EP1222245B1 - Cleaning composition, method for cleaning a silk screen and cleaning device - Google Patents

Abstract

The invention concerns a cleaning composition comprising an aqueous solution containing between 0.05 to 5 wt. % of sodium metaperiodate and between 0.05 and 0.75 wt. % of sulfuric acid, and an aqueous solution of 0.5 to 90 wt. % of a mixture of dialkylesters and of 0.5 to 50 wt. % of a non-ionic surfactant. The method for cleaning a silk screen consists in exposing it to such a composition to eliminate ink, the masking product and the ghost image. The device for cleaning comprises a first section (4) wherein are a first ramp (26) of nozzles for spraying a cleaning composition on the screen (2) and a second ramp (32) of nozzles for spraying water under high pressure, and with which is associated a drain tank (20) for recovering the cleaning product and a reservoir (14) of cleaning product separate from the drain tank (20).

Description

The present invention belongs to the field of maintenance of screens used in printing, and more particularly in screen printing.

In screen printing, screens made up of a frame are used. which is stretched a canvas, originally silk but today more commonly nylon / polyester, which has very fine meshes (of the order 100 µm). On these screens, a masking product is first applied intended to fill mesh of the fabric, then we apply ink which passes through the meshes left free and which correspond to the imprint of the pattern to reproduce on the print medium.

For each new pattern to be printed using this technique, you must clean the screen by removing the ink and masking agent.

• dans une première phase, on traite l'écran par un solvant organique qui permet d'éliminer l'encre, puis on effectue un rinçage à l'eau, sous haute pression pour évacuer le solvant et les résidus d'encre,
• dans une seconde phase, on applique sur l'écran une solution aqueuse d'un agent oxydant tel que le periodate de sodium, dite solution de dégravage, pour faire disparaítre le produit de masquage des mailles obstruées, puis on effectue un nouveau rinçage à l'eau, sous haute pression, et
• dans une troisième phase, on élimine l'image fantôme subsistant sur l'écran, au moyen d'un produit chloré, et on réalise un dernier rinçage à l'eau, sous haute pression.

Conventionally, the screen is cleaned in three phases which are as follows:

• in a first phase, the screen is treated with an organic solvent which makes it possible to remove the ink, then a rinsing is carried out with water, under high pressure to remove the solvent and the ink residues,
• in a second phase, an aqueous solution of an oxidizing agent such as sodium periodate, known as a degreasing solution, is applied to the screen in order to remove the masking product from the clogged meshes, then a new rinsing is carried out with water. water, under high pressure, and
• in a third phase, the ghost image remaining on the screen is eliminated, using a chlorine product, and a final rinsing with water is carried out under high pressure.

This cleaning is carried out either manually or automatically in washing tunnels where the stages take place successively in different compartments.

The devices currently used for this cleaning include four compartments. Each compartment is associated with a tray for contain a product corresponding to the above phases.

In the first compartment, there is a tray containing a solvent that can dissolve inks used in screen printing. In this compartment, the screen is sprayed with the product in the tray by nozzles which are mounted on a vertical boom. The vertical ramp is moves in a horizontal direction to spray the entire area of the screen. The sprayed product falls by gravity, with the ink, into the tank.

The second compartment also has a tray containing solvent. The latter is also sprayed using a vertical ramp moving in a horizontal direction on the screen. This solvent is cleaner than that of the first bin. Solvent recycling devices found in the first and second tanks are provided to increase the service life of the product contained in these bins.

Before moving from the second to the third compartment, the screen is washed with high pressure water.

In the third compartment, the corresponding tray contains a degreasing product for removing the masking product. This product is applied to the screen also using nozzles arranged on a ramp vertical that moves horizontally.

In the last fourth compartment, the screen is washed with high pressure water.

The screen is then ready to undergo a new step, that of removal of the ghost image.

During cleaning, the screen is therefore unavailable for a period of up to a day or more.

