WO2015185784A1 - Conveyor belt having a biocide composition and composition, production method and corresponding uses - Google Patents

Abstract

The invention relates to a conveyor belt having a biocide composition and composition, production method and corresponding uses. The conveyor belt, having an external face (3) formed using a layer of plastic material (1), comprises a biocide composition which has at least two biocides of the group formed by zinc pyrithione, 1,2-benzisothiazol-3-one, 2-Methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, zinc oxide, and titanium oxide, and which can be encapsulated. Preferred combinations are, for example: zinc pyrithione and 1,2-benzisothiazol-3-one; zinc pyrithione and 2-Methyl-4-isothiazolin-3-one and/or 5-chloro-2-methyl-4-isothiazolin-3-one; zinc oxide or titanium oxide and 1,2-benzisothiazol-3-one. In the latter case, it is interesting that 2-Methyl-4-isothiazolin-3-one is also included. These belts are preferably used for transporting pharmaceutical and/or food products, for transporting products in hospitals, and/or for transporting goods or luggage in ports or airports.

Description

 CONVEYOR BAND WITH A BIOCIDE COMPOSITION AND COMPOSITION, MANUFACTURING PROCEDURE AND USES

 CORRESPONDING DESCRIPTION

Field of the Invention

The invention relates to a conveyor belt comprising an outer layer formed with a sheet of plastic material comprising a biocidal composition and a manufacturing process and a use thereof.

The invention also relates to a biocidal composition for the prevention of the proliferation of microorganisms and a use thereof.

State of the art

Conveyor belts are known, which are used in a plurality of industrial applications for the transport of all kinds of products. Reference is made in the present invention to those comprising an outer layer formed with a sheet of plastic material. The outer layer, that is, the one on the outer surface, is the one that is in contact with the material to be transported, that is, it is the one that is oriented upwards in the forward path of the conveyor belt and downwards in The return path.

These conveyor belts are subject to environmental aggressions. In particular, they are subject to possible colonization by microorganisms. This may be particularly relevant in the case of conveyor belts dedicated to the transport of food, pharmaceutical or cosmetic products, etc.

This forces the conveyor belts to have to be treated properly (washed, disinfected) to keep them in the right conditions. suitable for use, as many times as necessary. This implies a cost and, in certain cases, stoppages in the facilities, to be able to carry out the necessary disinfection and cleaning actions. In addition, these actions can affect the duration of the band's life.

Exhibition of the invention

The object of the invention is to overcome these drawbacks. This purpose is achieved by a conveyor belt of the type indicated at the beginning, characterized in that the biocidal composition comprises at least 2 biocides selected from the group consisting of:

 zinc pyrithione (ZnP),

1,2-bencisothiazol-3-one (BIT) (this compound can be found in the literature under several equivalent names: 1,2-bencisothiazol-3-one, 1, 2- benzothiazol-3 (2H) -one and N- butyl-1, 2-benzothiazol-3-one, in English its denomination is 1,2-benzisothiazoline-3-one or 1,2-benzisothiazoline-3 (2H) -one, in any case it is the compound with the n ^e CAS 2634-33-5),

 2-methyl-4-isothiazolin-3-one (MIT),

- 5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT),

 zinc oxide (ZnO), and

titanium oxide (Ti0 ₂ ).

Indeed, in this way the band has a very low risk of colonization and / or proliferation of microorganisms. In this way, different cleaning strategies can be proposed, while maintaining the necessary technical and legal requirements.

These biocides are particularly effective in their antimicrobial activity and, simultaneously, have a low toxicity so they are particularly suitable in the case that the band is intended for the transport of food, pharmaceutical, cosmetic or similar materials. Additionally, they are biocides whose duration is high. It should be noted that some Known biocides, such as those based on silver ions, lose their effectiveness very quickly with the cleaning cycles to which a band is subjected, so they are not as suitable when it comes to bands that should be cleaned frequently . The possible cost problems must also be taken into account since, for example, the attempt to compensate for the loss of effectiveness over time by means of a higher initial concentration of biocide can significantly increase the cost.

