FR3096686A1 - SOLID COMPOSITION TO FORM SURFACE COATINGS - Google Patents

Abstract

The present invention relates to a solid composition in the form of a powder capable of forming a surface coating on a support, said composition comprising at least one film-forming organic material, zirconium hydrogenphosphate and at least one material chosen from coloring materials. organic and pigments. It also relates to a process for preparing this composition and its use for the purposes of forming surface coatings on supports, in particular glass.

Description

SOLID COMPOSITION FOR FORMING SURFACE COATINGS

The invention relates to a solid composition of the powder type capable of forming a surface coating on a support, in particular formed of a glass, ceramic, metal or plastic material. The invention also relates to a process for preparing this composition and a process for preparing a coating from this composition.

Solid compositions dedicated to forming surface coatings on supports of all types of wood, steel, plastic, glass are now recognized as being advantageous alternatives to liquid formulations such as paints and varnishes. In contrast to these liquid formulations, powder-type compositions do not require the use of a solvent. Their use is easy and clean. Thus, they are most often applied by electrostatic spraying or by a triboelectric process. Depending on the nature of the support considered, heating of the part or its surface to be treated can sometimes be carried out before or after the immobilization of the solid composition on the surface to be treated.

In general, these solid compositions consist essentially of an organic material of the synthetic resin(s) type capable of forming the expected coating and of an inorganic material of the mineral filler and pigment type, the latter having more particularly the purpose of conferring a translucent and/or colored effect on the final coating.

Thus, in the case of a formulation dedicated to forming a surface varnish, the transparent or translucent appearance is adjusted by the choice of these inorganic materials and most often, the pigment retained for this purpose is titanium dioxide. White in color, it increases the whiteness or shine of coatings. These pigments also have interesting opacity and covering power and satisfactory mechanical properties. Titanium dioxide pigments are thus particularly considered to confer a decorative effect of the opaline type, that is to say translucent, to surface coatings. These coatings are particularly very useful for imparting decorative effects to articles of the architectural type in public building works, in the glass industry, for example for the ornamentation of hollow glasses, bottles in perfumery, bottles, containers cosmetics, and also in the ceramics industry such as with respect to tableware and sanitary ware. These titanium dioxide pigments are also widely used to modify the color hues provided by other organic or inorganic coloring agents.

However, there is a desire to significantly reduce or even eliminate the use of titanium dioxide pigments because their safety with regard to living organisms is now in question. An alternative pigment to titanium dioxide is zinc sulfide. However, the dispersion of this second pigment within an organic material such as synthetic resin(s) proves to be more difficult.

Indeed, the constituent raw materials of the solid compositions dedicated to forming coatings are conventionally combined by successively considering the production of premixes of certain raw materials, the mixing of these premixes by extrusion, their grinding and a micronization of the final mixture thus obtained for the turn into a fine powder. However, this mode of preparation does not give complete satisfaction in terms of coloring modulation. In particular, the color effect is not always reproduced optimally. It can therefore be difficult to faithfully reproduce a specific effect such as a shade using currently available powders.

The object of the present invention is precisely to propose new solid compositions for coating making it possible to overcome the aforementioned problems.

More specifically, the present invention provides access to solid powder-type compositions capable of forming coatings with improved surface qualities.

In particular, the present invention provides access to solid powder-type compositions capable of forming translucent or colored coatings and whose visual effect is uniform and optimized.

The present invention also aims to provide solid compositions of the powder type capable of forming coatings endowed with increased mechanical strength.

The present invention also aims to provide a solid composition of powder type for forming coatings, having a reduced and preferably zero amount of titanium dioxide.

Thus, according to a first of its aspects, the present invention relates to a solid composition in the form of a powder capable of forming a surface coating on a support, said composition comprising at least one film-forming organic material, zirconium hydrogen phosphate and at least one material chosen from organic dyestuffs and pigments.

