Plastic substrate coated with a black or deep black coating, identifiable by near-infrared spectroscopy

Abstract

Plastic substrate coated with a black or deep black coating identifiable by near-infrared spectroscopy. The invention relates to a substrate (2) made of a plastic material identifiable by near-infrared spectroscopy, coated with a coating (3c) having a specific color in the black or deep black range. Said coating (3c) comprises: - optionally an adhesion layer (5); - a topcoat (4). If the coating (3c) comprises pigments absorbing near-infrared rays, their mass content: - does not exceed 10.00% for pigments partially absorbing near-infrared rays, - does not exceed 1.14% for pigments totally absorbing near-infrared rays, and the thickness of the coating (3c) is between 3 µm and 30 µm. Figure for the abstract: Figure 3

Description

Title of the invention: Plastic material substrate coated with a black or deep black coating identifiable by near-infrared spectroscopy

[0001] The present invention relates to a plastic material substrate of black or deep black color identifiable by near-infrared spectroscopy.

[0002] In the context of the present invention, the substrate can be any part made of plastic (or, in other words, polymeric) material. This may include parts obtained by injection molding or injection blow molding. Preferably, the substrate is packaging made of plastic material obtained by injection molding or injection blow molding. Most preferably, this is packaging for a cosmetic product.

[0003] Nowadays, for economic and environmental reasons, plastic packaging is increasingly being recycled.

[0004] To achieve this, waste sorting centers are generally equipped with machines that perform optical sorting by near-infrared spectroscopy. This technique uses wavelengths in the near-infrared, that is, wavelengths between approximately 600 nm and approximately 2800 nm. More specifically, the sorting machine includes a near-infrared light emitter and a near-infrared light detector. It directs beams of near-infrared light onto the plastic items (for example, packaging) to be sorted, which are conveyed on a conveyor belt. Each piece of plastic to be sorted absorbs some of this emitted light and, more importantly, re-emits it within a range of near-infrared wavelengths that is characteristic of the plastic material from which the item to be sorted is made.In other words, the range of wavelengths of light re-emitted by the part to be sorted constitutes its "spectroscopy signature" and can be easily compared to reference spectra, allowing for a quick, reliable, and certain determination of the plastic material from which the part to be sorted is made.

[0005] The black coloration of plastic parts can be achieved by incorporating dyes and / or pigments (such as carbon black). For example, carbon black may have been incorporated as an additive in the masterbatch of polymeric materials from which the plastic part to be sorted originates.

[0006] However, carbon black has the disadvantage of absorbing rays in the near-infrared, making identification by near-infrared spectroscopy difficult, if not virtually impossible, and therefore the sorting of plastic materials from parts to be sorted. They understand this. Furthermore, the use of carbon black is on the verge of being banned due to regulatory changes in chemical products.

[0007] This is why, in waste sorting centers, parts to be sorted made of black plastic material must be sorted by techniques other than near-infrared spectroscopy; which is not at all advantageous from an economic and logistical point of view.

[0008] In order to overcome these drawbacks associated with the use of carbon black to color plastic materials black, it has been proposed to replace carbon black with pigments that absorb less near-infrared radiation than carbon black. Thus, oxides such as black iron oxide, chromium, and manganese, used alone or in mixtures thereof, have been used as additives in masterbatches as a substitute for carbon black to color plastic materials "throughout."

[0009] However, this alternative solution using other pigments has the following drawbacks: - problems with reproducibility and uniformity of the black coloring; - the desired black or deep black colour is not always obtained with polymers such as polyethylene (hereinafter abbreviated "PE"), as well as recycled polymeric raw materials such as recycled polyethylene terephalate (hereinafter abbreviated "PET").

[0010] This alternative solution is therefore not fully satisfactory.

[0011] In view of these drawbacks regarding the use of carbon black and its replacements by other pigments that absorb less near-infrared radiation than carbon black, the inventors of the present invention sought to develop an alternative technical solution for producing black or deep black plastic parts that can be quickly, reliably, and accurately sorted in sorting centers using near-infrared spectroscopy. To this end, the inventors of the present invention conceived the idea of ​​developing a coating that covers the surface of a plastic substrate in such a way that the coated substrate is black or deep black and that the plastic material can be identified by near-infrared spectroscopy as detailed above.

[0012] The invention thus relates to a substrate made of at least one plastic material that is identifiable by near-infrared spectroscopy, coated with a coating characterized in that: the assembly consisting of the substrate and the coating has a specific color (in other words, a "target color") located in the black or deep black range, and in that the coating comprises: - optionally at least one bonding coat; - at least one topcoat which is applied to the substrate or, where the coating includes at least one bonding coat, said at least one topcoat is applied to said at least one bonding coat, at least one of the coating layers includes at least one colouring agent selected from the group consisting of pigments that do not absorb near-infrared rays, pigments that absorb near-infrared rays and dyes, taken alone or in mixtures thereof, if the coating includes pigments that absorb near-infrared rays, the mass content of said near-infrared pigments, expressed as a percentage of the total mass of the coating: - does not exceed 10.00%, preferably not exceeding 6.50%, when dealing with pigments that partially absorb near-infrared rays, - does not exceed 1.14%, preferably does not exceed 1.00%, when dealing with pigments totally absorbing near-infrared rays, the thickness of said coating is between 3 pm and 30 pm.

[0013] In the context of the present invention, "pigments" means colored particles.

[0014] In the context of the present invention, "near-infrared absorbing pigments" means pigments that can absorb near-infrared rays totally or partially. In other words, in the context of the present invention, the expression "near-infrared absorbing pigments" can refer to pigments that partially absorb near-infrared rays as well as pigments that completely absorb near-infrared rays. In the context of the present invention, "partially absorbing near-infrared rays" is the opposite of "totally absorbing near-infrared rays." Thus, in the context of the present invention, pigments that partially absorb near-infrared rays mean that they absorb a portion of the infrared rays, even a very small portion of them.

[0015] A person skilled in the art has perfect control over pigments that do not absorb near-infrared rays, pigments that partially absorb near-infrared rays, and pigments that totally absorb near-infrared rays.

[0016] Examples of pigments that totally absorb near-infrared rays include carbon black and azinic pigment.

[0017] ) Examples of pigments that partially absorb near-infrared rays Red pigments include black metallic oxides (for example, black iron oxide or manganese oxide). These pigments partially absorb light. Near-infrared rays can also be chromium oxide. It could also be perylene black.

[0018] In other words, pigments that absorb near-infrared radiation are distinguished from one another according to their capacity to absorb near-infrared radiation as a function of their concentration. For example, a smaller quantity (in other words, a lower concentration) of carbon black than of black iron oxide is required to absorb the same quantity of near-infrared radiation.

[0019] Thus, within the framework of the present invention, it is essential that if the coating comprises pigments which absorb near-infrared rays, their mass content expressed in relation to the total mass of said coating shall not exceed: - 10.00%, preferably not 6.50%, when it concerns pigments which partially absorb near-infrared rays, - 1.14%, preferably not 1.00%, when it concerns pigments which totally absorb near-infrared rays.