On the other hand, biocides composed of nanoparticles are preferably avoided since their use is usually restricted in certain applications (such as foodstuffs) since their possible toxicity is unknown.

In general, the biocidal composition can be added as a surface coating or it can be included in the mass of the material that forms the sheet that defines the outer face (i.e., the outer layer). The band can be formed by a single sheet of plastic material, in which case the biocidal composition can be added to the material that makes up the entire band, but usually the band can have a more complex structure, with a plurality of sheets. In the latter case, it is sufficient that only the material of the sheet defining the outer face (which is the upper one in the path of the conveyor belt) includes the biocidal composition. The manufacturing process can be, for example, by hot extrusion, which is carried out with the plastic material already mixed with the biocidal composition. The biocides of this selection have a higher microbiological activity, a lower toxicity and can be used at concentrations such that the cost of the band is not negatively affected. The combination of two of these biocides allows the use of lower concentrations of each of them. The following combinations are particularly advantageous:

- zinc pyrithione and 1,2-benzothiazol-3-one. Preferably the concentration of zinc pyrithione is between 10 and 50,000 ppm by weight with respect to total weight of the composition, and most preferably between 100 and 20,000 ppm by weight with respect to the total weight of the composition. On the other hand, the concentration of 1,2-benzothiazol-3-one is advantageously between 10 and 10,000 ppm by weight with respect to the total weight of the composition, and most preferably between 100 and 1,000 ppm by weight with respect to the total weight. of the composition.

- zinc pyrithione and a biocide selected from the group consisting of 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one and a mixture of both. Preferably the concentration of zinc pyrithione is between 10 and 50,000 ppm by weight with respect to the total weight of the composition, and most preferably between 100 and 20,000 ppm by weight with respect to the total weight of the composition. The concentration of the biocide selected from the group consisting of 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one and a mixture of both is advantageously comprised between 10 and 10,000 ppm by weight with respect to the total weight of the composition, and most preferably between 100 and 1,000 ppm by weight with respect to the total weight of the composition.

- zinc oxide and 1,2-benzothiazol-3-one or titanium oxide and 1,2-benzothiazol-3- one. Preferably the concentration of zinc oxide or titanium oxide is between 100 and 100,000 ppm by weight with respect to the total weight of the composition, and most preferably between 0.5% and 5% by weight with respect to the total weight of the composition. Advantageously zinc oxide and titanium oxide are always accompanied by another biocide since, in isolation, they have reduced biocidal properties. On the other hand, the concentration of 1, 2-benzothiazol-3-one is preferably between 10 and 1, 000 ppm by weight with respect to the total weight of the composition, and most preferably between 100 and 1, 000 ppm by weight with respect to the total weight of the composition. Titanium oxide is a suitable substitute for zinc oxide, for example in cases where zinc oxide cannot be used for legal or technological reasons.

Preferably the compositions with two biocides indicated above further comprise a third biocide, specifically 2-methyl-4-isothiazolin-3-one. Advantageously the concentration of 2-methyl-4-isothiazolin-3-one it is comprised between 10 and 10,000 ppm by weight with respect to the total weight of the composition.

Advantageously at least one of said biocides is at least partially encapsulated. This is because the inclusion in the band of these biocides is complex and has multiple limitations. Indeed, biocides can interfere in different ways with their environment, since they can react with the components that surround them, they can alter the polymerization kinetics of the polymers in which they want to be included, they can undergo transformations and degradations during the various manufacturing processes of products, etc.

Thus, biocides may be responsible for: - Color changes of the product.

 Changes in mechanical properties: lower tensile strength (fragility), lower elongation resistance (deformations),

Therefore it can be advantageous to encapsulate them.

There are various encapsulation techniques, such as the commonly known as spray drying, SBR precipitate (styrene butadiene rubber), fluidized bed, etc. There are also encapsulation techniques that combine two or more of the above. In general, the encapsulation technique itself is not part of the present invention and is also known to a person skilled in the art and is therefore not detailed in more detail.

