Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1997-12-08
2001-01-16
Gupta, Yogendra (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, C510S206000, C510S207000, C510S212000, C134S038000
Reexamination Certificate
active
06174847
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition for stripping paints, varnishes or lacquers coating a substrate, such as metals and wood.
BACKGROUND OF THE INVENTION
In the industrial stripping sector, shutters, windows, doors and radiators are stripped, as is any mechanical component (e.g.: wheel hubs, wheel rims, etc.). The industrial stripping of paints and the like is carried out by immersing the components to be stripped in a liquid bath formulated under hot or cold conditions, it being possible for this liquid bath to be stirred or not to be stirred. The components are left in the bath for a certain period until stripping is achieved (degradation or removal of the paint, depending on the systems). Next, the components are removed from the bath and are rinsed with a jet of pressurized water (“carcher”), the flakes or lumps of paint then being removed by the pressure of the water jet. When the bath contains a strong base of the NaOH type, a neutralization operation is carried out in an acid bath consisting of a solution of sulphur or hydrochloric acid.
The formulation currently used in industrial stripping are either chloride-based or alkali-based. Chloride baths or formulations are mixtures based on methylene chloride, methanol (5 to 10% by weight) and aromatics (toluene, xylene in a proportion of a few percent). The mixtures can also contain activators, which can be acidic (such as formic acid) or basic (such as monoethanolamine). Chloride baths are used cold since methylene chloride is very volatile and the odor it gives off is highly suffocating. The stripping action takes place by removal of the paint with formation of flakes. Industrial stripping technicians currently wish to replace chloride by a substitute for environmental reasons.
Alkaline baths or formulations are essentially based on sodium hydroxide in water to which are added sodium glycolate, complexing agents and wetting agents. The mixtures are used hot, at a temperature of about 50° C. to 100° C., and the stripping time is halved for every 20° C. rise in temperature.
The mechanism of action is totally different to that of the chloride formulations since these formulations degrade the paint by reaction of the sodium hydroxide with the polymer.
In particular, with glycerophthalic paints and alkyd paints, saponification of the ester functions takes place, which degrades the paint, reducing it to powder. When dispersed in the bath, this powder forms a sludge, which is a pet hate of stripping technicians. This sludge is virtually unfilterable (blocking). Moreover, alkaline formulations are less effective on other types of paint (epoxy, polyurethane, etc.). Industrial stripping technicians thus also wish to find a substitute formulation of greater versatility which does not lead to degradation of the paint.
SUMMARY OF THE INVENTION
Novel stripping formulations for paints, varnishes or lacquers, have been investigated so as to satisfy the current needs described above and constitute good-value formulations an advantageous replacement for the known chloride and alkaline formulations.
The novel stripping composition according to the present invention satisfies these aims; it is characterized in that it consists of or comprises:
(A) 5 to 90 parts by weight, preferably 10 to 80 parts by weight, of water;
(B) 2 to 47.5 parts by weight, preferably 5 to 45 parts by weight, of benzyl alcohol;
(C) 2 to 47.5 parts by weight, preferably 5 to 45 parts by weight, of dimethyl sulphoxide or of N-methylpyrrolidone, (A)+(B)+(C) representing 100 parts by weight.
The proportion of water, which can be large, makes this composition a very advantageous formulation in terms of costs.
The stripping composition according to the invention can also comprise:
(D) at least one activator, which may be chosen in particular from monoethanolamine (MEA), triethanolamine (TEA), formic acid, pyrrole, TEA/formic acid mixtures, benzaldehyde, MEA/benzaldehyde mixtures and alkali metal hydroxides such as sodium hydroxide (NaOH), in a proportion in particular of from 0.1 to 10 parts by weight per 100 parts by weight of (A)+(B)+(C).
The preferred activators are MEA/benzaldehyde mixtures (in particular 1 part by weight of MEA and 2 parts by weight of benzaldehyde), benzaldehyde and NaOH.
The stripping composition according to the invention can also additionally comprise:
(E) at least one surfactant, in a proportion in particular of from 0.1 to 10 parts by weight per 100 parts by weight of (A)+(B)+(C); as examples of nonionic surfactants, mention may be made of ethoxylated surfactants of the “Metox” series, sold by the company “SEPPIC” (for example the ethoxylated methyl ester fraction comprising 20 units of ethylene oxide “Metox 20 EO”); as examples of ionic surfactants, mention may be made of sodium dodecyl sulphate;
(F) at least one thickener chosen in particular from acrylic thickeners, in a proportion in particular of from 0.1 to 10 parts by weight per 100 parts by weight of (A)+(B)+(C); as specific examples of acrylic thickeners, mention may be made of the acrylic resins sold under the name “Carbopol” by the company Goodrich, BF, Co., whose production process is described in American patent U.S. Pat. No. 4,419,502 entitled “Polymerization process for carboxyl-containing polymers”.
In accordance with a particularly advantageous embodiment of the present invention, the stripping composition comprises neither surfactant nor thickener, and in this case is in the form of an unstable emulsion.
In accordance with two other embodiments of the present invention, the stripping composition comprises at least one surfactant and no thickener, and in this case is in the form of a microemulsion, or it comprises at least one thickener and no surfactant and is in the form of a thickened emulsion.
The present invention also relates to a process for stripping paints, lacquers and varnishes applied to a substrate, using a stripping composition as defined above, characterized in that the said substrate is immersed in a bath which is optionally heated (for example to a temperature of between 40 and 70° C.) and the stripping composition is optionally stirred when it is in the abovementioned microemulsion or unstable emulsion forms, for a duration which is sufficient to bring about the removal of the paint, varnish or lacquer, or in that a stripping composition in the abovementioned thickened emulsion form is applied to the said substrate and is left to act for a duration which is sufficient to bring about the removal of the paint, varnish or lacquer.
The examples which follow illustrate the present invention without, however, limiting its scope. In these examples, the percentages of the compositions are given on a weight basis.
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Database WPI, Week 8948, AN 89-350370 (ES 2 008 593), Derwent Publications, Ltd., London GB.
Elf Atochem S.A.
Gupta Yogendra
Millen White Zelano & Branigan P.C.
Petruncio John M
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