Indeed, and as an example to illustrate the waste of time dedicated to cleaning a screen, the last phase which consists in eliminating the ghost image is performed by application on both sides of the screen, a product based on chlorine and soda, which is left to act for minus half a day. At the end of this action time, the screen is washed with a solvent to cause residues of ink, masking product and chlorine product, the solvent is left to act, then the screen is rinsed with water, under high pressure. After drying, the screen is again available for next use.

Another disadvantage of cleaning screens is the very great pollution they cause, because effective solvents, such as example of halogenated hydrocarbons, are harmful and not biodegradable, and moreover, the residual mixture of water, solvents and ink collected is difficult to recycle. These solvents are also flammable and their handling especially in large quantities is dangerous.

The problem of the heaviness and the duration of the cleaning process has already been studied. Thus, according to document FR-A-2 354 377, there is known screen cleaning composition for both removing ink and the masking product, this composition consisting of a mixture of a organic solvent, in particular gamma-butyrolactone, N-methyl-2-pyrrolidone or dimethylformamide (DMF), an oxidizing agent such as sodium periodate, and optionally a surfactant.

The treatment of the screen by this composition is however not completely satisfactory because a preliminary step of processing the screen by white spirit is necessary to remove excess ink. In addition, this solution does not solve the problem of solvent pollution residual organic, and can use solvents particularly toxic like DMF.

To limit pollution caused by cleaning compositions and their consequences on the environment, document WO-A-90/08603 provides a composition in which the organic solvents conventionally employees are replaced by a mixture of dibasic esters such as dimethyl esters chosen from succinate, adipate and glutarate dimethyl, which is used in the presence of a surfactant. This mixture of esters, active on printing ink, is not toxic and is biodegradable. The preferred surfactant is nonionic such as an ethoxylated aliphatic alcohol or a ethoxylated alkylphenol. An advantageous composition comprises from 90-100% in weight of the above-mentioned mixture of esters and 10-0% by weight of an aliphatic alcohol ethoxylated.

This composition does not, however, dissolve the masking product, and its action must be supplemented in a conventional manner by a step of degreasing, then a step of treatment with a chlorinated product to eliminate the ghost image.

In the absence of a truly effective solution, the cleaning screens have remained the same for many years, that is to say for at least thirty years, and widely followed in screen printing, despite their many drawbacks.

Document FR-A-2 354 377 describes cleaning compositions which can be used in screen or screen printing processes, based on oxidizing agent and solvent, advantageously based on periodate, of solvent (miscible or not with 'water), and surfactant.

According to the invention, a cleaning composition has been developed which solves all the disadvantages encountered by the methods traditional cleaning, including partial solutions of the prior art.

The invention provides a cleaning composition and method of an effective screen printing screen which lead, in a single step, to removing both the ink and the masking product. This composition is very advantageous because it has a specific activity vis-à-vis products to be removed from the screen, but has no corrosive effect likely damage the canvas or cause early aging.

In addition, the cleaning according to the invention does not leave or substantially no ghost image subsist so that the screen after drying, can be directly reused.

The advantage of the cleaning power of the composition is twofold. First, and as said before, this power is exercised over all products and residues to be removed from the mesh of the canvas, but, moreover; he is almost immediate, and therefore the period of immobilization of the screen due cleaning is greatly reduced.

Despite its effectiveness, this composition is not polluting. Based non-toxic products and safe neither for the manipulator nor for the environment, it is very advantageous.

une solution aqueuse comprenant de 0,05 à 5% en poids de métaperiodate de sodium et de 0,05 à 0,75% en poids d'acide sulfurique, et

une solution de 0,5 à 90% en poids d'un mélange de dialkylesters et de 0,5 à 50% en poids d'un tensioactif non ionique.

Thus, a first object of the invention is a cleaning composition comprising:

an aqueous solution comprising from 0.05 to 5% by weight of sodium metaperiodate and from 0.05 to 0.75% by weight of sulfuric acid, and

a solution of 0.5 to 90% by weight of a mixture of dialkylesters and of 0.5 to 50% by weight of a nonionic surfactant.