The benefits of using encapsulated biocides are, among others: - Greater durability of the biocidal effect by retention thereof. Thanks to this biocidal activity is achieved after two years of use or 500 washing cycles, the band sufficient to pass the tests of ISO 22196: 201 1. Less migration to transported products. This is particularly interesting in the case of applications in which food, pharmaceuticals, cosmetic products, etc. are transported, since it allows to be within the legal margins.

- Prevention of alterations in the material in which it is included: changes in color or physical properties, such as tensile strength or fragility.

Preferably the band additionally has a biocidal composition on its inner face. Indeed, although the possible contamination of the inner face is less relevant, it must also be controlled to avoid exceeding risk levels, so its protection is also advantageous. The underside can be formed by a layer that includes a textile material. In a manner analogous to the case of the outer face, the biocidal composition can be included by a surface coating or it can be included in the mass of the material that forms the layer that defines the inner face. In the case of being a textile material, the biocidal composition can be included in the material that will be used to manufacture the corresponding thread.

Advantageously the biocidal composition and / or the biocidal composition of the inner side of the band comprise a photocatalytic biocide. Indeed, photocatalytic biocides generate a very interesting oxidizing potential due to their biocidal properties. In addition, these photocatalytic biocides can also oxidize the organic matter that can reach the band (such as traces of water with protein, blood, etc.), which facilitates the cleaning of the band.

Advantageously, the photocatalytic biocide is titanium oxide, zinc oxide or a mixture of both. In the case of titanium oxide, the preferred form is anatase. Preferably the concentration of said photocatalytic biocide is between 0.01% and 10% by weight with respect to the total biocidal composition of the inner side of the band (or the outer face of the band), and most preferably between 0, 5% and 5% by weight with respect to the total weight of the composition. Another advantageous solution is to include a photocatalytic biocide in the biocidal composition of the outer face, in combination with other biocides, such as the preferred cases already described above. A particularly advantageous solution is obtained when the band is formed by a single sheet of plastic material that has the biocidal composition included in its mass. In this way it is achieved in a particularly simple way that both the outer and inner faces have a biocidal composition.

Another particularly advantageous solution is obtained when, in the case of conveyor belts composed of more than one sheet, both the outer face and the inner face have the same biocidal composition. The invention also aims at a biocidal composition suitable for the prevention of the proliferation of microorganisms on the external surface of a conveyor belt, as described above as well as facilitating its cleaning and disinfection by the usual sanitation processes used in the industry. .

A subject of the invention is also a method of manufacturing a conveyor belt, wherein said conveyor belt comprises an outer face formed with a sheet of plastic material, characterized in that said sheet of plastic material is manufactured from a mass of plastic material comprising a biocidal composition according to the invention.

The object of the invention is also the use of a biocidal composition according to the invention for the manufacture of a conveyor belt. Finally, the object of the invention is also the use of a conveyor belt according to the invention for the transport of pharmaceutical and / or food products. Other preferred uses are for the transport of products in hospitals (particularly for the transport of surgical material to operating rooms or similar), and for the transport of goods or luggage in ports or airports.

Brief description of the drawings

Other advantages and features of the invention can be seen from the following description, in which, without any limitation, preferred embodiments of the invention are mentioned, mentioning the accompanying drawings. The figures show:

Figs. 1 to 4, four schematic views of a partial longitudinal section of four embodiments of a band according to the invention.

Detailed description of embodiments of the invention

Fig. 1 shows a first embodiment of a conveyor belt according to the invention. In this case the band is formed by a single sheet of plastic material 1 which has a biocidal composition according to the invention included in its mass. Thus, both the outer face 3 and the inner face 5 are formed by a sheet of plastic material 1, which is the same for both sides 3, 5, and which, in both cases, comprises a biocidal composition, which is the same for both sides 3, 5.

