ES2844924T3 - Decorated abrasive cloth - Google Patents

Abstract

Abrasive cloth, comprising an abrasive support (10), comprising abrasive fillers, characterized in that a protective layer (20) has a pattern (20a, 20b, 20c) comprising at least two different colors, in which the layer Protection (20) is deposited on the abrasive substrate (10) by screen printing and covers at least 80% of an abrasive support surface (10).

Description

DESCRIPTION

Decorated abrasive cloth

Invention sector

The present invention relates to a decorated high performance abrasive cloth, as well as a combination article including said abrasive cloth and a method of manufacturing said abrasive cloth.

State of the art

The market for abrasive cloths, as known for example from document FR 2956968 A1, as well as the market for combined cleaning articles combining a sponge and an abrasive cloth, which is very competitive, has become essential to stand out from the competition both in terms of quality, offering abrasive cloths that are both effective and durable, but also in terms of marketing, offering attractive appearances.

In this regard, decorated abrasive cloths have been proposed in which a pattern comprising several colors is placed on the surface of the abrasive cloth.

However, in these known decorated abrasive cloths, this decoration is arranged on the surface of the abrasive cloth by thermal transfer of a decorated film.

However, said heat transfer subjects the abrasive material of the abrasive cloth to high temperatures, which generally entails a partial melting of the abrasive material and therefore a deterioration of its abrasive quality; which also entails an undesired stiffening of the abrasive cloth. Furthermore, said heat transfer requires a compression of the abrasive cloth at the time of transfer of the decorated film: the abrasive cloth being therefore crushed, which leads to a reduction in the thickness of the latter.

There is therefore a real need for a high performance decorated abrasive cloth that lacks, at least in part, the drawbacks inherent in the known method cited above.

Object of the invention

The present description refers to an abrasive cloth, which comprises an abrasive support, which comprises abrasive fillers, and a protection layer that has a pattern comprising at least two different colors, in which the protection layer is deposited on the support. abrasive by screen printing and covers at least 80% of a surface of the abrasive support.

Thanks to the use of screen printing, the depositing of the protection layer can be carried out at room temperature, which avoids subjecting the abrasive support to high temperatures and therefore allows a high abrasive quality and good flexibility to be preserved.

In addition, screen printing does not require excessive and prolonged compression of the abrasive support and therefore does not affect, practically nothing, the thickness of the latter. In any case, even in the case of compression, thanks to the absence of heat, the abrasive support retains sufficient flexibility after depositing the protective layer to practically recover its initial thickness.

On the other hand, the use of screen printing offers significant freedom in the composition of the protection layer, which allows in particular to introduce compounds that allow the abrasive support to be protected and therefore increase its durability, especially reducing the formation of balls. The thickness of a protection layer can likewise be easily adjusted in order to adjust the protection of the abrasive support.

The use of screen printing also offers a great deal of freedom in the conception of the motif, the latter being able in particular to comprise any number of different colors: it is sufficient for this to use as many successive silkscreen frames as there are colors in the motif.

Incidentally, it will be noted that a person skilled in the art, in the presence of said decorated abrasive cloth, will be able, by a possible careful observation of the protection layer, to recognize that the latter has been obtained by screen printing. In fact, since the silkscreen formulation is deposited through a multi-perforated frame, it is possible to observe a remanence of the structure of this action in the protection layer; it is also possible to observe agglomerates or webbed.

Furthermore, as the protective layer covers at least 80% of the surface of the abrasive cloth, it allows the abrasive support to be effectively protected, thus increasing the durability of the latter. Therefore, the chosen pattern may be extended or repeated sufficiently to substantially cover the abrasive support and / or the pattern may comprise a solid background, possibly the same color as the abrasive support, which allows the support to be protected. abrasive included among the colored motif ornaments. Therefore, the motif does not play a simple decoration role, it also makes it possible to protect the whole of the abrasive support, which makes it possible to maintain the effectiveness of the abrasive cloth for a longer time.