[0020] This maximum content combined with a coating thickness which must be between 3p and 30 pm makes it possible to identify by near-infrared spectroscopy the plastic material which, once coated with said coating, has a black or deep black color appearance.

[0021] In one embodiment of the invention, the coating may include pigments totally absorbing rays in the near-infrared (for example, carbon black, azinic pigment), the mass content of which, expressed in relation to the total mass of the coating, may be between 0.05% and 1.14%, preferably between 0.08% and 1.00%.

[0022] In one embodiment of the invention, the coating may include pigments partially absorbing rays in the near-infrared (for example, black-colored metal oxides such as black iron oxide or manganese oxide), the mass content of which, expressed in relation to the total mass of the coating, may be between 2.00% and 10.00%, preferably between 2.00% and 6.50%.

[0023] In the context of the present invention, "colorants" means colored substances soluble in the medium in which they are incorporated (for example, a colored topcoat, primer or undercoat formulation as detailed below).

[0024] The mass content of the colorants expressed in relation to the total mass of the coating, can be between 0.01% and 3.50%, preferably between 0.08% and 3.30%.

[0025] The determined colour or in other words the target colour of the assembly consisting of the substrate and the coating can range from black to deep black (also called "piano black").

[0026] Black results from the total or near-total absorption of visible light, as well as light in the infrared and near-infrared. Deep black is a very intense black that reflects very little received radiation.

[0027] In general, colors are defined and characterizable in the CIELAB color space (also known as "CIE L*a*b*"). A glossy shade will always be perceived as more intense (deeper) than a satin or matte shade. Deep, glossy blacks have lightness (L*) values ​​of less than 5%, equivalent to a light reflectance of less than 0.1%; this is too low for precise characterization. Therefore, other parameters have been created to better characterize black and deep blacks.

[0028] Among these parameters is the blackness parameter (abbreviated "My") which determines only the brightness of a sample without taking into account the color shade. From a value of 200, the shade is described as black, and above 300, it is described as "deep black".

[0029] In this regard, the article, in German entitled “Schwarz - der feine Unterschied” (translating as “Black - the ultimate difference”) by Kai Krauss et al., published in January 2019 in the journal Farbe und Lack, precisely defines this parameter of blackness to characterize the colours black and deep black.

[0030] Thus, the assembly consisting of the substrate and the coating has a determined color that is in the black or deep black, that is to say, whose blackness My is greater than or equal to 200.

[0031] The determined color of the assembly consisting of the substrate and the coating, located in black or deep black, is obtained by: - a selection of a plastic substrate material having a certain original color (in other words, the color of the plastic material in the absence of the coating) which is combined with - a suitable selection of a coating with a thickness between 3 µm and 30 µm, containing colorants and / or pigments in specific quantities such that the mass content in said coating does not exceed 1.14% for pigments that totally absorb infrared radiation and 10.00% for pigments that partially absorb infrared radiation, if such pigments are present in said coating. These selections of the plastic material, colorants, and pigments are perfectly within the capabilities of a person skilled in the art, with a view to producing a plastic substrate coated with a black or deep black coating.

[0032] At least one plastic material of the substrate is identifiable by near-infrared spectroscopy. It may advantageously be selected from polyethylene (hereinafter abbreviated as "PE"), polyethylene terephthalate (hereinafter abbreviated as "PET"), high-density PE, low-density PE, polypropylene, polystyrene, polyamide, acrylonitrile butadiene styrene, ethylene vinyl acetate, styrene acrylonitrile, polymethyl methacrylate, styrene methyl methacrylate, and polyethylene terephthalate glycol. The plastic material may also be one of the bio-based polymers, namely polylactic acid, polyhydroxyalkanoate, or polyhydroxybutyrate. Said plastic material may be one of these polymers, alone or in a mixture thereof.

[0033] This can be a virgin plastic material or a recycled plastic material (for example, mechanically or chemically recycled).

[0034] Advantageously, said plastic material of the substrate has as such (i.e. in the absence of the coating) a color close to the determined color of the assembly consisting of the substrate and the coating.

[0035] In the context of the present invention, "close color" means that the plastic material of the substrate can have a color having a blackness value My of at least 130. For example, it can be a color described as grey to the naked eye.

[0036] The plastic material substrate may have been colored throughout.

[0037] However, unlike the state of the art, the black or deep black coloring of The combination of the substrate and the coating does not result solely from a color within the substrate itself, but is primarily achieved through the coating specifically designed so that the plastic material of the substrate can be identified by near-infrared spectroscopy.

[0038] In addition to the fact that, thanks to a coating specifically designed to give the substrate and coating an appearance (i.e., to the naked eye) of black or deep black and to allow the plastic material to be identified by near-infrared spectroscopy, the present invention also has the advantage that said coated substrate can, after grinding, be perfectly recycled. Indeed, while it may contain pigments that could be subject to current or future regulatory restrictions (in particular, pigments absorbing near-infrared rays such as carbon black as mentioned above), these pigments are present in very small quantities and therefore below the acceptable threshold values ​​for recycling ground plastic materials containing such pigments.In other words, the quantities of these pigments subject to regulatory restrictions which are implemented in the coating of the present invention are so minute that said pigments are not likely to constitute a source of . pollution of the plastic material of the substrate which has been coated with such a coating and thus do not hinder the recycling of said plastic material.

[0039] As explained above, the coating comprises dyes and / or pigments that absorb or do not absorb near-infrared radiation. If the coating comprises pigments that absorb near-infrared radiation, their mass content, expressed relative to the total mass of the coating, has been selected such that it does not exceed: - 1.14%, preferably 1.00%, when dealing with pigments that completely absorb near-infrared rays, - 10.00%, preferably 6.50%, when dealing with pigments that partially absorb near-infrared rays, so that the plastic material of the substrate can be identified by near-infrared spectroscopy.

[0040] In an embodiment of the invention in which the coating comprises, as a coloring agent, only pigments absorbing near-infrared rays, the thickness of said coating is advantageously between 5 pm and 25 pm.

[0041] In an embodiment of the invention in which the coating comprises only colorants as a coloring agent, the thickness of said coating is advantageously between 10 pm and 28 pm.

[0042] In other words, when the coating comprises only pigments, its thickness can advantageously be slightly thinner than when it comprises only dyes.

[0043] In one embodiment of the invention, the coating may further comprise at least one colored undercoat (also referred to in English as a "basecoat") which is disposed between the substrate and at least one topcoat or, where the coating comprises at least one tack coat, said at least one colored undercoat is disposed between the at least one tack coat and the at least one topcoat. The at least one colored undercoat contributes to the color of the coating applied to the plastic substrate.

[0044] The at least one coloured underlayer may include dyes and / or pigments that absorb or do not absorb near-infrared rays.

