PROCEDE POUR ENDUIRE ET DECORER DES SURFACES EN GENERAL

METHOD FOR COATING AND DECORATING SURFACES IN GENERAL

Abrégé français

La présente invention se rapporte à un procédé pour enduire des surfaces en général, et pour les décorer à l'aide de poudres de couleurs différentes. Ce procédé consiste à: appliquer sur la surface à décorer, préalablement traitée en vue de cette opération, une couche d'un matériau pour enduire sous forme de poudre, dont la couleur correspond à l'arrière-plan souhaité pour la décoration envisagée; chauffer la surface ainsi traitée jusqu'à une température inférieure à la température de cuisson du matériau pour enduire sous forme de poudre, mais suffisante pour assurer ce matériau sur la surface à décorer; appliquer sur la surface ainsi préparée au moins une poudre de couleur correspondant au motif coloré à reproduire, et à l'étendre suivant le dessin souhaité du motif; soumettre la surface ainsi traitée à une cuisson finale pendant un temps et à une température suffisants pour fixer solidement ladite poudre sur ladite surface.

Abrégé anglais

A method for coating surfaces in general, and decorating them with powders of
various colours characterised by: applying to the surface to be decorated,
previously treated for this application, a layer of powdered coating material
of colour corresponding to the desired background for the decoration to be
obtained, heating the surface treated in this manner to a temperature lower
than the baking temperature of the powdered coating material, but sufficient
to fix it to the surface to be decorated, applying to the surface prepared in
this manner at least one powder of colour corresponding to the coloured motif
to be reproduced, distributing it in accordance with the desired pattern of
this motif, subjecting the surface treated in this manner to final baking for
a time and at a temperature sufficient to securely fix said powder to said
surface.

Revendications

1. A method for coating surfaces in general, and decorating them with
powders of various colour characterised by:
-applying to the surface to be decorated, previously treated for this
application, a layer of powdered coating material of colour corresponding to
the desired background for the decoration to be obtained,
-heating the surface treated in this manner to a temperature lower than the
baking temperature of the powdered coating material, but sufficient to fix it tothe surface to be decorated,
-applying to the surface prepared in this manner at least one powder of colour
corresponding to the coloured motif to be reproduced, distributing it in
accordance with the desired pattern of this motif,
-subjecting the surface treated in this manner to final baking for a time and at a temperature sufficient to securely fix said powder to said surface.
2. A method as claimed in claim 1, characterised in that before applying
the powder of colour corresponding to the coloured motif to be reproduced, a
further layer of powdered coating material corresponding to the desired
backgroung is applied and the surface treated in this manner is heated, said
two stages being able to be repeated several times.
3. A method as claimed in claim 1, characterised in that the surface to be
decorated is of metal, metal alloy, wood, glass, ceramic or plastic.
4. A method as claimed in claim 1, characterised by heating the surface
to be decorated, covered with the layer of powdered coating material, to a

temperature of between 75 and 90°C.
5. A method as claimed in claim 1, characterised by passing the surface
to be decorated, covered with the layer of powdered coating material, in front
of a heat source provided in a powder coating line.
6. A method as claimed in claim 5, characterised by passing the surface
to be decorated in front of an ultraviolet source.
7. A method as claimed in claim 5, characterised by passing the surface
to be decorated in front of heating panels.
8 A method as claimed in claim 5, characterised by passing the surface
to be decorated in front of heat lamps.
9. A method as claimed in claim 1, characterised in that a suspension of
powdered coating material in a slow-drying liquid is applied to the surface
already treated with powdered coating material and already subjected to
heating.
10. A method as claimed in claim 9, characterised in that the slow-drying
liquid is an acrylic compound.
11. A method as claimed in claim 9, characterised by using a suspension
of powdered coating material in a slowly evaporating liquid.
12. A method as claimed in claim 1, characterised in that a coating
material in the form of dry powder is applied to the surface already treated with
powdered coating material and already subjected to heating.
13. A method as claimed in claim 12, characterised by applying to the
surface a uniform layer of powdered coating material and then removing a part

of this latter, so that the remaining part forms the required decoration.
14. A method as claimed in claim 13, characterised by removing, by
suction, part of the powder previously deposited on the surface to be
decorated.
15. A method as claimed in claim 13, characterised by removing, by
wiping, part of the powder previously deposited on the surface to be
decorated.
16. A method as claimed in claim 15, characterised in that the wiping is
effected under moist conditions.
17. A method as claimed in claim 15, characterised in that the removal of
the powder by wiping is effected with a manually operated tool.
18. A method as claimed in claim 15, characterised in that the removal of
the powder by wiping is effected with a mechanically operated tool.
19. A method as claimed in claim 13, characterised by applying the
powdered coating material using a silkscreen stencil reproducing the pattern
of the desired decorations.
20. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of polyester resins.
21. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of epoxy resins.
22. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of epoxypolyester resins.
23. A method as claimed in claim 1, characterised by using powdered