The percentages mentioned in this description and the claims are expressed by weight of constituents relative to the weight of the solution when we define a solution as above, or with respect to final weight of the composition when defining the composition, as will be encountered in the following description.

Thus, the proportions of the different constituents of a composition of the invention are defined to obtain a composition suitable for the ink to eliminate.

Advantageously, a composition as defined above further comprises 1 to 15% by weight of periodic acid.

0,05 à 5% en poids de métaperiodate de sodium,

0,05 à 0,75% en poids d'acide sulfurique,

1 à 15% d'acide periodique,

0,5 à 90% en poids d'un mélange de dialkylesters, et

0,5 à 50% en poids d'un tensioactif non ionique.

A particular composition of the invention comprises:

0.05 to 5% by weight of sodium metaperiodate,

0.05 to 0.75% by weight of sulfuric acid,

1 to 15% of periodic acid,

0.5 to 90% by weight of a mixture of dialkylesters, and

0.5 to 50% by weight of a nonionic surfactant.

A composition of the invention also meets the following characteristics, considered independently or in combination.

The mixture of dialkylesters comprises or consists of a mixture glutarate, succinate and dialkyl adipate; preferably it is a mixture of glutarate, succinate and dimethyl adipate, the proportions are advantageously 61-67% for glutarate, 20-26% for succinate and 13-19% for adipate.

The nonionic surfactant is an alkylphenol ethoxide, and preferably nonylphenol ethoxide.

une solution aqueuse de 0,1 à 0,5% en poids de métaperiodate de sodium et de 0,1 à 0,5% en poids d'acide sulfurique,

une solution aqueuse de 1 à 20% en poids d'un mélange de dialkylesters et de 1 à 22% en poids d'un tensioactif non ionique.

A particularly suitable composition includes:

an aqueous solution of 0.1 to 0.5% by weight of sodium metaperiodate and of 0.1 to 0.5% by weight of sulfuric acid,

an aqueous solution of 1 to 20% by weight of a mixture of dialkylesters and from 1 to 22% by weight of a nonionic surfactant.

Another object of the invention is a method for cleaning a screen screen printing, whereby the screen printing screen is exposed to a composition as it has just been defined.

For this purpose, before the exposure step, the two are mixed aqueous solutions of said composition.

Preferably, the exposure of the screen to the composition is carried out by spraying (or vaporization), a technique which will be more particularly used if cleaning is carried out in tunnels; it can also be manual by application, for example by means of a window moistener.

After the exposure time, which can vary from one to five minutes, the screen is rinsed with water, preferably under high pressure.

The inventon also relates to the use of a composition as defined previously for cleaning a screen used in screen printing.

The implementation of the method of the invention no longer requires large installations, a single compartment being sufficient to expose the screen with the cleaning composition, to rinse it or even to dry it.

Thus, yet another object of the invention is a device for the cleaning of screens (2) used in screen printing where a screen screen is exposed to a composition as defined above, said device comprising at least a first compartment (4) in which there is a first ramp (26) of nozzles intended to spray a cleaning composition on the screen (2) and a second ramp (32) of nozzles intended to spray water under high pressure, and which is associated with a tank (20) for recovering the product from cleaning, said device further comprising a reservoir (14) of composition separate cleaning tank (20).

In this way, the product that is sprayed on the screen to be cleaned is a clean product, which does not contain diluted ink. This results in a more efficient cleaning, no longer need two compartments for cleaning the screen. This structure also allows the use of a same bin for recovering the cleaning product.

The container for the cleaning composition is preferably equipped with a filtration system, in order to comply with the legislation in force governing discharge into the sewer. The filtration system will be adapted for reject only product including D.C.O. is less than 2000.

In an advantageous embodiment, the first and second ramps are joined to each other so as to form one unit.

Preferably, the ramps are arranged horizontally. In in this case, we will preferably choose to have mobile ramps and a fixed screen during spraying. The ramps then move advantageously from bottom up then top down to get a good cleaning.

To complete the cleaning, the device advantageously includes motorized rotary brushes, with an axis substantially perpendicular to the plane of the screen.