[0045] At least one colored undercoat is obtained, after application (for example by spraying) onto the plastic material substrate or, where applicable, onto at least one tack coat when the coating includes such at least one tack coat, of a colored undercoat formulation designed for coating a plastic material substrate and perfectly within the grasp of a person skilled in the art, followed of a drying process (e.g., drying under infrared rays, under hot air convection or at room temperature), followed by cross-linking under ultraviolet rays.

[0046] The thickness of at least one colored underlayer can be between 5 pm and 12 pm, preferably between 7 pm and 10 pm.

[0047] In the context of the present invention, "topcoat" means a varnish or lacquer coating which is obtained, after application (for example by spraying) on ​​the plastic material substrate or, where applicable, on the tack coat when the coating includes such a tack coat or on the colored undercoat when the coating includes such a colored undercoat, of a varnish or lacquer formulation designed for coating a plastic material substrate and perfectly within the reach of a person skilled in the art, followed by drying (for example, drying under infrared rays, under hot air convection or at room temperature), and then cross-linking under ultraviolet rays.

[0048] The thickness of at least one finishing layer can be between 3 pm and 22 pm, preferably between 3 pm and 20 pm, more preferably between 3 pm and 14 pm, even more preferably between 5 pm and 10 pm.

[0049] At least one topcoat may be coloured or colourless.

[0050] Besides the possible colouring when it contains pigments and / or dyes, said finishing layer mainly provides resistance to the coating, in particular scratch resistance.

[0051] When the topcoat is a varnish layer, said varnish layer may be colored or colorless. When it is a colored varnish layer, said varnish layer may contain colorants. When it is a colorless varnish layer, said varnish layer is free of colorants. The varnish layer is transparent. This means that one can see through said varnish layer.

[0052] When the topcoat is a colorless varnish layer, its thickness is advantageously less than 20 pm.

[0053] When the topcoat is a lacquer layer, said lacquer layer is colored. The lacquer layer comprises pigments, including opacifying pigments (for example, carbon black, aniline black, and black iron oxide) and optionally colorants. Unlike a varnish layer, the lacquer layer is therefore opaque. Indeed, all or part of the pigments it contains limit the passage of light and make the topcoat opaque to the human eye.

[0054] Due to the absence of pigments, a layer of varnish is more resistant (in particular scratch-resistant) than a layer of lacquer.

[0055] Any scratches will be more visible in a colored varnish layer than in a clear varnish layer. Therefore, it is advantageous for the coating to include a colored primer and / or undercoat, as well as a clear varnish topcoat. The clear varnish layer provides scratch resistance, and any scratches will be less visible than if the varnish layer were colored.

[0056] In the context of the present invention, "adhesion layer" means a layer of the coating which is designed to facilitate adhesion to the substrate of the topcoat or, where the coating includes a coloured undercoat, to facilitate adhesion of said coloured undercoat.

[0057] At least one tack coat is obtained after application (for example, by spraying) of a tack coat formulation designed for coating a plastic substrate and readily applicable by a person skilled in the art, followed by drying (for example, by drying under infrared rays, hot air convection, or at ambient temperature). To aid the formation of a film that can be coated with a topcoat or a colored undercoat and then a topcoat, the tack coat may contain hardeners. The presence of these hardeners also has the advantage of reducing the drying time of the tack coat, since these hardeners react under the action of heat (for example, under infrared rays or hot air convection).

[0058] The thickness of at least one tack coat can be between 1 pm and 12 pm, preferably between 1 pm and 10 pm, more preferably between 1 pm and 5 pm, even more preferably between 1 pm and 3 pm.

[0059] At least one tack coat may be colored or colorless. The tack coat may include dyes and / or pigments that absorb or do not absorb near-infrared rays.

[0060] As explained above, the substrate can be any part made of plastic (or, in other words, polymeric) material. This may include parts obtained by injection molding or injection blow molding. Preferably, the substrate is packaging made of plastic material obtained by injection molding or injection blow molding. Most preferably, this is packaging for a cosmetic product.

[0061] Different embodiments of substrates coated with a coating according to the invention are now described.

[0062] In a first embodiment of the invention, the coating comprises at least one colored topcoat disposed on the substrate. The colored topcoat is a layer of lacquer or a layer of colored varnish as described above in the description of the topcoat. In this first embodiment of the invention, the coating may comprise one or more finishing layers, at least one of which is colored.

[0063] In a second embodiment of the invention, the coating comprises: - at least one coloured or colourless bonding layer that is placed on the substrate; - at least one colored or colorless topcoat which is applied over said colored or colorless primer. In this second embodiment of the invention, the coating may comprise one or more primer coats, as well as one or more colored or colorless topcoats.

[0064] In a third embodiment of the invention, the coating comprises: - at least one coloured or colourless bonding layer that is placed on the substrate; - at least one coloured undercoat which is placed on said at least one colourless or coloured bonding coat; - at least one coloured or colourless topcoat which is placed on said at least one coloured undercoat.

[0065] In this 3rd embodiment of the invention, the coating may comprise one or more bonding layers, one or more coloured undercoats, and one or more coloured or colourless finishing layers.

[0066] In a fourth embodiment of the invention, the coating comprises: - at least one colored underlayer which is placed on the substrate; - at least one coloured or colourless topcoat which is placed on said at least one coloured undercoat.

[0067] In this 4th embodiment of the invention, the coating may comprise one or more colored undercoats, as well as one or more colored or colorless topcoats.

[0068] In these 4 embodiments of the invention, the bonding layer, the colored undercoat and the finishing layer may have the technical characteristics that have been described above.

[0069] The invention also relates to a method for manufacturing a plastic material substrate coated with a coating according to the invention and as described above; said manufacturing method is characterized in that it comprises at least the following steps: 1) We have a substrate made of plastic material identifiable by near-infrared spectroscopy,

[0070] 2) Optionally, at least one layer formulation is applied to the substrate adhesion method to obtain at least one adhesion layer or at least one colored undercoat formulation to obtain at least one colored undercoat, or at least one adhesion layer formulation is applied to the substrate in order to obtain at least one tack coat, then at least one colored undercoat formulation is applied over said at least one tack coat in order to obtain at least one colored undercoat, 3) at least one topcoat formulation is applied to the substrate, where appropriate when the coating includes at least one tack coat and is without a coloured undercoat, at least one topcoat formulation is applied to said at least one tack coat, where appropriate when the coating includes at least one coloured undercoat, at least one topcoat formulation is applied to said at least one coloured undercoat, the application of at least one topcoat being followed by a crosslinking step under ultraviolet rays so as to obtain said substrate coated with a coating.

[0071] The formulations of the at least one topcoat and the optional layers, namely the at least one bonding coat and the at least one coloured undercoat, are perfectly within the grasp of a person skilled in the art and are chosen appropriately so that the coating thus obtained has the technical characteristics as detailed above.