10
coating materials in the form of polyester-hydroxyalkylamide resins.
24. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of polyurethane resins.
25. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of acrylic resins.
26. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of epoxyacrylic resins.
27. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of acrylo-polyurethane resins.
28. A method as claimed in claim 1, characterised by using powdered
coating materials in the form of acrylopolyester resins.
29. A method as claimed in claim 1, characterised by subjecting the
surface to be treated to final baking at a temperature of 170-190°C for a time
of 15-25 minutes.

Description

CA 0222~34 1998-02-0~
WO 97/05965 PCT/EP96/03264
METHOD FOR COATING AND DECORATING SURFACES IN GENERAL
This invention relates to a method for coating surfaces in general and
decorating them with powders of various colours.
The surfaces of natural materials, such as wood and marble, have an
5 outer appearance which is very pleasing to the view These natural materials
have however numerous drawbacks such as high cost, an increasingly more
limited availability due to environmental problems and often poor resistsnce to
atmospheric agents.
In addition marble has the added drawbacks of considerable weight, as
10 it can be formed only into slabs of a certain minimum thickness, and with only
flat surfaces, unless further costly surface machining is undertaken.
To combine the aesthetic merits of these natural mal:erials with low
cost and a large variety of shapes and dimensions, it has already been
proposed to decorate metal, plastic, ceramic and other surfaces to imitate
15 these natural materials.
A known method of decoration is photofiliming, in which a powder or
liquid coating forming the background colour is applied to the surface to be
decorated, followed by the application thereon of a film reproducing the
required decoration. This method has various drawbacks, including:
20 - high cost due both to the intrinsic cost of the materials and the cost of
adapting a traditional coating plant,
~ -an unsatisfactory result from the aesthetic viewpoint due to the excessive
uniformity of the decoration,

-
CA 0222~34 1998-02-0
- limited resistance to atmospheric agents.
Another known decoration method is to apply a PVC covering to the
surface concerned! and in particular to form by traditional methods a PVC film
reproducing the desired decorations. in irnitation of wood or marble. and to
glue this film to the surface to be decorated.
This method has also proved unsatisfactory in that it also has
numerous drawbacks! including:
- an aesthetic result which is not natural
- a hi~h final cost of the product obtained!
10 - limited resistance to atmospheric agents.
FR-A- 2 340 1~0 discloses a method of coating a surface comprising:
- applying a first coating powder
- partially melting the powder and maintaining the temperature lower than the
temperature at whlch a second powder melts completely
15 - applying a second powder
- melting the whole of applied powder.
All these drawbacks are overcome by a method for coating and
decorating with powders of various colours surfaces in general as described in
claim 1.
A preferred embodiment of the present invention is described in
greater detail hereinafter with reference to the accompanying drawings! in
which
Figure 1 is a perspective view of a surface to be subjected to the treatment
~~NDE0 si~

CA 02225534 1998-02-05
-~a-
according to the invention:
Figure 2 shows it after the initial heatin~ stage, and
Figure 3 shows it after final baking.
The method of the invention is applicable to any metal. seramic.
5 plastic, wood or glass surface to be decorated, in such a manner as .o assume
the typical appearance of a natural surface. such as wood or marble.
A~i,"l~'rr ''~