The conveyor belt of Fig. 2 is also formed by a single sheet of plastic material 1. However, in this case, the outer face 3 has a surface coating 7 with the biocidal composition. In this case, the sheet 1 may not have any biocidal composition or it may have a second biocidal composition, so that the inner face 5 has a different biocidal composition from the outer face 3. The conveyor belt of Fig. 3 is formed by three sheets of plastic material, an upper sheet 1, an intermediate sheet 1 'and a lower sheet 1 ". In this case the upper sheet 1, which is what forms the outer face 3 has a biocidal composition in its mass. On the other hand, the lower sheet 1 ", which forms the inner face 5, may not have any biocidal composition, have the same biocidal composition as the upper sheet 1, or have a different biocidal composition to the biocidal composition of the topsheet 1.

The conveyor belt of Fig. 4 is formed by two sheets of plastic material, the top sheet 1 and the bottom sheet 1 ". In this case, the top sheet 1 has a surface coating 7, which is the one with the biocidal composition On the other hand, the bottom sheet 1 "may not have any biocidal composition, have the same biocidal composition as the surface coating 7 or have a different biocidal composition.

As can be seen, many other combinations are possible, for example with surface coatings on the inner face 7, with more or less sheets, etc.

Examples

All percentages are by weight with respect to the total composition, that is, the mass that forms the sheet that defines the outer face. Example 1 :

Three mixtures are made with the following compositions:

Zinc pyrithione (1,000 ppm) + free or encapsulated BIT (100 ppm):

BIT (500 ppm) + free or encapsulated Zn Oxide (1%):

MIT (250 ppm) + BIT (250 ppm) + free or encapsulated Zn Oxide (1%): In all these 6 cases, the mixtures are included in the polymeric material of the outer sheet of the conveyor belt, at the indicated concentrations. In fact, it is a band with a single sheet of plastic material, like the one in fig. one . The polymeric material used is thermoplastic polyurethane (TPU). Reductions greater than 2 logs are achieved (1 log (logarithm) is to pass from a microbial count of a logarithmic unit superior to a lower one) with the microorganisms and procedures indicated in ISO 22196: 201 1, after subjecting the material to 500 industrial wash cycles Each industrial wash cycle comprises the following stages:

- the samples were subjected to a rinse with plenty of water at room temperature, to eliminate all possible residues on the surface. This process was performed for 5 minutes. - subsequently it was applied by immersion alkaline detergent solution 50 ^and C, with a contact time of 15 minutes.

- After this time, he turned to make a rinse with water 40 ^and C, with immersion and stirring to verify the complete elimination of foam in the product. The necessary time was around 15 minutes.

- After this process, the material was dried.

This process was repeated serially, simulating intense industrial cleaning. The industrial wash cycles used in the following examples have been the same as those described above.

Example 2: A mixture is made with the following composition:

Silver ions and particle mixtures (clays, silicon, borosilicate, silicates, zeolites, polystyrene, acrylamide, polyvinyl, acrylates, gelatin or ceramics) that incorporate silver ions (1 000 ppm). In all these cases, the mixtures are included in the polymeric material of the single sheet that forms the conveyor belt, at the indicated concentrations. The polymeric material used is thermoplastic polyurethane (TPU). Reductions greater than 2 logs are achieved at time 0 (the time before the first wash has been called "time 0"), with the microorganisms and procedures indicated in ISO 22196: 201 1. However, the biocidal property disappears quickly when the material is subjected to between 1 and 10 cycles of industrial washing. The action of these compounds is based on the attraction they feel for the bacterial wall and the interference they generate there. However, the products added with silver ions have a very low efficiency (from 1 to 10 cleaning cycles). Efficiency is likely to be lost due to its leachate in the water cleaning process or precipitation with the water chloride or the disinfectants used.

Example 3:

A mixture is made with the following composition:

ZnO only, without mixing with another biocide, in concentrations up to 1%

It is included in thermoplastic polyurethane (TPU) at the indicated concentration. The biocidal effect is low, with microbial reductions of less than 1 log with the microorganisms and procedures indicated in ISO 22196: 201 1

Example 4:

A mixture is made with the following composition:

BIT only, at its maximum legal concentration (500 ppm) The biocide is included in thermoplastic polyurethane (TPU). Its biocidal action, measured according to the procedures and microorganisms indicated in ISO 22196: 201 1, does not reach 1.5 logarithms of reduction at time 0 and is completely lost after subjecting the material to 100 cycles of industrial washing.