In certain embodiments, the abrasive backing comprises textile fibers.

In certain embodiments, the textile fibers form a nonwoven. Said nonwoven provides support to abrasive loads while maintaining a certain flexibility.

In certain embodiments, the textile fibers comprise at least fibers of one or more materials, artificial or natural, included among the following: polyester; polyamide; viscose, aramid; Polypropylene; sisal; cotton.

According to the invention, the abrasive support comprises abrasive fillers. These abrasive fillers allow the surface to be cleaned to be rubbed in order to remove any existing dirt.

In certain embodiments, the abrasive fillers of the abrasive support have a hardness between 3.5 and 9.5, preferably between 8.5 and 9.5, on the Mohs scale. Said hardnesses are particularly adapted to rub difficult stains on resistant materials such as stainless steel, glass or even cast iron.

In certain embodiments, the abrasive fillers on the abrasive backing are mineral particles.

In certain embodiments, the abrasive fillers of the abrasive support comprise at least one or more materials among the following: plastic (especially melamine or PVC), pumice stone, silica, corundum, silicon carbide. Preferably, to obtain higher efficiency, mostly corundum and / or silicon carbide is used.

In certain embodiments, the abrasive backing comprises a binder. The binder makes it possible to bind the abrasive fillers with the textile fibers of the abrasive support.

In certain embodiments, the binder of the abrasive backing comprises at least one thermoplastic or thermosetting polymer.

In certain embodiments, the binder of the abrasive support comprises at least one or more materials, thermoplastic or thermosetting, among the following: acrylic; polyurethane; acrylonitrile; styrene butadiene; acrylic styrene; acrylic vinyl; phenolic resin; urea resin; melamine-formaldehyde.

In certain embodiments, the abrasive support has a thickness between 6 and 10 mm, preferably between 7 and 9 mm.

In certain embodiments, the abrasive support has a surface density between 500 and 900 g / m2, preferably between 600 and 800 g / m2.

In certain embodiments, the protective layer comprises at least one polymeric binder, preferably of the elastomeric and / or thermoplastic type. This polymeric binder allows, on the one hand, to bind the fibers of the abrasive support on the surface, which increases the cohesion of the fibers and therefore the durability of the abrasive cloth; and on the other hand to provide a support for the pigments that ensure the color of the protection layer. In certain embodiments, the polymeric binder of the protective layer comprises at least one styrenic polymer, such as acrylonitrile, styrene butadiene, or acrylic styrene, or a urethane polymer such as polyurethane. These binders make it possible to increase the surface resistance of the abrasive (mechanical and chemical) without penalizing other properties. In particular, the protective layer is prevented from becoming hard and brittle, which would weaken the resistance of the abrasive surface.

In certain embodiments, the protective layer comprises at least one pigment. This pigment colors the protective layer. In particular, different areas of the protective layer may contain different pigments and therefore have different colors, which helps to form the pattern of the protective layer.

In certain embodiments, the protective layer comprises at least one thickener. Said thickener makes it possible to adjust the flexibility of the protection layer.

In certain embodiments, the thickener of the protective layer comprises at least one material or several materials among the following: sodium polyacrylate; polyurethane; cellulose.

In certain embodiments, the protective layer covers at least 99% of an abrasive support surface.

In certain embodiments, the protective layer has a surface density between 30 and 320 g / m2, preferably between 200 and 300 g / m2. Therefore, a compromise is ensured between the grammage sufficient to effectively bind the surface fibers of the abrasive support and therefore reinforce the durability of the abrasive cloth, and a grammage not too important to preserve the relief of the abrasive loads and therefore the abrasive quality of the abrasive cloth.

In certain embodiments, the protective layer has a thickness of less than 1 mm, preferably less than 0.5 mm. Therefore, a compromise is ensured between a sufficient thickness to effectively bind the fibers on the surface of the abrasive support and therefore reinforce the durability of the abrasive cloth, and a thickness that is not too important to preserve the relief of the abrasive loads and therefore the abrasive quality of the abrasive cloth.