[0072] Advantageously, prior to optional steps 2) and 3), the plastic substrate is subjected to a surface treatment. The surface treatment may consist of flame treatment, plasma treatment, or corona treatment. The surface treatment increases the surface tension of the plastic substrate to provide suitable wettability for the application of a primer, a colored undercoat, or a topcoat, thus ensuring good adhesion of the coating to the substrate.

[0073] Advantageously, the applications of tack coat, coloured undercoat and topcoat formulations are carried out by spraying.

[0074] Advantageously, after each application (preferably by spraying) of a primer, colored undercoat, or topcoat formulation, drying is carried out. This allows for desolvation. In other words, it removes the solvents present in these primer, colored undercoat, or topcoat formulations. Drying can be carried out under infrared light, hot air (for example, in an oven), or at ambient temperature.

[0075] The execution of steps 2) and 3) of the manufacturing process according to the invention is perfectly within the reach of a person skilled in the art, as they correspond to steps usually implemented during the coating of a substrate with plastic material.

[0076] During step 3) of the manufacturing process according to the invention, cross-linking is carried out under ultraviolet rays. This allows the topcoat and the optional colored undercoat to be cross-linked simultaneously.

[0077] The originality of the manufacturing process according to the invention lies in the appropriate choice of the formulations of the bonding layer, coloured undercoat and topcoat so that the coating has the technical characteristics as described above and which are essential for obtaining a substrate in plastic material coated with this coating in black or deep black colour and whose plastic material can be identified by near-infrared spectroscopy.

[0078] The invention will be better understood with the aid of the detailed description set forth below with reference to the attached drawing representing, by way of non-limiting example, embodiments of substrates coated with a coating according to the invention.

[0079] [Fig.1] Fig.1 is a schematic cross-sectional view of one embodiment of a substrate coated with a coating according to the invention.

[0080] [Fig.2] The [Fig.2] is a schematic cross-sectional view of a 2nd embodiment of a substrate coated with a coating according to the invention.

[0081] [Fig.3] The [Fig.3] is a schematic cross-sectional view of a 3rd embodiment of a substrate coated with a coating according to the invention.

[0082] [Fig.4] The [Fig.4] is a schematic cross-sectional view of a 4th embodiment of a substrate coated with a coating according to the invention.

[0083] Figure 1 shows a schematic cross-sectional view of a first embodiment of a plastic material substrate 2 coated with a coating 3a according to the invention. The coating 3a comprises a colored topcoat 4 which is disposed on the substrate 2. The topcoat 4 may be a lacquer layer or a colored varnish layer as described above in the description of the topcoat. As explained above, if the topcoat 4 is a lacquer layer, said lacquer layer 4 comprises opacifying pigments and optionally colorants, said opacifying pigments being pigments that absorb or do not absorb near-infrared rays. If the topcoat 4 is a colored varnish layer, said varnish layer comprises colorants.

[0084] Figure 2 shows a schematic cross-sectional view of a second embodiment of a plastic material substrate 2 coated with a coating 3b according to invention 1b. The coating 3b comprises: - an adhesion layer 5 which is placed on the substrate 2; - a finishing layer 4 which is placed on said bonding layer 5.

[0085] The tack coat 5 is a tack coat as described above in the description of the tack coat. It may be colorless or colored. If the layer d'accroche 5 is coloured, it includes dyes and / or pigments, said pigments may or may not absorb near-infrared rays.

[0086] The topcoat 4 of the second embodiment of the invention may be colored or colorless. If the topcoat 4 of this second embodiment of the invention is colored, it may have the same technical characteristics as those of the topcoat 4 of the first embodiment of the invention described above. If the topcoat 4 of this second embodiment of the invention is colorless, it is a colorless varnish layer.

[0087] If in this 2nd embodiment of the invention, the tack coat 5 is a colorless tack coat, the top coat 4 is colored and it can have the technical characteristics described just above.

[0088] In this second embodiment of the invention, if the primer 5 is a colored primer, the topcoat 4 can be colored or colorless. It can thus have the technical characteristics described above, depending on whether it is a colored or colorless topcoat 4. Advantageously, the topcoat 4 is colorless. It is therefore preferably a colorless varnish layer. This has the advantage that the coating 3b has a scratch-resistant topcoat 4, and any scratches will be less visible than if the varnish layer were colored.

[0089] Figure 3 shows a schematic cross-sectional view of a third embodiment of a plastic material substrate 2 coated with a coating 3c according to the invention. The coating 3c comprises: - an adhesion layer 5 which is placed on the substrate 2; - a colored undercoat 6 which is placed on said bonding layer 5; - a finishing layer 4 which is placed on said underlayer 6.

[0090] The tack layer 5 is a tack layer as described above in the description of the tack layer. It may be colorless or colored. If the tack layer 5 is colored, it comprises dyes and / or pigments, said pigments either absorbing or not absorbing near-infrared rays.

[0091] The colored undercoat 6 is a colored undercoat as described above in the description of the colored undercoat. It is colored to enhance the color of the coating 3c. It comprises dyes and / or pigments, said pigments absorbing or not absorbing near-infrared rays.

[0092] The topcoat 4 of the third embodiment of the invention may be colored or colorless and may thus have technical characteristics identical to those of the topcoat 4 of the second embodiment of the invention described above. The topcoat 4 of the third embodiment may be a a layer of lacquer or a layer of colorless or colored varnish. Preferably, the topcoat 4 of the third embodiment of the invention is a layer of colorless or colored varnish, and more preferably a layer of colorless varnish. This has the advantage that the coating 3c has a scratch-resistant topcoat 4, and any scratches will be less visible than if the varnish layer were colored.

[0093] Figure 4 shows a schematic cross-sectional view of a fourth embodiment of a plastic material substrate 2 coated with a 3D coating according to the invention. The 3D coating comprises: - a colored underlayer 6 which is placed on the substrate 2; - a finishing layer 4 which is placed on the said underlayer 6.

[0094] The colored undercoat 6 is a colored undercoat as described above in the description of the bonding layer. It may have technical characteristics identical to those of the 3rd embodiment of the invention and which have been described above.

[0095] The topcoat 4 of the fourth embodiment of the invention may be colored or colorless and thus may have technical characteristics identical to those of the topcoats 4 of the second and third embodiments of the invention described above. The topcoat 4 of the fourth embodiment may be a lacquer layer or a colorless or colored varnish layer. Preferably, the topcoat 4 of the fourth embodiment of the invention is a colorless or colored varnish layer, and more preferably a colorless varnish layer. This has the advantage that the 3D coating has a scratch-resistant topcoat 4, and any scratches will be less visible than if the varnish layer were colored.

[0096] EXPERIMENTAL SECTION

[0097] The following experiments were carried out.

[0098] A - Coating composed of a lacquer finish layer

[0099] 8 lacquer compositions (namely compositions A1 to A8) comprising the The following components: - a basic formulation of colorless lacquer; - a thinner; - a lacquer coloring formulation which comprised 5% by mass of carbon black, said mass percentage of 5% being expressed in relation to the mass of said formulation, were prepared.