In one embodiment, the ramps are movable relative to to a screen to be cleaned which remains fixed during the composition spraying cleaner and water, as already mentioned above. However, we could have a mobile screen and fixed ramps. In this case, the ramps would be preferably vertical.

To allow better cleaning, the device includes advantageously a second double ramp arranged so that the screen to be cleaned is located between the two double ramps and can be sprayed on both sides.

Advantageously, the device comprises two dosers, one taking a predetermined amount of a metaperiodate solution from sodium and sulfuric acid, the other taking a predetermined amount a solution of a mixture of dialkylesters and a nonionic surfactant, said dosers being equipped with a water supply. Within one of dispensers, we will obtain an aqueous solution of sodium metaperiodate and sulfuric acid, and within the other doser, we will get a solution aqueous mixture of dialkylesters and a nonionic surfactant. The products to be collected are stored in tanks placed inside or at outside the device. The dosers are hydraulic or electric.

To also allow the elimination of any images ghosts, the device advantageously comprises a second compartment provided with spray means movable relative to the screen. These means of mobile sprayers include for example a double boom, a boom being intended for the spraying of a product allowing the elimination of images ghosts and the other ramp to spraying water under high pressure.

In order to allow rapid drying of the product allowing the elimination of ghost images, the second compartment is provided advantageously of a forced air system making it possible to propel air warm in the second compartment. To further improve drying, we can provide that the second compartment has a mobile ramp by report to the screen allowing the blowing of hot air towards the screen. A better drying is still achieved when the first compartment has a ramp movable relative to the screen, this ramp being a suction ramp intended to initiate drying of the screen.

To avoid the appearance of streaks on the screen after passing through the device according to the invention, means are advantageously provided for oscillate the screen. In this way, during operations concerning the rinsing and drying the screen, a better distribution of the flow is obtained over the screen, which avoids the appearance of streaks corresponding to the limits two adjacent nozzles.

The invention also relates to a kit for cleaning and release of a screen used in screen printing, this kit including a first chamber containing an optionally aqueous solution of alkyl phenol ethoxide and dialkylesters and a second chamber containing a solution aqueous sodium metaperiodate and sulfuric acid.

Figure 1 est une vue en perspective partiellement éclatée d'un dispositif selon l'invention, et

Figure 2 est une vue en coupe selon la ligne de coupe II-II de la figure 1.

In any case, the invention will be clearly understood with the aid of the description which follows, providing an example of a preferred composition of the invention, then with reference to the appended schematic drawing, representing by way of nonlimiting example a preferential embodiment of a device according to the invention and according to which:

FIG. 1 is a partially exploded perspective view of a device according to the invention, and

Figure 2 is a sectional view along the section line II-II of Figure 1.

• on place tout d'abord 20% en poids d'alkyl phénol éthoxyde,
• on ajoute ensuite 13% d'un mélange d'esters diméthyliques disponible dans le commerce,
• on dissout l'ensemble dans 66,4% d'eau,
• on ajoute 0,25% d'acide sulfurique, et
• on rajoute 0,25% en poids de métaperiodate de sodium.

In a preferred reallation example, an aqueous composition is obtained intended for cleaning a screen used in screen printing as follows:

• first of all 20% by weight of alkyl phenol ethoxide is placed,
• then 13% of a mixture of commercially available dimethyl esters is added,
• the whole is dissolved in 66.4% of water,
• 0.25% sulfuric acid is added, and
• 0.25% by weight of sodium metaperiodate is added.

The composition thus obtained makes it possible to clean a screen of screen printing by removing both the inks deposited on this screen and the masking emulsions therein.

The use of a product to remove the ghost image is generally useless after using the cleaning composition described above. Well heard, depending on the inks and emulsions used, the proportions shown above may vary.

The composition thus obtained is non-flammable. Its pH is slightly acidic (between 5.5 and 6). It is not harmful, and responds to European standards in terms of biodegradability which define the threshold minimum of 90% biodegradability.

The cleaning composition described above can be easily filtered after use. Thus after filtration, the filtrate and the reuse for high pressure rinsing.

