Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-07-19
2002-03-19
Boyer, 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...
C510S202000, C510S210000, C510S212000, C510S407000, C510S432000, C134S038000
Reexamination Certificate
active
06358901
ABSTRACT:
The present invention relates to a composition for stripping coatings, for example paint-based coatings.
The invention also relates to a method for stripping paints deposited on a substance, using said composition.
The first paint stripping compositions were based on methylene chloride and/or 1,1,1-trichloroethane (T.1.1.1.) (see, for example, United States patent U.S. Pat. No. 2,507,983 and German patent DE-A-2 524 752).
Such paint stripping compositions have the advantage of being highly effective and cheap. However, they can cause environmental damage and in particular can damage the ozone layer (Montreal protocol aimed at halting the use of T.1.1.1., normally at the end of 1995).
A substantial advance was made when such chlorinated solvents were replaced either by lactames or lactones, usually N-methyl-2-pyrrolidone or &ggr;-butyrolactone (U.S. Pat. No. 4,120,810) or by a mixture of alkyl diesters of dibasic acids, a by-product of the production of monomers required to prepare polyamides (DE-A-3 438 399).
The above compositions are not always suitable for stripping coatings of different types such as water-based paint oil-based paint, lacquers, varnishes and plastic resins.
U.S. Pat. No. 2,694,658 discloses the use of dimethylsulphoxide as a paint stripping solvent. However, that type of solvent has the disadvantage of being very expensive and has to be used in large quantities.
European patent EP-A-0 573 339 discloses a novel stripping composition comprising a polar aprotic solvent and an ether comprising one or more methoxy groups and with well defined characteristics such as a flash point of more than 0° C. and a gram-molecular volume of less than 160.
The most economically interesting ether claimed is anisole. However, anisole has an unsatisfactory flash point as regards certain regulations in particular those concerning transport of flammable materials.
Further, anisole has a very strong odour which necessitates the use of an agent to mask the odour.
The market therefore has a need for an improved stripping composition.
Put precisely, the present invention aims to provide a stripping composition, in particular for stripping paints, characterized in that it comprises at least one aromatic ether comprising an alkoxy group containing at least two carbon atoms and at least one polar aprotic solvent.
Preferably, the flash point of the aromatic ether is 50° C. or higher.
In the present text, the term “alkoxy” is used generically as it also designates other ether groups as will be described below.
More particularly, aromatic ethers which are suitable for the invention and which can be cited are those with formula (I):
where:
R represents an alkyl, cycloalkyl or aralkyl radical containing at least two carbon atoms, preferably 2 to 12 carbon atoms;
X represents a hydrogen atom, an alkyl or alkoxy radical containing 1 to 4 carbon atoms, or a halogen atom, preferably a fluorine or chlorine atom.
Preferably, the ethers used have formula (I) where R represents an alkyl, cycloalkyl or aralkyl radical containing 2 to 7 carbon atoms.
Preferred ethers with formula (I) are those comprising a radical R which represents an ethyl. n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl radical, a cyclohexyl radical, a benzyl radical or an alkoxy radical containing 1 to 4 carbon atoms, preferably 2 to 4 carbon atoms such as ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy or tert-butoxy.
Regarding X, more particularly this represents a hydrogen atom, a fluorine atom, a methyl, ethyl, methoxy or an ethoxy radical.
The invention does not exclude the presence of a plurality of groups X, preferably at most 3.
Examples of aromatic ethers which can be mentioned include the following compounds;
phenetole;
4-ethylphenetole;
2-fluorophenetole;
3-fluorophenetole;
4-fluorophenetole;
propylphenylether;
isopropylphenylether
butylphenylether;
isobutylphenylether;
pentylphenylether;
sec-butylphenylether.
Preferably, the ether used in the compositions of the invention is phenetole.
In accordance with the invention, the stripping compositions of the invention associate an ether as defined above with a polar aprotic solvent.