Against all expectations, the inventors have in fact observed that the combination of zirconium hydrogen phosphate with a film-forming organic material proves to be very particularly effective in improving the performance of the coatings formed from these compositions.

It is possible to access translucent surface coatings, colored or not, without titanium dioxide.

These coatings have a mechanical strength clearly superior to those exhibited by coatings devoid of zirconium hydrogen phosphate.

As for the color effect, it is optimized in terms of dispersion, depth of intensity, homogeneity and durability at the level of the coating.

• mélanger par broyage mécanique, un matériau particulaire filmogène et l’hydrogénophosphate de zirconium avec au moins un prémélange comprenant des composants annexes de ladite composition dont au moins une matière colorante organique ou un pigment,
• le cas échéant, tamiser le mélange homogène pulvérulent ainsi obtenu à une taille inférieure ou égale à 150µm et de préférence inférieure ou égale à environ 100µm et
• le cas échéant, fluidiser ledit mélange tamisé.

According to another of its aspects, the present invention relates to a process for the preparation of a composition in accordance with the invention comprising at least the steps consisting in:

• mixing, by mechanical grinding, a film-forming particulate material and the zirconium hydrogen phosphate with at least one premix comprising additional components of said composition including at least one organic coloring material or a pigment,
• if necessary, sieving the powdery homogeneous mixture thus obtained to a size less than or equal to 150 μm and preferably less than or equal to about 100 μm and
• if necessary, fluidizing said screened mixture.

Advantageously, the method of the invention does not implement an extrusion step.

The present invention further relates to the use of at least one composition according to the invention to form a surface coating, in particular transparent or translucent and colored or not, on a support.

• former par pulvérisation électrostatique un dépôt d’au moins une composition selon l’invention en surface de la zone à traiter dudit support, et
• si nécessaire, exposer ledit dépôt à des conditions efficaces pour le transformer en un revêtement adhérent à ladite zone.

It also relates to a method for forming a coating on the surface of a support comprising at least the steps consisting in

• form by electrostatic spraying a deposit of at least one composition according to the invention on the surface of the area to be treated of said support, and
• if necessary, exposing said deposit to conditions effective to convert it into a coating adherent to said area.

detailed description

Film-forming organic material

Within the meaning of the invention, the term film-forming is intended to qualify the fact that the material considered is able to organize itself in the form of a film when it is applied to a support. This film is also advantageously capable of constituting a matrix for the materials which are combined with it with a view to giving it particular properties. These properties can be qualities of adhesion, mechanical resistance, UV resistance, thermal resistance and also be linked to the manifestation of an aesthetic effect, for example decorative.

Thus, it is particularly considered in the context of the present invention, obtaining surface coatings which are transparent or translucent and colored or not.

The organic film-forming materials that are most particularly suitable for the invention are preferably synthetic resins.

These resins can be thermo- or photo-curable or thermoplastic. This type of materials is well known and the conditions required to transform them into a film are well documented.

Thus, organic film-forming materials suitable for the invention may need to be stimulated by a trigger element, heating, UV exposure or other to form the film constituting the expected coating. Thus, if necessary, the film-forming organic material can incorporate a crosslinking agent.

These film-forming organic materials are implemented in a particulate form and advantageously their particle size varies from 1 to 100 μm.

By way of representative and non-limiting example of these resins, mention may very particularly be made of epoxy, polyurethane, polyacrylate and polyester resins, modified or not, and mixtures thereof.

Advantageously, the film-forming organic material is at least one polyurethane resin or at least one polyester resin.

A composition according to the invention may contain from 90 to 95% by weight of film-forming material relative to its total weight.

The weight of film-forming material is expressed in dry weight in the context of the present description.

As stated previously, this film-forming organic material is combined with zirconium hydrogen phosphate.

The content of zirconium hydrogen phosphate varies from 0.5 to 10% by weight and in particular from 1 to 5% by weight relative to the total weight of the composition.