[0100] The basic lacquer formulation was a basic lacquer formulation conventionally used for application to plastic substrates.

[0101] The thinner was a thinner conventionally used to dilute lacquer formulations applied to plastic substrates.

[0102] The lacquer colouring formulation which included 5% by mass of carbon black was a formulation classically used to colour a lacquer black.

[0103] Table 1 below details, for each of the compositions Al to A8, the mass percentages of the basic lacquer formulation and the lacquer coloring formulation, these mass percentages being expressed in relation to the sum of the masses of the basic lacquer formulation and the lacquer coloring formulation. [Tables 1] Mass Percentages Base Lacquer Formulation (%) Lacquer Coloring Formulation (%) Composition A1 95.5 Composition A2 93.7 Composition A3 91.9 Composition A4 88.12 Composition A5 87.13 Composition A6 83.17 Composition A7 80.20 Composition A8 77.23

[0104] Table 1

[0105] The quantity of diluent used in each of these Al to A8 compositions was adjusted by the operator at the time of applying these Al to A8 compositions to plastic substrates as detailed below in order to ensure proper application of said compositions and good coverage of the coating on the plastic substrate.

[0106] A-1: ​​Experiments at iso-thickness of the coating of 13 pm + / - 2 pm

[0107] First, each of the compositions A2 to A8 was sprayed onto the surface of a high-density polyethylene (HDPE) substrate, hereinafter referred to as "HDPE", with a parallelepiped shape and dimensions of 8 cm x 5 cm x 0.2 cm, so as to form a layer 13 µm + / - 2 µm thick on said substrate. Next, the layers thus obtained were first dried in a hot air oven. Following From this drying, the layers were cross-linked by exposure to ultraviolet rays in order to obtain 7 substrates coated with a coating consisting of a finishing layer which was a layer of lacquer, hereafter referred to as Tests Al-1 to Al-7.

[0108] The blackness (My) of substrates A2 to A8 was determined according to DIN 55979.

[0109] Table 2 below summarizes, for Tests Al-1 to Al-7, the blackness value (My) and whether the substrate could be identified by near-infrared spectroscopy ("OK") or not ("not OK") by comparing the near-infrared spectra obtained for these Tests Al-1 to Al-7 with a near-infrared reference spectrum of HDPE. The first column of Table 2 indicates the mass content of carbon black in the lacquer layer (i.e., the coating) thus obtained. [Tables 2] Mass content of carbon black (%) Blackness (My) Identification Test Al-1 0.35 220.1 OK Test A-1-2 0.45 225.9 OK Test Al-3 0.58 223.1 OK Test A-1-4 0.65 228.0 OK Test Al-5 0.83 231.5 OK Test Al-6 1.00 231.2 OK Test Al-7 1.15 233.6 NO OK

[0110] Table 2

[0111] In view of the detailed results in Table 2, it is noted that increasing the carbon black content in the coating increases the blackness of the substrates thus coated and that at a mass content of 1.15% carbon black, the coated substrate is no longer identifiable by near-infrared spectroscopy.

[0112] A-2: Experiments with increasing coating thicknesses and a fixed carbon black content

[0113] The Al composition was applied by spraying to the surface of the same substrate as for the experiments at point Al above, but in two different thicknesses (10 µm and 18 µm). The fabrication of the two substrates thus coated with a layer of colored varnish, hereinafter referred to as "Tests A-2-1 and A-2-2", was carried out in the same manner as for the experiments at point Al above.

[0114] Composition A2 was applied by spraying to the surface of the same substrate as for tests A1, but in 3 different thicknesses (6 µm, 13 µm and 16 µm). The fabrication of the 3 substrates thus coated with a lacquer layer, hereinafter referred to as Tests A-2-3 to A-2-5, was carried out in the same manner as for the experiments at point A1 above.

[0115] Composition A3 was applied by spraying to the surface of the same substrate as for the experiments at point Al above, but in two different thicknesses (9 µm and 14 µm). The fabrication of the two substrates thus coated with a lacquer layer, hereinafter referred to as Tests A-2-6 and A-2-7, was carried out in the same manner as for the experiments at point Al above.

[0116] Table 3 below summarizes, for Tests A-2-1 to A-2-7, the blackness value (My) and whether substrate identification by near-infrared spectroscopy was successful ("OK") or not ("not OK") by comparing the near-infrared spectra obtained for these Tests A-2-1 to A-2-7 with a near-infrared reference spectrum of HDPE. The first column of Table 3 shows the mass content of carbon black in the coating. The second column of Table 3 shows the coating thickness. [Tables 3] Mass content of carbon black (%) Total coating thickness (pm) Blackness (μm) Identification Test A-2-1 0.24 10 214.3 OK Test A-2-2 0.24 18 217.5 OK Test A-2-3 0.35 6 216.4 OK Test A-2-4 0.35 13 220.1 OK Test A-2-5 0.35 16 221.4 OK Test A-2-6 0.45 9 225.9 OK Test A-2 -7 0.45 14 225.9 OK

[0117] Table 3

[0118] In view of the results detailed in Table 3 above, it is noted that at the same mass content of carbon black in the coating, the thickness of said coating does not have a significant impact on the blackness.

[0119] B - Coating composed of an adhesion layer comprising carbon black and black iron oxide and a topcoat of colorless varnish

[0120] A B1 tack coat composition comprising the following components: - a black colour tack coat formulation containing by mass between 10% and 20% black colour iron oxide; - a thinner; - a hardener; - a colorant formulation of the tack coat formulation which included 5% by mass of carbon black, was prepared.

[0121] The tack coat formulation was a formulation classically used for obtaining a tack coat for a plastic substrate.

[0122] The thinner was a thinner conventionally used to dilute a tack coat formulation as described above.

[0123] The colouring formulation of the tack coat formulation which included 5% by mass of carbon black was a formulation classically used to colour a tack coat formulation black.

[0124] Table 4 below details for composition B1 the mass percentages of the tack coat formulation, the hardener and the tack coat colour formulation, these mass percentages being expressed in relation to the sum of the masses of the tack coat formulation, the hardener and the tack coat colour formulation. [Tables 4] Mass percentages Bonding coat formulation (%) Hardener (%) Colour formulation of bonding coat formulation (%) Composition B1 86 7 7

[0125] Table 4

[0126] The quantity of diluent used in composition B1 was adjusted by the operator at the time of applying said composition B1 to plastic substrates as detailed below in order to ensure proper application of said compositions and good coverage of the coating on the plastic substrate.

[0127] Composition B1 was sprayed onto the surface of an HDPE substrate identical to that used in experiments in point A above, so as to form a first layer of the thickness defined in Table 5 below on said HDPE substrate. The layers thus obtained were then dried in a hot air oven.

[0128] Following this drying, a colorless varnish composition was sprayed onto the surface of the layers thus obtained from composition B1 to form a second layer of the thickness defined in Table 5 below on said first layer. The second layers thus obtained were then dried in a hot air oven. After this drying, the second layer was cross-linked by exposure to ultraviolet rays to obtain four substrates coated with a coating composed of: - a first layer called the bonding layer; - a 2nd layer called the finishing layer of colorless varnish, and hereafter designated Tests Bl to B-4.