A device allowing the implementation of the method of the invention is described below with reference to the figures presented above.

Figure 1 shows a cleaning device for remove ink, release and remove ghost images a screen 2 used in screen printing. It has a first compartment 4 and a second compartment 6. Each compartment is in the form of a caisson. The dimensions of the assembly are adapted to the dimension of screens to be cleaned.

A conveyor allows to introduce a screen 2 in the first compartment then pass it to the second compartment. This conveyor comprises a motorized transfer chain 8 and an upper guide 10. The screen 2 is placed on the chain and is kept in vertical position thanks to the upper guide 10. An opening 12 made in an outer wall of the first compartment 4 allows the introduction of the screen 2 on the conveyor.

The first compartment is associated with a reservoir 14 intended for contain a cleaning solution, a pump 16 to pump the product is finding in this tank 14, a high pressure pump 18 for pumping water, a drain pan 20, a double ramp 22 of nozzles and a system chain 24 allowing the displacement of the double ramp 22.

The reservoir 14 is intended to contain a composition of the invention. The pump 16 makes it possible to pump the composition contained in the reservoir 14 towards the double ramp 22. This double ramp 22 is arranged horizontally. It is formed by two parallel, horizontal ramps, joined to each other. A first ramp 26 is connected to the pump 16 by a flexible pipe 28. This first ramp 26 is equipped with small nozzles 30 used to spray the product contained in the reservoir 14. The pressure of spraying is for example between 2 and 4 bars.

The second ramp 32 of the double ramp 22 is connected to the pump high pressure 18 by a flexible hose 34. This second ramp 32 is provided larger nozzles 36 for spraying water under pressure about 120 bars.

The double ramp 22 is arranged horizontally. The system chain 24 makes it possible to move this double ramp 22 from bottom to top and then motorized up and down. The double ramp 22 is fixed close to each of its ends to a chain itself mounted around two pulleys, one of which is driven by a motor. Such a system is known from skilled in the art and is not described in detail herein description. Any other system allowing the double ramp to be moved can also agree.

On the other side of screen 2, there is a simple ramp 38 of vacuum drying. This ramp 38 also extends horizontally and can move up and down and up and down using two systems chain 24 as described above.

Under the screen 2 and the endless belt 8, is the drain pan 20. This tank is intended to recover the product and the water falling by gravity after have been sprayed by one of the booms of the double boom 22. This tank is connected to the sewer or to a filtration system. If we use the composition indicated above, we can directly connect this tray 20 to the sewer because the composition is biodegradable. However, to achieve water savings, it is also possible to connect the drain pan to a filtration system to recycle water. So the high pressure pump 18 can be supplied directly with water by a water supply network or it can be supplied with water by recycled water. The filtration system has not been shown in the drawing but it could of course be incorporated into this device.

When provided, the second compartment 6 has a structure very close to that of the first compartment. We find in this second compartment 6 a reservoir 40, a pump 42 associated with this reservoir, a high pressure pump 44 intended to pump water, and a tank not shown. There is also one side of the treadmill 8 which also crosses the second compartment, a double ramp mounted on two chain systems such as chain systems 24. On the other side of the treadmill 8 there is also a single ramp mounted on two chain systems. For the sake of clarity, this double ramp and this ramp were not shown in the drawing.

The reservoir 40 contains a product, known to those skilled in the art, eliminating ghost images on a screen serigraphy. This product is a chlorinated gel. The pump 42 allows, by via a flexible hose not shown, to send the contained product in the reservoir 40 towards a ramp of the corresponding double ramp. The product used to eliminate a ghost image is then sprayed with nozzles at a pressure of approximately 2 bars. The high pressure pump 44 is quant to it connected to the other ramp of the double ramp of the second compartment by another flexible hose. This ramp also includes nozzles intended spraying water under a pressure of around 120 bars.

The single ramp is in contrast to the single ramp of the first compartment 4, provided with nozzles blowing hot air. A fan and a heating resistor, not shown in the drawing, allow to send air at about 30 ° to this ramp from where it is blown in the direction of the screen.