In certain embodiments, the pattern of the protective layer comprises at least three different colors. Furthermore, it can be any motive, not necessarily contained in a given direction.

In certain embodiments, the abrasive cloth comprises a white abrasion greater than 600 mg / 1000 cycles, preferably greater than 700 mg / 1000 cycles. A Branca abrasion measurement protocol is given later in the description.

The present description refers in the same way to a combined cleaning article, comprising a sponge and an abrasive cloth according to any one of the previous embodiments fixed on a surface of the sponge.

The present description refers in the same way to a method of manufacturing an abrasive cloth, which comprises the following steps: provision of an abrasive support, which comprises abrasive fillers; depositing a protection layer on the abrasive support by screen printing with the help of at least two successive screen printing frames so that a pattern is made that comprises at least two different colors, the protection layer covering at least 80% of the surface of the abrasive backing.

The technical effects and advantages of said screen printing procedure have been given above. Furthermore, all the structural characteristics stated in the object of different embodiments of the abrasive cloth can be transposed to the present manufacturing method.

In particular, the abrasive backing provided in this way may comprise any number of characteristics among those listed above.

In certain embodiments, the screen printing frames used during the depositing of the protective layer are rotating screen printing frames. The latter allow a faster execution speed and can be installed in series in a continuous manufacturing chain. However, flat screen printing frames can be viewed in the same way.

In certain embodiments, at least one, and preferably each, screen printing frame has a mesh between 50 and 650 pm, preferably between 100 and 200 pm. This mesh offers a satisfactory resolution for the motif while ensuring a sufficient pass section for the screen printing formulation.

In certain embodiments, at least one, and preferably each, screen-printing formulation used during the depositing of the protective layer comprises a polymeric binder, preferably of the elastomer and / or thermoplastic type. As indicated above, this polymeric binder makes it possible to bind the fibers of the abrasive support on the surface, which increases the connection of the fibers and therefore the durability of the abrasive cloth.

In certain embodiments, the polymeric binder of at least one screen printing formulation comprises at least one styrenic polymer, such as acrylonitrile, styrene butadiene, or acrylic styrene, or a urethane polymer such as polyurethane. These binders make it possible to increase the surface resistance of the abrasive (mechanical and chemical) without penalizing other properties. In particular, the protective layer is prevented from becoming hard and brittle, which would weaken the surface resistance of the abrasive.

In certain embodiments, the mass concentration of the polymeric binder in at least one screen printing formulation is between 65 and 85%, preferably between 70 and 80%. This concentration facilitates the depositing of the protective layer.

In certain embodiments, at least one, and preferably each, screen printing formulation used during the depositing of the protective layer comprises a solvent, preferably water.

In certain embodiments, the mass concentration of the solvent in at least one screen printing formulation is between 10 and 90%, preferably between 10 and 50%, preferably even between 15 and 20%. The concentration of the solvent influences the viscosity of the screen printing formulation and therefore the amount of formulation deposited.

In certain embodiments, at least one, and preferably each, screen printing formulation used during the depositing of the protective layer comprises a pigment paste. This pigment paste makes it possible to color the screen printing formulation and therefore color the area of the affected protection layer. In particular, each screen printing formulation used with different screen printing frames may contain a different pigment paste such that different areas of the top coat display different colors, which helps to form the top coat pattern.

In certain embodiments, the mass concentration of the pigment paste in at least one screen printing formulation is between 1 and 5%, preferably between 2 and 4%.

In certain embodiments, at least one, and preferably each, screen printing formulation used during the depositing of the protective layer comprises a thickener. Said thickener makes it possible to adjust the viscosity of the screen printing formulation, so that the amount of formulation deposited and the definition of the patterns are adjusted. It allows in the same way to adjust the flexibility of the protection layer.