Advantageously, the zirconium hydrogen phosphate and the film-forming organic material are used in a weight ratio varying from 1/20 to 1/200.

As illustrated in the examples below, the presence of this zirconium hydrogen phosphate makes it possible to increase the mechanical strength of the coating formed according to the invention and to give it an optimized decorative effect in terms of intensity and homogeneity.

A composition according to the invention also contains at least one organic coloring material or one pigment.

These materials are present for the purpose of imparting particular properties to the expected coating

As far as the pigments are concerned, these materials generally have a particle size between 30 microns and 100 microns, better still between 20 and 60 microns, even better still between 5 and 40 microns.

A composition according to the invention advantageously contains less than 3% by weight of titanium dioxide relative to its total weight and preferably is devoid of it.

In particular, a composition according to the invention contains as pigment at least zinc sulphide. Such a pigment is very particularly advantageous for accessing so-called colorless or even transparent or even translucent coatings. Thus, in terms of decorative effect, zinc sulphide is particularly interesting for obtaining coatings with an opaline effect or even a milky appearance.

According to one embodiment variant, a composition according to the invention contains at least 90 to 95% in weight of at least one film-forming organic material, preferably at least one polyurethane or polyester resin, from 0.5% to 10% and in particular from 1 to 5% by weight of zirconium hydrogen phosphate and preferably from 1% to 10% in particular from 2.5% to 6% by weight of zinc sulphide relative to its total weight.

Of course, a composition according to the invention may also comprise at least one dyestuff other than titanium dioxide or zinc sulphide.

According to a variant embodiment, this dyestuff, different from titanium dioxide and zinc sulphide, can be chosen from among fluorescent, phosphorescent or else interference pigments.

They may for example be phosphorescent pigments based on alkaline earth metal aluminates doped with rare earths, in particular covered at least partially by smaller grains of a metal oxide, in particular ferrous. These grains of metal oxides can be used to give a color and to modify the color of luminescence, which can thus, if desired, be different from the green or yellow light most frequently encountered in phosphorescence.

As regards the organic dyestuffs, they can in particular be chosen from the organic pigments conventionally used in surface coatings, such as for example those considered in the examples below.

According to one embodiment variant, a composition according to the invention may comprise at least
90 to 92% by weight of at least film-forming organic material, in particular of polyurethane resin
2.5 to 4% by weight of zirconium hydrogen phosphate,
2 to 4% by weight of zinc sulphide,
2 to 4% by weight of calcium carbonate and
where appropriate up to 1% by weight of fumed silica relative to its total weight.

Such a composition is particularly effective for forming a coating with an opaline effect, that is to say translucent and of milky white appearance.

According to another variant embodiment, a composition according to the invention may comprise at least
90 to 95% by weight of at least film-forming organic material, in particular polyurethane resin,
2.5 to 4% by weight of zirconium hydrogen phosphate and
3 to 6% by weight of a dyestuff different from titanium dioxide and zinc sulphide and in particular capable of providing a color distinct from white relative to its total weight.

Such a composition is most particularly effective for forming a colored coating.

Of course, other compositions in accordance with the invention can be obtained and in particular by mixing different compositions according to the invention.

Thus, a composition according to the invention may contain at least
90 to 95% by weight of at least film-forming organic material, in particular polyurethane resin
2.5 to 4% by weight of zirconium hydrogen phosphate
2 to 4% by weight of zinc sulphide,
2 to 4% by weight of calcium carbonate and
3 to 6% by weight of a dyestuff of a color other than white, relative to its total weight.

Such a composition is very particularly effective for forming a coating with a colored opaline effect.

The mixtures mentioned above can in particular be prepared directly during the manufacture of the surface coating.

The user can thus, as he wishes, combine several compositions in accordance with the invention to adjust a particular color or decorative effect at the level of the surface coating to be produced.

Of course, a composition according to the invention can also contain other ancillary components and in particular chosen from the usual additives of solid compositions dedicated to forming surface coatings.