The drain pan receives the products which fall by gravitation of screen 2. In addition to the ramp blowing hot air, we plan to level from the second compartment a forced air system 46.

The operation of this device is then as follows.

Screen 2 is routed automatically by conveyor 8 and using of the upper guide 10 inside the first compartment 4. The double ramp 22 is then in the low position. Once screen 2 is in place, the first ramp 26 is supplied by the pump 16 with the composition of the invention. The double ramp then begins to move up. Once in top of screen 2, it moves downwards while continuing to spray the composition. Surplus product, mixed with ink and product masking then falls into the drain pan 20. After allowing the produces a few seconds, or a few tens of seconds, on screen 2, the second ramp 32 of the double ramp 22 is supplied with water by the pump high pressure 18. The double ramp 22 then moves again towards the up until you get to the top of screen 2 then it moves down to return to its original position. This rinses the screen perfectly. Water rinse, to which the composition has been mixed, as well as inks and of the masking product, then ends up in the drain pan 20.

Screen 2 is pre-dried using the suction ramp 38. This ramp is also moved from its initial position being at the bottom of screen 2 up to the top of screen 2 and then towards its position initial. Any excess water is thus removed from screen 2. Preferably, screen 2 swings horizontally from left to right to avoid streaking vertical. A cam system not shown allows this movement. The amplitude of the oscillations is for example a few centimeters.

Once the suction boom 38 has returned to its position initial, the screen 2 is conveyed to the second compartment 6. From the product eliminating ghost images is then sprayed by the nozzles of a ramp of the double ramp of this compartment. Pump 42 sends the product towards this ramp. The latter moves from bottom to top and then from up and down to spray the product over the entire surface of the screen. The forced air system 46 is then started. It blows air inside compartment to try to keep it cool about 30 °. A dehumidifier not shown can be associated with the forced air system 46 so that it sends dry air into the second compartment 6. Meanwhile, the single ramp blowing hot air moves up and down and up and down to blow hot air out the whole screen 2 and dry the product well to eliminate any possible ghost image. Several passages from bottom to top and then from top to bottom of the Fan ramp can be provided. The product to eliminate the image ghost acts when dry. Once this product is thoroughly dried and has acted, the double ramp of the second compartment 4 is then supplied with water under pressure by the high pressure pump 44. The ramp then moves from bottom to top then top to bottom by spraying each time with water on all the surface of the screen 2. The water spray and the product intended to eliminate the ghost images then fall into the second bin compartment 6.

To avoid making vertical streaks on screen 2, you can in the second compartment also plan to oscillate the screen 2 in horizontal direction. Here too, an oscillation of an amplitude of a few centimeters is sufficient.

Once the screen is rinsed, it is automatically routed to the outside of the second compartment 6 and of the device described above. he can then be received manually or we can also imagine a automatic tray for receiving screens at the output of this second compartment 6. Similarly, it is possible to have an automatic charger screens at the entrance to the first compartment 4.

It goes without saying that the invention is not limited to the form of preferred embodiment described above by way of nonlimiting example; she in on the contrary embraces all variants of execution within the framework of claims below.

So, for example, instead of having just one tank for the composition at the level of the first compartment, we could have two separate tanks, one of them containing an aqueous solution comprising 0.05 to 5% by weight of sodium metaperiodate and 0.05 to 0.75% by weight sulfuric acid, and the other containing an aqueous solution of 0.5 to 90% by weight of a mixture of dialkylesters and 0.5 to 50% by weight of a surfactant non-ionic. The same boom could spray these two simultaneously products.

The fact that the ramps move from bottom to top and then from top to bottom bottom is a preferred embodiment. A moving vertical ramp horizontally can also be considered.

The fact of providing a double ramp (composition + water) is optional. We could indeed have two separate ramps.

The cleaning of a screen according to the method of the invention does not entail usually not the appearance of a ghost image. In the majority of cases, it is therefore unnecessary to have a second compartment.

The suction and blower bars are optional. Thereby, the systems allowing these ramps to oscillate are also optional.