In certain embodiments, the thickener of at least one screen printing formulation comprises at least one material or several materials among the following: sodium polyacrylate; polyurethane; cellulose.

In certain embodiments, the mass concentration of the thickener in at least one screen printing formulation is between 1 and 5%, preferably between 2 and 4%.

In certain embodiments, the viscosity of at least one, preferably each, screen printing formulation is between 2000 and 16,000 mPa.s, preferably between 3000 and 5000 mPa.s.

In certain embodiments, the protective layer has, at the end of the depositing stage, a surface density between 30 and 320 g / m2, preferably between 200 and 300 g / m2.

In certain embodiments, the protective layer is deposited on at least 50% and preferably 100% of an abrasive support surface. Therefore, the protection layer allows to decorate but in the same way protect the entire surface of the abrasive support.

In certain embodiments, the method comprises, after the step of depositing the protective layer, a step of crosslinking the protective layer. Said crosslinking step makes it possible to activate the crosslinking of the polymeric binder and therefore solidify the protective layer.

In certain embodiments, the crosslinking step comprises a heating step at a temperature between 100 ° C and 180 ° C, preferably between 140 ° C and 160 ° C, for a duration between 1 and 10 minutes, preferably between 3 and 8 minutes. In this way, the articulation of the polymeric agglomerate is activated without, or practically without, damaging the abrasive backing. However, the crosslinking can be triggered in other ways, for example with the aid of radiation, and in particular UV, IR or microwave radiation.

In certain embodiments, the depositing of the protection layer comprises the use of at least three silkscreen frames.

In certain embodiments, the final protective layer has a thickness of less than 1 mm, preferably less than 0.5 mm. Therefore, a compromise is ensured between a sufficient thickness to effectively bind the fibers on the surface of the abrasive support and therefore reinforce the durability of the abrasive cloth, and a thickness that is not too important to preserve the mobility of the abrasive loads and therefore the abrasive quality of the abrasive cloth.

In certain embodiments, the abrasive cloth is never set at a temperature higher than 200 ° C. This makes it possible to reduce the risk of damaging the abrasive backing by thermal degradation.

The characteristics and advantages mentioned above, as well as others, will appear from a reading of the following detailed description, of embodiments of the abrasive cloth and of the proposed procedure. This detailed description refers to the accompanying drawings.

Description of the figures

The accompanying drawings are schematic and are primarily intended to illustrate the principles of the description.

In these drawings, from one figure (figure) to the other, identical elements (or parts of the element) are represented by the same reference signs.

Fig. 1 is a perspective view of a cleaning combination article according to the description.

Figure 2 is a sectional view according to the M-M plane of Figure 1.

FIG. 3 is a block diagram of a method according to the description.

Figure 4 is a detailed view of a screen printing cylinder.

Detailed description of the invention

In order to make the description more concrete, an example of a combined cleaning and manufacturing method article is described in detail below with reference to the accompanying drawings. It is recalled that the invention is not limited to this example.

Figure 1 represents, in perspective, a combined cleaning article 1 according to the invention. This same cleaning combo item 1 is represented in the same way in section in figure 2.

This combined cleaning article 1 comprises an abrasive cloth 2 mounted on the upper surface of a sponge 3. The sponge 3 can be of any known type.

The abrasive cloth 2 comprises for its part an abrasive support 10 and a protective layer 20 that covers the entire upper surface of the abrasive support 10.

The abrasive backing 10 is a non-woven textile layer comprising in this example polyester and polyamide fibers; the abrasive support 10 also comprises abrasive fillers, in the form of a mixture of corundum and silicon carbide at a height of 350 g / m2, and a binder, in the form of a phenolic resin at a height of 150 g / m2, which it ensures the cohesion of abrasive loads in the textile layer and that adjusts the consistency of the abrasive support.