CA 0222~34 1998-02-0~
WO 97/05965 PCT/EP96/03264
The surface 2 is firstly subjected to specific treatment depending on
the nature of the surface to be decorated, but which in itself does not form part
of the invention.
To the surface 2 treated in this manner there is then electrostatically
applied a layer of powdered coating material 4, in particulsr of polyester,
epoxy or epoxypolyester resins, of colour corresponding to the desidered
background colour for the decoration to be obtained. Polyester-
hydroxyalkylamide resins, polyurethane resins, acrylic resins, epoxyacrylic
resins, ~crylopolyure~h~ne r~sins or acrylopolyester resins can a!so be
10 applied. After the powdered coating material 4 has been applied to the
surface, it is heated to a temperature less than the baking temperature of said
coating, but sufficient to cause it to fix to the surface to be decorated
Indicatively the heating temperature is about 75-gO~C and can be achieved by
providing, in a traditional powder coating line, pairs of catalytic heating panels,
15 heating lamps, ultraviolet lamps, etc., between which the surface to be
decorated is passed.
In the case of particular decorations for which one application stage
and one heating stage for the coating layer are found to be insufficient, these
two stages can be repeated.
After the heating stage, the purpose of which is to fix a layer of
powdered coating material 4 to the surface to be decorated, a second
powdered coating material 6 of colour corresponding to the coloured motif to
be reproduced is applied to the surface prepared in this manner.

CA 0222C.C.34 1998-02-0C.
WO 97/05965 PCT/EP96/03264
This second powdered coating material also preferably consists of the
aforesaid resins.
The second powdered coating material 6 can be applied either as a
suspension of the powder 6 in a slow-drying liquid vehicle, or can be applied
5 in the dry state. In the first case a liquid of slow evaporation or a slow-drying
acrylic liquid is preferably used, the powdered coating material 6 being mixed
into this liquid to form a suspension The suspension is then spread over the
surface to be decorated with automatic or manual applicators which arrange
the powdered coating material 6 in the required decorative pattern. In
10 particular in reproducina, the pattern of wood grains, because of the slow
drying of the acrylic liquid, the decoration can also be modified by direct
intervention of the operator, who can even produce ~he characteristic form of
wood knots.
To solve special problems, intermediate treatments other than the
15 application of powders and their heating can be provided.
If the powdered coating material 6 is applied dry, its application can be
by various methods.
A first method ccnsists of applying to the surface to be decorated a
uniform layer of powder 6 and then removing the excessive portion so as to
20 form the desired graining,. This removal can be achieved either by suction or by a process of coordinated wiping by mechanically or manually operated
tools, such as brushes, blades, pads, sponges etc.
In particular, a tool can consist of an autom.atic applicator formed from

CA 0222F7F734 1998 - 02 - 0~.
WO 97/05965 PCT/EP96/03264
a pair of cylindrical rotary pads with the surface worked according to the notifto be reproduced or rotary brushes sprayed with liquids and used for partially
removing the excess c~uantity of powder, previously applied to the piece to be
treated, to leave on its surface the particular decoration to be obtained.
A different method of applying the powder 6 is to use a sort of
silkscreen stencil reproducing the required decorative pattern.
On termination of this stage, the entire assembly is balced, indicatively
at 180~G for 20 minutes.
The result of this treatment is a surface having an outer appearance
totally simil~3r to the surfaces of natural materials, but with decidedly bettercharacteristics than those obtainable by traditional methods.
Costing tearing tests, chequering tests and acetic salt-spray tests were
carried out on samples of surfaces obtained in this manner and gave positive
results. In particular, these latter tests exceeded more than 1000 hours withoutany formation of bubbles or blisters.
From the aforegoing it is apparent that the method of the invention has
numerous advantages, and in particular:
- it enables existing coating plants to be used, with only simple modifications,- it achieves an aesthetically satisfying result to the extent of not revealing the
artificial nature of the support,
- it presents optimum resistance to atmospheric agents,
- it is of low cost because of the use of low-cost materials,
- it enables surfaces of any geometry and area to be decorated,

CA 0222~34 1998-02-0~
WO 97/05965 PCT/EP96/03264
- it enables the surfaces of small-thickness and hence low-weight supports to
be decorated.
The method of the invention can be used for forming a large number o
products, including:
5 -metal section bars for window frames with a wooden or marble outer
appearance,
-metal plates for houselhold electrical appliances with a wooden or marble
outer appearance,
- chipboard or MI~F panels for kitchens with a wooden or marble outer
1 0 appearance,
- metal urban furniture elements with a wooden or marble outer appearance,
- metal sheets and sec,tion bars for use in the automobile, naval and
aeronautical sectors.
It should be noted that in addition to the wooden or marble outer
15 appearance, other appearances are possible comprising multiple coloration.