Any other conveying, loading, unloading system of screens may of course be suitable in the present invention.

Claims (15)

1. Cleaning composition, characterized in that it comprises, in an aqueous phase:

   from 0.05 to 5% by weight of sodium metaperiodate

   from 0.05 to 0.75% by weight of sulfuric acid,

   from 0.5 to 90% by weight of a mixture of dialkyl esters,

   from 0.5 to 50% by weight of a nonionic surfactant.
2. Composition according to Claim 1, characterized in that it comprises:

   from 0.1 to 0.5% by weight of sodium metaperiodate,

   from 0.1 to 0.5% by weight of sulfuric acid,

   from 1 to 20% by weight of a mixture of dialkyl esters,

   from 1 to 22% by weight of a nonionic surfactant.
3. Composition according to Claim 1, characterized in that the mixture of dialkyl esters comprises or consists of a mixture of dialkyl glutarate, succinate and adipate.
4. Composition according to Claim 3, characterized in that the mixture of dialkyl esters comprises or consists of a mixture of dimethyl glutarate, succinate and adipate.
5. Composition according to Claim 4, characterized in that the mixture of dialkyl esters comprises or consists of a mixture of 61 - 67% dimethyl glutarate, 20 - 26% dimethyl succinate and 13 - 19% dimethyl adipate.
6. Composition according to Claim 1, characterized in that the nonionic surfactant is an ethoxylated alkylphenol.
7. Composition according to Claim 6, characterized in that the ethoxylated alkylphenol is ethoxylated nonylphenol.
8. Composition according to Claim 1, characterized in that it furthermore comprises 1 to 15% by weight of periodic acid.
9. Kit for preparing by mixing a cleaning composition according to any one of claims 1 to 8, characterized in that it comprises, separately, a first aqueous solution comprising the sodium metaperiodate and the sulfuric acid, and a second aqueous solution comprising the mixture of dialkyl esters and the nonionic surfactant.
10. Use of a composition according to any one of claims 1 to 8, for cleaning a screen used in screen printing, said screen having, before cleaning, a fabric, a masking product filling some mesh cells of said fabric and leaving free the other mesh cells of said fabric, and ink coating the whole screen.
11. Process for cleaning a screen (2) used in screen printing, said screen having, before cleaning, a fabric, a masking product filling some mesh cells of said fabric and leaving free the other mesh cells of said fabric, and ink coating the whole screen, characterized in that, in a single step, the ink and the masking product are removed, a single cleaning composition for removing the ink and the masking product being obtained by spraying, contacting the screen to be cleaned, said composition being defined in any one of claims 1 to 8.
12. Process for implementing a machine for cleaning a screen (2) used in screen printing, said screen having, before cleaning, a fabric, a masking product filling some mesh cells of said fabric and leaving free the other mesh cells of said fabric, and ink coating the whole screen, said machine comprising a compartment, spraying means in said compartment, means for installing said screen in said compartment facing the spraying means, said implementation being characterized in that, in said single compartment, the ink and the masking product are removed using a single cleaning composition as defined in any one of claims 1 to 8, said composition contacting the screen to be cleaned, being determined for removing both the ink and the masking product, and being obtained with the spraying means.
13. Process for implementing according to claim 12, characterized in that the spraying means are arranged in order to comprise a first spray bar (26) having nozzles intended to spray a cleaning composition onto the screen (2) and a second spray bar (32) having nozzles intended to spray high-pressure water for rinsing the screen.
14. Process for implementing according to claim 13, characterized in that a recovery tank (20) for recovering the cleaning composition is combined to said compartment, and a cleaning composition reservoir (14) for the cleaning composition is combined to said compartment, separate from said recovery tank.
15. Machine for cleaning a screen (2) arranged for the implementation according to claim 12, characterized in that it comprises two metering devices, one taking off a predetermined quantity of sodium metaperiodate and sulfuric acid, the other taking off a predetermined quantity of a mixture of dialkyl esters and a nonionic surfactant, said metering devices being fitted with a water feed.

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