In the present example, this abrasive support 10 has a thickness of 8 mm and a surface density of 700 g / m2. The protection layer 20 is for its part of a polymeric coating comprising a thermoplastic polymer, in the form of styrene butadiene, pigments and a thickener, in the form of sodium polycarbonate.

The protection layer 20 is divided into several zones 20a, 20b, 20c which comprise different pigments and therefore have different colors. These different areas 20a, 20b, 20c of three different colors in the present example are arranged so as to form a pattern on the protection layer 20, thereby decorating the upper face of the combined cleaning article 1.

A manufacturing process of this abrasive cloth 2 and this combined cleaning article 1 will be described below with reference to Figures 3 and 4.

First, the abrasive backing 10 and the sponge 3 are manufactured in advance in a known manner. The abrasive backing 10 is thus provided in the form of plates or a continuous roll and is positioned at the entrance of the conveyor 51 of a screen printing machine 50.

This screen printing machine 50 is provided with a plurality of rotating frames 60a, 60b, 60c arranged in series along the conveyor 51; more particularly, it comprises at least as many rotating frames 60 as zones 20a, 20b, 20c of different colors in the protective layer 20 of the abrasive cloth 2 to be manufactured: therefore, in the present example, the screen printing machine comprises three frames 60a, 60b, 60c successive rotaries provided, each one, to cover one of the zones 20a, 20b, 20c of the protection layer 20.

Each rotary frame 60a, 60b, 60c comprises a perforated cylinder 61 with multiple holes 62, arranged in a regular network, and driven in rotation in synchronization with the conveyor 51. As is otherwise known, each perforated cylinder 61 is lined with a mask 63, normally formed of a solidified resin, whose extension corresponds to the negative of the zone 20a, 20b, 20c of the protection layer 20, which must cover this rotating frame 60a, 60b, 60c: therefore, as it is visible in FIG. 4, the mask 63 covers certain holes 62 of the cylinder 61 in such a way that it only allows the screen printing formulation to pass in areas corresponding to the area 20a, 20b, 20c of the protection layer 20 to be coated.

In the present description, the holes 62 of each cylinder 61 are distributed according to a hexagonal network whose mesh measures approximately 125 pm.

Each rotary frame 60a, 60b, 60c further comprises a slat 64 that extends vertically from the hub 65 of the rotary frame 60a, 60b, 60c to the cylinder 61.

The hub 65 comprises, on the other hand, a fluid inlet 66 that allows the introduction of a silkscreen formulation 67a, 67b, 67c into the interior space of the cylinder 61, upstream of the slat 64, in such a way as to form a retention for the silkscreen formulation 67a, 67b, 67c.

Furthermore, a metal drum 68 is present in the interior space of the cylinder 61, upstream of the slat 64 and therefore within the silkscreen formulation retention 67a, 67b, 67c. In addition to its intrinsic weight, an electromagnet 69 arranged opposite the cylinder 61, below the conveyor 51, makes it possible to regulate the pressing force of the metal drum 68 against the internal wall of the cylinder 61.

The composition of the screen printing formulation 67a, 67b, 67c is substantially the same for each screen printing frame 60a, 60b, 60c and only differs as regards the nature and / or concentration of the pigment (s) used.

Therefore, in the present example, each screen printing formulation 67a, 67b, 67c is obtained, for 1000 g of formulation, by mixing:

- Approximately 750 g of styrene butadiene-based latex;

- Approximately 30 g of pigment paste;

- Approximately 37 g of sodium polyacrylate as a thickener;

- The rest of the water.

Thus, screen printing formulations are obtained which have a viscosity of approximately 3400 mPa.s. Naturally, each pigment paste is chosen in such a way as to provide the silkscreen formulation 67a, 67b, 67c under consideration with the desired color for the corresponding zone 20a, 20b, 20c of the protective layer 20.