These components are of course compatible with a formulation in a solid state, that is to say in the form of a powder according to the invention.

Advantageously, a composition according to the invention contains at least one material, also called mineral filler according to the invention, chosen from clays, fumed silicas, calcium carbonate, barium sulphate and mixtures thereof .

These compounds can represent from 0.1 to 10% by weight of the total weight of the composition

A composition according to the invention may also comprise between 0.5 and 2% by dry weight of gelling agent relative to its total weight. This makes it possible to obtain a better hold of the composition on the substrate on which it is sprayed.

A composition according to the invention advantageously has a particle size less than or equal to 100 μm and preferably less than or equal to approximately 60 μm.

Process for the preparation of the compositions according to the invention.

• mélanger par broyage mécanique, le matériau particulaire filmogène et l’hydrogénophosphate de zirconium avec si présent, au moins un prémélange de composants annexes de ladite composition dont au moins une matière colorante organique ou un pigment,
• le cas échéant, tamiser le mélange homogène pulvérulent ainsi obtenu à une taille inférieure ou égale à 150µm et de préférence inférieure ou égale à environ 100µm et
• le cas échéant, fluidiser ledit mélange tamisé.

As stated above, the solid compositions according to the invention can be prepared according to a process comprising at least the steps consisting in

• mixing, by mechanical grinding, the film-forming particulate material and the zirconium hydrogen phosphate with, if present, at least one premix of ancillary components of the said composition, including at least one organic coloring material or one pigment,
• if necessary, sieving the powdery homogeneous mixture thus obtained to a size less than or equal to 150 μm and preferably less than or equal to about 100 μm and
• if necessary, fluidizing said screened mixture.

Advantageously, the process considered according to the invention does not require an extrusion step to form a composition according to the invention.

The inventors have observed that mechanical grinding of a mixture of all the raw materials makes it possible to obtain a very homogeneous composition thanks to the presence of zirconium hydrogen phosphate.

The mixture obtained at the end of the grinding step according to the invention and before sieving has particles of size varying from 1 to 100 μm.

The process according to the invention makes it possible to obtain a composition having a particle size less than or equal to 100 μm and preferably less than or equal to about 60 μm.

It has also been found that it is advantageous to have one or more premixes of the ingredients intended to be combined with the film-forming organic material.

These premixes can be prepared by mechanical grinding of their components and preferably in the presence of zirconium hydrogen phosphate to form homogeneous premixes which are easier to disperse homogeneously according to the method of the invention.

In general, zirconium hydrogen phosphate is implemented with all the compounds which are combined with it at a rate varying between 0.1 and 5% by weight expressed in relation to the total weight of the corresponding mixture.

According to a variant embodiment, a premix comprises at least one mineral filler, zinc sulphide and zirconium hydrogen phosphate, preferably in an inorganic materials/zirconium hydrogen phosphate weight ratio ranging from 1/100 to 1/20.

According to another variant embodiment, a premix comprises at least one organic coloring material and zirconium hydrogen phosphate, preferably in a coloring material/zirconium hydrogen phosphate weight ratio ranging from 1/1000 to 1/20.

Mechanical grinding operations can be carried out in a ball mill. The number and size of the balls are adjusted there according to the volume to be ground and the desired particle size.

For example, a particulate premix as identified above can be made by mechanically grinding these components and the zirconium hydrogen phosphate, to form particles ranging in size from 1 to 100 µm. An adequate sieving operation can be carried out following the grinding.

If necessary, the powder obtained after grinding and sieving can be fluidized in a fluidization bed.

As stated above, a composition according to the invention can also be prepared by simple mixing of several compositions according to the invention. It is thus possible to obtain a wide range of compositions according to the invention capable of respectively providing distinct color effects of great diversity.