Example 5:

A mixture is made with the following composition: ZnP only, at 1% w / w.

The biocide is included in thermoplastic polyurethane (TPU). Its biocidal action measured according to the procedures and microorganisms indicated in ISO 22196: 201 1, exceeds 4 logarithms of reduction in time 0 and is maintained between 4 and 2 logarithms after subjecting the material to 500 cycles of industrial washing, equivalent to one year of use.

Example 6: A mixture is made with the following composition: ZnP only but encapsulated, at 2% w / w.

The biocide is included in thermoplastic polyurethane (TPU). Its biocidal action measured according to the procedures and microorganisms indicated in ISO 22196: 201 1, exceeds 4 logarithms of reduction in time 0, showing no loss of biocidal action after subjecting the material to 500 cycles of industrial washing, equivalent to a year of use Example 7:

An uncapsulated ZnO (1%) + BIT (500 ppm) mixture added to a thermoplastic polyurethane (TPU) band has migration values of 5 mg / kg. When the BIT is encapsulated by "spray drying" with a coating based on polysaccharides, migration reductions are achieved at least of an order of logarithmic magnitude. The mixture is included in the polymeric material of the conveyor belt, at the indicated concentration. The polymeric material used is thermoplastic polyurethane (TPU). Its biocidal action is good from the first moment, with reductions greater than 3 logs that remain above the 2 logs, after subjecting the material to 500 cycles of industrial washing, with the microorganisms and procedures indicated in ISO 22196 : 201 1.

Example 8:

A mixture of ZnO (1%) + BIT (500 ppm) without encapsulation.

The mixture is included in thermoplastic polyurethane (TPU) of the conveyor belt, at the indicated concentration. Thus, reductions greater than 2 logs are achieved with the microorganisms and procedures indicated in ISO 22196: 201 1, after subjecting the material to 100 cycles of industrial washing.

Example 9:

A mixture of ZnO (1%) + BIT (500 ppm) encapsulated in precipitated SBR.

The mixture is included in thermoplastic polyurethane (TPU), which is the polymeric material of the outer sheet of the conveyor belt, at the indicated concentration. Thus, reductions greater than 2 logs are achieved with the microorganisms and procedures indicated in ISO 22196: 201 1, after subjecting the material to 500 cycles of industrial washing. Example 10:

A mixture of T0 ₂ (1%) + BIT (500 ppm) without encapsulation. The mixture is included in thermoplastic polyurethane (TPU), which is the polymeric material of the conveyor belt, at the indicated concentration. Thus, reductions greater than 2 logs are achieved with the microorganisms and procedures indicated in ISO 22196: 201 1, after subjecting the material to 100 cycles of industrial washing.

Example 1 1:

A mixture of Ti0 ₂ (1%) + BIT (500 ppm) encapsulated in precipitated SBR. The mixture is included in thermoplastic polyurethane (TPU), which is the polymeric material of the band, at the indicated concentration. Reductions greater than 2 logs are achieved with the microorganisms indicated in ISO 22196: 201 1, after subjecting the material to 500 cycles of industrial washing. Example 12:

Addition of Ti0 ₂ (1%).

The product is added in the polymeric material of the conveyor belt, at the indicated concentration. The polymeric material used is thermoplastic polyurethane (TPU). Reductions of around 1.5 logs are achieved with the microorganisms and procedures indicated in ISO 27447: 2009, after subjecting the material to 500 cycles of industrial washing. Example 13:

Addition of Ti0 ₂ microcrystals (1%). The product is added in the polymeric material of the conveyor belt, at the indicated concentration. The polymeric material used is thermoplastic polyurethane (TPU). Reductions greater than 1.5 logs are achieved with the microorganisms indicated in ISO 27447: 2009, after subjecting the material to 500 cycles of industrial washing.