Therefore, when the conveyor 51 advances, the abrasive support 10 passes under the cylinders 61 of each successively rotating frame 20a, 20b, 20c. The space left between the surface of the conveyor 51 and the cylinders 61 can, in particular, be regulated in order to more or less compress the abrasive support 10 during its passage: in the present example, this space is approximately 5 mm. As the compression is rapid, of the order of approximately 1 second, the abrasive support 10 immediately returns to its initial thickness after passing under each cylinder 61.

The action of the metal drum 68 and of the louver 64 therefore makes it possible to push a part of the silkscreen formulation present in the retention 67 through the holes 62 of the cylinder 61 not obstructed by the mask 63 so that the formulation 67a is deposited. , 67b, 67c of screen printing only in the desired zone 20a, 20b, 20c of the protection layer 20. This operation is carried out at room temperature.

The weight of the drum 68, the force of the electromagnet 69 and the speed of movement of the conveyor 51 make it possible to regulate the amount of screen printing formulation coated on the abrasive support 10 as well as the thickness of the protective layer 20. In the present example, these parameters are regulated identically for all rotating frames 60a, 60b, 60c so that a protection layer 20 is obtained having a surface density of 220 g / m2 (plus or minus 10%) after drying, leading to a thickness less than 1mm.

After each pass over a different rotating frame 60a, 60b, 60c, a supplementary zone 20a, 20b, 20c of the protective layer 20 is deposited on the abrasive backing 10 until the latter is completely covered.

The conveyor therefore continues on its way to a heating chamber 52 in which the abrasive cloth 2 is heated at approximately 150 ° C for 5 minutes in order to cross-link the polymer of the protective layer 20 and thus solidify the latter.

At the end of this stage, the abrasive cloth 2 is ready and can be cut and divided to the desired size: it can therefore be marketed in this state or mounted by counter-gluing or flaming on a sponge 3 in order to form the article 1 cleaning combo.

Performance and durability tests will now be described in order to demonstrate the qualities of the abrasive cloths 2 as described.

The first test is a performance test called Branca whose objective is to measure the abrasion of the abrasive cloth. To carry out this test, a 2017 T4 aluminum plate measuring 160 mm x 160 mm x 2 mm is provided, as well as a 90 mm diameter disk cut into the abrasive cloth to be studied. The trial therefore follows the following protocol:

- Cleaning the aluminum plate with acetone;

- Pass the aluminum plate once dry;

- Fixing the aluminum plate on the support;

- Fixation of the abrasive cloth disc on a rotating mandrel;

- Application of a force of 30 N on the mandrel so that the abrasive cloth disc is pressed on the aluminum plate;

- Placing a flow of water along the aluminum plate;

- Rotation of a chuck for 1000 turns at a speed of 40 turns per minute;

- Removal of the aluminum plate, cleaning the acetone and drying;

- Passing of the aluminum plate to reduce the loss of mass after abrasion: the result of the test is the value of this loss of mass.

The second test is a durability test that aims to measure the balling resistance of the abrasive cloth. To carry out this test, a first 160 mm diameter disc and a second 38 mm diameter disc cut out of the abrasive cloth to be studied are provided. The trial therefore follows the following protocol:

- Fixing the first disc on the fixed support of a Martindale machine;

- Fixing the second disc on a mobile support of the Martindale machine;

- Application of a pressure of 24 kPa on a mobile support so that the second disk is pressed on the first disk;

- Start-up of the Martindale machine, setting in motion the mobile support of the Martindale machine according to standard Lissajous trajectories;

- Martindale machine stop after 200 cycles; removal of the second disc;

- Visual comparison of the balling state of the second disc with reference samples forming a scale from 0 (excellent, i.e. no balling) to 5 (poor, i.e. strong balling) and attribution of a note with respect to this scale;

- Carrying out this same protocol for three different series of samplings: the result of the test is the average of the marks of these three series of samplings.

Therefore, the abrasive cloth 2 according to the example described above has been subjected to these tests and a result of 797 mg has been obtained in the Branca abrasion test and a score of 0.5 in the resistance to ball formation test. , which is much better than the known decorated abrasive cloths.