Use

The solid compositions according to the invention are particularly useful for forming a transparent, translucent and colored or colorless surface coating on a support or even a substrate. These supports can be formed from a wide variety of materials such as metal, ceramic, plastic or glass and preferably is glass. In view of this diversity of possible supports, the compositions according to the invention can be used in very different technical fields such as that of metallurgy, the hollow glass and flat glass industry, the wood and ceramics industry.

The compositions according to the invention are particularly useful for forming surface coatings endowed with a decorative effect on glass articles, such as for example bottles, perfume bottles, cosmetic receptacles, articles of the art of table, glazing.

Depending on the nature of the pigments and dyestuffs present in the composition used, the coating obtained is colored or not. It can thus only be translucent or even transparent in the absence of any material capable of providing a colored effect.

The compositions according to the invention also prove to be suitable for being mixed to form new compositions either before their use or at the time of their implementation to form a surface coating on a support.

Method for forming a coating

• former par pulvérisation électrostatique un dépôt d’au moins une composition selon l’invention en surface de la zone à traiter dudit support, et
• si nécessaire, exposer ce dépôt à des conditions efficaces pour le transformer en un revêtement adhérent à ladite zone.

Another subject of the invention is a process for forming a surface coating on a support, in particular made of glass, comprising

• form by electrostatic spraying a deposit of at least one composition according to the invention on the surface of the area to be treated of said support, and
• if necessary, exposing this deposit to conditions effective to transform it into a coating adherent to said zone.

The electrostatic spraying is carried out according to an electrostatic process or Corona effect or even a triboelectric process or even fluidization.

Depending on the nature of the film-forming organic material present in the solid composition and/or the nature of the support considered, for example metallic or not, it may be necessary to expose the deposit to a trigger element to form the expected coating.

This triggering element can be in particular heating, UV exposure.

For example, in the case of a metallic support, the deposit can be formed at room temperature, i.e. between 18 and 25°C.

When the support is made of glass, it is preferable to form the surface deposit of glass brought to a temperature of 100 to 180°C.

The method according to the invention makes it possible to form the coating directly in contact with the substrate.

Advantageously, the coating obtained is formed from a single deposit of composition.

The coating obtained according to the process of the invention can have a thickness varying from 50 to 120 μm.

Its surface qualities in terms of aesthetic effect, for example colored or not, translucent or not, are directly linked to the nature of the components of the composition used.

It is also possible to consider the simultaneous implementation of several conforming compositions according to the invention to create decorative effects at the level of the same coating. Thus, by adjusting the spraying of two compositions according to the invention differently, it is possible, for example, to create a gradient effect at the level of the coating.

For example, according to one embodiment, the composition according to the invention contains at least 3% by weight of zinc sulphide and the coating formed from this composition is translucent or even said to have an opaline effect.

The examples below are submitted by way of illustration and not limitation of the field of the invention.

Material and methods

Resin-like materials are

- a polyurethane base varnish sold in the 44 series by the company Tiger Coating,

- a polyester base varnish called N°1 marketed under the name Series 16 from the company Tiger Coating and

- a polyester base varnish called No. 2 marketed under the trade name GZ C642C8202 from Protech Oxyplast

The powder mixtures are made in a grinding jar using ceramic balls as detailed below. The volume of the jar is distributed in 1/3 balls 1/3 air and 1/3 mixture of materials.

The mechanical resistances are checked according to the methods defined by the ISO 8113 standard.

To) Scotch tape test on a grid surface

Equipment used

Adhesive tape with an adhesive power of between 350 and 450 N/cm² and a width of 19mm (for example reference 616M from the 3M Company)

Cutter for the grid

Operating mode

Make a grid of 5 vertical lines and 5 horizontal lines on a surface of 1 to 2 cm²,

Carefully apply the adhesive tape to the gridded surface by pressing down with your thumb,

Wait 1 minute and

Tear off the adhesive tape with a sharp blow, exerting the effort at an angle between 45° and 90° in relation to the support

If the coating is satisfactory, there should be no departure on the entire grid surface.

b) Action test on contained product or G1 cold

Material

A transparent crystallizer,

G1 product (70% ethyl alcohol + 20% turpentine + 10% ethyl phthalate) and a white soft cloth .