[0129] Table 5 below summarizes, for Tests Bl to B-4, the thicknesses of the 1st and 2nd layers, the total thickness of the coating, the blackness value (My), the mass content of carbon black expressed in relation to the total mass of the coating considered and whether the identification of the substrate by near-infrared spectroscopy could be carried out (“OK”) or not (“not OK”). [Tables 5] Thickness of the 1st layer Thickness of the 2nd layer Total thickness of the coating Mass content in n Mass content in Blackness (My) Identification layer: me layer garment (black carboxide layer of:layer pm) one expressed black iron ex 'adhesion of finished by relative to (pm) tion (pm) ratio to the total mass of the coating considered relative to the total mass of the coating considered Test B1 5 10 15 0.11 6.66 289.6 OK Test B2 5 15 20 0.08 5.00 290.1 ​​OK Test B3 10 10 20 0.17 10.00 291.3 OK Test B4 10 15 25 0.13 8.00 291.2 OK

[0130] Table 5

[0131] In view of the results detailed in Table 5 above, it is noted that: - the HDPE substrate can be identified by near-infrared spectroscopy, with a coating thickness between 6 pm and 25 pm; - by comparing the blackness of tests Bl and B-3 on the one hand and tests B-2 and B-4 on the other hand, the thickness of the bonding layer has no impact on the blackness.

[0132] C - Coating composed of a bonding layer comprising black iron oxide and a topcoat of colorless varnish

[0133] A composition Cl was prepared which comprised the following components: - a black coloured tack coat formulation which contained by mass between 10% and 20% of black coloured iron oxide; - a thinner; - a hardener.

[0134] Table 6 below details for composition Cl the mass percentages of the tack coat formulation and the hardener, these mass percentages being expressed in relation to the sum of the masses of the tack coat formulation and the hardener. [Tableauxô] Mass percentages Bonding coat formulation (%) Hardener (%) Composition B1 92 8

[0135] Table 6

[0136] The quantity of diluent used in composition Cl was adjusted by the operator at the time of applying said composition Cl to plastic substrates as detailed below in order to ensure proper application of said compositions and good coverage of the coating on the plastic substrate.

[0137] The tack coat formulation, thinner and hardener were identical to those used in the experiments in point B above.

[0138] Composition Cl was sprayed onto the surface of 3 HDPE substrates identical to those used in experiments A and B above, forming a first layer 5 µm thick on said HDPE substrate. The 3 layers thus obtained were then dried in a hot air oven.

[0139] After this drying, the same colorless varnish composition as that used in the experiments at point B above was sprayed onto the surface of these three layers obtained from composition Cl, so as to form a second layer of the thickness defined in Table 7 below on said first layer. The second layers thus obtained were then dried in a hot air oven. After this drying, the second layers were cross-linked by exposure to ultraviolet rays to obtain three substrates coated with a coating composed of: - a first layer called the bonding layer; - a 2nd layer called the finishing layer of colorless varnish, and hereafter referred to as Tests Cl to C-3.

[0140] Table 7 below summarizes, for Tests Cl to C-3, the thickness of the 1st layer and of each of the 2nd layers, the total thickness of the coating, as well as the blackness value (My) and whether the identification of the substrate by near-infrared spectroscopy could be carried out (“OK”) or not (“not OK”). [Tables 7] Thickness of 1st layer: base coat (pm) Thickness of 2nd layer: finishing coat (pm) Total thickness of the coating (pm) Mass content of black iron oxide expressed relative to the total mass of the coating considered Blackness (My) Identification Test C1 5 10 15 6.66 207.9 OK Test C-2 5 15 20 5.00 208.6 OK Test C-3 5 20 25 4.00 213.0 OK limit

[0141] Table 7

[0142] In Table 7 above, "OK limit" means that the identification of the plastic material by near-infrared spectroscopy is not totally reliable.

[0143] In view of the detailed results in Tables 6 and 7 above, it is noted that: - by comparing the blackness values ​​of the Bl and Cl tests on the one hand and the B-2 and C-2 tests on the other hand, the presence of carbon black in the bonding layer makes it possible to intensify the black (in other words to increase the blackness); - the thickness of the colorless varnish topcoat is advantageously less than 20 pm so as not to make the coating opaque to near-infrared rays in order to be able to properly identify the plastic material of the coated substrate by near-infrared spectroscopy.

[0144] D- Coatings composed of an adhesion layer comprising a colorant and a topcoat of colorless varnish or comprising a colorant

[0145] 6 compositions (namely compositions DI to D6) comprising the components following: - a ready-to-use tack coat formulation for coating plastic material substrates; - a first solution or a second solution of black colour comprising black dyes and designed to colour a ready-to-use tack coat formulation, were prepared according to the mass percentages, expressed in relation to the total mass of the composition considered, which are detailed in Table 8 below.

[0146] The ready-to-use tack coat formulation for coating plastic material substrate was a formulation conventionally used for obtaining a tack coat for a plastic material substrate.

[0147] The first and second black solutions were designed to color a ready-to-use tack coat formulation. They were pigment-free. They contained black dyes, namely substances soluble in the ready-to-use tack coat formulation. The dry extract of these black dyes was between 0.1% and 10% in these first and second solutions. The second black solution was twice as concentrated in black dyes as the first black solution. [Tables 8] Mass percentages Bonding layer formulation (%) 1st black solution (%) 2nd black solution (%) Composition DI 95 5 0 Composition D2 94 6 0 Composition D3 93 7 0 Composition D4 90 10 0 Composition D5 94 0 6 Composition D6 90 0 10

[0148] Table 8

[0149] Compositions DI and D6 were sprayed onto the surface of a black-tinted HDPE substrate of the same geometric shape and dimensions as the substrate used in experiments A to C above, so as to form a first layer 3 µm thick on said black-tinted HDPE substrate. The resulting layer was then dried in a hot air oven.

[0150] Following this drying, composition B6, as described in point B above, was sprayed onto the surface of the layers thus obtained from compositions DI and D6 to form second layers 14 µm thick on said first layer. These second layers were then dried in a hot air oven. After drying, the second layers were cross-linked by exposure to ultraviolet rays to obtain substrates coated with a coating composed of: - a first layer called the colored bonding layer; - a 2nd layer called the finishing layer of colorless varnish, and hereafter respectively designated Tests Dl and D-2.

[0151] The steps leading to the coated substrate designated Test D-2 were repeated identically with the sole exception that the substrate was replaced by recycled PET dyed black so as to obtain a substrate coated with a coating composed of: - a first layer called the colored adhesion layer; - a 2nd coat called the finishing coat of colorless varnish, and hereafter designated Test D-3.