Although the present invention has been described with reference to specific embodiments, it is clear that modifications and changes can be made to the examples without departing from the general scope of the invention as defined by the claims. In particular, the individual characteristics of the different illustrated / mentioned embodiments can be combined in additional embodiments. Accordingly, the description and designs should be considered in an illustrative rather than a restrictive sense.

In the same way it is evident that all the characteristics described with reference to a method can be translated, alone or in combination, to a device and conversely all the characteristics described with reference to a device can be translated, alone or in combination, to a device. process.

Claims (15)

1. Abrasive cloth, comprising an abrasive support (10), comprising abrasive fillers, characterized in that a protective layer (20) has a pattern (20a, 20b, 20c) comprising at least two different colors, in which the protective layer (20) is deposited on the abrasive substrate (10) by screen printing and covers at least 80% of an abrasive support surface (10). 2. An abrasive cloth according to claim 1, in which the abrasive backing (10) comprises a non-woven. Abrasive cloth according to claim 1 or 2, in which the protective layer (20) comprises at least one polymeric binder, preferably of the elastomer and / or thermoplastic type, and a pigment. Abrasive cloth according to any one of Claims 1 to 3, in which the protective layer (20) covers at least 99% of a surface of the abrasive support (10). Abrasive cloth according to any one of Claims 1 to 4, in which the protective layer (20) has a thickness of less than 1 mm, preferably less than 0.5 mm. Cleaning combination article, comprising a sponge (3) and an abrasive cloth (2) according to any one of the preceding claims affixed to the surface of the sponge (3). 7. Procedure for the manufacture of an abrasive cloth, which comprises the following stages: provision of an abrasive backing (10) comprising abrasive fillers; depositing a protective layer (20) on the abrasive support (10) by screen printing with the help of at least two successive screen printing frames (60a, 60b, 60c) so that a motif (20a, 20b, 20c) is produced comprising at least two different colors, the protective layer (20) covering at least 80% of a surface of the abrasive device (10). Method according to claim 7, in which the screen printing frames (60a, 60b, 60c) used during the depositing of the protective layer (20) are rotating screen printing frames and in which at least one, and preferably each, screen printing frame (60a, 60b, 60c) has a mesh between 50 and 650 pm, preferably between 100 and 200 pm. 9. Process according to claim 7 or 8, in which at least one, and preferably each, screen printing formulation (67a, 67b, 67c) used for depositing the protective layer (20) comprises a polymeric binder, with preferably of the elastomeric and / or thermoplastic type, and a pigment paste. 10. Process according to claim 9, in which the mass concentration of the polymeric binder in at least one screen printing formulation (67a, 67b, 67c) is between 60 and 80%, preferably between 65 and 75 %. Process according to claim 9 or 10, in which at least one, and preferably each, screen printing formulation (67a, 67b, 67c) used during the depositing of the protective layer (20) comprises a thickener, the mass concentration of the thickener between 1 and 5%, preferably between 2 and 4%. 12. Process according to any one of Claims 9 to 11, in which the viscosity of at least one, and preferably each, screen printing formulation (67a, 67b, 67c) is between 2000 and 16,000 mPa.s., with preferably between 3000 and 5000 mPa.s. 13. Process according to any one of claims 7 to 12, in which the protection layer (20) has, at the end of the depositing step, a surface density between 30 and 320g / m2, preferably between 200 and 300 g / m2. Process according to any one of claims 7 to 13, further comprising, after the step of depositing the protective layer (20), a step of crosslinking the protective layer (20), the crosslinking step comprising a heating step at a temperature between 100 ° C and 180 ° C, preferably between 140 ° C and 160 ° C, for a duration between 1 and 10 minutes, preferably between 3 and 8 minutes. Process according to any one of claims 7 to 14, in which the abrasive cloth (2) is never placed at a temperature higher than 200 ° C.