Operating mode

Immerse the surfaces to be tested for 24 hours (+/- 1 hour) in the product at room temperature.

The tested surface is then rubbed lightly with the thumb or the white cloth.

There should be no entrainment or variation in shades of color or bleeding in the bath liquid.

Example 1 : preparation of a composition according to the invention.

Preparation of a premix A

20 g (15.38%) of zirconium hydrogen phosphate, 50 g (38.46%) of zinc sulphide, 50 g (38.46%) of calcium carbonate and 10 g (07.69%) of silica pyrogen (Aerosil 200 from the company EVONIK) are introduced into a ceramic jar containing ceramic balls with a diameter of 10 to 30 mm. The mixture is ground there for 30 minutes and then sieved at 100 μm.

Preparation of a premix B

3 g of Paliogen® NOIR L 0086 BASF pigment (perylene) and 1 g of zirconium hydrogen phosphate are introduced into a plastic jar (120ml) containing zirconium balls with a diameter of 2 to 20 mm. The mixture is ground there for 30 minutes and then sieved at 63 μm.

Composition preparation solid according to the invention

100g (90.5%) of polyurethane resin (series 44 from the company TIGER) are introduced into a plastic pot with a diameter of 80mm by 10cm in height containing 5 zirconium balls with a diameter of 30mm.

7.5 g (6.79%) of premix A and 3 g (2.71%) of zirconium hydrogen phosphate are added and the whole is ground for 10 minutes, sieved at 100 µm then fluidized in a fluidization bath.

With premix A, the pulverulent composition obtained is suitable for forming a translucent coating with an opaline hue.

100g (96%) of polyurethane resin (series 44 from TIGER) are mixed with 1.2g (1.1%) of premix B and 3g (2.9%) of zirconium hydrogen phosphate according to the protocol described above. The solid composition of the powder type obtained makes it possible to form a colored translucent coating.

Example 2: Formation of a coating on a support from a composition according to the invention.

The composition of Example 1 obtained with premix A is sprayed by an electrostatic process onto a glass bottle to form therein a surface coating having a thickness of 50 to 80 microns.

The surface qualities of the coating are tested as follows.

The treated glass bottle is immersed for 20 minutes in hot water at a temperature of 60° C. and then recovered.

The glass bottle is first rubbed with the finger at the level of its coating. No alteration of the coating applied was observed. This is not driven and remains fully attached to the container. Its color aspect also remains intact.

The grid test is then carried out according to the standard (scotch tape Ref 3M brand 616 Made in USA 5704 - 1) detailed in equipment and method. At the end of this treatment, a visual examination of the coating on the glass container is carried out. No degradation of this coating is also observed.

Example 3: Formation of coating in accordance with the invention and controls.

Table 1 below shows the solid compositions tested. They were prepared by reproducing the operating protocol described in example 1 with the quantities specified in this table. Their surface qualities were tested according to the water test and the G1 test described in example 2. The results are also indicated in table 1.

Raw materials Membership 2 grams Membership 3 grams Witness 1 grams Witness 2 grams Pigment Paliogen® BLACK L 0086 BASF 1.2 1.2 1.2 1.2 zirconium hydrogen phosphate for premixing with pigment 0.3 0.3 - - Polyester Resin N°1 (series 16 tiger) 100 _ 100 _ Polyester resin N°2GZ C642C8202 from Protech Oxyplast - 100 _ 100 zirconium hydrogen phosphate 3 3 _ - Hot water test with grid No detachment No detachment Coating peeling Coating peeling G1 test No peeling Very low degradation No peelingVery low degradation Strong degradation of the coating Strong Coating Degradation

Claims (24)