[0152] Table 9 below details, for each of these coated substrates, namely Tests D1 to D-3: - the composition resulting in the 1st layer with a thickness of 3 pm; - the composition resulting in the 2nd layer with a thickness of 14 pm; - the substrate material. [Tables 9] 1st layer (3 pm) 2nd layer (14 pm) Substrate material Test D1 Composition DI Composition B 6 HDPE dyed black Test D-2 Composition D6 Composition B 6 HDPE dyed black Test D-3 Composition D6 Composition B 6 Recycled PET dyed black

[0153] Table 9

[0154] Furthermore, 5 compositions D7 to DI 1 comprising the following components: - a ready-to-use varnish formulation for coating plastic material substrates with a varnish topcoat, - a first solution or a second solution of black colour comprising black dyes and designed to colour a ready-to-use varnish formulation, were prepared, according to the mass percentages expressed in relation to the total mass of the composition which are detailed in Table 10 below.

[0155] The ready-to-use varnish formulation for coating plastic material substrates with a varnish topcoat was a formulation conventionally used for obtaining a topcoat varnish for a plastic material substrate.

[0156] The first and second black solutions were designed to color a ready-to-use varnish formulation. The dry extract of black dyes was between 0.1% and 10% in these first and second solutions. The second black solution was twice as concentrated in black dyes as the first black solution. [Tables 10] Mass Percentages Varnish Formulation (%) 1st Solution, Black Color (%) 2nd Solution, Black Color (%) Composition D7 95 5 0 Composition D8 94 6 0 Composition D9 90 10 0 Composition D10 94 0 6 Composition D10 90 0 10

[0157] Table 10

[0158] 5 substrates coated with a coating as detailed in Table 11 below and hereinafter referred to as Tests D-4 to D-8 were obtained in the same way as the substrates of Tests D1 to D-3.

[0159] Table 11 below details for each of the coated substrates: - the composition resulting in the first layer with a thickness of 3 pm; - the composition resulting in the 2nd layer with a thickness of 14 pm; - the substrate material. [Tableauxll] 1st layer (3 µm) 2nd layer (14 µm) Substrate material Test D-4 Composition D1 Composition D7 Black-tinted HDPE Test D-5 Composition D3 Composition D11 Black-tinted HDPE Test D-6 Composition D2 Composition D8 Black-tinted recycled PET Test D-7 Composition D5 Composition D10 Black-tinted recycled PET Test D-8 Composition D4 Composition D9 Black-tinted recycled PET

[0160] Table 11

[0161] Table 12 below summarizes, for Tests D1 to D-8, the blackness value (My) and whether the substrate identification by near-infrared spectroscopy could be carried out ("OK") or not ("not OK"). [Tables 12] Darkness (My) Identification Test D1 250.2 OK Test D-2 276.5 OK Test D-3 401.2 OK Test D-4 256.4 OK Test D-5 313.5 OK Test D-6 309.0 OK Test D-7 428.4 OK Test D-8 373.9 OK

[0162] Table 12

[0163] In view of the results detailed in Table 12 above, it is noted that: - by comparing the blackness values ​​of tests D-2 and D-3, from the recycled PET substrate dyed black, we obtain a substrate coated with a higher blackness and in deep black than with an HDPE substrate dyed black; - by comparing in particular the blackness values ​​of tests D-6 and D-7, the 2nd black colour solutions comprising black dyes and designed to colour the adhesion and topcoat formulations of varnishes which were twice as concentrated in dyes as the 1st black colour solutions comprising black dyes and designed to colour the adhesion and topcoat formulations of varnishes made it possible to obtain substrates coated with the highest blackness coatings, and in particular in deep black for substrates in recycled PET dyed black, and this while allowing the identification of the plastic material of the substrate by near-infrared spectroscopy.

[0164] E- Coatings composed of a primer layer comprising a colorant, a colored undercoat comprising a colorant and a topcoat of colorless varnish

[0165] 5 compositions (namely compositions E1 to E5) comprising the components following: - a ready-to-use coloured undercoat formulation for coating plastic material substrates with a coloured undercoat; - a first solution or a second solution of black colour comprising dyes and designed to colour a coloured undercoat formulation, were prepared, according to the mass percentages expressed in relation to the total mass of the composition which are detailed in Table 13 below.

[0166] The formulation of the ready-to-use colored undercoat for coating plastic material substrates with a colored undercoat was a formulation classically used for obtaining a colored undercoat for a plastic material substrate.

[0167] The first and second black solutions were designed to color a ready-to-use colored undercoat formulation. They were pigment-free. They contained black dyes, namely substances soluble in the ready-to-use colored undercoat formulation. The dry extract of these black dyes was between 0.1% and 10% in these first and second solutions. The second black solution was twice as concentrated in black dyes as the first black solution. Mass percentages Colored undercoat formulation (%) 1st black color solution (%) 2nd black color solution (%) Composition E1 95 5 0 Composition E2 94 6 0 Composition E3 93 7 0 Composition E4 95 0 5 Composition E5 94 0 6

[0168] Table 13

[0169] 5 coated substrates and hereinafter referred to as Tests E1 to E-5 were obtained in the following manner:

[0170] A composition selected from compositions D3, D5, and D6 described in point D above and as specified in Table 12 below in the column entitled "first layer" was sprayed onto the surface of a substrate as defined in the last column of Table 12 so as to form a first layer 3 µm thick on said substrate. The layer thus obtained was then dried in a hot air oven.

[0171] Following this drying, a composition selected from those detailed in Table 12 below in the column entitled "2nd layer" was sprayed onto the surface of the first layers thus obtained to form 2nd layers 10 µm thick on the said 1st layers. The 2nd layers thus obtained were then dried in a hot air oven. After this drying, the 2nd layers were cross-linked by exposure to ultraviolet rays.

[0172] Next, the same colorless varnish composition as that used in the experiments in point B above was sprayed onto the surface of the second layers to form third layers 10 µm thick on said second layers. The resulting third layers were then dried in a hot air oven. After drying, the third layers were cross-linked by exposure to ultraviolet rays to obtain substrates coated with a coating composed of: - a first layer called the bonding layer; - a second layer called a colored undercoat; - a 3rd layer called the finishing layer of colorless varnish, and hereinafter respectively designated Tests El to E-5.