Claims

1 - Conveyor belt comprising an outer face (3) formed with a sheet of plastic material (1), wherein said sheet of plastic material (1) comprises a biocidal composition, characterized in that said biocidal composition comprises at least 2 biocides selected from between the group formed by:  zinc pyrithione, - 1,2-bencisothiazol-3-one,  2-methyl-4-isothiazolin-3-one,  5-Chloro-2-methyl-4-isothiazolin-3-one,  zinc oxide, and  titanium oxide. 2 - Band according to claim 1, characterized in that said composition comprises zinc pyrithione and 1,2-benzothiazol-3-one. 3 - Band according to one of claims 1 or 2, characterized in that the concentration of zinc pyrithione is between 10 and 50,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 20,000 ppm by weight with respect to the total weight of the composition. 4 - Band according to any one of claims 1 to 3, characterized in that the concentration of 1,2-benzothiazol-3-one is between 10 and 10,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 1,000. ppm by weight with respect to the total weight of the composition. 5 - A band according to claim 1, characterized in that said composition comprises zinc pyrithione and a biocide selected from the group consisting of 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin- 3-one and a mixture of both. 6 - Band according to claim 5, characterized in that the concentration of zinc pyrithione is between 10 and 50,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 20,000 ppm by weight with respect to the total weight of the composition. 7 - Band according to any one of claims 1 to 6, characterized in that the concentration of the biocide selected from the group consisting of 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3 -one and a mixture of both is between 10 and 10,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 1, 000 ppm by weight with respect to the total weight of the composition. 8 - A band according to claim 1, characterized in that said composition comprises zinc oxide and 1,2-benzothiazol-3-one or titanium oxide and 1,2-benzothiazol-3-one. 9 - Band according to any one of claims 1 to 8, characterized in that the concentration of zinc oxide or titanium oxide is between 100 and 100,000 ppm by weight with respect to the total weight of the composition, preferably between 0.5% and 5 % by weight with respect to the total weight of the composition. 10 - Band according to one of claims 8 or 9, characterized in that the concentration of 1,2-benzothiazol-3-one is between 10 and 1, 000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 1 .000 ppm by weight with respect to the total weight of the composition. 1 - A band according to any one of claims 8 to 10, characterized in that said composition additionally comprises 2-methyl-4-isothiazolin-3-one. 12 - Band according to claim 1, characterized in that the concentration of 2- methyl-4-isothiazolin-3-one is between 10 and 10,000 ppm by weight with respect to the total weight of the composition. 13 - Band according to any of claims 1 to 12, characterized in that at least one of said biocides is at least partially encapsulated. 14 - Band according to any of claims 1 to 13 characterized in that it additionally has a biocidal composition on its inner face (5). 15 - Band according to any of claims 1 to 14, characterized in that the biocidal composition and / or the biocidal composition of the inner face (5) of the band comprises a photocatalytic biocide. 16 - Band according to claim 15, characterized in that said photocatalytic biocide is titanium oxide, zinc oxide or a mixture of both. 17 - Band according to claim 16, characterized in that the concentration of said photocatalytic biocide is between 0.01% and 10% by weight with respect to the total biocidal composition of the inner face (5) of the band, preferably between 0, 5% and 5% by weight with respect to the total weight of the composition. 18 - Band according to any of claims 1 to 17, characterized in that it is formed by a single sheet (1) of plastic material that simultaneously forms an outer face (3) and an inner face (5), wherein said sheet (1) has said biocidal composition included in its mass. 19 - Band according to any of claims 14 to 18, characterized in that it is formed by a plurality of bands of plastic material (1, 1 ', 1 "), wherein said outer face (3) and said inner face (5) comprise the same biocidal composition 20 - Biocidal composition suitable for the prevention of the proliferation of microorganisms on the outer surface of a conveyor belt, characterized in that it comprises at least two biocides selected from the group consisting of: zinc pyrithione,  1,2-bencisothiazol-3-one,  2-methyl-4-isothiazolin-3-one, - 5-Chloro-2-methyl-4-isothiazolin-3-one,  zinc oxide, and  titanium oxide. 