Examples of polar aprotic solvents which can be cited are dimethylsulphoxide (DMSO), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N-methylmorpholine, &ggr;-butyrolactone, acetylacetone, acetonitrile and mixtures thereof.
Preferably, dimethylsulphoxide is used.
The present invention provides a composition for stripping paints comprising, by volume:
(1) 1% to 90% of a polar aprotic solvent;
(2) 1% to 90% of at least one aromatic ether comprising an alkoxy group containing at least two carbon atoms and with a flash point of more than 50° C.
Preferred compositions of the invention thus comprise at least, by volume:
(1) 20% to 80% of a polar aprotic solvent, more preferably 50% to 70%;
(2) 20% to 80% of an aromatic ether comprising an alkoxy group containing at least two carbon atoms, more preferably 30% to 50%.
The following are examples of compositions of the invention:
(1) 1% to 90%, preferably 20% to 80%, more preferably 50% to 70%, of a polar aprotic solvent selected from dimethylsulphoxide, dimethylformamide, N-methyl-2-pyrrolidone, N-methylmorpholine, &ggr;-butyrolactone, acetylacetone, acetonitrile and mixtures thereof;
(2) 1% to 90%, preferably 20% to 80%, more preferably 30% to 50%, of an aromatic ether comprising an alkoxy group containing at least two carbon atoms.
Preferred compositions of the invention comprise:
(1) 1% to 90%, preferably 20% to 80%, more preferably 50% to 70% of a polar aprotic solvent selected from dimethylsulphoxide, dimethylformamide, N-methyl-2-pyrrolidone, N-methylmorpholine, &ggr;-butyrolactone, acetylacetone, acetonitrile and mixtures thereof;
(2) 1% to 90%, preferably 20% to 80%, more preferably 30% to 50%, of phenetole.
The compositions of the invention can also contain other conventional additives.
Examples of such additives which can be mentioned include a co-solvent, a surfactant, a thickener, an activator, a corrosion inhibitor, an evaporation retardant or any other additive provided that it is not a chlorinated solvent.
Adding a co-solvent can generally increase the stripping performance of a composition by facilitating dissolution of the plasticisers present in the paint.
Examples of co-solvents which can be used are an aromatic or aliphatic, odour-free liquid hydrocarbon solvent with a flash point of more than 50° C., preferably more than 70° C., such that this solvent is not classifiable as a flammable solvent.
Examples of such solvents derived from petroleum and with a high flash point are mineral spirits such as white spirit and naphthas.
Commercially available products which can be used in the compositions of the invention are ISOPAR® from Exxon, SOLTROL® from Shell and HI-SOL® solvents from Ashland, in particular SOLVESSO® 100, 150 and 200.
However, as these hydrocarbon derivatives are classified as Xn (harmful), they are gradually being replaced by solvents of the dialkyl ester of a dibasic aliphatic acid type to avoid the final product being labelled as Xn.
Thus, preferably, a C
1
-C
4
dialkyl ester of at least one dibasic C
4
-C
6
aliphatic acid is used.
The dibasic acid ester mixture is a mixture of ester derivatives essentially of adipic, glutaric and succinic acids; in particular the alkyl groups of the ester portion are selected from methyl and ethyl groups, but they can also be propyl, isopropyl, butyl, n-butyl or isobutyl groups.
The above C
4
to C
6
dibasic acids are in fact by-products from preparing adipic acid which is one of the principal monomers of polyamides, and the dialkyl esters are obtained by esterification of this by-product which generally contains, by weight, 15% to 30% of succinic acid, 50% to 75% of glutaric acid and 5% to 25% of adipic acid.
The dibasic acid esters are products which are commercially available. Commercially available products which can in particular be cited are Rhodiasolv RPDE® sold by Rhone-Poulenc and “Du Pont Dibasic Esterst®” sold by Du Pont de Nemours.
Rega
Galliot Jean-Claude
Joye Jean-Luc
Boyer Charles
Rhodia Chimie
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