[0173]

[0174]

[0175]

[0176]

[0177] Table 14 below details for each of the coated substrates: - the composition resulting in the first layer with a thickness of 3 pm; - the composition resulting in the 2nd layer with a thickness of 10 pm; - the total thickness of the coating - the substrate material. In these tests E1 to E-5, the black-tinted HDPE and recycled black-tinted PET substrates were identical (i.e., same geometric shape and same dimensions) to the substrates in the tests at point D above. [Tables 14] 1st layer (3 µm) 2nd layer (10 µm) 3rd layer (10 µm) Total coating thickness (µm) Substrate material Test E1 Composition D3 Composition E4 Composition B6 23 Black-dyed HDPE Test E2 Composition D5 Composition E5 Composition B6 23 Black-dyed HDPE Test E3 Composition D3 Composition E3 Composition B6 23 Black-dyed HDPE Test E4 Composition D5 Composition E2 Composition B6 23 Black-dyed recycled PET Test E5 Composition D6 Composition E1 Composition B6 23 Black-dyed recycled PET Table 14 Table 15 below summarizes the blackness value for Tests E1 to E-5 (My) and if the identification of the substrate by near-infrared spectroscopy was able to be carried out ("OK") or not ("not OK"). [Tables 15] Blackness (My) Identification Test E-1 327.8 OK Test E-2 423.4 OK Test E-3 303.4 OK Test E-4 304.5 OK Test E-5 276.5 OK Table 15

[0178] In view of the results detailed in Table 15 above, it is noted that: - the colored underlayer contributes to the blackness of the substrate coated with a coating; - the highest blackness value was obtained when the 2nd black colour solutions designed to colour the ready-to-use coloured undercoat formulation and the ready-to-use tack coat formulation were used, namely the black colour solutions which contained colourants in a concentrated form; - By comparing the blackness values ​​of tests Dl to D-8 with those of tests E1 to E-5, the clear varnish topcoat did not alter the blackness of the coated substrates, nor did it compromise the identification of the plastic material by near-infrared spectroscopy. Thanks to the clear varnish topcoat, the coated substrates from tests E1 to E-5 are more scratch-resistant than the coated substrates from tests Dl to D-8.

Claims

Demands

1. Substrate (2) of at least one plastic material which is identifiable by near-infrared spectroscopy, coated with a coating (3a, 3b, 3c, 3d), characterized in that: the assembly (la,lb, lc,ld) consisting of the substrate (2) and the coating (3a, 3b, 3c, 3d) has a determined color in the black or deep black range and in that the coating (3a, 3b, 3c, 3d) comprises: - optionally at least one tack layer (5); - at least one topcoat (4) which is disposed on the substrate (2) or, where the coating (3c) includes at least one tack coat (5), said at least one topcoat (4) is disposed on said at least one tack coat (5), at least one of the layers (4,5) of the coating (3a, 3b, 3c, 3d) includes at least one colouring agent selected from the group consisting of pigments not absorbing near-infrared rays,pigments absorbing near-infrared rays and colorants, alone or in mixtures thereof, if the coating (3a, 3b, 3c, 3d) comprises pigments absorbing near-infrared rays, the mass content of said pigments absorbing near-infrared rays, expressed as a percentage of the total mass of the coating (3a, 3b, 3c, 3d): - does not exceed 10.00%, preferably not exceeding 6.50%, when dealing with pigments partially absorbing near-infrared rays, - does not exceed 1.14%, preferably not exceeding 1.00%, when dealing with pigments totally absorbing near-infrared rays, the thickness of said coating (3a, 3b, 3c, 3d) is between 3 pm and 30 pm.

2. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to claim 1, characterized in that at least one plastic material is selected from polyethylene (hereinafter abbreviated as "PE"), polyethylene terephthalate, high-density PE, low-density PE, polypropylene, polystyrene, polyamide, acrylonitrile butadiene styrene, ethylene vinyl acetate, styrene acrylo- nitrile, polymethyl methacrylate acrylic, styrene methyl methacrylate, polyethylene terephthalate glycol, polylactic acid, polyhydroxyalkanoate and polyhydroxybutyrate, taken alone or in mixtures thereof.

3. Substrate (2) coated with a coating (3c,3d) according to claim 1 or 2, characterized in that the coating (3c) further comprises at least one colored undercoat (6) which is disposed between the substrate (2) and at least one topcoat (4) or, where the coating (3d) comprises at least one tack coat (5), said at least one colored undercoat (6) is disposed between at least one tack coat (5) and at least one topcoat (4).

4. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 3, characterized in that the coating (3a, 3b, 3c, 3d) comprises only dyes as a coloring agent and the thickness of said coating (3a, 3b, 3c, 3d) is between 10 pm and 28 pm.

5. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 3, characterized in that the coating (3a, 3b, 3c, 3d) comprises as a colouring agent only pigments absorbing near-infrared rays and the thickness of said coating (3a, 3b, 3c, 3d) is between 5 pm and 25 pm.

6. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 5, characterized in that the topcoat (4) is a colorless varnish layer and the thickness of said topcoat is less than 20 pm.

7. Substrate (2) coated with a coating (3a) according to claim 1 or 2, characterized in that the coating (3a) comprises at least one colored topcoat (4) which is disposed on the substrate (2).

8. Substrate (2) coated with a coating (3b) according to claim 1 or 2, characterized in that the coating (3b) comprises: - at least one coloured or colourless tack coat (5) which is disposed on the substrate (2); - at least one coloured or colourless topcoat (4) which is disposed on said coloured or colourless tack coat (5).

9. Substrate (2) coated with a coating (3c) according to claim 1 or 2, characterized in that the coating (3c) comprises: - at least one coloured or colourless tack coat (5) which is disposed on the substrate (2); - at least one coloured undercoat (6) which is disposed on said at least one colourless or coloured tack coat (5); - at least one coloured or colourless topcoat (4) which is disposed on said at least one coloured undercoat (6).

10. Substrate (2) coated with a coating (3d) according to claim 1 or 2, characterized in that the coating (3d) comprises: - at least one coloured undercoat (6) which is disposed on the substrate (2); - at least one coloured or colourless topcoat which is disposed on said at least one coloured undercoat (6).

11. Substrate (2) coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 10, characterized in that the substrate (2) is a plastic material packaging which has been obtained by injection or injection blow molding.

12. Substrate coated with a coating according to claim 11, characterized in that the substrate (2) is a packaging for a cosmetic product.

13. A method for manufacturing a substrate (2) made of plastic material coated with a coating (3a, 3b, 3c, 3d) according to any one of claims 1 to 12, characterized in that it comprises at least the following steps: 1) a substrate (2) made of plastic material identifiable by near-infrared spectroscopy is made available, 2) optionally, at least one tack coat formulation (5) is applied to the substrate (2) so as to obtain at least one tack coat (5) or at least one colored undercoat formulation (6) is applied so as to obtain at least one colored undercoat (6), or at least one tack coat formulation (5) is applied to the substrate (2) so as to obtain at least one tack coat (5), and then at least one colored undercoat formulation (6) is applied to said at least one tack coat (5) so as to obtain at least one colored undercoat (6),3) at least one topcoat formulation (4) is applied to the substrate (2), where appropriate, when the coating (3b) includes at least one tack coat (5) and is devoid of a coloured undercoat (6), at least one topcoat formulation is applied, finish (4) on said at least one tack coat (5), where appropriate when the coating (3c,3d) includes at least one coloured undercoat (6), at least one topcoat formulation (4) is applied on said at least one coloured undercoat (6), the application of at least one topcoat being followed by an ultraviolet curing step so as to obtain the substrate (2) coated with a coating (3a, 3b, 3c, 3d).

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