Solid composition in the form of a powder capable of forming a surface coating on a support, said composition comprising at least one film-forming organic material, zirconium hydrogen phosphate and at least one material chosen from organic coloring matters and pigments. Composition according to the preceding claim comprising from 0.5 to 10% by weight and in particular from 1 to 5% by weight of zirconium hydrogen phosphate relative to its total weight. Composition according to claim 1 or 2 comprising zinc sulphide as pigment. Composition according to any one of the preceding claims comprising less than 3% by weight of titanium dioxide relative to its total weight and preferably devoid of titanium dioxide. Composition according to any one of the preceding claims, further comprising at least one material chosen from clays, fumed silicas, calcium carbonate, barium sulphate and mixtures thereof . Composition according to any one of the preceding claims, in which the organic film-forming material is chosen from epoxy resins, polyurethanes, polyacrylates, modified or unmodified polyester and mixtures thereof. Composition according to any one of the preceding claims, in which the film-forming particulate material is at least one polyester resin. Composition according to any one of the preceding claims, in which the film-forming particulate material is at least one polyurethane resin. Composition according to any one of the preceding claims, in which the zirconium hydrogen phosphate and the said film-forming organic material are used in a weight ratio varying from 1/20 to 1/200. Composition according to any one of the preceding claims comprising at least from 90 to 95% in weight at least one film-forming organic material, preferably at least one polyurethane or polyester resin, from 0.5% to 10% by weight of zirconium hydrogen phosphate and preferably from 1% to 10% of zinc sulphide per relative to its total weight. Composition according to any one of the preceding claims, further comprising at least one dyestuff other than titanium dioxide and zinc sulphide and preferably chosen from fluorescent, phosphorescent or interference pigments. Composition according to any one of the preceding claims, the particle size of which is less than or equal to 100 μm and preferably less than or equal to about 60 μm. Process for the preparation of a composition according to any one of the preceding claims, comprising at least the steps consisting in:

• mixing, by mechanical grinding, the film-forming particulate material and the zirconium hydrogen phosphate with at least one premix of ancillary components of said composition including at least one organic coloring material or one pigment,
• if necessary, sieve the homogeneous powdery mixture thus obtained to a size less than or equal to 100 μm and preferably less than or equal to about 60 μm and
• If necessary, fluidize said sieved mixture.

Process according to the preceding claim, in which the mechanical grinding is carried out in a ball mill. Process according to one of Claims 13 or 14, in which the said premix is obtained by mechanical grinding of a premix comprising at least one mineral filler, zinc sulphide and zirconium hydrogen phosphate, preferably in an inorganic materials/ zirconium hydrogen phosphate varying from 1/100 to 1/20. Process according to one of Claims 13 or 14, in which the said premix is obtained by mechanical grinding of at least one organic dyestuff and zirconium hydrogen phosphate, preferably in a dyestuff/zirconium hydrogen phosphate weight ratio varying from 1/1000 at 1/20. Use of at least one composition according to any one of Claims 1 to 12 to form a surface coating on a support. Use according to Claim 17, in which the support is formed from a material chosen from among plastic, ceramic, glass and metal and preferably is a glass. Process for forming a coating on the surface of a support comprising at least the steps consisting in

• form by electrostatic spraying a deposit of at least one composition according to any one of claims 1 to 12 on the surface of the area to be treated of said support, and
• if necessary, exposing said deposit to conditions effective to convert it into a coating adherent to said area.

Method according to the preceding claim, in which the electrostatic spraying is carried out according to an electrostatic or Corona effect method or even a triboelectric method. Process according to Claim 19 or 20, in which the support is metallic and the deposit is formed at ambient temperature. Process according to Claim 19 or 20, in which the support is made of glass and the deposit is formed on the surface of the said glass brought to a temperature of 100 to 180°C. Process according to any one of Claims 19 to 22, in which the coating obtained is formed from a single deposit of composition. Process according to any one of Claims 19 to 23, in which the coating obtained has a thickness varying from 50 to 120 µm.