21 - Composition according to claim 20, characterized in that it comprises zinc pyrithione and 1,2-benzothiazol-3-one. 22 - Composition according to one of claims 20 or 21, characterized in that the concentration of zinc pyrithione is between 10 and 50,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 20,000 ppm by weight with respect to the total weight of the composition. 23 - Composition according to any one of claims 20 to 22, characterized in that the concentration of 1,2-benzothiazol-3-one is between 10 and 10,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 1,000. ppm by weight with respect to the total weight of the composition. 24 - Composition according to claim 20, characterized in that it comprises zinc pyrithione and a biocide selected from the group consisting of 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3- one and a mixture of both. 25 - Composition according to claim 24, characterized in that the concentration of zinc pyrithione is between 10 and 50,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 20,000 ppm by weight with respect to the total weight of the composition. 26 - Composition according to any of claims 20 to 25, characterized in that the concentration of the biocide selected from the group consisting of 2- methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3 -one and a mixture of both it is comprised between 10 and 10,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 1,000 ppm by weight with respect to the total weight of the composition. 27 - Composition according to claim 20, characterized in that it comprises zinc oxide and 1,2-benzothiazol-3-one or titanium oxide and 1,2-benzothiazol-3-one. 28 - Composition according to any of claims 20 to 27, characterized in that the concentration of zinc oxide or titanium oxide is between 100 and 100,000 ppm by weight with respect to the total weight of the composition, preferably between 0.5% and 5 % by weight with respect to the total weight of the composition. 29 - Composition according to one of claims 20 or 28, characterized in that the concentration of 1,2-benzothiazol-3-one is between 10 and 1,000 ppm by weight with respect to the total weight of the composition, preferably between 100 and 1 .000 ppm by weight with respect to the total weight of the composition. Composition according to any one of claims 27 to 29, characterized in that it additionally comprises 2-methyl-4-isothiazolin-3-one. Composition according to claim 30, characterized in that the concentration of 2-methyl-4-isothiazolin-3-one is between 10 and 10,000 ppm by weight with respect to the total weight of the composition. 32 - Composition according to any of claims 20 to 31, characterized in that at least one of said biocides is at least partially encapsulated. 33 - Method of manufacturing a conveyor belt, wherein said conveyor belt comprises an outer face (3) formed with a sheet of plastic material (1), characterized in that said sheet of plastic material (1) is manufactured to from a mass of plastic material comprising a biocidal composition according to any one of claims 20 to 32. 34 - Use of a biocidal composition comprising at least 2 biocides selected from the group consisting of:  zinc pyrithione,  1,2-bencisothiazol-3-one,  2-methyl-4-isothiazolin-3-one,  5-Chloro-2-methyl-4-isothiazolin-3-one, - zinc oxide, and  titanium oxide, for the manufacture of a conveyor belt. 35 - Use of a biocidal composition according to any of claims 20 to 32, for the manufacture of a conveyor belt. 36 - Use of a biocidal composition comprising at least 2 biocides selected from the group consisting of: - zinc pyrithione,  1,2-bencisothiazol-3-one,  2-methyl-4-isothiazolin-3-one,  5-Chloro-2-methyl-4-isothiazolin-3-one,  zinc oxide, and - titanium oxide, for the manufacture of a piece or sheet of polymeric material (1, 1 "). 37 - Use of a biocidal composition according to any of claims 20 to 32, for the manufacture of a piece or sheet of polymeric material (1, 1 "). 38 - Use of a conveyor belt according to any one of claims 1 to 19, for the transport of pharmaceutical and / or food products. 39 - Use of a conveyor belt according to any of claims 1 to 19, for the transport of products in hospitals. 40 - Use of a conveyor belt according to any of claims 1 to 19, for the transport of goods or luggage in ports or airports.