Reactivity Subgroup Meeting, Sacramento, Calif. (Oct. 17, 1995).
There has also been developed a “K
OH
scale”, which provides a relative scale of the reactivity of VOC with the OH radicals involved in the complex reactions that produce ozone. See, for instance, Picquet et al.,
Int J. Chem. Kinet.
30, 839-847 (1998); Bilde et al.,
J. Phys. Chem. A
101, 3514-3525 (1997).
Numerous other reactivity scales are known and new reactivity scales are constantly being developed. Since this is a rapidly changing area of research, the most up-to-date information is often obtained via the internet. One example is Airsite, the Atmospheric Chemistry International Research Site for Information and Technology Exchange, sponsored by the University of North Carolina and the University of Leeds, at http://airsite.unc.edu.
Another way to measure the reactivity of a chemical in ozone formation is by using a technique developed by Dr. Carter (supra) at the Center for Environmental Research and Technology (CERT), University of California at Riverside. The CERT technique measures “incremental reactivities”, the incremental amount of ozone that is produced when the chemical is added to an already polluted atmosphere.
Two experiments are conducted to measure the incremental reactivity. A base case experiment measures the ozone produced in an environmental smog chamber under atmospheric conditions designed to represent a polluted atmosphere. The second experiment called “the test case” adds the chemical to the “polluted” smog chamber to determine how much more ozone is produced by the newly added chemical. The results of these tests under certain conditions of VOC and nitrogen oxide ratios are then used in mechanistic models to determine the Maximum Incremental Reactivities (MIR), which is a measure of ozone formation by the compound.
The State of California has adopted a reactivity program for alternative fuels based on this technique and the EPA has exempted several compounds due to studies conducted by CERT. See, for instance, Federal Register 31,633 (Jun. 16, 1995) (acetone); 59 Federal Register 50,693 (Oct. 5, 1994) (methyl siloxanes), Federal Register 17,331 (Apr. 9, 1998) (methyl acetate). CARB and EPA have adopted a weight average MIR for regulatory purposes, wherein the weight average MIR of a solvent blend is
Knudsen George Andrew
Larson Thomas Marshall
Schlosberg Richard Henry
Yezrielev Albert Ilya
Bell Mark L.
DiVerdi Michael J.
Exxon Chemical Patents Inc.
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