Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Liquid composition
Reexamination Certificate
2002-07-10
2004-02-10
Webb, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Liquid composition
C510S177000, C510S365000, C510S407000, C510S411000, C510S412000, C510S505000, C510S506000, C134S038000, C134S040000
Reexamination Certificate
active
06689734
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns chemical solvating, degreasing, stripping and cleaning agents. More particularly, this invention relates to cleaning and solvating mixtures of mono brominated compounds with highly fluorinated compounds and/or other agents that improve and enhance the properties of the original mixture.
The present invention was made in response to concerns with ozone depleting materials, and toxicity concerns with non ozone depleting chlorinated materials. In September 1987, the United States and 22 other countries signed the Montreal Protocol on Substances that Deplete the Ozone Layer (the “Protocol”). The Protocol called for a freeze in the production and consumption of ozone depleting chemicals (“ODP's” or “ODC's”) by the year 2000 for developed countries and 2010 for developing countries. In 1990 the United States enacted the Clean Air act mandating that the use of ozone depleting chemicals be phased out by the year 2000. In September 1991, the U.S. Environmental Protection Agency announced that ozone layer depletion over North America was greater than expected. In response to this announcement, President George Bush issued an executive order accelerating the phase-out of the production of ozone depleting materials to Dec. 31, 1995. More than 90 nations, representing well over 90% of the world's consumption of ODP's, have now agreed to accelerate the phase-out of production of high ozone depleting materials to Dec. 31, 1995 for developed countries and Dec. 31, 2005 for developing countries pursuant to the protocol.
Historically fluorine and chlorine based solvents were widely used for degreasing, solvating, solvent cleaning, aerosol cleaning, stripping, drying, cold cleaning, and vapor degreasing applications. In the most basic form the cleaning process required contacting a workpiece with the solvent to remove an undesired material, soil or contaminant. In solvating applications these materials were added to dissolve materials in such applications as adhesive or paint formulations.
Cold cleaning, aerosol cleaning, stripping and basic degreasing were simple applications where a number of solvents were used. In most of these processes the soiled item was immersed in the fluid, sprayed with the fluid, or wiped with cloths or similar objects that had been soaked with the fluid. The soil was removed and the item was allowed to air dry.
Drying, vapor degreasing and/or solvent cleaning consisted of exposing a room temperature workpiece to the vapors of a boiling fluid. Vapors condensing on the workpiece provided a clean distilled fluid to wash away soils and contaminants. Evaporation of the fluid from the workpiece provided a clean item similar to cleaning the same in uncontaminated fluid.
More difficult cleaning of difficult soils or stripping of siccative coatings such as photomasks and coatings required enhancing the cleaning process through the use of elevated fluid temperatures along with mechanical energy provided by pressure sprays, ultrasonic energy and or mechanical agitation of the fluid. In addition these process enhancements were also used to accelerate the cleaning process for less difficult soils, but were required for rapid cleaning of large volumes of workpieces. In these applications the use of immersion into one or more boiling sumps, combined with the use of the above mentioned process enhancements was used to remove the bulk of the contaminant. This was followed by immersion of the workpiece into a sump that contained freshly distilled fluid, then followed by exposing the workpiece to fluid vapors which condensed on the workpiece providing a final cleaning and rinsing. The workpiece was removed and the fluid evaporated. Vapor degreasers suitable in the above-described process are well known in art.
In recent years the art was continually seeking new fluorocarbon based mixtures which offered similar cleaning characteristics to the chlorinated and CFC based mixtures and azeotropes. In the early 1990's materials based on the compounds of HCFC began to appear. Three molecules in particular 1,1-dichloro-1-fluoro ethane (HCFC-141b), dichloro trifluoro ethane (HCFC-123), and dichloro pentafluoro propane (HCFC-225) were proposed as replacements for methyl chloroform and CFC blends. As more highly fluorinated materials these materials were less ozone depleting than current ODP's however these materials were weaker solvents and in order to properly clean required the use of co-solvents through the use of blends and azeotropes. Later toxicity studies performed on these materials, however, showed them to have unacceptable character for broad commercial use in cleaning applications. Consequently HCFC-123 was immediately limited in cleaning use, however new toxicity data may allow use in cleaning uses, and HCFC-141b was scheduled for phase out in the U.S. by Apr. 1, 1997. HCFC-225 is still used, however the material is scheduled for phase out by the Clean Air Act after the year 2000. Toxicity concerns with HCFC-225 are a concern to many users and the recommended commercial exposure level of blends of the various isomers of the material is 50 ppm.
The art in the mid 1990's changed as aqueous and semi-aqueous materials became the major choice of replacement for ODP's. The shift to these materials however had two drawbacks for some users. First was the requirement for new cleaning apparatus and machinery capable of handling and drying water. The second was the fact that certain niche applications in the marketplace could not tolerate the use of water in the cleaning process due to damage to the workpiece. This damage was caused by either incompatibility of water with the workpiece, or residual water remaining on the workpiece due to the geometry of the workpiece. This second factor resulted in the art shifting to processes cleaning with solvents and either rinsing with volatile flammable solvents such as acetone and isopropanol, or rinsing with highly fluorinated materials called perfluorocarbons (PFC's).
These PFC rinsing agents were investigated by some users. Other solvents such as low molecular weight alcohols, ketones and alkanes, were also evaluated since they provided users with acceptable rinsing and cleaning, however they were flammable and concerns were raised about their use in production applications. Systems that operated with these inexpensive solvents were very expensive and required explosion-proof machinery and buildings. Perfluorocarbons were deemed to be viable replacements in that they could potentially be operated in inexpensive vapor degreasing equipment such as was used for CFC's. Additionally these materials were inert, inflammable, and had very low toxicity. However, being inert these materials had no solvency, i.e., they did not dissolve the soils they were meant to remove from the workpieces, and were found to be poor cleaning materials. Other perceived drawbacks with these rinsing agents were that they were extremely expensive and required the use of modified vapor degreasers. Later work conducted by the U.S. EPA deemed PFC's to be unacceptable materials due to the fact that they had huge global warming potentials and would remain in the environment for thousands of years.
The art then evolved today to seeking materials for these specialty applications that required PFC like materials that had lower global warming potentials. Highly fluorinated materials such as hydrofluorocarbons (HFC's) and hydrofluoroethers (HFE's) and other highly fluorinated compounds are the result of the most recent disclosures. Like PFC, HFC's and HFE's exhibit the same characteristics, with the exception they are slightly less expensive than PFC's but are still orders of magnitude more expensive than CFC's and chlorinated solvents. Primarily used as rinsing, drying and inerting agents these materials exhibit poor solvency for the soils commonly encountered in most cleaning applications, and will require the use of solvent blends, co-solvent syste
Bixenman Michael L.
Doyel Kyle J.
Gholson Kristie L.
Overstreet Patricia D.
Porter Valerie G.
Crowell & Moring LLP
Kyzen Corporation
Webb Gregory
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