Coating processes – Coating pavement or the earth
Reexamination Certificate
2000-03-15
2001-12-25
Beck, Shrive (Department: 1762)
Coating processes
Coating pavement or the earth
C427S385500, C427S393600, C427S421100, C106S310000, C106S287170, C106S287180, C524S398000, C524S399000
Reexamination Certificate
active
06333068
ABSTRACT:
This invention relates to a drying time accelerator for a water-based paint comprising:
mineral particles,
a polymer binder in aqueous dispersion,
a dispersing agent consisting of an emulsion polymerisation agent, and
a drying time accelerator.
The mineral particles of the paint may comprise notably pigments as well as fillers.
The invention also relates to a water-based paint and to a method of application for such paint corresponding to the drying time accelerator.
Horizontal markings, notably for carriage ways are usually made with a coating machine provided with paint spray nozzles and light-reflecting ball dispensers.
In order to preserve the environment, the road users and the workers from solvent emanations, solvent-based road paints are gradually and advantageously replaced with water-phase paints, of the type defined above. The emulsion polymerisation agent enabling polymer dispersion consists generally of surfactants with anionic charge that ultimately stabilise the particle dispersion of the polymer binder.
The draw back of this paint type lies in the fact that the drying time is generally longer than in the case of a solvent-based paint. Indeed, the formation of the continuous binder film is obtained by water evaporation. However, the latter is less volatile than the solvents used commonly for solvent-based paints. The drying time is particularly long in case of high humidity content in the air and when the paint is coated in chilly conditions.
However, the road should be put back into operation as quickly as possible to reduce traffic delays and facilitate the good performance of the various operations on the site.
In order to shorten the drying time of water-based paint, it has been suggested to add water-soluble salts. This embodiment is however little efficient in the very frequent cases when the binder particles are stabilised simultaneously by anionic emulsifiers and by non-ionic emulsifiers. The drying time is then not reduced significantly.
The addition of acid has also been suggested in order to reduce the pH sufficiently. Below a certain pH threshold, the surfactants with anionic charge that stabilise the dispersion lose their anionic character while inducing coagulation of the dispersion. The efficiency of this method depends however very much on the nature of the anionic emulsifier and decreases in the case of an important presence of non-ionic emulsifier. On the other hand, the presence of acid gives an accelerated yellowing of the paint with the elapsed time.
This invention relates to a drying time accelerator for a water-based paint as defined above, which enables quick drying of the paint with respect to the existing methods, including with the significant presence of non-ionic emulsifier.
The accelerator according to the invention may also enable to provide high resistance to wear as well as ageing caused by weather exposition, while preventing degradation of the aspect of the paint with the elapsed time.
The accelerator according to the invention may also advantageously be neither toxic nor detrimental to human health or the environment since it may be used notably in weakly acid medium or in neutral medium.
The invention also relates to a water-based paint and a method for applying a water-based paint, with the advantages mentioned above.
To this end, the invention relates to a drying time accelerator for a water-based paint comprising:
mineral particles,
a polymer binder in aqueous dispersion,
a dispersing agent consisting of an emulsion polymerisation agent, and
a drying time accelerator.
According to the invention, the accelerator has a polymeric structure, it is water-soluble and comprises cationic charges.
Thus, the accelerator acts simultaneously by coagulation and by bridging between the binder particles. This accelerator may for instance enable to shorten the drying time of the paint by more than 30 minutes in average and common coating conditions, to less than 2 minutes.
According to a first embodiment, the drying time accelerator is a mineral accelerator selected among the metallic polychlorides, such as aluminium polychlorides and the metallic polyoxychlorides, such as iron polyoxychloride.
According to a second embodiment, it consists of an organic accelerator selected among cationic nitrogen polymers, notably synthesis polymers derived from polyacrylamide.
Advantageously, the dosage of the accelerator ranges between 0.2% and 2% in active material with respect to paint and preferably between 0.1% and 1%.
It is advisable that the accelerator should be in a weakly acid or neutral medium. The invention also relates to a water-based paint comprising:
mineral particles,
a polymer binder in aqueous dispersion,
a dispersing agent consisting of an emulsion polymerisation agent, and
a drying time accelerator.
This water-based paint is characterised in that the accelerator is according to the invention.
Advantageously, the paint comprises non-ionic emulsifiers. These contribute efficiently to stabilising the binder particles.
Preferably, the polymer binder is of acrylic, styrene-acrylic and/or vinyl-acrylic type.
The invention also relates to a method for applying a water-based paint on a support, according to which:
the paint is sprayed onto the support, and
light-reflecting balls are distributed in the paint.
Moreover, a drying time accelerator is incorporated to the paint.
This method is characterised in that the paint is according to the invention.
The light-reflecting balls are preferably glass balls.
The drying time accelerator can be applied by specific and stand-alone equipment, by adding a complementary system to the paint application machines or by transformation of the said machines.
Incorporation of the accelerator into the paint can be made by gravity or pressure spraying.
Preferably, the accelerator is incorporated into the paint after ball distribution.
Thus, the light-reflecting balls have the time to be nested sufficiently within the paint film before rapid drying by addition of the accelerator.
According to another embodiment, the accelerator is incorporated directly into the paint at the time of applying the paint, before distributing the light-reflecting balls.
REFERENCES:
patent: 4839198 (1989-06-01), Lonis et al.
patent: 4900592 (1990-02-01), Hahn, Jr. et al.
patent: 5312863 (1994-05-01), Van Rheenen et al.
patent: 5340870 (1994-08-01), Clinnin et al.
patent: 5348870 (1994-09-01), Miyazawa et al.
patent: 5544972 (1996-08-01), Boldt
patent: 5861188 (1999-01-01), Schall et al.
patent: 200249 (1986-12-01), None
patent: 525977 (1993-02-01), None
Derwent Publication XP002099083 and the abstract of JP 58 036683, (Mar., 1983).
Calvin Pierre
Durand Graziella
Poirier Jean-Eric
Beck Shrive
Calcagni Jennifer
Colas
Greenblum & Bernstein
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