Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-11-28
2003-04-15
Bozer, Charles (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S201000, C510S245000, C510S254000, C510S255000, C510S405000, C510S407000, C510S432000, C134S038000
Reexamination Certificate
active
06548464
ABSTRACT:
TECHNICAL FIELD
This invention relates to compositions for paint and coating removal. More particularly, this invention relates to compositions containing an alkylene carbonate or dialkyl carbonate or both, and an alcohol.
BACKGROUND OF THE INVENTION
Paint removing compositions are commonly used in industry, such as for stripping paint from airplane fuselages. Conventional paint remover compositions include methylene chloride, phenol, or caustic. Each of these materials, however, has inherent problems during use. While methylene chloride based compositions are very effective as paint removers, methylene chloride is a highly volatile material that is considered toxic. Phenol is also highly toxic. Caustic, while not posing problems with toxicity, can burn and corrode aluminum. Additionally, methylene chloride, phenol or caustic-based strippers will attack, soften and remove all layers of paint including the primer or undercoat, making selective removal difficult.
In some applications it is desirable to be able to remove one or more layers of coating, while leaving the priming coats intact. Aircraft applications are examples of situations in which it is not desirable to remove all of the paint layers. By removing the upper coating layers while leaving the highly toxic chromium-based primer material intact, the paint removal process would generate much less hazardous waste and thus be much less costly to perform. Due to the deficiencies and disadvantages of conventional paint removing compositions, new paint removing compositions, especially those capable of selective removal, are highly desirable.
SUMMARY OF THE INVENTION
The invention is a composition useful as a paint remover, comprising alkylene carbonate and an alcohol. This composition may also contain a thickener, a surfactant, or a corrosion inhibitor.
In another broad aspect, this invention is a process for removing paint, comprising applying a composition containing alkylene carbonate and an alcohol to a painted surface for a time, and under conditions effective to cause separation of the interface between the topcoats and the primer or undercoat of the paint. The composition may also contain a thickener, a surfactant, or a corrosion inhibitor.
In another broad aspect, this invention is a process for removing paint, comprising applying a composition containing an alkylene carbonate, a dialkyl carbonate, or both and an alcohol to a painted surface for a time, and under conditions effective to reduce adhesion between the topcoats and the primer or undercoat of the paint. The composition may also contain a thickener, a surfactant, or a corrosion inhibitor.
In another broad aspect, this invention is a process for removing paint, comprising applying a composition containing a dialkyl carbonate and an alcohol to a painted surface for a time, and under conditions effective to reduce adhesion between the topcoats and the primer or undercoat of the paint. The composition may also contain a thickener.
The surfaces to be treated may be sealed with a variety of sealants, such as polysulfide, polyurethane, lacquer, epoxy, and the like. The compositions can be used to remove paints and coatings from furniture, automobiles, boats, trains, airplanes, military vehicles, and so forth.
The present invention has a number of advantages. For example, the compositions have several important attributes, including low toxicity, high efficacy in removing paint and coatings, and neutral pH (or slightly acidic or slightly basic pH). Furthermore, in the case of propylene carbonate, the propylene carbonate breaks down into propylene glycol, which is non-toxic. Thus, the propylene carbonate compositions of this invention are environmentally friendly, particularly as compared to chlorinated hydrocarbons and the like which are commonly used for paint and coating removal. In addition, the compositions of this invention reduce adhesion between the topcoats and the primer or undercoat of the paint in such a short period of time that it is envisioned that the compositions of this invention might be applied in liquid form, as opposed to the gels that are commonly used.
The compositions of the present invention have surprisingly superior paint removing properties. The compositions may be blended with additional co-solvents, corrosion inhibitors, surfactants and thickeners, or may be used directly to effect paint removal. The compositions of this invention are nonflammable, of low volatility, and free of carcinogenic chemicals.
DETAILED DESCRIPTION OF THE INVENTION
The compositions of this invention contain an alkylene carbonate or a dialkyl carbonate or both, and an alcohol.
The alkylene carbonate used in the present invention can contain from 3 to 10 carbon atoms. Representative examples of alkylene carbonates that may be employed in the practice of this invention include, but are not limited to, ethylene carbonate, propylene carbonate and butylene carbonate, but the preferred carbonate is propylene.
The dialkyl carbonate used in the present invention may contain from 3 to 25 carbon atoms. The dialkyl carbonate may be of formula R—CO
3
—R′, wherein R and R′ may be the same or different, and may independently in each occurrence be an alkyl group of from 1 to about 12 carbon atoms. In one embodiment, the dialkyl carbonate may be dimethyl carbonate, diethyl carbonate, or a mixture of those two.
The compositions of this invention include an alcohol. Representative examples of such alcohols include methanol, ethanol, propanol, butanol, and benzyl alcohol, but the preferred alcohol is benzyl. Generally, compositions of this invention contain from about 0.1 to about 10 percent by weight alcohol.
In certain embodiments of this invention, the compositions contain from about 90 to about 99.9 percent by weight alkylene carbonate. In certain other embodiments of this invention, the compositions contain from about 90 to about 99.9 percent by weight dialkyl carbonate, and from about 0.01 to 10 percent alcohol.
In addition to the components described above, the compositions of this invention may optionally contain thickeners, glycol ethers such as propylene glycol methyl ether (PM), dipropylene glycol methyl ether (DPM), or dipropylene glycol n-butyl ether (DPNB), surfactants, stabilizers, corrosion inhibitors, and other additives commonly used in paint removers.
Thickeners may be used in the present invention include, but are not limited to, cellulose ethers such hydroxypropyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, methyl cellulose, and other alkyl or hydroxyalkyl cellulose, silica including colloidal silica, clays such as bentonite and montmorillonite starch, alumina including colloidal alumina, high molecular weight polyethylene oxides, polyvinyl pyrrolidone and methyl vinyl ether/maleic anhydride copolymers. Certain hydroxy alkyl cellulose ethers and certain experimental polymers are particularly effective and resistant to breakdown in the practice of this invention. Such cellulose ethers are available commercially from The Dow Chemical Company under the trade name Methocel® F4MPRG and Dow's Experimental Polymer SCS 41067.06. When a thickener is used, the amount of such thickener can vary depending on the desired level of thickening for the given application. In general, the amount of thickener employed is about 1 to about 4 percent by weight.
Corrosion inhibitors that may be used in the present invention include, but are not limited to, ethoxylated butynediol, petroleum sulfonates, blends of propargyl alcohol and thiourea. If used, the amount of such corrosion inhibitors is typically up to about 10% by weight of the total composition.
Surfactants which may optionally be used in the practice of this invention include, but are not limited to, non-ionic, anionic, cationic and amphoteric surfactants, such as monocarboxyl cocoimidoazoline, higher alkyl sulfate sodium salts, tridecyloxy poly(alkyleneoxy ethanol), ethoxylated or propoxylated alkyl phenol, alkyl sulfoamides, C10-18 alkylaryl sulfonates such as alkylbenzene sulfonates, coco
Machac, Jr. James R.
Marquis Edward T.
Nieh Edward Chung-Yit
Woodrum Susan A.
Bozer Charles
Gardere Wynne & Sewell LLP
Huntsman Petrochemical Corporation
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